From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gdb-return-30424-listarch-gdb=sources.redhat.com@sourceware.org>
Received: (qmail 15034 invoked by alias); 4 Dec 2007 21:07:04 -0000
Received: (qmail 14960 invoked by uid 22791); 4 Dec 2007 21:07:03 -0000
X-Spam-Check-By: sourceware.org
Received: from romy.inter.net.il (HELO romy.inter.net.il) (213.8.233.24)     by sourceware.org (qpsmtpd/0.31) with ESMTP; Tue, 04 Dec 2007 21:06:47 +0000
Received: from HOME-C4E4A596F7 (IGLD-84-229-222-88.inter.net.il [84.229.222.88]) 	by romy.inter.net.il (MOS 3.7.3-GA) 	with ESMTP id JNW37912 (AUTH halo1); 	Tue, 4 Dec 2007 23:05:40 +0200 (IST)
Date: Tue, 04 Dec 2007 21:07:00 -0000
Message-Id: <uhciyyxu2.fsf@gnu.org>
From: Eli Zaretskii <eliz@gnu.org>
To: Jim Blandy <jimb@codesourcery.com>
CC: msnyder@specifix.com, gdb@sourceware.org
In-reply-to: <m3zlwqfk5z.fsf@codesourcery.com> (message from Jim Blandy on 	Tue, 04 Dec 2007 09:23:52 -0800)
Subject: Re: Watchpoints with condition
Reply-to: Eli Zaretskii <eliz@gnu.org>
References: <200711301925.20196.vladimir@codesourcery.com> 	<uhcj31lko.fsf@gnu.org> <m3eje7ux9u.fsf@codesourcery.com> 	<20071130234853.GA27583@caradoc.them.org> 	<m3odd74qam.fsf@codesourcery.com> <uodd7ze86.fsf@gnu.org> 	<m37ijvz8bc.fsf@codesourcery.com> <uk5nvyto9.fsf@gnu.org> 	<1196744257.2501.268.camel@localhost.localdomain> <m3zlwqfk5z.fsf@codesourcery.com>
X-IsSubscribed: yes
Mailing-List: contact gdb-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <gdb.sourceware.org>
List-Subscribe: <mailto:gdb-subscribe@sourceware.org>
List-Archive: <http://sourceware.org/ml/gdb/>
List-Post: <mailto:gdb@sourceware.org>
List-Help: <mailto:gdb-help@sourceware.org>, <http://sourceware.org/ml/#faqs>
Sender: gdb-owner@sourceware.org
X-SW-Source: 2007-12/txt/msg00030.txt.bz2

> Cc: Eli Zaretskii <eliz@gnu.org>,  gdb@sourceware.org
> From: Jim Blandy <jimb@codesourcery.com>
> Date: Tue, 04 Dec 2007 09:23:52 -0800
> 
> I guess I don't see why 'GDB stops your program whenever the value of
> this expression changes' is hard to understand.

Two reasons: (1) most people think watchpoints watch variables, not
expressions; and (2) the notion of "foo == 1" being an expression
whose value is either 1 or zero is natural only to C hackers.

> Explaining conditional watchpoints is a superset of explaining
> watchpoints, so I don't see how it could be simpler.

It is simpler because you still watch a simple variable, and the
condition is kept separately.  It is similar to

   x = y + (foo == 1);

vs

   if (foo == 1)
     x = y + 1;
   else
     x = y;

The latter shows what the code does more clearly (and in fact some
coding standards advise against the former style).