Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!orion.oac.uci.edu!ucivax!milne
From: milne@ics.uci.edu (Alastair Milne)
Newsgroups: comp.lang.pascal
Subject: Re: For statement bug?
Message-ID: <283C6140.6182@ics.uci.edu>
Date: 24 May 91 00:41:35 GMT
References: <13134@uhccux.uhcc.Hawaii.Edu>
Distribution: na
Organization: UC Irvine Department of ICS
Lines: 40

In <13134@uhccux.uhcc.Hawaii.Edu> wyuu@uhunix1.uhcc.Hawaii.Edu writes:

> procedure makescreen;
>   var level :integer;
>       i     : integer;
>  begin
>    level := 1;
>    level := level + 4;
>    for i := 1 to level do  {this is the line that wonks my program..}
>     begin
>      { code.. code.. code..}
>     end;
>  end;

>and if I call this procedure.. WHAMMO! I am creating a video game and
>when it comes to this procedure, all these random pixels fills up my
>screen and locks up my system.. I have to cold start my system to get it
>back running.. but if I put a integer.. ie.. 4 or sumthin in the for i
>statement.. everything is hunky dory.. am I missing something here? any
>comments help.. is appreciated.
>								thanks.

   It would be better if you showed the actual code that does this.
   I know the principle works just fine in Turbo 5 -- I've done it
   a *lot*.

   Check whether your for-loop target is actually initalised, or 
   perhaps has suffered integer overflow when it was computed, etc. etc..
   Hint: if you're calling another procedure to initalise this target,
   just before you run the loop, make *Sure* the parameter to which
   you pass it is VAR parameter.  I couldn't say how often I've seen
   severe failures just because a procedure wasn't passing something
   back when it was supposed to.

   There are other possibilities, of course, but that's what occurs
   to me just now.

   Good luck,

   Alastair Milne