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_Aux; use Sem_Aux;
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 is not
92 -- 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
123 Ent : constant Entity_Id := Entity (N);
126 if Ekind (Ent) = E_In_Parameter then
128 ("assignment to IN mode parameter not allowed", N);
130 -- Renamings of protected private components are turned into
131 -- constants when compiling a protected function. In the case
132 -- of single protected types, the private component appears
135 elsif (Is_Prival (Ent)
137 (Ekind (Current_Scope) = E_Function
138 or else Ekind (Enclosing_Dynamic_Scope (
139 Current_Scope)) = E_Function))
141 (Ekind (Ent) = E_Component
142 and then Is_Protected_Type (Scope (Ent)))
145 ("protected function cannot modify protected object", N);
147 elsif Ekind (Ent) = E_Loop_Parameter then
149 ("assignment to loop parameter not allowed", N);
153 ("left hand side of assignment must be a variable", N);
157 -- For indexed components or selected components, test prefix
159 elsif Nkind (N) = N_Indexed_Component then
160 Diagnose_Non_Variable_Lhs (Prefix (N));
162 -- Another special case for assignment to discriminant
164 elsif Nkind (N) = N_Selected_Component then
165 if Present (Entity (Selector_Name (N)))
166 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
169 ("assignment to discriminant not allowed", N);
171 Diagnose_Non_Variable_Lhs (Prefix (N));
175 -- If we fall through, we have no special message to issue!
177 Error_Msg_N ("left hand side of assignment must be a variable", N);
179 end Diagnose_Non_Variable_Lhs;
185 procedure Kill_Lhs is
187 if Is_Entity_Name (Lhs) then
189 Ent : constant Entity_Id := Entity (Lhs);
191 if Present (Ent) then
192 Kill_Current_Values (Ent);
198 -------------------------
199 -- Set_Assignment_Type --
200 -------------------------
202 procedure Set_Assignment_Type
204 Opnd_Type : in out Entity_Id)
207 Require_Entity (Opnd);
209 -- If the assignment operand is an in-out or out parameter, then we
210 -- get the actual subtype (needed for the unconstrained case).
211 -- If the operand is the actual in an entry declaration, then within
212 -- the accept statement it is replaced with a local renaming, which
213 -- may also have an actual subtype.
215 if Is_Entity_Name (Opnd)
216 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
217 or else Ekind (Entity (Opnd)) =
219 or else Ekind (Entity (Opnd)) =
220 E_Generic_In_Out_Parameter
222 (Ekind (Entity (Opnd)) = E_Variable
223 and then Nkind (Parent (Entity (Opnd))) =
224 N_Object_Renaming_Declaration
225 and then Nkind (Parent (Parent (Entity (Opnd)))) =
228 Opnd_Type := Get_Actual_Subtype (Opnd);
230 -- If assignment operand is a component reference, then we get the
231 -- actual subtype of the component for the unconstrained case.
233 elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference)
234 and then not Is_Unchecked_Union (Opnd_Type)
236 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
238 if Present (Decl) then
239 Insert_Action (N, Decl);
240 Mark_Rewrite_Insertion (Decl);
242 Opnd_Type := Defining_Identifier (Decl);
243 Set_Etype (Opnd, Opnd_Type);
244 Freeze_Itype (Opnd_Type, N);
246 elsif Is_Constrained (Etype (Opnd)) then
247 Opnd_Type := Etype (Opnd);
250 -- For slice, use the constrained subtype created for the slice
252 elsif Nkind (Opnd) = N_Slice then
253 Opnd_Type := Etype (Opnd);
255 end Set_Assignment_Type;
257 -- Start of processing for Analyze_Assignment
260 Mark_Coextensions (N, Rhs);
265 -- Start type analysis for assignment
269 -- In the most general case, both Lhs and Rhs can be overloaded, and we
270 -- must compute the intersection of the possible types on each side.
272 if Is_Overloaded (Lhs) then
279 Get_First_Interp (Lhs, I, It);
281 while Present (It.Typ) loop
282 if Has_Compatible_Type (Rhs, It.Typ) then
283 if T1 /= Any_Type then
285 -- An explicit dereference is overloaded if the prefix
286 -- is. Try to remove the ambiguity on the prefix, the
287 -- error will be posted there if the ambiguity is real.
289 if Nkind (Lhs) = N_Explicit_Dereference then
292 PI1 : Interp_Index := 0;
298 Get_First_Interp (Prefix (Lhs), PI, PIt);
300 while Present (PIt.Typ) loop
301 if Is_Access_Type (PIt.Typ)
302 and then Has_Compatible_Type
303 (Rhs, Designated_Type (PIt.Typ))
307 Disambiguate (Prefix (Lhs),
310 if PIt = No_Interp then
312 ("ambiguous left-hand side"
313 & " in assignment", Lhs);
316 Resolve (Prefix (Lhs), PIt.Typ);
326 Get_Next_Interp (PI, PIt);
332 ("ambiguous left-hand side in assignment", Lhs);
340 Get_Next_Interp (I, It);
344 if T1 = Any_Type then
346 ("no valid types for left-hand side for assignment", Lhs);
352 -- The resulting assignment type is T1, so now we will resolve the
353 -- left hand side of the assignment using this determined type.
357 -- Cases where Lhs is not a variable
359 if not Is_Variable (Lhs) then
361 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
362 -- a protected object.
369 if Ada_Version >= Ada_05 then
371 -- Handle chains of renamings
374 while Nkind (Ent) in N_Has_Entity
375 and then Present (Entity (Ent))
376 and then Present (Renamed_Object (Entity (Ent)))
378 Ent := Renamed_Object (Entity (Ent));
381 if (Nkind (Ent) = N_Attribute_Reference
382 and then Attribute_Name (Ent) = Name_Priority)
384 -- Renamings of the attribute Priority applied to protected
385 -- objects have been previously expanded into calls to the
386 -- Get_Ceiling run-time subprogram.
389 (Nkind (Ent) = N_Function_Call
390 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
392 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
394 -- The enclosing subprogram cannot be a protected function
397 while not (Is_Subprogram (S)
398 and then Convention (S) = Convention_Protected)
399 and then S /= Standard_Standard
404 if Ekind (S) = E_Function
405 and then Convention (S) = Convention_Protected
408 ("protected function cannot modify protected object",
412 -- Changes of the ceiling priority of the protected object
413 -- are only effective if the Ceiling_Locking policy is in
414 -- effect (AARM D.5.2 (5/2)).
416 if Locking_Policy /= 'C' then
417 Error_Msg_N ("assignment to the attribute PRIORITY has " &
419 Error_Msg_N ("\since no Locking_Policy has been " &
428 Diagnose_Non_Variable_Lhs (Lhs);
431 -- Error of assigning to limited type. We do however allow this in
432 -- certain cases where the front end generates the assignments.
