[libcxx-commits] [libcxx] 30d6806 - [libc++][doc] Update the release notes for LLVM 18 (#78324)
via libcxx-commits
libcxx-commits at lists.llvm.org
Sun Jan 21 10:48:37 PST 2024
Author: Mark de Wever
Date: 2024-01-21T19:48:33+01:00
New Revision: 30d6806a08f8f453d6389bdfeae4c32e937a9821
URL: https://github.com/llvm/llvm-project/commit/30d6806a08f8f453d6389bdfeae4c32e937a9821
DIFF: https://github.com/llvm/llvm-project/commit/30d6806a08f8f453d6389bdfeae4c32e937a9821.diff
LOG: [libc++][doc] Update the release notes for LLVM 18 (#78324)
This is a preparation for the upcoming LLVM 18 release.
Added:
Modified:
libcxx/docs/Hardening.rst
libcxx/docs/ReleaseNotes/18.rst
libcxx/docs/Status/Parallelism.rst
libcxx/docs/Status/Ranges.rst
Removed:
################################################################################
diff --git a/libcxx/docs/Hardening.rst b/libcxx/docs/Hardening.rst
index 33a168d6e16837..0761f42368e921 100644
--- a/libcxx/docs/Hardening.rst
+++ b/libcxx/docs/Hardening.rst
@@ -1,3 +1,5 @@
+.. _hardening-modes:
+
===============
Hardening Modes
===============
diff --git a/libcxx/docs/ReleaseNotes/18.rst b/libcxx/docs/ReleaseNotes/18.rst
index 799347b646e639..0b43d76650a9d3 100644
--- a/libcxx/docs/ReleaseNotes/18.rst
+++ b/libcxx/docs/ReleaseNotes/18.rst
@@ -35,9 +35,26 @@ see the `releases page <https://llvm.org/releases/>`_.
What's New in Libc++ 18.0.0?
==============================
-- A new debug mode has been added, replacing the legacy debug mode that was
- removed in the LLVM 17 release. See ``libcxx/docs/Hardening.rst`` for more
- details.
+The main focus of the libc++ team has been to implement new C++20, C++23,
+and C++26 features.
+
+New hardened modes for the library have been added, replacing the legacy debug mode that was
+removed in the LLVM 17 release. Unlike the legacy debug mode, some of these hardening modes are
+also intended to be used in production. See :ref:`hardening-modes` for more details.
+
+Work on the ranges support has progressed. See
+:ref:`ranges-status` for the current status.
+
+Work on the experimental C++23 module support has progressed. The ``std.compat``
+module is available and the feature is retroactively available in C++20. See
+:ref:`ModulesInLibcxx` for more information.
+
+Work on the experimental C++17 Parallel STL has progressed. See
+:ref:`pstl-status` for the current status.
+
+Work on the experimental C++17 SIMD support has progressed. See
+:ref:`parallelism-status` for the current status.
+
Implemented Papers
------------------
@@ -68,8 +85,9 @@ Implemented Papers
Improvements and New Features
-----------------------------
-- ``std::ranges::count`` is now optimized for ``vector<bool>::iterator``, which
- can lead up to 350x performance improvements.
+- ``std::ranges::count`` and ``std::ranges::find`` are now optimized for
+ ``std::vector<bool>::iterator``, which can lead up to 350x performance
+ improvements.
- ``std::for_each`` has been optimized for segmented iterators like ``std::deque::iterator`` in C++23 and
later, which can lead up to 40x performance improvements.
@@ -106,6 +124,11 @@ Improvements and New Features
``-DLIBCXX_INSTALL_MODULE_DIR=<path>``. The default location is
``${PREFIX}/share/libc++/v1``.
+- AddressSanitizer annotations have been added to ``std::basic_string``.
+
+- The libc++ source code has been formatted with ``clang-format``. This
+ `discourse thread <https://discourse.llvm.org/t/rfc-clang-formatting-all-of-libc-once-and-for-all>`_
+ contains information how to rebase downstream patches.
Deprecations and Removals
-------------------------
@@ -118,7 +141,7 @@ Deprecations and Removals
- The non-conforming constructor ``std::future_error(std::error_code)`` has been removed. Please use the
``std::future_error(std::future_errc)`` constructor provided in C++17 instead.
-- `P1957 <https://wg21.link/P1957>` has been implemented in Clang and libc++ removed a code path that led to
+- `P1957 <https://wg21.link/P1957>`_ has been implemented in Clang and libc++ removed a code path that led to
narrowing conversions in ``std::variant`` behaving in a non-standard way. This may change how some uses of
``std::variant``'s constructor behave in user code. The ``_LIBCPP_ENABLE_NARROWING_CONVERSIONS_IN_VARIANT``
macro is provided to restore the previous behavior, and it will be supported in the LLVM 18 release only.
@@ -155,6 +178,14 @@ Deprecations and Removals
that were removed in the C++17 and C++20 standards. Instead of using these
macros, please use the macros to re-enable individual features.
+- The macro ``_LIBCPP_INLINE_VISIBILITY`` has been deprecated in LLVM 18 and
+ will be removed entirely in LLVM 19. The macro ``_LIBCPP_HIDE_FROM_ABI`` is
+ the drop-in replacement.
+
+- The macro ``_VSTD`` has been deprecated in LLVM 18 and will be removed
+ entirely in LLVM 19. The code ``std`` is the drop-in replacement.
+
+
Upcoming Deprecations and Removals
----------------------------------
@@ -163,6 +194,9 @@ Upcoming Deprecations and Removals
LLVM 19
~~~~~~~
+- The ``LIBCXX_EXECUTOR`` CMake variable has been deprecated. LLVM 19 will
+ completely remove support for the ``*_EXECUTOR`` variables.
