python - 用 C 和 Python 实现汇编程序

Question

我试图理解一段汇编程序，但没有解释:

;x is stored at 8(%ebp)

  movl 8(%ebp), %edx
  movl $0, %eax
  testl %edx, %edx
  je .L7

.L10:
  xorl %edx, %eax
  shrl %edx
  jne .L10

.L7:
  andl $1, %eax

我用 C 和 Python 实现它:

unsigned fun_a(unsigned x) {
    int val = 0;
    while (x != 0) {
        val = val ^ x;
        x = x >> 1;
    }
    return val && 1;
}

def fun_a(x):
    val = 0
    while x != 0:
        val = val ^ x
        x = x >> 1
    return val & 1

但结果却产生了不同的结果:

//C
fun_a(0) = 0
fun_a(1) = 1
fun_a(2) = 1
fun_a(3) = 1
fun_a(4) = 1
fun_a(5) = 1
fun_a(6) = 1
fun_a(7) = 1
fun_a(8) = 1
fun_a(9) = 1

#Python
fun_a(0) = 0
fun_a(1) = 1
fun_a(2) = 1
fun_a(3) = 0
fun_a(4) = 1
fun_a(5) = 0
fun_a(6) = 0
fun_a(7) = 1
fun_a(8) = 1
fun_a(9) = 0

我的 C/Python 程序出了什么问题？

Answer 1

在 c 中，您返回 val && 1，这是一个逻辑与。在 python 中，返回 val & 1 是按位的。