Is there a built in swap function in C?

Question

Is there any built in swap function in C which works without using a third variable?

Answer 1

Assuming you want a C solotion, not a C++ one, you could make it a macro, at least using GCC extension to have it generic enough, something like

 #define SWAP(x,y) do {   \ 
   typeof(x) _x = x;      \
   typeof(y) _y = y;      \
   x = _y;                \
   y = _x;                \
 } while(0)

beware of tricks like invocations swap(t[i++],i); to avoid them, use the address operator &. And you'll better use a temporary (for integers, there is a famous and useless trick with exclusive-or).

^{PS: I'm using two local variables _x and _y (but I could have used one local variable only) for better readability, and perhaps also to enable more optimizations from the compiler.}