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Added verbose parameter to boost::diagnostic_information.

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[SVN r82179]
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Emil Dotchevski
2012-12-23 03:31:48 +00:00
parent 2ebfd49b4f
commit 9b100b0c9d
17 changed files with 3811 additions and 4014 deletions
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doc/boost_exception_all_hpp.html
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@ -40,7 +40,7 @@
#include &lt;<span class="RenoLink"><a href="boost_exception_ptr_hpp.html">boost/exception_ptr.hpp</a></span>&gt;
#endif</span></pre>
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See also: <span class="RenoPageList"><a href="boost_exception_hpp.html">boost/exception.hpp</a>&nbsp;| <a href="tutorial_diagnostic_information.html">Diagnostic Information</a>&nbsp;| <a href="tutorial_enable_error_info.html">Integrating Boost Exception in Existing Exception Class Hierarchies</a>&nbsp;| <a href="synopsis.html">Synopsis</a></span>
See also: <span class="RenoPageList"><a href="tutorial_diagnostic_information.html">Diagnostic Information</a>&nbsp;| <a href="tutorial_enable_error_info.html">Integrating Boost Exception in Existing Exception Class Hierarchies</a>&nbsp;| <a href="synopsis.html">Synopsis</a></span>
</div>
<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. -->
<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->

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@ -30,11 +30,11 @@ boost
<span class="RenoIncludeSPAN"> class <span class="RenoLink"><a href="exception.html">exception</a></span>;</span>
<span class="RenoIncludeSPAN"> <span class="RenoIncludeSPAN">template &lt;class E&gt;
std::string <span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span>( E const &amp; e );
std::string <span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span>( E const &amp; e, bool verbose=true );
std::string <span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span>( <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> const &amp; p );</span>
std::string <span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span>( <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> const &amp; p, bool verbose=true );</span>
<span class="RenoIncludeSPAN">char const * <span class="RenoLink"><a href="diagnostic_information_what.html">diagnostic_information_what</a></span>( boost::<span class="RenoLink"><a href="exception.html">exception</a></span> const &amp; e ) throw();</span>
<span class="RenoIncludeSPAN">char const * <span class="RenoLink"><a href="diagnostic_information_what.html">diagnostic_information_what</a></span>( boost::<span class="RenoLink"><a href="exception.html">exception</a></span> const &amp; e, bool verbose=true ) throw();</span>
<span class="RenoIncludeSPAN">std::string <span class="RenoLink"><a href="current_exception_diagnostic_information.html">current_exception_diagnostic_information</a></span>();</span></span>
}</pre>

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<h1>Boost Exception</h1>
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<p>This header has been deprecated.</p>
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<p><b>BOOST_THROW_EXCEPTION_CURRENT_FUNCTION</b></p>
<p>The <span class="RenoLink"><a href="BOOST_THROW_EXCEPTION.html">BOOST_THROW_EXCEPTION</a></span> macro uses BOOST_THROW_EXCEPTION_CURRENT_FUNCTION to record the name of the current function in the exception object. Unless overridden by the user, BOOST_THROW_EXCEPTION_CURRENT_FUNCTION expands to BOOST_CURRENT_FUNCTION.</p>
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See also: <span class="RenoPageList"><a href="BOOST_THROW_EXCEPTION.html">BOOST_THROW_EXCEPTION</a>&nbsp;| <a href="boost-exception.html">Boost Exception</a>&nbsp;| <a href="boost_exception_all_hpp.html">boost/exception/all.hpp</a>&nbsp;| <a href="frequently_asked_questions.html">Frequently Asked Questions</a>&nbsp;| <a href="get_error_info.html">get_error_info</a></span>
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@ -52,7 +52,7 @@ main()
}
}</pre>
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See also: <span class="RenoPageList"><a href="boost-exception.html">Boost Exception</a>&nbsp;| <a href="boost_exception_diagnostic_information_hpp.html">boost/exception/diagnostic_information.hpp</a>&nbsp;| <a href="diagnostic_information.html">diagnostic_information</a>&nbsp;| <a href="frequently_asked_questions.html">Frequently Asked Questions</a></span>
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<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. -->
<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->

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@ -26,25 +26,21 @@
boost
{
<span class="RenoIncludeSPAN"> template &lt;class E&gt;
std::string <span class="RenoLink">diagnostic_information</span>( E const &amp; e );
std::string <span class="RenoLink">diagnostic_information</span>( E const &amp; e, bool verbose=true );
std::string <span class="RenoLink">diagnostic_information</span>( <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> const &amp; p );</span>
