linux-kernel - Re: [PATCH] [RFC v2] qnx: avoid -Wstringop-overread warning, again

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Message-ID: <CAHk-=wi=CZ_fsUwDQCBbgPB4MTFx1ywgyERjFb7DNUk9Pix_Nw@mail.gmail.com>
Date:   Mon, 20 Sep 2021 10:26:21 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Anders Larsen <al@...rsen.net>, Arnd Bergmann <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RFC v2] qnx: avoid -Wstringop-overread warning, again

On Mon, Sep 20, 2021 at 5:12 AM Arnd Bergmann <arnd@...nel.org> wrote:
>
> +               /*
> +                * work around gcc-11.x using the first field it observes
> +                * to determing the actual length
> +                * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578
> +                */
> +               char __empty[0];
> +               char de_name[];

Ugh. That looks _really_ hacky.

It sounds like we can avoid the gcc bug if we just always use
"de->de_name[]". Then we don't need to depend on magical behavior
about one particular gcc version and a strange empty array in front of
it.

IOW, something like the attached simpler thing that just does that
"always use de_name[]" and has a comment about why we don't do the
natural thing

Also, just what version of gcc is the broken one? You say "gcc-11",
but I certainly don't see it with _my_ version of gcc-11, so can we
(just for that comment) document more precisely what version you have
(or possibly what config you use to trigger it).

                Linus

View attachment "patch.diff" of type "text/x-patch" (2210 bytes)