Re: Representation Clauses And Freezing

[Simon Wright <simon@pogner.demon.co.uk>]

"Marin D. Condic" <mcondic-nospam@acm.com> writes:

> Try to imagine that you want to line up a data type to match a
> hardware register or a message coming into a system from the outside
> world. You have to put a rep clause on the data type so that
> specific bits, bytes and words fall into specific positions. Having
> the compiler reject your rep clause and suggest another does
> absolutely no good and is totally pointless.

I do agree. But, you are trying to do this with tagged types, and the
tag part is not specified by the standard.

If you have the same release of the same compiler on the same hardware
at both ends, why use rep clauses? (I'm assuming that the tag isn't a
pointer to a type-specific dope structure -- if it was you would be
completely wrong to try to send such data over the wire or even
inter-process).

If you have any difference at all, you *can not* sensibly send tags
over the wire.

-Simon