std::string <span class="RenoLink">diagnostic_information</span>( <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> const &amp; p, bool verbose=true );</span>
}</pre>
</div><h4>Returns:</h4>
<p>A string value that contains varying amount of implementation-specific diagnostic information about the passed object:</p>
<div><ul><li>If E can be statically converted to boost::<span class="RenoLink"><a href="exception.html">exception</a></span>, the returned value contains the string representations of all <span class="RenoLink"><a href="error_info.html">error_info</a></span> objects stored in the boost::<span class="RenoLink"><a href="exception.html">exception</a></span> through <span class="RenoLink"><a href="exception_operator_shl.html">operator&lt;&lt;</a></span>, along with other diagnostic information relevant to the exception. If e can be dynamically converted to std::exception, the returned value also contains the what() string.</li>
<li>Otherwise, if E can be statically converted to std::exception:<div><ul><li>if e can be dynamically converted to boost::exception, the returned value is the same as if E could be statically converted to boost::<span class="RenoLink"><a href="exception.html">exception</a></span>;</li>
<li>otherwise the returned value contains the what() string.</li>
<p>A string value that contains varying amount of diagnostic information about the passed object:</p>
<div><ul><li> If E can be statically converted to either boost::<span class="RenoLink"><a href="exception.html">exception</a></span> or to std::exception, dynamic_cast is used to access both the boost::<span class="RenoLink"><a href="exception.html">exception</a></span> and std::exception subobjects of e; otherwise, the boost::<span class="RenoLink">diagnostic_information</span> template is not available.</li>
<li> The returned value contains the string representations of all <span class="RenoLink"><a href="error_info.html">error_info</a></span> objects stored in the boost::<span class="RenoLink"><a href="exception.html">exception</a></span> subobject through <span class="RenoLink"><a href="exception_operator_shl.html">operator&lt;&lt;</a></span>.</li>
<li> In addition, if verbose is true, it contains other diagnostic information relevant to the exception, including the string returned by std::exception::what().</li>
</ul></div>
</li>
<li>Otherwise, the boost::<span class="RenoLink">diagnostic_information</span> template is not available.</li>
</ul></div>
<p>The string representation of each <span class="RenoLink"><a href="error_info.html">error_info</a></span> object is deduced by a function call that is bound at the time the <span class="RenoLink"><a href="error_info.html">error_info</a></span>&lt;Tag,T&gt; template is instantiated. The following overload resolutions are attempted in order:</p>
<div><ol><li>Unqualified call to to_string(x), where x is of type <span class="RenoLink"><a href="error_info.html">error_info</a></span>&lt;Tag,T&gt; (the return value is expected to be of type std::string.)</li>
<li>Unqualified call to to_string(x.<span class="RenoLink"><a href="error_info_value.html">value</a></span>()) (the return value is expected to be of type std::string.)</li>
<p>The string representation of each <span class="RenoLink"><a href="error_info.html">error_info</a></span> object is deduced by an unqualified call to to_string(x), where x is of type <span class="RenoLink"><a href="error_info.html">error_info</a></span>&lt;Tag,T&gt;, for which Boost Exception defines a generic overload. It converts x.<span class="RenoLink"><a href="error_info_value.html">value</a></span>() to string, attempting to bind (at the time the <span class="RenoLink"><a href="error_info.html">error_info</a></span>&lt;Tag,T&gt; template is instantiated) the following functions in order:</p>
<div><ol><li>Unqualified call to to_string(x.<span class="RenoLink"><a href="error_info_value.html">value</a></span>()) (the return value is expected to be of type std::string.)</li>
<li>Unqualified call to s &lt;&lt; x.<span class="RenoLink"><a href="error_info_value.html">value</a></span>(), where s is a std::ostringstream.</li>
</ol></div>
<p>The first successfully bound function is used at the time <span class="RenoLink">diagnostic_information</span> is called; if all 3 overload resolutions are unsuccessful, the system is unable to convert the <span class="RenoLink"><a href="error_info.html">error_info</a></span> object to string, and <i>an unspecified stub string value is used without issuing a compile error.</i></p>
<p>The first successfully bound function is used at the time <span class="RenoLink">diagnostic_information</span> is called; if both overload resolutions are unsuccessful, the system is unable to convert the <span class="RenoLink"><a href="error_info.html">error_info</a></span> object to string, and <i>an unspecified stub string value is used without issuing a compile error.</i></p>
<p>The <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> overload of <span class="RenoLink">diagnostic_information</span> is equivalent to:</p>
<pre>if( p )
try
@ -53,14 +49,9 @@ boost
}
catch(...)
