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138 .\" ======================================================================
139 .\"
140 .IX Title "GCOV 1"
141 .TH GCOV 1 "gcc-3.4.2" "2004-09-20" "GNU"
142 .UC
143 .SH "NAME"
144 gcov \- coverage testing tool
145 .SH "SYNOPSIS"
146 .IX Header "SYNOPSIS"
147 gcov [\fB\-v\fR|\fB\*(--version\fR] [\fB\-h\fR|\fB\*(--help\fR]
148 [\fB\-a\fR|\fB\*(--all-blocks\fR]
149 [\fB\-b\fR|\fB\*(--branch-probabilities\fR]
150 [\fB\-c\fR|\fB\*(--branch-counts\fR]
151 [\fB\-n\fR|\fB\*(--no-output\fR]
152 [\fB\-l\fR|\fB\*(--long-file-names\fR]
153 [\fB\-p\fR|\fB\*(--preserve-paths\fR]
154 [\fB\-f\fR|\fB\*(--function-summaries\fR]
155 [\fB\-o\fR|\fB\*(--object-directory\fR \fIdirectory|file\fR] \fIsourcefile\fR
156 [\fB\-u\fR|\fB\*(--unconditional-branches\fR]
157 .SH "DESCRIPTION"
158 .IX Header "DESCRIPTION"
159 \&\fBgcov\fR is a test coverage program. Use it in concert with \s-1GCC\s0
160 to analyze your programs to help create more efficient, faster running
161 code and to discover untested parts of your program. You can use
162 \&\fBgcov\fR as a profiling tool to help discover where your
163 optimization efforts will best affect your code. You can also use
164 \&\fBgcov\fR along with the other profiling tool, \fBgprof\fR, to
165 assess which parts of your code use the greatest amount of computing
166 time.
167 .PP
168 Profiling tools help you analyze your code's performance. Using a
169 profiler such as \fBgcov\fR or \fBgprof\fR, you can find out some
170 basic performance statistics, such as:
171 .Ip "\(bu" 4
172 how often each line of code executes
173 .Ip "\(bu" 4
174 what lines of code are actually executed
175 .Ip "\(bu" 4
176 how much computing time each section of code uses
177 .PP
178 Once you know these things about how your code works when compiled, you
179 can look at each module to see which modules should be optimized.
180 \&\fBgcov\fR helps you determine where to work on optimization.
181 .PP
182 Software developers also use coverage testing in concert with
183 testsuites, to make sure software is actually good enough for a release.
184 Testsuites can verify that a program works as expected; a coverage
185 program tests to see how much of the program is exercised by the
186 testsuite. Developers can then determine what kinds of test cases need
187 to be added to the testsuites to create both better testing and a better
188 final product.
189 .PP
190 You should compile your code without optimization if you plan to use
191 \&\fBgcov\fR because the optimization, by combining some lines of code
192 into one function, may not give you as much information as you need to
193 look for `hot spots' where the code is using a great deal of computer
194 time. Likewise, because \fBgcov\fR accumulates statistics by line (at
195 the lowest resolution), it works best with a programming style that
196 places only one statement on each line. If you use complicated macros
197 that expand to loops or to other control structures, the statistics are
198 less helpful\-\-\-they only report on the line where the macro call
199 appears. If your complex macros behave like functions, you can replace
200 them with inline functions to solve this problem.
201 .PP
202 \&\fBgcov\fR creates a logfile called \fI\fIsourcefile\fI.gcov\fR which
203 indicates how many times each line of a source file \fI\fIsourcefile\fI.c\fR
204 has executed. You can use these logfiles along with \fBgprof\fR to aid
205 in fine-tuning the performance of your programs. \fBgprof\fR gives
206 timing information you can use along with the information you get from
207 \&\fBgcov\fR.
208 .PP
209 \&\fBgcov\fR works only on code compiled with \s-1GCC\s0. It is not
210 compatible with any other profiling or test coverage mechanism.
211 .SH "OPTIONS"
212 .IX Header "OPTIONS"
213 .Ip "\fB\-h\fR" 4
214 .IX Item "-h"
215 .PD 0
216 .Ip "\fB\*(--help\fR" 4
217 .IX Item "help"
218 .PD
219 Display help about using \fBgcov\fR (on the standard output), and
220 exit without doing any further processing.
