1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2008, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Atree; use Atree;
27 with Checks; use Checks;
28 with Einfo; use Einfo;
29 with Errout; use Errout;
30 with Expander; use Expander;
31 with Exp_Util; use Exp_Util;
32 with Freeze; use Freeze;
34 with Lib.Xref; use Lib.Xref;
35 with Namet; use Namet;
36 with Nlists; use Nlists;
37 with Nmake; use Nmake;
39 with Rtsfind; use Rtsfind;
41 with Sem_Case; use Sem_Case;
42 with Sem_Ch3; use Sem_Ch3;
43 with Sem_Ch8; use Sem_Ch8;
44 with Sem_Disp; use Sem_Disp;
45 with Sem_Elab; use Sem_Elab;
46 with Sem_Eval; use Sem_Eval;
47 with Sem_Res; use Sem_Res;
48 with Sem_Type; use Sem_Type;
49 with Sem_Util; use Sem_Util;
50 with Sem_Warn; use Sem_Warn;
51 with Snames; use Snames;
52 with Stand; use Stand;
53 with Sinfo; use Sinfo;
54 with Targparm; use Targparm;
55 with Tbuild; use Tbuild;
56 with Uintp; use Uintp;
58 package body Sem_Ch5 is
60 Unblocked_Exit_Count : Nat := 0;
61 -- This variable is used when processing if statements, case statements,
62 -- and block statements. It counts the number of exit points that are not
63 -- blocked by unconditional transfer instructions: for IF and CASE, these
64 -- are the branches of the conditional; for a block, they are the statement
65 -- sequence of the block, and the statement sequences of any exception
66 -- handlers that are part of the block. When processing is complete, if
67 -- this count is zero, it means that control cannot fall through the IF,
68 -- CASE or block statement. This is used for the generation of warning
69 -- messages. This variable is recursively saved on entry to processing the
70 -- construct, and restored on exit.
72 -----------------------
73 -- Local Subprograms --
74 -----------------------
76 procedure Analyze_Iteration_Scheme (N : Node_Id);
78 ------------------------
79 -- Analyze_Assignment --
80 ------------------------
82 procedure Analyze_Assignment (N : Node_Id) is
83 Lhs : constant Node_Id := Name (N);
84 Rhs : constant Node_Id := Expression (N);
89 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
90 -- N is the node for the left hand side of an assignment, and it
91 -- is not a variable. This routine issues an appropriate diagnostic.
94 -- This is called to kill current value settings of a simple variable
95 -- on the left hand side. We call it if we find any error in analyzing
96 -- the assignment, and at the end of processing before setting any new
97 -- current values in place.
99 procedure Set_Assignment_Type
101 Opnd_Type : in out Entity_Id);
102 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
103 -- is the nominal subtype. This procedure is used to deal with cases
104 -- where the nominal subtype must be replaced by the actual subtype.
106 -------------------------------
107 -- Diagnose_Non_Variable_Lhs --
108 -------------------------------
110 procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
112 -- Not worth posting another error if left hand side already
113 -- flagged as being illegal in some respect.
115 if Error_Posted (N) then
118 -- Some special bad cases of entity names
120 elsif Is_Entity_Name (N) then
122 Ent : constant Entity_Id := Entity (N);
125 if Ekind (Ent) = E_In_Parameter then
127 ("assignment to IN mode parameter not allowed", N);
129 -- Renamings of protected private components are turned into
130 -- constants when compiling a protected function. In the case
131 -- of single protected types, the private component appears
134 elsif (Is_Prival (Ent)
136 (Ekind (Current_Scope) = E_Function
137 or else Ekind (Enclosing_Dynamic_Scope (
138 Current_Scope)) = E_Function))
140 (Ekind (Ent) = E_Component
141 and then Is_Protected_Type (Scope (Ent)))
144 ("protected function cannot modify protected object", N);
146 elsif Ekind (Ent) = E_Loop_Parameter then
148 ("assignment to loop parameter not allowed", N);
152 ("left hand side of assignment must be a variable", N);
156 -- For indexed components or selected components, test prefix
158 elsif Nkind (N) = N_Indexed_Component then
159 Diagnose_Non_Variable_Lhs (Prefix (N));
161 -- Another special case for assignment to discriminant
163 elsif Nkind (N) = N_Selected_Component then
164 if Present (Entity (Selector_Name (N)))
165 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
168 ("assignment to discriminant not allowed", N);
170 Diagnose_Non_Variable_Lhs (Prefix (N));
174 -- If we fall through, we have no special message to issue!
176 Error_Msg_N ("left hand side of assignment must be a variable", N);
178 end Diagnose_Non_Variable_Lhs;
184 procedure Kill_Lhs is
186 if Is_Entity_Name (Lhs) then
188 Ent : constant Entity_Id := Entity (Lhs);
190 if Present (Ent) then
191 Kill_Current_Values (Ent);
197 -------------------------
198 -- Set_Assignment_Type --
199 -------------------------
201 procedure Set_Assignment_Type
203 Opnd_Type : in out Entity_Id)
206 Require_Entity (Opnd);
208 -- If the assignment operand is an in-out or out parameter, then we
209 -- get the actual subtype (needed for the unconstrained case).
210 -- If the operand is the actual in an entry declaration, then within
211 -- the accept statement it is replaced with a local renaming, which
212 -- may also have an actual subtype.
214 if Is_Entity_Name (Opnd)
215 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
216 or else Ekind (Entity (Opnd)) =
218 or else Ekind (Entity (Opnd)) =
219 E_Generic_In_Out_Parameter
221 (Ekind (Entity (Opnd)) = E_Variable
222 and then Nkind (Parent (Entity (Opnd))) =
223 N_Object_Renaming_Declaration
224 and then Nkind (Parent (Parent (Entity (Opnd)))) =
227 Opnd_Type := Get_Actual_Subtype (Opnd);
229 -- If assignment operand is a component reference, then we get the
230 -- actual subtype of the component for the unconstrained case.
232 elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference)
233 and then not Is_Unchecked_Union (Opnd_Type)
235 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
237 if Present (Decl) then
238 Insert_Action (N, Decl);
239 Mark_Rewrite_Insertion (Decl);
241 Opnd_Type := Defining_Identifier (Decl);
242 Set_Etype (Opnd, Opnd_Type);
243 Freeze_Itype (Opnd_Type, N);
245 elsif Is_Constrained (Etype (Opnd)) then
246 Opnd_Type := Etype (Opnd);
249 -- For slice, use the constrained subtype created for the slice
251 elsif Nkind (Opnd) = N_Slice then
252 Opnd_Type := Etype (Opnd);
254 end Set_Assignment_Type;
256 -- Start of processing for Analyze_Assignment
259 Mark_Coextensions (N, Rhs);
264 -- Start type analysis for assignment
268 -- In the most general case, both Lhs and Rhs can be overloaded, and we
269 -- must compute the intersection of the possible types on each side.
271 if Is_Overloaded (Lhs) then
278 Get_First_Interp (Lhs, I, It);
280 while Present (It.Typ) loop
281 if Has_Compatible_Type (Rhs, It.Typ) then
282 if T1 /= Any_Type then
284 -- An explicit dereference is overloaded if the prefix
285 -- is. Try to remove the ambiguity on the prefix, the
286 -- error will be posted there if the ambiguity is real.
