c++ sizeof() 位运算

sizeof() 函数是返回值的单位是 Byte，1 Byte = 8 bits.
目前，c++ 最长的数值类型可以有 64 位。

 1 #include <iostream>
 2 #include <climits>
 3 
 4 int main()
 5 {
 6    unsigned long long int a = 1;    /* 1 = 0000 0001 */
 7    unsigned long long int b = 0;
 8    // unsigned long long int c = pow(2,64) - 1;           
 9 
10    b = a << 63;     /*4  = 0000 0000 */
11    std::cout << "b = " << b << std::endl;
12 
13    std::cout << "size of int = " << sizeof(int) << std::endl;
14    std::cout << "size of unsigned long long int = " << sizeof(unsigned long long int) << std::endl;
15 
16    return 0;
17 }

out

1 b = 9223372036854775808
2 size of int = 4
3 size of unsigned long long int = 8