1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2007, 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 Atree; use Atree;
27 with Checks; use Checks;
28 with Einfo; use Einfo;
29 with Errout; use Errout;
30 with Expander; use Expander;
31 with Exp_Util; use Exp_Util;
32 with Freeze; use Freeze;
34 with Lib.Xref; use Lib.Xref;
35 with Namet; use Namet;
36 with Nlists; use Nlists;
37 with Nmake; use Nmake;
39 with Rtsfind; use Rtsfind;
41 with Sem_Case; use Sem_Case;
42 with Sem_Ch3; use Sem_Ch3;
43 with Sem_Ch8; use Sem_Ch8;
44 with Sem_Disp; use Sem_Disp;
45 with Sem_Elab; use Sem_Elab;
46 with Sem_Eval; use Sem_Eval;
47 with Sem_Res; use Sem_Res;
48 with Sem_Type; use Sem_Type;
49 with Sem_Util; use Sem_Util;
50 with Sem_Warn; use Sem_Warn;
51 with Snames; use Snames;
52 with Stand; use Stand;
53 with Sinfo; use Sinfo;
54 with Targparm; use Targparm;
55 with Tbuild; use Tbuild;
56 with Uintp; use Uintp;
58 package body Sem_Ch5 is
60 Unblocked_Exit_Count : Nat := 0;
61 -- This variable is used when processing if statements, case statements,
62 -- and block statements. It counts the number of exit points that are not
63 -- blocked by unconditional transfer instructions: for IF and CASE, these
64 -- are the branches of the conditional; for a block, they are the statement
65 -- sequence of the block, and the statement sequences of any exception
66 -- handlers that are part of the block. When processing is complete, if
67 -- this count is zero, it means that control cannot fall through the IF,
68 -- CASE or block statement. This is used for the generation of warning
69 -- messages. This variable is recursively saved on entry to processing the
70 -- construct, and restored on exit.
72 -----------------------
73 -- Local Subprograms --
74 -----------------------
76 procedure Analyze_Iteration_Scheme (N : Node_Id);
78 ------------------------
79 -- Analyze_Assignment --
80 ------------------------
82 procedure Analyze_Assignment (N : Node_Id) is
83 Lhs : constant Node_Id := Name (N);
84 Rhs : constant Node_Id := Expression (N);
89 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
90 -- N is the node for the left hand side of an assignment, and it
91 -- is not a variable. This routine issues an appropriate diagnostic.
94 -- This is called to kill current value settings of a simple variable
95 -- on the left hand side. We call it if we find any error in analyzing
96 -- the assignment, and at the end of processing before setting any new
97 -- current values in place.
99 procedure Set_Assignment_Type
101 Opnd_Type : in out Entity_Id);
102 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
103 -- is the nominal subtype. This procedure is used to deal with cases
104 -- where the nominal subtype must be replaced by the actual subtype.
106 -------------------------------
107 -- Diagnose_Non_Variable_Lhs --
108 -------------------------------
110 procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
112 -- Not worth posting another error if left hand side already
113 -- flagged as being illegal in some respect.
115 if Error_Posted (N) then
118 -- Some special bad cases of entity names
120 elsif Is_Entity_Name (N) then
121 if Ekind (Entity (N)) = E_In_Parameter then
123 ("assignment to IN mode parameter not allowed", N);
125 -- Private declarations in a protected object are turned into
126 -- constants when compiling a protected function.
128 elsif Present (Scope (Entity (N)))
129 and then Is_Protected_Type (Scope (Entity (N)))
131 (Ekind (Current_Scope) = E_Function
133 Ekind (Enclosing_Dynamic_Scope (Current_Scope)) = E_Function)
136 ("protected function cannot modify protected object", N);
138 elsif Ekind (Entity (N)) = E_Loop_Parameter then
140 ("assignment to loop parameter not allowed", N);
144 ("left hand side of assignment must be a variable", N);
147 -- For indexed components or selected components, test prefix
149 elsif Nkind (N) = N_Indexed_Component then
150 Diagnose_Non_Variable_Lhs (Prefix (N));
152 -- Another special case for assignment to discriminant
154 elsif Nkind (N) = N_Selected_Component then
155 if Present (Entity (Selector_Name (N)))
156 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
159 ("assignment to discriminant not allowed", N);
161 Diagnose_Non_Variable_Lhs (Prefix (N));
165 -- If we fall through, we have no special message to issue!
167 Error_Msg_N ("left hand side of assignment must be a variable", N);
169 end Diagnose_Non_Variable_Lhs;
175 procedure Kill_Lhs is
177 if Is_Entity_Name (Lhs) then
179 Ent : constant Entity_Id := Entity (Lhs);
181 if Present (Ent) then
182 Kill_Current_Values (Ent);
188 -------------------------
189 -- Set_Assignment_Type --
190 -------------------------
192 procedure Set_Assignment_Type
194 Opnd_Type : in out Entity_Id)
197 Require_Entity (Opnd);
199 -- If the assignment operand is an in-out or out parameter, then we
200 -- get the actual subtype (needed for the unconstrained case).
201 -- If the operand is the actual in an entry declaration, then within
202 -- the accept statement it is replaced with a local renaming, which
203 -- may also have an actual subtype.
205 if Is_Entity_Name (Opnd)
206 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
207 or else Ekind (Entity (Opnd)) =
209 or else Ekind (Entity (Opnd)) =
210 E_Generic_In_Out_Parameter
212 (Ekind (Entity (Opnd)) = E_Variable
213 and then Nkind (Parent (Entity (Opnd))) =
214 N_Object_Renaming_Declaration
215 and then Nkind (Parent (Parent (Entity (Opnd)))) =
218 Opnd_Type := Get_Actual_Subtype (Opnd);
220 -- If assignment operand is a component reference, then we get the
221 -- actual subtype of the component for the unconstrained case.
224 (Nkind (Opnd) = N_Selected_Component
225 or else Nkind (Opnd) = N_Explicit_Dereference)
226 and then not Is_Unchecked_Union (Opnd_Type)
228 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
230 if Present (Decl) then
231 Insert_Action (N, Decl);
232 Mark_Rewrite_Insertion (Decl);
234 Opnd_Type := Defining_Identifier (Decl);
235 Set_Etype (Opnd, Opnd_Type);
236 Freeze_Itype (Opnd_Type, N);
238 elsif Is_Constrained (Etype (Opnd)) then
239 Opnd_Type := Etype (Opnd);
242 -- For slice, use the constrained subtype created for the slice
244 elsif Nkind (Opnd) = N_Slice then
245 Opnd_Type := Etype (Opnd);
247 end Set_Assignment_Type;
249 -- Start of processing for Analyze_Assignment
252 Mark_Coextensions (N, Rhs);
257 -- Start type analysis for assignment
261 -- In the most general case, both Lhs and Rhs can be overloaded, and we
262 -- must compute the intersection of the possible types on each side.
