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From: opus@drutx.UUCP (ShanklandJA)
Newsgroups: net.unix-wizards
Subject: Re: getc() != EOF
Message-ID: <407@drutx.UUCP>
Date: Wed, 30-May-84 13:03:26 EDT
Article-I.D.: drutx.407
Posted: Wed May 30 13:03:26 1984
Date-Received: Fri, 1-Jun-84 22:21:54 EDT
References: <30@utastro.UUCP> <307@basser.SUN>
Organization: AT&T Information Systems Laboratories, Denver
Lines: 28

(sigh.)

> > >	while ( (c = getc()) != EOF )
> > >
> > >ought to work.  If somebody is to be blamed, it is surely not the
> > >people who wrote the code, but the people who made a C implementation
> > >that broke it.
> > 
> > It will work if "c" is declared "int."
> > It will not work if "c" is declared "char."
> > 
> 
> WRONG! The code above will work if c is int or char.
> Char variables are promoted to int in expressions (see C manual)
> and a char -1 is IDENTICAL with an int -1. Unsigned char c could be
> different (Any C implementors there? (kvm?)). 
> 
> Chris Maltby
> University of Sydney

But it is not defined whether char is a signed of unsigned type in C.
On machines where char is unsigned, c will never have the value -1,
and the comparison with EOF will always fail.

All this is quite clearly described on page 40 of K&R.

Jim Shankland
..!ihnp4!druxy!opus