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Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]15 <a href="https://llvm.org/">LLVM Home</a>
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]16 </div>
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]17
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]18 <div class="submenu">
19 <label>libc++ Info</label>
20 <a href="/index.html">About</a>
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22
23 <div class="submenu">
24 <label>Quick Links</label>
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]25 <a href="https://lists.llvm.org/mailman/listinfo/cfe-dev">cfe-dev</a>
26 <a href="https://lists.llvm.org/mailman/listinfo/cfe-commits">cfe-commits</a>
Eric Fiselier5d604012017-02-17 08:37:03 +0000[diff] [blame]27 <a href="https://bugs.llvm.org/">Bug Reports</a>
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]28 <a href="https://llvm.org/svn/llvm-project/libcxx/trunk/">Browse SVN</a>
29 <a href="https://llvm.org/viewvc/llvm-project/libcxx/trunk/">Browse ViewVC</a>
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]30 </div>
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32
33<div id="content">
34 <!--*********************************************************************-->
35 <h1>"libc++" C++ Standard Library</h1>
36 <!--*********************************************************************-->
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]37
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]38 <p>libc++ is a new implementation of the C++ standard library, targeting
Howard Hinnantd04724c2012-07-19 15:57:51 +0000[diff] [blame]39 C++11.</p>
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]40
Chris Lattner7b2aacc2010-11-16 21:40:19 +0000[diff] [blame]41 <p>All of the code in libc++ is <a
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]42 href="https://llvm.org/docs/DeveloperPolicy.html#license">dual licensed</a>
Chris Lattner7b2aacc2010-11-16 21:40:19 +0000[diff] [blame]43 under the MIT license and the UIUC License (a BSD-like license).</p>
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]44
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]45 <!--=====================================================================-->
Eric Fiselier35a5b842015-10-14 20:51:33 +0000[diff] [blame]46 <h2>New Documentation Coming Soon!</h2>
47 <!--=====================================================================-->
48
49 <p> Looking for documentation on how to use, build and test libc++? If so
50 checkout the new libc++ documentation.</p>
51
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]52 <p><a href="https://libcxx.llvm.org/docs/">
Eric Fiselier35a5b842015-10-14 20:51:33 +0000[diff] [blame]53 Click here for the new libc++ documentation.</a></p>
54
55 <!--=====================================================================-->
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]56 <h2 id="goals">Features and Goals</h2>
57 <!--=====================================================================-->
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]58
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]59 <ul>
Howard Hinnantd04724c2012-07-19 15:57:51 +0000[diff] [blame]60 <li>Correctness as defined by the C++11 standard.</li>
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]61 <li>Fast execution.</li>
62 <li>Minimal memory use.</li>
63 <li>Fast compile times.</li>
64 <li>ABI compatibility with gcc's libstdc++ for some low-level features
65 such as exception objects, rtti and memory allocation.</li>
66 <li>Extensive unit tests.</li>
67 </ul>
68
69 <!--=====================================================================-->
Marshall Clowb6a04fe2012-11-14 16:31:15 +0000[diff] [blame]70 <h2 id="why">Why a new C++ Standard Library for C++11?</h2>