221 .Ip "\fB\-v\fR" 4
222 .IX Item "-v"
223 .PD 0
224 .Ip "\fB\*(--version\fR" 4
225 .IX Item "version"
226 .PD
227 Display the \fBgcov\fR version number (on the standard output),
228 and exit without doing any further processing.
229 .Ip "\fB\-a\fR" 4
230 .IX Item "-a"
231 .PD 0
232 .Ip "\fB\*(--all-blocks\fR" 4
233 .IX Item "all-blocks"
234 .PD
235 Write individual execution counts for every basic block. Normally gcov
236 outputs execution counts only for the main blocks of a line. With this
237 option you can determine if blocks within a single line are not being
238 executed.
239 .Ip "\fB\-b\fR" 4
240 .IX Item "-b"
241 .PD 0
242 .Ip "\fB\*(--branch-probabilities\fR" 4
243 .IX Item "branch-probabilities"
244 .PD
245 Write branch frequencies to the output file, and write branch summary
246 info to the standard output. This option allows you to see how often
247 each branch in your program was taken. Unconditional branches will not
248 be shown, unless the \fB\-u\fR option is given.
249 .Ip "\fB\-c\fR" 4
250 .IX Item "-c"
251 .PD 0
252 .Ip "\fB\*(--branch-counts\fR" 4
253 .IX Item "branch-counts"
254 .PD
255 Write branch frequencies as the number of branches taken, rather than
256 the percentage of branches taken.
257 .Ip "\fB\-n\fR" 4
258 .IX Item "-n"
259 .PD 0
260 .Ip "\fB\*(--no-output\fR" 4
261 .IX Item "no-output"
262 .PD
263 Do not create the \fBgcov\fR output file.
264 .Ip "\fB\-l\fR" 4
265 .IX Item "-l"
266 .PD 0
267 .Ip "\fB\*(--long-file-names\fR" 4
268 .IX Item "long-file-names"
269 .PD
270 Create long file names for included source files. For example, if the
271 header file \fIx.h\fR contains code, and was included in the file
272 \&\fIa.c\fR, then running \fBgcov\fR on the file \fIa.c\fR will produce
273 an output file called \fIa.c##x.h.gcov\fR instead of \fIx.h.gcov\fR.
274 This can be useful if \fIx.h\fR is included in multiple source
275 files. If you uses the \fB\-p\fR option, both the including and
276 included file names will be complete path names.
277 .Ip "\fB\-p\fR" 4
278 .IX Item "-p"
279 .PD 0
280 .Ip "\fB\*(--preserve-paths\fR" 4
281 .IX Item "preserve-paths"
282 .PD
283 Preserve complete path information in the names of generated
284 \&\fI.gcov\fR files. Without this option, just the filename component is
285 used. With this option, all directories are used, with '/' characters
286 translated to '#' characters, '.' directory components removed and '..'
287 components renamed to '^'. This is useful if sourcefiles are in several
288 different directories. It also affects the \fB\-l\fR option.
289 .Ip "\fB\-f\fR" 4
290 .IX Item "-f"
291 .PD 0
292 .Ip "\fB\*(--function-summaries\fR" 4
293 .IX Item "function-summaries"
294 .PD
295 Output summaries for each function in addition to the file level summary.
296 .Ip "\fB\-o\fR \fIdirectory|file\fR" 4
297 .IX Item "-o directory|file"
298 .PD 0
299 .Ip "\fB\*(--object-directory\fR \fIdirectory\fR" 4
300 .IX Item "object-directory directory"
301 .Ip "\fB\*(--object-file\fR \fIfile\fR" 4
302 .IX Item "object-file file"
303 .PD
304 Specify either the directory containing the gcov data files, or the
305 object path name. The \fI.gcno\fR, and
306 \&\fI.gcda\fR data files are searched for using this option. If a directory
307 is specified, the data files are in that directory and named after the
308 source file name, without its extension. If a file is specified here,
309 the data files are named after that file, without its extension. If this
310 option is not supplied, it defaults to the current directory.
311 .Ip "\fB\-u\fR" 4
312 .IX Item "-u"
313 .PD 0
314 .Ip "\fB\*(--unconditional-branches\fR" 4
315 .IX Item "unconditional-branches"
316 .PD
317 When branch counts are given, include those of unconditional branches.
318 Unconditional branches are normally not interesting.
319 .PP
320 \&\fBgcov\fR should be run with the current directory the same as that
321 when you invoked the compiler. Otherwise it will not be able to locate
322 the source files. \fBgcov\fR produces files called
323 \&\fI\fImangledname\fI.gcov\fR in the current directory. These contain
324 the coverage information of the source file they correspond to.
