1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 51 Franklin Street, Fifth Floor,
93 Boston, MA 02110-1301, USA@*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN} Version
120 Copyright (C) 1988-2006 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Copying:: GNU General Public License says
163 how you can copy and share GDB
164 * GNU Free Documentation License:: The license for this documentation
173 @unnumbered Summary of @value{GDBN}
175 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
176 going on ``inside'' another program while it executes---or what another
177 program was doing at the moment it crashed.
179 @value{GDBN} can do four main kinds of things (plus other things in support of
180 these) to help you catch bugs in the act:
184 Start your program, specifying anything that might affect its behavior.
187 Make your program stop on specified conditions.
190 Examine what has happened, when your program has stopped.
193 Change things in your program, so you can experiment with correcting the
194 effects of one bug and go on to learn about another.
197 You can use @value{GDBN} to debug programs written in C and C@t{++}.
198 For more information, see @ref{Supported languages,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
475 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
477 Jim Blandy added support for preprocessor macros, while working for Red
480 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
481 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
482 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
483 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
484 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
485 with the migration of old architectures to this new framework.
487 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
488 unwinder framework, this consisting of a fresh new design featuring
489 frame IDs, independent frame sniffers, and the sentinel frame. Mark
490 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
491 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
492 trad unwinders. The architecture specific changes, each involving a
493 complete rewrite of the architecture's frame code, were carried out by
494 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
495 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
496 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
497 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
501 @chapter A Sample @value{GDBN} Session
503 You can use this manual at your leisure to read all about @value{GDBN}.
504 However, a handful of commands are enough to get started using the
505 debugger. This chapter illustrates those commands.
508 In this sample session, we emphasize user input like this: @b{input},
509 to make it easier to pick out from the surrounding output.
512 @c FIXME: this example may not be appropriate for some configs, where
513 @c FIXME...primary interest is in remote use.
515 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
516 processor) exhibits the following bug: sometimes, when we change its
517 quote strings from the default, the commands used to capture one macro
518 definition within another stop working. In the following short @code{m4}
519 session, we define a macro @code{foo} which expands to @code{0000}; we
520 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
521 same thing. However, when we change the open quote string to
522 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
523 procedure fails to define a new synonym @code{baz}:
532 @b{define(bar,defn(`foo'))}
536 @b{changequote(<QUOTE>,<UNQUOTE>)}
538 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
541 m4: End of input: 0: fatal error: EOF in string
545 Let us use @value{GDBN} to try to see what is going on.
548 $ @b{@value{GDBP} m4}
549 @c FIXME: this falsifies the exact text played out, to permit smallbook
550 @c FIXME... format to come out better.
551 @value{GDBN} is free software and you are welcome to distribute copies
552 of it under certain conditions; type "show copying" to see
554 There is absolutely no warranty for @value{GDBN}; type "show warranty"
557 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
562 @value{GDBN} reads only enough symbol data to know where to find the
563 rest when needed; as a result, the first prompt comes up very quickly.
564 We now tell @value{GDBN} to use a narrower display width than usual, so
565 that examples fit in this manual.
568 (@value{GDBP}) @b{set width 70}
572 We need to see how the @code{m4} built-in @code{changequote} works.
573 Having looked at the source, we know the relevant subroutine is
574 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
575 @code{break} command.
578 (@value{GDBP}) @b{break m4_changequote}
579 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
583 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
584 control; as long as control does not reach the @code{m4_changequote}
585 subroutine, the program runs as usual:
588 (@value{GDBP}) @b{run}
589 Starting program: /work/Editorial/gdb/gnu/m4/m4
597 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
598 suspends execution of @code{m4}, displaying information about the
599 context where it stops.
602 @b{changequote(<QUOTE>,<UNQUOTE>)}
604 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
606 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
610 Now we use the command @code{n} (@code{next}) to advance execution to
611 the next line of the current function.
615 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
620 @code{set_quotes} looks like a promising subroutine. We can go into it
621 by using the command @code{s} (@code{step}) instead of @code{next}.
622 @code{step} goes to the next line to be executed in @emph{any}
623 subroutine, so it steps into @code{set_quotes}.
627 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
629 530 if (lquote != def_lquote)
633 The display that shows the subroutine where @code{m4} is now
634 suspended (and its arguments) is called a stack frame display. It
635 shows a summary of the stack. We can use the @code{backtrace}
636 command (which can also be spelled @code{bt}), to see where we are
637 in the stack as a whole: the @code{backtrace} command displays a
638 stack frame for each active subroutine.
641 (@value{GDBP}) @b{bt}
642 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
644 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
646 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
647 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
649 #4 0x79dc in expand_input () at macro.c:40
650 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
654 We step through a few more lines to see what happens. The first two
655 times, we can use @samp{s}; the next two times we use @code{n} to avoid
656 falling into the @code{xstrdup} subroutine.
660 0x3b5c 532 if (rquote != def_rquote)
662 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
663 def_lquote : xstrdup(lq);
665 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
668 538 len_lquote = strlen(rquote);
672 The last line displayed looks a little odd; we can examine the variables
673 @code{lquote} and @code{rquote} to see if they are in fact the new left
674 and right quotes we specified. We use the command @code{p}
675 (@code{print}) to see their values.
678 (@value{GDBP}) @b{p lquote}
679 $1 = 0x35d40 "<QUOTE>"
680 (@value{GDBP}) @b{p rquote}
681 $2 = 0x35d50 "<UNQUOTE>"
685 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
686 To look at some context, we can display ten lines of source
687 surrounding the current line with the @code{l} (@code{list}) command.
693 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
695 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
698 538 len_lquote = strlen(rquote);
699 539 len_rquote = strlen(lquote);
706 Let us step past the two lines that set @code{len_lquote} and
707 @code{len_rquote}, and then examine the values of those variables.
711 539 len_rquote = strlen(lquote);
714 (@value{GDBP}) @b{p len_lquote}
716 (@value{GDBP}) @b{p len_rquote}
721 That certainly looks wrong, assuming @code{len_lquote} and
722 @code{len_rquote} are meant to be the lengths of @code{lquote} and
723 @code{rquote} respectively. We can set them to better values using
724 the @code{p} command, since it can print the value of
725 any expression---and that expression can include subroutine calls and
729 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
731 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
736 Is that enough to fix the problem of using the new quotes with the
737 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
738 executing with the @code{c} (@code{continue}) command, and then try the
739 example that caused trouble initially:
745 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
752 Success! The new quotes now work just as well as the default ones. The
753 problem seems to have been just the two typos defining the wrong
754 lengths. We allow @code{m4} exit by giving it an EOF as input:
758 Program exited normally.
762 The message @samp{Program exited normally.} is from @value{GDBN}; it
763 indicates @code{m4} has finished executing. We can end our @value{GDBN}
764 session with the @value{GDBN} @code{quit} command.
767 (@value{GDBP}) @b{quit}
771 @chapter Getting In and Out of @value{GDBN}
773 This chapter discusses how to start @value{GDBN}, and how to get out of it.
777 type @samp{@value{GDBP}} to start @value{GDBN}.
779 type @kbd{quit} or @kbd{Ctrl-d} to exit.
783 * Invoking GDB:: How to start @value{GDBN}
784 * Quitting GDB:: How to quit @value{GDBN}
785 * Shell Commands:: How to use shell commands inside @value{GDBN}
786 * Logging output:: How to log @value{GDBN}'s output to a file
790 @section Invoking @value{GDBN}
792 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
793 @value{GDBN} reads commands from the terminal until you tell it to exit.
795 You can also run @code{@value{GDBP}} with a variety of arguments and options,
796 to specify more of your debugging environment at the outset.
798 The command-line options described here are designed
799 to cover a variety of situations; in some environments, some of these
800 options may effectively be unavailable.
802 The most usual way to start @value{GDBN} is with one argument,
803 specifying an executable program:
806 @value{GDBP} @var{program}
810 You can also start with both an executable program and a core file
814 @value{GDBP} @var{program} @var{core}
817 You can, instead, specify a process ID as a second argument, if you want
818 to debug a running process:
821 @value{GDBP} @var{program} 1234
825 would attach @value{GDBN} to process @code{1234} (unless you also have a file
826 named @file{1234}; @value{GDBN} does check for a core file first).
828 Taking advantage of the second command-line argument requires a fairly
829 complete operating system; when you use @value{GDBN} as a remote
830 debugger attached to a bare board, there may not be any notion of
831 ``process'', and there is often no way to get a core dump. @value{GDBN}
832 will warn you if it is unable to attach or to read core dumps.
834 You can optionally have @code{@value{GDBP}} pass any arguments after the
835 executable file to the inferior using @code{--args}. This option stops
838 gdb --args gcc -O2 -c foo.c
840 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
841 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
843 You can run @code{@value{GDBP}} without printing the front material, which describes
844 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
851 You can further control how @value{GDBN} starts up by using command-line
852 options. @value{GDBN} itself can remind you of the options available.
862 to display all available options and briefly describe their use
863 (@samp{@value{GDBP} -h} is a shorter equivalent).
865 All options and command line arguments you give are processed
866 in sequential order. The order makes a difference when the
867 @samp{-x} option is used.
871 * File Options:: Choosing files
872 * Mode Options:: Choosing modes
873 * Startup:: What @value{GDBN} does during startup
877 @subsection Choosing files
879 When @value{GDBN} starts, it reads any arguments other than options as
880 specifying an executable file and core file (or process ID). This is
881 the same as if the arguments were specified by the @samp{-se} and
882 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
883 first argument that does not have an associated option flag as
884 equivalent to the @samp{-se} option followed by that argument; and the
885 second argument that does not have an associated option flag, if any, as
886 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
887 If the second argument begins with a decimal digit, @value{GDBN} will
888 first attempt to attach to it as a process, and if that fails, attempt
889 to open it as a corefile. If you have a corefile whose name begins with
890 a digit, you can prevent @value{GDBN} from treating it as a pid by
891 prefixing it with @file{./}, e.g.@: @file{./12345}.
893 If @value{GDBN} has not been configured to included core file support,
894 such as for most embedded targets, then it will complain about a second
895 argument and ignore it.
897 Many options have both long and short forms; both are shown in the
898 following list. @value{GDBN} also recognizes the long forms if you truncate
899 them, so long as enough of the option is present to be unambiguous.
900 (If you prefer, you can flag option arguments with @samp{--} rather
901 than @samp{-}, though we illustrate the more usual convention.)
903 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
904 @c way, both those who look for -foo and --foo in the index, will find
908 @item -symbols @var{file}
910 @cindex @code{--symbols}
912 Read symbol table from file @var{file}.
914 @item -exec @var{file}
916 @cindex @code{--exec}
918 Use file @var{file} as the executable file to execute when appropriate,
919 and for examining pure data in conjunction with a core dump.
923 Read symbol table from file @var{file} and use it as the executable
926 @item -core @var{file}
928 @cindex @code{--core}
930 Use file @var{file} as a core dump to examine.
932 @item -c @var{number}
933 @item -pid @var{number}
934 @itemx -p @var{number}
937 Connect to process ID @var{number}, as with the @code{attach} command.
938 If there is no such process, @value{GDBN} will attempt to open a core
939 file named @var{number}.
941 @item -command @var{file}
943 @cindex @code{--command}
945 Execute @value{GDBN} commands from file @var{file}. @xref{Command
946 Files,, Command files}.
948 @item -eval-command @var{command}
949 @itemx -ex @var{command}
950 @cindex @code{--eval-command}
952 Execute a single @value{GDBN} command.
954 This option may be used multiple times to call multiple commands. It may
955 also be interleaved with @samp{-command} as required.
958 @value{GDBP} -ex 'target sim' -ex 'load' \
959 -x setbreakpoints -ex 'run' a.out
962 @item -directory @var{directory}
963 @itemx -d @var{directory}
964 @cindex @code{--directory}
966 Add @var{directory} to the path to search for source and script files.
970 @cindex @code{--readnow}
972 Read each symbol file's entire symbol table immediately, rather than
973 the default, which is to read it incrementally as it is needed.
974 This makes startup slower, but makes future operations faster.
979 @subsection Choosing modes
981 You can run @value{GDBN} in various alternative modes---for example, in
982 batch mode or quiet mode.
989 Do not execute commands found in any initialization files. Normally,
990 @value{GDBN} executes the commands in these files after all the command
991 options and arguments have been processed. @xref{Command Files,,Command
997 @cindex @code{--quiet}
998 @cindex @code{--silent}
1000 ``Quiet''. Do not print the introductory and copyright messages. These
1001 messages are also suppressed in batch mode.
1004 @cindex @code{--batch}
1005 Run in batch mode. Exit with status @code{0} after processing all the
1006 command files specified with @samp{-x} (and all commands from
1007 initialization files, if not inhibited with @samp{-n}). Exit with
1008 nonzero status if an error occurs in executing the @value{GDBN} commands
1009 in the command files.
1011 Batch mode may be useful for running @value{GDBN} as a filter, for
1012 example to download and run a program on another computer; in order to
1013 make this more useful, the message
1016 Program exited normally.
1020 (which is ordinarily issued whenever a program running under
1021 @value{GDBN} control terminates) is not issued when running in batch
1025 @cindex @code{--batch-silent}
1026 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1027 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1028 unaffected). This is much quieter than @samp{-silent} and would be useless
1029 for an interactive session.
1031 This is particularly useful when using targets that give @samp{Loading section}
1032 messages, for example.
1034 Note that targets that give their output via @value{GDBN}, as opposed to
1035 writing directly to @code{stdout}, will also be made silent.
1037 @item -return-child-result
1038 @cindex @code{--return-child-result}
1039 The return code from @value{GDBN} will be the return code from the child
1040 process (the process being debugged), with the following exceptions:
1044 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1045 internal error. In this case the exit code is the same as it would have been
1046 without @samp{-return-child-result}.
1048 The user quits with an explicit value. E.g., @samp{quit 1}.
1050 The child process never runs, or is not allowed to terminate, in which case
1051 the exit code will be -1.
1054 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1055 when @value{GDBN} is being used as a remote program loader or simulator
1060 @cindex @code{--nowindows}
1062 ``No windows''. If @value{GDBN} comes with a graphical user interface
1063 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1064 interface. If no GUI is available, this option has no effect.
1068 @cindex @code{--windows}
1070 If @value{GDBN} includes a GUI, then this option requires it to be
1073 @item -cd @var{directory}
1075 Run @value{GDBN} using @var{directory} as its working directory,
1076 instead of the current directory.
1080 @cindex @code{--fullname}
1082 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1083 subprocess. It tells @value{GDBN} to output the full file name and line
1084 number in a standard, recognizable fashion each time a stack frame is
1085 displayed (which includes each time your program stops). This
1086 recognizable format looks like two @samp{\032} characters, followed by
1087 the file name, line number and character position separated by colons,
1088 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1089 @samp{\032} characters as a signal to display the source code for the
1093 @cindex @code{--epoch}
1094 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1095 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1096 routines so as to allow Epoch to display values of expressions in a
1099 @item -annotate @var{level}
1100 @cindex @code{--annotate}
1101 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1102 effect is identical to using @samp{set annotate @var{level}}
1103 (@pxref{Annotations}). The annotation @var{level} controls how much
1104 information @value{GDBN} prints together with its prompt, values of
1105 expressions, source lines, and other types of output. Level 0 is the
1106 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1107 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1108 that control @value{GDBN}, and level 2 has been deprecated.
1110 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1114 @cindex @code{--args}
1115 Change interpretation of command line so that arguments following the
1116 executable file are passed as command line arguments to the inferior.
1117 This option stops option processing.
1119 @item -baud @var{bps}
1121 @cindex @code{--baud}
1123 Set the line speed (baud rate or bits per second) of any serial
1124 interface used by @value{GDBN} for remote debugging.
1126 @item -l @var{timeout}
1128 Set the timeout (in seconds) of any communication used by @value{GDBN}
1129 for remote debugging.
1131 @item -tty @var{device}
1132 @itemx -t @var{device}
1133 @cindex @code{--tty}
1135 Run using @var{device} for your program's standard input and output.
1136 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1138 @c resolve the situation of these eventually
1140 @cindex @code{--tui}
1141 Activate the @dfn{Text User Interface} when starting. The Text User
1142 Interface manages several text windows on the terminal, showing
1143 source, assembly, registers and @value{GDBN} command outputs
1144 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1145 Text User Interface can be enabled by invoking the program
1146 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1147 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1150 @c @cindex @code{--xdb}
1151 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1152 @c For information, see the file @file{xdb_trans.html}, which is usually
1153 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1156 @item -interpreter @var{interp}
1157 @cindex @code{--interpreter}
1158 Use the interpreter @var{interp} for interface with the controlling
1159 program or device. This option is meant to be set by programs which
1160 communicate with @value{GDBN} using it as a back end.
1161 @xref{Interpreters, , Command Interpreters}.
1163 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1164 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1165 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1166 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1167 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1168 @sc{gdb/mi} interfaces are no longer supported.
1171 @cindex @code{--write}
1172 Open the executable and core files for both reading and writing. This
1173 is equivalent to the @samp{set write on} command inside @value{GDBN}
1177 @cindex @code{--statistics}
1178 This option causes @value{GDBN} to print statistics about time and
1179 memory usage after it completes each command and returns to the prompt.
1182 @cindex @code{--version}
1183 This option causes @value{GDBN} to print its version number and
1184 no-warranty blurb, and exit.
1189 @subsection What @value{GDBN} does during startup
1190 @cindex @value{GDBN} startup
1192 Here's the description of what @value{GDBN} does during session startup:
1196 Sets up the command interpreter as specified by the command line
1197 (@pxref{Mode Options, interpreter}).
1201 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1202 DOS/Windows systems, the home directory is the one pointed to by the
1203 @code{HOME} environment variable.} and executes all the commands in
1207 Processes command line options and operands.
1210 Reads and executes the commands from init file (if any) in the current
1211 working directory. This is only done if the current directory is
1212 different from your home directory. Thus, you can have more than one
1213 init file, one generic in your home directory, and another, specific
1214 to the program you are debugging, in the directory where you invoke
1218 Reads command files specified by the @samp{-x} option. @xref{Command
1219 Files}, for more details about @value{GDBN} command files.
1222 Reads the command history recorded in the @dfn{history file}.
1223 @xref{Command History}, for more details about the command history and the
1224 files where @value{GDBN} records it.
1227 Init files use the same syntax as @dfn{command files} (@pxref{Command
1228 Files}) and are processed by @value{GDBN} in the same way. The init
1229 file in your home directory can set options (such as @samp{set
1230 complaints}) that affect subsequent processing of command line options
1231 and operands. Init files are not executed if you use the @samp{-nx}
1232 option (@pxref{Mode Options, ,Choosing modes}).
1234 @cindex init file name
1235 @cindex @file{.gdbinit}
1236 The @value{GDBN} init files are normally called @file{.gdbinit}.
1237 On some configurations of @value{GDBN}, the init file is known by a
1238 different name (these are typically environments where a specialized
1239 form of @value{GDBN} may need to coexist with other forms, hence a
1240 different name for the specialized version's init file). These are the
1241 environments with special init file names:
1244 @cindex @file{gdb.ini}
1246 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1247 the limitations of file names imposed by DOS filesystems. The Windows
1248 ports of @value{GDBN} use the standard name, but if they find a
1249 @file{gdb.ini} file, they warn you about that and suggest to rename
1250 the file to the standard name.
1252 @cindex @file{.vxgdbinit}
1254 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1256 @cindex @file{.os68gdbinit}
1258 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1260 @cindex @file{.esgdbinit}
1262 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1265 CISCO 68k: @file{.cisco-gdbinit}
1270 @section Quitting @value{GDBN}
1271 @cindex exiting @value{GDBN}
1272 @cindex leaving @value{GDBN}
1275 @kindex quit @r{[}@var{expression}@r{]}
1276 @kindex q @r{(@code{quit})}
1277 @item quit @r{[}@var{expression}@r{]}
1279 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1280 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1281 do not supply @var{expression}, @value{GDBN} will terminate normally;
1282 otherwise it will terminate using the result of @var{expression} as the
1287 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1288 terminates the action of any @value{GDBN} command that is in progress and
1289 returns to @value{GDBN} command level. It is safe to type the interrupt
1290 character at any time because @value{GDBN} does not allow it to take effect
1291 until a time when it is safe.
1293 If you have been using @value{GDBN} to control an attached process or
1294 device, you can release it with the @code{detach} command
1295 (@pxref{Attach, ,Debugging an already-running process}).
1297 @node Shell Commands
1298 @section Shell commands
1300 If you need to execute occasional shell commands during your
1301 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1302 just use the @code{shell} command.
1306 @cindex shell escape
1307 @item shell @var{command string}
1308 Invoke a standard shell to execute @var{command string}.
1309 If it exists, the environment variable @code{SHELL} determines which
1310 shell to run. Otherwise @value{GDBN} uses the default shell
1311 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1314 The utility @code{make} is often needed in development environments.
1315 You do not have to use the @code{shell} command for this purpose in
1320 @cindex calling make
1321 @item make @var{make-args}
1322 Execute the @code{make} program with the specified
1323 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1326 @node Logging output
1327 @section Logging output
1328 @cindex logging @value{GDBN} output
1329 @cindex save @value{GDBN} output to a file
1331 You may want to save the output of @value{GDBN} commands to a file.
1332 There are several commands to control @value{GDBN}'s logging.
1336 @item set logging on
1338 @item set logging off
1340 @cindex logging file name
1341 @item set logging file @var{file}
1342 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1343 @item set logging overwrite [on|off]
1344 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1345 you want @code{set logging on} to overwrite the logfile instead.
1346 @item set logging redirect [on|off]
1347 By default, @value{GDBN} output will go to both the terminal and the logfile.
1348 Set @code{redirect} if you want output to go only to the log file.
1349 @kindex show logging
1351 Show the current values of the logging settings.
1355 @chapter @value{GDBN} Commands
1357 You can abbreviate a @value{GDBN} command to the first few letters of the command
1358 name, if that abbreviation is unambiguous; and you can repeat certain
1359 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1360 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1361 show you the alternatives available, if there is more than one possibility).
1364 * Command Syntax:: How to give commands to @value{GDBN}
1365 * Completion:: Command completion
1366 * Help:: How to ask @value{GDBN} for help
1369 @node Command Syntax
1370 @section Command syntax
1372 A @value{GDBN} command is a single line of input. There is no limit on
1373 how long it can be. It starts with a command name, which is followed by
1374 arguments whose meaning depends on the command name. For example, the
1375 command @code{step} accepts an argument which is the number of times to
1376 step, as in @samp{step 5}. You can also use the @code{step} command
1377 with no arguments. Some commands do not allow any arguments.
1379 @cindex abbreviation
1380 @value{GDBN} command names may always be truncated if that abbreviation is
1381 unambiguous. Other possible command abbreviations are listed in the
1382 documentation for individual commands. In some cases, even ambiguous
1383 abbreviations are allowed; for example, @code{s} is specially defined as
1384 equivalent to @code{step} even though there are other commands whose
1385 names start with @code{s}. You can test abbreviations by using them as
1386 arguments to the @code{help} command.
1388 @cindex repeating commands
1389 @kindex RET @r{(repeat last command)}
1390 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1391 repeat the previous command. Certain commands (for example, @code{run})
1392 will not repeat this way; these are commands whose unintentional
1393 repetition might cause trouble and which you are unlikely to want to
1394 repeat. User-defined commands can disable this feature; see
1395 @ref{Define, dont-repeat}.
1397 The @code{list} and @code{x} commands, when you repeat them with
1398 @key{RET}, construct new arguments rather than repeating
1399 exactly as typed. This permits easy scanning of source or memory.
1401 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1402 output, in a way similar to the common utility @code{more}
1403 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1404 @key{RET} too many in this situation, @value{GDBN} disables command
1405 repetition after any command that generates this sort of display.
1407 @kindex # @r{(a comment)}
1409 Any text from a @kbd{#} to the end of the line is a comment; it does
1410 nothing. This is useful mainly in command files (@pxref{Command
1411 Files,,Command files}).
1413 @cindex repeating command sequences
1414 @kindex Ctrl-o @r{(operate-and-get-next)}
1415 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1416 commands. This command accepts the current line, like @key{RET}, and
1417 then fetches the next line relative to the current line from the history
1421 @section Command completion
1424 @cindex word completion
1425 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1426 only one possibility; it can also show you what the valid possibilities
1427 are for the next word in a command, at any time. This works for @value{GDBN}
1428 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1430 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1431 of a word. If there is only one possibility, @value{GDBN} fills in the
1432 word, and waits for you to finish the command (or press @key{RET} to
1433 enter it). For example, if you type
1435 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1436 @c complete accuracy in these examples; space introduced for clarity.
1437 @c If texinfo enhancements make it unnecessary, it would be nice to
1438 @c replace " @key" by "@key" in the following...
1440 (@value{GDBP}) info bre @key{TAB}
1444 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1445 the only @code{info} subcommand beginning with @samp{bre}:
1448 (@value{GDBP}) info breakpoints
1452 You can either press @key{RET} at this point, to run the @code{info
1453 breakpoints} command, or backspace and enter something else, if
1454 @samp{breakpoints} does not look like the command you expected. (If you
1455 were sure you wanted @code{info breakpoints} in the first place, you
1456 might as well just type @key{RET} immediately after @samp{info bre},
1457 to exploit command abbreviations rather than command completion).
1459 If there is more than one possibility for the next word when you press
1460 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1461 characters and try again, or just press @key{TAB} a second time;
1462 @value{GDBN} displays all the possible completions for that word. For
1463 example, you might want to set a breakpoint on a subroutine whose name
1464 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1465 just sounds the bell. Typing @key{TAB} again displays all the
1466 function names in your program that begin with those characters, for
1470 (@value{GDBP}) b make_ @key{TAB}
1471 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1472 make_a_section_from_file make_environ
1473 make_abs_section make_function_type
1474 make_blockvector make_pointer_type
1475 make_cleanup make_reference_type
1476 make_command make_symbol_completion_list
1477 (@value{GDBP}) b make_
1481 After displaying the available possibilities, @value{GDBN} copies your
1482 partial input (@samp{b make_} in the example) so you can finish the
1485 If you just want to see the list of alternatives in the first place, you
1486 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1487 means @kbd{@key{META} ?}. You can type this either by holding down a
1488 key designated as the @key{META} shift on your keyboard (if there is
1489 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1491 @cindex quotes in commands
1492 @cindex completion of quoted strings
1493 Sometimes the string you need, while logically a ``word'', may contain
1494 parentheses or other characters that @value{GDBN} normally excludes from
1495 its notion of a word. To permit word completion to work in this
1496 situation, you may enclose words in @code{'} (single quote marks) in
1497 @value{GDBN} commands.
1499 The most likely situation where you might need this is in typing the
1500 name of a C@t{++} function. This is because C@t{++} allows function
1501 overloading (multiple definitions of the same function, distinguished
1502 by argument type). For example, when you want to set a breakpoint you
1503 may need to distinguish whether you mean the version of @code{name}
1504 that takes an @code{int} parameter, @code{name(int)}, or the version
1505 that takes a @code{float} parameter, @code{name(float)}. To use the
1506 word-completion facilities in this situation, type a single quote
1507 @code{'} at the beginning of the function name. This alerts
1508 @value{GDBN} that it may need to consider more information than usual
1509 when you press @key{TAB} or @kbd{M-?} to request word completion:
1512 (@value{GDBP}) b 'bubble( @kbd{M-?}
1513 bubble(double,double) bubble(int,int)
1514 (@value{GDBP}) b 'bubble(
1517 In some cases, @value{GDBN} can tell that completing a name requires using
1518 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1519 completing as much as it can) if you do not type the quote in the first
1523 (@value{GDBP}) b bub @key{TAB}
1524 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1525 (@value{GDBP}) b 'bubble(
1529 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1530 you have not yet started typing the argument list when you ask for
1531 completion on an overloaded symbol.
1533 For more information about overloaded functions, see @ref{C plus plus
1534 expressions, ,C@t{++} expressions}. You can use the command @code{set
1535 overload-resolution off} to disable overload resolution;
1536 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1540 @section Getting help
1541 @cindex online documentation
1544 You can always ask @value{GDBN} itself for information on its commands,
1545 using the command @code{help}.
1548 @kindex h @r{(@code{help})}
1551 You can use @code{help} (abbreviated @code{h}) with no arguments to
1552 display a short list of named classes of commands:
1556 List of classes of commands:
1558 aliases -- Aliases of other commands
1559 breakpoints -- Making program stop at certain points
1560 data -- Examining data
1561 files -- Specifying and examining files
1562 internals -- Maintenance commands
1563 obscure -- Obscure features
1564 running -- Running the program
1565 stack -- Examining the stack
1566 status -- Status inquiries
1567 support -- Support facilities
1568 tracepoints -- Tracing of program execution without@*
1569 stopping the program
1570 user-defined -- User-defined commands
1572 Type "help" followed by a class name for a list of
1573 commands in that class.
1574 Type "help" followed by command name for full
1576 Command name abbreviations are allowed if unambiguous.
1579 @c the above line break eliminates huge line overfull...
1581 @item help @var{class}
1582 Using one of the general help classes as an argument, you can get a
1583 list of the individual commands in that class. For example, here is the
1584 help display for the class @code{status}:
1587 (@value{GDBP}) help status
1592 @c Line break in "show" line falsifies real output, but needed
1593 @c to fit in smallbook page size.
1594 info -- Generic command for showing things
1595 about the program being debugged
1596 show -- Generic command for showing things
1599 Type "help" followed by command name for full
1601 Command name abbreviations are allowed if unambiguous.
1605 @item help @var{command}
1606 With a command name as @code{help} argument, @value{GDBN} displays a
1607 short paragraph on how to use that command.
1610 @item apropos @var{args}
1611 The @code{apropos} command searches through all of the @value{GDBN}
1612 commands, and their documentation, for the regular expression specified in
1613 @var{args}. It prints out all matches found. For example:
1624 set symbol-reloading -- Set dynamic symbol table reloading
1625 multiple times in one run
1626 show symbol-reloading -- Show dynamic symbol table reloading
1627 multiple times in one run
1632 @item complete @var{args}
1633 The @code{complete @var{args}} command lists all the possible completions
1634 for the beginning of a command. Use @var{args} to specify the beginning of the
1635 command you want completed. For example:
1641 @noindent results in:
1652 @noindent This is intended for use by @sc{gnu} Emacs.
1655 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1656 and @code{show} to inquire about the state of your program, or the state
1657 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1658 manual introduces each of them in the appropriate context. The listings
1659 under @code{info} and under @code{show} in the Index point to
1660 all the sub-commands. @xref{Index}.
1665 @kindex i @r{(@code{info})}
1667 This command (abbreviated @code{i}) is for describing the state of your
1668 program. For example, you can list the arguments given to your program
1669 with @code{info args}, list the registers currently in use with @code{info
1670 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1671 You can get a complete list of the @code{info} sub-commands with
1672 @w{@code{help info}}.
1676 You can assign the result of an expression to an environment variable with
1677 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1678 @code{set prompt $}.
1682 In contrast to @code{info}, @code{show} is for describing the state of
1683 @value{GDBN} itself.
1684 You can change most of the things you can @code{show}, by using the
1685 related command @code{set}; for example, you can control what number
1686 system is used for displays with @code{set radix}, or simply inquire
1687 which is currently in use with @code{show radix}.
1690 To display all the settable parameters and their current
1691 values, you can use @code{show} with no arguments; you may also use
1692 @code{info set}. Both commands produce the same display.
1693 @c FIXME: "info set" violates the rule that "info" is for state of
1694 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1695 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1699 Here are three miscellaneous @code{show} subcommands, all of which are
1700 exceptional in lacking corresponding @code{set} commands:
1703 @kindex show version
1704 @cindex @value{GDBN} version number
1706 Show what version of @value{GDBN} is running. You should include this
1707 information in @value{GDBN} bug-reports. If multiple versions of
1708 @value{GDBN} are in use at your site, you may need to determine which
1709 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1710 commands are introduced, and old ones may wither away. Also, many
1711 system vendors ship variant versions of @value{GDBN}, and there are
1712 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1713 The version number is the same as the one announced when you start
1716 @kindex show copying
1717 @kindex info copying
1718 @cindex display @value{GDBN} copyright
1721 Display information about permission for copying @value{GDBN}.
1723 @kindex show warranty
1724 @kindex info warranty
1726 @itemx info warranty
1727 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1728 if your version of @value{GDBN} comes with one.
1733 @chapter Running Programs Under @value{GDBN}
1735 When you run a program under @value{GDBN}, you must first generate
1736 debugging information when you compile it.
1738 You may start @value{GDBN} with its arguments, if any, in an environment
1739 of your choice. If you are doing native debugging, you may redirect
1740 your program's input and output, debug an already running process, or
1741 kill a child process.
1744 * Compilation:: Compiling for debugging
1745 * Starting:: Starting your program
1746 * Arguments:: Your program's arguments
1747 * Environment:: Your program's environment
1749 * Working Directory:: Your program's working directory
1750 * Input/Output:: Your program's input and output
1751 * Attach:: Debugging an already-running process
1752 * Kill Process:: Killing the child process
1754 * Threads:: Debugging programs with multiple threads
1755 * Processes:: Debugging programs with multiple processes
1756 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1760 @section Compiling for debugging
1762 In order to debug a program effectively, you need to generate
1763 debugging information when you compile it. This debugging information
1764 is stored in the object file; it describes the data type of each
1765 variable or function and the correspondence between source line numbers
1766 and addresses in the executable code.
1768 To request debugging information, specify the @samp{-g} option when you run
1771 Programs that are to be shipped to your customers are compiled with
1772 optimizations, using the @samp{-O} compiler option. However, many
1773 compilers are unable to handle the @samp{-g} and @samp{-O} options
1774 together. Using those compilers, you cannot generate optimized
1775 executables containing debugging information.
1777 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1778 without @samp{-O}, making it possible to debug optimized code. We
1779 recommend that you @emph{always} use @samp{-g} whenever you compile a
1780 program. You may think your program is correct, but there is no sense
1781 in pushing your luck.
1783 @cindex optimized code, debugging
1784 @cindex debugging optimized code
1785 When you debug a program compiled with @samp{-g -O}, remember that the
1786 optimizer is rearranging your code; the debugger shows you what is
1787 really there. Do not be too surprised when the execution path does not
1788 exactly match your source file! An extreme example: if you define a
1789 variable, but never use it, @value{GDBN} never sees that
1790 variable---because the compiler optimizes it out of existence.
1792 Some things do not work as well with @samp{-g -O} as with just
1793 @samp{-g}, particularly on machines with instruction scheduling. If in
1794 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1795 please report it to us as a bug (including a test case!).
1796 @xref{Variables}, for more information about debugging optimized code.
1798 Older versions of the @sc{gnu} C compiler permitted a variant option
1799 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1800 format; if your @sc{gnu} C compiler has this option, do not use it.
1802 @value{GDBN} knows about preprocessor macros and can show you their
1803 expansion (@pxref{Macros}). Most compilers do not include information
1804 about preprocessor macros in the debugging information if you specify
1805 the @option{-g} flag alone, because this information is rather large.
1806 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1807 provides macro information if you specify the options
1808 @option{-gdwarf-2} and @option{-g3}; the former option requests
1809 debugging information in the Dwarf 2 format, and the latter requests
1810 ``extra information''. In the future, we hope to find more compact
1811 ways to represent macro information, so that it can be included with
1816 @section Starting your program
1822 @kindex r @r{(@code{run})}
1825 Use the @code{run} command to start your program under @value{GDBN}.
1826 You must first specify the program name (except on VxWorks) with an
1827 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1828 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1829 (@pxref{Files, ,Commands to specify files}).
1833 If you are running your program in an execution environment that
1834 supports processes, @code{run} creates an inferior process and makes
1835 that process run your program. (In environments without processes,
1836 @code{run} jumps to the start of your program.)
1838 The execution of a program is affected by certain information it
1839 receives from its superior. @value{GDBN} provides ways to specify this
1840 information, which you must do @emph{before} starting your program. (You
1841 can change it after starting your program, but such changes only affect
1842 your program the next time you start it.) This information may be
1843 divided into four categories:
1846 @item The @emph{arguments.}
1847 Specify the arguments to give your program as the arguments of the
1848 @code{run} command. If a shell is available on your target, the shell
1849 is used to pass the arguments, so that you may use normal conventions
1850 (such as wildcard expansion or variable substitution) in describing
1852 In Unix systems, you can control which shell is used with the
1853 @code{SHELL} environment variable.
1854 @xref{Arguments, ,Your program's arguments}.
1856 @item The @emph{environment.}
1857 Your program normally inherits its environment from @value{GDBN}, but you can
1858 use the @value{GDBN} commands @code{set environment} and @code{unset
1859 environment} to change parts of the environment that affect
1860 your program. @xref{Environment, ,Your program's environment}.
1862 @item The @emph{working directory.}
1863 Your program inherits its working directory from @value{GDBN}. You can set
1864 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1865 @xref{Working Directory, ,Your program's working directory}.
1867 @item The @emph{standard input and output.}
1868 Your program normally uses the same device for standard input and
1869 standard output as @value{GDBN} is using. You can redirect input and output
1870 in the @code{run} command line, or you can use the @code{tty} command to
1871 set a different device for your program.
1872 @xref{Input/Output, ,Your program's input and output}.
1875 @emph{Warning:} While input and output redirection work, you cannot use
1876 pipes to pass the output of the program you are debugging to another
1877 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1881 When you issue the @code{run} command, your program begins to execute
1882 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1883 of how to arrange for your program to stop. Once your program has
1884 stopped, you may call functions in your program, using the @code{print}
1885 or @code{call} commands. @xref{Data, ,Examining Data}.
1887 If the modification time of your symbol file has changed since the last
1888 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1889 table, and reads it again. When it does this, @value{GDBN} tries to retain
1890 your current breakpoints.
1895 @cindex run to main procedure
1896 The name of the main procedure can vary from language to language.
1897 With C or C@t{++}, the main procedure name is always @code{main}, but
1898 other languages such as Ada do not require a specific name for their
1899 main procedure. The debugger provides a convenient way to start the
1900 execution of the program and to stop at the beginning of the main
1901 procedure, depending on the language used.
1903 The @samp{start} command does the equivalent of setting a temporary
1904 breakpoint at the beginning of the main procedure and then invoking
1905 the @samp{run} command.
1907 @cindex elaboration phase
1908 Some programs contain an @dfn{elaboration} phase where some startup code is
1909 executed before the main procedure is called. This depends on the
1910 languages used to write your program. In C@t{++}, for instance,
1911 constructors for static and global objects are executed before
1912 @code{main} is called. It is therefore possible that the debugger stops
1913 before reaching the main procedure. However, the temporary breakpoint
1914 will remain to halt execution.
1916 Specify the arguments to give to your program as arguments to the
1917 @samp{start} command. These arguments will be given verbatim to the
1918 underlying @samp{run} command. Note that the same arguments will be
1919 reused if no argument is provided during subsequent calls to
1920 @samp{start} or @samp{run}.
1922 It is sometimes necessary to debug the program during elaboration. In
1923 these cases, using the @code{start} command would stop the execution of
1924 your program too late, as the program would have already completed the
1925 elaboration phase. Under these circumstances, insert breakpoints in your
1926 elaboration code before running your program.
1930 @section Your program's arguments
1932 @cindex arguments (to your program)
1933 The arguments to your program can be specified by the arguments of the
1935 They are passed to a shell, which expands wildcard characters and
1936 performs redirection of I/O, and thence to your program. Your
1937 @code{SHELL} environment variable (if it exists) specifies what shell
1938 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1939 the default shell (@file{/bin/sh} on Unix).
1941 On non-Unix systems, the program is usually invoked directly by
1942 @value{GDBN}, which emulates I/O redirection via the appropriate system
1943 calls, and the wildcard characters are expanded by the startup code of
1944 the program, not by the shell.
1946 @code{run} with no arguments uses the same arguments used by the previous
1947 @code{run}, or those set by the @code{set args} command.
1952 Specify the arguments to be used the next time your program is run. If
1953 @code{set args} has no arguments, @code{run} executes your program
1954 with no arguments. Once you have run your program with arguments,
1955 using @code{set args} before the next @code{run} is the only way to run
1956 it again without arguments.
1960 Show the arguments to give your program when it is started.
1964 @section Your program's environment
1966 @cindex environment (of your program)
1967 The @dfn{environment} consists of a set of environment variables and
1968 their values. Environment variables conventionally record such things as
1969 your user name, your home directory, your terminal type, and your search
1970 path for programs to run. Usually you set up environment variables with
1971 the shell and they are inherited by all the other programs you run. When
1972 debugging, it can be useful to try running your program with a modified
1973 environment without having to start @value{GDBN} over again.
1977 @item path @var{directory}
1978 Add @var{directory} to the front of the @code{PATH} environment variable
1979 (the search path for executables) that will be passed to your program.
1980 The value of @code{PATH} used by @value{GDBN} does not change.
1981 You may specify several directory names, separated by whitespace or by a
1982 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1983 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1984 is moved to the front, so it is searched sooner.
1986 You can use the string @samp{$cwd} to refer to whatever is the current
1987 working directory at the time @value{GDBN} searches the path. If you
1988 use @samp{.} instead, it refers to the directory where you executed the
1989 @code{path} command. @value{GDBN} replaces @samp{.} in the
1990 @var{directory} argument (with the current path) before adding
1991 @var{directory} to the search path.
1992 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1993 @c document that, since repeating it would be a no-op.
1997 Display the list of search paths for executables (the @code{PATH}
1998 environment variable).
2000 @kindex show environment
2001 @item show environment @r{[}@var{varname}@r{]}
2002 Print the value of environment variable @var{varname} to be given to
2003 your program when it starts. If you do not supply @var{varname},
2004 print the names and values of all environment variables to be given to
2005 your program. You can abbreviate @code{environment} as @code{env}.
2007 @kindex set environment
2008 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2009 Set environment variable @var{varname} to @var{value}. The value
2010 changes for your program only, not for @value{GDBN} itself. @var{value} may
2011 be any string; the values of environment variables are just strings, and
2012 any interpretation is supplied by your program itself. The @var{value}
2013 parameter is optional; if it is eliminated, the variable is set to a
2015 @c "any string" here does not include leading, trailing
2016 @c blanks. Gnu asks: does anyone care?
2018 For example, this command:
2025 tells the debugged program, when subsequently run, that its user is named
2026 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2027 are not actually required.)
2029 @kindex unset environment
2030 @item unset environment @var{varname}
2031 Remove variable @var{varname} from the environment to be passed to your
2032 program. This is different from @samp{set env @var{varname} =};
2033 @code{unset environment} removes the variable from the environment,
2034 rather than assigning it an empty value.
2037 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2039 by your @code{SHELL} environment variable if it exists (or
2040 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2041 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2042 @file{.bashrc} for BASH---any variables you set in that file affect
2043 your program. You may wish to move setting of environment variables to
2044 files that are only run when you sign on, such as @file{.login} or
2047 @node Working Directory
2048 @section Your program's working directory
2050 @cindex working directory (of your program)
2051 Each time you start your program with @code{run}, it inherits its
2052 working directory from the current working directory of @value{GDBN}.
2053 The @value{GDBN} working directory is initially whatever it inherited
2054 from its parent process (typically the shell), but you can specify a new
2055 working directory in @value{GDBN} with the @code{cd} command.
2057 The @value{GDBN} working directory also serves as a default for the commands
2058 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2063 @cindex change working directory
2064 @item cd @var{directory}
2065 Set the @value{GDBN} working directory to @var{directory}.
2069 Print the @value{GDBN} working directory.
2072 It is generally impossible to find the current working directory of
2073 the process being debugged (since a program can change its directory
2074 during its run). If you work on a system where @value{GDBN} is
2075 configured with the @file{/proc} support, you can use the @code{info
2076 proc} command (@pxref{SVR4 Process Information}) to find out the
2077 current working directory of the debuggee.
2080 @section Your program's input and output
2085 By default, the program you run under @value{GDBN} does input and output to
2086 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2087 to its own terminal modes to interact with you, but it records the terminal
2088 modes your program was using and switches back to them when you continue
2089 running your program.
2092 @kindex info terminal
2094 Displays information recorded by @value{GDBN} about the terminal modes your
2098 You can redirect your program's input and/or output using shell
2099 redirection with the @code{run} command. For example,
2106 starts your program, diverting its output to the file @file{outfile}.
2109 @cindex controlling terminal
2110 Another way to specify where your program should do input and output is
2111 with the @code{tty} command. This command accepts a file name as
2112 argument, and causes this file to be the default for future @code{run}
2113 commands. It also resets the controlling terminal for the child
2114 process, for future @code{run} commands. For example,
2121 directs that processes started with subsequent @code{run} commands
2122 default to do input and output on the terminal @file{/dev/ttyb} and have
2123 that as their controlling terminal.
2125 An explicit redirection in @code{run} overrides the @code{tty} command's
2126 effect on the input/output device, but not its effect on the controlling
2129 When you use the @code{tty} command or redirect input in the @code{run}
2130 command, only the input @emph{for your program} is affected. The input
2131 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2132 for @code{set inferior-tty}.
2134 @cindex inferior tty
2135 @cindex set inferior controlling terminal
2136 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2137 display the name of the terminal that will be used for future runs of your
2141 @item set inferior-tty /dev/ttyb
2142 @kindex set inferior-tty
2143 Set the tty for the program being debugged to /dev/ttyb.
2145 @item show inferior-tty
2146 @kindex show inferior-tty
2147 Show the current tty for the program being debugged.
2151 @section Debugging an already-running process
2156 @item attach @var{process-id}
2157 This command attaches to a running process---one that was started
2158 outside @value{GDBN}. (@code{info files} shows your active
2159 targets.) The command takes as argument a process ID. The usual way to
2160 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2161 or with the @samp{jobs -l} shell command.
2163 @code{attach} does not repeat if you press @key{RET} a second time after
2164 executing the command.
2167 To use @code{attach}, your program must be running in an environment
2168 which supports processes; for example, @code{attach} does not work for
2169 programs on bare-board targets that lack an operating system. You must
2170 also have permission to send the process a signal.
2172 When you use @code{attach}, the debugger finds the program running in
2173 the process first by looking in the current working directory, then (if
2174 the program is not found) by using the source file search path
2175 (@pxref{Source Path, ,Specifying source directories}). You can also use
2176 the @code{file} command to load the program. @xref{Files, ,Commands to
2179 The first thing @value{GDBN} does after arranging to debug the specified
2180 process is to stop it. You can examine and modify an attached process
2181 with all the @value{GDBN} commands that are ordinarily available when
2182 you start processes with @code{run}. You can insert breakpoints; you
2183 can step and continue; you can modify storage. If you would rather the
2184 process continue running, you may use the @code{continue} command after
2185 attaching @value{GDBN} to the process.
2190 When you have finished debugging the attached process, you can use the
2191 @code{detach} command to release it from @value{GDBN} control. Detaching
2192 the process continues its execution. After the @code{detach} command,
2193 that process and @value{GDBN} become completely independent once more, and you
2194 are ready to @code{attach} another process or start one with @code{run}.
2195 @code{detach} does not repeat if you press @key{RET} again after
2196 executing the command.
2199 If you exit @value{GDBN} or use the @code{run} command while you have an
2200 attached process, you kill that process. By default, @value{GDBN} asks
2201 for confirmation if you try to do either of these things; you can
2202 control whether or not you need to confirm by using the @code{set
2203 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2207 @section Killing the child process
2212 Kill the child process in which your program is running under @value{GDBN}.
2215 This command is useful if you wish to debug a core dump instead of a
2216 running process. @value{GDBN} ignores any core dump file while your program
2219 On some operating systems, a program cannot be executed outside @value{GDBN}
2220 while you have breakpoints set on it inside @value{GDBN}. You can use the
2221 @code{kill} command in this situation to permit running your program
2222 outside the debugger.
2224 The @code{kill} command is also useful if you wish to recompile and
2225 relink your program, since on many systems it is impossible to modify an
2226 executable file while it is running in a process. In this case, when you
2227 next type @code{run}, @value{GDBN} notices that the file has changed, and
2228 reads the symbol table again (while trying to preserve your current
2229 breakpoint settings).
2232 @section Debugging programs with multiple threads
2234 @cindex threads of execution
2235 @cindex multiple threads
2236 @cindex switching threads
2237 In some operating systems, such as HP-UX and Solaris, a single program
2238 may have more than one @dfn{thread} of execution. The precise semantics
2239 of threads differ from one operating system to another, but in general
2240 the threads of a single program are akin to multiple processes---except
2241 that they share one address space (that is, they can all examine and
2242 modify the same variables). On the other hand, each thread has its own
2243 registers and execution stack, and perhaps private memory.
2245 @value{GDBN} provides these facilities for debugging multi-thread
2249 @item automatic notification of new threads
2250 @item @samp{thread @var{threadno}}, a command to switch among threads
2251 @item @samp{info threads}, a command to inquire about existing threads
2252 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2253 a command to apply a command to a list of threads
2254 @item thread-specific breakpoints
2258 @emph{Warning:} These facilities are not yet available on every
2259 @value{GDBN} configuration where the operating system supports threads.
2260 If your @value{GDBN} does not support threads, these commands have no
2261 effect. For example, a system without thread support shows no output
2262 from @samp{info threads}, and always rejects the @code{thread} command,
2266 (@value{GDBP}) info threads
2267 (@value{GDBP}) thread 1
2268 Thread ID 1 not known. Use the "info threads" command to
2269 see the IDs of currently known threads.
2271 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2272 @c doesn't support threads"?
2275 @cindex focus of debugging
2276 @cindex current thread
2277 The @value{GDBN} thread debugging facility allows you to observe all
2278 threads while your program runs---but whenever @value{GDBN} takes
2279 control, one thread in particular is always the focus of debugging.
2280 This thread is called the @dfn{current thread}. Debugging commands show
2281 program information from the perspective of the current thread.
2283 @cindex @code{New} @var{systag} message
2284 @cindex thread identifier (system)
2285 @c FIXME-implementors!! It would be more helpful if the [New...] message
2286 @c included GDB's numeric thread handle, so you could just go to that
2287 @c thread without first checking `info threads'.
2288 Whenever @value{GDBN} detects a new thread in your program, it displays
2289 the target system's identification for the thread with a message in the
2290 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2291 whose form varies depending on the particular system. For example, on
2292 LynxOS, you might see
2295 [New process 35 thread 27]
2299 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2300 the @var{systag} is simply something like @samp{process 368}, with no
2303 @c FIXME!! (1) Does the [New...] message appear even for the very first
2304 @c thread of a program, or does it only appear for the
2305 @c second---i.e.@: when it becomes obvious we have a multithread
2307 @c (2) *Is* there necessarily a first thread always? Or do some
2308 @c multithread systems permit starting a program with multiple
2309 @c threads ab initio?
2311 @cindex thread number
2312 @cindex thread identifier (GDB)
2313 For debugging purposes, @value{GDBN} associates its own thread
2314 number---always a single integer---with each thread in your program.
2317 @kindex info threads
2319 Display a summary of all threads currently in your
2320 program. @value{GDBN} displays for each thread (in this order):
2324 the thread number assigned by @value{GDBN}
2327 the target system's thread identifier (@var{systag})
2330 the current stack frame summary for that thread
2334 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2335 indicates the current thread.
2339 @c end table here to get a little more width for example
2342 (@value{GDBP}) info threads
2343 3 process 35 thread 27 0x34e5 in sigpause ()
2344 2 process 35 thread 23 0x34e5 in sigpause ()
2345 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2351 @cindex debugging multithreaded programs (on HP-UX)
2352 @cindex thread identifier (GDB), on HP-UX
2353 For debugging purposes, @value{GDBN} associates its own thread
2354 number---a small integer assigned in thread-creation order---with each
2355 thread in your program.
2357 @cindex @code{New} @var{systag} message, on HP-UX
2358 @cindex thread identifier (system), on HP-UX
2359 @c FIXME-implementors!! It would be more helpful if the [New...] message
2360 @c included GDB's numeric thread handle, so you could just go to that
2361 @c thread without first checking `info threads'.
2362 Whenever @value{GDBN} detects a new thread in your program, it displays
2363 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2364 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2365 whose form varies depending on the particular system. For example, on
2369 [New thread 2 (system thread 26594)]
2373 when @value{GDBN} notices a new thread.
2376 @kindex info threads (HP-UX)
2378 Display a summary of all threads currently in your
2379 program. @value{GDBN} displays for each thread (in this order):
2382 @item the thread number assigned by @value{GDBN}
2384 @item the target system's thread identifier (@var{systag})
2386 @item the current stack frame summary for that thread
2390 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2391 indicates the current thread.
2395 @c end table here to get a little more width for example
2398 (@value{GDBP}) info threads
2399 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2401 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2402 from /usr/lib/libc.2
2403 1 system thread 27905 0x7b003498 in _brk () \@*
2404 from /usr/lib/libc.2
2407 On Solaris, you can display more information about user threads with a
2408 Solaris-specific command:
2411 @item maint info sol-threads
2412 @kindex maint info sol-threads
2413 @cindex thread info (Solaris)
2414 Display info on Solaris user threads.
2418 @kindex thread @var{threadno}
2419 @item thread @var{threadno}
2420 Make thread number @var{threadno} the current thread. The command
2421 argument @var{threadno} is the internal @value{GDBN} thread number, as
2422 shown in the first field of the @samp{info threads} display.
2423 @value{GDBN} responds by displaying the system identifier of the thread
2424 you selected, and its current stack frame summary:
2427 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2428 (@value{GDBP}) thread 2
2429 [Switching to process 35 thread 23]
2430 0x34e5 in sigpause ()
2434 As with the @samp{[New @dots{}]} message, the form of the text after
2435 @samp{Switching to} depends on your system's conventions for identifying
2438 @kindex thread apply
2439 @cindex apply command to several threads
2440 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2441 The @code{thread apply} command allows you to apply the named
2442 @var{command} to one or more threads. Specify the numbers of the
2443 threads that you want affected with the command argument
2444 @var{threadno}. It can be a single thread number, one of the numbers
2445 shown in the first field of the @samp{info threads} display; or it
2446 could be a range of thread numbers, as in @code{2-4}. To apply a
2447 command to all threads, type @kbd{thread apply all @var{command}}.
2450 @cindex automatic thread selection
2451 @cindex switching threads automatically
2452 @cindex threads, automatic switching
2453 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2454 signal, it automatically selects the thread where that breakpoint or
2455 signal happened. @value{GDBN} alerts you to the context switch with a
2456 message of the form @samp{[Switching to @var{systag}]} to identify the
2459 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2460 more information about how @value{GDBN} behaves when you stop and start
2461 programs with multiple threads.
2463 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2464 watchpoints in programs with multiple threads.
2467 @section Debugging programs with multiple processes
2469 @cindex fork, debugging programs which call
2470 @cindex multiple processes
2471 @cindex processes, multiple
2472 On most systems, @value{GDBN} has no special support for debugging
2473 programs which create additional processes using the @code{fork}
2474 function. When a program forks, @value{GDBN} will continue to debug the
2475 parent process and the child process will run unimpeded. If you have
2476 set a breakpoint in any code which the child then executes, the child
2477 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2478 will cause it to terminate.
2480 However, if you want to debug the child process there is a workaround
2481 which isn't too painful. Put a call to @code{sleep} in the code which
2482 the child process executes after the fork. It may be useful to sleep
2483 only if a certain environment variable is set, or a certain file exists,
2484 so that the delay need not occur when you don't want to run @value{GDBN}
2485 on the child. While the child is sleeping, use the @code{ps} program to
2486 get its process ID. Then tell @value{GDBN} (a new invocation of
2487 @value{GDBN} if you are also debugging the parent process) to attach to
2488 the child process (@pxref{Attach}). From that point on you can debug
2489 the child process just like any other process which you attached to.
2491 On some systems, @value{GDBN} provides support for debugging programs that
2492 create additional processes using the @code{fork} or @code{vfork} functions.
2493 Currently, the only platforms with this feature are HP-UX (11.x and later
2494 only?) and GNU/Linux (kernel version 2.5.60 and later).
2496 By default, when a program forks, @value{GDBN} will continue to debug
2497 the parent process and the child process will run unimpeded.
2499 If you want to follow the child process instead of the parent process,
2500 use the command @w{@code{set follow-fork-mode}}.
2503 @kindex set follow-fork-mode
2504 @item set follow-fork-mode @var{mode}
2505 Set the debugger response to a program call of @code{fork} or
2506 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2507 process. The @var{mode} argument can be:
2511 The original process is debugged after a fork. The child process runs
2512 unimpeded. This is the default.
2515 The new process is debugged after a fork. The parent process runs
2520 @kindex show follow-fork-mode
2521 @item show follow-fork-mode
2522 Display the current debugger response to a @code{fork} or @code{vfork} call.
2525 @cindex debugging multiple processes
2526 On Linux, if you want to debug both the parent and child processes, use the
2527 command @w{@code{set detach-on-fork}}.
2530 @kindex set detach-on-fork
2531 @item set detach-on-fork @var{mode}
2532 Tells gdb whether to detach one of the processes after a fork, or
2533 retain debugger control over them both.
2537 The child process (or parent process, depending on the value of
2538 @code{follow-fork-mode}) will be detached and allowed to run
2539 independently. This is the default.
2542 Both processes will be held under the control of @value{GDBN}.
2543 One process (child or parent, depending on the value of
2544 @code{follow-fork-mode}) is debugged as usual, while the other
2549 @kindex show detach-on-follow
2550 @item show detach-on-follow
2551 Show whether detach-on-follow mode is on/off.
2554 If you choose to set @var{detach-on-follow} mode off, then
2555 @value{GDBN} will retain control of all forked processes (including
2556 nested forks). You can list the forked processes under the control of
2557 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2558 from one fork to another by using the @w{@code{fork}} command.
2563 Print a list of all forked processes under the control of @value{GDBN}.
2564 The listing will include a fork id, a process id, and the current
2565 position (program counter) of the process.
2568 @kindex fork @var{fork-id}
2569 @item fork @var{fork-id}
2570 Make fork number @var{fork-id} the current process. The argument
2571 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2572 as shown in the first field of the @samp{info forks} display.
2576 To quit debugging one of the forked processes, you can either detach
2577 from it by using the @w{@code{detach fork}} command (allowing it to
2578 run independently), or delete (and kill) it using the
2579 @w{@code{delete fork}} command.
2582 @kindex detach fork @var{fork-id}
2583 @item detach fork @var{fork-id}
2584 Detach from the process identified by @value{GDBN} fork number
2585 @var{fork-id}, and remove it from the fork list. The process will be
2586 allowed to run independently.
2588 @kindex delete fork @var{fork-id}
2589 @item delete fork @var{fork-id}
2590 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2591 and remove it from the fork list.
2595 If you ask to debug a child process and a @code{vfork} is followed by an
2596 @code{exec}, @value{GDBN} executes the new target up to the first
2597 breakpoint in the new target. If you have a breakpoint set on
2598 @code{main} in your original program, the breakpoint will also be set on
2599 the child process's @code{main}.
2601 When a child process is spawned by @code{vfork}, you cannot debug the
2602 child or parent until an @code{exec} call completes.
2604 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2605 call executes, the new target restarts. To restart the parent process,
2606 use the @code{file} command with the parent executable name as its
2609 You can use the @code{catch} command to make @value{GDBN} stop whenever
2610 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2611 Catchpoints, ,Setting catchpoints}.
2613 @node Checkpoint/Restart
2614 @section Setting a @emph{bookmark} to return to later
2619 @cindex snapshot of a process
2620 @cindex rewind program state
2622 On certain operating systems@footnote{Currently, only
2623 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2624 program's state, called a @dfn{checkpoint}, and come back to it
2627 Returning to a checkpoint effectively undoes everything that has
2628 happened in the program since the @code{checkpoint} was saved. This
2629 includes changes in memory, registers, and even (within some limits)
2630 system state. Effectively, it is like going back in time to the
2631 moment when the checkpoint was saved.
2633 Thus, if you're stepping thru a program and you think you're
2634 getting close to the point where things go wrong, you can save
2635 a checkpoint. Then, if you accidentally go too far and miss
2636 the critical statement, instead of having to restart your program
2637 from the beginning, you can just go back to the checkpoint and
2638 start again from there.
2640 This can be especially useful if it takes a lot of time or
2641 steps to reach the point where you think the bug occurs.
2643 To use the @code{checkpoint}/@code{restart} method of debugging:
2648 Save a snapshot of the debugged program's current execution state.
2649 The @code{checkpoint} command takes no arguments, but each checkpoint
2650 is assigned a small integer id, similar to a breakpoint id.
2652 @kindex info checkpoints
2653 @item info checkpoints
2654 List the checkpoints that have been saved in the current debugging
2655 session. For each checkpoint, the following information will be
2662 @item Source line, or label
2665 @kindex restart @var{checkpoint-id}
2666 @item restart @var{checkpoint-id}
2667 Restore the program state that was saved as checkpoint number
2668 @var{checkpoint-id}. All program variables, registers, stack frames
2669 etc.@: will be returned to the values that they had when the checkpoint
2670 was saved. In essence, gdb will ``wind back the clock'' to the point
2671 in time when the checkpoint was saved.
2673 Note that breakpoints, @value{GDBN} variables, command history etc.
2674 are not affected by restoring a checkpoint. In general, a checkpoint
2675 only restores things that reside in the program being debugged, not in
2678 @kindex delete checkpoint @var{checkpoint-id}
2679 @item delete checkpoint @var{checkpoint-id}
2680 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2684 Returning to a previously saved checkpoint will restore the user state
2685 of the program being debugged, plus a significant subset of the system
2686 (OS) state, including file pointers. It won't ``un-write'' data from
2687 a file, but it will rewind the file pointer to the previous location,
2688 so that the previously written data can be overwritten. For files
2689 opened in read mode, the pointer will also be restored so that the
2690 previously read data can be read again.
2692 Of course, characters that have been sent to a printer (or other
2693 external device) cannot be ``snatched back'', and characters received
2694 from eg.@: a serial device can be removed from internal program buffers,
2695 but they cannot be ``pushed back'' into the serial pipeline, ready to
2696 be received again. Similarly, the actual contents of files that have
2697 been changed cannot be restored (at this time).
2699 However, within those constraints, you actually can ``rewind'' your
2700 program to a previously saved point in time, and begin debugging it
2701 again --- and you can change the course of events so as to debug a
2702 different execution path this time.
2704 @cindex checkpoints and process id
2705 Finally, there is one bit of internal program state that will be
2706 different when you return to a checkpoint --- the program's process
2707 id. Each checkpoint will have a unique process id (or @var{pid}),
2708 and each will be different from the program's original @var{pid}.
2709 If your program has saved a local copy of its process id, this could
2710 potentially pose a problem.
2712 @subsection A non-obvious benefit of using checkpoints
2714 On some systems such as @sc{gnu}/Linux, address space randomization
2715 is performed on new processes for security reasons. This makes it
2716 difficult or impossible to set a breakpoint, or watchpoint, on an
2717 absolute address if you have to restart the program, since the
2718 absolute location of a symbol will change from one execution to the
2721 A checkpoint, however, is an @emph{identical} copy of a process.
2722 Therefore if you create a checkpoint at (eg.@:) the start of main,
2723 and simply return to that checkpoint instead of restarting the
2724 process, you can avoid the effects of address randomization and
2725 your symbols will all stay in the same place.
2728 @chapter Stopping and Continuing
2730 The principal purposes of using a debugger are so that you can stop your
2731 program before it terminates; or so that, if your program runs into
2732 trouble, you can investigate and find out why.
2734 Inside @value{GDBN}, your program may stop for any of several reasons,
2735 such as a signal, a breakpoint, or reaching a new line after a
2736 @value{GDBN} command such as @code{step}. You may then examine and
2737 change variables, set new breakpoints or remove old ones, and then
2738 continue execution. Usually, the messages shown by @value{GDBN} provide
2739 ample explanation of the status of your program---but you can also
2740 explicitly request this information at any time.
2743 @kindex info program
2745 Display information about the status of your program: whether it is
2746 running or not, what process it is, and why it stopped.
2750 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2751 * Continuing and Stepping:: Resuming execution
2753 * Thread Stops:: Stopping and starting multi-thread programs
2757 @section Breakpoints, watchpoints, and catchpoints
2760 A @dfn{breakpoint} makes your program stop whenever a certain point in
2761 the program is reached. For each breakpoint, you can add conditions to
2762 control in finer detail whether your program stops. You can set
2763 breakpoints with the @code{break} command and its variants (@pxref{Set
2764 Breaks, ,Setting breakpoints}), to specify the place where your program
2765 should stop by line number, function name or exact address in the
2768 On some systems, you can set breakpoints in shared libraries before
2769 the executable is run. There is a minor limitation on HP-UX systems:
2770 you must wait until the executable is run in order to set breakpoints
2771 in shared library routines that are not called directly by the program
2772 (for example, routines that are arguments in a @code{pthread_create}
2776 @cindex data breakpoints
2777 @cindex memory tracing
2778 @cindex breakpoint on memory address
2779 @cindex breakpoint on variable modification
2780 A @dfn{watchpoint} is a special breakpoint that stops your program
2781 when the value of an expression changes. The expression may be a value
2782 of a variable, or it could involve values of one or more variables
2783 combined by operators, such as @samp{a + b}. This is sometimes called
2784 @dfn{data breakpoints}. You must use a different command to set
2785 watchpoints (@pxref{Set Watchpoints, ,Setting watchpoints}), but aside
2786 from that, you can manage a watchpoint like any other breakpoint: you
2787 enable, disable, and delete both breakpoints and watchpoints using the
2790 You can arrange to have values from your program displayed automatically
2791 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2795 @cindex breakpoint on events
2796 A @dfn{catchpoint} is another special breakpoint that stops your program
2797 when a certain kind of event occurs, such as the throwing of a C@t{++}
2798 exception or the loading of a library. As with watchpoints, you use a
2799 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2800 catchpoints}), but aside from that, you can manage a catchpoint like any
2801 other breakpoint. (To stop when your program receives a signal, use the
2802 @code{handle} command; see @ref{Signals, ,Signals}.)
2804 @cindex breakpoint numbers
2805 @cindex numbers for breakpoints
2806 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2807 catchpoint when you create it; these numbers are successive integers
2808 starting with one. In many of the commands for controlling various
2809 features of breakpoints you use the breakpoint number to say which
2810 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2811 @dfn{disabled}; if disabled, it has no effect on your program until you
2814 @cindex breakpoint ranges
2815 @cindex ranges of breakpoints
2816 Some @value{GDBN} commands accept a range of breakpoints on which to
2817 operate. A breakpoint range is either a single breakpoint number, like
2818 @samp{5}, or two such numbers, in increasing order, separated by a
2819 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2820 all breakpoint in that range are operated on.
2823 * Set Breaks:: Setting breakpoints
2824 * Set Watchpoints:: Setting watchpoints
2825 * Set Catchpoints:: Setting catchpoints
2826 * Delete Breaks:: Deleting breakpoints
2827 * Disabling:: Disabling breakpoints
2828 * Conditions:: Break conditions
2829 * Break Commands:: Breakpoint command lists
2830 * Breakpoint Menus:: Breakpoint menus
2831 * Error in Breakpoints:: ``Cannot insert breakpoints''
2832 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2836 @subsection Setting breakpoints
2838 @c FIXME LMB what does GDB do if no code on line of breakpt?
2839 @c consider in particular declaration with/without initialization.
2841 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2844 @kindex b @r{(@code{break})}
2845 @vindex $bpnum@r{, convenience variable}
2846 @cindex latest breakpoint
2847 Breakpoints are set with the @code{break} command (abbreviated
2848 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2849 number of the breakpoint you've set most recently; see @ref{Convenience
2850 Vars,, Convenience variables}, for a discussion of what you can do with
2851 convenience variables.
2853 You have several ways to say where the breakpoint should go.
2856 @item break @var{function}
2857 Set a breakpoint at entry to function @var{function}.
2858 When using source languages that permit overloading of symbols, such as
2859 C@t{++}, @var{function} may refer to more than one possible place to break.
2860 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2862 @item break +@var{offset}
2863 @itemx break -@var{offset}
2864 Set a breakpoint some number of lines forward or back from the position
2865 at which execution stopped in the currently selected @dfn{stack frame}.
2866 (@xref{Frames, ,Frames}, for a description of stack frames.)
2868 @item break @var{linenum}
2869 Set a breakpoint at line @var{linenum} in the current source file.
2870 The current source file is the last file whose source text was printed.
2871 The breakpoint will stop your program just before it executes any of the
2874 @item break @var{filename}:@var{linenum}
2875 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2877 @item break @var{filename}:@var{function}
2878 Set a breakpoint at entry to function @var{function} found in file
2879 @var{filename}. Specifying a file name as well as a function name is
2880 superfluous except when multiple files contain similarly named
2883 @item break *@var{address}
2884 Set a breakpoint at address @var{address}. You can use this to set
2885 breakpoints in parts of your program which do not have debugging
2886 information or source files.
2889 When called without any arguments, @code{break} sets a breakpoint at
2890 the next instruction to be executed in the selected stack frame
2891 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2892 innermost, this makes your program stop as soon as control
2893 returns to that frame. This is similar to the effect of a
2894 @code{finish} command in the frame inside the selected frame---except
2895 that @code{finish} does not leave an active breakpoint. If you use
2896 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2897 the next time it reaches the current location; this may be useful
2900 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2901 least one instruction has been executed. If it did not do this, you
2902 would be unable to proceed past a breakpoint without first disabling the
2903 breakpoint. This rule applies whether or not the breakpoint already
2904 existed when your program stopped.
2906 @item break @dots{} if @var{cond}
2907 Set a breakpoint with condition @var{cond}; evaluate the expression
2908 @var{cond} each time the breakpoint is reached, and stop only if the
2909 value is nonzero---that is, if @var{cond} evaluates as true.
2910 @samp{@dots{}} stands for one of the possible arguments described
2911 above (or no argument) specifying where to break. @xref{Conditions,
2912 ,Break conditions}, for more information on breakpoint conditions.
2915 @item tbreak @var{args}
2916 Set a breakpoint enabled only for one stop. @var{args} are the
2917 same as for the @code{break} command, and the breakpoint is set in the same
2918 way, but the breakpoint is automatically deleted after the first time your
2919 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2922 @cindex hardware breakpoints
2923 @item hbreak @var{args}
2924 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2925 @code{break} command and the breakpoint is set in the same way, but the
2926 breakpoint requires hardware support and some target hardware may not
2927 have this support. The main purpose of this is EPROM/ROM code
2928 debugging, so you can set a breakpoint at an instruction without
2929 changing the instruction. This can be used with the new trap-generation
2930 provided by SPARClite DSU and most x86-based targets. These targets
2931 will generate traps when a program accesses some data or instruction
2932 address that is assigned to the debug registers. However the hardware
2933 breakpoint registers can take a limited number of breakpoints. For
2934 example, on the DSU, only two data breakpoints can be set at a time, and
2935 @value{GDBN} will reject this command if more than two are used. Delete
2936 or disable unused hardware breakpoints before setting new ones
2937 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2938 For remote targets, you can restrict the number of hardware
2939 breakpoints @value{GDBN} will use, see @ref{set remote
2940 hardware-breakpoint-limit}.
2944 @item thbreak @var{args}
2945 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2946 are the same as for the @code{hbreak} command and the breakpoint is set in
2947 the same way. However, like the @code{tbreak} command,
2948 the breakpoint is automatically deleted after the
2949 first time your program stops there. Also, like the @code{hbreak}
2950 command, the breakpoint requires hardware support and some target hardware
2951 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2952 See also @ref{Conditions, ,Break conditions}.
2955 @cindex regular expression
2956 @cindex breakpoints in functions matching a regexp
2957 @cindex set breakpoints in many functions
2958 @item rbreak @var{regex}
2959 Set breakpoints on all functions matching the regular expression
2960 @var{regex}. This command sets an unconditional breakpoint on all
2961 matches, printing a list of all breakpoints it set. Once these
2962 breakpoints are set, they are treated just like the breakpoints set with
2963 the @code{break} command. You can delete them, disable them, or make
2964 them conditional the same way as any other breakpoint.
2966 The syntax of the regular expression is the standard one used with tools
2967 like @file{grep}. Note that this is different from the syntax used by
2968 shells, so for instance @code{foo*} matches all functions that include
2969 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2970 @code{.*} leading and trailing the regular expression you supply, so to
2971 match only functions that begin with @code{foo}, use @code{^foo}.
2973 @cindex non-member C@t{++} functions, set breakpoint in
2974 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2975 breakpoints on overloaded functions that are not members of any special
2978 @cindex set breakpoints on all functions
2979 The @code{rbreak} command can be used to set breakpoints in
2980 @strong{all} the functions in a program, like this:
2983 (@value{GDBP}) rbreak .
2986 @kindex info breakpoints
2987 @cindex @code{$_} and @code{info breakpoints}
2988 @item info breakpoints @r{[}@var{n}@r{]}
2989 @itemx info break @r{[}@var{n}@r{]}
2990 @itemx info watchpoints @r{[}@var{n}@r{]}
2991 Print a table of all breakpoints, watchpoints, and catchpoints set and
2992 not deleted. Optional argument @var{n} means print information only
2993 about the specified breakpoint (or watchpoint or catchpoint). For
2994 each breakpoint, following columns are printed:
2997 @item Breakpoint Numbers
2999 Breakpoint, watchpoint, or catchpoint.
3001 Whether the breakpoint is marked to be disabled or deleted when hit.
3002 @item Enabled or Disabled
3003 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3004 that are not enabled.
3006 Where the breakpoint is in your program, as a memory address. If the
3007 breakpoint is pending (see below for details) on a future load of a shared library, the address
3008 will be listed as @samp{<PENDING>}.
3010 Where the breakpoint is in the source for your program, as a file and
3011 line number. For a pending breakpoint, the original string passed to
3012 the breakpoint command will be listed as it cannot be resolved until
3013 the appropriate shared library is loaded in the future.
3017 If a breakpoint is conditional, @code{info break} shows the condition on
3018 the line following the affected breakpoint; breakpoint commands, if any,
3019 are listed after that. A pending breakpoint is allowed to have a condition
3020 specified for it. The condition is not parsed for validity until a shared
3021 library is loaded that allows the pending breakpoint to resolve to a
3025 @code{info break} with a breakpoint
3026 number @var{n} as argument lists only that breakpoint. The
3027 convenience variable @code{$_} and the default examining-address for
3028 the @code{x} command are set to the address of the last breakpoint
3029 listed (@pxref{Memory, ,Examining memory}).
3032 @code{info break} displays a count of the number of times the breakpoint
3033 has been hit. This is especially useful in conjunction with the
3034 @code{ignore} command. You can ignore a large number of breakpoint
3035 hits, look at the breakpoint info to see how many times the breakpoint
3036 was hit, and then run again, ignoring one less than that number. This
3037 will get you quickly to the last hit of that breakpoint.
3040 @value{GDBN} allows you to set any number of breakpoints at the same place in
3041 your program. There is nothing silly or meaningless about this. When
3042 the breakpoints are conditional, this is even useful
3043 (@pxref{Conditions, ,Break conditions}).
3045 @cindex pending breakpoints
3046 If a specified breakpoint location cannot be found, it may be due to the fact
3047 that the location is in a shared library that is yet to be loaded. In such
3048 a case, you may want @value{GDBN} to create a special breakpoint (known as
3049 a @dfn{pending breakpoint}) that
3050 attempts to resolve itself in the future when an appropriate shared library
3053 Pending breakpoints are useful to set at the start of your
3054 @value{GDBN} session for locations that you know will be dynamically loaded
3055 later by the program being debugged. When shared libraries are loaded,
3056 a check is made to see if the load resolves any pending breakpoint locations.
3057 If a pending breakpoint location gets resolved,
3058 a regular breakpoint is created and the original pending breakpoint is removed.
3060 @value{GDBN} provides some additional commands for controlling pending
3063 @kindex set breakpoint pending
3064 @kindex show breakpoint pending
3066 @item set breakpoint pending auto
3067 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3068 location, it queries you whether a pending breakpoint should be created.
3070 @item set breakpoint pending on
3071 This indicates that an unrecognized breakpoint location should automatically
3072 result in a pending breakpoint being created.
3074 @item set breakpoint pending off
3075 This indicates that pending breakpoints are not to be created. Any
3076 unrecognized breakpoint location results in an error. This setting does
3077 not affect any pending breakpoints previously created.
3079 @item show breakpoint pending
3080 Show the current behavior setting for creating pending breakpoints.
3083 @cindex operations allowed on pending breakpoints
3084 Normal breakpoint operations apply to pending breakpoints as well. You may
3085 specify a condition for a pending breakpoint and/or commands to run when the
3086 breakpoint is reached. You can also enable or disable
3087 the pending breakpoint. When you specify a condition for a pending breakpoint,
3088 the parsing of the condition will be deferred until the point where the
3089 pending breakpoint location is resolved. Disabling a pending breakpoint
3090 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3091 shared library load. When a pending breakpoint is re-enabled,
3092 @value{GDBN} checks to see if the location is already resolved.
3093 This is done because any number of shared library loads could have
3094 occurred since the time the breakpoint was disabled and one or more
3095 of these loads could resolve the location.
3097 @cindex negative breakpoint numbers
3098 @cindex internal @value{GDBN} breakpoints
3099 @value{GDBN} itself sometimes sets breakpoints in your program for
3100 special purposes, such as proper handling of @code{longjmp} (in C
3101 programs). These internal breakpoints are assigned negative numbers,
3102 starting with @code{-1}; @samp{info breakpoints} does not display them.
3103 You can see these breakpoints with the @value{GDBN} maintenance command
3104 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3107 @node Set Watchpoints
3108 @subsection Setting watchpoints
3110 @cindex setting watchpoints
3111 You can use a watchpoint to stop execution whenever the value of an
3112 expression changes, without having to predict a particular place where
3113 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3114 The expression may be as simple as the value of a single variable, or
3115 as complex as many variables combined by operators. Examples include:
3119 A reference to the value of a single variable.
3122 An address cast to an appropriate data type. For example,
3123 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3124 address (assuming an @code{int} occupies 4 bytes).
3127 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3128 expression can use any operators valid in the program's native
3129 language (@pxref{Languages}).
3132 @cindex software watchpoints
3133 @cindex hardware watchpoints
3134 Depending on your system, watchpoints may be implemented in software or
3135 hardware. @value{GDBN} does software watchpointing by single-stepping your
3136 program and testing the variable's value each time, which is hundreds of
3137 times slower than normal execution. (But this may still be worth it, to
3138 catch errors where you have no clue what part of your program is the
3141 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3142 x86-based targets, @value{GDBN} includes support for hardware
3143 watchpoints, which do not slow down the running of your program.
3147 @item watch @var{expr}
3148 Set a watchpoint for an expression. @value{GDBN} will break when the
3149 expression @var{expr} is written into by the program and its value
3150 changes. The simplest (and the most popular) use of this command is
3151 to watch the value of a single variable:
3154 (@value{GDBP}) watch foo
3158 @item rwatch @var{expr}
3159 Set a watchpoint that will break when the value of @var{expr} is read
3163 @item awatch @var{expr}
3164 Set a watchpoint that will break when @var{expr} is either read from
3165 or written into by the program.
3167 @kindex info watchpoints @r{[}@var{n}@r{]}
3168 @item info watchpoints
3169 This command prints a list of watchpoints, breakpoints, and catchpoints;
3170 it is the same as @code{info break} (@pxref{Set Breaks}).
3173 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3174 watchpoints execute very quickly, and the debugger reports a change in
3175 value at the exact instruction where the change occurs. If @value{GDBN}
3176 cannot set a hardware watchpoint, it sets a software watchpoint, which
3177 executes more slowly and reports the change in value at the next
3178 @emph{statement}, not the instruction, after the change occurs.
3180 @cindex use only software watchpoints
3181 You can force @value{GDBN} to use only software watchpoints with the
3182 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3183 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3184 the underlying system supports them. (Note that hardware-assisted
3185 watchpoints that were set @emph{before} setting
3186 @code{can-use-hw-watchpoints} to zero will still use the hardware
3187 mechanism of watching expressiion values.)
3190 @item set can-use-hw-watchpoints
3191 @kindex set can-use-hw-watchpoints
3192 Set whether or not to use hardware watchpoints.
3194 @item show can-use-hw-watchpoints
3195 @kindex show can-use-hw-watchpoints
3196 Show the current mode of using hardware watchpoints.
3199 For remote targets, you can restrict the number of hardware
3200 watchpoints @value{GDBN} will use, see @ref{set remote
3201 hardware-breakpoint-limit}.
3203 When you issue the @code{watch} command, @value{GDBN} reports
3206 Hardware watchpoint @var{num}: @var{expr}
3210 if it was able to set a hardware watchpoint.
3212 Currently, the @code{awatch} and @code{rwatch} commands can only set
3213 hardware watchpoints, because accesses to data that don't change the
3214 value of the watched expression cannot be detected without examining
3215 every instruction as it is being executed, and @value{GDBN} does not do
3216 that currently. If @value{GDBN} finds that it is unable to set a
3217 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3218 will print a message like this:
3221 Expression cannot be implemented with read/access watchpoint.
3224 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3225 data type of the watched expression is wider than what a hardware
3226 watchpoint on the target machine can handle. For example, some systems
3227 can only watch regions that are up to 4 bytes wide; on such systems you
3228 cannot set hardware watchpoints for an expression that yields a
3229 double-precision floating-point number (which is typically 8 bytes
3230 wide). As a work-around, it might be possible to break the large region
3231 into a series of smaller ones and watch them with separate watchpoints.
3233 If you set too many hardware watchpoints, @value{GDBN} might be unable
3234 to insert all of them when you resume the execution of your program.
3235 Since the precise number of active watchpoints is unknown until such
3236 time as the program is about to be resumed, @value{GDBN} might not be
3237 able to warn you about this when you set the watchpoints, and the
3238 warning will be printed only when the program is resumed:
3241 Hardware watchpoint @var{num}: Could not insert watchpoint
3245 If this happens, delete or disable some of the watchpoints.
3247 Watching complex expressions that reference many variables can also
3248 exhaust the resources available for hardware-assisted watchpoints.
3249 That's because @value{GDBN} needs to watch every variable in the
3250 expression with separately allocated resources.
3252 The SPARClite DSU will generate traps when a program accesses some data
3253 or instruction address that is assigned to the debug registers. For the
3254 data addresses, DSU facilitates the @code{watch} command. However the
3255 hardware breakpoint registers can only take two data watchpoints, and
3256 both watchpoints must be the same kind. For example, you can set two
3257 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3258 @strong{or} two with @code{awatch} commands, but you cannot set one
3259 watchpoint with one command and the other with a different command.
3260 @value{GDBN} will reject the command if you try to mix watchpoints.
3261 Delete or disable unused watchpoint commands before setting new ones.
3263 If you call a function interactively using @code{print} or @code{call},
3264 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3265 kind of breakpoint or the call completes.
3267 @value{GDBN} automatically deletes watchpoints that watch local
3268 (automatic) variables, or expressions that involve such variables, when
3269 they go out of scope, that is, when the execution leaves the block in
3270 which these variables were defined. In particular, when the program
3271 being debugged terminates, @emph{all} local variables go out of scope,
3272 and so only watchpoints that watch global variables remain set. If you
3273 rerun the program, you will need to set all such watchpoints again. One
3274 way of doing that would be to set a code breakpoint at the entry to the
3275 @code{main} function and when it breaks, set all the watchpoints.
