linux-kernel - Re: [PATCH] xfs: avoid harmless gcc-7 warnings

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Date:   Thu, 11 May 2017 07:02:23 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "Darrick J. Wong" <darrick.wong@...cle.com>,
        linux-xfs@...r.kernel.org, Dave Chinner <dchinner@...hat.com>,
        Brian Foster <bfoster@...hat.com>,
        Eric Sandeen <sandeen@...hat.com>,
        Calvin Owens <calvinowens@...com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xfs: avoid harmless gcc-7 warnings

On Thu, May 11, 2017 at 02:49:21PM +0200, Arnd Bergmann wrote:
> gcc-7 flags the use of integer math inside of a condition
> as a potential bug:
> 
> fs/xfs/xfs_bmap_util.c: In function 'xfs_swap_extents_check_format':
> fs/xfs/xfs_bmap_util.c:1619:8: error: '<<' in boolean context, did you mean '<' ? [-Werror=int-in-bool-context]
> fs/xfs/xfs_bmap_util.c:1629:8: error: '<<' in boolean context, did you mean '<' ? [-Werror=int-in-bool-context]
> 
> This one is clearly fine, and we can add a comparison to zero
> to shut up the warning.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  fs/xfs/xfs_bmap_util.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 2b954308a1d6..cbd3ffe42f39 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -1613,7 +1613,7 @@ xfs_swap_extents_check_format(
>  	 * extent format...
>  	 */
>  	if (tip->i_d.di_format == XFS_DINODE_FMT_BTREE) {
> -		if (XFS_IFORK_BOFF(ip) &&
> +		if ((XFS_IFORK_BOFF(ip) != 0) &&

Even if we were fine with fixing this odd warning the additional braces
are simply bogus.