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From: schweitz@lexvmc.vnet.ibm.com ("Eric Schweitz")
Newsgroups: comp.lang.c++
Subject: Re: Can a friend access members that were inherited as protected?
Message-ID: <9104031422.AA01270@ucbvax.Berkeley.EDU>
Date: 3 Apr 91 14:19:05 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 40

Cay Horstman writes:
| class B
|  {
|   friend class PB;
|  };
| class PB
|  {
|   protected:
|      B* pb;
|   //...
|  };
| class PD2 : public PB
|  {
|   void print() { if (pb) cout << ((D*)pb)->d << " " << pb->b; }
|  };
|
| why does the second example below, ... , not compile?

PD2 is derived from PB in your example, so PD2 has access to all of the
members of PB.  PB is a friend of B so it has access to all the members
of B. ``Friendship'' is not inherited, so PD2 does NOT have access to the
members of B through PB.

I hope this answers the question.

Also note that in your example, PD2 can actually access members of B via
the class D.  PD2 is a friend of D which is derived (publicly) from B.
So, if you wrote PD2::print() as:

void PD2::print() { if (pb) ((D*) pb)->print(); }

it should compile.  (I'm assuming pb points to the B part of a D, as you
showed.)

Eric.

-=- Standard Disclaimer Here -=-.

Eric Schweitz
Lexmark International