Date: Wed, 21 Jan 2009 18:28:37 +0100
From: Sam Ravnborg <sam@ravnborg.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Helge Deller <deller@gmx.de>, David Miller <davem@davemloft.net>,
       jaswinder@kernel.org, mingo@elte.hu, x86@kernel.org,
       linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org,
       Kyle McMartin <kyle@mcmartin.ca>
Subject: Re: Confusion in usr/include/asm-generic/fcntl.h
Message-ID: <20090121172837.GA4386@uranus.ravnborg.org>
References: <1232496257.3123.19.camel@localhost.localdomain> <200901210924.23484.arnd@arndb.de> <20090121113853.GB1579@uranus.ravnborg.org> <200901211313.17394.arnd@arndb.de>
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On Wed, Jan 21, 2009 at 01:13:16PM +0100, Arnd Bergmann wrote:
> On Wednesday 21 January 2009, Sam Ravnborg wrote:
> > Could we add a new symbol for this?
> > We know we are going to use this in several places so a simpler variant
> > would be more readable.
> > 
> > Something like:
> > 
> > #ifdef __64BIT
> > ...
> > #endif
> > 
> > When we define __64BIT we would use the ?__BITS_PER_LONG == 64 check.
> 
> I would prefer using the __BITS_PER_LONG == 64 check directly, because
> it gives you a warning when __BITS_PER_LONG is undefined, whereas the
> #ifdef check gets easily fooled by include order problems. Note that
> this is not a problem in the kernel for CONFIG_* symbols which are
> always defined before the first #include.

It gives the warning only if you add -Wundef which IIRC is not default
with -Wall. And using the "__BITS_PER_LONG == 64" the risk of gitting
the expression wrong is much higher than the simpler variant where
you only write:

    __64BIT

But I have no strong feelings for it.

	Sam
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