Re: Casting from a virtual base class to a parent in a diamond inheritance?
lindahlb@hotmail.com wrote:
class a {};
class b : public a {};
class c : public a {};
class d : public virtual b, public virtual c {};
This is a suspicious usage of virtual inheritance.
To make the "diamond" hierarchy, it's the class to be shared
that needs to be virtually inherited; in this case, class a.
class a {};
class b : public virtual a {};
class c : public virtual a {};
class d : public b, public c {};
a * ptr = 0;
d * ptr2 = static_cast<d *>(ptr);
d * ptr3 = static_cast<d *>(static_cast<b *>(ptr));
If I have a pointer to class a, how do I turn that into a pointer to
class d? I get an ambiguity error for the ptr2 conversion, and I get
an implied error for the ptr3 conversion. Compiler is MSVC++ 8.0.5.
Given a pointer to a virtual base, you don't know the exact layout of
the object statically. Make class a polymorphic (by adding a virtual
function), and use dynamic_cast.
--
Seungbeom Kim
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