The following code:

void f() {}

template <typename T> void g(const T*) { }

int main() {
    g(f);
}

raises an error with this note:

    types 'const T' and 'void()' have incompatible cv-qualifiers

Attempting to instantiate g creates a function that takes a pointer to a const T where T = void(). Since there's no such thing as a "const function", this explains the note. However, C++11 8.3.5/6 says

"The effect of a cv-qualifier-seq in a function declarator is not the same as adding cv-qualification on top of the function type. In the latter case, the cv-qualifiers are ignored."

Hence, the const qualifier should be ignored and the code should compile. (It does compile with clang and visual studio.)

For more information see:
http://stackoverflow.com/questions/15578298/can-a-const-t-match-a-pointer-to-free-function