Re: Thread switching and stepping bug

[Jonathan Larmour <jlarmour@redhat.com>]

David Smith wrote:
> 
> Jonathan,
> 
> If I understand you correctly, you may have hit a problem I'm familiar with.
>   Basically your target (which you didn't mention) hasn't implemented
> PREPARE_TO_PROCEED which gets called in infrun.c.  I submitted a patch back
> at the end of March to implement a generic PREPARE_TO_PROCEED which should
> work for most targets.
> 
> For more details, here's the start of the thread where we discussed this:
> 
> < http://sources.redhat.com/ml/gdb-patches/2001-03/msg00541.html >

I've gone through it again with current CVS GDB, and I'm afraid there's no
change in behaviour. I was slightly wrong in my description below actually.
All that's needed is actually:

b breakme
c
[ hits breakpoint in thread 3 ]
thread 5
step

I've already tried to debug it but got lost in wait_for_inferior(). Perhaps
someone could give me an idea what should be the correct course of events
in wait_for_inferior() in the above situation after the final step, and I
can compare with what happens?

Thanks,

Jifl


> Jonathan Larmour wrote:
> 
> > It seems GDB (a fairly recent CVS) doesn't do the right thing when a thread
> > view has been switched and then the system stepped.
> >
> > I've got a program with a bunch of threads. The default one is thread 3 and
> > has a function breakme which I set a breakpoint. The other threads run
> > other stuff.
> >
> > If I set a breakpoint on breakme, thread 3 hits it. If I manually step off
> > that breakpoint, switch to e.g. thread 5 then do another step, GDB can't
> > recognise that it hit a sensible breakpoint, and instead reports a SIGTRAP.
> >
> > So the commands I'm doing are:
> >
> > b breakme
> > c
> > [ hits breakpoint in thread 3]
> > step
> > thread 5
> > step
> >
> > I'm surprised no-one has noticed this before, so is my understanding wrong?
> >
> > I've tried looking in wait_for_inferior() but got lost quickly :-). I think
> > the problem may be that step_resume_breakpoint is changed when GDB notices
> > the thread has changed. But I'm no expert.
> >
> > Jifl
> 
> --
> David Smith
> dsmith@redhat.com
> Red Hat, Inc.
> http://www.redhat.com
> 256.704.9222 (direct)
> 256.837.3839 (fax)

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