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* sh.h (REG_CLASS_FROM_LETTER): Change to:
[official-gcc.git] / gcc / ada / sem_disp.adb
blob29b8e409e2134d5ceb07aa33c23e70414cf033dd
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) 1992-2002 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 Sinfo; use Sinfo;
45 with Uintp; use Uintp;
46
47 package body Sem_Disp is
48
49 -----------------------
50 -- Local Subprograms --
51 -----------------------
52
53 procedure Override_Dispatching_Operation
54 (Tagged_Type : Entity_Id;
55 Prev_Op : Entity_Id;
56 New_Op : Entity_Id);
57 -- Replace an implicit dispatching operation with an explicit one.
58 -- Prev_Op is an inherited primitive operation which is overridden
59 -- by the explicit declaration of New_Op.
60
61 procedure Add_Dispatching_Operation
62 (Tagged_Type : Entity_Id;
63 New_Op : Entity_Id);
64 -- Add New_Op in the list of primitive operations of Tagged_Type
65
66 function Check_Controlling_Type
67 (T : Entity_Id;
68 Subp : Entity_Id)
69 return Entity_Id;
70 -- T is the type of a formal parameter of subp. Returns the tagged
71 -- if the parameter can be a controlling argument, empty otherwise
72
73 --------------------------------
74 -- Add_Dispatching_Operation --
75 --------------------------------
76
77 procedure Add_Dispatching_Operation
78 (Tagged_Type : Entity_Id;
79 New_Op : Entity_Id)
80 is
81 List : constant Elist_Id := Primitive_Operations (Tagged_Type);
82
83 begin
84 Append_Elmt (New_Op, List);
85 end Add_Dispatching_Operation;
86
87 -------------------------------
88 -- Check_Controlling_Formals --
89 -------------------------------
90
91 procedure Check_Controlling_Formals
92 (Typ : Entity_Id;
93 Subp : Entity_Id)
94 is
95 Formal : Entity_Id;
96 Ctrl_Type : Entity_Id;
97 Remote : constant Boolean :=
98 Is_Remote_Types (Current_Scope)
99 and then Comes_From_Source (Subp)
100 and then Scope (Typ) = Current_Scope;
101
102 begin
103 Formal := First_Formal (Subp);
104
105 while Present (Formal) loop
106 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
107
108 if Present (Ctrl_Type) then
109 if Ctrl_Type = Typ then
110 Set_Is_Controlling_Formal (Formal);
111
112 -- Check that the parameter's nominal subtype statically
113 -- matches the first subtype.
114
115 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
116 if not Subtypes_Statically_Match
117 (Typ, Designated_Type (Etype (Formal)))
118 then
119 Error_Msg_N
120 ("parameter subtype does not match controlling type",
121 Formal);
122 end if;
123
124 elsif not Subtypes_Statically_Match (Typ, Etype (Formal)) then
125 Error_Msg_N
126 ("parameter subtype does not match controlling type",
127 Formal);
128 end if;
129
130 if Present (Default_Value (Formal)) then
131 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
132 Error_Msg_N
133 ("default not allowed for controlling access parameter",
134 Default_Value (Formal));
135
136 elsif not Is_Tag_Indeterminate (Default_Value (Formal)) then
137 Error_Msg_N
138 ("default expression must be a tag indeterminate" &
139 " function call", Default_Value (Formal));
140 end if;
141 end if;
142
143 elsif Comes_From_Source (Subp) then
144 Error_Msg_N
145 ("operation can be dispatching in only one type", Subp);
146 end if;
147
148 -- Verify that the restriction in E.2.2 (1) is obeyed.
149
150 elsif Remote
151 and then Ekind (Etype (Formal)) = E_Anonymous_Access_Type
152 then
153 Error_Msg_N
154 ("Access parameter of a remote subprogram must be controlling",
155 Formal);
156 end if;
157
158 Next_Formal (Formal);
159 end loop;
160
161 if Present (Etype (Subp)) then
162 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
163
164 if Present (Ctrl_Type) then
165 if Ctrl_Type = Typ then
166 Set_Has_Controlling_Result (Subp);
167
168 -- Check that the result subtype statically matches
169 -- the first subtype.
