--- /dev/null
+This is gprof.info, produced by makeinfo version 4.8 from gprof.texi.
+
+START-INFO-DIR-ENTRY
+* gprof: (gprof). Profiling your program's execution
+END-INFO-DIR-ENTRY
+
+ This file documents the gprof profiler of the GNU system.
+
+ Copyright (C) 1988, 92, 97, 98, 99, 2000, 2001, 2003, 2007 Free
+Software Foundation, Inc.
+
+ Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
+Texts. A copy of the license is included in the section entitled "GNU
+Free Documentation License".
+
+\1f
+File: gprof.info, Node: Top, Next: Introduction, Up: (dir)
+
+Profiling a Program: Where Does It Spend Its Time?
+**************************************************
+
+This manual describes the GNU profiler, `gprof', and how you can use it
+to determine which parts of a program are taking most of the execution
+time. We assume that you know how to write, compile, and execute
+programs. GNU `gprof' was written by Jay Fenlason.
+
+ This manual is for `gprof' (GNU Binutils) version 2.18.90.
+
+ This document is distributed under the terms of the GNU Free
+Documentation License. A copy of the license is included in the
+section entitled "GNU Free Documentation License".
+
+* Menu:
+
+* Introduction:: What profiling means, and why it is useful.
+
+* Compiling:: How to compile your program for profiling.
+* Executing:: Executing your program to generate profile data
+* Invoking:: How to run `gprof', and its options
+
+* Output:: Interpreting `gprof''s output
+
+* Inaccuracy:: Potential problems you should be aware of
+* How do I?:: Answers to common questions
+* Incompatibilities:: (between GNU `gprof' and Unix `gprof'.)
+* Details:: Details of how profiling is done
+* GNU Free Documentation License:: GNU Free Documentation License
+
+\1f
+File: gprof.info, Node: Introduction, Next: Compiling, Prev: Top, Up: Top
+
+1 Introduction to Profiling
+***************************
+
+Profiling allows you to learn where your program spent its time and
+which functions called which other functions while it was executing.
+This information can show you which pieces of your program are slower
+than you expected, and might be candidates for rewriting to make your
+program execute faster. It can also tell you which functions are being
+called more or less often than you expected. This may help you spot
+bugs that had otherwise been unnoticed.
+
+ Since the profiler uses information collected during the actual
+execution of your program, it can be used on programs that are too
+large or too complex to analyze by reading the source. However, how
+your program is run will affect the information that shows up in the
+profile data. If you don't use some feature of your program while it
+is being profiled, no profile information will be generated for that
+feature.
+
+ Profiling has several steps:
+
+ * You must compile and link your program with profiling enabled.
+ *Note Compiling a Program for Profiling: Compiling.
+
+ * You must execute your program to generate a profile data file.
+ *Note Executing the Program: Executing.
+
+ * You must run `gprof' to analyze the profile data. *Note `gprof'
+ Command Summary: Invoking.
+
+ The next three chapters explain these steps in greater detail.
+
+ Several forms of output are available from the analysis.
+
+ The "flat profile" shows how much time your program spent in each
+function, and how many times that function was called. If you simply
+want to know which functions burn most of the cycles, it is stated
+concisely here. *Note The Flat Profile: Flat Profile.
+
+ The "call graph" shows, for each function, which functions called
+it, which other functions it called, and how many times. There is also
+an estimate of how much time was spent in the subroutines of each
+function. This can suggest places where you might try to eliminate
+function calls that use a lot of time. *Note The Call Graph: Call
+Graph.
+
+ The "annotated source" listing is a copy of the program's source
+code, labeled with the number of times each line of the program was
+executed. *Note The Annotated Source Listing: Annotated Source.
+
+ To better understand how profiling works, you may wish to read a
+description of its implementation. *Note Implementation of Profiling:
+Implementation.
+
+\1f
+File: gprof.info, Node: Compiling, Next: Executing, Prev: Introduction, Up: Top
+
+2 Compiling a Program for Profiling
+***********************************
+
+The first step in generating profile information for your program is to
+compile and link it with profiling enabled.
+
+ To compile a source file for profiling, specify the `-pg' option when
+you run the compiler. (This is in addition to the options you normally
+use.)
+
+ To link the program for profiling, if you use a compiler such as `cc'
+to do the linking, simply specify `-pg' in addition to your usual
+options. The same option, `-pg', alters either compilation or linking
+to do what is necessary for profiling. Here are examples:
+
+ cc -g -c myprog.c utils.c -pg
+ cc -o myprog myprog.o utils.o -pg
+
+ The `-pg' option also works with a command that both compiles and
+links:
+
+ cc -o myprog myprog.c utils.c -g -pg
+
+ Note: The `-pg' option must be part of your compilation options as
+well as your link options. If it is not then no call-graph data will
+be gathered and when you run `gprof' you will get an error message like
+this:
+
+ gprof: gmon.out file is missing call-graph data
+
+ If you add the `-Q' switch to suppress the printing of the call
+graph data you will still be able to see the time samples:
+
+ Flat profile:
+
+ Each sample counts as 0.01 seconds.
+ % cumulative self self total
+ time seconds seconds calls Ts/call Ts/call name
+ 44.12 0.07 0.07 zazLoop
+ 35.29 0.14 0.06 main
+ 20.59 0.17 0.04 bazMillion
+
+ If you run the linker `ld' directly instead of through a compiler
+such as `cc', you may have to specify a profiling startup file
+`gcrt0.o' as the first input file instead of the usual startup file
+`crt0.o'. In addition, you would probably want to specify the
+profiling C library, `libc_p.a', by writing `-lc_p' instead of the
+usual `-lc'. This is not absolutely necessary, but doing this gives
+you number-of-calls information for standard library functions such as
+`read' and `open'. For example:
+
+ ld -o myprog /lib/gcrt0.o myprog.o utils.o -lc_p
+
+ If you compile only some of the modules of the program with `-pg',
+you can still profile the program, but you won't get complete
+information about the modules that were compiled without `-pg'. The
+only information you get for the functions in those modules is the
+total time spent in them; there is no record of how many times they
+were called, or from where. This will not affect the flat profile
+(except that the `calls' field for the functions will be blank), but
+will greatly reduce the usefulness of the call graph.
+
+ If you wish to perform line-by-line profiling you should use the
+`gcov' tool instead of `gprof'. See that tool's manual or info pages
+for more details of how to do this.
+
+ Note, older versions of `gcc' produce line-by-line profiling
+information that works with `gprof' rather than `gcov' so there is
+still support for displaying this kind of information in `gprof'. *Note
+Line-by-line Profiling: Line-by-line.
+
+ It also worth noting that `gcc' implements a
+`-finstrument-functions' command line option which will insert calls to
+special user supplied instrumentation routines at the entry and exit of
+every function in their program. This can be used to implement an
+alternative profiling scheme.
+
+\1f
+File: gprof.info, Node: Executing, Next: Invoking, Prev: Compiling, Up: Top
+
+3 Executing the Program
+***********************
+
+Once the program is compiled for profiling, you must run it in order to
+generate the information that `gprof' needs. Simply run the program as
+usual, using the normal arguments, file names, etc. The program should
+run normally, producing the same output as usual. It will, however, run
+somewhat slower than normal because of the time spent collecting and
+writing the profile data.
+
+ The way you run the program--the arguments and input that you give
+it--may have a dramatic effect on what the profile information shows.
+The profile data will describe the parts of the program that were
+activated for the particular input you use. For example, if the first
+command you give to your program is to quit, the profile data will show
+the time used in initialization and in cleanup, but not much else.
+
+ Your program will write the profile data into a file called
+`gmon.out' just before exiting. If there is already a file called
+`gmon.out', its contents are overwritten. There is currently no way to
+tell the program to write the profile data under a different name, but
+you can rename the file afterwards if you are concerned that it may be
+overwritten.
+
+ In order to write the `gmon.out' file properly, your program must
+exit normally: by returning from `main' or by calling `exit'. Calling
+the low-level function `_exit' does not write the profile data, and
+neither does abnormal termination due to an unhandled signal.
+
+ The `gmon.out' file is written in the program's _current working
+directory_ at the time it exits. This means that if your program calls
+`chdir', the `gmon.out' file will be left in the last directory your
+program `chdir''d to. If you don't have permission to write in this
+directory, the file is not written, and you will get an error message.
+
+ Older versions of the GNU profiling library may also write a file
+called `bb.out'. This file, if present, contains an human-readable
+listing of the basic-block execution counts. Unfortunately, the
+appearance of a human-readable `bb.out' means the basic-block counts
+didn't get written into `gmon.out'. The Perl script `bbconv.pl',
+included with the `gprof' source distribution, will convert a `bb.out'
+file into a format readable by `gprof'. Invoke it like this:
+
+ bbconv.pl < bb.out > BH-DATA
+
+ This translates the information in `bb.out' into a form that `gprof'
+can understand. But you still need to tell `gprof' about the existence
+of this translated information. To do that, include BB-DATA on the
+`gprof' command line, _along with `gmon.out'_, like this:
+
+ gprof OPTIONS EXECUTABLE-FILE gmon.out BB-DATA [YET-MORE-PROFILE-DATA-FILES...] [> OUTFILE]
+
+\1f
+File: gprof.info, Node: Invoking, Next: Output, Prev: Executing, Up: Top
+
+4 `gprof' Command Summary
+*************************
+
+After you have a profile data file `gmon.out', you can run `gprof' to
+interpret the information in it. The `gprof' program prints a flat
+profile and a call graph on standard output. Typically you would
+redirect the output of `gprof' into a file with `>'.
+
+ You run `gprof' like this:
+
+ gprof OPTIONS [EXECUTABLE-FILE [PROFILE-DATA-FILES...]] [> OUTFILE]
+
+Here square-brackets indicate optional arguments.
+
+ If you omit the executable file name, the file `a.out' is used. If
+you give no profile data file name, the file `gmon.out' is used. If
+any file is not in the proper format, or if the profile data file does
+not appear to belong to the executable file, an error message is
+printed.
+
+ You can give more than one profile data file by entering all their
+names after the executable file name; then the statistics in all the
+data files are summed together.
+
+ The order of these options does not matter.
+
+* Menu:
+
+* Output Options:: Controlling `gprof''s output style
+* Analysis Options:: Controlling how `gprof' analyzes its data
+* Miscellaneous Options::
+* Deprecated Options:: Options you no longer need to use, but which
+ have been retained for compatibility
+* Symspecs:: Specifying functions to include or exclude
+
+\1f
+File: gprof.info, Node: Output Options, Next: Analysis Options, Up: Invoking
+
+4.1 Output Options
+==================
+
+These options specify which of several output formats `gprof' should
+produce.
+
+ Many of these options take an optional "symspec" to specify
+functions to be included or excluded. These options can be specified
+multiple times, with different symspecs, to include or exclude sets of
+symbols. *Note Symspecs: Symspecs.
+
+ Specifying any of these options overrides the default (`-p -q'),
+which prints a flat profile and call graph analysis for all functions.
+
+`-A[SYMSPEC]'
+`--annotated-source[=SYMSPEC]'
+ The `-A' option causes `gprof' to print annotated source code. If
+ SYMSPEC is specified, print output only for matching symbols.
+ *Note The Annotated Source Listing: Annotated Source.
