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 Check_Formal_Restriction ("block statement is not allowed", N);
811 -- If no handled statement sequence is present, things are really
812 -- messed up, and we just return immediately (this is a defence
813 -- against previous errors).
819 -- Normal processing with HSS present
822 EH : constant List_Id := Exception_Handlers (HSS);
823 Ent : Entity_Id := Empty;
826 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
827 -- Recursively save value of this global, will be restored on exit
830 -- Initialize unblocked exit count for statements of begin block
831 -- plus one for each exception handler that is present.
833 Unblocked_Exit_Count := 1;
836 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
839 -- If a label is present analyze it and mark it as referenced
845 -- An error defense. If we have an identifier, but no entity,
846 -- then something is wrong. If we have previous errors, then
847 -- just remove the identifier and continue, otherwise raise
851 if Total_Errors_Detected /= 0 then
852 Set_Identifier (N, Empty);
858 Set_Ekind (Ent, E_Block);
859 Generate_Reference (Ent, N, ' ');
860 Generate_Definition (Ent);
862 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
863 Set_Label_Construct (Parent (Ent), N);
868 -- If no entity set, create a label entity
871 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
872 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
876 Set_Etype (Ent, Standard_Void_Type);
877 Set_Block_Node (Ent, Identifier (N));
880 if Present (Decls) then
881 Analyze_Declarations (Decls);
883 Inspect_Deferred_Constant_Completion (Decls);
887 Process_End_Label (HSS, 'e', Ent);
889 -- If exception handlers are present, then we indicate that
890 -- enclosing scopes contain a block with handlers. We only
891 -- need to mark non-generic scopes.
896 Set_Has_Nested_Block_With_Handler (S);
897 exit when Is_Overloadable (S)
898 or else Ekind (S) = E_Package
899 or else Is_Generic_Unit (S);
904 Check_References (Ent);
905 Warn_On_Useless_Assignments (Ent);
908 if Unblocked_Exit_Count = 0 then
909 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
910 Check_Unreachable_Code (N);
912 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
915 end Analyze_Block_Statement;
917 ----------------------------
918 -- Analyze_Case_Statement --
919 ----------------------------
921 procedure Analyze_Case_Statement (N : Node_Id) is
923 Exp_Type : Entity_Id;
924 Exp_Btype : Entity_Id;
927 Others_Present : Boolean;
929 pragma Warnings (Off, Last_Choice);
930 pragma Warnings (Off, Dont_Care);
931 -- Don't care about assigned values
933 Statements_Analyzed : Boolean := False;
934 -- Set True if at least some statement sequences get analyzed.
935 -- If False on exit, means we had a serious error that prevented
936 -- full analysis of the case statement, and as a result it is not
937 -- a good idea to output warning messages about unreachable code.
939 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
940 -- Recursively save value of this global, will be restored on exit
942 procedure Non_Static_Choice_Error (Choice : Node_Id);
943 -- Error routine invoked by the generic instantiation below when
944 -- the case statement has a non static choice.
946 procedure Process_Statements (Alternative : Node_Id);
947 -- Analyzes all the statements associated with a case alternative.
948 -- Needed by the generic instantiation below.
950 package Case_Choices_Processing is new
951 Generic_Choices_Processing
952 (Get_Alternatives => Alternatives,
953 Get_Choices => Discrete_Choices,
954 Process_Empty_Choice => No_OP,
955 Process_Non_Static_Choice => Non_Static_Choice_Error,
956 Process_Associated_Node => Process_Statements);
957 use Case_Choices_Processing;
958 -- Instantiation of the generic choice processing package
960 -----------------------------
961 -- Non_Static_Choice_Error --
962 -----------------------------
964 procedure Non_Static_Choice_Error (Choice : Node_Id) is
967 ("choice given in case statement is not static!", Choice);
968 end Non_Static_Choice_Error;
970 ------------------------
971 -- Process_Statements --
972 ------------------------
974 procedure Process_Statements (Alternative : Node_Id) is
975 Choices : constant List_Id := Discrete_Choices (Alternative);
979 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
980 Statements_Analyzed := True;
982 -- An interesting optimization. If the case statement expression
983 -- is a simple entity, then we can set the current value within
984 -- an alternative if the alternative has one possible value.
988 -- when 2 | 3 => beta
989 -- when others => gamma
991 -- Here we know that N is initially 1 within alpha, but for beta
992 -- and gamma, we do not know anything more about the initial value.
994 if Is_Entity_Name (Exp) then
997 if Ekind_In (Ent, E_Variable,
1001 if List_Length (Choices) = 1
1002 and then Nkind (First (Choices)) in N_Subexpr
1003 and then Compile_Time_Known_Value (First (Choices))
1005 Set_Current_Value (Entity (Exp), First (Choices));
1008 Analyze_Statements (Statements (Alternative));
1010 -- After analyzing the case, set the current value to empty
1011 -- since we won't know what it is for the next alternative
1012 -- (unless reset by this same circuit), or after the case.
1014 Set_Current_Value (Entity (Exp), Empty);
1019 -- Case where expression is not an entity name of a variable
1021 Analyze_Statements (Statements (Alternative));
1022 end Process_Statements;
1024 -- Start of processing for Analyze_Case_Statement
1027 Unblocked_Exit_Count := 0;
1028 Exp := Expression (N);
1031 -- The expression must be of any discrete type. In rare cases, the
1032 -- expander constructs a case statement whose expression has a private
1033 -- type whose full view is discrete. This can happen when generating
1034 -- a stream operation for a variant type after the type is frozen,
1035 -- when the partial of view of the type of the discriminant is private.
1036 -- In that case, use the full view to analyze case alternatives.