264 if Is_Overloaded (Lhs) then
271 Get_First_Interp (Lhs, I, It);
273 while Present (It.Typ) loop
274 if Has_Compatible_Type (Rhs, It.Typ) then
275 if T1 /= Any_Type then
277 -- An explicit dereference is overloaded if the prefix
278 -- is. Try to remove the ambiguity on the prefix, the
279 -- error will be posted there if the ambiguity is real.
281 if Nkind (Lhs) = N_Explicit_Dereference then
284 PI1 : Interp_Index := 0;
290 Get_First_Interp (Prefix (Lhs), PI, PIt);
292 while Present (PIt.Typ) loop
293 if Is_Access_Type (PIt.Typ)
294 and then Has_Compatible_Type
295 (Rhs, Designated_Type (PIt.Typ))
299 Disambiguate (Prefix (Lhs),
302 if PIt = No_Interp then
304 ("ambiguous left-hand side"
305 & " in assignment", Lhs);
308 Resolve (Prefix (Lhs), PIt.Typ);
318 Get_Next_Interp (PI, PIt);
324 ("ambiguous left-hand side in assignment", Lhs);
332 Get_Next_Interp (I, It);
336 if T1 = Any_Type then
338 ("no valid types for left-hand side for assignment", Lhs);
344 -- The resulting assignment type is T1, so now we will resolve the
345 -- left hand side of the assignment using this determined type.
349 -- Cases where Lhs is not a variable
351 if not Is_Variable (Lhs) then
353 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
354 -- a protected object.
361 if Ada_Version >= Ada_05 then
363 -- Handle chains of renamings
366 while Nkind (Ent) in N_Has_Entity
367 and then Present (Entity (Ent))
368 and then Present (Renamed_Object (Entity (Ent)))
370 Ent := Renamed_Object (Entity (Ent));
373 if (Nkind (Ent) = N_Attribute_Reference
374 and then Attribute_Name (Ent) = Name_Priority)
376 -- Renamings of the attribute Priority applied to protected
377 -- objects have been previously expanded into calls to the
378 -- Get_Ceiling run-time subprogram.
381 (Nkind (Ent) = N_Function_Call
382 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
384 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
386 -- The enclosing subprogram cannot be a protected function
389 while not (Is_Subprogram (S)
390 and then Convention (S) = Convention_Protected)
391 and then S /= Standard_Standard
396 if Ekind (S) = E_Function
397 and then Convention (S) = Convention_Protected
400 ("protected function cannot modify protected object",
404 -- Changes of the ceiling priority of the protected object
405 -- are only effective if the Ceiling_Locking policy is in
406 -- effect (AARM D.5.2 (5/2)).
408 if Locking_Policy /= 'C' then
409 Error_Msg_N ("assignment to the attribute PRIORITY has " &
411 Error_Msg_N ("\since no Locking_Policy has been " &
420 Diagnose_Non_Variable_Lhs (Lhs);
423 -- Error of assigning to limited type. We do however allow this in
424 -- certain cases where the front end generates the assignments.
426 elsif Is_Limited_Type (T1)
427 and then not Assignment_OK (Lhs)
428 and then not Assignment_OK (Original_Node (Lhs))
429 and then not Is_Value_Type (T1)
432 ("left hand of assignment must not be limited type", Lhs);
433 Explain_Limited_Type (T1, Lhs);
437 -- Resolution may have updated the subtype, in case the left-hand
438 -- side is a private protected component. Use the correct subtype
439 -- to avoid scoping issues in the back-end.
443 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
444 -- type. For example:
448 -- type Acc is access P.T;
451 -- with Pkg; use Acc;
452 -- procedure Example is
455 -- A.all := B.all; -- ERROR
458 if Nkind (Lhs) = N_Explicit_Dereference
459 and then Ekind (T1) = E_Incomplete_Type
461 Error_Msg_N ("invalid use of incomplete type", Lhs);
466 -- Now we can complete the resolution of the right hand side
468 Set_Assignment_Type (Lhs, T1);
471 -- This is the point at which we check for an unset reference
473 Check_Unset_Reference (Rhs);
475 -- Remaining steps are skipped if Rhs was syntactically in error
484 if not Covers (T1, T2) then
485 Wrong_Type (Rhs, Etype (Lhs));
490 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
491 -- types, use the non-limited view if available
493 if Nkind (Rhs) = N_Explicit_Dereference
494 and then Ekind (T2) = E_Incomplete_Type
495 and then Is_Tagged_Type (T2)
496 and then Present (Non_Limited_View (T2))
498 T2 := Non_Limited_View (T2);
501 Set_Assignment_Type (Rhs, T2);
503 if Total_Errors_Detected /= 0 then
513 if T1 = Any_Type or else T2 = Any_Type then
518 -- If the rhs is class-wide or dynamically tagged, then require the lhs
519 -- to be class-wide. The case where the rhs is a dynamically tagged call
520 -- to a dispatching operation with a controlling access result is
521 -- excluded from this check, since the target has an access type (and
522 -- no tag propagation occurs in that case).
524 if (Is_Class_Wide_Type (T2)
525 or else (Is_Dynamically_Tagged (Rhs)
526 and then not Is_Access_Type (T1)))
527 and then not Is_Class_Wide_Type (T1)
529 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
531 elsif Is_Class_Wide_Type (T1)
532 and then not Is_Class_Wide_Type (T2)
533 and then not Is_Tag_Indeterminate (Rhs)
534 and then not Is_Dynamically_Tagged (Rhs)
536 Error_Msg_N ("dynamically tagged expression required!", Rhs);
539 -- Propagate the tag from a class-wide target to the rhs when the rhs
540 -- is a tag-indeterminate call.
542 if Is_Tag_Indeterminate (Rhs) then
543 if Is_Class_Wide_Type (T1) then
544 Propagate_Tag (Lhs, Rhs);
546 elsif Nkind (Rhs) = N_Function_Call
547 and then Is_Entity_Name (Name (Rhs))
548 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
551 ("call to abstract function must be dispatching", Name (Rhs));
553 elsif Nkind (Rhs) = N_Qualified_Expression
554 and then Nkind (Expression (Rhs)) = N_Function_Call
555 and then Is_Entity_Name (Name (Expression (Rhs)))
557 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
560 ("call to abstract function must be dispatching",
561 Name (Expression (Rhs)));
565 -- Ada 2005 (AI-230 and AI-385): When the lhs type is an anonymous
566 -- access type, apply an implicit conversion of the rhs to that type
567 -- to force appropriate static and run-time accessibility checks.
569 if Ada_Version >= Ada_05
570 and then Ekind (T1) = E_Anonymous_Access_Type
572 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
573 Analyze_And_Resolve (Rhs, T1);
576 -- Ada 2005 (AI-231): Assignment to not null variable
578 if Ada_Version >= Ada_05
579 and then Can_Never_Be_Null (T1)
580 and then not Assignment_OK (Lhs)
582 -- Case where we know the right hand side is null
584 if Known_Null (Rhs) then
585 Apply_Compile_Time_Constraint_Error
587 Msg => "(Ada 2005) null not allowed in null-excluding objects?",
588 Reason => CE_Null_Not_Allowed);
590 -- We still mark this as a possible modification, that's necessary
591 -- to reset Is_True_Constant, and desirable for xref purposes.