+
+`-b'
+`--brief'
+ If the `-b' option is given, `gprof' doesn't print the verbose
+ blurbs that try to explain the meaning of all of the fields in the
+ tables. This is useful if you intend to print out the output, or
+ are tired of seeing the blurbs.
+
+`-C[SYMSPEC]'
+`--exec-counts[=SYMSPEC]'
+ The `-C' option causes `gprof' to print a tally of functions and
+ the number of times each was called. If SYMSPEC is specified,
+ print tally only for matching symbols.
+
+ If the profile data file contains basic-block count records,
+ specifying the `-l' option, along with `-C', will cause basic-block
+ execution counts to be tallied and displayed.
+
+`-i'
+`--file-info'
+ The `-i' option causes `gprof' to display summary information
+ about the profile data file(s) and then exit. The number of
+ histogram, call graph, and basic-block count records is displayed.
+
+`-I DIRS'
+`--directory-path=DIRS'
+ The `-I' option specifies a list of search directories in which to
+ find source files. Environment variable GPROF_PATH can also be
+ used to convey this information. Used mostly for annotated source
+ output.
+
+`-J[SYMSPEC]'
+`--no-annotated-source[=SYMSPEC]'
+ The `-J' option causes `gprof' not to print annotated source code.
+ If SYMSPEC is specified, `gprof' prints annotated source, but
+ excludes matching symbols.
+
+`-L'
+`--print-path'
+ Normally, source filenames are printed with the path component
+ suppressed. The `-L' option causes `gprof' to print the full
+ pathname of source filenames, which is determined from symbolic
+ debugging information in the image file and is relative to the
+ directory in which the compiler was invoked.
+
+`-p[SYMSPEC]'
+`--flat-profile[=SYMSPEC]'
+ The `-p' option causes `gprof' to print a flat profile. If
+ SYMSPEC is specified, print flat profile only for matching symbols.
+ *Note The Flat Profile: Flat Profile.
+
+`-P[SYMSPEC]'
+`--no-flat-profile[=SYMSPEC]'
+ The `-P' option causes `gprof' to suppress printing a flat profile.
+ If SYMSPEC is specified, `gprof' prints a flat profile, but
+ excludes matching symbols.
+
+`-q[SYMSPEC]'
+`--graph[=SYMSPEC]'
+ The `-q' option causes `gprof' to print the call graph analysis.
+ If SYMSPEC is specified, print call graph only for matching symbols
+ and their children. *Note The Call Graph: Call Graph.
+
+`-Q[SYMSPEC]'
+`--no-graph[=SYMSPEC]'
+ The `-Q' option causes `gprof' to suppress printing the call graph.
+ If SYMSPEC is specified, `gprof' prints a call graph, but excludes
+ matching symbols.
+
+`-t'
+`--table-length=NUM'
+ The `-t' option causes the NUM most active source lines in each
+ source file to be listed when source annotation is enabled. The
+ default is 10.
+
+`-y'
+`--separate-files'
+ This option affects annotated source output only. Normally,
+ `gprof' prints annotated source files to standard-output. If this
+ option is specified, annotated source for a file named
+ `path/FILENAME' is generated in the file `FILENAME-ann'. If the
+ underlying file system would truncate `FILENAME-ann' so that it
+ overwrites the original `FILENAME', `gprof' generates annotated
+ source in the file `FILENAME.ann' instead (if the original file
+ name has an extension, that extension is _replaced_ with `.ann').
+
+`-Z[SYMSPEC]'
+`--no-exec-counts[=SYMSPEC]'
+ The `-Z' option causes `gprof' not to print a tally of functions
+ and the number of times each was called. If SYMSPEC is specified,
+ print tally, but exclude matching symbols.
+
+`-r'
+`--function-ordering'
+ The `--function-ordering' option causes `gprof' to print a
+ suggested function ordering for the program based on profiling
+ data. This option suggests an ordering which may improve paging,
+ tlb and cache behavior for the program on systems which support
+ arbitrary ordering of functions in an executable.
+
+ The exact details of how to force the linker to place functions in
+ a particular order is system dependent and out of the scope of this
+ manual.
+
+`-R MAP_FILE'
+`--file-ordering MAP_FILE'
+ The `--file-ordering' option causes `gprof' to print a suggested
+ .o link line ordering for the program based on profiling data.
+ This option suggests an ordering which may improve paging, tlb and
+ cache behavior for the program on systems which do not support
+ arbitrary ordering of functions in an executable.
+
+ Use of the `-a' argument is highly recommended with this option.
+
+ The MAP_FILE argument is a pathname to a file which provides
+ function name to object file mappings. The format of the file is
+ similar to the output of the program `nm'.
+
+ c-parse.o:00000000 T yyparse
+ c-parse.o:00000004 C yyerrflag
+ c-lang.o:00000000 T maybe_objc_method_name
+ c-lang.o:00000000 T print_lang_statistics
+ c-lang.o:00000000 T recognize_objc_keyword
+ c-decl.o:00000000 T print_lang_identifier
+ c-decl.o:00000000 T print_lang_type
+ ...
+
+ To create a MAP_FILE with GNU `nm', type a command like `nm
+ --extern-only --defined-only -v --print-file-name program-name'.
+
+`-T'
+`--traditional'
+ The `-T' option causes `gprof' to print its output in
+ "traditional" BSD style.
+
+`-w WIDTH'
+`--width=WIDTH'
+ Sets width of output lines to WIDTH. Currently only used when
+ printing the function index at the bottom of the call graph.
+
+`-x'
+`--all-lines'
+ This option affects annotated source output only. By default,
+ only the lines at the beginning of a basic-block are annotated.
+ If this option is specified, every line in a basic-block is
+ annotated by repeating the annotation for the first line. This
+ behavior is similar to `tcov''s `-a'.
+
+`--demangle[=STYLE]'
+`--no-demangle'
+ These options control whether C++ symbol names should be demangled
+ when printing output. The default is to demangle symbols. The
+ `--no-demangle' option may be used to turn off demangling.
+ Different compilers have different mangling styles. The optional
+ demangling style argument can be used to choose an appropriate
+ demangling style for your compiler.
+
+\1f
+File: gprof.info, Node: Analysis Options, Next: Miscellaneous Options, Prev: Output Options, Up: Invoking
+
+4.2 Analysis Options
+====================
+
+`-a'
+`--no-static'
+ The `-a' option causes `gprof' to suppress the printing of
+ statically declared (private) functions. (These are functions
+ whose names are not listed as global, and which are not visible
+ outside the file/function/block where they were defined.) Time
+ spent in these functions, calls to/from them, etc., will all be
+ attributed to the function that was loaded directly before it in
+ the executable file. This option affects both the flat profile
+ and the call graph.
+
+`-c'
+`--static-call-graph'
+ The `-c' option causes the call graph of the program to be
+ augmented by a heuristic which examines the text space of the
+ object file and identifies function calls in the binary machine
+ code. Since normal call graph records are only generated when
+ functions are entered, this option identifies children that could
+ have been called, but never were. Calls to functions that were
+ not compiled with profiling enabled are also identified, but only
+ if symbol table entries are present for them. Calls to dynamic
+ library routines are typically _not_ found by this option.
+ Parents or children identified via this heuristic are indicated in
+ the call graph with call counts of `0'.
+
+`-D'
+`--ignore-non-functions'
+ The `-D' option causes `gprof' to ignore symbols which are not
+ known to be functions. This option will give more accurate
+ profile data on systems where it is supported (Solaris and HPUX for
+ example).
+
+`-k FROM/TO'
+ The `-k' option allows you to delete from the call graph any arcs
+ from symbols matching symspec FROM to those matching symspec TO.
+
+`-l'
+`--line'
+ The `-l' option enables line-by-line profiling, which causes
+ histogram hits to be charged to individual source code lines,
+ instead of functions. This feature only works with programs
+ compiled by older versions of the `gcc' compiler. Newer versions
+ of `gcc' are designed to work with the `gcov' tool instead.
+
+ If the program was compiled with basic-block counting enabled,
+ this option will also identify how many times each line of code
+ was executed. While line-by-line profiling can help isolate where
+ in a large function a program is spending its time, it also
+ significantly increases the running time of `gprof', and magnifies
+ statistical inaccuracies. *Note Statistical Sampling Error:
+ Sampling Error.
+
+`-m NUM'
+`--min-count=NUM'
+ This option affects execution count output only. Symbols that are
+ executed less than NUM times are suppressed.
+
+`-nSYMSPEC'
+`--time=SYMSPEC'
+ The `-n' option causes `gprof', in its call graph analysis, to
+ only propagate times for symbols matching SYMSPEC.
+
+`-NSYMSPEC'
+`--no-time=SYMSPEC'
+ The `-n' option causes `gprof', in its call graph analysis, not to
+ propagate times for symbols matching SYMSPEC.
+
+`-z'
+`--display-unused-functions'
+ If you give the `-z' option, `gprof' will mention all functions in
+ the flat profile, even those that were never called, and that had
+ no time spent in them. This is useful in conjunction with the
+ `-c' option for discovering which routines were never called.
+
+
+\1f
+File: gprof.info, Node: Miscellaneous Options, Next: Deprecated Options, Prev: Analysis Options, Up: Invoking
+
+4.3 Miscellaneous Options
+=========================
+
+`-d[NUM]'
+`--debug[=NUM]'
+ The `-d NUM' option specifies debugging options. If NUM is not
+ specified, enable all debugging. *Note Debugging `gprof':
+ Debugging.
+
+`-h'
+`--help'
+ The `-h' option prints command line usage.
+
+`-ONAME'
+`--file-format=NAME'
+ Selects the format of the profile data files. Recognized formats
+ are `auto' (the default), `bsd', `4.4bsd', `magic', and `prof'
+ (not yet supported).
+
+`-s'
+`--sum'
+ The `-s' option causes `gprof' to summarize the information in the
+ profile data files it read in, and write out a profile data file
+ called `gmon.sum', which contains all the information from the
+ profile data files that `gprof' read in. The file `gmon.sum' may
+ be one of the specified input files; the effect of this is to
+ merge the data in the other input files into `gmon.sum'.
+
+ Eventually you can run `gprof' again without `-s' to analyze the
+ cumulative data in the file `gmon.sum'.
+
+`-v'
+`--version'
+ The `-v' flag causes `gprof' to print the current version number,
+ and then exit.
+
+
+\1f
+File: gprof.info, Node: Deprecated Options, Next: Symspecs, Prev: Miscellaneous Options, Up: Invoking
+
+4.4 Deprecated Options
+======================
+
+ These options have been replaced with newer versions that use
+ symspecs.
+
+`-e FUNCTION_NAME'
+ The `-e FUNCTION' option tells `gprof' to not print information
+ about the function FUNCTION_NAME (and its children...) in the call
+ graph. The function will still be listed as a child of any
+ functions that call it, but its index number will be shown as
+ `[not printed]'. More than one `-e' option may be given; only one
+ FUNCTION_NAME may be indicated with each `-e' option.
+
+`-E FUNCTION_NAME'
+ The `-E FUNCTION' option works like the `-e' option, but time
+ spent in the function (and children who were not called from
+ anywhere else), will not be used to compute the
+ percentages-of-time for the call graph. More than one `-E' option
+ may be given; only one FUNCTION_NAME may be indicated with each
+ `-E' option.
+
+`-f FUNCTION_NAME'
+ The `-f FUNCTION' option causes `gprof' to limit the call graph to
+ the function FUNCTION_NAME and its children (and their
+ children...). More than one `-f' option may be given; only one
+ FUNCTION_NAME may be indicated with each `-f' option.
