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1 | ------------------------------------------------------------------------------ |
2 | -- -- | |
3 | -- GNAT COMPILER COMPONENTS -- | |
4 | -- -- | |
5 | -- A C C E S S I B I L I T Y -- | |
6 | -- -- | |
7 | -- B o d y -- | |
8 | -- -- | |
cccef051 | 9 | -- Copyright (C) 2022-2023, Free Software Foundation, Inc. -- |
f459afaa JS |
10 | -- -- |
11 | -- GNAT is free software; you can redistribute it and/or modify it under -- | |
12 | -- terms of the GNU General Public License as published by the Free Soft- -- | |
13 | -- ware Foundation; either version 3, or (at your option) any later ver- -- | |
14 | -- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- | |
15 | -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- | |
16 | -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- | |
17 | -- for more details. You should have received a copy of the GNU General -- | |
18 | -- Public License distributed with GNAT; see file COPYING3. If not, go to -- | |
19 | -- http://www.gnu.org/licenses for a complete copy of the license. -- | |
20 | -- -- | |
21 | -- GNAT was originally developed by the GNAT team at New York University. -- | |
22 | -- Extensive contributions were provided by Ada Core Technologies Inc. -- | |
23 | -- -- | |
24 | ------------------------------------------------------------------------------ | |
25 | ||
26 | with Atree; use Atree; | |
27 | with Checks; use Checks; | |
28 | with Debug; use Debug; | |
29 | with Einfo; use Einfo; | |
30 | with Einfo.Entities; use Einfo.Entities; | |
31 | with Elists; use Elists; | |
32 | with Errout; use Errout; | |
33 | with Einfo.Utils; use Einfo.Utils; | |
34 | with Exp_Atag; use Exp_Atag; | |
35 | with Exp_Ch3; use Exp_Ch3; | |
36 | with Exp_Ch7; use Exp_Ch7; | |
37 | with Exp_Tss; use Exp_Tss; | |
38 | with Exp_Util; use Exp_Util; | |
39 | with Namet; use Namet; | |
40 | with Nlists; use Nlists; | |
41 | with Nmake; use Nmake; | |
42 | with Opt; use Opt; | |
43 | with Restrict; use Restrict; | |
44 | with Rtsfind; use Rtsfind; | |
45 | with Sem; use Sem; | |
46 | with Sem_Aux; use Sem_Aux; | |
47 | with Sem_Ch8; use Sem_Ch8; | |
48 | with Sem_Res; use Sem_Res; | |
49 | with Sem_Util; use Sem_Util; | |
50 | with Sinfo; use Sinfo; | |
51 | with Sinfo.Nodes; use Sinfo.Nodes; | |
52 | with Sinfo.Utils; use Sinfo.Utils; | |
53 | with Snames; use Snames; | |
54 | with Stand; use Stand; | |
55 | with Tbuild; use Tbuild; | |
56 | ||
57 | package body Accessibility is | |
58 | ||
59 | --------------------------- | |
60 | -- Accessibility_Message -- | |
61 | --------------------------- | |
62 | ||
63 | procedure Accessibility_Message (N : Node_Id; Typ : Entity_Id) is | |
64 | Loc : constant Source_Ptr := Sloc (N); | |
65 | P : constant Node_Id := Prefix (N); | |
66 | Indic : Node_Id := Parent (Parent (N)); | |
67 | ||
68 | begin | |
69 | -- In an instance, this is a runtime check, but one we know will fail, | |
70 | -- so generate an appropriate warning. | |
71 | ||
72 | if In_Instance_Body then | |
73 | Error_Msg_Warn := SPARK_Mode /= On; | |
74 | Error_Msg_F | |
75 | ("non-local pointer cannot point to local object<<", P); | |
76 | Error_Msg_F ("\Program_Error [<<", P); | |
77 | Rewrite (N, | |
78 | Make_Raise_Program_Error (Loc, | |
79 | Reason => PE_Accessibility_Check_Failed)); | |
80 | Set_Etype (N, Typ); | |
81 | return; | |
82 | ||
83 | else | |
84 | Error_Msg_F ("non-local pointer cannot point to local object", P); | |
85 | ||
86 | -- Check for case where we have a missing access definition | |
87 | ||
88 | if Is_Record_Type (Current_Scope) | |
89 | and then | |
90 | Nkind (Parent (N)) in N_Discriminant_Association | |
91 | | N_Index_Or_Discriminant_Constraint | |
92 | then | |
93 | Indic := Parent (Parent (N)); | |
94 | while Present (Indic) | |
95 | and then Nkind (Indic) /= N_Subtype_Indication | |
96 | loop | |
97 | Indic := Parent (Indic); | |
98 | end loop; | |
99 | ||
100 | if Present (Indic) then | |
101 | Error_Msg_NE | |
102 | ("\use an access definition for" & | |
103 | " the access discriminant of&", | |
104 | N, Entity (Subtype_Mark (Indic))); | |
105 | end if; | |
106 | end if; | |
107 | end if; | |
108 | end Accessibility_Message; | |
109 | ||
110 | ------------------------- | |
111 | -- Accessibility_Level -- | |
112 | ------------------------- | |
113 | ||
114 | function Accessibility_Level | |
115 | (Expr : Node_Id; | |
116 | Level : Accessibility_Level_Kind; | |
117 | In_Return_Context : Boolean := False; | |
118 | Allow_Alt_Model : Boolean := True) return Node_Id | |
119 | is | |
120 | Loc : constant Source_Ptr := Sloc (Expr); | |
121 | ||
553c37be BD |
122 | function Accessibility_Level (Expr : Node_Id) return Node_Id is |
123 | (Accessibility_Level | |
124 | (Expr, Level, In_Return_Context, Allow_Alt_Model)); | |
f459afaa JS |
125 | -- Renaming of the enclosing function to facilitate recursive calls |
126 | ||
127 | function Make_Level_Literal (Level : Uint) return Node_Id; | |
128 | -- Construct an integer literal representing an accessibility level with | |
129 | -- its type set to Natural. | |
130 | ||
131 | function Innermost_Master_Scope_Depth (N : Node_Id) return Uint; | |
132 | -- Returns the scope depth of the given node's innermost enclosing scope | |
133 | -- (effectively the accessibility level of the innermost enclosing | |
134 | -- master). | |
135 | ||
136 | function Function_Call_Or_Allocator_Level (N : Node_Id) return Node_Id; | |
137 | -- Centralized processing of subprogram calls which may appear in prefix | |
138 | -- notation. | |
139 | ||
140 | function Typ_Access_Level (Typ : Entity_Id) return Uint | |
141 | is (Type_Access_Level (Typ, Allow_Alt_Model)); | |
142 | -- Renaming of Type_Access_Level with Allow_Alt_Model specified to avoid | |
143 | -- passing the parameter specifically in every call. | |
144 | ||
145 | ---------------------------------- | |
146 | -- Innermost_Master_Scope_Depth -- | |
147 | ---------------------------------- | |
148 | ||
149 | function Innermost_Master_Scope_Depth (N : Node_Id) return Uint is | |
150 | Encl_Scop : Entity_Id; | |
151 | Ent : Entity_Id; | |
152 | Node_Par : Node_Id := Parent (N); | |
153 | Master_Lvl_Modifier : Int := 0; | |
154 | ||
155 | begin | |
156 | -- Locate the nearest enclosing node (by traversing Parents) | |
157 | -- that Defining_Entity can be applied to, and return the | |
158 | -- depth of that entity's nearest enclosing scope. | |
159 | ||
160 | -- The RM 7.6.1(3) definition of "master" includes statements | |
161 | -- and conditions for loops among other things. Are these cases | |
162 | -- detected properly ??? | |
163 | ||
164 | while Present (Node_Par) loop | |
165 | Ent := Defining_Entity_Or_Empty (Node_Par); | |
166 | ||
167 | if Present (Ent) then | |
553c37be BD |
168 | -- X'Old is nested within the current subprogram, so we do not |
169 | -- want Find_Enclosing_Scope of that subprogram. If this is an | |
170 | -- allocator, then we're looking for the innermost master of | |
171 | -- the call, so again we do not want Find_Enclosing_Scope. | |
172 | ||
173 | if (Nkind (N) = N_Attribute_Reference | |
174 | and then Attribute_Name (N) = Name_Old) | |
175 | or else Nkind (N) = N_Allocator | |
176 | then | |
177 | Encl_Scop := Ent; | |
178 | else | |
179 | Encl_Scop := Find_Enclosing_Scope (Ent); | |
180 | end if; | |
f459afaa JS |
181 | |
182 | -- Ignore transient scopes made during expansion while also | |
183 | -- taking into account certain expansions - like iterators | |
184 | -- which get expanded into renamings and thus not marked | |
185 | -- as coming from source. | |
186 | ||
187 | if Comes_From_Source (Node_Par) | |
188 | or else (Nkind (Node_Par) = N_Object_Renaming_Declaration | |
189 | and then Comes_From_Iterator (Node_Par)) | |
190 | then | |
191 | -- Note that in some rare cases the scope depth may not be | |
192 | -- set, for example, when we are in the middle of analyzing | |
553c37be BD |
193 | -- a type and the enclosing scope is said type. In that case |
194 | -- simply return zero for the outermost scope. | |
195 | ||
196 | if Scope_Depth_Set (Encl_Scop) then | |
197 | return Scope_Depth (Encl_Scop) + Master_Lvl_Modifier; | |
f459afaa | 198 | else |
553c37be | 199 | return Uint_0; |
f459afaa JS |
200 | end if; |
201 | end if; | |
202 | ||
203 | -- For a return statement within a function, return | |
204 | -- the depth of the function itself. This is not just | |
205 | -- a small optimization, but matters when analyzing | |
206 | -- the expression in an expression function before | |
207 | -- the body is created. | |
208 | ||
209 | elsif Nkind (Node_Par) in N_Extended_Return_Statement | |
210 | | N_Simple_Return_Statement | |
211 | then | |
212 | return Scope_Depth (Enclosing_Subprogram (Node_Par)); | |
213 | ||
214 | -- Statements are counted as masters | |
215 | ||
216 | elsif Is_Master (Node_Par) then | |
217 | Master_Lvl_Modifier := Master_Lvl_Modifier + 1; | |
218 | ||
219 | end if; | |
220 | ||
221 | Node_Par := Parent (Node_Par); | |
222 | end loop; | |
223 | ||
224 | -- Should never reach the following return | |
225 | ||
226 | pragma Assert (False); | |
227 | ||
228 | return Scope_Depth (Current_Scope) + 1; | |
229 | end Innermost_Master_Scope_Depth; | |
230 | ||
231 | ------------------------ | |
232 | -- Make_Level_Literal -- | |
233 | ------------------------ | |
234 | ||
235 | function Make_Level_Literal (Level : Uint) return Node_Id is | |
236 | Result : constant Node_Id := Make_Integer_Literal (Loc, Level); | |
237 | ||
238 | begin | |
239 | Set_Etype (Result, Standard_Natural); | |
240 | return Result; | |
241 | end Make_Level_Literal; | |
242 | ||
243 | -------------------------------------- | |
244 | -- Function_Call_Or_Allocator_Level -- | |
245 | -------------------------------------- | |
246 | ||
247 | function Function_Call_Or_Allocator_Level (N : Node_Id) return Node_Id is | |
248 | Par : Node_Id; | |
249 | Prev_Par : Node_Id; | |
250 | begin | |
251 | -- Results of functions are objects, so we either get the | |
252 | -- accessibility of the function or, in case of a call which is | |
253 | -- indirect, the level of the access-to-subprogram type. | |
254 | ||
255 | -- This code looks wrong ??? | |
256 | ||
257 | if Nkind (N) = N_Function_Call | |
258 | and then Ada_Version < Ada_2005 | |
259 | then | |
260 | if Is_Entity_Name (Name (N)) then | |
261 | return Make_Level_Literal | |
262 | (Subprogram_Access_Level (Entity (Name (N)))); | |
263 | else | |
264 | return Make_Level_Literal | |
265 | (Typ_Access_Level (Etype (Prefix (Name (N))))); | |
266 | end if; | |
267 | ||
268 | -- We ignore coextensions as they cannot be implemented under the | |
269 | -- "small-integer" model. | |
270 | ||
271 | elsif Nkind (N) = N_Allocator | |
272 | and then (Is_Static_Coextension (N) | |
273 | or else Is_Dynamic_Coextension (N)) | |
274 | then | |
275 | return Make_Level_Literal (Scope_Depth (Standard_Standard)); | |
276 | end if; | |
277 | ||
278 | -- Named access types have a designated level | |
279 | ||
280 | if Is_Named_Access_Type (Etype (N)) then | |
