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++" C++ Standard Library</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++ 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://libcxxabi.llvm.org/">libc++abi</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://llvm.org/svn/llvm-project/libcxx/trunk/">Browse SVN</a> 30 <a href="https://llvm.org/viewvc/llvm-project/libcxx/trunk/">Browse ViewVC</a> 31 </div> 32 </div> 33 34 <div id="content"> 35 <!--*********************************************************************--> 36 <h1>"libc++" C++ Standard Library</h1> 37 <!--*********************************************************************--> 38 39 <p>libc++ is an implementation of the C++ standard library, targeting 40 C++11, C++14 and above.</p> 41 42 <p>All of the code in libc++ is <a 43 href="https://llvm.org/docs/DeveloperPolicy.html#license">dual licensed</a> 44 under the MIT license and the UIUC License (a BSD-like license).</p> 45 46 <!--=====================================================================--> 47 <h2>New Documentation Coming Soon!</h2> 48 <!--=====================================================================--> 49 50 <p> Looking for documentation on how to use, build and test libc++? If so 51 checkout the new libc++ documentation.</p> 52 53 <p><a href="https://libcxx.llvm.org/docs/"> 54 Click here for the new libc++ documentation.</a></p> 55 56 <!--=====================================================================--> 57 <h2 id="goals">Features and Goals</h2> 58 <!--=====================================================================--> 59 60 <ul> 61 <li>Correctness as defined by the C++11 standard.</li> 62 <li>Fast execution.</li> 63 <li>Minimal memory use.</li> 64 <li>Fast compile times.</li> 65 <li>ABI compatibility with gcc's libstdc++ for some low-level features 66 such as exception objects, rtti and memory allocation.</li> 67 <li>Extensive unit tests.</li> 68 </ul> 69 70 <!--=====================================================================--> 71 <h2 id="why">Why a new C++ Standard Library for C++11?</h2> 72 <!--=====================================================================--> 73 74 <p>After its initial introduction, many people have asked "why start a new 75 library instead of contributing to an existing library?" (like Apache's 76 libstdcxx, GNU's libstdc++, STLport, etc). There are many contributing 77 reasons, but some of the major ones are:</p> 78 79 <ul> 80 <li><p>From years of experience (including having implemented the standard 81 library before), we've learned many things about implementing 82 the standard containers which require ABI breakage and fundamental changes 83 to how they are implemented. For example, it is generally accepted that 84 building std::string using the "short string optimization" instead of 85 using Copy On Write (COW) is a superior approach for multicore 86 machines (particularly in C++11, which has rvalue references). Breaking 87 ABI compatibility with old versions of the library was 88 determined to be critical to achieving the performance goals of 89 libc++.</p></li> 90 91 <li><p>Mainline libstdc++ has switched to GPL3, a license which the developers 92 of libc++ cannot use. libstdc++ 4.2 (the last GPL2 version) could be 93 independently extended to support C++11, but this would be a fork of the 94 codebase (which is often seen as worse for a project than starting a new 95 independent one). Another problem with libstdc++ is that it is tightly 96 integrated with G++ development, tending to be tied fairly closely to the 97 matching version of G++.</p> 98 </li> 99 100 <li><p>STLport and the Apache libstdcxx library are two other popular 101 candidates, but both lack C++11 support. Our experience (and the 102 experience of libstdc++ developers) is that adding support for C++11 (in 103 particular rvalue references and move-only types) requires changes to 104 almost every class and function, essentially amounting to a rewrite. 105 Faced with a rewrite, we decided to start from scratch and evaluate every 106 design decision from first principles based on experience.</p> 107 108 <p>Further, both projects are apparently abandoned: STLport 5.2.1 was 109 released in Oct'08, and STDCXX 4.2.1 in May'08.</p> 110 111 </ul> 112 113 <!--=====================================================================--> 114 <h2 id="requirements">Platform Support</h2> 115 <!--=====================================================================--> 116 117 <p> 118 libc++ is known to work on the following platforms, using g++ and 119 clang. Note that functionality provided by <atomic> is only functional with 120 clang. 