+
+`-F FUNCTION_NAME'
+ The `-F FUNCTION' option works like the `-f' option, but only time
+ spent in the function and its children (and their children...)
+ will be used to determine total-time and percentages-of-time for
+ the call graph. More than one `-F' option may be given; only one
+ FUNCTION_NAME may be indicated with each `-F' option. The `-F'
+ option overrides the `-E' option.
+
+
+ Note that only one function can be specified with each `-e', `-E',
+`-f' or `-F' option. To specify more than one function, use multiple
+options. For example, this command:
+
+ gprof -e boring -f foo -f bar myprogram > gprof.output
+
+lists in the call graph all functions that were reached from either
+`foo' or `bar' and were not reachable from `boring'.
+
+\1f
+File: gprof.info, Node: Symspecs, Prev: Deprecated Options, Up: Invoking
+
+4.5 Symspecs
+============
+
+Many of the output options allow functions to be included or excluded
+using "symspecs" (symbol specifications), which observe the following
+syntax:
+
+ filename_containing_a_dot
+ | funcname_not_containing_a_dot
+ | linenumber
+ | ( [ any_filename ] `:' ( any_funcname | linenumber ) )
+
+ Here are some sample symspecs:
+
+`main.c'
+ Selects everything in file `main.c'--the dot in the string tells
+ `gprof' to interpret the string as a filename, rather than as a
+ function name. To select a file whose name does not contain a
+ dot, a trailing colon should be specified. For example, `odd:' is
+ interpreted as the file named `odd'.
+
+`main'
+ Selects all functions named `main'.
+
+ Note that there may be multiple instances of the same function name
+ because some of the definitions may be local (i.e., static).
+ Unless a function name is unique in a program, you must use the
+ colon notation explained below to specify a function from a
+ specific source file.
+
+ Sometimes, function names contain dots. In such cases, it is
+ necessary to add a leading colon to the name. For example,
+ `:.mul' selects function `.mul'.
+
+ In some object file formats, symbols have a leading underscore.
+ `gprof' will normally not print these underscores. When you name a
+ symbol in a symspec, you should type it exactly as `gprof' prints
+ it in its output. For example, if the compiler produces a symbol
+ `_main' from your `main' function, `gprof' still prints it as
+ `main' in its output, so you should use `main' in symspecs.
+
+`main.c:main'
+ Selects function `main' in file `main.c'.
+
+`main.c:134'
+ Selects line 134 in file `main.c'.
+
+\1f
+File: gprof.info, Node: Output, Next: Inaccuracy, Prev: Invoking, Up: Top
+
+5 Interpreting `gprof''s Output
+*******************************
+
+`gprof' can produce several different output styles, the most important
+of which are described below. The simplest output styles (file
+information, execution count, and function and file ordering) are not
+described here, but are documented with the respective options that
+trigger them. *Note Output Options: Output Options.
+
+* Menu:
+
+* Flat Profile:: The flat profile shows how much time was spent
+ executing directly in each function.
+* Call Graph:: The call graph shows which functions called which
+ others, and how much time each function used
+ when its subroutine calls are included.
+* Line-by-line:: `gprof' can analyze individual source code lines
+* Annotated Source:: The annotated source listing displays source code
+ labeled with execution counts
+
+\1f
+File: gprof.info, Node: Flat Profile, Next: Call Graph, Up: Output
+
+5.1 The Flat Profile
+====================
+
+The "flat profile" shows the total amount of time your program spent
+executing each function. Unless the `-z' option is given, functions
+with no apparent time spent in them, and no apparent calls to them, are
+not mentioned. Note that if a function was not compiled for profiling,
+and didn't run long enough to show up on the program counter histogram,
+it will be indistinguishable from a function that was never called.
+
+ This is part of a flat profile for a small program:
+
+ Flat profile:
+
+ Each sample counts as 0.01 seconds.
+ % cumulative self self total
+ time seconds seconds calls ms/call ms/call name
+ 33.34 0.02 0.02 7208 0.00 0.00 open
+ 16.67 0.03 0.01 244 0.04 0.12 offtime
+ 16.67 0.04 0.01 8 1.25 1.25 memccpy
+ 16.67 0.05 0.01 7 1.43 1.43 write
+ 16.67 0.06 0.01 mcount
+ 0.00 0.06 0.00 236 0.00 0.00 tzset
+ 0.00 0.06 0.00 192 0.00 0.00 tolower
+ 0.00 0.06 0.00 47 0.00 0.00 strlen
+ 0.00 0.06 0.00 45 0.00 0.00 strchr
+ 0.00 0.06 0.00 1 0.00 50.00 main
+ 0.00 0.06 0.00 1 0.00 0.00 memcpy
+ 0.00 0.06 0.00 1 0.00 10.11 print
+ 0.00 0.06 0.00 1 0.00 0.00 profil
+ 0.00 0.06 0.00 1 0.00 50.00 report
+ ...
+
+The functions are sorted first by decreasing run-time spent in them,
+then by decreasing number of calls, then alphabetically by name. The
+functions `mcount' and `profil' are part of the profiling apparatus and
+appear in every flat profile; their time gives a measure of the amount
+of overhead due to profiling.
+
+ Just before the column headers, a statement appears indicating how
+much time each sample counted as. This "sampling period" estimates the
+margin of error in each of the time figures. A time figure that is not
+much larger than this is not reliable. In this example, each sample
+counted as 0.01 seconds, suggesting a 100 Hz sampling rate. The
+program's total execution time was 0.06 seconds, as indicated by the
+`cumulative seconds' field. Since each sample counted for 0.01
+seconds, this means only six samples were taken during the run. Two of
+the samples occurred while the program was in the `open' function, as
+indicated by the `self seconds' field. Each of the other four samples
+occurred one each in `offtime', `memccpy', `write', and `mcount'.
+Since only six samples were taken, none of these values can be regarded
+as particularly reliable. In another run, the `self seconds' field for
+`mcount' might well be `0.00' or `0.02'. *Note Statistical Sampling
+Error: Sampling Error, for a complete discussion.
+
+ The remaining functions in the listing (those whose `self seconds'
+field is `0.00') didn't appear in the histogram samples at all.
+However, the call graph indicated that they were called, so therefore
+they are listed, sorted in decreasing order by the `calls' field.
+Clearly some time was spent executing these functions, but the paucity
+of histogram samples prevents any determination of how much time each
+took.
+
+ Here is what the fields in each line mean:
+
+`% time'
+ This is the percentage of the total execution time your program
+ spent in this function. These should all add up to 100%.
+
+`cumulative seconds'
+ This is the cumulative total number of seconds the computer spent
+ executing this functions, plus the time spent in all the functions
+ above this one in this table.
+
+`self seconds'
+ This is the number of seconds accounted for by this function alone.
+ The flat profile listing is sorted first by this number.
+
+`calls'
+ This is the total number of times the function was called. If the
+ function was never called, or the number of times it was called
+ cannot be determined (probably because the function was not
+ compiled with profiling enabled), the "calls" field is blank.
+
+`self ms/call'
+ This represents the average number of milliseconds spent in this
+ function per call, if this function is profiled. Otherwise, this
+ field is blank for this function.
+
+`total ms/call'
+ This represents the average number of milliseconds spent in this
+ function and its descendants per call, if this function is
+ profiled. Otherwise, this field is blank for this function. This
+ is the only field in the flat profile that uses call graph
+ analysis.
+
+`name'
+ This is the name of the function. The flat profile is sorted by
+ this field alphabetically after the "self seconds" and "calls"
+ fields are sorted.
+
+\1f
+File: gprof.info, Node: Call Graph, Next: Line-by-line, Prev: Flat Profile, Up: Output
+
+5.2 The Call Graph
+==================
+
+The "call graph" shows how much time was spent in each function and its
+children. From this information, you can find functions that, while
+they themselves may not have used much time, called other functions
+that did use unusual amounts of time.
+
+ Here is a sample call from a small program. This call came from the
+same `gprof' run as the flat profile example in the previous section.
+
+ granularity: each sample hit covers 2 byte(s) for 20.00% of 0.05 seconds
+
+ index % time self children called name
+ <spontaneous>
+ [1] 100.0 0.00 0.05 start [1]
+ 0.00 0.05 1/1 main [2]
+ 0.00 0.00 1/2 on_exit [28]
+ 0.00 0.00 1/1 exit [59]
+ -----------------------------------------------
+ 0.00 0.05 1/1 start [1]
+ [2] 100.0 0.00 0.05 1 main [2]
+ 0.00 0.05 1/1 report [3]
+ -----------------------------------------------
+ 0.00 0.05 1/1 main [2]
+ [3] 100.0 0.00 0.05 1 report [3]
+ 0.00 0.03 8/8 timelocal [6]
+ 0.00 0.01 1/1 print [9]
+ 0.00 0.01 9/9 fgets [12]
+ 0.00 0.00 12/34 strncmp <cycle 1> [40]
+ 0.00 0.00 8/8 lookup [20]
+ 0.00 0.00 1/1 fopen [21]
+ 0.00 0.00 8/8 chewtime [24]
+ 0.00 0.00 8/16 skipspace [44]
+ -----------------------------------------------
+ [4] 59.8 0.01 0.02 8+472 <cycle 2 as a whole> [4]
+ 0.01 0.02 244+260 offtime <cycle 2> [7]
+ 0.00 0.00 236+1 tzset <cycle 2> [26]
+ -----------------------------------------------
+
+ The lines full of dashes divide this table into "entries", one for
+each function. Each entry has one or more lines.
+
+ In each entry, the primary line is the one that starts with an index
+number in square brackets. The end of this line says which function
+the entry is for. The preceding lines in the entry describe the
+callers of this function and the following lines describe its
+subroutines (also called "children" when we speak of the call graph).
+
+ The entries are sorted by time spent in the function and its
+subroutines.
+
+ The internal profiling function `mcount' (*note The Flat Profile:
+Flat Profile.) is never mentioned in the call graph.
+
+* Menu:
+
+* Primary:: Details of the primary line's contents.
+* Callers:: Details of caller-lines' contents.
+* Subroutines:: Details of subroutine-lines' contents.
+* Cycles:: When there are cycles of recursion,
+ such as `a' calls `b' calls `a'...
+
+\1f
+File: gprof.info, Node: Primary, Next: Callers, Up: Call Graph
+
+5.2.1 The Primary Line
+----------------------
+
+The "primary line" in a call graph entry is the line that describes the
+function which the entry is about and gives the overall statistics for
+this function.
+
+ For reference, we repeat the primary line from the entry for function
+`report' in our main example, together with the heading line that shows
+the names of the fields:
+
+ index % time self children called name
+ ...
+ [3] 100.0 0.00 0.05 1 report [3]
+
+ Here is what the fields in the primary line mean:
+
+`index'
+ Entries are numbered with consecutive integers. Each function
+ therefore has an index number, which appears at the beginning of
+ its primary line.
+
+ Each cross-reference to a function, as a caller or subroutine of
+ another, gives its index number as well as its name. The index
+ number guides you if you wish to look for the entry for that
+ function.
+
+`% time'
+ This is the percentage of the total time that was spent in this
+ function, including time spent in subroutines called from this
+ function.
+
+ The time spent in this function is counted again for the callers of
+ this function. Therefore, adding up these percentages is
+ meaningless.
