1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2009, 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)
439 -- CPP constructors can only be called in declarations
441 if Is_CPP_Constructor_Call (Rhs) then
442 Error_Msg_N ("invalid use of 'C'P'P constructor", Rhs);
445 ("left hand of assignment must not be limited type", Lhs);
446 Explain_Limited_Type (T1, Lhs);
450 -- Enforce RM 3.9.3 (8): left-hand side cannot be abstract
452 elsif Is_Interface (T1)
453 and then not Is_Class_Wide_Type (T1)
456 ("target of assignment operation may not be abstract", Lhs);
460 -- Resolution may have updated the subtype, in case the left-hand
461 -- side is a private protected component. Use the correct subtype
462 -- to avoid scoping issues in the back-end.
466 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
467 -- type. For example:
471 -- type Acc is access P.T;
474 -- with Pkg; use Acc;
475 -- procedure Example is
478 -- A.all := B.all; -- ERROR
481 if Nkind (Lhs) = N_Explicit_Dereference
482 and then Ekind (T1) = E_Incomplete_Type
484 Error_Msg_N ("invalid use of incomplete type", Lhs);
489 -- Now we can complete the resolution of the right hand side
491 Set_Assignment_Type (Lhs, T1);
494 -- This is the point at which we check for an unset reference
496 Check_Unset_Reference (Rhs);
497 Check_Unprotected_Access (Lhs, Rhs);
499 -- Remaining steps are skipped if Rhs was syntactically in error
508 if not Covers (T1, T2) then
509 Wrong_Type (Rhs, Etype (Lhs));
514 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
515 -- types, use the non-limited view if available
517 if Nkind (Rhs) = N_Explicit_Dereference
518 and then Ekind (T2) = E_Incomplete_Type
519 and then Is_Tagged_Type (T2)
520 and then Present (Non_Limited_View (T2))
522 T2 := Non_Limited_View (T2);
525 Set_Assignment_Type (Rhs, T2);
527 if Total_Errors_Detected /= 0 then
537 if T1 = Any_Type or else T2 = Any_Type then
542 -- If the rhs is class-wide or dynamically tagged, then require the lhs
543 -- to be class-wide. The case where the rhs is a dynamically tagged call
544 -- to a dispatching operation with a controlling access result is
545 -- excluded from this check, since the target has an access type (and
546 -- no tag propagation occurs in that case).
548 if (Is_Class_Wide_Type (T2)
549 or else (Is_Dynamically_Tagged (Rhs)
550 and then not Is_Access_Type (T1)))
551 and then not Is_Class_Wide_Type (T1)
553 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
555 elsif Is_Class_Wide_Type (T1)
556 and then not Is_Class_Wide_Type (T2)
557 and then not Is_Tag_Indeterminate (Rhs)
558 and then not Is_Dynamically_Tagged (Rhs)
560 Error_Msg_N ("dynamically tagged expression required!", Rhs);
563 -- Propagate the tag from a class-wide target to the rhs when the rhs
564 -- is a tag-indeterminate call.
566 if Is_Tag_Indeterminate (Rhs) then
567 if Is_Class_Wide_Type (T1) then
568 Propagate_Tag (Lhs, Rhs);
570 elsif Nkind (Rhs) = N_Function_Call
571 and then Is_Entity_Name (Name (Rhs))
572 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
575 ("call to abstract function must be dispatching", Name (Rhs));
577 elsif Nkind (Rhs) = N_Qualified_Expression
578 and then Nkind (Expression (Rhs)) = N_Function_Call
579 and then Is_Entity_Name (Name (Expression (Rhs)))
581 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
584 ("call to abstract function must be dispatching",
585 Name (Expression (Rhs)));
589 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
590 -- apply an implicit conversion of the rhs to that type to force
591 -- appropriate static and run-time accessibility checks. This applies
592 -- as well to anonymous access-to-subprogram types that are component
593 -- subtypes or formal parameters.
595 if Ada_Version >= Ada_05
596 and then Is_Access_Type (T1)
598 if Is_Local_Anonymous_Access (T1)
599 or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
601 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
602 Analyze_And_Resolve (Rhs, T1);
606 -- Ada 2005 (AI-231): Assignment to not null variable
608 if Ada_Version >= Ada_05
609 and then Can_Never_Be_Null (T1)
610 and then not Assignment_OK (Lhs)
612 -- Case where we know the right hand side is null
614 if Known_Null (Rhs) then
615 Apply_Compile_Time_Constraint_Error
617 Msg => "(Ada 2005) null not allowed in null-excluding objects?",
618 Reason => CE_Null_Not_Allowed);
620 -- We still mark this as a possible modification, that's necessary
621 -- to reset Is_True_Constant, and desirable for xref purposes.
623 Note_Possible_Modification (Lhs, Sure => True);
626 -- If we know the right hand side is non-null, then we convert to the
627 -- target type, since we don't need a run time check in that case.
629 elsif not Can_Never_Be_Null (T2) then
630 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
631 Analyze_And_Resolve (Rhs, T1);
635 if Is_Scalar_Type (T1) then
636 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
638 -- For array types, verify that lengths match. If the right hand side
639 -- if a function call that has been inlined, the assignment has been
640 -- rewritten as a block, and the constraint check will be applied to the
641 -- assignment within the block.
643 elsif Is_Array_Type (T1)
645 (Nkind (Rhs) /= N_Type_Conversion
646 or else Is_Constrained (Etype (Rhs)))
648 (Nkind (Rhs) /= N_Function_Call
649 or else Nkind (N) /= N_Block_Statement)
651 -- Assignment verifies that the length of the Lsh and Rhs are equal,
652 -- but of course the indices do not have to match. If the right-hand
653 -- side is a type conversion to an unconstrained type, a length check
654 -- is performed on the expression itself during expansion. In rare
655 -- cases, the redundant length check is computed on an index type
656 -- with a different representation, triggering incorrect code in
659 Apply_Length_Check (Rhs, Etype (Lhs));
662 -- Discriminant checks are applied in the course of expansion
667 -- Note: modifications of the Lhs may only be recorded after
668 -- checks have been applied.
670 Note_Possible_Modification (Lhs, Sure => True);
672 -- ??? a real accessibility check is needed when ???
