1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2010, 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_SCIL; use Sem_SCIL;
50 with Sem_Type; use Sem_Type;
51 with Sem_Util; use Sem_Util;
52 with Sem_Warn; use Sem_Warn;
53 with Snames; use Snames;
54 with Stand; use Stand;
55 with Sinfo; use Sinfo;
56 with Targparm; use Targparm;
57 with Tbuild; use Tbuild;
58 with Uintp; use Uintp;
60 package body Sem_Ch5 is
62 Unblocked_Exit_Count : Nat := 0;
63 -- This variable is used when processing if statements, case statements,
64 -- and block statements. It counts the number of exit points that are not
65 -- blocked by unconditional transfer instructions: for IF and CASE, these
66 -- are the branches of the conditional; for a block, they are the statement
67 -- sequence of the block, and the statement sequences of any exception
68 -- handlers that are part of the block. When processing is complete, if
69 -- this count is zero, it means that control cannot fall through the IF,
70 -- CASE or block statement. This is used for the generation of warning
71 -- messages. This variable is recursively saved on entry to processing the
72 -- construct, and restored on exit.
74 -----------------------
75 -- Local Subprograms --
76 -----------------------
78 procedure Analyze_Iteration_Scheme (N : Node_Id);
80 ------------------------
81 -- Analyze_Assignment --
82 ------------------------
84 procedure Analyze_Assignment (N : Node_Id) is
85 Lhs : constant Node_Id := Name (N);
86 Rhs : constant Node_Id := Expression (N);
91 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
92 -- N is the node for the left hand side of an assignment, and it is not
93 -- a variable. This routine issues an appropriate diagnostic.
96 -- This is called to kill current value settings of a simple variable
97 -- on the left hand side. We call it if we find any error in analyzing
98 -- the assignment, and at the end of processing before setting any new
99 -- current values in place.
101 procedure Set_Assignment_Type
103 Opnd_Type : in out Entity_Id);
104 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
105 -- is the nominal subtype. This procedure is used to deal with cases
106 -- where the nominal subtype must be replaced by the actual subtype.
108 -------------------------------
109 -- Diagnose_Non_Variable_Lhs --
110 -------------------------------
112 procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
114 -- Not worth posting another error if left hand side already
115 -- flagged as being illegal in some respect.
117 if Error_Posted (N) then
120 -- Some special bad cases of entity names
122 elsif Is_Entity_Name (N) then
124 Ent : constant Entity_Id := Entity (N);
127 if Ekind (Ent) = E_In_Parameter then
129 ("assignment to IN mode parameter not allowed", N);
131 -- Renamings of protected private components are turned into
132 -- constants when compiling a protected function. In the case
133 -- of single protected types, the private component appears
136 elsif (Is_Prival (Ent)
138 (Ekind (Current_Scope) = E_Function
139 or else Ekind (Enclosing_Dynamic_Scope (
140 Current_Scope)) = E_Function))
142 (Ekind (Ent) = E_Component
143 and then Is_Protected_Type (Scope (Ent)))
146 ("protected function cannot modify protected object", N);
148 elsif Ekind (Ent) = E_Loop_Parameter then
150 ("assignment to loop parameter not allowed", N);
154 ("left hand side of assignment must be a variable", N);
158 -- For indexed components or selected components, test prefix
160 elsif Nkind (N) = N_Indexed_Component then
161 Diagnose_Non_Variable_Lhs (Prefix (N));
163 -- Another special case for assignment to discriminant
165 elsif Nkind (N) = N_Selected_Component then
166 if Present (Entity (Selector_Name (N)))
167 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
170 ("assignment to discriminant not allowed", N);
172 Diagnose_Non_Variable_Lhs (Prefix (N));
176 -- If we fall through, we have no special message to issue!
178 Error_Msg_N ("left hand side of assignment must be a variable", N);
180 end Diagnose_Non_Variable_Lhs;
186 procedure Kill_Lhs is
188 if Is_Entity_Name (Lhs) then
190 Ent : constant Entity_Id := Entity (Lhs);
192 if Present (Ent) then
193 Kill_Current_Values (Ent);
199 -------------------------
200 -- Set_Assignment_Type --
201 -------------------------
203 procedure Set_Assignment_Type
205 Opnd_Type : in out Entity_Id)
208 Require_Entity (Opnd);
210 -- If the assignment operand is an in-out or out parameter, then we
211 -- get the actual subtype (needed for the unconstrained case).
212 -- If the operand is the actual in an entry declaration, then within
213 -- the accept statement it is replaced with a local renaming, which
214 -- may also have an actual subtype.
216 if Is_Entity_Name (Opnd)
217 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
218 or else Ekind (Entity (Opnd)) =
220 or else Ekind (Entity (Opnd)) =
221 E_Generic_In_Out_Parameter
223 (Ekind (Entity (Opnd)) = E_Variable
224 and then Nkind (Parent (Entity (Opnd))) =
225 N_Object_Renaming_Declaration
226 and then Nkind (Parent (Parent (Entity (Opnd)))) =
229 Opnd_Type := Get_Actual_Subtype (Opnd);
231 -- If assignment operand is a component reference, then we get the
232 -- actual subtype of the component for the unconstrained case.
234 elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference)
235 and then not Is_Unchecked_Union (Opnd_Type)
237 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
239 if Present (Decl) then
240 Insert_Action (N, Decl);
241 Mark_Rewrite_Insertion (Decl);
243 Opnd_Type := Defining_Identifier (Decl);
244 Set_Etype (Opnd, Opnd_Type);
245 Freeze_Itype (Opnd_Type, N);
247 elsif Is_Constrained (Etype (Opnd)) then
248 Opnd_Type := Etype (Opnd);
251 -- For slice, use the constrained subtype created for the slice
253 elsif Nkind (Opnd) = N_Slice then
254 Opnd_Type := Etype (Opnd);
256 end Set_Assignment_Type;
258 -- Start of processing for Analyze_Assignment
261 Mark_Coextensions (N, Rhs);
266 -- Start type analysis for assignment
270 -- In the most general case, both Lhs and Rhs can be overloaded, and we
271 -- must compute the intersection of the possible types on each side.
273 if Is_Overloaded (Lhs) then
280 Get_First_Interp (Lhs, I, It);
282 while Present (It.Typ) loop
283 if Has_Compatible_Type (Rhs, It.Typ) then
284 if T1 /= Any_Type then
286 -- An explicit dereference is overloaded if the prefix
287 -- is. Try to remove the ambiguity on the prefix, the
288 -- error will be posted there if the ambiguity is real.
290 if Nkind (Lhs) = N_Explicit_Dereference then
293 PI1 : Interp_Index := 0;
299 Get_First_Interp (Prefix (Lhs), PI, PIt);
301 while Present (PIt.Typ) loop
302 if Is_Access_Type (PIt.Typ)
303 and then Has_Compatible_Type
304 (Rhs, Designated_Type (PIt.Typ))
308 Disambiguate (Prefix (Lhs),
311 if PIt = No_Interp then
313 ("ambiguous left-hand side"
314 & " in assignment", Lhs);
317 Resolve (Prefix (Lhs), PIt.Typ);
327 Get_Next_Interp (PI, PIt);
333 ("ambiguous left-hand side in assignment", Lhs);
341 Get_Next_Interp (I, It);
345 if T1 = Any_Type then
347 ("no valid types for left-hand side for assignment", Lhs);
353 -- The resulting assignment type is T1, so now we will resolve the
354 -- left hand side of the assignment using this determined type.
