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15 <a href="http://llvm.org/">LLVM Home</a>
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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>
Chris Lattnerf9e7e3a2010-05-11 20:53:16 +0000[diff] [blame]25 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a>
26 <a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits</a>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]27 <a href="http://llvm.org/bugs/">Bug Reports</a>
Howard Hinnant38a59272010-05-11 20:51:20 +0000[diff] [blame]28 <a href="http://llvm.org/svn/llvm-project/libcxx/trunk/">Browse SVN</a>
29 <a href="http://llvm.org/viewvc/llvm-project/libcxx/trunk/">Browse ViewVC</a>
Howard Hinnant3e519522010-05-11 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 Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]37
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]38 <p>libc++ is a new implementation of the C++ standard library, targeting
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]39 C++11.</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
42 href="http://llvm.org/docs/DeveloperPolicy.html#license">dual licensed</a>
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 <!--=====================================================================-->
46 <h2 id="goals">Features and Goals</h2>
47 <!--=====================================================================-->
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]48
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]49 <ul>
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]50 <li>Correctness as defined by the C++11 standard.</li>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]51 <li>Fast execution.</li>
52 <li>Minimal memory use.</li>
53 <li>Fast compile times.</li>
54 <li>ABI compatibility with gcc's libstdc++ for some low-level features
55 such as exception objects, rtti and memory allocation.</li>
56 <li>Extensive unit tests.</li>
57 </ul>
58
59 <!--=====================================================================-->
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]60 <h2 id="why">Why a new C++ Standard Library for C++'0x?</h2>
61 <!--=====================================================================-->
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]62
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]63 <p>After its initial introduction, many people have asked "why start a new
64 library instead of contributing to an existing library?" (like Apache's
65 libstdcxx, GNU's libstdc++, STLport, etc). There are many contributing
66 reasons, but some of the major ones are:</p>
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]67
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]68 <ul>
69 <li><p>From years of experience (including having implemented the standard
70 library before), we've learned many things about implementing
71 the standard containers which require ABI breakage and fundamental changes
72 to how they are implemented. For example, it is generally accepted that
73 building std::string using the "short string optimization" instead of
74 using Copy On Write (COW) is a superior approach for multicore
Chris Lattnerf005e8d2010-05-12 22:30:22 +0000[diff] [blame]75 machines (particularly in C++'0x, which has rvalue references). Breaking
76 ABI compatibility with old versions of the library was
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]77 determined to be critical to achieving the performance goals of
78 libc++.</p></li>
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]79
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]80 <li><p>Mainline libstdc++ has switched to GPL3, a license which the developers
81 of libc++ cannot use. libstdc++ 4.2 (the last GPL2 version) could be
82 independently extended to support C++'0x, but this would be a fork of the
Chris Lattnera940b5b2010-05-12 22:33:00 +0000[diff] [blame]83 codebase (which is often seen as worse for a project than starting a new
84 independent one). Another problem with libstdc++ is that it is tightly
85 integrated with G++ development, tending to be tied fairly closely to the
86 matching version of G++.</p>
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]87 </li>
88
89 <li><p>STLport and the Apache libstdcxx library are two other popular
90 candidates, but both lack C++'0x support. Our experience (and the
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]91 experience of libstdc++ developers) is that adding support for C++11 (in
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]92 particular rvalue references and move-only types) requires changes to
93 almost every class and function, essentially amounting to a rewrite.
Chris Lattnerd55fd112010-05-12 22:34:21 +0000[diff] [blame]94 Faced with a rewrite, we decided to start from scratch and evaluate every
95 design decision from first principles based on experience.</p>
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]96
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]97 <p>Further, both projects are apparently abandoned: STLport 5.2.1 was
98 released in Oct'08, and STDCXX 4.2.1 in May'08.</p>
99
100 </ul>
101
102 <!--=====================================================================-->
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]103 <h2 id="requirements">Platform Support</h2>
104 <!--=====================================================================-->
105
106 <p>libc++ is known to work on the following platforms, using g++-4.2 and
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]107 clang (lack of C++11 language support disables some functionality).</p>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]108
109 <ul>
110 <li>Mac OS X i386</li>
111 <li>Mac OS X x86_64</li>
112 </ul>
113
114 <!--=====================================================================-->
115 <h2 id="dir-structure">Current Status</h2>
116 <!--=====================================================================-->
117
Howard Hinnant97ae3d52010-05-13 20:10:39 +0000[diff] [blame]118 <p><a href="libcxx_by_chapter.pdf">Here</a> is a by-chapter breakdown of what
119 is passing tests and what isn't. This chart is currently based on testing
Howard Hinnantfe9fe2d2012-07-30 02:29:34 +0000[diff] [blame]120 against clang++ with -std=c++11 on Apple's OS X. </p>
Howard Hinnant97ae3d52010-05-13 20:10:39 +0000[diff] [blame]121
Howard Hinnantd7aac282011-09-28 15:44:39 +0000[diff] [blame]122 <p>
Howard Hinnant8eb04fe2012-07-31 21:30:28 +0000[diff] [blame^]123 Ports to other platforms are underway. Here are recent test
124 results for <a href="results.Windows.html">Windows</a>
125 and <a href="results.Linux.html">Linux</a>.
