608 lines
23 KiB
Groff
608 lines
23 KiB
Groff
.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.14
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.\" ========================================================================
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.\"
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.IX Title "GCOV 1"
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.TH GCOV 1 "2006-03-06" "gcc-3.4.6" "GNU"
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.SH "NAME"
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gcov \- coverage testing tool
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.SH "SYNOPSIS"
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.IX Header "SYNOPSIS"
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gcov [\fB\-v\fR|\fB\-\-version\fR] [\fB\-h\fR|\fB\-\-help\fR]
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[\fB\-a\fR|\fB\-\-all\-blocks\fR]
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[\fB\-b\fR|\fB\-\-branch\-probabilities\fR]
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[\fB\-c\fR|\fB\-\-branch\-counts\fR]
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[\fB\-n\fR|\fB\-\-no\-output\fR]
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[\fB\-l\fR|\fB\-\-long\-file\-names\fR]
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[\fB\-p\fR|\fB\-\-preserve\-paths\fR]
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[\fB\-f\fR|\fB\-\-function\-summaries\fR]
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[\fB\-o\fR|\fB\-\-object\-directory\fR \fIdirectory|file\fR] \fIsourcefile\fR
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[\fB\-u\fR|\fB\-\-unconditional\-branches\fR]
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.SH "DESCRIPTION"
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.IX Header "DESCRIPTION"
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\&\fBgcov\fR is a test coverage program. Use it in concert with \s-1GCC\s0
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to analyze your programs to help create more efficient, faster running
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code and to discover untested parts of your program. You can use
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\&\fBgcov\fR as a profiling tool to help discover where your
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optimization efforts will best affect your code. You can also use
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\&\fBgcov\fR along with the other profiling tool, \fBgprof\fR, to
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assess which parts of your code use the greatest amount of computing
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time.
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.PP
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Profiling tools help you analyze your code's performance. Using a
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profiler such as \fBgcov\fR or \fBgprof\fR, you can find out some
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basic performance statistics, such as:
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.IP "\(bu" 4
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how often each line of code executes
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.IP "\(bu" 4
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what lines of code are actually executed
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.IP "\(bu" 4
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how much computing time each section of code uses
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.PP
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Once you know these things about how your code works when compiled, you
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can look at each module to see which modules should be optimized.
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\&\fBgcov\fR helps you determine where to work on optimization.
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.PP
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Software developers also use coverage testing in concert with
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testsuites, to make sure software is actually good enough for a release.
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Testsuites can verify that a program works as expected; a coverage
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program tests to see how much of the program is exercised by the
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testsuite. Developers can then determine what kinds of test cases need
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to be added to the testsuites to create both better testing and a better
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final product.
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.PP
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You should compile your code without optimization if you plan to use
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\&\fBgcov\fR because the optimization, by combining some lines of code
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into one function, may not give you as much information as you need to
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look for `hot spots' where the code is using a great deal of computer
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time. Likewise, because \fBgcov\fR accumulates statistics by line (at
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the lowest resolution), it works best with a programming style that
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places only one statement on each line. If you use complicated macros
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that expand to loops or to other control structures, the statistics are
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less helpful\-\-\-they only report on the line where the macro call
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appears. If your complex macros behave like functions, you can replace
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them with inline functions to solve this problem.
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.PP
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\&\fBgcov\fR creates a logfile called \fI\fIsourcefile\fI.gcov\fR which
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indicates how many times each line of a source file \fI\fIsourcefile\fI.c\fR
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has executed. You can use these logfiles along with \fBgprof\fR to aid
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in fine-tuning the performance of your programs. \fBgprof\fR gives
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timing information you can use along with the information you get from
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\&\fBgcov\fR.
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.PP
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\&\fBgcov\fR works only on code compiled with \s-1GCC\s0. It is not
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compatible with any other profiling or test coverage mechanism.
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.SH "OPTIONS"
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.IX Header "OPTIONS"
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.IP "\fB\-h\fR" 4
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.IX Item "-h"
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.PD 0
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.IP "\fB\-\-help\fR" 4
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.IX Item "--help"
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.PD
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Display help about using \fBgcov\fR (on the standard output), and
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exit without doing any further processing.
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.IP "\fB\-v\fR" 4
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.IX Item "-v"
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.PD 0
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.IP "\fB\-\-version\fR" 4
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.IX Item "--version"
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.PD
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Display the \fBgcov\fR version number (on the standard output),
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and exit without doing any further processing.
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.IP "\fB\-a\fR" 4
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.IX Item "-a"
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.PD 0
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.IP "\fB\-\-all\-blocks\fR" 4
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.IX Item "--all-blocks"
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.PD
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Write individual execution counts for every basic block. Normally gcov
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outputs execution counts only for the main blocks of a line. With this
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option you can determine if blocks within a single line are not being
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executed.
