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    SubjectRE: [PATCH] drivers: staging: lustre: lustre: include: add "__attribute__((packed))" for the related union
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    From: Dan Carpenter
    > On Sat, Feb 01, 2014 at 09:57:39PM +0800, Chen Gang wrote:
    > > It seems, our kernel still stick to treate 'pack' region have effect
    > > with both 'align' and 'sizeof'.
    >
    > It's not about packed regions. It's about unions. It's saying the
    > sizeof() a union is a multiple of 4 unless it's packed.
    >
    > union foo {
    > short x;
    > short y;
    > };
    >
    > The author intended the sizeof(union foo) to be 2 but on metag arch then
    > it is 4.

    The same is probably be true of: struct foo { _u16 bar; };

    Architectures that define such alignment rules are a right PITA.
    You either need to get the size to 2 without using 'packed', or
    just not define such structures.
    It is worth seeing if adding aligned(2) will change the size - I'm
    not sure.

    David





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