From owner-freebsd-current@FreeBSD.ORG  Fri Jul 27 12:31:36 2012
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: current@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 7AE6B106566B
	for <current@freebsd.org>; Fri, 27 Jul 2012 12:31:36 +0000 (UTC)
	(envelope-from luigi@onelab2.iet.unipi.it)
Received: from onelab2.iet.unipi.it (onelab2.iet.unipi.it [131.114.59.238])
	by mx1.freebsd.org (Postfix) with ESMTP id 3B5E58FC08
	for <current@freebsd.org>; Fri, 27 Jul 2012 12:31:36 +0000 (UTC)
Received: by onelab2.iet.unipi.it (Postfix, from userid 275)
	id 914C27300A; Fri, 27 Jul 2012 14:51:34 +0200 (CEST)
Date: Fri, 27 Jul 2012 14:51:34 +0200
From: Luigi Rizzo <rizzo@iet.unipi.it>
To: Poul-Henning Kamp <phk@phk.freebsd.dk>
Message-ID: <20120727125134.GA58187@onelab2.iet.unipi.it>
References: <20120727093824.GB56662@onelab2.iet.unipi.it>
	<9654.1343388048@critter.freebsd.dk>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <9654.1343388048@critter.freebsd.dk>
User-Agent: Mutt/1.4.2.3i
Cc: current@freebsd.org
Subject: Re: (void)foo or __unused foo ?
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
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: Fri, 27 Jul 2012 12:31:36 -0000

On Fri, Jul 27, 2012 at 11:20:48AM +0000, Poul-Henning Kamp wrote:
> In message <20120727093824.GB56662@onelab2.iet.unipi.it>, Luigi Rizzo writes:
> 
> >The alternative way to avoid an 'unused' warning from the compiler
> >is an empty statement
> >
> >	(void)foo;
> 
> The thing I don't like about this form, is that it doesn't communicate
> your intention, only your action.
> 
> Somewhere down my TODO list I have an item to propose instead:
> 
> 	typedef void unused_t;
> 
> 	int main(int argc, char **argv)
> 	{
> 
> 		(unused_t)argc;
> 		(unused_t)argv;
> 		return (0);
> 	}

i certainly like this better, my only concern is that some other
platform might come with an incompatible usage of the name 'unused_t'
same as it happened for __unused, and we are back with the problem.

A comment might be used to explain the intention in even more detail:

	(void)foo;	/* unused on XyBSD and Babbage-OS */

cheers
luigi