1038 if not Is_Overloaded (Exp)
1039 and then not Comes_From_Source (N)
1040 and then Is_Private_Type (Etype (Exp))
1041 and then Present (Full_View (Etype (Exp)))
1042 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1044 Resolve (Exp, Etype (Exp));
1045 Exp_Type := Full_View (Etype (Exp));
1048 Analyze_And_Resolve (Exp, Any_Discrete);
1049 Exp_Type := Etype (Exp);
1052 Check_Unset_Reference (Exp);
1053 Exp_Btype := Base_Type (Exp_Type);
1055 -- The expression must be of a discrete type which must be determinable
1056 -- independently of the context in which the expression occurs, but
1057 -- using the fact that the expression must be of a discrete type.
1058 -- Moreover, the type this expression must not be a character literal
1059 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1061 -- If error already reported by Resolve, nothing more to do
1063 if Exp_Btype = Any_Discrete
1064 or else Exp_Btype = Any_Type
1068 elsif Exp_Btype = Any_Character then
1070 ("character literal as case expression is ambiguous", Exp);
1073 elsif Ada_Version = Ada_83
1074 and then (Is_Generic_Type (Exp_Btype)
1075 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1078 ("(Ada 83) case expression cannot be of a generic type", Exp);
1082 -- If the case expression is a formal object of mode in out, then
1083 -- treat it as having a nonstatic subtype by forcing use of the base
1084 -- type (which has to get passed to Check_Case_Choices below). Also
1085 -- use base type when the case expression is parenthesized.
1087 if Paren_Count (Exp) > 0
1088 or else (Is_Entity_Name (Exp)
1089 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1091 Exp_Type := Exp_Btype;
1094 -- Call instantiated Analyze_Choices which does the rest of the work
1096 Analyze_Choices (N, Exp_Type, Dont_Care, Others_Present);
1098 -- A case statement with a single OTHERS alternative is not allowed
1099 -- in SPARK or ALFA.
1102 and then List_Length (Alternatives (N)) = 1
1104 Check_Formal_Restriction
1105 ("OTHERS as unique case alternative is not allowed", N);
1108 if Exp_Type = Universal_Integer and then not Others_Present then
1109 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1112 -- If all our exits were blocked by unconditional transfers of control,
1113 -- then the entire CASE statement acts as an unconditional transfer of
1114 -- control, so treat it like one, and check unreachable code. Skip this
1115 -- test if we had serious errors preventing any statement analysis.
1117 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1118 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1119 Check_Unreachable_Code (N);
1121 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1124 if not Expander_Active
1125 and then Compile_Time_Known_Value (Expression (N))
1126 and then Serious_Errors_Detected = 0
1129 Chosen : constant Node_Id := Find_Static_Alternative (N);
1133 Alt := First (Alternatives (N));
1134 while Present (Alt) loop
1135 if Alt /= Chosen then
1136 Remove_Warning_Messages (Statements (Alt));
1143 end Analyze_Case_Statement;
1145 ----------------------------
1146 -- Analyze_Exit_Statement --
1147 ----------------------------
1149 -- If the exit includes a name, it must be the name of a currently open
1150 -- loop. Otherwise there must be an innermost open loop on the stack,
1151 -- to which the statement implicitly refers.
1153 -- Additionally, in formal mode:
1154 -- * the exit can only name the closest enclosing loop;
1155 -- * an exit with a when clause must be directly contained in a loop;
1156 -- * an exit without a when clause must be directly contained in an
1157 -- if-statement with no elsif or else, which is itself directly contained
1158 -- in a loop. The exit must be the last statement in the if-statement.
1160 procedure Analyze_Exit_Statement (N : Node_Id) is
1161 Target : constant Node_Id := Name (N);
1162 Cond : constant Node_Id := Condition (N);
1163 Scope_Id : Entity_Id;
1169 Check_Unreachable_Code (N);
1172 if Present (Target) then
1174 U_Name := Entity (Target);
1176 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1177 Error_Msg_N ("invalid loop name in exit statement", N);
1180 if Has_Loop_In_Inner_Open_Scopes (U_Name) then
1181 Check_Formal_Restriction
1182 ("exit label must name the closest enclosing loop", N);
1185 Set_Has_Exit (U_Name);
1191 for J in reverse 0 .. Scope_Stack.Last loop
1192 Scope_Id := Scope_Stack.Table (J).Entity;
1193 Kind := Ekind (Scope_Id);
1196 and then (No (Target) or else Scope_Id = U_Name) then
1197 Set_Has_Exit (Scope_Id);
1200 elsif Kind = E_Block
1201 or else Kind = E_Loop
1202 or else Kind = E_Return_Statement
1208 ("cannot exit from program unit or accept statement", N);
1213 -- Verify that if present the condition is a Boolean expression
1215 if Present (Cond) then
1216 Analyze_And_Resolve (Cond, Any_Boolean);
1217 Check_Unset_Reference (Cond);
1220 -- In formal mode, verify that the exit statement respects the SPARK
1223 if Present (Cond) then
1224 if Nkind (Parent (N)) /= N_Loop_Statement then
1225 Check_Formal_Restriction
1226 ("exit with when clause must be directly in loop", N);
1230 if Nkind (Parent (N)) /= N_If_Statement then
1231 if Nkind (Parent (N)) = N_Elsif_Part then
1232 Check_Formal_Restriction
1233 ("exit must be in IF without ELSIF", N);
1235 Check_Formal_Restriction ("exit must be directly in IF", N);
1238 elsif Nkind (Parent (Parent (N))) /= N_Loop_Statement then
1239 Check_Formal_Restriction
1240 ("exit must be in IF directly in loop", N);
1242 -- First test the presence of ELSE, so that an exit in an ELSE
1243 -- leads to an error mentioning the ELSE.