281 | return Make_Level_Literal (Typ_Access_Level (Etype (N))); | |
282 | ||
283 | -- Otherwise, the level is dictated by RM 3.10.2 (10.7/3) | |
284 | ||
285 | else | |
286 | -- Check No_Dynamic_Accessibility_Checks restriction override for | |
287 | -- alternative accessibility model. | |
288 | ||
289 | if Allow_Alt_Model | |
290 | and then No_Dynamic_Accessibility_Checks_Enabled (N) | |
291 | and then Is_Anonymous_Access_Type (Etype (N)) | |
292 | then | |
293 | -- In the alternative model the level is that of the | |
294 | -- designated type. | |
295 | ||
296 | if Debug_Flag_Underscore_B then | |
297 | return Make_Level_Literal (Typ_Access_Level (Etype (N))); | |
298 | ||
299 | -- For function calls the level is that of the innermost | |
300 | -- master, otherwise (for allocators etc.) we get the level | |
301 | -- of the corresponding anonymous access type, which is | |
302 | -- calculated through the normal path of execution. | |
303 | ||
304 | elsif Nkind (N) = N_Function_Call then | |
305 | return Make_Level_Literal | |
306 | (Innermost_Master_Scope_Depth (Expr)); | |
307 | end if; | |
308 | end if; | |
309 | ||
310 | if Nkind (N) = N_Function_Call then | |
311 | -- Dynamic checks are generated when we are within a return | |
312 | -- value or we are in a function call within an anonymous | |
313 | -- access discriminant constraint of a return object (signified | |
314 | -- by In_Return_Context) on the side of the callee. | |
315 | ||
316 | -- So, in this case, return accessibility level of the | |
317 | -- enclosing subprogram. | |
318 | ||
319 | if In_Return_Value (N) | |
320 | or else In_Return_Context | |
321 | then | |
322 | return Make_Level_Literal | |
323 | (Subprogram_Access_Level (Current_Subprogram)); | |
324 | end if; | |
325 | end if; | |
326 | ||
327 | -- When the call is being dereferenced the level is that of the | |
328 | -- enclosing master of the dereferenced call. | |
329 | ||
330 | if Nkind (Parent (N)) in N_Explicit_Dereference | |
331 | | N_Indexed_Component | |
332 | | N_Selected_Component | |
333 | then | |
334 | return Make_Level_Literal | |
335 | (Innermost_Master_Scope_Depth (Expr)); | |
336 | end if; | |
337 | ||
338 | -- Find any relevant enclosing parent nodes that designate an | |
339 | -- object being initialized. | |
340 | ||
341 | -- Note: The above is only relevant if the result is used "in its | |
342 | -- entirety" as RM 3.10.2 (10.2/3) states. However, this is | |
343 | -- accounted for in the case statement in the main body of | |
344 | -- Accessibility_Level for N_Selected_Component. | |
345 | ||
346 | Par := Parent (Expr); | |
347 | Prev_Par := Empty; | |
348 | while Present (Par) loop | |
349 | -- Detect an expanded implicit conversion, typically this | |
350 | -- occurs on implicitly converted actuals in calls. | |
351 | ||
352 | -- Does this catch all implicit conversions ??? | |
353 | ||
354 | if Nkind (Par) = N_Type_Conversion | |
355 | and then Is_Named_Access_Type (Etype (Par)) | |
356 | then | |
357 | return Make_Level_Literal | |
358 | (Typ_Access_Level (Etype (Par))); | |
359 | end if; | |
360 | ||
361 | -- Jump out when we hit an object declaration or the right-hand | |
362 | -- side of an assignment, or a construct such as an aggregate | |
363 | -- subtype indication which would be the result is not used | |
364 | -- "in its entirety." | |
365 | ||
366 | exit when Nkind (Par) in N_Object_Declaration | |
367 | or else (Nkind (Par) = N_Assignment_Statement | |
368 | and then Name (Par) /= Prev_Par); | |
369 | ||
370 | Prev_Par := Par; | |
371 | Par := Parent (Par); | |
372 | end loop; | |
373 | ||
374 | -- Assignment statements are handled in a similar way in | |
375 | -- accordance to the left-hand part. However, strictly speaking, | |
376 | -- this is illegal according to the RM, but this change is needed | |
377 | -- to pass an ACATS C-test and is useful in general ??? | |
378 | ||
379 | case Nkind (Par) is | |
380 | when N_Object_Declaration => | |
381 | return Make_Level_Literal | |
382 | (Scope_Depth | |
383 | (Scope (Defining_Identifier (Par)))); | |
384 | ||
385 | when N_Assignment_Statement => | |
386 | -- Return the accessibility level of the left-hand part | |
387 | ||
388 | return Accessibility_Level | |
389 | (Expr => Name (Par), | |
390 | Level => Object_Decl_Level, | |
391 | In_Return_Context => In_Return_Context); | |
392 | ||
393 | when others => | |
394 | return Make_Level_Literal | |
395 | (Innermost_Master_Scope_Depth (Expr)); | |
396 | end case; | |
397 | end if; | |
398 | end Function_Call_Or_Allocator_Level; | |
399 | ||
400 | -- Local variables | |
401 | ||
402 | E : Node_Id := Original_Node (Expr); | |
403 | Pre : Node_Id; | |
404 | ||
405 | -- Start of processing for Accessibility_Level | |
406 | ||
407 | begin | |
408 | -- We could be looking at a reference to a formal due to the expansion | |
409 | -- of entries and other cases, so obtain the renaming if necessary. | |
410 | ||
411 | if Present (Param_Entity (Expr)) then | |
412 | E := Param_Entity (Expr); | |
413 | end if; | |
414 | ||
415 | -- Extract the entity | |
416 | ||
417 | if Nkind (E) in N_Has_Entity and then Present (Entity (E)) then | |
418 | E := Entity (E); | |
419 | ||
420 | -- Deal with a possible renaming of a private protected component | |
421 | ||
422 | if Ekind (E) in E_Constant | E_Variable and then Is_Prival (E) then | |
423 | E := Prival_Link (E); | |
424 | end if; | |
425 | end if; | |
426 | ||
427 | -- Perform the processing on the expression | |
428 | ||
429 | case Nkind (E) is | |
430 | -- The level of an aggregate is that of the innermost master that | |
431 | -- evaluates it as defined in RM 3.10.2 (10/4). | |
432 | ||
433 | when N_Aggregate => | |
434 | return Make_Level_Literal (Innermost_Master_Scope_Depth (Expr)); | |
435 | ||
553c37be | 436 | -- The accessibility level is that of the access type, except for |
f459afaa JS |
437 | -- anonymous allocators which have special rules defined in RM 3.10.2 |
438 | -- (14/3). | |
439 | ||
440 | when N_Allocator => | |
441 | return Function_Call_Or_Allocator_Level (E); | |
442 | ||
443 | -- We could reach this point for two reasons. Either the expression | |
444 | -- applies to a special attribute ('Loop_Entry, 'Result, or 'Old), or | |
445 | -- we are looking at the access attributes directly ('Access, | |
446 | -- 'Address, or 'Unchecked_Access). | |
447 | ||
448 | when N_Attribute_Reference => | |
449 | Pre := Original_Node (Prefix (E)); | |
450 | ||
451 | -- Regular 'Access attribute presence means we have to look at the | |
452 | -- prefix. | |
453 | ||
454 | if Attribute_Name (E) = Name_Access then | |
455 | return Accessibility_Level (Prefix (E)); | |
456 | ||
457 | -- Unchecked or unrestricted attributes have unlimited depth | |
458 | ||
459 | elsif Attribute_Name (E) in Name_Address | |
460 | | Name_Unchecked_Access | |
461 | | Name_Unrestricted_Access | |
462 | then | |
463 | return Make_Level_Literal (Scope_Depth (Standard_Standard)); | |
464 | ||
465 | -- 'Access can be taken further against other special attributes, | |
466 | -- so handle these cases explicitly. | |
467 | ||
468 | elsif Attribute_Name (E) | |
469 | in Name_Old | Name_Loop_Entry | Name_Result | |
470 | then | |
471 | -- Named access types | |
472 | ||
473 | if Is_Named_Access_Type (Etype (Pre)) then | |
474 | return Make_Level_Literal | |
475 | (Typ_Access_Level (Etype (Pre))); | |
476 | ||
477 | -- Anonymous access types | |
478 | ||
479 | elsif Nkind (Pre) in N_Has_Entity | |
480 | and then Ekind (Entity (Pre)) not in Subprogram_Kind | |
481 | and then Present (Get_Dynamic_Accessibility (Entity (Pre))) | |
482 | and then Level = Dynamic_Level | |
483 | then | |
553c37be | 484 | pragma Assert (Is_Anonymous_Access_Type (Etype (Pre))); |
f459afaa JS |
485 | return New_Occurrence_Of |
486 | (Get_Dynamic_Accessibility (Entity (Pre)), Loc); | |
487 | ||
488 | -- Otherwise the level is treated in a similar way as | |
489 | -- aggregates according to RM 6.1.1 (35.1/4) which concerns | |
490 | -- an implicit constant declaration - in turn defining the | |
491 | -- accessibility level to be that of the implicit constant | |
492 | -- declaration. | |
493 | ||
494 | else | |
495 | return Make_Level_Literal | |
496 | (Innermost_Master_Scope_Depth (Expr)); | |
497 | end if; | |
498 | ||
499 | else | |
500 | raise Program_Error; | |
501 | end if; | |
502 | ||
503 | -- This is the "base case" for accessibility level calculations which | |
504 | -- means we are near the end of our recursive traversal. | |
505 | ||
506 | when N_Defining_Identifier => | |
507 | -- A dynamic check is performed on the side of the callee when we | |
508 | -- are within a return statement, so return a library-level | |
509 | -- accessibility level to null out checks on the side of the | |
510 | -- caller. | |
511 | ||
512 | if Is_Explicitly_Aliased (E) | |
513 | and then (In_Return_Context | |
514 | or else (Level /= Dynamic_Level | |
515 | and then In_Return_Value (Expr))) | |
516 | then | |
517 | return Make_Level_Literal (Scope_Depth (Standard_Standard)); | |
518 | ||
519 | -- Something went wrong and an extra accessibility formal has not | |
520 | -- been generated when one should have ??? | |
521 | ||
522 | elsif Is_Formal (E) | |
523 | and then No (Get_Dynamic_Accessibility (E)) | |
524 | and then Ekind (Etype (E)) = E_Anonymous_Access_Type | |
525 | then | |
526 | return Make_Level_Literal (Scope_Depth (Standard_Standard)); | |
527 | ||
528 | -- Stand-alone object of an anonymous access type "SAOAAT" | |
529 | ||
530 | elsif (Is_Formal (E) | |
531 | or else Ekind (E) in E_Variable | |
532 | | E_Constant) | |
533 | and then Present (Get_Dynamic_Accessibility (E)) | |
534 | and then (Level = Dynamic_Level | |
535 | or else Level = Zero_On_Dynamic_Level) | |
536 | then | |
537 | if Level = Zero_On_Dynamic_Level then | |
538 | return Make_Level_Literal | |
539 | (Scope_Depth (Standard_Standard)); | |
540 | end if; | |
541 | ||
542 | -- No_Dynamic_Accessibility_Checks restriction override for | |
543 | -- alternative accessibility model. | |
544 | ||
545 | if Allow_Alt_Model | |
546 | and then No_Dynamic_Accessibility_Checks_Enabled (E) | |
547 | then | |
548 | -- In the alternative model the level is that of the | |
549 | -- designated type entity's context. | |
550 | ||
551 | if Debug_Flag_Underscore_B then | |
552 | return Make_Level_Literal (Typ_Access_Level (Etype (E))); | |
553 | ||
554 | -- Otherwise the level depends on the entity's context | |
555 | ||
556 | elsif Is_Formal (E) then | |
557 | return Make_Level_Literal | |
558 | (Subprogram_Access_Level | |
559 | (Enclosing_Subprogram (E))); | |
560 | else | |
561 | return Make_Level_Literal | |
562 | (Scope_Depth (Enclosing_Dynamic_Scope (E))); | |
563 | end if; | |
564 | end if; | |
565 | ||
566 | -- Return the dynamic level in the normal case | |
567 | ||
568 | return New_Occurrence_Of | |
569 | (Get_Dynamic_Accessibility (E), Loc); | |
570 | ||
571 | -- Initialization procedures have a special extra accessibility | |
572 | -- parameter associated with the level at which the object | |