288 if Nkind (Lhs) = N_Explicit_Dereference then
291 PI1 : Interp_Index := 0;
297 Get_First_Interp (Prefix (Lhs), PI, PIt);
299 while Present (PIt.Typ) loop
300 if Is_Access_Type (PIt.Typ)
301 and then Has_Compatible_Type
302 (Rhs, Designated_Type (PIt.Typ))
306 Disambiguate (Prefix (Lhs),
309 if PIt = No_Interp then
311 ("ambiguous left-hand side"
312 & " in assignment", Lhs);
315 Resolve (Prefix (Lhs), PIt.Typ);
325 Get_Next_Interp (PI, PIt);
331 ("ambiguous left-hand side in assignment", Lhs);
339 Get_Next_Interp (I, It);
343 if T1 = Any_Type then
345 ("no valid types for left-hand side for assignment", Lhs);
351 -- The resulting assignment type is T1, so now we will resolve the
352 -- left hand side of the assignment using this determined type.
356 -- Cases where Lhs is not a variable
358 if not Is_Variable (Lhs) then
360 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
361 -- a protected object.
368 if Ada_Version >= Ada_05 then
370 -- Handle chains of renamings
373 while Nkind (Ent) in N_Has_Entity
374 and then Present (Entity (Ent))
375 and then Present (Renamed_Object (Entity (Ent)))
377 Ent := Renamed_Object (Entity (Ent));
380 if (Nkind (Ent) = N_Attribute_Reference
381 and then Attribute_Name (Ent) = Name_Priority)
383 -- Renamings of the attribute Priority applied to protected
384 -- objects have been previously expanded into calls to the
385 -- Get_Ceiling run-time subprogram.
388 (Nkind (Ent) = N_Function_Call
389 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
391 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
393 -- The enclosing subprogram cannot be a protected function
396 while not (Is_Subprogram (S)
397 and then Convention (S) = Convention_Protected)
398 and then S /= Standard_Standard
403 if Ekind (S) = E_Function
404 and then Convention (S) = Convention_Protected
407 ("protected function cannot modify protected object",
411 -- Changes of the ceiling priority of the protected object
412 -- are only effective if the Ceiling_Locking policy is in
413 -- effect (AARM D.5.2 (5/2)).
415 if Locking_Policy /= 'C' then
416 Error_Msg_N ("assignment to the attribute PRIORITY has " &
418 Error_Msg_N ("\since no Locking_Policy has been " &
427 Diagnose_Non_Variable_Lhs (Lhs);
430 -- Error of assigning to limited type. We do however allow this in
431 -- certain cases where the front end generates the assignments.
433 elsif Is_Limited_Type (T1)
434 and then not Assignment_OK (Lhs)
435 and then not Assignment_OK (Original_Node (Lhs))
436 and then not Is_Value_Type (T1)
439 ("left hand of assignment must not be limited type", Lhs);
440 Explain_Limited_Type (T1, Lhs);
443 -- Enforce RM 3.9.3 (8): left-hand side cannot be abstract
445 elsif Is_Interface (T1)
446 and then not Is_Class_Wide_Type (T1)
449 ("target of assignment operation may not be abstract", Lhs);
453 -- Resolution may have updated the subtype, in case the left-hand
454 -- side is a private protected component. Use the correct subtype
455 -- to avoid scoping issues in the back-end.
459 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
460 -- type. For example:
464 -- type Acc is access P.T;
467 -- with Pkg; use Acc;
468 -- procedure Example is
471 -- A.all := B.all; -- ERROR
474 if Nkind (Lhs) = N_Explicit_Dereference
475 and then Ekind (T1) = E_Incomplete_Type
477 Error_Msg_N ("invalid use of incomplete type", Lhs);
482 -- Now we can complete the resolution of the right hand side
484 Set_Assignment_Type (Lhs, T1);
487 -- This is the point at which we check for an unset reference
489 Check_Unset_Reference (Rhs);
490 Check_Unprotected_Access (Lhs, Rhs);
492 -- Remaining steps are skipped if Rhs was syntactically in error
501 if not Covers (T1, T2) then
502 Wrong_Type (Rhs, Etype (Lhs));
507 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
508 -- types, use the non-limited view if available
510 if Nkind (Rhs) = N_Explicit_Dereference
511 and then Ekind (T2) = E_Incomplete_Type
512 and then Is_Tagged_Type (T2)
513 and then Present (Non_Limited_View (T2))
515 T2 := Non_Limited_View (T2);
518 Set_Assignment_Type (Rhs, T2);
520 if Total_Errors_Detected /= 0 then
530 if T1 = Any_Type or else T2 = Any_Type then
535 -- If the rhs is class-wide or dynamically tagged, then require the lhs
536 -- to be class-wide. The case where the rhs is a dynamically tagged call
537 -- to a dispatching operation with a controlling access result is
538 -- excluded from this check, since the target has an access type (and
539 -- no tag propagation occurs in that case).
541 if (Is_Class_Wide_Type (T2)
542 or else (Is_Dynamically_Tagged (Rhs)
543 and then not Is_Access_Type (T1)))
544 and then not Is_Class_Wide_Type (T1)
546 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
548 elsif Is_Class_Wide_Type (T1)
549 and then not Is_Class_Wide_Type (T2)
550 and then not Is_Tag_Indeterminate (Rhs)
551 and then not Is_Dynamically_Tagged (Rhs)
553 Error_Msg_N ("dynamically tagged expression required!", Rhs);
556 -- Propagate the tag from a class-wide target to the rhs when the rhs
557 -- is a tag-indeterminate call.
559 if Is_Tag_Indeterminate (Rhs) then
560 if Is_Class_Wide_Type (T1) then
561 Propagate_Tag (Lhs, Rhs);
563 elsif Nkind (Rhs) = N_Function_Call
564 and then Is_Entity_Name (Name (Rhs))
565 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
568 ("call to abstract function must be dispatching", Name (Rhs));
570 elsif Nkind (Rhs) = N_Qualified_Expression
571 and then Nkind (Expression (Rhs)) = N_Function_Call
572 and then Is_Entity_Name (Name (Expression (Rhs)))
574 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
577 ("call to abstract function must be dispatching",
578 Name (Expression (Rhs)));
582 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
583 -- apply an implicit conversion of the rhs to that type to force
584 -- appropriate static and run-time accessibility checks. This applies
585 -- as well to anonymous access-to-subprogram types that are component
586 -- subtypes or formal parameters.
588 if Ada_Version >= Ada_05
589 and then Is_Access_Type (T1)
591 if Is_Local_Anonymous_Access (T1)
592 or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
594 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
595 Analyze_And_Resolve (Rhs, T1);
599 -- Ada 2005 (AI-231): Assignment to not null variable
601 if Ada_Version >= Ada_05
602 and then Can_Never_Be_Null (T1)
603 and then not Assignment_OK (Lhs)
605 -- Case where we know the right hand side is null
607 if Known_Null (Rhs) then
608 Apply_Compile_Time_Constraint_Error
610 Msg => "(Ada 2005) null not allowed in null-excluding objects?",
611 Reason => CE_Null_Not_Allowed);
613 -- We still mark this as a possible modification, that's necessary
614 -- to reset Is_True_Constant, and desirable for xref purposes.
