1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2015, 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 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Aspects; use Aspects;
27 with Atree; use Atree;
28 with Checks; use Checks;
29 with Einfo; use Einfo;
30 with Errout; use Errout;
31 with Expander; use Expander;
32 with Exp_Ch6; use Exp_Ch6;
33 with Exp_Ch7; use Exp_Ch7;
34 with Exp_Util; use Exp_Util;
35 with Freeze; use Freeze;
36 with Ghost; use Ghost;
38 with Lib.Xref; use Lib.Xref;
39 with Namet; use Namet;
40 with Nlists; use Nlists;
41 with Nmake; use Nmake;
43 with Restrict; use Restrict;
44 with Rident; use Rident;
45 with Rtsfind; use Rtsfind;
47 with Sem_Aux; use Sem_Aux;
48 with Sem_Case; use Sem_Case;
49 with Sem_Ch3; use Sem_Ch3;
50 with Sem_Ch6; use Sem_Ch6;
51 with Sem_Ch8; use Sem_Ch8;
52 with Sem_Dim; use Sem_Dim;
53 with Sem_Disp; use Sem_Disp;
54 with Sem_Elab; use Sem_Elab;
55 with Sem_Eval; use Sem_Eval;
56 with Sem_Res; use Sem_Res;
57 with Sem_Type; use Sem_Type;
58 with Sem_Util; use Sem_Util;
59 with Sem_Warn; use Sem_Warn;
60 with Snames; use Snames;
61 with Stand; use Stand;
62 with Sinfo; use Sinfo;
63 with Targparm; use Targparm;
64 with Tbuild; use Tbuild;
65 with Uintp; use Uintp;
67 package body Sem_Ch5 is
69 Unblocked_Exit_Count : Nat := 0;
70 -- This variable is used when processing if statements, case statements,
71 -- and block statements. It counts the number of exit points that are not
72 -- blocked by unconditional transfer instructions: for IF and CASE, these
73 -- are the branches of the conditional; for a block, they are the statement
74 -- sequence of the block, and the statement sequences of any exception
75 -- handlers that are part of the block. When processing is complete, if
76 -- this count is zero, it means that control cannot fall through the IF,
77 -- CASE or block statement. This is used for the generation of warning
78 -- messages. This variable is recursively saved on entry to processing the
79 -- construct, and restored on exit.
81 procedure Preanalyze_Range (R_Copy : Node_Id);
82 -- Determine expected type of range or domain of iteration of Ada 2012
83 -- loop by analyzing separate copy. Do the analysis and resolution of the
84 -- copy of the bound(s) with expansion disabled, to prevent the generation
85 -- of finalization actions. This prevents memory leaks when the bounds
86 -- contain calls to functions returning controlled arrays or when the
87 -- domain of iteration is a container.
89 ------------------------
90 -- Analyze_Assignment --
91 ------------------------
93 procedure Analyze_Assignment (N : Node_Id) is
94 Lhs : constant Node_Id := Name (N);
95 Rhs : constant Node_Id := Expression (N);
100 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
101 -- N is the node for the left hand side of an assignment, and it is not
102 -- a variable. This routine issues an appropriate diagnostic.
105 -- This is called to kill current value settings of a simple variable
106 -- on the left hand side. We call it if we find any error in analyzing
107 -- the assignment, and at the end of processing before setting any new
108 -- current values in place.
110 procedure Set_Assignment_Type
112 Opnd_Type : in out Entity_Id);
113 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type is the
114 -- nominal subtype. This procedure is used to deal with cases where the
115 -- nominal subtype must be replaced by the actual subtype.
117 -------------------------------
118 -- Diagnose_Non_Variable_Lhs --
119 -------------------------------
121 procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
123 -- Not worth posting another error if left hand side already flagged
124 -- as being illegal in some respect.
126 if Error_Posted (N) then
129 -- Some special bad cases of entity names
131 elsif Is_Entity_Name (N) then
133 Ent : constant Entity_Id := Entity (N);
136 if Ekind (Ent) = E_In_Parameter then
138 ("assignment to IN mode parameter not allowed", N);
141 -- Renamings of protected private components are turned into
142 -- constants when compiling a protected function. In the case
143 -- of single protected types, the private component appears
146 elsif (Is_Prival (Ent)
148 (Ekind (Current_Scope) = E_Function
149 or else Ekind (Enclosing_Dynamic_Scope
150 (Current_Scope)) = E_Function))
152 (Ekind (Ent) = E_Component
153 and then Is_Protected_Type (Scope (Ent)))
156 ("protected function cannot modify protected object", N);
159 elsif Ekind (Ent) = E_Loop_Parameter then
160 Error_Msg_N ("assignment to loop parameter not allowed", N);
165 -- For indexed components, test prefix if it is in array. We do not
166 -- want to recurse for cases where the prefix is a pointer, since we
167 -- may get a message confusing the pointer and what it references.
169 elsif Nkind (N) = N_Indexed_Component
170 and then Is_Array_Type (Etype (Prefix (N)))
172 Diagnose_Non_Variable_Lhs (Prefix (N));
175 -- Another special case for assignment to discriminant
177 elsif Nkind (N) = N_Selected_Component then
178 if Present (Entity (Selector_Name (N)))
179 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
181 Error_Msg_N ("assignment to discriminant not allowed", N);
184 -- For selection from record, diagnose prefix, but note that again
185 -- we only do this for a record, not e.g. for a pointer.
187 elsif Is_Record_Type (Etype (Prefix (N))) then
188 Diagnose_Non_Variable_Lhs (Prefix (N));
193 -- If we fall through, we have no special message to issue
195 Error_Msg_N ("left hand side of assignment must be a variable", N);
196 end Diagnose_Non_Variable_Lhs;
202 procedure Kill_Lhs is
204 if Is_Entity_Name (Lhs) then
206 Ent : constant Entity_Id := Entity (Lhs);
208 if Present (Ent) then
209 Kill_Current_Values (Ent);
215 -------------------------
216 -- Set_Assignment_Type --
217 -------------------------
219 procedure Set_Assignment_Type
221 Opnd_Type : in out Entity_Id)
224 Require_Entity (Opnd);
226 -- If the assignment operand is an in-out or out parameter, then we
227 -- get the actual subtype (needed for the unconstrained case). If the
228 -- operand is the actual in an entry declaration, then within the
229 -- accept statement it is replaced with a local renaming, which may
230 -- also have an actual subtype.
232 if Is_Entity_Name (Opnd)
233 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
234 or else Ekind_In (Entity (Opnd),
236 E_Generic_In_Out_Parameter)
238 (Ekind (Entity (Opnd)) = E_Variable
239 and then Nkind (Parent (Entity (Opnd))) =
240 N_Object_Renaming_Declaration
241 and then Nkind (Parent (Parent (Entity (Opnd)))) =
244 Opnd_Type := Get_Actual_Subtype (Opnd);
246 -- If assignment operand is a component reference, then we get the
247 -- actual subtype of the component for the unconstrained case.
249 elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference)
250 and then not Is_Unchecked_Union (Opnd_Type)
252 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
254 if Present (Decl) then
255 Insert_Action (N, Decl);
256 Mark_Rewrite_Insertion (Decl);
258 Opnd_Type := Defining_Identifier (Decl);
259 Set_Etype (Opnd, Opnd_Type);
260 Freeze_Itype (Opnd_Type, N);
262 elsif Is_Constrained (Etype (Opnd)) then
263 Opnd_Type := Etype (Opnd);
266 -- For slice, use the constrained subtype created for the slice
268 elsif Nkind (Opnd) = N_Slice then
269 Opnd_Type := Etype (Opnd);
271 end Set_Assignment_Type;
275 Save_Ghost_Mode : constant Ghost_Mode_Type := Ghost_Mode;
277 -- Start of processing for Analyze_Assignment
280 Mark_Coextensions (N, Rhs);
282 -- Analyze the target of the assignment first in case the expression
283 -- contains references to Ghost entities. The checks that verify the
284 -- proper use of a Ghost entity need to know the enclosing context.
288 -- An assignment statement is Ghost when the left hand side denotes a
289 -- Ghost entity. Set the mode now to ensure that any nodes generated
290 -- during analysis and expansion are properly marked as Ghost.
295 -- Ensure that we never do an assignment on a variable marked as
296 -- as Safe_To_Reevaluate.
298 pragma Assert (not Is_Entity_Name (Lhs)
299 or else Ekind (Entity (Lhs)) /= E_Variable
300 or else not Is_Safe_To_Reevaluate (Entity (Lhs)));
302 -- Start type analysis for assignment
306 -- In the most general case, both Lhs and Rhs can be overloaded, and we
307 -- must compute the intersection of the possible types on each side.
309 if Is_Overloaded (Lhs) then
316 Get_First_Interp (Lhs, I, It);
318 while Present (It.Typ) loop
320 -- An indexed component with generalized indexing is always
321 -- overloaded with the corresponding dereference. Discard the
322 -- interpretation that yields a reference type, which is not
325 if Nkind (Lhs) = N_Indexed_Component
326 and then Present (Generalized_Indexing (Lhs))
327 and then Has_Implicit_Dereference (It.Typ)
331 elsif Has_Compatible_Type (Rhs, It.Typ) then
332 if T1 /= Any_Type then
334 -- An explicit dereference is overloaded if the prefix
335 -- is. Try to remove the ambiguity on the prefix, the
336 -- error will be posted there if the ambiguity is real.
338 if Nkind (Lhs) = N_Explicit_Dereference then
341 PI1 : Interp_Index := 0;
347 Get_First_Interp (Prefix (Lhs), PI, PIt);
349 while Present (PIt.Typ) loop
350 if Is_Access_Type (PIt.Typ)
351 and then Has_Compatible_Type
352 (Rhs, Designated_Type (PIt.Typ))
356 Disambiguate (Prefix (Lhs),
359 if PIt = No_Interp then
361 ("ambiguous left-hand side"
362 & " in assignment", Lhs);
365 Resolve (Prefix (Lhs), PIt.Typ);
375 Get_Next_Interp (PI, PIt);
381 ("ambiguous left-hand side in assignment", Lhs);
389 Get_Next_Interp (I, It);
393 if T1 = Any_Type then
395 ("no valid types for left-hand side for assignment", Lhs);
397 Ghost_Mode := Save_Ghost_Mode;
402 -- The resulting assignment type is T1, so now we will resolve the left
403 -- hand side of the assignment using this determined type.
407 -- Cases where Lhs is not a variable
409 -- Cases where Lhs is not a variable. In an instance or an inlined body
410 -- no need for further check because assignment was legal in template.
412 if In_Inlined_Body then
415 elsif not Is_Variable (Lhs) then
417 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of a
425 if Ada_Version >= Ada_2005 then
427 -- Handle chains of renamings
430 while Nkind (Ent) in N_Has_Entity
431 and then Present (Entity (Ent))
432 and then Present (Renamed_Object (Entity (Ent)))
434 Ent := Renamed_Object (Entity (Ent));
437 if (Nkind (Ent) = N_Attribute_Reference
438 and then Attribute_Name (Ent) = Name_Priority)
440 -- Renamings of the attribute Priority applied to protected
441 -- objects have been previously expanded into calls to the
442 -- Get_Ceiling run-time subprogram.
445 (Nkind (Ent) = N_Function_Call
446 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
448 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
450 -- The enclosing subprogram cannot be a protected function
453 while not (Is_Subprogram (S)
454 and then Convention (S) = Convention_Protected)
455 and then S /= Standard_Standard
460 if Ekind (S) = E_Function
461 and then Convention (S) = Convention_Protected
464 ("protected function cannot modify protected object",
468 -- Changes of the ceiling priority of the protected object
469 -- are only effective if the Ceiling_Locking policy is in
470 -- effect (AARM D.5.2 (5/2)).
472 if Locking_Policy /= 'C' then
473 Error_Msg_N ("assignment to the attribute PRIORITY has " &
475 Error_Msg_N ("\since no Locking_Policy has been " &
479 Ghost_Mode := Save_Ghost_Mode;
485 Diagnose_Non_Variable_Lhs (Lhs);
486 Ghost_Mode := Save_Ghost_Mode;
489 -- Error of assigning to limited type. We do however allow this in
490 -- certain cases where the front end generates the assignments.
492 elsif Is_Limited_Type (T1)
493 and then not Assignment_OK (Lhs)
494 and then not Assignment_OK (Original_Node (Lhs))
496 -- CPP constructors can only be called in declarations
498 if Is_CPP_Constructor_Call (Rhs) then
499 Error_Msg_N ("invalid use of 'C'P'P constructor", Rhs);
502 ("left hand of assignment must not be limited type", Lhs);
503 Explain_Limited_Type (T1, Lhs);
506 Ghost_Mode := Save_Ghost_Mode;
509 -- A class-wide type may be a limited view. This illegal case is not
510 -- caught by previous checks.
512 elsif Ekind (T1) = E_Class_Wide_Type
513 and then From_Limited_With (T1)
515 Error_Msg_NE ("invalid use of limited view of&", Lhs, T1);
518 -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
519 -- abstract. This is only checked when the assignment Comes_From_Source,
520 -- because in some cases the expander generates such assignments (such
521 -- in the _assign operation for an abstract type).
523 elsif Is_Abstract_Type (T1) and then Comes_From_Source (N) then
525 ("target of assignment operation must not be abstract", Lhs);
528 -- Resolution may have updated the subtype, in case the left-hand side
529 -- is a private protected component. Use the correct subtype to avoid
530 -- scoping issues in the back-end.
