int32_t floor_divide(int32_t a, int32_t b) {
        if (a < 0 != b < 0)
                if (b < 0)
                        return (a - b - 1) / b;
                else
                        return (a - b + 1) / b;
        else
                return a / b;
}

#define DIV(a,b) (((a) < 0) != ((b) < 0)) ? \
        ((b) < 0) ? ((a) - (b) - 1) / (b) : ((a) - (b) + 1) / (b) : (a) / (b)

VS

int32_t floor_divide(int32_t a, int32_t b) {
        if (a < 0 != b < 0)
                return (a - b + 1 - 2*(b < 0)) / b;
        else
                return a / b;
}

#define DIV(a,b) (((a) < 0) != ((b) < 0)) ? \
        ((a) - (b) + 1 - 2*((b) < 0)) / (b) : (a) / (b)