Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!news.glorb.com!npeer03.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!border3.nntp.dca.giganews.com!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!nntp.earthlink.com!news.earthlink.com.POSTED!not-for-mail
NNTP-Posting-Date: Tue, 27 Nov 2012 22:48:28 -0600
Message-ID: <50B5979D.7F60@mindspring.com>
Date: Tue, 27 Nov 2012 23:48:29 -0500
From: pete <pfiland@mindspring.com>
Reply-To: pfiland@mindspring.com
Organization: PF
X-Mailer: Mozilla 3.04Gold (WinNT; I)
MIME-Version: 1.0
Newsgroups: comp.lang.c
Subject: Re: what is the best way
References: <50b4d9fc$0$3108$ba620e4c@news.skynet.be> <k931s6$jk1$1@dont-email.me> <lna9u2jz7c.fsf@nuthaus.mib.org>
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 53
X-Usenet-Provider: http://www.giganews.com
NNTP-Posting-Host: 4.154.220.227
X-Trace: sv3-GcjfgBs4jegJhdsVTG4GgnB3qIX9uDZn+1UYoSl11jGmhWnKCmHmlTTQ0XwE9R1pVG4lNMR0hIBTEuY!OBSmSi71aPfQFwYtvuqsxLYJtWwyb4nYn2YGe6dFL0kjt9u0IzO+l/UHmGDVB867MKvYKJU548xk!e1zuYAXH4wY=
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.3.40
X-Original-Bytes: 2454
X-Received-Bytes: 2595
Xref: csiph.com comp.lang.c:28714

Keith Thompson wrote:
> 
> Les Cargill <lcargill99@comcast.com> writes:
> [...]
> > - Have this basic structure:
> >
> > thing.h:
> >
> > #ifndef _THING_H_
> > #define _THING_H_ 1
> > ...
> > #endif
> >
> > guarding all header files.
> [...]
> 
> Identifiers starting with an underscore and an uppercase letter
> (or with two underscores) are reserved to the implementation for
> any use; in other words, you should never use such identifiers in
> your own code.
> 
> Just use this:
> 
> #ifndef THING_H
> #define THING_H
> ...
> #endif /* THING_H */
> 
> (or some scheme that maps reasonably well from file names to
> identifiers without stepping on anything that's reserved).
> 
> Note that identifiers starting with E and either a digit or an
> uppercase letter may be used for implementation-defined macros
> in <errno.h>, so a header name that happens to start with E might
> cause problems.  One way to avoid that is:
> 
> #ifndef H_THING
> #define H_THING
> ...
> #endif /* H_THING */
> 
> It's not terribly likely that an implementation is going to use
> _THING_H_ or EXTRA_FOO for its own purposes, so you can very likely
> get away with using such identifiers yourself, but if you avoid
> reserved identifiers you have one less thing to worry about.

I use

#ifndef H_THING_H
#define H_THING_H

-- 
pete