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132 .\" ========================================================================
135 .TH CPP 1 "2008-06-06" "gcc-4.3.1" "GNU"
136 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
137 .\" way too many mistakes in technical documents.
141 cpp \- The C Preprocessor
143 .IX Header "SYNOPSIS"
144 cpp [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR]
145 [\fB\-I\fR\fIdir\fR...] [\fB\-iquote\fR\fIdir\fR...]
146 [\fB\-W\fR\fIwarn\fR...]
147 [\fB\-M\fR|\fB\-MM\fR] [\fB\-MG\fR] [\fB\-MF\fR \fIfilename\fR]
148 [\fB\-MP\fR] [\fB\-MQ\fR \fItarget\fR...]
149 [\fB\-MT\fR \fItarget\fR...]
150 [\fB\-P\fR] [\fB\-fno\-working\-directory\fR]
151 [\fB\-x\fR \fIlanguage\fR] [\fB\-std=\fR\fIstandard\fR]
152 \fIinfile\fR \fIoutfile\fR
154 Only the most useful options are listed here; see below for the remainder.
156 .IX Header "DESCRIPTION"
157 The C preprocessor, often known as \fIcpp\fR, is a \fImacro processor\fR
158 that is used automatically by the C compiler to transform your program
159 before compilation. It is called a macro processor because it allows
160 you to define \fImacros\fR, which are brief abbreviations for longer
163 The C preprocessor is intended to be used only with C, \*(C+, and
164 Objective-C source code. In the past, it has been abused as a general
165 text processor. It will choke on input which does not obey C's lexical
166 rules. For example, apostrophes will be interpreted as the beginning of
167 character constants, and cause errors. Also, you cannot rely on it
168 preserving characteristics of the input which are not significant to
169 C\-family languages. If a Makefile is preprocessed, all the hard tabs
170 will be removed, and the Makefile will not work.
172 Having said that, you can often get away with using cpp on things which
173 are not C. Other Algol-ish programming languages are often safe
174 (Pascal, Ada, etc.) So is assembly, with caution. \fB\-traditional\-cpp\fR
175 mode preserves more white space, and is otherwise more permissive. Many
176 of the problems can be avoided by writing C or \*(C+ style comments
177 instead of native language comments, and keeping macros simple.
179 Wherever possible, you should use a preprocessor geared to the language
180 you are writing in. Modern versions of the \s-1GNU\s0 assembler have macro
181 facilities. Most high level programming languages have their own
182 conditional compilation and inclusion mechanism. If all else fails,
183 try a true general text processor, such as \s-1GNU\s0 M4.
185 C preprocessors vary in some details. This manual discusses the \s-1GNU\s0 C
186 preprocessor, which provides a small superset of the features of \s-1ISO\s0
187 Standard C. In its default mode, the \s-1GNU\s0 C preprocessor does not do a
188 few things required by the standard. These are features which are
189 rarely, if ever, used, and may cause surprising changes to the meaning
190 of a program which does not expect them. To get strict \s-1ISO\s0 Standard C,
191 you should use the \fB\-std=c89\fR or \fB\-std=c99\fR options, depending
192 on which version of the standard you want. To get all the mandatory
193 diagnostics, you must also use \fB\-pedantic\fR.
195 This manual describes the behavior of the \s-1ISO\s0 preprocessor. To
196 minimize gratuitous differences, where the \s-1ISO\s0 preprocessor's
197 behavior does not conflict with traditional semantics, the
198 traditional preprocessor should behave the same way. The various
199 differences that do exist are detailed in the section \fBTraditional
202 For clarity, unless noted otherwise, references to \fB\s-1CPP\s0\fR in this
203 manual refer to \s-1GNU\s0 \s-1CPP\s0.
206 The C preprocessor expects two file names as arguments, \fIinfile\fR and
207 \&\fIoutfile\fR. The preprocessor reads \fIinfile\fR together with any
208 other files it specifies with \fB#include\fR. All the output generated
209 by the combined input files is written in \fIoutfile\fR.
211 Either \fIinfile\fR or \fIoutfile\fR may be \fB\-\fR, which as
212 \&\fIinfile\fR means to read from standard input and as \fIoutfile\fR
213 means to write to standard output. Also, if either file is omitted, it
214 means the same as if \fB\-\fR had been specified for that file.
216 Unless otherwise noted, or the option ends in \fB=\fR, all options
217 which take an argument may have that argument appear either immediately
218 after the option, or with a space between option and argument:
219 \&\fB\-Ifoo\fR and \fB\-I foo\fR have the same effect.
