1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2004 Free Software Foundation, Inc. --
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. --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
25 ------------------------------------------------------------------------------
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;
38 with Output; use Output;
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;
48 package body Sem_Disp is
50 -----------------------
51 -- Local Subprograms --
52 -----------------------
54 procedure Override_Dispatching_Operation
55 (Tagged_Type : 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.
62 procedure Add_Dispatching_Operation
63 (Tagged_Type : Entity_Id;
65 -- Add New_Op in the list of primitive operations of Tagged_Type
67 function Check_Controlling_Type
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
74 --------------------------------
75 -- Add_Dispatching_Operation --
76 --------------------------------
78 procedure Add_Dispatching_Operation
79 (Tagged_Type : Entity_Id;
82 List : constant Elist_Id := Primitive_Operations (Tagged_Type);
85 Append_Elmt (New_Op, List);
86 end Add_Dispatching_Operation;
88 -------------------------------
89 -- Check_Controlling_Formals --
90 -------------------------------
92 procedure Check_Controlling_Formals
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;
104 Formal := First_Formal (Subp);
106 while Present (Formal) loop
107 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
109 if Present (Ctrl_Type) then
110 if Ctrl_Type = Typ then
111 Set_Is_Controlling_Formal (Formal);
113 -- Check that the parameter's nominal subtype statically
114 -- matches the first subtype.
116 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
117 if not Subtypes_Statically_Match
118 (Typ, Designated_Type (Etype (Formal)))
121 ("parameter subtype does not match controlling type",
125 elsif not Subtypes_Statically_Match (Typ, Etype (Formal)) then
127 ("parameter subtype does not match controlling type",
131 if Present (Default_Value (Formal)) then
132 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
134 ("default not allowed for controlling access parameter",
135 Default_Value (Formal));
137 elsif not Is_Tag_Indeterminate (Default_Value (Formal)) then
139 ("default expression must be a tag indeterminate" &
140 " function call", Default_Value (Formal));
144 elsif Comes_From_Source (Subp) then
146 ("operation can be dispatching in only one type", Subp);
149 -- Verify that the restriction in E.2.2 (14) is obeyed
152 and then Ekind (Etype (Formal)) = E_Anonymous_Access_Type
155 ("Access parameter of a remote subprogram must be controlling",
159 Next_Formal (Formal);
162 if Present (Etype (Subp)) then
163 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
165 if Present (Ctrl_Type) then
166 if Ctrl_Type = Typ then
167 Set_Has_Controlling_Result (Subp);
169 -- Check that the result subtype statically matches
170 -- the first subtype.
172 if not Subtypes_Statically_Match (Typ, Etype (Subp)) then
174 ("result subtype does not match controlling type", Subp);
177 elsif Comes_From_Source (Subp) then
179 ("operation can be dispatching in only one type", Subp);
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
189 and then Is_Limited_Type (Typ)
190 and then Etype (Subp) = Class_Wide_Type (Typ)
192 Error_Msg_N ("return type has no stream attributes", Subp);
195 end Check_Controlling_Formals;
197 ----------------------------
198 -- Check_Controlling_Type --
199 ----------------------------
201 function Check_Controlling_Type
206 Tagged_Type : Entity_Id := Empty;
209 if Is_Tagged_Type (T) then
210 if Is_First_Subtype (T) then
213 Tagged_Type := Base_Type (T);
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
220 if Is_First_Subtype (Designated_Type (T)) then
221 Tagged_Type := Designated_Type (T);
223 Tagged_Type := Base_Type (Designated_Type (T));
228 or else Is_Class_Wide_Type (Tagged_Type)
232 -- The dispatching type and the primitive operation must be defined
233 -- in the same scope except for internal operations.
235 elsif (Scope (Subp) = Scope (Tagged_Type)
236 or else Is_Internal (Subp))
238 (not Is_Generic_Type (Tagged_Type)
239 or else not Comes_From_Source (Subp))
246 end Check_Controlling_Type;
248 ----------------------------
249 -- Check_Dispatching_Call --
250 ----------------------------
252 procedure Check_Dispatching_Call (N : Node_Id) is
254 Control : Node_Id := Empty;
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.