434 elsif Is_Limited_Type (T1)
435 and then not Assignment_OK (Lhs)
436 and then not Assignment_OK (Original_Node (Lhs))
437 and then not Is_Value_Type (T1)
440 ("left hand of assignment must not be limited type", Lhs);
441 Explain_Limited_Type (T1, Lhs);
444 -- Enforce RM 3.9.3 (8): left-hand side cannot be abstract
446 elsif Is_Interface (T1)
447 and then not Is_Class_Wide_Type (T1)
450 ("target of assignment operation may not be abstract", Lhs);
454 -- Resolution may have updated the subtype, in case the left-hand
455 -- side is a private protected component. Use the correct subtype
456 -- to avoid scoping issues in the back-end.
460 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
461 -- type. For example:
465 -- type Acc is access P.T;
468 -- with Pkg; use Acc;
469 -- procedure Example is
472 -- A.all := B.all; -- ERROR
475 if Nkind (Lhs) = N_Explicit_Dereference
476 and then Ekind (T1) = E_Incomplete_Type
478 Error_Msg_N ("invalid use of incomplete type", Lhs);
483 -- Now we can complete the resolution of the right hand side
485 Set_Assignment_Type (Lhs, T1);
488 -- This is the point at which we check for an unset reference
490 Check_Unset_Reference (Rhs);
491 Check_Unprotected_Access (Lhs, Rhs);
493 -- Remaining steps are skipped if Rhs was syntactically in error
502 if not Covers (T1, T2) then
503 Wrong_Type (Rhs, Etype (Lhs));
508 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
509 -- types, use the non-limited view if available
511 if Nkind (Rhs) = N_Explicit_Dereference
512 and then Ekind (T2) = E_Incomplete_Type
513 and then Is_Tagged_Type (T2)
514 and then Present (Non_Limited_View (T2))
516 T2 := Non_Limited_View (T2);
519 Set_Assignment_Type (Rhs, T2);
521 if Total_Errors_Detected /= 0 then
531 if T1 = Any_Type or else T2 = Any_Type then
536 -- If the rhs is class-wide or dynamically tagged, then require the lhs
537 -- to be class-wide. The case where the rhs is a dynamically tagged call
538 -- to a dispatching operation with a controlling access result is
539 -- excluded from this check, since the target has an access type (and
540 -- no tag propagation occurs in that case).
542 if (Is_Class_Wide_Type (T2)
543 or else (Is_Dynamically_Tagged (Rhs)
544 and then not Is_Access_Type (T1)))
545 and then not Is_Class_Wide_Type (T1)
547 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
549 elsif Is_Class_Wide_Type (T1)
550 and then not Is_Class_Wide_Type (T2)
551 and then not Is_Tag_Indeterminate (Rhs)
552 and then not Is_Dynamically_Tagged (Rhs)
554 Error_Msg_N ("dynamically tagged expression required!", Rhs);
557 -- Propagate the tag from a class-wide target to the rhs when the rhs
558 -- is a tag-indeterminate call.
560 if Is_Tag_Indeterminate (Rhs) then
561 if Is_Class_Wide_Type (T1) then
562 Propagate_Tag (Lhs, Rhs);
564 elsif Nkind (Rhs) = N_Function_Call
565 and then Is_Entity_Name (Name (Rhs))
566 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
569 ("call to abstract function must be dispatching", Name (Rhs));
571 elsif Nkind (Rhs) = N_Qualified_Expression
572 and then Nkind (Expression (Rhs)) = N_Function_Call
573 and then Is_Entity_Name (Name (Expression (Rhs)))
575 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
578 ("call to abstract function must be dispatching",
579 Name (Expression (Rhs)));
583 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
584 -- apply an implicit conversion of the rhs to that type to force
585 -- appropriate static and run-time accessibility checks. This applies
586 -- as well to anonymous access-to-subprogram types that are component
587 -- subtypes or formal parameters.
589 if Ada_Version >= Ada_05
590 and then Is_Access_Type (T1)
592 if Is_Local_Anonymous_Access (T1)
593 or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
595 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
596 Analyze_And_Resolve (Rhs, T1);
600 -- Ada 2005 (AI-231): Assignment to not null variable
602 if Ada_Version >= Ada_05
603 and then Can_Never_Be_Null (T1)
604 and then not Assignment_OK (Lhs)
606 -- Case where we know the right hand side is null
608 if Known_Null (Rhs) then
609 Apply_Compile_Time_Constraint_Error
611 Msg => "(Ada 2005) null not allowed in null-excluding objects?",
612 Reason => CE_Null_Not_Allowed);
614 -- We still mark this as a possible modification, that's necessary
615 -- to reset Is_True_Constant, and desirable for xref purposes.
617 Note_Possible_Modification (Lhs, Sure => True);
620 -- If we know the right hand side is non-null, then we convert to the
621 -- target type, since we don't need a run time check in that case.
623 elsif not Can_Never_Be_Null (T2) then
624 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
625 Analyze_And_Resolve (Rhs, T1);
629 if Is_Scalar_Type (T1) then
630 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
632 -- For array types, verify that lengths match. If the right hand side
633 -- if a function call that has been inlined, the assignment has been
634 -- rewritten as a block, and the constraint check will be applied to the
635 -- assignment within the block.
637 elsif Is_Array_Type (T1)
639 (Nkind (Rhs) /= N_Type_Conversion
640 or else Is_Constrained (Etype (Rhs)))
642 (Nkind (Rhs) /= N_Function_Call
643 or else Nkind (N) /= N_Block_Statement)
645 -- Assignment verifies that the length of the Lsh and Rhs are equal,
646 -- but of course the indices do not have to match. If the right-hand
647 -- side is a type conversion to an unconstrained type, a length check
648 -- is performed on the expression itself during expansion. In rare
649 -- cases, the redundant length check is computed on an index type
650 -- with a different representation, triggering incorrect code in
653 Apply_Length_Check (Rhs, Etype (Lhs));
656 -- Discriminant checks are applied in the course of expansion
661 -- Note: modifications of the Lhs may only be recorded after
662 -- checks have been applied.
664 Note_Possible_Modification (Lhs, Sure => True);
666 -- ??? a real accessibility check is needed when ???
668 -- Post warning for redundant assignment or variable to itself
670 if Warn_On_Redundant_Constructs
672 -- We only warn for source constructs
674 and then Comes_From_Source (N)
676 -- Where the object is the same on both sides
678 and then Same_Object (Lhs, Original_Node (Rhs))
680 -- But exclude the case where the right side was an operation
681 -- that got rewritten (e.g. JUNK + K, where K was known to be
682 -- zero). We don't want to warn in such a case, since it is
683 -- reasonable to write such expressions especially when K is
684 -- defined symbolically in some other package.
686 and then Nkind (Original_Node (Rhs)) not in N_Op
688 if Nkind (Lhs) in N_Has_Entity then
690 ("?useless assignment of & to itself!", N, Entity (Lhs));
693 ("?useless assignment of object to itself!", N);
697 -- Check for non-allowed composite assignment
699 if not Support_Composite_Assign_On_Target
700 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
701 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
703 Error_Msg_CRT ("composite assignment", N);
706 -- Check elaboration warning for left side if not in elab code
708 if not In_Subprogram_Or_Concurrent_Unit then
709 Check_Elab_Assign (Lhs);
712 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
713 -- assignment is a source assignment in the extended main source unit.
