1<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Strict//EN' 2'http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd'> 3<html xmlns='http://www.w3.org/1999/xhtml' xml:lang='en' lang='en'> 4<head> 5 <meta http-equiv='Content-Type' content='text/html; charset=utf-8'/> 6 <title>error_info</title> 7 <link href='reno.css' type='text/css' rel='stylesheet'/> 8</head> 9<body> 10<div class="body-0"> 11<div class="body-1"> 12<div class="body-2"> 13<div> 14<div id="boost_logo"> 15<a href="http://www.boost.org"><img style="border:0" src="../../../boost.png" alt="Boost" width="277" height="86"/></a> 16</div> 17<h1>Boost Exception</h1> 18</div> 19<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. --> 20<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying --> 21<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> 22<div class="RenoIncludeDIV"><div class="RenoAutoDIV"><h3>error_info</h3> 23</div> 24<div class="RenoIncludeDIV"><p><span class="RenoEscape">#<!--<wiki>`#</wiki>--></span>include <<span class="RenoLink"><a href="boost_exception_info_hpp.html">boost/exception/info.hpp</a></span>></p> 25<pre>namespace 26boost 27 { 28<span class="RenoIncludeSPAN"> template <class Tag,class T> 29 class 30 <span class="RenoLink">error_info</span> 31 { 32 public: 33 34 <span class="RenoIncludeSPAN"> typedef T <span class="RenoLink"><a href="error_info_value_type.html">value_type</a></span>;</span> 35 36 <span class="RenoIncludeSPAN"> <span class="RenoLink"><a href="error_info_error_info.html">error_info</a></span>( <span class="RenoLink"><a href="error_info_value_type.html">value_type</a></span> const & v );</span> 37 <span class="RenoIncludeSPAN"> <span class="RenoLink"><a href="error_info_value_type.html">value_type</a></span> const & <span class="RenoLink"><a href="error_info_value.html">value</a></span>() const; 38 <span class="RenoLink"><a href="error_info_value_type.html">value_type</a></span> & <span class="RenoLink"><a href="error_info_value.html">value</a></span>();</span> 39 };</span> 40 }</pre> 41</div><h4>Requirements:</h4> 42<p>T must have accessible copy constructor and must not be a reference (there is no requirement that T's copy constructor does not throw.)</p> 43<h4>Description:</h4> 44<p>This class template is used to associate a Tag type with a value type T. Objects of type <span class="RenoLink">error_info</span><Tag,T> can be passed to <span class="RenoLink"><a href="exception_operator_shl.html">operator<<</a></span> to be stored in objects of type boost::<span class="RenoLink"><a href="exception.html">exception</a></span>.</p> 45<h4>Usage:</h4> 46<p>The header <<span class="RenoLink"><a href="boost_exception_error_info_hpp.html">boost/exception/error_info.hpp</a></span>> provides a declaration of the <span class="RenoLink">error_info</span> template, which is sufficient for the purpose of typedefing an instance for specific Tag and T, for example:</p> 47<pre>#include <<span class="RenoLink"><a href="boost_exception_error_info_hpp.html">boost/exception/error_info.hpp</a></span>> 48 49struct tag_errno; 50typedef boost::<span class="RenoLink">error_info</span><tag_errno,int> errno_info;</pre> 51<p>Or, the shorter equivalent:</p> 52<pre>#include <<span class="RenoLink"><a href="boost_exception_error_info_hpp.html">boost/exception/error_info.hpp</a></span>> 53 54typedef boost::<span class="RenoLink">error_info</span><struct tag_errno,int> errno_info;</pre> 55<p>This errno_info typedef can be passed to <span class="RenoLink"><a href="exception_operator_shl.html">operator<<</a></span> (#include <<span class="RenoLink"><a href="boost_exception_info_hpp.html">boost/exception/info.hpp</a></span>> first) to store an int named tag_errno in exceptions of