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Update concepts branch to revision 131834
[official-gcc.git] / gcc / ada / sem_disp.adb
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1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT COMPILER COMPONENTS --
4 -- --
5 -- S E M _ D I S P --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 1992-2008, Free Software Foundation, Inc. --
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 Debug; use Debug;
28 with Elists; use Elists;
29 with Einfo; use Einfo;
30 with Exp_Disp; use Exp_Disp;
31 with Exp_Ch7; use Exp_Ch7;
32 with Exp_Tss; use Exp_Tss;
33 with Errout; use Errout;
34 with Lib.Xref; use Lib.Xref;
35 with Namet; use Namet;
36 with Nlists; use Nlists;
37 with Nmake; use Nmake;
38 with Opt; use Opt;
39 with Output; use Output;
40 with Restrict; use Restrict;
41 with Rident; use Rident;
42 with Sem; use Sem;
43 with Sem_Ch6; use Sem_Ch6;
44 with Sem_Eval; use Sem_Eval;
45 with Sem_Type; use Sem_Type;
46 with Sem_Util; use Sem_Util;
47 with Snames; use Snames;
48 with Stand; use Stand;
49 with Sinfo; use Sinfo;
50 with Targparm; use Targparm;
51 with Tbuild; use Tbuild;
52 with Uintp; use Uintp;
53
54 package body Sem_Disp is
55
56 -----------------------
57 -- Local Subprograms --
58 -----------------------
59
60 procedure Add_Dispatching_Operation
61 (Tagged_Type : Entity_Id;
62 New_Op : Entity_Id);
63 -- Add New_Op in the list of primitive operations of Tagged_Type
64
65 function Check_Controlling_Type
66 (T : Entity_Id;
67 Subp : Entity_Id) return Entity_Id;
68 -- T is the tagged type of a formal parameter or the result of Subp.
69 -- If the subprogram has a controlling parameter or result that matches
70 -- the type, then returns the tagged type of that parameter or result
71 -- (returning the designated tagged type in the case of an access
72 -- parameter); otherwise returns empty.
73
74 -------------------------------
75 -- Add_Dispatching_Operation --
76 -------------------------------
77
78 procedure Add_Dispatching_Operation
79 (Tagged_Type : Entity_Id;
80 New_Op : Entity_Id)
81 is
82 List : constant Elist_Id := Primitive_Operations (Tagged_Type);
83
84 begin
85 -- The dispatching operation may already be on the list, if it the
86 -- wrapper for an inherited function of a null extension (see exp_ch3
87 -- for the construction of function wrappers). The list of primitive
88 -- operations must not contain duplicates.
89
90 Append_Unique_Elmt (New_Op, List);
91 end Add_Dispatching_Operation;
92
93 -------------------------------
94 -- Check_Controlling_Formals --
95 -------------------------------
96
97 procedure Check_Controlling_Formals
98 (Typ : Entity_Id;
99 Subp : Entity_Id)
100 is
101 Formal : Entity_Id;
102 Ctrl_Type : Entity_Id;
103
104 begin
105 Formal := First_Formal (Subp);
106
107 while Present (Formal) loop
108 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
109
110 if Present (Ctrl_Type) then
111
112 -- When the controlling type is concurrent and declared within a
113 -- generic or inside an instance, use its corresponding record
114 -- type.
115
116 if Is_Concurrent_Type (Ctrl_Type)
117 and then Present (Corresponding_Record_Type (Ctrl_Type))
118 then
119 Ctrl_Type := Corresponding_Record_Type (Ctrl_Type);
120 end if;
121
122 if Ctrl_Type = Typ then
123 Set_Is_Controlling_Formal (Formal);
124
125 -- Ada 2005 (AI-231): Anonymous access types used in
126 -- controlling parameters exclude null because it is necessary
127 -- to read the tag to dispatch, and null has no tag.
128
129 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
130 Set_Can_Never_Be_Null (Etype (Formal));
131 Set_Is_Known_Non_Null (Etype (Formal));
132 end if;
133
134 -- Check that the parameter's nominal subtype statically
135 -- matches the first subtype.
136
137 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
138 if not Subtypes_Statically_Match
139 (Typ, Designated_Type (Etype (Formal)))
140 then
141 Error_Msg_N
142 ("parameter subtype does not match controlling type",
143 Formal);
144 end if;
145
146 elsif not Subtypes_Statically_Match (Typ, Etype (Formal)) then
147 Error_Msg_N
148 ("parameter subtype does not match controlling type",
149 Formal);
150 end if;
151
152 if Present (Default_Value (Formal)) then
153
154 -- In Ada 2005, access parameters can have defaults
155
156 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type
157 and then Ada_Version < Ada_05
158 then
159 Error_Msg_N
160 ("default not allowed for controlling access parameter",
161 Default_Value (Formal));
162
163 elsif not Is_Tag_Indeterminate (Default_Value (Formal)) then
164 Error_Msg_N
165 ("default expression must be a tag indeterminate" &
166 " function call", Default_Value (Formal));
167 end if;
168 end if;
169
170 elsif Comes_From_Source (Subp) then
171 Error_Msg_N
172 ("operation can be dispatching in only one type", Subp);
173 end if;
174 end if;
175
176 Next_Formal (Formal);
177 end loop;
178
179 if Present (Etype (Subp)) then
180 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
181
182 if Present (Ctrl_Type) then
183 if Ctrl_Type = Typ then
184 Set_Has_Controlling_Result (Subp);
185
186 -- Check that result subtype statically matches first subtype
187 -- (Ada 2005) : Subp may have a controlling access result.
188
189 if Subtypes_Statically_Match (Typ, Etype (Subp))
190 or else (Ekind (Etype (Subp)) = E_Anonymous_Access_Type
191 and then
192 Subtypes_Statically_Match
193 (Typ, Designated_Type (Etype (Subp))))
194 then
195 null;
196
197 else
198 Error_Msg_N
199 ("result subtype does not match controlling type", Subp);
200 end if;
201
202 elsif Comes_From_Source (Subp) then
203 Error_Msg_N
204 ("operation can be dispatching in only one type", Subp);
205 end if;
206 end if;
207 end if;
208 end Check_Controlling_Formals;
209
210 ----------------------------
211 -- Check_Controlling_Type --
212 ----------------------------
213
214 function Check_Controlling_Type
215 (T : Entity_Id;
216 Subp : Entity_Id) return Entity_Id
217 is
218 Tagged_Type : Entity_Id := Empty;
219
220 begin
221 if Is_Tagged_Type (T) then
222 if Is_First_Subtype (T) then
223 Tagged_Type := T;
224 else
225 Tagged_Type := Base_Type (T);
226 end if;
227
228 elsif Ekind (T) = E_Anonymous_Access_Type
229 and then Is_Tagged_Type (Designated_Type (T))
230 then
231 if Ekind (Designated_Type (T)) /= E_Incomplete_Type then
232 if Is_First_Subtype (Designated_Type (T)) then
233 Tagged_Type := Designated_Type (T);
234 else
235 Tagged_Type := Base_Type (Designated_Type (T));
236 end if;
237
238 -- Ada 2005 : an incomplete type can be tagged. An operation with
239 -- an access parameter of the type is dispatching.
