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diff --git a/libcxx/docs/ReleaseNotes.rst b/libcxx/docs/ReleaseNotes.rst index 96e98fd..f5ebc4e 100644 --- a/libcxx/docs/ReleaseNotes.rst +++ b/libcxx/docs/ReleaseNotes.rst @@ -1,5 +1,5 @@ ========================================= -Libc++ 15.0.0 (In-Progress) Release Notes +Libc++ 16.0.0 (In-Progress) Release Notes ========================================= .. contents:: @@ -10,7 +10,7 @@ Written by the `Libc++ Team <https://libcxx.llvm.org>`_ .. warning:: - These are in-progress notes for the upcoming libc++ 15 release. + These are in-progress notes for the upcoming libc++ 16 release. Release notes for previous releases can be found on `the Download Page <https://releases.llvm.org/download.html>`_. @@ -18,7 +18,7 @@ Introduction ============ This document contains the release notes for the libc++ C++ Standard Library, -part of the LLVM Compiler Infrastructure, release 15.0.0. Here we describe the +part of the LLVM Compiler Infrastructure, release 16.0.0. Here we describe the status of libc++ in some detail, including major improvements from the previous release and new feature work. For the general LLVM release notes, see `the LLVM documentation <https://llvm.org/docs/ReleaseNotes.html>`_. All LLVM releases may @@ -32,237 +32,23 @@ main Libc++ web page, this document applies to the *next* release, not the current one. To see the release notes for a specific release, please see the `releases page <https://llvm.org/releases/>`_. -What's New in Libc++ 15.0.0? +What's New in Libc++ 16.0.0? ============================ -The main focus of the libc++ team has been to implement new C++20 and C++23 -features. - -The C++20 ``format`` library is feature complete, but not all Standard LWG -issues have been addressed. Since it is expected that at least one of these -issues will cause an ABI break the ``format`` library is considered -experimental. - -The C++20 ``ranges`` library has progressed a lot since the last release and is -almost complete. The ``ranges`` library is considered experimental. - - Implemented Papers ------------------ -- P0627R6 - Function to mark unreachable code -- P1165R1 - Make stateful allocator propagation more consistent for ``operator+(basic_string)`` -- P0674R1 - Support arrays in ``make_shared`` and ``allocate_shared`` -- P0980R1 - Making ``std::string`` constexpr -- P2216R3 - ``std::format`` improvements -- P0174R2 - Deprecating Vestigial Library Parts in C++17 -- N4190 - Removing ``auto_ptr``, ``random_shuffle()``, And Old ``<functional>`` Stuff -- P0154R1 - Hardware inference size -- P0618R0 - Deprecating ``<codecvt>`` -- P2418R2 - Add support for ``std::generator``-like types to ``std::format`` -- LWG3659 - Consider ``ATOMIC_FLAG_INIT`` undeprecation -- P1423R3 - ``char8_t`` backward compatibility remediation - -- Marked the following papers as "Complete" (note that some of those might have - been implemented in a previous release but not marked as such): - - - P1207R4 - Movability of Single-pass Iterators - - P1474R1 - Helpful pointers for ``ContiguousIterator`` - - P1522R1 - Iterator Difference Type and Integer Overflow - - P1523R1 - Views and Size Types - - P1456R1 - Move-only views - - P1870R1 - ``forwarding-range`` is too subtle - - P1878R1 - Constraining Readable Types - - P1970R2 - Consistency for ``size()`` functions: Add ``ranges::ssize`` - - P1983R0 - Wording for GB301, US296, US292, US291, and US283 - Improvements and New Features ----------------------------- -- ``std::pop_heap`` now uses an algorithm known as "bottom-up heapsort" or - "heapsort with bounce" to reduce the number of comparisons, and rearranges - elements using move-assignment instead of ``std::swap``. - -- Libc++ now supports a variety of assertions that can be turned on to help catch - undefined behavior in user code. This new support is now separate from the old - (and incomplete) Debug Mode. Vendors can select whether the library they ship - should include assertions or not by default. For details, see - :ref:`the documentation <assertions-mode>` about this new feature. - -- Clang now implements the ``-fexperimental-library`` flag. This flag can be used to - enable experimental library features such as TSes and other in-progress work like - ``<ranges>`` and ``<format>``. Using this flag makes it unnecessary to manually link - against ``libc++experimental.a`` -- just use ``-fexperimental-library`` and the - compiler will do what's needed to make experimental features work. However, be - aware that experimental features are not stable! - -- The implementation of the function ``std::to_chars`` for integral types using - base 10 has moved from the dylib to the header. This means the function no - longer has a minimum deployment target. - -- The performance for ``std::to_chars``, for integral types using base 2, 8, - 10, or 16 has been improved. - -- The