1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2006, 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, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, 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 Exp_Util; use Exp_Util;
35 with Errout; use Errout;
36 with Hostparm; use Hostparm;
37 with Nlists; use Nlists;
38 with Nmake; use Nmake;
40 with Output; use Output;
41 with Restrict; use Restrict;
42 with Rident; use Rident;
44 with Sem_Ch6; use Sem_Ch6;
45 with Sem_Eval; use Sem_Eval;
46 with Sem_Type; use Sem_Type;
47 with Sem_Util; use Sem_Util;
48 with Snames; use Snames;
49 with Stand; use Stand;
50 with Sinfo; use Sinfo;
51 with Tbuild; use Tbuild;
52 with Uintp; use Uintp;
54 package body Sem_Disp is
56 -----------------------
57 -- Local Subprograms --
58 -----------------------
60 procedure Add_Dispatching_Operation
61 (Tagged_Type : Entity_Id;
63 -- Add New_Op in the list of primitive operations of Tagged_Type
65 function Check_Controlling_Type
67 Subp : Entity_Id) return Entity_Id;
68 -- T is the tagged type of a formal parameter or the result of Subp.
69 -- If the subprogram has a controlling parameter or result that matches
70 -- the type, then returns the tagged type of that parameter or result
71 -- (returning the designated tagged type in the case of an access
72 -- parameter); otherwise returns empty.
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);
84 Append_Elmt (New_Op, List);
85 end Add_Dispatching_Operation;
87 -------------------------------
88 -- Check_Controlling_Formals --
89 -------------------------------
91 procedure Check_Controlling_Formals
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;
103 Formal := First_Formal (Subp);
105 while Present (Formal) loop
106 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
108 if Present (Ctrl_Type) then
109 if Ctrl_Type = Typ then
110 Set_Is_Controlling_Formal (Formal);
112 -- Ada 2005 (AI-231):Anonymous access types used in controlling
113 -- parameters exclude null because it is necessary to read the
114 -- tag to dispatch, and null has no tag.
116 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
117 Set_Can_Never_Be_Null (Etype (Formal));
118 Set_Is_Known_Non_Null (Etype (Formal));
121 -- Check that the parameter's nominal subtype statically
122 -- matches the first subtype.
124 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
125 if not Subtypes_Statically_Match
126 (Typ, Designated_Type (Etype (Formal)))
129 ("parameter subtype does not match controlling type",
133 elsif not Subtypes_Statically_Match (Typ, Etype (Formal)) then
135 ("parameter subtype does not match controlling type",
139 if Present (Default_Value (Formal)) then
140 if Ekind (Etype (Formal)) = E_Anonymous_Access_Type then
142 ("default not allowed for controlling access parameter",
143 Default_Value (Formal));
145 elsif not Is_Tag_Indeterminate (Default_Value (Formal)) then
147 ("default expression must be a tag indeterminate" &
148 " function call", Default_Value (Formal));
152 elsif Comes_From_Source (Subp) then
154 ("operation can be dispatching in only one type", Subp);
157 -- Verify that the restriction in E.2.2 (14) is obeyed
160 and then Ekind (Etype (Formal)) = E_Anonymous_Access_Type
163 ("access parameter of remote object primitive"
164 & " must be controlling",
168 Next_Formal (Formal);
171 if Present (Etype (Subp)) then
172 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
174 if Present (Ctrl_Type) then
175 if Ctrl_Type = Typ then
176 Set_Has_Controlling_Result (Subp);
178 -- Check that the result subtype statically matches
179 -- the first subtype.
181 if not Subtypes_Statically_Match (Typ, Etype (Subp)) then
183 ("result subtype does not match controlling type", Subp);
186 elsif Comes_From_Source (Subp) then
188 ("operation can be dispatching in only one type", Subp);
191 -- The following check is clearly required, although the RM says
192 -- nothing about return types. If the return type is a limited
193 -- class-wide type declared in the current scope, there is no way
194 -- to declare stream procedures for it, so the return cannot be
198 and then Is_Limited_Type (Typ)
199 and then Etype (Subp) = Class_Wide_Type (Typ)
201 Error_Msg_N ("return type has no stream attributes", Subp);
204 end Check_Controlling_Formals;
206 ----------------------------
207 -- Check_Controlling_Type --
208 ----------------------------
210 function Check_Controlling_Type
212 Subp : Entity_Id) return Entity_Id
214 Tagged_Type : Entity_Id := Empty;
217 if Is_Tagged_Type (T) then
218 if Is_First_Subtype (T) then
221 Tagged_Type := Base_Type (T);
224 elsif Ekind (T) = E_Anonymous_Access_Type
225 and then Is_Tagged_Type (Designated_Type (T))
227 if Ekind (Designated_Type (T)) /= E_Incomplete_Type then
228 if Is_First_Subtype (Designated_Type (T)) then
229 Tagged_Type := Designated_Type (T);
231 Tagged_Type := Base_Type (Designated_Type (T));
234 -- Ada 2005 (AI-50217)
236 elsif From_With_Type (Designated_Type (T))
237 and then Present (Non_Limited_View (Designated_Type (T)))
239 if Is_First_Subtype (Non_Limited_View (Designated_Type (T))) then
240 Tagged_Type := Non_Limited_View (Designated_Type (T));
242 Tagged_Type := Base_Type (Non_Limited_View
243 (Designated_Type (T)));
249 or else Is_Class_Wide_Type (Tagged_Type)
253 -- The dispatching type and the primitive operation must be defined
254 -- in the same scope, except in the case of internal operations and
255 -- formal abstract subprograms.
