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llvm-project/clang-tools-extra/docs/ReleaseNotes.rst
tigbr 7b8f7beadc
[clang-tidy] Add new check bugprone-tagged-union-member-count (#89925) 
This patch introduces a new check to find mismatches between the number
of data members in a union and the number enum values present in
variant-like structures.

Variant-like types can look something like this:

```c++
struct variant {
    enum {
        tag1,
        tag2,
    } kind;
    union {
        int i;
        char c;
    } data;
};
```

The kind data member of the variant is supposed to tell which data
member of the union is valid, however if there are fewer enum values
than union members, then it is likely a mistake.

The opposite is not that obvious, because it might be fine to have more
enum values than union data members, but for the time being I am curious
how many real bugs can be caught if we give a warning regardless.

This patch also contains a heuristic where we try to guess whether the
last enum constant is actually supposed to be a tag value for the
variant or whether it is just holding how many enum constants have been
created.

Patch by Gábor Tóthvári!
2024-10-01 13:24:32 +02:00

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====================================================
Extra Clang Tools |release| |ReleaseNotesTitle|
====================================================
.. contents::
:local:
:depth: 3
Written by the `LLVM Team <https://llvm.org/>`_
.. only:: PreRelease
.. warning::
These are in-progress notes for the upcoming Extra Clang Tools |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 Extra Clang Tools, part of the
Clang release |release|. Here we describe the status of the Extra Clang Tools in
some detail, including major improvements from the previous release and new
feature work. 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 Extra Clang Tools |release|?
==========================================
Some of the major new features and improvements to Extra Clang Tools are listed
here. Generic improvements to Extra Clang Tools as a whole or to its underlying
infrastructure are described first, followed by tool-specific sections.
Major New Features
------------------
- The ``clang-pseudo`` tool is incomplete and does not have active maintainers,
so it has been removed. See
`the RFC <https://discourse.llvm.org/t/removing-pseudo-parser/71131/>`_ for
more details.
...
Improvements to clangd
----------------------
Inlay hints
^^^^^^^^^^^
Diagnostics
^^^^^^^^^^^
Semantic Highlighting
^^^^^^^^^^^^^^^^^^^^^
Compile flags
^^^^^^^^^^^^^
Hover
^^^^^
Code completion
^^^^^^^^^^^^^^^
Code actions
^^^^^^^^^^^^
Signature help
^^^^^^^^^^^^^^
Cross-references
^^^^^^^^^^^^^^^^
Objective-C
^^^^^^^^^^^
Miscellaneous
^^^^^^^^^^^^^
Improvements to clang-doc
-------------------------
Improvements to clang-query
---------------------------
The improvements are...
Improvements to clang-tidy
--------------------------
- Improved :program:`run-clang-tidy.py` script. Fixed minor shutdown noise
happening on certain platforms when interrupting the script.
New checks
^^^^^^^^^^
- New :doc:`bugprone-tagged-union-member-count
<clang-tidy/checks/bugprone/tagged-union-member-count>` check.
Gives warnings for tagged unions, where the number of tags is
different from the number of data members inside the union.
New check aliases
^^^^^^^^^^^^^^^^^
- New alias :doc:`cert-arr39-c <clang-tidy/checks/cert/arr39-c>` to
:doc:`bugprone-sizeof-expression
<clang-tidy/checks/bugprone/sizeof-expression>` was added.
Changes in existing checks
^^^^^^^^^^^^^^^^^^^^^^^^^^
- Improved :doc:`bugprone-casting-through-void
<clang-tidy/checks/bugprone/casting-through-void>` check to suggest replacing
the offending code with ``reinterpret_cast``, to more clearly express intent.
- Improved :doc:`bugprone-dangling-handle
<clang-tidy/checks/bugprone/dangling-handle>` check to treat `std::span` as a
handle class.
