Re: [Qemu-devel] Re: monitor: check for readline in monitor_event()

[Luiz Capitulino <lcapitulino@redhat.com>]

On Tue, 16 Jun 2009 00:42:26 +0200
Jan Kiszka <jan.kiszka@web.de> wrote:

> Luiz Capitulino wrote:
> > The call of readline_show_prompt() in CHR_EVENT_RESET's body will
> > trig a segfault if readline is not being used, because 'mon->rs'
> > will be NULL.
> > 
> > This fixes the problem by adding the proper check.
> > 
> > I've trigged this while playing with an off-tree code that disables
> > readline support, I'm not sure whether in-tree code can trig this.
> > 
> > Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
> > ---
> >  monitor.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/monitor.c b/monitor.c
> > index 6b45f6c..787101d 100644
> > --- a/monitor.c
> > +++ b/monitor.c
> > @@ -3002,7 +3002,7 @@ static void monitor_event(void *opaque, int
> > event) case CHR_EVENT_RESET:
> >          monitor_printf(mon, "QEMU %s monitor - type 'help' for
> > more " "information\n", QEMU_VERSION);
> > -        if (mon->chr->focus == 0)
> > +        if (mon->rs && mon->chr->focus == 0)
> >              readline_show_prompt(mon->rs);
> >          break;
> >      }
> 
> In-tree code is not affected as no monitor user will call
> qemu_chr_reset for the associated char device if there is no readline
> active as well. Yeah, secret de-facto rule.

 Ok.

> The patch is not incorrect, but I would like to understand the
> out-of-tree use case behind it. So you do want the info line printed,
> but provide your own readline processor? What kind of terminal is
> this?

 I'm working on a machine-friendly monitor for QEMU, which disables
readline.

 I didn't want to get into the details now, it will be better to
discuss the prototype I'm writing, should be finished soon.