616 Note_Possible_Modification (Lhs, Sure => True);
619 -- If we know the right hand side is non-null, then we convert to the
620 -- target type, since we don't need a run time check in that case.
622 elsif not Can_Never_Be_Null (T2) then
623 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
624 Analyze_And_Resolve (Rhs, T1);
628 if Is_Scalar_Type (T1) then
629 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
631 -- For array types, verify that lengths match. If the right hand side
632 -- if a function call that has been inlined, the assignment has been
633 -- rewritten as a block, and the constraint check will be applied to the
634 -- assignment within the block.
636 elsif Is_Array_Type (T1)
638 (Nkind (Rhs) /= N_Type_Conversion
639 or else Is_Constrained (Etype (Rhs)))
641 (Nkind (Rhs) /= N_Function_Call
642 or else Nkind (N) /= N_Block_Statement)
644 -- Assignment verifies that the length of the Lsh and Rhs are equal,
645 -- but of course the indices do not have to match. If the right-hand
646 -- side is a type conversion to an unconstrained type, a length check
647 -- is performed on the expression itself during expansion. In rare
648 -- cases, the redundant length check is computed on an index type
649 -- with a different representation, triggering incorrect code in
652 Apply_Length_Check (Rhs, Etype (Lhs));
655 -- Discriminant checks are applied in the course of expansion
660 -- Note: modifications of the Lhs may only be recorded after
661 -- checks have been applied.
663 Note_Possible_Modification (Lhs, Sure => True);
665 -- ??? a real accessibility check is needed when ???
667 -- Post warning for redundant assignment or variable to itself
669 if Warn_On_Redundant_Constructs
671 -- We only warn for source constructs
673 and then Comes_From_Source (N)
675 -- Where the object is the same on both sides
677 and then Same_Object (Lhs, Original_Node (Rhs))
679 -- But exclude the case where the right side was an operation
680 -- that got rewritten (e.g. JUNK + K, where K was known to be
681 -- zero). We don't want to warn in such a case, since it is
682 -- reasonable to write such expressions especially when K is
683 -- defined symbolically in some other package.
685 and then Nkind (Original_Node (Rhs)) not in N_Op
687 if Nkind (Lhs) in N_Has_Entity then
689 ("?useless assignment of & to itself!", N, Entity (Lhs));
692 ("?useless assignment of object to itself!", N);
696 -- Check for non-allowed composite assignment
698 if not Support_Composite_Assign_On_Target
699 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
700 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
702 Error_Msg_CRT ("composite assignment", N);
705 -- Check elaboration warning for left side if not in elab code
707 if not In_Subprogram_Or_Concurrent_Unit then
708 Check_Elab_Assign (Lhs);
711 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
712 -- assignment is a source assignment in the extended main source unit.
713 -- We are not interested in any reference information outside this
714 -- context, or in compiler generated assignment statements.
716 if Comes_From_Source (N)
717 and then In_Extended_Main_Source_Unit (Lhs)
719 Set_Referenced_Modified (Lhs, Out_Param => False);
722 -- Final step. If left side is an entity, then we may be able to
723 -- reset the current tracked values to new safe values. We only have
724 -- something to do if the left side is an entity name, and expansion
725 -- has not modified the node into something other than an assignment,
726 -- and of course we only capture values if it is safe to do so.
728 if Is_Entity_Name (Lhs)
729 and then Nkind (N) = N_Assignment_Statement
732 Ent : constant Entity_Id := Entity (Lhs);
735 if Safe_To_Capture_Value (N, Ent) then
737 -- If simple variable on left side, warn if this assignment
738 -- blots out another one (rendering it useless) and note
739 -- location of assignment in case no one references value.
740 -- We only do this for source assignments, otherwise we can
741 -- generate bogus warnings when an assignment is rewritten as
742 -- another assignment, and gets tied up with itself.
744 -- Note: we don't use Record_Last_Assignment here, because we
745 -- have lots of other stuff to do under control of this test.
747 if Warn_On_Modified_Unread
748 and then Is_Assignable (Ent)
749 and then Comes_From_Source (N)
750 and then In_Extended_Main_Source_Unit (Ent)
752 Warn_On_Useless_Assignment (Ent, N);
753 Set_Last_Assignment (Ent, Lhs);
756 -- If we are assigning an access type and the left side is an
757 -- entity, then make sure that the Is_Known_[Non_]Null flags
758 -- properly reflect the state of the entity after assignment.
760 if Is_Access_Type (T1) then
761 if Known_Non_Null (Rhs) then
762 Set_Is_Known_Non_Null (Ent, True);
764 elsif Known_Null (Rhs)
765 and then not Can_Never_Be_Null (Ent)
767 Set_Is_Known_Null (Ent, True);
770 Set_Is_Known_Null (Ent, False);
772 if not Can_Never_Be_Null (Ent) then
773 Set_Is_Known_Non_Null (Ent, False);
777 -- For discrete types, we may be able to set the current value
778 -- if the value is known at compile time.
780 elsif Is_Discrete_Type (T1)
781 and then Compile_Time_Known_Value (Rhs)
783 Set_Current_Value (Ent, Rhs);
785 Set_Current_Value (Ent, Empty);
788 -- If not safe to capture values, kill them
795 end Analyze_Assignment;
797 -----------------------------
798 -- Analyze_Block_Statement --
799 -----------------------------
801 procedure Analyze_Block_Statement (N : Node_Id) is
802 Decls : constant List_Id := Declarations (N);
803 Id : constant Node_Id := Identifier (N);
804 HSS : constant Node_Id := Handled_Statement_Sequence (N);
807 -- If no handled statement sequence is present, things are really
808 -- messed up, and we just return immediately (this is a defence
809 -- against previous errors).
815 -- Normal processing with HSS present
818 EH : constant List_Id := Exception_Handlers (HSS);
819 Ent : Entity_Id := Empty;
822 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
823 -- Recursively save value of this global, will be restored on exit
826 -- Initialize unblocked exit count for statements of begin block
827 -- plus one for each exception handler that is present.
829 Unblocked_Exit_Count := 1;
832 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
835 -- If a label is present analyze it and mark it as referenced
841 -- An error defense. If we have an identifier, but no entity,
842 -- then something is wrong. If we have previous errors, then
843 -- just remove the identifier and continue, otherwise raise
847 if Total_Errors_Detected /= 0 then
848 Set_Identifier (N, Empty);
854 Set_Ekind (Ent, E_Block);
855 Generate_Reference (Ent, N, ' ');
856 Generate_Definition (Ent);
858 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
859 Set_Label_Construct (Parent (Ent), N);
864 -- If no entity set, create a label entity
867 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
868 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
872 Set_Etype (Ent, Standard_Void_Type);
873 Set_Block_Node (Ent, Identifier (N));
876 if Present (Decls) then
877 Analyze_Declarations (Decls);
879 Inspect_Deferred_Constant_Completion (Decls);
883 Process_End_Label (HSS, 'e', Ent);
885 -- If exception handlers are present, then we indicate that
886 -- enclosing scopes contain a block with handlers. We only
887 -- need to mark non-generic scopes.