240
241 elsif Scope (Designated_Type (T)) = Current_Scope then
242 Tagged_Type := Designated_Type (T);
243
244 -- Ada 2005 (AI-50217)
245
246 elsif From_With_Type (Designated_Type (T))
247 and then Present (Non_Limited_View (Designated_Type (T)))
248 then
249 if Is_First_Subtype (Non_Limited_View (Designated_Type (T))) then
250 Tagged_Type := Non_Limited_View (Designated_Type (T));
251 else
252 Tagged_Type := Base_Type (Non_Limited_View
253 (Designated_Type (T)));
254 end if;
255 end if;
256 end if;
257
258 if No (Tagged_Type)
259 or else Is_Class_Wide_Type (Tagged_Type)
260 then
261 return Empty;
262
263 -- The dispatching type and the primitive operation must be defined
264 -- in the same scope, except in the case of internal operations and
265 -- formal abstract subprograms.
266
267 elsif ((Scope (Subp) = Scope (Tagged_Type) or else Is_Internal (Subp))
268 and then (not Is_Generic_Type (Tagged_Type)
269 or else not Comes_From_Source (Subp)))
270 or else
271 (Is_Formal_Subprogram (Subp) and then Is_Abstract_Subprogram (Subp))
272 or else
273 (Nkind (Parent (Parent (Subp))) = N_Subprogram_Renaming_Declaration
274 and then
275 Present (Corresponding_Formal_Spec (Parent (Parent (Subp))))
276 and then
277 Is_Abstract_Subprogram (Subp))
278 then
279 return Tagged_Type;
280
281 else
282 return Empty;
283 end if;
284 end Check_Controlling_Type;
285
286 ----------------------------
287 -- Check_Dispatching_Call --
288 ----------------------------
289
290 procedure Check_Dispatching_Call (N : Node_Id) is
291 Loc : constant Source_Ptr := Sloc (N);
292 Actual : Node_Id;
293 Formal : Entity_Id;
294 Control : Node_Id := Empty;
295 Func : Entity_Id;
296 Subp_Entity : Entity_Id;
297 Indeterm_Ancestor_Call : Boolean := False;
298 Indeterm_Ctrl_Type : Entity_Id;
299
300 Static_Tag : Node_Id := Empty;
301 -- If a controlling formal has a statically tagged actual, the tag of
302 -- this actual is to be used for any tag-indeterminate actual
303
304 procedure Check_Dispatching_Context;
305 -- If the call is tag-indeterminate and the entity being called is
306 -- abstract, verify that the context is a call that will eventually
307 -- provide a tag for dispatching, or has provided one already.
308
309 -------------------------------
310 -- Check_Dispatching_Context --
311 -------------------------------
312
313 procedure Check_Dispatching_Context is
314 Subp : constant Entity_Id := Entity (Name (N));
315 Par : Node_Id;
316
317 begin
318 if Is_Abstract_Subprogram (Subp)
319 and then No (Controlling_Argument (N))
320 then
321 if Present (Alias (Subp))
322 and then not Is_Abstract_Subprogram (Alias (Subp))
323 and then No (DTC_Entity (Subp))
324 then
325 -- Private overriding of inherited abstract operation,
326 -- call is legal.
327
328 Set_Entity (Name (N), Alias (Subp));
329 return;
330
331 else
332 Par := Parent (N);
333
334 while Present (Par) loop
335
336 if (Nkind (Par) = N_Function_Call or else
337 Nkind (Par) = N_Procedure_Call_Statement or else
338 Nkind (Par) = N_Assignment_Statement or else
339 Nkind (Par) = N_Op_Eq or else
340 Nkind (Par) = N_Op_Ne)
341 and then Is_Tagged_Type (Etype (Subp))
342 then
343 return;
344
345 elsif Nkind (Par) = N_Qualified_Expression
346 or else Nkind (Par) = N_Unchecked_Type_Conversion
347 then
348 Par := Parent (Par);
349
350 else
351 if Ekind (Subp) = E_Function then
352 Error_Msg_N
353 ("call to abstract function must be dispatching", N);
354
355 -- This error can occur for a procedure in the case of a
356 -- call to an abstract formal procedure with a statically
357 -- tagged operand.
358
359 else
360 Error_Msg_N
361 ("call to abstract procedure must be dispatching",
362 N);
363 end if;
364
365 return;
366 end if;
367 end loop;
368 end if;
369 end if;
370 end Check_Dispatching_Context;
371
372 -- Start of processing for Check_Dispatching_Call
373
374 begin
375 -- Find a controlling argument, if any
376
377 if Present (Parameter_Associations (N)) then
378 Actual := First_Actual (N);
379
380 Subp_Entity := Entity (Name (N));
381 Formal := First_Formal (Subp_Entity);
382
383 while Present (Actual) loop
384 Control := Find_Controlling_Arg (Actual);
385 exit when Present (Control);
386
387 -- Check for the case where the actual is a tag-indeterminate call
388 -- whose result type is different than the tagged type associated
389 -- with the containing call, but is an ancestor of the type.
390
391 if Is_Controlling_Formal (Formal)
392 and then Is_Tag_Indeterminate (Actual)
393 and then Base_Type (Etype (Actual)) /= Base_Type (Etype (Formal))
394 and then Is_Ancestor (Etype (Actual), Etype (Formal))
395 then
396 Indeterm_Ancestor_Call := True;
397 Indeterm_Ctrl_Type := Etype (Formal);
398
399 -- If the formal is controlling but the actual is not, the type
400 -- of the actual is statically known, and may be used as the
401 -- controlling tag for some other-indeterminate actual.
402
403 elsif Is_Controlling_Formal (Formal)
404 and then Is_Entity_Name (Actual)
405 and then Is_Tagged_Type (Etype (Actual))
406 then
407 Static_Tag := Actual;
408 end if;
409
410 Next_Actual (Actual);
411 Next_Formal (Formal);
412 end loop;
413
414 -- If the call doesn't have a controlling actual but does have
415 -- an indeterminate actual that requires dispatching treatment,
416 -- then an object is needed that will serve as the controlling
417 -- argument for a dispatching call on the indeterminate actual.
418 -- This can only occur in the unusual situation of a default
419 -- actual given by a tag-indeterminate call and where the type
420 -- of the call is an ancestor of the type associated with a
421 -- containing call to an inherited operation (see AI-239).
422 -- Rather than create an object of the tagged type, which would
423 -- be problematic for various reasons (default initialization,
424 -- discriminants), the tag of the containing call's associated
425 -- tagged type is directly used to control the dispatching.
426
427 if No (Control)
428 and then Indeterm_Ancestor_Call
429 and then No (Static_Tag)
430 then
431 Control :=
432 Make_Attribute_Reference (Loc,
433 Prefix => New_Occurrence_Of (Indeterm_Ctrl_Type, Loc),
434 Attribute_Name => Name_Tag);
435
436 Analyze (Control);
437 end if;
438
439 if Present (Control) then
440
441 -- Verify that no controlling arguments are statically tagged
442
443 if Debug_Flag_E then
444 Write_Str ("Found Dispatching call");
445 Write_Int (Int (N));
446 Write_Eol;
447 end if;
448
449 Actual := First_Actual (N);
450
451 while Present (Actual) loop
452 if Actual /= Control then
453
454 if not Is_Controlling_Actual (Actual) then
455 null; -- Can be anything
456
457 elsif Is_Dynamically_Tagged (Actual) then
458 null; -- Valid parameter
459
460 elsif Is_Tag_Indeterminate (Actual) then
461
462 -- The tag is inherited from the enclosing call (the
463 -- node we are currently analyzing). Explicitly expand
464 -- the actual, since the previous call to Expand
465 -- (from Resolve_Call) had no way of knowing about
466 -- the required dispatching.
