Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!mcvax!kth!draken!tut!tukki!sakkinen
From: sakkinen@tukki.jyu.fi (Markku Sakkinen)
Newsgroups: comp.lang.c++
Subject: Re: do destructors descend hierarchy?
Message-ID: <982@tukki.jyu.fi>
Date: 5 Jul 89 05:41:35 GMT
References: <1570@cadillac.CAD.MCC.COM> <9555@alice.UUCP>
Reply-To: markku@jytko.jyu.fi (Markku Sakkinen)
          SAKKINEN@FINJYU.bitnet (alternative)
Organization: University of Jyvaskyla, Finland
Lines: 50

In article <9555@alice.UUCP> ark@alice.UUCP (Andrew Koenig) writes:
-In article <1570@cadillac.CAD.MCC.COM>, rpj@redcloud.cad.mcc.com (Rich Johns) writes:
-
-> Assume the class Blue, which is a PrimaryColor, which is a Color.  All three classes
-> have destructors. If I have a Blue b allocated from free store:
-
->    Blue* b = new Blue;
-
-In other words, your declarations look like this:
-
-	class Color { /* stuff */ };
-	class PrimaryColor: public Color { /* more stuff */ };
-	class Blue: public PrimaryColor { /* still more stuff */ };
-
-> Now if I:
-
->    delete b;
-
-> will the destructors for PrimaryColor and Color be called?
-
-Yes.
-
-More specifically, when you said `new Blue,' that caused the
-constructors for Color, PrimaryColor, and Blue to be executed
-in that order.  When you say `delete b,' it causes the destructors
-for Blue, PrimaryColor, and Color to be executed in that order.
--- 
-				--Andrew Koenig
-				  ark@europa.att.com

Please, remember that you are using C++ release 2.0 yourself
but we others outside Bell Labs have not got it (at least yet)!
The sad fact about earlier AT&T releases is that if there is
an assignment to the variable this in a constructor (destructor)
of a derived class, the constructor (destructor) of its base class
will never be called. I don't know about those C++ compilers
(Oregon Software, Zortech, GNU, others?) that are not based on
AT&T's product.

As shown in my paper at ECOOP'88, the whole idea of assigning
to "this" in constructors and destructors causes a mess.
Fortunately it seems to get replaced by an orderly possibility
to overload the operators new and delete in release 2.0.

Markku Sakkinen
Department of Computer Science
University of Jyvaskyla (a's with umlauts)
Seminaarinkatu 15
SF-40100 Jyvaskyla (umlauts again)
Finland