- Improved :doc:`bugprone-forwarding-reference-overload
<clang-tidy/checks/bugprone/forwarding-reference-overload>` check by fixing
a crash when determining if an ``enable_if[_t]`` was found.
- Improved :doc:`bugprone-posix-return
<clang-tidy/checks/bugprone/posix-return>` check to support integer literals
as LHS and posix call as RHS of comparison.
- Improved :doc:`bugprone-sizeof-expression
<clang-tidy/checks/bugprone/sizeof-expression>` check to find suspicious
usages of ``sizeof()``, ``alignof()``, and ``offsetof()`` when adding or
subtracting from a pointer.
- Improved :doc:`bugprone-unchecked-optional-access
<clang-tidy/checks/bugprone/unchecked-optional-access>` to support
`bsl::optional` and `bdlb::NullableValue` from
<https://github.com/bloomberg/bde>_.
- Improved :doc:`bugprone-unsafe-functions
<clang-tidy/checks/bugprone/unsafe-functions>` check to allow specifying
additional functions to match.
- Improved :doc:`cert-flp30-c <clang-tidy/checks/cert/flp30-c>` check to
fix false positive that floating point variable is only used in increment
expression.
- Improved :doc:`cppcoreguidelines-prefer-member-initializer
<clang-tidy/checks/cppcoreguidelines/prefer-member-initializer>` check to
avoid false positive when member initialization depends on a structured
binding variable.
- Improved :doc:`misc-definitions-in-headers
<clang-tidy/checks/misc/definitions-in-headers>` check by rewording the
diagnostic note that suggests adding ``inline``.
- Improved :doc:`modernize-avoid-c-arrays
<clang-tidy/checks/modernize/avoid-c-arrays>` check to suggest using ``std::span``
as a replacement for parameters of incomplete C array type in C++20 and
``std::array`` or ``std::vector`` before C++20.
- Improved :doc:`modernize-use-std-format
<clang-tidy/checks/modernize/use-std-format>` check to support replacing
member function calls too.
- Improved :doc:`misc-unconventional-assign-operator
<clang-tidy/checks/misc/unconventional-assign-operator>` check to avoid
false positive for C++23 deducing this.
- Improved :doc:`modernize-min-max-use-initializer-list
<clang-tidy/checks/modernize/min-max-use-initializer-list>` check by fixing
a false positive when only an implicit conversion happened inside an
initializer list.
- Improved :doc:`modernize-use-nullptr
<clang-tidy/checks/modernize/use-nullptr>` check to also recognize
``NULL``/``__null`` (but not ``0``) when used with a templated type.
- Improved :doc:`modernize-use-std-print
<clang-tidy/checks/modernize/use-std-print>` check to support replacing
member function calls too.
- Improved :doc:`readability-enum-initial-value
<clang-tidy/checks/readability/enum-initial-value>` check by only issuing
diagnostics for the definition of an ``enum``, and by fixing a typo in the
diagnostic.
- Improved :doc:`performance-avoid-endl
<clang-tidy/checks/performance/avoid-endl>` check to use ``std::endl`` as
placeholder when lexer cannot get source text.
- Improved :doc:`readability-container-contains
<clang-tidy/checks/readability/container-contains>` check to let it work on
any class that has a ``contains`` method.
- Improved :doc:`readability-implicit-bool-conversion
<clang-tidy/checks/readability/implicit-bool-conversion>` check
by adding the option `UseUpperCaseLiteralSuffix` to select the
case of the literal suffix in fixes.
- Improved :doc:`readability-redundant-smartptr-get
<clang-tidy/checks/readability/redundant-smartptr-get>` check to
remove `->`, when redundant `get()` is removed.
Removed checks
^^^^^^^^^^^^^^
Miscellaneous
^^^^^^^^^^^^^
Improvements to include-fixer
-----------------------------
The improvements are...
Improvements to clang-include-fixer
-----------------------------------
The improvements are...
Improvements to modularize
--------------------------
The improvements are...
Improvements to pp-trace
------------------------
Clang-tidy Visual Studio plugin
-------------------------------
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