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Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!houxm!houxz!vax135!cornell!uw-beaver!tektronix!orca!andrew
From: andrew@orca.UUCP (Andrew Klossner)
Newsgroups: net.unix,net.lang.c,net.unix-wizards
Subject: Re: Standardized predefined CPP symbols, down with folklore
Message-ID: <936@orca.UUCP>
Date: Wed, 11-Jul-84 17:06:39 EDT
Article-I.D.: orca.936
Posted: Wed Jul 11 17:06:39 1984
Date-Received: Fri, 13-Jul-84 03:30:36 EDT
References: <2065@rlgvax.UUCP>  <142@pyuxt.UUCP>  <8241@watmath.UUCP> <297@watdcsu.UUCP> <4842@utcsrgv.UUCP>
Organization: Tektronix, Wilsonville OR
Lines: 24

[]

	"Actually, it wouldn't matter if the implementors had had the
	sense to have cpp implcitly "#define unix unix", instead of
	"#define unix 1".  The first would still permit all "#ifdef
	unix" work, while the actual implementation caused me grief one
	day when I tried to create a function called unix()"

Nope.  "#define unix unix" followed by a use of "unix" will put the
preprocessor into a loop, scanning "unix" over and over, until the
recursion depth is hit and it punts with a fatal error message.

Here's what it does under 4.2BSD:

	% cat >unix.c
	#define unix unix
	unix() {}
	% cc unix.c
	unix.c: 1: unix redefined
	unix.c: 2: unix: macro recursion
	% 

  -- Andrew Klossner   (decvax!tektronix!orca!andrew)      [UUCP]
                       (orca!andrew.tektronix@rand-relay)  [ARPA]