221 Many options have multi-letter names; therefore multiple single-letter
222 options may \fInot\fR be grouped: \fB\-dM\fR is very different from
224 .IP "\fB\-D\fR \fIname\fR" 4
226 Predefine \fIname\fR as a macro, with definition \f(CW1\fR.
227 .IP "\fB\-D\fR \fIname\fR\fB=\fR\fIdefinition\fR" 4
228 .IX Item "-D name=definition"
229 The contents of \fIdefinition\fR are tokenized and processed as if
230 they appeared during translation phase three in a \fB#define\fR
231 directive. In particular, the definition will be truncated by
232 embedded newline characters.
234 If you are invoking the preprocessor from a shell or shell-like
235 program you may need to use the shell's quoting syntax to protect
236 characters such as spaces that have a meaning in the shell syntax.
238 If you wish to define a function-like macro on the command line, write
239 its argument list with surrounding parentheses before the equals sign
240 (if any). Parentheses are meaningful to most shells, so you will need
241 to quote the option. With \fBsh\fR and \fBcsh\fR,
242 \&\fB\-D'\fR\fIname\fR\fB(\fR\fIargs...\fR\fB)=\fR\fIdefinition\fR\fB'\fR works.
244 \&\fB\-D\fR and \fB\-U\fR options are processed in the order they
245 are given on the command line. All \fB\-imacros\fR \fIfile\fR and
246 \&\fB\-include\fR \fIfile\fR options are processed after all
247 \&\fB\-D\fR and \fB\-U\fR options.
248 .IP "\fB\-U\fR \fIname\fR" 4
250 Cancel any previous definition of \fIname\fR, either built in or
251 provided with a \fB\-D\fR option.
252 .IP "\fB\-undef\fR" 4
254 Do not predefine any system-specific or GCC-specific macros. The
255 standard predefined macros remain defined.
256 .IP "\fB\-I\fR \fIdir\fR" 4
258 Add the directory \fIdir\fR to the list of directories to be searched
261 Directories named by \fB\-I\fR are searched before the standard
262 system include directories. If the directory \fIdir\fR is a standard
263 system include directory, the option is ignored to ensure that the
264 default search order for system directories and the special treatment
265 of system headers are not defeated
267 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
268 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
269 .IP "\fB\-o\fR \fIfile\fR" 4
271 Write output to \fIfile\fR. This is the same as specifying \fIfile\fR
272 as the second non-option argument to \fBcpp\fR. \fBgcc\fR has a
273 different interpretation of a second non-option argument, so you must
274 use \fB\-o\fR to specify the output file.
277 Turns on all optional warnings which are desirable for normal code.
278 At present this is \fB\-Wcomment\fR, \fB\-Wtrigraphs\fR,
279 \&\fB\-Wmultichar\fR and a warning about integer promotion causing a
280 change of sign in \f(CW\*(C`#if\*(C'\fR expressions. Note that many of the
281 preprocessor's warnings are on by default and have no options to
283 .IP "\fB\-Wcomment\fR" 4
286 .IP "\fB\-Wcomments\fR" 4
287 .IX Item "-Wcomments"
289 Warn whenever a comment-start sequence \fB/*\fR appears in a \fB/*\fR
290 comment, or whenever a backslash-newline appears in a \fB//\fR comment.
291 (Both forms have the same effect.)
292 .IP "\fB\-Wtrigraphs\fR" 4
293 .IX Item "-Wtrigraphs"
294 Most trigraphs in comments cannot affect the meaning of the program.
295 However, a trigraph that would form an escaped newline (\fB??/\fR at
296 the end of a line) can, by changing where the comment begins or ends.
297 Therefore, only trigraphs that would form escaped newlines produce
298 warnings inside a comment.
300 This option is implied by \fB\-Wall\fR. If \fB\-Wall\fR is not
301 given, this option is still enabled unless trigraphs are enabled. To
302 get trigraph conversion without warnings, but get the other
303 \&\fB\-Wall\fR warnings, use \fB\-trigraphs \-Wall \-Wno\-trigraphs\fR.
304 .IP "\fB\-Wtraditional\fR" 4
305 .IX Item "-Wtraditional"
306 Warn about certain constructs that behave differently in traditional and
307 \&\s-1ISO\s0 C. Also warn about \s-1ISO\s0 C constructs that have no traditional C
308 equivalent, and problematic constructs which should be avoided.
309 .IP "\fB\-Wimport\fR" 4
311 Warn the first time \fB#import\fR is used.
312 .IP "\fB\-Wundef\fR" 4
314 Warn whenever an identifier which is not a macro is encountered in an
315 \&\fB#if\fR directive, outside of \fBdefined\fR. Such identifiers are
317 .IP "\fB\-Wunused\-macros\fR" 4
318 .IX Item "-Wunused-macros"
319 Warn about macros defined in the main file that are unused. A macro
320 is \fIused\fR if it is expanded or tested for existence at least once.
321 The preprocessor will also warn if the macro has not been used at the
322 time it is redefined or undefined.
324 Built-in macros, macros defined on the command line, and macros
325 defined in include files are not warned about.
