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This is gprof.info, produced by makeinfo version 4.8 from gprof.texi.
2
 
3
START-INFO-DIR-ENTRY
4
* gprof: (gprof).                Profiling your program's execution
5
END-INFO-DIR-ENTRY
6
 
7
   This file documents the gprof profiler of the GNU system.
8
 
9
   Copyright (C) 1988, 92, 97, 98, 99, 2000, 2001, 2003, 2007 Free
10
Software Foundation, Inc.
11
 
12
   Permission is granted to copy, distribute and/or modify this document
13
under the terms of the GNU Free Documentation License, Version 1.1 or
14
any later version published by the Free Software Foundation; with no
15
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
16
Texts.  A copy of the license is included in the section entitled "GNU
17
Free Documentation License".
18
 
19

20
File: gprof.info,  Node: Top,  Next: Introduction,  Up: (dir)
21
 
22
Profiling a Program: Where Does It Spend Its Time?
23
**************************************************
24
 
25
This manual describes the GNU profiler, `gprof', and how you can use it
26
to determine which parts of a program are taking most of the execution
27
time.  We assume that you know how to write, compile, and execute
28
programs.  GNU `gprof' was written by Jay Fenlason.
29
 
30
   This manual is for `gprof' (GNU Binutils) version 2.18.50.
31
 
32
   This document is distributed under the terms of the GNU Free
33
Documentation License.  A copy of the license is included in the
34
section entitled "GNU Free Documentation License".
35
 
36
* Menu:
37
 
38
* Introduction::        What profiling means, and why it is useful.
39
 
40
* Compiling::           How to compile your program for profiling.
41
* Executing::           Executing your program to generate profile data
42
* Invoking::            How to run `gprof', and its options
43
 
44
* Output::              Interpreting `gprof''s output
45
 
46
* Inaccuracy::          Potential problems you should be aware of
47
* How do I?::           Answers to common questions
48
* Incompatibilities::   (between GNU `gprof' and Unix `gprof'.)
49
* Details::             Details of how profiling is done
50
* GNU Free Documentation License::  GNU Free Documentation License
51
 
52

53
File: gprof.info,  Node: Introduction,  Next: Compiling,  Prev: Top,  Up: Top
54
 
55
1 Introduction to Profiling
56
***************************
57
 
58
Profiling allows you to learn where your program spent its time and
59
which functions called which other functions while it was executing.
60
This information can show you which pieces of your program are slower
61
than you expected, and might be candidates for rewriting to make your
62
program execute faster.  It can also tell you which functions are being
63
called more or less often than you expected.  This may help you spot
64
bugs that had otherwise been unnoticed.
65
 
66
   Since the profiler uses information collected during the actual
67
execution of your program, it can be used on programs that are too
68
large or too complex to analyze by reading the source.  However, how
69
your program is run will affect the information that shows up in the
70
profile data.  If you don't use some feature of your program while it
71
is being profiled, no profile information will be generated for that
72
feature.
73
 
74
   Profiling has several steps:
75
 
76
   * You must compile and link your program with profiling enabled.
77
     *Note Compiling a Program for Profiling: Compiling.
78
 
79
   * You must execute your program to generate a profile data file.
80
     *Note Executing the Program: Executing.
81
 
82
   * You must run `gprof' to analyze the profile data.  *Note `gprof'
83
     Command Summary: Invoking.
84
 
85
   The next three chapters explain these steps in greater detail.
86
 
87
   Several forms of output are available from the analysis.
88
 
89
   The "flat profile" shows how much time your program spent in each
90
function, and how many times that function was called.  If you simply
91
want to know which functions burn most of the cycles, it is stated
92
concisely here.  *Note The Flat Profile: Flat Profile.
93
 
94
   The "call graph" shows, for each function, which functions called
95
it, which other functions it called, and how many times.  There is also
96
an estimate of how much time was spent in the subroutines of each
97
function.  This can suggest places where you might try to eliminate
98
function calls that use a lot of time.  *Note The Call Graph: Call
99
Graph.
100
 
101
   The "annotated source" listing is a copy of the program's source
102
code, labeled with the number of times each line of the program was
103
executed.  *Note The Annotated Source Listing: Annotated Source.
104
 
105
   To better understand how profiling works, you may wish to read a
106
description of its implementation.  *Note Implementation of Profiling:
107
Implementation.
108
 
109

110
File: gprof.info,  Node: Compiling,  Next: Executing,  Prev: Introduction,  Up: Top
111
 
112
2 Compiling a Program for Profiling
113
***********************************
114
 
115
The first step in generating profile information for your program is to
116
compile and link it with profiling enabled.
117
 
118
   To compile a source file for profiling, specify the `-pg' option when
119
you run the compiler.  (This is in addition to the options you normally
120
use.)
121
 
122
   To link the program for profiling, if you use a compiler such as `cc'
123
to do the linking, simply specify `-pg' in addition to your usual
124
options.  The same option, `-pg', alters either compilation or linking
125
to do what is necessary for profiling.  Here are examples:
126
 
127
     cc -g -c myprog.c utils.c -pg
128
     cc -o myprog myprog.o utils.o -pg
129
 
130
   The `-pg' option also works with a command that both compiles and
131
links:
132
 
133
     cc -o myprog myprog.c utils.c -g -pg
134
 
135
   Note: The `-pg' option must be part of your compilation options as
136
well as your link options.  If it is not then no call-graph data will
137
be gathered and when you run `gprof' you will get an error message like
138
this:
139
 
140
     gprof: gmon.out file is missing call-graph data
141
 
142
   If you add the `-Q' switch to suppress the printing of the call
143
graph data you will still be able to see the time samples:
144
 
145
     Flat profile:
146
 
147
     Each sample counts as 0.01 seconds.
148
       %   cumulative   self              self     total
149
      time   seconds   seconds    calls  Ts/call  Ts/call  name
150
      44.12      0.07     0.07                             zazLoop
151
      35.29      0.14     0.06                             main
152
      20.59      0.17     0.04                             bazMillion
153
 
154
   If you run the linker `ld' directly instead of through a compiler
155
such as `cc', you may have to specify a profiling startup file
156
`gcrt0.o' as the first input file instead of the usual startup file
157
`crt0.o'.  In addition, you would probably want to specify the
158
profiling C library, `libc_p.a', by writing `-lc_p' instead of the
159
usual `-lc'.  This is not absolutely necessary, but doing this gives
160
you number-of-calls information for standard library functions such as
161
`read' and `open'.  For example:
162
 
163
     ld -o myprog /lib/gcrt0.o myprog.o utils.o -lc_p
164
 
165
   If you compile only some of the modules of the program with `-pg',
166
you can still profile the program, but you won't get complete
167
information about the modules that were compiled without `-pg'.  The
168
only information you get for the functions in those modules is the
169
total time spent in them; there is no record of how many times they
170
were called, or from where.  This will not affect the flat profile
171
(except that the `calls' field for the functions will be blank), but
172
will greatly reduce the usefulness of the call graph.
173
 
174
   If you wish to perform line-by-line profiling you should use the
175
`gcov' tool instead of `gprof'.  See that tool's manual or info pages
176
for more details of how to do this.
177
 
178
   Note, older versions of `gcc' produce line-by-line profiling
179
information that works with `gprof' rather than `gcov' so there is
180
still support for displaying this kind of information in `gprof'. *Note
181
Line-by-line Profiling: Line-by-line.
182
 
183
   It also worth noting that `gcc' implements a
184
`-finstrument-functions' command line option which will insert calls to
185
special user supplied instrumentation routines at the entry and exit of
186
every function in their program.  This can be used to implement an
187
alternative profiling scheme.
188
 
189

190
File: gprof.info,  Node: Executing,  Next: Invoking,  Prev: Compiling,  Up: Top
191
 
192
3 Executing the Program
193
***********************
194
 
195
Once the program is compiled for profiling, you must run it in order to
196
generate the information that `gprof' needs.  Simply run the program as
197
usual, using the normal arguments, file names, etc.  The program should
198
run normally, producing the same output as usual.  It will, however, run
199
somewhat slower than normal because of the time spent collecting and
200
writing the profile data.
201
 
202
   The way you run the program--the arguments and input that you give
203
it--may have a dramatic effect on what the profile information shows.
204
The profile data will describe the parts of the program that were
205
activated for the particular input you use.  For example, if the first
206
command you give to your program is to quit, the profile data will show
207
the time used in initialization and in cleanup, but not much else.
208
 
209
   Your program will write the profile data into a file called
210
`gmon.out' just before exiting.  If there is already a file called
211
`gmon.out', its contents are overwritten.  There is currently no way to
212
tell the program to write the profile data under a different name, but
213
you can rename the file afterwards if you are concerned that it may be
214
overwritten.
215
 
216
   In order to write the `gmon.out' file properly, your program must
217
exit normally: by returning from `main' or by calling `exit'.  Calling
218
the low-level function `_exit' does not write the profile data, and
219
neither does abnormal termination due to an unhandled signal.
220
 
221
   The `gmon.out' file is written in the program's _current working
222
directory_ at the time it exits.  This means that if your program calls
223
`chdir', the `gmon.out' file will be left in the last directory your
224
program `chdir''d to.  If you don't have permission to write in this
225
directory, the file is not written, and you will get an error message.
226
 
227
   Older versions of the GNU profiling library may also write a file
228
called `bb.out'.  This file, if present, contains an human-readable
229
listing of the basic-block execution counts.  Unfortunately, the
230
appearance of a human-readable `bb.out' means the basic-block counts
231
didn't get written into `gmon.out'.  The Perl script `bbconv.pl',
232
included with the `gprof' source distribution, will convert a `bb.out'
233
file into a format readable by `gprof'.  Invoke it like this:
234
 
235
     bbconv.pl < bb.out > BH-DATA
236
 
237
   This translates the information in `bb.out' into a form that `gprof'
238
can understand.  But you still need to tell `gprof' about the existence
239
of this translated information.  To do that, include BB-DATA on the
240
`gprof' command line, _along with `gmon.out'_, like this:
241
 
242
     gprof OPTIONS EXECUTABLE-FILE gmon.out BB-DATA [YET-MORE-PROFILE-DATA-FILES...] [> OUTFILE]
243
 
244

245
File: gprof.info,  Node: Invoking,  Next: Output,  Prev: Executing,  Up: Top
246
 
247
4 `gprof' Command Summary
248
*************************
249
 
250
After you have a profile data file `gmon.out', you can run `gprof' to
251
interpret the information in it.  The `gprof' program prints a flat
252
profile and a call graph on standard output.  Typically you would
253
redirect the output of `gprof' into a file with `>'.
254
 
255
   You run `gprof' like this:
256
 
257
     gprof OPTIONS [EXECUTABLE-FILE [PROFILE-DATA-FILES...]] [> OUTFILE]
258
 
259
Here square-brackets indicate optional arguments.
260
 
261
   If you omit the executable file name, the file `a.out' is used.  If
262
you give no profile data file name, the file `gmon.out' is used.  If
263
any file is not in the proper format, or if the profile data file does
264
not appear to belong to the executable file, an error message is
265
printed.
266
 
267
   You can give more than one profile data file by entering all their
268
names after the executable file name; then the statistics in all the
269
data files are summed together.
270
 
271
   The order of these options does not matter.
272
 
273
* Menu:
274
 
275
* Output Options::      Controlling `gprof''s output style
276
* Analysis Options::    Controlling how `gprof' analyzes its data
277
* Miscellaneous Options::
278
* Deprecated Options::  Options you no longer need to use, but which
279
                            have been retained for compatibility
280
* Symspecs::            Specifying functions to include or exclude
281
 
282

283
File: gprof.info,  Node: Output Options,  Next: Analysis Options,  Up: Invoking
284
 
285
4.1 Output Options
286
==================
287
 
288
These options specify which of several output formats `gprof' should
289
produce.
290
 
291
   Many of these options take an optional "symspec" to specify
292
functions to be included or excluded.  These options can be specified
293
multiple times, with different symspecs, to include or exclude sets of
294
symbols.  *Note Symspecs: Symspecs.
295
 
296
   Specifying any of these options overrides the default (`-p -q'),
297
which prints a flat profile and call graph analysis for all functions.
298
 
299
`-A[SYMSPEC]'
300
`--annotated-source[=SYMSPEC]'
301
     The `-A' option causes `gprof' to print annotated source code.  If
302
     SYMSPEC is specified, print output only for matching symbols.
303
     *Note The Annotated Source Listing: Annotated Source.
304
 
305
`-b'
306
`--brief'
307
     If the `-b' option is given, `gprof' doesn't print the verbose
308
     blurbs that try to explain the meaning of all of the fields in the
309
     tables.  This is useful if you intend to print out the output, or
310
     are tired of seeing the blurbs.
311
 
