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- From: Daniel Berlin <dan at cgsoftware dot com>
- To: Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>
- Cc: <gcc-patches at gcc dot gnu dot org>
- Date: Mon, 3 Dec 2001 08:23:47 -0500 (EST)
- Subject: Re: alias.c:nonoverlapping_component_refs_p
On Mon, 3 Dec 2001, Richard Kenner wrote:
> > I don't believe it is safe to conclude that if two fields aren't the
> > same, they don't overlap. An example of a case where they do is an Ada
> > subtype of a variant record.
> On a RECORD_TYPE, it should be safe.
> No, the example I just gave will be a RECORD_TYPE.
> If Ada has different semantics, it needs a different tree code, or some
> easy way to differentiate.
> I'm sorry, I'm missing your point. Where in tree.def does it say that fields
> may not overlap?
The part that says RECORD_TYPE represents a c struct or a pascal record.
If Ada's semantics are significantly different, then it shouldn't be using
that tree code, or should be differentiable in a way that allows for us to
simply say "Oh, it's an ada subtype of a variant record, we can't assume
if two fields arent the same, they don't overlap".
Because as far as I know, in C, this is a valid assumption.
Of course, it's early, i could be wrong.