inject2.c

gcc-you can use this code to learn something about gcc, and inquire further into linux,

// Build don't link:
// Origin: Mark Mitchell <[e-mail]>
// Special g++ Options: -Wno-non-template-friend

template<int I>
class C {
    friend void f(struct X *);
};

template class C<0>;

class D {
    friend void f(struct X*);
};