下面的代码报出bad allocation错误，求教为什么？
#include<iostream>
#include<string>
using namespace std;
class Student
{
public:
Student();
Student(int,string,float);//构造函数不能声明为虚函数，，，一般析构函数都声明都虚函数
//在声明构造函数时，在最左边加virtual，声明为虚函数，用同一种方式调用同一类族中不同类的所有的同名函数。当基类的一个成员函数声明为虚函数时，默认其派生类中的同名函数自动成为虚函数
virtual void display();
protected:
int num;
string name;
float score;
};
Student::Student():num(0),name("NULL"),score(0){}
Student::Student(int n,string nam,float sco):num(n),name(nam),score(sco){
cout<<"this is Student constructor."<<endl;
}
void Student::display()//在类外定义该函数时不必在加virtual
{
cout<<"student"<<endl;
cout<<"num:"<<num<<endl;
cout<<"name:"<<name<<endl;
cout<<"score:"<<score<<endl;
}
class Graduate:public Student//注意此处为:而不是::
{
public:
Graduate();
Graduate(int,string,float,float);
void display();
protected:
float pay;
};
Graduate::Graduate():Student(),pay(0){}
Graduate::Graduate(int n,string nam,float sco,float p):Student(n,nam,sco),pay(p){
cout<<"this is Graduate constructor."<<endl;
}
void Graduate::display()
{
cout<<"graduate"<<endl;
cout<<"num:"<<num<<endl;
cout<<"name:"<<name<<endl;
cout<<"score:"<<score<<endl;
cout<<"pay:"<<pay<<endl;
}
class Doctor:public Graduate
{
public:
Doctor();
Doctor(int,string,float,float,int);
void display();
private:
int age;
};
Doctor::Doctor():Graduate(),age(0){}
Doctor::Doctor(int n,string nam,float sco,float p,int a):Graduate(n,name,sco,p),age(a){
cout<<"this is Doctor constructor."<<endl;
}
void Doctor::display()
{
cout<<"Doctor"<<endl;
cout<<"num:"<<num<<endl;
cout<<"name:"<<name<<endl;
cout<<"score:"<<score<<endl;
cout<<"pay:"<<pay<<endl;
cout<<"age"<<age<<endl;
}
void main()
{
Student stud1(1,"haha",89.0);
Graduate grad1(2,"fang",98.0,2000);
Student *pt=&stud1;
pt->display();
pt=&grad1;
pt->display();
grad1.display();
try{
Doctor doc1(3,"lili",97.3,2090,20);//此处报错！！
pt=&doc1;
pt->display();
doc1.display();
}catch(std::exception const &ex)
{
cout<<ex.what()<<endl;
}
}
