From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ferruh Yigit <ferruh.yigit@intel.com>
Subject: Re: [PATCH 08/10] lpm6: fix compilation with -Og
Date: Fri, 6 Oct 2017 01:18:00 +0100
Message-ID: <228abb94-4939-8425-9451-2fb57fd1c567@intel.com>
References: <20170911151333.5727-1-olivier.matz@6wind.com>
 <20170911151333.5727-9-olivier.matz@6wind.com>
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To: Olivier Matz <olivier.matz@6wind.com>, dev@dpdk.org,
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On 9/11/2017 4:13 PM, Olivier Matz wrote:
> The compilation with gcc-6.3.0 and EXTRA_CFLAGS=-Og gives the following
> error:
> 
>   CC rte_lpm6.o
>   rte_lpm6.c: In function ‘rte_lpm6_add_v1705’:
>   rte_lpm6.c:442:11: error: ‘tbl_next’ may be used uninitialized in
>                              this function [-Werror=maybe-uninitialized]
>      if (!tbl[tbl_index].valid) {
>              ^
>   rte_lpm6.c:521:29: note: ‘tbl_next’ was declared here
>     struct rte_lpm6_tbl_entry *tbl_next;
>                                ^~~~~~~~
> 
> This is a false positive from gcc. Fix it by initializing tbl_next
> to NULL.

This is hard to trace, and it seems there is a way to have it, not sure
practically possible:

rte_lpm6_add_v1705
    add_step
        if (depth <= bits_covered) {
            ...
            return 0 <--- so tbl_next stays untouched.
    tbl = tbl_next
    add_step
        tbl[tbl_index]


So same comment as previous, if there is a practically available path,
this patch makes it harder to find by hiding compiler warning, so adding
maintainer for decision.


> 
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> ---
>  lib/librte_lpm/rte_lpm6.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/librte_lpm/rte_lpm6.c b/lib/librte_lpm/rte_lpm6.c
> index b4a7df348..f9496fe1b 100644
> --- a/lib/librte_lpm/rte_lpm6.c
> +++ b/lib/librte_lpm/rte_lpm6.c
> @@ -518,7 +518,7 @@ rte_lpm6_add_v1705(struct rte_lpm6 *lpm, uint8_t *ip, uint8_t depth,
>  		uint32_t next_hop)
>  {
>  	struct rte_lpm6_tbl_entry *tbl;
> -	struct rte_lpm6_tbl_entry *tbl_next;
> +	struct rte_lpm6_tbl_entry *tbl_next = NULL;
>  	int32_t rule_index;
>  	int status;
>  	uint8_t masked_ip[RTE_LPM6_IPV6_ADDR_SIZE];
>