linux-kernel - Re: [PATCH] net: ethernet: mscc: fix missing brace warning for old compilers

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Date:   Mon, 2 Nov 2020 23:19:20 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     Pujin Shi <shipujin.t@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: ethernet: mscc: fix missing brace warning for old
 compilers

On Mon, Nov 02, 2020 at 02:08:08PM -0800, Jakub Kicinski wrote:
> Old GCC does not like the 0, if the members of struct are not scalars.
>
> struct ocelot_vcap_u16 {
>         u8 value[2];
>         u8 mask[2];
> };
>
> In this case the first member is an array.
>
> It wants us to add another curly brace:
>
> struct ocelot_vcap_u16 etype = {{0}};
>
> ... or we can just skip the 0.

I am reading that the empty set initializer is a GNU extension. I would
not like to see yet another patch from clang folks coming as a follow-up
to this one.

> That's just FWIW. I don't remember which versions of GCC behave like
> that, I just know we get a constant stream of this sort of fixes.
> I think clang may generate a similar warning.
>
> Pujin, please specify the version of GCC you're using and repost.

If the initializer really has to be changed, I would prefer to see a memset.