Welcome to the CHICKEN Scheme pasting service

;; my tests:
;; 2015 klm@kth /s/p/a/a/s/ais-sse ➤ csi -version
;; 
;; CHICKEN
;; (c) 2008-2017, The CHICKEN Team
;; (c) 2000-2007, Felix L. Winkelmann
;; Version 4.12.0 (rev 6ea24b6)
;; linux-unix-gnu-x86-64 [ 64bit manyargs dload ptables ]
;; compiled 2017-02-19 on yves.more-magic.net (Linux)
;; 
;; 2016 klm@kth /s/p/a/a/s/ais-sse ➤ csi -s weak-test.scm
;; locking mutex
;; unlocking mutex ...
;; weak locative: #(123)
;; weak locative: #f
;; weak locative: #f
;; weak locative: #f
;; ^C
;; *** user interrupt ***
;;
;; if I remove srfi-13 import, it works:
;;
;; 2017 klm@kth /s/p/a/a/s/ais-sse ➤ cat weak-test.scm  | csi -p '(read)'
;; (use srfi-18 lolevel)
;; 2017 klm@kth /s/p/a/a/s/ais-sse ➤ csi -s weak-test.scm
;; locking mutex
;; unlocking mutex ...
;; weak locative: #(123)
;; weak locative: #(123)
;; weak locative: #(123)
;; weak locative: #(123)
;; ^C
;; *** user interrupt ***
;;
;;
;; I think the reason that the amound of imports affects the
;; weak-locatives is because it changes the top-level environment
;; somehow.

(use srfi-13 ;; <-- killer import (any import will breaks things, try srfi-4 too for example)
     srfi-18 lolevel)

(define wl #f)

(thread-start!
 (lambda ()
   (define mutex (make-mutex))
   (define cv (make-condition-variable))
   (print "locking mutex")
   (mutex-lock! mutex)
   (let ((REFERENCE (vector 123)))
     (set! wl (make-weak-locative REFERENCE))
     (print "unlocking mutex ...")
     (mutex-unlock! mutex cv)
     (print "unlocked!")
     (print "DONE (REFERENCE may now be out of scope) " REFERENCE))))

(thread-start!
 (lambda ()
   (let loop ()
     (print "weak locative: " (locative->object wl))
     (thread-sleep! 1)
     (gc #t)
     (loop))))

(thread-sleep! 10)