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From: stt@houdini.camb.inmet.com (Tucker Taft)
Subject: Re: Definition of "aliased"
Date: 1998/10/26
Message-ID: <F1FzzC.MK8.0.-s@inmet.camb.inmet.com>#1/1
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References: <m37lxo6pii.fsf@mheaney.ni.net>
Organization: Intermetrics, Inc.
Newsgroups: comp.lang.ada
Date: 1998-10-26T00:00:00+00:00
List-Id: <comp.lang.ada>

Matthew Heaney (matthew_heaney@acm.org) wrote:

: What is the definition of "aliased"?  I thought
: --per RM95 3.10 (9)-- that the "current instance" of a limited type was
: defined to be aliased.

: Yet when I try to compile this code fragment...

You seem to have run into a compiler bug.  Our Ada 95
front end has no problem with the following code.

: package P is
:    type T is tagged limited private;
: private
:    function Op (O : access T) return Integer;
:    type T is
:       tagged limited record
:          I : Integer := Op (T'Access);
:       end record;
: end P;


: with P;
: procedure Test_P is
:    O : P.T;
: begin
:    null;
: end;

: ...my compiler is telling me that

: (start of message)
: $ gnatmake test_p
: gcc -c test_p.adb
: p.ads:7:29: prefix of "Access" attribute must be aliased
: gnatmake: "test_p.adb" compilation error
: (end of message)

: The behavior of function Op appears to be no different from Initialize
: for a Controlled type.  What's the difference?

: I was trying to do some non-trivial default initialization for objects
: of the type, without deriving from Controlled and overriding
: Initialize.  The latter approach seems like too heavy a solution.

Perhaps it is time to file a bug report... (or experiment with
additional compilers ;-).

: Thanks,
: Matt

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