[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, 25 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 007dcf2..41c1684 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -1289,6 +1289,19 @@ void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) {
   if (emission.IsByRef)
     emitByrefStructureInit(emission);
 
+  // Initialize the variable here if it doesn't have a initializer and it is a
+  // C struct that is non-trivial to initialize or an array containing such a
+  // struct.
+  if (!Init &&
+      type.isNonTrivialToPrimitiveDefaultInitialize() ==
+          QualType::PDIK_Struct) {
+    LValue Dst = MakeAddrLValue(emission.getAllocatedAddress(), type);
+    if (emission.IsByRef)
+      drillIntoBlockVariable(*this, Dst, &D);
+    defaultInitNonTrivialCStructVar(Dst);
+    return;
+  }
+
   if (isTrivialInitializer(Init))
     return;
 
@@ -1464,6 +1477,10 @@ void CodeGenFunction::emitAutoVarTypeCleanup(
 
   case QualType::DK_objc_weak_lifetime:
     break;
+
+  case QualType::DK_nontrivial_c_struct:
+    destroyer = CodeGenFunction::destroyNonTrivialCStruct;
+    break;
   }
 
   // If we haven't chosen a more specific destroyer, use the default.
@@ -1525,6 +1542,8 @@ CodeGenFunction::getDestroyer(QualType::DestructionKind kind) {
     return destroyARCStrongPrecise;
   case QualType::DK_objc_weak_lifetime:
     return destroyARCWeak;
+  case QualType::DK_nontrivial_c_struct:
+    return destroyNonTrivialCStruct;
   }
   llvm_unreachable("Unknown DestructionKind");
 }
@@ -1876,9 +1895,12 @@ void CodeGenFunction::EmitParmDecl(const VarDecl &D, ParamValue Arg,
     // cleanup.
     if (!IsScalar && !CurFuncIsThunk &&
         getContext().isParamDestroyedInCallee(Ty)) {
-      const CXXRecordDecl *RD = Ty->getAsCXXRecordDecl();
-      if (RD && RD->hasNonTrivialDestructor())
-        pushDestroy(QualType::DK_cxx_destructor, DeclPtr, Ty);
+      if (QualType::DestructionKind DtorKind = Ty.isDestructedType()) {
+        assert((DtorKind == QualType::DK_cxx_destructor ||
+                DtorKind == QualType::DK_nontrivial_c_struct) &&
+               "unexpected destructor type");
+        pushDestroy(DtorKind, DeclPtr, Ty);
+      }
     }
   } else {
     // Otherwise, create a temporary to hold the value.