1245 elsif Present (Else_Statements (Parent (N))) then
1246 Check_Formal_Restriction ("exit must be in IF without ELSE", N);
1248 -- An exit in an ELSIF does not reach here, as it would have been
1249 -- detected in the case (Nkind (Parent (N)) /= N_If_Statement).
1251 elsif Present (Elsif_Parts (Parent (N))) then
1252 Check_Formal_Restriction ("exit must be in IF without ELSIF", N);
1256 -- Chain exit statement to associated loop entity
1258 Set_Next_Exit_Statement (N, First_Exit_Statement (Scope_Id));
1259 Set_First_Exit_Statement (Scope_Id, N);
1261 -- Since the exit may take us out of a loop, any previous assignment
1262 -- statement is not useless, so clear last assignment indications. It
1263 -- is OK to keep other current values, since if the exit statement
1264 -- does not exit, then the current values are still valid.
1266 Kill_Current_Values (Last_Assignment_Only => True);
1267 end Analyze_Exit_Statement;
1269 ----------------------------
1270 -- Analyze_Goto_Statement --
1271 ----------------------------
1273 procedure Analyze_Goto_Statement (N : Node_Id) is
1274 Label : constant Node_Id := Name (N);
1275 Scope_Id : Entity_Id;
1276 Label_Scope : Entity_Id;
1277 Label_Ent : Entity_Id;
1280 Check_Formal_Restriction ("goto statement is not allowed", N);
1282 -- Actual semantic checks
1284 Check_Unreachable_Code (N);
1285 Kill_Current_Values (Last_Assignment_Only => True);
1288 Label_Ent := Entity (Label);
1290 -- Ignore previous error
1292 if Label_Ent = Any_Id then
1295 -- We just have a label as the target of a goto
1297 elsif Ekind (Label_Ent) /= E_Label then
1298 Error_Msg_N ("target of goto statement must be a label", Label);
1301 -- Check that the target of the goto is reachable according to Ada
1302 -- scoping rules. Note: the special gotos we generate for optimizing
1303 -- local handling of exceptions would violate these rules, but we mark
1304 -- such gotos as analyzed when built, so this code is never entered.
1306 elsif not Reachable (Label_Ent) then
1307 Error_Msg_N ("target of goto statement is not reachable", Label);
1311 -- Here if goto passes initial validity checks
1313 Label_Scope := Enclosing_Scope (Label_Ent);
1315 for J in reverse 0 .. Scope_Stack.Last loop
1316 Scope_Id := Scope_Stack.Table (J).Entity;
1318 if Label_Scope = Scope_Id
1319 or else (Ekind (Scope_Id) /= E_Block
1320 and then Ekind (Scope_Id) /= E_Loop
1321 and then Ekind (Scope_Id) /= E_Return_Statement)
1323 if Scope_Id /= Label_Scope then
1325 ("cannot exit from program unit or accept statement", N);
1332 raise Program_Error;
1333 end Analyze_Goto_Statement;
1335 --------------------------
1336 -- Analyze_If_Statement --
1337 --------------------------
1339 -- A special complication arises in the analysis of if statements
1341 -- The expander has circuitry to completely delete code that it
1342 -- can tell will not be executed (as a result of compile time known
1343 -- conditions). In the analyzer, we ensure that code that will be
1344 -- deleted in this manner is analyzed but not expanded. This is
1345 -- obviously more efficient, but more significantly, difficulties
1346 -- arise if code is expanded and then eliminated (e.g. exception
1347 -- table entries disappear). Similarly, itypes generated in deleted
1348 -- code must be frozen from start, because the nodes on which they
1349 -- depend will not be available at the freeze point.
1351 procedure Analyze_If_Statement (N : Node_Id) is
1354 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1355 -- Recursively save value of this global, will be restored on exit
1357 Save_In_Deleted_Code : Boolean;
1359 Del : Boolean := False;
1360 -- This flag gets set True if a True condition has been found,
1361 -- which means that remaining ELSE/ELSIF parts are deleted.
1363 procedure Analyze_Cond_Then (Cnode : Node_Id);
1364 -- This is applied to either the N_If_Statement node itself or
1365 -- to an N_Elsif_Part node. It deals with analyzing the condition
1366 -- and the THEN statements associated with it.
1368 -----------------------
1369 -- Analyze_Cond_Then --
1370 -----------------------
1372 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1373 Cond : constant Node_Id := Condition (Cnode);
1374 Tstm : constant List_Id := Then_Statements (Cnode);
1377 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1378 Analyze_And_Resolve (Cond, Any_Boolean);
1379 Check_Unset_Reference (Cond);
1380 Set_Current_Value_Condition (Cnode);
1382 -- If already deleting, then just analyze then statements
1385 Analyze_Statements (Tstm);
1387 -- Compile time known value, not deleting yet
1389 elsif Compile_Time_Known_Value (Cond) then
1390 Save_In_Deleted_Code := In_Deleted_Code;
1392 -- If condition is True, then analyze the THEN statements
1393 -- and set no expansion for ELSE and ELSIF parts.
1395 if Is_True (Expr_Value (Cond)) then
1396 Analyze_Statements (Tstm);
1398 Expander_Mode_Save_And_Set (False);
1399 In_Deleted_Code := True;
1401 -- If condition is False, analyze THEN with expansion off
1403 else -- Is_False (Expr_Value (Cond))
1404 Expander_Mode_Save_And_Set (False);
1405 In_Deleted_Code := True;
1406 Analyze_Statements (Tstm);
1407 Expander_Mode_Restore;
1408 In_Deleted_Code := Save_In_Deleted_Code;
1411 -- Not known at compile time, not deleting, normal analysis
1414 Analyze_Statements (Tstm);
1416 end Analyze_Cond_Then;
1418 -- Start of Analyze_If_Statement
1421 -- Initialize exit count for else statements. If there is no else
1422 -- part, this count will stay non-zero reflecting the fact that the
1423 -- uncovered else case is an unblocked exit.
