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: unassig...@gcc.gnu.org ReportedBy: frankhb1...@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.