{
return <span class="RenoLink"><a href="current_exception_diagnostic_information.html">current_exception_diagnostic_information</a></span>();
return <span class="RenoLink"><a href="current_exception_diagnostic_information.html">current_exception_diagnostic_information</a></span>(verbose);
}
else return &lt;unspecified-string-value&gt;;</pre>
<h4>Notes:</h4>
<div><ul><li>The format of the returned string is unspecified.</li>
<li>The returned string is <i>not</i> user-friendly.</li>
<li>The returned string may include additional platform-specific diagnostic information.</li>
</ul></div>
<div class="RenoIncludeDIV"><h4>Example:</h4>
<p>this is a possible output from the <span class="RenoLink">diagnostic_information</span> function, as used in <i>libs/exception/example/example_io.cpp:</i></p>
<pre>example_io.cpp(70): Throw in function class boost::shared_ptr&lt;struct _iobuf&gt; __cdecl my_fopen(const char *,const char *)

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<pre>namespace
boost
{
<span class="RenoIncludeSPAN"> char const * <span class="RenoLink">diagnostic_information_what</span>( boost::<span class="RenoLink"><a href="exception.html">exception</a></span> const &amp; e ) throw();</span>
<span class="RenoIncludeSPAN"> char const * <span class="RenoLink">diagnostic_information_what</span>( boost::<span class="RenoLink"><a href="exception.html">exception</a></span> const &amp; e, bool verbose=true ) throw();</span>
}</pre>
</div><p>The <span class="RenoLink">diagnostic_information_what</span> function is intended to be called from a user-defined std::exception::what() override. This allows diagnostic information to be returned as the what() string.</p>
<h4>Returns:</h4>

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@ -48,7 +48,7 @@ throw boost::<span class="RenoLink">enable_current_exception</span>(my_exception
<h4>Note:</h4>
<p>Instead of using the throw keyword directly, it is preferable to call boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span>. This is guaranteed to throw an exception that derives from boost::<span class="RenoLink"><a href="exception.html">exception</a></span> and supports the <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> functionality.</p>
</div><div class="RenoAutoDIV"><div class="RenoHR"><hr/></div>
See also: <span class="RenoPageList"><a href="boost-exception.html">Boost Exception</a>&nbsp;| <a href="boost_exception_enable_current_exception_hpp.html">boost/exception/enable_current_exception.hpp</a>&nbsp;| <a href="configuration_macros.html">Configuration Macros</a>&nbsp;| <a href="copy_exception.html">copy_exception</a>&nbsp;| <a href="current_exception.html">current_exception</a>&nbsp;| <a href="frequently_asked_questions.html">Frequently Asked Questions</a>&nbsp;| <a href="tutorial_exception_ptr.html">Transporting of Exceptions Between Threads</a></span>
See also: <span class="RenoPageList"><a href="boost-exception.html">Boost Exception</a>&nbsp;| <a href="boost_exception_enable_current_exception_hpp.html">boost/exception/enable_current_exception.hpp</a>&nbsp;| <a href="configuration_macros.html">Configuration Macros</a>&nbsp;| <a href="copy_exception.html">copy_exception</a>&nbsp;| <a href="current_exception.html">current_exception</a>&nbsp;| <a href="tutorial_exception_ptr.html">Transporting of Exceptions Between Threads</a></span>
</div>
<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. -->
<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->

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<h4>Nesting of exceptions:</h4>
<p>An <span class="RenoLink">exception_ptr</span> can be added as <span class="RenoLink"><a href="error_info.html">error_info</a></span> to any boost::<span class="RenoLink"><a href="exception.html">exception</a></span>. This is a convenient way to nest exceptions. There is no limit on the depth of the nesting, however cyclic references result in undefined behavior.</p>
</div><div class="RenoAutoDIV"><div class="RenoHR"><hr/></div>