467
468 Propagate_Tag (Control, Actual);
469
470 else
471 Error_Msg_N
472 ("controlling argument is not dynamically tagged",
473 Actual);
474 return;
475 end if;
476 end if;
477
478 Next_Actual (Actual);
479 end loop;
480
481 -- Mark call as a dispatching call
482
483 Set_Controlling_Argument (N, Control);
484 Check_Restriction (No_Dispatching_Calls, N);
485
486 -- If there is a statically tagged actual and a tag-indeterminate
487 -- call to a function of the ancestor (such as that provided by a
488 -- default), then treat this as a dispatching call and propagate
489 -- the tag to the tag-indeterminate call(s).
490
491 elsif Present (Static_Tag) and then Indeterm_Ancestor_Call then
492 Control :=
493 Make_Attribute_Reference (Loc,
494 Prefix =>
495 New_Occurrence_Of (Etype (Static_Tag), Loc),
496 Attribute_Name => Name_Tag);
497
498 Analyze (Control);
499
500 Actual := First_Actual (N);
501 Formal := First_Formal (Subp_Entity);
502 while Present (Actual) loop
503 if Is_Tag_Indeterminate (Actual)
504 and then Is_Controlling_Formal (Formal)
505 then
506 Propagate_Tag (Control, Actual);
507 end if;
508
509 Next_Actual (Actual);
510 Next_Formal (Formal);
511 end loop;
512
513 Check_Dispatching_Context;
514
515 else
516 -- The call is not dispatching, so check that there aren't any
517 -- tag-indeterminate abstract calls left.
518
519 Actual := First_Actual (N);
520 while Present (Actual) loop
521 if Is_Tag_Indeterminate (Actual) then
522
523 -- Function call case
524
525 if Nkind (Original_Node (Actual)) = N_Function_Call then
526 Func := Entity (Name (Original_Node (Actual)));
527
528 -- If the actual is an attribute then it can't be abstract
529 -- (the only current case of a tag-indeterminate attribute
530 -- is the stream Input attribute).
531
532 elsif
533 Nkind (Original_Node (Actual)) = N_Attribute_Reference
534 then
535 Func := Empty;
536
537 -- Only other possibility is a qualified expression whose
538 -- constituent expression is itself a call.
539
540 else
541 Func :=
542 Entity (Name
543 (Original_Node
544 (Expression (Original_Node (Actual)))));
545 end if;
546
547 if Present (Func) and then Is_Abstract_Subprogram (Func) then
548 Error_Msg_N (
549 "call to abstract function must be dispatching", N);
550 end if;
551 end if;
552
553 Next_Actual (Actual);
554 end loop;
555
556 Check_Dispatching_Context;
557 end if;
558
559 else
560 -- If dispatching on result, the enclosing call, if any, will
561 -- determine the controlling argument. Otherwise this is the
562 -- primitive operation of the root type.
563
564 Check_Dispatching_Context;
565 end if;
566 end Check_Dispatching_Call;
567
568 ---------------------------------
569 -- Check_Dispatching_Operation --
570 ---------------------------------
571
572 procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id) is
573 Tagged_Type : Entity_Id;
574 Has_Dispatching_Parent : Boolean := False;
575 Body_Is_Last_Primitive : Boolean := False;
576
577 function Is_Visibly_Controlled (T : Entity_Id) return Boolean;
578 -- Check whether T is derived from a visibly controlled type.
579 -- This is true if the root type is declared in Ada.Finalization.
580 -- If T is derived instead from a private type whose full view
581 -- is controlled, an explicit Initialize/Adjust/Finalize subprogram
582 -- does not override the inherited one.
583
584 ---------------------------
585 -- Is_Visibly_Controlled --
586 ---------------------------
587
588 function Is_Visibly_Controlled (T : Entity_Id) return Boolean is
589 Root : constant Entity_Id := Root_Type (T);
590 begin
591 return Chars (Scope (Root)) = Name_Finalization
592 and then Chars (Scope (Scope (Root))) = Name_Ada
593 and then Scope (Scope (Scope (Root))) = Standard_Standard;
594 end Is_Visibly_Controlled;
595
596 -- Start of processing for Check_Dispatching_Operation
597
598 begin
599 if Ekind (Subp) /= E_Procedure and then Ekind (Subp) /= E_Function then
600 return;
601 end if;
602
603 Set_Is_Dispatching_Operation (Subp, False);
604 Tagged_Type := Find_Dispatching_Type (Subp);
605
606 -- Ada 2005 (AI-345)
607
608 if Ada_Version = Ada_05
609 and then Present (Tagged_Type)
610 and then Is_Concurrent_Type (Tagged_Type)
611 then
612 -- Protect the frontend against previously detected errors
613
614 if No (Corresponding_Record_Type (Tagged_Type)) then
615 return;
616 end if;
617
618 Tagged_Type := Corresponding_Record_Type (Tagged_Type);
619 end if;
620
621 -- (AI-345): The task body procedure is not a primitive of the tagged
622 -- type
623
624 if Present (Tagged_Type)
625 and then Is_Concurrent_Record_Type (Tagged_Type)
626 and then Present (Corresponding_Concurrent_Type (Tagged_Type))
627 and then Is_Task_Type (Corresponding_Concurrent_Type (Tagged_Type))
628 and then Subp = Get_Task_Body_Procedure
629 (Corresponding_Concurrent_Type (Tagged_Type))
630 then
631 return;
632 end if;
633
634 -- If Subp is derived from a dispatching operation then it should
635 -- always be treated as dispatching. In this case various checks
636 -- below will be bypassed. Makes sure that late declarations for
637 -- inherited private subprograms are treated as dispatching, even
638 -- if the associated tagged type is already frozen.
639
640 Has_Dispatching_Parent :=
641 Present (Alias (Subp))
642 and then Is_Dispatching_Operation (Alias (Subp));
643
644 if No (Tagged_Type) then
645
646 -- Ada 2005 (AI-251): Check that Subp is not a primitive associated
647 -- with an abstract interface type unless the interface acts as a
648 -- parent type in a derivation. If the interface type is a formal
649 -- type then the operation is not primitive and therefore legal.
650
651 declare
652 E : Entity_Id;
653 Typ : Entity_Id;
654
655 begin
656 E := First_Entity (Subp);
657 while Present (E) loop
658
659 -- For an access parameter, check designated type.
