Home | History | Annotate | Download | only in info
      1 This is gprof.info, produced by makeinfo version 4.13 from
      2 /tmp/android-8532/src/build/../binutils/binutils-2.21/gprof/gprof.texi.
      3 
      4 INFO-DIR-SECTION Software development
      5 START-INFO-DIR-ENTRY
      6 * gprof: (gprof).                Profiling your program's execution
      7 END-INFO-DIR-ENTRY
      8 
      9    This file documents the gprof profiler of the GNU system.
     10 
     11    Copyright (C) 1988, 1992, 1997, 1998, 1999, 2000, 2001, 2003, 2007,
     12 2008, 2009 Free Software Foundation, Inc.
     13 
     14    Permission is granted to copy, distribute and/or modify this document
     15 under the terms of the GNU Free Documentation License, Version 1.3 or
     16 any later version published by the Free Software Foundation; with no
     17 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
     18 Texts.  A copy of the license is included in the section entitled "GNU
     19 Free Documentation License".
     20 
     21 
     22 File: gprof.info,  Node: Top,  Next: Introduction,  Up: (dir)
     23 
     24 Profiling a Program: Where Does It Spend Its Time?
     25 **************************************************
     26 
     27 This manual describes the GNU profiler, `gprof', and how you can use it
     28 to determine which parts of a program are taking most of the execution
     29 time.  We assume that you know how to write, compile, and execute
     30 programs.  GNU `gprof' was written by Jay Fenlason.
     31 
     32    This manual is for `gprof' (GNU Binutils) version 2.21.
     33 
     34    This document is distributed under the terms of the GNU Free
     35 Documentation License version 1.3.  A copy of the license is included
     36 in the section entitled "GNU Free Documentation License".
     37 
     38 * Menu:
     39 
     40 * Introduction::        What profiling means, and why it is useful.
     41 
     42 * Compiling::           How to compile your program for profiling.
     43 * Executing::           Executing your program to generate profile data
     44 * Invoking::            How to run `gprof', and its options
     45 
     46 * Output::              Interpreting `gprof''s output
     47 
     48 * Inaccuracy::          Potential problems you should be aware of
     49 * How do I?::           Answers to common questions
     50 * Incompatibilities::   (between GNU `gprof' and Unix `gprof'.)
     51 * Details::             Details of how profiling is done
     52 * GNU Free Documentation License::  GNU Free Documentation License
     53 
     54 
     55 File: gprof.info,  Node: Introduction,  Next: Compiling,  Prev: Top,  Up: Top
     56 
     57 1 Introduction to Profiling
     58 ***************************
     59 
     60 Profiling allows you to learn where your program spent its time and
     61 which functions called which other functions while it was executing.
     62 This information can show you which pieces of your program are slower
     63 than you expected, and might be candidates for rewriting to make your
     64 program execute faster.  It can also tell you which functions are being
     65 called more or less often than you expected.  This may help you spot
     66 bugs that had otherwise been unnoticed.
     67 
     68    Since the profiler uses information collected during the actual
     69 execution of your program, it can be used on programs that are too
     70 large or too complex to analyze by reading the source.  However, how
     71 your program is run will affect the information that shows up in the
     72 profile data.  If you don't use some feature of your program while it
     73 is being profiled, no profile information will be generated for that
     74 feature.
     75 
     76    Profiling has several steps:
     77 
     78    * You must compile and link your program with profiling enabled.
     79      *Note Compiling a Program for Profiling: Compiling.
     80 
     81    * You must execute your program to generate a profile data file.
     82      *Note Executing the Program: Executing.
     83 
     84    * You must run `gprof' to analyze the profile data.  *Note `gprof'
     85      Command Summary: Invoking.
     86 
     87    The next three chapters explain these steps in greater detail.
     88 
     89    Several forms of output are available from the analysis.
     90 
     91    The "flat profile" shows how much time your program spent in each
     92 function, and how many times that function was called.  If you simply
     93 want to know which functions burn most of the cycles, it is stated
     94 concisely here.  *Note The Flat Profile: Flat Profile.
     95 
     96    The "call graph" shows, for each function, which functions called
     97 it, which other functions it called, and how many times.  There is also
     98 an estimate of how much time was spent in the subroutines of each
     99 function.  This can suggest places where you might try to eliminate
    100 function calls that use a lot of time.  *Note The Call Graph: Call
    101 Graph.
    102 
    103    The "annotated source" listing is a copy of the program's source
    104 code, labeled with the number of times each line of the program was
    105 executed.  *Note The Annotated Source Listing: Annotated Source.
    106 
    107    To better understand how profiling works, you may wish to read a
    108 description of its implementation.  *Note Implementation of Profiling:
    109 Implementation.
    110 
    111 
    112 File: gprof.info,  Node: Compiling,  Next: Executing,  Prev: Introduction,  Up: Top
    113 
    114 2 Compiling a Program for Profiling
    115 ***********************************
    116 
    117 The first step in generating profile information for your program is to
    118 compile and link it with profiling enabled.
    119 
    120    To compile a source file for profiling, specify the `-pg' option when
    121 you run the compiler.  (This is in addition to the options you normally
    122 use.)
    123 
    124    To link the program for profiling, if you use a compiler such as `cc'
    125 to do the linking, simply specify `-pg' in addition to your usual
    126 options.  The same option, `-pg', alters either compilation or linking
    127 to do what is necessary for profiling.  Here are examples:
    128 
    129      cc -g -c myprog.c utils.c -pg
    130      cc -o myprog myprog.o utils.o -pg
    131 
    132    The `-pg' option also works with a command that both compiles and
    133 links:
    134 
    135      cc -o myprog myprog.c utils.c -g -pg
    136 
    137    Note: The `-pg' option must be part of your compilation options as
    138 well as your link options.  If it is not then no call-graph data will
    139 be gathered and when you run `gprof' you will get an error message like
    140 this:
    141 
    142      gprof: gmon.out file is missing call-graph data
    143 
    144    If you add the `-Q' switch to suppress the printing of the call
    145 graph data you will still be able to see the time samples:
    146 
    147      Flat profile:
    148 
    149      Each sample counts as 0.01 seconds.
    150        %   cumulative   self              self     total
    151       time   seconds   seconds    calls  Ts/call  Ts/call  name
    152       44.12      0.07     0.07                             zazLoop
    153       35.29      0.14     0.06                             main
    154       20.59      0.17     0.04                             bazMillion
    155 
    156    If you run the linker `ld' directly instead of through a compiler
    157 such as `cc', you may have to specify a profiling startup file
    158 `gcrt0.o' as the first input file instead of the usual startup file
    159 `crt0.o'.  In addition, you would probably want to specify the
    160 profiling C library, `libc_p.a', by writing `-lc_p' instead of the
    161 usual `-lc'.  This is not absolutely necessary, but doing this gives
    162 you number-of-calls information for standard library functions such as
    163 `read' and `open'.  For example:
    164 
    165      ld -o myprog /lib/gcrt0.o myprog.o utils.o -lc_p
    166 
    167    If you are running the program on a system which supports shared
    168 libraries you may run into problems with the profiling support code in
    169 a shared library being called before that library has been fully
    170 initialised.  This is usually detected by the program encountering a
    171 segmentation fault as soon as it is run.  The solution is to link
    172 against a static version of the library containing the profiling
    173 support code, which for `gcc' users can be done via the `-static' or
    174 `-static-libgcc' command line option.  For example:
    175 
    176      gcc -g -pg -static-libgcc myprog.c utils.c -o myprog
    177 
    178    If you compile only some of the modules of the program with `-pg',
    179 you can still profile the program, but you won't get complete
    180 information about the modules that were compiled without `-pg'.  The
    181 only information you get for the functions in those modules is the
    182 total time spent in them; there is no record of how many times they
    183 were called, or from where.  This will not affect the flat profile
    184 (except that the `calls' field for the functions will be blank), but
    185 will greatly reduce the usefulness of the call graph.
    186 
    187    If you wish to perform line-by-line profiling you should use the
    188 `gcov' tool instead of `gprof'.  See that tool's manual or info pages
    189 for more details of how to do this.
    190 
    191    Note, older versions of `gcc' produce line-by-line profiling
    192 information that works with `gprof' rather than `gcov' so there is
    193 still support for displaying this kind of information in `gprof'. *Note
    194 Line-by-line Profiling: Line-by-line.
    195 
    196    It also worth noting that `gcc' implements a
    197 `-finstrument-functions' command line option which will insert calls to
    198 special user supplied instrumentation routines at the entry and exit of
    199 every function in their program.  This can be used to implement an
    200 alternative profiling scheme.
    201 
    202 
    203 File: gprof.info,  Node: Executing,  Next: Invoking,  Prev: Compiling,  Up: Top
    204 
    205 3 Executing the Program
    206 ***********************
    207 
    208 Once the program is compiled for profiling, you must run it in order to
    209 generate the information that `gprof' needs.  Simply run the program as
    210 usual, using the normal arguments, file names, etc.  The program should
    211 run normally, producing the same output as usual.  It will, however, run
    212 somewhat slower than normal because of the time spent collecting and
    213 writing the profile data.
    214 
    215    The way you run the program--the arguments and input that you give
    216 it--may have a dramatic effect on what the profile information shows.
    217 The profile data will describe the parts of the program that were
    218 activated for the particular input you use.  For example, if the first
    219 command you give to your program is to quit, the profile data will show
    220 the time used in initialization and in cleanup, but not much else.
    221 
    222    Your program will write the profile data into a file called
    223 `gmon.out' just before exiting.  If there is already a file called
    224 `gmon.out', its contents are overwritten.  There is currently no way to
    225 tell the program to write the profile data under a different name, but
    226 you can rename the file afterwards if you are concerned that it may be
    227 overwritten.
    228 
    229    In order to write the `gmon.out' file properly, your program must
    230 exit normally: by returning from `main' or by calling `exit'.  Calling
    231 the low-level function `_exit' does not write the profile data, and
    232 neither does abnormal termination due to an unhandled signal.
    233 
    234    The `gmon.out' file is written in the program's _current working
    235 directory_ at the time it exits.  This means that if your program calls
    236 `chdir', the `gmon.out' file will be left in the last directory your
    237 program `chdir''d to.  If you don't have permission to write in this
    238 directory, the file is not written, and you will get an error message.
    239 
    240    Older versions of the GNU profiling library may also write a file
    241 called `bb.out'.  This file, if present, contains an human-readable
    242 listing of the basic-block execution counts.  Unfortunately, the
    243 appearance of a human-readable `bb.out' means the basic-block counts
    244 didn't get written into `gmon.out'.  The Perl script `bbconv.pl',
    245 included with the `gprof' source distribution, will convert a `bb.out'
    246 file into a format readable by `gprof'.  Invoke it like this:
    247 
    248      bbconv.pl < bb.out > BH-DATA
    249 
    250    This translates the information in `bb.out' into a form that `gprof'
    251 can understand.  But you still need to tell `gprof' about the existence
    252 of this translated information.  To do that, include BB-DATA on the
    253 `gprof' command line, _along with `gmon.out'_, like this:
    254 
    255      gprof OPTIONS EXECUTABLE-FILE gmon.out BB-DATA [YET-MORE-PROFILE-DATA-FILES...] [> OUTFILE]
    256 
    257 
    258 File: gprof.info,  Node: Invoking,  Next: Output,  Prev: Executing,  Up: Top
    259 
    260 4 `gprof' Command Summary
    261 *************************
    262 
    263 After you have a profile data file `gmon.out', you can run `gprof' to
    264 interpret the information in it.  The `gprof' program prints a flat
    265 profile and a call graph on standard output.  Typically you would
    266 redirect the output of `gprof' into a file with `>'.
    267 
    268    You run `gprof' like this:
    269 
    270      gprof OPTIONS [EXECUTABLE-FILE [PROFILE-DATA-FILES...]] [> OUTFILE]
    271 
    272 Here square-brackets indicate optional arguments.
    273 
    274    If you omit the executable file name, the file `a.out' is used.  If
    275 you give no profile data file name, the file `gmon.out' is used.  If
    276 any file is not in the proper format, or if the profile data file does
    277 not appear to belong to the executable file, an error message is
    278 printed.
    279 
    280    You can give more than one profile data file by entering all their
    281 names after the executable file name; then the statistics in all the
    282 data files are summed together.
    283 
    284    The order of these options does not matter.
    285 
    286 * Menu:
    287 
    288 * Output Options::      Controlling `gprof''s output style
    289 * Analysis Options::    Controlling how `gprof' analyzes its data
    290 * Miscellaneous Options::
    291 * Deprecated Options::  Options you no longer need to use, but which
    292                             have been retained for compatibility
    293 * Symspecs::            Specifying functions to include or exclude
    294 
    295 
    296 File: gprof.info,  Node: Output Options,  Next: Analysis Options,  Up: Invoking
    297 
    298 4.1 Output Options
    299 ==================
    300 
    301 These options specify which of several output formats `gprof' should
    302 produce.
    303 
    304    Many of these options take an optional "symspec" to specify
    305 functions to be included or excluded.  These options can be specified
    306 multiple times, with different symspecs, to include or exclude sets of
    307 symbols.  *Note Symspecs: Symspecs.
    308 
    309    Specifying any of these options overrides the default (`-p -q'),
    310 which prints a flat profile and call graph analysis for all functions.
    311 
    312 `-A[SYMSPEC]'
    313 `--annotated-source[=SYMSPEC]'
    314      The `-A' option causes `gprof' to print annotated source code.  If
    315      SYMSPEC is specified, print output only for matching symbols.
    316      *Note The Annotated Source Listing: Annotated Source.
    317 
    318 `-b'
    319 `--brief'
    320      If the `-b' option is given, `gprof' doesn't print the verbose
    321      blurbs that try to explain the meaning of all of the fields in the
    322      tables.  This is useful if you intend to print out the output, or
    323      are tired of seeing the blurbs.
