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_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 -- Analyze_Assignment --
75 ------------------------
77 procedure Analyze_Assignment (N : Node_Id) is
78 Lhs : constant Node_Id := Name (N);
79 Rhs : constant Node_Id := Expression (N);
84 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
85 -- N is the node for the left hand side of an assignment, and it is not
86 -- a variable. This routine issues an appropriate diagnostic.
89 -- This is called to kill current value settings of a simple variable
90 -- on the left hand side. We call it if we find any error in analyzing
91 -- the assignment, and at the end of processing before setting any new
92 -- current values in place.
94 procedure Set_Assignment_Type
96 Opnd_Type : in out Entity_Id);
97 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
98 -- is the nominal subtype. This procedure is used to deal with cases
99 -- where the nominal subtype must be replaced by the actual subtype.
101 -------------------------------
102 -- Diagnose_Non_Variable_Lhs --
103 -------------------------------
105 procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
107 -- Not worth posting another error if left hand side already
108 -- flagged as being illegal in some respect.
110 if Error_Posted (N) then
113 -- Some special bad cases of entity names
115 elsif Is_Entity_Name (N) then
117 Ent : constant Entity_Id := Entity (N);
120 if Ekind (Ent) = E_In_Parameter then
122 ("assignment to IN mode parameter not allowed", N);
124 -- Renamings of protected private components are turned into
125 -- constants when compiling a protected function. In the case
126 -- of single protected types, the private component appears
129 elsif (Is_Prival (Ent)
131 (Ekind (Current_Scope) = E_Function
132 or else Ekind (Enclosing_Dynamic_Scope (
133 Current_Scope)) = E_Function))
135 (Ekind (Ent) = E_Component
136 and then Is_Protected_Type (Scope (Ent)))
139 ("protected function cannot modify protected object", N);
141 elsif Ekind (Ent) = E_Loop_Parameter then
143 ("assignment to loop parameter not allowed", N);
147 ("left hand side of assignment must be a variable", N);
151 -- For indexed components or selected components, test prefix
153 elsif Nkind (N) = N_Indexed_Component then
154 Diagnose_Non_Variable_Lhs (Prefix (N));
156 -- Another special case for assignment to discriminant
158 elsif Nkind (N) = N_Selected_Component then
159 if Present (Entity (Selector_Name (N)))
160 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
163 ("assignment to discriminant not allowed", N);
165 Diagnose_Non_Variable_Lhs (Prefix (N));
169 -- If we fall through, we have no special message to issue!
171 Error_Msg_N ("left hand side of assignment must be a variable", N);
173 end Diagnose_Non_Variable_Lhs;
179 procedure Kill_Lhs is
181 if Is_Entity_Name (Lhs) then
183 Ent : constant Entity_Id := Entity (Lhs);
185 if Present (Ent) then
186 Kill_Current_Values (Ent);
192 -------------------------
193 -- Set_Assignment_Type --
194 -------------------------
196 procedure Set_Assignment_Type
198 Opnd_Type : in out Entity_Id)
201 Require_Entity (Opnd);
203 -- If the assignment operand is an in-out or out parameter, then we
204 -- get the actual subtype (needed for the unconstrained case).
205 -- If the operand is the actual in an entry declaration, then within
206 -- the accept statement it is replaced with a local renaming, which
207 -- may also have an actual subtype.
209 if Is_Entity_Name (Opnd)
210 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
211 or else Ekind (Entity (Opnd)) =
213 or else Ekind (Entity (Opnd)) =
214 E_Generic_In_Out_Parameter
216 (Ekind (Entity (Opnd)) = E_Variable
217 and then Nkind (Parent (Entity (Opnd))) =
218 N_Object_Renaming_Declaration
219 and then Nkind (Parent (Parent (Entity (Opnd)))) =
222 Opnd_Type := Get_Actual_Subtype (Opnd);
224 -- If assignment operand is a component reference, then we get the
225 -- actual subtype of the component for the unconstrained case.
227 elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference)
228 and then not Is_Unchecked_Union (Opnd_Type)
230 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
232 if Present (Decl) then
233 Insert_Action (N, Decl);
234 Mark_Rewrite_Insertion (Decl);
236 Opnd_Type := Defining_Identifier (Decl);
237 Set_Etype (Opnd, Opnd_Type);
238 Freeze_Itype (Opnd_Type, N);
240 elsif Is_Constrained (Etype (Opnd)) then
241 Opnd_Type := Etype (Opnd);
244 -- For slice, use the constrained subtype created for the slice
246 elsif Nkind (Opnd) = N_Slice then
247 Opnd_Type := Etype (Opnd);
249 end Set_Assignment_Type;
251 -- Start of processing for Analyze_Assignment
254 Mark_Coextensions (N, Rhs);
259 -- Start type analysis for assignment
263 -- In the most general case, both Lhs and Rhs can be overloaded, and we
264 -- must compute the intersection of the possible types on each side.
266 if Is_Overloaded (Lhs) then
273 Get_First_Interp (Lhs, I, It);
275 while Present (It.Typ) loop
276 if Has_Compatible_Type (Rhs, It.Typ) then
277 if T1 /= Any_Type then
279 -- An explicit dereference is overloaded if the prefix
280 -- is. Try to remove the ambiguity on the prefix, the
281 -- error will be posted there if the ambiguity is real.
283 if Nkind (Lhs) = N_Explicit_Dereference then
286 PI1 : Interp_Index := 0;
292 Get_First_Interp (Prefix (Lhs), PI, PIt);
294 while Present (PIt.Typ) loop
295 if Is_Access_Type (PIt.Typ)
296 and then Has_Compatible_Type
297 (Rhs, Designated_Type (PIt.Typ))
301 Disambiguate (Prefix (Lhs),
304 if PIt = No_Interp then
306 ("ambiguous left-hand side"
307 & " in assignment", Lhs);
310 Resolve (Prefix (Lhs), PIt.Typ);
320 Get_Next_Interp (PI, PIt);
326 ("ambiguous left-hand side in assignment", Lhs);
334 Get_Next_Interp (I, It);
338 if T1 = Any_Type then
340 ("no valid types for left-hand side for assignment", Lhs);
346 -- The resulting assignment type is T1, so now we will resolve the
347 -- left hand side of the assignment using this determined type.
351 -- Cases where Lhs is not a variable
353 if not Is_Variable (Lhs) then
355 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
356 -- a protected object.
363 if Ada_Version >= Ada_2005 then
365 -- Handle chains of renamings
368 while Nkind (Ent) in N_Has_Entity
369 and then Present (Entity (Ent))
370 and then Present (Renamed_Object (Entity (Ent)))
372 Ent := Renamed_Object (Entity (Ent));
375 if (Nkind (Ent) = N_Attribute_Reference
376 and then Attribute_Name (Ent) = Name_Priority)
378 -- Renamings of the attribute Priority applied to protected
379 -- objects have been previously expanded into calls to the
380 -- Get_Ceiling run-time subprogram.
383 (Nkind (Ent) = N_Function_Call
384 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
386 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
388 -- The enclosing subprogram cannot be a protected function
391 while not (Is_Subprogram (S)
392 and then Convention (S) = Convention_Protected)
393 and then S /= Standard_Standard
398 if Ekind (S) = E_Function
399 and then Convention (S) = Convention_Protected
402 ("protected function cannot modify protected object",
406 -- Changes of the ceiling priority of the protected object
407 -- are only effective if the Ceiling_Locking policy is in
408 -- effect (AARM D.5.2 (5/2)).
