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4 Transforming C++ ABI identifiers (like RTTI symbols) into the
5 original C++ source identifiers is called
6 “<span class="quote">demangling.</span>”
8 If you have read the <a class="ulink" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/namespaceabi.html" target="_top">source
9 documentation for <code class="code">namespace abi</code></a> then you are
10 aware of the cross-vendor C++ ABI in use by GCC. One of the
11 exposed functions is used for demangling,
12 <code class="code">abi::__cxa_demangle</code>.
14 In programs like <span class="command"><strong>c++filt</strong></span>, the linker, and other tools
15 have the ability to decode C++ ABI names, and now so can you.
17 (The function itself might use different demanglers, but that's the
18 whole point of abstract interfaces. If we change the implementation,
21 Probably the only times you'll be interested in demangling at runtime
22 are when you're seeing <code class="code">typeid</code> strings in RTTI, or when
23 you're handling the runtime-support exception classes. For example:
24 </p><pre class="programlisting">
25 #include <exception>
26 #include <iostream>
27 #include <cxxabi.h>
31 template <typename T, int N>
40 // exception classes not in <stdexcept>, thrown by the implementation
41 // instead of the user
43 realname = abi::__cxa_demangle(e.what(), 0, 0, &status);
44 std::cout << e.what() << "\t=> " << realname << "\t: " << status << '\n';
49 bar<empty,17> u;
50 const std::type_info &ti = typeid(u);
52 realname = abi::__cxa_demangle(ti.name(), 0, 0, &status);
53 std::cout << ti.name() << "\t=> " << realname << "\t: " << status << '\n';
60 </p><pre class="screen">
61 <code class="computeroutput">
62 St13bad_exception => std::bad_exception : 0
63 3barI5emptyLi17EE => bar<empty, 17> : 0
66 The demangler interface is described in the source documentation
67 linked to above. It is actually written in C, so you don't need to
68 be writing C++ in order to demangle C++. (That also means we have to
69 use crummy memory management facilities, so don't forget to free()
70 the returned char array.)
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