C++ 指针一题

#include <iostream>

using namespace std;

class A {
    int i;
public:
    void Hello() {cout << "Hello" << endl;}
};


int main()
{
    A *p = NULL;
    p->Hello();

    return 0;
}

Hello

#include <stdio.h>

struct A {
    int i;
};

void Hello(struct A *sp)
{
    printf("Hello\n");
}

int main()
{
    struct A ×a = NULL;
    Hello(a);

    return 0;
}