Chris Lattnere2b07272010-05-12 22:21:15 +0000[diff] [blame]71 <!--=====================================================================-->
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]72
Chris Lattnere2b07272010-05-12 22:21:15 +0000[diff] [blame]73 <p>After its initial introduction, many people have asked "why start a new
74 library instead of contributing to an existing library?" (like Apache's
75 libstdcxx, GNU's libstdc++, STLport, etc). There are many contributing
76 reasons, but some of the major ones are:</p>
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]77
Chris Lattnere2b07272010-05-12 22:21:15 +0000[diff] [blame]78 <ul>
79 <li><p>From years of experience (including having implemented the standard
80 library before), we've learned many things about implementing
81 the standard containers which require ABI breakage and fundamental changes
82 to how they are implemented. For example, it is generally accepted that
83 building std::string using the "short string optimization" instead of
84 using Copy On Write (COW) is a superior approach for multicore
Marshall Clowb6a04fe2012-11-14 16:31:15 +0000[diff] [blame]85 machines (particularly in C++11, which has rvalue references). Breaking
Chris Lattnerc67061b2010-05-12 22:30:22 +0000[diff] [blame]86 ABI compatibility with old versions of the library was
Chris Lattnere2b07272010-05-12 22:21:15 +0000[diff] [blame]87 determined to be critical to achieving the performance goals of
88 libc++.</p></li>
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]89
Chris Lattnere2b07272010-05-12 22:21:15 +0000[diff] [blame]90 <li><p>Mainline libstdc++ has switched to GPL3, a license which the developers
91 of libc++ cannot use. libstdc++ 4.2 (the last GPL2 version) could be
Marshall Clowb6a04fe2012-11-14 16:31:15 +0000[diff] [blame]92 independently extended to support C++11, but this would be a fork of the
Chris Lattnere7bdfe62010-05-12 22:33:00 +0000[diff] [blame]93 codebase (which is often seen as worse for a project than starting a new
94 independent one). Another problem with libstdc++ is that it is tightly
95 integrated with G++ development, tending to be tied fairly closely to the
96 matching version of G++.</p>
Chris Lattnere2b07272010-05-12 22:21:15 +0000[diff] [blame]97 </li>
98
99 <li><p>STLport and the Apache libstdcxx library are two other popular
Marshall Clowb6a04fe2012-11-14 16:31:15 +0000[diff] [blame]100 candidates, but both lack C++11 support. Our experience (and the
Howard Hinnantd04724c2012-07-19 15:57:51 +0000[diff] [blame]101 experience of libstdc++ developers) is that adding support for C++11 (in
Chris Lattnere2b07272010-05-12 22:21:15 +0000[diff] [blame]102 particular rvalue references and move-only types) requires changes to
103 almost every class and function, essentially amounting to a rewrite.
Chris Lattner48035ce2010-05-12 22:34:21 +0000[diff] [blame]104 Faced with a rewrite, we decided to start from scratch and evaluate every
105 design decision from first principles based on experience.</p>
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]106
Chris Lattnere2b07272010-05-12 22:21:15 +0000[diff] [blame]107 <p>Further, both projects are apparently abandoned: STLport 5.2.1 was
108 released in Oct'08, and STDCXX 4.2.1 in May'08.</p>
109
110 </ul>
111
112 <!--=====================================================================-->
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]113 <h2 id="requirements">Platform Support</h2>
114 <!--=====================================================================-->
115
Dan Albertce369362014-08-11 15:12:46 +0000[diff] [blame]116 <p>
117 libc++ is known to work on the following platforms, using g++-4.2 and
118 clang (lack of C++11 language support disables some functionality). Note
119 that functionality provided by &lt;atomic&gt; is only functional with
120 clang.
