| blob | d95b20db6a5117c56d303419d113100a004576a6 |
1 .\" Automatically generated by Pod::Man 2.23 (Pod::Simple 3.14)
2 .\"
3 .\" Standard preamble:
4 .\" ========================================================================
5 .de Sp \" Vertical space (when we can't use .PP)
6 .if t .sp .5v
7 .if n .sp
8 ..
9 .de Vb \" Begin verbatim text
10 .ft CW
11 .nf
12 .ne \\$1
13 ..
14 .de Ve \" End verbatim text
15 .ft R
16 .fi
17 ..
18 .\" Set up some character translations and predefined strings. \*(-- will
19 .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
20 .\" double quote, and \*(R" will give a right double quote. \*(C+ will
21 .\" give a nicer C++. Capital omega is used to do unbreakable dashes and
22 .\" therefore won't be available. \*(C` and \*(C' expand to `' in nroff,
23 .\" nothing in troff, for use with C<>.
24 .tr \(*W-
25 .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
26 .ie n \{\
27 . ds -- \(*W-
28 . ds PI pi
29 . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
30 . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch
31 . ds L" ""
32 . ds R" ""
33 . ds C` ""
34 . ds C' ""
35 'br\}
36 .el\{\
37 . ds -- \|\(em\|
38 . ds PI \(*p
39 . ds L" ``
40 . ds R" ''
41 'br\}
42 .\"
43 .\" Escape single quotes in literal strings from groff's Unicode transform.
44 .ie \n(.g .ds Aq \(aq
45 .el .ds Aq '
46 .\"
47 .\" If the F register is turned on, we'll generate index entries on stderr for
48 .\" titles (.TH), headers (.SH), subsections (.SS), items (.Ip), and index
49 .\" entries marked with X<> in POD. Of course, you'll have to process the
50 .\" output yourself in some meaningful fashion.
51 .ie \nF \{\
52 . de IX
53 . tm Index:\\$1\t\\n%\t"\\$2"
54 ..
55 . nr % 0
56 . rr F
57 .\}
58 .el \{\
59 . de IX
60 ..
61 .\}
62 .\"
63 .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
64 .\" Fear. Run. Save yourself. No user-serviceable parts.
65 . \" fudge factors for nroff and troff
66 .if n \{\
67 . ds #H 0
68 . ds #V .8m
69 . ds #F .3m
70 . ds #[ \f1
71 . ds #] \fP
72 .\}
73 .if t \{\
74 . ds #H ((1u-(\\\\n(.fu%2u))*.13m)
75 . ds #V .6m
76 . ds #F 0
77 . ds #[ \&
78 . ds #] \&
79 .\}
80 . \" simple accents for nroff and troff
81 .if n \{\
82 . ds ' \&
83 . ds ` \&
84 . ds ^ \&
85 . ds , \&
86 . ds ~ ~
87 . ds /
88 .\}
89 .if t \{\
90 . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
91 . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
92 . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
93 . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
94 . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
95 . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
96 .\}
97 . \" troff and (daisy-wheel) nroff accents
98 .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
99 .ds 8 \h'\*(#H'\(*b\h'-\*(#H'
100 .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
101 .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
102 .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
103 .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
104 .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
105 .ds ae a\h'-(\w'a'u*4/10)'e
106 .ds Ae A\h'-(\w'A'u*4/10)'E
107 . \" corrections for vroff
108 .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
109 .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
110 . \" for low resolution devices (crt and lpr)
111 .if \n(.H>23 .if \n(.V>19 \
112 \{\
113 . ds : e
114 . ds 8 ss
115 . ds o a
116 . ds d- d\h'-1'\(ga
117 . ds D- D\h'-1'\(hy
118 . ds th \o'bp'
119 . ds Th \o'LP'
120 . ds ae ae
121 . ds Ae AE
122 .\}
123 .rm #[ #] #H #V #F C
124 .\" ========================================================================
125 .\"
126 .IX Title "GCOV 1"
127 .TH GCOV 1 "2011-06-23" "gcc-4.1.3" "GNU"
128 .\" For nroff, turn off justification. Always turn off hyphenation; it makes
129 .\" way too many mistakes in technical documents.
