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llvm-project/clang/docs/ReleaseNotes.rst

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===========================================
Clang |release| |ReleaseNotesTitle|
===========================================
.. contents::
:local:
:depth: 2
Written by the `LLVM Team <https://llvm.org/>`_
.. only:: PreRelease
.. warning::
These are in-progress notes for the upcoming Clang |version| 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 Clang C/C++/Objective-C
frontend, part of the LLVM Compiler Infrastructure, release |release|. Here we
describe the status of Clang 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 Clang or LLVM, including information about the
latest release, please see the `Clang Web Site <https://clang.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 Clang 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 Clang |release|?
==============================
Some of the major new features and improvements to Clang are listed
here. Generic improvements to Clang as a whole or to its underlying
infrastructure are described first, followed by language-specific
sections with improvements to Clang's support for those languages.
Major New Features
------------------
Bug Fixes
---------
- Fixes an accepts-invalid bug in C when using a ``_Noreturn`` function
specifier on something other than a function declaration. This fixes
`Issue 56800 <https://github.com/llvm/llvm-project/issues/56800>`_.
- Fix `#56772 <https://github.com/llvm/llvm-project/issues/56772>`_ - invalid
destructor names were incorrectly accepted on template classes.
- Improve compile-times with large dynamic array allocations with trivial
constructors. This fixes
`Issue 56774 <https://github.com/llvm/llvm-project/issues/56774>`_.
- No longer assert/miscompile when trying to make a vectorized ``_BitInt`` type
using the ``ext_vector_type`` attribute (the ``vector_size`` attribute was
already properly diagnosing this case).
- Fix clang not properly diagnosing the failing subexpression when chained
binary operators are used in a ``static_assert`` expression.
- Fix a crash when evaluating a multi-dimensional array's array filler
expression is element-dependent. This fixes
`Issue 50601 <https://github.com/llvm/llvm-project/issues/56016>`_.
Improvements to Clang's diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Clang will now correctly diagnose as ill-formed a constant expression where an
enum without a fixed underlying type is set to a value outside the range of
the enumeration's values. Due to the extended period of time this bug was
present in major C++ implementations (including Clang), this error has the
ability to be downgraded into a warning (via: -Wno-error=enum-constexpr-conversion)
to provide a transition period for users. This diagnostic is expected to turn
into an error-only diagnostic in the next Clang release. Fixes
`Issue 50055: <https://github.com/llvm/llvm-project/issues/50055>`_.
- Clang will now check compile-time determinable string literals as format strings.
Fixes `Issue 55805: <https://github.com/llvm/llvm-project/issues/55805>`_.
- ``-Wformat`` now recognizes ``%b`` for the ``printf``/``scanf`` family of
functions and ``%B`` for the ``printf`` family of functions. Fixes
`Issue 56885: <https://github.com/llvm/llvm-project/issues/56885>`_.
- ``-Wbitfield-constant-conversion`` now diagnoses implicit truncation when 1 is
assigned to a 1-bit signed integer bitfield. This fixes
`Issue 53253 <https://github.com/llvm/llvm-project/issues/53253>`_.
- ``-Wincompatible-function-pointer-types`` now defaults to an error in all C
language modes. It may be downgraded to a warning with
``-Wno-error=incompatible-function-pointer-types`` or disabled entirely with
``-Wno-implicit-function-pointer-types``.
- When including a PCH from a GCC style directory with multiple alternative PCH
files, Clang now requires all defines set on the command line while generating
the PCH and when including it to match. This matches GCC's behaviour.
Previously Clang would tolerate defines to be set when creating the PCH but
missing when used, or vice versa. This makes sure that Clang picks the
correct one, where it previously would consider multiple ones as potentially
acceptable (and erroneously use whichever one is tried first).
Non-comprehensive list of changes in this release
-------------------------------------------------
New Compiler Flags
------------------
Deprecated Compiler Flags
-------------------------
Modified Compiler Flags
-----------------------
Removed Compiler Flags
-------------------------
New Pragmas in Clang
--------------------
- ...
Attribute Changes in Clang
--------------------------
Windows Support
---------------
AIX Support
-----------
C Language Changes in Clang
---------------------------
C2x Feature Support
-------------------
C++ Language Changes in Clang
-----------------------------
C++20 Feature Support
^^^^^^^^^^^^^^^^^^^^^
- Support capturing structured bindings in lambdas
(`P1091R3 <https://wg21.link/p1091r3>`_ and `P1381R1 <https://wg21.link/P1381R1>`).
This fixes issues `GH52720 <https://github.com/llvm/llvm-project/issues/52720>`_,
`GH54300 <https://github.com/llvm/llvm-project/issues/54300>`_,
`GH54301 <https://github.com/llvm/llvm-project/issues/54301>`_,
and `GH49430 <https://github.com/llvm/llvm-project/issues/49430>`_.
C++2b Feature Support
^^^^^^^^^^^^^^^^^^^^^
CUDA/HIP Language Changes in Clang
----------------------------------
Objective-C Language Changes in Clang
-------------------------------------
OpenCL C Language Changes in Clang
----------------------------------
...
ABI Changes in Clang
--------------------
OpenMP Support in Clang
-----------------------
...
CUDA Support in Clang
---------------------
- ...
X86 Support in Clang
--------------------
- Support ``-mindirect-branch-cs-prefix`` for call and jmp to indirect thunk.
DWARF Support in Clang
----------------------
Arm and AArch64 Support in Clang
--------------------------------
Floating Point Support in Clang
-------------------------------
Internal API Changes
--------------------
Build System Changes
--------------------
AST Matchers
------------
clang-format
------------
clang-extdef-mapping
--------------------
libclang
--------
Static Analyzer
---------------
.. _release-notes-ubsan:
Undefined Behavior Sanitizer (UBSan)
------------------------------------
Core Analysis Improvements
==========================
- ...
New Issues Found
================
- ...
Python Binding Changes
----------------------
The following methods have been added:
- ...
Significant Known Problems
==========================
Additional Information
======================
A wide variety of additional information is available on the `Clang web
page <https://clang.llvm.org/>`_. The web page contains versions of the
API documentation which are up-to-date with the Git version of
the source code. You can access versions of these documents specific to
this release by going into the "``clang/docs/``" directory in the Clang
tree.
If you have any questions or comments about Clang, please feel free to
contact us on the Discourse forums (Clang Frontend category)
<https://discourse.llvm.org/c/clang/6>`_.
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