Why can't static_cast be used to down-cast when virtual inheritance is involved?

Question

Consider the following code:

struct Base {};
struct Derived : public virtual Base {};

void f()
{
    Base* b = new Derived;
    Derived* d = static_cast<         


        

Answer 1

I suppose, this is due to classes with virtual inheritance having different memory layout. The parent has to be shared between children, therefore only one of them could be laid out continuously. That means, you are not guaranteed to be able to separate a continuous area of memory to treat it as a derived object.