[Bug c/16186] gcc should have an option to warn about enumerations with duplicate values

[marxin at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=16186

--- Comment #4 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Marek Polacek from comment #3)
> FWIW, Clang implements this warning:

Oh, I was unable to find the option (only tried -Werror and -Wextra).

@Marek: please add it!