On Friday 05 December 2008 00:36:56, Pedro Alves wrote:
> On Friday 05 December 2008 00:18:00, Ulrich Weigand wrote:
> > Pedro Alves wrote:
> > > On Thursday 04 December 2008 22:32:12, Doug Evans wrote:
> > > > In the original code, is there a case when stop_pc != registers.pc?
> > > 
> > > Here,
> > > 
> > > <stopped at 0x1234, thread 1>
> > >  (gdb) set $pc = 0xf00
> > >  (gdb) call func()
> > 
> > Huh.  But that case is in fact *broken*, because GDB will use stop_pc
> > incorrectly: for example, the check whether we are about to continue
> > at a breakpoint will look at stop_pc, but then continue at $pc.  
> 
> This one I believe was the original intention.  The rationale being
> that you'd not want to hit a breakpoint again at stop_pc (0x1234),
> because there's where you stopped; but, you'd want to hit a a breakpoint
> at 0xf00, sort of like jump *$pc hits a breakpoint at $pc.
> 
> Note, I'm not saying I agree with this.  I did say that probably nobody
> would notice if we got rid of stop_pc.
> 
> > It seems to me just about every current user of stop_pc *really* wants
> > to look at regcache_read_pc (get_current_regcache ()) ...

Is using read_pc instead OK with you?  It's what I had written already.

> I've been sneaking the idea of getting rid of stop_pc for a while now:
>  http://sourceware.org/ml/gdb-patches/2008-06/msg00450.html
> 
> In fact, I have a months old patch here that completelly removes stop_pc.
> IIRC, there were no visible changes in the testsuite.  Say the word,
> and I'll brush it up, regtest, submit it.

Here it is, it still applied cleanly.  It's smallish.  Regtested on
x86-64-unknown-linux-gnu.

My original motivation was to get rid of the ugly checks
in switch_to_thread, and to try to minimize the extra thread
switching and register reads in non-stop mode.

I had held posting this when I wrote it, since I was not sure we'd not
miss stop_pc in some case.

-- 
Pedro Alves