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From: NamJae Jeon <linkinjeon@gmail.com>
To: linux-kernel@vger.kernel.org, arnd@arndb.de, linux-arch@vger.kernel.org
Subject: WARNING:'hweight_long' include/linux/bitops.h compile warning problem.
Date: Mon, 20 Jun 2011 17:08:21 +0900	[thread overview]
Message-ID: <BANLkTimuqNey8jUHkLS-MkmBWf8Tcu9=Cg@mail.gmail.com> (raw)

Hello. Arnd

I found compile warning while compiling module when using -Wsign-compare option.

include/linux/bitops.h: In function 'hweight_long':
include/linux/bitops.h:49: warning: signed and unsigned type in
conditional expression

I found the reason of this problem that the default return value of
the below macro is signed.

#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))) )

So, I try to add (unsigned long) in __const_hweight8 like this.

#define __const_hweight8(w)     (unsigned long )        \
     ( (!!((w) & (1ULL << 0))) +       \
       (!!((w) & (1ULL << 1))) +       \
       (!!((w) & (1ULL << 2))) +       \
       (!!((w) & (1ULL << 3))) +       \
       (!!((w) & (1ULL << 4))) +       \
       (!!((w) & (1ULL << 5))) +       \
       (!!((w) & (1ULL << 6))) +       \
       (!!((w) & (1ULL << 7))) )

so, I can't see compile warning after fixing it, Would you plz check this ?

Thanks.

                 reply	other threads:[~2011-06-20  8:08 UTC|newest]

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