1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2006, 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 ------------------------
75 -- Analyze_Assignment --
76 ------------------------
78 procedure Analyze_Assignment (N : Node_Id) is
79 Lhs : constant Node_Id := Name (N);
80 Rhs : constant Node_Id := Expression (N);
85 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
86 -- N is the node for the left hand side of an assignment, and it
87 -- is not a variable. This routine issues an appropriate diagnostic.
90 -- This is called to kill current value settings of a simple variable
91 -- on the left hand side. We call it if we find any error in analyzing
92 -- the assignment, and at the end of processing before setting any new
93 -- current values in place.
95 procedure Set_Assignment_Type
97 Opnd_Type : in out Entity_Id);
98 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
99 -- is the nominal subtype. This procedure is used to deal with cases
100 -- where the nominal subtype must be replaced by the actual subtype.
102 -------------------------------
103 -- Diagnose_Non_Variable_Lhs --
104 -------------------------------
106 procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
108 -- Not worth posting another error if left hand side already
109 -- flagged as being illegal in some respect
111 if Error_Posted (N) then
114 -- Some special bad cases of entity names
116 elsif Is_Entity_Name (N) then
117 if Ekind (Entity (N)) = E_In_Parameter then
119 ("assignment to IN mode parameter not allowed", N);
121 -- Private declarations in a protected object are turned into
122 -- constants when compiling a protected function.
124 elsif Present (Scope (Entity (N)))
125 and then Is_Protected_Type (Scope (Entity (N)))
127 (Ekind (Current_Scope) = E_Function
129 Ekind (Enclosing_Dynamic_Scope (Current_Scope)) = E_Function)
132 ("protected function cannot modify protected object", N);
134 elsif Ekind (Entity (N)) = E_Loop_Parameter then
136 ("assignment to loop parameter not allowed", N);
140 ("left hand side of assignment must be a variable", N);
143 -- For indexed components or selected components, test prefix
145 elsif Nkind (N) = N_Indexed_Component then
146 Diagnose_Non_Variable_Lhs (Prefix (N));
148 -- Another special case for assignment to discriminant
150 elsif Nkind (N) = N_Selected_Component then
151 if Present (Entity (Selector_Name (N)))
152 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
155 ("assignment to discriminant not allowed", N);
157 Diagnose_Non_Variable_Lhs (Prefix (N));
161 -- If we fall through, we have no special message to issue!
163 Error_Msg_N ("left hand side of assignment must be a variable", N);
165 end Diagnose_Non_Variable_Lhs;
171 procedure Kill_Lhs is
173 if Is_Entity_Name (Lhs) then
175 Ent : constant Entity_Id := Entity (Lhs);
177 if Present (Ent) then
178 Kill_Current_Values (Ent);
184 -------------------------
185 -- Set_Assignment_Type --
186 -------------------------
188 procedure Set_Assignment_Type
190 Opnd_Type : in out Entity_Id)
193 Require_Entity (Opnd);
195 -- If the assignment operand is an in-out or out parameter, then we
196 -- get the actual subtype (needed for the unconstrained case).
197 -- If the operand is the actual in an entry declaration, then within
198 -- the accept statement it is replaced with a local renaming, which
199 -- may also have an actual subtype.
201 if Is_Entity_Name (Opnd)
202 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
203 or else Ekind (Entity (Opnd)) =
205 or else Ekind (Entity (Opnd)) =
206 E_Generic_In_Out_Parameter
208 (Ekind (Entity (Opnd)) = E_Variable
209 and then Nkind (Parent (Entity (Opnd))) =
210 N_Object_Renaming_Declaration
211 and then Nkind (Parent (Parent (Entity (Opnd)))) =
214 Opnd_Type := Get_Actual_Subtype (Opnd);
216 -- If assignment operand is a component reference, then we get the
217 -- actual subtype of the component for the unconstrained case.
