C++ sizeof

#include <iostream>
using namespace std;

void f(char str[]) {
    cout << sizeof(str)<<endl;
}

// error C2084: 函数“void f(char [])”已有主体
void f(char str[100]) {
    cout << sizeof(str) << endl;
}

int main()
{
    char str[] = "http://www.bilibili.com/";
    char* p = str;
    int n = 10;
    cout << sizeof(str)<<endl;
    cout << sizeof(p) << endl;
    cout << sizeof(n) << endl;

    char s[100];
    cout << sizeof(s) << endl;

    f(str);
    f(s);

    void *tp = malloc(100);
    cout << sizeof(tp) << endl;

    return 0;
}

x86输出：
25
4
4
100
4
4
4
x64输出：
25
8
4
100
8
8
8