1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2005 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 2, 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 COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
25 ------------------------------------------------------------------------------
27 with Atree; use Atree;
28 with Checks; use Checks;
29 with Einfo; use Einfo;
30 with Errout; use Errout;
31 with Expander; use Expander;
32 with Exp_Util; use Exp_Util;
33 with Freeze; use Freeze;
34 with Lib.Xref; use Lib.Xref;
35 with Nlists; use Nlists;
36 with Nmake; use Nmake;
39 with Sem_Case; use Sem_Case;
40 with Sem_Ch3; use Sem_Ch3;
41 with Sem_Ch8; use Sem_Ch8;
42 with Sem_Disp; use Sem_Disp;
43 with Sem_Eval; use Sem_Eval;
44 with Sem_Res; use Sem_Res;
45 with Sem_Type; use Sem_Type;
46 with Sem_Util; use Sem_Util;
47 with Sem_Warn; use Sem_Warn;
48 with Stand; use Stand;
49 with Sinfo; use Sinfo;
50 with Targparm; use Targparm;
51 with Tbuild; use Tbuild;
52 with Uintp; use Uintp;
54 package body Sem_Ch5 is
56 Unblocked_Exit_Count : Nat := 0;
57 -- This variable is used when processing if statements, case statements,
58 -- and block statements. It counts the number of exit points that are
59 -- not blocked by unconditional transfer instructions (for IF and CASE,
60 -- these are the branches of the conditional, for a block, they are the
61 -- statement sequence of the block, and the statement sequences of any
62 -- exception handlers that are part of the block. When processing is
63 -- complete, if this count is zero, it means that control cannot fall
64 -- through the IF, CASE or block statement. This is used for the
65 -- generation of warning messages. This variable is recursively saved
66 -- on entry to processing the construct, and restored on exit.
68 -----------------------
69 -- Local Subprograms --
70 -----------------------
72 procedure Analyze_Iteration_Scheme (N : Node_Id);
74 procedure Check_Possible_Current_Value_Condition (Cnode : Node_Id);
75 -- Cnode is N_If_Statement, N_Elsif_Part, or N_Iteration_Scheme
76 -- (the latter when a WHILE condition is present). This call checks
77 -- if Condition (Cnode) is of the form ([NOT] var op val), where var
78 -- is a simple object, val is known at compile time, and op is one
79 -- of the six relational operators. If this is the case, and the
80 -- Current_Value field of "var" is not set, then it is set to Cnode.
81 -- See Exp_Util.Set_Current_Value_Condition for further details.
83 ------------------------
84 -- Analyze_Assignment --
85 ------------------------
87 procedure Analyze_Assignment (N : Node_Id) is
88 Lhs : constant Node_Id := Name (N);
89 Rhs : constant Node_Id := Expression (N);
95 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
96 -- N is the node for the left hand side of an assignment, and it
97 -- is not a variable. This routine issues an appropriate diagnostic.
99 procedure Set_Assignment_Type
101 Opnd_Type : in out Entity_Id);
102 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
103 -- is the nominal subtype. This procedure is used to deal with cases
104 -- where the nominal subtype must be replaced by the actual subtype.
106 -------------------------------
107 -- Diagnose_Non_Variable_Lhs --
108 -------------------------------
110 procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
112 -- Not worth posting another error if left hand side already
113 -- flagged as being illegal in some respect
115 if Error_Posted (N) then
118 -- Some special bad cases of entity names
120 elsif Is_Entity_Name (N) then
121 if Ekind (Entity (N)) = E_In_Parameter then
123 ("assignment to IN mode parameter not allowed", N);
125 -- Private declarations in a protected object are turned into
126 -- constants when compiling a protected function.
128 elsif Present (Scope (Entity (N)))
129 and then Is_Protected_Type (Scope (Entity (N)))
131 (Ekind (Current_Scope) = E_Function
133 Ekind (Enclosing_Dynamic_Scope (Current_Scope)) = E_Function)
136 ("protected function cannot modify protected object", N);
138 elsif Ekind (Entity (N)) = E_Loop_Parameter then
140 ("assignment to loop parameter not allowed", N);
144 ("left hand side of assignment must be a variable", N);
147 -- For indexed components or selected components, test prefix
149 elsif Nkind (N) = N_Indexed_Component then
150 Diagnose_Non_Variable_Lhs (Prefix (N));
152 -- Another special case for assignment to discriminant
154 elsif Nkind (N) = N_Selected_Component then
155 if Present (Entity (Selector_Name (N)))
156 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
159 ("assignment to discriminant not allowed", N);
161 Diagnose_Non_Variable_Lhs (Prefix (N));
165 -- If we fall through, we have no special message to issue!
167 Error_Msg_N ("left hand side of assignment must be a variable", N);
169 end Diagnose_Non_Variable_Lhs;
171 -------------------------
172 -- Set_Assignment_Type --
173 -------------------------
175 procedure Set_Assignment_Type
177 Opnd_Type : in out Entity_Id)
180 Require_Entity (Opnd);
182 -- If the assignment operand is an in-out or out parameter, then we
183 -- get the actual subtype (needed for the unconstrained case).
184 -- If the operand is the actual in an entry declaration, then within
185 -- the accept statement it is replaced with a local renaming, which
186 -- may also have an actual subtype.
188 if Is_Entity_Name (Opnd)
189 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
190 or else Ekind (Entity (Opnd)) =
192 or else Ekind (Entity (Opnd)) =
193 E_Generic_In_Out_Parameter
195 (Ekind (Entity (Opnd)) = E_Variable
196 and then Nkind (Parent (Entity (Opnd))) =
197 N_Object_Renaming_Declaration
198 and then Nkind (Parent (Parent (Entity (Opnd)))) =
201 Opnd_Type := Get_Actual_Subtype (Opnd);
203 -- If assignment operand is a component reference, then we get the
204 -- actual subtype of the component for the unconstrained case.
