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Stephan T. Lavavej69c2e132017-08-31 17:59:42 +0000[diff] [blame]15 <a href="https://llvm.org/">LLVM Home</a>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]16 </div>
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]17
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]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>
Sylvestre Ledru8e5a0b12018-09-20 07:58:43 +0000[diff] [blame]25 <a href="https://libcxxabi.llvm.org/">libc++abi</a>
Eric Fiselier0ef540b2018-09-22 19:49:29 +0000[diff] [blame]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>
Eric Fiselier3c354912017-02-17 08:37:03 +0000[diff] [blame]28 <a href="https://bugs.llvm.org/">Bug Reports</a>
James Y Knight5d71fc52019-01-29 16:37:27 +0000[diff] [blame]29 <a href="https://github.com/llvm/llvm-project/tree/master/libcxx/">Browse Sources</a>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]30 </div>
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33<div id="content">
34 <!--*********************************************************************-->
35 <h1>"libc++" C++ Standard Library</h1>
36 <!--*********************************************************************-->
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]37
Sylvestre Ledru0296eea2018-09-20 07:57:31 +0000[diff] [blame]38 <p>libc++ is an implementation of the C++ standard library, targeting
39 C++11, C++14 and above.</p>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]40
Chris Lattner58dffe62010-11-16 21:40:19 +0000[diff] [blame]41 <p>All of the code in libc++ is <a
Stephan T. Lavavej2e4f1e12019-10-23 16:42:47 -0700[diff] [blame]42 href="https://llvm.org/docs/DeveloperPolicy.html#copyright-license-and-patents">dual licensed</a>
Chris Lattner58dffe62010-11-16 21:40:19 +0000[diff] [blame]43 under the MIT license and the UIUC License (a BSD-like license).</p>
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]44
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]45 <!--=====================================================================-->
Eric Fiselier9da4c8e2015-10-14 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. Lavavej69c2e132017-08-31 17:59:42 +0000[diff] [blame]52 <p><a href="https://libcxx.llvm.org/docs/">
Eric Fiselier9da4c8e2015-10-14 20:51:33 +0000[diff] [blame]53 Click here for the new libc++ documentation.</a></p>
54
55 <!--=====================================================================-->
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]56 <h2 id="goals">Features and Goals</h2>
57 <!--=====================================================================-->
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]58
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]59 <ul>
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]60 <li>Correctness as defined by the C++11 standard.</li>
Howard Hinnant3e519522010-05-11 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 Clow497d9d22012-11-14 16:31:15 +0000[diff] [blame]70 <h2 id="why">Why a new C++ Standard Library for C++11?</h2>
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]71 <!--=====================================================================-->
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]72
Chris Lattner27de3d62010-05-12 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 Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]77
Chris Lattner27de3d62010-05-12 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 Clow497d9d22012-11-14 16:31:15 +0000[diff] [blame]85 machines (particularly in C++11, which has rvalue references). Breaking
Chris Lattnerf005e8d2010-05-12 22:30:22 +0000[diff] [blame]86 ABI compatibility with old versions of the library was
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]87 determined to be critical to achieving the performance goals of
88 libc++.</p></li>
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]89
Chris Lattner27de3d62010-05-12 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 Clow497d9d22012-11-14 16:31:15 +0000[diff] [blame]92 independently extended to support C++11, but this would be a fork of the
Chris Lattnera940b5b2010-05-12 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 Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]97 </li>
98
99 <li><p>STLport and the Apache libstdcxx library are two other popular
Marshall Clow497d9d22012-11-14 16:31:15 +0000[diff] [blame]100 candidates, but both lack C++11 support. Our experience (and the
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]101 experience of libstdc++ developers) is that adding support for C++11 (in
Chris Lattner27de3d62010-05-12 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 Lattnerd55fd112010-05-12 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 Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]106
Chris Lattner27de3d62010-05-12 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 Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]113 <h2 id="requirements">Platform Support</h2>
114 <!--=====================================================================-->
115
Dan Albertec4de782014-08-11 15:12:46 +0000[diff] [blame]116 <p>
Sylvestre Ledru0296eea2018-09-20 07:57:31 +0000[diff] [blame]117 libc++ is known to work on the following platforms, using g++ and
118 clang. Note that functionality provided by &lt;atomic&gt; is only functional with
Dan Albertec4de782014-08-11 15:12:46 +0000[diff] [blame]119 clang.
