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,FREEMAIL_FROM
	autolearn=unavailable autolearn_force=no version=3.4.4
X-Received: by 10.224.137.137 with SMTP id w9mr46477568qat.6.1375068446908;
        Sun, 28 Jul 2013 20:27:26 -0700 (PDT)
X-Received: by 10.50.101.110 with SMTP id ff14mr363170igb.9.1375068446874;
 Sun, 28 Jul 2013 20:27:26 -0700 (PDT)
Path: 
 eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!news.eternal-september.org!news.eternal-september.org!news.eternal-september.org!feeder.eternal-september.org!usenet.blueworldhosting.com!feeder02.blueworldhosting.com!npeer01.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!cb17no999449qab.0!news-out.google.com!ce7ni0qab.0!nntp.google.com!cb17no999447qab.0!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail
Newsgroups: comp.lang.ada
Date: Sun, 28 Jul 2013 20:27:26 -0700 (PDT)
In-Reply-To: <kt47f2$1vca$1@adenine.netfront.net>
Complaints-To: groups-abuse@google.com
Injection-Info: glegroupsg2000goo.googlegroups.com;
 posting-host=69.20.190.126;
 posting-account=lJ3JNwoAAAAQfH3VV9vttJLkThaxtTfC
NNTP-Posting-Host: 69.20.190.126
References: <kt3d9j$vmp$1@adenine.netfront.net>
 <15i0rfwzpj7cy$.ob5l4ffr5iqa$.dlg@40tude.net>
 <kt3q27$18qs$1@adenine.netfront.net>
 <559b2a61-4e5e-4adf-a228-30506d255b08@googlegroups.com>
 <kt47f2$1vca$1@adenine.netfront.net>
User-Agent: G2/1.0
MIME-Version: 1.0
Message-ID: <30a1a22b-a003-4be5-a7c6-4fd5742d17fc@googlegroups.com>
Subject: Re: System.Address to Access to function/procedure conversion
From: Shark8 <onewingedshark@gmail.com>
Injection-Date: Mon, 29 Jul 2013 03:27:26 +0000
Content-Type: text/plain; charset=ISO-8859-1
X-Received-Bytes: 3348
Xref: news.eternal-september.org comp.lang.ada:16595
Date: 2013-07-28T20:27:26-07:00
List-Id: <comp.lang.ada>

On Sunday, July 28, 2013 4:54:27 PM UTC-6, Tarek Ghaleb wrote:
> On 2013-07-28, Shark8 wrote:
> 
> >> I agree completely. Using C convention is the way to do it. But is it
> >> *possible* to call a function using its address? (even if not a such a
> >> great idea)
> 
> > Yes. It's actually absurdly easy. Here's a sample of how to do it in
> > Ada 2012, the same will work in earliet versions of Ada using
> > Pargmas... all the way back to 83, IIUC.

Oops; a little overzealous there.
You have to use attribute definition clauses, which IIRC came in Ada 95.
Below compiles and runs in GNAT using Ada83-mode:

--  Pragma Ada_2012;
Pragma Ada_83;
Pragma Assertion_Policy( Check );

With
Text_IO,
System;

Procedure Test is

Begin
    Text_IO.Put_Line("Starting Test:");


    ACTUAL_TEST:
    declare

	-- Note: Pragma CONVENTION is non-standard.
	Procedure K;
	Pragma Convention( C, K );
	
	Procedure K is
	begin
	    Text_IO.Put_Line( "K was called" );
	end K;
	
	Procedure Execute( Addr : System.Address ) is
	    -- Note: Pragma IMPORT is non-standard.
	    Procedure Stub;
	    Pragma Import( C, Stub );

	    -- Note: The Ada 83 LRM, 13.5 (Address Clauses) gives the following:
	    --         for CONTROL use at 16#0020#; -- assuming that SYSTEM.ADDRESS is an integer
	    --   with the following warning:
	    --    Address clauses should not be used to achieve overlays of
	    --    objects or overlays of program units. Nor should a given
	    --    interrupt be linked to more than one entry. Any program using
	    --    address clauses to achieve such effects is erroneous.      
	    --
	    --  In Ada 95 we get propper Attribute Definition Clauses and so
	    --  we would use the following:
	    --    For Stub'Address Use Addr;
	    For Stub use at Addr;

	    Use Text_IO;
	Begin
	    Put_Line( "Executing:" );
	    Put( ASCII.HT );
	    Stub;
	End Execute;
	
    begin
	Execute( K'Address );
    end ACTUAL_TEST;
    
    
    Text_IO.Put_Line("Testing complete.");
End Test;