get_param_size.cc

#include <iostream>
#include <type_traits>
 
template<typename ... Args>
struct get_size;

template<>
struct get_size<> {
    static constexpr int size = 0;
};

template<typename T, typename ... Args>
struct get_size<T, Args...> {
    static constexpr int size = sizeof(T) + get_size<Args...>::size;
};

template<typename>
struct get_param_size;

template<typename Ret, typename ... Types>
struct get_param_size<Ret(Types ...)> {
    static constexpr int size = get_size<Types...>::size;
};

int func(int a, int arr[4]) {
}

int main() {
    std::cout << get_param_size<decltype(func)>::size << std::endl;
}