Passing and Assigning New Value to Pointer C++

Question

I\'m passing a pointer to a function. I\'d like to assign a new address to the passed pointer inside the function, and I\'d like that address to be used after the function retu

Answer 1

Pass a reference to the pointer:

void foo( int *& fooPtr, int & newInt )

The reason why your method does not work is that you're passing the pointer by-value. Passing by-value creates a temporary within the function, so as soon as the function returns, any changes to the temporary go away.

It is no different than this:

void foo(int x)
{
   x = 10;
}

int main()
{
   int a = 0;
   foo( a );
   // a is still 0, not 10
}

The a is passed by value, so the foo() function changes the parameter to 10 within the function. However, you will see that a in main does not change to 10 after the function returns.

To change a, you need to pass the int by reference:

void foo(int& x)
{
   x = 10;
}

int main()
{
   int a = 0;
   foo( a );
   // a is now 10
}