Question

Is the size of a pointer the same as the size as the type it’s pointing to, or do pointers always have a fixed size? For example…

int x = 10;
int * xPtr = &x;
char y = 'a';
char * yPtr = &y;

std::cout << sizeof(x) << "\n";
std::cout << sizeof(xPtr) << "\n";
std::cout << sizeof(y) << "\n";
std::cout << sizeof(yPtr) << "\n";

What would the output of this be? Would sizeof(xPtr) return 4 and sizeof(yPtr) return 1, or would the 2 pointers actually return the same size?

The reason I ask this is because the pointers are storing a memory address and not the values of their respective stored addresses.

Answer 1

Pointers generally have a fixed size, for ex. on a 32-bit executable they’re usually 32-bit. There are some exceptions, like on old 16-bit windows when you had to distinguish between 32-bit pointers and 16-bit… It’s usually pretty safe to assume they’re going to be uniform within a given executable on modern desktop OS’s.

Edit: Even so, I would strongly caution against making this assumption in your code. If you’re going to write something that absolutely has to have a pointers of a certain size, you’d better check it!

Function pointers are a different story — see Jens’ answer for more info.