From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: Re: [PATCH v2] netfilter: save the hash of the tuple in the original direction for latter use Date: Fri, 20 Aug 2010 09:43:14 -0400 Message-ID: <20100820134314.GA3283@Krystal> References: <1282228389-3029-1-git-send-email-xiaosuo@gmail.com> <20100819152149.GA19744@Krystal> <1282232786.2549.60.camel@edumazet-laptop> <20100819161112.GA24357@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: Eric Dumazet , Patrick McHardy , "David S. Miller" , netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org To: Changli Gao Return-path: Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org [ executive summary: trying to explain why static variable declarations within the body of functions is bad in kernel code. ] * Changli Gao (xiaosuo@gmail.com) wrote: > On Fri, Aug 20, 2010 at 12:11 AM, Mathieu Desnoyers > wrote: > > > > Ah, I see. But I think the static variable should stay declared outside > > of the function scope, with a nice comment explaining why it's not > > initialized at init-time. > > > > Hiding global state in function code is usually frowned upon. > > > > I don't agree with you. We'd better not expose the variable which > isn't expected to be used by others. If not, maybe someone will misuse > it. We are talking about a static variable usable only within a single file, where is the problem ? A nice comment can have this effect. > The user should only reply on the interface, but not the internal > implementation. I'm talking about good practice to help code review. This is way more important than the potential "encapsulation" benefit of hiding global state (a static variable) within the body of a function. I remember that Andrew Morton has strong opinions about this, and I remember being in complete agreement with him on the topic. Thanks, Mathieu > > Thanks. > > -- > Regards, > Changli Gao(xiaosuo@gmail.com) -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com