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[libc++][doc] Update the release notes for LLVM 20. #124403

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Jan 27, 2025
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[libc++][doc] Update the release notes for LLVM 20. #124403

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b03e001
[libc++][doc] Update the release notes for LLVM 20.
mordante Jan 25, 2025
aa2cbfe
Address review comment.
mordante Jan 26, 2025
e0e0d0d
flat_map updates
ldionne Jan 27, 2025
5a29360
Merge branch 'main' into review/release_notes
ldionne Jan 27, 2025
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24 changes: 14 additions & 10 deletions libcxx/docs/ReleaseNotes/20.rst
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Expand Up @@ -35,6 +35,8 @@ see the `releases page <https://llvm.org/releases/>`_.
What's New in Libc++ 20.0.0?
==============================

The main focus of the libc++ team has been to implement new C++20, C++23, and C++26 features.

Implemented Papers
------------------

Expand All @@ -44,7 +46,7 @@ Implemented Papers
- P2985R0: A type trait for detecting virtual base classes (`Github <https://github.com/llvm/llvm-project/issues/105432>`__)
- ``std::jthread`` and ``<stop_token>`` are not guarded behind ``-fexperimental-library`` anymore
- P2674R1: A trait for implicit lifetime types (`Github <https://github.com/llvm/llvm-project/issues/105259>`__)
- P0429R9: A Standard ``flat_map`` is partially implemented and ``flat_map`` is provided (`Github <https://github.com/llvm/llvm-project/issues/105190>`__)
- P0429R9: A Standard ``flat_map`` (`Github <https://github.com/llvm/llvm-project/issues/105190>`__)

Improvements and New Features
-----------------------------
Expand Down Expand Up @@ -111,6 +113,13 @@ Improvements and New Features
std::errc::not_a_directory``, or use ``err.default_error_condition()`` to map to an ``error_condition``, and then test
its ``value()`` and ``category()``.

- ``std::stable_sort`` uses radix sort for integral types now, which can improve the performance up to 10 times, depending
on type of sorted elements and the initial state of the sorted array.

- Reduced the amount of debug information generated for internal typedefs. This reduces the size of debug builds.

- Added :ref:`hardening mode <hardening>` support for ``forward_list`` and ``bitset``.

Deprecations and Removals
-------------------------

Expand All @@ -129,10 +138,10 @@ Deprecations and Removals
supported as an extension anymore, please migrate any code that uses e.g. ``std::vector<const T>`` to be
standards conforming.

- Non-conforming member typedefs ``base``, ``iterator``, ``const_iterator``, and ``const_reference`` of ``std::bitset``,
and member typedef ``base`` of ``std::forward_list`` and ``std::list`` are removed. Previously, these member typedefs
(except ``const_reference``) were private but could cause ambiguity in name lookup. Code that expects such ambiguity
will possibly not compile in LLVM 20.
- Non-conforming member typedefs ``base``, ``iterator``, ``const_iterator``, ``size_type``, ``difference_type``, and
``const_reference`` of ``std::bitset``, and member typedef ``base`` of ``std::forward_list`` and ``std::list`` are
removed. Previously, these member typedefs (except ``const_reference``) were private but could cause ambiguity in name
lookup. Code that expects such ambiguity will possibly not compile in LLVM 20.

- The function ``__libcpp_verbose_abort()`` is now ``noexcept``, to match ``std::terminate()``. (The combination of
``noexcept`` and ``[[noreturn]]`` has special significance for function effects analysis.) For backwards compatibility,
Expand Down Expand Up @@ -196,8 +205,3 @@ ABI Affecting Changes

- The localization support base API has been reimplemented, leading to different functions being exported from the
libc++ built library on Windows and Windows-like platforms.

Build System Changes
--------------------

- TODO
2 changes: 1 addition & 1 deletion libcxx/docs/Status/Cxx23Papers.csv
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Expand Up @@ -52,7 +52,7 @@
"`P2443R1 <https://wg21.link/P2443R1>`__","``views::chunk_by``","2022-02 (Virtual)","|Complete|","18",""
"","","","","",""
"`P0009R18 <https://wg21.link/P0009R18>`__","mdspan: A Non-Owning Multidimensional Array Reference","2022-07 (Virtual)","|Complete|","18",""
"`P0429R9 <https://wg21.link/P0429R9>`__","A Standard ``flat_map``","2022-07 (Virtual)","|Complete|","",""
"`P0429R9 <https://wg21.link/P0429R9>`__","A Standard ``flat_map``","2022-07 (Virtual)","|Complete|","20",""
"`P1169R4 <https://wg21.link/P1169R4>`__","``static operator()``","2022-07 (Virtual)","|Complete|","16",""
"`P1222R4 <https://wg21.link/P1222R4>`__","A Standard ``flat_set``","2022-07 (Virtual)","","",""
"`P1223R5 <https://wg21.link/P1223R5>`__","``ranges::find_last()``, ``ranges::find_last_if()``, and ``ranges::find_last_if_not()``","2022-07 (Virtual)","|Complete|","19",""
Expand Down
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