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========================================
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Clang 13.0.0 (In-Progress) Release Notes
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========================================
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.. contents::
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:local:
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:depth: 2
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Written by the `LLVM Team <https://llvm.org/>`_
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.. warning::
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These are in-progress notes for the upcoming Clang 13 release.
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Release notes for previous releases can be found on
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`the Download Page <https://releases.llvm.org/download.html>`_.
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Introduction
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============
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This document contains the release notes for the Clang C/C++/Objective-C
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frontend, part of the LLVM Compiler Infrastructure, release 13.0.0. Here we
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describe the status of Clang in some detail, including major
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improvements from the previous release and new feature work. For the
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general LLVM release notes, see `the LLVM
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documentation <https://llvm.org/docs/ReleaseNotes.html>`_. All LLVM
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releases may be downloaded from the `LLVM releases web
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site <https://llvm.org/releases/>`_.
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For more information about Clang or LLVM, including information about the
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latest release, please see the `Clang Web Site <https://clang.llvm.org>`_ or the
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`LLVM Web Site <https://llvm.org>`_.
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Note that if you are reading this file from a Git checkout or the
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main Clang web page, this document applies to the *next* release, not
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the current one. To see the release notes for a specific release, please
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see the `releases page <https://llvm.org/releases/>`_.
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What's New in Clang 13.0.0?
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===========================
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Some of the major new features and improvements to Clang are listed
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here. Generic improvements to Clang as a whole or to its underlying
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infrastructure are described first, followed by language-specific
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sections with improvements to Clang's support for those languages.
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Major New Features
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------------------
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- Guaranteed tail calls are now supported with statement attributes
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``[[clang::musttail]]`` in C++ and ``__attribute__((musttail))`` in C. The
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attribute is applied to a return statement (not a function declaration),
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and an error is emitted if a tail call cannot be guaranteed, for example if
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the function signatures of caller and callee are not compatible. Guaranteed
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tail calls enable a class of algorithms that would otherwise use an
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arbitrary amount of stack space.
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Improvements to Clang's diagnostics
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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- ...
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Non-comprehensive list of changes in this release
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-------------------------------------------------
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- The default value of _MSC_VER was raised from 1911 to 1914. MSVC 19.14 has the
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support to overaligned objects on x86_32 which is required for some LLVM
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passes.
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New Compiler Flags
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------------------
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- ``-Wreserved-identifier`` emits warning when user code uses reserved
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identifiers.
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- ``-fstack-usage`` generates an extra .su file per input source file. The .su
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file contains frame size information for each function defined in the source
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file.
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Deprecated Compiler Flags
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-------------------------
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- ...
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Modified Compiler Flags
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-----------------------
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- -Wshadow now also checks for shadowed structured bindings
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- ``-B <prefix>`` (when ``<prefix>`` is a directory) was overloaded to additionally
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detect GCC installations under ``<prefix>`` (``lib{,32,64}/gcc{,-cross}/$triple``).
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This behavior was incompatible with GCC, caused interop issues with
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``--gcc-toolchain``, and was thus dropped. Specify ``--gcc-toolchain=<dir>``
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instead. ``-B``'s other GCC-compatible semantics are preserved:
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``$prefix/$triple-$file`` and ``$prefix$file`` are searched for executables,
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libraries, includes, and data files used by the compiler.
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Removed Compiler Flags
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-------------------------
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- The clang-cl ``/fallback`` flag, which made clang-cl invoke Microsoft Visual
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C++ on files it couldn't compile itself, has been removed.
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- ``-Wreturn-std-move-in-c++11``, which checked whether an entity is affected by
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`CWG1579 <https://wg21.link/CWG1579>`_ to become implicitly movable, has been
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removed.
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New Pragmas in Clang
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--------------------
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- ...
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Attribute Changes in Clang
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--------------------------
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- ...
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- Added support for C++11-style ``[[]]`` attributes on using-declarations, as a
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clang extension.
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Windows Support
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---------------
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C Language Changes in Clang
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---------------------------
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- ...
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C++ Language Changes in Clang
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-----------------------------
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- The oldest supported GNU libstdc++ is now 4.8.3 (released 2014-05-22).
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Clang workarounds for bugs in earlier versions have been removed.
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- ...
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C++20 Feature Support
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^^^^^^^^^^^^^^^^^^^^^
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...
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C++2b Feature Support
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^^^^^^^^^^^^^^^^^^^^^
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...
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Objective-C Language Changes in Clang
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-------------------------------------
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OpenCL C Language Changes in Clang
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----------------------------------
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...
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ABI Changes in Clang
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--------------------
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OpenMP Support in Clang
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-----------------------
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- ...
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CUDA Support in Clang
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---------------------
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- ...
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X86 Support in Clang
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--------------------
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- ...
