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-- C3A2002.A

--

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--     Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,

--     F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained

--     unlimited rights in the software and documentation contained herein.

--     Unlimited rights are defined in DFAR 252.227-7013(a)(19).  By making

--     this public release, the Government intends to confer upon all

--     recipients unlimited rights  equal to those held by the Government.

--     These rights include rights to use, duplicate, release or disclose the

--     released technical data and computer software in whole or in part, in

--     any manner and for any purpose whatsoever, and to have or permit others

--     to do so.

--

--                                    DISCLAIMER

--

--     ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR

--     DISCLOSED ARE AS IS.  THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED

--     WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE

--     SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE

--     OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A

--     PARTICULAR PURPOSE OF SAID MATERIAL.

--*

--

-- OBJECTIVE:

--      Check that, for X'Access of a general access type A, Program_Error is

--      raised if the accessibility level of X is deeper than that of A.

--      Check for the case where X denotes a view that is a dereference of an

--      access parameter, or a rename thereof.

--

--      Check for cases where the actual corresponding to X is:

--         (a) An allocator.

--         (b) An expression of a named access type.

--         (c) Obj'Access.

--

-- TEST DESCRIPTION:

--      In order to satisfy accessibility requirements, the designated

--      object X must be at the same or a less deep nesting level than the

--      general access type A -- X must "live" as long as A. Nesting

--      levels are the run-time nestings of masters: block statements;

--      subprogram, task, and entry bodies; and accept statements. Packages

--      are invisible to accessibility rules.

--

--      This test declares subprograms with access parameters, within which

--      'Access is attempted on a dereference of the access parameter, and

--      assigned to an access object whose type A is declared at some nesting

--      level. The test verifies that Program_Error is raised if the actual

--      corresponding to the access parameter is:

--

--         (1) an allocator, and the accessibility level of the execution

--             of the called subprogram is deeper than that of the access

--             type A.

--

--         (2) an expression of a named access type, and the accessibility

--             level of the named access type is deeper than that of the

--             access type A.

--

--         (3) a reference to the Access attribute (e.g., X'Access), and

--             the accessibility level of X is deeper than that of the

--             access type A.

--

--      Note that the static nesting level of the actual corresponding to the

--      access parameter can be deeper than that of the type A -- it is

--      the run-time nesting that matters for accessibility rules. Consider

--      the case where the access type A is declared within the called

--      subprogram. The accessibility check will never fail, even if the

--      actual happens to have a deeper static nesting level:

--

--         procedure P (X: access T) is

--            type A is access all T;   -- Static level = 2, e.g.

--            Acc : A := X.all'Access;  -- Check should never fail.

--         begin null; end;

--         . . .

--         declare

--            Actual : aliased T;       -- Static level = 3, e.g.

--         begin

--            P (Actual'Access);

--         end;

--

--         For the execution of P, the accessibility level of type A will

--         always be deeper than that of Actual, so there is no danger of a

--         dangling reference arising from the assignment to Acc. Thus,

--         X.all'Access is safe, even though the static nesting level of

--         Actual is deeper than that of A.

--

--

-- CHANGE HISTORY:

--      06 Dec 94   SAIC    ACVC 2.0

--

--!

package C3A2002_0 is

   type Desig is array (1 .. 10) of Integer;

   X0 : aliased Desig;                                            -- Level = 0.

   type Acc_L0 is access all Desig;                               -- Level = 0.

   A0 : Acc_L0;

   type Result_Kind is (OK, P_E, O_E);

   procedure A_Is_Level_0 (X: access Desig; R : out Result_Kind);

   procedure Never_Fails  (X: access Desig; R : out Result_Kind);

end C3A2002_0;

     --==================================================================--

package body C3A2002_0 is

   procedure A_Is_Level_0 (X : access Desig;

                           R : out Result_Kind) is

   begin

      -- The accessibility level of the type of A0 is 0.

      A0 := X.all'Access;

      R  := OK;

   exception

      when Program_Error =>

         R := P_E;

      when others        =>

         R := O_E;

   end A_Is_Level_0;

   -----------------------------------------------

   procedure Never_Fails (X: access Desig;

                          R : out Result_Kind) is

      type Acc_Local is access all Desig;

      AL : Acc_Local;

   begin

      -- X.all'Access below will always be safe, since the accessibility

      -- level (although not necessarily the static nesting depth) of the

      -- type of AL will always be deeper than or the same as that of the

      -- actual corresponding to Y.

      AL := X.all'Access;

      R  := OK;

   exception

      when Program_Error =>

         R := P_E;

      when others        =>

         R := O_E;

   end Never_Fails;

end C3A2002_0;

     --==================================================================--

with C3A2002_0;

with Report;

procedure C3A2002 is

   X1 : aliased C3A2002_0.Desig;                                  -- Level = 1.

   type Acc_L1 is access all C3A2002_0.Desig;                     -- Level = 1.

