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From: Rod Kay <rod.kay@aulace.com>
Newsgroups: comp.lang.ada
Subject: Problem where a function is invoked once but called twice (when
 invocation is within an allocator).
Date: Wed, 4 May 2011 20:52:06 -0700 (PDT)
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Date: 2011-05-04T20:52:06-07:00
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hi,

   Any clues on why the use of an allocator would cause a single
function invocation to be called twice ?


   the_Movie : media.Video.view := new_Movie;

   the_next_Frame :              openGL.Image :=
the_Movie.next_Frame;                                        -- case 1
   the_next_Frame : access openGL.Image := new
opengl.Image' (the_Movie.next_Frame);   -- case 2

   In the 1st case, the 'next_Frame' function is called once.
   In the 2nd case, it is called twice.


   'the_Movie' is an access to an object of tagged type
'media.Video.item'.

   package media.Video is
      type Item is tagged limited private;
      type View is access all Item;
      ...
      function  next_Frame  (Self : access Item) return opengl.Image;
      ...
   end media.Video;



   'opengl.Image' is an array with two unconstrained indices ...

   package openGL is
      ...
      type Image is array (Index_t range <>, Index_t range <>) of
Color;
   end openGL;



   In case it matters, the 'next_Frame' function contains a rendezvous
with a decoder task.
   The decoder task is a component of the 'media.Video.item' record.



regards,
Rod.