593 Note_Possible_Modification (Lhs);
596 -- If we know the right hand side is non-null, then we convert to the
597 -- target type, since we don't need a run time check in that case.
599 elsif not Can_Never_Be_Null (T2) then
600 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
601 Analyze_And_Resolve (Rhs, T1);
605 if Is_Scalar_Type (T1) then
606 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
608 -- For array types, verify that lengths match. If the right hand side
609 -- if a function call that has been inlined, the assignment has been
610 -- rewritten as a block, and the constraint check will be applied to the
611 -- assignment within the block.
613 elsif Is_Array_Type (T1)
615 (Nkind (Rhs) /= N_Type_Conversion
616 or else Is_Constrained (Etype (Rhs)))
618 (Nkind (Rhs) /= N_Function_Call
619 or else Nkind (N) /= N_Block_Statement)
621 -- Assignment verifies that the length of the Lsh and Rhs are equal,
622 -- but of course the indices do not have to match. If the right-hand
623 -- side is a type conversion to an unconstrained type, a length check
624 -- is performed on the expression itself during expansion. In rare
625 -- cases, the redundant length check is computed on an index type
626 -- with a different representation, triggering incorrect code in
629 Apply_Length_Check (Rhs, Etype (Lhs));
632 -- Discriminant checks are applied in the course of expansion
637 -- Note: modifications of the Lhs may only be recorded after
638 -- checks have been applied.
640 Note_Possible_Modification (Lhs);
642 -- ??? a real accessibility check is needed when ???
644 -- Post warning for redundant assignment or variable to itself
646 if Warn_On_Redundant_Constructs
648 -- We only warn for source constructs
650 and then Comes_From_Source (N)
652 -- Where the object is the same on both sides
654 and then Same_Object (Lhs, Original_Node (Rhs))
656 -- But exclude the case where the right side was an operation
657 -- that got rewritten (e.g. JUNK + K, where K was known to be
658 -- zero). We don't want to warn in such a case, since it is
659 -- reasonable to write such expressions especially when K is
660 -- defined symbolically in some other package.
662 and then Nkind (Original_Node (Rhs)) not in N_Op
664 if Nkind (Lhs) in N_Has_Entity then
666 ("?useless assignment of & to itself!", N, Entity (Lhs));
669 ("?useless assignment of object to itself!", N);
673 -- Check for non-allowed composite assignment
675 if not Support_Composite_Assign_On_Target
676 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
677 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
679 Error_Msg_CRT ("composite assignment", N);
682 -- Check elaboration warning for left side if not in elab code
684 if not In_Subprogram_Or_Concurrent_Unit then
685 Check_Elab_Assign (Lhs);
688 -- Final step. If left side is an entity, then we may be able to
689 -- reset the current tracked values to new safe values. We only have
690 -- something to do if the left side is an entity name, and expansion
691 -- has not modified the node into something other than an assignment,
692 -- and of course we only capture values if it is safe to do so.
694 if Is_Entity_Name (Lhs)
695 and then Nkind (N) = N_Assignment_Statement
698 Ent : constant Entity_Id := Entity (Lhs);
701 if Safe_To_Capture_Value (N, Ent) then
703 -- If simple variable on left side, warn if this assignment
704 -- blots out another one (rendering it useless) and note
705 -- location of assignment in case no one references value.
706 -- We only do this for source assignments, otherwise we can
707 -- generate bogus warnings when an assignment is rewritten as
708 -- another assignment, and gets tied up with itself.
710 if Warn_On_Modified_Unread
711 and then Ekind (Ent) = E_Variable
712 and then Comes_From_Source (N)
713 and then In_Extended_Main_Source_Unit (Ent)
715 Warn_On_Useless_Assignment (Ent, Sloc (N));
716 Set_Last_Assignment (Ent, Lhs);
719 -- If we are assigning an access type and the left side is an
720 -- entity, then make sure that the Is_Known_[Non_]Null flags
721 -- properly reflect the state of the entity after assignment.
723 if Is_Access_Type (T1) then
724 if Known_Non_Null (Rhs) then
725 Set_Is_Known_Non_Null (Ent, True);
727 elsif Known_Null (Rhs)
728 and then not Can_Never_Be_Null (Ent)
730 Set_Is_Known_Null (Ent, True);
733 Set_Is_Known_Null (Ent, False);
735 if not Can_Never_Be_Null (Ent) then
736 Set_Is_Known_Non_Null (Ent, False);
740 -- For discrete types, we may be able to set the current value
741 -- if the value is known at compile time.
743 elsif Is_Discrete_Type (T1)
744 and then Compile_Time_Known_Value (Rhs)
746 Set_Current_Value (Ent, Rhs);
748 Set_Current_Value (Ent, Empty);
751 -- If not safe to capture values, kill them
758 end Analyze_Assignment;
760 -----------------------------
761 -- Analyze_Block_Statement --
762 -----------------------------
764 procedure Analyze_Block_Statement (N : Node_Id) is
765 Decls : constant List_Id := Declarations (N);
766 Id : constant Node_Id := Identifier (N);
767 HSS : constant Node_Id := Handled_Statement_Sequence (N);
770 -- If no handled statement sequence is present, things are really
771 -- messed up, and we just return immediately (this is a defence
772 -- against previous errors).
778 -- Normal processing with HSS present
781 EH : constant List_Id := Exception_Handlers (HSS);
782 Ent : Entity_Id := Empty;
785 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
786 -- Recursively save value of this global, will be restored on exit
789 -- Initialize unblocked exit count for statements of begin block
790 -- plus one for each excption handler that is present.
792 Unblocked_Exit_Count := 1;
795 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
798 -- If a label is present analyze it and mark it as referenced
804 -- An error defense. If we have an identifier, but no entity,
805 -- then something is wrong. If we have previous errors, then
806 -- just remove the identifier and continue, otherwise raise
810 if Total_Errors_Detected /= 0 then
811 Set_Identifier (N, Empty);
817 Set_Ekind (Ent, E_Block);
818 Generate_Reference (Ent, N, ' ');
819 Generate_Definition (Ent);
821 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
822 Set_Label_Construct (Parent (Ent), N);
827 -- If no entity set, create a label entity
830 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
831 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
835 Set_Etype (Ent, Standard_Void_Type);
836 Set_Block_Node (Ent, Identifier (N));
839 if Present (Decls) then
840 Analyze_Declarations (Decls);
845 Process_End_Label (HSS, 'e', Ent);
847 -- If exception handlers are present, then we indicate that
848 -- enclosing scopes contain a block with handlers. We only
849 -- need to mark non-generic scopes.