410 if Locking_Policy /= 'C' then
411 Error_Msg_N ("assignment to the attribute PRIORITY has " &
413 Error_Msg_N ("\since no Locking_Policy has been " &
422 Diagnose_Non_Variable_Lhs (Lhs);
425 -- Error of assigning to limited type. We do however allow this in
426 -- certain cases where the front end generates the assignments.
428 elsif Is_Limited_Type (T1)
429 and then not Assignment_OK (Lhs)
430 and then not Assignment_OK (Original_Node (Lhs))
431 and then not Is_Value_Type (T1)
433 -- CPP constructors can only be called in declarations
435 if Is_CPP_Constructor_Call (Rhs) then
436 Error_Msg_N ("invalid use of 'C'P'P constructor", Rhs);
439 ("left hand of assignment must not be limited type", Lhs);
440 Explain_Limited_Type (T1, Lhs);
444 -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
445 -- abstract. This is only checked when the assignment Comes_From_Source,
446 -- because in some cases the expander generates such assignments (such
447 -- in the _assign operation for an abstract type).
449 elsif Is_Abstract_Type (T1) and then Comes_From_Source (N) then
451 ("target of assignment operation must not be abstract", Lhs);
454 -- Resolution may have updated the subtype, in case the left-hand
455 -- side is a private protected component. Use the correct subtype
456 -- to avoid scoping issues in the back-end.
460 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
461 -- type. For example:
465 -- type Acc is access P.T;
468 -- with Pkg; use Acc;
469 -- procedure Example is
472 -- A.all := B.all; -- ERROR
475 if Nkind (Lhs) = N_Explicit_Dereference
476 and then Ekind (T1) = E_Incomplete_Type
478 Error_Msg_N ("invalid use of incomplete type", Lhs);
483 -- Now we can complete the resolution of the right hand side
485 Set_Assignment_Type (Lhs, T1);
488 -- This is the point at which we check for an unset reference
490 Check_Unset_Reference (Rhs);
491 Check_Unprotected_Access (Lhs, Rhs);
493 -- Remaining steps are skipped if Rhs was syntactically in error
502 if not Covers (T1, T2) then
503 Wrong_Type (Rhs, Etype (Lhs));
508 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
509 -- types, use the non-limited view if available
511 if Nkind (Rhs) = N_Explicit_Dereference
512 and then Ekind (T2) = E_Incomplete_Type
513 and then Is_Tagged_Type (T2)
514 and then Present (Non_Limited_View (T2))
516 T2 := Non_Limited_View (T2);
519 Set_Assignment_Type (Rhs, T2);
521 if Total_Errors_Detected /= 0 then
531 if T1 = Any_Type or else T2 = Any_Type then
536 -- If the rhs is class-wide or dynamically tagged, then require the lhs
537 -- to be class-wide. The case where the rhs is a dynamically tagged call
538 -- to a dispatching operation with a controlling access result is
539 -- excluded from this check, since the target has an access type (and
540 -- no tag propagation occurs in that case).
542 if (Is_Class_Wide_Type (T2)
543 or else (Is_Dynamically_Tagged (Rhs)
544 and then not Is_Access_Type (T1)))
545 and then not Is_Class_Wide_Type (T1)
547 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
549 elsif Is_Class_Wide_Type (T1)
550 and then not Is_Class_Wide_Type (T2)
551 and then not Is_Tag_Indeterminate (Rhs)
552 and then not Is_Dynamically_Tagged (Rhs)
554 Error_Msg_N ("dynamically tagged expression required!", Rhs);
557 -- Propagate the tag from a class-wide target to the rhs when the rhs
558 -- is a tag-indeterminate call.
560 if Is_Tag_Indeterminate (Rhs) then
561 if Is_Class_Wide_Type (T1) then
562 Propagate_Tag (Lhs, Rhs);
564 elsif Nkind (Rhs) = N_Function_Call
565 and then Is_Entity_Name (Name (Rhs))
566 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
569 ("call to abstract function must be dispatching", Name (Rhs));
571 elsif Nkind (Rhs) = N_Qualified_Expression
572 and then Nkind (Expression (Rhs)) = N_Function_Call
573 and then Is_Entity_Name (Name (Expression (Rhs)))
575 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
578 ("call to abstract function must be dispatching",
579 Name (Expression (Rhs)));
583 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
584 -- apply an implicit conversion of the rhs to that type to force
585 -- appropriate static and run-time accessibility checks. This applies
586 -- as well to anonymous access-to-subprogram types that are component
587 -- subtypes or formal parameters.
589 if Ada_Version >= Ada_2005
590 and then Is_Access_Type (T1)
592 if Is_Local_Anonymous_Access (T1)
593 or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
595 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
596 Analyze_And_Resolve (Rhs, T1);
600 -- Ada 2005 (AI-231): Assignment to not null variable
602 if Ada_Version >= Ada_2005
603 and then Can_Never_Be_Null (T1)
604 and then not Assignment_OK (Lhs)
606 -- Case where we know the right hand side is null
608 if Known_Null (Rhs) then
609 Apply_Compile_Time_Constraint_Error
611 Msg => "(Ada 2005) null not allowed in null-excluding objects?",
612 Reason => CE_Null_Not_Allowed);
614 -- We still mark this as a possible modification, that's necessary
615 -- to reset Is_True_Constant, and desirable for xref purposes.
617 Note_Possible_Modification (Lhs, Sure => True);
620 -- If we know the right hand side is non-null, then we convert to the
621 -- target type, since we don't need a run time check in that case.
623 elsif not Can_Never_Be_Null (T2) then
624 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
625 Analyze_And_Resolve (Rhs, T1);
629 if Is_Scalar_Type (T1) then
630 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
632 -- For array types, verify that lengths match. If the right hand side
633 -- if a function call that has been inlined, the assignment has been
634 -- rewritten as a block, and the constraint check will be applied to the
635 -- assignment within the block.
637 elsif Is_Array_Type (T1)
639 (Nkind (Rhs) /= N_Type_Conversion
640 or else Is_Constrained (Etype (Rhs)))
642 (Nkind (Rhs) /= N_Function_Call
643 or else Nkind (N) /= N_Block_Statement)
645 -- Assignment verifies that the length of the Lsh and Rhs are equal,
646 -- but of course the indexes do not have to match. If the right-hand
647 -- side is a type conversion to an unconstrained type, a length check
648 -- is performed on the expression itself during expansion. In rare
649 -- cases, the redundant length check is computed on an index type
650 -- with a different representation, triggering incorrect code in
653 Apply_Length_Check (Rhs, Etype (Lhs));
656 -- Discriminant checks are applied in the course of expansion
661 -- Note: modifications of the Lhs may only be recorded after
662 -- checks have been applied.
664 Note_Possible_Modification (Lhs, Sure => True);
665 Check_Order_Dependence;
667 -- ??? a real accessibility check is needed when ???
669 -- Post warning for redundant assignment or variable to itself
671 if Warn_On_Redundant_Constructs
673 -- We only warn for source constructs
675 and then Comes_From_Source (N)
677 -- Where the object is the same on both sides
679 and then Same_Object (Lhs, Original_Node (Rhs))
681 -- But exclude the case where the right side was an operation
682 -- that got rewritten (e.g. JUNK + K, where K was known to be
683 -- zero). We don't want to warn in such a case, since it is
684 -- reasonable to write such expressions especially when K is
685 -- defined symbolically in some other package.