674 -- Post warning for redundant assignment or variable to itself
676 if Warn_On_Redundant_Constructs
678 -- We only warn for source constructs
680 and then Comes_From_Source (N)
682 -- Where the object is the same on both sides
684 and then Same_Object (Lhs, Original_Node (Rhs))
686 -- But exclude the case where the right side was an operation
687 -- that got rewritten (e.g. JUNK + K, where K was known to be
688 -- zero). We don't want to warn in such a case, since it is
689 -- reasonable to write such expressions especially when K is
690 -- defined symbolically in some other package.
692 and then Nkind (Original_Node (Rhs)) not in N_Op
694 if Nkind (Lhs) in N_Has_Entity then
696 ("?useless assignment of & to itself!", N, Entity (Lhs));
699 ("?useless assignment of object to itself!", N);
703 -- Check for non-allowed composite assignment
705 if not Support_Composite_Assign_On_Target
706 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
707 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
709 Error_Msg_CRT ("composite assignment", N);
712 -- Check elaboration warning for left side if not in elab code
714 if not In_Subprogram_Or_Concurrent_Unit then
715 Check_Elab_Assign (Lhs);
718 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
719 -- assignment is a source assignment in the extended main source unit.
720 -- We are not interested in any reference information outside this
721 -- context, or in compiler generated assignment statements.
723 if Comes_From_Source (N)
724 and then In_Extended_Main_Source_Unit (Lhs)
726 Set_Referenced_Modified (Lhs, Out_Param => False);
729 -- Final step. If left side is an entity, then we may be able to
730 -- reset the current tracked values to new safe values. We only have
731 -- something to do if the left side is an entity name, and expansion
732 -- has not modified the node into something other than an assignment,
733 -- and of course we only capture values if it is safe to do so.
735 if Is_Entity_Name (Lhs)
736 and then Nkind (N) = N_Assignment_Statement
739 Ent : constant Entity_Id := Entity (Lhs);
742 if Safe_To_Capture_Value (N, Ent) then
744 -- If simple variable on left side, warn if this assignment
745 -- blots out another one (rendering it useless) and note
746 -- location of assignment in case no one references value.
747 -- We only do this for source assignments, otherwise we can
748 -- generate bogus warnings when an assignment is rewritten as
749 -- another assignment, and gets tied up with itself.
751 -- Note: we don't use Record_Last_Assignment here, because we
752 -- have lots of other stuff to do under control of this test.
754 if Warn_On_Modified_Unread
755 and then Is_Assignable (Ent)
756 and then Comes_From_Source (N)
757 and then In_Extended_Main_Source_Unit (Ent)
759 Warn_On_Useless_Assignment (Ent, N);
760 Set_Last_Assignment (Ent, Lhs);
763 -- If we are assigning an access type and the left side is an
764 -- entity, then make sure that the Is_Known_[Non_]Null flags
765 -- properly reflect the state of the entity after assignment.
767 if Is_Access_Type (T1) then
768 if Known_Non_Null (Rhs) then
769 Set_Is_Known_Non_Null (Ent, True);
771 elsif Known_Null (Rhs)
772 and then not Can_Never_Be_Null (Ent)
774 Set_Is_Known_Null (Ent, True);
777 Set_Is_Known_Null (Ent, False);
779 if not Can_Never_Be_Null (Ent) then
780 Set_Is_Known_Non_Null (Ent, False);
784 -- For discrete types, we may be able to set the current value
785 -- if the value is known at compile time.
787 elsif Is_Discrete_Type (T1)
788 and then Compile_Time_Known_Value (Rhs)
790 Set_Current_Value (Ent, Rhs);
792 Set_Current_Value (Ent, Empty);
795 -- If not safe to capture values, kill them
802 end Analyze_Assignment;
804 -----------------------------
805 -- Analyze_Block_Statement --
806 -----------------------------
808 procedure Analyze_Block_Statement (N : Node_Id) is
809 Decls : constant List_Id := Declarations (N);
810 Id : constant Node_Id := Identifier (N);
811 HSS : constant Node_Id := Handled_Statement_Sequence (N);
814 -- If no handled statement sequence is present, things are really
815 -- messed up, and we just return immediately (this is a defence
816 -- against previous errors).
822 -- Normal processing with HSS present
825 EH : constant List_Id := Exception_Handlers (HSS);
826 Ent : Entity_Id := Empty;
829 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
830 -- Recursively save value of this global, will be restored on exit
833 -- Initialize unblocked exit count for statements of begin block
834 -- plus one for each exception handler that is present.
836 Unblocked_Exit_Count := 1;
839 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
842 -- If a label is present analyze it and mark it as referenced
848 -- An error defense. If we have an identifier, but no entity,
849 -- then something is wrong. If we have previous errors, then
850 -- just remove the identifier and continue, otherwise raise
854 if Total_Errors_Detected /= 0 then
855 Set_Identifier (N, Empty);
861 Set_Ekind (Ent, E_Block);
862 Generate_Reference (Ent, N, ' ');
863 Generate_Definition (Ent);
865 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
866 Set_Label_Construct (Parent (Ent), N);
871 -- If no entity set, create a label entity
874 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
875 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
879 Set_Etype (Ent, Standard_Void_Type);
880 Set_Block_Node (Ent, Identifier (N));
883 if Present (Decls) then
884 Analyze_Declarations (Decls);
886 Inspect_Deferred_Constant_Completion (Decls);
890 Process_End_Label (HSS, 'e', Ent);
892 -- If exception handlers are present, then we indicate that
893 -- enclosing scopes contain a block with handlers. We only
894 -- need to mark non-generic scopes.
899 Set_Has_Nested_Block_With_Handler (S);
900 exit when Is_Overloadable (S)
901 or else Ekind (S) = E_Package
902 or else Is_Generic_Unit (S);
907 Check_References (Ent);
908 Warn_On_Useless_Assignments (Ent);
911 if Unblocked_Exit_Count = 0 then
912 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
913 Check_Unreachable_Code (N);
915 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
918 end Analyze_Block_Statement;
920 ----------------------------
921 -- Analyze_Case_Statement --
922 ----------------------------
924 procedure Analyze_Case_Statement (N : Node_Id) is
926 Exp_Type : Entity_Id;
927 Exp_Btype : Entity_Id;
930 Others_Present : Boolean;
932 pragma Warnings (Off, Last_Choice);
933 pragma Warnings (Off, Dont_Care);
934 -- Don't care about assigned values
936 Statements_Analyzed : Boolean := False;
937 -- Set True if at least some statement sequences get analyzed.
