linux-kernel - Re: [PATCH] Add spaces on either side of case "..." operator.

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Date:	Tue, 10 Apr 2007 09:05:55 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Robert P. J. Day" <rpjday@...dspring.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Add spaces on either side of case "..." operator.

On Tue, 10 Apr 2007 07:23:35 -0400 (EDT) "Robert P. J. Day" <rpjday@...dspring.com> wrote:

> Following the programming advice laid down in the gcc manual, make
> sure the case "..." operator has spaces on either side.
> 
> Signed-off-by: Robert P. J. Day <rpjday@...dspring.com>
> 
> ---
> 
> According to:
> 
> http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Case-Ranges.html#Case-Ranges:
> 
>   "Be careful: Write spaces around the ..., for otherwise it may be
> parsed wrong when you use it with integer values."
> 
> 
> diff --git a/kernel/audit.c b/kernel/audit.c
> index 76c9a11..d963a04 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -515,8 +515,8 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)
>  			err = -EPERM;
>  		break;
>  	case AUDIT_USER:
> -	case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
> -	case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:
> +	case AUDIT_FIRST_USER_MSG ... AUDIT_LAST_USER_MSG:
> +	case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2:

hm... We have: 

#define AUDIT_FIRST_USER_MSG    1100    /* Userspace messages mostly uninteresting to kernel */
#define AUDIT_USER_AVC          1107    /* We filter this differently */
#define AUDIT_LAST_USER_MSG     1199

and CPP turns that into

 case 1100 ...1199:
 case 2100 ...2999:

and it does the same when the comments are stripped from the #defines.

So we were saved by the trailing space which cpp added to the expanded
macro.  I wonder why cpp did that, and to what extent one can rely cpp
doing that.

Oh well.  I guess we should apply the patch.
-
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