netdev - Re: [PATCH 06/15] netfilter: conntrack: avoid gcc-10 zero-length-bounds warning

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Message-ID: <20200510214829.GA9032@salvia>
Date:   Sun, 10 May 2020 23:48:29 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     linux-kernel@...r.kernel.org,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jeremy Sowden <jeremy@...zel.net>,
        Li RongQing <lirongqing@...du.com>,
        Joe Perches <joe@...ches.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jules Irenge <jbi.octave@...il.com>,
        Dirk Morris <dmorris@...aloft.com>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 06/15] netfilter: conntrack: avoid gcc-10
 zero-length-bounds warning

On Thu, Apr 30, 2020 at 11:30:48PM +0200, Arnd Bergmann wrote:
> gcc-10 warns around a suspicious access to an empty struct member:
> 
> net/netfilter/nf_conntrack_core.c: In function '__nf_conntrack_alloc':
> net/netfilter/nf_conntrack_core.c:1522:9: warning: array subscript 0 is outside the bounds of an interior zero-length array 'u8[0]' {aka 'unsigned char[0]'} [-Wzero-length-bounds]
>  1522 |  memset(&ct->__nfct_init_offset[0], 0,
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from net/netfilter/nf_conntrack_core.c:37:
> include/net/netfilter/nf_conntrack.h:90:5: note: while referencing '__nfct_init_offset'
>    90 |  u8 __nfct_init_offset[0];
>       |     ^~~~~~~~~~~~~~~~~~
> 
> The code is correct but a bit unusual. Rework it slightly in a way that
> does not trigger the warning, using an empty struct instead of an empty
> array. There are probably more elegant ways to do this, but this is the
> smallest change.

Applied, thanks.