207 (Nkind (Opnd) = N_Selected_Component
208 or else Nkind (Opnd) = N_Explicit_Dereference)
209 and then not Is_Unchecked_Union (Opnd_Type)
211 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
213 if Present (Decl) then
214 Insert_Action (N, Decl);
215 Mark_Rewrite_Insertion (Decl);
217 Opnd_Type := Defining_Identifier (Decl);
218 Set_Etype (Opnd, Opnd_Type);
219 Freeze_Itype (Opnd_Type, N);
221 elsif Is_Constrained (Etype (Opnd)) then
222 Opnd_Type := Etype (Opnd);
225 -- For slice, use the constrained subtype created for the slice
227 elsif Nkind (Opnd) = N_Slice then
228 Opnd_Type := Etype (Opnd);
230 end Set_Assignment_Type;
232 -- Start of processing for Analyze_Assignment
239 -- In the most general case, both Lhs and Rhs can be overloaded, and we
240 -- must compute the intersection of the possible types on each side.
242 if Is_Overloaded (Lhs) then
249 Get_First_Interp (Lhs, I, It);
251 while Present (It.Typ) loop
252 if Has_Compatible_Type (Rhs, It.Typ) then
253 if T1 /= Any_Type then
255 -- An explicit dereference is overloaded if the prefix
256 -- is. Try to remove the ambiguity on the prefix, the
257 -- error will be posted there if the ambiguity is real.
259 if Nkind (Lhs) = N_Explicit_Dereference then
262 PI1 : Interp_Index := 0;
268 Get_First_Interp (Prefix (Lhs), PI, PIt);
270 while Present (PIt.Typ) loop
271 if Is_Access_Type (PIt.Typ)
272 and then Has_Compatible_Type
273 (Rhs, Designated_Type (PIt.Typ))
277 Disambiguate (Prefix (Lhs),
280 if PIt = No_Interp then
282 ("ambiguous left-hand side"
283 & " in assignment", Lhs);
286 Resolve (Prefix (Lhs), PIt.Typ);
296 Get_Next_Interp (PI, PIt);
302 ("ambiguous left-hand side in assignment", Lhs);
310 Get_Next_Interp (I, It);
314 if T1 = Any_Type then
316 ("no valid types for left-hand side for assignment", Lhs);
323 if not Is_Variable (Lhs) then
324 Diagnose_Non_Variable_Lhs (Lhs);
327 elsif Is_Limited_Type (T1)
328 and then not Assignment_OK (Lhs)
329 and then not Assignment_OK (Original_Node (Lhs))
332 ("left hand of assignment must not be limited type", Lhs);
333 Explain_Limited_Type (T1, Lhs);
337 -- Resolution may have updated the subtype, in case the left-hand
338 -- side is a private protected component. Use the correct subtype
339 -- to avoid scoping issues in the back-end.
343 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
344 -- type. For example:
348 -- type Acc is access P.T;
351 -- with Pkg; use Acc;
352 -- procedure Example is
355 -- A.all := B.all; -- ERROR
358 if Nkind (Lhs) = N_Explicit_Dereference
359 and then Ekind (T1) = E_Incomplete_Type
361 Error_Msg_N ("invalid use of incomplete type", Lhs);
365 Set_Assignment_Type (Lhs, T1);
368 Check_Unset_Reference (Rhs);
370 -- Remaining steps are skipped if Rhs was syntactically in error
378 if Covers (T1, T2) then
381 Wrong_Type (Rhs, Etype (Lhs));
385 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
386 -- types, use the non-limited view if available
388 if Nkind (Rhs) = N_Explicit_Dereference
389 and then Ekind (T2) = E_Incomplete_Type
390 and then Is_Tagged_Type (T2)
391 and then Present (Non_Limited_View (T2))
393 T2 := Non_Limited_View (T2);
396 Set_Assignment_Type (Rhs, T2);
398 if Total_Errors_Detected /= 0 then
408 if T1 = Any_Type or else T2 = Any_Type then
412 if (Is_Class_Wide_Type (T2) or else Is_Dynamically_Tagged (Rhs))
413 and then not Is_Class_Wide_Type (T1)
415 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
417 elsif Is_Class_Wide_Type (T1)
418 and then not Is_Class_Wide_Type (T2)
419 and then not Is_Tag_Indeterminate (Rhs)
420 and then not Is_Dynamically_Tagged (Rhs)
422 Error_Msg_N ("dynamically tagged expression required!", Rhs);
425 -- Tag propagation is done only in semantics mode only. If expansion
426 -- is on, the rhs tag indeterminate function call has been expanded
427 -- and tag propagation would have happened too late, so the
428 -- propagation take place in expand_call instead.
430 if not Expander_Active
431 and then Is_Class_Wide_Type (T1)
432 and then Is_Tag_Indeterminate (Rhs)
434 Propagate_Tag (Lhs, Rhs);
437 -- Ada 2005 (AI-230 and AI-385): When the lhs type is an anonymous
438 -- access type, apply an implicit conversion of the rhs to that type
439 -- to force appropriate static and run-time accessibility checks.
441 if Ada_Version >= Ada_05
442 and then Ekind (T1) = E_Anonymous_Access_Type
444 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
445 Analyze_And_Resolve (Rhs, T1);
450 if Ada_Version >= Ada_05
451 and then Nkind (Rhs) = N_Null
452 and then Is_Access_Type (T1)
453 and then not Assignment_OK (Lhs)
454 and then ((Is_Entity_Name (Lhs)
455 and then Can_Never_Be_Null (Entity (Lhs)))
456 or else Can_Never_Be_Null (Etype (Lhs)))
458 Apply_Compile_Time_Constraint_Error
460 Msg => "(Ada 2005) NULL not allowed in null-excluding objects?",
461 Reason => CE_Null_Not_Allowed);
464 if Is_Scalar_Type (T1) then
465 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
467 elsif Is_Array_Type (T1)
469 (Nkind (Rhs) /= N_Type_Conversion
470 or else Is_Constrained (Etype (Rhs)))
472 -- Assignment verifies that the length of the Lsh and Rhs are equal,
473 -- but of course the indices do not have to match. If the right-hand
474 -- side is a type conversion to an unconstrained type, a length check
475 -- is performed on the expression itself during expansion. In rare
476 -- cases, the redundant length check is computed on an index type
477 -- with a different representation, triggering incorrect code in
480 Apply_Length_Check (Rhs, Etype (Lhs));
483 -- Discriminant checks are applied in the course of expansion
488 -- Note: modifications of the Lhs may only be recorded after
489 -- checks have been applied.
491 Note_Possible_Modification (Lhs);
493 -- ??? a real accessibility check is needed when ???