892 Set_Has_Nested_Block_With_Handler (S);
893 exit when Is_Overloadable (S)
894 or else Ekind (S) = E_Package
895 or else Is_Generic_Unit (S);
900 Check_References (Ent);
901 Warn_On_Useless_Assignments (Ent);
904 if Unblocked_Exit_Count = 0 then
905 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
906 Check_Unreachable_Code (N);
908 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
911 end Analyze_Block_Statement;
913 ----------------------------
914 -- Analyze_Case_Statement --
915 ----------------------------
917 procedure Analyze_Case_Statement (N : Node_Id) is
919 Exp_Type : Entity_Id;
920 Exp_Btype : Entity_Id;
923 Others_Present : Boolean;
925 pragma Warnings (Off, Last_Choice);
926 pragma Warnings (Off, Dont_Care);
927 -- Don't care about assigned values
929 Statements_Analyzed : Boolean := False;
930 -- Set True if at least some statement sequences get analyzed.
931 -- If False on exit, means we had a serious error that prevented
932 -- full analysis of the case statement, and as a result it is not
933 -- a good idea to output warning messages about unreachable code.
935 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
936 -- Recursively save value of this global, will be restored on exit
938 procedure Non_Static_Choice_Error (Choice : Node_Id);
939 -- Error routine invoked by the generic instantiation below when
940 -- the case statement has a non static choice.
942 procedure Process_Statements (Alternative : Node_Id);
943 -- Analyzes all the statements associated to a case alternative.
944 -- Needed by the generic instantiation below.
946 package Case_Choices_Processing is new
947 Generic_Choices_Processing
948 (Get_Alternatives => Alternatives,
949 Get_Choices => Discrete_Choices,
950 Process_Empty_Choice => No_OP,
951 Process_Non_Static_Choice => Non_Static_Choice_Error,
952 Process_Associated_Node => Process_Statements);
953 use Case_Choices_Processing;
954 -- Instantiation of the generic choice processing package
956 -----------------------------
957 -- Non_Static_Choice_Error --
958 -----------------------------
960 procedure Non_Static_Choice_Error (Choice : Node_Id) is
963 ("choice given in case statement is not static!", Choice);
964 end Non_Static_Choice_Error;
966 ------------------------
967 -- Process_Statements --
968 ------------------------
970 procedure Process_Statements (Alternative : Node_Id) is
971 Choices : constant List_Id := Discrete_Choices (Alternative);
975 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
976 Statements_Analyzed := True;
978 -- An interesting optimization. If the case statement expression
979 -- is a simple entity, then we can set the current value within
980 -- an alternative if the alternative has one possible value.
984 -- when 2 | 3 => beta
985 -- when others => gamma
987 -- Here we know that N is initially 1 within alpha, but for beta
988 -- and gamma, we do not know anything more about the initial value.
990 if Is_Entity_Name (Exp) then
993 if Ekind (Ent) = E_Variable
995 Ekind (Ent) = E_In_Out_Parameter
997 Ekind (Ent) = E_Out_Parameter
999 if List_Length (Choices) = 1
1000 and then Nkind (First (Choices)) in N_Subexpr
1001 and then Compile_Time_Known_Value (First (Choices))
1003 Set_Current_Value (Entity (Exp), First (Choices));
1006 Analyze_Statements (Statements (Alternative));
1008 -- After analyzing the case, set the current value to empty
1009 -- since we won't know what it is for the next alternative
1010 -- (unless reset by this same circuit), or after the case.
1012 Set_Current_Value (Entity (Exp), Empty);
1017 -- Case where expression is not an entity name of a variable
1019 Analyze_Statements (Statements (Alternative));
1020 end Process_Statements;
1022 -- Table to record choices. Put after subprograms since we make
1023 -- a call to Number_Of_Choices to get the right number of entries.
1025 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
1026 pragma Warnings (Off, Case_Table);
1028 -- Start of processing for Analyze_Case_Statement
1031 Unblocked_Exit_Count := 0;
1032 Exp := Expression (N);
1035 -- The expression must be of any discrete type. In rare cases, the
1036 -- expander constructs a case statement whose expression has a private
1037 -- type whose full view is discrete. This can happen when generating
1038 -- a stream operation for a variant type after the type is frozen,
1039 -- when the partial of view of the type of the discriminant is private.
1040 -- In that case, use the full view to analyze case alternatives.
1042 if not Is_Overloaded (Exp)
1043 and then not Comes_From_Source (N)
1044 and then Is_Private_Type (Etype (Exp))
1045 and then Present (Full_View (Etype (Exp)))
1046 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1048 Resolve (Exp, Etype (Exp));
1049 Exp_Type := Full_View (Etype (Exp));
1052 Analyze_And_Resolve (Exp, Any_Discrete);
1053 Exp_Type := Etype (Exp);
1056 Check_Unset_Reference (Exp);
1057 Exp_Btype := Base_Type (Exp_Type);
1059 -- The expression must be of a discrete type which must be determinable
1060 -- independently of the context in which the expression occurs, but
1061 -- using the fact that the expression must be of a discrete type.
1062 -- Moreover, the type this expression must not be a character literal
1063 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1065 -- If error already reported by Resolve, nothing more to do
1067 if Exp_Btype = Any_Discrete
1068 or else Exp_Btype = Any_Type
1072 elsif Exp_Btype = Any_Character then
1074 ("character literal as case expression is ambiguous", Exp);
1077 elsif Ada_Version = Ada_83
1078 and then (Is_Generic_Type (Exp_Btype)
1079 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1082 ("(Ada 83) case expression cannot be of a generic type", Exp);
1086 -- If the case expression is a formal object of mode in out, then
1087 -- treat it as having a nonstatic subtype by forcing use of the base
1088 -- type (which has to get passed to Check_Case_Choices below). Also
1089 -- use base type when the case expression is parenthesized.
1091 if Paren_Count (Exp) > 0
1092 or else (Is_Entity_Name (Exp)
1093 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1095 Exp_Type := Exp_Btype;
1098 -- Call instantiated Analyze_Choices which does the rest of the work
1101 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
1103 if Exp_Type = Universal_Integer and then not Others_Present then
1104 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1107 -- If all our exits were blocked by unconditional transfers of control,
1108 -- then the entire CASE statement acts as an unconditional transfer of
1109 -- control, so treat it like one, and check unreachable code. Skip this
1110 -- test if we had serious errors preventing any statement analysis.
1112 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1113 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1114 Check_Unreachable_Code (N);
1116 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1119 if not Expander_Active
1120 and then Compile_Time_Known_Value (Expression (N))
1121 and then Serious_Errors_Detected = 0
1124 Chosen : constant Node_Id := Find_Static_Alternative (N);
1128 Alt := First (Alternatives (N));
1129 while Present (Alt) loop
1130 if Alt /= Chosen then
1131 Remove_Warning_Messages (Statements (Alt));
1138 end Analyze_Case_Statement;
1140 ----------------------------
1141 -- Analyze_Exit_Statement --
1142 ----------------------------
1144 -- If the exit includes a name, it must be the name of a currently open
1145 -- loop. Otherwise there must be an innermost open loop on the stack,
1146 -- to which the statement implicitly refers.
