想问问这个c++单例模式的代码为啥会是这样的输出

Question

#include <iostream>

using namespace std;

class Single
{
private:
    int m_num;
    Single(int num):m_num(num){};
public:
    static Single* Get_instance(int num){
        static Single instance(num);
        return &instance;
    }
    static void Destroy(Single* instance){
        delete instance;    
        instance = NULL;
    }
    void show(){  cout<<m_num<<endl; } 
};

int main(){
    Single* tmp = Single::Get_instance(1);
    tmp->show();
    Single* second_try = Single::Get_instance(2);
    second_try->show();
    cout<<tmp<< ' ' << second_try << endl;
    return 0;
}

就是实现了一个单例模式，要了两个实例改变了一下成员变量，然后想问下为啥运行结果是这样

 

Answer 1

这。。好像是函数里面定义的静态变量，初始化只会执行一次，无论该函数被调用几次