对于界面而言,它甚至更为重要。该类的任何用户都可能持有指向该接口的指针,而不是指向具体实现的指针。当他们删除它时,如果析构函数不是虚拟的,他们将调用接口的析构函数(如果未指定,则为编译器提供的默认值),而不是派生类的析构函数。即时内存泄漏。例如class Interface{ virtual void doSomething() = 0;};class Derived : public Interface{ Derived(); ~Derived() { // Do some important cleanup... }};void myFunc(void){ Interface* p = new Derived(); // The behaviour of the next line is undefined. It probably // calls Interface::~Interface, not Derived::~Derived delete p; }