debugger behaves unexpectedly when using function visibility patterns

[rparnas]

The context is the exercises from SICP chapter 2.5 "Systems with Generic Operations" but the function visibility management the text introduces (Example 2) doesn't seem debug-able.

;;;; Example 1: Unexpected
(define functions-a (make-hashtable equal-hash equal?))

((lambda ()
  (define (breaker-a x)
    (break)
    x)
  (define (not-breaker-a z)
    (breaker-a z))
  (hashtable-set! functions-a 'fa not-breaker-a)))

(define (fa x) ((hashtable-ref functions-a 'fa #f) x))

;; > (fa 1)
;; break> i
;; #<continuation in not-breaker-a>                                  : sl
;;   continuation:          #<system continuation in new-cafe>
;;   procedure code:        (lambda (z) (breaker-a z))
;;   call code:             (break)
;;   frame variables:
;;   0. z:                  1

;;;; Example 2: Unexpected
(define functions-b (make-hashtable equal-hash equal?))

(define (install-b)
  (define (breaker-b x)
    (break)
    x)
  (define (not-breaker-b z)
    (breaker-b z))
  (hashtable-set! functions-b 'fb not-breaker-b))

(install-b)

(define (fb x) ((hashtable-ref functions-b 'fb #f) x))

;; > (fb 1)
;; break> i
;; #<continuation in not-breaker-d>                                  : sl
;;   continuation:          #<system continuation in new-cafe>
;;   procedure code:        (lambda (z) (breaker-d z))
;;   call code:             (break)
;;   frame variables:
;;   0. z:                  1

;;;; Example 3: Expected
(define functions-c (make-hashtable equal-hash equal?))

(define (breaker-c x)
  (break)
  x)
(define (not-breaker-c z)
  (breaker-c z))
(hashtable-set! functions-c 'fc not-breaker-c)

(define (fc x) ((hashtable-ref functions-c 'fc #f) x))

;; > (fc 1)
;; break> i
;; #<continuation in breaker-c>                                      : sl
;;   continuation:          #<system continuation in new-cafe>
;;   procedure code:        (lambda (x) (break) x)
;;   call code:             (break)
;;   frame variables:
;;   0. x:                  1

;;;; Example 4: Expected
(define functions-d (make-hashtable equal-hash equal?))

(define (breaker-d x)
  (break)
  x)

(define (install-d)
  (define (not-breaker-d z)
    (breaker-d z))
  (hashtable-set! functions-d 'fd not-breaker-d))

(install-d)

(define (fd x) ((hashtable-ref functions-d 'fd #f) x))

;; > (fd 1)
;; break> i
;; #<continuation in breaker-d>                                      : sl
;;   continuation:          #<system continuation in new-cafe>
;;   procedure code:        (lambda (x) (break) x)
;;   call code:             (break)
;;   frame variables:
;;   0. x:                  1

[laqrix]

Try disabling cp0 and see if that helps. It may have inlined your procedures.

(run-cp0 (lambda (cp0 x) x))