C++实现单实例模式

用C++实现一个简单的单实例模式（支持多线程安全）
代码如下：
./h声明
class CSingleCarFactory
{
public:
static CSingleCarFactory * GetInstance();
std::string ProduceACar();
private:
CSingleCarFactory();
CSingleCarFactory(const CSingleCarFactory &x) {}; //拷贝构造函数
CSingleCarFactory& operator =(const CSingleCarFactory &) {};
private:
static CSingleCarFactory *m_Instance;
static std::mutex m_Mutex; //互斥锁
int m_CarNum;
std::string m_CarName;

};
./cpp实现
CSingleCarFactory * CSingleCarFactory::m_Instance = nullptr;
std::mutex CSingleCarFactory::m_Mutex;
CSingleCarFactory::CSingleCarFactory()
{
m_CarNum = 0;
m_CarName = "Car_0";
}

std::string CSingleCarFactory::ProduceACar()
{
m_CarNum++;
char buf[10] = { 0 };
sprintf_s(buf, "Car_%d", m_CarNum);
m_CarName = std::string(buf);
return m_CarName;
}

CSingleCarFactory * CSingleCarFactory::GetInstance()
{
m_Mutex.lock();
if (nullptr == m_Instance)
{
m_Instance = new CSingleCarFactory();
}
m_Mutex.unlock();
return m_Instance;
}

int main()
{
for (int idx = 0; idx < 10; idx++)
{
std::string car = CSingleCarFactory::GetInstance()->ProduceACar();
std::cout << car << std::endl;
}

std::cout << "helloWorld" << std::endl;
std::cin.get();
}