312
`-C[SYMSPEC]'
313
`--exec-counts[=SYMSPEC]'
314
     The `-C' option causes `gprof' to print a tally of functions and
315
     the number of times each was called.  If SYMSPEC is specified,
316
     print tally only for matching symbols.
317
 
318
     If the profile data file contains basic-block count records,
319
     specifying the `-l' option, along with `-C', will cause basic-block
320
     execution counts to be tallied and displayed.
321
 
322
`-i'
323
`--file-info'
324
     The `-i' option causes `gprof' to display summary information
325
     about the profile data file(s) and then exit.  The number of
326
     histogram, call graph, and basic-block count records is displayed.
327
 
328
`-I DIRS'
329
`--directory-path=DIRS'
330
     The `-I' option specifies a list of search directories in which to
331
     find source files.  Environment variable GPROF_PATH can also be
332
     used to convey this information.  Used mostly for annotated source
333
     output.
334
 
335
`-J[SYMSPEC]'
336
`--no-annotated-source[=SYMSPEC]'
337
     The `-J' option causes `gprof' not to print annotated source code.
338
     If SYMSPEC is specified, `gprof' prints annotated source, but
339
     excludes matching symbols.
340
 
341
`-L'
342
`--print-path'
343
     Normally, source filenames are printed with the path component
344
     suppressed.  The `-L' option causes `gprof' to print the full
345
     pathname of source filenames, which is determined from symbolic
346
     debugging information in the image file and is relative to the
347
     directory in which the compiler was invoked.
348
 
349
`-p[SYMSPEC]'
350
`--flat-profile[=SYMSPEC]'
351
     The `-p' option causes `gprof' to print a flat profile.  If
352
     SYMSPEC is specified, print flat profile only for matching symbols.
353
     *Note The Flat Profile: Flat Profile.
354
 
355
`-P[SYMSPEC]'
356
`--no-flat-profile[=SYMSPEC]'
357
     The `-P' option causes `gprof' to suppress printing a flat profile.
358
     If SYMSPEC is specified, `gprof' prints a flat profile, but
359
     excludes matching symbols.
360
 
361
`-q[SYMSPEC]'
362
`--graph[=SYMSPEC]'
363
     The `-q' option causes `gprof' to print the call graph analysis.
364
     If SYMSPEC is specified, print call graph only for matching symbols
365
     and their children.  *Note The Call Graph: Call Graph.
366
 
367
`-Q[SYMSPEC]'
368
`--no-graph[=SYMSPEC]'
369
     The `-Q' option causes `gprof' to suppress printing the call graph.
370
     If SYMSPEC is specified, `gprof' prints a call graph, but excludes
371
     matching symbols.
372
 
373
`-t'
374
`--table-length=NUM'
375
     The `-t' option causes the NUM most active source lines in each
376
     source file to be listed when source annotation is enabled.  The
377
     default is 10.
378
 
379
`-y'
380
`--separate-files'
381
     This option affects annotated source output only.  Normally,
382
     `gprof' prints annotated source files to standard-output.  If this
383
     option is specified, annotated source for a file named
384
     `path/FILENAME' is generated in the file `FILENAME-ann'.  If the
385
     underlying file system would truncate `FILENAME-ann' so that it
386
     overwrites the original `FILENAME', `gprof' generates annotated
387
     source in the file `FILENAME.ann' instead (if the original file
388
     name has an extension, that extension is _replaced_ with `.ann').
389
 
390
`-Z[SYMSPEC]'
391
`--no-exec-counts[=SYMSPEC]'
392
     The `-Z' option causes `gprof' not to print a tally of functions
393
     and the number of times each was called.  If SYMSPEC is specified,
394
     print tally, but exclude matching symbols.
395
 
396
`-r'
397
`--function-ordering'
398
     The `--function-ordering' option causes `gprof' to print a
399
     suggested function ordering for the program based on profiling
400
     data.  This option suggests an ordering which may improve paging,
401
     tlb and cache behavior for the program on systems which support
402
     arbitrary ordering of functions in an executable.
403
 
404
     The exact details of how to force the linker to place functions in
405
     a particular order is system dependent and out of the scope of this
406
     manual.
407
 
408
`-R MAP_FILE'
409
`--file-ordering MAP_FILE'
410
     The `--file-ordering' option causes `gprof' to print a suggested
411
     .o link line ordering for the program based on profiling data.
412
     This option suggests an ordering which may improve paging, tlb and
413
     cache behavior for the program on systems which do not support
414
     arbitrary ordering of functions in an executable.
415
 
416
     Use of the `-a' argument is highly recommended with this option.
417
 
418
     The MAP_FILE argument is a pathname to a file which provides
419
     function name to object file mappings.  The format of the file is
420
     similar to the output of the program `nm'.
421
 
422
          c-parse.o:00000000 T yyparse
423
          c-parse.o:00000004 C yyerrflag
424
          c-lang.o:00000000 T maybe_objc_method_name
425
          c-lang.o:00000000 T print_lang_statistics
426
          c-lang.o:00000000 T recognize_objc_keyword
427
          c-decl.o:00000000 T print_lang_identifier
428
          c-decl.o:00000000 T print_lang_type
429
          ...
430
 
431
     To create a MAP_FILE with GNU `nm', type a command like `nm
432
     --extern-only --defined-only -v --print-file-name program-name'.
433
 
434
`-T'
435
`--traditional'
436
     The `-T' option causes `gprof' to print its output in
437
     "traditional" BSD style.
438
 
439
`-w WIDTH'
440
`--width=WIDTH'
441
     Sets width of output lines to WIDTH.  Currently only used when
442
     printing the function index at the bottom of the call graph.
443
 
444
`-x'
445
`--all-lines'
446
     This option affects annotated source output only.  By default,
447
     only the lines at the beginning of a basic-block are annotated.
448
     If this option is specified, every line in a basic-block is
449
     annotated by repeating the annotation for the first line.  This
450
     behavior is similar to `tcov''s `-a'.
451
 
452
`--demangle[=STYLE]'
453
`--no-demangle'
454
     These options control whether C++ symbol names should be demangled
455
     when printing output.  The default is to demangle symbols.  The
456
     `--no-demangle' option may be used to turn off demangling.
457
     Different compilers have different mangling styles.  The optional
458
     demangling style argument can be used to choose an appropriate
459
     demangling style for your compiler.
460
 
461

462
File: gprof.info,  Node: Analysis Options,  Next: Miscellaneous Options,  Prev: Output Options,  Up: Invoking
463
 
464
4.2 Analysis Options
465
====================
466
 
467
`-a'
468
`--no-static'
469
     The `-a' option causes `gprof' to suppress the printing of
470
     statically declared (private) functions.  (These are functions
471
     whose names are not listed as global, and which are not visible
472
     outside the file/function/block where they were defined.)  Time
473
     spent in these functions, calls to/from them, etc., will all be
474
     attributed to the function that was loaded directly before it in
475
     the executable file.  This option affects both the flat profile
476
     and the call graph.
477
 
478
`-c'
479
`--static-call-graph'
480
     The `-c' option causes the call graph of the program to be
481
     augmented by a heuristic which examines the text space of the
482
     object file and identifies function calls in the binary machine
483
     code.  Since normal call graph records are only generated when
484
     functions are entered, this option identifies children that could
485
     have been called, but never were.  Calls to functions that were
486
     not compiled with profiling enabled are also identified, but only
487
     if symbol table entries are present for them.  Calls to dynamic
488
     library routines are typically _not_ found by this option.
489
     Parents or children identified via this heuristic are indicated in
490
     the call graph with call counts of `0'.
491
 
492
`-D'
493
`--ignore-non-functions'
494
     The `-D' option causes `gprof' to ignore symbols which are not
495
     known to be functions.  This option will give more accurate
496
     profile data on systems where it is supported (Solaris and HPUX for
497
     example).
498
 
499
`-k FROM/TO'
500
     The `-k' option allows you to delete from the call graph any arcs
501
     from symbols matching symspec FROM to those matching symspec TO.
502
 
503
`-l'
504
`--line'
505
     The `-l' option enables line-by-line profiling, which causes
506
     histogram hits to be charged to individual source code lines,
507
     instead of functions.  This feature only works with programs
508
     compiled by older versions of the `gcc' compiler.  Newer versions
509
     of `gcc' are designed to work with the `gcov' tool instead.
510
 
511
     If the program was compiled with basic-block counting enabled,
512
     this option will also identify how many times each line of code
513
     was executed.  While line-by-line profiling can help isolate where
514
     in a large function a program is spending its time, it also
515
     significantly increases the running time of `gprof', and magnifies
516
     statistical inaccuracies.  *Note Statistical Sampling Error:
517
     Sampling Error.
518
 
519
`-m NUM'
520
`--min-count=NUM'
521
     This option affects execution count output only.  Symbols that are
522
     executed less than NUM times are suppressed.
523
 
524
`-nSYMSPEC'
525
`--time=SYMSPEC'
526
     The `-n' option causes `gprof', in its call graph analysis, to
527
     only propagate times for symbols matching SYMSPEC.
528
 
529
`-NSYMSPEC'
530
`--no-time=SYMSPEC'
531
     The `-n' option causes `gprof', in its call graph analysis, not to
532
     propagate times for symbols matching SYMSPEC.
533
 
534
`-z'
535
`--display-unused-functions'
536
     If you give the `-z' option, `gprof' will mention all functions in
537
     the flat profile, even those that were never called, and that had
538
     no time spent in them.  This is useful in conjunction with the
539
     `-c' option for discovering which routines were never called.
540
 
541
 
542

543
File: gprof.info,  Node: Miscellaneous Options,  Next: Deprecated Options,  Prev: Analysis Options,  Up: Invoking
544
 
545
4.3 Miscellaneous Options
546
=========================
547
 
548
`-d[NUM]'
549
`--debug[=NUM]'
550
     The `-d NUM' option specifies debugging options.  If NUM is not
551
     specified, enable all debugging.  *Note Debugging `gprof':
552
     Debugging.
553
 
554
`-h'
555
`--help'
556
     The `-h' option prints command line usage.
557
 
558
`-ONAME'
559
`--file-format=NAME'
560
     Selects the format of the profile data files.  Recognized formats
561
     are `auto' (the default), `bsd', `4.4bsd', `magic', and `prof'
562
     (not yet supported).
563
 
564
`-s'
565
`--sum'
566
     The `-s' option causes `gprof' to summarize the information in the
567
     profile data files it read in, and write out a profile data file
568
     called `gmon.sum', which contains all the information from the
569
     profile data files that `gprof' read in.  The file `gmon.sum' may
570
     be one of the specified input files; the effect of this is to
571
     merge the data in the other input files into `gmon.sum'.
572
 
573
     Eventually you can run `gprof' again without `-s' to analyze the
574
     cumulative data in the file `gmon.sum'.
575
 
576
`-v'
577
`--version'
578
     The `-v' flag causes `gprof' to print the current version number,
579
     and then exit.
580
 
581
 
582

583
File: gprof.info,  Node: Deprecated Options,  Next: Symspecs,  Prev: Miscellaneous Options,  Up: Invoking
584
 
585
4.4 Deprecated Options
586
======================
587
 
588
     These options have been replaced with newer versions that use
589
     symspecs.
590
 
591
`-e FUNCTION_NAME'
592
     The `-e FUNCTION' option tells `gprof' to not print information
593
     about the function FUNCTION_NAME (and its children...) in the call
594
     graph.  The function will still be listed as a child of any
595
     functions that call it, but its index number will be shown as
596
     `[not printed]'.  More than one `-e' option may be given; only one
597
     FUNCTION_NAME may be indicated with each `-e' option.
598
 
599
`-E FUNCTION_NAME'
600
     The `-E FUNCTION' option works like the `-e' option, but time
601
     spent in the function (and children who were not called from
602
     anywhere else), will not be used to compute the
603
     percentages-of-time for the call graph.  More than one `-E' option
604
     may be given; only one FUNCTION_NAME may be indicated with each
605
     `-E' option.
606
 
607
`-f FUNCTION_NAME'
608
     The `-f FUNCTION' option causes `gprof' to limit the call graph to
609
     the function FUNCTION_NAME and its children (and their
610
     children...).  More than one `-f' option may be given; only one
611
     FUNCTION_NAME may be indicated with each `-f' option.
612
 
613
`-F FUNCTION_NAME'
614
     The `-F FUNCTION' option works like the `-f' option, but only time
615
     spent in the function and its children (and their children...)
616
     will be used to determine total-time and percentages-of-time for
617
     the call graph.  More than one `-F' option may be given; only one
618
     FUNCTION_NAME may be indicated with each `-F' option.  The `-F'
619
     option overrides the `-E' option.
620
 
