[dpdk-dev] [PATCH] hash: fix gcc 10 maybe-uninitialized warning

[Wang, Yipeng1]

> -----Original Message-----
> From: Kevin Traynor <ktraynor at redhat.com>
> Sent: Friday, May 15, 2020 7:28 AM
> To: dev at dpdk.org; Wang, Yipeng1 <yipeng1.wang at intel.com>; Gobriel,
> Sameh <sameh.gobriel at intel.com>; Richardson, Bruce
> <bruce.richardson at intel.com>
> Cc: honnappa.nagarahalli at arm.com; Yigit, Ferruh <ferruh.yigit at intel.com>;
> david.marchand at redhat.com; Kevin Traynor <ktraynor at redhat.com>;
> stable at dpdk.org
> Subject: [PATCH] hash: fix gcc 10 maybe-uninitialized warning
> 
> gcc 10.1.1 reports a warning for the ext_bkt_id variable:
> 
> ../lib/librte_hash/rte_cuckoo_hash.c:
> In function ‘__rte_hash_add_key_with_hash’:
> ../lib/librte_hash/rte_cuckoo_hash.c:1104:29:
> warning: ‘ext_bkt_id’ may be used uninitialized in this function [-Wmaybe-
> uninitialized]
>  1104 |  (h->buckets_ext[ext_bkt_id - 1]).sig_current[0] = short_sig;
>       |                  ~~~~~~~~~~~^~~
> 
> The return value of rte_ring_sc_dequeue_elem() is already checked, but
> also initialize ext_bkt_id to zero (invalid value) and check that it also
> overwritten.
> 
> Fixes: fbfe568103b0 ("hash: use 32-bit elements rings to save memory")
> Cc: stable at dpdk.org
> 
> Signed-off-by: Kevin Traynor <ktraynor at redhat.com>
> ---
>  lib/librte_hash/rte_cuckoo_hash.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_hash/rte_cuckoo_hash.c
> b/lib/librte_hash/rte_cuckoo_hash.c
> index 38767a8a1..90cb99b0e 100644
> --- a/lib/librte_hash/rte_cuckoo_hash.c
> +++ b/lib/librte_hash/rte_cuckoo_hash.c
> @@ -940,6 +940,6 @@ __rte_hash_add_key_with_hash(const struct
> rte_hash *h, const void *key,
>  	struct rte_hash_bucket *prim_bkt, *sec_bkt, *cur_bkt;
>  	struct rte_hash_key *new_k, *keys = h->key_store;
> +	uint32_t ext_bkt_id = 0;
>  	uint32_t slot_id;
> -	uint32_t ext_bkt_id;
>  	int ret;
>  	unsigned n_slots;
> @@ -1096,5 +1096,6 @@ __rte_hash_add_key_with_hash(const struct
> rte_hash *h, const void *key,
>  	 */
>  	if (rte_ring_sc_dequeue_elem(h->free_ext_bkts, &ext_bkt_id,
> -						sizeof(uint32_t)) != 0) {
> +						sizeof(uint32_t)) != 0 ||
> +					ext_bkt_id == 0) {
[Wang, Yipeng] 
If convenient, it would be better to make the two lines aligned with same indent...

>  		ret = -ENOSPC;
>  		goto failure;
> --
> 2.21.3
[Wang, Yipeng] 
Thanks for the fix. I think It is also better code in general.

Acked-by: Yipeng Wang <yipeng1.wang at intel.com>