Question

struct B {};
struct D : private B {
  B* fun () { return new D; }  // ok
}
struct DD : public D {
  B* foo () { return 0; } // error: ‘struct B B::B’ is inaccessible !
};

This error seems unreasonable to me. If we can use simple B* in global scope then why not in its privately derived classes? g++ demo.

We are Not trying to convert DD* to B*, which is forbidden by the language rules (this, this, this are related questions).
Note that, if I change B* foo() to int foo(), things go fine.

Answer 1

So apparently the compiler thinks B is referring to the private constructor of B rather than the type.

Qualifying B apparently fixes that error:

class B* foo () { return 0; }

or this:

::B* foo () { return 0; }

I don’t know why that’s happening, but maybe this will help.

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Update: maybe it’s related to 11.2.4 of standard? The only problem is that my standardese isn’t good enough to fully understand it.

(sorry for the image, copy/pasting isn’t working for me)