130 .if n .ad l
131 .nh
132 .SH "NAME"
133 gcov \- coverage testing tool
134 .SH "SYNOPSIS"
135 .IX Header "SYNOPSIS"
136 gcov [\fB\-v\fR|\fB\-\-version\fR] [\fB\-h\fR|\fB\-\-help\fR]
137 [\fB\-a\fR|\fB\-\-all\-blocks\fR]
138 [\fB\-b\fR|\fB\-\-branch\-probabilities\fR]
139 [\fB\-c\fR|\fB\-\-branch\-counts\fR]
140 [\fB\-n\fR|\fB\-\-no\-output\fR]
141 [\fB\-l\fR|\fB\-\-long\-file\-names\fR]
142 [\fB\-p\fR|\fB\-\-preserve\-paths\fR]
143 [\fB\-f\fR|\fB\-\-function\-summaries\fR]
144 [\fB\-o\fR|\fB\-\-object\-directory\fR \fIdirectory|file\fR]
145 [\fB\-u\fR|\fB\-\-unconditional\-branches\fR]
146 \fIsourcefile\fR
147 .SH "DESCRIPTION"
148 .IX Header "DESCRIPTION"
149 \&\fBgcov\fR is a test coverage program. Use it in concert with \s-1GCC\s0
150 to analyze your programs to help create more efficient, faster running
151 code and to discover untested parts of your program. You can use
152 \&\fBgcov\fR as a profiling tool to help discover where your
153 optimization efforts will best affect your code. You can also use
154 \&\fBgcov\fR along with the other profiling tool, \fBgprof\fR, to
155 assess which parts of your code use the greatest amount of computing
156 time.
157 .PP
158 Profiling tools help you analyze your code's performance. Using a
159 profiler such as \fBgcov\fR or \fBgprof\fR, you can find out some
160 basic performance statistics, such as:
161 .IP "\(bu" 4
162 how often each line of code executes
163 .IP "\(bu" 4
164 what lines of code are actually executed
165 .IP "\(bu" 4
166 how much computing time each section of code uses
167 .PP
168 Once you know these things about how your code works when compiled, you
169 can look at each module to see which modules should be optimized.
170 \&\fBgcov\fR helps you determine where to work on optimization.
171 .PP
172 Software developers also use coverage testing in concert with
173 testsuites, to make sure software is actually good enough for a release.
174 Testsuites can verify that a program works as expected; a coverage
175 program tests to see how much of the program is exercised by the
176 testsuite. Developers can then determine what kinds of test cases need
177 to be added to the testsuites to create both better testing and a better
178 final product.
179 .PP
180 You should compile your code without optimization if you plan to use
181 \&\fBgcov\fR because the optimization, by combining some lines of code
182 into one function, may not give you as much information as you need to
183 look for `hot spots' where the code is using a great deal of computer
184 time. Likewise, because \fBgcov\fR accumulates statistics by line (at
185 the lowest resolution), it works best with a programming style that
186 places only one statement on each line. If you use complicated macros
187 that expand to loops or to other control structures, the statistics are
188 less helpful\-\-\-they only report on the line where the macro call
189 appears. If your complex macros behave like functions, you can replace
190 them with inline functions to solve this problem.
191 .PP
192 \&\fBgcov\fR creates a logfile called \fI\fIsourcefile\fI.gcov\fR which
193 indicates how many times each line of a source file \fI\fIsourcefile\fI.c\fR
194 has executed. You can use these logfiles along with \fBgprof\fR to aid
195 in fine-tuning the performance of your programs. \fBgprof\fR gives
196 timing information you can use along with the information you get from
197 \&\fBgcov\fR.
198 .PP
199 \&\fBgcov\fR works only on code compiled with \s-1GCC\s0. It is not
200 compatible with any other profiling or test coverage mechanism.
201 .SH "OPTIONS"
202 .IX Header "OPTIONS"
203 .IP "\fB\-h\fR" 4
204 .IX Item "-h"
205 .PD 0
206 .IP "\fB\-\-help\fR" 4
207 .IX Item "--help"
208 .PD
209 Display help about using \fBgcov\fR (on the standard output), and
210 exit without doing any further processing.
211 .IP "\fB\-v\fR" 4
212 .IX Item "-v"
213 .PD 0
214 .IP "\fB\-\-version\fR" 4
215 .IX Item "--version"
216 .PD
217 Display the \fBgcov\fR version number (on the standard output),
218 and exit without doing any further processing.
219 .IP "\fB\-a\fR" 4
220 .IX Item "-a"
221 .PD 0
222 .IP "\fB\-\-all\-blocks\fR" 4
223 .IX Item "--all-blocks"
224 .PD
225 Write individual execution counts for every basic block. Normally gcov
226 outputs execution counts only for the main blocks of a line. With this
227 option you can determine if blocks within a single line are not being
228 executed.