358 -- Cases where Lhs is not a variable
360 if not Is_Variable (Lhs) then
362 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
363 -- a protected object.
370 if Ada_Version >= Ada_05 then
372 -- Handle chains of renamings
375 while Nkind (Ent) in N_Has_Entity
376 and then Present (Entity (Ent))
377 and then Present (Renamed_Object (Entity (Ent)))
379 Ent := Renamed_Object (Entity (Ent));
382 if (Nkind (Ent) = N_Attribute_Reference
383 and then Attribute_Name (Ent) = Name_Priority)
385 -- Renamings of the attribute Priority applied to protected
386 -- objects have been previously expanded into calls to the
387 -- Get_Ceiling run-time subprogram.
390 (Nkind (Ent) = N_Function_Call
391 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
393 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
395 -- The enclosing subprogram cannot be a protected function
398 while not (Is_Subprogram (S)
399 and then Convention (S) = Convention_Protected)
400 and then S /= Standard_Standard
405 if Ekind (S) = E_Function
406 and then Convention (S) = Convention_Protected
409 ("protected function cannot modify protected object",
413 -- Changes of the ceiling priority of the protected object
414 -- are only effective if the Ceiling_Locking policy is in
415 -- effect (AARM D.5.2 (5/2)).
417 if Locking_Policy /= 'C' then
418 Error_Msg_N ("assignment to the attribute PRIORITY has " &
420 Error_Msg_N ("\since no Locking_Policy has been " &
429 Diagnose_Non_Variable_Lhs (Lhs);
432 -- Error of assigning to limited type. We do however allow this in
433 -- certain cases where the front end generates the assignments.
435 elsif Is_Limited_Type (T1)
436 and then not Assignment_OK (Lhs)
437 and then not Assignment_OK (Original_Node (Lhs))
438 and then not Is_Value_Type (T1)
440 -- CPP constructors can only be called in declarations
442 if Is_CPP_Constructor_Call (Rhs) then
443 Error_Msg_N ("invalid use of 'C'P'P constructor", Rhs);
446 ("left hand of assignment must not be limited type", Lhs);
447 Explain_Limited_Type (T1, Lhs);
451 -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
452 -- abstract. This is only checked when the assignment Comes_From_Source,
453 -- because in some cases the expander generates such assignments (such
454 -- in the _assign operation for an abstract type).
456 elsif Is_Abstract_Type (T1) and then Comes_From_Source (N) then
458 ("target of assignment operation must not be abstract", Lhs);
461 -- Resolution may have updated the subtype, in case the left-hand
462 -- side is a private protected component. Use the correct subtype
463 -- to avoid scoping issues in the back-end.
467 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
468 -- type. For example:
472 -- type Acc is access P.T;
475 -- with Pkg; use Acc;
476 -- procedure Example is
479 -- A.all := B.all; -- ERROR
482 if Nkind (Lhs) = N_Explicit_Dereference
483 and then Ekind (T1) = E_Incomplete_Type
485 Error_Msg_N ("invalid use of incomplete type", Lhs);
490 -- Now we can complete the resolution of the right hand side
492 Set_Assignment_Type (Lhs, T1);
495 -- This is the point at which we check for an unset reference
497 Check_Unset_Reference (Rhs);
498 Check_Unprotected_Access (Lhs, Rhs);
500 -- Remaining steps are skipped if Rhs was syntactically in error
509 if not Covers (T1, T2) then
510 Wrong_Type (Rhs, Etype (Lhs));
515 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
516 -- types, use the non-limited view if available
518 if Nkind (Rhs) = N_Explicit_Dereference
519 and then Ekind (T2) = E_Incomplete_Type
520 and then Is_Tagged_Type (T2)
521 and then Present (Non_Limited_View (T2))
523 T2 := Non_Limited_View (T2);
526 Set_Assignment_Type (Rhs, T2);
528 if Total_Errors_Detected /= 0 then
538 if T1 = Any_Type or else T2 = Any_Type then
543 -- If the rhs is class-wide or dynamically tagged, then require the lhs
544 -- to be class-wide. The case where the rhs is a dynamically tagged call
545 -- to a dispatching operation with a controlling access result is
546 -- excluded from this check, since the target has an access type (and
547 -- no tag propagation occurs in that case).
549 if (Is_Class_Wide_Type (T2)
550 or else (Is_Dynamically_Tagged (Rhs)
551 and then not Is_Access_Type (T1)))
552 and then not Is_Class_Wide_Type (T1)
554 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
556 elsif Is_Class_Wide_Type (T1)
557 and then not Is_Class_Wide_Type (T2)
558 and then not Is_Tag_Indeterminate (Rhs)
559 and then not Is_Dynamically_Tagged (Rhs)
561 Error_Msg_N ("dynamically tagged expression required!", Rhs);
564 -- Propagate the tag from a class-wide target to the rhs when the rhs
565 -- is a tag-indeterminate call.
567 if Is_Tag_Indeterminate (Rhs) then
568 if Is_Class_Wide_Type (T1) then
569 Propagate_Tag (Lhs, Rhs);
571 elsif Nkind (Rhs) = N_Function_Call
572 and then Is_Entity_Name (Name (Rhs))
573 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
576 ("call to abstract function must be dispatching", Name (Rhs));
578 elsif Nkind (Rhs) = N_Qualified_Expression
579 and then Nkind (Expression (Rhs)) = N_Function_Call
580 and then Is_Entity_Name (Name (Expression (Rhs)))
582 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
585 ("call to abstract function must be dispatching",
586 Name (Expression (Rhs)));
590 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
591 -- apply an implicit conversion of the rhs to that type to force
592 -- appropriate static and run-time accessibility checks. This applies
593 -- as well to anonymous access-to-subprogram types that are component
594 -- subtypes or formal parameters.
596 if Ada_Version >= Ada_05
597 and then Is_Access_Type (T1)
599 if Is_Local_Anonymous_Access (T1)
600 or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
602 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
603 Analyze_And_Resolve (Rhs, T1);
607 -- Ada 2005 (AI-231): Assignment to not null variable
609 if Ada_Version >= Ada_05
610 and then Can_Never_Be_Null (T1)
611 and then not Assignment_OK (Lhs)
613 -- Case where we know the right hand side is null
615 if Known_Null (Rhs) then
616 Apply_Compile_Time_Constraint_Error
618 Msg => "(Ada 2005) null not allowed in null-excluding objects?",
619 Reason => CE_Null_Not_Allowed);
621 -- We still mark this as a possible modification, that's necessary
622 -- to reset Is_True_Constant, and desirable for xref purposes.
624 Note_Possible_Modification (Lhs, Sure => True);
627 -- If we know the right hand side is non-null, then we convert to the
628 -- target type, since we don't need a run time check in that case.
630 elsif not Can_Never_Be_Null (T2) then
631 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
632 Analyze_And_Resolve (Rhs, T1);
636 if Is_Scalar_Type (T1) then
637 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
639 -- For array types, verify that lengths match. If the right hand side
640 -- if a function call that has been inlined, the assignment has been
641 -- rewritten as a block, and the constraint check will be applied to the
642 -- assignment within the block.
