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From: "frankhb1989 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/57183] New: [C++11]auto and -Wunused-variable
Date: Mon, 06 May 2013 06:41:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57183

             Bug #: 57183
           Summary: [C++11]auto and -Wunused-variable
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: frankhb1989@gmail.com


Case:
constexpr float PI_0 = 3.1415926F;
constexpr auto PI_1 = 3.1415926F;
const float PI_2 = 3.1415926F;
const auto PI_3 = 3.1415926F;

int main(){}


Using gcc version 4.8.0 (rev2, Built by MinGW-builds project).

g++ a.cc -std=c++11 -Wall
a.cc:2:16: warning: 'PI_1' defined but not used [-Wunused-variable]
 constexpr auto PI_1 = 3.1415926F;
                ^
a.cc:4:12: warning: 'PI_3' defined but not used [-Wunused-variable]
 const auto PI_3 = 3.1415926F;
            ^

The difference between auto and non-auto declarations seems to be not intended.