[all-commits] [llvm/llvm-project] 2e7913: [clang] Improve `_Alignas` on a `struct` declarati...

[Jerin Philip via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2e7913342eb9d5cd1744d4c24e1898588429b80d
      https://github.com/llvm/llvm-project/commit/2e7913342eb9d5cd1744d4c24e1898588429b80d
  Author: Jerin Philip <jerinphilip at live.in>
  Date:   2023-11-07 (Tue, 07 Nov 2023)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/include/clang/Basic/AttributeCommonInfo.h
    M clang/lib/Sema/SemaDecl.cpp
    M clang/test/C/drs/dr4xx.c
    M clang/test/Parser/c1x-alignas.c
    A clang/test/Parser/c2x-alignas.c
    M clang/test/Parser/cxx0x-attributes.cpp

  Log Message:
  -----------
  [clang] Improve `_Alignas` on a `struct` declaration diagnostic (#65638)

Fixes https://github.com/llvm/llvm-project/issues/58637. 

Adds `isAlignas()` method on `AttributeCommonInfo` which accounts for
C++ `alignas` as well as C11 `_Alignas`.

The method is used to improve diagnostic in C when `_Alignas` is used in
C at the wrong location.  This corrects the previously suggested move
of `_Alignas` past the declaration specifier, now warns attribute
`_Alignas` is ignored.

Based on https://reviews.llvm.org/D141177.