Re: [Qemu-devel] [PATCH 07/18] block/bochs.c: fix warning with _FORTIFY_SOURCE

[Blue Swirl <blauwirbel@gmail.com>]

On Sun, Dec 20, 2009 at 1:39 AM, Kirill A. Shutemov
<kirill@shutemov.name> wrote:
>  CC    block/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>
> ---
>  block/bochs.c |    3 ++-
>  1 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)
>     // read in bitmap for current extent
>     lseek(s->fd, bitmap_offset + (extent_offset / 8), SEEK_SET);
>
> -    read(s->fd, &bitmap_entry, 1);
> +    if (read(s->fd, &bitmap_entry, 1) != 1)
> +        return -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.