220 (Nkind (Opnd) = N_Selected_Component
221 or else Nkind (Opnd) = N_Explicit_Dereference)
222 and then not Is_Unchecked_Union (Opnd_Type)
224 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
226 if Present (Decl) then
227 Insert_Action (N, Decl);
228 Mark_Rewrite_Insertion (Decl);
230 Opnd_Type := Defining_Identifier (Decl);
231 Set_Etype (Opnd, Opnd_Type);
232 Freeze_Itype (Opnd_Type, N);
234 elsif Is_Constrained (Etype (Opnd)) then
235 Opnd_Type := Etype (Opnd);
238 -- For slice, use the constrained subtype created for the slice
240 elsif Nkind (Opnd) = N_Slice then
241 Opnd_Type := Etype (Opnd);
243 end Set_Assignment_Type;
245 -- Start of processing for Analyze_Assignment
251 -- Start type analysis for assignment
255 -- In the most general case, both Lhs and Rhs can be overloaded, and we
256 -- must compute the intersection of the possible types on each side.
258 if Is_Overloaded (Lhs) then
265 Get_First_Interp (Lhs, I, It);
267 while Present (It.Typ) loop
268 if Has_Compatible_Type (Rhs, It.Typ) then
269 if T1 /= Any_Type then
271 -- An explicit dereference is overloaded if the prefix
272 -- is. Try to remove the ambiguity on the prefix, the
273 -- error will be posted there if the ambiguity is real.
275 if Nkind (Lhs) = N_Explicit_Dereference then
278 PI1 : Interp_Index := 0;
284 Get_First_Interp (Prefix (Lhs), PI, PIt);
286 while Present (PIt.Typ) loop
287 if Is_Access_Type (PIt.Typ)
288 and then Has_Compatible_Type
289 (Rhs, Designated_Type (PIt.Typ))
293 Disambiguate (Prefix (Lhs),
296 if PIt = No_Interp then
298 ("ambiguous left-hand side"
299 & " in assignment", Lhs);
302 Resolve (Prefix (Lhs), PIt.Typ);
312 Get_Next_Interp (PI, PIt);
318 ("ambiguous left-hand side in assignment", Lhs);
326 Get_Next_Interp (I, It);
330 if T1 = Any_Type then
332 ("no valid types for left-hand side for assignment", Lhs);
340 if not Is_Variable (Lhs) then
341 Diagnose_Non_Variable_Lhs (Lhs);
344 elsif Is_Limited_Type (T1)
345 and then not Assignment_OK (Lhs)
346 and then not Assignment_OK (Original_Node (Lhs))
349 ("left hand of assignment must not be limited type", Lhs);
350 Explain_Limited_Type (T1, Lhs);
354 -- Resolution may have updated the subtype, in case the left-hand
355 -- side is a private protected component. Use the correct subtype
356 -- to avoid scoping issues in the back-end.
360 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
361 -- type. For example:
365 -- type Acc is access P.T;
368 -- with Pkg; use Acc;
369 -- procedure Example is
372 -- A.all := B.all; -- ERROR
375 if Nkind (Lhs) = N_Explicit_Dereference
376 and then Ekind (T1) = E_Incomplete_Type
378 Error_Msg_N ("invalid use of incomplete type", Lhs);
383 Set_Assignment_Type (Lhs, T1);
386 Check_Unset_Reference (Rhs);
388 -- Remaining steps are skipped if Rhs was syntactically in error
397 if not Covers (T1, T2) then
398 Wrong_Type (Rhs, Etype (Lhs));
403 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
404 -- types, use the non-limited view if available
406 if Nkind (Rhs) = N_Explicit_Dereference
407 and then Ekind (T2) = E_Incomplete_Type
408 and then Is_Tagged_Type (T2)
409 and then Present (Non_Limited_View (T2))
411 T2 := Non_Limited_View (T2);
414 Set_Assignment_Type (Rhs, T2);
416 if Total_Errors_Detected /= 0 then
426 if T1 = Any_Type or else T2 = Any_Type then
431 if (Is_Class_Wide_Type (T2) or else Is_Dynamically_Tagged (Rhs))
432 and then not Is_Class_Wide_Type (T1)
434 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
436 elsif Is_Class_Wide_Type (T1)
437 and then not Is_Class_Wide_Type (T2)
438 and then not Is_Tag_Indeterminate (Rhs)
439 and then not Is_Dynamically_Tagged (Rhs)
441 Error_Msg_N ("dynamically tagged expression required!", Rhs);
444 -- Propagate the tag from a class-wide target to the rhs when the rhs
445 -- is a tag-indeterminate call.
