Example showing difference between pointer-to-pointer and reference-to-pointer in C++

ref_to_ptr.cpp

// Example that shows difference between pointer-to-pointer
// and reference-to-pointer.

#include <cstdio>

void func_ptr(int **x)
{
    *x = new int;
    **x = 100;
}

void func_ref(int * &x)
{
    x = new int;
    *x = 99;
}

int main()
{
    // Pointer-to-pointer
    {
        int *xp = nullptr;
        func_ptr(&xp);
        printf("%d\n", *xp);
        delete xp;
    }

    // Reference-to-pointer
    {
        int *xp = nullptr;
        func_ref(xp);
        printf("%d\n", *xp);
        delete xp;
    }

    return 0;
}