714 -- We are not interested in any reference information outside this
715 -- context, or in compiler generated assignment statements.
717 if Comes_From_Source (N)
718 and then In_Extended_Main_Source_Unit (Lhs)
720 Set_Referenced_Modified (Lhs, Out_Param => False);
723 -- Final step. If left side is an entity, then we may be able to
724 -- reset the current tracked values to new safe values. We only have
725 -- something to do if the left side is an entity name, and expansion
726 -- has not modified the node into something other than an assignment,
727 -- and of course we only capture values if it is safe to do so.
729 if Is_Entity_Name (Lhs)
730 and then Nkind (N) = N_Assignment_Statement
733 Ent : constant Entity_Id := Entity (Lhs);
736 if Safe_To_Capture_Value (N, Ent) then
738 -- If simple variable on left side, warn if this assignment
739 -- blots out another one (rendering it useless) and note
740 -- location of assignment in case no one references value.
741 -- We only do this for source assignments, otherwise we can
742 -- generate bogus warnings when an assignment is rewritten as
743 -- another assignment, and gets tied up with itself.
745 -- Note: we don't use Record_Last_Assignment here, because we
746 -- have lots of other stuff to do under control of this test.
748 if Warn_On_Modified_Unread
749 and then Is_Assignable (Ent)
750 and then Comes_From_Source (N)
751 and then In_Extended_Main_Source_Unit (Ent)
753 Warn_On_Useless_Assignment (Ent, N);
754 Set_Last_Assignment (Ent, Lhs);
757 -- If we are assigning an access type and the left side is an
758 -- entity, then make sure that the Is_Known_[Non_]Null flags
759 -- properly reflect the state of the entity after assignment.
761 if Is_Access_Type (T1) then
762 if Known_Non_Null (Rhs) then
763 Set_Is_Known_Non_Null (Ent, True);
765 elsif Known_Null (Rhs)
766 and then not Can_Never_Be_Null (Ent)
768 Set_Is_Known_Null (Ent, True);
771 Set_Is_Known_Null (Ent, False);
773 if not Can_Never_Be_Null (Ent) then
774 Set_Is_Known_Non_Null (Ent, False);
778 -- For discrete types, we may be able to set the current value
779 -- if the value is known at compile time.
781 elsif Is_Discrete_Type (T1)
782 and then Compile_Time_Known_Value (Rhs)
784 Set_Current_Value (Ent, Rhs);
786 Set_Current_Value (Ent, Empty);
789 -- If not safe to capture values, kill them
796 end Analyze_Assignment;
798 -----------------------------
799 -- Analyze_Block_Statement --
800 -----------------------------
802 procedure Analyze_Block_Statement (N : Node_Id) is
803 Decls : constant List_Id := Declarations (N);
804 Id : constant Node_Id := Identifier (N);
805 HSS : constant Node_Id := Handled_Statement_Sequence (N);
808 -- If no handled statement sequence is present, things are really
809 -- messed up, and we just return immediately (this is a defence
810 -- against previous errors).
816 -- Normal processing with HSS present
819 EH : constant List_Id := Exception_Handlers (HSS);
820 Ent : Entity_Id := Empty;
823 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
824 -- Recursively save value of this global, will be restored on exit
827 -- Initialize unblocked exit count for statements of begin block
828 -- plus one for each exception handler that is present.
830 Unblocked_Exit_Count := 1;
833 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
836 -- If a label is present analyze it and mark it as referenced
842 -- An error defense. If we have an identifier, but no entity,
843 -- then something is wrong. If we have previous errors, then
844 -- just remove the identifier and continue, otherwise raise
848 if Total_Errors_Detected /= 0 then
849 Set_Identifier (N, Empty);
855 Set_Ekind (Ent, E_Block);
856 Generate_Reference (Ent, N, ' ');
857 Generate_Definition (Ent);
859 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
860 Set_Label_Construct (Parent (Ent), N);
865 -- If no entity set, create a label entity
868 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
869 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
873 Set_Etype (Ent, Standard_Void_Type);
874 Set_Block_Node (Ent, Identifier (N));
877 if Present (Decls) then
878 Analyze_Declarations (Decls);
880 Inspect_Deferred_Constant_Completion (Decls);
884 Process_End_Label (HSS, 'e', Ent);
886 -- If exception handlers are present, then we indicate that
887 -- enclosing scopes contain a block with handlers. We only
888 -- need to mark non-generic scopes.
893 Set_Has_Nested_Block_With_Handler (S);
894 exit when Is_Overloadable (S)
895 or else Ekind (S) = E_Package
896 or else Is_Generic_Unit (S);
901 Check_References (Ent);
902 Warn_On_Useless_Assignments (Ent);
905 if Unblocked_Exit_Count = 0 then
906 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
907 Check_Unreachable_Code (N);
909 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
912 end Analyze_Block_Statement;
914 ----------------------------
915 -- Analyze_Case_Statement --
916 ----------------------------
918 procedure Analyze_Case_Statement (N : Node_Id) is
920 Exp_Type : Entity_Id;
921 Exp_Btype : Entity_Id;
924 Others_Present : Boolean;
926 pragma Warnings (Off, Last_Choice);
927 pragma Warnings (Off, Dont_Care);
928 -- Don't care about assigned values
930 Statements_Analyzed : Boolean := False;
931 -- Set True if at least some statement sequences get analyzed.
932 -- If False on exit, means we had a serious error that prevented
933 -- full analysis of the case statement, and as a result it is not
934 -- a good idea to output warning messages about unreachable code.
936 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
937 -- Recursively save value of this global, will be restored on exit
939 procedure Non_Static_Choice_Error (Choice : Node_Id);
940 -- Error routine invoked by the generic instantiation below when
941 -- the case statement has a non static choice.
943 procedure Process_Statements (Alternative : Node_Id);
944 -- Analyzes all the statements associated to a case alternative.
945 -- Needed by the generic instantiation below.
947 package Case_Choices_Processing is new
948 Generic_Choices_Processing
949 (Get_Alternatives => Alternatives,
950 Get_Choices => Discrete_Choices,
951 Process_Empty_Choice => No_OP,
952 Process_Non_Static_Choice => Non_Static_Choice_Error,
953 Process_Associated_Node => Process_Statements);
954 use Case_Choices_Processing;
955 -- Instantiation of the generic choice processing package
957 -----------------------------
958 -- Non_Static_Choice_Error --
959 -----------------------------
961 procedure Non_Static_Choice_Error (Choice : Node_Id) is
964 ("choice given in case statement is not static!", Choice);
965 end Non_Static_Choice_Error;
967 ------------------------
968 -- Process_Statements --
969 ------------------------
971 procedure Process_Statements (Alternative : Node_Id) is
972 Choices : constant List_Id := Discrete_Choices (Alternative);
976 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
977 Statements_Analyzed := True;
979 -- An interesting optimization. If the case statement expression
980 -- is a simple entity, then we can set the current value within
981 -- an alternative if the alternative has one possible value.