3278 @cindex watchpoints and threads
3279 @cindex threads and watchpoints
3280 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3281 usefulness. With the current watchpoint implementation, @value{GDBN}
3282 can only watch the value of an expression @emph{in a single thread}. If
3283 you are confident that the expression can only change due to the current
3284 thread's activity (and if you are also confident that no other thread
3285 can become current), then you can use watchpoints as usual. However,
3286 @value{GDBN} may not notice when a non-current thread's activity changes
3289 @c FIXME: this is almost identical to the previous paragraph.
3290 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3291 have only limited usefulness. If @value{GDBN} creates a software
3292 watchpoint, it can only watch the value of an expression @emph{in a
3293 single thread}. If you are confident that the expression can only
3294 change due to the current thread's activity (and if you are also
3295 confident that no other thread can become current), then you can use
3296 software watchpoints as usual. However, @value{GDBN} may not notice
3297 when a non-current thread's activity changes the expression. (Hardware
3298 watchpoints, in contrast, watch an expression in all threads.)
3301 @xref{set remote hardware-watchpoint-limit}.
3303 @node Set Catchpoints
3304 @subsection Setting catchpoints
3305 @cindex catchpoints, setting
3306 @cindex exception handlers
3307 @cindex event handling
3309 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3310 kinds of program events, such as C@t{++} exceptions or the loading of a
3311 shared library. Use the @code{catch} command to set a catchpoint.
3315 @item catch @var{event}
3316 Stop when @var{event} occurs. @var{event} can be any of the following:
3319 @cindex stop on C@t{++} exceptions
3320 The throwing of a C@t{++} exception.
3323 The catching of a C@t{++} exception.
3326 @cindex break on fork/exec
3327 A call to @code{exec}. This is currently only available for HP-UX.
3330 A call to @code{fork}. This is currently only available for HP-UX.
3333 A call to @code{vfork}. This is currently only available for HP-UX.
3336 @itemx load @var{libname}
3337 @cindex break on load/unload of shared library
3338 The dynamic loading of any shared library, or the loading of the library
3339 @var{libname}. This is currently only available for HP-UX.
3342 @itemx unload @var{libname}
3343 The unloading of any dynamically loaded shared library, or the unloading
3344 of the library @var{libname}. This is currently only available for HP-UX.
3347 @item tcatch @var{event}
3348 Set a catchpoint that is enabled only for one stop. The catchpoint is
3349 automatically deleted after the first time the event is caught.
3353 Use the @code{info break} command to list the current catchpoints.
3355 There are currently some limitations to C@t{++} exception handling
3356 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3360 If you call a function interactively, @value{GDBN} normally returns
3361 control to you when the function has finished executing. If the call
3362 raises an exception, however, the call may bypass the mechanism that
3363 returns control to you and cause your program either to abort or to
3364 simply continue running until it hits a breakpoint, catches a signal
3365 that @value{GDBN} is listening for, or exits. This is the case even if
3366 you set a catchpoint for the exception; catchpoints on exceptions are
3367 disabled within interactive calls.
3370 You cannot raise an exception interactively.
3373 You cannot install an exception handler interactively.
3376 @cindex raise exceptions
3377 Sometimes @code{catch} is not the best way to debug exception handling:
3378 if you need to know exactly where an exception is raised, it is better to
3379 stop @emph{before} the exception handler is called, since that way you
3380 can see the stack before any unwinding takes place. If you set a
3381 breakpoint in an exception handler instead, it may not be easy to find
3382 out where the exception was raised.
3384 To stop just before an exception handler is called, you need some
3385 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3386 raised by calling a library function named @code{__raise_exception}
3387 which has the following ANSI C interface:
3390 /* @var{addr} is where the exception identifier is stored.
3391 @var{id} is the exception identifier. */
3392 void __raise_exception (void **addr, void *id);
3396 To make the debugger catch all exceptions before any stack
3397 unwinding takes place, set a breakpoint on @code{__raise_exception}
3398 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3400 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3401 that depends on the value of @var{id}, you can stop your program when
3402 a specific exception is raised. You can use multiple conditional
3403 breakpoints to stop your program when any of a number of exceptions are
3408 @subsection Deleting breakpoints
3410 @cindex clearing breakpoints, watchpoints, catchpoints
3411 @cindex deleting breakpoints, watchpoints, catchpoints
3412 It is often necessary to eliminate a breakpoint, watchpoint, or
3413 catchpoint once it has done its job and you no longer want your program
3414 to stop there. This is called @dfn{deleting} the breakpoint. A
3415 breakpoint that has been deleted no longer exists; it is forgotten.
3417 With the @code{clear} command you can delete breakpoints according to
3418 where they are in your program. With the @code{delete} command you can
3419 delete individual breakpoints, watchpoints, or catchpoints by specifying
3420 their breakpoint numbers.
3422 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3423 automatically ignores breakpoints on the first instruction to be executed
3424 when you continue execution without changing the execution address.
3429 Delete any breakpoints at the next instruction to be executed in the
3430 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3431 the innermost frame is selected, this is a good way to delete a
3432 breakpoint where your program just stopped.
3434 @item clear @var{function}
3435 @itemx clear @var{filename}:@var{function}
3436 Delete any breakpoints set at entry to the named @var{function}.
3438 @item clear @var{linenum}
3439 @itemx clear @var{filename}:@var{linenum}
3440 Delete any breakpoints set at or within the code of the specified
3441 @var{linenum} of the specified @var{filename}.
3443 @cindex delete breakpoints
3445 @kindex d @r{(@code{delete})}
3446 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3447 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3448 ranges specified as arguments. If no argument is specified, delete all
3449 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3450 confirm off}). You can abbreviate this command as @code{d}.
3454 @subsection Disabling breakpoints
3456 @cindex enable/disable a breakpoint
3457 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3458 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3459 it had been deleted, but remembers the information on the breakpoint so
3460 that you can @dfn{enable} it again later.
3462 You disable and enable breakpoints, watchpoints, and catchpoints with
3463 the @code{enable} and @code{disable} commands, optionally specifying one
3464 or more breakpoint numbers as arguments. Use @code{info break} or
3465 @code{info watch} to print a list of breakpoints, watchpoints, and
3466 catchpoints if you do not know which numbers to use.
3468 A breakpoint, watchpoint, or catchpoint can have any of four different
3469 states of enablement:
3473 Enabled. The breakpoint stops your program. A breakpoint set
3474 with the @code{break} command starts out in this state.
3476 Disabled. The breakpoint has no effect on your program.
3478 Enabled once. The breakpoint stops your program, but then becomes
3481 Enabled for deletion. The breakpoint stops your program, but
3482 immediately after it does so it is deleted permanently. A breakpoint
3483 set with the @code{tbreak} command starts out in this state.
3486 You can use the following commands to enable or disable breakpoints,
3487 watchpoints, and catchpoints:
3491 @kindex dis @r{(@code{disable})}
3492 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3493 Disable the specified breakpoints---or all breakpoints, if none are
3494 listed. A disabled breakpoint has no effect but is not forgotten. All
3495 options such as ignore-counts, conditions and commands are remembered in
3496 case the breakpoint is enabled again later. You may abbreviate
3497 @code{disable} as @code{dis}.
3500 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3501 Enable the specified breakpoints (or all defined breakpoints). They
3502 become effective once again in stopping your program.
3504 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3505 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3506 of these breakpoints immediately after stopping your program.
3508 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3509 Enable the specified breakpoints to work once, then die. @value{GDBN}
3510 deletes any of these breakpoints as soon as your program stops there.
3511 Breakpoints set by the @code{tbreak} command start out in this state.
3514 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3515 @c confusing: tbreak is also initially enabled.
3516 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3517 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3518 subsequently, they become disabled or enabled only when you use one of
3519 the commands above. (The command @code{until} can set and delete a
3520 breakpoint of its own, but it does not change the state of your other
3521 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3525 @subsection Break conditions
3526 @cindex conditional breakpoints
3527 @cindex breakpoint conditions
3529 @c FIXME what is scope of break condition expr? Context where wanted?
3530 @c in particular for a watchpoint?
3531 The simplest sort of breakpoint breaks every time your program reaches a
3532 specified place. You can also specify a @dfn{condition} for a
3533 breakpoint. A condition is just a Boolean expression in your
3534 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3535 a condition evaluates the expression each time your program reaches it,
3536 and your program stops only if the condition is @emph{true}.
3538 This is the converse of using assertions for program validation; in that
3539 situation, you want to stop when the assertion is violated---that is,
3540 when the condition is false. In C, if you want to test an assertion expressed
3541 by the condition @var{assert}, you should set the condition
3542 @samp{! @var{assert}} on the appropriate breakpoint.
3544 Conditions are also accepted for watchpoints; you may not need them,
3545 since a watchpoint is inspecting the value of an expression anyhow---but
3546 it might be simpler, say, to just set a watchpoint on a variable name,
3547 and specify a condition that tests whether the new value is an interesting
3550 Break conditions can have side effects, and may even call functions in
3551 your program. This can be useful, for example, to activate functions
3552 that log program progress, or to use your own print functions to
3553 format special data structures. The effects are completely predictable
3554 unless there is another enabled breakpoint at the same address. (In
3555 that case, @value{GDBN} might see the other breakpoint first and stop your
3556 program without checking the condition of this one.) Note that
3557 breakpoint commands are usually more convenient and flexible than break
3559 purpose of performing side effects when a breakpoint is reached
3560 (@pxref{Break Commands, ,Breakpoint command lists}).
3562 Break conditions can be specified when a breakpoint is set, by using
3563 @samp{if} in the arguments to the @code{break} command. @xref{Set
3564 Breaks, ,Setting breakpoints}. They can also be changed at any time
3565 with the @code{condition} command.
3567 You can also use the @code{if} keyword with the @code{watch} command.
3568 The @code{catch} command does not recognize the @code{if} keyword;
3569 @code{condition} is the only way to impose a further condition on a
3574 @item condition @var{bnum} @var{expression}
3575 Specify @var{expression} as the break condition for breakpoint,
3576 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3577 breakpoint @var{bnum} stops your program only if the value of
3578 @var{expression} is true (nonzero, in C). When you use
3579 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3580 syntactic correctness, and to determine whether symbols in it have
3581 referents in the context of your breakpoint. If @var{expression} uses
3582 symbols not referenced in the context of the breakpoint, @value{GDBN}
3583 prints an error message:
3586 No symbol "foo" in current context.
3591 not actually evaluate @var{expression} at the time the @code{condition}
3592 command (or a command that sets a breakpoint with a condition, like
3593 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3595 @item condition @var{bnum}
3596 Remove the condition from breakpoint number @var{bnum}. It becomes
3597 an ordinary unconditional breakpoint.
3600 @cindex ignore count (of breakpoint)
3601 A special case of a breakpoint condition is to stop only when the
3602 breakpoint has been reached a certain number of times. This is so
3603 useful that there is a special way to do it, using the @dfn{ignore
3604 count} of the breakpoint. Every breakpoint has an ignore count, which
3605 is an integer. Most of the time, the ignore count is zero, and
3606 therefore has no effect. But if your program reaches a breakpoint whose
3607 ignore count is positive, then instead of stopping, it just decrements
3608 the ignore count by one and continues. As a result, if the ignore count
3609 value is @var{n}, the breakpoint does not stop the next @var{n} times
3610 your program reaches it.
3614 @item ignore @var{bnum} @var{count}
3615 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3616 The next @var{count} times the breakpoint is reached, your program's
3617 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3620 To make the breakpoint stop the next time it is reached, specify
3623 When you use @code{continue} to resume execution of your program from a
3624 breakpoint, you can specify an ignore count directly as an argument to
3625 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3626 Stepping,,Continuing and stepping}.
3628 If a breakpoint has a positive ignore count and a condition, the
3629 condition is not checked. Once the ignore count reaches zero,
3630 @value{GDBN} resumes checking the condition.
3632 You could achieve the effect of the ignore count with a condition such
3633 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3634 is decremented each time. @xref{Convenience Vars, ,Convenience
3638 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3641 @node Break Commands
3642 @subsection Breakpoint command lists
3644 @cindex breakpoint commands
3645 You can give any breakpoint (or watchpoint or catchpoint) a series of
3646 commands to execute when your program stops due to that breakpoint. For
3647 example, you might want to print the values of certain expressions, or
3648 enable other breakpoints.
3652 @kindex end@r{ (breakpoint commands)}
3653 @item commands @r{[}@var{bnum}@r{]}
3654 @itemx @dots{} @var{command-list} @dots{}
3656 Specify a list of commands for breakpoint number @var{bnum}. The commands
3657 themselves appear on the following lines. Type a line containing just
3658 @code{end} to terminate the commands.
3660 To remove all commands from a breakpoint, type @code{commands} and
3661 follow it immediately with @code{end}; that is, give no commands.
3663 With no @var{bnum} argument, @code{commands} refers to the last
3664 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3665 recently encountered).
3668 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3669 disabled within a @var{command-list}.
3671 You can use breakpoint commands to start your program up again. Simply
3672 use the @code{continue} command, or @code{step}, or any other command
3673 that resumes execution.
3675 Any other commands in the command list, after a command that resumes
3676 execution, are ignored. This is because any time you resume execution
3677 (even with a simple @code{next} or @code{step}), you may encounter
3678 another breakpoint---which could have its own command list, leading to
3679 ambiguities about which list to execute.
3682 If the first command you specify in a command list is @code{silent}, the
3683 usual message about stopping at a breakpoint is not printed. This may
3684 be desirable for breakpoints that are to print a specific message and
3685 then continue. If none of the remaining commands print anything, you
3686 see no sign that the breakpoint was reached. @code{silent} is
3687 meaningful only at the beginning of a breakpoint command list.
3689 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3690 print precisely controlled output, and are often useful in silent
3691 breakpoints. @xref{Output, ,Commands for controlled output}.
3693 For example, here is how you could use breakpoint commands to print the
3694 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3700 printf "x is %d\n",x
3705 One application for breakpoint commands is to compensate for one bug so
3706 you can test for another. Put a breakpoint just after the erroneous line
3707 of code, give it a condition to detect the case in which something
3708 erroneous has been done, and give it commands to assign correct values
3709 to any variables that need them. End with the @code{continue} command
3710 so that your program does not stop, and start with the @code{silent}
3711 command so that no output is produced. Here is an example:
3722 @node Breakpoint Menus
3723 @subsection Breakpoint menus
3725 @cindex symbol overloading
3727 Some programming languages (notably C@t{++} and Objective-C) permit a
3728 single function name
3729 to be defined several times, for application in different contexts.
3730 This is called @dfn{overloading}. When a function name is overloaded,
3731 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3732 a breakpoint. If you realize this is a problem, you can use
3733 something like @samp{break @var{function}(@var{types})} to specify which
3734 particular version of the function you want. Otherwise, @value{GDBN} offers
3735 you a menu of numbered choices for different possible breakpoints, and
3736 waits for your selection with the prompt @samp{>}. The first two
3737 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3738 sets a breakpoint at each definition of @var{function}, and typing
3739 @kbd{0} aborts the @code{break} command without setting any new
3742 For example, the following session excerpt shows an attempt to set a
3743 breakpoint at the overloaded symbol @code{String::after}.
3744 We choose three particular definitions of that function name:
3746 @c FIXME! This is likely to change to show arg type lists, at least
3749 (@value{GDBP}) b String::after
3752 [2] file:String.cc; line number:867
3753 [3] file:String.cc; line number:860
3754 [4] file:String.cc; line number:875
3755 [5] file:String.cc; line number:853
3756 [6] file:String.cc; line number:846
3757 [7] file:String.cc; line number:735
3759 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3760 Breakpoint 2 at 0xb344: file String.cc, line 875.
3761 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3762 Multiple breakpoints were set.
3763 Use the "delete" command to delete unwanted
3769 @c @ifclear BARETARGET
3770 @node Error in Breakpoints
3771 @subsection ``Cannot insert breakpoints''
3773 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3775 Under some operating systems, breakpoints cannot be used in a program if
3776 any other process is running that program. In this situation,
3777 attempting to run or continue a program with a breakpoint causes
3778 @value{GDBN} to print an error message:
3781 Cannot insert breakpoints.
3782 The same program may be running in another process.
3785 When this happens, you have three ways to proceed:
3789 Remove or disable the breakpoints, then continue.
3792 Suspend @value{GDBN}, and copy the file containing your program to a new
3793 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3794 that @value{GDBN} should run your program under that name.
3795 Then start your program again.
3798 Relink your program so that the text segment is nonsharable, using the
3799 linker option @samp{-N}. The operating system limitation may not apply
3800 to nonsharable executables.
3804 A similar message can be printed if you request too many active
3805 hardware-assisted breakpoints and watchpoints:
3807 @c FIXME: the precise wording of this message may change; the relevant
3808 @c source change is not committed yet (Sep 3, 1999).
3810 Stopped; cannot insert breakpoints.
3811 You may have requested too many hardware breakpoints and watchpoints.
3815 This message is printed when you attempt to resume the program, since
3816 only then @value{GDBN} knows exactly how many hardware breakpoints and
3817 watchpoints it needs to insert.
3819 When this message is printed, you need to disable or remove some of the
3820 hardware-assisted breakpoints and watchpoints, and then continue.
3822 @node Breakpoint related warnings
3823 @subsection ``Breakpoint address adjusted...''
3824 @cindex breakpoint address adjusted
3826 Some processor architectures place constraints on the addresses at
3827 which breakpoints may be placed. For architectures thus constrained,
3828 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3829 with the constraints dictated by the architecture.
3831 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3832 a VLIW architecture in which a number of RISC-like instructions may be
3833 bundled together for parallel execution. The FR-V architecture
3834 constrains the location of a breakpoint instruction within such a
3835 bundle to the instruction with the lowest address. @value{GDBN}
3836 honors this constraint by adjusting a breakpoint's address to the
3837 first in the bundle.
3839 It is not uncommon for optimized code to have bundles which contain
3840 instructions from different source statements, thus it may happen that
3841 a breakpoint's address will be adjusted from one source statement to
3842 another. Since this adjustment may significantly alter @value{GDBN}'s
3843 breakpoint related behavior from what the user expects, a warning is
3844 printed when the breakpoint is first set and also when the breakpoint
3847 A warning like the one below is printed when setting a breakpoint
3848 that's been subject to address adjustment:
3851 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3854 Such warnings are printed both for user settable and @value{GDBN}'s
3855 internal breakpoints. If you see one of these warnings, you should
3856 verify that a breakpoint set at the adjusted address will have the
3857 desired affect. If not, the breakpoint in question may be removed and
3858 other breakpoints may be set which will have the desired behavior.
3859 E.g., it may be sufficient to place the breakpoint at a later
3860 instruction. A conditional breakpoint may also be useful in some
3861 cases to prevent the breakpoint from triggering too often.
3863 @value{GDBN} will also issue a warning when stopping at one of these
3864 adjusted breakpoints:
3867 warning: Breakpoint 1 address previously adjusted from 0x00010414
3871 When this warning is encountered, it may be too late to take remedial
3872 action except in cases where the breakpoint is hit earlier or more
3873 frequently than expected.
3875 @node Continuing and Stepping
3876 @section Continuing and stepping
3880 @cindex resuming execution
3881 @dfn{Continuing} means resuming program execution until your program
3882 completes normally. In contrast, @dfn{stepping} means executing just
3883 one more ``step'' of your program, where ``step'' may mean either one
3884 line of source code, or one machine instruction (depending on what
3885 particular command you use). Either when continuing or when stepping,
3886 your program may stop even sooner, due to a breakpoint or a signal. (If
3887 it stops due to a signal, you may want to use @code{handle}, or use
3888 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3892 @kindex c @r{(@code{continue})}
3893 @kindex fg @r{(resume foreground execution)}
3894 @item continue @r{[}@var{ignore-count}@r{]}
3895 @itemx c @r{[}@var{ignore-count}@r{]}
3896 @itemx fg @r{[}@var{ignore-count}@r{]}
3897 Resume program execution, at the address where your program last stopped;
3898 any breakpoints set at that address are bypassed. The optional argument
3899 @var{ignore-count} allows you to specify a further number of times to
3900 ignore a breakpoint at this location; its effect is like that of
3901 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3903 The argument @var{ignore-count} is meaningful only when your program
3904 stopped due to a breakpoint. At other times, the argument to
3905 @code{continue} is ignored.
3907 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3908 debugged program is deemed to be the foreground program) are provided
3909 purely for convenience, and have exactly the same behavior as
3913 To resume execution at a different place, you can use @code{return}
3914 (@pxref{Returning, ,Returning from a function}) to go back to the
3915 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3916 different address}) to go to an arbitrary location in your program.
3918 A typical technique for using stepping is to set a breakpoint
3919 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3920 beginning of the function or the section of your program where a problem
3921 is believed to lie, run your program until it stops at that breakpoint,
3922 and then step through the suspect area, examining the variables that are
3923 interesting, until you see the problem happen.
3927 @kindex s @r{(@code{step})}
3929 Continue running your program until control reaches a different source
3930 line, then stop it and return control to @value{GDBN}. This command is
3931 abbreviated @code{s}.
3934 @c "without debugging information" is imprecise; actually "without line
3935 @c numbers in the debugging information". (gcc -g1 has debugging info but
3936 @c not line numbers). But it seems complex to try to make that
3937 @c distinction here.
3938 @emph{Warning:} If you use the @code{step} command while control is
3939 within a function that was compiled without debugging information,
3940 execution proceeds until control reaches a function that does have
3941 debugging information. Likewise, it will not step into a function which
3942 is compiled without debugging information. To step through functions
3943 without debugging information, use the @code{stepi} command, described
3947 The @code{step} command only stops at the first instruction of a source
3948 line. This prevents the multiple stops that could otherwise occur in
3949 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3950 to stop if a function that has debugging information is called within
3951 the line. In other words, @code{step} @emph{steps inside} any functions
3952 called within the line.
3954 Also, the @code{step} command only enters a function if there is line
3955 number information for the function. Otherwise it acts like the
3956 @code{next} command. This avoids problems when using @code{cc -gl}
3957 on MIPS machines. Previously, @code{step} entered subroutines if there
3958 was any debugging information about the routine.
3960 @item step @var{count}
3961 Continue running as in @code{step}, but do so @var{count} times. If a
3962 breakpoint is reached, or a signal not related to stepping occurs before
3963 @var{count} steps, stepping stops right away.
3966 @kindex n @r{(@code{next})}
3967 @item next @r{[}@var{count}@r{]}
3968 Continue to the next source line in the current (innermost) stack frame.
3969 This is similar to @code{step}, but function calls that appear within
3970 the line of code are executed without stopping. Execution stops when
3971 control reaches a different line of code at the original stack level
3972 that was executing when you gave the @code{next} command. This command
3973 is abbreviated @code{n}.
3975 An argument @var{count} is a repeat count, as for @code{step}.
3978 @c FIX ME!! Do we delete this, or is there a way it fits in with
3979 @c the following paragraph? --- Vctoria
3981 @c @code{next} within a function that lacks debugging information acts like
3982 @c @code{step}, but any function calls appearing within the code of the
3983 @c function are executed without stopping.
3985 The @code{next} command only stops at the first instruction of a
3986 source line. This prevents multiple stops that could otherwise occur in
3987 @code{switch} statements, @code{for} loops, etc.
3989 @kindex set step-mode
3991 @cindex functions without line info, and stepping
3992 @cindex stepping into functions with no line info
3993 @itemx set step-mode on
3994 The @code{set step-mode on} command causes the @code{step} command to
3995 stop at the first instruction of a function which contains no debug line
3996 information rather than stepping over it.
3998 This is useful in cases where you may be interested in inspecting the
3999 machine instructions of a function which has no symbolic info and do not
4000 want @value{GDBN} to automatically skip over this function.
4002 @item set step-mode off
4003 Causes the @code{step} command to step over any functions which contains no
4004 debug information. This is the default.
4006 @item show step-mode
4007 Show whether @value{GDBN} will stop in or step over functions without
4008 source line debug information.
4012 Continue running until just after function in the selected stack frame
4013 returns. Print the returned value (if any).
4015 Contrast this with the @code{return} command (@pxref{Returning,
4016 ,Returning from a function}).
4019 @kindex u @r{(@code{until})}
4020 @cindex run until specified location
4023 Continue running until a source line past the current line, in the
4024 current stack frame, is reached. This command is used to avoid single
4025 stepping through a loop more than once. It is like the @code{next}
4026 command, except that when @code{until} encounters a jump, it
4027 automatically continues execution until the program counter is greater
4028 than the address of the jump.
4030 This means that when you reach the end of a loop after single stepping
4031 though it, @code{until} makes your program continue execution until it
4032 exits the loop. In contrast, a @code{next} command at the end of a loop
4033 simply steps back to the beginning of the loop, which forces you to step
4034 through the next iteration.
4036 @code{until} always stops your program if it attempts to exit the current
4039 @code{until} may produce somewhat counterintuitive results if the order
4040 of machine code does not match the order of the source lines. For
4041 example, in the following excerpt from a debugging session, the @code{f}
4042 (@code{frame}) command shows that execution is stopped at line
4043 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4047 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4049 (@value{GDBP}) until
4050 195 for ( ; argc > 0; NEXTARG) @{
4053 This happened because, for execution efficiency, the compiler had
4054 generated code for the loop closure test at the end, rather than the
4055 start, of the loop---even though the test in a C @code{for}-loop is
4056 written before the body of the loop. The @code{until} command appeared
4057 to step back to the beginning of the loop when it advanced to this
4058 expression; however, it has not really gone to an earlier
4059 statement---not in terms of the actual machine code.
4061 @code{until} with no argument works by means of single
4062 instruction stepping, and hence is slower than @code{until} with an
4065 @item until @var{location}
4066 @itemx u @var{location}
4067 Continue running your program until either the specified location is
4068 reached, or the current stack frame returns. @var{location} is any of
4069 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4070 ,Setting breakpoints}). This form of the command uses breakpoints, and
4071 hence is quicker than @code{until} without an argument. The specified
4072 location is actually reached only if it is in the current frame. This
4073 implies that @code{until} can be used to skip over recursive function
4074 invocations. For instance in the code below, if the current location is
4075 line @code{96}, issuing @code{until 99} will execute the program up to
4076 line @code{99} in the same invocation of factorial, i.e. after the inner
4077 invocations have returned.
4080 94 int factorial (int value)
4082 96 if (value > 1) @{
4083 97 value *= factorial (value - 1);
4090 @kindex advance @var{location}
4091 @itemx advance @var{location}
4092 Continue running the program up to the given @var{location}. An argument is
4093 required, which should be of the same form as arguments for the @code{break}
4094 command. Execution will also stop upon exit from the current stack
4095 frame. This command is similar to @code{until}, but @code{advance} will
4096 not skip over recursive function calls, and the target location doesn't
4097 have to be in the same frame as the current one.
4101 @kindex si @r{(@code{stepi})}
4103 @itemx stepi @var{arg}
4105 Execute one machine instruction, then stop and return to the debugger.
4107 It is often useful to do @samp{display/i $pc} when stepping by machine
4108 instructions. This makes @value{GDBN} automatically display the next
4109 instruction to be executed, each time your program stops. @xref{Auto
4110 Display,, Automatic display}.
4112 An argument is a repeat count, as in @code{step}.
4116 @kindex ni @r{(@code{nexti})}
4118 @itemx nexti @var{arg}
4120 Execute one machine instruction, but if it is a function call,
4121 proceed until the function returns.
4123 An argument is a repeat count, as in @code{next}.
4130 A signal is an asynchronous event that can happen in a program. The
4131 operating system defines the possible kinds of signals, and gives each
4132 kind a name and a number. For example, in Unix @code{SIGINT} is the
4133 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4134 @code{SIGSEGV} is the signal a program gets from referencing a place in
4135 memory far away from all the areas in use; @code{SIGALRM} occurs when
4136 the alarm clock timer goes off (which happens only if your program has
4137 requested an alarm).
4139 @cindex fatal signals
4140 Some signals, including @code{SIGALRM}, are a normal part of the
4141 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4142 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4143 program has not specified in advance some other way to handle the signal.
4144 @code{SIGINT} does not indicate an error in your program, but it is normally
4145 fatal so it can carry out the purpose of the interrupt: to kill the program.
4147 @value{GDBN} has the ability to detect any occurrence of a signal in your
4148 program. You can tell @value{GDBN} in advance what to do for each kind of
4151 @cindex handling signals
4152 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4153 @code{SIGALRM} be silently passed to your program
4154 (so as not to interfere with their role in the program's functioning)
4155 but to stop your program immediately whenever an error signal happens.
4156 You can change these settings with the @code{handle} command.
4159 @kindex info signals
4163 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4164 handle each one. You can use this to see the signal numbers of all
4165 the defined types of signals.
4167 @item info signals @var{sig}
4168 Similar, but print information only about the specified signal number.
4170 @code{info handle} is an alias for @code{info signals}.
4173 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4174 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4175 can be the number of a signal or its name (with or without the
4176 @samp{SIG} at the beginning); a list of signal numbers of the form
4177 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4178 known signals. Optional arguments @var{keywords}, described below,
4179 say what change to make.
4183 The keywords allowed by the @code{handle} command can be abbreviated.
4184 Their full names are:
4188 @value{GDBN} should not stop your program when this signal happens. It may
4189 still print a message telling you that the signal has come in.
4192 @value{GDBN} should stop your program when this signal happens. This implies
4193 the @code{print} keyword as well.
4196 @value{GDBN} should print a message when this signal happens.
4199 @value{GDBN} should not mention the occurrence of the signal at all. This
4200 implies the @code{nostop} keyword as well.
4204 @value{GDBN} should allow your program to see this signal; your program
4205 can handle the signal, or else it may terminate if the signal is fatal
4206 and not handled. @code{pass} and @code{noignore} are synonyms.
4210 @value{GDBN} should not allow your program to see this signal.
4211 @code{nopass} and @code{ignore} are synonyms.
4215 When a signal stops your program, the signal is not visible to the
4217 continue. Your program sees the signal then, if @code{pass} is in
4218 effect for the signal in question @emph{at that time}. In other words,
4219 after @value{GDBN} reports a signal, you can use the @code{handle}
4220 command with @code{pass} or @code{nopass} to control whether your
4221 program sees that signal when you continue.
4223 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4224 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4225 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4228 You can also use the @code{signal} command to prevent your program from
4229 seeing a signal, or cause it to see a signal it normally would not see,
4230 or to give it any signal at any time. For example, if your program stopped
4231 due to some sort of memory reference error, you might store correct
4232 values into the erroneous variables and continue, hoping to see more
4233 execution; but your program would probably terminate immediately as
4234 a result of the fatal signal once it saw the signal. To prevent this,
4235 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4239 @section Stopping and starting multi-thread programs
4241 When your program has multiple threads (@pxref{Threads,, Debugging
4242 programs with multiple threads}), you can choose whether to set
4243 breakpoints on all threads, or on a particular thread.
4246 @cindex breakpoints and threads
4247 @cindex thread breakpoints
4248 @kindex break @dots{} thread @var{threadno}
4249 @item break @var{linespec} thread @var{threadno}
4250 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4251 @var{linespec} specifies source lines; there are several ways of
4252 writing them, but the effect is always to specify some source line.
4254 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4255 to specify that you only want @value{GDBN} to stop the program when a
4256 particular thread reaches this breakpoint. @var{threadno} is one of the
4257 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4258 column of the @samp{info threads} display.
4260 If you do not specify @samp{thread @var{threadno}} when you set a
4261 breakpoint, the breakpoint applies to @emph{all} threads of your
4264 You can use the @code{thread} qualifier on conditional breakpoints as
4265 well; in this case, place @samp{thread @var{threadno}} before the
4266 breakpoint condition, like this:
4269 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4274 @cindex stopped threads
4275 @cindex threads, stopped
4276 Whenever your program stops under @value{GDBN} for any reason,
4277 @emph{all} threads of execution stop, not just the current thread. This
4278 allows you to examine the overall state of the program, including
4279 switching between threads, without worrying that things may change
4282 @cindex thread breakpoints and system calls
4283 @cindex system calls and thread breakpoints
4284 @cindex premature return from system calls
4285 There is an unfortunate side effect. If one thread stops for a
4286 breakpoint, or for some other reason, and another thread is blocked in a
4287 system call, then the system call may return prematurely. This is a
4288 consequence of the interaction between multiple threads and the signals
4289 that @value{GDBN} uses to implement breakpoints and other events that
4292 To handle this problem, your program should check the return value of
4293 each system call and react appropriately. This is good programming
4296 For example, do not write code like this:
4302 The call to @code{sleep} will return early if a different thread stops
4303 at a breakpoint or for some other reason.
4305 Instead, write this:
4310 unslept = sleep (unslept);
4313 A system call is allowed to return early, so the system is still
4314 conforming to its specification. But @value{GDBN} does cause your
4315 multi-threaded program to behave differently than it would without
4318 Also, @value{GDBN} uses internal breakpoints in the thread library to
4319 monitor certain events such as thread creation and thread destruction.
4320 When such an event happens, a system call in another thread may return
4321 prematurely, even though your program does not appear to stop.
4323 @cindex continuing threads
4324 @cindex threads, continuing
4325 Conversely, whenever you restart the program, @emph{all} threads start
4326 executing. @emph{This is true even when single-stepping} with commands
4327 like @code{step} or @code{next}.
4329 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4330 Since thread scheduling is up to your debugging target's operating
4331 system (not controlled by @value{GDBN}), other threads may
4332 execute more than one statement while the current thread completes a
4333 single step. Moreover, in general other threads stop in the middle of a
4334 statement, rather than at a clean statement boundary, when the program
4337 You might even find your program stopped in another thread after
4338 continuing or even single-stepping. This happens whenever some other
4339 thread runs into a breakpoint, a signal, or an exception before the
4340 first thread completes whatever you requested.
4342 On some OSes, you can lock the OS scheduler and thus allow only a single
4346 @item set scheduler-locking @var{mode}
4347 @cindex scheduler locking mode
4348 @cindex lock scheduler
4349 Set the scheduler locking mode. If it is @code{off}, then there is no
4350 locking and any thread may run at any time. If @code{on}, then only the
4351 current thread may run when the inferior is resumed. The @code{step}
4352 mode optimizes for single-stepping. It stops other threads from
4353 ``seizing the prompt'' by preempting the current thread while you are
4354 stepping. Other threads will only rarely (or never) get a chance to run
4355 when you step. They are more likely to run when you @samp{next} over a
4356 function call, and they are completely free to run when you use commands
4357 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4358 thread hits a breakpoint during its timeslice, they will never steal the
4359 @value{GDBN} prompt away from the thread that you are debugging.
4361 @item show scheduler-locking
4362 Display the current scheduler locking mode.
4367 @chapter Examining the Stack
4369 When your program has stopped, the first thing you need to know is where it
4370 stopped and how it got there.
4373 Each time your program performs a function call, information about the call
4375 That information includes the location of the call in your program,
4376 the arguments of the call,
4377 and the local variables of the function being called.
4378 The information is saved in a block of data called a @dfn{stack frame}.
4379 The stack frames are allocated in a region of memory called the @dfn{call
4382 When your program stops, the @value{GDBN} commands for examining the
4383 stack allow you to see all of this information.
4385 @cindex selected frame
4386 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4387 @value{GDBN} commands refer implicitly to the selected frame. In
4388 particular, whenever you ask @value{GDBN} for the value of a variable in
4389 your program, the value is found in the selected frame. There are
4390 special @value{GDBN} commands to select whichever frame you are
4391 interested in. @xref{Selection, ,Selecting a frame}.
4393 When your program stops, @value{GDBN} automatically selects the
4394 currently executing frame and describes it briefly, similar to the
4395 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4398 * Frames:: Stack frames
4399 * Backtrace:: Backtraces
4400 * Selection:: Selecting a frame
4401 * Frame Info:: Information on a frame
4406 @section Stack frames
4408 @cindex frame, definition
4410 The call stack is divided up into contiguous pieces called @dfn{stack
4411 frames}, or @dfn{frames} for short; each frame is the data associated
4412 with one call to one function. The frame contains the arguments given
4413 to the function, the function's local variables, and the address at
4414 which the function is executing.
4416 @cindex initial frame
4417 @cindex outermost frame
4418 @cindex innermost frame
4419 When your program is started, the stack has only one frame, that of the
4420 function @code{main}. This is called the @dfn{initial} frame or the
4421 @dfn{outermost} frame. Each time a function is called, a new frame is
4422 made. Each time a function returns, the frame for that function invocation
4423 is eliminated. If a function is recursive, there can be many frames for
4424 the same function. The frame for the function in which execution is
4425 actually occurring is called the @dfn{innermost} frame. This is the most
4426 recently created of all the stack frames that still exist.
4428 @cindex frame pointer
4429 Inside your program, stack frames are identified by their addresses. A
4430 stack frame consists of many bytes, each of which has its own address; each
4431 kind of computer has a convention for choosing one byte whose
4432 address serves as the address of the frame. Usually this address is kept
4433 in a register called the @dfn{frame pointer register}
4434 (@pxref{Registers, $fp}) while execution is going on in that frame.
4436 @cindex frame number
4437 @value{GDBN} assigns numbers to all existing stack frames, starting with
4438 zero for the innermost frame, one for the frame that called it,
4439 and so on upward. These numbers do not really exist in your program;
4440 they are assigned by @value{GDBN} to give you a way of designating stack
4441 frames in @value{GDBN} commands.
4443 @c The -fomit-frame-pointer below perennially causes hbox overflow
4444 @c underflow problems.
4445 @cindex frameless execution
4446 Some compilers provide a way to compile functions so that they operate
4447 without stack frames. (For example, the @value{GCC} option
4449 @samp{-fomit-frame-pointer}
4451 generates functions without a frame.)
4452 This is occasionally done with heavily used library functions to save
4453 the frame setup time. @value{GDBN} has limited facilities for dealing
4454 with these function invocations. If the innermost function invocation
4455 has no stack frame, @value{GDBN} nevertheless regards it as though
4456 it had a separate frame, which is numbered zero as usual, allowing
4457 correct tracing of the function call chain. However, @value{GDBN} has
4458 no provision for frameless functions elsewhere in the stack.
4461 @kindex frame@r{, command}
4462 @cindex current stack frame
4463 @item frame @var{args}
4464 The @code{frame} command allows you to move from one stack frame to another,
4465 and to print the stack frame you select. @var{args} may be either the
4466 address of the frame or the stack frame number. Without an argument,
4467 @code{frame} prints the current stack frame.
4469 @kindex select-frame
4470 @cindex selecting frame silently
4472 The @code{select-frame} command allows you to move from one stack frame
4473 to another without printing the frame. This is the silent version of
4481 @cindex call stack traces
4482 A backtrace is a summary of how your program got where it is. It shows one
4483 line per frame, for many frames, starting with the currently executing
4484 frame (frame zero), followed by its caller (frame one), and on up the
4489 @kindex bt @r{(@code{backtrace})}
4492 Print a backtrace of the entire stack: one line per frame for all
4493 frames in the stack.
4495 You can stop the backtrace at any time by typing the system interrupt
4496 character, normally @kbd{Ctrl-c}.
4498 @item backtrace @var{n}
4500 Similar, but print only the innermost @var{n} frames.
4502 @item backtrace -@var{n}
4504 Similar, but print only the outermost @var{n} frames.
4506 @item backtrace full
4508 @itemx bt full @var{n}
4509 @itemx bt full -@var{n}
4510 Print the values of the local variables also. @var{n} specifies the
4511 number of frames to print, as described above.
4516 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4517 are additional aliases for @code{backtrace}.
4519 @cindex multiple threads, backtrace
4520 In a multi-threaded program, @value{GDBN} by default shows the
4521 backtrace only for the current thread. To display the backtrace for
4522 several or all of the threads, use the command @code{thread apply}
4523 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4524 apply all backtrace}, @value{GDBN} will display the backtrace for all
4525 the threads; this is handy when you debug a core dump of a
4526 multi-threaded program.
4528 Each line in the backtrace shows the frame number and the function name.
4529 The program counter value is also shown---unless you use @code{set
4530 print address off}. The backtrace also shows the source file name and
4531 line number, as well as the arguments to the function. The program
4532 counter value is omitted if it is at the beginning of the code for that
4535 Here is an example of a backtrace. It was made with the command
4536 @samp{bt 3}, so it shows the innermost three frames.
4540 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4542 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4543 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4545 (More stack frames follow...)
4550 The display for frame zero does not begin with a program counter
4551 value, indicating that your program has stopped at the beginning of the
4552 code for line @code{993} of @code{builtin.c}.
4554 @cindex value optimized out, in backtrace
4555 @cindex function call arguments, optimized out
4556 If your program was compiled with optimizations, some compilers will
4557 optimize away arguments passed to functions if those arguments are
4558 never used after the call. Such optimizations generate code that
4559 passes arguments through registers, but doesn't store those arguments
4560 in the stack frame. @value{GDBN} has no way of displaying such
4561 arguments in stack frames other than the innermost one. Here's what
4562 such a backtrace might look like:
4566 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4568 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4569 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4571 (More stack frames follow...)
4576 The values of arguments that were not saved in their stack frames are
4577 shown as @samp{<value optimized out>}.
4579 If you need to display the values of such optimized-out arguments,
4580 either deduce that from other variables whose values depend on the one
4581 you are interested in, or recompile without optimizations.
4583 @cindex backtrace beyond @code{main} function
4584 @cindex program entry point
4585 @cindex startup code, and backtrace
4586 Most programs have a standard user entry point---a place where system
4587 libraries and startup code transition into user code. For C this is
4588 @code{main}@footnote{
4589 Note that embedded programs (the so-called ``free-standing''
4590 environment) are not required to have a @code{main} function as the
4591 entry point. They could even have multiple entry points.}.
4592 When @value{GDBN} finds the entry function in a backtrace
4593 it will terminate the backtrace, to avoid tracing into highly
4594 system-specific (and generally uninteresting) code.
4596 If you need to examine the startup code, or limit the number of levels
4597 in a backtrace, you can change this behavior:
4600 @item set backtrace past-main
4601 @itemx set backtrace past-main on
4602 @kindex set backtrace
4603 Backtraces will continue past the user entry point.
4605 @item set backtrace past-main off
4606 Backtraces will stop when they encounter the user entry point. This is the
4609 @item show backtrace past-main
4610 @kindex show backtrace
4611 Display the current user entry point backtrace policy.
4613 @item set backtrace past-entry
4614 @itemx set backtrace past-entry on
4615 Backtraces will continue past the internal entry point of an application.
4616 This entry point is encoded by the linker when the application is built,
4617 and is likely before the user entry point @code{main} (or equivalent) is called.
4619 @item set backtrace past-entry off
4620 Backtraces will stop when they encouter the internal entry point of an
4621 application. This is the default.
4623 @item show backtrace past-entry
4624 Display the current internal entry point backtrace policy.
4626 @item set backtrace limit @var{n}
4627 @itemx set backtrace limit 0
4628 @cindex backtrace limit
4629 Limit the backtrace to @var{n} levels. A value of zero means
4632 @item show backtrace limit
4633 Display the current limit on backtrace levels.
4637 @section Selecting a frame
4639 Most commands for examining the stack and other data in your program work on
4640 whichever stack frame is selected at the moment. Here are the commands for
4641 selecting a stack frame; all of them finish by printing a brief description
4642 of the stack frame just selected.
4645 @kindex frame@r{, selecting}
4646 @kindex f @r{(@code{frame})}
4649 Select frame number @var{n}. Recall that frame zero is the innermost
4650 (currently executing) frame, frame one is the frame that called the
4651 innermost one, and so on. The highest-numbered frame is the one for
4654 @item frame @var{addr}
4656 Select the frame at address @var{addr}. This is useful mainly if the
4657 chaining of stack frames has been damaged by a bug, making it
4658 impossible for @value{GDBN} to assign numbers properly to all frames. In
4659 addition, this can be useful when your program has multiple stacks and
4660 switches between them.
4662 On the SPARC architecture, @code{frame} needs two addresses to
4663 select an arbitrary frame: a frame pointer and a stack pointer.
4665 On the MIPS and Alpha architecture, it needs two addresses: a stack
4666 pointer and a program counter.
4668 On the 29k architecture, it needs three addresses: a register stack
4669 pointer, a program counter, and a memory stack pointer.
4673 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4674 advances toward the outermost frame, to higher frame numbers, to frames
4675 that have existed longer. @var{n} defaults to one.
4678 @kindex do @r{(@code{down})}
4680 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4681 advances toward the innermost frame, to lower frame numbers, to frames
4682 that were created more recently. @var{n} defaults to one. You may
4683 abbreviate @code{down} as @code{do}.
4686 All of these commands end by printing two lines of output describing the
4687 frame. The first line shows the frame number, the function name, the
4688 arguments, and the source file and line number of execution in that
4689 frame. The second line shows the text of that source line.
4697 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4699 10 read_input_file (argv[i]);
4703 After such a printout, the @code{list} command with no arguments
4704 prints ten lines centered on the point of execution in the frame.
4705 You can also edit the program at the point of execution with your favorite
4706 editing program by typing @code{edit}.
4707 @xref{List, ,Printing source lines},
4711 @kindex down-silently
4713 @item up-silently @var{n}
4714 @itemx down-silently @var{n}
4715 These two commands are variants of @code{up} and @code{down},
4716 respectively; they differ in that they do their work silently, without
4717 causing display of the new frame. They are intended primarily for use
4718 in @value{GDBN} command scripts, where the output might be unnecessary and
4723 @section Information about a frame
4725 There are several other commands to print information about the selected
4731 When used without any argument, this command does not change which
4732 frame is selected, but prints a brief description of the currently
4733 selected stack frame. It can be abbreviated @code{f}. With an
4734 argument, this command is used to select a stack frame.
4735 @xref{Selection, ,Selecting a frame}.
4738 @kindex info f @r{(@code{info frame})}
4741 This command prints a verbose description of the selected stack frame,
4746 the address of the frame
4748 the address of the next frame down (called by this frame)
4750 the address of the next frame up (caller of this frame)
4752 the language in which the source code corresponding to this frame is written
4754 the address of the frame's arguments
4756 the address of the frame's local variables
4758 the program counter saved in it (the address of execution in the caller frame)
4760 which registers were saved in the frame
4763 @noindent The verbose description is useful when
4764 something has gone wrong that has made the stack format fail to fit
4765 the usual conventions.
4767 @item info frame @var{addr}
4768 @itemx info f @var{addr}
4769 Print a verbose description of the frame at address @var{addr}, without
4770 selecting that frame. The selected frame remains unchanged by this
4771 command. This requires the same kind of address (more than one for some
4772 architectures) that you specify in the @code{frame} command.
4773 @xref{Selection, ,Selecting a frame}.
4777 Print the arguments of the selected frame, each on a separate line.
4781 Print the local variables of the selected frame, each on a separate
4782 line. These are all variables (declared either static or automatic)
4783 accessible at the point of execution of the selected frame.
4786 @cindex catch exceptions, list active handlers
4787 @cindex exception handlers, how to list
4789 Print a list of all the exception handlers that are active in the
4790 current stack frame at the current point of execution. To see other
4791 exception handlers, visit the associated frame (using the @code{up},
4792 @code{down}, or @code{frame} commands); then type @code{info catch}.
4793 @xref{Set Catchpoints, , Setting catchpoints}.
4799 @chapter Examining Source Files
4801 @value{GDBN} can print parts of your program's source, since the debugging
4802 information recorded in the program tells @value{GDBN} what source files were
4803 used to build it. When your program stops, @value{GDBN} spontaneously prints
4804 the line where it stopped. Likewise, when you select a stack frame
4805 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4806 execution in that frame has stopped. You can print other portions of
4807 source files by explicit command.
4809 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4810 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4811 @value{GDBN} under @sc{gnu} Emacs}.
4814 * List:: Printing source lines
4815 * Edit:: Editing source files
4816 * Search:: Searching source files
4817 * Source Path:: Specifying source directories
4818 * Machine Code:: Source and machine code
4822 @section Printing source lines
4825 @kindex l @r{(@code{list})}
4826 To print lines from a source file, use the @code{list} command
4827 (abbreviated @code{l}). By default, ten lines are printed.
4828 There are several ways to specify what part of the file you want to print.
4830 Here are the forms of the @code{list} command most commonly used:
4833 @item list @var{linenum}
4834 Print lines centered around line number @var{linenum} in the
4835 current source file.
4837 @item list @var{function}
4838 Print lines centered around the beginning of function
4842 Print more lines. If the last lines printed were printed with a
4843 @code{list} command, this prints lines following the last lines
4844 printed; however, if the last line printed was a solitary line printed
4845 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4846 Stack}), this prints lines centered around that line.
4849 Print lines just before the lines last printed.
4852 @cindex @code{list}, how many lines to display
4853 By default, @value{GDBN} prints ten source lines with any of these forms of
4854 the @code{list} command. You can change this using @code{set listsize}:
4857 @kindex set listsize
4858 @item set listsize @var{count}
4859 Make the @code{list} command display @var{count} source lines (unless
4860 the @code{list} argument explicitly specifies some other number).
4862 @kindex show listsize
4864 Display the number of lines that @code{list} prints.
4867 Repeating a @code{list} command with @key{RET} discards the argument,
4868 so it is equivalent to typing just @code{list}. This is more useful
4869 than listing the same lines again. An exception is made for an
4870 argument of @samp{-}; that argument is preserved in repetition so that
4871 each repetition moves up in the source file.
4874 In general, the @code{list} command expects you to supply zero, one or two
4875 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4876 of writing them, but the effect is always to specify some source line.
4877 Here is a complete description of the possible arguments for @code{list}:
4880 @item list @var{linespec}
4881 Print lines centered around the line specified by @var{linespec}.
4883 @item list @var{first},@var{last}
4884 Print lines from @var{first} to @var{last}. Both arguments are
4887 @item list ,@var{last}
4888 Print lines ending with @var{last}.
4890 @item list @var{first},
4891 Print lines starting with @var{first}.
4894 Print lines just after the lines last printed.
4897 Print lines just before the lines last printed.
4900 As described in the preceding table.
4903 Here are the ways of specifying a single source line---all the
4908 Specifies line @var{number} of the current source file.
4909 When a @code{list} command has two linespecs, this refers to
4910 the same source file as the first linespec.
4913 Specifies the line @var{offset} lines after the last line printed.
4914 When used as the second linespec in a @code{list} command that has
4915 two, this specifies the line @var{offset} lines down from the
4919 Specifies the line @var{offset} lines before the last line printed.
4921 @item @var{filename}:@var{number}
4922 Specifies line @var{number} in the source file @var{filename}.
4924 @item @var{function}
4925 Specifies the line that begins the body of the function @var{function}.
4926 For example: in C, this is the line with the open brace.
4928 @item @var{filename}:@var{function}
4929 Specifies the line of the open-brace that begins the body of the
4930 function @var{function} in the file @var{filename}. You only need the
4931 file name with a function name to avoid ambiguity when there are
4932 identically named functions in different source files.
4934 @item *@var{address}
4935 Specifies the line containing the program address @var{address}.
4936 @var{address} may be any expression.
4940 @section Editing source files
4941 @cindex editing source files
4944 @kindex e @r{(@code{edit})}
4945 To edit the lines in a source file, use the @code{edit} command.
4946 The editing program of your choice
4947 is invoked with the current line set to
4948 the active line in the program.
4949 Alternatively, there are several ways to specify what part of the file you
4950 want to print if you want to see other parts of the program.
4952 Here are the forms of the @code{edit} command most commonly used:
4956 Edit the current source file at the active line number in the program.
4958 @item edit @var{number}
4959 Edit the current source file with @var{number} as the active line number.
4961 @item edit @var{function}
4962 Edit the file containing @var{function} at the beginning of its definition.
4964 @item edit @var{filename}:@var{number}
4965 Specifies line @var{number} in the source file @var{filename}.
4967 @item edit @var{filename}:@var{function}
4968 Specifies the line that begins the body of the
4969 function @var{function} in the file @var{filename}. You only need the
4970 file name with a function name to avoid ambiguity when there are
4971 identically named functions in different source files.
4973 @item edit *@var{address}
4974 Specifies the line containing the program address @var{address}.
4975 @var{address} may be any expression.
4978 @subsection Choosing your editor
4979 You can customize @value{GDBN} to use any editor you want
4981 The only restriction is that your editor (say @code{ex}), recognizes the
4982 following command-line syntax:
4984 ex +@var{number} file
4986 The optional numeric value +@var{number} specifies the number of the line in
4987 the file where to start editing.}.
4988 By default, it is @file{@value{EDITOR}}, but you can change this
4989 by setting the environment variable @code{EDITOR} before using
4990 @value{GDBN}. For example, to configure @value{GDBN} to use the
4991 @code{vi} editor, you could use these commands with the @code{sh} shell:
4997 or in the @code{csh} shell,
4999 setenv EDITOR /usr/bin/vi
5004 @section Searching source files
5005 @cindex searching source files
5007 There are two commands for searching through the current source file for a
5012 @kindex forward-search
5013 @item forward-search @var{regexp}
5014 @itemx search @var{regexp}
5015 The command @samp{forward-search @var{regexp}} checks each line,
5016 starting with the one following the last line listed, for a match for
5017 @var{regexp}. It lists the line that is found. You can use the
5018 synonym @samp{search @var{regexp}} or abbreviate the command name as
5021 @kindex reverse-search
5022 @item reverse-search @var{regexp}
5023 The command @samp{reverse-search @var{regexp}} checks each line, starting
5024 with the one before the last line listed and going backward, for a match
5025 for @var{regexp}. It lists the line that is found. You can abbreviate
5026 this command as @code{rev}.
5030 @section Specifying source directories
5033 @cindex directories for source files
5034 Executable programs sometimes do not record the directories of the source
5035 files from which they were compiled, just the names. Even when they do,
5036 the directories could be moved between the compilation and your debugging
5037 session. @value{GDBN} has a list of directories to search for source files;
5038 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5039 it tries all the directories in the list, in the order they are present
5040 in the list, until it finds a file with the desired name.
5042 For example, suppose an executable references the file
5043 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5044 @file{/mnt/cross}. The file is first looked up literally; if this
5045 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5046 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5047 message is printed. @value{GDBN} does not look up the parts of the
5048 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5049 Likewise, the subdirectories of the source path are not searched: if
5050 the source path is @file{/mnt/cross}, and the binary refers to
5051 @file{foo.c}, @value{GDBN} would not find it under
5052 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5054 Plain file names, relative file names with leading directories, file
5055 names containing dots, etc.@: are all treated as described above; for
5056 instance, if the source path is @file{/mnt/cross}, and the source file
5057 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5058 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5059 that---@file{/mnt/cross/foo.c}.
5061 Note that the executable search path is @emph{not} used to locate the
5064 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5065 any information it has cached about where source files are found and where
5066 each line is in the file.
5070 When you start @value{GDBN}, its source path includes only @samp{cdir}
5071 and @samp{cwd}, in that order.
5072 To add other directories, use the @code{directory} command.
5074 The search path is used to find both program source files and @value{GDBN}
5075 script files (read using the @samp{-command} option and @samp{source} command).
5077 In addition to the source path, @value{GDBN} provides a set of commands
5078 that manage a list of source path substitution rules. A @dfn{substitution
5079 rule} specifies how to rewrite source directories stored in the program's
5080 debug information in case the sources were moved to a different
5081 directory between compilation and debugging. A rule is made of
5082 two strings, the first specifying what needs to be rewritten in
5083 the path, and the second specifying how it should be rewritten.
5084 In @ref{set substitute-path}, we name these two parts @var{from} and
5085 @var{to} respectively. @value{GDBN} does a simple string replacement
5086 of @var{from} with @var{to} at the start of the directory part of the
5087 source file name, and uses that result instead of the original file
5088 name to look up the sources.
5090 Using the previous example, suppose the @file{foo-1.0} tree has been
5091 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5092 GDB to replace @file{/usr/src} in all source path names with
5093 @file{/mnt/cross}. The first lookup will then be
5094 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5095 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5096 substitution rule, use the @code{set substitute-path} command
5097 (@pxref{set substitute-path}).
5099 To avoid unexpected substitution results, a rule is applied only if the
5100 @var{from} part of the directory name ends at a directory separator.
5101 For instance, a rule substituting @file{/usr/source} into
5102 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5103 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5104 is applied only at the begining of the directory name, this rule will
5105 not be applied to @file{/root/usr/source/baz.c} either.
5107 In many cases, you can achieve the same result using the @code{directory}
5108 command. However, @code{set substitute-path} can be more efficient in
5109 the case where the sources are organized in a complex tree with multiple
5110 subdirectories. With the @code{directory} command, you need to add each
5111 subdirectory of your project. If you moved the entire tree while
5112 preserving its internal organization, then @code{set substitute-path}
5113 allows you to direct the debugger to all the sources with one single
5116 @code{set substitute-path} is also more than just a shortcut command.
5117 The source path is only used if the file at the original location no
5118 longer exists. On the other hand, @code{set substitute-path} modifies
5119 the debugger behavior to look at the rewritten location instead. So, if
5120 for any reason a source file that is not relevant to your executable is
5121 located at the original location, a substitution rule is the only
5122 method available to point GDB at the new location.
5125 @item directory @var{dirname} @dots{}
5126 @item dir @var{dirname} @dots{}
5127 Add directory @var{dirname} to the front of the source path. Several
5128 directory names may be given to this command, separated by @samp{:}
5129 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5130 part of absolute file names) or
5131 whitespace. You may specify a directory that is already in the source
5132 path; this moves it forward, so @value{GDBN} searches it sooner.
5136 @vindex $cdir@r{, convenience variable}
5137 @vindex $cwdr@r{, convenience variable}
5138 @cindex compilation directory
5139 @cindex current directory
5140 @cindex working directory
5141 @cindex directory, current
5142 @cindex directory, compilation
5143 You can use the string @samp{$cdir} to refer to the compilation
5144 directory (if one is recorded), and @samp{$cwd} to refer to the current
5145 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5146 tracks the current working directory as it changes during your @value{GDBN}
5147 session, while the latter is immediately expanded to the current
5148 directory at the time you add an entry to the source path.
5151 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5153 @c RET-repeat for @code{directory} is explicitly disabled, but since
5154 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5156 @item show directories
5157 @kindex show directories
5158 Print the source path: show which directories it contains.
5160 @anchor{set substitute-path}
5161 @item set substitute-path @var{from} @var{to}
5162 @kindex set substitute-path
5163 Define a source path substitution rule, and add it at the end of the
5164 current list of existing substitution rules. If a rule with the same
5165 @var{from} was already defined, then the old rule is also deleted.
5167 For example, if the file @file{/foo/bar/baz.c} was moved to
5168 @file{/mnt/cross/baz.c}, then the command
5171 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5175 will tell @value{GDBN} to replace @samp{/usr/src} with
5176 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5177 @file{baz.c} even though it was moved.
5179 In the case when more than one substitution rule have been defined,
5180 the rules are evaluated one by one in the order where they have been
5181 defined. The first one matching, if any, is selected to perform
5184 For instance, if we had entered the following commands:
5187 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5188 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5192 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5193 @file{/mnt/include/defs.h} by using the first rule. However, it would
5194 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5195 @file{/mnt/src/lib/foo.c}.
5198 @item unset substitute-path [path]
5199 @kindex unset substitute-path
5200 If a path is specified, search the current list of substitution rules
5201 for a rule that would rewrite that path. Delete that rule if found.
5202 A warning is emitted by the debugger if no rule could be found.
5204 If no path is specified, then all substitution rules are deleted.
5206 @item show substitute-path [path]
5207 @kindex show substitute-path
5208 If a path is specified, then print the source path substitution rule
5209 which would rewrite that path, if any.
5211 If no path is specified, then print all existing source path substitution
5216 If your source path is cluttered with directories that are no longer of
5217 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5218 versions of source. You can correct the situation as follows:
5222 Use @code{directory} with no argument to reset the source path to its default value.
5225 Use @code{directory} with suitable arguments to reinstall the
5226 directories you want in the source path. You can add all the
5227 directories in one command.
5231 @section Source and machine code
5232 @cindex source line and its code address
5234 You can use the command @code{info line} to map source lines to program
5235 addresses (and vice versa), and the command @code{disassemble} to display
5236 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5237 mode, the @code{info line} command causes the arrow to point to the
5238 line specified. Also, @code{info line} prints addresses in symbolic form as
5243 @item info line @var{linespec}
5244 Print the starting and ending addresses of the compiled code for
5245 source line @var{linespec}. You can specify source lines in any of
5246 the ways understood by the @code{list} command (@pxref{List, ,Printing
5250 For example, we can use @code{info line} to discover the location of
5251 the object code for the first line of function
5252 @code{m4_changequote}:
5254 @c FIXME: I think this example should also show the addresses in
5255 @c symbolic form, as they usually would be displayed.
5257 (@value{GDBP}) info line m4_changequote
5258 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5262 @cindex code address and its source line
5263 We can also inquire (using @code{*@var{addr}} as the form for
5264 @var{linespec}) what source line covers a particular address:
5266 (@value{GDBP}) info line *0x63ff
5267 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5270 @cindex @code{$_} and @code{info line}
5271 @cindex @code{x} command, default address
5272 @kindex x@r{(examine), and} info line
5273 After @code{info line}, the default address for the @code{x} command
5274 is changed to the starting address of the line, so that @samp{x/i} is
5275 sufficient to begin examining the machine code (@pxref{Memory,
5276 ,Examining memory}). Also, this address is saved as the value of the
5277 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5282 @cindex assembly instructions
5283 @cindex instructions, assembly
5284 @cindex machine instructions
5285 @cindex listing machine instructions
5287 This specialized command dumps a range of memory as machine
5288 instructions. The default memory range is the function surrounding the
5289 program counter of the selected frame. A single argument to this
5290 command is a program counter value; @value{GDBN} dumps the function
5291 surrounding this value. Two arguments specify a range of addresses
5292 (first inclusive, second exclusive) to dump.
5295 The following example shows the disassembly of a range of addresses of
5296 HP PA-RISC 2.0 code:
5299 (@value{GDBP}) disas 0x32c4 0x32e4
5300 Dump of assembler code from 0x32c4 to 0x32e4:
5301 0x32c4 <main+204>: addil 0,dp
5302 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5303 0x32cc <main+212>: ldil 0x3000,r31
5304 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5305 0x32d4 <main+220>: ldo 0(r31),rp
5306 0x32d8 <main+224>: addil -0x800,dp
5307 0x32dc <main+228>: ldo 0x588(r1),r26
5308 0x32e0 <main+232>: ldil 0x3000,r31
5309 End of assembler dump.
5312 Some architectures have more than one commonly-used set of instruction
5313 mnemonics or other syntax.
5315 For programs that were dynamically linked and use shared libraries,
5316 instructions that call functions or branch to locations in the shared
5317 libraries might show a seemingly bogus location---it's actually a
5318 location of the relocation table. On some architectures, @value{GDBN}
5319 might be able to resolve these to actual function names.
5322 @kindex set disassembly-flavor
5323 @cindex Intel disassembly flavor
5324 @cindex AT&T disassembly flavor
5325 @item set disassembly-flavor @var{instruction-set}
5326 Select the instruction set to use when disassembling the
5327 program via the @code{disassemble} or @code{x/i} commands.
5329 Currently this command is only defined for the Intel x86 family. You
5330 can set @var{instruction-set} to either @code{intel} or @code{att}.
5331 The default is @code{att}, the AT&T flavor used by default by Unix
5332 assemblers for x86-based targets.
5334 @kindex show disassembly-flavor
5335 @item show disassembly-flavor
5336 Show the current setting of the disassembly flavor.
5341 @chapter Examining Data
5343 @cindex printing data
5344 @cindex examining data
5347 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5348 @c document because it is nonstandard... Under Epoch it displays in a
5349 @c different window or something like that.
5350 The usual way to examine data in your program is with the @code{print}
5351 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5352 evaluates and prints the value of an expression of the language your
5353 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5354 Different Languages}).
5357 @item print @var{expr}
5358 @itemx print /@var{f} @var{expr}
5359 @var{expr} is an expression (in the source language). By default the
5360 value of @var{expr} is printed in a format appropriate to its data type;
5361 you can choose a different format by specifying @samp{/@var{f}}, where
5362 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5366 @itemx print /@var{f}
5367 @cindex reprint the last value
5368 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5369 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5370 conveniently inspect the same value in an alternative format.
5373 A more low-level way of examining data is with the @code{x} command.
5374 It examines data in memory at a specified address and prints it in a
5375 specified format. @xref{Memory, ,Examining memory}.
5377 If you are interested in information about types, or about how the
5378 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5379 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5383 * Expressions:: Expressions
5384 * Variables:: Program variables
5385 * Arrays:: Artificial arrays
5386 * Output Formats:: Output formats
5387 * Memory:: Examining memory
5388 * Auto Display:: Automatic display
5389 * Print Settings:: Print settings
5390 * Value History:: Value history
5391 * Convenience Vars:: Convenience variables
5392 * Registers:: Registers
5393 * Floating Point Hardware:: Floating point hardware
5394 * Vector Unit:: Vector Unit
5395 * OS Information:: Auxiliary data provided by operating system
5396 * Memory Region Attributes:: Memory region attributes
5397 * Dump/Restore Files:: Copy between memory and a file
5398 * Core File Generation:: Cause a program dump its core
5399 * Character Sets:: Debugging programs that use a different
5400 character set than GDB does
5401 * Caching Remote Data:: Data caching for remote targets
5405 @section Expressions
5408 @code{print} and many other @value{GDBN} commands accept an expression and
5409 compute its value. Any kind of constant, variable or operator defined
5410 by the programming language you are using is valid in an expression in
5411 @value{GDBN}. This includes conditional expressions, function calls,
5412 casts, and string constants. It also includes preprocessor macros, if
5413 you compiled your program to include this information; see
5416 @cindex arrays in expressions
5417 @value{GDBN} supports array constants in expressions input by
5418 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5419 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5420 memory that is @code{malloc}ed in the target program.
5422 Because C is so widespread, most of the expressions shown in examples in
5423 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5424 Languages}, for information on how to use expressions in other
5427 In this section, we discuss operators that you can use in @value{GDBN}
5428 expressions regardless of your programming language.
5430 @cindex casts, in expressions
5431 Casts are supported in all languages, not just in C, because it is so
5432 useful to cast a number into a pointer in order to examine a structure
5433 at that address in memory.
5434 @c FIXME: casts supported---Mod2 true?
5436 @value{GDBN} supports these operators, in addition to those common
5437 to programming languages:
5441 @samp{@@} is a binary operator for treating parts of memory as arrays.
5442 @xref{Arrays, ,Artificial arrays}, for more information.
5445 @samp{::} allows you to specify a variable in terms of the file or
5446 function where it is defined. @xref{Variables, ,Program variables}.
5448 @cindex @{@var{type}@}
5449 @cindex type casting memory
5450 @cindex memory, viewing as typed object
5451 @cindex casts, to view memory
5452 @item @{@var{type}@} @var{addr}
5453 Refers to an object of type @var{type} stored at address @var{addr} in
5454 memory. @var{addr} may be any expression whose value is an integer or
5455 pointer (but parentheses are required around binary operators, just as in
5456 a cast). This construct is allowed regardless of what kind of data is
5457 normally supposed to reside at @var{addr}.
5461 @section Program variables
5463 The most common kind of expression to use is the name of a variable
5466 Variables in expressions are understood in the selected stack frame
5467 (@pxref{Selection, ,Selecting a frame}); they must be either:
5471 global (or file-static)
5478 visible according to the scope rules of the
5479 programming language from the point of execution in that frame
5482 @noindent This means that in the function
5497 you can examine and use the variable @code{a} whenever your program is
5498 executing within the function @code{foo}, but you can only use or
5499 examine the variable @code{b} while your program is executing inside
5500 the block where @code{b} is declared.
5502 @cindex variable name conflict
5503 There is an exception: you can refer to a variable or function whose
5504 scope is a single source file even if the current execution point is not
5505 in this file. But it is possible to have more than one such variable or
5506 function with the same name (in different source files). If that
5507 happens, referring to that name has unpredictable effects. If you wish,
5508 you can specify a static variable in a particular function or file,
5509 using the colon-colon (@code{::}) notation:
5511 @cindex colon-colon, context for variables/functions
5513 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5514 @cindex @code{::}, context for variables/functions
5517 @var{file}::@var{variable}
5518 @var{function}::@var{variable}
5522 Here @var{file} or @var{function} is the name of the context for the
5523 static @var{variable}. In the case of file names, you can use quotes to
5524 make sure @value{GDBN} parses the file name as a single word---for example,
5525 to print a global value of @code{x} defined in @file{f2.c}:
5528 (@value{GDBP}) p 'f2.c'::x
5531 @cindex C@t{++} scope resolution
5532 This use of @samp{::} is very rarely in conflict with the very similar
5533 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5534 scope resolution operator in @value{GDBN} expressions.
5535 @c FIXME: Um, so what happens in one of those rare cases where it's in
5538 @cindex wrong values
5539 @cindex variable values, wrong
5540 @cindex function entry/exit, wrong values of variables
5541 @cindex optimized code, wrong values of variables
5543 @emph{Warning:} Occasionally, a local variable may appear to have the
5544 wrong value at certain points in a function---just after entry to a new
5545 scope, and just before exit.
5547 You may see this problem when you are stepping by machine instructions.
5548 This is because, on most machines, it takes more than one instruction to
5549 set up a stack frame (including local variable definitions); if you are
5550 stepping by machine instructions, variables may appear to have the wrong
5551 values until the stack frame is completely built. On exit, it usually
5552 also takes more than one machine instruction to destroy a stack frame;
5553 after you begin stepping through that group of instructions, local
5554 variable definitions may be gone.
5556 This may also happen when the compiler does significant optimizations.
5557 To be sure of always seeing accurate values, turn off all optimization
5560 @cindex ``No symbol "foo" in current context''
5561 Another possible effect of compiler optimizations is to optimize
5562 unused variables out of existence, or assign variables to registers (as
5563 opposed to memory addresses). Depending on the support for such cases
5564 offered by the debug info format used by the compiler, @value{GDBN}
5565 might not be able to display values for such local variables. If that
5566 happens, @value{GDBN} will print a message like this:
5569 No symbol "foo" in current context.
5572 To solve such problems, either recompile without optimizations, or use a
5573 different debug info format, if the compiler supports several such
5574 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5575 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5576 produces debug info in a format that is superior to formats such as
5577 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5578 an effective form for debug info. @xref{Debugging Options,,Options
5579 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5580 @xref{C, , Debugging C++}, for more info about debug info formats
5581 that are best suited to C@t{++} programs.
5583 If you ask to print an object whose contents are unknown to
5584 @value{GDBN}, e.g., because its data type is not completely specified
5585 by the debug information, @value{GDBN} will say @samp{<incomplete
5586 type>}. @xref{Symbols, incomplete type}, for more about this.
5589 @section Artificial arrays
5591 @cindex artificial array
5593 @kindex @@@r{, referencing memory as an array}
5594 It is often useful to print out several successive objects of the
5595 same type in memory; a section of an array, or an array of
5596 dynamically determined size for which only a pointer exists in the
5599 You can do this by referring to a contiguous span of memory as an
5600 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5601 operand of @samp{@@} should be the first element of the desired array
5602 and be an individual object. The right operand should be the desired length
5603 of the array. The result is an array value whose elements are all of
5604 the type of the left argument. The first element is actually the left
5605 argument; the second element comes from bytes of memory immediately
5606 following those that hold the first element, and so on. Here is an
5607 example. If a program says
5610 int *array = (int *) malloc (len * sizeof (int));
5614 you can print the contents of @code{array} with
5620 The left operand of @samp{@@} must reside in memory. Array values made
5621 with @samp{@@} in this way behave just like other arrays in terms of
5622 subscripting, and are coerced to pointers when used in expressions.
5623 Artificial arrays most often appear in expressions via the value history
5624 (@pxref{Value History, ,Value history}), after printing one out.
5626 Another way to create an artificial array is to use a cast.
5627 This re-interprets a value as if it were an array.
5628 The value need not be in memory:
5630 (@value{GDBP}) p/x (short[2])0x12345678
5631 $1 = @{0x1234, 0x5678@}
5634 As a convenience, if you leave the array length out (as in
5635 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5636 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5638 (@value{GDBP}) p/x (short[])0x12345678
5639 $2 = @{0x1234, 0x5678@}
5642 Sometimes the artificial array mechanism is not quite enough; in
5643 moderately complex data structures, the elements of interest may not
5644 actually be adjacent---for example, if you are interested in the values
5645 of pointers in an array. One useful work-around in this situation is
5646 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5647 variables}) as a counter in an expression that prints the first
5648 interesting value, and then repeat that expression via @key{RET}. For
5649 instance, suppose you have an array @code{dtab} of pointers to
5650 structures, and you are interested in the values of a field @code{fv}
5651 in each structure. Here is an example of what you might type:
5661 @node Output Formats
5662 @section Output formats
5664 @cindex formatted output
5665 @cindex output formats
5666 By default, @value{GDBN} prints a value according to its data type. Sometimes
5667 this is not what you want. For example, you might want to print a number
5668 in hex, or a pointer in decimal. Or you might want to view data in memory
5669 at a certain address as a character string or as an instruction. To do
5670 these things, specify an @dfn{output format} when you print a value.
5672 The simplest use of output formats is to say how to print a value
5673 already computed. This is done by starting the arguments of the
5674 @code{print} command with a slash and a format letter. The format
5675 letters supported are:
5679 Regard the bits of the value as an integer, and print the integer in
5683 Print as integer in signed decimal.
5686 Print as integer in unsigned decimal.
5689 Print as integer in octal.
5692 Print as integer in binary. The letter @samp{t} stands for ``two''.
5693 @footnote{@samp{b} cannot be used because these format letters are also
5694 used with the @code{x} command, where @samp{b} stands for ``byte'';
5695 see @ref{Memory,,Examining memory}.}
5698 @cindex unknown address, locating
5699 @cindex locate address
5700 Print as an address, both absolute in hexadecimal and as an offset from
5701 the nearest preceding symbol. You can use this format used to discover
5702 where (in what function) an unknown address is located:
5705 (@value{GDBP}) p/a 0x54320
5706 $3 = 0x54320 <_initialize_vx+396>
5710 The command @code{info symbol 0x54320} yields similar results.
5711 @xref{Symbols, info symbol}.
5714 Regard as an integer and print it as a character constant. This
5715 prints both the numerical value and its character representation. The
5716 character representation is replaced with the octal escape @samp{\nnn}
5717 for characters outside the 7-bit @sc{ascii} range.
5720 Regard the bits of the value as a floating point number and print
5721 using typical floating point syntax.
5724 For example, to print the program counter in hex (@pxref{Registers}), type
5731 Note that no space is required before the slash; this is because command
5732 names in @value{GDBN} cannot contain a slash.
5734 To reprint the last value in the value history with a different format,
5735 you can use the @code{print} command with just a format and no
5736 expression. For example, @samp{p/x} reprints the last value in hex.
5739 @section Examining memory
5741 You can use the command @code{x} (for ``examine'') to examine memory in
5742 any of several formats, independently of your program's data types.
5744 @cindex examining memory
5746 @kindex x @r{(examine memory)}
5747 @item x/@var{nfu} @var{addr}
5750 Use the @code{x} command to examine memory.
5753 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5754 much memory to display and how to format it; @var{addr} is an
5755 expression giving the address where you want to start displaying memory.
5756 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5757 Several commands set convenient defaults for @var{addr}.
5760 @item @var{n}, the repeat count
5761 The repeat count is a decimal integer; the default is 1. It specifies
5762 how much memory (counting by units @var{u}) to display.
5763 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5766 @item @var{f}, the display format
5767 The display format is one of the formats used by @code{print}
5768 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5769 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5770 @samp{i} (for machine instructions). The default is @samp{x}
5771 (hexadecimal) initially. The default changes each time you use either
5772 @code{x} or @code{print}.
5774 @item @var{u}, the unit size
5775 The unit size is any of
5781 Halfwords (two bytes).
5783 Words (four bytes). This is the initial default.
5785 Giant words (eight bytes).
5788 Each time you specify a unit size with @code{x}, that size becomes the
5789 default unit the next time you use @code{x}. (For the @samp{s} and
5790 @samp{i} formats, the unit size is ignored and is normally not written.)
5792 @item @var{addr}, starting display address
5793 @var{addr} is the address where you want @value{GDBN} to begin displaying
5794 memory. The expression need not have a pointer value (though it may);
5795 it is always interpreted as an integer address of a byte of memory.
5796 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5797 @var{addr} is usually just after the last address examined---but several
5798 other commands also set the default address: @code{info breakpoints} (to
5799 the address of the last breakpoint listed), @code{info line} (to the
5800 starting address of a line), and @code{print} (if you use it to display
5801 a value from memory).
5804 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5805 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5806 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5807 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5808 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5810 Since the letters indicating unit sizes are all distinct from the
5811 letters specifying output formats, you do not have to remember whether
5812 unit size or format comes first; either order works. The output
5813 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5814 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5816 Even though the unit size @var{u} is ignored for the formats @samp{s}
5817 and @samp{i}, you might still want to use a count @var{n}; for example,
5818 @samp{3i} specifies that you want to see three machine instructions,
5819 including any operands. The command @code{disassemble} gives an
5820 alternative way of inspecting machine instructions; see @ref{Machine
5821 Code,,Source and machine code}.
5823 All the defaults for the arguments to @code{x} are designed to make it
5824 easy to continue scanning memory with minimal specifications each time
5825 you use @code{x}. For example, after you have inspected three machine
5826 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5827 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5828 the repeat count @var{n} is used again; the other arguments default as
5829 for successive uses of @code{x}.
5831 @cindex @code{$_}, @code{$__}, and value history
5832 The addresses and contents printed by the @code{x} command are not saved
5833 in the value history because there is often too much of them and they
5834 would get in the way. Instead, @value{GDBN} makes these values available for
5835 subsequent use in expressions as values of the convenience variables
5836 @code{$_} and @code{$__}. After an @code{x} command, the last address
5837 examined is available for use in expressions in the convenience variable
5838 @code{$_}. The contents of that address, as examined, are available in
5839 the convenience variable @code{$__}.
5841 If the @code{x} command has a repeat count, the address and contents saved
5842 are from the last memory unit printed; this is not the same as the last
5843 address printed if several units were printed on the last line of output.
5845 @cindex remote memory comparison
5846 @cindex verify remote memory image
5847 When you are debugging a program running on a remote target machine
5848 (@pxref{Remote}), you may wish to verify the program's image in the
5849 remote machine's memory against the executable file you downloaded to
5850 the target. The @code{compare-sections} command is provided for such
5854 @kindex compare-sections
5855 @item compare-sections @r{[}@var{section-name}@r{]}
5856 Compare the data of a loadable section @var{section-name} in the
5857 executable file of the program being debugged with the same section in
5858 the remote machine's memory, and report any mismatches. With no
5859 arguments, compares all loadable sections. This command's
5860 availability depends on the target's support for the @code{"qCRC"}
5865 @section Automatic display
5866 @cindex automatic display
5867 @cindex display of expressions
5869 If you find that you want to print the value of an expression frequently
5870 (to see how it changes), you might want to add it to the @dfn{automatic
5871 display list} so that @value{GDBN} prints its value each time your program stops.
5872 Each expression added to the list is given a number to identify it;
5873 to remove an expression from the list, you specify that number.
5874 The automatic display looks like this:
5878 3: bar[5] = (struct hack *) 0x3804
5882 This display shows item numbers, expressions and their current values. As with
5883 displays you request manually using @code{x} or @code{print}, you can
5884 specify the output format you prefer; in fact, @code{display} decides
5885 whether to use @code{print} or @code{x} depending on how elaborate your
5886 format specification is---it uses @code{x} if you specify a unit size,
5887 or one of the two formats (@samp{i} and @samp{s}) that are only
5888 supported by @code{x}; otherwise it uses @code{print}.
5892 @item display @var{expr}
5893 Add the expression @var{expr} to the list of expressions to display
5894 each time your program stops. @xref{Expressions, ,Expressions}.
5896 @code{display} does not repeat if you press @key{RET} again after using it.
5898 @item display/@var{fmt} @var{expr}
5899 For @var{fmt} specifying only a display format and not a size or
5900 count, add the expression @var{expr} to the auto-display list but
5901 arrange to display it each time in the specified format @var{fmt}.
5902 @xref{Output Formats,,Output formats}.
5904 @item display/@var{fmt} @var{addr}
5905 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5906 number of units, add the expression @var{addr} as a memory address to
5907 be examined each time your program stops. Examining means in effect
5908 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5911 For example, @samp{display/i $pc} can be helpful, to see the machine
5912 instruction about to be executed each time execution stops (@samp{$pc}
5913 is a common name for the program counter; @pxref{Registers, ,Registers}).
5916 @kindex delete display
5918 @item undisplay @var{dnums}@dots{}
5919 @itemx delete display @var{dnums}@dots{}
5920 Remove item numbers @var{dnums} from the list of expressions to display.
5922 @code{undisplay} does not repeat if you press @key{RET} after using it.
5923 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5925 @kindex disable display
5926 @item disable display @var{dnums}@dots{}
5927 Disable the display of item numbers @var{dnums}. A disabled display
5928 item is not printed automatically, but is not forgotten. It may be
5929 enabled again later.
5931 @kindex enable display
5932 @item enable display @var{dnums}@dots{}
5933 Enable display of item numbers @var{dnums}. It becomes effective once
5934 again in auto display of its expression, until you specify otherwise.
5937 Display the current values of the expressions on the list, just as is
5938 done when your program stops.
5940 @kindex info display
5942 Print the list of expressions previously set up to display
5943 automatically, each one with its item number, but without showing the
5944 values. This includes disabled expressions, which are marked as such.
5945 It also includes expressions which would not be displayed right now
5946 because they refer to automatic variables not currently available.
5949 @cindex display disabled out of scope
5950 If a display expression refers to local variables, then it does not make
5951 sense outside the lexical context for which it was set up. Such an
5952 expression is disabled when execution enters a context where one of its
5953 variables is not defined. For example, if you give the command
5954 @code{display last_char} while inside a function with an argument
5955 @code{last_char}, @value{GDBN} displays this argument while your program
5956 continues to stop inside that function. When it stops elsewhere---where
5957 there is no variable @code{last_char}---the display is disabled
5958 automatically. The next time your program stops where @code{last_char}
5959 is meaningful, you can enable the display expression once again.
5961 @node Print Settings
5962 @section Print settings
5964 @cindex format options
5965 @cindex print settings
5966 @value{GDBN} provides the following ways to control how arrays, structures,
5967 and symbols are printed.
5970 These settings are useful for debugging programs in any language:
5974 @item set print address
5975 @itemx set print address on
5976 @cindex print/don't print memory addresses
5977 @value{GDBN} prints memory addresses showing the location of stack
5978 traces, structure values, pointer values, breakpoints, and so forth,
5979 even when it also displays the contents of those addresses. The default
5980 is @code{on}. For example, this is what a stack frame display looks like with
5981 @code{set print address on}:
5986 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5988 530 if (lquote != def_lquote)
5992 @item set print address off
5993 Do not print addresses when displaying their contents. For example,
5994 this is the same stack frame displayed with @code{set print address off}:
5998 (@value{GDBP}) set print addr off
6000 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6001 530 if (lquote != def_lquote)
6005 You can use @samp{set print address off} to eliminate all machine
6006 dependent displays from the @value{GDBN} interface. For example, with
6007 @code{print address off}, you should get the same text for backtraces on
6008 all machines---whether or not they involve pointer arguments.
