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 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 Einfo; use Einfo;
30 with Errout; use Errout;
31 with Expander; use Expander;
32 with Exp_Util; use Exp_Util;
33 with Freeze; use Freeze;
35 with Lib.Xref; use Lib.Xref;
36 with Namet; use Namet;
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 not
64 -- blocked by unconditional transfer instructions: for IF and CASE, these
65 -- are the branches of the conditional; for a block, they are the statement
66 -- sequence of the block, and the statement sequences of any exception
67 -- handlers that are part of the block. When processing is complete, if
68 -- this count is zero, it means that control cannot fall through the IF,
69 -- CASE or block statement. This is used for the generation of warning
70 -- messages. This variable is recursively saved on entry to processing the
71 -- 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
253 Mark_Static_Coextensions (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);
578 if Ada_Version >= Ada_05
579 and then Can_Never_Be_Null (T1)
580 and then not Assignment_OK (Lhs)
582 if Nkind (Rhs) = N_Null then
583 Apply_Compile_Time_Constraint_Error
585 Msg => "(Ada 2005) NULL not allowed in null-excluding objects?",
586 Reason => CE_Null_Not_Allowed);
589 elsif not Can_Never_Be_Null (T2) then
591 Convert_To (T1, Relocate_Node (Rhs)));
592 Analyze_And_Resolve (Rhs, T1);
596 if Is_Scalar_Type (T1) then
597 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
599 -- For array types, verify that lengths match. If the right hand side
600 -- if a function call that has been inlined, the assignment has been
601 -- rewritten as a block, and the constraint check will be applied to the
602 -- assignment within the block.
604 elsif Is_Array_Type (T1)
606 (Nkind (Rhs) /= N_Type_Conversion
607 or else Is_Constrained (Etype (Rhs)))
609 (Nkind (Rhs) /= N_Function_Call
610 or else Nkind (N) /= N_Block_Statement)
612 -- Assignment verifies that the length of the Lsh and Rhs are equal,
613 -- but of course the indices do not have to match. If the right-hand
614 -- side is a type conversion to an unconstrained type, a length check
615 -- is performed on the expression itself during expansion. In rare
616 -- cases, the redundant length check is computed on an index type
617 -- with a different representation, triggering incorrect code in
620 Apply_Length_Check (Rhs, Etype (Lhs));
623 -- Discriminant checks are applied in the course of expansion
628 -- Note: modifications of the Lhs may only be recorded after
629 -- checks have been applied.
631 Note_Possible_Modification (Lhs);
633 -- ??? a real accessibility check is needed when ???
635 -- Post warning for redundant assignment or variable to itself
637 if Warn_On_Redundant_Constructs
639 -- We only warn for source constructs
641 and then Comes_From_Source (N)
643 -- Where the entity is the same on both sides
645 and then Is_Entity_Name (Lhs)
646 and then Is_Entity_Name (Original_Node (Rhs))
647 and then Entity (Lhs) = Entity (Original_Node (Rhs))
649 -- But exclude the case where the right side was an operation
650 -- that got rewritten (e.g. JUNK + K, where K was known to be
651 -- zero). We don't want to warn in such a case, since it is
652 -- reasonable to write such expressions especially when K is
653 -- defined symbolically in some other package.
655 and then Nkind (Original_Node (Rhs)) not in N_Op
658 ("?useless assignment of & to itself", N, Entity (Lhs));
661 -- Check for non-allowed composite assignment
663 if not Support_Composite_Assign_On_Target
664 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
665 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
667 Error_Msg_CRT ("composite assignment", N);
670 -- Check elaboration warning for left side if not in elab code
672 if not In_Subprogram_Or_Concurrent_Unit then
673 Check_Elab_Assign (Lhs);
676 -- Final step. If left side is an entity, then we may be able to
677 -- reset the current tracked values to new safe values. We only have
678 -- something to do if the left side is an entity name, and expansion
679 -- has not modified the node into something other than an assignment,
680 -- and of course we only capture values if it is safe to do so.
682 if Is_Entity_Name (Lhs)
683 and then Nkind (N) = N_Assignment_Statement
686 Ent : constant Entity_Id := Entity (Lhs);
689 if Safe_To_Capture_Value (N, Ent) then
691 -- If simple variable on left side, warn if this assignment
692 -- blots out another one (rendering it useless) and note
693 -- location of assignment in case no one references value.
694 -- We only do this for source assignments, otherwise we can
695 -- generate bogus warnings when an assignment is rewritten as
696 -- another assignment, and gets tied up with itself.
698 if Warn_On_Modified_Unread
699 and then Ekind (Ent) = E_Variable
700 and then Comes_From_Source (N)
701 and then In_Extended_Main_Source_Unit (Ent)
703 Warn_On_Useless_Assignment (Ent, Sloc (N));
704 Set_Last_Assignment (Ent, Lhs);
707 -- If we are assigning an access type and the left side is an
708 -- entity, then make sure that the Is_Known_[Non_]Null flags
709 -- properly reflect the state of the entity after assignment.
711 if Is_Access_Type (T1) then
712 if Known_Non_Null (Rhs) then
713 Set_Is_Known_Non_Null (Ent, True);
715 elsif Known_Null (Rhs)
716 and then not Can_Never_Be_Null (Ent)
718 Set_Is_Known_Null (Ent, True);
721 Set_Is_Known_Null (Ent, False);
723 if not Can_Never_Be_Null (Ent) then
724 Set_Is_Known_Non_Null (Ent, False);
728 -- For discrete types, we may be able to set the current value
729 -- if the value is known at compile time.
