Merge branch 'vendor/GCC44'
[dragonfly.git] / contrib / gcc-4.4 / gcc / doc / gcov.1
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123.rm #[ #] #H #V #F C
124.\" ========================================================================
125.\"
126.IX Title "GCOV 1"
4b1e227d 127.TH GCOV 1 "2010-10-01" "gcc-4.4.5" "GNU"
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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"
133gcov \- coverage testing tool
134.SH "SYNOPSIS"
135.IX Header "SYNOPSIS"
136gcov [\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] \fIsourcefiles\fR
145 [\fB\-u\fR|\fB\-\-unconditional\-branches\fR]
146.SH "DESCRIPTION"
147.IX Header "DESCRIPTION"
148\&\fBgcov\fR is a test coverage program. Use it in concert with \s-1GCC\s0
149to analyze your programs to help create more efficient, faster running
150code and to discover untested parts of your program. You can use
151\&\fBgcov\fR as a profiling tool to help discover where your
152optimization efforts will best affect your code. You can also use
153\&\fBgcov\fR along with the other profiling tool, \fBgprof\fR, to
154assess which parts of your code use the greatest amount of computing
155time.
156.PP
157Profiling tools help you analyze your code's performance. Using a
158profiler such as \fBgcov\fR or \fBgprof\fR, you can find out some
159basic performance statistics, such as:
160.IP "\(bu" 4
161how often each line of code executes
162.IP "\(bu" 4
163what lines of code are actually executed
164.IP "\(bu" 4
165how much computing time each section of code uses
166.PP
167Once you know these things about how your code works when compiled, you
168can look at each module to see which modules should be optimized.
169\&\fBgcov\fR helps you determine where to work on optimization.
170.PP
171Software developers also use coverage testing in concert with
172testsuites, to make sure software is actually good enough for a release.
173Testsuites can verify that a program works as expected; a coverage
174program tests to see how much of the program is exercised by the
175testsuite. Developers can then determine what kinds of test cases need
176to be added to the testsuites to create both better testing and a better
177final product.
178.PP
179You should compile your code without optimization if you plan to use
180\&\fBgcov\fR because the optimization, by combining some lines of code
181into one function, may not give you as much information as you need to
182look for `hot spots' where the code is using a great deal of computer
183time. Likewise, because \fBgcov\fR accumulates statistics by line (at
184the lowest resolution), it works best with a programming style that
185places only one statement on each line. If you use complicated macros
186that expand to loops or to other control structures, the statistics are
187less helpful\-\-\-they only report on the line where the macro call
188appears. If your complex macros behave like functions, you can replace
189them with inline functions to solve this problem.
190.PP
191\&\fBgcov\fR creates a logfile called \fI\fIsourcefile\fI.gcov\fR which
192indicates how many times each line of a source file \fI\fIsourcefile\fI.c\fR
193has executed. You can use these logfiles along with \fBgprof\fR to aid
194in fine-tuning the performance of your programs. \fBgprof\fR gives
195timing information you can use along with the information you get from
196\&\fBgcov\fR.
197.PP
198\&\fBgcov\fR works only on code compiled with \s-1GCC\s0. It is not
199compatible with any other profiling or test coverage mechanism.
200.SH "OPTIONS"
201.IX Header "OPTIONS"
202.IP "\fB\-h\fR" 4
203.IX Item "-h"
204.PD 0
205.IP "\fB\-\-help\fR" 4
206.IX Item "--help"
207.PD
208Display help about using \fBgcov\fR (on the standard output), and
209exit without doing any further processing.
210.IP "\fB\-v\fR" 4
211.IX Item "-v"
212.PD 0
213.IP "\fB\-\-version\fR" 4
214.IX Item "--version"
215.PD
216Display the \fBgcov\fR version number (on the standard output),
217and exit without doing any further processing.
218.IP "\fB\-a\fR" 4
219.IX Item "-a"
220.PD 0
221.IP "\fB\-\-all\-blocks\fR" 4
222.IX Item "--all-blocks"
223.PD
224Write individual execution counts for every basic block. Normally gcov
225outputs execution counts only for the main blocks of a line. With this
226option you can determine if blocks within a single line are not being
227executed.
