Re: [PATCH 1/2 v4] libc-internal.h: add ALIGN helper macros

[Mike Frysinger <vapier at gentoo dot org>]

On Wednesday 05 June 2013 08:15:12 Rasmus Villemoes wrote:
> Mike Frysinger <vapier@gentoo.org> writes:
> > On Tuesday 04 June 2013 06:49:00 Rasmus Villemoes wrote:
> >> I'm afraid one would have to deal with types anyway, as recently seen
> >> in the kernel http://lwn.net/Articles/548336/.
> > 
> > this is easily solved in the macro form:
> > 	#define ALIGN_DOWN(base, size) ((base) & ~((__typeof__(base))(size) -
> > 	1))
> > 
> > which isn't easily achievable with inline funcs
> 
> (I wasn't trying to argue for inline funcs.)
> 
> Yes, this seems to work. At first I thought one would have the
> opposite problem when typeof(base) was narrower than typeof(size) in
> the case of ALIGN_UP. But in that case the __typeof__ is actually
> applied to ((base)+(size)-1), which is of course sufficiently wide.
> 
> Is the extra expansion of size in ALIGN_UP a problem?

if someone passes a value with side effects, then yes.  that seems a bit 
unusual for these types of funcs (doing something like aligning to val++).  i 
don't see a way past it short of not providing the macro.
-mike

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