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: 103376,28b389d4503cb555
X-Google-Attributes: gid103376,public
From: Robert A Duff <bobduff@world.std.com>
Subject: Re: generic package dilemma
Date: 1999/12/01
Message-ID: <wccaenu9vp0.fsf@world.std.com>#1/1
X-Deja-AN: 555497052
Sender: bobduff@world.std.com (Robert A Duff)
References: <80u48b$ghr$1@bunyip.cc.uq.edu.au> <3832e27f_1@news1.prserv.net>
 <3832E75D.5B1BA719@mail.com> <383319e8_4@news1.prserv.net>
 <3833F615.5AD7166C@mail.com> <383442e1_1@news1.prserv.net>
 <383510EA.9DFEE8B6@mail.com> <383569db_2@news1.prserv.net>
 <3835CF7A.5604C6A3@mail.com> <81bt4v$7cr$1@nnrp1.deja.com>
 <wcczow6flxa.fsf@world.std.com> <81cru4$url$1@nnrp1.deja.com>
Organization: The World Public Access UNIX, Brookline, MA
Newsgroups: comp.lang.ada
Date: 1999-12-01T00:00:00+00:00
List-Id: <comp.lang.ada>

Robert Dewar <robert_dewar@my-deja.com> writes:

> What don't you like about the GNAT scheme, it seems to work
> remarkably well in practice. There is of course no fully
> upwards compatible solution (there are halting problem issues),
> but so what?

I'm not so worried about the case that involve halting problem issues.
That would be an example like:

Package body A says (in elaboration code):

    if <some expression> then
        B.Do_Something;
    end if;

And package body B says (also in elaboration code):

    if <some expression> then
        A.Do_Something;
    end if;

I would be perfectly happy to make examples like that illegal at
link time.

I'm more concerned about a case where two packages 'with' each other,
like the example above, but remove one of those if statements, so it is
provable at link time that only one calls the other during elaboration.
(Also, the Do_Something procedure had better not call back to the other
package.)  Making *that* example illegal is my concern.

- Bob