854 Set_Has_Nested_Block_With_Handler (S);
855 exit when Is_Overloadable (S)
856 or else Ekind (S) = E_Package
857 or else Is_Generic_Unit (S);
862 Check_References (Ent);
863 Warn_On_Useless_Assignments (Ent);
866 if Unblocked_Exit_Count = 0 then
867 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
868 Check_Unreachable_Code (N);
870 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
873 end Analyze_Block_Statement;
875 ----------------------------
876 -- Analyze_Case_Statement --
877 ----------------------------
879 procedure Analyze_Case_Statement (N : Node_Id) is
881 Exp_Type : Entity_Id;
882 Exp_Btype : Entity_Id;
885 Others_Present : Boolean;
887 Statements_Analyzed : Boolean := False;
888 -- Set True if at least some statement sequences get analyzed.
889 -- If False on exit, means we had a serious error that prevented
890 -- full analysis of the case statement, and as a result it is not
891 -- a good idea to output warning messages about unreachable code.
893 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
894 -- Recursively save value of this global, will be restored on exit
896 procedure Non_Static_Choice_Error (Choice : Node_Id);
897 -- Error routine invoked by the generic instantiation below when
898 -- the case statment has a non static choice.
900 procedure Process_Statements (Alternative : Node_Id);
901 -- Analyzes all the statements associated to a case alternative.
902 -- Needed by the generic instantiation below.
904 package Case_Choices_Processing is new
905 Generic_Choices_Processing
906 (Get_Alternatives => Alternatives,
907 Get_Choices => Discrete_Choices,
908 Process_Empty_Choice => No_OP,
909 Process_Non_Static_Choice => Non_Static_Choice_Error,
910 Process_Associated_Node => Process_Statements);
911 use Case_Choices_Processing;
912 -- Instantiation of the generic choice processing package
914 -----------------------------
915 -- Non_Static_Choice_Error --
916 -----------------------------
918 procedure Non_Static_Choice_Error (Choice : Node_Id) is
921 ("choice given in case statement is not static!", Choice);
922 end Non_Static_Choice_Error;
924 ------------------------
925 -- Process_Statements --
926 ------------------------
928 procedure Process_Statements (Alternative : Node_Id) is
929 Choices : constant List_Id := Discrete_Choices (Alternative);
933 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
934 Statements_Analyzed := True;
936 -- An interesting optimization. If the case statement expression
937 -- is a simple entity, then we can set the current value within
938 -- an alternative if the alternative has one possible value.
942 -- when 2 | 3 => beta
943 -- when others => gamma
945 -- Here we know that N is initially 1 within alpha, but for beta
946 -- and gamma, we do not know anything more about the initial value.
948 if Is_Entity_Name (Exp) then
951 if Ekind (Ent) = E_Variable
953 Ekind (Ent) = E_In_Out_Parameter
955 Ekind (Ent) = E_Out_Parameter
957 if List_Length (Choices) = 1
958 and then Nkind (First (Choices)) in N_Subexpr
959 and then Compile_Time_Known_Value (First (Choices))
961 Set_Current_Value (Entity (Exp), First (Choices));
964 Analyze_Statements (Statements (Alternative));
966 -- After analyzing the case, set the current value to empty
967 -- since we won't know what it is for the next alternative
968 -- (unless reset by this same circuit), or after the case.
970 Set_Current_Value (Entity (Exp), Empty);
975 -- Case where expression is not an entity name of a variable
977 Analyze_Statements (Statements (Alternative));
978 end Process_Statements;
980 -- Table to record choices. Put after subprograms since we make
981 -- a call to Number_Of_Choices to get the right number of entries.
983 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
985 -- Start of processing for Analyze_Case_Statement
988 Unblocked_Exit_Count := 0;
989 Exp := Expression (N);
992 -- The expression must be of any discrete type. In rare cases, the
993 -- expander constructs a case statement whose expression has a private
994 -- type whose full view is discrete. This can happen when generating
995 -- a stream operation for a variant type after the type is frozen,
996 -- when the partial of view of the type of the discriminant is private.
997 -- In that case, use the full view to analyze case alternatives.
999 if not Is_Overloaded (Exp)
1000 and then not Comes_From_Source (N)
1001 and then Is_Private_Type (Etype (Exp))
1002 and then Present (Full_View (Etype (Exp)))
1003 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1005 Resolve (Exp, Etype (Exp));
1006 Exp_Type := Full_View (Etype (Exp));
1009 Analyze_And_Resolve (Exp, Any_Discrete);
1010 Exp_Type := Etype (Exp);
1013 Check_Unset_Reference (Exp);
1014 Exp_Btype := Base_Type (Exp_Type);
1016 -- The expression must be of a discrete type which must be determinable
1017 -- independently of the context in which the expression occurs, but
1018 -- using the fact that the expression must be of a discrete type.
1019 -- Moreover, the type this expression must not be a character literal
1020 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1022 -- If error already reported by Resolve, nothing more to do
1024 if Exp_Btype = Any_Discrete
1025 or else Exp_Btype = Any_Type
1029 elsif Exp_Btype = Any_Character then
1031 ("character literal as case expression is ambiguous", Exp);
1034 elsif Ada_Version = Ada_83
1035 and then (Is_Generic_Type (Exp_Btype)
1036 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1039 ("(Ada 83) case expression cannot be of a generic type", Exp);
1043 -- If the case expression is a formal object of mode in out, then
1044 -- treat it as having a nonstatic subtype by forcing use of the base
1045 -- type (which has to get passed to Check_Case_Choices below). Also
1046 -- use base type when the case expression is parenthesized.
1048 if Paren_Count (Exp) > 0
1049 or else (Is_Entity_Name (Exp)
1050 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1052 Exp_Type := Exp_Btype;
1055 -- Call instantiated Analyze_Choices which does the rest of the work
1058 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
1060 if Exp_Type = Universal_Integer and then not Others_Present then
1061 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1064 -- If all our exits were blocked by unconditional transfers of control,
1065 -- then the entire CASE statement acts as an unconditional transfer of
1066 -- control, so treat it like one, and check unreachable code. Skip this
1067 -- test if we had serious errors preventing any statement analysis.
1069 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1070 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1071 Check_Unreachable_Code (N);
1073 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1076 if not Expander_Active
1077 and then Compile_Time_Known_Value (Expression (N))
1078 and then Serious_Errors_Detected = 0
1081 Chosen : constant Node_Id := Find_Static_Alternative (N);
1085 Alt := First (Alternatives (N));
1086 while Present (Alt) loop
1087 if Alt /= Chosen then
1088 Remove_Warning_Messages (Statements (Alt));
1095 end Analyze_Case_Statement;
1097 ----------------------------
1098 -- Analyze_Exit_Statement --
1099 ----------------------------
1101 -- If the exit includes a name, it must be the name of a currently open
1102 -- loop. Otherwise there must be an innermost open loop on the stack,
1103 -- to which the statement implicitly refers.