120 </p>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]121
Dan Albertec4de782014-08-11 15:12:46 +0000[diff] [blame]122 <ul>
123 <li>Mac OS X i386</li>
124 <li>Mac OS X x86_64</li>
125 <li>FreeBSD 10+ i386</li>
126 <li>FreeBSD 10+ x86_64</li>
127 <li>FreeBSD 10+ ARM</li>
Sylvestre Ledru0296eea2018-09-20 07:57:31 +0000[diff] [blame]128 <li>Linux i386</li>
129 <li>Linux x86_64</li>
Dan Albertec4de782014-08-11 15:12:46 +0000[diff] [blame]130 </ul>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]131
132 <!--=====================================================================-->
133 <h2 id="dir-structure">Current Status</h2>
134 <!--=====================================================================-->
135
Howard Hinnant6852b552012-11-27 18:52:32 +0000[diff] [blame]136 <p>libc++ is a 100% complete C++11 implementation on Apple's OS X. </p>
Michael J. Spencerbb8cfd02012-12-31 19:34:21 +0000[diff] [blame]137 <p>LLVM and Clang can self host in C++ and C++11 mode with libc++ on Linux.</p>
Marshall Clow6f73cf42018-01-29 21:28:46 +0000[diff] [blame]138 <p>libc++ is also a 100% complete C++14 implementation. A list of new features and
139 changes for C++14 can be found <a href="cxx1y_status.html">here</a>.</p>
140 <p>libc++'s C++17 implementation is not yet complete. A list of features and changes
141 for C++17 can be found <a href="cxx1z_status.html">here</a>.</p>
Marshall Clow68640682014-11-10 15:43:20 +0000[diff] [blame]142 <p>A list of features and changes for the next C++ standard, known here as
Marshall Clow5820ae42017-07-16 23:59:23 +0000[diff] [blame]143 "C++2a" (probably to be C++20) can be found <a href="cxx2a_status.html">here</a>.</p>
Marshall Clow6f73cf42018-01-29 21:28:46 +0000[diff] [blame]144 <p>Implementation of the post-C++14 Technical Specifications is in progress. A list of features
145 and the current status of these features can be found <a href="ts1z_status.html">here</a>.</p>
146 <p>As features get moved from the Technical Specifications into the main standard, we
147 will (after a period for migration) remove them from the TS implementation. This
Louis Dionne776acf22019-06-11 14:48:40 +0000[diff] [blame]148 process is detailed <a href="DesignDocs/ExperimentalFeatures.html">here</a>.</p>
Howard Hinnantd7aac282011-09-28 15:44:39 +0000[diff] [blame]149
Eric Fiseliercd6ac3a2014-08-18 05:25:04 +0000[diff] [blame]150 <!--======================================================================-->
Dan Albert2477bed2015-01-30 22:33:41 +0000[diff] [blame]151 <h2 id="buildbots">Build Bots</h2>
Eric Fiseliercd6ac3a2014-08-18 05:25:04 +0000[diff] [blame]152 <!--======================================================================-->
Eric Fiselierf60e4412014-12-09 22:53:21 +0000[diff] [blame]153 <p>The latest libc++ build results can be found at the following locations.</p>
Eric Fiseliercd6ac3a2014-08-18 05:25:04 +0000[diff] [blame]154 <ul>
Eric Fiselierf60e4412014-12-09 22:53:21 +0000[diff] [blame]155 <li><a href="http://lab.llvm.org:8011/console">
156 Buildbot libc++ builders
Eric Fiseliercd6ac3a2014-08-18 05:25:04 +0000[diff] [blame]157 </a></li>
Eric Fiselierf60e4412014-12-09 22:53:21 +0000[diff] [blame]158 <li><a href="http://lab.llvm.org:8080/green/view/Libcxx/">
159 Jenkins libc++ builders
Eric Fiselier8c5bc1c2014-10-16 02:48:59 +0000[diff] [blame]160 </a></li>
Eric Fiseliercd6ac3a2014-08-18 05:25:04 +0000[diff] [blame]161 </ul>
162
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]163 <!--=====================================================================-->
164 <h2>Get it and get involved!</h2>
165 <!--=====================================================================-->
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]166
Howard Hinnant4f4d3102011-09-30 16:58:02 +0000[diff] [blame]167 <p>First please review our
Stephan T. Lavavej69c2e132017-08-31 17:59:42 +0000[diff] [blame]168 <a href="https://llvm.org/docs/DeveloperPolicy.html">Developer's Policy</a>.
Howard Hinnant4f4d3102011-09-30 16:58:02 +0000[diff] [blame]169
Eric Fiseliere44604a2016-06-02 02:16:28 +0000[diff] [blame]170 The documentation for building and using libc++ can be found below.