687 and then Nkind (Original_Node (Rhs)) not in N_Op
689 if Nkind (Lhs) in N_Has_Entity then
690 Error_Msg_NE -- CODEFIX
691 ("?useless assignment of & to itself!", N, Entity (Lhs));
693 Error_Msg_N -- CODEFIX
694 ("?useless assignment of object to itself!", N);
698 -- Check for non-allowed composite assignment
700 if not Support_Composite_Assign_On_Target
701 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
702 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
704 Error_Msg_CRT ("composite assignment", N);
707 -- Check elaboration warning for left side if not in elab code
709 if not In_Subprogram_Or_Concurrent_Unit then
710 Check_Elab_Assign (Lhs);
713 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
714 -- assignment is a source assignment in the extended main source unit.
715 -- We are not interested in any reference information outside this
716 -- context, or in compiler generated assignment statements.
718 if Comes_From_Source (N)
719 and then In_Extended_Main_Source_Unit (Lhs)
721 Set_Referenced_Modified (Lhs, Out_Param => False);
724 -- Final step. If left side is an entity, then we may be able to
725 -- reset the current tracked values to new safe values. We only have
726 -- something to do if the left side is an entity name, and expansion
727 -- has not modified the node into something other than an assignment,
728 -- and of course we only capture values if it is safe to do so.
730 if Is_Entity_Name (Lhs)
731 and then Nkind (N) = N_Assignment_Statement
734 Ent : constant Entity_Id := Entity (Lhs);
737 if Safe_To_Capture_Value (N, Ent) then
739 -- If simple variable on left side, warn if this assignment
740 -- blots out another one (rendering it useless) and note
741 -- location of assignment in case no one references value.
742 -- We only do this for source assignments, otherwise we can
743 -- generate bogus warnings when an assignment is rewritten as
744 -- another assignment, and gets tied up with itself.
746 -- Note: we don't use Record_Last_Assignment here, because we
747 -- have lots of other stuff to do under control of this test.
749 if Warn_On_Modified_Unread
750 and then Is_Assignable (Ent)
751 and then Comes_From_Source (N)
752 and then In_Extended_Main_Source_Unit (Ent)
754 Warn_On_Useless_Assignment (Ent, N);
755 Set_Last_Assignment (Ent, Lhs);
758 -- If we are assigning an access type and the left side is an
759 -- entity, then make sure that the Is_Known_[Non_]Null flags
760 -- properly reflect the state of the entity after assignment.
762 if Is_Access_Type (T1) then
763 if Known_Non_Null (Rhs) then
764 Set_Is_Known_Non_Null (Ent, True);
766 elsif Known_Null (Rhs)
767 and then not Can_Never_Be_Null (Ent)
769 Set_Is_Known_Null (Ent, True);
772 Set_Is_Known_Null (Ent, False);
774 if not Can_Never_Be_Null (Ent) then
775 Set_Is_Known_Non_Null (Ent, False);
779 -- For discrete types, we may be able to set the current value
780 -- if the value is known at compile time.
782 elsif Is_Discrete_Type (T1)
783 and then Compile_Time_Known_Value (Rhs)
785 Set_Current_Value (Ent, Rhs);
787 Set_Current_Value (Ent, Empty);
790 -- If not safe to capture values, kill them
797 end Analyze_Assignment;
799 -----------------------------
800 -- Analyze_Block_Statement --
801 -----------------------------
803 procedure Analyze_Block_Statement (N : Node_Id) is
804 Decls : constant List_Id := Declarations (N);
805 Id : constant Node_Id := Identifier (N);
806 HSS : constant Node_Id := Handled_Statement_Sequence (N);
809 -- Block statement is not allowed in SPARK or ALFA
811 if Formal_Verification_Mode then
812 Error_Msg_F ("|~~block statement is not allowed", 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 -- Start of processing for Analyze_Case_Statement
1031 Unblocked_Exit_Count := 0;
1032 Exp := Expression (N);
1035 -- The expression must be of any discrete type. In rare cases, the
1036 -- expander constructs a case statement whose expression has a private
1037 -- type whose full view is discrete. This can happen when generating
1038 -- a stream operation for a variant type after the type is frozen,
1039 -- when the partial of view of the type of the discriminant is private.
1040 -- In that case, use the full view to analyze case alternatives.
1042 if not Is_Overloaded (Exp)
1043 and then not Comes_From_Source (N)
1044 and then Is_Private_Type (Etype (Exp))
1045 and then Present (Full_View (Etype (Exp)))
1046 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1048 Resolve (Exp, Etype (Exp));
1049 Exp_Type := Full_View (Etype (Exp));
1052 Analyze_And_Resolve (Exp, Any_Discrete);
1053 Exp_Type := Etype (Exp);
1056 Check_Unset_Reference (Exp);
1057 Exp_Btype := Base_Type (Exp_Type);
1059 -- The expression must be of a discrete type which must be determinable
1060 -- independently of the context in which the expression occurs, but
1061 -- using the fact that the expression must be of a discrete type.
1062 -- Moreover, the type this expression must not be a character literal
1063 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1065 -- If error already reported by Resolve, nothing more to do
1067 if Exp_Btype = Any_Discrete
1068 or else Exp_Btype = Any_Type
1072 elsif Exp_Btype = Any_Character then
1074 ("character literal as case expression is ambiguous", Exp);
1077 elsif Ada_Version = Ada_83
1078 and then (Is_Generic_Type (Exp_Btype)
1079 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1082 ("(Ada 83) case expression cannot be of a generic type", Exp);
1086 -- If the case expression is a formal object of mode in out, then
1087 -- treat it as having a nonstatic subtype by forcing use of the base
1088 -- type (which has to get passed to Check_Case_Choices below). Also
1089 -- use base type when the case expression is parenthesized.
1091 if Paren_Count (Exp) > 0
1092 or else (Is_Entity_Name (Exp)
1093 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1095 Exp_Type := Exp_Btype;
1098 -- Call instantiated Analyze_Choices which does the rest of the work
1100 Analyze_Choices (N, Exp_Type, Dont_Care, Others_Present);
1102 -- A case statement with a single "others" alternative is not allowed
1103 -- in SPARK or ALFA.
1105 if Formal_Verification_Mode
1106 and then Others_Present
1107 and then List_Length (Alternatives (N)) = 1
1110 ("|~~OTHERS as unique case alternative is not allowed", N);
1113 if Exp_Type = Universal_Integer and then not Others_Present then
1114 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1117 -- If all our exits were blocked by unconditional transfers of control,
1118 -- then the entire CASE statement acts as an unconditional transfer of
1119 -- control, so treat it like one, and check unreachable code. Skip this
1120 -- test if we had serious errors preventing any statement analysis.
1122 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1123 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1124 Check_Unreachable_Code (N);
1126 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1129 if not Expander_Active
1130 and then Compile_Time_Known_Value (Expression (N))
1131 and then Serious_Errors_Detected = 0
1134 Chosen : constant Node_Id := Find_Static_Alternative (N);
1138 Alt := First (Alternatives (N));
1139 while Present (Alt) loop
1140 if Alt /= Chosen then
1141 Remove_Warning_Messages (Statements (Alt));
1148 end Analyze_Case_Statement;
1150 ----------------------------
1151 -- Analyze_Exit_Statement --
1152 ----------------------------
1154 -- If the exit includes a name, it must be the name of a currently open
1155 -- loop. Otherwise there must be an innermost open loop on the stack,
1156 -- to which the statement implicitly refers.