6011 @item show print address
6012 Show whether or not addresses are to be printed.
6015 When @value{GDBN} prints a symbolic address, it normally prints the
6016 closest earlier symbol plus an offset. If that symbol does not uniquely
6017 identify the address (for example, it is a name whose scope is a single
6018 source file), you may need to clarify. One way to do this is with
6019 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6020 you can set @value{GDBN} to print the source file and line number when
6021 it prints a symbolic address:
6024 @item set print symbol-filename on
6025 @cindex source file and line of a symbol
6026 @cindex symbol, source file and line
6027 Tell @value{GDBN} to print the source file name and line number of a
6028 symbol in the symbolic form of an address.
6030 @item set print symbol-filename off
6031 Do not print source file name and line number of a symbol. This is the
6034 @item show print symbol-filename
6035 Show whether or not @value{GDBN} will print the source file name and
6036 line number of a symbol in the symbolic form of an address.
6039 Another situation where it is helpful to show symbol filenames and line
6040 numbers is when disassembling code; @value{GDBN} shows you the line
6041 number and source file that corresponds to each instruction.
6043 Also, you may wish to see the symbolic form only if the address being
6044 printed is reasonably close to the closest earlier symbol:
6047 @item set print max-symbolic-offset @var{max-offset}
6048 @cindex maximum value for offset of closest symbol
6049 Tell @value{GDBN} to only display the symbolic form of an address if the
6050 offset between the closest earlier symbol and the address is less than
6051 @var{max-offset}. The default is 0, which tells @value{GDBN}
6052 to always print the symbolic form of an address if any symbol precedes it.
6054 @item show print max-symbolic-offset
6055 Ask how large the maximum offset is that @value{GDBN} prints in a
6059 @cindex wild pointer, interpreting
6060 @cindex pointer, finding referent
6061 If you have a pointer and you are not sure where it points, try
6062 @samp{set print symbol-filename on}. Then you can determine the name
6063 and source file location of the variable where it points, using
6064 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6065 For example, here @value{GDBN} shows that a variable @code{ptt} points
6066 at another variable @code{t}, defined in @file{hi2.c}:
6069 (@value{GDBP}) set print symbol-filename on
6070 (@value{GDBP}) p/a ptt
6071 $4 = 0xe008 <t in hi2.c>
6075 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6076 does not show the symbol name and filename of the referent, even with
6077 the appropriate @code{set print} options turned on.
6080 Other settings control how different kinds of objects are printed:
6083 @item set print array
6084 @itemx set print array on
6085 @cindex pretty print arrays
6086 Pretty print arrays. This format is more convenient to read,
6087 but uses more space. The default is off.
6089 @item set print array off
6090 Return to compressed format for arrays.
6092 @item show print array
6093 Show whether compressed or pretty format is selected for displaying
6096 @cindex print array indexes
6097 @item set print array-indexes
6098 @itemx set print array-indexes on
6099 Print the index of each element when displaying arrays. May be more
6100 convenient to locate a given element in the array or quickly find the
6101 index of a given element in that printed array. The default is off.
6103 @item set print array-indexes off
6104 Stop printing element indexes when displaying arrays.
6106 @item show print array-indexes
6107 Show whether the index of each element is printed when displaying
6110 @item set print elements @var{number-of-elements}
6111 @cindex number of array elements to print
6112 @cindex limit on number of printed array elements
6113 Set a limit on how many elements of an array @value{GDBN} will print.
6114 If @value{GDBN} is printing a large array, it stops printing after it has
6115 printed the number of elements set by the @code{set print elements} command.
6116 This limit also applies to the display of strings.
6117 When @value{GDBN} starts, this limit is set to 200.
6118 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6120 @item show print elements
6121 Display the number of elements of a large array that @value{GDBN} will print.
6122 If the number is 0, then the printing is unlimited.
6124 @item set print repeats
6125 @cindex repeated array elements
6126 Set the threshold for suppressing display of repeated array
6127 elelments. When the number of consecutive identical elements of an
6128 array exceeds the threshold, @value{GDBN} prints the string
6129 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6130 identical repetitions, instead of displaying the identical elements
6131 themselves. Setting the threshold to zero will cause all elements to
6132 be individually printed. The default threshold is 10.
6134 @item show print repeats
6135 Display the current threshold for printing repeated identical
6138 @item set print null-stop
6139 @cindex @sc{null} elements in arrays
6140 Cause @value{GDBN} to stop printing the characters of an array when the first
6141 @sc{null} is encountered. This is useful when large arrays actually
6142 contain only short strings.
6145 @item show print null-stop
6146 Show whether @value{GDBN} stops printing an array on the first
6147 @sc{null} character.
6149 @item set print pretty on
6150 @cindex print structures in indented form
6151 @cindex indentation in structure display
6152 Cause @value{GDBN} to print structures in an indented format with one member
6153 per line, like this:
6168 @item set print pretty off
6169 Cause @value{GDBN} to print structures in a compact format, like this:
6173 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6174 meat = 0x54 "Pork"@}
6179 This is the default format.
6181 @item show print pretty
6182 Show which format @value{GDBN} is using to print structures.
6184 @item set print sevenbit-strings on
6185 @cindex eight-bit characters in strings
6186 @cindex octal escapes in strings
6187 Print using only seven-bit characters; if this option is set,
6188 @value{GDBN} displays any eight-bit characters (in strings or
6189 character values) using the notation @code{\}@var{nnn}. This setting is
6190 best if you are working in English (@sc{ascii}) and you use the
6191 high-order bit of characters as a marker or ``meta'' bit.
6193 @item set print sevenbit-strings off
6194 Print full eight-bit characters. This allows the use of more
6195 international character sets, and is the default.
6197 @item show print sevenbit-strings
6198 Show whether or not @value{GDBN} is printing only seven-bit characters.
6200 @item set print union on
6201 @cindex unions in structures, printing
6202 Tell @value{GDBN} to print unions which are contained in structures
6203 and other unions. This is the default setting.
6205 @item set print union off
6206 Tell @value{GDBN} not to print unions which are contained in
6207 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6210 @item show print union
6211 Ask @value{GDBN} whether or not it will print unions which are contained in
6212 structures and other unions.
6214 For example, given the declarations
6217 typedef enum @{Tree, Bug@} Species;
6218 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6219 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6230 struct thing foo = @{Tree, @{Acorn@}@};
6234 with @code{set print union on} in effect @samp{p foo} would print
6237 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6241 and with @code{set print union off} in effect it would print
6244 $1 = @{it = Tree, form = @{...@}@}
6248 @code{set print union} affects programs written in C-like languages
6254 These settings are of interest when debugging C@t{++} programs:
6257 @cindex demangling C@t{++} names
6258 @item set print demangle
6259 @itemx set print demangle on
6260 Print C@t{++} names in their source form rather than in the encoded
6261 (``mangled'') form passed to the assembler and linker for type-safe
6262 linkage. The default is on.
6264 @item show print demangle
6265 Show whether C@t{++} names are printed in mangled or demangled form.
6267 @item set print asm-demangle
6268 @itemx set print asm-demangle on
6269 Print C@t{++} names in their source form rather than their mangled form, even
6270 in assembler code printouts such as instruction disassemblies.
6273 @item show print asm-demangle
6274 Show whether C@t{++} names in assembly listings are printed in mangled
6277 @cindex C@t{++} symbol decoding style
6278 @cindex symbol decoding style, C@t{++}
6279 @kindex set demangle-style
6280 @item set demangle-style @var{style}
6281 Choose among several encoding schemes used by different compilers to
6282 represent C@t{++} names. The choices for @var{style} are currently:
6286 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6289 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6290 This is the default.
6293 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6296 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6299 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6300 @strong{Warning:} this setting alone is not sufficient to allow
6301 debugging @code{cfront}-generated executables. @value{GDBN} would
6302 require further enhancement to permit that.
6305 If you omit @var{style}, you will see a list of possible formats.
6307 @item show demangle-style
6308 Display the encoding style currently in use for decoding C@t{++} symbols.
6310 @item set print object
6311 @itemx set print object on
6312 @cindex derived type of an object, printing
6313 @cindex display derived types
6314 When displaying a pointer to an object, identify the @emph{actual}
6315 (derived) type of the object rather than the @emph{declared} type, using
6316 the virtual function table.
6318 @item set print object off
6319 Display only the declared type of objects, without reference to the
6320 virtual function table. This is the default setting.
6322 @item show print object
6323 Show whether actual, or declared, object types are displayed.
6325 @item set print static-members
6326 @itemx set print static-members on
6327 @cindex static members of C@t{++} objects
6328 Print static members when displaying a C@t{++} object. The default is on.
6330 @item set print static-members off
6331 Do not print static members when displaying a C@t{++} object.
6333 @item show print static-members
6334 Show whether C@t{++} static members are printed or not.
6336 @item set print pascal_static-members
6337 @itemx set print pascal_static-members on
6338 @cindex static members of Pacal objects
6339 @cindex Pacal objects, static members display
6340 Print static members when displaying a Pascal object. The default is on.
6342 @item set print pascal_static-members off
6343 Do not print static members when displaying a Pascal object.
6345 @item show print pascal_static-members
6346 Show whether Pascal static members are printed or not.
6348 @c These don't work with HP ANSI C++ yet.
6349 @item set print vtbl
6350 @itemx set print vtbl on
6351 @cindex pretty print C@t{++} virtual function tables
6352 @cindex virtual functions (C@t{++}) display
6353 @cindex VTBL display
6354 Pretty print C@t{++} virtual function tables. The default is off.
6355 (The @code{vtbl} commands do not work on programs compiled with the HP
6356 ANSI C@t{++} compiler (@code{aCC}).)
6358 @item set print vtbl off
6359 Do not pretty print C@t{++} virtual function tables.
6361 @item show print vtbl
6362 Show whether C@t{++} virtual function tables are pretty printed, or not.
6366 @section Value history
6368 @cindex value history
6369 @cindex history of values printed by @value{GDBN}
6370 Values printed by the @code{print} command are saved in the @value{GDBN}
6371 @dfn{value history}. This allows you to refer to them in other expressions.
6372 Values are kept until the symbol table is re-read or discarded
6373 (for example with the @code{file} or @code{symbol-file} commands).
6374 When the symbol table changes, the value history is discarded,
6375 since the values may contain pointers back to the types defined in the
6380 @cindex history number
6381 The values printed are given @dfn{history numbers} by which you can
6382 refer to them. These are successive integers starting with one.
6383 @code{print} shows you the history number assigned to a value by
6384 printing @samp{$@var{num} = } before the value; here @var{num} is the
6387 To refer to any previous value, use @samp{$} followed by the value's
6388 history number. The way @code{print} labels its output is designed to
6389 remind you of this. Just @code{$} refers to the most recent value in
6390 the history, and @code{$$} refers to the value before that.
6391 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6392 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6393 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6395 For example, suppose you have just printed a pointer to a structure and
6396 want to see the contents of the structure. It suffices to type
6402 If you have a chain of structures where the component @code{next} points
6403 to the next one, you can print the contents of the next one with this:
6410 You can print successive links in the chain by repeating this
6411 command---which you can do by just typing @key{RET}.
6413 Note that the history records values, not expressions. If the value of
6414 @code{x} is 4 and you type these commands:
6422 then the value recorded in the value history by the @code{print} command
6423 remains 4 even though the value of @code{x} has changed.
6428 Print the last ten values in the value history, with their item numbers.
6429 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6430 values} does not change the history.
6432 @item show values @var{n}
6433 Print ten history values centered on history item number @var{n}.
6436 Print ten history values just after the values last printed. If no more
6437 values are available, @code{show values +} produces no display.
6440 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6441 same effect as @samp{show values +}.
6443 @node Convenience Vars
6444 @section Convenience variables
6446 @cindex convenience variables
6447 @cindex user-defined variables
6448 @value{GDBN} provides @dfn{convenience variables} that you can use within
6449 @value{GDBN} to hold on to a value and refer to it later. These variables
6450 exist entirely within @value{GDBN}; they are not part of your program, and
6451 setting a convenience variable has no direct effect on further execution
6452 of your program. That is why you can use them freely.
6454 Convenience variables are prefixed with @samp{$}. Any name preceded by
6455 @samp{$} can be used for a convenience variable, unless it is one of
6456 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6457 (Value history references, in contrast, are @emph{numbers} preceded
6458 by @samp{$}. @xref{Value History, ,Value history}.)
6460 You can save a value in a convenience variable with an assignment
6461 expression, just as you would set a variable in your program.
6465 set $foo = *object_ptr
6469 would save in @code{$foo} the value contained in the object pointed to by
6472 Using a convenience variable for the first time creates it, but its
6473 value is @code{void} until you assign a new value. You can alter the
6474 value with another assignment at any time.
6476 Convenience variables have no fixed types. You can assign a convenience
6477 variable any type of value, including structures and arrays, even if
6478 that variable already has a value of a different type. The convenience
6479 variable, when used as an expression, has the type of its current value.
6482 @kindex show convenience
6483 @cindex show all user variables
6484 @item show convenience
6485 Print a list of convenience variables used so far, and their values.
6486 Abbreviated @code{show conv}.
6488 @kindex init-if-undefined
6489 @cindex convenience variables, initializing
6490 @item init-if-undefined $@var{variable} = @var{expression}
6491 Set a convenience variable if it has not already been set. This is useful
6492 for user-defined commands that keep some state. It is similar, in concept,
6493 to using local static variables with initializers in C (except that
6494 convenience variables are global). It can also be used to allow users to
6495 override default values used in a command script.
6497 If the variable is already defined then the expression is not evaluated so
6498 any side-effects do not occur.
6501 One of the ways to use a convenience variable is as a counter to be
6502 incremented or a pointer to be advanced. For example, to print
6503 a field from successive elements of an array of structures:
6507 print bar[$i++]->contents
6511 Repeat that command by typing @key{RET}.
6513 Some convenience variables are created automatically by @value{GDBN} and given
6514 values likely to be useful.
6517 @vindex $_@r{, convenience variable}
6519 The variable @code{$_} is automatically set by the @code{x} command to
6520 the last address examined (@pxref{Memory, ,Examining memory}). Other
6521 commands which provide a default address for @code{x} to examine also
6522 set @code{$_} to that address; these commands include @code{info line}
6523 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6524 except when set by the @code{x} command, in which case it is a pointer
6525 to the type of @code{$__}.
6527 @vindex $__@r{, convenience variable}
6529 The variable @code{$__} is automatically set by the @code{x} command
6530 to the value found in the last address examined. Its type is chosen
6531 to match the format in which the data was printed.
6534 @vindex $_exitcode@r{, convenience variable}
6535 The variable @code{$_exitcode} is automatically set to the exit code when
6536 the program being debugged terminates.
6539 On HP-UX systems, if you refer to a function or variable name that
6540 begins with a dollar sign, @value{GDBN} searches for a user or system
6541 name first, before it searches for a convenience variable.
6547 You can refer to machine register contents, in expressions, as variables
6548 with names starting with @samp{$}. The names of registers are different
6549 for each machine; use @code{info registers} to see the names used on
6553 @kindex info registers
6554 @item info registers
6555 Print the names and values of all registers except floating-point
6556 and vector registers (in the selected stack frame).
6558 @kindex info all-registers
6559 @cindex floating point registers
6560 @item info all-registers
6561 Print the names and values of all registers, including floating-point
6562 and vector registers (in the selected stack frame).
6564 @item info registers @var{regname} @dots{}
6565 Print the @dfn{relativized} value of each specified register @var{regname}.
6566 As discussed in detail below, register values are normally relative to
6567 the selected stack frame. @var{regname} may be any register name valid on
6568 the machine you are using, with or without the initial @samp{$}.
6571 @cindex stack pointer register
6572 @cindex program counter register
6573 @cindex process status register
6574 @cindex frame pointer register
6575 @cindex standard registers
6576 @value{GDBN} has four ``standard'' register names that are available (in
6577 expressions) on most machines---whenever they do not conflict with an
6578 architecture's canonical mnemonics for registers. The register names
6579 @code{$pc} and @code{$sp} are used for the program counter register and
6580 the stack pointer. @code{$fp} is used for a register that contains a
6581 pointer to the current stack frame, and @code{$ps} is used for a
6582 register that contains the processor status. For example,
6583 you could print the program counter in hex with
6590 or print the instruction to be executed next with
6597 or add four to the stack pointer@footnote{This is a way of removing
6598 one word from the stack, on machines where stacks grow downward in
6599 memory (most machines, nowadays). This assumes that the innermost
6600 stack frame is selected; setting @code{$sp} is not allowed when other
6601 stack frames are selected. To pop entire frames off the stack,
6602 regardless of machine architecture, use @code{return};
6603 see @ref{Returning, ,Returning from a function}.} with
6609 Whenever possible, these four standard register names are available on
6610 your machine even though the machine has different canonical mnemonics,
6611 so long as there is no conflict. The @code{info registers} command
6612 shows the canonical names. For example, on the SPARC, @code{info
6613 registers} displays the processor status register as @code{$psr} but you
6614 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6615 is an alias for the @sc{eflags} register.
6617 @value{GDBN} always considers the contents of an ordinary register as an
6618 integer when the register is examined in this way. Some machines have
6619 special registers which can hold nothing but floating point; these
6620 registers are considered to have floating point values. There is no way
6621 to refer to the contents of an ordinary register as floating point value
6622 (although you can @emph{print} it as a floating point value with
6623 @samp{print/f $@var{regname}}).
6625 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6626 means that the data format in which the register contents are saved by
6627 the operating system is not the same one that your program normally
6628 sees. For example, the registers of the 68881 floating point
6629 coprocessor are always saved in ``extended'' (raw) format, but all C
6630 programs expect to work with ``double'' (virtual) format. In such
6631 cases, @value{GDBN} normally works with the virtual format only (the format
6632 that makes sense for your program), but the @code{info registers} command
6633 prints the data in both formats.
6635 @cindex SSE registers (x86)
6636 @cindex MMX registers (x86)
6637 Some machines have special registers whose contents can be interpreted
6638 in several different ways. For example, modern x86-based machines
6639 have SSE and MMX registers that can hold several values packed
6640 together in several different formats. @value{GDBN} refers to such
6641 registers in @code{struct} notation:
6644 (@value{GDBP}) print $xmm1
6646 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6647 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6648 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6649 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6650 v4_int32 = @{0, 20657912, 11, 13@},
6651 v2_int64 = @{88725056443645952, 55834574859@},
6652 uint128 = 0x0000000d0000000b013b36f800000000
6657 To set values of such registers, you need to tell @value{GDBN} which
6658 view of the register you wish to change, as if you were assigning
6659 value to a @code{struct} member:
6662 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6665 Normally, register values are relative to the selected stack frame
6666 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6667 value that the register would contain if all stack frames farther in
6668 were exited and their saved registers restored. In order to see the
6669 true contents of hardware registers, you must select the innermost
6670 frame (with @samp{frame 0}).
6672 However, @value{GDBN} must deduce where registers are saved, from the machine
6673 code generated by your compiler. If some registers are not saved, or if
6674 @value{GDBN} is unable to locate the saved registers, the selected stack
6675 frame makes no difference.
6677 @node Floating Point Hardware
6678 @section Floating point hardware
6679 @cindex floating point
6681 Depending on the configuration, @value{GDBN} may be able to give
6682 you more information about the status of the floating point hardware.
6687 Display hardware-dependent information about the floating
6688 point unit. The exact contents and layout vary depending on the
6689 floating point chip. Currently, @samp{info float} is supported on
6690 the ARM and x86 machines.
6694 @section Vector Unit
6697 Depending on the configuration, @value{GDBN} may be able to give you
6698 more information about the status of the vector unit.
6703 Display information about the vector unit. The exact contents and
6704 layout vary depending on the hardware.
6707 @node OS Information
6708 @section Operating system auxiliary information
6709 @cindex OS information
6711 @value{GDBN} provides interfaces to useful OS facilities that can help
6712 you debug your program.
6714 @cindex @code{ptrace} system call
6715 @cindex @code{struct user} contents
6716 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6717 machines), it interfaces with the inferior via the @code{ptrace}
6718 system call. The operating system creates a special sata structure,
6719 called @code{struct user}, for this interface. You can use the
6720 command @code{info udot} to display the contents of this data
6726 Display the contents of the @code{struct user} maintained by the OS
6727 kernel for the program being debugged. @value{GDBN} displays the
6728 contents of @code{struct user} as a list of hex numbers, similar to
6729 the @code{examine} command.
6732 @cindex auxiliary vector
6733 @cindex vector, auxiliary
6734 Some operating systems supply an @dfn{auxiliary vector} to programs at
6735 startup. This is akin to the arguments and environment that you
6736 specify for a program, but contains a system-dependent variety of
6737 binary values that tell system libraries important details about the
6738 hardware, operating system, and process. Each value's purpose is
6739 identified by an integer tag; the meanings are well-known but system-specific.
6740 Depending on the configuration and operating system facilities,
6741 @value{GDBN} may be able to show you this information. For remote
6742 targets, this functionality may further depend on the remote stub's
6743 support of the @samp{qXfer:auxv:read} packet, see
6744 @ref{qXfer auxiliary vector read}.
6749 Display the auxiliary vector of the inferior, which can be either a
6750 live process or a core dump file. @value{GDBN} prints each tag value
6751 numerically, and also shows names and text descriptions for recognized
6752 tags. Some values in the vector are numbers, some bit masks, and some
6753 pointers to strings or other data. @value{GDBN} displays each value in the
6754 most appropriate form for a recognized tag, and in hexadecimal for
6755 an unrecognized tag.
6759 @node Memory Region Attributes
6760 @section Memory region attributes
6761 @cindex memory region attributes
6763 @dfn{Memory region attributes} allow you to describe special handling
6764 required by regions of your target's memory. @value{GDBN} uses
6765 attributes to determine whether to allow certain types of memory
6766 accesses; whether to use specific width accesses; and whether to cache
6767 target memory. By default the description of memory regions is
6768 fetched from the target (if the current target supports this), but the
6769 user can override the fetched regions.
6771 Defined memory regions can be individually enabled and disabled. When a
6772 memory region is disabled, @value{GDBN} uses the default attributes when
6773 accessing memory in that region. Similarly, if no memory regions have
6774 been defined, @value{GDBN} uses the default attributes when accessing
6777 When a memory region is defined, it is given a number to identify it;
6778 to enable, disable, or remove a memory region, you specify that number.
6782 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6783 Define a memory region bounded by @var{lower} and @var{upper} with
6784 attributes @var{attributes}@dots{}, and add it to the list of regions
6785 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6786 case: it is treated as the the target's maximum memory address.
6787 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6790 Discard any user changes to the memory regions and use target-supplied
6791 regions, if available, or no regions if the target does not support.
6794 @item delete mem @var{nums}@dots{}
6795 Remove memory regions @var{nums}@dots{} from the list of regions
6796 monitored by @value{GDBN}.
6799 @item disable mem @var{nums}@dots{}
6800 Disable monitoring of memory regions @var{nums}@dots{}.
6801 A disabled memory region is not forgotten.
6802 It may be enabled again later.
6805 @item enable mem @var{nums}@dots{}
6806 Enable monitoring of memory regions @var{nums}@dots{}.
6810 Print a table of all defined memory regions, with the following columns
6814 @item Memory Region Number
6815 @item Enabled or Disabled.
6816 Enabled memory regions are marked with @samp{y}.
6817 Disabled memory regions are marked with @samp{n}.
6820 The address defining the inclusive lower bound of the memory region.
6823 The address defining the exclusive upper bound of the memory region.
6826 The list of attributes set for this memory region.
6831 @subsection Attributes
6833 @subsubsection Memory Access Mode
6834 The access mode attributes set whether @value{GDBN} may make read or
6835 write accesses to a memory region.
6837 While these attributes prevent @value{GDBN} from performing invalid
6838 memory accesses, they do nothing to prevent the target system, I/O DMA,
6839 etc.@: from accessing memory.
6843 Memory is read only.
6845 Memory is write only.
6847 Memory is read/write. This is the default.
6850 @subsubsection Memory Access Size
6851 The acccess size attributes tells @value{GDBN} to use specific sized
6852 accesses in the memory region. Often memory mapped device registers
6853 require specific sized accesses. If no access size attribute is
6854 specified, @value{GDBN} may use accesses of any size.
6858 Use 8 bit memory accesses.
6860 Use 16 bit memory accesses.
6862 Use 32 bit memory accesses.
6864 Use 64 bit memory accesses.
6867 @c @subsubsection Hardware/Software Breakpoints
6868 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6869 @c will use hardware or software breakpoints for the internal breakpoints
6870 @c used by the step, next, finish, until, etc. commands.
6874 @c Always use hardware breakpoints
6875 @c @item swbreak (default)
6878 @subsubsection Data Cache
6879 The data cache attributes set whether @value{GDBN} will cache target
6880 memory. While this generally improves performance by reducing debug
6881 protocol overhead, it can lead to incorrect results because @value{GDBN}
6882 does not know about volatile variables or memory mapped device
6887 Enable @value{GDBN} to cache target memory.
6889 Disable @value{GDBN} from caching target memory. This is the default.
6892 @c @subsubsection Memory Write Verification
6893 @c The memory write verification attributes set whether @value{GDBN}
6894 @c will re-reads data after each write to verify the write was successful.
6898 @c @item noverify (default)
6901 @node Dump/Restore Files
6902 @section Copy between memory and a file
6903 @cindex dump/restore files
6904 @cindex append data to a file
6905 @cindex dump data to a file
6906 @cindex restore data from a file
6908 You can use the commands @code{dump}, @code{append}, and
6909 @code{restore} to copy data between target memory and a file. The
6910 @code{dump} and @code{append} commands write data to a file, and the
6911 @code{restore} command reads data from a file back into the inferior's
6912 memory. Files may be in binary, Motorola S-record, Intel hex, or
6913 Tektronix Hex format; however, @value{GDBN} can only append to binary
6919 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6920 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6921 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6922 or the value of @var{expr}, to @var{filename} in the given format.
6924 The @var{format} parameter may be any one of:
6931 Motorola S-record format.
6933 Tektronix Hex format.
6936 @value{GDBN} uses the same definitions of these formats as the
6937 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6938 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6942 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6943 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6944 Append the contents of memory from @var{start_addr} to @var{end_addr},
6945 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6946 (@value{GDBN} can only append data to files in raw binary form.)
6949 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6950 Restore the contents of file @var{filename} into memory. The
6951 @code{restore} command can automatically recognize any known @sc{bfd}
6952 file format, except for raw binary. To restore a raw binary file you
6953 must specify the optional keyword @code{binary} after the filename.
6955 If @var{bias} is non-zero, its value will be added to the addresses
6956 contained in the file. Binary files always start at address zero, so
6957 they will be restored at address @var{bias}. Other bfd files have
6958 a built-in location; they will be restored at offset @var{bias}
6961 If @var{start} and/or @var{end} are non-zero, then only data between
6962 file offset @var{start} and file offset @var{end} will be restored.
6963 These offsets are relative to the addresses in the file, before
6964 the @var{bias} argument is applied.
6968 @node Core File Generation
6969 @section How to Produce a Core File from Your Program
6970 @cindex dump core from inferior
6972 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6973 image of a running process and its process status (register values
6974 etc.). Its primary use is post-mortem debugging of a program that
6975 crashed while it ran outside a debugger. A program that crashes
6976 automatically produces a core file, unless this feature is disabled by
6977 the user. @xref{Files}, for information on invoking @value{GDBN} in
6978 the post-mortem debugging mode.
6980 Occasionally, you may wish to produce a core file of the program you
6981 are debugging in order to preserve a snapshot of its state.
6982 @value{GDBN} has a special command for that.
6986 @kindex generate-core-file
6987 @item generate-core-file [@var{file}]
6988 @itemx gcore [@var{file}]
6989 Produce a core dump of the inferior process. The optional argument
6990 @var{file} specifies the file name where to put the core dump. If not
6991 specified, the file name defaults to @file{core.@var{pid}}, where
6992 @var{pid} is the inferior process ID.
6994 Note that this command is implemented only for some systems (as of
6995 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6998 @node Character Sets
6999 @section Character Sets
7000 @cindex character sets
7002 @cindex translating between character sets
7003 @cindex host character set
7004 @cindex target character set
7006 If the program you are debugging uses a different character set to
7007 represent characters and strings than the one @value{GDBN} uses itself,
7008 @value{GDBN} can automatically translate between the character sets for
7009 you. The character set @value{GDBN} uses we call the @dfn{host
7010 character set}; the one the inferior program uses we call the
7011 @dfn{target character set}.
7013 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7014 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7015 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
7016 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7017 then the host character set is Latin-1, and the target character set is
7018 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7019 target-charset EBCDIC-US}, then @value{GDBN} translates between
7020 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7021 character and string literals in expressions.
7023 @value{GDBN} has no way to automatically recognize which character set
7024 the inferior program uses; you must tell it, using the @code{set
7025 target-charset} command, described below.
7027 Here are the commands for controlling @value{GDBN}'s character set
7031 @item set target-charset @var{charset}
7032 @kindex set target-charset
7033 Set the current target character set to @var{charset}. We list the
7034 character set names @value{GDBN} recognizes below, but if you type
7035 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7036 list the target character sets it supports.
7040 @item set host-charset @var{charset}
7041 @kindex set host-charset
7042 Set the current host character set to @var{charset}.
7044 By default, @value{GDBN} uses a host character set appropriate to the
7045 system it is running on; you can override that default using the
7046 @code{set host-charset} command.
7048 @value{GDBN} can only use certain character sets as its host character
7049 set. We list the character set names @value{GDBN} recognizes below, and
7050 indicate which can be host character sets, but if you type
7051 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7052 list the host character sets it supports.
7054 @item set charset @var{charset}
7056 Set the current host and target character sets to @var{charset}. As
7057 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7058 @value{GDBN} will list the name of the character sets that can be used
7059 for both host and target.
7063 @kindex show charset
7064 Show the names of the current host and target charsets.
7066 @itemx show host-charset
7067 @kindex show host-charset
7068 Show the name of the current host charset.
7070 @itemx show target-charset
7071 @kindex show target-charset
7072 Show the name of the current target charset.
7076 @value{GDBN} currently includes support for the following character
7082 @cindex ASCII character set
7083 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7087 @cindex ISO 8859-1 character set
7088 @cindex ISO Latin 1 character set
7089 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7090 characters needed for French, German, and Spanish. @value{GDBN} can use
7091 this as its host character set.
7095 @cindex EBCDIC character set
7096 @cindex IBM1047 character set
7097 Variants of the @sc{ebcdic} character set, used on some of IBM's
7098 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7099 @value{GDBN} cannot use these as its host character set.
7103 Note that these are all single-byte character sets. More work inside
7104 GDB is needed to support multi-byte or variable-width character
7105 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7107 Here is an example of @value{GDBN}'s character set support in action.
7108 Assume that the following source code has been placed in the file
7109 @file{charset-test.c}:
7115 = @{72, 101, 108, 108, 111, 44, 32, 119,
7116 111, 114, 108, 100, 33, 10, 0@};
7117 char ibm1047_hello[]
7118 = @{200, 133, 147, 147, 150, 107, 64, 166,
7119 150, 153, 147, 132, 90, 37, 0@};
7123 printf ("Hello, world!\n");
7127 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7128 containing the string @samp{Hello, world!} followed by a newline,
7129 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7131 We compile the program, and invoke the debugger on it:
7134 $ gcc -g charset-test.c -o charset-test
7135 $ gdb -nw charset-test
7136 GNU gdb 2001-12-19-cvs
7137 Copyright 2001 Free Software Foundation, Inc.
7142 We can use the @code{show charset} command to see what character sets
7143 @value{GDBN} is currently using to interpret and display characters and
7147 (@value{GDBP}) show charset
7148 The current host and target character set is `ISO-8859-1'.
7152 For the sake of printing this manual, let's use @sc{ascii} as our
7153 initial character set:
7155 (@value{GDBP}) set charset ASCII
7156 (@value{GDBP}) show charset
7157 The current host and target character set is `ASCII'.
7161 Let's assume that @sc{ascii} is indeed the correct character set for our
7162 host system --- in other words, let's assume that if @value{GDBN} prints
7163 characters using the @sc{ascii} character set, our terminal will display
7164 them properly. Since our current target character set is also
7165 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7168 (@value{GDBP}) print ascii_hello
7169 $1 = 0x401698 "Hello, world!\n"
7170 (@value{GDBP}) print ascii_hello[0]
7175 @value{GDBN} uses the target character set for character and string
7176 literals you use in expressions:
7179 (@value{GDBP}) print '+'
7184 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7187 @value{GDBN} relies on the user to tell it which character set the
7188 target program uses. If we print @code{ibm1047_hello} while our target
7189 character set is still @sc{ascii}, we get jibberish:
7192 (@value{GDBP}) print ibm1047_hello
7193 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7194 (@value{GDBP}) print ibm1047_hello[0]
7199 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7200 @value{GDBN} tells us the character sets it supports:
7203 (@value{GDBP}) set target-charset
7204 ASCII EBCDIC-US IBM1047 ISO-8859-1
7205 (@value{GDBP}) set target-charset
7208 We can select @sc{ibm1047} as our target character set, and examine the
7209 program's strings again. Now the @sc{ascii} string is wrong, but
7210 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7211 target character set, @sc{ibm1047}, to the host character set,
7212 @sc{ascii}, and they display correctly:
7215 (@value{GDBP}) set target-charset IBM1047
7216 (@value{GDBP}) show charset
7217 The current host character set is `ASCII'.
7218 The current target character set is `IBM1047'.
7219 (@value{GDBP}) print ascii_hello
7220 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7221 (@value{GDBP}) print ascii_hello[0]
7223 (@value{GDBP}) print ibm1047_hello
7224 $8 = 0x4016a8 "Hello, world!\n"
7225 (@value{GDBP}) print ibm1047_hello[0]
7230 As above, @value{GDBN} uses the target character set for character and
7231 string literals you use in expressions:
7234 (@value{GDBP}) print '+'
7239 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7242 @node Caching Remote Data
7243 @section Caching Data of Remote Targets
7244 @cindex caching data of remote targets
7246 @value{GDBN} can cache data exchanged between the debugger and a
7247 remote target (@pxref{Remote}). Such caching generally improves
7248 performance, because it reduces the overhead of the remote protocol by
7249 bundling memory reads and writes into large chunks. Unfortunately,
7250 @value{GDBN} does not currently know anything about volatile
7251 registers, and thus data caching will produce incorrect results when
7252 volatile registers are in use.
7255 @kindex set remotecache
7256 @item set remotecache on
7257 @itemx set remotecache off
7258 Set caching state for remote targets. When @code{ON}, use data
7259 caching. By default, this option is @code{OFF}.
7261 @kindex show remotecache
7262 @item show remotecache
7263 Show the current state of data caching for remote targets.
7267 Print the information about the data cache performance. The
7268 information displayed includes: the dcache width and depth; and for
7269 each cache line, how many times it was referenced, and its data and
7270 state (dirty, bad, ok, etc.). This command is useful for debugging
7271 the data cache operation.
7276 @chapter C Preprocessor Macros
7278 Some languages, such as C and C@t{++}, provide a way to define and invoke
7279 ``preprocessor macros'' which expand into strings of tokens.
7280 @value{GDBN} can evaluate expressions containing macro invocations, show
7281 the result of macro expansion, and show a macro's definition, including
7282 where it was defined.
7284 You may need to compile your program specially to provide @value{GDBN}
7285 with information about preprocessor macros. Most compilers do not
7286 include macros in their debugging information, even when you compile
7287 with the @option{-g} flag. @xref{Compilation}.
7289 A program may define a macro at one point, remove that definition later,
7290 and then provide a different definition after that. Thus, at different
7291 points in the program, a macro may have different definitions, or have
7292 no definition at all. If there is a current stack frame, @value{GDBN}
7293 uses the macros in scope at that frame's source code line. Otherwise,
7294 @value{GDBN} uses the macros in scope at the current listing location;
7297 At the moment, @value{GDBN} does not support the @code{##}
7298 token-splicing operator, the @code{#} stringification operator, or
7299 variable-arity macros.
7301 Whenever @value{GDBN} evaluates an expression, it always expands any
7302 macro invocations present in the expression. @value{GDBN} also provides
7303 the following commands for working with macros explicitly.
7307 @kindex macro expand
7308 @cindex macro expansion, showing the results of preprocessor
7309 @cindex preprocessor macro expansion, showing the results of
7310 @cindex expanding preprocessor macros
7311 @item macro expand @var{expression}
7312 @itemx macro exp @var{expression}
7313 Show the results of expanding all preprocessor macro invocations in
7314 @var{expression}. Since @value{GDBN} simply expands macros, but does
7315 not parse the result, @var{expression} need not be a valid expression;
7316 it can be any string of tokens.
7319 @item macro expand-once @var{expression}
7320 @itemx macro exp1 @var{expression}
7321 @cindex expand macro once
7322 @i{(This command is not yet implemented.)} Show the results of
7323 expanding those preprocessor macro invocations that appear explicitly in
7324 @var{expression}. Macro invocations appearing in that expansion are
7325 left unchanged. This command allows you to see the effect of a
7326 particular macro more clearly, without being confused by further
7327 expansions. Since @value{GDBN} simply expands macros, but does not
7328 parse the result, @var{expression} need not be a valid expression; it
7329 can be any string of tokens.
7332 @cindex macro definition, showing
7333 @cindex definition, showing a macro's
7334 @item info macro @var{macro}
7335 Show the definition of the macro named @var{macro}, and describe the
7336 source location where that definition was established.
7338 @kindex macro define
7339 @cindex user-defined macros
7340 @cindex defining macros interactively
7341 @cindex macros, user-defined
7342 @item macro define @var{macro} @var{replacement-list}
7343 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7344 @i{(This command is not yet implemented.)} Introduce a definition for a
7345 preprocessor macro named @var{macro}, invocations of which are replaced
7346 by the tokens given in @var{replacement-list}. The first form of this
7347 command defines an ``object-like'' macro, which takes no arguments; the
7348 second form defines a ``function-like'' macro, which takes the arguments
7349 given in @var{arglist}.
7351 A definition introduced by this command is in scope in every expression
7352 evaluated in @value{GDBN}, until it is removed with the @command{macro
7353 undef} command, described below. The definition overrides all
7354 definitions for @var{macro} present in the program being debugged, as
7355 well as any previous user-supplied definition.
7358 @item macro undef @var{macro}
7359 @i{(This command is not yet implemented.)} Remove any user-supplied
7360 definition for the macro named @var{macro}. This command only affects
7361 definitions provided with the @command{macro define} command, described
7362 above; it cannot remove definitions present in the program being
7367 @i{(This command is not yet implemented.)} List all the macros
7368 defined using the @code{macro define} command.
7371 @cindex macros, example of debugging with
7372 Here is a transcript showing the above commands in action. First, we
7373 show our source files:
7381 #define ADD(x) (M + x)
7386 printf ("Hello, world!\n");
7388 printf ("We're so creative.\n");
7390 printf ("Goodbye, world!\n");
7397 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7398 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7399 compiler includes information about preprocessor macros in the debugging
7403 $ gcc -gdwarf-2 -g3 sample.c -o sample
7407 Now, we start @value{GDBN} on our sample program:
7411 GNU gdb 2002-05-06-cvs
7412 Copyright 2002 Free Software Foundation, Inc.
7413 GDB is free software, @dots{}
7417 We can expand macros and examine their definitions, even when the
7418 program is not running. @value{GDBN} uses the current listing position
7419 to decide which macro definitions are in scope:
7422 (@value{GDBP}) list main
7425 5 #define ADD(x) (M + x)
7430 10 printf ("Hello, world!\n");
7432 12 printf ("We're so creative.\n");
7433 (@value{GDBP}) info macro ADD
7434 Defined at /home/jimb/gdb/macros/play/sample.c:5
7435 #define ADD(x) (M + x)
7436 (@value{GDBP}) info macro Q
7437 Defined at /home/jimb/gdb/macros/play/sample.h:1
7438 included at /home/jimb/gdb/macros/play/sample.c:2
7440 (@value{GDBP}) macro expand ADD(1)
7441 expands to: (42 + 1)
7442 (@value{GDBP}) macro expand-once ADD(1)
7443 expands to: once (M + 1)
7447 In the example above, note that @command{macro expand-once} expands only
7448 the macro invocation explicit in the original text --- the invocation of
7449 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7450 which was introduced by @code{ADD}.
7452 Once the program is running, GDB uses the macro definitions in force at
7453 the source line of the current stack frame:
7456 (@value{GDBP}) break main
7457 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7459 Starting program: /home/jimb/gdb/macros/play/sample
7461 Breakpoint 1, main () at sample.c:10
7462 10 printf ("Hello, world!\n");
7466 At line 10, the definition of the macro @code{N} at line 9 is in force:
7469 (@value{GDBP}) info macro N
7470 Defined at /home/jimb/gdb/macros/play/sample.c:9
7472 (@value{GDBP}) macro expand N Q M
7474 (@value{GDBP}) print N Q M
7479 As we step over directives that remove @code{N}'s definition, and then
7480 give it a new definition, @value{GDBN} finds the definition (or lack
7481 thereof) in force at each point:
7486 12 printf ("We're so creative.\n");
7487 (@value{GDBP}) info macro N
7488 The symbol `N' has no definition as a C/C++ preprocessor macro
7489 at /home/jimb/gdb/macros/play/sample.c:12
7492 14 printf ("Goodbye, world!\n");
7493 (@value{GDBP}) info macro N
7494 Defined at /home/jimb/gdb/macros/play/sample.c:13
7496 (@value{GDBP}) macro expand N Q M
7497 expands to: 1729 < 42
7498 (@value{GDBP}) print N Q M
7505 @chapter Tracepoints
7506 @c This chapter is based on the documentation written by Michael
7507 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7510 In some applications, it is not feasible for the debugger to interrupt
7511 the program's execution long enough for the developer to learn
7512 anything helpful about its behavior. If the program's correctness
7513 depends on its real-time behavior, delays introduced by a debugger
7514 might cause the program to change its behavior drastically, or perhaps
7515 fail, even when the code itself is correct. It is useful to be able
7516 to observe the program's behavior without interrupting it.
7518 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7519 specify locations in the program, called @dfn{tracepoints}, and
7520 arbitrary expressions to evaluate when those tracepoints are reached.
7521 Later, using the @code{tfind} command, you can examine the values
7522 those expressions had when the program hit the tracepoints. The
7523 expressions may also denote objects in memory---structures or arrays,
7524 for example---whose values @value{GDBN} should record; while visiting
7525 a particular tracepoint, you may inspect those objects as if they were
7526 in memory at that moment. However, because @value{GDBN} records these
7527 values without interacting with you, it can do so quickly and
7528 unobtrusively, hopefully not disturbing the program's behavior.
7530 The tracepoint facility is currently available only for remote
7531 targets. @xref{Targets}. In addition, your remote target must know
7532 how to collect trace data. This functionality is implemented in the
7533 remote stub; however, none of the stubs distributed with @value{GDBN}
7534 support tracepoints as of this writing. The format of the remote
7535 packets used to implement tracepoints are described in @ref{Tracepoint
7538 This chapter describes the tracepoint commands and features.
7542 * Analyze Collected Data::
7543 * Tracepoint Variables::
7546 @node Set Tracepoints
7547 @section Commands to Set Tracepoints
7549 Before running such a @dfn{trace experiment}, an arbitrary number of
7550 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7551 tracepoint has a number assigned to it by @value{GDBN}. Like with
7552 breakpoints, tracepoint numbers are successive integers starting from
7553 one. Many of the commands associated with tracepoints take the
7554 tracepoint number as their argument, to identify which tracepoint to
7557 For each tracepoint, you can specify, in advance, some arbitrary set
7558 of data that you want the target to collect in the trace buffer when
7559 it hits that tracepoint. The collected data can include registers,
7560 local variables, or global data. Later, you can use @value{GDBN}
7561 commands to examine the values these data had at the time the
7564 This section describes commands to set tracepoints and associated
7565 conditions and actions.
7568 * Create and Delete Tracepoints::
7569 * Enable and Disable Tracepoints::
7570 * Tracepoint Passcounts::
7571 * Tracepoint Actions::
7572 * Listing Tracepoints::
7573 * Starting and Stopping Trace Experiment::
7576 @node Create and Delete Tracepoints
7577 @subsection Create and Delete Tracepoints
7580 @cindex set tracepoint
7583 The @code{trace} command is very similar to the @code{break} command.
7584 Its argument can be a source line, a function name, or an address in
7585 the target program. @xref{Set Breaks}. The @code{trace} command
7586 defines a tracepoint, which is a point in the target program where the
7587 debugger will briefly stop, collect some data, and then allow the
7588 program to continue. Setting a tracepoint or changing its commands
7589 doesn't take effect until the next @code{tstart} command; thus, you
7590 cannot change the tracepoint attributes once a trace experiment is
7593 Here are some examples of using the @code{trace} command:
7596 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7598 (@value{GDBP}) @b{trace +2} // 2 lines forward
7600 (@value{GDBP}) @b{trace my_function} // first source line of function
7602 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7604 (@value{GDBP}) @b{trace *0x2117c4} // an address
7608 You can abbreviate @code{trace} as @code{tr}.
7611 @cindex last tracepoint number
7612 @cindex recent tracepoint number
7613 @cindex tracepoint number
7614 The convenience variable @code{$tpnum} records the tracepoint number
7615 of the most recently set tracepoint.
7617 @kindex delete tracepoint
7618 @cindex tracepoint deletion
7619 @item delete tracepoint @r{[}@var{num}@r{]}
7620 Permanently delete one or more tracepoints. With no argument, the
7621 default is to delete all tracepoints.
7626 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7628 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7632 You can abbreviate this command as @code{del tr}.
7635 @node Enable and Disable Tracepoints
7636 @subsection Enable and Disable Tracepoints
7639 @kindex disable tracepoint
7640 @item disable tracepoint @r{[}@var{num}@r{]}
7641 Disable tracepoint @var{num}, or all tracepoints if no argument
7642 @var{num} is given. A disabled tracepoint will have no effect during
7643 the next trace experiment, but it is not forgotten. You can re-enable
7644 a disabled tracepoint using the @code{enable tracepoint} command.
7646 @kindex enable tracepoint
7647 @item enable tracepoint @r{[}@var{num}@r{]}
7648 Enable tracepoint @var{num}, or all tracepoints. The enabled
7649 tracepoints will become effective the next time a trace experiment is
7653 @node Tracepoint Passcounts
7654 @subsection Tracepoint Passcounts
7658 @cindex tracepoint pass count
7659 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7660 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7661 automatically stop a trace experiment. If a tracepoint's passcount is
7662 @var{n}, then the trace experiment will be automatically stopped on
7663 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7664 @var{num} is not specified, the @code{passcount} command sets the
7665 passcount of the most recently defined tracepoint. If no passcount is
7666 given, the trace experiment will run until stopped explicitly by the
7672 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7673 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7675 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7676 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7677 (@value{GDBP}) @b{trace foo}
7678 (@value{GDBP}) @b{pass 3}
7679 (@value{GDBP}) @b{trace bar}
7680 (@value{GDBP}) @b{pass 2}
7681 (@value{GDBP}) @b{trace baz}
7682 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7683 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7684 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7685 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7689 @node Tracepoint Actions
7690 @subsection Tracepoint Action Lists
7694 @cindex tracepoint actions
7695 @item actions @r{[}@var{num}@r{]}
7696 This command will prompt for a list of actions to be taken when the
7697 tracepoint is hit. If the tracepoint number @var{num} is not
7698 specified, this command sets the actions for the one that was most
7699 recently defined (so that you can define a tracepoint and then say
7700 @code{actions} without bothering about its number). You specify the
7701 actions themselves on the following lines, one action at a time, and
7702 terminate the actions list with a line containing just @code{end}. So
7703 far, the only defined actions are @code{collect} and
7704 @code{while-stepping}.
7706 @cindex remove actions from a tracepoint
7707 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7708 and follow it immediately with @samp{end}.
7711 (@value{GDBP}) @b{collect @var{data}} // collect some data
7713 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7715 (@value{GDBP}) @b{end} // signals the end of actions.
7718 In the following example, the action list begins with @code{collect}
7719 commands indicating the things to be collected when the tracepoint is
7720 hit. Then, in order to single-step and collect additional data
7721 following the tracepoint, a @code{while-stepping} command is used,
7722 followed by the list of things to be collected while stepping. The
7723 @code{while-stepping} command is terminated by its own separate
7724 @code{end} command. Lastly, the action list is terminated by an
7728 (@value{GDBP}) @b{trace foo}
7729 (@value{GDBP}) @b{actions}
7730 Enter actions for tracepoint 1, one per line:
7739 @kindex collect @r{(tracepoints)}
7740 @item collect @var{expr1}, @var{expr2}, @dots{}
7741 Collect values of the given expressions when the tracepoint is hit.
7742 This command accepts a comma-separated list of any valid expressions.
7743 In addition to global, static, or local variables, the following
7744 special arguments are supported:
7748 collect all registers
7751 collect all function arguments
7754 collect all local variables.
7757 You can give several consecutive @code{collect} commands, each one
7758 with a single argument, or one @code{collect} command with several
7759 arguments separated by commas: the effect is the same.
7761 The command @code{info scope} (@pxref{Symbols, info scope}) is
7762 particularly useful for figuring out what data to collect.
7764 @kindex while-stepping @r{(tracepoints)}
7765 @item while-stepping @var{n}
7766 Perform @var{n} single-step traces after the tracepoint, collecting
7767 new data at each step. The @code{while-stepping} command is
7768 followed by the list of what to collect while stepping (followed by
7769 its own @code{end} command):
7773 > collect $regs, myglobal
7779 You may abbreviate @code{while-stepping} as @code{ws} or
7783 @node Listing Tracepoints
7784 @subsection Listing Tracepoints
7787 @kindex info tracepoints
7789 @cindex information about tracepoints
7790 @item info tracepoints @r{[}@var{num}@r{]}
7791 Display information about the tracepoint @var{num}. If you don't specify
7792 a tracepoint number, displays information about all the tracepoints
7793 defined so far. For each tracepoint, the following information is
7800 whether it is enabled or disabled
7804 its passcount as given by the @code{passcount @var{n}} command
7806 its step count as given by the @code{while-stepping @var{n}} command
7808 where in the source files is the tracepoint set
7810 its action list as given by the @code{actions} command
7814 (@value{GDBP}) @b{info trace}
7815 Num Enb Address PassC StepC What
7816 1 y 0x002117c4 0 0 <gdb_asm>
7817 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7818 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7823 This command can be abbreviated @code{info tp}.
7826 @node Starting and Stopping Trace Experiment
7827 @subsection Starting and Stopping Trace Experiment
7831 @cindex start a new trace experiment
7832 @cindex collected data discarded
7834 This command takes no arguments. It starts the trace experiment, and
7835 begins collecting data. This has the side effect of discarding all
7836 the data collected in the trace buffer during the previous trace
7840 @cindex stop a running trace experiment
7842 This command takes no arguments. It ends the trace experiment, and
7843 stops collecting data.
7845 @strong{Note}: a trace experiment and data collection may stop
7846 automatically if any tracepoint's passcount is reached
7847 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7850 @cindex status of trace data collection
7851 @cindex trace experiment, status of
7853 This command displays the status of the current trace data
7857 Here is an example of the commands we described so far:
7860 (@value{GDBP}) @b{trace gdb_c_test}
7861 (@value{GDBP}) @b{actions}
7862 Enter actions for tracepoint #1, one per line.
7863 > collect $regs,$locals,$args
7868 (@value{GDBP}) @b{tstart}
7869 [time passes @dots{}]
7870 (@value{GDBP}) @b{tstop}
7874 @node Analyze Collected Data
7875 @section Using the collected data
7877 After the tracepoint experiment ends, you use @value{GDBN} commands
7878 for examining the trace data. The basic idea is that each tracepoint
7879 collects a trace @dfn{snapshot} every time it is hit and another
7880 snapshot every time it single-steps. All these snapshots are
7881 consecutively numbered from zero and go into a buffer, and you can
7882 examine them later. The way you examine them is to @dfn{focus} on a
7883 specific trace snapshot. When the remote stub is focused on a trace
7884 snapshot, it will respond to all @value{GDBN} requests for memory and
7885 registers by reading from the buffer which belongs to that snapshot,
7886 rather than from @emph{real} memory or registers of the program being
7887 debugged. This means that @strong{all} @value{GDBN} commands
7888 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7889 behave as if we were currently debugging the program state as it was
7890 when the tracepoint occurred. Any requests for data that are not in
7891 the buffer will fail.
7894 * tfind:: How to select a trace snapshot
7895 * tdump:: How to display all data for a snapshot
7896 * save-tracepoints:: How to save tracepoints for a future run
7900 @subsection @code{tfind @var{n}}
7903 @cindex select trace snapshot
7904 @cindex find trace snapshot
7905 The basic command for selecting a trace snapshot from the buffer is
7906 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7907 counting from zero. If no argument @var{n} is given, the next
7908 snapshot is selected.
7910 Here are the various forms of using the @code{tfind} command.
7914 Find the first snapshot in the buffer. This is a synonym for
7915 @code{tfind 0} (since 0 is the number of the first snapshot).
7918 Stop debugging trace snapshots, resume @emph{live} debugging.
7921 Same as @samp{tfind none}.
7924 No argument means find the next trace snapshot.
7927 Find the previous trace snapshot before the current one. This permits
7928 retracing earlier steps.
7930 @item tfind tracepoint @var{num}
7931 Find the next snapshot associated with tracepoint @var{num}. Search
7932 proceeds forward from the last examined trace snapshot. If no
7933 argument @var{num} is given, it means find the next snapshot collected
7934 for the same tracepoint as the current snapshot.
7936 @item tfind pc @var{addr}
7937 Find the next snapshot associated with the value @var{addr} of the
7938 program counter. Search proceeds forward from the last examined trace
7939 snapshot. If no argument @var{addr} is given, it means find the next
7940 snapshot with the same value of PC as the current snapshot.
7942 @item tfind outside @var{addr1}, @var{addr2}
7943 Find the next snapshot whose PC is outside the given range of
7946 @item tfind range @var{addr1}, @var{addr2}
7947 Find the next snapshot whose PC is between @var{addr1} and
7948 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7950 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7951 Find the next snapshot associated with the source line @var{n}. If
7952 the optional argument @var{file} is given, refer to line @var{n} in
7953 that source file. Search proceeds forward from the last examined
7954 trace snapshot. If no argument @var{n} is given, it means find the
7955 next line other than the one currently being examined; thus saying
7956 @code{tfind line} repeatedly can appear to have the same effect as
7957 stepping from line to line in a @emph{live} debugging session.
7960 The default arguments for the @code{tfind} commands are specifically
7961 designed to make it easy to scan through the trace buffer. For
7962 instance, @code{tfind} with no argument selects the next trace
7963 snapshot, and @code{tfind -} with no argument selects the previous
7964 trace snapshot. So, by giving one @code{tfind} command, and then
7965 simply hitting @key{RET} repeatedly you can examine all the trace
7966 snapshots in order. Or, by saying @code{tfind -} and then hitting
7967 @key{RET} repeatedly you can examine the snapshots in reverse order.
7968 The @code{tfind line} command with no argument selects the snapshot
7969 for the next source line executed. The @code{tfind pc} command with
7970 no argument selects the next snapshot with the same program counter
7971 (PC) as the current frame. The @code{tfind tracepoint} command with
7972 no argument selects the next trace snapshot collected by the same
7973 tracepoint as the current one.
7975 In addition to letting you scan through the trace buffer manually,
7976 these commands make it easy to construct @value{GDBN} scripts that
7977 scan through the trace buffer and print out whatever collected data
7978 you are interested in. Thus, if we want to examine the PC, FP, and SP
7979 registers from each trace frame in the buffer, we can say this:
7982 (@value{GDBP}) @b{tfind start}
7983 (@value{GDBP}) @b{while ($trace_frame != -1)}
7984 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7985 $trace_frame, $pc, $sp, $fp
7989 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7990 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7991 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7992 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7993 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7994 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7995 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7996 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7997 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7998 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7999 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8002 Or, if we want to examine the variable @code{X} at each source line in
8006 (@value{GDBP}) @b{tfind start}
8007 (@value{GDBP}) @b{while ($trace_frame != -1)}
8008 > printf "Frame %d, X == %d\n", $trace_frame, X
8018 @subsection @code{tdump}
8020 @cindex dump all data collected at tracepoint
8021 @cindex tracepoint data, display
8023 This command takes no arguments. It prints all the data collected at
8024 the current trace snapshot.
8027 (@value{GDBP}) @b{trace 444}
8028 (@value{GDBP}) @b{actions}
8029 Enter actions for tracepoint #2, one per line:
8030 > collect $regs, $locals, $args, gdb_long_test
8033 (@value{GDBP}) @b{tstart}
8035 (@value{GDBP}) @b{tfind line 444}
8036 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8038 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8040 (@value{GDBP}) @b{tdump}
8041 Data collected at tracepoint 2, trace frame 1:
8042 d0 0xc4aa0085 -995491707
8046 d4 0x71aea3d 119204413
8051 a1 0x3000668 50333288
8054 a4 0x3000698 50333336
8056 fp 0x30bf3c 0x30bf3c
8057 sp 0x30bf34 0x30bf34
8059 pc 0x20b2c8 0x20b2c8
8063 p = 0x20e5b4 "gdb-test"
8070 gdb_long_test = 17 '\021'
8075 @node save-tracepoints
8076 @subsection @code{save-tracepoints @var{filename}}
8077 @kindex save-tracepoints
8078 @cindex save tracepoints for future sessions
8080 This command saves all current tracepoint definitions together with
8081 their actions and passcounts, into a file @file{@var{filename}}
8082 suitable for use in a later debugging session. To read the saved
8083 tracepoint definitions, use the @code{source} command (@pxref{Command
8086 @node Tracepoint Variables
8087 @section Convenience Variables for Tracepoints
8088 @cindex tracepoint variables
8089 @cindex convenience variables for tracepoints
8092 @vindex $trace_frame
8093 @item (int) $trace_frame
8094 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8095 snapshot is selected.
8098 @item (int) $tracepoint
8099 The tracepoint for the current trace snapshot.
8102 @item (int) $trace_line
8103 The line number for the current trace snapshot.
8106 @item (char []) $trace_file
8107 The source file for the current trace snapshot.
8110 @item (char []) $trace_func
8111 The name of the function containing @code{$tracepoint}.
8114 Note: @code{$trace_file} is not suitable for use in @code{printf},
8115 use @code{output} instead.
8117 Here's a simple example of using these convenience variables for
8118 stepping through all the trace snapshots and printing some of their
8122 (@value{GDBP}) @b{tfind start}
8124 (@value{GDBP}) @b{while $trace_frame != -1}
8125 > output $trace_file
8126 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8132 @chapter Debugging Programs That Use Overlays
8135 If your program is too large to fit completely in your target system's
8136 memory, you can sometimes use @dfn{overlays} to work around this
8137 problem. @value{GDBN} provides some support for debugging programs that
8141 * How Overlays Work:: A general explanation of overlays.
8142 * Overlay Commands:: Managing overlays in @value{GDBN}.
8143 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8144 mapped by asking the inferior.
8145 * Overlay Sample Program:: A sample program using overlays.
8148 @node How Overlays Work
8149 @section How Overlays Work
8150 @cindex mapped overlays
8151 @cindex unmapped overlays
8152 @cindex load address, overlay's
8153 @cindex mapped address
8154 @cindex overlay area
8156 Suppose you have a computer whose instruction address space is only 64
8157 kilobytes long, but which has much more memory which can be accessed by
8158 other means: special instructions, segment registers, or memory
8159 management hardware, for example. Suppose further that you want to
8160 adapt a program which is larger than 64 kilobytes to run on this system.
8162 One solution is to identify modules of your program which are relatively
8163 independent, and need not call each other directly; call these modules
8164 @dfn{overlays}. Separate the overlays from the main program, and place
8165 their machine code in the larger memory. Place your main program in
8166 instruction memory, but leave at least enough space there to hold the
8167 largest overlay as well.
8169 Now, to call a function located in an overlay, you must first copy that
8170 overlay's machine code from the large memory into the space set aside
8171 for it in the instruction memory, and then jump to its entry point
8174 @c NB: In the below the mapped area's size is greater or equal to the
8175 @c size of all overlays. This is intentional to remind the developer
8176 @c that overlays don't necessarily need to be the same size.
8180 Data Instruction Larger
8181 Address Space Address Space Address Space
8182 +-----------+ +-----------+ +-----------+
8184 +-----------+ +-----------+ +-----------+<-- overlay 1
8185 | program | | main | .----| overlay 1 | load address
8186 | variables | | program | | +-----------+
8187 | and heap | | | | | |
8188 +-----------+ | | | +-----------+<-- overlay 2
8189 | | +-----------+ | | | load address
8190 +-----------+ | | | .-| overlay 2 |
8192 mapped --->+-----------+ | | +-----------+
8194 | overlay | <-' | | |
8195 | area | <---' +-----------+<-- overlay 3
8196 | | <---. | | load address
8197 +-----------+ `--| overlay 3 |
8204 @anchor{A code overlay}A code overlay
8208 The diagram (@pxref{A code overlay}) shows a system with separate data
8209 and instruction address spaces. To map an overlay, the program copies
8210 its code from the larger address space to the instruction address space.
8211 Since the overlays shown here all use the same mapped address, only one
8212 may be mapped at a time. For a system with a single address space for
8213 data and instructions, the diagram would be similar, except that the
8214 program variables and heap would share an address space with the main
8215 program and the overlay area.
8217 An overlay loaded into instruction memory and ready for use is called a
8218 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8219 instruction memory. An overlay not present (or only partially present)
8220 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8221 is its address in the larger memory. The mapped address is also called
8222 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8223 called the @dfn{load memory address}, or @dfn{LMA}.
8225 Unfortunately, overlays are not a completely transparent way to adapt a
8226 program to limited instruction memory. They introduce a new set of
8227 global constraints you must keep in mind as you design your program:
8232 Before calling or returning to a function in an overlay, your program
8233 must make sure that overlay is actually mapped. Otherwise, the call or
8234 return will transfer control to the right address, but in the wrong
8235 overlay, and your program will probably crash.
8238 If the process of mapping an overlay is expensive on your system, you
8239 will need to choose your overlays carefully to minimize their effect on
8240 your program's performance.
8243 The executable file you load onto your system must contain each
8244 overlay's instructions, appearing at the overlay's load address, not its
8245 mapped address. However, each overlay's instructions must be relocated
8246 and its symbols defined as if the overlay were at its mapped address.
8247 You can use GNU linker scripts to specify different load and relocation
8248 addresses for pieces of your program; see @ref{Overlay Description,,,
8249 ld.info, Using ld: the GNU linker}.
8252 The procedure for loading executable files onto your system must be able
8253 to load their contents into the larger address space as well as the
8254 instruction and data spaces.
8258 The overlay system described above is rather simple, and could be
8259 improved in many ways:
8264 If your system has suitable bank switch registers or memory management
8265 hardware, you could use those facilities to make an overlay's load area
8266 contents simply appear at their mapped address in instruction space.
8267 This would probably be faster than copying the overlay to its mapped
8268 area in the usual way.
8271 If your overlays are small enough, you could set aside more than one
8272 overlay area, and have more than one overlay mapped at a time.
8275 You can use overlays to manage data, as well as instructions. In
8276 general, data overlays are even less transparent to your design than
8277 code overlays: whereas code overlays only require care when you call or
8278 return to functions, data overlays require care every time you access
8279 the data. Also, if you change the contents of a data overlay, you
8280 must copy its contents back out to its load address before you can copy a
8281 different data overlay into the same mapped area.
8286 @node Overlay Commands
8287 @section Overlay Commands
8289 To use @value{GDBN}'s overlay support, each overlay in your program must
8290 correspond to a separate section of the executable file. The section's
8291 virtual memory address and load memory address must be the overlay's
8292 mapped and load addresses. Identifying overlays with sections allows
8293 @value{GDBN} to determine the appropriate address of a function or
8294 variable, depending on whether the overlay is mapped or not.
8296 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8297 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8302 Disable @value{GDBN}'s overlay support. When overlay support is
8303 disabled, @value{GDBN} assumes that all functions and variables are
8304 always present at their mapped addresses. By default, @value{GDBN}'s
8305 overlay support is disabled.
8307 @item overlay manual
8308 @cindex manual overlay debugging
8309 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8310 relies on you to tell it which overlays are mapped, and which are not,
8311 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8312 commands described below.
8314 @item overlay map-overlay @var{overlay}
8315 @itemx overlay map @var{overlay}
8316 @cindex map an overlay
8317 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8318 be the name of the object file section containing the overlay. When an
8319 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8320 functions and variables at their mapped addresses. @value{GDBN} assumes
8321 that any other overlays whose mapped ranges overlap that of
8322 @var{overlay} are now unmapped.
8324 @item overlay unmap-overlay @var{overlay}
8325 @itemx overlay unmap @var{overlay}
8326 @cindex unmap an overlay
8327 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8328 must be the name of the object file section containing the overlay.
8329 When an overlay is unmapped, @value{GDBN} assumes it can find the
8330 overlay's functions and variables at their load addresses.
8333 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8334 consults a data structure the overlay manager maintains in the inferior
8335 to see which overlays are mapped. For details, see @ref{Automatic
8338 @item overlay load-target
8340 @cindex reloading the overlay table
8341 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8342 re-reads the table @value{GDBN} automatically each time the inferior
8343 stops, so this command should only be necessary if you have changed the
8344 overlay mapping yourself using @value{GDBN}. This command is only
8345 useful when using automatic overlay debugging.
8347 @item overlay list-overlays
8349 @cindex listing mapped overlays
8350 Display a list of the overlays currently mapped, along with their mapped
8351 addresses, load addresses, and sizes.
8355 Normally, when @value{GDBN} prints a code address, it includes the name
8356 of the function the address falls in:
8359 (@value{GDBP}) print main
8360 $3 = @{int ()@} 0x11a0 <main>
8363 When overlay debugging is enabled, @value{GDBN} recognizes code in
8364 unmapped overlays, and prints the names of unmapped functions with
8365 asterisks around them. For example, if @code{foo} is a function in an
8366 unmapped overlay, @value{GDBN} prints it this way:
8369 (@value{GDBP}) overlay list
8370 No sections are mapped.
8371 (@value{GDBP}) print foo
8372 $5 = @{int (int)@} 0x100000 <*foo*>
8375 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8379 (@value{GDBP}) overlay list
8380 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8381 mapped at 0x1016 - 0x104a
8382 (@value{GDBP}) print foo
8383 $6 = @{int (int)@} 0x1016 <foo>
8386 When overlay debugging is enabled, @value{GDBN} can find the correct
8387 address for functions and variables in an overlay, whether or not the
8388 overlay is mapped. This allows most @value{GDBN} commands, like
8389 @code{break} and @code{disassemble}, to work normally, even on unmapped
8390 code. However, @value{GDBN}'s breakpoint support has some limitations:
8394 @cindex breakpoints in overlays
8395 @cindex overlays, setting breakpoints in
8396 You can set breakpoints in functions in unmapped overlays, as long as
8397 @value{GDBN} can write to the overlay at its load address.
8399 @value{GDBN} can not set hardware or simulator-based breakpoints in
8400 unmapped overlays. However, if you set a breakpoint at the end of your
8401 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8402 you are using manual overlay management), @value{GDBN} will re-set its
8403 breakpoints properly.
8407 @node Automatic Overlay Debugging
8408 @section Automatic Overlay Debugging
8409 @cindex automatic overlay debugging
8411 @value{GDBN} can automatically track which overlays are mapped and which
8412 are not, given some simple co-operation from the overlay manager in the
8413 inferior. If you enable automatic overlay debugging with the
8414 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8415 looks in the inferior's memory for certain variables describing the
8416 current state of the overlays.
8418 Here are the variables your overlay manager must define to support
8419 @value{GDBN}'s automatic overlay debugging:
8423 @item @code{_ovly_table}:
8424 This variable must be an array of the following structures:
8429 /* The overlay's mapped address. */
8432 /* The size of the overlay, in bytes. */
8435 /* The overlay's load address. */
8438 /* Non-zero if the overlay is currently mapped;
8440 unsigned long mapped;
8444 @item @code{_novlys}:
8445 This variable must be a four-byte signed integer, holding the total
8446 number of elements in @code{_ovly_table}.
8450 To decide whether a particular overlay is mapped or not, @value{GDBN}
8451 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8452 @code{lma} members equal the VMA and LMA of the overlay's section in the
8453 executable file. When @value{GDBN} finds a matching entry, it consults
8454 the entry's @code{mapped} member to determine whether the overlay is
8457 In addition, your overlay manager may define a function called
8458 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8459 will silently set a breakpoint there. If the overlay manager then
8460 calls this function whenever it has changed the overlay table, this
8461 will enable @value{GDBN} to accurately keep track of which overlays
8462 are in program memory, and update any breakpoints that may be set
8463 in overlays. This will allow breakpoints to work even if the
8464 overlays are kept in ROM or other non-writable memory while they
8465 are not being executed.
8467 @node Overlay Sample Program
8468 @section Overlay Sample Program
8469 @cindex overlay example program
8471 When linking a program which uses overlays, you must place the overlays
8472 at their load addresses, while relocating them to run at their mapped
8473 addresses. To do this, you must write a linker script (@pxref{Overlay
8474 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8475 since linker scripts are specific to a particular host system, target
8476 architecture, and target memory layout, this manual cannot provide
8477 portable sample code demonstrating @value{GDBN}'s overlay support.
8479 However, the @value{GDBN} source distribution does contain an overlaid
8480 program, with linker scripts for a few systems, as part of its test
8481 suite. The program consists of the following files from
8482 @file{gdb/testsuite/gdb.base}:
8486 The main program file.
8488 A simple overlay manager, used by @file{overlays.c}.
8493 Overlay modules, loaded and used by @file{overlays.c}.
8496 Linker scripts for linking the test program on the @code{d10v-elf}
8497 and @code{m32r-elf} targets.
8500 You can build the test program using the @code{d10v-elf} GCC
8501 cross-compiler like this:
8504 $ d10v-elf-gcc -g -c overlays.c
8505 $ d10v-elf-gcc -g -c ovlymgr.c
8506 $ d10v-elf-gcc -g -c foo.c
8507 $ d10v-elf-gcc -g -c bar.c
8508 $ d10v-elf-gcc -g -c baz.c
8509 $ d10v-elf-gcc -g -c grbx.c
8510 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8511 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8514 The build process is identical for any other architecture, except that
8515 you must substitute the appropriate compiler and linker script for the
8516 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8520 @chapter Using @value{GDBN} with Different Languages
8523 Although programming languages generally have common aspects, they are
8524 rarely expressed in the same manner. For instance, in ANSI C,
8525 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8526 Modula-2, it is accomplished by @code{p^}. Values can also be
8527 represented (and displayed) differently. Hex numbers in C appear as
8528 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8530 @cindex working language
8531 Language-specific information is built into @value{GDBN} for some languages,
8532 allowing you to express operations like the above in your program's
8533 native language, and allowing @value{GDBN} to output values in a manner
8534 consistent with the syntax of your program's native language. The
8535 language you use to build expressions is called the @dfn{working
8539 * Setting:: Switching between source languages
8540 * Show:: Displaying the language
8541 * Checks:: Type and range checks
8542 * Supported languages:: Supported languages
8543 * Unsupported languages:: Unsupported languages
8547 @section Switching between source languages
8549 There are two ways to control the working language---either have @value{GDBN}
8550 set it automatically, or select it manually yourself. You can use the
8551 @code{set language} command for either purpose. On startup, @value{GDBN}
8552 defaults to setting the language automatically. The working language is
8553 used to determine how expressions you type are interpreted, how values
8556 In addition to the working language, every source file that
8557 @value{GDBN} knows about has its own working language. For some object
8558 file formats, the compiler might indicate which language a particular
8559 source file is in. However, most of the time @value{GDBN} infers the
8560 language from the name of the file. The language of a source file
8561 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8562 show each frame appropriately for its own language. There is no way to
8563 set the language of a source file from within @value{GDBN}, but you can
8564 set the language associated with a filename extension. @xref{Show, ,
8565 Displaying the language}.
8567 This is most commonly a problem when you use a program, such
8568 as @code{cfront} or @code{f2c}, that generates C but is written in
8569 another language. In that case, make the
8570 program use @code{#line} directives in its C output; that way
8571 @value{GDBN} will know the correct language of the source code of the original
8572 program, and will display that source code, not the generated C code.
8575 * Filenames:: Filename extensions and languages.
8576 * Manually:: Setting the working language manually
8577 * Automatically:: Having @value{GDBN} infer the source language
8581 @subsection List of filename extensions and languages
8583 If a source file name ends in one of the following extensions, then
8584 @value{GDBN} infers that its language is the one indicated.
8605 Objective-C source file
8612 Modula-2 source file
8616 Assembler source file. This actually behaves almost like C, but
8617 @value{GDBN} does not skip over function prologues when stepping.
8620 In addition, you may set the language associated with a filename
8621 extension. @xref{Show, , Displaying the language}.
8624 @subsection Setting the working language
8626 If you allow @value{GDBN} to set the language automatically,
8627 expressions are interpreted the same way in your debugging session and
8630 @kindex set language
8631 If you wish, you may set the language manually. To do this, issue the
8632 command @samp{set language @var{lang}}, where @var{lang} is the name of
8634 @code{c} or @code{modula-2}.
8635 For a list of the supported languages, type @samp{set language}.
8637 Setting the language manually prevents @value{GDBN} from updating the working
8638 language automatically. This can lead to confusion if you try
8639 to debug a program when the working language is not the same as the
8640 source language, when an expression is acceptable to both
8641 languages---but means different things. For instance, if the current
8642 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8650 might not have the effect you intended. In C, this means to add
8651 @code{b} and @code{c} and place the result in @code{a}. The result
8652 printed would be the value of @code{a}. In Modula-2, this means to compare
8653 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8656 @subsection Having @value{GDBN} infer the source language
8658 To have @value{GDBN} set the working language automatically, use
8659 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8660 then infers the working language. That is, when your program stops in a
8661 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8662 working language to the language recorded for the function in that
8663 frame. If the language for a frame is unknown (that is, if the function
8664 or block corresponding to the frame was defined in a source file that
8665 does not have a recognized extension), the current working language is
8666 not changed, and @value{GDBN} issues a warning.
8668 This may not seem necessary for most programs, which are written
8669 entirely in one source language. However, program modules and libraries
8670 written in one source language can be used by a main program written in
8671 a different source language. Using @samp{set language auto} in this
8672 case frees you from having to set the working language manually.
8675 @section Displaying the language
8677 The following commands help you find out which language is the
8678 working language, and also what language source files were written in.
8682 @kindex show language
8683 Display the current working language. This is the
8684 language you can use with commands such as @code{print} to
8685 build and compute expressions that may involve variables in your program.
8688 @kindex info frame@r{, show the source language}
8689 Display the source language for this frame. This language becomes the
8690 working language if you use an identifier from this frame.
8691 @xref{Frame Info, ,Information about a frame}, to identify the other
8692 information listed here.
8695 @kindex info source@r{, show the source language}
8696 Display the source language of this source file.
8697 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8698 information listed here.
8701 In unusual circumstances, you may have source files with extensions
8702 not in the standard list. You can then set the extension associated
8703 with a language explicitly:
8706 @item set extension-language @var{ext} @var{language}
8707 @kindex set extension-language
8708 Tell @value{GDBN} that source files with extension @var{ext} are to be
8709 assumed as written in the source language @var{language}.
8711 @item info extensions
8712 @kindex info extensions
8713 List all the filename extensions and the associated languages.
8717 @section Type and range checking
8720 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8721 checking are included, but they do not yet have any effect. This
8722 section documents the intended facilities.
8724 @c FIXME remove warning when type/range code added
8726 Some languages are designed to guard you against making seemingly common
8727 errors through a series of compile- and run-time checks. These include
8728 checking the type of arguments to functions and operators, and making
8729 sure mathematical overflows are caught at run time. Checks such as
8730 these help to ensure a program's correctness once it has been compiled
8731 by eliminating type mismatches, and providing active checks for range
8732 errors when your program is running.
8734 @value{GDBN} can check for conditions like the above if you wish.
8735 Although @value{GDBN} does not check the statements in your program,
8736 it can check expressions entered directly into @value{GDBN} for
8737 evaluation via the @code{print} command, for example. As with the
8738 working language, @value{GDBN} can also decide whether or not to check
8739 automatically based on your program's source language.
8740 @xref{Supported languages, ,Supported languages}, for the default
8741 settings of supported languages.
8744 * Type Checking:: An overview of type checking
8745 * Range Checking:: An overview of range checking
8748 @cindex type checking
8749 @cindex checks, type
8751 @subsection An overview of type checking
8753 Some languages, such as Modula-2, are strongly typed, meaning that the
8754 arguments to operators and functions have to be of the correct type,
8755 otherwise an error occurs. These checks prevent type mismatch
8756 errors from ever causing any run-time problems. For example,
8764 The second example fails because the @code{CARDINAL} 1 is not
8765 type-compatible with the @code{REAL} 2.3.
8767 For the expressions you use in @value{GDBN} commands, you can tell the
8768 @value{GDBN} type checker to skip checking;
8769 to treat any mismatches as errors and abandon the expression;
8770 or to only issue warnings when type mismatches occur,
8771 but evaluate the expression anyway. When you choose the last of
8772 these, @value{GDBN} evaluates expressions like the second example above, but
8773 also issues a warning.
8775 Even if you turn type checking off, there may be other reasons
8776 related to type that prevent @value{GDBN} from evaluating an expression.
8777 For instance, @value{GDBN} does not know how to add an @code{int} and
8778 a @code{struct foo}. These particular type errors have nothing to do
8779 with the language in use, and usually arise from expressions, such as
8780 the one described above, which make little sense to evaluate anyway.
8782 Each language defines to what degree it is strict about type. For
8783 instance, both Modula-2 and C require the arguments to arithmetical
8784 operators to be numbers. In C, enumerated types and pointers can be
8785 represented as numbers, so that they are valid arguments to mathematical
8786 operators. @xref{Supported languages, ,Supported languages}, for further
8787 details on specific languages.
8789 @value{GDBN} provides some additional commands for controlling the type checker:
8791 @kindex set check type
8792 @kindex show check type
8794 @item set check type auto
8795 Set type checking on or off based on the current working language.
8796 @xref{Supported languages, ,Supported languages}, for the default settings for
8799 @item set check type on
8800 @itemx set check type off
8801 Set type checking on or off, overriding the default setting for the
8802 current working language. Issue a warning if the setting does not
8803 match the language default. If any type mismatches occur in
8804 evaluating an expression while type checking is on, @value{GDBN} prints a
8805 message and aborts evaluation of the expression.
8807 @item set check type warn
8808 Cause the type checker to issue warnings, but to always attempt to
8809 evaluate the expression. Evaluating the expression may still
8810 be impossible for other reasons. For example, @value{GDBN} cannot add
8811 numbers and structures.
8814 Show the current setting of the type checker, and whether or not @value{GDBN}
8815 is setting it automatically.
8818 @cindex range checking
8819 @cindex checks, range
8820 @node Range Checking
8821 @subsection An overview of range checking
8823 In some languages (such as Modula-2), it is an error to exceed the
8824 bounds of a type; this is enforced with run-time checks. Such range
8825 checking is meant to ensure program correctness by making sure
8826 computations do not overflow, or indices on an array element access do
8827 not exceed the bounds of the array.
8829 For expressions you use in @value{GDBN} commands, you can tell
8830 @value{GDBN} to treat range errors in one of three ways: ignore them,
8831 always treat them as errors and abandon the expression, or issue
8832 warnings but evaluate the expression anyway.
8834 A range error can result from numerical overflow, from exceeding an
8835 array index bound, or when you type a constant that is not a member
8836 of any type. Some languages, however, do not treat overflows as an
8837 error. In many implementations of C, mathematical overflow causes the
8838 result to ``wrap around'' to lower values---for example, if @var{m} is
8839 the largest integer value, and @var{s} is the smallest, then
8842 @var{m} + 1 @result{} @var{s}
8845 This, too, is specific to individual languages, and in some cases
8846 specific to individual compilers or machines. @xref{Supported languages, ,
8847 Supported languages}, for further details on specific languages.
8849 @value{GDBN} provides some additional commands for controlling the range checker:
8851 @kindex set check range
8852 @kindex show check range
8854 @item set check range auto
8855 Set range checking on or off based on the current working language.
8856 @xref{Supported languages, ,Supported languages}, for the default settings for
8859 @item set check range on
8860 @itemx set check range off
8861 Set range checking on or off, overriding the default setting for the
8862 current working language. A warning is issued if the setting does not
8863 match the language default. If a range error occurs and range checking is on,
8864 then a message is printed and evaluation of the expression is aborted.
8866 @item set check range warn
8867 Output messages when the @value{GDBN} range checker detects a range error,
8868 but attempt to evaluate the expression anyway. Evaluating the
8869 expression may still be impossible for other reasons, such as accessing
8870 memory that the process does not own (a typical example from many Unix
8874 Show the current setting of the range checker, and whether or not it is
8875 being set automatically by @value{GDBN}.
8878 @node Supported languages
8879 @section Supported languages
8881 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8882 assembly, Modula-2, and Ada.
8883 @c This is false ...
8884 Some @value{GDBN} features may be used in expressions regardless of the
8885 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8886 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8887 ,Expressions}) can be used with the constructs of any supported
8890 The following sections detail to what degree each source language is
8891 supported by @value{GDBN}. These sections are not meant to be language
8892 tutorials or references, but serve only as a reference guide to what the
8893 @value{GDBN} expression parser accepts, and what input and output
8894 formats should look like for different languages. There are many good
8895 books written on each of these languages; please look to these for a
8896 language reference or tutorial.
8900 * Objective-C:: Objective-C
8903 * Modula-2:: Modula-2
8908 @subsection C and C@t{++}
8910 @cindex C and C@t{++}
8911 @cindex expressions in C or C@t{++}
8913 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8914 to both languages. Whenever this is the case, we discuss those languages
8918 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8919 @cindex @sc{gnu} C@t{++}
8920 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8921 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8922 effectively, you must compile your C@t{++} programs with a supported
8923 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8924 compiler (@code{aCC}).
8926 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8927 format; if it doesn't work on your system, try the stabs+ debugging
8928 format. You can select those formats explicitly with the @code{g++}
8929 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8930 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8931 CC, gcc.info, Using @sc{gnu} CC}.
8934 * C Operators:: C and C@t{++} operators
8935 * C Constants:: C and C@t{++} constants
8936 * C plus plus expressions:: C@t{++} expressions
8937 * C Defaults:: Default settings for C and C@t{++}
8938 * C Checks:: C and C@t{++} type and range checks
8939 * Debugging C:: @value{GDBN} and C
8940 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8944 @subsubsection C and C@t{++} operators
8946 @cindex C and C@t{++} operators
8948 Operators must be defined on values of specific types. For instance,
8949 @code{+} is defined on numbers, but not on structures. Operators are
8950 often defined on groups of types.
8952 For the purposes of C and C@t{++}, the following definitions hold:
8957 @emph{Integral types} include @code{int} with any of its storage-class
8958 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8961 @emph{Floating-point types} include @code{float}, @code{double}, and
8962 @code{long double} (if supported by the target platform).
