From owner-freebsd-hackers@FreeBSD.ORG  Wed Aug 10 10:06:36 2005
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
X-Original-To: hackers@freebsd.org
Delivered-To: freebsd-hackers@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 6010216A41F
	for <hackers@freebsd.org>; Wed, 10 Aug 2005 10:06:36 +0000 (GMT)
	(envelope-from gouders@et.bocholt.fh-gelsenkirchen.de)
Received: from alice.et.bocholt.fh-gelsenkirchen.de
	(alice.et.bocholt.fh-gelsenkirchen.de [193.175.197.63])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 6062243D46
	for <hackers@freebsd.org>; Wed, 10 Aug 2005 10:06:34 +0000 (GMT)
	(envelope-from gouders@et.bocholt.fh-gelsenkirchen.de)
Received: from musashi.et.bocholt.fh-gelsenkirchen.de
	(musashi.et.bocholt.fh-gelsenkirchen.de [193.175.197.95])
	by alice.et.bocholt.fh-gelsenkirchen.de (8.12.9/8.12.9) with ESMTP id
	j7AA6VeD031378
	(version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO);
	Wed, 10 Aug 2005 12:06:32 +0200
Received: from localhost (localhost [127.0.0.1])
	by musashi.et.bocholt.fh-gelsenkirchen.de (8.13.3/8.13.3) with ESMTP id
	j7AA6VCB037633; Wed, 10 Aug 2005 12:06:31 +0200 (CEST)
	(envelope-from hank@musashi.et.bocholt.fh-gelsenkirchen.de)
Message-Id: <200508101006.j7AA6VCB037633@musashi.et.bocholt.fh-gelsenkirchen.de>
To: Garance A Drosihn <drosih@rpi.edu>
In-Reply-To: Message from Garance A Drosihn <drosih@rpi.edu> of "Tue,
	09 Aug 2005 20:04:52 EDT." <p06230929bf1eecb4d4fd@[128.113.24.47]> 
Date: Wed, 10 Aug 2005 12:06:31 +0200
From: Dirk GOUDERS <gouders@et.bocholt.fh-ge.de>
X-Scanned-By: MIMEDefang 2.43
Cc: hackers@freebsd.org
Subject: Re: Include files that depend on include files 
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 10 Aug 2005 10:06:36 -0000


 > To get around this in user-space, we do things like create
 > /usr/include/sys/_types.h
 > 
 > And then our include files include *that* file, and do not include
 > the standard <sys/types.h>.  This <sys/_types.h> file, in turn, does
 > not define any of the actual symbols.  Let's say that some include
 > file needs to know what typedef for 'off_t' is.  The sys/_types.h
 > file defines __off_t, and then the include file which needs off_t
 > will do something like:
 > 
 > #include <sys/_types.h>
 > #ifndef _OFF_T_DECLARED
 > typedef __off_t         off_t;
 > #define _OFF_T_DECLARED
 > #endif
 > 
 > Thus, it has only defined the one name it actually needs, instead
 > of defining all of the standard symbols in the real sys/types.h.

Can you point me to a real-life example where such a mechanism is
used?  I'd like to have a closer look at it.

Dirk