Re: [mi] watchpoint-scope exec async command

[Bob Rossi <bob@brasko.net>]

> > breakpoint.c:5761 is where the related_breakpoint is allocated
> > breakpoint.c:6721 is where the related_breakpoint is deleted
> > breakpoint.c:1022 is where the problem occurs (just the next sucker to 
> > read/write the free'd related_breakpoint field)
> > 
> > So, at breakpoint.c:5761 I do,
> >    (tgdb) p b
> >    $1 = (struct breakpoint *) 0x83b4878
> >    (tgdb) p b->related_breakpoint
> >    $2 = (struct breakpoint *) 0x83b49d0
> > 
> > Then at breakpoint.c:6721, I print the breakpoint to be deleted
> >    (tgdb) p bpt
> >    $3 = (struct breakpoint *) 0x83b49d0
> > 
> > This is the related_breakpoint!
> > 
> > at the end of breakpoint_delete I do
> >    (tgdb) p breakpoint_chain->next->next->next->next->next->next
> >    $30 = (struct breakpoint *) 0x83b4878
> > 
> >    (tgdb) p breakpoint_chain->next->next->next->next->next->next->related_breakpoint
> >    $32 = (struct breakpoint *) 0x83b49d0
> 
> So far, actually, so good - but is this still true when
> breakpoint_auto_delete returns?  Why isn't the other one deleted too?
> What's its "disposition" at this point?

Yes, 

(tgdb) p breakpoint_chain->next->next->next->next->next->next
$47 = (struct breakpoint *) 0x83b4878
(tgdb) p breakpoint_chain->next->next->next->next->next->next->disposition
$51 = disp_donttouch
(tgdb) p breakpoint_chain->next->next->next->next->next->next->related_breakpoint
$48 = (struct breakpoint *) 0x83b49d0
(tgdb) p breakpoint_chain->next->next->next->next->next->next->related_breakpoint->disposition
$49 = disp_del

I don't know why this seems OK to you. I must be missing something.
breakpoint_chain->next->next->next->next->next->next->related_breakpoint
was a pointer to a breakpoint that was deleted. Thus, the pointer is
invalid. The reference to the deleted breakpoint (related_breakpoint
field) must be set to NULL somehow. 

It seems that whenever a breakpoint is deleted, all other
breakpoints related_breakpoint field needs to be checked, to see if they
pointed to the data that was just deleted.

Please look at the comments at breakpoint.c:6723 and breakpoint.c:1325.

Thanks,
Bob Rossi