http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60978
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- This is documented to do this even in 4.8 (http://gcc.gnu.org/onlinedocs/gcc-4.8.2/gcc/Warning-Options.html): In C++ enumeral mismatches in conditional expressions are also diagnosed and the warning is enabled by default.