257 elsif ((Scope (Subp) = Scope (Tagged_Type) or else Is_Internal (Subp))
258 and then (not Is_Generic_Type (Tagged_Type)
259 or else not Comes_From_Source (Subp)))
261 (Is_Formal_Subprogram (Subp) and then Is_Abstract (Subp))
263 (Nkind (Parent (Parent (Subp))) = N_Subprogram_Renaming_Declaration
265 Present (Corresponding_Formal_Spec (Parent (Parent (Subp))))
274 end Check_Controlling_Type;
276 ----------------------------
277 -- Check_Dispatching_Call --
278 ----------------------------
280 procedure Check_Dispatching_Call (N : Node_Id) is
283 Control : Node_Id := Empty;
285 Subp_Entity : Entity_Id;
286 Loc : constant Source_Ptr := Sloc (N);
287 Indeterm_Ancestor_Call : Boolean := False;
288 Indeterm_Ctrl_Type : Entity_Id;
290 procedure Check_Dispatching_Context;
291 -- If the call is tag-indeterminate and the entity being called is
292 -- abstract, verify that the context is a call that will eventually
293 -- provide a tag for dispatching, or has provided one already.
295 -------------------------------
296 -- Check_Dispatching_Context --
297 -------------------------------
299 procedure Check_Dispatching_Context is
300 Subp : constant Entity_Id := Entity (Name (N));
304 if Is_Abstract (Subp)
305 and then No (Controlling_Argument (N))
307 if Present (Alias (Subp))
308 and then not Is_Abstract (Alias (Subp))
309 and then No (DTC_Entity (Subp))
311 -- Private overriding of inherited abstract operation,
314 Set_Entity (Name (N), Alias (Subp));
320 while Present (Par) loop
322 if (Nkind (Par) = N_Function_Call or else
323 Nkind (Par) = N_Procedure_Call_Statement or else
324 Nkind (Par) = N_Assignment_Statement or else
325 Nkind (Par) = N_Op_Eq or else
326 Nkind (Par) = N_Op_Ne)
327 and then Is_Tagged_Type (Etype (Subp))
331 elsif Nkind (Par) = N_Qualified_Expression
332 or else Nkind (Par) = N_Unchecked_Type_Conversion
337 if Ekind (Subp) = E_Function then
339 ("call to abstract function must be dispatching", N);
341 -- This error can occur for a procedure in the case of a
342 -- call to an abstract formal procedure with a statically
347 ("call to abstract procedure must be dispatching",
356 end Check_Dispatching_Context;
358 -- Start of processing for Check_Dispatching_Call
361 -- Find a controlling argument, if any
363 if Present (Parameter_Associations (N)) then
364 Actual := First_Actual (N);
366 Subp_Entity := Entity (Name (N));
367 Formal := First_Formal (Subp_Entity);
369 while Present (Actual) loop
370 Control := Find_Controlling_Arg (Actual);
371 exit when Present (Control);
373 -- Check for the case where the actual is a tag-indeterminate call
374 -- whose result type is different than the tagged type associated
375 -- with the containing call, but is an ancestor of the type.
377 if Is_Controlling_Formal (Formal)
378 and then Is_Tag_Indeterminate (Actual)
379 and then Base_Type (Etype (Actual)) /= Base_Type (Etype (Formal))
380 and then Is_Ancestor (Etype (Actual), Etype (Formal))
382 Indeterm_Ancestor_Call := True;
383 Indeterm_Ctrl_Type := Etype (Formal);
386 Next_Actual (Actual);
387 Next_Formal (Formal);
390 -- If the call doesn't have a controlling actual but does have
391 -- an indeterminate actual that requires dispatching treatment,
392 -- then an object is needed that will serve as the controlling
393 -- argument for a dispatching call on the indeterminate actual.
394 -- This can only occur in the unusual situation of a default
395 -- actual given by a tag-indeterminate call and where the type
396 -- of the call is an ancestor of the type associated with a
397 -- containing call to an inherited operation (see AI-239).
