分析程序执行过程
class Base {public: int m_a; Base (int a = 2) : m_a(a) {} virtual ~Base() {printf( " A %d", m_a);}};class Derived : public Base {public: Derived (int a =4) : Base (a) {} virtual ~ Derived () {printf( "B %d", m_a);}};int main(){ Base *aa, bb; Derived cc(3); aa = new Derived; delete aa; system( "pause"); return 0;}