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| <title>GNU Compiler Collection (GCC) Internals: gcov Testing</title> |
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| <a name="Support-for-testing-gcov"></a> |
| <h3 class="section">7.7 Support for testing <code>gcov</code></h3> |
| |
| <p>Language-independent support for testing <code>gcov</code>, and for checking |
| that branch profiling produces expected values, is provided by the |
| expect file <samp>lib/gcov.exp</samp>. <code>gcov</code> tests also rely on procedures |
| in <samp>lib/gcc-dg.exp</samp> to compile and run the test program. A typical |
| <code>gcov</code> test contains the following DejaGnu commands within comments: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">{ dg-options "-fprofile-arcs -ftest-coverage" } |
| { dg-do run { target native } } |
| { dg-final { run-gcov sourcefile } } |
| </pre></div> |
| |
| <p>Checks of <code>gcov</code> output can include line counts, branch percentages, |
| and call return percentages. All of these checks are requested via |
| commands that appear in comments in the test’s source file. |
| Commands to check line counts are processed by default. |
| Commands to check branch percentages and call return percentages are |
| processed if the <code>run-gcov</code> command has arguments <code>branches</code> |
| or <code>calls</code>, respectively. For example, the following specifies |
| checking both, as well as passing <samp>-b</samp> to <code>gcov</code>: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">{ dg-final { run-gcov branches calls { -b sourcefile } } } |
| </pre></div> |
| |
| <p>A line count command appears within a comment on the source line |
| that is expected to get the specified count and has the form |
| <code>count(<var>cnt</var>)</code>. A test should only check line counts for |
| lines that will get the same count for any architecture. |
| </p> |
| <p>Commands to check branch percentages (<code>branch</code>) and call |
| return percentages (<code>returns</code>) are very similar to each other. |
| A beginning command appears on or before the first of a range of |
| lines that will report the percentage, and the ending command |
| follows that range of lines. The beginning command can include a |
| list of percentages, all of which are expected to be found within |
| the range. A range is terminated by the next command of the same |
| kind. A command <code>branch(end)</code> or <code>returns(end)</code> marks |
| the end of a range without starting a new one. For example: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">if (i > 10 && j > i && j < 20) /* <span class="roman">branch(27 50 75)</span> */ |
| /* <span class="roman">branch(end)</span> */ |
| foo (i, j); |
| </pre></div> |
| |
| <p>For a call return percentage, the value specified is the |
| percentage of calls reported to return. For a branch percentage, |
| the value is either the expected percentage or 100 minus that |
| value, since the direction of a branch can differ depending on the |
| target or the optimization level. |
| </p> |
| <p>Not all branches and calls need to be checked. A test should not |
| check for branches that might be optimized away or replaced with |
| predicated instructions. Don’t check for calls inserted by the |
| compiler or ones that might be inlined or optimized away. |
| </p> |
| <p>A single test can check for combinations of line counts, branch |
| percentages, and call return percentages. The command to check a |
| line count must appear on the line that will report that count, but |
| commands to check branch percentages and call return percentages can |
| bracket the lines that report them. |
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