1105 procedure Analyze_Exit_Statement (N : Node_Id) is
1106 Target : constant Node_Id := Name (N);
1107 Cond : constant Node_Id := Condition (N);
1108 Scope_Id : Entity_Id;
1114 Check_Unreachable_Code (N);
1117 if Present (Target) then
1119 U_Name := Entity (Target);
1121 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1122 Error_Msg_N ("invalid loop name in exit statement", N);
1125 Set_Has_Exit (U_Name);
1132 for J in reverse 0 .. Scope_Stack.Last loop
1133 Scope_Id := Scope_Stack.Table (J).Entity;
1134 Kind := Ekind (Scope_Id);
1137 and then (No (Target) or else Scope_Id = U_Name) then
1138 Set_Has_Exit (Scope_Id);
1141 elsif Kind = E_Block
1142 or else Kind = E_Loop
1143 or else Kind = E_Return_Statement
1149 ("cannot exit from program unit or accept statement", N);
1154 -- Verify that if present the condition is a Boolean expression
1156 if Present (Cond) then
1157 Analyze_And_Resolve (Cond, Any_Boolean);
1158 Check_Unset_Reference (Cond);
1160 end Analyze_Exit_Statement;
1162 ----------------------------
1163 -- Analyze_Goto_Statement --
1164 ----------------------------
1166 procedure Analyze_Goto_Statement (N : Node_Id) is
1167 Label : constant Node_Id := Name (N);
1168 Scope_Id : Entity_Id;
1169 Label_Scope : Entity_Id;
1170 Label_Ent : Entity_Id;
1173 Check_Unreachable_Code (N);
1176 Label_Ent := Entity (Label);
1178 -- Ignore previous error
1180 if Label_Ent = Any_Id then
1183 -- We just have a label as the target of a goto
1185 elsif Ekind (Label_Ent) /= E_Label then
1186 Error_Msg_N ("target of goto statement must be a label", Label);
1189 -- Check that the target of the goto is reachable according to Ada
1190 -- scoping rules. Note: the special gotos we generate for optimizing
1191 -- local handling of exceptions would violate these rules, but we mark
1192 -- such gotos as analyzed when built, so this code is never entered.
1194 elsif not Reachable (Label_Ent) then
1195 Error_Msg_N ("target of goto statement is not reachable", Label);
1199 -- Here if goto passes initial validity checks
1201 Label_Scope := Enclosing_Scope (Label_Ent);
1203 for J in reverse 0 .. Scope_Stack.Last loop
1204 Scope_Id := Scope_Stack.Table (J).Entity;
1206 if Label_Scope = Scope_Id
1207 or else (Ekind (Scope_Id) /= E_Block
1208 and then Ekind (Scope_Id) /= E_Loop
1209 and then Ekind (Scope_Id) /= E_Return_Statement)
1211 if Scope_Id /= Label_Scope then
1213 ("cannot exit from program unit or accept statement", N);
1220 raise Program_Error;
1221 end Analyze_Goto_Statement;
1223 --------------------------
1224 -- Analyze_If_Statement --
1225 --------------------------
1227 -- A special complication arises in the analysis of if statements
1229 -- The expander has circuitry to completely delete code that it
1230 -- can tell will not be executed (as a result of compile time known
1231 -- conditions). In the analyzer, we ensure that code that will be
1232 -- deleted in this manner is analyzed but not expanded. This is
1233 -- obviously more efficient, but more significantly, difficulties
1234 -- arise if code is expanded and then eliminated (e.g. exception
1235 -- table entries disappear). Similarly, itypes generated in deleted
1236 -- code must be frozen from start, because the nodes on which they
1237 -- depend will not be available at the freeze point.
1239 procedure Analyze_If_Statement (N : Node_Id) is
1242 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1243 -- Recursively save value of this global, will be restored on exit
1245 Save_In_Deleted_Code : Boolean;
1247 Del : Boolean := False;
1248 -- This flag gets set True if a True condition has been found,
1249 -- which means that remaining ELSE/ELSIF parts are deleted.
1251 procedure Analyze_Cond_Then (Cnode : Node_Id);
1252 -- This is applied to either the N_If_Statement node itself or
1253 -- to an N_Elsif_Part node. It deals with analyzing the condition
1254 -- and the THEN statements associated with it.
1256 -----------------------
1257 -- Analyze_Cond_Then --
1258 -----------------------
1260 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1261 Cond : constant Node_Id := Condition (Cnode);
1262 Tstm : constant List_Id := Then_Statements (Cnode);
1265 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1266 Analyze_And_Resolve (Cond, Any_Boolean);
1267 Check_Unset_Reference (Cond);
1268 Set_Current_Value_Condition (Cnode);
1270 -- If already deleting, then just analyze then statements
1273 Analyze_Statements (Tstm);
1275 -- Compile time known value, not deleting yet
1277 elsif Compile_Time_Known_Value (Cond) then
1278 Save_In_Deleted_Code := In_Deleted_Code;
1280 -- If condition is True, then analyze the THEN statements
1281 -- and set no expansion for ELSE and ELSIF parts.
1283 if Is_True (Expr_Value (Cond)) then
1284 Analyze_Statements (Tstm);
1286 Expander_Mode_Save_And_Set (False);
1287 In_Deleted_Code := True;
1289 -- If condition is False, analyze THEN with expansion off
1291 else -- Is_False (Expr_Value (Cond))
1292 Expander_Mode_Save_And_Set (False);
1293 In_Deleted_Code := True;
1294 Analyze_Statements (Tstm);
1295 Expander_Mode_Restore;
1296 In_Deleted_Code := Save_In_Deleted_Code;
1299 -- Not known at compile time, not deleting, normal analysis
1302 Analyze_Statements (Tstm);
1304 end Analyze_Cond_Then;
1306 -- Start of Analyze_If_Statement
1309 -- Initialize exit count for else statements. If there is no else
1310 -- part, this count will stay non-zero reflecting the fact that the
1311 -- uncovered else case is an unblocked exit.
1313 Unblocked_Exit_Count := 1;
1314 Analyze_Cond_Then (N);
1316 -- Now to analyze the elsif parts if any are present
1318 if Present (Elsif_Parts (N)) then
1319 E := First (Elsif_Parts (N));
1320 while Present (E) loop
1321 Analyze_Cond_Then (E);
1326 if Present (Else_Statements (N)) then
1327 Analyze_Statements (Else_Statements (N));
1330 -- If all our exits were blocked by unconditional transfers of control,
1331 -- then the entire IF statement acts as an unconditional transfer of
1332 -- control, so treat it like one, and check unreachable code.