262 -------------------------------
263 -- Check_Dispatching_Context --
264 -------------------------------
266 procedure Check_Dispatching_Context is
267 Func : constant Entity_Id := Entity (Name (N));
271 if Is_Abstract (Func)
272 and then No (Controlling_Argument (N))
274 if Present (Alias (Func))
275 and then not Is_Abstract (Alias (Func))
276 and then No (DTC_Entity (Func))
278 -- Private overriding of inherited abstract operation,
281 Set_Entity (Name (N), Alias (Func));
287 while Present (Par) loop
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))
298 elsif Nkind (Par) = N_Qualified_Expression
299 or else Nkind (Par) = N_Unchecked_Type_Conversion
305 ("call to abstract function must be dispatching", N);
311 end Check_Dispatching_Context;
313 -- Start of processing for Check_Dispatching_Call
316 -- Find a controlling argument, if any
318 if Present (Parameter_Associations (N)) then
319 Actual := First_Actual (N);
321 while Present (Actual) loop
322 Control := Find_Controlling_Arg (Actual);
323 exit when Present (Control);
324 Next_Actual (Actual);
327 if Present (Control) then
329 -- Verify that no controlling arguments are statically tagged
332 Write_Str ("Found Dispatching call");
337 Actual := First_Actual (N);
339 while Present (Actual) loop
340 if Actual /= Control then
342 if not Is_Controlling_Actual (Actual) then
343 null; -- can be anything
345 elsif Is_Dynamically_Tagged (Actual) then
346 null; -- valid parameter
348 elsif Is_Tag_Indeterminate (Actual) then
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.
356 Propagate_Tag (Control, Actual);
360 ("controlling argument is not dynamically tagged",
366 Next_Actual (Actual);
369 -- Mark call as a dispatching call
371 Set_Controlling_Argument (N, Control);
374 -- The call is not dispatching, check that there isn't any
375 -- tag indeterminate abstract call left
377 Actual := First_Actual (N);
379 while Present (Actual) loop
380 if Is_Tag_Indeterminate (Actual) then
382 -- Function call case
384 if Nkind (Original_Node (Actual)) = N_Function_Call then
385 Func := Entity (Name (Original_Node (Actual)));
387 -- Only other possibility is a qualified expression whose
388 -- consituent expression is itself a call.
394 (Expression (Original_Node (Actual)))));
397 if Is_Abstract (Func) then
399 "call to abstract function must be dispatching", N);
403 Next_Actual (Actual);
406 Check_Dispatching_Context;
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.
414 Check_Dispatching_Context;
416 end Check_Dispatching_Call;
418 ---------------------------------
419 -- Check_Dispatching_Operation --
420 ---------------------------------
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;
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.
434 ---------------------------
435 -- Is_Visibly_Controlled --
436 ---------------------------
438 function Is_Visibly_Controlled (T : Entity_Id) return Boolean is
439 Root : constant Entity_Id := Root_Type (T);
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;
446 -- Start of processing for Check_Dispatching_Operation
449 if Ekind (Subp) /= E_Procedure and then Ekind (Subp) /= E_Function then
453 Set_Is_Dispatching_Operation (Subp, False);
454 Tagged_Type := Find_Dispatching_Type (Subp);
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.
462 Has_Dispatching_Parent :=
463 Present (Alias (Subp))
464 and then Is_Dispatching_Operation (Alias (Subp));
466 if No (Tagged_Type) then
469 -- The subprograms build internally after the freezing point (such as
470 -- the Init procedure) are not primitives
472 elsif Is_Frozen (Tagged_Type)
473 and then not Comes_From_Source (Subp)
474 and then not Has_Dispatching_Parent
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.
481 elsif Is_Child_Unit (Subp) then
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.