1158 -- Additionally, in formal mode:
1159 -- * the exit can only name the closest enclosing loop;
1160 -- * an exit with a when clause must be directly contained in a loop;
1161 -- * an exit without a when clause must be directly contained in an
1162 -- if-statement with no elsif or else, which is itself directly contained
1163 -- in a loop. The exit must be the last statement in the if-statement.
1165 procedure Analyze_Exit_Statement (N : Node_Id) is
1166 Target : constant Node_Id := Name (N);
1167 Cond : constant Node_Id := Condition (N);
1168 Scope_Id : Entity_Id;
1174 Check_Unreachable_Code (N);
1177 if Present (Target) then
1179 U_Name := Entity (Target);
1181 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1182 Error_Msg_N ("invalid loop name in exit statement", N);
1184 elsif Formal_Verification_Mode
1185 and then Has_Loop_In_Inner_Open_Scopes (U_Name)
1188 ("|~~exit label must name the closest enclosing loop", N);
1191 Set_Has_Exit (U_Name);
1198 for J in reverse 0 .. Scope_Stack.Last loop
1199 Scope_Id := Scope_Stack.Table (J).Entity;
1200 Kind := Ekind (Scope_Id);
1203 and then (No (Target) or else Scope_Id = U_Name) then
1204 Set_Has_Exit (Scope_Id);
1207 elsif Kind = E_Block
1208 or else Kind = E_Loop
1209 or else Kind = E_Return_Statement
1215 ("cannot exit from program unit or accept statement", N);
1220 -- Verify that if present the condition is a Boolean expression
1222 if Present (Cond) then
1223 Analyze_And_Resolve (Cond, Any_Boolean);
1224 Check_Unset_Reference (Cond);
1227 -- In formal mode, verify that the exit statement respects the SPARK
1230 if Formal_Verification_Mode then
1231 if Present (Cond) then
1232 if Nkind (Parent (N)) /= N_Loop_Statement then
1234 ("|~~exit with when clause must be directly in loop", N);
1238 if Nkind (Parent (N)) /= N_If_Statement then
1239 if Nkind (Parent (N)) = N_Elsif_Part then
1240 Error_Msg_F ("|~~exit must be in IF without ELSIF", N);
1242 Error_Msg_F ("|~~exit must be directly in IF", N);
1245 elsif Nkind (Parent (Parent (N))) /= N_Loop_Statement then
1246 Error_Msg_F ("|~~exit must be in IF directly in loop", N);
1248 -- First test the presence of ELSE, so that an exit in an ELSE
1249 -- leads to an error mentioning the ELSE.
1251 elsif Present (Else_Statements (Parent (N))) then
1252 Error_Msg_F ("|~~exit must be in IF without ELSE", N);
1254 -- An exit in an ELSIF does not reach here, as it would have been
1255 -- detected in the case (Nkind (Parent (N)) /= N_If_Statement).
1257 elsif Present (Elsif_Parts (Parent (N))) then
1258 Error_Msg_F ("|~~exit must be in IF without ELSIF", N);
1263 -- Chain exit statement to associated loop entity
1265 Set_Next_Exit_Statement (N, First_Exit_Statement (Scope_Id));
1266 Set_First_Exit_Statement (Scope_Id, N);
1268 -- Since the exit may take us out of a loop, any previous assignment
1269 -- statement is not useless, so clear last assignment indications. It
1270 -- is OK to keep other current values, since if the exit statement
1271 -- does not exit, then the current values are still valid.
1273 Kill_Current_Values (Last_Assignment_Only => True);
1274 end Analyze_Exit_Statement;
1276 ----------------------------
1277 -- Analyze_Goto_Statement --
1278 ----------------------------
1280 procedure Analyze_Goto_Statement (N : Node_Id) is
1281 Label : constant Node_Id := Name (N);
1282 Scope_Id : Entity_Id;
1283 Label_Scope : Entity_Id;
1284 Label_Ent : Entity_Id;
1287 -- Goto statement is not allowed in SPARK or ALFA
1289 if Formal_Verification_Mode then
1290 Error_Msg_F ("|~~goto statement is not allowed", N);
1293 -- Actual semantic checks
1295 Check_Unreachable_Code (N);
1296 Kill_Current_Values (Last_Assignment_Only => True);
1299 Label_Ent := Entity (Label);
1301 -- Ignore previous error
1303 if Label_Ent = Any_Id then
1306 -- We just have a label as the target of a goto
1308 elsif Ekind (Label_Ent) /= E_Label then
1309 Error_Msg_N ("target of goto statement must be a label", Label);
1312 -- Check that the target of the goto is reachable according to Ada
1313 -- scoping rules. Note: the special gotos we generate for optimizing
1314 -- local handling of exceptions would violate these rules, but we mark
1315 -- such gotos as analyzed when built, so this code is never entered.
1317 elsif not Reachable (Label_Ent) then
1318 Error_Msg_N ("target of goto statement is not reachable", Label);
1322 -- Here if goto passes initial validity checks
1324 Label_Scope := Enclosing_Scope (Label_Ent);
1326 for J in reverse 0 .. Scope_Stack.Last loop
1327 Scope_Id := Scope_Stack.Table (J).Entity;
1329 if Label_Scope = Scope_Id
1330 or else (Ekind (Scope_Id) /= E_Block
1331 and then Ekind (Scope_Id) /= E_Loop
1332 and then Ekind (Scope_Id) /= E_Return_Statement)
1334 if Scope_Id /= Label_Scope then
1336 ("cannot exit from program unit or accept statement", N);
1343 raise Program_Error;
1344 end Analyze_Goto_Statement;
1346 --------------------------
1347 -- Analyze_If_Statement --
1348 --------------------------
1350 -- A special complication arises in the analysis of if statements
1352 -- The expander has circuitry to completely delete code that it
1353 -- can tell will not be executed (as a result of compile time known
1354 -- conditions). In the analyzer, we ensure that code that will be
1355 -- deleted in this manner is analyzed but not expanded. This is
1356 -- obviously more efficient, but more significantly, difficulties
1357 -- arise if code is expanded and then eliminated (e.g. exception
1358 -- table entries disappear). Similarly, itypes generated in deleted
1359 -- code must be frozen from start, because the nodes on which they
1360 -- depend will not be available at the freeze point.
1362 procedure Analyze_If_Statement (N : Node_Id) is
1365 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1366 -- Recursively save value of this global, will be restored on exit
1368 Save_In_Deleted_Code : Boolean;
1370 Del : Boolean := False;
1371 -- This flag gets set True if a True condition has been found,
1372 -- which means that remaining ELSE/ELSIF parts are deleted.
1374 procedure Analyze_Cond_Then (Cnode : Node_Id);
1375 -- This is applied to either the N_If_Statement node itself or
1376 -- to an N_Elsif_Part node. It deals with analyzing the condition
1377 -- and the THEN statements associated with it.
1379 -----------------------
1380 -- Analyze_Cond_Then --
1381 -----------------------
1383 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1384 Cond : constant Node_Id := Condition (Cnode);
1385 Tstm : constant List_Id := Then_Statements (Cnode);
1388 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1389 Analyze_And_Resolve (Cond, Any_Boolean);
1390 Check_Unset_Reference (Cond);
1391 Set_Current_Value_Condition (Cnode);
1393 -- If already deleting, then just analyze then statements
1396 Analyze_Statements (Tstm);
1398 -- Compile time known value, not deleting yet
1400 elsif Compile_Time_Known_Value (Cond) then
1401 Save_In_Deleted_Code := In_Deleted_Code;
1403 -- If condition is True, then analyze the THEN statements
1404 -- and set no expansion for ELSE and ELSIF parts.
