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From: dyer@atari.UUcp (Landon Dyer)
Newsgroups: net.micro.atari16
Subject: Re: Bug in GEMDOS (was TVX bug)
Message-ID: <438@atari.UUcp>
Date: Thu, 9-Oct-86 22:14:02 EDT
Article-I.D.: atari.438
Posted: Thu Oct  9 22:14:02 1986
Date-Received: Sat, 11-Oct-86 21:05:11 EDT
References: <402@unmvax.UUCP>
Organization: Atari Corp., Sunnyvale CA
Lines: 43
Keywords: The real story (console I/O in GEMDOS)


The real culprit is what I would refer to as a "semi-circular" buffer
in GEMDOS's character I/O routines.  When you read with Cconin(), you
must read ALL the characters that are available before using Cconout()
or Cconws().  If you don't, the buffer will overflow and cause a
crash.  (The program at the end of this posting demonstrates the
problem quite dramatically).

The BIOS has no such problem.  My philosophy is (and always has
been) to avoid the GEMDOS console, aux and printer functions, and
go directly to the BIOS.

>  /*
>   *  holdkey --- semi-circular buffer test
>   *
>   *  Test:
>   *	Run it.  Hold down RETURN until auto-repeat starts.  Keep
>   *	holding RETURN down.  The system should crash (the exact
>   *	exception varies).
>   *
>   *  Status:
>   *	Fixed.
>   *
>   */
>  #include <osbind.h>
>  
>  main()
>  {
>    for (;;)
>      {
>        Cconws("Keep holding RETURN down.  A crash should happen soon.\r\n");
>        Cconin();
>      }
>  }

-- 

-Landon Dyer, Atari Corp.		        {sun,lll-lcc,imagen}!atari!dyer

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