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From: markv@kuhub.cc.ukans.edu
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Manx/Lattice divergant behaviour
Message-ID: <29017.27db6b70@kuhub.cc.ukans.edu>
Date: 11 Mar 91 17:35:12 GMT
References: <1001@caslon.cs.arizona.edu>
Organization: University of Kansas Academic Computing Services
Lines: 44

In article <1001@caslon.cs.arizona.edu>, dave@cs.arizona.edu (Dave P. Schaumann) writes:
> I've come across a curious incompatability between Manx and Lattice, and
> I'm hoping that someone can clear the air for me.
> 
>Through the course of events, a friend and I both compiled the following code.
>I with Manx 3.6a, he with a Lattice compiler (sorry, don't know the version):
> 
> /* Please excuse any typos; I typed this from memory.
> */
> #include <stdio.h>
> 
> main() {
> 
>   FILE *my_win ;
>   int c ;
> 
>  if( (my_win = fopen( "CON:10/10/100/200/C window", "a+" )) == NULL ) {
>     puts( "Can't open window!" ) ; exit(1) ;

You may be running into the fact that CON: is an Interactive stream
device and does not support seeking, so I wouldn't count on the
behavior of anything like fseek() or something that might call it
implicitly like an "a+" mode stream.

Try "r+" or "w+".
 
> My version of this works fine.  The version compiled with Lattice sees EOF
> at fgetc() the first time it is executed, and exits immediately, whatever
> the input is.

Probably Lattice is calling Seek() (Amiga DOS) internally which will
fail on CON:, and then returns an EOF because of it.
 
> My question is: is the Lattice compiler broken/deficient, or is this an
> example of code with undefined behaviour?
-- 
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