+
- The ``LIBCXX_ENABLE_ASSERTIONS`` CMake variable that was used to enable the safe mode will be deprecated and setting
it will trigger an error; use the ``LIBCXX_HARDENING_MODE`` variable with the value ``extensive`` instead. Similarly,
the ``_LIBCPP_ENABLE_ASSERTIONS`` macro will be deprecated (setting it to ``1`` still enables the extensive mode in
@@ -187,6 +221,12 @@ LLVM 19
``_LIBCPP_ENABLE_CXX20_REMOVED_FEATURES`` macros have been deprecated
in LLVM 18 and will be removed entirely in LLVM 19.
+- The macro ``_LIBCPP_INLINE_VISIBILITY`` has been deprecated in LLVM 18 and
+ will be removed entirely in LLVM 19.
+
+- The macro ``_VSTD`` has been deprecated in LLVM 18 and will be removed
+ entirely in LLVM 19.
+
LLVM 20
~~~~~~~
@@ -203,12 +243,12 @@ ABI Affecting Changes
- This release of libc++ added missing visibility annotations on some types in the library. Users compiling with
``-fvisbility=hidden`` may notice that additional type infos from libc++ are being exported from their ABI. This is
the correct behavior in almost all cases since exporting the RTTI is required for these types to work properly with
- dynamic_cast, exceptions and other mechanisms across binaries. However, if you intend to use libc++ purely as an
+ ``dynamic_cast``, exceptions and other mechanisms across binaries. However, if you intend to use libc++ purely as an
internal implementation detail (i.e. you use libc++ as a static archive and never export libc++ symbols from your ABI)
and you notice changes to your exported symbols list, then this means that you were not properly preventing libc++
symbols from being part of your ABI.
-- The name mangling for intantiations of ``std::projected`` has changed in order to implement P2538R1. This technically
+- The name mangling for instantiations of ``std::projected`` has changed in order to implement P2538R1. This technically
results in an ABI break, however in practice we expect uses of ``std::projected`` in ABI-sensitive places to be
extremely rare. Any error resulting from this change should result in a link-time error.
@@ -219,18 +259,30 @@ ABI Affecting Changes
to throw a
diff erent exception when attempting allocations that are too large
(``std::bad_alloc`` vs ``std::length_error``).
-- The layout of some views inside ``std::ranges`` that use the ``movable-box`` exposition-only type as an implementation
- detail has changed in order to fix a bug which could result in overwriting user data following the ``movable-box``
- <https://github.com/llvm/llvm-project/issues/70506>.
- This was caused by incorrect usage of the ``[[no_unique_address]]`` attribute inside the implementation of ``movable-box``.
- This only affects the layout of the following views: ``take_while_view``, ``filter_view``, ``single_view``, ``drop_while_view``,
- ``repeat_view``, ``transform_view``, ``chunk_by_view``. In order to avoid silent breakage, an ABI tag has been added to
- these views such that their mangled name will be
diff erent starting in this version of libc++.
- As a result, attempting to call a function that expects one of these views will fail to link until the code has been rebuilt
- against a matching version of libc++. In practice, we believe it is unusual for these views to appear at ABI boundaries so this
- should not be a major problem for most users. However it is probably worth auditing ranges-heavy code for ABI boundaries that
+- The layout of some range adaptors that use the ``movable-box`` exposition-only type as an implementation
+ detail has changed in order to fix a `bug <https://github.com/llvm/llvm-project/issues/70506>`_ which could result in
+ overwriting user data following the ``movable-box``.
+ This bug was caused by incorrect usage of the ``[[no_unique_address]]`` attribute inside the implementation of ``movable-box``.
+ This fix affects the layout of the following views: ``take_while_view``, ``filter_view``, ``single_view``, ``drop_while_view``,
+ ``repeat_view``, ``transform_view``, ``chunk_by_view``. In order to avoid silent breakage as a result of this fix, an ABI tag has been added to
+ these views such that their mangled name will be
diff erent starting in this version of libc++.
+ As a result, attempting to call a function that expects one of these views will fail to link until the code has been rebuilt
+ against a matching version of libc++. In practice, we believe it is unusual for these views to appear at ABI boundaries so this
+ should not be a major problem for most users. However it is probably worth auditing ranges-heavy code for ABI boundaries that
would contain these views, or for types that contain these views as members and which are passed across ABI boundaries.
+- Some properties of libc++ may cause ODR-violations when mixing multiple libc++
+ instances. To avoid these, often benign, ODR-violations the ODR-affecting
+ properties are now part of the ABI tag. The ODR-affecting properties are:
+
+ - library version (This was part of the ABI tag prior to LLVM 18.)
+ - exceptions vs no-exceptions
+ - hardening mode
+
+ This should not be ABI-affecting except that libc++ will be more robust
+ against
diff erent configurations of it being used in
diff erent translation
+ units.
+
Build System Changes
--------------------
diff --git a/libcxx/docs/Status/Parallelism.rst b/libcxx/docs/Status/Parallelism.rst
index 4fce429bbe6cee..9f8a326867f1ca 100644
--- a/libcxx/docs/Status/Parallelism.rst
+++ b/libcxx/docs/Status/Parallelism.rst
@@ -1,4 +1,4 @@
-.. parallelism-status:
+.. _parallelism-status:
====================================
libc++ Parallelism TS Status (N4808)
diff --git a/libcxx/docs/Status/Ranges.rst b/libcxx/docs/Status/Ranges.rst
index 7d36700d6545f0..cdbf68393b739d 100644
--- a/libcxx/docs/Status/Ranges.rst
+++ b/libcxx/docs/Status/Ranges.rst
@@ -1,4 +1,4 @@
-.. ranges-status:
+.. _ranges-status:
================================
libc++ Ranges Status
More information about the libcxx-commits
mailing list