495 -- Post warning for useless assignment
497 if Warn_On_Redundant_Constructs
499 -- We only warn for source constructs
501 and then Comes_From_Source (N)
503 -- Where the entity is the same on both sides
505 and then Is_Entity_Name (Lhs)
506 and then Is_Entity_Name (Original_Node (Rhs))
507 and then Entity (Lhs) = Entity (Original_Node (Rhs))
509 -- But exclude the case where the right side was an operation
510 -- that got rewritten (e.g. JUNK + K, where K was known to be
511 -- zero). We don't want to warn in such a case, since it is
512 -- reasonable to write such expressions especially when K is
513 -- defined symbolically in some other package.
515 and then Nkind (Original_Node (Rhs)) not in N_Op
518 ("?useless assignment of & to itself", N, Entity (Lhs));
521 -- Check for non-allowed composite assignment
523 if not Support_Composite_Assign_On_Target
524 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
525 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
527 Error_Msg_CRT ("composite assignment", N);
530 -- One more step. Let's see if we have a simple assignment of a
531 -- known at compile time value to a simple variable. If so, we
532 -- can record the value as the current value providing that:
534 -- We still have a simple assignment statement (no expansion
535 -- activity has modified it in some peculiar manner)
537 -- The type is a discrete type
539 -- The assignment is to a named entity
541 -- The value is known at compile time
543 if Nkind (N) /= N_Assignment_Statement
544 or else not Is_Discrete_Type (T1)
545 or else not Is_Entity_Name (Lhs)
546 or else not Compile_Time_Known_Value (Rhs)
553 -- Capture value if save to do so
555 if Safe_To_Capture_Value (N, Ent) then
556 Set_Current_Value (Ent, Rhs);
558 end Analyze_Assignment;
560 -----------------------------
561 -- Analyze_Block_Statement --
562 -----------------------------
564 procedure Analyze_Block_Statement (N : Node_Id) is
565 Decls : constant List_Id := Declarations (N);
566 Id : constant Node_Id := Identifier (N);
567 HSS : constant Node_Id := Handled_Statement_Sequence (N);
570 -- If no handled statement sequence is present, things are really
571 -- messed up, and we just return immediately (this is a defence
572 -- against previous errors).
578 -- Normal processing with HSS present
581 EH : constant List_Id := Exception_Handlers (HSS);
582 Ent : Entity_Id := Empty;
585 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
586 -- Recursively save value of this global, will be restored on exit
589 -- Initialize unblocked exit count for statements of begin block
590 -- plus one for each excption handler that is present.
592 Unblocked_Exit_Count := 1;
595 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
598 -- If a label is present analyze it and mark it as referenced
604 -- An error defense. If we have an identifier, but no entity,
605 -- then something is wrong. If we have previous errors, then
606 -- just remove the identifier and continue, otherwise raise
610 if Total_Errors_Detected /= 0 then
611 Set_Identifier (N, Empty);
617 Set_Ekind (Ent, E_Block);
618 Generate_Reference (Ent, N, ' ');
619 Generate_Definition (Ent);
621 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
622 Set_Label_Construct (Parent (Ent), N);
627 -- If no entity set, create a label entity
630 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
631 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
635 Set_Etype (Ent, Standard_Void_Type);
636 Set_Block_Node (Ent, Identifier (N));
639 if Present (Decls) then
640 Analyze_Declarations (Decls);
645 Process_End_Label (HSS, 'e', Ent);
647 -- If exception handlers are present, then we indicate that
648 -- enclosing scopes contain a block with handlers. We only
649 -- need to mark non-generic scopes.
654 Set_Has_Nested_Block_With_Handler (S);
655 exit when Is_Overloadable (S)
656 or else Ekind (S) = E_Package
657 or else Is_Generic_Unit (S);
662 Check_References (Ent);
665 if Unblocked_Exit_Count = 0 then
666 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
667 Check_Unreachable_Code (N);
669 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
672 end Analyze_Block_Statement;
674 ----------------------------
675 -- Analyze_Case_Statement --
676 ----------------------------
678 procedure Analyze_Case_Statement (N : Node_Id) is
680 Exp_Type : Entity_Id;
681 Exp_Btype : Entity_Id;
684 Others_Present : Boolean;
686 Statements_Analyzed : Boolean := False;
687 -- Set True if at least some statement sequences get analyzed.
688 -- If False on exit, means we had a serious error that prevented
689 -- full analysis of the case statement, and as a result it is not
690 -- a good idea to output warning messages about unreachable code.
692 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
693 -- Recursively save value of this global, will be restored on exit
695 procedure Non_Static_Choice_Error (Choice : Node_Id);
696 -- Error routine invoked by the generic instantiation below when
697 -- the case statment has a non static choice.
699 procedure Process_Statements (Alternative : Node_Id);
700 -- Analyzes all the statements associated to a case alternative.
701 -- Needed by the generic instantiation below.
703 package Case_Choices_Processing is new
704 Generic_Choices_Processing
705 (Get_Alternatives => Alternatives,
706 Get_Choices => Discrete_Choices,
707 Process_Empty_Choice => No_OP,
708 Process_Non_Static_Choice => Non_Static_Choice_Error,
709 Process_Associated_Node => Process_Statements);
710 use Case_Choices_Processing;
711 -- Instantiation of the generic choice processing package
713 -----------------------------
714 -- Non_Static_Choice_Error --
715 -----------------------------
717 procedure Non_Static_Choice_Error (Choice : Node_Id) is
720 ("choice given in case statement is not static!", Choice);
721 end Non_Static_Choice_Error;
723 ------------------------
724 -- Process_Statements --
725 ------------------------
727 procedure Process_Statements (Alternative : Node_Id) is
728 Choices : constant List_Id := Discrete_Choices (Alternative);
732 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
733 Statements_Analyzed := True;
735 -- An interesting optimization. If the case statement expression
736 -- is a simple entity, then we can set the current value within
737 -- an alternative if the alternative has one possible value.
741 -- when 2 | 3 => beta
742 -- when others => gamma
744 -- Here we know that N is initially 1 within alpha, but for beta
745 -- and gamma, we do not know anything more about the initial value.
