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.\" Automatically generated by Pod::Man 2.16 (Pod::Simple 3.05).\".\" Standard preamble:.\" ========================================================================.de Sh \" Subsection heading.br.if t .Sp.ne 5.PP\fB\\$1\fR.PP...de Sp \" Vertical space (when we can't use .PP).if t .sp .5v.if n .sp...de Vb \" Begin verbatim text.ft CW.nf.ne \\$1...de Ve \" End verbatim text.ft R.fi...\" Set up some character translations and predefined strings. \*(-- will.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left.\" double quote, and \*(R" will give a right double quote. \*(C+ will.\" give a nicer C++. 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Always turn off hyphenation; it makes.\" way too many mistakes in technical documents..if n .ad l.nh.SH "NAME"gcov \- coverage testing tool.SH "SYNOPSIS".IX Header "SYNOPSIS"gcov [\fB\-v\fR|\fB\-\-version\fR] [\fB\-h\fR|\fB\-\-help\fR][\fB\-a\fR|\fB\-\-all\-blocks\fR][\fB\-b\fR|\fB\-\-branch\-probabilities\fR][\fB\-c\fR|\fB\-\-branch\-counts\fR][\fB\-n\fR|\fB\-\-no\-output\fR][\fB\-l\fR|\fB\-\-long\-file\-names\fR][\fB\-p\fR|\fB\-\-preserve\-paths\fR][\fB\-f\fR|\fB\-\-function\-summaries\fR][\fB\-o\fR|\fB\-\-object\-directory\fR \fIdirectory|file\fR] \fIsourcefiles\fR[\fB\-u\fR|\fB\-\-unconditional\-branches\fR].SH "DESCRIPTION".IX Header "DESCRIPTION"\&\fBgcov\fR is a test coverage program. Use it in concert with \s-1GCC\s0to analyze your programs to help create more efficient, faster runningcode and to discover untested parts of your program. You can use\&\fBgcov\fR as a profiling tool to help discover where youroptimization efforts will best affect your code. You can also use\&\fBgcov\fR along with the other profiling tool, \fBgprof\fR, toassess which parts of your code use the greatest amount of computingtime..PPProfiling tools help you analyze your code's performance. Using aprofiler such as \fBgcov\fR or \fBgprof\fR, you can find out somebasic performance statistics, such as:.IP "\(bu" 4how often each line of code executes.IP "\(bu" 4what lines of code are actually executed.IP "\(bu" 4how much computing time each section of code uses.PPOnce you know these things about how your code works when compiled, youcan look at each module to see which modules should be optimized.\&\fBgcov\fR helps you determine where to work on optimization..PPSoftware developers also use coverage testing in concert withtestsuites, to make sure software is actually good enough for a release.Testsuites can verify that a program works as expected; a coverageprogram tests to see how much of the program is exercised by thetestsuite. Developers can then determine what kinds of test cases needto be added to the testsuites to create both better testing and a betterfinal product..PPYou should compile your code without optimization if you plan to use\&\fBgcov\fR because the optimization, by combining some lines of codeinto one function, may not give you as much information as you need tolook for `hot spots' where the code is using a great deal of computertime. Likewise, because \fBgcov\fR accumulates statistics by line (atthe lowest resolution), it works best with a programming style thatplaces only one statement on each line. If you use complicated macrosthat expand to loops or to other control structures, the statistics areless helpful\-\-\-they only report on the line where the macro callappears. If your complex macros behave like functions, you can replacethem with inline functions to solve this problem..PP\&\fBgcov\fR creates a logfile called \fI\fIsourcefile\fI.gcov\fR whichindicates how many times each line of a source file \fI\fIsourcefile\fI.c\fRhas executed. You can use these logfiles along with \fBgprof\fR to aidin fine-tuning the performance of your programs. \fBgprof\fR givestiming information