See also: <span class="RenoPageList"><a href="boost-exception.html">Boost Exception</a>&nbsp;| <a href="boost_exception_errinfo_nested_exception_hpp.html">boost/exception/errinfo_nested_exception.hpp</a>&nbsp;| <a href="boost_exception_ptr_hpp.html">boost/exception_ptr.hpp</a>&nbsp;| <a href="copy_exception.html">copy_exception</a>&nbsp;| <a href="current_exception.html">current_exception</a>&nbsp;| <a href="diagnostic_information.html">diagnostic_information</a>&nbsp;| <a href="enable_current_exception.html">enable_current_exception</a>&nbsp;| <a href="frequently_asked_questions.html">Frequently Asked Questions</a>&nbsp;| <a href="original_exception_type.html">original_exception_type</a>&nbsp;| <a href="rethrow_exception.html">rethrow_exception</a>&nbsp;| <a href="throw_exception.html">throw_exception</a>&nbsp;| <a href="unknown_exception.html">unknown_exception</a></span>
See also: <span class="RenoPageList"><a href="boost-exception.html">Boost Exception</a>&nbsp;| <a href="boost_exception_errinfo_nested_exception_hpp.html">boost/exception/errinfo_nested_exception.hpp</a>&nbsp;| <a href="boost_exception_ptr_hpp.html">boost/exception_ptr.hpp</a>&nbsp;| <a href="copy_exception.html">copy_exception</a>&nbsp;| <a href="current_exception.html">current_exception</a>&nbsp;| <a href="diagnostic_information.html">diagnostic_information</a>&nbsp;| <a href="enable_current_exception.html">enable_current_exception</a>&nbsp;| <a href="original_exception_type.html">original_exception_type</a>&nbsp;| <a href="rethrow_exception.html">rethrow_exception</a>&nbsp;| <a href="throw_exception.html">throw_exception</a>&nbsp;| <a href="unknown_exception.html">unknown_exception</a></span>
</div>
<!-- Copyright (c) 2006-2009 Emil Dotchevski and Reverge Studios, Inc. -->
<!-- Distributed under the Boost Software License, Version 1.0. (See accompanying -->

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@ -21,9 +21,35 @@
<!-- file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) -->
<div class="RenoIncludeDIV"><div class="RenoAutoDIV"><h2>Frequently Asked Questions</h2>
</div>
<h3>What is the cost of calling boost::throw_exception?</h3>
<p>The cost is that boost::<span class="RenoLink"><a href="exception.html">exception</a></span> is added as a base of the exception emitted by boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span> (unless the passed type already derives from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>.)</p>
<p>Calling boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span> does not cause dynamic memory allocations.</p>
<h3>What is the cost of BOOST_THROW_EXCEPTION?</h3>
<p>In addition to calling boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span>, <span class="RenoLink"><a href="BOOST_THROW_EXCEPTION.html">BOOST_THROW_EXCEPTION</a></span> invokes __FILE__, __LINE__ and the <span class="RenoLink"><a href="configuration_macros.html">BOOST_THROW_EXCEPTION_CURRENT_FUNCTION</a></span> macros. The space required to store the information is already included in sizeof(boost::<span class="RenoLink"><a href="exception.html">exception</a></span>).</p>
<p>Calling <span class="RenoLink"><a href="BOOST_THROW_EXCEPTION.html">BOOST_THROW_EXCEPTION</a></span> does not cause dynamic memory allocations.</p>
<h3>Should I use boost::throw_exception or BOOST_THROW_EXCEPTION or just throw?</h3>
<p>The benefit of calling boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span> instead of using throw directly is that it ensures that the emitted exception derives from boost::<span class="RenoLink"><a href="exception.html">exception</a></span> and that it is compatible with boost::<span class="RenoLink"><a href="current_exception.html">current_exception</a></span>.</p>
<p>The <span class="RenoLink"><a href="BOOST_THROW_EXCEPTION.html">BOOST_THROW_EXCEPTION</a></span> macro also results in a call to boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span>, but in addition it records in the exception object the __FILE__ and __LINE__ of the throw, as well as the pretty name of the function that throws. This enables boost::<span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span> to compose a more useful, if not user-friendly message.</p>
<p>Typical use of boost::<span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span> is:</p>
<pre>catch(...)
