Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!bloom-beacon!mit-eddie!mit-amt!peter
From: peter@mit-amt.MEDIA.MIT.EDU (Peter Schroeder)
Newsgroups: comp.lang.c++
Subject: Re: Protected members
Message-ID: <1111@mit-amt.MEDIA.MIT.EDU>
Date: 29 Nov 89 14:47:36 GMT
References: <1989Nov28.122925.20804@newcastle.ac.uk>
Reply-To: peter@media-lab.media.mit.edu (Peter Schroeder)
Organization: MIT Media Lab, Cambridge MA
Lines: 44

In article lindsay@stobhill.newcastle.ac.uk (Lindsay F. Marshall) writes:

	class A
	{
	protected::
		A();
		~A();
		void* data;
	};

	class B : public A
	{
	public:
		B();
		~B();
		A* next;
	};

	B::~B()
	{
		while (next != this)
		{
			delete next;
		}
	}

>The compiler will not permit this access saying that the destructor is
>protected. The same thing happens if one tries to access next->data.
>Is this correct or is the compiler being too strict?

This is correct. As a member of B, A* is just some class and can only be
accessed as allowed by the original class definition.

If we defined a class D which looks exactly like class A and then replaced
the occurence of A* in B by D* it would be clear that we cannot expect to
be able to access D's desctructor.

I stumbled over this a few times, since 1.2.1 of cfront did not seem to
enforce it, but I can now see that it makes sense to forbid this.

Hope this helps.

Peter
peter@media-lab.media.mit.edu