327 \&\fINote:\fR If a macro is actually used, but only used in skipped
328 conditional blocks, then \s-1CPP\s0 will report it as unused. To avoid the
329 warning in such a case, you might improve the scope of the macro's
330 definition by, for example, moving it into the first skipped block.
331 Alternatively, you could provide a dummy use with something like:
334 \& #if defined the_macro_causing_the_warning
337 .IP "\fB\-Wendif\-labels\fR" 4
338 .IX Item "-Wendif-labels"
339 Warn whenever an \fB#else\fR or an \fB#endif\fR are followed by text.
340 This usually happens in code of the form
350 The second and third \f(CW\*(C`FOO\*(C'\fR should be in comments, but often are not
351 in older programs. This warning is on by default.
352 .IP "\fB\-Werror\fR" 4
354 Make all warnings into hard errors. Source code which triggers warnings
356 .IP "\fB\-Wsystem\-headers\fR" 4
357 .IX Item "-Wsystem-headers"
358 Issue warnings for code in system headers. These are normally unhelpful
359 in finding bugs in your own code, therefore suppressed. If you are
360 responsible for the system library, you may want to see them.
363 Suppress all warnings, including those which \s-1GNU\s0 \s-1CPP\s0 issues by default.
364 .IP "\fB\-pedantic\fR" 4
366 Issue all the mandatory diagnostics listed in the C standard. Some of
367 them are left out by default, since they trigger frequently on harmless
369 .IP "\fB\-pedantic\-errors\fR" 4
370 .IX Item "-pedantic-errors"
371 Issue all the mandatory diagnostics, and make all mandatory diagnostics
372 into errors. This includes mandatory diagnostics that \s-1GCC\s0 issues
373 without \fB\-pedantic\fR but treats as warnings.
376 Instead of outputting the result of preprocessing, output a rule
377 suitable for \fBmake\fR describing the dependencies of the main
378 source file. The preprocessor outputs one \fBmake\fR rule containing
379 the object file name for that source file, a colon, and the names of all
380 the included files, including those coming from \fB\-include\fR or
381 \&\fB\-imacros\fR command line options.
383 Unless specified explicitly (with \fB\-MT\fR or \fB\-MQ\fR), the
384 object file name consists of the name of the source file with any
385 suffix replaced with object file suffix and with any leading directory
386 parts removed. If there are many included files then the rule is
387 split into several lines using \fB\e\fR\-newline. The rule has no
390 This option does not suppress the preprocessor's debug output, such as
391 \&\fB\-dM\fR. To avoid mixing such debug output with the dependency
392 rules you should explicitly specify the dependency output file with
393 \&\fB\-MF\fR, or use an environment variable like
394 \&\fB\s-1DEPENDENCIES_OUTPUT\s0\fR. Debug output
395 will still be sent to the regular output stream as normal.
397 Passing \fB\-M\fR to the driver implies \fB\-E\fR, and suppresses
398 warnings with an implicit \fB\-w\fR.
401 Like \fB\-M\fR but do not mention header files that are found in
402 system header directories, nor header files that are included,
403 directly or indirectly, from such a header.
405 This implies that the choice of angle brackets or double quotes in an
406 \&\fB#include\fR directive does not in itself determine whether that
407 header will appear in \fB\-MM\fR dependency output. This is a
408 slight change in semantics from \s-1GCC\s0 versions 3.0 and earlier.
409 .IP "\fB\-MF\fR \fIfile\fR" 4
411 When used with \fB\-M\fR or \fB\-MM\fR, specifies a
412 file to write the dependencies to. If no \fB\-MF\fR switch is given
413 the preprocessor sends the rules to the same place it would have sent
416 When used with the driver options \fB\-MD\fR or \fB\-MMD\fR,
417 \&\fB\-MF\fR overrides the default dependency output file.
420 In conjunction with an option such as \fB\-M\fR requesting
421 dependency generation, \fB\-MG\fR assumes missing header files are
422 generated files and adds them to the dependency list without raising
423 an error. The dependency filename is taken directly from the
424 \&\f(CW\*(C`#include\*(C'\fR directive without prepending any path. \fB\-MG\fR
425 also suppresses preprocessed output, as a missing header file renders
428 This feature is used in automatic updating of makefiles.
431 This option instructs \s-1CPP\s0 to add a phony target for each dependency
432 other than the main file, causing each to depend on nothing. These
433 dummy rules work around errors \fBmake\fR gives if you remove header
434 files without updating the \fIMakefile\fR to match.
436 This is typical output:
439 \& test.o: test.c test.h
443 .IP "\fB\-MT\fR \fItarget\fR" 4
444 .IX Item "-MT target"
445 Change the target of the rule emitted by dependency generation. By
446 default \s-1CPP\s0 takes the name of the main input file, deletes any
447 directory components and any file suffix such as \fB.c\fR, and
448 appends the platform's usual object suffix. The result is the target.