573 | -- being initialized exists | |
574 | ||
575 | elsif Ekind (E) = E_Record_Type | |
576 | and then Is_Limited_Record (E) | |
577 | and then Current_Scope = Init_Proc (E) | |
578 | and then Present (Init_Proc_Level_Formal (Current_Scope)) | |
579 | then | |
580 | return New_Occurrence_Of | |
581 | (Init_Proc_Level_Formal (Current_Scope), Loc); | |
582 | ||
583 | -- Current instance of the type is deeper than that of the type | |
584 | -- according to RM 3.10.2 (21). | |
585 | ||
586 | elsif Is_Type (E) then | |
587 | -- When restriction No_Dynamic_Accessibility_Checks is active | |
588 | -- along with -gnatd_b. | |
589 | ||
590 | if Allow_Alt_Model | |
591 | and then No_Dynamic_Accessibility_Checks_Enabled (E) | |
592 | and then Debug_Flag_Underscore_B | |
593 | then | |
594 | return Make_Level_Literal (Typ_Access_Level (E)); | |
595 | end if; | |
596 | ||
597 | -- Normal path | |
598 | ||
599 | return Make_Level_Literal (Typ_Access_Level (E) + 1); | |
600 | ||
601 | -- Move up the renamed entity or object if it came from source | |
602 | -- since expansion may have created a dummy renaming under | |
603 | -- certain circumstances. | |
604 | ||
605 | -- Note: We check if the original node of the renaming comes | |
606 | -- from source because the node may have been rewritten. | |
607 | ||
608 | elsif Present (Renamed_Entity_Or_Object (E)) | |
609 | and then Comes_From_Source | |
610 | (Original_Node (Renamed_Entity_Or_Object (E))) | |
611 | then | |
612 | return Accessibility_Level (Renamed_Entity_Or_Object (E)); | |
613 | ||
614 | -- Named access types get their level from their associated type | |
615 | ||
616 | elsif Is_Named_Access_Type (Etype (E)) then | |
617 | return Make_Level_Literal | |
618 | (Typ_Access_Level (Etype (E))); | |
619 | ||
620 | -- Check if E is an expansion-generated renaming of an iterator | |
621 | -- by examining Related_Expression. If so, determine the | |
622 | -- accessibility level based on the original expression. | |
623 | ||
624 | elsif Ekind (E) in E_Constant | E_Variable | |
625 | and then Present (Related_Expression (E)) | |
626 | then | |
627 | return Accessibility_Level (Related_Expression (E)); | |
628 | ||
629 | elsif Level = Dynamic_Level | |
630 | and then Ekind (E) in E_In_Parameter | E_In_Out_Parameter | |
631 | and then Present (Init_Proc_Level_Formal (Scope (E))) | |
632 | then | |
633 | return New_Occurrence_Of | |
634 | (Init_Proc_Level_Formal (Scope (E)), Loc); | |
635 | ||
636 | -- Normal object - get the level of the enclosing scope | |
637 | ||
638 | else | |
639 | return Make_Level_Literal | |
640 | (Scope_Depth (Enclosing_Dynamic_Scope (E))); | |
641 | end if; | |
642 | ||
643 | -- Handle indexed and selected components including the special cases | |
644 | -- whereby there is an implicit dereference, a component of a | |
645 | -- composite type, or a function call in prefix notation. | |
646 | ||
647 | -- We don't handle function calls in prefix notation correctly ??? | |
648 | ||
649 | when N_Indexed_Component | N_Selected_Component | N_Slice => | |
650 | Pre := Prefix (E); | |
651 | ||
652 | -- Fetch the original node when the prefix comes from the result | |
653 | -- of expanding a function call since we want to find the level | |
654 | -- of the original source call. | |
655 | ||
656 | if not Comes_From_Source (Pre) | |
657 | and then Nkind (Original_Node (Pre)) = N_Function_Call | |
658 | then | |
659 | Pre := Original_Node (Pre); | |
660 | end if; | |
661 | ||
662 | -- When E is an indexed component or selected component and | |
663 | -- the current Expr is a function call, we know that we are | |
664 | -- looking at an expanded call in prefix notation. | |
665 | ||
666 | if Nkind (Expr) = N_Function_Call then | |
667 | return Function_Call_Or_Allocator_Level (Expr); | |
668 | ||
669 | -- If the prefix is a named access type, then we are dealing | |
670 | -- with an implicit deferences. In that case the level is that | |
671 | -- of the named access type in the prefix. | |
672 | ||
673 | elsif Is_Named_Access_Type (Etype (Pre)) then | |
674 | return Make_Level_Literal | |
675 | (Typ_Access_Level (Etype (Pre))); | |
676 | ||
677 | -- The current expression is a named access type, so there is no | |
678 | -- reason to look at the prefix. Instead obtain the level of E's | |
679 | -- named access type. | |
680 | ||
681 | elsif Is_Named_Access_Type (Etype (E)) then | |
682 | return Make_Level_Literal | |
683 | (Typ_Access_Level (Etype (E))); | |
684 | ||
685 | -- A nondiscriminant selected component where the component | |
686 | -- is an anonymous access type means that its associated | |
687 | -- level is that of the containing type - see RM 3.10.2 (16). | |
688 | ||
689 | -- Note that when restriction No_Dynamic_Accessibility_Checks is | |
690 | -- in effect we treat discriminant components as regular | |
691 | -- components. | |
692 | ||
693 | elsif | |
694 | (Nkind (E) = N_Selected_Component | |
695 | and then Ekind (Etype (E)) = E_Anonymous_Access_Type | |
696 | and then Ekind (Etype (Pre)) /= E_Anonymous_Access_Type | |
697 | and then (not (Nkind (Selector_Name (E)) in N_Has_Entity | |
698 | and then Ekind (Entity (Selector_Name (E))) | |
699 | = E_Discriminant) | |
700 | ||
701 | -- The alternative accessibility models both treat | |
702 | -- discriminants as regular components. | |
703 | ||
704 | or else (No_Dynamic_Accessibility_Checks_Enabled (E) | |
705 | and then Allow_Alt_Model))) | |
706 | ||
707 | -- Arrays featuring components of anonymous access components | |
708 | -- get their corresponding level from their containing type's | |
709 | -- declaration. | |
710 | ||
711 | or else | |
712 | (Nkind (E) = N_Indexed_Component | |
713 | and then Ekind (Etype (E)) = E_Anonymous_Access_Type | |
714 | and then Ekind (Etype (Pre)) in Array_Kind | |
715 | and then Ekind (Component_Type (Base_Type (Etype (Pre)))) | |
716 | = E_Anonymous_Access_Type) | |
717 | then | |
718 | -- When restriction No_Dynamic_Accessibility_Checks is active | |
719 | -- and -gnatd_b set, the level is that of the designated type. | |
720 | ||
721 | if Allow_Alt_Model | |
722 | and then No_Dynamic_Accessibility_Checks_Enabled (E) | |
723 | and then Debug_Flag_Underscore_B | |
724 | then | |
725 | return Make_Level_Literal | |
726 | (Typ_Access_Level (Etype (E))); | |
727 | end if; | |
728 | ||
729 | -- Otherwise proceed normally | |
730 | ||
731 | return Make_Level_Literal | |
732 | (Typ_Access_Level (Etype (Prefix (E)))); | |
733 | ||
734 | -- The accessibility calculation routine that handles function | |
735 | -- calls (Function_Call_Level) assumes, in the case the | |
736 | -- result is of an anonymous access type, that the result will be | |
737 | -- used "in its entirety" when the call is present within an | |
738 | -- assignment or object declaration. | |
739 | ||
740 | -- To properly handle cases where the result is not used in its | |
741 | -- entirety, we test if the prefix of the component in question is | |
742 | -- a function call, which tells us that one of its components has | |
743 | -- been identified and is being accessed. Therefore we can | |
744 | -- conclude that the result is not used "in its entirety" | |
745 | -- according to RM 3.10.2 (10.2/3). | |
746 | ||
747 | elsif Nkind (Pre) = N_Function_Call | |
748 | and then not Is_Named_Access_Type (Etype (Pre)) | |
749 | then | |
750 | -- Dynamic checks are generated when we are within a return | |
751 | -- value or we are in a function call within an anonymous | |
752 | -- access discriminant constraint of a return object (signified | |
753 | -- by In_Return_Context) on the side of the callee. | |
754 | ||
755 | -- So, in this case, return a library accessibility level to | |
756 | -- null out the check on the side of the caller. | |
757 | ||
758 | if (In_Return_Value (E) | |
759 | or else In_Return_Context) | |
760 | and then Level /= Dynamic_Level | |
761 | then | |
762 | return Make_Level_Literal | |
763 | (Scope_Depth (Standard_Standard)); | |
764 | end if; | |
765 | ||
766 | return Make_Level_Literal | |
767 | (Innermost_Master_Scope_Depth (Expr)); | |
768 | ||
769 | -- Otherwise, continue recursing over the expression prefixes | |
770 | ||
771 | else | |
772 | return Accessibility_Level (Prefix (E)); | |
773 | end if; | |
774 | ||
775 | -- Qualified expressions | |
776 | ||
777 | when N_Qualified_Expression => | |
778 | if Is_Named_Access_Type (Etype (E)) then | |
779 | return Make_Level_Literal | |
780 | (Typ_Access_Level (Etype (E))); | |
781 | else | |
782 | return Accessibility_Level (Expression (E)); | |
783 | end if; | |
784 | ||
785 | -- Handle function calls | |
786 | ||
787 | when N_Function_Call => | |
788 | return Function_Call_Or_Allocator_Level (E); | |
789 | ||
790 | -- Explicit dereference accessibility level calculation | |
791 | ||
792 | when N_Explicit_Dereference => | |
793 | Pre := Original_Node (Prefix (E)); | |
794 | ||
795 | -- The prefix is a named access type so the level is taken from | |
796 | -- its type. | |
797 | ||
798 | if Is_Named_Access_Type (Etype (Pre)) then | |
799 | return Make_Level_Literal (Typ_Access_Level (Etype (Pre))); | |
800 | ||
801 | -- Otherwise, recurse deeper | |
802 | ||
803 | else | |
804 | return Accessibility_Level (Prefix (E)); | |
805 | end if; | |
806 | ||
807 | -- Type conversions | |
808 | ||
809 | when N_Type_Conversion | N_Unchecked_Type_Conversion => | |
810 | -- View conversions are special in that they require use to | |
811 | -- inspect the expression of the type conversion. | |
812 | ||
813 | -- Allocators of anonymous access types are internally generated, | |
814 | -- so recurse deeper in that case as well. | |
815 | ||
816 | if Is_View_Conversion (E) | |
817 | or else Ekind (Etype (E)) = E_Anonymous_Access_Type | |
818 | then | |
819 | return Accessibility_Level (Expression (E)); | |
820 | ||
821 | -- We don't care about the master if we are looking at a named | |
822 | -- access type. | |
823 | ||
824 | elsif Is_Named_Access_Type (Etype (E)) then | |
825 | return Make_Level_Literal | |
826 | (Typ_Access_Level (Etype (E))); | |
827 | ||
828 | -- In section RM 3.10.2 (10/4) the accessibility rules for | |
829 | -- aggregates and value conversions are outlined. Are these | |
830 | -- followed in the case of initialization of an object ??? | |
831 | ||
832 | -- Should use Innermost_Master_Scope_Depth ??? | |
833 | ||
834 | else | |
835 | return Accessibility_Level (Current_Scope); | |
836 | end if; | |
837 | ||
838 | -- Default to the type accessibility level for the type of the | |
839 | -- expression's entity. | |
840 | ||
841 | when others => | |
842 | return Make_Level_Literal (Typ_Access_Level (Etype (E))); | |
843 | end case; | |
844 | end Accessibility_Level; | |
845 | ||
846 | ------------------------------- | |
847 | -- Apply_Accessibility_Check -- | |
848 | ------------------------------- | |
849 | ||
850 | procedure Apply_Accessibility_Check | |
851 | (N : Node_Id; | |
852 | Typ : Entity_Id; | |
853 | Insert_Node : Node_Id) | |
854 | is | |
855 | Loc : constant Source_Ptr := Sloc (N); | |
856 | ||
