1.. _index: 2 3============================= 4"libc++" C++ Standard Library 5============================= 6 7Overview 8======== 9 10libc++ is a new implementation of the C++ standard library, targeting C++11 and 11above. 12 13* Features and Goals 14 15 * Correctness as defined by the C++11 standard. 16 * Fast execution. 17 * Minimal memory use. 18 * Fast compile times. 19 * ABI compatibility with gcc's libstdc++ for some low-level features 20 such as exception objects, rtti and memory allocation. 21 * Extensive unit tests. 22 23* Design and Implementation: 24 25 * Extensive unit tests 26 * Internal linker model can be dumped/read to textual format 27 * Additional linking features can be plugged in as "passes" 28 * OS specific and CPU specific code factored out 29 30 31Getting Started with libc++ 32--------------------------- 33 34.. toctree:: 35 :maxdepth: 2 36 37 UsingLibcxx 38 BuildingLibcxx 39 TestingLibcxx 40 41 42Current Status 43-------------- 44 45After its initial introduction, many people have asked "why start a new 46library instead of contributing to an existing library?" (like Apache's 47libstdcxx, GNU's libstdc++, STLport, etc). There are many contributing 48reasons, but some of the major ones are: 49 50* From years of experience (including having implemented the standard 51 library before), we've learned many things about implementing 52 the standard containers which require ABI breakage and fundamental changes 53 to how they are implemented. For example, it is generally accepted that 54 building std::string using the "short string optimization" instead of 55 using Copy On Write (COW) is a superior approach for multicore 56 machines (particularly in C++11, which has rvalue references). Breaking 57 ABI compatibility with old versions of the library was 58 determined to be critical to achieving the performance goals of 59 libc++. 60 61* Mainline libstdc++ has switched to GPL3, a license which the developers 62 of libc++ cannot use. libstdc++ 4.2 (the last GPL2 version) could be 63 independently extended to support C++11, but this would be a fork of the 64 codebase (which is often seen as worse for a project than starting a new 65 independent one). Another problem with libstdc++ is that it is tightly 66 integrated with G++ development, tending to be tied fairly closely to the 67 matching version of G++. 68 69* STLport and the Apache libstdcxx library are two other popular 70 candidates, but both lack C++11 support. Our experience (and the 71 experience of libstdc++ developers) is that adding support for C++11 (in 72 particular rvalue references and move-only types) requires changes to 73 almost every class and function, essentially amounting to a rewrite. 74 Faced with a rewrite, we decided to start from scratch and evaluate every 75 design decision from first principles based on experience. 76 Further, both projects are apparently abandoned: STLport 5.2.1 was 77 released in Oct'08, and STDCXX 4.2.1 in May'08. 78 79Platform and Compiler Support 80----------------------------- 81 82libc++ is known to work on the following platforms, using gcc-4.2 and 83clang (lack of C++11 language support disables some functionality). 84Note that functionality provided by ``<atomic>`` is only functional with clang 85and GCC. 86 87============ ==================== ============ ======================== 88OS Arch Compilers ABI Library 89============ ==================== ============ ======================== 90Mac OS X i386, x86_64 Clang, GCC libc++abi 91FreeBSD 10+ i386, x86_64, ARM Clang, GCC libcxxrt, libc++abi 92Linux i386, x86_64 Clang, GCC libc++abi 93============ ==================== ============ ======================== 94 95The following minimum compiler versions are strongly recommended. 96 97* Clang 3.5 and above 98* GCC 4.7 and above. 99 100Anything older *may* work. 101 102C++ Dialect Support 103--------------------- 104 105* C++11 - Complete 106* `C++14 - Complete <http://libcxx.llvm.org/cxx1y_status.html>`__ 107* `C++1z - In Progress <http://libcxx.llvm.org/cxx1z_status.html>`__ 108* `Post C++14 Technical Specifications - In Progress <http://libcxx.llvm.org/ts1z_status.html>`__ 109 110Notes and Known Issues 111---------------------- 112 113This list contains known issues with libc++ 114 115* Building libc++ with ``-fno-rtti`` is not supported. However 116 linking against it with ``-fno-rtti`` is supported. 117* On OS X v10.8 and older the CMake option ``-DLIBCXX_LIBCPPABI_VERSION=""`` 118 must be used during configuration. 119 120 121A full list of currently open libc++ bugs can be `found here`__. 122 123.. __: https://bugs.llvm.org/buglist.cgi?component=All%20Bugs&product=libc%2B%2B&query_format=advanced&resolution=---&order=changeddate%20DESC%2Cassigned_to%20DESC%2Cbug_status%2Cpriority%2Cbug_id&list_id=74184 124 125Design Documents 126---------------- 127 128.. toctree:: 129 :maxdepth: 1 130 131 DesignDocs/AvailabilityMarkup 132 DesignDocs/DebugMode 133 DesignDocs/CapturingConfigInfo 134 DesignDocs/ABIVersioning 135 DesignDocs/VisibilityMacros 136 DesignDocs/ThreadingSupportAPI 137 138* `<atomic> design <http://libcxx.llvm.org/atomic_design.html>`_ 139* `<type_traits> design <http://libcxx.llvm.org/type_traits_design.html>`_ 140* `Notes by Marshall Clow`__ 141 142.. __: https://cplusplusmusings.wordpress.com/2012/07/05/clang-and-standard-libraries-on-mac-os-x/ 143 144Build Bots and Test Coverage 145---------------------------- 146 147* `LLVM Buildbot Builders <http://lab.llvm.org:8011/console>`_ 148* `Apple Jenkins Builders <http://lab.llvm.org:8080/green/view/Libcxx/>`_ 149* `Windows Appveyor Builders <https://ci.appveyor.com/project/llvm-mirror/libcxx>`_ 150* `Code Coverage Results <http://efcs.ca/libcxx-coverage>`_ 151 152Getting Involved 153================ 154 155First please review our `Developer's Policy <http://llvm.org/docs/DeveloperPolicy.html>`__ 156and `Getting started with LLVM <http://llvm.org/docs/GettingStarted.html>`__. 157 158**Bug Reports** 159 160If you think you've found a bug in libc++, please report it using 161the `LLVM Bugzilla`_. If you're not sure, you 162can post a message to the `cfe-dev mailing list`_ or on IRC. 163Please include "libc++" in your subject. 164 165**Patches** 166 167If you want to contribute a patch to libc++, the best place for that is 168`Phabricator <http://llvm.org/docs/Phabricator.html>`_. Please include [libcxx] in the subject and 169add `cfe-commits` as a subscriber. Also make sure you are subscribed to the 170`cfe-commits mailing list <http://lists.llvm.org/mailman/listinfo/cfe-commits>`_. 171 172**Discussion and Questions** 173 174Send discussions and questions to the 175`cfe-dev mailing list <http://lists.llvm.org/mailman/listinfo/cfe-dev>`_. 176Please include [libcxx] in the subject. 177 178 179 180Quick Links 181=========== 182* `LLVM Homepage <http://llvm.org/>`_ 183* `libc++abi Homepage <http://libcxxabi.llvm.org/>`_ 184* `LLVM Bugzilla <https://bugs.llvm.org/>`_ 185* `cfe-commits Mailing List`_ 186* `cfe-dev Mailing List`_ 187* `Browse libc++ -- SVN <http://llvm.org/svn/llvm-project/libcxx/trunk/>`_ 188* `Browse libc++ -- ViewVC <http://llvm.org/viewvc/llvm-project/libcxx/trunk/>`_ 189