170
171 if not Subtypes_Statically_Match (Typ, Etype (Subp)) then
172 Error_Msg_N
173 ("result subtype does not match controlling type", Subp);
174 end if;
175
176 elsif Comes_From_Source (Subp) then
177 Error_Msg_N
178 ("operation can be dispatching in only one type", Subp);
179 end if;
180
181 -- The following check is clearly required, although the RM says
182 -- nothing about return types. If the return type is a limited
183 -- class-wide type declared in the current scope, there is no way
184 -- to declare stream procedures for it, so the return cannot be
185 -- marshalled.
186
187 elsif Remote
188 and then Is_Limited_Type (Typ)
189 and then Etype (Subp) = Class_Wide_Type (Typ)
190 then
191 Error_Msg_N ("return type has no stream attributes", Subp);
192 end if;
193 end if;
194 end Check_Controlling_Formals;
195
196 ----------------------------
197 -- Check_Controlling_Type --
198 ----------------------------
199
200 function Check_Controlling_Type
201 (T : Entity_Id;
202 Subp : Entity_Id)
203 return Entity_Id
204 is
205 Tagged_Type : Entity_Id := Empty;
206
207 begin
208 if Is_Tagged_Type (T) then
209 if Is_First_Subtype (T) then
210 Tagged_Type := T;
211 else
212 Tagged_Type := Base_Type (T);
213 end if;
214
215 elsif Ekind (T) = E_Anonymous_Access_Type
216 and then Is_Tagged_Type (Designated_Type (T))
217 and then Ekind (Designated_Type (T)) /= E_Incomplete_Type
218 then
219 if Is_First_Subtype (Designated_Type (T)) then
220 Tagged_Type := Designated_Type (T);
221 else
222 Tagged_Type := Base_Type (Designated_Type (T));
223 end if;
224 end if;
225
226 if No (Tagged_Type)
227 or else Is_Class_Wide_Type (Tagged_Type)
228 then
229 return Empty;
230
231 -- The dispatching type and the primitive operation must be defined
232 -- in the same scope except for internal operations.
233
234 elsif (Scope (Subp) = Scope (Tagged_Type)
235 or else Is_Internal (Subp))
236 and then
237 (not Is_Generic_Type (Tagged_Type)
238 or else not Comes_From_Source (Subp))
239 then
240 return Tagged_Type;
241
242 else
243 return Empty;
244 end if;
245 end Check_Controlling_Type;
246
247 ----------------------------
248 -- Check_Dispatching_Call --
249 ----------------------------
250
251 procedure Check_Dispatching_Call (N : Node_Id) is
252 Actual : Node_Id;
253 Control : Node_Id := Empty;
254 Func : Entity_Id;
255
256 procedure Check_Dispatching_Context;
257 -- If the call is tag-indeterminate and the entity being called is
258 -- abstract, verify that the context is a call that will eventually
259 -- provide a tag for dispatching, or has provided one already.
260
261 -------------------------------
262 -- Check_Dispatching_Context --
263 -------------------------------
264
265 procedure Check_Dispatching_Context is
266 Func : constant Entity_Id := Entity (Name (N));
267 Par : Node_Id;
268
269 begin
270 if Is_Abstract (Func)
271 and then No (Controlling_Argument (N))
272 then
273 if Present (Alias (Func))
274 and then not Is_Abstract (Alias (Func))
275 and then No (DTC_Entity (Func))
276 then
277 -- private overriding of inherited abstract operation,
278 -- call is legal
279
280 Set_Entity (Name (N), Alias (Func));
281 return;
282
283 else
284 Par := Parent (N);
285
286 while Present (Par) loop
287
288 if (Nkind (Par) = N_Function_Call or else
289 Nkind (Par) = N_Procedure_Call_Statement or else
290 Nkind (Par) = N_Assignment_Statement or else
291 Nkind (Par) = N_Op_Eq or else
292 Nkind (Par) = N_Op_Ne)
293 and then Is_Tagged_Type (Etype (Func))
294 then
295 return;
296
297 elsif Nkind (Par) = N_Qualified_Expression
298 or else Nkind (Par) = N_Unchecked_Type_Conversion
299 then
300 Par := Parent (Par);
301
302 else
303 Error_Msg_N
304 ("call to abstract function must be dispatching", N);
305 return;
306 end if;
307 end loop;
308 end if;
309 end if;
310 end Check_Dispatching_Context;
311
312 -- Start of processing for Check_Dispatching_Call
313
314 begin
315 -- Find a controlling argument, if any
316
317 if Present (Parameter_Associations (N)) then
318 Actual := First_Actual (N);
319
320 while Present (Actual) loop
321 Control := Find_Controlling_Arg (Actual);
322 exit when Present (Control);
323 Next_Actual (Actual);
324 end loop;
325
326 if Present (Control) then
327
328 -- Verify that no controlling arguments are statically tagged
329
330 if Debug_Flag_E then
331 Write_Str ("Found Dispatching call");
332 Write_Int (Int (N));
333 Write_Eol;
334 end if;
335
336 Actual := First_Actual (N);
337
338 while Present (Actual) loop
339 if Actual /= Control then
340
341 if not Is_Controlling_Actual (Actual) then
342 null; -- can be anything
343
344 elsif (Is_Dynamically_Tagged (Actual)) then
345 null; -- valid parameter
346
347 elsif Is_Tag_Indeterminate (Actual) then
348
349 -- The tag is inherited from the enclosing call (the
350 -- node we are currently analyzing). Explicitly expand
351 -- the actual, since the previous call to Expand
352 -- (from Resolve_Call) had no way of knowing about
353 -- the required dispatching.