+
+`self'
+ This is the total amount of time spent in this function. This
+ should be identical to the number printed in the `seconds' field
+ for this function in the flat profile.
+
+`children'
+ This is the total amount of time spent in the subroutine calls
+ made by this function. This should be equal to the sum of all the
+ `self' and `children' entries of the children listed directly
+ below this function.
+
+`called'
+ This is the number of times the function was called.
+
+ If the function called itself recursively, there are two numbers,
+ separated by a `+'. The first number counts non-recursive calls,
+ and the second counts recursive calls.
+
+ In the example above, the function `report' was called once from
+ `main'.
+
+`name'
+ This is the name of the current function. The index number is
+ repeated after it.
+
+ If the function is part of a cycle of recursion, the cycle number
+ is printed between the function's name and the index number (*note
+ How Mutually Recursive Functions Are Described: Cycles.). For
+ example, if function `gnurr' is part of cycle number one, and has
+ index number twelve, its primary line would be end like this:
+
+ gnurr <cycle 1> [12]
+
+\1f
+File: gprof.info, Node: Callers, Next: Subroutines, Prev: Primary, Up: Call Graph
+
+5.2.2 Lines for a Function's Callers
+------------------------------------
+
+A function's entry has a line for each function it was called by.
+These lines' fields correspond to the fields of the primary line, but
+their meanings are different because of the difference in context.
+
+ For reference, we repeat two lines from the entry for the function
+`report', the primary line and one caller-line preceding it, together
+with the heading line that shows the names of the fields:
+
+ index % time self children called name
+ ...
+ 0.00 0.05 1/1 main [2]
+ [3] 100.0 0.00 0.05 1 report [3]
+
+ Here are the meanings of the fields in the caller-line for `report'
+called from `main':
+
+`self'
+ An estimate of the amount of time spent in `report' itself when it
+ was called from `main'.
+
+`children'
+ An estimate of the amount of time spent in subroutines of `report'
+ when `report' was called from `main'.
+
+ The sum of the `self' and `children' fields is an estimate of the
+ amount of time spent within calls to `report' from `main'.
+
+`called'
+ Two numbers: the number of times `report' was called from `main',
+ followed by the total number of non-recursive calls to `report'
+ from all its callers.
+
+`name and index number'
+ The name of the caller of `report' to which this line applies,
+ followed by the caller's index number.
+
+ Not all functions have entries in the call graph; some options to
+ `gprof' request the omission of certain functions. When a caller
+ has no entry of its own, it still has caller-lines in the entries
+ of the functions it calls.
+
+ If the caller is part of a recursion cycle, the cycle number is
+ printed between the name and the index number.
+
+ If the identity of the callers of a function cannot be determined, a
+dummy caller-line is printed which has `<spontaneous>' as the "caller's
+name" and all other fields blank. This can happen for signal handlers.
+
+\1f
+File: gprof.info, Node: Subroutines, Next: Cycles, Prev: Callers, Up: Call Graph
+
+5.2.3 Lines for a Function's Subroutines
+----------------------------------------
+
+A function's entry has a line for each of its subroutines--in other
+words, a line for each other function that it called. These lines'
+fields correspond to the fields of the primary line, but their meanings
+are different because of the difference in context.
+
+ For reference, we repeat two lines from the entry for the function
+`main', the primary line and a line for a subroutine, together with the
+heading line that shows the names of the fields:
+
+ index % time self children called name
+ ...
+ [2] 100.0 0.00 0.05 1 main [2]
+ 0.00 0.05 1/1 report [3]
+
+ Here are the meanings of the fields in the subroutine-line for `main'
+calling `report':
+
+`self'
+ An estimate of the amount of time spent directly within `report'
+ when `report' was called from `main'.
+
+`children'
+ An estimate of the amount of time spent in subroutines of `report'
+ when `report' was called from `main'.
+
+ The sum of the `self' and `children' fields is an estimate of the
+ total time spent in calls to `report' from `main'.
+
+`called'
+ Two numbers, the number of calls to `report' from `main' followed
+ by the total number of non-recursive calls to `report'. This
+ ratio is used to determine how much of `report''s `self' and
+ `children' time gets credited to `main'. *Note Estimating
+ `children' Times: Assumptions.
+
+`name'
+ The name of the subroutine of `main' to which this line applies,
+ followed by the subroutine's index number.
+
+ If the caller is part of a recursion cycle, the cycle number is
+ printed between the name and the index number.
+
+\1f
+File: gprof.info, Node: Cycles, Prev: Subroutines, Up: Call Graph
+
+5.2.4 How Mutually Recursive Functions Are Described
+----------------------------------------------------
+
+The graph may be complicated by the presence of "cycles of recursion"
+in the call graph. A cycle exists if a function calls another function
+that (directly or indirectly) calls (or appears to call) the original
+function. For example: if `a' calls `b', and `b' calls `a', then `a'
+and `b' form a cycle.
+
+ Whenever there are call paths both ways between a pair of functions,
+they belong to the same cycle. If `a' and `b' call each other and `b'
+and `c' call each other, all three make one cycle. Note that even if
+`b' only calls `a' if it was not called from `a', `gprof' cannot
+determine this, so `a' and `b' are still considered a cycle.
+
+ The cycles are numbered with consecutive integers. When a function
+belongs to a cycle, each time the function name appears in the call
+graph it is followed by `<cycle NUMBER>'.
+
+ The reason cycles matter is that they make the time values in the
+call graph paradoxical. The "time spent in children" of `a' should
+include the time spent in its subroutine `b' and in `b''s
+subroutines--but one of `b''s subroutines is `a'! How much of `a''s
+time should be included in the children of `a', when `a' is indirectly
+recursive?
+
+ The way `gprof' resolves this paradox is by creating a single entry
+for the cycle as a whole. The primary line of this entry describes the
+total time spent directly in the functions of the cycle. The
+"subroutines" of the cycle are the individual functions of the cycle,
+and all other functions that were called directly by them. The
+"callers" of the cycle are the functions, outside the cycle, that
+called functions in the cycle.
+
+ Here is an example portion of a call graph which shows a cycle
+containing functions `a' and `b'. The cycle was entered by a call to
+`a' from `main'; both `a' and `b' called `c'.
+
+ index % time self children called name
+ ----------------------------------------
+ 1.77 0 1/1 main [2]
+ [3] 91.71 1.77 0 1+5 <cycle 1 as a whole> [3]
+ 1.02 0 3 b <cycle 1> [4]
+ 0.75 0 2 a <cycle 1> [5]
+ ----------------------------------------
+ 3 a <cycle 1> [5]
+ [4] 52.85 1.02 0 0 b <cycle 1> [4]
+ 2 a <cycle 1> [5]
+ 0 0 3/6 c [6]
+ ----------------------------------------
+ 1.77 0 1/1 main [2]
+ 2 b <cycle 1> [4]
+ [5] 38.86 0.75 0 1 a <cycle 1> [5]
+ 3 b <cycle 1> [4]
+ 0 0 3/6 c [6]
+ ----------------------------------------
+
+(The entire call graph for this program contains in addition an entry
+for `main', which calls `a', and an entry for `c', with callers `a' and
+`b'.)
+
+ index % time self children called name
+ <spontaneous>
+ [1] 100.00 0 1.93 0 start [1]
+ 0.16 1.77 1/1 main [2]
+ ----------------------------------------
+ 0.16 1.77 1/1 start [1]
+ [2] 100.00 0.16 1.77 1 main [2]
+ 1.77 0 1/1 a <cycle 1> [5]
+ ----------------------------------------
+ 1.77 0 1/1 main [2]
+ [3] 91.71 1.77 0 1+5 <cycle 1 as a whole> [3]
+ 1.02 0 3 b <cycle 1> [4]
+ 0.75 0 2 a <cycle 1> [5]
+ 0 0 6/6 c [6]
+ ----------------------------------------
+ 3 a <cycle 1> [5]
+ [4] 52.85 1.02 0 0 b <cycle 1> [4]
+ 2 a <cycle 1> [5]
+ 0 0 3/6 c [6]
+ ----------------------------------------
+ 1.77 0 1/1 main [2]
+ 2 b <cycle 1> [4]
+ [5] 38.86 0.75 0 1 a <cycle 1> [5]
+ 3 b <cycle 1> [4]
+ 0 0 3/6 c [6]
+ ----------------------------------------
+ 0 0 3/6 b <cycle 1> [4]
+ 0 0 3/6 a <cycle 1> [5]
+ [6] 0.00 0 0 6 c [6]
+ ----------------------------------------
+
+ The `self' field of the cycle's primary line is the total time spent
+in all the functions of the cycle. It equals the sum of the `self'
+fields for the individual functions in the cycle, found in the entry in
+the subroutine lines for these functions.
+
+ The `children' fields of the cycle's primary line and subroutine
+lines count only subroutines outside the cycle. Even though `a' calls
+`b', the time spent in those calls to `b' is not counted in `a''s
+`children' time. Thus, we do not encounter the problem of what to do
+when the time in those calls to `b' includes indirect recursive calls
+back to `a'.
+
+ The `children' field of a caller-line in the cycle's entry estimates
+the amount of time spent _in the whole cycle_, and its other
+subroutines, on the times when that caller called a function in the
+cycle.
+
+ The `called' field in the primary line for the cycle has two numbers:
+first, the number of times functions in the cycle were called by
+functions outside the cycle; second, the number of times they were
+called by functions in the cycle (including times when a function in
+the cycle calls itself). This is a generalization of the usual split
+into non-recursive and recursive calls.
+
+ The `called' field of a subroutine-line for a cycle member in the
+cycle's entry says how many time that function was called from
+functions in the cycle. The total of all these is the second number in
+the primary line's `called' field.
+
+ In the individual entry for a function in a cycle, the other
+functions in the same cycle can appear as subroutines and as callers.
+These lines show how many times each function in the cycle called or
+was called from each other function in the cycle. The `self' and
+`children' fields in these lines are blank because of the difficulty of
+defining meanings for them when recursion is going on.
+
+\1f
+File: gprof.info, Node: Line-by-line, Next: Annotated Source, Prev: Call Graph, Up: Output
+
+5.3 Line-by-line Profiling
+==========================
+
+`gprof''s `-l' option causes the program to perform "line-by-line"
+profiling. In this mode, histogram samples are assigned not to
+functions, but to individual lines of source code. This only works
+with programs compiled with older versions of the `gcc' compiler.
+Newer versions of `gcc' use a different program - `gcov' - to display
+line-by-line profiling information.
+
+ With the older versions of `gcc' the program usually has to be
+compiled with a `-g' option, in addition to `-pg', in order to generate
+debugging symbols for tracking source code lines. Note, in much older
+versions of `gcc' the program had to be compiled with the `-a' command
+line option as well.
+
+ The flat profile is the most useful output table in line-by-line
+mode. The call graph isn't as useful as normal, since the current
+version of `gprof' does not propagate call graph arcs from source code
+lines to the enclosing function. The call graph does, however, show
+each line of code that called each function, along with a count.
+
+ Here is a section of `gprof''s output, without line-by-line
+profiling. Note that `ct_init' accounted for four histogram hits, and
+13327 calls to `init_block'.
+
+ Flat profile:
+
+ Each sample counts as 0.01 seconds.