325 One \fI.gcov\fR file is produced for each source file containing code,
326 which was compiled to produce the data files. The \fImangledname\fR part
327 of the output file name is usually simply the source file name, but can
328 be something more complicated if the \fB\-l\fR or \fB\-p\fR options are
329 given. Refer to those options for details.
330 .PP
331 The \fI.gcov\fR files contain the ':' separated fields along with
332 program source code. The format is
333 .PP
334 .Vb 1
335 \& <execution_count>:<line_number>:<source line text>
336 .Ve
337 Additional block information may succeed each line, when requested by
338 command line option. The \fIexecution_count\fR is \fB-\fR for lines
339 containing no code and \fB#####\fR for lines which were never
340 executed. Some lines of information at the start have \fIline_number\fR
341 of zero.
342 .PP
343 When printing percentages, 0% and 100% are only printed when the values
344 are \fIexactly\fR 0% and 100% respectively. Other values which would
345 conventionally be rounded to 0% or 100% are instead printed as the
346 nearest non-boundary value.
347 .PP
348 When using \fBgcov\fR, you must first compile your program with two
349 special \s-1GCC\s0 options: \fB\-fprofile-arcs \-ftest-coverage\fR.
350 This tells the compiler to generate additional information needed by
351 gcov (basically a flow graph of the program) and also includes
352 additional code in the object files for generating the extra profiling
353 information needed by gcov. These additional files are placed in the
354 directory where the object file is located.
355 .PP
356 Running the program will cause profile output to be generated. For each
357 source file compiled with \fB\-fprofile-arcs\fR, an accompanying
358 \&\fI.gcda\fR file will be placed in the object file directory.
359 .PP
360 Running \fBgcov\fR with your program's source file names as arguments
361 will now produce a listing of the code along with frequency of execution
362 for each line. For example, if your program is called \fItmp.c\fR, this
363 is what you see when you use the basic \fBgcov\fR facility:
364 .PP
365 .Vb 5
366 \& $ gcc -fprofile-arcs -ftest-coverage tmp.c
367 \& $ a.out
368 \& $ gcov tmp.c
369 \& 90.00% of 10 source lines executed in file tmp.c
370 \& Creating tmp.c.gcov.
371 .Ve
372 The file \fItmp.c.gcov\fR contains output from \fBgcov\fR.
373 Here is a sample:
374 .PP
375 .Vb 23
376 \& -: 0:Source:tmp.c
377 \& -: 0:Graph:tmp.gcno
378 \& -: 0:Data:tmp.gcda
379 \& -: 0:Runs:1
380 \& -: 0:Programs:1
381 \& -: 1:#include <stdio.h>
382 \& -: 2:
383 \& -: 3:int main (void)
384 \& function main called 1 returned 1 blocks executed 75%
385 \& 1: 4:{
386 \& 1: 5: int i, total;
387 \& -: 6:
388 \& 1: 7: total = 0;
389 \& -: 8:
390 \& 11: 9: for (i = 0; i < 10; i++)
391 \& 10: 10: total += i;
392 \& -: 11:
393 \& 1: 12: if (total != 45)
394 \& #####: 13: printf ("Failure\en");
395 \& -: 14: else
396 \& 1: 15: printf ("Success\en");
397 \& 1: 16: return 0;
398 \& -: 17:}
399 .Ve
400 When you use the \fB\-a\fR option, you will get individual block
401 counts, and the output looks like this:
402 .PP
403 .Vb 30
404 \& -: 0:Source:tmp.c
405 \& -: 0:Graph:tmp.gcno
406 \& -: 0:Data:tmp.gcda
407 \& -: 0:Runs:1
408 \& -: 0:Programs:1
409 \& -: 1:#include <stdio.h>
410 \& -: 2:
411 \& -: 3:int main (void)
412 \& function main called 1 returned 1 blocks executed 75%
413 \& 1: 4:{
414 \& 1: 4-block 0
415 \& 1: 5: int i, total;
416 \& -: 6:
417 \& 1: 7: total = 0;
418 \& -: 8:
419 \& 11: 9: for (i = 0; i < 10; i++)
420 \& 11: 9-block 0
421 \& 10: 10: total += i;
422 \& 10: 10-block 0
423 \& -: 11:
424 \& 1: 12: if (total != 45)
425 \& 1: 12-block 0
426 \& #####: 13: printf ("Failure\en");
427 \& $$$$$: 13-block 0
428 \& -: 14: else
429 \& 1: 15: printf ("Success\en");
430 \& 1: 15-block 0
431 \& 1: 16: return 0;
432 \& 1: 16-block 0
433 \& -: 17:}
434 .Ve
435 In this mode, each basic block is only shown on one line \*(-- the last
436 line of the block. A multi-line block will only contribute to the
437 execution count of that last line, and other lines will not be shown
438 to contain code, unless previous blocks end on those lines.
