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a574ade231
It turns out that llvmorg-14.0.6 might be too new for dyld (the vector base class no longer exist in that release).
105 lines
4.9 KiB
ReStructuredText
105 lines
4.9 KiB
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=========================================
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Libc++ 13.0.0 Release Notes
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=========================================
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.. contents::
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:local:
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:depth: 2
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Written by the `Libc++ Team <https://libcxx.llvm.org>`_
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Introduction
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============
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This document contains the release notes for the libc++ C++ Standard Library,
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part of the LLVM Compiler Infrastructure, release 13.0.0. Here we describe the
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status of libc++ in some detail, including major improvements from the previous
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release and new feature work. For the general LLVM release notes, see `the LLVM
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documentation <https://llvm.org/docs/ReleaseNotes.html>`_. All LLVM releases may
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be downloaded from the `LLVM releases web site <https://llvm.org/releases/>`_.
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For more information about libc++, please see the `Libc++ Web Site
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<https://libcxx.llvm.org>`_ or the `LLVM Web Site <https://llvm.org>`_.
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Note that if you are reading this file from a Git checkout or the
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main Libc++ web page, this document applies to the *next* release, not
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the current one. To see the release notes for a specific release, please
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see the `releases page <https://llvm.org/releases/>`_.
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What's New in Libc++ 13.0.0?
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============================
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- Support for older compilers has been removed. Several additional platforms
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are now officially supported. :ref:`platform_and_compiler_support` contains
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the complete overview of platforms and compilers supported by libc++.
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- The large headers ``<algorithm>``, ``<iterator>``, and ``<utility>`` have
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been split in more granular headers. This reduces the size of included code
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when using libc++. This may lead to missing includes after upgrading to
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libc++13.
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New Features
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------------
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- ``std::filesystem`` is now feature complete for the Windows platform using
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MinGW. MSVC isn't supported since it lacks 128-bit integer support.
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- The implementation of the C++20 concepts library has been completed.
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- Several C++20 ``constexpr`` papers have been completed:
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- `P0879R0 <https://wg21.link/P0879R0>`_ ``constexpr`` for ``std::swap()``
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and swap related functions
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- `P1032R1 <https://wg21.link/P1032R1>`_ Misc ``constexpr`` bits
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- `P0883 <https://wg21.link/P0883>`_ Fixing Atomic Initialization
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- More C++20 features have been implemented. :doc:`Status/Cxx20` has the full
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overview of libc++'s C++20 implementation status.
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- More C++2b features have been implemented. :doc:`Status/Cxx2b` has the
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full overview of libc++'s C++2b implementation status.
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- The CMake option ``LIBCXX_ENABLE_INCOMPLETE_FEATURES`` has been added. This
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option allows libc++ vendors to disable headers that aren't production
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quality yet. Currently, turning the option off disables the headers
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``<format>`` and ``<ranges>``.
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- The documentation conversion from html to restructured text has been
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completed.
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API and ABI Changes
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-------------------
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- There has been several changes in the tuple constructors provided by libc++.
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Those changes were made as part of an effort to regularize libc++'s tuple
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implementation, which contained several subtle bugs due to these extensions.
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If you notice a build breakage when initializing a tuple, make sure you
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properly initialize all the tuple elements - this is probably the culprit.
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In particular, the extension allowing tuples to be constructed from fewer
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elements than the number of elements in the tuple (in which case the remaining
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elements would be default-constructed) has been removed. See https://godbolt.org/z/sqozjd.
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Also, the extension allowing a tuple to be constructed from an array has been
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removed. See https://godbolt.org/z/5esqbW.
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- The ``std::pointer_safety`` utility and related functions are not available
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in C++03 anymore. Furthermore, in other standard modes, it has changed from
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a struct to a scoped enumeration, which is an ABI break. Finally, the
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``std::get_pointer_safety`` function was previously in the dylib, but it
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is now defined as inline in the headers.
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While this is technically both an API and an ABI break, we do not expect
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``std::pointer_safety`` to have been used at all in real code, since we
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never implemented the underlying support for garbage collection.
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- The `LIBCXXABI_ENABLE_PIC` CMake option was removed. If you are building your
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own libc++abi from source and were using `LIBCXXABI_ENABLE_PIC`, please use
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`CMAKE_POSITION_INDEPENDENT_CODE=ON` instead.
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- When the header <variant> is included, it will no longer include <array> transitively.
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- The ``std::result_of`` and ``std::is_literal_type`` type traits have been removed in
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C++20 mode.
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- The C++20 type ``std::counted_semaphore<N>`` is now based on ``std::atomic``
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on all platforms, and does not use "native" semaphores such as pthreads
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``sem_t`` even on platforms that would support them. This changes the layout
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of ``counted_semaphore<N>`` notably on Linux, so it is an ABI break on that
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platform. This change is needed to conform to the Standard, which requires
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``counted_semaphore``'s constructor to be constexpr.
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