228.IP "\fB\-b\fR" 4
229.IX Item "-b"
230.PD 0
231.IP "\fB\-\-branch\-probabilities\fR" 4
232.IX Item "--branch-probabilities"
233.PD
234Write branch frequencies to the output file, and write branch summary
235info to the standard output. This option allows you to see how often
236each branch in your program was taken. Unconditional branches will not
237be shown, unless the \fB\-u\fR option is given.
238.IP "\fB\-c\fR" 4
239.IX Item "-c"
240.PD 0
241.IP "\fB\-\-branch\-counts\fR" 4
242.IX Item "--branch-counts"
243.PD
244Write branch frequencies as the number of branches taken, rather than
245the percentage of branches taken.
246.IP "\fB\-n\fR" 4
247.IX Item "-n"
248.PD 0
249.IP "\fB\-\-no\-output\fR" 4
250.IX Item "--no-output"
251.PD
252Do not create the \fBgcov\fR output file.
253.IP "\fB\-l\fR" 4
254.IX Item "-l"
255.PD 0
256.IP "\fB\-\-long\-file\-names\fR" 4
257.IX Item "--long-file-names"
258.PD
259Create long file names for included source files. For example, if the
260header file \fIx.h\fR contains code, and was included in the file
261\&\fIa.c\fR, then running \fBgcov\fR on the file \fIa.c\fR will produce
262an output file called \fIa.c##x.h.gcov\fR instead of \fIx.h.gcov\fR.
263This can be useful if \fIx.h\fR is included in multiple source
264files. If you use the \fB\-p\fR option, both the including and
265included file names will be complete path names.
266.IP "\fB\-p\fR" 4
267.IX Item "-p"
268.PD 0
269.IP "\fB\-\-preserve\-paths\fR" 4
270.IX Item "--preserve-paths"
271.PD
272Preserve complete path information in the names of generated
273\&\fI.gcov\fR files. Without this option, just the filename component is
274used. With this option, all directories are used, with \fB/\fR characters
275translated to \fB#\fR characters, \fI.\fR directory components
276removed and \fI..\fR
277components renamed to \fB^\fR. This is useful if sourcefiles are in several
278different directories. It also affects the \fB\-l\fR option.
279.IP "\fB\-f\fR" 4
280.IX Item "-f"
281.PD 0
282.IP "\fB\-\-function\-summaries\fR" 4
283.IX Item "--function-summaries"
284.PD
285Output summaries for each function in addition to the file level summary.
286.IP "\fB\-o\fR \fIdirectory|file\fR" 4
287.IX Item "-o directory|file"
288.PD 0
289.IP "\fB\-\-object\-directory\fR \fIdirectory\fR" 4
290.IX Item "--object-directory directory"
291.IP "\fB\-\-object\-file\fR \fIfile\fR" 4
292.IX Item "--object-file file"
293.PD
294Specify either the directory containing the gcov data files, or the
295object path name. The \fI.gcno\fR, and
296\&\fI.gcda\fR data files are searched for using this option. If a directory
297is specified, the data files are in that directory and named after the
298source file name, without its extension. If a file is specified here,
299the data files are named after that file, without its extension. If this
300option is not supplied, it defaults to the current directory.
301.IP "\fB\-u\fR" 4
302.IX Item "-u"
303.PD 0
304.IP "\fB\-\-unconditional\-branches\fR" 4
305.IX Item "--unconditional-branches"
306.PD
307When branch probabilities are given, include those of unconditional branches.
308Unconditional branches are normally not interesting.
309.PP
310\&\fBgcov\fR should be run with the current directory the same as that
311when you invoked the compiler. Otherwise it will not be able to locate
312the source files. \fBgcov\fR produces files called
313\&\fI\fImangledname\fI.gcov\fR in the current directory. These contain
314the coverage information of the source file they correspond to.
315One \fI.gcov\fR file is produced for each source file containing code,
316which was compiled to produce the data files. The \fImangledname\fR part
317of the output file name is usually simply the source file name, but can
318be something more complicated if the \fB\-l\fR or \fB\-p\fR options are
319given. Refer to those options for details.