450 An \fB\-MT\fR option will set the target to be exactly the string you
451 specify. If you want multiple targets, you can specify them as a single
452 argument to \fB\-MT\fR, or use multiple \fB\-MT\fR options.
454 For example, \fB\-MT\ '$(objpfx)foo.o'\fR might give
457 \& $(objpfx)foo.o: foo.c
459 .IP "\fB\-MQ\fR \fItarget\fR" 4
460 .IX Item "-MQ target"
461 Same as \fB\-MT\fR, but it quotes any characters which are special to
462 Make. \fB\-MQ\ '$(objpfx)foo.o'\fR gives
465 \& $$(objpfx)foo.o: foo.c
468 The default target is automatically quoted, as if it were given with
472 \&\fB\-MD\fR is equivalent to \fB\-M \-MF\fR \fIfile\fR, except that
473 \&\fB\-E\fR is not implied. The driver determines \fIfile\fR based on
474 whether an \fB\-o\fR option is given. If it is, the driver uses its
475 argument but with a suffix of \fI.d\fR, otherwise it takes the name
476 of the input file, removes any directory components and suffix, and
477 applies a \fI.d\fR suffix.
479 If \fB\-MD\fR is used in conjunction with \fB\-E\fR, any
480 \&\fB\-o\fR switch is understood to specify the dependency output file, but if used without \fB\-E\fR, each \fB\-o\fR
481 is understood to specify a target object file.
483 Since \fB\-E\fR is not implied, \fB\-MD\fR can be used to generate
484 a dependency output file as a side-effect of the compilation process.
487 Like \fB\-MD\fR except mention only user header files, not system
492 .IP "\fB\-x c++\fR" 4
494 .IP "\fB\-x objective-c\fR" 4
495 .IX Item "-x objective-c"
496 .IP "\fB\-x assembler-with-cpp\fR" 4
497 .IX Item "-x assembler-with-cpp"
499 Specify the source language: C, \*(C+, Objective-C, or assembly. This has
500 nothing to do with standards conformance or extensions; it merely
501 selects which base syntax to expect. If you give none of these options,
502 cpp will deduce the language from the extension of the source file:
503 \&\fB.c\fR, \fB.cc\fR, \fB.m\fR, or \fB.S\fR. Some other common
504 extensions for \*(C+ and assembly are also recognized. If cpp does not
505 recognize the extension, it will treat the file as C; this is the most
508 \&\fINote:\fR Previous versions of cpp accepted a \fB\-lang\fR option
509 which selected both the language and the standards conformance level.
510 This option has been removed, because it conflicts with the \fB\-l\fR
512 .IP "\fB\-std=\fR\fIstandard\fR" 4
513 .IX Item "-std=standard"
518 Specify the standard to which the code should conform. Currently \s-1CPP\s0
519 knows about C and \*(C+ standards; others may be added in the future.
524 .ie n .IP """iso9899:1990""" 4
525 .el .IP "\f(CWiso9899:1990\fR" 4
526 .IX Item "iso9899:1990"
528 .ie n .IP """c89""" 4
529 .el .IP "\f(CWc89\fR" 4
532 The \s-1ISO\s0 C standard from 1990. \fBc89\fR is the customary shorthand for
533 this version of the standard.
535 The \fB\-ansi\fR option is equivalent to \fB\-std=c89\fR.
536 .ie n .IP """iso9899:199409""" 4
537 .el .IP "\f(CWiso9899:199409\fR" 4
538 .IX Item "iso9899:199409"
539 The 1990 C standard, as amended in 1994.
540 .ie n .IP """iso9899:1999""" 4
541 .el .IP "\f(CWiso9899:1999\fR" 4
542 .IX Item "iso9899:1999"
544 .ie n .IP """c99""" 4
545 .el .IP "\f(CWc99\fR" 4
547 .ie n .IP """iso9899:199x""" 4
548 .el .IP "\f(CWiso9899:199x\fR" 4
549 .IX Item "iso9899:199x"
550 .ie n .IP """c9x""" 4
551 .el .IP "\f(CWc9x\fR" 4
554 The revised \s-1ISO\s0 C standard, published in December 1999. Before
555 publication, this was known as C9X.
556 .ie n .IP """gnu89""" 4
557 .el .IP "\f(CWgnu89\fR" 4
559 The 1990 C standard plus \s-1GNU\s0 extensions. This is the default.
560 .ie n .IP """gnu99""" 4
561 .el .IP "\f(CWgnu99\fR" 4
564 .ie n .IP """gnu9x""" 4
565 .el .IP "\f(CWgnu9x\fR" 4
568 The 1999 C standard plus \s-1GNU\s0 extensions.
569 .ie n .IP """c++98""" 4
570 .el .IP "\f(CWc++98\fR" 4
572 The 1998 \s-1ISO\s0 \*(C+ standard plus amendments.
573 .ie n .IP """gnu++98""" 4
574 .el .IP "\f(CWgnu++98\fR" 4
576 The same as \fB\-std=c++98\fR plus \s-1GNU\s0 extensions. This is the
577 default for \*(C+ code.
