source: branches/libc-0.6/src/binutils/gprof/gprof.texi@ 3102

\input texinfo @c -*-texinfo-*-
@setfilename gprof.info
@c Copyright 1988, 1992, 1993, 1998, 1999, 2000, 2001
@c Free Software Foundation, Inc.
@settitle GNU gprof
@setchapternewpage odd

@ifinfo
@c This is a dir.info fragment to support semi-automated addition of
@c manuals to an info tree.  [email protected] is developing this facility.
@format
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* gprof: (gprof).                Profiling your program's execution
END-INFO-DIR-ENTRY
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@ifinfo
This file documents the gprof profiler of the GNU system.

@c man begin COPYRIGHT
Copyright (C) 1988, 92, 97, 98, 99, 2000, 2001 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".

@c man end

@ignore
Permission is granted to process this file through Tex and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
(this paragraph not being relevant to the printed manual).

@end ignore
@end ifinfo

@finalout
@smallbook

@titlepage
@title GNU gprof
@subtitle The @sc{gnu} Profiler 
@author Jay Fenlason and Richard Stallman

@page

This manual describes the @sc{gnu} profiler, @code{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.  @sc{gnu} @code{gprof} was written by Jay Fenlason.

@vskip 0pt plus 1filll
Copyright @copyright{} 1988, 92, 97, 98, 99, 2000 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".

@end titlepage

@ifnottex
@node Top
@top Profiling a Program: Where Does It Spend Its Time?

This manual describes the @sc{gnu} profiler, @code{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.  @sc{gnu} @code{gprof} was written by Jay Fenlason.

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 @code{gprof}, and its options

* Output::              Interpreting @code{gprof}'s output

* Inaccuracy::          Potential problems you should be aware of
* How do I?::           Answers to common questions
* Incompatibilities::   (between @sc{gnu} @code{gprof} and Unix @code{gprof}.)
* Details::             Details of how profiling is done
* GNU Free Documentation License::  GNU Free Documentation License
@end menu
@end ifnottex

@node Introduction
@chapter Introduction to Profiling

@ifset man
@c man title gprof display call graph profile data

@smallexample
@c man begin SYNOPSIS
gprof [ -[abcDhilLsTvwxyz] ] [ -[ACeEfFJnNOpPqQZ][@var{name}] ] 
 [ -I @var{dirs} ] [ -d[@var{num}] ] [ -k @var{from/to} ]
 [ -m @var{min-count} ] [ -t @var{table-length} ]
 [ --[no-]annotated-source[=@var{name}] ] 
 [ --[no-]exec-counts[=@var{name}] ]
 [ --[no-]flat-profile[=@var{name}] ] [ --[no-]graph[=@var{name}] ]
 [ --[no-]time=@var{name}] [ --all-lines ] [ --brief ] 
 [ --debug[=@var{level}] ] [ --function-ordering ] 
 [ --file-ordering ] [ --directory-path=@var{dirs} ]
 [ --display-unused-functions ] [ --file-format=@var{name} ]
 [ --file-info ] [ --help ] [ --line ] [ --min-count=@var{n} ]
 [ --no-static ] [ --print-path ] [ --separate-files ]
 [ --static-call-graph ] [ --sum ] [ --table-length=@var{len} ]
 [ --traditional ] [ --version ] [ --width=@var{n} ]
 [ --ignore-non-functions ] [ --demangle[=@var{STYLE}] ]
 [ --no-demangle ] [ @var{image-file} ] [ @var{profile-file} @dots{} ]
@c man end
@end smallexample

@c man begin DESCRIPTION
@code{gprof} produces an execution profile of C, Pascal, or Fortran77 
programs.  The effect of called routines is incorporated in the profile 
of each caller.  The profile data is taken from the call graph profile file
(@file{gmon.out} default) which is created by programs
that are compiled with the @samp{-pg} option of
@code{cc}, @code{pc}, and @code{f77}.
The @samp{-pg} option also links in versions of the library routines
that are compiled for profiling.  @code{Gprof} reads the given object 
file (the default is @code{a.out}) and establishes the relation between
its symbol table and the call graph profile from @file{gmon.out}.
If more than one profile file is specified, the @code{gprof}
output shows the sum of the profile information in the given profile files.

