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Re: interrupting the Scheme process
Ken Raeburn <raeburn@raeburn.org> writes:
> Guile has some hooks for recording that an interrupt has occurred and,
> at certain times, throwing an exception of some sort. If we could set
> that flag at C-g time, if Scheme code is currently running, might that
> do the trick? Then Scheme can trap the exception if it wants, but
> otherwise we throw back to the containing Lisp call. Propagating the
> unwind through possibly multiple lisp<->scheme interfaces could be
> hairy though; I haven't looked very closely at that stuff.
It seems Emacs catches the interrupt by interrupt_signal in keyboard.c,
so we could modify this function so that it also sets the Guile's flag.
If this works, we can convert the signal from Guile into a Emacs's quit
signal. In case this doesn't work, I don't know what to do.
/* This routine is called at interrupt level in response to C-G.
If interrupt_input, this is the handler for SIGINT.
Otherwise, it is called from kbd_buffer_store_event,
in handling SIGIO or SIGTINT.
If `waiting_for_input' is non zero, then unless `echoing' is nonzero,
immediately throw back to read_char.
Otherwise it sets the Lisp variable quit-flag not-nil.
This causes eval to throw, when it gets a chance.
If quit-flag is already non-nil, it stops the job right away. */
SIGTYPE
interrupt_signal (signalnum) /* If we don't have an argument, */
int signalnum; /* some compilers complain in signal calls. */
> Hm...that might be a way to do it. I also wonder if we might have
> cases where we want to send the interrupt to multiple threads -- i.e.,
> if the "foreground" thread is sitting around waiting for N tasks to
> finish (e.g., get new news from news.mycompany.com, get email from
> pop.mycompany.com, get new news from news.redhat.com, etc), might we
> want to interrupt all of them and unwind the main thread only after
> they've died off?
Probably. We should kill the parent thread and its children at the same
time, though I guess we would still need kill-thread to kill detached
threads, which are "background" threads. We don't want to close a GTK
window, which may run in a separate thread, just by typing C-g, for example.
> I suppose we could have a "spawn and wait for multiple threads"
> function which implements all of this on top of the scheme^Wplan you
> describe, by trapping the interrupt...
Anyway, we can't work on this until your Guile-based Emacs appears :)
-- Kei