534 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
535 -- type. For example:
539 -- type Acc is access P.T;
542 -- with Pkg; use Acc;
543 -- procedure Example is
546 -- A.all := B.all; -- ERROR
549 if Nkind (Lhs) = N_Explicit_Dereference
550 and then Ekind (T1) = E_Incomplete_Type
552 Error_Msg_N ("invalid use of incomplete type", Lhs);
554 Ghost_Mode := Save_Ghost_Mode;
558 -- Now we can complete the resolution of the right hand side
560 Set_Assignment_Type (Lhs, T1);
563 -- This is the point at which we check for an unset reference
565 Check_Unset_Reference (Rhs);
566 Check_Unprotected_Access (Lhs, Rhs);
568 -- Remaining steps are skipped if Rhs was syntactically in error
572 Ghost_Mode := Save_Ghost_Mode;
578 if not Covers (T1, T2) then
579 Wrong_Type (Rhs, Etype (Lhs));
581 Ghost_Mode := Save_Ghost_Mode;
585 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
586 -- types, use the non-limited view if available
588 if Nkind (Rhs) = N_Explicit_Dereference
589 and then Is_Tagged_Type (T2)
590 and then Has_Non_Limited_View (T2)
592 T2 := Non_Limited_View (T2);
595 Set_Assignment_Type (Rhs, T2);
597 if Total_Errors_Detected /= 0 then
607 if T1 = Any_Type or else T2 = Any_Type then
609 Ghost_Mode := Save_Ghost_Mode;
613 -- If the rhs is class-wide or dynamically tagged, then require the lhs
614 -- to be class-wide. The case where the rhs is a dynamically tagged call
615 -- to a dispatching operation with a controlling access result is
616 -- excluded from this check, since the target has an access type (and
617 -- no tag propagation occurs in that case).
619 if (Is_Class_Wide_Type (T2)
620 or else (Is_Dynamically_Tagged (Rhs)
621 and then not Is_Access_Type (T1)))
622 and then not Is_Class_Wide_Type (T1)
624 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
626 elsif Is_Class_Wide_Type (T1)
627 and then not Is_Class_Wide_Type (T2)
628 and then not Is_Tag_Indeterminate (Rhs)
629 and then not Is_Dynamically_Tagged (Rhs)
631 Error_Msg_N ("dynamically tagged expression required!", Rhs);
634 -- Propagate the tag from a class-wide target to the rhs when the rhs
635 -- is a tag-indeterminate call.
637 if Is_Tag_Indeterminate (Rhs) then
638 if Is_Class_Wide_Type (T1) then
639 Propagate_Tag (Lhs, Rhs);
641 elsif Nkind (Rhs) = N_Function_Call
642 and then Is_Entity_Name (Name (Rhs))
643 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
646 ("call to abstract function must be dispatching", Name (Rhs));
648 elsif Nkind (Rhs) = N_Qualified_Expression
649 and then Nkind (Expression (Rhs)) = N_Function_Call
650 and then Is_Entity_Name (Name (Expression (Rhs)))
652 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
655 ("call to abstract function must be dispatching",
656 Name (Expression (Rhs)));
660 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
661 -- apply an implicit conversion of the rhs to that type to force
662 -- appropriate static and run-time accessibility checks. This applies
663 -- as well to anonymous access-to-subprogram types that are component
664 -- subtypes or formal parameters.
666 if Ada_Version >= Ada_2005 and then Is_Access_Type (T1) then
667 if Is_Local_Anonymous_Access (T1)
668 or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
670 -- Handle assignment to an Ada 2012 stand-alone object
671 -- of an anonymous access type.
673 or else (Ekind (T1) = E_Anonymous_Access_Type
674 and then Nkind (Associated_Node_For_Itype (T1)) =
675 N_Object_Declaration)
678 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
679 Analyze_And_Resolve (Rhs, T1);
683 -- Ada 2005 (AI-231): Assignment to not null variable
685 if Ada_Version >= Ada_2005
686 and then Can_Never_Be_Null (T1)
687 and then not Assignment_OK (Lhs)
689 -- Case where we know the right hand side is null
691 if Known_Null (Rhs) then
692 Apply_Compile_Time_Constraint_Error
695 "(Ada 2005) null not allowed in null-excluding objects??",
696 Reason => CE_Null_Not_Allowed);
698 -- We still mark this as a possible modification, that's necessary
699 -- to reset Is_True_Constant, and desirable for xref purposes.
701 Note_Possible_Modification (Lhs, Sure => True);
702 Ghost_Mode := Save_Ghost_Mode;
705 -- If we know the right hand side is non-null, then we convert to the
706 -- target type, since we don't need a run time check in that case.
708 elsif not Can_Never_Be_Null (T2) then
709 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
710 Analyze_And_Resolve (Rhs, T1);
714 if Is_Scalar_Type (T1) then
715 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
717 -- For array types, verify that lengths match. If the right hand side
718 -- is a function call that has been inlined, the assignment has been
719 -- rewritten as a block, and the constraint check will be applied to the
720 -- assignment within the block.
722 elsif Is_Array_Type (T1)
723 and then (Nkind (Rhs) /= N_Type_Conversion
724 or else Is_Constrained (Etype (Rhs)))
725 and then (Nkind (Rhs) /= N_Function_Call
726 or else Nkind (N) /= N_Block_Statement)
728 -- Assignment verifies that the length of the Lsh and Rhs are equal,
729 -- but of course the indexes do not have to match. If the right-hand
730 -- side is a type conversion to an unconstrained type, a length check
731 -- is performed on the expression itself during expansion. In rare
732 -- cases, the redundant length check is computed on an index type
733 -- with a different representation, triggering incorrect code in the
736 Apply_Length_Check (Rhs, Etype (Lhs));
739 -- Discriminant checks are applied in the course of expansion
744 -- Note: modifications of the Lhs may only be recorded after
745 -- checks have been applied.
747 Note_Possible_Modification (Lhs, Sure => True);
749 -- ??? a real accessibility check is needed when ???
751 -- Post warning for redundant assignment or variable to itself
753 if Warn_On_Redundant_Constructs
755 -- We only warn for source constructs
757 and then Comes_From_Source (N)
759 -- Where the object is the same on both sides
761 and then Same_Object (Lhs, Original_Node (Rhs))
763 -- But exclude the case where the right side was an operation that
764 -- got rewritten (e.g. JUNK + K, where K was known to be zero). We
765 -- don't want to warn in such a case, since it is reasonable to write
766 -- such expressions especially when K is defined symbolically in some
769 and then Nkind (Original_Node (Rhs)) not in N_Op
771 if Nkind (Lhs) in N_Has_Entity then
772 Error_Msg_NE -- CODEFIX
773 ("?r?useless assignment of & to itself!", N, Entity (Lhs));
775 Error_Msg_N -- CODEFIX
776 ("?r?useless assignment of object to itself!", N);
780 -- Check for non-allowed composite assignment
782 if not Support_Composite_Assign_On_Target
783 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
784 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
786 Error_Msg_CRT ("composite assignment", N);
789 -- Check elaboration warning for left side if not in elab code
791 if not In_Subprogram_Or_Concurrent_Unit then
792 Check_Elab_Assign (Lhs);
795 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
796 -- assignment is a source assignment in the extended main source unit.
797 -- We are not interested in any reference information outside this
798 -- context, or in compiler generated assignment statements.
800 if Comes_From_Source (N)
801 and then In_Extended_Main_Source_Unit (Lhs)
803 Set_Referenced_Modified (Lhs, Out_Param => False);
806 -- RM 7.3.2 (12/3): An assignment to a view conversion (from a type
807 -- to one of its ancestors) requires an invariant check. Apply check
808 -- only if expression comes from source, otherwise it will be applied
809 -- when value is assigned to source entity.
811 if Nkind (Lhs) = N_Type_Conversion
812 and then Has_Invariants (Etype (Expression (Lhs)))
813 and then Comes_From_Source (Expression (Lhs))
815 Insert_After (N, Make_Invariant_Call (Expression (Lhs)));
818 -- Final step. If left side is an entity, then we may be able to reset
819 -- the current tracked values to new safe values. We only have something
820 -- to do if the left side is an entity name, and expansion has not
821 -- modified the node into something other than an assignment, and of
822 -- course we only capture values if it is safe to do so.
824 if Is_Entity_Name (Lhs)
825 and then Nkind (N) = N_Assignment_Statement
828 Ent : constant Entity_Id := Entity (Lhs);
831 if Safe_To_Capture_Value (N, Ent) then
833 -- If simple variable on left side, warn if this assignment
834 -- blots out another one (rendering it useless). We only do
835 -- this for source assignments, otherwise we can generate bogus
836 -- warnings when an assignment is rewritten as another
837 -- assignment, and gets tied up with itself.
839 if Warn_On_Modified_Unread
840 and then Is_Assignable (Ent)
841 and then Comes_From_Source (N)
842 and then In_Extended_Main_Source_Unit (Ent)
844 Warn_On_Useless_Assignment (Ent, N);
847 -- If we are assigning an access type and the left side is an
848 -- entity, then make sure that the Is_Known_[Non_]Null flags
849 -- properly reflect the state of the entity after assignment.
851 if Is_Access_Type (T1) then
852 if Known_Non_Null (Rhs) then
853 Set_Is_Known_Non_Null (Ent, True);
855 elsif Known_Null (Rhs)
856 and then not Can_Never_Be_Null (Ent)
858 Set_Is_Known_Null (Ent, True);
861 Set_Is_Known_Null (Ent, False);
863 if not Can_Never_Be_Null (Ent) then
864 Set_Is_Known_Non_Null (Ent, False);
868 -- For discrete types, we may be able to set the current value
869 -- if the value is known at compile time.
871 elsif Is_Discrete_Type (T1)
872 and then Compile_Time_Known_Value (Rhs)
874 Set_Current_Value (Ent, Rhs);
876 Set_Current_Value (Ent, Empty);
879 -- If not safe to capture values, kill them
887 -- If assigning to an object in whole or in part, note location of
888 -- assignment in case no one references value. We only do this for
889 -- source assignments, otherwise we can generate bogus warnings when an
890 -- assignment is rewritten as another assignment, and gets tied up with
894 Ent : constant Entity_Id := Get_Enclosing_Object (Lhs);
897 and then Safe_To_Capture_Value (N, Ent)
898 and then Nkind (N) = N_Assignment_Statement
899 and then Warn_On_Modified_Unread
900 and then Is_Assignable (Ent)
901 and then Comes_From_Source (N)
902 and then In_Extended_Main_Source_Unit (Ent)
904 Set_Last_Assignment (Ent, Lhs);
908 Analyze_Dimension (N);
909 Ghost_Mode := Save_Ghost_Mode;
910 end Analyze_Assignment;
912 -----------------------------
913 -- Analyze_Block_Statement --
914 -----------------------------
916 procedure Analyze_Block_Statement (N : Node_Id) is
917 procedure Install_Return_Entities (Scop : Entity_Id);
918 -- Install all entities of return statement scope Scop in the visibility
919 -- chain except for the return object since its entity is reused in a
922 -----------------------------
923 -- Install_Return_Entities --
924 -----------------------------
926 procedure Install_Return_Entities (Scop : Entity_Id) is
930 Id := First_Entity (Scop);
931 while Present (Id) loop
933 -- Do not install the return object
935 if not Ekind_In (Id, E_Constant, E_Variable)
936 or else not Is_Return_Object (Id)
943 end Install_Return_Entities;
945 -- Local constants and variables
947 Decls : constant List_Id := Declarations (N);
948 Id : constant Node_Id := Identifier (N);
949 HSS : constant Node_Id := Handled_Statement_Sequence (N);
951 Is_BIP_Return_Statement : Boolean;
953 -- Start of processing for Analyze_Block_Statement
956 -- In SPARK mode, we reject block statements. Note that the case of
957 -- block statements generated by the expander is fine.
959 if Nkind (Original_Node (N)) = N_Block_Statement then
960 Check_SPARK_05_Restriction ("block statement is not allowed", N);
963 -- If no handled statement sequence is present, things are really messed
964 -- up, and we just return immediately (defence against previous errors).
967 Check_Error_Detected;
971 -- Detect whether the block is actually a rewritten return statement of
972 -- a build-in-place function.
974 Is_BIP_Return_Statement :=
976 and then Present (Entity (Id))
977 and then Ekind (Entity (Id)) = E_Return_Statement
978 and then Is_Build_In_Place_Function
979 (Return_Applies_To (Entity (Id)));
981 -- Normal processing with HSS present
984 EH : constant List_Id := Exception_Handlers (HSS);
985 Ent : Entity_Id := Empty;
988 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
989 -- Recursively save value of this global, will be restored on exit
992 -- Initialize unblocked exit count for statements of begin block
993 -- plus one for each exception handler that is present.
995 Unblocked_Exit_Count := 1;
998 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
1001 -- If a label is present analyze it and mark it as referenced
1003 if Present (Id) then
1007 -- An error defense. If we have an identifier, but no entity, then
1008 -- something is wrong. If previous errors, then just remove the
1009 -- identifier and continue, otherwise raise an exception.
1012 Check_Error_Detected;
1013 Set_Identifier (N, Empty);
1016 Set_Ekind (Ent, E_Block);
1017 Generate_Reference (Ent, N, ' ');
1018 Generate_Definition (Ent);
1020 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
1021 Set_Label_Construct (Parent (Ent), N);
1026 -- If no entity set, create a label entity
1029 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
1030 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
1031 Set_Parent (Ent, N);
1034 Set_Etype (Ent, Standard_Void_Type);
1035 Set_Block_Node (Ent, Identifier (N));
1038 -- The block served as an extended return statement. Ensure that any
1039 -- entities created during the analysis and expansion of the return
1040 -- object declaration are once again visible.
