1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2006, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 2, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
25 ------------------------------------------------------------------------------
27 with Atree; use Atree;
28 with Checks; use Checks;
29 with Debug; use Debug;
30 with Einfo; use Einfo;
31 with Errout; use Errout;
32 with Expander; use Expander;
33 with Exp_Util; use Exp_Util;
34 with Freeze; use Freeze;
36 with Lib.Xref; use Lib.Xref;
37 with Nlists; use Nlists;
38 with Nmake; use Nmake;
40 with Rtsfind; use Rtsfind;
42 with Sem_Case; use Sem_Case;
43 with Sem_Ch3; use Sem_Ch3;
44 with Sem_Ch8; use Sem_Ch8;
45 with Sem_Disp; use Sem_Disp;
46 with Sem_Elab; use Sem_Elab;
47 with Sem_Eval; use Sem_Eval;
48 with Sem_Res; use Sem_Res;
49 with Sem_Type; use Sem_Type;
50 with Sem_Util; use Sem_Util;
51 with Sem_Warn; use Sem_Warn;
52 with Snames; use Snames;
53 with Stand; use Stand;
54 with Sinfo; use Sinfo;
55 with Targparm; use Targparm;
56 with Tbuild; use Tbuild;
57 with Uintp; use Uintp;
59 package body Sem_Ch5 is
61 Unblocked_Exit_Count : Nat := 0;
62 -- This variable is used when processing if statements, case statements,
63 -- and block statements. It counts the number of exit points that are
64 -- not blocked by unconditional transfer instructions: for IF and CASE,
65 -- these are the branches of the conditional; for a block, they are the
66 -- statement sequence of the block, and the statement sequences of any
67 -- exception handlers that are part of the block. When processing is
68 -- complete, if this count is zero, it means that control cannot fall
69 -- through the IF, CASE or block statement. This is used for the
70 -- generation of warning messages. This variable is recursively saved
71 -- on entry to processing the construct, and restored on exit.
73 -----------------------
74 -- Local Subprograms --
75 -----------------------
77 procedure Analyze_Iteration_Scheme (N : Node_Id);
79 ------------------------
80 -- Analyze_Assignment --
81 ------------------------
83 procedure Analyze_Assignment (N : Node_Id) is
84 Lhs : constant Node_Id := Name (N);
85 Rhs : constant Node_Id := Expression (N);
90 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
91 -- N is the node for the left hand side of an assignment, and it
92 -- is not a variable. This routine issues an appropriate diagnostic.
95 -- This is called to kill current value settings of a simple variable
96 -- on the left hand side. We call it if we find any error in analyzing
97 -- the assignment, and at the end of processing before setting any new
98 -- current values in place.
100 procedure Set_Assignment_Type
102 Opnd_Type : in out Entity_Id);
103 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
104 -- is the nominal subtype. This procedure is used to deal with cases
105 -- where the nominal subtype must be replaced by the actual subtype.
107 -------------------------------
108 -- Diagnose_Non_Variable_Lhs --
109 -------------------------------
111 procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
113 -- Not worth posting another error if left hand side already
114 -- flagged as being illegal in some respect
116 if Error_Posted (N) then
119 -- Some special bad cases of entity names
121 elsif Is_Entity_Name (N) then
122 if Ekind (Entity (N)) = E_In_Parameter then
124 ("assignment to IN mode parameter not allowed", N);
126 -- Private declarations in a protected object are turned into
127 -- constants when compiling a protected function.
129 elsif Present (Scope (Entity (N)))
130 and then Is_Protected_Type (Scope (Entity (N)))
132 (Ekind (Current_Scope) = E_Function
134 Ekind (Enclosing_Dynamic_Scope (Current_Scope)) = E_Function)
137 ("protected function cannot modify protected object", N);
139 elsif Ekind (Entity (N)) = E_Loop_Parameter then
141 ("assignment to loop parameter not allowed", N);
145 ("left hand side of assignment must be a variable", N);
148 -- For indexed components or selected components, test prefix
150 elsif Nkind (N) = N_Indexed_Component then
151 Diagnose_Non_Variable_Lhs (Prefix (N));
153 -- Another special case for assignment to discriminant
155 elsif Nkind (N) = N_Selected_Component then
156 if Present (Entity (Selector_Name (N)))
157 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
160 ("assignment to discriminant not allowed", N);
162 Diagnose_Non_Variable_Lhs (Prefix (N));
166 -- If we fall through, we have no special message to issue!
168 Error_Msg_N ("left hand side of assignment must be a variable", N);
170 end Diagnose_Non_Variable_Lhs;
176 procedure Kill_Lhs is
178 if Is_Entity_Name (Lhs) then
180 Ent : constant Entity_Id := Entity (Lhs);
182 if Present (Ent) then
183 Kill_Current_Values (Ent);
189 -------------------------
190 -- Set_Assignment_Type --
191 -------------------------
193 procedure Set_Assignment_Type
195 Opnd_Type : in out Entity_Id)
198 Require_Entity (Opnd);
200 -- If the assignment operand is an in-out or out parameter, then we
201 -- get the actual subtype (needed for the unconstrained case).
202 -- If the operand is the actual in an entry declaration, then within
203 -- the accept statement it is replaced with a local renaming, which
204 -- may also have an actual subtype.
206 if Is_Entity_Name (Opnd)
207 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
208 or else Ekind (Entity (Opnd)) =
210 or else Ekind (Entity (Opnd)) =
211 E_Generic_In_Out_Parameter
213 (Ekind (Entity (Opnd)) = E_Variable
214 and then Nkind (Parent (Entity (Opnd))) =
215 N_Object_Renaming_Declaration
216 and then Nkind (Parent (Parent (Entity (Opnd)))) =
219 Opnd_Type := Get_Actual_Subtype (Opnd);
221 -- If assignment operand is a component reference, then we get the
222 -- actual subtype of the component for the unconstrained case.
225 (Nkind (Opnd) = N_Selected_Component
226 or else Nkind (Opnd) = N_Explicit_Dereference)
227 and then not Is_Unchecked_Union (Opnd_Type)
229 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
231 if Present (Decl) then
232 Insert_Action (N, Decl);
233 Mark_Rewrite_Insertion (Decl);
235 Opnd_Type := Defining_Identifier (Decl);
236 Set_Etype (Opnd, Opnd_Type);
237 Freeze_Itype (Opnd_Type, N);
239 elsif Is_Constrained (Etype (Opnd)) then
240 Opnd_Type := Etype (Opnd);
243 -- For slice, use the constrained subtype created for the slice
245 elsif Nkind (Opnd) = N_Slice then
246 Opnd_Type := Etype (Opnd);
248 end Set_Assignment_Type;
250 -- Start of processing for Analyze_Assignment
256 -- Start type analysis for assignment
260 -- In the most general case, both Lhs and Rhs can be overloaded, and we
261 -- must compute the intersection of the possible types on each side.
263 if Is_Overloaded (Lhs) then
270 Get_First_Interp (Lhs, I, It);
272 while Present (It.Typ) loop
273 if Has_Compatible_Type (Rhs, It.Typ) then
274 if T1 /= Any_Type then
276 -- An explicit dereference is overloaded if the prefix
277 -- is. Try to remove the ambiguity on the prefix, the
278 -- error will be posted there if the ambiguity is real.