985 -- when 2 | 3 => beta
986 -- when others => gamma
988 -- Here we know that N is initially 1 within alpha, but for beta
989 -- and gamma, we do not know anything more about the initial value.
991 if Is_Entity_Name (Exp) then
994 if Ekind (Ent) = E_Variable
996 Ekind (Ent) = E_In_Out_Parameter
998 Ekind (Ent) = E_Out_Parameter
1000 if List_Length (Choices) = 1
1001 and then Nkind (First (Choices)) in N_Subexpr
1002 and then Compile_Time_Known_Value (First (Choices))
1004 Set_Current_Value (Entity (Exp), First (Choices));
1007 Analyze_Statements (Statements (Alternative));
1009 -- After analyzing the case, set the current value to empty
1010 -- since we won't know what it is for the next alternative
1011 -- (unless reset by this same circuit), or after the case.
1013 Set_Current_Value (Entity (Exp), Empty);
1018 -- Case where expression is not an entity name of a variable
1020 Analyze_Statements (Statements (Alternative));
1021 end Process_Statements;
1023 -- Table to record choices. Put after subprograms since we make
1024 -- a call to Number_Of_Choices to get the right number of entries.
1026 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
1027 pragma Warnings (Off, Case_Table);
1029 -- Start of processing for Analyze_Case_Statement
1032 Unblocked_Exit_Count := 0;
1033 Exp := Expression (N);
1036 -- The expression must be of any discrete type. In rare cases, the
1037 -- expander constructs a case statement whose expression has a private
1038 -- type whose full view is discrete. This can happen when generating
1039 -- a stream operation for a variant type after the type is frozen,
1040 -- when the partial of view of the type of the discriminant is private.
1041 -- In that case, use the full view to analyze case alternatives.
1043 if not Is_Overloaded (Exp)
1044 and then not Comes_From_Source (N)
1045 and then Is_Private_Type (Etype (Exp))
1046 and then Present (Full_View (Etype (Exp)))
1047 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1049 Resolve (Exp, Etype (Exp));
1050 Exp_Type := Full_View (Etype (Exp));
1053 Analyze_And_Resolve (Exp, Any_Discrete);
1054 Exp_Type := Etype (Exp);
1057 Check_Unset_Reference (Exp);
1058 Exp_Btype := Base_Type (Exp_Type);
1060 -- The expression must be of a discrete type which must be determinable
1061 -- independently of the context in which the expression occurs, but
1062 -- using the fact that the expression must be of a discrete type.
1063 -- Moreover, the type this expression must not be a character literal
1064 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1066 -- If error already reported by Resolve, nothing more to do
1068 if Exp_Btype = Any_Discrete
1069 or else Exp_Btype = Any_Type
1073 elsif Exp_Btype = Any_Character then
1075 ("character literal as case expression is ambiguous", Exp);
1078 elsif Ada_Version = Ada_83
1079 and then (Is_Generic_Type (Exp_Btype)
1080 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1083 ("(Ada 83) case expression cannot be of a generic type", Exp);
1087 -- If the case expression is a formal object of mode in out, then
1088 -- treat it as having a nonstatic subtype by forcing use of the base
1089 -- type (which has to get passed to Check_Case_Choices below). Also
1090 -- use base type when the case expression is parenthesized.
1092 if Paren_Count (Exp) > 0
1093 or else (Is_Entity_Name (Exp)
1094 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1096 Exp_Type := Exp_Btype;
1099 -- Call instantiated Analyze_Choices which does the rest of the work
1102 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
1104 if Exp_Type = Universal_Integer and then not Others_Present then
1105 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1108 -- If all our exits were blocked by unconditional transfers of control,
1109 -- then the entire CASE statement acts as an unconditional transfer of
1110 -- control, so treat it like one, and check unreachable code. Skip this
1111 -- test if we had serious errors preventing any statement analysis.
1113 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1114 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1115 Check_Unreachable_Code (N);
1117 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1120 if not Expander_Active
1121 and then Compile_Time_Known_Value (Expression (N))
1122 and then Serious_Errors_Detected = 0
1125 Chosen : constant Node_Id := Find_Static_Alternative (N);
1129 Alt := First (Alternatives (N));
1130 while Present (Alt) loop
1131 if Alt /= Chosen then
1132 Remove_Warning_Messages (Statements (Alt));
1139 end Analyze_Case_Statement;
1141 ----------------------------
1142 -- Analyze_Exit_Statement --
1143 ----------------------------
1145 -- If the exit includes a name, it must be the name of a currently open
1146 -- loop. Otherwise there must be an innermost open loop on the stack,
1147 -- to which the statement implicitly refers.
1149 procedure Analyze_Exit_Statement (N : Node_Id) is
1150 Target : constant Node_Id := Name (N);
1151 Cond : constant Node_Id := Condition (N);
1152 Scope_Id : Entity_Id;
1158 Check_Unreachable_Code (N);
1161 if Present (Target) then
1163 U_Name := Entity (Target);
1165 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1166 Error_Msg_N ("invalid loop name in exit statement", N);
1169 Set_Has_Exit (U_Name);
1176 for J in reverse 0 .. Scope_Stack.Last loop
1177 Scope_Id := Scope_Stack.Table (J).Entity;
1178 Kind := Ekind (Scope_Id);
1181 and then (No (Target) or else Scope_Id = U_Name) then
1182 Set_Has_Exit (Scope_Id);
1185 elsif Kind = E_Block
1186 or else Kind = E_Loop
1187 or else Kind = E_Return_Statement
1193 ("cannot exit from program unit or accept statement", N);
1198 -- Verify that if present the condition is a Boolean expression
1200 if Present (Cond) then
1201 Analyze_And_Resolve (Cond, Any_Boolean);
1202 Check_Unset_Reference (Cond);
1204 end Analyze_Exit_Statement;
1206 ----------------------------
1207 -- Analyze_Goto_Statement --
1208 ----------------------------
1210 procedure Analyze_Goto_Statement (N : Node_Id) is
1211 Label : constant Node_Id := Name (N);
1212 Scope_Id : Entity_Id;
1213 Label_Scope : Entity_Id;
1214 Label_Ent : Entity_Id;
1217 Check_Unreachable_Code (N);
1218 Kill_Current_Values (Last_Assignment_Only => True);
1221 Label_Ent := Entity (Label);
1223 -- Ignore previous error
1225 if Label_Ent = Any_Id then
1228 -- We just have a label as the target of a goto
1230 elsif Ekind (Label_Ent) /= E_Label then
1231 Error_Msg_N ("target of goto statement must be a label", Label);
1234 -- Check that the target of the goto is reachable according to Ada
1235 -- scoping rules. Note: the special gotos we generate for optimizing
1236 -- local handling of exceptions would violate these rules, but we mark
1237 -- such gotos as analyzed when built, so this code is never entered.