747 if Is_Entity_Name (Exp) then
750 if Ekind (Ent) = E_Variable
752 Ekind (Ent) = E_In_Out_Parameter
754 Ekind (Ent) = E_Out_Parameter
756 if List_Length (Choices) = 1
757 and then Nkind (First (Choices)) in N_Subexpr
758 and then Compile_Time_Known_Value (First (Choices))
760 Set_Current_Value (Entity (Exp), First (Choices));
763 Analyze_Statements (Statements (Alternative));
765 -- After analyzing the case, set the current value to empty
766 -- since we won't know what it is for the next alternative
767 -- (unless reset by this same circuit), or after the case.
769 Set_Current_Value (Entity (Exp), Empty);
774 -- Case where expression is not an entity name of a variable
776 Analyze_Statements (Statements (Alternative));
777 end Process_Statements;
779 -- Table to record choices. Put after subprograms since we make
780 -- a call to Number_Of_Choices to get the right number of entries.
782 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
784 -- Start of processing for Analyze_Case_Statement
787 Unblocked_Exit_Count := 0;
788 Exp := Expression (N);
791 -- The expression must be of any discrete type. In rare cases, the
792 -- expander constructs a case statement whose expression has a private
793 -- type whose full view is discrete. This can happen when generating
794 -- a stream operation for a variant type after the type is frozen,
795 -- when the partial of view of the type of the discriminant is private.
796 -- In that case, use the full view to analyze case alternatives.
798 if not Is_Overloaded (Exp)
799 and then not Comes_From_Source (N)
800 and then Is_Private_Type (Etype (Exp))
801 and then Present (Full_View (Etype (Exp)))
802 and then Is_Discrete_Type (Full_View (Etype (Exp)))
804 Resolve (Exp, Etype (Exp));
805 Exp_Type := Full_View (Etype (Exp));
808 Analyze_And_Resolve (Exp, Any_Discrete);
809 Exp_Type := Etype (Exp);
812 Check_Unset_Reference (Exp);
813 Exp_Btype := Base_Type (Exp_Type);
815 -- The expression must be of a discrete type which must be determinable
816 -- independently of the context in which the expression occurs, but
817 -- using the fact that the expression must be of a discrete type.
818 -- Moreover, the type this expression must not be a character literal
819 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
821 -- If error already reported by Resolve, nothing more to do
823 if Exp_Btype = Any_Discrete
824 or else Exp_Btype = Any_Type
828 elsif Exp_Btype = Any_Character then
830 ("character literal as case expression is ambiguous", Exp);
833 elsif Ada_Version = Ada_83
834 and then (Is_Generic_Type (Exp_Btype)
835 or else Is_Generic_Type (Root_Type (Exp_Btype)))
838 ("(Ada 83) case expression cannot be of a generic type", Exp);
842 -- If the case expression is a formal object of mode in out, then
843 -- treat it as having a nonstatic subtype by forcing use of the base
844 -- type (which has to get passed to Check_Case_Choices below). Also
845 -- use base type when the case expression is parenthesized.
847 if Paren_Count (Exp) > 0
848 or else (Is_Entity_Name (Exp)
849 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
851 Exp_Type := Exp_Btype;
854 -- Call instantiated Analyze_Choices which does the rest of the work
857 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
859 if Exp_Type = Universal_Integer and then not Others_Present then
860 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
863 -- If all our exits were blocked by unconditional transfers of control,
864 -- then the entire CASE statement acts as an unconditional transfer of
865 -- control, so treat it like one, and check unreachable code. Skip this
866 -- test if we had serious errors preventing any statement analysis.
868 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
869 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
870 Check_Unreachable_Code (N);
872 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
875 if not Expander_Active
876 and then Compile_Time_Known_Value (Expression (N))
877 and then Serious_Errors_Detected = 0
880 Chosen : constant Node_Id := Find_Static_Alternative (N);
884 Alt := First (Alternatives (N));
886 while Present (Alt) loop
887 if Alt /= Chosen then
888 Remove_Warning_Messages (Statements (Alt));
895 end Analyze_Case_Statement;
897 ----------------------------
898 -- Analyze_Exit_Statement --
899 ----------------------------
901 -- If the exit includes a name, it must be the name of a currently open
902 -- loop. Otherwise there must be an innermost open loop on the stack,
903 -- to which the statement implicitly refers.
905 procedure Analyze_Exit_Statement (N : Node_Id) is
906 Target : constant Node_Id := Name (N);
907 Cond : constant Node_Id := Condition (N);
908 Scope_Id : Entity_Id;
914 Check_Unreachable_Code (N);
917 if Present (Target) then
919 U_Name := Entity (Target);
921 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
922 Error_Msg_N ("invalid loop name in exit statement", N);
925 Set_Has_Exit (U_Name);
932 for J in reverse 0 .. Scope_Stack.Last loop
933 Scope_Id := Scope_Stack.Table (J).Entity;
934 Kind := Ekind (Scope_Id);
937 and then (No (Target) or else Scope_Id = U_Name) then
938 Set_Has_Exit (Scope_Id);
941 elsif Kind = E_Block or else Kind = E_Loop then
946 ("cannot exit from program unit or accept statement", N);
951 -- Verify that if present the condition is a Boolean expression
953 if Present (Cond) then
954 Analyze_And_Resolve (Cond, Any_Boolean);
955 Check_Unset_Reference (Cond);
957 end Analyze_Exit_Statement;
959 ----------------------------
960 -- Analyze_Goto_Statement --
961 ----------------------------
963 procedure Analyze_Goto_Statement (N : Node_Id) is
964 Label : constant Node_Id := Name (N);
965 Scope_Id : Entity_Id;
966 Label_Scope : Entity_Id;
969 Check_Unreachable_Code (N);
973 if Entity (Label) = Any_Id then
976 elsif Ekind (Entity (Label)) /= E_Label then
977 Error_Msg_N ("target of goto statement must be a label", Label);
980 elsif not Reachable (Entity (Label)) then
981 Error_Msg_N ("target of goto statement is not reachable", Label);
985 Label_Scope := Enclosing_Scope (Entity (Label));
987 for J in reverse 0 .. Scope_Stack.Last loop
988 Scope_Id := Scope_Stack.Table (J).Entity;
990 if Label_Scope = Scope_Id
991 or else (Ekind (Scope_Id) /= E_Block
992 and then Ekind (Scope_Id) /= E_Loop)
994 if Scope_Id /= Label_Scope then
996 ("cannot exit from program unit or accept statement", N);
1003 raise Program_Error;
1004 end Analyze_Goto_Statement;
1006 --------------------------
1007 -- Analyze_If_Statement --
1008 --------------------------
1010 -- A special complication arises in the analysis of if statements
1012 -- The expander has circuitry to completely delete code that it
1013 -- can tell will not be executed (as a result of compile time known
1014 -- conditions). In the analyzer, we ensure that code that will be
1015 -- deleted in this manner is analyzed but not expanded. This is
1016 -- obviously more efficient, but more significantly, difficulties
1017 -- arise if code is expanded and then eliminated (e.g. exception
1018 -- table entries disappear). Similarly, itypes generated in deleted
1019 -- code must be frozen from start, because the nodes on which they
1020 -- depend will not be available at the freeze point.