660
661 if Ekind (Etype (E)) = E_Anonymous_Access_Type then
662 Typ := Designated_Type (Etype (E));
663 else
664 Typ := Etype (E);
665 end if;
666
667 if Comes_From_Source (Subp)
668 and then Is_Interface (Typ)
669 and then not Is_Class_Wide_Type (Typ)
670 and then not Is_Derived_Type (Typ)
671 and then not Is_Generic_Type (Typ)
672 and then not In_Instance
673 then
674 Error_Msg_N ("?declaration of& is too late!", Subp);
675 Error_Msg_NE
676 ("\spec should appear immediately after declaration of &!",
677 Subp, Typ);
678 exit;
679 end if;
680
681 Next_Entity (E);
682 end loop;
683
684 -- In case of functions check also the result type
685
686 if Ekind (Subp) = E_Function then
687 if Is_Access_Type (Etype (Subp)) then
688 Typ := Designated_Type (Etype (Subp));
689 else
690 Typ := Etype (Subp);
691 end if;
692
693 if not Is_Class_Wide_Type (Typ)
694 and then Is_Interface (Typ)
695 and then not Is_Derived_Type (Typ)
696 then
697 Error_Msg_N ("?declaration of& is too late!", Subp);
698 Error_Msg_NE
699 ("\spec should appear immediately after declaration of &!",
700 Subp, Typ);
701 end if;
702 end if;
703 end;
704
705 return;
706
707 -- The subprograms build internally after the freezing point (such as
708 -- the Init procedure) are not primitives
709
710 elsif Is_Frozen (Tagged_Type)
711 and then not Comes_From_Source (Subp)
712 and then not Has_Dispatching_Parent
713 then
714 return;
715
716 -- The operation may be a child unit, whose scope is the defining
717 -- package, but which is not a primitive operation of the type.
718
719 elsif Is_Child_Unit (Subp) then
720 return;
721
722 -- If the subprogram is not defined in a package spec, the only case
723 -- where it can be a dispatching op is when it overrides an operation
724 -- before the freezing point of the type.
725
726 elsif ((not Is_Package_Or_Generic_Package (Scope (Subp)))
727 or else In_Package_Body (Scope (Subp)))
728 and then not Has_Dispatching_Parent
729 then
730 if not Comes_From_Source (Subp)
731 or else (Present (Old_Subp) and then not Is_Frozen (Tagged_Type))
732 then
733 null;
734
735 -- If the type is already frozen, the overriding is not allowed
736 -- except when Old_Subp is not a dispatching operation (which
737 -- can occur when Old_Subp was inherited by an untagged type).
738 -- However, a body with no previous spec freezes the type "after"
739 -- its declaration, and therefore is a legal overriding (unless
740 -- the type has already been frozen). Only the first such body
741 -- is legal.
742
743 elsif Present (Old_Subp)
744 and then Is_Dispatching_Operation (Old_Subp)
745 then
746 if Comes_From_Source (Subp)
747 and then
748 (Nkind (Unit_Declaration_Node (Subp)) = N_Subprogram_Body
749 or else Nkind (Unit_Declaration_Node (Subp)) in N_Body_Stub)
750 then
751 declare
752 Subp_Body : constant Node_Id := Unit_Declaration_Node (Subp);
753 Decl_Item : Node_Id := Next (Parent (Tagged_Type));
754
755 begin
756 -- ??? The checks here for whether the type has been
757 -- frozen prior to the new body are not complete. It's
758 -- not simple to check frozenness at this point since
759 -- the body has already caused the type to be prematurely
760 -- frozen in Analyze_Declarations, but we're forced to
761 -- recheck this here because of the odd rule interpretation
762 -- that allows the overriding if the type wasn't frozen
763 -- prior to the body. The freezing action should probably
764 -- be delayed until after the spec is seen, but that's
765 -- a tricky change to the delicate freezing code.
766
767 -- Look at each declaration following the type up
768 -- until the new subprogram body. If any of the
769 -- declarations is a body then the type has been
770 -- frozen already so the overriding primitive is
771 -- illegal.
772
773 while Present (Decl_Item)
774 and then (Decl_Item /= Subp_Body)
775 loop
776 if Comes_From_Source (Decl_Item)
777 and then (Nkind (Decl_Item) in N_Proper_Body
778 or else Nkind (Decl_Item) in N_Body_Stub)
779 then
780 Error_Msg_N ("overriding of& is too late!", Subp);
781 Error_Msg_N
782 ("\spec should appear immediately after the type!",
783 Subp);
784 exit;
785 end if;
786
787 Next (Decl_Item);
788 end loop;
789
790 -- If the subprogram doesn't follow in the list of
791 -- declarations including the type then the type
792 -- has definitely been frozen already and the body
793 -- is illegal.
794
795 if No (Decl_Item) then
796 Error_Msg_N ("overriding of& is too late!", Subp);
797 Error_Msg_N
798 ("\spec should appear immediately after the type!",
799 Subp);
800
801 elsif Is_Frozen (Subp) then
802
803 -- The subprogram body declares a primitive operation.
804 -- if the subprogram is already frozen, we must update
805 -- its dispatching information explicitly here. The
806 -- information is taken from the overridden subprogram.
807 -- We must also generate a cross-reference entry because
808 -- references to other primitives were already created
809 -- when type was frozen.
810
811 Body_Is_Last_Primitive := True;
812
813 if Present (DTC_Entity (Old_Subp)) then
814 Set_DTC_Entity (Subp, DTC_Entity (Old_Subp));
815 Set_DT_Position (Subp, DT_Position (Old_Subp));
816
817 if not Restriction_Active (No_Dispatching_Calls) then
818 if Building_Static_DT (Tagged_Type) then
819
820 -- If the static dispatch table has not been
821 -- built then there is nothing else to do now;
822 -- otherwise we notify that we cannot build the
823 -- static dispatch table.
824
825 if Has_Dispatch_Table (Tagged_Type) then
826 Error_Msg_N
827 ("overriding of& is too late for building" &
828 " static dispatch tables!", Subp);
829 Error_Msg_N
830 ("\spec should appear immediately after" &
831 " the type!", Subp);
832 end if;
833
834 else
835 Register_Primitive (Sloc (Subp_Body),
836 Prim => Subp,
837 Ins_Nod => Subp_Body);
838 end if;
839
840 Generate_Reference (Tagged_Type, Subp, 'p', False);
841 end if;
842 end if;
843 end if;
844 end;
845
846 else
847 Error_Msg_N ("overriding of& is too late!", Subp);
848 Error_Msg_N
849 ("\subprogram spec should appear immediately after the type!",
850 Subp);
851 end if;
852
853 -- If the type is not frozen yet and we are not in the overriding
854 -- case it looks suspiciously like an attempt to define a primitive
855 -- operation.
856
857 elsif not Is_Frozen (Tagged_Type) then
858 Error_Msg_N
859 ("?not dispatching (must be defined in a package spec)", Subp);
860 return;
861
862 -- When the type is frozen, it is legitimate to define a new
863 -- non-primitive operation.
