单例模式

#include <iostream>
#include <mutex>
using namespace std;


class Singleton 
{
private:
    Singleton() {};
    Singleton(const Singleton& other) = delete;
public:
    static Singleton* getInstance();
    static Singleton* m_instance;
};

Singleton* Singleton::m_instance = NULL;
Singleton* Singleton::getInstance()
{
    std::once_flag myflag;
    std::call_once(myflag, []() { Singleton::m_instance = new Singleton; });
    return m_instance;
}

int main()
{
    Singleton* instance = Singleton::getInstance();
    return 0;
}