Strong retain calls should always return the instance pointer.

This fixes a regression in 73132a6 (#200) where nil was returned
from a retain call after the object begins deallocating. Normal
retains of a deallocating object are still expected to return an
instance pointer inside its dealloc method and code compiled with ARC
will generate calls to objc_storeStrong() when a block captures the
self pointer inside the dealloc method.

Test/FastRefCount.m

@@ -2,6 +2,20 @@
 
 void direct_saturation_test();
 
+@interface TestWithDelloc : Test
+@end
+
+@implementation TestWithDelloc
+- (void)dealloc
+{
+	id obj = nil;
+	objc_storeStrong(&obj, self);
+	assert(obj == self);
+	assert(object_getRetainCount_np(obj) == 0);
+	[super dealloc];
+}
+@end
+
 int main()
 {
 	id obj = [Test new];
@@ -27,7 +41,7 @@ int main()
 		// Final release should prevent further retains and releases.
 		assert(objc_release_fast_no_destroy_np(obj) == YES);
 		assert(object_getRetainCount_np(obj) == 0);
-		assert(objc_retain_fast_np(obj) == nil);
+		assert(objc_retain_fast_np(obj) == obj);
 		assert(object_getRetainCount_np(obj) == 0);
 		assert(objc_release_fast_no_destroy_np(obj) == NO);
 		assert(object_getRetainCount_np(obj) == 0);
@@ -54,7 +68,11 @@ int main()
 		assert(objc_delete_weak_refs(obj) == YES);
 	}
 	
-	obj = object_dispose(obj);
+	object_dispose(obj);
+	// Check we can use strong references inside a dealloc method.
+	obj = [TestWithDelloc new];
+	[obj release];
+	obj = nil;
 	
 	direct_saturation_test();
 	return 0;

arc.mm

@@ -244,7 +244,7 @@ extern "C" OBJC_PUBLIC size_t object_getRetainCount_np(id obj)
 	return realCount == refcount_mask ? 0 : realCount + 1;
 }
 
-extern "C" OBJC_PUBLIC id objc_retain_fast_np(id obj)
+static id retain_fast(id obj, BOOL isWeak)
 {
 	uintptr_t *refCount = ((uintptr_t*)obj) - 1;
 	uintptr_t refCountVal = __sync_fetch_and_add(refCount, 0);
@@ -268,7 +268,7 @@ extern "C" OBJC_PUBLIC id objc_retain_fast_np(id obj)
 		// this and we don't zero the references or deallocate.
 		if (realCount == refcount_mask)
 		{
-			return nil;
+			return isWeak ? nil : obj;
 		}
 		// If the reference count is saturated, don't increment it.
 		if (realCount == refcount_max)
@@ -283,6 +283,11 @@ extern "C" OBJC_PUBLIC id objc_retain_fast_np(id obj)
 	return obj;
 }
 
+extern "C" OBJC_PUBLIC id objc_retain_fast_np(id obj)
+{
+	return retain_fast(obj, NO);
+}
+
 __attribute__((always_inline))
 static inline BOOL isPersistentObject(id obj)
 {
@@ -301,7 +306,7 @@ static inline BOOL isPersistentObject(id obj)
 	return objc_test_class_flag(obj->isa, objc_class_flag_permanent_instances);
 }
 
-static inline id retain(id obj)
+static inline id retain(id obj, BOOL isWeak)
 {
 	if (isPersistentObject(obj)) { return obj; }
 	Class cls = obj->isa;
@@ -312,7 +317,7 @@ static inline id retain(id obj)
 	}
 	if (objc_test_class_flag(cls, objc_class_flag_fast_arc))
 	{
-		return objc_retain_fast_np(obj);
+		return retain_fast(obj, isWeak);
 	}
 	return [obj retain];
 }
@@ -593,7 +598,7 @@ extern "C" OBJC_PUBLIC id objc_retainAutoreleasedReturnValue(id obj)
 extern "C" OBJC_PUBLIC id objc_retain(id obj)
 {
 	if (nil == obj) { return nil; }
-	return retain(obj);
+	return retain(obj, NO);
 }
 
 extern "C" OBJC_PUBLIC id objc_retainAutorelease(id obj)
@@ -604,7 +609,7 @@ extern "C" OBJC_PUBLIC id objc_retainAutorelease(id obj)
 extern "C" OBJC_PUBLIC id objc_retainAutoreleaseReturnValue(id obj)
 {
 	if (nil == obj) { return obj; }
-	return objc_autoreleaseReturnValue(retain(obj));
+	return objc_autoreleaseReturnValue(retain(obj, NO));
 }
 
 
@@ -912,7 +917,9 @@ extern "C" OBJC_PUBLIC id objc_loadWeakRetained(id* addr)
 	{
 		obj = _objc_weak_load(obj);
 	}
-	return objc_retain(obj);
+	// block_load_weak() or _objc_weak_load() can return nil
+	if (obj == nil) { return nil; }
+	return retain(obj, YES);
 }
 
 extern "C" OBJC_PUBLIC id objc_loadWeak(id* object)