1042 if Is_BIP_Return_Statement then
1043 Install_Return_Entities (Ent);
1046 if Present (Decls) then
1047 Analyze_Declarations (Decls);
1049 Inspect_Deferred_Constant_Completion (Decls);
1053 Process_End_Label (HSS, 'e', Ent);
1055 -- If exception handlers are present, then we indicate that enclosing
1056 -- scopes contain a block with handlers. We only need to mark non-
1059 if Present (EH) then
1062 Set_Has_Nested_Block_With_Handler (S);
1063 exit when Is_Overloadable (S)
1064 or else Ekind (S) = E_Package
1065 or else Is_Generic_Unit (S);
1070 Check_References (Ent);
1071 Warn_On_Useless_Assignments (Ent);
1074 if Unblocked_Exit_Count = 0 then
1075 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1076 Check_Unreachable_Code (N);
1078 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1081 end Analyze_Block_Statement;
1083 --------------------------------
1084 -- Analyze_Compound_Statement --
1085 --------------------------------
1087 procedure Analyze_Compound_Statement (N : Node_Id) is
1089 Analyze_List (Actions (N));
1090 end Analyze_Compound_Statement;
1092 ----------------------------
1093 -- Analyze_Case_Statement --
1094 ----------------------------
1096 procedure Analyze_Case_Statement (N : Node_Id) is
1098 Exp_Type : Entity_Id;
1099 Exp_Btype : Entity_Id;
1102 Others_Present : Boolean;
1103 -- Indicates if Others was present
1105 pragma Warnings (Off, Last_Choice);
1106 -- Don't care about assigned value
1108 Statements_Analyzed : Boolean := False;
1109 -- Set True if at least some statement sequences get analyzed. If False
1110 -- on exit, means we had a serious error that prevented full analysis of
1111 -- the case statement, and as a result it is not a good idea to output
1112 -- warning messages about unreachable code.
1114 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1115 -- Recursively save value of this global, will be restored on exit
1117 procedure Non_Static_Choice_Error (Choice : Node_Id);
1118 -- Error routine invoked by the generic instantiation below when the
1119 -- case statement has a non static choice.
1121 procedure Process_Statements (Alternative : Node_Id);
1122 -- Analyzes the statements associated with a case alternative. Needed
1123 -- by instantiation below.
1125 package Analyze_Case_Choices is new
1126 Generic_Analyze_Choices
1127 (Process_Associated_Node => Process_Statements);
1128 use Analyze_Case_Choices;
1129 -- Instantiation of the generic choice analysis package
1131 package Check_Case_Choices is new
1132 Generic_Check_Choices
1133 (Process_Empty_Choice => No_OP,
1134 Process_Non_Static_Choice => Non_Static_Choice_Error,
1135 Process_Associated_Node => No_OP);
1136 use Check_Case_Choices;
1137 -- Instantiation of the generic choice processing package
1139 -----------------------------
1140 -- Non_Static_Choice_Error --
1141 -----------------------------
1143 procedure Non_Static_Choice_Error (Choice : Node_Id) is
1145 Flag_Non_Static_Expr
1146 ("choice given in case statement is not static!", Choice);
1147 end Non_Static_Choice_Error;
1149 ------------------------
1150 -- Process_Statements --
1151 ------------------------
1153 procedure Process_Statements (Alternative : Node_Id) is
1154 Choices : constant List_Id := Discrete_Choices (Alternative);
1158 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1159 Statements_Analyzed := True;
1161 -- An interesting optimization. If the case statement expression
1162 -- is a simple entity, then we can set the current value within an
1163 -- alternative if the alternative has one possible value.
1167 -- when 2 | 3 => beta
1168 -- when others => gamma
1170 -- Here we know that N is initially 1 within alpha, but for beta and
1171 -- gamma, we do not know anything more about the initial value.
1173 if Is_Entity_Name (Exp) then
1174 Ent := Entity (Exp);
1176 if Ekind_In (Ent, E_Variable,
1180 if List_Length (Choices) = 1
1181 and then Nkind (First (Choices)) in N_Subexpr
1182 and then Compile_Time_Known_Value (First (Choices))
1184 Set_Current_Value (Entity (Exp), First (Choices));
1187 Analyze_Statements (Statements (Alternative));
1189 -- After analyzing the case, set the current value to empty
1190 -- since we won't know what it is for the next alternative
1191 -- (unless reset by this same circuit), or after the case.
1193 Set_Current_Value (Entity (Exp), Empty);
1198 -- Case where expression is not an entity name of a variable
1200 Analyze_Statements (Statements (Alternative));
1201 end Process_Statements;
1203 -- Start of processing for Analyze_Case_Statement
1206 Unblocked_Exit_Count := 0;
1207 Exp := Expression (N);
1210 -- The expression must be of any discrete type. In rare cases, the
1211 -- expander constructs a case statement whose expression has a private
1212 -- type whose full view is discrete. This can happen when generating
1213 -- a stream operation for a variant type after the type is frozen,
1214 -- when the partial of view of the type of the discriminant is private.
1215 -- In that case, use the full view to analyze case alternatives.
1217 if not Is_Overloaded (Exp)
1218 and then not Comes_From_Source (N)
1219 and then Is_Private_Type (Etype (Exp))
1220 and then Present (Full_View (Etype (Exp)))
1221 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1223 Resolve (Exp, Etype (Exp));
1224 Exp_Type := Full_View (Etype (Exp));
1227 Analyze_And_Resolve (Exp, Any_Discrete);
1228 Exp_Type := Etype (Exp);
1231 Check_Unset_Reference (Exp);
1232 Exp_Btype := Base_Type (Exp_Type);
1234 -- The expression must be of a discrete type which must be determinable
1235 -- independently of the context in which the expression occurs, but
1236 -- using the fact that the expression must be of a discrete type.
1237 -- Moreover, the type this expression must not be a character literal
1238 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1240 -- If error already reported by Resolve, nothing more to do
1242 if Exp_Btype = Any_Discrete or else Exp_Btype = Any_Type then
1245 elsif Exp_Btype = Any_Character then
1247 ("character literal as case expression is ambiguous", Exp);
1250 elsif Ada_Version = Ada_83
1251 and then (Is_Generic_Type (Exp_Btype)
1252 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1255 ("(Ada 83) case expression cannot be of a generic type", Exp);
1259 -- If the case expression is a formal object of mode in out, then treat
1260 -- it as having a nonstatic subtype by forcing use of the base type
1261 -- (which has to get passed to Check_Case_Choices below). Also use base
1262 -- type when the case expression is parenthesized.
1264 if Paren_Count (Exp) > 0
1265 or else (Is_Entity_Name (Exp)
1266 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1268 Exp_Type := Exp_Btype;
1271 -- Call instantiated procedures to analyzwe and check discrete choices
1273 Analyze_Choices (Alternatives (N), Exp_Type);
1274 Check_Choices (N, Alternatives (N), Exp_Type, Others_Present);
1276 -- Case statement with single OTHERS alternative not allowed in SPARK
1278 if Others_Present and then List_Length (Alternatives (N)) = 1 then
1279 Check_SPARK_05_Restriction
1280 ("OTHERS as unique case alternative is not allowed", N);
1283 if Exp_Type = Universal_Integer and then not Others_Present then
1284 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1287 -- If all our exits were blocked by unconditional transfers of control,
1288 -- then the entire CASE statement acts as an unconditional transfer of
1289 -- control, so treat it like one, and check unreachable code. Skip this
1290 -- test if we had serious errors preventing any statement analysis.
1292 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1293 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1294 Check_Unreachable_Code (N);
1296 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1299 -- If the expander is active it will detect the case of a statically
1300 -- determined single alternative and remove warnings for the case, but
1301 -- if we are not doing expansion, that circuit won't be active. Here we
1302 -- duplicate the effect of removing warnings in the same way, so that
1303 -- we will get the same set of warnings in -gnatc mode.
1305 if not Expander_Active
1306 and then Compile_Time_Known_Value (Expression (N))
1307 and then Serious_Errors_Detected = 0
1310 Chosen : constant Node_Id := Find_Static_Alternative (N);
1314 Alt := First (Alternatives (N));
1315 while Present (Alt) loop
1316 if Alt /= Chosen then
1317 Remove_Warning_Messages (Statements (Alt));
1324 end Analyze_Case_Statement;
1326 ----------------------------
1327 -- Analyze_Exit_Statement --
1328 ----------------------------
1330 -- If the exit includes a name, it must be the name of a currently open
1331 -- loop. Otherwise there must be an innermost open loop on the stack, to
1332 -- which the statement implicitly refers.
1334 -- Additionally, in SPARK mode:
1336 -- The exit can only name the closest enclosing loop;
1338 -- An exit with a when clause must be directly contained in a loop;
1340 -- An exit without a when clause must be directly contained in an
1341 -- if-statement with no elsif or else, which is itself directly contained
1342 -- in a loop. The exit must be the last statement in the if-statement.
1344 procedure Analyze_Exit_Statement (N : Node_Id) is
1345 Target : constant Node_Id := Name (N);
1346 Cond : constant Node_Id := Condition (N);
1347 Scope_Id : Entity_Id;
1353 Check_Unreachable_Code (N);
1356 if Present (Target) then
1358 U_Name := Entity (Target);
1360 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1361 Error_Msg_N ("invalid loop name in exit statement", N);
1365 if Has_Loop_In_Inner_Open_Scopes (U_Name) then
1366 Check_SPARK_05_Restriction
1367 ("exit label must name the closest enclosing loop", N);
1370 Set_Has_Exit (U_Name);
1377 for J in reverse 0 .. Scope_Stack.Last loop
1378 Scope_Id := Scope_Stack.Table (J).Entity;
1379 Kind := Ekind (Scope_Id);
1381 if Kind = E_Loop and then (No (Target) or else Scope_Id = U_Name) then
1382 Set_Has_Exit (Scope_Id);
1385 elsif Kind = E_Block
1386 or else Kind = E_Loop
1387 or else Kind = E_Return_Statement
1393 ("cannot exit from program unit or accept statement", N);
1398 -- Verify that if present the condition is a Boolean expression
1400 if Present (Cond) then
1401 Analyze_And_Resolve (Cond, Any_Boolean);
1402 Check_Unset_Reference (Cond);
1405 -- In SPARK mode, verify that the exit statement respects the SPARK
1408 if Present (Cond) then
1409 if Nkind (Parent (N)) /= N_Loop_Statement then
1410 Check_SPARK_05_Restriction
1411 ("exit with when clause must be directly in loop", N);
1415 if Nkind (Parent (N)) /= N_If_Statement then
1416 if Nkind (Parent (N)) = N_Elsif_Part then
1417 Check_SPARK_05_Restriction
1418 ("exit must be in IF without ELSIF", N);
1420 Check_SPARK_05_Restriction ("exit must be directly in IF", N);
1423 elsif Nkind (Parent (Parent (N))) /= N_Loop_Statement then
1424 Check_SPARK_05_Restriction
1425 ("exit must be in IF directly in loop", N);
1427 -- First test the presence of ELSE, so that an exit in an ELSE leads
1428 -- to an error mentioning the ELSE.
1430 elsif Present (Else_Statements (Parent (N))) then
1431 Check_SPARK_05_Restriction ("exit must be in IF without ELSE", N);
1433 -- An exit in an ELSIF does not reach here, as it would have been
1434 -- detected in the case (Nkind (Parent (N)) /= N_If_Statement).
1436 elsif Present (Elsif_Parts (Parent (N))) then
1437 Check_SPARK_05_Restriction ("exit must be in IF without ELSIF", N);
1441 -- Chain exit statement to associated loop entity
1443 Set_Next_Exit_Statement (N, First_Exit_Statement (Scope_Id));
1444 Set_First_Exit_Statement (Scope_Id, N);
1446 -- Since the exit may take us out of a loop, any previous assignment
1447 -- statement is not useless, so clear last assignment indications. It
1448 -- is OK to keep other current values, since if the exit statement
1449 -- does not exit, then the current values are still valid.
1451 Kill_Current_Values (Last_Assignment_Only => True);
1452 end Analyze_Exit_Statement;
1454 ----------------------------
1455 -- Analyze_Goto_Statement --
1456 ----------------------------
1458 procedure Analyze_Goto_Statement (N : Node_Id) is
1459 Label : constant Node_Id := Name (N);
1460 Scope_Id : Entity_Id;
1461 Label_Scope : Entity_Id;
1462 Label_Ent : Entity_Id;
1465 Check_SPARK_05_Restriction ("goto statement is not allowed", N);
1467 -- Actual semantic checks
1469 Check_Unreachable_Code (N);
1470 Kill_Current_Values (Last_Assignment_Only => True);
1473 Label_Ent := Entity (Label);
1475 -- Ignore previous error
1477 if Label_Ent = Any_Id then
1478 Check_Error_Detected;
1481 -- We just have a label as the target of a goto
1483 elsif Ekind (Label_Ent) /= E_Label then
1484 Error_Msg_N ("target of goto statement must be a label", Label);
1487 -- Check that the target of the goto is reachable according to Ada
1488 -- scoping rules. Note: the special gotos we generate for optimizing
1489 -- local handling of exceptions would violate these rules, but we mark
1490 -- such gotos as analyzed when built, so this code is never entered.