121 </p>
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]122
Dan Albertce369362014-08-11 15:12:46 +0000[diff] [blame]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 </ul>
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]130
131 <!--=====================================================================-->
132 <h2 id="dir-structure">Current Status</h2>
133 <!--=====================================================================-->
134
Howard Hinnant09ce6822012-11-27 18:52:32 +0000[diff] [blame]135 <p>libc++ is a 100% complete C++11 implementation on Apple's OS X. </p>
Michael J. Spencera86f97e2012-12-31 19:34:21 +0000[diff] [blame]136 <p>LLVM and Clang can self host in C++ and C++11 mode with libc++ on Linux.</p>
Marshall Clowb84b8522018-01-29 21:28:46 +0000[diff] [blame^]137 <p>libc++ is also a 100% complete C++14 implementation. A list of new features and
138 changes for C++14 can be found <a href="cxx1y_status.html">here</a>.</p>
139 <p>libc++'s C++17 implementation is not yet complete. A list of features and changes
140 for C++17 can be found <a href="cxx1z_status.html">here</a>.</p>
Marshall Clow5ac35df2014-11-10 15:43:20 +0000[diff] [blame]141 <p>A list of features and changes for the next C++ standard, known here as
Marshall Clowa413f582017-07-16 23:59:23 +0000[diff] [blame]142 "C++2a" (probably to be C++20) can be found <a href="cxx2a_status.html">here</a>.</p>
Marshall Clowb84b8522018-01-29 21:28:46 +0000[diff] [blame^]143 <p>Implementation of the post-C++14 Technical Specifications is in progress. A list of features
144 and the current status of these features can be found <a href="ts1z_status.html">here</a>.</p>
145 <p>As features get moved from the Technical Specifications into the main standard, we
146 will (after a period for migration) remove them from the TS implementation. This
147 process is detailed <a href="TS_deprecation.html">here</a>.</p>
Howard Hinnant2347d2f2011-09-28 15:44:39 +0000[diff] [blame]148
Eric Fiselierdc770102014-08-18 05:25:04 +0000[diff] [blame]149 <!--======================================================================-->
Dan Albert66ddf1f2015-01-30 22:33:41 +0000[diff] [blame]150 <h2 id="buildbots">Build Bots</h2>
Eric Fiselierdc770102014-08-18 05:25:04 +0000[diff] [blame]151 <!--======================================================================-->
Eric Fiselierf4e7fc22014-12-09 22:53:21 +0000[diff] [blame]152 <p>The latest libc++ build results can be found at the following locations.</p>
Eric Fiselierdc770102014-08-18 05:25:04 +0000[diff] [blame]153 <ul>
Eric Fiselierf4e7fc22014-12-09 22:53:21 +0000[diff] [blame]154 <li><a href="http://lab.llvm.org:8011/console">
155 Buildbot libc++ builders
Eric Fiselierdc770102014-08-18 05:25:04 +0000[diff] [blame]156 </a></li>
Eric Fiselierf4e7fc22014-12-09 22:53:21 +0000[diff] [blame]157 <li><a href="http://lab.llvm.org:8080/green/view/Libcxx/">
158 Jenkins libc++ builders
Eric Fiselier7b7ef162014-10-16 02:48:59 +0000[diff] [blame]159 </a></li>
Eric Fiselierdc770102014-08-18 05:25:04 +0000[diff] [blame]160 </ul>
161
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]162 <!--=====================================================================-->
163 <h2>Get it and get involved!</h2>
164 <!--=====================================================================-->
Howard Hinnant3e1b0422010-08-22 01:04:38 +0000[diff] [blame]165
Howard Hinnantf0721aa2011-09-30 16:58:02 +0000[diff] [blame]166 <p>First please review our
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]167 <a href="https://llvm.org/docs/DeveloperPolicy.html">Developer's Policy</a>.
Howard Hinnantf0721aa2011-09-30 16:58:02 +0000[diff] [blame]168
Eric Fiseliera0733922016-06-02 02:16:28 +0000[diff] [blame]169 The documentation for building and using libc++ can be found below.
