Adds a weak reference from weak_pointer to this to indicate that the pointer located at
weak_pointer_location is only valid during the lifetime of this.
When the this is finalized,
weak_pointer will be set to null.
Note that as with weak_ref, the weak references created by this method are not thread-safe: they cannot safely be used in one thread if the object's last unref might happen in another thread. Use WeakRef if thread-safety is required.
The object that should be weak referenced.
The memory address of a pointer.