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.IP "\fB\-b\fR" 4
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.IX Item "-b"
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.PD 0
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.IP "\fB\-\-branch\-probabilities\fR" 4
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.IX Item "--branch-probabilities"
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.PD
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Write branch frequencies to the output file, and write branch summary
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info to the standard output. This option allows you to see how often
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each branch in your program was taken. Unconditional branches will not
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be shown, unless the \fB\-u\fR option is given.
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.IP "\fB\-c\fR" 4
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.IX Item "-c"
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.PD 0
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.IP "\fB\-\-branch\-counts\fR" 4
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.IX Item "--branch-counts"
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.PD
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Write branch frequencies as the number of branches taken, rather than
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the percentage of branches taken.
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.IP "\fB\-n\fR" 4
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.IX Item "-n"
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.PD 0
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.IP "\fB\-\-no\-output\fR" 4
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.IX Item "--no-output"
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.PD
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Do not create the \fBgcov\fR output file.
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.IP "\fB\-l\fR" 4
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.IX Item "-l"
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.PD 0
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.IP "\fB\-\-long\-file\-names\fR" 4
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.IX Item "--long-file-names"
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.PD
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Create long file names for included source files. For example, if the
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header file \fIx.h\fR contains code, and was included in the file
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\&\fIa.c\fR, then running \fBgcov\fR on the file \fIa.c\fR will produce
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an output file called \fIa.c##x.h.gcov\fR instead of \fIx.h.gcov\fR.
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This can be useful if \fIx.h\fR is included in multiple source
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files. If you uses the \fB\-p\fR option, both the including and
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included file names will be complete path names.
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.IP "\fB\-p\fR" 4
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.IX Item "-p"
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.PD 0
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.IP "\fB\-\-preserve\-paths\fR" 4
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.IX Item "--preserve-paths"
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.PD
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Preserve complete path information in the names of generated
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\&\fI.gcov\fR files. Without this option, just the filename component is
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used. With this option, all directories are used, with '/' characters
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translated to '#' characters, '.' directory components removed and '..'
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components renamed to '^'. This is useful if sourcefiles are in several
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different directories. It also affects the \fB\-l\fR option.
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.IP "\fB\-f\fR" 4
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.IX Item "-f"
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.PD 0
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.IP "\fB\-\-function\-summaries\fR" 4
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.IX Item "--function-summaries"
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.PD
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Output summaries for each function in addition to the file level summary.
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.IP "\fB\-o\fR \fIdirectory|file\fR" 4
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.IX Item "-o directory|file"
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.PD 0
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.IP "\fB\-\-object\-directory\fR \fIdirectory\fR" 4
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.IX Item "--object-directory directory"
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.IP "\fB\-\-object\-file\fR \fIfile\fR" 4
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.IX Item "--object-file file"
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.PD
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Specify either the directory containing the gcov data files, or the
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object path name. The \fI.gcno\fR, and
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\&\fI.gcda\fR data files are searched for using this option. If a directory
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is specified, the data files are in that directory and named after the
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source file name, without its extension. If a file is specified here,
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the data files are named after that file, without its extension. If this
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option is not supplied, it defaults to the current directory.
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.IP "\fB\-u\fR" 4
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.IX Item "-u"
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.PD 0
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.IP "\fB\-\-unconditional\-branches\fR" 4
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.IX Item "--unconditional-branches"
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.PD
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When branch counts are given, include those of unconditional branches.
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Unconditional branches are normally not interesting.
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.PP
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\&\fBgcov\fR should be run with the current directory the same as that
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when you invoked the compiler. Otherwise it will not be able to locate
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the source files. \fBgcov\fR produces files called
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\&\fI\fImangledname\fI.gcov\fR in the current directory. These contain
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the coverage information of the source file they correspond to.
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One \fI.gcov\fR file is produced for each source file containing code,
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which was compiled to produce the data files. The \fImangledname\fR part
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of the output file name is usually simply the source file name, but can
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be something more complicated if the \fB\-l\fR or \fB\-p\fR options are
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given. Refer to those options for details.
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.PP
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The \fI.gcov\fR files contain the ':' separated fields along with
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program source code. The format is
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.PP
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.Vb 1
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\& <execution_count>:<line_number>:<source line text>
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.Ve
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.PP
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Additional block information may succeed each line, when requested by
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command line option. The \fIexecution_count\fR is \fB\-\fR for lines
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containing no code and \fB#####\fR for lines which were never
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executed. Some lines of information at the start have \fIline_number\fR
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of zero.
