https://github.com/wingo/fibers/issues/21

Le mar. 17 juil. 2018 à 20:17, Clément Lassieur <clement@lassieur.org> a
écrit :

> Clément Lassieur <clement@lassieur.org> writes:
>
> > Ludovic Courtès <ludo@gnu.org> writes:
> >
> >> Hello Clément,
> >>
> >> Clément Lassieur <clement@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!
>
> Hi Andy,
>
> I'm adding you to this conversation to notify you about this Fibers
> issue.  (I don't have a Github account to report the bug there.)
>
> Thanks,
> Clément
>
>