Question

The following question was asked in a recent microsoft interview.

What is the difference between the two declarations?

int p=*(int*)i; 
int p=*(int*)&i; 

I think in the first one i is a pointer and in the second one i is a variable.
Is there anything else?

Answer 1

The first is taking the value contained in i, treating it as a pointer, and retrieving whatever int value is at that address (if possible).

The second takes the address of i, casts it to pointer to int, and retrieves the value at that address. If i is an int, it’s equivalent to p=i;. If it’s not, it’s going to take the first CHAR_BIT *sizeof(int) bits starting at the address of i, and (attempt to) treat them as an int, and assign whatever value that creates to p.

Edit: and yes, as @R. Martinho Fernandes pointed out, if i has an overloaded operator &, it may do something rather different from any of the above (i.e., instead of the address of i it’ll start with whatever its operator & returns).