Is it OK to pass reference to a pointer as a function argument?

December 10, 2021

I had the understanding that in c++ & and * cancel each other i.e int *&p is essentially equal to p as its value at address of integer p.

Now is it valid to pass reference to a pointer in view of above i.e say i am trying to pass reference to a pointer as an argument in a function as below?

void func(int* &p)

Won’t the above result in cancellation of * with & and will just be int p?
How correct is it if i try to pass reference to pointer of a class object on similar terms?

#include <iostream>

using namespace std;

int gobal_var = 42;

// function to change Reference to pointer value
void changeReferenceValue(int*& pp)
{
    pp = &gobal_var;
}

int main()
{
    int var = 23;
    int* ptr_to_var = &var;

    cout << "Passing a Reference to a pointer to function" << endl;

    cout << "Before :" << *ptr_to_var << endl; // display 23

    changeReferenceValue(ptr_to_var);

    cout << "After :" << *ptr_to_var << endl; // display 42

    return 0;
}

>Solution :

You are correct that the & address-of operator and the * indirection operator cancel each other out when used inside an expression.

However, when used inside a declaration, these operators have a very different meaning. Inside a declaration, * means "pointer" and & means "reference". Therefore, when used inside a declaration, they do not cancel each other out.

An object of type int*& is simply a reference to a pointer to an int.