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From: lindsay@stobhill.newcastle.ac.uk (Lindsay F. Marshall)
Newsgroups: comp.lang.c++
Subject: Protected members
Message-ID: <1989Nov28.122925.20804@newcastle.ac.uk>
Date: 28 Nov 89 12:29:25 GMT
Sender: news@newcastle.ac.uk
Organization: Computing Laboratory, University of Newcastle upon Tyne, UK, NE1 7RU
Lines: 47

I have an application that worked under the 1.2 rules but wil not
compile under 2.0. This seems to be to a considerable tightening of
the rules for protected members. What I am not sure is whether or not
it is correct!! The situation

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

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

So B is derived from and A and an instance of class B can access the
field data without problems. However, if the class B uses an instance
of class A inside one of its members, for example:


	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? If it's correct
is there any point in having a protected, non-virtual destructor - it
might as well be private.

This happens with both C++ 2.0 and g++ 1.36.1 .

Lindsay
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