1425 Unblocked_Exit_Count := 1;
1426 Analyze_Cond_Then (N);
1428 -- Now to analyze the elsif parts if any are present
1430 if Present (Elsif_Parts (N)) then
1431 E := First (Elsif_Parts (N));
1432 while Present (E) loop
1433 Analyze_Cond_Then (E);
1438 if Present (Else_Statements (N)) then
1439 Analyze_Statements (Else_Statements (N));
1442 -- If all our exits were blocked by unconditional transfers of control,
1443 -- then the entire IF statement acts as an unconditional transfer of
1444 -- control, so treat it like one, and check unreachable code.
1446 if Unblocked_Exit_Count = 0 then
1447 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1448 Check_Unreachable_Code (N);
1450 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1454 Expander_Mode_Restore;
1455 In_Deleted_Code := Save_In_Deleted_Code;
1458 if not Expander_Active
1459 and then Compile_Time_Known_Value (Condition (N))
1460 and then Serious_Errors_Detected = 0
1462 if Is_True (Expr_Value (Condition (N))) then
1463 Remove_Warning_Messages (Else_Statements (N));
1465 if Present (Elsif_Parts (N)) then
1466 E := First (Elsif_Parts (N));
1467 while Present (E) loop
1468 Remove_Warning_Messages (Then_Statements (E));
1474 Remove_Warning_Messages (Then_Statements (N));
1477 end Analyze_If_Statement;
1479 ----------------------------------------
1480 -- Analyze_Implicit_Label_Declaration --
1481 ----------------------------------------
1483 -- An implicit label declaration is generated in the innermost
1484 -- enclosing declarative part. This is done for labels as well as
1485 -- block and loop names.
1487 -- Note: any changes in this routine may need to be reflected in
1488 -- Analyze_Label_Entity.
1490 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1491 Id : constant Node_Id := Defining_Identifier (N);
1494 Set_Ekind (Id, E_Label);
1495 Set_Etype (Id, Standard_Void_Type);
1496 Set_Enclosing_Scope (Id, Current_Scope);
1497 end Analyze_Implicit_Label_Declaration;
1499 ------------------------------
1500 -- Analyze_Iteration_Scheme --
1501 ------------------------------
1503 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1505 procedure Process_Bounds (R : Node_Id);
1506 -- If the iteration is given by a range, create temporaries and
1507 -- assignment statements block to capture the bounds and perform
1508 -- required finalization actions in case a bound includes a function
1509 -- call that uses the temporary stack. We first pre-analyze a copy of
1510 -- the range in order to determine the expected type, and analyze and
1511 -- resolve the original bounds.
1513 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1514 -- If the bounds are given by a 'Range reference on a function call
1515 -- that returns a controlled array, introduce an explicit declaration
1516 -- to capture the bounds, so that the function result can be finalized
1517 -- in timely fashion.
1519 --------------------
1520 -- Process_Bounds --
1521 --------------------
1523 procedure Process_Bounds (R : Node_Id) is
1524 Loc : constant Source_Ptr := Sloc (N);
1525 R_Copy : constant Node_Id := New_Copy_Tree (R);
1526 Lo : constant Node_Id := Low_Bound (R);
1527 Hi : constant Node_Id := High_Bound (R);
1528 New_Lo_Bound : Node_Id;
1529 New_Hi_Bound : Node_Id;
1531 Save_Analysis : Boolean;
1534 (Original_Bound : Node_Id;
1535 Analyzed_Bound : Node_Id) return Node_Id;
1536 -- Capture value of bound and return captured value
1543 (Original_Bound : Node_Id;
1544 Analyzed_Bound : Node_Id) return Node_Id
1551 -- If the bound is a constant or an object, no need for a separate
1552 -- declaration. If the bound is the result of previous expansion
1553 -- it is already analyzed and should not be modified. Note that
1554 -- the Bound will be resolved later, if needed, as part of the
1555 -- call to Make_Index (literal bounds may need to be resolved to
1558 if Analyzed (Original_Bound) then
1559 return Original_Bound;
1561 elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
1562 N_Character_Literal)
1563 or else Is_Entity_Name (Analyzed_Bound)
1565 Analyze_And_Resolve (Original_Bound, Typ);
1566 return Original_Bound;
1569 -- Here we need to capture the value
1571 Analyze_And_Resolve (Original_Bound, Typ);
1573 Id := Make_Temporary (Loc, 'S', Original_Bound);
1575 -- Normally, the best approach is simply to generate a constant
1576 -- declaration that captures the bound. However, there is a nasty
1577 -- case where this is wrong. If the bound is complex, and has a
1578 -- possible use of the secondary stack, we need to generate a
1579 -- separate assignment statement to ensure the creation of a block
1580 -- which will release the secondary stack.
1582 -- We prefer the constant declaration, since it leaves us with a
1583 -- proper trace of the value, useful in optimizations that get rid
1584 -- of junk range checks.
1586 -- Probably we want something like the Side_Effect_Free routine
1587 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1588 -- and 'First applied to an entity, since these are the important
1589 -- cases for range check optimizations.
1591 if Nkind (Original_Bound) = N_Attribute_Reference
1592 and then (Attribute_Name (Original_Bound) = Name_First
1594 Attribute_Name (Original_Bound) = Name_Last)
1595 and then Is_Entity_Name (Prefix (Original_Bound))
1598 Make_Object_Declaration (Loc,
1599 Defining_Identifier => Id,
1600 Constant_Present => True,
1601 Object_Definition => New_Occurrence_Of (Typ, Loc),
1602 Expression => Relocate_Node (Original_Bound));
1604 -- Insert declaration at proper place. If loop comes from an
1605 -- enclosing quantified expression, the insertion point is
1606 -- arbitrarily far up in the tree.