   A1 : Acc_L1;

   Expr_L0 : C3A2002_0.Acc_L0 := C3A2002_0.X0'Access;

   Expr_L1 : Acc_L1           := X1'Access;

   Res : C3A2002_0.Result_Kind;

   use type C3A2002_0.Result_Kind;

   -----------------------------------------------

   procedure A_Is_Level_1 (X : access C3A2002_0.Desig;

                           R : out C3A2002_0.Result_Kind) is

      -- Dereference of an access_to_object value is aliased.

      Ren : C3A2002_0.Desig renames X.all;      -- Renaming of a dereference

   begin                                        -- of an access parameter.

      -- The accessibility level of the type of A1 is 1.

      A1 := Ren'Access;

      R  := C3A2002_0.OK;

   exception

      when Program_Error =>

         R := C3A2002_0.P_E;

      when others        =>

         R := C3A2002_0.O_E;

   end A_Is_Level_1;

   -----------------------------------------------

   procedure Display_Results (Result  : in C3A2002_0.Result_Kind;

                              Expected: in C3A2002_0.Result_Kind;

                              Message : in String) is

   begin

      if Result /= Expected then

         case Result is

            when C3A2002_0.OK  => Report.Failed ("No exception raised: "  &

                                                 Message);

            when C3A2002_0.P_E => Report.Failed ("Program_Error raised: " &

                                                 Message);

            when C3A2002_0.O_E => Report.Failed ("Unexpected exception "  &

                                                 "raised: " & Message);

         end case;

      end if;

   end Display_Results;

begin -- C3A2002

   Report.Test ("C3A2002", "Check that, for X'Access of general access "   &

                "type A, Program_Error is raised if the accessibility "    &

                "level of X is deeper than that of A: X is an access "     &

                "parameter; corresponding actual is an allocator, "        &

                "expression of a named access type, Obj'Access, or a "     &

                "rename thereof");

   -- Actual is X'Access:

   C3A2002_0.Never_Fails (C3A2002_0.X0'Access, Res);

   Display_Results (Res, C3A2002_0.OK, "X0'Access, local access type");

   C3A2002_0.A_Is_Level_0 (C3A2002_0.X0'Access, Res);

   Display_Results (Res, C3A2002_0.OK, "X0'Access, level 0 access type");

   C3A2002_0.A_Is_Level_0 (X1'Access, Res);

   Display_Results (Res, C3A2002_0.P_E, "X1'Access, level 0 access type");

   A_Is_Level_1 (X1'Access, Res);

   Display_Results (Res, C3A2002_0.OK, "X1'Access, level 1 access type");

   -- Actual is expression of a named access type:

   C3A2002_0.Never_Fails (Expr_L1, Res);

   Display_Results (Res, C3A2002_0.OK, "Expr_L1, local access type");

   C3A2002_0.A_Is_Level_0 (Expr_L1, Res);

   Display_Results (Res, C3A2002_0.P_E, "Expr_L1, level 0 access type");

   A_Is_Level_1 (Expr_L0, Res);

   Display_Results (Res, C3A2002_0.OK, "Expr_L0, level 1 access type");

   A_Is_Level_1 (Expr_L1, Res);

   Display_Results (Res, C3A2002_0.OK, "Expr_L1, level 1 access type");

   -- Actual is allocator (level of execution = 2):

   C3A2002_0.Never_Fails (new C3A2002_0.Desig, Res);

   Display_Results (Res, C3A2002_0.OK, "Allocator level 2, " &

                                       "local access type");

   -- Since actual is an allocator, its accessibility level is that of

   -- the execution of the called subprogram, i.e., level 2.

   C3A2002_0.A_Is_Level_0 (new C3A2002_0.Desig, Res);

   Display_Results (Res, C3A2002_0.P_E, "Allocator level 2, " &

                                        "level 0 access type");

   A_Is_Level_1 (new C3A2002_0.Desig, Res);

   Display_Results (Res, C3A2002_0.P_E, "Allocator level 2, " &

                                        "level 1 access type");

   Block_L2:

   declare

      X2 : aliased C3A2002_0.Desig;                               -- Level = 2.

      type Acc_L2 is access all C3A2002_0.Desig;                  -- Level = 2.

      Expr_L2 : Acc_L2 := X1'Access;

   begin

      -- Actual is X'Access:

      C3A2002_0.Never_Fails (X2'Access, Res);

      Display_Results (Res, C3A2002_0.OK, "X2'Access, local access type");

      C3A2002_0.A_Is_Level_0 (X2'Access, Res);

      Display_Results (Res, C3A2002_0.P_E, "X2'Access, level 0 access type");

      -- Actual is expression of a named access type:

      A_Is_Level_1 (Expr_L2, Res);

      Display_Results (Res, C3A2002_0.P_E, "Expr_L2, level 1 access type");

      -- Actual is allocator (level of execution = 3):

      C3A2002_0.Never_Fails (new C3A2002_0.Desig, Res);

      Display_Results (Res, C3A2002_0.OK, "Allocator level 3, " &

                                          "local access type");

      A_Is_Level_1 (new C3A2002_0.Desig, Res);

      Display_Results (Res, C3A2002_0.P_E, "Allocator level 3, " &

                                           "level 1 access type");

   end Block_L2;

   Report.Result;

end C3A2002;