[PATCH] D62988: Add an attribute to allow fields of non-trivial types in C unions

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak created this revision.
ahatanak added a reviewer: rjmccall.
ahatanak added a project: clang.
Herald added subscribers: dexonsmith, jkorous.

clang currently disallows fields of non-trivial types (e.g., `__strong`) in unions in C mode since it's not possible for the compiler to determine how the unions should be initialized, destructed, or copied.

This patch adds support for a new attribute `non_trivial_union_member`, which causes fields annotated with the attribute to be trivial when computing the trivialness of the containing union. This means the users are responsible for patching up the code so that the union is initialized, destructed, and copied in a functionally correct way.

rdar://problem/50591731


Repository:
  rC Clang

https://reviews.llvm.org/D62988

Files:
  include/clang/AST/Decl.h
  include/clang/Basic/Attr.td
  include/clang/Basic/AttrDocs.td
  lib/AST/Decl.cpp
  lib/AST/Type.cpp
  lib/Sema/SemaDecl.cpp
  lib/Sema/SemaDeclAttr.cpp
  test/CodeGenObjC/strong-in-c-struct.m
  test/SemaObjC/attr-non-trivial-union-member.m

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