644 elsif Is_Array_Type (T1)
646 (Nkind (Rhs) /= N_Type_Conversion
647 or else Is_Constrained (Etype (Rhs)))
649 (Nkind (Rhs) /= N_Function_Call
650 or else Nkind (N) /= N_Block_Statement)
652 -- Assignment verifies that the length of the Lsh and Rhs are equal,
653 -- but of course the indices do not have to match. If the right-hand
654 -- side is a type conversion to an unconstrained type, a length check
655 -- is performed on the expression itself during expansion. In rare
656 -- cases, the redundant length check is computed on an index type
657 -- with a different representation, triggering incorrect code in
660 Apply_Length_Check (Rhs, Etype (Lhs));
663 -- Discriminant checks are applied in the course of expansion
668 -- Note: modifications of the Lhs may only be recorded after
669 -- checks have been applied.
671 Note_Possible_Modification (Lhs, Sure => True);
673 -- ??? a real accessibility check is needed when ???
675 -- Post warning for redundant assignment or variable to itself
677 if Warn_On_Redundant_Constructs
679 -- We only warn for source constructs
681 and then Comes_From_Source (N)
683 -- Where the object is the same on both sides
685 and then Same_Object (Lhs, Original_Node (Rhs))
687 -- But exclude the case where the right side was an operation
688 -- that got rewritten (e.g. JUNK + K, where K was known to be
689 -- zero). We don't want to warn in such a case, since it is
690 -- reasonable to write such expressions especially when K is
691 -- defined symbolically in some other package.
693 and then Nkind (Original_Node (Rhs)) not in N_Op
695 if Nkind (Lhs) in N_Has_Entity then
696 Error_Msg_NE -- CODEFIX
697 ("?useless assignment of & to itself!", N, Entity (Lhs));
699 Error_Msg_N -- CODEFIX
700 ("?useless assignment of object to itself!", N);
704 -- Check for non-allowed composite assignment
706 if not Support_Composite_Assign_On_Target
707 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
708 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
710 Error_Msg_CRT ("composite assignment", N);
713 -- Check elaboration warning for left side if not in elab code
715 if not In_Subprogram_Or_Concurrent_Unit then
716 Check_Elab_Assign (Lhs);
719 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
720 -- assignment is a source assignment in the extended main source unit.
721 -- We are not interested in any reference information outside this
722 -- context, or in compiler generated assignment statements.
724 if Comes_From_Source (N)
725 and then In_Extended_Main_Source_Unit (Lhs)
727 Set_Referenced_Modified (Lhs, Out_Param => False);
730 -- Final step. If left side is an entity, then we may be able to
731 -- reset the current tracked values to new safe values. We only have
732 -- something to do if the left side is an entity name, and expansion
733 -- has not modified the node into something other than an assignment,
734 -- and of course we only capture values if it is safe to do so.
736 if Is_Entity_Name (Lhs)
737 and then Nkind (N) = N_Assignment_Statement
740 Ent : constant Entity_Id := Entity (Lhs);
743 if Safe_To_Capture_Value (N, Ent) then
745 -- If simple variable on left side, warn if this assignment
746 -- blots out another one (rendering it useless) and note
747 -- location of assignment in case no one references value.
748 -- We only do this for source assignments, otherwise we can
749 -- generate bogus warnings when an assignment is rewritten as
750 -- another assignment, and gets tied up with itself.
752 -- Note: we don't use Record_Last_Assignment here, because we
753 -- have lots of other stuff to do under control of this test.
755 if Warn_On_Modified_Unread
756 and then Is_Assignable (Ent)
757 and then Comes_From_Source (N)
758 and then In_Extended_Main_Source_Unit (Ent)
760 Warn_On_Useless_Assignment (Ent, N);
761 Set_Last_Assignment (Ent, Lhs);
764 -- If we are assigning an access type and the left side is an
765 -- entity, then make sure that the Is_Known_[Non_]Null flags
766 -- properly reflect the state of the entity after assignment.
768 if Is_Access_Type (T1) then
769 if Known_Non_Null (Rhs) then
770 Set_Is_Known_Non_Null (Ent, True);
772 elsif Known_Null (Rhs)
773 and then not Can_Never_Be_Null (Ent)
775 Set_Is_Known_Null (Ent, True);
778 Set_Is_Known_Null (Ent, False);
780 if not Can_Never_Be_Null (Ent) then
781 Set_Is_Known_Non_Null (Ent, False);
785 -- For discrete types, we may be able to set the current value
786 -- if the value is known at compile time.
788 elsif Is_Discrete_Type (T1)
789 and then Compile_Time_Known_Value (Rhs)
791 Set_Current_Value (Ent, Rhs);
793 Set_Current_Value (Ent, Empty);
796 -- If not safe to capture values, kill them
803 end Analyze_Assignment;
805 -----------------------------
806 -- Analyze_Block_Statement --
807 -----------------------------
809 procedure Analyze_Block_Statement (N : Node_Id) is
810 Decls : constant List_Id := Declarations (N);
811 Id : constant Node_Id := Identifier (N);
812 HSS : constant Node_Id := Handled_Statement_Sequence (N);
815 -- If no handled statement sequence is present, things are really
816 -- messed up, and we just return immediately (this is a defence
817 -- against previous errors).
823 -- Normal processing with HSS present
826 EH : constant List_Id := Exception_Handlers (HSS);
827 Ent : Entity_Id := Empty;
830 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
831 -- Recursively save value of this global, will be restored on exit
834 -- Initialize unblocked exit count for statements of begin block
835 -- plus one for each exception handler that is present.
837 Unblocked_Exit_Count := 1;
840 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
843 -- If a label is present analyze it and mark it as referenced
849 -- An error defense. If we have an identifier, but no entity,
850 -- then something is wrong. If we have previous errors, then
851 -- just remove the identifier and continue, otherwise raise
855 if Total_Errors_Detected /= 0 then
856 Set_Identifier (N, Empty);
862 Set_Ekind (Ent, E_Block);
863 Generate_Reference (Ent, N, ' ');
864 Generate_Definition (Ent);
866 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
867 Set_Label_Construct (Parent (Ent), N);
872 -- If no entity set, create a label entity
875 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
876 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
880 Set_Etype (Ent, Standard_Void_Type);
881 Set_Block_Node (Ent, Identifier (N));
884 if Present (Decls) then
885 Analyze_Declarations (Decls);
887 Inspect_Deferred_Constant_Completion (Decls);
891 Process_End_Label (HSS, 'e', Ent);
893 -- If exception handlers are present, then we indicate that
894 -- enclosing scopes contain a block with handlers. We only
895 -- need to mark non-generic scopes.
900 Set_Has_Nested_Block_With_Handler (S);
901 exit when Is_Overloadable (S)
902 or else Ekind (S) = E_Package
903 or else Is_Generic_Unit (S);
908 Check_References (Ent);
909 Warn_On_Useless_Assignments (Ent);
912 if Unblocked_Exit_Count = 0 then
913 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
914 Check_Unreachable_Code (N);
916 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
919 end Analyze_Block_Statement;
921 ----------------------------
922 -- Analyze_Case_Statement --
923 ----------------------------
925 procedure Analyze_Case_Statement (N : Node_Id) is
927 Exp_Type : Entity_Id;
928 Exp_Btype : Entity_Id;
931 Others_Present : Boolean;
933 pragma Warnings (Off, Last_Choice);
934 pragma Warnings (Off, Dont_Care);
935 -- Don't care about assigned values
937 Statements_Analyzed : Boolean := False;
938 -- Set True if at least some statement sequences get analyzed.
