谁给一个可继承的单例模式（Singleton）例子
谢谢
[解决办法]
这种问题咋不问google，来着等不嫌慢呢？？
///////////////////////////////////singleton template file//SingleEx.h#ifndef SINGLETONEX__H__#define SINGLETONEX__H__//File Name : SingletonEx.h//作用 : 提供单件模板功能(singleton template)//C++（C++培训 ）opyright(C) C++//Microsoft Visual C++ 6.0 , GCC Ver2.95.3-6 编译通过//作者:古斌亮//时间:2002.12.25//EMail : KingLinux@163.comtemplateclass CSingletonBase{protected:inline static T* Create(void){if(m_pt==NULL){m_pt=new T();}return m_pt;}inline static void Free(void){delete m_pt;m_pt=NULL;}protected:CSingletonBase(){}virtual ~CSingletonBase(){delete m_pt;}private:CSingletonBase(const CSingletonBase& sig){}CSingletonBase& operator = (const CSingletonBase& sig){}private:static T * m_pt;};templateT* CSingletonBase::m_pt = NULL;templateclass CSingletonEx : private CSingletonBase{public:CSingletonEx(){}virtual ~CSingletonEx(){}public:virtual T* Instance(void){return CSingletonBase::Create();}virtual void Release(void){CSingletonBase::Free();}private:CSingletonEx(const CSingletonEx& sig){}CSingletonEx& operator = (const CSingletonEx& sig){}};#endif //SINGLETONEX__H__//////////////////////////////////测试类//Doc.h#ifndef CDOC__H__#define CDOC__H__class CDoc //测试类{public:CDoc(const std::string name = "NoName"):m_name(name){}virtual ~CDoc(){}public:inlinestd::string Name(){return m_name;}inlinevoid SetName(const std::string& name){m_name=name;}protected:std::string m_name;};#endif //CDOC__H__//////////////////////////////////////测试文件//main.cpp#include#include#include "singletonex.h"#include "doc.h"void TestSingletonEx(void){CSingletonEx s;CDoc *pdoc = s.Instance();std::cout<Name()< pdoc->SetName("pdoc change: My SingletonEx");CDoc *p2 = s.Instance();std::cout<Name()< p2->SetName("p2 change: SingletonEx ");std::cout<Name()< }void main(void){std::cout<<"******** Test SingletonEx Start ******** "< TestSingletonEx();}//the end!!