From: Linus Torvalds <torvalds@linux-foundation.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: kernel test robot <lkp@intel.com>,
Xiaomeng Tong <xiam0nd.tong@gmail.com>,
kbuild-all@lists.01.org, Jakob Koschel <jakobkoschel@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>,
Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>, Netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH 1/6] Kbuild: compile kernel with gnu11 std
Date: Tue, 1 Mar 2022 13:15:06 -0800 [thread overview]
Message-ID: <CAHk-=wiuZGzc2UaNVPr6rZnK7buvaQWfadZMcDXavE=MeCXw3g@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wiFbzpyt1-9ZAigFYU7R8g9mEgJho3w7yGYe0h-W==nsw@mail.gmail.com>
On Tue, Mar 1, 2022 at 1:04 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Yeah, looks like that "<< 16" is likely just wrong.
.. and perhaps more importantly, I guess that means that -Wshift-overflow is
(a) somehow new to -std=gnu11
(b) possibly a lot more relevant and good than that
-Wshift-negative-value thing was
doing some grepping, it seems like we have never had that
'-Wshift-overflow' even in any extra warnings.
And trying it myself (keeping -std=gnu89), enabling it doesn't report
anything on a x86-64 allmodconfig build.
So I think this is likely a good new warning that -std=gnu11 brought
in by accident. No false positives that I can see, and one report for
a MIPS bug that looks real (but admittedly not a "sky-is-falling" one
;)
There's apparently a '-Wshift-overflow=2' mode too, but that warns
about things that change the sign bit, ie expressions like
1<<31
warns.
And I would not be in the least surprised if we had a ton of those
kinds of things all over (but I didn't check).
So the plain -Wshift-overflow seems to work just fine, and while it's
surprising that it got enabled by gnu11, I think it's all good.
Famous last words.
Linus
next prev parent reply other threads:[~2022-03-01 21:15 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-01 7:58 [PATCH 0/6] list_for_each_entry*: make iterator invisiable outside the loop Xiaomeng Tong
2022-03-01 7:58 ` [PATCH 1/6] Kbuild: compile kernel with gnu11 std Xiaomeng Tong
2022-03-01 17:59 ` kernel test robot
2022-03-01 20:16 ` Linus Torvalds
2022-03-01 20:54 ` Arnd Bergmann
2022-03-01 21:04 ` Linus Torvalds
2022-03-01 21:15 ` Linus Torvalds [this message]
2022-03-01 21:43 ` Xiaomeng Tong
2022-03-01 7:58 ` [PATCH 2/6] list: add new MACROs to make iterator invisiable outside the loop Xiaomeng Tong
2022-03-02 2:52 ` kernel test robot
2022-03-02 13:02 ` James Bottomley
2022-03-03 3:31 ` Xiaomeng Tong
2022-03-06 14:33 ` James Bottomley
2022-03-03 20:02 ` Linus Torvalds
2022-03-04 2:51 ` Xiaomeng Tong
2022-03-05 21:09 ` Linus Torvalds
2022-03-06 0:35 ` Linus Torvalds
2022-03-06 12:19 ` Jakob Koschel
2022-03-06 18:57 ` Linus Torvalds
2022-03-06 14:06 ` Xiaomeng Tong
2022-03-10 23:54 ` [PATCH 2/6] list: add new MACROs to make iterator invisiable Michał Mirosław
2022-03-11 0:46 ` Linus Torvalds
2022-03-12 10:24 ` Michał Mirosław
2022-03-12 21:43 ` Linus Torvalds
2022-03-11 7:15 ` [RFC PATCH] list: test: Add a test for list_traverse David Gow
2022-03-11 14:27 ` [PATCH 2/6] list: add new MACROs to make iterator invisiable outside the loop Daniel Thompson
2022-03-11 18:41 ` Linus Torvalds
2022-03-16 15:45 ` Daniel Thompson
2022-03-01 7:58 ` [PATCH 3/6] kernel: remove iterator use " Xiaomeng Tong
2022-03-01 10:41 ` Greg KH
2022-03-01 11:34 ` Xiaomeng Tong
2022-03-01 11:48 ` Xiaomeng Tong
2022-03-01 7:58 ` [PATCH 4/6] mm: " Xiaomeng Tong
2022-03-01 12:19 ` Xiaomeng Tong
2022-03-01 7:58 ` [PATCH 5/6] net/core: " Xiaomeng Tong
2022-03-01 12:23 ` Xiaomeng Tong
2022-03-01 7:58 ` [PATCH 6/6] drivers/dma: " Xiaomeng Tong
2022-03-01 12:25 ` Xiaomeng Tong
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