398 -- Rather than create an object of the tagged type, which would
399 -- be problematic for various reasons (default initialization,
400 -- discriminants), the tag of the containing call's associated
401 -- tagged type is directly used to control the dispatching.
404 and then Indeterm_Ancestor_Call
407 Make_Attribute_Reference (Loc,
408 Prefix => New_Occurrence_Of (Indeterm_Ctrl_Type, Loc),
409 Attribute_Name => Name_Tag);
413 if Present (Control) then
415 -- Verify that no controlling arguments are statically tagged
418 Write_Str ("Found Dispatching call");
423 Actual := First_Actual (N);
425 while Present (Actual) loop
426 if Actual /= Control then
428 if not Is_Controlling_Actual (Actual) then
429 null; -- Can be anything
431 elsif Is_Dynamically_Tagged (Actual) then
432 null; -- Valid parameter
434 elsif Is_Tag_Indeterminate (Actual) then
436 -- The tag is inherited from the enclosing call (the
437 -- node we are currently analyzing). Explicitly expand
438 -- the actual, since the previous call to Expand
439 -- (from Resolve_Call) had no way of knowing about
440 -- the required dispatching.
442 Propagate_Tag (Control, Actual);
446 ("controlling argument is not dynamically tagged",
452 Next_Actual (Actual);
455 -- Mark call as a dispatching call
457 Set_Controlling_Argument (N, Control);
460 -- The call is not dispatching, so check that there aren't any
461 -- tag-indeterminate abstract calls left.
463 Actual := First_Actual (N);
465 while Present (Actual) loop
466 if Is_Tag_Indeterminate (Actual) then
468 -- Function call case
470 if Nkind (Original_Node (Actual)) = N_Function_Call then
471 Func := Entity (Name (Original_Node (Actual)));
473 -- If the actual is an attribute then it can't be abstract
474 -- (the only current case of a tag-indeterminate attribute
475 -- is the stream Input attribute).
478 Nkind (Original_Node (Actual)) = N_Attribute_Reference
482 -- Only other possibility is a qualified expression whose
483 -- consituent expression is itself a call.
489 (Expression (Original_Node (Actual)))));
492 if Present (Func) and then Is_Abstract (Func) then
494 "call to abstract function must be dispatching", N);
498 Next_Actual (Actual);
501 Check_Dispatching_Context;
505 -- If dispatching on result, the enclosing call, if any, will
506 -- determine the controlling argument. Otherwise this is the
507 -- primitive operation of the root type.
509 Check_Dispatching_Context;
511 end Check_Dispatching_Call;
513 ---------------------------------
514 -- Check_Dispatching_Operation --
515 ---------------------------------
517 procedure Check_Dispatching_Operation (Subp, Old_Subp : Entity_Id) is
518 Tagged_Type : Entity_Id;
519 Has_Dispatching_Parent : Boolean := False;
520 Body_Is_Last_Primitive : Boolean := False;
522 function Is_Visibly_Controlled (T : Entity_Id) return Boolean;
523 -- Check whether T is derived from a visibly controlled type.
524 -- This is true if the root type is declared in Ada.Finalization.
525 -- If T is derived instead from a private type whose full view
526 -- is controlled, an explicit Initialize/Adjust/Finalize subprogram
527 -- does not override the inherited one.
529 ---------------------------
530 -- Is_Visibly_Controlled --
531 ---------------------------
533 function Is_Visibly_Controlled (T : Entity_Id) return Boolean is
534 Root : constant Entity_Id := Root_Type (T);
536 return Chars (Scope (Root)) = Name_Finalization
537 and then Chars (Scope (Scope (Root))) = Name_Ada
538 and then Scope (Scope (Scope (Root))) = Standard_Standard;
539 end Is_Visibly_Controlled;
541 -- Start of processing for Check_Dispatching_Operation
544 if Ekind (Subp) /= E_Procedure and then Ekind (Subp) /= E_Function then
548 Set_Is_Dispatching_Operation (Subp, False);
549 Tagged_Type := Find_Dispatching_Type (Subp);
553 if Ada_Version = Ada_05
554 and then Present (Tagged_Type)
555 and then Is_Concurrent_Type (Tagged_Type)
557 -- Protect the frontend against previously detected errors
559 if No (Corresponding_Record_Type (Tagged_Type)) then
563 Tagged_Type := Corresponding_Record_Type (Tagged_Type);
566 -- If Subp is derived from a dispatching operation then it should
567 -- always be treated as dispatching. In this case various checks
568 -- below will be bypassed. Makes sure that late declarations for
569 -- inherited private subprograms are treated as dispatching, even
570 -- if the associated tagged type is already frozen.
