netdev - Re: [PATCH] net: bareudp: avoid uninitialized variable warning

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Message-Id: <20200507.172833.1823250580053812142.davem@davemloft.net>
Date:   Thu, 07 May 2020 17:28:33 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     arnd@...db.de
Cc:     kuba@...nel.org, willemb@...gle.com, martin.varghese@...ia.com,
        ap420073@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH] net: bareudp: avoid uninitialized variable warning

From: Arnd Bergmann <arnd@...db.de>
Date: Tue,  5 May 2020 19:22:14 +0200

> clang points out that building without IPv6 would lead to returning
> an uninitialized variable if a packet with family!=AF_INET is
> passed into bareudp_udp_encap_recv():
> 
> drivers/net/bareudp.c:139:6: error: variable 'err' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
>         if (family == AF_INET)
>             ^~~~~~~~~~~~~~~~~
> drivers/net/bareudp.c:146:15: note: uninitialized use occurs here
>         if (unlikely(err)) {
>                      ^~~
> include/linux/compiler.h:78:42: note: expanded from macro 'unlikely'
>  # define unlikely(x)    __builtin_expect(!!(x), 0)
>                                             ^
> drivers/net/bareudp.c:139:2: note: remove the 'if' if its condition is always true
>         if (family == AF_INET)
>         ^~~~~~~~~~~~~~~~~~~~~~
> 
> This cannot happen in practice, so change the condition in a way that
> gcc sees the IPv4 case as unconditionally true here.
> For consistency, change all the similar constructs in this file the
> same way, using "if(IS_ENABLED())" instead of #if IS_ENABLED()".
> 
> Fixes: 571912c69f0e ("net: UDP tunnel encapsulation module for tunnelling different protocols like MPLS, IP, NSH etc.")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Applied, thanks.