• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
2          "http://www.w3.org/TR/html4/strict.dtd">
3<!-- Material used from: HTML 4.01 specs: http://www.w3.org/TR/html401/ -->
4<html>
5<head>
6  <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
7  <title>"libc++abi" C++ Standard Library Support</title>
8  <link type="text/css" rel="stylesheet" href="menu.css">
9  <link type="text/css" rel="stylesheet" href="content.css">
10</head>
11
12<body>
13<div id="menu">
14  <div>
15    <a href="https://llvm.org/">LLVM Home</a>
16  </div>
17
18  <div class="submenu">
19    <label>libc++abi Info</label>
20    <a href="/index.html">About</a>
21  </div>
22
23  <div class="submenu">
24    <label>Quick Links</label>
25    <a href="https://libcxx.llvm.org/">libc++</a>
26    <a href="https://lists.llvm.org/mailman/listinfo/libcxx-dev">libcxx-dev</a>
27    <a href="https://lists.llvm.org/mailman/listinfo/libcxx-commits">libcxx-commits</a>
28    <a href="https://bugs.llvm.org/">Bug Reports</a>
29    <a href="https://github.com/llvm/llvm-project/tree/master/libcxxabi/">Browse Sources</a>
30  </div>
31</div>
32
33<div id="content">
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="https://llvm.org/docs/DeveloperPolicy.html#copyright-license-and-patents">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>
51        <li>Provide a portable sublayer to ease the porting of <a href="https://libcxx.llvm.org/">libc++</a></li>
52        <li>On Mac OS X, be ABI compatible with the existing low-level support.</li>
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>
62    <li>Darwin</li>
63    </ul>
64
65  <!--=====================================================================-->
66  <h2 id="dir-structure">Current Status</h2>
67  <!--=====================================================================-->
68
69   <p>libc++abi is complete.  <a href="spec.html">Here</a> is a
70   list of functionality.</p>
71
72  <!--=====================================================================-->
73  <h2>Get it and get involved!</h2>
74  <!--=====================================================================-->
75
76  <p>To check out the code (including llvm and others), use:</p>
77
78  <ul>
79  <li><code>git clone https://github.com/llvm/llvm-project.git</code></li>
80  </ul>
81
82  <p>To build:</p>
83  <ul>
84  <li><code>cd llvm-project</code></li>
85  <li><code>mkdir build &amp;&amp; cd build</code></li>
86  <li><code>cmake -DLLVM_ENABLE_PROJECTS=libcxxabi ../llvm # on linux you may need to specify -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++</code></li>
87  <li><code>make</code></li>
88  </ul>
89
90  <p>To do a standalone build:</p>
91  <ul>
92  <li>
93    Check out the source tree. This includes the other subprojects, but you'll only use the libcxxabi part.
94  </li>
95  <li><code>cd llvm-project</code></li>
96  <li><code>mkdir build-libcxxabi &amp;&amp; cd build-libcxxabi</code></li>
97  <li><code>cmake ../libcxxabi # on linux you may need -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++</code></li>
98  <li><code>make</code></li>
99  </ul>
100  <p> By default CMake uses <code>llvm-config</code> to locate the required
101      LLVM sources. If CMake cannot find <code>llvm-config</code> then you must
102      configure CMake using either of the following options.
103  </p>
104  <ul>
105  <li><code>-DLLVM_CONFIG_PATH=path/to/llvm-config</code></li>
106  <li><code>-DLLVM_PATH=path/to/llvm-source-root</code></li>
107  </ul>
108
109  </p>
110
111  <p>To run the tests:</p>
112  <ul>
113  <li><code>make check-cxxabi</code></li>
114  </ul>
115  <p>Note: in a standalone build, the system's libc++ will be used for tests. If
116  the system's libc++ was statically linked against libc++abi (or linked against
117  a different ABI library), this may interfere with test results.</p>
118
119  <p>Send discussions to the
120  (<a href="https://lists.llvm.org/mailman/listinfo/libcxx-dev">libcxx-dev mailing list</a>).</p>
121
122  <!--=====================================================================-->
123  <h2>Frequently asked questions</h2>
124  <!--=====================================================================-->
125
126  <p>Q: Why are the destructors for the standard exception classes defined in libc++abi?
127     They're just empty, can't they be defined inline?</p>
128  <p>A: The destructors for them live in libc++abi because they are "key" functions.
129     The Itanium ABI describes a "key" function as the first virtual declared.
130     And wherever the key function is defined, that is where the <code>type_info</code> gets defined.
131     And in libc++ types are the same type if and only if they have the same <code>type_info</code>
132     (as in there must be only one type info per type in the entire application).
133     And on OS X, libstdc++ and libc++ share these exception types.
134     So to be able to throw in one dylib and catch in another (a <code>std::exception</code> for example),
135     there must be only one <code>std::exception type_info</code> in the entire app.
136     That typeinfo gets laid down beside <code>~exception()</code> in libc++abi (for both libstdc++ and libc++).</p>
137     <p>--Howard Hinnant</p>
138
139</div>
140</body>
141</html>
142