1239 elsif not Reachable (Label_Ent) then
1240 Error_Msg_N ("target of goto statement is not reachable", Label);
1244 -- Here if goto passes initial validity checks
1246 Label_Scope := Enclosing_Scope (Label_Ent);
1248 for J in reverse 0 .. Scope_Stack.Last loop
1249 Scope_Id := Scope_Stack.Table (J).Entity;
1251 if Label_Scope = Scope_Id
1252 or else (Ekind (Scope_Id) /= E_Block
1253 and then Ekind (Scope_Id) /= E_Loop
1254 and then Ekind (Scope_Id) /= E_Return_Statement)
1256 if Scope_Id /= Label_Scope then
1258 ("cannot exit from program unit or accept statement", N);
1265 raise Program_Error;
1266 end Analyze_Goto_Statement;
1268 --------------------------
1269 -- Analyze_If_Statement --
1270 --------------------------
1272 -- A special complication arises in the analysis of if statements
1274 -- The expander has circuitry to completely delete code that it
1275 -- can tell will not be executed (as a result of compile time known
1276 -- conditions). In the analyzer, we ensure that code that will be
1277 -- deleted in this manner is analyzed but not expanded. This is
1278 -- obviously more efficient, but more significantly, difficulties
1279 -- arise if code is expanded and then eliminated (e.g. exception
1280 -- table entries disappear). Similarly, itypes generated in deleted
1281 -- code must be frozen from start, because the nodes on which they
1282 -- depend will not be available at the freeze point.
1284 procedure Analyze_If_Statement (N : Node_Id) is
1287 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1288 -- Recursively save value of this global, will be restored on exit
1290 Save_In_Deleted_Code : Boolean;
1292 Del : Boolean := False;
1293 -- This flag gets set True if a True condition has been found,
1294 -- which means that remaining ELSE/ELSIF parts are deleted.
1296 procedure Analyze_Cond_Then (Cnode : Node_Id);
1297 -- This is applied to either the N_If_Statement node itself or
1298 -- to an N_Elsif_Part node. It deals with analyzing the condition
1299 -- and the THEN statements associated with it.
1301 -----------------------
1302 -- Analyze_Cond_Then --
1303 -----------------------
1305 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1306 Cond : constant Node_Id := Condition (Cnode);
1307 Tstm : constant List_Id := Then_Statements (Cnode);
1310 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1311 Analyze_And_Resolve (Cond, Any_Boolean);
1312 Check_Unset_Reference (Cond);
1313 Set_Current_Value_Condition (Cnode);
1315 -- If already deleting, then just analyze then statements
1318 Analyze_Statements (Tstm);
1320 -- Compile time known value, not deleting yet
1322 elsif Compile_Time_Known_Value (Cond) then
1323 Save_In_Deleted_Code := In_Deleted_Code;
1325 -- If condition is True, then analyze the THEN statements
1326 -- and set no expansion for ELSE and ELSIF parts.
1328 if Is_True (Expr_Value (Cond)) then
1329 Analyze_Statements (Tstm);
1331 Expander_Mode_Save_And_Set (False);
1332 In_Deleted_Code := True;
1334 -- If condition is False, analyze THEN with expansion off
1336 else -- Is_False (Expr_Value (Cond))
1337 Expander_Mode_Save_And_Set (False);
1338 In_Deleted_Code := True;
1339 Analyze_Statements (Tstm);
1340 Expander_Mode_Restore;
1341 In_Deleted_Code := Save_In_Deleted_Code;
1344 -- Not known at compile time, not deleting, normal analysis
1347 Analyze_Statements (Tstm);
1349 end Analyze_Cond_Then;
1351 -- Start of Analyze_If_Statement
1354 -- Initialize exit count for else statements. If there is no else
1355 -- part, this count will stay non-zero reflecting the fact that the
1356 -- uncovered else case is an unblocked exit.
1358 Unblocked_Exit_Count := 1;
1359 Analyze_Cond_Then (N);
1361 -- Now to analyze the elsif parts if any are present
1363 if Present (Elsif_Parts (N)) then
1364 E := First (Elsif_Parts (N));
1365 while Present (E) loop
1366 Analyze_Cond_Then (E);
1371 if Present (Else_Statements (N)) then
1372 Analyze_Statements (Else_Statements (N));
1375 -- If all our exits were blocked by unconditional transfers of control,
1376 -- then the entire IF statement acts as an unconditional transfer of
1377 -- control, so treat it like one, and check unreachable code.
1379 if Unblocked_Exit_Count = 0 then
1380 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1381 Check_Unreachable_Code (N);
1383 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1387 Expander_Mode_Restore;
1388 In_Deleted_Code := Save_In_Deleted_Code;
1391 if not Expander_Active
1392 and then Compile_Time_Known_Value (Condition (N))
1393 and then Serious_Errors_Detected = 0
1395 if Is_True (Expr_Value (Condition (N))) then
1396 Remove_Warning_Messages (Else_Statements (N));
1398 if Present (Elsif_Parts (N)) then
1399 E := First (Elsif_Parts (N));
1400 while Present (E) loop
1401 Remove_Warning_Messages (Then_Statements (E));
1407 Remove_Warning_Messages (Then_Statements (N));
1410 end Analyze_If_Statement;
1412 ----------------------------------------
1413 -- Analyze_Implicit_Label_Declaration --
1414 ----------------------------------------
1416 -- An implicit label declaration is generated in the innermost
1417 -- enclosing declarative part. This is done for labels as well as
1418 -- block and loop names.
1420 -- Note: any changes in this routine may need to be reflected in
1421 -- Analyze_Label_Entity.
1423 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1424 Id : constant Node_Id := Defining_Identifier (N);
1427 Set_Ekind (Id, E_Label);
1428 Set_Etype (Id, Standard_Void_Type);
1429 Set_Enclosing_Scope (Id, Current_Scope);
1430 end Analyze_Implicit_Label_Declaration;
1432 ------------------------------
1433 -- Analyze_Iteration_Scheme --
1434 ------------------------------
1436 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1438 procedure Process_Bounds (R : Node_Id);
1439 -- If the iteration is given by a range, create temporaries and
1440 -- assignment statements block to capture the bounds and perform
1441 -- required finalization actions in case a bound includes a function
1442 -- call that uses the temporary stack. We first pre-analyze a copy of
1443 -- the range in order to determine the expected type, and analyze and
1444 -- resolve the original bounds.
1446 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1447 -- If the bounds are given by a 'Range reference on a function call
1448 -- that returns a controlled array, introduce an explicit declaration
1449 -- to capture the bounds, so that the function result can be finalized
1450 -- in timely fashion.