572 Has_Dispatching_Parent :=
573 Present (Alias (Subp))
574 and then Is_Dispatching_Operation (Alias (Subp));
576 if No (Tagged_Type) then
579 -- The subprograms build internally after the freezing point (such as
580 -- the Init procedure) are not primitives
582 elsif Is_Frozen (Tagged_Type)
583 and then not Comes_From_Source (Subp)
584 and then not Has_Dispatching_Parent
588 -- The operation may be a child unit, whose scope is the defining
589 -- package, but which is not a primitive operation of the type.
591 elsif Is_Child_Unit (Subp) then
594 -- If the subprogram is not defined in a package spec, the only case
595 -- where it can be a dispatching op is when it overrides an operation
596 -- before the freezing point of the type.
598 elsif ((not Is_Package_Or_Generic_Package (Scope (Subp)))
599 or else In_Package_Body (Scope (Subp)))
600 and then not Has_Dispatching_Parent
602 if not Comes_From_Source (Subp)
603 or else (Present (Old_Subp) and then not Is_Frozen (Tagged_Type))
607 -- If the type is already frozen, the overriding is not allowed
608 -- except when Old_Subp is not a dispatching operation (which
609 -- can occur when Old_Subp was inherited by an untagged type).
610 -- However, a body with no previous spec freezes the type "after"
611 -- its declaration, and therefore is a legal overriding (unless
612 -- the type has already been frozen). Only the first such body
615 elsif Present (Old_Subp)
616 and then Is_Dispatching_Operation (Old_Subp)
618 if Comes_From_Source (Subp)
620 (Nkind (Unit_Declaration_Node (Subp)) = N_Subprogram_Body
621 or else Nkind (Unit_Declaration_Node (Subp)) in N_Body_Stub)
624 Subp_Body : constant Node_Id := Unit_Declaration_Node (Subp);
625 Decl_Item : Node_Id := Next (Parent (Tagged_Type));
628 -- ??? The checks here for whether the type has been
629 -- frozen prior to the new body are not complete. It's
630 -- not simple to check frozenness at this point since
631 -- the body has already caused the type to be prematurely
632 -- frozen in Analyze_Declarations, but we're forced to
633 -- recheck this here because of the odd rule interpretation
634 -- that allows the overriding if the type wasn't frozen
635 -- prior to the body. The freezing action should probably
636 -- be delayed until after the spec is seen, but that's
637 -- a tricky change to the delicate freezing code.
639 -- Look at each declaration following the type up
640 -- until the new subprogram body. If any of the
641 -- declarations is a body then the type has been
642 -- frozen already so the overriding primitive is
645 while Present (Decl_Item)
646 and then (Decl_Item /= Subp_Body)
648 if Comes_From_Source (Decl_Item)
649 and then (Nkind (Decl_Item) in N_Proper_Body
650 or else Nkind (Decl_Item) in N_Body_Stub)
652 Error_Msg_N ("overriding of& is too late!", Subp);
654 ("\spec should appear immediately after the type!",
662 -- If the subprogram doesn't follow in the list of
663 -- declarations including the type then the type
664 -- has definitely been frozen already and the body
667 if No (Decl_Item) then
668 Error_Msg_N ("overriding of& is too late!", Subp);
670 ("\spec should appear immediately after the type!",
673 elsif Is_Frozen (Subp) then
675 -- The subprogram body declares a primitive operation.
676 -- if the subprogram is already frozen, we must update
677 -- its dispatching information explicitly here. The
678 -- information is taken from the overridden subprogram.
680 Body_Is_Last_Primitive := True;
682 if Present (DTC_Entity (Old_Subp)) then
683 Set_DTC_Entity (Subp, DTC_Entity (Old_Subp));
684 Set_DT_Position (Subp, DT_Position (Old_Subp));
686 if not Restriction_Active (No_Dispatching_Calls) then
687 Insert_After (Subp_Body,
688 Fill_DT_Entry (Sloc (Subp_Body), Subp));
695 Error_Msg_N ("overriding of& is too late!", Subp);
697 ("\subprogram spec should appear immediately after the type!",
701 -- If the type is not frozen yet and we are not in the overridding
702 -- case it looks suspiciously like an attempt to define a primitive
705 elsif not Is_Frozen (Tagged_Type) then
707 ("?not dispatching (must be defined in a package spec)", Subp);
710 -- When the type is frozen, it is legitimate to define a new
711 -- non-primitive operation.