121 </p> 122 123 <ul> 124 <li>Mac OS X i386</li> 125 <li>Mac OS X x86_64</li> 126 <li>FreeBSD 10+ i386</li> 127 <li>FreeBSD 10+ x86_64</li> 128 <li>FreeBSD 10+ ARM</li> 129 <li>Linux i386</li> 130 <li>Linux x86_64</li> 131 </ul> 132 133 <!--=====================================================================--> 134 <h2 id="dir-structure">Current Status</h2> 135 <!--=====================================================================--> 136 137 <p>libc++ is a 100% complete C++11 implementation on Apple's OS X. </p> 138 <p>LLVM and Clang can self host in C++ and C++11 mode with libc++ on Linux.</p> 139 <p>libc++ is also a 100% complete C++14 implementation. A list of new features and 140 changes for C++14 can be found <a href="cxx1y_status.html">here</a>.</p> 141 <p>libc++'s C++17 implementation is not yet complete. A list of features and changes 142 for C++17 can be found <a href="cxx1z_status.html">here</a>.</p> 143 <p>A list of features and changes for the next C++ standard, known here as 144 "C++2a" (probably to be C++20) can be found <a href="cxx2a_status.html">here</a>.</p> 145 <p>Implementation of the post-C++14 Technical Specifications is in progress. A list of features 146 and the current status of these features can be found <a href="ts1z_status.html">here</a>.</p> 147 <p>As features get moved from the Technical Specifications into the main standard, we 148 will (after a period for migration) remove them from the TS implementation. This 149 process is detailed <a href="TS_deprecation.html">here</a>.</p> 150 151 <!--======================================================================--> 152 <h2 id="buildbots">Build Bots</h2> 153 <!--======================================================================--> 154 <p>The latest libc++ build results can be found at the following locations.</p> 155 <ul> 156 <li><a href="http://lab.llvm.org:8011/console"> 157 Buildbot libc++ builders 158 </a></li> 159 <li><a href="http://lab.llvm.org:8080/green/view/Libcxx/"> 160 Jenkins libc++ builders 161 </a></li> 162 </ul> 163 164 <!--=====================================================================--> 165 <h2>Get it and get involved!</h2> 166 <!--=====================================================================--> 167 168 <p>First please review our 169 <a href="https://llvm.org/docs/DeveloperPolicy.html">Developer's Policy</a>. 170 171 The documentation for building and using libc++ can be found below. 172 <ul> 173 <li><a href="https://libcxx.llvm.org/docs/UsingLibcxx.html"> 174 <b>Using libc++</b></a> 175 Documentation on using the library in your programs</li> 176 <li><a href="https://libcxx.llvm.org/docs/BuildingLibcxx.html"> 177 <b>Building libc++</b></a> 178 Documentation on building the library using CMake</li> 179 <li><a href="https://libcxx.llvm.org/docs/TestingLibcxx.html"> 180 <b>Testing libc++</b></a> 181 Documentation for developers wishing to test the library</li> 182 </ul> 183 184 <!--=====================================================================--> 185 <h3>Notes and Known Issues</h3> 186 <!--=====================================================================--> 187 188 <p> 189 <ul> 190 <li> 191 Building libc++ with <code>-fno-rtti</code> is not supported. However 192 linking against it with <code>-fno-rtti</code> is supported. 193 </li> 194 <li> 195 On OS X v10.8 and older the CMake option 196 <code>-DLIBCXX_LIBCPPABI_VERSION=""</code> must be used during 197 configuration. 198 </li> 199 </ul> 200 </p> 201 202 <p>Send discussions to the 203 <a href="https://lists.llvm.org/mailman/listinfo/libcxx-dev">libc++ mailing list</a>.</p> 204 205 <!--=====================================================================--> 206 <h2>Bug reports and patches</h2> 207 <!--=====================================================================--> 208 209 <p> 210 If you think you've found a bug in libc++, please report it using 211 the <a href="https://bugs.llvm.org/">LLVM Bugzilla</a>. If you're not sure, you 212 can post a message to the <a href="https://lists.llvm.org/mailman/listinfo/libcxx-dev">libcxx-dev</a> 213 mailing list or on IRC. 214 </p> 215 216 <p> 217 If you want to contribute a patch to libc++, the best place for that is 218 <a href="https://llvm.org/docs/Phabricator.html">Phabricator</a>. Please 219 add libcxx-commits as a subscriber. 220 </p> 221 222 <!--=====================================================================--> 223 <h2>Design Documents</h2> 224 <!--=====================================================================--> 225 226 <ul> 227 <li><a href="atomic_design.html"><tt><atomic></tt></a></li> 228 <li><a href="type_traits_design.html"><tt><type_traits></tt></a></li> 229 <li><a href="https://cplusplusmusings.wordpress.com/2012/07/05/clang-and-standard-libraries-on-mac-os-x/">Excellent notes by Marshall Clow</a></li> 230 </ul> 231 232 </div> 233 </body> 234 </html> 235