Howard Hinnantd7aac282011-09-28 15:44:39 +0000[diff] [blame]126 </p>
127
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]128 <!--=====================================================================-->
129 <h2>Get it and get involved!</h2>
130 <!--=====================================================================-->
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]131
Howard Hinnant4f4d3102011-09-30 16:58:02 +0000[diff] [blame]132 <p>First please review our
133 <a href="http://llvm.org/docs/DeveloperPolicy.html">Developer's Policy</a>.
134
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]135 <p>To check out the code, use:</p>
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]136
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]137 <ul>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]138 <li><code>svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx</code></li>
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]139 </ul>
140
Howard Hinnant73191602011-11-17 17:14:16 +0000[diff] [blame]141 <p>
142 On Mac OS 10.7 (Lion), the easiest way to get this library is to install
143 Xcode 4.2 or later. However if you want to install tip-of-trunk from here
Howard Hinnant6e3e78a2012-04-03 15:08:42 +0000[diff] [blame]144 (getting the bleeding edge), read on. However, be warned that Mac OS
145 10.7 will not boot without a valid copy of <code>libc++.1.dylib</code> in
146 <code>/usr/lib</code>.
Howard Hinnant73191602011-11-17 17:14:16 +0000[diff] [blame]147 </p>
148
149 <p>To build on Mac OS X 10.6 (Snow Leopard), you need a helper library and header
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]150 <a href="http://home.roadrunner.com/~hinnant/libcppabi.zip">found here</a>.
Howard Hinnant73191602011-11-17 17:14:16 +0000[diff] [blame]151 cp cxxabi.h to /usr/include, and cp libc++abi.dylib to /usr/lib. On Mac OS
152 X 10.7 (Lion) and later, this helper library and header are already installed
153 for you.
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]154 <p>
155
156 <p>
157 Next:
158 </p>
159
160 <ul>
161 <li><code>cd libcxx/lib</code></li>
162 <li><code>export TRIPLE=-apple-</code></li>
Howard Hinnant73191602011-11-17 17:14:16 +0000[diff] [blame]163 <li>Only on 10.6: <code>export MACOSX_DEPLOYMENT_TARGET=10.6</code></li>
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]164 <li><code>./buildit</code></li>
165 </ul>
166
167 <p>
168 That should result in a libc++.1.dylib. To install it I like to use links
169 instead of copying, but either should work:
170 </p>
171
172 <ul>
173 <li><code>cd /usr/lib</code></li>
Howard Hinnant80a3cad2011-02-22 14:18:34 +0000[diff] [blame]174 <li><code>sudo ln -sf path-to-libcxx/lib/libc++.1.dylib libc++.1.dylib</code></li>
175 <li><code>sudo ln -sf libc++.1.dylib libc++.dylib</code></li>
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]176 <li><code>cd /usr/include/c++</code></li>
177 <li><code>sudo ln -sf path-to-libcxx/include v1</code></li>
178 </ul>
179
180 <p>
181 To use with clang you can:
182 </p>
183
184 <ul>
185 <li><code>clang++ -stdlib=libc++ test.cpp</code></li>
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]186 <li><code>clang++ -std=c++11 -stdlib=libc++ test.cpp</code></li>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]187 </ul>
188
189 <p>To run the libc++ test suit (recommended):</p>
190
191 <ul>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]192 <li><code>cd libcxx/test</code></li>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]193 <li><code>./testit</code></li>
Howard Hinnant8298b9c2011-06-22 12:13:55 +0000[diff] [blame]194 <ul>
Howard Hinnant55f2a502011-09-12 14:15:45 +0000[diff] [blame]195 <li>On Mac OS 10.6, to work around bugs in libc headers like
196 math.h and inttypes.h, add "-U__STRICT_ANSI__" and
197 "-D__STDC_FORMAT_MACROS" to the command line with:
198 <blockquote>
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]199 <pre>export OPTIONS="-std=c++11 -stdlib=libc++ -U__STRICT_ANSI__ -D__STDC_FORMAT_MACROS"</pre>
Howard Hinnant55f2a502011-09-12 14:15:45 +0000[diff] [blame]200 </blockquote></li>
201 <li>People porting libc++ to other OSes will likely have to
202 define similar macros.</li>
Howard Hinnant8298b9c2011-06-22 12:13:55 +0000[diff] [blame]203 </ul>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]204 </ul>
205
Howard Hinnant49c3b202012-05-20 13:03:53 +0000[diff] [blame]206 <!--=====================================================================-->
207 <h3>Notes</h3>
208 <!--=====================================================================-->
209
210<p>
211Building libc++ with <code>-fno-rtti</code> is not supported. However linking
212against it with <code>-fno-rtti</code> is supported.
213</p>
214
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]215 <p>Send discussions to the
Howard Hinnant180e1d72010-05-11 19:53:34 +0000[diff] [blame]216 (<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">clang mailing list</a>).</p>
217
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]218 <!--=====================================================================-->
219 <h2>Design Documents</h2>
220 <!--=====================================================================-->
221
222<ul>
223<li><a href="atomic_design.html"><tt>&lt;atomic&gt;</tt></a></li>
Howard Hinnant4b889672010-11-19 01:38:58 +0000[diff] [blame]224<li><a href="type_traits_design.html"><tt>&lt;type_traits&gt;</tt></a></li>
Howard Hinnant6b456602012-07-06 00:39:38 +0000[diff] [blame]225<li><a href="http://marshall.calepin.co/llvmclang-and-standard-libraries-on-mac-os-x.html">Excellent notes by Marshall Clow</a></li>
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]226</ul>
227
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]228</div>
229</body>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]230</html>