About virtual destructor

心碎飞了

Virtual is added to inherit polymorphism

Doesn't it mean that destructors cannot be inherited?

hzxszmh

Is to use the base class pointer to be able to delete derived class objects

心碎飞了

I didn't understand the words upstairs-_-b

Let me make the question more clear:
Virtual is used to implement polymorphism for functions that can be inherited, while destructors cannot be inherited!

firegun

If the destructor does not use virtual, then
Base *p = new Derive();
delete p;
Here, delete p deletes the Base component in the Derive class, but cannot delete Derive members. Therefore, in order to delete correctly, you must use the virtual destructor. For details, please refer to effective c++ 3td

firegun

Article Seven

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In the structure of the C++ object, if there is a virtual function, there will be a virtual function table, as everyone knows, and the destructor will be placed in the second index position of the virtual function table, and the first index position is placed in type_info , Used to support RTTI. This is the case regardless of the class. The polymorphism of the destructor is different from the ordinary function, and there is only one destructor for each class, which can guarantee the calling conditions of polymorphism, and it does not use inheritance itself. Come to realize it, so you don't need to be surprised

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A Pure Virtual Destructor

Unlike ordinary member functions, a virtual destructor is not overridden when redefined in a derived class. Rather, it is extended: the lower-most destructor first invokes the destructor of its base class and only then, it is executed. Consequently, when you try to declare a pure virtual destructor, you may encounter compilation errors, or worse: a runtime crash. However, there's no need to despair--you can enjoy both worlds by declaring a pure virtual destructor without a risk. The abstract class should contain a declaration (without a definition) of a pure virtual destructor:

//Interface.h file
class Interface {
public:
virtual ~Interface() = 0; //pure virtual destructor declaration
};

Somewhere outside the class declaration, the pure virtual destructor has to be defined like this:

//Interface.cpp file
Interface::~Interface()
{} //definition of a pure virtual destructor; should always be empty

This text should be more clear

心碎飞了

E text is not good, upstairs bothered.

The problem comes again, since adding virtual before the destructor is not to allow subclasses to inherit,
1>>>>What does Nagata do?
2>>>> Can it be said that after adding virtual, the destructor of the subclass is added to the virtual function table? (At this time, both the base class and subclass destructors are called)
Without virtual, the subclass will not be added to the virtual function table, and will not be called at the end? (At this time, only the destructor of the base class is called)

心碎飞了

To add, I know that virtual is added to prevent the member memory defined by the subclass from being released when the base class pointer is destructed

心碎飞了

But now I don’t know why this can be done
Prevent the member memory defined by the subclass from being released when the base class pointer is destructed