you can use along with the information you get from\&\fBgcov\fR..PP\&\fBgcov\fR works only on code compiled with \s-1GCC\s0. It is notcompatible with any other profiling or test coverage mechanism..SH "OPTIONS".IX Header "OPTIONS".IP "\fB\-h\fR" 4.IX Item "-h".PD 0.IP "\fB\-\-help\fR" 4.IX Item "--help".PDDisplay help about using \fBgcov\fR (on the standard output), andexit without doing any further processing..IP "\fB\-v\fR" 4.IX Item "-v".PD 0.IP "\fB\-\-version\fR" 4.IX Item "--version".PDDisplay the \fBgcov\fR version number (on the standard output),and exit without doing any further processing..IP "\fB\-a\fR" 4.IX Item "-a".PD 0.IP "\fB\-\-all\-blocks\fR" 4.IX Item "--all-blocks".PDWrite individual execution counts for every basic block. Normally gcovoutputs execution counts only for the main blocks of a line. With thisoption you can determine if blocks within a single line are not beingexecuted..IP "\fB\-b\fR" 4.IX Item "-b".PD 0.IP "\fB\-\-branch\-probabilities\fR" 4.IX Item "--branch-probabilities".PDWrite branch frequencies to the output file, and write branch summaryinfo to the standard output. This option allows you to see how ofteneach branch in your program was taken. Unconditional branches will notbe shown, unless the \fB\-u\fR option is given..IP "\fB\-c\fR" 4.IX Item "-c".PD 0.IP "\fB\-\-branch\-counts\fR" 4.IX Item "--branch-counts".PDWrite branch frequencies as the number of branches taken, rather thanthe percentage of branches taken..IP "\fB\-n\fR" 4.IX Item "-n".PD 0.IP "\fB\-\-no\-output\fR" 4.IX Item "--no-output".PDDo not create the \fBgcov\fR output file..IP "\fB\-l\fR" 4.IX Item "-l".PD 0.IP "\fB\-\-long\-file\-names\fR" 4.IX Item "--long-file-names".PDCreate long file names for included source files. For example, if theheader file \fIx.h\fR contains code, and was included in the file\&\fIa.c\fR, then running \fBgcov\fR on the file \fIa.c\fR will producean output file called \fIa.c##x.h.gcov\fR instead of \fIx.h.gcov\fR.This can be useful if \fIx.h\fR is included in multiple sourcefiles. If you use the \fB\-p\fR option, both the including andincluded file names will be complete path names..IP "\fB\-p\fR" 4.IX Item "-p".PD 0.IP "\fB\-\-preserve\-paths\fR" 4.IX Item "--preserve-paths".PDPreserve complete path information in the names of generated\&\fI.gcov\fR files. Without this option, just the filename component isused. With this option, all directories are used, with \fB/\fR characterstranslated to \fB#\fR characters, \fI.\fR directory componentsremoved and \fI..\fRcomponents renamed to \fB^\fR. This is useful if sourcefiles are in severaldifferent directories. It also affects the \fB\-l\fR option..IP "\fB\-f\fR" 4.IX Item "-f".PD 0.IP "\fB\-\-function\-summaries\fR" 4.IX Item "--function-summaries".PDOutput summaries for each function in addition to the file level summary..IP "\fB\-o\fR \fIdirectory|file\fR" 4.IX Item "-o directory|file".PD 0.IP "\fB\-\-object\-directory\fR \fIdirectory\fR" 4.IX Item "--object-directory directory".IP "\fB\-\-object\-file\fR \fIfile\fR" 4.IX Item "--object-file file".PDSpecify either the directory containing the gcov data files, or theobject path name. The \fI.gcno\fR, and\&\fI.gcda\fR data files are searched for using this option. If a directoryis specified, the data files are in that directory and named after thesource file name, without its extension. If a file is specified here,the data files are named after that file, without its extension. If thisoption is not supplied, it defaults to the current directory..IP "\fB\-u\fR" 4.IX Item "-u".PD 0.IP "\fB\-\-unconditional\-branches\fR" 4.IX Item "--unconditional-branches".PDWhen branch probabilities are given, include those of unconditional branches.Unconditional branches are normally not interesting..PP\&\fBgcov\fR should be run with the current directory the