Re: [PATCH] net/iavf: fix old GCC compilation warnings

[David Marchand <david.marchand@redhat.com>]

On Fri, Jun 9, 2023 at 7:35 AM Zhichao Zeng <zhichaox.zeng@intel.com> wrote:
>
> The code uses the Wimplicit-fallthrough compile option to ignore
> falls through warnings in switch case, but this option was introduced
> by GCC 7 and old GCC do not recognize the option.
>
> Add judgment to avoid warnings about unrecognized options in old GCC.
>
> Fixes: 95a1b0b23140 ("net/iavf: support Rx timestamp offload on SSE")
> Fixes: 4f58266da4d3 ("net/iavf: support Rx timestamp offload on AVX2")
> Fixes: d65eadb9e178 ("net/iavf: support Rx timestamp offload on AVX512")
> Signed-off-by: Zhichao Zeng <zhichaox.zeng@intel.com>

This is ugly.

I don't think we introduced a marker for this in EAL, but at least I
see other drivers use /* fallthrough */.
Prefer this form, please.

IOW:

diff --git a/drivers/net/iavf/iavf_rxtx_vec_sse.c
b/drivers/net/iavf/iavf_rxtx_vec_sse.c
index b754122c51..81ea154519 100644
--- a/drivers/net/iavf/iavf_rxtx_vec_sse.c
+++ b/drivers/net/iavf/iavf_rxtx_vec_sse.c
@@ -1126,24 +1126,26 @@ _recv_raw_pkts_vec_flex_rxd(struct iavf_rx_queue *rxq,
                nb_pkts_recd += var;

 #ifndef RTE_LIBRTE_IAVF_16BYTE_RX_DESC
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wimplicit-fallthrough"
                if (rxq->offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP) {
                        inflection_point = (inflection_point <= var) ?
inflection_point : 0;
                        switch (inflection_point) {
                        case 1:
                                *RTE_MBUF_DYNFIELD(rx_pkts[pos + 0],
                                        iavf_timestamp_dynfield_offset
+ 4, uint32_t *) += 1;
+                               /* fallthrough */
                        case 2:

etc...


-- 
David Marchand