[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

3 files changed, 34 insertions, 2 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");
     }
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index df1d02d8faa..111d131b480 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -11324,6 +11324,9 @@ void Sema::CheckCompleteVariableDeclaration(VarDecl *var) {
     }
   }
 
+  if (var->getType().isDestructedType() == QualType::DK_nontrivial_c_struct)
+    getCurFunction()->setHasBranchProtectedScope();
+
   // Warn about externally-visible variables being defined without a
   // prior declaration.  We only want to do this for global
   // declarations, but we also specifically need to avoid doing it for
@@ -15214,6 +15217,7 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
 
     // Get the type for the field.
     const Type *FDTy = FD->getType().getTypePtr();
+    Qualifiers QS = FD->getType().getQualifiers();
 
     if (!FD->isAnonymousStructOrUnion()) {
       // Remember all fields written by the user.
@@ -15355,7 +15359,9 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
       FD->setType(T);
     } else if (getLangOpts().allowsNonTrivialObjCLifetimeQualifiers() &&
                Record && !ObjCFieldLifetimeErrReported &&
-               (!getLangOpts().CPlusPlus || Record->isUnion())) {
+               ((!getLangOpts().CPlusPlus &&
+                 QS.getObjCLifetime() == Qualifiers::OCL_Weak) ||
+                Record->isUnion())) {
       // It's an error in ARC or Weak if a field has lifetime.
       // We don't want to report this in a system header, though,
       // so we just make the field unavailable.
@@ -15391,6 +15397,18 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
                Record->setHasObjectMember(true);
       }
     }
+
+    if (Record && !getLangOpts().CPlusPlus) {
+      QualType FT = FD->getType();
+      if (FT.isNonTrivialToPrimitiveDefaultInitialize())
+        Record->setNonTrivialToPrimitiveDefaultInitialize();
+      QualType::PrimitiveCopyKind PCK = FT.isNonTrivialToPrimitiveCopy();
+      if (PCK != QualType::PCK_Trivial && PCK != QualType::PCK_VolatileTrivial)
+        Record->setNonTrivialToPrimitiveCopy();
+      if (FT.isDestructedType())
+        Record->setNonTrivialToPrimitiveDestroy();
+    }
+
     if (Record && FD->getType().isVolatileQualified())
       Record->setHasVolatileMember(true);
     // Keep track of the number of named members.
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 53a4a4c7834..134415646d3 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -776,6 +776,9 @@ Sema::VarArgKind Sema::isValidVarArgType(const QualType &Ty) {
     return VAK_Valid;
   }
 
+  if (Ty.isDestructedType() == QualType::DK_nontrivial_c_struct)
+    return VAK_Invalid;
+
   if (Ty.isCXX98PODType(Context))
     return VAK_Valid;
 
@@ -837,7 +840,10 @@ void Sema::checkVariadicArgument(const Expr *E, VariadicCallType CT) {
     break;
 
   case VAK_Invalid:
-    if (Ty->isObjCObjectType())
+    if (Ty.isDestructedType() == QualType::DK_nontrivial_c_struct)
+      Diag(E->getLocStart(),
+           diag::err_cannot_pass_non_trivial_c_struct_to_vararg) << Ty << CT;
+    else if (Ty->isObjCObjectType())
       DiagRuntimeBehavior(
           E->getLocStart(), nullptr,
           PDiag(diag::err_cannot_pass_objc_interface_to_vararg)