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    Subject__bitwise versus __bitwise__ [Was: [PATCH] mac80211: check endianness/types in sparse runs]
    Al - can I ask you to explain the difference between __bitwise
    and __bitwise__ as used by the kernel.

    Se below for a bit of background info.

    Thanks,
    Sam

    On Thu, Feb 21, 2008 at 12:01:31PM -0800, Harvey Harrison wrote:
    > On Thu, 2008-02-21 at 13:42 +0100, Johannes Berg wrote:
    > > >> [patch doing CHECKFLAGS += -D__CHECK_ENDIAN__ in the
    > > >> net/mac80211/Makefile]
    > >
    > > > I would prefer it to be kernel wide enabled.
    > > > Tried a defconfig build.
    > >
    > > Hm. I tend to think there was a reason for this, since this is actually
    > > explicitly disabled by include/linux/types.h:
    > >
    > > #ifdef __CHECKER__
    > > #define __bitwise__ __attribute__((bitwise))
    > > #else
    > > #define __bitwise__
    > > #endif
    > >
    > > #ifdef __CHECK_ENDIAN__
    > > #define __bitwise __bitwise__
    > > #else
    > > #define __bitwise
    > > #endif
    > >
    >
    > This seems somewhat suspect.
    >
    > > I recently ran sparse on my config and was surprised by the number of
    > > warnings. Then again, something in mmzone.h or so generated billions of
    > > them...
    >
    > Potentially expensive pointer subtraction 640:....
    >
    > Patch in -mm.
    >
    > >
    > > In any case, I would love to have __CHECK_ENDIAN__ enabled by default at
    > > least on the wireless code (just caught another bug with it...)
    > >
    >
    > I'd love to have it too, but there are so many trivial warnings that
    > clutter up valid warnings that it is prohibitive. I'm working on
    > reducing the noise level a bit for 2.6.26, we'll see about turning
    > it on then.
    >
    > Harvey
    >


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