-- 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;