{
std::cerr &lt;&lt;
"Unexpected exception, diagnostic information follows:\n" &lt;&lt;
<span class="RenoLink"><a href="current_exception_diagnostic_information.html">current_exception_diagnostic_information</a></span>();
}</pre>
<p>This is a possible message it may display -- the information in the first line is only available if <span class="RenoLink"><a href="BOOST_THROW_EXCEPTION.html">BOOST_THROW_EXCEPTION</a></span> was used to throw:</p>
<pre>example_io.cpp(70): Throw in function class boost::shared_ptr&lt;struct _iobuf&gt; __cdecl my_fopen(const char *,const char *)
Dynamic exception type: class boost::exception_detail::clone_impl&lt;class fopen_error&gt;
std::exception::what: example_io error
[struct boost::<span class="RenoLink"><a href="errinfo_api_function.html">errinfo_api_function</a></span>_ *] = fopen
[struct boost::<span class="RenoLink"><a href="errinfo_errno.html">errinfo_errno</a></span>_ *] = 2, "No such file or directory"
[struct boost::<span class="RenoLink"><a href="errinfo_file_name.html">errinfo_file_name</a></span>_ *] = tmp1.txt
[struct boost::<span class="RenoLink"><a href="errinfo_file_open_mode.html">errinfo_file_open_mode</a></span>_ *] = rb</pre>
<p>In some development environments, the first line in that message can be clicked to show the location of the throw in the debugger, so it's easy to set a break point and run again to see the unexpected throw in the context of its call stack.</p>
<h3>Why doesn't boost::exception derive from std::exception?</h3>
<p>Despite that <span class="RenoLink"><a href="using_virtual_inheritance_in_exception_types.html">virtual inheritance should be used in deriving from base exception types</a></span>, many programmers fail to follow this principle when deriving from std::exception. If boost::<span class="RenoLink"><a href="exception.html">exception</a></span> derives from std::exception, using the <span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span> function with such user-defined types would introduce dangerous ambiguity which would break all catch(std::exception &amp;) statements.</p>
<p>Of course, boost::<span class="RenoLink"><a href="exception.html">exception</a></span> should not be used to replace std::exception as a base type in exception type hierarchies. Instead, it should be included as a virtual base, in addition to std::exception (which should also be derived virtually.)</p>
<p>Despite that <span class="RenoLink"><a href="using_virtual_inheritance_in_exception_types.html">virtual inheritance should be used in deriving from base exception types</a></span>, quite often exception types (including the ones defined in the standard library) don't derive from std::exception virtually.</p>
<p>If boost::<span class="RenoLink"><a href="exception.html">exception</a></span> derives from std::exception, using the <span class="RenoLink"><a href="enable_error_info.html">enable_error_info</a></span> function with such user-defined types would introduce dangerous ambiguity which would break all catch(std::exception &amp;) statements.</p>
<p>Of course, boost::<span class="RenoLink"><a href="exception.html">exception</a></span> should not be used to replace std::exception as a base type in exception type hierarchies. Instead, it should be included as a virtual base, in addition to std::exception (which should probably also be derived virtually.)</p>
<h3>Why is boost::exception abstract?</h3>
<p>To prevent exception-neutral contexts from erroneously erasing the type of the original exception when adding <span class="RenoLink"><a href="error_info.html">error_info</a></span> to an active exception object:</p>
<pre>catch( boost::<span class="RenoLink"><a href="exception.html">exception</a></span> &amp; e )
@ -37,51 +63,9 @@
e <span class="RenoLink"><a href="exception_operator_shl.html">&lt;&lt;</a></span> foo_info(foo);
throw; //Okay, re-throwing the original exception object.
