Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!usc!rutgers!att!dptg!ulysses!andante!alice!shopiro
From: shopiro@alice.UUCP (Jonathan Shopiro)
Newsgroups: comp.lang.c++
Subject: Re: True Virtual
Summary: Destructors can never be pure virtual
Message-ID: <10424@alice.UUCP>
Date: 1 Feb 90 17:35:33 GMT
References: <4800082@m.cs.uiuc.edu> <4924@drutx.ATT.COM> <10382@alice.UUCP> <4982@drutx.ATT.COM>
Organization: AT&T Bell Laboratories, Murray Hill NJ
Lines: 25



Kim Tran wants to know why he can't have a pure virtual destructor,
that is

	class Foo {
		virtual ~Foo() = 0;	// error
	};

The reason is that whenever an object is destroyed, the destructors
for all its base classes are executed.  The pure virtual syntax says
that the function will never be called, but its name is a legitimate
function name so the compiler tries to call it in the destructor of
the derived class.

Instead just write an empty destructor, e.g.,

	class Foo {
		virtual ~Foo() {};	// okay
	};

-- 
		Jonathan Shopiro
		AT&T Bell Laboratories, Warren, NJ  07060-0908
		research!shopiro   (201) 580-4229