    324 
    325 `-C[SYMSPEC]'
    326 `--exec-counts[=SYMSPEC]'
    327      The `-C' option causes `gprof' to print a tally of functions and
    328      the number of times each was called.  If SYMSPEC is specified,
    329      print tally only for matching symbols.
    330 
    331      If the profile data file contains basic-block count records,
    332      specifying the `-l' option, along with `-C', will cause basic-block
    333      execution counts to be tallied and displayed.
    334 
    335 `-i'
    336 `--file-info'
    337      The `-i' option causes `gprof' to display summary information
    338      about the profile data file(s) and then exit.  The number of
    339      histogram, call graph, and basic-block count records is displayed.
    340 
    341 `-I DIRS'
    342 `--directory-path=DIRS'
    343      The `-I' option specifies a list of search directories in which to
    344      find source files.  Environment variable GPROF_PATH can also be
    345      used to convey this information.  Used mostly for annotated source
    346      output.
    347 
    348 `-J[SYMSPEC]'
    349 `--no-annotated-source[=SYMSPEC]'
    350      The `-J' option causes `gprof' not to print annotated source code.
    351      If SYMSPEC is specified, `gprof' prints annotated source, but
    352      excludes matching symbols.
    353 
    354 `-L'
    355 `--print-path'
    356      Normally, source filenames are printed with the path component
    357      suppressed.  The `-L' option causes `gprof' to print the full
    358      pathname of source filenames, which is determined from symbolic
    359      debugging information in the image file and is relative to the
    360      directory in which the compiler was invoked.
    361 
    362 `-p[SYMSPEC]'
    363 `--flat-profile[=SYMSPEC]'
    364      The `-p' option causes `gprof' to print a flat profile.  If
    365      SYMSPEC is specified, print flat profile only for matching symbols.
    366      *Note The Flat Profile: Flat Profile.
    367 
    368 `-P[SYMSPEC]'
    369 `--no-flat-profile[=SYMSPEC]'
    370      The `-P' option causes `gprof' to suppress printing a flat profile.
    371      If SYMSPEC is specified, `gprof' prints a flat profile, but
    372      excludes matching symbols.
    373 
    374 `-q[SYMSPEC]'
    375 `--graph[=SYMSPEC]'
    376      The `-q' option causes `gprof' to print the call graph analysis.
    377      If SYMSPEC is specified, print call graph only for matching symbols
    378      and their children.  *Note The Call Graph: Call Graph.
    379 
    380 `-Q[SYMSPEC]'
    381 `--no-graph[=SYMSPEC]'
    382      The `-Q' option causes `gprof' to suppress printing the call graph.
    383      If SYMSPEC is specified, `gprof' prints a call graph, but excludes
    384      matching symbols.
    385 
    386 `-t'
    387 `--table-length=NUM'
    388      The `-t' option causes the NUM most active source lines in each
    389      source file to be listed when source annotation is enabled.  The
    390      default is 10.
    391 
    392 `-y'
    393 `--separate-files'
    394      This option affects annotated source output only.  Normally,
    395      `gprof' prints annotated source files to standard-output.  If this
    396      option is specified, annotated source for a file named
    397      `path/FILENAME' is generated in the file `FILENAME-ann'.  If the
    398      underlying file system would truncate `FILENAME-ann' so that it
    399      overwrites the original `FILENAME', `gprof' generates annotated
    400      source in the file `FILENAME.ann' instead (if the original file
    401      name has an extension, that extension is _replaced_ with `.ann').
    402 
    403 `-Z[SYMSPEC]'
    404 `--no-exec-counts[=SYMSPEC]'
    405      The `-Z' option causes `gprof' not to print a tally of functions
    406      and the number of times each was called.  If SYMSPEC is specified,
    407      print tally, but exclude matching symbols.
    408 
    409 `-r'
    410 `--function-ordering'
    411      The `--function-ordering' option causes `gprof' to print a
    412      suggested function ordering for the program based on profiling
    413      data.  This option suggests an ordering which may improve paging,
    414      tlb and cache behavior for the program on systems which support
    415      arbitrary ordering of functions in an executable.
    416 
    417      The exact details of how to force the linker to place functions in
    418      a particular order is system dependent and out of the scope of this
    419      manual.
    420 
    421 `-R MAP_FILE'
    422 `--file-ordering MAP_FILE'
    423      The `--file-ordering' option causes `gprof' to print a suggested
    424      .o link line ordering for the program based on profiling data.
    425      This option suggests an ordering which may improve paging, tlb and
    426      cache behavior for the program on systems which do not support
    427      arbitrary ordering of functions in an executable.
    428 
    429      Use of the `-a' argument is highly recommended with this option.
    430 
    431      The MAP_FILE argument is a pathname to a file which provides
    432      function name to object file mappings.  The format of the file is
    433      similar to the output of the program `nm'.
    434 
    435           c-parse.o:00000000 T yyparse
    436           c-parse.o:00000004 C yyerrflag
    437           c-lang.o:00000000 T maybe_objc_method_name
    438           c-lang.o:00000000 T print_lang_statistics
    439           c-lang.o:00000000 T recognize_objc_keyword
    440           c-decl.o:00000000 T print_lang_identifier
    441           c-decl.o:00000000 T print_lang_type
    442           ...
    443 
    444      To create a MAP_FILE with GNU `nm', type a command like `nm
    445      --extern-only --defined-only -v --print-file-name program-name'.
    446 
    447 `-T'
    448 `--traditional'
    449      The `-T' option causes `gprof' to print its output in
    450      "traditional" BSD style.
    451 
    452 `-w WIDTH'
    453 `--width=WIDTH'
    454      Sets width of output lines to WIDTH.  Currently only used when
    455      printing the function index at the bottom of the call graph.
    456 
    457 `-x'
    458 `--all-lines'
    459      This option affects annotated source output only.  By default,
    460      only the lines at the beginning of a basic-block are annotated.
    461      If this option is specified, every line in a basic-block is
    462      annotated by repeating the annotation for the first line.  This
    463      behavior is similar to `tcov''s `-a'.
    464 
    465 `--demangle[=STYLE]'
    466 `--no-demangle'
    467      These options control whether C++ symbol names should be demangled
    468      when printing output.  The default is to demangle symbols.  The
    469      `--no-demangle' option may be used to turn off demangling.
    470      Different compilers have different mangling styles.  The optional
    471      demangling style argument can be used to choose an appropriate
    472      demangling style for your compiler.
    473 
    474 
    475 File: gprof.info,  Node: Analysis Options,  Next: Miscellaneous Options,  Prev: Output Options,  Up: Invoking
    476 
    477 4.2 Analysis Options
    478 ====================
    479 
    480 `-a'
    481 `--no-static'
    482      The `-a' option causes `gprof' to suppress the printing of
    483      statically declared (private) functions.  (These are functions
    484      whose names are not listed as global, and which are not visible
    485      outside the file/function/block where they were defined.)  Time
    486      spent in these functions, calls to/from them, etc., will all be
    487      attributed to the function that was loaded directly before it in
    488      the executable file.  This option affects both the flat profile
    489      and the call graph.
    490 
    491 `-c'
    492 `--static-call-graph'
    493      The `-c' option causes the call graph of the program to be
    494      augmented by a heuristic which examines the text space of the
    495      object file and identifies function calls in the binary machine
    496      code.  Since normal call graph records are only generated when
    497      functions are entered, this option identifies children that could
    498      have been called, but never were.  Calls to functions that were
    499      not compiled with profiling enabled are also identified, but only
    500      if symbol table entries are present for them.  Calls to dynamic
    501      library routines are typically _not_ found by this option.
    502      Parents or children identified via this heuristic are indicated in
    503      the call graph with call counts of `0'.
    504 
    505 `-D'
    506 `--ignore-non-functions'
    507      The `-D' option causes `gprof' to ignore symbols which are not
    508      known to be functions.  This option will give more accurate
    509      profile data on systems where it is supported (Solaris and HPUX for
    510      example).
    511 
    512 `-k FROM/TO'
    513      The `-k' option allows you to delete from the call graph any arcs
    514      from symbols matching symspec FROM to those matching symspec TO.
    515 
    516 `-l'
    517 `--line'
    518      The `-l' option enables line-by-line profiling, which causes
    519      histogram hits to be charged to individual source code lines,
    520      instead of functions.  This feature only works with programs
    521      compiled by older versions of the `gcc' compiler.  Newer versions
    522      of `gcc' are designed to work with the `gcov' tool instead.
    523 
    524      If the program was compiled with basic-block counting enabled,
    525      this option will also identify how many times each line of code
    526      was executed.  While line-by-line profiling can help isolate where
    527      in a large function a program is spending its time, it also
    528      significantly increases the running time of `gprof', and magnifies
    529      statistical inaccuracies.  *Note Statistical Sampling Error:
    530      Sampling Error.
    531 
    532 `-m NUM'
    533 `--min-count=NUM'
    534      This option affects execution count output only.  Symbols that are
    535      executed less than NUM times are suppressed.
    536 
    537 `-nSYMSPEC'
    538 `--time=SYMSPEC'
    539      The `-n' option causes `gprof', in its call graph analysis, to
    540      only propagate times for symbols matching SYMSPEC.
    541 
    542 `-NSYMSPEC'
    543 `--no-time=SYMSPEC'
    544      The `-n' option causes `gprof', in its call graph analysis, not to
    545      propagate times for symbols matching SYMSPEC.
    546 
    547 `-SFILENAME'
    548 `--external-symbol-table=FILENAME'
    549      The `-S' option causes `gprof' to read an external symbol table
    550      file, such as `/proc/kallsyms', rather than read the symbol table
    551      from the given object file (the default is `a.out'). This is useful
    552      for profiling kernel modules.
    553 
    554 `-z'
    555 `--display-unused-functions'
    556      If you give the `-z' option, `gprof' will mention all functions in
    557      the flat profile, even those that were never called, and that had
    558      no time spent in them.  This is useful in conjunction with the
    559      `-c' option for discovering which routines were never called.
    560 
    561 
    562 
    563 File: gprof.info,  Node: Miscellaneous Options,  Next: Deprecated Options,  Prev: Analysis Options,  Up: Invoking
    564 
    565 4.3 Miscellaneous Options
    566 =========================
    567 
    568 `-d[NUM]'
    569 `--debug[=NUM]'
    570      The `-d NUM' option specifies debugging options.  If NUM is not
    571      specified, enable all debugging.  *Note Debugging `gprof':
    572      Debugging.
    573 
    574 `-h'
    575 `--help'
    576      The `-h' option prints command line usage.
    577 
    578 `-ONAME'
    579 `--file-format=NAME'
    580      Selects the format of the profile data files.  Recognized formats
    581      are `auto' (the default), `bsd', `4.4bsd', `magic', and `prof'
    582      (not yet supported).
    583 
    584 `-s'
    585 `--sum'
    586      The `-s' option causes `gprof' to summarize the information in the
    587      profile data files it read in, and write out a profile data file
    588      called `gmon.sum', which contains all the information from the
    589      profile data files that `gprof' read in.  The file `gmon.sum' may
    590      be one of the specified input files; the effect of this is to
    591      merge the data in the other input files into `gmon.sum'.
    592 
    593      Eventually you can run `gprof' again without `-s' to analyze the
    594      cumulative data in the file `gmon.sum'.
    595 
    596 `-v'
    597 `--version'
    598      The `-v' flag causes `gprof' to print the current version number,
    599      and then exit.
    600 
    601 
    602 
    603 File: gprof.info,  Node: Deprecated Options,  Next: Symspecs,  Prev: Miscellaneous Options,  Up: Invoking
    604 
    605 4.4 Deprecated Options
    606 ======================
    607 
    608 These options have been replaced with newer versions that use symspecs.
    609 
    610 `-e FUNCTION_NAME'
    611      The `-e FUNCTION' option tells `gprof' to not print information
    612      about the function FUNCTION_NAME (and its children...) in the call
    613      graph.  The function will still be listed as a child of any
    614      functions that call it, but its index number will be shown as
    615      `[not printed]'.  More than one `-e' option may be given; only one
    616      FUNCTION_NAME may be indicated with each `-e' option.
    617 
    618 `-E FUNCTION_NAME'
    619      The `-E FUNCTION' option works like the `-e' option, but time
    620      spent in the function (and children who were not called from
    621      anywhere else), will not be used to compute the
    622      percentages-of-time for the call graph.  More than one `-E' option
    623      may be given; only one FUNCTION_NAME may be indicated with each
    624      `-E' option.
    625 
    626 `-f FUNCTION_NAME'
    627      The `-f FUNCTION' option causes `gprof' to limit the call graph to
    628      the function FUNCTION_NAME and its children (and their
    629      children...).  More than one `-f' option may be given; only one
    630      FUNCTION_NAME may be indicated with each `-f' option.
    631 
    632 `-F FUNCTION_NAME'
    633      The `-F FUNCTION' option works like the `-f' option, but only time
    634      spent in the function and its children (and their children...)
    635      will be used to determine total-time and percentages-of-time for
    636      the call graph.  More than one `-F' option may be given; only one
    637      FUNCTION_NAME may be indicated with each `-F' option.  The `-F'
    638      option overrides the `-E' option.
    639 
    640 
    641    Note that only one function can be specified with each `-e', `-E',
    642 `-f' or `-F' option.  To specify more than one function, use multiple
    643 options.  For example, this command:
    644 
    645      gprof -e boring -f foo -f bar myprogram > gprof.output
    646 
    647 lists in the call graph all functions that were reached from either
    648 `foo' or `bar' and were not reachable from `boring'.
