我们见到经常有人用 static 局部对象的方式实现了类似单例模式,最近发现一篇文章明确写明 编译器在处理  static局部变量的时候 并不是线程安全的 ！！！

http://blogs.msdn.com/b/oldnewthing/archive/2004/03/08/85901.aspx     

于是实现了一个单例工厂  并且是线程安全的

#ifndef SINGLETONFACTORY_H
#define SINGLETONFACTORY_H
#include "windows.h"
#include <memory>
namespace Tools
{
template<class T>class SingletonFactory
{
public:
    virtual ~SingletonFactory()
    {
      ::DeleteCriticalSection(&__criticalSection);
    }
    std::auto_ptr<T>& GetInstance();
    static SingletonFactory<T>* CreateSingletonFactory();
private:
    SingletonFactory()
    {
       ::InitializeCriticalSection(&__criticalSection);
    }
    std::auto_ptr<T> __singletonObj;
    CRITICAL_SECTION __criticalSection;
};

//初始化创建  后续在多线程中使用
//还有另一种写法是单独的函数直接返回内部单例包装静态成员在 多线程情况下不安全
//SingletonFactory::CreateSingletonFactory().GetInstance();
template<class T> SingletonFactory<T>* SingletonFactory<T>::CreateSingletonFactory(){
    static SingletonFactory<T> temObj;
    return &temObj;
}
//工厂实例
template<class T> std::auto_ptr<T>&  SingletonFactory<T>::GetInstance()
{
    if(__singletonObj.get()==0)
    {
        ::EnterCriticalSection(&__criticalSection);
        if(__singletonObj.get()==0)
            __singletonObj=std::auto_ptr<T>(new T);
        ::LeaveCriticalSection(&__criticalSection);
    }
    return  __singletonObj;
}
}

#endif // SINGLETONFACTORY_H

测试代码 

    SingletonFactory<Data1>*singleton1=SingletonFactory<Data1>::CreateSingletonFactory();
    singleton1->GetInstance()->x=100;
    cout<<singleton1->GetInstance()->x<<endl;
    singleton1->GetInstance()->y=200;
    cout<<singleton1->GetInstance()->x<<endl;
    cout<<singleton1->GetInstance()->y<<endl;

    SingletonFactory<Data2>*singleton2=SingletonFactory<Data2>::CreateSingletonFactory();
    singleton2->GetInstance()->x=100;
    cout<<singleton2->GetInstance()->x<<endl;
    singleton2->GetInstance()->y=200;
    cout<<singleton2->GetInstance()->x<<endl;
    cout<<singleton2->GetInstance()->y<<endl;