621
 
622
   Note that only one function can be specified with each `-e', `-E',
623
`-f' or `-F' option.  To specify more than one function, use multiple
624
options.  For example, this command:
625
 
626
     gprof -e boring -f foo -f bar myprogram > gprof.output
627
 
628
lists in the call graph all functions that were reached from either
629
`foo' or `bar' and were not reachable from `boring'.
630
 
631

632
File: gprof.info,  Node: Symspecs,  Prev: Deprecated Options,  Up: Invoking
633
 
634
4.5 Symspecs
635
============
636
 
637
Many of the output options allow functions to be included or excluded
638
using "symspecs" (symbol specifications), which observe the following
639
syntax:
640
 
641
       filename_containing_a_dot
642
     | funcname_not_containing_a_dot
643
     | linenumber
644
     | ( [ any_filename ] `:' ( any_funcname | linenumber ) )
645
 
646
   Here are some sample symspecs:
647
 
648
`main.c'
649
     Selects everything in file `main.c'--the dot in the string tells
650
     `gprof' to interpret the string as a filename, rather than as a
651
     function name.  To select a file whose name does not contain a
652
     dot, a trailing colon should be specified.  For example, `odd:' is
653
     interpreted as the file named `odd'.
654
 
655
`main'
656
     Selects all functions named `main'.
657
 
658
     Note that there may be multiple instances of the same function name
659
     because some of the definitions may be local (i.e., static).
660
     Unless a function name is unique in a program, you must use the
661
     colon notation explained below to specify a function from a
662
     specific source file.
663
 
664
     Sometimes, function names contain dots.  In such cases, it is
665
     necessary to add a leading colon to the name.  For example,
666
     `:.mul' selects function `.mul'.
667
 
668
     In some object file formats, symbols have a leading underscore.
669
     `gprof' will normally not print these underscores.  When you name a
670
     symbol in a symspec, you should type it exactly as `gprof' prints
671
     it in its output.  For example, if the compiler produces a symbol
672
     `_main' from your `main' function, `gprof' still prints it as
673
     `main' in its output, so you should use `main' in symspecs.
674
 
675
`main.c:main'
676
     Selects function `main' in file `main.c'.
677
 
678
`main.c:134'
679
     Selects line 134 in file `main.c'.
680
 
681

682
File: gprof.info,  Node: Output,  Next: Inaccuracy,  Prev: Invoking,  Up: Top
683
 
684
5 Interpreting `gprof''s Output
685
*******************************
686
 
687
`gprof' can produce several different output styles, the most important
688
of which are described below.  The simplest output styles (file
689
information, execution count, and function and file ordering) are not
690
described here, but are documented with the respective options that
691
trigger them.  *Note Output Options: Output Options.
692
 
693
* Menu:
694
 
695
* Flat Profile::        The flat profile shows how much time was spent
696
                            executing directly in each function.
697
* Call Graph::          The call graph shows which functions called which
698
                            others, and how much time each function used
699
                            when its subroutine calls are included.
700
* Line-by-line::        `gprof' can analyze individual source code lines
701
* Annotated Source::    The annotated source listing displays source code
702
                            labeled with execution counts
703
 
704

705
File: gprof.info,  Node: Flat Profile,  Next: Call Graph,  Up: Output
706
 
707
5.1 The Flat Profile
708
====================
709
 
710
The "flat profile" shows the total amount of time your program spent
711
executing each function.  Unless the `-z' option is given, functions
712
with no apparent time spent in them, and no apparent calls to them, are
713
not mentioned.  Note that if a function was not compiled for profiling,
714
and didn't run long enough to show up on the program counter histogram,
715
it will be indistinguishable from a function that was never called.
716
 
717
   This is part of a flat profile for a small program:
718
 
719
     Flat profile:
720
 
721
     Each sample counts as 0.01 seconds.
722
       %   cumulative   self              self     total
723
      time   seconds   seconds    calls  ms/call  ms/call  name
724
      33.34      0.02     0.02     7208     0.00     0.00  open
725
      16.67      0.03     0.01      244     0.04     0.12  offtime
726
      16.67      0.04     0.01        8     1.25     1.25  memccpy
727
      16.67      0.05     0.01        7     1.43     1.43  write
728
      16.67      0.06     0.01                             mcount
729
       0.00      0.06     0.00      236     0.00     0.00  tzset
730
       0.00      0.06     0.00      192     0.00     0.00  tolower
731
       0.00      0.06     0.00       47     0.00     0.00  strlen
732
       0.00      0.06     0.00       45     0.00     0.00  strchr
733
       0.00      0.06     0.00        1     0.00    50.00  main
734
       0.00      0.06     0.00        1     0.00     0.00  memcpy
735
       0.00      0.06     0.00        1     0.00    10.11  print
736
       0.00      0.06     0.00        1     0.00     0.00  profil
737
       0.00      0.06     0.00        1     0.00    50.00  report
738
     ...
739
 
740
The functions are sorted first by decreasing run-time spent in them,
741
then by decreasing number of calls, then alphabetically by name.  The
742
functions `mcount' and `profil' are part of the profiling apparatus and
743
appear in every flat profile; their time gives a measure of the amount
744
of overhead due to profiling.
745
 
746
   Just before the column headers, a statement appears indicating how
747
much time each sample counted as.  This "sampling period" estimates the
748
margin of error in each of the time figures.  A time figure that is not
749
much larger than this is not reliable.  In this example, each sample
750
counted as 0.01 seconds, suggesting a 100 Hz sampling rate.  The
751
program's total execution time was 0.06 seconds, as indicated by the
752
`cumulative seconds' field.  Since each sample counted for 0.01
753
seconds, this means only six samples were taken during the run.  Two of
754
the samples occurred while the program was in the `open' function, as
755
indicated by the `self seconds' field.  Each of the other four samples
756
occurred one each in `offtime', `memccpy', `write', and `mcount'.
757
Since only six samples were taken, none of these values can be regarded
758
as particularly reliable.  In another run, the `self seconds' field for
759
`mcount' might well be `0.00' or `0.02'.  *Note Statistical Sampling
760
Error: Sampling Error, for a complete discussion.
761
 
762
   The remaining functions in the listing (those whose `self seconds'
763
field is `0.00') didn't appear in the histogram samples at all.
764
However, the call graph indicated that they were called, so therefore
765
they are listed, sorted in decreasing order by the `calls' field.
766
Clearly some time was spent executing these functions, but the paucity
767
of histogram samples prevents any determination of how much time each
768
took.
769
 
770
   Here is what the fields in each line mean:
771
 
772
`% time'
773
     This is the percentage of the total execution time your program
774
     spent in this function.  These should all add up to 100%.
775
 
776
`cumulative seconds'
777
     This is the cumulative total number of seconds the computer spent
778
     executing this functions, plus the time spent in all the functions
779
     above this one in this table.
780
 
781
`self seconds'
782
     This is the number of seconds accounted for by this function alone.
783
     The flat profile listing is sorted first by this number.
784
 
785
`calls'
786
     This is the total number of times the function was called.  If the
787
     function was never called, or the number of times it was called
788
     cannot be determined (probably because the function was not
789
     compiled with profiling enabled), the "calls" field is blank.
790
 
791
`self ms/call'
792
     This represents the average number of milliseconds spent in this
793
     function per call, if this function is profiled.  Otherwise, this
794
     field is blank for this function.
795
 
796
`total ms/call'
797
     This represents the average number of milliseconds spent in this
798
     function and its descendants per call, if this function is
799
     profiled.  Otherwise, this field is blank for this function.  This
800
     is the only field in the flat profile that uses call graph
801
     analysis.
802
 
803
`name'
804
     This is the name of the function.   The flat profile is sorted by
805
     this field alphabetically after the "self seconds" and "calls"
806
     fields are sorted.
807
 
808

809
File: gprof.info,  Node: Call Graph,  Next: Line-by-line,  Prev: Flat Profile,  Up: Output
810
 
811
5.2 The Call Graph
812
==================
813
 
814
The "call graph" shows how much time was spent in each function and its
815
children.  From this information, you can find functions that, while
816
they themselves may not have used much time, called other functions
817
that did use unusual amounts of time.
818
 
819
   Here is a sample call from a small program.  This call came from the
820
same `gprof' run as the flat profile example in the previous section.
821
 
822
     granularity: each sample hit covers 2 byte(s) for 20.00% of 0.05 seconds
823
 
824
     index % time    self  children    called     name
825
                                                      
826
     [1]    100.0    0.00    0.05                 start [1]
827
                     0.00    0.05       1/1           main [2]
828
                     0.00    0.00       1/2           on_exit [28]
829
                     0.00    0.00       1/1           exit [59]
830
     -----------------------------------------------
831
                     0.00    0.05       1/1           start [1]
832
     [2]    100.0    0.00    0.05       1         main [2]
833
                     0.00    0.05       1/1           report [3]
834
     -----------------------------------------------
835
                     0.00    0.05       1/1           main [2]
836
     [3]    100.0    0.00    0.05       1         report [3]
837
                     0.00    0.03       8/8           timelocal [6]
838
                     0.00    0.01       1/1           print [9]
839
                     0.00    0.01       9/9           fgets [12]
840
                     0.00    0.00      12/34          strncmp  [40]
841
                     0.00    0.00       8/8           lookup [20]
842
                     0.00    0.00       1/1           fopen [21]
843
                     0.00    0.00       8/8           chewtime [24]
844
                     0.00    0.00       8/16          skipspace [44]
845
     -----------------------------------------------
846
     [4]     59.8    0.01        0.02       8+472      [4]
847
                     0.01        0.02     244+260         offtime  [7]
848
                     0.00        0.00     236+1           tzset  [26]
849
     -----------------------------------------------
850
 
851
   The lines full of dashes divide this table into "entries", one for
852
each function.  Each entry has one or more lines.
853
 
854
   In each entry, the primary line is the one that starts with an index
855
number in square brackets.  The end of this line says which function
856
the entry is for.  The preceding lines in the entry describe the
857
callers of this function and the following lines describe its
858
subroutines (also called "children" when we speak of the call graph).
859
 
860
   The entries are sorted by time spent in the function and its
861
subroutines.
862
 
863
   The internal profiling function `mcount' (*note The Flat Profile:
864
Flat Profile.) is never mentioned in the call graph.
865
 
866
* Menu:
867
 
868
* Primary::       Details of the primary line's contents.
869
* Callers::       Details of caller-lines' contents.
870
* Subroutines::   Details of subroutine-lines' contents.
871
* Cycles::        When there are cycles of recursion,
872
                   such as `a' calls `b' calls `a'...
873
 
874

875
File: gprof.info,  Node: Primary,  Next: Callers,  Up: Call Graph
876
 
877
5.2.1 The Primary Line
878
----------------------
879
 
880
The "primary line" in a call graph entry is the line that describes the
881
function which the entry is about and gives the overall statistics for
882
this function.
883
 
884
   For reference, we repeat the primary line from the entry for function
885
`report' in our main example, together with the heading line that shows
886
the names of the fields:
887
 
888
     index  % time    self  children called     name
889
     ...
890
     [3]    100.0    0.00    0.05       1         report [3]
891
 
892
   Here is what the fields in the primary line mean:
893
 
894
`index'
895
     Entries are numbered with consecutive integers.  Each function
896
     therefore has an index number, which appears at the beginning of
897
     its primary line.
898
 
899
     Each cross-reference to a function, as a caller or subroutine of
900
     another, gives its index number as well as its name.  The index
901
     number guides you if you wish to look for the entry for that
902
     function.
903
 
904
`% time'
905
     This is the percentage of the total time that was spent in this
906
     function, including time spent in subroutines called from this
907
     function.
908
 
909
     The time spent in this function is counted again for the callers of
910
     this function.  Therefore, adding up these percentages is
911
     meaningless.
912
 
913
`self'
914
     This is the total amount of time spent in this function.  This
915
     should be identical to the number printed in the `seconds' field
916
     for this function in the flat profile.
917
 
918
`children'
919
     This is the total amount of time spent in the subroutine calls
920
     made by this function.  This should be equal to the sum of all the
921
     `self' and `children' entries of the children listed directly
922
     below this function.
923
 
924
`called'
925
     This is the number of times the function was called.
926
 
927
     If the function called itself recursively, there are two numbers,
928
     separated by a `+'.  The first number counts non-recursive calls,
929
     and the second counts recursive calls.
930
 
931
     In the example above, the function `report' was called once from
932
     `main'.
933
 
934
`name'
935
     This is the name of the current function.  The index number is
936
     repeated after it.
937
 
