netdev - Re: [PATCH] net: use the macros defined for the members of flowi

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Message-Id: <20101115.175648.226754712.davem@davemloft.net>
Date:	Mon, 15 Nov 2010 17:56:48 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	brian.haley@...com, xiaosuo@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH] net: use the macros defined for the members of flowi

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Mon, 15 Nov 2010 22:38:46 +0100

> Le lundi 15 novembre 2010 à 16:33 -0500, Brian Haley a écrit :
>> On 11/12/2010 11:43 PM, Changli Gao wrote:
>> > Use the macros defined for the members of flowi to clean the code up.
>> > 
>> > diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
>> > index 865fd76..36cd0b7 100644
>> > --- a/net/bridge/br_netfilter.c
>> > +++ b/net/bridge/br_netfilter.c
>> > @@ -412,13 +412,8 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb)
>> >  	if (dnat_took_place(skb)) {
>> >  		if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
>> >  			struct flowi fl = {
>> > -				.nl_u = {
>> > -					.ip4_u = {
>> > -						 .daddr = iph->daddr,
>> > -						 .saddr = 0,
>> > -						 .tos = RT_TOS(iph->tos) },
>> > -				},
>> > -				.proto = 0,
>> > +				.fl4_dst = iph->daddr,
>> > +				.fl4_tos = RT_TOS(iph->tos),
>> >  			};
>> 
>> Are these actually equivalent?  You dropped two assignments to zero.
>> I always thought things on the stack weren't.
> 
> Same question on lkml few hours ago. I think gcc does the assignement to
> zero, even on automatic variables (at least done on x86), but could not
> find a doc on it.

It always has, it always will.  "type var = { };" always zeros
out the structure.

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