From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-352482-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 663 invoked by alias); 5 Apr 2011 06:49:44 -0000
Received: (qmail 655 invoked by uid 22791); 5 Apr 2011 06:49:44 -0000
X-SWARE-Spam-Status: No, hits=-2.8 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, 05 Apr 2011 06:49:40 +0000
From: "daniel.kruegler at googlemail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/48451] New: [C++0x][SFINAE] Failures with n-ary initialization expressions (with template default argument)
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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: <bug-48451-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Date: Tue, 05 Apr 2011 06:49:00 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2011-04/txt/msg00386.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48451

           Summary: [C++0x][SFINAE] Failures with n-ary initialization
                    expressions (with template default argument)
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: daniel.kruegler@googlemail.com
                CC: jason@redhat.com


Some n-ary initialization expressions in a SFINAE context used in function
template default arguments either give a hard error:

  a) any T => abstract class

or give the wrong result:

  b) when the destination is a class type constructed from valid arguments

#include <utility> // for declval

template<class T, class... Args,
 class = decltype(T(std::declval<Args>()...))
>
char f(int);

template<class, class...>
char (&f(...))[2];

struct A { virtual ~A() = 0; };
struct From2Ints { From2Ints(int, int); };

static_assert(sizeof(f<A, int, int>(0)) != 1, "Error"); // a
static_assert(sizeof(f<From2Ints, int, int>(0)) == 1, "Error"); // b

a) "error: cannot allocate an object of abstract type 'A' because the
following virtual functions are pure within 'A': virtual A::~A()"
b) Assertion triggers!