linux-kernel - Re: [RFC PATCH] compiler.h: give up __compiletime_assert

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Message-ID: <CAGXu5j+g97kaCimRd1euRdFNg1aNQFoaVV7V6PBPOA0P51=3xg@mail.gmail.com>
Date:   Tue, 21 Aug 2018 12:04:50 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        James Hogan <james.hogan@...tec.com>,
        Joe Stringer <joe@....org>,
        Daniel Santos <daniel.santos@...ox.com>,
        Rusty Russell <rusty@...tcorp.com.au>,
        Arnd Bergmann <arnd@...db.de>,
        Christopher Li <sparse@...isli.org>,
        Sparse Mailing-list <linux-sparse@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        George Burgess <gbiv@...gle.com>,
        James Y Knight <jyknight@...gle.com>
Subject: Re: [RFC PATCH] compiler.h: give up __compiletime_assert_fallback()

On Tue, Aug 21, 2018 at 9:15 AM, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>> Note that there are a few definitions of BUILD_BUG_ON that still use
>> this negative array size trick.  Should that pattern be removed from
>> them as well?  See:
>> * arch/x86/boot/boot.h#L33
>> * include/linux/build_bug.h#L66
>> * tools/include/linux/kernel.h#L38
>
> At this moment, -Wvla is the warning-3 level
> in scripts/Makefile.extrawarn.

We're down to a handful of VLA uses, but I don't think the negative
cases should matter since they're _intended_ to break a compile.

-Kees

-- 
Kees Cook
Pixel Security