857 | Check_Cond : Node_Id; | |
858 | Param_Ent : Entity_Id := Param_Entity (N); | |
859 | Param_Level : Node_Id; | |
860 | Type_Level : Node_Id; | |
861 | ||
862 | begin | |
863 | -- Verify we haven't tried to add a dynamic accessibility check when we | |
864 | -- shouldn't. | |
865 | ||
866 | pragma Assert (not No_Dynamic_Accessibility_Checks_Enabled (N)); | |
867 | ||
868 | if Ada_Version >= Ada_2012 | |
869 | and then No (Param_Ent) | |
870 | and then Is_Entity_Name (N) | |
871 | and then Ekind (Entity (N)) in E_Constant | E_Variable | |
872 | and then Present (Effective_Extra_Accessibility (Entity (N))) | |
873 | then | |
874 | Param_Ent := Entity (N); | |
875 | while Present (Renamed_Object (Param_Ent)) loop | |
876 | -- Renamed_Object must return an Entity_Name here | |
877 | -- because of preceding "Present (E_E_A (...))" test. | |
878 | ||
879 | Param_Ent := Entity (Renamed_Object (Param_Ent)); | |
880 | end loop; | |
881 | end if; | |
882 | ||
883 | if Inside_A_Generic then | |
884 | return; | |
885 | ||
886 | -- Only apply the run-time check if the access parameter has an | |
887 | -- associated extra access level parameter and when accessibility checks | |
888 | -- are enabled. | |
889 | ||
890 | elsif Present (Param_Ent) | |
891 | and then Present (Get_Dynamic_Accessibility (Param_Ent)) | |
892 | and then not Accessibility_Checks_Suppressed (Param_Ent) | |
893 | and then not Accessibility_Checks_Suppressed (Typ) | |
894 | then | |
895 | -- Obtain the parameter's accessibility level | |
896 | ||
897 | Param_Level := | |
898 | New_Occurrence_Of (Get_Dynamic_Accessibility (Param_Ent), Loc); | |
899 | ||
900 | -- Use the dynamic accessibility parameter for the function's result | |
901 | -- when one has been created instead of statically referring to the | |
902 | -- deepest type level so as to appropriatly handle the rules for | |
903 | -- RM 3.10.2 (10.1/3). | |
904 | ||
905 | if Ekind (Scope (Param_Ent)) = E_Function | |
906 | and then In_Return_Value (N) | |
907 | and then Ekind (Typ) = E_Anonymous_Access_Type | |
908 | then | |
909 | -- Associate the level of the result type to the extra result | |
910 | -- accessibility parameter belonging to the current function. | |
911 | ||
912 | if Present (Extra_Accessibility_Of_Result (Scope (Param_Ent))) then | |
913 | Type_Level := | |
914 | New_Occurrence_Of | |
915 | (Extra_Accessibility_Of_Result (Scope (Param_Ent)), Loc); | |
916 | ||
917 | -- In Ada 2005 and earlier modes, a result extra accessibility | |
918 | -- parameter is not generated and no dynamic check is performed. | |
919 | ||
920 | else | |
921 | return; | |
922 | end if; | |
923 | ||
924 | -- Otherwise get the type's accessibility level normally | |
925 | ||
926 | else | |
927 | Type_Level := | |
928 | Make_Integer_Literal (Loc, Deepest_Type_Access_Level (Typ)); | |
929 | end if; | |
930 | ||
931 | -- Raise Program_Error if the accessibility level of the access | |
932 | -- parameter is deeper than the level of the target access type. | |
933 | ||
934 | Check_Cond := | |
935 | Make_Op_Gt (Loc, | |
936 | Left_Opnd => Param_Level, | |
937 | Right_Opnd => Type_Level); | |
938 | ||
939 | Insert_Action (Insert_Node, | |
940 | Make_Raise_Program_Error (Loc, | |
941 | Condition => Check_Cond, | |
942 | Reason => PE_Accessibility_Check_Failed)); | |
943 | ||
944 | Analyze_And_Resolve (N); | |
945 | ||
946 | -- If constant folding has happened on the condition for the | |
947 | -- generated error, then warn about it being unconditional. | |
948 | ||
949 | if Nkind (Check_Cond) = N_Identifier | |
950 | and then Entity (Check_Cond) = Standard_True | |
951 | then | |
952 | Error_Msg_Warn := SPARK_Mode /= On; | |
953 | Error_Msg_N ("accessibility check fails<<", N); | |
954 | Error_Msg_N ("\Program_Error [<<", N); | |
955 | end if; | |
956 | end if; | |
957 | end Apply_Accessibility_Check; | |
958 | ||
959 | --------------------------------------------- | |
960 | -- Apply_Accessibility_Check_For_Allocator -- | |
961 | --------------------------------------------- | |
962 | ||
963 | procedure Apply_Accessibility_Check_For_Allocator | |
964 | (N : Node_Id; | |
965 | Exp : Node_Id; | |
966 | Ref : Node_Id; | |
967 | Built_In_Place : Boolean := False) | |
968 | is | |
969 | Loc : constant Source_Ptr := Sloc (N); | |
970 | PtrT : constant Entity_Id := Etype (N); | |
971 | DesigT : constant Entity_Id := Designated_Type (PtrT); | |
972 | Pool_Id : constant Entity_Id := Associated_Storage_Pool (PtrT); | |
973 | Cond : Node_Id; | |
974 | Fin_Call : Node_Id; | |
975 | Free_Stmt : Node_Id; | |
976 | Obj_Ref : Node_Id; | |
977 | Stmts : List_Id; | |
978 | ||
979 | begin | |
980 | if Ada_Version >= Ada_2005 | |
981 | and then Is_Class_Wide_Type (DesigT) | |
982 | and then Tagged_Type_Expansion | |
983 | and then not Scope_Suppress.Suppress (Accessibility_Check) | |
984 | and then not No_Dynamic_Accessibility_Checks_Enabled (Ref) | |
985 | and then | |
986 | (Type_Access_Level (Etype (Exp)) > Type_Access_Level (PtrT) | |
987 | or else | |
988 | (Is_Class_Wide_Type (Etype (Exp)) | |
989 | and then Scope (PtrT) /= Current_Scope)) | |
990 | then | |
991 | -- If the allocator was built in place, Ref is already a reference | |
992 | -- to the access object initialized to the result of the allocator | |
993 | -- (see Exp_Ch6.Make_Build_In_Place_Call_In_Allocator). We call | |
994 | -- Remove_Side_Effects for cases where the build-in-place call may | |
995 | -- still be the prefix of the reference (to avoid generating | |
996 | -- duplicate calls). Otherwise, it is the entity associated with | |
997 | -- the object containing the address of the allocated object. | |
998 | ||
999 | if Built_In_Place then | |
1000 | Remove_Side_Effects (Ref); | |
1001 | Obj_Ref := New_Copy_Tree (Ref); | |
1002 | else | |
1003 | Obj_Ref := New_Occurrence_Of (Ref, Loc); | |
1004 | end if; | |
1005 | ||
1006 | -- For access to interface types we must generate code to displace | |
1007 | -- the pointer to the base of the object since the subsequent code | |
1008 | -- references components located in the TSD of the object (which | |
1009 | -- is associated with the primary dispatch table --see a-tags.ads) | |
1010 | -- and also generates code invoking Free, which requires also a | |
1011 | -- reference to the base of the unallocated object. | |
1012 | ||
1013 | if Is_Interface (DesigT) and then Tagged_Type_Expansion then | |
1014 | Obj_Ref := | |
1015 | Unchecked_Convert_To (Etype (Obj_Ref), | |
1016 | Make_Function_Call (Loc, | |
1017 | Name => | |
1018 | New_Occurrence_Of (RTE (RE_Base_Address), Loc), | |
1019 | Parameter_Associations => New_List ( | |
1020 | Unchecked_Convert_To (RTE (RE_Address), | |
1021 | New_Copy_Tree (Obj_Ref))))); | |
1022 | end if; | |
1023 | ||
1024 | -- Step 1: Create the object clean up code | |
1025 | ||
1026 | Stmts := New_List; | |
1027 | ||
1028 | -- Deallocate the object if the accessibility check fails. This is | |
1029 | -- done only on targets or profiles that support deallocation. | |
1030 | ||
1031 | -- Free (Obj_Ref); | |
1032 | ||
1033 | if RTE_Available (RE_Free) then | |
1034 | Free_Stmt := Make_Free_Statement (Loc, New_Copy_Tree (Obj_Ref)); | |
1035 | Set_Storage_Pool (Free_Stmt, Pool_Id); | |
1036 | ||
1037 | Append_To (Stmts, Free_Stmt); | |
1038 | ||
1039 | -- The target or profile cannot deallocate objects | |
1040 | ||
1041 | else | |
1042 | Free_Stmt := Empty; | |
1043 | end if; | |
1044 | ||
1045 | -- Finalize the object if applicable. Generate: | |
1046 | ||
1047 | -- [Deep_]Finalize (Obj_Ref.all); | |
1048 | ||
1049 | if Needs_Finalization (DesigT) | |
1050 | and then not No_Heap_Finalization (PtrT) | |
1051 | then | |
1052 | Fin_Call := | |
1053 | Make_Final_Call | |
1054 | (Obj_Ref => | |
1055 | Make_Explicit_Dereference (Loc, New_Copy (Obj_Ref)), | |
1056 | Typ => DesigT); | |
1057 | ||
1058 | -- Guard against a missing [Deep_]Finalize when the designated | |
1059 | -- type was not properly frozen. | |
1060 | ||
1061 | if No (Fin_Call) then | |
1062 | Fin_Call := Make_Null_Statement (Loc); | |
1063 | end if; | |
1064 | ||
1065 | -- When the target or profile supports deallocation, wrap the | |
1066 | -- finalization call in a block to ensure proper deallocation even | |
1067 | -- if finalization fails. Generate: | |
1068 | ||
1069 | -- begin | |
1070 | -- <Fin_Call> | |
1071 | -- exception | |
1072 | -- when others => | |
1073 | -- <Free_Stmt> | |
1074 | -- raise; | |
1075 | -- end; | |
1076 | ||
1077 | if Present (Free_Stmt) then | |
1078 | Fin_Call := | |
1079 | Make_Block_Statement (Loc, | |
1080 | Handled_Statement_Sequence => | |
1081 | Make_Handled_Sequence_Of_Statements (Loc, | |
1082 | Statements => New_List (Fin_Call), | |
1083 | ||
1084 | Exception_Handlers => New_List ( | |
1085 | Make_Exception_Handler (Loc, | |
1086 | Exception_Choices => New_List ( | |
1087 | Make_Others_Choice (Loc)), | |
1088 | Statements => New_List ( | |
1089 | New_Copy_Tree (Free_Stmt), | |
1090 | Make_Raise_Statement (Loc)))))); | |
1091 | end if; | |
1092 | ||
1093 | Prepend_To (Stmts, Fin_Call); | |
1094 | end if; | |
1095 | ||
1096 | -- Signal the accessibility failure through a Program_Error | |
1097 | ||
1098 | Append_To (Stmts, | |
1099 | Make_Raise_Program_Error (Loc, | |
1100 | Reason => PE_Accessibility_Check_Failed)); | |
1101 | ||
1102 | -- Step 2: Create the accessibility comparison | |
1103 | ||
1104 | -- Generate: | |
1105 | -- Ref'Tag | |
1106 | ||
1107 | Obj_Ref := | |
1108 | Make_Attribute_Reference (Loc, | |
1109 | Prefix => Obj_Ref, | |
1110 | Attribute_Name => Name_Tag); | |
1111 | ||
1112 | -- For tagged types, determine the accessibility level by looking at | |
1113 | -- the type specific data of the dispatch table. Generate: | |
1114 | ||
1115 | -- Type_Specific_Data (Address (Ref'Tag)).Access_Level | |
1116 | ||
1117 | if Tagged_Type_Expansion then | |
1118 | Cond := Build_Get_Access_Level (Loc, Obj_Ref); | |
1119 | ||
1120 | -- Use a runtime call to determine the accessibility level when | |
1121 | -- compiling on virtual machine targets. Generate: | |
1122 | ||
1123 | -- Get_Access_Level (Ref'Tag) | |
1124 | ||
1125 | else | |
1126 | Cond := | |
1127 | Make_Function_Call (Loc, | |
1128 | Name => | |
1129 | New_Occurrence_Of (RTE (RE_Get_Access_Level), Loc), | |
1130 | Parameter_Associations => New_List (Obj_Ref)); | |
1131 | end if; | |
1132 | ||
1133 | Cond := | |
1134 | Make_Op_Gt (Loc, | |
1135 | Left_Opnd => Cond, | |
1136 | Right_Opnd => Accessibility_Level (N, Dynamic_Level)); | |
1137 | ||
1138 | -- Due to the complexity and side effects of the check, utilize an if | |
1139 | -- statement instead of the regular Program_Error circuitry. | |
1140 | ||
1141 | Insert_Action (N, | |
1142 | Make_Implicit_If_Statement (N, | |
1143 | Condition => Cond, | |
1144 | Then_Statements => Stmts)); | |
1145 | end if; | |
1146 | end Apply_Accessibility_Check_For_Allocator; | |
1147 | ||
1148 | ------------------------------------------ | |
1149 | -- Check_Return_Construct_Accessibility -- | |
1150 | ------------------------------------------ | |
1151 | ||
1152 | procedure Check_Return_Construct_Accessibility | |
