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===========================================
Libc++ 20.0.0 (In-Progress) Release Notes
===========================================
.. contents::
:local:
:depth: 2
Written by the `Libc++ Team <https://libcxx.llvm.org>`_
.. warning::
These are in-progress notes for the upcoming libc++ 20.0.0 release.
Release notes for previous releases can be found on
`the Download Page <https://releases.llvm.org/download.html>`_.
Introduction
============
This document contains the release notes for the libc++ C++ Standard Library,
part of the LLVM Compiler Infrastructure, release 20.0.0. 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
be downloaded from the `LLVM releases web site <https://llvm.org/releases/>`_.
For more information about libc++, please see the `Libc++ Web Site
<https://libcxx.llvm.org>`_ or the `LLVM Web Site <https://llvm.org>`_.
Note that if you are reading this file from a Git checkout or the
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++ 20.0.0?
==============================
Implemented Papers
------------------
- TODO
Improvements and New Features
-----------------------------
- TODO
Deprecations and Removals
-------------------------
- TODO: The ``LIBCXX_ENABLE_ASSERTIONS`` CMake variable and the ``_LIBCPP_ENABLE_ASSERTIONS`` macro that were used to enable
the safe mode will be removed in LLVM 20.
- TODO: The C++20 synchronization library will be removed entirely in language modes prior to C++20 in LLVM 20.
- TODO: The relational operators for ``std::chrono::weekday`` will be removed entirely, and the
``_LIBCPP_ENABLE_REMOVED_WEEKDAY_RELATIONAL_OPERATORS`` macro that was used to re-enable this extension will be
ignored in LLVM 20.
- TODO: The ``_LIBCPP_ENABLE_REMOVED_ALLOCATOR_CONST`` macro will no longer have an effect.
Upcoming Deprecations and Removals
----------------------------------
LLVM 20
~~~~~~~
- TODO
LLVM 21
~~~~~~~
- The status of the C++03 implementation will be frozen after the LLVM 21 release. This means that starting in LLVM 22, non-critical bug fixes may not be back-ported
to C++03, including LWG issues. C++03 is a legacy platform, where most projects are no longer actively maintained. To
reduce the amount of fixes required to keep such legacy projects compiling with up-to-date toolchains, libc++ will aim to freeze the status of the headers in C++03 mode to avoid unintended breaking changes.
See https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc for more details.
If you are using C++03 in your project, you should consider moving to a newer version of the Standard to get the most out of libc++.
ABI Affecting Changes
---------------------
- TODO
Build System Changes
--------------------
- TODO
|