+ % cumulative self self total
+ time seconds seconds calls us/call us/call name
+ 30.77 0.13 0.04 6335 6.31 6.31 ct_init
+
+
+ Call graph (explanation follows)
+
+
+ granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
+
+ index % time self children called name
+
+ 0.00 0.00 1/13496 name_too_long
+ 0.00 0.00 40/13496 deflate
+ 0.00 0.00 128/13496 deflate_fast
+ 0.00 0.00 13327/13496 ct_init
+ [7] 0.0 0.00 0.00 13496 init_block
+
+ Now let's look at some of `gprof''s output from the same program run,
+this time with line-by-line profiling enabled. Note that `ct_init''s
+four histogram hits are broken down into four lines of source code--one
+hit occurred on each of lines 349, 351, 382 and 385. In the call graph,
+note how `ct_init''s 13327 calls to `init_block' are broken down into
+one call from line 396, 3071 calls from line 384, 3730 calls from line
+385, and 6525 calls from 387.
+
+ Flat profile:
+
+ Each sample counts as 0.01 seconds.
+ % cumulative self
+ time seconds seconds calls name
+ 7.69 0.10 0.01 ct_init (trees.c:349)
+ 7.69 0.11 0.01 ct_init (trees.c:351)
+ 7.69 0.12 0.01 ct_init (trees.c:382)
+ 7.69 0.13 0.01 ct_init (trees.c:385)
+
+
+ Call graph (explanation follows)
+
+
+ granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
+
+ % time self children called name
+
+ 0.00 0.00 1/13496 name_too_long (gzip.c:1440)
+ 0.00 0.00 1/13496 deflate (deflate.c:763)
+ 0.00 0.00 1/13496 ct_init (trees.c:396)
+ 0.00 0.00 2/13496 deflate (deflate.c:727)
+ 0.00 0.00 4/13496 deflate (deflate.c:686)
+ 0.00 0.00 5/13496 deflate (deflate.c:675)
+ 0.00 0.00 12/13496 deflate (deflate.c:679)
+ 0.00 0.00 16/13496 deflate (deflate.c:730)
+ 0.00 0.00 128/13496 deflate_fast (deflate.c:654)
+ 0.00 0.00 3071/13496 ct_init (trees.c:384)
+ 0.00 0.00 3730/13496 ct_init (trees.c:385)
+ 0.00 0.00 6525/13496 ct_init (trees.c:387)
+ [6] 0.0 0.00 0.00 13496 init_block (trees.c:408)
+
+\1f
+File: gprof.info, Node: Annotated Source, Prev: Line-by-line, Up: Output
+
+5.4 The Annotated Source Listing
+================================
+
+`gprof''s `-A' option triggers an annotated source listing, which lists
+the program's source code, each function labeled with the number of
+times it was called. You may also need to specify the `-I' option, if
+`gprof' can't find the source code files.
+
+ With older versions of `gcc' compiling with `gcc ... -g -pg -a'
+augments your program with basic-block counting code, in addition to
+function counting code. This enables `gprof' to determine how many
+times each line of code was executed. With newer versions of `gcc'
+support for displaying basic-block counts is provided by the `gcov'
+program.
+
+ For example, consider the following function, taken from gzip, with
+line numbers added:
+
+ 1 ulg updcrc(s, n)
+ 2 uch *s;
+ 3 unsigned n;
+ 4 {
+ 5 register ulg c;
+ 6
+ 7 static ulg crc = (ulg)0xffffffffL;
+ 8
+ 9 if (s == NULL) {
+ 10 c = 0xffffffffL;
+ 11 } else {
+ 12 c = crc;
+ 13 if (n) do {
+ 14 c = crc_32_tab[...];
+ 15 } while (--n);
+ 16 }
+ 17 crc = c;
+ 18 return c ^ 0xffffffffL;
+ 19 }
+
+ `updcrc' has at least five basic-blocks. One is the function
+itself. The `if' statement on line 9 generates two more basic-blocks,
+one for each branch of the `if'. A fourth basic-block results from the
+`if' on line 13, and the contents of the `do' loop form the fifth
+basic-block. The compiler may also generate additional basic-blocks to
+handle various special cases.
+
+ A program augmented for basic-block counting can be analyzed with
+`gprof -l -A'. The `-x' option is also helpful, to ensure that each
+line of code is labeled at least once. Here is `updcrc''s annotated
+source listing for a sample `gzip' run:
+
+ ulg updcrc(s, n)
+ uch *s;
+ unsigned n;
+ 2 ->{
+ register ulg c;
+
+ static ulg crc = (ulg)0xffffffffL;
+
+ 2 -> if (s == NULL) {
+ 1 -> c = 0xffffffffL;
+ 1 -> } else {
+ 1 -> c = crc;
+ 1 -> if (n) do {
+ 26312 -> c = crc_32_tab[...];
+ 26312,1,26311 -> } while (--n);
+ }
+ 2 -> crc = c;
+ 2 -> return c ^ 0xffffffffL;
+ 2 ->}
+
+ In this example, the function was called twice, passing once through
+each branch of the `if' statement. The body of the `do' loop was
+executed a total of 26312 times. Note how the `while' statement is
+annotated. It began execution 26312 times, once for each iteration
+through the loop. One of those times (the last time) it exited, while
+it branched back to the beginning of the loop 26311 times.
+
+\1f
+File: gprof.info, Node: Inaccuracy, Next: How do I?, Prev: Output, Up: Top
+
+6 Inaccuracy of `gprof' Output
+******************************
+
+* Menu:
+
+* Sampling Error:: Statistical margins of error
+* Assumptions:: Estimating children times
+
+\1f
+File: gprof.info, Node: Sampling Error, Next: Assumptions, Up: Inaccuracy
+
+6.1 Statistical Sampling Error
+==============================
+
+The run-time figures that `gprof' gives you are based on a sampling
+process, so they are subject to statistical inaccuracy. If a function
+runs only a small amount of time, so that on the average the sampling
+process ought to catch that function in the act only once, there is a
+pretty good chance it will actually find that function zero times, or
+twice.
+
+ By contrast, the number-of-calls and basic-block figures are derived
+by counting, not sampling. They are completely accurate and will not
+vary from run to run if your program is deterministic.
+
+ The "sampling period" that is printed at the beginning of the flat
+profile says how often samples are taken. The rule of thumb is that a
+run-time figure is accurate if it is considerably bigger than the
+sampling period.
+
+ The actual amount of error can be predicted. For N samples, the
+_expected_ error is the square-root of N. For example, if the sampling
+period is 0.01 seconds and `foo''s run-time is 1 second, N is 100
+samples (1 second/0.01 seconds), sqrt(N) is 10 samples, so the expected
+error in `foo''s run-time is 0.1 seconds (10*0.01 seconds), or ten
+percent of the observed value. Again, if the sampling period is 0.01
+seconds and `bar''s run-time is 100 seconds, N is 10000 samples,
+sqrt(N) is 100 samples, so the expected error in `bar''s run-time is 1
+second, or one percent of the observed value. It is likely to vary
+this much _on the average_ from one profiling run to the next.
+(_Sometimes_ it will vary more.)
+
+ This does not mean that a small run-time figure is devoid of
+information. If the program's _total_ run-time is large, a small
+run-time for one function does tell you that that function used an
+insignificant fraction of the whole program's time. Usually this means
+it is not worth optimizing.
+
+ One way to get more accuracy is to give your program more (but
+similar) input data so it will take longer. Another way is to combine
+the data from several runs, using the `-s' option of `gprof'. Here is
+how:
+
+ 1. Run your program once.
+
+ 2. Issue the command `mv gmon.out gmon.sum'.
+
+ 3. Run your program again, the same as before.
+
+ 4. Merge the new data in `gmon.out' into `gmon.sum' with this command:
+
+ gprof -s EXECUTABLE-FILE gmon.out gmon.sum
+
+ 5. Repeat the last two steps as often as you wish.
+
+ 6. Analyze the cumulative data using this command:
+
+ gprof EXECUTABLE-FILE gmon.sum > OUTPUT-FILE
+
+\1f
+File: gprof.info, Node: Assumptions, Prev: Sampling Error, Up: Inaccuracy
+
+6.2 Estimating `children' Times
+===============================
+
+Some of the figures in the call graph are estimates--for example, the
+`children' time values and all the time figures in caller and
+subroutine lines.
+
+ There is no direct information about these measurements in the
+profile data itself. Instead, `gprof' estimates them by making an
+assumption about your program that might or might not be true.
+
+ The assumption made is that the average time spent in each call to
+any function `foo' is not correlated with who called `foo'. If `foo'
+used 5 seconds in all, and 2/5 of the calls to `foo' came from `a',
+then `foo' contributes 2 seconds to `a''s `children' time, by
+assumption.
+
+ This assumption is usually true enough, but for some programs it is
+far from true. Suppose that `foo' returns very quickly when its
+argument is zero; suppose that `a' always passes zero as an argument,
+while other callers of `foo' pass other arguments. In this program,
+all the time spent in `foo' is in the calls from callers other than `a'.
+But `gprof' has no way of knowing this; it will blindly and incorrectly
+charge 2 seconds of time in `foo' to the children of `a'.
+
+ We hope some day to put more complete data into `gmon.out', so that
+this assumption is no longer needed, if we can figure out how. For the
+novice, the estimated figures are usually more useful than misleading.
+
+\1f
+File: gprof.info, Node: How do I?, Next: Incompatibilities, Prev: Inaccuracy, Up: Top
+
+7 Answers to Common Questions
+*****************************
+
+How can I get more exact information about hot spots in my program?
+ Looking at the per-line call counts only tells part of the story.
+ Because `gprof' can only report call times and counts by function,
+ the best way to get finer-grained information on where the program
+ is spending its time is to re-factor large functions into sequences
+ of calls to smaller ones. Beware however that this can introduce
+ artificial hot spots since compiling with `-pg' adds a significant
+ overhead to function calls. An alternative solution is to use a
+ non-intrusive profiler, e.g. oprofile.
+
+How do I find which lines in my program were executed the most times?
+ Use the `gcov' program.
+
+How do I find which lines in my program called a particular function?
+ Use `gprof -l' and lookup the function in the call graph. The
+ callers will be broken down by function and line number.
+
+How do I analyze a program that runs for less than a second?
+ Try using a shell script like this one:
+
+ for i in `seq 1 100`; do
+ fastprog
+ mv gmon.out gmon.out.$i
+ done
+
+ gprof -s fastprog gmon.out.*
+
+ gprof fastprog gmon.sum
+
+ If your program is completely deterministic, all the call counts
+ will be simple multiples of 100 (i.e., a function called once in
+ each run will appear with a call count of 100).
+
+
+\1f
+File: gprof.info, Node: Incompatibilities, Next: Details, Prev: How do I?, Up: Top
+
+8 Incompatibilities with Unix `gprof'
+*************************************
+
+GNU `gprof' and Berkeley Unix `gprof' use the same data file
+`gmon.out', and provide essentially the same information. But there
+are a few differences.
+
+ * GNU `gprof' uses a new, generalized file format with support for
+ basic-block execution counts and non-realtime histograms. A magic
+ cookie and version number allows `gprof' to easily identify new
+ style files. Old BSD-style files can still be read. *Note
+ Profiling Data File Format: File Format.
+
+ * For a recursive function, Unix `gprof' lists the function as a
+ parent and as a child, with a `calls' field that lists the number
+ of recursive calls. GNU `gprof' omits these lines and puts the
+ number of recursive calls in the primary line.
