libstdc++-v3/doc/html/manual/ext_demangling.html

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