面试题2：C++ 单例模式最简单最安全实现

本代码采用饿汉模式，是线程安全的，而且静态对象在生命周期结束的时候也会自动析构。

#include <cstdlib>
#include <cstdio>
#include <iostream>

class Singleton {
private:
    Singleton() { std::cout << "ctor" << std::endl; }
    ~Singleton() { std::cout << "dtor" << std::endl; }
    static Singleton one;

public:
    static Singleton *getInstance() { return &one; }
};
Singleton Singleton::one;

int main()
{
    Singleton *one = Singleton::getInstance();
    Singleton *two = Singleton::getInstance();
    if (one == two) std::cout << "same instance!" << std::endl;
    else std::cout << "Not the same!" << std::endl;

    return 0;
}
//"ctor"
//"same instance!"
//"dtor"