+
+ * When a function is suppressed from the call graph with `-e', GNU
+ `gprof' still lists it as a subroutine of functions that call it.
+
+ * GNU `gprof' accepts the `-k' with its argument in the form
+ `from/to', instead of `from to'.
+
+ * In the annotated source listing, if there are multiple basic
+ blocks on the same line, GNU `gprof' prints all of their counts,
+ separated by commas.
+
+ * The blurbs, field widths, and output formats are different. GNU
+ `gprof' prints blurbs after the tables, so that you can see the
+ tables without skipping the blurbs.
+
+\1f
+File: gprof.info, Node: Details, Next: GNU Free Documentation License, Prev: Incompatibilities, Up: Top
+
+9 Details of Profiling
+**********************
+
+* Menu:
+
+* Implementation:: How a program collects profiling information
+* File Format:: Format of `gmon.out' files
+* Internals:: `gprof''s internal operation
+* Debugging:: Using `gprof''s `-d' option
+
+\1f
+File: gprof.info, Node: Implementation, Next: File Format, Up: Details
+
+9.1 Implementation of Profiling
+===============================
+
+Profiling works by changing how every function in your program is
+compiled so that when it is called, it will stash away some information
+about where it was called from. From this, the profiler can figure out
+what function called it, and can count how many times it was called.
+This change is made by the compiler when your program is compiled with
+the `-pg' option, which causes every function to call `mcount' (or
+`_mcount', or `__mcount', depending on the OS and compiler) as one of
+its first operations.
+
+ The `mcount' routine, included in the profiling library, is
+responsible for recording in an in-memory call graph table both its
+parent routine (the child) and its parent's parent. This is typically
+done by examining the stack frame to find both the address of the
+child, and the return address in the original parent. Since this is a
+very machine-dependent operation, `mcount' itself is typically a short
+assembly-language stub routine that extracts the required information,
+and then calls `__mcount_internal' (a normal C function) with two
+arguments--`frompc' and `selfpc'. `__mcount_internal' is responsible
+for maintaining the in-memory call graph, which records `frompc',
+`selfpc', and the number of times each of these call arcs was traversed.
+
+ GCC Version 2 provides a magical function
+(`__builtin_return_address'), which allows a generic `mcount' function
+to extract the required information from the stack frame. However, on
+some architectures, most notably the SPARC, using this builtin can be
+very computationally expensive, and an assembly language version of
+`mcount' is used for performance reasons.
+
+ Number-of-calls information for library routines is collected by
+using a special version of the C library. The programs in it are the
+same as in the usual C library, but they were compiled with `-pg'. If
+you link your program with `gcc ... -pg', it automatically uses the
+profiling version of the library.
+
+ Profiling also involves watching your program as it runs, and
+keeping a histogram of where the program counter happens to be every
+now and then. Typically the program counter is looked at around 100
+times per second of run time, but the exact frequency may vary from
+system to system.
+
+ This is done is one of two ways. Most UNIX-like operating systems
+provide a `profil()' system call, which registers a memory array with
+the kernel, along with a scale factor that determines how the program's
+address space maps into the array. Typical scaling values cause every
+2 to 8 bytes of address space to map into a single array slot. On
+every tick of the system clock (assuming the profiled program is
+running), the value of the program counter is examined and the
+corresponding slot in the memory array is incremented. Since this is
+done in the kernel, which had to interrupt the process anyway to handle
+the clock interrupt, very little additional system overhead is required.
+
+ However, some operating systems, most notably Linux 2.0 (and
+earlier), do not provide a `profil()' system call. On such a system,
+arrangements are made for the kernel to periodically deliver a signal
+to the process (typically via `setitimer()'), which then performs the
+same operation of examining the program counter and incrementing a slot
+in the memory array. Since this method requires a signal to be
+delivered to user space every time a sample is taken, it uses
+considerably more overhead than kernel-based profiling. Also, due to
+the added delay required to deliver the signal, this method is less
+accurate as well.
+
+ A special startup routine allocates memory for the histogram and
+either calls `profil()' or sets up a clock signal handler. This
+routine (`monstartup') can be invoked in several ways. On Linux
+systems, a special profiling startup file `gcrt0.o', which invokes
+`monstartup' before `main', is used instead of the default `crt0.o'.
+Use of this special startup file is one of the effects of using `gcc
+... -pg' to link. On SPARC systems, no special startup files are used.
+Rather, the `mcount' routine, when it is invoked for the first time
+(typically when `main' is called), calls `monstartup'.
+
+ If the compiler's `-a' option was used, basic-block counting is also
+enabled. Each object file is then compiled with a static array of
+counts, initially zero. In the executable code, every time a new
+basic-block begins (i.e., when an `if' statement appears), an extra
+instruction is inserted to increment the corresponding count in the
+array. At compile time, a paired array was constructed that recorded
+the starting address of each basic-block. Taken together, the two
+arrays record the starting address of every basic-block, along with the
+number of times it was executed.
+
+ The profiling library also includes a function (`mcleanup') which is
+typically registered using `atexit()' to be called as the program
+exits, and is responsible for writing the file `gmon.out'. Profiling
+is turned off, various headers are output, and the histogram is
+written, followed by the call-graph arcs and the basic-block counts.
+
+ The output from `gprof' gives no indication of parts of your program
+that are limited by I/O or swapping bandwidth. This is because samples
+of the program counter are taken at fixed intervals of the program's
+run time. Therefore, the time measurements in `gprof' output say
+nothing about time that your program was not running. For example, a
+part of the program that creates so much data that it cannot all fit in
+physical memory at once may run very slowly due to thrashing, but
+`gprof' will say it uses little time. On the other hand, sampling by
+run time has the advantage that the amount of load due to other users
+won't directly affect the output you get.
+
+\1f
+File: gprof.info, Node: File Format, Next: Internals, Prev: Implementation, Up: Details
+
+9.2 Profiling Data File Format
+==============================
+
+The old BSD-derived file format used for profile data does not contain a
+magic cookie that allows to check whether a data file really is a
+`gprof' file. Furthermore, it does not provide a version number, thus
+rendering changes to the file format almost impossible. GNU `gprof'
+uses a new file format that provides these features. For backward
+compatibility, GNU `gprof' continues to support the old BSD-derived
+format, but not all features are supported with it. For example,
+basic-block execution counts cannot be accommodated by the old file
+format.
+
+ The new file format is defined in header file `gmon_out.h'. It
+consists of a header containing the magic cookie and a version number,
+as well as some spare bytes available for future extensions. All data
+in a profile data file is in the native format of the target for which
+the profile was collected. GNU `gprof' adapts automatically to the
+byte-order in use.
+
+ In the new file format, the header is followed by a sequence of
+records. Currently, there are three different record types: histogram
+records, call-graph arc records, and basic-block execution count
+records. Each file can contain any number of each record type. When
+reading a file, GNU `gprof' will ensure records of the same type are
+compatible with each other and compute the union of all records. For
+example, for basic-block execution counts, the union is simply the sum
+of all execution counts for each basic-block.
+
+9.2.1 Histogram Records
+-----------------------
+
+Histogram records consist of a header that is followed by an array of
+bins. The header contains the text-segment range that the histogram
+spans, the size of the histogram in bytes (unlike in the old BSD
+format, this does not include the size of the header), the rate of the
+profiling clock, and the physical dimension that the bin counts
+represent after being scaled by the profiling clock rate. The physical
+dimension is specified in two parts: a long name of up to 15 characters
+and a single character abbreviation. For example, a histogram
+representing real-time would specify the long name as "seconds" and the
+abbreviation as "s". This feature is useful for architectures that
+support performance monitor hardware (which, fortunately, is becoming
+increasingly common). For example, under DEC OSF/1, the "uprofile"
+command can be used to produce a histogram of, say, instruction cache
+misses. In this case, the dimension in the histogram header could be
+set to "i-cache misses" and the abbreviation could be set to "1"
+(because it is simply a count, not a physical dimension). Also, the
+profiling rate would have to be set to 1 in this case.
+
+ Histogram bins are 16-bit numbers and each bin represent an equal
+amount of text-space. For example, if the text-segment is one thousand
+bytes long and if there are ten bins in the histogram, each bin
+represents one hundred bytes.
+
+9.2.2 Call-Graph Records
+------------------------
+
+Call-graph records have a format that is identical to the one used in
+the BSD-derived file format. It consists of an arc in the call graph
+and a count indicating the number of times the arc was traversed during
+program execution. Arcs are specified by a pair of addresses: the
+first must be within caller's function and the second must be within
+the callee's function. When performing profiling at the function
+level, these addresses can point anywhere within the respective
+function. However, when profiling at the line-level, it is better if
+the addresses are as close to the call-site/entry-point as possible.
+This will ensure that the line-level call-graph is able to identify
+exactly which line of source code performed calls to a function.
+
+9.2.3 Basic-Block Execution Count Records
+-----------------------------------------
+
+Basic-block execution count records consist of a header followed by a
+sequence of address/count pairs. The header simply specifies the
+length of the sequence. In an address/count pair, the address
+identifies a basic-block and the count specifies the number of times
+that basic-block was executed. Any address within the basic-address can
+be used.
+
+\1f
+File: gprof.info, Node: Internals, Next: Debugging, Prev: File Format, Up: Details
+
+9.3 `gprof''s Internal Operation
+================================
+
+Like most programs, `gprof' begins by processing its options. During
+this stage, it may building its symspec list (`sym_ids.c:sym_id_add'),
+if options are specified which use symspecs. `gprof' maintains a
+single linked list of symspecs, which will eventually get turned into
+12 symbol tables, organized into six include/exclude pairs--one pair
+each for the flat profile (INCL_FLAT/EXCL_FLAT), the call graph arcs
+(INCL_ARCS/EXCL_ARCS), printing in the call graph
+(INCL_GRAPH/EXCL_GRAPH), timing propagation in the call graph
+(INCL_TIME/EXCL_TIME), the annotated source listing
+(INCL_ANNO/EXCL_ANNO), and the execution count listing
+(INCL_EXEC/EXCL_EXEC).
+
+ After option processing, `gprof' finishes building the symspec list
+by adding all the symspecs in `default_excluded_list' to the exclude
+lists EXCL_TIME and EXCL_GRAPH, and if line-by-line profiling is
+specified, EXCL_FLAT as well. These default excludes are not added to
+EXCL_ANNO, EXCL_ARCS, and EXCL_EXEC.
+
+ Next, the BFD library is called to open the object file, verify that
+it is an object file, and read its symbol table (`core.c:core_init'),
+using `bfd_canonicalize_symtab' after mallocing an appropriately sized
+array of symbols. At this point, function mappings are read (if the
+`--file-ordering' option has been specified), and the core text space
+is read into memory (if the `-c' option was given).
+
+ `gprof''s own symbol table, an array of Sym structures, is now built.
+This is done in one of two ways, by one of two routines, depending on
+whether line-by-line profiling (`-l' option) has been enabled. For
+normal profiling, the BFD canonical symbol table is scanned. For
+line-by-line profiling, every text space address is examined, and a new
+symbol table entry gets created every time the line number changes. In
+either case, two passes are made through the symbol table--one to count
+the size of the symbol table required, and the other to actually read
+the symbols. In between the two passes, a single array of type `Sym'
+is created of the appropriate length. Finally,
+`symtab.c:symtab_finalize' is called to sort the symbol table and
+remove duplicate entries (entries with the same memory address).