717 -- Now, we are sure that the scope is a package spec. If the subprogram
718 -- is declared after the freezing point ot the type that's an error
720 elsif Is_Frozen (Tagged_Type) and then not Has_Dispatching_Parent then
721 Error_Msg_N ("this primitive operation is declared too late", Subp);
723 ("?no primitive operations for& after this line",
724 Freeze_Node (Tagged_Type),
729 Check_Controlling_Formals (Tagged_Type, Subp);
731 -- Now it should be a correct primitive operation, put it in the list
733 if Present (Old_Subp) then
734 Check_Subtype_Conformant (Subp, Old_Subp);
735 if (Chars (Subp) = Name_Initialize
736 or else Chars (Subp) = Name_Adjust
737 or else Chars (Subp) = Name_Finalize)
738 and then Is_Controlled (Tagged_Type)
739 and then not Is_Visibly_Controlled (Tagged_Type)
741 Set_Is_Overriding_Operation (Subp, False);
743 ("operation does not override inherited&?", Subp, Subp);
745 Override_Dispatching_Operation (Tagged_Type, Old_Subp, Subp);
746 Set_Is_Overriding_Operation (Subp);
749 -- If no old subprogram, then we add this as a dispatching operation,
750 -- but we avoid doing this if an error was posted, to prevent annoying
753 elsif not Error_Posted (Subp) then
754 Add_Dispatching_Operation (Tagged_Type, Subp);
757 Set_Is_Dispatching_Operation (Subp, True);
759 if not Body_Is_Last_Primitive then
760 Set_DT_Position (Subp, No_Uint);
762 elsif Has_Controlled_Component (Tagged_Type)
764 (Chars (Subp) = Name_Initialize
765 or else Chars (Subp) = Name_Adjust
766 or else Chars (Subp) = Name_Finalize)
769 F_Node : constant Node_Id := Freeze_Node (Tagged_Type);
773 Old_Spec : Entity_Id;
775 C_Names : constant array (1 .. 3) of Name_Id :=
780 D_Names : constant array (1 .. 3) of TSS_Name_Type :=
781 (TSS_Deep_Initialize,
786 -- Remove previous controlled function, which was constructed
787 -- and analyzed when the type was frozen. This requires
788 -- removing the body of the redefined primitive, as well as
789 -- its specification if needed (there is no spec created for
790 -- Deep_Initialize, see exp_ch3.adb). We must also dismantle
791 -- the exception information that may have been generated for
792 -- it when front end zero-cost tables are enabled.
794 for J in D_Names'Range loop
795 Old_P := TSS (Tagged_Type, D_Names (J));
798 and then Chars (Subp) = C_Names (J)
800 Old_Bod := Unit_Declaration_Node (Old_P);
802 Set_Is_Eliminated (Old_P);
803 Set_Scope (Old_P, Scope (Current_Scope));
805 if Nkind (Old_Bod) = N_Subprogram_Body
806 and then Present (Corresponding_Spec (Old_Bod))
808 Old_Spec := Corresponding_Spec (Old_Bod);
809 Set_Has_Completion (Old_Spec, False);
814 Build_Late_Proc (Tagged_Type, Chars (Subp));
816 -- The new operation is added to the actions of the freeze
817 -- node for the type, but this node has already been analyzed,
818 -- so we must retrieve and analyze explicitly the one new body,
821 and then Present (Actions (F_Node))
823 Decl := Last (Actions (F_Node));
828 end Check_Dispatching_Operation;
830 ------------------------------------------
831 -- Check_Operation_From_Incomplete_Type --
832 ------------------------------------------
834 procedure Check_Operation_From_Incomplete_Type
838 Full : constant Entity_Id := Full_View (Typ);
839 Parent_Typ : constant Entity_Id := Etype (Full);
840 Old_Prim : constant Elist_Id := Primitive_Operations (Parent_Typ);
841 New_Prim : constant Elist_Id := Primitive_Operations (Full);
843 Prev : Elmt_Id := No_Elmt;
845 function Derives_From (Proc : Entity_Id) return Boolean;
846 -- Check that Subp has the signature of an operation derived from Proc.
847 -- Subp has an access parameter that designates Typ.
853 function Derives_From (Proc : Entity_Id) return Boolean is
857 if Chars (Proc) /= Chars (Subp) then
861 F1 := First_Formal (Proc);
862 F2 := First_Formal (Subp);
864 while Present (F1) and then Present (F2) loop
866 if Ekind (Etype (F1)) = E_Anonymous_Access_Type then
868 if Ekind (Etype (F2)) /= E_Anonymous_Access_Type then
871 elsif Designated_Type (Etype (F1)) = Parent_Typ
872 and then Designated_Type (Etype (F2)) /= Full
877 elsif Ekind (Etype (F2)) = E_Anonymous_Access_Type then
880 elsif Etype (F1) /= Etype (F2) then
888 return No (F1) and then No (F2);
891 -- Start of processing for Check_Operation_From_Incomplete_Type
894 -- The operation may override an inherited one, or may be a new one
895 -- altogether. The inherited operation will have been hidden by the
896 -- current one at the point of the type derivation, so it does not
897 -- appear in the list of primitive operations of the type. We have to
898 -- find the proper place of insertion in the list of primitive opera-
899 -- tions by iterating over the list for the parent type.
