C++ doesn't need a function specification in header

--example.h--
// empty file

--example.cpp--
int add(int x, int y)
{
    return x + y;
}

--main.cpp--
#include <iostream>
#include "example.h"
int add(int x, int y); // forward declaration using function prototype

int main()
{
    using namespace std;
    cout << "The sum of 3 and 4 is " << add(3, 4) << endl;
    return 0;
}

//works fine under g++