Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!sun-barr!rutgers!att!ulysses!andante!alice!ark
From: ark@alice.UUCP (Andrew Koenig)
Newsgroups: comp.lang.c++
Subject: Re: Virtual functions and missing constructors
Message-ID: <9346@alice.UUCP>
Date: 11 May 89 14:13:06 GMT
References: <583@hrc63.co.uk>
Organization: AT&T Bell Laboratories, Liberty Corner NJ
Lines: 38

In article <583@hrc63.co.uk>, andrew@hrc63.co.uk (Andrew Haylett "Baddow") writes:

The problem you describe appears to be an unplanned feature in your compiler.

	class A {
	public:
	    A() { };
	    A(int z) { };
	    virtual void f() { cout << "a\n"; };
	};
	
	class B : public A {
	public:
	    B() { };
	    // B(int z) { };	// This constructor is missing
	    void f() { cout << "b\n"; };
	};
	
	main()
	{
	    A a (1);	// instance of A, one argument
	    B b1   ;	// instance of B, calls B's constructor
	    B b2(1);	// instance of B, calls A's constructor

Bug #1 -- B doesn't have a B::B(int) constructor,
so the compiler should reject this call.  Constructors are
not inherited.

	    a.f();	// says "a"
	    b1.f();	// says "b"
	    b2.f();	// says "a" -- WRONG -- should be "b"

Bug #2.  b2 is a B, not an A, and should say so.

	}
-- 
				--Andrew Koenig
				  ark@europa.att.com