<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
<html>
|
<!-- Copyright (C) 1988-2016 Free Software Foundation, Inc.
|
|
Permission is granted to copy, distribute and/or modify this document
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
any later version published by the Free Software Foundation; with the
|
Invariant Sections being "Funding Free Software", the Front-Cover
|
Texts being (a) (see below), and with the Back-Cover Texts being (b)
|
(see below). A copy of the license is included in the section entitled
|
"GNU Free Documentation License".
|
|
(a) The FSF's Front-Cover Text is:
|
|
A GNU Manual
|
|
(b) The FSF's Back-Cover Text is:
|
|
You have freedom to copy and modify this GNU Manual, like GNU
|
software. Copies published by the Free Software Foundation raise
|
funds for GNU development. -->
|
<!-- Created by GNU Texinfo 5.2, http://www.gnu.org/software/texinfo/ -->
|
<head>
|
<title>GNU Compiler Collection (GCC) Internals: GIMPLE Exception Handling</title>
|
|
<meta name="description" content="GNU Compiler Collection (GCC) Internals: GIMPLE Exception Handling">
|
<meta name="keywords" content="GNU Compiler Collection (GCC) Internals: GIMPLE Exception Handling">
|
<meta name="resource-type" content="document">
|
<meta name="distribution" content="global">
|
<meta name="Generator" content="makeinfo">
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
<link href="index.html#Top" rel="start" title="Top">
|
<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
<link href="GIMPLE.html#GIMPLE" rel="up" title="GIMPLE">
|
<link href="Temporaries.html#Temporaries" rel="next" title="Temporaries">
|
<link href="GIMPLE-instruction-set.html#GIMPLE-instruction-set" rel="prev" title="GIMPLE instruction set">
|
<style type="text/css">
|
<!--
|
a.summary-letter {text-decoration: none}
|
blockquote.smallquotation {font-size: smaller}
|
div.display {margin-left: 3.2em}
|
div.example {margin-left: 3.2em}
|
div.indentedblock {margin-left: 3.2em}
|
div.lisp {margin-left: 3.2em}
|
div.smalldisplay {margin-left: 3.2em}
|
div.smallexample {margin-left: 3.2em}
|
div.smallindentedblock {margin-left: 3.2em; font-size: smaller}
|
div.smalllisp {margin-left: 3.2em}
|
kbd {font-style:oblique}
|
pre.display {font-family: inherit}
|
pre.format {font-family: inherit}
|
pre.menu-comment {font-family: serif}
|
pre.menu-preformatted {font-family: serif}
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
pre.smallexample {font-size: smaller}
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
pre.smalllisp {font-size: smaller}
|
span.nocodebreak {white-space:nowrap}
|
span.nolinebreak {white-space:nowrap}
|
span.roman {font-family:serif; font-weight:normal}
|
span.sansserif {font-family:sans-serif; font-weight:normal}
|
ul.no-bullet {list-style: none}
|
-->
|
</style>
|
|
|
</head>
|
|
<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
|
<a name="GIMPLE-Exception-Handling"></a>
|
<div class="header">
|
<p>
|
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>
|
</div>
|
<hr>
|
<a name="Exception-Handling-1"></a>
|
<h3 class="section">11.4 Exception Handling</h3>
|
<a name="index-GIMPLE-Exception-Handling"></a>
|
|
<p>Other exception handling constructs are represented using
|
<code>GIMPLE_TRY_CATCH</code>. <code>GIMPLE_TRY_CATCH</code> has two operands. The
|
first operand is a sequence of statements to execute. If executing
|
these statements does not throw an exception, then the second operand
|
is ignored. Otherwise, if an exception is thrown, then the second
|
operand of the <code>GIMPLE_TRY_CATCH</code> is checked. The second
|
operand may have the following forms:
|
</p>
|
<ol>
|
<li> A sequence of statements to execute. When an exception occurs,
|
these statements are executed, and then the exception is rethrown.
|
|
</li><li> A sequence of <code>GIMPLE_CATCH</code> statements. Each
|
<code>GIMPLE_CATCH</code> has a list of applicable exception types and
|
handler code. If the thrown exception matches one of the caught
|
types, the associated handler code is executed. If the handler
|
code falls off the bottom, execution continues after the original
|
<code>GIMPLE_TRY_CATCH</code>.
|
|
</li><li> A <code>GIMPLE_EH_FILTER</code> statement. This has a list of
|
permitted exception types, and code to handle a match failure. If the
|
thrown exception does not match one of the allowed types, the
|
associated match failure code is executed. If the thrown exception
|
does match, it continues unwinding the stack looking for the next
|
handler.
|
|
</li></ol>
|
|
<p>Currently throwing an exception is not directly represented in
|
GIMPLE, since it is implemented by calling a function. At some
|
point in the future we will want to add some way to express that
|
the call will throw an exception of a known type.
|
</p>
|
<p>Just before running the optimizers, the compiler lowers the
|
high-level EH constructs above into a set of ‘<samp>goto</samp>’s, magic
|
labels, and EH regions. Continuing to unwind at the end of a
|
cleanup is represented with a <code>GIMPLE_RESX</code>.
|
</p>
|
|
<hr>
|
<div class="header">
|
<p>
|
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>
|
</div>
|
|
|
|
</body>
|
</html>
|