938 -- If False on exit, means we had a serious error that prevented
939 -- full analysis of the case statement, and as a result it is not
940 -- a good idea to output warning messages about unreachable code.
942 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
943 -- Recursively save value of this global, will be restored on exit
945 procedure Non_Static_Choice_Error (Choice : Node_Id);
946 -- Error routine invoked by the generic instantiation below when
947 -- the case statement has a non static choice.
949 procedure Process_Statements (Alternative : Node_Id);
950 -- Analyzes all the statements associated to a case alternative.
951 -- Needed by the generic instantiation below.
953 package Case_Choices_Processing is new
954 Generic_Choices_Processing
955 (Get_Alternatives => Alternatives,
956 Get_Choices => Discrete_Choices,
957 Process_Empty_Choice => No_OP,
958 Process_Non_Static_Choice => Non_Static_Choice_Error,
959 Process_Associated_Node => Process_Statements);
960 use Case_Choices_Processing;
961 -- Instantiation of the generic choice processing package
963 -----------------------------
964 -- Non_Static_Choice_Error --
965 -----------------------------
967 procedure Non_Static_Choice_Error (Choice : Node_Id) is
970 ("choice given in case statement is not static!", Choice);
971 end Non_Static_Choice_Error;
973 ------------------------
974 -- Process_Statements --
975 ------------------------
977 procedure Process_Statements (Alternative : Node_Id) is
978 Choices : constant List_Id := Discrete_Choices (Alternative);
982 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
983 Statements_Analyzed := True;
985 -- An interesting optimization. If the case statement expression
986 -- is a simple entity, then we can set the current value within
987 -- an alternative if the alternative has one possible value.
991 -- when 2 | 3 => beta
992 -- when others => gamma
994 -- Here we know that N is initially 1 within alpha, but for beta
995 -- and gamma, we do not know anything more about the initial value.
997 if Is_Entity_Name (Exp) then
1000 if Ekind (Ent) = E_Variable
1002 Ekind (Ent) = E_In_Out_Parameter
1004 Ekind (Ent) = E_Out_Parameter
1006 if List_Length (Choices) = 1
1007 and then Nkind (First (Choices)) in N_Subexpr
1008 and then Compile_Time_Known_Value (First (Choices))
1010 Set_Current_Value (Entity (Exp), First (Choices));
1013 Analyze_Statements (Statements (Alternative));
1015 -- After analyzing the case, set the current value to empty
1016 -- since we won't know what it is for the next alternative
1017 -- (unless reset by this same circuit), or after the case.
1019 Set_Current_Value (Entity (Exp), Empty);
1024 -- Case where expression is not an entity name of a variable
1026 Analyze_Statements (Statements (Alternative));
1027 end Process_Statements;
1029 -- Table to record choices. Put after subprograms since we make
1030 -- a call to Number_Of_Choices to get the right number of entries.
1032 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
1033 pragma Warnings (Off, Case_Table);
1035 -- Start of processing for Analyze_Case_Statement
1038 Unblocked_Exit_Count := 0;
1039 Exp := Expression (N);
1042 -- The expression must be of any discrete type. In rare cases, the
1043 -- expander constructs a case statement whose expression has a private
1044 -- type whose full view is discrete. This can happen when generating
1045 -- a stream operation for a variant type after the type is frozen,
1046 -- when the partial of view of the type of the discriminant is private.
1047 -- In that case, use the full view to analyze case alternatives.
1049 if not Is_Overloaded (Exp)
1050 and then not Comes_From_Source (N)
1051 and then Is_Private_Type (Etype (Exp))
1052 and then Present (Full_View (Etype (Exp)))
1053 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1055 Resolve (Exp, Etype (Exp));
1056 Exp_Type := Full_View (Etype (Exp));
1059 Analyze_And_Resolve (Exp, Any_Discrete);
1060 Exp_Type := Etype (Exp);
1063 Check_Unset_Reference (Exp);
1064 Exp_Btype := Base_Type (Exp_Type);
1066 -- The expression must be of a discrete type which must be determinable
1067 -- independently of the context in which the expression occurs, but
1068 -- using the fact that the expression must be of a discrete type.
1069 -- Moreover, the type this expression must not be a character literal
1070 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1072 -- If error already reported by Resolve, nothing more to do
1074 if Exp_Btype = Any_Discrete
1075 or else Exp_Btype = Any_Type
1079 elsif Exp_Btype = Any_Character then
1081 ("character literal as case expression is ambiguous", Exp);
1084 elsif Ada_Version = Ada_83
1085 and then (Is_Generic_Type (Exp_Btype)
1086 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1089 ("(Ada 83) case expression cannot be of a generic type", Exp);
1093 -- If the case expression is a formal object of mode in out, then
1094 -- treat it as having a nonstatic subtype by forcing use of the base
1095 -- type (which has to get passed to Check_Case_Choices below). Also
1096 -- use base type when the case expression is parenthesized.
1098 if Paren_Count (Exp) > 0
1099 or else (Is_Entity_Name (Exp)
1100 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1102 Exp_Type := Exp_Btype;
1105 -- Call instantiated Analyze_Choices which does the rest of the work
1108 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
1110 if Exp_Type = Universal_Integer and then not Others_Present then
1111 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1114 -- If all our exits were blocked by unconditional transfers of control,
1115 -- then the entire CASE statement acts as an unconditional transfer of
1116 -- control, so treat it like one, and check unreachable code. Skip this
1117 -- test if we had serious errors preventing any statement analysis.
