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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Mon, 6 Sep 2021 18:12:06 -0700
Message-ID: <CAHk-=wjvfUpPJLbWz6Jezr4ZNjhC6j2WYi5MHUd9bjK94JC24A@mail.gmail.com>
Subject: Re: [PATCH] Enable '-Werror' by default for all kernel builds
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Christian Koenig <christian.koenig@amd.com>,
        Huang Rui <ray.huang@amd.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-sparc <sparclinux@vger.kernel.org>
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On Mon, Sep 6, 2021 at 4:49 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> > but I'm not seeing why that one happens on sparc64, but not on arm64
> > or x86-64. There doesn't seem to be anything architecture-specific
> > anywhere in that area.
> >
> > Funky.
>
> Not really. That is because de->di_fname is always 16 bytes but size
> can be 48 if the node is really a link. The use of de is overloaded
> in that case; de is struct qnx4_inode_entry (where di_fname is 16 bytes)
> but the actual data is struct qnx4_link_info where the name is 48 bytes
> long. A possible fix (compile tested only) is below.
>
> I think the warning/error is only reported with gcc 11.x. Do you possibly
> use an older compiler for x86/arm64 ?

No. Literally the same exact version. All of them are

    gcc version 11.2.1 20210728

from F34.

I suspect it's something about the config - a sparc64 allmodconfig
presumably doesn't end up having some of the things x86-64 has enabled
(because of different core config parameters), and then optimizes
differently as a result and shows the issue that way.

Or something. <wild handwaving>

                Linus