functions ``std::from_chars`` and ``std::to_chars`` now have 128-bit integral - support. - -- The format functions (``std::format``, ``std::format_to``, ``std::format_to_n``, and - ``std::formatted_size``) now validate the format string at compile time. - When the format string is invalid this will make the code ill-formed instead - of throwing an exception at run-time. (This does not affect the ``v`` - functions.) - -- All format functions in ``<format>`` allow the usage of non-copyable types as - argument for the formatting functions. This change causes bit fields to become - invalid arguments for the formatting functions. - -- The ``_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_VOID_SPECIALIZATION`` macro has been added to allow - re-enabling the ``allocator<void>`` specialization. When used in conjunction with - ``_LIBCPP_ENABLE_CXX20_REMOVED_ALLOCATOR_MEMBERS``, this ensures that the members of - ``allocator<void>`` removed in C++20 can be accessed. - -- ``boyer_moore_searcher`` and ``boyer_moore_horspool_searcher`` have been implemented. - -- ``vector<bool>::const_reference``, ``vector<bool>::const_iterator::reference`` - and ``bitset::const_reference`` are now aliases for `bool` in the unstable ABI, - which improves libc++'s conformance to the Standard. - Deprecations and Removals ------------------------- -- The header ``<experimental/filesystem>`` has been removed. Instead, use - ``<filesystem>`` header. The associated macro - ``_LIBCPP_DEPRECATED_EXPERIMENTAL_FILESYSTEM`` has been removed too. - -- The C++14 function ``std::quoted(const char*)`` is no longer supported in - C++03 or C++11 modes. - -- Setting a custom debug handler with ``std::__libcpp_debug_function`` is not - supported anymore. Please migrate to using the new support for - :ref:`assertions <assertions-mode>` instead. - -- ``std::function`` has been removed in C++03. If you are using it, please remove usages - or upgrade to C++11 or later. It is possible to re-enable ``std::function`` in C++03 by defining - ``_LIBCPP_ENABLE_CXX03_FUNCTION``. This option will be removed in LLVM 16. - -- ``unary_function`` and ``binary_function`` are no longer available in C++17 and C++20. - They can be re-enabled by defining ``_LIBCPP_ENABLE_CXX17_REMOVED_UNARY_BINARY_FUNCTION``. - They are also marked as ``[[deprecated]]`` in C++11 and later. To disable deprecation warnings - you have to define ``_LIBCPP_DISABLE_DEPRECATION_WARNINGS``. Note that this disables - all deprecation warnings. - -- The contents of ``<codecvt>``, ``wstring_convert`` and ``wbuffer_convert`` have been marked as deprecated. - To disable deprecation warnings you have to define ``_LIBCPP_DISABLE_DEPRECATION_WARNINGS``. Note that this - disables all deprecation warnings. - -- The ``_LIBCPP_DISABLE_EXTERN_TEMPLATE`` macro is not honored anymore when defined by - users of libc++. Instead, users not wishing to take a dependency on libc++ should link - against the static version of libc++, which will result in no dependency being - taken against the shared library. - -- The ``_LIBCPP_ABI_UNSTABLE`` macro has been removed in favour of setting - ``_LIBCPP_ABI_VERSION=2``. This should not have any impact on users because - they were not supposed to set ``_LIBCPP_ABI_UNSTABLE`` manually, however we - still feel that it is worth mentioning in the release notes in case some users - had been doing it. - -- The integer distributions ``binomial_distribution``, ``discrete_distribution``, - ``geometric_distribution``, ``negative_binomial_distribution``, ``poisson_distribution``, - and ``uniform_int_distribution`` now conform to the Standard by rejecting - template parameter types other than ``short``, ``int``, ``long``, ``long long``, - and the unsigned versions thereof. As an extension, ``int8_t``, ``__int128_t`` and - their unsigned versions are supported too. In particular, instantiating these - distributions with non-integer types like ``bool`` and ``char`` will not compile - anymore. - Upcoming Deprecations and Removals ---------------------------------- -- The ``_LIBCPP_DEBUG`` macro is not supported anymore. It will be honoured until - LLVM 16, and then it will be an error to define that macro. To enable basic - assertions (previously ``_LIBCPP_DEBUG=0``), please use ``_LIBCPP_ENABLE_ASSERTIONS=1``. - To enable the debug mode (previously ``_LIBCPP_DEBUG=1|2``), please ensure that - the library has been built with support for the debug mode, and it will be - enabled automatically (no need to define ``_LIBCPP_DEBUG``). - -- The experimental versions of ``boyer_moore_searcher`` and ``boyer_moore_horspool_searcher`` - will be removed in LLVM 17. You can disable the deprecation warnings by defining - ``_LIBCPP_NO_EXPERIMENTAL_DEPRECATION_WARNING_SEARCHERS``. - -- The implementation of the Coroutines TS in ``std::experimental`` will be removed in LLVM 16. - -- Libc++ is getting