}</pre>
<h3>What is the space overhead of the boost::exception base class?</h3>
<p>The space overhead for the boost::exception data members is negligible in the context of exception handling. Throwing objects that derive from boost::<span class="RenoLink"><a href="exception.html">exception</a></span> does not by itself cause dynamic memory allocations.</p>
<p>Deriving from boost::<span class="RenoLink"><a href="exception.html">exception</a></span> enables any data to be added to exceptions, which usually does allocate memory. However, this memory is reclaimed when the exception has been handled, and since typically user code does not allocate memory during the unrolling of the stack, adding error info to exceptions should not cause memory fragmentation.</p>
<h3>What is the speed overhead of the boost::exception base class?</h3>
<p>Throwing objects that derive from boost::exception does not have any speed overhead by itself.</p>
<p>Deriving from boost::<span class="RenoLink"><a href="exception.html">exception</a></span> enables any data to be added to exceptions, which internally uses constructs that can be considered quite heavy (such as std::map and std::string.) This is still negligible compared to the typical overhead of throwing and handling of exceptions.</p>
<h3>Should I use boost::throw_exception or BOOST_THROW_EXCEPTION or just throw?</h3>
<p>The benefit of calling boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span> instead of using throw directly is that it ensures that the emitted exception derives from boost::<span class="RenoLink"><a href="exception.html">exception</a></span> and that it is compatible with boost::<span class="RenoLink"><a href="current_exception.html">current_exception</a></span>.</p>
<p>The <span class="RenoLink"><a href="BOOST_THROW_EXCEPTION.html">BOOST_THROW_EXCEPTION</a></span> macro also results in a call to boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span>, but in addition it records in the exception object the __FILE__ and __LINE__ of the throw, as well as the pretty name of the function that throws. This has virtually no overhead, yet enables boost::<span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span> to compose a more useful, if not user-friendly message.</p>
<p>Typical use of boost::<span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span> is:</p>
<pre>catch( boost::exception &amp; e )
{
std::cerr &lt;&lt; "OMG!" &lt;&lt; boost::diagnostic_information(e);
}
catch( ... )
{
std::cerr &lt;&lt; "OMG!!!";
}</pre>
<p>This is a possible message it may display, the first line is only possible if <span class="RenoLink"><a href="BOOST_THROW_EXCEPTION.html">BOOST_THROW_EXCEPTION</a></span> is used:</p>
<pre>example_io.cpp(70): Throw in function class boost::shared_ptr&lt;struct _iobuf&gt; __cdecl my_fopen(const char *,const char *)
Dynamic exception type: class boost::exception_detail::clone_impl&lt;class fopen_error&gt;
std::exception::what: example_io error
[struct boost::<span class="RenoLink"><a href="errinfo_api_function.html">errinfo_api_function</a></span>_ *] = fopen
[struct boost::<span class="RenoLink"><a href="errinfo_errno.html">errinfo_errno</a></span>_ *] = 2, "No such file or directory"
[struct boost::<span class="RenoLink"><a href="errinfo_file_name.html">errinfo_file_name</a></span>_ *] = tmp1.txt
[struct boost::<span class="RenoLink"><a href="errinfo_file_open_mode.html">errinfo_file_open_mode</a></span>_ *] = rb</pre>
<h3>Why is boost::exception integrated in boost::throw_exception?</h3>
<p>The boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span> function predates the Boost Exception library and there has been some concern about its current behavior of injecting boost::<span class="RenoLink"><a href="exception.html">exception</a></span> as a base of any exception passed to boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span>. Such concerns are dictated by the typical strict interpretation of a common principle in C and C++, that users only pay for features they actually use.</p>
<p>The problem is that users of Boost Exception can't by themselves cause a library to throw types that derive from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>, and without this they can't use any of the Boost Exception facilities.</p>
<p>For example, if a user wants to use Boost Serialization in a separate thread, it is desirable to be able to transport exceptions emitted by that library into the main thread where they can be analyzed to generate a user-friendly message. This can be easily achieved using boost::<span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span>, but this requires that Boost Serialization throws exceptions using boost::<span class="RenoLink"><a href="enable_current_exception.html">enable_current_exception</a></span>. If Boost Serialization calls boost::<span class="RenoLink"><a href="throw_exception.html">throw_exception</a></span> to throw, this behavior happens automatically and transparently.</p>