1119 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1120 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1121 Check_Unreachable_Code (N);
1123 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1126 if not Expander_Active
1127 and then Compile_Time_Known_Value (Expression (N))
1128 and then Serious_Errors_Detected = 0
1131 Chosen : constant Node_Id := Find_Static_Alternative (N);
1135 Alt := First (Alternatives (N));
1136 while Present (Alt) loop
1137 if Alt /= Chosen then
1138 Remove_Warning_Messages (Statements (Alt));
1145 end Analyze_Case_Statement;
1147 ----------------------------
1148 -- Analyze_Exit_Statement --
1149 ----------------------------
1151 -- If the exit includes a name, it must be the name of a currently open
1152 -- loop. Otherwise there must be an innermost open loop on the stack,
1153 -- to which the statement implicitly refers.
1155 procedure Analyze_Exit_Statement (N : Node_Id) is
1156 Target : constant Node_Id := Name (N);
1157 Cond : constant Node_Id := Condition (N);
1158 Scope_Id : Entity_Id;
1164 Check_Unreachable_Code (N);
1167 if Present (Target) then
1169 U_Name := Entity (Target);
1171 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1172 Error_Msg_N ("invalid loop name in exit statement", N);
1175 Set_Has_Exit (U_Name);
1182 for J in reverse 0 .. Scope_Stack.Last loop
1183 Scope_Id := Scope_Stack.Table (J).Entity;
1184 Kind := Ekind (Scope_Id);
1187 and then (No (Target) or else Scope_Id = U_Name) then
1188 Set_Has_Exit (Scope_Id);
1191 elsif Kind = E_Block
1192 or else Kind = E_Loop
1193 or else Kind = E_Return_Statement
1199 ("cannot exit from program unit or accept statement", N);
1204 -- Verify that if present the condition is a Boolean expression
1206 if Present (Cond) then
1207 Analyze_And_Resolve (Cond, Any_Boolean);
1208 Check_Unset_Reference (Cond);
1211 -- Since the exit may take us out of a loop, any previous assignment
1212 -- statement is not useless, so clear last assignment indications. It
1213 -- is OK to keep other current values, since if the exit statement
1214 -- does not exit, then the current values are still valid.
1216 Kill_Current_Values (Last_Assignment_Only => True);
1217 end Analyze_Exit_Statement;
1219 ----------------------------
1220 -- Analyze_Goto_Statement --
1221 ----------------------------
1223 procedure Analyze_Goto_Statement (N : Node_Id) is
1224 Label : constant Node_Id := Name (N);
1225 Scope_Id : Entity_Id;
1226 Label_Scope : Entity_Id;
1227 Label_Ent : Entity_Id;
1230 Check_Unreachable_Code (N);
1231 Kill_Current_Values (Last_Assignment_Only => True);
1234 Label_Ent := Entity (Label);
1236 -- Ignore previous error
1238 if Label_Ent = Any_Id then
1241 -- We just have a label as the target of a goto
1243 elsif Ekind (Label_Ent) /= E_Label then
1244 Error_Msg_N ("target of goto statement must be a label", Label);
1247 -- Check that the target of the goto is reachable according to Ada
1248 -- scoping rules. Note: the special gotos we generate for optimizing
1249 -- local handling of exceptions would violate these rules, but we mark
1250 -- such gotos as analyzed when built, so this code is never entered.
1252 elsif not Reachable (Label_Ent) then
1253 Error_Msg_N ("target of goto statement is not reachable", Label);
1257 -- Here if goto passes initial validity checks
1259 Label_Scope := Enclosing_Scope (Label_Ent);
1261 for J in reverse 0 .. Scope_Stack.Last loop
1262 Scope_Id := Scope_Stack.Table (J).Entity;
1264 if Label_Scope = Scope_Id
1265 or else (Ekind (Scope_Id) /= E_Block
1266 and then Ekind (Scope_Id) /= E_Loop
1267 and then Ekind (Scope_Id) /= E_Return_Statement)
1269 if Scope_Id /= Label_Scope then
1271 ("cannot exit from program unit or accept statement", N);
1278 raise Program_Error;
1279 end Analyze_Goto_Statement;
1281 --------------------------
1282 -- Analyze_If_Statement --
1283 --------------------------
1285 -- A special complication arises in the analysis of if statements
1287 -- The expander has circuitry to completely delete code that it
1288 -- can tell will not be executed (as a result of compile time known
1289 -- conditions). In the analyzer, we ensure that code that will be
1290 -- deleted in this manner is analyzed but not expanded. This is
1291 -- obviously more efficient, but more significantly, difficulties
1292 -- arise if code is expanded and then eliminated (e.g. exception
1293 -- table entries disappear). Similarly, itypes generated in deleted
1294 -- code must be frozen from start, because the nodes on which they
1295 -- depend will not be available at the freeze point.
1297 procedure Analyze_If_Statement (N : Node_Id) is
1300 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1301 -- Recursively save value of this global, will be restored on exit
1303 Save_In_Deleted_Code : Boolean;
1305 Del : Boolean := False;
1306 -- This flag gets set True if a True condition has been found,
1307 -- which means that remaining ELSE/ELSIF parts are deleted.
1309 procedure Analyze_Cond_Then (Cnode : Node_Id);
1310 -- This is applied to either the N_If_Statement node itself or
1311 -- to an N_Elsif_Part node. It deals with analyzing the condition
1312 -- and the THEN statements associated with it.
1314 -----------------------
1315 -- Analyze_Cond_Then --
1316 -----------------------
1318 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1319 Cond : constant Node_Id := Condition (Cnode);
1320 Tstm : constant List_Id := Then_Statements (Cnode);
1323 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1324 Analyze_And_Resolve (Cond, Any_Boolean);
1325 Check_Unset_Reference (Cond);
1326 Set_Current_Value_Condition (Cnode);
1328 -- If already deleting, then just analyze then statements
1331 Analyze_Statements (Tstm);
1333 -- Compile time known value, not deleting yet
1335 elsif Compile_Time_Known_Value (Cond) then
1336 Save_In_Deleted_Code := In_Deleted_Code;
1338 -- If condition is True, then analyze the THEN statements
1339 -- and set no expansion for ELSE and ELSIF parts.
