Pass a function pointer with variable parameters as an argument in C++

Question

I'm trying to pass a function, with a variable amount of parameters, as an argument to my function baz(). I'm not really sure how to go about doing this, but hopefully the example I've provided below shows my current thought-process.

#include <iostream>

template<typename... Ts>
void foo(void (*func)(Ts...)){
    func(Ts...);
}

void bar(int a, int b, std::string c){
    std::cout << "Test a: " << a << " Test b: " << b << " Test c: " << c << "\n";
}

void baz(int x, int y){
    std::cout << x+y << "\n";
}

int main()
{
    foo(&bar, 10, 20, "Hello!"); // Expected: "Test a: 10 Test b: 20 Test c: Hello!"
    foo(&baz, 2, 2);             // Expected: "4"
    // main.cpp:13:12: error: expected primary-expression before ‘...’ token

    return 0;
}

Any help is greatly appreciated.

Answer 1

You can pass a function type

#include <iostream>

template<typename Fn, typename ... Ts>
void foo( Fn&& func, Ts...ts ){
    func(ts...);
}

void bar(int a, int b, std::string c){
    std::cout << "Test a: " << a << " Test b: " << b << " Test c: " << c << "\n";
}

void baz(int x, int y){
    std::cout << x+y << "\n";
}

int main()
{
    foo(&bar, 10, 20, "Hello!"); // Expected: "Test a: 10 Test b: 20 Test c: Hello!"
    foo(&baz, 2, 2);             // Expected: "4"
    return 0;
}

Produces

Program stdout
Test a: 10 Test b: 20 Test c: Hello!
4

Godbolt: https://godbolt.org/z/beMv6a9a4