实现一个单例

class Singleton {
 public:
  static Singleton& Instance() {
    static Singleton instance;
    return instance;
  }

  Singleton(Singleton const&) = delete;
  Singleton(Singleton&&) = delete;
  Singleton& operator=(Singleton const&) = delete;
  Singleton& operator=(Singleton &&) = delete;

 protected:
  Singleton() = default;
  ~Singleton() = default;
}

可以使用下面的宏简化代码实现，禁止类的拷贝和移动构造

#define DISALLOW_COPY(ClassName)     \
  ClassName(const ClassName&) = delete; \
  ClassName& operator=(const ClassName&) = delete

#define DISALLOW_MOVE(ClassName) \
  ClassName(ClassName&&) = delete;  \
  ClassName& operator=(ClassName&&) = delete

#define DISALLOW_COPY_AND_MOVE(ClassName) \
  DISALLOW_COPY(ClassName);               \
  DISALLOW_MOVE(ClassName)

class ClassA final {
 public:
  ClassA(){}
  ~ClassA() {}
  DISALLOW_COPY_AND_MOVE(ClassA);

  void Reset();
  void CopyFrom(const ClassA* src);
  void Swap(ClassA* other);

 private:
  void* buffer_;
  size_t buffer_size_;
};