1406 if Is_True (Expr_Value (Cond)) then
1407 Analyze_Statements (Tstm);
1409 Expander_Mode_Save_And_Set (False);
1410 In_Deleted_Code := True;
1412 -- If condition is False, analyze THEN with expansion off
1414 else -- Is_False (Expr_Value (Cond))
1415 Expander_Mode_Save_And_Set (False);
1416 In_Deleted_Code := True;
1417 Analyze_Statements (Tstm);
1418 Expander_Mode_Restore;
1419 In_Deleted_Code := Save_In_Deleted_Code;
1422 -- Not known at compile time, not deleting, normal analysis
1425 Analyze_Statements (Tstm);
1427 end Analyze_Cond_Then;
1429 -- Start of Analyze_If_Statement
1432 -- Initialize exit count for else statements. If there is no else
1433 -- part, this count will stay non-zero reflecting the fact that the
1434 -- uncovered else case is an unblocked exit.
1436 Unblocked_Exit_Count := 1;
1437 Analyze_Cond_Then (N);
1439 -- Now to analyze the elsif parts if any are present
1441 if Present (Elsif_Parts (N)) then
1442 E := First (Elsif_Parts (N));
1443 while Present (E) loop
1444 Analyze_Cond_Then (E);
1449 if Present (Else_Statements (N)) then
1450 Analyze_Statements (Else_Statements (N));
1453 -- If all our exits were blocked by unconditional transfers of control,
1454 -- then the entire IF statement acts as an unconditional transfer of
1455 -- control, so treat it like one, and check unreachable code.
1457 if Unblocked_Exit_Count = 0 then
1458 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1459 Check_Unreachable_Code (N);
1461 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1465 Expander_Mode_Restore;
1466 In_Deleted_Code := Save_In_Deleted_Code;
1469 if not Expander_Active
1470 and then Compile_Time_Known_Value (Condition (N))
1471 and then Serious_Errors_Detected = 0
1473 if Is_True (Expr_Value (Condition (N))) then
1474 Remove_Warning_Messages (Else_Statements (N));
1476 if Present (Elsif_Parts (N)) then
1477 E := First (Elsif_Parts (N));
1478 while Present (E) loop
1479 Remove_Warning_Messages (Then_Statements (E));
1485 Remove_Warning_Messages (Then_Statements (N));
1488 end Analyze_If_Statement;
1490 ----------------------------------------
1491 -- Analyze_Implicit_Label_Declaration --
1492 ----------------------------------------
1494 -- An implicit label declaration is generated in the innermost
1495 -- enclosing declarative part. This is done for labels as well as
1496 -- block and loop names.
1498 -- Note: any changes in this routine may need to be reflected in
1499 -- Analyze_Label_Entity.
1501 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1502 Id : constant Node_Id := Defining_Identifier (N);
1505 Set_Ekind (Id, E_Label);
1506 Set_Etype (Id, Standard_Void_Type);
1507 Set_Enclosing_Scope (Id, Current_Scope);
1508 end Analyze_Implicit_Label_Declaration;
1510 ------------------------------
1511 -- Analyze_Iteration_Scheme --
1512 ------------------------------
1514 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1516 procedure Process_Bounds (R : Node_Id);
1517 -- If the iteration is given by a range, create temporaries and
1518 -- assignment statements block to capture the bounds and perform
1519 -- required finalization actions in case a bound includes a function
1520 -- call that uses the temporary stack. We first pre-analyze a copy of
1521 -- the range in order to determine the expected type, and analyze and
1522 -- resolve the original bounds.
1524 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1525 -- If the bounds are given by a 'Range reference on a function call
1526 -- that returns a controlled array, introduce an explicit declaration
1527 -- to capture the bounds, so that the function result can be finalized
1528 -- in timely fashion.
1530 --------------------
1531 -- Process_Bounds --
1532 --------------------
1534 procedure Process_Bounds (R : Node_Id) is
1535 Loc : constant Source_Ptr := Sloc (N);
1536 R_Copy : constant Node_Id := New_Copy_Tree (R);
1537 Lo : constant Node_Id := Low_Bound (R);
1538 Hi : constant Node_Id := High_Bound (R);
1539 New_Lo_Bound : Node_Id;
1540 New_Hi_Bound : Node_Id;
1542 Save_Analysis : Boolean;
1545 (Original_Bound : Node_Id;
1546 Analyzed_Bound : Node_Id) return Node_Id;
1547 -- Capture value of bound and return captured value
1554 (Original_Bound : Node_Id;
1555 Analyzed_Bound : Node_Id) return Node_Id
1562 -- If the bound is a constant or an object, no need for a separate
1563 -- declaration. If the bound is the result of previous expansion
1564 -- it is already analyzed and should not be modified. Note that
1565 -- the Bound will be resolved later, if needed, as part of the
1566 -- call to Make_Index (literal bounds may need to be resolved to
1569 if Analyzed (Original_Bound) then
1570 return Original_Bound;
1572 elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
1573 N_Character_Literal)
1574 or else Is_Entity_Name (Analyzed_Bound)
1576 Analyze_And_Resolve (Original_Bound, Typ);
1577 return Original_Bound;
1580 -- Here we need to capture the value
1582 Analyze_And_Resolve (Original_Bound, Typ);
1584 Id := Make_Temporary (Loc, 'S', Original_Bound);
1586 -- Normally, the best approach is simply to generate a constant
1587 -- declaration that captures the bound. However, there is a nasty
1588 -- case where this is wrong. If the bound is complex, and has a
1589 -- possible use of the secondary stack, we need to generate a
1590 -- separate assignment statement to ensure the creation of a block
1591 -- which will release the secondary stack.
1593 -- We prefer the constant declaration, since it leaves us with a
1594 -- proper trace of the value, useful in optimizations that get rid
1595 -- of junk range checks.
1597 -- Probably we want something like the Side_Effect_Free routine
1598 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1599 -- and 'First applied to an entity, since these are the important
1600 -- cases for range check optimizations.
1602 if Nkind (Original_Bound) = N_Attribute_Reference
1603 and then (Attribute_Name (Original_Bound) = Name_First
1605 Attribute_Name (Original_Bound) = Name_Last)
1606 and then Is_Entity_Name (Prefix (Original_Bound))
1609 Make_Object_Declaration (Loc,
1610 Defining_Identifier => Id,
1611 Constant_Present => True,
1612 Object_Definition => New_Occurrence_Of (Typ, Loc),
1613 Expression => Relocate_Node (Original_Bound));
1615 -- Insert declaration at proper place. If loop comes from an
1616 -- enclosing quantified expression, the insertion point is
1617 -- arbitrarily far up in the tree.
1619 Insert_Action (Parent (N), Decl);
1620 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1621 return Expression (Decl);
1624 -- Here we make a declaration with a separate assignment
1625 -- statement, and insert before loop header.
