i386 int3 handling, running vs stepping

Mark Kettenis mark.kettenis@xs4all.nl
Tue Feb 3 09:22:00 GMT 2009

> Date: Mon, 2 Feb 2009 16:49:15 -0500
> From: Daniel Jacobowitz <drow@false.org>
> > I guess the issue is whether int3's in programs are supported by gdb,
> > and by supported I mean users can rely on gdb flagging a SIGTRAP when
> > they're executed.  As you say, there are people who take advantage of
> > this for hardwired breakpoints.
> Since it works today, and we know that people use it, I think we have
> no choice but to consider it supported.
> > There are various situations where gdb itself will singlestep code
> > (e.g., "step", "next", s/w watchpoints).  Can users expect to see the
> > SIGTRAP in these situations (and all others)?  And if the program is
> > being run by a script, can the script expect to see the SIGTRAP in all
> > cases?
> That's certainly not the case today.  If you want to make it work, and
> add a couple of tests for it, I've no objection - it seems a plausible
> thing to do.  But I would prefer that any solution did not involve
> reading the instruction at every step; that's quite slow, on a target
> where we otherwise do not need to.

I don't really see any reason to change things here.

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