Ludovic Courtès <l...@gnu.org> writes:
> Hello Clément,
>
> Clément Lassieur <clem...@lassieur.org> skribis:
>
>> ;; bad
>> (define (test4)
>> (run-fibers
>> (lambda ()
>> (spawn-fiber
>> (lambda ()
>> (let ((channel (make-channel)))
>> (call-with-new-thread
>> (lambda ()
>> (put-message channel "hello world")))))))
>> #:drain? #t))
>> ⊣ scheme@(guile-user)> In
>> /home/clement/.guix-profile/share/guile/site/2.2/fibers/internal.scm:
>> 402:6 1 (suspend-current-fiber _)
>> In unknown file:
>> 0 (scm-error misc-error #f "~A" ("Attempt to suspend fiber
>> within continuation barrier") #f)
>> ERROR: In procedure scm-error:
>> Attempt to suspend fiber within continuation barrier
>
> I think the problem here is that the new thread inherit the dynamic
> environment of the spawning thread. Thus, ‘put-message’, called in that
> new thread, thinks it’s running within a Fiber, but it’s not.
>
> Because of that, ‘put-message’ tries to suspend itself, but it cannot:
> ‘call-with-new-thread’ is written in C, so it’s a “continuation barrier”
> (meaning that it’s a continuation that cannot be captured and resumed
> later.)
>
> So I think if you really want that, you can perhaps do something like
> (untested):
>
> (call-with-new-thread
> (lambda ()
> (parameterize ((current-fiber #f))
> (put-message channel "hello world"))))
It works, but only with (@@ (fibers internal) current-fiber) because the
parameter isn't exported.
Thank you Ludo!