280 if Nkind (Lhs) = N_Explicit_Dereference then
283 PI1 : Interp_Index := 0;
289 Get_First_Interp (Prefix (Lhs), PI, PIt);
291 while Present (PIt.Typ) loop
292 if Is_Access_Type (PIt.Typ)
293 and then Has_Compatible_Type
294 (Rhs, Designated_Type (PIt.Typ))
298 Disambiguate (Prefix (Lhs),
301 if PIt = No_Interp then
303 ("ambiguous left-hand side"
304 & " in assignment", Lhs);
307 Resolve (Prefix (Lhs), PIt.Typ);
317 Get_Next_Interp (PI, PIt);
323 ("ambiguous left-hand side in assignment", Lhs);
331 Get_Next_Interp (I, It);
335 if T1 = Any_Type then
337 ("no valid types for left-hand side for assignment", Lhs);
345 if not Is_Variable (Lhs) then
347 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
348 -- a protected object.
355 if Ada_Version >= Ada_05 then
357 -- Handle chains of renamings
360 while Nkind (Ent) in N_Has_Entity
361 and then Present (Entity (Ent))
362 and then Present (Renamed_Object (Entity (Ent)))
364 Ent := Renamed_Object (Entity (Ent));
367 if (Nkind (Ent) = N_Attribute_Reference
368 and then Attribute_Name (Ent) = Name_Priority)
370 -- Renamings of the attribute Priority applied to protected
371 -- objects have been previously expanded into calls to the
372 -- Get_Ceiling run-time subprogram.
375 (Nkind (Ent) = N_Function_Call
376 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
378 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
380 -- The enclosing subprogram cannot be a protected function
383 while not (Is_Subprogram (S)
384 and then Convention (S) = Convention_Protected)
385 and then S /= Standard_Standard
390 if Ekind (S) = E_Function
391 and then Convention (S) = Convention_Protected
394 ("protected function cannot modify protected object",
398 -- Changes of the ceiling priority of the protected object
399 -- are only effective if the Ceiling_Locking policy is in
400 -- effect (AARM D.5.2 (5/2)).
402 if Locking_Policy /= 'C' then
403 Error_Msg_N ("assignment to the attribute PRIORITY has " &
405 Error_Msg_N ("\since no Locking_Policy has been " &
414 Diagnose_Non_Variable_Lhs (Lhs);
417 elsif Is_Limited_Type (T1)
418 and then not Assignment_OK (Lhs)
419 and then not Assignment_OK (Original_Node (Lhs))
422 ("left hand of assignment must not be limited type", Lhs);
423 Explain_Limited_Type (T1, Lhs);
427 -- Resolution may have updated the subtype, in case the left-hand
428 -- side is a private protected component. Use the correct subtype
429 -- to avoid scoping issues in the back-end.
433 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
434 -- type. For example:
438 -- type Acc is access P.T;
441 -- with Pkg; use Acc;
442 -- procedure Example is
445 -- A.all := B.all; -- ERROR
448 if Nkind (Lhs) = N_Explicit_Dereference
449 and then Ekind (T1) = E_Incomplete_Type
451 Error_Msg_N ("invalid use of incomplete type", Lhs);
456 Set_Assignment_Type (Lhs, T1);
459 Check_Unset_Reference (Rhs);
461 -- Remaining steps are skipped if Rhs was syntactically in error
470 if not Covers (T1, T2) then
471 Wrong_Type (Rhs, Etype (Lhs));
476 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
477 -- types, use the non-limited view if available
479 if Nkind (Rhs) = N_Explicit_Dereference
480 and then Ekind (T2) = E_Incomplete_Type
481 and then Is_Tagged_Type (T2)
482 and then Present (Non_Limited_View (T2))
484 T2 := Non_Limited_View (T2);
487 Set_Assignment_Type (Rhs, T2);
489 if Total_Errors_Detected /= 0 then
499 if T1 = Any_Type or else T2 = Any_Type then
504 if (Is_Class_Wide_Type (T2) or else Is_Dynamically_Tagged (Rhs))
505 and then not Is_Class_Wide_Type (T1)
507 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
509 elsif Is_Class_Wide_Type (T1)
510 and then not Is_Class_Wide_Type (T2)
511 and then not Is_Tag_Indeterminate (Rhs)
512 and then not Is_Dynamically_Tagged (Rhs)
514 Error_Msg_N ("dynamically tagged expression required!", Rhs);
517 -- Propagate the tag from a class-wide target to the rhs when the rhs
518 -- is a tag-indeterminate call.
520 if Is_Tag_Indeterminate (Rhs) then
521 if Is_Class_Wide_Type (T1) then
522 Propagate_Tag (Lhs, Rhs);
524 elsif Nkind (Rhs) = N_Function_Call
525 and then Is_Entity_Name (Name (Rhs))
526 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
529 ("call to abstract function must be dispatching", Name (Rhs));
531 elsif Nkind (Rhs) = N_Qualified_Expression
532 and then Nkind (Expression (Rhs)) = N_Function_Call
533 and then Is_Entity_Name (Name (Expression (Rhs)))
535 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
538 ("call to abstract function must be dispatching",
539 Name (Expression (Rhs)));
543 -- Ada 2005 (AI-230 and AI-385): When the lhs type is an anonymous
544 -- access type, apply an implicit conversion of the rhs to that type
545 -- to force appropriate static and run-time accessibility checks.
547 if Ada_Version >= Ada_05
548 and then Ekind (T1) = E_Anonymous_Access_Type
550 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
551 Analyze_And_Resolve (Rhs, T1);
556 if Ada_Version >= Ada_05
557 and then Can_Never_Be_Null (T1)
558 and then not Assignment_OK (Lhs)
560 if Nkind (Rhs) = N_Null then
561 Apply_Compile_Time_Constraint_Error
563 Msg => "(Ada 2005) NULL not allowed in null-excluding objects?",
564 Reason => CE_Null_Not_Allowed);
567 elsif not Can_Never_Be_Null (T2) then
569 Convert_To (T1, Relocate_Node (Rhs)));
570 Analyze_And_Resolve (Rhs, T1);
574 if Is_Scalar_Type (T1) then
575 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
577 -- For array types, verify that lengths match. If the right hand side
578 -- if a function call that has been inlined, the assignment has been
579 -- rewritten as a block, and the constraint check will be applied to the
580 -- assignment within the block.
582 elsif Is_Array_Type (T1)
584 (Nkind (Rhs) /= N_Type_Conversion
585 or else Is_Constrained (Etype (Rhs)))
587 (Nkind (Rhs) /= N_Function_Call
588 or else Nkind (N) /= N_Block_Statement)
590 -- Assignment verifies that the length of the Lsh and Rhs are equal,
591 -- but of course the indices do not have to match. If the right-hand
592 -- side is a type conversion to an unconstrained type, a length check
593 -- is performed on the expression itself during expansion. In rare
594 -- cases, the redundant length check is computed on an index type
595 -- with a different representation, triggering incorrect code in
598 Apply_Length_Check (Rhs, Etype (Lhs));
601 -- Discriminant checks are applied in the course of expansion
606 -- Note: modifications of the Lhs may only be recorded after
607 -- checks have been applied.
609 Note_Possible_Modification (Lhs);
611 -- ??? a real accessibility check is needed when ???
613 -- Post warning for redundant assignment or variable to itself
615 if Warn_On_Redundant_Constructs
617 -- We only warn for source constructs
619 and then Comes_From_Source (N)
621 -- Where the entity is the same on both sides
623 and then Is_Entity_Name (Lhs)
624 and then Is_Entity_Name (Original_Node (Rhs))
625 and then Entity (Lhs) = Entity (Original_Node (Rhs))
627 -- But exclude the case where the right side was an operation
628 -- that got rewritten (e.g. JUNK + K, where K was known to be
629 -- zero). We don't want to warn in such a case, since it is
630 -- reasonable to write such expressions especially when K is
631 -- defined symbolically in some other package.
