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From: dewar@cs.nyu.edu (Robert Dewar)
Subject: Re: Elaboration order
Date: 1996/03/25
Message-ID: <dewar.827756008@schonberg>#1/1
X-Deja-AN: 144170814
references: <314701A1.469D@lfwc.lockheed.com>
 <314D2E1C.5C72@lfwc.lockheed.com> <4in4am$klb@watnews1.watson.ibm.com>
 <4inpiv$alk@cliffy.lfwc.lockheed.com> <DoJqBL.362@world.std.com>
 <4ip58c$gqo@cliffy.lfwc.lockheed.com> <696076745wnr@diphi.demon.co.uk>
organization: Courant Institute of Mathematical Sciences
newsgroups: comp.lang.ada
Date: 1996-03-25T00:00:00+00:00
List-Id: <comp.lang.ada>

JP Thornley writes

"FWIW, the safety critical code we write uses a subset that avoids any
elaboration order dependencies (and there is a tool to ensure conformance to
the subset)."

This seems a perfectly reasonable approach to me. Another is to eliminate
all possible ABE's by some uniform scheme. A fierce one (too fierce I
think, but it certainly does the job) is one that I heard was being
used in one giant project: always put pragma Elaborate for every with.
Of course this eliminates all ABE's, but also eliminates mutual recursion
between packages.

An interesting question for JP is how closely the subset corresponds
to the built in notion of pragma Preelaborate in Ada 95. I think it
is quite possible to consider using pragma Preelaborate for all
packages in such an implementation, and then the compiler acts as
the tool for enforcement without depending on implementatin dependent
features.