cpu efficient c one-liners

interesting c one-liners

bool isPowOf2(val)
{
   return val && !( val & ( val - 1));
   // val && is required so that val=0 is handled. 0 is not the pow of 2
}


/* increment val only if MAX_UINT val not reached. Use-case: for stats incr, you dont want the val to cycle */
#define STAT(S) (S) += (!!(S ^ 0xffffffff))  // S will incr by 1 only till it reach 0xffffffff


/* Set flag if C is non-zero, Reset flag in val if C is zero */
#define SET_FLAG_IF(VAL, FLAG, C) \
     (VAL) &= ~(FLAG); /* Reset the flag */ \
     (VAL) |= -!!(C) & (FLAG); /* Set the flag if C is non-zero */


/* Count Macro arguments */
#define _GET_NTH_ARG(_1, _2, _3, _4, _5, N, ...) N
#define CNT(...) _GET_NTH_ARG("ignore", ##__VA_ARGS__, 4, 3, 2, 1, 0)
int main()
{
    printf("one arg: %d\n", CNT());  // outputs 0
    printf("one arg: %d\n", CNT(1));  // outputs 1
    printf("three args: %d\n", CNT(1, 2, 3)); // outputs 3
}