1-- C3A2002.A
2--
3--                             Grant of Unlimited Rights
4--
5--     Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,
6--     F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained
7--     unlimited rights in the software and documentation contained herein.
8--     Unlimited rights are defined in DFAR 252.227-7013(a)(19).  By making
9--     this public release, the Government intends to confer upon all
10--     recipients unlimited rights  equal to those held by the Government.
11--     These rights include rights to use, duplicate, release or disclose the
12--     released technical data and computer software in whole or in part, in
13--     any manner and for any purpose whatsoever, and to have or permit others
14--     to do so.
15--
16--                                    DISCLAIMER
17--
18--     ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR
19--     DISCLOSED ARE AS IS.  THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED
20--     WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE
21--     SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE
22--     OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A
23--     PARTICULAR PURPOSE OF SAID MATERIAL.
24--*
25--
26-- OBJECTIVE:
27--      Check that, for X'Access of a general access type A, Program_Error is
28--      raised if the accessibility level of X is deeper than that of A.
29--      Check for the case where X denotes a view that is a dereference of an
30--      access parameter, or a rename thereof.
31--
32--      Check for cases where the actual corresponding to X is:
33--         (a) An allocator.
34--         (b) An expression of a named access type.
35--         (c) Obj'Access.
36--
37-- TEST DESCRIPTION:
38--      In order to satisfy accessibility requirements, the designated
39--      object X must be at the same or a less deep nesting level than the
40--      general access type A -- X must "live" as long as A. Nesting
41--      levels are the run-time nestings of masters: block statements;
42--      subprogram, task, and entry bodies; and accept statements. Packages
43--      are invisible to accessibility rules.
44--
45--      This test declares subprograms with access parameters, within which
46--      'Access is attempted on a dereference of the access parameter, and
47--      assigned to an access object whose type A is declared at some nesting
48--      level. The test verifies that Program_Error is raised if the actual
49--      corresponding to the access parameter is:
50--
51--         (1) an allocator, and the accessibility level of the execution
52--             of the called subprogram is deeper than that of the access
53--             type A.
54--
55--         (2) an expression of a named access type, and the accessibility
56--             level of the named access type is deeper than that of the
57--             access type A.
58--
59--         (3) a reference to the Access attribute (e.g., X'Access), and
60--             the accessibility level of X is deeper than that of the
61--             access type A.
62--
63--      Note that the static nesting level of the actual corresponding to the
64--      access parameter can be deeper than that of the type A -- it is
65--      the run-time nesting that matters for accessibility rules. Consider
66--      the case where the access type A is declared within the called
67--      subprogram. The accessibility check will never fail, even if the
68--      actual happens to have a deeper static nesting level:
69--
70--         procedure P (X: access T) is
71--            type A is access all T;   -- Static level = 2, e.g.
72--            Acc : A := X.all'Access;  -- Check should never fail.
73--         begin null; end;
74--         . . .
75--         declare
76--            Actual : aliased T;       -- Static level = 3, e.g.
77--         begin
78--            P (Actual'Access);
79--         end;
80--
81--         For the execution of P, the accessibility level of type A will
82--         always be deeper than that of Actual, so there is no danger of a
83--         dangling reference arising from the assignment to Acc. Thus,
84--         X.all'Access is safe, even though the static nesting level of
85--         Actual is deeper than that of A.
86--
87--
88-- CHANGE HISTORY:
89--      06 Dec 94   SAIC    ACVC 2.0
90--
91--!
92
93package C3A2002_0 is
94
95   type Desig is array (1 .. 10) of Integer;
96
97   X0 : aliased Desig;                                            -- Level = 0.
98
99   type Acc_L0 is access all Desig;                               -- Level = 0.
100   A0 : Acc_L0;
101
102   type Result_Kind is (OK, P_E, O_E);
103
104   procedure A_Is_Level_0 (X: access Desig; R : out Result_Kind);
105   procedure Never_Fails  (X: access Desig; R : out Result_Kind);
106
107end C3A2002_0;
108
109
110     --==================================================================--
111
112package body C3A2002_0 is
113
114   procedure A_Is_Level_0 (X : access Desig;
115                           R : out Result_Kind) is
116   begin
117      -- The accessibility level of the type of A0 is 0.
118      A0 := X.all'Access;
119      R  := OK;
120   exception
121      when Program_Error =>
122         R := P_E;
123      when others        =>
124         R := O_E;
125   end A_Is_Level_0;
126
127   -----------------------------------------------
128   procedure Never_Fails (X: access Desig;
129                          R : out Result_Kind) is
130      type Acc_Local is access all Desig;
131      AL : Acc_Local;
132   begin
133      -- X.all'Access below will always be safe, since the accessibility
134      -- level (although not necessarily the static nesting depth) of the
135      -- type of AL will always be deeper than or the same as that of the
136      -- actual corresponding to Y.
137      AL := X.all'Access;
138      R  := OK;
139   exception
140      when Program_Error =>
141         R := P_E;
142      when others        =>
143         R := O_E;
144   end Never_Fails;
145
146end C3A2002_0;
147
148
149     --==================================================================--
150
151
152with C3A2002_0;
153with Report;
154
155procedure C3A2002 is
156
157   X1 : aliased C3A2002_0.Desig;                                  -- Level = 1.
158
159   type Acc_L1 is access all C3A2002_0.Desig;                     -- Level = 1.