488 elsif ((not Is_Package (Scope (Subp)))
489 or else In_Package_Body (Scope (Subp)))
490 and then not Has_Dispatching_Parent
492 if not Comes_From_Source (Subp)
493 or else (Present (Old_Subp) and then not Is_Frozen (Tagged_Type))
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
505 elsif Present (Old_Subp)
506 and then Is_Dispatching_Operation (Old_Subp)
508 if Nkind (Unit_Declaration_Node (Subp)) = N_Subprogram_Body
509 and then Comes_From_Source (Subp)
512 Subp_Body : constant Node_Id := Unit_Declaration_Node (Subp);
513 Decl_Item : Node_Id := Next (Parent (Tagged_Type));
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.
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
533 while Present (Decl_Item)
534 and then (Decl_Item /= Subp_Body)
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)
540 Error_Msg_N ("overriding of& is too late!", Subp);
542 ("\spec should appear immediately after the type!",
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
555 if not Present (Decl_Item) then
556 Error_Msg_N ("overriding of& is too late!", Subp);
558 ("\spec should appear immediately after the type!",
561 elsif Is_Frozen (Subp) then
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.
568 Body_Is_Last_Primitive := True;
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));
574 Subp_Body, Fill_DT_Entry (Sloc (Subp_Body), Subp));
580 Error_Msg_N ("overriding of& is too late!", Subp);
582 ("\subprogram spec should appear immediately after the type!",
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
590 elsif not Is_Frozen (Tagged_Type) then
592 ("?not dispatching (must be defined in a package spec)", Subp);
595 -- When the type is frozen, it is legitimate to define a new
596 -- non-primitive operation.
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
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);
608 ("?no primitive operations for& after this line",
609 Freeze_Node (Tagged_Type),
614 Check_Controlling_Formals (Tagged_Type, Subp);
616 -- Now it should be a correct primitive operation, put it in the list
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)
626 Set_Is_Overriding_Operation (Subp, False);
628 ("operation does not override inherited&?", Subp, Subp);
630 Override_Dispatching_Operation (Tagged_Type, Old_Subp, Subp);
631 Set_Is_Overriding_Operation (Subp);
634 Add_Dispatching_Operation (Tagged_Type, Subp);
637 Set_Is_Dispatching_Operation (Subp, True);
639 if not Body_Is_Last_Primitive then
640 Set_DT_Position (Subp, No_Uint);
642 elsif Has_Controlled_Component (Tagged_Type)
644 (Chars (Subp) = Name_Initialize
645 or else Chars (Subp) = Name_Adjust
646 or else Chars (Subp) = Name_Finalize)
649 F_Node : constant Node_Id := Freeze_Node (Tagged_Type);
653 Old_Spec : Entity_Id;
655 C_Names : constant array (1 .. 3) of Name_Id :=
660 D_Names : constant array (1 .. 3) of TSS_Name_Type :=
661 (TSS_Deep_Initialize,
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.
674 for J in D_Names'Range loop
675 Old_P := TSS (Tagged_Type, D_Names (J));
678 and then Chars (Subp) = C_Names (J)
680 Old_Bod := Unit_Declaration_Node (Old_P);
682 Set_Is_Eliminated (Old_P);
683 Set_Scope (Old_P, Scope (Current_Scope));
685 if Nkind (Old_Bod) = N_Subprogram_Body
686 and then Present (Corresponding_Spec (Old_Bod))
688 Old_Spec := Corresponding_Spec (Old_Bod);
689 Set_Has_Completion (Old_Spec, False);
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);
701 Build_Late_Proc (Tagged_Type, Chars (Subp));
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,
708 and then Present (Actions (F_Node))
710 Decl := Last (Actions (F_Node));
715 end Check_Dispatching_Operation;
717 ------------------------------------------
718 -- Check_Operation_From_Incomplete_Type --
719 ------------------------------------------
721 procedure Check_Operation_From_Incomplete_Type
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);
730 Prev : Elmt_Id := No_Elmt;
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.
