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| <div class="section"> |
| <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> |
| </tr></table> |
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