1022 procedure Analyze_If_Statement (N : Node_Id) is
1025 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1026 -- Recursively save value of this global, will be restored on exit
1028 Save_In_Deleted_Code : Boolean;
1030 Del : Boolean := False;
1031 -- This flag gets set True if a True condition has been found,
1032 -- which means that remaining ELSE/ELSIF parts are deleted.
1034 procedure Analyze_Cond_Then (Cnode : Node_Id);
1035 -- This is applied to either the N_If_Statement node itself or
1036 -- to an N_Elsif_Part node. It deals with analyzing the condition
1037 -- and the THEN statements associated with it.
1039 -----------------------
1040 -- Analyze_Cond_Then --
1041 -----------------------
1043 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1044 Cond : constant Node_Id := Condition (Cnode);
1045 Tstm : constant List_Id := Then_Statements (Cnode);
1048 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1049 Analyze_And_Resolve (Cond, Any_Boolean);
1050 Check_Unset_Reference (Cond);
1051 Check_Possible_Current_Value_Condition (Cnode);
1053 -- If already deleting, then just analyze then statements
1056 Analyze_Statements (Tstm);
1058 -- Compile time known value, not deleting yet
1060 elsif Compile_Time_Known_Value (Cond) then
1061 Save_In_Deleted_Code := In_Deleted_Code;
1063 -- If condition is True, then analyze the THEN statements
1064 -- and set no expansion for ELSE and ELSIF parts.
1066 if Is_True (Expr_Value (Cond)) then
1067 Analyze_Statements (Tstm);
1069 Expander_Mode_Save_And_Set (False);
1070 In_Deleted_Code := True;
1072 -- If condition is False, analyze THEN with expansion off
1074 else -- Is_False (Expr_Value (Cond))
1075 Expander_Mode_Save_And_Set (False);
1076 In_Deleted_Code := True;
1077 Analyze_Statements (Tstm);
1078 Expander_Mode_Restore;
1079 In_Deleted_Code := Save_In_Deleted_Code;
1082 -- Not known at compile time, not deleting, normal analysis
1085 Analyze_Statements (Tstm);
1087 end Analyze_Cond_Then;
1089 -- Start of Analyze_If_Statement
1092 -- Initialize exit count for else statements. If there is no else
1093 -- part, this count will stay non-zero reflecting the fact that the
1094 -- uncovered else case is an unblocked exit.
1096 Unblocked_Exit_Count := 1;
1097 Analyze_Cond_Then (N);
1099 -- Now to analyze the elsif parts if any are present
1101 if Present (Elsif_Parts (N)) then
1102 E := First (Elsif_Parts (N));
1103 while Present (E) loop
1104 Analyze_Cond_Then (E);
1109 if Present (Else_Statements (N)) then
1110 Analyze_Statements (Else_Statements (N));
1113 -- If all our exits were blocked by unconditional transfers of control,
1114 -- then the entire IF statement acts as an unconditional transfer of
1115 -- control, so treat it like one, and check unreachable code.
1117 if Unblocked_Exit_Count = 0 then
1118 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1119 Check_Unreachable_Code (N);
1121 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1125 Expander_Mode_Restore;
1126 In_Deleted_Code := Save_In_Deleted_Code;
1129 if not Expander_Active
1130 and then Compile_Time_Known_Value (Condition (N))
1131 and then Serious_Errors_Detected = 0
1133 if Is_True (Expr_Value (Condition (N))) then
1134 Remove_Warning_Messages (Else_Statements (N));
1136 if Present (Elsif_Parts (N)) then
1137 E := First (Elsif_Parts (N));
1139 while Present (E) loop
1140 Remove_Warning_Messages (Then_Statements (E));
1146 Remove_Warning_Messages (Then_Statements (N));
1149 end Analyze_If_Statement;
1151 ----------------------------------------
1152 -- Analyze_Implicit_Label_Declaration --
1153 ----------------------------------------
1155 -- An implicit label declaration is generated in the innermost
1156 -- enclosing declarative part. This is done for labels as well as
1157 -- block and loop names.
1159 -- Note: any changes in this routine may need to be reflected in
1160 -- Analyze_Label_Entity.
1162 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1163 Id : constant Node_Id := Defining_Identifier (N);
1166 Set_Ekind (Id, E_Label);
1167 Set_Etype (Id, Standard_Void_Type);
1168 Set_Enclosing_Scope (Id, Current_Scope);
1169 end Analyze_Implicit_Label_Declaration;
1171 ------------------------------
1172 -- Analyze_Iteration_Scheme --
1173 ------------------------------
1175 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1177 procedure Process_Bounds (R : Node_Id);
1178 -- If the iteration is given by a range, create temporaries and
1179 -- assignment statements block to capture the bounds and perform
1180 -- required finalization actions in case a bound includes a function
1181 -- call that uses the temporary stack. We first pre-analyze a copy of
1182 -- the range in order to determine the expected type, and analyze and
1183 -- resolve the original bounds.
1185 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1186 -- If the bounds are given by a 'Range reference on a function call
1187 -- that returns a controlled array, introduce an explicit declaration
1188 -- to capture the bounds, so that the function result can be finalized
1189 -- in timely fashion.