1492 elsif not Reachable (Label_Ent) then
1493 Error_Msg_N ("target of goto statement is not reachable", Label);
1497 -- Here if goto passes initial validity checks
1499 Label_Scope := Enclosing_Scope (Label_Ent);
1501 for J in reverse 0 .. Scope_Stack.Last loop
1502 Scope_Id := Scope_Stack.Table (J).Entity;
1504 if Label_Scope = Scope_Id
1505 or else not Ekind_In (Scope_Id, E_Block, E_Loop, E_Return_Statement)
1507 if Scope_Id /= Label_Scope then
1509 ("cannot exit from program unit or accept statement", N);
1516 raise Program_Error;
1517 end Analyze_Goto_Statement;
1519 --------------------------
1520 -- Analyze_If_Statement --
1521 --------------------------
1523 -- A special complication arises in the analysis of if statements
1525 -- The expander has circuitry to completely delete code that it can tell
1526 -- will not be executed (as a result of compile time known conditions). In
1527 -- the analyzer, we ensure that code that will be deleted in this manner
1528 -- is analyzed but not expanded. This is obviously more efficient, but
1529 -- more significantly, difficulties arise if code is expanded and then
1530 -- eliminated (e.g. exception table entries disappear). Similarly, itypes
1531 -- generated in deleted code must be frozen from start, because the nodes
1532 -- on which they depend will not be available at the freeze point.
1534 procedure Analyze_If_Statement (N : Node_Id) is
1537 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1538 -- Recursively save value of this global, will be restored on exit
1540 Save_In_Deleted_Code : Boolean;
1542 Del : Boolean := False;
1543 -- This flag gets set True if a True condition has been found, which
1544 -- means that remaining ELSE/ELSIF parts are deleted.
1546 procedure Analyze_Cond_Then (Cnode : Node_Id);
1547 -- This is applied to either the N_If_Statement node itself or to an
1548 -- N_Elsif_Part node. It deals with analyzing the condition and the THEN
1549 -- statements associated with it.
1551 -----------------------
1552 -- Analyze_Cond_Then --
1553 -----------------------
1555 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1556 Cond : constant Node_Id := Condition (Cnode);
1557 Tstm : constant List_Id := Then_Statements (Cnode);
1560 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1561 Analyze_And_Resolve (Cond, Any_Boolean);
1562 Check_Unset_Reference (Cond);
1563 Set_Current_Value_Condition (Cnode);
1565 -- If already deleting, then just analyze then statements
1568 Analyze_Statements (Tstm);
1570 -- Compile time known value, not deleting yet
1572 elsif Compile_Time_Known_Value (Cond) then
1573 Save_In_Deleted_Code := In_Deleted_Code;
1575 -- If condition is True, then analyze the THEN statements and set
1576 -- no expansion for ELSE and ELSIF parts.
1578 if Is_True (Expr_Value (Cond)) then
1579 Analyze_Statements (Tstm);
1581 Expander_Mode_Save_And_Set (False);
1582 In_Deleted_Code := True;
1584 -- If condition is False, analyze THEN with expansion off
1586 else -- Is_False (Expr_Value (Cond))
1587 Expander_Mode_Save_And_Set (False);
1588 In_Deleted_Code := True;
1589 Analyze_Statements (Tstm);
1590 Expander_Mode_Restore;
1591 In_Deleted_Code := Save_In_Deleted_Code;
1594 -- Not known at compile time, not deleting, normal analysis
1597 Analyze_Statements (Tstm);
1599 end Analyze_Cond_Then;
1601 -- Start of processing for Analyze_If_Statement
1604 -- Initialize exit count for else statements. If there is no else part,
1605 -- this count will stay non-zero reflecting the fact that the uncovered
1606 -- else case is an unblocked exit.
1608 Unblocked_Exit_Count := 1;
1609 Analyze_Cond_Then (N);
1611 -- Now to analyze the elsif parts if any are present
1613 if Present (Elsif_Parts (N)) then
1614 E := First (Elsif_Parts (N));
1615 while Present (E) loop
1616 Analyze_Cond_Then (E);
1621 if Present (Else_Statements (N)) then
1622 Analyze_Statements (Else_Statements (N));
1625 -- If all our exits were blocked by unconditional transfers of control,
1626 -- then the entire IF statement acts as an unconditional transfer of
1627 -- control, so treat it like one, and check unreachable code.
1629 if Unblocked_Exit_Count = 0 then
1630 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1631 Check_Unreachable_Code (N);
1633 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1637 Expander_Mode_Restore;
1638 In_Deleted_Code := Save_In_Deleted_Code;
1641 if not Expander_Active
1642 and then Compile_Time_Known_Value (Condition (N))
1643 and then Serious_Errors_Detected = 0
1645 if Is_True (Expr_Value (Condition (N))) then
1646 Remove_Warning_Messages (Else_Statements (N));
1648 if Present (Elsif_Parts (N)) then
1649 E := First (Elsif_Parts (N));
1650 while Present (E) loop
1651 Remove_Warning_Messages (Then_Statements (E));
1657 Remove_Warning_Messages (Then_Statements (N));
1661 -- Warn on redundant if statement that has no effect
1663 -- Note, we could also check empty ELSIF parts ???
1665 if Warn_On_Redundant_Constructs
1667 -- If statement must be from source
1669 and then Comes_From_Source (N)
1671 -- Condition must not have obvious side effect
1673 and then Has_No_Obvious_Side_Effects (Condition (N))
1675 -- No elsif parts of else part
1677 and then No (Elsif_Parts (N))
1678 and then No (Else_Statements (N))
1680 -- Then must be a single null statement
1682 and then List_Length (Then_Statements (N)) = 1
1684 -- Go to original node, since we may have rewritten something as
1685 -- a null statement (e.g. a case we could figure the outcome of).
1688 T : constant Node_Id := First (Then_Statements (N));
1689 S : constant Node_Id := Original_Node (T);
1692 if Comes_From_Source (S) and then Nkind (S) = N_Null_Statement then
1693 Error_Msg_N ("if statement has no effect?r?", N);
1697 end Analyze_If_Statement;
1699 ----------------------------------------
1700 -- Analyze_Implicit_Label_Declaration --
1701 ----------------------------------------
1703 -- An implicit label declaration is generated in the innermost enclosing
1704 -- declarative part. This is done for labels, and block and loop names.
1706 -- Note: any changes in this routine may need to be reflected in
1707 -- Analyze_Label_Entity.
1709 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1710 Id : constant Node_Id := Defining_Identifier (N);
1713 Set_Ekind (Id, E_Label);
1714 Set_Etype (Id, Standard_Void_Type);
1715 Set_Enclosing_Scope (Id, Current_Scope);
1716 end Analyze_Implicit_Label_Declaration;
1718 ------------------------------
1719 -- Analyze_Iteration_Scheme --
1720 ------------------------------
1722 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1724 Iter_Spec : Node_Id;
1725 Loop_Spec : Node_Id;
1728 -- For an infinite loop, there is no iteration scheme
1734 Cond := Condition (N);
1735 Iter_Spec := Iterator_Specification (N);
1736 Loop_Spec := Loop_Parameter_Specification (N);
1738 if Present (Cond) then
1739 Analyze_And_Resolve (Cond, Any_Boolean);
1740 Check_Unset_Reference (Cond);
1741 Set_Current_Value_Condition (N);
1743 elsif Present (Iter_Spec) then
1744 Analyze_Iterator_Specification (Iter_Spec);
1747 Analyze_Loop_Parameter_Specification (Loop_Spec);
1749 end Analyze_Iteration_Scheme;
1751 ------------------------------------
1752 -- Analyze_Iterator_Specification --
1753 ------------------------------------
1755 procedure Analyze_Iterator_Specification (N : Node_Id) is
1756 Loc : constant Source_Ptr := Sloc (N);
1757 Def_Id : constant Node_Id := Defining_Identifier (N);
1758 Subt : constant Node_Id := Subtype_Indication (N);
1759 Iter_Name : constant Node_Id := Name (N);
1764 procedure Check_Reverse_Iteration (Typ : Entity_Id);
1765 -- For an iteration over a container, if the loop carries the Reverse
1766 -- indicator, verify that the container type has an Iterate aspect that
1767 -- implements the reversible iterator interface.
1769 function Get_Cursor_Type (Typ : Entity_Id) return Entity_Id;
1770 -- For containers with Iterator and related aspects, the cursor is
1771 -- obtained by locating an entity with the proper name in the scope
1774 -----------------------------
1775 -- Check_Reverse_Iteration --
1776 -----------------------------
1778 procedure Check_Reverse_Iteration (Typ : Entity_Id) is
1780 if Reverse_Present (N)
1781 and then not Is_Array_Type (Typ)
1782 and then not Is_Reversible_Iterator (Typ)
1785 ("container type does not support reverse iteration", N, Typ);
1787 end Check_Reverse_Iteration;
1789 ---------------------
1790 -- Get_Cursor_Type --
1791 ---------------------
1793 function Get_Cursor_Type (Typ : Entity_Id) return Entity_Id is
1797 -- If iterator type is derived, the cursor is declared in the scope
1798 -- of the parent type.
1800 if Is_Derived_Type (Typ) then
1801 Ent := First_Entity (Scope (Etype (Typ)));
1803 Ent := First_Entity (Scope (Typ));
1806 while Present (Ent) loop
1807 exit when Chars (Ent) = Name_Cursor;
1815 -- The cursor is the target of generated assignments in the
1816 -- loop, and cannot have a limited type.
1818 if Is_Limited_Type (Etype (Ent)) then
1819 Error_Msg_N ("cursor type cannot be limited", N);
1823 end Get_Cursor_Type;
1825 -- Start of processing for Analyze_iterator_Specification
1828 Enter_Name (Def_Id);
1830 -- AI12-0151 specifies that when the subtype indication is present, it
1831 -- must statically match the type of the array or container element.
1832 -- To simplify this check, we introduce a subtype declaration with the
1833 -- given subtype indication when it carries a constraint, and rewrite
1834 -- the original as a reference to the created subtype entity.
1836 if Present (Subt) then
1837 if Nkind (Subt) = N_Subtype_Indication then
1839 S : constant Entity_Id := Make_Temporary (Sloc (Subt), 'S');
1840 Decl : constant Node_Id :=
1841 Make_Subtype_Declaration (Loc,
1842 Defining_Identifier => S,
1843 Subtype_Indication => New_Copy_Tree (Subt));
1845 Insert_Before (Parent (Parent (N)), Decl);
1847 Rewrite (Subt, New_Occurrence_Of (S, Sloc (Subt)));
1853 -- Save entity of subtype indication for subsequent check
1855 Bas := Entity (Subt);
1858 Preanalyze_Range (Iter_Name);
1860 -- Set the kind of the loop variable, which is not visible within
1861 -- the iterator name.
1863 Set_Ekind (Def_Id, E_Variable);
1865 -- Provide a link between the iterator variable and the container, for
1866 -- subsequent use in cross-reference and modification information.
1868 if Of_Present (N) then
1869 Set_Related_Expression (Def_Id, Iter_Name);
1871 -- For a container, the iterator is specified through the aspect
1873 if not Is_Array_Type (Etype (Iter_Name)) then
1875 Iterator : constant Entity_Id :=
1876 Find_Value_Of_Aspect
1877 (Etype (Iter_Name), Aspect_Default_Iterator);
1883 if No (Iterator) then
1884 null; -- error reported below.
1886 elsif not Is_Overloaded (Iterator) then
1887 Check_Reverse_Iteration (Etype (Iterator));
1889 -- If Iterator is overloaded, use reversible iterator if
1890 -- one is available.
1892 elsif Is_Overloaded (Iterator) then
1893 Get_First_Interp (Iterator, I, It);
1894 while Present (It.Nam) loop
1895 if Ekind (It.Nam) = E_Function
1896 and then Is_Reversible_Iterator (Etype (It.Nam))
1898 Set_Etype (Iterator, It.Typ);
1899 Set_Entity (Iterator, It.Nam);
1903 Get_Next_Interp (I, It);
1906 Check_Reverse_Iteration (Etype (Iterator));
1912 -- If the domain of iteration is an expression, create a declaration for
1913 -- it, so that finalization actions are introduced outside of the loop.
1914 -- The declaration must be a renaming because the body of the loop may
1915 -- assign to elements.
1917 if not Is_Entity_Name (Iter_Name)
1919 -- When the context is a quantified expression, the renaming
1920 -- declaration is delayed until the expansion phase if we are
1923 and then (Nkind (Parent (N)) /= N_Quantified_Expression
1924 or else Operating_Mode = Check_Semantics)
1926 -- Do not perform this expansion in SPARK mode, since the formal
1927 -- verification directly deals with the source form of the iterator.
1928 -- Ditto for ASIS, where the temporary may hide the transformation
1929 -- of a selected component into a prefixed function call.
1931 and then not GNATprove_Mode
1932 and then not ASIS_Mode
1935 Id : constant Entity_Id := Make_Temporary (Loc, 'R', Iter_Name);
1941 -- If the domain of iteration is an array component that depends
1942 -- on a discriminant, create actual subtype for it. Pre-analysis
1943 -- does not generate the actual subtype of a selected component.
