linux-kernel - Re: [PATCH] ieee802154: fix gcc-4.9 warnings

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Message-ID: <1505255692.8969.2.camel@perches.com>
Date:   Tue, 12 Sep 2017 15:34:52 -0700
From:   Joe Perches <joe@...ches.com>
To:     Arnd Bergmann <arnd@...db.de>, Harry Morris <h.morris@...coda.com>,
        linuxdev@...coda.com, Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@....samsung.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        "David S. Miller" <davem@...emloft.net>,
        Markus Elfring <elfring@...rs.sourceforge.net>,
        "Gustavo A. R. Silva" <garsilva@...eddedor.com>,
        Florian Westphal <fw@...len.de>,
        Johannes Berg <johannes.berg@...el.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Colin Ian King <colin.king@...onical.com>,
        linux-wpan@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ieee802154: fix gcc-4.9 warnings

On Tue, 2017-09-12 at 12:16 +0200, Arnd Bergmann wrote:
> All older compiler versions up to gcc-4.9 produce these
> harmless warnings:
> 
> drivers/net/ieee802154/ca8210.c: In function 'ca8210_skb_tx':
> drivers/net/ieee802154/ca8210.c:1947:9: warning: missing braces around initializer [-Wmissing-braces]
> 
> This changes the syntax to something that works on all versions
> without warnings.
> 
> Fixes: ded845a781a5 ("ieee802154: Add CA8210 IEEE 802.15.4 device driver")
[]
> diff --git a/drivers/net/ieee802154/ca8210.c b/drivers/net/ieee802154/ca8210.c
[]
> @@ -1944,7 +1944,7 @@ static int ca8210_skb_tx(
>  )
>  {
>  	int status;
> -	struct ieee802154_hdr header = { 0 };
> +	struct ieee802154_hdr header = { };
>  	struct secspec secspec;
>  	unsigned int mac_len;

Presumably gcc does this because the first member
of struct ieee802154_hdr is another struct.

I wonder if "struct foo bar = { 0 };" should be
discouraged by checkpatch.

Right now it's about 4:3 in favor of
	struct foo bar = {};
over
	struct foo bar = { 0 };

$ git grep -E "struct\s+\w+\s+\w+\s*=\s*\{\s*0\s*\}\s*[,;]" | wc -l
826
$ git grep -E "struct\s+\w+\s+\w+\s*=\s*\{\s*\}\s*[,;]" | wc -l
990

There are many instances on multiple lines too.
The git grep above doesn't span multiple lines.