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: [PATCH] bitops: fix signedness of compile-time hweight implementations
Date: Wed, 18 Dec 2013 05:02:14 -0800 [thread overview]
Message-ID: <alpine.DEB.2.02.1312180459580.30198@tamien> (raw)
[-- Attachment #1: Type: text/plain, Size: 2113 bytes --]
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.
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
next reply other threads:[~2013-12-18 13:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-18 13:02 Paul Walmsley [this message]
2014-01-22 17:19 ` [PATCH] bitops: fix signedness of compile-time hweight implementations Paul Walmsley
2014-01-22 17:47 ` Peter Zijlstra
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