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* gnu/regexp/CharIndexedReader.java: Removed.
[official-gcc.git] / gcc / ada / sem_disp.adb
blob5c85af2d600b1a28c30436cd9a526f572ec9dca9
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) 1992-2004 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 2, 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 COPYING. If not, write --
19 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
20 -- MA 02111-1307, USA. --
21 -- --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 -- --
25 ------------------------------------------------------------------------------
26
27 with Atree; use Atree;
28 with Debug; use Debug;
29 with Elists; use Elists;
30 with Einfo; use Einfo;
31 with Exp_Disp; use Exp_Disp;
32 with Exp_Ch7; use Exp_Ch7;
33 with Exp_Tss; use Exp_Tss;
34 with Errout; use Errout;
35 with Hostparm; use Hostparm;
36 with Nlists; use Nlists;
37 with Opt; use Opt;
38 with Output; use Output;
39 with Sem; use Sem;
40 with Sem_Ch6; use Sem_Ch6;
41 with Sem_Eval; use Sem_Eval;
42 with Sem_Util; use Sem_Util;
43 with Snames; use Snames;
44 with Stand; use Stand;
45 with Sinfo; use Sinfo;
46 with Uintp; use Uintp;
47
48 package body Sem_Disp is
49
50 -----------------------
51 -- Local Subprograms --
52 -----------------------
53
54 procedure Override_Dispatching_Operation
55 (Tagged_Type : Entity_Id;
56 Prev_Op : Entity_Id;
57 New_Op : Entity_Id);
58 -- Replace an implicit dispatching operation with an explicit one.
59 -- Prev_Op is an inherited primitive operation which is overridden
60 -- by the explicit declaration of New_Op.
61
62 procedure Add_Dispatching_Operation
63 (Tagged_Type : Entity_Id;
64 New_Op : Entity_Id);
65 -- Add New_Op in the list of primitive operations of Tagged_Type
66
67 function Check_Controlling_Type
68 (T : Entity_Id;
69 Subp : Entity_Id)
70 return Entity_Id;
71 -- T is the type of a formal parameter of subp. Returns the tagged
72 -- if the parameter can be a controlling argument, empty otherwise
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 Append_Elmt (New_Op, List);
86 end Add_Dispatching_Operation;
87
88 -------------------------------
89 -- Check_Controlling_Formals --
90 -------------------------------
91
92 procedure Check_Controlling_Formals
93 (Typ : Entity_Id;
94 Subp : Entity_Id)
95 is
96 Formal : Entity_Id;
97 Ctrl_Type : Entity_Id;
98 Remote : constant Boolean :=
99 Is_Remote_Types (Current_Scope)
100 and then Comes_From_Source (Subp)
101 and then Scope (Typ) = Current_Scope;
102
103 begin
104 Formal := First_Formal (Subp);
105
106 while Present (Formal) loop
107 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
108
109 if Present (Ctrl_Type) then
110 if Ctrl_Type = Typ then
111 Set_Is_Controlling_Formal (Formal);
112
113 -- Check that the parameter's nominal subtype statically
114 -- matches the first subtype.
115
116 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
117 if not Subtypes_Statically_Match
118 (Typ, Designated_Type (Etype (Formal)))
119 then
120 Error_Msg_N
121 ("parameter subtype does not match controlling type",
122 Formal);
123 end if;
124
125 elsif not Subtypes_Statically_Match (Typ, Etype (Formal)) then
126 Error_Msg_N
127 ("parameter subtype does not match controlling type",
128 Formal);
129 end if;
130
131 if Present (Default_Value (Formal)) then
132 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
133 Error_Msg_N
134 ("default not allowed for controlling access parameter",
135 Default_Value (Formal));
136
137 elsif not Is_Tag_Indeterminate (Default_Value (Formal)) then
138 Error_Msg_N
139 ("default expression must be a tag indeterminate" &
140 " function call", Default_Value (Formal));
141 end if;
142 end if;
143
144 elsif Comes_From_Source (Subp) then
145 Error_Msg_N
146 ("operation can be dispatching in only one type", Subp);
147 end if;
148
149 -- Verify that the restriction in E.2.2 (14) is obeyed
150
151 elsif Remote
152 and then Ekind (Etype (Formal)) = E_Anonymous_Access_Type
153 then
154 Error_Msg_N
155 ("Access parameter of a remote subprogram must be controlling",
156 Formal);
157 end if;
158
159 Next_Formal (Formal);
160 end loop;
161
162 if Present (Etype (Subp)) then
163 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
164
165 if Present (Ctrl_Type) then
166 if Ctrl_Type = Typ then
167 Set_Has_Controlling_Result (Subp);
168
169 -- Check that the result subtype statically matches
170 -- the first subtype.
