From owner-freebsd-ports  Wed Jul 10 16:45:02 1996
Return-Path: owner-ports
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.5/8.7.3) id QAA26501
          for ports-outgoing; Wed, 10 Jul 1996 16:45:02 -0700 (PDT)
Received: from phaeton.artisoft.com (phaeton.Artisoft.COM [198.17.250.211])
          by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id QAA26487;
          Wed, 10 Jul 1996 16:45:00 -0700 (PDT)
Received: (from terry@localhost) by phaeton.artisoft.com (8.6.11/8.6.9) id QAA27767; Wed, 10 Jul 1996 16:39:50 -0700
From: Terry Lambert <terry@lambert.org>
Message-Id: <199607102339.QAA27767@phaeton.artisoft.com>
Subject: Re: Q: macro expansion
To: dgy@rtd.com (Don Yuniskis)
Date: Wed, 10 Jul 1996 16:39:49 -0700 (MST)
Cc: freebsd-hackers@freefall.freebsd.org, freebsd-ports@freefall.freebsd.org
In-Reply-To: <199607102103.OAA05637@seagull.rtd.com> from "Don Yuniskis" at Jul 10, 96 02:03:54 pm
X-Mailer: ELM [version 2.4 PL24]
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: owner-ports@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

> 
> Greetings!
>      I was working on a port last night and stumbled upon this code
> fragment (paraphrased here):
> 	#define X 1
> 	#define Y 2
> 	X+Y
> I was surprised to see that ``X+Y'' was expanded to ``1 +2''.  So,
> I started digging through ANSI and couldn't seem to locate something
> to clearly define this behaviour.
> 	- why the inserted whitespace?
> 	- why no whitespace after `+'?
> 
> Any insight would be appreciated...

Because the ANSI C preprocessor didn't want people to use X/**/Y to
concatenate X and Y because the people in charge of the decision
were weenies with their own axe to grind (and wanted you to use X ## Y
instead).

__CONCAT(__CONCAT(X,+),Y)

...or take advantage of the whit space insertion ordering:

_CONCAT(X,+Y)

*bletch*.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.