938
     If the function is part of a cycle of recursion, the cycle number
939
     is printed between the function's name and the index number (*note
940
     How Mutually Recursive Functions Are Described: Cycles.).  For
941
     example, if function `gnurr' is part of cycle number one, and has
942
     index number twelve, its primary line would be end like this:
943
 
944
          gnurr  [12]
945
 
946

947
File: gprof.info,  Node: Callers,  Next: Subroutines,  Prev: Primary,  Up: Call Graph
948
 
949
5.2.2 Lines for a Function's Callers
950
------------------------------------
951
 
952
A function's entry has a line for each function it was called by.
953
These lines' fields correspond to the fields of the primary line, but
954
their meanings are different because of the difference in context.
955
 
956
   For reference, we repeat two lines from the entry for the function
957
`report', the primary line and one caller-line preceding it, together
958
with the heading line that shows the names of the fields:
959
 
960
     index  % time    self  children called     name
961
     ...
962
                     0.00    0.05       1/1           main [2]
963
     [3]    100.0    0.00    0.05       1         report [3]
964
 
965
   Here are the meanings of the fields in the caller-line for `report'
966
called from `main':
967
 
968
`self'
969
     An estimate of the amount of time spent in `report' itself when it
970
     was called from `main'.
971
 
972
`children'
973
     An estimate of the amount of time spent in subroutines of `report'
974
     when `report' was called from `main'.
975
 
976
     The sum of the `self' and `children' fields is an estimate of the
977
     amount of time spent within calls to `report' from `main'.
978
 
979
`called'
980
     Two numbers: the number of times `report' was called from `main',
981
     followed by the total number of non-recursive calls to `report'
982
     from all its callers.
983
 
984
`name and index number'
985
     The name of the caller of `report' to which this line applies,
986
     followed by the caller's index number.
987
 
988
     Not all functions have entries in the call graph; some options to
989
     `gprof' request the omission of certain functions.  When a caller
990
     has no entry of its own, it still has caller-lines in the entries
991
     of the functions it calls.
992
 
993
     If the caller is part of a recursion cycle, the cycle number is
994
     printed between the name and the index number.
995
 
996
   If the identity of the callers of a function cannot be determined, a
997
dummy caller-line is printed which has `' as the "caller's
998
name" and all other fields blank.  This can happen for signal handlers.
999
 
1000

1001
File: gprof.info,  Node: Subroutines,  Next: Cycles,  Prev: Callers,  Up: Call Graph
1002
 
1003
5.2.3 Lines for a Function's Subroutines
1004
----------------------------------------
1005
 
1006
A function's entry has a line for each of its subroutines--in other
1007
words, a line for each other function that it called.  These lines'
1008
fields correspond to the fields of the primary line, but their meanings
1009
are different because of the difference in context.
1010
 
1011
   For reference, we repeat two lines from the entry for the function
1012
`main', the primary line and a line for a subroutine, together with the
1013
heading line that shows the names of the fields:
1014
 
1015
     index  % time    self  children called     name
1016
     ...
1017
     [2]    100.0    0.00    0.05       1         main [2]
1018
                     0.00    0.05       1/1           report [3]
1019
 
1020
   Here are the meanings of the fields in the subroutine-line for `main'
1021
calling `report':
1022
 
1023
`self'
1024
     An estimate of the amount of time spent directly within `report'
1025
     when `report' was called from `main'.
1026
 
1027
`children'
1028
     An estimate of the amount of time spent in subroutines of `report'
1029
     when `report' was called from `main'.
1030
 
1031
     The sum of the `self' and `children' fields is an estimate of the
1032
     total time spent in calls to `report' from `main'.
1033
 
1034
`called'
1035
     Two numbers, the number of calls to `report' from `main' followed
1036
     by the total number of non-recursive calls to `report'.  This
1037
     ratio is used to determine how much of `report''s `self' and
1038
     `children' time gets credited to `main'.  *Note Estimating
1039
     `children' Times: Assumptions.
1040
 
1041
`name'
1042
     The name of the subroutine of `main' to which this line applies,
1043
     followed by the subroutine's index number.
1044
 
1045
     If the caller is part of a recursion cycle, the cycle number is
1046
     printed between the name and the index number.
1047
 
1048

1049
File: gprof.info,  Node: Cycles,  Prev: Subroutines,  Up: Call Graph
1050
 
1051
5.2.4 How Mutually Recursive Functions Are Described
1052
----------------------------------------------------
1053
 
1054
The graph may be complicated by the presence of "cycles of recursion"
1055
in the call graph.  A cycle exists if a function calls another function
1056
that (directly or indirectly) calls (or appears to call) the original
1057
function.  For example: if `a' calls `b', and `b' calls `a', then `a'
1058
and `b' form a cycle.
1059
 
1060
   Whenever there are call paths both ways between a pair of functions,
1061
they belong to the same cycle.  If `a' and `b' call each other and `b'
1062
and `c' call each other, all three make one cycle.  Note that even if
1063
`b' only calls `a' if it was not called from `a', `gprof' cannot
1064
determine this, so `a' and `b' are still considered a cycle.
1065
 
1066
   The cycles are numbered with consecutive integers.  When a function
1067
belongs to a cycle, each time the function name appears in the call
1068
graph it is followed by `'.
1069
 
1070
   The reason cycles matter is that they make the time values in the
1071
call graph paradoxical.  The "time spent in children" of `a' should
1072
include the time spent in its subroutine `b' and in `b''s
1073
subroutines--but one of `b''s subroutines is `a'!  How much of `a''s
1074
time should be included in the children of `a', when `a' is indirectly
1075
recursive?
1076
 
1077
   The way `gprof' resolves this paradox is by creating a single entry
1078
for the cycle as a whole.  The primary line of this entry describes the
1079
total time spent directly in the functions of the cycle.  The
1080
"subroutines" of the cycle are the individual functions of the cycle,
1081
and all other functions that were called directly by them.  The
1082
"callers" of the cycle are the functions, outside the cycle, that
1083
called functions in the cycle.
1084
 
1085
   Here is an example portion of a call graph which shows a cycle
1086
containing functions `a' and `b'.  The cycle was entered by a call to
1087
`a' from `main'; both `a' and `b' called `c'.
1088
 
1089
     index  % time    self  children called     name
1090
     ----------------------------------------
1091
                      1.77        0    1/1        main [2]
1092
     [3]     91.71    1.77        0    1+5     [3]
1093
                      1.02        0    3          b  [4]
1094
                      0.75        0    2          a  [5]
1095
     ----------------------------------------
1096
                                       3          a  [5]
1097
     [4]     52.85    1.02        0    0      b  [4]
1098
                                       2          a  [5]
1099
 
1100
     ----------------------------------------
1101
                      1.77        0    1/1        main [2]
1102
                                       2          b  [4]
1103
     [5]     38.86    0.75        0    1      a  [5]
1104
                                       3          b  [4]
1105
 
1106
     ----------------------------------------
1107
 
1108
(The entire call graph for this program contains in addition an entry
1109
for `main', which calls `a', and an entry for `c', with callers `a' and
1110
`b'.)
1111
 
1112
     index  % time    self  children called     name
1113
                                                  
1114
     [1]    100.00       0     1.93    0      start [1]
1115
                      0.16     1.77    1/1        main [2]
1116
     ----------------------------------------
1117
                      0.16     1.77    1/1        start [1]
1118
     [2]    100.00    0.16     1.77    1      main [2]
1119
                      1.77        0    1/1        a  [5]
1120
     ----------------------------------------
1121
                      1.77        0    1/1        main [2]
1122
     [3]     91.71    1.77        0    1+5     [3]
1123
                      1.02        0    3          b  [4]
1124
                      0.75        0    2          a  [5]
1125
 
1126
     ----------------------------------------
1127
                                       3          a  [5]
1128
     [4]     52.85    1.02        0    0      b  [4]
1129
                                       2          a  [5]
1130
 
1131
     ----------------------------------------
1132
                      1.77        0    1/1        main [2]
1133
                                       2          b  [4]
1134
     [5]     38.86    0.75        0    1      a  [5]
1135
                                       3          b  [4]
1136
 
1137
     ----------------------------------------
1138
 
1139
 
1140
     [6]      0.00       0        0    6      c [6]
1141
     ----------------------------------------
1142
 
1143
   The `self' field of the cycle's primary line is the total time spent
1144
in all the functions of the cycle.  It equals the sum of the `self'
1145
fields for the individual functions in the cycle, found in the entry in
1146
the subroutine lines for these functions.
1147
 
1148
   The `children' fields of the cycle's primary line and subroutine
1149
lines count only subroutines outside the cycle.  Even though `a' calls
1150
`b', the time spent in those calls to `b' is not counted in `a''s
1151
`children' time.  Thus, we do not encounter the problem of what to do
1152
when the time in those calls to `b' includes indirect recursive calls
1153
back to `a'.
1154
 
1155
   The `children' field of a caller-line in the cycle's entry estimates
1156
the amount of time spent _in the whole cycle_, and its other
1157
subroutines, on the times when that caller called a function in the
1158
cycle.
1159
 
1160
   The `called' field in the primary line for the cycle has two numbers:
1161
first, the number of times functions in the cycle were called by
1162
functions outside the cycle; second, the number of times they were
1163
called by functions in the cycle (including times when a function in
1164
the cycle calls itself).  This is a generalization of the usual split
1165
into non-recursive and recursive calls.
1166
 
1167
   The `called' field of a subroutine-line for a cycle member in the
1168
cycle's entry says how many time that function was called from
1169
functions in the cycle.  The total of all these is the second number in
1170
the primary line's `called' field.
1171
 
1172
   In the individual entry for a function in a cycle, the other
1173
functions in the same cycle can appear as subroutines and as callers.
1174
These lines show how many times each function in the cycle called or
1175
was called from each other function in the cycle.  The `self' and
1176
`children' fields in these lines are blank because of the difficulty of
1177
defining meanings for them when recursion is going on.
1178
 
1179

1180
File: gprof.info,  Node: Line-by-line,  Next: Annotated Source,  Prev: Call Graph,  Up: Output
1181
 
1182
5.3 Line-by-line Profiling
1183
==========================
1184
 
1185
`gprof''s `-l' option causes the program to perform "line-by-line"
1186
profiling.  In this mode, histogram samples are assigned not to
1187
functions, but to individual lines of source code.  This only works
1188
with programs compiled with older versions of the `gcc' compiler.
1189
Newer versions of `gcc' use a different program - `gcov' - to display
1190
line-by-line profiling information.
1191
 
1192
   With the older versions of `gcc' the program usually has to be
1193
compiled with a `-g' option, in addition to `-pg', in order to generate
1194
debugging symbols for tracking source code lines.  Note, in much older
1195
versions of `gcc' the program had to be compiled with the `-a' command
1196
line option as well.
1197
 
1198
   The flat profile is the most useful output table in line-by-line
1199
mode.  The call graph isn't as useful as normal, since the current
1200
version of `gprof' does not propagate call graph arcs from source code
1201
lines to the enclosing function.  The call graph does, however, show
1202
each line of code that called each function, along with a count.
1203
 
1204
   Here is a section of `gprof''s output, without line-by-line
1205
profiling.  Note that `ct_init' accounted for four histogram hits, and
1206
13327 calls to `init_block'.
1207
 
1208
     Flat profile:
1209
 
1210
     Each sample counts as 0.01 seconds.
1211
       %   cumulative   self              self     total
1212
      time   seconds   seconds    calls  us/call  us/call  name
1213
      30.77      0.13     0.04     6335     6.31     6.31  ct_init
1214
 
1215
 
1216
                     Call graph (explanation follows)
1217
 
1218
 
1219
     granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
1220
 
1221
     index % time    self  children    called     name
1222
 
1223
                     0.00    0.00       1/13496       name_too_long
1224
                     0.00    0.00      40/13496       deflate
1225
                     0.00    0.00     128/13496       deflate_fast
1226
                     0.00    0.00   13327/13496       ct_init
1227
     [7]      0.0    0.00    0.00   13496         init_block
1228
 
1229
   Now let's look at some of `gprof''s output from the same program run,
1230
this time with line-by-line profiling enabled.  Note that `ct_init''s
1231
four histogram hits are broken down into four lines of source code--one
1232
hit occurred on each of lines 349, 351, 382 and 385.  In the call graph,
1233
note how `ct_init''s 13327 calls to `init_block' are broken down into
1234
one call from line 396, 3071 calls from line 384, 3730 calls from line
1235
385, and 6525 calls from 387.
1236
 
1237
     Flat profile:
1238
 
1239
     Each sample counts as 0.01 seconds.
1240
       %   cumulative   self
1241
      time   seconds   seconds    calls  name
1242
       7.69      0.10     0.01           ct_init (trees.c:349)
1243
       7.69      0.11     0.01           ct_init (trees.c:351)
1244
       7.69      0.12     0.01           ct_init (trees.c:382)
1245
       7.69      0.13     0.01           ct_init (trees.c:385)
1246
 