731 elsif Is_Discrete_Type (T1)
732 and then Compile_Time_Known_Value (Rhs)
734 Set_Current_Value (Ent, Rhs);
736 Set_Current_Value (Ent, Empty);
739 -- If not safe to capture values, kill them
746 end Analyze_Assignment;
748 -----------------------------
749 -- Analyze_Block_Statement --
750 -----------------------------
752 procedure Analyze_Block_Statement (N : Node_Id) is
753 Decls : constant List_Id := Declarations (N);
754 Id : constant Node_Id := Identifier (N);
755 HSS : constant Node_Id := Handled_Statement_Sequence (N);
758 -- If no handled statement sequence is present, things are really
759 -- messed up, and we just return immediately (this is a defence
760 -- against previous errors).
766 -- Normal processing with HSS present
769 EH : constant List_Id := Exception_Handlers (HSS);
770 Ent : Entity_Id := Empty;
773 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
774 -- Recursively save value of this global, will be restored on exit
777 -- Initialize unblocked exit count for statements of begin block
778 -- plus one for each excption handler that is present.
780 Unblocked_Exit_Count := 1;
783 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
786 -- If a label is present analyze it and mark it as referenced
792 -- An error defense. If we have an identifier, but no entity,
793 -- then something is wrong. If we have previous errors, then
794 -- just remove the identifier and continue, otherwise raise
798 if Total_Errors_Detected /= 0 then
799 Set_Identifier (N, Empty);
805 Set_Ekind (Ent, E_Block);
806 Generate_Reference (Ent, N, ' ');
807 Generate_Definition (Ent);
809 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
810 Set_Label_Construct (Parent (Ent), N);
815 -- If no entity set, create a label entity
818 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
819 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
823 Set_Etype (Ent, Standard_Void_Type);
824 Set_Block_Node (Ent, Identifier (N));
827 if Present (Decls) then
828 Analyze_Declarations (Decls);
833 Process_End_Label (HSS, 'e', Ent);
835 -- If exception handlers are present, then we indicate that
836 -- enclosing scopes contain a block with handlers. We only
837 -- need to mark non-generic scopes.
842 Set_Has_Nested_Block_With_Handler (S);
843 exit when Is_Overloadable (S)
844 or else Ekind (S) = E_Package
845 or else Is_Generic_Unit (S);
850 Check_References (Ent);
851 Warn_On_Useless_Assignments (Ent);
854 if Unblocked_Exit_Count = 0 then
855 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
856 Check_Unreachable_Code (N);
858 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
861 end Analyze_Block_Statement;
863 ----------------------------
864 -- Analyze_Case_Statement --
865 ----------------------------
867 procedure Analyze_Case_Statement (N : Node_Id) is
869 Exp_Type : Entity_Id;
870 Exp_Btype : Entity_Id;
873 Others_Present : Boolean;
875 Statements_Analyzed : Boolean := False;
876 -- Set True if at least some statement sequences get analyzed.
877 -- If False on exit, means we had a serious error that prevented
878 -- full analysis of the case statement, and as a result it is not
879 -- a good idea to output warning messages about unreachable code.
881 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
882 -- Recursively save value of this global, will be restored on exit
884 procedure Non_Static_Choice_Error (Choice : Node_Id);
885 -- Error routine invoked by the generic instantiation below when
886 -- the case statment has a non static choice.
888 procedure Process_Statements (Alternative : Node_Id);
889 -- Analyzes all the statements associated to a case alternative.
890 -- Needed by the generic instantiation below.
892 package Case_Choices_Processing is new
893 Generic_Choices_Processing
894 (Get_Alternatives => Alternatives,
895 Get_Choices => Discrete_Choices,
896 Process_Empty_Choice => No_OP,
897 Process_Non_Static_Choice => Non_Static_Choice_Error,
898 Process_Associated_Node => Process_Statements);
899 use Case_Choices_Processing;
900 -- Instantiation of the generic choice processing package
902 -----------------------------
903 -- Non_Static_Choice_Error --
904 -----------------------------
906 procedure Non_Static_Choice_Error (Choice : Node_Id) is
909 ("choice given in case statement is not static!", Choice);
910 end Non_Static_Choice_Error;
912 ------------------------
913 -- Process_Statements --
914 ------------------------
916 procedure Process_Statements (Alternative : Node_Id) is
917 Choices : constant List_Id := Discrete_Choices (Alternative);
921 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
922 Statements_Analyzed := True;
924 -- An interesting optimization. If the case statement expression
925 -- is a simple entity, then we can set the current value within
926 -- an alternative if the alternative has one possible value.
930 -- when 2 | 3 => beta
931 -- when others => gamma
933 -- Here we know that N is initially 1 within alpha, but for beta
934 -- and gamma, we do not know anything more about the initial value.
936 if Is_Entity_Name (Exp) then
939 if Ekind (Ent) = E_Variable
941 Ekind (Ent) = E_In_Out_Parameter
943 Ekind (Ent) = E_Out_Parameter
945 if List_Length (Choices) = 1
946 and then Nkind (First (Choices)) in N_Subexpr
947 and then Compile_Time_Known_Value (First (Choices))
949 Set_Current_Value (Entity (Exp), First (Choices));
952 Analyze_Statements (Statements (Alternative));
954 -- After analyzing the case, set the current value to empty
955 -- since we won't know what it is for the next alternative
956 -- (unless reset by this same circuit), or after the case.