901 Op1 := First_Elmt (Old_Prim);
902 Op2 := First_Elmt (New_Prim);
904 while Present (Op1) and then Present (Op2) loop
906 if Derives_From (Node (Op1)) then
909 Prepend_Elmt (Subp, New_Prim);
911 Insert_Elmt_After (Subp, Prev);
922 -- Operation is a new primitive
924 Append_Elmt (Subp, New_Prim);
925 end Check_Operation_From_Incomplete_Type;
927 ---------------------------------------
928 -- Check_Operation_From_Private_View --
929 ---------------------------------------
931 procedure Check_Operation_From_Private_View (Subp, Old_Subp : Entity_Id) is
932 Tagged_Type : Entity_Id;
935 if Is_Dispatching_Operation (Alias (Subp)) then
936 Set_Scope (Subp, Current_Scope);
937 Tagged_Type := Find_Dispatching_Type (Subp);
939 if Present (Tagged_Type) and then Is_Tagged_Type (Tagged_Type) then
940 Append_Elmt (Old_Subp, Primitive_Operations (Tagged_Type));
942 -- If Old_Subp isn't already marked as dispatching then
943 -- this is the case of an operation of an untagged private
944 -- type fulfilled by a tagged type that overrides an
945 -- inherited dispatching operation, so we set the necessary
946 -- dispatching attributes here.
948 if not Is_Dispatching_Operation (Old_Subp) then
950 -- If the untagged type has no discriminants, and the full
951 -- view is constrained, there will be a spurious mismatch
952 -- of subtypes on the controlling arguments, because the tagged
953 -- type is the internal base type introduced in the derivation.
954 -- Use the original type to verify conformance, rather than the
957 if not Comes_From_Source (Tagged_Type)
958 and then Has_Discriminants (Tagged_Type)
963 Formal := First_Formal (Old_Subp);
964 while Present (Formal) loop
965 if Tagged_Type = Base_Type (Etype (Formal)) then
966 Tagged_Type := Etype (Formal);
969 Next_Formal (Formal);
973 if Tagged_Type = Base_Type (Etype (Old_Subp)) then
974 Tagged_Type := Etype (Old_Subp);
978 Check_Controlling_Formals (Tagged_Type, Old_Subp);
979 Set_Is_Dispatching_Operation (Old_Subp, True);
980 Set_DT_Position (Old_Subp, No_Uint);
983 -- If the old subprogram is an explicit renaming of some other
984 -- entity, it is not overridden by the inherited subprogram.
985 -- Otherwise, update its alias and other attributes.
987 if Present (Alias (Old_Subp))
988 and then Nkind (Unit_Declaration_Node (Old_Subp))
989 /= N_Subprogram_Renaming_Declaration
991 Set_Alias (Old_Subp, Alias (Subp));
993 -- The derived subprogram should inherit the abstractness
994 -- of the parent subprogram (except in the case of a function
995 -- returning the type). This sets the abstractness properly
996 -- for cases where a private extension may have inherited
997 -- an abstract operation, but the full type is derived from
998 -- a descendant type and inherits a nonabstract version.
1000 if Etype (Subp) /= Tagged_Type then
1001 Set_Is_Abstract (Old_Subp, Is_Abstract (Alias (Subp)));
1006 end Check_Operation_From_Private_View;
1008 --------------------------
1009 -- Find_Controlling_Arg --
1010 --------------------------
1012 function Find_Controlling_Arg (N : Node_Id) return Node_Id is
1013 Orig_Node : constant Node_Id := Original_Node (N);
1017 if Nkind (Orig_Node) = N_Qualified_Expression then
1018 return Find_Controlling_Arg (Expression (Orig_Node));
1021 -- Dispatching on result case
1023 if Nkind (Orig_Node) = N_Function_Call
1024 and then Present (Controlling_Argument (Orig_Node))
1025 and then Has_Controlling_Result (Entity (Name (Orig_Node)))
1027 return Controlling_Argument (Orig_Node);
1031 elsif Is_Controlling_Actual (N)
1033 (Nkind (Parent (N)) = N_Qualified_Expression
1034 and then Is_Controlling_Actual (Parent (N)))
1038 if Is_Access_Type (Typ) then
1039 -- In the case of an Access attribute, use the type of
1040 -- the prefix, since in the case of an actual for an
1041 -- access parameter, the attribute's type may be of a
1042 -- specific designated type, even though the prefix
1043 -- type is class-wide.