1247
 
1248
                     Call graph (explanation follows)
1249
 
1250
 
1251
     granularity: each sample hit covers 4 byte(s) for 7.69% of 0.13 seconds
1252
 
1253
       % time    self  children    called     name
1254
 
1255
                 0.00    0.00       1/13496       name_too_long (gzip.c:1440)
1256
                 0.00    0.00       1/13496       deflate (deflate.c:763)
1257
                 0.00    0.00       1/13496       ct_init (trees.c:396)
1258
                 0.00    0.00       2/13496       deflate (deflate.c:727)
1259
                 0.00    0.00       4/13496       deflate (deflate.c:686)
1260
                 0.00    0.00       5/13496       deflate (deflate.c:675)
1261
                 0.00    0.00      12/13496       deflate (deflate.c:679)
1262
                 0.00    0.00      16/13496       deflate (deflate.c:730)
1263
                 0.00    0.00     128/13496       deflate_fast (deflate.c:654)
1264
                 0.00    0.00    3071/13496       ct_init (trees.c:384)
1265
                 0.00    0.00    3730/13496       ct_init (trees.c:385)
1266
                 0.00    0.00    6525/13496       ct_init (trees.c:387)
1267
     [6]  0.0    0.00    0.00   13496         init_block (trees.c:408)
1268
 
1269

1270
File: gprof.info,  Node: Annotated Source,  Prev: Line-by-line,  Up: Output
1271
 
1272
5.4 The Annotated Source Listing
1273
================================
1274
 
1275
`gprof''s `-A' option triggers an annotated source listing, which lists
1276
the program's source code, each function labeled with the number of
1277
times it was called.  You may also need to specify the `-I' option, if
1278
`gprof' can't find the source code files.
1279
 
1280
   With older versions of `gcc' compiling with `gcc ... -g -pg -a'
1281
augments your program with basic-block counting code, in addition to
1282
function counting code.  This enables `gprof' to determine how many
1283
times each line of code was executed.  With newer versions of `gcc'
1284
support for displaying basic-block counts is provided by the `gcov'
1285
program.
1286
 
1287
   For example, consider the following function, taken from gzip, with
1288
line numbers added:
1289
 
1290
      1 ulg updcrc(s, n)
1291
      2     uch *s;
1292
      3     unsigned n;
1293
      4 {
1294
      5     register ulg c;
1295
      6
1296
      7     static ulg crc = (ulg)0xffffffffL;
1297
      8
1298
      9     if (s == NULL) {
1299
     10         c = 0xffffffffL;
1300
     11     } else {
1301
     12         c = crc;
1302
     13         if (n) do {
1303
     14             c = crc_32_tab[...];
1304
     15         } while (--n);
1305
     16     }
1306
     17     crc = c;
1307
     18     return c ^ 0xffffffffL;
1308
     19 }
1309
 
1310
   `updcrc' has at least five basic-blocks.  One is the function
1311
itself.  The `if' statement on line 9 generates two more basic-blocks,
1312
one for each branch of the `if'.  A fourth basic-block results from the
1313
`if' on line 13, and the contents of the `do' loop form the fifth
1314
basic-block.  The compiler may also generate additional basic-blocks to
1315
handle various special cases.
1316
 
1317
   A program augmented for basic-block counting can be analyzed with
1318
`gprof -l -A'.  The `-x' option is also helpful, to ensure that each
1319
line of code is labeled at least once.  Here is `updcrc''s annotated
1320
source listing for a sample `gzip' run:
1321
 
1322
                     ulg updcrc(s, n)
1323
                         uch *s;
1324
                         unsigned n;
1325
                 2 ->{
1326
                         register ulg c;
1327
 
1328
                         static ulg crc = (ulg)0xffffffffL;
1329
 
1330
                 2 ->    if (s == NULL) {
1331
                 1 ->        c = 0xffffffffL;
1332
                 1 ->    } else {
1333
                 1 ->        c = crc;
1334
                 1 ->        if (n) do {
1335
             26312 ->            c = crc_32_tab[...];
1336
     26312,1,26311 ->        } while (--n);
1337
                         }
1338
                 2 ->    crc = c;
1339
                 2 ->    return c ^ 0xffffffffL;
1340
                 2 ->}
1341
 
1342
   In this example, the function was called twice, passing once through
1343
each branch of the `if' statement.  The body of the `do' loop was
1344
executed a total of 26312 times.  Note how the `while' statement is
1345
annotated.  It began execution 26312 times, once for each iteration
1346
through the loop.  One of those times (the last time) it exited, while
1347
it branched back to the beginning of the loop 26311 times.
1348
 
1349

1350
File: gprof.info,  Node: Inaccuracy,  Next: How do I?,  Prev: Output,  Up: Top
1351
 
1352
6 Inaccuracy of `gprof' Output
1353
******************************
1354
 
1355
* Menu:
1356
 
1357
* Sampling Error::      Statistical margins of error
1358
* Assumptions::         Estimating children times
1359
 
1360

1361
File: gprof.info,  Node: Sampling Error,  Next: Assumptions,  Up: Inaccuracy
1362
 
1363
6.1 Statistical Sampling Error
1364
==============================
1365
 
1366
The run-time figures that `gprof' gives you are based on a sampling
1367
process, so they are subject to statistical inaccuracy.  If a function
1368
runs only a small amount of time, so that on the average the sampling
1369
process ought to catch that function in the act only once, there is a
1370
pretty good chance it will actually find that function zero times, or
1371
twice.
1372
 
1373
   By contrast, the number-of-calls and basic-block figures are derived
1374
by counting, not sampling.  They are completely accurate and will not
1375
vary from run to run if your program is deterministic.
1376
 
1377
   The "sampling period" that is printed at the beginning of the flat
1378
profile says how often samples are taken.  The rule of thumb is that a
1379
run-time figure is accurate if it is considerably bigger than the
1380
sampling period.
1381
 
1382
   The actual amount of error can be predicted.  For N samples, the
1383
_expected_ error is the square-root of N.  For example, if the sampling
1384
period is 0.01 seconds and `foo''s run-time is 1 second, N is 100
1385
samples (1 second/0.01 seconds), sqrt(N) is 10 samples, so the expected
1386
error in `foo''s run-time is 0.1 seconds (10*0.01 seconds), or ten
1387
percent of the observed value.  Again, if the sampling period is 0.01
1388
seconds and `bar''s run-time is 100 seconds, N is 10000 samples,
1389
sqrt(N) is 100 samples, so the expected error in `bar''s run-time is 1
1390
second, or one percent of the observed value.  It is likely to vary
1391
this much _on the average_ from one profiling run to the next.
1392
(_Sometimes_ it will vary more.)
1393
 
1394
   This does not mean that a small run-time figure is devoid of
1395
information.  If the program's _total_ run-time is large, a small
1396
run-time for one function does tell you that that function used an
1397
insignificant fraction of the whole program's time.  Usually this means
1398
it is not worth optimizing.
1399
 
1400
   One way to get more accuracy is to give your program more (but
1401
similar) input data so it will take longer.  Another way is to combine
1402
the data from several runs, using the `-s' option of `gprof'.  Here is
1403
how:
1404
 
1405
  1. Run your program once.
1406
 
1407
  2. Issue the command `mv gmon.out gmon.sum'.
1408
 
1409
  3. Run your program again, the same as before.
1410
 
1411
  4. Merge the new data in `gmon.out' into `gmon.sum' with this command:
1412
 
1413
          gprof -s EXECUTABLE-FILE gmon.out gmon.sum
1414
 
1415
  5. Repeat the last two steps as often as you wish.
1416
 
1417
  6. Analyze the cumulative data using this command:
1418
 
1419
          gprof EXECUTABLE-FILE gmon.sum > OUTPUT-FILE
1420
 
1421

1422
File: gprof.info,  Node: Assumptions,  Prev: Sampling Error,  Up: Inaccuracy
1423
 
1424
6.2 Estimating `children' Times
1425
===============================
1426
 
1427
Some of the figures in the call graph are estimates--for example, the
1428
`children' time values and all the time figures in caller and
1429
subroutine lines.
1430
 
1431
   There is no direct information about these measurements in the
1432
profile data itself.  Instead, `gprof' estimates them by making an
1433
assumption about your program that might or might not be true.
1434
 
1435
   The assumption made is that the average time spent in each call to
1436
any function `foo' is not correlated with who called `foo'.  If `foo'
1437
used 5 seconds in all, and 2/5 of the calls to `foo' came from `a',
1438
then `foo' contributes 2 seconds to `a''s `children' time, by
1439
assumption.
1440
 
1441
   This assumption is usually true enough, but for some programs it is
1442
far from true.  Suppose that `foo' returns very quickly when its
1443
argument is zero; suppose that `a' always passes zero as an argument,
1444
while other callers of `foo' pass other arguments.  In this program,
1445
all the time spent in `foo' is in the calls from callers other than `a'.
1446
But `gprof' has no way of knowing this; it will blindly and incorrectly
1447
charge 2 seconds of time in `foo' to the children of `a'.
1448
 
1449
   We hope some day to put more complete data into `gmon.out', so that
1450
this assumption is no longer needed, if we can figure out how.  For the
1451
novice, the estimated figures are usually more useful than misleading.
1452
 
1453

1454
File: gprof.info,  Node: How do I?,  Next: Incompatibilities,  Prev: Inaccuracy,  Up: Top
1455
 
1456
7 Answers to Common Questions
1457
*****************************
1458
 
1459
How can I get more exact information about hot spots in my program?
1460
     Looking at the per-line call counts only tells part of the story.
1461
     Because `gprof' can only report call times and counts by function,
1462
     the best way to get finer-grained information on where the program
1463
     is spending its time is to re-factor large functions into sequences
1464
     of calls to smaller ones.  Beware however that this can introduce
1465
     artificial hot spots since compiling with `-pg' adds a significant
1466
     overhead to function calls.  An alternative solution is to use a
1467
     non-intrusive profiler, e.g. oprofile.
1468
 
1469
How do I find which lines in my program were executed the most times?
1470
     Use the `gcov' program.
1471
 
1472
How do I find which lines in my program called a particular function?
1473
     Use `gprof -l' and lookup the function in the call graph.  The
1474
     callers will be broken down by function and line number.
1475
 
1476
How do I analyze a program that runs for less than a second?
1477
     Try using a shell script like this one:
1478
 
1479
          for i in `seq 1 100`; do
1480
            fastprog
1481
            mv gmon.out gmon.out.$i
1482
          done
1483
 
1484
          gprof -s fastprog gmon.out.*
1485
 
1486
          gprof fastprog gmon.sum
1487
 
1488
     If your program is completely deterministic, all the call counts
1489
     will be simple multiples of 100 (i.e., a function called once in
1490
     each run will appear with a call count of 100).
1491
 
1492
 
1493

1494
File: gprof.info,  Node: Incompatibilities,  Next: Details,  Prev: How do I?,  Up: Top
1495
 
1496
8 Incompatibilities with Unix `gprof'
1497
*************************************
1498
 
1499
GNU `gprof' and Berkeley Unix `gprof' use the same data file
1500
`gmon.out', and provide essentially the same information.  But there
1501
are a few differences.
1502
 
1503
   * GNU `gprof' uses a new, generalized file format with support for
1504
     basic-block execution counts and non-realtime histograms.  A magic
1505
     cookie and version number allows `gprof' to easily identify new
1506
     style files.  Old BSD-style files can still be read.  *Note
1507
     Profiling Data File Format: File Format.
1508
 
1509
   * For a recursive function, Unix `gprof' lists the function as a
1510
     parent and as a child, with a `calls' field that lists the number
1511
     of recursive calls.  GNU `gprof' omits these lines and puts the
1512
     number of recursive calls in the primary line.
1513
 
1514
   * When a function is suppressed from the call graph with `-e', GNU
1515
     `gprof' still lists it as a subroutine of functions that call it.
1516
 
1517
   * GNU `gprof' accepts the `-k' with its argument in the form
1518
     `from/to', instead of `from to'.
1519
 
1520
   * In the annotated source listing, if there are multiple basic
1521
     blocks on the same line, GNU `gprof' prints all of their counts,
1522
     separated by commas.
1523
 
1524
   * The blurbs, field widths, and output formats are different.  GNU
1525
     `gprof' prints blurbs after the tables, so that you can see the
1526
     tables without skipping the blurbs.
1527
 
