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114 lines
5.4 KiB
HTML
114 lines
5.4 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>Gcov Intro - Using the GNU Compiler Collection (GCC)</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="Using the GNU Compiler Collection (GCC)">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Gcov.html#Gcov" title="Gcov">
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<link rel="next" href="Invoking-Gcov.html#Invoking-Gcov" title="Invoking Gcov">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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Copyright (C) 1988-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with the
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Invariant Sections being ``Funding Free Software'', the Front-Cover
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Texts being (a) (see below), and with the Back-Cover Texts being (b)
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(see below). A copy of the license is included in the section entitled
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``GNU Free Documentation License''.
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(a) The FSF's Front-Cover Text is:
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A GNU Manual
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(b) The FSF's Back-Cover Text is:
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You have freedom to copy and modify this GNU Manual, like GNU
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software. Copies published by the Free Software Foundation raise
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funds for GNU development.-->
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<style type="text/css"><!--
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--></style>
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</head>
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<body>
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<div class="node">
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<a name="Gcov-Intro"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Invoking-Gcov.html#Invoking-Gcov">Invoking Gcov</a>,
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Up: <a rel="up" accesskey="u" href="Gcov.html#Gcov">Gcov</a>
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<hr>
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</div>
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<h3 class="section">10.1 Introduction to <samp><span class="command">gcov</span></samp></h3>
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<!-- man begin DESCRIPTION -->
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<p><samp><span class="command">gcov</span></samp> is a test coverage program. Use it in concert with GCC
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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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<samp><span class="command">gcov</span></samp> 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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<samp><span class="command">gcov</span></samp> along with the other profiling tool, <samp><span class="command">gprof</span></samp>, 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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<p>Profiling tools help you analyze your code's performance. Using a
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profiler such as <samp><span class="command">gcov</span></samp> or <samp><span class="command">gprof</span></samp>, you can find out some
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basic performance statistics, such as:
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<ul>
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<li>how often each line of code executes
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<li>what lines of code are actually executed
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<li>how much computing time each section of code uses
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</ul>
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<p>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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<samp><span class="command">gcov</span></samp> helps you determine where to work on optimization.
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<p>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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<p>You should compile your code without optimization if you plan to use
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<samp><span class="command">gcov</span></samp> 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 <samp><span class="command">gcov</span></samp> 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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<p><samp><span class="command">gcov</span></samp> creates a logfile called <samp><var>sourcefile</var><span class="file">.gcov</span></samp> which
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indicates how many times each line of a source file <samp><var>sourcefile</var><span class="file">.c</span></samp>
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has executed. You can use these logfiles along with <samp><span class="command">gprof</span></samp> to aid
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in fine-tuning the performance of your programs. <samp><span class="command">gprof</span></samp> gives
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timing information you can use along with the information you get from
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<samp><span class="command">gcov</span></samp>.
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<p><samp><span class="command">gcov</span></samp> works only on code compiled with GCC. It is not
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compatible with any other profiling or test coverage mechanism.
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<!-- man end -->
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</body></html>
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