From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25521 invoked by alias); 29 Nov 2011 07:09:05 -0000 Received: (qmail 25510 invoked by uid 22791); 29 Nov 2011 07:09:03 -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; Tue, 29 Nov 2011 07:08:48 +0000 From: "daniel.kruegler at googlemail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/51336] [C++11] is_abstract and sfinae Date: Tue, 29 Nov 2011 08:49:00 -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: 2011-11/txt/msg02739.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D51336 --- Comment #3 from Daniel Kr=C3=BCgler 2011-11-29 07:08:45 UTC --- (In reply to comment #1) > When you instantiate A, the declaration of the template construct= or is=20 > also instantiated, but at that point A is an incomplete type. I just recognize that the last part of this is a bit misleading, please read this as: "When you instantiate A, the declaration of the template constructo= r is=20 also instantiated, but this turns out to be an ill-formed signature" The argument in regard to type-completeness was intended to point to the library specification, which requires A to be complete, which means that A may be instantiated including it's member declarations, which again is the cause of the error, because we have no sfinae situation here. In regard to the __is_abstract builtin question it seems that in simple cas= es like these (no dependent base classes involved), it may be possible to implement the intrinsic without instantiating A, but maybe the curr= ent behavior is actually better, because it makes portable programming easier;-)