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From: pete@borland.com (Pete Becker)
Newsgroups: comp.lang.c++
Subject: Re: Pure virtual destructors are illegal?
Keywords: virtual destructor
Message-ID: <1991Jun4.223627.29139@borland.com>
Date: 4 Jun 91 22:36:27 GMT
References: <183@swampthing.sbi.com> <1991Jun1.192610.18321@borland.com> <185@swampthing.sbi.com>
Organization: Borland International
Lines: 22

In article <185@swampthing.sbi.com> wfl@swampthing.sbi.com (W. Linke CPE) writes:
>>     	"Pure virtual" does not mean "no implementation"!  It only means that
>> a derived class must override the pure virtual function.  In the case of a
>> pure virtual destructor, since it will be called by the destructor for the
>> derived class, you must provide an implementation.
>

>A pure virtual member function *MAY* be defined for the abstract class in which
>it is declared, but it *MUST* be overridden in some class derived from the
>abstract class in order to create class objects,
>
>but a pure virtual destructor *MUST* be defined for the abstract class in which
>it is declared, while it *MAY* be "overridden" in classes derived from the
>abstract class.

	Well, there really is an underlying consistency.  Every pure virtual
function must be overridden in a derived class, whether it's a destructor or
not.  The reason you also have to define a pure virtual destructor is that
the pure virtual declaration IS a declaration, and tells the compiler not to
provide one for you.
	I agree that this is somewhat less than obvious.