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* 'hweight_long' include/linux/bitops.h compile warning problem.
@ 2011-06-20  7:59 NamJae Jeon
  2011-06-20 13:00 ` Arnd Bergmann
  0 siblings, 1 reply; 4+ messages in thread
From: NamJae Jeon @ 2011-06-20  7:59 UTC (permalink / raw)
  To: arnd, linux-arch

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.

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2011-06-21  6:11 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2011-06-20  7:59 'hweight_long' include/linux/bitops.h compile warning problem NamJae Jeon
2011-06-20 13:00 ` Arnd Bergmann
2011-06-21  6:11   ` NamJae Jeon
2011-06-21  6:11     ` NamJae Jeon

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