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From: landauer@morocco.Eng.Sun.COM (@morocco.eng [Doug Landauer])
Newsgroups: comp.lang.c++
Subject: Re: C++ Static Members and Inheritance
Keywords: C++ Static Members  Inheritance
Message-ID: <12533@exodus.Eng.Sun.COM>
Date: 30 Apr 91 17:50:58 GMT
References: <5069@servax0.essex.ac.uk>
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Organization: Sun Microsystems, Mt. View, Ca.
Lines: 39

> Now I know that a static member is the same for every object of a class,
> but is the same for every object of a DERIVED class?  My two objects were
> not of class "base" but of classes "derived1" and "derived2" respectively.

The whole point of inheritance (public inheritance, at least) is that
the derived "is a" base, so that you can use the derived object as if
it were a base object.  The static member is shared among all instances
(objects) of the base class, including the embedded "base" object that
lives inside each derived object.

> I've searched literature high and low for an answer to this.  Nowhere do
> they mention what happens when you inherit a static member (data or
> function).

Yeah, I think you're right -- I can't find a particularly explicit mention
either of this particular issue (inheritance vs static members), or of the
general principle that a derived "is a" base.  Perhaps X3J16's editor could 
add a sentence or two to make these things more clear.  Here's the things
I found that came closest to these issues:

    E&S, Section 9.4:
	There is only one copy of a static data member, shared by
	all objects of the class in a program.

    E&S, Section 10:
	A derived class can itself serve as a base class ...

    E&S, Section 11.2:
	Specifying a base class "private" does not affect access to
	static members of the base class.

    (Note that the latter has been rewritten a bit in the current draft --
    it says something more like
	Because of the rules on pointer conversion (section 4.6), a static
	member of a private base class may be inaccessible as an inherited
	name, but accessible directly.
    now.  But remember that it's still just a Draft.)
-- 
Doug Landauer - Sun Microsystems, Inc. - Languages - landauer@eng.sun.com