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