--- Begin Message ---
|
Subject: |
Using a guardian on a value in a weak hash |
|
Date: |
Fri, 28 Oct 2011 21:42:45 +0100 |
|
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.2 (gnu/linux) |
Hi guilers,
If I 'guard' a value, and store it in a weak-key hashtable, then it
doesn't appear in the guardian even after it is removed from the
weak-hash by a garbage collection. Note, this only happens in a
_script_, and will work fine in a REPL (you should only need two GCs,
one for the weak hash, and one for the now free value).
e.g.
(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)
(write finalizer-table)
(newline)
(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)(gc)
(write finalizer-table)
(newline)
(write (guardian))
(newline)
will produce the output
address@hidden guile]$ guile -s /tmp/gcbug.scm
#<weak−key−hash−table 1/31>
#<weak−key−hash−table 0/31>
#f
address@hidden guile]$
--
Ian Price
"Programming is like pinball. The reward for doing it well is
the opportunity to do it again" - from "The Wizardy Compiled"
--- End Message ---