160   A1 : Acc_L1;
161
162   Expr_L0 : C3A2002_0.Acc_L0 := C3A2002_0.X0'Access;
163   Expr_L1 : Acc_L1           := X1'Access;
164
165   Res : C3A2002_0.Result_Kind;
166
167   use type C3A2002_0.Result_Kind;
168
169   -----------------------------------------------
170   procedure A_Is_Level_1 (X : access C3A2002_0.Desig;
171                           R : out C3A2002_0.Result_Kind) is
172      -- Dereference of an access_to_object value is aliased.
173      Ren : C3A2002_0.Desig renames X.all;      -- Renaming of a dereference
174   begin                                        -- of an access parameter.
175      -- The accessibility level of the type of A1 is 1.
176      A1 := Ren'Access;
177      R  := C3A2002_0.OK;
178   exception
179      when Program_Error =>
180         R := C3A2002_0.P_E;
181      when others        =>
182         R := C3A2002_0.O_E;
183   end A_Is_Level_1;
184
185   -----------------------------------------------
186   procedure Display_Results (Result  : in C3A2002_0.Result_Kind;
187                              Expected: in C3A2002_0.Result_Kind;
188                              Message : in String) is
189   begin
190      if Result /= Expected then
191         case Result is
192            when C3A2002_0.OK  => Report.Failed ("No exception raised: "  &
193                                                 Message);
194            when C3A2002_0.P_E => Report.Failed ("Program_Error raised: " &
195                                                 Message);
196            when C3A2002_0.O_E => Report.Failed ("Unexpected exception "  &
197                                                 "raised: " & Message);
198         end case;
199      end if;
200   end Display_Results;
201
202begin -- C3A2002
203
204   Report.Test ("C3A2002", "Check that, for X'Access of general access "   &
205                "type A, Program_Error is raised if the accessibility "    &
206                "level of X is deeper than that of A: X is an access "     &
207                "parameter; corresponding actual is an allocator, "        &
208                "expression of a named access type, Obj'Access, or a "     &
209                "rename thereof");
210
211
212   -- Actual is X'Access:
213
214   C3A2002_0.Never_Fails (C3A2002_0.X0'Access, Res);
215   Display_Results (Res, C3A2002_0.OK, "X0'Access, local access type");
216
217   C3A2002_0.A_Is_Level_0 (C3A2002_0.X0'Access, Res);
218   Display_Results (Res, C3A2002_0.OK, "X0'Access, level 0 access type");
219
220   C3A2002_0.A_Is_Level_0 (X1'Access, Res);
221   Display_Results (Res, C3A2002_0.P_E, "X1'Access, level 0 access type");
222
223   A_Is_Level_1 (X1'Access, Res);
224   Display_Results (Res, C3A2002_0.OK, "X1'Access, level 1 access type");
225
226
227   -- Actual is expression of a named access type:
228
229   C3A2002_0.Never_Fails (Expr_L1, Res);
230   Display_Results (Res, C3A2002_0.OK, "Expr_L1, local access type");
231
232   C3A2002_0.A_Is_Level_0 (Expr_L1, Res);
233   Display_Results (Res, C3A2002_0.P_E, "Expr_L1, level 0 access type");
234
235   A_Is_Level_1 (Expr_L0, Res);
236   Display_Results (Res, C3A2002_0.OK, "Expr_L0, level 1 access type");
237
238   A_Is_Level_1 (Expr_L1, Res);
239   Display_Results (Res, C3A2002_0.OK, "Expr_L1, level 1 access type");
240
241   -- Actual is allocator (level of execution = 2):
242
243   C3A2002_0.Never_Fails (new C3A2002_0.Desig, Res);
244   Display_Results (Res, C3A2002_0.OK, "Allocator level 2, " &
245                                       "local access type");
246
247   -- Since actual is an allocator, its accessibility level is that of
248   -- the execution of the called subprogram, i.e., level 2.
249
250   C3A2002_0.A_Is_Level_0 (new C3A2002_0.Desig, Res);
251   Display_Results (Res, C3A2002_0.P_E, "Allocator level 2, " &
252                                        "level 0 access type");
253
254   A_Is_Level_1 (new C3A2002_0.Desig, Res);
255   Display_Results (Res, C3A2002_0.P_E, "Allocator level 2, " &
256                                        "level 1 access type");
257
258
259   Block_L2:
260   declare
261      X2 : aliased C3A2002_0.Desig;                               -- Level = 2.
262      type Acc_L2 is access all C3A2002_0.Desig;                  -- Level = 2.
263      Expr_L2 : Acc_L2 := X1'Access;
264   begin
265
266      -- Actual is X'Access:
267
268      C3A2002_0.Never_Fails (X2'Access, Res);
269      Display_Results (Res, C3A2002_0.OK, "X2'Access, local access type");
270
271      C3A2002_0.A_Is_Level_0 (X2'Access, Res);
272      Display_Results (Res, C3A2002_0.P_E, "X2'Access, level 0 access type");
273
274
275      -- Actual is expression of a named access type:
276
277      A_Is_Level_1 (Expr_L2, Res);
278      Display_Results (Res, C3A2002_0.P_E, "Expr_L2, level 1 access type");
279
280
281      -- Actual is allocator (level of execution = 3):
282
283      C3A2002_0.Never_Fails (new C3A2002_0.Desig, Res);
284      Display_Results (Res, C3A2002_0.OK, "Allocator level 3, " &
285                                          "local access type");
286
287      A_Is_Level_1 (new C3A2002_0.Desig, Res);
288      Display_Results (Res, C3A2002_0.P_E, "Allocator level 3, " &
289                                           "level 1 access type");
290
291   end Block_L2;
292
293   Report.Result;
294
295end C3A2002;
296