same as thatwhen you invoked the compiler. Otherwise it will not be able to locatethe source files. \fBgcov\fR produces files called\&\fI\fImangledname\fI.gcov\fR in the current directory. These containthe coverage information of the source file they correspond to.One \fI.gcov\fR file is produced for each source file containing code,which was compiled to produce the data files. The \fImangledname\fR partof the output file name is usually simply the source file name, but canbe something more complicated if the \fB\-l\fR or \fB\-p\fR options aregiven. Refer to those options for details..PPThe \fI.gcov\fR files contain the \fB:\fR separated fields along withprogram source code. The format is.PP.Vb 1\& <execution_count>:<line_number>:<source line text>.Ve.PPAdditional block information may succeed each line, when requested bycommand line option. The \fIexecution_count\fR is \fB\-\fR for linescontaining no code and \fB#####\fR for lines which were never executed.Some lines of information at the start have \fIline_number\fR of zero..PPThe preamble lines are of the form.PP.Vb 1\& \-:0:<tag>:<value>.Ve.PPThe ordering and number of these preamble lines will be augmented as\&\fBgcov\fR development progresses \-\-\- do not rely on them remainingunchanged. Use \fItag\fR to locate a particular preamble line..PPThe additional block information is of the form.PP.Vb 1\& <tag> <information>.Ve.PPThe \fIinformation\fR is human readable, but designed to be simpleenough for machine parsing too..PPWhen printing percentages, 0% and 100% are only printed when the valuesare \fIexactly\fR 0% and 100% respectively. Other values which wouldconventionally be rounded to 0% or 100% are instead printed as thenearest non-boundary value..PPWhen using \fBgcov\fR, you must first compile your program with twospecial \s-1GCC\s0 options: \fB\-fprofile\-arcs \-ftest\-coverage\fR.This tells the compiler to generate additional information needed bygcov (basically a flow graph of the program) and also includesadditional code in the object files for generating the extra profilinginformation needed by gcov. These additional files are placed in thedirectory where the object file is located..PPRunning the program will cause profile output to be generated. For eachsource file compiled with \fB\-fprofile\-arcs\fR, an accompanying\&\fI.gcda\fR file will be placed in the object file directory..PPRunning \fBgcov\fR with your program's source file names as argumentswill now produce a listing of the code along with frequency of executionfor each line. For example, if your program is called \fItmp.c\fR, thisis what you see when you use the basic \fBgcov\fR facility:.PP.Vb 5\& $ gcc \-fprofile\-arcs \-ftest\-coverage tmp.c\& $ a.out\& $ gcov tmp.c\& 90.00% of 10 source lines executed in file tmp.c\& Creating tmp.c.gcov..Ve.PPThe file \fItmp.c.gcov\fR contains output from \fBgcov\fR.Here is a sample:.PP.Vb 10\& \-: 0:Source:tmp.c\& \-: 0:Graph:tmp.gcno\& \-: 0:Data:tmp.gcda\& \-: 0:Runs:1\& \-: 0:Programs:1\& \-: 1:#include <stdio.h>\& \-: 2:\& \-: 3:int main (void)\& 1: 4:{\& 1: 5: int i, total;\& \-: 6:\& 1: 7: total = 0;\& \-: 8:\& 11: 9: for (i = 0; i < 10; i++)\& 10: 10: total += i;\& \-: 11:\& 1: 12: if (total != 45)\& #####: 13: printf ("Failure\en");\& \-: 14: else\& 1: 15: printf ("Success\en");\& 1: 16: return 0;\& \-: 17:}.Ve.PPWhen you use the \fB\-a\fR option, you will get individual blockcounts, and the output looks like this:.PP.Vb 10\& \-: 0:Source:tmp.c\& \-: 0:Graph:tmp.gcno\& \-: 0:Data:tmp.gcda\& \-: 0:Runs:1\& \-: 0:Programs:1\& \-: 1:#include <stdio.h>\& \-: 2:\& \-: 3:int main (void)\& 1: 4:{\& 1: 4\-block 0\& 1: 5: int i, total;\& \-: 6:\& 1: 7: total = 0;\& \-: 8:\& 11: 9: for (i = 0; i < 10; i++)\& 11: 9\-block 0\& 10: 10: total += i;\& 10: 10\-block 0\& \-: 11:\& 1: 12: if (total != 45)\& 1: 12\-block 