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| <h3 class="section">10.1 Introduction to <samp><span class="command">gcov</span></samp></h3> |
| |
| <!-- man begin DESCRIPTION --> |
| <p><samp><span class="command">gcov</span></samp> is a test coverage program. Use it in concert with GCC |
| to analyze your programs to help create more efficient, faster running |
| code and to discover untested parts of your program. You can use |
| <samp><span class="command">gcov</span></samp> as a profiling tool to help discover where your |
| optimization efforts will best affect your code. You can also use |
| <samp><span class="command">gcov</span></samp> along with the other profiling tool, <samp><span class="command">gprof</span></samp>, to |
| assess which parts of your code use the greatest amount of computing |
| time. |
| |
| <p>Profiling tools help you analyze your code's performance. Using a |
| profiler such as <samp><span class="command">gcov</span></samp> or <samp><span class="command">gprof</span></samp>, you can find out some |
| basic performance statistics, such as: |
| |
| <ul> |
| <li>how often each line of code executes |
| |
| <li>what lines of code are actually executed |
| |
| <li>how much computing time each section of code uses |
| </ul> |
| |
| <p>Once you know these things about how your code works when compiled, you |
| can look at each module to see which modules should be optimized. |
| <samp><span class="command">gcov</span></samp> helps you determine where to work on optimization. |
| |
| <p>Software developers also use coverage testing in concert with |
| testsuites, to make sure software is actually good enough for a release. |
| Testsuites can verify that a program works as expected; a coverage |
| program tests to see how much of the program is exercised by the |
| testsuite. Developers can then determine what kinds of test cases need |
| to be added to the testsuites to create both better testing and a better |
| final product. |
| |
| <p>You should compile your code without optimization if you plan to use |
| <samp><span class="command">gcov</span></samp> because the optimization, by combining some lines of code |
| into one function, may not give you as much information as you need to |
| look for `hot spots' where the code is using a great deal of computer |
| time. Likewise, because <samp><span class="command">gcov</span></samp> accumulates statistics by line (at |
| the lowest resolution), it works best with a programming style that |
| places only one statement on each line. If you use complicated macros |
| that expand to loops or to other control structures, the statistics are |
| less helpful—they only report on the line where the macro call |
| appears. If your complex macros behave like functions, you can replace |
| them with inline functions to solve this problem. |
| |
| <p><samp><span class="command">gcov</span></samp> creates a logfile called <samp><var>sourcefile</var><span class="file">.gcov</span></samp> which |
| indicates how many times each line of a source file <samp><var>sourcefile</var><span class="file">.c</span></samp> |
| has executed. You can use these logfiles along with <samp><span class="command">gprof</span></samp> to aid |
| in fine-tuning the performance of your programs. <samp><span class="command">gprof</span></samp> gives |
| timing information you can use along with the information you get from |
| <samp><span class="command">gcov</span></samp>. |
| |
| <p><samp><span class="command">gcov</span></samp> works only on code compiled with GCC. It is not |
| compatible with any other profiling or test coverage mechanism. |
| |
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