C++单例结合智能指针解决释放

头文件：

#include "singleton.h"

#include <mutex>
#include<iostream>

std::shared_ptr<Singleton> Singleton::s_instance;
Singleton *Singleton::getInstance()
{
    static std::mutex s_mutex;
    if (s_instance.get() == NULL)
    {
        s_mutex.lock();
        if (s_instance.get() == NULL)
        {
            s_instance.reset(new Singleton());
        }
        s_mutex.unlock();
    }
    return s_instance.get();
}

Singleton::Singleton()
{

}

源文件：

#include "singleton.h"

#include <mutex>
#include<iostream>

std::shared_ptr<Singleton> Singleton::s_instance;
Singleton *Singleton::getInstance()
{
    static std::mutex s_mutex;
    if (s_instance.get() == NULL)
    {
        s_mutex.lock();
        if (s_instance.get() == NULL)
        {
            s_instance.reset(new Singleton());
        }
        s_mutex.unlock();
    }
    return s_instance.get();
}

Singleton::Singleton()
{

}