1148 procedure Analyze_Exit_Statement (N : Node_Id) is
1149 Target : constant Node_Id := Name (N);
1150 Cond : constant Node_Id := Condition (N);
1151 Scope_Id : Entity_Id;
1157 Check_Unreachable_Code (N);
1160 if Present (Target) then
1162 U_Name := Entity (Target);
1164 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1165 Error_Msg_N ("invalid loop name in exit statement", N);
1168 Set_Has_Exit (U_Name);
1175 for J in reverse 0 .. Scope_Stack.Last loop
1176 Scope_Id := Scope_Stack.Table (J).Entity;
1177 Kind := Ekind (Scope_Id);
1180 and then (No (Target) or else Scope_Id = U_Name) then
1181 Set_Has_Exit (Scope_Id);
1184 elsif Kind = E_Block
1185 or else Kind = E_Loop
1186 or else Kind = E_Return_Statement
1192 ("cannot exit from program unit or accept statement", N);
1197 -- Verify that if present the condition is a Boolean expression
1199 if Present (Cond) then
1200 Analyze_And_Resolve (Cond, Any_Boolean);
1201 Check_Unset_Reference (Cond);
1203 end Analyze_Exit_Statement;
1205 ----------------------------
1206 -- Analyze_Goto_Statement --
1207 ----------------------------
1209 procedure Analyze_Goto_Statement (N : Node_Id) is
1210 Label : constant Node_Id := Name (N);
1211 Scope_Id : Entity_Id;
1212 Label_Scope : Entity_Id;
1213 Label_Ent : Entity_Id;
1216 Check_Unreachable_Code (N);
1217 Kill_Current_Values (Last_Assignment_Only => True);
1220 Label_Ent := Entity (Label);
1222 -- Ignore previous error
1224 if Label_Ent = Any_Id then
1227 -- We just have a label as the target of a goto
1229 elsif Ekind (Label_Ent) /= E_Label then
1230 Error_Msg_N ("target of goto statement must be a label", Label);
1233 -- Check that the target of the goto is reachable according to Ada
1234 -- scoping rules. Note: the special gotos we generate for optimizing
1235 -- local handling of exceptions would violate these rules, but we mark
1236 -- such gotos as analyzed when built, so this code is never entered.
1238 elsif not Reachable (Label_Ent) then
1239 Error_Msg_N ("target of goto statement is not reachable", Label);
1243 -- Here if goto passes initial validity checks
1245 Label_Scope := Enclosing_Scope (Label_Ent);
1247 for J in reverse 0 .. Scope_Stack.Last loop
1248 Scope_Id := Scope_Stack.Table (J).Entity;
1250 if Label_Scope = Scope_Id
1251 or else (Ekind (Scope_Id) /= E_Block
1252 and then Ekind (Scope_Id) /= E_Loop
1253 and then Ekind (Scope_Id) /= E_Return_Statement)
1255 if Scope_Id /= Label_Scope then
1257 ("cannot exit from program unit or accept statement", N);
1264 raise Program_Error;
1265 end Analyze_Goto_Statement;
1267 --------------------------
1268 -- Analyze_If_Statement --
1269 --------------------------
1271 -- A special complication arises in the analysis of if statements
1273 -- The expander has circuitry to completely delete code that it
1274 -- can tell will not be executed (as a result of compile time known
1275 -- conditions). In the analyzer, we ensure that code that will be
1276 -- deleted in this manner is analyzed but not expanded. This is
1277 -- obviously more efficient, but more significantly, difficulties
1278 -- arise if code is expanded and then eliminated (e.g. exception
1279 -- table entries disappear). Similarly, itypes generated in deleted
1280 -- code must be frozen from start, because the nodes on which they
1281 -- depend will not be available at the freeze point.
1283 procedure Analyze_If_Statement (N : Node_Id) is
1286 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1287 -- Recursively save value of this global, will be restored on exit
1289 Save_In_Deleted_Code : Boolean;
1291 Del : Boolean := False;
1292 -- This flag gets set True if a True condition has been found,
1293 -- which means that remaining ELSE/ELSIF parts are deleted.
1295 procedure Analyze_Cond_Then (Cnode : Node_Id);
1296 -- This is applied to either the N_If_Statement node itself or
1297 -- to an N_Elsif_Part node. It deals with analyzing the condition
1298 -- and the THEN statements associated with it.
1300 -----------------------
1301 -- Analyze_Cond_Then --
1302 -----------------------
1304 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1305 Cond : constant Node_Id := Condition (Cnode);
1306 Tstm : constant List_Id := Then_Statements (Cnode);
1309 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1310 Analyze_And_Resolve (Cond, Any_Boolean);
1311 Check_Unset_Reference (Cond);
1312 Set_Current_Value_Condition (Cnode);
1314 -- If already deleting, then just analyze then statements
1317 Analyze_Statements (Tstm);
1319 -- Compile time known value, not deleting yet
1321 elsif Compile_Time_Known_Value (Cond) then
1322 Save_In_Deleted_Code := In_Deleted_Code;
1324 -- If condition is True, then analyze the THEN statements
1325 -- and set no expansion for ELSE and ELSIF parts.
1327 if Is_True (Expr_Value (Cond)) then
1328 Analyze_Statements (Tstm);
1330 Expander_Mode_Save_And_Set (False);
1331 In_Deleted_Code := True;
1333 -- If condition is False, analyze THEN with expansion off
1335 else -- Is_False (Expr_Value (Cond))
1336 Expander_Mode_Save_And_Set (False);
1337 In_Deleted_Code := True;
1338 Analyze_Statements (Tstm);
1339 Expander_Mode_Restore;
1340 In_Deleted_Code := Save_In_Deleted_Code;
1343 -- Not known at compile time, not deleting, normal analysis
1346 Analyze_Statements (Tstm);
1348 end Analyze_Cond_Then;
1350 -- Start of Analyze_If_Statement
1353 -- Initialize exit count for else statements. If there is no else
1354 -- part, this count will stay non-zero reflecting the fact that the
1355 -- uncovered else case is an unblocked exit.
1357 Unblocked_Exit_Count := 1;
1358 Analyze_Cond_Then (N);
1360 -- Now to analyze the elsif parts if any are present
1362 if Present (Elsif_Parts (N)) then
1363 E := First (Elsif_Parts (N));
1364 while Present (E) loop
1365 Analyze_Cond_Then (E);
1370 if Present (Else_Statements (N)) then
1371 Analyze_Statements (Else_Statements (N));
1374 -- If all our exits were blocked by unconditional transfers of control,
1375 -- then the entire IF statement acts as an unconditional transfer of
1376 -- control, so treat it like one, and check unreachable code.
1378 if Unblocked_Exit_Count = 0 then
1379 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1380 Check_Unreachable_Code (N);
1382 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1386 Expander_Mode_Restore;
1387 In_Deleted_Code := Save_In_Deleted_Code;
1390 if not Expander_Active
1391 and then Compile_Time_Known_Value (Condition (N))
1392 and then Serious_Errors_Detected = 0
1394 if Is_True (Expr_Value (Condition (N))) then
1395 Remove_Warning_Messages (Else_Statements (N));
1397 if Present (Elsif_Parts (N)) then
1398 E := First (Elsif_Parts (N));
1399 while Present (E) loop
1400 Remove_Warning_Messages (Then_Statements (E));
1406 Remove_Warning_Messages (Then_Statements (N));
1409 end Analyze_If_Statement;
1411 ----------------------------------------
1412 -- Analyze_Implicit_Label_Declaration --
1413 ----------------------------------------
1415 -- An implicit label declaration is generated in the innermost
1416 -- enclosing declarative part. This is done for labels as well as
1417 -- block and loop names.
