BOOL (*allowsWeakReference)(objc_object *, SEL) =
(BOOL(*)(objc_object *, SEL))
object_getMethodImplementation((id)referent, @selector(allowsWeakReference));
BOOL (*allowsWeakReference)(objc_object *, SEL) =
(BOOL(*)(objc_object *, SEL))
object_getMethodImplementation((id)referent, @selector(allowsWeakReference));