1153 | (Return_Stmt : Node_Id; | |
1154 | Stm_Entity : Entity_Id) | |
1155 | is | |
1156 | Loc : constant Source_Ptr := Sloc (Return_Stmt); | |
1157 | Scope_Id : constant Entity_Id := Return_Applies_To (Stm_Entity); | |
1158 | ||
1159 | R_Type : constant Entity_Id := Etype (Scope_Id); | |
1160 | -- Function result subtype | |
1161 | ||
1162 | function First_Selector (Assoc : Node_Id) return Node_Id; | |
1163 | -- Obtain the first selector or choice from a given association | |
1164 | ||
1165 | function Is_Formal_Of_Current_Function | |
da59893d | 1166 | (Assoc_Expr : Node_Id) return Boolean; |
f459afaa JS |
1167 | -- Predicate to test if a given expression associated with a |
1168 | -- discriminant is a formal parameter to the function in which the | |
1169 | -- return construct we checking applies to. | |
1170 | ||
1171 | -------------------- | |
1172 | -- First_Selector -- | |
1173 | -------------------- | |
1174 | ||
1175 | function First_Selector (Assoc : Node_Id) return Node_Id is | |
1176 | begin | |
1177 | if Nkind (Assoc) = N_Component_Association then | |
1178 | return First (Choices (Assoc)); | |
1179 | ||
1180 | elsif Nkind (Assoc) = N_Discriminant_Association then | |
1181 | return (First (Selector_Names (Assoc))); | |
1182 | ||
1183 | else | |
1184 | raise Program_Error; | |
1185 | end if; | |
1186 | end First_Selector; | |
1187 | ||
1188 | ----------------------------------- | |
1189 | -- Is_Formal_Of_Current_Function -- | |
1190 | ----------------------------------- | |
1191 | ||
1192 | function Is_Formal_Of_Current_Function | |
da59893d | 1193 | (Assoc_Expr : Node_Id) return Boolean is |
f459afaa JS |
1194 | begin |
1195 | return Is_Entity_Name (Assoc_Expr) | |
1196 | and then Enclosing_Subprogram | |
1197 | (Entity (Assoc_Expr)) = Scope_Id | |
1198 | and then Is_Formal (Entity (Assoc_Expr)); | |
1199 | end Is_Formal_Of_Current_Function; | |
1200 | ||
1201 | -- Local declarations | |
1202 | ||
1203 | Assoc : Node_Id := Empty; | |
1204 | -- Assoc should perhaps be renamed and declared as a | |
1205 | -- Node_Or_Entity_Id since it encompasses not only component and | |
1206 | -- discriminant associations, but also discriminant components within | |
1207 | -- a type declaration or subtype indication ??? | |
1208 | ||
1209 | Assoc_Expr : Node_Id; | |
1210 | Assoc_Present : Boolean := False; | |
1211 | ||
1212 | Check_Cond : Node_Id; | |
1213 | Unseen_Disc_Count : Nat := 0; | |
1214 | Seen_Discs : Elist_Id; | |
1215 | Disc : Entity_Id; | |
1216 | First_Disc : Entity_Id; | |
1217 | ||
1218 | Obj_Decl : Node_Id; | |
1219 | Return_Con : Node_Id; | |
1220 | Unqual : Node_Id; | |
1221 | ||
1222 | -- Start of processing for Check_Return_Construct_Accessibility | |
1223 | ||
1224 | begin | |
1225 | -- Only perform checks on record types with access discriminants and | |
1226 | -- non-internally generated functions. | |
1227 | ||
1228 | if not Is_Record_Type (R_Type) | |
1229 | or else not Has_Anonymous_Access_Discriminant (R_Type) | |
1230 | or else not Comes_From_Source (Return_Stmt) | |
1231 | then | |
1232 | return; | |
1233 | end if; | |
1234 | ||
1235 | -- We are only interested in return statements | |
1236 | ||
1237 | if Nkind (Return_Stmt) not in | |
1238 | N_Extended_Return_Statement | N_Simple_Return_Statement | |
1239 | then | |
1240 | return; | |
1241 | end if; | |
1242 | ||
1243 | -- Fetch the object from the return statement, in the case of a | |
1244 | -- simple return statement the expression is part of the node. | |
1245 | ||
1246 | if Nkind (Return_Stmt) = N_Extended_Return_Statement then | |
1247 | -- Obtain the object definition from the expanded extended return | |
1248 | ||
1249 | Return_Con := First (Return_Object_Declarations (Return_Stmt)); | |
1250 | while Present (Return_Con) loop | |
1251 | -- Inspect the original node to avoid object declarations | |
1252 | -- expanded into renamings. | |
1253 | ||
1254 | if Nkind (Original_Node (Return_Con)) = N_Object_Declaration | |
1255 | and then Comes_From_Source (Original_Node (Return_Con)) | |
1256 | then | |
1257 | exit; | |
1258 | end if; | |
1259 | ||
1260 | Nlists.Next (Return_Con); | |
1261 | end loop; | |
1262 | ||
1263 | pragma Assert (Present (Return_Con)); | |
1264 | ||
1265 | -- Could be dealing with a renaming | |
1266 | ||
1267 | Return_Con := Original_Node (Return_Con); | |
1268 | else | |
1269 | Return_Con := Expression (Return_Stmt); | |
1270 | end if; | |
1271 | ||
1272 | -- Obtain the accessibility levels of the expressions associated | |
1273 | -- with all anonymous access discriminants, then generate a | |
1274 | -- dynamic check or static error when relevant. | |
1275 | ||
1276 | -- Note the repeated use of Original_Node to avoid checking | |
1277 | -- expanded code. | |
1278 | ||
1279 | Unqual := Original_Node (Unqualify (Original_Node (Return_Con))); | |
1280 | ||
1281 | -- Get the corresponding declaration based on the return object's | |
1282 | -- identifier. | |
1283 | ||
1284 | if Nkind (Unqual) = N_Identifier | |
1285 | and then Nkind (Parent (Entity (Unqual))) | |
1286 | in N_Object_Declaration | |
1287 | | N_Object_Renaming_Declaration | |
1288 | then | |
1289 | Obj_Decl := Original_Node (Parent (Entity (Unqual))); | |
1290 | ||
1291 | -- We were passed the object declaration directly, so use it | |
1292 | ||
1293 | elsif Nkind (Unqual) in N_Object_Declaration | |
1294 | | N_Object_Renaming_Declaration | |
1295 | then | |
1296 | Obj_Decl := Unqual; | |
1297 | ||
1298 | -- Otherwise, we are looking at something else | |
1299 | ||
1300 | else | |
1301 | Obj_Decl := Empty; | |
1302 | ||
1303 | end if; | |
1304 | ||
1305 | -- Hop up object renamings when present | |
1306 | ||
1307 | if Present (Obj_Decl) | |
1308 | and then Nkind (Obj_Decl) = N_Object_Renaming_Declaration | |
1309 | then | |
1310 | while Nkind (Obj_Decl) = N_Object_Renaming_Declaration loop | |
1311 | ||
1312 | if Nkind (Name (Obj_Decl)) not in N_Entity then | |
1313 | -- We may be looking at the expansion of iterators or | |
1314 | -- some other internally generated construct, so it is safe | |
1315 | -- to ignore checks ??? | |
1316 | ||
1317 | if not Comes_From_Source (Obj_Decl) then | |
1318 | return; | |
1319 | end if; | |
1320 | ||
1321 | Obj_Decl := Original_Node | |
1322 | (Declaration_Node | |
1323 | (Ultimate_Prefix (Name (Obj_Decl)))); | |
1324 | ||
1325 | -- Move up to the next declaration based on the object's name | |
1326 | ||
1327 | else | |
1328 | Obj_Decl := Original_Node | |
1329 | (Declaration_Node (Name (Obj_Decl))); | |
1330 | end if; | |
1331 | end loop; | |
1332 | end if; | |
1333 | ||
1334 | -- Obtain the discriminant values from the return aggregate | |
1335 | ||
1336 | -- Do we cover extension aggregates correctly ??? | |
1337 | ||
1338 | if Nkind (Unqual) = N_Aggregate then | |
1339 | if Present (Expressions (Unqual)) then | |
1340 | Assoc := First (Expressions (Unqual)); | |
1341 | else | |
1342 | Assoc := First (Component_Associations (Unqual)); | |
1343 | end if; | |
1344 | ||
1345 | -- There is an object declaration for the return object | |
1346 | ||
1347 | elsif Present (Obj_Decl) then | |
1348 | -- When a subtype indication is present in an object declaration | |
1349 | -- it must contain the object's discriminants. | |
1350 | ||
1351 | if Nkind (Object_Definition (Obj_Decl)) = N_Subtype_Indication then | |
1352 | Assoc := First | |
1353 | (Constraints | |
1354 | (Constraint | |
1355 | (Object_Definition (Obj_Decl)))); | |
1356 | ||
1357 | -- The object declaration contains an aggregate | |
1358 | ||
1359 | elsif Present (Expression (Obj_Decl)) then | |
1360 | ||
1361 | if Nkind (Unqualify (Expression (Obj_Decl))) = N_Aggregate then | |
1362 | -- Grab the first associated discriminant expresion | |
1363 | ||
1364 | if Present | |
1365 | (Expressions (Unqualify (Expression (Obj_Decl)))) | |
1366 | then | |
1367 | Assoc := First | |
1368 | (Expressions | |
1369 | (Unqualify (Expression (Obj_Decl)))); | |
1370 | else | |
1371 | Assoc := First | |
1372 | (Component_Associations | |
1373 | (Unqualify (Expression (Obj_Decl)))); | |
1374 | end if; | |
1375 | ||
1376 | -- Otherwise, this is something else | |
1377 | ||
1378 | else | |
1379 | return; | |
1380 | end if; | |
1381 | ||
1382 | -- There are no supplied discriminants in the object declaration, | |
1383 | -- so get them from the type definition since they must be default | |
1384 | -- initialized. | |
1385 | ||
1386 | -- Do we handle constrained subtypes correctly ??? | |
1387 | ||
1388 | elsif Nkind (Unqual) = N_Object_Declaration then | |
1389 | Assoc := First_Discriminant | |
1390 | (Etype (Object_Definition (Obj_Decl))); | |
1391 | ||
1392 | else | |
1393 | Assoc := First_Discriminant (Etype (Unqual)); | |
1394 | end if; | |
1395 | ||
1396 | -- When we are not looking at an aggregate or an identifier, return | |
1397 | -- since any other construct (like a function call) is not | |
1398 | -- applicable since checks will be performed on the side of the | |
1399 | -- callee. | |
1400 | ||
1401 | else | |
1402 | return; | |
1403 | end if; | |
1404 | ||
1405 | -- Obtain the discriminants so we know the actual type in case the | |
1406 | -- value of their associated expression gets implicitly converted. | |
1407 | ||
1408 | if No (Obj_Decl) then | |
1409 | pragma Assert (Nkind (Unqual) = N_Aggregate); | |
1410 | ||
1411 | Disc := First_Discriminant (Etype (Unqual)); | |
1412 | ||
1413 | else | |
1414 | Disc := First_Discriminant | |
1415 | (Etype (Defining_Identifier (Obj_Decl))); | |
1416 | end if; | |
1417 | ||
1418 | -- Preserve the first discriminant for checking named associations | |
1419 | ||
1420 | First_Disc := Disc; | |
1421 | ||
1422 | -- Count the number of discriminants for processing an aggregate | |
1423 | -- which includes an others. | |
1424 | ||
1425 | Disc := First_Disc; | |
1426 | while Present (Disc) loop | |
1427 | Unseen_Disc_Count := Unseen_Disc_Count + 1; | |
1428 | ||
1429 | Next_Discriminant (Disc); | |
1430 | end loop; | |
1431 | ||
1432 | Seen_Discs := New_Elmt_List; | |
1433 | ||
1434 | -- Loop through each of the discriminants and check each expression | |
1435 | -- associated with an anonymous access discriminant. | |
1436 | ||
1437 | -- When named associations occur in the return aggregate then | |
1438 | -- discriminants can be in any order, so we need to ensure we do | |
1439 | -- not continue to loop when all discriminants have been seen. | |
1440 | ||
1441 | Disc := First_Disc; | |
1442 | while Present (Assoc) | |
1443 | and then (Present (Disc) or else Assoc_Present) | |
1444 | and then Unseen_Disc_Count > 0 | |
1445 | loop | |
1446 | -- Handle named associations by searching through the names of | |
1447 | -- the relevant discriminant components. | |
1448 | ||
1449 | if Nkind (Assoc) | |
1450 | in N_Component_Association | N_Discriminant_Association | |
1451 | then | |
1452 | Assoc_Expr := Expression (Assoc); | |
1453 | Assoc_Present := True; | |
1454 | ||
1455 | -- We currently don't handle box initialized discriminants, | |
1456 | -- however, since default initialized anonymous access | |
