Path: utzoo!attcan!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!uwm.edu!gem.mps.ohio-state.edu!ginosko!uunet!modcomp!joe
From: joe@modcomp.UUCP
Newsgroups: comp.lang.c
Subject: Re: A solution to the multiple inclusio
Message-ID: <90700006@modcomp>
Date: 25 Oct 89 03:34:00 GMT
References: <14240@well.UUCP>
Lines: 22
Nf-ID: #R:well.UUCP:14240:modcomp:90700006:000:1000
Nf-From: modcomp.UUCP!joe    Oct 24 23:34:00 1989


Lawrence Crowl writes:
> Each include file defines a symbol (preferably related to its name).  For
> example, in foo.h:
>         #define foo_h
> Each file that includes foo.h, protects the inclusion with a #ifndef:
>         #ifndef foo_h
>         #include "foo.h"
>         #endif foo_h
> I have used this solution as a matter of course since shortly after I learned
> to program in C.  It is an obvious solution, and leads me to wonder why it is
> not common practice.  Any explainations?

Well, for one thing, it's clumsy to enter.  For another, it's clumsy to
read.  Finally, it places this dirt at point-of-use, rather than
point-of-definition, where it really belongs (reason: thingys defined
once; used many times).  For many of us, these are sufficient reasons
to put this mechanism entirely in the include file, in spite of the
obvious (machine) inefficiencies involved.
--
joe korty			"for every vengence there is an equal and
uunet!modcomp!joe		opposite revengence." (from Cartoon Laws)