<p>The cost of this integration is:</p>
<div><ul><li> In terms of space: a pointer and 3 ints are added to the static size of exception objects.</li>
<li> In terms of speed: the pointer is initialized to null at the point of the throw.</li>
<li> In terms of coupling: about 400 self-contained lines of C++ with no external includes.</li>
</ul></div>
<h3>Why use operator&lt;&lt; overload for adding info to exceptions?</h3>
<p>Before throwing an object of type that derives from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>, it is often desirable to add one or more <span class="RenoLink"><a href="error_info.html">error_info</a></span> objects in it. The syntactic sugar provided by <span class="RenoLink"><a href="exception_operator_shl.html">exception/operator&lt;&lt;</a></span> allows this to be done directly in a throw expression:</p>
<p>Before throwing an object of type that derives from boost::<span class="RenoLink"><a href="exception.html">exception</a></span>, it is often desirable to add one or more <span class="RenoLink"><a href="error_info.html">error_info</a></span> objects in it. The syntactic sugar provided by <span class="RenoLink"><a href="exception_operator_shl.html">operator&lt;&lt;</a></span> allows this to be done directly in a throw expression:</p>
<pre>throw error() <span class="RenoLink"><a href="exception_operator_shl.html">&lt;&lt;</a></span> foo_info(foo) <span class="RenoLink"><a href="exception_operator_shl.html">&lt;&lt;</a></span> bar_info(bar);</pre>
<p>which saves typing compared to this possible alternative:</p>
<pre>error e;
e.add(foo_info(foo));
e.add(bar_info(bar));
throw e;</pre>
<p>and looks better than something like:</p>
<pre>throw error().add(foo_info(foo)).add(bar_info(bar));</pre>
<h3>Why is operator&lt;&lt; allowed to throw?</h3>
<p>This question is referring to the following issue. Consider this throw statement example:</p>
<pre>throw file_open_error() <span class="RenoLink"><a href="exception_operator_shl.html">&lt;&lt;</a></span> file_name(fn);</pre>

7589
doc/source/boost-exception.reno
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6
doc/synopsis.html
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@ -103,11 +103,11 @@ boost
<span class="RenoIncludeSPAN"> class <span class="RenoLink"><a href="exception.html">exception</a></span>;</span>
<span class="RenoIncludeSPAN"> <span class="RenoIncludeSPAN">template &lt;class E&gt;
std::string <span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span>( E const &amp; e );
std::string <span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span>( E const &amp; e, bool verbose=true );
std::string <span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span>( <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> const &amp; p );</span>
std::string <span class="RenoLink"><a href="diagnostic_information.html">diagnostic_information</a></span>( <span class="RenoLink"><a href="exception_ptr.html">exception_ptr</a></span> const &amp; p, bool verbose=true );</span>
<span class="RenoIncludeSPAN">char const * <span class="RenoLink"><a href="diagnostic_information_what.html">diagnostic_information_what</a></span>( boost::<span class="RenoLink"><a href="exception.html">exception</a></span> const &amp; e ) throw();</span>
<span class="RenoIncludeSPAN">char const * <span class="RenoLink"><a href="diagnostic_information_what.html">diagnostic_information_what</a></span>( boost::<span class="RenoLink"><a href="exception.html">exception</a></span> const &amp; e, bool verbose=true ) throw();</span>
<span class="RenoIncludeSPAN">std::string <span class="RenoLink"><a href="current_exception_diagnostic_information.html">current_exception_diagnostic_information</a></span>();</span></span>
}</span></pre>

6
include/boost/exception/detail/error_info_impl.hpp
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@ -25,8 +25,7 @@ boost
{
public:
virtual std::string tag_typeid_name() const = 0;
virtual std::string value_as_string() const = 0;
virtual std::string name_value_string() const = 0;
protected:
@ -63,8 +62,7 @@ boost
private:
std::string tag_typeid_name() const;
std::string value_as_string() const;
std::string name_value_string() const;
value_type value_;
};

4
include/boost/exception/detail/exception_ptr.hpp
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@ -467,7 +467,7 @@ boost
inline
std::string
