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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 6. Termination</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="support.html" title="Part II. Support" /><link rel="prev" href="dynamic_memory.html" title="Chapter 5. Dynamic Memory" /><link rel="next" href="verbose_termination.html" title="Verbose Terminate Handler" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 6. Termination</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="dynamic_memory.html">Prev</a> </td><th width="60%" align="center">Part II.
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Support
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</th><td width="20%" align="right"> <a accesskey="n" href="verbose_termination.html">Next</a></td></tr></table><hr /></div><div class="chapter" title="Chapter 6. Termination"><div class="titlepage"><div><div><h2 class="title"><a id="manual.support.termination"></a>Chapter 6. Termination</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="termination.html#support.termination.handlers">Termination Handlers</a></span></dt><dt><span class="sect1"><a href="verbose_termination.html">Verbose Terminate Handler</a></span></dt></dl></div><div class="sect1" title="Termination Handlers"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="support.termination.handlers"></a>Termination Handlers</h2></div></div></div><p>
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Not many changes here to <code class="filename">cstdlib</code>. You should note that the
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<code class="function">abort()</code> function does not call the
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destructors of automatic nor static objects, so if you're
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depending on those to do cleanup, it isn't going to happen.
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(The functions registered with <code class="function">atexit()</code>
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don't get called either, so you can forget about that
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possibility, too.)
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</p><p>
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The good old <code class="function">exit()</code> function can be a bit
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funky, too, until you look closer. Basically, three points to
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remember are:
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</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
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Static objects are destroyed in reverse order of their creation.
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</p></li><li class="listitem"><p>
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Functions registered with <code class="function">atexit()</code> are called in
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reverse order of registration, once per registration call.
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(This isn't actually new.)
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</p></li><li class="listitem"><p>
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The previous two actions are <span class="quote">“<span class="quote">interleaved,</span>”</span> that is,
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given this pseudocode:
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</p><pre class="programlisting">
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extern "C or C++" void f1 (void);
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extern "C or C++" void f2 (void);
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static Thing obj1;
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atexit(f1);
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static Thing obj2;
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atexit(f2);
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</pre><p>
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then at a call of <code class="function">exit()</code>,
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<code class="varname">f2</code> will be called, then
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<code class="varname">obj2</code> will be destroyed, then
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<code class="varname">f1</code> will be called, and finally
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<code class="varname">obj1</code> will be destroyed. If
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<code class="varname">f1</code> or <code class="varname">f2</code> allow an
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exception to propagate out of them, Bad Things happen.
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</p></li></ol></div><p>
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Note also that <code class="function">atexit()</code> is only required to store 32
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functions, and the compiler/library might already be using some of
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those slots. If you think you may run out, we recommend using
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the <code class="function">xatexit</code>/<code class="function">xexit</code> combination from <code class="literal">libiberty</code>, which has no such limit.
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</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="dynamic_memory.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="support.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="verbose_termination.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 5. Dynamic Memory </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Verbose Terminate Handler</td></tr></table></div></body></html>
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