439 The total execution count of a line is shown and subsequent lines show
440 the execution counts for individual blocks that end on that line. After each
441 block, the branch and call counts of the block will be shown, if the
442 \&\fB\-b\fR option is given.
443 .PP
444 Because of the way \s-1GCC\s0 instruments calls, a call count can be shown
445 after a line with no individual blocks.
446 As you can see, line 13 contains a basic block that was not executed.
447 .PP
448 When you use the \fB\-b\fR option, your output looks like this:
449 .PP
450 .Vb 6
451 \& $ gcov -b tmp.c
452 \& 90.00% of 10 source lines executed in file tmp.c
453 \& 80.00% of 5 branches executed in file tmp.c
454 \& 80.00% of 5 branches taken at least once in file tmp.c
455 \& 50.00% of 2 calls executed in file tmp.c
456 \& Creating tmp.c.gcov.
457 .Ve
458 Here is a sample of a resulting \fItmp.c.gcov\fR file:
459 .PP
460 .Vb 29
461 \& -: 0:Source:tmp.c
462 \& -: 0:Graph:tmp.gcno
463 \& -: 0:Data:tmp.gcda
464 \& -: 0:Runs:1
465 \& -: 0:Programs:1
466 \& -: 1:#include <stdio.h>
467 \& -: 2:
468 \& -: 3:int main (void)
469 \& function main called 1 returned 1 blocks executed 75%
470 \& 1: 4:{
471 \& 1: 5: int i, total;
472 \& -: 6:
473 \& 1: 7: total = 0;
474 \& -: 8:
475 \& 11: 9: for (i = 0; i < 10; i++)
476 \& branch 0 taken 91% (fallthrough)
477 \& branch 1 taken 9%
478 \& 10: 10: total += i;
479 \& -: 11:
480 \& 1: 12: if (total != 45)
481 \& branch 0 taken 0% (fallthrough)
482 \& branch 1 taken 100%
483 \& #####: 13: printf ("Failure\en");
484 \& call 0 never executed
485 \& -: 14: else
486 \& 1: 15: printf ("Success\en");
487 \& call 0 called 1 returned 100%
488 \& 1: 16: return 0;
489 \& -: 17:}
490 .Ve
491 For each basic block, a line is printed after the last line of the basic
492 block describing the branch or call that ends the basic block. There can
493 be multiple branches and calls listed for a single source line if there
494 are multiple basic blocks that end on that line. In this case, the
495 branches and calls are each given a number. There is no simple way to map
496 these branches and calls back to source constructs. In general, though,
497 the lowest numbered branch or call will correspond to the leftmost construct
498 on the source line.
499 .PP
500 For a branch, if it was executed at least once, then a percentage
501 indicating the number of times the branch was taken divided by the
502 number of times the branch was executed will be printed. Otherwise, the
503 message ``never executed'' is printed.
504 .PP
505 For a call, if it was executed at least once, then a percentage
506 indicating the number of times the call returned divided by the number
507 of times the call was executed will be printed. This will usually be
508 100%, but may be less for functions call \f(CW\*(C`exit\*(C'\fR or \f(CW\*(C`longjmp\*(C'\fR,
509 and thus may not return every time they are called.
510 .PP
511 The execution counts are cumulative. If the example program were
512 executed again without removing the \fI.gcda\fR file, the count for the
513 number of times each line in the source was executed would be added to
514 the results of the previous \fIrun\fR\|(s). This is potentially useful in
515 several ways. For example, it could be used to accumulate data over a
516 number of program runs as part of a test verification suite, or to
517 provide more accurate long-term information over a large number of
518 program runs.