171
172 if not Subtypes_Statically_Match (Typ, Etype (Subp)) then
173 Error_Msg_N
174 ("result subtype does not match controlling type", Subp);
175 end if;
176
177 elsif Comes_From_Source (Subp) then
178 Error_Msg_N
179 ("operation can be dispatching in only one type", Subp);
180 end if;
181
182 -- The following check is clearly required, although the RM says
183 -- nothing about return types. If the return type is a limited
184 -- class-wide type declared in the current scope, there is no way
185 -- to declare stream procedures for it, so the return cannot be
186 -- marshalled.
187
188 elsif Remote
189 and then Is_Limited_Type (Typ)
190 and then Etype (Subp) = Class_Wide_Type (Typ)
191 then
192 Error_Msg_N ("return type has no stream attributes", Subp);
193 end if;
194 end if;
195 end Check_Controlling_Formals;
196
197 ----------------------------
198 -- Check_Controlling_Type --
199 ----------------------------
200
201 function Check_Controlling_Type
202 (T : Entity_Id;
203 Subp : Entity_Id)
204 return Entity_Id
205 is
206 Tagged_Type : Entity_Id := Empty;
207
208 begin
209 if Is_Tagged_Type (T) then
210 if Is_First_Subtype (T) then
211 Tagged_Type := T;
212 else
213 Tagged_Type := Base_Type (T);
214 end if;
215
216 elsif Ekind (T) = E_Anonymous_Access_Type
217 and then Is_Tagged_Type (Designated_Type (T))
218 and then Ekind (Designated_Type (T)) /= E_Incomplete_Type
219 then
220 if Is_First_Subtype (Designated_Type (T)) then
221 Tagged_Type := Designated_Type (T);
222 else
223 Tagged_Type := Base_Type (Designated_Type (T));
224 end if;
225 end if;
226
227 if No (Tagged_Type)
228 or else Is_Class_Wide_Type (Tagged_Type)
229 then
230 return Empty;
231
232 -- The dispatching type and the primitive operation must be defined
233 -- in the same scope except for internal operations.
234
235 elsif (Scope (Subp) = Scope (Tagged_Type)
236 or else Is_Internal (Subp))
237 and then
238 (not Is_Generic_Type (Tagged_Type)
239 or else not Comes_From_Source (Subp))
240 then
241 return Tagged_Type;
242
243 else
244 return Empty;
245 end if;
246 end Check_Controlling_Type;
247
248 ----------------------------
249 -- Check_Dispatching_Call --
250 ----------------------------
251
252 procedure Check_Dispatching_Call (N : Node_Id) is
253 Actual : Node_Id;
254 Control : Node_Id := Empty;
255 Func : Entity_Id;
256
257 procedure Check_Dispatching_Context;
258 -- If the call is tag-indeterminate and the entity being called is
259 -- abstract, verify that the context is a call that will eventually
260 -- provide a tag for dispatching, or has provided one already.
261
262 -------------------------------
263 -- Check_Dispatching_Context --
264 -------------------------------
265
266 procedure Check_Dispatching_Context is
267 Func : constant Entity_Id := Entity (Name (N));
268 Par : Node_Id;
269
270 begin
271 if Is_Abstract (Func)
272 and then No (Controlling_Argument (N))
273 then
274 if Present (Alias (Func))
275 and then not Is_Abstract (Alias (Func))
276 and then No (DTC_Entity (Func))
277 then
278 -- Private overriding of inherited abstract operation,
279 -- call is legal.
280
281 Set_Entity (Name (N), Alias (Func));
282 return;
283
284 else
285 Par := Parent (N);
286
287 while Present (Par) loop
288
289 if (Nkind (Par) = N_Function_Call or else
290 Nkind (Par) = N_Procedure_Call_Statement or else
291 Nkind (Par) = N_Assignment_Statement or else
292 Nkind (Par) = N_Op_Eq or else
293 Nkind (Par) = N_Op_Ne)
294 and then Is_Tagged_Type (Etype (Func))
295 then
296 return;
297
298 elsif Nkind (Par) = N_Qualified_Expression
299 or else Nkind (Par) = N_Unchecked_Type_Conversion
300 then
301 Par := Parent (Par);
302
303 else
304 Error_Msg_N
305 ("call to abstract function must be dispatching", N);
306 return;
307 end if;
308 end loop;
309 end if;
310 end if;
311 end Check_Dispatching_Context;
312
313 -- Start of processing for Check_Dispatching_Call
314
315 begin
316 -- Find a controlling argument, if any
317
318 if Present (Parameter_Associations (N)) then
319 Actual := First_Actual (N);
320
321 while Present (Actual) loop
322 Control := Find_Controlling_Arg (Actual);
323 exit when Present (Control);
324 Next_Actual (Actual);
325 end loop;
326
327 if Present (Control) then
328
329 -- Verify that no controlling arguments are statically tagged
330
331 if Debug_Flag_E then
332 Write_Str ("Found Dispatching call");
333 Write_Int (Int (N));
334 Write_Eol;
335 end if;
336
337 Actual := First_Actual (N);
338
339 while Present (Actual) loop
340 if Actual /= Control then
341
342 if not Is_Controlling_Actual (Actual) then
343 null; -- can be anything
344
345 elsif Is_Dynamically_Tagged (Actual) then
346 null; -- valid parameter
347
348 elsif Is_Tag_Indeterminate (Actual) then
349
350 -- The tag is inherited from the enclosing call (the
351 -- node we are currently analyzing). Explicitly expand
352 -- the actual, since the previous call to Expand
353 -- (from Resolve_Call) had no way of knowing about
354 -- the required dispatching.