740 function Derives_From (Proc : Entity_Id) return Boolean is
744 if Chars (Proc) /= Chars (Subp) then
748 F1 := First_Formal (Proc);
749 F2 := First_Formal (Subp);
751 while Present (F1) and then Present (F2) loop
753 if Ekind (Etype (F1)) = E_Anonymous_Access_Type then
755 if Ekind (Etype (F2)) /= E_Anonymous_Access_Type then
758 elsif Designated_Type (Etype (F1)) = Parent_Typ
759 and then Designated_Type (Etype (F2)) /= Full
764 elsif Ekind (Etype (F2)) = E_Anonymous_Access_Type then
767 elsif Etype (F1) /= Etype (F2) then
775 return No (F1) and then No (F2);
778 -- Start of processing for Check_Operation_From_Incomplete_Type
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.
788 Op1 := First_Elmt (Old_Prim);
789 Op2 := First_Elmt (New_Prim);
791 while Present (Op1) and then Present (Op2) loop
793 if Derives_From (Node (Op1)) then
796 Prepend_Elmt (Subp, New_Prim);
798 Insert_Elmt_After (Subp, Prev);
809 -- Operation is a new primitive
811 Append_Elmt (Subp, New_Prim);
812 end Check_Operation_From_Incomplete_Type;
814 ---------------------------------------
815 -- Check_Operation_From_Private_View --
816 ---------------------------------------
818 procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id) is
819 Tagged_Type : Entity_Id;
822 if Is_Dispatching_Operation (Alias (Subp)) then
823 Set_Scope (Subp, Current_Scope);
824 Tagged_Type := Find_Dispatching_Type (Subp);
826 if Present (Tagged_Type) and then Is_Tagged_Type (Tagged_Type) then
827 Append_Elmt (Old_Subp, Primitive_Operations (Tagged_Type));
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.
835 if not Is_Dispatching_Operation (Old_Subp) then
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
844 if not Comes_From_Source (Tagged_Type)
845 and then Has_Discriminants (Tagged_Type)
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);
856 Next_Formal (Formal);
860 if Tagged_Type = Base_Type (Etype (Old_Subp)) then
861 Tagged_Type := Etype (Old_Subp);
865 Check_Controlling_Formals (Tagged_Type, Old_Subp);
866 Set_Is_Dispatching_Operation (Old_Subp, True);
867 Set_DT_Position (Old_Subp, No_Uint);
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.
874 if Present (Alias (Old_Subp))
875 and then Nkind (Unit_Declaration_Node (Old_Subp))
876 /= N_Subprogram_Renaming_Declaration
878 Set_Alias (Old_Subp, Alias (Subp));
880 -- The derived subprogram should inherit the abstractness
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.
888 if Etype (Subp) /= Tagged_Type then
889 Set_Is_Abstract (Old_Subp, Is_Abstract (Alias (Subp)));
894 end Check_Operation_From_Private_View;
896 --------------------------
897 -- Find_Controlling_Arg --
898 --------------------------
900 function Find_Controlling_Arg (N : Node_Id) return Node_Id is
901 Orig_Node : constant Node_Id := Original_Node (N);
905 if Nkind (Orig_Node) = N_Qualified_Expression then
906 return Find_Controlling_Arg (Expression (Orig_Node));
909 -- Dispatching on result case
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)))
915 return Controlling_Argument (Orig_Node);
919 elsif Is_Controlling_Actual (N)
921 (Nkind (Parent (N)) = N_Qualified_Expression
922 and then Is_Controlling_Actual (Parent (N)))
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.
