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- From: Geert Bosch <bosch at gnat dot com>
- To: Daniel Berlin <dan at cgsoftware dot com>
- Cc: Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>, <rth at redhat dot com>,<gcc-patches at gcc dot gnu dot org>
- Date: Mon, 3 Dec 2001 10:56:20 -0500
- Subject: Re: alias.c:nonoverlapping_component_refs_p
On Monday, December 3, 2001, at 08:11 , Daniel Berlin wrote:
> 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
>> of a variant record.
> On a RECORD_TYPE, it should be safe.
Even for C I'm not sure this is always safe. For example, if we have a
struct in C with two tightly packed char's, then it may be the case
that writing to one field requires updating both (presumably using
masking to preserve the old value). How would one represent this kind