From owner-freebsd-current@FreeBSD.ORG  Thu Jul 10 01:19:57 2003
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 9A6CC37B401
	for <current@freebsd.org>; Thu, 10 Jul 2003 01:19:57 -0700 (PDT)
Received: from xorpc.icir.org (xorpc.icir.org [192.150.187.68])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 2485843FBD
	for <current@freebsd.org>; Thu, 10 Jul 2003 01:19:57 -0700 (PDT)
	(envelope-from rizzo@xorpc.icir.org)
Received: from xorpc.icir.org (localhost [127.0.0.1])
	by xorpc.icir.org (8.12.8p1/8.12.3) with ESMTP id h6A8JukN071416;
	Thu, 10 Jul 2003 01:19:56 -0700 (PDT)
	(envelope-from rizzo@xorpc.icir.org)
Received: (from rizzo@localhost)
	by xorpc.icir.org (8.12.8p1/8.12.3/Submit) id h6A8JuBY071415;
	Thu, 10 Jul 2003 01:19:56 -0700 (PDT)
	(envelope-from rizzo)
Date: Thu, 10 Jul 2003 01:19:56 -0700
From: Luigi Rizzo <rizzo@icir.org>
To: current@freebsd.org
Message-ID: <20030710011956.A61125@xorpc.icir.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.2.5.1i
Subject: what is the suggested way to do void * arithmetic ?
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 10 Jul 2003 08:19:57 -0000


Hi,
in several places in ipfw2.c i have to move pointers across
structures of variable length (lists of ipfw2 instructions
returned by the getsockopt()), and i use the following type of code:

	void *next;
	foo *p;

	...

	next = (void *)p + len;
	...
	foo = (foo *)p + len;

When using WARNS=5, the compiler in -current flags them with 'Warning
void * arithmetic'.

What is the best way to do the above given that i do need to use
these variable-size structures ?

	cheers
	luigi