    649 
    650 
    651 File: gprof.info,  Node: Symspecs,  Prev: Deprecated Options,  Up: Invoking
    652 
    653 4.5 Symspecs
    654 ============
    655 
    656 Many of the output options allow functions to be included or excluded
    657 using "symspecs" (symbol specifications), which observe the following
    658 syntax:
    659 
    660        filename_containing_a_dot
    661      | funcname_not_containing_a_dot
    662      | linenumber
    663      | ( [ any_filename ] `:' ( any_funcname | linenumber ) )
    664 
    665    Here are some sample symspecs:
    666 
    667 `main.c'
    668      Selects everything in file `main.c'--the dot in the string tells
    669      `gprof' to interpret the string as a filename, rather than as a
    670      function name.  To select a file whose name does not contain a
    671      dot, a trailing colon should be specified.  For example, `odd:' is
    672      interpreted as the file named `odd'.
    673 
    674 `main'
    675      Selects all functions named `main'.
    676 
    677      Note that there may be multiple instances of the same function name
    678      because some of the definitions may be local (i.e., static).
    679      Unless a function name is unique in a program, you must use the
    680      colon notation explained below to specify a function from a
    681      specific source file.
    682 
    683      Sometimes, function names contain dots.  In such cases, it is
    684      necessary to add a leading colon to the name.  For example,
    685      `:.mul' selects function `.mul'.
    686 
    687      In some object file formats, symbols have a leading underscore.
    688      `gprof' will normally not print these underscores.  When you name a
    689      symbol in a symspec, you should type it exactly as `gprof' prints
    690      it in its output.  For example, if the compiler produces a symbol
    691      `_main' from your `main' function, `gprof' still prints it as
    692      `main' in its output, so you should use `main' in symspecs.
    693 
    694 `main.c:main'
    695      Selects function `main' in file `main.c'.
    696 
    697 `main.c:134'
    698      Selects line 134 in file `main.c'.
    699 
    700 
    701 File: gprof.info,  Node: Output,  Next: Inaccuracy,  Prev: Invoking,  Up: Top
    702 
    703 5 Interpreting `gprof''s Output
    704 *******************************
    705 
    706 `gprof' can produce several different output styles, the most important
    707 of which are described below.  The simplest output styles (file
    708 information, execution count, and function and file ordering) are not
    709 described here, but are documented with the respective options that
    710 trigger them.  *Note Output Options: Output Options.
    711 
    712 * Menu:
    713 
    714 * Flat Profile::        The flat profile shows how much time was spent
    715                             executing directly in each function.
    716 * Call Graph::          The call graph shows which functions called which
    717                             others, and how much time each function used
    718                             when its subroutine calls are included.
    719 * Line-by-line::        `gprof' can analyze individual source code lines
    720 * Annotated Source::    The annotated source listing displays source code
    721                             labeled with execution counts
    722 
    723 
    724 File: gprof.info,  Node: Flat Profile,  Next: Call Graph,  Up: Output
    725 
    726 5.1 The Flat Profile
    727 ====================
    728 
    729 The "flat profile" shows the total amount of time your program spent
    730 executing each function.  Unless the `-z' option is given, functions
    731 with no apparent time spent in them, and no apparent calls to them, are
    732 not mentioned.  Note that if a function was not compiled for profiling,
    733 and didn't run long enough to show up on the program counter histogram,
    734 it will be indistinguishable from a function that was never called.
    735 
    736    This is part of a flat profile for a small program:
    737 
    738      Flat profile:
    739 
    740      Each sample counts as 0.01 seconds.
    741        %   cumulative   self              self     total
    742       time   seconds   seconds    calls  ms/call  ms/call  name
    743       33.34      0.02     0.02     7208     0.00     0.00  open
    744       16.67      0.03     0.01      244     0.04     0.12  offtime
    745       16.67      0.04     0.01        8     1.25     1.25  memccpy
    746       16.67      0.05     0.01        7     1.43     1.43  write
    747       16.67      0.06     0.01                             mcount
    748        0.00      0.06     0.00      236     0.00     0.00  tzset
    749        0.00      0.06     0.00      192     0.00     0.00  tolower
    750        0.00      0.06     0.00       47     0.00     0.00  strlen
    751        0.00      0.06     0.00       45     0.00     0.00  strchr
    752        0.00      0.06     0.00        1     0.00    50.00  main
    753        0.00      0.06     0.00        1     0.00     0.00  memcpy
    754        0.00      0.06     0.00        1     0.00    10.11  print
    755        0.00      0.06     0.00        1     0.00     0.00  profil
    756        0.00      0.06     0.00        1     0.00    50.00  report
    757      ...
    758 
    759 The functions are sorted first by decreasing run-time spent in them,
    760 then by decreasing number of calls, then alphabetically by name.  The
    761 functions `mcount' and `profil' are part of the profiling apparatus and
    762 appear in every flat profile; their time gives a measure of the amount
    763 of overhead due to profiling.
    764 
    765    Just before the column headers, a statement appears indicating how
    766 much time each sample counted as.  This "sampling period" estimates the
    767 margin of error in each of the time figures.  A time figure that is not
    768 much larger than this is not reliable.  In this example, each sample
    769 counted as 0.01 seconds, suggesting a 100 Hz sampling rate.  The
    770 program's total execution time was 0.06 seconds, as indicated by the
    771 `cumulative seconds' field.  Since each sample counted for 0.01
    772 seconds, this means only six samples were taken during the run.  Two of
    773 the samples occurred while the program was in the `open' function, as
    774 indicated by the `self seconds' field.  Each of the other four samples
    775 occurred one each in `offtime', `memccpy', `write', and `mcount'.
    776 Since only six samples were taken, none of these values can be regarded
    777 as particularly reliable.  In another run, the `self seconds' field for
    778 `mcount' might well be `0.00' or `0.02'.  *Note Statistical Sampling
    779 Error: Sampling Error, for a complete discussion.
    780 
    781    The remaining functions in the listing (those whose `self seconds'
    782 field is `0.00') didn't appear in the histogram samples at all.
    783 However, the call graph indicated that they were called, so therefore
    784 they are listed, sorted in decreasing order by the `calls' field.
    785 Clearly some time was spent executing these functions, but the paucity
    786 of histogram samples prevents any determination of how much time each
    787 took.
    788 
    789    Here is what the fields in each line mean:
    790 
    791 `% time'
    792      This is the percentage of the total execution time your program
    793      spent in this function.  These should all add up to 100%.
    794 
    795 `cumulative seconds'
    796      This is the cumulative total number of seconds the computer spent
    797      executing this functions, plus the time spent in all the functions
    798      above this one in this table.
    799 
    800 `self seconds'
    801      This is the number of seconds accounted for by this function alone.
    802      The flat profile listing is sorted first by this number.
    803 
    804 `calls'
    805      This is the total number of times the function was called.  If the
    806      function was never called, or the number of times it was called
    807      cannot be determined (probably because the function was not
    808      compiled with profiling enabled), the "calls" field is blank.
    809 
    810 `self ms/call'
    811      This represents the average number of milliseconds spent in this
    812      function per call, if this function is profiled.  Otherwise, this
    813      field is blank for this function.
    814 
    815 `total ms/call'
    816      This represents the average number of milliseconds spent in this
    817      function and its descendants per call, if this function is
    818      profiled.  Otherwise, this field is blank for this function.  This
    819      is the only field in the flat profile that uses call graph
    820      analysis.
    821 
    822 `name'
    823      This is the name of the function.   The flat profile is sorted by
    824      this field alphabetically after the "self seconds" and "calls"
    825      fields are sorted.
    826 
    827 
    828 File: gprof.info,  Node: Call Graph,  Next: Line-by-line,  Prev: Flat Profile,  Up: Output
    829 
    830 5.2 The Call Graph
    831 ==================
    832 
    833 The "call graph" shows how much time was spent in each function and its
    834 children.  From this information, you can find functions that, while
    835 they themselves may not have used much time, called other functions
    836 that did use unusual amounts of time.
    837 
    838    Here is a sample call from a small program.  This call came from the
    839 same `gprof' run as the flat profile example in the previous section.
    840 
    841      granularity: each sample hit covers 2 byte(s) for 20.00% of 0.05 seconds
    842 
    843      index % time    self  children    called     name
    844                                                       <spontaneous>
    845      [1]    100.0    0.00    0.05                 start [1]
    846                      0.00    0.05       1/1           main [2]
    847                      0.00    0.00       1/2           on_exit [28]
    848                      0.00    0.00       1/1           exit [59]
    849      -----------------------------------------------
    850                      0.00    0.05       1/1           start [1]
    851      [2]    100.0    0.00    0.05       1         main [2]
    852                      0.00    0.05       1/1           report [3]
    853      -----------------------------------------------
    854                      0.00    0.05       1/1           main [2]
    855      [3]    100.0    0.00    0.05       1         report [3]
    856                      0.00    0.03       8/8           timelocal [6]
    857                      0.00    0.01       1/1           print [9]
    858                      0.00    0.01       9/9           fgets [12]
    859                      0.00    0.00      12/34          strncmp <cycle 1> [40]
    860                      0.00    0.00       8/8           lookup [20]
    861                      0.00    0.00       1/1           fopen [21]
    862                      0.00    0.00       8/8           chewtime [24]
    863                      0.00    0.00       8/16          skipspace [44]
    864      -----------------------------------------------
    865      [4]     59.8    0.01        0.02       8+472     <cycle 2 as a whole> [4]
    866                      0.01        0.02     244+260         offtime <cycle 2> [7]
    867                      0.00        0.00     236+1           tzset <cycle 2> [26]
    868      -----------------------------------------------
    869 
    870    The lines full of dashes divide this table into "entries", one for
    871 each function.  Each entry has one or more lines.
    872 
    873    In each entry, the primary line is the one that starts with an index
    874 number in square brackets.  The end of this line says which function
    875 the entry is for.  The preceding lines in the entry describe the
    876 callers of this function and the following lines describe its
    877 subroutines (also called "children" when we speak of the call graph).
    878 
    879    The entries are sorted by time spent in the function and its
    880 subroutines.
    881 
    882    The internal profiling function `mcount' (*note The Flat Profile:
    883 Flat Profile.) is never mentioned in the call graph.
    884 
    885 * Menu:
    886 
    887 * Primary::       Details of the primary line's contents.
    888 * Callers::       Details of caller-lines' contents.
    889 * Subroutines::   Details of subroutine-lines' contents.
    890 * Cycles::        When there are cycles of recursion,
    891                    such as `a' calls `b' calls `a'...
    892 
    893 
    894 File: gprof.info,  Node: Primary,  Next: Callers,  Up: Call Graph
    895 
    896 5.2.1 The Primary Line
    897 ----------------------
    898 
    899 The "primary line" in a call graph entry is the line that describes the
    900 function which the entry is about and gives the overall statistics for
    901 this function.
    902 
    903    For reference, we repeat the primary line from the entry for function
    904 `report' in our main example, together with the heading line that shows
    905 the names of the fields:
    906 
    907      index  % time    self  children called     name
    908      ...
    909      [3]    100.0    0.00    0.05       1         report [3]
    910 
    911    Here is what the fields in the primary line mean:
    912 
    913 `index'
    914      Entries are numbered with consecutive integers.  Each function
    915      therefore has an index number, which appears at the beginning of
    916      its primary line.
    917 
    918      Each cross-reference to a function, as a caller or subroutine of
    919      another, gives its index number as well as its name.  The index
    920      number guides you if you wish to look for the entry for that
    921      function.
    922 
    923 `% time'
    924      This is the percentage of the total time that was spent in this
    925      function, including time spent in subroutines called from this
    926      function.
    927 
    928      The time spent in this function is counted again for the callers of
    929      this function.  Therefore, adding up these percentages is
    930      meaningless.
    931 
    932 `self'
    933      This is the total amount of time spent in this function.  This
    934      should be identical to the number printed in the `seconds' field
    935      for this function in the flat profile.
    936 
    937 `children'
    938      This is the total amount of time spent in the subroutine calls
    939      made by this function.  This should be equal to the sum of all the
    940      `self' and `children' entries of the children listed directly
    941      below this function.
    942 
    943 `called'
    944      This is the number of times the function was called.
    945 
    946      If the function called itself recursively, there are two numbers,
    947      separated by a `+'.  The first number counts non-recursive calls,
    948      and the second counts recursive calls.
    949 
    950      In the example above, the function `report' was called once from
    951      `main'.
    952 
    953 `name'
    954      This is the name of the current function.  The index number is
    955      repeated after it.
    956 
    957      If the function is part of a cycle of recursion, the cycle number
    958      is printed between the function's name and the index number (*note
    959      How Mutually Recursive Functions Are Described: Cycles.).  For
    960      example, if function `gnurr' is part of cycle number one, and has
    961      index number twelve, its primary line would be end like this:
    962 
    963           gnurr <cycle 1> [12]
    964 
    965 
    966 File: gprof.info,  Node: Callers,  Next: Subroutines,  Prev: Primary,  Up: Call Graph
    967 
    968 5.2.2 Lines for a Function's Callers
    969 ------------------------------------
    970 
    971 A function's entry has a line for each function it was called by.
    972 These lines' fields correspond to the fields of the primary line, but
    973 their meanings are different because of the difference in context.
    974 
    975    For reference, we repeat two lines from the entry for the function
    976 `report', the primary line and one caller-line preceding it, together
    977 with the heading line that shows the names of the fields:
    978 
    979      index  % time    self  children called     name
    980      ...
    981                      0.00    0.05       1/1           main [2]
    982      [3]    100.0    0.00    0.05       1         report [3]
    983 
    984    Here are the meanings of the fields in the caller-line for `report'
    985 called from `main':
    986 
    987 `self'
    988      An estimate of the amount of time spent in `report' itself when it
    989      was called from `main'.
    990 
    991 `children'
    992      An estimate of the amount of time spent in subroutines of `report'
    993      when `report' was called from `main'.
    994 
    995      The sum of the `self' and `children' fields is an estimate of the
    996      amount of time spent within calls to `report' from `main'.
    997 
    998 `called'
    999      Two numbers: the number of times `report' was called from `main',
   1000      followed by the total number of non-recursive calls to `report'
   1001      from all its callers.