1045 if Nkind (N) = N_Attribute_Reference then
1046 Typ := Etype (Prefix (N));
1048 -- An allocator is dispatching if the type of qualified
1049 -- expression is class_wide, in which case this is the
1050 -- controlling type.
1052 elsif Nkind (Orig_Node) = N_Allocator
1053 and then Nkind (Expression (Orig_Node)) = N_Qualified_Expression
1055 Typ := Etype (Expression (Orig_Node));
1058 Typ := Designated_Type (Typ);
1062 if Is_Class_Wide_Type (Typ)
1064 (Nkind (Parent (N)) = N_Qualified_Expression
1065 and then Is_Access_Type (Etype (N))
1066 and then Is_Class_Wide_Type (Designated_Type (Etype (N))))
1073 end Find_Controlling_Arg;
1075 ---------------------------
1076 -- Find_Dispatching_Type --
1077 ---------------------------
1079 function Find_Dispatching_Type (Subp : Entity_Id) return Entity_Id is
1081 Ctrl_Type : Entity_Id;
1084 if Present (DTC_Entity (Subp)) then
1085 return Scope (DTC_Entity (Subp));
1088 Formal := First_Formal (Subp);
1089 while Present (Formal) loop
1090 Ctrl_Type := Check_Controlling_Type (Etype (Formal), Subp);
1092 if Present (Ctrl_Type) then
1096 Next_Formal (Formal);
1099 -- The subprogram may also be dispatching on result
1101 if Present (Etype (Subp)) then
1102 Ctrl_Type := Check_Controlling_Type (Etype (Subp), Subp);
1104 if Present (Ctrl_Type) then
1111 end Find_Dispatching_Type;
1113 ---------------------------
1114 -- Is_Dynamically_Tagged --
1115 ---------------------------
1117 function Is_Dynamically_Tagged (N : Node_Id) return Boolean is
1119 return Find_Controlling_Arg (N) /= Empty;
1120 end Is_Dynamically_Tagged;
1122 --------------------------
1123 -- Is_Tag_Indeterminate --
1124 --------------------------
1126 function Is_Tag_Indeterminate (N : Node_Id) return Boolean is
1129 Orig_Node : constant Node_Id := Original_Node (N);
1132 if Nkind (Orig_Node) = N_Function_Call
1133 and then Is_Entity_Name (Name (Orig_Node))
1135 Nam := Entity (Name (Orig_Node));
1137 if not Has_Controlling_Result (Nam) then
1140 -- An explicit dereference means that the call has already been
1141 -- expanded and there is no tag to propagate.
1143 elsif Nkind (N) = N_Explicit_Dereference then
1146 -- If there are no actuals, the call is tag-indeterminate
1148 elsif No (Parameter_Associations (Orig_Node)) then
1152 Actual := First_Actual (Orig_Node);
1153 while Present (Actual) loop
1154 if Is_Controlling_Actual (Actual)
1155 and then not Is_Tag_Indeterminate (Actual)
1157 return False; -- one operand is dispatching
1160 Next_Actual (Actual);
1166 elsif Nkind (Orig_Node) = N_Qualified_Expression then
1167 return Is_Tag_Indeterminate (Expression (Orig_Node));
1169 -- Case of a call to the Input attribute (possibly rewritten), which is
1170 -- always tag-indeterminate except when its prefix is a Class attribute.
1172 elsif Nkind (Orig_Node) = N_Attribute_Reference
1174 Get_Attribute_Id (Attribute_Name (Orig_Node)) = Attribute_Input
1176 Nkind (Prefix (Orig_Node)) /= N_Attribute_Reference
1182 end Is_Tag_Indeterminate;
1184 ------------------------------------
1185 -- Override_Dispatching_Operation --
1186 ------------------------------------
1188 procedure Override_Dispatching_Operation
1189 (Tagged_Type : Entity_Id;
1190 Prev_Op : Entity_Id;
1193 Op_Elmt : Elmt_Id := First_Elmt (Primitive_Operations (Tagged_Type));
1198 function Is_Interface_Subprogram (Op : Entity_Id) return Boolean;
1199 -- Traverse the list of aliased entities to check if the overriden
1200 -- entity corresponds with a primitive operation of an abstract
1203 -----------------------------
1204 -- Is_Interface_Subprogram --
1205 -----------------------------
1207 function Is_Interface_Subprogram (Op : Entity_Id) return Boolean is
1212 while Present (Alias (Aux))
1213 and then Present (DTC_Entity (Alias (Aux)))
1215 if Is_Interface (Scope (DTC_Entity (Alias (Aux)))) then
1222 end Is_Interface_Subprogram;
1224 -- Start of processing for Override_Dispatching_Operation
1227 -- Diagnose failure to match No_Return in parent (Ada-2005, AI-414, but
1228 -- we do it unconditionally in Ada 95 now, since this is our pragma!)
