Re: PATCH: `__norestrict' type qualifier

[Chip Salzenberg <chip at perlsupport dot com>]

According to Jamie Lokier:
> The C9X draft defines alignment already:

Marvy.

> I think this fixes every problem raised so far:

I agree.  :-)

>     For conversion to and from other pointer types, pointers of type
>     `__norestrict B *', for all B, are subject to the same guarantees and
>     restrictions as pointers of type `B *'.  See 6.3.2.3 [#7].
> 
>     In particular, if the result of converting a pointer to `__norestrict B
>     *' is not correctly aligned for the type B, the behaviour is undefined.
> 
>     Reading through a pointer of type `__norestrict B *' shall have the
>     same, implementation-defined behaviour as converting the pointer to
>     type `const char *', copying sizeof B characters from that address into
>     field `a' of a temporary of type `union { char a [sizeof B]; B b; }',
>     and then reading field `b'.
> 
>     Writing through a pointer of type `__norestrict B *' shall have the
>     same, implementation-defined behaviour as writing to field `b' of a
>     temporary of type `union { char a [sizeof B]; B b; }', converting the
>     pointer to type `char *', and then copying sizeof B characters to that
>     address from field `a'.
> 
>     The order of character copies is not defined -- they may occur
>     simultaneously, independently or in any combination.  A volatile
>     qualification on B does not change this.  A const qualification is
>     honoured by disallowing writes in the usual way.

-- 
Chip Salzenberg      - a.k.a. -      <chip@perlsupport.com>
      "When do you work?"   "Whenever I'm not busy."