libcxx/docs/ReleaseNotes.rst

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Libc++ 13.0.0 (In-Progress) Release Notes
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Written by the `Libc++ Team <https://libcxx.llvm.org>`_

.. warning::

   These are in-progress notes for the upcoming libc++ 13 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 13.0.0. 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++ 13.0.0?
============================

New Features
------------

- ...

API Changes
-----------

- There has been several changes in the tuple constructors provided by libc++.
  Those changes were made as part of an effort to regularize libc++'s tuple
  implementation, which contained several subtle bugs due to these extensions.
  If you notice a build breakage when initializing a tuple, make sure you
  properly initialize all the tuple elements - this is probably the culprit.

  In particular, the extension allowing tuples to be constructed from fewer
  elements than the number of elements in the tuple (in which case the remaining
  elements would be default-constructed) has been removed. See https://godbolt.org/z/sqozjd.

  Also, the extension allowing a tuple to be constructed from an array has been
  removed. See https://godbolt.org/z/5esqbW.

- The ``std::pointer_safety`` utility and related functions are not available
  in C++03 anymore. Furthermore, in other standard modes, it has changed from
  a struct to a scoped enumeration, which is an ABI break. Finally, the
  ``std::get_pointer_safety`` function was previously in the dylib, but it
  is now defined as inline in the headers.

  While this is technically both an API and an ABI break, we do not expect
  ``std::pointer_safety`` to have been used at all in real code, since we
  never implemented the underlying support for garbage collection.

- The `LIBCXXABI_ENABLE_PIC` CMake option was removed. If you are building your
  own libc++abi from source and were using `LIBCXXABI_ENABLE_PIC`, please use
  `CMAKE_POSITION_INDEPENDENT_CODE=ON` instead.

- When the header <variant> is included, it will no longer include <array> transitively.