From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-420266-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 22921 invoked by alias); 14 Apr 2013 19:59:54 -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
Received: (qmail 22901 invoked by uid 48); 14 Apr 2013 19:59:51 -0000
From: "lucdanton at free dot fr" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/56958] New: Spurious unused variable warning in empty pack expansion
Date: Sun, 14 Apr 2013 19:59:00 -0000
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: lucdanton at free dot fr
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-56958-4@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
X-SW-Source: 2013-04/txt/msg01411.txt.bz2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56958

             Bug #: 56958
           Summary: Spurious unused variable warning in empty pack
                    expansion
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: lucdanton@free.fr


Created attachment 29872
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29872
Minimal testcase

Using:

g++-snapshot (Debian 20130330-1) 4.9.0 20130330 (experimental) [trunk revision
197260]

$ cat main.cpp 
template<typename... T>
int foo(T... t)
{
    int spurious = 0;
    return false ? foo(t + spurious...) : 0;
}

int main()
{
    return foo();
}

$ g++-snapshot -Wall -std=c++11 main.cpp 
main.cpp: In instantiation of 'int foo(T ...) [with T = {}]':
main.cpp:10:16:   required from here
main.cpp:4:9: warning: variable 'spurious' set but not used
[-Wunused-but-set-variable]
     int spurious = 0;
         ^

No such warning is produced when passing arguments to foo.