1191 --------------------
1192 -- Process_Bounds --
1193 --------------------
1195 procedure Process_Bounds (R : Node_Id) is
1196 Loc : constant Source_Ptr := Sloc (N);
1197 R_Copy : constant Node_Id := New_Copy_Tree (R);
1198 Lo : constant Node_Id := Low_Bound (R);
1199 Hi : constant Node_Id := High_Bound (R);
1200 New_Lo_Bound : Node_Id := Empty;
1201 New_Hi_Bound : Node_Id := Empty;
1205 (Original_Bound : Node_Id;
1206 Analyzed_Bound : Node_Id) return Node_Id;
1207 -- Create one declaration followed by one assignment statement
1208 -- to capture the value of bound. We create a separate assignment
1209 -- in order to force the creation of a block in case the bound
1210 -- contains a call that uses the secondary stack.
1217 (Original_Bound : Node_Id;
1218 Analyzed_Bound : Node_Id) return Node_Id
1225 -- If the bound is a constant or an object, no need for a separate
1226 -- declaration. If the bound is the result of previous expansion
1227 -- it is already analyzed and should not be modified. Note that
1228 -- the Bound will be resolved later, if needed, as part of the
1229 -- call to Make_Index (literal bounds may need to be resolved to
1232 if Analyzed (Original_Bound) then
1233 return Original_Bound;
1235 elsif Nkind (Analyzed_Bound) = N_Integer_Literal
1236 or else Is_Entity_Name (Analyzed_Bound)
1238 Analyze_And_Resolve (Original_Bound, Typ);
1239 return Original_Bound;
1242 Analyze_And_Resolve (Original_Bound, Typ);
1246 Make_Defining_Identifier (Loc,
1247 Chars => New_Internal_Name ('S'));
1250 Make_Object_Declaration (Loc,
1251 Defining_Identifier => Id,
1252 Object_Definition => New_Occurrence_Of (Typ, Loc));
1254 Insert_Before (Parent (N), Decl);
1258 Make_Assignment_Statement (Loc,
1259 Name => New_Occurrence_Of (Id, Loc),
1260 Expression => Relocate_Node (Original_Bound));
1262 Insert_Before (Parent (N), Assign);
1265 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1267 if Nkind (Assign) = N_Assignment_Statement then
1268 return Expression (Assign);
1270 return Original_Bound;
1274 -- Start of processing for Process_Bounds
1277 -- Determine expected type of range by analyzing separate copy.
1279 Set_Parent (R_Copy, Parent (R));
1280 Pre_Analyze_And_Resolve (R_Copy);
1281 Typ := Etype (R_Copy);
1283 -- If the type of the discrete range is Universal_Integer, then
1284 -- the bound's type must be resolved to Integer, and any object
1285 -- used to hold the bound must also have type Integer.
1287 if Typ = Universal_Integer then
1288 Typ := Standard_Integer;
1293 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1294 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1296 -- Propagate staticness to loop range itself, in case the
1297 -- corresponding subtype is static.
1299 if New_Lo_Bound /= Lo
1300 and then Is_Static_Expression (New_Lo_Bound)
1302 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1305 if New_Hi_Bound /= Hi
1306 and then Is_Static_Expression (New_Hi_Bound)
1308 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1312 --------------------------------------
1313 -- Check_Controlled_Array_Attribute --
1314 --------------------------------------
1316 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1318 if Nkind (DS) = N_Attribute_Reference
1319 and then Is_Entity_Name (Prefix (DS))
1320 and then Ekind (Entity (Prefix (DS))) = E_Function
1321 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1324 Component_Type (Etype (Entity (Prefix (DS)))))
1325 and then Expander_Active
1328 Loc : constant Source_Ptr := Sloc (N);
1329 Arr : constant Entity_Id :=
1330 Etype (Entity (Prefix (DS)));
1331 Indx : constant Entity_Id :=
1332 Base_Type (Etype (First_Index (Arr)));
1333 Subt : constant Entity_Id :=
1334 Make_Defining_Identifier
1335 (Loc, New_Internal_Name ('S'));
1340 Make_Subtype_Declaration (Loc,
1341 Defining_Identifier => Subt,
1342 Subtype_Indication =>
1343 Make_Subtype_Indication (Loc,
1344 Subtype_Mark => New_Reference_To (Indx, Loc),
1346 Make_Range_Constraint (Loc,
1347 Relocate_Node (DS))));
1348 Insert_Before (Parent (N), Decl);
1352 Make_Attribute_Reference (Loc,
1353 Prefix => New_Reference_To (Subt, Loc),
1354 Attribute_Name => Attribute_Name (DS)));
1358 end Check_Controlled_Array_Attribute;
1360 -- Start of processing for Analyze_Iteration_Scheme
1363 -- For an infinite loop, there is no iteration scheme
1370 Cond : constant Node_Id := Condition (N);
1373 -- For WHILE loop, verify that the condition is a Boolean
1374 -- expression and resolve and check it.
1376 if Present (Cond) then
1377 Analyze_And_Resolve (Cond, Any_Boolean);
1378 Check_Unset_Reference (Cond);
1380 -- Else we have a FOR loop
1384 LP : constant Node_Id := Loop_Parameter_Specification (N);
1385 Id : constant Entity_Id := Defining_Identifier (LP);
1386 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1391 -- We always consider the loop variable to be referenced,
1392 -- since the loop may be used just for counting purposes.
1394 Generate_Reference (Id, N, ' ');
1396 -- Check for case of loop variable hiding a local
1397 -- variable (used later on to give a nice warning
1398 -- if the hidden variable is never assigned).
1401 H : constant Entity_Id := Homonym (Id);
1404 and then Enclosing_Dynamic_Scope (H) =
1405 Enclosing_Dynamic_Scope (Id)
1406 and then Ekind (H) = E_Variable
1407 and then Is_Discrete_Type (Etype (H))
1409 Set_Hiding_Loop_Variable (H, Id);
1413 -- Now analyze the subtype definition. If it is
1414 -- a range, create temporaries for bounds.
1416 if Nkind (DS) = N_Range
1417 and then Expander_Active
1419 Process_Bounds (DS);
1428 -- The subtype indication may denote the completion
1429 -- of an incomplete type declaration.