+
+ The symbol table must be a contiguous array for two reasons. First,
+the `qsort' library function (which sorts an array) will be used to
+sort the symbol table. Also, the symbol lookup routine
+(`symtab.c:sym_lookup'), which finds symbols based on memory address,
+uses a binary search algorithm which requires the symbol table to be a
+sorted array. Function symbols are indicated with an `is_func' flag.
+Line number symbols have no special flags set. Additionally, a symbol
+can have an `is_static' flag to indicate that it is a local symbol.
+
+ With the symbol table read, the symspecs can now be translated into
+Syms (`sym_ids.c:sym_id_parse'). Remember that a single symspec can
+match multiple symbols. An array of symbol tables (`syms') is created,
+each entry of which is a symbol table of Syms to be included or
+excluded from a particular listing. The master symbol table and the
+symspecs are examined by nested loops, and every symbol that matches a
+symspec is inserted into the appropriate syms table. This is done
+twice, once to count the size of each required symbol table, and again
+to build the tables, which have been malloced between passes. From now
+on, to determine whether a symbol is on an include or exclude symspec
+list, `gprof' simply uses its standard symbol lookup routine on the
+appropriate table in the `syms' array.
+
+ Now the profile data file(s) themselves are read
+(`gmon_io.c:gmon_out_read'), first by checking for a new-style
+`gmon.out' header, then assuming this is an old-style BSD `gmon.out' if
+the magic number test failed.
+
+ New-style histogram records are read by `hist.c:hist_read_rec'. For
+the first histogram record, allocate a memory array to hold all the
+bins, and read them in. When multiple profile data files (or files
+with multiple histogram records) are read, the memory ranges of each
+pair of histogram records must be either equal, or non-overlapping.
+For each pair of histogram records, the resolution (memory region size
+divided by the number of bins) must be the same. The time unit must be
+the same for all histogram records. If the above containts are met, all
+histograms for the same memory range are merged.
+
+ As each call graph record is read (`call_graph.c:cg_read_rec'), the
+parent and child addresses are matched to symbol table entries, and a
+call graph arc is created by `cg_arcs.c:arc_add', unless the arc fails
+a symspec check against INCL_ARCS/EXCL_ARCS. As each arc is added, a
+linked list is maintained of the parent's child arcs, and of the child's
+parent arcs. Both the child's call count and the arc's call count are
+incremented by the record's call count.
+
+ Basic-block records are read (`basic_blocks.c:bb_read_rec'), but
+only if line-by-line profiling has been selected. Each basic-block
+address is matched to a corresponding line symbol in the symbol table,
+and an entry made in the symbol's bb_addr and bb_calls arrays. Again,
+if multiple basic-block records are present for the same address, the
+call counts are cumulative.
+
+ A gmon.sum file is dumped, if requested (`gmon_io.c:gmon_out_write').
+
+ If histograms were present in the data files, assign them to symbols
+(`hist.c:hist_assign_samples') by iterating over all the sample bins
+and assigning them to symbols. Since the symbol table is sorted in
+order of ascending memory addresses, we can simple follow along in the
+symbol table as we make our pass over the sample bins. This step
+includes a symspec check against INCL_FLAT/EXCL_FLAT. Depending on the
+histogram scale factor, a sample bin may span multiple symbols, in
+which case a fraction of the sample count is allocated to each symbol,
+proportional to the degree of overlap. This effect is rare for normal
+profiling, but overlaps are more common during line-by-line profiling,
+and can cause each of two adjacent lines to be credited with half a
+hit, for example.
+
+ If call graph data is present, `cg_arcs.c:cg_assemble' is called.
+First, if `-c' was specified, a machine-dependent routine (`find_call')
+scans through each symbol's machine code, looking for subroutine call
+instructions, and adding them to the call graph with a zero call count.
+A topological sort is performed by depth-first numbering all the
+symbols (`cg_dfn.c:cg_dfn'), so that children are always numbered less
+than their parents, then making a array of pointers into the symbol
+table and sorting it into numerical order, which is reverse topological
+order (children appear before parents). Cycles are also detected at
+this point, all members of which are assigned the same topological
+number. Two passes are now made through this sorted array of symbol
+pointers. The first pass, from end to beginning (parents to children),
+computes the fraction of child time to propagate to each parent and a
+print flag. The print flag reflects symspec handling of
+INCL_GRAPH/EXCL_GRAPH, with a parent's include or exclude (print or no
+print) property being propagated to its children, unless they
+themselves explicitly appear in INCL_GRAPH or EXCL_GRAPH. A second
+pass, from beginning to end (children to parents) actually propagates
+the timings along the call graph, subject to a check against
+INCL_TIME/EXCL_TIME. With the print flag, fractions, and timings now
+stored in the symbol structures, the topological sort array is now
+discarded, and a new array of pointers is assembled, this time sorted
+by propagated time.
+
+ Finally, print the various outputs the user requested, which is now
+fairly straightforward. The call graph (`cg_print.c:cg_print') and
+flat profile (`hist.c:hist_print') are regurgitations of values already
+computed. The annotated source listing
+(`basic_blocks.c:print_annotated_source') uses basic-block information,
+if present, to label each line of code with call counts, otherwise only
+the function call counts are presented.
+
+ The function ordering code is marginally well documented in the
+source code itself (`cg_print.c'). Basically, the functions with the
+most use and the most parents are placed first, followed by other
+functions with the most use, followed by lower use functions, followed
+by unused functions at the end.
+
+\1f
+File: gprof.info, Node: Debugging, Prev: Internals, Up: Details
+
+9.4 Debugging `gprof'
+=====================
+
+If `gprof' was compiled with debugging enabled, the `-d' option
+triggers debugging output (to stdout) which can be helpful in
+understanding its operation. The debugging number specified is
+interpreted as a sum of the following options:
+
+2 - Topological sort
+ Monitor depth-first numbering of symbols during call graph analysis
+
+4 - Cycles
+ Shows symbols as they are identified as cycle heads
+
+16 - Tallying
+ As the call graph arcs are read, show each arc and how the total
+ calls to each function are tallied
+
+32 - Call graph arc sorting
+ Details sorting individual parents/children within each call graph
+ entry
+
+64 - Reading histogram and call graph records
+ Shows address ranges of histograms as they are read, and each call
+ graph arc
+
+128 - Symbol table
+ Reading, classifying, and sorting the symbol table from the object
+ file. For line-by-line profiling (`-l' option), also shows line
+ numbers being assigned to memory addresses.
+
+256 - Static call graph
+ Trace operation of `-c' option
+
+512 - Symbol table and arc table lookups
+ Detail operation of lookup routines
+
+1024 - Call graph propagation
+ Shows how function times are propagated along the call graph
+
+2048 - Basic-blocks
+ Shows basic-block records as they are read from profile data (only
+ meaningful with `-l' option)
+
+4096 - Symspecs
+ Shows symspec-to-symbol pattern matching operation
+
+8192 - Annotate source
+ Tracks operation of `-A' option
+
+\1f
+File: gprof.info, Node: GNU Free Documentation License, Prev: Details, Up: Top
+
+Appendix A GNU Free Documentation License
+*****************************************
+
+ Version 1.1, March 2000
+
+ Copyright (C) 2000, 2003 Free Software Foundation, Inc.
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+
+ 0. PREAMBLE
+
+ The purpose of this License is to make a manual, textbook, or other
+ written document "free" in the sense of freedom: to assure everyone
+ the effective freedom to copy and redistribute it, with or without
+ modifying it, either commercially or noncommercially. Secondarily,
+ this License preserves for the author and publisher a way to get
+ credit for their work, while not being considered responsible for
+ modifications made by others.
+
+ This License is a kind of "copyleft", which means that derivative
+ works of the document must themselves be free in the same sense.
+ It complements the GNU General Public License, which is a copyleft
+ license designed for free software.
+
+ We have designed this License in order to use it for manuals for
+ free software, because free software needs free documentation: a
+ free program should come with manuals providing the same freedoms
+ that the software does. But this License is not limited to
+ software manuals; it can be used for any textual work, regardless
+ of subject matter or whether it is published as a printed book.
+ We recommend this License principally for works whose purpose is
+ instruction or reference.
+
+
+ 1. APPLICABILITY AND DEFINITIONS
+
+ This License applies to any manual or other work that contains a
+ notice placed by the copyright holder saying it can be distributed
+ under the terms of this License. The "Document", below, refers to
+ any such manual or work. Any member of the public is a licensee,
+ and is addressed as "you."
+
+ A "Modified Version" of the Document means any work containing the
+ Document or a portion of it, either copied verbatim, or with
+ modifications and/or translated into another language.
+
+ A "Secondary Section" is a named appendix or a front-matter
+ section of the Document that deals exclusively with the
+ relationship of the publishers or authors of the Document to the
+ Document's overall subject (or to related matters) and contains
+ nothing that could fall directly within that overall subject.
+ (For example, if the Document is in part a textbook of
+ mathematics, a Secondary Section may not explain any mathematics.)
+ The relationship could be a matter of historical connection with
+ the subject or with related matters, or of legal, commercial,
+ philosophical, ethical or political position regarding them.
+
+ The "Invariant Sections" are certain Secondary Sections whose
+ titles are designated, as being those of Invariant Sections, in
+ the notice that says that the Document is released under this
+ License.
+
+ The "Cover Texts" are certain short passages of text that are
+ listed, as Front-Cover Texts or Back-Cover Texts, in the notice
+ that says that the Document is released under this License.
+
+ A "Transparent" copy of the Document means a machine-readable copy,
+ represented in a format whose specification is available to the
+ general public, whose contents can be viewed and edited directly
+ and straightforwardly with generic text editors or (for images
+ composed of pixels) generic paint programs or (for drawings) some
+ widely available drawing editor, and that is suitable for input to
+ text formatters or for automatic translation to a variety of
+ formats suitable for input to text formatters. A copy made in an
+ otherwise Transparent file format whose markup has been designed
+ to thwart or discourage subsequent modification by readers is not
+ Transparent. A copy that is not "Transparent" is called "Opaque."
+
+ Examples of suitable formats for Transparent copies include plain
+ ASCII without markup, Texinfo input format, LaTeX input format,
+ SGML or XML using a publicly available DTD, and
+ standard-conforming simple HTML designed for human modification.
+ Opaque formats include PostScript, PDF, proprietary formats that
+ can be read and edited only by proprietary word processors, SGML
+ or XML for which the DTD and/or processing tools are not generally
+ available, and the machine-generated HTML produced by some word
+ processors for output purposes only.
+
+ The "Title Page" means, for a printed book, the title page itself,
+ plus such following pages as are needed to hold, legibly, the
+ material this License requires to appear in the title page. For
+ works in formats which do not have any title page as such, "Title
+ Page" means the text near the most prominent appearance of the
+ work's title, preceding the beginning of the body of the text.
+
+ 2. VERBATIM COPYING
+
+ You may copy and distribute the Document in any medium, either
+ commercially or noncommercially, provided that this License, the
+ copyright notices, and the license notice saying this License
+ applies to the Document are reproduced in all copies, and that you
+ add no other conditions whatsoever to those of this License. You
+ may not use technical measures to obstruct or control the reading
+ or further copying of the copies you make or distribute. However,
+ you may accept compensation in exchange for copies. If you
+ distribute a large enough number of copies you must also follow
+ the conditions in section 3.
+
+ You may also lend copies, under the same conditions stated above,
+ and you may publicly display copies.
