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From: Blue Swirl <blauwirbel@gmail.com>
Date: Tue, 22 Dec 2009 21:02:05 +0000
Message-ID: <f43fc5580912221302w1416b442q50882dc369fcb6cf@mail.gmail.com>
Subject: Re: [Qemu-devel] [PATCH 07/18] block/bochs.c: fix warning with
	_FORTIFY_SOURCE
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To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: qemu-devel@nongnu.org

On Sun, Dec 20, 2009 at 1:39 AM, Kirill A. Shutemov
<kirill@shutemov.name> wrote:
> =C2=A0CC =C2=A0 =C2=A0block/bochs.o
> cc1: warnings being treated as errors
> block/bochs.c: In function 'seek_to_sector':
> block/bochs.c:202: error: ignoring return value of 'read', declared with =
attribute warn_unused_result
> make: *** [block/bochs.o] Error 1
>
> Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
> ---
> =C2=A0block/bochs.c | =C2=A0 =C2=A03 ++-
> =C2=A01 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/block/bochs.c b/block/bochs.c
> index bac81c4..f6a18f2 100644
> --- a/block/bochs.c
> +++ b/block/bochs.c
> @@ -199,7 +199,8 @@ static inline int seek_to_sector(BlockDriverState *bs=
, int64_t sector_num)
> =C2=A0 =C2=A0 // read in bitmap for current extent
> =C2=A0 =C2=A0 lseek(s->fd, bitmap_offset + (extent_offset / 8), SEEK_SET)=
;
>
> - =C2=A0 =C2=A0read(s->fd, &bitmap_entry, 1);
> + =C2=A0 =C2=A0if (read(s->fd, &bitmap_entry, 1) !=3D 1)
> + =C2=A0 =C2=A0 =C2=A0 =C2=A0return -1;

I think a short read can't happen with 1 bytes, so this looks fine.

Though error checking is incomplete unless it is extended to lseek() calls =
too.