1419 -- Note: any changes in this routine may need to be reflected in
1420 -- Analyze_Label_Entity.
1422 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1423 Id : constant Node_Id := Defining_Identifier (N);
1426 Set_Ekind (Id, E_Label);
1427 Set_Etype (Id, Standard_Void_Type);
1428 Set_Enclosing_Scope (Id, Current_Scope);
1429 end Analyze_Implicit_Label_Declaration;
1431 ------------------------------
1432 -- Analyze_Iteration_Scheme --
1433 ------------------------------
1435 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1437 procedure Process_Bounds (R : Node_Id);
1438 -- If the iteration is given by a range, create temporaries and
1439 -- assignment statements block to capture the bounds and perform
1440 -- required finalization actions in case a bound includes a function
1441 -- call that uses the temporary stack. We first pre-analyze a copy of
1442 -- the range in order to determine the expected type, and analyze and
1443 -- resolve the original bounds.
1445 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1446 -- If the bounds are given by a 'Range reference on a function call
1447 -- that returns a controlled array, introduce an explicit declaration
1448 -- to capture the bounds, so that the function result can be finalized
1449 -- in timely fashion.
1451 --------------------
1452 -- Process_Bounds --
1453 --------------------
1455 procedure Process_Bounds (R : Node_Id) is
1456 Loc : constant Source_Ptr := Sloc (N);
1457 R_Copy : constant Node_Id := New_Copy_Tree (R);
1458 Lo : constant Node_Id := Low_Bound (R);
1459 Hi : constant Node_Id := High_Bound (R);
1460 New_Lo_Bound : Node_Id := Empty;
1461 New_Hi_Bound : Node_Id := Empty;
1463 Save_Analysis : Boolean;
1466 (Original_Bound : Node_Id;
1467 Analyzed_Bound : Node_Id) return Node_Id;
1468 -- Capture value of bound and return captured value
1475 (Original_Bound : Node_Id;
1476 Analyzed_Bound : Node_Id) return Node_Id
1483 -- If the bound is a constant or an object, no need for a separate
1484 -- declaration. If the bound is the result of previous expansion
1485 -- it is already analyzed and should not be modified. Note that
1486 -- the Bound will be resolved later, if needed, as part of the
1487 -- call to Make_Index (literal bounds may need to be resolved to
1490 if Analyzed (Original_Bound) then
1491 return Original_Bound;
1493 elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
1494 N_Character_Literal)
1495 or else Is_Entity_Name (Analyzed_Bound)
1497 Analyze_And_Resolve (Original_Bound, Typ);
1498 return Original_Bound;
1501 -- Here we need to capture the value
1503 Analyze_And_Resolve (Original_Bound, Typ);
1506 Make_Defining_Identifier (Loc,
1507 Chars => New_Internal_Name ('S'));
1509 -- Normally, the best approach is simply to generate a constant
1510 -- declaration that captures the bound. However, there is a nasty
1511 -- case where this is wrong. If the bound is complex, and has a
1512 -- possible use of the secondary stack, we need to generate a
1513 -- separate assignment statement to ensure the creation of a block
1514 -- which will release the secondary stack.
1516 -- We prefer the constant declaration, since it leaves us with a
1517 -- proper trace of the value, useful in optimizations that get rid
1518 -- of junk range checks.
1520 -- Probably we want something like the Side_Effect_Free routine
1521 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1522 -- and 'First applied to an entity, since these are the important
1523 -- cases for range check optimizations.
1525 if Nkind (Original_Bound) = N_Attribute_Reference
1526 and then (Attribute_Name (Original_Bound) = Name_First
1528 Attribute_Name (Original_Bound) = Name_Last)
1529 and then Is_Entity_Name (Prefix (Original_Bound))
1532 Make_Object_Declaration (Loc,
1533 Defining_Identifier => Id,
1534 Constant_Present => True,
1535 Object_Definition => New_Occurrence_Of (Typ, Loc),
1536 Expression => Relocate_Node (Original_Bound));
1538 Insert_Before (Parent (N), Decl);
1540 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1541 return Expression (Decl);
1544 -- Here we make a declaration with a separate assignment statement
1547 Make_Object_Declaration (Loc,
1548 Defining_Identifier => Id,
1549 Object_Definition => New_Occurrence_Of (Typ, Loc));
1551 Insert_Before (Parent (N), Decl);
1555 Make_Assignment_Statement (Loc,
1556 Name => New_Occurrence_Of (Id, Loc),
1557 Expression => Relocate_Node (Original_Bound));
1559 Insert_Before (Parent (N), Assign);
1562 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1564 if Nkind (Assign) = N_Assignment_Statement then
1565 return Expression (Assign);
1567 return Original_Bound;
1571 -- Start of processing for Process_Bounds
1574 -- Determine expected type of range by analyzing separate copy
1575 -- Do the analysis and resolution of the copy of the bounds with
1576 -- expansion disabled, to prevent the generation of finalization
1577 -- actions on each bound. This prevents memory leaks when the
1578 -- bounds contain calls to functions returning controlled arrays.
1580 Set_Parent (R_Copy, Parent (R));
1581 Save_Analysis := Full_Analysis;
1582 Full_Analysis := False;
1583 Expander_Mode_Save_And_Set (False);
1587 if Is_Overloaded (R_Copy) then
1589 -- Apply preference rules for range of predefined integer types,
1590 -- or diagnose true ambiguity.
1595 Found : Entity_Id := Empty;
1598 Get_First_Interp (R_Copy, I, It);
1599 while Present (It.Typ) loop
1600 if Is_Discrete_Type (It.Typ) then
1604 if Scope (Found) = Standard_Standard then
1607 elsif Scope (It.Typ) = Standard_Standard then
1611 -- Both of them are user-defined
1614 ("ambiguous bounds in range of iteration",
1616 Error_Msg_N ("\possible interpretations:", R_Copy);
1617 Error_Msg_NE ("\\} ", R_Copy, Found);
1618 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1624 Get_Next_Interp (I, It);
1630 Expander_Mode_Restore;
1631 Full_Analysis := Save_Analysis;
1633 Typ := Etype (R_Copy);
1635 -- If the type of the discrete range is Universal_Integer, then
1636 -- the bound's type must be resolved to Integer, and any object
1637 -- used to hold the bound must also have type Integer, unless the
1638 -- literal bounds are constant-folded expressions that carry a user-
1641 if Typ = Universal_Integer then
1642 if Nkind (Lo) = N_Integer_Literal
1643 and then Present (Etype (Lo))
1644 and then Scope (Etype (Lo)) /= Standard_Standard
1648 elsif Nkind (Hi) = N_Integer_Literal
1649 and then Present (Etype (Hi))
1650 and then Scope (Etype (Hi)) /= Standard_Standard
1655 Typ := Standard_Integer;
1661 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1662 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1664 -- Propagate staticness to loop range itself, in case the
1665 -- corresponding subtype is static.
