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Date: Mon, 16 May 2022 15:31:03 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Arnd Bergmann <arnd@kernel.org>, linux-kbuild@vger.kernel.org,
	Arnd Bergmann <arnd@arndb.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Masahiro Yamada <masahiroy@kernel.org>, llvm@lists.linux.dev,
	Jonathan Corbet <corbet@lwn.net>,
	Federico Vaga <federico.vaga@vaga.pv.it>,
	Alex Shi <alexs@kernel.org>, Hu Haowen <src.res@email.cn>,
	Michal Marek <michal.lkml@markovi.net>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-doc-tw-discuss@lists.sourceforge.net,
	linux-arm-kernel@lists.infradead.org,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	greybus-dev@lists.linaro.org, linux-staging@lists.linux.dev,
	linux-btrfs@vger.kernel.org
Subject: Re: [greybus-dev] Re: [PATCH] [v2] Kbuild: move to -std=gnu11
Message-ID: <YoJSF8T5K9pPx3Ap@kroah.com>
References: <20220228103142.3301082-1-arnd@kernel.org>
 <20220516131023.GA2329080@roeck-us.net>
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In-Reply-To: <20220516131023.GA2329080@roeck-us.net>

On Mon, May 16, 2022 at 06:10:23AM -0700, Guenter Roeck wrote:
> On Mon, Feb 28, 2022 at 11:27:43AM +0100, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> > 
> > During a patch discussion, Linus brought up the option of changing
> > the C standard version from gnu89 to gnu99, which allows using variable
> > declaration inside of a for() loop. While the C99, C11 and later standards
> > introduce many other features, most of these are already available in
> > gnu89 as GNU extensions as well.
> 
> The downside is that backporting affected patches to older kernel branches
> now fails with error messages such as
> 
> mm/kfence/core.c: In function ‘kfence_init_pool’:
> mm/kfence/core.c:595:2: error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
> 
> Just something to keep in mind when writing patches.

I just ran across this very issue on this commit.  It's an easy fixup
for 5.17.y to make this work, so I did that in my tree.  If this gets to
be too much, we might need to reconsider adding c11 to older stable
kernels.

thanks,

greg k-h