Re: gdb requires watchpoints to fire after the write

[Joel Brobecker <brobecker@adacore.com>]

> Pedro> Yeah, it's confusing.
> 
> [... great explanation ... ]
> 
> This would be great as comments in gdbarch.sh and target.h.
> None of these things have comments currently.

Agreed. I was going to send a patch doing so when I read Pedro's
message, and then read this. I'm happy to do the patch, but don't
want to start if Pedro is already on it.

> Pedro> We could most probably streamline all of this and come up with a better
> Pedro> design with some thought.  See also the comment in mips-tdep.c:
> 
> Pedro>   /* FIXME: cagney/2003-08-29: The macros target_have_steppable_watchpoint,
> Pedro>      HAVE_NONSTEPPABLE_WATCHPOINT, and target_have_continuable_watchpoint
> Pedro>      need to all be folded into the target vector.  Since they are
> Pedro>      being used as guards for target_stopped_by_watchpoint, why not have
> Pedro>      target_stopped_by_watchpoint return the type of watchpoint that the code
> Pedro>      is sitting on?  */
> Pedro>   set_gdbarch_have_nonsteppable_watchpoint (gdbarch, 1);
> 
> I'm curious about why this should be in the target rather than in the
> gdbarch.  It seems like a property of the ISA.
> 
> Is it possible for gdbserver to do the single-step itself, avoiding a
> round trip?  That was the only rationale I could think of.

It might not be gdbserver itself, which I don't think should try
to remain as minimalistic as possible in terms of this kind of
"intelligence", but maybe some other stubs?  For instance, a stub
might be designed to be usable against another kind of debugger
which might be expecting a certain type of behavior forcing
the stub to have to do the single-step itself. (?)

My perspective is that, if we don't have a concrete situation where
this functionality should be a property of the target, and we find
that it simplifies the code or avoids confusion to remove that target
property, then let's. The obvious question then becomes - what to do
with ia64-linux? Is this platform still in use and relevant enough
for us to invest energy into redesigning the watchpoint support on
this platform a bit?

-- 
Joel