   1002 
   1003 `name and index number'
   1004      The name of the caller of `report' to which this line applies,
   1005      followed by the caller's index number.
   1006 
   1007      Not all functions have entries in the call graph; some options to
   1008      `gprof' request the omission of certain functions.  When a caller
   1009      has no entry of its own, it still has caller-lines in the entries
   1010      of the functions it calls.
   1011 
   1012      If the caller is part of a recursion cycle, the cycle number is
   1013      printed between the name and the index number.
   1014 
   1015    If the identity of the callers of a function cannot be determined, a
   1016 dummy caller-line is printed which has `<spontaneous>' as the "caller's
   1017 name" and all other fields blank.  This can happen for signal handlers.
   1018 
   1019 
   1020 File: gprof.info,  Node: Subroutines,  Next: Cycles,  Prev: Callers,  Up: Call Graph
   1021 
   1022 5.2.3 Lines for a Function's Subroutines
   1023 ----------------------------------------
   1024 
   1025 A function's entry has a line for each of its subroutines--in other
   1026 words, a line for each other function that it called.  These lines'
   1027 fields correspond to the fields of the primary line, but their meanings
   1028 are different because of the difference in context.
   1029 
   1030    For reference, we repeat two lines from the entry for the function
   1031 `main', the primary line and a line for a subroutine, together with the
   1032 heading line that shows the names of the fields:
   1033 
   1034      index  % time    self  children called     name
   1035      ...
   1036      [2]    100.0    0.00    0.05       1         main [2]
   1037                      0.00    0.05       1/1           report [3]
   1038 
   1039    Here are the meanings of the fields in the subroutine-line for `main'
   1040 calling `report':
   1041 
   1042 `self'
   1043      An estimate of the amount of time spent directly within `report'
   1044      when `report' was called from `main'.
   1045 
   1046 `children'
   1047      An estimate of the amount of time spent in subroutines of `report'
   1048      when `report' was called from `main'.
   1049 
   1050      The sum of the `self' and `children' fields is an estimate of the
   1051      total time spent in calls to `report' from `main'.
   1052 
   1053 `called'
   1054      Two numbers, the number of calls to `report' from `main' followed
   1055      by the total number of non-recursive calls to `report'.  This
   1056      ratio is used to determine how much of `report''s `self' and
   1057      `children' time gets credited to `main'.  *Note Estimating
   1058      `children' Times: Assumptions.
   1059 
   1060 `name'
   1061      The name of the subroutine of `main' to which this line applies,
   1062      followed by the subroutine's index number.
   1063 
   1064      If the caller is part of a recursion cycle, the cycle number is
   1065      printed between the name and the index number.
   1066 
   1067 
   1068 File: gprof.info,  Node: Cycles,  Prev: Subroutines,  Up: Call Graph
   1069 
   1070 5.2.4 How Mutually Recursive Functions Are Described
   1071 ----------------------------------------------------
   1072 
   1073 The graph may be complicated by the presence of "cycles of recursion"
   1074 in the call graph.  A cycle exists if a function calls another function
   1075 that (directly or indirectly) calls (or appears to call) the original
   1076 function.  For example: if `a' calls `b', and `b' calls `a', then `a'
   1077 and `b' form a cycle.
   1078 
   1079    Whenever there are call paths both ways between a pair of functions,
   1080 they belong to the same cycle.  If `a' and `b' call each other and `b'
   1081 and `c' call each other, all three make one cycle.  Note that even if
   1082 `b' only calls `a' if it was not called from `a', `gprof' cannot
   1083 determine this, so `a' and `b' are still considered a cycle.
   1084 
   1085    The cycles are numbered with consecutive integers.  When a function
   1086 belongs to a cycle, each time the function name appears in the call
   1087 graph it is followed by `<cycle NUMBER>'.
   1088 
   1089    The reason cycles matter is that they make the time values in the
   1090 call graph paradoxical.  The "time spent in children" of `a' should
   1091 include the time spent in its subroutine `b' and in `b''s
   1092 subroutines--but one of `b''s subroutines is `a'!  How much of `a''s
   1093 time should be included in the children of `a', when `a' is indirectly
   1094 recursive?
   1095 
   1096    The way `gprof' resolves this paradox is by creating a single entry
   1097 for the cycle as a whole.  The primary line of this entry describes the
   1098 total time spent directly in the functions of the cycle.  The
   1099 "subroutines" of the cycle are the individual functions of the cycle,
   1100 and all other functions that were called directly by them.  The
   1101 "callers" of the cycle are the functions, outside the cycle, that
   1102 called functions in the cycle.
   1103 
   1104    Here is an example portion of a call graph which shows a cycle
   1105 containing functions `a' and `b'.  The cycle was entered by a call to
   1106 `a' from `main'; both `a' and `b' called `c'.
   1107 
   1108      index  % time    self  children called     name
   1109      ----------------------------------------
   1110                       1.77        0    1/1        main [2]
   1111      [3]     91.71    1.77        0    1+5    <cycle 1 as a whole> [3]
   1112                       1.02        0    3          b <cycle 1> [4]
   1113                       0.75        0    2          a <cycle 1> [5]
   1114      ----------------------------------------
   1115                                        3          a <cycle 1> [5]
   1116      [4]     52.85    1.02        0    0      b <cycle 1> [4]
   1117                                        2          a <cycle 1> [5]
   1118                          0        0    3/6        c [6]
   1119      ----------------------------------------
   1120                       1.77        0    1/1        main [2]
   1121                                        2          b <cycle 1> [4]
   1122      [5]     38.86    0.75        0    1      a <cycle 1> [5]
   1123                                        3          b <cycle 1> [4]
   1124                          0        0    3/6        c [6]
   1125      ----------------------------------------
   1126 
   1127 (The entire call graph for this program contains in addition an entry
   1128 for `main', which calls `a', and an entry for `c', with callers `a' and
   1129 `b'.)
   1130 
   1131      index  % time    self  children called     name
   1132                                                   <spontaneous>
   1133      [1]    100.00       0     1.93    0      start [1]
   1134                       0.16     1.77    1/1        main [2]
   1135      ----------------------------------------
   1136                       0.16     1.77    1/1        start [1]
   1137      [2]    100.00    0.16     1.77    1      main [2]
   1138                       1.77        0    1/1        a <cycle 1> [5]
   1139      ----------------------------------------
   1140                       1.77        0    1/1        main [2]
   1141      [3]     91.71    1.77        0    1+5    <cycle 1 as a whole> [3]
   1142                       1.02        0    3          b <cycle 1> [4]
   1143                       0.75        0    2          a <cycle 1> [5]
   1144                          0        0    6/6        c [6]
   1145      ----------------------------------------
   1146                                        3          a <cycle 1> [5]
   1147      [4]     52.85    1.02        0    0      b <cycle 1> [4]
   1148                                        2          a <cycle 1> [5]
   1149                          0        0    3/6        c [6]
   1150      ----------------------------------------
   1151                       1.77        0    1/1        main [2]
   1152                                        2          b <cycle 1> [4]
   1153      [5]     38.86    0.75        0    1      a <cycle 1> [5]
   1154                                        3          b <cycle 1> [4]
   1155                          0        0    3/6        c [6]
   1156      ----------------------------------------
   1157                          0        0    3/6        b <cycle 1> [4]
   1158                          0        0    3/6        a <cycle 1> [5]
   1159      [6]      0.00       0        0    6      c [6]
   1160      ----------------------------------------
   1161 
   1162    The `self' field of the cycle's primary line is the total time spent
   1163 in all the functions of the cycle.  It equals the sum of the `self'
   1164 fields for the individual functions in the cycle, found in the entry in
   1165 the subroutine lines for these functions.
   1166 
   1167    The `children' fields of the cycle's primary line and subroutine
   1168 lines count only subroutines outside the cycle.  Even though `a' calls
   1169 `b', the time spent in those calls to `b' is not counted in `a''s
   1170 `children' time.  Thus, we do not encounter the problem of what to do
   1171 when the time in those calls to `b' includes indirect recursive calls
   1172 back to `a'.
   1173 
   1174    The `children' field of a caller-line in the cycle's entry estimates
   1175 the amount of time spent _in the whole cycle_, and its other
   1176 subroutines, on the times when that caller called a function in the
   1177 cycle.
   1178 
   1179    The `called' field in the primary line for the cycle has two numbers:
   1180 first, the number of times functions in the cycle were called by
   1181 functions outside the cycle; second, the number of times they were
   1182 called by functions in the cycle (including times when a function in
   1183 the cycle calls itself).  This is a generalization of the usual split
   1184 into non-recursive and recursive calls.
   1185 
   1186    The `called' field of a subroutine-line for a cycle member in the
   1187 cycle's entry says how many time that function was called from
   1188 functions in the cycle.  The total of all these is the second number in
   1189 the primary line's `called' field.
   1190 
   1191    In the individual entry for a function in a cycle, the other
   1192 functions in the same cycle can appear as subroutines and as callers.
   1193 These lines show how many times each function in the cycle called or
   1194 was called from each other function in the cycle.  The `self' and
   1195 `children' fields in these lines are blank because of the difficulty of
   1196 defining meanings for them when recursion is going on.
   1197 
   1198 
   1199 File: gprof.info,  Node: Line-by-line,  Next: Annotated Source,  Prev: Call Graph,  Up: Output
   1200 
   1201 5.3 Line-by-line Profiling
   1202 ==========================
   1203 
   1204 `gprof''s `-l' option causes the program to perform "line-by-line"
   1205 profiling.  In this mode, histogram samples are assigned not to
   1206 functions, but to individual lines of source code.  This only works
   1207 with programs compiled with older versions of the `gcc' compiler.
   1208 Newer versions of `gcc' use a different program - `gcov' - to display
   1209 line-by-line profiling information.
   1210 
   1211    With the older versions of `gcc' the program usually has to be
   1212 compiled with a `-g' option, in addition to `-pg', in order to generate
   1213 debugging symbols for tracking source code lines.  Note, in much older
   1214 versions of `gcc' the program had to be compiled with the `-a' command
   1215 line option as well.
   1216 
   1217    The flat profile is the most useful output table in line-by-line
   1218 mode.  The call graph isn't as useful as normal, since the current
   1219 version of `gprof' does not propagate call graph arcs from source code
   1220 lines to the enclosing function.  The call graph does, however, show
   1221 each line of code that called each function, along with a count.
   1222 
   1223    Here is a section of `gprof''s output, without line-by-line
   1224 profiling.  Note that `ct_init' accounted for four histogram hits, and
   1225 13327 calls to `init_block'.
   1226 
   1227      Flat profile:
   1228 
   1229      Each sample counts as 0.01 seconds.
   1230        %   cumulative   self              self     total
   1231       time   seconds   seconds    calls  us/call  us/call  name
   1232       30.77      0.13     0.04     6335     6.31     6.31  ct_init
   1233 
   1234 
   1235      		     Call graph (explanation follows)
   1236 
   1237 
   1238      granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
   1239 
   1240      index % time    self  children    called     name
   1241 
   1242                      0.00    0.00       1/13496       name_too_long
   1243                      0.00    0.00      40/13496       deflate
   1244                      0.00    0.00     128/13496       deflate_fast
   1245                      0.00    0.00   13327/13496       ct_init
   1246      [7]      0.0    0.00    0.00   13496         init_block
   1247 
   1248    Now let's look at some of `gprof''s output from the same program run,
   1249 this time with line-by-line profiling enabled.  Note that `ct_init''s
   1250 four histogram hits are broken down into four lines of source code--one
   1251 hit occurred on each of lines 349, 351, 382 and 385.  In the call graph,
   1252 note how `ct_init''s 13327 calls to `init_block' are broken down into
   1253 one call from line 396, 3071 calls from line 384, 3730 calls from line
   1254 385, and 6525 calls from 387.
   1255 
   1256      Flat profile:
   1257 
   1258      Each sample counts as 0.01 seconds.
   1259        %   cumulative   self
   1260       time   seconds   seconds    calls  name
   1261        7.69      0.10     0.01           ct_init (trees.c:349)
   1262        7.69      0.11     0.01           ct_init (trees.c:351)
   1263        7.69      0.12     0.01           ct_init (trees.c:382)
   1264        7.69      0.13     0.01           ct_init (trees.c:385)
   1265 
   1266 
   1267      		     Call graph (explanation follows)
   1268 
   1269 
   1270      granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
   1271 
   1272        % time    self  children    called     name
   1273 
   1274                  0.00    0.00       1/13496       name_too_long (gzip.c:1440)
   1275                  0.00    0.00       1/13496       deflate (deflate.c:763)
   1276                  0.00    0.00       1/13496       ct_init (trees.c:396)
   1277                  0.00    0.00       2/13496       deflate (deflate.c:727)
   1278                  0.00    0.00       4/13496       deflate (deflate.c:686)
   1279                  0.00    0.00       5/13496       deflate (deflate.c:675)
   1280                  0.00    0.00      12/13496       deflate (deflate.c:679)
   1281                  0.00    0.00      16/13496       deflate (deflate.c:730)
   1282                  0.00    0.00     128/13496       deflate_fast (deflate.c:654)
   1283                  0.00    0.00    3071/13496       ct_init (trees.c:384)
   1284                  0.00    0.00    3730/13496       ct_init (trees.c:385)
   1285                  0.00    0.00    6525/13496       ct_init (trees.c:387)
   1286      [6]  0.0    0.00    0.00   13496         init_block (trees.c:408)
   1287 
   1288 
   1289 File: gprof.info,  Node: Annotated Source,  Prev: Line-by-line,  Up: Output
   1290 
   1291 5.4 The Annotated Source Listing
   1292 ================================
   1293 
   1294 `gprof''s `-A' option triggers an annotated source listing, which lists
   1295 the program's source code, each function labeled with the number of
   1296 times it was called.  You may also need to specify the `-I' option, if
   1297 `gprof' can't find the source code files.
