Xref: utzoo comp.object:2427 comp.lang.pascal:5236
Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!bellcore!bytor
From: bytor@ctt.bellcore.com (Ross Huitt)
Newsgroups: comp.object,comp.lang.pascal
Subject: Re: Shouldn't debuggers be able to debug dynamic objects?
Message-ID: <1991Jan25.145947.16431@bellcore.bellcore.com>
Date: 25 Jan 91 14:59:47 GMT
References: <1991Jan24.152256.24273@resam.dk>
Sender: usenet@bellcore.bellcore.com (Poster of News)
Followup-To: comp.object,comp.lang.pascal
Distribution: comp
Organization: Computer Technology Transfer, Bellcore
Lines: 31

In article <1991Jan24.152256.24273@resam.dk> andrew@resam.dk (Leif Andrew Rump) writes:
>I experienced a rather annoying feature in TurboPascal 5.5 (but I
>think the problem may exist in a lot of other (integrated) debuggers
>used to debug object oriented programmes.
>The program enclosed create two (2) dynamic objects: a square & a
>box.
>The first thing to notice is that the compiler only allow squareptr
>to be used as a general object for squares & boxes! Well I could
>accept that _IF_ the debugger (integrated & external (TD)) at least
>would notice when I create a box! But no - it only display the
>content of a square - the length has to be extracted manually!!!
>
...code deleted
>
>Leif Andrew Rump, AmbraSoft A/S, Stroedamvej 50, DK-2100 Copenhagen OE, Denmark
>UUCP: andrew@ambra.dk, phone: +45 39 27 11 77                /
>Currently at Scandinavian Airline Systems                =======/
>UUCP: andrew@resam.dk, phone: +45 32 32 51 54                \
>SAS, RESAM Project Office, CPHML-V, P.O.BOX 150, DK-2770 Kastrup, Denmark
>
>> > Read oe as: o <backspace> / (slash) and OE as O <backspace> / (slash) < <

When I _know_ which derived class a base class ptr is pointing to
and I want to inspect or display the object as a derived class, a cast
is usually sufficient to get the job done.  With the Turbo products,
simply type in 'squareptr(general_object(1))' at the Display or 
Evaluate prompts.  I don't know for sure that the technique works with
Turbo Pascal or if this particular syntax is correct, but I do use the
technique with C++ frequently.

	-ross aka bytor@ctt.bellcore.com