229 .IP "\fB\-b\fR" 4
230 .IX Item "-b"
231 .PD 0
232 .IP "\fB\-\-branch\-probabilities\fR" 4
233 .IX Item "--branch-probabilities"
234 .PD
235 Write branch frequencies to the output file, and write branch summary
236 info to the standard output. This option allows you to see how often
237 each branch in your program was taken. Unconditional branches will not
238 be shown, unless the \fB\-u\fR option is given.
239 .IP "\fB\-c\fR" 4
240 .IX Item "-c"
241 .PD 0
242 .IP "\fB\-\-branch\-counts\fR" 4
243 .IX Item "--branch-counts"
244 .PD
245 Write branch frequencies as the number of branches taken, rather than
246 the percentage of branches taken.
247 .IP "\fB\-n\fR" 4
248 .IX Item "-n"
249 .PD 0
250 .IP "\fB\-\-no\-output\fR" 4
251 .IX Item "--no-output"
252 .PD
253 Do not create the \fBgcov\fR output file.
254 .IP "\fB\-l\fR" 4
255 .IX Item "-l"
256 .PD 0
257 .IP "\fB\-\-long\-file\-names\fR" 4
258 .IX Item "--long-file-names"
259 .PD
260 Create long file names for included source files. For example, if the
261 header file \fIx.h\fR contains code, and was included in the file
262 \&\fIa.c\fR, then running \fBgcov\fR on the file \fIa.c\fR will produce
263 an output file called \fIa.c##x.h.gcov\fR instead of \fIx.h.gcov\fR.
264 This can be useful if \fIx.h\fR is included in multiple source
265 files. If you use the \fB\-p\fR option, both the including and
266 included file names will be complete path names.
267 .IP "\fB\-p\fR" 4
268 .IX Item "-p"
269 .PD 0
270 .IP "\fB\-\-preserve\-paths\fR" 4
271 .IX Item "--preserve-paths"
272 .PD
273 Preserve complete path information in the names of generated
274 \&\fI.gcov\fR files. Without this option, just the filename component is
275 used. With this option, all directories are used, with \fB/\fR characters
276 translated to \fB#\fR characters, \fI.\fR directory components
277 removed and \fI..\fR
278 components renamed to \fB^\fR. This is useful if sourcefiles are in several
279 different directories. It also affects the \fB\-l\fR option.
280 .IP "\fB\-f\fR" 4
281 .IX Item "-f"
282 .PD 0
283 .IP "\fB\-\-function\-summaries\fR" 4
284 .IX Item "--function-summaries"
285 .PD
286 Output summaries for each function in addition to the file level summary.
287 .IP "\fB\-o\fR \fIdirectory|file\fR" 4
288 .IX Item "-o directory|file"
289 .PD 0
290 .IP "\fB\-\-object\-directory\fR \fIdirectory\fR" 4
291 .IX Item "--object-directory directory"
292 .IP "\fB\-\-object\-file\fR \fIfile\fR" 4
293 .IX Item "--object-file file"
294 .PD
295 Specify either the directory containing the gcov data files, or the
296 object path name. The \fI.gcno\fR, and
297 \&\fI.gcda\fR data files are searched for using this option. If a directory
298 is specified, the data files are in that directory and named after the
299 source file name, without its extension. If a file is specified here,
300 the data files are named after that file, without its extension. If this
301 option is not supplied, it defaults to the current directory.
302 .IP "\fB\-u\fR" 4
303 .IX Item "-u"
304 .PD 0
305 .IP "\fB\-\-unconditional\-branches\fR" 4
306 .IX Item "--unconditional-branches"
307 .PD
308 When branch probabilities are given, include those of unconditional branches.
309 Unconditional branches are normally not interesting.
310 .PP
311 \&\fBgcov\fR should be run with the current directory the same as that
312 when you invoked the compiler. Otherwise it will not be able to locate
313 the source files. \fBgcov\fR produces files called
314 \&\fI\fImangledname\fI.gcov\fR in the current directory. These contain
315 the coverage information of the source file they correspond to.
316 One \fI.gcov\fR file is produced for each source file containing code,
317 which was compiled to produce the data files. The \fImangledname\fR part
318 of the output file name is usually simply the source file name, but can
319 be something more complicated if the \fB\-l\fR or \fB\-p\fR options are
320 given. Refer to those options for details.