939 -- If False on exit, means we had a serious error that prevented
940 -- full analysis of the case statement, and as a result it is not
941 -- a good idea to output warning messages about unreachable code.
943 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
944 -- Recursively save value of this global, will be restored on exit
946 procedure Non_Static_Choice_Error (Choice : Node_Id);
947 -- Error routine invoked by the generic instantiation below when
948 -- the case statement has a non static choice.
950 procedure Process_Statements (Alternative : Node_Id);
951 -- Analyzes all the statements associated with a case alternative.
952 -- Needed by the generic instantiation below.
954 package Case_Choices_Processing is new
955 Generic_Choices_Processing
956 (Get_Alternatives => Alternatives,
957 Get_Choices => Discrete_Choices,
958 Process_Empty_Choice => No_OP,
959 Process_Non_Static_Choice => Non_Static_Choice_Error,
960 Process_Associated_Node => Process_Statements);
961 use Case_Choices_Processing;
962 -- Instantiation of the generic choice processing package
964 -----------------------------
965 -- Non_Static_Choice_Error --
966 -----------------------------
968 procedure Non_Static_Choice_Error (Choice : Node_Id) is
971 ("choice given in case statement is not static!", Choice);
972 end Non_Static_Choice_Error;
974 ------------------------
975 -- Process_Statements --
976 ------------------------
978 procedure Process_Statements (Alternative : Node_Id) is
979 Choices : constant List_Id := Discrete_Choices (Alternative);
983 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
984 Statements_Analyzed := True;
986 -- An interesting optimization. If the case statement expression
987 -- is a simple entity, then we can set the current value within
988 -- an alternative if the alternative has one possible value.
992 -- when 2 | 3 => beta
993 -- when others => gamma
995 -- Here we know that N is initially 1 within alpha, but for beta
996 -- and gamma, we do not know anything more about the initial value.
998 if Is_Entity_Name (Exp) then
1001 if Ekind_In (Ent, E_Variable,
1005 if List_Length (Choices) = 1
1006 and then Nkind (First (Choices)) in N_Subexpr
1007 and then Compile_Time_Known_Value (First (Choices))
1009 Set_Current_Value (Entity (Exp), First (Choices));
1012 Analyze_Statements (Statements (Alternative));
1014 -- After analyzing the case, set the current value to empty
1015 -- since we won't know what it is for the next alternative
1016 -- (unless reset by this same circuit), or after the case.
1018 Set_Current_Value (Entity (Exp), Empty);
1023 -- Case where expression is not an entity name of a variable
1025 Analyze_Statements (Statements (Alternative));
1026 end Process_Statements;
1028 -- Table to record choices. Put after subprograms since we make
1029 -- a call to Number_Of_Choices to get the right number of entries.
1031 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
1032 pragma Warnings (Off, Case_Table);
1034 -- Start of processing for Analyze_Case_Statement
1037 Unblocked_Exit_Count := 0;
1038 Exp := Expression (N);
1041 -- The expression must be of any discrete type. In rare cases, the
1042 -- expander constructs a case statement whose expression has a private
1043 -- type whose full view is discrete. This can happen when generating
1044 -- a stream operation for a variant type after the type is frozen,
1045 -- when the partial of view of the type of the discriminant is private.
1046 -- In that case, use the full view to analyze case alternatives.
1048 if not Is_Overloaded (Exp)
1049 and then not Comes_From_Source (N)
1050 and then Is_Private_Type (Etype (Exp))
1051 and then Present (Full_View (Etype (Exp)))
1052 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1054 Resolve (Exp, Etype (Exp));
1055 Exp_Type := Full_View (Etype (Exp));
1058 Analyze_And_Resolve (Exp, Any_Discrete);
1059 Exp_Type := Etype (Exp);
1062 Check_Unset_Reference (Exp);
1063 Exp_Btype := Base_Type (Exp_Type);
1065 -- The expression must be of a discrete type which must be determinable
1066 -- independently of the context in which the expression occurs, but
1067 -- using the fact that the expression must be of a discrete type.
1068 -- Moreover, the type this expression must not be a character literal
1069 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1071 -- If error already reported by Resolve, nothing more to do
1073 if Exp_Btype = Any_Discrete
1074 or else Exp_Btype = Any_Type
1078 elsif Exp_Btype = Any_Character then
1080 ("character literal as case expression is ambiguous", Exp);
1083 elsif Ada_Version = Ada_83
1084 and then (Is_Generic_Type (Exp_Btype)
1085 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1088 ("(Ada 83) case expression cannot be of a generic type", Exp);
1092 -- If the case expression is a formal object of mode in out, then
1093 -- treat it as having a nonstatic subtype by forcing use of the base
1094 -- type (which has to get passed to Check_Case_Choices below). Also
1095 -- use base type when the case expression is parenthesized.
1097 if Paren_Count (Exp) > 0
1098 or else (Is_Entity_Name (Exp)
1099 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1101 Exp_Type := Exp_Btype;
1104 -- Call instantiated Analyze_Choices which does the rest of the work
1107 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
1109 if Exp_Type = Universal_Integer and then not Others_Present then
1110 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1113 -- If all our exits were blocked by unconditional transfers of control,
1114 -- then the entire CASE statement acts as an unconditional transfer of
1115 -- control, so treat it like one, and check unreachable code. Skip this
1116 -- test if we had serious errors preventing any statement analysis.
1118 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1119 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1120 Check_Unreachable_Code (N);
1122 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1125 if not Expander_Active
1126 and then Compile_Time_Known_Value (Expression (N))
1127 and then Serious_Errors_Detected = 0
1130 Chosen : constant Node_Id := Find_Static_Alternative (N);
1134 Alt := First (Alternatives (N));
1135 while Present (Alt) loop
1136 if Alt /= Chosen then
1137 Remove_Warning_Messages (Statements (Alt));
1144 end Analyze_Case_Statement;
1146 ----------------------------
1147 -- Analyze_Exit_Statement --
1148 ----------------------------
1150 -- If the exit includes a name, it must be the name of a currently open
1151 -- loop. Otherwise there must be an innermost open loop on the stack,
1152 -- to which the statement implicitly refers.
1154 procedure Analyze_Exit_Statement (N : Node_Id) is
1155 Target : constant Node_Id := Name (N);
1156 Cond : constant Node_Id := Condition (N);
1157 Scope_Id : Entity_Id;
1163 Check_Unreachable_Code (N);
1166 if Present (Target) then
1168 U_Name := Entity (Target);
1170 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1171 Error_Msg_N ("invalid loop name in exit statement", N);
1174 Set_Has_Exit (U_Name);
1181 for J in reverse 0 .. Scope_Stack.Last loop
1182 Scope_Id := Scope_Stack.Table (J).Entity;
1183 Kind := Ekind (Scope_Id);
1186 and then (No (Target) or else Scope_Id = U_Name) then
1187 Set_Has_Exit (Scope_Id);
1190 elsif Kind = E_Block
1191 or else Kind = E_Loop
1192 or else Kind = E_Return_Statement
1198 ("cannot exit from program unit or accept statement", N);
1203 -- Verify that if present the condition is a Boolean expression
1205 if Present (Cond) then
1206 Analyze_And_Resolve (Cond, Any_Boolean);
1207 Check_Unset_Reference (Cond);
1210 -- Chain exit statement to associated loop entity
1212 Set_Next_Exit_Statement (N, First_Exit_Statement (Scope_Id));
1213 Set_First_Exit_Statement (Scope_Id, N);
1215 -- Since the exit may take us out of a loop, any previous assignment
1216 -- statement is not useless, so clear last assignment indications. It
1217 -- is OK to keep other current values, since if the exit statement
1218 -- does not exit, then the current values are still valid.
