6 hours ago, Dexter wrote

No problem, anyway my answer isn't quite right. void(int) will only work with std::function, what std::function does to achieve this is close to magic

In your case you'll have to stick to something simpler:
1
guard<S_FUNC> g(func);

Damn tunnel vision !

Thank you for the help.

Sorry for not providing enough info (as STL complained about)

template <typename F>
class guard {
    F m_func;
public:
    explicit guard(F func) : m_func(func) {}
    ~guard() {
        m_func(123);
    }
};

What is the function type (i think it's called that) for this functor

struct S_FUNC {
void operator()(int i) const {
}
};

S_FUNC func;

guard<void (*)(int)> g(func);

For some reason, vs2010 doesn't think it is "void (*)(int)"
so if it's not that then what is it ?