From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-return-143561-listarch-gcc=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 11539 invoked by alias); 17 Jan 2008 17:12:22 -0000
Received: (qmail 11527 invoked by uid 22791); 17 Jan 2008 17:12:22 -0000
X-Spam-Check-By: sourceware.org
Received: from fg-out-1718.google.com (HELO fg-out-1718.google.com) (72.14.220.156)     by sourceware.org (qpsmtpd/0.31) with ESMTP; Thu, 17 Jan 2008 17:11:59 +0000
Received: by fg-out-1718.google.com with SMTP id d23so701553fga.28         for <gcc@gcc.gnu.org>; Thu, 17 Jan 2008 09:11:56 -0800 (PST)
Received: by 10.82.140.20 with SMTP id n20mr4049423bud.27.1200589916743;         Thu, 17 Jan 2008 09:11:56 -0800 (PST)
Received: by 10.82.173.1 with HTTP; Thu, 17 Jan 2008 09:11:56 -0800 (PST)
Message-ID: <84fc9c000801170911p199d1913i796e92bba9a17cb7@mail.gmail.com>
Date: Thu, 17 Jan 2008 18:09:00 -0000
From: "Richard Guenther" <richard.guenther@gmail.com>
To: "Ian Lance Taylor" <iant@google.com>
Subject: Re: A simple sample code involving templates, friends and lookup
Cc: "Dragan Milenkovic" <dragan@plusplus.co.yu>, gcc@gcc.gnu.org
In-Reply-To: <m3fxwwl6p9.fsf@localhost.localdomain>
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
References: <478F3175.2050809@plusplus.co.yu> 	 <84fc9c000801170449j332abd0bp501bbc2fd9d04c46@mail.gmail.com> 	 <478F544F.9060509@plusplus.co.yu> 	 <84fc9c000801170535k1bd3eb89p6f95d63ee6f58647@mail.gmail.com> 	 <m3fxwwl6p9.fsf@localhost.localdomain>
X-IsSubscribed: yes
Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc.gcc.gnu.org>
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
X-SW-Source: 2008-01/txt/msg00276.txt.bz2

On 17 Jan 2008 09:09:38 -0800, Ian Lance Taylor <iant@google.com> wrote:
>
> "Richard Guenther" <richard.guenther@gmail.com> writes:
>
> > On Jan 17, 2008 2:12 PM, Dragan Milenkovic <dragan@plusplus.co.yu> wrote:
> > > Richard Guenther wrote:
> > > [snip]
> > > >> template <typename T>
> > > >> struct Foo
> > > >> {
> > > >>      template <typename Z>
> > > >>      friend void func(const Foo &);
> > > >> };
> > > >>
> > > >> void check(const Foo<int> & x)
> > > >> {
> > > >>      // Foo<int> weird;  // uncomment this line and all works
> > > >>
> > > >>      func<int>(x);    // <-- ERROR
> > > >> }
> > > >>
> > > >>
> > > >> Tested with gcc 4.0 - 4.3, and all behave the same:
> > > >>
> > > >> "error: 'func' was not declared in this scope"
> > > >>
> > > >> but it works if you uncomment the weird line.
> > > >
> > > > Actually even with the weird line the program is invalid.  What are
> > > > you trying to do? ;)
> > > >
> > > > Richard.
> > >
> > > Ok... afaik, that func should be defined on that very place where it is
> > > declared as friend. But could you please elaborate why it is invalid,
> > > since you made me start questioning my C++ knowledge... :-D
> >
> > How should name-lookup find func?
>
> It should use argument dependent lookup.  This is like the common case
> of
>
> class x
> {
>   friend x operator+(const& x, const& x) { return x.var + x.var; }
> };
>
> in which x::operator+ is found without taking special action.

Well, first I think you'd need friend-injection or otherwise a global
decl of the function.  Second I thought argument dependent
name-lookup only applies to namespaces, not classes.

EDG rejects this consistently btw.

Richard.