8965 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8968 @emph{Scalar types} include all of the above.
8973 The following operators are supported. They are listed here
8974 in order of increasing precedence:
8978 The comma or sequencing operator. Expressions in a comma-separated list
8979 are evaluated from left to right, with the result of the entire
8980 expression being the last expression evaluated.
8983 Assignment. The value of an assignment expression is the value
8984 assigned. Defined on scalar types.
8987 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8988 and translated to @w{@code{@var{a} = @var{a op b}}}.
8989 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8990 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8991 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8994 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8995 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8999 Logical @sc{or}. Defined on integral types.
9002 Logical @sc{and}. Defined on integral types.
9005 Bitwise @sc{or}. Defined on integral types.
9008 Bitwise exclusive-@sc{or}. Defined on integral types.
9011 Bitwise @sc{and}. Defined on integral types.
9014 Equality and inequality. Defined on scalar types. The value of these
9015 expressions is 0 for false and non-zero for true.
9017 @item <@r{, }>@r{, }<=@r{, }>=
9018 Less than, greater than, less than or equal, greater than or equal.
9019 Defined on scalar types. The value of these expressions is 0 for false
9020 and non-zero for true.
9023 left shift, and right shift. Defined on integral types.
9026 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9029 Addition and subtraction. Defined on integral types, floating-point types and
9032 @item *@r{, }/@r{, }%
9033 Multiplication, division, and modulus. Multiplication and division are
9034 defined on integral and floating-point types. Modulus is defined on
9038 Increment and decrement. When appearing before a variable, the
9039 operation is performed before the variable is used in an expression;
9040 when appearing after it, the variable's value is used before the
9041 operation takes place.
9044 Pointer dereferencing. Defined on pointer types. Same precedence as
9048 Address operator. Defined on variables. Same precedence as @code{++}.
9050 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9051 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9052 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9053 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9057 Negative. Defined on integral and floating-point types. Same
9058 precedence as @code{++}.
9061 Logical negation. Defined on integral types. Same precedence as
9065 Bitwise complement operator. Defined on integral types. Same precedence as
9070 Structure member, and pointer-to-structure member. For convenience,
9071 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9072 pointer based on the stored type information.
9073 Defined on @code{struct} and @code{union} data.
9076 Dereferences of pointers to members.
9079 Array indexing. @code{@var{a}[@var{i}]} is defined as
9080 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9083 Function parameter list. Same precedence as @code{->}.
9086 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9087 and @code{class} types.
9090 Doubled colons also represent the @value{GDBN} scope operator
9091 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9095 If an operator is redefined in the user code, @value{GDBN} usually
9096 attempts to invoke the redefined version instead of using the operator's
9104 @subsubsection C and C@t{++} constants
9106 @cindex C and C@t{++} constants
9108 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9113 Integer constants are a sequence of digits. Octal constants are
9114 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9115 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9116 @samp{l}, specifying that the constant should be treated as a
9120 Floating point constants are a sequence of digits, followed by a decimal
9121 point, followed by a sequence of digits, and optionally followed by an
9122 exponent. An exponent is of the form:
9123 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9124 sequence of digits. The @samp{+} is optional for positive exponents.
9125 A floating-point constant may also end with a letter @samp{f} or
9126 @samp{F}, specifying that the constant should be treated as being of
9127 the @code{float} (as opposed to the default @code{double}) type; or with
9128 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9132 Enumerated constants consist of enumerated identifiers, or their
9133 integral equivalents.
9136 Character constants are a single character surrounded by single quotes
9137 (@code{'}), or a number---the ordinal value of the corresponding character
9138 (usually its @sc{ascii} value). Within quotes, the single character may
9139 be represented by a letter or by @dfn{escape sequences}, which are of
9140 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9141 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9142 @samp{@var{x}} is a predefined special character---for example,
9143 @samp{\n} for newline.
9146 String constants are a sequence of character constants surrounded by
9147 double quotes (@code{"}). Any valid character constant (as described
9148 above) may appear. Double quotes within the string must be preceded by
9149 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9153 Pointer constants are an integral value. You can also write pointers
9154 to constants using the C operator @samp{&}.
9157 Array constants are comma-separated lists surrounded by braces @samp{@{}
9158 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9159 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9160 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9164 * C plus plus expressions::
9171 @node C plus plus expressions
9172 @subsubsection C@t{++} expressions
9174 @cindex expressions in C@t{++}
9175 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9177 @cindex debugging C@t{++} programs
9178 @cindex C@t{++} compilers
9179 @cindex debug formats and C@t{++}
9180 @cindex @value{NGCC} and C@t{++}
9182 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9183 proper compiler and the proper debug format. Currently, @value{GDBN}
9184 works best when debugging C@t{++} code that is compiled with
9185 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9186 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9187 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9188 stabs+ as their default debug format, so you usually don't need to
9189 specify a debug format explicitly. Other compilers and/or debug formats
9190 are likely to work badly or not at all when using @value{GDBN} to debug
9196 @cindex member functions
9198 Member function calls are allowed; you can use expressions like
9201 count = aml->GetOriginal(x, y)
9204 @vindex this@r{, inside C@t{++} member functions}
9205 @cindex namespace in C@t{++}
9207 While a member function is active (in the selected stack frame), your
9208 expressions have the same namespace available as the member function;
9209 that is, @value{GDBN} allows implicit references to the class instance
9210 pointer @code{this} following the same rules as C@t{++}.
9212 @cindex call overloaded functions
9213 @cindex overloaded functions, calling
9214 @cindex type conversions in C@t{++}
9216 You can call overloaded functions; @value{GDBN} resolves the function
9217 call to the right definition, with some restrictions. @value{GDBN} does not
9218 perform overload resolution involving user-defined type conversions,
9219 calls to constructors, or instantiations of templates that do not exist
9220 in the program. It also cannot handle ellipsis argument lists or
9223 It does perform integral conversions and promotions, floating-point
9224 promotions, arithmetic conversions, pointer conversions, conversions of
9225 class objects to base classes, and standard conversions such as those of
9226 functions or arrays to pointers; it requires an exact match on the
9227 number of function arguments.
9229 Overload resolution is always performed, unless you have specified
9230 @code{set overload-resolution off}. @xref{Debugging C plus plus,
9231 ,@value{GDBN} features for C@t{++}}.
9233 You must specify @code{set overload-resolution off} in order to use an
9234 explicit function signature to call an overloaded function, as in
9236 p 'foo(char,int)'('x', 13)
9239 The @value{GDBN} command-completion facility can simplify this;
9240 see @ref{Completion, ,Command completion}.
9242 @cindex reference declarations
9244 @value{GDBN} understands variables declared as C@t{++} references; you can use
9245 them in expressions just as you do in C@t{++} source---they are automatically
9248 In the parameter list shown when @value{GDBN} displays a frame, the values of
9249 reference variables are not displayed (unlike other variables); this
9250 avoids clutter, since references are often used for large structures.
9251 The @emph{address} of a reference variable is always shown, unless
9252 you have specified @samp{set print address off}.
9255 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9256 expressions can use it just as expressions in your program do. Since
9257 one scope may be defined in another, you can use @code{::} repeatedly if
9258 necessary, for example in an expression like
9259 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9260 resolving name scope by reference to source files, in both C and C@t{++}
9261 debugging (@pxref{Variables, ,Program variables}).
9264 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9265 calling virtual functions correctly, printing out virtual bases of
9266 objects, calling functions in a base subobject, casting objects, and
9267 invoking user-defined operators.
9270 @subsubsection C and C@t{++} defaults
9272 @cindex C and C@t{++} defaults
9274 If you allow @value{GDBN} to set type and range checking automatically, they
9275 both default to @code{off} whenever the working language changes to
9276 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9277 selects the working language.
9279 If you allow @value{GDBN} to set the language automatically, it
9280 recognizes source files whose names end with @file{.c}, @file{.C}, or
9281 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9282 these files, it sets the working language to C or C@t{++}.
9283 @xref{Automatically, ,Having @value{GDBN} infer the source language},
9284 for further details.
9286 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9287 @c unimplemented. If (b) changes, it might make sense to let this node
9288 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9291 @subsubsection C and C@t{++} type and range checks
9293 @cindex C and C@t{++} checks
9295 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9296 is not used. However, if you turn type checking on, @value{GDBN}
9297 considers two variables type equivalent if:
9301 The two variables are structured and have the same structure, union, or
9305 The two variables have the same type name, or types that have been
9306 declared equivalent through @code{typedef}.
9309 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9312 The two @code{struct}, @code{union}, or @code{enum} variables are
9313 declared in the same declaration. (Note: this may not be true for all C
9318 Range checking, if turned on, is done on mathematical operations. Array
9319 indices are not checked, since they are often used to index a pointer
9320 that is not itself an array.
9323 @subsubsection @value{GDBN} and C
9325 The @code{set print union} and @code{show print union} commands apply to
9326 the @code{union} type. When set to @samp{on}, any @code{union} that is
9327 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9328 appears as @samp{@{...@}}.
9330 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9331 with pointers and a memory allocation function. @xref{Expressions,
9335 * Debugging C plus plus::
9338 @node Debugging C plus plus
9339 @subsubsection @value{GDBN} features for C@t{++}
9341 @cindex commands for C@t{++}
9343 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9344 designed specifically for use with C@t{++}. Here is a summary:
9347 @cindex break in overloaded functions
9348 @item @r{breakpoint menus}
9349 When you want a breakpoint in a function whose name is overloaded,
9350 @value{GDBN} breakpoint menus help you specify which function definition
9351 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
9353 @cindex overloading in C@t{++}
9354 @item rbreak @var{regex}
9355 Setting breakpoints using regular expressions is helpful for setting
9356 breakpoints on overloaded functions that are not members of any special
9358 @xref{Set Breaks, ,Setting breakpoints}.
9360 @cindex C@t{++} exception handling
9363 Debug C@t{++} exception handling using these commands. @xref{Set
9364 Catchpoints, , Setting catchpoints}.
9367 @item ptype @var{typename}
9368 Print inheritance relationships as well as other information for type
9370 @xref{Symbols, ,Examining the Symbol Table}.
9372 @cindex C@t{++} symbol display
9373 @item set print demangle
9374 @itemx show print demangle
9375 @itemx set print asm-demangle
9376 @itemx show print asm-demangle
9377 Control whether C@t{++} symbols display in their source form, both when
9378 displaying code as C@t{++} source and when displaying disassemblies.
9379 @xref{Print Settings, ,Print settings}.
9381 @item set print object
9382 @itemx show print object
9383 Choose whether to print derived (actual) or declared types of objects.
9384 @xref{Print Settings, ,Print settings}.
9386 @item set print vtbl
9387 @itemx show print vtbl
9388 Control the format for printing virtual function tables.
9389 @xref{Print Settings, ,Print settings}.
9390 (The @code{vtbl} commands do not work on programs compiled with the HP
9391 ANSI C@t{++} compiler (@code{aCC}).)
9393 @kindex set overload-resolution
9394 @cindex overloaded functions, overload resolution
9395 @item set overload-resolution on
9396 Enable overload resolution for C@t{++} expression evaluation. The default
9397 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9398 and searches for a function whose signature matches the argument types,
9399 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9400 expressions}, for details). If it cannot find a match, it emits a
9403 @item set overload-resolution off
9404 Disable overload resolution for C@t{++} expression evaluation. For
9405 overloaded functions that are not class member functions, @value{GDBN}
9406 chooses the first function of the specified name that it finds in the
9407 symbol table, whether or not its arguments are of the correct type. For
9408 overloaded functions that are class member functions, @value{GDBN}
9409 searches for a function whose signature @emph{exactly} matches the
9412 @kindex show overload-resolution
9413 @item show overload-resolution
9414 Show the current setting of overload resolution.
9416 @item @r{Overloaded symbol names}
9417 You can specify a particular definition of an overloaded symbol, using
9418 the same notation that is used to declare such symbols in C@t{++}: type
9419 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9420 also use the @value{GDBN} command-line word completion facilities to list the
9421 available choices, or to finish the type list for you.
9422 @xref{Completion,, Command completion}, for details on how to do this.
9426 @subsection Objective-C
9429 This section provides information about some commands and command
9430 options that are useful for debugging Objective-C code. See also
9431 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9432 few more commands specific to Objective-C support.
9435 * Method Names in Commands::
9436 * The Print Command with Objective-C::
9439 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
9440 @subsubsection Method Names in Commands
9442 The following commands have been extended to accept Objective-C method
9443 names as line specifications:
9445 @kindex clear@r{, and Objective-C}
9446 @kindex break@r{, and Objective-C}
9447 @kindex info line@r{, and Objective-C}
9448 @kindex jump@r{, and Objective-C}
9449 @kindex list@r{, and Objective-C}
9453 @item @code{info line}
9458 A fully qualified Objective-C method name is specified as
9461 -[@var{Class} @var{methodName}]
9464 where the minus sign is used to indicate an instance method and a
9465 plus sign (not shown) is used to indicate a class method. The class
9466 name @var{Class} and method name @var{methodName} are enclosed in
9467 brackets, similar to the way messages are specified in Objective-C
9468 source code. For example, to set a breakpoint at the @code{create}
9469 instance method of class @code{Fruit} in the program currently being
9473 break -[Fruit create]
9476 To list ten program lines around the @code{initialize} class method,
9480 list +[NSText initialize]
9483 In the current version of @value{GDBN}, the plus or minus sign is
9484 required. In future versions of @value{GDBN}, the plus or minus
9485 sign will be optional, but you can use it to narrow the search. It
9486 is also possible to specify just a method name:
9492 You must specify the complete method name, including any colons. If
9493 your program's source files contain more than one @code{create} method,
9494 you'll be presented with a numbered list of classes that implement that
9495 method. Indicate your choice by number, or type @samp{0} to exit if
9498 As another example, to clear a breakpoint established at the
9499 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9502 clear -[NSWindow makeKeyAndOrderFront:]
9505 @node The Print Command with Objective-C
9506 @subsubsection The Print Command With Objective-C
9507 @cindex Objective-C, print objects
9508 @kindex print-object
9509 @kindex po @r{(@code{print-object})}
9511 The print command has also been extended to accept methods. For example:
9514 print -[@var{object} hash]
9517 @cindex print an Objective-C object description
9518 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9520 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9521 and print the result. Also, an additional command has been added,
9522 @code{print-object} or @code{po} for short, which is meant to print
9523 the description of an object. However, this command may only work
9524 with certain Objective-C libraries that have a particular hook
9525 function, @code{_NSPrintForDebugger}, defined.
9529 @cindex Fortran-specific support in @value{GDBN}
9531 @value{GDBN} can be used to debug programs written in Fortran, but it
9532 currently supports only the features of Fortran 77 language.
9534 @cindex trailing underscore, in Fortran symbols
9535 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9536 among them) append an underscore to the names of variables and
9537 functions. When you debug programs compiled by those compilers, you
9538 will need to refer to variables and functions with a trailing
9542 * Fortran Operators:: Fortran operators and expressions
9543 * Fortran Defaults:: Default settings for Fortran
9544 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9547 @node Fortran Operators
9548 @subsubsection Fortran operators and expressions
9550 @cindex Fortran operators and expressions
9552 Operators must be defined on values of specific types. For instance,
9553 @code{+} is defined on numbers, but not on characters or other non-
9554 arithmetic types. Operators are often defined on groups of types.
9558 The exponentiation operator. It raises the first operand to the power
9562 The range operator. Normally used in the form of array(low:high) to
9563 represent a section of array.
9566 @node Fortran Defaults
9567 @subsubsection Fortran Defaults
9569 @cindex Fortran Defaults
9571 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9572 default uses case-insensitive matches for Fortran symbols. You can
9573 change that with the @samp{set case-insensitive} command, see
9574 @ref{Symbols}, for the details.
9576 @node Special Fortran commands
9577 @subsubsection Special Fortran commands
9579 @cindex Special Fortran commands
9581 @value{GDBN} had some commands to support Fortran specific feature,
9582 such as common block displaying.
9585 @cindex @code{COMMON} blocks, Fortran
9587 @item info common @r{[}@var{common-name}@r{]}
9588 This command prints the values contained in the Fortran @code{COMMON}
9589 block whose name is @var{common-name}. With no argument, the names of
9590 all @code{COMMON} blocks visible at current program location are
9597 @cindex Pascal support in @value{GDBN}, limitations
9598 Debugging Pascal programs which use sets, subranges, file variables, or
9599 nested functions does not currently work. @value{GDBN} does not support
9600 entering expressions, printing values, or similar features using Pascal
9603 The Pascal-specific command @code{set print pascal_static-members}
9604 controls whether static members of Pascal objects are displayed.
9605 @xref{Print Settings, pascal_static-members}.
9608 @subsection Modula-2
9610 @cindex Modula-2, @value{GDBN} support
9612 The extensions made to @value{GDBN} to support Modula-2 only support
9613 output from the @sc{gnu} Modula-2 compiler (which is currently being
9614 developed). Other Modula-2 compilers are not currently supported, and
9615 attempting to debug executables produced by them is most likely
9616 to give an error as @value{GDBN} reads in the executable's symbol
9619 @cindex expressions in Modula-2
9621 * M2 Operators:: Built-in operators
9622 * Built-In Func/Proc:: Built-in functions and procedures
9623 * M2 Constants:: Modula-2 constants
9624 * M2 Types:: Modula-2 types
9625 * M2 Defaults:: Default settings for Modula-2
9626 * Deviations:: Deviations from standard Modula-2
9627 * M2 Checks:: Modula-2 type and range checks
9628 * M2 Scope:: The scope operators @code{::} and @code{.}
9629 * GDB/M2:: @value{GDBN} and Modula-2
9633 @subsubsection Operators
9634 @cindex Modula-2 operators
9636 Operators must be defined on values of specific types. For instance,
9637 @code{+} is defined on numbers, but not on structures. Operators are
9638 often defined on groups of types. For the purposes of Modula-2, the
9639 following definitions hold:
9644 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9648 @emph{Character types} consist of @code{CHAR} and its subranges.
9651 @emph{Floating-point types} consist of @code{REAL}.
9654 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9658 @emph{Scalar types} consist of all of the above.
9661 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9664 @emph{Boolean types} consist of @code{BOOLEAN}.
9668 The following operators are supported, and appear in order of
9669 increasing precedence:
9673 Function argument or array index separator.
9676 Assignment. The value of @var{var} @code{:=} @var{value} is
9680 Less than, greater than on integral, floating-point, or enumerated
9684 Less than or equal to, greater than or equal to
9685 on integral, floating-point and enumerated types, or set inclusion on
9686 set types. Same precedence as @code{<}.
9688 @item =@r{, }<>@r{, }#
9689 Equality and two ways of expressing inequality, valid on scalar types.
9690 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9691 available for inequality, since @code{#} conflicts with the script
9695 Set membership. Defined on set types and the types of their members.
9696 Same precedence as @code{<}.
9699 Boolean disjunction. Defined on boolean types.
9702 Boolean conjunction. Defined on boolean types.
9705 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9708 Addition and subtraction on integral and floating-point types, or union
9709 and difference on set types.
9712 Multiplication on integral and floating-point types, or set intersection
9716 Division on floating-point types, or symmetric set difference on set
9717 types. Same precedence as @code{*}.
9720 Integer division and remainder. Defined on integral types. Same
9721 precedence as @code{*}.
9724 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9727 Pointer dereferencing. Defined on pointer types.
9730 Boolean negation. Defined on boolean types. Same precedence as
9734 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9735 precedence as @code{^}.
9738 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9741 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9745 @value{GDBN} and Modula-2 scope operators.
9749 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9750 treats the use of the operator @code{IN}, or the use of operators
9751 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9752 @code{<=}, and @code{>=} on sets as an error.
9756 @node Built-In Func/Proc
9757 @subsubsection Built-in functions and procedures
9758 @cindex Modula-2 built-ins
9760 Modula-2 also makes available several built-in procedures and functions.
9761 In describing these, the following metavariables are used:
9766 represents an @code{ARRAY} variable.
9769 represents a @code{CHAR} constant or variable.
9772 represents a variable or constant of integral type.
9775 represents an identifier that belongs to a set. Generally used in the
9776 same function with the metavariable @var{s}. The type of @var{s} should
9777 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9780 represents a variable or constant of integral or floating-point type.
9783 represents a variable or constant of floating-point type.
9789 represents a variable.
9792 represents a variable or constant of one of many types. See the
9793 explanation of the function for details.
9796 All Modula-2 built-in procedures also return a result, described below.
9800 Returns the absolute value of @var{n}.
9803 If @var{c} is a lower case letter, it returns its upper case
9804 equivalent, otherwise it returns its argument.
9807 Returns the character whose ordinal value is @var{i}.
9810 Decrements the value in the variable @var{v} by one. Returns the new value.
9812 @item DEC(@var{v},@var{i})
9813 Decrements the value in the variable @var{v} by @var{i}. Returns the
9816 @item EXCL(@var{m},@var{s})
9817 Removes the element @var{m} from the set @var{s}. Returns the new
9820 @item FLOAT(@var{i})
9821 Returns the floating point equivalent of the integer @var{i}.
9824 Returns the index of the last member of @var{a}.
9827 Increments the value in the variable @var{v} by one. Returns the new value.
9829 @item INC(@var{v},@var{i})
9830 Increments the value in the variable @var{v} by @var{i}. Returns the
9833 @item INCL(@var{m},@var{s})
9834 Adds the element @var{m} to the set @var{s} if it is not already
9835 there. Returns the new set.
9838 Returns the maximum value of the type @var{t}.
9841 Returns the minimum value of the type @var{t}.
9844 Returns boolean TRUE if @var{i} is an odd number.
9847 Returns the ordinal value of its argument. For example, the ordinal
9848 value of a character is its @sc{ascii} value (on machines supporting the
9849 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9850 integral, character and enumerated types.
9853 Returns the size of its argument. @var{x} can be a variable or a type.
9855 @item TRUNC(@var{r})
9856 Returns the integral part of @var{r}.
9858 @item VAL(@var{t},@var{i})
9859 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9863 @emph{Warning:} Sets and their operations are not yet supported, so
9864 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9868 @cindex Modula-2 constants
9870 @subsubsection Constants
9872 @value{GDBN} allows you to express the constants of Modula-2 in the following
9878 Integer constants are simply a sequence of digits. When used in an
9879 expression, a constant is interpreted to be type-compatible with the
9880 rest of the expression. Hexadecimal integers are specified by a
9881 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9884 Floating point constants appear as a sequence of digits, followed by a
9885 decimal point and another sequence of digits. An optional exponent can
9886 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9887 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9888 digits of the floating point constant must be valid decimal (base 10)
9892 Character constants consist of a single character enclosed by a pair of
9893 like quotes, either single (@code{'}) or double (@code{"}). They may
9894 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9895 followed by a @samp{C}.
9898 String constants consist of a sequence of characters enclosed by a
9899 pair of like quotes, either single (@code{'}) or double (@code{"}).
9900 Escape sequences in the style of C are also allowed. @xref{C
9901 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9905 Enumerated constants consist of an enumerated identifier.
9908 Boolean constants consist of the identifiers @code{TRUE} and
9912 Pointer constants consist of integral values only.
9915 Set constants are not yet supported.
9919 @subsubsection Modula-2 Types
9920 @cindex Modula-2 types
9922 Currently @value{GDBN} can print the following data types in Modula-2
9923 syntax: array types, record types, set types, pointer types, procedure
9924 types, enumerated types, subrange types and base types. You can also
9925 print the contents of variables declared using these type.
9926 This section gives a number of simple source code examples together with
9927 sample @value{GDBN} sessions.
9929 The first example contains the following section of code:
9938 and you can request @value{GDBN} to interrogate the type and value of
9939 @code{r} and @code{s}.
9942 (@value{GDBP}) print s
9944 (@value{GDBP}) ptype s
9946 (@value{GDBP}) print r
9948 (@value{GDBP}) ptype r
9953 Likewise if your source code declares @code{s} as:
9961 then you may query the type of @code{s} by:
9964 (@value{GDBP}) ptype s
9965 type = SET ['A'..'Z']
9969 Note that at present you cannot interactively manipulate set
9970 expressions using the debugger.
9972 The following example shows how you might declare an array in Modula-2
9973 and how you can interact with @value{GDBN} to print its type and contents:
9977 s: ARRAY [-10..10] OF CHAR ;
9981 (@value{GDBP}) ptype s
9982 ARRAY [-10..10] OF CHAR
9985 Note that the array handling is not yet complete and although the type
9986 is printed correctly, expression handling still assumes that all
9987 arrays have a lower bound of zero and not @code{-10} as in the example
9988 above. Unbounded arrays are also not yet recognized in @value{GDBN}.
9990 Here are some more type related Modula-2 examples:
9994 colour = (blue, red, yellow, green) ;
9995 t = [blue..yellow] ;
10003 The @value{GDBN} interaction shows how you can query the data type
10004 and value of a variable.
10007 (@value{GDBP}) print s
10009 (@value{GDBP}) ptype t
10010 type = [blue..yellow]
10014 In this example a Modula-2 array is declared and its contents
10015 displayed. Observe that the contents are written in the same way as
10016 their @code{C} counterparts.
10020 s: ARRAY [1..5] OF CARDINAL ;
10026 (@value{GDBP}) print s
10027 $1 = @{1, 0, 0, 0, 0@}
10028 (@value{GDBP}) ptype s
10029 type = ARRAY [1..5] OF CARDINAL
10032 The Modula-2 language interface to @value{GDBN} also understands
10033 pointer types as shown in this example:
10037 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10044 and you can request that @value{GDBN} describes the type of @code{s}.
10047 (@value{GDBP}) ptype s
10048 type = POINTER TO ARRAY [1..5] OF CARDINAL
10051 @value{GDBN} handles compound types as we can see in this example.
10052 Here we combine array types, record types, pointer types and subrange
10063 myarray = ARRAY myrange OF CARDINAL ;
10064 myrange = [-2..2] ;
10066 s: POINTER TO ARRAY myrange OF foo ;
10070 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10074 (@value{GDBP}) ptype s
10075 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10078 f3 : ARRAY [-2..2] OF CARDINAL;
10083 @subsubsection Modula-2 defaults
10084 @cindex Modula-2 defaults
10086 If type and range checking are set automatically by @value{GDBN}, they
10087 both default to @code{on} whenever the working language changes to
10088 Modula-2. This happens regardless of whether you or @value{GDBN}
10089 selected the working language.
10091 If you allow @value{GDBN} to set the language automatically, then entering
10092 code compiled from a file whose name ends with @file{.mod} sets the
10093 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
10094 the language automatically}, for further details.
10097 @subsubsection Deviations from standard Modula-2
10098 @cindex Modula-2, deviations from
10100 A few changes have been made to make Modula-2 programs easier to debug.
10101 This is done primarily via loosening its type strictness:
10105 Unlike in standard Modula-2, pointer constants can be formed by
10106 integers. This allows you to modify pointer variables during
10107 debugging. (In standard Modula-2, the actual address contained in a
10108 pointer variable is hidden from you; it can only be modified
10109 through direct assignment to another pointer variable or expression that
10110 returned a pointer.)
10113 C escape sequences can be used in strings and characters to represent
10114 non-printable characters. @value{GDBN} prints out strings with these
10115 escape sequences embedded. Single non-printable characters are
10116 printed using the @samp{CHR(@var{nnn})} format.
10119 The assignment operator (@code{:=}) returns the value of its right-hand
10123 All built-in procedures both modify @emph{and} return their argument.
10127 @subsubsection Modula-2 type and range checks
10128 @cindex Modula-2 checks
10131 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10134 @c FIXME remove warning when type/range checks added
10136 @value{GDBN} considers two Modula-2 variables type equivalent if:
10140 They are of types that have been declared equivalent via a @code{TYPE
10141 @var{t1} = @var{t2}} statement
10144 They have been declared on the same line. (Note: This is true of the
10145 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10148 As long as type checking is enabled, any attempt to combine variables
10149 whose types are not equivalent is an error.
10151 Range checking is done on all mathematical operations, assignment, array
10152 index bounds, and all built-in functions and procedures.
10155 @subsubsection The scope operators @code{::} and @code{.}
10157 @cindex @code{.}, Modula-2 scope operator
10158 @cindex colon, doubled as scope operator
10160 @vindex colon-colon@r{, in Modula-2}
10161 @c Info cannot handle :: but TeX can.
10164 @vindex ::@r{, in Modula-2}
10167 There are a few subtle differences between the Modula-2 scope operator
10168 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10173 @var{module} . @var{id}
10174 @var{scope} :: @var{id}
10178 where @var{scope} is the name of a module or a procedure,
10179 @var{module} the name of a module, and @var{id} is any declared
10180 identifier within your program, except another module.
10182 Using the @code{::} operator makes @value{GDBN} search the scope
10183 specified by @var{scope} for the identifier @var{id}. If it is not
10184 found in the specified scope, then @value{GDBN} searches all scopes
10185 enclosing the one specified by @var{scope}.
10187 Using the @code{.} operator makes @value{GDBN} search the current scope for
10188 the identifier specified by @var{id} that was imported from the
10189 definition module specified by @var{module}. With this operator, it is
10190 an error if the identifier @var{id} was not imported from definition
10191 module @var{module}, or if @var{id} is not an identifier in
10195 @subsubsection @value{GDBN} and Modula-2
10197 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10198 Five subcommands of @code{set print} and @code{show print} apply
10199 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10200 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10201 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10202 analogue in Modula-2.
10204 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10205 with any language, is not useful with Modula-2. Its
10206 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10207 created in Modula-2 as they can in C or C@t{++}. However, because an
10208 address can be specified by an integral constant, the construct
10209 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10211 @cindex @code{#} in Modula-2
10212 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10213 interpreted as the beginning of a comment. Use @code{<>} instead.
10219 The extensions made to @value{GDBN} for Ada only support
10220 output from the @sc{gnu} Ada (GNAT) compiler.
10221 Other Ada compilers are not currently supported, and
10222 attempting to debug executables produced by them is most likely
10226 @cindex expressions in Ada
10228 * Ada Mode Intro:: General remarks on the Ada syntax
10229 and semantics supported by Ada mode
10231 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10232 * Additions to Ada:: Extensions of the Ada expression syntax.
10233 * Stopping Before Main Program:: Debugging the program during elaboration.
10234 * Ada Glitches:: Known peculiarities of Ada mode.
10237 @node Ada Mode Intro
10238 @subsubsection Introduction
10239 @cindex Ada mode, general
10241 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10242 syntax, with some extensions.
10243 The philosophy behind the design of this subset is
10247 That @value{GDBN} should provide basic literals and access to operations for
10248 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10249 leaving more sophisticated computations to subprograms written into the
10250 program (which therefore may be called from @value{GDBN}).
10253 That type safety and strict adherence to Ada language restrictions
10254 are not particularly important to the @value{GDBN} user.
10257 That brevity is important to the @value{GDBN} user.
10260 Thus, for brevity, the debugger acts as if there were
10261 implicit @code{with} and @code{use} clauses in effect for all user-written
10262 packages, making it unnecessary to fully qualify most names with
10263 their packages, regardless of context. Where this causes ambiguity,
10264 @value{GDBN} asks the user's intent.
10266 The debugger will start in Ada mode if it detects an Ada main program.
10267 As for other languages, it will enter Ada mode when stopped in a program that
10268 was translated from an Ada source file.
10270 While in Ada mode, you may use `@t{--}' for comments. This is useful
10271 mostly for documenting command files. The standard @value{GDBN} comment
10272 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10273 middle (to allow based literals).
10275 The debugger supports limited overloading. Given a subprogram call in which
10276 the function symbol has multiple definitions, it will use the number of
10277 actual parameters and some information about their types to attempt to narrow
10278 the set of definitions. It also makes very limited use of context, preferring
10279 procedures to functions in the context of the @code{call} command, and
10280 functions to procedures elsewhere.
10282 @node Omissions from Ada
10283 @subsubsection Omissions from Ada
10284 @cindex Ada, omissions from
10286 Here are the notable omissions from the subset:
10290 Only a subset of the attributes are supported:
10294 @t{'First}, @t{'Last}, and @t{'Length}
10295 on array objects (not on types and subtypes).
10298 @t{'Min} and @t{'Max}.
10301 @t{'Pos} and @t{'Val}.
10307 @t{'Range} on array objects (not subtypes), but only as the right
10308 operand of the membership (@code{in}) operator.
10311 @t{'Access}, @t{'Unchecked_Access}, and
10312 @t{'Unrestricted_Access} (a GNAT extension).
10320 @code{Characters.Latin_1} are not available and
10321 concatenation is not implemented. Thus, escape characters in strings are
10322 not currently available.
10325 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10326 equality of representations. They will generally work correctly
10327 for strings and arrays whose elements have integer or enumeration types.
10328 They may not work correctly for arrays whose element
10329 types have user-defined equality, for arrays of real values
10330 (in particular, IEEE-conformant floating point, because of negative
10331 zeroes and NaNs), and for arrays whose elements contain unused bits with
10332 indeterminate values.
10335 The other component-by-component array operations (@code{and}, @code{or},
10336 @code{xor}, @code{not}, and relational tests other than equality)
10337 are not implemented.
10340 @cindex array aggregates (Ada)
10341 @cindex record aggregates (Ada)
10342 @cindex aggregates (Ada)
10343 There is limited support for array and record aggregates. They are
10344 permitted only on the right sides of assignments, as in these examples:
10347 set An_Array := (1, 2, 3, 4, 5, 6)
10348 set An_Array := (1, others => 0)
10349 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10350 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10351 set A_Record := (1, "Peter", True);
10352 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10356 discriminant's value by assigning an aggregate has an
10357 undefined effect if that discriminant is used within the record.
10358 However, you can first modify discriminants by directly assigning to
10359 them (which normally would not be allowed in Ada), and then performing an
10360 aggregate assignment. For example, given a variable @code{A_Rec}
10361 declared to have a type such as:
10364 type Rec (Len : Small_Integer := 0) is record
10366 Vals : IntArray (1 .. Len);
10370 you can assign a value with a different size of @code{Vals} with two
10375 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10378 As this example also illustrates, @value{GDBN} is very loose about the usual
10379 rules concerning aggregates. You may leave out some of the
10380 components of an array or record aggregate (such as the @code{Len}
10381 component in the assignment to @code{A_Rec} above); they will retain their
10382 original values upon assignment. You may freely use dynamic values as
10383 indices in component associations. You may even use overlapping or
10384 redundant component associations, although which component values are
10385 assigned in such cases is not defined.
10388 Calls to dispatching subprograms are not implemented.
10391 The overloading algorithm is much more limited (i.e., less selective)
10392 than that of real Ada. It makes only limited use of the context in which a subexpression
10393 appears to resolve its meaning, and it is much looser in its rules for allowing
10394 type matches. As a result, some function calls will be ambiguous, and the user
10395 will be asked to choose the proper resolution.
10398 The @code{new} operator is not implemented.
10401 Entry calls are not implemented.
10404 Aside from printing, arithmetic operations on the native VAX floating-point
10405 formats are not supported.
10408 It is not possible to slice a packed array.
10411 @node Additions to Ada
10412 @subsubsection Additions to Ada
10413 @cindex Ada, deviations from
10415 As it does for other languages, @value{GDBN} makes certain generic
10416 extensions to Ada (@pxref{Expressions}):
10420 If the expression @var{E} is a variable residing in memory
10421 (typically a local variable or array element) and @var{N} is
10422 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
10423 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
10424 In Ada, this operator is generally not necessary, since its prime use
10425 is in displaying parts of an array, and slicing will usually do this in Ada.
10426 However, there are occasional uses when debugging programs
10427 in which certain debugging information has been optimized away.
10430 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
10431 in function or file @var{B}.'' When @var{B} is a file name, you must typically
10432 surround it in single quotes.
10435 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10436 @var{type} that appears at address @var{addr}.''
10439 A name starting with @samp{$} is a convenience variable
10440 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10443 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
10448 The assignment statement is allowed as an expression, returning
10449 its right-hand operand as its value. Thus, you may enter
10453 print A(tmp := y + 1)
10457 The semicolon is allowed as an ``operator,'' returning as its value
10458 the value of its right-hand operand.
10459 This allows, for example,
10460 complex conditional breaks:
10464 condition 1 (report(i); k += 1; A(k) > 100)
10468 Rather than use catenation and symbolic character names to introduce special
10469 characters into strings, one may instead use a special bracket notation,
10470 which is also used to print strings. A sequence of characters of the form
10471 @samp{["@var{XX}"]} within a string or character literal denotes the
10472 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10473 sequence of characters @samp{["""]} also denotes a single quotation mark
10474 in strings. For example,
10476 "One line.["0a"]Next line.["0a"]"
10479 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
10483 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10484 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10492 When printing arrays, @value{GDBN} uses positional notation when the
10493 array has a lower bound of 1, and uses a modified named notation otherwise.
10494 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
10501 That is, in contrast to valid Ada, only the first component has a @code{=>}
10505 You may abbreviate attributes in expressions with any unique,
10506 multi-character subsequence of
10507 their names (an exact match gets preference).
10508 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10509 in place of @t{a'length}.
10512 @cindex quoting Ada internal identifiers
10513 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10514 to lower case. The GNAT compiler uses upper-case characters for
10515 some of its internal identifiers, which are normally of no interest to users.
10516 For the rare occasions when you actually have to look at them,
10517 enclose them in angle brackets to avoid the lower-case mapping.
10520 @value{GDBP} print <JMPBUF_SAVE>[0]
10524 Printing an object of class-wide type or dereferencing an
10525 access-to-class-wide value will display all the components of the object's
10526 specific type (as indicated by its run-time tag). Likewise, component
10527 selection on such a value will operate on the specific type of the
10532 @node Stopping Before Main Program
10533 @subsubsection Stopping at the Very Beginning
10535 @cindex breakpointing Ada elaboration code
10536 It is sometimes necessary to debug the program during elaboration, and
10537 before reaching the main procedure.
10538 As defined in the Ada Reference
10539 Manual, the elaboration code is invoked from a procedure called
10540 @code{adainit}. To run your program up to the beginning of
10541 elaboration, simply use the following two commands:
10542 @code{tbreak adainit} and @code{run}.
10545 @subsubsection Known Peculiarities of Ada Mode
10546 @cindex Ada, problems
10548 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10549 we know of several problems with and limitations of Ada mode in
10551 some of which will be fixed with planned future releases of the debugger
10552 and the GNU Ada compiler.
10556 Currently, the debugger
10557 has insufficient information to determine whether certain pointers represent
10558 pointers to objects or the objects themselves.
10559 Thus, the user may have to tack an extra @code{.all} after an expression
10560 to get it printed properly.
10563 Static constants that the compiler chooses not to materialize as objects in
10564 storage are invisible to the debugger.
10567 Named parameter associations in function argument lists are ignored (the
10568 argument lists are treated as positional).
10571 Many useful library packages are currently invisible to the debugger.
10574 Fixed-point arithmetic, conversions, input, and output is carried out using
10575 floating-point arithmetic, and may give results that only approximate those on
10579 The type of the @t{'Address} attribute may not be @code{System.Address}.
10582 The GNAT compiler never generates the prefix @code{Standard} for any of
10583 the standard symbols defined by the Ada language. @value{GDBN} knows about
10584 this: it will strip the prefix from names when you use it, and will never
10585 look for a name you have so qualified among local symbols, nor match against
10586 symbols in other packages or subprograms. If you have
10587 defined entities anywhere in your program other than parameters and
10588 local variables whose simple names match names in @code{Standard},
10589 GNAT's lack of qualification here can cause confusion. When this happens,
10590 you can usually resolve the confusion
10591 by qualifying the problematic names with package
10592 @code{Standard} explicitly.
10595 @node Unsupported languages
10596 @section Unsupported languages
10598 @cindex unsupported languages
10599 @cindex minimal language
10600 In addition to the other fully-supported programming languages,
10601 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10602 It does not represent a real programming language, but provides a set
10603 of capabilities close to what the C or assembly languages provide.
10604 This should allow most simple operations to be performed while debugging
10605 an application that uses a language currently not supported by @value{GDBN}.
10607 If the language is set to @code{auto}, @value{GDBN} will automatically
10608 select this language if the current frame corresponds to an unsupported
10612 @chapter Examining the Symbol Table
10614 The commands described in this chapter allow you to inquire about the
10615 symbols (names of variables, functions and types) defined in your
10616 program. This information is inherent in the text of your program and
10617 does not change as your program executes. @value{GDBN} finds it in your
10618 program's symbol table, in the file indicated when you started @value{GDBN}
10619 (@pxref{File Options, ,Choosing files}), or by one of the
10620 file-management commands (@pxref{Files, ,Commands to specify files}).
10622 @cindex symbol names
10623 @cindex names of symbols
10624 @cindex quoting names
10625 Occasionally, you may need to refer to symbols that contain unusual
10626 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10627 most frequent case is in referring to static variables in other
10628 source files (@pxref{Variables,,Program variables}). File names
10629 are recorded in object files as debugging symbols, but @value{GDBN} would
10630 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10631 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10632 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10639 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10642 @cindex case-insensitive symbol names
10643 @cindex case sensitivity in symbol names
10644 @kindex set case-sensitive
10645 @item set case-sensitive on
10646 @itemx set case-sensitive off
10647 @itemx set case-sensitive auto
10648 Normally, when @value{GDBN} looks up symbols, it matches their names
10649 with case sensitivity determined by the current source language.
10650 Occasionally, you may wish to control that. The command @code{set
10651 case-sensitive} lets you do that by specifying @code{on} for
10652 case-sensitive matches or @code{off} for case-insensitive ones. If
10653 you specify @code{auto}, case sensitivity is reset to the default
10654 suitable for the source language. The default is case-sensitive
10655 matches for all languages except for Fortran, for which the default is
10656 case-insensitive matches.
10658 @kindex show case-sensitive
10659 @item show case-sensitive
10660 This command shows the current setting of case sensitivity for symbols
10663 @kindex info address
10664 @cindex address of a symbol
10665 @item info address @var{symbol}
10666 Describe where the data for @var{symbol} is stored. For a register
10667 variable, this says which register it is kept in. For a non-register
10668 local variable, this prints the stack-frame offset at which the variable
10671 Note the contrast with @samp{print &@var{symbol}}, which does not work
10672 at all for a register variable, and for a stack local variable prints
10673 the exact address of the current instantiation of the variable.
10675 @kindex info symbol
10676 @cindex symbol from address
10677 @cindex closest symbol and offset for an address
10678 @item info symbol @var{addr}
10679 Print the name of a symbol which is stored at the address @var{addr}.
10680 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10681 nearest symbol and an offset from it:
10684 (@value{GDBP}) info symbol 0x54320
10685 _initialize_vx + 396 in section .text
10689 This is the opposite of the @code{info address} command. You can use
10690 it to find out the name of a variable or a function given its address.
10693 @item whatis [@var{arg}]
10694 Print the data type of @var{arg}, which can be either an expression or
10695 a data type. With no argument, print the data type of @code{$}, the
10696 last value in the value history. If @var{arg} is an expression, it is
10697 not actually evaluated, and any side-effecting operations (such as
10698 assignments or function calls) inside it do not take place. If
10699 @var{arg} is a type name, it may be the name of a type or typedef, or
10700 for C code it may have the form @samp{class @var{class-name}},
10701 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10702 @samp{enum @var{enum-tag}}.
10703 @xref{Expressions, ,Expressions}.
10706 @item ptype [@var{arg}]
10707 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10708 detailed description of the type, instead of just the name of the type.
10709 @xref{Expressions, ,Expressions}.
10711 For example, for this variable declaration:
10714 struct complex @{double real; double imag;@} v;
10718 the two commands give this output:
10722 (@value{GDBP}) whatis v
10723 type = struct complex
10724 (@value{GDBP}) ptype v
10725 type = struct complex @{
10733 As with @code{whatis}, using @code{ptype} without an argument refers to
10734 the type of @code{$}, the last value in the value history.
10736 @cindex incomplete type
10737 Sometimes, programs use opaque data types or incomplete specifications
10738 of complex data structure. If the debug information included in the
10739 program does not allow @value{GDBN} to display a full declaration of
10740 the data type, it will say @samp{<incomplete type>}. For example,
10741 given these declarations:
10745 struct foo *fooptr;
10749 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10752 (@value{GDBP}) ptype foo
10753 $1 = <incomplete type>
10757 ``Incomplete type'' is C terminology for data types that are not
10758 completely specified.
10761 @item info types @var{regexp}
10763 Print a brief description of all types whose names match the regular
10764 expression @var{regexp} (or all types in your program, if you supply
10765 no argument). Each complete typename is matched as though it were a
10766 complete line; thus, @samp{i type value} gives information on all
10767 types in your program whose names include the string @code{value}, but
10768 @samp{i type ^value$} gives information only on types whose complete
10769 name is @code{value}.
10771 This command differs from @code{ptype} in two ways: first, like
10772 @code{whatis}, it does not print a detailed description; second, it
10773 lists all source files where a type is defined.
10776 @cindex local variables
10777 @item info scope @var{location}
10778 List all the variables local to a particular scope. This command
10779 accepts a @var{location} argument---a function name, a source line, or
10780 an address preceded by a @samp{*}, and prints all the variables local
10781 to the scope defined by that location. For example:
10784 (@value{GDBP}) @b{info scope command_line_handler}
10785 Scope for command_line_handler:
10786 Symbol rl is an argument at stack/frame offset 8, length 4.
10787 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10788 Symbol linelength is in static storage at address 0x150a1c, length 4.
10789 Symbol p is a local variable in register $esi, length 4.
10790 Symbol p1 is a local variable in register $ebx, length 4.
10791 Symbol nline is a local variable in register $edx, length 4.
10792 Symbol repeat is a local variable at frame offset -8, length 4.
10796 This command is especially useful for determining what data to collect
10797 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10800 @kindex info source
10802 Show information about the current source file---that is, the source file for
10803 the function containing the current point of execution:
10806 the name of the source file, and the directory containing it,
10808 the directory it was compiled in,
10810 its length, in lines,
10812 which programming language it is written in,
10814 whether the executable includes debugging information for that file, and
10815 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10817 whether the debugging information includes information about
10818 preprocessor macros.
10822 @kindex info sources
10824 Print the names of all source files in your program for which there is
10825 debugging information, organized into two lists: files whose symbols
10826 have already been read, and files whose symbols will be read when needed.
10828 @kindex info functions
10829 @item info functions
10830 Print the names and data types of all defined functions.
10832 @item info functions @var{regexp}
10833 Print the names and data types of all defined functions
10834 whose names contain a match for regular expression @var{regexp}.
10835 Thus, @samp{info fun step} finds all functions whose names
10836 include @code{step}; @samp{info fun ^step} finds those whose names
10837 start with @code{step}. If a function name contains characters
10838 that conflict with the regular expression language (e.g.@:
10839 @samp{operator*()}), they may be quoted with a backslash.
10841 @kindex info variables
10842 @item info variables
10843 Print the names and data types of all variables that are declared
10844 outside of functions (i.e.@: excluding local variables).
10846 @item info variables @var{regexp}
10847 Print the names and data types of all variables (except for local
10848 variables) whose names contain a match for regular expression
10851 @kindex info classes
10852 @cindex Objective-C, classes and selectors
10854 @itemx info classes @var{regexp}
10855 Display all Objective-C classes in your program, or
10856 (with the @var{regexp} argument) all those matching a particular regular
10859 @kindex info selectors
10860 @item info selectors
10861 @itemx info selectors @var{regexp}
10862 Display all Objective-C selectors in your program, or
10863 (with the @var{regexp} argument) all those matching a particular regular
10867 This was never implemented.
10868 @kindex info methods
10870 @itemx info methods @var{regexp}
10871 The @code{info methods} command permits the user to examine all defined
10872 methods within C@t{++} program, or (with the @var{regexp} argument) a
10873 specific set of methods found in the various C@t{++} classes. Many
10874 C@t{++} classes provide a large number of methods. Thus, the output
10875 from the @code{ptype} command can be overwhelming and hard to use. The
10876 @code{info-methods} command filters the methods, printing only those
10877 which match the regular-expression @var{regexp}.
10880 @cindex reloading symbols
10881 Some systems allow individual object files that make up your program to
10882 be replaced without stopping and restarting your program. For example,
10883 in VxWorks you can simply recompile a defective object file and keep on
10884 running. If you are running on one of these systems, you can allow
10885 @value{GDBN} to reload the symbols for automatically relinked modules:
10888 @kindex set symbol-reloading
10889 @item set symbol-reloading on
10890 Replace symbol definitions for the corresponding source file when an
10891 object file with a particular name is seen again.
10893 @item set symbol-reloading off
10894 Do not replace symbol definitions when encountering object files of the
10895 same name more than once. This is the default state; if you are not
10896 running on a system that permits automatic relinking of modules, you
10897 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10898 may discard symbols when linking large programs, that may contain
10899 several modules (from different directories or libraries) with the same
10902 @kindex show symbol-reloading
10903 @item show symbol-reloading
10904 Show the current @code{on} or @code{off} setting.
10907 @cindex opaque data types
10908 @kindex set opaque-type-resolution
10909 @item set opaque-type-resolution on
10910 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10911 declared as a pointer to a @code{struct}, @code{class}, or
10912 @code{union}---for example, @code{struct MyType *}---that is used in one
10913 source file although the full declaration of @code{struct MyType} is in
10914 another source file. The default is on.
10916 A change in the setting of this subcommand will not take effect until
10917 the next time symbols for a file are loaded.
10919 @item set opaque-type-resolution off
10920 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10921 is printed as follows:
10923 @{<no data fields>@}
10926 @kindex show opaque-type-resolution
10927 @item show opaque-type-resolution
10928 Show whether opaque types are resolved or not.
10930 @kindex maint print symbols
10931 @cindex symbol dump
10932 @kindex maint print psymbols
10933 @cindex partial symbol dump
10934 @item maint print symbols @var{filename}
10935 @itemx maint print psymbols @var{filename}
10936 @itemx maint print msymbols @var{filename}
10937 Write a dump of debugging symbol data into the file @var{filename}.
10938 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10939 symbols with debugging data are included. If you use @samp{maint print
10940 symbols}, @value{GDBN} includes all the symbols for which it has already
10941 collected full details: that is, @var{filename} reflects symbols for
10942 only those files whose symbols @value{GDBN} has read. You can use the
10943 command @code{info sources} to find out which files these are. If you
10944 use @samp{maint print psymbols} instead, the dump shows information about
10945 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10946 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10947 @samp{maint print msymbols} dumps just the minimal symbol information
10948 required for each object file from which @value{GDBN} has read some symbols.
10949 @xref{Files, ,Commands to specify files}, for a discussion of how
10950 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10952 @kindex maint info symtabs
10953 @kindex maint info psymtabs
10954 @cindex listing @value{GDBN}'s internal symbol tables
10955 @cindex symbol tables, listing @value{GDBN}'s internal
10956 @cindex full symbol tables, listing @value{GDBN}'s internal
10957 @cindex partial symbol tables, listing @value{GDBN}'s internal
10958 @item maint info symtabs @r{[} @var{regexp} @r{]}
10959 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10961 List the @code{struct symtab} or @code{struct partial_symtab}
10962 structures whose names match @var{regexp}. If @var{regexp} is not
10963 given, list them all. The output includes expressions which you can
10964 copy into a @value{GDBN} debugging this one to examine a particular
10965 structure in more detail. For example:
10968 (@value{GDBP}) maint info psymtabs dwarf2read
10969 @{ objfile /home/gnu/build/gdb/gdb
10970 ((struct objfile *) 0x82e69d0)
10971 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10972 ((struct partial_symtab *) 0x8474b10)
10975 text addresses 0x814d3c8 -- 0x8158074
10976 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10977 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10978 dependencies (none)
10981 (@value{GDBP}) maint info symtabs
10985 We see that there is one partial symbol table whose filename contains
10986 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10987 and we see that @value{GDBN} has not read in any symtabs yet at all.
10988 If we set a breakpoint on a function, that will cause @value{GDBN} to
10989 read the symtab for the compilation unit containing that function:
10992 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10993 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10995 (@value{GDBP}) maint info symtabs
10996 @{ objfile /home/gnu/build/gdb/gdb
10997 ((struct objfile *) 0x82e69d0)
10998 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10999 ((struct symtab *) 0x86c1f38)
11002 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11003 debugformat DWARF 2
11012 @chapter Altering Execution
11014 Once you think you have found an error in your program, you might want to
11015 find out for certain whether correcting the apparent error would lead to
11016 correct results in the rest of the run. You can find the answer by
11017 experiment, using the @value{GDBN} features for altering execution of the
11020 For example, you can store new values into variables or memory
11021 locations, give your program a signal, restart it at a different
11022 address, or even return prematurely from a function.
11025 * Assignment:: Assignment to variables
11026 * Jumping:: Continuing at a different address
11027 * Signaling:: Giving your program a signal
11028 * Returning:: Returning from a function
11029 * Calling:: Calling your program's functions
11030 * Patching:: Patching your program
11034 @section Assignment to variables
11037 @cindex setting variables
11038 To alter the value of a variable, evaluate an assignment expression.
11039 @xref{Expressions, ,Expressions}. For example,
11046 stores the value 4 into the variable @code{x}, and then prints the
11047 value of the assignment expression (which is 4).
11048 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11049 information on operators in supported languages.
11051 @kindex set variable
11052 @cindex variables, setting
11053 If you are not interested in seeing the value of the assignment, use the
11054 @code{set} command instead of the @code{print} command. @code{set} is
11055 really the same as @code{print} except that the expression's value is
11056 not printed and is not put in the value history (@pxref{Value History,
11057 ,Value history}). The expression is evaluated only for its effects.
11059 If the beginning of the argument string of the @code{set} command
11060 appears identical to a @code{set} subcommand, use the @code{set
11061 variable} command instead of just @code{set}. This command is identical
11062 to @code{set} except for its lack of subcommands. For example, if your
11063 program has a variable @code{width}, you get an error if you try to set
11064 a new value with just @samp{set width=13}, because @value{GDBN} has the
11065 command @code{set width}:
11068 (@value{GDBP}) whatis width
11070 (@value{GDBP}) p width
11072 (@value{GDBP}) set width=47
11073 Invalid syntax in expression.
11077 The invalid expression, of course, is @samp{=47}. In
11078 order to actually set the program's variable @code{width}, use
11081 (@value{GDBP}) set var width=47
11084 Because the @code{set} command has many subcommands that can conflict
11085 with the names of program variables, it is a good idea to use the
11086 @code{set variable} command instead of just @code{set}. For example, if
11087 your program has a variable @code{g}, you run into problems if you try
11088 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11089 the command @code{set gnutarget}, abbreviated @code{set g}:
11093 (@value{GDBP}) whatis g
11097 (@value{GDBP}) set g=4
11101 The program being debugged has been started already.
11102 Start it from the beginning? (y or n) y
11103 Starting program: /home/smith/cc_progs/a.out
11104 "/home/smith/cc_progs/a.out": can't open to read symbols:
11105 Invalid bfd target.
11106 (@value{GDBP}) show g
11107 The current BFD target is "=4".
11112 The program variable @code{g} did not change, and you silently set the
11113 @code{gnutarget} to an invalid value. In order to set the variable
11117 (@value{GDBP}) set var g=4
11120 @value{GDBN} allows more implicit conversions in assignments than C; you can
11121 freely store an integer value into a pointer variable or vice versa,
11122 and you can convert any structure to any other structure that is the
11123 same length or shorter.
11124 @comment FIXME: how do structs align/pad in these conversions?
11125 @comment /doc@cygnus.com 18dec1990
11127 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11128 construct to generate a value of specified type at a specified address
11129 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11130 to memory location @code{0x83040} as an integer (which implies a certain size
11131 and representation in memory), and
11134 set @{int@}0x83040 = 4
11138 stores the value 4 into that memory location.
11141 @section Continuing at a different address
11143 Ordinarily, when you continue your program, you do so at the place where
11144 it stopped, with the @code{continue} command. You can instead continue at
11145 an address of your own choosing, with the following commands:
11149 @item jump @var{linespec}
11150 Resume execution at line @var{linespec}. Execution stops again
11151 immediately if there is a breakpoint there. @xref{List, ,Printing
11152 source lines}, for a description of the different forms of
11153 @var{linespec}. It is common practice to use the @code{tbreak} command
11154 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11157 The @code{jump} command does not change the current stack frame, or
11158 the stack pointer, or the contents of any memory location or any
11159 register other than the program counter. If line @var{linespec} is in
11160 a different function from the one currently executing, the results may
11161 be bizarre if the two functions expect different patterns of arguments or
11162 of local variables. For this reason, the @code{jump} command requests
11163 confirmation if the specified line is not in the function currently
11164 executing. However, even bizarre results are predictable if you are
11165 well acquainted with the machine-language code of your program.
11167 @item jump *@var{address}
11168 Resume execution at the instruction at address @var{address}.
11171 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11172 On many systems, you can get much the same effect as the @code{jump}
11173 command by storing a new value into the register @code{$pc}. The
11174 difference is that this does not start your program running; it only
11175 changes the address of where it @emph{will} run when you continue. For
11183 makes the next @code{continue} command or stepping command execute at
11184 address @code{0x485}, rather than at the address where your program stopped.
11185 @xref{Continuing and Stepping, ,Continuing and stepping}.
11187 The most common occasion to use the @code{jump} command is to back
11188 up---perhaps with more breakpoints set---over a portion of a program
11189 that has already executed, in order to examine its execution in more
11194 @section Giving your program a signal
11195 @cindex deliver a signal to a program
11199 @item signal @var{signal}
11200 Resume execution where your program stopped, but immediately give it the
11201 signal @var{signal}. @var{signal} can be the name or the number of a
11202 signal. For example, on many systems @code{signal 2} and @code{signal
11203 SIGINT} are both ways of sending an interrupt signal.
11205 Alternatively, if @var{signal} is zero, continue execution without
11206 giving a signal. This is useful when your program stopped on account of
11207 a signal and would ordinary see the signal when resumed with the
11208 @code{continue} command; @samp{signal 0} causes it to resume without a
11211 @code{signal} does not repeat when you press @key{RET} a second time
11212 after executing the command.
11216 Invoking the @code{signal} command is not the same as invoking the
11217 @code{kill} utility from the shell. Sending a signal with @code{kill}
11218 causes @value{GDBN} to decide what to do with the signal depending on
11219 the signal handling tables (@pxref{Signals}). The @code{signal} command
11220 passes the signal directly to your program.
11224 @section Returning from a function
11227 @cindex returning from a function
11230 @itemx return @var{expression}
11231 You can cancel execution of a function call with the @code{return}
11232 command. If you give an
11233 @var{expression} argument, its value is used as the function's return
11237 When you use @code{return}, @value{GDBN} discards the selected stack frame
11238 (and all frames within it). You can think of this as making the
11239 discarded frame return prematurely. If you wish to specify a value to
11240 be returned, give that value as the argument to @code{return}.
11242 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11243 frame}), and any other frames inside of it, leaving its caller as the
11244 innermost remaining frame. That frame becomes selected. The
11245 specified value is stored in the registers used for returning values
11248 The @code{return} command does not resume execution; it leaves the
11249 program stopped in the state that would exist if the function had just
11250 returned. In contrast, the @code{finish} command (@pxref{Continuing
11251 and Stepping, ,Continuing and stepping}) resumes execution until the
11252 selected stack frame returns naturally.
11255 @section Calling program functions
11258 @cindex calling functions
11259 @cindex inferior functions, calling
11260 @item print @var{expr}
11261 Evaluate the expression @var{expr} and display the resuling value.
11262 @var{expr} may include calls to functions in the program being
11266 @item call @var{expr}
11267 Evaluate the expression @var{expr} without displaying @code{void}
11270 You can use this variant of the @code{print} command if you want to
11271 execute a function from your program that does not return anything
11272 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11273 with @code{void} returned values that @value{GDBN} will otherwise
11274 print. If the result is not void, it is printed and saved in the
11278 It is possible for the function you call via the @code{print} or
11279 @code{call} command to generate a signal (e.g., if there's a bug in
11280 the function, or if you passed it incorrect arguments). What happens
11281 in that case is controlled by the @code{set unwindonsignal} command.
11284 @item set unwindonsignal
11285 @kindex set unwindonsignal
11286 @cindex unwind stack in called functions
11287 @cindex call dummy stack unwinding
11288 Set unwinding of the stack if a signal is received while in a function
11289 that @value{GDBN} called in the program being debugged. If set to on,
11290 @value{GDBN} unwinds the stack it created for the call and restores
11291 the context to what it was before the call. If set to off (the
11292 default), @value{GDBN} stops in the frame where the signal was
11295 @item show unwindonsignal
11296 @kindex show unwindonsignal
11297 Show the current setting of stack unwinding in the functions called by
11301 @cindex weak alias functions
11302 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11303 for another function. In such case, @value{GDBN} might not pick up
11304 the type information, including the types of the function arguments,
11305 which causes @value{GDBN} to call the inferior function incorrectly.
11306 As a result, the called function will function erroneously and may
11307 even crash. A solution to that is to use the name of the aliased
11311 @section Patching programs
11313 @cindex patching binaries
11314 @cindex writing into executables
11315 @cindex writing into corefiles
11317 By default, @value{GDBN} opens the file containing your program's
11318 executable code (or the corefile) read-only. This prevents accidental
11319 alterations to machine code; but it also prevents you from intentionally
11320 patching your program's binary.
11322 If you'd like to be able to patch the binary, you can specify that
11323 explicitly with the @code{set write} command. For example, you might
11324 want to turn on internal debugging flags, or even to make emergency
11330 @itemx set write off
11331 If you specify @samp{set write on}, @value{GDBN} opens executable and
11332 core files for both reading and writing; if you specify @samp{set write
11333 off} (the default), @value{GDBN} opens them read-only.
11335 If you have already loaded a file, you must load it again (using the
11336 @code{exec-file} or @code{core-file} command) after changing @code{set
11337 write}, for your new setting to take effect.
11341 Display whether executable files and core files are opened for writing
11342 as well as reading.
11346 @chapter @value{GDBN} Files
11348 @value{GDBN} needs to know the file name of the program to be debugged,
11349 both in order to read its symbol table and in order to start your
11350 program. To debug a core dump of a previous run, you must also tell
11351 @value{GDBN} the name of the core dump file.
11354 * Files:: Commands to specify files
11355 * Separate Debug Files:: Debugging information in separate files
11356 * Symbol Errors:: Errors reading symbol files
11360 @section Commands to specify files
11362 @cindex symbol table
11363 @cindex core dump file
11365 You may want to specify executable and core dump file names. The usual
11366 way to do this is at start-up time, using the arguments to
11367 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11368 Out of @value{GDBN}}).
11370 Occasionally it is necessary to change to a different file during a
11371 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11372 specify a file you want to use. Or you are debugging a remote target
11373 via @code{gdbserver} (@pxref{Server, file}). In these situations the
11374 @value{GDBN} commands to specify new files are useful.
11377 @cindex executable file
11379 @item file @var{filename}
11380 Use @var{filename} as the program to be debugged. It is read for its
11381 symbols and for the contents of pure memory. It is also the program
11382 executed when you use the @code{run} command. If you do not specify a
11383 directory and the file is not found in the @value{GDBN} working directory,
11384 @value{GDBN} uses the environment variable @code{PATH} as a list of
11385 directories to search, just as the shell does when looking for a program
11386 to run. You can change the value of this variable, for both @value{GDBN}
11387 and your program, using the @code{path} command.
11389 @cindex unlinked object files
11390 @cindex patching object files
11391 You can load unlinked object @file{.o} files into @value{GDBN} using
11392 the @code{file} command. You will not be able to ``run'' an object
11393 file, but you can disassemble functions and inspect variables. Also,
11394 if the underlying BFD functionality supports it, you could use
11395 @kbd{gdb -write} to patch object files using this technique. Note
11396 that @value{GDBN} can neither interpret nor modify relocations in this
11397 case, so branches and some initialized variables will appear to go to
11398 the wrong place. But this feature is still handy from time to time.
11401 @code{file} with no argument makes @value{GDBN} discard any information it
11402 has on both executable file and the symbol table.
11405 @item exec-file @r{[} @var{filename} @r{]}
11406 Specify that the program to be run (but not the symbol table) is found
11407 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11408 if necessary to locate your program. Omitting @var{filename} means to
11409 discard information on the executable file.
11411 @kindex symbol-file
11412 @item symbol-file @r{[} @var{filename} @r{]}
11413 Read symbol table information from file @var{filename}. @code{PATH} is
11414 searched when necessary. Use the @code{file} command to get both symbol
11415 table and program to run from the same file.
11417 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11418 program's symbol table.
11420 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11421 some breakpoints and auto-display expressions. This is because they may
11422 contain pointers to the internal data recording symbols and data types,
11423 which are part of the old symbol table data being discarded inside
11426 @code{symbol-file} does not repeat if you press @key{RET} again after
11429 When @value{GDBN} is configured for a particular environment, it
11430 understands debugging information in whatever format is the standard
11431 generated for that environment; you may use either a @sc{gnu} compiler, or
11432 other compilers that adhere to the local conventions.
11433 Best results are usually obtained from @sc{gnu} compilers; for example,
11434 using @code{@value{GCC}} you can generate debugging information for
11437 For most kinds of object files, with the exception of old SVR3 systems
11438 using COFF, the @code{symbol-file} command does not normally read the
11439 symbol table in full right away. Instead, it scans the symbol table
11440 quickly to find which source files and which symbols are present. The
11441 details are read later, one source file at a time, as they are needed.
11443 The purpose of this two-stage reading strategy is to make @value{GDBN}
11444 start up faster. For the most part, it is invisible except for
11445 occasional pauses while the symbol table details for a particular source
11446 file are being read. (The @code{set verbose} command can turn these
11447 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11448 warnings and messages}.)
11450 We have not implemented the two-stage strategy for COFF yet. When the
11451 symbol table is stored in COFF format, @code{symbol-file} reads the
11452 symbol table data in full right away. Note that ``stabs-in-COFF''
11453 still does the two-stage strategy, since the debug info is actually
11457 @cindex reading symbols immediately
11458 @cindex symbols, reading immediately
11459 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11460 @itemx file @var{filename} @r{[} -readnow @r{]}
11461 You can override the @value{GDBN} two-stage strategy for reading symbol
11462 tables by using the @samp{-readnow} option with any of the commands that
11463 load symbol table information, if you want to be sure @value{GDBN} has the
11464 entire symbol table available.
11466 @c FIXME: for now no mention of directories, since this seems to be in
11467 @c flux. 13mar1992 status is that in theory GDB would look either in
11468 @c current dir or in same dir as myprog; but issues like competing
11469 @c GDB's, or clutter in system dirs, mean that in practice right now
11470 @c only current dir is used. FFish says maybe a special GDB hierarchy
11471 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11475 @item core-file @r{[}@var{filename}@r{]}
11477 Specify the whereabouts of a core dump file to be used as the ``contents
11478 of memory''. Traditionally, core files contain only some parts of the
11479 address space of the process that generated them; @value{GDBN} can access the
11480 executable file itself for other parts.
11482 @code{core-file} with no argument specifies that no core file is
11485 Note that the core file is ignored when your program is actually running
11486 under @value{GDBN}. So, if you have been running your program and you
11487 wish to debug a core file instead, you must kill the subprocess in which
11488 the program is running. To do this, use the @code{kill} command
11489 (@pxref{Kill Process, ,Killing the child process}).
11491 @kindex add-symbol-file
11492 @cindex dynamic linking
11493 @item add-symbol-file @var{filename} @var{address}
11494 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11495 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11496 The @code{add-symbol-file} command reads additional symbol table
11497 information from the file @var{filename}. You would use this command
11498 when @var{filename} has been dynamically loaded (by some other means)
11499 into the program that is running. @var{address} should be the memory
11500 address at which the file has been loaded; @value{GDBN} cannot figure
11501 this out for itself. You can additionally specify an arbitrary number
11502 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11503 section name and base address for that section. You can specify any
11504 @var{address} as an expression.
11506 The symbol table of the file @var{filename} is added to the symbol table
11507 originally read with the @code{symbol-file} command. You can use the
11508 @code{add-symbol-file} command any number of times; the new symbol data
11509 thus read keeps adding to the old. To discard all old symbol data
11510 instead, use the @code{symbol-file} command without any arguments.
11512 @cindex relocatable object files, reading symbols from
11513 @cindex object files, relocatable, reading symbols from
11514 @cindex reading symbols from relocatable object files
11515 @cindex symbols, reading from relocatable object files
11516 @cindex @file{.o} files, reading symbols from
11517 Although @var{filename} is typically a shared library file, an
11518 executable file, or some other object file which has been fully
11519 relocated for loading into a process, you can also load symbolic
11520 information from relocatable @file{.o} files, as long as:
11524 the file's symbolic information refers only to linker symbols defined in
11525 that file, not to symbols defined by other object files,
11527 every section the file's symbolic information refers to has actually
11528 been loaded into the inferior, as it appears in the file, and
11530 you can determine the address at which every section was loaded, and
11531 provide these to the @code{add-symbol-file} command.
11535 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11536 relocatable files into an already running program; such systems
11537 typically make the requirements above easy to meet. However, it's
11538 important to recognize that many native systems use complex link
11539 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11540 assembly, for example) that make the requirements difficult to meet. In
11541 general, one cannot assume that using @code{add-symbol-file} to read a
11542 relocatable object file's symbolic information will have the same effect
11543 as linking the relocatable object file into the program in the normal
11546 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11548 @kindex add-symbol-file-from-memory
11549 @cindex @code{syscall DSO}
11550 @cindex load symbols from memory
11551 @item add-symbol-file-from-memory @var{address}
11552 Load symbols from the given @var{address} in a dynamically loaded
11553 object file whose image is mapped directly into the inferior's memory.
11554 For example, the Linux kernel maps a @code{syscall DSO} into each
11555 process's address space; this DSO provides kernel-specific code for
11556 some system calls. The argument can be any expression whose
11557 evaluation yields the address of the file's shared object file header.
11558 For this command to work, you must have used @code{symbol-file} or
11559 @code{exec-file} commands in advance.
11561 @kindex add-shared-symbol-files
11563 @item add-shared-symbol-files @var{library-file}
11564 @itemx assf @var{library-file}
11565 The @code{add-shared-symbol-files} command can currently be used only
11566 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11567 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11568 @value{GDBN} automatically looks for shared libraries, however if
11569 @value{GDBN} does not find yours, you can invoke
11570 @code{add-shared-symbol-files}. It takes one argument: the shared
11571 library's file name. @code{assf} is a shorthand alias for
11572 @code{add-shared-symbol-files}.
11575 @item section @var{section} @var{addr}
11576 The @code{section} command changes the base address of the named
11577 @var{section} of the exec file to @var{addr}. This can be used if the
11578 exec file does not contain section addresses, (such as in the
11579 @code{a.out} format), or when the addresses specified in the file
11580 itself are wrong. Each section must be changed separately. The
11581 @code{info files} command, described below, lists all the sections and
11585 @kindex info target
11588 @code{info files} and @code{info target} are synonymous; both print the
11589 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11590 including the names of the executable and core dump files currently in
11591 use by @value{GDBN}, and the files from which symbols were loaded. The
11592 command @code{help target} lists all possible targets rather than
11595 @kindex maint info sections
11596 @item maint info sections
11597 Another command that can give you extra information about program sections
11598 is @code{maint info sections}. In addition to the section information
11599 displayed by @code{info files}, this command displays the flags and file
11600 offset of each section in the executable and core dump files. In addition,
11601 @code{maint info sections} provides the following command options (which
11602 may be arbitrarily combined):
11606 Display sections for all loaded object files, including shared libraries.
11607 @item @var{sections}
11608 Display info only for named @var{sections}.
11609 @item @var{section-flags}
11610 Display info only for sections for which @var{section-flags} are true.
11611 The section flags that @value{GDBN} currently knows about are:
11614 Section will have space allocated in the process when loaded.
11615 Set for all sections except those containing debug information.
11617 Section will be loaded from the file into the child process memory.
11618 Set for pre-initialized code and data, clear for @code{.bss} sections.
11620 Section needs to be relocated before loading.
11622 Section cannot be modified by the child process.
11624 Section contains executable code only.
11626 Section contains data only (no executable code).
11628 Section will reside in ROM.
11630 Section contains data for constructor/destructor lists.
11632 Section is not empty.
11634 An instruction to the linker to not output the section.
11635 @item COFF_SHARED_LIBRARY
11636 A notification to the linker that the section contains
11637 COFF shared library information.
11639 Section contains common symbols.
11642 @kindex set trust-readonly-sections
11643 @cindex read-only sections
11644 @item set trust-readonly-sections on
11645 Tell @value{GDBN} that readonly sections in your object file
11646 really are read-only (i.e.@: that their contents will not change).
11647 In that case, @value{GDBN} can fetch values from these sections
11648 out of the object file, rather than from the target program.
11649 For some targets (notably embedded ones), this can be a significant
11650 enhancement to debugging performance.
11652 The default is off.
11654 @item set trust-readonly-sections off
11655 Tell @value{GDBN} not to trust readonly sections. This means that
11656 the contents of the section might change while the program is running,
11657 and must therefore be fetched from the target when needed.
11659 @item show trust-readonly-sections
11660 Show the current setting of trusting readonly sections.
11663 All file-specifying commands allow both absolute and relative file names
11664 as arguments. @value{GDBN} always converts the file name to an absolute file
11665 name and remembers it that way.
11667 @cindex shared libraries
11668 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11669 and IBM RS/6000 AIX shared libraries.
11671 @value{GDBN} automatically loads symbol definitions from shared libraries
11672 when you use the @code{run} command, or when you examine a core file.
11673 (Before you issue the @code{run} command, @value{GDBN} does not understand
11674 references to a function in a shared library, however---unless you are
11675 debugging a core file).
11677 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11678 automatically loads the symbols at the time of the @code{shl_load} call.
11680 @c FIXME: some @value{GDBN} release may permit some refs to undef
11681 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11682 @c FIXME...lib; check this from time to time when updating manual
11684 There are times, however, when you may wish to not automatically load
11685 symbol definitions from shared libraries, such as when they are
11686 particularly large or there are many of them.
11688 To control the automatic loading of shared library symbols, use the
11692 @kindex set auto-solib-add
11693 @item set auto-solib-add @var{mode}
11694 If @var{mode} is @code{on}, symbols from all shared object libraries
11695 will be loaded automatically when the inferior begins execution, you
11696 attach to an independently started inferior, or when the dynamic linker
11697 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11698 is @code{off}, symbols must be loaded manually, using the
11699 @code{sharedlibrary} command. The default value is @code{on}.
11701 @cindex memory used for symbol tables
11702 If your program uses lots of shared libraries with debug info that
11703 takes large amounts of memory, you can decrease the @value{GDBN}
11704 memory footprint by preventing it from automatically loading the
11705 symbols from shared libraries. To that end, type @kbd{set
11706 auto-solib-add off} before running the inferior, then load each
11707 library whose debug symbols you do need with @kbd{sharedlibrary
11708 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11709 the libraries whose symbols you want to be loaded.
11711 @kindex show auto-solib-add
11712 @item show auto-solib-add
11713 Display the current autoloading mode.
11716 @cindex load shared library
11717 To explicitly load shared library symbols, use the @code{sharedlibrary}
11721 @kindex info sharedlibrary
11724 @itemx info sharedlibrary
11725 Print the names of the shared libraries which are currently loaded.
11727 @kindex sharedlibrary
11729 @item sharedlibrary @var{regex}
11730 @itemx share @var{regex}
11731 Load shared object library symbols for files matching a
11732 Unix regular expression.
11733 As with files loaded automatically, it only loads shared libraries
11734 required by your program for a core file or after typing @code{run}. If
11735 @var{regex} is omitted all shared libraries required by your program are
11738 @item nosharedlibrary
11739 @kindex nosharedlibrary
11740 @cindex unload symbols from shared libraries
11741 Unload all shared object library symbols. This discards all symbols
11742 that have been loaded from all shared libraries. Symbols from shared
11743 libraries that were loaded by explicit user requests are not
11747 Sometimes you may wish that @value{GDBN} stops and gives you control
11748 when any of shared library events happen. Use the @code{set
11749 stop-on-solib-events} command for this:
11752 @item set stop-on-solib-events
11753 @kindex set stop-on-solib-events
11754 This command controls whether @value{GDBN} should give you control
11755 when the dynamic linker notifies it about some shared library event.
11756 The most common event of interest is loading or unloading of a new
11759 @item show stop-on-solib-events
11760 @kindex show stop-on-solib-events
11761 Show whether @value{GDBN} stops and gives you control when shared
11762 library events happen.
11765 Shared libraries are also supported in many cross or remote debugging
11766 configurations. A copy of the target's libraries need to be present on the
11767 host system; they need to be the same as the target libraries, although the
11768 copies on the target can be stripped as long as the copies on the host are
11771 @cindex where to look for shared libraries
11772 For remote debugging, you need to tell @value{GDBN} where the target
11773 libraries are, so that it can load the correct copies---otherwise, it
11774 may try to load the host's libraries. @value{GDBN} has two variables
11775 to specify the search directories for target libraries.
11778 @cindex prefix for shared library file names
11779 @kindex set solib-absolute-prefix
11780 @item set solib-absolute-prefix @var{path}
11781 If this variable is set, @var{path} will be used as a prefix for any
11782 absolute shared library paths; many runtime loaders store the absolute
11783 paths to the shared library in the target program's memory. If you use
11784 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11785 out in the same way that they are on the target, with e.g.@: a
11786 @file{/usr/lib} hierarchy under @var{path}.
11788 @cindex default value of @samp{solib-absolute-prefix}
11789 @cindex @samp{--with-sysroot}
11790 You can set the default value of @samp{solib-absolute-prefix} by using the
11791 configure-time @samp{--with-sysroot} option.
11793 @kindex show solib-absolute-prefix
11794 @item show solib-absolute-prefix
11795 Display the current shared library prefix.
11797 @kindex set solib-search-path
11798 @item set solib-search-path @var{path}
11799 If this variable is set, @var{path} is a colon-separated list of directories
11800 to search for shared libraries. @samp{solib-search-path} is used after
11801 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11802 the library is relative instead of absolute. If you want to use
11803 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11804 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11805 @value{GDBN} from finding your host's libraries.
11807 @kindex show solib-search-path
11808 @item show solib-search-path
11809 Display the current shared library search path.
11813 @node Separate Debug Files
11814 @section Debugging Information in Separate Files
11815 @cindex separate debugging information files
11816 @cindex debugging information in separate files
11817 @cindex @file{.debug} subdirectories
11818 @cindex debugging information directory, global
11819 @cindex global debugging information directory
11821 @value{GDBN} allows you to put a program's debugging information in a
11822 file separate from the executable itself, in a way that allows
11823 @value{GDBN} to find and load the debugging information automatically.
11824 Since debugging information can be very large --- sometimes larger
11825 than the executable code itself --- some systems distribute debugging
11826 information for their executables in separate files, which users can
11827 install only when they need to debug a problem.
11829 If an executable's debugging information has been extracted to a
11830 separate file, the executable should contain a @dfn{debug link} giving
11831 the name of the debugging information file (with no directory
11832 components), and a checksum of its contents. (The exact form of a
11833 debug link is described below.) If the full name of the directory
11834 containing the executable is @var{execdir}, and the executable has a
11835 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11836 will automatically search for the debugging information file in three
11841 the directory containing the executable file (that is, it will look
11842 for a file named @file{@var{execdir}/@var{debugfile}},
11844 a subdirectory of that directory named @file{.debug} (that is, the
11845 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11847 a subdirectory of the global debug file directory that includes the
11848 executable's full path, and the name from the link (that is, the file
11849 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11850 @var{globaldebugdir} is the global debug file directory, and
11851 @var{execdir} has been turned into a relative path).
11854 @value{GDBN} checks under each of these names for a debugging
11855 information file whose checksum matches that given in the link, and
11856 reads the debugging information from the first one it finds.
11858 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11859 which has a link containing the name @file{ls.debug}, and the global
11860 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11861 for debug information in @file{/usr/bin/ls.debug},
11862 @file{/usr/bin/.debug/ls.debug}, and
11863 @file{/usr/lib/debug/usr/bin/ls.debug}.
11865 You can set the global debugging info directory's name, and view the
11866 name @value{GDBN} is currently using.
11870 @kindex set debug-file-directory
11871 @item set debug-file-directory @var{directory}
11872 Set the directory which @value{GDBN} searches for separate debugging
11873 information files to @var{directory}.
11875 @kindex show debug-file-directory
11876 @item show debug-file-directory
11877 Show the directory @value{GDBN} searches for separate debugging
11882 @cindex @code{.gnu_debuglink} sections
11883 @cindex debug links
11884 A debug link is a special section of the executable file named
11885 @code{.gnu_debuglink}. The section must contain:
11889 A filename, with any leading directory components removed, followed by
11892 zero to three bytes of padding, as needed to reach the next four-byte
11893 boundary within the section, and
11895 a four-byte CRC checksum, stored in the same endianness used for the
11896 executable file itself. The checksum is computed on the debugging
11897 information file's full contents by the function given below, passing
11898 zero as the @var{crc} argument.
11901 Any executable file format can carry a debug link, as long as it can
11902 contain a section named @code{.gnu_debuglink} with the contents
11905 The debugging information file itself should be an ordinary
11906 executable, containing a full set of linker symbols, sections, and
11907 debugging information. The sections of the debugging information file
11908 should have the same names, addresses and sizes as the original file,
11909 but they need not contain any data --- much like a @code{.bss} section
11910 in an ordinary executable.
11912 As of December 2002, there is no standard GNU utility to produce
11913 separated executable / debugging information file pairs. Ulrich
11914 Drepper's @file{elfutils} package, starting with version 0.53,
11915 contains a version of the @code{strip} command such that the command
11916 @kbd{strip foo -f foo.debug} removes the debugging information from
11917 the executable file @file{foo}, places it in the file
11918 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11920 Since there are many different ways to compute CRC's (different
11921 polynomials, reversals, byte ordering, etc.), the simplest way to
11922 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11923 complete code for a function that computes it:
11925 @kindex gnu_debuglink_crc32
11928 gnu_debuglink_crc32 (unsigned long crc,
11929 unsigned char *buf, size_t len)
11931 static const unsigned long crc32_table[256] =
11933 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11934 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11935 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11936 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11937 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11938 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11939 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11940 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11941 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11942 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11943 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11944 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11945 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11946 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11947 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11948 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11949 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11950 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11951 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11952 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11953 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11954 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11955 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11956 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11957 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11958 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11959 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11960 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11961 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11962 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11963 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11964 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11965 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11966 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11967 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11968 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11969 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11970 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11971 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11972 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11973 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11974 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11975 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11976 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11977 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11978 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11979 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11980 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11981 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11982 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11983 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11986 unsigned char *end;
11988 crc = ~crc & 0xffffffff;
11989 for (end = buf + len; buf < end; ++buf)
11990 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11991 return ~crc & 0xffffffff;
11996 @node Symbol Errors
11997 @section Errors reading symbol files
11999 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12000 such as symbol types it does not recognize, or known bugs in compiler
12001 output. By default, @value{GDBN} does not notify you of such problems, since
12002 they are relatively common and primarily of interest to people
12003 debugging compilers. If you are interested in seeing information
12004 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12005 only one message about each such type of problem, no matter how many
12006 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12007 to see how many times the problems occur, with the @code{set
12008 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
12011 The messages currently printed, and their meanings, include:
12014 @item inner block not inside outer block in @var{symbol}
12016 The symbol information shows where symbol scopes begin and end
12017 (such as at the start of a function or a block of statements). This
12018 error indicates that an inner scope block is not fully contained
12019 in its outer scope blocks.
