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    Subject[PATCH AUTOSEL 5.4 43/49] gcc-10: disable 'array-bounds' warning for now
    Date
    From: Linus Torvalds <torvalds@linux-foundation.org>

    [ Upstream commit 44720996e2d79e47d508b0abe99b931a726a3197 ]

    This is another fine warning, related to the 'zero-length-bounds' one,
    but hitting the same historical code in the kernel.

    Because C didn't historically support flexible array members, we have
    code that instead uses a one-sized array, the same way we have cases of
    zero-sized arrays.

    The one-sized arrays come from either not wanting to use the gcc
    zero-sized array extension, or from a slight convenience-feature, where
    particularly for strings, the size of the structure now includes the
    allocation for the final NUL character.

    So with a "char name[1];" at the end of a structure, you can do things
    like

    v = my_malloc(sizeof(struct vendor) + strlen(name));

    and avoid the "+1" for the terminator.

    Yes, the modern way to do that is with a flexible array, and using
    'offsetof()' instead of 'sizeof()', and adding the "+1" by hand. That
    also technically gets the size "more correct" in that it avoids any
    alignment (and thus padding) issues, but this is another long-term
    cleanup thing that will not happen for 5.7.

    So disable the warning for now, even though it's potentially quite
    useful. Having a slew of warnings that then hide more urgent new issues
    is not an improvement.

    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    Makefile | 1 +
    1 file changed, 1 insertion(+)

    diff --git a/Makefile b/Makefile
    index 49c74e8b55df4..8c8ad7e25e15e 100644
    --- a/Makefile
    +++ b/Makefile
    @@ -859,6 +859,7 @@ KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)

    # We'll want to enable this eventually, but it's not going away for 5.7 at least
    KBUILD_CFLAGS += $(call cc-disable-warning, zero-length-bounds)
    +KBUILD_CFLAGS += $(call cc-disable-warning, array-bounds)

    # Enabled with W=2, disabled by default as noisy
    KBUILD_CFLAGS += $(call cc-disable-warning, maybe-uninitialized)
    --
    2.20.1
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