Re: how to get the field_id for member of structure in gcc front end

[Mike Stump <mrs at apple dot com>]

On Mar 29, 2006, at 12:15 AM, Tianwei Sheng wrote:
> but it's my be too aggressive. as you said, you mean "base,ofst"  
> rule is enough,
> a more safe method is "base,ofst, lenght" rule.

Right.  I didn't mean to exclude length, just that I didn't expound  
on the idea, as I wanted to get the simple concept across; there are  
any small details that have to be perfect for it to work, length is  
but one of them.

> int *p = &pair.a
> int *q = &pair.a;;
> p = p+1;
> *p = 1;
> *q = 2;
>
> (*p) and (*q) are not aliased because of p = p +1; now p points to  
> pair.b.

Right.

a + 0 != a + 0 + 8

(or so)

I just didn't want you to do:

&pair.a + 1 != &pair.b

because .a != .b because the `names' don't match.  By comparing the  
offset, we `know' that the bytes in positions 0-3 can't be the same  
as the bytes if positions 4-7, it just isn't possible.