2010-05-12 03:42:16 +08:00
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<label>libc++ Info</label>
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<label>Quick Links</label>
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2010-05-12 04:53:16 +08:00
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<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">cfe-dev</a>
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<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits">cfe-commits</a>
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2010-05-12 03:42:16 +08:00
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<a href="http://llvm.org/bugs/">Bug Reports</a>
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2010-05-12 04:51:20 +08:00
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<a href="http://llvm.org/svn/llvm-project/libcxx/trunk/">Browse SVN</a>
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2010-05-12 03:42:16 +08:00
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<div id="content">
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<!--*********************************************************************-->
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<h1>"libc++" C++ Standard Library</h1>
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<!--*********************************************************************-->
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<p>libc++ is a new implementation of the C++ standard library, targeting
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C++0X.</p>
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<p>All of the code in libc++ is available under the standard
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<a href="http://llvm.org/docs/DeveloperPolicy.html#license">LLVM
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License</a>, a "BSD-style" license.</p>
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<!--=====================================================================-->
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<h2 id="goals">Features and Goals</h2>
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<!--=====================================================================-->
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<ul>
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<li>Correctness as defined by the (currently draft) C++0X standard.</li>
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<li>Fast execution.</li>
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<li>Minimal memory use.</li>
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<li>Fast compile times.</li>
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<li>ABI compatibility with gcc's libstdc++ for some low-level features
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such as exception objects, rtti and memory allocation.</li>
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<li>Extensive unit tests.</li>
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</ul>
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2010-05-13 06:21:15 +08:00
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<!--=====================================================================-->
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<h2 id="why">Why a new C++ Standard Library for C++'0x?</h2>
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<!--=====================================================================-->
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<p>After its initial introduction, many people have asked "why start a new
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library instead of contributing to an existing library?" (like Apache's
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libstdcxx, GNU's libstdc++, STLport, etc). There are many contributing
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reasons, but some of the major ones are:</p>
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<ul>
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<li><p>From years of experience (including having implemented the standard
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library before), we've learned many things about implementing
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the standard containers which require ABI breakage and fundamental changes
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to how they are implemented. For example, it is generally accepted that
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building std::string using the "short string optimization" instead of
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using Copy On Write (COW) is a superior approach for multicore
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2010-05-13 06:30:22 +08:00
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machines (particularly in C++'0x, which has rvalue references). Breaking
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ABI compatibility with old versions of the library was
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2010-05-13 06:21:15 +08:00
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determined to be critical to achieving the performance goals of
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libc++.</p></li>
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<li><p>Mainline libstdc++ has switched to GPL3, a license which the developers
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of libc++ cannot use. libstdc++ 4.2 (the last GPL2 version) could be
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independently extended to support C++'0x, but this would be a fork of the
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2010-05-13 06:33:00 +08:00
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codebase (which is often seen as worse for a project than starting a new
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independent one). Another problem with libstdc++ is that it is tightly
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integrated with G++ development, tending to be tied fairly closely to the
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matching version of G++.</p>
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2010-05-13 06:21:15 +08:00
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</li>
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<li><p>STLport and the Apache libstdcxx library are two other popular
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candidates, but both lack C++'0x support. Our experience (and the
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experience of libstdc++ developers) is that adding support for C++0x (in
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particular rvalue references and move-only types) requires changes to
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almost every class and function, essentially amounting to a rewrite.
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2010-05-13 06:34:21 +08:00
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Faced with a rewrite, we decided to start from scratch and evaluate every
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design decision from first principles based on experience.</p>
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2010-05-13 06:21:15 +08:00
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<p>Further, both projects are apparently abandoned: STLport 5.2.1 was
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released in Oct'08, and STDCXX 4.2.1 in May'08.</p>
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</ul>
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2010-05-12 03:42:16 +08:00
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<!--=====================================================================-->
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<h2 id="requirements">Platform Support</h2>
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<!--=====================================================================-->
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<p>libc++ is known to work on the following platforms, using g++-4.2 and
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clang (lack of C++0X language support disables some functionality).</p>
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<ul>
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<li>Mac OS X i386</li>
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<li>Mac OS X x86_64</li>
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</ul>
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<!--=====================================================================-->
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<h2 id="dir-structure">Current Status</h2>
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<!--=====================================================================-->
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<p>libc++ is still under development. It has about 85% of
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<a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3092.pdf">N3092</a>
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2010-05-13 06:21:15 +08:00
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implemented/tested. C++'98 support is fully featured, and most of C++'0x
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support is as well. The only major missing pieces of C++'0x support are
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<code><future></code> and <code><regex></code>, and parts of
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<code><random></code>.</p>
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2010-05-12 03:42:16 +08:00
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<p>libc++ is currently dependent upon a separate library for the low-level
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ABI compatibility with gcc. As a workaround it can be linked against
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gcc's libstdc++.</p>
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2010-05-14 04:10:39 +08:00
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<p><a href="libcxx_by_chapter.pdf">Here</a> is a by-chapter breakdown of what
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is passing tests and what isn't. This chart is currently based on testing
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against g++-4.4.0 with -stdc++0x. </p>
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2010-05-12 03:42:16 +08:00
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<!--=====================================================================-->
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<h2>Get it and get involved!</h2>
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<!--=====================================================================-->
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<p>To check out the code, use:</p>
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<ul>
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2010-05-12 04:37:52 +08:00
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<li><code>svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx</code></li>
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<li><code>cd libcxx/lib</code></li>
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2010-05-12 03:42:16 +08:00
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<li><code>./buildit</code></li>
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</ul>
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<p>To run the libc++ test suit (recommended):</p>
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<ul>
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2010-05-12 04:37:52 +08:00
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<li><code>cd libcxx/test</code></li>
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2010-05-12 03:42:16 +08:00
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<li><code>./testit</code></li>
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</ul>
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2010-05-12 03:53:34 +08:00
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<p>Send discussions to the
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(<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">clang mailing list</a>).</p>
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2010-05-12 03:42:16 +08:00
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</div>
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</body>
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2010-05-12 04:37:52 +08:00
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</html>
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