1341 if Is_True (Expr_Value (Cond)) then
1342 Analyze_Statements (Tstm);
1344 Expander_Mode_Save_And_Set (False);
1345 In_Deleted_Code := True;
1347 -- If condition is False, analyze THEN with expansion off
1349 else -- Is_False (Expr_Value (Cond))
1350 Expander_Mode_Save_And_Set (False);
1351 In_Deleted_Code := True;
1352 Analyze_Statements (Tstm);
1353 Expander_Mode_Restore;
1354 In_Deleted_Code := Save_In_Deleted_Code;
1357 -- Not known at compile time, not deleting, normal analysis
1360 Analyze_Statements (Tstm);
1362 end Analyze_Cond_Then;
1364 -- Start of Analyze_If_Statement
1367 -- Initialize exit count for else statements. If there is no else
1368 -- part, this count will stay non-zero reflecting the fact that the
1369 -- uncovered else case is an unblocked exit.
1371 Unblocked_Exit_Count := 1;
1372 Analyze_Cond_Then (N);
1374 -- Now to analyze the elsif parts if any are present
1376 if Present (Elsif_Parts (N)) then
1377 E := First (Elsif_Parts (N));
1378 while Present (E) loop
1379 Analyze_Cond_Then (E);
1384 if Present (Else_Statements (N)) then
1385 Analyze_Statements (Else_Statements (N));
1388 -- If all our exits were blocked by unconditional transfers of control,
1389 -- then the entire IF statement acts as an unconditional transfer of
1390 -- control, so treat it like one, and check unreachable code.
1392 if Unblocked_Exit_Count = 0 then
1393 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1394 Check_Unreachable_Code (N);
1396 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1400 Expander_Mode_Restore;
1401 In_Deleted_Code := Save_In_Deleted_Code;
1404 if not Expander_Active
1405 and then Compile_Time_Known_Value (Condition (N))
1406 and then Serious_Errors_Detected = 0
1408 if Is_True (Expr_Value (Condition (N))) then
1409 Remove_Warning_Messages (Else_Statements (N));
1411 if Present (Elsif_Parts (N)) then
1412 E := First (Elsif_Parts (N));
1413 while Present (E) loop
1414 Remove_Warning_Messages (Then_Statements (E));
1420 Remove_Warning_Messages (Then_Statements (N));
1423 end Analyze_If_Statement;
1425 ----------------------------------------
1426 -- Analyze_Implicit_Label_Declaration --
1427 ----------------------------------------
1429 -- An implicit label declaration is generated in the innermost
1430 -- enclosing declarative part. This is done for labels as well as
1431 -- block and loop names.
1433 -- Note: any changes in this routine may need to be reflected in
1434 -- Analyze_Label_Entity.
1436 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1437 Id : constant Node_Id := Defining_Identifier (N);
1440 Set_Ekind (Id, E_Label);
1441 Set_Etype (Id, Standard_Void_Type);
1442 Set_Enclosing_Scope (Id, Current_Scope);
1443 end Analyze_Implicit_Label_Declaration;
1445 ------------------------------
1446 -- Analyze_Iteration_Scheme --
1447 ------------------------------
1449 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1451 procedure Process_Bounds (R : Node_Id);
1452 -- If the iteration is given by a range, create temporaries and
1453 -- assignment statements block to capture the bounds and perform
1454 -- required finalization actions in case a bound includes a function
1455 -- call that uses the temporary stack. We first pre-analyze a copy of
1456 -- the range in order to determine the expected type, and analyze and
1457 -- resolve the original bounds.
1459 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1460 -- If the bounds are given by a 'Range reference on a function call
1461 -- that returns a controlled array, introduce an explicit declaration
1462 -- to capture the bounds, so that the function result can be finalized
1463 -- in timely fashion.
1465 --------------------
1466 -- Process_Bounds --
1467 --------------------
1469 procedure Process_Bounds (R : Node_Id) is
1470 Loc : constant Source_Ptr := Sloc (N);
1471 R_Copy : constant Node_Id := New_Copy_Tree (R);
1472 Lo : constant Node_Id := Low_Bound (R);
1473 Hi : constant Node_Id := High_Bound (R);
1474 New_Lo_Bound : Node_Id := Empty;
1475 New_Hi_Bound : Node_Id := Empty;
1477 Save_Analysis : Boolean;
1480 (Original_Bound : Node_Id;
1481 Analyzed_Bound : Node_Id) return Node_Id;
1482 -- Capture value of bound and return captured value
1489 (Original_Bound : Node_Id;
1490 Analyzed_Bound : Node_Id) return Node_Id
1497 -- If the bound is a constant or an object, no need for a separate
1498 -- declaration. If the bound is the result of previous expansion
1499 -- it is already analyzed and should not be modified. Note that
1500 -- the Bound will be resolved later, if needed, as part of the
1501 -- call to Make_Index (literal bounds may need to be resolved to
1504 if Analyzed (Original_Bound) then
1505 return Original_Bound;
1507 elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
1508 N_Character_Literal)
1509 or else Is_Entity_Name (Analyzed_Bound)
1511 Analyze_And_Resolve (Original_Bound, Typ);
1512 return Original_Bound;
1515 -- Here we need to capture the value
1517 Analyze_And_Resolve (Original_Bound, Typ);
1520 Make_Defining_Identifier (Loc,
1521 Chars => New_Internal_Name ('S'));
1523 -- Normally, the best approach is simply to generate a constant
1524 -- declaration that captures the bound. However, there is a nasty
1525 -- case where this is wrong. If the bound is complex, and has a
1526 -- possible use of the secondary stack, we need to generate a
1527 -- separate assignment statement to ensure the creation of a block
1528 -- which will release the secondary stack.
1530 -- We prefer the constant declaration, since it leaves us with a
1531 -- proper trace of the value, useful in optimizations that get rid
1532 -- of junk range checks.
1534 -- Probably we want something like the Side_Effect_Free routine
1535 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1536 -- and 'First applied to an entity, since these are the important
1537 -- cases for range check optimizations.