1945 if Nkind (Iter_Name) = N_Selected_Component
1946 and then Is_Array_Type (Etype (Iter_Name))
1949 Build_Actual_Subtype_Of_Component
1950 (Etype (Selector_Name (Iter_Name)), Iter_Name);
1951 Insert_Action (N, Act_S);
1953 if Present (Act_S) then
1954 Typ := Defining_Identifier (Act_S);
1956 Typ := Etype (Iter_Name);
1960 Typ := Etype (Iter_Name);
1962 -- Verify that the expression produces an iterator
1964 if not Of_Present (N) and then not Is_Iterator (Typ)
1965 and then not Is_Array_Type (Typ)
1966 and then No (Find_Aspect (Typ, Aspect_Iterable))
1969 ("expect object that implements iterator interface",
1974 -- Protect against malformed iterator
1976 if Typ = Any_Type then
1977 Error_Msg_N ("invalid expression in loop iterator", Iter_Name);
1981 if not Of_Present (N) then
1982 Check_Reverse_Iteration (Typ);
1985 -- The name in the renaming declaration may be a function call.
1986 -- Indicate that it does not come from source, to suppress
1987 -- spurious warnings on renamings of parameterless functions,
1988 -- a common enough idiom in user-defined iterators.
1991 Make_Object_Renaming_Declaration (Loc,
1992 Defining_Identifier => Id,
1993 Subtype_Mark => New_Occurrence_Of (Typ, Loc),
1995 New_Copy_Tree (Iter_Name, New_Sloc => Loc));
1997 -- Create a transient scope to ensure that all the temporaries
1998 -- generated by Remove_Side_Effects as part of processing this
1999 -- renaming declaration (if any) are attached by Insert_Actions
2000 -- to it. It has no effect on the generated code if no actions
2001 -- are added to it (see Wrap_Transient_Declaration).
2003 if Expander_Active then
2004 Establish_Transient_Scope (Name (Decl), Sec_Stack => True);
2007 Insert_Actions (Parent (Parent (N)), New_List (Decl));
2008 Rewrite (Name (N), New_Occurrence_Of (Id, Loc));
2009 Set_Etype (Id, Typ);
2010 Set_Etype (Name (N), Typ);
2013 -- Container is an entity or an array with uncontrolled components, or
2014 -- else it is a container iterator given by a function call, typically
2015 -- called Iterate in the case of predefined containers, even though
2016 -- Iterate is not a reserved name. What matters is that the return type
2017 -- of the function is an iterator type.
2019 elsif Is_Entity_Name (Iter_Name) then
2020 Analyze (Iter_Name);
2022 if Nkind (Iter_Name) = N_Function_Call then
2024 C : constant Node_Id := Name (Iter_Name);
2029 if not Is_Overloaded (Iter_Name) then
2030 Resolve (Iter_Name, Etype (C));
2033 Get_First_Interp (C, I, It);
2034 while It.Typ /= Empty loop
2035 if Reverse_Present (N) then
2036 if Is_Reversible_Iterator (It.Typ) then
2037 Resolve (Iter_Name, It.Typ);
2041 elsif Is_Iterator (It.Typ) then
2042 Resolve (Iter_Name, It.Typ);
2046 Get_Next_Interp (I, It);
2051 -- Domain of iteration is not overloaded
2054 Resolve (Iter_Name, Etype (Iter_Name));
2057 if not Of_Present (N) then
2058 Check_Reverse_Iteration (Etype (Iter_Name));
2062 -- Get base type of container, for proper retrieval of Cursor type
2063 -- and primitive operations.
2065 Typ := Base_Type (Etype (Iter_Name));
2067 if Is_Array_Type (Typ) then
2068 if Of_Present (N) then
2069 Set_Etype (Def_Id, Component_Type (Typ));
2071 -- The loop variable is aliased if the array components are
2074 Set_Is_Aliased (Def_Id, Has_Aliased_Components (Typ));
2076 -- AI12-0047 stipulates that the domain (array or container)
2077 -- cannot be a component that depends on a discriminant if the
2078 -- enclosing object is mutable, to prevent a modification of the
2079 -- dowmain of iteration in the course of an iteration.
2081 -- If the object is an expression it has been captured in a
2082 -- temporary, so examine original node.
2084 if Nkind (Original_Node (Iter_Name)) = N_Selected_Component
2085 and then Is_Dependent_Component_Of_Mutable_Object
2086 (Original_Node (Iter_Name))
2089 ("iterable name cannot be a discriminant-dependent "
2090 & "component of a mutable object", N);
2095 (Base_Type (Bas) /= Base_Type (Component_Type (Typ))
2097 not Subtypes_Statically_Match (Bas, Component_Type (Typ)))
2100 ("subtype indication does not match component type", Subt);
2103 -- Here we have a missing Range attribute
2107 ("missing Range attribute in iteration over an array", N);
2109 -- In Ada 2012 mode, this may be an attempt at an iterator
2111 if Ada_Version >= Ada_2012 then
2113 ("\if& is meant to designate an element of the array, use OF",
2117 -- Prevent cascaded errors
2119 Set_Ekind (Def_Id, E_Loop_Parameter);
2120 Set_Etype (Def_Id, Etype (First_Index (Typ)));
2123 -- Check for type error in iterator
2125 elsif Typ = Any_Type then
2128 -- Iteration over a container
2131 Set_Ekind (Def_Id, E_Loop_Parameter);
2132 Error_Msg_Ada_2012_Feature ("container iterator", Sloc (N));
2136 if Of_Present (N) then
2137 if Has_Aspect (Typ, Aspect_Iterable) then
2139 Elt : constant Entity_Id :=
2140 Get_Iterable_Type_Primitive (Typ, Name_Element);
2144 ("missing Element primitive for iteration", N);
2146 Set_Etype (Def_Id, Etype (Elt));
2150 -- For a predefined container, The type of the loop variable is
2151 -- the Iterator_Element aspect of the container type.
2155 Element : constant Entity_Id :=
2156 Find_Value_Of_Aspect (Typ, Aspect_Iterator_Element);
2157 Iterator : constant Entity_Id :=
2158 Find_Value_Of_Aspect (Typ, Aspect_Default_Iterator);
2159 Cursor_Type : Entity_Id;
2162 if No (Element) then
2163 Error_Msg_NE ("cannot iterate over&", N, Typ);
2167 Set_Etype (Def_Id, Entity (Element));
2168 Cursor_Type := Get_Cursor_Type (Typ);
2169 pragma Assert (Present (Cursor_Type));
2171 -- If subtype indication was given, verify that it covers
2172 -- the element type of the container.
2175 and then (not Covers (Bas, Etype (Def_Id))
2176 or else not Subtypes_Statically_Match
2177 (Bas, Etype (Def_Id)))
2180 ("subtype indication does not match element type",
2184 -- If the container has a variable indexing aspect, the
2185 -- element is a variable and is modifiable in the loop.
2187 if Has_Aspect (Typ, Aspect_Variable_Indexing) then
2188 Set_Ekind (Def_Id, E_Variable);
2191 -- If the container is a constant, iterating over it
2192 -- requires a Constant_Indexing operation.
2194 if not Is_Variable (Iter_Name)
2195 and then not Has_Aspect (Typ, Aspect_Constant_Indexing)
2197 Error_Msg_N ("iteration over constant container "
2198 & "require constant_indexing aspect", N);
2200 -- The Iterate function may have an in_out parameter,
2201 -- and a constant container is thus illegal.
2203 elsif Present (Iterator)
2204 and then Ekind (Entity (Iterator)) = E_Function
2205 and then Ekind (First_Formal (Entity (Iterator))) /=
2207 and then not Is_Variable (Iter_Name)
2210 ("variable container expected", N);
2213 if Nkind (Original_Node (Iter_Name))
2214 = N_Selected_Component
2216 Is_Dependent_Component_Of_Mutable_Object
2217 (Original_Node (Iter_Name))
2220 ("container cannot be a discriminant-dependent "
2221 & "component of a mutable object", N);
2227 -- IN iterator, domain is a range, or a call to Iterate function
2230 -- For an iteration of the form IN, the name must denote an
2231 -- iterator, typically the result of a call to Iterate. Give a
2232 -- useful error message when the name is a container by itself.
2234 -- The type may be a formal container type, which has to have
2235 -- an Iterable aspect detailing the required primitives.
2237 if Is_Entity_Name (Original_Node (Name (N)))
2238 and then not Is_Iterator (Typ)
2240 if Has_Aspect (Typ, Aspect_Iterable) then
2243 elsif not Has_Aspect (Typ, Aspect_Iterator_Element) then
2245 ("cannot iterate over&", Name (N), Typ);
2248 ("name must be an iterator, not a container", Name (N));
2251 if Has_Aspect (Typ, Aspect_Iterable) then
2255 ("\to iterate directly over the elements of a container, "
2256 & "write `of &`", Name (N), Original_Node (Name (N)));
2258 -- No point in continuing analysis of iterator spec
2264 -- If the name is a call (typically prefixed) to some Iterate
2265 -- function, it has been rewritten as an object declaration.
2266 -- If that object is a selected component, verify that it is not
2267 -- a component of an unconstrained mutable object.
2269 if Nkind (Iter_Name) = N_Identifier then
2271 Orig_Node : constant Node_Id := Original_Node (Iter_Name);
2272 Iter_Kind : constant Node_Kind := Nkind (Orig_Node);
2276 if Iter_Kind = N_Selected_Component then
2277 Obj := Prefix (Orig_Node);
2279 elsif Iter_Kind = N_Function_Call then
2280 Obj := First_Actual (Orig_Node);
2282 -- If neither, the name comes from source
2288 if Nkind (Obj) = N_Selected_Component
2289 and then Is_Dependent_Component_Of_Mutable_Object (Obj)
2292 ("container cannot be a discriminant-dependent "
2293 & "component of a mutable object", N);
2298 -- The result type of Iterate function is the classwide type of
2299 -- the interface parent. We need the specific Cursor type defined
2300 -- in the container package. We obtain it by name for a predefined
2301 -- container, or through the Iterable aspect for a formal one.
2303 if Has_Aspect (Typ, Aspect_Iterable) then
2306 (Parent (Find_Value_Of_Aspect (Typ, Aspect_Iterable)),
2310 Set_Etype (Def_Id, Get_Cursor_Type (Typ));
2315 end Analyze_Iterator_Specification;
2321 -- Note: the semantic work required for analyzing labels (setting them as
2322 -- reachable) was done in a prepass through the statements in the block,
2323 -- so that forward gotos would be properly handled. See Analyze_Statements
2324 -- for further details. The only processing required here is to deal with
2325 -- optimizations that depend on an assumption of sequential control flow,
2326 -- since of course the occurrence of a label breaks this assumption.
2328 procedure Analyze_Label (N : Node_Id) is
2329 pragma Warnings (Off, N);
2331 Kill_Current_Values;
2334 --------------------------
2335 -- Analyze_Label_Entity --
2336 --------------------------
2338 procedure Analyze_Label_Entity (E : Entity_Id) is
2340 Set_Ekind (E, E_Label);
2341 Set_Etype (E, Standard_Void_Type);
2342 Set_Enclosing_Scope (E, Current_Scope);
2343 Set_Reachable (E, True);
2344 end Analyze_Label_Entity;
2346 ------------------------------------------
2347 -- Analyze_Loop_Parameter_Specification --
2348 ------------------------------------------
2350 procedure Analyze_Loop_Parameter_Specification (N : Node_Id) is
2351 Loop_Nod : constant Node_Id := Parent (Parent (N));
2353 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
2354 -- If the bounds are given by a 'Range reference on a function call
2355 -- that returns a controlled array, introduce an explicit declaration
2356 -- to capture the bounds, so that the function result can be finalized
2357 -- in timely fashion.
2359 procedure Check_Predicate_Use (T : Entity_Id);
2360 -- Diagnose Attempt to iterate through non-static predicate. Note that
2361 -- a type with inherited predicates may have both static and dynamic
2362 -- forms. In this case it is not sufficent to check the static predicate
2363 -- function only, look for a dynamic predicate aspect as well.
2365 function Has_Call_Using_Secondary_Stack (N : Node_Id) return Boolean;
2366 -- N is the node for an arbitrary construct. This function searches the
2367 -- construct N to see if any expressions within it contain function
2368 -- calls that use the secondary stack, returning True if any such call
2369 -- is found, and False otherwise.
2371 procedure Process_Bounds (R : Node_Id);
2372 -- If the iteration is given by a range, create temporaries and
2373 -- assignment statements block to capture the bounds and perform
2374 -- required finalization actions in case a bound includes a function
2375 -- call that uses the temporary stack. We first pre-analyze a copy of
2376 -- the range in order to determine the expected type, and analyze and
2377 -- resolve the original bounds.
2379 --------------------------------------
2380 -- Check_Controlled_Array_Attribute --
2381 --------------------------------------
2383 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
2385 if Nkind (DS) = N_Attribute_Reference
2386 and then Is_Entity_Name (Prefix (DS))
2387 and then Ekind (Entity (Prefix (DS))) = E_Function
2388 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
2390 Is_Controlled (Component_Type (Etype (Entity (Prefix (DS)))))
2391 and then Expander_Active
2394 Loc : constant Source_Ptr := Sloc (N);
2395 Arr : constant Entity_Id := Etype (Entity (Prefix (DS)));
2396 Indx : constant Entity_Id :=
2397 Base_Type (Etype (First_Index (Arr)));
2398 Subt : constant Entity_Id := Make_Temporary (Loc, 'S');
2403 Make_Subtype_Declaration (Loc,
2404 Defining_Identifier => Subt,
2405 Subtype_Indication =>
2406 Make_Subtype_Indication (Loc,
2407 Subtype_Mark => New_Occurrence_Of (Indx, Loc),
2409 Make_Range_Constraint (Loc, Relocate_Node (DS))));
2410 Insert_Before (Loop_Nod, Decl);
2414 Make_Attribute_Reference (Loc,
2415 Prefix => New_Occurrence_Of (Subt, Loc),
2416 Attribute_Name => Attribute_Name (DS)));
2421 end Check_Controlled_Array_Attribute;
2423 -------------------------
2424 -- Check_Predicate_Use --
2425 -------------------------
2427 procedure Check_Predicate_Use (T : Entity_Id) is
2429 -- A predicated subtype is illegal in loops and related constructs
2430 -- if the predicate is not static, or if it is a non-static subtype
2431 -- of a statically predicated subtype.