958 Set_Current_Value (Entity (Exp), Empty);
963 -- Case where expression is not an entity name of a variable
965 Analyze_Statements (Statements (Alternative));
966 end Process_Statements;
968 -- Table to record choices. Put after subprograms since we make
969 -- a call to Number_Of_Choices to get the right number of entries.
971 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
973 -- Start of processing for Analyze_Case_Statement
976 Unblocked_Exit_Count := 0;
977 Exp := Expression (N);
980 -- The expression must be of any discrete type. In rare cases, the
981 -- expander constructs a case statement whose expression has a private
982 -- type whose full view is discrete. This can happen when generating
983 -- a stream operation for a variant type after the type is frozen,
984 -- when the partial of view of the type of the discriminant is private.
985 -- In that case, use the full view to analyze case alternatives.
987 if not Is_Overloaded (Exp)
988 and then not Comes_From_Source (N)
989 and then Is_Private_Type (Etype (Exp))
990 and then Present (Full_View (Etype (Exp)))
991 and then Is_Discrete_Type (Full_View (Etype (Exp)))
993 Resolve (Exp, Etype (Exp));
994 Exp_Type := Full_View (Etype (Exp));
997 Analyze_And_Resolve (Exp, Any_Discrete);
998 Exp_Type := Etype (Exp);
1001 Check_Unset_Reference (Exp);
1002 Exp_Btype := Base_Type (Exp_Type);
1004 -- The expression must be of a discrete type which must be determinable
1005 -- independently of the context in which the expression occurs, but
1006 -- using the fact that the expression must be of a discrete type.
1007 -- Moreover, the type this expression must not be a character literal
1008 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1010 -- If error already reported by Resolve, nothing more to do
1012 if Exp_Btype = Any_Discrete
1013 or else Exp_Btype = Any_Type
1017 elsif Exp_Btype = Any_Character then
1019 ("character literal as case expression is ambiguous", Exp);
1022 elsif Ada_Version = Ada_83
1023 and then (Is_Generic_Type (Exp_Btype)
1024 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1027 ("(Ada 83) case expression cannot be of a generic type", Exp);
1031 -- If the case expression is a formal object of mode in out, then
1032 -- treat it as having a nonstatic subtype by forcing use of the base
1033 -- type (which has to get passed to Check_Case_Choices below). Also
1034 -- use base type when the case expression is parenthesized.
1036 if Paren_Count (Exp) > 0
1037 or else (Is_Entity_Name (Exp)
1038 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1040 Exp_Type := Exp_Btype;
1043 -- Call instantiated Analyze_Choices which does the rest of the work
1046 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
1048 if Exp_Type = Universal_Integer and then not Others_Present then
1049 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1052 -- If all our exits were blocked by unconditional transfers of control,
1053 -- then the entire CASE statement acts as an unconditional transfer of
1054 -- control, so treat it like one, and check unreachable code. Skip this
1055 -- test if we had serious errors preventing any statement analysis.
1057 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1058 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1059 Check_Unreachable_Code (N);
1061 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1064 if not Expander_Active
1065 and then Compile_Time_Known_Value (Expression (N))
1066 and then Serious_Errors_Detected = 0
1069 Chosen : constant Node_Id := Find_Static_Alternative (N);
1073 Alt := First (Alternatives (N));
1075 while Present (Alt) loop
1076 if Alt /= Chosen then
1077 Remove_Warning_Messages (Statements (Alt));
1084 end Analyze_Case_Statement;
1086 ----------------------------
1087 -- Analyze_Exit_Statement --
1088 ----------------------------
1090 -- If the exit includes a name, it must be the name of a currently open
1091 -- loop. Otherwise there must be an innermost open loop on the stack,
1092 -- to which the statement implicitly refers.
1094 procedure Analyze_Exit_Statement (N : Node_Id) is
1095 Target : constant Node_Id := Name (N);
1096 Cond : constant Node_Id := Condition (N);
1097 Scope_Id : Entity_Id;
1103 Check_Unreachable_Code (N);
1106 if Present (Target) then
1108 U_Name := Entity (Target);
1110 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1111 Error_Msg_N ("invalid loop name in exit statement", N);
1114 Set_Has_Exit (U_Name);
1121 for J in reverse 0 .. Scope_Stack.Last loop
1122 Scope_Id := Scope_Stack.Table (J).Entity;
1123 Kind := Ekind (Scope_Id);
1126 and then (No (Target) or else Scope_Id = U_Name) then
1127 Set_Has_Exit (Scope_Id);
1130 elsif Kind = E_Block
1131 or else Kind = E_Loop
1132 or else Kind = E_Return_Statement
1138 ("cannot exit from program unit or accept statement", N);
1143 -- Verify that if present the condition is a Boolean expression
1145 if Present (Cond) then
1146 Analyze_And_Resolve (Cond, Any_Boolean);
1147 Check_Unset_Reference (Cond);
1149 end Analyze_Exit_Statement;
1151 ----------------------------
1152 -- Analyze_Goto_Statement --
1153 ----------------------------
1155 procedure Analyze_Goto_Statement (N : Node_Id) is
1156 Label : constant Node_Id := Name (N);
1157 Scope_Id : Entity_Id;
1158 Label_Scope : Entity_Id;
1159 Label_Ent : Entity_Id;
1162 Check_Unreachable_Code (N);
1165 Label_Ent := Entity (Label);
1167 -- Ignore previous error
1169 if Label_Ent = Any_Id then
1172 -- We just have a label as the target of a goto
1174 elsif Ekind (Label_Ent) /= E_Label then
1175 Error_Msg_N ("target of goto statement must be a label", Label);
1178 -- Check that the target of the goto is reachable according to Ada
1179 -- scoping rules. Note: the special gotos we generate for optimizing
1180 -- local handling of exceptions would violate these rules, but we mark
1181 -- such gotos as analyzed when built, so this code is never entered.
