Re: [RFA]: Watchpoints per thread patch

["Eli Zaretskii" <eliz at gnu dot org>]

> Date: Tue, 9 Nov 2004 14:31:24 -0500
> From: Daniel Jacobowitz <drow@false.org>
> Cc: Andrew Cagney <cagney@gnu.org>, Eli Zaretskii <eliz@gnu.org>,
> 	gdb-patches@sources.redhat.com
> 
> We could use a Linux native specific observer, or handle this through
> the target stack.  I think handling it through the target stack makes
> more sense, but I haven't sketched out what the target method would
> look like.  If other GDB developers think that the precedent of a
> native-code-only observer isn't a bad one, then maybe we should go back
> to your previous placement of the observer and give it a Linux specific
> name.

Is there any significant difference between native-code-only observers
and the other kind?  Could you elaborate?

Anyway, I said in the past several times that I don't really like to
use the observers too much.  The reason for that is that with a
mechanism such as this, which is like hooks in Emacs or interrupt
handlers in the old DOS days, you often get in trouble once more than
one observer is hooked to some event: the order of the the observers'
invocation might matter, and AFAIK we do not have any way to control
that (nor would we know what order is ``right'', even if we had a way
to control it).

So in general, if there's a reasonably good design that avoids using
observers, I'd favor that.