1608 Insert_Action (Parent (N), Decl);
1609 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1610 return Expression (Decl);
1613 -- Here we make a declaration with a separate assignment
1614 -- statement, and insert before loop header.
1617 Make_Object_Declaration (Loc,
1618 Defining_Identifier => Id,
1619 Object_Definition => New_Occurrence_Of (Typ, Loc));
1622 Make_Assignment_Statement (Loc,
1623 Name => New_Occurrence_Of (Id, Loc),
1624 Expression => Relocate_Node (Original_Bound));
1626 Insert_Actions (Parent (N), New_List (Decl, Assign));
1628 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1630 if Nkind (Assign) = N_Assignment_Statement then
1631 return Expression (Assign);
1633 return Original_Bound;
1637 -- Start of processing for Process_Bounds
1640 -- Determine expected type of range by analyzing separate copy
1641 -- Do the analysis and resolution of the copy of the bounds with
1642 -- expansion disabled, to prevent the generation of finalization
1643 -- actions on each bound. This prevents memory leaks when the
1644 -- bounds contain calls to functions returning controlled arrays.
1646 Set_Parent (R_Copy, Parent (R));
1647 Save_Analysis := Full_Analysis;
1648 Full_Analysis := False;
1649 Expander_Mode_Save_And_Set (False);
1653 if Is_Overloaded (R_Copy) then
1655 -- Apply preference rules for range of predefined integer types,
1656 -- or diagnose true ambiguity.
1661 Found : Entity_Id := Empty;
1664 Get_First_Interp (R_Copy, I, It);
1665 while Present (It.Typ) loop
1666 if Is_Discrete_Type (It.Typ) then
1670 if Scope (Found) = Standard_Standard then
1673 elsif Scope (It.Typ) = Standard_Standard then
1677 -- Both of them are user-defined
1680 ("ambiguous bounds in range of iteration",
1682 Error_Msg_N ("\possible interpretations:", R_Copy);
1683 Error_Msg_NE ("\\} ", R_Copy, Found);
1684 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1690 Get_Next_Interp (I, It);
1696 Expander_Mode_Restore;
1697 Full_Analysis := Save_Analysis;
1699 Typ := Etype (R_Copy);
1701 -- If the type of the discrete range is Universal_Integer, then
1702 -- the bound's type must be resolved to Integer, and any object
1703 -- used to hold the bound must also have type Integer, unless the
1704 -- literal bounds are constant-folded expressions that carry a user-
1707 if Typ = Universal_Integer then
1708 if Nkind (Lo) = N_Integer_Literal
1709 and then Present (Etype (Lo))
1710 and then Scope (Etype (Lo)) /= Standard_Standard
1714 elsif Nkind (Hi) = N_Integer_Literal
1715 and then Present (Etype (Hi))
1716 and then Scope (Etype (Hi)) /= Standard_Standard
1721 Typ := Standard_Integer;
1727 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1728 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1730 -- Propagate staticness to loop range itself, in case the
1731 -- corresponding subtype is static.
1733 if New_Lo_Bound /= Lo
1734 and then Is_Static_Expression (New_Lo_Bound)
1736 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1739 if New_Hi_Bound /= Hi
1740 and then Is_Static_Expression (New_Hi_Bound)
1742 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1746 --------------------------------------
1747 -- Check_Controlled_Array_Attribute --
1748 --------------------------------------
1750 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1752 if Nkind (DS) = N_Attribute_Reference
1753 and then Is_Entity_Name (Prefix (DS))
1754 and then Ekind (Entity (Prefix (DS))) = E_Function
1755 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1758 Component_Type (Etype (Entity (Prefix (DS)))))
1759 and then Expander_Active
1762 Loc : constant Source_Ptr := Sloc (N);
1763 Arr : constant Entity_Id := Etype (Entity (Prefix (DS)));
1764 Indx : constant Entity_Id :=
1765 Base_Type (Etype (First_Index (Arr)));
1766 Subt : constant Entity_Id := Make_Temporary (Loc, 'S');
1771 Make_Subtype_Declaration (Loc,
1772 Defining_Identifier => Subt,
1773 Subtype_Indication =>
1774 Make_Subtype_Indication (Loc,
1775 Subtype_Mark => New_Reference_To (Indx, Loc),
1777 Make_Range_Constraint (Loc,
1778 Relocate_Node (DS))));
1779 Insert_Before (Parent (N), Decl);
1783 Make_Attribute_Reference (Loc,
1784 Prefix => New_Reference_To (Subt, Loc),
1785 Attribute_Name => Attribute_Name (DS)));
1789 end Check_Controlled_Array_Attribute;
1791 -- Start of processing for Analyze_Iteration_Scheme
1794 -- If this is a rewritten quantified expression, the iteration
1795 -- scheme has been analyzed already. Do no repeat analysis because
1796 -- the loop variable is already declared.
1798 if Analyzed (N) then
1802 -- For an infinite loop, there is no iteration scheme
1808 -- Iteration scheme is present
1811 Cond : constant Node_Id := Condition (N);
1814 -- For WHILE loop, verify that the condition is a Boolean
1815 -- expression and resolve and check it.
1817 if Present (Cond) then
1818 Analyze_And_Resolve (Cond, Any_Boolean);
1819 Check_Unset_Reference (Cond);
1820 Set_Current_Value_Condition (N);
1823 elsif Present (Iterator_Specification (N)) then
1824 Analyze_Iterator_Specification (Iterator_Specification (N));
1826 -- Else we have a FOR loop
1830 LP : constant Node_Id := Loop_Parameter_Specification (N);
1831 Id : constant Entity_Id := Defining_Identifier (LP);
1832 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1837 -- We always consider the loop variable to be referenced,
1838 -- since the loop may be used just for counting purposes.