12021 @value{GDBN} circumvents the problem by treating the inner block as if it had
12022 the same scope as the outer block. In the error message, @var{symbol}
12023 may be shown as ``@code{(don't know)}'' if the outer block is not a
12026 @item block at @var{address} out of order
12028 The symbol information for symbol scope blocks should occur in
12029 order of increasing addresses. This error indicates that it does not
12032 @value{GDBN} does not circumvent this problem, and has trouble
12033 locating symbols in the source file whose symbols it is reading. (You
12034 can often determine what source file is affected by specifying
12035 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
12038 @item bad block start address patched
12040 The symbol information for a symbol scope block has a start address
12041 smaller than the address of the preceding source line. This is known
12042 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12044 @value{GDBN} circumvents the problem by treating the symbol scope block as
12045 starting on the previous source line.
12047 @item bad string table offset in symbol @var{n}
12050 Symbol number @var{n} contains a pointer into the string table which is
12051 larger than the size of the string table.
12053 @value{GDBN} circumvents the problem by considering the symbol to have the
12054 name @code{foo}, which may cause other problems if many symbols end up
12057 @item unknown symbol type @code{0x@var{nn}}
12059 The symbol information contains new data types that @value{GDBN} does
12060 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12061 uncomprehended information, in hexadecimal.
12063 @value{GDBN} circumvents the error by ignoring this symbol information.
12064 This usually allows you to debug your program, though certain symbols
12065 are not accessible. If you encounter such a problem and feel like
12066 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12067 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12068 and examine @code{*bufp} to see the symbol.
12070 @item stub type has NULL name
12072 @value{GDBN} could not find the full definition for a struct or class.
12074 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12075 The symbol information for a C@t{++} member function is missing some
12076 information that recent versions of the compiler should have output for
12079 @item info mismatch between compiler and debugger
12081 @value{GDBN} could not parse a type specification output by the compiler.
12086 @chapter Specifying a Debugging Target
12088 @cindex debugging target
12089 A @dfn{target} is the execution environment occupied by your program.
12091 Often, @value{GDBN} runs in the same host environment as your program;
12092 in that case, the debugging target is specified as a side effect when
12093 you use the @code{file} or @code{core} commands. When you need more
12094 flexibility---for example, running @value{GDBN} on a physically separate
12095 host, or controlling a standalone system over a serial port or a
12096 realtime system over a TCP/IP connection---you can use the @code{target}
12097 command to specify one of the target types configured for @value{GDBN}
12098 (@pxref{Target Commands, ,Commands for managing targets}).
12100 @cindex target architecture
12101 It is possible to build @value{GDBN} for several different @dfn{target
12102 architectures}. When @value{GDBN} is built like that, you can choose
12103 one of the available architectures with the @kbd{set architecture}
12107 @kindex set architecture
12108 @kindex show architecture
12109 @item set architecture @var{arch}
12110 This command sets the current target architecture to @var{arch}. The
12111 value of @var{arch} can be @code{"auto"}, in addition to one of the
12112 supported architectures.
12114 @item show architecture
12115 Show the current target architecture.
12117 @item set processor
12119 @kindex set processor
12120 @kindex show processor
12121 These are alias commands for, respectively, @code{set architecture}
12122 and @code{show architecture}.
12126 * Active Targets:: Active targets
12127 * Target Commands:: Commands for managing targets
12128 * Byte Order:: Choosing target byte order
12129 * Remote:: Remote debugging
12133 @node Active Targets
12134 @section Active targets
12136 @cindex stacking targets
12137 @cindex active targets
12138 @cindex multiple targets
12140 There are three classes of targets: processes, core files, and
12141 executable files. @value{GDBN} can work concurrently on up to three
12142 active targets, one in each class. This allows you to (for example)
12143 start a process and inspect its activity without abandoning your work on
12146 For example, if you execute @samp{gdb a.out}, then the executable file
12147 @code{a.out} is the only active target. If you designate a core file as
12148 well---presumably from a prior run that crashed and coredumped---then
12149 @value{GDBN} has two active targets and uses them in tandem, looking
12150 first in the corefile target, then in the executable file, to satisfy
12151 requests for memory addresses. (Typically, these two classes of target
12152 are complementary, since core files contain only a program's
12153 read-write memory---variables and so on---plus machine status, while
12154 executable files contain only the program text and initialized data.)
12156 When you type @code{run}, your executable file becomes an active process
12157 target as well. When a process target is active, all @value{GDBN}
12158 commands requesting memory addresses refer to that target; addresses in
12159 an active core file or executable file target are obscured while the
12160 process target is active.
12162 Use the @code{core-file} and @code{exec-file} commands to select a new
12163 core file or executable target (@pxref{Files, ,Commands to specify
12164 files}). To specify as a target a process that is already running, use
12165 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
12168 @node Target Commands
12169 @section Commands for managing targets
12172 @item target @var{type} @var{parameters}
12173 Connects the @value{GDBN} host environment to a target machine or
12174 process. A target is typically a protocol for talking to debugging
12175 facilities. You use the argument @var{type} to specify the type or
12176 protocol of the target machine.
12178 Further @var{parameters} are interpreted by the target protocol, but
12179 typically include things like device names or host names to connect
12180 with, process numbers, and baud rates.
12182 The @code{target} command does not repeat if you press @key{RET} again
12183 after executing the command.
12185 @kindex help target
12187 Displays the names of all targets available. To display targets
12188 currently selected, use either @code{info target} or @code{info files}
12189 (@pxref{Files, ,Commands to specify files}).
12191 @item help target @var{name}
12192 Describe a particular target, including any parameters necessary to
12195 @kindex set gnutarget
12196 @item set gnutarget @var{args}
12197 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12198 knows whether it is reading an @dfn{executable},
12199 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12200 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12201 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12204 @emph{Warning:} To specify a file format with @code{set gnutarget},
12205 you must know the actual BFD name.
12209 @xref{Files, , Commands to specify files}.
12211 @kindex show gnutarget
12212 @item show gnutarget
12213 Use the @code{show gnutarget} command to display what file format
12214 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12215 @value{GDBN} will determine the file format for each file automatically,
12216 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12219 @cindex common targets
12220 Here are some common targets (available, or not, depending on the GDB
12225 @item target exec @var{program}
12226 @cindex executable file target
12227 An executable file. @samp{target exec @var{program}} is the same as
12228 @samp{exec-file @var{program}}.
12230 @item target core @var{filename}
12231 @cindex core dump file target
12232 A core dump file. @samp{target core @var{filename}} is the same as
12233 @samp{core-file @var{filename}}.
12235 @item target remote @var{medium}
12236 @cindex remote target
12237 A remote system connected to @value{GDBN} via a serial line or network
12238 connection. This command tells @value{GDBN} to use its own remote
12239 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12241 For example, if you have a board connected to @file{/dev/ttya} on the
12242 machine running @value{GDBN}, you could say:
12245 target remote /dev/ttya
12248 @code{target remote} supports the @code{load} command. This is only
12249 useful if you have some other way of getting the stub to the target
12250 system, and you can put it somewhere in memory where it won't get
12251 clobbered by the download.
12254 @cindex built-in simulator target
12255 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12263 works; however, you cannot assume that a specific memory map, device
12264 drivers, or even basic I/O is available, although some simulators do
12265 provide these. For info about any processor-specific simulator details,
12266 see the appropriate section in @ref{Embedded Processors, ,Embedded
12271 Some configurations may include these targets as well:
12275 @item target nrom @var{dev}
12276 @cindex NetROM ROM emulator target
12277 NetROM ROM emulator. This target only supports downloading.
12281 Different targets are available on different configurations of @value{GDBN};
12282 your configuration may have more or fewer targets.
12284 Many remote targets require you to download the executable's code once
12285 you've successfully established a connection. You may wish to control
12286 various aspects of this process.
12291 @kindex set hash@r{, for remote monitors}
12292 @cindex hash mark while downloading
12293 This command controls whether a hash mark @samp{#} is displayed while
12294 downloading a file to the remote monitor. If on, a hash mark is
12295 displayed after each S-record is successfully downloaded to the
12299 @kindex show hash@r{, for remote monitors}
12300 Show the current status of displaying the hash mark.
12302 @item set debug monitor
12303 @kindex set debug monitor
12304 @cindex display remote monitor communications
12305 Enable or disable display of communications messages between
12306 @value{GDBN} and the remote monitor.
12308 @item show debug monitor
12309 @kindex show debug monitor
12310 Show the current status of displaying communications between
12311 @value{GDBN} and the remote monitor.
12316 @kindex load @var{filename}
12317 @item load @var{filename}
12318 Depending on what remote debugging facilities are configured into
12319 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12320 is meant to make @var{filename} (an executable) available for debugging
12321 on the remote system---by downloading, or dynamic linking, for example.
12322 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12323 the @code{add-symbol-file} command.
12325 If your @value{GDBN} does not have a @code{load} command, attempting to
12326 execute it gets the error message ``@code{You can't do that when your
12327 target is @dots{}}''
12329 The file is loaded at whatever address is specified in the executable.
12330 For some object file formats, you can specify the load address when you
12331 link the program; for other formats, like a.out, the object file format
12332 specifies a fixed address.
12333 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12335 Depending on the remote side capabilities, @value{GDBN} may be able to
12336 load programs into flash memory.
12338 @code{load} does not repeat if you press @key{RET} again after using it.
12342 @section Choosing target byte order
12344 @cindex choosing target byte order
12345 @cindex target byte order
12347 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12348 offer the ability to run either big-endian or little-endian byte
12349 orders. Usually the executable or symbol will include a bit to
12350 designate the endian-ness, and you will not need to worry about
12351 which to use. However, you may still find it useful to adjust
12352 @value{GDBN}'s idea of processor endian-ness manually.
12356 @item set endian big
12357 Instruct @value{GDBN} to assume the target is big-endian.
12359 @item set endian little
12360 Instruct @value{GDBN} to assume the target is little-endian.
12362 @item set endian auto
12363 Instruct @value{GDBN} to use the byte order associated with the
12367 Display @value{GDBN}'s current idea of the target byte order.
12371 Note that these commands merely adjust interpretation of symbolic
12372 data on the host, and that they have absolutely no effect on the
12376 @section Remote debugging
12377 @cindex remote debugging
12379 If you are trying to debug a program running on a machine that cannot run
12380 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12381 For example, you might use remote debugging on an operating system kernel,
12382 or on a small system which does not have a general purpose operating system
12383 powerful enough to run a full-featured debugger.
12385 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12386 to make this work with particular debugging targets. In addition,
12387 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12388 but not specific to any particular target system) which you can use if you
12389 write the remote stubs---the code that runs on the remote system to
12390 communicate with @value{GDBN}.
12392 Other remote targets may be available in your
12393 configuration of @value{GDBN}; use @code{help target} to list them.
12395 Once you've connected to the remote target, @value{GDBN} allows you to
12396 send arbitrary commands to the remote monitor:
12399 @item remote @var{command}
12400 @kindex remote@r{, a command}
12401 @cindex send command to remote monitor
12402 Send an arbitrary @var{command} string to the remote monitor.
12406 @node Remote Debugging
12407 @chapter Debugging remote programs
12410 * Connecting:: Connecting to a remote target
12411 * Server:: Using the gdbserver program
12412 * Remote configuration:: Remote configuration
12413 * remote stub:: Implementing a remote stub
12417 @section Connecting to a remote target
12419 On the @value{GDBN} host machine, you will need an unstripped copy of
12420 your program, since @value{GDBN} needs symobl and debugging information.
12421 Start up @value{GDBN} as usual, using the name of the local copy of your
12422 program as the first argument.
12424 @cindex @code{target remote}
12425 @value{GDBN} can communicate with the target over a serial line, or
12426 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12427 each case, @value{GDBN} uses the same protocol for debugging your
12428 program; only the medium carrying the debugging packets varies. The
12429 @code{target remote} command establishes a connection to the target.
12430 Its arguments indicate which medium to use:
12434 @item target remote @var{serial-device}
12435 @cindex serial line, @code{target remote}
12436 Use @var{serial-device} to communicate with the target. For example,
12437 to use a serial line connected to the device named @file{/dev/ttyb}:
12440 target remote /dev/ttyb
12443 If you're using a serial line, you may want to give @value{GDBN} the
12444 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12445 (@pxref{Remote configuration, set remotebaud}) before the
12446 @code{target} command.
12448 @item target remote @code{@var{host}:@var{port}}
12449 @itemx target remote @code{tcp:@var{host}:@var{port}}
12450 @cindex @acronym{TCP} port, @code{target remote}
12451 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12452 The @var{host} may be either a host name or a numeric @acronym{IP}
12453 address; @var{port} must be a decimal number. The @var{host} could be
12454 the target machine itself, if it is directly connected to the net, or
12455 it might be a terminal server which in turn has a serial line to the
12458 For example, to connect to port 2828 on a terminal server named
12462 target remote manyfarms:2828
12465 If your remote target is actually running on the same machine as your
12466 debugger session (e.g.@: a simulator for your target running on the
12467 same host), you can omit the hostname. For example, to connect to
12468 port 1234 on your local machine:
12471 target remote :1234
12475 Note that the colon is still required here.
12477 @item target remote @code{udp:@var{host}:@var{port}}
12478 @cindex @acronym{UDP} port, @code{target remote}
12479 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12480 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12483 target remote udp:manyfarms:2828
12486 When using a @acronym{UDP} connection for remote debugging, you should
12487 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12488 can silently drop packets on busy or unreliable networks, which will
12489 cause havoc with your debugging session.
12491 @item target remote | @var{command}
12492 @cindex pipe, @code{target remote} to
12493 Run @var{command} in the background and communicate with it using a
12494 pipe. The @var{command} is a shell command, to be parsed and expanded
12495 by the system's command shell, @code{/bin/sh}; it should expect remote
12496 protocol packets on its standard input, and send replies on its
12497 standard output. You could use this to run a stand-alone simulator
12498 that speaks the remote debugging protocol, to make net connections
12499 using programs like @code{ssh}, or for other similar tricks.
12501 If @var{command} closes its standard output (perhaps by exiting),
12502 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12503 program has already exited, this will have no effect.)
12507 Once the connection has been established, you can use all the usual
12508 commands to examine and change data and to step and continue the
12511 @cindex interrupting remote programs
12512 @cindex remote programs, interrupting
12513 Whenever @value{GDBN} is waiting for the remote program, if you type the
12514 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12515 program. This may or may not succeed, depending in part on the hardware
12516 and the serial drivers the remote system uses. If you type the
12517 interrupt character once again, @value{GDBN} displays this prompt:
12520 Interrupted while waiting for the program.
12521 Give up (and stop debugging it)? (y or n)
12524 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12525 (If you decide you want to try again later, you can use @samp{target
12526 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12527 goes back to waiting.
12530 @kindex detach (remote)
12532 When you have finished debugging the remote program, you can use the
12533 @code{detach} command to release it from @value{GDBN} control.
12534 Detaching from the target normally resumes its execution, but the results
12535 will depend on your particular remote stub. After the @code{detach}
12536 command, @value{GDBN} is free to connect to another target.
12540 The @code{disconnect} command behaves like @code{detach}, except that
12541 the target is generally not resumed. It will wait for @value{GDBN}
12542 (this instance or another one) to connect and continue debugging. After
12543 the @code{disconnect} command, @value{GDBN} is again free to connect to
12546 @cindex send command to remote monitor
12547 @cindex extend @value{GDBN} for remote targets
12548 @cindex add new commands for external monitor
12550 @item monitor @var{cmd}
12551 This command allows you to send arbitrary commands directly to the
12552 remote monitor. Since @value{GDBN} doesn't care about the commands it
12553 sends like this, this command is the way to extend @value{GDBN}---you
12554 can add new commands that only the external monitor will understand
12559 @section Using the @code{gdbserver} program
12562 @cindex remote connection without stubs
12563 @code{gdbserver} is a control program for Unix-like systems, which
12564 allows you to connect your program with a remote @value{GDBN} via
12565 @code{target remote}---but without linking in the usual debugging stub.
12567 @code{gdbserver} is not a complete replacement for the debugging stubs,
12568 because it requires essentially the same operating-system facilities
12569 that @value{GDBN} itself does. In fact, a system that can run
12570 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12571 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12572 because it is a much smaller program than @value{GDBN} itself. It is
12573 also easier to port than all of @value{GDBN}, so you may be able to get
12574 started more quickly on a new system by using @code{gdbserver}.
12575 Finally, if you develop code for real-time systems, you may find that
12576 the tradeoffs involved in real-time operation make it more convenient to
12577 do as much development work as possible on another system, for example
12578 by cross-compiling. You can use @code{gdbserver} to make a similar
12579 choice for debugging.
12581 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12582 or a TCP connection, using the standard @value{GDBN} remote serial
12586 @item On the target machine,
12587 you need to have a copy of the program you want to debug.
12588 @code{gdbserver} does not need your program's symbol table, so you can
12589 strip the program if necessary to save space. @value{GDBN} on the host
12590 system does all the symbol handling.
12592 To use the server, you must tell it how to communicate with @value{GDBN};
12593 the name of your program; and the arguments for your program. The usual
12597 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12600 @var{comm} is either a device name (to use a serial line) or a TCP
12601 hostname and portnumber. For example, to debug Emacs with the argument
12602 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12606 target> gdbserver /dev/com1 emacs foo.txt
12609 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12612 To use a TCP connection instead of a serial line:
12615 target> gdbserver host:2345 emacs foo.txt
12618 The only difference from the previous example is the first argument,
12619 specifying that you are communicating with the host @value{GDBN} via
12620 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12621 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12622 (Currently, the @samp{host} part is ignored.) You can choose any number
12623 you want for the port number as long as it does not conflict with any
12624 TCP ports already in use on the target system (for example, @code{23} is
12625 reserved for @code{telnet}).@footnote{If you choose a port number that
12626 conflicts with another service, @code{gdbserver} prints an error message
12627 and exits.} You must use the same port number with the host @value{GDBN}
12628 @code{target remote} command.
12630 On some targets, @code{gdbserver} can also attach to running programs.
12631 This is accomplished via the @code{--attach} argument. The syntax is:
12634 target> gdbserver @var{comm} --attach @var{pid}
12637 @var{pid} is the process ID of a currently running process. It isn't necessary
12638 to point @code{gdbserver} at a binary for the running process.
12641 @cindex attach to a program by name
12642 You can debug processes by name instead of process ID if your target has the
12643 @code{pidof} utility:
12646 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
12649 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
12650 has multiple threads, most versions of @code{pidof} support the
12651 @code{-s} option to only return the first process ID.
12653 @item On the host machine,
12654 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12655 For TCP connections, you must start up @code{gdbserver} prior to using
12656 the @code{target remote} command. Otherwise you may get an error whose
12657 text depends on the host system, but which usually looks something like
12658 @samp{Connection refused}. You don't need to use the @code{load}
12659 command in @value{GDBN} when using @code{gdbserver}, since the program is
12660 already on the target. However, if you want to load the symbols (as
12661 you normally would), do that with the @code{file} command, and issue
12662 it @emph{before} connecting to the server; otherwise, you will get an
12663 error message saying @code{"Program is already running"}, since the
12664 program is considered running after the connection.
12668 @node Remote configuration
12669 @section Remote configuration
12672 @kindex show remote
12673 This section documents the configuration options available when
12674 debugging remote programs. For the options related to the File I/O
12675 extensions of the remote protocol, see @ref{system,
12676 system-call-allowed}.
12679 @item set remoteaddresssize @var{bits}
12680 @cindex adress size for remote targets
12681 @cindex bits in remote address
12682 Set the maximum size of address in a memory packet to the specified
12683 number of bits. @value{GDBN} will mask off the address bits above
12684 that number, when it passes addresses to the remote target. The
12685 default value is the number of bits in the target's address.
12687 @item show remoteaddresssize
12688 Show the current value of remote address size in bits.
12690 @item set remotebaud @var{n}
12691 @cindex baud rate for remote targets
12692 Set the baud rate for the remote serial I/O to @var{n} baud. The
12693 value is used to set the speed of the serial port used for debugging
12696 @item show remotebaud
12697 Show the current speed of the remote connection.
12699 @item set remotebreak
12700 @cindex interrupt remote programs
12701 @cindex BREAK signal instead of Ctrl-C
12702 @anchor{set remotebreak}
12703 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12704 when you type @kbd{Ctrl-c} to interrupt the program running
12705 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12706 character instead. The default is off, since most remote systems
12707 expect to see @samp{Ctrl-C} as the interrupt signal.
12709 @item show remotebreak
12710 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12711 interrupt the remote program.
12713 @item set remotedevice @var{device}
12714 @cindex serial port name
12715 Set the name of the serial port through which to communicate to the
12716 remote target to @var{device}. This is the device used by
12717 @value{GDBN} to open the serial communications line to the remote
12718 target. There's no default, so you must set a valid port name for the
12719 remote serial communications to work. (Some varieties of the
12720 @code{target} command accept the port name as part of their
12723 @item show remotedevice
12724 Show the current name of the serial port.
12726 @item set remotelogbase @var{base}
12727 Set the base (a.k.a.@: radix) of logging serial protocol
12728 communications to @var{base}. Supported values of @var{base} are:
12729 @code{ascii}, @code{octal}, and @code{hex}. The default is
12732 @item show remotelogbase
12733 Show the current setting of the radix for logging remote serial
12736 @item set remotelogfile @var{file}
12737 @cindex record serial communications on file
12738 Record remote serial communications on the named @var{file}. The
12739 default is not to record at all.
12741 @item show remotelogfile.
12742 Show the current setting of the file name on which to record the
12743 serial communications.
12745 @item set remotetimeout @var{num}
12746 @cindex timeout for serial communications
12747 @cindex remote timeout
12748 Set the timeout limit to wait for the remote target to respond to
12749 @var{num} seconds. The default is 2 seconds.
12751 @item show remotetimeout
12752 Show the current number of seconds to wait for the remote target
12755 @cindex limit hardware breakpoints and watchpoints
12756 @cindex remote target, limit break- and watchpoints
12757 @anchor{set remote hardware-watchpoint-limit}
12758 @anchor{set remote hardware-breakpoint-limit}
12759 @item set remote hardware-watchpoint-limit @var{limit}
12760 @itemx set remote hardware-breakpoint-limit @var{limit}
12761 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12762 watchpoints. A limit of -1, the default, is treated as unlimited.
12765 @cindex remote packets, enabling and disabling
12766 The @value{GDBN} remote protocol autodetects the packets supported by
12767 your debugging stub. If you need to override the autodetection, you
12768 can use these commands to enable or disable individual packets. Each
12769 packet can be set to @samp{on} (the remote target supports this
12770 packet), @samp{off} (the remote target does not support this packet),
12771 or @samp{auto} (detect remote target support for this packet). They
12772 all default to @samp{auto}. For more information about each packet,
12773 see @ref{Remote Protocol}.
12775 During normal use, you should not have to use any of these commands.
12776 If you do, that may be a bug in your remote debugging stub, or a bug
12777 in @value{GDBN}. You may want to report the problem to the
12778 @value{GDBN} developers.
12780 The available settings are:
12782 @multitable @columnfractions 0.3 0.2 0.35
12785 @tab Related Features
12787 @item @code{fetch-register-packet}
12789 @tab @code{info registers}
12791 @item @code{set-register-packet}
12795 @item @code{binary-download-packet}
12797 @tab @code{load}, @code{set}
12799 @item @code{read-aux-vector-packet}
12800 @tab @code{qXfer:auxv:read}
12801 @tab @code{info auxv}
12803 @item @code{symbol-lookup-packet}
12804 @tab @code{qSymbol}
12805 @tab Detecting multiple threads
12807 @item @code{verbose-resume-packet}
12809 @tab Stepping or resuming multiple threads
12811 @item @code{software-breakpoint-packet}
12815 @item @code{hardware-breakpoint-packet}
12819 @item @code{write-watchpoint-packet}
12823 @item @code{read-watchpoint-packet}
12827 @item @code{access-watchpoint-packet}
12831 @item @code{get-thread-local-storage-address-packet}
12832 @tab @code{qGetTLSAddr}
12833 @tab Displaying @code{__thread} variables
12835 @item @code{supported-packets}
12836 @tab @code{qSupported}
12837 @tab Remote communications parameters
12842 @section Implementing a remote stub
12844 @cindex debugging stub, example
12845 @cindex remote stub, example
12846 @cindex stub example, remote debugging
12847 The stub files provided with @value{GDBN} implement the target side of the
12848 communication protocol, and the @value{GDBN} side is implemented in the
12849 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12850 these subroutines to communicate, and ignore the details. (If you're
12851 implementing your own stub file, you can still ignore the details: start
12852 with one of the existing stub files. @file{sparc-stub.c} is the best
12853 organized, and therefore the easiest to read.)
12855 @cindex remote serial debugging, overview
12856 To debug a program running on another machine (the debugging
12857 @dfn{target} machine), you must first arrange for all the usual
12858 prerequisites for the program to run by itself. For example, for a C
12863 A startup routine to set up the C runtime environment; these usually
12864 have a name like @file{crt0}. The startup routine may be supplied by
12865 your hardware supplier, or you may have to write your own.
12868 A C subroutine library to support your program's
12869 subroutine calls, notably managing input and output.
12872 A way of getting your program to the other machine---for example, a
12873 download program. These are often supplied by the hardware
12874 manufacturer, but you may have to write your own from hardware
12878 The next step is to arrange for your program to use a serial port to
12879 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12880 machine). In general terms, the scheme looks like this:
12884 @value{GDBN} already understands how to use this protocol; when everything
12885 else is set up, you can simply use the @samp{target remote} command
12886 (@pxref{Targets,,Specifying a Debugging Target}).
12888 @item On the target,
12889 you must link with your program a few special-purpose subroutines that
12890 implement the @value{GDBN} remote serial protocol. The file containing these
12891 subroutines is called a @dfn{debugging stub}.
12893 On certain remote targets, you can use an auxiliary program
12894 @code{gdbserver} instead of linking a stub into your program.
12895 @xref{Server,,Using the @code{gdbserver} program}, for details.
12898 The debugging stub is specific to the architecture of the remote
12899 machine; for example, use @file{sparc-stub.c} to debug programs on
12902 @cindex remote serial stub list
12903 These working remote stubs are distributed with @value{GDBN}:
12908 @cindex @file{i386-stub.c}
12911 For Intel 386 and compatible architectures.
12914 @cindex @file{m68k-stub.c}
12915 @cindex Motorola 680x0
12917 For Motorola 680x0 architectures.
12920 @cindex @file{sh-stub.c}
12923 For Renesas SH architectures.
12926 @cindex @file{sparc-stub.c}
12928 For @sc{sparc} architectures.
12930 @item sparcl-stub.c
12931 @cindex @file{sparcl-stub.c}
12934 For Fujitsu @sc{sparclite} architectures.
12938 The @file{README} file in the @value{GDBN} distribution may list other
12939 recently added stubs.
12942 * Stub Contents:: What the stub can do for you
12943 * Bootstrapping:: What you must do for the stub
12944 * Debug Session:: Putting it all together
12947 @node Stub Contents
12948 @subsection What the stub can do for you
12950 @cindex remote serial stub
12951 The debugging stub for your architecture supplies these three
12955 @item set_debug_traps
12956 @findex set_debug_traps
12957 @cindex remote serial stub, initialization
12958 This routine arranges for @code{handle_exception} to run when your
12959 program stops. You must call this subroutine explicitly near the
12960 beginning of your program.
12962 @item handle_exception
12963 @findex handle_exception
12964 @cindex remote serial stub, main routine
12965 This is the central workhorse, but your program never calls it
12966 explicitly---the setup code arranges for @code{handle_exception} to
12967 run when a trap is triggered.
12969 @code{handle_exception} takes control when your program stops during
12970 execution (for example, on a breakpoint), and mediates communications
12971 with @value{GDBN} on the host machine. This is where the communications
12972 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12973 representative on the target machine. It begins by sending summary
12974 information on the state of your program, then continues to execute,
12975 retrieving and transmitting any information @value{GDBN} needs, until you
12976 execute a @value{GDBN} command that makes your program resume; at that point,
12977 @code{handle_exception} returns control to your own code on the target
12981 @cindex @code{breakpoint} subroutine, remote
12982 Use this auxiliary subroutine to make your program contain a
12983 breakpoint. Depending on the particular situation, this may be the only
12984 way for @value{GDBN} to get control. For instance, if your target
12985 machine has some sort of interrupt button, you won't need to call this;
12986 pressing the interrupt button transfers control to
12987 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12988 simply receiving characters on the serial port may also trigger a trap;
12989 again, in that situation, you don't need to call @code{breakpoint} from
12990 your own program---simply running @samp{target remote} from the host
12991 @value{GDBN} session gets control.
12993 Call @code{breakpoint} if none of these is true, or if you simply want
12994 to make certain your program stops at a predetermined point for the
12995 start of your debugging session.
12998 @node Bootstrapping
12999 @subsection What you must do for the stub
13001 @cindex remote stub, support routines
13002 The debugging stubs that come with @value{GDBN} are set up for a particular
13003 chip architecture, but they have no information about the rest of your
13004 debugging target machine.
13006 First of all you need to tell the stub how to communicate with the
13010 @item int getDebugChar()
13011 @findex getDebugChar
13012 Write this subroutine to read a single character from the serial port.
13013 It may be identical to @code{getchar} for your target system; a
13014 different name is used to allow you to distinguish the two if you wish.
13016 @item void putDebugChar(int)
13017 @findex putDebugChar
13018 Write this subroutine to write a single character to the serial port.
13019 It may be identical to @code{putchar} for your target system; a
13020 different name is used to allow you to distinguish the two if you wish.
13023 @cindex control C, and remote debugging
13024 @cindex interrupting remote targets
13025 If you want @value{GDBN} to be able to stop your program while it is
13026 running, you need to use an interrupt-driven serial driver, and arrange
13027 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13028 character). That is the character which @value{GDBN} uses to tell the
13029 remote system to stop.
13031 Getting the debugging target to return the proper status to @value{GDBN}
13032 probably requires changes to the standard stub; one quick and dirty way
13033 is to just execute a breakpoint instruction (the ``dirty'' part is that
13034 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13036 Other routines you need to supply are:
13039 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13040 @findex exceptionHandler
13041 Write this function to install @var{exception_address} in the exception
13042 handling tables. You need to do this because the stub does not have any
13043 way of knowing what the exception handling tables on your target system
13044 are like (for example, the processor's table might be in @sc{rom},
13045 containing entries which point to a table in @sc{ram}).
13046 @var{exception_number} is the exception number which should be changed;
13047 its meaning is architecture-dependent (for example, different numbers
13048 might represent divide by zero, misaligned access, etc). When this
13049 exception occurs, control should be transferred directly to
13050 @var{exception_address}, and the processor state (stack, registers,
13051 and so on) should be just as it is when a processor exception occurs. So if
13052 you want to use a jump instruction to reach @var{exception_address}, it
13053 should be a simple jump, not a jump to subroutine.
13055 For the 386, @var{exception_address} should be installed as an interrupt
13056 gate so that interrupts are masked while the handler runs. The gate
13057 should be at privilege level 0 (the most privileged level). The
13058 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13059 help from @code{exceptionHandler}.
13061 @item void flush_i_cache()
13062 @findex flush_i_cache
13063 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13064 instruction cache, if any, on your target machine. If there is no
13065 instruction cache, this subroutine may be a no-op.
13067 On target machines that have instruction caches, @value{GDBN} requires this
13068 function to make certain that the state of your program is stable.
13072 You must also make sure this library routine is available:
13075 @item void *memset(void *, int, int)
13077 This is the standard library function @code{memset} that sets an area of
13078 memory to a known value. If you have one of the free versions of
13079 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13080 either obtain it from your hardware manufacturer, or write your own.
13083 If you do not use the GNU C compiler, you may need other standard
13084 library subroutines as well; this varies from one stub to another,
13085 but in general the stubs are likely to use any of the common library
13086 subroutines which @code{@value{GCC}} generates as inline code.
13089 @node Debug Session
13090 @subsection Putting it all together
13092 @cindex remote serial debugging summary
13093 In summary, when your program is ready to debug, you must follow these
13098 Make sure you have defined the supporting low-level routines
13099 (@pxref{Bootstrapping,,What you must do for the stub}):
13101 @code{getDebugChar}, @code{putDebugChar},
13102 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13106 Insert these lines near the top of your program:
13114 For the 680x0 stub only, you need to provide a variable called
13115 @code{exceptionHook}. Normally you just use:
13118 void (*exceptionHook)() = 0;
13122 but if before calling @code{set_debug_traps}, you set it to point to a
13123 function in your program, that function is called when
13124 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13125 error). The function indicated by @code{exceptionHook} is called with
13126 one parameter: an @code{int} which is the exception number.
13129 Compile and link together: your program, the @value{GDBN} debugging stub for
13130 your target architecture, and the supporting subroutines.
13133 Make sure you have a serial connection between your target machine and
13134 the @value{GDBN} host, and identify the serial port on the host.
13137 @c The "remote" target now provides a `load' command, so we should
13138 @c document that. FIXME.
13139 Download your program to your target machine (or get it there by
13140 whatever means the manufacturer provides), and start it.
13143 Start @value{GDBN} on the host, and connect to the target
13144 (@pxref{Connecting,,Connecting to a remote target}).
13148 @node Configurations
13149 @chapter Configuration-Specific Information
13151 While nearly all @value{GDBN} commands are available for all native and
13152 cross versions of the debugger, there are some exceptions. This chapter
13153 describes things that are only available in certain configurations.
13155 There are three major categories of configurations: native
13156 configurations, where the host and target are the same, embedded
13157 operating system configurations, which are usually the same for several
13158 different processor architectures, and bare embedded processors, which
13159 are quite different from each other.
13164 * Embedded Processors::
13171 This section describes details specific to particular native
13176 * BSD libkvm Interface:: Debugging BSD kernel memory images
13177 * SVR4 Process Information:: SVR4 process information
13178 * DJGPP Native:: Features specific to the DJGPP port
13179 * Cygwin Native:: Features specific to the Cygwin port
13180 * Hurd Native:: Features specific to @sc{gnu} Hurd
13181 * Neutrino:: Features specific to QNX Neutrino
13187 On HP-UX systems, if you refer to a function or variable name that
13188 begins with a dollar sign, @value{GDBN} searches for a user or system
13189 name first, before it searches for a convenience variable.
13192 @node BSD libkvm Interface
13193 @subsection BSD libkvm Interface
13196 @cindex kernel memory image
13197 @cindex kernel crash dump
13199 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13200 interface that provides a uniform interface for accessing kernel virtual
13201 memory images, including live systems and crash dumps. @value{GDBN}
13202 uses this interface to allow you to debug live kernels and kernel crash
13203 dumps on many native BSD configurations. This is implemented as a
13204 special @code{kvm} debugging target. For debugging a live system, load
13205 the currently running kernel into @value{GDBN} and connect to the
13209 (@value{GDBP}) @b{target kvm}
13212 For debugging crash dumps, provide the file name of the crash dump as an
13216 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13219 Once connected to the @code{kvm} target, the following commands are
13225 Set current context from the @dfn{Process Control Block} (PCB) address.
13228 Set current context from proc address. This command isn't available on
13229 modern FreeBSD systems.
13232 @node SVR4 Process Information
13233 @subsection SVR4 process information
13235 @cindex examine process image
13236 @cindex process info via @file{/proc}
13238 Many versions of SVR4 and compatible systems provide a facility called
13239 @samp{/proc} that can be used to examine the image of a running
13240 process using file-system subroutines. If @value{GDBN} is configured
13241 for an operating system with this facility, the command @code{info
13242 proc} is available to report information about the process running
13243 your program, or about any process running on your system. @code{info
13244 proc} works only on SVR4 systems that include the @code{procfs} code.
13245 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13246 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13252 @itemx info proc @var{process-id}
13253 Summarize available information about any running process. If a
13254 process ID is specified by @var{process-id}, display information about
13255 that process; otherwise display information about the program being
13256 debugged. The summary includes the debugged process ID, the command
13257 line used to invoke it, its current working directory, and its
13258 executable file's absolute file name.
13260 On some systems, @var{process-id} can be of the form
13261 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13262 within a process. If the optional @var{pid} part is missing, it means
13263 a thread from the process being debugged (the leading @samp{/} still
13264 needs to be present, or else @value{GDBN} will interpret the number as
13265 a process ID rather than a thread ID).
13267 @item info proc mappings
13268 @cindex memory address space mappings
13269 Report the memory address space ranges accessible in the program, with
13270 information on whether the process has read, write, or execute access
13271 rights to each range. On @sc{gnu}/Linux systems, each memory range
13272 includes the object file which is mapped to that range, instead of the
13273 memory access rights to that range.
13275 @item info proc stat
13276 @itemx info proc status
13277 @cindex process detailed status information
13278 These subcommands are specific to @sc{gnu}/Linux systems. They show
13279 the process-related information, including the user ID and group ID;
13280 how many threads are there in the process; its virtual memory usage;
13281 the signals that are pending, blocked, and ignored; its TTY; its
13282 consumption of system and user time; its stack size; its @samp{nice}
13283 value; etc. For more information, see the @samp{proc} man page
13284 (type @kbd{man 5 proc} from your shell prompt).
13286 @item info proc all
13287 Show all the information about the process described under all of the
13288 above @code{info proc} subcommands.
13291 @comment These sub-options of 'info proc' were not included when
13292 @comment procfs.c was re-written. Keep their descriptions around
13293 @comment against the day when someone finds the time to put them back in.
13294 @kindex info proc times
13295 @item info proc times
13296 Starting time, user CPU time, and system CPU time for your program and
13299 @kindex info proc id
13301 Report on the process IDs related to your program: its own process ID,
13302 the ID of its parent, the process group ID, and the session ID.
13305 @item set procfs-trace
13306 @kindex set procfs-trace
13307 @cindex @code{procfs} API calls
13308 This command enables and disables tracing of @code{procfs} API calls.
13310 @item show procfs-trace
13311 @kindex show procfs-trace
13312 Show the current state of @code{procfs} API call tracing.
13314 @item set procfs-file @var{file}
13315 @kindex set procfs-file
13316 Tell @value{GDBN} to write @code{procfs} API trace to the named
13317 @var{file}. @value{GDBN} appends the trace info to the previous
13318 contents of the file. The default is to display the trace on the
13321 @item show procfs-file
13322 @kindex show procfs-file
13323 Show the file to which @code{procfs} API trace is written.
13325 @item proc-trace-entry
13326 @itemx proc-trace-exit
13327 @itemx proc-untrace-entry
13328 @itemx proc-untrace-exit
13329 @kindex proc-trace-entry
13330 @kindex proc-trace-exit
13331 @kindex proc-untrace-entry
13332 @kindex proc-untrace-exit
13333 These commands enable and disable tracing of entries into and exits
13334 from the @code{syscall} interface.
13337 @kindex info pidlist
13338 @cindex process list, QNX Neutrino
13339 For QNX Neutrino only, this command displays the list of all the
13340 processes and all the threads within each process.
13343 @kindex info meminfo
13344 @cindex mapinfo list, QNX Neutrino
13345 For QNX Neutrino only, this command displays the list of all mapinfos.
13349 @subsection Features for Debugging @sc{djgpp} Programs
13350 @cindex @sc{djgpp} debugging
13351 @cindex native @sc{djgpp} debugging
13352 @cindex MS-DOS-specific commands
13355 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13356 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13357 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13358 top of real-mode DOS systems and their emulations.
13360 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13361 defines a few commands specific to the @sc{djgpp} port. This
13362 subsection describes those commands.
13367 This is a prefix of @sc{djgpp}-specific commands which print
13368 information about the target system and important OS structures.
13371 @cindex MS-DOS system info
13372 @cindex free memory information (MS-DOS)
13373 @item info dos sysinfo
13374 This command displays assorted information about the underlying
13375 platform: the CPU type and features, the OS version and flavor, the
13376 DPMI version, and the available conventional and DPMI memory.
13381 @cindex segment descriptor tables
13382 @cindex descriptor tables display
13384 @itemx info dos ldt
13385 @itemx info dos idt
13386 These 3 commands display entries from, respectively, Global, Local,
13387 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13388 tables are data structures which store a descriptor for each segment
13389 that is currently in use. The segment's selector is an index into a
13390 descriptor table; the table entry for that index holds the
13391 descriptor's base address and limit, and its attributes and access
13394 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13395 segment (used for both data and the stack), and a DOS segment (which
13396 allows access to DOS/BIOS data structures and absolute addresses in
13397 conventional memory). However, the DPMI host will usually define
13398 additional segments in order to support the DPMI environment.
13400 @cindex garbled pointers
13401 These commands allow to display entries from the descriptor tables.
13402 Without an argument, all entries from the specified table are
13403 displayed. An argument, which should be an integer expression, means
13404 display a single entry whose index is given by the argument. For
13405 example, here's a convenient way to display information about the
13406 debugged program's data segment:
13409 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13410 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13414 This comes in handy when you want to see whether a pointer is outside
13415 the data segment's limit (i.e.@: @dfn{garbled}).
13417 @cindex page tables display (MS-DOS)
13419 @itemx info dos pte
13420 These two commands display entries from, respectively, the Page
13421 Directory and the Page Tables. Page Directories and Page Tables are
13422 data structures which control how virtual memory addresses are mapped
13423 into physical addresses. A Page Table includes an entry for every
13424 page of memory that is mapped into the program's address space; there
13425 may be several Page Tables, each one holding up to 4096 entries. A
13426 Page Directory has up to 4096 entries, one each for every Page Table
13427 that is currently in use.
13429 Without an argument, @kbd{info dos pde} displays the entire Page
13430 Directory, and @kbd{info dos pte} displays all the entries in all of
13431 the Page Tables. An argument, an integer expression, given to the
13432 @kbd{info dos pde} command means display only that entry from the Page
13433 Directory table. An argument given to the @kbd{info dos pte} command
13434 means display entries from a single Page Table, the one pointed to by
13435 the specified entry in the Page Directory.
13437 @cindex direct memory access (DMA) on MS-DOS
13438 These commands are useful when your program uses @dfn{DMA} (Direct
13439 Memory Access), which needs physical addresses to program the DMA
13442 These commands are supported only with some DPMI servers.
13444 @cindex physical address from linear address
13445 @item info dos address-pte @var{addr}
13446 This command displays the Page Table entry for a specified linear
13447 address. The argument @var{addr} is a linear address which should
13448 already have the appropriate segment's base address added to it,
13449 because this command accepts addresses which may belong to @emph{any}
13450 segment. For example, here's how to display the Page Table entry for
13451 the page where a variable @code{i} is stored:
13454 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13455 @exdent @code{Page Table entry for address 0x11a00d30:}
13456 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13460 This says that @code{i} is stored at offset @code{0xd30} from the page
13461 whose physical base address is @code{0x02698000}, and shows all the
13462 attributes of that page.
13464 Note that you must cast the addresses of variables to a @code{char *},
13465 since otherwise the value of @code{__djgpp_base_address}, the base
13466 address of all variables and functions in a @sc{djgpp} program, will
13467 be added using the rules of C pointer arithmetics: if @code{i} is
13468 declared an @code{int}, @value{GDBN} will add 4 times the value of
13469 @code{__djgpp_base_address} to the address of @code{i}.
13471 Here's another example, it displays the Page Table entry for the
13475 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13476 @exdent @code{Page Table entry for address 0x29110:}
13477 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13481 (The @code{+ 3} offset is because the transfer buffer's address is the
13482 3rd member of the @code{_go32_info_block} structure.) The output
13483 clearly shows that this DPMI server maps the addresses in conventional
13484 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13485 linear (@code{0x29110}) addresses are identical.
13487 This command is supported only with some DPMI servers.
13490 @cindex DOS serial data link, remote debugging
13491 In addition to native debugging, the DJGPP port supports remote
13492 debugging via a serial data link. The following commands are specific
13493 to remote serial debugging in the DJGPP port of @value{GDBN}.
13496 @kindex set com1base
13497 @kindex set com1irq
13498 @kindex set com2base
13499 @kindex set com2irq
13500 @kindex set com3base
13501 @kindex set com3irq
13502 @kindex set com4base
13503 @kindex set com4irq
13504 @item set com1base @var{addr}
13505 This command sets the base I/O port address of the @file{COM1} serial
13508 @item set com1irq @var{irq}
13509 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13510 for the @file{COM1} serial port.
13512 There are similar commands @samp{set com2base}, @samp{set com3irq},
13513 etc.@: for setting the port address and the @code{IRQ} lines for the
13516 @kindex show com1base
13517 @kindex show com1irq
13518 @kindex show com2base
13519 @kindex show com2irq
13520 @kindex show com3base
13521 @kindex show com3irq
13522 @kindex show com4base
13523 @kindex show com4irq
13524 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13525 display the current settings of the base address and the @code{IRQ}
13526 lines used by the COM ports.
13529 @kindex info serial
13530 @cindex DOS serial port status
13531 This command prints the status of the 4 DOS serial ports. For each
13532 port, it prints whether it's active or not, its I/O base address and
13533 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13534 counts of various errors encountered so far.
13538 @node Cygwin Native
13539 @subsection Features for Debugging MS Windows PE executables
13540 @cindex MS Windows debugging
13541 @cindex native Cygwin debugging
13542 @cindex Cygwin-specific commands
13544 @value{GDBN} supports native debugging of MS Windows programs, including
13545 DLLs with and without symbolic debugging information. There are various
13546 additional Cygwin-specific commands, described in this subsection. The
13547 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13548 that have no debugging symbols.
13554 This is a prefix of MS Windows specific commands which print
13555 information about the target system and important OS structures.
13557 @item info w32 selector
13558 This command displays information returned by
13559 the Win32 API @code{GetThreadSelectorEntry} function.
13560 It takes an optional argument that is evaluated to
13561 a long value to give the information about this given selector.
13562 Without argument, this command displays information
13563 about the the six segment registers.
13567 This is a Cygwin specific alias of info shared.
13569 @kindex dll-symbols
13571 This command loads symbols from a dll similarly to
13572 add-sym command but without the need to specify a base address.
13574 @kindex set cygwin-exceptions
13575 @cindex debugging the Cygwin DLL
13576 @cindex Cygwin DLL, debugging
13577 @item set cygwin-exceptions @var{mode}
13578 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13579 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13580 @value{GDBN} will delay recognition of exceptions, and may ignore some
13581 exceptions which seem to be caused by internal Cygwin DLL
13582 ``bookkeeping''. This option is meant primarily for debugging the
13583 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13584 @value{GDBN} users with false @code{SIGSEGV} signals.
13586 @kindex show cygwin-exceptions
13587 @item show cygwin-exceptions
13588 Displays whether @value{GDBN} will break on exceptions that happen
13589 inside the Cygwin DLL itself.
13591 @kindex set new-console
13592 @item set new-console @var{mode}
13593 If @var{mode} is @code{on} the debuggee will
13594 be started in a new console on next start.
13595 If @var{mode} is @code{off}i, the debuggee will
13596 be started in the same console as the debugger.
13598 @kindex show new-console
13599 @item show new-console
13600 Displays whether a new console is used
13601 when the debuggee is started.
13603 @kindex set new-group
13604 @item set new-group @var{mode}
13605 This boolean value controls whether the debuggee should
13606 start a new group or stay in the same group as the debugger.
13607 This affects the way the Windows OS handles
13610 @kindex show new-group
13611 @item show new-group
13612 Displays current value of new-group boolean.
13614 @kindex set debugevents
13615 @item set debugevents
13616 This boolean value adds debug output concerning kernel events related
13617 to the debuggee seen by the debugger. This includes events that
13618 signal thread and process creation and exit, DLL loading and
13619 unloading, console interrupts, and debugging messages produced by the
13620 Windows @code{OutputDebugString} API call.
13622 @kindex set debugexec
13623 @item set debugexec
13624 This boolean value adds debug output concerning execute events
13625 (such as resume thread) seen by the debugger.
13627 @kindex set debugexceptions
13628 @item set debugexceptions
13629 This boolean value adds debug output concerning exceptions in the
13630 debuggee seen by the debugger.
13632 @kindex set debugmemory
13633 @item set debugmemory
13634 This boolean value adds debug output concerning debuggee memory reads
13635 and writes by the debugger.
13639 This boolean values specifies whether the debuggee is called
13640 via a shell or directly (default value is on).
13644 Displays if the debuggee will be started with a shell.
13649 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13652 @node Non-debug DLL symbols
13653 @subsubsection Support for DLLs without debugging symbols
13654 @cindex DLLs with no debugging symbols
13655 @cindex Minimal symbols and DLLs
13657 Very often on windows, some of the DLLs that your program relies on do
13658 not include symbolic debugging information (for example,
13659 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13660 symbols in a DLL, it relies on the minimal amount of symbolic
13661 information contained in the DLL's export table. This subsubsection
13662 describes working with such symbols, known internally to @value{GDBN} as
13663 ``minimal symbols''.
13665 Note that before the debugged program has started execution, no DLLs
13666 will have been loaded. The easiest way around this problem is simply to
13667 start the program --- either by setting a breakpoint or letting the
13668 program run once to completion. It is also possible to force
13669 @value{GDBN} to load a particular DLL before starting the executable ---
13670 see the shared library information in @pxref{Files} or the
13671 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13672 explicitly loading symbols from a DLL with no debugging information will
13673 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13674 which may adversely affect symbol lookup performance.
13676 @subsubsection DLL name prefixes
13678 In keeping with the naming conventions used by the Microsoft debugging
13679 tools, DLL export symbols are made available with a prefix based on the
13680 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13681 also entered into the symbol table, so @code{CreateFileA} is often
13682 sufficient. In some cases there will be name clashes within a program
13683 (particularly if the executable itself includes full debugging symbols)
13684 necessitating the use of the fully qualified name when referring to the
13685 contents of the DLL. Use single-quotes around the name to avoid the
13686 exclamation mark (``!'') being interpreted as a language operator.
13688 Note that the internal name of the DLL may be all upper-case, even
13689 though the file name of the DLL is lower-case, or vice-versa. Since
13690 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13691 some confusion. If in doubt, try the @code{info functions} and
13692 @code{info variables} commands or even @code{maint print msymbols} (see
13693 @pxref{Symbols}). Here's an example:
13696 (@value{GDBP}) info function CreateFileA
13697 All functions matching regular expression "CreateFileA":
13699 Non-debugging symbols:
13700 0x77e885f4 CreateFileA
13701 0x77e885f4 KERNEL32!CreateFileA
13705 (@value{GDBP}) info function !
13706 All functions matching regular expression "!":
13708 Non-debugging symbols:
13709 0x6100114c cygwin1!__assert
13710 0x61004034 cygwin1!_dll_crt0@@0
13711 0x61004240 cygwin1!dll_crt0(per_process *)
13715 @subsubsection Working with minimal symbols
13717 Symbols extracted from a DLL's export table do not contain very much
13718 type information. All that @value{GDBN} can do is guess whether a symbol
13719 refers to a function or variable depending on the linker section that
13720 contains the symbol. Also note that the actual contents of the memory
13721 contained in a DLL are not available unless the program is running. This
13722 means that you cannot examine the contents of a variable or disassemble
13723 a function within a DLL without a running program.
13725 Variables are generally treated as pointers and dereferenced
13726 automatically. For this reason, it is often necessary to prefix a
13727 variable name with the address-of operator (``&'') and provide explicit
13728 type information in the command. Here's an example of the type of
13732 (@value{GDBP}) print 'cygwin1!__argv'
13737 (@value{GDBP}) x 'cygwin1!__argv'
13738 0x10021610: "\230y\""
13741 And two possible solutions:
13744 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13745 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13749 (@value{GDBP}) x/2x &'cygwin1!__argv'
13750 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13751 (@value{GDBP}) x/x 0x10021608
13752 0x10021608: 0x0022fd98
13753 (@value{GDBP}) x/s 0x0022fd98
13754 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13757 Setting a break point within a DLL is possible even before the program
13758 starts execution. However, under these circumstances, @value{GDBN} can't
13759 examine the initial instructions of the function in order to skip the
13760 function's frame set-up code. You can work around this by using ``*&''
13761 to set the breakpoint at a raw memory address:
13764 (@value{GDBP}) break *&'python22!PyOS_Readline'
13765 Breakpoint 1 at 0x1e04eff0
13768 The author of these extensions is not entirely convinced that setting a
13769 break point within a shared DLL like @file{kernel32.dll} is completely
13773 @subsection Commands specific to @sc{gnu} Hurd systems
13774 @cindex @sc{gnu} Hurd debugging
13776 This subsection describes @value{GDBN} commands specific to the
13777 @sc{gnu} Hurd native debugging.
13782 @kindex set signals@r{, Hurd command}
13783 @kindex set sigs@r{, Hurd command}
13784 This command toggles the state of inferior signal interception by
13785 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13786 affected by this command. @code{sigs} is a shorthand alias for
13791 @kindex show signals@r{, Hurd command}
13792 @kindex show sigs@r{, Hurd command}
13793 Show the current state of intercepting inferior's signals.
13795 @item set signal-thread
13796 @itemx set sigthread
13797 @kindex set signal-thread
13798 @kindex set sigthread
13799 This command tells @value{GDBN} which thread is the @code{libc} signal
13800 thread. That thread is run when a signal is delivered to a running
13801 process. @code{set sigthread} is the shorthand alias of @code{set
13804 @item show signal-thread
13805 @itemx show sigthread
13806 @kindex show signal-thread
13807 @kindex show sigthread
13808 These two commands show which thread will run when the inferior is
13809 delivered a signal.
13812 @kindex set stopped@r{, Hurd command}
13813 This commands tells @value{GDBN} that the inferior process is stopped,
13814 as with the @code{SIGSTOP} signal. The stopped process can be
13815 continued by delivering a signal to it.
13818 @kindex show stopped@r{, Hurd command}
13819 This command shows whether @value{GDBN} thinks the debuggee is
13822 @item set exceptions
13823 @kindex set exceptions@r{, Hurd command}
13824 Use this command to turn off trapping of exceptions in the inferior.
13825 When exception trapping is off, neither breakpoints nor
13826 single-stepping will work. To restore the default, set exception
13829 @item show exceptions
13830 @kindex show exceptions@r{, Hurd command}
13831 Show the current state of trapping exceptions in the inferior.
13833 @item set task pause
13834 @kindex set task@r{, Hurd commands}
13835 @cindex task attributes (@sc{gnu} Hurd)
13836 @cindex pause current task (@sc{gnu} Hurd)
13837 This command toggles task suspension when @value{GDBN} has control.
13838 Setting it to on takes effect immediately, and the task is suspended
13839 whenever @value{GDBN} gets control. Setting it to off will take
13840 effect the next time the inferior is continued. If this option is set
13841 to off, you can use @code{set thread default pause on} or @code{set
13842 thread pause on} (see below) to pause individual threads.
13844 @item show task pause
13845 @kindex show task@r{, Hurd commands}
13846 Show the current state of task suspension.
13848 @item set task detach-suspend-count
13849 @cindex task suspend count
13850 @cindex detach from task, @sc{gnu} Hurd
13851 This command sets the suspend count the task will be left with when
13852 @value{GDBN} detaches from it.
13854 @item show task detach-suspend-count
13855 Show the suspend count the task will be left with when detaching.
13857 @item set task exception-port
13858 @itemx set task excp
13859 @cindex task exception port, @sc{gnu} Hurd
13860 This command sets the task exception port to which @value{GDBN} will
13861 forward exceptions. The argument should be the value of the @dfn{send
13862 rights} of the task. @code{set task excp} is a shorthand alias.
13864 @item set noninvasive
13865 @cindex noninvasive task options
13866 This command switches @value{GDBN} to a mode that is the least
13867 invasive as far as interfering with the inferior is concerned. This
13868 is the same as using @code{set task pause}, @code{set exceptions}, and
13869 @code{set signals} to values opposite to the defaults.
13871 @item info send-rights
13872 @itemx info receive-rights
13873 @itemx info port-rights
13874 @itemx info port-sets
13875 @itemx info dead-names
13878 @cindex send rights, @sc{gnu} Hurd
13879 @cindex receive rights, @sc{gnu} Hurd
13880 @cindex port rights, @sc{gnu} Hurd
13881 @cindex port sets, @sc{gnu} Hurd
13882 @cindex dead names, @sc{gnu} Hurd
13883 These commands display information about, respectively, send rights,
13884 receive rights, port rights, port sets, and dead names of a task.
13885 There are also shorthand aliases: @code{info ports} for @code{info
13886 port-rights} and @code{info psets} for @code{info port-sets}.
13888 @item set thread pause
13889 @kindex set thread@r{, Hurd command}
13890 @cindex thread properties, @sc{gnu} Hurd
13891 @cindex pause current thread (@sc{gnu} Hurd)
13892 This command toggles current thread suspension when @value{GDBN} has
13893 control. Setting it to on takes effect immediately, and the current
13894 thread is suspended whenever @value{GDBN} gets control. Setting it to
13895 off will take effect the next time the inferior is continued.
13896 Normally, this command has no effect, since when @value{GDBN} has
13897 control, the whole task is suspended. However, if you used @code{set
13898 task pause off} (see above), this command comes in handy to suspend
13899 only the current thread.
13901 @item show thread pause
13902 @kindex show thread@r{, Hurd command}
13903 This command shows the state of current thread suspension.
13905 @item set thread run
13906 This comamnd sets whether the current thread is allowed to run.
13908 @item show thread run
13909 Show whether the current thread is allowed to run.
13911 @item set thread detach-suspend-count
13912 @cindex thread suspend count, @sc{gnu} Hurd
13913 @cindex detach from thread, @sc{gnu} Hurd
13914 This command sets the suspend count @value{GDBN} will leave on a
13915 thread when detaching. This number is relative to the suspend count
13916 found by @value{GDBN} when it notices the thread; use @code{set thread
13917 takeover-suspend-count} to force it to an absolute value.
13919 @item show thread detach-suspend-count
13920 Show the suspend count @value{GDBN} will leave on the thread when
13923 @item set thread exception-port
13924 @itemx set thread excp
13925 Set the thread exception port to which to forward exceptions. This
13926 overrides the port set by @code{set task exception-port} (see above).
13927 @code{set thread excp} is the shorthand alias.
13929 @item set thread takeover-suspend-count
13930 Normally, @value{GDBN}'s thread suspend counts are relative to the
13931 value @value{GDBN} finds when it notices each thread. This command
13932 changes the suspend counts to be absolute instead.
13934 @item set thread default
13935 @itemx show thread default
13936 @cindex thread default settings, @sc{gnu} Hurd
13937 Each of the above @code{set thread} commands has a @code{set thread
13938 default} counterpart (e.g., @code{set thread default pause}, @code{set
13939 thread default exception-port}, etc.). The @code{thread default}
13940 variety of commands sets the default thread properties for all
13941 threads; you can then change the properties of individual threads with
13942 the non-default commands.
13947 @subsection QNX Neutrino
13948 @cindex QNX Neutrino
13950 @value{GDBN} provides the following commands specific to the QNX
13954 @item set debug nto-debug
13955 @kindex set debug nto-debug
13956 When set to on, enables debugging messages specific to the QNX
13959 @item show debug nto-debug
13960 @kindex show debug nto-debug
13961 Show the current state of QNX Neutrino messages.
13966 @section Embedded Operating Systems
13968 This section describes configurations involving the debugging of
13969 embedded operating systems that are available for several different
13973 * VxWorks:: Using @value{GDBN} with VxWorks
13976 @value{GDBN} includes the ability to debug programs running on
13977 various real-time operating systems.
13980 @subsection Using @value{GDBN} with VxWorks
13986 @kindex target vxworks
13987 @item target vxworks @var{machinename}
13988 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13989 is the target system's machine name or IP address.
13993 On VxWorks, @code{load} links @var{filename} dynamically on the
13994 current target system as well as adding its symbols in @value{GDBN}.
13996 @value{GDBN} enables developers to spawn and debug tasks running on networked
13997 VxWorks targets from a Unix host. Already-running tasks spawned from
13998 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13999 both the Unix host and on the VxWorks target. The program
14000 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14001 installed with the name @code{vxgdb}, to distinguish it from a
14002 @value{GDBN} for debugging programs on the host itself.)
14005 @item VxWorks-timeout @var{args}
14006 @kindex vxworks-timeout
14007 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14008 This option is set by the user, and @var{args} represents the number of
14009 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14010 your VxWorks target is a slow software simulator or is on the far side
14011 of a thin network line.
14014 The following information on connecting to VxWorks was current when
14015 this manual was produced; newer releases of VxWorks may use revised
14018 @findex INCLUDE_RDB
14019 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14020 to include the remote debugging interface routines in the VxWorks
14021 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14022 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14023 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14024 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14025 information on configuring and remaking VxWorks, see the manufacturer's
14027 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14029 Once you have included @file{rdb.a} in your VxWorks system image and set
14030 your Unix execution search path to find @value{GDBN}, you are ready to
14031 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14032 @code{vxgdb}, depending on your installation).
14034 @value{GDBN} comes up showing the prompt:
14041 * VxWorks Connection:: Connecting to VxWorks
14042 * VxWorks Download:: VxWorks download
14043 * VxWorks Attach:: Running tasks
14046 @node VxWorks Connection
14047 @subsubsection Connecting to VxWorks
14049 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14050 network. To connect to a target whose host name is ``@code{tt}'', type:
14053 (vxgdb) target vxworks tt
14057 @value{GDBN} displays messages like these:
14060 Attaching remote machine across net...
14065 @value{GDBN} then attempts to read the symbol tables of any object modules
14066 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14067 these files by searching the directories listed in the command search
14068 path (@pxref{Environment, ,Your program's environment}); if it fails
14069 to find an object file, it displays a message such as:
14072 prog.o: No such file or directory.
14075 When this happens, add the appropriate directory to the search path with
14076 the @value{GDBN} command @code{path}, and execute the @code{target}
14079 @node VxWorks Download
14080 @subsubsection VxWorks download
14082 @cindex download to VxWorks
14083 If you have connected to the VxWorks target and you want to debug an
14084 object that has not yet been loaded, you can use the @value{GDBN}
14085 @code{load} command to download a file from Unix to VxWorks
14086 incrementally. The object file given as an argument to the @code{load}
14087 command is actually opened twice: first by the VxWorks target in order
14088 to download the code, then by @value{GDBN} in order to read the symbol
14089 table. This can lead to problems if the current working directories on
14090 the two systems differ. If both systems have NFS mounted the same
14091 filesystems, you can avoid these problems by using absolute paths.
14092 Otherwise, it is simplest to set the working directory on both systems
14093 to the directory in which the object file resides, and then to reference
14094 the file by its name, without any path. For instance, a program
14095 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14096 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14097 program, type this on VxWorks:
14100 -> cd "@var{vxpath}/vw/demo/rdb"
14104 Then, in @value{GDBN}, type:
14107 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14108 (vxgdb) load prog.o
14111 @value{GDBN} displays a response similar to this:
14114 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14117 You can also use the @code{load} command to reload an object module
14118 after editing and recompiling the corresponding source file. Note that
14119 this makes @value{GDBN} delete all currently-defined breakpoints,
14120 auto-displays, and convenience variables, and to clear the value
14121 history. (This is necessary in order to preserve the integrity of
14122 debugger's data structures that reference the target system's symbol
14125 @node VxWorks Attach
14126 @subsubsection Running tasks
14128 @cindex running VxWorks tasks
14129 You can also attach to an existing task using the @code{attach} command as
14133 (vxgdb) attach @var{task}
14137 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14138 or suspended when you attach to it. Running tasks are suspended at
14139 the time of attachment.
14141 @node Embedded Processors
14142 @section Embedded Processors
14144 This section goes into details specific to particular embedded
14147 @cindex send command to simulator
14148 Whenever a specific embedded processor has a simulator, @value{GDBN}
14149 allows to send an arbitrary command to the simulator.
14152 @item sim @var{command}
14153 @kindex sim@r{, a command}
14154 Send an arbitrary @var{command} string to the simulator. Consult the
14155 documentation for the specific simulator in use for information about
14156 acceptable commands.
14162 * H8/300:: Renesas H8/300
14163 * H8/500:: Renesas H8/500
14164 * M32R/D:: Renesas M32R/D
14165 * M68K:: Motorola M68K
14166 * MIPS Embedded:: MIPS Embedded
14167 * OpenRISC 1000:: OpenRisc 1000
14168 * PA:: HP PA Embedded
14171 * Sparclet:: Tsqware Sparclet
14172 * Sparclite:: Fujitsu Sparclite
14173 * ST2000:: Tandem ST2000
14174 * Z8000:: Zilog Z8000
14177 * Super-H:: Renesas Super-H
14178 * WinCE:: Windows CE child processes
14187 @item target rdi @var{dev}
14188 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14189 use this target to communicate with both boards running the Angel
14190 monitor, or with the EmbeddedICE JTAG debug device.
14193 @item target rdp @var{dev}
14198 @value{GDBN} provides the following ARM-specific commands:
14201 @item set arm disassembler
14203 This commands selects from a list of disassembly styles. The
14204 @code{"std"} style is the standard style.
14206 @item show arm disassembler
14208 Show the current disassembly style.
14210 @item set arm apcs32
14211 @cindex ARM 32-bit mode
14212 This command toggles ARM operation mode between 32-bit and 26-bit.
14214 @item show arm apcs32
14215 Display the current usage of the ARM 32-bit mode.
14217 @item set arm fpu @var{fputype}
14218 This command sets the ARM floating-point unit (FPU) type. The
14219 argument @var{fputype} can be one of these:
14223 Determine the FPU type by querying the OS ABI.
14225 Software FPU, with mixed-endian doubles on little-endian ARM
14228 GCC-compiled FPA co-processor.
14230 Software FPU with pure-endian doubles.
14236 Show the current type of the FPU.
14239 This command forces @value{GDBN} to use the specified ABI.
14242 Show the currently used ABI.
14244 @item set debug arm
14245 Toggle whether to display ARM-specific debugging messages from the ARM
14246 target support subsystem.
14248 @item show debug arm
14249 Show whether ARM-specific debugging messages are enabled.
14252 The following commands are available when an ARM target is debugged
14253 using the RDI interface:
14256 @item rdilogfile @r{[}@var{file}@r{]}
14258 @cindex ADP (Angel Debugger Protocol) logging
14259 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14260 With an argument, sets the log file to the specified @var{file}. With
14261 no argument, show the current log file name. The default log file is
14264 @item rdilogenable @r{[}@var{arg}@r{]}
14265 @kindex rdilogenable
14266 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14267 enables logging, with an argument 0 or @code{"no"} disables it. With
14268 no arguments displays the current setting. When logging is enabled,
14269 ADP packets exchanged between @value{GDBN} and the RDI target device
14270 are logged to a file.
14272 @item set rdiromatzero
14273 @kindex set rdiromatzero
14274 @cindex ROM at zero address, RDI
14275 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14276 vector catching is disabled, so that zero address can be used. If off
14277 (the default), vector catching is enabled. For this command to take
14278 effect, it needs to be invoked prior to the @code{target rdi} command.
14280 @item show rdiromatzero
14281 @kindex show rdiromatzero
14282 Show the current setting of ROM at zero address.
14284 @item set rdiheartbeat
14285 @kindex set rdiheartbeat
14286 @cindex RDI heartbeat
14287 Enable or disable RDI heartbeat packets. It is not recommended to
14288 turn on this option, since it confuses ARM and EPI JTAG interface, as
14289 well as the Angel monitor.
14291 @item show rdiheartbeat
14292 @kindex show rdiheartbeat
14293 Show the setting of RDI heartbeat packets.
14298 @subsection Renesas H8/300
14302 @kindex target hms@r{, with H8/300}
14303 @item target hms @var{dev}
14304 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
14305 Use special commands @code{device} and @code{speed} to control the serial
14306 line and the communications speed used.
14308 @kindex target e7000@r{, with H8/300}
14309 @item target e7000 @var{dev}
14310 E7000 emulator for Renesas H8 and SH.
14312 @kindex target sh3@r{, with H8/300}
14313 @kindex target sh3e@r{, with H8/300}
14314 @item target sh3 @var{dev}
14315 @itemx target sh3e @var{dev}
14316 Renesas SH-3 and SH-3E target systems.
14320 @cindex download to H8/300 or H8/500
14321 @cindex H8/300 or H8/500 download
14322 @cindex download to Renesas SH
14323 @cindex Renesas SH download
14324 When you select remote debugging to a Renesas SH, H8/300, or H8/500
14325 board, the @code{load} command downloads your program to the Renesas
14326 board and also opens it as the current executable target for
14327 @value{GDBN} on your host (like the @code{file} command).
14329 @value{GDBN} needs to know these things to talk to your
14330 Renesas SH, H8/300, or H8/500:
14334 that you want to use @samp{target hms}, the remote debugging interface
14335 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
14336 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
14337 the default when @value{GDBN} is configured specifically for the Renesas SH,
14338 H8/300, or H8/500.)
14341 what serial device connects your host to your Renesas board (the first
14342 serial device available on your host is the default).
14345 what speed to use over the serial device.
14349 * Renesas Boards:: Connecting to Renesas boards.
14350 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
14351 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
14354 @node Renesas Boards
14355 @subsubsection Connecting to Renesas boards
14357 @c only for Unix hosts
14359 @cindex serial device, Renesas micros
14360 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
14361 need to explicitly set the serial device. The default @var{port} is the
14362 first available port on your host. This is only necessary on Unix
14363 hosts, where it is typically something like @file{/dev/ttya}.
14366 @cindex serial line speed, Renesas micros
14367 @code{@value{GDBN}} has another special command to set the communications
14368 speed: @samp{speed @var{bps}}. This command also is only used from Unix
14369 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
14370 the DOS @code{mode} command (for instance,
14371 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
14373 The @samp{device} and @samp{speed} commands are available only when you
14374 use a Unix host to debug your Renesas microprocessor programs. If you
14376 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
14377 called @code{asynctsr} to communicate with the development board
14378 through a PC serial port. You must also use the DOS @code{mode} command
14379 to set up the serial port on the DOS side.
14381 The following sample session illustrates the steps needed to start a
14382 program under @value{GDBN} control on an H8/300. The example uses a
14383 sample H8/300 program called @file{t.x}. The procedure is the same for
14384 the Renesas SH and the H8/500.
14386 First hook up your development board. In this example, we use a
14387 board attached to serial port @code{COM2}; if you use a different serial
14388 port, substitute its name in the argument of the @code{mode} command.
14389 When you call @code{asynctsr}, the auxiliary comms program used by the
14390 debugger, you give it just the numeric part of the serial port's name;
14391 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
14395 C:\H8300\TEST> asynctsr 2
14396 C:\H8300\TEST> mode com2:9600,n,8,1,p
14398 Resident portion of MODE loaded
14400 COM2: 9600, n, 8, 1, p
14405 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
14406 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
14407 disable it, or even boot without it, to use @code{asynctsr} to control
14408 your development board.
14411 @kindex target hms@r{, and serial protocol}
14412 Now that serial communications are set up, and the development board is
14413 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
14414 the name of your program as the argument. @code{@value{GDBN}} prompts
14415 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
14416 commands to begin your debugging session: @samp{target hms} to specify
14417 cross-debugging to the Renesas board, and the @code{load} command to
14418 download your program to the board. @code{load} displays the names of
14419 the program's sections, and a @samp{*} for each 2K of data downloaded.
14420 (If you want to refresh @value{GDBN} data on symbols or on the
14421 executable file without downloading, use the @value{GDBN} commands
14422 @code{file} or @code{symbol-file}. These commands, and @code{load}
14423 itself, are described in @ref{Files,,Commands to specify files}.)
14426 (eg-C:\H8300\TEST) @value{GDBP} t.x
14427 @value{GDBN} is free software and you are welcome to distribute copies
14428 of it under certain conditions; type "show copying" to see
14430 There is absolutely no warranty for @value{GDBN}; type "show warranty"
14432 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
14433 (@value{GDBP}) target hms
14434 Connected to remote H8/300 HMS system.
14435 (@value{GDBP}) load t.x
14436 .text : 0x8000 .. 0xabde ***********
14437 .data : 0xabde .. 0xad30 *
14438 .stack : 0xf000 .. 0xf014 *
14441 At this point, you're ready to run or debug your program. From here on,
14442 you can use all the usual @value{GDBN} commands. The @code{break} command
14443 sets breakpoints; the @code{run} command starts your program;
14444 @code{print} or @code{x} display data; the @code{continue} command
14445 resumes execution after stopping at a breakpoint. You can use the
14446 @code{help} command at any time to find out more about @value{GDBN} commands.
14448 Remember, however, that @emph{operating system} facilities aren't
14449 available on your development board; for example, if your program hangs,
14450 you can't send an interrupt---but you can press the @sc{reset} switch!
14452 Use the @sc{reset} button on the development board
14455 to interrupt your program (don't use @kbd{Ctrl-c} on the DOS host---it has
14456 no way to pass an interrupt signal to the development board); and
14459 to return to the @value{GDBN} command prompt after your program finishes
14460 normally. The communications protocol provides no other way for @value{GDBN}
14461 to detect program completion.
14464 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
14465 development board as a ``normal exit'' of your program.
14468 @subsubsection Using the E7000 in-circuit emulator
14470 @kindex target e7000@r{, with Renesas ICE}
14471 You can use the E7000 in-circuit emulator to develop code for either the
14472 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
14473 e7000} command to connect @value{GDBN} to your E7000:
14476 @item target e7000 @var{port} @var{speed}
14477 Use this form if your E7000 is connected to a serial port. The
14478 @var{port} argument identifies what serial port to use (for example,
14479 @samp{com2}). The third argument is the line speed in bits per second
14480 (for example, @samp{9600}).
14482 @item target e7000 @var{hostname}
14483 If your E7000 is installed as a host on a TCP/IP network, you can just
14484 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
14487 The following special commands are available when debugging with the
14491 @item e7000 @var{command}
14493 @cindex send command to E7000 monitor
14494 This sends the specified @var{command} to the E7000 monitor.
14496 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
14497 @kindex ftplogin@r{, E7000}
14498 This command records information for subsequent interface with the
14499 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
14500 named @var{machine} using specified @var{username} and @var{password},
14501 and then chdir to the named directory @var{dir}.
14503 @item ftpload @var{file}
14504 @kindex ftpload@r{, E7000}
14505 This command uses credentials recorded by @code{ftplogin} to fetch and
14506 load the named @var{file} from the E7000 monitor.
14509 @kindex drain@r{, E7000}
14510 This command drains any pending text buffers stored on the E7000.
14512 @item set usehardbreakpoints
14513 @itemx show usehardbreakpoints
14514 @kindex set usehardbreakpoints@r{, E7000}
14515 @kindex show usehardbreakpoints@r{, E7000}
14516 @cindex hardware breakpoints, and E7000
14517 These commands set and show the use of hardware breakpoints for all
14518 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14519 more information about using hardware breakpoints selectively.
14522 @node Renesas Special
14523 @subsubsection Special @value{GDBN} commands for Renesas micros
14525 Some @value{GDBN} commands are available only for the H8/300:
14529 @kindex set machine
14530 @kindex show machine
14531 @item set machine h8300
14532 @itemx set machine h8300h
14533 Condition @value{GDBN} for one of the two variants of the H8/300
14534 architecture with @samp{set machine}. You can use @samp{show machine}
14535 to check which variant is currently in effect.
14544 @kindex set memory @var{mod}
14545 @cindex memory models, H8/500
14546 @item set memory @var{mod}
14548 Specify which H8/500 memory model (@var{mod}) you are using with
14549 @samp{set memory}; check which memory model is in effect with @samp{show
14550 memory}. The accepted values for @var{mod} are @code{small},
14551 @code{big}, @code{medium}, and @code{compact}.
14556 @subsection Renesas M32R/D and M32R/SDI
14559 @kindex target m32r
14560 @item target m32r @var{dev}
14561 Renesas M32R/D ROM monitor.
14563 @kindex target m32rsdi
14564 @item target m32rsdi @var{dev}
14565 Renesas M32R SDI server, connected via parallel port to the board.
14568 The following @value{GDBN} commands are specific to the M32R monitor:
14571 @item set download-path @var{path}
14572 @kindex set download-path
14573 @cindex find downloadable @sc{srec} files (M32R)
14574 Set the default path for finding donwloadable @sc{srec} files.
14576 @item show download-path
14577 @kindex show download-path
14578 Show the default path for downloadable @sc{srec} files.
14580 @item set board-address @var{addr}
14581 @kindex set board-address
14582 @cindex M32-EVA target board address
14583 Set the IP address for the M32R-EVA target board.
14585 @item show board-address
14586 @kindex show board-address
14587 Show the current IP address of the target board.
14589 @item set server-address @var{addr}
14590 @kindex set server-address
14591 @cindex download server address (M32R)
14592 Set the IP address for the download server, which is the @value{GDBN}'s
14595 @item show server-address
14596 @kindex show server-address
14597 Display the IP address of the download server.
14599 @item upload @r{[}@var{file}@r{]}
14600 @kindex upload@r{, M32R}
14601 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14602 upload capability. If no @var{file} argument is given, the current
14603 executable file is uploaded.
14605 @item tload @r{[}@var{file}@r{]}
14606 @kindex tload@r{, M32R}
14607 Test the @code{upload} command.
14610 The following commands are available for M32R/SDI:
14615 @cindex reset SDI connection, M32R
14616 This command resets the SDI connection.
14620 This command shows the SDI connection status.
14623 @kindex debug_chaos
14624 @cindex M32R/Chaos debugging
14625 Instructs the remote that M32R/Chaos debugging is to be used.
14627 @item use_debug_dma
14628 @kindex use_debug_dma
14629 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14632 @kindex use_mon_code
14633 Instructs the remote to use the MON_CODE method of accessing memory.
14636 @kindex use_ib_break
14637 Instructs the remote to set breakpoints by IB break.
14639 @item use_dbt_break
14640 @kindex use_dbt_break
14641 Instructs the remote to set breakpoints by DBT.
14647 The Motorola m68k configuration includes ColdFire support, and
14648 target command for the following ROM monitors.
14652 @kindex target abug
14653 @item target abug @var{dev}
14654 ABug ROM monitor for M68K.
14656 @kindex target cpu32bug
14657 @item target cpu32bug @var{dev}
14658 CPU32BUG monitor, running on a CPU32 (M68K) board.
14660 @kindex target dbug
14661 @item target dbug @var{dev}
14662 dBUG ROM monitor for Motorola ColdFire.
14665 @item target est @var{dev}
14666 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14668 @kindex target rom68k
14669 @item target rom68k @var{dev}
14670 ROM 68K monitor, running on an M68K IDP board.
14676 @kindex target rombug
14677 @item target rombug @var{dev}
14678 ROMBUG ROM monitor for OS/9000.
14682 @node MIPS Embedded
14683 @subsection MIPS Embedded
14685 @cindex MIPS boards
14686 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14687 MIPS board attached to a serial line. This is available when
14688 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14691 Use these @value{GDBN} commands to specify the connection to your target board:
14694 @item target mips @var{port}
14695 @kindex target mips @var{port}
14696 To run a program on the board, start up @code{@value{GDBP}} with the
14697 name of your program as the argument. To connect to the board, use the
14698 command @samp{target mips @var{port}}, where @var{port} is the name of
14699 the serial port connected to the board. If the program has not already
14700 been downloaded to the board, you may use the @code{load} command to
14701 download it. You can then use all the usual @value{GDBN} commands.
14703 For example, this sequence connects to the target board through a serial
14704 port, and loads and runs a program called @var{prog} through the
14708 host$ @value{GDBP} @var{prog}
14709 @value{GDBN} is free software and @dots{}
14710 (@value{GDBP}) target mips /dev/ttyb
14711 (@value{GDBP}) load @var{prog}
14715 @item target mips @var{hostname}:@var{portnumber}
14716 On some @value{GDBN} host configurations, you can specify a TCP
14717 connection (for instance, to a serial line managed by a terminal
14718 concentrator) instead of a serial port, using the syntax
14719 @samp{@var{hostname}:@var{portnumber}}.
14721 @item target pmon @var{port}
14722 @kindex target pmon @var{port}
14725 @item target ddb @var{port}
14726 @kindex target ddb @var{port}
14727 NEC's DDB variant of PMON for Vr4300.
14729 @item target lsi @var{port}
14730 @kindex target lsi @var{port}
14731 LSI variant of PMON.
14733 @kindex target r3900
14734 @item target r3900 @var{dev}
14735 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14737 @kindex target array
14738 @item target array @var{dev}
14739 Array Tech LSI33K RAID controller board.
14745 @value{GDBN} also supports these special commands for MIPS targets:
14748 @item set mipsfpu double
14749 @itemx set mipsfpu single
14750 @itemx set mipsfpu none
14751 @itemx set mipsfpu auto
14752 @itemx show mipsfpu
14753 @kindex set mipsfpu
14754 @kindex show mipsfpu
14755 @cindex MIPS remote floating point
14756 @cindex floating point, MIPS remote
14757 If your target board does not support the MIPS floating point
14758 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14759 need this, you may wish to put the command in your @value{GDBN} init
14760 file). This tells @value{GDBN} how to find the return value of
14761 functions which return floating point values. It also allows
14762 @value{GDBN} to avoid saving the floating point registers when calling
14763 functions on the board. If you are using a floating point coprocessor
14764 with only single precision floating point support, as on the @sc{r4650}
14765 processor, use the command @samp{set mipsfpu single}. The default
14766 double precision floating point coprocessor may be selected using
14767 @samp{set mipsfpu double}.
14769 In previous versions the only choices were double precision or no
14770 floating point, so @samp{set mipsfpu on} will select double precision
14771 and @samp{set mipsfpu off} will select no floating point.
14773 As usual, you can inquire about the @code{mipsfpu} variable with
14774 @samp{show mipsfpu}.
14776 @item set timeout @var{seconds}
14777 @itemx set retransmit-timeout @var{seconds}
14778 @itemx show timeout
14779 @itemx show retransmit-timeout
14780 @cindex @code{timeout}, MIPS protocol
14781 @cindex @code{retransmit-timeout}, MIPS protocol
14782 @kindex set timeout
14783 @kindex show timeout
14784 @kindex set retransmit-timeout
14785 @kindex show retransmit-timeout
14786 You can control the timeout used while waiting for a packet, in the MIPS
14787 remote protocol, with the @code{set timeout @var{seconds}} command. The
14788 default is 5 seconds. Similarly, you can control the timeout used while
14789 waiting for an acknowledgement of a packet with the @code{set
14790 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14791 You can inspect both values with @code{show timeout} and @code{show
14792 retransmit-timeout}. (These commands are @emph{only} available when
14793 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14795 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14796 is waiting for your program to stop. In that case, @value{GDBN} waits
14797 forever because it has no way of knowing how long the program is going
14798 to run before stopping.
14800 @item set syn-garbage-limit @var{num}
14801 @kindex set syn-garbage-limit@r{, MIPS remote}
14802 @cindex synchronize with remote MIPS target
14803 Limit the maximum number of characters @value{GDBN} should ignore when
14804 it tries to synchronize with the remote target. The default is 10
14805 characters. Setting the limit to -1 means there's no limit.
14807 @item show syn-garbage-limit
14808 @kindex show syn-garbage-limit@r{, MIPS remote}
14809 Show the current limit on the number of characters to ignore when
14810 trying to synchronize with the remote system.
