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<a name="Support-for-testing-gcov"></a>
<h3 class="section">7.6 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 &quot;--coverage&quot; }
{ 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&rsquo;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>
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<pre class="smallexample">if (i &gt; 10 &amp;&amp; j &gt; i &amp;&amp; j &lt; 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&rsquo;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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