On 12/01/2012 07:05 PM, Neil Toronto wrote:
Ah. It prints #f for me when I have debugging info turned on in
DrRacket; otherwise I get #<procedure>. Must be inlining keeping it
around or something.
The problem with either finalizers or weak boxes is that neither
provides enough guarantees. Finalizers are never guaranteed to be run. A
weak box may not be the only reference to a procedure value, depending
on what optimizations are done. I'm trying to test something that's
normally not supposed to be observable.
[...]
Maybe a weak box containing a random closure would work. Hmm...
This seems to evaluate to #f under all circumstances:
#lang racket
(define (make-box-thing v)
(make-weak-box (λ (_) v)))
(define bx (make-box-thing (random)))
(collect-garbage)
(weak-box-value bx)
I can't think of a way the optimizer could defeat that. It *has* to
create a closure... right?
Neil ⊥
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