无法理解c中负数的右移运算符运算

Question

这个问题已经有答案了:

Right shifting negative numbers in C (6 个回答)

已关闭 6 年前。

我有这段简单的代码。谁能解释为什么输出是 ffff不是0fff ??

#include<stdio.h>

int main(){

   printf("\n%x",(-1>>4));

   return 1;
}

Answer 1

最好避免移动负数。对于 <<这是未定义的行为。对于 >>它是实现定义的:

The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1 has an unsigned type or if E1 has a signed type and a nonnegative value, the value of the result is the integral part of the quotient of E1 / 2E2. If E1 has a signed type and a negative value, the resulting value is implementation-defined.