355
356 Propagate_Tag (Control, Actual);
357
358 else
359 Error_Msg_N
360 ("controlling argument is not dynamically tagged",
361 Actual);
362 return;
363 end if;
364 end if;
365
366 Next_Actual (Actual);
367 end loop;
368
369 -- Mark call as a dispatching call
370
371 Set_Controlling_Argument (N, Control);
372
373 else
374 -- The call is not dispatching, check that there isn't any
375 -- tag indeterminate abstract call left
376
377 Actual := First_Actual (N);
378
379 while Present (Actual) loop
380 if Is_Tag_Indeterminate (Actual) then
381
382 -- Function call case
383
384 if Nkind (Original_Node (Actual)) = N_Function_Call then
385 Func := Entity (Name (Original_Node (Actual)));
386
387 -- Only other possibility is a qualified expression whose
388 -- consituent expression is itself a call.
389
390 else
391 Func :=
392 Entity (Name
393 (Original_Node
394 (Expression (Original_Node (Actual)))));
395 end if;
396
397 if Is_Abstract (Func) then
398 Error_Msg_N (
399 "call to abstract function must be dispatching", N);
400 end if;
401 end if;
402
403 Next_Actual (Actual);
404 end loop;
405
406 Check_Dispatching_Context;
407 end if;
408
409 else
410 -- If dispatching on result, the enclosing call, if any, will
411 -- determine the controlling argument. Otherwise this is the
412 -- primitive operation of the root type.
413
414 Check_Dispatching_Context;
415 end if;
416 end Check_Dispatching_Call;
417
418 ---------------------------------
419 -- Check_Dispatching_Operation --
420 ---------------------------------
421
422 procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id) is
423 Tagged_Type : Entity_Id;
424 Has_Dispatching_Parent : Boolean := False;
425 Body_Is_Last_Primitive : Boolean := False;
426
427 function Is_Visibly_Controlled (T : Entity_Id) return Boolean;
428 -- Check whether T is derived from a visibly controlled type.
429 -- This is true if the root type is declared in Ada.Finalization.
430 -- If T is derived instead from a private type whose full view
431 -- is controlled, an explicit Initialize/Adjust/Finalize subprogram
432 -- does not override the inherited one.
433
434 ---------------------------
435 -- Is_Visibly_Controlled --
436 ---------------------------
437
438 function Is_Visibly_Controlled (T : Entity_Id) return Boolean is
439 Root : constant Entity_Id := Root_Type (T);
440 begin
441 return Chars (Scope (Root)) = Name_Finalization
442 and then Chars (Scope (Scope (Root))) = Name_Ada
443 and then Scope (Scope (Scope (Root))) = Standard_Standard;
444 end Is_Visibly_Controlled;
445
446 -- Start of processing for Check_Dispatching_Operation
447
448 begin
449 if Ekind (Subp) /= E_Procedure and then Ekind (Subp) /= E_Function then
450 return;
451 end if;
452
453 Set_Is_Dispatching_Operation (Subp, False);
454 Tagged_Type := Find_Dispatching_Type (Subp);
455
456 -- If Subp is derived from a dispatching operation then it should
457 -- always be treated as dispatching. In this case various checks
458 -- below will be bypassed. Makes sure that late declarations for
459 -- inherited private subprograms are treated as dispatching, even
460 -- if the associated tagged type is already frozen.
461
462 Has_Dispatching_Parent :=
463 Present (Alias (Subp))
464 and then Is_Dispatching_Operation (Alias (Subp));
465
466 if No (Tagged_Type) then
467 return;
468
469 -- The subprograms build internally after the freezing point (such as
470 -- the Init procedure) are not primitives
471
472 elsif Is_Frozen (Tagged_Type)
473 and then not Comes_From_Source (Subp)
474 and then not Has_Dispatching_Parent
475 then
476 return;
477
478 -- The operation may be a child unit, whose scope is the defining
479 -- package, but which is not a primitive operation of the type.
