整数运算溢出判断

int tadd_ok(int x,int y) {
    int sum = x + y;
    int neg_over = x < 0 && y < 0 && sum >= 0;
    int pos_over = x >= 0 && y >= 0 && sum < 0;
    return !neg_over && !pos_over;
}

int tsub_ok(int x,int y) {
    y = - y;
    int sum = x + y;
    int neg_over = x < 0 && y < 0 && sum >= 0;
    int pos_over = x >= 0 && y >= 0 && sum < 0;
    return !neg_over && !pos_over;
}

int tmultiply_ok(int x,int y) {
    int multiply = x * y;
    int neg_over = ((x < 0 && y > 0) || (x > 0 && y < 0)) && multiply >= 0;
    int pos_over = ((x >= 0 && y >= 0) || (x < 0 && y < 0)) && multiply < 0;
    return !neg_over && !pos_over;
}

int uadd_ok(unsigned x,unsigned y) {
    unsigned sum = x + y;
    return sum >= x;
}

int usub_ok(unsigned x,unsigned y) {
    unsigned sum = x - y;
    return sum <= x;
}

int umultiply_ok(unsigned x,unsigned y) {
    unsigned sum = x * y;
    return sum >= x || sum == 0;
}