321 .PP
322 The \fI.gcov\fR files contain the \fB:\fR separated fields along with
323 program source code. The format is
324 .PP
325 .Vb 1
326 \& <execution_count>:<line_number>:<source line text>
327 .Ve
328 .PP
329 Additional block information may succeed each line, when requested by
330 command line option. The \fIexecution_count\fR is \fB\-\fR for lines
331 containing no code and \fB#####\fR for lines which were never executed.
332 Some lines of information at the start have \fIline_number\fR of zero.
333 .PP
334 The preamble lines are of the form
335 .PP
336 .Vb 1
337 \& \-:0:<tag>:<value>
338 .Ve
339 .PP
340 The ordering and number of these preamble lines will be augmented as
341 \&\fBgcov\fR development progresses \-\-\- do not rely on them remaining
342 unchanged. Use \fItag\fR to locate a particular preamble line.
343 .PP
344 The additional block information is of the form
345 .PP
346 .Vb 1
347 \& <tag> <information>
348 .Ve
349 .PP
350 The \fIinformation\fR is human readable, but designed to be simple
351 enough for machine parsing too.
352 .PP
353 When printing percentages, 0% and 100% are only printed when the values
354 are \fIexactly\fR 0% and 100% respectively. Other values which would
355 conventionally be rounded to 0% or 100% are instead printed as the
356 nearest non-boundary value.
357 .PP
358 When using \fBgcov\fR, you must first compile your program with two
359 special \s-1GCC\s0 options: \fB\-fprofile\-arcs \-ftest\-coverage\fR.
360 This tells the compiler to generate additional information needed by
361 gcov (basically a flow graph of the program) and also includes
362 additional code in the object files for generating the extra profiling
363 information needed by gcov. These additional files are placed in the
364 directory where the object file is located.
365 .PP
366 Running the program will cause profile output to be generated. For each
367 source file compiled with \fB\-fprofile\-arcs\fR, an accompanying
368 \&\fI.gcda\fR file will be placed in the object file directory.
369 .PP
370 Running \fBgcov\fR with your program's source file names as arguments
371 will now produce a listing of the code along with frequency of execution
372 for each line. For example, if your program is called \fItmp.c\fR, this
373 is what you see when you use the basic \fBgcov\fR facility:
374 .PP
375 .Vb 5
376 \& $ gcc \-fprofile\-arcs \-ftest\-coverage tmp.c
377 \& $ a.out
378 \& $ gcov tmp.c
379 \& 90.00% of 10 source lines executed in file tmp.c
380 \& Creating tmp.c.gcov.
381 .Ve
382 .PP
383 The file \fItmp.c.gcov\fR contains output from \fBgcov\fR.
384 Here is a sample:
385 .PP
386 .Vb 10
387 \& \-: 0:Source:tmp.c
388 \& \-: 0:Graph:tmp.gcno
389 \& \-: 0:Data:tmp.gcda
390 \& \-: 0:Runs:1
391 \& \-: 0:Programs:1
392 \& \-: 1:#include <stdio.h>
393 \& \-: 2:
394 \& \-: 3:int main (void)
395 \& 1: 4:{
396 \& 1: 5: int i, total;
397 \& \-: 6:
398 \& 1: 7: total = 0;
399 \& \-: 8:
400 \& 11: 9: for (i = 0; i < 10; i++)
401 \& 10: 10: total += i;
402 \& \-: 11:
403 \& 1: 12: if (total != 45)
404 \& #####: 13: printf ("Failure\en");
405 \& \-: 14: else
406 \& 1: 15: printf ("Success\en");
407 \& 1: 16: return 0;
408 \& \-: 17:}
409 .Ve
410 .PP
411 When you use the \fB\-a\fR option, you will get individual block
412 counts, and the output looks like this:
413 .PP
414 .Vb 10
415 \& \-: 0:Source:tmp.c
416 \& \-: 0:Graph:tmp.gcno
417 \& \-: 0:Data:tmp.gcda
418 \& \-: 0:Runs:1
419 \& \-: 0:Programs:1
420 \& \-: 1:#include <stdio.h>
421 \& \-: 2:
422 \& \-: 3:int main (void)
423 \& 1: 4:{
424 \& 1: 4\-block 0
425 \& 1: 5: int i, total;
426 \& \-: 6:
427 \& 1: 7: total = 0;
428 \& \-: 8:
429 \& 11: 9: for (i = 0; i < 10; i++)
430 \& 11: 9\-block 0
431 \& 10: 10: total += i;
432 \& 10: 10\-block 0
433 \& \-: 11:
434 \& 1: 12: if (total != 45)
435 \& 1: 12\-block 0
436 \& #####: 13: printf ("Failure\en");
437 \& $$$$$: 13\-block 0
438 \& \-: 14: else
439 \& 1: 15: printf ("Success\en");
440 \& 1: 15\-block 0
441 \& 1: 16: return 0;
442 \& 1: 16\-block 0
443 \& \-: 17:}
444 .Ve
445 .PP
446 In this mode, each basic block is only shown on one line \*(-- the last
447 line of the block. A multi-line block will only contribute to the
448 execution count of that last line, and other lines will not be shown
449 to contain code, unless previous blocks end on those lines.