583 Split the include path. Any directories specified with \fB\-I\fR
584 options before \fB\-I\-\fR are searched only for headers requested with
585 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
586 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR. If additional directories are
587 specified with \fB\-I\fR options after the \fB\-I\-\fR, those
588 directories are searched for all \fB#include\fR directives.
590 In addition, \fB\-I\-\fR inhibits the use of the directory of the current
591 file directory as the first search directory for \f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR.
593 This option has been deprecated.
594 .IP "\fB\-nostdinc\fR" 4
596 Do not search the standard system directories for header files.
597 Only the directories you have specified with \fB\-I\fR options
598 (and the directory of the current file, if appropriate) are searched.
599 .IP "\fB\-nostdinc++\fR" 4
600 .IX Item "-nostdinc++"
601 Do not search for header files in the \*(C+\-specific standard directories,
602 but do still search the other standard directories. (This option is
603 used when building the \*(C+ library.)
604 .IP "\fB\-include\fR \fIfile\fR" 4
605 .IX Item "-include file"
606 Process \fIfile\fR as if \f(CW\*(C`#include "file"\*(C'\fR appeared as the first
607 line of the primary source file. However, the first directory searched
608 for \fIfile\fR is the preprocessor's working directory \fIinstead of\fR
609 the directory containing the main source file. If not found there, it
610 is searched for in the remainder of the \f(CW\*(C`#include "..."\*(C'\fR search
613 If multiple \fB\-include\fR options are given, the files are included
614 in the order they appear on the command line.
615 .IP "\fB\-imacros\fR \fIfile\fR" 4
616 .IX Item "-imacros file"
617 Exactly like \fB\-include\fR, except that any output produced by
618 scanning \fIfile\fR is thrown away. Macros it defines remain defined.
619 This allows you to acquire all the macros from a header without also
620 processing its declarations.
622 All files specified by \fB\-imacros\fR are processed before all files
623 specified by \fB\-include\fR.
624 .IP "\fB\-idirafter\fR \fIdir\fR" 4
625 .IX Item "-idirafter dir"
626 Search \fIdir\fR for header files, but do it \fIafter\fR all
627 directories specified with \fB\-I\fR and the standard system directories
628 have been exhausted. \fIdir\fR is treated as a system include directory.
629 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
630 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
631 .IP "\fB\-iprefix\fR \fIprefix\fR" 4
632 .IX Item "-iprefix prefix"
633 Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR
634 options. If the prefix represents a directory, you should include the
636 .IP "\fB\-iwithprefix\fR \fIdir\fR" 4
637 .IX Item "-iwithprefix dir"
639 .IP "\fB\-iwithprefixbefore\fR \fIdir\fR" 4
640 .IX Item "-iwithprefixbefore dir"
642 Append \fIdir\fR to the prefix specified previously with
643 \&\fB\-iprefix\fR, and add the resulting directory to the include search
644 path. \fB\-iwithprefixbefore\fR puts it in the same place \fB\-I\fR
645 would; \fB\-iwithprefix\fR puts it where \fB\-idirafter\fR would.
646 .IP "\fB\-isysroot\fR \fIdir\fR" 4
647 .IX Item "-isysroot dir"
648 This option is like the \fB\-\-sysroot\fR option, but applies only to
649 header files. See the \fB\-\-sysroot\fR option for more information.
650 .IP "\fB\-imultilib\fR \fIdir\fR" 4
651 .IX Item "-imultilib dir"
652 Use \fIdir\fR as a subdirectory of the directory containing
653 target-specific \*(C+ headers.
654 .IP "\fB\-isystem\fR \fIdir\fR" 4
655 .IX Item "-isystem dir"
656 Search \fIdir\fR for header files, after all directories specified by
657 \&\fB\-I\fR but before the standard system directories. Mark it
658 as a system directory, so that it gets the same special treatment as
659 is applied to the standard system directories.
661 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
662 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
663 .IP "\fB\-iquote\fR \fIdir\fR" 4
664 .IX Item "-iquote dir"
665 Search \fIdir\fR only for header files requested with
666 \&\f(CW\*(C`#include\ "\f(CIfile\f(CW"\*(C'\fR; they are not searched for
667 \&\f(CW\*(C`#include\ <\f(CIfile\f(CW>\*(C'\fR, before all directories specified by
668 \&\fB\-I\fR and before the standard system directories.
670 If \fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced
671 by the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR.