1183 elsif not Reachable (Label_Ent) then
1184 Error_Msg_N ("target of goto statement is not reachable", Label);
1188 -- Here if goto passes initial validity checks
1190 Label_Scope := Enclosing_Scope (Label_Ent);
1192 for J in reverse 0 .. Scope_Stack.Last loop
1193 Scope_Id := Scope_Stack.Table (J).Entity;
1195 if Label_Scope = Scope_Id
1196 or else (Ekind (Scope_Id) /= E_Block
1197 and then Ekind (Scope_Id) /= E_Loop
1198 and then Ekind (Scope_Id) /= E_Return_Statement)
1200 if Scope_Id /= Label_Scope then
1202 ("cannot exit from program unit or accept statement", N);
1209 raise Program_Error;
1210 end Analyze_Goto_Statement;
1212 --------------------------
1213 -- Analyze_If_Statement --
1214 --------------------------
1216 -- A special complication arises in the analysis of if statements
1218 -- The expander has circuitry to completely delete code that it
1219 -- can tell will not be executed (as a result of compile time known
1220 -- conditions). In the analyzer, we ensure that code that will be
1221 -- deleted in this manner is analyzed but not expanded. This is
1222 -- obviously more efficient, but more significantly, difficulties
1223 -- arise if code is expanded and then eliminated (e.g. exception
1224 -- table entries disappear). Similarly, itypes generated in deleted
1225 -- code must be frozen from start, because the nodes on which they
1226 -- depend will not be available at the freeze point.
1228 procedure Analyze_If_Statement (N : Node_Id) is
1231 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1232 -- Recursively save value of this global, will be restored on exit
1234 Save_In_Deleted_Code : Boolean;
1236 Del : Boolean := False;
1237 -- This flag gets set True if a True condition has been found,
1238 -- which means that remaining ELSE/ELSIF parts are deleted.
1240 procedure Analyze_Cond_Then (Cnode : Node_Id);
1241 -- This is applied to either the N_If_Statement node itself or
1242 -- to an N_Elsif_Part node. It deals with analyzing the condition
1243 -- and the THEN statements associated with it.
1245 -----------------------
1246 -- Analyze_Cond_Then --
1247 -----------------------
1249 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1250 Cond : constant Node_Id := Condition (Cnode);
1251 Tstm : constant List_Id := Then_Statements (Cnode);
1254 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1255 Analyze_And_Resolve (Cond, Any_Boolean);
1256 Check_Unset_Reference (Cond);
1257 Set_Current_Value_Condition (Cnode);
1259 -- If already deleting, then just analyze then statements
1262 Analyze_Statements (Tstm);
1264 -- Compile time known value, not deleting yet
1266 elsif Compile_Time_Known_Value (Cond) then
1267 Save_In_Deleted_Code := In_Deleted_Code;
1269 -- If condition is True, then analyze the THEN statements
1270 -- and set no expansion for ELSE and ELSIF parts.
1272 if Is_True (Expr_Value (Cond)) then
1273 Analyze_Statements (Tstm);
1275 Expander_Mode_Save_And_Set (False);
1276 In_Deleted_Code := True;
1278 -- If condition is False, analyze THEN with expansion off
1280 else -- Is_False (Expr_Value (Cond))
1281 Expander_Mode_Save_And_Set (False);
1282 In_Deleted_Code := True;
1283 Analyze_Statements (Tstm);
1284 Expander_Mode_Restore;
1285 In_Deleted_Code := Save_In_Deleted_Code;
1288 -- Not known at compile time, not deleting, normal analysis
1291 Analyze_Statements (Tstm);
1293 end Analyze_Cond_Then;
1295 -- Start of Analyze_If_Statement
1298 -- Initialize exit count for else statements. If there is no else
1299 -- part, this count will stay non-zero reflecting the fact that the
1300 -- uncovered else case is an unblocked exit.
1302 Unblocked_Exit_Count := 1;
1303 Analyze_Cond_Then (N);
1305 -- Now to analyze the elsif parts if any are present
1307 if Present (Elsif_Parts (N)) then
1308 E := First (Elsif_Parts (N));
1309 while Present (E) loop
1310 Analyze_Cond_Then (E);
1315 if Present (Else_Statements (N)) then
1316 Analyze_Statements (Else_Statements (N));
1319 -- If all our exits were blocked by unconditional transfers of control,
1320 -- then the entire IF statement acts as an unconditional transfer of
1321 -- control, so treat it like one, and check unreachable code.
