-- C3A2003.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 the case where X is -- an access parameter and the corresponding actual is another access -- parameter. -- -- 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 an 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 another access parameter, -- and the actual corresponding to this second access parameter is: -- -- (1) 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. -- -- (2) 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; -- . . . -- procedure Q (Y: access T) is -- begin -- P(Y); -- end; -- . . . -- declare -- Actual : aliased T; -- Static level = 3, e.g. -- begin -- Q (Actual'Access); -- end; -- -- For the execution of Q (and hence 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 -- 15 Jul 98 EDS Avoid optimization. -- 28 Jun 02 RLB Added pragma Elaborate_All (Report);. --! with report; use report; pragma Elaborate_All (report); package C3A2003_0 is type Desig is array (1 .. 10) of Integer; X0 : aliased Desig := (Desig'Range => Ident_Int(3)); -- 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_Nest (Y: access Desig; S: out Result_Kind); procedure Never_Fails_Nest (Y: access Desig; S: out Result_Kind); procedure Never_Fails_Same (Y: access Desig; S: out Result_Kind); end C3A2003_0; --==================================================================-- package body C3A2003_0 is procedure Target_Is_Level_0_Nest (Y: access Desig; S: out Result_Kind) is -- This procedure utilizes 'Access on a dereference of an access -- parameter, and assigned to an access object whose type A is -- declared at some nesting level. Program_Error is raised if -- the accessibility level of the operand type is deeper than that -- of the target type. procedure Nested (X: access Desig; R: out Result_Kind) is -- Dereference of an access_to_object value is aliased. Ren : Desig renames X.all; -- Renaming of a dereference begin -- of an access parameter. -- The accessibility level of type A0 is 0. A0 := Ren'Access; R := OK; exception when Program_Error => R := P_E; when others => R := O_E; end Nested; begin -- Target_Is_Level_0_Nest Nested (Y, S); end Target_Is_Level_0_Nest; ------------------------------------------------------------------ procedure Never_Fails_Nest (Y: access Desig; S: out Result_Kind) is type Acc_Deeper is access all Desig; AD : Acc_Deeper; function Nested (X: access Desig) return Result_Kind is begin -- X.all'Access below will always be safe, since the accessibility -- level (although not necessarily the static nesting depth) of the -- type of AD will always be deeper than or the same as that of the -- actual corresponding to Y. AD := X.all'Access; if Ident_Int (AD(4)) /= 3 then --Avoid Optimization of AD FAILED ("Initial Values not correct."); end if; return OK; exception when Program_Error => return P_E; when others => return O_E; end Nested; begin -- Never_Fails_Nest S := Nested (Y); end Never_Fails_Nest; ------------------------------------------------------------------ procedure Called_By_Never_Fails_Same (X: access Desig; R: out Result_Kind) is type Acc_Local is access all Desig; AL : Acc_Local; -- Dereference of an access_to_object value is aliased. Ren : Desig renames X.all; -- Renaming of a dereference begin -- of an access parameter. -- Ren'Access below will always be safe, since the accessibility -- level (although not necessarily the static nesting depth) of -- type of AL will always be deeper than or the same as that of the -- actual corresponding to Y. AL := Ren'Access; if Ident_Int (AL(4)) /= 3 then --Avoid Optimization of AL FAILED ("Initial Values not correct."); end if; R := OK; exception when Program_Error => R := P_E; when others => R := O_E; end Called_By_Never_Fails_Same; ------------------------------------------------------------------ procedure Never_Fails_Same (Y: access Desig; S: out Result_Kind) is begin Called_By_Never_Fails_Same (Y, S); end Never_Fails_Same; end C3A2003_0; --==================================================================-- with C3A2003_0; use C3A2003_0; with Report; use report; procedure C3A2003 is type Acc_L1 is access all Desig; -- Level = 1. A1 : Acc_L1; X1 : aliased Desig := (Desig'Range => Ident_Int(3)); Res : Result_Kind; procedure Called_By_Target_L1 (X: access Desig; R: out Result_Kind) is begin -- The accessibility level of the type of A1 is 1. A1 := X.all'Access; if IDENT_INT (A1(4)) /= 3 then --Avoid optimization of A1 FAILED ("Initial values not correct."); end if; R := OK; exception when Program_Error => R := P_E; when others => R := O_E; end Called_By_Target_L1; ------------------------------------------------------------------ function Target_Is_Level_1_Same (Y: access Desig) return Result_Kind is S : Result_Kind; begin Called_By_Target_L1 (Y, S); return S; end Target_Is_Level_1_Same; ------------------------------------------------------------------ procedure Display_Results (Result : in Result_Kind; Expected: in Result_Kind; Msg : in String) is begin if Result /= Expected then case Result is when OK => Report.Failed ("No exception raised: " & Msg); when P_E => Report.Failed ("Program_Error raised: " & Msg); when O_E => Report.Failed ("Unexpected exception raised: " & Msg); end case; end if; end Display_Results; begin -- C3A2003 Report.Test ("C3A2003", "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 another access " & "parameter"); -- Accessibility level of actual is 0 (actual is X'Access): Never_Fails_Same (X0'Access, Res); Display_Results (Res, OK, "Never_Fails_Same, level 0 actual"); Never_Fails_Nest (X0'Access, Res); Display_Results (Res, OK, "Target_L1_Nest, level 0 actual"); Target_Is_Level_0_Nest (X0'Access, Res); Display_Results (Res, OK, "Target_L0_Nest, level 0 actual"); Res := Target_Is_Level_1_Same (X0'Access); Display_Results (Res, OK, "Target_L1_Same, level 0 actual"); -- Accessibility level of actual is 1 (actual is X'Access): Never_Fails_Same (X1'Access, Res); Display_Results (Res, OK, "Never_Fails_Same, level 1 actual"); Never_Fails_Nest (X1'Access, Res); Display_Results (Res, OK, "Target_L1_Nest, level 1 actual"); Target_Is_Level_0_Nest (X1'Access, Res); Display_Results (Res, P_E, "Target_L0_Nest, level 1 actual"); Res := Target_Is_Level_1_Same (X1'Access); Display_Results (Res, OK, "Target_L1_Same, level 1 actual"); Block_L2: declare X2 : aliased Desig := (Desig'Range => Ident_Int(3)); type Acc_L2 is access all Desig; -- Level = 2. Expr_L2 : Acc_L2 := X2'Access; begin -- Accessibility level of actual is 2 (actual is expression of named -- access type): Never_Fails_Same (Expr_L2, Res); Display_Results (Res, OK, "Never_Fails_Same, level 2 actual"); Never_Fails_Nest (Expr_L2, Res); Display_Results (Res, OK, "Target_L1_Nest, level 2 actual"); Target_Is_Level_0_Nest (Expr_L2, Res); Display_Results (Res, P_E, "Target_L0_Nest, level 2 actual"); Res := Target_Is_Level_1_Same (Expr_L2); Display_Results (Res, P_E, "Target_L1_Same, level 2 actual"); end Block_L2; Report.Result; end C3A2003;