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 && 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 && 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