1323 if Unblocked_Exit_Count = 0 then
1324 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1325 Check_Unreachable_Code (N);
1327 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1331 Expander_Mode_Restore;
1332 In_Deleted_Code := Save_In_Deleted_Code;
1335 if not Expander_Active
1336 and then Compile_Time_Known_Value (Condition (N))
1337 and then Serious_Errors_Detected = 0
1339 if Is_True (Expr_Value (Condition (N))) then
1340 Remove_Warning_Messages (Else_Statements (N));
1342 if Present (Elsif_Parts (N)) then
1343 E := First (Elsif_Parts (N));
1345 while Present (E) loop
1346 Remove_Warning_Messages (Then_Statements (E));
1352 Remove_Warning_Messages (Then_Statements (N));
1355 end Analyze_If_Statement;
1357 ----------------------------------------
1358 -- Analyze_Implicit_Label_Declaration --
1359 ----------------------------------------
1361 -- An implicit label declaration is generated in the innermost
1362 -- enclosing declarative part. This is done for labels as well as
1363 -- block and loop names.
1365 -- Note: any changes in this routine may need to be reflected in
1366 -- Analyze_Label_Entity.
1368 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1369 Id : constant Node_Id := Defining_Identifier (N);
1372 Set_Ekind (Id, E_Label);
1373 Set_Etype (Id, Standard_Void_Type);
1374 Set_Enclosing_Scope (Id, Current_Scope);
1375 end Analyze_Implicit_Label_Declaration;
1377 ------------------------------
1378 -- Analyze_Iteration_Scheme --
1379 ------------------------------
1381 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1383 procedure Process_Bounds (R : Node_Id);
1384 -- If the iteration is given by a range, create temporaries and
1385 -- assignment statements block to capture the bounds and perform
1386 -- required finalization actions in case a bound includes a function
1387 -- call that uses the temporary stack. We first pre-analyze a copy of
1388 -- the range in order to determine the expected type, and analyze and
1389 -- resolve the original bounds.
1391 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1392 -- If the bounds are given by a 'Range reference on a function call
1393 -- that returns a controlled array, introduce an explicit declaration
1394 -- to capture the bounds, so that the function result can be finalized
1395 -- in timely fashion.
1397 --------------------
1398 -- Process_Bounds --
1399 --------------------
1401 procedure Process_Bounds (R : Node_Id) is
1402 Loc : constant Source_Ptr := Sloc (N);
1403 R_Copy : constant Node_Id := New_Copy_Tree (R);
1404 Lo : constant Node_Id := Low_Bound (R);
1405 Hi : constant Node_Id := High_Bound (R);
1406 New_Lo_Bound : Node_Id := Empty;
1407 New_Hi_Bound : Node_Id := Empty;
1409 Save_Analysis : Boolean;
1412 (Original_Bound : Node_Id;
1413 Analyzed_Bound : Node_Id) return Node_Id;
1414 -- Create one declaration followed by one assignment statement
1415 -- to capture the value of bound. We create a separate assignment
1416 -- in order to force the creation of a block in case the bound
1417 -- contains a call that uses the secondary stack.
1424 (Original_Bound : Node_Id;
1425 Analyzed_Bound : Node_Id) return Node_Id
1432 -- If the bound is a constant or an object, no need for a separate
1433 -- declaration. If the bound is the result of previous expansion
1434 -- it is already analyzed and should not be modified. Note that
1435 -- the Bound will be resolved later, if needed, as part of the
1436 -- call to Make_Index (literal bounds may need to be resolved to
1439 if Analyzed (Original_Bound) then
1440 return Original_Bound;
1442 elsif Nkind (Analyzed_Bound) = N_Integer_Literal
1443 or else Nkind (Analyzed_Bound) = N_Character_Literal
1444 or else Is_Entity_Name (Analyzed_Bound)
1446 Analyze_And_Resolve (Original_Bound, Typ);
1447 return Original_Bound;
1450 Analyze_And_Resolve (Original_Bound, Typ);
1454 Make_Defining_Identifier (Loc,
1455 Chars => New_Internal_Name ('S'));
1458 Make_Object_Declaration (Loc,
1459 Defining_Identifier => Id,
1460 Object_Definition => New_Occurrence_Of (Typ, Loc));
1462 Insert_Before (Parent (N), Decl);
1466 Make_Assignment_Statement (Loc,
1467 Name => New_Occurrence_Of (Id, Loc),
1468 Expression => Relocate_Node (Original_Bound));
1470 Insert_Before (Parent (N), Assign);
1473 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1475 if Nkind (Assign) = N_Assignment_Statement then
1476 return Expression (Assign);
1478 return Original_Bound;
1482 -- Start of processing for Process_Bounds
1485 -- Determine expected type of range by analyzing separate copy
1486 -- Do the analysis and resolution of the copy of the bounds with
1487 -- expansion disabled, to prevent the generation of finalization
1488 -- actions on each bound. This prevents memory leaks when the
1489 -- bounds contain calls to functions returning controlled arrays.
1491 Set_Parent (R_Copy, Parent (R));
1492 Save_Analysis := Full_Analysis;
1493 Full_Analysis := False;
1494 Expander_Mode_Save_And_Set (False);
1498 if Is_Overloaded (R_Copy) then
1500 -- Apply preference rules for range of predefined integer types,
1501 -- or diagnose true ambiguity.
