Effective C + + clause 7 declaring a virtual destructor for a polymorphic base class

1. If a class is going to be a base class, it should have a virtual destructor to prevent the "partial destruction" problem that occurs when the delete is directed to a derived class object by a base-class pointer, avoiding memory leaks, corrupted data structures, wasting time on the debugger, and so on; Any class with a virtual function almost certainly needs a virtual destructor.

2. The member function should not be set to a virtual function if it is not required, otherwise, if a class that does not have a virtual function has a virtual function, it will add an implied vptr (virtual table pointer) pointer (to the virtual function table to support dynamic binding), in which case , the "volume" of the class increases, not only because of the increased level of indirection reduces efficiency, but also may be due to the increase in volume caused it can not be put into the buffer cache, and so on.

3. It is best not to inherit classes that do not have virtual destructors (for reasons 1), including all STL containers, and not all base classes are designed for polymorphic purposes.

4. You can make a class with a pure virtual function as an abstract base class, but you must give the destructor a definition (because the invocation of a derived class destructor inevitably leads to the invocation of the base class destructor).

Effective C + + clause 7 declaring a virtual destructor for a polymorphic base class