1628 Make_Object_Declaration (Loc,
1629 Defining_Identifier => Id,
1630 Object_Definition => New_Occurrence_Of (Typ, Loc));
1633 Make_Assignment_Statement (Loc,
1634 Name => New_Occurrence_Of (Id, Loc),
1635 Expression => Relocate_Node (Original_Bound));
1637 Insert_Actions (Parent (N), New_List (Decl, Assign));
1639 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1641 if Nkind (Assign) = N_Assignment_Statement then
1642 return Expression (Assign);
1644 return Original_Bound;
1648 -- Start of processing for Process_Bounds
1651 -- Determine expected type of range by analyzing separate copy
1652 -- Do the analysis and resolution of the copy of the bounds with
1653 -- expansion disabled, to prevent the generation of finalization
1654 -- actions on each bound. This prevents memory leaks when the
1655 -- bounds contain calls to functions returning controlled arrays.
1657 Set_Parent (R_Copy, Parent (R));
1658 Save_Analysis := Full_Analysis;
1659 Full_Analysis := False;
1660 Expander_Mode_Save_And_Set (False);
1664 if Is_Overloaded (R_Copy) then
1666 -- Apply preference rules for range of predefined integer types,
1667 -- or diagnose true ambiguity.
1672 Found : Entity_Id := Empty;
1675 Get_First_Interp (R_Copy, I, It);
1676 while Present (It.Typ) loop
1677 if Is_Discrete_Type (It.Typ) then
1681 if Scope (Found) = Standard_Standard then
1684 elsif Scope (It.Typ) = Standard_Standard then
1688 -- Both of them are user-defined
1691 ("ambiguous bounds in range of iteration",
1693 Error_Msg_N ("\possible interpretations:", R_Copy);
1694 Error_Msg_NE ("\\} ", R_Copy, Found);
1695 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1701 Get_Next_Interp (I, It);
1707 Expander_Mode_Restore;
1708 Full_Analysis := Save_Analysis;
1710 Typ := Etype (R_Copy);
1712 -- If the type of the discrete range is Universal_Integer, then
1713 -- the bound's type must be resolved to Integer, and any object
1714 -- used to hold the bound must also have type Integer, unless the
1715 -- literal bounds are constant-folded expressions that carry a user-
1718 if Typ = Universal_Integer then
1719 if Nkind (Lo) = N_Integer_Literal
1720 and then Present (Etype (Lo))
1721 and then Scope (Etype (Lo)) /= Standard_Standard
1725 elsif Nkind (Hi) = N_Integer_Literal
1726 and then Present (Etype (Hi))
1727 and then Scope (Etype (Hi)) /= Standard_Standard
1732 Typ := Standard_Integer;
1738 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1739 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1741 -- Propagate staticness to loop range itself, in case the
1742 -- corresponding subtype is static.
1744 if New_Lo_Bound /= Lo
1745 and then Is_Static_Expression (New_Lo_Bound)
1747 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1750 if New_Hi_Bound /= Hi
1751 and then Is_Static_Expression (New_Hi_Bound)
1753 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1757 --------------------------------------
1758 -- Check_Controlled_Array_Attribute --
1759 --------------------------------------
1761 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1763 if Nkind (DS) = N_Attribute_Reference
1764 and then Is_Entity_Name (Prefix (DS))
1765 and then Ekind (Entity (Prefix (DS))) = E_Function
1766 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1769 Component_Type (Etype (Entity (Prefix (DS)))))
1770 and then Expander_Active
1773 Loc : constant Source_Ptr := Sloc (N);
1774 Arr : constant Entity_Id := Etype (Entity (Prefix (DS)));
1775 Indx : constant Entity_Id :=
1776 Base_Type (Etype (First_Index (Arr)));
1777 Subt : constant Entity_Id := Make_Temporary (Loc, 'S');
1782 Make_Subtype_Declaration (Loc,
1783 Defining_Identifier => Subt,
1784 Subtype_Indication =>
1785 Make_Subtype_Indication (Loc,
1786 Subtype_Mark => New_Reference_To (Indx, Loc),
1788 Make_Range_Constraint (Loc,
1789 Relocate_Node (DS))));
1790 Insert_Before (Parent (N), Decl);
1794 Make_Attribute_Reference (Loc,
1795 Prefix => New_Reference_To (Subt, Loc),
1796 Attribute_Name => Attribute_Name (DS)));
1800 end Check_Controlled_Array_Attribute;
1802 -- Start of processing for Analyze_Iteration_Scheme
1805 -- If this is a rewritten quantified expression, the iteration
1806 -- scheme has been analyzed already. Do no repeat analysis because
1807 -- the loop variable is already declared.
1809 if Analyzed (N) then
1813 -- For an infinite loop, there is no iteration scheme
1819 -- Iteration scheme is present
1822 Cond : constant Node_Id := Condition (N);
1825 -- For WHILE loop, verify that the condition is a Boolean
1826 -- expression and resolve and check it.
1828 if Present (Cond) then
1829 Analyze_And_Resolve (Cond, Any_Boolean);
1830 Check_Unset_Reference (Cond);
1831 Set_Current_Value_Condition (N);
1834 elsif Present (Iterator_Specification (N)) then
1835 Analyze_Iterator_Specification (Iterator_Specification (N));
1837 -- Else we have a FOR loop
1841 LP : constant Node_Id := Loop_Parameter_Specification (N);
1842 Id : constant Entity_Id := Defining_Identifier (LP);
1843 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1848 -- We always consider the loop variable to be referenced,
1849 -- since the loop may be used just for counting purposes.
1851 Generate_Reference (Id, N, ' ');
1853 -- Check for the case of loop variable hiding a local variable
1854 -- (used later on to give a nice warning if the hidden variable
1855 -- is never assigned).
1858 H : constant Entity_Id := Homonym (Id);
1861 and then Enclosing_Dynamic_Scope (H) =
1862 Enclosing_Dynamic_Scope (Id)
1863 and then Ekind (H) = E_Variable
1864 and then Is_Discrete_Type (Etype (H))
1866 Set_Hiding_Loop_Variable (H, Id);
1870 -- Loop parameter specification must include subtype mark in
1873 if Formal_Verification_Mode
1874 and then Nkind (DS) = N_Range
1876 Error_Msg_F ("|~~loop parameter specification must "
1877 & "include subtype mark", N);
1880 -- Now analyze the subtype definition. If it is a range, create
1881 -- temporaries for bounds.
1883 if Nkind (DS) = N_Range
1884 and then Expander_Active
1886 Process_Bounds (DS);
1888 -- Not a range or expander not active (is that right???)
1893 if Nkind (DS) = N_Function_Call
1895 (Is_Entity_Name (DS)
1896 and then not Is_Type (Entity (DS)))
1898 -- This is an iterator specification. Rewrite as such
1902 I_Spec : constant Node_Id :=
1903 Make_Iterator_Specification (Sloc (LP),
1904 Defining_Identifier =>
1908 Subtype_Indication =>
1911 Reverse_Present (LP));
1913 Set_Iterator_Specification (N, I_Spec);
1914 Set_Loop_Parameter_Specification (N, Empty);
1915 Analyze_Iterator_Specification (I_Spec);
1925 -- Some additional checks if we are iterating through a type
1927 if Is_Entity_Name (DS)
1928 and then Present (Entity (DS))
1929 and then Is_Type (Entity (DS))
1931 -- The subtype indication may denote the completion of an
1932 -- incomplete type declaration.
