Re: Multiple locations vs. watchpoints.

[Daniel Jacobowitz <drow at mvista dot com>]

On Thu, Oct 30, 2003 at 08:21:44AM +0200, Eli Zaretskii wrote:
> > Date: Thu, 30 Oct 2003 00:53:45 -0500
> > From: Daniel Jacobowitz <drow@mvista.com>
> > 
> > Suppose we have this:
> > foo.c:static int *bar;
> > 
> > (gdb) watch *bar
> > 
> > My idea has sort of been to create a watchpoint with multiple locations, one
> > for bar and one for *bar, each representing a conceptual hardware watchpoint
> > (though not necessarily one hardware watchpoint resource).
> 
> Yes, we do it now, albeit differently at the high level.
> 
> > And for this:
> > foo.c:static int foo()
> > bar.c:static int foo()
> > 
> > (gdb) break foo
> > 
> > My idea has sort of been that we should have a breakpoint with two
> > bp_locations, one for foo.c:foo and one for bar.c:foo.
> 
> I don't think we should do that.  I think we should leave things as
> they are now, namely, that "break foo" means the function foo in the
> _current_ module, be that foo.c or bar.c.  For the other, the user is
> required to type "break bar.c:foo".
> 
> In C++ and other OO languages, this is different, but in C we
> shouldn't introduce confusion, IMHO.  Someone who debugs a C program
> doesn't expect to get a breakpoint on a completely different function.

And when neither of these functions is in the "current" file (I hate
transparent state like that)?

We tend to get one at random.  This kills me once in a while when
working on BFD.
> > But suppose we have this:
> > foo.c:static int *bar;
> > bar.c:static int *bar;
> > 
> > (gdb) watch *bar
> > 
> > 
> > It watches whatever *bar would print, which is one of them.  No easy way to
> > get at the other or describe the ambiguity.  I wonder once again whether the
> > two-level scheme is really correctly designed; but I have no better ideas.
> 
> Accept my position about static functions in C, and this problem goes
> away.
> 
> But if you still want to put a watchpoint on both static variables,
> then there might be no reason for multi-level schemes: simply have the
> chain of addresses include foo.c:bar, foo.c:*bar, bar.c:bar, and
> bar.c:*bar.
> 
> Does this make sense?

Yes, I think so.

Hmm.  This suggests that I may be overloading one data structure for
two incompatible purposes.  I need to think about it a little.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer