Re: [dpdk-stable] [dpdk-dev] [PATCH V2 1/3] net: avoid cast-align warning in VLAN insert function

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 21 Oct 2021 11:51:30 +0300
Eli Britstein <elibr@nvidia.com> wrote:

> In rte_vlan_insert there is a casting of rte_pktmbuf_prepend returned
> value to (struct rte_ether_hdr *), which causes cast-align warning when
> using strict cast align flag with supporting gcc:
> gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
> CFLAGS="-Wcast-align=strict" make V=1 -C examples/l2fwd clean static
> 
> In file included from main.c:35:
> /dpdk/build/include/rte_ether.h:370:7: warning: cast increases required
> alignment of target type [-Wcast-align]
>   370 |  nh = (struct rte_ether_hdr *)
>       |       ^
> 
> As the code assumes correct alignment, add first a (void *) casting, to
> avoid the warning.
> 
> Fixes: c974021a5949 ("ether: add soft vlan encap/decap")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Eli Britstein <elibr@nvidia.com>
> Acked-by: Olivier Matz <olivier.matz@6wind.com>

After cast to void * the second cast is not necessary.

	nh = (void *)rte_pktmbuf_prepend(...)

Ideally rte_pktmbuf_prepend() should return void * but that is
an API change.