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From: Simon Wright <simon@pogner.demon.co.uk>
Subject: Re: Freeing Pointers to classwide types
Date: 1998/09/26
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Date: 1998-09-26T00:00:00+00:00
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If you have said

  type Event is <some tagged type>
  type Event_P is access Event'Class;

then you need to say

  procedure Delete is new Unchecked_Deallocation (Event'Class, Event_P);
                                                       ^^^^^^
because we have (from GNAT's source)

generic
   type Object (<>) is limited private;
   type Name is access Object;
procedure Unchecked_Deallocation (X : in out Name);

so you fill in the blanks from the declaration of type Event_P.

It took me ages to find this answer when I first had the problem!