1840 Generate_Reference (Id, N, ' ');
1842 -- Check for the case of loop variable hiding a local variable
1843 -- (used later on to give a nice warning if the hidden variable
1844 -- is never assigned).
1847 H : constant Entity_Id := Homonym (Id);
1850 and then Enclosing_Dynamic_Scope (H) =
1851 Enclosing_Dynamic_Scope (Id)
1852 and then Ekind (H) = E_Variable
1853 and then Is_Discrete_Type (Etype (H))
1855 Set_Hiding_Loop_Variable (H, Id);
1859 -- Loop parameter specification must include subtype mark in
1862 if Nkind (DS) = N_Range then
1863 Check_Formal_Restriction ("loop parameter specification "
1864 & "must include subtype mark", N);
1867 -- Now analyze the subtype definition. If it is a range, create
1868 -- temporaries for bounds.
1870 if Nkind (DS) = N_Range
1871 and then Expander_Active
1873 Process_Bounds (DS);
1875 -- Not a range or expander not active (is that right???)
1880 if Nkind (DS) = N_Function_Call
1882 (Is_Entity_Name (DS)
1883 and then not Is_Type (Entity (DS)))
1885 -- This is an iterator specification. Rewrite as such
1889 I_Spec : constant Node_Id :=
1890 Make_Iterator_Specification (Sloc (LP),
1891 Defining_Identifier =>
1895 Subtype_Indication =>
1898 Reverse_Present (LP));
1900 Set_Iterator_Specification (N, I_Spec);
1901 Set_Loop_Parameter_Specification (N, Empty);
1902 Analyze_Iterator_Specification (I_Spec);
1912 -- Some additional checks if we are iterating through a type
1914 if Is_Entity_Name (DS)
1915 and then Present (Entity (DS))
1916 and then Is_Type (Entity (DS))
1918 -- The subtype indication may denote the completion of an
1919 -- incomplete type declaration.
1921 if Ekind (Entity (DS)) = E_Incomplete_Type then
1922 Set_Entity (DS, Get_Full_View (Entity (DS)));
1923 Set_Etype (DS, Entity (DS));
1926 -- Attempt to iterate through non-static predicate
1928 if Is_Discrete_Type (Entity (DS))
1929 and then Present (Predicate_Function (Entity (DS)))
1930 and then No (Static_Predicate (Entity (DS)))
1932 Bad_Predicated_Subtype_Use
1933 ("cannot use subtype& with non-static "
1934 & "predicate for loop iteration", DS, Entity (DS));
1938 -- Error if not discrete type
1940 if not Is_Discrete_Type (Etype (DS)) then
1941 Wrong_Type (DS, Any_Discrete);
1942 Set_Etype (DS, Any_Type);
1945 Check_Controlled_Array_Attribute (DS);
1947 Make_Index (DS, LP);
1949 Set_Ekind (Id, E_Loop_Parameter);
1951 -- If the loop is part of a predicate or precondition, it may
1952 -- be analyzed twice, once in the source and once on the copy
1953 -- used to check conformance. Preserve the original itype
1954 -- because the second one may be created in a different scope,
1955 -- e.g. a precondition procedure, leading to a crash in GIGI.
1957 if No (Etype (Id)) or else Etype (Id) = Any_Type then
1958 Set_Etype (Id, Etype (DS));
1961 -- Treat a range as an implicit reference to the type, to
1962 -- inhibit spurious warnings.
1964 Generate_Reference (Base_Type (Etype (DS)), N, ' ');
1965 Set_Is_Known_Valid (Id, True);
1967 -- The loop is not a declarative part, so the only entity
1968 -- declared "within" must be frozen explicitly.
1971 Flist : constant List_Id := Freeze_Entity (Id, N);
1973 if Is_Non_Empty_List (Flist) then
1974 Insert_Actions (N, Flist);
1978 -- Check for null or possibly null range and issue warning. We
1979 -- suppress such messages in generic templates and instances,
1980 -- because in practice they tend to be dubious in these cases.
1982 if Nkind (DS) = N_Range and then Comes_From_Source (N) then
1984 L : constant Node_Id := Low_Bound (DS);
1985 H : constant Node_Id := High_Bound (DS);
1988 -- If range of loop is null, issue warning
1990 if Compile_Time_Compare
1991 (L, H, Assume_Valid => True) = GT
1993 -- Suppress the warning if inside a generic template
1994 -- or instance, since in practice they tend to be
1995 -- dubious in these cases since they can result from
1996 -- intended parametrization.
1998 if not Inside_A_Generic
1999 and then not In_Instance
2001 -- Specialize msg if invalid values could make
2002 -- the loop non-null after all.
2004 if Compile_Time_Compare
2005 (L, H, Assume_Valid => False) = GT
2008 ("?loop range is null, loop will not execute",
2011 -- Since we know the range of the loop is
2012 -- null, set the appropriate flag to remove
2013 -- the loop entirely during expansion.
2015 Set_Is_Null_Loop (Parent (N));
2017 -- Here is where the loop could execute because
2018 -- of invalid values, so issue appropriate
2019 -- message and in this case we do not set the
2020 -- Is_Null_Loop flag since the loop may execute.
2024 ("?loop range may be null, "
2025 & "loop may not execute",
2028 ("?can only execute if invalid values "
2034 -- In either case, suppress warnings in the body of
2035 -- the loop, since it is likely that these warnings
2036 -- will be inappropriate if the loop never actually
2037 -- executes, which is likely.
