Add new checker-specific attribute 'objc_ownership_returns'. This isn't hooked

up to the checker yet, but essentially it allows a user to specify that an
Objective-C method or C function returns an owned an Objective-C object.

llvm-svn: 70001

clang/include/clang/AST/Attr.h

@@ -51,6 +51,7 @@ public:
     NonNull,
     ObjCException,
     ObjCNSObject,
+    ObjCOwnershipReturns, // Clang/Checker-specific.
     Overloadable, // Clang-specific
     Packed,
     Pure,
@@ -587,6 +588,21 @@ public:
   static bool classof(const Attr *A) { return A->getKind() == Regparm; }
   static bool classof(const RegparmAttr *A) { return true; }
 };
+  
+  
+#define DEF_SIMPLE_ATTR(ATTR)\
+class ATTR##Attr : public Attr {\
+public:\
+  ATTR##Attr() : Attr(ATTR) {}\
+  static bool classof(const Attr *A) { return A->getKind() == ATTR; }\
+  static bool classof(const ATTR##Attr *A) { return true; }\
+};
+
+// Checker-specific attributes.
+DEF_SIMPLE_ATTR(ObjCOwnershipReturns)
+
+#undef DEF_SIMPLE_ATTR
+  
 }  // end namespace clang
 
 #endif

clang/include/clang/Parse/AttributeList.h

@@ -75,8 +75,9 @@ public:
     AT_nothrow,
     AT_nsobject,
     AT_objc_exception,
+    AT_objc_ownership_returns, // Clang-specific.
     AT_objc_gc,
-    AT_overloadable,      // Clang-specific
+    AT_overloadable,      // Clang-specific.
     AT_packed,
     AT_pure,
     AT_regparm,

clang/lib/Frontend/PCHReader.cpp

@@ -3045,6 +3045,7 @@ Attr *PCHReader::ReadAttributes() {
 
     SIMPLE_ATTR(ObjCException);
     SIMPLE_ATTR(ObjCNSObject);
+    SIMPLE_ATTR(ObjCOwnershipReturns);
     SIMPLE_ATTR(Overloadable);
     UNSIGNED_ATTR(Packed);
     SIMPLE_ATTR(Pure);

clang/lib/Frontend/PCHWriter.cpp

@@ -2181,6 +2181,7 @@ void PCHWriter::WriteAttributeRecord(const Attr *Attr) {
 
     case Attr::ObjCException:
     case Attr::ObjCNSObject:
+    case Attr::ObjCOwnershipReturns:
     case Attr::Overloadable:
       break;
 

clang/lib/Parse/AttributeList.cpp

@@ -133,6 +133,10 @@ AttributeList::Kind AttributeList::getKind(const IdentifierInfo *Name) {
   case 18:
     if (!memcmp(Str, "warn_unused_result", 18)) return AT_warn_unused_result;
     break;
+  case 22:
+    if (!memcmp(Str, "objc_ownership_returns", 22))
+      return AT_objc_ownership_returns;
+    break;
   }
   return UnknownAttribute;
 }

clang/lib/Sema/SemaDeclAttr.cpp

@@ -1517,6 +1517,22 @@ static void HandleRegparmAttr(Decl *d, const AttributeList &Attr, Sema &S) {
   d->addAttr(::new (S.Context) RegparmAttr(NumParams.getZExtValue()));
 }
 
+//===----------------------------------------------------------------------===//
+// Checker-specific attribute handlers.
+//===----------------------------------------------------------------------===//
+
+static void HandleObjCOwnershipReturnsAttr(Decl *d, const AttributeList &Attr,
+                                           Sema &S) {
+
+  if (!isa<ObjCMethodDecl>(d) && !isa<FunctionDecl>(d)) {
+    S.Diag(Attr.getLoc(), diag::warn_attribute_wrong_decl_type) <<
+      "objc_ownership_returns" << 3 /* function or method */;
+    return;
+  }
+  
+  d->addAttr(::new (S.Context) ObjCOwnershipReturnsAttr());
+}
+
 //===----------------------------------------------------------------------===//
 // Top Level Sema Entry Points
 //===----------------------------------------------------------------------===//
@@ -1553,6 +1569,11 @@ static void ProcessDeclAttribute(Decl *D, const AttributeList &Attr, Sema &S) {
   case AttributeList::AT_nonnull:     HandleNonNullAttr   (D, Attr, S); break;
   case AttributeList::AT_noreturn:    HandleNoReturnAttr  (D, Attr, S); break;
   case AttributeList::AT_nothrow:     HandleNothrowAttr   (D, Attr, S); break;
+
+  // Checker-specific.
+  case AttributeList::AT_objc_ownership_returns:
+    HandleObjCOwnershipReturnsAttr(D, Attr, S); break;
+
   case AttributeList::AT_packed:      HandlePackedAttr    (D, Attr, S); break;
   case AttributeList::AT_section:     HandleSectionAttr   (D, Attr, S); break;
   case AttributeList::AT_stdcall:     HandleStdCallAttr   (D, Attr, S); break;

clang/test/Analysis/retain-release.m

@@ -405,3 +405,15 @@ void rdar6704930(unsigned char *s, unsigned int length) {
   }
 }
 
+//===----------------------------------------------------------------------===//
+// Tests of ownership attributes.
+//===----------------------------------------------------------------------===//
+
+@interface TestOwnershipAttr : NSObject
+- (NSString*) returnsAnOwnedString __attribute__((objc_ownership_returns));
+@end
+
+void test_attr_1(TestOwnershipAttr *X) {
+  NSString *str = [X returnsAnOwnedString];
+}
+