c3a2002.a

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-- C3A2002.A
--
--                             Grant of Unlimited Rights
--
--     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;