CPP11 — 1 of 4 issues with Abstract interfaces

1. The resolution that we seemed to be converging on for issue 674
allows programmers to inherit servant implementations like this:

// IDL

interface A {
};

interface B : A {
};

// C++

class MyA : public virtual POA_A {
};

class MyB : public virtual POA_B, public virtual MyA {
};

However, this paradigm breaks when using abstract interfaces:

// IDL
abstract interface A {
};

interface B : A {
};

since the spec does not require a POA skeleton be generated for A.

I think we should change the spec to state that POA skeletons for
abstract interfaces are generated, but that these skeletons do not
inherit from ServantBase, and do not contain a _this() member function.
This will allow inheritence of implementations, even for abstract
interfaces.

I considered just having POA_B just inherit directly from the abstract
class A, but that would allow POA_B skeletons to be widened implicitly
to an abstract interface pointer (for implementations which define A_ptr
as A *), and that seems to be too trouble prone. If someone can think
of a way to do this and prevent implicit widening, then this would be
better, since it would even allow sharing of implementation between a
servant and a valutype that both inherit from the same abstract
interface.

resolved/closed