linux-kernel - Re: [PATCH trivial] include/linux/coda.h: remove useless '#else'

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Date:	Mon, 05 Aug 2013 17:00:22 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Joe Perches <joe@...ches.com>
CC:	Chen Gang F T <chen.gang.flying.transformer@...il.com>,
	'Jiri Kosina' <trivial@...nel.org>, jaharkes@...cmu.edu,
	coda@...cmu.edu, codalist@...a.cs.cmu.edu,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH trivial] include/linux/coda.h: remove useless '#else'

On 08/05/2013 10:12 AM, Chen Gang wrote:
> On 08/05/2013 09:53 AM, Chen Gang wrote:
>> On 08/05/2013 09:21 AM, Joe Perches wrote:
>>> On Mon, 2013-08-05 at 08:24 +0800, Chen Gang wrote:
>>>> On 07/31/2013 11:16 AM, Chen Gang F T wrote:
>>>>> On 07/31/2013 09:53 AM, Chen Gang wrote:
>>>>>> On 07/31/2013 09:44 AM, Chen Gang wrote:
>>>>>>> On 07/30/2013 08:29 PM, Joe Perches wrote:
>>>>>>>> On Tue, 2013-07-30 at 15:30 +0800, Chen Gang wrote:
>>>>>>>>> '#else' is useless, need remove.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Chen Gang <gang.chen@...anux.com>
>>>>>>>>> ---
>>>>>>>>>  include/linux/coda.h |    1 -
>>>>>>>>>  1 files changed, 0 insertions(+), 1 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/include/linux/coda.h b/include/linux/coda.h
>>>>>>>>> index cff544f..d30209b 100644
>>>>>>>>> --- a/include/linux/cod
>>>>>>>>> +++ b/include/linux/coda.h
>>>>>>>>> @@ -60,7 +60,6 @@ Mellon the rights to redistribute these changes without encumbrance.
>>>>>>>>>  
>>>>>>>>>  #if defined(__linux__)
>>>>>>>>>  typedef unsigned long long u_quad_t;
>>>>>>>>> -#else
>>>>>>>>>  #endif
>>>>>>>>>  #include <uapi/linux/coda.h>
>>>>>>>>>  #endif 
>>>>>>>>
>>>>>>>> Why have the #if at all?
>>>>>>>>
>>>>
>>>> Hmm... if any members have some questions about the fix, commonly it
>>>> means the related fix need additional improvement.
>>>>
>>>> Is it better to use BUILD_BUG() for the fix ?
>>>
>>> Probably not.  __linux__ is predefined by gcc.
>>>
>>> Using an #ifdef __linux__ might make some sense in
>>> in include/uapi, but not in include/linux.
>>>
>>>
>>

In "include/uapi/", only 2 files contant __linux__: (especially latest
compiler has already defined __linux__)

  [root@...enlinux uapi]# grep -rn __linux__ *
  drm/drm.h:39:#if defined(__KERNEL__) || defined(__linux__)
  linux/coda.h:100:#if defined(__linux__)

So now and future, it is not common enough to check __linux__ globally.

So I still suggest to let the related modules theirselves to check
__linux__ whether defined.


> 
> In fact, in my opinion "uapi/linux/coda.h" should not content "#ifdef
> __linux__", since it is already in "uapi/linux/" sub-directory.
> 
> If it still wants to universal enough to multiple OS, need move it from
> "uapi/linux/coda.h" to "uapi/coda/coda.h".
> 
> :-)
> 
> 
>> Hmm... since "linux/coda.h" will include "uapi/linux/coda.h", it is
>> necessary to check __linux__ whether defined.
>>
>> For some old compilers which is still widely used, they really do not
>> define __linux__, when use these compilers, we need give a necessary
>> check, if can not pass, need report BUILD_BUG().
>>
>> e.g. for some versions of openrisc, please ref:
>> https://lkml.org/lkml/2013/7/30/888. (it is in applying work flow).
>>
>>
>> Thanks.
>>
> 
> 


-- 
Chen Gang
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