1528

1529
File: gprof.info,  Node: Details,  Next: GNU Free Documentation License,  Prev: Incompatibilities,  Up: Top
1530
 
1531
9 Details of Profiling
1532
**********************
1533
 
1534
* Menu:
1535
 
1536
* Implementation::      How a program collects profiling information
1537
* File Format::         Format of `gmon.out' files
1538
* Internals::           `gprof''s internal operation
1539
* Debugging::           Using `gprof''s `-d' option
1540
 
1541

1542
File: gprof.info,  Node: Implementation,  Next: File Format,  Up: Details
1543
 
1544
9.1 Implementation of Profiling
1545
===============================
1546
 
1547
Profiling works by changing how every function in your program is
1548
compiled so that when it is called, it will stash away some information
1549
about where it was called from.  From this, the profiler can figure out
1550
what function called it, and can count how many times it was called.
1551
This change is made by the compiler when your program is compiled with
1552
the `-pg' option, which causes every function to call `mcount' (or
1553
`_mcount', or `__mcount', depending on the OS and compiler) as one of
1554
its first operations.
1555
 
1556
   The `mcount' routine, included in the profiling library, is
1557
responsible for recording in an in-memory call graph table both its
1558
parent routine (the child) and its parent's parent.  This is typically
1559
done by examining the stack frame to find both the address of the
1560
child, and the return address in the original parent.  Since this is a
1561
very machine-dependent operation, `mcount' itself is typically a short
1562
assembly-language stub routine that extracts the required information,
1563
and then calls `__mcount_internal' (a normal C function) with two
1564
arguments--`frompc' and `selfpc'.  `__mcount_internal' is responsible
1565
for maintaining the in-memory call graph, which records `frompc',
1566
`selfpc', and the number of times each of these call arcs was traversed.
1567
 
1568
   GCC Version 2 provides a magical function
1569
(`__builtin_return_address'), which allows a generic `mcount' function
1570
to extract the required information from the stack frame.  However, on
1571
some architectures, most notably the SPARC, using this builtin can be
1572
very computationally expensive, and an assembly language version of
1573
`mcount' is used for performance reasons.
1574
 
1575
   Number-of-calls information for library routines is collected by
1576
using a special version of the C library.  The programs in it are the
1577
same as in the usual C library, but they were compiled with `-pg'.  If
1578
you link your program with `gcc ... -pg', it automatically uses the
1579
profiling version of the library.
1580
 
1581
   Profiling also involves watching your program as it runs, and
1582
keeping a histogram of where the program counter happens to be every
1583
now and then.  Typically the program counter is looked at around 100
1584
times per second of run time, but the exact frequency may vary from
1585
system to system.
1586
 
1587
   This is done is one of two ways.  Most UNIX-like operating systems
1588
provide a `profil()' system call, which registers a memory array with
1589
the kernel, along with a scale factor that determines how the program's
1590
address space maps into the array.  Typical scaling values cause every
1591
2 to 8 bytes of address space to map into a single array slot.  On
1592
every tick of the system clock (assuming the profiled program is
1593
running), the value of the program counter is examined and the
1594
corresponding slot in the memory array is incremented.  Since this is
1595
done in the kernel, which had to interrupt the process anyway to handle
1596
the clock interrupt, very little additional system overhead is required.
1597
 
1598
   However, some operating systems, most notably Linux 2.0 (and
1599
earlier), do not provide a `profil()' system call.  On such a system,
1600
arrangements are made for the kernel to periodically deliver a signal
1601
to the process (typically via `setitimer()'), which then performs the
1602
same operation of examining the program counter and incrementing a slot
1603
in the memory array.  Since this method requires a signal to be
1604
delivered to user space every time a sample is taken, it uses
1605
considerably more overhead than kernel-based profiling.  Also, due to
1606
the added delay required to deliver the signal, this method is less
1607
accurate as well.
1608
 
1609
   A special startup routine allocates memory for the histogram and
1610
either calls `profil()' or sets up a clock signal handler.  This
1611
routine (`monstartup') can be invoked in several ways.  On Linux
1612
systems, a special profiling startup file `gcrt0.o', which invokes
1613
`monstartup' before `main', is used instead of the default `crt0.o'.
1614
Use of this special startup file is one of the effects of using `gcc
1615
... -pg' to link.  On SPARC systems, no special startup files are used.
1616
Rather, the `mcount' routine, when it is invoked for the first time
1617
(typically when `main' is called), calls `monstartup'.
1618
 
1619
   If the compiler's `-a' option was used, basic-block counting is also
1620
enabled.  Each object file is then compiled with a static array of
1621
counts, initially zero.  In the executable code, every time a new
1622
basic-block begins (i.e., when an `if' statement appears), an extra
1623
instruction is inserted to increment the corresponding count in the
1624
array.  At compile time, a paired array was constructed that recorded
1625
the starting address of each basic-block.  Taken together, the two
1626
arrays record the starting address of every basic-block, along with the
1627
number of times it was executed.
1628
 
1629
   The profiling library also includes a function (`mcleanup') which is
1630
typically registered using `atexit()' to be called as the program
1631
exits, and is responsible for writing the file `gmon.out'.  Profiling
1632
is turned off, various headers are output, and the histogram is
1633
written, followed by the call-graph arcs and the basic-block counts.
1634
 
1635
   The output from `gprof' gives no indication of parts of your program
1636
that are limited by I/O or swapping bandwidth.  This is because samples
1637
of the program counter are taken at fixed intervals of the program's
1638
run time.  Therefore, the time measurements in `gprof' output say
1639
nothing about time that your program was not running.  For example, a
1640
part of the program that creates so much data that it cannot all fit in
1641
physical memory at once may run very slowly due to thrashing, but
1642
`gprof' will say it uses little time.  On the other hand, sampling by
1643
run time has the advantage that the amount of load due to other users
1644
won't directly affect the output you get.
1645
 
1646

1647
File: gprof.info,  Node: File Format,  Next: Internals,  Prev: Implementation,  Up: Details
1648
 
1649
9.2 Profiling Data File Format
1650
==============================
1651
 
1652
The old BSD-derived file format used for profile data does not contain a
1653
magic cookie that allows to check whether a data file really is a
1654
`gprof' file.  Furthermore, it does not provide a version number, thus
1655
rendering changes to the file format almost impossible.  GNU `gprof'
1656
uses a new file format that provides these features.  For backward
1657
compatibility, GNU `gprof' continues to support the old BSD-derived
1658
format, but not all features are supported with it.  For example,
1659
basic-block execution counts cannot be accommodated by the old file
1660
format.
1661
 
1662
   The new file format is defined in header file `gmon_out.h'.  It
1663
consists of a header containing the magic cookie and a version number,
1664
as well as some spare bytes available for future extensions.  All data
1665
in a profile data file is in the native format of the target for which
1666
the profile was collected.  GNU `gprof' adapts automatically to the
1667
byte-order in use.
1668
 
1669
   In the new file format, the header is followed by a sequence of
1670
records.  Currently, there are three different record types: histogram
1671
records, call-graph arc records, and basic-block execution count
1672
records.  Each file can contain any number of each record type.  When
1673
reading a file, GNU `gprof' will ensure records of the same type are
1674
compatible with each other and compute the union of all records.  For
1675
example, for basic-block execution counts, the union is simply the sum
1676
of all execution counts for each basic-block.
1677
 
1678
9.2.1 Histogram Records
1679
-----------------------
1680
 
1681
Histogram records consist of a header that is followed by an array of
1682
bins.  The header contains the text-segment range that the histogram
1683
spans, the size of the histogram in bytes (unlike in the old BSD
1684
format, this does not include the size of the header), the rate of the
1685
profiling clock, and the physical dimension that the bin counts
1686
represent after being scaled by the profiling clock rate.  The physical
1687
dimension is specified in two parts: a long name of up to 15 characters
1688
and a single character abbreviation.  For example, a histogram
1689
representing real-time would specify the long name as "seconds" and the
1690
abbreviation as "s".  This feature is useful for architectures that
1691
support performance monitor hardware (which, fortunately, is becoming
1692
increasingly common).  For example, under DEC OSF/1, the "uprofile"
1693
command can be used to produce a histogram of, say, instruction cache
1694
misses.  In this case, the dimension in the histogram header could be
1695
set to "i-cache misses" and the abbreviation could be set to "1"
1696
(because it is simply a count, not a physical dimension).  Also, the
1697
profiling rate would have to be set to 1 in this case.
1698
 
1699
   Histogram bins are 16-bit numbers and each bin represent an equal
1700
amount of text-space.  For example, if the text-segment is one thousand
1701
bytes long and if there are ten bins in the histogram, each bin
1702
represents one hundred bytes.
1703
 
1704
9.2.2 Call-Graph Records
1705
------------------------
1706
 
1707
Call-graph records have a format that is identical to the one used in
1708
the BSD-derived file format.  It consists of an arc in the call graph
1709
and a count indicating the number of times the arc was traversed during
1710
program execution.  Arcs are specified by a pair of addresses: the
1711
first must be within caller's function and the second must be within
1712
the callee's function.  When performing profiling at the function
1713
level, these addresses can point anywhere within the respective
1714
function.  However, when profiling at the line-level, it is better if
1715
the addresses are as close to the call-site/entry-point as possible.
1716
This will ensure that the line-level call-graph is able to identify
1717
exactly which line of source code performed calls to a function.
1718
 
1719
9.2.3 Basic-Block Execution Count Records
1720
-----------------------------------------
1721
 
1722
Basic-block execution count records consist of a header followed by a
1723
sequence of address/count pairs.  The header simply specifies the
1724
length of the sequence.  In an address/count pair, the address
1725
identifies a basic-block and the count specifies the number of times
1726
that basic-block was executed.  Any address within the basic-address can
1727
be used.
1728
 
1729

1730
File: gprof.info,  Node: Internals,  Next: Debugging,  Prev: File Format,  Up: Details
1731
 
1732
9.3 `gprof''s Internal Operation
1733
================================
1734
 
1735
Like most programs, `gprof' begins by processing its options.  During
1736
this stage, it may building its symspec list (`sym_ids.c:sym_id_add'),
1737
if options are specified which use symspecs.  `gprof' maintains a
1738
single linked list of symspecs, which will eventually get turned into
1739
12 symbol tables, organized into six include/exclude pairs--one pair
1740
each for the flat profile (INCL_FLAT/EXCL_FLAT), the call graph arcs
1741
(INCL_ARCS/EXCL_ARCS), printing in the call graph
1742
(INCL_GRAPH/EXCL_GRAPH), timing propagation in the call graph
1743
(INCL_TIME/EXCL_TIME), the annotated source listing
1744
(INCL_ANNO/EXCL_ANNO), and the execution count listing
1745
(INCL_EXEC/EXCL_EXEC).
1746
 
1747
   After option processing, `gprof' finishes building the symspec list
1748
by adding all the symspecs in `default_excluded_list' to the exclude
1749
lists EXCL_TIME and EXCL_GRAPH, and if line-by-line profiling is
1750
specified, EXCL_FLAT as well.  These default excludes are not added to
1751
EXCL_ANNO, EXCL_ARCS, and EXCL_EXEC.
1752
 
1753
   Next, the BFD library is called to open the object file, verify that
1754
it is an object file, and read its symbol table (`core.c:core_init'),
1755
using `bfd_canonicalize_symtab' after mallocing an appropriately sized
1756
array of symbols.  At this point, function mappings are read (if the
1757
`--file-ordering' option has been specified), and the core text space
1758
is read into memory (if the `-c' option was given).
1759
 
1760
   `gprof''s own symbol table, an array of Sym structures, is now built.
1761
This is done in one of two ways, by one of two routines, depending on
1762
whether line-by-line profiling (`-l' option) has been enabled.  For
1763
normal profiling, the BFD canonical symbol table is scanned.  For
1764
line-by-line profiling, every text space address is examined, and a new
1765
symbol table entry gets created every time the line number changes.  In
1766
either case, two passes are made through the symbol table--one to count
1767
the size of the symbol table required, and the other to actually read
1768
the symbols.  In between the two passes, a single array of type `Sym'
1769
is created of the appropriate length.  Finally,
1770
`symtab.c:symtab_finalize' is called to sort the symbol table and
1771
remove duplicate entries (entries with the same memory address).
1772
 
1773
   The symbol table must be a contiguous array for two reasons.  First,
1774
the `qsort' library function (which sorts an array) will be used to
1775
sort the symbol table.  Also, the symbol lookup routine
1776
(`symtab.c:sym_lookup'), which finds symbols based on memory address,
1777
uses a binary search algorithm which requires the symbol table to be a
1778
sorted array.  Function symbols are indicated with an `is_func' flag.
1779
Line number symbols have no special flags set.  Additionally, a symbol
1780
can have an `is_static' flag to indicate that it is a local symbol.
1781
 