1506 Found : Entity_Id := Empty;
1509 Get_First_Interp (R_Copy, I, It);
1510 while Present (It.Typ) loop
1511 if Is_Discrete_Type (It.Typ) then
1515 if Scope (Found) = Standard_Standard then
1518 elsif Scope (It.Typ) = Standard_Standard then
1522 -- Both of them are user-defined
1525 ("ambiguous bounds in range of iteration",
1527 Error_Msg_N ("\possible interpretations:", R_Copy);
1528 Error_Msg_NE ("\\} ", R_Copy, Found);
1529 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1535 Get_Next_Interp (I, It);
1541 Expander_Mode_Restore;
1542 Full_Analysis := Save_Analysis;
1544 Typ := Etype (R_Copy);
1546 -- If the type of the discrete range is Universal_Integer, then
1547 -- the bound's type must be resolved to Integer, and any object
1548 -- used to hold the bound must also have type Integer, unless the
1549 -- literal bounds are constant-folded expressions that carry a user-
1552 if Typ = Universal_Integer then
1553 if Nkind (Lo) = N_Integer_Literal
1554 and then Present (Etype (Lo))
1555 and then Scope (Etype (Lo)) /= Standard_Standard
1559 elsif Nkind (Hi) = N_Integer_Literal
1560 and then Present (Etype (Hi))
1561 and then Scope (Etype (Hi)) /= Standard_Standard
1566 Typ := Standard_Integer;
1572 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1573 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1575 -- Propagate staticness to loop range itself, in case the
1576 -- corresponding subtype is static.
1578 if New_Lo_Bound /= Lo
1579 and then Is_Static_Expression (New_Lo_Bound)
1581 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1584 if New_Hi_Bound /= Hi
1585 and then Is_Static_Expression (New_Hi_Bound)
1587 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1591 --------------------------------------
1592 -- Check_Controlled_Array_Attribute --
1593 --------------------------------------
1595 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1597 if Nkind (DS) = N_Attribute_Reference
1598 and then Is_Entity_Name (Prefix (DS))
1599 and then Ekind (Entity (Prefix (DS))) = E_Function
1600 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1603 Component_Type (Etype (Entity (Prefix (DS)))))
1604 and then Expander_Active
1607 Loc : constant Source_Ptr := Sloc (N);
1608 Arr : constant Entity_Id :=
1609 Etype (Entity (Prefix (DS)));
1610 Indx : constant Entity_Id :=
1611 Base_Type (Etype (First_Index (Arr)));
1612 Subt : constant Entity_Id :=
1613 Make_Defining_Identifier
1614 (Loc, New_Internal_Name ('S'));
1619 Make_Subtype_Declaration (Loc,
1620 Defining_Identifier => Subt,
1621 Subtype_Indication =>
1622 Make_Subtype_Indication (Loc,
1623 Subtype_Mark => New_Reference_To (Indx, Loc),
1625 Make_Range_Constraint (Loc,
1626 Relocate_Node (DS))));
1627 Insert_Before (Parent (N), Decl);
1631 Make_Attribute_Reference (Loc,
1632 Prefix => New_Reference_To (Subt, Loc),
1633 Attribute_Name => Attribute_Name (DS)));
1637 end Check_Controlled_Array_Attribute;
1639 -- Start of processing for Analyze_Iteration_Scheme
1642 -- For an infinite loop, there is no iteration scheme
1649 Cond : constant Node_Id := Condition (N);
1652 -- For WHILE loop, verify that the condition is a Boolean
1653 -- expression and resolve and check it.
1655 if Present (Cond) then
1656 Analyze_And_Resolve (Cond, Any_Boolean);
1657 Check_Unset_Reference (Cond);
1658 Set_Current_Value_Condition (N);
1661 -- Else we have a FOR loop
1665 LP : constant Node_Id := Loop_Parameter_Specification (N);
1666 Id : constant Entity_Id := Defining_Identifier (LP);
1667 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1672 -- We always consider the loop variable to be referenced,
1673 -- since the loop may be used just for counting purposes.
1675 Generate_Reference (Id, N, ' ');
1677 -- Check for case of loop variable hiding a local
1678 -- variable (used later on to give a nice warning
1679 -- if the hidden variable is never assigned).
1682 H : constant Entity_Id := Homonym (Id);
1685 and then Enclosing_Dynamic_Scope (H) =
1686 Enclosing_Dynamic_Scope (Id)
1687 and then Ekind (H) = E_Variable
1688 and then Is_Discrete_Type (Etype (H))
1690 Set_Hiding_Loop_Variable (H, Id);
1694 -- Now analyze the subtype definition. If it is
1695 -- a range, create temporaries for bounds.
1697 if Nkind (DS) = N_Range
1698 and then Expander_Active
1700 Process_Bounds (DS);
1709 -- The subtype indication may denote the completion
1710 -- of an incomplete type declaration.
1712 if Is_Entity_Name (DS)
1713 and then Present (Entity (DS))
1714 and then Is_Type (Entity (DS))
1715 and then Ekind (Entity (DS)) = E_Incomplete_Type
1717 Set_Entity (DS, Get_Full_View (Entity (DS)));
1718 Set_Etype (DS, Entity (DS));
1721 if not Is_Discrete_Type (Etype (DS)) then
1722 Wrong_Type (DS, Any_Discrete);
1723 Set_Etype (DS, Any_Type);
1726 Check_Controlled_Array_Attribute (DS);
1728 Make_Index (DS, LP);
1730 Set_Ekind (Id, E_Loop_Parameter);
1731 Set_Etype (Id, Etype (DS));
1732 Set_Is_Known_Valid (Id, True);
1734 -- The loop is not a declarative part, so the only entity
1735 -- declared "within" must be frozen explicitly.
