Problem with using new libs with old app (without relink)

[Olenin Vladimir <vahvarh at rbcmail dot ru>]

Salut,

We started to make a library, and found a
problem(?), there is an example:

class A {
public:
  A();
  virtual void b();
};
class B: public A {
public:
  B();
  virtual void d();
};

, in test we call dynamic_cast<B*>(test)->d();

if we switch to a newer lib (without relinking
test program) in which added 'virtual void c()'
into class A, we get 'A::c()' executed instead
of 'B::d()'.

We understand, that it is not a bug in common
meaning, but could you help us with advise
haw to make it work (other then relink - this
must not be done due to specific of our project).

Is there any specific switches or params to gcc
which can solve this problem ?
Or something ?

Yours, Olenin Vladimir