[Sema] Diagnose default-initialization, destruction, and copying of

non-trivial C union types

This recommits r365985, which was reverted because it broke a few
projects using unions containing non-trivial ObjC pointer fields in
system headers. We now have a patch to fix the problem (see
https://reviews.llvm.org/D65256).

Original commit message:

This patch diagnoses uses of non-trivial C unions and structs/unions
containing non-trivial C unions in the following contexts, which require
default-initialization, destruction, or copying of the union objects,
instead of disallowing fields of non-trivial types in C unions, which is
what we currently do:

- function parameters.
- function returns.
- assignments.
- compound literals.
- block captures except capturing of `__block` variables by non-escaping blocks.
- local and global variable definitions.
- lvalue-to-rvalue conversions of volatile types.

See the discussion in https://reviews.llvm.org/D62988 for more background.

rdar://problem/50679094

Differential Revision: https://reviews.llvm.org/D63753

llvm-svn: 371275

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 3d9dd7131b1..b71315505de 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -476,6 +476,9 @@ void ASTDeclWriter::VisitRecordDecl(RecordDecl *D) {
   Record.push_back(D->isNonTrivialToPrimitiveDefaultInitialize());
   Record.push_back(D->isNonTrivialToPrimitiveCopy());
   Record.push_back(D->isNonTrivialToPrimitiveDestroy());
+  Record.push_back(D->hasNonTrivialToPrimitiveDefaultInitializeCUnion());
+  Record.push_back(D->hasNonTrivialToPrimitiveDestructCUnion());
+  Record.push_back(D->hasNonTrivialToPrimitiveCopyCUnion());
   Record.push_back(D->isParamDestroyedInCallee());
   Record.push_back(D->getArgPassingRestrictions());
 
@@ -1999,6 +2002,12 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
   // isNonTrivialToPrimitiveDestroy
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
+  // hasNonTrivialToPrimitiveDefaultInitializeCUnion
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
+  // hasNonTrivialToPrimitiveDestructCUnion
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
+  // hasNonTrivialToPrimitiveCopyCUnion
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
   // isParamDestroyedInCallee
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
   // getArgPassingRestrictions