1738 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1740 if Is_Non_Empty_List (Flist) then
1741 Insert_Actions (N, Flist);
1745 -- Check for null or possibly null range and issue warning.
1746 -- We suppress such messages in generic templates and
1747 -- instances, because in practice they tend to be dubious
1750 if Nkind (DS) = N_Range
1751 and then Comes_From_Source (N)
1754 L : constant Node_Id := Low_Bound (DS);
1755 H : constant Node_Id := High_Bound (DS);
1765 Determine_Range (L, LOK, Llo, Lhi);
1766 Determine_Range (H, HOK, Hlo, Hhi);
1768 -- If range of loop is null, issue warning
1770 if (LOK and HOK) and then Llo > Hhi then
1772 -- Suppress the warning if inside a generic
1773 -- template or instance, since in practice
1774 -- they tend to be dubious in these cases since
1775 -- they can result from intended parametrization.
1777 if not Inside_A_Generic
1778 and then not In_Instance
1781 ("?loop range is null, loop will not execute",
1785 -- Since we know the range of the loop is null,
1786 -- set the appropriate flag to suppress any
1787 -- warnings that would otherwise be issued in
1788 -- the body of the loop that will not execute.
1789 -- We do this even in the generic case, since
1790 -- if it is dubious to warn on the null loop
1791 -- itself, it is certainly dubious to warn for
1792 -- conditions that occur inside it!
1794 Set_Is_Null_Loop (Parent (N));
1796 -- The other case for a warning is a reverse loop
1797 -- where the upper bound is the integer literal
1798 -- zero or one, and the lower bound can be positive.
1800 -- For example, we have
1802 -- for J in reverse N .. 1 loop
1804 -- In practice, this is very likely to be a case
1805 -- of reversing the bounds incorrectly in the range.
1807 elsif Reverse_Present (LP)
1808 and then Nkind (Original_Node (H)) =
1810 and then (Intval (H) = Uint_0
1812 Intval (H) = Uint_1)
1815 Error_Msg_N ("?loop range may be null", DS);
1816 Error_Msg_N ("\?bounds may be wrong way round", DS);
1824 end Analyze_Iteration_Scheme;
1830 -- Note: the semantic work required for analyzing labels (setting them as
1831 -- reachable) was done in a prepass through the statements in the block,
1832 -- so that forward gotos would be properly handled. See Analyze_Statements
1833 -- for further details. The only processing required here is to deal with
1834 -- optimizations that depend on an assumption of sequential control flow,
1835 -- since of course the occurrence of a label breaks this assumption.
1837 procedure Analyze_Label (N : Node_Id) is
1838 pragma Warnings (Off, N);
1840 Kill_Current_Values;
1843 --------------------------
1844 -- Analyze_Label_Entity --
1845 --------------------------
1847 procedure Analyze_Label_Entity (E : Entity_Id) is
1849 Set_Ekind (E, E_Label);
1850 Set_Etype (E, Standard_Void_Type);
1851 Set_Enclosing_Scope (E, Current_Scope);
1852 Set_Reachable (E, True);
1853 end Analyze_Label_Entity;
1855 ----------------------------
1856 -- Analyze_Loop_Statement --
1857 ----------------------------
1859 procedure Analyze_Loop_Statement (N : Node_Id) is
1860 Loop_Statement : constant Node_Id := N;
1862 Id : constant Node_Id := Identifier (Loop_Statement);
1863 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
1867 if Present (Id) then
1869 -- Make name visible, e.g. for use in exit statements. Loop
1870 -- labels are always considered to be referenced.
1874 Generate_Reference (Ent, Loop_Statement, ' ');
1875 Generate_Definition (Ent);
1877 -- If we found a label, mark its type. If not, ignore it, since it
1878 -- means we have a conflicting declaration, which would already have
1879 -- been diagnosed at declaration time. Set Label_Construct of the
1880 -- implicit label declaration, which is not created by the parser
1881 -- for generic units.
1883 if Ekind (Ent) = E_Label then
1884 Set_Ekind (Ent, E_Loop);
1886 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
1887 Set_Label_Construct (Parent (Ent), Loop_Statement);
1891 -- Case of no identifier present
1896 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
1897 Set_Etype (Ent, Standard_Void_Type);
1898 Set_Parent (Ent, Loop_Statement);
1901 -- Kill current values on entry to loop, since statements in body
1902 -- of loop may have been executed before the loop is entered.
1903 -- Similarly we kill values after the loop, since we do not know
1904 -- that the body of the loop was executed.
1906 Kill_Current_Values;
1908 Analyze_Iteration_Scheme (Iter);
1909 Analyze_Statements (Statements (Loop_Statement));
1910 Process_End_Label (Loop_Statement, 'e', Ent);
1912 Kill_Current_Values;
1913 Check_Infinite_Loop_Warning (N);
1914 end Analyze_Loop_Statement;
1916 ----------------------------
1917 -- Analyze_Null_Statement --
1918 ----------------------------
1920 -- Note: the semantics of the null statement is implemented by a single
1921 -- null statement, too bad everything isn't as simple as this!
