设置长度未知的整数类型的高位

static_cast<uintptr_t>(1) << (CHAR_BIT * sizeof(void*) - 1)

(请注意,目前的英特尔芯片有48位指针在引擎盖下。)

要获取指针的字节大小,可以使用 sizeof(void *) ,以位表示 sizeof(void *) * CHAR_BIT 1ULL << (sizeof(void *) * CHAR_BIT - 1) . 那就用你的号码吧。

考虑以下代码:

int *x = (int*)-1;                           //You set all the bits of `x`
int *y = (int*)((unsigned long long)x >> 1); //y has all bits set besides the msb
x = (int*)(x - y);                           //subtract y from x to have only th msb set