1667 if New_Lo_Bound /= Lo
1668 and then Is_Static_Expression (New_Lo_Bound)
1670 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1673 if New_Hi_Bound /= Hi
1674 and then Is_Static_Expression (New_Hi_Bound)
1676 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1680 --------------------------------------
1681 -- Check_Controlled_Array_Attribute --
1682 --------------------------------------
1684 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1686 if Nkind (DS) = N_Attribute_Reference
1687 and then Is_Entity_Name (Prefix (DS))
1688 and then Ekind (Entity (Prefix (DS))) = E_Function
1689 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1692 Component_Type (Etype (Entity (Prefix (DS)))))
1693 and then Expander_Active
1696 Loc : constant Source_Ptr := Sloc (N);
1697 Arr : constant Entity_Id :=
1698 Etype (Entity (Prefix (DS)));
1699 Indx : constant Entity_Id :=
1700 Base_Type (Etype (First_Index (Arr)));
1701 Subt : constant Entity_Id :=
1702 Make_Defining_Identifier
1703 (Loc, New_Internal_Name ('S'));
1708 Make_Subtype_Declaration (Loc,
1709 Defining_Identifier => Subt,
1710 Subtype_Indication =>
1711 Make_Subtype_Indication (Loc,
1712 Subtype_Mark => New_Reference_To (Indx, Loc),
1714 Make_Range_Constraint (Loc,
1715 Relocate_Node (DS))));
1716 Insert_Before (Parent (N), Decl);
1720 Make_Attribute_Reference (Loc,
1721 Prefix => New_Reference_To (Subt, Loc),
1722 Attribute_Name => Attribute_Name (DS)));
1726 end Check_Controlled_Array_Attribute;
1728 -- Start of processing for Analyze_Iteration_Scheme
1731 -- For an infinite loop, there is no iteration scheme
1738 Cond : constant Node_Id := Condition (N);
1741 -- For WHILE loop, verify that the condition is a Boolean
1742 -- expression and resolve and check it.
1744 if Present (Cond) then
1745 Analyze_And_Resolve (Cond, Any_Boolean);
1746 Check_Unset_Reference (Cond);
1747 Set_Current_Value_Condition (N);
1750 -- Else we have a FOR loop
1754 LP : constant Node_Id := Loop_Parameter_Specification (N);
1755 Id : constant Entity_Id := Defining_Identifier (LP);
1756 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1761 -- We always consider the loop variable to be referenced,
1762 -- since the loop may be used just for counting purposes.
1764 Generate_Reference (Id, N, ' ');
1766 -- Check for case of loop variable hiding a local
1767 -- variable (used later on to give a nice warning
1768 -- if the hidden variable is never assigned).
1771 H : constant Entity_Id := Homonym (Id);
1774 and then Enclosing_Dynamic_Scope (H) =
1775 Enclosing_Dynamic_Scope (Id)
1776 and then Ekind (H) = E_Variable
1777 and then Is_Discrete_Type (Etype (H))
1779 Set_Hiding_Loop_Variable (H, Id);
1783 -- Now analyze the subtype definition. If it is
1784 -- a range, create temporaries for bounds.
1786 if Nkind (DS) = N_Range
1787 and then Expander_Active
1789 Process_Bounds (DS);
1798 -- The subtype indication may denote the completion
1799 -- of an incomplete type declaration.
1801 if Is_Entity_Name (DS)
1802 and then Present (Entity (DS))
1803 and then Is_Type (Entity (DS))
1804 and then Ekind (Entity (DS)) = E_Incomplete_Type
1806 Set_Entity (DS, Get_Full_View (Entity (DS)));
1807 Set_Etype (DS, Entity (DS));
1810 if not Is_Discrete_Type (Etype (DS)) then
1811 Wrong_Type (DS, Any_Discrete);
1812 Set_Etype (DS, Any_Type);
1815 Check_Controlled_Array_Attribute (DS);
1817 Make_Index (DS, LP);
1819 Set_Ekind (Id, E_Loop_Parameter);
1820 Set_Etype (Id, Etype (DS));
1821 Set_Is_Known_Valid (Id, True);
1823 -- The loop is not a declarative part, so the only entity
1824 -- declared "within" must be frozen explicitly.
1827 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1829 if Is_Non_Empty_List (Flist) then
1830 Insert_Actions (N, Flist);
1834 -- Check for null or possibly null range and issue warning.
1835 -- We suppress such messages in generic templates and
1836 -- instances, because in practice they tend to be dubious
1839 if Nkind (DS) = N_Range
1840 and then Comes_From_Source (N)
1843 L : constant Node_Id := Low_Bound (DS);
1844 H : constant Node_Id := High_Bound (DS);
1853 pragma Warnings (Off, Hlo);
1856 Determine_Range (L, LOK, Llo, Lhi);
1857 Determine_Range (H, HOK, Hlo, Hhi);
1859 -- If range of loop is null, issue warning
1861 if (LOK and HOK) and then Llo > Hhi then
1863 -- Suppress the warning if inside a generic
1864 -- template or instance, since in practice
1865 -- they tend to be dubious in these cases since
1866 -- they can result from intended parametrization.
1868 if not Inside_A_Generic
1869 and then not In_Instance
1872 ("?loop range is null, loop will not execute",
1876 -- Since we know the range of the loop is null,
1877 -- set the appropriate flag to suppress any
1878 -- warnings that would otherwise be issued in
1879 -- the body of the loop that will not execute.
1880 -- We do this even in the generic case, since
1881 -- if it is dubious to warn on the null loop
1882 -- itself, it is certainly dubious to warn for
1883 -- conditions that occur inside it!
1885 Set_Is_Null_Loop (Parent (N));
1887 -- The other case for a warning is a reverse loop
1888 -- where the upper bound is the integer literal
1889 -- zero or one, and the lower bound can be positive.
1891 -- For example, we have
1893 -- for J in reverse N .. 1 loop
1895 -- In practice, this is very likely to be a case
1896 -- of reversing the bounds incorrectly in the range.
1898 elsif Reverse_Present (LP)
1899 and then Nkind (Original_Node (H)) =
1901 and then (Intval (H) = Uint_0
1903 Intval (H) = Uint_1)
1906 Error_Msg_N ("?loop range may be null", DS);
1907 Error_Msg_N ("\?bounds may be wrong way round", DS);
1915 end Analyze_Iteration_Scheme;
1921 -- Note: the semantic work required for analyzing labels (setting them as
1922 -- reachable) was done in a prepass through the statements in the block,
1923 -- so that forward gotos would be properly handled. See Analyze_Statements
1924 -- for further details. The only processing required here is to deal with
1925 -- optimizations that depend on an assumption of sequential control flow,
1926 -- since of course the occurrence of a label breaks this assumption.
1928 procedure Analyze_Label (N : Node_Id) is
1929 pragma Warnings (Off, N);
1931 Kill_Current_Values;
1934 --------------------------
1935 -- Analyze_Label_Entity --
1936 --------------------------
1938 procedure Analyze_Label_Entity (E : Entity_Id) is
1940 Set_Ekind (E, E_Label);
1941 Set_Etype (E, Standard_Void_Type);
1942 Set_Enclosing_Scope (E, Current_Scope);
1943 Set_Reachable (E, True);
1944 end Analyze_Label_Entity;
1946 ----------------------------
1947 -- Analyze_Loop_Statement --
1948 ----------------------------
1950 procedure Analyze_Loop_Statement (N : Node_Id) is
1951 Loop_Statement : constant Node_Id := N;
1953 Id : constant Node_Id := Identifier (Loop_Statement);
1954 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
1958 if Present (Id) then
1960 -- Make name visible, e.g. for use in exit statements. Loop
1961 -- labels are always considered to be referenced.