0\& #####: 13: printf ("Failure\en");\& $$$$$: 13\-block 0\& \-: 14: else\& 1: 15: printf ("Success\en");\& 1: 15\-block 0\& 1: 16: return 0;\& 1: 16\-block 0\& \-: 17:}.Ve.PPIn this mode, each basic block is only shown on one line \*(-- the lastline of the block. A multi-line block will only contribute to theexecution count of that last line, and other lines will not be shownto contain code, unless previous blocks end on those lines.The total execution count of a line is shown and subsequent lines showthe execution counts for individual blocks that end on that line. After eachblock, the branch and call counts of the block will be shown, if the\&\fB\-b\fR option is given..PPBecause of the way \s-1GCC\s0 instruments calls, a call count can be shownafter a line with no individual blocks.As you can see, line 13 contains a basic block that was not executed..PPWhen you use the \fB\-b\fR option, your output looks like this:.PP.Vb 6\& $ gcov \-b tmp.c\& 90.00% of 10 source lines executed in file tmp.c\& 80.00% of 5 branches executed in file tmp.c\& 80.00% of 5 branches taken at least once in file tmp.c\& 50.00% of 2 calls executed in file tmp.c\& Creating tmp.c.gcov..Ve.PPHere is a sample of a resulting \fItmp.c.gcov\fR file:.PP.Vb 10\& \-: 0:Source:tmp.c\& \-: 0:Graph:tmp.gcno\& \-: 0:Data:tmp.gcda\& \-: 0:Runs:1\& \-: 0:Programs:1\& \-: 1:#include <stdio.h>\& \-: 2:\& \-: 3:int main (void)\& function main called 1 returned 1 blocks executed 75%\& 1: 4:{\& 1: 5: int i, total;\& \-: 6:\& 1: 7: total = 0;\& \-: 8:\& 11: 9: for (i = 0; i < 10; i++)\& branch 0 taken 91% (fallthrough)\& branch 1 taken 9%\& 10: 10: total += i;\& \-: 11:\& 1: 12: if (total != 45)\& branch 0 taken 0% (fallthrough)\& branch 1 taken 100%\& #####: 13: printf ("Failure\en");\& call 0 never executed\& \-: 14: else\& 1: 15: printf ("Success\en");\& call 0 called 1 returned 100%\& 1: 16: return 0;\& \-: 17:}.Ve.PPFor each function, a line is printed showing how many times the functionis called, how many times it returns and what percentage of thefunction's blocks were executed..PPFor each basic block, a line is printed after the last line of the basicblock describing the branch or call that ends the basic block. There canbe multiple branches and calls listed for a single source line if thereare multiple basic blocks that end on that line. In this case, thebranches and calls are each given a number. There is no simple way to mapthese branches and calls back to source constructs. In general, though,the lowest numbered branch or call will correspond to the leftmost constructon the source line..PPFor a branch, if it was executed at least once, then a percentageindicating the number of times the branch was taken divided by thenumber of times the branch was executed will be printed. Otherwise, themessage \*(L"never executed\*(R" is printed..PPFor a call, if it was executed at least once, then a percentageindicating the number of times the call returned divided by the numberof times the call was executed will be printed. This will usually be100%, but may be less for functions that call \f(CW\*(C`exit\*(C'\fR or \f(CW\*(C`longjmp\*(C'\fR,and thus may not return every time they are called..PPThe execution counts are cumulative. If the example program wereexecuted again without removing the \fI.gcda\fR file, the count for thenumber of times each line in the source was executed would be added tothe results of the previous run(s). This is potentially useful inseveral ways. For example, it could be used to accumulate data over anumber of program runs as part of a test verification suite, or toprovide more accurate long-term information over a large number ofprogram runs..PPThe data in the \fI.gcda\fR files is saved immediately before the programexits. For each source file compiled with \fB\-fprofile\-arcs\fR, theprofiling