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
Date: Wed, 22 Jan 2014 17:19:58 +0000 (UTC) [thread overview]
Message-ID: <alpine.DEB.2.02.1401221718500.4071@utopia.booyaka.com> (raw)
In-Reply-To: <alpine.DEB.2.02.1312180459580.30198@tamien>
[-- Attachment #1: Type: TEXT/PLAIN, Size: 2512 bytes --]
Hi Peter, hpa, Arnd,
On Wed, 18 Dec 2013, Paul Walmsley wrote:
>
> Enabling '-Wsign-compare' compiler warnings on code that includes
> include/linux/bitops.h can generate the following warning:
>
> In file included from include/linux/kernel.h:10:0,
> from <random filename>:48:
> include/linux/bitops.h: In function ‘hweight_long’:
> include/linux/bitops.h:77:26: error: signed and unsigned type in conditional
> expression [-Werror=sign-compare]
>
> (converted to an error with -Werror)
>
> 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.
>
> Fix by explicitly casting the __const_hweight8 macro expansion to
> 'unsigned int'. While here, clean up several checkpatch.pl warnings.
>
> 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
you're planning to send it upstream for v3.14.
- Paul
>
> include/asm-generic/bitops/const_hweight.h | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> 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) \
> - ( (!!((w) & (1ULL << 0))) + \
> - (!!((w) & (1ULL << 1))) + \
> - (!!((w) & (1ULL << 2))) + \
> - (!!((w) & (1ULL << 3))) + \
> - (!!((w) & (1ULL << 4))) + \
> - (!!((w) & (1ULL << 5))) + \
> - (!!((w) & (1ULL << 6))) + \
> - (!!((w) & (1ULL << 7))) )
> + ((unsigned int) \
> + ((!!((w) & (1ULL << 0))) + \
> + (!!((w) & (1ULL << 1))) + \
> + (!!((w) & (1ULL << 2))) + \
> + (!!((w) & (1ULL << 3))) + \
> + (!!((w) & (1ULL << 4))) + \
> + (!!((w) & (1ULL << 5))) + \
> + (!!((w) & (1ULL << 6))) + \
> + (!!((w) & (1ULL << 7)))))
>
> #define __const_hweight16(w) (__const_hweight8(w) + __const_hweight8((w) >>
> 8 ))
> #define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >>
> 16))
> --
> 1.8.5.1
>
- Paul
next prev parent reply other threads:[~2014-01-22 17:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-18 13:02 [PATCH] bitops: fix signedness of compile-time hweight implementations Paul Walmsley
2013-12-18 13:02 ` Paul Walmsley
2014-01-22 17:19 ` Paul Walmsley [this message]
2014-01-22 17:47 ` Peter Zijlstra
2014-02-10 13:30 ` [tip:core/types] bitops: Fix " tip-bot for Paul Walmsley
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