diagnostic_information( exception_ptr const & p )
diagnostic_information( exception_ptr const & p, bool verbose=true )
{
if( p )
try
@ -477,7 +477,7 @@ boost
catch(
... )
{
return current_exception_diagnostic_information();
return current_exception_diagnostic_information(verbose);
}
return "<empty>";
}

27
include/boost/exception/diagnostic_information.hpp
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@ -31,17 +31,17 @@ boost
namespace
exception_detail
{
std::string diagnostic_information_impl( boost::exception const *, std::exception const *, bool );
std::string diagnostic_information_impl( boost::exception const *, std::exception const *, bool, bool );
}
inline
std::string
current_exception_diagnostic_information()
current_exception_diagnostic_information( bool verbose=true)
{
boost::exception const * be=current_exception_cast<boost::exception const>();
std::exception const * se=current_exception_cast<std::exception const>();
if( be || se )
return exception_detail::diagnostic_information_impl(be,se,true);
return exception_detail::diagnostic_information_impl(be,se,true,verbose);
else
return "No diagnostic information available.";
}
@ -107,7 +107,7 @@ boost
inline
std::string
diagnostic_information_impl( boost::exception const * be, std::exception const * se, bool with_what )
diagnostic_information_impl( boost::exception const * be, std::exception const * se, bool with_what, bool verbose )
{
if( !be && !se )
return "Unknown exception.";
@ -125,7 +125,7 @@ boost
return wh;
}
std::ostringstream tmp;
if( be )
if( be && verbose )
{
char const * const * f=get_error_info<throw_file>(*be);
int const * l=get_error_info<throw_line>(*be);
@ -149,36 +149,37 @@ boost
}
}
#ifndef BOOST_NO_RTTI
tmp << std::string("Dynamic exception type: ") <<
units::detail::demangle((be?(BOOST_EXCEPTION_DYNAMIC_TYPEID(*be)):(BOOST_EXCEPTION_DYNAMIC_TYPEID(*se))).type_->name()) << '\n';
if ( verbose )
tmp << std::string("Dynamic exception type: ") <<
units::detail::demangle((be?(BOOST_EXCEPTION_DYNAMIC_TYPEID(*be)):(BOOST_EXCEPTION_DYNAMIC_TYPEID(*se))).type_->name()) << '\n';
#endif
if( with_what && se )
if( with_what && se && verbose )
tmp << "std::exception::what: " << wh << '\n';
if( be )
if( char const * s=exception_detail::get_diagnostic_information(*be,tmp.str().c_str()) )
if( *s )
return s;
return std::string(s);
return tmp.str();
}
}
template <class T>
std::string
diagnostic_information( T const & e )
diagnostic_information( T const & e, bool verbose=true )
{
return exception_detail::diagnostic_information_impl(exception_detail::get_boost_exception(&e),exception_detail::get_std_exception(&e),true);
return exception_detail::diagnostic_information_impl(exception_detail::get_boost_exception(&e),exception_detail::get_std_exception(&e),true,verbose);
}
inline
char const *
diagnostic_information_what( exception const & e ) throw()
diagnostic_information_what( exception const & e, bool verbose=true ) throw()
{
char const * w=0;
#ifndef BOOST_NO_EXCEPTIONS
try
{
#endif
(void) exception_detail::diagnostic_information_impl(&e,0,false);
(void) exception_detail::diagnostic_information_impl(&e,0,false,verbose);
if( char const * di=exception_detail::get_diagnostic_information(e,0) )
return di;
else

25
include/boost/exception/info.hpp
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@ -24,10 +24,18 @@ boost
{
template <class Tag,class T>
inline
typename enable_if<has_to_string<T>,std::string>::type
std::string
error_info_name( error_info<Tag,T> const & x )
{
return tag_type_name<Tag>();
}
template <class Tag,class T>
inline
std::string
to_string( error_info<Tag,T> const & x )
{
return to_string(x.value());
return '[' + error_info_name(x) + "] = " + to_string_stub(x.value()) + '\n';
}
template <class Tag,class T>
@ -49,16 +57,7 @@ boost
inline
std::string
error_info<Tag,T>::
tag_typeid_name() const
{
return tag_type_name<Tag>();
}
template <class Tag,class T>
inline
std::string
error_info<Tag,T>::
value_as_string() const
name_value_string() const
{
return to_string_stub(*this);
}
@ -114,7 +113,7 @@ boost
for( error_info_map::const_iterator i=info_.begin(),end=info_.end(); i!=end; ++i )
{
error_info_base const & x = *i->second;
tmp << '[' << x.tag_typeid_name() << "] = " << x.value_as_string() << '\n';
tmp << x.name_value_string();
}
tmp.str().swap(diagnostic_info_str_);
}

5
test/diagnostic_information_test.cpp
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@ -19,10 +19,7 @@ typedef boost::error_info<struct test_tag2,int> tagged_int2;
std::string
to_string( tagged_int2 const & x )
{
if( x.value()==42 )
return "fourty-two";
else
return "bad value";
return '[' +boost::error_info_name(x) + "] = " + (x.value()==42 ? "fourty-two" : "bad value");
}
struct