[all-commits] [llvm/llvm-project] 3c84e4: [C11] Improve the diagnostic when accessing a memb...

[Aaron Ballman via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3c84e4a0dbd08fc03bbcdd8354a984e0efcf7672
      https://github.com/llvm/llvm-project/commit/3c84e4a0dbd08fc03bbcdd8354a984e0efcf7672
  Author: Aaron Ballman <aaron at aaronballman.com>
  Date:   2022-03-29 (Tue, 29 Mar 2022)

  Changed paths:
    M clang/docs/ReleaseNotes.rst
    M clang/include/clang/Basic/DiagnosticSemaKinds.td
    M clang/lib/Sema/SemaExprMember.cpp
    M clang/test/Sema/atomic-expr.c

  Log Message:
  -----------
  [C11] Improve the diagnostic when accessing a member of an atomic struct

Member access for an atomic structure or union is unconditional
undefined behavior (C11 6.5.2.3p5). However, we would issue a confusing
error message about the base expression not being a structure or union
type.

GCC issues a warning for this case. Clang now warns as well, but the
warning is defaulted to an error because the actual access is still
unsafe.

This fixes Issue 54563.