2433 if Is_Discrete_Type (T)
2434 and then Has_Predicates (T)
2435 and then (not Has_Static_Predicate (T)
2436 or else not Is_Static_Subtype (T)
2437 or else Has_Dynamic_Predicate_Aspect (T))
2439 -- Seems a confusing message for the case of a static predicate
2440 -- with a non-static subtype???
2442 Bad_Predicated_Subtype_Use
2443 ("cannot use subtype& with non-static predicate for loop "
2444 & "iteration", Discrete_Subtype_Definition (N),
2445 T, Suggest_Static => True);
2447 elsif Inside_A_Generic and then Is_Generic_Formal (T) then
2448 Set_No_Dynamic_Predicate_On_Actual (T);
2450 end Check_Predicate_Use;
2452 ------------------------------------
2453 -- Has_Call_Using_Secondary_Stack --
2454 ------------------------------------
2456 function Has_Call_Using_Secondary_Stack (N : Node_Id) return Boolean is
2458 function Check_Call (N : Node_Id) return Traverse_Result;
2459 -- Check if N is a function call which uses the secondary stack
2465 function Check_Call (N : Node_Id) return Traverse_Result is
2468 Return_Typ : Entity_Id;
2471 if Nkind (N) = N_Function_Call then
2474 -- Call using access to subprogram with explicit dereference
2476 if Nkind (Nam) = N_Explicit_Dereference then
2477 Subp := Etype (Nam);
2479 -- Call using a selected component notation or Ada 2005 object
2480 -- operation notation
2482 elsif Nkind (Nam) = N_Selected_Component then
2483 Subp := Entity (Selector_Name (Nam));
2488 Subp := Entity (Nam);
2491 Return_Typ := Etype (Subp);
2493 if Is_Composite_Type (Return_Typ)
2494 and then not Is_Constrained (Return_Typ)
2498 elsif Sec_Stack_Needed_For_Return (Subp) then
2503 -- Continue traversing the tree
2508 function Check_Calls is new Traverse_Func (Check_Call);
2510 -- Start of processing for Has_Call_Using_Secondary_Stack
2513 return Check_Calls (N) = Abandon;
2514 end Has_Call_Using_Secondary_Stack;
2516 --------------------
2517 -- Process_Bounds --
2518 --------------------
2520 procedure Process_Bounds (R : Node_Id) is
2521 Loc : constant Source_Ptr := Sloc (N);
2524 (Original_Bound : Node_Id;
2525 Analyzed_Bound : Node_Id;
2526 Typ : Entity_Id) return Node_Id;
2527 -- Capture value of bound and return captured value
2534 (Original_Bound : Node_Id;
2535 Analyzed_Bound : Node_Id;
2536 Typ : Entity_Id) return Node_Id
2543 -- If the bound is a constant or an object, no need for a separate
2544 -- declaration. If the bound is the result of previous expansion
2545 -- it is already analyzed and should not be modified. Note that
2546 -- the Bound will be resolved later, if needed, as part of the
2547 -- call to Make_Index (literal bounds may need to be resolved to
2550 if Analyzed (Original_Bound) then
2551 return Original_Bound;
2553 elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
2554 N_Character_Literal)
2555 or else Is_Entity_Name (Analyzed_Bound)
2557 Analyze_And_Resolve (Original_Bound, Typ);
2558 return Original_Bound;
2561 -- Normally, the best approach is simply to generate a constant
2562 -- declaration that captures the bound. However, there is a nasty
2563 -- case where this is wrong. If the bound is complex, and has a
2564 -- possible use of the secondary stack, we need to generate a
2565 -- separate assignment statement to ensure the creation of a block
2566 -- which will release the secondary stack.
2568 -- We prefer the constant declaration, since it leaves us with a
2569 -- proper trace of the value, useful in optimizations that get rid
2570 -- of junk range checks.
2572 if not Has_Call_Using_Secondary_Stack (Analyzed_Bound) then
2573 Analyze_And_Resolve (Original_Bound, Typ);
2575 -- Ensure that the bound is valid. This check should not be
2576 -- generated when the range belongs to a quantified expression
2577 -- as the construct is still not expanded into its final form.
2579 if Nkind (Parent (R)) /= N_Loop_Parameter_Specification
2580 or else Nkind (Parent (Parent (R))) /= N_Quantified_Expression
2582 Ensure_Valid (Original_Bound);
2585 Force_Evaluation (Original_Bound);
2586 return Original_Bound;
2589 Id := Make_Temporary (Loc, 'R', Original_Bound);
2591 -- Here we make a declaration with a separate assignment
2592 -- statement, and insert before loop header.
2595 Make_Object_Declaration (Loc,
2596 Defining_Identifier => Id,
2597 Object_Definition => New_Occurrence_Of (Typ, Loc));
2600 Make_Assignment_Statement (Loc,
2601 Name => New_Occurrence_Of (Id, Loc),
2602 Expression => Relocate_Node (Original_Bound));
2604 Insert_Actions (Loop_Nod, New_List (Decl, Assign));
2606 -- Now that this temporary variable is initialized we decorate it
2607 -- as safe-to-reevaluate to inform to the backend that no further
2608 -- asignment will be issued and hence it can be handled as side
2609 -- effect free. Note that this decoration must be done when the
2610 -- assignment has been analyzed because otherwise it will be
2611 -- rejected (see Analyze_Assignment).
2613 Set_Is_Safe_To_Reevaluate (Id);
2615 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
2617 if Nkind (Assign) = N_Assignment_Statement then
2618 return Expression (Assign);
2620 return Original_Bound;
2624 Hi : constant Node_Id := High_Bound (R);
2625 Lo : constant Node_Id := Low_Bound (R);
2626 R_Copy : constant Node_Id := New_Copy_Tree (R);
2631 -- Start of processing for Process_Bounds
2634 Set_Parent (R_Copy, Parent (R));
2635 Preanalyze_Range (R_Copy);
2636 Typ := Etype (R_Copy);
2638 -- If the type of the discrete range is Universal_Integer, then the
2639 -- bound's type must be resolved to Integer, and any object used to
2640 -- hold the bound must also have type Integer, unless the literal
2641 -- bounds are constant-folded expressions with a user-defined type.
2643 if Typ = Universal_Integer then
2644 if Nkind (Lo) = N_Integer_Literal
2645 and then Present (Etype (Lo))
2646 and then Scope (Etype (Lo)) /= Standard_Standard
2650 elsif Nkind (Hi) = N_Integer_Literal
2651 and then Present (Etype (Hi))
2652 and then Scope (Etype (Hi)) /= Standard_Standard
2657 Typ := Standard_Integer;
2663 New_Lo := One_Bound (Lo, Low_Bound (R_Copy), Typ);
2664 New_Hi := One_Bound (Hi, High_Bound (R_Copy), Typ);
2666 -- Propagate staticness to loop range itself, in case the
2667 -- corresponding subtype is static.
2669 if New_Lo /= Lo and then Is_OK_Static_Expression (New_Lo) then
2670 Rewrite (Low_Bound (R), New_Copy (New_Lo));
2673 if New_Hi /= Hi and then Is_OK_Static_Expression (New_Hi) then
2674 Rewrite (High_Bound (R), New_Copy (New_Hi));
2680 DS : constant Node_Id := Discrete_Subtype_Definition (N);
2681 Id : constant Entity_Id := Defining_Identifier (N);
2685 -- Start of processing for Analyze_Loop_Parameter_Specification
2690 -- We always consider the loop variable to be referenced, since the loop
2691 -- may be used just for counting purposes.
2693 Generate_Reference (Id, N, ' ');
2695 -- Check for the case of loop variable hiding a local variable (used
2696 -- later on to give a nice warning if the hidden variable is never
2700 H : constant Entity_Id := Homonym (Id);
2703 and then Ekind (H) = E_Variable
2704 and then Is_Discrete_Type (Etype (H))
2705 and then Enclosing_Dynamic_Scope (H) = Enclosing_Dynamic_Scope (Id)
2707 Set_Hiding_Loop_Variable (H, Id);
2711 -- Loop parameter specification must include subtype mark in SPARK
2713 if Nkind (DS) = N_Range then
2714 Check_SPARK_05_Restriction
2715 ("loop parameter specification must include subtype mark", N);
2718 -- Analyze the subtype definition and create temporaries for the bounds.
2719 -- Do not evaluate the range when preanalyzing a quantified expression
2720 -- because bounds expressed as function calls with side effects will be
2721 -- incorrectly replicated.
2723 if Nkind (DS) = N_Range
2724 and then Expander_Active
2725 and then Nkind (Parent (N)) /= N_Quantified_Expression
2727 Process_Bounds (DS);
2729 -- Either the expander not active or the range of iteration is a subtype
2730 -- indication, an entity, or a function call that yields an aggregate or
2734 DS_Copy := New_Copy_Tree (DS);
2735 Set_Parent (DS_Copy, Parent (DS));
2736 Preanalyze_Range (DS_Copy);
2738 -- Ada 2012: If the domain of iteration is:
2740 -- a) a function call,
2741 -- b) an identifier that is not a type,
2742 -- c) an attribute reference 'Old (within a postcondition),
2743 -- d) an unchecked conversion or a qualified expression with
2744 -- the proper iterator type.
2746 -- then it is an iteration over a container. It was classified as
2747 -- a loop specification by the parser, and must be rewritten now
2748 -- to activate container iteration. The last case will occur within
2749 -- an expanded inlined call, where the expansion wraps an actual in
2750 -- an unchecked conversion when needed. The expression of the
2751 -- conversion is always an object.
2753 if Nkind (DS_Copy) = N_Function_Call
2755 or else (Is_Entity_Name (DS_Copy)
2756 and then not Is_Type (Entity (DS_Copy)))
2758 or else (Nkind (DS_Copy) = N_Attribute_Reference
2759 and then Nam_In (Attribute_Name (DS_Copy),
2760 Name_Loop_Entry, Name_Old))
2762 or else Has_Aspect (Etype (DS_Copy), Aspect_Iterable)
2764 or else Nkind (DS_Copy) = N_Unchecked_Type_Conversion
2765 or else (Nkind (DS_Copy) = N_Qualified_Expression
2766 and then Is_Iterator (Etype (DS_Copy)))
2768 -- This is an iterator specification. Rewrite it as such and
2769 -- analyze it to capture function calls that may require
2770 -- finalization actions.
2773 I_Spec : constant Node_Id :=
2774 Make_Iterator_Specification (Sloc (N),
2775 Defining_Identifier => Relocate_Node (Id),
2777 Subtype_Indication => Empty,
2778 Reverse_Present => Reverse_Present (N));
2779 Scheme : constant Node_Id := Parent (N);
2782 Set_Iterator_Specification (Scheme, I_Spec);
2783 Set_Loop_Parameter_Specification (Scheme, Empty);
2784 Analyze_Iterator_Specification (I_Spec);
2786 -- In a generic context, analyze the original domain of
2787 -- iteration, for name capture.
2789 if not Expander_Active then
2793 -- Set kind of loop parameter, which may be used in the
2794 -- subsequent analysis of the condition in a quantified
2797 Set_Ekind (Id, E_Loop_Parameter);
2801 -- Domain of iteration is not a function call, and is side-effect
2805 -- A quantified expression that appears in a pre/post condition
2806 -- is pre-analyzed several times. If the range is given by an
2807 -- attribute reference it is rewritten as a range, and this is
2808 -- done even with expansion disabled. If the type is already set
2809 -- do not reanalyze, because a range with static bounds may be
2810 -- typed Integer by default.
2812 if Nkind (Parent (N)) = N_Quantified_Expression
2813 and then Present (Etype (DS))
2826 -- Some additional checks if we are iterating through a type
2828 if Is_Entity_Name (DS)
2829 and then Present (Entity (DS))
2830 and then Is_Type (Entity (DS))
2832 -- The subtype indication may denote the completion of an incomplete
2833 -- type declaration.
2835 if Ekind (Entity (DS)) = E_Incomplete_Type then
2836 Set_Entity (DS, Get_Full_View (Entity (DS)));
2837 Set_Etype (DS, Entity (DS));
2840 Check_Predicate_Use (Entity (DS));
2843 -- Error if not discrete type
2845 if not Is_Discrete_Type (Etype (DS)) then
2846 Wrong_Type (DS, Any_Discrete);
2847 Set_Etype (DS, Any_Type);
2850 Check_Controlled_Array_Attribute (DS);
2852 if Nkind (DS) = N_Subtype_Indication then
2853 Check_Predicate_Use (Entity (Subtype_Mark (DS)));
2856 Make_Index (DS, N, In_Iter_Schm => True);
2857 Set_Ekind (Id, E_Loop_Parameter);
2859 -- A quantified expression which appears in a pre- or post-condition may
2860 -- be analyzed multiple times. The analysis of the range creates several
2861 -- itypes which reside in different scopes depending on whether the pre-
2862 -- or post-condition has been expanded. Update the type of the loop
2863 -- variable to reflect the proper itype at each stage of analysis.