171 <ul>
Stephan T. Lavavej69c2e132017-08-31 17:59:42 +0000[diff] [blame]172 <li><a href="https://libcxx.llvm.org/docs/UsingLibcxx.html">
Eric Fiseliere44604a2016-06-02 02:16:28 +0000[diff] [blame]173 <b>Using libc++</b></a>
174 Documentation on using the library in your programs</li>
Stephan T. Lavavej69c2e132017-08-31 17:59:42 +0000[diff] [blame]175 <li><a href="https://libcxx.llvm.org/docs/BuildingLibcxx.html">
Eric Fiseliere44604a2016-06-02 02:16:28 +0000[diff] [blame]176 <b>Building libc++</b></a>
177 Documentation on building the library using CMake</li>
Stephan T. Lavavej69c2e132017-08-31 17:59:42 +0000[diff] [blame]178 <li><a href="https://libcxx.llvm.org/docs/TestingLibcxx.html">
Eric Fiseliere44604a2016-06-02 02:16:28 +0000[diff] [blame]179 <b>Testing libc++</b></a>
180 Documentation for developers wishing to test the library</li>
181 </ul>
Dan Albertec4de782014-08-11 15:12:46 +0000[diff] [blame]182
183 <!--=====================================================================-->
Eric Fiselier9243c762015-05-12 22:55:30 +0000[diff] [blame]184 <h3>Notes and Known Issues</h3>
Dan Albertec4de782014-08-11 15:12:46 +0000[diff] [blame]185 <!--=====================================================================-->
186
187 <p>
Eric Fiselier9243c762015-05-12 22:55:30 +0000[diff] [blame]188 <ul>
189 <li>
190 Building libc++ with <code>-fno-rtti</code> is not supported. However
191 linking against it with <code>-fno-rtti</code> is supported.
192 </li>
Eric Fiselier9243c762015-05-12 22:55:30 +0000[diff] [blame]193 </ul>
Dan Albertec4de782014-08-11 15:12:46 +0000[diff] [blame]194 </p>
195
196 <p>Send discussions to the
Eric Fiselier0ef540b2018-09-22 19:49:29 +0000[diff] [blame]197 <a href="https://lists.llvm.org/mailman/listinfo/libcxx-dev">libc++ mailing list</a>.</p>
Dan Albertec4de782014-08-11 15:12:46 +0000[diff] [blame]198
199 <!--=====================================================================-->
Marshall Clow17c6aa02014-04-03 03:13:12 +0000[diff] [blame]200 <h2>Bug reports and patches</h2>
201 <!--=====================================================================-->
202
Dan Albert2477bed2015-01-30 22:33:41 +0000[diff] [blame]203 <p>
204 If you think you've found a bug in libc++, please report it using
Stephan T. Lavavej98fa5d42017-08-31 17:59:46 +0000[diff] [blame]205 the <a href="https://bugs.llvm.org/">LLVM Bugzilla</a>. If you're not sure, you
Eric Fiselier0ef540b2018-09-22 19:49:29 +0000[diff] [blame]206 can post a message to the <a href="https://lists.llvm.org/mailman/listinfo/libcxx-dev">libcxx-dev</a>
207 mailing list or on IRC.
Dan Albert2477bed2015-01-30 22:33:41 +0000[diff] [blame]208 </p>
Marshall Clow17c6aa02014-04-03 03:13:12 +0000[diff] [blame]209
Dan Albert2477bed2015-01-30 22:33:41 +0000[diff] [blame]210 <p>
211 If you want to contribute a patch to libc++, the best place for that is
Stephan T. Lavavej69c2e132017-08-31 17:59:42 +0000[diff] [blame]212 <a href="https://llvm.org/docs/Phabricator.html">Phabricator</a>. Please
Eric Fiselier0ef540b2018-09-22 19:49:29 +0000[diff] [blame]213 add libcxx-commits as a subscriber.
Dan Albert2477bed2015-01-30 22:33:41 +0000[diff] [blame]214 </p>
Marshall Clow17c6aa02014-04-03 03:13:12 +0000[diff] [blame]215
216 <!--=====================================================================-->
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]217 <h2>Design Documents</h2>
218 <!--=====================================================================-->
219
220<ul>
221<li><a href="atomic_design.html"><tt>&lt;atomic&gt;</tt></a></li>
Howard Hinnant4b889672010-11-19 01:38:58 +0000[diff] [blame]222<li><a href="type_traits_design.html"><tt>&lt;type_traits&gt;</tt></a></li>
Stephan T. Lavavej69c2e132017-08-31 17:59:42 +0000[diff] [blame]223<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 Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]224</ul>
225
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]226</div>
227</body>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]228</html>