1457 | -- discriminants are a corner case, this is ok for now ??? | |
1458 | ||
1459 | if Nkind (Assoc) = N_Component_Association | |
1460 | and then Box_Present (Assoc) | |
1461 | then | |
1462 | if Nkind (First_Selector (Assoc)) = N_Others_Choice then | |
1463 | Unseen_Disc_Count := 0; | |
1464 | end if; | |
1465 | ||
1466 | -- When others is present we must identify a discriminant we | |
1467 | -- haven't already seen so as to get the appropriate type for | |
1468 | -- the static accessibility check. | |
1469 | ||
1470 | -- This works because all components within an others clause | |
1471 | -- must have the same type. | |
1472 | ||
1473 | elsif Nkind (First_Selector (Assoc)) = N_Others_Choice then | |
1474 | ||
1475 | Disc := First_Disc; | |
1476 | Outer : while Present (Disc) loop | |
1477 | declare | |
1478 | Current_Seen_Disc : Elmt_Id; | |
1479 | begin | |
1480 | -- Move through the list of identified discriminants | |
1481 | ||
1482 | Current_Seen_Disc := First_Elmt (Seen_Discs); | |
1483 | while Present (Current_Seen_Disc) loop | |
1484 | -- Exit the loop when we found a match | |
1485 | ||
1486 | exit when | |
1487 | Chars (Node (Current_Seen_Disc)) = Chars (Disc); | |
1488 | ||
1489 | Next_Elmt (Current_Seen_Disc); | |
1490 | end loop; | |
1491 | ||
1492 | -- When we have exited the above loop without finding | |
1493 | -- a match then we know that Disc has not been seen. | |
1494 | ||
1495 | exit Outer when No (Current_Seen_Disc); | |
1496 | end; | |
1497 | ||
1498 | Next_Discriminant (Disc); | |
1499 | end loop Outer; | |
1500 | ||
1501 | -- If we got to an others clause with a non-zero | |
1502 | -- discriminant count there must be a discriminant left to | |
1503 | -- check. | |
1504 | ||
1505 | pragma Assert (Present (Disc)); | |
1506 | ||
1507 | -- Set the unseen discriminant count to zero because we know | |
1508 | -- an others clause sets all remaining components of an | |
1509 | -- aggregate. | |
1510 | ||
1511 | Unseen_Disc_Count := 0; | |
1512 | ||
1513 | -- Move through each of the selectors in the named association | |
1514 | -- and obtain a discriminant for accessibility checking if one | |
1515 | -- is referenced in the list. Also track which discriminants | |
1516 | -- are referenced for the purpose of handling an others clause. | |
1517 | ||
1518 | else | |
1519 | declare | |
1520 | Assoc_Choice : Node_Id; | |
1521 | Curr_Disc : Node_Id; | |
1522 | begin | |
1523 | ||
1524 | Disc := Empty; | |
1525 | Curr_Disc := First_Disc; | |
1526 | while Present (Curr_Disc) loop | |
1527 | -- Check each of the choices in the associations for a | |
1528 | -- match to the name of the current discriminant. | |
1529 | ||
1530 | Assoc_Choice := First_Selector (Assoc); | |
1531 | while Present (Assoc_Choice) loop | |
1532 | -- When the name matches we track that we have seen | |
1533 | -- the discriminant, but instead of exiting the | |
1534 | -- loop we continue iterating to make sure all the | |
1535 | -- discriminants within the named association get | |
1536 | -- tracked. | |
1537 | ||
1538 | if Chars (Assoc_Choice) = Chars (Curr_Disc) then | |
1539 | Append_Elmt (Curr_Disc, Seen_Discs); | |
1540 | ||
1541 | Disc := Curr_Disc; | |
1542 | Unseen_Disc_Count := Unseen_Disc_Count - 1; | |
1543 | end if; | |
1544 | ||
1545 | Next (Assoc_Choice); | |
1546 | end loop; | |
1547 | ||
1548 | Next_Discriminant (Curr_Disc); | |
1549 | end loop; | |
1550 | end; | |
1551 | end if; | |
1552 | ||
1553 | -- Unwrap the associated expression if we are looking at a default | |
1554 | -- initialized type declaration. In this case Assoc is not really | |
1555 | -- an association, but a component declaration. Should Assoc be | |
1556 | -- renamed in some way to be more clear ??? | |
1557 | ||
1558 | -- This occurs when the return object does not initialize | |
1559 | -- discriminant and instead relies on the type declaration for | |
1560 | -- their supplied values. | |
1561 | ||
1562 | elsif Nkind (Assoc) in N_Entity | |
1563 | and then Ekind (Assoc) = E_Discriminant | |
1564 | then | |
1565 | Append_Elmt (Disc, Seen_Discs); | |
1566 | ||
1567 | Assoc_Expr := Discriminant_Default_Value (Assoc); | |
1568 | Unseen_Disc_Count := Unseen_Disc_Count - 1; | |
1569 | ||
1570 | -- Otherwise, there is nothing to do because Assoc is an | |
1571 | -- expression within the return aggregate itself. | |
1572 | ||
1573 | else | |
1574 | Append_Elmt (Disc, Seen_Discs); | |
1575 | ||
1576 | Assoc_Expr := Assoc; | |
1577 | Unseen_Disc_Count := Unseen_Disc_Count - 1; | |
1578 | end if; | |
1579 | ||
1580 | -- Check the accessibility level of the expression when the | |
1581 | -- discriminant is of an anonymous access type. | |
1582 | ||
1583 | if Present (Assoc_Expr) | |
1584 | and then Present (Disc) | |
1585 | and then Ekind (Etype (Disc)) = E_Anonymous_Access_Type | |
1586 | ||
1587 | -- We disable the check when we have a tagged return type and | |
1588 | -- the associated expression for the discriminant is a formal | |
1589 | -- parameter since the check would require us to compare the | |
1590 | -- accessibility level of Assoc_Expr to the level of the | |
1591 | -- Extra_Accessibility_Of_Result of the function - which is | |
1592 | -- currently disabled for functions with tagged return types. | |
1593 | -- This may change in the future ??? | |
1594 | ||
1595 | -- See Needs_Result_Accessibility_Level for details. | |
1596 | ||
1597 | and then not | |
1598 | (No (Extra_Accessibility_Of_Result (Scope_Id)) | |
1599 | and then Is_Formal_Of_Current_Function (Assoc_Expr) | |
1600 | and then Is_Tagged_Type (Etype (Scope_Id))) | |
1601 | then | |
1602 | -- Generate a dynamic check based on the extra accessibility of | |
1603 | -- the result or the scope of the current function. | |
1604 | ||
1605 | Check_Cond := | |
1606 | Make_Op_Gt (Loc, | |
1607 | Left_Opnd => Accessibility_Level | |
1608 | (Expr => Assoc_Expr, | |
1609 | Level => Dynamic_Level, | |
1610 | In_Return_Context => True), | |
1611 | Right_Opnd => | |
1612 | (if Present (Extra_Accessibility_Of_Result (Scope_Id)) | |
1613 | ||
1614 | -- When Assoc_Expr is a formal we have to look at the | |
1615 | -- extra accessibility-level formal associated with | |
1616 | -- the result. | |
1617 | ||
1618 | and then Is_Formal_Of_Current_Function (Assoc_Expr) | |
1619 | then | |
1620 | New_Occurrence_Of | |
1621 | (Extra_Accessibility_Of_Result (Scope_Id), Loc) | |
1622 | ||
1623 | -- Otherwise, we compare the level of Assoc_Expr to the | |
1624 | -- scope of the current function. | |
1625 | ||
1626 | else | |
1627 | Make_Integer_Literal | |
1628 | (Loc, Scope_Depth (Scope (Scope_Id))))); | |
1629 | ||
1630 | Insert_Before_And_Analyze (Return_Stmt, | |
1631 | Make_Raise_Program_Error (Loc, | |
1632 | Condition => Check_Cond, | |
1633 | Reason => PE_Accessibility_Check_Failed)); | |
1634 | ||
1635 | -- If constant folding has happened on the condition for the | |
1636 | -- generated error, then warn about it being unconditional when | |
1637 | -- we know an error will be raised. | |
1638 | ||
1639 | if Nkind (Check_Cond) = N_Identifier | |
1640 | and then Entity (Check_Cond) = Standard_True | |
1641 | then | |
1642 | Error_Msg_N | |
1643 | ("access discriminant in return object would be a dangling" | |
1644 | & " reference", Return_Stmt); | |
1645 | end if; | |
1646 | end if; | |
1647 | ||
1648 | -- Iterate over the discriminants, except when we have encountered | |
1649 | -- a named association since the discriminant order becomes | |
1650 | -- irrelevant in that case. | |
1651 | ||
1652 | if not Assoc_Present then | |
1653 | Next_Discriminant (Disc); | |
1654 | end if; | |
1655 | ||
1656 | -- Iterate over associations | |
1657 | ||
1658 | if not Is_List_Member (Assoc) then | |
1659 | exit; | |
1660 | else | |
1661 | Nlists.Next (Assoc); | |
1662 | end if; | |
1663 | end loop; | |
1664 | end Check_Return_Construct_Accessibility; | |
1665 | ||
1666 | ------------------------------- | |
1667 | -- Deepest_Type_Access_Level -- | |
1668 | ------------------------------- | |
1669 | ||
1670 | function Deepest_Type_Access_Level | |
1671 | (Typ : Entity_Id; | |
1672 | Allow_Alt_Model : Boolean := True) return Uint | |
1673 | is | |
1674 | begin | |
1675 | if Ekind (Typ) = E_Anonymous_Access_Type | |
1676 | and then not Is_Local_Anonymous_Access (Typ) | |
1677 | and then Nkind (Associated_Node_For_Itype (Typ)) = N_Object_Declaration | |
1678 | then | |
1679 | -- No_Dynamic_Accessibility_Checks override for alternative | |
1680 | -- accessibility model. | |
1681 | ||
1682 | if Allow_Alt_Model | |
1683 | and then No_Dynamic_Accessibility_Checks_Enabled (Typ) | |
1684 | then | |
1685 | return Type_Access_Level (Typ, Allow_Alt_Model); | |
1686 | end if; | |
1687 | ||
1688 | -- Typ is the type of an Ada 2012 stand-alone object of an anonymous | |
1689 | -- access type. | |
1690 | ||
1691 | return | |
1692 | Scope_Depth (Enclosing_Dynamic_Scope | |
1693 | (Defining_Identifier | |
1694 | (Associated_Node_For_Itype (Typ)))); | |
1695 | ||
1696 | -- For generic formal type, return Int'Last (infinite). | |
1697 | -- See comment preceding Is_Generic_Type call in Type_Access_Level. | |
1698 | ||
1699 | elsif Is_Generic_Type (Root_Type (Typ)) then | |
1700 | return UI_From_Int (Int'Last); | |
1701 | ||
1702 | else | |
1703 | return Type_Access_Level (Typ, Allow_Alt_Model); | |
1704 | end if; | |
1705 | end Deepest_Type_Access_Level; | |
1706 | ||
1707 | ----------------------------------- | |
1708 | -- Effective_Extra_Accessibility -- | |
1709 | ----------------------------------- | |
1710 | ||
1711 | function Effective_Extra_Accessibility (Id : Entity_Id) return Entity_Id is | |
1712 | begin | |
1713 | if Present (Renamed_Object (Id)) | |
1714 | and then Is_Entity_Name (Renamed_Object (Id)) | |
1715 | then | |
1716 | return Effective_Extra_Accessibility (Entity (Renamed_Object (Id))); | |
1717 | else | |
1718 | return Extra_Accessibility (Id); | |
1719 | end if; | |
1720 | end Effective_Extra_Accessibility; | |
1721 | ||
1722 | ------------------------------- | |
1723 | -- Get_Dynamic_Accessibility -- | |
1724 | ------------------------------- | |
1725 | ||
1726 | function Get_Dynamic_Accessibility (E : Entity_Id) return Entity_Id is | |
1727 | begin | |
1728 | -- When minimum accessibility is set for E then we utilize it - except | |
1729 | -- in a few edge cases like the expansion of select statements where | |
1730 | -- generated subprogram may attempt to unnecessarily use a minimum | |
1731 | -- accessibility object declared outside of scope. | |
1732 | ||
1733 | -- To avoid these situations where expansion may get complex we verify | |
1734 | -- that the minimum accessibility object is within scope. | |
1735 | ||
1736 | if Is_Formal (E) | |
1737 | and then Present (Minimum_Accessibility (E)) | |
1738 | and then In_Open_Scopes (Scope (Minimum_Accessibility (E))) | |
1739 | then | |
1740 | return Minimum_Accessibility (E); | |
1741 | end if; | |
1742 | ||
1743 | return Extra_Accessibility (E); | |
1744 | end Get_Dynamic_Accessibility; | |
1745 | ||
1746 | ----------------------- | |
1747 | -- Has_Access_Values -- | |