480
481 elsif Is_Child_Unit (Subp) then
482 return;
483
484 -- If the subprogram is not defined in a package spec, the only case
485 -- where it can be a dispatching op is when it overrides an operation
486 -- before the freezing point of the type.
487
488 elsif ((not Is_Package (Scope (Subp)))
489 or else In_Package_Body (Scope (Subp)))
490 and then not Has_Dispatching_Parent
491 then
492 if not Comes_From_Source (Subp)
493 or else (Present (Old_Subp) and then not Is_Frozen (Tagged_Type))
494 then
495 null;
496
497 -- If the type is already frozen, the overriding is not allowed
498 -- except when Old_Subp is not a dispatching operation (which
499 -- can occur when Old_Subp was inherited by an untagged type).
500 -- However, a body with no previous spec freezes the type "after"
501 -- its declaration, and therefore is a legal overriding (unless
502 -- the type has already been frozen). Only the first such body
503 -- is legal.
504
505 elsif Present (Old_Subp)
506 and then Is_Dispatching_Operation (Old_Subp)
507 then
508 if Nkind (Unit_Declaration_Node (Subp)) = N_Subprogram_Body
509 and then Comes_From_Source (Subp)
510 then
511 declare
512 Subp_Body : constant Node_Id := Unit_Declaration_Node (Subp);
513 Decl_Item : Node_Id := Next (Parent (Tagged_Type));
514
515 begin
516 -- ??? The checks here for whether the type has been
517 -- frozen prior to the new body are not complete. It's
518 -- not simple to check frozenness at this point since
519 -- the body has already caused the type to be prematurely
520 -- frozen in Analyze_Declarations, but we're forced to
521 -- recheck this here because of the odd rule interpretation
522 -- that allows the overriding if the type wasn't frozen
523 -- prior to the body. The freezing action should probably
524 -- be delayed until after the spec is seen, but that's
525 -- a tricky change to the delicate freezing code.
526
527 -- Look at each declaration following the type up
528 -- until the new subprogram body. If any of the
529 -- declarations is a body then the type has been
530 -- frozen already so the overriding primitive is
531 -- illegal.
532
533 while Present (Decl_Item)
534 and then (Decl_Item /= Subp_Body)
535 loop
536 if Comes_From_Source (Decl_Item)
537 and then (Nkind (Decl_Item) in N_Proper_Body
538 or else Nkind (Decl_Item) in N_Body_Stub)
539 then
540 Error_Msg_N ("overriding of& is too late!", Subp);
541 Error_Msg_N
542 ("\spec should appear immediately after the type!",
543 Subp);
544 exit;
545 end if;
546
547 Next (Decl_Item);
548 end loop;
549
550 -- If the subprogram doesn't follow in the list of
551 -- declarations including the type then the type
552 -- has definitely been frozen already and the body
553 -- is illegal.
554
555 if not Present (Decl_Item) then
556 Error_Msg_N ("overriding of& is too late!", Subp);
557 Error_Msg_N
558 ("\spec should appear immediately after the type!",
559 Subp);
560
561 elsif Is_Frozen (Subp) then
562
563 -- The subprogram body declares a primitive operation.
564 -- if the subprogram is already frozen, we must update
565 -- its dispatching information explicitly here. The
566 -- information is taken from the overridden subprogram.
567
568 Body_Is_Last_Primitive := True;
569
570 if Present (DTC_Entity (Old_Subp)) then
571 Set_DTC_Entity (Subp, DTC_Entity (Old_Subp));
572 Set_DT_Position (Subp, DT_Position (Old_Subp));
573 Insert_After (
574 Subp_Body, Fill_DT_Entry (Sloc (Subp_Body), Subp));
575 end if;
576 end if;
577 end;
578
579 else
580 Error_Msg_N ("overriding of& is too late!", Subp);
581 Error_Msg_N
582 ("\subprogram spec should appear immediately after the type!",
583 Subp);
584 end if;
585
586 -- If the type is not frozen yet and we are not in the overridding
587 -- case it looks suspiciously like an attempt to define a primitive
588 -- operation.
589
590 elsif not Is_Frozen (Tagged_Type) then
591 Error_Msg_N
592 ("?not dispatching (must be defined in a package spec)", Subp);
593 return;
594
595 -- When the type is frozen, it is legitimate to define a new
596 -- non-primitive operation.