1539 if Nkind (Original_Bound) = N_Attribute_Reference
1540 and then (Attribute_Name (Original_Bound) = Name_First
1542 Attribute_Name (Original_Bound) = Name_Last)
1543 and then Is_Entity_Name (Prefix (Original_Bound))
1546 Make_Object_Declaration (Loc,
1547 Defining_Identifier => Id,
1548 Constant_Present => True,
1549 Object_Definition => New_Occurrence_Of (Typ, Loc),
1550 Expression => Relocate_Node (Original_Bound));
1552 Insert_Before (Parent (N), Decl);
1554 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1555 return Expression (Decl);
1558 -- Here we make a declaration with a separate assignment statement
1561 Make_Object_Declaration (Loc,
1562 Defining_Identifier => Id,
1563 Object_Definition => New_Occurrence_Of (Typ, Loc));
1565 Insert_Before (Parent (N), Decl);
1569 Make_Assignment_Statement (Loc,
1570 Name => New_Occurrence_Of (Id, Loc),
1571 Expression => Relocate_Node (Original_Bound));
1573 Insert_Before (Parent (N), Assign);
1576 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1578 if Nkind (Assign) = N_Assignment_Statement then
1579 return Expression (Assign);
1581 return Original_Bound;
1585 -- Start of processing for Process_Bounds
1588 -- Determine expected type of range by analyzing separate copy
1589 -- Do the analysis and resolution of the copy of the bounds with
1590 -- expansion disabled, to prevent the generation of finalization
1591 -- actions on each bound. This prevents memory leaks when the
1592 -- bounds contain calls to functions returning controlled arrays.
1594 Set_Parent (R_Copy, Parent (R));
1595 Save_Analysis := Full_Analysis;
1596 Full_Analysis := False;
1597 Expander_Mode_Save_And_Set (False);
1601 if Is_Overloaded (R_Copy) then
1603 -- Apply preference rules for range of predefined integer types,
1604 -- or diagnose true ambiguity.
1609 Found : Entity_Id := Empty;
1612 Get_First_Interp (R_Copy, I, It);
1613 while Present (It.Typ) loop
1614 if Is_Discrete_Type (It.Typ) then
1618 if Scope (Found) = Standard_Standard then
1621 elsif Scope (It.Typ) = Standard_Standard then
1625 -- Both of them are user-defined
1628 ("ambiguous bounds in range of iteration",
1630 Error_Msg_N ("\possible interpretations:", R_Copy);
1631 Error_Msg_NE ("\\} ", R_Copy, Found);
1632 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1638 Get_Next_Interp (I, It);
1644 Expander_Mode_Restore;
1645 Full_Analysis := Save_Analysis;
1647 Typ := Etype (R_Copy);
1649 -- If the type of the discrete range is Universal_Integer, then
1650 -- the bound's type must be resolved to Integer, and any object
1651 -- used to hold the bound must also have type Integer, unless the
1652 -- literal bounds are constant-folded expressions that carry a user-
1655 if Typ = Universal_Integer then
1656 if Nkind (Lo) = N_Integer_Literal
1657 and then Present (Etype (Lo))
1658 and then Scope (Etype (Lo)) /= Standard_Standard
1662 elsif Nkind (Hi) = N_Integer_Literal
1663 and then Present (Etype (Hi))
1664 and then Scope (Etype (Hi)) /= Standard_Standard
1669 Typ := Standard_Integer;
1675 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1676 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1678 -- Propagate staticness to loop range itself, in case the
1679 -- corresponding subtype is static.
1681 if New_Lo_Bound /= Lo
1682 and then Is_Static_Expression (New_Lo_Bound)
1684 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1687 if New_Hi_Bound /= Hi
1688 and then Is_Static_Expression (New_Hi_Bound)
1690 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1694 --------------------------------------
1695 -- Check_Controlled_Array_Attribute --
1696 --------------------------------------
1698 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1700 if Nkind (DS) = N_Attribute_Reference
1701 and then Is_Entity_Name (Prefix (DS))
1702 and then Ekind (Entity (Prefix (DS))) = E_Function
1703 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1706 Component_Type (Etype (Entity (Prefix (DS)))))
1707 and then Expander_Active
1710 Loc : constant Source_Ptr := Sloc (N);
1711 Arr : constant Entity_Id :=
1712 Etype (Entity (Prefix (DS)));
1713 Indx : constant Entity_Id :=
1714 Base_Type (Etype (First_Index (Arr)));
1715 Subt : constant Entity_Id :=
1716 Make_Defining_Identifier
1717 (Loc, New_Internal_Name ('S'));
1722 Make_Subtype_Declaration (Loc,
1723 Defining_Identifier => Subt,
1724 Subtype_Indication =>
1725 Make_Subtype_Indication (Loc,
1726 Subtype_Mark => New_Reference_To (Indx, Loc),
1728 Make_Range_Constraint (Loc,
1729 Relocate_Node (DS))));
1730 Insert_Before (Parent (N), Decl);
1734 Make_Attribute_Reference (Loc,
1735 Prefix => New_Reference_To (Subt, Loc),
1736 Attribute_Name => Attribute_Name (DS)));
1740 end Check_Controlled_Array_Attribute;
1742 -- Start of processing for Analyze_Iteration_Scheme
1745 -- For an infinite loop, there is no iteration scheme
1752 Cond : constant Node_Id := Condition (N);
1755 -- For WHILE loop, verify that the condition is a Boolean
1756 -- expression and resolve and check it.
1758 if Present (Cond) then
1759 Analyze_And_Resolve (Cond, Any_Boolean);
1760 Check_Unset_Reference (Cond);
1761 Set_Current_Value_Condition (N);
1764 -- Else we have a FOR loop
1768 LP : constant Node_Id := Loop_Parameter_Specification (N);
1769 Id : constant Entity_Id := Defining_Identifier (LP);
1770 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1775 -- We always consider the loop variable to be referenced,
1776 -- since the loop may be used just for counting purposes.
1778 Generate_Reference (Id, N, ' ');
1780 -- Check for case of loop variable hiding a local
1781 -- variable (used later on to give a nice warning
1782 -- if the hidden variable is never assigned).
1785 H : constant Entity_Id := Homonym (Id);
1788 and then Enclosing_Dynamic_Scope (H) =
1789 Enclosing_Dynamic_Scope (Id)
1790 and then Ekind (H) = E_Variable
1791 and then Is_Discrete_Type (Etype (H))
1793 Set_Hiding_Loop_Variable (H, Id);
1797 -- Now analyze the subtype definition. If it is
1798 -- a range, create temporaries for bounds.
1800 if Nkind (DS) = N_Range
1801 and then Expander_Active
1803 Process_Bounds (DS);
1812 -- The subtype indication may denote the completion
1813 -- of an incomplete type declaration.
