linux-kernel - Re: [PATCH 4/5] rt2x00: Compiler warning unmasked by fix of BUILD_BUG

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Message-ID: <a32f33a40809010627m1a030307y84d54182203c6efd@mail.gmail.com>
Date:	Mon, 1 Sep 2008 15:27:01 +0200
From:	"Ivo Van Doorn" <ivdoorn@...il.com>
To:	"Boaz Harrosh" <bharrosh@...asas.com>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Rusty Russell" <rusty@...tcorp.com.au>,
	"David S. Miller" <davem@...emloft.net>,
	"John W. Linville" <linville@...driver.com>,
	"Alexey Dobriyan" <adobriyan@...il.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Theodore Tso" <tytso@....edu>,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Jan Beulich" <jbeulich@...ell.com>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] rt2x00: Compiler warning unmasked by fix of BUILD_BUG_ON

On Mon, Sep 1, 2008 at 3:21 PM, Boaz Harrosh <bharrosh@...asas.com> wrote:
>
> A "Set" of the sign-bit in an "&" operation causes a compiler warning.
> Make calculations unsigned.
>
> [ The warning was masked by the use of (void)() cast in the old
>  BUILD_BUG_ON() ]
>
> Signed-off-by: Boaz Harrosh <bharrosh@...asas.com>
> TO: Ivo van Doorn <IvDoorn@...il.com>
> TO: John W. Linville <linville@...driver.com>
> CC: Ingo Molnar <mingo@...e.hu>
> CC: Rusty Russell <rusty@...tcorp.com.au>
> ---
>  drivers/net/wireless/rt2x00/rt2x00reg.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/wireless/rt2x00/rt2x00reg.h b/drivers/net/wireless/rt2x00/rt2x00reg.h
> index 7e88ce5..c0e8706 100644
> --- a/drivers/net/wireless/rt2x00/rt2x00reg.h
> +++ b/drivers/net/wireless/rt2x00/rt2x00reg.h
> @@ -134,8 +134,8 @@ struct rt2x00_field32 {
>  * Note that we cannot use the is_power_of_2() function since this
>  * check must be done at compile-time.
>  */
> -#define is_power_of_two(x)     ( !((x) & ((x)-1)) )
> -#define low_bit_mask(x)                ( ((x)-1) & ~(x) )
> +#define is_power_of_two(x)     ( !((unsigned)(x) & ((x)-1)) )
> +#define low_bit_mask(x)                ( ((unsigned)(x)-1) & ~(x) )
>  #define is_valid_mask(x)       is_power_of_two(1 + (x) + low_bit_mask(x))

Could the patch not become a lot easier (and perhaps cleaner) when the
only change is:
#define is_valid_mask(x)       is_power_of_two(1 + (x) +
low_bit_mask((unsigned)x))
that way all instances of x will be cast to unsigned...

Ivo
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