Hello Clément,
Clément Lassieur <[email protected]> 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"))))
HTH!
Ludo’.