1452 --------------------
1453 -- Process_Bounds --
1454 --------------------
1456 procedure Process_Bounds (R : Node_Id) is
1457 Loc : constant Source_Ptr := Sloc (N);
1458 R_Copy : constant Node_Id := New_Copy_Tree (R);
1459 Lo : constant Node_Id := Low_Bound (R);
1460 Hi : constant Node_Id := High_Bound (R);
1461 New_Lo_Bound : Node_Id := Empty;
1462 New_Hi_Bound : Node_Id := Empty;
1464 Save_Analysis : Boolean;
1467 (Original_Bound : Node_Id;
1468 Analyzed_Bound : Node_Id) return Node_Id;
1469 -- Capture value of bound and return captured value
1476 (Original_Bound : Node_Id;
1477 Analyzed_Bound : Node_Id) return Node_Id
1484 -- If the bound is a constant or an object, no need for a separate
1485 -- declaration. If the bound is the result of previous expansion
1486 -- it is already analyzed and should not be modified. Note that
1487 -- the Bound will be resolved later, if needed, as part of the
1488 -- call to Make_Index (literal bounds may need to be resolved to
1491 if Analyzed (Original_Bound) then
1492 return Original_Bound;
1494 elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
1495 N_Character_Literal)
1496 or else Is_Entity_Name (Analyzed_Bound)
1498 Analyze_And_Resolve (Original_Bound, Typ);
1499 return Original_Bound;
1502 -- Here we need to capture the value
1504 Analyze_And_Resolve (Original_Bound, Typ);
1507 Make_Defining_Identifier (Loc,
1508 Chars => New_Internal_Name ('S'));
1510 -- Normally, the best approach is simply to generate a constant
1511 -- declaration that captures the bound. However, there is a nasty
1512 -- case where this is wrong. If the bound is complex, and has a
1513 -- possible use of the secondary stack, we need to generate a
1514 -- separate assignment statement to ensure the creation of a block
1515 -- which will release the secondary stack.
1517 -- We prefer the constant declaration, since it leaves us with a
1518 -- proper trace of the value, useful in optimizations that get rid
1519 -- of junk range checks.
1521 -- Probably we want something like the Side_Effect_Free routine
1522 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1523 -- and 'First applied to an entity, since these are the important
1524 -- cases for range check optimizations.
1526 if Nkind (Original_Bound) = N_Attribute_Reference
1527 and then (Attribute_Name (Original_Bound) = Name_First
1529 Attribute_Name (Original_Bound) = Name_Last)
1530 and then Is_Entity_Name (Prefix (Original_Bound))
1533 Make_Object_Declaration (Loc,
1534 Defining_Identifier => Id,
1535 Constant_Present => True,
1536 Object_Definition => New_Occurrence_Of (Typ, Loc),
1537 Expression => Relocate_Node (Original_Bound));
1539 Insert_Before (Parent (N), Decl);
1541 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1542 return Expression (Decl);
1545 -- Here we make a declaration with a separate assignment statement
1548 Make_Object_Declaration (Loc,
1549 Defining_Identifier => Id,
1550 Object_Definition => New_Occurrence_Of (Typ, Loc));
1552 Insert_Before (Parent (N), Decl);
1556 Make_Assignment_Statement (Loc,
1557 Name => New_Occurrence_Of (Id, Loc),
1558 Expression => Relocate_Node (Original_Bound));
1560 Insert_Before (Parent (N), Assign);
1563 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1565 if Nkind (Assign) = N_Assignment_Statement then
1566 return Expression (Assign);
1568 return Original_Bound;
1572 -- Start of processing for Process_Bounds
1575 -- Determine expected type of range by analyzing separate copy
1576 -- Do the analysis and resolution of the copy of the bounds with
1577 -- expansion disabled, to prevent the generation of finalization
1578 -- actions on each bound. This prevents memory leaks when the
1579 -- bounds contain calls to functions returning controlled arrays.
1581 Set_Parent (R_Copy, Parent (R));
1582 Save_Analysis := Full_Analysis;
1583 Full_Analysis := False;
1584 Expander_Mode_Save_And_Set (False);
1588 if Is_Overloaded (R_Copy) then
1590 -- Apply preference rules for range of predefined integer types,
1591 -- or diagnose true ambiguity.
1596 Found : Entity_Id := Empty;
1599 Get_First_Interp (R_Copy, I, It);
1600 while Present (It.Typ) loop
1601 if Is_Discrete_Type (It.Typ) then
1605 if Scope (Found) = Standard_Standard then
1608 elsif Scope (It.Typ) = Standard_Standard then
1612 -- Both of them are user-defined
1615 ("ambiguous bounds in range of iteration",
1617 Error_Msg_N ("\possible interpretations:", R_Copy);
1618 Error_Msg_NE ("\\} ", R_Copy, Found);
1619 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1625 Get_Next_Interp (I, It);
1631 Expander_Mode_Restore;
1632 Full_Analysis := Save_Analysis;
1634 Typ := Etype (R_Copy);
1636 -- If the type of the discrete range is Universal_Integer, then
1637 -- the bound's type must be resolved to Integer, and any object
1638 -- used to hold the bound must also have type Integer, unless the
1639 -- literal bounds are constant-folded expressions that carry a user-
1642 if Typ = Universal_Integer then
1643 if Nkind (Lo) = N_Integer_Literal
1644 and then Present (Etype (Lo))
1645 and then Scope (Etype (Lo)) /= Standard_Standard
1649 elsif Nkind (Hi) = N_Integer_Literal
1650 and then Present (Etype (Hi))
1651 and then Scope (Etype (Hi)) /= Standard_Standard
1656 Typ := Standard_Integer;
1662 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1663 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1665 -- Propagate staticness to loop range itself, in case the
1666 -- corresponding subtype is static.
1668 if New_Lo_Bound /= Lo
1669 and then Is_Static_Expression (New_Lo_Bound)
1671 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1674 if New_Hi_Bound /= Hi
1675 and then Is_Static_Expression (New_Hi_Bound)
1677 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1681 --------------------------------------
1682 -- Check_Controlled_Array_Attribute --
1683 --------------------------------------
1685 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1687 if Nkind (DS) = N_Attribute_Reference
1688 and then Is_Entity_Name (Prefix (DS))
1689 and then Ekind (Entity (Prefix (DS))) = E_Function
1690 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1693 Component_Type (Etype (Entity (Prefix (DS)))))
1694 and then Expander_Active
1697 Loc : constant Source_Ptr := Sloc (N);
1698 Arr : constant Entity_Id :=
1699 Etype (Entity (Prefix (DS)));
1700 Indx : constant Entity_Id :=
1701 Base_Type (Etype (First_Index (Arr)));
1702 Subt : constant Entity_Id :=
1703 Make_Defining_Identifier
1704 (Loc, New_Internal_Name ('S'));
1709 Make_Subtype_Declaration (Loc,
1710 Defining_Identifier => Subt,
1711 Subtype_Indication =>
1712 Make_Subtype_Indication (Loc,
1713 Subtype_Mark => New_Reference_To (Indx, Loc),
1715 Make_Range_Constraint (Loc,
1716 Relocate_Node (DS))));
1717 Insert_Before (Parent (N), Decl);
1721 Make_Attribute_Reference (Loc,
1722 Prefix => New_Reference_To (Subt, Loc),
1723 Attribute_Name => Attribute_Name (DS)));
1727 end Check_Controlled_Array_Attribute;
1729 -- Start of processing for Analyze_Iteration_Scheme
1732 -- For an infinite loop, there is no iteration scheme
1739 Cond : constant Node_Id := Condition (N);
1742 -- For WHILE loop, verify that the condition is a Boolean
1743 -- expression and resolve and check it.
