From: Mark H Weaver <mhw@netris.org>
To: Caleb Ristvedt <caleb.ristvedt@cune.org>
Cc: guile-user@gnu.org
Subject: Re: Continuations in custom port: "cannot invoke continuation from this context"
Date: Mon, 01 Apr 2019 05:12:45 -0400 [thread overview]
Message-ID: <87o95q6qc7.fsf@netris.org> (raw)
In-Reply-To: <CAELvotxs0kCqo4cs6WsONKQhx+SjV4=OdDwHXE+WEx6+S54C1A@mail.gmail.com> (Caleb Ristvedt's message of "Mon, 1 Apr 2019 02:06:16 +0000")
Hi Caleb,
Caleb Ristvedt <caleb.ristvedt@cune.org> writes:
> On Thu, Mar 28, 2019 at 12:58 PM Stefan Israelsson Tampe <
> stefan.itampe@gmail.com> wrote:
>
>> I have not looked at this more carefully. But I suspect that the code is
>> going to C land and then enters the scheme again
>> via the hooks and then continuations won't work as expected.
> Any idea why it would still be going to C land even with suspendable ports
> installed? The manual says they're implemented in scheme for precisely this
> reason.
'install-suspendable-ports!' replaces only a subset of the C port
functions with Scheme implementations, namely the ones listed in
'port-bindings' in suspendable-ports.scm.
The problem here is the custom port. Custom ports are implemented in C,
and are not reimplemented by suspendable-ports.scm. When you perform
I/O on the custom port, it enters C code in r6rs-ports.c which calls
back into Scheme code to call your custom I/O handlers 'read!' and
'write!'.
Mark
next prev parent reply other threads:[~2019-04-01 9:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-28 4:30 Continuations in custom port: "cannot invoke continuation from this context" Caleb Ristvedt
[not found] ` <CAGua6m0eTYuXW3tq8o-pR7fgRH5yi8D6kjF1HdLPgC16Cc2=jg@mail.gmail.com>
2019-04-01 2:06 ` Caleb Ristvedt
2019-04-01 9:12 ` Mark H Weaver [this message]
2019-04-18 0:47 ` Mark H Weaver
2019-04-27 21:04 ` Ludovic Courtès
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