@code{Gprof} calculates the amount of time spent in each routine.
Next, these times are propagated along the edges of the call graph.
Cycles are discovered, and calls into a cycle are made to share the time
of the cycle.

@c man end

@c man begin BUGS
The granularity of the sampling is shown, but remains
statistical at best.
We assume that the time for each execution of a function
can be expressed by the total time for the function divided
by the number of times the function is called.
Thus the time propagated along the call graph arcs to the function's
parents is directly proportional to the number of times that
arc is traversed.

Parents that are not themselves profiled will have the time of
their profiled children propagated to them, but they will appear
to be spontaneously invoked in the call graph listing, and will
not have their time propagated further.
Similarly, signal catchers, even though profiled, will appear
to be spontaneous (although for more obscure reasons).
Any profiled children of signal catchers should have their times
propagated properly, unless the signal catcher was invoked during
the execution of the profiling routine, in which case all is lost.

The profiled program must call @code{exit}(2)
or return normally for the profiling information to be saved
in the @file{gmon.out} file.
@c man end

@c man begin FILES
@table @code
@item @file{a.out}
the namelist and text space.
@item @file{gmon.out}
dynamic call graph and profile.
@item @file{gmon.sum}
summarized dynamic call graph and profile.  
@end table
@c man end

@c man begin SEEALSO
monitor(3), profil(2), cc(1), prof(1), and the Info entry for @file{gprof}.

``An Execution Profiler for Modular Programs'',
by S. Graham, P. Kessler, M. McKusick;
Software - Practice and Experience,
Vol. 13, pp. 671-685, 1983.

``gprof: A Call Graph Execution Profiler'',
by S. Graham, P. Kessler, M. McKusick;
Proceedings of the SIGPLAN '82 Symposium on Compiler Construction,
SIGPLAN Notices, Vol. 17, No  6, pp. 120-126, June 1982.
@c man end
@end ifset

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:

@itemize @bullet
@item
You must compile and link your program with profiling enabled.
@xref{Compiling}.

@item
You must execute your program to generate a profile data file.
@xref{Executing}.

@item
You must run @code{gprof} to analyze the profile data.
@xref{Invoking}.
@end itemize

The next three chapters explain these steps in greater detail.

@c man begin DESCRIPTION

Several forms of output are available from the analysis.

The @dfn{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.
@xref{Flat Profile}.

The @dfn{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.  @xref{Call Graph}.

The @dfn{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.  @xref{Annotated Source}.
@c man end

To better understand how profiling works, you may wish to read
a description of its implementation.
@xref{Implementation}.

@node Compiling
@chapter 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 @samp{-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 @code{cc}
to do the linking, simply specify @samp{-pg} in addition to your usual
options.  The same option, @samp{-pg}, alters either compilation or linking
to do what is necessary for profiling.  Here are examples:

@example
cc -g -c myprog.c utils.c -pg
cc -o myprog myprog.o utils.o -pg
@end example

The @samp{-pg} option also works with a command that both compiles and links:

@example
cc -o myprog myprog.c utils.c -g -pg
@end example

If you run the linker @code{ld} directly instead of through a compiler
such as @code{cc}, you may have to specify a profiling startup file
@file{gcrt0.o} as the first input file instead of the usual startup
file @file{crt0.o}.  In addition, you would probably want to
specify the profiling C library, @file{libc_p.a}, by writing
@samp{-lc_p} instead of the usual @samp{-lc}.  This is not absolutely
necessary, but doing this gives you number-of-calls information for
standard library functions such as @code{read} and @code{open}.  For
example:

@example
ld -o myprog /lib/gcrt0.o myprog.o utils.o -lc_p
@end example

If you compile only some of the modules of the program with @samp{-pg}, you
can still profile the program, but you won't get complete information about
the modules that were compiled without @samp{-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 @code{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 will also need to specify the @samp{-g} option,
instructing the compiler to insert debugging symbols into the program
that match program addresses to source code lines.
@xref{Line-by-line}.

