1<html lang="en"> 2<head> 3<title>Gcov Intro - Using the GNU Compiler Collection (GCC)</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Using the GNU Compiler Collection (GCC)"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Gcov.html#Gcov" title="Gcov"> 9<link rel="next" href="Invoking-Gcov.html#Invoking-Gcov" title="Invoking Gcov"> 10<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 11<!-- 12Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 131998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 142010 Free Software Foundation, Inc. 15 16Permission is granted to copy, distribute and/or modify this document 17under the terms of the GNU Free Documentation License, Version 1.3 or 18any later version published by the Free Software Foundation; with the 19Invariant Sections being ``Funding Free Software'', the Front-Cover 20Texts being (a) (see below), and with the Back-Cover Texts being (b) 21(see below). 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Use it in concert with GCC 60to analyze your programs to help create more efficient, faster running 61code and to discover untested parts of your program. You can use 62<samp><span class="command">gcov</span></samp> as a profiling tool to help discover where your 63optimization efforts will best affect your code. You can also use 64<samp><span class="command">gcov</span></samp> along with the other profiling tool, <samp><span class="command">gprof</span></samp>, to 65assess which parts of your code use the greatest amount of computing 66time. 67 68 <p>Profiling tools help you analyze your code's performance. Using a 69profiler such as <samp><span class="command">gcov</span></samp> or <samp><span class="command">gprof</span></samp>, you can find out some 70basic performance statistics, such as: 71 72 <ul> 73<li>how often each line of code executes 74 75 <li>what lines of code are actually executed 76 77 <li>how much computing time each section of code uses 78</ul> 79 80 <p>Once you know these things about how your code works when compiled, you 81can look at each module to see which modules should be optimized. 82<samp><span class="command">gcov</span></samp> helps you determine where to work on optimization. 83 84 <p>Software developers also use coverage testing in concert with 85testsuites, to make sure software is actually good enough for a release. 86Testsuites can verify that a program works as expected; a coverage 87program tests to see how much of the program is exercised by the 88testsuite. Developers can then determine what kinds of test cases need 89to be added to the testsuites to create both better testing and a better 90final product. 91 92 <p>You should compile your code without optimization if you plan to use 93<samp><span class="command">gcov</span></samp> because the optimization, by combining some lines of code 94into one function, may not give you as much information as you need to 95look for `hot spots' where the code is using a great deal of computer 96time. Likewise, because <samp><span class="command">gcov</span></samp> accumulates statistics by line (at 97the lowest resolution), it works best with a programming style that 98places only one statement on each line. If you use complicated macros 99that expand to loops or to other control structures, the statistics are 100less helpful—they only report on the line where the macro call 101appears. If your complex macros behave like functions, you can replace 102them with inline functions to solve this problem. 103 104 <p><samp><span class="command">gcov</span></samp> creates a logfile called <samp><var>sourcefile</var><span class="file">.gcov</span></samp> which 105indicates how many times each line of a source file <samp><var>sourcefile</var><span class="file">.c</span></samp> 106has executed. You can use these logfiles along with <samp><span class="command">gprof</span></samp> to aid 107in fine-tuning the performance of your programs. <samp><span class="command">gprof</span></samp> gives 108timing information you can use along with the information you get from 109<samp><span class="command">gcov</span></samp>. 110 111 <p><samp><span class="command">gcov</span></samp> works only on code compiled with GCC. It is not 112compatible with any other profiling or test coverage mechanism. 113 114<!-- man end --> 115 </body></html> 116 117