From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 31685 invoked by alias); 31 Oct 2011 10:18:24 -0000 Received: (qmail 31676 invoked by uid 22791); 31 Oct 2011 10:18:23 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 31 Oct 2011 10:18:09 +0000 From: "daniel.kruegler at googlemail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/50929] [C++0x] Wrong function selected for overload with template and rvalue reference Date: Mon, 31 Oct 2011 10:18:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: c++ X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: daniel.kruegler at googlemail dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2011-10/txt/msg03194.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D50929 --- Comment #5 from Daniel Kr=C3=BCgler 2011-10-31 10:18:04 UTC --- (In reply to comment #4) > I didn't realise that A(A&) was a better match. I was thinking of C++ code > where you might write: >=20 > template > A(const T& t); >=20 > A(const A& rhs); >=20 > in which case A(const A&) would be chosen.=20 Sure. But if you had provided template A(T& t); instead that would again be a better match for a non-const A lvalue. Non-template functions only win over templates, if they are otherwise equal= in matching. > I didn't realise that the rvalue reference puts a spanner in the works. Note that "rvalue-reference" is a red herring for the perfect-forwarding signature template A(T&& t); It depends on whether the argument is an lvalue or not to decide whether the finally deduced type is effectively A& or A&& (or whatever argument type had been provided). In your example the argument was an lvalue of type A, there= fore the deduced signature was effectively template <> A(A& t);