GNU bug report logs - #21897
escape continuation passes barrier

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Zefram <zefram <at> fysh.org>
To: bug-guile <at> gnu.org
Subject: escape continuation passes barrier
Date: Fri, 13 Nov 2015 03:31:26 +0000

scheme@(guile-user)> (use-modules (ice-9 control))
scheme@(guile-user)> (call/ec (lambda (c) (with-continuation-barrier (lambda () (c "through continuation"))) "c-w-b returned"))
$1 = "through continuation"

The continuation barrier works fine on call/cc continuations and
on throw/catch, but doesn't block call/ec continuations.  The manual
doesn't mention any difference in behaviour for this case, nor can I
see any obvious justification for it.  The manual's statement that

#      Thus, `with-continuation-barrier' returns exactly once.

is false in this case.  I think a continuation barrier should block the
use of the call/ec continuation.

-zefram

Message #8 received at 21897 <at> debbugs.gnu.org (full text, mbox):

From: Andy Wingo <wingo <at> pobox.com>
To: Zefram <zefram <at> fysh.org>
Cc: 21897 <at> debbugs.gnu.org
Subject: Re: bug#21897: escape continuation passes barrier
Date: Fri, 24 Jun 2016 18:23:11 +0200

On Fri 13 Nov 2015 04:31, Zefram <zefram <at> fysh.org> writes:

> scheme@(guile-user)> (use-modules (ice-9 control))
> scheme@(guile-user)> (call/ec (lambda (c) (with-continuation-barrier (lambda () (c "through continuation"))) "c-w-b returned"))
> $1 = "through continuation"
>
> The continuation barrier works fine on call/cc continuations and
> on throw/catch, but doesn't block call/ec continuations.  The manual
> doesn't mention any difference in behaviour for this case, nor can I
> see any obvious justification for it.  The manual's statement that
>
> #      Thus, `with-continuation-barrier' returns exactly once.
>
> is false in this case.  I think a continuation barrier should block the
> use of the call/ec continuation.

I agree, good catch.

Andy

Message #11 received at 21897 <at> debbugs.gnu.org (full text, mbox):

From: Matt Wette <matt.wette <at> gmail.com>
To: 21897 <at> debbugs.gnu.org
Subject: verified in 3.0.2
Date: Sun, 29 Mar 2020 10:28:36 -0700

This still exists in 3.0.2

scheme@(guile-user)> ,use (ice-9 control)

scheme@(guile-user)> (call/ec (lambda (c) (with-continuation-barrier (lambda () (c "through continuation"))) "c-w-b returned"))
$1 = "through continuation"

scheme@(guile-user)> (version)
$2 = "3.0.2"

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