170 <ul>
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]171 <li><a href="https://libcxx.llvm.org/docs/UsingLibcxx.html">
Eric Fiseliera0733922016-06-02 02:16:28 +0000[diff] [blame]172 <b>Using libc++</b></a>
173 Documentation on using the library in your programs</li>
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]174 <li><a href="https://libcxx.llvm.org/docs/BuildingLibcxx.html">
Eric Fiseliera0733922016-06-02 02:16:28 +0000[diff] [blame]175 <b>Building libc++</b></a>
176 Documentation on building the library using CMake</li>
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]177 <li><a href="https://libcxx.llvm.org/docs/TestingLibcxx.html">
Eric Fiseliera0733922016-06-02 02:16:28 +0000[diff] [blame]178 <b>Testing libc++</b></a>
179 Documentation for developers wishing to test the library</li>
180 </ul>
Dan Albertce369362014-08-11 15:12:46 +0000[diff] [blame]181
182 <!--=====================================================================-->
Eric Fiselier24186c72015-05-12 22:55:30 +0000[diff] [blame]183 <h3>Notes and Known Issues</h3>
Dan Albertce369362014-08-11 15:12:46 +0000[diff] [blame]184 <!--=====================================================================-->
185
186 <p>
Eric Fiselier24186c72015-05-12 22:55:30 +0000[diff] [blame]187 <ul>
188 <li>
189 Building libc++ with <code>-fno-rtti</code> is not supported. However
190 linking against it with <code>-fno-rtti</code> is supported.
191 </li>
192 <li>
193 On OS X v10.8 and older the CMake option
194 <code>-DLIBCXX_LIBCPPABI_VERSION=""</code> must be used during
195 configuration.
196 </li>
197 </ul>
Dan Albertce369362014-08-11 15:12:46 +0000[diff] [blame]198 </p>
199
200 <p>Send discussions to the
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]201 <a href="https://lists.llvm.org/mailman/listinfo/cfe-dev">clang mailing list</a>.</p>
Dan Albertce369362014-08-11 15:12:46 +0000[diff] [blame]202
203 <!--=====================================================================-->
Marshall Clowf7cc9a12014-04-03 03:13:12 +0000[diff] [blame]204 <h2>Bug reports and patches</h2>
205 <!--=====================================================================-->
206
Dan Albert66ddf1f2015-01-30 22:33:41 +0000[diff] [blame]207 <p>
208 If you think you've found a bug in libc++, please report it using
Stephan T. Lavavej9d889652017-08-31 17:59:46 +0000[diff] [blame]209 the <a href="https://bugs.llvm.org/">LLVM Bugzilla</a>. If you're not sure, you
Stephan T. Lavavejff510982017-08-31 17:59:48 +0000[diff] [blame]210 can post a message to the <a href="https://lists.llvm.org/mailman/listinfo/cfe-dev">cfe-dev</a>
Dan Albert66ddf1f2015-01-30 22:33:41 +0000[diff] [blame]211 mailing list or on IRC. Please include "libc++" in your subject.
212 </p>
Marshall Clowf7cc9a12014-04-03 03:13:12 +0000[diff] [blame]213
Dan Albert66ddf1f2015-01-30 22:33:41 +0000[diff] [blame]214 <p>
215 If you want to contribute a patch to libc++, the best place for that is
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]216 <a href="https://llvm.org/docs/Phabricator.html">Phabricator</a>. Please
Dan Albert66ddf1f2015-01-30 22:33:41 +0000[diff] [blame]217 include [libc++] in the subject and add cfe-commits as a subscriber.
218 </p>
Marshall Clowf7cc9a12014-04-03 03:13:12 +0000[diff] [blame]219
220 <!--=====================================================================-->
Howard Hinnantbded6c92010-10-05 16:44:40 +0000[diff] [blame]221 <h2>Design Documents</h2>
222 <!--=====================================================================-->
223
224<ul>
225<li><a href="atomic_design.html"><tt>&lt;atomic&gt;</tt></a></li>
Howard Hinnante20b8de2010-11-19 01:38:58 +0000[diff] [blame]226<li><a href="type_traits_design.html"><tt>&lt;type_traits&gt;</tt></a></li>
Stephan T. Lavavej1e7fbda2017-08-31 17:59:42 +0000[diff] [blame]227<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>
Howard Hinnantbded6c92010-10-05 16:44:40 +0000[diff] [blame]228</ul>
229
Howard Hinnantc51e1022010-05-11 19:42:16 +0000[diff] [blame]230</div>
231</body>
Chris Lattnere66f1e32010-05-11 20:37:52 +0000[diff] [blame]232</html>