633 and then Nkind (Original_Node (Rhs)) not in N_Op
636 ("?useless assignment of & to itself", N, Entity (Lhs));
639 -- Check for non-allowed composite assignment
641 if not Support_Composite_Assign_On_Target
642 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
643 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
645 Error_Msg_CRT ("composite assignment", N);
648 -- Check elaboration warning for left side if not in elab code
650 if not In_Subprogram_Or_Concurrent_Unit then
651 Check_Elab_Assign (Lhs);
654 -- Final step. If left side is an entity, then we may be able to
655 -- reset the current tracked values to new safe values. We only have
656 -- something to do if the left side is an entity name, and expansion
657 -- has not modified the node into something other than an assignment,
658 -- and of course we only capture values if it is safe to do so.
660 if Is_Entity_Name (Lhs)
661 and then Nkind (N) = N_Assignment_Statement
664 Ent : constant Entity_Id := Entity (Lhs);
667 if Safe_To_Capture_Value (N, Ent) then
669 -- If simple variable on left side, warn if this assignment
670 -- blots out another one (rendering it useless) and note
671 -- location of assignment in case no one references value.
672 -- We only do this for source assignments, otherwise we can
673 -- generate bogus warnings when an assignment is rewritten as
674 -- another assignment, and gets tied up with itself.
676 if Warn_On_Modified_Unread
677 and then Ekind (Ent) = E_Variable
678 and then Comes_From_Source (N)
679 and then In_Extended_Main_Source_Unit (Ent)
681 Warn_On_Useless_Assignment (Ent, Sloc (N));
682 Set_Last_Assignment (Ent, Lhs);
685 -- If we are assigning an access type and the left side is an
686 -- entity, then make sure that the Is_Known_[Non_]Null flags
687 -- properly reflect the state of the entity after assignment.
689 if Is_Access_Type (T1) then
690 if Known_Non_Null (Rhs) then
691 Set_Is_Known_Non_Null (Ent, True);
693 elsif Known_Null (Rhs)
694 and then not Can_Never_Be_Null (Ent)
696 Set_Is_Known_Null (Ent, True);
699 Set_Is_Known_Null (Ent, False);
701 if not Can_Never_Be_Null (Ent) then
702 Set_Is_Known_Non_Null (Ent, False);
706 -- For discrete types, we may be able to set the current value
707 -- if the value is known at compile time.
709 elsif Is_Discrete_Type (T1)
710 and then Compile_Time_Known_Value (Rhs)
712 Set_Current_Value (Ent, Rhs);
714 Set_Current_Value (Ent, Empty);
717 -- If not safe to capture values, kill them
724 end Analyze_Assignment;
726 -----------------------------
727 -- Analyze_Block_Statement --
728 -----------------------------
730 procedure Analyze_Block_Statement (N : Node_Id) is
731 Decls : constant List_Id := Declarations (N);
732 Id : constant Node_Id := Identifier (N);
733 HSS : constant Node_Id := Handled_Statement_Sequence (N);
736 -- If no handled statement sequence is present, things are really
737 -- messed up, and we just return immediately (this is a defence
738 -- against previous errors).
744 -- Normal processing with HSS present
747 EH : constant List_Id := Exception_Handlers (HSS);
748 Ent : Entity_Id := Empty;
751 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
752 -- Recursively save value of this global, will be restored on exit
755 -- Initialize unblocked exit count for statements of begin block
756 -- plus one for each excption handler that is present.
758 Unblocked_Exit_Count := 1;
761 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
764 -- If a label is present analyze it and mark it as referenced
770 -- An error defense. If we have an identifier, but no entity,
771 -- then something is wrong. If we have previous errors, then
772 -- just remove the identifier and continue, otherwise raise
776 if Total_Errors_Detected /= 0 then
777 Set_Identifier (N, Empty);
783 Set_Ekind (Ent, E_Block);
784 Generate_Reference (Ent, N, ' ');
785 Generate_Definition (Ent);
787 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
788 Set_Label_Construct (Parent (Ent), N);
793 -- If no entity set, create a label entity
796 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
797 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
801 Set_Etype (Ent, Standard_Void_Type);
802 Set_Block_Node (Ent, Identifier (N));
805 if Present (Decls) then
806 Analyze_Declarations (Decls);
811 Process_End_Label (HSS, 'e', Ent);
813 -- If exception handlers are present, then we indicate that
814 -- enclosing scopes contain a block with handlers. We only
815 -- need to mark non-generic scopes.
820 Set_Has_Nested_Block_With_Handler (S);
821 exit when Is_Overloadable (S)
822 or else Ekind (S) = E_Package
823 or else Is_Generic_Unit (S);
828 Check_References (Ent);
829 Warn_On_Useless_Assignments (Ent);
832 if Unblocked_Exit_Count = 0 then
833 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
834 Check_Unreachable_Code (N);
836 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
839 end Analyze_Block_Statement;
841 ----------------------------
842 -- Analyze_Case_Statement --
843 ----------------------------
845 procedure Analyze_Case_Statement (N : Node_Id) is
847 Exp_Type : Entity_Id;
848 Exp_Btype : Entity_Id;
851 Others_Present : Boolean;
853 Statements_Analyzed : Boolean := False;
854 -- Set True if at least some statement sequences get analyzed.
855 -- If False on exit, means we had a serious error that prevented
856 -- full analysis of the case statement, and as a result it is not
857 -- a good idea to output warning messages about unreachable code.
859 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
860 -- Recursively save value of this global, will be restored on exit
862 procedure Non_Static_Choice_Error (Choice : Node_Id);
863 -- Error routine invoked by the generic instantiation below when
864 -- the case statment has a non static choice.
866 procedure Process_Statements (Alternative : Node_Id);
867 -- Analyzes all the statements associated to a case alternative.
868 -- Needed by the generic instantiation below.
870 package Case_Choices_Processing is new
871 Generic_Choices_Processing
872 (Get_Alternatives => Alternatives,
873 Get_Choices => Discrete_Choices,
874 Process_Empty_Choice => No_OP,
875 Process_Non_Static_Choice => Non_Static_Choice_Error,
876 Process_Associated_Node => Process_Statements);
877 use Case_Choices_Processing;
878 -- Instantiation of the generic choice processing package
880 -----------------------------
881 -- Non_Static_Choice_Error --
882 -----------------------------
884 procedure Non_Static_Choice_Error (Choice : Node_Id) is
887 ("choice given in case statement is not static!", Choice);
888 end Non_Static_Choice_Error;
890 ------------------------
891 -- Process_Statements --
892 ------------------------
894 procedure Process_Statements (Alternative : Node_Id) is
895 Choices : constant List_Id := Discrete_Choices (Alternative);
899 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
900 Statements_Analyzed := True;
902 -- An interesting optimization. If the case statement expression
903 -- is a simple entity, then we can set the current value within
904 -- an alternative if the alternative has one possible value.
908 -- when 2 | 3 => beta
909 -- when others => gamma
911 -- Here we know that N is initially 1 within alpha, but for beta
912 -- and gamma, we do not know anything more about the initial value.
