Re: [PATCH] fsnotify: avoid gcc-10 zero-length-bounds warning

From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Arnd Bergmann <arnd@arndb.de>, Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
	Jan Kara <jack@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Amir Goldstein <amir73il@gmail.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] fsnotify: avoid gcc-10 zero-length-bounds warning
Date: Tue, 5 May 2020 09:39:36 -0500	[thread overview]
Message-ID: <b287bb2f-28e2-7a41-e015-aa5a0cb3b5d7@embeddedor.com> (raw)
In-Reply-To: <20200505143028.1290686-1-arnd@arndb.de>

On 5/5/20 09:30, Arnd Bergmann wrote:
> gcc-10 warns about accesses into the f_handle[] zero-length array.
> 
> fs/notify/fdinfo.c: In function 'show_mark_fhandle':
> fs/notify/fdinfo.c:66:47: error: array subscript 'i' is outside the bounds of an interior zero-length array 'unsigned char[0]' [-Werror=zero-length-bounds]
>    66 |   seq_printf(m, "%02x", (int)f.handle.f_handle[i]);
>       |                              ~~~~~~~~~~~~~~~~~^~~
> In file included from fs/notify/fdinfo.c:3:
> include/linux/fs.h:988:16: note: while referencing 'f_handle'
>   988 |  unsigned char f_handle[0];
>       |                ^~~~~~~~
> 
> This is solved by using a flexible array instead.
> 
> Cc: Gustavo A. R. Silva <gustavo@embeddedor.com>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> Gustavo has done the same thing as part of a treewide change, but keeping
> this separate lets us backport it to stable kernels more easily later.

Arnd,

I wonder why would we need to backport these changes to -stable... merely
because of the use of a new version of GCC?

Thanks
--
Gustavo