519 .PP
520 The data in the \fI.gcda\fR files is saved immediately before the program
521 exits. For each source file compiled with \fB\-fprofile-arcs\fR, the
522 profiling code first attempts to read in an existing \fI.gcda\fR file; if
523 the file doesn't match the executable (differing number of basic block
524 counts) it will ignore the contents of the file. It then adds in the
525 new execution counts and finally writes the data to the file.
526 .Sh "Using \fBgcov\fP with \s-1GCC\s0 Optimization"
527 .IX Subsection "Using gcov with GCC Optimization"
528 If you plan to use \fBgcov\fR to help optimize your code, you must
529 first compile your program with two special \s-1GCC\s0 options:
530 \&\fB\-fprofile-arcs \-ftest-coverage\fR. Aside from that, you can use any
531 other \s-1GCC\s0 options; but if you want to prove that every single line
532 in your program was executed, you should not compile with optimization
533 at the same time. On some machines the optimizer can eliminate some
534 simple code lines by combining them with other lines. For example, code
535 like this:
536 .PP
537 .Vb 4
538 \& if (a != b)
539 \& c = 1;
540 \& else
541 \& c = 0;
542 .Ve
543 can be compiled into one instruction on some machines. In this case,
544 there is no way for \fBgcov\fR to calculate separate execution counts
545 for each line because there isn't separate code for each line. Hence
546 the \fBgcov\fR output looks like this if you compiled the program with
547 optimization:
548 .PP
549 .Vb 4
550 \& 100: 12:if (a != b)
551 \& 100: 13: c = 1;
552 \& 100: 14:else
553 \& 100: 15: c = 0;
554 .Ve
555 The output shows that this block of code, combined by optimization,
556 executed 100 times. In one sense this result is correct, because there
557 was only one instruction representing all four of these lines. However,
558 the output does not indicate how many times the result was 0 and how
559 many times the result was 1.
560 .PP
561 Inlineable functions can create unexpected line counts. Line counts are
562 shown for the source code of the inlineable function, but what is shown
563 depends on where the function is inlined, or if it is not inlined at all.
564 .PP
565 If the function is not inlined, the compiler must emit an out of line
566 copy of the function, in any object file that needs it. If
567 \&\fIfileA.o\fR and \fIfileB.o\fR both contain out of line bodies of a
568 particular inlineable function, they will also both contain coverage
569 counts for that function. When \fIfileA.o\fR and \fIfileB.o\fR are
570 linked together, the linker will, on many systems, select one of those
571 out of line bodies for all calls to that function, and remove or ignore
572 the other. Unfortunately, it will not remove the coverage counters for
573 the unused function body. Hence when instrumented, all but one use of
574 that function will show zero counts.
575 .PP
576 If the function is inlined in several places, the block structure in
577 each location might not be the same. For instance, a condition might
578 now be calculable at compile time in some instances. Because the
579 coverage of all the uses of the inline function will be shown for the
580 same source lines, the line counts themselves might seem inconsistent.
581 .SH "SEE ALSO"
582 .IX Header "SEE ALSO"
583 \&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf-funding\fR\|(7), \fIgcc\fR\|(1) and the Info entry for \fIgcc\fR.
584 .SH "COPYRIGHT"
585 .IX Header "COPYRIGHT"
586 Copyright (c) 1996, 1997, 1999, 2000, 2001, 2002, 2003
587 Free Software Foundation, Inc.
588 .PP
589 Permission is granted to copy, distribute and/or modify this document
590 under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
591 any later version published by the Free Software Foundation; with the
592 Invariant Sections being ``\s-1GNU\s0 General Public License'' and ``Funding
593 Free Software'', the Front-Cover texts being (a) (see below), and with
594 the Back-Cover Texts being (b) (see below). A copy of the license is
595 included in the \fIgfdl\fR\|(7) man page.
596 .PP
597 (a) The \s-1FSF\s0's Front-Cover Text is:
598 .PP
599 .Vb 1
600 \& A GNU Manual
601 .Ve
602 (b) The \s-1FSF\s0's Back-Cover Text is:
603 .PP
604 .Vb 3
605 \& You have freedom to copy and modify this GNU Manual, like GNU
606 \& software. Copies published by the Free Software Foundation raise
607 \& funds for GNU development.
608 .Ve