-(defun register-user-data (object &optional destroy-function)
- (check-type destroy-function (or null symbol function))
-; (incf *user-data-count*)
- (setq *user-data-count* (the fixnum (1+ *user-data-count*)))
- (setf
- (gethash *user-data-count* *user-data*)
- (cons object destroy-function))
- *user-data-count*)