14812 @item set monitor-prompt @var{prompt}
14813 @kindex set monitor-prompt@r{, MIPS remote}
14814 @cindex remote monitor prompt
14815 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14816 remote monitor. The default depends on the target:
14826 @item show monitor-prompt
14827 @kindex show monitor-prompt@r{, MIPS remote}
14828 Show the current strings @value{GDBN} expects as the prompt from the
14831 @item set monitor-warnings
14832 @kindex set monitor-warnings@r{, MIPS remote}
14833 Enable or disable monitor warnings about hardware breakpoints. This
14834 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14835 display warning messages whose codes are returned by the @code{lsi}
14836 PMON monitor for breakpoint commands.
14838 @item show monitor-warnings
14839 @kindex show monitor-warnings@r{, MIPS remote}
14840 Show the current setting of printing monitor warnings.
14842 @item pmon @var{command}
14843 @kindex pmon@r{, MIPS remote}
14844 @cindex send PMON command
14845 This command allows sending an arbitrary @var{command} string to the
14846 monitor. The monitor must be in debug mode for this to work.
14849 @node OpenRISC 1000
14850 @subsection OpenRISC 1000
14851 @cindex OpenRISC 1000
14853 @cindex or1k boards
14854 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14855 about platform and commands.
14859 @kindex target jtag
14860 @item target jtag jtag://@var{host}:@var{port}
14862 Connects to remote JTAG server.
14863 JTAG remote server can be either an or1ksim or JTAG server,
14864 connected via parallel port to the board.
14866 Example: @code{target jtag jtag://localhost:9999}
14869 @item or1ksim @var{command}
14870 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14871 Simulator, proprietary commands can be executed.
14873 @kindex info or1k spr
14874 @item info or1k spr
14875 Displays spr groups.
14877 @item info or1k spr @var{group}
14878 @itemx info or1k spr @var{groupno}
14879 Displays register names in selected group.
14881 @item info or1k spr @var{group} @var{register}
14882 @itemx info or1k spr @var{register}
14883 @itemx info or1k spr @var{groupno} @var{registerno}
14884 @itemx info or1k spr @var{registerno}
14885 Shows information about specified spr register.
14888 @item spr @var{group} @var{register} @var{value}
14889 @itemx spr @var{register @var{value}}
14890 @itemx spr @var{groupno} @var{registerno @var{value}}
14891 @itemx spr @var{registerno @var{value}}
14892 Writes @var{value} to specified spr register.
14895 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14896 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14897 program execution and is thus much faster. Hardware breakpoints/watchpoint
14898 triggers can be set using:
14901 Load effective address/data
14903 Store effective address/data
14905 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14910 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14911 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14913 @code{htrace} commands:
14914 @cindex OpenRISC 1000 htrace
14917 @item hwatch @var{conditional}
14918 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14919 or Data. For example:
14921 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14923 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14927 Display information about current HW trace configuration.
14929 @item htrace trigger @var{conditional}
14930 Set starting criteria for HW trace.
14932 @item htrace qualifier @var{conditional}
14933 Set acquisition qualifier for HW trace.
14935 @item htrace stop @var{conditional}
14936 Set HW trace stopping criteria.
14938 @item htrace record [@var{data}]*
14939 Selects the data to be recorded, when qualifier is met and HW trace was
14942 @item htrace enable
14943 @itemx htrace disable
14944 Enables/disables the HW trace.
14946 @item htrace rewind [@var{filename}]
14947 Clears currently recorded trace data.
14949 If filename is specified, new trace file is made and any newly collected data
14950 will be written there.
14952 @item htrace print [@var{start} [@var{len}]]
14953 Prints trace buffer, using current record configuration.
14955 @item htrace mode continuous
14956 Set continuous trace mode.
14958 @item htrace mode suspend
14959 Set suspend trace mode.
14964 @subsection PowerPC
14967 @kindex target dink32
14968 @item target dink32 @var{dev}
14969 DINK32 ROM monitor.
14971 @kindex target ppcbug
14972 @item target ppcbug @var{dev}
14973 @kindex target ppcbug1
14974 @item target ppcbug1 @var{dev}
14975 PPCBUG ROM monitor for PowerPC.
14978 @item target sds @var{dev}
14979 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14982 @cindex SDS protocol
14983 The following commands specifi to the SDS protocol are supported
14987 @item set sdstimeout @var{nsec}
14988 @kindex set sdstimeout
14989 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14990 default is 2 seconds.
14992 @item show sdstimeout
14993 @kindex show sdstimeout
14994 Show the current value of the SDS timeout.
14996 @item sds @var{command}
14997 @kindex sds@r{, a command}
14998 Send the specified @var{command} string to the SDS monitor.
15003 @subsection HP PA Embedded
15007 @kindex target op50n
15008 @item target op50n @var{dev}
15009 OP50N monitor, running on an OKI HPPA board.
15011 @kindex target w89k
15012 @item target w89k @var{dev}
15013 W89K monitor, running on a Winbond HPPA board.
15018 @subsection Renesas SH
15022 @kindex target hms@r{, with Renesas SH}
15023 @item target hms @var{dev}
15024 A Renesas SH board attached via serial line to your host. Use special
15025 commands @code{device} and @code{speed} to control the serial line and
15026 the communications speed used.
15028 @kindex target e7000@r{, with Renesas SH}
15029 @item target e7000 @var{dev}
15030 E7000 emulator for Renesas SH.
15032 @kindex target sh3@r{, with SH}
15033 @kindex target sh3e@r{, with SH}
15034 @item target sh3 @var{dev}
15035 @item target sh3e @var{dev}
15036 Renesas SH-3 and SH-3E target systems.
15041 @subsection Tsqware Sparclet
15045 @value{GDBN} enables developers to debug tasks running on
15046 Sparclet targets from a Unix host.
15047 @value{GDBN} uses code that runs on
15048 both the Unix host and on the Sparclet target. The program
15049 @code{@value{GDBP}} is installed and executed on the Unix host.
15052 @item remotetimeout @var{args}
15053 @kindex remotetimeout
15054 @value{GDBN} supports the option @code{remotetimeout}.
15055 This option is set by the user, and @var{args} represents the number of
15056 seconds @value{GDBN} waits for responses.
15059 @cindex compiling, on Sparclet
15060 When compiling for debugging, include the options @samp{-g} to get debug
15061 information and @samp{-Ttext} to relocate the program to where you wish to
15062 load it on the target. You may also want to add the options @samp{-n} or
15063 @samp{-N} in order to reduce the size of the sections. Example:
15066 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15069 You can use @code{objdump} to verify that the addresses are what you intended:
15072 sparclet-aout-objdump --headers --syms prog
15075 @cindex running, on Sparclet
15077 your Unix execution search path to find @value{GDBN}, you are ready to
15078 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15079 (or @code{sparclet-aout-gdb}, depending on your installation).
15081 @value{GDBN} comes up showing the prompt:
15088 * Sparclet File:: Setting the file to debug
15089 * Sparclet Connection:: Connecting to Sparclet
15090 * Sparclet Download:: Sparclet download
15091 * Sparclet Execution:: Running and debugging
15094 @node Sparclet File
15095 @subsubsection Setting file to debug
15097 The @value{GDBN} command @code{file} lets you choose with program to debug.
15100 (gdbslet) file prog
15104 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15105 @value{GDBN} locates
15106 the file by searching the directories listed in the command search
15108 If the file was compiled with debug information (option "-g"), source
15109 files will be searched as well.
15110 @value{GDBN} locates
15111 the source files by searching the directories listed in the directory search
15112 path (@pxref{Environment, ,Your program's environment}).
15114 to find a file, it displays a message such as:
15117 prog: No such file or directory.
15120 When this happens, add the appropriate directories to the search paths with
15121 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15122 @code{target} command again.
15124 @node Sparclet Connection
15125 @subsubsection Connecting to Sparclet
15127 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15128 To connect to a target on serial port ``@code{ttya}'', type:
15131 (gdbslet) target sparclet /dev/ttya
15132 Remote target sparclet connected to /dev/ttya
15133 main () at ../prog.c:3
15137 @value{GDBN} displays messages like these:
15143 @node Sparclet Download
15144 @subsubsection Sparclet download
15146 @cindex download to Sparclet
15147 Once connected to the Sparclet target,
15148 you can use the @value{GDBN}
15149 @code{load} command to download the file from the host to the target.
15150 The file name and load offset should be given as arguments to the @code{load}
15152 Since the file format is aout, the program must be loaded to the starting
15153 address. You can use @code{objdump} to find out what this value is. The load
15154 offset is an offset which is added to the VMA (virtual memory address)
15155 of each of the file's sections.
15156 For instance, if the program
15157 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15158 and bss at 0x12010170, in @value{GDBN}, type:
15161 (gdbslet) load prog 0x12010000
15162 Loading section .text, size 0xdb0 vma 0x12010000
15165 If the code is loaded at a different address then what the program was linked
15166 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15167 to tell @value{GDBN} where to map the symbol table.
15169 @node Sparclet Execution
15170 @subsubsection Running and debugging
15172 @cindex running and debugging Sparclet programs
15173 You can now begin debugging the task using @value{GDBN}'s execution control
15174 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15175 manual for the list of commands.
15179 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15181 Starting program: prog
15182 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15183 3 char *symarg = 0;
15185 4 char *execarg = "hello!";
15190 @subsection Fujitsu Sparclite
15194 @kindex target sparclite
15195 @item target sparclite @var{dev}
15196 Fujitsu sparclite boards, used only for the purpose of loading.
15197 You must use an additional command to debug the program.
15198 For example: target remote @var{dev} using @value{GDBN} standard
15204 @subsection Tandem ST2000
15206 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
15209 To connect your ST2000 to the host system, see the manufacturer's
15210 manual. Once the ST2000 is physically attached, you can run:
15213 target st2000 @var{dev} @var{speed}
15217 to establish it as your debugging environment. @var{dev} is normally
15218 the name of a serial device, such as @file{/dev/ttya}, connected to the
15219 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
15220 connection (for example, to a serial line attached via a terminal
15221 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
15223 The @code{load} and @code{attach} commands are @emph{not} defined for
15224 this target; you must load your program into the ST2000 as you normally
15225 would for standalone operation. @value{GDBN} reads debugging information
15226 (such as symbols) from a separate, debugging version of the program
15227 available on your host computer.
15228 @c FIXME!! This is terribly vague; what little content is here is
15229 @c basically hearsay.
15231 @cindex ST2000 auxiliary commands
15232 These auxiliary @value{GDBN} commands are available to help you with the ST2000
15236 @item st2000 @var{command}
15237 @kindex st2000 @var{cmd}
15238 @cindex STDBUG commands (ST2000)
15239 @cindex commands to STDBUG (ST2000)
15240 Send a @var{command} to the STDBUG monitor. See the manufacturer's
15241 manual for available commands.
15244 @cindex connect (to STDBUG)
15245 Connect the controlling terminal to the STDBUG command monitor. When
15246 you are done interacting with STDBUG, typing either of two character
15247 sequences gets you back to the @value{GDBN} command prompt:
15248 @kbd{@key{RET} ~ .} (Return, followed by tilde and period) or
15249 @kbd{@key{RET} ~ Ctrl-d} (Return, followed by tilde and control-D).
15253 @subsection Zilog Z8000
15256 @cindex simulator, Z8000
15257 @cindex Zilog Z8000 simulator
15259 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15262 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15263 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15264 segmented variant). The simulator recognizes which architecture is
15265 appropriate by inspecting the object code.
15268 @item target sim @var{args}
15270 @kindex target sim@r{, with Z8000}
15271 Debug programs on a simulated CPU. If the simulator supports setup
15272 options, specify them via @var{args}.
15276 After specifying this target, you can debug programs for the simulated
15277 CPU in the same style as programs for your host computer; use the
15278 @code{file} command to load a new program image, the @code{run} command
15279 to run your program, and so on.
15281 As well as making available all the usual machine registers
15282 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15283 additional items of information as specially named registers:
15288 Counts clock-ticks in the simulator.
15291 Counts instructions run in the simulator.
15294 Execution time in 60ths of a second.
15298 You can refer to these values in @value{GDBN} expressions with the usual
15299 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15300 conditional breakpoint that suspends only after at least 5000
15301 simulated clock ticks.
15304 @subsection Atmel AVR
15307 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15308 following AVR-specific commands:
15311 @item info io_registers
15312 @kindex info io_registers@r{, AVR}
15313 @cindex I/O registers (Atmel AVR)
15314 This command displays information about the AVR I/O registers. For
15315 each register, @value{GDBN} prints its number and value.
15322 When configured for debugging CRIS, @value{GDBN} provides the
15323 following CRIS-specific commands:
15326 @item set cris-version @var{ver}
15327 @cindex CRIS version
15328 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15329 The CRIS version affects register names and sizes. This command is useful in
15330 case autodetection of the CRIS version fails.
15332 @item show cris-version
15333 Show the current CRIS version.
15335 @item set cris-dwarf2-cfi
15336 @cindex DWARF-2 CFI and CRIS
15337 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15338 Change to @samp{off} when using @code{gcc-cris} whose version is below
15341 @item show cris-dwarf2-cfi
15342 Show the current state of using DWARF-2 CFI.
15344 @item set cris-mode @var{mode}
15346 Set the current CRIS mode to @var{mode}. It should only be changed when
15347 debugging in guru mode, in which case it should be set to
15348 @samp{guru} (the default is @samp{normal}).
15350 @item show cris-mode
15351 Show the current CRIS mode.
15355 @subsection Renesas Super-H
15358 For the Renesas Super-H processor, @value{GDBN} provides these
15363 @kindex regs@r{, Super-H}
15364 Show the values of all Super-H registers.
15368 @subsection Windows CE
15371 The following commands are available for Windows CE:
15374 @item set remotedirectory @var{dir}
15375 @kindex set remotedirectory
15376 Tell @value{GDBN} to upload files from the named directory @var{dir}.
15377 The default is @file{/gdb}, i.e.@: the root directory on the current
15380 @item show remotedirectory
15381 @kindex show remotedirectory
15382 Show the current value of the upload directory.
15384 @item set remoteupload @var{method}
15385 @kindex set remoteupload
15386 Set the method used to upload files to remote device. Valid values
15387 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
15388 The default is @samp{newer}.
15390 @item show remoteupload
15391 @kindex show remoteupload
15392 Show the current setting of the upload method.
15394 @item set remoteaddhost
15395 @kindex set remoteaddhost
15396 Tell @value{GDBN} whether to add this host to the remote stub's
15397 arguments when you debug over a network.
15399 @item show remoteaddhost
15400 @kindex show remoteaddhost
15401 Show whether to add this host to remote stub's arguments when
15402 debugging over a network.
15406 @node Architectures
15407 @section Architectures
15409 This section describes characteristics of architectures that affect
15410 all uses of @value{GDBN} with the architecture, both native and cross.
15417 * HPPA:: HP PA architecture
15421 @subsection x86 Architecture-specific issues.
15424 @item set struct-convention @var{mode}
15425 @kindex set struct-convention
15426 @cindex struct return convention
15427 @cindex struct/union returned in registers
15428 Set the convention used by the inferior to return @code{struct}s and
15429 @code{union}s from functions to @var{mode}. Possible values of
15430 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15431 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15432 are returned on the stack, while @code{"reg"} means that a
15433 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15434 be returned in a register.
15436 @item show struct-convention
15437 @kindex show struct-convention
15438 Show the current setting of the convention to return @code{struct}s
15447 @kindex set rstack_high_address
15448 @cindex AMD 29K register stack
15449 @cindex register stack, AMD29K
15450 @item set rstack_high_address @var{address}
15451 On AMD 29000 family processors, registers are saved in a separate
15452 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15453 extent of this stack. Normally, @value{GDBN} just assumes that the
15454 stack is ``large enough''. This may result in @value{GDBN} referencing
15455 memory locations that do not exist. If necessary, you can get around
15456 this problem by specifying the ending address of the register stack with
15457 the @code{set rstack_high_address} command. The argument should be an
15458 address, which you probably want to precede with @samp{0x} to specify in
15461 @kindex show rstack_high_address
15462 @item show rstack_high_address
15463 Display the current limit of the register stack, on AMD 29000 family
15471 See the following section.
15476 @cindex stack on Alpha
15477 @cindex stack on MIPS
15478 @cindex Alpha stack
15480 Alpha- and MIPS-based computers use an unusual stack frame, which
15481 sometimes requires @value{GDBN} to search backward in the object code to
15482 find the beginning of a function.
15484 @cindex response time, MIPS debugging
15485 To improve response time (especially for embedded applications, where
15486 @value{GDBN} may be restricted to a slow serial line for this search)
15487 you may want to limit the size of this search, using one of these
15491 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15492 @item set heuristic-fence-post @var{limit}
15493 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15494 search for the beginning of a function. A value of @var{0} (the
15495 default) means there is no limit. However, except for @var{0}, the
15496 larger the limit the more bytes @code{heuristic-fence-post} must search
15497 and therefore the longer it takes to run. You should only need to use
15498 this command when debugging a stripped executable.
15500 @item show heuristic-fence-post
15501 Display the current limit.
15505 These commands are available @emph{only} when @value{GDBN} is configured
15506 for debugging programs on Alpha or MIPS processors.
15508 Several MIPS-specific commands are available when debugging MIPS
15512 @item set mips saved-gpreg-size @var{size}
15513 @kindex set mips saved-gpreg-size
15514 @cindex MIPS GP register size on stack
15515 Set the size of MIPS general-purpose registers saved on the stack.
15516 The argument @var{size} can be one of the following:
15520 32-bit GP registers
15522 64-bit GP registers
15524 Use the target's default setting or autodetect the saved size from the
15525 information contained in the executable. This is the default
15528 @item show mips saved-gpreg-size
15529 @kindex show mips saved-gpreg-size
15530 Show the current size of MIPS GP registers on the stack.
15532 @item set mips stack-arg-size @var{size}
15533 @kindex set mips stack-arg-size
15534 @cindex MIPS stack space for arguments
15535 Set the amount of stack space reserved for arguments to functions.
15536 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15539 @item set mips abi @var{arg}
15540 @kindex set mips abi
15541 @cindex set ABI for MIPS
15542 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15543 values of @var{arg} are:
15547 The default ABI associated with the current binary (this is the
15558 @item show mips abi
15559 @kindex show mips abi
15560 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15563 @itemx show mipsfpu
15564 @xref{MIPS Embedded, set mipsfpu}.
15566 @item set mips mask-address @var{arg}
15567 @kindex set mips mask-address
15568 @cindex MIPS addresses, masking
15569 This command determines whether the most-significant 32 bits of 64-bit
15570 MIPS addresses are masked off. The argument @var{arg} can be
15571 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15572 setting, which lets @value{GDBN} determine the correct value.
15574 @item show mips mask-address
15575 @kindex show mips mask-address
15576 Show whether the upper 32 bits of MIPS addresses are masked off or
15579 @item set remote-mips64-transfers-32bit-regs
15580 @kindex set remote-mips64-transfers-32bit-regs
15581 This command controls compatibility with 64-bit MIPS targets that
15582 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15583 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15584 and 64 bits for other registers, set this option to @samp{on}.
15586 @item show remote-mips64-transfers-32bit-regs
15587 @kindex show remote-mips64-transfers-32bit-regs
15588 Show the current setting of compatibility with older MIPS 64 targets.
15590 @item set debug mips
15591 @kindex set debug mips
15592 This command turns on and off debugging messages for the MIPS-specific
15593 target code in @value{GDBN}.
15595 @item show debug mips
15596 @kindex show debug mips
15597 Show the current setting of MIPS debugging messages.
15603 @cindex HPPA support
15605 When @value{GDBN} is debugging te HP PA architecture, it provides the
15606 following special commands:
15609 @item set debug hppa
15610 @kindex set debug hppa
15611 THis command determines whether HPPA architecture specific debugging
15612 messages are to be displayed.
15614 @item show debug hppa
15615 Show whether HPPA debugging messages are displayed.
15617 @item maint print unwind @var{address}
15618 @kindex maint print unwind@r{, HPPA}
15619 This command displays the contents of the unwind table entry at the
15620 given @var{address}.
15625 @node Controlling GDB
15626 @chapter Controlling @value{GDBN}
15628 You can alter the way @value{GDBN} interacts with you by using the
15629 @code{set} command. For commands controlling how @value{GDBN} displays
15630 data, see @ref{Print Settings, ,Print settings}. Other settings are
15635 * Editing:: Command editing
15636 * Command History:: Command history
15637 * Screen Size:: Screen size
15638 * Numbers:: Numbers
15639 * ABI:: Configuring the current ABI
15640 * Messages/Warnings:: Optional warnings and messages
15641 * Debugging Output:: Optional messages about internal happenings
15649 @value{GDBN} indicates its readiness to read a command by printing a string
15650 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15651 can change the prompt string with the @code{set prompt} command. For
15652 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15653 the prompt in one of the @value{GDBN} sessions so that you can always tell
15654 which one you are talking to.
15656 @emph{Note:} @code{set prompt} does not add a space for you after the
15657 prompt you set. This allows you to set a prompt which ends in a space
15658 or a prompt that does not.
15662 @item set prompt @var{newprompt}
15663 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15665 @kindex show prompt
15667 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15671 @section Command editing
15673 @cindex command line editing
15675 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15676 @sc{gnu} library provides consistent behavior for programs which provide a
15677 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15678 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15679 substitution, and a storage and recall of command history across
15680 debugging sessions.
15682 You may control the behavior of command line editing in @value{GDBN} with the
15683 command @code{set}.
15686 @kindex set editing
15689 @itemx set editing on
15690 Enable command line editing (enabled by default).
15692 @item set editing off
15693 Disable command line editing.
15695 @kindex show editing
15697 Show whether command line editing is enabled.
15700 @xref{Command Line Editing}, for more details about the Readline
15701 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15702 encouraged to read that chapter.
15704 @node Command History
15705 @section Command history
15706 @cindex command history
15708 @value{GDBN} can keep track of the commands you type during your
15709 debugging sessions, so that you can be certain of precisely what
15710 happened. Use these commands to manage the @value{GDBN} command
15713 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15714 package, to provide the history facility. @xref{Using History
15715 Interactively}, for the detailed description of the History library.
15717 To issue a command to @value{GDBN} without affecting certain aspects of
15718 the state which is seen by users, prefix it with @samp{server }. This
15719 means that this command will not affect the command history, nor will it
15720 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15721 pressed on a line by itself.
15723 @cindex @code{server}, command prefix
15724 The server prefix does not affect the recording of values into the value
15725 history; to print a value without recording it into the value history,
15726 use the @code{output} command instead of the @code{print} command.
15728 Here is the description of @value{GDBN} commands related to command
15732 @cindex history substitution
15733 @cindex history file
15734 @kindex set history filename
15735 @cindex @env{GDBHISTFILE}, environment variable
15736 @item set history filename @var{fname}
15737 Set the name of the @value{GDBN} command history file to @var{fname}.
15738 This is the file where @value{GDBN} reads an initial command history
15739 list, and where it writes the command history from this session when it
15740 exits. You can access this list through history expansion or through
15741 the history command editing characters listed below. This file defaults
15742 to the value of the environment variable @code{GDBHISTFILE}, or to
15743 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15746 @cindex save command history
15747 @kindex set history save
15748 @item set history save
15749 @itemx set history save on
15750 Record command history in a file, whose name may be specified with the
15751 @code{set history filename} command. By default, this option is disabled.
15753 @item set history save off
15754 Stop recording command history in a file.
15756 @cindex history size
15757 @kindex set history size
15758 @cindex @env{HISTSIZE}, environment variable
15759 @item set history size @var{size}
15760 Set the number of commands which @value{GDBN} keeps in its history list.
15761 This defaults to the value of the environment variable
15762 @code{HISTSIZE}, or to 256 if this variable is not set.
15765 History expansion assigns special meaning to the character @kbd{!}.
15766 @xref{Event Designators}, for more details.
15768 @cindex history expansion, turn on/off
15769 Since @kbd{!} is also the logical not operator in C, history expansion
15770 is off by default. If you decide to enable history expansion with the
15771 @code{set history expansion on} command, you may sometimes need to
15772 follow @kbd{!} (when it is used as logical not, in an expression) with
15773 a space or a tab to prevent it from being expanded. The readline
15774 history facilities do not attempt substitution on the strings
15775 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15777 The commands to control history expansion are:
15780 @item set history expansion on
15781 @itemx set history expansion
15782 @kindex set history expansion
15783 Enable history expansion. History expansion is off by default.
15785 @item set history expansion off
15786 Disable history expansion.
15789 @kindex show history
15791 @itemx show history filename
15792 @itemx show history save
15793 @itemx show history size
15794 @itemx show history expansion
15795 These commands display the state of the @value{GDBN} history parameters.
15796 @code{show history} by itself displays all four states.
15801 @kindex show commands
15802 @cindex show last commands
15803 @cindex display command history
15804 @item show commands
15805 Display the last ten commands in the command history.
15807 @item show commands @var{n}
15808 Print ten commands centered on command number @var{n}.
15810 @item show commands +
15811 Print ten commands just after the commands last printed.
15815 @section Screen size
15816 @cindex size of screen
15817 @cindex pauses in output
15819 Certain commands to @value{GDBN} may produce large amounts of
15820 information output to the screen. To help you read all of it,
15821 @value{GDBN} pauses and asks you for input at the end of each page of
15822 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15823 to discard the remaining output. Also, the screen width setting
15824 determines when to wrap lines of output. Depending on what is being
15825 printed, @value{GDBN} tries to break the line at a readable place,
15826 rather than simply letting it overflow onto the following line.
15828 Normally @value{GDBN} knows the size of the screen from the terminal
15829 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15830 together with the value of the @code{TERM} environment variable and the
15831 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15832 you can override it with the @code{set height} and @code{set
15839 @kindex show height
15840 @item set height @var{lpp}
15842 @itemx set width @var{cpl}
15844 These @code{set} commands specify a screen height of @var{lpp} lines and
15845 a screen width of @var{cpl} characters. The associated @code{show}
15846 commands display the current settings.
15848 If you specify a height of zero lines, @value{GDBN} does not pause during
15849 output no matter how long the output is. This is useful if output is to a
15850 file or to an editor buffer.
15852 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15853 from wrapping its output.
15855 @item set pagination on
15856 @itemx set pagination off
15857 @kindex set pagination
15858 Turn the output pagination on or off; the default is on. Turning
15859 pagination off is the alternative to @code{set height 0}.
15861 @item show pagination
15862 @kindex show pagination
15863 Show the current pagination mode.
15868 @cindex number representation
15869 @cindex entering numbers
15871 You can always enter numbers in octal, decimal, or hexadecimal in
15872 @value{GDBN} by the usual conventions: octal numbers begin with
15873 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15874 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15875 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15876 10; likewise, the default display for numbers---when no particular
15877 format is specified---is base 10. You can change the default base for
15878 both input and output with the commands described below.
15881 @kindex set input-radix
15882 @item set input-radix @var{base}
15883 Set the default base for numeric input. Supported choices
15884 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15885 specified either unambiguously or using the current input radix; for
15889 set input-radix 012
15890 set input-radix 10.
15891 set input-radix 0xa
15895 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15896 leaves the input radix unchanged, no matter what it was, since
15897 @samp{10}, being without any leading or trailing signs of its base, is
15898 interpreted in the current radix. Thus, if the current radix is 16,
15899 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15902 @kindex set output-radix
15903 @item set output-radix @var{base}
15904 Set the default base for numeric display. Supported choices
15905 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15906 specified either unambiguously or using the current input radix.
15908 @kindex show input-radix
15909 @item show input-radix
15910 Display the current default base for numeric input.
15912 @kindex show output-radix
15913 @item show output-radix
15914 Display the current default base for numeric display.
15916 @item set radix @r{[}@var{base}@r{]}
15920 These commands set and show the default base for both input and output
15921 of numbers. @code{set radix} sets the radix of input and output to
15922 the same base; without an argument, it resets the radix back to its
15923 default value of 10.
15928 @section Configuring the current ABI
15930 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15931 application automatically. However, sometimes you need to override its
15932 conclusions. Use these commands to manage @value{GDBN}'s view of the
15939 One @value{GDBN} configuration can debug binaries for multiple operating
15940 system targets, either via remote debugging or native emulation.
15941 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15942 but you can override its conclusion using the @code{set osabi} command.
15943 One example where this is useful is in debugging of binaries which use
15944 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15945 not have the same identifying marks that the standard C library for your
15950 Show the OS ABI currently in use.
15953 With no argument, show the list of registered available OS ABI's.
15955 @item set osabi @var{abi}
15956 Set the current OS ABI to @var{abi}.
15959 @cindex float promotion
15961 Generally, the way that an argument of type @code{float} is passed to a
15962 function depends on whether the function is prototyped. For a prototyped
15963 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15964 according to the architecture's convention for @code{float}. For unprototyped
15965 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15966 @code{double} and then passed.
15968 Unfortunately, some forms of debug information do not reliably indicate whether
15969 a function is prototyped. If @value{GDBN} calls a function that is not marked
15970 as prototyped, it consults @kbd{set coerce-float-to-double}.
15973 @kindex set coerce-float-to-double
15974 @item set coerce-float-to-double
15975 @itemx set coerce-float-to-double on
15976 Arguments of type @code{float} will be promoted to @code{double} when passed
15977 to an unprototyped function. This is the default setting.
15979 @item set coerce-float-to-double off
15980 Arguments of type @code{float} will be passed directly to unprototyped
15983 @kindex show coerce-float-to-double
15984 @item show coerce-float-to-double
15985 Show the current setting of promoting @code{float} to @code{double}.
15989 @kindex show cp-abi
15990 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15991 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15992 used to build your application. @value{GDBN} only fully supports
15993 programs with a single C@t{++} ABI; if your program contains code using
15994 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15995 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15996 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15997 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15998 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15999 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
16004 Show the C@t{++} ABI currently in use.
16007 With no argument, show the list of supported C@t{++} ABI's.
16009 @item set cp-abi @var{abi}
16010 @itemx set cp-abi auto
16011 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
16014 @node Messages/Warnings
16015 @section Optional warnings and messages
16017 @cindex verbose operation
16018 @cindex optional warnings
16019 By default, @value{GDBN} is silent about its inner workings. If you are
16020 running on a slow machine, you may want to use the @code{set verbose}
16021 command. This makes @value{GDBN} tell you when it does a lengthy
16022 internal operation, so you will not think it has crashed.
16024 Currently, the messages controlled by @code{set verbose} are those
16025 which announce that the symbol table for a source file is being read;
16026 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
16029 @kindex set verbose
16030 @item set verbose on
16031 Enables @value{GDBN} output of certain informational messages.
16033 @item set verbose off
16034 Disables @value{GDBN} output of certain informational messages.
16036 @kindex show verbose
16038 Displays whether @code{set verbose} is on or off.
16041 By default, if @value{GDBN} encounters bugs in the symbol table of an
16042 object file, it is silent; but if you are debugging a compiler, you may
16043 find this information useful (@pxref{Symbol Errors, ,Errors reading
16048 @kindex set complaints
16049 @item set complaints @var{limit}
16050 Permits @value{GDBN} to output @var{limit} complaints about each type of
16051 unusual symbols before becoming silent about the problem. Set
16052 @var{limit} to zero to suppress all complaints; set it to a large number
16053 to prevent complaints from being suppressed.
16055 @kindex show complaints
16056 @item show complaints
16057 Displays how many symbol complaints @value{GDBN} is permitted to produce.
16061 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
16062 lot of stupid questions to confirm certain commands. For example, if
16063 you try to run a program which is already running:
16067 The program being debugged has been started already.
16068 Start it from the beginning? (y or n)
16071 If you are willing to unflinchingly face the consequences of your own
16072 commands, you can disable this ``feature'':
16076 @kindex set confirm
16078 @cindex confirmation
16079 @cindex stupid questions
16080 @item set confirm off
16081 Disables confirmation requests.
16083 @item set confirm on
16084 Enables confirmation requests (the default).
16086 @kindex show confirm
16088 Displays state of confirmation requests.
16092 @cindex command tracing
16093 If you need to debug user-defined commands or sourced files you may find it
16094 useful to enable @dfn{command tracing}. In this mode each command will be
16095 printed as it is executed, prefixed with one or more @samp{+} symbols, the
16096 quantity denoting the call depth of each command.
16099 @kindex set trace-commands
16100 @cindex command scripts, debugging
16101 @item set trace-commands on
16102 Enable command tracing.
16103 @item set trace-commands off
16104 Disable command tracing.
16105 @item show trace-commands
16106 Display the current state of command tracing.
16109 @node Debugging Output
16110 @section Optional messages about internal happenings
16111 @cindex optional debugging messages
16113 @value{GDBN} has commands that enable optional debugging messages from
16114 various @value{GDBN} subsystems; normally these commands are of
16115 interest to @value{GDBN} maintainers, or when reporting a bug. This
16116 section documents those commands.
16119 @kindex set exec-done-display
16120 @item set exec-done-display
16121 Turns on or off the notification of asynchronous commands'
16122 completion. When on, @value{GDBN} will print a message when an
16123 asynchronous command finishes its execution. The default is off.
16124 @kindex show exec-done-display
16125 @item show exec-done-display
16126 Displays the current setting of asynchronous command completion
16129 @cindex gdbarch debugging info
16130 @cindex architecture debugging info
16131 @item set debug arch
16132 Turns on or off display of gdbarch debugging info. The default is off
16134 @item show debug arch
16135 Displays the current state of displaying gdbarch debugging info.
16136 @item set debug aix-thread
16137 @cindex AIX threads
16138 Display debugging messages about inner workings of the AIX thread
16140 @item show debug aix-thread
16141 Show the current state of AIX thread debugging info display.
16142 @item set debug event
16143 @cindex event debugging info
16144 Turns on or off display of @value{GDBN} event debugging info. The
16146 @item show debug event
16147 Displays the current state of displaying @value{GDBN} event debugging
16149 @item set debug expression
16150 @cindex expression debugging info
16151 Turns on or off display of debugging info about @value{GDBN}
16152 expression parsing. The default is off.
16153 @item show debug expression
16154 Displays the current state of displaying debugging info about
16155 @value{GDBN} expression parsing.
16156 @item set debug frame
16157 @cindex frame debugging info
16158 Turns on or off display of @value{GDBN} frame debugging info. The
16160 @item show debug frame
16161 Displays the current state of displaying @value{GDBN} frame debugging
16163 @item set debug infrun
16164 @cindex inferior debugging info
16165 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16166 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16167 for implementing operations such as single-stepping the inferior.
16168 @item show debug infrun
16169 Displays the current state of @value{GDBN} inferior debugging.
16170 @item set debug lin-lwp
16171 @cindex @sc{gnu}/Linux LWP debug messages
16172 @cindex Linux lightweight processes
16173 Turns on or off debugging messages from the Linux LWP debug support.
16174 @item show debug lin-lwp
16175 Show the current state of Linux LWP debugging messages.
16176 @item set debug observer
16177 @cindex observer debugging info
16178 Turns on or off display of @value{GDBN} observer debugging. This
16179 includes info such as the notification of observable events.
16180 @item show debug observer
16181 Displays the current state of observer debugging.
16182 @item set debug overload
16183 @cindex C@t{++} overload debugging info
16184 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16185 info. This includes info such as ranking of functions, etc. The default
16187 @item show debug overload
16188 Displays the current state of displaying @value{GDBN} C@t{++} overload
16190 @cindex packets, reporting on stdout
16191 @cindex serial connections, debugging
16192 @cindex debug remote protocol
16193 @cindex remote protocol debugging
16194 @cindex display remote packets
16195 @item set debug remote
16196 Turns on or off display of reports on all packets sent back and forth across
16197 the serial line to the remote machine. The info is printed on the
16198 @value{GDBN} standard output stream. The default is off.
16199 @item show debug remote
16200 Displays the state of display of remote packets.
16201 @item set debug serial
16202 Turns on or off display of @value{GDBN} serial debugging info. The
16204 @item show debug serial
16205 Displays the current state of displaying @value{GDBN} serial debugging
16207 @item set debug solib-frv
16208 @cindex FR-V shared-library debugging
16209 Turns on or off debugging messages for FR-V shared-library code.
16210 @item show debug solib-frv
16211 Display the current state of FR-V shared-library code debugging
16213 @item set debug target
16214 @cindex target debugging info
16215 Turns on or off display of @value{GDBN} target debugging info. This info
16216 includes what is going on at the target level of GDB, as it happens. The
16217 default is 0. Set it to 1 to track events, and to 2 to also track the
16218 value of large memory transfers. Changes to this flag do not take effect
16219 until the next time you connect to a target or use the @code{run} command.
16220 @item show debug target
16221 Displays the current state of displaying @value{GDBN} target debugging
16223 @item set debugvarobj
16224 @cindex variable object debugging info
16225 Turns on or off display of @value{GDBN} variable object debugging
16226 info. The default is off.
16227 @item show debugvarobj
16228 Displays the current state of displaying @value{GDBN} variable object
16233 @chapter Canned Sequences of Commands
16235 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16236 command lists}), @value{GDBN} provides two ways to store sequences of
16237 commands for execution as a unit: user-defined commands and command
16241 * Define:: How to define your own commands
16242 * Hooks:: Hooks for user-defined commands
16243 * Command Files:: How to write scripts of commands to be stored in a file
16244 * Output:: Commands for controlled output
16248 @section User-defined commands
16250 @cindex user-defined command
16251 @cindex arguments, to user-defined commands
16252 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16253 which you assign a new name as a command. This is done with the
16254 @code{define} command. User commands may accept up to 10 arguments
16255 separated by whitespace. Arguments are accessed within the user command
16256 via @code{$arg0@dots{}$arg9}. A trivial example:
16260 print $arg0 + $arg1 + $arg2
16265 To execute the command use:
16272 This defines the command @code{adder}, which prints the sum of
16273 its three arguments. Note the arguments are text substitutions, so they may
16274 reference variables, use complex expressions, or even perform inferior
16277 @cindex argument count in user-defined commands
16278 @cindex how many arguments (user-defined commands)
16279 In addition, @code{$argc} may be used to find out how many arguments have
16280 been passed. This expands to a number in the range 0@dots{}10.
16285 print $arg0 + $arg1
16288 print $arg0 + $arg1 + $arg2
16296 @item define @var{commandname}
16297 Define a command named @var{commandname}. If there is already a command
16298 by that name, you are asked to confirm that you want to redefine it.
16300 The definition of the command is made up of other @value{GDBN} command lines,
16301 which are given following the @code{define} command. The end of these
16302 commands is marked by a line containing @code{end}.
16305 @kindex end@r{ (user-defined commands)}
16306 @item document @var{commandname}
16307 Document the user-defined command @var{commandname}, so that it can be
16308 accessed by @code{help}. The command @var{commandname} must already be
16309 defined. This command reads lines of documentation just as @code{define}
16310 reads the lines of the command definition, ending with @code{end}.
16311 After the @code{document} command is finished, @code{help} on command
16312 @var{commandname} displays the documentation you have written.
16314 You may use the @code{document} command again to change the
16315 documentation of a command. Redefining the command with @code{define}
16316 does not change the documentation.
16318 @kindex dont-repeat
16319 @cindex don't repeat command
16321 Used inside a user-defined command, this tells @value{GDBN} that this
16322 command should not be repeated when the user hits @key{RET}
16323 (@pxref{Command Syntax, repeat last command}).
16325 @kindex help user-defined
16326 @item help user-defined
16327 List all user-defined commands, with the first line of the documentation
16332 @itemx show user @var{commandname}
16333 Display the @value{GDBN} commands used to define @var{commandname} (but
16334 not its documentation). If no @var{commandname} is given, display the
16335 definitions for all user-defined commands.
16337 @cindex infinite recursion in user-defined commands
16338 @kindex show max-user-call-depth
16339 @kindex set max-user-call-depth
16340 @item show max-user-call-depth
16341 @itemx set max-user-call-depth
16342 The value of @code{max-user-call-depth} controls how many recursion
16343 levels are allowed in user-defined commands before GDB suspects an
16344 infinite recursion and aborts the command.
16347 In addition to the above commands, user-defined commands frequently
16348 use control flow commands, described in @ref{Command Files}.
16350 When user-defined commands are executed, the
16351 commands of the definition are not printed. An error in any command
16352 stops execution of the user-defined command.
16354 If used interactively, commands that would ask for confirmation proceed
16355 without asking when used inside a user-defined command. Many @value{GDBN}
16356 commands that normally print messages to say what they are doing omit the
16357 messages when used in a user-defined command.
16360 @section User-defined command hooks
16361 @cindex command hooks
16362 @cindex hooks, for commands
16363 @cindex hooks, pre-command
16366 You may define @dfn{hooks}, which are a special kind of user-defined
16367 command. Whenever you run the command @samp{foo}, if the user-defined
16368 command @samp{hook-foo} exists, it is executed (with no arguments)
16369 before that command.
16371 @cindex hooks, post-command
16373 A hook may also be defined which is run after the command you executed.
16374 Whenever you run the command @samp{foo}, if the user-defined command
16375 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16376 that command. Post-execution hooks may exist simultaneously with
16377 pre-execution hooks, for the same command.
16379 It is valid for a hook to call the command which it hooks. If this
16380 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16382 @c It would be nice if hookpost could be passed a parameter indicating
16383 @c if the command it hooks executed properly or not. FIXME!
16385 @kindex stop@r{, a pseudo-command}
16386 In addition, a pseudo-command, @samp{stop} exists. Defining
16387 (@samp{hook-stop}) makes the associated commands execute every time
16388 execution stops in your program: before breakpoint commands are run,
16389 displays are printed, or the stack frame is printed.
16391 For example, to ignore @code{SIGALRM} signals while
16392 single-stepping, but treat them normally during normal execution,
16397 handle SIGALRM nopass
16401 handle SIGALRM pass
16404 define hook-continue
16405 handle SIGLARM pass
16409 As a further example, to hook at the begining and end of the @code{echo}
16410 command, and to add extra text to the beginning and end of the message,
16418 define hookpost-echo
16422 (@value{GDBP}) echo Hello World
16423 <<<---Hello World--->>>
16428 You can define a hook for any single-word command in @value{GDBN}, but
16429 not for command aliases; you should define a hook for the basic command
16430 name, e.g.@: @code{backtrace} rather than @code{bt}.
16431 @c FIXME! So how does Joe User discover whether a command is an alias
16433 If an error occurs during the execution of your hook, execution of
16434 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16435 (before the command that you actually typed had a chance to run).
16437 If you try to define a hook which does not match any known command, you
16438 get a warning from the @code{define} command.
16440 @node Command Files
16441 @section Command files
16443 @cindex command files
16444 @cindex scripting commands
16445 A command file for @value{GDBN} is a text file made of lines that are
16446 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16447 also be included. An empty line in a command file does nothing; it
16448 does not mean to repeat the last command, as it would from the
16451 You can request the execution of a command file with the @code{source}
16456 @cindex execute commands from a file
16457 @item source [@code{-v}] @var{filename}
16458 Execute the command file @var{filename}.
16461 The lines in a command file are generally executed sequentially,
16462 unless the order of execution is changed by one of the
16463 @emph{flow-control commands} described below. The commands are not
16464 printed as they are executed. An error in any command terminates
16465 execution of the command file and control is returned to the console.
16467 @value{GDBN} searches for @var{filename} in the current directory and then
16468 on the search path (specified with the @samp{directory} command).
16470 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16471 each command as it is executed. The option must be given before
16472 @var{filename}, and is interpreted as part of the filename anywhere else.
16474 Commands that would ask for confirmation if used interactively proceed
16475 without asking when used in a command file. Many @value{GDBN} commands that
16476 normally print messages to say what they are doing omit the messages
16477 when called from command files.
16479 @value{GDBN} also accepts command input from standard input. In this
16480 mode, normal output goes to standard output and error output goes to
16481 standard error. Errors in a command file supplied on standard input do
16482 not terminate execution of the command file---execution continues with
16486 gdb < cmds > log 2>&1
16489 (The syntax above will vary depending on the shell used.) This example
16490 will execute commands from the file @file{cmds}. All output and errors
16491 would be directed to @file{log}.
16493 Since commands stored on command files tend to be more general than
16494 commands typed interactively, they frequently need to deal with
16495 complicated situations, such as different or unexpected values of
16496 variables and symbols, changes in how the program being debugged is
16497 built, etc. @value{GDBN} provides a set of flow-control commands to
16498 deal with these complexities. Using these commands, you can write
16499 complex scripts that loop over data structures, execute commands
16500 conditionally, etc.
16507 This command allows to include in your script conditionally executed
16508 commands. The @code{if} command takes a single argument, which is an
16509 expression to evaluate. It is followed by a series of commands that
16510 are executed only if the expression is true (its value is nonzero).
16511 There can then optionally be an @code{else} line, followed by a series
16512 of commands that are only executed if the expression was false. The
16513 end of the list is marked by a line containing @code{end}.
16517 This command allows to write loops. Its syntax is similar to
16518 @code{if}: the command takes a single argument, which is an expression
16519 to evaluate, and must be followed by the commands to execute, one per
16520 line, terminated by an @code{end}. These commands are called the
16521 @dfn{body} of the loop. The commands in the body of @code{while} are
16522 executed repeatedly as long as the expression evaluates to true.
16526 This command exits the @code{while} loop in whose body it is included.
16527 Execution of the script continues after that @code{while}s @code{end}
16530 @kindex loop_continue
16531 @item loop_continue
16532 This command skips the execution of the rest of the body of commands
16533 in the @code{while} loop in whose body it is included. Execution
16534 branches to the beginning of the @code{while} loop, where it evaluates
16535 the controlling expression.
16537 @kindex end@r{ (if/else/while commands)}
16539 Terminate the block of commands that are the body of @code{if},
16540 @code{else}, or @code{while} flow-control commands.
16545 @section Commands for controlled output
16547 During the execution of a command file or a user-defined command, normal
16548 @value{GDBN} output is suppressed; the only output that appears is what is
16549 explicitly printed by the commands in the definition. This section
16550 describes three commands useful for generating exactly the output you
16555 @item echo @var{text}
16556 @c I do not consider backslash-space a standard C escape sequence
16557 @c because it is not in ANSI.
16558 Print @var{text}. Nonprinting characters can be included in
16559 @var{text} using C escape sequences, such as @samp{\n} to print a
16560 newline. @strong{No newline is printed unless you specify one.}
16561 In addition to the standard C escape sequences, a backslash followed
16562 by a space stands for a space. This is useful for displaying a
16563 string with spaces at the beginning or the end, since leading and
16564 trailing spaces are otherwise trimmed from all arguments.
16565 To print @samp{@w{ }and foo =@w{ }}, use the command
16566 @samp{echo \@w{ }and foo = \@w{ }}.
16568 A backslash at the end of @var{text} can be used, as in C, to continue
16569 the command onto subsequent lines. For example,
16572 echo This is some text\n\
16573 which is continued\n\
16574 onto several lines.\n
16577 produces the same output as
16580 echo This is some text\n
16581 echo which is continued\n
16582 echo onto several lines.\n
16586 @item output @var{expression}
16587 Print the value of @var{expression} and nothing but that value: no
16588 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16589 value history either. @xref{Expressions, ,Expressions}, for more information
16592 @item output/@var{fmt} @var{expression}
16593 Print the value of @var{expression} in format @var{fmt}. You can use
16594 the same formats as for @code{print}. @xref{Output Formats,,Output
16595 formats}, for more information.
16598 @item printf @var{string}, @var{expressions}@dots{}
16599 Print the values of the @var{expressions} under the control of
16600 @var{string}. The @var{expressions} are separated by commas and may be
16601 either numbers or pointers. Their values are printed as specified by
16602 @var{string}, exactly as if your program were to execute the C
16604 @c FIXME: the above implies that at least all ANSI C formats are
16605 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16606 @c Either this is a bug, or the manual should document what formats are
16610 printf (@var{string}, @var{expressions}@dots{});
16613 For example, you can print two values in hex like this:
16616 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16619 The only backslash-escape sequences that you can use in the format
16620 string are the simple ones that consist of backslash followed by a
16625 @chapter Command Interpreters
16626 @cindex command interpreters
16628 @value{GDBN} supports multiple command interpreters, and some command
16629 infrastructure to allow users or user interface writers to switch
16630 between interpreters or run commands in other interpreters.
16632 @value{GDBN} currently supports two command interpreters, the console
16633 interpreter (sometimes called the command-line interpreter or @sc{cli})
16634 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16635 describes both of these interfaces in great detail.
16637 By default, @value{GDBN} will start with the console interpreter.
16638 However, the user may choose to start @value{GDBN} with another
16639 interpreter by specifying the @option{-i} or @option{--interpreter}
16640 startup options. Defined interpreters include:
16644 @cindex console interpreter
16645 The traditional console or command-line interpreter. This is the most often
16646 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16647 @value{GDBN} will use this interpreter.
16650 @cindex mi interpreter
16651 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16652 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16653 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16657 @cindex mi2 interpreter
16658 The current @sc{gdb/mi} interface.
16661 @cindex mi1 interpreter
16662 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16666 @cindex invoke another interpreter
16667 The interpreter being used by @value{GDBN} may not be dynamically
16668 switched at runtime. Although possible, this could lead to a very
16669 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16670 enters the command "interpreter-set console" in a console view,
16671 @value{GDBN} would switch to using the console interpreter, rendering
16672 the IDE inoperable!
16674 @kindex interpreter-exec
16675 Although you may only choose a single interpreter at startup, you may execute
16676 commands in any interpreter from the current interpreter using the appropriate
16677 command. If you are running the console interpreter, simply use the
16678 @code{interpreter-exec} command:
16681 interpreter-exec mi "-data-list-register-names"
16684 @sc{gdb/mi} has a similar command, although it is only available in versions of
16685 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16688 @chapter @value{GDBN} Text User Interface
16690 @cindex Text User Interface
16693 * TUI Overview:: TUI overview
16694 * TUI Keys:: TUI key bindings
16695 * TUI Single Key Mode:: TUI single key mode
16696 * TUI Commands:: TUI specific commands
16697 * TUI Configuration:: TUI configuration variables
16700 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16701 interface which uses the @code{curses} library to show the source
16702 file, the assembly output, the program registers and @value{GDBN}
16703 commands in separate text windows.
16705 The TUI is enabled by invoking @value{GDBN} using either
16707 @samp{gdbtui} or @samp{gdb -tui}.
16710 @section TUI overview
16712 The TUI has two display modes that can be switched while
16717 A curses (or TUI) mode in which it displays several text
16718 windows on the terminal.
16721 A standard mode which corresponds to the @value{GDBN} configured without
16725 In the TUI mode, @value{GDBN} can display several text window
16730 This window is the @value{GDBN} command window with the @value{GDBN}
16731 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16732 managed using readline but through the TUI. The @emph{command}
16733 window is always visible.
16736 The source window shows the source file of the program. The current
16737 line as well as active breakpoints are displayed in this window.
16740 The assembly window shows the disassembly output of the program.
16743 This window shows the processor registers. It detects when
16744 a register is changed and when this is the case, registers that have
16745 changed are highlighted.
16749 The source and assembly windows show the current program position
16750 by highlighting the current line and marking them with the @samp{>} marker.
16751 Breakpoints are also indicated with two markers. A first one
16752 indicates the breakpoint type:
16756 Breakpoint which was hit at least once.
16759 Breakpoint which was never hit.
16762 Hardware breakpoint which was hit at least once.
16765 Hardware breakpoint which was never hit.
16769 The second marker indicates whether the breakpoint is enabled or not:
16773 Breakpoint is enabled.
16776 Breakpoint is disabled.
16780 The source, assembly and register windows are attached to the thread
16781 and the frame position. They are updated when the current thread
16782 changes, when the frame changes or when the program counter changes.
16783 These three windows are arranged by the TUI according to several
16784 layouts. The layout defines which of these three windows are visible.
16785 The following layouts are available:
16795 source and assembly
16798 source and registers
16801 assembly and registers
16805 On top of the command window a status line gives various information
16806 concerning the current process begin debugged. The status line is
16807 updated when the information it shows changes. The following fields
16812 Indicates the current gdb target
16813 (@pxref{Targets, ,Specifying a Debugging Target}).
16816 Gives information about the current process or thread number.
16817 When no process is being debugged, this field is set to @code{No process}.
16820 Gives the current function name for the selected frame.
16821 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16822 When there is no symbol corresponding to the current program counter
16823 the string @code{??} is displayed.
16826 Indicates the current line number for the selected frame.
16827 When the current line number is not known the string @code{??} is displayed.
16830 Indicates the current program counter address.
16835 @section TUI Key Bindings
16836 @cindex TUI key bindings
16838 The TUI installs several key bindings in the readline keymaps
16839 (@pxref{Command Line Editing}).
16840 They allow to leave or enter in the TUI mode or they operate
16841 directly on the TUI layout and windows. The TUI also provides
16842 a @emph{SingleKey} keymap which binds several keys directly to
16843 @value{GDBN} commands. The following key bindings
16844 are installed for both TUI mode and the @value{GDBN} standard mode.
16853 Enter or leave the TUI mode. When the TUI mode is left,
16854 the curses window management is left and @value{GDBN} operates using
16855 its standard mode writing on the terminal directly. When the TUI
16856 mode is entered, the control is given back to the curses windows.
16857 The screen is then refreshed.
16861 Use a TUI layout with only one window. The layout will
16862 either be @samp{source} or @samp{assembly}. When the TUI mode
16863 is not active, it will switch to the TUI mode.
16865 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16869 Use a TUI layout with at least two windows. When the current
16870 layout shows already two windows, a next layout with two windows is used.
16871 When a new layout is chosen, one window will always be common to the
16872 previous layout and the new one.
16874 Think of it as the Emacs @kbd{C-x 2} binding.
16878 Change the active window. The TUI associates several key bindings
16879 (like scrolling and arrow keys) to the active window. This command
16880 gives the focus to the next TUI window.
16882 Think of it as the Emacs @kbd{C-x o} binding.
16886 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16887 (@pxref{TUI Single Key Mode}).
16891 The following key bindings are handled only by the TUI mode:
16896 Scroll the active window one page up.
16900 Scroll the active window one page down.
16904 Scroll the active window one line up.
16908 Scroll the active window one line down.
16912 Scroll the active window one column left.
16916 Scroll the active window one column right.
16920 Refresh the screen.
16924 In the TUI mode, the arrow keys are used by the active window
16925 for scrolling. This means they are available for readline when the
16926 active window is the command window. When the command window
16927 does not have the focus, it is necessary to use other readline
16928 key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b} and @kbd{C-f}.
16930 @node TUI Single Key Mode
16931 @section TUI Single Key Mode
16932 @cindex TUI single key mode
16934 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16935 key binding in the readline keymaps to connect single keys to
16939 @kindex c @r{(SingleKey TUI key)}
16943 @kindex d @r{(SingleKey TUI key)}
16947 @kindex f @r{(SingleKey TUI key)}
16951 @kindex n @r{(SingleKey TUI key)}
16955 @kindex q @r{(SingleKey TUI key)}
16957 exit the @emph{SingleKey} mode.
16959 @kindex r @r{(SingleKey TUI key)}
16963 @kindex s @r{(SingleKey TUI key)}
16967 @kindex u @r{(SingleKey TUI key)}
16971 @kindex v @r{(SingleKey TUI key)}
16975 @kindex w @r{(SingleKey TUI key)}
16981 Other keys temporarily switch to the @value{GDBN} command prompt.
16982 The key that was pressed is inserted in the editing buffer so that
16983 it is possible to type most @value{GDBN} commands without interaction
16984 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16985 @emph{SingleKey} mode is restored. The only way to permanently leave
16986 this mode is by typing @kbd{q} or @kbd{C-x s}.
16990 @section TUI specific commands
16991 @cindex TUI commands
16993 The TUI has specific commands to control the text windows.
16994 These commands are always available, that is they do not depend on
16995 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16996 is in the standard mode, using these commands will automatically switch
17002 List and give the size of all displayed windows.
17006 Display the next layout.
17009 Display the previous layout.
17012 Display the source window only.
17015 Display the assembly window only.
17018 Display the source and assembly window.
17021 Display the register window together with the source or assembly window.
17023 @item focus next | prev | src | asm | regs | split
17025 Set the focus to the named window.
17026 This command allows to change the active window so that scrolling keys
17027 can be affected to another window.
17031 Refresh the screen. This is similar to typing @kbd{C-L}.
17033 @item tui reg float
17035 Show the floating point registers in the register window.
17037 @item tui reg general
17038 Show the general registers in the register window.
17041 Show the next register group. The list of register groups as well as
17042 their order is target specific. The predefined register groups are the
17043 following: @code{general}, @code{float}, @code{system}, @code{vector},
17044 @code{all}, @code{save}, @code{restore}.
17046 @item tui reg system
17047 Show the system registers in the register window.
17051 Update the source window and the current execution point.
17053 @item winheight @var{name} +@var{count}
17054 @itemx winheight @var{name} -@var{count}
17056 Change the height of the window @var{name} by @var{count}
17057 lines. Positive counts increase the height, while negative counts
17061 @kindex tabset @var{nchars}
17062 Set the width of tab stops to be @var{nchars} characters.
17066 @node TUI Configuration
17067 @section TUI configuration variables
17068 @cindex TUI configuration variables
17070 The TUI has several configuration variables that control the
17071 appearance of windows on the terminal.
17074 @item set tui border-kind @var{kind}
17075 @kindex set tui border-kind
17076 Select the border appearance for the source, assembly and register windows.
17077 The possible values are the following:
17080 Use a space character to draw the border.
17083 Use ascii characters + - and | to draw the border.
17086 Use the Alternate Character Set to draw the border. The border is
17087 drawn using character line graphics if the terminal supports them.
17091 @item set tui active-border-mode @var{mode}
17092 @kindex set tui active-border-mode
17093 Select the attributes to display the border of the active window.
17094 The possible values are @code{normal}, @code{standout}, @code{reverse},
17095 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
17097 @item set tui border-mode @var{mode}
17098 @kindex set tui border-mode
17099 Select the attributes to display the border of other windows.
17100 The @var{mode} can be one of the following:
17103 Use normal attributes to display the border.
17109 Use reverse video mode.
17112 Use half bright mode.
17114 @item half-standout
17115 Use half bright and standout mode.
17118 Use extra bright or bold mode.
17120 @item bold-standout
17121 Use extra bright or bold and standout mode.
17128 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17131 @cindex @sc{gnu} Emacs
17132 A special interface allows you to use @sc{gnu} Emacs to view (and
17133 edit) the source files for the program you are debugging with
17136 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17137 executable file you want to debug as an argument. This command starts
17138 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17139 created Emacs buffer.
17140 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17142 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
17147 All ``terminal'' input and output goes through the Emacs buffer.
17150 This applies both to @value{GDBN} commands and their output, and to the input
17151 and output done by the program you are debugging.
17153 This is useful because it means that you can copy the text of previous
17154 commands and input them again; you can even use parts of the output
17157 All the facilities of Emacs' Shell mode are available for interacting
17158 with your program. In particular, you can send signals the usual
17159 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17164 @value{GDBN} displays source code through Emacs.
17167 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17168 source file for that frame and puts an arrow (@samp{=>}) at the
17169 left margin of the current line. Emacs uses a separate buffer for
17170 source display, and splits the screen to show both your @value{GDBN} session
17173 Explicit @value{GDBN} @code{list} or search commands still produce output as
17174 usual, but you probably have no reason to use them from Emacs.
17176 If you specify an absolute file name when prompted for the @kbd{M-x
17177 gdb} argument, then Emacs sets your current working directory to where
17178 your program resides. If you only specify the file name, then Emacs
17179 sets your current working directory to to the directory associated
17180 with the previous buffer. In this case, @value{GDBN} may find your
17181 program by searching your environment's @code{PATH} variable, but on
17182 some operating systems it might not find the source. So, although the
17183 @value{GDBN} input and output session proceeds normally, the auxiliary
17184 buffer does not display the current source and line of execution.
17186 The initial working directory of @value{GDBN} is printed on the top
17187 line of the @value{GDBN} I/O buffer and this serves as a default for
17188 the commands that specify files for @value{GDBN} to operate
17189 on. @xref{Files, ,Commands to specify files}.
17191 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17192 need to call @value{GDBN} by a different name (for example, if you
17193 keep several configurations around, with different names) you can
17194 customize the Emacs variable @code{gud-gdb-command-name} to run the
17197 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
17198 addition to the standard Shell mode commands:
17202 Describe the features of Emacs' @value{GDBN} Mode.
17205 Execute to another source line, like the @value{GDBN} @code{step} command; also
17206 update the display window to show the current file and location.
17209 Execute to next source line in this function, skipping all function
17210 calls, like the @value{GDBN} @code{next} command. Then update the display window
17211 to show the current file and location.
17214 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17215 display window accordingly.
17218 Execute until exit from the selected stack frame, like the @value{GDBN}
17219 @code{finish} command.
17222 Continue execution of your program, like the @value{GDBN} @code{continue}
17226 Go up the number of frames indicated by the numeric argument
17227 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17228 like the @value{GDBN} @code{up} command.
17231 Go down the number of frames indicated by the numeric argument, like the
17232 @value{GDBN} @code{down} command.
17235 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17236 tells @value{GDBN} to set a breakpoint on the source line point is on.
17238 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
17239 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
17240 point to any frame in the stack and type @key{RET} to make it become the
17241 current frame and display the associated source in the source buffer.
17242 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
17245 If you accidentally delete the source-display buffer, an easy way to get
17246 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17247 request a frame display; when you run under Emacs, this recreates
17248 the source buffer if necessary to show you the context of the current
17251 The source files displayed in Emacs are in ordinary Emacs buffers
17252 which are visiting the source files in the usual way. You can edit
17253 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17254 communicates with Emacs in terms of line numbers. If you add or
17255 delete lines from the text, the line numbers that @value{GDBN} knows cease
17256 to correspond properly with the code.
17258 The description given here is for GNU Emacs version 21.3 and a more
17259 detailed description of its interaction with @value{GDBN} is given in
17260 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
17262 @c The following dropped because Epoch is nonstandard. Reactivate
17263 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17265 @kindex Emacs Epoch environment
17269 Version 18 of @sc{gnu} Emacs has a built-in window system
17270 called the @code{epoch}
17271 environment. Users of this environment can use a new command,
17272 @code{inspect} which performs identically to @code{print} except that
17273 each value is printed in its own window.
17278 @chapter The @sc{gdb/mi} Interface
17280 @unnumberedsec Function and Purpose
17282 @cindex @sc{gdb/mi}, its purpose
17283 @sc{gdb/mi} is a line based machine oriented text interface to
17284 @value{GDBN} and is activated by specifying using the
17285 @option{--interpreter} command line option (@pxref{Mode Options}). It
17286 is specifically intended to support the development of systems which
17287 use the debugger as just one small component of a larger system.
17289 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17290 in the form of a reference manual.
17292 Note that @sc{gdb/mi} is still under construction, so some of the
17293 features described below are incomplete and subject to change
17294 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17296 @unnumberedsec Notation and Terminology
17298 @cindex notational conventions, for @sc{gdb/mi}
17299 This chapter uses the following notation:
17303 @code{|} separates two alternatives.
17306 @code{[ @var{something} ]} indicates that @var{something} is optional:
17307 it may or may not be given.
17310 @code{( @var{group} )*} means that @var{group} inside the parentheses
17311 may repeat zero or more times.
17314 @code{( @var{group} )+} means that @var{group} inside the parentheses
17315 may repeat one or more times.
17318 @code{"@var{string}"} means a literal @var{string}.
17322 @heading Dependencies
17326 * GDB/MI Command Syntax::
17327 * GDB/MI Compatibility with CLI::
17328 * GDB/MI Development and Front Ends::
17329 * GDB/MI Output Records::
17330 * GDB/MI Simple Examples::
17331 * GDB/MI Command Description Format::
17332 * GDB/MI Breakpoint Commands::
17333 * GDB/MI Program Context::
17334 * GDB/MI Thread Commands::
17335 * GDB/MI Program Execution::
17336 * GDB/MI Stack Manipulation::
17337 * GDB/MI Variable Objects::
17338 * GDB/MI Data Manipulation::
17339 * GDB/MI Tracepoint Commands::
17340 * GDB/MI Symbol Query::
17341 * GDB/MI File Commands::
17343 * GDB/MI Kod Commands::
17344 * GDB/MI Memory Overlay Commands::
17345 * GDB/MI Signal Handling Commands::
17347 * GDB/MI Target Manipulation::
17348 * GDB/MI Miscellaneous Commands::
17351 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17352 @node GDB/MI Command Syntax
17353 @section @sc{gdb/mi} Command Syntax
17356 * GDB/MI Input Syntax::
17357 * GDB/MI Output Syntax::
17360 @node GDB/MI Input Syntax
17361 @subsection @sc{gdb/mi} Input Syntax
17363 @cindex input syntax for @sc{gdb/mi}
17364 @cindex @sc{gdb/mi}, input syntax
17366 @item @var{command} @expansion{}
17367 @code{@var{cli-command} | @var{mi-command}}
17369 @item @var{cli-command} @expansion{}
17370 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17371 @var{cli-command} is any existing @value{GDBN} CLI command.
17373 @item @var{mi-command} @expansion{}
17374 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17375 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17377 @item @var{token} @expansion{}
17378 "any sequence of digits"
17380 @item @var{option} @expansion{}
17381 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17383 @item @var{parameter} @expansion{}
17384 @code{@var{non-blank-sequence} | @var{c-string}}
17386 @item @var{operation} @expansion{}
17387 @emph{any of the operations described in this chapter}
17389 @item @var{non-blank-sequence} @expansion{}
17390 @emph{anything, provided it doesn't contain special characters such as
17391 "-", @var{nl}, """ and of course " "}
17393 @item @var{c-string} @expansion{}
17394 @code{""" @var{seven-bit-iso-c-string-content} """}
17396 @item @var{nl} @expansion{}
17405 The CLI commands are still handled by the @sc{mi} interpreter; their
17406 output is described below.
17409 The @code{@var{token}}, when present, is passed back when the command
17413 Some @sc{mi} commands accept optional arguments as part of the parameter
17414 list. Each option is identified by a leading @samp{-} (dash) and may be
17415 followed by an optional argument parameter. Options occur first in the
17416 parameter list and can be delimited from normal parameters using
17417 @samp{--} (this is useful when some parameters begin with a dash).
17424 We want easy access to the existing CLI syntax (for debugging).
17427 We want it to be easy to spot a @sc{mi} operation.
17430 @node GDB/MI Output Syntax
17431 @subsection @sc{gdb/mi} Output Syntax
17433 @cindex output syntax of @sc{gdb/mi}
17434 @cindex @sc{gdb/mi}, output syntax
17435 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17436 followed, optionally, by a single result record. This result record
17437 is for the most recent command. The sequence of output records is
17438 terminated by @samp{(gdb)}.
17440 If an input command was prefixed with a @code{@var{token}} then the
17441 corresponding output for that command will also be prefixed by that same
17445 @item @var{output} @expansion{}
17446 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17448 @item @var{result-record} @expansion{}
17449 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17451 @item @var{out-of-band-record} @expansion{}
17452 @code{@var{async-record} | @var{stream-record}}
17454 @item @var{async-record} @expansion{}
17455 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17457 @item @var{exec-async-output} @expansion{}
17458 @code{[ @var{token} ] "*" @var{async-output}}
17460 @item @var{status-async-output} @expansion{}
17461 @code{[ @var{token} ] "+" @var{async-output}}
17463 @item @var{notify-async-output} @expansion{}
17464 @code{[ @var{token} ] "=" @var{async-output}}
17466 @item @var{async-output} @expansion{}
17467 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17469 @item @var{result-class} @expansion{}
17470 @code{"done" | "running" | "connected" | "error" | "exit"}
17472 @item @var{async-class} @expansion{}
17473 @code{"stopped" | @var{others}} (where @var{others} will be added
17474 depending on the needs---this is still in development).
17476 @item @var{result} @expansion{}
17477 @code{ @var{variable} "=" @var{value}}
17479 @item @var{variable} @expansion{}
17480 @code{ @var{string} }
17482 @item @var{value} @expansion{}
17483 @code{ @var{const} | @var{tuple} | @var{list} }
17485 @item @var{const} @expansion{}
17486 @code{@var{c-string}}
17488 @item @var{tuple} @expansion{}
17489 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17491 @item @var{list} @expansion{}
17492 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17493 @var{result} ( "," @var{result} )* "]" }
17495 @item @var{stream-record} @expansion{}
17496 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17498 @item @var{console-stream-output} @expansion{}
17499 @code{"~" @var{c-string}}
17501 @item @var{target-stream-output} @expansion{}
17502 @code{"@@" @var{c-string}}
17504 @item @var{log-stream-output} @expansion{}
17505 @code{"&" @var{c-string}}
17507 @item @var{nl} @expansion{}
17510 @item @var{token} @expansion{}
17511 @emph{any sequence of digits}.
17519 All output sequences end in a single line containing a period.
17522 The @code{@var{token}} is from the corresponding request. If an execution
17523 command is interrupted by the @samp{-exec-interrupt} command, the
17524 @var{token} associated with the @samp{*stopped} message is the one of the
17525 original execution command, not the one of the interrupt command.
17528 @cindex status output in @sc{gdb/mi}
17529 @var{status-async-output} contains on-going status information about the
17530 progress of a slow operation. It can be discarded. All status output is
17531 prefixed by @samp{+}.
17534 @cindex async output in @sc{gdb/mi}
17535 @var{exec-async-output} contains asynchronous state change on the target
17536 (stopped, started, disappeared). All async output is prefixed by
17540 @cindex notify output in @sc{gdb/mi}
17541 @var{notify-async-output} contains supplementary information that the
17542 client should handle (e.g., a new breakpoint information). All notify
17543 output is prefixed by @samp{=}.
17546 @cindex console output in @sc{gdb/mi}
17547 @var{console-stream-output} is output that should be displayed as is in the
17548 console. It is the textual response to a CLI command. All the console
17549 output is prefixed by @samp{~}.
17552 @cindex target output in @sc{gdb/mi}
17553 @var{target-stream-output} is the output produced by the target program.
17554 All the target output is prefixed by @samp{@@}.
17557 @cindex log output in @sc{gdb/mi}
17558 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17559 instance messages that should be displayed as part of an error log. All
17560 the log output is prefixed by @samp{&}.
17563 @cindex list output in @sc{gdb/mi}
17564 New @sc{gdb/mi} commands should only output @var{lists} containing
17570 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17571 details about the various output records.
17573 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17574 @node GDB/MI Compatibility with CLI
17575 @section @sc{gdb/mi} Compatibility with CLI
17577 @cindex compatibility, @sc{gdb/mi} and CLI
17578 @cindex @sc{gdb/mi}, compatibility with CLI
17580 For the developers convenience CLI commands can be entered directly,
17581 but there may be some unexpected behaviour. For example, commands
17582 that query the user will behave as if the user replied yes, breakpoint
17583 command lists are not executed and some CLI commands, such as
17584 @code{if}, @code{when} and @code{define}, prompt for further input with
17585 @samp{>}, which is not valid MI output.
17587 This feature may be removed at some stage in the future and it is
17588 recommended that front ends use the @code{-interpreter-exec} command
17589 (@pxref{-interpreter-exec}).
17591 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17592 @node GDB/MI Development and Front Ends
17593 @section @sc{gdb/mi} Development and Front Ends
17594 @cindex @sc{gdb/mi} development
17596 The application which takes the MI output and presents the state of the
17597 program being debugged to the user is called a @dfn{front end}.
17599 Although @sc{gdb/mi} is still incomplete, it is currently being used
17600 by a variety of front ends to @value{GDBN}. This makes it difficult
17601 to introduce new functionality without breaking existing usage. This
17602 section tries to minimize the problems by describing how the protocol
17605 Some changes in MI need not break a carefully designed front end, and
17606 for these the MI version will remain unchanged. The following is a
17607 list of changes that may occur within one level, so front ends should
17608 parse MI output in a way that can handle them:
17612 New MI commands may be added.
17615 New fields may be added to the output of any MI command.
17617 @c The format of field's content e.g type prefix, may change so parse it
17618 @c at your own risk. Yes, in general?
17620 @c The order of fields may change? Shouldn't really matter but it might
17621 @c resolve inconsistencies.
17624 If the changes are likely to break front ends, the MI version level
17625 will be increased by one. This will allow the front end to parse the
17626 output according to the MI version. Apart from mi0, new versions of
17627 @value{GDBN} will not support old versions of MI and it will be the
17628 responsibility of the front end to work with the new one.
17630 @c Starting with mi3, add a new command -mi-version that prints the MI
17633 The best way to avoid unexpected changes in MI that might break your front
17634 end is to make your project known to @value{GDBN} developers and
17635 follow development on @email{gdb@@sourceware.org} and
17636 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17637 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17638 Group, which has the aim of creating a a more general MI protocol
17639 called Debugger Machine Interface (DMI) that will become a standard
17640 for all debuggers, not just @value{GDBN}.
17641 @cindex mailing lists
17643 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17644 @node GDB/MI Output Records
17645 @section @sc{gdb/mi} Output Records
17648 * GDB/MI Result Records::
17649 * GDB/MI Stream Records::
17650 * GDB/MI Out-of-band Records::
17653 @node GDB/MI Result Records
17654 @subsection @sc{gdb/mi} Result Records
17656 @cindex result records in @sc{gdb/mi}
17657 @cindex @sc{gdb/mi}, result records
17658 In addition to a number of out-of-band notifications, the response to a
17659 @sc{gdb/mi} command includes one of the following result indications:
17663 @item "^done" [ "," @var{results} ]
17664 The synchronous operation was successful, @code{@var{results}} are the return
17669 @c Is this one correct? Should it be an out-of-band notification?
17670 The asynchronous operation was successfully started. The target is
17675 GDB has connected to a remote target.
17677 @item "^error" "," @var{c-string}
17679 The operation failed. The @code{@var{c-string}} contains the corresponding
17684 GDB has terminated.
17688 @node GDB/MI Stream Records
17689 @subsection @sc{gdb/mi} Stream Records
17691 @cindex @sc{gdb/mi}, stream records
17692 @cindex stream records in @sc{gdb/mi}
17693 @value{GDBN} internally maintains a number of output streams: the console, the
17694 target, and the log. The output intended for each of these streams is
17695 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17697 Each stream record begins with a unique @dfn{prefix character} which
17698 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17699 Syntax}). In addition to the prefix, each stream record contains a
17700 @code{@var{string-output}}. This is either raw text (with an implicit new
17701 line) or a quoted C string (which does not contain an implicit newline).
17704 @item "~" @var{string-output}
17705 The console output stream contains text that should be displayed in the
17706 CLI console window. It contains the textual responses to CLI commands.
17708 @item "@@" @var{string-output}
17709 The target output stream contains any textual output from the running
17710 target. This is only present when GDB's event loop is truly
17711 asynchronous, which is currently only the case for remote targets.
17713 @item "&" @var{string-output}
17714 The log stream contains debugging messages being produced by @value{GDBN}'s
17718 @node GDB/MI Out-of-band Records
17719 @subsection @sc{gdb/mi} Out-of-band Records
17721 @cindex out-of-band records in @sc{gdb/mi}
17722 @cindex @sc{gdb/mi}, out-of-band records
17723 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17724 additional changes that have occurred. Those changes can either be a
17725 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17726 target activity (e.g., target stopped).
17728 The following is a preliminary list of possible out-of-band records.
17729 In particular, the @var{exec-async-output} records.
17732 @item *stopped,reason="@var{reason}"
17735 @var{reason} can be one of the following:
17738 @item breakpoint-hit
17739 A breakpoint was reached.
17740 @item watchpoint-trigger
17741 A watchpoint was triggered.
17742 @item read-watchpoint-trigger
17743 A read watchpoint was triggered.
17744 @item access-watchpoint-trigger
17745 An access watchpoint was triggered.
17746 @item function-finished
17747 An -exec-finish or similar CLI command was accomplished.
17748 @item location-reached
17749 An -exec-until or similar CLI command was accomplished.
17750 @item watchpoint-scope
17751 A watchpoint has gone out of scope.
17752 @item end-stepping-range
17753 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17754 similar CLI command was accomplished.
17755 @item exited-signalled
17756 The inferior exited because of a signal.
17758 The inferior exited.
17759 @item exited-normally
17760 The inferior exited normally.
17761 @item signal-received
17762 A signal was received by the inferior.
17766 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17767 @node GDB/MI Simple Examples
17768 @section Simple Examples of @sc{gdb/mi} Interaction
17769 @cindex @sc{gdb/mi}, simple examples
17771 This subsection presents several simple examples of interaction using
17772 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17773 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17774 the output received from @sc{gdb/mi}.
17776 Note the the line breaks shown in the examples are here only for
17777 readability, they don't appear in the real output.
17779 @subheading Setting a breakpoint
17781 Setting a breakpoint generates synchronous output which contains detailed
17782 information of the breakpoint.
17785 -> -break-insert main
17786 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17787 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17788 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17792 @subheading Program Execution
17794 Program execution generates asynchronous records and MI gives the
17795 reason that execution stopped.
17801 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17802 frame=@{addr="0x08048564",func="main",
17803 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17804 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17809 <- *stopped,reason="exited-normally"
17813 @subheading Quitting GDB
17815 Quitting GDB just prints the result class @samp{^exit}.
17823 @subheading A Bad Command
17825 Here's what happens if you pass a non-existent command:
17829 <- ^error,msg="Undefined MI command: rubbish"
17834 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17835 @node GDB/MI Command Description Format
17836 @section @sc{gdb/mi} Command Description Format
17838 The remaining sections describe blocks of commands. Each block of
17839 commands is laid out in a fashion similar to this section.
17841 @subheading Motivation
17843 The motivation for this collection of commands.
17845 @subheading Introduction
17847 A brief introduction to this collection of commands as a whole.
17849 @subheading Commands
17851 For each command in the block, the following is described:
17853 @subsubheading Synopsis
17856 -command @var{args}@dots{}
17859 @subsubheading Result
17861 @subsubheading @value{GDBN} Command
17863 The corresponding @value{GDBN} CLI command(s), if any.
17865 @subsubheading Example
17867 Example(s) formatted for readability. Some of the described commands have
17868 not been implemented yet and these are labeled N.A.@: (not available).
17871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17872 @node GDB/MI Breakpoint Commands
17873 @section @sc{gdb/mi} Breakpoint Commands
17875 @cindex breakpoint commands for @sc{gdb/mi}
17876 @cindex @sc{gdb/mi}, breakpoint commands
17877 This section documents @sc{gdb/mi} commands for manipulating
17880 @subheading The @code{-break-after} Command
17881 @findex -break-after
17883 @subsubheading Synopsis
17886 -break-after @var{number} @var{count}
17889 The breakpoint number @var{number} is not in effect until it has been
17890 hit @var{count} times. To see how this is reflected in the output of
17891 the @samp{-break-list} command, see the description of the
17892 @samp{-break-list} command below.
17894 @subsubheading @value{GDBN} Command
17896 The corresponding @value{GDBN} command is @samp{ignore}.
17898 @subsubheading Example
17903 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17904 fullname="/home/foo/hello.c",line="5",times="0"@}
17911 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17912 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17913 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17914 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17915 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17916 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17917 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17918 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17919 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17920 line="5",times="0",ignore="3"@}]@}
17925 @subheading The @code{-break-catch} Command
17926 @findex -break-catch
17928 @subheading The @code{-break-commands} Command
17929 @findex -break-commands
17933 @subheading The @code{-break-condition} Command
17934 @findex -break-condition
17936 @subsubheading Synopsis
17939 -break-condition @var{number} @var{expr}
17942 Breakpoint @var{number} will stop the program only if the condition in
17943 @var{expr} is true. The condition becomes part of the
17944 @samp{-break-list} output (see the description of the @samp{-break-list}
17947 @subsubheading @value{GDBN} Command
17949 The corresponding @value{GDBN} command is @samp{condition}.
17951 @subsubheading Example
17955 -break-condition 1 1
17959 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17960 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17961 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17962 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17963 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17964 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17965 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17966 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17967 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17968 line="5",cond="1",times="0",ignore="3"@}]@}
17972 @subheading The @code{-break-delete} Command
17973 @findex -break-delete
17975 @subsubheading Synopsis
17978 -break-delete ( @var{breakpoint} )+
17981 Delete the breakpoint(s) whose number(s) are specified in the argument
17982 list. This is obviously reflected in the breakpoint list.
17984 @subsubheading @value{GDBN} command
17986 The corresponding @value{GDBN} command is @samp{delete}.
17988 @subsubheading Example
17996 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17997 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17998 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17999 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18000 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18001 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18002 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18007 @subheading The @code{-break-disable} Command
18008 @findex -break-disable
18010 @subsubheading Synopsis
18013 -break-disable ( @var{breakpoint} )+
18016 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
18017 break list is now set to @samp{n} for the named @var{breakpoint}(s).
18019 @subsubheading @value{GDBN} Command
18021 The corresponding @value{GDBN} command is @samp{disable}.
18023 @subsubheading Example
18031 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18032 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18033 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18034 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18035 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18036 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18037 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18038 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
18039 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18040 line="5",times="0"@}]@}
18044 @subheading The @code{-break-enable} Command
18045 @findex -break-enable
18047 @subsubheading Synopsis
18050 -break-enable ( @var{breakpoint} )+
18053 Enable (previously disabled) @var{breakpoint}(s).
18055 @subsubheading @value{GDBN} Command
18057 The corresponding @value{GDBN} command is @samp{enable}.
18059 @subsubheading Example
18067 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18068 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18069 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18070 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18071 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18072 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18073 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18074 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18075 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
18076 line="5",times="0"@}]@}
18080 @subheading The @code{-break-info} Command
18081 @findex -break-info
18083 @subsubheading Synopsis
18086 -break-info @var{breakpoint}
18090 Get information about a single breakpoint.
18092 @subsubheading @value{GDBN} command
18094 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18096 @subsubheading Example
18099 @subheading The @code{-break-insert} Command
18100 @findex -break-insert
18102 @subsubheading Synopsis
18105 -break-insert [ -t ] [ -h ] [ -r ]
18106 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18107 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
18111 If specified, @var{line}, can be one of:
18118 @item filename:linenum
18119 @item filename:function
18123 The possible optional parameters of this command are:
18127 Insert a temporary breakpoint.
18129 Insert a hardware breakpoint.
18130 @item -c @var{condition}
18131 Make the breakpoint conditional on @var{condition}.
18132 @item -i @var{ignore-count}
18133 Initialize the @var{ignore-count}.
18135 Insert a regular breakpoint in all the functions whose names match the
18136 given regular expression. Other flags are not applicable to regular
18140 @subsubheading Result
18142 The result is in the form:
18145 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18146 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18147 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18148 times="@var{times}"@}
18152 where @var{number} is the @value{GDBN} number for this breakpoint,
18153 @var{funcname} is the name of the function where the breakpoint was
18154 inserted, @var{filename} is the name of the source file which contains
18155 this function, @var{lineno} is the source line number within that file
18156 and @var{times} the number of times that the breakpoint has been hit
18157 (always 0 for -break-insert but may be greater for -break-info or -break-list
18158 which use the same output).
18160 Note: this format is open to change.
18161 @c An out-of-band breakpoint instead of part of the result?
