Re: Call virtual function in constructor

junw2000@[EMAIL PROTECTED]
 wrote:
> Is there any problem if call virtual function in constructor? For
> example:
> 
> class A
> {
> public:
>      A()
>      {
>            setvalue();
>      }
> 
>     setvalue()
>     {
>            data = getnumber();
>     }
> 
>     print() { cout << data << endl;
> 
> private:
>     virtual int getnumber() {return 100;}
>     int data;
> }
> 
> class B : public A
> {
> public:
>          B() { }
> 
> private:
>          virtual int getnumber() {return 22222;}
> 
> }
> 
> int main()
> {
>      A test1;
>      test1.print() ;
> 
>      B test2;
>      test2.print() ;
> 
> }
> 
> Thanks.
>

Yes, there's a problem.  When you construct a B, at the time the virtual 
function is called from A's constructor, the B hasn't been constructed 
yet, so you get either A's version or undefined behavior (I can't 
remember which, and my copy of the Standard is at work).