1923 procedure Analyze_Null_Statement (N : Node_Id) is
1924 pragma Warnings (Off, N);
1927 end Analyze_Null_Statement;
1929 ------------------------
1930 -- Analyze_Statements --
1931 ------------------------
1933 procedure Analyze_Statements (L : List_Id) is
1938 -- The labels declared in the statement list are reachable from
1939 -- statements in the list. We do this as a prepass so that any
1940 -- goto statement will be properly flagged if its target is not
1941 -- reachable. This is not required, but is nice behavior!
1944 while Present (S) loop
1945 if Nkind (S) = N_Label then
1946 Analyze (Identifier (S));
1947 Lab := Entity (Identifier (S));
1949 -- If we found a label mark it as reachable
1951 if Ekind (Lab) = E_Label then
1952 Generate_Definition (Lab);
1953 Set_Reachable (Lab);
1955 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
1956 Set_Label_Construct (Parent (Lab), S);
1959 -- If we failed to find a label, it means the implicit declaration
1960 -- of the label was hidden. A for-loop parameter can do this to
1961 -- a label with the same name inside the loop, since the implicit
1962 -- label declaration is in the innermost enclosing body or block
1966 Error_Msg_Sloc := Sloc (Lab);
1968 ("implicit label declaration for & is hidden#",
1976 -- Perform semantic analysis on all statements
1978 Conditional_Statements_Begin;
1981 while Present (S) loop
1986 Conditional_Statements_End;
1988 -- Make labels unreachable. Visibility is not sufficient, because
1989 -- labels in one if-branch for example are not reachable from the
1990 -- other branch, even though their declarations are in the enclosing
1991 -- declarative part.
1994 while Present (S) loop
1995 if Nkind (S) = N_Label then
1996 Set_Reachable (Entity (Identifier (S)), False);
2001 end Analyze_Statements;
2003 ----------------------------
2004 -- Check_Unreachable_Code --
2005 ----------------------------
2007 procedure Check_Unreachable_Code (N : Node_Id) is
2008 Error_Loc : Source_Ptr;
2012 if Is_List_Member (N)
2013 and then Comes_From_Source (N)
2019 Nxt := Original_Node (Next (N));
2021 -- If a label follows us, then we never have dead code, since
2022 -- someone could branch to the label, so we just ignore it.
2024 if Nkind (Nxt) = N_Label then
2027 -- Otherwise see if we have a real statement following us
2030 and then Comes_From_Source (Nxt)
2031 and then Is_Statement (Nxt)
2033 -- Special very annoying exception. If we have a return that
2034 -- follows a raise, then we allow it without a warning, since
2035 -- the Ada RM annoyingly requires a useless return here!
2037 if Nkind (Original_Node (N)) /= N_Raise_Statement
2038 or else Nkind (Nxt) /= N_Return_Statement
2040 -- The rather strange shenanigans with the warning message
2041 -- here reflects the fact that Kill_Dead_Code is very good
2042 -- at removing warnings in deleted code, and this is one
2043 -- warning we would prefer NOT to have removed.
2045 Error_Loc := Sloc (Nxt);
2047 -- If we have unreachable code, analyze and remove the
2048 -- unreachable code, since it is useless and we don't
2049 -- want to generate junk warnings.
2051 -- We skip this step if we are not in code generation mode.
2052 -- This is the one case where we remove dead code in the
2053 -- semantics as opposed to the expander, and we do not want
2054 -- to remove code if we are not in code generation mode,
2055 -- since this messes up the ASIS trees.
2057 -- Note that one might react by moving the whole circuit to
2058 -- exp_ch5, but then we lose the warning in -gnatc mode.
2060 if Operating_Mode = Generate_Code then
2064 -- Quit deleting when we have nothing more to delete
2065 -- or if we hit a label (since someone could transfer
2066 -- control to a label, so we should not delete it).
2068 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2070 -- Statement/declaration is to be deleted
2074 Kill_Dead_Code (Nxt);
2078 -- Now issue the warning
2080 Error_Msg ("?unreachable code", Error_Loc);
2083 -- If the unconditional transfer of control instruction is
2084 -- the last statement of a sequence, then see if our parent
2085 -- is one of the constructs for which we count unblocked exits,
2086 -- and if so, adjust the count.
2091 -- Statements in THEN part or ELSE part of IF statement
2093 if Nkind (P) = N_If_Statement then
2096 -- Statements in ELSIF part of an IF statement
2098 elsif Nkind (P) = N_Elsif_Part then
2100 pragma Assert (Nkind (P) = N_If_Statement);
2102 -- Statements in CASE statement alternative
2104 elsif Nkind (P) = N_Case_Statement_Alternative then
2106 pragma Assert (Nkind (P) = N_Case_Statement);
2108 -- Statements in body of block
2110 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2111 and then Nkind (Parent (P)) = N_Block_Statement
2115 -- Statements in exception handler in a block
2117 elsif Nkind (P) = N_Exception_Handler
2118 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2119 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2123 -- None of these cases, so return
2129 -- This was one of the cases we are looking for (i.e. the
2130 -- parent construct was IF, CASE or block) so decrement count.
2132 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2136 end Check_Unreachable_Code;