450 The total execution count of a line is shown and subsequent lines show
451 the execution counts for individual blocks that end on that line. After each
452 block, the branch and call counts of the block will be shown, if the
453 \&\fB\-b\fR option is given.
454 .PP
455 Because of the way \s-1GCC\s0 instruments calls, a call count can be shown
456 after a line with no individual blocks.
457 As you can see, line 13 contains a basic block that was not executed.
458 .PP
459 When you use the \fB\-b\fR option, your output looks like this:
460 .PP
461 .Vb 6
462 \& $ gcov \-b tmp.c
463 \& 90.00% of 10 source lines executed in file tmp.c
464 \& 80.00% of 5 branches executed in file tmp.c
465 \& 80.00% of 5 branches taken at least once in file tmp.c
466 \& 50.00% of 2 calls executed in file tmp.c
467 \& Creating tmp.c.gcov.
468 .Ve
469 .PP
470 Here is a sample of a resulting \fItmp.c.gcov\fR file:
471 .PP
472 .Vb 10
473 \& \-: 0:Source:tmp.c
474 \& \-: 0:Graph:tmp.gcno
475 \& \-: 0:Data:tmp.gcda
476 \& \-: 0:Runs:1
477 \& \-: 0:Programs:1
478 \& \-: 1:#include <stdio.h>
479 \& \-: 2:
480 \& \-: 3:int main (void)
481 \& function main called 1 returned 1 blocks executed 75%
482 \& 1: 4:{
483 \& 1: 5: int i, total;
484 \& \-: 6:
485 \& 1: 7: total = 0;
486 \& \-: 8:
487 \& 11: 9: for (i = 0; i < 10; i++)
488 \& branch 0 taken 91% (fallthrough)
489 \& branch 1 taken 9%
490 \& 10: 10: total += i;
491 \& \-: 11:
492 \& 1: 12: if (total != 45)
493 \& branch 0 taken 0% (fallthrough)
494 \& branch 1 taken 100%
495 \& #####: 13: printf ("Failure\en");
496 \& call 0 never executed
497 \& \-: 14: else
498 \& 1: 15: printf ("Success\en");
499 \& call 0 called 1 returned 100%
500 \& 1: 16: return 0;
501 \& \-: 17:}
502 .Ve
503 .PP
504 For each function, a line is printed showing how many times the function
505 is called, how many times it returns and what percentage of the
506 function's blocks were executed.
507 .PP
508 For each basic block, a line is printed after the last line of the basic
509 block describing the branch or call that ends the basic block. There can
510 be multiple branches and calls listed for a single source line if there
511 are multiple basic blocks that end on that line. In this case, the
512 branches and calls are each given a number. There is no simple way to map
513 these branches and calls back to source constructs. In general, though,
514 the lowest numbered branch or call will correspond to the leftmost construct
515 on the source line.
516 .PP
517 For a branch, if it was executed at least once, then a percentage
518 indicating the number of times the branch was taken divided by the
519 number of times the branch was executed will be printed. Otherwise, the
520 message \*(L"never executed\*(R" is printed.
521 .PP
522 For a call, if it was executed at least once, then a percentage
523 indicating the number of times the call returned divided by the number
524 of times the call was executed will be printed. This will usually be
525 100%, but may be less for functions that call \f(CW\*(C`exit\*(C'\fR or \f(CW\*(C`longjmp\*(C'\fR,
526 and thus may not return every time they are called.
527 .PP
528 The execution counts are cumulative. If the example program were
529 executed again without removing the \fI.gcda\fR file, the count for the
530 number of times each line in the source was executed would be added to
531 the results of the previous run(s). This is potentially useful in
532 several ways. For example, it could be used to accumulate data over a
533 number of program runs as part of a test verification suite, or to
534 provide more accurate long-term information over a large number of
535 program runs.
