Re: [PATCH 4/5] net/mlx5: fix build with gcc 7.1

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

On Tue, Jun 13, 2017 at 05:42:11PM +0100, Ferruh Yigit wrote:
> build error:
> .../dpdk/drivers/net/mlx5/mlx5_fdir.c:
>   In function ‘fdir_filter_to_flow_desc’:
> .../dpdk/drivers/net/mlx5/mlx5_fdir.c:146:18:
>  error: this statement may fall through [-Werror=implicit-fallthrough=]
>    desc->dst_port = fdir_filter->input.flow.udp4_flow.dst_port;
>    ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> .../dpdk/drivers/net/mlx5/mlx5_fdir.c:147:2: note: here
>   case RTE_ETH_FLOW_NONFRAG_IPV4_OTHER:
>   ^~~~
> 
> Fixed by adding fallthrough comment to the code.
> 
> Fixes: 76f5c99e6840 ("mlx5: support flow director")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> ---
>  drivers/net/mlx5/mlx5_fdir.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/mlx5/mlx5_fdir.c b/drivers/net/mlx5/mlx5_fdir.c
> index 1cff41bab..c8d47489f 100644
> --- a/drivers/net/mlx5/mlx5_fdir.c
> +++ b/drivers/net/mlx5/mlx5_fdir.c
> @@ -144,6 +144,7 @@ fdir_filter_to_flow_desc(const struct rte_eth_fdir_filter *fdir_filter,
>  	case RTE_ETH_FLOW_NONFRAG_IPV4_TCP:
>  		desc->src_port = fdir_filter->input.flow.udp4_flow.src_port;
>  		desc->dst_port = fdir_filter->input.flow.udp4_flow.dst_port;
> +		/* fallthrough */
>  	case RTE_ETH_FLOW_NONFRAG_IPV4_OTHER:
>  		desc->src_ip[0] = fdir_filter->input.flow.ip4_flow.src_ip;
>  		desc->dst_ip[0] = fdir_filter->input.flow.ip4_flow.dst_ip;

That's a fine workaround, therefore:

Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>

On a personal note though, GCC, seriously? While I understand missing breaks
inside switch statements is a common mistake, having the compiler rely on a
comment that basically says "yes, it's done on purpose" just doesn't feel
right; compilers should discard comments and not attempt to interpret them,
otherwise they have to deal with locale-related issues. It's like enforcing
checkpatch.pl rules in GCC by default. Anyway, back to work.

-- 
Adrien Mazarguil
6WIND