linux-kernel - Re: [RFC][PATCH] fix abs() macro to work with types wider than int

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Message-ID: <4628B5B6.90303@student.ltu.se>
Date:	Fri, 20 Apr 2007 14:44:38 +0200
From:	Richard Knutsson <ricknu-0@...dent.ltu.se>
To:	Randy Dunlap <randy.dunlap@...cle.com>
CC:	Jiri Bohac <jbohac@...e.cz>, akpm@...l.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] fix abs() macro to work with types wider than int

Randy Dunlap wrote:
> On Thu, 19 Apr 2007 11:23:39 +0200 Jiri Bohac wrote:
>
>   
>> Hi,
>>
>> is there any reason to use an explicit int instead of a typeof in
>> the abs() macro? The current implementation will return bogus
>> results when used with longs.
>>     
>
> I think it's like it is just to be consistent with abs() in C,
> which also contains labs() and llabs().
>   
We actually had labs() before (few months ago), but since it was not 
used, and if it would it seemed better to just fix abs(), it was 
removed. So I think this is the appropriate way to go.
>   
>> How about changing the int to a typeof like this?:
>>
>>
>>
>> Fix the abs() macro to work with wider types than int.
>>
>> Signed-off-by: Jiri Bohac <jbohac@...e.cz>
>>
>> --- linux-2.6.21-rc5.orig/include/linux/kernel.h
>> +++ linux-2.6.21-rc5/include/linux/kernel.h
>> @@ -89,7 +89,7 @@ extern int cond_resched(void);
>>  #define might_sleep_if(cond) do { if (cond) might_sleep(); } while (0)
>>  
>>  #define abs(x) ({				\
>> -		int __x = (x);			\
>> +		typeof(x) __x = (x);			\
>>  		(__x < 0) ? -__x : __x;		\
>>  	})
>>  
>>
>>
>>     
-
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