ObjC lifetime: pull sugar off when the qualifiers conflict.

[manmanren]

Summary

It's possible to have multiple local ObjCLifetime qualifiers. When there is
a conflict, we can't stop after we reach a type that is directly qualified.
We need to keep pulling sugar off and removing the ObjCLifetime qualifers.

One example:
@implementation A

• init { attribute((objc_ownership(strong))) typeof(self) self_strong; attribute((objc_ownership(weak))) typeof(self_strong) self_weak;

}
@end

[rjmccall]

Oh sure, because we don't strip the original type if there isn't a conflict. LGTM.

[manmanren]

In D20843#445756, @rjmccall wrote:

Oh sure, because we don't strip the original type if there isn't a conflict. LGTM.

Exactly, thanks for reviewing!

Manman

lib/Sema/SemaType.cpp

if (Qualifiers::ObjCLifetime previousLifetime
     // If it's written directly, that's an error.
     if (hasDirectOwnershipQualifier(type)) {
       S.Diag(AttrLoc, diag::err_attr_objc_ownership_redundant)
         << type;
       return true;
     }
 
     // Otherwise, if the qualifiers actually conflict, pull sugar off
-    // until we reach a type that is directly qualified.
+    // and remove the ObjCLifetime qualifiers.
     if (previousLifetime != lifetime) {
-      // This should always terminate: the canonical type is
-      // qualified, so some bit of sugar must be hiding it.
-      while (!underlyingType.Quals.hasObjCLifetime()) {
+      // It's possible to have multiple local ObjCLifetime qualifiers. We
+      // can't stop after we reach a type that is directly qualified.
+      const Type *prevTy = nullptr;
+      while (!prevTy || prevTy != underlyingType.Ty) {
+        prevTy = underlyingType.Ty;
         underlyingType = underlyingType.getSingleStepDesugaredType();
       }
       underlyingType.Quals.removeObjCLifetime();
     }
   }
 
   underlyingType.Quals.addObjCLifetime(lifetime);
 

test/SemaObjC/arc-objc-lifetime-conflict.m

+// RUN: %clang_cc1 -triple x86_64-apple-darwin11 -fobjc-arc -fobjc-runtime-has-weak %s -emit-llvm -o - | FileCheck %s
+
+// CHECK: bitcast {{.*}} %self_weak_s_w_s
+// CHECK-NEXT: objc_destroyWeak
+// CHECK-NEXT: bitcast {{.*}} %self_strong_w_s
+// CHECK-NEXT: objc_storeStrong
+// CHECK-NEXT: bitcast {{.*}} %self_weak_s
+// CHECK-NEXT: objc_destroyWeak
+// CHECK-NEXT: bitcast {{.*}} %self_weak_s3
+// CHECK-NEXT: objc_destroyWeak
+// CHECK-NEXT: bitcast {{.*}} %self_strong3
+// CHECK-NEXT: objc_storeStrong
+// CHECK-NEXT: bitcast {{.*}} %self_strong2
+// CHECK-NEXT: objc_storeStrong
+// CHECK-NEXT: bitcast {{.*}} %self_strong
+// CHECK-NEXT: objc_storeStrong
+@interface NSObject
+@end
+@interface A : NSObject
+@end
+@implementation A
+- (void)test {
+  __attribute__((objc_ownership(strong))) __typeof__(self) self_strong;
+  __attribute__((objc_ownership(strong))) __typeof__(self_strong) self_strong2;
+  __attribute__((objc_ownership(strong))) __typeof__(self_strong2) self_strong3;
+  __attribute__((objc_ownership(weak))) __typeof__(self_strong3) self_weak_s3;
+ 
+  __attribute__((objc_ownership(weak))) __typeof__(self_strong) self_weak_s;
+  __attribute__((objc_ownership(strong))) __typeof__(self_weak_s) self_strong_w_s;
+  __attribute__((objc_ownership(weak))) __typeof__(self_strong_w_s) self_weak_s_w_s;
+}
+@end