Xref: utzoo comp.object:2425 comp.lang.pascal:5220
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From: andrew@resam.dk (Leif Andrew Rump)
Newsgroups: comp.object,comp.lang.pascal
Subject: Shouldn't debuggers be able to debug dynamic objects?
Message-ID: <1991Jan24.152256.24273@resam.dk>
Date: 24 Jan 91 15:22:56 GMT
Distribution: comp
Organization: RESAM Project Office, SAS, CPHML-V
Lines: 76

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!!!

program dynamic;

type
  generalptr = ^general;
  general =
    object
      destructor done;               virtual;
    end;

  squareptr = ^square;
  square =
    object(general)
      height, width : real;

      constructor init(h, w : real);
    end;

  boxptr = ^box;
  box =
    object(square)
      length : real;

      constructor init(h, w, l : real);
    end;

  destructor general.done; begin end; (* everything is done behind our back *)

  constructor square.init(h, w : real);
  begin
    height := h;
    width := w;
  end;

  constructor box.init(h, w, l : real);
  begin
    square.init(h, w);
    length := l;
  end;

const
  n = 2;

var
  general_object : array(.1..n.) of squareptr;
  nr : integer;

begin
  for nr := 1 to n do
    if odd(nr) then
      general_object(.nr.) := new(squareptr, init(3, 4))
    else
      general_object(.nr.) := new(boxptr, init(3, 4, 2));

  for nr := 1 to n do
    dispose(general_object(.nr.), done);
end.


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

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