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

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Message-ID: <87zlkhb6wh.fsf@infovore.xs4all.nl>
Date:	Mon, 03 Nov 2008 08:33:34 +0100
From:	Olaf Weber <olaf@...ovore.xs4all.nl>
To:	Theodore Tso <tytso@....edu>
Cc:	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

Theodore Tso writes:
> On Wed, Oct 22, 2008 at 05:22:21PM -0700, Andrew Morton wrote:

>> > +		if (((int) c) == -1) {
>> 
>> 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.

> 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.

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

Why not write the test like this?

	if ((char)-1 > 0) {
		/* char is unsigned */
	} else {
		/* char is signed */
	}

-- 
Olaf Weber
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