c++ multiple-inheritance

Question

Possible Duplicates:
C++ pointer multi-inheritance fun.
more c++ multiple inheritance fun

This is a problem that arose from dealing with ref-counted pointer base class and threading fun.

Given:

class A{int x, y;};
class B{int xx, yy;};
class C: public A, public B {int z;};
C c;
C* pc = &c;
B* pb = CtoB(pc);
A* pa = CtoA(pc);

assert(pc == AtoC(pa));
assert(pc == BtoC(pb));

How do I write CtoB and CtoA to get the B & A parts of C?

How to I write AtoC and BtoC to get back the original C?

Thanks!

Why the votes to close?

My previous two questions asked if something was valid (the answer was "no"); this question asks "what is the valid way to do pointer conversion."

Answer 1

To get the B & A parts of C, you could try:

 B* pbb = static_cast<B*>(pc); 
 A* pba = static_cast<A*>(pc); 

This should be safe.

Answer 2

You don't need any function, since C only derives once from A and B. Unless you derive from A or B multiple times (without virtual inheritance), you only need to use:

A *pbb = pc;
B *pba = pc;

AtoC and BtoC are only safe through:

C *c = dynamic_cast<C*>(a_or_b_pointer);