2039 Set_Suppress_Loop_Warnings (Parent (N));
2041 -- The other case for a warning is a reverse loop
2042 -- where the upper bound is the integer literal zero
2043 -- or one, and the lower bound can be positive.
2045 -- For example, we have
2047 -- for J in reverse N .. 1 loop
2049 -- In practice, this is very likely to be a case of
2050 -- reversing the bounds incorrectly in the range.
2052 elsif Reverse_Present (LP)
2053 and then Nkind (Original_Node (H)) =
2055 and then (Intval (Original_Node (H)) = Uint_0
2057 Intval (Original_Node (H)) = Uint_1)
2059 Error_Msg_N ("?loop range may be null", DS);
2060 Error_Msg_N ("\?bounds may be wrong way round", DS);
2067 end Analyze_Iteration_Scheme;
2069 -------------------------------------
2070 -- Analyze_Iterator_Specification --
2071 -------------------------------------
2073 procedure Analyze_Iterator_Specification (N : Node_Id) is
2074 Def_Id : constant Node_Id := Defining_Identifier (N);
2075 Subt : constant Node_Id := Subtype_Indication (N);
2076 Container : constant Node_Id := Name (N);
2082 Enter_Name (Def_Id);
2083 Set_Ekind (Def_Id, E_Variable);
2085 if Present (Subt) then
2089 Analyze_And_Resolve (Container);
2090 Typ := Etype (Container);
2092 if Is_Array_Type (Typ) then
2093 if Of_Present (N) then
2094 Set_Etype (Def_Id, Component_Type (Typ));
2097 ("to iterate over the elements of an array, use OF", N);
2098 Set_Etype (Def_Id, Etype (First_Index (Typ)));
2101 -- Iteration over a container
2104 Set_Ekind (Def_Id, E_Loop_Parameter);
2106 if Of_Present (N) then
2108 -- Find the Element_Type in the package instance that defines the
2111 Ent := First_Entity (Scope (Typ));
2112 while Present (Ent) loop
2113 if Chars (Ent) = Name_Element_Type then
2114 Set_Etype (Def_Id, Ent);
2122 -- Find the Cursor type in similar fashion
2124 Ent := First_Entity (Scope (Typ));
2125 while Present (Ent) loop
2126 if Chars (Ent) = Name_Cursor then
2127 Set_Etype (Def_Id, Ent);
2135 end Analyze_Iterator_Specification;
2141 -- Note: the semantic work required for analyzing labels (setting them as
2142 -- reachable) was done in a prepass through the statements in the block,
2143 -- so that forward gotos would be properly handled. See Analyze_Statements
2144 -- for further details. The only processing required here is to deal with
2145 -- optimizations that depend on an assumption of sequential control flow,
2146 -- since of course the occurrence of a label breaks this assumption.
2148 procedure Analyze_Label (N : Node_Id) is
2149 pragma Warnings (Off, N);
2151 Kill_Current_Values;
2154 --------------------------
2155 -- Analyze_Label_Entity --
2156 --------------------------
2158 procedure Analyze_Label_Entity (E : Entity_Id) is
2160 Set_Ekind (E, E_Label);
2161 Set_Etype (E, Standard_Void_Type);
2162 Set_Enclosing_Scope (E, Current_Scope);
2163 Set_Reachable (E, True);
2164 end Analyze_Label_Entity;
2166 ----------------------------
2167 -- Analyze_Loop_Statement --
2168 ----------------------------
2170 procedure Analyze_Loop_Statement (N : Node_Id) is
2171 Loop_Statement : constant Node_Id := N;
2173 Id : constant Node_Id := Identifier (Loop_Statement);
2174 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
2178 if Present (Id) then
2180 -- Make name visible, e.g. for use in exit statements. Loop
2181 -- labels are always considered to be referenced.
2186 -- Guard against serious error (typically, a scope mismatch when
2187 -- semantic analysis is requested) by creating loop entity to
2188 -- continue analysis.
2191 if Total_Errors_Detected /= 0 then
2194 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2196 raise Program_Error;
2200 Generate_Reference (Ent, Loop_Statement, ' ');
2201 Generate_Definition (Ent);
2203 -- If we found a label, mark its type. If not, ignore it, since it
2204 -- means we have a conflicting declaration, which would already
2205 -- have been diagnosed at declaration time. Set Label_Construct
2206 -- of the implicit label declaration, which is not created by the
2207 -- parser for generic units.
2209 if Ekind (Ent) = E_Label then
2210 Set_Ekind (Ent, E_Loop);
2212 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
2213 Set_Label_Construct (Parent (Ent), Loop_Statement);
2218 -- Case of no identifier present
2223 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2224 Set_Etype (Ent, Standard_Void_Type);
2225 Set_Parent (Ent, Loop_Statement);
2228 -- Kill current values on entry to loop, since statements in body of
2229 -- loop may have been executed before the loop is entered. Similarly we
2230 -- kill values after the loop, since we do not know that the body of the
2231 -- loop was executed.
2233 Kill_Current_Values;
2235 Analyze_Iteration_Scheme (Iter);
2236 Analyze_Statements (Statements (Loop_Statement));
2237 Process_End_Label (Loop_Statement, 'e', Ent);
2239 Kill_Current_Values;
2241 -- Check for infinite loop. Skip check for generated code, since it
2242 -- justs waste time and makes debugging the routine called harder.
2244 -- Note that we have to wait till the body of the loop is fully analyzed
2245 -- before making this call, since Check_Infinite_Loop_Warning relies on
2246 -- being able to use semantic visibility information to find references.
2248 if Comes_From_Source (N) then
2249 Check_Infinite_Loop_Warning (N);
2252 -- Code after loop is unreachable if the loop has no WHILE or FOR
2253 -- and contains no EXIT statements within the body of the loop.