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.PP
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When printing percentages, 0% and 100% are only printed when the values
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are \fIexactly\fR 0% and 100% respectively. Other values which would
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conventionally be rounded to 0% or 100% are instead printed as the
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nearest non-boundary value.
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.PP
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When using \fBgcov\fR, you must first compile your program with two
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special \s-1GCC\s0 options: \fB\-fprofile\-arcs \-ftest\-coverage\fR.
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|
This tells the compiler to generate additional information needed by
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gcov (basically a flow graph of the program) and also includes
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additional code in the object files for generating the extra profiling
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information needed by gcov. These additional files are placed in the
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directory where the object file is located.
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.PP
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Running the program will cause profile output to be generated. For each
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source file compiled with \fB\-fprofile\-arcs\fR, an accompanying
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\&\fI.gcda\fR file will be placed in the object file directory.
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.PP
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Running \fBgcov\fR with your program's source file names as arguments
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will now produce a listing of the code along with frequency of execution
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for each line. For example, if your program is called \fItmp.c\fR, this
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is what you see when you use the basic \fBgcov\fR facility:
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.PP
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.Vb 5
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\& $ gcc -fprofile-arcs -ftest-coverage tmp.c
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\& $ a.out
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\& $ gcov tmp.c
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\& 90.00% of 10 source lines executed in file tmp.c
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\& Creating tmp.c.gcov.
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.Ve
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.PP
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The file \fItmp.c.gcov\fR contains output from \fBgcov\fR.
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Here is a sample:
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.PP
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.Vb 23
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\& -: 0:Source:tmp.c
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\& -: 0:Graph:tmp.gcno
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\& -: 0:Data:tmp.gcda
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\& -: 0:Runs:1
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\& -: 0:Programs:1
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\& -: 1:#include <stdio.h>
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\& -: 2:
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\& -: 3:int main (void)
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\& function main called 1 returned 1 blocks executed 75%
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\& 1: 4:{
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\& 1: 5: int i, total;
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\& -: 6:
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\& 1: 7: total = 0;
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\& -: 8:
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\& 11: 9: for (i = 0; i < 10; i++)
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\& 10: 10: total += i;
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\& -: 11:
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\& 1: 12: if (total != 45)
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\& #####: 13: printf ("Failure\en");
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\& -: 14: else
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\& 1: 15: printf ("Success\en");
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\& 1: 16: return 0;
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\& -: 17:}
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.Ve
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.PP
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When you use the \fB\-a\fR option, you will get individual block
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counts, and the output looks like this:
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.PP
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.Vb 30
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\& -: 0:Source:tmp.c
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\& -: 0:Graph:tmp.gcno
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\& -: 0:Data:tmp.gcda
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\& -: 0:Runs:1
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\& -: 0:Programs:1
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\& -: 1:#include <stdio.h>
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\& -: 2:
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\& -: 3:int main (void)
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\& function main called 1 returned 1 blocks executed 75%
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\& 1: 4:{
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\& 1: 4-block 0
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\& 1: 5: int i, total;
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\& -: 6:
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\& 1: 7: total = 0;
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\& -: 8:
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\& 11: 9: for (i = 0; i < 10; i++)
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\& 11: 9-block 0
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\& 10: 10: total += i;
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\& 10: 10-block 0
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\& -: 11:
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\& 1: 12: if (total != 45)
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\& 1: 12-block 0
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\& #####: 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
|
|
.PP
|
|
In this mode, each basic block is only shown on one line \*(-- the last
|
|
line of the block. A multi-line block will only contribute to the
|
|
execution count of that last line, and other lines will not be shown
|
|
to contain code, unless previous blocks end on those lines.
|
|
The total execution count of a line is shown and subsequent lines show
|
|
the execution counts for individual blocks that end on that line. After each
|
|
block, the branch and call counts of the block will be shown, if the
|
|
\&\fB\-b\fR option is given.
|
|
.PP
|
|
Because of the way \s-1GCC\s0 instruments calls, a call count can be shown
|
|
after a line with no individual blocks.
|
|
As you can see, line 13 contains a basic block that was not executed.
|
|
.PP
|
|
When 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
|
|
.PP
|
|
Here is a sample of a resulting \fItmp.c.gcov\fR file:
|
|
.PP
|
|
.Vb 29
|
|
\& -: 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
|
|
.PP
|
|
For each basic block, a line is printed after the last line of the basic
|
|
block describing the branch or call that ends the basic block. There can
|
|
be multiple branches and calls listed for a single source line if there
|
|
are multiple basic blocks that end on that line. In this case, the
|
|
branches and calls are each given a number. There is no simple way to map
|
|
these branches and calls back to source constructs. In general, though,
|
|
the lowest numbered branch or call will correspond to the leftmost construct
|
|
on the source line.