In addition to the @samp{-pg} and @samp{-g} options,
you may also wish to specify the @samp{-a} option when compiling.
This will instrument
the program to perform basic-block counting.  As the program runs,
it will count how many times it executed each branch of each @samp{if}
statement, each iteration of each @samp{do} loop, etc.  This will
enable @code{gprof} to construct an annotated source code
listing showing how many times each line of code was executed.

@node Executing
@chapter Executing the Program

Once the program is compiled for profiling, you must run it in order to
generate the information that @code{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 the
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 @file{gmon.out}
just before exiting.  If there is already a file called @file{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 afterward if you are concerned that it may be overwritten.

In order to write the @file{gmon.out} file properly, your program must exit
normally: by returning from @code{main} or by calling @code{exit}.  Calling
the low-level function @code{_exit} does not write the profile data, and
neither does abnormal termination due to an unhandled signal.

The @file{gmon.out} file is written in the program's @emph{current working
directory} at the time it exits.  This means that if your program calls
@code{chdir}, the @file{gmon.out} file will be left in the last directory
your program @code{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 @sc{gnu} profiling library may also write a file
called @file{bb.out}.  This file, if present, contains an human-readable
listing of the basic-block execution counts.  Unfortunately, the
appearance of a human-readable @file{bb.out} means the basic-block
counts didn't get written into @file{gmon.out}.
The Perl script @code{bbconv.pl}, included with the @code{gprof}
source distribution, will convert a @file{bb.out} file into
a format readable by @code{gprof}.  Invoke it like this:

@smallexample
bbconv.pl < bb.out > @var{bh-data}
@end smallexample

This translates the information in @file{bb.out} into a form that
@code{gprof} can understand.  But you still need to tell @code{gprof}
about the existence of this translated information.  To do that, include
@var{bb-data} on the @code{gprof} command line, @emph{along with
@file{gmon.out}}, like this:

@smallexample
gprof @var{options} @var{executable-file} gmon.out @var{bb-data} [@var{yet-more-profile-data-files}@dots{}] [> @var{outfile}]
@end smallexample

@node Invoking
@chapter @code{gprof} Command Summary

After you have a profile data file @file{gmon.out}, you can run @code{gprof}
to interpret the information in it.  The @code{gprof} program prints a
flat profile and a call graph on standard output.  Typically you would
redirect the output of @code{gprof} into a file with @samp{>}.

You run @code{gprof} like this:

@smallexample
gprof @var{options} [@var{executable-file} [@var{profile-data-files}@dots{}]] [> @var{outfile}]
@end smallexample

@noindent
Here square-brackets indicate optional arguments.

If you omit the executable file name, the file @file{a.out} is used.  If
you give no profile data file name, the file @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 @code{gprof}'s output style
* Analysis Options::    Controlling how @code{gprof} analyses 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
@end menu

@node Output Options,Analysis Options,,Invoking
@section Output Options

@c man begin OPTIONS
These options specify which of several output formats
@code{gprof} should produce.

Many of these options take an optional @dfn{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.  @xref{Symspecs}.

Specifying any of these options overrides the default (@samp{-p -q}),
which prints a flat profile and call graph analysis
for all functions.

@table @code

@item -A[@var{symspec}]
@itemx --annotated-source[=@var{symspec}]
The @samp{-A} option causes @code{gprof} to print annotated source code.
If @var{symspec} is specified, print output only for matching symbols.
@xref{Annotated Source}.

@item -b
@itemx --brief
If the @samp{-b} option is given, @code{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.

