[Chicken-janitors] #1356: weak-locatives references return #f when it shouldn't

[Chicken Trac]

#1356: weak-locatives references return #f when it shouldn't
------------------------+-------------------------------
 Reporter:  kristianlm  |                 Owner:
     Type:  defect      |                Status:  new
 Priority:  major       |             Milestone:  4.13.0
Component:  unknown     |               Version:  4.12.0
 Keywords:              |  Estimated difficulty:
------------------------+-------------------------------
 version:

 {{{
 ;; 2015 address@hidden /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)
 }}}

 running the program below '''should''' output this:

 {{{
 ;; 2017 address@hidden /s/p/a/a/s/ais-sse ➤ cat weak-test.scm  | csi -p 
'(read)'
 ;; (use srfi-18 lolevel)
 ;; 2017 address@hidden /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 ***
 ;;
 }}}

 Where the locative to REFERENCE is kept alive forever. However, it looses
 track of this REFERENCE:

 {{{

 ;;
 ;; 2016 address@hidden /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 ***
 }}}

 There are several ways you can make this program work:

 - compile it and run it
 - remove the srfi-13 import (it's not used)
 - assign the first thread to a top variable

 Here's the program in question that doesn't work:

 {{{
 (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)
 }}}

--
Ticket URL: <https://bugs.call-cc.org/ticket/1356>
CHICKEN Scheme <https://www.call-cc.org/>
CHICKEN Scheme is a compiler for the Scheme programming language.