354
355 Propagate_Tag (Control, Actual);
356
357 else
358 Error_Msg_N
359 ("controlling argument is not dynamically tagged",
360 Actual);
361 return;
362 end if;
363 end if;
364
365 Next_Actual (Actual);
366 end loop;
367
368 -- Mark call as a dispatching call
369
370 Set_Controlling_Argument (N, Control);
371
372 else
373 -- The call is not dispatching, check that there isn't any
374 -- tag indeterminate abstract call left
375
376 Actual := First_Actual (N);
377
378 while Present (Actual) loop
379 if Is_Tag_Indeterminate (Actual) then
380
381 -- Function call case
382
383 if Nkind (Original_Node (Actual)) = N_Function_Call then
384 Func := Entity (Name (Original_Node (Actual)));
385
386 -- Only other possibility is a qualified expression whose
387 -- consituent expression is itself a call.
388
389 else
390 Func :=
391 Entity (Name
392 (Original_Node
393 (Expression (Original_Node (Actual)))));
394 end if;
395
396 if Is_Abstract (Func) then
397 Error_Msg_N (
398 "call to abstract function must be dispatching", N);
399 end if;
400 end if;
401
402 Next_Actual (Actual);
403 end loop;
404
405 Check_Dispatching_Context;
406 end if;
407
408 else
409 -- If dispatching on result, the enclosing call, if any, will
410 -- determine the controlling argument. Otherwise this is the
411 -- primitive operation of the root type.
412
413 Check_Dispatching_Context;
414 end if;
415 end Check_Dispatching_Call;
416
417 ---------------------------------
418 -- Check_Dispatching_Operation --
419 ---------------------------------
420
421 procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id) is
422 Tagged_Type : Entity_Id;
423 Has_Dispatching_Parent : Boolean := False;
424 Body_Is_Last_Primitive : Boolean := False;
425
426 begin
427 if Ekind (Subp) /= E_Procedure and then Ekind (Subp) /= E_Function then
428 return;
429 end if;
430
431 Set_Is_Dispatching_Operation (Subp, False);
432 Tagged_Type := Find_Dispatching_Type (Subp);
433
434 -- If Subp is derived from a dispatching operation then it should
435 -- always be treated as dispatching. In this case various checks
436 -- below will be bypassed. Makes sure that late declarations for
437 -- inherited private subprograms are treated as dispatching, even
438 -- if the associated tagged type is already frozen.
439
440 Has_Dispatching_Parent := Present (Alias (Subp))
441 and then Is_Dispatching_Operation (Alias (Subp));
442
443 if No (Tagged_Type) then
444 return;
445
446 -- The subprograms build internally after the freezing point (such as
447 -- the Init procedure) are not primitives
448
449 elsif Is_Frozen (Tagged_Type)
450 and then not Comes_From_Source (Subp)
451 and then not Has_Dispatching_Parent
452 then
453 return;
454
455 -- The operation may be a child unit, whose scope is the defining
456 -- package, but which is not a primitive operation of the type.
