Re: [RFA/RFC] QUIT doesn't seem to be working !?

[Daniel Jacobowitz <drow@mvista.com>]

On Thu, Aug 28, 2003 at 10:41:16AM -0400, Daniel Jacobowitz wrote:
> On Tue, Aug 12, 2003 at 03:22:11PM -0700, Joel Brobecker wrote:
> > Hello,
> > 
> > it's bizarre, we noticed that we were unable to interrupt certain
> > commands that can be time greedy. For instance, when messing up in the
> > addresses given to the "disass" command, it can take GDB a loooooong
> > time to print all instructions. Unexpectedly, hitting Control-C did not
> > interrupt the command.
> > 
> > I see in disassemble_command() that there is a call to QUIT in the while
> > loop that prints all instructions. But this macro tests for quit_flag
> > to see if we should stop now or not. However, handle_sigint() does
> > not set this flag when Control-C is pressed, unless immediate_quit is
> > set. But immediate_quit is not really what we are looking for, because
> > it tells GDB that SIGINT events should be processed immediately, which
> > obviously means that GDB does not wait for the next call to QUIT to
> > perform the abortion.
> > 
> > So far, what handle_sigint() does is set the "ready" flag in GDB's
> > SIGINT async signal handler. This flag seems to take effect only
> > at the top-level loop level. So in our case, its effect arrives too
> > late.
> > 
> > So I couldn't understand how QUIT was working....
> > 
> > I applied the following change, which allows GDB to aboart at QUIT
> > points if the user has pressed C-c. But I feel like I'm missing
> > something...
> > 
> > 2003-08-12  J. Brobecker  <brobecker@gnat.com>
> > 
> >         * event-top.c (handle_sigint): Set quit_flag.
> > 
> > Comments? Ok to apply?
> 
> I see two functions which are intended to handle SIGINT.  One of them
> is handle_sigint; the other is request_quit.  If event_loop_p, we use
> the async version, which does not quit immediately.  This is the case
> unless gdb is started with --noasync.
> 
> The comments in handle_sigint suggest that deferring the C-c to the
> next time through the event loop is desired behavior.  I'm not entirely
> sure why.  It loses the use of the QUIT macro entirely.  There's a
> whole lot of complicated async infrastructure in event-top.c and
> event-loop.c but it seems that the async handlers are never called
> except from gdb_do_one_event, and I don't see any actual asynchronous
> way of getting there.
> 
> Elena seems to have written most of this code.  She might have a better
> idea of how this is supposed to work - and conveniently, she's listed
> as its maintainer, too :)
> 
> I suspect your patch is right, but I don't know if some additional
> cleanup is required for the asynchronous signal handlers, to prevent
> the quit from being processed twice.

Hi Elena,

Do you have any comments on this patch?

> 
> > Index: event-top.c
> > ===================================================================
> > RCS file: /nile.c/cvs/Dev/gdb/gdb-5.3/gdb/event-top.c,v
> > retrieving revision 1.1
> > diff -u -p -r1.1 event-top.c
> > --- event-top.c	16 Jan 2003 09:46:22 -0000	1.1
> > +++ event-top.c	12 Aug 2003 21:27:57 -0000
> > @@ -967,9 +967,14 @@ handle_sigint (int sig)
> >    if (immediate_quit)
> >      async_request_quit (0);
> >    else
> > -    /* If immediate quit is not set, we process SIGINT the next time
> > -       through the loop, which is fine. */
> > -    mark_async_signal_handler_wrapper (sigint_token);
> > +    {
> > +      /* If immediate quit is not set, we process SIGINT the next time
> > +         through the loop, which is fine. */
> > +      mark_async_signal_handler_wrapper (sigint_token);
> > +      /* We can also process the signal at certain specific locations
> > +         which are explicitely marked by a call to QUIT.  */
> > +      quit_flag = 1;
> > +    }
> >  }
> >  
> >  /* Do the quit. All the checks have been done by the caller. */
> 
> 
> -- 
> Daniel Jacobowitz
> MontaVista Software                         Debian GNU/Linux Developer
> 

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer