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

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