Re: [Qemu-devel] [PATCH 4/4] ivshmem: check the value returned by fstat()

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 04, 2014 at 04:25:44PM +0800, zhanghailiang wrote:
> The function fstat() may fail, so check its return value.
> 
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> ---
>  hw/misc/ivshmem.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/misc/ivshmem.c b/hw/misc/ivshmem.c
> index 768e528..2667e9f 100644
> --- a/hw/misc/ivshmem.c
> +++ b/hw/misc/ivshmem.c
> @@ -324,7 +324,10 @@ static int check_shm_size(IVShmemState *s, int fd) {
>  
>      struct stat buf;
>  
> -    fstat(fd, &buf);
> +    if (fstat(fd, &buf) < 0) {
> +        fprintf(stderr, "Cannot stat IVSHMEM: %s\n", strerror(errno));
> +        return -1;
> +    }
>

That's a confusing error message:
1. You don't stat ivshmem. You stat a shmem fd. Also best to print fd #.
2. Tell the user what action was taken, e.g. IVSHMEM failed to start.
  
>      if (s->ivshmem_size > buf.st_size) {
>          fprintf(stderr,
> -- 
> 1.7.12.4
>