1========================================= 2Libc++ 13.0.0 (In-Progress) Release Notes 3========================================= 4 5.. contents:: 6 :local: 7 :depth: 2 8 9Written by the `Libc++ Team <https://libcxx.llvm.org>`_ 10 11.. warning:: 12 13 These are in-progress notes for the upcoming libc++ 13 release. 14 Release notes for previous releases can be found on 15 `the Download Page <https://releases.llvm.org/download.html>`_. 16 17Introduction 18============ 19 20This document contains the release notes for the libc++ C++ Standard Library, 21part of the LLVM Compiler Infrastructure, release 13.0.0. Here we describe the 22status of libc++ in some detail, including major improvements from the previous 23release and new feature work. For the general LLVM release notes, see `the LLVM 24documentation <https://llvm.org/docs/ReleaseNotes.html>`_. All LLVM releases may 25be downloaded from the `LLVM releases web site <https://llvm.org/releases/>`_. 26 27For more information about libc++, please see the `Libc++ Web Site 28<https://libcxx.llvm.org>`_ or the `LLVM Web Site <https://llvm.org>`_. 29 30Note that if you are reading this file from a Git checkout or the 31main Libc++ web page, this document applies to the *next* release, not 32the current one. To see the release notes for a specific release, please 33see the `releases page <https://llvm.org/releases/>`_. 34 35What's New in Libc++ 13.0.0? 36============================ 37 38- Support for older compilers has been removed. Several additional platforms 39 are now officially supported. :ref:`platform_and_compiler_support` contains 40 the complete overview of platforms and compilers supported by libc++. 41- The large headers ``<algorithm>``, ``<iterator>``, and ``<utility>`` have 42 been split in more granular headers. This reduces the size of included code 43 when using libc++. This may lead to missing includes after upgrading to 44 libc++13. 45 46New Features 47------------ 48 49- ``std::filesystem`` is now feature complete for the Windows platform using 50 MinGW. MSVC isn't supported since it lacks 128-bit integer support. 51- The implementation of the C++20 concepts library has been completed. 52- Several C++20 ``constexpr`` papers have been completed: 53 54 - `P0879R0 <https://wg21.link/P0879R0>`_ ``constexpr`` for ``std::swap()`` 55 and swap related functions 56 - `P1032R1 <https://wg21.link/P1032R1>`_ Misc ``constexpr`` bits 57 - `P0883 <https://wg21.link/P0883>`_ Fixing Atomic Initialization 58 59- More C++20 features have been implemented. :doc:`Status/Cxx20` has the full 60 overview of libc++'s C++20 implementation status. 61- More C++2b features have been implemented. :doc:`Status/Cxx2b` has the 62 full overview of libc++'s C++2b implementation status. 63- The CMake option ``LIBCXX_ENABLE_INCOMPLETE_FEATURES`` has been added. This 64 option allows libc++ vendors to disable headers that aren't production 65 quality yet. Currently, turning the option off disables the headers 66 ``<format>`` and ``<ranges>``. 67- The documentation conversion from html to restructured text has been 68 completed. 69 70API Changes 71----------- 72 73- There has been several changes in the tuple constructors provided by libc++. 74 Those changes were made as part of an effort to regularize libc++'s tuple 75 implementation, which contained several subtle bugs due to these extensions. 76 If you notice a build breakage when initializing a tuple, make sure you 77 properly initialize all the tuple elements - this is probably the culprit. 78 79 In particular, the extension allowing tuples to be constructed from fewer 80 elements than the number of elements in the tuple (in which case the remaining 81 elements would be default-constructed) has been removed. See https://godbolt.org/z/sqozjd. 82 83 Also, the extension allowing a tuple to be constructed from an array has been 84 removed. See https://godbolt.org/z/5esqbW. 85 86- The ``std::pointer_safety`` utility and related functions are not available 87 in C++03 anymore. Furthermore, in other standard modes, it has changed from 88 a struct to a scoped enumeration, which is an ABI break. Finally, the 89 ``std::get_pointer_safety`` function was previously in the dylib, but it 90 is now defined as inline in the headers. 91 92 While this is technically both an API and an ABI break, we do not expect 93 ``std::pointer_safety`` to have been used at all in real code, since we 94 never implemented the underlying support for garbage collection. 95 96- The `LIBCXXABI_ENABLE_PIC` CMake option was removed. If you are building your 97 own libc++abi from source and were using `LIBCXXABI_ENABLE_PIC`, please use 98 `CMAKE_POSITION_INDEPENDENT_CODE=ON` instead. 99 100- When the header <variant> is included, it will no longer include <array> transitively. 101 102- The ``std::result_of`` and ``std::is_literal_type`` type traits have been removed in 103 C++20 mode. 104