597
598 else
599 return;
600 end if;
601
602 -- Now, we are sure that the scope is a package spec. If the subprogram
603 -- is declared after the freezing point ot the type that's an error
604
605 elsif Is_Frozen (Tagged_Type) and then not Has_Dispatching_Parent then
606 Error_Msg_N ("this primitive operation is declared too late", Subp);
607 Error_Msg_NE
608 ("?no primitive operations for& after this line",
609 Freeze_Node (Tagged_Type),
610 Tagged_Type);
611 return;
612 end if;
613
614 Check_Controlling_Formals (Tagged_Type, Subp);
615
616 -- Now it should be a correct primitive operation, put it in the list
617
618 if Present (Old_Subp) then
619 Check_Subtype_Conformant (Subp, Old_Subp);
620 if (Chars (Subp) = Name_Initialize
621 or else Chars (Subp) = Name_Adjust
622 or else Chars (Subp) = Name_Finalize)
623 and then Is_Controlled (Tagged_Type)
624 and then not Is_Visibly_Controlled (Tagged_Type)
625 then
626 Set_Is_Overriding_Operation (Subp, False);
627 Error_Msg_NE
628 ("operation does not override inherited&?", Subp, Subp);
629 else
630 Override_Dispatching_Operation (Tagged_Type, Old_Subp, Subp);
631 Set_Is_Overriding_Operation (Subp);
632 end if;
633 else
634 Add_Dispatching_Operation (Tagged_Type, Subp);
635 end if;
636
637 Set_Is_Dispatching_Operation (Subp, True);
638
639 if not Body_Is_Last_Primitive then
640 Set_DT_Position (Subp, No_Uint);
641
642 elsif Has_Controlled_Component (Tagged_Type)
643 and then
644 (Chars (Subp) = Name_Initialize
645 or else Chars (Subp) = Name_Adjust
646 or else Chars (Subp) = Name_Finalize)
647 then
648 declare
649 F_Node : constant Node_Id := Freeze_Node (Tagged_Type);
650 Decl : Node_Id;
651 Old_P : Entity_Id;
652 Old_Bod : Node_Id;
653 Old_Spec : Entity_Id;
654
655 C_Names : constant array (1 .. 3) of Name_Id :=
656 (Name_Initialize,
657 Name_Adjust,
658 Name_Finalize);
659
660 D_Names : constant array (1 .. 3) of TSS_Name_Type :=
661 (TSS_Deep_Initialize,
662 TSS_Deep_Adjust,
663 TSS_Deep_Finalize);
664
665 begin
666 -- Remove previous controlled function, which was constructed
667 -- and analyzed when the type was frozen. This requires
668 -- removing the body of the redefined primitive, as well as
669 -- its specification if needed (there is no spec created for
670 -- Deep_Initialize, see exp_ch3.adb). We must also dismantle
671 -- the exception information that may have been generated for
672 -- it when front end zero-cost tables are enabled.
673
674 for J in D_Names'Range loop
675 Old_P := TSS (Tagged_Type, D_Names (J));
676
677 if Present (Old_P)
678 and then Chars (Subp) = C_Names (J)
679 then
680 Old_Bod := Unit_Declaration_Node (Old_P);
681 Remove (Old_Bod);
682 Set_Is_Eliminated (Old_P);
683 Set_Scope (Old_P, Scope (Current_Scope));
684
685 if Nkind (Old_Bod) = N_Subprogram_Body
686 and then Present (Corresponding_Spec (Old_Bod))
687 then
688 Old_Spec := Corresponding_Spec (Old_Bod);
689 Set_Has_Completion (Old_Spec, False);
690
691 if Exception_Mechanism = Front_End_ZCX_Exceptions then
692 Set_Has_Subprogram_Descriptor (Old_Spec, False);
693 Set_Handler_Records (Old_Spec, No_List);
694 Set_Is_Eliminated (Old_Spec);
695 end if;
696 end if;
697
698 end if;
699 end loop;
700
701 Build_Late_Proc (Tagged_Type, Chars (Subp));
702
703 -- The new operation is added to the actions of the freeze
704 -- node for the type, but this node has already been analyzed,
705 -- so we must retrieve and analyze explicitly the one new body,
706
707 if Present (F_Node)
708 and then Present (Actions (F_Node))
709 then
710 Decl := Last (Actions (F_Node));
711 Analyze (Decl);
712 end if;
713 end;
714 end if;
715 end Check_Dispatching_Operation;
716
717 ------------------------------------------
718 -- Check_Operation_From_Incomplete_Type --
719 ------------------------------------------
720
721 procedure Check_Operation_From_Incomplete_Type
722 (Subp : Entity_Id;
723 Typ : Entity_Id)
724 is
725 Full : constant Entity_Id := Full_View (Typ);
726 Parent_Typ : constant Entity_Id := Etype (Full);
727 Old_Prim : constant Elist_Id := Primitive_Operations (Parent_Typ);
728 New_Prim : constant Elist_Id := Primitive_Operations (Full);
729 Op1, Op2 : Elmt_Id;
730 Prev : Elmt_Id := No_Elmt;
731
732 function Derives_From (Proc : Entity_Id) return Boolean;
733 -- Check that Subp has the signature of an operation derived from Proc.
734 -- Subp has an access parameter that designates Typ.
735
736 ------------------
737 -- Derives_From --
738 ------------------
739
740 function Derives_From (Proc : Entity_Id) return Boolean is
741 F1, F2 : Entity_Id;
742
743 begin
744 if Chars (Proc) /= Chars (Subp) then
745 return False;
746 end if;
747
748 F1 := First_Formal (Proc);
749 F2 := First_Formal (Subp);
750
751 while Present (F1) and then Present (F2) loop
752
753 if Ekind (Etype (F1)) = E_Anonymous_Access_Type then
754
755 if Ekind (Etype (F2)) /= E_Anonymous_Access_Type then
756 return False;
757
758 elsif Designated_Type (Etype (F1)) = Parent_Typ
759 and then Designated_Type (Etype (F2)) /= Full
760 then
761 return False;
762 end if;
763
764 elsif Ekind (Etype (F2)) = E_Anonymous_Access_Type then
765 return False;
766
767 elsif Etype (F1) /= Etype (F2) then
768 return False;
769 end if;
770
771 Next_Formal (F1);
772 Next_Formal (F2);
773 end loop;
774
775 return No (F1) and then No (F2);
776 end Derives_From;
777
778 -- Start of processing for Check_Operation_From_Incomplete_Type
779
780 begin
781 -- The operation may override an inherited one, or may be a new one
782 -- altogether. The inherited operation will have been hidden by the
783 -- current one at the point of the type derivation, so it does not
784 -- appear in the list of primitive operations of the type. We have to
785 -- find the proper place of insertion in the list of primitive opera-
786 -- tions by iterating over the list for the parent type.
787
788 Op1 := First_Elmt (Old_Prim);
789 Op2 := First_Elmt (New_Prim);
790
791 while Present (Op1) and then Present (Op2) loop
792
793 if Derives_From (Node (Op1)) then
794
795 if No (Prev) then
796 Prepend_Elmt (Subp, New_Prim);
797 else
798 Insert_Elmt_After (Subp, Prev);
799 end if;
800
801 return;
802 end if;
803
804 Prev := Op2;
805 Next_Elmt (Op1);
806 Next_Elmt (Op2);
807 end loop;
808
809 -- Operation is a new primitive
810
811 Append_Elmt (Subp, New_Prim);
812 end Check_Operation_From_Incomplete_Type;
813
814 ---------------------------------------
815 -- Check_Operation_From_Private_View --
816 ---------------------------------------
817
818 procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id) is
819 Tagged_Type : Entity_Id;
820
821 begin
822 if Is_Dispatching_Operation (Alias (Subp)) then
823 Set_Scope (Subp, Current_Scope);
824 Tagged_Type := Find_Dispatching_Type (Subp);
825
826 if Present (Tagged_Type) and then Is_Tagged_Type (Tagged_Type) then
827 Append_Elmt (Old_Subp, Primitive_Operations (Tagged_Type));
828
829 -- If Old_Subp isn't already marked as dispatching then
830 -- this is the case of an operation of an untagged private
831 -- type fulfilled by a tagged type that overrides an
832 -- inherited dispatching operation, so we set the necessary
833 -- dispatching attributes here.
834
835 if not Is_Dispatching_Operation (Old_Subp) then
836
837 -- If the untagged type has no discriminants, and the full
838 -- view is constrained, there will be a spurious mismatch
839 -- of subtypes on the controlling arguments, because the tagged
840 -- type is the internal base type introduced in the derivation.
841 -- Use the original type to verify conformance, rather than the
842 -- base type.
843
844 if not Comes_From_Source (Tagged_Type)
845 and then Has_Discriminants (Tagged_Type)
846 then
847 declare
848 Formal : Entity_Id;
849 begin
850 Formal := First_Formal (Old_Subp);
851 while Present (Formal) loop
852 if Tagged_Type = Base_Type (Etype (Formal)) then
853 Tagged_Type := Etype (Formal);
854 end if;
855
856 Next_Formal (Formal);
857 end loop;
858 end;
859
860 if Tagged_Type = Base_Type (Etype (Old_Subp)) then
861 Tagged_Type := Etype (Old_Subp);
862 end if;
863 end if;
864
865 Check_Controlling_Formals (Tagged_Type, Old_Subp);
866 Set_Is_Dispatching_Operation (Old_Subp, True);
867 Set_DT_Position (Old_Subp, No_Uint);
868 end if;
869
870 -- If the old subprogram is an explicit renaming of some other
871 -- entity, it is not overridden by the inherited subprogram.
872 -- Otherwise, update its alias and other attributes.