1934 if Ekind (Entity (DS)) = E_Incomplete_Type then
1935 Set_Entity (DS, Get_Full_View (Entity (DS)));
1936 Set_Etype (DS, Entity (DS));
1939 -- Attempt to iterate through non-static predicate
1941 if Is_Discrete_Type (Entity (DS))
1942 and then Present (Predicate_Function (Entity (DS)))
1943 and then No (Static_Predicate (Entity (DS)))
1945 Bad_Predicated_Subtype_Use
1946 ("cannot use subtype& with non-static "
1947 & "predicate for loop iteration", DS, Entity (DS));
1951 -- Error if not discrete type
1953 if not Is_Discrete_Type (Etype (DS)) then
1954 Wrong_Type (DS, Any_Discrete);
1955 Set_Etype (DS, Any_Type);
1958 Check_Controlled_Array_Attribute (DS);
1960 Make_Index (DS, LP);
1962 Set_Ekind (Id, E_Loop_Parameter);
1964 -- If the loop is part of a predicate or precondition, it may
1965 -- be analyzed twice, once in the source and once on the copy
1966 -- used to check conformance. Preserve the original itype
1967 -- because the second one may be created in a different scope,
1968 -- e.g. a precondition procedure, leading to a crash in GIGI.
1970 if No (Etype (Id)) or else Etype (Id) = Any_Type then
1971 Set_Etype (Id, Etype (DS));
1974 -- Treat a range as an implicit reference to the type, to
1975 -- inhibit spurious warnings.
1977 Generate_Reference (Base_Type (Etype (DS)), N, ' ');
1978 Set_Is_Known_Valid (Id, True);
1980 -- The loop is not a declarative part, so the only entity
1981 -- declared "within" must be frozen explicitly.
1984 Flist : constant List_Id := Freeze_Entity (Id, N);
1986 if Is_Non_Empty_List (Flist) then
1987 Insert_Actions (N, Flist);
1991 -- Check for null or possibly null range and issue warning. We
1992 -- suppress such messages in generic templates and instances,
1993 -- because in practice they tend to be dubious in these cases.
1995 if Nkind (DS) = N_Range and then Comes_From_Source (N) then
1997 L : constant Node_Id := Low_Bound (DS);
1998 H : constant Node_Id := High_Bound (DS);
2001 -- If range of loop is null, issue warning
2003 if Compile_Time_Compare
2004 (L, H, Assume_Valid => True) = GT
2006 -- Suppress the warning if inside a generic template
2007 -- or instance, since in practice they tend to be
2008 -- dubious in these cases since they can result from
2009 -- intended parametrization.
2011 if not Inside_A_Generic
2012 and then not In_Instance
2014 -- Specialize msg if invalid values could make
2015 -- the loop non-null after all.
2017 if Compile_Time_Compare
2018 (L, H, Assume_Valid => False) = GT
2021 ("?loop range is null, loop will not execute",
2024 -- Since we know the range of the loop is
2025 -- null, set the appropriate flag to remove
2026 -- the loop entirely during expansion.
2028 Set_Is_Null_Loop (Parent (N));
2030 -- Here is where the loop could execute because
2031 -- of invalid values, so issue appropriate
2032 -- message and in this case we do not set the
2033 -- Is_Null_Loop flag since the loop may execute.
2037 ("?loop range may be null, "
2038 & "loop may not execute",
2041 ("?can only execute if invalid values "
2047 -- In either case, suppress warnings in the body of
2048 -- the loop, since it is likely that these warnings
2049 -- will be inappropriate if the loop never actually
2050 -- executes, which is likely.
2052 Set_Suppress_Loop_Warnings (Parent (N));
2054 -- The other case for a warning is a reverse loop
2055 -- where the upper bound is the integer literal zero
2056 -- or one, and the lower bound can be positive.
2058 -- For example, we have
2060 -- for J in reverse N .. 1 loop
2062 -- In practice, this is very likely to be a case of
2063 -- reversing the bounds incorrectly in the range.
2065 elsif Reverse_Present (LP)
2066 and then Nkind (Original_Node (H)) =
2068 and then (Intval (Original_Node (H)) = Uint_0
2070 Intval (Original_Node (H)) = Uint_1)
2072 Error_Msg_N ("?loop range may be null", DS);
2073 Error_Msg_N ("\?bounds may be wrong way round", DS);
2080 end Analyze_Iteration_Scheme;
2082 -------------------------------------
2083 -- Analyze_Iterator_Specification --
2084 -------------------------------------
2086 procedure Analyze_Iterator_Specification (N : Node_Id) is
2087 Def_Id : constant Node_Id := Defining_Identifier (N);
2088 Subt : constant Node_Id := Subtype_Indication (N);
2089 Container : constant Node_Id := Name (N);
2095 Enter_Name (Def_Id);
2096 Set_Ekind (Def_Id, E_Variable);
2098 if Present (Subt) then
2102 Analyze_And_Resolve (Container);
2103 Typ := Etype (Container);
2105 if Is_Array_Type (Typ) then
2106 if Of_Present (N) then
2107 Set_Etype (Def_Id, Component_Type (Typ));
2110 ("to iterate over the elements of an array, use OF", N);
2111 Set_Etype (Def_Id, Etype (First_Index (Typ)));
2114 -- Iteration over a container
2117 Set_Ekind (Def_Id, E_Loop_Parameter);
2119 if Of_Present (N) then
2121 -- Find the Element_Type in the package instance that defines the
2124 Ent := First_Entity (Scope (Typ));
2125 while Present (Ent) loop
2126 if Chars (Ent) = Name_Element_Type then
2127 Set_Etype (Def_Id, Ent);
2135 -- Find the Cursor type in similar fashion
2137 Ent := First_Entity (Scope (Typ));
2138 while Present (Ent) loop
2139 if Chars (Ent) = Name_Cursor then
2140 Set_Etype (Def_Id, Ent);
2148 end Analyze_Iterator_Specification;
2154 -- Note: the semantic work required for analyzing labels (setting them as
2155 -- reachable) was done in a prepass through the statements in the block,
2156 -- so that forward gotos would be properly handled. See Analyze_Statements
2157 -- for further details. The only processing required here is to deal with
2158 -- optimizations that depend on an assumption of sequential control flow,
2159 -- since of course the occurrence of a label breaks this assumption.
2161 procedure Analyze_Label (N : Node_Id) is
2162 pragma Warnings (Off, N);
2164 Kill_Current_Values;
2167 --------------------------
2168 -- Analyze_Label_Entity --
2169 --------------------------
2171 procedure Analyze_Label_Entity (E : Entity_Id) is
2173 Set_Ekind (E, E_Label);
2174 Set_Etype (E, Standard_Void_Type);
2175 Set_Enclosing_Scope (E, Current_Scope);
2176 Set_Reachable (E, True);
2177 end Analyze_Label_Entity;
2179 ----------------------------
2180 -- Analyze_Loop_Statement --
2181 ----------------------------
2183 procedure Analyze_Loop_Statement (N : Node_Id) is
2184 Loop_Statement : constant Node_Id := N;
2186 Id : constant Node_Id := Identifier (Loop_Statement);
2187 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
2191 if Present (Id) then
2193 -- Make name visible, e.g. for use in exit statements. Loop
2194 -- labels are always considered to be referenced.
2199 -- Guard against serious error (typically, a scope mismatch when
2200 -- semantic analysis is requested) by creating loop entity to
2201 -- continue analysis.
