From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-return-105947-listarch-gcc=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 26260 invoked by alias); 29 Nov 2004 17:59:48 -0000
Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Archive: <http://gcc.gnu.org/ml/gcc/>
List-Post: <mailto:gcc@gcc.gnu.org>
List-Help: <http://gcc.gnu.org/ml/>
Sender: gcc-owner@gcc.gnu.org
Received: (qmail 26196 invoked from network); 29 Nov 2004 17:59:41 -0000
Received: from unknown (HELO vaxjo.synopsys.com) (198.182.60.75)
  by sourceware.org with SMTP; 29 Nov 2004 17:59:41 -0000
Received: from crone.synopsys.com (crone.synopsys.com [146.225.7.23])
	by vaxjo.synopsys.com (Postfix) with ESMTP
	id A17D0DCC7; Mon, 29 Nov 2004 09:59:40 -0800 (PST)
Received: from piper.synopsys.com (localhost [127.0.0.1])
	by crone.synopsys.com (8.9.1/8.9.1) with ESMTP id JAA16061;
	Mon, 29 Nov 2004 09:59:40 -0800 (PST)
Received: (from jbuck@localhost)
	by piper.synopsys.com (8.11.6/8.11.6) id iATHxdN02037;
	Mon, 29 Nov 2004 09:59:39 -0800
X-Authentication-Warning: piper.synopsys.com: jbuck set sender to Joe.Buck@synopsys.com using -f
Date: Mon, 29 Nov 2004 18:06:00 -0000
From: Joe Buck <Joe.Buck@synopsys.COM>
To: Matt Austern <austern@apple.com>
Cc: Gabriel Dos Reis <gdr@integrable-solutions.net>, gcc@gcc.gnu.org,
	Ian Lance Taylor <ian@wasabisystems.com>,
	"Joseph S. Myers" <joseph@codesourcery.com>
Subject: Re: generalized lvalues -- patch outline
Message-ID: <20041129095939.D1687@synopsys.com>
References: <4D2CF60C-3919-11D9-8BD2-000A95BCF344@apple.com> <200411232305.56192.ebotcazou@libertysurf.fr> <Pine.LNX.4.61.0411232219040.9421@digraph.polyomino.org.uk> <200411240051.19500.ebotcazou@libertysurf.fr> <Pine.LNX.4.61.0411240001400.9421@digraph.polyomino.org.uk> <m3wtwa7c5i.fsf@gossamer.airs.com> <m31xehhdsr.fsf@uniton.integrable-solutions.net> <E8097517-3F25-11D9-B018-000A95BCF344@apple.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.2.5.1i
In-Reply-To: <E8097517-3F25-11D9-B018-000A95BCF344@apple.com>; from austern@apple.com on Thu, Nov 25, 2004 at 01:06:42PM -0800
X-SW-Source: 2004-11/txt/msg01140.txt.bz2

On Thu, Nov 25, 2004 at 01:06:42PM -0800, Matt Austern wrote:
[ cast-as-lvalue extension ]
> I changed my mind, and reluctantly agreed that immediate removal was 
> the best option, because of what Joe Buck pointed out: that this wasn't 
> a pure extension, but that it actually changed the meaning of legal C++ 
> programs by causing them to select the wrong overload in some cases.  
> This was a serious bug. Seen in that light, removal seemed like the 
> only possible answer: obviously we have to fix bugs.

There is another possible answer if it is decided that some limited form
of cast-as-lvalue must be kept (presumably under the control of some
option, or maybe just for Objective-C++): casts can be considered to be
non-lvalues for the purpose of overload resolution, unless there is no
match (at which point it can be considered an lvalue so that the
appropriate operator= or operator++ can be looked up).  This would turn
the extension back into a pure extension, at the cost of kludging up the
front end.