Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!rochester!kodak!sisd!news
From: jdg@sisd.kodak.com (Jeff Gortatowsky CUST)
Newsgroups: comp.lang.c++
Subject: Fairly simple Multiple Inheritance Question
Message-ID: <1990Jul25.121614.16958@sisd.kodak.com>
Date: 25 Jul 90 12:16:14 GMT
Sender: news@sisd.kodak.com
Distribution: na
Organization: Eastman Kodak Company, Rochester NY
Lines: 36

Like many others I'm just getting started using g++ and TC++. Here's
the question in code (shortened quite a bit).

class A { .......  };
class B { ......   };
// C inherits A and B
class C : public A, public B { .... };   // Note: has class B
// D inherits only A
class D : public A { ..... };            // Note: no class B

// E should have everthing.  2 copies of A?? Better fix that virtually!
class E : public C, public D { .... };

main ()
{
	E myObject();  // Construct a class E object
	B *ptrToB;      // Pointer to class B object

	ptrToB = &myObject;       // Illegal????  TC++ say it is.
	ptrToB = (B *) &myObject; // legal????
}

Is the first assignment legal?  One of the base classes of class E is 
class C which did inherit a class B object.  However the other class
inherited by class E was class D which did not inherit a class B object.
Is that why the first assignment is wrong?  The second works, it
even runs right.  I just want to know why if there is a base class
object of type B in an object of class E I can't use a base class pointer
without a cast. Please excuse any obvious stupidity on my part, I'm
just starting to make the shift.

--
Jeff Gortatowsky-Eastman Kodak Company  .....uunet!atexnet!kodak!elmgate!jdg
(716)-726-0084
Eastman Kodak makes film not comments.  Therefore these comments are mine
not theirs.