873
874 if Present (Alias (Old_Subp))
875 and then Nkind (Unit_Declaration_Node (Old_Subp))
876 /= N_Subprogram_Renaming_Declaration
877 then
878 Set_Alias (Old_Subp, Alias (Subp));
879
880 -- The derived subprogram should inherit the abstractness
881
882 -- of the parent subprogram (except in the case of a function
883 -- returning the type). This sets the abstractness properly
884 -- for cases where a private extension may have inherited
885 -- an abstract operation, but the full type is derived from
886 -- a descendant type and inherits a nonabstract version.
887
888 if Etype (Subp) /= Tagged_Type then
889 Set_Is_Abstract (Old_Subp, Is_Abstract (Alias (Subp)));
890 end if;
891 end if;
892 end if;
893 end if;
894 end Check_Operation_From_Private_View;
895
896 --------------------------
897 -- Find_Controlling_Arg --
898 --------------------------
899
900 function Find_Controlling_Arg (N : Node_Id) return Node_Id is
901 Orig_Node : constant Node_Id := Original_Node (N);
902 Typ : Entity_Id;
903
904 begin
905 if Nkind (Orig_Node) = N_Qualified_Expression then
906 return Find_Controlling_Arg (Expression (Orig_Node));
907 end if;
908
909 -- Dispatching on result case
910
911 if Nkind (Orig_Node) = N_Function_Call
912 and then Present (Controlling_Argument (Orig_Node))
913 and then Has_Controlling_Result (Entity (Name (Orig_Node)))
914 then
915 return Controlling_Argument (Orig_Node);
916
917 -- Normal case
918
919 elsif Is_Controlling_Actual (N)
920 or else
921 (Nkind (Parent (N)) = N_Qualified_Expression
922 and then Is_Controlling_Actual (Parent (N)))
923 then
924 Typ := Etype (N);
925
926 if Is_Access_Type (Typ) then
927 -- In the case of an Access attribute, use the type of
928 -- the prefix, since in the case of an actual for an
929 -- access parameter, the attribute's type may be of a
930 -- specific designated type, even though the prefix
931 -- type is class-wide.
932
933 if Nkind (N) = N_Attribute_Reference then
934 Typ := Etype (Prefix (N));
935
936 -- An allocator is dispatching if the type of qualified
937 -- expression is class_wide, in which case this is the
938 -- controlling type.
939
940 elsif Nkind (Orig_Node) = N_Allocator
941 and then Nkind (Expression (Orig_Node)) = N_Qualified_Expression
942 then
943 Typ := Etype (Expression (Orig_Node));
944
945 else
946 Typ := Designated_Type (Typ);
947 end if;
948 end if;
949
950 if Is_Class_Wide_Type (Typ)
951 or else
952 (Nkind (Parent (N)) = N_Qualified_Expression
953 and then Is_Access_Type (Etype (N))
954 and then Is_Class_Wide_Type (Designated_Type (Etype (N))))
955 then
956 return N;
957 end if;
958 end if;
959
960 return Empty;
961 end Find_Controlling_Arg;
962
963 ---------------------------
964 -- Find_Dispatching_Type --
965 ---------------------------
966
967 function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id is
968 Formal : Entity_Id;
969 Ctrl_Type : Entity_Id;
970
971 begin
972 if Present (DTC_Entity (Subp)) then
973 return Scope (DTC_Entity (Subp));
974
975 else
976 Formal := First_Formal (Subp);
977 while Present (Formal) loop
978 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
979
980 if Present (Ctrl_Type) then
981 return Ctrl_Type;
982 end if;
983
984 Next_Formal (Formal);
985 end loop;
986
987 -- The subprogram may also be dispatching on result
988
989 if Present (Etype (Subp)) then
990 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
991
992 if Present (Ctrl_Type) then
993 return Ctrl_Type;
994 end if;
995 end if;
996 end if;
997
998 return Empty;
999 end Find_Dispatching_Type;
1000
1001 ---------------------------
1002 -- Is_Dynamically_Tagged --
1003 ---------------------------
1004
1005 function Is_Dynamically_Tagged (N : Node_Id) return Boolean is
1006 begin
1007 return Find_Controlling_Arg (N) /= Empty;
1008 end Is_Dynamically_Tagged;
1009
1010 --------------------------
1011 -- Is_Tag_Indeterminate --
1012 --------------------------
1013
1014 function Is_Tag_Indeterminate (N : Node_Id) return Boolean is
1015 Nam : Entity_Id;
1016 Actual : Node_Id;
1017 Orig_Node : constant Node_Id := Original_Node (N);
1018
1019 begin
1020 if Nkind (Orig_Node) = N_Function_Call
1021 and then Is_Entity_Name (Name (Orig_Node))
1022 then
1023 Nam := Entity (Name (Orig_Node));
1024
1025 if not Has_Controlling_Result (Nam) then
1026 return False;
1027
1028 -- An explicit dereference means that the call has already been
1029 -- expanded and there is no tag to propagate.
