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: 103376,7fd93e3c8a8e5521,start
X-Google-Attributes: gid103376,public
From: mr101@ccsr.cam.ac.uk (Michael Roe)
Subject: Annex E.4, clause 18
Date: 1999/01/29
Message-ID: <78sipr$je1$1@pegasus.csx.cam.ac.uk>#1/1
X-Deja-AN: 438354420
Sender: mr101@kamloops.ccsr.cam.ac.uk (Michael Roe)
Organization: University of Cambridge, England
Newsgroups: comp.lang.ada
Date: 1999-01-29T00:00:00+00:00
List-Id: <comp.lang.ada>

Ok, so I've been bitten by this one too!
 
The LRM says:

"In a remote subprogram call with a formal parameter of a class-wide type,
 a check is made that the tag of the actual parameter identifies a tagged
 type declared in a declared-pure or shared passive library unit, or in
 the visible part of a remote types or remote call interface library unit.
 Program_Error is raised if this check fails."


GNAT 3.11p enforces this check, although earlier versions of GNAT didn't.
This *isn't* a bug in GNAT - the check is clearly required by the LRM.

Unfortunately, enforcing this check breaks a very large number of existing
(incorrect) programs. For example, the Aegis simulation provided as a demo
with Adept violates this. (And quite a few of my programs do too...)

The trouble is, the typical use of RACW types to implement callbacks is
prohibited by this check. Getting aroud the check often involves a radical
restructuring of the entire program, separating packages into two parts so
that the part that declares a RACW type can be declared Remote_Types.

I understand what the LRM *says* - I'm just not sure why it says it!
Particularly as earlier versions of GNAT/GLADE worked without enforcing
it. Do any of the readers of this newsgroup understand the rationale for
it? I can just about imagine why it's there, but I've so far failed to
come up with a coherent explanation of it!

Mike