1815 if Is_Entity_Name (DS)
1816 and then Present (Entity (DS))
1817 and then Is_Type (Entity (DS))
1818 and then Ekind (Entity (DS)) = E_Incomplete_Type
1820 Set_Entity (DS, Get_Full_View (Entity (DS)));
1821 Set_Etype (DS, Entity (DS));
1824 if not Is_Discrete_Type (Etype (DS)) then
1825 Wrong_Type (DS, Any_Discrete);
1826 Set_Etype (DS, Any_Type);
1829 Check_Controlled_Array_Attribute (DS);
1831 Make_Index (DS, LP);
1833 Set_Ekind (Id, E_Loop_Parameter);
1834 Set_Etype (Id, Etype (DS));
1836 -- Treat a range as an implicit reference to the type, to
1837 -- inhibit spurious warnings.
1839 Generate_Reference (Base_Type (Etype (DS)), N, ' ');
1840 Set_Is_Known_Valid (Id, True);
1842 -- The loop is not a declarative part, so the only entity
1843 -- declared "within" must be frozen explicitly.
1846 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1848 if Is_Non_Empty_List (Flist) then
1849 Insert_Actions (N, Flist);
1853 -- Check for null or possibly null range and issue warning.
1854 -- We suppress such messages in generic templates and
1855 -- instances, because in practice they tend to be dubious
1858 if Nkind (DS) = N_Range
1859 and then Comes_From_Source (N)
1862 L : constant Node_Id := Low_Bound (DS);
1863 H : constant Node_Id := High_Bound (DS);
1866 -- If range of loop is null, issue warning
1868 if Compile_Time_Compare
1869 (L, H, Assume_Valid => True) = GT
1871 -- Suppress the warning if inside a generic
1872 -- template or instance, since in practice
1873 -- they tend to be dubious in these cases since
1874 -- they can result from intended parametrization.
1876 if not Inside_A_Generic
1877 and then not In_Instance
1879 -- Specialize msg if invalid values could make
1880 -- the loop non-null after all.
1882 if Compile_Time_Compare
1883 (L, H, Assume_Valid => False) = GT
1886 ("?loop range is null, "
1887 & "loop will not execute",
1890 -- Since we know the range of the loop is
1891 -- null, set the appropriate flag to remove
1892 -- the loop entirely during expansion.
1894 Set_Is_Null_Loop (Parent (N));
1896 -- Here is where the loop could execute because
1897 -- of invalid values, so issue appropriate
1898 -- message and in this case we do not set the
1899 -- Is_Null_Loop flag since the loop may execute.
1903 ("?loop range may be null, "
1904 & "loop may not execute",
1907 ("?can only execute if invalid values "
1913 -- In either case, suppress warnings in the body of
1914 -- the loop, since it is likely that these warnings
1915 -- will be inappropriate if the loop never actually
1916 -- executes, which is unlikely.
1918 Set_Suppress_Loop_Warnings (Parent (N));
1920 -- The other case for a warning is a reverse loop
1921 -- where the upper bound is the integer literal
1922 -- zero or one, and the lower bound can be positive.
1924 -- For example, we have
1926 -- for J in reverse N .. 1 loop
1928 -- In practice, this is very likely to be a case
1929 -- of reversing the bounds incorrectly in the range.
1931 elsif Reverse_Present (LP)
1932 and then Nkind (Original_Node (H)) =
1934 and then (Intval (Original_Node (H)) = Uint_0
1936 Intval (Original_Node (H)) = Uint_1)
1938 Error_Msg_N ("?loop range may be null", DS);
1939 Error_Msg_N ("\?bounds may be wrong way round", DS);
1947 end Analyze_Iteration_Scheme;
1953 -- Note: the semantic work required for analyzing labels (setting them as
1954 -- reachable) was done in a prepass through the statements in the block,
1955 -- so that forward gotos would be properly handled. See Analyze_Statements
1956 -- for further details. The only processing required here is to deal with
1957 -- optimizations that depend on an assumption of sequential control flow,
1958 -- since of course the occurrence of a label breaks this assumption.
1960 procedure Analyze_Label (N : Node_Id) is
1961 pragma Warnings (Off, N);
1963 Kill_Current_Values;
1966 --------------------------
1967 -- Analyze_Label_Entity --
1968 --------------------------
1970 procedure Analyze_Label_Entity (E : Entity_Id) is
1972 Set_Ekind (E, E_Label);
1973 Set_Etype (E, Standard_Void_Type);
1974 Set_Enclosing_Scope (E, Current_Scope);
1975 Set_Reachable (E, True);
1976 end Analyze_Label_Entity;
1978 ----------------------------
1979 -- Analyze_Loop_Statement --
1980 ----------------------------
1982 procedure Analyze_Loop_Statement (N : Node_Id) is
1983 Loop_Statement : constant Node_Id := N;
1985 Id : constant Node_Id := Identifier (Loop_Statement);
1986 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
1990 if Present (Id) then
1992 -- Make name visible, e.g. for use in exit statements. Loop
1993 -- labels are always considered to be referenced.
1998 -- Guard against serious error (typically, a scope mismatch when
1999 -- semantic analysis is requested) by creating loop entity to
2000 -- continue analysis.
2003 if Total_Errors_Detected /= 0 then
2006 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2008 raise Program_Error;
2012 Generate_Reference (Ent, Loop_Statement, ' ');
2013 Generate_Definition (Ent);
2015 -- If we found a label, mark its type. If not, ignore it, since it
2016 -- means we have a conflicting declaration, which would already
2017 -- have been diagnosed at declaration time. Set Label_Construct
2018 -- of the implicit label declaration, which is not created by the
2019 -- parser for generic units.
2021 if Ekind (Ent) = E_Label then
2022 Set_Ekind (Ent, E_Loop);
2024 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
2025 Set_Label_Construct (Parent (Ent), Loop_Statement);
2030 -- Case of no identifier present
2035 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2036 Set_Etype (Ent, Standard_Void_Type);
2037 Set_Parent (Ent, Loop_Statement);
2040 -- Kill current values on entry to loop, since statements in body of
2041 -- loop may have been executed before the loop is entered. Similarly we
2042 -- kill values after the loop, since we do not know that the body of the
2043 -- loop was executed.
