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129 lines
5.8 KiB
HTML
129 lines
5.8 KiB
HTML
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<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
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<head>
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<title>GIMPLE Exception Handling (GNU Compiler Collection (GCC) Internals)</title>
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<meta name="description" content="GIMPLE Exception Handling (GNU Compiler Collection (GCC) Internals)">
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<link href="index.html#Top" rel="start" title="Top">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="GIMPLE.html#GIMPLE" rel="up" title="GIMPLE">
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<link href="Temporaries.html#Temporaries" rel="next" title="Temporaries">
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<link href="GIMPLE-instruction-set.html#GIMPLE-instruction-set" rel="prev" title="GIMPLE instruction set">
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</head>
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<a name="GIMPLE-Exception-Handling"></a>
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<div class="header">
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<p>
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Next: <a href="Temporaries.html#Temporaries" accesskey="n" rel="next">Temporaries</a>, Previous: <a href="GIMPLE-instruction-set.html#GIMPLE-instruction-set" accesskey="p" rel="prev">GIMPLE instruction set</a>, Up: <a href="GIMPLE.html#GIMPLE" accesskey="u" rel="up">GIMPLE</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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</div>
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<hr>
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<a name="Exception-Handling-1"></a>
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<h3 class="section">12.4 Exception Handling</h3>
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<a name="index-GIMPLE-Exception-Handling"></a>
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<p>Other exception handling constructs are represented using
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<code>GIMPLE_TRY_CATCH</code>. <code>GIMPLE_TRY_CATCH</code> has two operands. The
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first operand is a sequence of statements to execute. If executing
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these statements does not throw an exception, then the second operand
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is ignored. Otherwise, if an exception is thrown, then the second
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operand of the <code>GIMPLE_TRY_CATCH</code> is checked. The second
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operand may have the following forms:
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</p>
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<ol>
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<li> A sequence of statements to execute. When an exception occurs,
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these statements are executed, and then the exception is rethrown.
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</li><li> A sequence of <code>GIMPLE_CATCH</code> statements. Each
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<code>GIMPLE_CATCH</code> has a list of applicable exception types and
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handler code. If the thrown exception matches one of the caught
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types, the associated handler code is executed. If the handler
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code falls off the bottom, execution continues after the original
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<code>GIMPLE_TRY_CATCH</code>.
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</li><li> A <code>GIMPLE_EH_FILTER</code> statement. This has a list of
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permitted exception types, and code to handle a match failure. If the
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thrown exception does not match one of the allowed types, the
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associated match failure code is executed. If the thrown exception
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does match, it continues unwinding the stack looking for the next
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handler.
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</li></ol>
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<p>Currently throwing an exception is not directly represented in
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GIMPLE, since it is implemented by calling a function. At some
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point in the future we will want to add some way to express that
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the call will throw an exception of a known type.
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</p>
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<p>Just before running the optimizers, the compiler lowers the
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high-level EH constructs above into a set of ‘<samp>goto</samp>’s, magic
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labels, and EH regions. Continuing to unwind at the end of a
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cleanup is represented with a <code>GIMPLE_RESX</code>.
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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="Temporaries.html#Temporaries" accesskey="n" rel="next">Temporaries</a>, Previous: <a href="GIMPLE-instruction-set.html#GIMPLE-instruction-set" accesskey="p" rel="prev">GIMPLE instruction set</a>, Up: <a href="GIMPLE.html#GIMPLE" accesskey="u" rel="up">GIMPLE</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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</body>
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</html>
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