linux-kernel - Re: [PATCH] net/ipv6: warning: %u in format string (no. 2) requires 'unsigned int' but the argument type is 'signed int'.

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Message-ID: <20210109130030.733e8bb1@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Sat, 9 Jan 2021 13:00:30 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jiapeng Zhong <abaci-bugfix@...ux.alibaba.com>
Cc:     davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/ipv6: warning: %u in format string (no. 2) requires
 'unsigned int' but the argument type is 'signed int'.

On Thu,  7 Jan 2021 10:47:34 +0800 Jiapeng Zhong wrote:
> The print format of this parameter does not match, because it is defined
> as int type, so modify the matching format of this parameter to %d format.
> 
> Signed-off-by: Jiapeng Zhong <abaci-bugfix@...ux.alibaba.com>
> Reported-by: Abaci <abaci@...ux.alibaba.com>
> ---
>  net/ipv6/proc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
> index d6306aa..26c702b 100644
> --- a/net/ipv6/proc.c
> +++ b/net/ipv6/proc.c
> @@ -169,7 +169,7 @@ static void snmp6_seq_show_icmpv6msg(struct seq_file *seq, atomic_long_t *smib)
>  		val = atomic_long_read(smib + i);
>  		if (!val)
>  			continue;
> -		snprintf(name, sizeof(name), "Icmp6%sType%u",
> +		snprintf(name, sizeof(name), "Icmp6%sType%d",
>  			i & 0x100 ?  "Out" : "In", i & 0xff);
>  		seq_printf(seq, "%-32s\t%lu\n", name, val);
>  	}

Type can't be negative, there is no reason for @i to be signed.
Changing type of @i sounds like a better idea.