linux-kernel - Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'

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Date:	Thu, 30 May 2013 17:55:33 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	edumazet@...gle.com, Pravin Shelar <pshelar@...ira.com>,
	mgorman@...e.de
CC:	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] include/linux/skbuff.h: using '0xffff' instead of '~0U'


It seems a good idea to "fgrep -rn '~0U'" all source code, and check
each one by one.

:-)


On 05/30/2013 02:03 PM, Chen Gang wrote:
> 
> Both 'transport_header' and 'mac_header' are u16, which are never equal
> to '~0U'.
> 
> So need use '0xffff' instead of '~0U'.
> 
> The related warning (with EXTRA_CFLAGS=-W ARCH=m68k for allmodconfig)
>   include/linux/skbuff.h:1587:2: warning: comparison is always true due to limited range of data type [-Wtype-limits]
>   ...
> 
> 
> Signed-off-by: Chen Gang <gang.chen@...anux.com>
> ---
>  include/linux/skbuff.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 2e0ced1..03ba058 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -1581,7 +1581,7 @@ static inline void skb_set_inner_mac_header(struct sk_buff *skb,
>  }
>  static inline bool skb_transport_header_was_set(const struct sk_buff *skb)
>  {
> -	return skb->transport_header != ~0U;
> +	return skb->transport_header != 0xffff;
>  }
>  
>  static inline unsigned char *skb_transport_header(const struct sk_buff *skb)
> @@ -1624,7 +1624,7 @@ static inline unsigned char *skb_mac_header(const struct sk_buff *skb)
>  
>  static inline int skb_mac_header_was_set(const struct sk_buff *skb)
>  {
> -	return skb->mac_header != ~0U;
> +	return skb->mac_header != 0xffff;
>  }
>  
>  static inline void skb_reset_mac_header(struct sk_buff *skb)
> 


-- 
Chen Gang

Asianux Corporation
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