672 .IP "\fB\-fdirectives\-only\fR" 4
673 .IX Item "-fdirectives-only"
674 When preprocessing, handle directives, but do not expand macros.
676 The option's behavior depends on the \fB\-E\fR and \fB\-fpreprocessed\fR
679 With \fB\-E\fR, preprocessing is limited to the handling of directives
680 such as \f(CW\*(C`#define\*(C'\fR, \f(CW\*(C`#ifdef\*(C'\fR, and \f(CW\*(C`#error\*(C'\fR. Other
681 preprocessor operations, such as macro expansion and trigraph
682 conversion are not performed. In addition, the \fB\-dD\fR option is
685 With \fB\-fpreprocessed\fR, predefinition of command line and most
686 builtin macros is disabled. Macros such as \f(CW\*(C`_\|_LINE_\|_\*(C'\fR, which are
687 contextually dependent, are handled normally. This enables compilation of
688 files previously preprocessed with \f(CW\*(C`\-E \-fdirectives\-only\*(C'\fR.
690 With both \fB\-E\fR and \fB\-fpreprocessed\fR, the rules for
691 \&\fB\-fpreprocessed\fR take precedence. This enables full preprocessing of
692 files previously preprocessed with \f(CW\*(C`\-E \-fdirectives\-only\*(C'\fR.
693 .IP "\fB\-fdollars\-in\-identifiers\fR" 4
694 .IX Item "-fdollars-in-identifiers"
695 Accept \fB$\fR in identifiers.
696 .IP "\fB\-fextended\-identifiers\fR" 4
697 .IX Item "-fextended-identifiers"
698 Accept universal character names in identifiers. This option is
699 experimental; in a future version of \s-1GCC\s0, it will be enabled by
700 default for C99 and \*(C+.
701 .IP "\fB\-fpreprocessed\fR" 4
702 .IX Item "-fpreprocessed"
703 Indicate to the preprocessor that the input file has already been
704 preprocessed. This suppresses things like macro expansion, trigraph
705 conversion, escaped newline splicing, and processing of most directives.
706 The preprocessor still recognizes and removes comments, so that you can
707 pass a file preprocessed with \fB\-C\fR to the compiler without
708 problems. In this mode the integrated preprocessor is little more than
709 a tokenizer for the front ends.
711 \&\fB\-fpreprocessed\fR is implicit if the input file has one of the
712 extensions \fB.i\fR, \fB.ii\fR or \fB.mi\fR. These are the
713 extensions that \s-1GCC\s0 uses for preprocessed files created by
714 \&\fB\-save\-temps\fR.
715 .IP "\fB\-ftabstop=\fR\fIwidth\fR" 4
716 .IX Item "-ftabstop=width"
717 Set the distance between tab stops. This helps the preprocessor report
718 correct column numbers in warnings or errors, even if tabs appear on the
719 line. If the value is less than 1 or greater than 100, the option is
720 ignored. The default is 8.
721 .IP "\fB\-fexec\-charset=\fR\fIcharset\fR" 4
722 .IX Item "-fexec-charset=charset"
723 Set the execution character set, used for string and character
724 constants. The default is \s-1UTF\-8\s0. \fIcharset\fR can be any encoding
725 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
726 .IP "\fB\-fwide\-exec\-charset=\fR\fIcharset\fR" 4
727 .IX Item "-fwide-exec-charset=charset"
728 Set the wide execution character set, used for wide string and
729 character constants. The default is \s-1UTF\-32\s0 or \s-1UTF\-16\s0, whichever
730 corresponds to the width of \f(CW\*(C`wchar_t\*(C'\fR. As with
731 \&\fB\-fexec\-charset\fR, \fIcharset\fR can be any encoding supported
732 by the system's \f(CW\*(C`iconv\*(C'\fR library routine; however, you will have
733 problems with encodings that do not fit exactly in \f(CW\*(C`wchar_t\*(C'\fR.
734 .IP "\fB\-finput\-charset=\fR\fIcharset\fR" 4
735 .IX Item "-finput-charset=charset"
736 Set the input character set, used for translation from the character
737 set of the input file to the source character set used by \s-1GCC\s0. If the
738 locale does not specify, or \s-1GCC\s0 cannot get this information from the
739 locale, the default is \s-1UTF\-8\s0. This can be overridden by either the locale
740 or this command line option. Currently the command line option takes
741 precedence if there's a conflict. \fIcharset\fR can be any encoding
742 supported by the system's \f(CW\*(C`iconv\*(C'\fR library routine.
