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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>
31</div>
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 <!--=====================================================================-->
Marshall Clow497d9d22012-11-14 16:31:15 +0000[diff] [blame]60 <h2 id="why">Why a new C++ Standard Library for C++11?</h2>
Chris Lattner27de3d62010-05-12 22:21:15 +0000[diff] [blame]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
Marshall Clow497d9d22012-11-14 16:31:15 +0000[diff] [blame]75 machines (particularly in C++11, which has rvalue references). Breaking
Chris Lattnerf005e8d2010-05-12 22:30:22 +0000[diff] [blame]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
Marshall Clow497d9d22012-11-14 16:31:15 +0000[diff] [blame]82 independently extended to support C++11, 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
Marshall Clow497d9d22012-11-14 16:31:15 +0000[diff] [blame]90 candidates, but both lack C++11 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 Hinnant6852b552012-11-27 18:52:32 +0000[diff] [blame]118 <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]119 <p>LLVM and Clang can self host in C++ and C++11 mode with libc++ on Linux.</p>
Marshall Clowf77718a2013-08-13 14:58:39 +0000[diff] [blame]120 <p>C++1Y (C++14) implementation is in progress. The current status is
Marshall Clow873e8902013-08-13 14:59:44 +0000[diff] [blame]121 <a href="cxx1y_status.html">here</a></p>
Marshall Clowf77718a2013-08-13 14:58:39 +0000[diff] [blame]122
Howard Hinnantd7aac282011-09-28 15:44:39 +0000[diff] [blame]123 <p>
Howard Hinnant8eb04fe2012-07-31 21:30:28 +0000[diff] [blame]124 Ports to other platforms are underway. Here are recent test
125 results for <a href="results.Windows.html">Windows</a>
126 and <a href="results.Linux.html">Linux</a>.
Howard Hinnantd7aac282011-09-28 15:44:39 +0000[diff] [blame]127 </p>
128
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]129 <!--=====================================================================-->
130 <h2>Get it and get involved!</h2>
131 <!--=====================================================================-->
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]132
Howard Hinnant4f4d3102011-09-30 16:58:02 +0000[diff] [blame]133 <p>First please review our
134 <a href="http://llvm.org/docs/DeveloperPolicy.html">Developer's Policy</a>.
135
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]136 <p>To check out the code, use:</p>
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]137
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]138 <ul>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]139 <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]140 </ul>
141
Howard Hinnant73191602011-11-17 17:14:16 +0000[diff] [blame]142 <p>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]143 On Mac OS 10.7 (Lion) and later, the easiest way to get this library is to install
Howard Hinnant73191602011-11-17 17:14:16 +0000[diff] [blame]144 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]145 (getting the bleeding edge), read on. However, be warned that Mac OS
146 10.7 will not boot without a valid copy of <code>libc++.1.dylib</code> in
147 <code>/usr/lib</code>.
Howard Hinnant73191602011-11-17 17:14:16 +0000[diff] [blame]148 </p>
149
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]150 <p>
151 Next:
152 </p>
153
154 <ul>
155 <li><code>cd libcxx/lib</code></li>
156 <li><code>export TRIPLE=-apple-</code></li>
157 <li><code>./buildit</code></li>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]158 <li><code>ln -sf libc++.1.dylib libc++.dylib</code></li>
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]159 </ul>
160
161 <p>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]162 That should result in a libc++.1.dylib and libc++.dylib. The safest thing
163 to do is to use it from where your libcxx is installed instead of replacing
164 these in your Mac OS.
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]165 </p>
166
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]167 <p>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]168 To use your system-installed libc++ with clang you can:
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]169 </p>
170
171 <ul>
172 <li><code>clang++ -stdlib=libc++ test.cpp</code></li>
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]173 <li><code>clang++ -std=c++11 -stdlib=libc++ test.cpp</code></li>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]174 </ul>
175
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]176 <p>
177 To use your tip-of-trunk libc++ on Mac OS with clang you can:
178 </p>
179
180 <ul>
181 <li><code>export DYLD_LIBRARY_PATH=&lt;path-to-libcxx&gt;/lib</code>
182 <li><code>clang++ -std=c++11 -stdlib=libc++ -nostdinc++
183 -I&lt;path-to-libcxx&gt;/include -L&lt;path-to-libcxx&gt;/lib
184 test.cpp</code></li>
185 </ul>
186
Marshall Clowc740e052012-08-22 00:57:11 +0000[diff] [blame]187 <p>To run the libc++ test suite (recommended):</p>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]188
189 <ul>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]190 <li><code>cd libcxx/test</code></li>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]191 <li><code>./testit</code></li>
Howard Hinnant8298b9c2011-06-22 12:13:55 +0000[diff] [blame]192 <ul>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]193 <li>You can alter the command line options <code>testit</code> uses
194 with <code>export OPTIONS="whatever you need"</code></li>
Howard Hinnant8298b9c2011-06-22 12:13:55 +0000[diff] [blame]195 </ul>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]196 </ul>
197
Howard Hinnant49c3b202012-05-20 13:03:53 +0000[diff] [blame]198 <!--=====================================================================-->
199 <h3>Notes</h3>
200 <!--=====================================================================-->
201
202<p>
203Building libc++ with <code>-fno-rtti</code> is not supported. However linking
204against it with <code>-fno-rtti</code> is supported.
