Stack Overflow during SWAP

Question

How can we take care of the overflow happening during swapping of two variables without using a third variable. I believe the XOR solution can be used only for integers. what about other variable types?

Answer 1

XOR will work for anything you can get your XOR operator to process; it's a property of binary data, not of binary data used to represent integers.

Answer 2

This isn't an answer but it doesn't fit in a comment.

Under what circumstances would you be running so close to the edge of your available stack storage that the additional use of a temporary variable for the swap is going to cause you difficulties?

I could see some embedded scenarios, but I'm hard pressed to imagine a scenario where you'd be so tight on stack space that this would matter (where you're not writing code in assembly language).

Answer 3

The XOR solution works with any type that can be bitwise copied, not just integers. However, do not XOR a variable with itself: i.e.

int x = 10;
int *p1 = &x;
int *p2 = p1;

*p1 = *p1 ^ *p2;
*p2 = *p1 ^ *p2;
*p1 = *p1 ^ *p2;

/* now x == 0 :( */

Answer 4

By not doing it at all. The XOR swap algorithm is cool hack. It shouldn't be used in production code.

Answer 5

What's wrong with XCHG? No stack needed, no overflow(carry flag)? set either :).

Answer 6

a = a + b;
b = a - b;
a = a - b;

This will work for integers and float.