   1298 
   1299    With older versions of `gcc' compiling with `gcc ... -g -pg -a'
   1300 augments your program with basic-block counting code, in addition to
   1301 function counting code.  This enables `gprof' to determine how many
   1302 times each line of code was executed.  With newer versions of `gcc'
   1303 support for displaying basic-block counts is provided by the `gcov'
   1304 program.
   1305 
   1306    For example, consider the following function, taken from gzip, with
   1307 line numbers added:
   1308 
   1309       1 ulg updcrc(s, n)
   1310       2     uch *s;
   1311       3     unsigned n;
   1312       4 {
   1313       5     register ulg c;
   1314       6
   1315       7     static ulg crc = (ulg)0xffffffffL;
   1316       8
   1317       9     if (s == NULL) {
   1318      10         c = 0xffffffffL;
   1319      11     } else {
   1320      12         c = crc;
   1321      13         if (n) do {
   1322      14             c = crc_32_tab[...];
   1323      15         } while (--n);
   1324      16     }
   1325      17     crc = c;
   1326      18     return c ^ 0xffffffffL;
   1327      19 }
   1328 
   1329    `updcrc' has at least five basic-blocks.  One is the function
   1330 itself.  The `if' statement on line 9 generates two more basic-blocks,
   1331 one for each branch of the `if'.  A fourth basic-block results from the
   1332 `if' on line 13, and the contents of the `do' loop form the fifth
   1333 basic-block.  The compiler may also generate additional basic-blocks to
   1334 handle various special cases.
   1335 
   1336    A program augmented for basic-block counting can be analyzed with
   1337 `gprof -l -A'.  The `-x' option is also helpful, to ensure that each
   1338 line of code is labeled at least once.  Here is `updcrc''s annotated
   1339 source listing for a sample `gzip' run:
   1340 
   1341                      ulg updcrc(s, n)
   1342                          uch *s;
   1343                          unsigned n;
   1344                  2 ->{
   1345                          register ulg c;
   1346 
   1347                          static ulg crc = (ulg)0xffffffffL;
   1348 
   1349                  2 ->    if (s == NULL) {
   1350                  1 ->        c = 0xffffffffL;
   1351                  1 ->    } else {
   1352                  1 ->        c = crc;
   1353                  1 ->        if (n) do {
   1354              26312 ->            c = crc_32_tab[...];
   1355      26312,1,26311 ->        } while (--n);
   1356                          }
   1357                  2 ->    crc = c;
   1358                  2 ->    return c ^ 0xffffffffL;
   1359                  2 ->}
   1360 
   1361    In this example, the function was called twice, passing once through
   1362 each branch of the `if' statement.  The body of the `do' loop was
   1363 executed a total of 26312 times.  Note how the `while' statement is
   1364 annotated.  It began execution 26312 times, once for each iteration
   1365 through the loop.  One of those times (the last time) it exited, while
   1366 it branched back to the beginning of the loop 26311 times.
   1367 
   1368 
   1369 File: gprof.info,  Node: Inaccuracy,  Next: How do I?,  Prev: Output,  Up: Top
   1370 
   1371 6 Inaccuracy of `gprof' Output
   1372 ******************************
   1373 
   1374 * Menu:
   1375 
   1376 * Sampling Error::      Statistical margins of error
   1377 * Assumptions::         Estimating children times
   1378 
   1379 
   1380 File: gprof.info,  Node: Sampling Error,  Next: Assumptions,  Up: Inaccuracy
   1381 
   1382 6.1 Statistical Sampling Error
   1383 ==============================
   1384 
   1385 The run-time figures that `gprof' gives you are based on a sampling
   1386 process, so they are subject to statistical inaccuracy.  If a function
   1387 runs only a small amount of time, so that on the average the sampling
   1388 process ought to catch that function in the act only once, there is a
   1389 pretty good chance it will actually find that function zero times, or
   1390 twice.
   1391 
   1392    By contrast, the number-of-calls and basic-block figures are derived
   1393 by counting, not sampling.  They are completely accurate and will not
   1394 vary from run to run if your program is deterministic and single
   1395 threaded.  In multi-threaded applications, or single threaded
   1396 applications that link with multi-threaded libraries, the counts are
   1397 only deterministic if the counting function is thread-safe.  (Note:
   1398 beware that the mcount counting function in glibc is _not_
   1399 thread-safe).  *Note Implementation of Profiling: Implementation.
   1400 
   1401    The "sampling period" that is printed at the beginning of the flat
   1402 profile says how often samples are taken.  The rule of thumb is that a
   1403 run-time figure is accurate if it is considerably bigger than the
   1404 sampling period.
   1405 
   1406    The actual amount of error can be predicted.  For N samples, the
   1407 _expected_ error is the square-root of N.  For example, if the sampling
   1408 period is 0.01 seconds and `foo''s run-time is 1 second, N is 100
   1409 samples (1 second/0.01 seconds), sqrt(N) is 10 samples, so the expected
   1410 error in `foo''s run-time is 0.1 seconds (10*0.01 seconds), or ten
   1411 percent of the observed value.  Again, if the sampling period is 0.01
   1412 seconds and `bar''s run-time is 100 seconds, N is 10000 samples,
   1413 sqrt(N) is 100 samples, so the expected error in `bar''s run-time is 1
   1414 second, or one percent of the observed value.  It is likely to vary
   1415 this much _on the average_ from one profiling run to the next.
   1416 (_Sometimes_ it will vary more.)
   1417 
   1418    This does not mean that a small run-time figure is devoid of
   1419 information.  If the program's _total_ run-time is large, a small
   1420 run-time for one function does tell you that that function used an
   1421 insignificant fraction of the whole program's time.  Usually this means
   1422 it is not worth optimizing.
   1423 
   1424    One way to get more accuracy is to give your program more (but
   1425 similar) input data so it will take longer.  Another way is to combine
   1426 the data from several runs, using the `-s' option of `gprof'.  Here is
   1427 how:
   1428 
   1429   1. Run your program once.
   1430 
   1431   2. Issue the command `mv gmon.out gmon.sum'.
   1432 
   1433   3. Run your program again, the same as before.
   1434 
   1435   4. Merge the new data in `gmon.out' into `gmon.sum' with this command:
   1436 
   1437           gprof -s EXECUTABLE-FILE gmon.out gmon.sum
   1438 
   1439   5. Repeat the last two steps as often as you wish.
   1440 
   1441   6. Analyze the cumulative data using this command:
   1442 
   1443           gprof EXECUTABLE-FILE gmon.sum > OUTPUT-FILE
   1444 
   1445 
   1446 File: gprof.info,  Node: Assumptions,  Prev: Sampling Error,  Up: Inaccuracy
   1447 
   1448 6.2 Estimating `children' Times
   1449 ===============================
   1450 
   1451 Some of the figures in the call graph are estimates--for example, the
   1452 `children' time values and all the time figures in caller and
   1453 subroutine lines.
   1454 
   1455    There is no direct information about these measurements in the
   1456 profile data itself.  Instead, `gprof' estimates them by making an
   1457 assumption about your program that might or might not be true.
   1458 
   1459    The assumption made is that the average time spent in each call to
   1460 any function `foo' is not correlated with who called `foo'.  If `foo'
   1461 used 5 seconds in all, and 2/5 of the calls to `foo' came from `a',
   1462 then `foo' contributes 2 seconds to `a''s `children' time, by
   1463 assumption.
   1464 
   1465    This assumption is usually true enough, but for some programs it is
   1466 far from true.  Suppose that `foo' returns very quickly when its
   1467 argument is zero; suppose that `a' always passes zero as an argument,
   1468 while other callers of `foo' pass other arguments.  In this program,
   1469 all the time spent in `foo' is in the calls from callers other than `a'.
   1470 But `gprof' has no way of knowing this; it will blindly and incorrectly
   1471 charge 2 seconds of time in `foo' to the children of `a'.
   1472 
   1473    We hope some day to put more complete data into `gmon.out', so that
   1474 this assumption is no longer needed, if we can figure out how.  For the
   1475 novice, the estimated figures are usually more useful than misleading.
   1476 
   1477 
   1478 File: gprof.info,  Node: How do I?,  Next: Incompatibilities,  Prev: Inaccuracy,  Up: Top
   1479 
   1480 7 Answers to Common Questions
   1481 *****************************
   1482 
   1483 How can I get more exact information about hot spots in my program?
   1484      Looking at the per-line call counts only tells part of the story.
   1485      Because `gprof' can only report call times and counts by function,
   1486      the best way to get finer-grained information on where the program
   1487      is spending its time is to re-factor large functions into sequences
   1488      of calls to smaller ones.  Beware however that this can introduce
   1489      artificial hot spots since compiling with `-pg' adds a significant
   1490      overhead to function calls.  An alternative solution is to use a
   1491      non-intrusive profiler, e.g. oprofile.
   1492 
   1493 How do I find which lines in my program were executed the most times?
   1494      Use the `gcov' program.
   1495 
   1496 How do I find which lines in my program called a particular function?
   1497      Use `gprof -l' and lookup the function in the call graph.  The
   1498      callers will be broken down by function and line number.
   1499 
   1500 How do I analyze a program that runs for less than a second?
   1501      Try using a shell script like this one:
   1502 
   1503           for i in `seq 1 100`; do
   1504             fastprog
   1505             mv gmon.out gmon.out.$i
   1506           done
   1507 
   1508           gprof -s fastprog gmon.out.*
   1509 
   1510           gprof fastprog gmon.sum
   1511 
   1512      If your program is completely deterministic, all the call counts
   1513      will be simple multiples of 100 (i.e., a function called once in
   1514      each run will appear with a call count of 100).
   1515 
   1516 
   1517 
   1518 File: gprof.info,  Node: Incompatibilities,  Next: Details,  Prev: How do I?,  Up: Top
   1519 
   1520 8 Incompatibilities with Unix `gprof'
   1521 *************************************
   1522 
   1523 GNU `gprof' and Berkeley Unix `gprof' use the same data file
   1524 `gmon.out', and provide essentially the same information.  But there
   1525 are a few differences.
   1526 
   1527    * GNU `gprof' uses a new, generalized file format with support for
   1528      basic-block execution counts and non-realtime histograms.  A magic
   1529      cookie and version number allows `gprof' to easily identify new
   1530      style files.  Old BSD-style files can still be read.  *Note
   1531      Profiling Data File Format: File Format.
   1532 
   1533    * For a recursive function, Unix `gprof' lists the function as a
   1534      parent and as a child, with a `calls' field that lists the number
   1535      of recursive calls.  GNU `gprof' omits these lines and puts the
   1536      number of recursive calls in the primary line.
   1537 
   1538    * When a function is suppressed from the call graph with `-e', GNU
   1539      `gprof' still lists it as a subroutine of functions that call it.
   1540 
   1541    * GNU `gprof' accepts the `-k' with its argument in the form
   1542      `from/to', instead of `from to'.
   1543 
   1544    * In the annotated source listing, if there are multiple basic
   1545      blocks on the same line, GNU `gprof' prints all of their counts,
   1546      separated by commas.
   1547 
   1548    * The blurbs, field widths, and output formats are different.  GNU
   1549      `gprof' prints blurbs after the tables, so that you can see the
   1550      tables without skipping the blurbs.
   1551 
   1552 
   1553 File: gprof.info,  Node: Details,  Next: GNU Free Documentation License,  Prev: Incompatibilities,  Up: Top
   1554 
   1555 9 Details of Profiling
   1556 **********************
   1557 
   1558 * Menu:
   1559 
   1560 * Implementation::      How a program collects profiling information
   1561 * File Format::         Format of `gmon.out' files
   1562 * Internals::           `gprof''s internal operation
   1563 * Debugging::           Using `gprof''s `-d' option
   1564 
   1565 
   1566 File: gprof.info,  Node: Implementation,  Next: File Format,  Up: Details
   1567 
   1568 9.1 Implementation of Profiling
   1569 ===============================
   1570 
   1571 Profiling works by changing how every function in your program is
   1572 compiled so that when it is called, it will stash away some information
   1573 about where it was called from.  From this, the profiler can figure out
   1574 what function called it, and can count how many times it was called.
   1575 This change is made by the compiler when your program is compiled with
   1576 the `-pg' option, which causes every function to call `mcount' (or
   1577 `_mcount', or `__mcount', depending on the OS and compiler) as one of
   1578 its first operations.
   1579 
   1580    The `mcount' routine, included in the profiling library, is
   1581 responsible for recording in an in-memory call graph table both its
   1582 parent routine (the child) and its parent's parent.  This is typically
   1583 done by examining the stack frame to find both the address of the
   1584 child, and the return address in the original parent.  Since this is a
   1585 very machine-dependent operation, `mcount' itself is typically a short
   1586 assembly-language stub routine that extracts the required information,
   1587 and then calls `__mcount_internal' (a normal C function) with two
   1588 arguments--`frompc' and `selfpc'.  `__mcount_internal' is responsible
   1589 for maintaining the in-memory call graph, which records `frompc',
   1590 `selfpc', and the number of times each of these call arcs was traversed.
   1591 
   1592    GCC Version 2 provides a magical function
   1593 (`__builtin_return_address'), which allows a generic `mcount' function
   1594 to extract the required information from the stack frame.  However, on
   1595 some architectures, most notably the SPARC, using this builtin can be
   1596 very computationally expensive, and an assembly language version of
   1597 `mcount' is used for performance reasons.
   1598 
   1599    Number-of-calls information for library routines is collected by
   1600 using a special version of the C library.  The programs in it are the
   1601 same as in the usual C library, but they were compiled with `-pg'.  If
   1602 you link your program with `gcc ... -pg', it automatically uses the
   1603 profiling version of the library.
