Proposed resolution to aliasing issue.

[Mark Mitchell]

Mike Stump wrote:

> We need to teach it about the meaning of constants.
> 
> One can:
> 
> #include "foo.h"
> 
> main() {
>     printf ("%d\n", offsetof (s, m));
> }
> 
> and then in another file, read and use that on an address.  One can  
> also transform it into a #define S_M_OFFSET 8, and #include it.  So,  
> I'd claim the optimizer has to know about constants already.

I fail to see your point, unless it is that whether or not you spell "8" 
as "8", "&s.x - &s.y", or "offsetof (S, x) - offsetof (S, y)" should not 
matter, in which case I certainly agree.

-- 
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304