Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!bloom-beacon!eru!luth!sunic!mcsun!ukc!mucs!r6!ian
From: ian@r6.uucp (Ian Cottam)
Newsgroups: comp.lang.c
Subject: EOF considered harmful
Summary: use feof() not EOF
Message-ID: <266@m1.cs.man.ac.uk>
Date: 22 Oct 89 15:44:55 GMT
Sender: news@cs.man.ac.uk
Reply-To: ian@r6.UUCP (Ian Cottam)
Organization: University of Manchester, UK
Lines: 51

Some observations on the little program below (following some recent
discussions in this group):
_______________________
#include <stdio.h>

int
main()
{
	char ch;
	while ( ! feof(stdin) ) {
		ch= getchar();
		putchar(ch);
	}

	return 0;
}
______________________

1) This program runs as quickly as the ``((ch= getchar()) != EOF)''
   version (on my SUN3 with gcc).

2) Although in this specific example the variable ch is redundant, I
   include it to show that declaring it to be a char is quite sensible
   given the feof() test.  Thus a common error in C code -- a colleague
   of mine even found this error in K&R first edition -- the sign extension
   (or not) character comparison with EOF is avoided.

3) The, to my mind, awful idiom in 1) above is avoided, with the extra
   benefit that the ``(ch= getchar() != EOF)'' slip up will not be made.

4) This code is completely portable to implementations that have:
		sizeof(char) == sizeof(int)

5) Although, to my mind, the above is a compelling argument to abandon the
   explicit test for EOF, everyone reading this newsgroup (except me of
   course :-) ) will ignore it!
-----------------------------------------------------------------
Ian Cottam, Room IT101, Department of Computer Science,
University of Manchester, Oxford Road, Manchester, M13 9PL, U.K.
Tel: (+44) 61-275 6157         FAX: (+44) 61-275-6280
Internet: ian%cs.man.ac.uk@nss.cs.ucl.ac.uk   
JANET: ian@uk.ac.man.cs    UUCP: ..!mcvax!ukc!man.cs!ian
-----------------------------------------------------------------

-----------------------------------------------------------------
Ian Cottam, Room IT101, Department of Computer Science,
University of Manchester, Oxford Road, Manchester, M13 9PL, U.K.
Tel: (+44) 61-275 6157         FAX: (+44) 61-275-6280
Internet: ian%cs.man.ac.uk@nss.cs.ucl.ac.uk   
JANET: ian@uk.ac.man.cs    UUCP: ..!mcvax!ukc!man.cs!ian
-----------------------------------------------------------------