Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!decwrl!
From: ontologic!vilot@erl.mit.edu (Michael J. Vilot)
Newsgroups: comp.lang.c++
Subject: Re: Visibility Bug in 1.2?
Message-ID: <8901130337.AA11580@EDDIE.MIT.EDU>
Date: 13 Jan 89 03:33:50 GMT
Organization: Digital Equipment Corporation
Lines: 42


Summary:  It's not a bug!

I did a little more research on the example.  In particular, I re-read pp.
196-197 more carefully:

	"It is also possible to declare some, but not all, of the
	public members of a base class public members of a derived class.
	^^^^^^                         ^^^^^^
	...
	    [on p. 192, employee::name & employee::department are _public_]
	...
	Naturally, it is -> NOT <- possible to make a 
	private member of a base class a public member of a derived class.
	^^^^^^^                          ^^^^^^
	It is not possible to make overloaded names public using this
	notation." 

In his 1987 Usenix paper "The Evolution of C++: 1985 to 1987", Bjarne
clears up some issues and adds some features to the language.  Among the
clarifications is a mention of this visibility issue (p. 4):
	"It was always possible to specify that a member of
	a private base should be considered public:
	...
		[another example where the base members are _public_]
	...

	"The complementary operation, making a member of
	public base private, is also allowed...
<< I tried this, it didn't seem supported ... >>
	Note that [doing this] implies that [the base class] is no longer a
	sub-type of [the derived class]: that is, there is no implicit
	coercion of a pointer to [the derived class] to a pointer to [the
	base class] and public members of [the base class] are not
	automatically public members of [the derived class]."

I have also encountered a related issue:  a friend of a derived class is
_not_ automatically a friend of the base class -- if you really want this,
you have to explicitly declare the function/class a friend of each.
* BUT * (p. 195 of the book):
	"An alternative, and sometimes cleaner, solution is for the derived
	class to use only the public members of its base class."