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19 <label>libc++abi Info</label>
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24 <label>Quick Links</label>
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34 <!--*********************************************************************-->
35 <h1>"libc++abi" C++ Standard Library Support</h1>
36 <!--*********************************************************************-->
37
38 <p>libc++abi is a new implementation of low level support for a standard
39 C++ library.</p>
40
41 <p>All of the code in libc++abi is <a
42 href="http://llvm.org/docs/DeveloperPolicy.html#license">dual licensed</a>
43 under the MIT license and the UIUC License (a BSD-like license).</p>
44
45 <!--=====================================================================-->
46 <h2 id="goals">Features and Goals</h2>
47 <!--=====================================================================-->
48
49 <ul>
50 <li>Correctness as defined by the C++11 standard.</li>
Sylvestre Ledruf59526d2012-07-20 17:21:42 +0000[diff] [blame]51 <li>Provide a portable sublayer to ease the porting of <a href="http://libcxx.llvm.org/">libc++</a></li>
Howard Hinnant628bfc42011-05-19 23:38:38 +0000[diff] [blame]52 <li>On Mac OS X, be ABI compatible with the existing low-level support.</li>
Howard Hinnantd213ffd2011-05-05 15:27:28 +0000[diff] [blame]53 </ul>
54
55 <!--=====================================================================-->
56 <h2 id="requirements">Platform Support</h2>
57 <!--=====================================================================-->
58
59 <p>libc++abi is known to work on the following platforms, using clang.</p>
60
61 <ul>
Howard Hinnantde2b1092012-08-02 22:06:41 +0000[diff] [blame]62 <li>Darwin</li>
Howard Hinnantd213ffd2011-05-05 15:27:28 +0000[diff] [blame]63 </ul>
64
65 <!--=====================================================================-->
66 <h2 id="dir-structure">Current Status</h2>
67 <!--=====================================================================-->
68
Howard Hinnantde2b1092012-08-02 22:06:41 +0000[diff] [blame]69 <p>libc++abi is complete. <a href="spec.html">Here</a> is a
70 list of functionality.</p>
Howard Hinnantd213ffd2011-05-05 15:27:28 +0000[diff] [blame]71
72 <!--=====================================================================-->
73 <h2>Get it and get involved!</h2>
74 <!--=====================================================================-->
75
76 <p>To check out the code, use:</p>
77
78 <ul>
79 <li><code>svn co http://llvm.org/svn/llvm-project/libcxxabi/trunk libcxxabi</code></li>
80 </ul>
81
82 <p>Send discussions to the
83 (<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">clang mailing list</a>).</p>
84
Marshall Clowc9d6b422014-06-11 16:54:09 +0000[diff] [blame^]85 <!--=====================================================================-->
86 <h2>Frequently asked questions</h2>
87 <!--=====================================================================-->
88
89 <p>Q: Why are the destructors for the standard exception classes defined in libc++abi?
90 They're just empty, can't they be defined inline?</p>
91 <p>A: The destructors for them live in libc++abi because they are "key" functions.
92 The Itanium ABI describes a "key" function as the first virtual declared.
93 And wherever the key function is defined, that is where the <code>type_info</code> gets defined.
94 And in libc++ types are the same type if and only if they have the same <code>type_info</code>
95 (as in there must be only one type info per type in the entire application).
96 And on OS X, libstdc++ and libc++ share these exception types.
97 So to be able to throw in one dylib and catch in another (a <code>std::exception</code> for example),
98 there must be only one <code>std::exception type_info</code> in the entire app.
99 That typeinfo gets laid down beside <code>~exception()</code> in libc++abi (for both libstdc++ and libc++).</p>
100 <p>--Howard Hinnant</p>
Howard Hinnantd213ffd2011-05-05 15:27:28 +0000[diff] [blame]101
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