linux-kernel - Re: + kbuild-disable-wformat-truncation-warnings-by-default.patch added to -mm tree

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Date:   Mon, 21 Aug 2017 10:45:22 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        mm-commits@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        gregkh <gregkh@...uxfoundation.org>
Subject: Re: + kbuild-disable-wformat-truncation-warnings-by-default.patch
 added to -mm tree

Hi Arnd,

2017-08-21 4:51 GMT+09:00 Arnd Bergmann <arnd@...db.de>:
> On Sun, Aug 20, 2017 at 3:19 PM, Masahiro Yamada
> <yamada.masahiro@...ionext.com> wrote:
>> 2017-07-20 16:24 GMT+09:00 Arnd Bergmann <arnd@...db.de>:
>>> - enable all three warnings with "make W=1" in 4.13, but leave them
>>>   disabled by default.
>>> - backport Linus' patch, plus the follow-up for W=1 to stable kernels,
>>>   to allow stable kernels to build cleanly
>>> - backport the patches that address any other gcc-7 warnings, as
>>>   well as those that are not obvious false-positives to stable kernels
>>> - In 4.14+, use my version above and address all int-in-bool-context
>>>   and format-overflow warnings, but only use -Wformat-truncation
>>>   with make W=1.
>>>
>>
>> Talking about 4.14+, shall we move -Wformat-truncation
>> from the top Makefile (always disable) to
>> Makefile.extrawarn (enable with W=1) ?
>
> I dropped the ball on this one, sorry. I think we should do this for
> all three warnings (format-overflow, format-truncation and
> int-in-bool-context) for the time being.
>
> In case of format-truncation, there are countless warnings,
> most of them false-postives, so we simply can't enable them
> by default.
>
> For -Wformat-overflow, there is one patch that I need to
> rewrite, all my other patches are pending for 4.14, see
> https://patchwork.kernel.org/patch/9840801/ for the missing
> one. This should be trivial to fix. However, enabling
> CONFIG_UBSAN_SANITIZE_ALL results in seven additional
> false positives. I created an patch for this in
> https://pastebin.com/CD7nhRNp but can't submit that as it's
> obviously bogus. I reported the gcc bug as
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81592
>
> What we could do there is to disable the warning if
> CONFIG_UBSAN_SANITIZE_ALL is turned on (like
> we do for -Wmaybe-uninitialized in
> CONFIG_UBSAN_SANITIZE_ALL) but leave it on otherwise.
>
> I submitted patches for all -Wint-in-bool-context in arm/arm64/x86
> randconfig builds, but there are still six known warnings for which
> my patches did not get queued for 4.14.
> I have to revisit those all to decide whether we can find an
> acceptable workaround in the kernel and enable the warning again
> by default, or leave it in W=1 until gcc improves enough.
>

I was just wondering how to handle your original patch.
I do not mean to press you.
We can take our time to make the right decision.  Thanks!



-- 
Best Regards
Masahiro Yamada