visus
/
toolchain-gcc-arm-embedded

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<!-- Copyright (C) 1988-2020 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 6.5, http://www.gnu.org/software/texinfo/ -->
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Exceptions (Using the GNU Compiler Collection (GCC))</title>

<meta name="description" content="Exceptions (Using the GNU Compiler Collection (GCC))">
<meta name="keywords" content="Exceptions (Using the GNU Compiler Collection (GCC))">
<meta name="resource-type" content="document">
<meta name="distribution" content="global">
<meta name="Generator" content="makeinfo">
<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="Objective_002dC.html#Objective_002dC" rel="up" title="Objective-C">
<link href="Synchronization.html#Synchronization" rel="next" title="Synchronization">
<link href="compatibility_005falias.html#compatibility_005falias" rel="prev" title="compatibility_alias">
<style type="text/css">
<!--
a.summary-letter {text-decoration: none}
blockquote.indentedblock {margin-right: 0em}
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
blockquote.smallquotation {font-size: smaller}
div.display {margin-left: 3.2em}
div.example {margin-left: 3.2em}
div.lisp {margin-left: 3.2em}
div.smalldisplay {margin-left: 3.2em}
div.smallexample {margin-left: 3.2em}
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.nolinebreak {white-space: nowrap}
span.roman {font-family: initial; font-weight: normal}
span.sansserif {font-family: sans-serif; font-weight: normal}
ul.no-bullet {list-style: none}
-->
</style>


</head>

<body lang="en">
<a name="Exceptions"></a>
<div class="header">
<p>
Next: <a href="Synchronization.html#Synchronization" accesskey="n" rel="next">Synchronization</a>, Previous: <a href="compatibility_005falias.html#compatibility_005falias" accesskey="p" rel="prev">compatibility_alias</a>, Up: <a href="Objective_002dC.html#Objective_002dC" accesskey="u" rel="up">Objective-C</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>
</div>
<hr>
<a name="Exceptions-1"></a>
<h3 class="section">8.7 Exceptions</h3>

<p>GNU Objective-C provides exception support built into the language, as
in the following example:
</p>
<div class="smallexample">
<pre class="smallexample">  @try {
    &hellip;
       @throw expr;
    &hellip;
  }
  @catch (AnObjCClass *exc) {
    &hellip;
      @throw expr;
    &hellip;
      @throw;
    &hellip;
  }
  @catch (AnotherClass *exc) {
    &hellip;
  }
  @catch (id allOthers) {
    &hellip;
  }
  @finally {
    &hellip;
      @throw expr;
    &hellip;
  }
</pre></div>

<p>The <code>@throw</code> statement may appear anywhere in an Objective-C or
Objective-C++ program; when used inside of a <code>@catch</code> block, the
<code>@throw</code> may appear without an argument (as shown above), in
which case the object caught by the <code>@catch</code> will be rethrown.
</p>
<p>Note that only (pointers to) Objective-C objects may be thrown and
caught using this scheme.  When an object is thrown, it will be caught
by the nearest <code>@catch</code> clause capable of handling objects of
that type, analogously to how <code>catch</code> blocks work in C++ and
Java.  A <code>@catch(id &hellip;)</code> clause (as shown above) may also
be provided to catch any and all Objective-C exceptions not caught by
previous <code>@catch</code> clauses (if any).
</p>
<p>The <code>@finally</code> clause, if present, will be executed upon exit
from the immediately preceding <code>@try &hellip; @catch</code> section.
This will happen regardless of whether any exceptions are thrown,
caught or rethrown inside the <code>@try &hellip; @catch</code> section,
analogously to the behavior of the <code>finally</code> clause in Java.
</p>
<p>There are several caveats to using the new exception mechanism:
</p>
<ul>
<li> The <samp>-fobjc-exceptions</samp> command line option must be used when
compiling Objective-C files that use exceptions.

</li><li> With the GNU runtime, exceptions are always implemented as &ldquo;native&rdquo;
exceptions and it is recommended that the <samp>-fexceptions</samp> and
<samp>-shared-libgcc</samp> options are used when linking.

</li><li> With the NeXT runtime, although currently designed to be binary
compatible with <code>NS_HANDLER</code>-style idioms provided by the
<code>NSException</code> class, the new exceptions can only be used on Mac
OS X 10.3 (Panther) and later systems, due to additional functionality
needed in the NeXT Objective-C runtime.

</li><li> As mentioned above, the new exceptions do not support handling
types other than Objective-C objects.   Furthermore, when used from
Objective-C++, the Objective-C exception model does not interoperate with C++
exceptions at this time.  This means you cannot <code>@throw</code> an exception
from Objective-C and <code>catch</code> it in C++, or vice versa
(i.e., <code>throw &hellip; @catch</code>).
</li></ul>

<hr>
<div class="header">
<p>
Next: <a href="Synchronization.html#Synchronization" accesskey="n" rel="next">Synchronization</a>, Previous: <a href="compatibility_005falias.html#compatibility_005falias" accesskey="p" rel="prev">compatibility_alias</a>, Up: <a href="Objective_002dC.html#Objective_002dC" accesskey="u" rel="up">Objective-C</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>
</div>


</body>
</html>