Re: [PATCH] pdump: fix build issue with GCC 12

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

On Mon, Mar 27, 2023 at 07:07:12AM +0000, Joyce Kong wrote:
> The following warning is observed with GCC12 compilation
> with release 20.11:
> 
> In function ‘__rte_ring_enqueue_elems_64’,
>     inlined from ‘__rte_ring_enqueue_elems’ at
>             ../lib/librte_ring/rte_ring_elem.h:225:3,
>     inlined from ‘__rte_ring_do_enqueue_elem’ at
>             ../lib/librte_ring/rte_ring_elem.h:424:2,
>     inlined from ‘rte_ring_mp_enqueue_burst_elem’ at
>             ../lib/librte_ring/rte_ring_elem.h:884:9,
>     inlined from ‘rte_ring_enqueue_burst_elem’ at
>             ../lib/librte_ring/rte_ring_elem.h:946:10,
>     inlined from ‘rte_ring_enqueue_burst’ at
>             ../lib/librte_ring/rte_ring.h:721:9,
>     inlined from ‘pdump_copy’ at
>             ../lib/librte_pdump/rte_pdump.c:94:13:
> ../lib/librte_ring/rte_ring_elem.h:162:40: warning: ‘*dup_bufs.36_42
> + _89’ may be used uninitialized [-Wmaybe-uninitialized]
>   162 |                         ring[idx] = obj[i];
>       |                                     ~~~^~~
> ../lib/librte_ring/rte_ring_elem.h:163:44: warning: ‘*dup_bufs.36_42
> + _98’ may be used uninitialized [-Wmaybe-uninitialized]
>   163 |                         ring[idx + 1] = obj[i + 1];
>       |                                         ~~~^~~~~~~
> ../lib/librte_ring/rte_ring_elem.h:164:44: warning: ‘*dup_bufs.36_42
> + _107’ may be used uninitialized [-Wmaybe-uninitialized]
>   164 |                         ring[idx + 2] = obj[i + 2];
>       |                                         ~~~^~~~~~~
> ../lib/librte_ring/rte_ring_elem.h:165:44: warning: ‘*dup_bufs.36_42
> + _116’ may be used uninitialized [-Wmaybe-uninitialized]
>   165 |                         ring[idx + 3] = obj[i + 3];
>       |                                         ~~~^~~~~~~
> ../lib/librte_ring/rte_ring_elem.h:169:42: warning: ‘*dup_bufs.36_42
> + _129’ may be used uninitialized [-Wmaybe-uninitialized]
>   169 |                         ring[idx++] = obj[i++]; /* fallthrough */
>       |                                       ~~~^~~~~
> ../lib/librte_ring/rte_ring_elem.h:171:42: warning: ‘*dup_bufs.36_42
> + _139’ may be used uninitialized [-Wmaybe-uninitialized]
>   171 |                         ring[idx++] = obj[i++]; /* fallthrough */
>       |                                       ~~~^~~~~
> ../lib/librte_ring/rte_ring_elem.h:173:42: warning: ‘*dup_bufs.36_42
> + _149’ may be used uninitialized [-Wmaybe-uninitialized]
>   173 |                         ring[idx++] = obj[i++];
> 
> Actually, this is an alias warning as -O3 enables strict alias.
> This patch fixes it by replacing 'dup_bufs' with '&dup_bufs[0]'
> as the compiler represents them differently.
> 
> Fixes: 278f945402c5 ("pdump: add new library for packet capture")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Joyce Kong <joyce.kong@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---

Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>

>  lib/pdump/rte_pdump.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/pdump/rte_pdump.c b/lib/pdump/rte_pdump.c
> index 9bc4bab4f2..53cca1034d 100644
> --- a/lib/pdump/rte_pdump.c
> +++ b/lib/pdump/rte_pdump.c
> @@ -134,7 +134,7 @@ pdump_copy(uint16_t port_id, uint16_t queue,
>  
>  	__atomic_fetch_add(&stats->accepted, d_pkts, __ATOMIC_RELAXED);
>  
> -	ring_enq = rte_ring_enqueue_burst(ring, (void *)dup_bufs, d_pkts, NULL);
> +	ring_enq = rte_ring_enqueue_burst(ring, (void *)&dup_bufs[0], d_pkts, NULL);

nit: i would drop the cast to void *, it shouldn't be needed?