743 .IP "\fB\-fworking\-directory\fR" 4
744 .IX Item "-fworking-directory"
745 Enable generation of linemarkers in the preprocessor output that will
746 let the compiler know the current working directory at the time of
747 preprocessing. When this option is enabled, the preprocessor will
748 emit, after the initial linemarker, a second linemarker with the
749 current working directory followed by two slashes. \s-1GCC\s0 will use this
750 directory, when it's present in the preprocessed input, as the
751 directory emitted as the current working directory in some debugging
752 information formats. This option is implicitly enabled if debugging
753 information is enabled, but this can be inhibited with the negated
754 form \fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is
755 present in the command line, this option has no effect, since no
756 \&\f(CW\*(C`#line\*(C'\fR directives are emitted whatsoever.
757 .IP "\fB\-fno\-show\-column\fR" 4
758 .IX Item "-fno-show-column"
759 Do not print column numbers in diagnostics. This may be necessary if
760 diagnostics are being scanned by a program that does not understand the
761 column numbers, such as \fBdejagnu\fR.
762 .IP "\fB\-A\fR \fIpredicate\fR\fB=\fR\fIanswer\fR" 4
763 .IX Item "-A predicate=answer"
764 Make an assertion with the predicate \fIpredicate\fR and answer
765 \&\fIanswer\fR. This form is preferred to the older form \fB\-A\fR
766 \&\fIpredicate\fR\fB(\fR\fIanswer\fR\fB)\fR, which is still supported, because
767 it does not use shell special characters.
768 .IP "\fB\-A \-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4
769 .IX Item "-A -predicate=answer"
770 Cancel an assertion with the predicate \fIpredicate\fR and answer
772 .IP "\fB\-dCHARS\fR" 4
774 \&\fI\s-1CHARS\s0\fR is a sequence of one or more of the following characters,
775 and must not be preceded by a space. Other characters are interpreted
776 by the compiler proper, or reserved for future versions of \s-1GCC\s0, and so
777 are silently ignored. If you specify characters whose behavior
778 conflicts, the result is undefined.
782 Instead of the normal output, generate a list of \fB#define\fR
783 directives for all the macros defined during the execution of the
784 preprocessor, including predefined macros. This gives you a way of
785 finding out what is predefined in your version of the preprocessor.
786 Assuming you have no file \fIfoo.h\fR, the command
789 \& touch foo.h; cpp \-dM foo.h
792 will show all the predefined macros.
794 If you use \fB\-dM\fR without the \fB\-E\fR option, \fB\-dM\fR is
795 interpreted as a synonym for \fB\-fdump\-rtl\-mach\fR.
798 Like \fBM\fR except in two respects: it does \fInot\fR include the
799 predefined macros, and it outputs \fIboth\fR the \fB#define\fR
800 directives and the result of preprocessing. Both kinds of output go to
801 the standard output file.
804 Like \fBD\fR, but emit only the macro names, not their expansions.
807 Output \fB#include\fR directives in addition to the result of
814 Inhibit generation of linemarkers in the output from the preprocessor.
815 This might be useful when running the preprocessor on something that is
816 not C code, and will be sent to a program which might be confused by the
820 Do not discard comments. All comments are passed through to the output
821 file, except for comments in processed directives, which are deleted
822 along with the directive.
824 You should be prepared for side effects when using \fB\-C\fR; it
825 causes the preprocessor to treat comments as tokens in their own right.
826 For example, comments appearing at the start of what would be a
827 directive line have the effect of turning that line into an ordinary
828 source line, since the first token on the line is no longer a \fB#\fR.
831 Do not discard comments, including during macro expansion. This is
832 like \fB\-C\fR, except that comments contained within macros are
833 also passed through to the output file where the macro is expanded.
835 In addition to the side-effects of the \fB\-C\fR option, the
836 \&\fB\-CC\fR option causes all \*(C+\-style comments inside a macro
837 to be converted to C\-style comments. This is to prevent later use
838 of that macro from inadvertently commenting out the remainder of
841 The \fB\-CC\fR option is generally used to support lint comments.
842 .IP "\fB\-traditional\-cpp\fR" 4
843 .IX Item "-traditional-cpp"
844 Try to imitate the behavior of old-fashioned C preprocessors, as
845 opposed to \s-1ISO\s0 C preprocessors.
846 .IP "\fB\-trigraphs\fR" 4
847 .IX Item "-trigraphs"
848 Process trigraph sequences.
849 .IP "\fB\-remap\fR" 4
851 Enable special code to work around file systems which only permit very
852 short file names, such as MS-DOS.
853 .IP "\fB\-\-help\fR" 4
856 .IP "\fB\-\-target\-help\fR" 4
857 .IX Item "--target-help"
859 Print text describing all the command line options instead of
860 preprocessing anything.
863 Verbose mode. Print out \s-1GNU\s0 \s-1CPP\s0's version number at the beginning of
864 execution, and report the final form of the include path.
867 Print the name of each header file used, in addition to other normal
868 activities. Each name is indented to show how deep in the
869 \&\fB#include\fR stack it is. Precompiled header files are also
870 printed, even if they are found to be invalid; an invalid precompiled
871 header file is printed with \fB...x\fR and a valid one with \fB...!\fR .