1748 | ----------------------- | |
1749 | ||
1750 | function Has_Access_Values (T : Entity_Id) return Boolean | |
1751 | is | |
1752 | Typ : constant Entity_Id := Underlying_Type (T); | |
1753 | ||
1754 | begin | |
1755 | -- Case of a private type which is not completed yet. This can only | |
1756 | -- happen in the case of a generic formal type appearing directly, or | |
1757 | -- as a component of the type to which this function is being applied | |
1758 | -- at the top level. Return False in this case, since we certainly do | |
1759 | -- not know that the type contains access types. | |
1760 | ||
1761 | if No (Typ) then | |
1762 | return False; | |
1763 | ||
1764 | elsif Is_Access_Type (Typ) then | |
1765 | return True; | |
1766 | ||
1767 | elsif Is_Array_Type (Typ) then | |
1768 | return Has_Access_Values (Component_Type (Typ)); | |
1769 | ||
1770 | elsif Is_Record_Type (Typ) then | |
1771 | declare | |
1772 | Comp : Entity_Id; | |
1773 | ||
1774 | begin | |
1775 | -- Loop to check components | |
1776 | ||
1777 | Comp := First_Component_Or_Discriminant (Typ); | |
1778 | while Present (Comp) loop | |
1779 | ||
1780 | -- Check for access component, tag field does not count, even | |
1781 | -- though it is implemented internally using an access type. | |
1782 | ||
1783 | if Has_Access_Values (Etype (Comp)) | |
1784 | and then Chars (Comp) /= Name_uTag | |
1785 | then | |
1786 | return True; | |
1787 | end if; | |
1788 | ||
1789 | Next_Component_Or_Discriminant (Comp); | |
1790 | end loop; | |
1791 | end; | |
1792 | ||
1793 | return False; | |
1794 | ||
1795 | else | |
1796 | return False; | |
1797 | end if; | |
1798 | end Has_Access_Values; | |
1799 | ||
1800 | --------------------------------------- | |
1801 | -- Has_Anonymous_Access_Discriminant -- | |
1802 | --------------------------------------- | |
1803 | ||
1804 | function Has_Anonymous_Access_Discriminant (Typ : Entity_Id) return Boolean | |
1805 | is | |
1806 | Disc : Node_Id; | |
1807 | ||
1808 | begin | |
1809 | if not Has_Discriminants (Typ) then | |
1810 | return False; | |
1811 | end if; | |
1812 | ||
1813 | Disc := First_Discriminant (Typ); | |
1814 | while Present (Disc) loop | |
1815 | if Ekind (Etype (Disc)) = E_Anonymous_Access_Type then | |
1816 | return True; | |
1817 | end if; | |
1818 | ||
1819 | Next_Discriminant (Disc); | |
1820 | end loop; | |
1821 | ||
1822 | return False; | |
1823 | end Has_Anonymous_Access_Discriminant; | |
1824 | ||
1825 | -------------------------------------------- | |
1826 | -- Has_Unconstrained_Access_Discriminants -- | |
1827 | -------------------------------------------- | |
1828 | ||
1829 | function Has_Unconstrained_Access_Discriminants | |
1830 | (Subtyp : Entity_Id) return Boolean | |
1831 | is | |
1832 | Discr : Entity_Id; | |
1833 | ||
1834 | begin | |
1835 | if Has_Discriminants (Subtyp) | |
1836 | and then not Is_Constrained (Subtyp) | |
1837 | then | |
1838 | Discr := First_Discriminant (Subtyp); | |
1839 | while Present (Discr) loop | |
1840 | if Ekind (Etype (Discr)) = E_Anonymous_Access_Type then | |
1841 | return True; | |
1842 | end if; | |
1843 | ||
1844 | Next_Discriminant (Discr); | |
1845 | end loop; | |
1846 | end if; | |
1847 | ||
1848 | return False; | |
1849 | end Has_Unconstrained_Access_Discriminants; | |
1850 | ||
1851 | -------------------------------- | |
1852 | -- Is_Anonymous_Access_Actual -- | |
1853 | -------------------------------- | |
1854 | ||
1855 | function Is_Anonymous_Access_Actual (N : Node_Id) return Boolean is | |
1856 | Par : Node_Id; | |
1857 | begin | |
1858 | if Ekind (Etype (N)) /= E_Anonymous_Access_Type then | |
1859 | return False; | |
1860 | end if; | |
1861 | ||
1862 | Par := Parent (N); | |
1863 | while Present (Par) | |
1864 | and then Nkind (Par) in N_Case_Expression | |
1865 | | N_If_Expression | |
1866 | | N_Parameter_Association | |
1867 | loop | |
1868 | Par := Parent (Par); | |
1869 | end loop; | |
1870 | return Nkind (Par) in N_Subprogram_Call; | |
1871 | end Is_Anonymous_Access_Actual; | |
1872 | ||
1873 | -------------------------------------- | |
1874 | -- Is_Special_Aliased_Formal_Access -- | |
1875 | -------------------------------------- | |
1876 | ||
1877 | function Is_Special_Aliased_Formal_Access | |
1878 | (Exp : Node_Id; | |
1879 | In_Return_Context : Boolean := False) return Boolean | |
1880 | is | |
1881 | Scop : constant Entity_Id := Current_Subprogram; | |
1882 | begin | |
1883 | -- Verify the expression is an access reference to 'Access within a | |
1884 | -- return statement as this is the only time an explicitly aliased | |
1885 | -- formal has different semantics. | |
1886 | ||
1887 | if Nkind (Exp) /= N_Attribute_Reference | |
1888 | or else Get_Attribute_Id (Attribute_Name (Exp)) /= Attribute_Access | |
1889 | or else not (In_Return_Value (Exp) | |
1890 | or else In_Return_Context) | |
1891 | or else not Needs_Result_Accessibility_Level (Scop) | |
1892 | then | |
1893 | return False; | |
1894 | end if; | |
1895 | ||
1896 | -- Check if the prefix of the reference is indeed an explicitly aliased | |
1897 | -- formal parameter for the function Scop. Additionally, we must check | |
1898 | -- that Scop returns an anonymous access type, otherwise the special | |
1899 | -- rules dictating a need for a dynamic check are not in effect. | |
1900 | ||
1901 | return Is_Entity_Name (Prefix (Exp)) | |
1902 | and then Is_Explicitly_Aliased (Entity (Prefix (Exp))); | |
1903 | end Is_Special_Aliased_Formal_Access; | |
1904 | ||
1905 | -------------------------------------- | |
1906 | -- Needs_Result_Accessibility_Level -- | |
1907 | -------------------------------------- | |
1908 | ||
1909 | function Needs_Result_Accessibility_Level | |
1910 | (Func_Id : Entity_Id) return Boolean | |
1911 | is | |
1912 | Func_Typ : constant Entity_Id := Underlying_Type (Etype (Func_Id)); | |
1913 | ||
1914 | function Has_Unconstrained_Access_Discriminant_Component | |
1915 | (Comp_Typ : Entity_Id) return Boolean; | |
1916 | -- Returns True if any component of the type has an unconstrained access | |
1917 | -- discriminant. | |
1918 | ||
1919 | ----------------------------------------------------- | |
1920 | -- Has_Unconstrained_Access_Discriminant_Component -- | |
1921 | ----------------------------------------------------- | |
1922 | ||
1923 | function Has_Unconstrained_Access_Discriminant_Component | |
1924 | (Comp_Typ : Entity_Id) return Boolean | |
1925 | is | |
1926 | begin | |
1927 | if not Is_Limited_Type (Comp_Typ) then | |
1928 | return False; | |
1929 | ||
1930 | -- Only limited types can have access discriminants with | |
1931 | -- defaults. | |
1932 | ||
1933 | elsif Has_Unconstrained_Access_Discriminants (Comp_Typ) then | |
1934 | return True; | |
1935 | ||
1936 | elsif Is_Array_Type (Comp_Typ) then | |
1937 | return Has_Unconstrained_Access_Discriminant_Component | |
1938 | (Underlying_Type (Component_Type (Comp_Typ))); | |
1939 | ||
1940 | elsif Is_Record_Type (Comp_Typ) then | |
1941 | declare | |
1942 | Comp : Entity_Id; | |
1943 | ||
1944 | begin | |
1945 | Comp := First_Component (Comp_Typ); | |
1946 | while Present (Comp) loop | |
1947 | if Has_Unconstrained_Access_Discriminant_Component | |
1948 | (Underlying_Type (Etype (Comp))) | |
1949 | then | |
1950 | return True; | |
1951 | end if; | |
1952 | ||
1953 | Next_Component (Comp); | |
1954 | end loop; | |
1955 | end; | |
1956 | end if; | |
1957 | ||
1958 | return False; | |
1959 | end Has_Unconstrained_Access_Discriminant_Component; | |
1960 | ||
1961 | Disable_Tagged_Cases : constant Boolean := True; | |
1962 | -- Flag used to temporarily disable a "True" result for tagged types. | |
1963 | -- See comments further below for details. | |
1964 | ||
545af80a | 1965 | -- Start of processing for Needs_Result_Accessibility_Level |
f459afaa JS |
1966 | |
1967 | begin | |
1968 | -- False if completion unavailable, which can happen when we are | |
1969 | -- analyzing an abstract subprogram or if the subprogram has | |
1970 | -- delayed freezing. | |
1971 | ||
1972 | if No (Func_Typ) then | |
1973 | return False; | |
1974 | ||
1975 | -- False if not a function, also handle enum-lit renames case | |
1976 | ||
1977 | elsif Func_Typ = Standard_Void_Type | |
1978 | or else Is_Scalar_Type (Func_Typ) | |
1979 | then | |
1980 | return False; | |
1981 | ||
1982 | -- Handle a corner case, a cross-dialect subp renaming. For example, | |
1983 | -- an Ada 2012 renaming of an Ada 2005 subprogram. This can occur when | |
1984 | -- an Ada 2005 (or earlier) unit references predefined run-time units. | |
1985 | ||
1986 | elsif Present (Alias (Func_Id)) then | |
1987 | ||
1988 | -- Unimplemented: a cross-dialect subp renaming which does not set | |
1989 | -- the Alias attribute (e.g., a rename of a dereference of an access | |
1990 | -- to subprogram value). ??? | |
1991 | ||
1992 | return Present (Extra_Accessibility_Of_Result (Alias (Func_Id))); | |
1993 | ||
1994 | -- Remaining cases require Ada 2012 mode, unless they are dispatching | |
1995 | -- operations, since they may be overridden by Ada_2012 primitives. | |
1996 | ||
1997 | elsif Ada_Version < Ada_2012 | |
1998 | and then not Is_Dispatching_Operation (Func_Id) | |
1999 | then | |
2000 | return False; | |
2001 | ||
2002 | -- Handle the situation where a result is an anonymous access type | |
2003 | -- RM 3.10.2 (10.3/3). | |
2004 | ||
2005 | elsif Ekind (Func_Typ) = E_Anonymous_Access_Type then | |
2006 | return True; | |
2007 | ||
2008 | -- In the case of, say, a null tagged record result type, the need for | |
2009 | -- this extra parameter might not be obvious so this function returns | |
2010 | -- True for all tagged types for compatibility reasons. | |
2011 | ||
2012 | -- A function with, say, a tagged null controlling result type might | |
2013 | -- be overridden by a primitive of an extension having an access | |
2014 | -- discriminant and the overrider and overridden must have compatible | |
2015 | -- calling conventions (including implicitly declared parameters). | |
2016 | ||
2017 | -- Similarly, values of one access-to-subprogram type might designate | |
2018 | -- both a primitive subprogram of a given type and a function which is, | |
2019 | -- for example, not a primitive subprogram of any type. Again, this | |
2020 | -- requires calling convention compatibility. It might be possible to | |
2021 | -- solve these issues by introducing wrappers, but that is not the | |
2022 | -- approach that was chosen. | |
2023 | ||
2024 | -- Note: Despite the reasoning noted above, the extra accessibility | |
2025 | -- parameter for tagged types is disabled for performance reasons. | |
2026 | ||
2027 | elsif Is_Tagged_Type (Func_Typ) then | |
2028 | return not Disable_Tagged_Cases; | |
2029 | ||
2030 | elsif Has_Unconstrained_Access_Discriminants (Func_Typ) then | |
2031 | return True; | |
2032 | ||
2033 | elsif Has_Unconstrained_Access_Discriminant_Component (Func_Typ) then | |
2034 | return True; | |
2035 | ||
2036 | -- False for all other cases | |
2037 | ||
2038 | else | |
2039 | return False; | |
2040 | end if; | |