1220 Kill_Current_Values (Last_Assignment_Only => True);
1221 end Analyze_Exit_Statement;
1223 ----------------------------
1224 -- Analyze_Goto_Statement --
1225 ----------------------------
1227 procedure Analyze_Goto_Statement (N : Node_Id) is
1228 Label : constant Node_Id := Name (N);
1229 Scope_Id : Entity_Id;
1230 Label_Scope : Entity_Id;
1231 Label_Ent : Entity_Id;
1234 Check_Unreachable_Code (N);
1235 Kill_Current_Values (Last_Assignment_Only => True);
1238 Label_Ent := Entity (Label);
1240 -- Ignore previous error
1242 if Label_Ent = Any_Id then
1245 -- We just have a label as the target of a goto
1247 elsif Ekind (Label_Ent) /= E_Label then
1248 Error_Msg_N ("target of goto statement must be a label", Label);
1251 -- Check that the target of the goto is reachable according to Ada
1252 -- scoping rules. Note: the special gotos we generate for optimizing
1253 -- local handling of exceptions would violate these rules, but we mark
1254 -- such gotos as analyzed when built, so this code is never entered.
1256 elsif not Reachable (Label_Ent) then
1257 Error_Msg_N ("target of goto statement is not reachable", Label);
1261 -- Here if goto passes initial validity checks
1263 Label_Scope := Enclosing_Scope (Label_Ent);
1265 for J in reverse 0 .. Scope_Stack.Last loop
1266 Scope_Id := Scope_Stack.Table (J).Entity;
1268 if Label_Scope = Scope_Id
1269 or else (Ekind (Scope_Id) /= E_Block
1270 and then Ekind (Scope_Id) /= E_Loop
1271 and then Ekind (Scope_Id) /= E_Return_Statement)
1273 if Scope_Id /= Label_Scope then
1275 ("cannot exit from program unit or accept statement", N);
1282 raise Program_Error;
1283 end Analyze_Goto_Statement;
1285 --------------------------
1286 -- Analyze_If_Statement --
1287 --------------------------
1289 -- A special complication arises in the analysis of if statements
1291 -- The expander has circuitry to completely delete code that it
1292 -- can tell will not be executed (as a result of compile time known
1293 -- conditions). In the analyzer, we ensure that code that will be
1294 -- deleted in this manner is analyzed but not expanded. This is
1295 -- obviously more efficient, but more significantly, difficulties
1296 -- arise if code is expanded and then eliminated (e.g. exception
1297 -- table entries disappear). Similarly, itypes generated in deleted
1298 -- code must be frozen from start, because the nodes on which they
1299 -- depend will not be available at the freeze point.
1301 procedure Analyze_If_Statement (N : Node_Id) is
1304 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1305 -- Recursively save value of this global, will be restored on exit
1307 Save_In_Deleted_Code : Boolean;
1309 Del : Boolean := False;
1310 -- This flag gets set True if a True condition has been found,
1311 -- which means that remaining ELSE/ELSIF parts are deleted.
1313 procedure Analyze_Cond_Then (Cnode : Node_Id);
1314 -- This is applied to either the N_If_Statement node itself or
1315 -- to an N_Elsif_Part node. It deals with analyzing the condition
1316 -- and the THEN statements associated with it.
1318 -----------------------
1319 -- Analyze_Cond_Then --
1320 -----------------------
1322 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1323 Cond : constant Node_Id := Condition (Cnode);
1324 Tstm : constant List_Id := Then_Statements (Cnode);
1327 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1328 Analyze_And_Resolve (Cond, Any_Boolean);
1329 Check_Unset_Reference (Cond);
1330 Set_Current_Value_Condition (Cnode);
1332 -- If already deleting, then just analyze then statements
1335 Analyze_Statements (Tstm);
1337 -- Compile time known value, not deleting yet
1339 elsif Compile_Time_Known_Value (Cond) then
1340 Save_In_Deleted_Code := In_Deleted_Code;
1342 -- If condition is True, then analyze the THEN statements
1343 -- and set no expansion for ELSE and ELSIF parts.
1345 if Is_True (Expr_Value (Cond)) then
1346 Analyze_Statements (Tstm);
1348 Expander_Mode_Save_And_Set (False);
1349 In_Deleted_Code := True;
1351 -- If condition is False, analyze THEN with expansion off
1353 else -- Is_False (Expr_Value (Cond))
1354 Expander_Mode_Save_And_Set (False);
1355 In_Deleted_Code := True;
1356 Analyze_Statements (Tstm);
1357 Expander_Mode_Restore;
1358 In_Deleted_Code := Save_In_Deleted_Code;
1361 -- Not known at compile time, not deleting, normal analysis
1364 Analyze_Statements (Tstm);
1366 end Analyze_Cond_Then;
1368 -- Start of Analyze_If_Statement
1371 -- Initialize exit count for else statements. If there is no else
1372 -- part, this count will stay non-zero reflecting the fact that the
1373 -- uncovered else case is an unblocked exit.
1375 Unblocked_Exit_Count := 1;
1376 Analyze_Cond_Then (N);
1378 -- Now to analyze the elsif parts if any are present
1380 if Present (Elsif_Parts (N)) then
1381 E := First (Elsif_Parts (N));
1382 while Present (E) loop
1383 Analyze_Cond_Then (E);
1388 if Present (Else_Statements (N)) then
1389 Analyze_Statements (Else_Statements (N));
1392 -- If all our exits were blocked by unconditional transfers of control,
1393 -- then the entire IF statement acts as an unconditional transfer of
1394 -- control, so treat it like one, and check unreachable code.
1396 if Unblocked_Exit_Count = 0 then
1397 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1398 Check_Unreachable_Code (N);
1400 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1404 Expander_Mode_Restore;
1405 In_Deleted_Code := Save_In_Deleted_Code;
1408 if not Expander_Active
1409 and then Compile_Time_Known_Value (Condition (N))
1410 and then Serious_Errors_Detected = 0
1412 if Is_True (Expr_Value (Condition (N))) then
1413 Remove_Warning_Messages (Else_Statements (N));
1415 if Present (Elsif_Parts (N)) then
1416 E := First (Elsif_Parts (N));
1417 while Present (E) loop
1418 Remove_Warning_Messages (Then_Statements (E));
1424 Remove_Warning_Messages (Then_Statements (N));
1427 end Analyze_If_Statement;
1429 ----------------------------------------
1430 -- Analyze_Implicit_Label_Declaration --
1431 ----------------------------------------
1433 -- An implicit label declaration is generated in the innermost
1434 -- enclosing declarative part. This is done for labels as well as
1435 -- block and loop names.
1437 -- Note: any changes in this routine may need to be reflected in
1438 -- Analyze_Label_Entity.
1440 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1441 Id : constant Node_Id := Defining_Identifier (N);
1444 Set_Ekind (Id, E_Label);
1445 Set_Etype (Id, Standard_Void_Type);
1446 Set_Enclosing_Scope (Id, Current_Scope);
1447 end Analyze_Implicit_Label_Declaration;
1449 ------------------------------
1450 -- Analyze_Iteration_Scheme --
1451 ------------------------------
1453 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1455 procedure Process_Bounds (R : Node_Id);
1456 -- If the iteration is given by a range, create temporaries and
1457 -- assignment statements block to capture the bounds and perform
1458 -- required finalization actions in case a bound includes a function
1459 -- call that uses the temporary stack. We first pre-analyze a copy of
1460 -- the range in order to determine the expected type, and analyze and
1461 -- resolve the original bounds.
