linux-kernel - Re: [PATCH] pinctrl: Include <linux/bug.h> to prevent compile errors

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Message-ID: <CAP=VYLpZv-g5ZqONzhk51nth3Wn=zHmcfytdEBH3ZX7CJKjaZw@mail.gmail.com>
Date:	Fri, 9 Mar 2012 16:29:20 -0500
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pinctrl: Include <linux/bug.h> to prevent compile errors

On Fri, Mar 9, 2012 at 3:43 PM, Stephen Warren <swarren@...dotorg.org> wrote:
> On 03/09/2012 01:32 PM, Paul Gortmaker wrote:
>> [[PATCH] pinctrl: Include <linux/bug.h> to prevent compile errors] On 09/03/2012 (Fri 13:18) Stephen Warren wrote:
>>
>>> Macros in <linux/pinctrl/machine.h> call ARRAY_SIZE(), the definition of
>>> which eventually calls BUILD_BUG_ON_ZERO(), which is defined in
>>> <linux/bug.h>. Include that so that every .c file using the pinctrl macros
>>> doesn't have to do that itself.
>>
>> Which C files are failing?  The approach was to be adding it only
>> for headers with static inlines which use it, and add it to C files
>> that are actually *deploying* the macros.
>
> For me, the files that are failing haven't been committed upstream yet;
> I expect them to be very soon after the 3.4 merge window completes.
>
> However, I expect you'll see this issue with arch/arm/mach-u300/core.c,
> since it uses the same macros defined in pinctrl/machine.h that cause
> the problem for me, unless one of the include files there picks up bug.h
> already.
>
> As a general statement though, once pinctrl becomes more widely adopted,
> I expect to see many files start to use macros from pinctrl/machine.h,
> and hence implicitly use ARRAY_SIZE(), and hence even more implicitly
> depend on linux/bug.h. I don't think it's at all reasonable to force the
> author of every one of those files to track down 3 or 4 levels of header
> file dependencies to find that they need linux/bug.h even though they
> make no direct use of its features, when it's known that almost any user
> of pinctrl/machine.h is going to hit this issue.

There was a similar discussion before, where there was concern over
"every one of those files" but in the end the number is a fraction of
a percent.   There is no harm in the author knowing they are making
_use_ of BUG stuff -- in fact if you happened to be trying to write some
fault tolerant code, you might really be glad to know, so you could take
steps to avoid it....

Paul.


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