320.PP
321The \fI.gcov\fR files contain the \fB:\fR separated fields along with
322program source code. The format is
323.PP
324.Vb 1
325\& <execution_count>:<line_number>:<source line text>
326.Ve
327.PP
328Additional block information may succeed each line, when requested by
329command line option. The \fIexecution_count\fR is \fB\-\fR for lines
330containing no code and \fB#####\fR for lines which were never executed.
331Some lines of information at the start have \fIline_number\fR of zero.
332.PP
333The preamble lines are of the form
334.PP
335.Vb 1
336\& \-:0:<tag>:<value>
337.Ve
338.PP
339The ordering and number of these preamble lines will be augmented as
340\&\fBgcov\fR development progresses \-\-\- do not rely on them remaining
341unchanged. Use \fItag\fR to locate a particular preamble line.
342.PP
343The additional block information is of the form
344.PP
345.Vb 1
346\& <tag> <information>
347.Ve
348.PP
349The \fIinformation\fR is human readable, but designed to be simple
350enough for machine parsing too.
351.PP
352When printing percentages, 0% and 100% are only printed when the values
353are \fIexactly\fR 0% and 100% respectively. Other values which would
354conventionally be rounded to 0% or 100% are instead printed as the
355nearest non-boundary value.
356.PP
357When using \fBgcov\fR, you must first compile your program with two
358special \s-1GCC\s0 options: \fB\-fprofile\-arcs \-ftest\-coverage\fR.
359This tells the compiler to generate additional information needed by
360gcov (basically a flow graph of the program) and also includes
361additional code in the object files for generating the extra profiling
362information needed by gcov. These additional files are placed in the
363directory where the object file is located.
364.PP
365Running the program will cause profile output to be generated. For each
366source file compiled with \fB\-fprofile\-arcs\fR, an accompanying
367\&\fI.gcda\fR file will be placed in the object file directory.
368.PP
369Running \fBgcov\fR with your program's source file names as arguments
370will now produce a listing of the code along with frequency of execution
371for each line. For example, if your program is called \fItmp.c\fR, this
372is what you see when you use the basic \fBgcov\fR facility:
373.PP
374.Vb 5
375\& $ gcc \-fprofile\-arcs \-ftest\-coverage tmp.c
376\& $ a.out
377\& $ gcov tmp.c
378\& 90.00% of 10 source lines executed in file tmp.c
379\& Creating tmp.c.gcov.
380.Ve
381.PP
382The file \fItmp.c.gcov\fR contains output from \fBgcov\fR.
383Here is a sample:
384.PP
385.Vb 10
386\& \-: 0:Source:tmp.c
387\& \-: 0:Graph:tmp.gcno
388\& \-: 0:Data:tmp.gcda
389\& \-: 0:Runs:1
390\& \-: 0:Programs:1
391\& \-: 1:#include <stdio.h>
392\& \-: 2:
393\& \-: 3:int main (void)
394\& 1: 4:{
395\& 1: 5: int i, total;
396\& \-: 6:
397\& 1: 7: total = 0;
398\& \-: 8:
399\& 11: 9: for (i = 0; i < 10; i++)
400\& 10: 10: total += i;
401\& \-: 11:
402\& 1: 12: if (total != 45)
403\& #####: 13: printf ("Failure\en");
404\& \-: 14: else
405\& 1: 15: printf ("Success\en");
406\& 1: 16: return 0;
407\& \-: 17:}
408.Ve
409.PP
410When you use the \fB\-a\fR option, you will get individual block
411counts, and the output looks like this:
412.PP
413.Vb 10
414\& \-: 0:Source:tmp.c
415\& \-: 0:Graph:tmp.gcno
416\& \-: 0:Data:tmp.gcda
417\& \-: 0:Runs:1
418\& \-: 0:Programs:1
419\& \-: 1:#include <stdio.h>
420\& \-: 2:
421\& \-: 3:int main (void)
422\& 1: 4:{
423\& 1: 4\-block 0
424\& 1: 5: int i, total;
425\& \-: 6:
426\& 1: 7: total = 0;
427\& \-: 8:
428\& 11: 9: for (i = 0; i < 10; i++)
429\& 11: 9\-block 0
430\& 10: 10: total += i;
431\& 10: 10\-block 0
432\& \-: 11:
433\& 1: 12: if (total != 45)
434\& 1: 12\-block 0
435\& #####: 13: printf ("Failure\en");
436\& $$$$$: 13\-block 0
437\& \-: 14: else
438\& 1: 15: printf ("Success\en");
439\& 1: 15\-block 0
440\& 1: 16: return 0;
441\& 1: 16\-block 0
442\& \-: 17:}
443.Ve
444.PP
445In this mode, each basic block is only shown on one line \*(-- the last
446line of the block. A multi-line block will only contribute to the
447execution count of that last line, and other lines will not be shown
448to contain code, unless previous blocks end on those lines.