1966 -- Guard against serious error (typically, a scope mismatch when
1967 -- semantic analysis is requested) by creating loop entity to
1968 -- continue analysis.
1971 if Total_Errors_Detected /= 0 then
1974 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
1976 raise Program_Error;
1980 Generate_Reference (Ent, Loop_Statement, ' ');
1981 Generate_Definition (Ent);
1983 -- If we found a label, mark its type. If not, ignore it, since it
1984 -- means we have a conflicting declaration, which would already
1985 -- have been diagnosed at declaration time. Set Label_Construct
1986 -- of the implicit label declaration, which is not created by the
1987 -- parser for generic units.
1989 if Ekind (Ent) = E_Label then
1990 Set_Ekind (Ent, E_Loop);
1992 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
1993 Set_Label_Construct (Parent (Ent), Loop_Statement);
1998 -- Case of no identifier present
2003 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2004 Set_Etype (Ent, Standard_Void_Type);
2005 Set_Parent (Ent, Loop_Statement);
2008 -- Kill current values on entry to loop, since statements in body of
2009 -- loop may have been executed before the loop is entered. Similarly we
2010 -- kill values after the loop, since we do not know that the body of the
2011 -- loop was executed.
2013 Kill_Current_Values;
2015 Analyze_Iteration_Scheme (Iter);
2016 Analyze_Statements (Statements (Loop_Statement));
2017 Process_End_Label (Loop_Statement, 'e', Ent);
2019 Kill_Current_Values;
2020 Check_Infinite_Loop_Warning (N);
2022 -- Code after loop is unreachable if the loop has no WHILE or FOR
2023 -- and contains no EXIT statements within the body of the loop.
2025 if No (Iter) and then not Has_Exit (Ent) then
2026 Check_Unreachable_Code (N);
2028 end Analyze_Loop_Statement;
2030 ----------------------------
2031 -- Analyze_Null_Statement --
2032 ----------------------------
2034 -- Note: the semantics of the null statement is implemented by a single
2035 -- null statement, too bad everything isn't as simple as this!
2037 procedure Analyze_Null_Statement (N : Node_Id) is
2038 pragma Warnings (Off, N);
2041 end Analyze_Null_Statement;
2043 ------------------------
2044 -- Analyze_Statements --
2045 ------------------------
2047 procedure Analyze_Statements (L : List_Id) is
2052 -- The labels declared in the statement list are reachable from
2053 -- statements in the list. We do this as a prepass so that any
2054 -- goto statement will be properly flagged if its target is not
2055 -- reachable. This is not required, but is nice behavior!
2058 while Present (S) loop
2059 if Nkind (S) = N_Label then
2060 Analyze (Identifier (S));
2061 Lab := Entity (Identifier (S));
2063 -- If we found a label mark it as reachable
2065 if Ekind (Lab) = E_Label then
2066 Generate_Definition (Lab);
2067 Set_Reachable (Lab);
2069 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
2070 Set_Label_Construct (Parent (Lab), S);
2073 -- If we failed to find a label, it means the implicit declaration
2074 -- of the label was hidden. A for-loop parameter can do this to
2075 -- a label with the same name inside the loop, since the implicit
2076 -- label declaration is in the innermost enclosing body or block
2080 Error_Msg_Sloc := Sloc (Lab);
2082 ("implicit label declaration for & is hidden#",
2090 -- Perform semantic analysis on all statements
2092 Conditional_Statements_Begin;
2095 while Present (S) loop
2100 Conditional_Statements_End;
2102 -- Make labels unreachable. Visibility is not sufficient, because
2103 -- labels in one if-branch for example are not reachable from the
2104 -- other branch, even though their declarations are in the enclosing
2105 -- declarative part.
2108 while Present (S) loop
2109 if Nkind (S) = N_Label then
2110 Set_Reachable (Entity (Identifier (S)), False);
2115 end Analyze_Statements;
2117 ----------------------------
2118 -- Check_Unreachable_Code --
2119 ----------------------------
2121 procedure Check_Unreachable_Code (N : Node_Id) is
2122 Error_Loc : Source_Ptr;
2126 if Is_List_Member (N)
2127 and then Comes_From_Source (N)
2133 Nxt := Original_Node (Next (N));
2135 -- If a label follows us, then we never have dead code, since
2136 -- someone could branch to the label, so we just ignore it.
2138 if Nkind (Nxt) = N_Label then
2141 -- Otherwise see if we have a real statement following us
2144 and then Comes_From_Source (Nxt)
2145 and then Is_Statement (Nxt)
2147 -- Special very annoying exception. If we have a return that
2148 -- follows a raise, then we allow it without a warning, since
2149 -- the Ada RM annoyingly requires a useless return here!
2151 if Nkind (Original_Node (N)) /= N_Raise_Statement
2152 or else Nkind (Nxt) /= N_Simple_Return_Statement
2154 -- The rather strange shenanigans with the warning message
2155 -- here reflects the fact that Kill_Dead_Code is very good
2156 -- at removing warnings in deleted code, and this is one
2157 -- warning we would prefer NOT to have removed.
2159 Error_Loc := Sloc (Nxt);
2161 -- If we have unreachable code, analyze and remove the
2162 -- unreachable code, since it is useless and we don't
2163 -- want to generate junk warnings.
2165 -- We skip this step if we are not in code generation mode.
2166 -- This is the one case where we remove dead code in the
2167 -- semantics as opposed to the expander, and we do not want
2168 -- to remove code if we are not in code generation mode,
2169 -- since this messes up the ASIS trees.
2171 -- Note that one might react by moving the whole circuit to
2172 -- exp_ch5, but then we lose the warning in -gnatc mode.
2174 if Operating_Mode = Generate_Code then
2178 -- Quit deleting when we have nothing more to delete
2179 -- or if we hit a label (since someone could transfer
2180 -- control to a label, so we should not delete it).
2182 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2184 -- Statement/declaration is to be deleted
2188 Kill_Dead_Code (Nxt);
2192 -- Now issue the warning
2194 Error_Msg ("?unreachable code!", Error_Loc);
2197 -- If the unconditional transfer of control instruction is
2198 -- the last statement of a sequence, then see if our parent
2199 -- is one of the constructs for which we count unblocked exits,
2200 -- and if so, adjust the count.
2205 -- Statements in THEN part or ELSE part of IF statement
2207 if Nkind (P) = N_If_Statement then
2210 -- Statements in ELSIF part of an IF statement
2212 elsif Nkind (P) = N_Elsif_Part then
2214 pragma Assert (Nkind (P) = N_If_Statement);
2216 -- Statements in CASE statement alternative
2218 elsif Nkind (P) = N_Case_Statement_Alternative then
2220 pragma Assert (Nkind (P) = N_Case_Statement);
2222 -- Statements in body of block
2224 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2225 and then Nkind (Parent (P)) = N_Block_Statement
2229 -- Statements in exception handler in a block
2231 elsif Nkind (P) = N_Exception_Handler
2232 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2233 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2237 -- None of these cases, so return
2243 -- This was one of the cases we are looking for (i.e. the
2244 -- parent construct was IF, CASE or block) so decrement count.
2246 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2250 end Check_Unreachable_Code;