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From: lowey@sask.UUCP (Kevin Lowey)
Newsgroups: comp.sys.ibm.pc,comp.lang.pascal
Subject: Bug in Turbo Pascal 3.01a (append)
Message-ID: <918@sask.UUCP>
Date: Wed, 28-Oct-87 14:21:28 EST
Article-I.D.: sask.918
Posted: Wed Oct 28 14:21:28 1987
Date-Received: Wed, 4-Nov-87 06:40:29 EST
Organization: University of Saskatchewan
Lines: 72
Keywords: pascal, msdos, turbo
Xref: mnetor comp.sys.ibm.pc:9579 comp.lang.pascal:435


Hi,

  I've discovered a bug in Turbo Pascal version 3.01a (PC-DOS).  This 
version has a function called APPEND which is used to open a file 
at the end of the file, so that you can append information to the 
end.

  In version 3.01a of Turbo Pascal, if you try to append to a file
of length 0 (an empty file), when Turbo tries to write the first 
buffer to the file (either with the CLOSE command or a lot of 
write/writeln commands) you get IO error F0, Disk Write Error.

  The following program demonstrates this problem:
======================================================
program bug;
{Demonstates a bug in Turbo Pascal version 3.01    }
{appending to a null file creates an error message }

var fil:text;

begin
  {create file of length 0}
  assign (fil,'test.fil');
  rewrite (fil);
  close (fil);

  { append to the file }
  append (fil);
  write (fil,'Testing, 1,2,3');
  close (fil);  {<<< IO error F0, "Disk Write Error", occurs here }
end.
===================================================================

The following program fixes this problem:
===================================================================
program fix;
{Demonstates fix to bug in Turbo Pascal version 3.01 }
{appending to a null file creates an error message   }

var fil:text;

procedure myappend ( var fil:text);
begin
  reset (fil);
  if EOF(fil) then
    rewrite(fil)
  else
    append (fil);
end;

begin
  {create file of length 0}
  assign (fil,'test.fil');
  rewrite (fil);
  close (fil);

  { append to the file }
  myappend (fil);
  write (fil,'Testing, 1,2,3');
  close (fil);
end.
========================================================

______________________________________________________________________________
| Kevin Lowey                    |The above is the personal opinion of Kevin |
| University of Saskatchewan     |Lowey.  It does not reflect the position of|
| Computing Services             |the University of Saskatchewan in any way. |
| SaskTel: (306) 966-4826        |                                           |
| Bitnet:LOWEY@SASK. (preferred) |I am in no way affiliated with any of the  |
| UUCP:    ihnp4!sask!lowey.uucp |above mentioned companies other than U of S|
|________________________________|___________________________________________|