@item -C[@var{symspec}]
@itemx --exec-counts[=@var{symspec}]
The @samp{-C} option causes @code{gprof} to
print a tally of functions and the number of times each was called.
If @var{symspec} is specified, print tally only for matching symbols.

If the profile data file contains basic-block count records, specifying
the @samp{-l} option, along with @samp{-C}, will cause basic-block
execution counts to be tallied and displayed.

@item -i
@itemx --file-info
The @samp{-i} option causes @code{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.

@item -I @var{dirs}
@itemx --directory-path=@var{dirs}
The @samp{-I} option specifies a list of search directories in
which to find source files.  Environment variable @var{GPROF_PATH}
can also be used to convey this information.
Used mostly for annotated source output.

@item -J[@var{symspec}]
@itemx --no-annotated-source[=@var{symspec}]
The @samp{-J} option causes @code{gprof} not to
print annotated source code.
If @var{symspec} is specified, @code{gprof} prints annotated source,
but excludes matching symbols.

@item -L
@itemx --print-path
Normally, source filenames are printed with the path
component suppressed.  The @samp{-L} option causes @code{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.

@item -p[@var{symspec}]
@itemx --flat-profile[=@var{symspec}]
The @samp{-p} option causes @code{gprof} to print a flat profile.
If @var{symspec} is specified, print flat profile only for matching symbols.
@xref{Flat Profile}.

@item -P[@var{symspec}]
@itemx --no-flat-profile[=@var{symspec}]
The @samp{-P} option causes @code{gprof} to suppress printing a flat profile.
If @var{symspec} is specified, @code{gprof} prints a flat profile,
but excludes matching symbols.

@item -q[@var{symspec}]
@itemx --graph[=@var{symspec}]
The @samp{-q} option causes @code{gprof} to print the call graph analysis.
If @var{symspec} is specified, print call graph only for matching symbols
and their children.
@xref{Call Graph}.

@item -Q[@var{symspec}]
@itemx --no-graph[=@var{symspec}]
The @samp{-Q} option causes @code{gprof} to suppress printing the
call graph.
If @var{symspec} is specified, @code{gprof} prints a call graph,
but excludes matching symbols.

@item -y
@itemx --separate-files
This option affects annotated source output only.
Normally, @code{gprof} prints annotated source files
to standard-output.  If this option is specified,
annotated source for a file named @file{path/@var{filename}}
is generated in the file @file{@var{filename}-ann}.  If the underlying
filesystem would truncate @file{@var{filename}-ann} so that it
overwrites the original @file{@var{filename}}, @code{gprof} generates
annotated source in the file @file{@var{filename}.ann} instead (if the
original file name has an extension, that extension is @emph{replaced}
with @file{.ann}).

@item -Z[@var{symspec}]
@itemx --no-exec-counts[=@var{symspec}]
The @samp{-Z} option causes @code{gprof} not to
print a tally of functions and the number of times each was called.
If @var{symspec} is specified, print tally, but exclude matching symbols.

@item --function-ordering
The @samp{--function-ordering} option causes @code{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.

@item --file-ordering @var{map_file}
The @samp{--file-ordering} option causes @code{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 @samp{-a} argument is highly recommended with this option.

The @var{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 @code{nm}.

@smallexample
@group
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
@dots{}

@end group
@end smallexample

To create a @var{map_file} with @sc{gnu} @code{nm}, type a command like
@kbd{nm --extern-only --defined-only -v --print-file-name program-name}.

@item -T
@itemx --traditional
The @samp{-T} option causes @code{gprof} to print its output in
``traditional'' BSD style.

@item -w @var{width}
@itemx --width=@var{width}
Sets width of output lines to @var{width}.
Currently only used when printing the function index at the bottom
of the call graph.

@item -x
@itemx --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 @code{tcov}'s @samp{-a}.

