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| <h2><span class="refentrytitle">Macro BOOST_SCOPE_EXIT_TPL</span></h2> |
| <p>BOOST_SCOPE_EXIT_TPL — This macro is a workaround for various versions of GCC to declare scope exits within templates. </p> |
| </div> |
| <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2> |
| <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>> |
| |
| </span>BOOST_SCOPE_EXIT_TPL(capture_list)</pre></div> |
| <div class="refsect1"> |
| <a name="id835969"></a><h2>Description</h2> |
| <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> |
| <pre class="programlisting"> <span class="special">{</span> <span class="comment">// Some local scope.</span> |
| <span class="special">...</span> |
| <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> |
| <span class="special">...</span> <span class="comment">// Body code.</span> |
| <span class="special">}</span> <span class="identifier">BOOST_SCOPE_EXIT_END</span> |
| <span class="special">...</span> |
| <span class="special">}</span> |
| </pre> |
| <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> |
| <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> |
| <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> |
| <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> |
| <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">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> |
| <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">x</span><span class="special">)</span> <span class="identifier">typeof_x</span><span class="special">;</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_x</span> <span class="identifier">x_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="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> |
| </pre> |
| <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> |
| <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> |
| <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> |
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| 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>) |
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