914 if Is_Entity_Name (Exp) then
917 if Ekind (Ent) = E_Variable
919 Ekind (Ent) = E_In_Out_Parameter
921 Ekind (Ent) = E_Out_Parameter
923 if List_Length (Choices) = 1
924 and then Nkind (First (Choices)) in N_Subexpr
925 and then Compile_Time_Known_Value (First (Choices))
927 Set_Current_Value (Entity (Exp), First (Choices));
930 Analyze_Statements (Statements (Alternative));
932 -- After analyzing the case, set the current value to empty
933 -- since we won't know what it is for the next alternative
934 -- (unless reset by this same circuit), or after the case.
936 Set_Current_Value (Entity (Exp), Empty);
941 -- Case where expression is not an entity name of a variable
943 Analyze_Statements (Statements (Alternative));
944 end Process_Statements;
946 -- Table to record choices. Put after subprograms since we make
947 -- a call to Number_Of_Choices to get the right number of entries.
949 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
951 -- Start of processing for Analyze_Case_Statement
954 Unblocked_Exit_Count := 0;
955 Exp := Expression (N);
958 -- The expression must be of any discrete type. In rare cases, the
959 -- expander constructs a case statement whose expression has a private
960 -- type whose full view is discrete. This can happen when generating
961 -- a stream operation for a variant type after the type is frozen,
962 -- when the partial of view of the type of the discriminant is private.
963 -- In that case, use the full view to analyze case alternatives.
965 if not Is_Overloaded (Exp)
966 and then not Comes_From_Source (N)
967 and then Is_Private_Type (Etype (Exp))
968 and then Present (Full_View (Etype (Exp)))
969 and then Is_Discrete_Type (Full_View (Etype (Exp)))
971 Resolve (Exp, Etype (Exp));
972 Exp_Type := Full_View (Etype (Exp));
975 Analyze_And_Resolve (Exp, Any_Discrete);
976 Exp_Type := Etype (Exp);
979 Check_Unset_Reference (Exp);
980 Exp_Btype := Base_Type (Exp_Type);
982 -- The expression must be of a discrete type which must be determinable
983 -- independently of the context in which the expression occurs, but
984 -- using the fact that the expression must be of a discrete type.
985 -- Moreover, the type this expression must not be a character literal
986 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
988 -- If error already reported by Resolve, nothing more to do
990 if Exp_Btype = Any_Discrete
991 or else Exp_Btype = Any_Type
995 elsif Exp_Btype = Any_Character then
997 ("character literal as case expression is ambiguous", Exp);
1000 elsif Ada_Version = Ada_83
1001 and then (Is_Generic_Type (Exp_Btype)
1002 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1005 ("(Ada 83) case expression cannot be of a generic type", Exp);
1009 -- If the case expression is a formal object of mode in out, then
1010 -- treat it as having a nonstatic subtype by forcing use of the base
1011 -- type (which has to get passed to Check_Case_Choices below). Also
1012 -- use base type when the case expression is parenthesized.
1014 if Paren_Count (Exp) > 0
1015 or else (Is_Entity_Name (Exp)
1016 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1018 Exp_Type := Exp_Btype;
1021 -- Call instantiated Analyze_Choices which does the rest of the work
1024 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
1026 if Exp_Type = Universal_Integer and then not Others_Present then
1027 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1030 -- If all our exits were blocked by unconditional transfers of control,
1031 -- then the entire CASE statement acts as an unconditional transfer of
1032 -- control, so treat it like one, and check unreachable code. Skip this
1033 -- test if we had serious errors preventing any statement analysis.
1035 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1036 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1037 Check_Unreachable_Code (N);
1039 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1042 if not Expander_Active
1043 and then Compile_Time_Known_Value (Expression (N))
1044 and then Serious_Errors_Detected = 0
1047 Chosen : constant Node_Id := Find_Static_Alternative (N);
1051 Alt := First (Alternatives (N));
1053 while Present (Alt) loop
1054 if Alt /= Chosen then
1055 Remove_Warning_Messages (Statements (Alt));
1062 end Analyze_Case_Statement;
1064 ----------------------------
1065 -- Analyze_Exit_Statement --
1066 ----------------------------
1068 -- If the exit includes a name, it must be the name of a currently open
1069 -- loop. Otherwise there must be an innermost open loop on the stack,
1070 -- to which the statement implicitly refers.
1072 procedure Analyze_Exit_Statement (N : Node_Id) is
1073 Target : constant Node_Id := Name (N);
1074 Cond : constant Node_Id := Condition (N);
1075 Scope_Id : Entity_Id;
1081 Check_Unreachable_Code (N);
1084 if Present (Target) then
1086 U_Name := Entity (Target);
1088 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1089 Error_Msg_N ("invalid loop name in exit statement", N);
1092 Set_Has_Exit (U_Name);
1099 for J in reverse 0 .. Scope_Stack.Last loop
1100 Scope_Id := Scope_Stack.Table (J).Entity;
1101 Kind := Ekind (Scope_Id);
1104 and then (No (Target) or else Scope_Id = U_Name) then
1105 Set_Has_Exit (Scope_Id);
1108 elsif Kind = E_Block
1109 or else Kind = E_Loop
1110 or else Kind = E_Return_Statement
1116 ("cannot exit from program unit or accept statement", N);
1121 -- Verify that if present the condition is a Boolean expression
1123 if Present (Cond) then
1124 Analyze_And_Resolve (Cond, Any_Boolean);
1125 Check_Unset_Reference (Cond);
1127 end Analyze_Exit_Statement;
1129 ----------------------------
1130 -- Analyze_Goto_Statement --
1131 ----------------------------
1133 procedure Analyze_Goto_Statement (N : Node_Id) is
1134 Label : constant Node_Id := Name (N);
1135 Scope_Id : Entity_Id;
1136 Label_Scope : Entity_Id;
1137 Label_Ent : Entity_Id;
1140 Check_Unreachable_Code (N);
1143 Label_Ent := Entity (Label);
1145 -- Ignore previous error
1147 if Label_Ent = Any_Id then
1150 -- We just have a label as the target of a goto
1152 elsif Ekind (Label_Ent) /= E_Label then
1153 Error_Msg_N ("target of goto statement must be a label", Label);
1156 -- Check that the target of the goto is reachable according to Ada
1157 -- scoping rules. Note: the special gotos we generate for optimizing
1158 -- local handling of exceptions would violate these rules, but we mark
1159 -- such gotos as analyzed when built, so this code is never entered.
1161 elsif not Reachable (Label_Ent) then
1162 Error_Msg_N ("target of goto statement is not reachable", Label);
1166 -- Here if goto passes initial validity checks
1168 Label_Scope := Enclosing_Scope (Label_Ent);
1170 for J in reverse 0 .. Scope_Stack.Last loop
1171 Scope_Id := Scope_Stack.Table (J).Entity;
1173 if Label_Scope = Scope_Id
1174 or else (Ekind (Scope_Id) /= E_Block
1175 and then Ekind (Scope_Id) /= E_Loop
1176 and then Ekind (Scope_Id) /= E_Return_Statement)
1178 if Scope_Id /= Label_Scope then
1180 ("cannot exit from program unit or accept statement", N);
1187 raise Program_Error;
1188 end Analyze_Goto_Statement;
1190 --------------------------
1191 -- Analyze_If_Statement --
1192 --------------------------
1194 -- A special complication arises in the analysis of if statements
1196 -- The expander has circuitry to completely delete code that it
1197 -- can tell will not be executed (as a result of compile time known
1198 -- conditions). In the analyzer, we ensure that code that will be
1199 -- deleted in this manner is analyzed but not expanded. This is
1200 -- obviously more efficient, but more significantly, difficulties
1201 -- arise if code is expanded and then eliminated (e.g. exception
1202 -- table entries disappear). Similarly, itypes generated in deleted
1203 -- code must be frozen from start, because the nodes on which they
1204 -- depend will not be available at the freeze point.