2204 if Total_Errors_Detected /= 0 then
2207 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2209 raise Program_Error;
2213 Generate_Reference (Ent, Loop_Statement, ' ');
2214 Generate_Definition (Ent);
2216 -- If we found a label, mark its type. If not, ignore it, since it
2217 -- means we have a conflicting declaration, which would already
2218 -- have been diagnosed at declaration time. Set Label_Construct
2219 -- of the implicit label declaration, which is not created by the
2220 -- parser for generic units.
2222 if Ekind (Ent) = E_Label then
2223 Set_Ekind (Ent, E_Loop);
2225 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
2226 Set_Label_Construct (Parent (Ent), Loop_Statement);
2231 -- Case of no identifier present
2236 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2237 Set_Etype (Ent, Standard_Void_Type);
2238 Set_Parent (Ent, Loop_Statement);
2241 -- Kill current values on entry to loop, since statements in body of
2242 -- loop may have been executed before the loop is entered. Similarly we
2243 -- kill values after the loop, since we do not know that the body of the
2244 -- loop was executed.
2246 Kill_Current_Values;
2248 Analyze_Iteration_Scheme (Iter);
2249 Analyze_Statements (Statements (Loop_Statement));
2250 Process_End_Label (Loop_Statement, 'e', Ent);
2252 Kill_Current_Values;
2254 -- Check for infinite loop. Skip check for generated code, since it
2255 -- justs waste time and makes debugging the routine called harder.
2257 -- Note that we have to wait till the body of the loop is fully analyzed
2258 -- before making this call, since Check_Infinite_Loop_Warning relies on
2259 -- being able to use semantic visibility information to find references.
2261 if Comes_From_Source (N) then
2262 Check_Infinite_Loop_Warning (N);
2265 -- Code after loop is unreachable if the loop has no WHILE or FOR
2266 -- and contains no EXIT statements within the body of the loop.
2268 if No (Iter) and then not Has_Exit (Ent) then
2269 Check_Unreachable_Code (N);
2271 end Analyze_Loop_Statement;
2273 ----------------------------
2274 -- Analyze_Null_Statement --
2275 ----------------------------
2277 -- Note: the semantics of the null statement is implemented by a single
2278 -- null statement, too bad everything isn't as simple as this!
2280 procedure Analyze_Null_Statement (N : Node_Id) is
2281 pragma Warnings (Off, N);
2284 end Analyze_Null_Statement;
2286 ------------------------
2287 -- Analyze_Statements --
2288 ------------------------
2290 procedure Analyze_Statements (L : List_Id) is
2295 -- The labels declared in the statement list are reachable from
2296 -- statements in the list. We do this as a prepass so that any
2297 -- goto statement will be properly flagged if its target is not
2298 -- reachable. This is not required, but is nice behavior!
2301 while Present (S) loop
2302 if Nkind (S) = N_Label then
2303 Analyze (Identifier (S));
2304 Lab := Entity (Identifier (S));
2306 -- If we found a label mark it as reachable
2308 if Ekind (Lab) = E_Label then
2309 Generate_Definition (Lab);
2310 Set_Reachable (Lab);
2312 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
2313 Set_Label_Construct (Parent (Lab), S);
2316 -- If we failed to find a label, it means the implicit declaration
2317 -- of the label was hidden. A for-loop parameter can do this to
2318 -- a label with the same name inside the loop, since the implicit
2319 -- label declaration is in the innermost enclosing body or block
2323 Error_Msg_Sloc := Sloc (Lab);
2325 ("implicit label declaration for & is hidden#",
2333 -- Perform semantic analysis on all statements
2335 Conditional_Statements_Begin;
2338 while Present (S) loop
2343 Conditional_Statements_End;
2345 -- Make labels unreachable. Visibility is not sufficient, because
2346 -- labels in one if-branch for example are not reachable from the
2347 -- other branch, even though their declarations are in the enclosing
2348 -- declarative part.
2351 while Present (S) loop
2352 if Nkind (S) = N_Label then
2353 Set_Reachable (Entity (Identifier (S)), False);
2358 end Analyze_Statements;
2360 ----------------------------
2361 -- Check_Unreachable_Code --
2362 ----------------------------
2364 procedure Check_Unreachable_Code (N : Node_Id) is
2365 Error_Loc : Source_Ptr;
2369 if Is_List_Member (N)
2370 and then Comes_From_Source (N)
2376 Nxt := Original_Node (Next (N));
2378 -- If a label follows us, then we never have dead code, since
2379 -- someone could branch to the label, so we just ignore it,
2380 -- unless we are in formal mode where goto statements are not
2383 if Nkind (Nxt) = N_Label and then not Formal_Verification_Mode then
2386 -- Otherwise see if we have a real statement following us
2389 and then Comes_From_Source (Nxt)
2390 and then Is_Statement (Nxt)
2392 -- Special very annoying exception. If we have a return that
2393 -- follows a raise, then we allow it without a warning, since
2394 -- the Ada RM annoyingly requires a useless return here!
2396 if Nkind (Original_Node (N)) /= N_Raise_Statement
2397 or else Nkind (Nxt) /= N_Simple_Return_Statement
2399 -- The rather strange shenanigans with the warning message
2400 -- here reflects the fact that Kill_Dead_Code is very good
2401 -- at removing warnings in deleted code, and this is one
2402 -- warning we would prefer NOT to have removed.
2404 Error_Loc := Sloc (Nxt);
2406 -- If we have unreachable code, analyze and remove the
2407 -- unreachable code, since it is useless and we don't
2408 -- want to generate junk warnings.
2410 -- We skip this step if we are not in code generation mode.
2411 -- This is the one case where we remove dead code in the
2412 -- semantics as opposed to the expander, and we do not want
2413 -- to remove code if we are not in code generation mode,
2414 -- since this messes up the ASIS trees.
2416 -- Note that one might react by moving the whole circuit to
2417 -- exp_ch5, but then we lose the warning in -gnatc mode.
2419 if Operating_Mode = Generate_Code then
2423 -- Quit deleting when we have nothing more to delete
2424 -- or if we hit a label (since someone could transfer
2425 -- control to a label, so we should not delete it).
2427 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2429 -- Statement/declaration is to be deleted
2433 Kill_Dead_Code (Nxt);
2437 -- Now issue the warning (or error in formal mode)
2439 if Formal_Verification_Mode then
2441 ("|~~unreachable code is not allowed", Error_Loc);
2443 Error_Msg ("?unreachable code!", Error_Loc);
2447 -- If the unconditional transfer of control instruction is
2448 -- the last statement of a sequence, then see if our parent
2449 -- is one of the constructs for which we count unblocked exits,
2450 -- and if so, adjust the count.
2455 -- Statements in THEN part or ELSE part of IF statement
2457 if Nkind (P) = N_If_Statement then
2460 -- Statements in ELSIF part of an IF statement
2462 elsif Nkind (P) = N_Elsif_Part then
2464 pragma Assert (Nkind (P) = N_If_Statement);
2466 -- Statements in CASE statement alternative
2468 elsif Nkind (P) = N_Case_Statement_Alternative then
2470 pragma Assert (Nkind (P) = N_Case_Statement);
2472 -- Statements in body of block
2474 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2475 and then Nkind (Parent (P)) = N_Block_Statement
2479 -- Statements in exception handler in a block
2481 elsif Nkind (P) = N_Exception_Handler
2482 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2483 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2487 -- None of these cases, so return
2493 -- This was one of the cases we are looking for (i.e. the
2494 -- parent construct was IF, CASE or block) so decrement count.
2496 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2500 end Check_Unreachable_Code;