c460001.a

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-- C460001.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 if the target type of a type conversion is a general
--      access type, Program_Error is raised if the accessibility level
--      of the operand type is deeper than that of the target type.
--      Check for the case where the operand is an access parameter.
--      
--      Check for cases where the actual corresponding to the access
--      parameter is:
--         (a) An allocator.
--         (b) An expression of a named access type.
--         (c) Obj'Access.
--      
-- TEST DESCRIPTION:
--      In order to satisfy accessibility requirements, the operand type
--      must be at the same or a less deep nesting level than the target
--      type -- the operand type must "live" as long as the target type.
--      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
--      a type conversion is attempted on the access parameter to an access
--      type A 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 target type -- 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 := A(X);          -- 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, the
--         type conversion 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 C460001_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 Target_Is_Level_0 (X: access Desig; R : out Result_Kind);
   procedure Never_Fails       (X: access Desig; R : out Result_Kind);

end C460001_0;


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


package body C460001_0 is

   procedure Target_Is_Level_0 (X : access Desig;
                                R : out Result_Kind) is
   begin
      -- The accessibility level of type Acc_L0 is 0.
      A0 := Acc_L0(X);
      R  := OK;
   exception
      when Program_Error =>    
         R := P_E;
      when others        =>    
         R := O_E;
   end Target_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
      -- The type conversion below will always be safe, since the
      -- accessibility level (although not necessarily the static nesting
      -- depth) of Acc_Local will always be deeper than or the same as that 
      -- of the actual corresponding to X. 
      AL := Acc_Local(X);
      R  := OK;
   exception
      when Program_Error =>    
         R := P_E;
      when others        =>    
         R := O_E;
   end Never_Fails;

end C460001_0;


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


with C460001_0;
with Report;

procedure C460001 is

   X1 : aliased C460001_0.Desig;                                  -- Level = 1.

   type Acc_L1 is access all C460001_0.Desig;                     -- Level = 1.
   A1 : Acc_L1;

   Expr_L0 : C460001_0.Acc_L0 := C460001_0.X0'Access;
   Expr_L1 : Acc_L1           := X1'Access;

   Res : C460001_0.Result_Kind;

   use type C460001_0.Result_Kind;

   -----------------------------------------------
   procedure Target_Is_Level_1 (X : access C460001_0.Desig;
                                R : out C460001_0.Result_Kind) is
   begin
      -- The accessibility level of type Acc_L1 is 1.
      A1 := Acc_L1(X);
      R  := C460001_0.OK;
   exception
      when Program_Error =>    
         R := C460001_0.P_E;
      when others        =>    
         R := C460001_0.O_E;
   end Target_Is_Level_1;

   -----------------------------------------------
   procedure Display_Results (Result  : in C460001_0.Result_Kind;
                              Expected: in C460001_0.Result_Kind;
                              Message : in String) is
   begin
      if Result /= Expected then
         case Result is
            when C460001_0.OK  => Report.Failed ("No exception raised: "  & 
                                                 Message);
            when C460001_0.P_E => Report.Failed ("Program_Error raised: " & 
                                                 Message);
            when C460001_0.O_E => Report.Failed ("Unexpected exception "  &
                                                 "raised: " & Message);
         end case;
      end if;
   end Display_Results;

begin -- C460001

   Report.Test ("C460001", "Check that if the target type of a type "      &
                "conversion is a general access type, Program_Error is "   &
                "raised if the accessibility level of the operand type "   &
                "is deeper than that of the target type: operand is an "   &
                "access parameter; corresponding actual is an allocator, " &
                "expression of a named access type, Obj'Access");


   -- Actual is X'Access:

   C460001_0.Never_Fails (X1'Access, Res);
   Display_Results (Res, C460001_0.OK, "X1'Access, local access type");

   C460001_0.Target_Is_Level_0 (X1'Access, Res);
   Display_Results (Res, C460001_0.P_E, "X1'Access, level 0 access type");

   Target_Is_Level_1 (C460001_0.X0'Access, Res);
   Display_Results (Res, C460001_0.OK, "X0'Access, level 1 access type");

   Target_Is_Level_1 (X1'Access, Res);
   Display_Results (Res, C460001_0.OK, "X1'Access, level 1 access type");

   C460001_0.Target_Is_Level_0 (C460001_0.X0'Access, Res);
   Display_Results (Res, C460001_0.OK, "X0'Access, level 0 access type");


   -- Actual is expression of a named access type:

   C460001_0.Never_Fails (Expr_L0, Res);
   Display_Results (Res, C460001_0.OK, "Expr_L0, local access type");

   C460001_0.Target_Is_Level_0 (Expr_L0, Res);
   Display_Results (Res, C460001_0.OK, "Expr_L0, level 0 access type");

   C460001_0.Target_Is_Level_0 (Expr_L1, Res);
   Display_Results (Res, C460001_0.P_E, "Expr_L1, level 0 access type");

   Target_Is_Level_1 (Expr_L1, Res);
   Display_Results (Res, C460001_0.OK, "Expr_L1, level 1 access type");

   Target_Is_Level_1 (Expr_L0, Res);
   Display_Results (Res, C460001_0.OK, "Expr_L0, level 1 access type");

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

   C460001_0.Never_Fails (new C460001_0.Desig, Res);
   Display_Results (Res, C460001_0.OK, "Allocator level 2, " &
                                       "local access type");

   C460001_0.Target_Is_Level_0 (new C460001_0.Desig, Res);
   Display_Results (Res, C460001_0.P_E, "Allocator level 2, " &
                                        "level 0 access type");

   Target_Is_Level_1 (new C460001_0.Desig, Res);
   Display_Results (Res, C460001_0.P_E, "Allocator level 2, " &
                                        "level 1 access type");


   Block_L2:
   declare
      X2 : aliased C460001_0.Desig;                               -- Level = 2.
      type Acc_L2 is access all C460001_0.Desig;                  -- Level = 2.
      Expr_L2 : Acc_L2 := X1'Access;
   begin

      -- Actual is X'Access:

      C460001_0.Never_Fails (X2'Access, Res);
      Display_Results (Res, C460001_0.OK, "X2'Access, local access type");

      Target_Is_Level_1 (X2'Access, Res);
      Display_Results (Res, C460001_0.P_E, "X2'Access, level 1 access type");

      -- Actual is expression of a named access type:

      C460001_0.Never_Fails (Expr_L2, Res);
      Display_Results (Res, C460001_0.OK, "Expr_L2, local access type");

      C460001_0.Target_Is_Level_0 (Expr_L2, Res);
      Display_Results (Res, C460001_0.P_E, "Expr_L2, level 0 access type");


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

      C460001_0.Never_Fails (new C460001_0.Desig, Res);
      Display_Results (Res, C460001_0.OK, "Allocator level 3, " &
                                          "local access type");

      Target_Is_Level_1 (new C460001_0.Desig, Res);
      Display_Results (Res, C460001_0.P_E, "Allocator level 3, " &
                                           "level 1 access type");

   end Block_L2;

   Report.Result;

end C460001;