vtable

问题 We all know what virtual functions are in C++, but how are they implemented at a deep level? Can the vtable be modified or even directly accessed at runtime? Does the vtable exist for all classes, or only those that have at least one virtual function? Do abstract classes simply have a NULL for the function pointer of at least one entry? Does having a single virtual function slow down the whole class? Or only the call to the function that is virtual? And does the speed get affected if the

问题 This question already has an answer here: Undefined reference to vtable. Trying to compile a Qt project 17 answers This is my header: #ifndef BARELYSOCKET_H #define BARELYSOCKET_H #include <QObject> //! The First Draw of the BarelySocket! class BarelySocket: public QObject { Q_OBJECT public: BarelySocket(); public slots: void sendMessage(Message aMessage); signals: void reciveMessage(Message aMessage); private: // QVector<Message> reciveMessages; }; #endif // BARELYSOCKET_H This is my class: