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Date: Sun, 17 Oct 2021 01:41:15 -0700 (PDT)
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Subject: Re: Is this legal?
From: AdaMagica <christ-usch.grein@t-online.de>
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Xref: reader02.eternal-september.org comp.lang.ada:63026
List-Id: <comp.lang.ada>

> procedure Main is=20
>=20
> subtype str5 is string(1..5);=20
> type s5_ptr is access all str5;=20

Ptr: s5_ptr;

> type T is=20
> record=20
> --current : access str5;=20
> current : s5_ptr; -- "aliased actual has wrong accessibility"=20
> foo : aliased str5;=20
> end record;=20

The accessibility rules are far too complicated and unreadable (I'm not abo=
ut trying to grock them), but the component current has a type that has a l=
ifetime as long as Main. Your object o may be declared in an inner scope wi=
th less lifetime. Thus the assignment must be illegal.

begin
  declare
    o : T :=3D (Acurrent =3D> null, --Ncurrent =3D> null,
             foo =3D> "Hello");
  begin
    P (o);
    --Ptr :=3D o.Ncurrent;  -- global point to disappearing object
    Ptr :=3D o.Acurrent;  -- global point to disappearing object
  end;
  put_line(Ptr.all);  -- prints Hello
end Main;

But it occurs to me that GNAT CE 2021 has a problem here. (Comment out all =
occurrences of Ncurrent.)