1206 procedure Analyze_If_Statement (N : Node_Id) is
1209 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1210 -- Recursively save value of this global, will be restored on exit
1212 Save_In_Deleted_Code : Boolean;
1214 Del : Boolean := False;
1215 -- This flag gets set True if a True condition has been found,
1216 -- which means that remaining ELSE/ELSIF parts are deleted.
1218 procedure Analyze_Cond_Then (Cnode : Node_Id);
1219 -- This is applied to either the N_If_Statement node itself or
1220 -- to an N_Elsif_Part node. It deals with analyzing the condition
1221 -- and the THEN statements associated with it.
1223 -----------------------
1224 -- Analyze_Cond_Then --
1225 -----------------------
1227 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1228 Cond : constant Node_Id := Condition (Cnode);
1229 Tstm : constant List_Id := Then_Statements (Cnode);
1232 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1233 Analyze_And_Resolve (Cond, Any_Boolean);
1234 Check_Unset_Reference (Cond);
1235 Set_Current_Value_Condition (Cnode);
1237 -- If already deleting, then just analyze then statements
1240 Analyze_Statements (Tstm);
1242 -- Compile time known value, not deleting yet
1244 elsif Compile_Time_Known_Value (Cond) then
1245 Save_In_Deleted_Code := In_Deleted_Code;
1247 -- If condition is True, then analyze the THEN statements
1248 -- and set no expansion for ELSE and ELSIF parts.
1250 if Is_True (Expr_Value (Cond)) then
1251 Analyze_Statements (Tstm);
1253 Expander_Mode_Save_And_Set (False);
1254 In_Deleted_Code := True;
1256 -- If condition is False, analyze THEN with expansion off
1258 else -- Is_False (Expr_Value (Cond))
1259 Expander_Mode_Save_And_Set (False);
1260 In_Deleted_Code := True;
1261 Analyze_Statements (Tstm);
1262 Expander_Mode_Restore;
1263 In_Deleted_Code := Save_In_Deleted_Code;
1266 -- Not known at compile time, not deleting, normal analysis
1269 Analyze_Statements (Tstm);
1271 end Analyze_Cond_Then;
1273 -- Start of Analyze_If_Statement
1276 -- Initialize exit count for else statements. If there is no else
1277 -- part, this count will stay non-zero reflecting the fact that the
1278 -- uncovered else case is an unblocked exit.
1280 Unblocked_Exit_Count := 1;
1281 Analyze_Cond_Then (N);
1283 -- Now to analyze the elsif parts if any are present
1285 if Present (Elsif_Parts (N)) then
1286 E := First (Elsif_Parts (N));
1287 while Present (E) loop
1288 Analyze_Cond_Then (E);
1293 if Present (Else_Statements (N)) then
1294 Analyze_Statements (Else_Statements (N));
1297 -- If all our exits were blocked by unconditional transfers of control,
1298 -- then the entire IF statement acts as an unconditional transfer of
1299 -- control, so treat it like one, and check unreachable code.
1301 if Unblocked_Exit_Count = 0 then
1302 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1303 Check_Unreachable_Code (N);
1305 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1309 Expander_Mode_Restore;
1310 In_Deleted_Code := Save_In_Deleted_Code;
1313 if not Expander_Active
1314 and then Compile_Time_Known_Value (Condition (N))
1315 and then Serious_Errors_Detected = 0
1317 if Is_True (Expr_Value (Condition (N))) then
1318 Remove_Warning_Messages (Else_Statements (N));
1320 if Present (Elsif_Parts (N)) then
1321 E := First (Elsif_Parts (N));
1323 while Present (E) loop
1324 Remove_Warning_Messages (Then_Statements (E));
1330 Remove_Warning_Messages (Then_Statements (N));
1333 end Analyze_If_Statement;
1335 ----------------------------------------
1336 -- Analyze_Implicit_Label_Declaration --
1337 ----------------------------------------
1339 -- An implicit label declaration is generated in the innermost
1340 -- enclosing declarative part. This is done for labels as well as
1341 -- block and loop names.
1343 -- Note: any changes in this routine may need to be reflected in
1344 -- Analyze_Label_Entity.
1346 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1347 Id : constant Node_Id := Defining_Identifier (N);
1350 Set_Ekind (Id, E_Label);
1351 Set_Etype (Id, Standard_Void_Type);
1352 Set_Enclosing_Scope (Id, Current_Scope);
1353 end Analyze_Implicit_Label_Declaration;
1355 ------------------------------
1356 -- Analyze_Iteration_Scheme --
1357 ------------------------------
1359 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1361 procedure Process_Bounds (R : Node_Id);
1362 -- If the iteration is given by a range, create temporaries and
1363 -- assignment statements block to capture the bounds and perform
1364 -- required finalization actions in case a bound includes a function
1365 -- call that uses the temporary stack. We first pre-analyze a copy of
1366 -- the range in order to determine the expected type, and analyze and
1367 -- resolve the original bounds.
1369 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1370 -- If the bounds are given by a 'Range reference on a function call
1371 -- that returns a controlled array, introduce an explicit declaration
1372 -- to capture the bounds, so that the function result can be finalized
1373 -- in timely fashion.
1375 --------------------
1376 -- Process_Bounds --
1377 --------------------
1379 procedure Process_Bounds (R : Node_Id) is
1380 Loc : constant Source_Ptr := Sloc (N);
1381 R_Copy : constant Node_Id := New_Copy_Tree (R);
1382 Lo : constant Node_Id := Low_Bound (R);
1383 Hi : constant Node_Id := High_Bound (R);
1384 New_Lo_Bound : Node_Id := Empty;
1385 New_Hi_Bound : Node_Id := Empty;
1387 Save_Analysis : Boolean;
1390 (Original_Bound : Node_Id;
1391 Analyzed_Bound : Node_Id) return Node_Id;
1392 -- Create one declaration followed by one assignment statement
1393 -- to capture the value of bound. We create a separate assignment
1394 -- in order to force the creation of a block in case the bound
1395 -- contains a call that uses the secondary stack.
1402 (Original_Bound : Node_Id;
1403 Analyzed_Bound : Node_Id) return Node_Id
1410 -- If the bound is a constant or an object, no need for a separate
1411 -- declaration. If the bound is the result of previous expansion
1412 -- it is already analyzed and should not be modified. Note that
1413 -- the Bound will be resolved later, if needed, as part of the
1414 -- call to Make_Index (literal bounds may need to be resolved to
1417 if Analyzed (Original_Bound) then
1418 return Original_Bound;
1420 elsif Nkind (Analyzed_Bound) = N_Integer_Literal
1421 or else Is_Entity_Name (Analyzed_Bound)
1423 Analyze_And_Resolve (Original_Bound, Typ);
1424 return Original_Bound;
1427 Analyze_And_Resolve (Original_Bound, Typ);
1431 Make_Defining_Identifier (Loc,
1432 Chars => New_Internal_Name ('S'));
1435 Make_Object_Declaration (Loc,
1436 Defining_Identifier => Id,
1437 Object_Definition => New_Occurrence_Of (Typ, Loc));
1439 Insert_Before (Parent (N), Decl);
1443 Make_Assignment_Statement (Loc,
1444 Name => New_Occurrence_Of (Id, Loc),
1445 Expression => Relocate_Node (Original_Bound));
1447 Insert_Before (Parent (N), Assign);
1450 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1452 if Nkind (Assign) = N_Assignment_Statement then
1453 return Expression (Assign);
1455 return Original_Bound;
1459 -- Start of processing for Process_Bounds
1462 -- Determine expected type of range by analyzing separate copy
1463 -- Do the analysis and resolution of the copy of the bounds with
1464 -- expansion disabled, to prevent the generation of finalization
1465 -- actions on each bound. This prevents memory leaks when the
1466 -- bounds contain calls to functions returning controlled arrays.
