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61 lines
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HTML
61 lines
3.8 KiB
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'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'>
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<html xmlns='http://www.w3.org/1999/xhtml' xml:lang='en' lang='en'>
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<head>
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<meta http-equiv='Content-Type' content='text/html; charset=utf-8'/>
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<title>Tutorial: Logging of boost::exception Objects</title>
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<link href='reno.css' type='text/css' rel='stylesheet'/>
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</head>
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<div class="body-0">
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<div>
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<div id="boost_logo">
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<a href="http://www.boost.org"><img style="border:0" src="http://www.boost.org/boost.png" alt="Boost" width="277" height="86"/></a>
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</div>
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<h1>Boost Exception</h1>
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</div>
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<div class="RenoIncludeDIV"><h2>Logging of boost::exception Objects</h2>
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<p>Class <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span></tt> provides a virtual member function <tt><span class="RenoLink"><a href="exception_what.html">what</a></span>()</tt>, with a signature identical to the familiar <tt>std::exception::what()</tt> function. The default implementation returns a string value that is not presentable as a friendly user message, but because it is generated automatically, it is useful for debugging or logging purposes. Here is an example:</p>
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<pre>#include <<span class="RenoLink"><a href="exception_hpp.html">boost/exception.hpp</a></span>>
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#include <iostream>
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void f(); //throws unknown types that derive from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>.
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void
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g()
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{
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try
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{
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f();
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}
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catch(
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boost::<span class="RenoLink"><a href="exception.html">exception</a></span> & e )
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{
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std::cerr << e.<span class="RenoLink"><a href="exception_what.html">what</a></span>();
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}
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}</pre>
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<p>The <tt><span class="RenoLink"><a href="exception_what.html">what</a></span>()</tt> member function iterates over all data objects stored in the <tt>boost::<span class="RenoLink"><a href="exception.html">exception</a></span></tt> through <tt><span class="RenoLink"><a href="operator_shl_exception.html">operator<<</a></span>()</tt>. The returned string is constructed by converting each data object to string and then concatenating these strings together.</p>
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<p>When the <tt><span class="RenoLink"><a href="error_info.html">error_info</a></span><Tag,T></tt> template is instantiated, the system attempts overload resolution for an unqualified call to <tt>to_string(x)</tt>, where <tt>x</tt> is of type <tt>T</tt>. If this is successful, the <tt>to_string()</tt> overload is used to convert objects of type <tt>T</tt> to string.</p>
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<p>Otherwise, the system attempts overload resolution for <tt>s << x</tt>, where <tt>s</tt> is a <tt>std::ostringstream</tt> and <tt>x</tt> is of type <tt>T</tt>. If this is successful, the <tt>operator<<</tt> overload is used to convert objects of type <tt>T</tt> to string.</p>
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<p>Otherwise the system is unable to convert objects of type <tt>T</tt> to string, and an unspecified stub string value is used without issuing a compile error.</p>
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</div><h3>See also:</h3>
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<div class="RenoPageList"><a href="boost-exception.html">Boost Exception<br/>
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</a></div>
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<div id="footer">
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<p> </p>
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<hr/>
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<p>
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<a class="logo" href="http://jigsaw.w3.org/css-validator/validator?uri=http://revergestudios.com/boost-exception/reno.css"><img class="logo_pic" src="valid-css.png" alt="Valid CSS" height="31" width="88"/></a>
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<small>Copyright (c) 2006-2008 by Emil Dotchevski and Reverge Studios, Inc.<br/>
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Distributed under the <a href="http://www.boost.org/LICENSE_1_0.txt">Boost Software License, Version 1.0</a>.</small>
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</p>
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</div>
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</body>
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</html>
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