864
865 else
866 return;
867 end if;
868
869 -- Now, we are sure that the scope is a package spec. If the subprogram
870 -- is declared after the freezing point of the type that's an error
871
872 elsif Is_Frozen (Tagged_Type) and then not Has_Dispatching_Parent then
873 Error_Msg_N ("this primitive operation is declared too late", Subp);
874 Error_Msg_NE
875 ("?no primitive operations for& after this line",
876 Freeze_Node (Tagged_Type),
877 Tagged_Type);
878 return;
879 end if;
880
881 Check_Controlling_Formals (Tagged_Type, Subp);
882
883 -- Now it should be a correct primitive operation, put it in the list
884
885 if Present (Old_Subp) then
886
887 -- If the type has interfaces we complete this check after we
888 -- set attribute Is_Dispatching_Operation
889
890 Check_Subtype_Conformant (Subp, Old_Subp);
891
892 if (Chars (Subp) = Name_Initialize
893 or else Chars (Subp) = Name_Adjust
894 or else Chars (Subp) = Name_Finalize)
895 and then Is_Controlled (Tagged_Type)
896 and then not Is_Visibly_Controlled (Tagged_Type)
897 then
898 Set_Is_Overriding_Operation (Subp, False);
899 Error_Msg_NE
900 ("operation does not override inherited&?", Subp, Subp);
901 else
902 Override_Dispatching_Operation (Tagged_Type, Old_Subp, Subp);
903 Set_Is_Overriding_Operation (Subp);
904
905 -- Ada 2005 (AI-251): In case of late overriding of a primitive
906 -- that covers abstract interface subprograms we must register it
907 -- in all the secondary dispatch tables associated with abstract
908 -- interfaces.
909
910 if Body_Is_Last_Primitive then
911 declare
912 Subp_Body : constant Node_Id := Unit_Declaration_Node (Subp);
913 Elmt : Elmt_Id;
914 Prim : Node_Id;
915
916 begin
917 Elmt := First_Elmt (Primitive_Operations (Tagged_Type));
918 while Present (Elmt) loop
919 Prim := Node (Elmt);
920
921 if Present (Alias (Prim))
922 and then Present (Interface_Alias (Prim))
923 and then Alias (Prim) = Subp
924 then
925 Register_Primitive (Sloc (Prim),
926 Prim => Prim,
927 Ins_Nod => Subp_Body);
928 end if;
929
930 Next_Elmt (Elmt);
931 end loop;
932
933 -- Redisplay the contents of the updated dispatch table
934
935 if Debug_Flag_ZZ then
936 Write_Str ("Late overriding: ");
937 Write_DT (Tagged_Type);
938 end if;
939 end;
940 end if;
941 end if;
942
943 -- If no old subprogram, then we add this as a dispatching operation,
944 -- but we avoid doing this if an error was posted, to prevent annoying
945 -- cascaded errors.
946
947 elsif not Error_Posted (Subp) then
948 Add_Dispatching_Operation (Tagged_Type, Subp);
949 end if;
950
951 Set_Is_Dispatching_Operation (Subp, True);
952
953 -- Ada 2005 (AI-251): If the type implements interfaces we must check
954 -- subtype conformance against all the interfaces covered by this
955 -- primitive.
956
957 if Present (Old_Subp)
958 and then Has_Interfaces (Tagged_Type)
959 then
960 declare
961 Ifaces_List : Elist_Id;
962 Iface_Elmt : Elmt_Id;
963 Iface_Prim_Elmt : Elmt_Id;
964 Iface_Prim : Entity_Id;
965 Ret_Typ : Entity_Id;
966
967 begin
968 Collect_Interfaces (Tagged_Type, Ifaces_List);
969
970 Iface_Elmt := First_Elmt (Ifaces_List);
971 while Present (Iface_Elmt) loop
972 if not Is_Ancestor (Node (Iface_Elmt), Tagged_Type) then
973 Iface_Prim_Elmt :=
974 First_Elmt (Primitive_Operations (Node (Iface_Elmt)));
975 while Present (Iface_Prim_Elmt) loop
976 Iface_Prim := Node (Iface_Prim_Elmt);
977
978 if Is_Interface_Conformant
979 (Tagged_Type, Iface_Prim, Subp)
980 then
981 -- Handle procedures, functions whose return type
982 -- matches, or functions not returning interfaces
983
984 if Ekind (Subp) = E_Procedure
985 or else Etype (Iface_Prim) = Etype (Subp)
986 or else not Is_Interface (Etype (Iface_Prim))
987 then
988 Check_Subtype_Conformant
989 (New_Id => Subp,
990 Old_Id => Iface_Prim,
991 Err_Loc => Subp,
992 Skip_Controlling_Formals => True);
993
994 -- Handle functions returning interfaces
995
996 elsif Implements_Interface
997 (Etype (Subp), Etype (Iface_Prim))
998 then
999 -- Temporarily force both entities to return the
1000 -- same type. Required because Subtype_Conformant
1001 -- does not handle this case.
1002
1003 Ret_Typ := Etype (Iface_Prim);
1004 Set_Etype (Iface_Prim, Etype (Subp));
1005
1006 Check_Subtype_Conformant
1007 (New_Id => Subp,
1008 Old_Id => Iface_Prim,
1009 Err_Loc => Subp,
1010 Skip_Controlling_Formals => True);
1011
1012 Set_Etype (Iface_Prim, Ret_Typ);
1013 end if;
1014 end if;
1015
1016 Next_Elmt (Iface_Prim_Elmt);
1017 end loop;
1018 end if;
1019
1020 Next_Elmt (Iface_Elmt);
1021 end loop;
1022 end;
1023 end if;
1024
1025 if not Body_Is_Last_Primitive then
1026 Set_DT_Position (Subp, No_Uint);
1027
1028 elsif Has_Controlled_Component (Tagged_Type)
1029 and then
1030 (Chars (Subp) = Name_Initialize
1031 or else Chars (Subp) = Name_Adjust
1032 or else Chars (Subp) = Name_Finalize)
1033 then
1034 declare
1035 F_Node : constant Node_Id := Freeze_Node (Tagged_Type);
1036 Decl : Node_Id;
1037 Old_P : Entity_Id;
1038 Old_Bod : Node_Id;
1039 Old_Spec : Entity_Id;
1040
1041 C_Names : constant array (1 .. 3) of Name_Id :=
1042 (Name_Initialize,
1043 Name_Adjust,
1044 Name_Finalize);
1045
1046 D_Names : constant array (1 .. 3) of TSS_Name_Type :=
1047 (TSS_Deep_Initialize,
1048 TSS_Deep_Adjust,
1049 TSS_Deep_Finalize);
1050
1051 begin
1052 -- Remove previous controlled function, which was constructed
1053 -- and analyzed when the type was frozen. This requires
1054 -- removing the body of the redefined primitive, as well as
1055 -- its specification if needed (there is no spec created for
1056 -- Deep_Initialize, see exp_ch3.adb). We must also dismantle
1057 -- the exception information that may have been generated for
1058 -- it when front end zero-cost tables are enabled.
1059
1060 for J in D_Names'Range loop
1061 Old_P := TSS (Tagged_Type, D_Names (J));
1062
1063 if Present (Old_P)
1064 and then Chars (Subp) = C_Names (J)
1065 then
1066 Old_Bod := Unit_Declaration_Node (Old_P);
1067 Remove (Old_Bod);
1068 Set_Is_Eliminated (Old_P);
1069 Set_Scope (Old_P, Scope (Current_Scope));
1070
1071 if Nkind (Old_Bod) = N_Subprogram_Body
1072 and then Present (Corresponding_Spec (Old_Bod))
1073 then
1074 Old_Spec := Corresponding_Spec (Old_Bod);
1075 Set_Has_Completion (Old_Spec, False);
1076 end if;
1077 end if;
1078 end loop;
1079
1080 Build_Late_Proc (Tagged_Type, Chars (Subp));
1081
1082 -- The new operation is added to the actions of the freeze
1083 -- node for the type, but this node has already been analyzed,
1084 -- so we must retrieve and analyze explicitly the new body.
