index.html revision 9835d761695b7d54e7d231dd1fe682597f249349
1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 2 "http://www.w3.org/TR/html4/strict.dtd"> 3<!-- Material used from: HTML 4.01 specs: http://www.w3.org/TR/html401/ --> 4<html> 5<head> 6 <META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 7 <title>"libc++" C++ Standard Library</title> 8 <link type="text/css" rel="stylesheet" href="menu.css"> 9 <link type="text/css" rel="stylesheet" href="content.css"> 10</head> 11 12<body> 13<div id="menu"> 14 <div> 15 <a href="http://llvm.org/">LLVM Home</a> 16 </div> 17 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> 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> 27 <a href="http://llvm.org/bugs/">Bug Reports</a> 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> 30 </div> 31</div> 32 33<div id="content"> 34 <!--*********************************************************************--> 35 <h1>"libc++" C++ Standard Library</h1> 36 <!--*********************************************************************--> 37 38 <p>libc++ is a new implementation of the C++ standard library, targeting 39 C++0X.</p> 40 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> 44 45 <!--=====================================================================--> 46 <h2 id="goals">Features and Goals</h2> 47 <!--=====================================================================--> 48 49 <ul> 50 <li>Correctness as defined by the (currently draft) C++0X standard.</li> 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 <!--=====================================================================--> 60 <h2 id="why">Why a new C++ Standard Library for C++'0x?</h2> 61 <!--=====================================================================--> 62 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> 67 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 75 machines (particularly in C++'0x, which has rvalue references). Breaking 76 ABI compatibility with old versions of the library was 77 determined to be critical to achieving the performance goals of 78 libc++.</p></li> 79 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 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> 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 91 experience of libstdc++ developers) is that adding support for C++0x (in 92 particular rvalue references and move-only types) requires changes to 93 almost every class and function, essentially amounting to a rewrite. 94 Faced with a rewrite, we decided to start from scratch and evaluate every 95 design decision from first principles based on experience.</p> 96 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 <!--=====================================================================--> 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 107 clang (lack of C++0X language support disables some functionality).</p> 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 <!--=====================================================================--> 117 118 <p>libc++ is still under development. It has about 98% of 119 <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3126.pdf">N3126</a> 120 implemented/tested. C++'98 support is fully featured, and most of C++'0x 121 support is as well. The only major missing piece of C++'0x support is 122 <code><atomic></code>.</p> 123 124 <p>libc++ is currently dependent upon a separate library for the low-level 125 ABI compatibility with gcc. As a workaround it can be linked against 126 gcc's libstdc++, or on Mac OS X 127 <a href="http://home.roadrunner.com/~hinnant/libcppabi.zip">this library</a>.</p> 128 129 <p><a href="libcxx_by_chapter.pdf">Here</a> is a by-chapter breakdown of what 130 is passing tests and what isn't. This chart is currently based on testing 131 against g++-4.4.0 with -std=c++0x. </p> 132 133 <!--=====================================================================--> 134 <h2>Get it and get involved!</h2> 135 <!--=====================================================================--> 136 137 <p>To check out the code, use:</p> 138 139 <ul> 140 <li><code>svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx</code></li> 141 <li><code>cd libcxx/lib</code></li> 142 <li><code>/buildit</code></li> 143 </ul> 144 145 <p>To run the libc++ test suit (recommended):</p> 146 147 <ul> 148 <li><code>cd libcxx/test</code></li> 149 <li><code>/testit</code></li> 150 </ul> 151 152 <p>Send discussions to the 153 (<a href="http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev">clang mailing list</a>).</p> 154 155 <!--=====================================================================--> 156 <h2>Design Documents</h2> 157 <!--=====================================================================--> 158 159<ul> 160<li><a href="atomic_design.html"><tt><atomic></tt></a></li> 161<li><a href="type_traits_design.html"><tt><type_traits></tt></a></li> 162</ul> 163 164</div> 165</body> 166</html> 167