1463 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1464 -- If the bounds are given by a 'Range reference on a function call
1465 -- that returns a controlled array, introduce an explicit declaration
1466 -- to capture the bounds, so that the function result can be finalized
1467 -- in timely fashion.
1469 --------------------
1470 -- Process_Bounds --
1471 --------------------
1473 procedure Process_Bounds (R : Node_Id) is
1474 Loc : constant Source_Ptr := Sloc (N);
1475 R_Copy : constant Node_Id := New_Copy_Tree (R);
1476 Lo : constant Node_Id := Low_Bound (R);
1477 Hi : constant Node_Id := High_Bound (R);
1478 New_Lo_Bound : Node_Id := Empty;
1479 New_Hi_Bound : Node_Id := Empty;
1481 Save_Analysis : Boolean;
1484 (Original_Bound : Node_Id;
1485 Analyzed_Bound : Node_Id) return Node_Id;
1486 -- Capture value of bound and return captured value
1493 (Original_Bound : Node_Id;
1494 Analyzed_Bound : Node_Id) return Node_Id
1501 -- If the bound is a constant or an object, no need for a separate
1502 -- declaration. If the bound is the result of previous expansion
1503 -- it is already analyzed and should not be modified. Note that
1504 -- the Bound will be resolved later, if needed, as part of the
1505 -- call to Make_Index (literal bounds may need to be resolved to
1508 if Analyzed (Original_Bound) then
1509 return Original_Bound;
1511 elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
1512 N_Character_Literal)
1513 or else Is_Entity_Name (Analyzed_Bound)
1515 Analyze_And_Resolve (Original_Bound, Typ);
1516 return Original_Bound;
1519 -- Here we need to capture the value
1521 Analyze_And_Resolve (Original_Bound, Typ);
1523 Id := Make_Temporary (Loc, 'S', Original_Bound);
1525 -- Normally, the best approach is simply to generate a constant
1526 -- declaration that captures the bound. However, there is a nasty
1527 -- case where this is wrong. If the bound is complex, and has a
1528 -- possible use of the secondary stack, we need to generate a
1529 -- separate assignment statement to ensure the creation of a block
1530 -- which will release the secondary stack.
1532 -- We prefer the constant declaration, since it leaves us with a
1533 -- proper trace of the value, useful in optimizations that get rid
1534 -- of junk range checks.
1536 -- Probably we want something like the Side_Effect_Free routine
1537 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1538 -- and 'First applied to an entity, since these are the important
1539 -- cases for range check optimizations.
1541 if Nkind (Original_Bound) = N_Attribute_Reference
1542 and then (Attribute_Name (Original_Bound) = Name_First
1544 Attribute_Name (Original_Bound) = Name_Last)
1545 and then Is_Entity_Name (Prefix (Original_Bound))
1548 Make_Object_Declaration (Loc,
1549 Defining_Identifier => Id,
1550 Constant_Present => True,
1551 Object_Definition => New_Occurrence_Of (Typ, Loc),
1552 Expression => Relocate_Node (Original_Bound));
1554 Insert_Before (Parent (N), Decl);
1556 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1557 return Expression (Decl);
1560 -- Here we make a declaration with a separate assignment statement
1563 Make_Object_Declaration (Loc,
1564 Defining_Identifier => Id,
1565 Object_Definition => New_Occurrence_Of (Typ, Loc));
1567 Insert_Before (Parent (N), Decl);
1571 Make_Assignment_Statement (Loc,
1572 Name => New_Occurrence_Of (Id, Loc),
1573 Expression => Relocate_Node (Original_Bound));
1575 -- If the relocated node is a function call then check if some
1576 -- SCIL node references it and needs readjustment.
1579 and then Nkind (Original_Bound) = N_Function_Call
1581 Adjust_SCIL_Node (Original_Bound, Expression (Assign));
1584 Insert_Before (Parent (N), Assign);
1587 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1589 if Nkind (Assign) = N_Assignment_Statement then
1590 return Expression (Assign);
1592 return Original_Bound;
1596 -- Start of processing for Process_Bounds
1599 -- Determine expected type of range by analyzing separate copy
1600 -- Do the analysis and resolution of the copy of the bounds with
1601 -- expansion disabled, to prevent the generation of finalization
1602 -- actions on each bound. This prevents memory leaks when the
1603 -- bounds contain calls to functions returning controlled arrays.
1605 Set_Parent (R_Copy, Parent (R));
1606 Save_Analysis := Full_Analysis;
1607 Full_Analysis := False;
1608 Expander_Mode_Save_And_Set (False);
1612 if Is_Overloaded (R_Copy) then
1614 -- Apply preference rules for range of predefined integer types,
1615 -- or diagnose true ambiguity.
1620 Found : Entity_Id := Empty;
1623 Get_First_Interp (R_Copy, I, It);
1624 while Present (It.Typ) loop
1625 if Is_Discrete_Type (It.Typ) then
1629 if Scope (Found) = Standard_Standard then
1632 elsif Scope (It.Typ) = Standard_Standard then
1636 -- Both of them are user-defined
1639 ("ambiguous bounds in range of iteration",
1641 Error_Msg_N ("\possible interpretations:", R_Copy);
1642 Error_Msg_NE ("\\} ", R_Copy, Found);
1643 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1649 Get_Next_Interp (I, It);
1655 Expander_Mode_Restore;
1656 Full_Analysis := Save_Analysis;
1658 Typ := Etype (R_Copy);
1660 -- If the type of the discrete range is Universal_Integer, then
1661 -- the bound's type must be resolved to Integer, and any object
1662 -- used to hold the bound must also have type Integer, unless the
1663 -- literal bounds are constant-folded expressions that carry a user-
1666 if Typ = Universal_Integer then
1667 if Nkind (Lo) = N_Integer_Literal
1668 and then Present (Etype (Lo))
1669 and then Scope (Etype (Lo)) /= Standard_Standard
1673 elsif Nkind (Hi) = N_Integer_Literal
1674 and then Present (Etype (Hi))
1675 and then Scope (Etype (Hi)) /= Standard_Standard
1680 Typ := Standard_Integer;
1686 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1687 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1689 -- Propagate staticness to loop range itself, in case the
1690 -- corresponding subtype is static.