1745 if Present (Cond) then
1746 Analyze_And_Resolve (Cond, Any_Boolean);
1747 Check_Unset_Reference (Cond);
1748 Set_Current_Value_Condition (N);
1751 -- Else we have a FOR loop
1755 LP : constant Node_Id := Loop_Parameter_Specification (N);
1756 Id : constant Entity_Id := Defining_Identifier (LP);
1757 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1762 -- We always consider the loop variable to be referenced,
1763 -- since the loop may be used just for counting purposes.
1765 Generate_Reference (Id, N, ' ');
1767 -- Check for case of loop variable hiding a local
1768 -- variable (used later on to give a nice warning
1769 -- if the hidden variable is never assigned).
1772 H : constant Entity_Id := Homonym (Id);
1775 and then Enclosing_Dynamic_Scope (H) =
1776 Enclosing_Dynamic_Scope (Id)
1777 and then Ekind (H) = E_Variable
1778 and then Is_Discrete_Type (Etype (H))
1780 Set_Hiding_Loop_Variable (H, Id);
1784 -- Now analyze the subtype definition. If it is
1785 -- a range, create temporaries for bounds.
1787 if Nkind (DS) = N_Range
1788 and then Expander_Active
1790 Process_Bounds (DS);
1799 -- The subtype indication may denote the completion
1800 -- of an incomplete type declaration.
1802 if Is_Entity_Name (DS)
1803 and then Present (Entity (DS))
1804 and then Is_Type (Entity (DS))
1805 and then Ekind (Entity (DS)) = E_Incomplete_Type
1807 Set_Entity (DS, Get_Full_View (Entity (DS)));
1808 Set_Etype (DS, Entity (DS));
1811 if not Is_Discrete_Type (Etype (DS)) then
1812 Wrong_Type (DS, Any_Discrete);
1813 Set_Etype (DS, Any_Type);
1816 Check_Controlled_Array_Attribute (DS);
1818 Make_Index (DS, LP);
1820 Set_Ekind (Id, E_Loop_Parameter);
1821 Set_Etype (Id, Etype (DS));
1822 Set_Is_Known_Valid (Id, True);
1824 -- The loop is not a declarative part, so the only entity
1825 -- declared "within" must be frozen explicitly.
1828 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1830 if Is_Non_Empty_List (Flist) then
1831 Insert_Actions (N, Flist);
1835 -- Check for null or possibly null range and issue warning.
1836 -- We suppress such messages in generic templates and
1837 -- instances, because in practice they tend to be dubious
1840 if Nkind (DS) = N_Range
1841 and then Comes_From_Source (N)
1844 L : constant Node_Id := Low_Bound (DS);
1845 H : constant Node_Id := High_Bound (DS);
1848 -- If range of loop is null, issue warning
1850 if Compile_Time_Compare
1851 (L, H, Assume_Valid => True) = GT
1853 -- Suppress the warning if inside a generic
1854 -- template or instance, since in practice
1855 -- they tend to be dubious in these cases since
1856 -- they can result from intended parametrization.
1858 if not Inside_A_Generic
1859 and then not In_Instance
1861 -- Specialize msg if invalid values could make
1862 -- the loop non-null after all.
1864 if Compile_Time_Compare
1865 (L, H, Assume_Valid => False) = GT
1868 ("?loop range is null, "
1869 & "loop will not execute",
1872 -- Since we know the range of the loop is
1873 -- null, set the appropriate flag to remove
1874 -- the loop entirely during expansion.
1876 Set_Is_Null_Loop (Parent (N));
1878 -- Here is where the loop could execute because
1879 -- of invalid values, so issue appropriate
1880 -- message and in this case we do not set the
1881 -- Is_Null_Loop flag since the loop may execute.
1885 ("?loop range may be null, "
1886 & "loop may not execute",
1889 ("?can only execute if invalid values "
1895 -- In either case, suppress warnings in the body of
1896 -- the loop, since it is likely that these warnings
1897 -- will be inappropriate if the loop never actually
1898 -- executes, which is unlikely.
1900 Set_Suppress_Loop_Warnings (Parent (N));
1902 -- The other case for a warning is a reverse loop
1903 -- where the upper bound is the integer literal
1904 -- zero or one, and the lower bound can be positive.
1906 -- For example, we have
1908 -- for J in reverse N .. 1 loop
1910 -- In practice, this is very likely to be a case
1911 -- of reversing the bounds incorrectly in the range.
1913 elsif Reverse_Present (LP)
1914 and then Nkind (Original_Node (H)) =
1916 and then (Intval (Original_Node (H)) = Uint_0
1918 Intval (Original_Node (H)) = Uint_1)
1920 Error_Msg_N ("?loop range may be null", DS);
1921 Error_Msg_N ("\?bounds may be wrong way round", DS);
1929 end Analyze_Iteration_Scheme;
1935 -- Note: the semantic work required for analyzing labels (setting them as
1936 -- reachable) was done in a prepass through the statements in the block,
1937 -- so that forward gotos would be properly handled. See Analyze_Statements
1938 -- for further details. The only processing required here is to deal with
1939 -- optimizations that depend on an assumption of sequential control flow,
1940 -- since of course the occurrence of a label breaks this assumption.
1942 procedure Analyze_Label (N : Node_Id) is
1943 pragma Warnings (Off, N);
1945 Kill_Current_Values;
1948 --------------------------
1949 -- Analyze_Label_Entity --
1950 --------------------------
1952 procedure Analyze_Label_Entity (E : Entity_Id) is
1954 Set_Ekind (E, E_Label);
1955 Set_Etype (E, Standard_Void_Type);
1956 Set_Enclosing_Scope (E, Current_Scope);
1957 Set_Reachable (E, True);
1958 end Analyze_Label_Entity;
1960 ----------------------------
1961 -- Analyze_Loop_Statement --
1962 ----------------------------
1964 procedure Analyze_Loop_Statement (N : Node_Id) is
1965 Loop_Statement : constant Node_Id := N;
1967 Id : constant Node_Id := Identifier (Loop_Statement);
1968 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
1972 if Present (Id) then
1974 -- Make name visible, e.g. for use in exit statements. Loop
1975 -- labels are always considered to be referenced.
1980 -- Guard against serious error (typically, a scope mismatch when
1981 -- semantic analysis is requested) by creating loop entity to
1982 -- continue analysis.
