[ObjC] Allow declaring __strong pointer fields in structs in Objective-C

ARC mode.

Declaring __strong pointer fields in structs was not allowed in
Objective-C ARC until now because that would make the struct non-trivial
to default-initialize, copy/move, and destroy, which is not something C
was designed to do. This patch lifts that restriction.

Special functions for non-trivial C structs are synthesized that are
needed to default-initialize, copy/move, and destroy the structs and
manage the ownership of the objects the __strong pointer fields point
to. Non-trivial structs passed to functions are destructed in the callee
function.

rdar://problem/33599681

Differential Revision: https://reviews.llvm.org/D41228

llvm-svn: 326307

1 files changed, 8 insertions, 0 deletions

diff --git a/clang/lib/Sema/JumpDiagnostics.cpp b/clang/lib/Sema/JumpDiagnostics.cpp
index 64fa2c34b23..55582f8c61b 100644
--- a/clang/lib/Sema/JumpDiagnostics.cpp
+++ b/clang/lib/Sema/JumpDiagnostics.cpp
@@ -154,6 +154,10 @@ static ScopePair GetDiagForGotoScopeDecl(Sema &S, const Decl *D) {
         return ScopePair(diag::note_protected_by_objc_weak_init,
                          diag::note_exits_objc_weak);
 
+      case QualType::DK_nontrivial_c_struct:
+        return ScopePair(diag::note_protected_by_non_trivial_c_struct_init,
+                         diag::note_exits_dtor);
+
       case QualType::DK_cxx_destructor:
         OutDiag = diag::note_exits_dtor;
         break;
@@ -254,6 +258,10 @@ void JumpScopeChecker::BuildScopeInformation(VarDecl *D,
         Diags = ScopePair(diag::note_enters_block_captures_weak,
                           diag::note_exits_block_captures_weak);
         break;
+      case QualType::DK_nontrivial_c_struct:
+        Diags = ScopePair(diag::note_enters_block_captures_non_trivial_c_struct,
+                          diag::note_exits_block_captures_non_trivial_c_struct);
+        break;
       case QualType::DK_none:
         llvm_unreachable("non-lifetime captured variable");
     }