Thread: Help with "virtual"

hi all.im new to this forum.
ive got a problem with this program:

Code:

class X {
      public:
             X() { }
             X( int xx ) : x( xx ) { }
             
             int getx() const { return x; }
      private:
             int x;
};

class Y : virtual public X {
      public:
             Y( int xx ) : X( xx ) { }
};

class Z : public Y {
      public:
             Z( int xx ) : Y( xx ) { }
};

int main()
{
Z zobj( 100 );
cout << zobj.getx() << endl;

it seems the "virtual" word changes something in my program and instead of getting 100 from print function i get 43-million-something.
i have been trying to find some reference of virtual and what it does but i seem to be unlucky up till now.
any help would be much appreciated,thank you.

well thanks for taking the time to answer but it really doesnt make much sense to me.
this is a given example and im trying to understand why virtual makes 100 go to whatever-millions when i print it.

i mean can you tell me what exactly happens if i put "virtual" in front of my class inheritance reference?

noone out there knows what virtual does?
im new to c++ and im trying to understand some basic things...

thanks a lot for this link...
the actual page doesnt give me any clues as it doesnt refer to this example of virtual but to virtual functions, but there was a link inside to what i wanted.

Code:

// Two classes virtually inheriting Animal:
class Mammal : public virtual Animal {
 public:
  virtual Color GetHairColor();
};
class WingedAnimal : public virtual Animal {
 public:
  virtual void Flap();
};

i know im probably sounding very stupid saying this but i still cannot understand what the use of virtual in front of inheritance class does.

That link (http://en.wikipedia.org/wiki/Virtual_inheritance) gives good information. You're using multiple inheritance, and you want to derive a class from two different base classes, but those base classes are each derived from another base class, which is the same for both. Or in the example, you are creating a Bat class, and a Bat is a Mammal and a Bat is a WingedAnimal. The problem is that the Bat is still only a single Animal, so you only want one version of the Animal traits in the Bat object. Having the Mammal and WingedAnimal classes use virtual inheritance solves this issue.

As CornedBee alluded to, virtual inheritance is not a common C++ technique, why do you think you need to use it in your program?

thank you all for the info.
here's the deal:
we are given this example as stated above and i need to understand and write down why it gives millions as answer instead of 100.
i understand the diamond problem very well the thing is he doesnt give us a diamond but actually a straight line!so why the heck would he use virtual?and past that, why does this 100-to-millions thing happen?
thats what im actually asking.
my deepest apologies for any misunderstanding and/or frustration i have caused.

thanks again to all.

thanks for the info cornedBee really helpful...