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Internal API Changes
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--------------------
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These are major API changes that have happened since the 12.0.0 release of
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Clang. If upgrading an external codebase that uses Clang as a library,
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this section should help get you past the largest hurdles of upgrading.
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- ...
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Build System Changes
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--------------------
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These are major changes to the build system that have happened since the 12.0.0
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release of Clang. Users of the build system should adjust accordingly.
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- The option ``LIBCLANG_INCLUDE_CLANG_TOOLS_EXTRA`` no longer exists. There were
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two releases with that flag forced off, and no uses were added that forced it
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on. The recommended replacement is clangd.
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- ...
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AST Matchers
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------------
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- ...
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clang-format
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------------
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- Option ``SpacesInLineCommentPrefix`` has been added to control the
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number of spaces in a line comments prefix.
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- Option ``SortIncludes`` has been updated from a ``bool`` to an
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``enum`` with backwards compatibility. In addition to the previous
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``true``/``false`` states (now ``CaseSensitive``/``Never``), a third
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state has been added (``CaseInsensitive``) which causes an alphabetical sort
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with case used as a tie-breaker.
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.. code-block:: c++
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// Never (previously false)
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#include "B/A.h"
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#include "A/B.h"
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#include "a/b.h"
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#include "A/b.h"
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#include "B/a.h"
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// CaseSensitive (previously true)
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#include "A/B.h"
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#include "A/b.h"
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#include "B/A.h"
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#include "B/a.h"
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#include "a/b.h"
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// CaseInsensitive
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#include "A/B.h"
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#include "A/b.h"
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#include "a/b.h"
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#include "B/A.h"
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#include "B/a.h"
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- ``BasedOnStyle: InheritParentConfig`` allows to use the ``.clang-format`` of
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the parent directories to overwrite only parts of it.
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- Option ``IndentAccessModifiers`` has been added to be able to give access
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modifiers their own indentation level inside records.
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- Option ``PPIndentWidth`` has been added to be able to configure pre-processor
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indentation independent from regular code.
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- Option ``ShortNamespaceLines`` has been added to give better control
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over ``FixNamespaceComments`` when determining a namespace length.
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- Support for Whitesmiths has been improved, with fixes for ``namespace`` blocks
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and ``case`` blocks and labels.
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- Option ``EmptyLineAfterAccessModifier`` has been added to remove, force or keep
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new lines after access modifiers.
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- Checks for newlines in option ``EmptyLineBeforeAccessModifier`` are now based
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on the formatted new lines and not on the new lines in the file. (Fixes
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https://llvm.org/PR41870.)
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- Option ``SpacesInAngles`` has been improved, it now accepts ``Leave`` value
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that allows to keep spaces where they are already present.
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- Option ``AllowShortIfStatementsOnASingleLine`` has been improved, it now
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accepts ``AllIfsAndElse`` value that allows to put "else if" and "else" short
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statements on a single line. (Fixes https://llvm.org/PR50019.)
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- Option ``BreakInheritanceList`` gets a new style, ``AfterComma``. It breaks
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only after the commas that separate the base-specifiers.
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- Option ``LambdaBodyIndentation`` has been added to control how the body of a
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lambda is indented. The default ``Signature`` value indents the body one level
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relative to whatever indentation the signature has. ``OuterScope`` lets you
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change that so that the lambda body is indented one level relative to the scope
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containing the lambda, regardless of where the lambda signature was placed.
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- Option ``IfMacros`` has been added. This lets you define macros that get
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formatted like conditionals much like ``ForEachMacros`` get styled like
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foreach loops.
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- ``git-clang-format`` no longer formats changes to symbolic links. (Fixes
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https://llvm.org/PR46992.)
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- Makes ``PointerAligment: Right`` working with ``AlignConsecutiveDeclarations``.
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(Fixes https://llvm.org/PR27353)
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- Option ``AlignArrayOfStructure`` has been added to allow for ordering array-like
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initializers.
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- Support for formatting JSON file (\*.json) has been added to clang-format.
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libclang
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--------
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- ...
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Static Analyzer
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---------------
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- ...
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.. _release-notes-ubsan:
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Undefined Behavior Sanitizer (UBSan)
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------------------------------------
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Core Analysis Improvements
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==========================
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- ...
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New Issues Found
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================
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- ...
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Python Binding Changes
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----------------------
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The following methods have been added:
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- ...
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Significant Known Problems
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==========================
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Additional Information
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======================
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A wide variety of additional information is available on the `Clang web
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page <https://clang.llvm.org/>`_. The web page contains versions of the
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API documentation which are up-to-date with the Git version of
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the source code. You can access versions of these documents specific to
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this release by going into the "``clang/docs/``" directory in the Clang
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tree.
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If you have any questions or comments about Clang, please feel free to
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contact us via the `mailing
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list <https://lists.llvm.org/mailman/listinfo/cfe-dev>`_.
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