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

[Thomas Huth <thuth@redhat.com>]

On 17/12/2019 18.55, Thomas Huth wrote:
> 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 <philmd@redhat.com>
>> ---
>> Cc: Peter Chubb <peter.chubb@nicta.com.au>
>> Cc: Peter Maydell <peter.maydell@linaro.org>
>> Cc: Jason Wang <jasowang@redhat.com>
>> Cc: qemu-arm@nongnu.org
>> ---
>>  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.

/me needsmorecoffee

... of course this hunk was fine. Good that you kept it in v2.

 Thomas


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