ready to remove unnecessary transitive inclusions. This may - break your code in the future. To future-proof your code to these removals, - please compile your code with ``_LIBCPP_REMOVE_TRANSITIVE_INCLUDES`` defined - and fix any compilation error resulting from missing includes. - ABI Affecting Changes --------------------- -- The ``_LIBCPP_ABI_USE_CXX03_NULLPTR_EMULATION`` macro controlling whether we use an - emulation for ``std::nullptr_t`` in C++03 mode has been removed. After this change, - ``_LIBCPP_ABI_USE_CXX03_NULLPTR_EMULATION`` will not be honoured anymore and there - will be no way to opt back into the C++03 emulation of ``std::nullptr_t``. - -- On FreeBSD, NetBSD, DragonFlyBSD and Solaris, ``std::random_device`` is now implemented on - top of ``arc4random()`` instead of reading from ``/dev/urandom``. Any implementation-defined - token used when constructing a ``std::random_device`` will now be ignored instead of - interpreted as a file to read entropy from. - -- ``std::valarray``'s unary operators ``!``, ``+``, ``~`` and ``-`` now return an expression - object instead of a ``valarray``. This was done to fix an issue where any expression involving - other ``valarray`` operators and one of these unary operators would end up with a dangling - reference. This is a potential ABI break for code that exposes ``std::valarray`` on an ABI - boundary, specifically if the return type of an ABI-boundary function is ``auto``-deduced - from an expression involving unary operators on ``valarray``. If you are concerned by this, - you can audit whether your executable or library exports any function that returns a - ``valarray``, and if so ensure that any such function uses ``std::valarray`` directly - as a return type instead of relying on the type of ``valarray``-expressions, which is - not guaranteed by the Standard anyway. - -- By default, the legacy debug mode symbols are not provided with the library anymore. If - you are a vendor and need to re-enable them, please use the ``LIBCXX_ENABLE_BACKWARDS_COMPATIBILITY_DEBUG_MODE_SYMBOLS`` - CMake flag, and contact the libc++ developers as this will be removed in LLVM 16. - Furthermore, please note that ``LIBCXX_ENABLE_DEBUG_MODE_SUPPORT`` is not honored anymore. - Build System Changes -------------------- - -- Support for standalone builds have been entirely removed from libc++, libc++abi and - libunwind. Please use :ref:`these instructions <build instructions>` for building - libc++, libc++abi and/or libunwind. - -- The ``{LIBCXX,LIBCXXABI,LIBUNWIND}_TARGET_TRIPLE``, ``{LIBCXX,LIBCXXABI,LIBUNWIND}_SYSROOT`` and - ``{LIBCXX,LIBCXXABI,LIBUNWIND}_GCC_TOOLCHAIN`` CMake variables have been removed. Instead, please - use the ``CMAKE_CXX_COMPILER_TARGET``, ``CMAKE_SYSROOT`` and ``CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN`` - variables provided by CMake. - -- When building for Windows, vendors who want to avoid dll-exporting symbols from the static libc++abi - library should set ``LIBCXXABI_HERMETIC_STATIC_LIBRARY=ON`` when configuring CMake. The current - behavior, which tries to guess the correct dll-export semantics based on whether we're building - the libc++ shared library, will be removed in LLVM 16. - -- Previously, the C++ ABI library headers would be installed inside ``<prefix>/include/c++/v1`` - alongside the libc++ headers as part of building libc++. This is not the case anymore -- the - ABI library is expected to install its headers where it wants them as part of its own build. - Note that no action is required for most users, who build libc++ against libc++abi, since - libc++abi already installs its headers in the right location. However, vendors building - libc++ against alternate ABI libraries should make sure that their ABI library installs - its own headers. - -- The legacy testing configuration is now deprecated and will be removed in LLVM 16. For - most users, this should not have any impact. However, if you are testing libc++, libc++abi, or - libunwind in a configuration or on a platform that used to be supported by the legacy testing - configuration and isn't supported by one of the configurations in ``libcxx/test/configs``, - ``libcxxabi/test/configs``, or ``libunwind/test/configs``, please move to one of those - configurations or define your own. - -- MinGW DLL builds of libc++ no longer use dllimport in their headers, which - means that the same set of installed headers works for both DLL and static - linkage. This means that distributors finally can build both library - versions with a single CMake invocation. - -- The ``LIBCXX_HIDE_FROM_ABI_PER_TU_BY_DEFAULT`` configuration option has been removed. Indeed, - the risk of ODR violations from mixing different versions of libc++ in the same program has - been mitigated with a different technique that is simpler and does not have the drawbacks of - using internal linkage. |