536 .PP
537 The data in the \fI.gcda\fR files is saved immediately before the program
538 exits. For each source file compiled with \fB\-fprofile\-arcs\fR, the
539 profiling code first attempts to read in an existing \fI.gcda\fR file; if
540 the file doesn't match the executable (differing number of basic block
541 counts) it will ignore the contents of the file. It then adds in the
542 new execution counts and finally writes the data to the file.
543 .SS "Using \fBgcov\fP with \s-1GCC\s0 Optimization"
544 .IX Subsection "Using gcov with GCC Optimization"
545 If you plan to use \fBgcov\fR to help optimize your code, you must
546 first compile your program with two special \s-1GCC\s0 options:
547 \&\fB\-fprofile\-arcs \-ftest\-coverage\fR. Aside from that, you can use any
548 other \s-1GCC\s0 options; but if you want to prove that every single line
549 in your program was executed, you should not compile with optimization
550 at the same time. On some machines the optimizer can eliminate some
551 simple code lines by combining them with other lines. For example, code
552 like this:
553 .PP
554 .Vb 4
555 \& if (a != b)
556 \& c = 1;
557 \& else
558 \& c = 0;
559 .Ve
560 .PP
561 can be compiled into one instruction on some machines. In this case,
562 there is no way for \fBgcov\fR to calculate separate execution counts
563 for each line because there isn't separate code for each line. Hence
564 the \fBgcov\fR output looks like this if you compiled the program with
565 optimization:
566 .PP
567 .Vb 4
568 \& 100: 12:if (a != b)
569 \& 100: 13: c = 1;
570 \& 100: 14:else
571 \& 100: 15: c = 0;
572 .Ve
573 .PP
574 The output shows that this block of code, combined by optimization,
575 executed 100 times. In one sense this result is correct, because there
576 was only one instruction representing all four of these lines. However,
577 the output does not indicate how many times the result was 0 and how
578 many times the result was 1.
579 .PP
580 Inlineable functions can create unexpected line counts. Line counts are
581 shown for the source code of the inlineable function, but what is shown
582 depends on where the function is inlined, or if it is not inlined at all.
583 .PP
584 If the function is not inlined, the compiler must emit an out of line
585 copy of the function, in any object file that needs it. If
586 \&\fIfileA.o\fR and \fIfileB.o\fR both contain out of line bodies of a
587 particular inlineable function, they will also both contain coverage
588 counts for that function. When \fIfileA.o\fR and \fIfileB.o\fR are
589 linked together, the linker will, on many systems, select one of those
590 out of line bodies for all calls to that function, and remove or ignore
591 the other. Unfortunately, it will not remove the coverage counters for
592 the unused function body. Hence when instrumented, all but one use of
593 that function will show zero counts.
594 .PP
595 If the function is inlined in several places, the block structure in
596 each location might not be the same. For instance, a condition might
597 now be calculable at compile time in some instances. Because the
598 coverage of all the uses of the inline function will be shown for the
599 same source lines, the line counts themselves might seem inconsistent.
600 .SH "SEE ALSO"
601 .IX Header "SEE ALSO"
602 \&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7), \fIgcc\fR\|(1) and the Info entry for \fIgcc\fR.
603 .SH "COPYRIGHT"
604 .IX Header "COPYRIGHT"
605 Copyright (c) 1996, 1997, 1999, 2000, 2001, 2002, 2003, 2004, 2005
606 Free Software Foundation, Inc.
607 .PP
608 Permission is granted to copy, distribute and/or modify this document
609 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
610 any later version published by the Free Software Foundation; with the
611 Invariant Sections being \*(L"\s-1GNU\s0 General Public License\*(R" and \*(L"Funding
612 Free Software\*(R", the Front-Cover texts being (a) (see below), and with
613 the Back-Cover Texts being (b) (see below). A copy of the license is
614 included in the \fIgfdl\fR\|(7) man page.
615 .PP
616 (a) The \s-1FSF\s0's Front-Cover Text is:
617 .PP
618 .Vb 1
619 \& A GNU Manual
620 .Ve
621 .PP
622 (b) The \s-1FSF\s0's Back-Cover Text is:
623 .PP
624 .Vb 3
625 \& You have freedom to copy and modify this GNU Manual, like GNU
626 \& software. Copies published by the Free Software Foundation raise
627 \& funds for GNU development.
628 .Ve