|
|
.PP
|
|
For a branch, if it was executed at least once, then a percentage
|
|
indicating the number of times the branch was taken divided by the
|
|
number of times the branch was executed will be printed. Otherwise, the
|
|
message ``never executed'' is printed.
|
|
.PP
|
|
For a call, if it was executed at least once, then a percentage
|
|
indicating the number of times the call returned divided by the number
|
|
of times the call was executed will be printed. This will usually be
|
|
100%, but may be less for functions call \f(CW\*(C`exit\*(C'\fR or \f(CW\*(C`longjmp\*(C'\fR,
|
|
and thus may not return every time they are called.
|
|
.PP
|
|
The execution counts are cumulative. If the example program were
|
|
executed again without removing the \fI.gcda\fR file, the count for the
|
|
number of times each line in the source was executed would be added to
|
|
the results of the previous run(s). This is potentially useful in
|
|
several ways. For example, it could be used to accumulate data over a
|
|
number of program runs as part of a test verification suite, or to
|
|
provide more accurate long-term information over a large number of
|
|
program runs.
|
|
.PP
|
|
The data in the \fI.gcda\fR files is saved immediately before the program
|
|
exits. For each source file compiled with \fB\-fprofile\-arcs\fR, the
|
|
profiling code first attempts to read in an existing \fI.gcda\fR file; if
|
|
the file doesn't match the executable (differing number of basic block
|
|
counts) it will ignore the contents of the file. It then adds in the
|
|
new 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 must
|
|
first compile your program with two special \s-1GCC\s0 options:
|
|
\&\fB\-fprofile\-arcs \-ftest\-coverage\fR. Aside from that, you can use any
|
|
other \s-1GCC\s0 options; but if you want to prove that every single line
|
|
in your program was executed, you should not compile with optimization
|
|
at the same time. On some machines the optimizer can eliminate some
|
|
simple code lines by combining them with other lines. For example, code
|
|
like this:
|
|
.PP
|
|
.Vb 4
|
|
\& if (a != b)
|
|
\& c = 1;
|
|
\& else
|
|
\& c = 0;
|
|
.Ve
|
|
.PP
|
|
can be compiled into one instruction on some machines. In this case,
|
|
there is no way for \fBgcov\fR to calculate separate execution counts
|
|
for each line because there isn't separate code for each line. Hence
|
|
the \fBgcov\fR output looks like this if you compiled the program with
|
|
optimization:
|
|
.PP
|
|
.Vb 4
|
|
\& 100: 12:if (a != b)
|
|
\& 100: 13: c = 1;
|
|
\& 100: 14:else
|
|
\& 100: 15: c = 0;
|
|
.Ve
|
|
.PP
|
|
The output shows that this block of code, combined by optimization,
|
|
executed 100 times. In one sense this result is correct, because there
|
|
was only one instruction representing all four of these lines. However,
|
|
the output does not indicate how many times the result was 0 and how
|
|
many times the result was 1.
|
|
.PP
|
|
Inlineable functions can create unexpected line counts. Line counts are
|
|
shown for the source code of the inlineable function, but what is shown
|
|
depends on where the function is inlined, or if it is not inlined at all.
|
|
.PP
|
|
If the function is not inlined, the compiler must emit an out of line
|
|
copy 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 a
|
|
particular inlineable function, they will also both contain coverage
|
|
counts for that function. When \fIfileA.o\fR and \fIfileB.o\fR are
|
|
linked together, the linker will, on many systems, select one of those
|
|
out of line bodies for all calls to that function, and remove or ignore
|
|
the other. Unfortunately, it will not remove the coverage counters for
|
|
the unused function body. Hence when instrumented, all but one use of
|
|
that function will show zero counts.
|
|
.PP
|
|
If the function is inlined in several places, the block structure in
|
|
each location might not be the same. For instance, a condition might
|
|
now be calculable at compile time in some instances. Because the
|
|
coverage of all the uses of the inline function will be shown for the
|
|
same 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
|
|
Free Software Foundation, Inc.
|
|
.PP
|
|
Permission is granted to copy, distribute and/or modify this document
|
|
under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.2 or
|
|
any later version published by the Free Software Foundation; with the
|
|
Invariant Sections being ``\s-1GNU\s0 General Public License'' and ``Funding
|
|
Free Software'', the Front-Cover texts being (a) (see below), and with
|
|
the Back-Cover Texts being (b) (see below). A copy of the license is
|
|
included 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
|