From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Bambach <eric@cisu.net>
Subject: Re: #include problem
Date: Fri, 15 Oct 2004 12:04:17 -0500
Sender: linux-c-programming-owner@vger.kernel.org
Message-ID: <200410151204.17172.eric@cisu.net>
References: <200410151648.i9FGmlqM026477@students.fct.unl.pt>
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To: C-16  <pmr17184@students.fct.unl.pt>
Cc: linux-c-programming@vger.kernel.org

On Friday 15 October 2004 11:48 am, C-16 wrote:
> Howdy,
> i have a file main.c in my program that needs to include four headers
> aaa.h , bbb.h ,ccc.h and ddd.h . Each one of these headers need to
> include another header xxx.h . With this implementation i get a
> "redefinition" compilation error. How can i solve this problem ? Thanks
> in advance.
> -
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You want to use whats called header guards.

-----------------aaa.h----------

#ifndef AAA_H
#define AAA_H

#include "xxx.h"

...some code

#endif
----------------end aaa.h---------
----------------xxx.h--------------

#ifndef XXX_H
#define XXX_H

.....some code

#endif
----------------end xxx.h----------

Notice that the endif must be the very last line of the file or you defeat the 
whole purpose of header guards. Others may or may not actually call them 
header guards, but thats the phrase I was taught. Its good practice to 
*always* use these in your header files. It solves many simple double 
inclusion and inclusion loop problems.

----------------------------------------
EB

> All is fine except that I can reliably "oops" it simply by trying to read
> from /proc/apm (e.g. cat /proc/apm).
> oops output and ksymoops-2.3.4 output is attached.
> Is there anything else I can contribute?

The latitude and longtitude of the bios writers current position, and
a ballistic missile.

		--Alan Cox 2000-12-08 

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