1692 if New_Lo_Bound /= Lo
1693 and then Is_Static_Expression (New_Lo_Bound)
1695 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1698 if New_Hi_Bound /= Hi
1699 and then Is_Static_Expression (New_Hi_Bound)
1701 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1705 --------------------------------------
1706 -- Check_Controlled_Array_Attribute --
1707 --------------------------------------
1709 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1711 if Nkind (DS) = N_Attribute_Reference
1712 and then Is_Entity_Name (Prefix (DS))
1713 and then Ekind (Entity (Prefix (DS))) = E_Function
1714 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1717 Component_Type (Etype (Entity (Prefix (DS)))))
1718 and then Expander_Active
1721 Loc : constant Source_Ptr := Sloc (N);
1722 Arr : constant Entity_Id := Etype (Entity (Prefix (DS)));
1723 Indx : constant Entity_Id :=
1724 Base_Type (Etype (First_Index (Arr)));
1725 Subt : constant Entity_Id := Make_Temporary (Loc, 'S');
1730 Make_Subtype_Declaration (Loc,
1731 Defining_Identifier => Subt,
1732 Subtype_Indication =>
1733 Make_Subtype_Indication (Loc,
1734 Subtype_Mark => New_Reference_To (Indx, Loc),
1736 Make_Range_Constraint (Loc,
1737 Relocate_Node (DS))));
1738 Insert_Before (Parent (N), Decl);
1742 Make_Attribute_Reference (Loc,
1743 Prefix => New_Reference_To (Subt, Loc),
1744 Attribute_Name => Attribute_Name (DS)));
1748 end Check_Controlled_Array_Attribute;
1750 -- Start of processing for Analyze_Iteration_Scheme
1753 -- For an infinite loop, there is no iteration scheme
1760 Cond : constant Node_Id := Condition (N);
1763 -- For WHILE loop, verify that the condition is a Boolean
1764 -- expression and resolve and check it.
1766 if Present (Cond) then
1767 Analyze_And_Resolve (Cond, Any_Boolean);
1768 Check_Unset_Reference (Cond);
1769 Set_Current_Value_Condition (N);
1772 -- Else we have a FOR loop
1776 LP : constant Node_Id := Loop_Parameter_Specification (N);
1777 Id : constant Entity_Id := Defining_Identifier (LP);
1778 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1783 -- We always consider the loop variable to be referenced,
1784 -- since the loop may be used just for counting purposes.
1786 Generate_Reference (Id, N, ' ');
1788 -- Check for case of loop variable hiding a local
1789 -- variable (used later on to give a nice warning
1790 -- if the hidden variable is never assigned).
1793 H : constant Entity_Id := Homonym (Id);
1796 and then Enclosing_Dynamic_Scope (H) =
1797 Enclosing_Dynamic_Scope (Id)
1798 and then Ekind (H) = E_Variable
1799 and then Is_Discrete_Type (Etype (H))
1801 Set_Hiding_Loop_Variable (H, Id);
1805 -- Now analyze the subtype definition. If it is
1806 -- a range, create temporaries for bounds.
1808 if Nkind (DS) = N_Range
1809 and then Expander_Active
1811 Process_Bounds (DS);
1820 -- The subtype indication may denote the completion
1821 -- of an incomplete type declaration.
1823 if Is_Entity_Name (DS)
1824 and then Present (Entity (DS))
1825 and then Is_Type (Entity (DS))
1826 and then Ekind (Entity (DS)) = E_Incomplete_Type
1828 Set_Entity (DS, Get_Full_View (Entity (DS)));
1829 Set_Etype (DS, Entity (DS));
1832 if not Is_Discrete_Type (Etype (DS)) then
1833 Wrong_Type (DS, Any_Discrete);
1834 Set_Etype (DS, Any_Type);
1837 Check_Controlled_Array_Attribute (DS);
1839 Make_Index (DS, LP);
1841 Set_Ekind (Id, E_Loop_Parameter);
1842 Set_Etype (Id, Etype (DS));
1844 -- Treat a range as an implicit reference to the type, to
1845 -- inhibit spurious warnings.
1847 Generate_Reference (Base_Type (Etype (DS)), N, ' ');
1848 Set_Is_Known_Valid (Id, True);
1850 -- The loop is not a declarative part, so the only entity
1851 -- declared "within" must be frozen explicitly.
1854 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1856 if Is_Non_Empty_List (Flist) then
1857 Insert_Actions (N, Flist);
1861 -- Check for null or possibly null range and issue warning.
1862 -- We suppress such messages in generic templates and
1863 -- instances, because in practice they tend to be dubious
1866 if Nkind (DS) = N_Range
1867 and then Comes_From_Source (N)
1870 L : constant Node_Id := Low_Bound (DS);
1871 H : constant Node_Id := High_Bound (DS);
1874 -- If range of loop is null, issue warning
1876 if Compile_Time_Compare
1877 (L, H, Assume_Valid => True) = GT
1879 -- Suppress the warning if inside a generic
1880 -- template or instance, since in practice
1881 -- they tend to be dubious in these cases since
1882 -- they can result from intended parametrization.
1884 if not Inside_A_Generic
1885 and then not In_Instance
1887 -- Specialize msg if invalid values could make
1888 -- the loop non-null after all.
1890 if Compile_Time_Compare
1891 (L, H, Assume_Valid => False) = GT
1894 ("?loop range is null, "
1895 & "loop will not execute",
1898 -- Since we know the range of the loop is
1899 -- null, set the appropriate flag to remove
1900 -- the loop entirely during expansion.
1902 Set_Is_Null_Loop (Parent (N));
1904 -- Here is where the loop could execute because
1905 -- of invalid values, so issue appropriate
1906 -- message and in this case we do not set the
1907 -- Is_Null_Loop flag since the loop may execute.
1911 ("?loop range may be null, "
1912 & "loop may not execute",
1915 ("?can only execute if invalid values "
1921 -- In either case, suppress warnings in the body of
1922 -- the loop, since it is likely that these warnings
1923 -- will be inappropriate if the loop never actually
1924 -- executes, which is unlikely.
1926 Set_Suppress_Loop_Warnings (Parent (N));
1928 -- The other case for a warning is a reverse loop
1929 -- where the upper bound is the integer literal
1930 -- zero or one, and the lower bound can be positive.
1932 -- For example, we have
1934 -- for J in reverse N .. 1 loop
1936 -- In practice, this is very likely to be a case
1937 -- of reversing the bounds incorrectly in the range.
1939 elsif Reverse_Present (LP)
1940 and then Nkind (Original_Node (H)) =
1942 and then (Intval (Original_Node (H)) = Uint_0
1944 Intval (Original_Node (H)) = Uint_1)
1946 Error_Msg_N ("?loop range may be null", DS);
1947 Error_Msg_N ("\?bounds may be wrong way round", DS);
1955 end Analyze_Iteration_Scheme;
1961 -- Note: the semantic work required for analyzing labels (setting them as
1962 -- reachable) was done in a prepass through the statements in the block,
1963 -- so that forward gotos would be properly handled. See Analyze_Statements
1964 -- for further details. The only processing required here is to deal with
1965 -- optimizations that depend on an assumption of sequential control flow,
1966 -- since of course the occurrence of a label breaks this assumption.
1968 procedure Analyze_Label (N : Node_Id) is
1969 pragma Warnings (Off, N);
1971 Kill_Current_Values;
1974 --------------------------
1975 -- Analyze_Label_Entity --
1976 --------------------------
1978 procedure Analyze_Label_Entity (E : Entity_Id) is
1980 Set_Ekind (E, E_Label);
1981 Set_Etype (E, Standard_Void_Type);
1982 Set_Enclosing_Scope (E, Current_Scope);
1983 Set_Reachable (E, True);
1984 end Analyze_Label_Entity;
1986 ----------------------------
1987 -- Analyze_Loop_Statement --
1988 ----------------------------
1990 procedure Analyze_Loop_Statement (N : Node_Id) is
1991 Loop_Statement : constant Node_Id := N;
1993 Id : constant Node_Id := Identifier (Loop_Statement);
1994 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
1998 if Present (Id) then
2000 -- Make name visible, e.g. for use in exit statements. Loop
2001 -- labels are always considered to be referenced.
2006 -- Guard against serious error (typically, a scope mismatch when
2007 -- semantic analysis is requested) by creating loop entity to
2008 -- continue analysis.