   1604 
   1605    Profiling also involves watching your program as it runs, and
   1606 keeping a histogram of where the program counter happens to be every
   1607 now and then.  Typically the program counter is looked at around 100
   1608 times per second of run time, but the exact frequency may vary from
   1609 system to system.
   1610 
   1611    This is done is one of two ways.  Most UNIX-like operating systems
   1612 provide a `profil()' system call, which registers a memory array with
   1613 the kernel, along with a scale factor that determines how the program's
   1614 address space maps into the array.  Typical scaling values cause every
   1615 2 to 8 bytes of address space to map into a single array slot.  On
   1616 every tick of the system clock (assuming the profiled program is
   1617 running), the value of the program counter is examined and the
   1618 corresponding slot in the memory array is incremented.  Since this is
   1619 done in the kernel, which had to interrupt the process anyway to handle
   1620 the clock interrupt, very little additional system overhead is required.
   1621 
   1622    However, some operating systems, most notably Linux 2.0 (and
   1623 earlier), do not provide a `profil()' system call.  On such a system,
   1624 arrangements are made for the kernel to periodically deliver a signal
   1625 to the process (typically via `setitimer()'), which then performs the
   1626 same operation of examining the program counter and incrementing a slot
   1627 in the memory array.  Since this method requires a signal to be
   1628 delivered to user space every time a sample is taken, it uses
   1629 considerably more overhead than kernel-based profiling.  Also, due to
   1630 the added delay required to deliver the signal, this method is less
   1631 accurate as well.
   1632 
   1633    A special startup routine allocates memory for the histogram and
   1634 either calls `profil()' or sets up a clock signal handler.  This
   1635 routine (`monstartup') can be invoked in several ways.  On Linux
   1636 systems, a special profiling startup file `gcrt0.o', which invokes
   1637 `monstartup' before `main', is used instead of the default `crt0.o'.
   1638 Use of this special startup file is one of the effects of using `gcc
   1639 ... -pg' to link.  On SPARC systems, no special startup files are used.
   1640 Rather, the `mcount' routine, when it is invoked for the first time
   1641 (typically when `main' is called), calls `monstartup'.
   1642 
   1643    If the compiler's `-a' option was used, basic-block counting is also
   1644 enabled.  Each object file is then compiled with a static array of
   1645 counts, initially zero.  In the executable code, every time a new
   1646 basic-block begins (i.e., when an `if' statement appears), an extra
   1647 instruction is inserted to increment the corresponding count in the
   1648 array.  At compile time, a paired array was constructed that recorded
   1649 the starting address of each basic-block.  Taken together, the two
   1650 arrays record the starting address of every basic-block, along with the
   1651 number of times it was executed.
   1652 
   1653    The profiling library also includes a function (`mcleanup') which is
   1654 typically registered using `atexit()' to be called as the program
   1655 exits, and is responsible for writing the file `gmon.out'.  Profiling
   1656 is turned off, various headers are output, and the histogram is
   1657 written, followed by the call-graph arcs and the basic-block counts.
   1658 
   1659    The output from `gprof' gives no indication of parts of your program
   1660 that are limited by I/O or swapping bandwidth.  This is because samples
   1661 of the program counter are taken at fixed intervals of the program's
   1662 run time.  Therefore, the time measurements in `gprof' output say
   1663 nothing about time that your program was not running.  For example, a
   1664 part of the program that creates so much data that it cannot all fit in
   1665 physical memory at once may run very slowly due to thrashing, but
   1666 `gprof' will say it uses little time.  On the other hand, sampling by
   1667 run time has the advantage that the amount of load due to other users
   1668 won't directly affect the output you get.
   1669 
   1670 
   1671 File: gprof.info,  Node: File Format,  Next: Internals,  Prev: Implementation,  Up: Details
   1672 
   1673 9.2 Profiling Data File Format
   1674 ==============================
   1675 
   1676 The old BSD-derived file format used for profile data does not contain a
   1677 magic cookie that allows to check whether a data file really is a
   1678 `gprof' file.  Furthermore, it does not provide a version number, thus
   1679 rendering changes to the file format almost impossible.  GNU `gprof'
   1680 uses a new file format that provides these features.  For backward
   1681 compatibility, GNU `gprof' continues to support the old BSD-derived
   1682 format, but not all features are supported with it.  For example,
   1683 basic-block execution counts cannot be accommodated by the old file
   1684 format.
   1685 
   1686    The new file format is defined in header file `gmon_out.h'.  It
   1687 consists of a header containing the magic cookie and a version number,
   1688 as well as some spare bytes available for future extensions.  All data
   1689 in a profile data file is in the native format of the target for which
   1690 the profile was collected.  GNU `gprof' adapts automatically to the
   1691 byte-order in use.
   1692 
   1693    In the new file format, the header is followed by a sequence of
   1694 records.  Currently, there are three different record types: histogram
   1695 records, call-graph arc records, and basic-block execution count
   1696 records.  Each file can contain any number of each record type.  When
   1697 reading a file, GNU `gprof' will ensure records of the same type are
   1698 compatible with each other and compute the union of all records.  For
   1699 example, for basic-block execution counts, the union is simply the sum
   1700 of all execution counts for each basic-block.
   1701 
   1702 9.2.1 Histogram Records
   1703 -----------------------
   1704 
   1705 Histogram records consist of a header that is followed by an array of
   1706 bins.  The header contains the text-segment range that the histogram
   1707 spans, the size of the histogram in bytes (unlike in the old BSD
   1708 format, this does not include the size of the header), the rate of the
   1709 profiling clock, and the physical dimension that the bin counts
   1710 represent after being scaled by the profiling clock rate.  The physical
   1711 dimension is specified in two parts: a long name of up to 15 characters
   1712 and a single character abbreviation.  For example, a histogram
   1713 representing real-time would specify the long name as "seconds" and the
   1714 abbreviation as "s".  This feature is useful for architectures that
   1715 support performance monitor hardware (which, fortunately, is becoming
   1716 increasingly common).  For example, under DEC OSF/1, the "uprofile"
   1717 command can be used to produce a histogram of, say, instruction cache
   1718 misses.  In this case, the dimension in the histogram header could be
   1719 set to "i-cache misses" and the abbreviation could be set to "1"
   1720 (because it is simply a count, not a physical dimension).  Also, the
   1721 profiling rate would have to be set to 1 in this case.
   1722 
   1723    Histogram bins are 16-bit numbers and each bin represent an equal
   1724 amount of text-space.  For example, if the text-segment is one thousand
   1725 bytes long and if there are ten bins in the histogram, each bin
   1726 represents one hundred bytes.
   1727 
   1728 9.2.2 Call-Graph Records
   1729 ------------------------
   1730 
   1731 Call-graph records have a format that is identical to the one used in
   1732 the BSD-derived file format.  It consists of an arc in the call graph
   1733 and a count indicating the number of times the arc was traversed during
   1734 program execution.  Arcs are specified by a pair of addresses: the
   1735 first must be within caller's function and the second must be within
   1736 the callee's function.  When performing profiling at the function
   1737 level, these addresses can point anywhere within the respective
   1738 function.  However, when profiling at the line-level, it is better if
   1739 the addresses are as close to the call-site/entry-point as possible.
   1740 This will ensure that the line-level call-graph is able to identify
   1741 exactly which line of source code performed calls to a function.
   1742 
   1743 9.2.3 Basic-Block Execution Count Records
   1744 -----------------------------------------
   1745 
   1746 Basic-block execution count records consist of a header followed by a
   1747 sequence of address/count pairs.  The header simply specifies the
   1748 length of the sequence.  In an address/count pair, the address
   1749 identifies a basic-block and the count specifies the number of times
   1750 that basic-block was executed.  Any address within the basic-address can
   1751 be used.
   1752 
   1753 
   1754 File: gprof.info,  Node: Internals,  Next: Debugging,  Prev: File Format,  Up: Details
   1755 
   1756 9.3 `gprof''s Internal Operation
   1757 ================================
   1758 
   1759 Like most programs, `gprof' begins by processing its options.  During
   1760 this stage, it may building its symspec list (`sym_ids.c:sym_id_add'),
   1761 if options are specified which use symspecs.  `gprof' maintains a
   1762 single linked list of symspecs, which will eventually get turned into
   1763 12 symbol tables, organized into six include/exclude pairs--one pair
   1764 each for the flat profile (INCL_FLAT/EXCL_FLAT), the call graph arcs
   1765 (INCL_ARCS/EXCL_ARCS), printing in the call graph
   1766 (INCL_GRAPH/EXCL_GRAPH), timing propagation in the call graph
   1767 (INCL_TIME/EXCL_TIME), the annotated source listing
   1768 (INCL_ANNO/EXCL_ANNO), and the execution count listing
   1769 (INCL_EXEC/EXCL_EXEC).
   1770 
   1771    After option processing, `gprof' finishes building the symspec list
   1772 by adding all the symspecs in `default_excluded_list' to the exclude
   1773 lists EXCL_TIME and EXCL_GRAPH, and if line-by-line profiling is
   1774 specified, EXCL_FLAT as well.  These default excludes are not added to
   1775 EXCL_ANNO, EXCL_ARCS, and EXCL_EXEC.
   1776 
   1777    Next, the BFD library is called to open the object file, verify that
   1778 it is an object file, and read its symbol table (`core.c:core_init'),
   1779 using `bfd_canonicalize_symtab' after mallocing an appropriately sized
   1780 array of symbols.  At this point, function mappings are read (if the
   1781 `--file-ordering' option has been specified), and the core text space
   1782 is read into memory (if the `-c' option was given).
   1783 
   1784    `gprof''s own symbol table, an array of Sym structures, is now built.
   1785 This is done in one of two ways, by one of two routines, depending on
   1786 whether line-by-line profiling (`-l' option) has been enabled.  For
   1787 normal profiling, the BFD canonical symbol table is scanned.  For
   1788 line-by-line profiling, every text space address is examined, and a new
   1789 symbol table entry gets created every time the line number changes.  In
   1790 either case, two passes are made through the symbol table--one to count
   1791 the size of the symbol table required, and the other to actually read
   1792 the symbols.  In between the two passes, a single array of type `Sym'
   1793 is created of the appropriate length.  Finally,
   1794 `symtab.c:symtab_finalize' is called to sort the symbol table and
   1795 remove duplicate entries (entries with the same memory address).
   1796 
   1797    The symbol table must be a contiguous array for two reasons.  First,
   1798 the `qsort' library function (which sorts an array) will be used to
   1799 sort the symbol table.  Also, the symbol lookup routine
   1800 (`symtab.c:sym_lookup'), which finds symbols based on memory address,
   1801 uses a binary search algorithm which requires the symbol table to be a
   1802 sorted array.  Function symbols are indicated with an `is_func' flag.
   1803 Line number symbols have no special flags set.  Additionally, a symbol
   1804 can have an `is_static' flag to indicate that it is a local symbol.
   1805 
   1806    With the symbol table read, the symspecs can now be translated into
   1807 Syms (`sym_ids.c:sym_id_parse').  Remember that a single symspec can
   1808 match multiple symbols.  An array of symbol tables (`syms') is created,
   1809 each entry of which is a symbol table of Syms to be included or
   1810 excluded from a particular listing.  The master symbol table and the
   1811 symspecs are examined by nested loops, and every symbol that matches a
   1812 symspec is inserted into the appropriate syms table.  This is done
   1813 twice, once to count the size of each required symbol table, and again
   1814 to build the tables, which have been malloced between passes.  From now
   1815 on, to determine whether a symbol is on an include or exclude symspec
   1816 list, `gprof' simply uses its standard symbol lookup routine on the
   1817 appropriate table in the `syms' array.
   1818 
   1819    Now the profile data file(s) themselves are read
   1820 (`gmon_io.c:gmon_out_read'), first by checking for a new-style
   1821 `gmon.out' header, then assuming this is an old-style BSD `gmon.out' if
   1822 the magic number test failed.
   1823 
   1824    New-style histogram records are read by `hist.c:hist_read_rec'.  For
   1825 the first histogram record, allocate a memory array to hold all the
   1826 bins, and read them in.  When multiple profile data files (or files
   1827 with multiple histogram records) are read, the memory ranges of each
   1828 pair of histogram records must be either equal, or non-overlapping.
   1829 For each pair of histogram records, the resolution (memory region size
   1830 divided by the number of bins) must be the same.  The time unit must be
   1831 the same for all histogram records. If the above containts are met, all
   1832 histograms for the same memory range are merged.
   1833 
   1834    As each call graph record is read (`call_graph.c:cg_read_rec'), the
   1835 parent and child addresses are matched to symbol table entries, and a
   1836 call graph arc is created by `cg_arcs.c:arc_add', unless the arc fails
   1837 a symspec check against INCL_ARCS/EXCL_ARCS.  As each arc is added, a
   1838 linked list is maintained of the parent's child arcs, and of the child's
   1839 parent arcs.  Both the child's call count and the arc's call count are
   1840 incremented by the record's call count.
   1841 
   1842    Basic-block records are read (`basic_blocks.c:bb_read_rec'), but
   1843 only if line-by-line profiling has been selected.  Each basic-block
   1844 address is matched to a corresponding line symbol in the symbol table,
   1845 and an entry made in the symbol's bb_addr and bb_calls arrays.  Again,
   1846 if multiple basic-block records are present for the same address, the
   1847 call counts are cumulative.
   1848 
   1849    A gmon.sum file is dumped, if requested (`gmon_io.c:gmon_out_write').
   1850 
   1851    If histograms were present in the data files, assign them to symbols
   1852 (`hist.c:hist_assign_samples') by iterating over all the sample bins
   1853 and assigning them to symbols.  Since the symbol table is sorted in
   1854 order of ascending memory addresses, we can simple follow along in the
   1855 symbol table as we make our pass over the sample bins.  This step
   1856 includes a symspec check against INCL_FLAT/EXCL_FLAT.  Depending on the
   1857 histogram scale factor, a sample bin may span multiple symbols, in
   1858 which case a fraction of the sample count is allocated to each symbol,
   1859 proportional to the degree of overlap.  This effect is rare for normal
   1860 profiling, but overlaps are more common during line-by-line profiling,
   1861 and can cause each of two adjacent lines to be credited with half a
   1862 hit, for example.
