linux-kernel - RE: [PATCH] net_sched: use explicit size of struct tcmsg, remove need to declare tcm

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Date:   Mon, 18 Sep 2017 12:18:58 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Colin King' <colin.king@...onical.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S . Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] net_sched: use explicit size of struct tcmsg, remove
 need to declare tcm

From: Colin King
> Sent: 18 September 2017 12:41
> Pointer tcm is being initialized and is never read, it is only being used
> to determine the size of struct tcmsg.  Clean this up by removing
> variable tcm and explicitly using the sizeof struct tcmsg rather than *tcm.
> Cleans up clang warning:
> 
> warning: Value stored to 'tcm' during its initialization is never read
> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  net/sched/sch_api.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> index c6deb74e3d2f..aa82116ed10c 100644
> --- a/net/sched/sch_api.c
> +++ b/net/sched/sch_api.c
> @@ -1500,7 +1500,6 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
>  	int s_idx, s_q_idx;
>  	struct net_device *dev;
>  	const struct nlmsghdr *nlh = cb->nlh;
> -	struct tcmsg *tcm = nlmsg_data(nlh);
>  	struct nlattr *tca[TCA_MAX + 1];
>  	int err;
> 
> @@ -1510,7 +1509,7 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
>  	idx = 0;
>  	ASSERT_RTNL();
> 
> -	err = nlmsg_parse(nlh, sizeof(*tcm), tca, TCA_MAX, NULL, NULL);
> +	err = nlmsg_parse(nlh, sizeof(struct tcmsg), tca, TCA_MAX, NULL, NULL);

Would sizeof(*nlmsg_data(nlh)) be cleaner??

	David