Messages in this thread | | | Date | Fri, 20 Aug 2010 09:43:14 -0400 | From | Mathieu Desnoyers <> | Subject | Re: [PATCH v2] netfilter: save the hash of the tuple in the original direction for latter use |
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[ 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 > <mathieu.desnoyers@polymtl.ca> 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
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