@item --demangle[=@var{style}]
@itemx --no-demangle
These options control whether C++ symbol names should be demangled when
printing output.  The default is to demangle symbols.  The
@code{--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.
@end table

@node Analysis Options,Miscellaneous Options,Output Options,Invoking
@section Analysis Options

@table @code

@item -a
@itemx --no-static
The @samp{-a} option causes @code{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.
@c This is compatible with Unix @code{gprof}, but a bad idea.  
This option affects both the flat profile and the call graph.

@item -c
@itemx --static-call-graph
The @samp{-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 @emph{not} found
by this option.
Parents or children identified via this heuristic
are indicated in the call graph with call counts of @samp{0}.

@item -D
@itemx --ignore-non-functions
The @samp{-D} option causes @code{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).

@item -k @var{from}/@var{to}
The @samp{-k} option allows you to delete from the call graph any arcs from
symbols matching symspec @var{from} to those matching symspec @var{to}.

@item -l
@itemx --line
The @samp{-l} option enables line-by-line profiling, which causes
histogram hits to be charged to individual source code lines,
instead of functions.
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 @code{gprof}, and magnifies statistical
inaccuracies.
@xref{Sampling Error}.

@item -m @var{num}
@itemx --min-count=@var{num}
This option affects execution count output only.
Symbols that are executed less than @var{num} times are suppressed.

@item -n[@var{symspec}]
@itemx --time[=@var{symspec}]
The @samp{-n} option causes @code{gprof}, in its call graph analysis,
to only propagate times for symbols matching @var{symspec}.

@item -N[@var{symspec}]
@itemx --no-time[=@var{symspec}]
The @samp{-n} option causes @code{gprof}, in its call graph analysis,
not to propagate times for symbols matching @var{symspec}.

@item -z
@itemx --display-unused-functions
If you give the @samp{-z} option, @code{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
@samp{-c} option for discovering which routines were never called.

@end table

@node Miscellaneous Options,Deprecated Options,Analysis Options,Invoking
@section Miscellaneous Options

@table @code

@item -d[@var{num}]
@itemx --debug[=@var{num}]
The @samp{-d @var{num}} option specifies debugging options.
If @var{num} is not specified, enable all debugging.
@xref{Debugging}.

@item -O@var{name}
@itemx --file-format=@var{name}
Selects the format of the profile data files.  Recognized formats are
@samp{auto} (the default), @samp{bsd}, @samp{4.4bsd}, @samp{magic}, and
@samp{prof} (not yet supported).

@item -s
@itemx --sum
The @samp{-s} option causes @code{gprof} to summarize the information
in the profile data files it read in, and write out a profile data
file called @file{gmon.sum}, which contains all the information from
the profile data files that @code{gprof} read in.  The file @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 @file{gmon.sum}.

Eventually you can run @code{gprof} again without @samp{-s} to analyze the
cumulative data in the file @file{gmon.sum}.

@item -v
@itemx --version
The @samp{-v} flag causes @code{gprof} to print the current version
number, and then exit.

@end table

@node Deprecated Options,Symspecs,Miscellaneous Options,Invoking
@section Deprecated Options

@table @code

These options have been replaced with newer versions that use symspecs.

@item -e @var{function_name}
The @samp{-e @var{function}} option tells @code{gprof} to not print
information about the function @var{function_name} (and its
children@dots{}) 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 @samp{[not printed]}.  More than one @samp{-e} option may be
given; only one @var{function_name} may be indicated with each @samp{-e}
option. 

@item -E @var{function_name}
The @code{-E @var{function}} option works like the @code{-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 @samp{-E} option may be given; only one
@var{function_name} may be indicated with each @samp{-E} option.

@item -f @var{function_name}
The @samp{-f @var{function}} option causes @code{gprof} to limit the
call graph to the function @var{function_name} and its children (and
their children@dots{}).  More than one @samp{-f} option may be given;
only one @var{function_name} may be indicated with each @samp{-f}
option.  

