As per Michael Stoffregen suggestion in the comment, I've tried to move arguments outside and it worked (even with gcc 4.9.2)! So I can finally say C(11) has Fortran-like function “overloading” — type generic functions.
I have often wondered why C hasn't any kind of function overloading. The typical answer is that we don't want to live with name mangling in C — the hell of the C++ — that would break a lot of things which must stay as they are. I agree… except that you don't need to implement it the C++ way when you have a bright example like Fortran.