2255 if No (Iter) and then not Has_Exit (Ent) then
2256 Check_Unreachable_Code (N);
2258 end Analyze_Loop_Statement;
2260 ----------------------------
2261 -- Analyze_Null_Statement --
2262 ----------------------------
2264 -- Note: the semantics of the null statement is implemented by a single
2265 -- null statement, too bad everything isn't as simple as this!
2267 procedure Analyze_Null_Statement (N : Node_Id) is
2268 pragma Warnings (Off, N);
2271 end Analyze_Null_Statement;
2273 ------------------------
2274 -- Analyze_Statements --
2275 ------------------------
2277 procedure Analyze_Statements (L : List_Id) is
2282 -- The labels declared in the statement list are reachable from
2283 -- statements in the list. We do this as a prepass so that any
2284 -- goto statement will be properly flagged if its target is not
2285 -- reachable. This is not required, but is nice behavior!
2288 while Present (S) loop
2289 if Nkind (S) = N_Label then
2290 Analyze (Identifier (S));
2291 Lab := Entity (Identifier (S));
2293 -- If we found a label mark it as reachable
2295 if Ekind (Lab) = E_Label then
2296 Generate_Definition (Lab);
2297 Set_Reachable (Lab);
2299 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
2300 Set_Label_Construct (Parent (Lab), S);
2303 -- If we failed to find a label, it means the implicit declaration
2304 -- of the label was hidden. A for-loop parameter can do this to
2305 -- a label with the same name inside the loop, since the implicit
2306 -- label declaration is in the innermost enclosing body or block
2310 Error_Msg_Sloc := Sloc (Lab);
2312 ("implicit label declaration for & is hidden#",
2320 -- Perform semantic analysis on all statements
2322 Conditional_Statements_Begin;
2325 while Present (S) loop
2330 Conditional_Statements_End;
2332 -- Make labels unreachable. Visibility is not sufficient, because
2333 -- labels in one if-branch for example are not reachable from the
2334 -- other branch, even though their declarations are in the enclosing
2335 -- declarative part.
2338 while Present (S) loop
2339 if Nkind (S) = N_Label then
2340 Set_Reachable (Entity (Identifier (S)), False);
2345 end Analyze_Statements;
2347 ----------------------------
2348 -- Check_Unreachable_Code --
2349 ----------------------------
2351 procedure Check_Unreachable_Code (N : Node_Id) is
2352 Error_Loc : Source_Ptr;
2356 if Is_List_Member (N)
2357 and then Comes_From_Source (N)
2363 Nxt := Original_Node (Next (N));
2365 -- If a label follows us, then we never have dead code, since
2366 -- someone could branch to the label, so we just ignore it,
2367 -- unless we are in formal mode where goto statements are not
2370 if Nkind (Nxt) = N_Label and then not Formal_Verification_Mode then
2373 -- Otherwise see if we have a real statement following us
2376 and then Comes_From_Source (Nxt)
2377 and then Is_Statement (Nxt)
2379 -- Special very annoying exception. If we have a return that
2380 -- follows a raise, then we allow it without a warning, since
2381 -- the Ada RM annoyingly requires a useless return here!
2383 if Nkind (Original_Node (N)) /= N_Raise_Statement
2384 or else Nkind (Nxt) /= N_Simple_Return_Statement
2386 -- The rather strange shenanigans with the warning message
2387 -- here reflects the fact that Kill_Dead_Code is very good
2388 -- at removing warnings in deleted code, and this is one
2389 -- warning we would prefer NOT to have removed.
2391 Error_Loc := Sloc (Nxt);
2393 -- If we have unreachable code, analyze and remove the
2394 -- unreachable code, since it is useless and we don't
2395 -- want to generate junk warnings.
2397 -- We skip this step if we are not in code generation mode.
2398 -- This is the one case where we remove dead code in the
2399 -- semantics as opposed to the expander, and we do not want
2400 -- to remove code if we are not in code generation mode,
2401 -- since this messes up the ASIS trees.
2403 -- Note that one might react by moving the whole circuit to
2404 -- exp_ch5, but then we lose the warning in -gnatc mode.
2406 if Operating_Mode = Generate_Code then
2410 -- Quit deleting when we have nothing more to delete
2411 -- or if we hit a label (since someone could transfer
2412 -- control to a label, so we should not delete it).
2414 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2416 -- Statement/declaration is to be deleted
2420 Kill_Dead_Code (Nxt);
2424 -- Now issue the warning (or error in formal mode)
2426 if Formal_Verification_Mode then
2428 ("|~~unreachable code is not allowed", Error_Loc);
2430 Error_Msg ("?unreachable code!", Error_Loc);
2434 -- If the unconditional transfer of control instruction is
2435 -- the last statement of a sequence, then see if our parent
2436 -- is one of the constructs for which we count unblocked exits,
2437 -- and if so, adjust the count.
2442 -- Statements in THEN part or ELSE part of IF statement
2444 if Nkind (P) = N_If_Statement then
2447 -- Statements in ELSIF part of an IF statement
2449 elsif Nkind (P) = N_Elsif_Part then
2451 pragma Assert (Nkind (P) = N_If_Statement);
2453 -- Statements in CASE statement alternative
2455 elsif Nkind (P) = N_Case_Statement_Alternative then
2457 pragma Assert (Nkind (P) = N_Case_Statement);
2459 -- Statements in body of block
2461 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2462 and then Nkind (Parent (P)) = N_Block_Statement
2466 -- Statements in exception handler in a block
2468 elsif Nkind (P) = N_Exception_Handler
2469 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2470 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2474 -- None of these cases, so return
2480 -- This was one of the cases we are looking for (i.e. the
2481 -- parent construct was IF, CASE or block) so decrement count.
2483 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2487 end Check_Unreachable_Code;