Re: PATCH: `__norestrict' type qualifier

[Chip Salzenberg <chip at perlsupport dot com>]

According to Jamie Lokier:
> Chip Salzenberg wrote:
> > > > (And alignment _can_ be a property of pointers on a word- addressed
> > > > machine.)
> > > 
> > > In the scope of ISO C?
> > 
> > Yes.  On a word-addressed machine, a native pointer addresses a single
> > word, which contains multiple bytes.  To address a byte you need an
> > address and a byte index within the addressed word.  So sizeof(char*)
> > is greater than sizeof(struct*), for example.
> 
> I don't think that's relevant to alignment as we meant it: there are
> no unaligned pointers on those machines!

That's my point.  A char* can be incorrectly aligned to extract a
word, if the byte index is nonzero.  But a word* can't be.  Therefore
if you define __norestrict pointers in terms of char* copying, then
you must allow for nonaligned words, and therefore you must make all
__norestrict pointers "fat".  This would be a Bad Thing.
-- 
Chip Salzenberg      - a.k.a. -      <chip@perlsupport.com>
      "When do you work?"   "Whenever I'm not busy."