1468 Set_Parent (R_Copy, Parent (R));
1469 Save_Analysis := Full_Analysis;
1470 Full_Analysis := False;
1471 Expander_Mode_Save_And_Set (False);
1475 if Is_Overloaded (R_Copy) then
1477 -- Apply preference rules for range of predefined integer types,
1478 -- or diagnose true ambiguity.
1483 Found : Entity_Id := Empty;
1486 Get_First_Interp (R_Copy, I, It);
1487 while Present (It.Typ) loop
1488 if Is_Discrete_Type (It.Typ) then
1492 if Scope (Found) = Standard_Standard then
1495 elsif Scope (It.Typ) = Standard_Standard then
1499 -- Both of them are user-defined
1502 ("ambiguous bounds in range of iteration",
1504 Error_Msg_N ("\possible interpretations:", R_Copy);
1505 Error_Msg_NE ("\\} ", R_Copy, Found);
1506 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1512 Get_Next_Interp (I, It);
1518 Expander_Mode_Restore;
1519 Full_Analysis := Save_Analysis;
1521 Typ := Etype (R_Copy);
1523 -- If the type of the discrete range is Universal_Integer, then
1524 -- the bound's type must be resolved to Integer, and any object
1525 -- used to hold the bound must also have type Integer, unless the
1526 -- literal bounds are constant-folded expressions that carry a user-
1529 if Typ = Universal_Integer then
1530 if Nkind (Lo) = N_Integer_Literal
1531 and then Present (Etype (Lo))
1532 and then Scope (Etype (Lo)) /= Standard_Standard
1536 elsif Nkind (Hi) = N_Integer_Literal
1537 and then Present (Etype (Hi))
1538 and then Scope (Etype (Hi)) /= Standard_Standard
1543 Typ := Standard_Integer;
1549 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1550 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1552 -- Propagate staticness to loop range itself, in case the
1553 -- corresponding subtype is static.
1555 if New_Lo_Bound /= Lo
1556 and then Is_Static_Expression (New_Lo_Bound)
1558 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1561 if New_Hi_Bound /= Hi
1562 and then Is_Static_Expression (New_Hi_Bound)
1564 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1568 --------------------------------------
1569 -- Check_Controlled_Array_Attribute --
1570 --------------------------------------
1572 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1574 if Nkind (DS) = N_Attribute_Reference
1575 and then Is_Entity_Name (Prefix (DS))
1576 and then Ekind (Entity (Prefix (DS))) = E_Function
1577 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1580 Component_Type (Etype (Entity (Prefix (DS)))))
1581 and then Expander_Active
1584 Loc : constant Source_Ptr := Sloc (N);
1585 Arr : constant Entity_Id :=
1586 Etype (Entity (Prefix (DS)));
1587 Indx : constant Entity_Id :=
1588 Base_Type (Etype (First_Index (Arr)));
1589 Subt : constant Entity_Id :=
1590 Make_Defining_Identifier
1591 (Loc, New_Internal_Name ('S'));
1596 Make_Subtype_Declaration (Loc,
1597 Defining_Identifier => Subt,
1598 Subtype_Indication =>
1599 Make_Subtype_Indication (Loc,
1600 Subtype_Mark => New_Reference_To (Indx, Loc),
1602 Make_Range_Constraint (Loc,
1603 Relocate_Node (DS))));
1604 Insert_Before (Parent (N), Decl);
1608 Make_Attribute_Reference (Loc,
1609 Prefix => New_Reference_To (Subt, Loc),
1610 Attribute_Name => Attribute_Name (DS)));
1614 end Check_Controlled_Array_Attribute;
1616 -- Start of processing for Analyze_Iteration_Scheme
1619 -- For an infinite loop, there is no iteration scheme
1626 Cond : constant Node_Id := Condition (N);
1629 -- For WHILE loop, verify that the condition is a Boolean
1630 -- expression and resolve and check it.
1632 if Present (Cond) then
1633 Analyze_And_Resolve (Cond, Any_Boolean);
1634 Check_Unset_Reference (Cond);
1635 Set_Current_Value_Condition (N);
1638 -- Else we have a FOR loop
1642 LP : constant Node_Id := Loop_Parameter_Specification (N);
1643 Id : constant Entity_Id := Defining_Identifier (LP);
1644 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1649 -- We always consider the loop variable to be referenced,
1650 -- since the loop may be used just for counting purposes.
1652 Generate_Reference (Id, N, ' ');
1654 -- Check for case of loop variable hiding a local
1655 -- variable (used later on to give a nice warning
1656 -- if the hidden variable is never assigned).
1659 H : constant Entity_Id := Homonym (Id);
1662 and then Enclosing_Dynamic_Scope (H) =
1663 Enclosing_Dynamic_Scope (Id)
1664 and then Ekind (H) = E_Variable
1665 and then Is_Discrete_Type (Etype (H))
1667 Set_Hiding_Loop_Variable (H, Id);
1671 -- Now analyze the subtype definition. If it is
1672 -- a range, create temporaries for bounds.
1674 if Nkind (DS) = N_Range
1675 and then Expander_Active
1677 Process_Bounds (DS);
1686 -- The subtype indication may denote the completion
1687 -- of an incomplete type declaration.
1689 if Is_Entity_Name (DS)
1690 and then Present (Entity (DS))
1691 and then Is_Type (Entity (DS))
1692 and then Ekind (Entity (DS)) = E_Incomplete_Type
1694 Set_Entity (DS, Get_Full_View (Entity (DS)));
1695 Set_Etype (DS, Entity (DS));
1698 if not Is_Discrete_Type (Etype (DS)) then
1699 Wrong_Type (DS, Any_Discrete);
1700 Set_Etype (DS, Any_Type);
1703 Check_Controlled_Array_Attribute (DS);
1705 Make_Index (DS, LP);
1707 Set_Ekind (Id, E_Loop_Parameter);
1708 Set_Etype (Id, Etype (DS));
1709 Set_Is_Known_Valid (Id, True);
1711 -- The loop is not a declarative part, so the only entity
1712 -- declared "within" must be frozen explicitly.
1715 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1717 if Is_Non_Empty_List (Flist) then
1718 Insert_Actions (N, Flist);
1722 -- Check for null or possibly null range and issue warning.
1723 -- We suppress such messages in generic templates and
1724 -- instances, because in practice they tend to be dubious
1727 if Nkind (DS) = N_Range
1728 and then Comes_From_Source (N)
1731 L : constant Node_Id := Low_Bound (DS);
1732 H : constant Node_Id := High_Bound (DS);
1742 Determine_Range (L, LOK, Llo, Lhi);
1743 Determine_Range (H, HOK, Hlo, Hhi);
1745 -- If range of loop is null, issue warning
1747 if (LOK and HOK) and then Llo > Hhi then
1749 -- Suppress the warning if inside a generic
1750 -- template or instance, since in practice
1751 -- they tend to be dubious in these cases since
1752 -- they can result from intended parametrization.