449The total execution count of a line is shown and subsequent lines show
450the execution counts for individual blocks that end on that line. After each
451block, the branch and call counts of the block will be shown, if the
452\&\fB\-b\fR option is given.
453.PP
454Because of the way \s-1GCC\s0 instruments calls, a call count can be shown
455after a line with no individual blocks.
456As you can see, line 13 contains a basic block that was not executed.
457.PP
458When you use the \fB\-b\fR option, your output looks like this:
459.PP
460.Vb 6
461\& $ gcov \-b tmp.c
462\& 90.00% of 10 source lines executed in file tmp.c
463\& 80.00% of 5 branches executed in file tmp.c
464\& 80.00% of 5 branches taken at least once in file tmp.c
465\& 50.00% of 2 calls executed in file tmp.c
466\& Creating tmp.c.gcov.
467.Ve
468.PP
469Here is a sample of a resulting \fItmp.c.gcov\fR file:
470.PP
471.Vb 10
472\& \-: 0:Source:tmp.c
473\& \-: 0:Graph:tmp.gcno
474\& \-: 0:Data:tmp.gcda
475\& \-: 0:Runs:1
476\& \-: 0:Programs:1
477\& \-: 1:#include <stdio.h>
478\& \-: 2:
479\& \-: 3:int main (void)
480\& function main called 1 returned 1 blocks executed 75%
481\& 1: 4:{
482\& 1: 5: int i, total;
483\& \-: 6:
484\& 1: 7: total = 0;
485\& \-: 8:
486\& 11: 9: for (i = 0; i < 10; i++)
487\& branch 0 taken 91% (fallthrough)
488\& branch 1 taken 9%
489\& 10: 10: total += i;
490\& \-: 11:
491\& 1: 12: if (total != 45)
492\& branch 0 taken 0% (fallthrough)
493\& branch 1 taken 100%
494\& #####: 13: printf ("Failure\en");
495\& call 0 never executed
496\& \-: 14: else
497\& 1: 15: printf ("Success\en");
498\& call 0 called 1 returned 100%
499\& 1: 16: return 0;
500\& \-: 17:}
501.Ve
502.PP
503For each function, a line is printed showing how many times the function
504is called, how many times it returns and what percentage of the
505function's blocks were executed.
506.PP
507For each basic block, a line is printed after the last line of the basic
508block describing the branch or call that ends the basic block. There can
509be multiple branches and calls listed for a single source line if there
510are multiple basic blocks that end on that line. In this case, the
511branches and calls are each given a number. There is no simple way to map
512these branches and calls back to source constructs. In general, though,
513the lowest numbered branch or call will correspond to the leftmost construct
514on the source line.
515.PP
516For a branch, if it was executed at least once, then a percentage
517indicating the number of times the branch was taken divided by the
518number of times the branch was executed will be printed. Otherwise, the
519message \*(L"never executed\*(R" is printed.
520.PP
521For a call, if it was executed at least once, then a percentage
522indicating the number of times the call returned divided by the number
523of times the call was executed will be printed. This will usually be
524100%, but may be less for functions that call \f(CW\*(C`exit\*(C'\fR or \f(CW\*(C`longjmp\*(C'\fR,
525and thus may not return every time they are called.
526.PP
527The execution counts are cumulative. If the example program were
528executed again without removing the \fI.gcda\fR file, the count for the
529number of times each line in the source was executed would be added to
530the results of the previous run(s). This is potentially useful in
531several ways. For example, it could be used to accumulate data over a
532number of program runs as part of a test verification suite, or to
533provide more accurate long-term information over a large number of
534program runs.