1085
1086 if Present (F_Node)
1087 and then Present (Actions (F_Node))
1088 then
1089 Decl := Last (Actions (F_Node));
1090 Analyze (Decl);
1091 end if;
1092 end;
1093 end if;
1094 end Check_Dispatching_Operation;
1095
1096 ------------------------------------------
1097 -- Check_Operation_From_Incomplete_Type --
1098 ------------------------------------------
1099
1100 procedure Check_Operation_From_Incomplete_Type
1101 (Subp : Entity_Id;
1102 Typ : Entity_Id)
1103 is
1104 Full : constant Entity_Id := Full_View (Typ);
1105 Parent_Typ : constant Entity_Id := Etype (Full);
1106 Old_Prim : constant Elist_Id := Primitive_Operations (Parent_Typ);
1107 New_Prim : constant Elist_Id := Primitive_Operations (Full);
1108 Op1, Op2 : Elmt_Id;
1109 Prev : Elmt_Id := No_Elmt;
1110
1111 function Derives_From (Proc : Entity_Id) return Boolean;
1112 -- Check that Subp has the signature of an operation derived from Proc.
1113 -- Subp has an access parameter that designates Typ.
1114
1115 ------------------
1116 -- Derives_From --
1117 ------------------
1118
1119 function Derives_From (Proc : Entity_Id) return Boolean is
1120 F1, F2 : Entity_Id;
1121
1122 begin
1123 if Chars (Proc) /= Chars (Subp) then
1124 return False;
1125 end if;
1126
1127 F1 := First_Formal (Proc);
1128 F2 := First_Formal (Subp);
1129
1130 while Present (F1) and then Present (F2) loop
1131
1132 if Ekind (Etype (F1)) = E_Anonymous_Access_Type then
1133
1134 if Ekind (Etype (F2)) /= E_Anonymous_Access_Type then
1135 return False;
1136
1137 elsif Designated_Type (Etype (F1)) = Parent_Typ
1138 and then Designated_Type (Etype (F2)) /= Full
1139 then
1140 return False;
1141 end if;
1142
1143 elsif Ekind (Etype (F2)) = E_Anonymous_Access_Type then
1144 return False;
1145
1146 elsif Etype (F1) /= Etype (F2) then
1147 return False;
1148 end if;
1149
1150 Next_Formal (F1);
1151 Next_Formal (F2);
1152 end loop;
1153
1154 return No (F1) and then No (F2);
1155 end Derives_From;
1156
1157 -- Start of processing for Check_Operation_From_Incomplete_Type
1158
1159 begin
1160 -- The operation may override an inherited one, or may be a new one
1161 -- altogether. The inherited operation will have been hidden by the
1162 -- current one at the point of the type derivation, so it does not
1163 -- appear in the list of primitive operations of the type. We have to
1164 -- find the proper place of insertion in the list of primitive opera-
1165 -- tions by iterating over the list for the parent type.
1166
1167 Op1 := First_Elmt (Old_Prim);
1168 Op2 := First_Elmt (New_Prim);
1169
1170 while Present (Op1) and then Present (Op2) loop
1171
1172 if Derives_From (Node (Op1)) then
1173
1174 if No (Prev) then
1175
1176 -- Avoid adding it to the list of primitives if already there!
1177
1178 if Node (Op2) /= Subp then
1179 Prepend_Elmt (Subp, New_Prim);
1180 end if;
1181
1182 else
1183 Insert_Elmt_After (Subp, Prev);
1184 end if;
1185
1186 return;
1187 end if;
1188
1189 Prev := Op2;
1190 Next_Elmt (Op1);
1191 Next_Elmt (Op2);
1192 end loop;
1193
1194 -- Operation is a new primitive
1195
1196 Append_Elmt (Subp, New_Prim);
1197 end Check_Operation_From_Incomplete_Type;
1198
1199 ---------------------------------------
1200 -- Check_Operation_From_Private_View --
1201 ---------------------------------------
1202
1203 procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id) is
1204 Tagged_Type : Entity_Id;
1205
1206 begin
1207 if Is_Dispatching_Operation (Alias (Subp)) then
1208 Set_Scope (Subp, Current_Scope);
1209 Tagged_Type := Find_Dispatching_Type (Subp);
1210
1211 -- Add Old_Subp to primitive operations if not already present.
1212
1213 if Present (Tagged_Type) and then Is_Tagged_Type (Tagged_Type) then
1214 Append_Unique_Elmt (Old_Subp, Primitive_Operations (Tagged_Type));
1215
1216 -- If Old_Subp isn't already marked as dispatching then
1217 -- this is the case of an operation of an untagged private
1218 -- type fulfilled by a tagged type that overrides an
1219 -- inherited dispatching operation, so we set the necessary
1220 -- dispatching attributes here.
1221
1222 if not Is_Dispatching_Operation (Old_Subp) then
1223
1224 -- If the untagged type has no discriminants, and the full
1225 -- view is constrained, there will be a spurious mismatch
1226 -- of subtypes on the controlling arguments, because the tagged
1227 -- type is the internal base type introduced in the derivation.
1228 -- Use the original type to verify conformance, rather than the
1229 -- base type.
1230
1231 if not Comes_From_Source (Tagged_Type)
1232 and then Has_Discriminants (Tagged_Type)
1233 then
1234 declare
1235 Formal : Entity_Id;
1236 begin
1237 Formal := First_Formal (Old_Subp);
1238 while Present (Formal) loop
1239 if Tagged_Type = Base_Type (Etype (Formal)) then
1240 Tagged_Type := Etype (Formal);
1241 end if;
1242
1243 Next_Formal (Formal);
1244 end loop;
1245 end;
1246
1247 if Tagged_Type = Base_Type (Etype (Old_Subp)) then
1248 Tagged_Type := Etype (Old_Subp);
1249 end if;
1250 end if;
1251
1252 Check_Controlling_Formals (Tagged_Type, Old_Subp);
1253 Set_Is_Dispatching_Operation (Old_Subp, True);
1254 Set_DT_Position (Old_Subp, No_Uint);
1255 end if;
1256
1257 -- If the old subprogram is an explicit renaming of some other
1258 -- entity, it is not overridden by the inherited subprogram.
1259 -- Otherwise, update its alias and other attributes.
1260
1261 if Present (Alias (Old_Subp))
1262 and then Nkind (Unit_Declaration_Node (Old_Subp))
1263 /= N_Subprogram_Renaming_Declaration
1264 then
1265 Set_Alias (Old_Subp, Alias (Subp));
1266
1267 -- The derived subprogram should inherit the abstractness
1268 -- of the parent subprogram (except in the case of a function
1269 -- returning the type). This sets the abstractness properly
1270 -- for cases where a private extension may have inherited
1271 -- an abstract operation, but the full type is derived from
1272 -- a descendant type and inherits a nonabstract version.