   1863 
   1864    If call graph data is present, `cg_arcs.c:cg_assemble' is called.
   1865 First, if `-c' was specified, a machine-dependent routine (`find_call')
   1866 scans through each symbol's machine code, looking for subroutine call
   1867 instructions, and adding them to the call graph with a zero call count.
   1868 A topological sort is performed by depth-first numbering all the
   1869 symbols (`cg_dfn.c:cg_dfn'), so that children are always numbered less
   1870 than their parents, then making a array of pointers into the symbol
   1871 table and sorting it into numerical order, which is reverse topological
   1872 order (children appear before parents).  Cycles are also detected at
   1873 this point, all members of which are assigned the same topological
   1874 number.  Two passes are now made through this sorted array of symbol
   1875 pointers.  The first pass, from end to beginning (parents to children),
   1876 computes the fraction of child time to propagate to each parent and a
   1877 print flag.  The print flag reflects symspec handling of
   1878 INCL_GRAPH/EXCL_GRAPH, with a parent's include or exclude (print or no
   1879 print) property being propagated to its children, unless they
   1880 themselves explicitly appear in INCL_GRAPH or EXCL_GRAPH.  A second
   1881 pass, from beginning to end (children to parents) actually propagates
   1882 the timings along the call graph, subject to a check against
   1883 INCL_TIME/EXCL_TIME.  With the print flag, fractions, and timings now
   1884 stored in the symbol structures, the topological sort array is now
   1885 discarded, and a new array of pointers is assembled, this time sorted
   1886 by propagated time.
   1887 
   1888    Finally, print the various outputs the user requested, which is now
   1889 fairly straightforward.  The call graph (`cg_print.c:cg_print') and
   1890 flat profile (`hist.c:hist_print') are regurgitations of values already
   1891 computed.  The annotated source listing
   1892 (`basic_blocks.c:print_annotated_source') uses basic-block information,
   1893 if present, to label each line of code with call counts, otherwise only
   1894 the function call counts are presented.
   1895 
   1896    The function ordering code is marginally well documented in the
   1897 source code itself (`cg_print.c').  Basically, the functions with the
   1898 most use and the most parents are placed first, followed by other
   1899 functions with the most use, followed by lower use functions, followed
   1900 by unused functions at the end.
   1901 
   1902 
   1903 File: gprof.info,  Node: Debugging,  Prev: Internals,  Up: Details
   1904 
   1905 9.4 Debugging `gprof'
   1906 =====================
   1907 
   1908 If `gprof' was compiled with debugging enabled, the `-d' option
   1909 triggers debugging output (to stdout) which can be helpful in
   1910 understanding its operation.  The debugging number specified is
   1911 interpreted as a sum of the following options:
   1912 
   1913 2 - Topological sort
   1914      Monitor depth-first numbering of symbols during call graph analysis
   1915 
   1916 4 - Cycles
   1917      Shows symbols as they are identified as cycle heads
   1918 
   1919 16 - Tallying
   1920      As the call graph arcs are read, show each arc and how the total
   1921      calls to each function are tallied
   1922 
   1923 32 - Call graph arc sorting
   1924      Details sorting individual parents/children within each call graph
   1925      entry
   1926 
   1927 64 - Reading histogram and call graph records
   1928      Shows address ranges of histograms as they are read, and each call
   1929      graph arc
   1930 
   1931 128 - Symbol table
   1932      Reading, classifying, and sorting the symbol table from the object
   1933      file.  For line-by-line profiling (`-l' option), also shows line
   1934      numbers being assigned to memory addresses.
   1935 
   1936 256 - Static call graph
   1937      Trace operation of `-c' option
   1938 
   1939 512 - Symbol table and arc table lookups
   1940      Detail operation of lookup routines
   1941 
   1942 1024 - Call graph propagation
   1943      Shows how function times are propagated along the call graph
   1944 
   1945 2048 - Basic-blocks
   1946      Shows basic-block records as they are read from profile data (only
   1947      meaningful with `-l' option)
   1948 
   1949 4096 - Symspecs
   1950      Shows symspec-to-symbol pattern matching operation
   1951 
   1952 8192 - Annotate source
   1953      Tracks operation of `-A' option
   1954 
   1955 
   1956 File: gprof.info,  Node: GNU Free Documentation License,  Prev: Details,  Up: Top
   1957 
   1958 Appendix A GNU Free Documentation License
   1959 *****************************************
   1960 
   1961                      Version 1.3, 3 November 2008
   1962 
   1963      Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
   1964      `http://fsf.org/'
   1965 
   1966      Everyone is permitted to copy and distribute verbatim copies
   1967      of this license document, but changing it is not allowed.
   1968 
   1969   0. PREAMBLE
   1970 
   1971      The purpose of this License is to make a manual, textbook, or other
   1972      functional and useful document "free" in the sense of freedom: to
   1973      assure everyone the effective freedom to copy and redistribute it,
   1974      with or without modifying it, either commercially or
   1975      noncommercially.  Secondarily, this License preserves for the
   1976      author and publisher a way to get credit for their work, while not
   1977      being considered responsible for modifications made by others.
   1978 
   1979      This License is a kind of "copyleft", which means that derivative
   1980      works of the document must themselves be free in the same sense.
   1981      It complements the GNU General Public License, which is a copyleft
   1982      license designed for free software.
   1983 
   1984      We have designed this License in order to use it for manuals for
   1985      free software, because free software needs free documentation: a
   1986      free program should come with manuals providing the same freedoms
   1987      that the software does.  But this License is not limited to
   1988      software manuals; it can be used for any textual work, regardless
   1989      of subject matter or whether it is published as a printed book.
   1990      We recommend this License principally for works whose purpose is
   1991      instruction or reference.
   1992 
   1993   1. APPLICABILITY AND DEFINITIONS
   1994 
   1995      This License applies to any manual or other work, in any medium,
   1996      that contains a notice placed by the copyright holder saying it
   1997      can be distributed under the terms of this License.  Such a notice
   1998      grants a world-wide, royalty-free license, unlimited in duration,
   1999      to use that work under the conditions stated herein.  The
   2000      "Document", below, refers to any such manual or work.  Any member
   2001      of the public is a licensee, and is addressed as "you".  You
   2002      accept the license if you copy, modify or distribute the work in a
   2003      way requiring permission under copyright law.
   2004 
   2005      A "Modified Version" of the Document means any work containing the
   2006      Document or a portion of it, either copied verbatim, or with
   2007      modifications and/or translated into another language.
   2008 
   2009      A "Secondary Section" is a named appendix or a front-matter section
   2010      of the Document that deals exclusively with the relationship of the
   2011      publishers or authors of the Document to the Document's overall
   2012      subject (or to related matters) and contains nothing that could
   2013      fall directly within that overall subject.  (Thus, if the Document
   2014      is in part a textbook of mathematics, a Secondary Section may not
   2015      explain any mathematics.)  The relationship could be a matter of
   2016      historical connection with the subject or with related matters, or
   2017      of legal, commercial, philosophical, ethical or political position
   2018      regarding them.
   2019 
   2020      The "Invariant Sections" are certain Secondary Sections whose
   2021      titles are designated, as being those of Invariant Sections, in
   2022      the notice that says that the Document is released under this
   2023      License.  If a section does not fit the above definition of
   2024      Secondary then it is not allowed to be designated as Invariant.
   2025      The Document may contain zero Invariant Sections.  If the Document
   2026      does not identify any Invariant Sections then there are none.
   2027 
   2028      The "Cover Texts" are certain short passages of text that are
   2029      listed, as Front-Cover Texts or Back-Cover Texts, in the notice
   2030      that says that the Document is released under this License.  A
   2031      Front-Cover Text may be at most 5 words, and a Back-Cover Text may
   2032      be at most 25 words.
   2033 
   2034      A "Transparent" copy of the Document means a machine-readable copy,
   2035      represented in a format whose specification is available to the
   2036      general public, that is suitable for revising the document
   2037      straightforwardly with generic text editors or (for images
   2038      composed of pixels) generic paint programs or (for drawings) some
   2039      widely available drawing editor, and that is suitable for input to
   2040      text formatters or for automatic translation to a variety of
   2041      formats suitable for input to text formatters.  A copy made in an
   2042      otherwise Transparent file format whose markup, or absence of
   2043      markup, has been arranged to thwart or discourage subsequent
   2044      modification by readers is not Transparent.  An image format is
   2045      not Transparent if used for any substantial amount of text.  A
   2046      copy that is not "Transparent" is called "Opaque".
   2047 
   2048      Examples of suitable formats for Transparent copies include plain
   2049      ASCII without markup, Texinfo input format, LaTeX input format,
   2050      SGML or XML using a publicly available DTD, and
   2051      standard-conforming simple HTML, PostScript or PDF designed for
   2052      human modification.  Examples of transparent image formats include
   2053      PNG, XCF and JPG.  Opaque formats include proprietary formats that
   2054      can be read and edited only by proprietary word processors, SGML or
   2055      XML for which the DTD and/or processing tools are not generally
   2056      available, and the machine-generated HTML, PostScript or PDF
   2057      produced by some word processors for output purposes only.
   2058 
   2059      The "Title Page" means, for a printed book, the title page itself,
   2060      plus such following pages as are needed to hold, legibly, the
   2061      material this License requires to appear in the title page.  For
   2062      works in formats which do not have any title page as such, "Title
   2063      Page" means the text near the most prominent appearance of the
   2064      work's title, preceding the beginning of the body of the text.
   2065 
   2066      The "publisher" means any person or entity that distributes copies
   2067      of the Document to the public.
   2068 
   2069      A section "Entitled XYZ" means a named subunit of the Document
   2070      whose title either is precisely XYZ or contains XYZ in parentheses
   2071      following text that translates XYZ in another language.  (Here XYZ
   2072      stands for a specific section name mentioned below, such as
   2073      "Acknowledgements", "Dedications", "Endorsements", or "History".)
   2074      To "Preserve the Title" of such a section when you modify the
   2075      Document means that it remains a section "Entitled XYZ" according
   2076      to this definition.
   2077 
   2078      The Document may include Warranty Disclaimers next to the notice
   2079      which states that this License applies to the Document.  These
   2080      Warranty Disclaimers are considered to be included by reference in
   2081      this License, but only as regards disclaiming warranties: any other
   2082      implication that these Warranty Disclaimers may have is void and
   2083      has no effect on the meaning of this License.
   2084 
   2085   2. VERBATIM COPYING
   2086 
   2087      You may copy and distribute the Document in any medium, either
   2088      commercially or noncommercially, provided that this License, the
   2089      copyright notices, and the license notice saying this License
   2090      applies to the Document are reproduced in all copies, and that you
   2091      add no other conditions whatsoever to those of this License.  You
   2092      may not use technical measures to obstruct or control the reading
   2093      or further copying of the copies you make or distribute.  However,
   2094      you may accept compensation in exchange for copies.  If you
   2095      distribute a large enough number of copies you must also follow
   2096      the conditions in section 3.
   2097 
   2098      You may also lend copies, under the same conditions stated above,
   2099      and you may publicly display copies.
   2100 
   2101   3. COPYING IN QUANTITY
   2102 
   2103      If you publish printed copies (or copies in media that commonly
   2104      have printed covers) of the Document, numbering more than 100, and
   2105      the Document's license notice requires Cover Texts, you must
   2106      enclose the copies in covers that carry, clearly and legibly, all
   2107      these Cover Texts: Front-Cover Texts on the front cover, and
   2108      Back-Cover Texts on the back cover.  Both covers must also clearly
   2109      and legibly identify you as the publisher of these copies.  The
   2110      front cover must present the full title with all words of the
   2111      title equally prominent and visible.  You may add other material
   2112      on the covers in addition.  Copying with changes limited to the
   2113      covers, as long as they preserve the title of the Document and
   2114      satisfy these conditions, can be treated as verbatim copying in
   2115      other respects.
   2116 
   2117      If the required texts for either cover are too voluminous to fit
   2118      legibly, you should put the first ones listed (as many as fit
   2119      reasonably) on the actual cover, and continue the rest onto
   2120      adjacent pages.
   2121 
   2122      If you publish or distribute Opaque copies of the Document
   2123      numbering more than 100, you must either include a
   2124      machine-readable Transparent copy along with each Opaque copy, or
   2125      state in or with each Opaque copy a computer-network location from
   2126      which the general network-using public has access to download
   2127      using public-standard network protocols a complete Transparent
   2128      copy of the Document, free of added material.  If you use the
   2129      latter option, you must take reasonably prudent steps, when you
   2130      begin distribution of Opaque copies in quantity, to ensure that
   2131      this Transparent copy will remain thus accessible at the stated
   2132      location until at least one year after the last time you
   2133      distribute an Opaque copy (directly or through your agents or
   2134      retailers) of that edition to the public.
   2135 
   2136      It is requested, but not required, that you contact the authors of
   2137      the Document well before redistributing any large number of
   2138      copies, to give them a chance to provide you with an updated
   2139      version of the Document.
   2140 
   2141   4. MODIFICATIONS
   2142 
   2143      You may copy and distribute a Modified Version of the Document
   2144      under the conditions of sections 2 and 3 above, provided that you
   2145      release the Modified Version under precisely this License, with
   2146      the Modified Version filling the role of the Document, thus
   2147      licensing distribution and modification of the Modified Version to
   2148      whoever possesses a copy of it.  In addition, you must do these
   2149      things in the Modified Version:
   2150 
   2151        A. Use in the Title Page (and on the covers, if any) a title
   2152           distinct from that of the Document, and from those of
   2153           previous versions (which should, if there were any, be listed
   2154           in the History section of the Document).  You may use the
   2155           same title as a previous version if the original publisher of
   2156           that version gives permission.
