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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="scope_exit.ref"></a> Reference</h2></div></div></div>
<a name="ref.boost_scope_exit"></a><h4>
<a name="id763687"></a>
BOOST_SCOPE_EXIT
</h4>
<p>
A <a class="link" href="../index.html" title="Chapter 1. Boost.ScopeExit">ScopeExit</a> declaration has the following
synopsis:
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">scope_exit</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="identifier">BOOST_SCOPE_EXIT</span> <span class="special">(</span> <span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span><span class="special">-</span><span class="identifier">list</span> <span class="special">)</span>
<span class="identifier">function</span><span class="special">-</span><span class="identifier">body</span>
<span class="identifier">BOOST_SCOPE_EXIT_END</span>
</pre>
<p>
where
</p>
<pre class="programlisting"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span><span class="special">-</span><span class="identifier">list</span><span class="special">:</span>
<span class="special">(</span> <span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span> <span class="special">)</span>
<span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span><span class="special">-</span><span class="identifier">list</span> <span class="special">(</span> <span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span> <span class="special">)</span>
<span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span><span class="special">:</span>
<span class="identifier">identifier</span>
<span class="special">&</span><span class="identifier">identifier</span>
</pre>
<p>
The <a class="link" href="../index.html" title="Chapter 1. Boost.ScopeExit">ScopeExit</a> declaration schedules an execution
of <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">body</span></code>
at the end of the current scope. The <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">body</span></code> statements are executed in the reverse
order of <a class="link" href="../index.html" title="Chapter 1. Boost.ScopeExit">ScopeExit</a> declarations in the given
scope. The scope must be local.
</p>
<p>
Each <code class="computeroutput"><span class="identifier">identifier</span></code> in <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span><span class="special">-</span><span class="identifier">list</span></code> must
be a valid name in enclosing scope and it must appear exactly once in the list.
If a <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span></code>
starts with the ampersand sign <code class="computeroutput"><span class="special">&</span></code>,
the corresponding <code class="computeroutput"><span class="identifier">identifier</span></code>
will be available inside <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">body</span></code>; otherwise, a copy of it will be made
at the point of <a class="link" href="../index.html" title="Chapter 1. Boost.ScopeExit">ScopeExit</a> declaration and
that copy will be available inside <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">body</span></code>. In the latter case, the <code class="computeroutput"><span class="identifier">idenitifer</span></code> must be <code class="computeroutput"><span class="identifier">CopyConstructible</span></code>.
</p>
<p>
Only identifiers listed in <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span><span class="special">-</span><span class="identifier">list</span></code>, static variables, <code class="computeroutput"><span class="keyword">extern</span></code>
variables and functions, and enumerations from the enclosing scope can be used
inside the <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">body</span></code>.
</p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
<code class="computeroutput"><span class="keyword">this</span></code> pointer is not an identifier
and cannot be passed to <code class="computeroutput"> <span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span><span class="special">-</span><span class="identifier">list</span></code>.
</p></td></tr>
</table></div>
<p>
The <a class="link" href="../index.html" title="Chapter 1. Boost.ScopeExit">ScopeExit</a> uses <a href="../../../../../libs/typeof/index.html" target="_top">Boost.Typeof</a>
to determine types of <code class="computeroutput"><span class="identifier">scope</span><span class="special">-</span><span class="identifier">exit</span><span class="special">-</span><span class="identifier">capture</span><span class="special">-</span><span class="identifier">list</span></code> elements. In order to compile code in
<a href="../../../../../libs/typeof/index.html" target="_top">typeof emulation</a> mode,
all types should be registered with <a href="../../../../../doc/html/typeof/refe.html#typeof.regtype" target="_top">BOOST_TYPEOF_REGISTER_TYPE</a>
or <a href="../../../../../doc/html/typeof/refe.html#typeof.regtemp" target="_top">BOOST_TYPEOF_REGISTER_TEMPLATE</a>
macros, or appropriate <a href="../../../../../libs/typeof/index.html" target="_top">Boost.Typeof</a>
headers should be included.
</p>
<a name="ref.boost_scope_exit_tpl"></a><h4>
<a name="id764391"></a>
BOOST_SCOPE_EXIT_TPL
</h4>
<p>
This macro is a workaround for various versions of gcc. These compilers don't
compile <a class="link" href="../index.html" title="Chapter 1. Boost.ScopeExit">ScopeExit</a> declaration inside function
templates. As a workaround, the <code class="computeroutput"><span class="identifier">_TPL</span></code>
suffix should be appended to <code class="computeroutput"><span class="identifier">BOOST_SCOPE_EXIT</span></code>.
</p>
<p>
The problem boils down to the following code:
</p>
<pre class="programlisting"><span class="keyword">template</span><span class="special"><</span><span class="keyword">class</span> <span class="identifier">T</span><span class="special">></span> <span class="keyword">void</span> <span class="identifier">foo</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">t</span><span class="special">)</span> <span class="special">{</span>
<span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span>
<span class="keyword">struct</span> <span class="identifier">Local</span> <span class="special">{</span>
<span class="keyword">typedef</span> <span class="identifier">__typeof__</span><span class="special">(</span><span class="identifier">i</span><span class="special">)</span> <span class="identifier">typeof_i</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">__typeof__</span><span class="special">(</span><span class="identifier">t</span><span class="special">)</span> <span class="identifier">typeof_t</span><span class="special">;</span>
<span class="special">};</span>
<span class="keyword">typedef</span> <span class="identifier">Local</span><span class="special">::</span><span class="identifier">typeof_i</span> <span class="identifier">i_type</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">Local</span><span class="special">::</span><span class="identifier">typeof_t</span> <span class="identifier">t_type</span><span class="special">;</span>
<span class="special">}</span>
<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span> <span class="special">{</span> <span class="identifier">foo</span><span class="special">(</span><span class="number">0</span><span class="special">);</span> <span class="special">}</span>
</pre>
<p>
This can be fixed by adding <code class="computeroutput"><span class="keyword">typename</span></code>
in front of <code class="computeroutput"><span class="identifier">Local</span><span class="special">::</span><span class="identifier">typeof_i</span></code> and <code class="computeroutput"><span class="identifier">Local</span><span class="special">::</span><span class="identifier">typeof_t</span></code>.
</p>
<p>
See also <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37920" target="_top">GCC
bug 37920</a>.
</p>
<div class="note"><table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../doc/src/images/note.png"></td>
<th align="left">Note</th>
</tr>
<tr><td align="left" valign="top"><p>
Although <code class="computeroutput"><span class="identifier">BOOST_SCOPE_EXIT_TPL</span></code>
has the same suffix as the <code class="computeroutput"><span class="identifier">BOOST_TYPEOF_TPL</span></code>,
it doesn't follow a convention of the <a href="../../../../../libs/typeof/index.html" target="_top">Boost.Typeof</a>.
</p></td></tr>
</table></div>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2006 -2009 Alexander Nasonov<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <ulink url="http://www.boost.org/LICENSE_1_0.txt">
http://www.boost.org/LICENSE_1_0.txt </ulink>)
</p>
</div></td>
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