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Date: Thu, 17 Jan 2002 22:11:10 +0000
From: Christopher Turcksin <turcksin@raleigh.ibm.com>
Organization: IBM Global Services
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To: linux-kernel@vger.kernel.org
CC: Linus Torvalds <torvalds@transmeta.com>
Subject: Re: [PATCH] Re: 2.5.3-pre1 compile error
In-Reply-To: <20020115194316.I17477@redhat.com> <Pine.LNX.4.33.0201151644180.1213-100000@penguin.transmeta.com>
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Linus Torvalds wrote:

> > Well, I actually disagree on this.  For large include files (fs.h is the
> > worst), and complicated arrangement, this technique eliminates spurious
> > includes and saves a lot on compile time (really!).
> 
> Numbers please.

The GNU C preprocessor remembers if an include file was completely
inside an #ifndef/#endif conditional (modulo whitespace and comments)
and will skip the #include for the same file if the macro in #ifndef is
already defined. I suspect putting guards around the include will not
save any more time.

bfn,
Christopher Turcksin <turcksin@uk.ibm.com>

IBM Global Services
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