933 if Nkind (N) = N_Attribute_Reference then
934 Typ := Etype (Prefix (N));
936 -- An allocator is dispatching if the type of qualified
937 -- expression is class_wide, in which case this is the
940 elsif Nkind (Orig_Node) = N_Allocator
941 and then Nkind (Expression (Orig_Node)) = N_Qualified_Expression
943 Typ := Etype (Expression (Orig_Node));
946 Typ := Designated_Type (Typ);
950 if Is_Class_Wide_Type (Typ)
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))))
961 end Find_Controlling_Arg;
963 ---------------------------
964 -- Find_Dispatching_Type --
965 ---------------------------
967 function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id is
969 Ctrl_Type : Entity_Id;
972 if Present (DTC_Entity (Subp)) then
973 return Scope (DTC_Entity (Subp));
976 Formal := First_Formal (Subp);
977 while Present (Formal) loop
978 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
980 if Present (Ctrl_Type) then
984 Next_Formal (Formal);
987 -- The subprogram may also be dispatching on result
989 if Present (Etype (Subp)) then
990 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
992 if Present (Ctrl_Type) then
999 end Find_Dispatching_Type;
1001 ---------------------------
1002 -- Is_Dynamically_Tagged --
1003 ---------------------------
1005 function Is_Dynamically_Tagged (N : Node_Id) return Boolean is
1007 return Find_Controlling_Arg (N) /= Empty;
1008 end Is_Dynamically_Tagged;
1010 --------------------------
1011 -- Is_Tag_Indeterminate --
1012 --------------------------
1014 function Is_Tag_Indeterminate (N : Node_Id) return Boolean is
1017 Orig_Node : constant Node_Id := Original_Node (N);
1020 if Nkind (Orig_Node) = N_Function_Call
1021 and then Is_Entity_Name (Name (Orig_Node))
1023 Nam := Entity (Name (Orig_Node));
1025 if not Has_Controlling_Result (Nam) then
1028 -- An explicit dereference means that the call has already been
1029 -- expanded and there is no tag to propagate.
1031 elsif Nkind (N) = N_Explicit_Dereference then
1034 -- If there are no actuals, the call is tag-indeterminate
1036 elsif No (Parameter_Associations (Orig_Node)) then
1040 Actual := First_Actual (Orig_Node);
1042 while Present (Actual) loop
1043 if Is_Controlling_Actual (Actual)
1044 and then not Is_Tag_Indeterminate (Actual)
1046 return False; -- one operand is dispatching
1049 Next_Actual (Actual);
1056 elsif Nkind (Orig_Node) = N_Qualified_Expression then
1057 return Is_Tag_Indeterminate (Expression (Orig_Node));
1062 end Is_Tag_Indeterminate;
1064 ------------------------------------
1065 -- Override_Dispatching_Operation --
1066 ------------------------------------
1068 procedure Override_Dispatching_Operation
1069 (Tagged_Type : Entity_Id;
1070 Prev_Op : Entity_Id;
1073 Op_Elmt : Elmt_Id := First_Elmt (Primitive_Operations (Tagged_Type));
1076 -- Patch the primitive operation list
1078 while Present (Op_Elmt)
1079 and then Node (Op_Elmt) /= Prev_Op
1081 Next_Elmt (Op_Elmt);
1084 -- If there is no previous operation to override, the type declaration
1085 -- was malformed, and an error must have been emitted already.
1087 if No (Op_Elmt) then
1091 Replace_Elmt (Op_Elmt, New_Op);
1093 if (not Is_Package (Current_Scope))
1094 or else not In_Private_Part (Current_Scope)
1096 -- Not a private primitive
1100 else pragma Assert (Is_Inherited_Operation (Prev_Op));
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.
1109 Set_Alias (Prev_Op, New_Op);
1110 Set_DTC_Entity (Prev_Op, Empty);
1113 end Override_Dispatching_Operation;
1119 procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id) is
1120 Call_Node : Node_Id;
1124 if Nkind (Actual) = N_Function_Call then
1125 Call_Node := Actual;
1127 elsif Nkind (Actual) = N_Identifier
1128 and then Nkind (Original_Node (Actual)) = N_Function_Call
1130 -- Call rewritten as object declaration when stack-checking
1131 -- is enabled. Propagate tag to expression in declaration, which
1132 -- is original call.
1134 Call_Node := Expression (Parent (Entity (Actual)));
1136 -- Only other possibility is parenthesized or qualified expression
1139 Call_Node := Expression (Actual);
1142 -- Do not set the Controlling_Argument if already set. This happens
1143 -- in the special case of _Input (see Exp_Attr, case Input).
1145 if No (Controlling_Argument (Call_Node)) then
1146 Set_Controlling_Argument (Call_Node, Control);
1149 Arg := First_Actual (Call_Node);
1151 while Present (Arg) loop
1152 if Is_Tag_Indeterminate (Arg) then
1153 Propagate_Tag (Control, Arg);
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.
1164 Expand_Dispatch_Call (Call_Node);