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    SubjectRe: [PATCH 00/16] mm: prepare for converting vm->vm_flags to 64-bit
    Konstantin Khlebnikov wrote:
    > Andrew Morton wrote:
    >> On Thu, 22 Mar 2012 21:28:11 +0000
    >> Al Viro<viro@ZenIV.linux.org.uk> wrote:
    >>
    >>> On Thu, Mar 22, 2012 at 02:26:47PM -0700, Andrew Morton wrote:
    >>>> It would be nice to find some way of triggering compiler warnings or
    >>>> sparse warnings if someone mixes a 32-bit type with a vm_flags_t. Any
    >>>> thoughts on this?
    >>>>
    >>>> (Maybe that's what __nocast does, but Documentation/sparse.txt doesn't
    >>>> describe it)
    >>>
    >>> Use __bitwise for that - check how gfp_t is handled.
    >>
    >> So what does __nocast do?
    >
    > Actually it forbid any non-forced casts, but its implementation in sparse seems buggy:
    > __nocast generates some strange false positives. For example it sometimes forgot about
    > type attributes in function arguments, I saw this for vm_flags argument in ksm_madvise().
    > I can reproduce this bug, if somebody interested.
    >

    1.c:

    # define __nocast __attribute__((nocast))

    typedef long __nocast long_t;

    static void f(long_t *x)
    {
    }

    static void g(void)
    {
    long_t x;

    f(&x);
    }

    $ sparse 1.c
    1.c:13:12: warning: incorrect type in argument 1 (different modifiers)
    1.c:13:12: expected int [nocast] [usertype] *x
    1.c:13:12: got int *<noident>
    1.c:13:12: warning: implicit cast to nocast type

    Is this ok?



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