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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 Clow079402d2014-04-03 02:38:12 +0000[diff] [blame^]120 <p>libc++ is also a 100% complete C++14 implementation. A list of new features and changes for
Marshall Clowca6e3662014-04-03 02:35:29 +0000[diff] [blame]121 C++14 can be found <a href="cxx1y_status.html">here</a>.</p>
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>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]142 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]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
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]149 <p>
150 Next:
151 </p>
152
153 <ul>
154 <li><code>cd libcxx/lib</code></li>
155 <li><code>export TRIPLE=-apple-</code></li>
156 <li><code>./buildit</code></li>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]157 <li><code>ln -sf libc++.1.dylib libc++.dylib</code></li>
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]158 </ul>
159
160 <p>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]161 That should result in a libc++.1.dylib and libc++.dylib. The safest thing
162 to do is to use it from where your libcxx is installed instead of replacing
163 these in your Mac OS.
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]164 </p>
165
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]166 <p>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]167 To use your system-installed libc++ with clang you can:
Howard Hinnante4de2792011-01-27 23:18:19 +0000[diff] [blame]168 </p>
169
170 <ul>
171 <li><code>clang++ -stdlib=libc++ test.cpp</code></li>
Howard Hinnant51eb2ad2012-07-19 15:57:51 +0000[diff] [blame]172 <li><code>clang++ -std=c++11 -stdlib=libc++ test.cpp</code></li>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]173 </ul>
174
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]175 <p>
176 To use your tip-of-trunk libc++ on Mac OS with clang you can:
177 </p>
178
179 <ul>
180 <li><code>export DYLD_LIBRARY_PATH=&lt;path-to-libcxx&gt;/lib</code>
181 <li><code>clang++ -std=c++11 -stdlib=libc++ -nostdinc++
182 -I&lt;path-to-libcxx&gt;/include -L&lt;path-to-libcxx&gt;/lib
183 test.cpp</code></li>
184 </ul>
185
Marshall Clowc740e052012-08-22 00:57:11 +0000[diff] [blame]186 <p>To run the libc++ test suite (recommended):</p>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]187
188 <ul>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]189 <li><code>cd libcxx/test</code></li>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]190 <li><code>./testit</code></li>
Howard Hinnant8298b9c2011-06-22 12:13:55 +0000[diff] [blame]191 <ul>
Howard Hinnant1c8358c2012-11-06 21:31:37 +0000[diff] [blame]192 <li>You can alter the command line options <code>testit</code> uses
193 with <code>export OPTIONS="whatever you need"</code></li>
Howard Hinnant8298b9c2011-06-22 12:13:55 +0000[diff] [blame]194 </ul>
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]195 </ul>
196
Howard Hinnant49c3b202012-05-20 13:03:53 +0000[diff] [blame]197 <!--=====================================================================-->
198 <h3>Notes</h3>
199 <!--=====================================================================-->
200
201<p>
202Building libc++ with <code>-fno-rtti</code> is not supported. However linking
203against it with <code>-fno-rtti</code> is supported.
204</p>
205
Howard Hinnant2807d4a2010-08-22 01:04:38 +0000[diff] [blame]206 <p>Send discussions to the
Howard Hinnant180e1d72010-05-11 19:53:34 +0000[diff] [blame]207 (<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">clang mailing list</a>).</p>
208
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]209 <!--=====================================================================-->
Michael J. Spencerbb8cfd02012-12-31 19:34:21 +0000[diff] [blame]210 <h2>Build on Linux using CMake and libsupc++.</h2>
211 <!--=====================================================================-->
212
213 <p>
214 You will need libstdc++ in order to provide libsupc++.
215 </p>
216
217 <p>
218 Figure out where the libsupc++ headers are on your system. On Ubuntu this
219 is <code>/usr/include/c++/&lt;version&gt;</code> and
220 <code>/usr/include/c++/&lt;version&gt;/&lt;target-triple&gt;</code>
221 </p>
222
223 <p>
224 You can also figure this out by running
225 <pre>
226$ echo | g++ -Wp,-v -x c++ - -fsyntax-only
227ignoring nonexistent directory "/usr/local/include/x86_64-linux-gnu"
228ignoring nonexistent directory "/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../x86_64-linux-gnu/include"
229#include "..." search starts here:
230#include &lt;...&gt; search starts here:
231 /usr/include/c++/4.7
232 /usr/include/c++/4.7/x86_64-linux-gnu
233 /usr/include/c++/4.7/backward
234 /usr/lib/gcc/x86_64-linux-gnu/4.7/include
235 /usr/local/include
236 /usr/lib/gcc/x86_64-linux-gnu/4.7/include-fixed
237 /usr/include/x86_64-linux-gnu
238 /usr/include
239End of search list.
240 </pre>
241
242 Note the first two entries happen to be what we are looking for. This
243 may not be correct on other platforms.
244 </p>
245
246 <p>
247 We can now run CMake:
248 <ul>
249 <li><code>CC=clang CXX=clang++ cmake -G "Unix Makefiles"
Peter Collingbourne26dd09e2013-10-06 22:13:19 +0000[diff] [blame]250 -DLIBCXX_CXX_ABI=libstdc++
Michael J. Spencerbb8cfd02012-12-31 19:34:21 +0000[diff] [blame]251 -DLIBCXX_LIBSUPCXX_INCLUDE_PATHS="/usr/include/c++/4.7/;/usr/include/c++/4.7/x86_64-linux-gnu/"
252 -DCMAKE_BUILD_TYPE=Release
253 -DCMAKE_INSTALL_PREFIX=/usr
254 &lt;libc++-source-dir&gt;</code></li>
Peter Collingbourne26dd09e2013-10-06 22:13:19 +0000[diff] [blame]255 <li>You can also substitute <code>-DLIBCXX_CXX_ABI=libsupc++</code>
256 above, which will cause the library to be linked to libsupc++ instead
257 of libstdc++, but this is only recommended if you know that you will
258 never need to link against libstdc++ in the same executable as libc++.
