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    SubjectRe: SLUB: Return ZERO_SIZE_PTR for kmalloc(0)


    On Mon, 4 Jun 2007, Pekka Enberg wrote:
    >
    > Ok, makes sense. I guess I might as well throw my suggestion in the
    > mix. Lets create a new kmalloc cache for zero-length objects where
    > object size is zero but there are regular red-zones on both sides.

    Well, the red-zones won't catch readers, and more importantly, even for
    writers they are *really* inconvenient, because it will just tell you
    something bad happened, it won't tell you *where* it happened.

    Since comparing the addresses of two zero-sized allocations is insane and
    not done _anyway_, it's just much better to return an invalid address.

    The thing is, why *should* we care about comparing addresses? We'll give
    the right result (you got many perfectly separate allocations, they're
    just zero bytes apart, exactly like you asked for!). The fact that C++ has
    some semantics for it is not a good argument - C++ is a broken language,
    and it's not the language we use for the kernel anyway.

    Linus
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