@item -F @var{function_name}
The @samp{-F @var{function}} option works like the @code{-f} option, but
only time spent in the function and its children (and their
children@dots{}) will be used to determine total-time and
percentages-of-time for the call graph.  More than one @samp{-F} option
may be given; only one @var{function_name} may be indicated with each
@samp{-F} option.  The @samp{-F} option overrides the @samp{-E} option.

@end table

@c man end

Note that only one function can be specified with each @code{-e},
@code{-E}, @code{-f} or @code{-F} option.  To specify more than one
function, use multiple options.  For example, this command:

@example
gprof -e boring -f foo -f bar myprogram > gprof.output
@end example

@noindent
lists in the call graph all functions that were reached from either
@code{foo} or @code{bar} and were not reachable from @code{boring}.

@node Symspecs,,Deprecated Options,Invoking
@section Symspecs

Many of the output options allow functions to be included or excluded
using @dfn{symspecs} (symbol specifications), which observe the
following syntax:

@example
  filename_containing_a_dot
| funcname_not_containing_a_dot
| linenumber
| ( [ any_filename ] `:' ( any_funcname | linenumber ) )
@end example

Here are some sample symspecs:

@table @samp
@item main.c
Selects everything in file @file{main.c}---the
dot in the string tells @code{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, @samp{odd:} is
interpreted as the file named @file{odd}.

@item main
Selects all functions named @samp{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, @samp{:.mul} selects
function @samp{.mul}.

In some object file formats, symbols have a leading underscore.
@code{gprof} will normally not print these underscores.  When you name a
symbol in a symspec, you should type it exactly as @code{gprof} prints
it in its output.  For example, if the compiler produces a symbol
@samp{_main} from your @code{main} function, @code{gprof} still prints
it as @samp{main} in its output, so you should use @samp{main} in
symspecs.

@item main.c:main
Selects function @samp{main} in file @file{main.c}.

@item main.c:134
Selects line 134 in file @file{main.c}.
@end table

@node Output
@chapter Interpreting @code{gprof}'s Output

@code{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.
@xref{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::        @code{gprof} can analyze individual source code lines
* Annotated Source::    The annotated source listing displays source code
                            labeled with execution counts
@end menu


@node Flat Profile,Call Graph,,Output
@section The Flat Profile
@cindex flat profile

The @dfn{flat profile} shows the total amount of time your program
spent executing each function.  Unless the @samp{-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:

@smallexample
@group
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
@dots{}
@end group
@end smallexample

@noindent
The functions are sorted by first by decreasing run-time spent in them,
then by decreasing number of calls, then alphabetically by name.  The
functions @samp{mcount} and @samp{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 @dfn{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 @samp{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 @samp{open} function, as indicated by the
@samp{self seconds} field.  Each of the other four samples
occurred one each in @samp{offtime}, @samp{memccpy}, @samp{write},
and @samp{mcount}.
Since only six samples were taken, none of these values can
be regarded as particularly reliable.
In another run,
the @samp{self seconds} field for
@samp{mcount} might well be @samp{0.00} or @samp{0.02}.
@xref{Sampling Error}, for a complete discussion.

The remaining functions in the listing (those whose
@samp{self seconds} field is @samp{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 @samp{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:

@table @code
@item % time
This is the percentage of the total execution time your program spent
in this function.  These should all add up to 100%.

@item 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.

@item self seconds
This is the number of seconds accounted for by this function alone.
The flat profile listing is sorted first by this number.

@item 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 @dfn{calls} field is blank.

@item 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.

@item 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.

@item name
This is the name of the function.   The flat profile is sorted by this
field alphabetically after the @dfn{self seconds} and @dfn{calls}
fields are sorted.
@end table

@node Call Graph,Line-by-line,Flat Profile,Output
@section The Call Graph
@cindex call graph

The @dfn{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 @code{gprof} run as the flat profile example in the previous
chapter.

@smallexample
@group
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]
-----------------------------------------------
@end group
@end smallexample