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

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Message-Id: <20070419084339.418dbe69.randy.dunlap@oracle.com>
Date:	Thu, 19 Apr 2007 08:43:39 -0700
From:	Randy Dunlap <randy.dunlap@...cle.com>
To:	Jiri Bohac <jbohac@...e.cz>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] fix abs() macro to work with types wider than int

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().

> 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;		\
>  	})
>  
> 
> 
> 
> -- 
> Jiri Bohac <jbohac@...e.cz>
> SUSE Labs, SUSE CZ

---
~Randy
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