Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!uwvax!gumby!bezanson
From: bezanson@gumby.WISC.EDU (Brian Bezanson)
Newsgroups: net.micro.mac
Subject: Re: TML Pascal ver 2.01 bug
Message-ID: <440@gumby.WISC.EDU>
Date: Sun, 2-Nov-86 00:44:47 EST
Article-I.D.: gumby.440
Posted: Sun Nov  2 00:44:47 1986
Date-Received: Mon, 3-Nov-86 23:59:40 EST
References: <12125@watnot.UUCP>
Distribution: net
Organization: Manta Software Corporation
Lines: 38
Summary: TML and Programming Bug

In article <12125@watnot.UUCP>, mjmartin@watnot.UUCP (Marie-Josee Martin) writes:
> Using the "Plain Vanilla" mode, TML doesn't pass variable text parameters
> correctly, at least for input and output.  The following piece of code
> compiles correctly but never runs correctly.  Actually, the program hangs
> (and sometimes crashes.)
 
>   procedure Sread (var f : text);
>     begin
>       writeln (SizeOf (f));
>       get (f);
>       while f^ <> 'q' do
>         get (f)
>     end;
 
> By defining the procedure as:
>   procedure Sread (f : text);
> the program compiles correctly AND executes properly. (Try to figure
> that out.)

I tried a similiar procedure recently in a program running under Lightspeed
Pascal.  But when it tried to compile a procedure similiar to your second
one, WITHOUT the VARiable parameter, Lightspeed gave me an error.  What you
have to do is change it to a VAR parameter, no mater if you plan on changing
it or not.  The reason why (correct me somebody because this may not be perfect)
is that a file of type TEXT (or a file of char) is a pointer or start of
a buffer in memory for this file.  By passing it as a straight parameter,
the computer would try and pass a copy of the buffer onto the stack.  
By using a VAR parameter you are passing a pointer to this buffer, thus 
giving no memory problems at all.  Lightspeed is set up to watch for this
possible error, either TML misses this, or Leonard lets you try it and
when it gets pushed on the stack, the program either bombs or hangs.

I made the fix in my procedures and used VAR parameters and everything
worked fine, I would assume this should fix your problem with TML.

-- 
Brian Bezanson {seismo,ihnp4,allegra,topaz,harvard}!uwvax!gumby!bezanson
Manta Software Corp.				  bezanson@gumby.wisc.edu