linux-kernel - Re: [PATCH] Enable '-Werror' by default for all kernel builds

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Date:   Mon, 6 Sep 2021 19:29:17 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-sparc <sparclinux@...r.kernel.org>,
        Arnd Bergmann <arnd@...nel.org>
Subject: Re: [PATCH] Enable '-Werror' by default for all kernel builds

On 9/6/21 6:12 PM, Linus Torvalds wrote:
> On Mon, Sep 6, 2021 at 4:49 PM Guenter Roeck <linux@...ck-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>
> 

Looks like Arnd stumbled into the qnx4 problem before:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578

He might have an idea how to fix it for good.

Guenter