weakhash_vs_guardian.scm

(define guardian (make-guardian))
(define finalizer-table (make-weak-key-hash-table))

(let ((f (lambda () (display "test\n"))))
  (guardian f)
  (hashq-set! finalizer-table (cons #f #f) f)
  #f) ;; just in case you want to test at repl

(write finalizer-table)
(newline)

(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc) ;; surely a dozen should do?

(write finalizer-table)
(newline)

(write (guardian))
(write (guardian))
(write (guardian))
(write (guardian))
(gc)
(write (guardian))
(write (guardian))
(write (guardian))
(newline)

You'd think at least one of those (write (guardians)) (quadrupled for dramatic effect) would display something other than #f.

[ian@Kagami tmp]$ guile -s weakhash_vs_guardian.scm 
;;; note: source file /tmp/weakhash_vs_guardian.scm
;;;       newer than compiled /home/ian/.cache/guile/ccache/2.0−LE−4−2.0/tmp/weakhash_vs_guardian.scm.go
;;; note: auto−compilation is enabled, set GUILE_AUTO_COMPILE=0
;;;       or pass the −−no−auto−compile argument to disable.
;;; compiling /tmp/weakhash_vs_guardian.scm
;;; compiled /home/ian/.cache/guile/ccache/2.0−LE−4−2.0/tmp/weakhash_vs_guardian.scm.go
#<weak−key−hash−table 1/31>
#<weak−key−hash−table 0/31>
#f#f#f#f#f#f#f
[ian@Kagami tmp]$