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From: "Stuart Golodetz" <sgolodetz@dial.pipex.com>
Newsgroups: comp.std.c++,comp.lang.c++
Subject: Re: Inheritance Problems
Date: Mon, 14 May 2001 11:17:24 GMT
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"Chris Newton" <chrisnewton@no.junk.please.btinternet.com> wrote in message
news:9dh57t$uj$1@uranium.btinternet.com...
> O.Petzold <opetzold@wit.regiocom.net> wrote...
> > the follwoing code isn't working (with the gcc-2.95.2).
> > If I see the inharritance it should !
> >
> > class A {
> > public:
> >   void ModifyAnother(A* a2) {
> >     b = 1;              // is working
> >     a2->b = 1;          // woking as well
> >   }
> > protected:
> >   int b;
> > };
> >
> >
> > class B : public A {
> > public:
> >   void ModifyAnother(A* a2)  {
> >     b = 1;              // is working
> >     a2->b = 1;          // not working
> >   }
> > };
> >
> > int main() {
> >     B b;
> > }
> >
> > `int A::b' is protected
> >
> > Well but, B is derived from A !!
> > What says the standard about ?
>
> Your compiler is correct. You can only access a protected member of A in
> B via a pointer or reference to a B object. An A* isn't good enough.
> This is from 11.5/1 in the standard if you want to check.
>
> If you replaced B::ModifyAnother's parameter with (B* a2) instead, it
> should then work, because member access is controlled on a per-class and
> not per-object basis, so this B can access another B's protected
> members.

Can a B also access another B's private members? Cos before I read this I
worked on the assumption that it was only on a per-object basis...

Stuart.


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