types that derive from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>:</p> 56<pre>throw file_read_error() <span class="RenoLink"><a href="exception_operator_shl.html"><<</a></span> errno_info(errno);</pre> 57<p>It can also be passed to <span class="RenoLink"><a href="get_error_info.html">get_error_info</a></span> (#include <<span class="RenoLink"><a href="boost_exception_get_error_info_hpp.html">boost/exception/get_error_info.hpp</a></span>> first) to retrieve the tag_errno int from a boost::<span class="RenoLink"><a href="exception.html">exception</a></span>:</p> 58<pre>catch( boost::<span class="RenoLink"><a href="exception.html">exception</a></span> & x ) 59 { 60 if( int const * e=boost::<span class="RenoLink"><a href="get_error_info.html">get_error_info</a></span><errno_info>(x) ) 61 .... 62 }</pre> 63<p>For convenience and uniformity, Boost Exception defines the following commonly used <span class="RenoLink">error_info</span> typedefs, ready for use with <span class="RenoLink"><a href="exception_operator_shl.html">operator<<</a></span>:</p> 64<div class="RenoPageList"><a href="errinfo_api_function.html">errinfo_api_function</a><br/> 65<a href="errinfo_at_line.html">errinfo_at_line</a><br/> 66<a href="errinfo_errno.html">errinfo_errno</a><br/> 67<a href="errinfo_file_handle.html">errinfo_file_handle</a><br/> 68<a href="errinfo_file_name.html">errinfo_file_name</a><br/> 69<a href="errinfo_file_open_mode.html">errinfo_file_open_mode</a><br/> 70<a href="errinfo_nested_exception.html">errinfo_nested_exception</a><br/> 71<a href="errinfo_type_info_name.html">errinfo_type_info_name</a></div> 72</div><div class="RenoAutoDIV"><div class="RenoHR"><hr/></div> 73See also: <span class="RenoPageList"><a href="boost-exception.html">Boost Exception</a> | <a href="boost_exception_error_info_hpp.html">boost/exception/error_info.hpp</a> | <a href="boost_exception_exception_hpp.html">boost/exception/exception.hpp</a> | <a href="boost_exception_info_hpp.html">boost/exception/info.hpp</a> | <a href="diagnostic_information.html">diagnostic_information</a> | <a href="diagnostic_information_what.html">diagnostic_information_what</a> | <a href="error_info_error_info.html">error_info::error_info</a> | <a href="error_info_value.html">error_info::value</a> | <a href="error_info_value_type.html">error_info::value_type</a> | <a href="exception.html">exception</a> | <a href="exception_operator_shl.html">exception/operator<<</a> | <a href="exception_ptr.html">exception_ptr</a> | <a href="frequently_asked_questions.html">Frequently Asked Questions</a> | <a href="get_error_info.html">get_error_info</a> | <a href="tutorial_enable_error_info.html">Integrating Boost Exception in Existing Exception Class Hierarchies</a> | <a href="motivation.html">Motivation</a> | <a href="original_exception_type.html">original_exception_type</a> | <a href="tuple_operator_shl.html">tuple/operator<<</a></span> 74</div> 75<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. --> 76<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying --> 77<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) --> 78<div id="footer"> 79<p> 80<a class="logo" href="http://jigsaw.w3.org/css-validator/check/referer"><img class="logo_pic" src="valid-css.png" alt="Valid CSS" height="31" width="88"/></a> 81<a class="logo" href="http://validator.w3.org/check?uri=referer"><img class="logo_pic" src="valid-xhtml.png" alt="Valid XHTML 1.0" height="31" width="88"/></a> 82<small>Copyright (c) 2006-2009 by Emil Dotchevski and Reverge Studios, Inc.<br/> 83Distributed under the <a href="http://www.boost.org/LICENSE_1_0.txt">Boost Software License, Version 1.0</a>.</small> 84</p> 85</div> 86</div> 87</div> 88</div> 89</body> 90</html> 91