1754 if not Inside_A_Generic
1755 and then not In_Instance
1758 ("?loop range is null, loop will not execute",
1762 -- Since we know the range of the loop is null,
1763 -- set the appropriate flag to suppress any
1764 -- warnings that would otherwise be issued in
1765 -- the body of the loop that will not execute.
1766 -- We do this even in the generic case, since
1767 -- if it is dubious to warn on the null loop
1768 -- itself, it is certainly dubious to warn for
1769 -- conditions that occur inside it!
1771 Set_Is_Null_Loop (Parent (N));
1773 -- The other case for a warning is a reverse loop
1774 -- where the upper bound is the integer literal
1775 -- zero or one, and the lower bound can be positive.
1777 -- For example, we have
1779 -- for J in reverse N .. 1 loop
1781 -- In practice, this is very likely to be a case
1782 -- of reversing the bounds incorrectly in the range.
1784 elsif Reverse_Present (LP)
1785 and then Nkind (Original_Node (H)) =
1787 and then (Intval (H) = Uint_0
1789 Intval (H) = Uint_1)
1792 Error_Msg_N ("?loop range may be null", DS);
1793 Error_Msg_N ("\?bounds may be wrong way round", DS);
1801 end Analyze_Iteration_Scheme;
1807 -- Note: the semantic work required for analyzing labels (setting them as
1808 -- reachable) was done in a prepass through the statements in the block,
1809 -- so that forward gotos would be properly handled. See Analyze_Statements
1810 -- for further details. The only processing required here is to deal with
1811 -- optimizations that depend on an assumption of sequential control flow,
1812 -- since of course the occurrence of a label breaks this assumption.
1814 procedure Analyze_Label (N : Node_Id) is
1815 pragma Warnings (Off, N);
1817 Kill_Current_Values;
1820 --------------------------
1821 -- Analyze_Label_Entity --
1822 --------------------------
1824 procedure Analyze_Label_Entity (E : Entity_Id) is
1826 Set_Ekind (E, E_Label);
1827 Set_Etype (E, Standard_Void_Type);
1828 Set_Enclosing_Scope (E, Current_Scope);
1829 Set_Reachable (E, True);
1830 end Analyze_Label_Entity;
1832 ----------------------------
1833 -- Analyze_Loop_Statement --
1834 ----------------------------
1836 procedure Analyze_Loop_Statement (N : Node_Id) is
1837 Id : constant Node_Id := Identifier (N);
1838 Iter : constant Node_Id := Iteration_Scheme (N);
1842 if Present (Id) then
1844 -- Make name visible, e.g. for use in exit statements. Loop
1845 -- labels are always considered to be referenced.
1849 Generate_Reference (Ent, N, ' ');
1850 Generate_Definition (Ent);
1852 -- If we found a label, mark its type. If not, ignore it, since it
1853 -- means we have a conflicting declaration, which would already have
1854 -- been diagnosed at declaration time. Set Label_Construct of the
1855 -- implicit label declaration, which is not created by the parser
1856 -- for generic units.
1858 if Ekind (Ent) = E_Label then
1859 Set_Ekind (Ent, E_Loop);
1861 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
1862 Set_Label_Construct (Parent (Ent), N);
1866 -- Case of no identifier present
1869 Ent := New_Internal_Entity (E_Loop, Current_Scope, Sloc (N), 'L');
1870 Set_Etype (Ent, Standard_Void_Type);
1871 Set_Parent (Ent, N);
1874 -- Kill current values on entry to loop, since statements in body
1875 -- of loop may have been executed before the loop is entered.
1876 -- Similarly we kill values after the loop, since we do not know
1877 -- that the body of the loop was executed.
1879 Kill_Current_Values;
1881 Analyze_Iteration_Scheme (Iter);
1882 Analyze_Statements (Statements (N));
1883 Process_End_Label (N, 'e', Ent);
1885 Kill_Current_Values;
1887 -- Check for possible infinite loop which we can diagnose successfully.
1888 -- The case we look for is a while loop which tests a local variable,
1889 -- where there is no obvious direct or indirect update of the variable
1890 -- within the body of the loop.
1892 -- Note: we don't try to give a warning if condition actions are
1893 -- present, since the loop structure can be very complex in this case.
1896 or else No (Condition (Iter))
1897 or else Present (Condition_Actions (Iter))
1898 or else Debug_Flag_Dot_W
1903 -- Initial conditions met, see if condition is of right form
1906 Loc : Node_Id := Empty;
1907 Var : Entity_Id := Empty;
1909 function Has_Indirection (T : Entity_Id) return Boolean;
1910 -- If the controlling variable is an access type, or is a record type
1911 -- with access components, assume that it is changed indirectly and
1912 -- suppress the warning. As a concession to low-level programming, in
1913 -- particular within Declib, we also suppress warnings on a record
1914 -- type that contains components of type Address or Short_Address.
1916 procedure Find_Var (N : Node_Id);
1917 -- Find whether the condition in a while-loop can be reduced to
1918 -- a test on a single variable. Recurse if condition is negation.
1920 ---------------------
1921 -- Has_Indirection --
1922 ---------------------
1924 function Has_Indirection (T : Entity_Id) return Boolean is
1929 if Is_Access_Type (T) then
1932 elsif Is_Private_Type (T)
1933 and then Present (Full_View (T))
1934 and then Is_Access_Type (Full_View (T))
1938 elsif Is_Record_Type (T) then
1941 elsif Is_Private_Type (T)
1942 and then Present (Full_View (T))
1943 and then Is_Record_Type (Full_View (T))
1945 Rec := Full_View (T);
1950 Comp := First_Component (Rec);
1951 while Present (Comp) loop
1952 if Is_Access_Type (Etype (Comp))
1953 or else Is_Descendent_Of_Address (Etype (Comp))
1958 Next_Component (Comp);
1962 end Has_Indirection;
1968 procedure Find_Var (N : Node_Id) is
1970 -- Condition is a direct variable reference
1972 if Is_Entity_Name (N)
1973 and then not Is_Library_Level_Entity (Entity (N))
1977 -- Case of condition is a comparison with compile time known value
1979 elsif Nkind (N) in N_Op_Compare then
1980 if Is_Entity_Name (Left_Opnd (N))
1981 and then Compile_Time_Known_Value (Right_Opnd (N))
1983 Loc := Left_Opnd (N);
1985 elsif Is_Entity_Name (Right_Opnd (N))
1986 and then Compile_Time_Known_Value (Left_Opnd (N))
1988 Loc := Right_Opnd (N);
1994 -- If condition is a negation, check whether the operand has the
1997 elsif Nkind (N) = N_Op_Not then
1998 Find_Var (Right_Opnd (N));
2000 -- Case of condition is function call with one parameter
2002 elsif Nkind (N) = N_Function_Call then
2004 PA : constant List_Id := Parameter_Associations (N);
2007 and then List_Length (PA) = 1
2008 and then Is_Entity_Name (First (PA))
2022 Find_Var (Condition (Iter));
2024 if Present (Loc) then
2025 Var := Entity (Loc);
2029 and then Ekind (Var) = E_Variable
2030 and then not Is_Library_Level_Entity (Var)
2031 and then Comes_From_Source (Var)
2033 if Has_Indirection (Etype (Var)) then
2035 -- Assume that the designated object is modified in some
2036 -- other way, to avoid false positives.
2040 elsif Is_Volatile (Var) then
2042 -- If the variable is marked as volatile, we assume that
2043 -- the condition may be affected by other tasks.
