gcc-4_8-branch/libstdc++-v3/doc/html/manual/ext_demangling.html

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   3   Extensions
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   6     Transforming C++ ABI identifiers (like RTTI symbols) into the
   7     original C++ source identifiers is called
   8     <span class="quote">“<span class="quote">demangling.</span>”</span>
   9   </p><p>
  10     If you have read the <a class="link" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/a01115.html" target="_top">source
  11     documentation for <code class="code">namespace abi</code></a> then you are
  12     aware of the cross-vendor C++ ABI in use by GCC.  One of the
  13     exposed functions is used for demangling,
  14     <code class="code">abi::__cxa_demangle</code>.
  15   </p><p>
  16     In programs like <span class="command"><strong>c++filt</strong></span>, the linker, and other tools
  17     have the ability to decode C++ ABI names, and now so can you.
  18   </p><p>
  19     (The function itself might use different demanglers, but that's the
  20     whole point of abstract interfaces.  If we change the implementation,
  21     you won't notice.)
  22   </p><p>
  23     Probably the only times you'll be interested in demangling at runtime
  24     are when you're seeing <code class="code">typeid</code> strings in RTTI, or when
  25     you're handling the runtime-support exception classes.  For example:
  26   </p><pre class="programlisting">
  27 #include &lt;exception&gt;
  28 #include &lt;iostream&gt;
  29 #include &lt;cxxabi.h&gt;
  30
  31 struct empty { };
  32
  33 template &lt;typename T, int N&gt;
  34   struct bar { };
  35
  36
  37 int main()
  38 {
  39   int     status;
  40   char   *realname;
  41
  42   // exception classes not in &lt;stdexcept&gt;, thrown by the implementation
  43   // instead of the user
  44   std::bad_exception  e;
  45   realname = abi::__cxa_demangle(e.what(), 0, 0, &amp;status);
  46   std::cout &lt;&lt; e.what() &lt;&lt; "\t=&gt; " &lt;&lt; realname &lt;&lt; "\t: " &lt;&lt; status &lt;&lt; '\n';
  47   free(realname);
  48
  49
  50   // typeid
  51   bar&lt;empty,17&gt;          u;
  52   const std::type_info  &amp;ti = typeid(u);
  53
  54   realname = abi::__cxa_demangle(ti.name(), 0, 0, &amp;status);
  55   std::cout &lt;&lt; ti.name() &lt;&lt; "\t=&gt; " &lt;&lt; realname &lt;&lt; "\t: " &lt;&lt; status &lt;&lt; '\n';
  56   free(realname);
  57
  58   return 0;
  59 }
  60    </pre><p>
  61      This prints
  62    </p><pre class="screen">
  63    <code class="computeroutput">
  64       St13bad_exception       =&gt; std::bad_exception   : 0
  65       3barI5emptyLi17EE       =&gt; bar&lt;empty, 17&gt;       : 0
  66    </code>
  67    </pre><p>
  68      The demangler interface is described in the source documentation
  69      linked to above.  It is actually written in C, so you don't need to
  70      be writing C++ in order to demangle C++.  (That also means we have to
  71      use crummy memory management facilities, so don't forget to free()
  72      the returned char array.)
  73    </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ext_io.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="extensions.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ext_concurrency.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 28. Input and Output </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 30. Concurrency</td></tr></table></div></body></html>