2866 or else Etype (Id) = Any_Type
2868 (Present (Etype (Id))
2869 and then Is_Itype (Etype (Id))
2870 and then Nkind (Parent (Loop_Nod)) = N_Expression_With_Actions
2871 and then Nkind (Original_Node (Parent (Loop_Nod))) =
2872 N_Quantified_Expression)
2874 Set_Etype (Id, Etype (DS));
2877 -- Treat a range as an implicit reference to the type, to inhibit
2878 -- spurious warnings.
2880 Generate_Reference (Base_Type (Etype (DS)), N, ' ');
2881 Set_Is_Known_Valid (Id, True);
2883 -- The loop is not a declarative part, so the loop variable must be
2884 -- frozen explicitly. Do not freeze while preanalyzing a quantified
2885 -- expression because the freeze node will not be inserted into the
2886 -- tree due to flag Is_Spec_Expression being set.
2888 if Nkind (Parent (N)) /= N_Quantified_Expression then
2890 Flist : constant List_Id := Freeze_Entity (Id, N);
2892 if Is_Non_Empty_List (Flist) then
2893 Insert_Actions (N, Flist);
2898 -- Case where we have a range or a subtype, get type bounds
2900 if Nkind_In (DS, N_Range, N_Subtype_Indication)
2901 and then not Error_Posted (DS)
2902 and then Etype (DS) /= Any_Type
2903 and then Is_Discrete_Type (Etype (DS))
2910 if Nkind (DS) = N_Range then
2911 L := Low_Bound (DS);
2912 H := High_Bound (DS);
2915 Type_Low_Bound (Underlying_Type (Etype (Subtype_Mark (DS))));
2917 Type_High_Bound (Underlying_Type (Etype (Subtype_Mark (DS))));
2920 -- Check for null or possibly null range and issue warning. We
2921 -- suppress such messages in generic templates and instances,
2922 -- because in practice they tend to be dubious in these cases. The
2923 -- check applies as well to rewritten array element loops where a
2924 -- null range may be detected statically.
2926 if Compile_Time_Compare (L, H, Assume_Valid => True) = GT then
2928 -- Suppress the warning if inside a generic template or
2929 -- instance, since in practice they tend to be dubious in these
2930 -- cases since they can result from intended parameterization.
2932 if not Inside_A_Generic and then not In_Instance then
2934 -- Specialize msg if invalid values could make the loop
2935 -- non-null after all.
2937 if Compile_Time_Compare
2938 (L, H, Assume_Valid => False) = GT
2940 -- Since we know the range of the loop is null, set the
2941 -- appropriate flag to remove the loop entirely during
2944 Set_Is_Null_Loop (Loop_Nod);
2946 if Comes_From_Source (N) then
2948 ("??loop range is null, loop will not execute", DS);
2951 -- Here is where the loop could execute because of
2952 -- invalid values, so issue appropriate message and in
2953 -- this case we do not set the Is_Null_Loop flag since
2954 -- the loop may execute.
2956 elsif Comes_From_Source (N) then
2958 ("??loop range may be null, loop may not execute",
2961 ("??can only execute if invalid values are present",
2966 -- In either case, suppress warnings in the body of the loop,
2967 -- since it is likely that these warnings will be inappropriate
2968 -- if the loop never actually executes, which is likely.
2970 Set_Suppress_Loop_Warnings (Loop_Nod);
2972 -- The other case for a warning is a reverse loop where the
2973 -- upper bound is the integer literal zero or one, and the
2974 -- lower bound may exceed this value.
2976 -- For example, we have
2978 -- for J in reverse N .. 1 loop
2980 -- In practice, this is very likely to be a case of reversing
2981 -- the bounds incorrectly in the range.
2983 elsif Reverse_Present (N)
2984 and then Nkind (Original_Node (H)) = N_Integer_Literal
2986 (Intval (Original_Node (H)) = Uint_0
2988 Intval (Original_Node (H)) = Uint_1)
2990 -- Lower bound may in fact be known and known not to exceed
2991 -- upper bound (e.g. reverse 0 .. 1) and that's OK.
2993 if Compile_Time_Known_Value (L)
2994 and then Expr_Value (L) <= Expr_Value (H)
2998 -- Otherwise warning is warranted
3001 Error_Msg_N ("??loop range may be null", DS);
3002 Error_Msg_N ("\??bounds may be wrong way round", DS);
3006 -- Check if either bound is known to be outside the range of the
3007 -- loop parameter type, this is e.g. the case of a loop from
3008 -- 20..X where the type is 1..19.
3010 -- Such a loop is dubious since either it raises CE or it executes
3011 -- zero times, and that cannot be useful!
3013 if Etype (DS) /= Any_Type
3014 and then not Error_Posted (DS)
3015 and then Nkind (DS) = N_Subtype_Indication
3016 and then Nkind (Constraint (DS)) = N_Range_Constraint
3019 LLo : constant Node_Id :=
3020 Low_Bound (Range_Expression (Constraint (DS)));
3021 LHi : constant Node_Id :=
3022 High_Bound (Range_Expression (Constraint (DS)));
3024 Bad_Bound : Node_Id := Empty;
3025 -- Suspicious loop bound
3028 -- At this stage L, H are the bounds of the type, and LLo
3029 -- Lhi are the low bound and high bound of the loop.
3031 if Compile_Time_Compare (LLo, L, Assume_Valid => True) = LT
3033 Compile_Time_Compare (LLo, H, Assume_Valid => True) = GT
3038 if Compile_Time_Compare (LHi, L, Assume_Valid => True) = LT
3040 Compile_Time_Compare (LHi, H, Assume_Valid => True) = GT
3045 if Present (Bad_Bound) then
3047 ("suspicious loop bound out of range of "
3048 & "loop subtype??", Bad_Bound);
3050 ("\loop executes zero times or raises "
3051 & "Constraint_Error??", Bad_Bound);
3056 -- This declare block is about warnings, if we get an exception while
3057 -- testing for warnings, we simply abandon the attempt silently. This
3058 -- most likely occurs as the result of a previous error, but might
3059 -- just be an obscure case we have missed. In either case, not giving
3060 -- the warning is perfectly acceptable.
3063 when others => null;
3067 -- A loop parameter cannot be effectively volatile (SPARK RM 7.1.3(4)).
3068 -- This check is relevant only when SPARK_Mode is on as it is not a
3069 -- standard Ada legality check.
3071 if SPARK_Mode = On and then Is_Effectively_Volatile (Id) then
3072 Error_Msg_N ("loop parameter cannot be volatile", Id);
3074 end Analyze_Loop_Parameter_Specification;
3076 ----------------------------
3077 -- Analyze_Loop_Statement --
3078 ----------------------------
3080 procedure Analyze_Loop_Statement (N : Node_Id) is
3082 function Is_Container_Iterator (Iter : Node_Id) return Boolean;
3083 -- Given a loop iteration scheme, determine whether it is an Ada 2012
3084 -- container iteration.
3086 function Is_Wrapped_In_Block (N : Node_Id) return Boolean;
3087 -- Determine whether loop statement N has been wrapped in a block to
3088 -- capture finalization actions that may be generated for container
3089 -- iterators. Prevents infinite recursion when block is analyzed.
3090 -- Routine is a noop if loop is single statement within source block.
3092 ---------------------------
3093 -- Is_Container_Iterator --
3094 ---------------------------
3096 function Is_Container_Iterator (Iter : Node_Id) return Boolean is
3105 elsif Present (Condition (Iter)) then
3108 -- for Def_Id in [reverse] Name loop
3109 -- for Def_Id [: Subtype_Indication] of [reverse] Name loop
3111 elsif Present (Iterator_Specification (Iter)) then
3113 Nam : constant Node_Id := Name (Iterator_Specification (Iter));
3117 Nam_Copy := New_Copy_Tree (Nam);
3118 Set_Parent (Nam_Copy, Parent (Nam));
3119 Preanalyze_Range (Nam_Copy);
3121 -- The only two options here are iteration over a container or
3124 return not Is_Array_Type (Etype (Nam_Copy));
3127 -- for Def_Id in [reverse] Discrete_Subtype_Definition loop
3131 LP : constant Node_Id := Loop_Parameter_Specification (Iter);
3132 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
3136 DS_Copy := New_Copy_Tree (DS);
3137 Set_Parent (DS_Copy, Parent (DS));
3138 Preanalyze_Range (DS_Copy);
3140 -- Check for a call to Iterate () or an expression with
3141 -- an iterator type.
3144 (Nkind (DS_Copy) = N_Function_Call
3145 and then Needs_Finalization (Etype (DS_Copy)))
3146 or else Is_Iterator (Etype (DS_Copy));
3149 end Is_Container_Iterator;
3151 -------------------------
3152 -- Is_Wrapped_In_Block --
3153 -------------------------
3155 function Is_Wrapped_In_Block (N : Node_Id) return Boolean is
3161 -- Check if current scope is a block that is not a transient block.
3163 if Ekind (Current_Scope) /= E_Block
3164 or else No (Block_Node (Current_Scope))
3170 Handled_Statement_Sequence (Parent (Block_Node (Current_Scope)));
3172 -- Skip leading pragmas that may be introduced for invariant and
3173 -- predicate checks.
3175 Stat := First (Statements (HSS));
3176 while Present (Stat) and then Nkind (Stat) = N_Pragma loop
3177 Stat := Next (Stat);
3180 return Stat = N and then No (Next (Stat));
3182 end Is_Wrapped_In_Block;
3184 -- Local declarations
3186 Id : constant Node_Id := Identifier (N);
3187 Iter : constant Node_Id := Iteration_Scheme (N);
3188 Loc : constant Source_Ptr := Sloc (N);
3192 -- Start of processing for Analyze_Loop_Statement
3195 if Present (Id) then
3197 -- Make name visible, e.g. for use in exit statements. Loop labels
3198 -- are always considered to be referenced.
3203 -- Guard against serious error (typically, a scope mismatch when
3204 -- semantic analysis is requested) by creating loop entity to
3205 -- continue analysis.
3208 if Total_Errors_Detected /= 0 then
3209 Ent := New_Internal_Entity (E_Loop, Current_Scope, Loc, 'L');
3211 raise Program_Error;
3214 -- Verify that the loop name is hot hidden by an unrelated
3215 -- declaration in an inner scope.
3217 elsif Ekind (Ent) /= E_Label and then Ekind (Ent) /= E_Loop then
3218 Error_Msg_Sloc := Sloc (Ent);
3219 Error_Msg_N ("implicit label declaration for & is hidden#", Id);
3221 if Present (Homonym (Ent))
3222 and then Ekind (Homonym (Ent)) = E_Label
3224 Set_Entity (Id, Ent);
3225 Set_Ekind (Ent, E_Loop);
3229 Generate_Reference (Ent, N, ' ');
3230 Generate_Definition (Ent);
3232 -- If we found a label, mark its type. If not, ignore it, since it
3233 -- means we have a conflicting declaration, which would already
3234 -- have been diagnosed at declaration time. Set Label_Construct
3235 -- of the implicit label declaration, which is not created by the
3236 -- parser for generic units.
3238 if Ekind (Ent) = E_Label then
3239 Set_Ekind (Ent, E_Loop);
3241 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
3242 Set_Label_Construct (Parent (Ent), N);
3247 -- Case of no identifier present. Create one and attach it to the
3248 -- loop statement for use as a scope and as a reference for later
3249 -- expansions. Indicate that the label does not come from source,
3250 -- and attach it to the loop statement so it is part of the tree,
3251 -- even without a full declaration.
3254 Ent := New_Internal_Entity (E_Loop, Current_Scope, Loc, 'L');
3255 Set_Etype (Ent, Standard_Void_Type);
3256 Set_Identifier (N, New_Occurrence_Of (Ent, Loc));
3257 Set_Parent (Ent, N);
3258 Set_Has_Created_Identifier (N);
3261 -- Iteration over a container in Ada 2012 involves the creation of a
3262 -- controlled iterator object. Wrap the loop in a block to ensure the
3263 -- timely finalization of the iterator and release of container locks.
3264 -- The same applies to the use of secondary stack when obtaining an
3267 if Ada_Version >= Ada_2012
3268 and then Is_Container_Iterator (Iter)
3269 and then not Is_Wrapped_In_Block (N)
3272 Block_Nod : Node_Id;
3273 Block_Id : Entity_Id;
3277 Make_Block_Statement (Loc,
3278 Declarations => New_List,
3279 Handled_Statement_Sequence =>
3280 Make_Handled_Sequence_Of_Statements (Loc,
3281 Statements => New_List (Relocate_Node (N))));
3283 Add_Block_Identifier (Block_Nod, Block_Id);
3285 -- The expansion of iterator loops generates an iterator in order
3286 -- to traverse the elements of a container:
3288 -- Iter : <iterator type> := Iterate (Container)'reference;
3290 -- The iterator is controlled and returned on the secondary stack.
3291 -- The analysis of the call to Iterate establishes a transient
3292 -- scope to deal with the secondary stack management, but never
3293 -- really creates a physical block as this would kill the iterator
3294 -- too early (see Wrap_Transient_Declaration). To address this
3295 -- case, mark the generated block as needing secondary stack
3298 Set_Uses_Sec_Stack (Block_Id);
3300 Rewrite (N, Block_Nod);
3306 -- Kill current values on entry to loop, since statements in the body of
3307 -- the loop may have been executed before the loop is entered. Similarly
3308 -- we kill values after the loop, since we do not know that the body of
3309 -- the loop was executed.
3311 Kill_Current_Values;
3313 Analyze_Iteration_Scheme (Iter);
3315 -- Check for following case which merits a warning if the type E of is
3316 -- a multi-dimensional array (and no explicit subscript ranges present).