1334 if Unblocked_Exit_Count = 0 then
1335 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1336 Check_Unreachable_Code (N);
1338 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1342 Expander_Mode_Restore;
1343 In_Deleted_Code := Save_In_Deleted_Code;
1346 if not Expander_Active
1347 and then Compile_Time_Known_Value (Condition (N))
1348 and then Serious_Errors_Detected = 0
1350 if Is_True (Expr_Value (Condition (N))) then
1351 Remove_Warning_Messages (Else_Statements (N));
1353 if Present (Elsif_Parts (N)) then
1354 E := First (Elsif_Parts (N));
1355 while Present (E) loop
1356 Remove_Warning_Messages (Then_Statements (E));
1362 Remove_Warning_Messages (Then_Statements (N));
1365 end Analyze_If_Statement;
1367 ----------------------------------------
1368 -- Analyze_Implicit_Label_Declaration --
1369 ----------------------------------------
1371 -- An implicit label declaration is generated in the innermost
1372 -- enclosing declarative part. This is done for labels as well as
1373 -- block and loop names.
1375 -- Note: any changes in this routine may need to be reflected in
1376 -- Analyze_Label_Entity.
1378 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1379 Id : constant Node_Id := Defining_Identifier (N);
1382 Set_Ekind (Id, E_Label);
1383 Set_Etype (Id, Standard_Void_Type);
1384 Set_Enclosing_Scope (Id, Current_Scope);
1385 end Analyze_Implicit_Label_Declaration;
1387 ------------------------------
1388 -- Analyze_Iteration_Scheme --
1389 ------------------------------
1391 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1393 procedure Process_Bounds (R : Node_Id);
1394 -- If the iteration is given by a range, create temporaries and
1395 -- assignment statements block to capture the bounds and perform
1396 -- required finalization actions in case a bound includes a function
1397 -- call that uses the temporary stack. We first pre-analyze a copy of
1398 -- the range in order to determine the expected type, and analyze and
1399 -- resolve the original bounds.
1401 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1402 -- If the bounds are given by a 'Range reference on a function call
1403 -- that returns a controlled array, introduce an explicit declaration
1404 -- to capture the bounds, so that the function result can be finalized
1405 -- in timely fashion.
1407 --------------------
1408 -- Process_Bounds --
1409 --------------------
1411 procedure Process_Bounds (R : Node_Id) is
1412 Loc : constant Source_Ptr := Sloc (N);
1413 R_Copy : constant Node_Id := New_Copy_Tree (R);
1414 Lo : constant Node_Id := Low_Bound (R);
1415 Hi : constant Node_Id := High_Bound (R);
1416 New_Lo_Bound : Node_Id := Empty;
1417 New_Hi_Bound : Node_Id := Empty;
1419 Save_Analysis : Boolean;
1422 (Original_Bound : Node_Id;
1423 Analyzed_Bound : Node_Id) return Node_Id;
1424 -- Create one declaration followed by one assignment statement
1425 -- to capture the value of bound. We create a separate assignment
1426 -- in order to force the creation of a block in case the bound
1427 -- contains a call that uses the secondary stack.
1434 (Original_Bound : Node_Id;
1435 Analyzed_Bound : Node_Id) return Node_Id
1442 -- If the bound is a constant or an object, no need for a separate
1443 -- declaration. If the bound is the result of previous expansion
1444 -- it is already analyzed and should not be modified. Note that
1445 -- the Bound will be resolved later, if needed, as part of the
1446 -- call to Make_Index (literal bounds may need to be resolved to
1449 if Analyzed (Original_Bound) then
1450 return Original_Bound;
1452 elsif Nkind (Analyzed_Bound) = N_Integer_Literal
1453 or else Nkind (Analyzed_Bound) = N_Character_Literal
1454 or else Is_Entity_Name (Analyzed_Bound)
1456 Analyze_And_Resolve (Original_Bound, Typ);
1457 return Original_Bound;
1460 Analyze_And_Resolve (Original_Bound, Typ);
1464 Make_Defining_Identifier (Loc,
1465 Chars => New_Internal_Name ('S'));
1468 Make_Object_Declaration (Loc,
1469 Defining_Identifier => Id,
1470 Object_Definition => New_Occurrence_Of (Typ, Loc));
1472 Insert_Before (Parent (N), Decl);
1476 Make_Assignment_Statement (Loc,
1477 Name => New_Occurrence_Of (Id, Loc),
1478 Expression => Relocate_Node (Original_Bound));
1480 Insert_Before (Parent (N), Assign);
1483 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1485 if Nkind (Assign) = N_Assignment_Statement then
1486 return Expression (Assign);
1488 return Original_Bound;
1492 -- Start of processing for Process_Bounds
1495 -- Determine expected type of range by analyzing separate copy
1496 -- Do the analysis and resolution of the copy of the bounds with
1497 -- expansion disabled, to prevent the generation of finalization
1498 -- actions on each bound. This prevents memory leaks when the
1499 -- bounds contain calls to functions returning controlled arrays.
1501 Set_Parent (R_Copy, Parent (R));
1502 Save_Analysis := Full_Analysis;
1503 Full_Analysis := False;
1504 Expander_Mode_Save_And_Set (False);
1508 if Is_Overloaded (R_Copy) then
1510 -- Apply preference rules for range of predefined integer types,
1511 -- or diagnose true ambiguity.
1516 Found : Entity_Id := Empty;
1519 Get_First_Interp (R_Copy, I, It);
1520 while Present (It.Typ) loop
1521 if Is_Discrete_Type (It.Typ) then
1525 if Scope (Found) = Standard_Standard then
1528 elsif Scope (It.Typ) = Standard_Standard then
1532 -- Both of them are user-defined
1535 ("ambiguous bounds in range of iteration",
1537 Error_Msg_N ("\possible interpretations:", R_Copy);
1538 Error_Msg_NE ("\\} ", R_Copy, Found);
1539 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1545 Get_Next_Interp (I, It);
1551 Expander_Mode_Restore;
1552 Full_Analysis := Save_Analysis;
1554 Typ := Etype (R_Copy);
1556 -- If the type of the discrete range is Universal_Integer, then
1557 -- the bound's type must be resolved to Integer, and any object
1558 -- used to hold the bound must also have type Integer, unless the
1559 -- literal bounds are constant-folded expressions that carry a user-
1562 if Typ = Universal_Integer then
1563 if Nkind (Lo) = N_Integer_Literal
1564 and then Present (Etype (Lo))
1565 and then Scope (Etype (Lo)) /= Standard_Standard
1569 elsif Nkind (Hi) = N_Integer_Literal
1570 and then Present (Etype (Hi))
1571 and then Scope (Etype (Hi)) /= Standard_Standard
1576 Typ := Standard_Integer;
1582 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1583 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1585 -- Propagate staticness to loop range itself, in case the
1586 -- corresponding subtype is static.