872 .IP "\fB\-version\fR" 4
875 .IP "\fB\-\-version\fR" 4
878 Print out \s-1GNU\s0 \s-1CPP\s0's version number. With one dash, proceed to
879 preprocess as normal. With two dashes, exit immediately.
881 .IX Header "ENVIRONMENT"
882 This section describes the environment variables that affect how \s-1CPP\s0
883 operates. You can use them to specify directories or prefixes to use
884 when searching for include files, or to control dependency output.
886 Note that you can also specify places to search using options such as
887 \&\fB\-I\fR, and control dependency output with options like
888 \&\fB\-M\fR. These take precedence over
889 environment variables, which in turn take precedence over the
890 configuration of \s-1GCC\s0.
891 .IP "\fB\s-1CPATH\s0\fR" 4
894 .IP "\fBC_INCLUDE_PATH\fR" 4
895 .IX Item "C_INCLUDE_PATH"
896 .IP "\fB\s-1CPLUS_INCLUDE_PATH\s0\fR" 4
897 .IX Item "CPLUS_INCLUDE_PATH"
898 .IP "\fB\s-1OBJC_INCLUDE_PATH\s0\fR" 4
899 .IX Item "OBJC_INCLUDE_PATH"
901 Each variable's value is a list of directories separated by a special
902 character, much like \fB\s-1PATH\s0\fR, in which to look for header files.
903 The special character, \f(CW\*(C`PATH_SEPARATOR\*(C'\fR, is target-dependent and
904 determined at \s-1GCC\s0 build time. For Microsoft Windows-based targets it is a
905 semicolon, and for almost all other targets it is a colon.
907 \&\fB\s-1CPATH\s0\fR specifies a list of directories to be searched as if
908 specified with \fB\-I\fR, but after any paths given with \fB\-I\fR
909 options on the command line. This environment variable is used
910 regardless of which language is being preprocessed.
912 The remaining environment variables apply only when preprocessing the
913 particular language indicated. Each specifies a list of directories
914 to be searched as if specified with \fB\-isystem\fR, but after any
915 paths given with \fB\-isystem\fR options on the command line.
917 In all these variables, an empty element instructs the compiler to
918 search its current working directory. Empty elements can appear at the
919 beginning or end of a path. For instance, if the value of
920 \&\fB\s-1CPATH\s0\fR is \f(CW\*(C`:/special/include\*(C'\fR, that has the same
921 effect as \fB\-I.\ \-I/special/include\fR.
922 .IP "\fB\s-1DEPENDENCIES_OUTPUT\s0\fR" 4
923 .IX Item "DEPENDENCIES_OUTPUT"
924 If this variable is set, its value specifies how to output
925 dependencies for Make based on the non-system header files processed
926 by the compiler. System header files are ignored in the dependency
929 The value of \fB\s-1DEPENDENCIES_OUTPUT\s0\fR can be just a file name, in
930 which case the Make rules are written to that file, guessing the target
931 name from the source file name. Or the value can have the form
932 \&\fIfile\fR\fB \fR\fItarget\fR, in which case the rules are written to
933 file \fIfile\fR using \fItarget\fR as the target name.
935 In other words, this environment variable is equivalent to combining
936 the options \fB\-MM\fR and \fB\-MF\fR,
937 with an optional \fB\-MT\fR switch too.
938 .IP "\fB\s-1SUNPRO_DEPENDENCIES\s0\fR" 4
939 .IX Item "SUNPRO_DEPENDENCIES"
940 This variable is the same as \fB\s-1DEPENDENCIES_OUTPUT\s0\fR (see above),
941 except that system header files are not ignored, so it implies
942 \&\fB\-M\fR rather than \fB\-MM\fR. However, the dependence on the
943 main input file is omitted.
945 .IX Header "SEE ALSO"
946 \&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7),
947 \&\fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), and the Info entries for \fIcpp\fR, \fIgcc\fR, and
950 .IX Header "COPYRIGHT"
951 Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996,
952 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007
953 Free Software Foundation, Inc.
955 Permission is granted to copy, distribute and/or modify this document
956 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.1 or
957 any later version published by the Free Software Foundation. A copy of
958 the license is included in the
959 man page \fIgfdl\fR\|(7).
960 This manual contains no Invariant Sections. The Front-Cover Texts are
961 (a) (see below), and the Back-Cover Texts are (b) (see below).
963 (a) The \s-1FSF\s0's Front-Cover Text is:
969 (b) The \s-1FSF\s0's Back-Cover Text is:
972 \& You have freedom to copy and modify this GNU Manual, like GNU
973 \& software. Copies published by the Free Software Foundation raise
974 \& funds for GNU development.
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