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1 | <?xml version="1.0" encoding="UTF-8" standalone="no"?> |
| 2 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> | |
| 3 | <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 39. Demangling</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><meta name="keywords" content=" ISO C++ , library " /><link rel="start" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="extensions.html" title="Part XII. Extensions" /><link rel="prev" href="bk01pt12ch38.html" title="Chapter 38. Input and Output" /><link rel="next" href="concurrency.html" title="Chapter 40. Concurrency" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 39. Demangling</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bk01pt12ch38.html">Prev</a> </td><th width="60%" align="center">Part XII. Extensions</th><td width="20%" align="right"> <a accesskey="n" href="concurrency.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.demangle"></a>Chapter 39. Demangling</h2></div></div></div><p> | |
| 4394b61e | 4 | Transforming C++ ABI identifiers (like RTTI symbols) into the |
| 46abada0 BK |
5 | original C++ source identifiers is called |
| 6 | “<span class="quote">demangling.</span>” | |
| 7 | </p><p> | |
| 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>. | |
| 13 | </p><p> | |
| 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. | |
| 16 | </p><p> | |
| 17 | (The function itself might use different demanglers, but that's the | |
| 18 | whole point of abstract interfaces. If we change the implementation, | |
| 19 | you won't notice.) | |
| 20 | </p><p> | |
| 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> | |
| 28 | ||
| 29 | struct empty { }; | |
| 30 | ||
| 31 | template <typename T, int N> | |
| 32 | struct bar { }; | |
| 33 | ||
| 34 | ||
| 35 | int main() | |
| 36 | { | |
| 37 | int status; | |
| 38 | char *realname; | |
| 39 | ||
| 40 | // exception classes not in <stdexcept>, thrown by the implementation | |
| 41 | // instead of the user | |
| 42 | std::bad_exception e; | |
| 43 | realname = abi::__cxa_demangle(e.what(), 0, 0, &status); | |
| 44 | std::cout << e.what() << "\t=> " << realname << "\t: " << status << '\n'; | |
| 45 | free(realname); | |
| 46 | ||
| 47 | ||
| 48 | // typeid | |
| 49 | bar<empty,17> u; | |
| 50 | const std::type_info &ti = typeid(u); | |
| 51 | ||
| 52 | realname = abi::__cxa_demangle(ti.name(), 0, 0, &status); | |
| 53 | std::cout << ti.name() << "\t=> " << realname << "\t: " << status << '\n'; | |
| 54 | free(realname); | |
| 55 | ||
| 56 | return 0; | |
| 57 | } | |
| 58 | </pre><p> | |
| 59 | This prints | |
| 60 | </p><pre class="screen"> | |
| 61 | <code class="computeroutput"> | |
| 62 | St13bad_exception => std::bad_exception : 0 | |
| 63 | 3barI5emptyLi17EE => bar<empty, 17> : 0 | |
| 64 | </code> | |
| 65 | </pre><p> | |
| 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.) | |
| 71 | </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bk01pt12ch38.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="concurrency.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 38. 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 40. Concurrency</td></tr></table></div></body></html> |