205</p>
206
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]207 <p>Send discussions to the
Howard Hinnant180e1d72010-05-11 19:53:34 +0000[diff] [blame]208 (<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">clang mailing list</a>).</p>
209
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]210 <!--=====================================================================-->
Michael J. Spencerbb8cfd02012-12-31 19:34:21 +0000[diff] [blame]211 <h2>Build on Linux using CMake and libsupc++.</h2>
212 <!--=====================================================================-->
213
214 <p>
215 You will need libstdc++ in order to provide libsupc++.
216 </p>
217
218 <p>
219 Figure out where the libsupc++ headers are on your system. On Ubuntu this
220 is <code>/usr/include/c++/&lt;version&gt;</code> and
221 <code>/usr/include/c++/&lt;version&gt;/&lt;target-triple&gt;</code>
222 </p>
223
224 <p>
225 You can also figure this out by running
226 <pre>
227$ echo | g++ -Wp,-v -x c++ - -fsyntax-only
228ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
229ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../x86_64-linux-gnu/include"
230#include "..." search starts here:
231#include &lt;...&gt; search starts here:
232 /usr/include/c++/4.7
233 /usr/include/c++/4.7/x86_64-linux-gnu
234 /usr/include/c++/4.7/backward
235 /usr/lib/gcc/x86_64-linux-gnu/4.7/include
236 /usr/local/include
237 /usr/lib/gcc/x86_64-linux-gnu/4.7/include-fixed
238 /usr/include/x86_64-linux-gnu
239 /usr/include
240End of search list.
241 </pre>
242
243 Note the first two entries happen to be what we are looking for. This
244 may not be correct on other platforms.
245 </p>
246
247 <p>
248 We can now run CMake:
249 <ul>
250 <li><code>CC=clang CXX=clang++ cmake -G "Unix Makefiles"
Peter Collingbourne26dd09e2013-10-06 22:13:19 +0000[diff] [blame]251 -DLIBCXX_CXX_ABI=libstdc++
Michael J. Spencerbb8cfd02012-12-31 19:34:21 +0000[diff] [blame]252 -DLIBCXX_LIBSUPCXX_INCLUDE_PATHS="/usr/include/c++/4.7/;/usr/include/c++/4.7/x86_64-linux-gnu/"
253 -DCMAKE_BUILD_TYPE=Release
254 -DCMAKE_INSTALL_PREFIX=/usr
255 &lt;libc++-source-dir&gt;</code></li>
Peter Collingbourne26dd09e2013-10-06 22:13:19 +0000[diff] [blame]256 <li>You can also substitute <code>-DLIBCXX_CXX_ABI=libsupc++</code>
257 above, which will cause the library to be linked to libsupc++ instead
258 of libstdc++, but this is only recommended if you know that you will
259 never need to link against libstdc++ in the same executable as libc++.
260 GCC ships libsupc++ separately but only as a static library. If a
261 program also needs to link against libstdc++, it will provide its
262 own copy of libsupc++ and this can lead to subtle problems.
Michael J. Spencerbb8cfd02012-12-31 19:34:21 +0000[diff] [blame]263 <li><code>make</code></li>
264 <li><code>sudo make install</code></li>
265 </ul>
266 <p>
267 You can now run clang with -stdlib=libc++.
268 </p>
269 </p>
270
271 <!--=====================================================================-->
Howard Hinnantaf00dc02013-02-08 19:10:36 +0000[diff] [blame]272 <h2>Build on Linux using CMake and libc++abi.</h2>
273 <!--=====================================================================-->
274
275 <p>
276 You will need to keep the source tree of <a href="http://libcxxabi.llvm.org">libc++abi</a>
277 available on your build machine and your copy of the libc++abi shared library must
278 be placed where your linker will find it.
