[PATCH v4 5/5] bpf: replace use of VLA

[Marat Khalili]

> -----Original Message-----
> From: Stephen Hemminger <stephen at networkplumber.org>
> Sent: Tuesday 4 November 2025 16:08
> To: dev at dpdk.org
> Cc: Stephen Hemminger <stephen at networkplumber.org>; Konstantin Ananyev <konstantin.ananyev at huawei.com>
> Subject: [PATCH v4 5/5] bpf: replace use of VLA
> 
> Variable length arrays are extension not required in C standard
> and not available in Windows.
> Use alloca() instead of variable length array.
> 
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> ---
>  lib/bpf/bpf_pkt.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/bpf/bpf_pkt.c b/lib/bpf/bpf_pkt.c
> index 087ac0f244..5007f6aef5 100644
> --- a/lib/bpf/bpf_pkt.c
> +++ b/lib/bpf/bpf_pkt.c
> @@ -163,7 +163,7 @@ apply_filter(struct rte_mbuf *mb[], const uint64_t rc[], uint32_t num,
>  	uint32_t drop)
>  {
>  	uint32_t i, j, k;
> -	struct rte_mbuf *dr[num];
> +	struct rte_mbuf **dr = alloca(num * sizeof(struct rte_mbuf *));
> 
>  	for (i = 0, j = 0, k = 0; i != num; i++) {
> 
> @@ -192,8 +192,8 @@ pkt_filter_vm(const struct rte_bpf *bpf, struct rte_mbuf *mb[], uint32_t num,
>  	uint32_t drop)
>  {
>  	uint32_t i;
> -	void *dp[num];
> -	uint64_t rc[num];
> +	void **dp = alloca(num * sizeof(void *));
> +	uint64_t *rc = alloca(num * sizeof(uint64_t));
> 
>  	for (i = 0; i != num; i++)
>  		dp[i] = rte_pktmbuf_mtod(mb[i], void *);
> @@ -208,7 +208,7 @@ pkt_filter_jit(const struct rte_bpf_jit *jit, struct rte_mbuf *mb[],
>  {
>  	uint32_t i, n;
>  	void *dp;
> -	uint64_t rc[num];
> +	uint64_t *rc = alloca(num * sizeof(uint64_t));
> 
>  	n = 0;
>  	for (i = 0; i != num; i++) {
> @@ -227,7 +227,7 @@ static inline uint32_t
>  pkt_filter_mb_vm(const struct rte_bpf *bpf, struct rte_mbuf *mb[], uint32_t num,
>  	uint32_t drop)
>  {
> -	uint64_t rc[num];
> +	uint64_t *rc = alloca(num * sizeof(uint64_t));
> 
>  	rte_bpf_exec_burst(bpf, (void **)mb, rc, num);
>  	return apply_filter(mb, rc, num, drop);
> @@ -238,7 +238,7 @@ pkt_filter_mb_jit(const struct rte_bpf_jit *jit, struct rte_mbuf *mb[],
>  	uint32_t num, uint32_t drop)
>  {
>  	uint32_t i, n;
> -	uint64_t rc[num];
> +	uint64_t *rc = alloca(num * sizeof(uint64_t));
> 
>  	n = 0;
>  	for (i = 0; i != num; i++) {
> --
> 2.51.0

Reviewed-by: Marat Khalili <marat.khalili at huawei.com>