1========================================
2Libc++ 8.0.0 (In-Progress) Release Notes
3========================================
4
5.. contents::
6   :local:
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8
9Written by the `Libc++ Team <https://libcxx.llvm.org>`_
10
11.. warning::
12
13   These are in-progress notes for the upcoming libc++ 8 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 8.0.0. 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 Subversion 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++ 8.0.0?
36===========================
37
38New Features
39------------
40
41API Changes
42-----------
43- Building libc++ for Mac OSX 10.6 is not supported anymore.
44- Starting with LLVM 8.0.0, users that wish to link together translation units
45  built with different versions of libc++'s headers into the same final linked
46  image MUST define the _LIBCPP_HIDE_FROM_ABI_PER_TU macro to 1 when building
47  those translation units. Not defining _LIBCPP_HIDE_FROM_ABI_PER_TU to 1 and
48  linking translation units built with different versions of libc++'s headers
49  together may lead to ODR violations and ABI issues. On the flipside, code
50  size improvements should be expected for everyone not defining the macro.
51- Starting with LLVM 8.0.0, std::dynarray has been removed from the library.
52  std::dynarray was a feature proposed for C++14 that was pulled from the
53  Standard at the last minute and was never standardized. Since there are no
54  plans to standardize this facility it is being removed.
55- Starting with LLVM 8.0.0, std::bad_array_length has been removed from the
56  library. std::bad_array_length was a feature proposed for C++14 alongside
57  std::dynarray, but it never actually made it into the C++ Standard. There
58  are no plans to standardize this feature at this time. Formally speaking,
59  this removal constitutes an ABI break because the symbols were shipped in
60  the shared library. However, on macOS systems, the feature was not usable
61  because it was hidden behind availability annotations. We do not expect
62  any actual breakage to happen from this change.
63