279 </p>
280
281 <p>
282 We can now run CMake:
283 <ul>
284 <li><code>CC=clang CXX=clang++ cmake -G "Unix Makefiles"
285 -DLIBCXX_CXX_ABI=libcxxabi
286 -DLIBCXX_LIBCXXABI_INCLUDE_PATHS="&lt;libc++abi-source-dir&gt;/include"
287 -DCMAKE_BUILD_TYPE=Release
288 -DCMAKE_INSTALL_PREFIX=/usr
289 &lt;libc++-source-dir&gt;</code></li>
290 <li><code>make</code></li>
291 <li><code>sudo make install</code></li>
292 </ul>
293 <p>
294 Unfortunately you can't simply run clang with "-stdlib=libc++" at this point, as
295 clang is set up to link for libc++ linked to libsupc++. To get around this
296 you'll have to set up your linker yourself (or patch clang). For example,
297 <ul>
298 <li><code>clang++ -stdlib=libc++ helloworld.cpp -nodefaultlibs -lc++ -lc++abi -lm -lc -lgcc_s -lgcc</code></li>
299 </ul>
300 Alternately, you could just add libc++abi to your libraries list, which in most
301 situations will give the same result:
302 <ul>
303 <li><code>clang++ -stdlib=libc++ helloworld.cpp -lc++abi</code></li>
304 </ul>
305 </p>
306 </p>
307
308 <!--=====================================================================-->
309 <h2>Build on Linux using CMake and libcxxrt.</h2>
310 <!--=====================================================================-->
311
312 <p>
313 You will need to keep the source tree of
314 <a href="https://github.com/pathscale/libcxxrt/">libcxxrt</a> available
315 on your build machine and your copy of the libcxxrt shared library must
316 be placed where your linker will find it.
317 </p>
318
319 <p>
320 We can now run CMake:
321 <ul>
322 <li><code>CC=clang CXX=clang++ cmake -G "Unix Makefiles"
323 -DLIBCXX_CXX_ABI=libcxxrt
Howard Hinnant5b22e992013-02-26 16:27:55 +0000[diff] [blame]324 -DLIBCXX_LIBCXXRT_INCLUDE_PATHS="&lt;libcxxrt-source-dir&gt;/src"
Howard Hinnantaf00dc02013-02-08 19:10:36 +0000[diff] [blame]325 -DCMAKE_BUILD_TYPE=Release
326 -DCMAKE_INSTALL_PREFIX=/usr
327 &lt;libc++-source-dir&gt;</code></li>
328 <li><code>make</code></li>
329 <li><code>sudo make install</code></li>
330 </ul>
331 <p>
332 Unfortunately you can't simply run clang with "-stdlib=libc++" at this point, as
333 clang is set up to link for libc++ linked to libsupc++. To get around this
334 you'll have to set up your linker yourself (or patch clang). For example,
335 <ul>
336 <li><code>clang++ -stdlib=libc++ helloworld.cpp -nodefaultlibs -lc++ -lcxxrt -lm -lc -lgcc_s -lgcc</code></li>
337 </ul>
338 Alternately, you could just add libcxxrt to your libraries list, which in most
339 situations will give the same result:
340 <ul>
341 <li><code>clang++ -stdlib=libc++ helloworld.cpp -lcxxrt</code></li>
342 </ul>
343 </p>
344 </p>
345
346 <!--=====================================================================-->
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]347 <h2>Design Documents</h2>
348 <!--=====================================================================-->
349
350<ul>
351<li><a href="atomic_design.html"><tt>&lt;atomic&gt;</tt></a></li>
Howard Hinnant4b889672010-11-19 01:38:58 +0000[diff] [blame]352<li><a href="type_traits_design.html"><tt>&lt;type_traits&gt;</tt></a></li>
Marshall Clow928f65a2013-03-14 19:00:34 +0000[diff] [blame]353<li><a href="http://cplusplusmusings.wordpress.com/2012/07/05/clang-and-standard-libraries-on-mac-os-x/">Excellent notes by Marshall Clow</a></li>
Howard Hinnantd70e6572013-03-14 18:37:48 +0000[diff] [blame]354<li><a href="debug_mode.html">Status of debug mode</a></li>
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]355</ul>
356
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]357</div>
358</body>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]359</html>