1431 if Is_Entity_Name (DS)
1432 and then Present (Entity (DS))
1433 and then Is_Type (Entity (DS))
1434 and then Ekind (Entity (DS)) = E_Incomplete_Type
1436 Set_Entity (DS, Get_Full_View (Entity (DS)));
1437 Set_Etype (DS, Entity (DS));
1440 if not Is_Discrete_Type (Etype (DS)) then
1441 Wrong_Type (DS, Any_Discrete);
1442 Set_Etype (DS, Any_Type);
1445 Check_Controlled_Array_Attribute (DS);
1447 Make_Index (DS, LP);
1449 Set_Ekind (Id, E_Loop_Parameter);
1450 Set_Etype (Id, Etype (DS));
1451 Set_Is_Known_Valid (Id, True);
1453 -- The loop is not a declarative part, so the only entity
1454 -- declared "within" must be frozen explicitly.
1457 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1459 if Is_Non_Empty_List (Flist) then
1460 Insert_Actions (N, Flist);
1464 -- Check for null or possibly null range and issue warning.
1465 -- We suppress such messages in generic templates and
1466 -- instances, because in practice they tend to be dubious
1469 if Nkind (DS) = N_Range
1470 and then Comes_From_Source (N)
1473 L : constant Node_Id := Low_Bound (DS);
1474 H : constant Node_Id := High_Bound (DS);
1484 Determine_Range (L, LOK, Llo, Lhi);
1485 Determine_Range (H, HOK, Hlo, Hhi);
1487 -- If range of loop is null, issue warning
1489 if (LOK and HOK) and then Llo > Hhi then
1491 -- Suppress the warning if inside a generic
1492 -- template or instance, since in practice
1493 -- they tend to be dubious in these cases since
1494 -- they can result from intended parametrization.
1496 if not Inside_A_Generic
1497 and then not In_Instance
1500 ("?loop range is null, loop will not execute",
1504 -- Since we know the range of the loop is null,
1505 -- set the appropriate flag to suppress any
1506 -- warnings that would otherwise be issued in
1507 -- the body of the loop that will not execute.
1508 -- We do this even in the generic case, since
1509 -- if it is dubious to warn on the null loop
1510 -- itself, it is certainly dubious to warn for
1511 -- conditions that occur inside it!
1513 Set_Is_Null_Loop (Parent (N));
1515 -- The other case for a warning is a reverse loop
1516 -- where the upper bound is the integer literal
1517 -- zero or one, and the lower bound can be positive.
1519 -- For example, we have
1521 -- for J in reverse N .. 1 loop
1523 -- In practice, this is very likely to be a case
1524 -- of reversing the bounds incorrectly in the range.
1526 elsif Reverse_Present (LP)
1527 and then Nkind (H) = N_Integer_Literal
1528 and then (Intval (H) = Uint_0
1530 Intval (H) = Uint_1)
1533 Error_Msg_N ("?loop range may be null", DS);
1541 end Analyze_Iteration_Scheme;
1547 -- Note: the semantic work required for analyzing labels (setting them as
1548 -- reachable) was done in a prepass through the statements in the block,
1549 -- so that forward gotos would be properly handled. See Analyze_Statements
1550 -- for further details. The only processing required here is to deal with
1551 -- optimizations that depend on an assumption of sequential control flow,
1552 -- since of course the occurrence of a label breaks this assumption.
1554 procedure Analyze_Label (N : Node_Id) is
1555 pragma Warnings (Off, N);
1557 Kill_Current_Values;
1560 --------------------------
1561 -- Analyze_Label_Entity --
1562 --------------------------
1564 procedure Analyze_Label_Entity (E : Entity_Id) is
1566 Set_Ekind (E, E_Label);
1567 Set_Etype (E, Standard_Void_Type);
1568 Set_Enclosing_Scope (E, Current_Scope);
1569 Set_Reachable (E, True);
1570 end Analyze_Label_Entity;
1572 ----------------------------
1573 -- Analyze_Loop_Statement --
1574 ----------------------------
1576 procedure Analyze_Loop_Statement (N : Node_Id) is
1577 Id : constant Node_Id := Identifier (N);
1581 if Present (Id) then
1583 -- Make name visible, e.g. for use in exit statements. Loop
1584 -- labels are always considered to be referenced.
1588 Generate_Reference (Ent, N, ' ');
1589 Generate_Definition (Ent);
1591 -- If we found a label, mark its type. If not, ignore it, since it
1592 -- means we have a conflicting declaration, which would already have
1593 -- been diagnosed at declaration time. Set Label_Construct of the
1594 -- implicit label declaration, which is not created by the parser
1595 -- for generic units.
1597 if Ekind (Ent) = E_Label then
1598 Set_Ekind (Ent, E_Loop);
1600 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
1601 Set_Label_Construct (Parent (Ent), N);
1605 -- Case of no identifier present
1608 Ent := New_Internal_Entity (E_Loop, Current_Scope, Sloc (N), 'L');
1609 Set_Etype (Ent, Standard_Void_Type);
1610 Set_Parent (Ent, N);
1613 -- Kill current values on entry to loop, since statements in body
1614 -- of loop may have been executed before the loop is entered.
1615 -- Similarly we kill values after the loop, since we do not know
1616 -- that the body of the loop was executed.
1618 Kill_Current_Values;
1620 Analyze_Iteration_Scheme (Iteration_Scheme (N));
1621 Analyze_Statements (Statements (N));
1622 Process_End_Label (N, 'e', Ent);
1624 Kill_Current_Values;
1625 end Analyze_Loop_Statement;
1627 ----------------------------
1628 -- Analyze_Null_Statement --
1629 ----------------------------
1631 -- Note: the semantics of the null statement is implemented by a single
1632 -- null statement, too bad everything isn't as simple as this!
1634 procedure Analyze_Null_Statement (N : Node_Id) is
1635 pragma Warnings (Off, N);
1638 end Analyze_Null_Statement;
1640 ------------------------
1641 -- Analyze_Statements --
1642 ------------------------
1644 procedure Analyze_Statements (L : List_Id) is
1649 -- The labels declared in the statement list are reachable from
1650 -- statements in the list. We do this as a prepass so that any
1651 -- goto statement will be properly flagged if its target is not
1652 -- reachable. This is not required, but is nice behavior!
