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=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Thread: 103376,b9edf26d62bf8739
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Received: by 10.68.223.40 with SMTP id qr8mr9803673pbc.0.1338305912718;
        Tue, 29 May 2012 08:38:32 -0700 (PDT)
Path: 
 pr3ni62706pbb.0!nntp.google.com!news1.google.com!goblin1!goblin.stu.neva.ru!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail
From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: "duplicated external tag"
Date: Tue, 29 May 2012 16:38:31 +0100
Organization: A noiseless patient Spider
Message-ID: <m2k3zvt2tk.fsf@pushface.org>
References: <8f40f59a-0086-4065-a984-6c834114f69e@3g2000vbx.googlegroups.com>
Mime-Version: 1.0
Injection-Info: mx04.eternal-september.org;
 posting-host="IlSPLpZ1axUqMIpgfl65wA";
	logging-data="1024"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX1+X35+2mmSjrbnkGrtCQAF3j1vc6iq+SEk="
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (darwin)
Cancel-Lock: sha1:ZQfJEFGzf/WtD+IiuTcsZO5v0m4=
	sha1:Ve2icIU1tOLptio5SdSBtlBddeE=
Content-Type: text/plain; charset=us-ascii
Date: 2012-05-29T16:38:31+01:00
List-Id: <comp.lang.ada>

Anders Jansson <proara2@gmail.com> writes:

> I have a application that explicitly loads other Ada-Dll's (built as
> relocatables with GPR files and gprbuild) in GNAT 6.5.0.

Given that version of GNAT, I'd have thought you could get an answer
from AdaCore?

> When I try to load the same Dll the second time, Ada Elab generates
> exception "Program Error" with message "duplicated external tag"!
> I have tried to move all "tagged" types away from the visible/exported
> side of the Dll's, so it just have the entry points needed. I use
> a .def file to limit the visible entry points.
> And these entry points are only 5 procedures/functions!
> So here's the question!
> Is there any way to supress the elaboration checks on "tagged" types,
> so that I can load as many Dll's as needed?
> Or can this be done in anyother way?

>From a position of some ignorance, I would have thought you should put
the offending tagged types into DLLs of their own, so that each DLL only
gets loaded once.

In GCC 4.7.0, a-tags.adb has the comment

      --  Verify that the external tag of this TSD is not registered in
      --  the runtime hash table.

(TSD is "type-specific data"), and I guess the "runtime hash table" is
in the Ada RTS and shared by all DLLs, hence your problem.

debug.adb says that the compiler flag -gnatdQ suppresses the runtime
check.