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From: rae@gpu.utcs.toronto.edu (Reid Ellis)
Newsgroups: comp.lang.c++
Subject: MPW C++ 1.0b1 warning: changing storage class in virtual methods
Summary: MPW CFront 1.0b1 (9/21/89; AT&T 2.0) doesn't issue an error message for changing the storage class of a virtual method
Keywords: virtual, static
Message-ID: <rae.657414585@earth>
Date: 31 Oct 90 23:09:45 GMT
Sender: Reid Ellis <rae%alias@csri.toronto.edu>
Reply-To: Reid Ellis <rae@gpu.utcs.toronto.edu>
Organization: Alias Research, Inc. Toronto ON Canada
Lines: 54

MPW CFront 1.0b1 (9/21/89; AT&T 2.0) does not flag changing the
storage class of an overridden virtual method as an error.  Executing
the resulting code gives bogus values for any parameters reference
through the virtual mechanism.

Included below is code that illustrates this.

#include <stream.h>

struct base {
	virtual int method(int);
	virtual int virtual_method(int) = 0;
private:
	int qx;
};

struct derived : base {
	static int virtual_method(int);
private:
	static int qvlp;
};

int base::method(int v)
{
	int dv = virtual_method(v);

	cout << form("base::method v is %d and virtual_method(v) is %d\n", v, dv);
	return v+10;
}

int derived::virtual_method(int v)
{
	cout << form("derived::virtual_method v is %d\n", v);
	return v+100;
}


main()
	{
	derived d;

	d.method(1);
	d.virtual_method(2);
	return 0;
	}

// output is as follows:
//
// derived::virtual_method v is 7365176
// base::method v is 1 and virtual_method(v) is 7365276
// derived::virtual_method v is 2
--
Reid Ellis  264 Broadway Avenue, Toronto ON, M4P 1V9               Canada
rae@gpu.utcs.toronto.edu || rae%alias@csri.toronto.edu || +1 416 487 1383