Path: utzoo!attcan!ncrcan!hcr!stan
From: stan@hcr.UUCP (Stan Jarzabek)
Newsgroups: comp.lang.c++
Subject: deleting objects with virtual bases
Message-ID: <1984@hcr.UUCP>
Date: 7 Sep 89 14:17:06 GMT
Reply-To: stan@hcrvx1.UUCP (Stan Jarzabek)
Organization: HCR Corporation, Toronto
Lines: 30


Is it legal to delete an object with a virtual base through base pointer?

class A
{ int a; };

class B : virtual public A
{ int b; };

class C : public B
{ int c; };

main()
{
	A* ap = new C;  
	delete ap;

	C* cp = new C;  //core dumped
}

As 'ap' does not really point to the beginning of the area allocated by 'new C',
'delete ap' causes a problem. (In 2.0, operator delete() calls free().)
In fact, a subsequent call to operator new() causes core dump. The same problem 
may occur when you delete an object with multiple bases through a base pointer.

The language manual does not address this issue: is this a language definition 
problem, the problem of current implementation, or the thing a user should be 
responsible for?

Stan Jarzabek