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/// Checks that \a BaseT is first base class of \a DerivedT. Another words, the function template
/// checks whether casting from \a DerivedT down to \a BaseT can be safety performed through
/// reinterpret_cast<>() (instead of static_cast<>()), i.e.:
/// reinterpret_cast<BaseT*>(derived) == static_cast<BaseT*>(derived);
/// Example:
/// \code
/// class C: public A, public B { ... }
/// checkFirstBase<A>(C); // OK
/// checkFirstBase<B>(C); // runtime error
/// \endcode
/// \warning The function template assumes that compiler places in memory base classes in order of
/// declaration. This is not a requarement of the C++ Standard.
template <typename BaseT, typename DerivedT>
inline void checkFirstBase()
{
	DerivedT* const Derived = reinterpret_cast<DerivedT*>(1);
	Q_UNUSED(Derived);
	Q_ASSERT(reinterpret_cast<void*>(1) == reinterpret_cast<void*>(static_cast<BaseT*>(Derived))
		&& "DerivedT does not coincide with BaseT (BaseT is not first base class of DerivedT)");
}

<<<
/// checkFirstBase<A>(C); // OK
/// checkFirstBase<B>(C); // runtime error
>>>
/// checkFirstBase<A, C>(); // OK
/// checkFirstBase<B, C>(); // runtime error

class A {...};
class B {...};
class C : public A, public B {...};

C c;

B* pb = &c;
C* pc = &c;

void* pb_value = reinterpret_cast<void*>(pb);
void* pc_value = reinterpret_cast<void*>(pc);

assert(pb == pc);  // не вопрос
assert(pb_value == pc_value);  // Опс