Xref: utzoo comp.software-eng:1152 comp.lang.c++:2671
Path: utzoo!utgpu!utstat!jarvis.csri.toronto.edu!mailrus!cwjcc!tut.cis.ohio-state.edu!rutgers!att!pegasus!psrc
From: psrc@pegasus.ATT.COM (Paul S. R. Chisholm)
Newsgroups: comp.software-eng,comp.lang.c++
Subject: Re: Recursive #includes
Summary: see comp.lang.c++
Keywords: recursive includes, modularity
Message-ID: <2630@pegasus.ATT.COM>
Date: 27 Feb 89 03:28:13 GMT
References: <570@marob.MASA.COM>
Followup-To: comp.software-eng
Organization: AT&T Bell Laboratories
Lines: 30

In article <570@marob.MASA.COM>, samperi@marob.MASA.COM (Dominick Samperi) writes:
> <contents of foo.h>:
> 
> #ifndef H_FOO
> #define H_FOO
>...stuff...
> #endif

This issue was beaten to death a few weeks ago in the comp.lang.c++
news group.  The obvious proposal is to not #include a file that's
already been #included, even if you see a second (or third, or forty-
second) #include for it.  This would also be more efficient that what
you suggest above, since the file doesn't even need to be opened again,
let alone read.  Unfortunately, it can break existing C code.

We had such a cpp (back in the bad old days of Net 1000, a large
development project).  People tended to #include the whole world, just
in case; but it did speed up compilation quite a bit (we had lots of
big header files).

The C++ header files I've seen do things like #ifndef STDIO_H, as you
suggest above.  It may not the best solution, but it works.  For more
information, look at old comp.lang.c++ articles (no, I don't know of
any place that archives them).

>Dominick Samperi -- ESCC, samperi@marob.masa.com, uunet!hombre!samperi

Paul S. R. Chisholm, AT&T Bell Laboratories, att!pegasus!psrc
psrc@pegasus.att.com, AT&T Mail !psrchisholm
I'm not speaking for the company, I'm just speaking my mind.