Re: [PATCH 3/6] hw/net/imx_fec: Rewrite fall through comments

[Thomas Huth]

On 17/12/2019 18.34, Philippe Mathieu-Daudé wrote:
> GCC9 is confused by this comment when building with CFLAG
> -Wimplicit-fallthrough=2:
> 
>   hw/net/imx_fec.c: In function ‘imx_eth_write’:
>   hw/net/imx_fec.c:906:12: error: this statement may fall through 
> [-Werror=implicit-fallthrough=]
>     906 |         if (unlikely(single_tx_ring)) {
>         |            ^
>   hw/net/imx_fec.c:912:5: note: here
>     912 |     case ENET_TDAR:     /* FALLTHROUGH */
>         |     ^~~~
>   cc1: all warnings being treated as errors
> 
> Rewrite the comments in the correct place,  using 'fall through'
> which is recognized by GCC and static analyzers.
> 
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> ---
> Cc: Peter Chubb <address@hidden>
> Cc: Peter Maydell <address@hidden>
> Cc: Jason Wang <address@hidden>
> Cc: address@hidden
> ---
>  hw/net/imx_fec.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/net/imx_fec.c b/hw/net/imx_fec.c
> index bd99236864..30cc07753d 100644
> --- a/hw/net/imx_fec.c
> +++ b/hw/net/imx_fec.c
> @@ -901,15 +901,17 @@ static void imx_eth_write(void *opaque, hwaddr offset, 
> uint64_t value,
>              s->regs[index] = 0;
>          }
>          break;
> -    case ENET_TDAR1:    /* FALLTHROUGH */
> -    case ENET_TDAR2:    /* FALLTHROUGH */
> +        /* fall through */

Wrong location. And I think you don't need any comment here at all, GCC
should stay silent without it?

> +    case ENET_TDAR1:
> +    case ENET_TDAR2:
>          if (unlikely(single_tx_ring)) {
>              qemu_log_mask(LOG_GUEST_ERROR,
>                            "[%s]%s: trying to access TDAR2 or TDAR1\n",
>                            TYPE_IMX_FEC, __func__);
>              return;
>          }
> -    case ENET_TDAR:     /* FALLTHROUGH */
> +        /* fall through */

I'd suggest to simply remove it, too.

> +    case ENET_TDAR:
>          if (s->regs[ENET_ECR] & ENET_ECR_ETHEREN) {
>              s->regs[index] = ENET_TDAR_TDAR;
>              imx_eth_do_tx(s, index);
> 

 Thomas