Bit wise NOT 的计算

Question

如何手动计算~a？我经常看到这类问题。

#include <stdio.h>
int main()
{
    unsigned int a = 10;
    a = ~a;
    printf("%d\n", a);
}

Answer 1

The result of the ~ operator is the bitwise complement of its (promoted) operand
C11dr §6.5.3.3

当与 unsigned 一起使用时，用异或 UINT_MAX 模拟 ~ 就足够了，UINT_MAX 的类型和值与 (无符号)-1。 @EOF

unsigned int a = 10;
// a = ~a;
a ^= -1;