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[SVN r47250]
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Emil Dotchevski
2008-07-09 00:18:09 +00:00
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doc/tutorial_exception_ptr.html
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<html xmlns='http://www.w3.org/1999/xhtml' xml:lang='en' lang='en'>
<head>
<meta http-equiv='Content-Type' content='text/html; charset=utf-8'/>
<title>Tutorial: Transporting of Exceptions between Threads</title>
<title>tutorial: transporting of exceptions between threads</title>
<link href='reno.css' type='text/css' rel='stylesheet'/>
</head>
<body>
@ -19,11 +19,13 @@
<!-- Copyright (c) 2006-2008 Emil Dotchevski and Reverge Studios, Inc. -->
<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->
<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
<div class="RenoIncludeDIV"><h2>Transporting of Exceptions between Threads</h2>
<div class="RenoIncludeDIV"><div class="RenoAutoDIV"><h2>Tutorial: Transporting of Exceptions Between Threads</h2>
</div>
<p>Boost Exception supports transporting of exception objects between threads through cloning. This system is similar to <span class="RenoLink"><a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2179.html">N2179</a></span>, but because Boost Exception can not rely on language support, the use of <span class="RenoLink"><a href="enable_current_exception.html">enable_current_exception</a></span> at the time of the throw is required in order to use cloning.</p>
<h4>Note:</h4>
<p>All exceptions emitted by the familiar function boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span> are guaranteed to derive from boost::<span class="RenoLink"><a href="exception.html">exception</a></span> and to support cloning.</p>
<div class="RenoIncludeDIV"><h3>Using enable_current_exception at the Time of the Throw</h3>
<div class="RenoIncludeDIV"><div class="RenoAutoDIV"><h3>Tutorial: Using enable_current_exception at the Time of the Throw</h3>
</div>
<p>Here is how cloning can be enabled in a throw-expression (15.1):</p>
<pre>#include &lt;<span class="RenoLink"><a href="exception_enable_exception_cloning_hpp.html">boost/exception/enable_current_exception.hpp</a></span>&gt;
#include &lt;<span class="RenoLink"><a href="exception_error_info_hpp.html">boost/exception/info.hpp</a></span>&gt;
@ -42,7 +44,8 @@ file_read( FILE * f, void * buffer, size_t size )
errno_info(errno);
}</pre>
<p>Of course, <span class="RenoLink"><a href="enable_current_exception.html">enable_current_exception</a></span> may be used with any exception type; there is no requirement that it should derive from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>.</p>
</div><div class="RenoIncludeDIV"><h3>Cloning and Re-throwing an Exception</h3>
</div><div class="RenoIncludeDIV"><div class="RenoAutoDIV"><h3>Tutorial: Cloning and Re-Throwing an Exception</h3>
</div>
<p>When you catch an exception, you can call <span class="RenoLink"><a href="current_exception.html">current_exception</a></span> to get an <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> object:</p>
<pre>#include &lt;<span class="RenoLink"><a href="exception_cloning_hpp.html">boost/exception_ptr.hpp</a></span>&gt;
#include &lt;boost/thread.hpp&gt;
@ -76,13 +79,16 @@ work()
if( error )
boost::<span class="RenoLink"><a href="rethrow_exception.html">rethrow_exception</a></span>(error);
}</pre>
<p>Note that <span class="RenoLink"><a href="current_exception.html">current_exception</a></span> could fail to copy the original exception object in the following cases:* if there is not enough memory, in which case the returned <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> points to an instance of std::bad_alloc, or</p>
<div><ul><li> if <span class="RenoLink"><a href="enable_current_exception.html">enable_current_exception</a></span> was not used in the throw-expression passed to the original throw statement and the current implementation does not have the necessary compiler-specific support to copy the exception automatically, in which case the returned <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> points to an instance of <span class="RenoLink"><a href="unknown_exception.html">unknown_exception</a></span>.</li>
<p>Note that <span class="RenoLink"><a href="current_exception.html">current_exception</a></span> could fail to copy the original exception object in the following cases:</p>
<div><ul><li> if there is not enough memory, in which case the returned <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> points to an instance of std::bad_alloc, or</li>
<li> if <span class="RenoLink"><a href="enable_current_exception.html">enable_current_exception</a></span> was not used in the throw-expression passed to the original throw statement and the current implementation does not have the necessary compiler-specific support to copy the exception automatically, in which case the returned <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> points to an instance of <span class="RenoLink"><a href="unknown_exception.html">unknown_exception</a></span>.</li>
</ul></div>
<p>Regardless, the use of <span class="RenoLink"><a href="current_exception.html">current_exception</a></span> and <span class="RenoLink"><a href="rethrow_exception.html">rethrow_exception</a></span> in the above examples is well-formed.</p>
</div></div><h3>See also:</h3>
</div></div><div class="RenoAutoDIV"><div class="RenoHR"><hr/></div>
<h3>See Also:</h3>
<div class="RenoPageList"><a href="boost-exception.html">Boost Exception<br/>
</a></div>
</div>
<!-- Copyright (c) 2006-2008 Emil Dotchevski and Reverge Studios, Inc. -->
<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->
<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->