1273
1274 if Etype (Subp) /= Tagged_Type then
1275 Set_Is_Abstract_Subprogram
1276 (Old_Subp, Is_Abstract_Subprogram (Alias (Subp)));
1277 end if;
1278 end if;
1279 end if;
1280 end if;
1281 end Check_Operation_From_Private_View;
1282
1283 --------------------------
1284 -- Find_Controlling_Arg --
1285 --------------------------
1286
1287 function Find_Controlling_Arg (N : Node_Id) return Node_Id is
1288 Orig_Node : constant Node_Id := Original_Node (N);
1289 Typ : Entity_Id;
1290
1291 begin
1292 if Nkind (Orig_Node) = N_Qualified_Expression then
1293 return Find_Controlling_Arg (Expression (Orig_Node));
1294 end if;
1295
1296 -- Dispatching on result case. If expansion is disabled, the node still
1297 -- has the structure of a function call. However, if the function name
1298 -- is an operator and the call was given in infix form, the original
1299 -- node has no controlling result and we must examine the current node.
1300
1301 if Nkind (N) = N_Function_Call
1302 and then Present (Controlling_Argument (N))
1303 and then Has_Controlling_Result (Entity (Name (N)))
1304 then
1305 return Controlling_Argument (N);
1306
1307 -- If expansion is enabled, the call may have been transformed into
1308 -- an indirect call, and we need to recover the original node.
1309
1310 elsif Nkind (Orig_Node) = N_Function_Call
1311 and then Present (Controlling_Argument (Orig_Node))
1312 and then Has_Controlling_Result (Entity (Name (Orig_Node)))
1313 then
1314 return Controlling_Argument (Orig_Node);
1315
1316 -- Normal case
1317
1318 elsif Is_Controlling_Actual (N)
1319 or else
1320 (Nkind (Parent (N)) = N_Qualified_Expression
1321 and then Is_Controlling_Actual (Parent (N)))
1322 then
1323 Typ := Etype (N);
1324
1325 if Is_Access_Type (Typ) then
1326 -- In the case of an Access attribute, use the type of
1327 -- the prefix, since in the case of an actual for an
1328 -- access parameter, the attribute's type may be of a
1329 -- specific designated type, even though the prefix
1330 -- type is class-wide.
1331
1332 if Nkind (N) = N_Attribute_Reference then
1333 Typ := Etype (Prefix (N));
1334
1335 -- An allocator is dispatching if the type of qualified
1336 -- expression is class_wide, in which case this is the
1337 -- controlling type.
1338
1339 elsif Nkind (Orig_Node) = N_Allocator
1340 and then Nkind (Expression (Orig_Node)) = N_Qualified_Expression
1341 then
1342 Typ := Etype (Expression (Orig_Node));
1343
1344 else
1345 Typ := Designated_Type (Typ);
1346 end if;
1347 end if;
1348
1349 if Is_Class_Wide_Type (Typ)
1350 or else
1351 (Nkind (Parent (N)) = N_Qualified_Expression
1352 and then Is_Access_Type (Etype (N))
1353 and then Is_Class_Wide_Type (Designated_Type (Etype (N))))
1354 then
1355 return N;
1356 end if;
1357 end if;
1358
1359 return Empty;
1360 end Find_Controlling_Arg;
1361
1362 ---------------------------
1363 -- Find_Dispatching_Type --
1364 ---------------------------
1365
1366 function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id is
1367 Formal : Entity_Id;
1368 Ctrl_Type : Entity_Id;
1369
1370 begin
1371 if Present (DTC_Entity (Subp)) then
1372 return Scope (DTC_Entity (Subp));
1373
1374 else
1375 Formal := First_Formal (Subp);
1376 while Present (Formal) loop
1377 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
1378
1379 if Present (Ctrl_Type) then
1380 return Ctrl_Type;
1381 end if;
1382
1383 Next_Formal (Formal);
1384 end loop;
1385
1386 -- The subprogram may also be dispatching on result
1387
1388 if Present (Etype (Subp)) then
1389 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
1390
1391 if Present (Ctrl_Type) then
1392 return Ctrl_Type;
1393 end if;
1394 end if;
1395 end if;
1396
1397 return Empty;
1398 end Find_Dispatching_Type;
1399
1400 ---------------------------------------
1401 -- Find_Primitive_Covering_Interface --
1402 ---------------------------------------
1403
1404 function Find_Primitive_Covering_Interface
1405 (Tagged_Type : Entity_Id;
1406 Iface_Prim : Entity_Id) return Entity_Id
1407 is
1408 E : Entity_Id;
1409
1410 begin
1411 pragma Assert (Is_Interface (Find_Dispatching_Type (Iface_Prim))
1412 or else (Present (Alias (Iface_Prim))
1413 and then
1414 Is_Interface
1415 (Find_Dispatching_Type (Ultimate_Alias (Iface_Prim)))));
1416
1417 E := Current_Entity (Iface_Prim);
1418 while Present (E) loop
1419 if Is_Subprogram (E)
1420 and then Is_Dispatching_Operation (E)
1421 and then Is_Interface_Conformant (Tagged_Type, Iface_Prim, E)
1422 then
1423 return E;
1424 end if;
1425
1426 E := Homonym (E);
1427 end loop;
1428
1429 return Empty;
1430 end Find_Primitive_Covering_Interface;
1431
1432 ---------------------------
1433 -- Is_Dynamically_Tagged --
1434 ---------------------------
1435
1436 function Is_Dynamically_Tagged (N : Node_Id) return Boolean is
1437 begin
1438 if Nkind (N) = N_Error then
1439 return False;
1440 else
1441 return Find_Controlling_Arg (N) /= Empty;
1442 end if;
1443 end Is_Dynamically_Tagged;
1444
1445 --------------------------
1446 -- Is_Tag_Indeterminate --
1447 --------------------------
1448
1449 function Is_Tag_Indeterminate (N : Node_Id) return Boolean is
1450 Nam : Entity_Id;
1451 Actual : Node_Id;
1452 Orig_Node : constant Node_Id := Original_Node (N);
1453
1454 begin
1455 if Nkind (Orig_Node) = N_Function_Call
1456 and then Is_Entity_Name (Name (Orig_Node))
1457 then
1458 Nam := Entity (Name (Orig_Node));
1459
1460 if not Has_Controlling_Result (Nam) then
1461 return False;
1462
1463 -- An explicit dereference means that the call has already been
1464 -- expanded and there is no tag to propagate.
1465
1466 elsif Nkind (N) = N_Explicit_Dereference then
1467 return False;
1468
1469 -- If there are no actuals, the call is tag-indeterminate
1470
1471 elsif No (Parameter_Associations (Orig_Node)) then
1472 return True;
1473
1474 else
1475 Actual := First_Actual (Orig_Node);
1476 while Present (Actual) loop
1477 if Is_Controlling_Actual (Actual)
1478 and then not Is_Tag_Indeterminate (Actual)
1479 then
1480 return False; -- one operand is dispatching
1481 end if;
1482
1483 Next_Actual (Actual);
1484 end loop;
1485
1486 return True;
1487 end if;
1488
1489 elsif Nkind (Orig_Node) = N_Qualified_Expression then
1490 return Is_Tag_Indeterminate (Expression (Orig_Node));
1491
1492 -- Case of a call to the Input attribute (possibly rewritten), which is
1493 -- always tag-indeterminate except when its prefix is a Class attribute.