545af80a | 2041 | end Needs_Result_Accessibility_Level; |
f459afaa JS |
2042 | |
2043 | ------------------------------------------ | |
2044 | -- Prefix_With_Safe_Accessibility_Level -- | |
2045 | ------------------------------------------ | |
2046 | ||
2047 | function Prefix_With_Safe_Accessibility_Level | |
2048 | (N : Node_Id; | |
2049 | Typ : Entity_Id) return Boolean | |
2050 | is | |
2051 | P : constant Node_Id := Prefix (N); | |
2052 | Aname : constant Name_Id := Attribute_Name (N); | |
2053 | Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname); | |
2054 | Btyp : constant Entity_Id := Base_Type (Typ); | |
2055 | ||
2056 | function Safe_Value_Conversions return Boolean; | |
2057 | -- Return False if the prefix has a value conversion of an array type | |
2058 | ||
2059 | ---------------------------- | |
2060 | -- Safe_Value_Conversions -- | |
2061 | ---------------------------- | |
2062 | ||
2063 | function Safe_Value_Conversions return Boolean is | |
2064 | PP : Node_Id := P; | |
2065 | ||
2066 | begin | |
2067 | loop | |
2068 | if Nkind (PP) in N_Selected_Component | N_Indexed_Component then | |
2069 | PP := Prefix (PP); | |
2070 | ||
2071 | elsif Comes_From_Source (PP) | |
2072 | and then Nkind (PP) in N_Type_Conversion | |
2073 | | N_Unchecked_Type_Conversion | |
2074 | and then Is_Array_Type (Etype (PP)) | |
2075 | then | |
2076 | return False; | |
2077 | ||
2078 | elsif Comes_From_Source (PP) | |
2079 | and then Nkind (PP) = N_Qualified_Expression | |
2080 | and then Is_Array_Type (Etype (PP)) | |
2081 | and then Nkind (Original_Node (Expression (PP))) in | |
2082 | N_Aggregate | N_Extension_Aggregate | |
2083 | then | |
2084 | return False; | |
2085 | ||
2086 | else | |
2087 | exit; | |
2088 | end if; | |
2089 | end loop; | |
2090 | ||
2091 | return True; | |
2092 | end Safe_Value_Conversions; | |
2093 | ||
2094 | -- Start of processing for Prefix_With_Safe_Accessibility_Level | |
2095 | ||
2096 | begin | |
2097 | -- No check required for unchecked and unrestricted access | |
2098 | ||
2099 | if Attr_Id = Attribute_Unchecked_Access | |
2100 | or else Attr_Id = Attribute_Unrestricted_Access | |
2101 | then | |
2102 | return True; | |
2103 | ||
2104 | -- Check value conversions | |
2105 | ||
2106 | elsif Ekind (Btyp) = E_General_Access_Type | |
2107 | and then not Safe_Value_Conversions | |
2108 | then | |
2109 | return False; | |
2110 | end if; | |
2111 | ||
2112 | return True; | |
2113 | end Prefix_With_Safe_Accessibility_Level; | |
2114 | ||
2115 | ----------------------------- | |
2116 | -- Subprogram_Access_Level -- | |
2117 | ----------------------------- | |
2118 | ||
2119 | function Subprogram_Access_Level (Subp : Entity_Id) return Uint is | |
2120 | begin | |
2121 | if Present (Alias (Subp)) then | |
2122 | return Subprogram_Access_Level (Alias (Subp)); | |
2123 | else | |
2124 | return Scope_Depth (Enclosing_Dynamic_Scope (Subp)); | |
2125 | end if; | |
2126 | end Subprogram_Access_Level; | |
2127 | ||
2128 | -------------------------------- | |
2129 | -- Static_Accessibility_Level -- | |
2130 | -------------------------------- | |
2131 | ||
2132 | function Static_Accessibility_Level | |
2133 | (Expr : Node_Id; | |
2134 | Level : Static_Accessibility_Level_Kind; | |
2135 | In_Return_Context : Boolean := False) return Uint | |
2136 | is | |
2137 | begin | |
2138 | return Intval | |
2139 | (Accessibility_Level (Expr, Level, In_Return_Context)); | |
2140 | end Static_Accessibility_Level; | |
2141 | ||
2142 | ----------------------- | |
2143 | -- Type_Access_Level -- | |
2144 | ----------------------- | |
2145 | ||
2146 | function Type_Access_Level | |
2147 | (Typ : Entity_Id; | |
2148 | Allow_Alt_Model : Boolean := True; | |
2149 | Assoc_Ent : Entity_Id := Empty) return Uint | |
2150 | is | |
2151 | Btyp : Entity_Id := Base_Type (Typ); | |
2152 | Def_Ent : Entity_Id; | |
2153 | ||
2154 | begin | |
2155 | -- Ada 2005 (AI-230): For most cases of anonymous access types, we | |
2156 | -- simply use the level where the type is declared. This is true for | |
2157 | -- stand-alone object declarations, and for anonymous access types | |
2158 | -- associated with components the level is the same as that of the | |
2159 | -- enclosing composite type. However, special treatment is needed for | |
2160 | -- the cases of access parameters, return objects of an anonymous access | |
2161 | -- type, and, in Ada 95, access discriminants of limited types. | |
2162 | ||
2163 | if Is_Access_Type (Btyp) then | |
2164 | if Ekind (Btyp) = E_Anonymous_Access_Type then | |
2165 | -- No_Dynamic_Accessibility_Checks restriction override for | |
2166 | -- alternative accessibility model. | |
2167 | ||
2168 | if Allow_Alt_Model | |
2169 | and then No_Dynamic_Accessibility_Checks_Enabled (Btyp) | |
2170 | then | |
2171 | -- In the -gnatd_b model, the level of an anonymous access | |
2172 | -- type is always that of the designated type. | |
2173 | ||
2174 | if Debug_Flag_Underscore_B then | |
2175 | return Type_Access_Level | |
2176 | (Designated_Type (Btyp), Allow_Alt_Model); | |
2177 | end if; | |
2178 | ||
2179 | -- When an anonymous access type's Assoc_Ent is specified, | |
2180 | -- calculate the result based on the general accessibility | |
2181 | -- level routine. | |
2182 | ||
2183 | -- We would like to use Associated_Node_For_Itype here instead, | |
2184 | -- but in some cases it is not fine grained enough ??? | |
2185 | ||
2186 | if Present (Assoc_Ent) then | |
2187 | return Static_Accessibility_Level | |
2188 | (Assoc_Ent, Object_Decl_Level); | |
2189 | end if; | |
2190 | ||
2191 | -- Otherwise take the context of the anonymous access type into | |
2192 | -- account. | |
2193 | ||
2194 | -- Obtain the defining entity for the internally generated | |
2195 | -- anonymous access type. | |
2196 | ||
2197 | Def_Ent := Defining_Entity_Or_Empty | |
2198 | (Associated_Node_For_Itype (Typ)); | |
2199 | ||
2200 | if Present (Def_Ent) then | |
2201 | -- When the defining entity is a subprogram then we know the | |
2202 | -- anonymous access type Typ has been generated to either | |
2203 | -- describe an anonymous access type formal or an anonymous | |
2204 | -- access result type. | |
2205 | ||
2206 | -- Since we are only interested in the formal case, avoid | |
2207 | -- the anonymous access result type. | |
2208 | ||
2209 | if Is_Subprogram (Def_Ent) | |
2210 | and then not (Ekind (Def_Ent) = E_Function | |
2211 | and then Etype (Def_Ent) = Typ) | |
2212 | then | |
2213 | -- When the type comes from an anonymous access | |
2214 | -- parameter, the level is that of the subprogram | |
2215 | -- declaration. | |
2216 | ||
2217 | return Scope_Depth (Def_Ent); | |
2218 | ||
2219 | -- When the type is an access discriminant, the level is | |
2220 | -- that of the type. | |
2221 | ||
2222 | elsif Ekind (Def_Ent) = E_Discriminant then | |
2223 | return Scope_Depth (Scope (Def_Ent)); | |
2224 | end if; | |
2225 | end if; | |
2226 | ||
2227 | -- If the type is a nonlocal anonymous access type (such as for | |
2228 | -- an access parameter) we treat it as being declared at the | |
2229 | -- library level to ensure that names such as X.all'access don't | |
2230 | -- fail static accessibility checks. | |
2231 | ||
2232 | elsif not Is_Local_Anonymous_Access (Typ) then | |
2233 | return Scope_Depth (Standard_Standard); | |
2234 | ||
2235 | -- If this is a return object, the accessibility level is that of | |
2236 | -- the result subtype of the enclosing function. The test here is | |
2237 | -- little complicated, because we have to account for extended | |
2238 | -- return statements that have been rewritten as blocks, in which | |
2239 | -- case we have to find and the Is_Return_Object attribute of the | |
2240 | -- itype's associated object. It would be nice to find a way to | |
2241 | -- simplify this test, but it doesn't seem worthwhile to add a new | |
2242 | -- flag just for purposes of this test. ??? | |
2243 | ||
2244 | elsif Ekind (Scope (Btyp)) = E_Return_Statement | |
2245 | or else | |
2246 | (Is_Itype (Btyp) | |
2247 | and then Nkind (Associated_Node_For_Itype (Btyp)) = | |
2248 | N_Object_Declaration | |
2249 | and then Is_Return_Object | |
2250 | (Defining_Identifier | |
2251 | (Associated_Node_For_Itype (Btyp)))) | |
2252 | then | |
2253 | declare | |
2254 | Scop : Entity_Id; | |
2255 | ||
2256 | begin | |
2257 | Scop := Scope (Scope (Btyp)); | |
2258 | while Present (Scop) loop | |
2259 | exit when Ekind (Scop) = E_Function; | |
2260 | Scop := Scope (Scop); | |
2261 | end loop; | |
2262 | ||
2263 | -- Treat the return object's type as having the level of the | |
2264 | -- function's result subtype (as per RM05-6.5(5.3/2)). | |
2265 | ||
2266 | return Type_Access_Level (Etype (Scop), Allow_Alt_Model); | |
2267 | end; | |
2268 | end if; | |
2269 | end if; | |
2270 | ||
2271 | Btyp := Root_Type (Btyp); | |
2272 | ||
2273 | -- The accessibility level of anonymous access types associated with | |
2274 | -- discriminants is that of the current instance of the type, and | |
2275 | -- that's deeper than the type itself (AARM 3.10.2 (12.3.21)). | |
2276 | ||
2277 | -- AI-402: access discriminants have accessibility based on the | |
2278 | -- object rather than the type in Ada 2005, so the above paragraph | |
2279 | -- doesn't apply. | |
2280 | ||
2281 | -- ??? Needs completion with rules from AI-416 | |
2282 | ||
2283 | if Ada_Version <= Ada_95 | |
2284 | and then Ekind (Typ) = E_Anonymous_Access_Type | |
2285 | and then Present (Associated_Node_For_Itype (Typ)) | |
2286 | and then Nkind (Associated_Node_For_Itype (Typ)) = | |
2287 | N_Discriminant_Specification | |
2288 | then | |
2289 | return Scope_Depth (Enclosing_Dynamic_Scope (Btyp)) + 1; | |
2290 | end if; | |
2291 | end if; | |
2292 | ||
2293 | -- Return library level for a generic formal type. This is done because | |
2294 | -- RM(10.3.2) says that "The statically deeper relationship does not | |
2295 | -- apply to ... a descendant of a generic formal type". Rather than | |
2296 | -- checking at each point where a static accessibility check is | |
2297 | -- performed to see if we are dealing with a formal type, this rule is | |
2298 | -- implemented by having Type_Access_Level and Deepest_Type_Access_Level | |
2299 | -- return extreme values for a formal type; Deepest_Type_Access_Level | |
2300 | -- returns Int'Last. By calling the appropriate function from among the | |
2301 | -- two, we ensure that the static accessibility check will pass if we | |
2302 | -- happen to run into a formal type. More specifically, we should call | |
2303 | -- Deepest_Type_Access_Level instead of Type_Access_Level whenever the | |
2304 | -- call occurs as part of a static accessibility check and the error | |
2305 | -- case is the case where the type's level is too shallow (as opposed | |
2306 | -- to too deep). | |
2307 | ||
2308 | if Is_Generic_Type (Root_Type (Btyp)) then | |
2309 | return Scope_Depth (Standard_Standard); | |
2310 | end if; | |
2311 | ||
2312 | return Scope_Depth (Enclosing_Dynamic_Scope (Btyp)); | |
2313 | end Type_Access_Level; | |
2314 | ||
2315 | end Accessibility; |