1655 while Present (S) loop
1656 if Nkind (S) = N_Label then
1657 Analyze (Identifier (S));
1658 Lab := Entity (Identifier (S));
1660 -- If we found a label mark it as reachable
1662 if Ekind (Lab) = E_Label then
1663 Generate_Definition (Lab);
1664 Set_Reachable (Lab);
1666 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
1667 Set_Label_Construct (Parent (Lab), S);
1670 -- If we failed to find a label, it means the implicit declaration
1671 -- of the label was hidden. A for-loop parameter can do this to
1672 -- a label with the same name inside the loop, since the implicit
1673 -- label declaration is in the innermost enclosing body or block
1677 Error_Msg_Sloc := Sloc (Lab);
1679 ("implicit label declaration for & is hidden#",
1687 -- Perform semantic analysis on all statements
1689 Conditional_Statements_Begin;
1692 while Present (S) loop
1697 Conditional_Statements_End;
1699 -- Make labels unreachable. Visibility is not sufficient, because
1700 -- labels in one if-branch for example are not reachable from the
1701 -- other branch, even though their declarations are in the enclosing
1702 -- declarative part.
1705 while Present (S) loop
1706 if Nkind (S) = N_Label then
1707 Set_Reachable (Entity (Identifier (S)), False);
1712 end Analyze_Statements;
1714 --------------------------------------------
1715 -- Check_Possible_Current_Value_Condition --
1716 --------------------------------------------
1718 procedure Check_Possible_Current_Value_Condition (Cnode : Node_Id) is
1722 -- Loop to deal with (ignore for now) any NOT operators present
1724 Cond := Condition (Cnode);
1725 while Nkind (Cond) = N_Op_Not loop
1726 Cond := Right_Opnd (Cond);
1729 -- Check possible relational operator
1731 if Nkind (Cond) = N_Op_Eq
1733 Nkind (Cond) = N_Op_Ne
1735 Nkind (Cond) = N_Op_Ge
1737 Nkind (Cond) = N_Op_Le
1739 Nkind (Cond) = N_Op_Gt
1741 Nkind (Cond) = N_Op_Lt
1743 if Compile_Time_Known_Value (Right_Opnd (Cond))
1744 and then Nkind (Left_Opnd (Cond)) = N_Identifier
1747 Ent : constant Entity_Id := Entity (Left_Opnd (Cond));
1750 if Ekind (Ent) = E_Variable
1752 Ekind (Ent) = E_Constant
1756 Ekind (Ent) = E_Loop_Parameter
1758 -- Here we have a case where the Current_Value field
1759 -- may need to be set. We set it if it is not already
1760 -- set to a compile time expression value.
1762 -- Note that this represents a decision that one
1763 -- condition blots out another previous one. That's
1764 -- certainly right if they occur at the same level.
1765 -- If the second one is nested, then the decision is
1766 -- neither right nor wrong (it would be equally OK
1767 -- to leave the outer one in place, or take the new
1768 -- inner one. Really we should record both, but our
1769 -- data structures are not that elaborate.
1771 if Nkind (Current_Value (Ent)) not in N_Subexpr then
1772 Set_Current_Value (Ent, Cnode);
1778 end Check_Possible_Current_Value_Condition;
1780 ----------------------------
1781 -- Check_Unreachable_Code --
1782 ----------------------------
1784 procedure Check_Unreachable_Code (N : Node_Id) is
1785 Error_Loc : Source_Ptr;
1789 if Is_List_Member (N)
1790 and then Comes_From_Source (N)
1796 Nxt := Original_Node (Next (N));
1798 -- If a label follows us, then we never have dead code, since
1799 -- someone could branch to the label, so we just ignore it.
1801 if Nkind (Nxt) = N_Label then
1804 -- Otherwise see if we have a real statement following us
1807 and then Comes_From_Source (Nxt)
1808 and then Is_Statement (Nxt)
1810 -- Special very annoying exception. If we have a return that
1811 -- follows a raise, then we allow it without a warning, since
1812 -- the Ada RM annoyingly requires a useless return here!
1814 if Nkind (Original_Node (N)) /= N_Raise_Statement
1815 or else Nkind (Nxt) /= N_Return_Statement
1817 -- The rather strange shenanigans with the warning message
1818 -- here reflects the fact that Kill_Dead_Code is very good
1819 -- at removing warnings in deleted code, and this is one
1820 -- warning we would prefer NOT to have removed :-)
1822 Error_Loc := Sloc (Nxt);
1824 -- If we have unreachable code, analyze and remove the
1825 -- unreachable code, since it is useless and we don't
1826 -- want to generate junk warnings.
1828 -- We skip this step if we are not in code generation mode.
1829 -- This is the one case where we remove dead code in the
1830 -- semantics as opposed to the expander, and we do not want
1831 -- to remove code if we are not in code generation mode,
1832 -- since this messes up the ASIS trees.
1834 -- Note that one might react by moving the whole circuit to
1835 -- exp_ch5, but then we lose the warning in -gnatc mode.
1837 if Operating_Mode = Generate_Code then
1841 -- Quit deleting when we have nothing more to delete
1842 -- or if we hit a label (since someone could transfer
1843 -- control to a label, so we should not delete it).
1845 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
1847 -- Statement/declaration is to be deleted
1851 Kill_Dead_Code (Nxt);
1855 -- Now issue the warning
1857 Error_Msg ("?unreachable code", Error_Loc);
1860 -- If the unconditional transfer of control instruction is
1861 -- the last statement of a sequence, then see if our parent
1862 -- is one of the constructs for which we count unblocked exits,
1863 -- and if so, adjust the count.
1868 -- Statements in THEN part or ELSE part of IF statement
1870 if Nkind (P) = N_If_Statement then
1873 -- Statements in ELSIF part of an IF statement
1875 elsif Nkind (P) = N_Elsif_Part then
1877 pragma Assert (Nkind (P) = N_If_Statement);
1879 -- Statements in CASE statement alternative
1881 elsif Nkind (P) = N_Case_Statement_Alternative then
1883 pragma Assert (Nkind (P) = N_Case_Statement);
1885 -- Statements in body of block
1887 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
1888 and then Nkind (Parent (P)) = N_Block_Statement
1892 -- Statements in exception handler in a block
1894 elsif Nkind (P) = N_Exception_Handler
1895 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
1896 and then Nkind (Parent (Parent (P))) = N_Block_Statement
1900 -- None of these cases, so return
1906 -- This was one of the cases we are looking for (i.e. the
1907 -- parent construct was IF, CASE or block) so decrement count.
1909 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
1913 end Check_Unreachable_Code;