Hello, I've been experimenting with guile-fibers. I noticed that `with-parameters*' procedure included as an "extra" in Guile's srfi-39 creates a continuation barrier. From the documentation it is not clear that it does so.
Consider this sample program (which I ran with Guile 3.0.9 and Fibers
1.0.0, as they are defined in Guix
2fda889ac992977af7b4cd96d09f737d834e0b2d):
--8<---------------cut here---------------start------------->8---
(use-modules (fibers)
(fibers channels)
(srfi srfi-18)
((srfi srfi-39) #:select (with-parameters*)))
(define %my-channel
(make-channel))
(define %my-param
(make-parameter #f))
(define %my-thread
(make-thread (lambda ()
(run-fibers (lambda ()
(with-parameters* (list %my-param) '(hello)
(lambda ()
(put-message %my-channel (%my-param))
'ok)))))))
(thread-start! %my-thread)
(format #t "message: ~a~%" (get-message %my-channel))
(thread-join! %my-thread)
--8<---------------cut here---------------end--------------->8---
It prints:
> Uncaught exception in task:
> In fibers.scm:
> 186:20 6 (_)
> 145:21 5 (_)
> In unknown file:
> 4 (with-fluids* (#<fluid 7f192cf70d70>) (hello) #<procedure
> 100903e0 at <…>)
> In current input:
> 17:35 3 (_)
> In fibers/operations.scm:
> 154:10 2 (perform-operation _)
> In fibers/scheduler.scm:
> 357:6 1 (suspend-current-task _)
> In ice-9/boot-9.scm:
> 1685:16 0 (raise-exception _ #:continuable? _)
> ice-9/boot-9.scm:1685:16: In procedure raise-exception:
> Attempt to suspend fiber within continuation barrier
But if I use `parameterize' rather than `with-parameters*', no errors
occur. Here's an example of a working program:
--8<---------------cut here---------------start------------->8---
(use-modules (fibers)
(fibers channels)
(srfi srfi-18))
(define %my-channel
(make-channel))
(define %my-param
(make-parameter #f))
(define %my-thread
(make-thread (lambda ()
(run-fibers (lambda ()
(parameterize ((%my-param 'hello))
(put-message %my-channel (%my-param))
'ok))))))
(thread-start! %my-thread)
(format #t "message: ~a~%" (get-message %my-channel))
(thread-join! %my-thread)
--8<---------------cut here---------------end--------------->8---
It prints:
> message: hello
Is it a bug that `with-parameters*' doesn't work equivalently? Or am I
reading the info pages wrong?
Best :)
Wojtek
--
W. Kosior
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