1230 if No_Return (Prev_Op) and then not No_Return (New_Op) then
1231 Error_Msg_N ("procedure & must have No_Return pragma", New_Op);
1232 Error_Msg_N ("\since overridden procedure has No_Return", New_Op);
1235 -- Patch the primitive operation list
1237 while Present (Op_Elmt)
1238 and then Node (Op_Elmt) /= Prev_Op
1240 Next_Elmt (Op_Elmt);
1243 -- If there is no previous operation to override, the type declaration
1244 -- was malformed, and an error must have been emitted already.
1246 if No (Op_Elmt) then
1250 -- Ada 2005 (AI-251): Do not replace subprograms inherited from
1251 -- abstract interfaces. They will be used later to generate the
1252 -- corresponding thunks to initialize the Vtable (see subprogram
1253 -- Freeze_Subprogram). The inherited operation itself must also
1254 -- become hidden, to avoid spurious ambiguities; name resolution
1255 -- must pick up only the operation that implements it,
1257 if Is_Interface_Subprogram (Prev_Op) then
1258 Set_DT_Position (Prev_Op, DT_Position (Alias (Prev_Op)));
1259 Set_Is_Abstract (Prev_Op, Is_Abstract (New_Op));
1260 Set_Is_Overriding_Operation (Prev_Op);
1262 -- Traverse the list of aliased entities to look for the overriden
1263 -- abstract interface subprogram.
1265 E := Alias (Prev_Op);
1266 while Present (Alias (E))
1267 and then Present (DTC_Entity (E))
1268 and then not (Is_Abstract (E))
1269 and then not Is_Interface (Scope (DTC_Entity (E)))
1274 Set_Abstract_Interface_Alias (Prev_Op, E);
1275 Set_Alias (Prev_Op, New_Op);
1276 Set_Is_Internal (Prev_Op);
1277 Set_Is_Hidden (Prev_Op);
1279 -- Override predefined primitive operations
1281 if Is_Predefined_Dispatching_Operation (Prev_Op) then
1282 Replace_Elmt (Op_Elmt, New_Op);
1286 -- Check if this primitive operation was previously added for another
1289 Elmt := First_Elmt (Primitive_Operations (Tagged_Type));
1291 while Present (Elmt) loop
1292 if Node (Elmt) = New_Op then
1301 Append_Elmt (New_Op, Primitive_Operations (Tagged_Type));
1307 Replace_Elmt (Op_Elmt, New_Op);
1310 if (not Is_Package_Or_Generic_Package (Current_Scope))
1311 or else not In_Private_Part (Current_Scope)
1313 -- Not a private primitive
1317 else pragma Assert (Is_Inherited_Operation (Prev_Op));
1319 -- Make the overriding operation into an alias of the implicit one.
1320 -- In this fashion a call from outside ends up calling the new body
1321 -- even if non-dispatching, and a call from inside calls the
1322 -- overriding operation because it hides the implicit one. To
1323 -- indicate that the body of Prev_Op is never called, set its
1324 -- dispatch table entity to Empty.
1326 Set_Alias (Prev_Op, New_Op);
1327 Set_DTC_Entity (Prev_Op, Empty);
1330 end Override_Dispatching_Operation;
1336 procedure Propagate_Tag (Control : Node_Id; Actual : Node_Id) is
1337 Call_Node : Node_Id;
1341 if Nkind (Actual) = N_Function_Call then
1342 Call_Node := Actual;
1344 elsif Nkind (Actual) = N_Identifier
1345 and then Nkind (Original_Node (Actual)) = N_Function_Call
1347 -- Call rewritten as object declaration when stack-checking
1348 -- is enabled. Propagate tag to expression in declaration, which
1349 -- is original call.
1351 Call_Node := Expression (Parent (Entity (Actual)));
1353 -- Only other possibilities are parenthesized or qualified expression,
1354 -- or an expander-generated unchecked conversion of a function call to
1355 -- a stream Input attribute.
1358 Call_Node := Expression (Actual);
1361 -- Do not set the Controlling_Argument if already set. This happens
1362 -- in the special case of _Input (see Exp_Attr, case Input).
1364 if No (Controlling_Argument (Call_Node)) then
1365 Set_Controlling_Argument (Call_Node, Control);
1368 Arg := First_Actual (Call_Node);
1370 while Present (Arg) loop
1371 if Is_Tag_Indeterminate (Arg) then
1372 Propagate_Tag (Control, Arg);
1378 -- Expansion of dispatching calls is suppressed when Java_VM, because
1379 -- the JVM back end directly handles the generation of dispatching
1380 -- calls and would have to undo any expansion to an indirect call.
1383 Expand_Dispatching_Call (Call_Node);