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From: Jacob Sparre Andersen <jacob@jacob-sparre.dk>
Newsgroups: comp.lang.ada
Subject: Validity of renamed objects?
Date: Tue, 01 Apr 2014 15:04:58 +0200
Organization: Jacob Sparre Andersen Research & Innovation
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Date: 2014-04-01T15:04:58+02:00
List-Id: <comp.lang.ada>

I've been reading section 8.5.1 in the LRM, and I can't figure out when
the compiler is supposed to check the validity of a renamed object.

An example:

procedure Renaming_1 is
   Object  : String (1 .. 9) := "dead beef";
   Index   : Natural := 0;
   Renamed : Character renames Object (Index);
begin
   Index := (Object'First + Object'Last) / 2;
   if Renamed /= ' ' then
      raise Program_Error
        with "Expected Renamed to match the changed value of Index.";
   end if;
end Renaming_1;

1) Should I get a Constraint_Error when Renamed is declared?

2) What will the value of Renamed be after Index has been changed?

Greetings,

Jacob

PS: I know what the version of GNAT I have at hand does, but what it
    does is not completely obvious from my reading of the LRM.
-- 
»But you have to be a bit wary of a ship that collects
 snowflakes.«                                  -- Diziet Sma