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    SubjectRe: [patch 3.5-rc3] mm, mempolicy: fix mbind() to do synchronous migration
    On Thu, Jun 21, 2012 at 6:45 PM, Andrew Morton
    <akpm@linux-foundation.org> wrote:
    >
    >> I wonder if I should make sparse warn about any casts to/from enums.
    >> They tend to always be wrong.
    >
    > I think it would be worth trying, see how much fallout there is.  Also
    > casts from "enum a" to "enum b".  We've had a few of those,
    > unintentionally.

    Ugh. We have this all over. Well, at least in multiple places.

    Like <linux/personality.h>, which does things like

    PER_LINUX_32BIT = 0x0000 | ADDR_LIMIT_32BIT,

    where PER_LINUX_32BIT is one enum, and ADDR_LIMIT_32BIT is a different one.

    And things like

    WORK_STRUCT_PENDING = 1 << WORK_STRUCT_PENDING_BIT,

    in <linux/workqueue.h> is similar.

    Sure, my quick warning generator gives lots of extraneous warnings,
    and it complains about the above kind of "mixing enum with int"
    behavior, but the above is a very real example of casting an enum to
    an integer. And we *want* it to happen in the above cases.

    I'll see what it looks like if I only warn about casting *to* an enum.

    Linus
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