linux-kernel - Re: [PATCH] xfs: Silence bounds checking compiler warning

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Message-ID: <4E035CDE.5090304@gmail.com>
Date:	Thu, 23 Jun 2011 17:33:50 +0200
From:	Maarten Lankhorst <m.b.lankhorst@...il.com>
To:	Alex Elder <aelder@....com>
CC:	xfs-masters@....sgi.com, xfs@....sgi.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] xfs: Silence bounds checking compiler warning

On 06/23/2011 05:08 PM, Maarten Lankhorst wrote:
> gcc with -Warray-bounds generates a false positive on this
> since xfs defines the struct with u8 name[1]; to be able to
> add a tag at the end.
>
> Signed-off-by: Maarten Lankhorst <m.b.lankhorst@...il.com>
> ---
>  fs/xfs/xfs_dir2_block.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/xfs/xfs_dir2_block.c b/fs/xfs/xfs_dir2_block.c
> index 580d99c..09b4aed 100644
> --- a/fs/xfs/xfs_dir2_block.c
> +++ b/fs/xfs/xfs_dir2_block.c
> @@ -1148,7 +1148,7 @@ xfs_dir2_sf_to_block(
>  		((char *)block + XFS_DIR2_DATA_DOTDOT_OFFSET);
>  	dep->inumber = cpu_to_be64(xfs_dir2_sf_get_inumber(sfp, &sfp->hdr.parent));
>  	dep->namelen = 2;
> -	dep->name[0] = dep->name[1] = '.';
> +	dep->name[0] = ((__u8 *)dep->name)[1] = '.';
>  	tagp = xfs_dir2_data_entry_tag_p(dep);
>  	*tagp = cpu_to_be16((char *)dep - (char *)block);
>  	xfs_dir2_data_log_entry(tp, bp, dep);
Oops, that still gives a warning, I used (u8*) first which works, but it seems the type
conversion was what made it shut up. Is there any type I can cast __u8 to safely,
or is memset preferred? gcc was too smart and saw through my __u8 cast.

~Maarten
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