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

Andreas Dilger
2008-10-23T19:26:36Z

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.