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

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Message-ID: <51F86E1A.60404@asianux.com>
Date:	Wed, 31 Jul 2013 09:53:30 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Joe Perches <joe@...ches.com>
CC:	'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 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/coda.h
>>> +++ 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... some old version compilers do not define __linux__ automatically
> (e.g. or32-linux-gcc 4.5.1-or32-1.0rc1, which is the latest cross
> compiler for openrisc, though).
> 
> If not define __linux__, the compiler will report error (u_quad_t is
> not defined).
> 
> When we remove "#if defined(__linux__)" from "include/linux/coda.h",
> the compiler will not report error, and 'cdev_t' will be defined as
> 'dev_t', not 'u_quad_t' (I guess, it is an implicit bug).
> 
> 
> In "uapi/include/*", only "coda.h" has "#if defined(__linux__)", maybe
> they want multiple OS can share the same "coda.h" file (at least, we
> can not say it is a bad idea).
> 
> Neither suitable to define __linux__ in "include/linux/coda.h".
> 
> 
> All together, I think:
> 
>   the direct cause:
>     "uapi/include/coda.h" wants to share itself for multiple OS (so they need check __linux__).
>       (in "uapi/include/*", only coda.h need check __linux__)
> 
>   the root cause:
>     the compiler for linux should define __linux__ automatically, the latest version of gcc has done, but some of the old version is not.
>     most of cross compilers have merged their code into gcc main tree, but still left some (e.g. openrisc).
>       (at least, I can not build openrisc from gcc main tree correctly, but most of others can)
>     some of latest cross compilers still use old version of gcc, (still not define __linux__ automatically).
> 

Maybe what I said is incorrect (it is just my current understanding).

Welcome any other members' suggestions or completions for discussing and
checking.

Thanks.

> 
> The related code in "uapi/linux/coda.h" is below:
> 
> -------------------------------code begin-------------------------------
> 
>  73 #if defined(DJGPP) || defined(__CYGWIN32__)
>  74 #ifdef KERNEL
>  75 typedef unsigned long u_long;
>  76 typedef unsigned int u_int;
>  77 typedef unsigned short u_short;
>  78 typedef u_long ino_t;
>  79 typedef u_long dev_t;
>  80 typedef void * caddr_t;
>  81 #ifdef DOS
>  82 typedef unsigned __int64 u_quad_t;
>  83 #else
>  84 typedef unsigned long long u_quad_t;
>  85 #endif
>  86 
>  87 #define inline
>  88 
>  89 struct timespec {
>  90         long       ts_sec;
>  91         long       ts_nsec;
>  92 };
>  93 #else  /* DJGPP but not KERNEL */
>  94 #include <sys/time.h>
>  95 typedef unsigned long long u_quad_t;
>  96 #endif /* !KERNEL */
>  97 #endif /* !DJGPP */
>  98 
>  99 
> 100 #if defined(__linux__)
> 101 #include <linux/time.h>
> 102 #define cdev_t u_quad_t
> 103 #ifndef __KERNEL__
> 104 #if !defined(_UQUAD_T_) && (!defined(__GLIBC__) || __GLIBC__ < 2)
> 105 #define _UQUAD_T_ 1
> 106 typedef unsigned long long u_quad_t;
> 107 #endif
> 108 #endif /* __KERNEL__ */
> 109 #else
> 110 #define cdev_t dev_t
> 111 #endif
> 112 
> 
> -------------------------------code end---------------------------------
> 
> 
> Thanks.
> 


-- 
Chen Gang
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