259 GCC ships libsupc++ separately but only as a static library. If a
260 program also needs to link against libstdc++, it will provide its
261 own copy of libsupc++ and this can lead to subtle problems.
Michael J. Spencerbb8cfd02012-12-31 19:34:21 +0000[diff] [blame]262 <li><code>make</code></li>
263 <li><code>sudo make install</code></li>
264 </ul>
265 <p>
266 You can now run clang with -stdlib=libc++.
267 </p>
268 </p>
269
270 <!--=====================================================================-->
Howard Hinnantaf00dc02013-02-08 19:10:36 +0000[diff] [blame]271 <h2>Build on Linux using CMake and libc++abi.</h2>
272 <!--=====================================================================-->
273
274 <p>
275 You will need to keep the source tree of <a href="http://libcxxabi.llvm.org">libc++abi</a>
276 available on your build machine and your copy of the libc++abi shared library must
277 be placed where your linker will find it.
278 </p>
279
280 <p>
281 We can now run CMake:
282 <ul>
283 <li><code>CC=clang CXX=clang++ cmake -G "Unix Makefiles"
284 -DLIBCXX_CXX_ABI=libcxxabi
285 -DLIBCXX_LIBCXXABI_INCLUDE_PATHS="&lt;libc++abi-source-dir&gt;/include"
286 -DCMAKE_BUILD_TYPE=Release
287 -DCMAKE_INSTALL_PREFIX=/usr
288 &lt;libc++-source-dir&gt;</code></li>
289 <li><code>make</code></li>
290 <li><code>sudo make install</code></li>
291 </ul>
292 <p>
293 Unfortunately you can't simply run clang with "-stdlib=libc++" at this point, as
294 clang is set up to link for libc++ linked to libsupc++. To get around this
295 you'll have to set up your linker yourself (or patch clang). For example,
296 <ul>
297 <li><code>clang++ -stdlib=libc++ helloworld.cpp -nodefaultlibs -lc++ -lc++abi -lm -lc -lgcc_s -lgcc</code></li>
298 </ul>
299 Alternately, you could just add libc++abi to your libraries list, which in most
300 situations will give the same result:
301 <ul>
302 <li><code>clang++ -stdlib=libc++ helloworld.cpp -lc++abi</code></li>
303 </ul>
304 </p>
305 </p>
306
307 <!--=====================================================================-->
308 <h2>Build on Linux using CMake and libcxxrt.</h2>
309 <!--=====================================================================-->
310
311 <p>
312 You will need to keep the source tree of
313 <a href="https://github.com/pathscale/libcxxrt/">libcxxrt</a> available
314 on your build machine and your copy of the libcxxrt shared library must
315 be placed where your linker will find it.
316 </p>
317
318 <p>
319 We can now run CMake:
320 <ul>
321 <li><code>CC=clang CXX=clang++ cmake -G "Unix Makefiles"
322 -DLIBCXX_CXX_ABI=libcxxrt
Howard Hinnant5b22e992013-02-26 16:27:55 +0000[diff] [blame]323 -DLIBCXX_LIBCXXRT_INCLUDE_PATHS="&lt;libcxxrt-source-dir&gt;/src"
Howard Hinnantaf00dc02013-02-08 19:10:36 +0000[diff] [blame]324 -DCMAKE_BUILD_TYPE=Release
325 -DCMAKE_INSTALL_PREFIX=/usr
326 &lt;libc++-source-dir&gt;</code></li>
327 <li><code>make</code></li>
328 <li><code>sudo make install</code></li>
329 </ul>
330 <p>
331 Unfortunately you can't simply run clang with "-stdlib=libc++" at this point, as
332 clang is set up to link for libc++ linked to libsupc++. To get around this
333 you'll have to set up your linker yourself (or patch clang). For example,
334 <ul>
335 <li><code>clang++ -stdlib=libc++ helloworld.cpp -nodefaultlibs -lc++ -lcxxrt -lm -lc -lgcc_s -lgcc</code></li>
336 </ul>
337 Alternately, you could just add libcxxrt to your libraries list, which in most
338 situations will give the same result:
339 <ul>
340 <li><code>clang++ -stdlib=libc++ helloworld.cpp -lcxxrt</code></li>
341 </ul>
342 </p>
343 </p>
344
345 <!--=====================================================================-->
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]346 <h2>Design Documents</h2>
347 <!--=====================================================================-->
348
349<ul>
350<li><a href="atomic_design.html"><tt>&lt;atomic&gt;</tt></a></li>
Howard Hinnant4b889672010-11-19 01:38:58 +0000[diff] [blame]351<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]352<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]353<li><a href="debug_mode.html">Status of debug mode</a></li>
Howard Hinnant1de22662010-10-05 16:44:40 +0000[diff] [blame]354</ul>
355
Howard Hinnant3e519522010-05-11 19:42:16 +0000[diff] [blame]356</div>
357</body>
Chris Lattner6f12a7f2010-05-11 20:37:52 +0000[diff] [blame]358</html>