+
+ 3. COPYING IN QUANTITY
+
+ If you publish printed copies of the Document numbering more than
+ 100, and the Document's license notice requires Cover Texts, you
+ must enclose the copies in covers that carry, clearly and legibly,
+ all these Cover Texts: Front-Cover Texts on the front cover, and
+ Back-Cover Texts on the back cover. Both covers must also clearly
+ and legibly identify you as the publisher of these copies. The
+ front cover must present the full title with all words of the
+ title equally prominent and visible. You may add other material
+ on the covers in addition. Copying with changes limited to the
+ covers, as long as they preserve the title of the Document and
+ satisfy these conditions, can be treated as verbatim copying in
+ other respects.
+
+ If the required texts for either cover are too voluminous to fit
+ legibly, you should put the first ones listed (as many as fit
+ reasonably) on the actual cover, and continue the rest onto
+ adjacent pages.
+
+ If you publish or distribute Opaque copies of the Document
+ numbering more than 100, you must either include a
+ machine-readable Transparent copy along with each Opaque copy, or
+ state in or with each Opaque copy a publicly-accessible
+ computer-network location containing a complete Transparent copy
+ of the Document, free of added material, which the general
+ network-using public has access to download anonymously at no
+ charge using public-standard network protocols. If you use the
+ latter option, you must take reasonably prudent steps, when you
+ begin distribution of Opaque copies in quantity, to ensure that
+ this Transparent copy will remain thus accessible at the stated
+ location until at least one year after the last time you
+ distribute an Opaque copy (directly or through your agents or
+ retailers) of that edition to the public.
+
+ It is requested, but not required, that you contact the authors of
+ the Document well before redistributing any large number of
+ copies, to give them a chance to provide you with an updated
+ version of the Document.
+
+ 4. MODIFICATIONS
+
+ You may copy and distribute a Modified Version of the Document
+ under the conditions of sections 2 and 3 above, provided that you
+ release the Modified Version under precisely this License, with
+ the Modified Version filling the role of the Document, thus
+ licensing distribution and modification of the Modified Version to
+ whoever possesses a copy of it. In addition, you must do these
+ things in the Modified Version:
+
+ A. Use in the Title Page (and on the covers, if any) a title
+ distinct from that of the Document, and from those of previous
+ versions (which should, if there were any, be listed in the
+ History section of the Document). You may use the same title
+ as a previous version if the original publisher of that version
+ gives permission.
+ B. List on the Title Page, as authors, one or more persons or
+ entities responsible for authorship of the modifications in the
+ Modified Version, together with at least five of the principal
+ authors of the Document (all of its principal authors, if it
+ has less than five).
+ C. State on the Title page the name of the publisher of the
+ Modified Version, as the publisher.
+ D. Preserve all the copyright notices of the Document.
+ E. Add an appropriate copyright notice for your modifications
+ adjacent to the other copyright notices.
+ F. Include, immediately after the copyright notices, a license
+ notice giving the public permission to use the Modified Version
+ under the terms of this License, in the form shown in the
+ Addendum below.
+ G. Preserve in that license notice the full lists of Invariant
+ Sections and required Cover Texts given in the Document's
+ license notice.
+ H. Include an unaltered copy of this License.
+ I. Preserve the section entitled "History", and its title, and add
+ to it an item stating at least the title, year, new authors, and
+ publisher of the Modified Version as given on the Title Page.
+ If there is no section entitled "History" in the Document,
+ create one stating the title, year, authors, and publisher of
+ the Document as given on its Title Page, then add an item
+ describing the Modified Version as stated in the previous
+ sentence.
+ J. Preserve the network location, if any, given in the Document for
+ public access to a Transparent copy of the Document, and
+ likewise the network locations given in the Document for
+ previous versions it was based on. These may be placed in the
+ "History" section. You may omit a network location for a work
+ that was published at least four years before the Document
+ itself, or if the original publisher of the version it refers
+ to gives permission.
+ K. In any section entitled "Acknowledgements" or "Dedications",
+ preserve the section's title, and preserve in the section all the
+ substance and tone of each of the contributor acknowledgements
+ and/or dedications given therein.
+ L. Preserve all the Invariant Sections of the Document,
+ unaltered in their text and in their titles. Section numbers
+ or the equivalent are not considered part of the section titles.
+ M. Delete any section entitled "Endorsements." Such a section
+ may not be included in the Modified Version.
+ N. Do not retitle any existing section as "Endorsements" or to
+ conflict in title with any Invariant Section.
+
+ If the Modified Version includes new front-matter sections or
+ appendices that qualify as Secondary Sections and contain no
+ material copied from the Document, you may at your option
+ designate some or all of these sections as invariant. To do this,
+ add their titles to the list of Invariant Sections in the Modified
+ Version's license notice. These titles must be distinct from any
+ other section titles.
+
+ You may add a section entitled "Endorsements", provided it contains
+ nothing but endorsements of your Modified Version by various
+ parties-for example, statements of peer review or that the text has
+ been approved by an organization as the authoritative definition
+ of a standard.
+
+ You may add a passage of up to five words as a Front-Cover Text,
+ and a passage of up to 25 words as a Back-Cover Text, to the end
+ of the list of Cover Texts in the Modified Version. Only one
+ passage of Front-Cover Text and one of Back-Cover Text may be
+ added by (or through arrangements made by) any one entity. If the
+ Document already includes a cover text for the same cover,
+ previously added by you or by arrangement made by the same entity
+ you are acting on behalf of, you may not add another; but you may
+ replace the old one, on explicit permission from the previous
+ publisher that added the old one.
+
+ The author(s) and publisher(s) of the Document do not by this
+ License give permission to use their names for publicity for or to
+ assert or imply endorsement of any Modified Version.
+
+ 5. COMBINING DOCUMENTS
+
+ You may combine the Document with other documents released under
+ this License, under the terms defined in section 4 above for
+ modified versions, provided that you include in the combination
+ all of the Invariant Sections of all of the original documents,
+ unmodified, and list them all as Invariant Sections of your
+ combined work in its license notice.
+
+ The combined work need only contain one copy of this License, and
+ multiple identical Invariant Sections may be replaced with a single
+ copy. If there are multiple Invariant Sections with the same name
+ but different contents, make the title of each such section unique
+ by adding at the end of it, in parentheses, the name of the
+ original author or publisher of that section if known, or else a
+ unique number. Make the same adjustment to the section titles in
+ the list of Invariant Sections in the license notice of the
+ combined work.
+
+ In the combination, you must combine any sections entitled
+ "History" in the various original documents, forming one section
+ entitled "History"; likewise combine any sections entitled
+ "Acknowledgements", and any sections entitled "Dedications." You
+ must delete all sections entitled "Endorsements."
+
+ 6. COLLECTIONS OF DOCUMENTS
+
+ You may make a collection consisting of the Document and other
+ documents released under this License, and replace the individual
+ copies of this License in the various documents with a single copy
+ that is included in the collection, provided that you follow the
+ rules of this License for verbatim copying of each of the
+ documents in all other respects.
+
+ You may extract a single document from such a collection, and
+ distribute it individually under this License, provided you insert
+ a copy of this License into the extracted document, and follow
+ this License in all other respects regarding verbatim copying of
+ that document.
+
+ 7. AGGREGATION WITH INDEPENDENT WORKS
+
+ A compilation of the Document or its derivatives with other
+ separate and independent documents or works, in or on a volume of
+ a storage or distribution medium, does not as a whole count as a
+ Modified Version of the Document, provided no compilation
+ copyright is claimed for the compilation. Such a compilation is
+ called an "aggregate", and this License does not apply to the
+ other self-contained works thus compiled with the Document, on
+ account of their being thus compiled, if they are not themselves
+ derivative works of the Document.
+
+ If the Cover Text requirement of section 3 is applicable to these
+ copies of the Document, then if the Document is less than one
+ quarter of the entire aggregate, the Document's Cover Texts may be
+ placed on covers that surround only the Document within the
+ aggregate. Otherwise they must appear on covers around the whole
+ aggregate.
+
+ 8. TRANSLATION
+
+ Translation is considered a kind of modification, so you may
+ distribute translations of the Document under the terms of section
+ 4. Replacing Invariant Sections with translations requires special
+ permission from their copyright holders, but you may include
+ translations of some or all Invariant Sections in addition to the
+ original versions of these Invariant Sections. You may include a
+ translation of this License provided that you also include the
+ original English version of this License. In case of a
+ disagreement between the translation and the original English
+ version of this License, the original English version will prevail.
+
+ 9. TERMINATION
+
+ You may not copy, modify, sublicense, or distribute the Document
+ except as expressly provided for under this License. Any other
+ attempt to copy, modify, sublicense or distribute the Document is
+ void, and will automatically terminate your rights under this
+ License. However, parties who have received copies, or rights,
+ from you under this License will not have their licenses
+ terminated so long as such parties remain in full compliance.
+
+ 10. FUTURE REVISIONS OF THIS LICENSE
+
+ The Free Software Foundation may publish new, revised versions of
+ the GNU Free Documentation License from time to time. Such new
+ versions will be similar in spirit to the present version, but may
+ differ in detail to address new problems or concerns. See
+ http://www.gnu.org/copyleft/.
+
+ Each version of the License is given a distinguishing version
+ number. If the Document specifies that a particular numbered
+ version of this License "or any later version" applies to it, you
+ have the option of following the terms and conditions either of
+ that specified version or of any later version that has been
+ published (not as a draft) by the Free Software Foundation. If
+ the Document does not specify a version number of this License,
+ you may choose any version ever published (not as a draft) by the
+ Free Software Foundation.
+
+
+ADDENDUM: How to use this License for your documents
+====================================================
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and license
+notices just after the title page:
+
+ Copyright (C) YEAR YOUR NAME.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.1
+ or any later version published by the Free Software Foundation;
+ with the Invariant Sections being LIST THEIR TITLES, with the
+ Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
+ A copy of the license is included in the section entitled "GNU
+ Free Documentation License."
+
+ If you have no Invariant Sections, write "with no Invariant Sections"
+instead of saying which ones are invariant. If you have no Front-Cover
+Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being
+LIST"; likewise for Back-Cover Texts.
+
+ If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of
+free software license, such as the GNU General Public License, to
+permit their use in free software.
+
+
+\1f
+Tag Table:
+Node: Top\7f719
+Node: Introduction\7f2033
+Node: Compiling\7f4525
+Node: Executing\7f7996
+Node: Invoking\7f10784
+Node: Output Options\7f12199
+Node: Analysis Options\7f19288
+Node: Miscellaneous Options\7f22689
+Node: Deprecated Options\7f23944
+Node: Symspecs\7f26023
+Node: Output\7f27849
+Node: Flat Profile\7f28889
+Node: Call Graph\7f33842
+Node: Primary\7f37074
+Node: Callers\7f39662
+Node: Subroutines\7f41779
+Node: Cycles\7f43620
+Node: Line-by-line\7f50397
+Node: Annotated Source\7f54470
+Node: Inaccuracy\7f57469
+Node: Sampling Error\7f57727
+Node: Assumptions\7f60297
+Node: How do I?\7f61767
+Node: Incompatibilities\7f63321
+Node: Details\7f64815
+Node: Implementation\7f65208
+Node: File Format\7f71105
+Node: Internals\7f75395
+Node: Debugging\7f83890
+Node: GNU Free Documentation License\7f85491
+\1f
+End Tag Table
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