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diff --git a/libcxx/docs/index.rst b/libcxx/docs/index.rst new file mode 100644 index 00000000000..baca123609c --- /dev/null +++ b/libcxx/docs/index.rst @@ -0,0 +1,171 @@ +.. _index: + +============================= +"libc++" C++ Standard Library +============================= + +Overview +======== + +libc++ is a new implementation of the C++ standard library, targeting C++11. + +* Features and Goals + + * Correctness as defined by the C++11 standard. + * Fast execution. + * Minimal memory use. + * Fast compile times. + * ABI compatibility with gcc's libstdc++ for some low-level features + such as exception objects, rtti and memory allocation. + * Extensive unit tests. + +* Design and Implementation: + + * Extensive unit tests + * Internal linker model can be dumped/read to textual format + * Additional linking features can be plugged in as "passes" + * OS specific and CPU specific code factored out + + +Getting Started with libc++ +--------------------------- + +.. toctree:: + :maxdepth: 2 + + UsingLibcxx + BuildingLibcxx + TestingLibcxx + +Current Status +-------------- + +After its initial introduction, many people have asked "why start a new +library instead of contributing to an existing library?" (like Apache's +libstdcxx, GNU's libstdc++, STLport, etc). There are many contributing +reasons, but some of the major ones are: + +From years of experience (including having implemented the standard +library before), we've learned many things about implementing +the standard containers which require ABI breakage and fundamental changes +to how they are implemented. For example, it is generally accepted that +building std::string using the "short string optimization" instead of +using Copy On Write (COW) is a superior approach for multicore +machines (particularly in C++11, which has rvalue references). Breaking +ABI compatibility with old versions of the library was +determined to be critical to achieving the performance goals of +libc++. + +Mainline libstdc++ has switched to GPL3, a license which the developers +of libc++ cannot use. libstdc++ 4.2 (the last GPL2 version) could be +independently extended to support C++11, but this would be a fork of the +codebase (which is often seen as worse for a project than starting a new +independent one). Another problem with libstdc++ is that it is tightly +integrated with G++ development, tending to be tied fairly closely to the +matching version of G++. + +STLport and the Apache libstdcxx library are two other popular +candidates, but both lack C++11 support. Our experience (and the +experience of libstdc++ developers) is that adding support for C++11 (in +particular rvalue references and move-only types) requires changes to +almost every class and function, essentially amounting to a rewrite. +Faced with a rewrite, we decided to start from scratch and evaluate every +design decision from first principles based on experience. + +Further, both projects are apparently abandoned: STLport 5.2.1 was +released in Oct'08, and STDCXX 4.2.1 in May'08. + +Platform and Compiler Support +----------------------------- + +libc++ is known to work on the following platforms, using gcc-4.2 and +clang (lack of C++11 language support disables some functionality). +Note that functionality provided by ``<atomic>`` is only functional with clang +and GCC. + +============ ==================== ============ ======================== +OS Arch Compilers ABI Library +============ ==================== ============ ======================== +Mac OS X i386, x86_64 Clang, GCC libc++abi +FreeBSD 10+ i386, x86_64, ARM Clang, GCC libcxxrt, libc++abi +Linux i386, x86_64 Clang, GCC libc++abi +============ ==================== ============ ======================== + +The following minimum compiler versions are strongly recommended. + +* Clang 3.5 and above +* GCC 4.7 and above. + +Anything older *may* work. + +C++ Dialect Support +--------------------- + +* C++11 - Complete +* `C++14 - Complete <cxx14 status_>`__ +* `C++1z - In Progress <cxx1z status_>`__ +* `Post C++14 Technical Specifications - In Progress <ts status_>`__ + +.. _cxx14 status: http://libcxx.llvm.org/cxx1y_status.html +.. _cxx1z status: http://libcxx.llvm.org/cxx1z_status.html +.. _ts status: http://libcxx.llvm.org/ts1z_status.html + + +Notes and Known Issues +---------------------- + +This list contains known issues with libc++ + +* Building libc++ with ``-fno-rtti`` is not supported. However + linking against it with ``-fno-rtti`` is supported. +* On OS X v10.8 and older the CMake option ``-DLIBCXX_LIBCPPABI_VERSION=""`` + must be used during configuration. + + +A full list of currently open libc++ bugs can be `found here <libcxx bug list_>`__. + +.. _libcxx bug list: https://llvm.org/bugs/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 + +Design Documents +---------------- + +* `<atomic> design <http://libcxx.llvm.org/atomic_design.html>`_ +* `<type_traits> design <http://libcxx.llvm.org/type_traits_design.html>`_ +* `Status of debug mode <http://libcxx.llvm.org/debug_mode.html>`_ +* `Notes by Marshall Clow <clow notes_>`__ + +.. _clow notes: https://cplusplusmusings.wordpress.com/2012/07/05/clang-and-standard-libraries-on-mac-os-x/ + +Getting Involved +================ + +First please review our `Developer's Policy <http://llvm.org/docs/DeveloperPolicy.html>`__. + +**Bug Reports** + +If you think you've found a bug in libc++, please report it using +the _`LLVM Bugzilla`. If you're not sure, you +can post a message to the `cfe-dev`_. mailing list or on IRC. +Please include "libc++" in your subject. + +**Patches** + +If you want to contribute a patch to libc++, the best place for that is +`Phabricator <phab doc_>`__. Please include [libcxx] in the subject and +add `cfe-commits` as a subscriber. + +**Discussion and Questions** + +Send discussions and questions to the `clang mailing list <cfe-dev_>`__. +Please include [libcxx] in the subject. + +.. _phab doc: http://llvm.org/docs/Phabricator.html +.. _cfe-dev: http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev + +Links +===== + +* `Getting started with LLVM <http://llvm.org/docs/GettingStarted.html>`_ +* `libc++abi Homepage <libc++abi_>`__ + +.. _`libc++abi`: http://libcxxabi.llvm.org/ |