3322 and then Present (Loop_Parameter_Specification (Iter))
3325 LPS : constant Node_Id := Loop_Parameter_Specification (Iter);
3326 DSD : constant Node_Id :=
3327 Original_Node (Discrete_Subtype_Definition (LPS));
3329 if Nkind (DSD) = N_Attribute_Reference
3330 and then Attribute_Name (DSD) = Name_Range
3331 and then No (Expressions (DSD))
3334 Typ : constant Entity_Id := Etype (Prefix (DSD));
3336 if Is_Array_Type (Typ)
3337 and then Number_Dimensions (Typ) > 1
3338 and then Nkind (Parent (N)) = N_Loop_Statement
3339 and then Present (Iteration_Scheme (Parent (N)))
3342 OIter : constant Node_Id :=
3343 Iteration_Scheme (Parent (N));
3344 OLPS : constant Node_Id :=
3345 Loop_Parameter_Specification (OIter);
3346 ODSD : constant Node_Id :=
3347 Original_Node (Discrete_Subtype_Definition (OLPS));
3349 if Nkind (ODSD) = N_Attribute_Reference
3350 and then Attribute_Name (ODSD) = Name_Range
3351 and then No (Expressions (ODSD))
3352 and then Etype (Prefix (ODSD)) = Typ
3354 Error_Msg_Sloc := Sloc (ODSD);
3356 ("inner range same as outer range#??", DSD);
3365 -- Analyze the statements of the body except in the case of an Ada 2012
3366 -- iterator with the expander active. In this case the expander will do
3367 -- a rewrite of the loop into a while loop. We will then analyze the
3368 -- loop body when we analyze this while loop.
3370 -- We need to do this delay because if the container is for indefinite
3371 -- types the actual subtype of the components will only be determined
3372 -- when the cursor declaration is analyzed.
3374 -- If the expander is not active then we want to analyze the loop body
3375 -- now even in the Ada 2012 iterator case, since the rewriting will not
3376 -- be done. Insert the loop variable in the current scope, if not done
3377 -- when analysing the iteration scheme. Set its kind properly to detect
3378 -- improper uses in the loop body.
3380 -- In GNATprove mode, we do one of the above depending on the kind of
3381 -- loop. If it is an iterator over an array, then we do not analyze the
3382 -- loop now. We will analyze it after it has been rewritten by the
3383 -- special SPARK expansion which is activated in GNATprove mode. We need
3384 -- to do this so that other expansions that should occur in GNATprove
3385 -- mode take into account the specificities of the rewritten loop, in
3386 -- particular the introduction of a renaming (which needs to be
3389 -- In other cases in GNATprove mode then we want to analyze the loop
3390 -- body now, since no rewriting will occur.
3393 and then Present (Iterator_Specification (Iter))
3396 and then Is_Iterator_Over_Array (Iterator_Specification (Iter))
3400 elsif not Expander_Active then
3402 I_Spec : constant Node_Id := Iterator_Specification (Iter);
3403 Id : constant Entity_Id := Defining_Identifier (I_Spec);
3406 if Scope (Id) /= Current_Scope then
3410 -- In an element iterator, The loop parameter is a variable if
3411 -- the domain of iteration (container or array) is a variable.
3413 if not Of_Present (I_Spec)
3414 or else not Is_Variable (Name (I_Spec))
3416 Set_Ekind (Id, E_Loop_Parameter);
3420 Analyze_Statements (Statements (N));
3425 -- Pre-Ada2012 for-loops and while loops.
3427 Analyze_Statements (Statements (N));
3430 -- When the iteration scheme of a loop contains attribute 'Loop_Entry,
3431 -- the loop is transformed into a conditional block. Retrieve the loop.
3435 if Subject_To_Loop_Entry_Attributes (Stmt) then
3436 Stmt := Find_Loop_In_Conditional_Block (Stmt);
3439 -- Finish up processing for the loop. We kill all current values, since
3440 -- in general we don't know if the statements in the loop have been
3441 -- executed. We could do a bit better than this with a loop that we
3442 -- know will execute at least once, but it's not worth the trouble and
3443 -- the front end is not in the business of flow tracing.
3445 Process_End_Label (Stmt, 'e', Ent);
3447 Kill_Current_Values;
3449 -- Check for infinite loop. Skip check for generated code, since it
3450 -- justs waste time and makes debugging the routine called harder.
3452 -- Note that we have to wait till the body of the loop is fully analyzed
3453 -- before making this call, since Check_Infinite_Loop_Warning relies on
3454 -- being able to use semantic visibility information to find references.
3456 if Comes_From_Source (Stmt) then
3457 Check_Infinite_Loop_Warning (Stmt);
3460 -- Code after loop is unreachable if the loop has no WHILE or FOR and
3461 -- contains no EXIT statements within the body of the loop.
3463 if No (Iter) and then not Has_Exit (Ent) then
3464 Check_Unreachable_Code (Stmt);
3466 end Analyze_Loop_Statement;
3468 ----------------------------
3469 -- Analyze_Null_Statement --
3470 ----------------------------
3472 -- Note: the semantics of the null statement is implemented by a single
3473 -- null statement, too bad everything isn't as simple as this.
3475 procedure Analyze_Null_Statement (N : Node_Id) is
3476 pragma Warnings (Off, N);
3479 end Analyze_Null_Statement;
3481 ------------------------
3482 -- Analyze_Statements --
3483 ------------------------
3485 procedure Analyze_Statements (L : List_Id) is
3490 -- The labels declared in the statement list are reachable from
3491 -- statements in the list. We do this as a prepass so that any goto
3492 -- statement will be properly flagged if its target is not reachable.
3493 -- This is not required, but is nice behavior.
3496 while Present (S) loop
3497 if Nkind (S) = N_Label then
3498 Analyze (Identifier (S));
3499 Lab := Entity (Identifier (S));
3501 -- If we found a label mark it as reachable
3503 if Ekind (Lab) = E_Label then
3504 Generate_Definition (Lab);
3505 Set_Reachable (Lab);
3507 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
3508 Set_Label_Construct (Parent (Lab), S);
3511 -- If we failed to find a label, it means the implicit declaration
3512 -- of the label was hidden. A for-loop parameter can do this to
3513 -- a label with the same name inside the loop, since the implicit
3514 -- label declaration is in the innermost enclosing body or block
3518 Error_Msg_Sloc := Sloc (Lab);
3520 ("implicit label declaration for & is hidden#",
3528 -- Perform semantic analysis on all statements
3530 Conditional_Statements_Begin;
3533 while Present (S) loop
3536 -- Remove dimension in all statements
3538 Remove_Dimension_In_Statement (S);
3542 Conditional_Statements_End;
3544 -- Make labels unreachable. Visibility is not sufficient, because labels
3545 -- in one if-branch for example are not reachable from the other branch,
3546 -- even though their declarations are in the enclosing declarative part.
3549 while Present (S) loop
3550 if Nkind (S) = N_Label then
3551 Set_Reachable (Entity (Identifier (S)), False);
3556 end Analyze_Statements;
3558 ----------------------------
3559 -- Check_Unreachable_Code --
3560 ----------------------------
3562 procedure Check_Unreachable_Code (N : Node_Id) is
3563 Error_Node : Node_Id;
3567 if Is_List_Member (N) and then Comes_From_Source (N) then
3572 Nxt := Original_Node (Next (N));
3574 -- Skip past pragmas
3576 while Nkind (Nxt) = N_Pragma loop
3577 Nxt := Original_Node (Next (Nxt));
3580 -- If a label follows us, then we never have dead code, since
3581 -- someone could branch to the label, so we just ignore it, unless
3582 -- we are in formal mode where goto statements are not allowed.
3584 if Nkind (Nxt) = N_Label
3585 and then not Restriction_Check_Required (SPARK_05)
3589 -- Otherwise see if we have a real statement following us
3592 and then Comes_From_Source (Nxt)
3593 and then Is_Statement (Nxt)
3595 -- Special very annoying exception. If we have a return that
3596 -- follows a raise, then we allow it without a warning, since
3597 -- the Ada RM annoyingly requires a useless return here.
3599 if Nkind (Original_Node (N)) /= N_Raise_Statement
3600 or else Nkind (Nxt) /= N_Simple_Return_Statement
3602 -- The rather strange shenanigans with the warning message
3603 -- here reflects the fact that Kill_Dead_Code is very good
3604 -- at removing warnings in deleted code, and this is one
3605 -- warning we would prefer NOT to have removed.
3609 -- If we have unreachable code, analyze and remove the
3610 -- unreachable code, since it is useless and we don't
3611 -- want to generate junk warnings.
3613 -- We skip this step if we are not in code generation mode
3614 -- or CodePeer mode.
3616 -- This is the one case where we remove dead code in the
3617 -- semantics as opposed to the expander, and we do not want
3618 -- to remove code if we are not in code generation mode,
3619 -- since this messes up the ASIS trees or loses useful
3620 -- information in the CodePeer tree.
3622 -- Note that one might react by moving the whole circuit to
3623 -- exp_ch5, but then we lose the warning in -gnatc mode.
3625 if Operating_Mode = Generate_Code
3626 and then not CodePeer_Mode
3631 -- Quit deleting when we have nothing more to delete
3632 -- or if we hit a label (since someone could transfer
3633 -- control to a label, so we should not delete it).
3635 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
3637 -- Statement/declaration is to be deleted
3641 Kill_Dead_Code (Nxt);
3645 -- Now issue the warning (or error in formal mode)
3647 if Restriction_Check_Required (SPARK_05) then
3648 Check_SPARK_05_Restriction
3649 ("unreachable code is not allowed", Error_Node);
3651 Error_Msg ("??unreachable code!", Sloc (Error_Node));
3655 -- If the unconditional transfer of control instruction is the
3656 -- last statement of a sequence, then see if our parent is one of
3657 -- the constructs for which we count unblocked exits, and if so,
3658 -- adjust the count.
3663 -- Statements in THEN part or ELSE part of IF statement
3665 if Nkind (P) = N_If_Statement then
3668 -- Statements in ELSIF part of an IF statement
3670 elsif Nkind (P) = N_Elsif_Part then
3672 pragma Assert (Nkind (P) = N_If_Statement);
3674 -- Statements in CASE statement alternative
3676 elsif Nkind (P) = N_Case_Statement_Alternative then
3678 pragma Assert (Nkind (P) = N_Case_Statement);
3680 -- Statements in body of block
3682 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
3683 and then Nkind (Parent (P)) = N_Block_Statement
3685 -- The original loop is now placed inside a block statement
3686 -- due to the expansion of attribute 'Loop_Entry. Return as
3687 -- this is not a "real" block for the purposes of exit
3690 if Nkind (N) = N_Loop_Statement
3691 and then Subject_To_Loop_Entry_Attributes (N)
3696 -- Statements in exception handler in a block
3698 elsif Nkind (P) = N_Exception_Handler
3699 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
3700 and then Nkind (Parent (Parent (P))) = N_Block_Statement
3704 -- None of these cases, so return
3710 -- This was one of the cases we are looking for (i.e. the
3711 -- parent construct was IF, CASE or block) so decrement count.
3713 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
3717 end Check_Unreachable_Code;
3719 ----------------------
3720 -- Preanalyze_Range --
3721 ----------------------
3723 procedure Preanalyze_Range (R_Copy : Node_Id) is
3724 Save_Analysis : constant Boolean := Full_Analysis;
3728 Full_Analysis := False;
3729 Expander_Mode_Save_And_Set (False);
3733 if Nkind (R_Copy) in N_Subexpr and then Is_Overloaded (R_Copy) then
3735 -- Apply preference rules for range of predefined integer types, or
3736 -- diagnose true ambiguity.
3741 Found : Entity_Id := Empty;
3744 Get_First_Interp (R_Copy, I, It);
3745 while Present (It.Typ) loop
3746 if Is_Discrete_Type (It.Typ) then
3750 if Scope (Found) = Standard_Standard then
3753 elsif Scope (It.Typ) = Standard_Standard then
3757 -- Both of them are user-defined
3760 ("ambiguous bounds in range of iteration", R_Copy);
3761 Error_Msg_N ("\possible interpretations:", R_Copy);
3762 Error_Msg_NE ("\\} ", R_Copy, Found);
3763 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
3769 Get_Next_Interp (I, It);
3774 -- Subtype mark in iteration scheme
3776 if Is_Entity_Name (R_Copy) and then Is_Type (Entity (R_Copy)) then
3779 -- Expression in range, or Ada 2012 iterator
3781 elsif Nkind (R_Copy) in N_Subexpr then
3783 Typ := Etype (R_Copy);
3785 if Is_Discrete_Type (Typ) then
3788 -- Check that the resulting object is an iterable container
3790 elsif Has_Aspect (Typ, Aspect_Iterator_Element)
3791 or else Has_Aspect (Typ, Aspect_Constant_Indexing)
3792 or else Has_Aspect (Typ, Aspect_Variable_Indexing)
3796 -- The expression may yield an implicit reference to an iterable
3797 -- container. Insert explicit dereference so that proper type is
3798 -- visible in the loop.
3800 elsif Has_Implicit_Dereference (Etype (R_Copy)) then
3805 Disc := First_Discriminant (Typ);
3806 while Present (Disc) loop
3807 if Has_Implicit_Dereference (Disc) then
3808 Build_Explicit_Dereference (R_Copy, Disc);
3812 Next_Discriminant (Disc);
3819 Expander_Mode_Restore;
3820 Full_Analysis := Save_Analysis;
3821 end Preanalyze_Range;