;; Even though the filler slots are not used, if you remove any of
;; them, the hash of the instance will change after GC. But if the
;; filler slots are present, the hash will stay the same after GC.

(use srfi-69 lolevel)

(define-record-type box
  (make-box contents)
  box?
  ;; Remove or comment out any of the next three lines:
  (filler1  box-filler1)
  (filler2  box-filler2)
  (filler3  box-filler3)
  (contents box-contents))

(define my-box (make-box (make-locative "foo")))
(define old-hash (eq?-hash my-box))
(gc)
(define new-hash (eq?-hash my-box))

(printf "old hash: ~S~N" old-hash)
(printf "new hash: ~S~N" new-hash)