From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,16e3a8dd4f3ab3f3
X-Google-Attributes: gid103376,public
From: stt@henning.camb.inmet.com (Tucker Taft)
Subject: Re: Elaboration order
Date: 1996/03/20
Message-ID: <DoKMI0.IHp.0.-s@inmet.camb.inmet.com>#1/1
X-Deja-AN: 143389222
sender: news@inmet.camb.inmet.com (USENET news)
x-nntp-posting-host: henning.camb.inmet.com
references: <4io8rn$gfn@newsbf02.news.aol.com>
organization: Intermetrics, Inc.
newsgroups: comp.lang.ada
Date: 1996-03-20T00:00:00+00:00
List-Id: <comp.lang.ada>

DenReimer (denreimer@aol.com) wrote:
: Here's something that I'm trying to do in Ada83 and Ada95:

: with GENERIC_PACKAGE;
: package A_PKG is
:    package INSTANCE is new GENERIC_PACKAGE ( ... );
:    X : INTEGER := INSTANCE.SOME_FUNCTION;
: end A_PKG;

: The elaboration of X requires that the instantiated package INSTANCE be
: elaborated first (both spec and body.)  The compiler will not let me use
: pragma elaborate (INSTANCE);

You should write:
   with Generic_Package;
   pragma Elaborate(Generic_Package);

: It is not clear to me what the elaboration order should be in the case of
: nested packages.  I would like to assume that for nested packages, the
: elaboration is also nested.  In the case of generic instantiations, both
: spec and body would be elaborated at the point of instantiation. 

All true.

: Unfortunately, the LRM does not seem to make any requirements regarding
: elaboration order for nested packages.  

Not true.

: ... I've tried the above source code
: with Ada/ED and an Alsys Ada83 compiler and it seems to work OK.

: When I use gnat, I get a program error.  The Ada95 pragmas used for
: controlling elaboration order seem to only apply to library units.  

That's true in Ada 83 as well.

: ... In the
: example above, I believe that INSTANCE is a program unit but not a library
: unit.  Is there some way I can force the elaboration of INSTANCE to occur
: immediately?  

Your problem is not the elaboration of Instance.  It is the elaboration
of the body of Generic_Package.  You are falling afoul of the
elaboration check that takes place when you instantiate a generic,
which requires that the generic body has already been elaborated.

As a general rule, if a compilation unit has a "with" for a generic, 
it should also have a "pragma Elaborate" for it, if it contains 
any library-level instantiations of the generic.

By the way, you are in good company.  Several of the 2.0.1 ACVC tests
forget this general rule.

: ...
: Dennis Reimer

-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
Intermetrics, Inc.  Cambridge, MA  USA