Re: [RFC] control-c handling on Windows...

Joel Brobecker
2008-05-11T16:41:08Z

> >I wonder if there might be some sort of timing issue that causes
> >the signal to sometimes be delivered after we stopped ignoring control
> >events. In other words, some of the time, we receive the signal
> >reasonably close to when we receive the debug event for the new thread,
> >and so it gets ignored. But some other time, we receive the signal
> >sufficiently after we got the debug event that we already got out of
> >get_win32_debug_event and restored the regular SIGINT handler...
> >That would explain why we're seeing the QUIT message.
>
> i.e., it's a classic race.

Yes, and I'm still not sure how to solve it completely :-(. I double-checked
the cygwin case inside a cygwin window, and things seem to be pretty solid
as soon as the SetConsoleCtrlHandler wrapper is installed. Not sure whether
it's a coincidence or whether it's expected that I wouldn't see that race
with a cygwin window (and in fact, I'm not sure that the cygwin window
is relevant to the experiment either). I did verify it again in the case
of mingw.

So, I suggest we install you patch for now. Hopefully we'll find a way
to get rid of the race condition, but in the meantime, we have something
that makes the situation better.

> >On a side note, utils.c:quit is:
> >
> > void
> > quit (void)
> > {
> > #ifdef __MSDOS__
> > /* No steenking SIGINT will ever be coming our way when the
> > program is resumed. Don't lie. */
> > fatal ("Quit");
> > #else
> > if (job_control
> > /* If there is no terminal switching for this target, then we can't
> > possibly get screwed by the lack of job control. */
> > || current_target.to_terminal_ours == NULL)
> > fatal ("Quit");
> > else
> > fatal ("Quit (expect signal SIGINT when the program is resumed)");
> > #endif
> > }
> >
> >Not sure when __MSDOS__ is defined, but perhaps we should extend
> >that case to mingw & cygwin as well? At least we wouldn't get the
> >"expect signal SIGINT when the program is resumed" part which
> >I don't think can happen on Windows anymore.
>
> I'm still assuming that you're talking about mingw here since Cygwin should
> have different behavior. For instance, it implements tcsetpgrp.

Ah, you're right, that would cause job_control to be set on cygwin,
I think. So that means we would probably want to emulate the __MSDOS__
case for mingw only.

--
Joel