1782
   With the symbol table read, the symspecs can now be translated into
1783
Syms (`sym_ids.c:sym_id_parse').  Remember that a single symspec can
1784
match multiple symbols.  An array of symbol tables (`syms') is created,
1785
each entry of which is a symbol table of Syms to be included or
1786
excluded from a particular listing.  The master symbol table and the
1787
symspecs are examined by nested loops, and every symbol that matches a
1788
symspec is inserted into the appropriate syms table.  This is done
1789
twice, once to count the size of each required symbol table, and again
1790
to build the tables, which have been malloced between passes.  From now
1791
on, to determine whether a symbol is on an include or exclude symspec
1792
list, `gprof' simply uses its standard symbol lookup routine on the
1793
appropriate table in the `syms' array.
1794
 
1795
   Now the profile data file(s) themselves are read
1796
(`gmon_io.c:gmon_out_read'), first by checking for a new-style
1797
`gmon.out' header, then assuming this is an old-style BSD `gmon.out' if
1798
the magic number test failed.
1799
 
1800
   New-style histogram records are read by `hist.c:hist_read_rec'.  For
1801
the first histogram record, allocate a memory array to hold all the
1802
bins, and read them in.  When multiple profile data files (or files
1803
with multiple histogram records) are read, the memory ranges of each
1804
pair of histogram records must be either equal, or non-overlapping.
1805
For each pair of histogram records, the resolution (memory region size
1806
divided by the number of bins) must be the same.  The time unit must be
1807
the same for all histogram records. If the above containts are met, all
1808
histograms for the same memory range are merged.
1809
 
1810
   As each call graph record is read (`call_graph.c:cg_read_rec'), the
1811
parent and child addresses are matched to symbol table entries, and a
1812
call graph arc is created by `cg_arcs.c:arc_add', unless the arc fails
1813
a symspec check against INCL_ARCS/EXCL_ARCS.  As each arc is added, a
1814
linked list is maintained of the parent's child arcs, and of the child's
1815
parent arcs.  Both the child's call count and the arc's call count are
1816
incremented by the record's call count.
1817
 
1818
   Basic-block records are read (`basic_blocks.c:bb_read_rec'), but
1819
only if line-by-line profiling has been selected.  Each basic-block
1820
address is matched to a corresponding line symbol in the symbol table,
1821
and an entry made in the symbol's bb_addr and bb_calls arrays.  Again,
1822
if multiple basic-block records are present for the same address, the
1823
call counts are cumulative.
1824
 
1825
   A gmon.sum file is dumped, if requested (`gmon_io.c:gmon_out_write').
1826
 
1827
   If histograms were present in the data files, assign them to symbols
1828
(`hist.c:hist_assign_samples') by iterating over all the sample bins
1829
and assigning them to symbols.  Since the symbol table is sorted in
1830
order of ascending memory addresses, we can simple follow along in the
1831
symbol table as we make our pass over the sample bins.  This step
1832
includes a symspec check against INCL_FLAT/EXCL_FLAT.  Depending on the
1833
histogram scale factor, a sample bin may span multiple symbols, in
1834
which case a fraction of the sample count is allocated to each symbol,
1835
proportional to the degree of overlap.  This effect is rare for normal
1836
profiling, but overlaps are more common during line-by-line profiling,
1837
and can cause each of two adjacent lines to be credited with half a
1838
hit, for example.
1839
 
1840
   If call graph data is present, `cg_arcs.c:cg_assemble' is called.
1841
First, if `-c' was specified, a machine-dependent routine (`find_call')
1842
scans through each symbol's machine code, looking for subroutine call
1843
instructions, and adding them to the call graph with a zero call count.
1844
A topological sort is performed by depth-first numbering all the
1845
symbols (`cg_dfn.c:cg_dfn'), so that children are always numbered less
1846
than their parents, then making a array of pointers into the symbol
1847
table and sorting it into numerical order, which is reverse topological
1848
order (children appear before parents).  Cycles are also detected at
1849
this point, all members of which are assigned the same topological
1850
number.  Two passes are now made through this sorted array of symbol
1851
pointers.  The first pass, from end to beginning (parents to children),
1852
computes the fraction of child time to propagate to each parent and a
1853
print flag.  The print flag reflects symspec handling of
1854
INCL_GRAPH/EXCL_GRAPH, with a parent's include or exclude (print or no
1855
print) property being propagated to its children, unless they
1856
themselves explicitly appear in INCL_GRAPH or EXCL_GRAPH.  A second
1857
pass, from beginning to end (children to parents) actually propagates
1858
the timings along the call graph, subject to a check against
1859
INCL_TIME/EXCL_TIME.  With the print flag, fractions, and timings now
1860
stored in the symbol structures, the topological sort array is now
1861
discarded, and a new array of pointers is assembled, this time sorted
1862
by propagated time.
1863
 
1864
   Finally, print the various outputs the user requested, which is now
1865
fairly straightforward.  The call graph (`cg_print.c:cg_print') and
1866
flat profile (`hist.c:hist_print') are regurgitations of values already
1867
computed.  The annotated source listing
1868
(`basic_blocks.c:print_annotated_source') uses basic-block information,
1869
if present, to label each line of code with call counts, otherwise only
1870
the function call counts are presented.
1871
 
1872
   The function ordering code is marginally well documented in the
1873
source code itself (`cg_print.c').  Basically, the functions with the
1874
most use and the most parents are placed first, followed by other
1875
functions with the most use, followed by lower use functions, followed
1876
by unused functions at the end.
1877
 
1878

1879
File: gprof.info,  Node: Debugging,  Prev: Internals,  Up: Details
1880
 
1881
9.4 Debugging `gprof'
1882
=====================
1883
 
1884
If `gprof' was compiled with debugging enabled, the `-d' option
1885
triggers debugging output (to stdout) which can be helpful in
1886
understanding its operation.  The debugging number specified is
1887
interpreted as a sum of the following options:
1888
 
1889
2 - Topological sort
1890
     Monitor depth-first numbering of symbols during call graph analysis
1891
 
1892
4 - Cycles
1893
     Shows symbols as they are identified as cycle heads
1894
 
1895
16 - Tallying
1896
     As the call graph arcs are read, show each arc and how the total
1897
     calls to each function are tallied
1898
 
1899
32 - Call graph arc sorting
1900
     Details sorting individual parents/children within each call graph
1901
     entry
1902
 
1903
64 - Reading histogram and call graph records
1904
     Shows address ranges of histograms as they are read, and each call
1905
     graph arc
1906
 
1907
128 - Symbol table
1908
     Reading, classifying, and sorting the symbol table from the object
1909
     file.  For line-by-line profiling (`-l' option), also shows line
1910
     numbers being assigned to memory addresses.
1911
 
1912
256 - Static call graph
1913
     Trace operation of `-c' option
1914
 
1915
512 - Symbol table and arc table lookups
1916
     Detail operation of lookup routines
1917
 
1918
1024 - Call graph propagation
1919
     Shows how function times are propagated along the call graph
1920
 
1921
2048 - Basic-blocks
1922
     Shows basic-block records as they are read from profile data (only
1923
     meaningful with `-l' option)
1924
 
1925
4096 - Symspecs
1926
     Shows symspec-to-symbol pattern matching operation
1927
 
1928
8192 - Annotate source
1929
     Tracks operation of `-A' option
1930
 
1931

1932
File: gprof.info,  Node: GNU Free Documentation License,  Prev: Details,  Up: Top
1933
 
1934
Appendix A GNU Free Documentation License
1935
*****************************************
1936
 
1937
                        Version 1.1, March 2000
1938
 
1939
     Copyright (C) 2000, 2003 Free Software Foundation, Inc.
1940
     51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
1941
 
1942
     Everyone is permitted to copy and distribute verbatim copies
1943
     of this license document, but changing it is not allowed.
1944
 
1945
 
1946
  0. PREAMBLE
1947
 
1948
     The purpose of this License is to make a manual, textbook, or other
1949
     written document "free" in the sense of freedom: to assure everyone
1950
     the effective freedom to copy and redistribute it, with or without
1951
     modifying it, either commercially or noncommercially.  Secondarily,
1952
     this License preserves for the author and publisher a way to get
1953
     credit for their work, while not being considered responsible for
1954
     modifications made by others.
1955
 
1956
     This License is a kind of "copyleft", which means that derivative
1957
     works of the document must themselves be free in the same sense.
1958
     It complements the GNU General Public License, which is a copyleft
1959
     license designed for free software.
1960
 
1961
     We have designed this License in order to use it for manuals for
1962
     free software, because free software needs free documentation: a
1963
     free program should come with manuals providing the same freedoms
1964
     that the software does.  But this License is not limited to
1965
     software manuals; it can be used for any textual work, regardless
1966
     of subject matter or whether it is published as a printed book.
1967
     We recommend this License principally for works whose purpose is
1968
     instruction or reference.
1969
 
1970
 
1971
  1. APPLICABILITY AND DEFINITIONS
1972
 
1973
     This License applies to any manual or other work that contains a
1974
     notice placed by the copyright holder saying it can be distributed
1975
     under the terms of this License.  The "Document", below, refers to
1976
     any such manual or work.  Any member of the public is a licensee,
1977
     and is addressed as "you."
1978
 
1979
     A "Modified Version" of the Document means any work containing the
1980
     Document or a portion of it, either copied verbatim, or with
1981
     modifications and/or translated into another language.
1982
 
1983
     A "Secondary Section" is a named appendix or a front-matter
1984
     section of the Document that deals exclusively with the
1985
     relationship of the publishers or authors of the Document to the
1986
     Document's overall subject (or to related matters) and contains
1987
     nothing that could fall directly within that overall subject.
1988
     (For example, if the Document is in part a textbook of
1989
     mathematics, a Secondary Section may not explain any mathematics.)
1990
     The relationship could be a matter of historical connection with
1991
     the subject or with related matters, or of legal, commercial,
1992
     philosophical, ethical or political position regarding them.
1993
 
1994
     The "Invariant Sections" are certain Secondary Sections whose
1995
     titles are designated, as being those of Invariant Sections, in
1996
     the notice that says that the Document is released under this
1997
     License.
1998
 
1999
     The "Cover Texts" are certain short passages of text that are
2000
     listed, as Front-Cover Texts or Back-Cover Texts, in the notice
2001
     that says that the Document is released under this License.
2002
 
2003
     A "Transparent" copy of the Document means a machine-readable copy,
2004
     represented in a format whose specification is available to the
2005
     general public, whose contents can be viewed and edited directly
2006
     and straightforwardly with generic text editors or (for images
2007
     composed of pixels) generic paint programs or (for drawings) some
2008
     widely available drawing editor, and that is suitable for input to
2009
     text formatters or for automatic translation to a variety of
2010
     formats suitable for input to text formatters.  A copy made in an
2011
     otherwise Transparent file format whose markup has been designed
2012
     to thwart or discourage subsequent modification by readers is not
2013
     Transparent.  A copy that is not "Transparent" is called "Opaque."
2014
 
2015
     Examples of suitable formats for Transparent copies include plain
2016
     ASCII without markup, Texinfo input format, LaTeX input format,
2017
     SGML or XML using a publicly available DTD, and
2018
     standard-conforming simple HTML designed for human modification.
2019
     Opaque formats include PostScript, PDF, proprietary formats that
2020
     can be read and edited only by proprietary word processors, SGML
2021
     or XML for which the DTD and/or processing tools are not generally
2022
     available, and the machine-generated HTML produced by some word
2023
     processors for output purposes only.
2024
 
2025
     The "Title Page" means, for a printed book, the title page itself,
2026
     plus such following pages as are needed to hold, legibly, the
2027
     material this License requires to appear in the title page.  For
2028
     works in formats which do not have any title page as such, "Title
2029
     Page" means the text near the most prominent appearance of the
2030
     work's title, preceding the beginning of the body of the text.
2031
 
2032
  2. VERBATIM COPYING
2033
 
2034
     You may copy and distribute the Document in any medium, either
2035
     commercially or noncommercially, provided that this License, the
2036
     copyright notices, and the license notice saying this License
2037
     applies to the Document are reproduced in all copies, and that you
2038
     add no other conditions whatsoever to those of this License.  You
2039
     may not use technical measures to obstruct or control the reading
2040
     or further copying of the copies you make or distribute.  However,
2041
     you may accept compensation in exchange for copies.  If you
2042
     distribute a large enough number of copies you must also follow
2043
     the conditions in section 3.
2044
 
2045
     You may also lend copies, under the same conditions stated above,
2046
     and you may publicly display copies.
2047
 