2011 if Total_Errors_Detected /= 0 then
2014 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2016 raise Program_Error;
2020 Generate_Reference (Ent, Loop_Statement, ' ');
2021 Generate_Definition (Ent);
2023 -- If we found a label, mark its type. If not, ignore it, since it
2024 -- means we have a conflicting declaration, which would already
2025 -- have been diagnosed at declaration time. Set Label_Construct
2026 -- of the implicit label declaration, which is not created by the
2027 -- parser for generic units.
2029 if Ekind (Ent) = E_Label then
2030 Set_Ekind (Ent, E_Loop);
2032 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
2033 Set_Label_Construct (Parent (Ent), Loop_Statement);
2038 -- Case of no identifier present
2043 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2044 Set_Etype (Ent, Standard_Void_Type);
2045 Set_Parent (Ent, Loop_Statement);
2048 -- Kill current values on entry to loop, since statements in body of
2049 -- loop may have been executed before the loop is entered. Similarly we
2050 -- kill values after the loop, since we do not know that the body of the
2051 -- loop was executed.
2053 Kill_Current_Values;
2055 Analyze_Iteration_Scheme (Iter);
2056 Analyze_Statements (Statements (Loop_Statement));
2057 Process_End_Label (Loop_Statement, 'e', Ent);
2059 Kill_Current_Values;
2061 -- Check for infinite loop. Skip check for generated code, since it
2062 -- justs waste time and makes debugging the routine called harder.
2064 -- Note that we have to wait till the body of the loop is fully analyzed
2065 -- before making this call, since Check_Infinite_Loop_Warning relies on
2066 -- being able to use semantic visibility information to find references.
2068 if Comes_From_Source (N) then
2069 Check_Infinite_Loop_Warning (N);
2072 -- Code after loop is unreachable if the loop has no WHILE or FOR
2073 -- and contains no EXIT statements within the body of the loop.
2075 if No (Iter) and then not Has_Exit (Ent) then
2076 Check_Unreachable_Code (N);
2078 end Analyze_Loop_Statement;
2080 ----------------------------
2081 -- Analyze_Null_Statement --
2082 ----------------------------
2084 -- Note: the semantics of the null statement is implemented by a single
2085 -- null statement, too bad everything isn't as simple as this!
2087 procedure Analyze_Null_Statement (N : Node_Id) is
2088 pragma Warnings (Off, N);
2091 end Analyze_Null_Statement;
2093 ------------------------
2094 -- Analyze_Statements --
2095 ------------------------
2097 procedure Analyze_Statements (L : List_Id) is
2102 -- The labels declared in the statement list are reachable from
2103 -- statements in the list. We do this as a prepass so that any
2104 -- goto statement will be properly flagged if its target is not
2105 -- reachable. This is not required, but is nice behavior!
2108 while Present (S) loop
2109 if Nkind (S) = N_Label then
2110 Analyze (Identifier (S));
2111 Lab := Entity (Identifier (S));
2113 -- If we found a label mark it as reachable
2115 if Ekind (Lab) = E_Label then
2116 Generate_Definition (Lab);
2117 Set_Reachable (Lab);
2119 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
2120 Set_Label_Construct (Parent (Lab), S);
2123 -- If we failed to find a label, it means the implicit declaration
2124 -- of the label was hidden. A for-loop parameter can do this to
2125 -- a label with the same name inside the loop, since the implicit
2126 -- label declaration is in the innermost enclosing body or block
2130 Error_Msg_Sloc := Sloc (Lab);
2132 ("implicit label declaration for & is hidden#",
2140 -- Perform semantic analysis on all statements
2142 Conditional_Statements_Begin;
2145 while Present (S) loop
2150 Conditional_Statements_End;
2152 -- Make labels unreachable. Visibility is not sufficient, because
2153 -- labels in one if-branch for example are not reachable from the
2154 -- other branch, even though their declarations are in the enclosing
2155 -- declarative part.
2158 while Present (S) loop
2159 if Nkind (S) = N_Label then
2160 Set_Reachable (Entity (Identifier (S)), False);
2165 end Analyze_Statements;
2167 ----------------------------
2168 -- Check_Unreachable_Code --
2169 ----------------------------
2171 procedure Check_Unreachable_Code (N : Node_Id) is
2172 Error_Loc : Source_Ptr;
2176 if Is_List_Member (N)
2177 and then Comes_From_Source (N)
2183 Nxt := Original_Node (Next (N));
2185 -- If a label follows us, then we never have dead code, since
2186 -- someone could branch to the label, so we just ignore it.
2188 if Nkind (Nxt) = N_Label then
2191 -- Otherwise see if we have a real statement following us
2194 and then Comes_From_Source (Nxt)
2195 and then Is_Statement (Nxt)
2197 -- Special very annoying exception. If we have a return that
2198 -- follows a raise, then we allow it without a warning, since
2199 -- the Ada RM annoyingly requires a useless return here!
2201 if Nkind (Original_Node (N)) /= N_Raise_Statement
2202 or else Nkind (Nxt) /= N_Simple_Return_Statement
2204 -- The rather strange shenanigans with the warning message
2205 -- here reflects the fact that Kill_Dead_Code is very good
2206 -- at removing warnings in deleted code, and this is one
2207 -- warning we would prefer NOT to have removed.
2209 Error_Loc := Sloc (Nxt);
2211 -- If we have unreachable code, analyze and remove the
2212 -- unreachable code, since it is useless and we don't
2213 -- want to generate junk warnings.
2215 -- We skip this step if we are not in code generation mode.
2216 -- This is the one case where we remove dead code in the
2217 -- semantics as opposed to the expander, and we do not want
2218 -- to remove code if we are not in code generation mode,
2219 -- since this messes up the ASIS trees.
2221 -- Note that one might react by moving the whole circuit to
2222 -- exp_ch5, but then we lose the warning in -gnatc mode.
2224 if Operating_Mode = Generate_Code then
2228 -- Quit deleting when we have nothing more to delete
2229 -- or if we hit a label (since someone could transfer
2230 -- control to a label, so we should not delete it).
2232 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2234 -- Statement/declaration is to be deleted
2238 Kill_Dead_Code (Nxt);
2242 -- Now issue the warning
2244 Error_Msg ("?unreachable code!", Error_Loc);
2247 -- If the unconditional transfer of control instruction is
2248 -- the last statement of a sequence, then see if our parent
2249 -- is one of the constructs for which we count unblocked exits,
2250 -- and if so, adjust the count.
2255 -- Statements in THEN part or ELSE part of IF statement
2257 if Nkind (P) = N_If_Statement then
2260 -- Statements in ELSIF part of an IF statement
2262 elsif Nkind (P) = N_Elsif_Part then
2264 pragma Assert (Nkind (P) = N_If_Statement);
2266 -- Statements in CASE statement alternative
2268 elsif Nkind (P) = N_Case_Statement_Alternative then
2270 pragma Assert (Nkind (P) = N_Case_Statement);
2272 -- Statements in body of block
2274 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2275 and then Nkind (Parent (P)) = N_Block_Statement
2279 -- Statements in exception handler in a block
2281 elsif Nkind (P) = N_Exception_Handler
2282 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2283 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2287 -- None of these cases, so return
2293 -- This was one of the cases we are looking for (i.e. the
2294 -- parent construct was IF, CASE or block) so decrement count.
2296 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2300 end Check_Unreachable_Code;