C++条款 （构造 析构 赋值运算)

class Empty{};
等价于:
class Empty {
public:
	Empty(); // 构造函数
    Empty(const Emtpy& rhs) {...}; // copy构造函数
	~Empty(); // 析构函数
	Empty& operator = (const Empty *rhs) {...}; // copy assignment函数
}

为驳回编译器自动提供的机能，可将相应的成员函数申明为private并且不予实现。使用像Uncopyable这样的basic class也是一种做法。

class Uncopyable {
protected:
		Uncopyable(){ }
		~Uncopyable(){ }
private:
	Uncopyable(const Uncopyable&);
	Uncopyable operator= (const Uncopyable&);		
}
class HomeForSale:private Uncopyable {
	...  // class不再申明copy构造函数或copy assign操作符
};

polymorphic(带多态性质的)base classes应该申明一个virtual析构函数。如果class带有任何virtual函数，他就应该有一个virtual析构函数。
classes的设计目的如果不是作为base classes使用，或不是为了具备多态性(polymorphically)，就不该申明virtual析构函数。

class TimeKeeper {
public:
	TimeKeeper();
	~TimeKeeper();
	...
};
class AtomicClock: public TimeKeeper {...};
class WaterClock: public TimeKeeper {...};
class WristWatch: public Timekeeper {...};
TimeKeeper *ptk = getTimeKeeper();
delete pkt; // 内存泄漏

class TimeKeeper {
public:
	TimeKeeper();
	virtual ~TimeKeeper();
	...
};
class AtomicClock: public TimeKeeper {...};
class WaterClock: public TimeKeeper {...};
class WristWatch: public Timekeeper {...};
TimeKeeper *ptk = getTimeKeeper();
delete pkt; // OK