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From: Sam Ravnborg <sam@ravnborg.org>
To: David Howells <dhowells@redhat.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux Arch Mailing List <linux-arch@vger.kernel.org>,
	David Brownell <dbrownell@users.sourceforge.net>
Subject: Re: [PATCH 1/2] Add C99-style constructor macros for specific-sized integers
Date: Mon, 3 Mar 2008 13:40:50 +0100	[thread overview]
Message-ID: <20080303124050.GA24841@uranus.ravnborg.org> (raw)
In-Reply-To: <20080303114310.GA28139@flint.arm.linux.org.uk>

On Mon, Mar 03, 2008 at 11:43:10AM +0000, Russell King wrote:
> On Mon, Mar 03, 2008 at 10:57:32AM +0000, David Howells wrote:
> > H. Peter Anvin <hpa@zytor.com> wrote:
> > 
> > > +#define S8_C(x)	 x
> > > +#define U8_C(x)  x ## U
> > > +#define S16_C(x) x
> > > +#define U16_C(x) x ## U
> > > +#define S32_C(x) x
> > > +#define U32_C(x) x ## U
> > > +#define S64_C(x) x ## LL
> > > +#define U64_C(x) x ## ULL
> > 
> > And #if defined(__ASSEMBLY__), just splat x through as is.
> 
> We already have something like this on ARM - include/asm-arm/memory.h
> 
> /*
>  * Allow for constants defined here to be used from assembly code
>  * by prepending the UL suffix only with actual C code compilation.
>  */
> #ifndef __ASSEMBLY__
> #define UL(x) (x##UL)
> #else
> #define UL(x) (x)
> #endif

And in linux/const.h we have yet another variant:
/* Some constant macros are used in both assembler and
 * C code.  Therefore we cannot annotate them always with
 * 'UL' and other type specifiers unilaterally.  We
 * use the following macros to deal with this.
 *
 * Similarly, _AT() will cast an expression with a type in C, but
 * leave it unchanged in asm.
 */

#ifdef __ASSEMBLY__
#define _AC(X,Y)        X
#define _AT(T,X)        X
#else
#define __AC(X,Y)       (X##Y)
#define _AC(X,Y)        __AC(X,Y)
#define _AT(T,X)        ((T)(X))
#endif

Not as typestrict as hpa's and arm's version but
used in a few placed already.

	Sam

  reply	other threads:[~2008-03-03 12:40 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-03  0:09 H. Peter Anvin
2008-03-03  0:09 ` [PATCH 2/2] Use U64_C() instead of casts in kernel/time.c H. Peter Anvin
2008-03-03  2:38 ` [PATCH 1/2] Add C99-style constructor macros for specific-sized integers Matthew Wilcox
2008-03-03  4:43   ` H. Peter Anvin
2008-03-03  6:20     ` Al Viro
2008-03-03  6:12       ` H. Peter Anvin
2008-03-03  6:32         ` Al Viro
2008-03-03  6:28           ` H. Peter Anvin
2008-03-03  3:20 ` Segher Boessenkool
2008-03-03  4:14   ` David Brownell
2008-03-03  4:50     ` H. Peter Anvin
2008-03-03  4:45   ` H. Peter Anvin
2008-03-03 20:23     ` Segher Boessenkool
2008-03-03 10:57 ` David Howells
2008-03-03 11:43   ` Russell King
2008-03-03 12:40     ` Sam Ravnborg [this message]
2008-03-03 17:03       ` H. Peter Anvin
2008-03-03 12:15   ` David Howells

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