深入浅析c/c++ 中的static关键字

#include <iostream>
using namespace std;
class Test{
 friend void fun(const Test &t);
public:
 Test(int d = 0) : data(d){
  count++;
 }
 ~Test(){
  count--;
 }
private:
 int data;
 static int count;
};
void fun(const Test &t){
 cout << t.data << endl;
 cout << Test::count << endl;
}
//初始化static成员变量 
int Test::count = 0;
int main(){
 //int Test::count = 0;//编译不过，必须在外面初始化static成员变量
 //Test::count = 0;//编译不过，必须在外面初始化static成员变量
 Test t(10);
 fun(t);
 Test t1(11);
 fun(t1);
}