1588 if New_Lo_Bound /= Lo
1589 and then Is_Static_Expression (New_Lo_Bound)
1591 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1594 if New_Hi_Bound /= Hi
1595 and then Is_Static_Expression (New_Hi_Bound)
1597 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1601 --------------------------------------
1602 -- Check_Controlled_Array_Attribute --
1603 --------------------------------------
1605 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1607 if Nkind (DS) = N_Attribute_Reference
1608 and then Is_Entity_Name (Prefix (DS))
1609 and then Ekind (Entity (Prefix (DS))) = E_Function
1610 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1613 Component_Type (Etype (Entity (Prefix (DS)))))
1614 and then Expander_Active
1617 Loc : constant Source_Ptr := Sloc (N);
1618 Arr : constant Entity_Id :=
1619 Etype (Entity (Prefix (DS)));
1620 Indx : constant Entity_Id :=
1621 Base_Type (Etype (First_Index (Arr)));
1622 Subt : constant Entity_Id :=
1623 Make_Defining_Identifier
1624 (Loc, New_Internal_Name ('S'));
1629 Make_Subtype_Declaration (Loc,
1630 Defining_Identifier => Subt,
1631 Subtype_Indication =>
1632 Make_Subtype_Indication (Loc,
1633 Subtype_Mark => New_Reference_To (Indx, Loc),
1635 Make_Range_Constraint (Loc,
1636 Relocate_Node (DS))));
1637 Insert_Before (Parent (N), Decl);
1641 Make_Attribute_Reference (Loc,
1642 Prefix => New_Reference_To (Subt, Loc),
1643 Attribute_Name => Attribute_Name (DS)));
1647 end Check_Controlled_Array_Attribute;
1649 -- Start of processing for Analyze_Iteration_Scheme
1652 -- For an infinite loop, there is no iteration scheme
1659 Cond : constant Node_Id := Condition (N);
1662 -- For WHILE loop, verify that the condition is a Boolean
1663 -- expression and resolve and check it.
1665 if Present (Cond) then
1666 Analyze_And_Resolve (Cond, Any_Boolean);
1667 Check_Unset_Reference (Cond);
1668 Set_Current_Value_Condition (N);
1671 -- Else we have a FOR loop
1675 LP : constant Node_Id := Loop_Parameter_Specification (N);
1676 Id : constant Entity_Id := Defining_Identifier (LP);
1677 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1682 -- We always consider the loop variable to be referenced,
1683 -- since the loop may be used just for counting purposes.
1685 Generate_Reference (Id, N, ' ');
1687 -- Check for case of loop variable hiding a local
1688 -- variable (used later on to give a nice warning
1689 -- if the hidden variable is never assigned).
1692 H : constant Entity_Id := Homonym (Id);
1695 and then Enclosing_Dynamic_Scope (H) =
1696 Enclosing_Dynamic_Scope (Id)
1697 and then Ekind (H) = E_Variable
1698 and then Is_Discrete_Type (Etype (H))
1700 Set_Hiding_Loop_Variable (H, Id);
1704 -- Now analyze the subtype definition. If it is
1705 -- a range, create temporaries for bounds.
1707 if Nkind (DS) = N_Range
1708 and then Expander_Active
1710 Process_Bounds (DS);
1719 -- The subtype indication may denote the completion
1720 -- of an incomplete type declaration.
1722 if Is_Entity_Name (DS)
1723 and then Present (Entity (DS))
1724 and then Is_Type (Entity (DS))
1725 and then Ekind (Entity (DS)) = E_Incomplete_Type
1727 Set_Entity (DS, Get_Full_View (Entity (DS)));
1728 Set_Etype (DS, Entity (DS));
1731 if not Is_Discrete_Type (Etype (DS)) then
1732 Wrong_Type (DS, Any_Discrete);
1733 Set_Etype (DS, Any_Type);
1736 Check_Controlled_Array_Attribute (DS);
1738 Make_Index (DS, LP);
1740 Set_Ekind (Id, E_Loop_Parameter);
1741 Set_Etype (Id, Etype (DS));
1742 Set_Is_Known_Valid (Id, True);
1744 -- The loop is not a declarative part, so the only entity
1745 -- declared "within" must be frozen explicitly.
1748 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1750 if Is_Non_Empty_List (Flist) then
1751 Insert_Actions (N, Flist);
1755 -- Check for null or possibly null range and issue warning.
1756 -- We suppress such messages in generic templates and
1757 -- instances, because in practice they tend to be dubious
1760 if Nkind (DS) = N_Range
1761 and then Comes_From_Source (N)
1764 L : constant Node_Id := Low_Bound (DS);
1765 H : constant Node_Id := High_Bound (DS);
1775 Determine_Range (L, LOK, Llo, Lhi);
1776 Determine_Range (H, HOK, Hlo, Hhi);
1778 -- If range of loop is null, issue warning
1780 if (LOK and HOK) and then Llo > Hhi then
1782 -- Suppress the warning if inside a generic
1783 -- template or instance, since in practice
1784 -- they tend to be dubious in these cases since
1785 -- they can result from intended parametrization.
1787 if not Inside_A_Generic
1788 and then not In_Instance
1791 ("?loop range is null, loop will not execute",
1795 -- Since we know the range of the loop is null,
1796 -- set the appropriate flag to suppress any
1797 -- warnings that would otherwise be issued in
1798 -- the body of the loop that will not execute.
1799 -- We do this even in the generic case, since
1800 -- if it is dubious to warn on the null loop
1801 -- itself, it is certainly dubious to warn for
1802 -- conditions that occur inside it!
1804 Set_Is_Null_Loop (Parent (N));
1806 -- The other case for a warning is a reverse loop
1807 -- where the upper bound is the integer literal
1808 -- zero or one, and the lower bound can be positive.
1810 -- For example, we have
1812 -- for J in reverse N .. 1 loop
1814 -- In practice, this is very likely to be a case
1815 -- of reversing the bounds incorrectly in the range.
1817 elsif Reverse_Present (LP)
1818 and then Nkind (Original_Node (H)) =
1820 and then (Intval (H) = Uint_0
1822 Intval (H) = Uint_1)
1825 Error_Msg_N ("?loop range may be null", DS);
1826 Error_Msg_N ("\?bounds may be wrong way round", DS);
1834 end Analyze_Iteration_Scheme;
1840 -- Note: the semantic work required for analyzing labels (setting them as
1841 -- reachable) was done in a prepass through the statements in the block,
1842 -- so that forward gotos would be properly handled. See Analyze_Statements
1843 -- for further details. The only processing required here is to deal with
1844 -- optimizations that depend on an assumption of sequential control flow,
1845 -- since of course the occurrence of a label breaks this assumption.
1847 procedure Analyze_Label (N : Node_Id) is
1848 pragma Warnings (Off, N);
1850 Kill_Current_Values;
1853 --------------------------
1854 -- Analyze_Label_Entity --
1855 --------------------------
1857 procedure Analyze_Label_Entity (E : Entity_Id) is
1859 Set_Ekind (E, E_Label);
1860 Set_Etype (E, Standard_Void_Type);
1861 Set_Enclosing_Scope (E, Current_Scope);
1862 Set_Reachable (E, True);
1863 end Analyze_Label_Entity;
1865 ----------------------------
1866 -- Analyze_Loop_Statement --
1867 ----------------------------
1869 procedure Analyze_Loop_Statement (N : Node_Id) is
1870 Loop_Statement : constant Node_Id := N;
1872 Id : constant Node_Id := Identifier (Loop_Statement);
1873 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
1877 if Present (Id) then
1879 -- Make name visible, e.g. for use in exit statements. Loop
1880 -- labels are always considered to be referenced.
