[C++知识库]单例模式（c++11）

1.双重检查锁

mutex mt; 

class Singleton
{
private:
    Singleton(){};
    Singleton(const Singleton& rhs) = delete;
    Singleton& operator=(const Singleton& rhs) = delete;
    static Singleton* m_instance;

public:
    static Singleton* instance()
    {   
        if(m_instance == nullptr)
        {   
            mt.lock();
            if(m_instance == nullptr)
                m_instance = new Singleton();
            mt.unlock();
        }   
        return m_instance;
    }   
};
Singleton* Singleton::m_instance = nullptr;

2.局部静态变量

class singleton
  {
  public:
      static singleton& getInstance()
      {   
          static singleton m_instance;
          return m_instance;
      }   
  
  private:
      singleton(){};
      singleton(const singleton& rhs) = delete;
      singleton& operator=(const singleton& rhs) = delete;
  };