457
458 elsif Is_Child_Unit (Subp) then
459 return;
460
461 -- If the subprogram is not defined in a package spec, the only case
462 -- where it can be a dispatching op is when it overrides an operation
463 -- before the freezing point of the type.
464
465 elsif ((not Is_Package (Scope (Subp)))
466 or else In_Package_Body (Scope (Subp)))
467 and then not Has_Dispatching_Parent
468 then
469 if not Comes_From_Source (Subp)
470 or else (Present (Old_Subp) and then not Is_Frozen (Tagged_Type))
471 then
472 null;
473
474 -- If the type is already frozen, the overriding is not allowed
475 -- except when Old_Subp is not a dispatching operation (which
476 -- can occur when Old_Subp was inherited by an untagged type).
477 -- However, a body with no previous spec freezes the type "after"
478 -- its declaration, and therefore is a legal overriding (unless
479 -- the type has already been frozen). Only the first such body
480 -- is legal.
481
482 elsif Present (Old_Subp)
483 and then Is_Dispatching_Operation (Old_Subp)
484 then
485 if Nkind (Unit_Declaration_Node (Subp)) = N_Subprogram_Body
486 and then Comes_From_Source (Subp)
487 then
488 declare
489 Subp_Body : constant Node_Id := Unit_Declaration_Node (Subp);
490 Decl_Item : Node_Id := Next (Parent (Tagged_Type));
491
492 begin
493 -- ??? The checks here for whether the type has been
494 -- frozen prior to the new body are not complete. It's
495 -- not simple to check frozenness at this point since
496 -- the body has already caused the type to be prematurely
497 -- frozen in Analyze_Declarations, but we're forced to
498 -- recheck this here because of the odd rule interpretation
499 -- that allows the overriding if the type wasn't frozen
500 -- prior to the body. The freezing action should probably
501 -- be delayed until after the spec is seen, but that's
502 -- a tricky change to the delicate freezing code.
503
504 -- Look at each declaration following the type up
505 -- until the new subprogram body. If any of the
506 -- declarations is a body then the type has been
507 -- frozen already so the overriding primitive is
508 -- illegal.
509
510 while Present (Decl_Item)
511 and then (Decl_Item /= Subp_Body)
512 loop
513 if Comes_From_Source (Decl_Item)
514 and then (Nkind (Decl_Item) in N_Proper_Body
515 or else Nkind (Decl_Item) in N_Body_Stub)
516 then
517 Error_Msg_N ("overriding of& is too late!", Subp);
518 Error_Msg_N
519 ("\spec should appear immediately after the type!",
520 Subp);
521 exit;
522 end if;
523
524 Next (Decl_Item);
525 end loop;
526
527 -- If the subprogram doesn't follow in the list of
528 -- declarations including the type then the type
529 -- has definitely been frozen already and the body
530 -- is illegal.
531
532 if not Present (Decl_Item) then
533 Error_Msg_N ("overriding of& is too late!", Subp);
534 Error_Msg_N
535 ("\spec should appear immediately after the type!",
536 Subp);
537
538 elsif Is_Frozen (Subp) then
539
540 -- the subprogram body declares a primitive operation.
541 -- if the subprogram is already frozen, we must update
542 -- its dispatching information explicitly here. The
543 -- information is taken from the overridden subprogram.
544
545 Body_Is_Last_Primitive := True;
546
547 if Present (DTC_Entity (Old_Subp)) then
548 Set_DTC_Entity (Subp, DTC_Entity (Old_Subp));
549 Set_DT_Position (Subp, DT_Position (Old_Subp));
550 Insert_After (
551 Subp_Body, Fill_DT_Entry (Sloc (Subp_Body), Subp));
552 end if;
553 end if;
554 end;
555
556 else
557 Error_Msg_N ("overriding of& is too late!", Subp);
558 Error_Msg_N
559 ("\subprogram spec should appear immediately after the type!",
560 Subp);
561 end if;
562
563 -- If the type is not frozen yet and we are not in the overridding
564 -- case it looks suspiciously like an attempt to define a primitive
565 -- operation.
566
567 elsif not Is_Frozen (Tagged_Type) then
568 Error_Msg_N
569 ("?not dispatching (must be defined in a package spec)", Subp);
570 return;
571
572 -- When the type is frozen, it is legitimate to define a new
573 -- non-primitive operation.