   2157 
   2158        B. List on the Title Page, as authors, one or more persons or
   2159           entities responsible for authorship of the modifications in
   2160           the Modified Version, together with at least five of the
   2161           principal authors of the Document (all of its principal
   2162           authors, if it has fewer than five), unless they release you
   2163           from this requirement.
   2164 
   2165        C. State on the Title page the name of the publisher of the
   2166           Modified Version, as the publisher.
   2167 
   2168        D. Preserve all the copyright notices of the Document.
   2169 
   2170        E. Add an appropriate copyright notice for your modifications
   2171           adjacent to the other copyright notices.
   2172 
   2173        F. Include, immediately after the copyright notices, a license
   2174           notice giving the public permission to use the Modified
   2175           Version under the terms of this License, in the form shown in
   2176           the Addendum below.
   2177 
   2178        G. Preserve in that license notice the full lists of Invariant
   2179           Sections and required Cover Texts given in the Document's
   2180           license notice.
   2181 
   2182        H. Include an unaltered copy of this License.
   2183 
   2184        I. Preserve the section Entitled "History", Preserve its Title,
   2185           and add to it an item stating at least the title, year, new
   2186           authors, and publisher of the Modified Version as given on
   2187           the Title Page.  If there is no section Entitled "History" in
   2188           the Document, create one stating the title, year, authors,
   2189           and publisher of the Document as given on its Title Page,
   2190           then add an item describing the Modified Version as stated in
   2191           the previous sentence.
   2192 
   2193        J. Preserve the network location, if any, given in the Document
   2194           for public access to a Transparent copy of the Document, and
   2195           likewise the network locations given in the Document for
   2196           previous versions it was based on.  These may be placed in
   2197           the "History" section.  You may omit a network location for a
   2198           work that was published at least four years before the
   2199           Document itself, or if the original publisher of the version
   2200           it refers to gives permission.
   2201 
   2202        K. For any section Entitled "Acknowledgements" or "Dedications",
   2203           Preserve the Title of the section, and preserve in the
   2204           section all the substance and tone of each of the contributor
   2205           acknowledgements and/or dedications given therein.
   2206 
   2207        L. Preserve all the Invariant Sections of the Document,
   2208           unaltered in their text and in their titles.  Section numbers
   2209           or the equivalent are not considered part of the section
   2210           titles.
   2211 
   2212        M. Delete any section Entitled "Endorsements".  Such a section
   2213           may not be included in the Modified Version.
   2214 
   2215        N. Do not retitle any existing section to be Entitled
   2216           "Endorsements" or to conflict in title with any Invariant
   2217           Section.
   2218 
   2219        O. Preserve any Warranty Disclaimers.
   2220 
   2221      If the Modified Version includes new front-matter sections or
   2222      appendices that qualify as Secondary Sections and contain no
   2223      material copied from the Document, you may at your option
   2224      designate some or all of these sections as invariant.  To do this,
   2225      add their titles to the list of Invariant Sections in the Modified
   2226      Version's license notice.  These titles must be distinct from any
   2227      other section titles.
   2228 
   2229      You may add a section Entitled "Endorsements", provided it contains
   2230      nothing but endorsements of your Modified Version by various
   2231      parties--for example, statements of peer review or that the text
   2232      has been approved by an organization as the authoritative
   2233      definition of a standard.
   2234 
   2235      You may add a passage of up to five words as a Front-Cover Text,
   2236      and a passage of up to 25 words as a Back-Cover Text, to the end
   2237      of the list of Cover Texts in the Modified Version.  Only one
   2238      passage of Front-Cover Text and one of Back-Cover Text may be
   2239      added by (or through arrangements made by) any one entity.  If the
   2240      Document already includes a cover text for the same cover,
   2241      previously added by you or by arrangement made by the same entity
   2242      you are acting on behalf of, you may not add another; but you may
   2243      replace the old one, on explicit permission from the previous
   2244      publisher that added the old one.
   2245 
   2246      The author(s) and publisher(s) of the Document do not by this
   2247      License give permission to use their names for publicity for or to
   2248      assert or imply endorsement of any Modified Version.
   2249 
   2250   5. COMBINING DOCUMENTS
   2251 
   2252      You may combine the Document with other documents released under
   2253      this License, under the terms defined in section 4 above for
   2254      modified versions, provided that you include in the combination
   2255      all of the Invariant Sections of all of the original documents,
   2256      unmodified, and list them all as Invariant Sections of your
   2257      combined work in its license notice, and that you preserve all
   2258      their Warranty Disclaimers.
   2259 
   2260      The combined work need only contain one copy of this License, and
   2261      multiple identical Invariant Sections may be replaced with a single
   2262      copy.  If there are multiple Invariant Sections with the same name
   2263      but different contents, make the title of each such section unique
   2264      by adding at the end of it, in parentheses, the name of the
   2265      original author or publisher of that section if known, or else a
   2266      unique number.  Make the same adjustment to the section titles in
   2267      the list of Invariant Sections in the license notice of the
   2268      combined work.
   2269 
   2270      In the combination, you must combine any sections Entitled
   2271      "History" in the various original documents, forming one section
   2272      Entitled "History"; likewise combine any sections Entitled
   2273      "Acknowledgements", and any sections Entitled "Dedications".  You
   2274      must delete all sections Entitled "Endorsements."
   2275 
   2276   6. COLLECTIONS OF DOCUMENTS
   2277 
   2278      You may make a collection consisting of the Document and other
   2279      documents released under this License, and replace the individual
   2280      copies of this License in the various documents with a single copy
   2281      that is included in the collection, provided that you follow the
   2282      rules of this License for verbatim copying of each of the
   2283      documents in all other respects.
   2284 
   2285      You may extract a single document from such a collection, and
   2286      distribute it individually under this License, provided you insert
   2287      a copy of this License into the extracted document, and follow
   2288      this License in all other respects regarding verbatim copying of
   2289      that document.
   2290 
   2291   7. AGGREGATION WITH INDEPENDENT WORKS
   2292 
   2293      A compilation of the Document or its derivatives with other
   2294      separate and independent documents or works, in or on a volume of
   2295      a storage or distribution medium, is called an "aggregate" if the
   2296      copyright resulting from the compilation is not used to limit the
   2297      legal rights of the compilation's users beyond what the individual
   2298      works permit.  When the Document is included in an aggregate, this
   2299      License does not apply to the other works in the aggregate which
   2300      are not themselves derivative works of the Document.
   2301 
   2302      If the Cover Text requirement of section 3 is applicable to these
   2303      copies of the Document, then if the Document is less than one half
   2304      of the entire aggregate, the Document's Cover Texts may be placed
   2305      on covers that bracket the Document within the aggregate, or the
   2306      electronic equivalent of covers if the Document is in electronic
   2307      form.  Otherwise they must appear on printed covers that bracket
   2308      the whole aggregate.
   2309 
   2310   8. TRANSLATION
   2311 
   2312      Translation is considered a kind of modification, so you may
   2313      distribute translations of the Document under the terms of section
   2314      4.  Replacing Invariant Sections with translations requires special
   2315      permission from their copyright holders, but you may include
   2316      translations of some or all Invariant Sections in addition to the
   2317      original versions of these Invariant Sections.  You may include a
   2318      translation of this License, and all the license notices in the
   2319      Document, and any Warranty Disclaimers, provided that you also
   2320      include the original English version of this License and the
   2321      original versions of those notices and disclaimers.  In case of a
   2322      disagreement between the translation and the original version of
   2323      this License or a notice or disclaimer, the original version will
   2324      prevail.
   2325 
   2326      If a section in the Document is Entitled "Acknowledgements",
   2327      "Dedications", or "History", the requirement (section 4) to
   2328      Preserve its Title (section 1) will typically require changing the
   2329      actual title.
   2330 
   2331   9. TERMINATION
   2332 
   2333      You may not copy, modify, sublicense, or distribute the Document
   2334      except as expressly provided under this License.  Any attempt
   2335      otherwise to copy, modify, sublicense, or distribute it is void,
   2336      and will automatically terminate your rights under this License.
   2337 
   2338      However, if you cease all violation of this License, then your
   2339      license from a particular copyright holder is reinstated (a)
   2340      provisionally, unless and until the copyright holder explicitly
   2341      and finally terminates your license, and (b) permanently, if the
   2342      copyright holder fails to notify you of the violation by some
   2343      reasonable means prior to 60 days after the cessation.
   2344 
   2345      Moreover, your license from a particular copyright holder is
   2346      reinstated permanently if the copyright holder notifies you of the
   2347      violation by some reasonable means, this is the first time you have
   2348      received notice of violation of this License (for any work) from
   2349      that copyright holder, and you cure the violation prior to 30 days
   2350      after your receipt of the notice.
   2351 
   2352      Termination of your rights under this section does not terminate
   2353      the licenses of parties who have received copies or rights from
   2354      you under this License.  If your rights have been terminated and
   2355      not permanently reinstated, receipt of a copy of some or all of
   2356      the same material does not give you any rights to use it.
   2357 
   2358  10. FUTURE REVISIONS OF THIS LICENSE
   2359 
   2360      The Free Software Foundation may publish new, revised versions of
   2361      the GNU Free Documentation License from time to time.  Such new
   2362      versions will be similar in spirit to the present version, but may
   2363      differ in detail to address new problems or concerns.  See
   2364      `http://www.gnu.org/copyleft/'.
   2365 
   2366      Each version of the License is given a distinguishing version
   2367      number.  If the Document specifies that a particular numbered
   2368      version of this License "or any later version" applies to it, you
   2369      have the option of following the terms and conditions either of
   2370      that specified version or of any later version that has been
   2371      published (not as a draft) by the Free Software Foundation.  If
   2372      the Document does not specify a version number of this License,
   2373      you may choose any version ever published (not as a draft) by the
   2374      Free Software Foundation.  If the Document specifies that a proxy
   2375      can decide which future versions of this License can be used, that
   2376      proxy's public statement of acceptance of a version permanently
   2377      authorizes you to choose that version for the Document.
   2378 
   2379  11. RELICENSING
   2380 
   2381      "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
   2382      World Wide Web server that publishes copyrightable works and also
   2383      provides prominent facilities for anybody to edit those works.  A
   2384      public wiki that anybody can edit is an example of such a server.
   2385      A "Massive Multiauthor Collaboration" (or "MMC") contained in the
   2386      site means any set of copyrightable works thus published on the MMC
   2387      site.
   2388 
   2389      "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
   2390      license published by Creative Commons Corporation, a not-for-profit
   2391      corporation with a principal place of business in San Francisco,
   2392      California, as well as future copyleft versions of that license
   2393      published by that same organization.
   2394 
   2395      "Incorporate" means to publish or republish a Document, in whole or
   2396      in part, as part of another Document.
   2397 
   2398      An MMC is "eligible for relicensing" if it is licensed under this
   2399      License, and if all works that were first published under this
   2400      License somewhere other than this MMC, and subsequently
   2401      incorporated in whole or in part into the MMC, (1) had no cover
   2402      texts or invariant sections, and (2) were thus incorporated prior
   2403      to November 1, 2008.
   2404 
   2405      The operator of an MMC Site may republish an MMC contained in the
   2406      site under CC-BY-SA on the same site at any time before August 1,
   2407      2009, provided the MMC is eligible for relicensing.
   2408 
   2409 
   2410 ADDENDUM: How to use this License for your documents
   2411 ====================================================
   2412 
   2413 To use this License in a document you have written, include a copy of
   2414 the License in the document and put the following copyright and license
   2415 notices just after the title page:
   2416 
   2417        Copyright (C)  YEAR  YOUR NAME.
   2418        Permission is granted to copy, distribute and/or modify this document
   2419        under the terms of the GNU Free Documentation License, Version 1.3
   2420        or any later version published by the Free Software Foundation;
   2421        with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
   2422        Texts.  A copy of the license is included in the section entitled ``GNU
   2423        Free Documentation License''.
   2424 
   2425    If you have Invariant Sections, Front-Cover Texts and Back-Cover
   2426 Texts, replace the "with...Texts." line with this:
   2427 
   2428          with the Invariant Sections being LIST THEIR TITLES, with
   2429          the Front-Cover Texts being LIST, and with the Back-Cover Texts
   2430          being LIST.
   2431 
   2432    If you have Invariant Sections without Cover Texts, or some other
   2433 combination of the three, merge those two alternatives to suit the
   2434 situation.
   2435 
   2436    If your document contains nontrivial examples of program code, we
   2437 recommend releasing these examples in parallel under your choice of
   2438 free software license, such as the GNU General Public License, to
   2439 permit their use in free software.
   2440 
   2441 
   2442 
   2443 Tag Table:
   2444 Node: Top838
   2445 Node: Introduction2161
   2446 Node: Compiling4653
   2447 Node: Executing8709
   2448 Node: Invoking11497
   2449 Node: Output Options12912
   2450 Node: Analysis Options20001
   2451 Node: Miscellaneous Options23699
   2452 Node: Deprecated Options24954
   2453 Node: Symspecs27023
   2454 Node: Output28849
   2455 Node: Flat Profile29889
   2456 Node: Call Graph34842
   2457 Node: Primary38074
   2458 Node: Callers40662
   2459 Node: Subroutines42779
   2460 Node: Cycles44620
   2461 Node: Line-by-line51397
   2462 Node: Annotated Source55470
   2463 Node: Inaccuracy58469
   2464 Node: Sampling Error58727
   2465 Node: Assumptions61631
   2466 Node: How do I?63101
   2467 Node: Incompatibilities64655
   2468 Node: Details66149
   2469 Node: Implementation66542
   2470 Node: File Format72439
   2471 Node: Internals76729
   2472 Node: Debugging85224
   2473 Node: GNU Free Documentation License86825
   2474 
   2475 End Tag Table
   2476