Re: [Qemu-devel] [PATCH] vhost-user-bridge: fix iov_restore_front() warning

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Marc-André Lureau (marcandre.lureau@redhat.com) wrote:
>   CC      tests/vhost-user-bridge.o
> /home/dgilbert/git/qemu-world3/tests/vhost-user-bridge.c:228:23: warning: variables 'front' and 'iov' used in loop condition not modified in loop body [-Wfor-loop-analysis]
>     for (cur = front; front != iov; cur++) {
>                       ^~~~~    ~~~
> 1 warning generated.
> 
> Fix the loop, document the function, and fix some related assert().
> 
> In practice, the loop bug was harmless because the front sg buffer is
> enough to discard/restore the header size.
> 
> Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

> ---
>  tests/vhost-user-bridge.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
> index 8618c20d53..1e5b5ca3da 100644
> --- a/tests/vhost-user-bridge.c
> +++ b/tests/vhost-user-bridge.c
> @@ -220,12 +220,18 @@ vubr_handle_tx(VuDev *dev, int qidx)
>      free(elem);
>  }
>  
> +
> +/* this function reverse the effect of iov_discard_front() it must be
> + * called with 'front' being the original struct iovec and 'bytes'
> + * being the number of bytes you shaved off
> + */
>  static void
>  iov_restore_front(struct iovec *front, struct iovec *iov, size_t bytes)
>  {
>      struct iovec *cur;
>  
> -    for (cur = front; front != iov; cur++) {
> +    for (cur = front; cur != iov; cur++) {
> +        assert(bytes >= cur->iov_len);
>          bytes -= cur->iov_len;
>      }
>  
> @@ -302,7 +308,8 @@ vubr_backend_recv_cb(int sock, void *ctx)
>              }
>              iov_from_buf(sg, elem->in_num, 0, &hdr, sizeof hdr);
>              total += hdrlen;
> -            assert(iov_discard_front(&sg, &num, hdrlen) == hdrlen);
> +            ret = iov_discard_front(&sg, &num, hdrlen);
> +            assert(ret == hdrlen);
>          }
>  
>          struct msghdr msg = {
> -- 
> 2.13.0.91.g00982b8dd
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK