How to do unsigned saturating addition in C?

Question

What is the best (cleanest, most efficient) way to write saturating addition in C?

The function or macro should add two unsigned inputs (need both 16- and 32-bit ver

Answer 1

Just in case someone wants to know an implementation without branching using 2's complement 32bit integers.

Warning! This code uses the undefined operation: "shift right by -1" and therefore exploits the property of the Intel Pentium SAL instruction to mask the count operand to 5 bits.

int32_t sadd(int32_t a, int32_t b){
    int32_t sum = a+b;
    int32_t overflow = ((a^sum)&(b^sum))>>31;
    return (overflow<<31)^(sum>>overflow);
 }

It's the best implementation known to me