574
575 else
576 return;
577 end if;
578
579 -- Now, we are sure that the scope is a package spec. If the subprogram
580 -- is declared after the freezing point ot the type that's an error
581
582 elsif Is_Frozen (Tagged_Type) and then not Has_Dispatching_Parent then
583 Error_Msg_N ("this primitive operation is declared too late", Subp);
584 Error_Msg_NE
585 ("?no primitive operations for& after this line",
586 Freeze_Node (Tagged_Type),
587 Tagged_Type);
588 return;
589 end if;
590
591 Check_Controlling_Formals (Tagged_Type, Subp);
592
593 -- Now it should be a correct primitive operation, put it in the list
594
595 if Present (Old_Subp) then
596 Check_Subtype_Conformant (Subp, Old_Subp);
597 Override_Dispatching_Operation (Tagged_Type, Old_Subp, Subp);
598
599 else
600 Add_Dispatching_Operation (Tagged_Type, Subp);
601 end if;
602
603 Set_Is_Dispatching_Operation (Subp, True);
604
605 if not Body_Is_Last_Primitive then
606 Set_DT_Position (Subp, No_Uint);
607
608 elsif Has_Controlled_Component (Tagged_Type)
609 and then
610 (Chars (Subp) = Name_Initialize
611 or else Chars (Subp) = Name_Adjust
612 or else Chars (Subp) = Name_Finalize)
613 then
614 declare
615 F_Node : Node_Id := Freeze_Node (Tagged_Type);
616 Decl : Node_Id;
617 Old_P : Entity_Id;
618 Old_Bod : Node_Id;
619 Old_Spec : Entity_Id;
620
621 C_Names : constant array (1 .. 3) of Name_Id :=
622 (Name_Initialize,
623 Name_Adjust,
624 Name_Finalize);
625
626 D_Names : constant array (1 .. 3) of Name_Id :=
627 (Name_uDeep_Initialize,
628 Name_uDeep_Adjust,
629 Name_uDeep_Finalize);
630
631 begin
632 -- Remove previous controlled function, which was constructed
633 -- and analyzed when the type was frozen. This requires
634 -- removing the body of the redefined primitive, as well as its
635 -- specification if needed (there is no spec created for
636 -- Deep_Initialize, see exp_ch3.adb). We must also dismantle
637 -- the exception information that may have been generated for it
638 -- when zero-cost is enabled.
639
640 for J in D_Names'Range loop
641 Old_P := TSS (Tagged_Type, D_Names (J));
642
643 if Present (Old_P)
644 and then Chars (Subp) = C_Names (J)
645 then
646 Old_Bod := Unit_Declaration_Node (Old_P);
647 Remove (Old_Bod);
648 Set_Is_Eliminated (Old_P);
649 Set_Scope (Old_P, Scope (Current_Scope));
650
651 if Nkind (Old_Bod) = N_Subprogram_Body
652 and then Present (Corresponding_Spec (Old_Bod))
653 then
654 Old_Spec := Corresponding_Spec (Old_Bod);
655 Set_Has_Completion (Old_Spec, False);
656
657 if Exception_Mechanism = Front_End_ZCX then
658 Set_Has_Subprogram_Descriptor (Old_Spec, False);
659 Set_Handler_Records (Old_Spec, No_List);
660 Set_Is_Eliminated (Old_Spec);
661 end if;
662 end if;
663
664 end if;
665 end loop;
666
667 Build_Late_Proc (Tagged_Type, Chars (Subp));
668
669 -- The new operation is added to the actions of the freeze
670 -- node for the type, but this node has already been analyzed,
671 -- so we must retrieve and analyze explicitly the one new body,
672
673 if Present (F_Node)
674 and then Present (Actions (F_Node))
675 then
676 Decl := Last (Actions (F_Node));
677 Analyze (Decl);
678 end if;
679 end;
680 end if;
681 end Check_Dispatching_Operation;
682
683 ------------------------------------------
684 -- Check_Operation_From_Incomplete_Type --
685 ------------------------------------------
686
687 procedure Check_Operation_From_Incomplete_Type
688 (Subp : Entity_Id;
689 Typ : Entity_Id)
690 is
691 Full : constant Entity_Id := Full_View (Typ);
692 Parent_Typ : constant Entity_Id := Etype (Full);
693 Old_Prim : constant Elist_Id := Primitive_Operations (Parent_Typ);
694 New_Prim : constant Elist_Id := Primitive_Operations (Full);
695 Op1, Op2 : Elmt_Id;
696 Prev : Elmt_Id := No_Elmt;
697
698 function Derives_From (Proc : Entity_Id) return Boolean;
699 -- Check that Subp has the signature of an operation derived from Proc.