2047 elsif Nkind (Original_Node (First (Statements (N))))
2048 = N_Delay_Relative_Statement
2049 or else Nkind (Original_Node (First (Statements (N))))
2050 = N_Delay_Until_Statement
2053 -- Assume that this is a multitasking program, and the
2054 -- condition is affected by other threads.
2060 -- There no identifiable single variable in the condition
2066 -- Search for reference to variable in loop
2068 Ref_Search : declare
2069 function Test_Ref (N : Node_Id) return Traverse_Result;
2070 -- Test for reference to variable in question. Returns Abandon
2071 -- if matching reference found.
2073 function Find_Ref is new Traverse_Func (Test_Ref);
2074 -- Function to traverse body of procedure. Returns Abandon if
2075 -- matching reference found.
2081 function Test_Ref (N : Node_Id) return Traverse_Result is
2083 -- Waste of time to look at iteration scheme
2088 -- Direct reference to variable in question
2090 elsif Is_Entity_Name (N)
2091 and then Present (Entity (N))
2092 and then Entity (N) = Var
2093 and then May_Be_Lvalue (N)
2097 -- Reference to variable renaming variable in question
2099 elsif Is_Entity_Name (N)
2100 and then Present (Entity (N))
2101 and then Ekind (Entity (N)) = E_Variable
2102 and then Present (Renamed_Object (Entity (N)))
2103 and then Is_Entity_Name (Renamed_Object (Entity (N)))
2104 and then Entity (Renamed_Object (Entity (N))) = Var
2105 and then May_Be_Lvalue (N)
2109 -- Calls to subprograms are OK, unless the subprogram is
2110 -- within the scope of the entity in question and could
2111 -- therefore possibly modify it
2113 elsif Nkind (N) = N_Procedure_Call_Statement
2114 or else Nkind (N) = N_Function_Call
2116 if not Is_Entity_Name (Name (N))
2117 or else Scope_Within (Entity (Name (N)), Scope (Var))
2123 -- All OK, continue scan
2128 -- Start of processing for Ref_Search
2131 if Find_Ref (N) = OK then
2133 ("variable& is not modified in loop body?", Loc, Var);
2135 ("\possible infinite loop", Loc);
2139 end Analyze_Loop_Statement;
2141 ----------------------------
2142 -- Analyze_Null_Statement --
2143 ----------------------------
2145 -- Note: the semantics of the null statement is implemented by a single
2146 -- null statement, too bad everything isn't as simple as this!
2148 procedure Analyze_Null_Statement (N : Node_Id) is
2149 pragma Warnings (Off, N);
2152 end Analyze_Null_Statement;
2154 ------------------------
2155 -- Analyze_Statements --
2156 ------------------------
2158 procedure Analyze_Statements (L : List_Id) is
2163 -- The labels declared in the statement list are reachable from
2164 -- statements in the list. We do this as a prepass so that any
2165 -- goto statement will be properly flagged if its target is not
2166 -- reachable. This is not required, but is nice behavior!
2169 while Present (S) loop
2170 if Nkind (S) = N_Label then
2171 Analyze (Identifier (S));
2172 Lab := Entity (Identifier (S));
2174 -- If we found a label mark it as reachable
2176 if Ekind (Lab) = E_Label then
2177 Generate_Definition (Lab);
2178 Set_Reachable (Lab);
2180 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
2181 Set_Label_Construct (Parent (Lab), S);
2184 -- If we failed to find a label, it means the implicit declaration
2185 -- of the label was hidden. A for-loop parameter can do this to
2186 -- a label with the same name inside the loop, since the implicit
2187 -- label declaration is in the innermost enclosing body or block
2191 Error_Msg_Sloc := Sloc (Lab);
2193 ("implicit label declaration for & is hidden#",
2201 -- Perform semantic analysis on all statements
2203 Conditional_Statements_Begin;
2206 while Present (S) loop
2211 Conditional_Statements_End;
2213 -- Make labels unreachable. Visibility is not sufficient, because
2214 -- labels in one if-branch for example are not reachable from the
2215 -- other branch, even though their declarations are in the enclosing
2216 -- declarative part.
2219 while Present (S) loop
2220 if Nkind (S) = N_Label then
2221 Set_Reachable (Entity (Identifier (S)), False);
2226 end Analyze_Statements;
2228 ----------------------------
2229 -- Check_Unreachable_Code --
2230 ----------------------------
2232 procedure Check_Unreachable_Code (N : Node_Id) is
2233 Error_Loc : Source_Ptr;
2237 if Is_List_Member (N)
2238 and then Comes_From_Source (N)
2244 Nxt := Original_Node (Next (N));
2246 -- If a label follows us, then we never have dead code, since
2247 -- someone could branch to the label, so we just ignore it.
2249 if Nkind (Nxt) = N_Label then
2252 -- Otherwise see if we have a real statement following us
2255 and then Comes_From_Source (Nxt)
2256 and then Is_Statement (Nxt)
2258 -- Special very annoying exception. If we have a return that
2259 -- follows a raise, then we allow it without a warning, since
2260 -- the Ada RM annoyingly requires a useless return here!
2262 if Nkind (Original_Node (N)) /= N_Raise_Statement
2263 or else Nkind (Nxt) /= N_Return_Statement
2265 -- The rather strange shenanigans with the warning message
2266 -- here reflects the fact that Kill_Dead_Code is very good
2267 -- at removing warnings in deleted code, and this is one
2268 -- warning we would prefer NOT to have removed :-)
2270 Error_Loc := Sloc (Nxt);
2272 -- If we have unreachable code, analyze and remove the
2273 -- unreachable code, since it is useless and we don't
2274 -- want to generate junk warnings.
2276 -- We skip this step if we are not in code generation mode.
2277 -- This is the one case where we remove dead code in the
2278 -- semantics as opposed to the expander, and we do not want
2279 -- to remove code if we are not in code generation mode,
2280 -- since this messes up the ASIS trees.
2282 -- Note that one might react by moving the whole circuit to
2283 -- exp_ch5, but then we lose the warning in -gnatc mode.
2285 if Operating_Mode = Generate_Code then
2289 -- Quit deleting when we have nothing more to delete
2290 -- or if we hit a label (since someone could transfer
2291 -- control to a label, so we should not delete it).
2293 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2295 -- Statement/declaration is to be deleted
2299 Kill_Dead_Code (Nxt);
2303 -- Now issue the warning
2305 Error_Msg ("?unreachable code", Error_Loc);
2308 -- If the unconditional transfer of control instruction is
2309 -- the last statement of a sequence, then see if our parent
2310 -- is one of the constructs for which we count unblocked exits,
2311 -- and if so, adjust the count.
2316 -- Statements in THEN part or ELSE part of IF statement
2318 if Nkind (P) = N_If_Statement then
2321 -- Statements in ELSIF part of an IF statement
2323 elsif Nkind (P) = N_Elsif_Part then
2325 pragma Assert (Nkind (P) = N_If_Statement);
2327 -- Statements in CASE statement alternative
2329 elsif Nkind (P) = N_Case_Statement_Alternative then
2331 pragma Assert (Nkind (P) = N_Case_Statement);
2333 -- Statements in body of block
2335 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2336 and then Nkind (Parent (P)) = N_Block_Statement
2340 -- Statements in exception handler in a block
2342 elsif Nkind (P) = N_Exception_Handler
2343 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2344 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2348 -- None of these cases, so return
2354 -- This was one of the cases we are looking for (i.e. the
2355 -- parent construct was IF, CASE or block) so decrement count.
2357 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2361 end Check_Unreachable_Code;