code first attempts to read in an existing \fI.gcda\fR file; ifthe file doesn't match the executable (differing number of basic blockcounts) it will ignore the contents of the file. It then adds in thenew execution counts and finally writes the data to the file..Sh "Using \fBgcov\fP with \s-1GCC\s0 Optimization".IX Subsection "Using gcov with GCC Optimization"If you plan to use \fBgcov\fR to help optimize your code, you mustfirst compile your program with two special \s-1GCC\s0 options:\&\fB\-fprofile\-arcs \-ftest\-coverage\fR. Aside from that, you can use anyother \s-1GCC\s0 options; but if you want to prove that every single linein your program was executed, you should not compile with optimizationat the same time. On some machines the optimizer can eliminate somesimple code lines by combining them with other lines. For example, codelike this:.PP.Vb 4\& if (a != b)\& c = 1;\& else\& c = 0;.Ve.PPcan be compiled into one instruction on some machines. In this case,there is no way for \fBgcov\fR to calculate separate execution countsfor each line because there isn't separate code for each line. Hencethe \fBgcov\fR output looks like this if you compiled the program withoptimization:.PP.Vb 4\& 100: 12:if (a != b)\& 100: 13: c = 1;\& 100: 14:else\& 100: 15: c = 0;.Ve.PPThe output shows that this block of code, combined by optimization,executed 100 times. In one sense this result is correct, because therewas only one instruction representing all four of these lines. However,the output does not indicate how many times the result was 0 and howmany times the result was 1..PPInlineable functions can create unexpected line counts. Line counts areshown for the source code of the inlineable function, but what is showndepends on where the function is inlined, or if it is not inlined at all..PPIf the function is not inlined, the compiler must emit an out of linecopy of the function, in any object file that needs it. If\&\fIfileA.o\fR and \fIfileB.o\fR both contain out of line bodies of aparticular inlineable function, they will also both contain coveragecounts for that function. When \fIfileA.o\fR and \fIfileB.o\fR arelinked together, the linker will, on many systems, select one of thoseout of line bodies for all calls to that function, and remove or ignorethe other. Unfortunately, it will not remove the coverage counters forthe unused function body. Hence when instrumented, all but one use ofthat function will show zero counts..PPIf the function is inlined in several places, the block structure ineach location might not be the same. For instance, a condition mightnow be calculable at compile time in some instances. Because thecoverage of all the uses of the inline function will be shown for thesame source lines, the line counts themselves might seem inconsistent..SH "SEE ALSO".IX Header "SEE ALSO"\&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7), \fIgcc\fR\|(1) and the Info entry for \fIgcc\fR..SH "COPYRIGHT".IX Header "COPYRIGHT"Copyright (c) 1996, 1997, 1999, 2000, 2001, 2002, 2003, 2004, 2005,2008 Free Software Foundation, Inc..PPPermission is granted to copy, distribute and/or modify this documentunder the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 orany later version published by the Free Software Foundation; with theInvariant Sections being \*(L"\s-1GNU\s0 General Public License\*(R" and \*(L"FundingFree Software\*(R", the Front-Cover texts being (a) (see below), and withthe Back-Cover Texts being (b) (see below). A copy of the license isincluded in the \fIgfdl\fR\|(7) man page..PP(a) The \s-1FSF\s0's Front-Cover Text is:.PP.Vb 1\& A GNU Manual.Ve.PP(b) The \s-1FSF\s0's Back-Cover Text is:.PP.Vb 3\& You have freedom to copy and modify this GNU Manual, like GNU\& software. Copies published by the Free Software Foundation raise\& funds for GNU development..Ve
