1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII"> 4<title>Macro BOOST_SCOPE_EXIT_TPL</title> 5<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.78.1"> 7<link rel="home" href="index.html" title="Chapter 1. Boost.ScopeExit 1.1.0"> 8<link rel="up" href="reference.html#header.boost.scope_exit_hpp" title="Header <boost/scope_exit.hpp>"> 9<link rel="prev" href="BOOST_SCOPE_EXIT.html" title="Macro BOOST_SCOPE_EXIT"> 10<link rel="next" href="BOOST_SCOPE_EXIT_ID.html" title="Macro BOOST_SCOPE_EXIT_ID"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 15<td align="center"><a href="../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="BOOST_SCOPE_EXIT.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="reference.html#header.boost.scope_exit_hpp"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="index.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="BOOST_SCOPE_EXIT_ID.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="refentry"> 26<a name="BOOST_SCOPE_EXIT_TPL"></a><div class="titlepage"></div> 27<div class="refnamediv"> 28<h2><span class="refentrytitle">Macro BOOST_SCOPE_EXIT_TPL</span></h2> 29<p>BOOST_SCOPE_EXIT_TPL — This macro is a workaround for various versions of GCC to declare scope exits within templates. </p> 30</div> 31<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> 32<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: <<a class="link" href="reference.html#header.boost.scope_exit_hpp" title="Header <boost/scope_exit.hpp>">boost/scope_exit.hpp</a>> 33 34</span>BOOST_SCOPE_EXIT_TPL(capture_list)</pre></div> 35<div class="refsect1"> 36<a name="id876470"></a><h2>Description</h2> 37<p>Various versions of the GCC compiler do not compile <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT.html" title="Macro BOOST_SCOPE_EXIT">BOOST_SCOPE_EXIT</a></code> inside function templates. As a workaround, <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_TPL.html" title="Macro BOOST_SCOPE_EXIT_TPL">BOOST_SCOPE_EXIT_TPL</a></code> should be used instead of <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT.html" title="Macro BOOST_SCOPE_EXIT">BOOST_SCOPE_EXIT</a></code> in these cases:</p> 38<pre class="programlisting"><span class="special">{</span> <span class="comment">// Some local scope.</span> 39 <span class="special">...</span> 40 <span class="identifier">BOOST_SCOPE_EXIT_TPL</span><span class="special">(</span><span class="identifier">capture_list</span><span class="special">)</span> <span class="special">{</span> 41 <span class="special">...</span> <span class="comment">// Body code.</span> 42 <span class="special">}</span> <span class="identifier">BOOST_SCOPE_EXIT_END</span> 43 <span class="special">...</span> 44<span class="special">}</span> 45</pre> 46<p>The syntax of <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_TPL.html" title="Macro BOOST_SCOPE_EXIT_TPL">BOOST_SCOPE_EXIT_TPL</a></code> is the exact same as the one of <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT.html" title="Macro BOOST_SCOPE_EXIT">BOOST_SCOPE_EXIT</a></code> (see <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT.html" title="Macro BOOST_SCOPE_EXIT">BOOST_SCOPE_EXIT</a></code> for more information).</p> 47<p>On C++11 compilers, <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_TPL.html" title="Macro BOOST_SCOPE_EXIT_TPL">BOOST_SCOPE_EXIT_TPL</a></code> is not needed because <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT.html" title="Macro BOOST_SCOPE_EXIT">BOOST_SCOPE_EXIT</a></code> always compiles on GCC versions that support C++11. However, <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_TPL.html" title="Macro BOOST_SCOPE_EXIT_TPL">BOOST_SCOPE_EXIT_TPL</a></code> is still provided on C++11 so to write code that is portable between C++03 and C++11 compilers. It is recommended to always use <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_TPL.html" title="Macro BOOST_SCOPE_EXIT_TPL">BOOST_SCOPE_EXIT_TPL</a></code> within templates so to maximize portability.</p> 48<p>In general, the special macro <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_ID_TPL.html" title="Macro BOOST_SCOPE_EXIT_ID_TPL">BOOST_SCOPE_EXIT_ID_TPL</a></code> must be used instead of <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_TPL.html" title="Macro BOOST_SCOPE_EXIT_TPL">BOOST_SCOPE_EXIT_TPL</a></code> when it is necessary to expand multiple scope exit declarations on the same line within templates.</p> 49<p><span class="bold"><strong>Note:</strong></span> The issue in compiling scope exit declarations that some GCC versions have is illustrated by the following code (see also <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37920" target="_top">GCC bug 37920</a>): </p> 50<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> 51<span class="keyword">void</span> <span class="identifier">f</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">)</span> <span class="special">{</span> 52 <span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> 53 <span class="keyword">struct</span> <span class="identifier">local</span> <span class="special">{</span> 54 <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> 55 <span class="keyword">typedef</span> <span class="identifier">__typeof__</span><span class="special">(</span><span class="identifier">x</span><span class="special">)</span> <span class="identifier">typeof_x</span><span class="special">;</span> 56 <span class="special">}</span><span class="special">;</span> 57 <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> 58 <span class="keyword">typedef</span> <span class="identifier">local</span><span class="special">::</span><span class="identifier">typeof_x</span> <span class="identifier">x_type</span><span class="special">;</span> 59<span class="special">}</span> 60 61<span class="keyword">int</span> <span class="identifier">main</span><span class="special">(</span><span class="keyword">void</span><span class="special">)</span> <span class="special">{</span> <span class="identifier">f</span><span class="special">(</span><span class="number">0</span><span class="special">)</span><span class="special">;</span> <span class="special">}</span> 62</pre> 63<p> This can be fixed by adding <code class="computeroutput">typename</code> in front of <code class="computeroutput">local::typeof_i</code> and <code class="computeroutput">local::typeof_x</code> (which is the approach followed by the implementation of the <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_TPL.html" title="Macro BOOST_SCOPE_EXIT_TPL">BOOST_SCOPE_EXIT_TPL</a></code> macro).</p> 64<p><span class="bold"><strong>Note:</strong></span> Although <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_TPL.html" title="Macro BOOST_SCOPE_EXIT_TPL">BOOST_SCOPE_EXIT_TPL</a></code> has the same suffix as <code class="computeroutput">BOOST_TYPEOF_TPL</code>, it does not follow the Boost.Typeof convention.</p> 65<p><span class="bold"><strong>See:</strong></span> <a class="link" href="scope_exit/tutorial.html" title="Tutorial"> Tutorial</a> section, <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT.html" title="Macro BOOST_SCOPE_EXIT">BOOST_SCOPE_EXIT</a></code>, <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_END.html" title="Macro BOOST_SCOPE_EXIT_END">BOOST_SCOPE_EXIT_END</a></code>, <code class="computeroutput"><a class="link" href="BOOST_SCOPE_EXIT_ID_TPL.html" title="Macro BOOST_SCOPE_EXIT_ID_TPL">BOOST_SCOPE_EXIT_ID_TPL</a></code>. </p> 66</div> 67</div> 68<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 69<td align="left"></td> 70<td align="right"><div class="copyright-footer">Copyright © 2006-2012 Alexander Nasonov, Lorenzo Caminiti<p> 71 Distributed under the Boost Software License, Version 1.0 (see accompanying 72 file LICENSE_1_0.txt or a copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 73 </p> 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