Newsgroups: comp.std.c++
Path: utzoo!utgpu!cunews!csi.uottawa.ca!news
From: hitz@sim5.csi.uottawa.ca (Martin Hitz)
Subject: backward virtual function call
Message-ID: <1991Apr30.024010.4331@csi.uottawa.ca>
Sender: news@csi.uottawa.ca
Nntp-Posting-Host: sim5
Organization: University of Ottawa
Date: Tue, 30 Apr 91 02:40:10 GMT

I wonder if the following is guaranteed to print 1:

#include <stream.h>
struct X {
	virtual f() { return 1; }
};
struct Y : X {
	f() { return 2; }
};

main()
{
	X x;
	Y * y = (Y *) &x;
	cout << y->f();
}

The ARM explains the usual case, that a call of f() for an object of
class Y invokes Y::f(), even if it is called via a pointer to X,
but I couldn't find anything about the above case. Zortech and g++
both yield 1 for this example. Is this considered to be the standard
behaviour?

Martin Hitz (hitz@csi.uottawa.ca)