18163 @subsubheading @value{GDBN} Command
18165 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18166 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18168 @subsubheading Example
18173 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18174 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18176 -break-insert -t foo
18177 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18178 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18181 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18182 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18183 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18184 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18185 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18186 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18187 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18188 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18189 addr="0x0001072c", func="main",file="recursive2.c",
18190 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18191 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18192 addr="0x00010774",func="foo",file="recursive2.c",
18193 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18195 -break-insert -r foo.*
18196 ~int foo(int, int);
18197 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18198 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18202 @subheading The @code{-break-list} Command
18203 @findex -break-list
18205 @subsubheading Synopsis
18211 Displays the list of inserted breakpoints, showing the following fields:
18215 number of the breakpoint
18217 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18219 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18222 is the breakpoint enabled or no: @samp{y} or @samp{n}
18224 memory location at which the breakpoint is set
18226 logical location of the breakpoint, expressed by function name, file
18229 number of times the breakpoint has been hit
18232 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18233 @code{body} field is an empty list.
18235 @subsubheading @value{GDBN} Command
18237 The corresponding @value{GDBN} command is @samp{info break}.
18239 @subsubheading Example
18244 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18245 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18246 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18247 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18248 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18249 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18250 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18251 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18252 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18253 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18254 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18255 line="13",times="0"@}]@}
18259 Here's an example of the result when there are no breakpoints:
18264 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18265 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18266 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18267 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18268 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18269 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18270 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18275 @subheading The @code{-break-watch} Command
18276 @findex -break-watch
18278 @subsubheading Synopsis
18281 -break-watch [ -a | -r ]
18284 Create a watchpoint. With the @samp{-a} option it will create an
18285 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
18286 read from or on a write to the memory location. With the @samp{-r}
18287 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
18288 trigger only when the memory location is accessed for reading. Without
18289 either of the options, the watchpoint created is a regular watchpoint,
18290 i.e. it will trigger when the memory location is accessed for writing.
18291 @xref{Set Watchpoints, , Setting watchpoints}.
18293 Note that @samp{-break-list} will report a single list of watchpoints and
18294 breakpoints inserted.
18296 @subsubheading @value{GDBN} Command
18298 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18301 @subsubheading Example
18303 Setting a watchpoint on a variable in the @code{main} function:
18308 ^done,wpt=@{number="2",exp="x"@}
18312 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18313 value=@{old="-268439212",new="55"@},
18314 frame=@{func="main",args=[],file="recursive2.c",
18315 fullname="/home/foo/bar/recursive2.c",line="5"@}
18319 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18320 the program execution twice: first for the variable changing value, then
18321 for the watchpoint going out of scope.
18326 ^done,wpt=@{number="5",exp="C"@}
18330 ^done,reason="watchpoint-trigger",
18331 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18332 frame=@{func="callee4",args=[],
18333 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18334 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18338 ^done,reason="watchpoint-scope",wpnum="5",
18339 frame=@{func="callee3",args=[@{name="strarg",
18340 value="0x11940 \"A string argument.\""@}],
18341 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18342 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18346 Listing breakpoints and watchpoints, at different points in the program
18347 execution. Note that once the watchpoint goes out of scope, it is
18353 ^done,wpt=@{number="2",exp="C"@}
18356 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18357 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18358 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18359 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18360 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18361 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18362 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18363 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18364 addr="0x00010734",func="callee4",
18365 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18366 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18367 bkpt=@{number="2",type="watchpoint",disp="keep",
18368 enabled="y",addr="",what="C",times="0"@}]@}
18372 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18373 value=@{old="-276895068",new="3"@},
18374 frame=@{func="callee4",args=[],
18375 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18376 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18379 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18380 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18381 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18382 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18383 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18384 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18385 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18386 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18387 addr="0x00010734",func="callee4",
18388 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18389 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18390 bkpt=@{number="2",type="watchpoint",disp="keep",
18391 enabled="y",addr="",what="C",times="-5"@}]@}
18395 ^done,reason="watchpoint-scope",wpnum="2",
18396 frame=@{func="callee3",args=[@{name="strarg",
18397 value="0x11940 \"A string argument.\""@}],
18398 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18399 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18402 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18403 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18404 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18405 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18406 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18407 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18408 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18409 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18410 addr="0x00010734",func="callee4",
18411 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18412 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18417 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18418 @node GDB/MI Program Context
18419 @section @sc{gdb/mi} Program Context
18421 @subheading The @code{-exec-arguments} Command
18422 @findex -exec-arguments
18425 @subsubheading Synopsis
18428 -exec-arguments @var{args}
18431 Set the inferior program arguments, to be used in the next
18434 @subsubheading @value{GDBN} Command
18436 The corresponding @value{GDBN} command is @samp{set args}.
18438 @subsubheading Example
18441 Don't have one around.
18444 @subheading The @code{-exec-show-arguments} Command
18445 @findex -exec-show-arguments
18447 @subsubheading Synopsis
18450 -exec-show-arguments
18453 Print the arguments of the program.
18455 @subsubheading @value{GDBN} Command
18457 The corresponding @value{GDBN} command is @samp{show args}.
18459 @subsubheading Example
18463 @subheading The @code{-environment-cd} Command
18464 @findex -environment-cd
18466 @subsubheading Synopsis
18469 -environment-cd @var{pathdir}
18472 Set @value{GDBN}'s working directory.
18474 @subsubheading @value{GDBN} Command
18476 The corresponding @value{GDBN} command is @samp{cd}.
18478 @subsubheading Example
18482 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18488 @subheading The @code{-environment-directory} Command
18489 @findex -environment-directory
18491 @subsubheading Synopsis
18494 -environment-directory [ -r ] [ @var{pathdir} ]+
18497 Add directories @var{pathdir} to beginning of search path for source files.
18498 If the @samp{-r} option is used, the search path is reset to the default
18499 search path. If directories @var{pathdir} are supplied in addition to the
18500 @samp{-r} option, the search path is first reset and then addition
18502 Multiple directories may be specified, separated by blanks. Specifying
18503 multiple directories in a single command
18504 results in the directories added to the beginning of the
18505 search path in the same order they were presented in the command.
18506 If blanks are needed as
18507 part of a directory name, double-quotes should be used around
18508 the name. In the command output, the path will show up separated
18509 by the system directory-separator character. The directory-seperator
18510 character must not be used
18511 in any directory name.
18512 If no directories are specified, the current search path is displayed.
18514 @subsubheading @value{GDBN} Command
18516 The corresponding @value{GDBN} command is @samp{dir}.
18518 @subsubheading Example
18522 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18523 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18525 -environment-directory ""
18526 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18528 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18529 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18531 -environment-directory -r
18532 ^done,source-path="$cdir:$cwd"
18537 @subheading The @code{-environment-path} Command
18538 @findex -environment-path
18540 @subsubheading Synopsis
18543 -environment-path [ -r ] [ @var{pathdir} ]+
18546 Add directories @var{pathdir} to beginning of search path for object files.
18547 If the @samp{-r} option is used, the search path is reset to the original
18548 search path that existed at gdb start-up. If directories @var{pathdir} are
18549 supplied in addition to the
18550 @samp{-r} option, the search path is first reset and then addition
18552 Multiple directories may be specified, separated by blanks. Specifying
18553 multiple directories in a single command
18554 results in the directories added to the beginning of the
18555 search path in the same order they were presented in the command.
18556 If blanks are needed as
18557 part of a directory name, double-quotes should be used around
18558 the name. In the command output, the path will show up separated
18559 by the system directory-separator character. The directory-seperator
18560 character must not be used
18561 in any directory name.
18562 If no directories are specified, the current path is displayed.
18565 @subsubheading @value{GDBN} Command
18567 The corresponding @value{GDBN} command is @samp{path}.
18569 @subsubheading Example
18574 ^done,path="/usr/bin"
18576 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18577 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18579 -environment-path -r /usr/local/bin
18580 ^done,path="/usr/local/bin:/usr/bin"
18585 @subheading The @code{-environment-pwd} Command
18586 @findex -environment-pwd
18588 @subsubheading Synopsis
18594 Show the current working directory.
18596 @subsubheading @value{GDBN} command
18598 The corresponding @value{GDBN} command is @samp{pwd}.
18600 @subsubheading Example
18605 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18609 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18610 @node GDB/MI Thread Commands
18611 @section @sc{gdb/mi} Thread Commands
18614 @subheading The @code{-thread-info} Command
18615 @findex -thread-info
18617 @subsubheading Synopsis
18623 @subsubheading @value{GDBN} command
18627 @subsubheading Example
18631 @subheading The @code{-thread-list-all-threads} Command
18632 @findex -thread-list-all-threads
18634 @subsubheading Synopsis
18637 -thread-list-all-threads
18640 @subsubheading @value{GDBN} Command
18642 The equivalent @value{GDBN} command is @samp{info threads}.
18644 @subsubheading Example
18648 @subheading The @code{-thread-list-ids} Command
18649 @findex -thread-list-ids
18651 @subsubheading Synopsis
18657 Produces a list of the currently known @value{GDBN} thread ids. At the
18658 end of the list it also prints the total number of such threads.
18660 @subsubheading @value{GDBN} Command
18662 Part of @samp{info threads} supplies the same information.
18664 @subsubheading Example
18666 No threads present, besides the main process:
18671 ^done,thread-ids=@{@},number-of-threads="0"
18681 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18682 number-of-threads="3"
18687 @subheading The @code{-thread-select} Command
18688 @findex -thread-select
18690 @subsubheading Synopsis
18693 -thread-select @var{threadnum}
18696 Make @var{threadnum} the current thread. It prints the number of the new
18697 current thread, and the topmost frame for that thread.
18699 @subsubheading @value{GDBN} Command
18701 The corresponding @value{GDBN} command is @samp{thread}.
18703 @subsubheading Example
18710 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18711 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18715 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18716 number-of-threads="3"
18719 ^done,new-thread-id="3",
18720 frame=@{level="0",func="vprintf",
18721 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18722 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18726 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18727 @node GDB/MI Program Execution
18728 @section @sc{gdb/mi} Program Execution
18730 These are the asynchronous commands which generate the out-of-band
18731 record @samp{*stopped}. Currently GDB only really executes
18732 asynchronously with remote targets and this interaction is mimicked in
18735 @subheading The @code{-exec-continue} Command
18736 @findex -exec-continue
18738 @subsubheading Synopsis
18744 Resumes the execution of the inferior program until a breakpoint is
18745 encountered, or until the inferior exits.
18747 @subsubheading @value{GDBN} Command
18749 The corresponding @value{GDBN} corresponding is @samp{continue}.
18751 @subsubheading Example
18758 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18759 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18764 @subheading The @code{-exec-finish} Command
18765 @findex -exec-finish
18767 @subsubheading Synopsis
18773 Resumes the execution of the inferior program until the current
18774 function is exited. Displays the results returned by the function.
18776 @subsubheading @value{GDBN} Command
18778 The corresponding @value{GDBN} command is @samp{finish}.
18780 @subsubheading Example
18782 Function returning @code{void}.
18789 *stopped,reason="function-finished",frame=@{func="main",args=[],
18790 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18794 Function returning other than @code{void}. The name of the internal
18795 @value{GDBN} variable storing the result is printed, together with the
18802 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18803 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18804 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18805 gdb-result-var="$1",return-value="0"
18810 @subheading The @code{-exec-interrupt} Command
18811 @findex -exec-interrupt
18813 @subsubheading Synopsis
18819 Interrupts the background execution of the target. Note how the token
18820 associated with the stop message is the one for the execution command
18821 that has been interrupted. The token for the interrupt itself only
18822 appears in the @samp{^done} output. If the user is trying to
18823 interrupt a non-running program, an error message will be printed.
18825 @subsubheading @value{GDBN} Command
18827 The corresponding @value{GDBN} command is @samp{interrupt}.
18829 @subsubheading Example
18840 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18841 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18842 fullname="/home/foo/bar/try.c",line="13"@}
18847 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18852 @subheading The @code{-exec-next} Command
18855 @subsubheading Synopsis
18861 Resumes execution of the inferior program, stopping when the beginning
18862 of the next source line is reached.
18864 @subsubheading @value{GDBN} Command
18866 The corresponding @value{GDBN} command is @samp{next}.
18868 @subsubheading Example
18874 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18879 @subheading The @code{-exec-next-instruction} Command
18880 @findex -exec-next-instruction
18882 @subsubheading Synopsis
18885 -exec-next-instruction
18888 Executes one machine instruction. If the instruction is a function
18889 call, continues until the function returns. If the program stops at an
18890 instruction in the middle of a source line, the address will be
18893 @subsubheading @value{GDBN} Command
18895 The corresponding @value{GDBN} command is @samp{nexti}.
18897 @subsubheading Example
18901 -exec-next-instruction
18905 *stopped,reason="end-stepping-range",
18906 addr="0x000100d4",line="5",file="hello.c"
18911 @subheading The @code{-exec-return} Command
18912 @findex -exec-return
18914 @subsubheading Synopsis
18920 Makes current function return immediately. Doesn't execute the inferior.
18921 Displays the new current frame.
18923 @subsubheading @value{GDBN} Command
18925 The corresponding @value{GDBN} command is @samp{return}.
18927 @subsubheading Example
18931 200-break-insert callee4
18932 200^done,bkpt=@{number="1",addr="0x00010734",
18933 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18938 000*stopped,reason="breakpoint-hit",bkptno="1",
18939 frame=@{func="callee4",args=[],
18940 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18941 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18947 111^done,frame=@{level="0",func="callee3",
18948 args=[@{name="strarg",
18949 value="0x11940 \"A string argument.\""@}],
18950 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18951 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18956 @subheading The @code{-exec-run} Command
18959 @subsubheading Synopsis
18965 Starts execution of the inferior from the beginning. The inferior
18966 executes until either a breakpoint is encountered or the program
18967 exits. In the latter case the output will include an exit code, if
18968 the program has exited exceptionally.
18970 @subsubheading @value{GDBN} Command
18972 The corresponding @value{GDBN} command is @samp{run}.
18974 @subsubheading Examples
18979 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18984 *stopped,reason="breakpoint-hit",bkptno="1",
18985 frame=@{func="main",args=[],file="recursive2.c",
18986 fullname="/home/foo/bar/recursive2.c",line="4"@}
18991 Program exited normally:
18999 *stopped,reason="exited-normally"
19004 Program exited exceptionally:
19012 *stopped,reason="exited",exit-code="01"
19016 Another way the program can terminate is if it receives a signal such as
19017 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
19021 *stopped,reason="exited-signalled",signal-name="SIGINT",
19022 signal-meaning="Interrupt"
19026 @c @subheading -exec-signal
19029 @subheading The @code{-exec-step} Command
19032 @subsubheading Synopsis
19038 Resumes execution of the inferior program, stopping when the beginning
19039 of the next source line is reached, if the next source line is not a
19040 function call. If it is, stop at the first instruction of the called
19043 @subsubheading @value{GDBN} Command
19045 The corresponding @value{GDBN} command is @samp{step}.
19047 @subsubheading Example
19049 Stepping into a function:
19055 *stopped,reason="end-stepping-range",
19056 frame=@{func="foo",args=[@{name="a",value="10"@},
19057 @{name="b",value="0"@}],file="recursive2.c",
19058 fullname="/home/foo/bar/recursive2.c",line="11"@}
19068 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19073 @subheading The @code{-exec-step-instruction} Command
19074 @findex -exec-step-instruction
19076 @subsubheading Synopsis
19079 -exec-step-instruction
19082 Resumes the inferior which executes one machine instruction. The
19083 output, once @value{GDBN} has stopped, will vary depending on whether
19084 we have stopped in the middle of a source line or not. In the former
19085 case, the address at which the program stopped will be printed as
19088 @subsubheading @value{GDBN} Command
19090 The corresponding @value{GDBN} command is @samp{stepi}.
19092 @subsubheading Example
19096 -exec-step-instruction
19100 *stopped,reason="end-stepping-range",
19101 frame=@{func="foo",args=[],file="try.c",
19102 fullname="/home/foo/bar/try.c",line="10"@}
19104 -exec-step-instruction
19108 *stopped,reason="end-stepping-range",
19109 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19110 fullname="/home/foo/bar/try.c",line="10"@}
19115 @subheading The @code{-exec-until} Command
19116 @findex -exec-until
19118 @subsubheading Synopsis
19121 -exec-until [ @var{location} ]
19124 Executes the inferior until the @var{location} specified in the
19125 argument is reached. If there is no argument, the inferior executes
19126 until a source line greater than the current one is reached. The
19127 reason for stopping in this case will be @samp{location-reached}.
19129 @subsubheading @value{GDBN} Command
19131 The corresponding @value{GDBN} command is @samp{until}.
19133 @subsubheading Example
19137 -exec-until recursive2.c:6
19141 *stopped,reason="location-reached",frame=@{func="main",args=[],
19142 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19147 @subheading -file-clear
19148 Is this going away????
19151 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19152 @node GDB/MI Stack Manipulation
19153 @section @sc{gdb/mi} Stack Manipulation Commands
19156 @subheading The @code{-stack-info-frame} Command
19157 @findex -stack-info-frame
19159 @subsubheading Synopsis
19165 Get info on the selected frame.
19167 @subsubheading @value{GDBN} Command
19169 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19170 (without arguments).
19172 @subsubheading Example
19177 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19178 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19179 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19183 @subheading The @code{-stack-info-depth} Command
19184 @findex -stack-info-depth
19186 @subsubheading Synopsis
19189 -stack-info-depth [ @var{max-depth} ]
19192 Return the depth of the stack. If the integer argument @var{max-depth}
19193 is specified, do not count beyond @var{max-depth} frames.
19195 @subsubheading @value{GDBN} Command
19197 There's no equivalent @value{GDBN} command.
19199 @subsubheading Example
19201 For a stack with frame levels 0 through 11:
19208 -stack-info-depth 4
19211 -stack-info-depth 12
19214 -stack-info-depth 11
19217 -stack-info-depth 13
19222 @subheading The @code{-stack-list-arguments} Command
19223 @findex -stack-list-arguments
19225 @subsubheading Synopsis
19228 -stack-list-arguments @var{show-values}
19229 [ @var{low-frame} @var{high-frame} ]
19232 Display a list of the arguments for the frames between @var{low-frame}
19233 and @var{high-frame} (inclusive). If @var{low-frame} and
19234 @var{high-frame} are not provided, list the arguments for the whole
19235 call stack. If the two arguments are equal, show the single frame
19236 at the corresponding level. It is an error if @var{low-frame} is
19237 larger than the actual number of frames. On the other hand,
19238 @var{high-frame} may be larger than the actual number of frames, in
19239 which case only existing frames will be returned.
19241 The @var{show-values} argument must have a value of 0 or 1. A value of
19242 0 means that only the names of the arguments are listed, a value of 1
19243 means that both names and values of the arguments are printed.
19245 @subsubheading @value{GDBN} Command
19247 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19248 @samp{gdb_get_args} command which partially overlaps with the
19249 functionality of @samp{-stack-list-arguments}.
19251 @subsubheading Example
19258 frame=@{level="0",addr="0x00010734",func="callee4",
19259 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19260 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19261 frame=@{level="1",addr="0x0001076c",func="callee3",
19262 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19263 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19264 frame=@{level="2",addr="0x0001078c",func="callee2",
19265 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19266 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19267 frame=@{level="3",addr="0x000107b4",func="callee1",
19268 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19269 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19270 frame=@{level="4",addr="0x000107e0",func="main",
19271 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19272 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19274 -stack-list-arguments 0
19277 frame=@{level="0",args=[]@},
19278 frame=@{level="1",args=[name="strarg"]@},
19279 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19280 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19281 frame=@{level="4",args=[]@}]
19283 -stack-list-arguments 1
19286 frame=@{level="0",args=[]@},
19288 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19289 frame=@{level="2",args=[
19290 @{name="intarg",value="2"@},
19291 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19292 @{frame=@{level="3",args=[
19293 @{name="intarg",value="2"@},
19294 @{name="strarg",value="0x11940 \"A string argument.\""@},
19295 @{name="fltarg",value="3.5"@}]@},
19296 frame=@{level="4",args=[]@}]
19298 -stack-list-arguments 0 2 2
19299 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19301 -stack-list-arguments 1 2 2
19302 ^done,stack-args=[frame=@{level="2",
19303 args=[@{name="intarg",value="2"@},
19304 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19308 @c @subheading -stack-list-exception-handlers
19311 @subheading The @code{-stack-list-frames} Command
19312 @findex -stack-list-frames
19314 @subsubheading Synopsis
19317 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19320 List the frames currently on the stack. For each frame it displays the
19325 The frame number, 0 being the topmost frame, i.e. the innermost function.
19327 The @code{$pc} value for that frame.
19331 File name of the source file where the function lives.
19333 Line number corresponding to the @code{$pc}.
19336 If invoked without arguments, this command prints a backtrace for the
19337 whole stack. If given two integer arguments, it shows the frames whose
19338 levels are between the two arguments (inclusive). If the two arguments
19339 are equal, it shows the single frame at the corresponding level. It is
19340 an error if @var{low-frame} is larger than the actual number of
19341 frames. On the other hand, @var{high-frame} may be larger than the
19342 actual number of frames, in which case only existing frames will be returned.
19344 @subsubheading @value{GDBN} Command
19346 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19348 @subsubheading Example
19350 Full stack backtrace:
19356 [frame=@{level="0",addr="0x0001076c",func="foo",
19357 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19358 frame=@{level="1",addr="0x000107a4",func="foo",
19359 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19360 frame=@{level="2",addr="0x000107a4",func="foo",
19361 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19362 frame=@{level="3",addr="0x000107a4",func="foo",
19363 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19364 frame=@{level="4",addr="0x000107a4",func="foo",
19365 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19366 frame=@{level="5",addr="0x000107a4",func="foo",
19367 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19368 frame=@{level="6",addr="0x000107a4",func="foo",
19369 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19370 frame=@{level="7",addr="0x000107a4",func="foo",
19371 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19372 frame=@{level="8",addr="0x000107a4",func="foo",
19373 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19374 frame=@{level="9",addr="0x000107a4",func="foo",
19375 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19376 frame=@{level="10",addr="0x000107a4",func="foo",
19377 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19378 frame=@{level="11",addr="0x00010738",func="main",
19379 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19383 Show frames between @var{low_frame} and @var{high_frame}:
19387 -stack-list-frames 3 5
19389 [frame=@{level="3",addr="0x000107a4",func="foo",
19390 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19391 frame=@{level="4",addr="0x000107a4",func="foo",
19392 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19393 frame=@{level="5",addr="0x000107a4",func="foo",
19394 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19398 Show a single frame:
19402 -stack-list-frames 3 3
19404 [frame=@{level="3",addr="0x000107a4",func="foo",
19405 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19410 @subheading The @code{-stack-list-locals} Command
19411 @findex -stack-list-locals
19413 @subsubheading Synopsis
19416 -stack-list-locals @var{print-values}
19419 Display the local variable names for the selected frame. If
19420 @var{print-values} is 0 or @code{--no-values}, print only the names of
19421 the variables; if it is 1 or @code{--all-values}, print also their
19422 values; and if it is 2 or @code{--simple-values}, print the name,
19423 type and value for simple data types and the name and type for arrays,
19424 structures and unions. In this last case, a frontend can immediately
19425 display the value of simple data types and create variable objects for
19426 other data types when the the user wishes to explore their values in
19429 @subsubheading @value{GDBN} Command
19431 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19433 @subsubheading Example
19437 -stack-list-locals 0
19438 ^done,locals=[name="A",name="B",name="C"]
19440 -stack-list-locals --all-values
19441 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19442 @{name="C",value="@{1, 2, 3@}"@}]
19443 -stack-list-locals --simple-values
19444 ^done,locals=[@{name="A",type="int",value="1"@},
19445 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19450 @subheading The @code{-stack-select-frame} Command
19451 @findex -stack-select-frame
19453 @subsubheading Synopsis
19456 -stack-select-frame @var{framenum}
19459 Change the selected frame. Select a different frame @var{framenum} on
19462 @subsubheading @value{GDBN} Command
19464 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19465 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19467 @subsubheading Example
19471 -stack-select-frame 2
19476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19477 @node GDB/MI Variable Objects
19478 @section @sc{gdb/mi} Variable Objects
19481 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19483 For the implementation of a variable debugger window (locals, watched
19484 expressions, etc.), we are proposing the adaptation of the existing code
19485 used by @code{Insight}.
19487 The two main reasons for that are:
19491 It has been proven in practice (it is already on its second generation).
19494 It will shorten development time (needless to say how important it is
19498 The original interface was designed to be used by Tcl code, so it was
19499 slightly changed so it could be used through @sc{gdb/mi}. This section
19500 describes the @sc{gdb/mi} operations that will be available and gives some
19501 hints about their use.
19503 @emph{Note}: In addition to the set of operations described here, we
19504 expect the @sc{gui} implementation of a variable window to require, at
19505 least, the following operations:
19508 @item @code{-gdb-show} @code{output-radix}
19509 @item @code{-stack-list-arguments}
19510 @item @code{-stack-list-locals}
19511 @item @code{-stack-select-frame}
19514 @subheading Introduction to Variable Objects in @sc{gdb/mi}
19516 @cindex variable objects in @sc{gdb/mi}
19517 The basic idea behind variable objects is the creation of a named object
19518 to represent a variable, an expression, a memory location or even a CPU
19519 register. For each object created, a set of operations is available for
19520 examining or changing its properties.
19522 Furthermore, complex data types, such as C structures, are represented
19523 in a tree format. For instance, the @code{struct} type variable is the
19524 root and the children will represent the struct members. If a child
19525 is itself of a complex type, it will also have children of its own.
19526 Appropriate language differences are handled for C, C@t{++} and Java.
19528 When returning the actual values of the objects, this facility allows
19529 for the individual selection of the display format used in the result
19530 creation. It can be chosen among: binary, decimal, hexadecimal, octal
19531 and natural. Natural refers to a default format automatically
19532 chosen based on the variable type (like decimal for an @code{int}, hex
19533 for pointers, etc.).
19535 The following is the complete set of @sc{gdb/mi} operations defined to
19536 access this functionality:
19538 @multitable @columnfractions .4 .6
19539 @item @strong{Operation}
19540 @tab @strong{Description}
19542 @item @code{-var-create}
19543 @tab create a variable object
19544 @item @code{-var-delete}
19545 @tab delete the variable object and its children
19546 @item @code{-var-set-format}
19547 @tab set the display format of this variable
19548 @item @code{-var-show-format}
19549 @tab show the display format of this variable
19550 @item @code{-var-info-num-children}
19551 @tab tells how many children this object has
19552 @item @code{-var-list-children}
19553 @tab return a list of the object's children
19554 @item @code{-var-info-type}
19555 @tab show the type of this variable object
19556 @item @code{-var-info-expression}
19557 @tab print what this variable object represents
19558 @item @code{-var-show-attributes}
19559 @tab is this variable editable? does it exist here?
19560 @item @code{-var-evaluate-expression}
19561 @tab get the value of this variable
19562 @item @code{-var-assign}
19563 @tab set the value of this variable
19564 @item @code{-var-update}
19565 @tab update the variable and its children
19568 In the next subsection we describe each operation in detail and suggest
19569 how it can be used.
19571 @subheading Description And Use of Operations on Variable Objects
19573 @subheading The @code{-var-create} Command
19574 @findex -var-create
19576 @subsubheading Synopsis
19579 -var-create @{@var{name} | "-"@}
19580 @{@var{frame-addr} | "*"@} @var{expression}
19583 This operation creates a variable object, which allows the monitoring of
19584 a variable, the result of an expression, a memory cell or a CPU
19587 The @var{name} parameter is the string by which the object can be
19588 referenced. It must be unique. If @samp{-} is specified, the varobj
19589 system will generate a string ``varNNNNNN'' automatically. It will be
19590 unique provided that one does not specify @var{name} on that format.
19591 The command fails if a duplicate name is found.
19593 The frame under which the expression should be evaluated can be
19594 specified by @var{frame-addr}. A @samp{*} indicates that the current
19595 frame should be used.
19597 @var{expression} is any expression valid on the current language set (must not
19598 begin with a @samp{*}), or one of the following:
19602 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19605 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19608 @samp{$@var{regname}} --- a CPU register name
19611 @subsubheading Result
19613 This operation returns the name, number of children and the type of the
19614 object created. Type is returned as a string as the ones generated by
19615 the @value{GDBN} CLI:
19618 name="@var{name}",numchild="N",type="@var{type}"
19622 @subheading The @code{-var-delete} Command
19623 @findex -var-delete
19625 @subsubheading Synopsis
19628 -var-delete @var{name}
19631 Deletes a previously created variable object and all of its children.
19633 Returns an error if the object @var{name} is not found.
19636 @subheading The @code{-var-set-format} Command
19637 @findex -var-set-format
19639 @subsubheading Synopsis
19642 -var-set-format @var{name} @var{format-spec}
19645 Sets the output format for the value of the object @var{name} to be
19648 The syntax for the @var{format-spec} is as follows:
19651 @var{format-spec} @expansion{}
19652 @{binary | decimal | hexadecimal | octal | natural@}
19656 @subheading The @code{-var-show-format} Command
19657 @findex -var-show-format
19659 @subsubheading Synopsis
19662 -var-show-format @var{name}
19665 Returns the format used to display the value of the object @var{name}.
19668 @var{format} @expansion{}
19673 @subheading The @code{-var-info-num-children} Command
19674 @findex -var-info-num-children
19676 @subsubheading Synopsis
19679 -var-info-num-children @var{name}
19682 Returns the number of children of a variable object @var{name}:
19689 @subheading The @code{-var-list-children} Command
19690 @findex -var-list-children
19692 @subsubheading Synopsis
19695 -var-list-children [@var{print-values}] @var{name}
19697 @anchor{-var-list-children}
19699 Return a list of the children of the specified variable object and
19700 create variable objects for them, if they do not already exist. With
19701 a single argument or if @var{print-values} has a value for of 0 or
19702 @code{--no-values}, print only the names of the variables; if
19703 @var{print-values} is 1 or @code{--all-values}, also print their
19704 values; and if it is 2 or @code{--simple-values} print the name and
19705 value for simple data types and just the name for arrays, structures
19708 @subsubheading Example
19712 -var-list-children n
19713 ^done,numchild=@var{n},children=[@{name=@var{name},
19714 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19716 -var-list-children --all-values n
19717 ^done,numchild=@var{n},children=[@{name=@var{name},
19718 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19722 @subheading The @code{-var-info-type} Command
19723 @findex -var-info-type
19725 @subsubheading Synopsis
19728 -var-info-type @var{name}
19731 Returns the type of the specified variable @var{name}. The type is
19732 returned as a string in the same format as it is output by the
19736 type=@var{typename}
19740 @subheading The @code{-var-info-expression} Command
19741 @findex -var-info-expression
19743 @subsubheading Synopsis
19746 -var-info-expression @var{name}
19749 Returns what is represented by the variable object @var{name}:
19752 lang=@var{lang-spec},exp=@var{expression}
19756 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
19758 @subheading The @code{-var-show-attributes} Command
19759 @findex -var-show-attributes
19761 @subsubheading Synopsis
19764 -var-show-attributes @var{name}
19767 List attributes of the specified variable object @var{name}:
19770 status=@var{attr} [ ( ,@var{attr} )* ]
19774 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19776 @subheading The @code{-var-evaluate-expression} Command
19777 @findex -var-evaluate-expression
19779 @subsubheading Synopsis
19782 -var-evaluate-expression @var{name}
19785 Evaluates the expression that is represented by the specified variable
19786 object and returns its value as a string in the current format specified
19793 Note that one must invoke @code{-var-list-children} for a variable
19794 before the value of a child variable can be evaluated.
19796 @subheading The @code{-var-assign} Command
19797 @findex -var-assign
19799 @subsubheading Synopsis
19802 -var-assign @var{name} @var{expression}
19805 Assigns the value of @var{expression} to the variable object specified
19806 by @var{name}. The object must be @samp{editable}. If the variable's
19807 value is altered by the assign, the variable will show up in any
19808 subsequent @code{-var-update} list.
19810 @subsubheading Example
19818 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19822 @subheading The @code{-var-update} Command
19823 @findex -var-update
19825 @subsubheading Synopsis
19828 -var-update [@var{print-values}] @{@var{name} | "*"@}
19831 Update the value of the variable object @var{name} by evaluating its
19832 expression after fetching all the new values from memory or registers.
19833 A @samp{*} causes all existing variable objects to be updated. The
19834 option @var{print-values} determines whether names both and values, or
19835 just names are printed in the manner described for
19836 @code{-var-list-children} (@pxref{-var-list-children}).
19838 @subsubheading Example
19845 -var-update --all-values var1
19846 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19847 type_changed="false"@}]
19851 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19852 @node GDB/MI Data Manipulation
19853 @section @sc{gdb/mi} Data Manipulation
19855 @cindex data manipulation, in @sc{gdb/mi}
19856 @cindex @sc{gdb/mi}, data manipulation
19857 This section describes the @sc{gdb/mi} commands that manipulate data:
19858 examine memory and registers, evaluate expressions, etc.
19860 @c REMOVED FROM THE INTERFACE.
19861 @c @subheading -data-assign
19862 @c Change the value of a program variable. Plenty of side effects.
19863 @c @subsubheading GDB command
19865 @c @subsubheading Example
19868 @subheading The @code{-data-disassemble} Command
19869 @findex -data-disassemble
19871 @subsubheading Synopsis
19875 [ -s @var{start-addr} -e @var{end-addr} ]
19876 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
19884 @item @var{start-addr}
19885 is the beginning address (or @code{$pc})
19886 @item @var{end-addr}
19888 @item @var{filename}
19889 is the name of the file to disassemble
19890 @item @var{linenum}
19891 is the line number to disassemble around
19893 is the the number of disassembly lines to be produced. If it is -1,
19894 the whole function will be disassembled, in case no @var{end-addr} is
19895 specified. If @var{end-addr} is specified as a non-zero value, and
19896 @var{lines} is lower than the number of disassembly lines between
19897 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
19898 displayed; if @var{lines} is higher than the number of lines between
19899 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
19902 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
19906 @subsubheading Result
19908 The output for each instruction is composed of four fields:
19917 Note that whatever included in the instruction field, is not manipulated
19918 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
19920 @subsubheading @value{GDBN} Command
19922 There's no direct mapping from this command to the CLI.
19924 @subsubheading Example
19926 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
19930 -data-disassemble -s $pc -e "$pc + 20" -- 0
19933 @{address="0x000107c0",func-name="main",offset="4",
19934 inst="mov 2, %o0"@},
19935 @{address="0x000107c4",func-name="main",offset="8",
19936 inst="sethi %hi(0x11800), %o2"@},
19937 @{address="0x000107c8",func-name="main",offset="12",
19938 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
19939 @{address="0x000107cc",func-name="main",offset="16",
19940 inst="sethi %hi(0x11800), %o2"@},
19941 @{address="0x000107d0",func-name="main",offset="20",
19942 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
19946 Disassemble the whole @code{main} function. Line 32 is part of
19950 -data-disassemble -f basics.c -l 32 -- 0
19952 @{address="0x000107bc",func-name="main",offset="0",
19953 inst="save %sp, -112, %sp"@},
19954 @{address="0x000107c0",func-name="main",offset="4",
19955 inst="mov 2, %o0"@},
19956 @{address="0x000107c4",func-name="main",offset="8",
19957 inst="sethi %hi(0x11800), %o2"@},
19959 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
19960 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
19964 Disassemble 3 instructions from the start of @code{main}:
19968 -data-disassemble -f basics.c -l 32 -n 3 -- 0
19970 @{address="0x000107bc",func-name="main",offset="0",
19971 inst="save %sp, -112, %sp"@},
19972 @{address="0x000107c0",func-name="main",offset="4",
19973 inst="mov 2, %o0"@},
19974 @{address="0x000107c4",func-name="main",offset="8",
19975 inst="sethi %hi(0x11800), %o2"@}]
19979 Disassemble 3 instructions from the start of @code{main} in mixed mode:
19983 -data-disassemble -f basics.c -l 32 -n 3 -- 1
19985 src_and_asm_line=@{line="31",
19986 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19987 testsuite/gdb.mi/basics.c",line_asm_insn=[
19988 @{address="0x000107bc",func-name="main",offset="0",
19989 inst="save %sp, -112, %sp"@}]@},
19990 src_and_asm_line=@{line="32",
19991 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
19992 testsuite/gdb.mi/basics.c",line_asm_insn=[
19993 @{address="0x000107c0",func-name="main",offset="4",
19994 inst="mov 2, %o0"@},
19995 @{address="0x000107c4",func-name="main",offset="8",
19996 inst="sethi %hi(0x11800), %o2"@}]@}]
20001 @subheading The @code{-data-evaluate-expression} Command
20002 @findex -data-evaluate-expression
20004 @subsubheading Synopsis
20007 -data-evaluate-expression @var{expr}
20010 Evaluate @var{expr} as an expression. The expression could contain an
20011 inferior function call. The function call will execute synchronously.
20012 If the expression contains spaces, it must be enclosed in double quotes.
20014 @subsubheading @value{GDBN} Command
20016 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20017 @samp{call}. In @code{gdbtk} only, there's a corresponding
20018 @samp{gdb_eval} command.
20020 @subsubheading Example
20022 In the following example, the numbers that precede the commands are the
20023 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20024 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20028 211-data-evaluate-expression A
20031 311-data-evaluate-expression &A
20032 311^done,value="0xefffeb7c"
20034 411-data-evaluate-expression A+3
20037 511-data-evaluate-expression "A + 3"
20043 @subheading The @code{-data-list-changed-registers} Command
20044 @findex -data-list-changed-registers
20046 @subsubheading Synopsis
20049 -data-list-changed-registers
20052 Display a list of the registers that have changed.
20054 @subsubheading @value{GDBN} Command
20056 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20057 has the corresponding command @samp{gdb_changed_register_list}.
20059 @subsubheading Example
20061 On a PPC MBX board:
20069 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20070 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20072 -data-list-changed-registers
20073 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20074 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20075 "24","25","26","27","28","30","31","64","65","66","67","69"]
20080 @subheading The @code{-data-list-register-names} Command
20081 @findex -data-list-register-names
20083 @subsubheading Synopsis
20086 -data-list-register-names [ ( @var{regno} )+ ]
20089 Show a list of register names for the current target. If no arguments
20090 are given, it shows a list of the names of all the registers. If
20091 integer numbers are given as arguments, it will print a list of the
20092 names of the registers corresponding to the arguments. To ensure
20093 consistency between a register name and its number, the output list may
20094 include empty register names.
20096 @subsubheading @value{GDBN} Command
20098 @value{GDBN} does not have a command which corresponds to
20099 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20100 corresponding command @samp{gdb_regnames}.
20102 @subsubheading Example
20104 For the PPC MBX board:
20107 -data-list-register-names
20108 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20109 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20110 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20111 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20112 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20113 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20114 "", "pc","ps","cr","lr","ctr","xer"]
20116 -data-list-register-names 1 2 3
20117 ^done,register-names=["r1","r2","r3"]
20121 @subheading The @code{-data-list-register-values} Command
20122 @findex -data-list-register-values
20124 @subsubheading Synopsis
20127 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20130 Display the registers' contents. @var{fmt} is the format according to
20131 which the registers' contents are to be returned, followed by an optional
20132 list of numbers specifying the registers to display. A missing list of
20133 numbers indicates that the contents of all the registers must be returned.
20135 Allowed formats for @var{fmt} are:
20152 @subsubheading @value{GDBN} Command
20154 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20155 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20157 @subsubheading Example
20159 For a PPC MBX board (note: line breaks are for readability only, they
20160 don't appear in the actual output):
20164 -data-list-register-values r 64 65
20165 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20166 @{number="65",value="0x00029002"@}]
20168 -data-list-register-values x
20169 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20170 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20171 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20172 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20173 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20174 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20175 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20176 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20177 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20178 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20179 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20180 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20181 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20182 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20183 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20184 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20185 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20186 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20187 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20188 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20189 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20190 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20191 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20192 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20193 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20194 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20195 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20196 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20197 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20198 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20199 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20200 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20201 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20202 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20203 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20204 @{number="69",value="0x20002b03"@}]
20209 @subheading The @code{-data-read-memory} Command
20210 @findex -data-read-memory
20212 @subsubheading Synopsis
20215 -data-read-memory [ -o @var{byte-offset} ]
20216 @var{address} @var{word-format} @var{word-size}
20217 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20224 @item @var{address}
20225 An expression specifying the address of the first memory word to be
20226 read. Complex expressions containing embedded white space should be
20227 quoted using the C convention.
20229 @item @var{word-format}
20230 The format to be used to print the memory words. The notation is the
20231 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20234 @item @var{word-size}
20235 The size of each memory word in bytes.
20237 @item @var{nr-rows}
20238 The number of rows in the output table.
20240 @item @var{nr-cols}
20241 The number of columns in the output table.
20244 If present, indicates that each row should include an @sc{ascii} dump. The
20245 value of @var{aschar} is used as a padding character when a byte is not a
20246 member of the printable @sc{ascii} character set (printable @sc{ascii}
20247 characters are those whose code is between 32 and 126, inclusively).
20249 @item @var{byte-offset}
20250 An offset to add to the @var{address} before fetching memory.
20253 This command displays memory contents as a table of @var{nr-rows} by
20254 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20255 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20256 (returned as @samp{total-bytes}). Should less than the requested number
20257 of bytes be returned by the target, the missing words are identified
20258 using @samp{N/A}. The number of bytes read from the target is returned
20259 in @samp{nr-bytes} and the starting address used to read memory in
20262 The address of the next/previous row or page is available in
20263 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20266 @subsubheading @value{GDBN} Command
20268 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20269 @samp{gdb_get_mem} memory read command.
20271 @subsubheading Example
20273 Read six bytes of memory starting at @code{bytes+6} but then offset by
20274 @code{-6} bytes. Format as three rows of two columns. One byte per
20275 word. Display each word in hex.
20279 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20280 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20281 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20282 prev-page="0x0000138a",memory=[
20283 @{addr="0x00001390",data=["0x00","0x01"]@},
20284 @{addr="0x00001392",data=["0x02","0x03"]@},
20285 @{addr="0x00001394",data=["0x04","0x05"]@}]
20289 Read two bytes of memory starting at address @code{shorts + 64} and
20290 display as a single word formatted in decimal.
20294 5-data-read-memory shorts+64 d 2 1 1
20295 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20296 next-row="0x00001512",prev-row="0x0000150e",
20297 next-page="0x00001512",prev-page="0x0000150e",memory=[
20298 @{addr="0x00001510",data=["128"]@}]
20302 Read thirty two bytes of memory starting at @code{bytes+16} and format
20303 as eight rows of four columns. Include a string encoding with @samp{x}
20304 used as the non-printable character.
20308 4-data-read-memory bytes+16 x 1 8 4 x
20309 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20310 next-row="0x000013c0",prev-row="0x0000139c",
20311 next-page="0x000013c0",prev-page="0x00001380",memory=[
20312 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20313 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20314 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20315 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20316 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20317 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20318 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20319 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20323 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20324 @node GDB/MI Tracepoint Commands
20325 @section @sc{gdb/mi} Tracepoint Commands
20327 The tracepoint commands are not yet implemented.
20329 @c @subheading -trace-actions
20331 @c @subheading -trace-delete
20333 @c @subheading -trace-disable
20335 @c @subheading -trace-dump
20337 @c @subheading -trace-enable
20339 @c @subheading -trace-exists
20341 @c @subheading -trace-find
20343 @c @subheading -trace-frame-number
20345 @c @subheading -trace-info
20347 @c @subheading -trace-insert
20349 @c @subheading -trace-list
20351 @c @subheading -trace-pass-count
20353 @c @subheading -trace-save
20355 @c @subheading -trace-start
20357 @c @subheading -trace-stop
20360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20361 @node GDB/MI Symbol Query
20362 @section @sc{gdb/mi} Symbol Query Commands
20365 @subheading The @code{-symbol-info-address} Command
20366 @findex -symbol-info-address
20368 @subsubheading Synopsis
20371 -symbol-info-address @var{symbol}
20374 Describe where @var{symbol} is stored.
20376 @subsubheading @value{GDBN} Command
20378 The corresponding @value{GDBN} command is @samp{info address}.
20380 @subsubheading Example
20384 @subheading The @code{-symbol-info-file} Command
20385 @findex -symbol-info-file
20387 @subsubheading Synopsis
20393 Show the file for the symbol.
20395 @subsubheading @value{GDBN} Command
20397 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20398 @samp{gdb_find_file}.
20400 @subsubheading Example
20404 @subheading The @code{-symbol-info-function} Command
20405 @findex -symbol-info-function
20407 @subsubheading Synopsis
20410 -symbol-info-function
20413 Show which function the symbol lives in.
20415 @subsubheading @value{GDBN} Command
20417 @samp{gdb_get_function} in @code{gdbtk}.
20419 @subsubheading Example
20423 @subheading The @code{-symbol-info-line} Command
20424 @findex -symbol-info-line
20426 @subsubheading Synopsis
20432 Show the core addresses of the code for a source line.
20434 @subsubheading @value{GDBN} Command
20436 The corresponding @value{GDBN} command is @samp{info line}.
20437 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20439 @subsubheading Example
20443 @subheading The @code{-symbol-info-symbol} Command
20444 @findex -symbol-info-symbol
20446 @subsubheading Synopsis
20449 -symbol-info-symbol @var{addr}
20452 Describe what symbol is at location @var{addr}.
20454 @subsubheading @value{GDBN} Command
20456 The corresponding @value{GDBN} command is @samp{info symbol}.
20458 @subsubheading Example
20462 @subheading The @code{-symbol-list-functions} Command
20463 @findex -symbol-list-functions
20465 @subsubheading Synopsis
20468 -symbol-list-functions
20471 List the functions in the executable.
20473 @subsubheading @value{GDBN} Command
20475 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20476 @samp{gdb_search} in @code{gdbtk}.
20478 @subsubheading Example
20482 @subheading The @code{-symbol-list-lines} Command
20483 @findex -symbol-list-lines
20485 @subsubheading Synopsis
20488 -symbol-list-lines @var{filename}
20491 Print the list of lines that contain code and their associated program
20492 addresses for the given source filename. The entries are sorted in
20493 ascending PC order.
20495 @subsubheading @value{GDBN} Command
20497 There is no corresponding @value{GDBN} command.
20499 @subsubheading Example
20502 -symbol-list-lines basics.c
20503 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20508 @subheading The @code{-symbol-list-types} Command
20509 @findex -symbol-list-types
20511 @subsubheading Synopsis
20517 List all the type names.
20519 @subsubheading @value{GDBN} Command
20521 The corresponding commands are @samp{info types} in @value{GDBN},
20522 @samp{gdb_search} in @code{gdbtk}.
20524 @subsubheading Example
20528 @subheading The @code{-symbol-list-variables} Command
20529 @findex -symbol-list-variables
20531 @subsubheading Synopsis
20534 -symbol-list-variables
20537 List all the global and static variable names.
20539 @subsubheading @value{GDBN} Command
20541 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20543 @subsubheading Example
20547 @subheading The @code{-symbol-locate} Command
20548 @findex -symbol-locate
20550 @subsubheading Synopsis
20556 @subsubheading @value{GDBN} Command
20558 @samp{gdb_loc} in @code{gdbtk}.
20560 @subsubheading Example
20564 @subheading The @code{-symbol-type} Command
20565 @findex -symbol-type
20567 @subsubheading Synopsis
20570 -symbol-type @var{variable}
20573 Show type of @var{variable}.
20575 @subsubheading @value{GDBN} Command
20577 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20578 @samp{gdb_obj_variable}.
20580 @subsubheading Example
20584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20585 @node GDB/MI File Commands
20586 @section @sc{gdb/mi} File Commands
20588 This section describes the GDB/MI commands to specify executable file names
20589 and to read in and obtain symbol table information.
20591 @subheading The @code{-file-exec-and-symbols} Command
20592 @findex -file-exec-and-symbols
20594 @subsubheading Synopsis
20597 -file-exec-and-symbols @var{file}
20600 Specify the executable file to be debugged. This file is the one from
20601 which the symbol table is also read. If no file is specified, the
20602 command clears the executable and symbol information. If breakpoints
20603 are set when using this command with no arguments, @value{GDBN} will produce
20604 error messages. Otherwise, no output is produced, except a completion
20607 @subsubheading @value{GDBN} Command
20609 The corresponding @value{GDBN} command is @samp{file}.
20611 @subsubheading Example
20615 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20621 @subheading The @code{-file-exec-file} Command
20622 @findex -file-exec-file
20624 @subsubheading Synopsis
20627 -file-exec-file @var{file}
20630 Specify the executable file to be debugged. Unlike
20631 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20632 from this file. If used without argument, @value{GDBN} clears the information
20633 about the executable file. No output is produced, except a completion
20636 @subsubheading @value{GDBN} Command
20638 The corresponding @value{GDBN} command is @samp{exec-file}.
20640 @subsubheading Example
20644 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20650 @subheading The @code{-file-list-exec-sections} Command
20651 @findex -file-list-exec-sections
20653 @subsubheading Synopsis
20656 -file-list-exec-sections
20659 List the sections of the current executable file.
20661 @subsubheading @value{GDBN} Command
20663 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20664 information as this command. @code{gdbtk} has a corresponding command
20665 @samp{gdb_load_info}.
20667 @subsubheading Example
20671 @subheading The @code{-file-list-exec-source-file} Command
20672 @findex -file-list-exec-source-file
20674 @subsubheading Synopsis
20677 -file-list-exec-source-file
20680 List the line number, the current source file, and the absolute path
20681 to the current source file for the current executable.
20683 @subsubheading @value{GDBN} Command
20685 The @value{GDBN} equivalent is @samp{info source}
20687 @subsubheading Example
20691 123-file-list-exec-source-file
20692 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20697 @subheading The @code{-file-list-exec-source-files} Command
20698 @findex -file-list-exec-source-files
20700 @subsubheading Synopsis
20703 -file-list-exec-source-files
20706 List the source files for the current executable.
20708 It will always output the filename, but only when GDB can find the absolute
20709 file name of a source file, will it output the fullname.
20711 @subsubheading @value{GDBN} Command
20713 The @value{GDBN} equivalent is @samp{info sources}.
20714 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20716 @subsubheading Example
20719 -file-list-exec-source-files
20721 @{file=foo.c,fullname=/home/foo.c@},
20722 @{file=/home/bar.c,fullname=/home/bar.c@},
20723 @{file=gdb_could_not_find_fullpath.c@}]
20727 @subheading The @code{-file-list-shared-libraries} Command
20728 @findex -file-list-shared-libraries
20730 @subsubheading Synopsis
20733 -file-list-shared-libraries
20736 List the shared libraries in the program.
20738 @subsubheading @value{GDBN} Command
20740 The corresponding @value{GDBN} command is @samp{info shared}.
20742 @subsubheading Example
20746 @subheading The @code{-file-list-symbol-files} Command
20747 @findex -file-list-symbol-files
20749 @subsubheading Synopsis
20752 -file-list-symbol-files
20757 @subsubheading @value{GDBN} Command
20759 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20761 @subsubheading Example
20765 @subheading The @code{-file-symbol-file} Command
20766 @findex -file-symbol-file
20768 @subsubheading Synopsis
20771 -file-symbol-file @var{file}
20774 Read symbol table info from the specified @var{file} argument. When
20775 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20776 produced, except for a completion notification.
20778 @subsubheading @value{GDBN} Command
20780 The corresponding @value{GDBN} command is @samp{symbol-file}.
20782 @subsubheading Example
20786 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20793 @node GDB/MI Memory Overlay Commands
20794 @section @sc{gdb/mi} Memory Overlay Commands
20796 The memory overlay commands are not implemented.
20798 @c @subheading -overlay-auto
20800 @c @subheading -overlay-list-mapping-state
20802 @c @subheading -overlay-list-overlays
20804 @c @subheading -overlay-map
20806 @c @subheading -overlay-off
20808 @c @subheading -overlay-on
20810 @c @subheading -overlay-unmap
20812 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20813 @node GDB/MI Signal Handling Commands
20814 @section @sc{gdb/mi} Signal Handling Commands
20816 Signal handling commands are not implemented.
20818 @c @subheading -signal-handle
20820 @c @subheading -signal-list-handle-actions
20822 @c @subheading -signal-list-signal-types
20826 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20827 @node GDB/MI Target Manipulation
20828 @section @sc{gdb/mi} Target Manipulation Commands
20831 @subheading The @code{-target-attach} Command
20832 @findex -target-attach
20834 @subsubheading Synopsis
20837 -target-attach @var{pid} | @var{file}
20840 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20842 @subsubheading @value{GDBN} command
20844 The corresponding @value{GDBN} command is @samp{attach}.
20846 @subsubheading Example
20850 @subheading The @code{-target-compare-sections} Command
20851 @findex -target-compare-sections
20853 @subsubheading Synopsis
20856 -target-compare-sections [ @var{section} ]
20859 Compare data of section @var{section} on target to the exec file.
20860 Without the argument, all sections are compared.
20862 @subsubheading @value{GDBN} Command
20864 The @value{GDBN} equivalent is @samp{compare-sections}.
20866 @subsubheading Example
20870 @subheading The @code{-target-detach} Command
20871 @findex -target-detach
20873 @subsubheading Synopsis
20879 Detach from the remote target which normally resumes its execution.
20882 @subsubheading @value{GDBN} command
20884 The corresponding @value{GDBN} command is @samp{detach}.
20886 @subsubheading Example
20896 @subheading The @code{-target-disconnect} Command
20897 @findex -target-disconnect
20899 @subsubheading Synopsis
20905 Disconnect from the remote target. There's no output and the target is
20906 generally not resumed.
20908 @subsubheading @value{GDBN} command
20910 The corresponding @value{GDBN} command is @samp{disconnect}.
20912 @subsubheading Example
20922 @subheading The @code{-target-download} Command
20923 @findex -target-download
20925 @subsubheading Synopsis
20931 Loads the executable onto the remote target.
20932 It prints out an update message every half second, which includes the fields:
20936 The name of the section.
20938 The size of what has been sent so far for that section.
20940 The size of the section.
20942 The total size of what was sent so far (the current and the previous sections).
20944 The size of the overall executable to download.
20948 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20949 @sc{gdb/mi} Output Syntax}).
20951 In addition, it prints the name and size of the sections, as they are
20952 downloaded. These messages include the following fields:
20956 The name of the section.
20958 The size of the section.
20960 The size of the overall executable to download.
20964 At the end, a summary is printed.
20966 @subsubheading @value{GDBN} Command
20968 The corresponding @value{GDBN} command is @samp{load}.
20970 @subsubheading Example
20972 Note: each status message appears on a single line. Here the messages
20973 have been broken down so that they can fit onto a page.
20978 +download,@{section=".text",section-size="6668",total-size="9880"@}
20979 +download,@{section=".text",section-sent="512",section-size="6668",
20980 total-sent="512",total-size="9880"@}
20981 +download,@{section=".text",section-sent="1024",section-size="6668",
20982 total-sent="1024",total-size="9880"@}
20983 +download,@{section=".text",section-sent="1536",section-size="6668",
20984 total-sent="1536",total-size="9880"@}
20985 +download,@{section=".text",section-sent="2048",section-size="6668",
20986 total-sent="2048",total-size="9880"@}
20987 +download,@{section=".text",section-sent="2560",section-size="6668",
20988 total-sent="2560",total-size="9880"@}
20989 +download,@{section=".text",section-sent="3072",section-size="6668",
20990 total-sent="3072",total-size="9880"@}
20991 +download,@{section=".text",section-sent="3584",section-size="6668",
20992 total-sent="3584",total-size="9880"@}
20993 +download,@{section=".text",section-sent="4096",section-size="6668",
20994 total-sent="4096",total-size="9880"@}
20995 +download,@{section=".text",section-sent="4608",section-size="6668",
20996 total-sent="4608",total-size="9880"@}
20997 +download,@{section=".text",section-sent="5120",section-size="6668",
20998 total-sent="5120",total-size="9880"@}
20999 +download,@{section=".text",section-sent="5632",section-size="6668",
21000 total-sent="5632",total-size="9880"@}
21001 +download,@{section=".text",section-sent="6144",section-size="6668",
21002 total-sent="6144",total-size="9880"@}
21003 +download,@{section=".text",section-sent="6656",section-size="6668",
21004 total-sent="6656",total-size="9880"@}
21005 +download,@{section=".init",section-size="28",total-size="9880"@}
21006 +download,@{section=".fini",section-size="28",total-size="9880"@}
21007 +download,@{section=".data",section-size="3156",total-size="9880"@}
21008 +download,@{section=".data",section-sent="512",section-size="3156",
21009 total-sent="7236",total-size="9880"@}
21010 +download,@{section=".data",section-sent="1024",section-size="3156",
21011 total-sent="7748",total-size="9880"@}
21012 +download,@{section=".data",section-sent="1536",section-size="3156",
21013 total-sent="8260",total-size="9880"@}
21014 +download,@{section=".data",section-sent="2048",section-size="3156",
21015 total-sent="8772",total-size="9880"@}
21016 +download,@{section=".data",section-sent="2560",section-size="3156",
21017 total-sent="9284",total-size="9880"@}
21018 +download,@{section=".data",section-sent="3072",section-size="3156",
21019 total-sent="9796",total-size="9880"@}
21020 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21026 @subheading The @code{-target-exec-status} Command
21027 @findex -target-exec-status
21029 @subsubheading Synopsis
21032 -target-exec-status
21035 Provide information on the state of the target (whether it is running or
21036 not, for instance).
21038 @subsubheading @value{GDBN} Command
21040 There's no equivalent @value{GDBN} command.
21042 @subsubheading Example
21046 @subheading The @code{-target-list-available-targets} Command
21047 @findex -target-list-available-targets
21049 @subsubheading Synopsis
21052 -target-list-available-targets
21055 List the possible targets to connect to.
21057 @subsubheading @value{GDBN} Command
21059 The corresponding @value{GDBN} command is @samp{help target}.
21061 @subsubheading Example
21065 @subheading The @code{-target-list-current-targets} Command
21066 @findex -target-list-current-targets
21068 @subsubheading Synopsis
21071 -target-list-current-targets
21074 Describe the current target.
21076 @subsubheading @value{GDBN} Command
21078 The corresponding information is printed by @samp{info file} (among
21081 @subsubheading Example
21085 @subheading The @code{-target-list-parameters} Command
21086 @findex -target-list-parameters
21088 @subsubheading Synopsis
21091 -target-list-parameters
21096 @subsubheading @value{GDBN} Command
21100 @subsubheading Example
21104 @subheading The @code{-target-select} Command
21105 @findex -target-select
21107 @subsubheading Synopsis
21110 -target-select @var{type} @var{parameters @dots{}}
21113 Connect @value{GDBN} to the remote target. This command takes two args:
21117 The type of target, for instance @samp{async}, @samp{remote}, etc.
21118 @item @var{parameters}
21119 Device names, host names and the like. @xref{Target Commands, ,
21120 Commands for managing targets}, for more details.
21123 The output is a connection notification, followed by the address at
21124 which the target program is, in the following form:
21127 ^connected,addr="@var{address}",func="@var{function name}",
21128 args=[@var{arg list}]
21131 @subsubheading @value{GDBN} Command
21133 The corresponding @value{GDBN} command is @samp{target}.
21135 @subsubheading Example
21139 -target-select async /dev/ttya
21140 ^connected,addr="0xfe00a300",func="??",args=[]
21144 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21145 @node GDB/MI Miscellaneous Commands
21146 @section Miscellaneous @sc{gdb/mi} Commands
21148 @c @subheading -gdb-complete
21150 @subheading The @code{-gdb-exit} Command
21153 @subsubheading Synopsis
21159 Exit @value{GDBN} immediately.
21161 @subsubheading @value{GDBN} Command
21163 Approximately corresponds to @samp{quit}.
21165 @subsubheading Example
21174 @subheading The @code{-exec-abort} Command
21175 @findex -exec-abort
21177 @subsubheading Synopsis
21183 Kill the inferior running program.
21185 @subsubheading @value{GDBN} Command
21187 The corresponding @value{GDBN} command is @samp{kill}.
21189 @subsubheading Example
21193 @subheading The @code{-gdb-set} Command
21196 @subsubheading Synopsis
21202 Set an internal @value{GDBN} variable.
21203 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21205 @subsubheading @value{GDBN} Command
21207 The corresponding @value{GDBN} command is @samp{set}.
21209 @subsubheading Example
21219 @subheading The @code{-gdb-show} Command
21222 @subsubheading Synopsis
21228 Show the current value of a @value{GDBN} variable.
21230 @subsubheading @value{GDBN} command
21232 The corresponding @value{GDBN} command is @samp{show}.
21234 @subsubheading Example
21243 @c @subheading -gdb-source
21246 @subheading The @code{-gdb-version} Command
21247 @findex -gdb-version
21249 @subsubheading Synopsis
21255 Show version information for @value{GDBN}. Used mostly in testing.
21257 @subsubheading @value{GDBN} Command
21259 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21260 default shows this information when you start an interactive session.
21262 @subsubheading Example
21264 @c This example modifies the actual output from GDB to avoid overfull
21270 ~Copyright 2000 Free Software Foundation, Inc.
21271 ~GDB is free software, covered by the GNU General Public License, and
21272 ~you are welcome to change it and/or distribute copies of it under
21273 ~ certain conditions.
21274 ~Type "show copying" to see the conditions.
21275 ~There is absolutely no warranty for GDB. Type "show warranty" for
21277 ~This GDB was configured as
21278 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21283 @subheading The @code{-interpreter-exec} Command
21284 @findex -interpreter-exec
21286 @subheading Synopsis
21289 -interpreter-exec @var{interpreter} @var{command}
21291 @anchor{-interpreter-exec}
21293 Execute the specified @var{command} in the given @var{interpreter}.
21295 @subheading @value{GDBN} Command
21297 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21299 @subheading Example
21303 -interpreter-exec console "break main"
21304 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21305 &"During symbol reading, bad structure-type format.\n"
21306 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21311 @subheading The @code{-inferior-tty-set} Command
21312 @findex -inferior-tty-set
21314 @subheading Synopsis
21317 -inferior-tty-set /dev/pts/1
21320 Set terminal for future runs of the program being debugged.
21322 @subheading @value{GDBN} Command
21324 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21326 @subheading Example
21330 -inferior-tty-set /dev/pts/1
21335 @subheading The @code{-inferior-tty-show} Command
21336 @findex -inferior-tty-show
21338 @subheading Synopsis
21344 Show terminal for future runs of program being debugged.
21346 @subheading @value{GDBN} Command
21348 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21350 @subheading Example
21354 -inferior-tty-set /dev/pts/1
21358 ^done,inferior_tty_terminal="/dev/pts/1"
21363 @chapter @value{GDBN} Annotations
21365 This chapter describes annotations in @value{GDBN}. Annotations were
21366 designed to interface @value{GDBN} to graphical user interfaces or other
21367 similar programs which want to interact with @value{GDBN} at a
21368 relatively high level.
21370 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
21374 This is Edition @value{EDITION}, @value{DATE}.
21378 * Annotations Overview:: What annotations are; the general syntax.
21379 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21380 * Errors:: Annotations for error messages.
21381 * Invalidation:: Some annotations describe things now invalid.
21382 * Annotations for Running::
21383 Whether the program is running, how it stopped, etc.
21384 * Source Annotations:: Annotations describing source code.
21387 @node Annotations Overview
21388 @section What is an Annotation?
21389 @cindex annotations
21391 Annotations start with a newline character, two @samp{control-z}
21392 characters, and the name of the annotation. If there is no additional
21393 information associated with this annotation, the name of the annotation
21394 is followed immediately by a newline. If there is additional
21395 information, the name of the annotation is followed by a space, the
21396 additional information, and a newline. The additional information
21397 cannot contain newline characters.
21399 Any output not beginning with a newline and two @samp{control-z}
21400 characters denotes literal output from @value{GDBN}. Currently there is
21401 no need for @value{GDBN} to output a newline followed by two
21402 @samp{control-z} characters, but if there was such a need, the
21403 annotations could be extended with an @samp{escape} annotation which
21404 means those three characters as output.
21406 The annotation @var{level}, which is specified using the
21407 @option{--annotate} command line option (@pxref{Mode Options}), controls
21408 how much information @value{GDBN} prints together with its prompt,
21409 values of expressions, source lines, and other types of output. Level 0
21410 is for no anntations, level 1 is for use when @value{GDBN} is run as a
21411 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21412 for programs that control @value{GDBN}, and level 2 annotations have
21413 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21414 Interface, annotate, GDB's Obsolete Annotations}).
21417 @kindex set annotate
21418 @item set annotate @var{level}
21419 The @value{GDBN} command @code{set annotate} sets the level of
21420 annotations to the specified @var{level}.
21422 @item show annotate
21423 @kindex show annotate
21424 Show the current annotation level.
21427 This chapter describes level 3 annotations.
21429 A simple example of starting up @value{GDBN} with annotations is:
21432 $ @kbd{gdb --annotate=3}
21434 Copyright 2003 Free Software Foundation, Inc.
21435 GDB is free software, covered by the GNU General Public License,
21436 and you are welcome to change it and/or distribute copies of it
21437 under certain conditions.
21438 Type "show copying" to see the conditions.
21439 There is absolutely no warranty for GDB. Type "show warranty"
21441 This GDB was configured as "i386-pc-linux-gnu"
21452 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21453 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21454 denotes a @samp{control-z} character) are annotations; the rest is
21455 output from @value{GDBN}.
21458 @section Annotation for @value{GDBN} Input
21460 @cindex annotations for prompts
21461 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21462 to know when to send output, when the output from a given command is
21465 Different kinds of input each have a different @dfn{input type}. Each
21466 input type has three annotations: a @code{pre-} annotation, which
21467 denotes the beginning of any prompt which is being output, a plain
21468 annotation, which denotes the end of the prompt, and then a @code{post-}
21469 annotation which denotes the end of any echo which may (or may not) be
21470 associated with the input. For example, the @code{prompt} input type
21471 features the following annotations:
21479 The input types are
21482 @findex pre-prompt annotation
21483 @findex prompt annotation
21484 @findex post-prompt annotation
21486 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21488 @findex pre-commands annotation
21489 @findex commands annotation
21490 @findex post-commands annotation
21492 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21493 command. The annotations are repeated for each command which is input.
21495 @findex pre-overload-choice annotation
21496 @findex overload-choice annotation
21497 @findex post-overload-choice annotation
21498 @item overload-choice
21499 When @value{GDBN} wants the user to select between various overloaded functions.
21501 @findex pre-query annotation
21502 @findex query annotation
21503 @findex post-query annotation
21505 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21507 @findex pre-prompt-for-continue annotation
21508 @findex prompt-for-continue annotation
21509 @findex post-prompt-for-continue annotation
21510 @item prompt-for-continue
21511 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21512 expect this to work well; instead use @code{set height 0} to disable
21513 prompting. This is because the counting of lines is buggy in the
21514 presence of annotations.
21519 @cindex annotations for errors, warnings and interrupts
21521 @findex quit annotation
21526 This annotation occurs right before @value{GDBN} responds to an interrupt.
21528 @findex error annotation
21533 This annotation occurs right before @value{GDBN} responds to an error.
21535 Quit and error annotations indicate that any annotations which @value{GDBN} was
21536 in the middle of may end abruptly. For example, if a
21537 @code{value-history-begin} annotation is followed by a @code{error}, one
21538 cannot expect to receive the matching @code{value-history-end}. One
21539 cannot expect not to receive it either, however; an error annotation
21540 does not necessarily mean that @value{GDBN} is immediately returning all the way
21543 @findex error-begin annotation
21544 A quit or error annotation may be preceded by
21550 Any output between that and the quit or error annotation is the error
21553 Warning messages are not yet annotated.
21554 @c If we want to change that, need to fix warning(), type_error(),
21555 @c range_error(), and possibly other places.
21558 @section Invalidation Notices
21560 @cindex annotations for invalidation messages
21561 The following annotations say that certain pieces of state may have
21565 @findex frames-invalid annotation
21566 @item ^Z^Zframes-invalid
21568 The frames (for example, output from the @code{backtrace} command) may
21571 @findex breakpoints-invalid annotation
21572 @item ^Z^Zbreakpoints-invalid
21574 The breakpoints may have changed. For example, the user just added or
21575 deleted a breakpoint.
21578 @node Annotations for Running
21579 @section Running the Program
21580 @cindex annotations for running programs
21582 @findex starting annotation
21583 @findex stopping annotation
21584 When the program starts executing due to a @value{GDBN} command such as
21585 @code{step} or @code{continue},
21591 is output. When the program stops,
21597 is output. Before the @code{stopped} annotation, a variety of
21598 annotations describe how the program stopped.
21601 @findex exited annotation
21602 @item ^Z^Zexited @var{exit-status}
21603 The program exited, and @var{exit-status} is the exit status (zero for
21604 successful exit, otherwise nonzero).
21606 @findex signalled annotation
21607 @findex signal-name annotation
21608 @findex signal-name-end annotation
21609 @findex signal-string annotation
21610 @findex signal-string-end annotation
21611 @item ^Z^Zsignalled
21612 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21613 annotation continues:
21619 ^Z^Zsignal-name-end
21623 ^Z^Zsignal-string-end
21628 where @var{name} is the name of the signal, such as @code{SIGILL} or
21629 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21630 as @code{Illegal Instruction} or @code{Segmentation fault}.
21631 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21632 user's benefit and have no particular format.
21634 @findex signal annotation
21636 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21637 just saying that the program received the signal, not that it was
21638 terminated with it.
21640 @findex breakpoint annotation
21641 @item ^Z^Zbreakpoint @var{number}
21642 The program hit breakpoint number @var{number}.
21644 @findex watchpoint annotation
21645 @item ^Z^Zwatchpoint @var{number}
21646 The program hit watchpoint number @var{number}.
21649 @node Source Annotations
21650 @section Displaying Source
21651 @cindex annotations for source display
21653 @findex source annotation
21654 The following annotation is used instead of displaying source code:
21657 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21660 where @var{filename} is an absolute file name indicating which source
21661 file, @var{line} is the line number within that file (where 1 is the
21662 first line in the file), @var{character} is the character position
21663 within the file (where 0 is the first character in the file) (for most
21664 debug formats this will necessarily point to the beginning of a line),
21665 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21666 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21667 @var{addr} is the address in the target program associated with the
21668 source which is being displayed. @var{addr} is in the form @samp{0x}
21669 followed by one or more lowercase hex digits (note that this does not
21670 depend on the language).
21673 @chapter Reporting Bugs in @value{GDBN}
21674 @cindex bugs in @value{GDBN}
21675 @cindex reporting bugs in @value{GDBN}
21677 Your bug reports play an essential role in making @value{GDBN} reliable.
21679 Reporting a bug may help you by bringing a solution to your problem, or it
21680 may not. But in any case the principal function of a bug report is to help
21681 the entire community by making the next version of @value{GDBN} work better. Bug
21682 reports are your contribution to the maintenance of @value{GDBN}.
21684 In order for a bug report to serve its purpose, you must include the
21685 information that enables us to fix the bug.
21688 * Bug Criteria:: Have you found a bug?
21689 * Bug Reporting:: How to report bugs
21693 @section Have you found a bug?
21694 @cindex bug criteria
21696 If you are not sure whether you have found a bug, here are some guidelines:
21699 @cindex fatal signal
21700 @cindex debugger crash
21701 @cindex crash of debugger
21703 If the debugger gets a fatal signal, for any input whatever, that is a
21704 @value{GDBN} bug. Reliable debuggers never crash.
21706 @cindex error on valid input
21708 If @value{GDBN} produces an error message for valid input, that is a
21709 bug. (Note that if you're cross debugging, the problem may also be
21710 somewhere in the connection to the target.)
21712 @cindex invalid input
21714 If @value{GDBN} does not produce an error message for invalid input,
21715 that is a bug. However, you should note that your idea of
21716 ``invalid input'' might be our idea of ``an extension'' or ``support
21717 for traditional practice''.
21720 If you are an experienced user of debugging tools, your suggestions
21721 for improvement of @value{GDBN} are welcome in any case.
21724 @node Bug Reporting
21725 @section How to report bugs
21726 @cindex bug reports
21727 @cindex @value{GDBN} bugs, reporting
21729 A number of companies and individuals offer support for @sc{gnu} products.
21730 If you obtained @value{GDBN} from a support organization, we recommend you
21731 contact that organization first.
21733 You can find contact information for many support companies and
21734 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21736 @c should add a web page ref...
21738 In any event, we also recommend that you submit bug reports for
21739 @value{GDBN}. The prefered method is to submit them directly using
21740 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21741 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21744 @strong{Do not send bug reports to @samp{info-gdb}, or to
21745 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21746 not want to receive bug reports. Those that do have arranged to receive
21749 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21750 serves as a repeater. The mailing list and the newsgroup carry exactly
21751 the same messages. Often people think of posting bug reports to the
21752 newsgroup instead of mailing them. This appears to work, but it has one
21753 problem which can be crucial: a newsgroup posting often lacks a mail
21754 path back to the sender. Thus, if we need to ask for more information,
21755 we may be unable to reach you. For this reason, it is better to send
21756 bug reports to the mailing list.
21758 The fundamental principle of reporting bugs usefully is this:
21759 @strong{report all the facts}. If you are not sure whether to state a
21760 fact or leave it out, state it!
21762 Often people omit facts because they think they know what causes the
21763 problem and assume that some details do not matter. Thus, you might
21764 assume that the name of the variable you use in an example does not matter.
21765 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21766 stray memory reference which happens to fetch from the location where that
21767 name is stored in memory; perhaps, if the name were different, the contents
21768 of that location would fool the debugger into doing the right thing despite
21769 the bug. Play it safe and give a specific, complete example. That is the
21770 easiest thing for you to do, and the most helpful.
21772 Keep in mind that the purpose of a bug report is to enable us to fix the
21773 bug. It may be that the bug has been reported previously, but neither
21774 you nor we can know that unless your bug report is complete and
21777 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21778 bell?'' Those bug reports are useless, and we urge everyone to
21779 @emph{refuse to respond to them} except to chide the sender to report
21782 To enable us to fix the bug, you should include all these things:
21786 The version of @value{GDBN}. @value{GDBN} announces it if you start
21787 with no arguments; you can also print it at any time using @code{show
21790 Without this, we will not know whether there is any point in looking for
21791 the bug in the current version of @value{GDBN}.
21794 The type of machine you are using, and the operating system name and
21798 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21799 ``@value{GCC}--2.8.1''.
21802 What compiler (and its version) was used to compile the program you are
21803 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21804 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21805 information; for other compilers, see the documentation for those
21809 The command arguments you gave the compiler to compile your example and
21810 observe the bug. For example, did you use @samp{-O}? To guarantee
21811 you will not omit something important, list them all. A copy of the
21812 Makefile (or the output from make) is sufficient.
21814 If we were to try to guess the arguments, we would probably guess wrong
21815 and then we might not encounter the bug.
21818 A complete input script, and all necessary source files, that will
21822 A description of what behavior you observe that you believe is
21823 incorrect. For example, ``It gets a fatal signal.''
21825 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21826 will certainly notice it. But if the bug is incorrect output, we might
21827 not notice unless it is glaringly wrong. You might as well not give us
21828 a chance to make a mistake.
21830 Even if the problem you experience is a fatal signal, you should still
21831 say so explicitly. Suppose something strange is going on, such as, your
21832 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21833 the C library on your system. (This has happened!) Your copy might
21834 crash and ours would not. If you told us to expect a crash, then when
21835 ours fails to crash, we would know that the bug was not happening for
21836 us. If you had not told us to expect a crash, then we would not be able
21837 to draw any conclusion from our observations.
21840 @cindex recording a session script
21841 To collect all this information, you can use a session recording program
21842 such as @command{script}, which is available on many Unix systems.
21843 Just run your @value{GDBN} session inside @command{script} and then
21844 include the @file{typescript} file with your bug report.
21846 Another way to record a @value{GDBN} session is to run @value{GDBN}
21847 inside Emacs and then save the entire buffer to a file.
21850 If you wish to suggest changes to the @value{GDBN} source, send us context
21851 diffs. If you even discuss something in the @value{GDBN} source, refer to
21852 it by context, not by line number.
21854 The line numbers in our development sources will not match those in your
21855 sources. Your line numbers would convey no useful information to us.
21859 Here are some things that are not necessary:
21863 A description of the envelope of the bug.
21865 Often people who encounter a bug spend a lot of time investigating
21866 which changes to the input file will make the bug go away and which
21867 changes will not affect it.
21869 This is often time consuming and not very useful, because the way we
21870 will find the bug is by running a single example under the debugger
21871 with breakpoints, not by pure deduction from a series of examples.
21872 We recommend that you save your time for something else.
21874 Of course, if you can find a simpler example to report @emph{instead}
21875 of the original one, that is a convenience for us. Errors in the
21876 output will be easier to spot, running under the debugger will take
21877 less time, and so on.
21879 However, simplification is not vital; if you do not want to do this,
21880 report the bug anyway and send us the entire test case you used.
21883 A patch for the bug.
21885 A patch for the bug does help us if it is a good one. But do not omit
21886 the necessary information, such as the test case, on the assumption that
21887 a patch is all we need. We might see problems with your patch and decide
21888 to fix the problem another way, or we might not understand it at all.
21890 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21891 construct an example that will make the program follow a certain path
21892 through the code. If you do not send us the example, we will not be able
21893 to construct one, so we will not be able to verify that the bug is fixed.
21895 And if we cannot understand what bug you are trying to fix, or why your
21896 patch should be an improvement, we will not install it. A test case will
21897 help us to understand.
21900 A guess about what the bug is or what it depends on.
21902 Such guesses are usually wrong. Even we cannot guess right about such
21903 things without first using the debugger to find the facts.
21906 @c The readline documentation is distributed with the readline code
21907 @c and consists of the two following files:
21909 @c inc-hist.texinfo
21910 @c Use -I with makeinfo to point to the appropriate directory,
21911 @c environment var TEXINPUTS with TeX.
21912 @include rluser.texi
21913 @include inc-hist.texinfo
21916 @node Formatting Documentation
21917 @appendix Formatting Documentation
21919 @cindex @value{GDBN} reference card
21920 @cindex reference card
21921 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21922 for printing with PostScript or Ghostscript, in the @file{gdb}
21923 subdirectory of the main source directory@footnote{In
21924 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21925 release.}. If you can use PostScript or Ghostscript with your printer,
21926 you can print the reference card immediately with @file{refcard.ps}.
21928 The release also includes the source for the reference card. You
21929 can format it, using @TeX{}, by typing:
21935 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21936 mode on US ``letter'' size paper;
21937 that is, on a sheet 11 inches wide by 8.5 inches
21938 high. You will need to specify this form of printing as an option to
21939 your @sc{dvi} output program.
21941 @cindex documentation
21943 All the documentation for @value{GDBN} comes as part of the machine-readable
21944 distribution. The documentation is written in Texinfo format, which is
21945 a documentation system that uses a single source file to produce both
21946 on-line information and a printed manual. You can use one of the Info
21947 formatting commands to create the on-line version of the documentation
21948 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21950 @value{GDBN} includes an already formatted copy of the on-line Info
21951 version of this manual in the @file{gdb} subdirectory. The main Info
21952 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21953 subordinate files matching @samp{gdb.info*} in the same directory. If
21954 necessary, you can print out these files, or read them with any editor;
21955 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21956 Emacs or the standalone @code{info} program, available as part of the
21957 @sc{gnu} Texinfo distribution.
21959 If you want to format these Info files yourself, you need one of the
21960 Info formatting programs, such as @code{texinfo-format-buffer} or
21963 If you have @code{makeinfo} installed, and are in the top level
21964 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21965 version @value{GDBVN}), you can make the Info file by typing:
21972 If you want to typeset and print copies of this manual, you need @TeX{},
21973 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21974 Texinfo definitions file.
21976 @TeX{} is a typesetting program; it does not print files directly, but
21977 produces output files called @sc{dvi} files. To print a typeset
21978 document, you need a program to print @sc{dvi} files. If your system
21979 has @TeX{} installed, chances are it has such a program. The precise
21980 command to use depends on your system; @kbd{lpr -d} is common; another
21981 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21982 require a file name without any extension or a @samp{.dvi} extension.
21984 @TeX{} also requires a macro definitions file called
21985 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21986 written in Texinfo format. On its own, @TeX{} cannot either read or
21987 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21988 and is located in the @file{gdb-@var{version-number}/texinfo}
21991 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21992 typeset and print this manual. First switch to the the @file{gdb}
21993 subdirectory of the main source directory (for example, to
21994 @file{gdb-@value{GDBVN}/gdb}) and type:
22000 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22002 @node Installing GDB
22003 @appendix Installing @value{GDBN}
22004 @cindex installation
22007 * Requirements:: Requirements for building @value{GDBN}
22008 * Running Configure:: Invoking the @value{GDBN} @code{configure} script
22009 * Separate Objdir:: Compiling @value{GDBN} in another directory
22010 * Config Names:: Specifying names for hosts and targets
22011 * Configure Options:: Summary of options for configure
22015 @section Requirements for building @value{GDBN}
22016 @cindex building @value{GDBN}, requirements for
22018 Building @value{GDBN} requires various tools and packages to be available.
22019 Other packages will be used only if they are found.
22021 @heading Tools/packages necessary for building @value{GDBN}
22023 @item ISO C90 compiler
22024 @value{GDBN} is written in ISO C90. It should be buildable with any
22025 working C90 compiler, e.g.@: GCC.
22029 @heading Tools/packages optional for building @value{GDBN}
22032 @value{GDBN} can use the Expat XML parsing library. This library may be
22033 included with your operating system distribution; if it is not, you
22034 can get the latest version from @url{http://expat.sourceforge.net}.
22035 The @code{configure} script will search for this library in several
22036 standard locations; if it is installed in an unusual path, you can
22037 use the @option{--with-libexpat-prefix} option to specify its location.
22039 Expat is used currently only used to implement some remote-specific
22044 @node Running Configure
22045 @section Invoking the @value{GDBN} @code{configure} script
22046 @cindex configuring @value{GDBN}
22047 @value{GDBN} comes with a @code{configure} script that automates the process
22048 of preparing @value{GDBN} for installation; you can then use @code{make} to
22049 build the @code{gdb} program.
22051 @c irrelevant in info file; it's as current as the code it lives with.
22052 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22053 look at the @file{README} file in the sources; we may have improved the
22054 installation procedures since publishing this manual.}
22057 The @value{GDBN} distribution includes all the source code you need for
22058 @value{GDBN} in a single directory, whose name is usually composed by
22059 appending the version number to @samp{gdb}.
22061 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22062 @file{gdb-@value{GDBVN}} directory. That directory contains:
22065 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22066 script for configuring @value{GDBN} and all its supporting libraries
22068 @item gdb-@value{GDBVN}/gdb
22069 the source specific to @value{GDBN} itself
22071 @item gdb-@value{GDBVN}/bfd
22072 source for the Binary File Descriptor library
22074 @item gdb-@value{GDBVN}/include
22075 @sc{gnu} include files
22077 @item gdb-@value{GDBVN}/libiberty
22078 source for the @samp{-liberty} free software library
22080 @item gdb-@value{GDBVN}/opcodes
22081 source for the library of opcode tables and disassemblers
22083 @item gdb-@value{GDBVN}/readline
22084 source for the @sc{gnu} command-line interface
22086 @item gdb-@value{GDBVN}/glob
22087 source for the @sc{gnu} filename pattern-matching subroutine
22089 @item gdb-@value{GDBVN}/mmalloc
22090 source for the @sc{gnu} memory-mapped malloc package
22093 The simplest way to configure and build @value{GDBN} is to run @code{configure}
22094 from the @file{gdb-@var{version-number}} source directory, which in
22095 this example is the @file{gdb-@value{GDBVN}} directory.
