Handle case where @synchronized is used with a class.

objc/runtime.h

@@ -199,6 +199,9 @@ IMP method_setImplementation(Method method, IMP imp);
 
 Class objc_allocateClassPair(Class superclass, const char *name, size_t extraBytes);
 
+OBJC_NONPORTABLE
+Class objc_allocateMetaClass(Class superclass, size_t extraBytes);
+
 void objc_disposeClassPair(Class cls);
 
 id objc_getClass(const char *name);

runtime.c

@@ -771,6 +771,22 @@ Class objc_allocateClassPair(Class superclass, const char *name, size_t extraByt
 	return newClass;
 }
 
+Class objc_allocateMetaClass(Class superclass, size_t extraBytes)
+{
+	Class metaClass = calloc(1, sizeof(struct objc_class) + extraBytes);
+
+	// Initialize the metaclass
+	metaClass->class_pointer = superclass->class_pointer->class_pointer;
+	metaClass->super_class = superclass->class_pointer;
+	metaClass->name = strdup(superclass->name);
+	metaClass->info = _CLS_META | _CLS_RUNTIME | _CLS_NEW_ABI;
+	metaClass->dtable = __objc_uninstalled_dtable;
+	metaClass->instance_size = sizeof(struct objc_class);
+
+	return metaClass;
+}
+
+
 void *object_getIndexedIvars(id obj)
 {
 	if (class_isMetaClass(obj->isa))

sync.m

@@ -6,7 +6,6 @@
 
 int snprintf(char *restrict s, size_t n, const char *restrict format, ...);
 
-
 @interface Fake
 + (void)dealloc;
 @end
@@ -49,16 +48,27 @@ static inline Class findLockClass(id obj)
 
 static inline Class initLockObject(id obj)
 {
-	char nameBuffer[40];
-	snprintf(nameBuffer, 39, "hiddenlockClass%lld", lockClassId++);
-	Class lockClass = objc_allocateClassPair(obj->isa, nameBuffer,
-			sizeof(mutex_t));
+	Class lockClass; 
+	if (class_isMetaClass(obj->isa))
+	{
+		lockClass = objc_allocateMetaClass(obj, sizeof(mutex_t));
+	}
+	else
+	{
+		char nameBuffer[40];
+		snprintf(nameBuffer, 39, "hiddenlockClass%lld", lockClassId++);
+		lockClass = objc_allocateClassPair(obj->isa, nameBuffer,
+				sizeof(mutex_t));
+	}
 	const char *types =
 		method_getTypeEncoding(class_getInstanceMethod(obj->isa,
 					@selector(dealloc)));
 	class_addMethod(lockClass, @selector(dealloc), (IMP)deallocLockClass,
 			types);
-	objc_registerClassPair(lockClass);
+	if (!class_isMetaClass(obj->isa))
+	{
+		objc_registerClassPair(lockClass);
+	}
 
 	mutex_t *lock = object_getIndexedIvars(lockClass);
 	INIT_LOCK(*lock);
@@ -100,6 +110,7 @@ void objc_sync_enter(id obj)
 	mutex_t *lock = object_getIndexedIvars(lockClass);
 	LOCK(lock);
 }
+
 void objc_sync_exit(id obj)
 {
 	Class lockClass = findLockClass(obj);