2048
  3. COPYING IN QUANTITY
2049
 
2050
     If you publish printed copies of the Document numbering more than
2051
     100, and the Document's license notice requires Cover Texts, you
2052
     must enclose the copies in covers that carry, clearly and legibly,
2053
     all these Cover Texts: Front-Cover Texts on the front cover, and
2054
     Back-Cover Texts on the back cover.  Both covers must also clearly
2055
     and legibly identify you as the publisher of these copies.  The
2056
     front cover must present the full title with all words of the
2057
     title equally prominent and visible.  You may add other material
2058
     on the covers in addition.  Copying with changes limited to the
2059
     covers, as long as they preserve the title of the Document and
2060
     satisfy these conditions, can be treated as verbatim copying in
2061
     other respects.
2062
 
2063
     If the required texts for either cover are too voluminous to fit
2064
     legibly, you should put the first ones listed (as many as fit
2065
     reasonably) on the actual cover, and continue the rest onto
2066
     adjacent pages.
2067
 
2068
     If you publish or distribute Opaque copies of the Document
2069
     numbering more than 100, you must either include a
2070
     machine-readable Transparent copy along with each Opaque copy, or
2071
     state in or with each Opaque copy a publicly-accessible
2072
     computer-network location containing a complete Transparent copy
2073
     of the Document, free of added material, which the general
2074
     network-using public has access to download anonymously at no
2075
     charge using public-standard network protocols.  If you use the
2076
     latter option, you must take reasonably prudent steps, when you
2077
     begin distribution of Opaque copies in quantity, to ensure that
2078
     this Transparent copy will remain thus accessible at the stated
2079
     location until at least one year after the last time you
2080
     distribute an Opaque copy (directly or through your agents or
2081
     retailers) of that edition to the public.
2082
 
2083
     It is requested, but not required, that you contact the authors of
2084
     the Document well before redistributing any large number of
2085
     copies, to give them a chance to provide you with an updated
2086
     version of the Document.
2087
 
2088
  4. MODIFICATIONS
2089
 
2090
     You may copy and distribute a Modified Version of the Document
2091
     under the conditions of sections 2 and 3 above, provided that you
2092
     release the Modified Version under precisely this License, with
2093
     the Modified Version filling the role of the Document, thus
2094
     licensing distribution and modification of the Modified Version to
2095
     whoever possesses a copy of it.  In addition, you must do these
2096
     things in the Modified Version:
2097
 
2098
     A. Use in the Title Page (and on the covers, if any) a title
2099
     distinct    from that of the Document, and from those of previous
2100
     versions    (which should, if there were any, be listed in the
2101
     History section    of the Document).  You may use the same title
2102
     as a previous version    if the original publisher of that version
2103
     gives permission.
2104
     B. List on the Title Page, as authors, one or more persons or
2105
     entities    responsible for authorship of the modifications in the
2106
     Modified    Version, together with at least five of the principal
2107
     authors of the    Document (all of its principal authors, if it
2108
     has less than five).
2109
     C. State on the Title page the name of the publisher of the
2110
     Modified Version, as the publisher.
2111
     D. Preserve all the copyright notices of the Document.
2112
     E. Add an appropriate copyright notice for your modifications
2113
     adjacent to the other copyright notices.
2114
     F. Include, immediately after the copyright notices, a license
2115
     notice    giving the public permission to use the Modified Version
2116
     under the    terms of this License, in the form shown in the
2117
     Addendum below.
2118
     G. Preserve in that license notice the full lists of Invariant
2119
     Sections    and required Cover Texts given in the Document's
2120
     license notice.
2121
     H. Include an unaltered copy of this License.
2122
     I. Preserve the section entitled "History", and its title, and add
2123
     to    it an item stating at least the title, year, new authors, and
2124
       publisher of the Modified Version as given on the Title Page.
2125
     If    there is no section entitled "History" in the Document,
2126
     create one    stating the title, year, authors, and publisher of
2127
     the Document as    given on its Title Page, then add an item
2128
     describing the Modified    Version as stated in the previous
2129
     sentence.
2130
     J. Preserve the network location, if any, given in the Document for
2131
       public access to a Transparent copy of the Document, and
2132
     likewise    the network locations given in the Document for
2133
     previous versions    it was based on.  These may be placed in the
2134
     "History" section.     You may omit a network location for a work
2135
     that was published at    least four years before the Document
2136
     itself, or if the original    publisher of the version it refers
2137
     to gives permission.
2138
     K. In any section entitled "Acknowledgements" or "Dedications",
2139
     preserve the section's title, and preserve in the section all the
2140
      substance and tone of each of the contributor acknowledgements
2141
     and/or dedications given therein.
2142
     L. Preserve all the Invariant Sections of the Document,
2143
     unaltered in their text and in their titles.  Section numbers
2144
     or the equivalent are not considered part of the section titles.
2145
     M. Delete any section entitled "Endorsements."  Such a section
2146
     may not be included in the Modified Version.
2147
     N. Do not retitle any existing section as "Endorsements"    or to
2148
     conflict in title with any Invariant Section.
2149
 
2150
     If the Modified Version includes new front-matter sections or
2151
     appendices that qualify as Secondary Sections and contain no
2152
     material copied from the Document, you may at your option
2153
     designate some or all of these sections as invariant.  To do this,
2154
     add their titles to the list of Invariant Sections in the Modified
2155
     Version's license notice.  These titles must be distinct from any
2156
     other section titles.
2157
 
2158
     You may add a section entitled "Endorsements", provided it contains
2159
     nothing but endorsements of your Modified Version by various
2160
     parties-for example, statements of peer review or that the text has
2161
     been approved by an organization as the authoritative definition
2162
     of a standard.
2163
 
2164
     You may add a passage of up to five words as a Front-Cover Text,
2165
     and a passage of up to 25 words as a Back-Cover Text, to the end
2166
     of the list of Cover Texts in the Modified Version.  Only one
2167
     passage of Front-Cover Text and one of Back-Cover Text may be
2168
     added by (or through arrangements made by) any one entity.  If the
2169
     Document already includes a cover text for the same cover,
2170
     previously added by you or by arrangement made by the same entity
2171
     you are acting on behalf of, you may not add another; but you may
2172
     replace the old one, on explicit permission from the previous
2173
     publisher that added the old one.
2174
 
2175
     The author(s) and publisher(s) of the Document do not by this
2176
     License give permission to use their names for publicity for or to
2177
     assert or imply endorsement of any Modified Version.
2178
 
2179
  5. COMBINING DOCUMENTS
2180
 
2181
     You may combine the Document with other documents released under
2182
     this License, under the terms defined in section 4 above for
2183
     modified versions, provided that you include in the combination
2184
     all of the Invariant Sections of all of the original documents,
2185
     unmodified, and list them all as Invariant Sections of your
2186
     combined work in its license notice.
2187
 
2188
     The combined work need only contain one copy of this License, and
2189
     multiple identical Invariant Sections may be replaced with a single
2190
     copy.  If there are multiple Invariant Sections with the same name
2191
     but different contents, make the title of each such section unique
2192
     by adding at the end of it, in parentheses, the name of the
2193
     original author or publisher of that section if known, or else a
2194
     unique number.  Make the same adjustment to the section titles in
2195
     the list of Invariant Sections in the license notice of the
2196
     combined work.
2197
 
2198
     In the combination, you must combine any sections entitled
2199
     "History" in the various original documents, forming one section
2200
     entitled "History"; likewise combine any sections entitled
2201
     "Acknowledgements", and any sections entitled "Dedications."  You
2202
     must delete all sections entitled "Endorsements."
2203
 
2204
  6. COLLECTIONS OF DOCUMENTS
2205
 
2206
     You may make a collection consisting of the Document and other
2207
     documents released under this License, and replace the individual
2208
     copies of this License in the various documents with a single copy
2209
     that is included in the collection, provided that you follow the
2210
     rules of this License for verbatim copying of each of the
2211
     documents in all other respects.
2212
 
2213
     You may extract a single document from such a collection, and
2214
     distribute it individually under this License, provided you insert
2215
     a copy of this License into the extracted document, and follow
2216
     this License in all other respects regarding verbatim copying of
2217
     that document.
2218
 
2219
  7. AGGREGATION WITH INDEPENDENT WORKS
2220
 
2221
     A compilation of the Document or its derivatives with other
2222
     separate and independent documents or works, in or on a volume of
2223
     a storage or distribution medium, does not as a whole count as a
2224
     Modified Version of the Document, provided no compilation
2225
     copyright is claimed for the compilation.  Such a compilation is
2226
     called an "aggregate", and this License does not apply to the
2227
     other self-contained works thus compiled with the Document, on
2228
     account of their being thus compiled, if they are not themselves
2229
     derivative works of the Document.
2230
 
2231
     If the Cover Text requirement of section 3 is applicable to these
2232
     copies of the Document, then if the Document is less than one
2233
     quarter of the entire aggregate, the Document's Cover Texts may be
2234
     placed on covers that surround only the Document within the
2235
     aggregate.  Otherwise they must appear on covers around the whole
2236
     aggregate.
2237
 
2238
  8. TRANSLATION
2239
 
2240
     Translation is considered a kind of modification, so you may
2241
     distribute translations of the Document under the terms of section
2242
     4.  Replacing Invariant Sections with translations requires special
2243
     permission from their copyright holders, but you may include
2244
     translations of some or all Invariant Sections in addition to the
2245
     original versions of these Invariant Sections.  You may include a
2246
     translation of this License provided that you also include the
2247
     original English version of this License.  In case of a
2248
     disagreement between the translation and the original English
2249
     version of this License, the original English version will prevail.
2250
 
2251
  9. TERMINATION
2252
 
2253
     You may not copy, modify, sublicense, or distribute the Document
2254
     except as expressly provided for under this License.  Any other
2255
     attempt to copy, modify, sublicense or distribute the Document is
2256
     void, and will automatically terminate your rights under this
2257
     License.  However, parties who have received copies, or rights,
2258
     from you under this License will not have their licenses
2259
     terminated so long as such parties remain in full compliance.
2260
 
2261
 10. FUTURE REVISIONS OF THIS LICENSE
2262
 
2263
     The Free Software Foundation may publish new, revised versions of
2264
     the GNU Free Documentation License from time to time.  Such new
2265
     versions will be similar in spirit to the present version, but may
2266
     differ in detail to address new problems or concerns.  See
2267
     http://www.gnu.org/copyleft/.
2268
 
2269
     Each version of the License is given a distinguishing version
2270
     number.  If the Document specifies that a particular numbered
2271
     version of this License "or any later version" applies to it, you
2272
     have the option of following the terms and conditions either of
2273
     that specified version or of any later version that has been
2274
     published (not as a draft) by the Free Software Foundation.  If
2275
     the Document does not specify a version number of this License,
2276
     you may choose any version ever published (not as a draft) by the
2277
     Free Software Foundation.
2278
 
2279
 
2280
ADDENDUM: How to use this License for your documents
2281
====================================================
2282
 
2283
To use this License in a document you have written, include a copy of
2284
the License in the document and put the following copyright and license
2285
notices just after the title page:
2286
 
2287
     Copyright (C)  YEAR  YOUR NAME.
2288
     Permission is granted to copy, distribute and/or modify this document
2289
     under the terms of the GNU Free Documentation License, Version 1.1
2290
     or any later version published by the Free Software Foundation;
2291
     with the Invariant Sections being LIST THEIR TITLES, with the
2292
     Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
2293
     A copy of the license is included in the section entitled "GNU
2294
     Free Documentation License."
2295
 
2296
   If you have no Invariant Sections, write "with no Invariant Sections"
2297
instead of saying which ones are invariant.  If you have no Front-Cover
2298
Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being
2299
LIST"; likewise for Back-Cover Texts.
2300
 
2301
   If your document contains nontrivial examples of program code, we
2302
recommend releasing these examples in parallel under your choice of
2303
free software license, such as the GNU General Public License, to
2304
permit their use in free software.
2305
 
2306
 
2307

2308
Tag Table:
2309
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2310
Node: Introduction2033
2311
Node: Compiling4525
2312
Node: Executing7996
2313
Node: Invoking10784
2314
Node: Output Options12199
2315
Node: Analysis Options19288
2316
Node: Miscellaneous Options22689
2317
Node: Deprecated Options23944
2318
Node: Symspecs26023
2319
Node: Output27849
2320
Node: Flat Profile28889
2321
Node: Call Graph33842
2322
Node: Primary37074
2323
Node: Callers39662
2324
Node: Subroutines41779
2325
Node: Cycles43620
2326
Node: Line-by-line50397
2327
Node: Annotated Source54470
2328
Node: Inaccuracy57469
2329
Node: Sampling Error57727
2330
Node: Assumptions60297
2331
Node: How do I?61767
2332
Node: Incompatibilities63321
2333
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2334
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2335
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2336
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2337
Node: Debugging83890
2338
Node: GNU Free Documentation License85491
2339

2340
End Tag Table

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