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 <a name="Cleanups-1"></a>
 <h4 class="subsection">10.7.6 Cleanups</h4>
 <a name="index-Cleanups"></a>

 <p>Destructors for local C++ objects and similar dynamic cleanups are
 represented in GIMPLE by a <code>TRY_FINALLY_EXPR</code>.
 <code>TRY_FINALLY_EXPR</code> has two operands, both of which are a sequence
 of statements to execute.  The first sequence is executed.  When it
 completes the second sequence is executed.
 </p>
 <p>The first sequence may complete in the following ways:
 </p>
 <ol>
 <li> Execute the last statement in the sequence and fall off the
 end.

 </li><li> Execute a goto statement (<code>GOTO_EXPR</code>) to an ordinary
 label outside the sequence.

 </li><li> Execute a return statement (<code>RETURN_EXPR</code>).

 </li><li> Throw an exception.  This is currently not explicitly represented in
 GIMPLE.

 </li></ol>

 <p>The second sequence is not executed if the first sequence completes by
 calling <code>setjmp</code> or <code>exit</code> or any other function that does
 not return.  The second sequence is also not executed if the first
 sequence completes via a non-local goto or a computed goto (in general
 the compiler does not know whether such a goto statement exits the
 first sequence or not, so we assume that it doesn&rsquo;t).
 </p>
 <p>After the second sequence is executed, if it completes normally by
 falling off the end, execution continues wherever the first sequence
 would have continued, by falling off the end, or doing a goto, etc.
 </p>
 <p><code>TRY_FINALLY_EXPR</code> complicates the flow graph, since the cleanup
 needs to appear on every edge out of the controlled block; this
 reduces the freedom to move code across these edges.  Therefore, the
 EH lowering pass which runs before most of the optimization passes
 eliminates these expressions by explicitly adding the cleanup to each
 edge.  Rethrowing the exception is represented using <code>RESX_EXPR</code>.
 </p>
 <hr>
 <div class="header">
 <p>
 Next: <a href="OpenMP.html#OpenMP" accesskey="n" rel="next">OpenMP</a>, Previous: <a href="Jumps.html#Jumps" accesskey="p" rel="prev">Jumps</a>, Up: <a href="Statements.html#Statements" accesskey="u" rel="up">Statements</a> &nbsp; [<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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	<a name="Cleanups"></a>
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	<p>
	Next: <a href="OpenMP.html#OpenMP" accesskey="n" rel="next">OpenMP</a>, Previous: <a href="Jumps.html#Jumps" accesskey="p" rel="prev">Jumps</a>, Up: <a href="Statements.html#Statements" accesskey="u" rel="up">Statements</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>
	</div>
	<hr>
	<a name="Cleanups-1"></a>
	<h4 class="subsection">10.7.6 Cleanups</h4>
	<a name="index-Cleanups"></a>

	<p>Destructors for local C++ objects and similar dynamic cleanups are
	represented in GIMPLE by a <code>TRY_FINALLY_EXPR</code>.
	<code>TRY_FINALLY_EXPR</code> has two operands, both of which are a sequence
	of statements to execute. The first sequence is executed. When it
	completes the second sequence is executed.
	</p>
	<p>The first sequence may complete in the following ways:
	</p>
	<ol>
	<li> Execute the last statement in the sequence and fall off the
	end.

	</li><li> Execute a goto statement (<code>GOTO_EXPR</code>) to an ordinary
	label outside the sequence.

	</li><li> Execute a return statement (<code>RETURN_EXPR</code>).

	</li><li> Throw an exception. This is currently not explicitly represented in
	GIMPLE.

	</li></ol>

	<p>The second sequence is not executed if the first sequence completes by
	calling <code>setjmp</code> or <code>exit</code> or any other function that does
	not return. The second sequence is also not executed if the first
	sequence completes via a non-local goto or a computed goto (in general
	the compiler does not know whether such a goto statement exits the
	first sequence or not, so we assume that it doesn’t).
	</p>
	<p>After the second sequence is executed, if it completes normally by
	falling off the end, execution continues wherever the first sequence
	would have continued, by falling off the end, or doing a goto, etc.
	</p>
	<p><code>TRY_FINALLY_EXPR</code> complicates the flow graph, since the cleanup
	needs to appear on every edge out of the controlled block; this
	reduces the freedom to move code across these edges. Therefore, the
	EH lowering pass which runs before most of the optimization passes
	eliminates these expressions by explicitly adding the cleanup to each
	edge. Rethrowing the exception is represented using <code>RESX_EXPR</code>.
	</p>
	<hr>
	<div class="header">
	<p>
	Next: <a href="OpenMP.html#OpenMP" accesskey="n" rel="next">OpenMP</a>, Previous: <a href="Jumps.html#Jumps" accesskey="p" rel="prev">Jumps</a>, Up: <a href="Statements.html#Statements" accesskey="u" rel="up">Statements</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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