1884 Generate_Reference (Ent, Loop_Statement, ' ');
1885 Generate_Definition (Ent);
1887 -- If we found a label, mark its type. If not, ignore it, since it
1888 -- means we have a conflicting declaration, which would already have
1889 -- been diagnosed at declaration time. Set Label_Construct of the
1890 -- implicit label declaration, which is not created by the parser
1891 -- for generic units.
1893 if Ekind (Ent) = E_Label then
1894 Set_Ekind (Ent, E_Loop);
1896 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
1897 Set_Label_Construct (Parent (Ent), Loop_Statement);
1901 -- Case of no identifier present
1906 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
1907 Set_Etype (Ent, Standard_Void_Type);
1908 Set_Parent (Ent, Loop_Statement);
1911 -- Kill current values on entry to loop, since statements in body
1912 -- of loop may have been executed before the loop is entered.
1913 -- Similarly we kill values after the loop, since we do not know
1914 -- that the body of the loop was executed.
1916 Kill_Current_Values;
1918 Analyze_Iteration_Scheme (Iter);
1919 Analyze_Statements (Statements (Loop_Statement));
1920 Process_End_Label (Loop_Statement, 'e', Ent);
1922 Kill_Current_Values;
1923 Check_Infinite_Loop_Warning (N);
1924 end Analyze_Loop_Statement;
1926 ----------------------------
1927 -- Analyze_Null_Statement --
1928 ----------------------------
1930 -- Note: the semantics of the null statement is implemented by a single
1931 -- null statement, too bad everything isn't as simple as this!
1933 procedure Analyze_Null_Statement (N : Node_Id) is
1934 pragma Warnings (Off, N);
1937 end Analyze_Null_Statement;
1939 ------------------------
1940 -- Analyze_Statements --
1941 ------------------------
1943 procedure Analyze_Statements (L : List_Id) is
1948 -- The labels declared in the statement list are reachable from
1949 -- statements in the list. We do this as a prepass so that any
1950 -- goto statement will be properly flagged if its target is not
1951 -- reachable. This is not required, but is nice behavior!
1954 while Present (S) loop
1955 if Nkind (S) = N_Label then
1956 Analyze (Identifier (S));
1957 Lab := Entity (Identifier (S));
1959 -- If we found a label mark it as reachable
1961 if Ekind (Lab) = E_Label then
1962 Generate_Definition (Lab);
1963 Set_Reachable (Lab);
1965 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
1966 Set_Label_Construct (Parent (Lab), S);
1969 -- If we failed to find a label, it means the implicit declaration
1970 -- of the label was hidden. A for-loop parameter can do this to
1971 -- a label with the same name inside the loop, since the implicit
1972 -- label declaration is in the innermost enclosing body or block
1976 Error_Msg_Sloc := Sloc (Lab);
1978 ("implicit label declaration for & is hidden#",
1986 -- Perform semantic analysis on all statements
1988 Conditional_Statements_Begin;
1991 while Present (S) loop
1996 Conditional_Statements_End;
1998 -- Make labels unreachable. Visibility is not sufficient, because
1999 -- labels in one if-branch for example are not reachable from the
2000 -- other branch, even though their declarations are in the enclosing
2001 -- declarative part.
2004 while Present (S) loop
2005 if Nkind (S) = N_Label then
2006 Set_Reachable (Entity (Identifier (S)), False);
2011 end Analyze_Statements;
2013 ----------------------------
2014 -- Check_Unreachable_Code --
2015 ----------------------------
2017 procedure Check_Unreachable_Code (N : Node_Id) is
2018 Error_Loc : Source_Ptr;
2022 if Is_List_Member (N)
2023 and then Comes_From_Source (N)
2029 Nxt := Original_Node (Next (N));
2031 -- If a label follows us, then we never have dead code, since
2032 -- someone could branch to the label, so we just ignore it.
2034 if Nkind (Nxt) = N_Label then
2037 -- Otherwise see if we have a real statement following us
2040 and then Comes_From_Source (Nxt)
2041 and then Is_Statement (Nxt)
2043 -- Special very annoying exception. If we have a return that
2044 -- follows a raise, then we allow it without a warning, since
2045 -- the Ada RM annoyingly requires a useless return here!
2047 if Nkind (Original_Node (N)) /= N_Raise_Statement
2048 or else Nkind (Nxt) /= N_Simple_Return_Statement
2050 -- The rather strange shenanigans with the warning message
2051 -- here reflects the fact that Kill_Dead_Code is very good
2052 -- at removing warnings in deleted code, and this is one
2053 -- warning we would prefer NOT to have removed.
2055 Error_Loc := Sloc (Nxt);
2057 -- If we have unreachable code, analyze and remove the
2058 -- unreachable code, since it is useless and we don't
2059 -- want to generate junk warnings.
2061 -- We skip this step if we are not in code generation mode.
2062 -- This is the one case where we remove dead code in the
2063 -- semantics as opposed to the expander, and we do not want
2064 -- to remove code if we are not in code generation mode,
2065 -- since this messes up the ASIS trees.
2067 -- Note that one might react by moving the whole circuit to
2068 -- exp_ch5, but then we lose the warning in -gnatc mode.
2070 if Operating_Mode = Generate_Code then
2074 -- Quit deleting when we have nothing more to delete
2075 -- or if we hit a label (since someone could transfer
2076 -- control to a label, so we should not delete it).
2078 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2080 -- Statement/declaration is to be deleted
2084 Kill_Dead_Code (Nxt);
2088 -- Now issue the warning
2090 Error_Msg ("?unreachable code!", Error_Loc);
2093 -- If the unconditional transfer of control instruction is
2094 -- the last statement of a sequence, then see if our parent
2095 -- is one of the constructs for which we count unblocked exits,
2096 -- and if so, adjust the count.
2101 -- Statements in THEN part or ELSE part of IF statement
2103 if Nkind (P) = N_If_Statement then
2106 -- Statements in ELSIF part of an IF statement
2108 elsif Nkind (P) = N_Elsif_Part then
2110 pragma Assert (Nkind (P) = N_If_Statement);
2112 -- Statements in CASE statement alternative
2114 elsif Nkind (P) = N_Case_Statement_Alternative then
2116 pragma Assert (Nkind (P) = N_Case_Statement);
2118 -- Statements in body of block
2120 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2121 and then Nkind (Parent (P)) = N_Block_Statement
2125 -- Statements in exception handler in a block
2127 elsif Nkind (P) = N_Exception_Handler
2128 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2129 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2133 -- None of these cases, so return
2139 -- This was one of the cases we are looking for (i.e. the
2140 -- parent construct was IF, CASE or block) so decrement count.
2142 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2146 end Check_Unreachable_Code;