Re: [dpdk-dev] [PATCH v3] net: fix the way how L4 checksum choice is tested

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 28 Jun 2019 06:13:09 +0300
Ivan Malov <ivan.malov@oktetlabs.ru> wrote:

> The API to prepare checksum offloads mistreats L4
> checksum type enum values as self-contained flags.
> 
> Turning these flag checks into enum checks causes
> warnings by GCC about possibly uninitialised IPv4
> header pointer. The issue was found to show up in
> the case of GCC versions 4.8.5 and 5.4.0, however,
> it might be the case for a wider variety of other
> versions. Initialise the pointer upon declaration.
> and explain the reason behind this in the comment.
> 
> Fixes: 4fb7e803eb1a ("ethdev: add Tx preparation")
> Cc: Tomasz Kulasek <tomaszx.kulasek@intel.com>
> Cc: stable@dpdk.org
> 
> Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
> Reviewed-by: Andrew Rybchenko <arybchenko@solarflare.com>
> ---
>  lib/librte_net/rte_net.h | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_net/rte_net.h b/lib/librte_net/rte_net.h
> index 7be69f8..d240206 100644
> --- a/lib/librte_net/rte_net.h
> +++ b/lib/librte_net/rte_net.h
> @@ -112,7 +112,8 @@ uint32_t rte_net_get_ptype(const struct rte_mbuf *m,
>  static inline int
>  rte_net_intel_cksum_flags_prepare(struct rte_mbuf *m, uint64_t ol_flags)
>  {
> -	struct rte_ipv4_hdr *ipv4_hdr;
> +	/* Initialise ipv4_hdr to avoid false positive compiler warnings. */
> +	struct rte_ipv4_hdr *ipv4_hdr = NULL;
>  	struct rte_ipv6_hdr *ipv6_hdr;

Looks good, a smart compiler will just drop it.

Acked-by: Stephen Hemminger <stephen@networkplumber.org>