1494
1495 elsif Nkind (Orig_Node) = N_Attribute_Reference
1496 and then
1497 Get_Attribute_Id (Attribute_Name (Orig_Node)) = Attribute_Input
1498 and then
1499 Nkind (Prefix (Orig_Node)) /= N_Attribute_Reference
1500 then
1501 return True;
1502
1503 -- In Ada 2005 a function that returns an anonymous access type can
1504 -- dispatching, and the dereference of a call to such a function
1505 -- is also tag-indeterminate.
1506
1507 elsif Nkind (Orig_Node) = N_Explicit_Dereference
1508 and then Ada_Version >= Ada_05
1509 then
1510 return Is_Tag_Indeterminate (Prefix (Orig_Node));
1511
1512 else
1513 return False;
1514 end if;
1515 end Is_Tag_Indeterminate;
1516
1517 ------------------------------------
1518 -- Override_Dispatching_Operation --
1519 ------------------------------------
1520
1521 procedure Override_Dispatching_Operation
1522 (Tagged_Type : Entity_Id;
1523 Prev_Op : Entity_Id;
1524 New_Op : Entity_Id)
1525 is
1526 Elmt : Elmt_Id;
1527 Prim : Node_Id;
1528
1529 begin
1530 -- Diagnose failure to match No_Return in parent (Ada-2005, AI-414, but
1531 -- we do it unconditionally in Ada 95 now, since this is our pragma!)
1532
1533 if No_Return (Prev_Op) and then not No_Return (New_Op) then
1534 Error_Msg_N ("procedure & must have No_Return pragma", New_Op);
1535 Error_Msg_N ("\since overridden procedure has No_Return", New_Op);
1536 end if;
1537
1538 -- If there is no previous operation to override, the type declaration
1539 -- was malformed, and an error must have been emitted already.
1540
1541 Elmt := First_Elmt (Primitive_Operations (Tagged_Type));
1542 while Present (Elmt)
1543 and then Node (Elmt) /= Prev_Op
1544 loop
1545 Next_Elmt (Elmt);
1546 end loop;
1547
1548 if No (Elmt) then
1549 return;
1550 end if;
1551
1552 Replace_Elmt (Elmt, New_Op);
1553
1554 if Ada_Version >= Ada_05
1555 and then Has_Interfaces (Tagged_Type)
1556 then
1557 -- Ada 2005 (AI-251): Update the attribute alias of all the aliased
1558 -- entities of the overridden primitive to reference New_Op, and also
1559 -- propagate the proper value of Is_Abstract_Subprogram. Verify
1560 -- that the new operation is subtype conformant with the interface
1561 -- operations that it implements (for operations inherited from the
1562 -- parent itself, this check is made when building the derived type).
1563
1564 -- Note: This code is only executed in case of late overriding
1565
1566 Elmt := First_Elmt (Primitive_Operations (Tagged_Type));
1567 while Present (Elmt) loop
1568 Prim := Node (Elmt);
1569
1570 if Prim = New_Op then
1571 null;
1572
1573 -- Note: The check on Is_Subprogram protects the frontend against
1574 -- reading attributes in entities that are not yet fully decorated
1575
1576 elsif Is_Subprogram (Prim)
1577 and then Present (Interface_Alias (Prim))
1578 and then Alias (Prim) = Prev_Op
1579 and then Present (Etype (New_Op))
1580 then
1581 Set_Alias (Prim, New_Op);
1582 Check_Subtype_Conformant (New_Op, Prim);
1583 Set_Is_Abstract_Subprogram (Prim,
1584 Is_Abstract_Subprogram (New_Op));
1585
1586 -- Ensure that this entity will be expanded to fill the
1587 -- corresponding entry in its dispatch table.
1588
1589 if not Is_Abstract_Subprogram (Prim) then
1590 Set_Has_Delayed_Freeze (Prim);
1591 end if;
1592 end if;
1593
1594 Next_Elmt (Elmt);
1595 end loop;
1596 end if;
1597
1598 if (not Is_Package_Or_Generic_Package (Current_Scope))
1599 or else not In_Private_Part (Current_Scope)
1600 then
1601 -- Not a private primitive
1602
1603 null;
1604
1605 else pragma Assert (Is_Inherited_Operation (Prev_Op));
1606
1607 -- Make the overriding operation into an alias of the implicit one.
1608 -- In this fashion a call from outside ends up calling the new body
1609 -- even if non-dispatching, and a call from inside calls the
1610 -- overriding operation because it hides the implicit one. To
1611 -- indicate that the body of Prev_Op is never called, set its
1612 -- dispatch table entity to Empty.
1613
1614 Set_Alias (Prev_Op, New_Op);
1615 Set_DTC_Entity (Prev_Op, Empty);
1616 return;
1617 end if;
1618 end Override_Dispatching_Operation;
1619
1620 -------------------
1621 -- Propagate_Tag --
1622 -------------------
1623
1624 procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id) is
1625 Call_Node : Node_Id;
1626 Arg : Node_Id;
1627
1628 begin
1629 if Nkind (Actual) = N_Function_Call then
1630 Call_Node := Actual;
1631
1632 elsif Nkind (Actual) = N_Identifier
1633 and then Nkind (Original_Node (Actual)) = N_Function_Call
1634 then
1635 -- Call rewritten as object declaration when stack-checking
1636 -- is enabled. Propagate tag to expression in declaration, which
1637 -- is original call.
1638
1639 Call_Node := Expression (Parent (Entity (Actual)));
1640
1641 -- Ada 2005: If this is a dereference of a call to a function with a
1642 -- dispatching access-result, the tag is propagated when the dereference
1643 -- itself is expanded (see exp_ch6.adb) and there is nothing else to do.
1644
1645 elsif Nkind (Actual) = N_Explicit_Dereference
1646 and then Nkind (Original_Node (Prefix (Actual))) = N_Function_Call
1647 then
1648 return;
1649
1650 -- Only other possibilities are parenthesized or qualified expression,
1651 -- or an expander-generated unchecked conversion of a function call to
1652 -- a stream Input attribute.
1653
1654 else
1655 Call_Node := Expression (Actual);
1656 end if;
1657
1658 -- Do not set the Controlling_Argument if already set. This happens
1659 -- in the special case of _Input (see Exp_Attr, case Input).
1660
1661 if No (Controlling_Argument (Call_Node)) then
1662 Set_Controlling_Argument (Call_Node, Control);
1663 end if;
1664
1665 Arg := First_Actual (Call_Node);
1666
1667 while Present (Arg) loop
1668 if Is_Tag_Indeterminate (Arg) then
1669 Propagate_Tag (Control, Arg);
1670 end if;
1671
1672 Next_Actual (Arg);
1673 end loop;
1674
1675 -- Expansion of dispatching calls is suppressed when VM_Target, because
1676 -- the VM back-ends directly handle the generation of dispatching
1677 -- calls and would have to undo any expansion to an indirect call.
1678
1679 if VM_Target = No_VM then
1680 Expand_Dispatching_Call (Call_Node);
1681
1682 -- Expansion of a dispatching call results in an indirect call, which in
1683 -- turn causes current values to be killed (see Resolve_Call), so on VM
1684 -- targets we do the call here to ensure consistent warnings between VM
1685 -- and non-VM targets.
1686
1687 else
1688 Kill_Current_Values;
1689 end if;
1690 end Propagate_Tag;
1691
1692 end Sem_Disp;
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