Path: utzoo!attcan!uunet!ncrlnk!ncr-sd!hp-sdd!hplabs!analog2!ward!smith
From: smith@ward.UUCP (Tom Smith)
Newsgroups: comp.lang.c++
Subject: Re: Virtual Destructors?
Message-ID: <332@ward.UUCP>
Date: 27 Dec 88 20:13:01 GMT
References: <8590@alice.UUCP>
Organization: Analog Design Tools Inc., Sunnyvale, CA.
Lines: 20

From article <8590@alice.UUCP>, by ark@alice.UUCP (Andrew Koenig):
> If you want a destructor to be virtual, make it virtual:
> 
    [ example of virtual destructor ]
> 
> Be aware that there is a fairly widespread bug that causes virtual
> destructors not to work quite right unless all derived classes have
> explicit destructors, even if the destructors are empty.

There is also a bug in our translator (Glockenspiel, derived from AT&T)
that could well exist in most, if not all.  It goes thusly:
Ordinarily, the delete operator is defined to "do the correct thing"
when the operand is a pointer of any type set to zero.  However, if the
operand is a pointer to an instance of a class with a virtual destructor,
and the pointer is set to zero, the resulting code tries to dereference
the pointer to call the virtual function without checking for a zero value
first.  Of course, this crashes your application promptly.

    Thomas Smith
    hplabs!analog!smith