1985 if Total_Errors_Detected /= 0 then
1988 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
1990 raise Program_Error;
1994 Generate_Reference (Ent, Loop_Statement, ' ');
1995 Generate_Definition (Ent);
1997 -- If we found a label, mark its type. If not, ignore it, since it
1998 -- means we have a conflicting declaration, which would already
1999 -- have been diagnosed at declaration time. Set Label_Construct
2000 -- of the implicit label declaration, which is not created by the
2001 -- parser for generic units.
2003 if Ekind (Ent) = E_Label then
2004 Set_Ekind (Ent, E_Loop);
2006 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
2007 Set_Label_Construct (Parent (Ent), Loop_Statement);
2012 -- Case of no identifier present
2017 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2018 Set_Etype (Ent, Standard_Void_Type);
2019 Set_Parent (Ent, Loop_Statement);
2022 -- Kill current values on entry to loop, since statements in body of
2023 -- loop may have been executed before the loop is entered. Similarly we
2024 -- kill values after the loop, since we do not know that the body of the
2025 -- loop was executed.
2027 Kill_Current_Values;
2029 Analyze_Iteration_Scheme (Iter);
2030 Analyze_Statements (Statements (Loop_Statement));
2031 Process_End_Label (Loop_Statement, 'e', Ent);
2033 Kill_Current_Values;
2035 -- No point in checking for warnings in code we generated
2037 if Comes_From_Source (N) then
2038 Check_Infinite_Loop_Warning (N);
2041 -- Code after loop is unreachable if the loop has no WHILE or FOR
2042 -- and contains no EXIT statements within the body of the loop.
2044 if No (Iter) and then not Has_Exit (Ent) then
2045 Check_Unreachable_Code (N);
2047 end Analyze_Loop_Statement;
2049 ----------------------------
2050 -- Analyze_Null_Statement --
2051 ----------------------------
2053 -- Note: the semantics of the null statement is implemented by a single
2054 -- null statement, too bad everything isn't as simple as this!
2056 procedure Analyze_Null_Statement (N : Node_Id) is
2057 pragma Warnings (Off, N);
2060 end Analyze_Null_Statement;
2062 ------------------------
2063 -- Analyze_Statements --
2064 ------------------------
2066 procedure Analyze_Statements (L : List_Id) is
2071 -- The labels declared in the statement list are reachable from
2072 -- statements in the list. We do this as a prepass so that any
2073 -- goto statement will be properly flagged if its target is not
2074 -- reachable. This is not required, but is nice behavior!
2077 while Present (S) loop
2078 if Nkind (S) = N_Label then
2079 Analyze (Identifier (S));
2080 Lab := Entity (Identifier (S));
2082 -- If we found a label mark it as reachable
2084 if Ekind (Lab) = E_Label then
2085 Generate_Definition (Lab);
2086 Set_Reachable (Lab);
2088 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
2089 Set_Label_Construct (Parent (Lab), S);
2092 -- If we failed to find a label, it means the implicit declaration
2093 -- of the label was hidden. A for-loop parameter can do this to
2094 -- a label with the same name inside the loop, since the implicit
2095 -- label declaration is in the innermost enclosing body or block
2099 Error_Msg_Sloc := Sloc (Lab);
2101 ("implicit label declaration for & is hidden#",
2109 -- Perform semantic analysis on all statements
2111 Conditional_Statements_Begin;
2114 while Present (S) loop
2119 Conditional_Statements_End;
2121 -- Make labels unreachable. Visibility is not sufficient, because
2122 -- labels in one if-branch for example are not reachable from the
2123 -- other branch, even though their declarations are in the enclosing
2124 -- declarative part.
2127 while Present (S) loop
2128 if Nkind (S) = N_Label then
2129 Set_Reachable (Entity (Identifier (S)), False);
2134 end Analyze_Statements;
2136 ----------------------------
2137 -- Check_Unreachable_Code --
2138 ----------------------------
2140 procedure Check_Unreachable_Code (N : Node_Id) is
2141 Error_Loc : Source_Ptr;
2145 if Is_List_Member (N)
2146 and then Comes_From_Source (N)
2152 Nxt := Original_Node (Next (N));
2154 -- If a label follows us, then we never have dead code, since
2155 -- someone could branch to the label, so we just ignore it.
2157 if Nkind (Nxt) = N_Label then
2160 -- Otherwise see if we have a real statement following us
2163 and then Comes_From_Source (Nxt)
2164 and then Is_Statement (Nxt)
2166 -- Special very annoying exception. If we have a return that
2167 -- follows a raise, then we allow it without a warning, since
2168 -- the Ada RM annoyingly requires a useless return here!
2170 if Nkind (Original_Node (N)) /= N_Raise_Statement
2171 or else Nkind (Nxt) /= N_Simple_Return_Statement
2173 -- The rather strange shenanigans with the warning message
2174 -- here reflects the fact that Kill_Dead_Code is very good
2175 -- at removing warnings in deleted code, and this is one
2176 -- warning we would prefer NOT to have removed.
2178 Error_Loc := Sloc (Nxt);
2180 -- If we have unreachable code, analyze and remove the
2181 -- unreachable code, since it is useless and we don't
2182 -- want to generate junk warnings.
2184 -- We skip this step if we are not in code generation mode.
2185 -- This is the one case where we remove dead code in the
2186 -- semantics as opposed to the expander, and we do not want
2187 -- to remove code if we are not in code generation mode,
2188 -- since this messes up the ASIS trees.
2190 -- Note that one might react by moving the whole circuit to
2191 -- exp_ch5, but then we lose the warning in -gnatc mode.
2193 if Operating_Mode = Generate_Code then
2197 -- Quit deleting when we have nothing more to delete
2198 -- or if we hit a label (since someone could transfer
2199 -- control to a label, so we should not delete it).
2201 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2203 -- Statement/declaration is to be deleted
2207 Kill_Dead_Code (Nxt);
2211 -- Now issue the warning
2213 Error_Msg ("?unreachable code!", Error_Loc);
2216 -- If the unconditional transfer of control instruction is
2217 -- the last statement of a sequence, then see if our parent
2218 -- is one of the constructs for which we count unblocked exits,
2219 -- and if so, adjust the count.
2224 -- Statements in THEN part or ELSE part of IF statement
2226 if Nkind (P) = N_If_Statement then
2229 -- Statements in ELSIF part of an IF statement
2231 elsif Nkind (P) = N_Elsif_Part then
2233 pragma Assert (Nkind (P) = N_If_Statement);
2235 -- Statements in CASE statement alternative
2237 elsif Nkind (P) = N_Case_Statement_Alternative then
2239 pragma Assert (Nkind (P) = N_Case_Statement);
2241 -- Statements in body of block
2243 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2244 and then Nkind (Parent (P)) = N_Block_Statement
2248 -- Statements in exception handler in a block
2250 elsif Nkind (P) = N_Exception_Handler
2251 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2252 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2256 -- None of these cases, so return
2262 -- This was one of the cases we are looking for (i.e. the
2263 -- parent construct was IF, CASE or block) so decrement count.
2265 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2269 end Check_Unreachable_Code;