535.PP
536The data in the \fI.gcda\fR files is saved immediately before the program
537exits. For each source file compiled with \fB\-fprofile\-arcs\fR, the
538profiling code first attempts to read in an existing \fI.gcda\fR file; if
539the file doesn't match the executable (differing number of basic block
540counts) it will ignore the contents of the file. It then adds in the
541new execution counts and finally writes the data to the file.
4b1e227d 542.SS "Using \fBgcov\fP with \s-1GCC\s0 Optimization"
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543.IX Subsection "Using gcov with GCC Optimization"
544If you plan to use \fBgcov\fR to help optimize your code, you must
545first compile your program with two special \s-1GCC\s0 options:
546\&\fB\-fprofile\-arcs \-ftest\-coverage\fR. Aside from that, you can use any
547other \s-1GCC\s0 options; but if you want to prove that every single line
548in your program was executed, you should not compile with optimization
549at the same time. On some machines the optimizer can eliminate some
550simple code lines by combining them with other lines. For example, code
551like this:
552.PP
553.Vb 4
554\& if (a != b)
555\& c = 1;
556\& else
557\& c = 0;
558.Ve
559.PP
560can be compiled into one instruction on some machines. In this case,
561there is no way for \fBgcov\fR to calculate separate execution counts
562for each line because there isn't separate code for each line. Hence
563the \fBgcov\fR output looks like this if you compiled the program with
564optimization:
565.PP
566.Vb 4
567\& 100: 12:if (a != b)
568\& 100: 13: c = 1;
569\& 100: 14:else
570\& 100: 15: c = 0;
571.Ve
572.PP
573The output shows that this block of code, combined by optimization,
574executed 100 times. In one sense this result is correct, because there
575was only one instruction representing all four of these lines. However,
576the output does not indicate how many times the result was 0 and how
577many times the result was 1.
578.PP
579Inlineable functions can create unexpected line counts. Line counts are
580shown for the source code of the inlineable function, but what is shown
581depends on where the function is inlined, or if it is not inlined at all.
582.PP
583If the function is not inlined, the compiler must emit an out of line
584copy of the function, in any object file that needs it. If
585\&\fIfileA.o\fR and \fIfileB.o\fR both contain out of line bodies of a
586particular inlineable function, they will also both contain coverage
587counts for that function. When \fIfileA.o\fR and \fIfileB.o\fR are
588linked together, the linker will, on many systems, select one of those
589out of line bodies for all calls to that function, and remove or ignore
590the other. Unfortunately, it will not remove the coverage counters for
591the unused function body. Hence when instrumented, all but one use of
592that function will show zero counts.
593.PP
594If the function is inlined in several places, the block structure in
595each location might not be the same. For instance, a condition might
596now be calculable at compile time in some instances. Because the
597coverage of all the uses of the inline function will be shown for the
598same source lines, the line counts themselves might seem inconsistent.
599.SH "SEE ALSO"
600.IX Header "SEE ALSO"
601\&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7), \fIgcc\fR\|(1) and the Info entry for \fIgcc\fR.
602.SH "COPYRIGHT"
603.IX Header "COPYRIGHT"
604Copyright (c) 1996, 1997, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
6052008 Free Software Foundation, Inc.
606.PP
607Permission is granted to copy, distribute and/or modify this document
608under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
609any later version published by the Free Software Foundation; with the
610Invariant Sections being \*(L"\s-1GNU\s0 General Public License\*(R" and \*(L"Funding
611Free Software\*(R", the Front-Cover texts being (a) (see below), and with
612the Back-Cover Texts being (b) (see below). A copy of the license is
613included in the \fIgfdl\fR\|(7) man page.
614.PP
615(a) The \s-1FSF\s0's Front-Cover Text is:
616.PP
617.Vb 1
618\& A GNU Manual
619.Ve
620.PP
621(b) The \s-1FSF\s0's Back-Cover Text is:
622.PP
623.Vb 3
624\& You have freedom to copy and modify this GNU Manual, like GNU
625\& software. Copies published by the Free Software Foundation raise
626\& funds for GNU development.
627.Ve