2045 Kill_Current_Values;
2047 Analyze_Iteration_Scheme (Iter);
2048 Analyze_Statements (Statements (Loop_Statement));
2049 Process_End_Label (Loop_Statement, 'e', Ent);
2051 Kill_Current_Values;
2053 -- Check for infinite loop. We skip this check for generated code, since
2054 -- it justs waste time and makes debugging the routine called harder.
2056 if Comes_From_Source (N) then
2057 Check_Infinite_Loop_Warning (N);
2060 -- Code after loop is unreachable if the loop has no WHILE or FOR
2061 -- and contains no EXIT statements within the body of the loop.
2063 if No (Iter) and then not Has_Exit (Ent) then
2064 Check_Unreachable_Code (N);
2066 end Analyze_Loop_Statement;
2068 ----------------------------
2069 -- Analyze_Null_Statement --
2070 ----------------------------
2072 -- Note: the semantics of the null statement is implemented by a single
2073 -- null statement, too bad everything isn't as simple as this!
2075 procedure Analyze_Null_Statement (N : Node_Id) is
2076 pragma Warnings (Off, N);
2079 end Analyze_Null_Statement;
2081 ------------------------
2082 -- Analyze_Statements --
2083 ------------------------
2085 procedure Analyze_Statements (L : List_Id) is
2090 -- The labels declared in the statement list are reachable from
2091 -- statements in the list. We do this as a prepass so that any
2092 -- goto statement will be properly flagged if its target is not
2093 -- reachable. This is not required, but is nice behavior!
2096 while Present (S) loop
2097 if Nkind (S) = N_Label then
2098 Analyze (Identifier (S));
2099 Lab := Entity (Identifier (S));
2101 -- If we found a label mark it as reachable
2103 if Ekind (Lab) = E_Label then
2104 Generate_Definition (Lab);
2105 Set_Reachable (Lab);
2107 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
2108 Set_Label_Construct (Parent (Lab), S);
2111 -- If we failed to find a label, it means the implicit declaration
2112 -- of the label was hidden. A for-loop parameter can do this to
2113 -- a label with the same name inside the loop, since the implicit
2114 -- label declaration is in the innermost enclosing body or block
2118 Error_Msg_Sloc := Sloc (Lab);
2120 ("implicit label declaration for & is hidden#",
2128 -- Perform semantic analysis on all statements
2130 Conditional_Statements_Begin;
2133 while Present (S) loop
2138 Conditional_Statements_End;
2140 -- Make labels unreachable. Visibility is not sufficient, because
2141 -- labels in one if-branch for example are not reachable from the
2142 -- other branch, even though their declarations are in the enclosing
2143 -- declarative part.
2146 while Present (S) loop
2147 if Nkind (S) = N_Label then
2148 Set_Reachable (Entity (Identifier (S)), False);
2153 end Analyze_Statements;
2155 ----------------------------
2156 -- Check_Unreachable_Code --
2157 ----------------------------
2159 procedure Check_Unreachable_Code (N : Node_Id) is
2160 Error_Loc : Source_Ptr;
2164 if Is_List_Member (N)
2165 and then Comes_From_Source (N)
2171 Nxt := Original_Node (Next (N));
2173 -- If a label follows us, then we never have dead code, since
2174 -- someone could branch to the label, so we just ignore it.
2176 if Nkind (Nxt) = N_Label then
2179 -- Otherwise see if we have a real statement following us
2182 and then Comes_From_Source (Nxt)
2183 and then Is_Statement (Nxt)
2185 -- Special very annoying exception. If we have a return that
2186 -- follows a raise, then we allow it without a warning, since
2187 -- the Ada RM annoyingly requires a useless return here!
2189 if Nkind (Original_Node (N)) /= N_Raise_Statement
2190 or else Nkind (Nxt) /= N_Simple_Return_Statement
2192 -- The rather strange shenanigans with the warning message
2193 -- here reflects the fact that Kill_Dead_Code is very good
2194 -- at removing warnings in deleted code, and this is one
2195 -- warning we would prefer NOT to have removed.
2197 Error_Loc := Sloc (Nxt);
2199 -- If we have unreachable code, analyze and remove the
2200 -- unreachable code, since it is useless and we don't
2201 -- want to generate junk warnings.
2203 -- We skip this step if we are not in code generation mode.
2204 -- This is the one case where we remove dead code in the
2205 -- semantics as opposed to the expander, and we do not want
2206 -- to remove code if we are not in code generation mode,
2207 -- since this messes up the ASIS trees.
2209 -- Note that one might react by moving the whole circuit to
2210 -- exp_ch5, but then we lose the warning in -gnatc mode.
2212 if Operating_Mode = Generate_Code then
2216 -- Quit deleting when we have nothing more to delete
2217 -- or if we hit a label (since someone could transfer
2218 -- control to a label, so we should not delete it).
2220 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2222 -- Statement/declaration is to be deleted
2226 Kill_Dead_Code (Nxt);
2230 -- Now issue the warning
2232 Error_Msg ("?unreachable code!", Error_Loc);
2235 -- If the unconditional transfer of control instruction is
2236 -- the last statement of a sequence, then see if our parent
2237 -- is one of the constructs for which we count unblocked exits,
2238 -- and if so, adjust the count.
2243 -- Statements in THEN part or ELSE part of IF statement
2245 if Nkind (P) = N_If_Statement then
2248 -- Statements in ELSIF part of an IF statement
2250 elsif Nkind (P) = N_Elsif_Part then
2252 pragma Assert (Nkind (P) = N_If_Statement);
2254 -- Statements in CASE statement alternative
2256 elsif Nkind (P) = N_Case_Statement_Alternative then
2258 pragma Assert (Nkind (P) = N_Case_Statement);
2260 -- Statements in body of block
2262 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2263 and then Nkind (Parent (P)) = N_Block_Statement
2267 -- Statements in exception handler in a block
2269 elsif Nkind (P) = N_Exception_Handler
2270 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2271 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2275 -- None of these cases, so return
2281 -- This was one of the cases we are looking for (i.e. the
2282 -- parent construct was IF, CASE or block) so decrement count.
2284 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2288 end Check_Unreachable_Code;