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Date: Wed, 22 Jan 2014 17:19:58 +0000 (UTC)
From: Paul Walmsley <pwalmsley@nvidia.com>
To: "H. Peter Anvin" <hpa@zytor.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Arnd Bergmann <arnd@arndb.de>
cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] bitops: fix signedness of compile-time hweight
 implementations
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Hi Peter, hpa, Arnd,

On Wed, 18 Dec 2013, Paul Walmsley wrote:

>=20
> Enabling '-Wsign-compare' compiler warnings on code that includes
> include/linux/bitops.h can generate the following warning:
>=20
> In file included from include/linux/kernel.h:10:0,
>                  from <random filename>:48:
> include/linux/bitops.h: In function =A1hweight_long=A2:
> include/linux/bitops.h:77:26: error: signed and unsigned type in conditio=
nal
> expression [-Werror=3Dsign-compare]
>=20
> (converted to an error with -Werror)
>=20
> This is due to the use of the logical negation operator '!' in the
> __const_hweight8 macro in include/asm-generic/bitops/const_hweight.h.
> The use of that operator here results in a signed value.
>=20
> Fix by explicitly casting the __const_hweight8 macro expansion to
> 'unsigned int'.  While here, clean up several checkpatch.pl warnings.
>=20
> Signed-off-by: Paul Walmsley <pwalmsley@nvidia.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Arnd Bergmann <arnd@arndb.de>
> ---
> Intended for v3.14.

Ping.  Just checking to see if you have any comments on this one, or if=20
you're planning to send it upstream for v3.14.


- Paul

>=20
>  include/asm-generic/bitops/const_hweight.h | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>=20
> diff --git a/include/asm-generic/bitops/const_hweight.h
> b/include/asm-generic/bitops/const_hweight.h
> index fa2a50b7ee66..40966203804d 100644
> --- a/include/asm-generic/bitops/const_hweight.h
> +++ b/include/asm-generic/bitops/const_hweight.h
> @@ -5,14 +5,15 @@
>   * Compile time versions of __arch_hweightN()
>   */
>  #define __const_hweight8(w)=09=09\
> -      (=09(!!((w) & (1ULL << 0))) +=09\
> -=09(!!((w) & (1ULL << 1))) +=09\
> -=09(!!((w) & (1ULL << 2))) +=09\
> -=09(!!((w) & (1ULL << 3))) +=09\
> -=09(!!((w) & (1ULL << 4))) +=09\
> -=09(!!((w) & (1ULL << 5))) +=09\
> -=09(!!((w) & (1ULL << 6))) +=09\
> -=09(!!((w) & (1ULL << 7)))=09)
> +=09((unsigned int)=09=09\
> +=09 ((!!((w) & (1ULL << 0))) +=09\
> +=09  (!!((w) & (1ULL << 1))) +=09\
> +=09  (!!((w) & (1ULL << 2))) +=09\
> +=09  (!!((w) & (1ULL << 3))) +=09\
> +=09  (!!((w) & (1ULL << 4))) +=09\
> +=09  (!!((w) & (1ULL << 5))) +=09\
> +=09  (!!((w) & (1ULL << 6))) +=09\
> +=09  (!!((w) & (1ULL << 7)))))
>=20
>  #define __const_hweight16(w) (__const_hweight8(w)  + __const_hweight8((w=
)  >>
> 8 ))
>  #define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((=
w) >>
> 16))
> --=20
> 1.8.5.1
>=20


- Paul
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