22097 First switch to the @file{gdb-@var{version-number}} source directory
22098 if you are not already in it; then run @code{configure}. Pass the
22099 identifier for the platform on which @value{GDBN} will run as an
22105 cd gdb-@value{GDBVN}
22106 ./configure @var{host}
22111 where @var{host} is an identifier such as @samp{sun4} or
22112 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22113 (You can often leave off @var{host}; @code{configure} tries to guess the
22114 correct value by examining your system.)
22116 Running @samp{configure @var{host}} and then running @code{make} builds the
22117 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22118 libraries, then @code{gdb} itself. The configured source files, and the
22119 binaries, are left in the corresponding source directories.
22122 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22123 system does not recognize this automatically when you run a different
22124 shell, you may need to run @code{sh} on it explicitly:
22127 sh configure @var{host}
22130 If you run @code{configure} from a directory that contains source
22131 directories for multiple libraries or programs, such as the
22132 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
22133 creates configuration files for every directory level underneath (unless
22134 you tell it not to, with the @samp{--norecursion} option).
22136 You should run the @code{configure} script from the top directory in the
22137 source tree, the @file{gdb-@var{version-number}} directory. If you run
22138 @code{configure} from one of the subdirectories, you will configure only
22139 that subdirectory. That is usually not what you want. In particular,
22140 if you run the first @code{configure} from the @file{gdb} subdirectory
22141 of the @file{gdb-@var{version-number}} directory, you will omit the
22142 configuration of @file{bfd}, @file{readline}, and other sibling
22143 directories of the @file{gdb} subdirectory. This leads to build errors
22144 about missing include files such as @file{bfd/bfd.h}.
22146 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22147 However, you should make sure that the shell on your path (named by
22148 the @samp{SHELL} environment variable) is publicly readable. Remember
22149 that @value{GDBN} uses the shell to start your program---some systems refuse to
22150 let @value{GDBN} debug child processes whose programs are not readable.
22152 @node Separate Objdir
22153 @section Compiling @value{GDBN} in another directory
22155 If you want to run @value{GDBN} versions for several host or target machines,
22156 you need a different @code{gdb} compiled for each combination of
22157 host and target. @code{configure} is designed to make this easy by
22158 allowing you to generate each configuration in a separate subdirectory,
22159 rather than in the source directory. If your @code{make} program
22160 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22161 @code{make} in each of these directories builds the @code{gdb}
22162 program specified there.
22164 To build @code{gdb} in a separate directory, run @code{configure}
22165 with the @samp{--srcdir} option to specify where to find the source.
22166 (You also need to specify a path to find @code{configure}
22167 itself from your working directory. If the path to @code{configure}
22168 would be the same as the argument to @samp{--srcdir}, you can leave out
22169 the @samp{--srcdir} option; it is assumed.)
22171 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22172 separate directory for a Sun 4 like this:
22176 cd gdb-@value{GDBVN}
22179 ../gdb-@value{GDBVN}/configure sun4
22184 When @code{configure} builds a configuration using a remote source
22185 directory, it creates a tree for the binaries with the same structure
22186 (and using the same names) as the tree under the source directory. In
22187 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22188 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22189 @file{gdb-sun4/gdb}.
22191 Make sure that your path to the @file{configure} script has just one
22192 instance of @file{gdb} in it. If your path to @file{configure} looks
22193 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22194 one subdirectory of @value{GDBN}, not the whole package. This leads to
22195 build errors about missing include files such as @file{bfd/bfd.h}.
22197 One popular reason to build several @value{GDBN} configurations in separate
22198 directories is to configure @value{GDBN} for cross-compiling (where
22199 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22200 programs that run on another machine---the @dfn{target}).
22201 You specify a cross-debugging target by
22202 giving the @samp{--target=@var{target}} option to @code{configure}.
22204 When you run @code{make} to build a program or library, you must run
22205 it in a configured directory---whatever directory you were in when you
22206 called @code{configure} (or one of its subdirectories).
22208 The @code{Makefile} that @code{configure} generates in each source
22209 directory also runs recursively. If you type @code{make} in a source
22210 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22211 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22212 will build all the required libraries, and then build GDB.
22214 When you have multiple hosts or targets configured in separate
22215 directories, you can run @code{make} on them in parallel (for example,
22216 if they are NFS-mounted on each of the hosts); they will not interfere
22220 @section Specifying names for hosts and targets
22222 The specifications used for hosts and targets in the @code{configure}
22223 script are based on a three-part naming scheme, but some short predefined
22224 aliases are also supported. The full naming scheme encodes three pieces
22225 of information in the following pattern:
22228 @var{architecture}-@var{vendor}-@var{os}
22231 For example, you can use the alias @code{sun4} as a @var{host} argument,
22232 or as the value for @var{target} in a @code{--target=@var{target}}
22233 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22235 The @code{configure} script accompanying @value{GDBN} does not provide
22236 any query facility to list all supported host and target names or
22237 aliases. @code{configure} calls the Bourne shell script
22238 @code{config.sub} to map abbreviations to full names; you can read the
22239 script, if you wish, or you can use it to test your guesses on
22240 abbreviations---for example:
22243 % sh config.sub i386-linux
22245 % sh config.sub alpha-linux
22246 alpha-unknown-linux-gnu
22247 % sh config.sub hp9k700
22249 % sh config.sub sun4
22250 sparc-sun-sunos4.1.1
22251 % sh config.sub sun3
22252 m68k-sun-sunos4.1.1
22253 % sh config.sub i986v
22254 Invalid configuration `i986v': machine `i986v' not recognized
22258 @code{config.sub} is also distributed in the @value{GDBN} source
22259 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22261 @node Configure Options
22262 @section @code{configure} options
22264 Here is a summary of the @code{configure} options and arguments that
22265 are most often useful for building @value{GDBN}. @code{configure} also has
22266 several other options not listed here. @inforef{What Configure
22267 Does,,configure.info}, for a full explanation of @code{configure}.
22270 configure @r{[}--help@r{]}
22271 @r{[}--prefix=@var{dir}@r{]}
22272 @r{[}--exec-prefix=@var{dir}@r{]}
22273 @r{[}--srcdir=@var{dirname}@r{]}
22274 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22275 @r{[}--target=@var{target}@r{]}
22280 You may introduce options with a single @samp{-} rather than
22281 @samp{--} if you prefer; but you may abbreviate option names if you use
22286 Display a quick summary of how to invoke @code{configure}.
22288 @item --prefix=@var{dir}
22289 Configure the source to install programs and files under directory
22292 @item --exec-prefix=@var{dir}
22293 Configure the source to install programs under directory
22296 @c avoid splitting the warning from the explanation:
22298 @item --srcdir=@var{dirname}
22299 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22300 @code{make} that implements the @code{VPATH} feature.}@*
22301 Use this option to make configurations in directories separate from the
22302 @value{GDBN} source directories. Among other things, you can use this to
22303 build (or maintain) several configurations simultaneously, in separate
22304 directories. @code{configure} writes configuration specific files in
22305 the current directory, but arranges for them to use the source in the
22306 directory @var{dirname}. @code{configure} creates directories under
22307 the working directory in parallel to the source directories below
22310 @item --norecursion
22311 Configure only the directory level where @code{configure} is executed; do not
22312 propagate configuration to subdirectories.
22314 @item --target=@var{target}
22315 Configure @value{GDBN} for cross-debugging programs running on the specified
22316 @var{target}. Without this option, @value{GDBN} is configured to debug
22317 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22319 There is no convenient way to generate a list of all available targets.
22321 @item @var{host} @dots{}
22322 Configure @value{GDBN} to run on the specified @var{host}.
22324 There is no convenient way to generate a list of all available hosts.
22327 There are many other options available as well, but they are generally
22328 needed for special purposes only.
22330 @node Maintenance Commands
22331 @appendix Maintenance Commands
22332 @cindex maintenance commands
22333 @cindex internal commands
22335 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22336 includes a number of commands intended for @value{GDBN} developers,
22337 that are not documented elsewhere in this manual. These commands are
22338 provided here for reference. (For commands that turn on debugging
22339 messages, see @ref{Debugging Output}.)
22342 @kindex maint agent
22343 @item maint agent @var{expression}
22344 Translate the given @var{expression} into remote agent bytecodes.
22345 This command is useful for debugging the Agent Expression mechanism
22346 (@pxref{Agent Expressions}).
22348 @kindex maint info breakpoints
22349 @item @anchor{maint info breakpoints}maint info breakpoints
22350 Using the same format as @samp{info breakpoints}, display both the
22351 breakpoints you've set explicitly, and those @value{GDBN} is using for
22352 internal purposes. Internal breakpoints are shown with negative
22353 breakpoint numbers. The type column identifies what kind of breakpoint
22358 Normal, explicitly set breakpoint.
22361 Normal, explicitly set watchpoint.
22364 Internal breakpoint, used to handle correctly stepping through
22365 @code{longjmp} calls.
22367 @item longjmp resume
22368 Internal breakpoint at the target of a @code{longjmp}.
22371 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22374 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22377 Shared library events.
22381 @kindex maint check-symtabs
22382 @item maint check-symtabs
22383 Check the consistency of psymtabs and symtabs.
22385 @kindex maint cplus first_component
22386 @item maint cplus first_component @var{name}
22387 Print the first C@t{++} class/namespace component of @var{name}.
22389 @kindex maint cplus namespace
22390 @item maint cplus namespace
22391 Print the list of possible C@t{++} namespaces.
22393 @kindex maint demangle
22394 @item maint demangle @var{name}
22395 Demangle a C@t{++} or Objective-C manled @var{name}.
22397 @kindex maint deprecate
22398 @kindex maint undeprecate
22399 @cindex deprecated commands
22400 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22401 @itemx maint undeprecate @var{command}
22402 Deprecate or undeprecate the named @var{command}. Deprecated commands
22403 cause @value{GDBN} to issue a warning when you use them. The optional
22404 argument @var{replacement} says which newer command should be used in
22405 favor of the deprecated one; if it is given, @value{GDBN} will mention
22406 the replacement as part of the warning.
22408 @kindex maint dump-me
22409 @item maint dump-me
22410 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22411 Cause a fatal signal in the debugger and force it to dump its core.
22412 This is supported only on systems which support aborting a program
22413 with the @code{SIGQUIT} signal.
22415 @kindex maint internal-error
22416 @kindex maint internal-warning
22417 @item maint internal-error @r{[}@var{message-text}@r{]}
22418 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22419 Cause @value{GDBN} to call the internal function @code{internal_error}
22420 or @code{internal_warning} and hence behave as though an internal error
22421 or internal warning has been detected. In addition to reporting the
22422 internal problem, these functions give the user the opportunity to
22423 either quit @value{GDBN} or create a core file of the current
22424 @value{GDBN} session.
22426 These commands take an optional parameter @var{message-text} that is
22427 used as the text of the error or warning message.
22429 Here's an example of using @code{indernal-error}:
22432 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22433 @dots{}/maint.c:121: internal-error: testing, 1, 2
22434 A problem internal to GDB has been detected. Further
22435 debugging may prove unreliable.
22436 Quit this debugging session? (y or n) @kbd{n}
22437 Create a core file? (y or n) @kbd{n}
22441 @kindex maint packet
22442 @item maint packet @var{text}
22443 If @value{GDBN} is talking to an inferior via the serial protocol,
22444 then this command sends the string @var{text} to the inferior, and
22445 displays the response packet. @value{GDBN} supplies the initial
22446 @samp{$} character, the terminating @samp{#} character, and the
22449 @kindex maint print architecture
22450 @item maint print architecture @r{[}@var{file}@r{]}
22451 Print the entire architecture configuration. The optional argument
22452 @var{file} names the file where the output goes.
22454 @kindex maint print dummy-frames
22455 @item maint print dummy-frames
22456 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22459 (@value{GDBP}) @kbd{b add}
22461 (@value{GDBP}) @kbd{print add(2,3)}
22462 Breakpoint 2, add (a=2, b=3) at @dots{}
22464 The program being debugged stopped while in a function called from GDB.
22466 (@value{GDBP}) @kbd{maint print dummy-frames}
22467 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22468 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22469 call_lo=0x01014000 call_hi=0x01014001
22473 Takes an optional file parameter.
22475 @kindex maint print registers
22476 @kindex maint print raw-registers
22477 @kindex maint print cooked-registers
22478 @kindex maint print register-groups
22479 @item maint print registers @r{[}@var{file}@r{]}
22480 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22481 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22482 @itemx maint print register-groups @r{[}@var{file}@r{]}
22483 Print @value{GDBN}'s internal register data structures.
22485 The command @code{maint print raw-registers} includes the contents of
22486 the raw register cache; the command @code{maint print cooked-registers}
22487 includes the (cooked) value of all registers; and the command
22488 @code{maint print register-groups} includes the groups that each
22489 register is a member of. @xref{Registers,, Registers, gdbint,
22490 @value{GDBN} Internals}.
22492 These commands take an optional parameter, a file name to which to
22493 write the information.
22495 @kindex maint print reggroups
22496 @item maint print reggroups @r{[}@var{file}@r{]}
22497 Print @value{GDBN}'s internal register group data structures. The
22498 optional argument @var{file} tells to what file to write the
22501 The register groups info looks like this:
22504 (@value{GDBP}) @kbd{maint print reggroups}
22517 This command forces @value{GDBN} to flush its internal register cache.
22519 @kindex maint print objfiles
22520 @cindex info for known object files
22521 @item maint print objfiles
22522 Print a dump of all known object files. For each object file, this
22523 command prints its name, address in memory, and all of its psymtabs
22526 @kindex maint print statistics
22527 @cindex bcache statistics
22528 @item maint print statistics
22529 This command prints, for each object file in the program, various data
22530 about that object file followed by the byte cache (@dfn{bcache})
22531 statistics for the object file. The objfile data includes the number
22532 of minimal, partical, full, and stabs symbols, the number of types
22533 defined by the objfile, the number of as yet unexpanded psym tables,
22534 the number of line tables and string tables, and the amount of memory
22535 used by the various tables. The bcache statistics include the counts,
22536 sizes, and counts of duplicates of all and unique objects, max,
22537 average, and median entry size, total memory used and its overhead and
22538 savings, and various measures of the hash table size and chain
22541 @kindex maint print type
22542 @cindex type chain of a data type
22543 @item maint print type @var{expr}
22544 Print the type chain for a type specified by @var{expr}. The argument
22545 can be either a type name or a symbol. If it is a symbol, the type of
22546 that symbol is described. The type chain produced by this command is
22547 a recursive definition of the data type as stored in @value{GDBN}'s
22548 data structures, including its flags and contained types.
22550 @kindex maint set dwarf2 max-cache-age
22551 @kindex maint show dwarf2 max-cache-age
22552 @item maint set dwarf2 max-cache-age
22553 @itemx maint show dwarf2 max-cache-age
22554 Control the DWARF 2 compilation unit cache.
22556 @cindex DWARF 2 compilation units cache
22557 In object files with inter-compilation-unit references, such as those
22558 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22559 reader needs to frequently refer to previously read compilation units.
22560 This setting controls how long a compilation unit will remain in the
22561 cache if it is not referenced. A higher limit means that cached
22562 compilation units will be stored in memory longer, and more total
22563 memory will be used. Setting it to zero disables caching, which will
22564 slow down @value{GDBN} startup, but reduce memory consumption.
22566 @kindex maint set profile
22567 @kindex maint show profile
22568 @cindex profiling GDB
22569 @item maint set profile
22570 @itemx maint show profile
22571 Control profiling of @value{GDBN}.
22573 Profiling will be disabled until you use the @samp{maint set profile}
22574 command to enable it. When you enable profiling, the system will begin
22575 collecting timing and execution count data; when you disable profiling or
22576 exit @value{GDBN}, the results will be written to a log file. Remember that
22577 if you use profiling, @value{GDBN} will overwrite the profiling log file
22578 (often called @file{gmon.out}). If you have a record of important profiling
22579 data in a @file{gmon.out} file, be sure to move it to a safe location.
22581 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22582 compiled with the @samp{-pg} compiler option.
22584 @kindex maint show-debug-regs
22585 @cindex x86 hardware debug registers
22586 @item maint show-debug-regs
22587 Control whether to show variables that mirror the x86 hardware debug
22588 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22589 enabled, the debug registers values are shown when GDB inserts or
22590 removes a hardware breakpoint or watchpoint, and when the inferior
22591 triggers a hardware-assisted breakpoint or watchpoint.
22593 @kindex maint space
22594 @cindex memory used by commands
22596 Control whether to display memory usage for each command. If set to a
22597 nonzero value, @value{GDBN} will display how much memory each command
22598 took, following the command's own output. This can also be requested
22599 by invoking @value{GDBN} with the @option{--statistics} command-line
22600 switch (@pxref{Mode Options}).
22603 @cindex time of command execution
22605 Control whether to display the execution time for each command. If
22606 set to a nonzero value, @value{GDBN} will display how much time it
22607 took to execute each command, following the command's own output.
22608 This can also be requested by invoking @value{GDBN} with the
22609 @option{--statistics} command-line switch (@pxref{Mode Options}).
22611 @kindex maint translate-address
22612 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22613 Find the symbol stored at the location specified by the address
22614 @var{addr} and an optional section name @var{section}. If found,
22615 @value{GDBN} prints the name of the closest symbol and an offset from
22616 the symbol's location to the specified address. This is similar to
22617 the @code{info address} command (@pxref{Symbols}), except that this
22618 command also allows to find symbols in other sections.
22622 The following command is useful for non-interactive invocations of
22623 @value{GDBN}, such as in the test suite.
22626 @item set watchdog @var{nsec}
22627 @kindex set watchdog
22628 @cindex watchdog timer
22629 @cindex timeout for commands
22630 Set the maximum number of seconds @value{GDBN} will wait for the
22631 target operation to finish. If this time expires, @value{GDBN}
22632 reports and error and the command is aborted.
22634 @item show watchdog
22635 Show the current setting of the target wait timeout.
22638 @node Remote Protocol
22639 @appendix @value{GDBN} Remote Serial Protocol
22644 * Stop Reply Packets::
22645 * General Query Packets::
22646 * Register Packet Format::
22647 * Tracepoint Packets::
22650 * File-I/O remote protocol extension::
22651 * Memory map format::
22657 There may be occasions when you need to know something about the
22658 protocol---for example, if there is only one serial port to your target
22659 machine, you might want your program to do something special if it
22660 recognizes a packet meant for @value{GDBN}.
22662 In the examples below, @samp{->} and @samp{<-} are used to indicate
22663 transmitted and received data respectfully.
22665 @cindex protocol, @value{GDBN} remote serial
22666 @cindex serial protocol, @value{GDBN} remote
22667 @cindex remote serial protocol
22668 All @value{GDBN} commands and responses (other than acknowledgments) are
22669 sent as a @var{packet}. A @var{packet} is introduced with the character
22670 @samp{$}, the actual @var{packet-data}, and the terminating character
22671 @samp{#} followed by a two-digit @var{checksum}:
22674 @code{$}@var{packet-data}@code{#}@var{checksum}
22678 @cindex checksum, for @value{GDBN} remote
22680 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22681 characters between the leading @samp{$} and the trailing @samp{#} (an
22682 eight bit unsigned checksum).
22684 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22685 specification also included an optional two-digit @var{sequence-id}:
22688 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22691 @cindex sequence-id, for @value{GDBN} remote
22693 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22694 has never output @var{sequence-id}s. Stubs that handle packets added
22695 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22697 @cindex acknowledgment, for @value{GDBN} remote
22698 When either the host or the target machine receives a packet, the first
22699 response expected is an acknowledgment: either @samp{+} (to indicate
22700 the package was received correctly) or @samp{-} (to request
22704 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22709 The host (@value{GDBN}) sends @var{command}s, and the target (the
22710 debugging stub incorporated in your program) sends a @var{response}. In
22711 the case of step and continue @var{command}s, the response is only sent
22712 when the operation has completed (the target has again stopped).
22714 @var{packet-data} consists of a sequence of characters with the
22715 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22718 @cindex remote protocol, field separator
22719 Fields within the packet should be separated using @samp{,} @samp{;} or
22720 @samp{:}. Except where otherwise noted all numbers are represented in
22721 @sc{hex} with leading zeros suppressed.
22723 Implementors should note that prior to @value{GDBN} 5.0, the character
22724 @samp{:} could not appear as the third character in a packet (as it
22725 would potentially conflict with the @var{sequence-id}).
22727 @cindex remote protocol, binary data
22728 @anchor{Binary Data}
22729 Binary data in most packets is encoded either as two hexadecimal
22730 digits per byte of binary data. This allowed the traditional remote
22731 protocol to work over connections which were only seven-bit clean.
22732 Some packets designed more recently assume an eight-bit clean
22733 connection, and use a more efficient encoding to send and receive
22736 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22737 as an escape character. Any escaped byte is transmitted as the escape
22738 character followed by the original character XORed with @code{0x20}.
22739 For example, the byte @code{0x7d} would be transmitted as the two
22740 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22741 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22742 @samp{@}}) must always be escaped. Responses sent by the stub
22743 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22744 is not interpreted as the start of a run-length encoded sequence
22747 Response @var{data} can be run-length encoded to save space. A @samp{*}
22748 means that the next character is an @sc{ascii} encoding giving a repeat count
22749 which stands for that many repetitions of the character preceding the
22750 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22751 where @code{n >=3} (which is where rle starts to win). The printable
22752 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22753 value greater than 126 should not be used.
22760 means the same as "0000".
22762 The error response returned for some packets includes a two character
22763 error number. That number is not well defined.
22765 @cindex empty response, for unsupported packets
22766 For any @var{command} not supported by the stub, an empty response
22767 (@samp{$#00}) should be returned. That way it is possible to extend the
22768 protocol. A newer @value{GDBN} can tell if a packet is supported based
22771 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22772 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22778 The following table provides a complete list of all currently defined
22779 @var{command}s and their corresponding response @var{data}.
22780 @xref{File-I/O remote protocol extension}, for details about the File
22781 I/O extension of the remote protocol.
22783 Each packet's description has a template showing the packet's overall
22784 syntax, followed by an explanation of the packet's meaning. We
22785 include spaces in some of the templates for clarity; these are not
22786 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22787 separate its components. For example, a template like @samp{foo
22788 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22789 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22790 @var{baz}. GDB does not transmit a space character between the
22791 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22794 Note that all packet forms beginning with an upper- or lower-case
22795 letter, other than those described here, are reserved for future use.
22797 Here are the packet descriptions.
22802 @cindex @samp{!} packet
22803 Enable extended mode. In extended mode, the remote server is made
22804 persistent. The @samp{R} packet is used to restart the program being
22810 The remote target both supports and has enabled extended mode.
22814 @cindex @samp{?} packet
22815 Indicate the reason the target halted. The reply is the same as for
22819 @xref{Stop Reply Packets}, for the reply specifications.
22821 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22822 @cindex @samp{A} packet
22823 Initialized @code{argv[]} array passed into program. @var{arglen}
22824 specifies the number of bytes in the hex encoded byte stream
22825 @var{arg}. See @code{gdbserver} for more details.
22830 The arguments were set.
22836 @cindex @samp{b} packet
22837 (Don't use this packet; its behavior is not well-defined.)
22838 Change the serial line speed to @var{baud}.
22840 JTC: @emph{When does the transport layer state change? When it's
22841 received, or after the ACK is transmitted. In either case, there are
22842 problems if the command or the acknowledgment packet is dropped.}
22844 Stan: @emph{If people really wanted to add something like this, and get
22845 it working for the first time, they ought to modify ser-unix.c to send
22846 some kind of out-of-band message to a specially-setup stub and have the
22847 switch happen "in between" packets, so that from remote protocol's point
22848 of view, nothing actually happened.}
22850 @item B @var{addr},@var{mode}
22851 @cindex @samp{B} packet
22852 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22853 breakpoint at @var{addr}.
22855 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22856 (@pxref{insert breakpoint or watchpoint packet}).
22858 @item c @r{[}@var{addr}@r{]}
22859 @cindex @samp{c} packet
22860 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22861 resume at current address.
22864 @xref{Stop Reply Packets}, for the reply specifications.
22866 @item C @var{sig}@r{[};@var{addr}@r{]}
22867 @cindex @samp{C} packet
22868 Continue with signal @var{sig} (hex signal number). If
22869 @samp{;@var{addr}} is omitted, resume at same address.
22872 @xref{Stop Reply Packets}, for the reply specifications.
22875 @cindex @samp{d} packet
22878 Don't use this packet; instead, define a general set packet
22879 (@pxref{General Query Packets}).
22882 @cindex @samp{D} packet
22883 Detach @value{GDBN} from the remote system. Sent to the remote target
22884 before @value{GDBN} disconnects via the @code{detach} command.
22894 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22895 @cindex @samp{F} packet
22896 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22897 This is part of the File-I/O protocol extension. @xref{File-I/O
22898 remote protocol extension}, for the specification.
22901 @anchor{read registers packet}
22902 @cindex @samp{g} packet
22903 Read general registers.
22907 @item @var{XX@dots{}}
22908 Each byte of register data is described by two hex digits. The bytes
22909 with the register are transmitted in target byte order. The size of
22910 each register and their position within the @samp{g} packet are
22911 determined by the @value{GDBN} internal macros
22912 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
22913 specification of several standard @samp{g} packets is specified below.
22918 @item G @var{XX@dots{}}
22919 @cindex @samp{G} packet
22920 Write general registers. @xref{read registers packet}, for a
22921 description of the @var{XX@dots{}} data.
22931 @item H @var{c} @var{t}
22932 @cindex @samp{H} packet
22933 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22934 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22935 should be @samp{c} for step and continue operations, @samp{g} for other
22936 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22937 the threads, a thread number, or @samp{0} which means pick any thread.
22948 @c 'H': How restrictive (or permissive) is the thread model. If a
22949 @c thread is selected and stopped, are other threads allowed
22950 @c to continue to execute? As I mentioned above, I think the
22951 @c semantics of each command when a thread is selected must be
22952 @c described. For example:
22954 @c 'g': If the stub supports threads and a specific thread is
22955 @c selected, returns the register block from that thread;
22956 @c otherwise returns current registers.
22958 @c 'G' If the stub supports threads and a specific thread is
22959 @c selected, sets the registers of the register block of
22960 @c that thread; otherwise sets current registers.
22962 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22963 @anchor{cycle step packet}
22964 @cindex @samp{i} packet
22965 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22966 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22967 step starting at that address.
22970 @cindex @samp{I} packet
22971 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
22975 @cindex @samp{k} packet
22978 FIXME: @emph{There is no description of how to operate when a specific
22979 thread context has been selected (i.e.@: does 'k' kill only that
22982 @item m @var{addr},@var{length}
22983 @cindex @samp{m} packet
22984 Read @var{length} bytes of memory starting at address @var{addr}.
22985 Note that @var{addr} may not be aligned to any particular boundary.
22987 The stub need not use any particular size or alignment when gathering
22988 data from memory for the response; even if @var{addr} is word-aligned
22989 and @var{length} is a multiple of the word size, the stub is free to
22990 use byte accesses, or not. For this reason, this packet may not be
22991 suitable for accessing memory-mapped I/O devices.
22992 @cindex alignment of remote memory accesses
22993 @cindex size of remote memory accesses
22994 @cindex memory, alignment and size of remote accesses
22998 @item @var{XX@dots{}}
22999 Memory contents; each byte is transmitted as a two-digit hexadecimal
23000 number. The reply may contain fewer bytes than requested if the
23001 server was able to read only part of the region of memory.
23006 @item M @var{addr},@var{length}:@var{XX@dots{}}
23007 @cindex @samp{M} packet
23008 Write @var{length} bytes of memory starting at address @var{addr}.
23009 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23010 hexadecimal number.
23017 for an error (this includes the case where only part of the data was
23022 @cindex @samp{p} packet
23023 Read the value of register @var{n}; @var{n} is in hex.
23024 @xref{read registers packet}, for a description of how the returned
23025 register value is encoded.
23029 @item @var{XX@dots{}}
23030 the register's value
23034 Indicating an unrecognized @var{query}.
23037 @item P @var{n@dots{}}=@var{r@dots{}}
23038 @anchor{write register packet}
23039 @cindex @samp{P} packet
23040 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23041 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23042 digits for each byte in the register (target byte order).
23052 @item q @var{name} @var{params}@dots{}
23053 @itemx Q @var{name} @var{params}@dots{}
23054 @cindex @samp{q} packet
23055 @cindex @samp{Q} packet
23056 General query (@samp{q}) and set (@samp{Q}). These packets are
23057 described fully in @ref{General Query Packets}.
23060 @cindex @samp{r} packet
23061 Reset the entire system.
23063 Don't use this packet; use the @samp{R} packet instead.
23066 @cindex @samp{R} packet
23067 Restart the program being debugged. @var{XX}, while needed, is ignored.
23068 This packet is only available in extended mode.
23070 The @samp{R} packet has no reply.
23072 @item s @r{[}@var{addr}@r{]}
23073 @cindex @samp{s} packet
23074 Single step. @var{addr} is the address at which to resume. If
23075 @var{addr} is omitted, resume at same address.
23078 @xref{Stop Reply Packets}, for the reply specifications.
23080 @item S @var{sig}@r{[};@var{addr}@r{]}
23081 @anchor{step with signal packet}
23082 @cindex @samp{S} packet
23083 Step with signal. This is analogous to the @samp{C} packet, but
23084 requests a single-step, rather than a normal resumption of execution.
23087 @xref{Stop Reply Packets}, for the reply specifications.
23089 @item t @var{addr}:@var{PP},@var{MM}
23090 @cindex @samp{t} packet
23091 Search backwards starting at address @var{addr} for a match with pattern
23092 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23093 @var{addr} must be at least 3 digits.
23096 @cindex @samp{T} packet
23097 Find out if the thread XX is alive.
23102 thread is still alive
23108 Packets starting with @samp{v} are identified by a multi-letter name,
23109 up to the first @samp{;} or @samp{?} (or the end of the packet).
23111 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23112 @cindex @samp{vCont} packet
23113 Resume the inferior, specifying different actions for each thread.
23114 If an action is specified with no @var{tid}, then it is applied to any
23115 threads that don't have a specific action specified; if no default action is
23116 specified then other threads should remain stopped. Specifying multiple
23117 default actions is an error; specifying no actions is also an error.
23118 Thread IDs are specified in hexadecimal. Currently supported actions are:
23124 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23128 Step with signal @var{sig}. @var{sig} should be two hex digits.
23131 The optional @var{addr} argument normally associated with these packets is
23132 not supported in @samp{vCont}.
23135 @xref{Stop Reply Packets}, for the reply specifications.
23138 @cindex @samp{vCont?} packet
23139 Request a list of actions supporetd by the @samp{vCont} packet.
23143 @item vCont@r{[};@var{action}@dots{}@r{]}
23144 The @samp{vCont} packet is supported. Each @var{action} is a supported
23145 command in the @samp{vCont} packet.
23147 The @samp{vCont} packet is not supported.
23150 @item vFlashErase:@var{addr},@var{length}
23151 @cindex @samp{vFlashErase} packet
23152 Direct the stub to erase @var{length} bytes of flash starting at
23153 @var{addr}. The region may enclose any number of flash blocks, but
23154 its start and end must fall on block boundaries, as indicated by the
23155 flash block size appearing in the memory map (@pxref{Memory map
23156 format}). @value{GDBN} groups flash memory programming operations
23157 together, and sends a @samp{vFlashDone} request after each group; the
23158 stub is allowed to delay erase operation until the @samp{vFlashDone}
23159 packet is received.
23169 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23170 @cindex @samp{vFlashWrite} packet
23171 Direct the stub to write data to flash address @var{addr}. The data
23172 is passed in binary form using the same encoding as for the @samp{X}
23173 packet (@pxref{Binary Data}). The memory ranges specified by
23174 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23175 not overlap, and must appear in order of increasing addresses
23176 (although @samp{vFlashErase} packets for higher addresses may already
23177 have been received; the ordering is guaranteed only between
23178 @samp{vFlashWrite} packets). If a packet writes to an address that was
23179 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23180 target-specific method, the results are unpredictable.
23188 for vFlashWrite addressing non-flash memory
23194 @cindex @samp{vFlashDone} packet
23195 Indicate to the stub that flash programming operation is finished.
23196 The stub is permitted to delay or batch the effects of a group of
23197 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23198 @samp{vFlashDone} packet is received. The contents of the affected
23199 regions of flash memory are unpredictable until the @samp{vFlashDone}
23200 request is completed.
23202 @item X @var{addr},@var{length}:@var{XX@dots{}}
23204 @cindex @samp{X} packet
23205 Write data to memory, where the data is transmitted in binary.
23206 @var{addr} is address, @var{length} is number of bytes,
23207 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23217 @item z @var{type},@var{addr},@var{length}
23218 @itemx Z @var{type},@var{addr},@var{length}
23219 @anchor{insert breakpoint or watchpoint packet}
23220 @cindex @samp{z} packet
23221 @cindex @samp{Z} packets
23222 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23223 watchpoint starting at address @var{address} and covering the next
23224 @var{length} bytes.
23226 Each breakpoint and watchpoint packet @var{type} is documented
23229 @emph{Implementation notes: A remote target shall return an empty string
23230 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23231 remote target shall support either both or neither of a given
23232 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23233 avoid potential problems with duplicate packets, the operations should
23234 be implemented in an idempotent way.}
23236 @item z0,@var{addr},@var{length}
23237 @itemx Z0,@var{addr},@var{length}
23238 @cindex @samp{z0} packet
23239 @cindex @samp{Z0} packet
23240 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23241 @var{addr} of size @var{length}.
23243 A memory breakpoint is implemented by replacing the instruction at
23244 @var{addr} with a software breakpoint or trap instruction. The
23245 @var{length} is used by targets that indicates the size of the
23246 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23247 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23249 @emph{Implementation note: It is possible for a target to copy or move
23250 code that contains memory breakpoints (e.g., when implementing
23251 overlays). The behavior of this packet, in the presence of such a
23252 target, is not defined.}
23264 @item z1,@var{addr},@var{length}
23265 @itemx Z1,@var{addr},@var{length}
23266 @cindex @samp{z1} packet
23267 @cindex @samp{Z1} packet
23268 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23269 address @var{addr} of size @var{length}.
23271 A hardware breakpoint is implemented using a mechanism that is not
23272 dependant on being able to modify the target's memory.
23274 @emph{Implementation note: A hardware breakpoint is not affected by code
23287 @item z2,@var{addr},@var{length}
23288 @itemx Z2,@var{addr},@var{length}
23289 @cindex @samp{z2} packet
23290 @cindex @samp{Z2} packet
23291 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23303 @item z3,@var{addr},@var{length}
23304 @itemx Z3,@var{addr},@var{length}
23305 @cindex @samp{z3} packet
23306 @cindex @samp{Z3} packet
23307 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23319 @item z4,@var{addr},@var{length}
23320 @itemx Z4,@var{addr},@var{length}
23321 @cindex @samp{z4} packet
23322 @cindex @samp{Z4} packet
23323 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23337 @node Stop Reply Packets
23338 @section Stop Reply Packets
23339 @cindex stop reply packets
23341 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23342 receive any of the below as a reply. In the case of the @samp{C},
23343 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23344 when the target halts. In the below the exact meaning of @dfn{signal
23345 number} is poorly defined. In general one of the UNIX signal
23346 numbering conventions is used.
23348 As in the description of request packets, we include spaces in the
23349 reply templates for clarity; these are not part of the reply packet's
23350 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23356 The program received signal number @var{AA} (a two-digit hexadecimal
23357 number). This is equivalent to a @samp{T} response with no
23358 @var{n}:@var{r} pairs.
23360 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23361 @cindex @samp{T} packet reply
23362 The program received signal number @var{AA} (a two-digit hexadecimal
23363 number). This is equivalent to an @samp{S} response, except that the
23364 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23365 and other information directly in the stop reply packet, reducing
23366 round-trip latency. Single-step and breakpoint traps are reported
23367 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23370 If @var{n} is a hexadecimal number, it is a register number, and the
23371 corresponding @var{r} gives that register's value. @var{r} is a
23372 series of bytes in target byte order, with each byte given by a
23373 two-digit hex number.
23375 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23378 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23379 packet indicates a watchpoint hit, and @var{r} is the data address, in
23382 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23383 and go on to the next; this allows us to extend the protocol in the
23388 The process exited, and @var{AA} is the exit status. This is only
23389 applicable to certain targets.
23392 The process terminated with signal @var{AA}.
23394 @item O @var{XX}@dots{}
23395 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23396 written as the program's console output. This can happen at any time
23397 while the program is running and the debugger should continue to wait
23398 for @samp{W}, @samp{T}, etc.
23400 @item F @var{call-id},@var{parameter}@dots{}
23401 @var{call-id} is the identifier which says which host system call should
23402 be called. This is just the name of the function. Translation into the
23403 correct system call is only applicable as it's defined in @value{GDBN}.
23404 @xref{File-I/O remote protocol extension}, for a list of implemented
23407 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23408 this very system call.
23410 The target replies with this packet when it expects @value{GDBN} to
23411 call a host system call on behalf of the target. @value{GDBN} replies
23412 with an appropriate @samp{F} packet and keeps up waiting for the next
23413 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23414 or @samp{s} action is expected to be continued. @xref{File-I/O remote
23415 protocol extension}, for more details.
23419 @node General Query Packets
23420 @section General Query Packets
23421 @cindex remote query requests
23423 Packets starting with @samp{q} are @dfn{general query packets};
23424 packets starting with @samp{Q} are @dfn{general set packets}. General
23425 query and set packets are a semi-unified form for retrieving and
23426 sending information to and from the stub.
23428 The initial letter of a query or set packet is followed by a name
23429 indicating what sort of thing the packet applies to. For example,
23430 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23431 definitions with the stub. These packet names follow some
23436 The name must not contain commas, colons or semicolons.
23438 Most @value{GDBN} query and set packets have a leading upper case
23441 The names of custom vendor packets should use a company prefix, in
23442 lower case, followed by a period. For example, packets designed at
23443 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23444 foos) or @samp{Qacme.bar} (for setting bars).
23447 The name of a query or set packet should be separated from any
23448 parameters by a @samp{:}; the parameters themselves should be
23449 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23450 full packet name, and check for a separator or the end of the packet,
23451 in case two packet names share a common prefix. New packets should not begin
23452 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23453 packets predate these conventions, and have arguments without any terminator
23454 for the packet name; we suspect they are in widespread use in places that
23455 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23456 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23459 Like the descriptions of the other packets, each description here
23460 has a template showing the packet's overall syntax, followed by an
23461 explanation of the packet's meaning. We include spaces in some of the
23462 templates for clarity; these are not part of the packet's syntax. No
23463 @value{GDBN} packet uses spaces to separate its components.
23465 Here are the currently defined query and set packets:
23470 @cindex current thread, remote request
23471 @cindex @samp{qC} packet
23472 Return the current thread id.
23477 Where @var{pid} is an unsigned hexadecimal process id.
23478 @item @r{(anything else)}
23479 Any other reply implies the old pid.
23482 @item qCRC:@var{addr},@var{length}
23483 @cindex CRC of memory block, remote request
23484 @cindex @samp{qCRC} packet
23485 Compute the CRC checksum of a block of memory.
23489 An error (such as memory fault)
23490 @item C @var{crc32}
23491 The specified memory region's checksum is @var{crc32}.
23495 @itemx qsThreadInfo
23496 @cindex list active threads, remote request
23497 @cindex @samp{qfThreadInfo} packet
23498 @cindex @samp{qsThreadInfo} packet
23499 Obtain a list of all active thread ids from the target (OS). Since there
23500 may be too many active threads to fit into one reply packet, this query
23501 works iteratively: it may require more than one query/reply sequence to
23502 obtain the entire list of threads. The first query of the sequence will
23503 be the @samp{qfThreadInfo} query; subsequent queries in the
23504 sequence will be the @samp{qsThreadInfo} query.
23506 NOTE: This packet replaces the @samp{qL} query (see below).
23512 @item m @var{id},@var{id}@dots{}
23513 a comma-separated list of thread ids
23515 (lower case letter @samp{L}) denotes end of list.
23518 In response to each query, the target will reply with a list of one or
23519 more thread ids, in big-endian unsigned hex, separated by commas.
23520 @value{GDBN} will respond to each reply with a request for more thread
23521 ids (using the @samp{qs} form of the query), until the target responds
23522 with @samp{l} (lower-case el, for @dfn{last}).
23524 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23525 @cindex get thread-local storage address, remote request
23526 @cindex @samp{qGetTLSAddr} packet
23527 Fetch the address associated with thread local storage specified
23528 by @var{thread-id}, @var{offset}, and @var{lm}.
23530 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23531 thread for which to fetch the TLS address.
23533 @var{offset} is the (big endian, hex encoded) offset associated with the
23534 thread local variable. (This offset is obtained from the debug
23535 information associated with the variable.)
23537 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
23538 the load module associated with the thread local storage. For example,
23539 a @sc{gnu}/Linux system will pass the link map address of the shared
23540 object associated with the thread local storage under consideration.
23541 Other operating environments may choose to represent the load module
23542 differently, so the precise meaning of this parameter will vary.
23546 @item @var{XX}@dots{}
23547 Hex encoded (big endian) bytes representing the address of the thread
23548 local storage requested.
23551 An error occurred. @var{nn} are hex digits.
23554 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23557 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23558 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23559 digit) is one to indicate the first query and zero to indicate a
23560 subsequent query; @var{threadcount} (two hex digits) is the maximum
23561 number of threads the response packet can contain; and @var{nextthread}
23562 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23563 returned in the response as @var{argthread}.
23565 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23569 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23570 Where: @var{count} (two hex digits) is the number of threads being
23571 returned; @var{done} (one hex digit) is zero to indicate more threads
23572 and one indicates no further threads; @var{argthreadid} (eight hex
23573 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23574 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23575 digits). See @code{remote.c:parse_threadlist_response()}.
23579 @cindex section offsets, remote request
23580 @cindex @samp{qOffsets} packet
23581 Get section offsets that the target used when re-locating the downloaded
23582 image. @emph{Note: while a @code{Bss} offset is included in the
23583 response, @value{GDBN} ignores this and instead applies the @code{Data}
23584 offset to the @code{Bss} section.}
23588 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23591 @item qP @var{mode} @var{threadid}
23592 @cindex thread information, remote request
23593 @cindex @samp{qP} packet
23594 Returns information on @var{threadid}. Where: @var{mode} is a hex
23595 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23597 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23600 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23602 @item qRcmd,@var{command}
23603 @cindex execute remote command, remote request
23604 @cindex @samp{qRcmd} packet
23605 @var{command} (hex encoded) is passed to the local interpreter for
23606 execution. Invalid commands should be reported using the output
23607 string. Before the final result packet, the target may also respond
23608 with a number of intermediate @samp{O@var{output}} console output
23609 packets. @emph{Implementors should note that providing access to a
23610 stubs's interpreter may have security implications}.
23615 A command response with no output.
23617 A command response with the hex encoded output string @var{OUTPUT}.
23619 Indicate a badly formed request.
23621 An empty reply indicates that @samp{qRcmd} is not recognized.
23624 (Note that the @code{qRcmd} packet's name is separated from the
23625 command by a @samp{,}, not a @samp{:}, contrary to the naming
23626 conventions above. Please don't use this packet as a model for new
23629 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23630 @cindex supported packets, remote query
23631 @cindex features of the remote protocol
23632 @cindex @samp{qSupported} packet
23633 @anchor{qSupported}
23634 Tell the remote stub about features supported by @value{GDBN}, and
23635 query the stub for features it supports. This packet allows
23636 @value{GDBN} and the remote stub to take advantage of each others'
23637 features. @samp{qSupported} also consolidates multiple feature probes
23638 at startup, to improve @value{GDBN} performance---a single larger
23639 packet performs better than multiple smaller probe packets on
23640 high-latency links. Some features may enable behavior which must not
23641 be on by default, e.g.@: because it would confuse older clients or
23642 stubs. Other features may describe packets which could be
23643 automatically probed for, but are not. These features must be
23644 reported before @value{GDBN} will use them. This ``default
23645 unsupported'' behavior is not appropriate for all packets, but it
23646 helps to keep the initial connection time under control with new
23647 versions of @value{GDBN} which support increasing numbers of packets.
23651 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23652 The stub supports or does not support each returned @var{stubfeature},
23653 depending on the form of each @var{stubfeature} (see below for the
23656 An empty reply indicates that @samp{qSupported} is not recognized,
23657 or that no features needed to be reported to @value{GDBN}.
23660 The allowed forms for each feature (either a @var{gdbfeature} in the
23661 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23665 @item @var{name}=@var{value}
23666 The remote protocol feature @var{name} is supported, and associated
23667 with the specified @var{value}. The format of @var{value} depends
23668 on the feature, but it must not include a semicolon.
23670 The remote protocol feature @var{name} is supported, and does not
23671 need an associated value.
23673 The remote protocol feature @var{name} is not supported.
23675 The remote protocol feature @var{name} may be supported, and
23676 @value{GDBN} should auto-detect support in some other way when it is
23677 needed. This form will not be used for @var{gdbfeature} notifications,
23678 but may be used for @var{stubfeature} responses.
23681 Whenever the stub receives a @samp{qSupported} request, the
23682 supplied set of @value{GDBN} features should override any previous
23683 request. This allows @value{GDBN} to put the stub in a known
23684 state, even if the stub had previously been communicating with
23685 a different version of @value{GDBN}.
23687 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23688 are defined yet. Stubs should ignore any unknown values for
23689 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23690 packet supports receiving packets of unlimited length (earlier
23691 versions of @value{GDBN} may reject overly long responses). Values
23692 for @var{gdbfeature} may be defined in the future to let the stub take
23693 advantage of new features in @value{GDBN}, e.g.@: incompatible
23694 improvements in the remote protocol---support for unlimited length
23695 responses would be a @var{gdbfeature} example, if it were not implied by
23696 the @samp{qSupported} query. The stub's reply should be independent
23697 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23698 describes all the features it supports, and then the stub replies with
23699 all the features it supports.
23701 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23702 responses, as long as each response uses one of the standard forms.
23704 Some features are flags. A stub which supports a flag feature
23705 should respond with a @samp{+} form response. Other features
23706 require values, and the stub should respond with an @samp{=}
23709 Each feature has a default value, which @value{GDBN} will use if
23710 @samp{qSupported} is not available or if the feature is not mentioned
23711 in the @samp{qSupported} response. The default values are fixed; a
23712 stub is free to omit any feature responses that match the defaults.
23714 Not all features can be probed, but for those which can, the probing
23715 mechanism is useful: in some cases, a stub's internal
23716 architecture may not allow the protocol layer to know some information
23717 about the underlying target in advance. This is especially common in
23718 stubs which may be configured for multiple targets.
23720 These are the currently defined stub features and their properties:
23722 @multitable @columnfractions 0.25 0.2 0.2 0.2
23723 @c NOTE: The first row should be @headitem, but we do not yet require
23724 @c a new enough version of Texinfo (4.7) to use @headitem.
23726 @tab Value Required
23730 @item @samp{PacketSize}
23735 @item @samp{qXfer:auxv:read}
23740 @item @samp{qXfer:memory-map:read}
23747 These are the currently defined stub features, in more detail:
23750 @cindex packet size, remote protocol
23751 @item PacketSize=@var{bytes}
23752 The remote stub can accept packets up to at least @var{bytes} in
23753 length. @value{GDBN} will send packets up to this size for bulk
23754 transfers, and will never send larger packets. This is a limit on the
23755 data characters in the packet, including the frame and checksum.
23756 There is no trailing NUL byte in a remote protocol packet; if the stub
23757 stores packets in a NUL-terminated format, it should allow an extra
23758 byte in its buffer for the NUL. If this stub feature is not supported,
23759 @value{GDBN} guesses based on the size of the @samp{g} packet response.
23761 @item qXfer:auxv:read
23762 The remote stub understands the @samp{qXfer:auxv:read} packet
23763 (@pxref{qXfer auxiliary vector read}).
23768 @cindex symbol lookup, remote request
23769 @cindex @samp{qSymbol} packet
23770 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23771 requests. Accept requests from the target for the values of symbols.
23776 The target does not need to look up any (more) symbols.
23777 @item qSymbol:@var{sym_name}
23778 The target requests the value of symbol @var{sym_name} (hex encoded).
23779 @value{GDBN} may provide the value by using the
23780 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23784 @item qSymbol:@var{sym_value}:@var{sym_name}
23785 Set the value of @var{sym_name} to @var{sym_value}.
23787 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23788 target has previously requested.
23790 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23791 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23797 The target does not need to look up any (more) symbols.
23798 @item qSymbol:@var{sym_name}
23799 The target requests the value of a new symbol @var{sym_name} (hex
23800 encoded). @value{GDBN} will continue to supply the values of symbols
23801 (if available), until the target ceases to request them.
23806 @xref{Tracepoint Packets}.
23808 @item qThreadExtraInfo,@var{id}
23809 @cindex thread attributes info, remote request
23810 @cindex @samp{qThreadExtraInfo} packet
23811 Obtain a printable string description of a thread's attributes from
23812 the target OS. @var{id} is a thread-id in big-endian hex. This
23813 string may contain anything that the target OS thinks is interesting
23814 for @value{GDBN} to tell the user about the thread. The string is
23815 displayed in @value{GDBN}'s @code{info threads} display. Some
23816 examples of possible thread extra info strings are @samp{Runnable}, or
23817 @samp{Blocked on Mutex}.
23821 @item @var{XX}@dots{}
23822 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23823 comprising the printable string containing the extra information about
23824 the thread's attributes.
23827 (Note that the @code{qThreadExtraInfo} packet's name is separated from
23828 the command by a @samp{,}, not a @samp{:}, contrary to the naming
23829 conventions above. Please don't use this packet as a model for new
23837 @xref{Tracepoint Packets}.
23839 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
23840 @cindex read special object, remote request
23841 @cindex @samp{qXfer} packet
23842 @anchor{qXfer read}
23843 Read uninterpreted bytes from the target's special data area
23844 identified by the keyword @var{object}. Request @var{length} bytes
23845 starting at @var{offset} bytes into the data. The content and
23846 encoding of @var{annex} is specific to the object; it can supply
23847 additional details about what data to access.
23849 Here are the specific requests of this form defined so far. All
23850 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
23851 formats, listed below.
23854 @item qXfer:auxv:read::@var{offset},@var{length}
23855 @anchor{qXfer auxiliary vector read}
23856 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
23857 auxiliary vector}. Note @var{annex} must be empty.
23859 This packet is not probed by default; the remote stub must request it,
23860 by suppling an appropriate @samp{qSupported} response (@pxref{qSupported}).
23864 @item qXfer:memory-map:read::@var{offset},@var{length}
23865 @anchor{qXfer memory map read}
23866 Access the target's @dfn{memory-map}. @xref{Memory map format}. The
23867 annex part of the generic @samp{qXfer} packet must be empty
23868 (@pxref{qXfer read}).
23870 This packet is not probed by default; the remote stub must request it,
23871 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23877 Data @var{data} (@pxref{Binary Data}) has been read from the
23878 target. There may be more data at a higher address (although
23879 it is permitted to return @samp{m} even for the last valid
23880 block of data, as long as at least one byte of data was read).
23881 @var{data} may have fewer bytes than the @var{length} in the
23885 Data @var{data} (@pxref{Binary Data}) has been read from the target.
23886 There is no more data to be read. @var{data} may have fewer bytes
23887 than the @var{length} in the request.
23890 The @var{offset} in the request is at the end of the data.
23891 There is no more data to be read.
23894 The request was malformed, or @var{annex} was invalid.
23897 The offset was invalid, or there was an error encountered reading the data.
23898 @var{nn} is a hex-encoded @code{errno} value.
23901 An empty reply indicates the @var{object} string was not recognized by
23902 the stub, or that the object does not support reading.
23905 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
23906 @cindex write data into object, remote request
23907 Write uninterpreted bytes into the target's special data area
23908 identified by the keyword @var{object}, starting at @var{offset} bytes
23909 into the data. @samp{@var{data}@dots{}} is the binary-encoded data
23910 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
23911 is specific to the object; it can supply additional details about what data
23914 No requests of this form are presently in use. This specification
23915 serves as a placeholder to document the common format that new
23916 specific request specifications ought to use.
23921 @var{nn} (hex encoded) is the number of bytes written.
23922 This may be fewer bytes than supplied in the request.
23925 The request was malformed, or @var{annex} was invalid.
23928 The offset was invalid, or there was an error encountered writing the data.
23929 @var{nn} is a hex-encoded @code{errno} value.
23932 An empty reply indicates the @var{object} string was not
23933 recognized by the stub, or that the object does not support writing.
23936 @item qXfer:@var{object}:@var{operation}:@dots{}
23937 Requests of this form may be added in the future. When a stub does
23938 not recognize the @var{object} keyword, or its support for
23939 @var{object} does not recognize the @var{operation} keyword, the stub
23940 must respond with an empty packet.
23944 @node Register Packet Format
23945 @section Register Packet Format
23947 The following @code{g}/@code{G} packets have previously been defined.
23948 In the below, some thirty-two bit registers are transferred as
23949 sixty-four bits. Those registers should be zero/sign extended (which?)
23950 to fill the space allocated. Register bytes are transferred in target
23951 byte order. The two nibbles within a register byte are transferred
23952 most-significant - least-significant.
23958 All registers are transferred as thirty-two bit quantities in the order:
23959 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
23960 registers; fsr; fir; fp.
23964 All registers are transferred as sixty-four bit quantities (including
23965 thirty-two bit registers such as @code{sr}). The ordering is the same
23970 @node Tracepoint Packets
23971 @section Tracepoint Packets
23972 @cindex tracepoint packets
23973 @cindex packets, tracepoint
23975 Here we describe the packets @value{GDBN} uses to implement
23976 tracepoints (@pxref{Tracepoints}).
23980 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
23981 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
23982 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
23983 the tracepoint is disabled. @var{step} is the tracepoint's step
23984 count, and @var{pass} is its pass count. If the trailing @samp{-} is
23985 present, further @samp{QTDP} packets will follow to specify this
23986 tracepoint's actions.
23991 The packet was understood and carried out.
23993 The packet was not recognized.
23996 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
23997 Define actions to be taken when a tracepoint is hit. @var{n} and
23998 @var{addr} must be the same as in the initial @samp{QTDP} packet for
23999 this tracepoint. This packet may only be sent immediately after
24000 another @samp{QTDP} packet that ended with a @samp{-}. If the
24001 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24002 specifying more actions for this tracepoint.
24004 In the series of action packets for a given tracepoint, at most one
24005 can have an @samp{S} before its first @var{action}. If such a packet
24006 is sent, it and the following packets define ``while-stepping''
24007 actions. Any prior packets define ordinary actions --- that is, those
24008 taken when the tracepoint is first hit. If no action packet has an
24009 @samp{S}, then all the packets in the series specify ordinary
24010 tracepoint actions.
24012 The @samp{@var{action}@dots{}} portion of the packet is a series of
24013 actions, concatenated without separators. Each action has one of the
24019 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24020 a hexadecimal number whose @var{i}'th bit is set if register number
24021 @var{i} should be collected. (The least significant bit is numbered
24022 zero.) Note that @var{mask} may be any number of digits long; it may
24023 not fit in a 32-bit word.
24025 @item M @var{basereg},@var{offset},@var{len}
24026 Collect @var{len} bytes of memory starting at the address in register
24027 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24028 @samp{-1}, then the range has a fixed address: @var{offset} is the
24029 address of the lowest byte to collect. The @var{basereg},
24030 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24031 values (the @samp{-1} value for @var{basereg} is a special case).
24033 @item X @var{len},@var{expr}
24034 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24035 it directs. @var{expr} is an agent expression, as described in
24036 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24037 two-digit hex number in the packet; @var{len} is the number of bytes
24038 in the expression (and thus one-half the number of hex digits in the
24043 Any number of actions may be packed together in a single @samp{QTDP}
24044 packet, as long as the packet does not exceed the maximum packet
24045 length (400 bytes, for many stubs). There may be only one @samp{R}
24046 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24047 actions. Any registers referred to by @samp{M} and @samp{X} actions
24048 must be collected by a preceding @samp{R} action. (The
24049 ``while-stepping'' actions are treated as if they were attached to a
24050 separate tracepoint, as far as these restrictions are concerned.)
24055 The packet was understood and carried out.
24057 The packet was not recognized.
24060 @item QTFrame:@var{n}
24061 Select the @var{n}'th tracepoint frame from the buffer, and use the
24062 register and memory contents recorded there to answer subsequent
24063 request packets from @value{GDBN}.
24065 A successful reply from the stub indicates that the stub has found the
24066 requested frame. The response is a series of parts, concatenated
24067 without separators, describing the frame we selected. Each part has
24068 one of the following forms:
24072 The selected frame is number @var{n} in the trace frame buffer;
24073 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24074 was no frame matching the criteria in the request packet.
24077 The selected trace frame records a hit of tracepoint number @var{t};
24078 @var{t} is a hexadecimal number.
24082 @item QTFrame:pc:@var{addr}
24083 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24084 currently selected frame whose PC is @var{addr};
24085 @var{addr} is a hexadecimal number.
24087 @item QTFrame:tdp:@var{t}
24088 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24089 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24090 is a hexadecimal number.
24092 @item QTFrame:range:@var{start}:@var{end}
24093 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24094 currently selected frame whose PC is between @var{start} (inclusive)
24095 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24098 @item QTFrame:outside:@var{start}:@var{end}
24099 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24100 frame @emph{outside} the given range of addresses.
24103 Begin the tracepoint experiment. Begin collecting data from tracepoint
24104 hits in the trace frame buffer.
24107 End the tracepoint experiment. Stop collecting trace frames.
24110 Clear the table of tracepoints, and empty the trace frame buffer.
24112 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24113 Establish the given ranges of memory as ``transparent''. The stub
24114 will answer requests for these ranges from memory's current contents,
24115 if they were not collected as part of the tracepoint hit.
24117 @value{GDBN} uses this to mark read-only regions of memory, like those
24118 containing program code. Since these areas never change, they should
24119 still have the same contents they did when the tracepoint was hit, so
24120 there's no reason for the stub to refuse to provide their contents.
24123 Ask the stub if there is a trace experiment running right now.
24128 There is no trace experiment running.
24130 There is a trace experiment running.
24137 @section Interrupts
24138 @cindex interrupts (remote protocol)
24140 When a program on the remote target is running, @value{GDBN} may
24141 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24142 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24143 setting (@pxref{set remotebreak}).
24145 The precise meaning of @code{BREAK} is defined by the transport
24146 mechanism and may, in fact, be undefined. @value{GDBN} does
24147 not currently define a @code{BREAK} mechanism for any of the network
24150 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24151 transport mechanisms. It is represented by sending the single byte
24152 @code{0x03} without any of the usual packet overhead described in
24153 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24154 transmitted as part of a packet, it is considered to be packet data
24155 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24156 (@pxref{X packet}), used for binary downloads, may include an unescaped
24157 @code{0x03} as part of its packet.
24159 Stubs are not required to recognize these interrupt mechanisms and the
24160 precise meaning associated with receipt of the interrupt is
24161 implementation defined. If the stub is successful at interrupting the
24162 running program, it is expected that it will send one of the Stop
24163 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24164 of successfully stopping the program. Interrupts received while the
24165 program is stopped will be discarded.
24170 Example sequence of a target being re-started. Notice how the restart
24171 does not get any direct output:
24176 @emph{target restarts}
24179 <- @code{T001:1234123412341234}
24183 Example sequence of a target being stepped by a single instruction:
24186 -> @code{G1445@dots{}}
24191 <- @code{T001:1234123412341234}
24195 <- @code{1455@dots{}}
24199 @node File-I/O remote protocol extension
24200 @section File-I/O remote protocol extension
24201 @cindex File-I/O remote protocol extension
24204 * File-I/O Overview::
24205 * Protocol basics::
24206 * The F request packet::
24207 * The F reply packet::
24208 * The Ctrl-C message::
24210 * List of supported calls::
24211 * Protocol specific representation of datatypes::
24213 * File-I/O Examples::
24216 @node File-I/O Overview
24217 @subsection File-I/O Overview
24218 @cindex file-i/o overview
24220 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24221 target to use the host's file system and console I/O to perform various
24222 system calls. System calls on the target system are translated into a
24223 remote protocol packet to the host system, which then performs the needed
24224 actions and returns a response packet to the target system.
24225 This simulates file system operations even on targets that lack file systems.
24227 The protocol is defined to be independent of both the host and target systems.
24228 It uses its own internal representation of datatypes and values. Both
24229 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24230 translating the system-dependent value representations into the internal
24231 protocol representations when data is transmitted.
24233 The communication is synchronous. A system call is possible only when
24234 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24235 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24236 the target is stopped to allow deterministic access to the target's
24237 memory. Therefore File-I/O is not interruptible by target signals. On
24238 the other hand, it is possible to interrupt File-I/O by a user interrupt
24239 (@samp{Ctrl-C}) within @value{GDBN}.
24241 The target's request to perform a host system call does not finish
24242 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24243 after finishing the system call, the target returns to continuing the
24244 previous activity (continue, step). No additional continue or step
24245 request from @value{GDBN} is required.
24248 (@value{GDBP}) continue
24249 <- target requests 'system call X'
24250 target is stopped, @value{GDBN} executes system call
24251 -> GDB returns result
24252 ... target continues, GDB returns to wait for the target
24253 <- target hits breakpoint and sends a Txx packet
24256 The protocol only supports I/O on the console and to regular files on
24257 the host file system. Character or block special devices, pipes,
24258 named pipes, sockets or any other communication method on the host
24259 system are not supported by this protocol.
24261 @node Protocol basics
24262 @subsection Protocol basics
24263 @cindex protocol basics, file-i/o
24265 The File-I/O protocol uses the @code{F} packet as the request as well
24266 as reply packet. Since a File-I/O system call can only occur when
24267 @value{GDBN} is waiting for a response from the continuing or stepping target,
24268 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24269 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24270 This @code{F} packet contains all information needed to allow @value{GDBN}
24271 to call the appropriate host system call:
24275 A unique identifier for the requested system call.
24278 All parameters to the system call. Pointers are given as addresses
24279 in the target memory address space. Pointers to strings are given as
24280 pointer/length pair. Numerical values are given as they are.
24281 Numerical control flags are given in a protocol specific representation.
24285 At this point, @value{GDBN} has to perform the following actions.
24289 If the parameters include pointer values to data needed as input to a
24290 system call, @value{GDBN} requests this data from the target with a
24291 standard @code{m} packet request. This additional communication has to be
24292 expected by the target implementation and is handled as any other @code{m}
24296 @value{GDBN} translates all value from protocol representation to host
24297 representation as needed. Datatypes are coerced into the host types.
24300 @value{GDBN} calls the system call.
24303 It then coerces datatypes back to protocol representation.
24306 If the system call is expected to return data in buffer space specified
24307 by pointer parameters to the call, the data is transmitted to the
24308 target using a @code{M} or @code{X} packet. This packet has to be expected
24309 by the target implementation and is handled as any other @code{M} or @code{X}
24314 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24315 necessary information for the target to continue. This at least contains
24322 @code{errno}, if has been changed by the system call.
24329 After having done the needed type and value coercion, the target continues
24330 the latest continue or step action.
24332 @node The F request packet
24333 @subsection The @code{F} request packet
24334 @cindex file-i/o request packet
24335 @cindex @code{F} request packet
24337 The @code{F} request packet has the following format:
24340 @item F@var{call-id},@var{parameter@dots{}}
24342 @var{call-id} is the identifier to indicate the host system call to be called.
24343 This is just the name of the function.
24345 @var{parameter@dots{}} are the parameters to the system call.
24346 Parameters are hexadecimal integer values, either the actual values in case
24347 of scalar datatypes, pointers to target buffer space in case of compound
24348 datatypes and unspecified memory areas, or pointer/length pairs in case
24349 of string parameters. These are appended to the @var{call-id} as a
24350 comma-delimited list. All values are transmitted in ASCII
24351 string representation, pointer/length pairs separated by a slash.
24357 @node The F reply packet
24358 @subsection The @code{F} reply packet
24359 @cindex file-i/o reply packet
24360 @cindex @code{F} reply packet
24362 The @code{F} reply packet has the following format:
24366 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call specific attachment}
24368 @var{retcode} is the return code of the system call as hexadecimal value.
24370 @var{errno} is the @code{errno} set by the call, in protocol specific representation.
24371 This parameter can be omitted if the call was successful.
24373 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24374 case, @var{errno} must be sent as well, even if the call was successful.
24375 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24382 or, if the call was interrupted before the host call has been performed:
24389 assuming 4 is the protocol specific representation of @code{EINTR}.
24394 @node The Ctrl-C message
24395 @subsection The @samp{Ctrl-C} message
24396 @cindex ctrl-c message, in file-i/o protocol
24398 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
24399 reply packet (@pxref{The F reply packet}),
24400 the target should behave as if it had
24401 gotten a break message. The meaning for the target is ``system call
24402 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24403 (as with a break message) and return to @value{GDBN} with a @code{T02}
24406 It's important for the target to know in which
24407 state the system call was interrupted. There are two possible cases:
24411 The system call hasn't been performed on the host yet.
24414 The system call on the host has been finished.
24418 These two states can be distinguished by the target by the value of the
24419 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24420 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24421 on POSIX systems. In any other case, the target may presume that the
24422 system call has been finished --- successfully or not --- and should behave
24423 as if the break message arrived right after the system call.
24425 @value{GDBN} must behave reliably. If the system call has not been called
24426 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24427 @code{errno} in the packet. If the system call on the host has been finished
24428 before the user requests a break, the full action must be finished by
24429 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24430 The @code{F} packet may only be sent when either nothing has happened
24431 or the full action has been completed.
24434 @subsection Console I/O
24435 @cindex console i/o as part of file-i/o
24437 By default and if not explicitely closed by the target system, the file
24438 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24439 on the @value{GDBN} console is handled as any other file output operation
24440 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24441 by @value{GDBN} so that after the target read request from file descriptor
24442 0 all following typing is buffered until either one of the following
24447 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
24449 system call is treated as finished.
24452 The user presses @key{RET}. This is treated as end of input with a trailing
24456 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
24457 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
24461 If the user has typed more characters than fit in the buffer given to
24462 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24463 either another @code{read(0, @dots{})} is requested by the target, or debugging
24464 is stopped at the user's request.
24467 @node List of supported calls
24468 @subsection List of supported calls
24469 @cindex list of supported file-i/o calls
24486 @unnumberedsubsubsec open
24487 @cindex open, file-i/o system call
24492 int open(const char *pathname, int flags);
24493 int open(const char *pathname, int flags, mode_t mode);
24497 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24500 @var{flags} is the bitwise @code{OR} of the following values:
24504 If the file does not exist it will be created. The host
24505 rules apply as far as file ownership and time stamps
24509 When used with @code{O_CREAT}, if the file already exists it is
24510 an error and open() fails.
24513 If the file already exists and the open mode allows
24514 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24515 truncated to zero length.
24518 The file is opened in append mode.
24521 The file is opened for reading only.
24524 The file is opened for writing only.
24527 The file is opened for reading and writing.
24531 Other bits are silently ignored.
24535 @var{mode} is the bitwise @code{OR} of the following values:
24539 User has read permission.
24542 User has write permission.
24545 Group has read permission.
24548 Group has write permission.
24551 Others have read permission.
24554 Others have write permission.
24558 Other bits are silently ignored.
24561 @item Return value:
24562 @code{open} returns the new file descriptor or -1 if an error
24569 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24572 @var{pathname} refers to a directory.
24575 The requested access is not allowed.
24578 @var{pathname} was too long.
24581 A directory component in @var{pathname} does not exist.
24584 @var{pathname} refers to a device, pipe, named pipe or socket.
24587 @var{pathname} refers to a file on a read-only filesystem and
24588 write access was requested.
24591 @var{pathname} is an invalid pointer value.
24594 No space on device to create the file.
24597 The process already has the maximum number of files open.
24600 The limit on the total number of files open on the system
24604 The call was interrupted by the user.
24610 @unnumberedsubsubsec close
24611 @cindex close, file-i/o system call
24620 @samp{Fclose,@var{fd}}
24622 @item Return value:
24623 @code{close} returns zero on success, or -1 if an error occurred.
24629 @var{fd} isn't a valid open file descriptor.
24632 The call was interrupted by the user.
24638 @unnumberedsubsubsec read
24639 @cindex read, file-i/o system call
24644 int read(int fd, void *buf, unsigned int count);
24648 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24650 @item Return value:
24651 On success, the number of bytes read is returned.
24652 Zero indicates end of file. If count is zero, read
24653 returns zero as well. On error, -1 is returned.
24659 @var{fd} is not a valid file descriptor or is not open for
24663 @var{bufptr} is an invalid pointer value.
24666 The call was interrupted by the user.
24672 @unnumberedsubsubsec write
24673 @cindex write, file-i/o system call
24678 int write(int fd, const void *buf, unsigned int count);
24682 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
24684 @item Return value:
24685 On success, the number of bytes written are returned.
24686 Zero indicates nothing was written. On error, -1
24693 @var{fd} is not a valid file descriptor or is not open for
24697 @var{bufptr} is an invalid pointer value.
24700 An attempt was made to write a file that exceeds the
24701 host specific maximum file size allowed.
24704 No space on device to write the data.
24707 The call was interrupted by the user.
24713 @unnumberedsubsubsec lseek
24714 @cindex lseek, file-i/o system call
24719 long lseek (int fd, long offset, int flag);
24723 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
24725 @var{flag} is one of:
24729 The offset is set to @var{offset} bytes.
24732 The offset is set to its current location plus @var{offset}
24736 The offset is set to the size of the file plus @var{offset}
24740 @item Return value:
24741 On success, the resulting unsigned offset in bytes from
24742 the beginning of the file is returned. Otherwise, a
24743 value of -1 is returned.
24749 @var{fd} is not a valid open file descriptor.
24752 @var{fd} is associated with the @value{GDBN} console.
24755 @var{flag} is not a proper value.
24758 The call was interrupted by the user.
24764 @unnumberedsubsubsec rename
24765 @cindex rename, file-i/o system call
24770 int rename(const char *oldpath, const char *newpath);
24774 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
24776 @item Return value:
24777 On success, zero is returned. On error, -1 is returned.
24783 @var{newpath} is an existing directory, but @var{oldpath} is not a
24787 @var{newpath} is a non-empty directory.
24790 @var{oldpath} or @var{newpath} is a directory that is in use by some
24794 An attempt was made to make a directory a subdirectory
24798 A component used as a directory in @var{oldpath} or new
24799 path is not a directory. Or @var{oldpath} is a directory
24800 and @var{newpath} exists but is not a directory.
24803 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
24806 No access to the file or the path of the file.
24810 @var{oldpath} or @var{newpath} was too long.
24813 A directory component in @var{oldpath} or @var{newpath} does not exist.
24816 The file is on a read-only filesystem.
24819 The device containing the file has no room for the new
24823 The call was interrupted by the user.
24829 @unnumberedsubsubsec unlink
24830 @cindex unlink, file-i/o system call
24835 int unlink(const char *pathname);
24839 @samp{Funlink,@var{pathnameptr}/@var{len}}
24841 @item Return value:
24842 On success, zero is returned. On error, -1 is returned.
24848 No access to the file or the path of the file.
24851 The system does not allow unlinking of directories.
24854 The file @var{pathname} cannot be unlinked because it's
24855 being used by another process.
24858 @var{pathnameptr} is an invalid pointer value.
24861 @var{pathname} was too long.
24864 A directory component in @var{pathname} does not exist.
24867 A component of the path is not a directory.
24870 The file is on a read-only filesystem.
24873 The call was interrupted by the user.
24879 @unnumberedsubsubsec stat/fstat
24880 @cindex fstat, file-i/o system call
24881 @cindex stat, file-i/o system call
24886 int stat(const char *pathname, struct stat *buf);
24887 int fstat(int fd, struct stat *buf);
24891 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
24892 @samp{Ffstat,@var{fd},@var{bufptr}}
24894 @item Return value:
24895 On success, zero is returned. On error, -1 is returned.
24901 @var{fd} is not a valid open file.
24904 A directory component in @var{pathname} does not exist or the
24905 path is an empty string.
24908 A component of the path is not a directory.
24911 @var{pathnameptr} is an invalid pointer value.
24914 No access to the file or the path of the file.
24917 @var{pathname} was too long.
24920 The call was interrupted by the user.
24926 @unnumberedsubsubsec gettimeofday
24927 @cindex gettimeofday, file-i/o system call
24932 int gettimeofday(struct timeval *tv, void *tz);
24936 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
24938 @item Return value:
24939 On success, 0 is returned, -1 otherwise.
24945 @var{tz} is a non-NULL pointer.
24948 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
24954 @unnumberedsubsubsec isatty
24955 @cindex isatty, file-i/o system call
24960 int isatty(int fd);
24964 @samp{Fisatty,@var{fd}}
24966 @item Return value:
24967 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
24973 The call was interrupted by the user.
24978 Note that the @code{isatty} call is treated as a special case: it returns
24979 1 to the target if the file descriptor is attached
24980 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
24981 would require implementing @code{ioctl} and would be more complex than
24986 @unnumberedsubsubsec system
24987 @cindex system, file-i/o system call
24992 int system(const char *command);
24996 @samp{Fsystem,@var{commandptr}/@var{len}}
24998 @item Return value:
24999 If @var{len} is zero, the return value indicates whether a shell is
25000 available. A zero return value indicates a shell is not available.
25001 For non-zero @var{len}, the value returned is -1 on error and the
25002 return status of the command otherwise. Only the exit status of the
25003 command is returned, which is extracted from the host's @code{system}
25004 return value by calling @code{WEXITSTATUS(retval)}. In case
25005 @file{/bin/sh} could not be executed, 127 is returned.
25011 The call was interrupted by the user.
25016 @value{GDBN} takes over the full task of calling the necessary host calls
25017 to perform the @code{system} call. The return value of @code{system} on
25018 the host is simplified before it's returned
25019 to the target. Any termination signal information from the child process
25020 is discarded, and the return value consists
25021 entirely of the exit status of the called command.
25023 Due to security concerns, the @code{system} call is by default refused
25024 by @value{GDBN}. The user has to allow this call explicitly with the
25025 @code{set remote system-call-allowed 1} command.
25028 @item set remote system-call-allowed
25029 @kindex set remote system-call-allowed
25030 Control whether to allow the @code{system} calls in the File I/O
25031 protocol for the remote target. The default is zero (disabled).
25033 @item show remote system-call-allowed
25034 @kindex show remote system-call-allowed
25035 Show whether the @code{system} calls are allowed in the File I/O
25039 @node Protocol specific representation of datatypes
25040 @subsection Protocol specific representation of datatypes
25041 @cindex protocol specific representation of datatypes, in file-i/o protocol
25044 * Integral datatypes::
25046 * Memory transfer::
25051 @node Integral datatypes
25052 @unnumberedsubsubsec Integral datatypes
25053 @cindex integral datatypes, in file-i/o protocol
25055 The integral datatypes used in the system calls are @code{int},
25056 @code{unsigned int}, @code{long}, @code{unsigned long},
25057 @code{mode_t}, and @code{time_t}.
25059 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25060 implemented as 32 bit values in this protocol.
25062 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25064 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25065 in @file{limits.h}) to allow range checking on host and target.
25067 @code{time_t} datatypes are defined as seconds since the Epoch.
25069 All integral datatypes transferred as part of a memory read or write of a
25070 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25073 @node Pointer values
25074 @unnumberedsubsubsec Pointer values
25075 @cindex pointer values, in file-i/o protocol
25077 Pointers to target data are transmitted as they are. An exception
25078 is made for pointers to buffers for which the length isn't
25079 transmitted as part of the function call, namely strings. Strings
25080 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25087 which is a pointer to data of length 18 bytes at position 0x1aaf.
25088 The length is defined as the full string length in bytes, including
25089 the trailing null byte. For example, the string @code{"hello world"}
25090 at address 0x123456 is transmitted as
25096 @node Memory transfer
25097 @unnumberedsubsubsec Memory transfer
25098 @cindex memory transfer, in file-i/o protocol
25100 Structured data which is transferred using a memory read or write (for
25101 example, a @code{struct stat}) is expected to be in a protocol specific format
25102 with all scalar multibyte datatypes being big endian. Translation to
25103 this representation needs to be done both by the target before the @code{F}
25104 packet is sent, and by @value{GDBN} before
25105 it transfers memory to the target. Transferred pointers to structured
25106 data should point to the already-coerced data at any time.
25110 @unnumberedsubsubsec struct stat
25111 @cindex struct stat, in file-i/o protocol
25113 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25114 is defined as follows:
25118 unsigned int st_dev; /* device */
25119 unsigned int st_ino; /* inode */
25120 mode_t st_mode; /* protection */
25121 unsigned int st_nlink; /* number of hard links */
25122 unsigned int st_uid; /* user ID of owner */
25123 unsigned int st_gid; /* group ID of owner */
25124 unsigned int st_rdev; /* device type (if inode device) */
25125 unsigned long st_size; /* total size, in bytes */
25126 unsigned long st_blksize; /* blocksize for filesystem I/O */
25127 unsigned long st_blocks; /* number of blocks allocated */
25128 time_t st_atime; /* time of last access */
25129 time_t st_mtime; /* time of last modification */
25130 time_t st_ctime; /* time of last change */
25134 The integral datatypes conform to the definitions given in the
25135 appropriate section (see @ref{Integral datatypes}, for details) so this
25136 structure is of size 64 bytes.
25138 The values of several fields have a restricted meaning and/or
25144 A value of 0 represents a file, 1 the console.
25147 No valid meaning for the target. Transmitted unchanged.
25150 Valid mode bits are described in @ref{Constants}. Any other
25151 bits have currently no meaning for the target.
25156 No valid meaning for the target. Transmitted unchanged.
25161 These values have a host and file system dependent
25162 accuracy. Especially on Windows hosts, the file system may not
25163 support exact timing values.
25166 The target gets a @code{struct stat} of the above representation and is
25167 responsible for coercing it to the target representation before
25170 Note that due to size differences between the host, target, and protocol
25171 representations of @code{struct stat} members, these members could eventually
25172 get truncated on the target.
25174 @node struct timeval
25175 @unnumberedsubsubsec struct timeval
25176 @cindex struct timeval, in file-i/o protocol
25178 The buffer of type @code{struct timeval} used by the File-I/O protocol
25179 is defined as follows:
25183 time_t tv_sec; /* second */
25184 long tv_usec; /* microsecond */
25188 The integral datatypes conform to the definitions given in the
25189 appropriate section (see @ref{Integral datatypes}, for details) so this
25190 structure is of size 8 bytes.
25193 @subsection Constants
25194 @cindex constants, in file-i/o protocol
25196 The following values are used for the constants inside of the
25197 protocol. @value{GDBN} and target are responsible for translating these
25198 values before and after the call as needed.
25209 @unnumberedsubsubsec Open flags
25210 @cindex open flags, in file-i/o protocol
25212 All values are given in hexadecimal representation.
25224 @node mode_t values
25225 @unnumberedsubsubsec mode_t values
25226 @cindex mode_t values, in file-i/o protocol
25228 All values are given in octal representation.
25245 @unnumberedsubsubsec Errno values
25246 @cindex errno values, in file-i/o protocol
25248 All values are given in decimal representation.
25273 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25274 any error value not in the list of supported error numbers.
25277 @unnumberedsubsubsec Lseek flags
25278 @cindex lseek flags, in file-i/o protocol
25287 @unnumberedsubsubsec Limits
25288 @cindex limits, in file-i/o protocol
25290 All values are given in decimal representation.
25293 INT_MIN -2147483648
25295 UINT_MAX 4294967295
25296 LONG_MIN -9223372036854775808
25297 LONG_MAX 9223372036854775807
25298 ULONG_MAX 18446744073709551615
25301 @node File-I/O Examples
25302 @subsection File-I/O Examples
25303 @cindex file-i/o examples
25305 Example sequence of a write call, file descriptor 3, buffer is at target
25306 address 0x1234, 6 bytes should be written:
25309 <- @code{Fwrite,3,1234,6}
25310 @emph{request memory read from target}
25313 @emph{return "6 bytes written"}
25317 Example sequence of a read call, file descriptor 3, buffer is at target
25318 address 0x1234, 6 bytes should be read:
25321 <- @code{Fread,3,1234,6}
25322 @emph{request memory write to target}
25323 -> @code{X1234,6:XXXXXX}
25324 @emph{return "6 bytes read"}
25328 Example sequence of a read call, call fails on the host due to invalid
25329 file descriptor (@code{EBADF}):
25332 <- @code{Fread,3,1234,6}
25336 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
25340 <- @code{Fread,3,1234,6}
25345 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
25349 <- @code{Fread,3,1234,6}
25350 -> @code{X1234,6:XXXXXX}
25354 @node Memory map format
25355 @section Memory map format
25356 @cindex memory map format
25358 To be able to write into flash memory, @value{GDBN} needs to obtain a
25359 memory map from the target. This section describes the format of the
25362 The memory map is obtained using the @samp{qXfer:memory-map:read}
25363 (@pxref{qXfer memory map read}) packet and is an XML document that
25364 lists memory regions. The top-level structure of the document is shown below:
25367 <?xml version="1.0"?>
25368 <!DOCTYPE memory-map
25369 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25370 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25376 Each region can be either:
25381 A region of RAM starting at @var{addr} and extending for @var{length}
25385 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25390 A region of read-only memory:
25393 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25398 A region of flash memory, with erasure blocks @var{blocksize}
25402 <memory type="flash" start="@var{addr}" length="@var{length}">
25403 <property name="blocksize">@var{blocksize}</property>
25409 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25410 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25411 packets to write to addresses in such ranges.
25413 The formal DTD for memory map format is given below:
25416 <!-- ................................................... -->
25417 <!-- Memory Map XML DTD ................................ -->
25418 <!-- File: memory-map.dtd .............................. -->
25419 <!-- .................................... .............. -->
25420 <!-- memory-map.dtd -->
25421 <!-- memory-map: Root element with versioning -->
25422 <!ELEMENT memory-map (memory | property)>
25423 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25424 <!ELEMENT memory (property)>
25425 <!-- memory: Specifies a memory region,
25426 and its type, or device. -->
25427 <!ATTLIST memory type CDATA #REQUIRED
25428 start CDATA #REQUIRED
25429 length CDATA #REQUIRED
25430 device CDATA #IMPLIED>
25431 <!-- property: Generic attribute tag -->
25432 <!ELEMENT property (#PCDATA | property)*>
25433 <!ATTLIST property name CDATA #REQUIRED>
25436 @include agentexpr.texi
25450 % I think something like @colophon should be in texinfo. In the
25452 \long\def\colophon{\hbox to0pt{}\vfill
25453 \centerline{The body of this manual is set in}
25454 \centerline{\fontname\tenrm,}
25455 \centerline{with headings in {\bf\fontname\tenbf}}
25456 \centerline{and examples in {\tt\fontname\tentt}.}
25457 \centerline{{\it\fontname\tenit\/},}
25458 \centerline{{\bf\fontname\tenbf}, and}
25459 \centerline{{\sl\fontname\tensl\/}}
25460 \centerline{are used for emphasis.}\vfill}
25462 % Blame: doc@cygnus.com, 1991.