700 -- Subp has an access parameter that designates Typ.
701
702 ------------------
703 -- Derives_From --
704 ------------------
705
706 function Derives_From (Proc : Entity_Id) return Boolean is
707 F1, F2 : Entity_Id;
708
709 begin
710 if Chars (Proc) /= Chars (Subp) then
711 return False;
712 end if;
713
714 F1 := First_Formal (Proc);
715 F2 := First_Formal (Subp);
716
717 while Present (F1) and then Present (F2) loop
718
719 if Ekind (Etype (F1)) = E_Anonymous_Access_Type then
720
721 if Ekind (Etype (F2)) /= E_Anonymous_Access_Type then
722 return False;
723
724 elsif Designated_Type (Etype (F1)) = Parent_Typ
725 and then Designated_Type (Etype (F2)) /= Full
726 then
727 return False;
728 end if;
729
730 elsif Ekind (Etype (F2)) = E_Anonymous_Access_Type then
731 return False;
732
733 elsif Etype (F1) /= Etype (F2) then
734 return False;
735 end if;
736
737 Next_Formal (F1);
738 Next_Formal (F2);
739 end loop;
740
741 return No (F1) and then No (F2);
742 end Derives_From;
743
744 -- Start of processing for Check_Operation_From_Incomplete_Type
745
746 begin
747 -- The operation may override an inherited one, or may be a new one
748 -- altogether. The inherited operation will have been hidden by the
749 -- current one at the point of the type derivation, so it does not
750 -- appear in the list of primitive operations of the type. We have to
751 -- find the proper place of insertion in the list of primitive opera-
752 -- tions by iterating over the list for the parent type.
753
754 Op1 := First_Elmt (Old_Prim);
755 Op2 := First_Elmt (New_Prim);
756
757 while Present (Op1) and then Present (Op2) loop
758
759 if Derives_From (Node (Op1)) then
760
761 if No (Prev) then
762 Prepend_Elmt (Subp, New_Prim);
763 else
764 Insert_Elmt_After (Subp, Prev);
765 end if;
766
767 return;
768 end if;
769
770 Prev := Op2;
771 Next_Elmt (Op1);
772 Next_Elmt (Op2);
773 end loop;
774
775 -- Operation is a new primitive.
776
777 Append_Elmt (Subp, New_Prim);
778
779 end Check_Operation_From_Incomplete_Type;
780
781 ---------------------------------------
782 -- Check_Operation_From_Private_View --
783 ---------------------------------------
784
785 procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id) is
786 Tagged_Type : Entity_Id;
787
788 begin
789 if Is_Dispatching_Operation (Alias (Subp)) then
790 Set_Scope (Subp, Current_Scope);
791 Tagged_Type := Find_Dispatching_Type (Subp);
792
793 if Present (Tagged_Type) and then Is_Tagged_Type (Tagged_Type) then
794 Append_Elmt (Old_Subp, Primitive_Operations (Tagged_Type));
795
796 -- If Old_Subp isn't already marked as dispatching then
797 -- this is the case of an operation of an untagged private
798 -- type fulfilled by a tagged type that overrides an
799 -- inherited dispatching operation, so we set the necessary
800 -- dispatching attributes here.
801
802 if not Is_Dispatching_Operation (Old_Subp) then
803 Check_Controlling_Formals (Tagged_Type, Old_Subp);
804 Set_Is_Dispatching_Operation (Old_Subp, True);
805 Set_DT_Position (Old_Subp, No_Uint);
806 end if;
807
808 -- If the old subprogram is an explicit renaming of some other
809 -- entity, it is not overridden by the inherited subprogram.
810 -- Otherwise, update its alias and other attributes.
