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From: tmoran@acm.org
Newsgroups: comp.lang.ada
Subject: Re: Problem with intertask comm
References: <3ad5ecf3$0$191$456d72a3@news.skynet.be>
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Date: Thu, 12 Apr 2001 18:38:17 GMT
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Date: 2001-04-12T18:38:17+00:00
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>"The prefix to 'ACCESS shall not be statically deeper than that of the
>expected type, Continuing"
  Consider:
    type Monitor_Data_Pointer is access all Monitor_Data;
    Saved_Away : Monitor_Data pointer;
    procedure p(param: in Monitor_Data_Pointer);
    ...
    declare
      monitor_data_a : aliased Monitor_Data;
      ...
      p(monitor_data_a'access);
      ...
    end;
    Saved_Away.all := Stuff;
and suppose later
    procedure P(Param: in access Monitor_Data) is
    begin
      Saved_Away := Param;
      ...
Stuff will be copied to Saved_Away.all, but Saved_Away.all is
monitor_data_a, which, since we've left the declare block, no
longer exists.  This situation is possible because the prefix
to 'access, namely monitor_data.all, is declared statically
deeper than Saved_Away.  Either monitor_data_a needs to be moved
out of the declare block, to the same level as Saved_Away, or
else "type Monitor_Data_Pointer is access all Monitor_Data;"
needs to be moved down into the declare block, which forces
Saved_Away to be in the declare block and thus safe.