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From: sbelmont700@gmail.com
Newsgroups: comp.lang.ada
Subject: A Gnother Gnasty bug
Date: Fri, 6 Apr 2012 17:44:30 -0700 (PDT)
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Date: 2012-04-06T17:44:30-07:00
List-Id: <comp.lang.ada>

Hi everyone,

I've stumbled across another dubious GNAT GPL 2011 situation, yet this one =
is convoluted enough to perhaps be mistaken thinking on my part, so I would=
 be appreciative of any independent tests before I submit it.  Additionally=
, I would like to try to describe it using the rich Ada lexicon, so please =
check me on that as well:

"When an object of a limited record type containing an object of a non-limi=
ted controlled record type which contains an access value to a classwide ty=
pe is created from a value-returning function whose argument is supplied fr=
om another value-returning function whose argument is supplied from a class=
wide allocator, a constraint error is raised."

It's clearly an edge case, and would not surprise me if it is related to a =
different bug where allocating a classwide type mangles the dispatch table,=
 but as this behavior is different in that an exception is raised instead o=
f erroneous execution, perhaps it's something else entirely, or maybe even =
doing what it's supposed to do (in which case please explain it to me).

A small test procedure that demonstrates this behavior is as follows:

with Ada.Finalization;

procedure test is

  type I is limited interface;
 =20
  type I_Ptr is access I'class;
 =20
  type C is new Ada.Finalization.Limited_Controlled and I with
    record
      d : integer;
    end record;
 =20
  function F (arg : Integer) return I'class is
  begin
    return C'(Ada.Finalization.Limited_Controlled with d =3D> arg);
  end F;

 =20
  type K is new Ada.Finalization.Controlled with
    record
      e : I_Ptr;
    end record;
 =20
  function G (p_i : I_Ptr) return K is
  begin
    return K'(Ada.Finalization.Controlled with e =3D> p_i);
  end G;
 =20
  type J is limited record
    h : K;
  end record;
 =20
  function H (arg : K) return J is
  begin
    return J'(h =3D> arg);
  end H;
 =20
  x : J :=3D H(arg =3D>
               G(p_i =3D>=20
                  I_Ptr'(new I'class'(F(arg=3D> 42)))));

begin

   null;

end test;