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Date: Wed, 28 Jun 2006 13:42:21 +0400
From: Yar Tikhiy <yar@comp.chem.msu.su>
To: "M. Warner Losh" <imp@bsdimp.com>
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Cc: arch@freebsd.org
Subject: Re: SET, CLR, ISSET in types.h for _KERNEL builds
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On Tue, Jun 27, 2006 at 01:58:17PM -0600, M. Warner Losh wrote:
> NetBSD recently added SET, CLR, ISSET to sys/types.h (only if _KERNEL
> is defined).  I'd like to do something similar in FreeBSD.  I see no
> reason to needless deviate from NetBSD here.  One could make an
> argument for lots of different files, but at the end of the day does
> it really matter enough to justify having it be different than NetBSD?
> 
> Here's my proposed diff, inline, for your consideration:
> 
> Index: types.h
> ===================================================================
> RCS file: /home/ncvs/src/sys/sys/types.h,v
> retrieving revision 1.95
> diff -u -r1.95 types.h
> --- types.h	26 Nov 2005 12:42:35 -0000	1.95
> +++ types.h	27 Jun 2006 19:57:23 -0000
> @@ -294,6 +294,11 @@
>  
>  #define offsetof(type, field) __offsetof(type, field)
>  
> +/* Macros to clear/set/test flags. */
> +#define	SET(t, f)	(t) |= (f)
> +#define	CLR(t, f)	(t) &= ~(f)
> +#define	ISSET(t, f)	((t) & (f))
> +
>  #endif /* !_KERNEL */
>  
>  /*
> 
> NOTE: That /* !_KERNEL */ should have the '!' removed, but I didn't
> want to confuse things by doing that too.
> 
> Comments?

I'd rather enclose the whole RHS of SET and CLR in parentheses.
It's still C; SET and CLR can be used in expressions and cause
precedence artefacts if not parenthesised.

-- 
Yar