Re: [PATCH-for-5.2? v3 3/9] hw/usb: reorder fields in UASStatus

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 11/5/20 11:18 PM, Daniele Buono wrote:
> The UASStatus data structure has a variable sized field inside of type uas_iu,
> that however is not placed at the end of the data structure.
> 
> This placement triggers a warning with clang 11, and while not a bug right now,
> (the status is never a uas_iu_command, which is the variable-sized case),
> it could become one in the future.

The problem is uas_iu_command::add_cdb, indeed.

> 
> ../qemu-base/hw/usb/dev-uas.c:157:31: error: field 'status' with variable sized type 'uas_iu' not at the end of a struct or class is a GNU extension [-Werror,-Wgnu-variable-sized-type-not-at-end]

If possible remove the "../qemu-base/" as it does not provide
any useful information.

>     uas_iu                    status;
>                               ^
> 1 error generated.
> 
> Fix this by moving uas_iu at the end of the struct

Your patch silents the warning, but the problem is the same.
It would be safer/cleaner to make 'status' a pointer on the heap IMO.

> 
> Signed-off-by: Daniele Buono <dbuono@linux.vnet.ibm.com>
> ---
>  hw/usb/dev-uas.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/usb/dev-uas.c b/hw/usb/dev-uas.c
> index cec071d96c..5ef3f4fec9 100644
> --- a/hw/usb/dev-uas.c
> +++ b/hw/usb/dev-uas.c
> @@ -154,9 +154,9 @@ struct UASRequest {
>  
>  struct UASStatus {
>      uint32_t                  stream;
> -    uas_iu                    status;
>      uint32_t                  length;
>      QTAILQ_ENTRY(UASStatus)   next;
> +    uas_iu                    status;
>  };
>  
>  /* --------------------------------------------------------------------- */
>