1030
1031 elsif Nkind (N) = N_Explicit_Dereference then
1032 return False;
1033
1034 -- If there are no actuals, the call is tag-indeterminate
1035
1036 elsif No (Parameter_Associations (Orig_Node)) then
1037 return True;
1038
1039 else
1040 Actual := First_Actual (Orig_Node);
1041
1042 while Present (Actual) loop
1043 if Is_Controlling_Actual (Actual)
1044 and then not Is_Tag_Indeterminate (Actual)
1045 then
1046 return False; -- one operand is dispatching
1047 end if;
1048
1049 Next_Actual (Actual);
1050 end loop;
1051
1052 return True;
1053
1054 end if;
1055
1056 elsif Nkind (Orig_Node) = N_Qualified_Expression then
1057 return Is_Tag_Indeterminate (Expression (Orig_Node));
1058
1059 else
1060 return False;
1061 end if;
1062 end Is_Tag_Indeterminate;
1063
1064 ------------------------------------
1065 -- Override_Dispatching_Operation --
1066 ------------------------------------
1067
1068 procedure Override_Dispatching_Operation
1069 (Tagged_Type : Entity_Id;
1070 Prev_Op : Entity_Id;
1071 New_Op : Entity_Id)
1072 is
1073 Op_Elmt : Elmt_Id := First_Elmt (Primitive_Operations (Tagged_Type));
1074
1075 begin
1076 -- Patch the primitive operation list
1077
1078 while Present (Op_Elmt)
1079 and then Node (Op_Elmt) /= Prev_Op
1080 loop
1081 Next_Elmt (Op_Elmt);
1082 end loop;
1083
1084 -- If there is no previous operation to override, the type declaration
1085 -- was malformed, and an error must have been emitted already.
1086
1087 if No (Op_Elmt) then
1088 return;
1089 end if;
1090
1091 Replace_Elmt (Op_Elmt, New_Op);
1092
1093 if (not Is_Package (Current_Scope))
1094 or else not In_Private_Part (Current_Scope)
1095 then
1096 -- Not a private primitive
1097
1098 null;
1099
1100 else pragma Assert (Is_Inherited_Operation (Prev_Op));
1101
1102 -- Make the overriding operation into an alias of the implicit one.
1103 -- In this fashion a call from outside ends up calling the new
1104 -- body even if non-dispatching, and a call from inside calls the
1105 -- overriding operation because it hides the implicit one.
1106 -- To indicate that the body of Prev_Op is never called, set its
1107 -- dispatch table entity to Empty.
1108
1109 Set_Alias (Prev_Op, New_Op);
1110 Set_DTC_Entity (Prev_Op, Empty);
1111 return;
1112 end if;
1113 end Override_Dispatching_Operation;
1114
1115 -------------------
1116 -- Propagate_Tag --
1117 -------------------
1118
1119 procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id) is
1120 Call_Node : Node_Id;
1121 Arg : Node_Id;
1122
1123 begin
1124 if Nkind (Actual) = N_Function_Call then
1125 Call_Node := Actual;
1126
1127 elsif Nkind (Actual) = N_Identifier
1128 and then Nkind (Original_Node (Actual)) = N_Function_Call
1129 then
1130 -- Call rewritten as object declaration when stack-checking
1131 -- is enabled. Propagate tag to expression in declaration, which
1132 -- is original call.
1133
1134 Call_Node := Expression (Parent (Entity (Actual)));
1135
1136 -- Only other possibility is parenthesized or qualified expression
1137
1138 else
1139 Call_Node := Expression (Actual);
1140 end if;
1141
1142 -- Do not set the Controlling_Argument if already set. This happens
1143 -- in the special case of _Input (see Exp_Attr, case Input).
1144
1145 if No (Controlling_Argument (Call_Node)) then
1146 Set_Controlling_Argument (Call_Node, Control);
1147 end if;
1148
1149 Arg := First_Actual (Call_Node);
1150
1151 while Present (Arg) loop
1152 if Is_Tag_Indeterminate (Arg) then
1153 Propagate_Tag (Control, Arg);
1154 end if;
1155
1156 Next_Actual (Arg);
1157 end loop;
1158
1159 -- Expansion of dispatching calls is suppressed when Java_VM, because
1160 -- the JVM back end directly handles the generation of dispatching
1161 -- calls and would have to undo any expansion to an indirect call.
1162
1163 if not Java_VM then
1164 Expand_Dispatch_Call (Call_Node);
1165 end if;
1166 end Propagate_Tag;
1167
1168 end Sem_Disp;
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