Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!loft386!dpi
From: dpi@loft386.UUCP (Doug Ingraham)
Newsgroups: comp.lang.c
Subject: Re: A solution to the multiple inclusion problem
Summary: GNU gcc already has this.
Message-ID: <521@loft386.UUCP>
Date: 25 Oct 89 17:23:11 GMT
References: <14240@well.UUCP> <1989Oct23.191634.6345@cs.rochester.edu> <4643@buengc.BU.EDU>
Distribution: comp
Organization: Lofty Pursuits, Rapid City, SD USA
Lines: 36

In article <4643@buengc.BU.EDU>, bph@buengc.BU.EDU (Blair P. Houghton) writes:
> How about ( in <foo.h>):
> 
> 	#pragma Never_Again
> 
> Which tells the BlairTech/ANSI1.0 compiler that when it hits
> a #include to read this file again, it should just ignore it.
> 
> 				--Blair

In GNU gcc this is already implemented as a pragma.

#pragma once

Seems like an obvious enough thing that every compiler vendor
will eventually have their own incompatible version of this
construct.

I have put both constructs in my ANSI compatible header files so
that they look like this:

#pragma once
#ifndef _STRING_H
#define _STRING_H

/* REST OF HEADER */

#endif

In this way if compiled on a compiler that doesn't recognize the once
pragma, it still has the desired effect.

-- 
Doug Ingraham (SysAdmin)
Lofty Pursuits (Public Access for Rapid City SD USA)
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