811
812 if Present (Alias (Old_Subp))
813 and then Nkind (Unit_Declaration_Node (Old_Subp))
814 /= N_Subprogram_Renaming_Declaration
815 then
816 Set_Alias (Old_Subp, Alias (Subp));
817
818 -- The derived subprogram should inherit the abstractness
819 -- of the parent subprogram (except in the case of a function
820 -- returning the type). This sets the abstractness properly
821 -- for cases where a private extension may have inherited
822 -- an abstract operation, but the full type is derived from
823 -- a descendant type and inherits a nonabstract version.
824
825 if Etype (Subp) /= Tagged_Type then
826 Set_Is_Abstract (Old_Subp, Is_Abstract (Alias (Subp)));
827 end if;
828 end if;
829 end if;
830 end if;
831 end Check_Operation_From_Private_View;
832
833 --------------------------
834 -- Find_Controlling_Arg --
835 --------------------------
836
837 function Find_Controlling_Arg (N : Node_Id) return Node_Id is
838 Orig_Node : constant Node_Id := Original_Node (N);
839 Typ : Entity_Id;
840
841 begin
842 if Nkind (Orig_Node) = N_Qualified_Expression then
843 return Find_Controlling_Arg (Expression (Orig_Node));
844 end if;
845
846 -- Dispatching on result case
847
848 if Nkind (Orig_Node) = N_Function_Call
849 and then Present (Controlling_Argument (Orig_Node))
850 and then Has_Controlling_Result (Entity (Name (Orig_Node)))
851 then
852 return Controlling_Argument (Orig_Node);
853
854 -- Normal case
855
856 elsif Is_Controlling_Actual (N) then
857 Typ := Etype (N);
858
859 if Is_Access_Type (Typ) then
860 -- In the case of an Access attribute, use the type of
861 -- the prefix, since in the case of an actual for an
862 -- access parameter, the attribute's type may be of a
863 -- specific designated type, even though the prefix
864 -- type is class-wide.
865
866 if Nkind (N) = N_Attribute_Reference then
867 Typ := Etype (Prefix (N));
868
869 -- An allocator is dispatching if the type of qualified
870 -- expression is class_wide, in which case this is the
871 -- controlling type.
872
873 elsif Nkind (Orig_Node) = N_Allocator
874 and then Nkind (Expression (Orig_Node)) = N_Qualified_Expression
875 then
876 Typ := Etype (Expression (Orig_Node));
877
878 else
879 Typ := Designated_Type (Typ);
880 end if;
881 end if;
882
883 if Is_Class_Wide_Type (Typ) then
884 return N;
885 end if;
886 end if;
887
888 return Empty;
889 end Find_Controlling_Arg;
890
891 ---------------------------
892 -- Find_Dispatching_Type --
893 ---------------------------
894
895 function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id is
896 Formal : Entity_Id;
897 Ctrl_Type : Entity_Id;
898
899 begin
900 if Present (DTC_Entity (Subp)) then
901 return Scope (DTC_Entity (Subp));
902
903 else
904 Formal := First_Formal (Subp);
905 while Present (Formal) loop
906 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
907
908 if Present (Ctrl_Type) then
909 return Ctrl_Type;
910 end if;
911
912 Next_Formal (Formal);
913 end loop;
914
915 -- The subprogram may also be dispatching on result
916
917 if Present (Etype (Subp)) then
918 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
919
920 if Present (Ctrl_Type) then
921 return Ctrl_Type;
922 end if;
923 end if;
924 end if;
925
926 return Empty;
927 end Find_Dispatching_Type;
928
929 ---------------------------
930 -- Is_Dynamically_Tagged --
931 ---------------------------
932
933 function Is_Dynamically_Tagged (N : Node_Id) return Boolean is
934 begin
935 return Find_Controlling_Arg (N) /= Empty;
936 end Is_Dynamically_Tagged;
937
938 --------------------------
939 -- Is_Tag_Indeterminate --
940 --------------------------
941
942 function Is_Tag_Indeterminate (N : Node_Id) return Boolean is
943 Nam : Entity_Id;
944 Actual : Node_Id;
945 Orig_Node : constant Node_Id := Original_Node (N);
946
947 begin
948 if Nkind (Orig_Node) = N_Function_Call
949 and then Is_Entity_Name (Name (Orig_Node))
950 then
951 Nam := Entity (Name (Orig_Node));
