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From: Robert A Duff <bobduff@world.std.com>
Subject: Re: generic package dilemma
Date: 1999/11/22
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Date: 1999-11-22T00:00:00+00:00
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Mats Weber <matsw@mail.com> writes:

> BTW, I don't think I was just lucky: the elaboration order control was
> supposed to be automatic in Ada 80, which of course is not feasible.

I think it *is* feasible.  In fact, the latest GNAT does determine an
order automatically -- and if it can't, it complains at link time.  This
is just like any other compile-time or link-time rule -- the halting
problem tells us we have to make the rules somewhat conservative
compared to corresonding run-time rules -- but that *is* feasible in
many cases.

I certainly don't believe the designers of Ada 83 (in 1980) thought it's
possible for compiler to solve the halting problem.  I think they just
wrote the rule in a slightly sloppy way.  They could have rewritten it
to say what they always meant, but instead they chose to go with
run-time checking -- I presume because that makes things simpler by
avoiding a link-time analysis of the entire program's call graph.

- Bob