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Sender: Guenter Roeck <groeck7@gmail.com>
Date:   Mon, 16 May 2022 06:10:23 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Arnd Bergmann <arnd@kernel.org>
Cc:     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,
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        Federico Vaga <federico.vaga@vaga.pv.it>,
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Subject: Re: [PATCH] [v2] Kbuild: move to -std=gnu11
Message-ID: <20220516131023.GA2329080@roeck-us.net>
References: <20220228103142.3301082-1-arnd@kernel.org>
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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.

Guenter