952
953 if not Has_Controlling_Result (Nam) then
954 return False;
955
956 -- If there are no actuals, the call is tag-indeterminate
957
958 elsif No (Parameter_Associations (Orig_Node)) then
959 return True;
960
961 else
962 Actual := First_Actual (Orig_Node);
963
964 while Present (Actual) loop
965 if Is_Controlling_Actual (Actual)
966 and then not Is_Tag_Indeterminate (Actual)
967 then
968 return False; -- one operand is dispatching
969 end if;
970
971 Next_Actual (Actual);
972 end loop;
973
974 return True;
975
976 end if;
977
978 elsif Nkind (Orig_Node) = N_Qualified_Expression then
979 return Is_Tag_Indeterminate (Expression (Orig_Node));
980
981 else
982 return False;
983 end if;
984 end Is_Tag_Indeterminate;
985
986 ------------------------------------
987 -- Override_Dispatching_Operation --
988 ------------------------------------
989
990 procedure Override_Dispatching_Operation
991 (Tagged_Type : Entity_Id;
992 Prev_Op : Entity_Id;
993 New_Op : Entity_Id)
994 is
995 Op_Elmt : Elmt_Id := First_Elmt (Primitive_Operations (Tagged_Type));
996
997 begin
998 -- Patch the primitive operation list
999
1000 while Present (Op_Elmt)
1001 and then Node (Op_Elmt) /= Prev_Op
1002 loop
1003 Next_Elmt (Op_Elmt);
1004 end loop;
1005
1006 -- If there is no previous operation to override, the type declaration
1007 -- was malformed, and an error must have been emitted already.
1008
1009 if No (Op_Elmt) then
1010 return;
1011 end if;
1012
1013 Replace_Elmt (Op_Elmt, New_Op);
1014
1015 if (not Is_Package (Current_Scope))
1016 or else not In_Private_Part (Current_Scope)
1017 then
1018 -- Not a private primitive
1019
1020 null;
1021
1022 else pragma Assert (Is_Inherited_Operation (Prev_Op));
1023
1024 -- Make the overriding operation into an alias of the implicit one.
1025 -- In this fashion a call from outside ends up calling the new
1026 -- body even if non-dispatching, and a call from inside calls the
1027 -- overriding operation because it hides the implicit one.
1028 -- To indicate that the body of Prev_Op is never called, set its
1029 -- dispatch table entity to Empty.
1030
1031 Set_Alias (Prev_Op, New_Op);
1032 Set_DTC_Entity (Prev_Op, Empty);
1033 return;
1034 end if;
1035 end Override_Dispatching_Operation;
1036
1037 -------------------
1038 -- Propagate_Tag --
1039 -------------------
1040
1041 procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id) is
1042 Call_Node : Node_Id;
1043 Arg : Node_Id;
1044
1045 begin
1046 if Nkind (Actual) = N_Function_Call then
1047 Call_Node := Actual;
1048
1049 elsif Nkind (Actual) = N_Identifier
1050 and then Nkind (Original_Node (Actual)) = N_Function_Call
1051 then
1052 -- Call rewritten as object declaration when stack-checking
1053 -- is enabled. Propagate tag to expression in declaration, which
1054 -- is original call.
1055
1056 Call_Node := Expression (Parent (Entity (Actual)));
1057
1058 -- Only other possibility is parenthesized or qualified expression
1059
1060 else
1061 Call_Node := Expression (Actual);
1062 end if;
1063
1064 -- Do not set the Controlling_Argument if already set. This happens
1065 -- in the special case of _Input (see Exp_Attr, case Input).
1066
1067 if No (Controlling_Argument (Call_Node)) then
1068 Set_Controlling_Argument (Call_Node, Control);
1069 end if;
1070
1071 Arg := First_Actual (Call_Node);
1072
1073 while Present (Arg) loop
1074 if Is_Tag_Indeterminate (Arg) then
1075 Propagate_Tag (Control, Arg);
1076 end if;
1077
1078 Next_Actual (Arg);
1079 end loop;
1080
1081 -- Expansion of dispatching calls is suppressed when Java_VM, because
1082 -- the JVM back end directly handles the generation of dispatching
1083 -- calls and would have to undo any expansion to an indirect call.
1084
1085 if not Java_VM then
1086 Expand_Dispatch_Call (Call_Node);
1087 end if;
1088 end Propagate_Tag;
1089
1090 end Sem_Disp;
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