linux-kernel - Re: [PATCH] sched: Remove nested extern

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Message-ID: <D428C53D-F663-4846-ACAB-74922033B048@intel.com>
Date:	Mon, 22 Sep 2014 19:32:04 +0000
From:	"Rustad, Mark D" <mark.d.rustad@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	"sparse@...isli.org" <sparse@...isli.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"richard.weinberger@...il.com" <richard.weinberger@...il.com>,
	"linux-sparse@...r.kernel.org" <linux-sparse@...r.kernel.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"computersforpeace@...il.com" <computersforpeace@...il.com>
Subject: Re: [PATCH] sched: Remove nested extern

On Sep 22, 2014, at 12:01 PM, Peter Zijlstra <peterz@...radead.org> wrote:

> On Mon, Sep 22, 2014 at 10:55:11AM -0700, Mark D Rustad wrote:
>> Avoid W=2 nested-externs warning by moving the nested extern to
>> a normal extern. This eliminates that warning which is generated
>> for every inclusion of sched.h in a kernel build when W=2 is used.
>> This also removes a point of maintenance if the definition of
>> delayacct_on were ever to change.
> 
> Yeah, so why is that warning worth using? Just disable the warn if
> you're bothered by it.

I assume that nested-externs is included in W=2 because many uses of
them, especially with function prototypes, creates a risk of inconsistent
declarations. The kernel has a fair number of them that seem to have
been added to disentangle include files. If they are judged to be
worthwhile, then it would be good to silence the warnings so that
attention can be given to other instances of the warnings. If those
nested externs are not worth the risk, well that is a different conversation.

-- 
Mark Rustad, Networking Division, Intel Corporation

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