linux-kernel - Re: [PATCH,RFC] ext3: Add support for non-native signed/unsigned htree hash algorithms

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Message-id: <20081023192618.GS3184@webber.adilger.int>
Date:	Thu, 23 Oct 2008 13:26:18 -0600
From:	Andreas Dilger <adilger@....com>
To:	Theodore Tso <tytso@....edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH,RFC] ext3: Add support for non-native signed/unsigned	htree
 hash algorithms

On Oct 22, 2008  22:56 -0400, Theodore Ts'o wrote:
> On Wed, Oct 22, 2008 at 05:22:21PM -0700, Andrew Morton wrote:
> > arm says
> > 
> > fs/ext3/super.c: In function `ext3_fill_super':
> > fs/ext3/super.c:1750: warning: comparison is always false due to limited range of data type
> > 
> > Also, is there any way in which this new code can be, umm, cleaned up?
> 
> Hmm..... is it considered safe to depend on the userspace limits.h
> header file?  I guess if we trust that header file to be correct we
> could check the value of CHAR_MIN and/or CHAR_MAX as defined by
> limits.h.

That would likely fail on cross-compiled environments, right?

> Alternatively we could do an #ifdef __CHAR_UNSIGNED__, which is
> defined by gcc.  The manual for gcc tells us not to depend on it, but
> to depend on limits.h instead.

This warning likely is aimed at userspace for portable applications.

> Any thoughts, or comments?  Does anyone know if the Intel compiler
> will DTRT with either of these approaches?

If it doesn't, then it probably has some equivalent that can be #ifdef'd
in its place.

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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