c - 为什么以下代码打印 1 作为输出？

Question

指针的差异给出 1 作为输出..

#include<string.h>
#include<stdio.h>
int main()
{  
    int a=5,b=10;
    int *p=&a,*q=&b;
    int c=p-q;
    printf("%d",c); 
    return 0;
}

Answer 1

将两个不指向同一个数组的指针相减是没有意义的。

C11:6.5.6 加法运算符(p8)

[...] If both the pointer operand and the result point to elements of the same array object, or one past the last element of the array object, the evaluation shall not produce an overflow; otherwise, the behavior is undefined.