447 if Is_Class_Wide_Type (T1)
448 and then Is_Tag_Indeterminate (Rhs)
450 Propagate_Tag (Lhs, Rhs);
453 -- Ada 2005 (AI-230 and AI-385): When the lhs type is an anonymous
454 -- access type, apply an implicit conversion of the rhs to that type
455 -- to force appropriate static and run-time accessibility checks.
457 if Ada_Version >= Ada_05
458 and then Ekind (T1) = E_Anonymous_Access_Type
460 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
461 Analyze_And_Resolve (Rhs, T1);
466 if Ada_Version >= Ada_05
467 and then Can_Never_Be_Null (T1)
468 and then not Assignment_OK (Lhs)
470 if Nkind (Rhs) = N_Null then
471 Apply_Compile_Time_Constraint_Error
473 Msg => "(Ada 2005) NULL not allowed in null-excluding objects?",
474 Reason => CE_Null_Not_Allowed);
477 elsif not Can_Never_Be_Null (T2) then
479 Convert_To (T1, Relocate_Node (Rhs)));
480 Analyze_And_Resolve (Rhs, T1);
484 if Is_Scalar_Type (T1) then
485 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
487 -- For array types, verify that lengths match. If the right hand side
488 -- if a function call that has been inlined, the assignment has been
489 -- rewritten as a block, and the constraint check will be applied to the
490 -- assignment within the block.
492 elsif Is_Array_Type (T1)
494 (Nkind (Rhs) /= N_Type_Conversion
495 or else Is_Constrained (Etype (Rhs)))
497 (Nkind (Rhs) /= N_Function_Call
498 or else Nkind (N) /= N_Block_Statement)
500 -- Assignment verifies that the length of the Lsh and Rhs are equal,
501 -- but of course the indices do not have to match. If the right-hand
502 -- side is a type conversion to an unconstrained type, a length check
503 -- is performed on the expression itself during expansion. In rare
504 -- cases, the redundant length check is computed on an index type
505 -- with a different representation, triggering incorrect code in
508 Apply_Length_Check (Rhs, Etype (Lhs));
511 -- Discriminant checks are applied in the course of expansion
516 -- Note: modifications of the Lhs may only be recorded after
517 -- checks have been applied.
519 Note_Possible_Modification (Lhs);
521 -- ??? a real accessibility check is needed when ???
523 -- Post warning for useless assignment
525 if Warn_On_Redundant_Constructs
527 -- We only warn for source constructs
529 and then Comes_From_Source (N)
531 -- Where the entity is the same on both sides
533 and then Is_Entity_Name (Lhs)
534 and then Is_Entity_Name (Original_Node (Rhs))
535 and then Entity (Lhs) = Entity (Original_Node (Rhs))
537 -- But exclude the case where the right side was an operation
538 -- that got rewritten (e.g. JUNK + K, where K was known to be
539 -- zero). We don't want to warn in such a case, since it is
540 -- reasonable to write such expressions especially when K is
541 -- defined symbolically in some other package.
543 and then Nkind (Original_Node (Rhs)) not in N_Op
546 ("?useless assignment of & to itself", N, Entity (Lhs));
549 -- Check for non-allowed composite assignment
551 if not Support_Composite_Assign_On_Target
552 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
553 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
555 Error_Msg_CRT ("composite assignment", N);
558 -- Final step. If left side is an entity, then we may be able to
559 -- reset the current tracked values to new safe values. We only have
560 -- something to do if the left side is an entity name, and expansion
561 -- has not modified the node into something other than an assignment,
562 -- and of course we only capture values if it is safe to do so.
564 if Is_Entity_Name (Lhs)
565 and then Nkind (N) = N_Assignment_Statement
568 Ent : constant Entity_Id := Entity (Lhs);
571 if Safe_To_Capture_Value (N, Ent) then
573 -- If we are assigning an access type and the left side is an
574 -- entity, then make sure that the Is_Known_[Non_]Null flags
575 -- properly reflect the state of the entity after assignment.
577 if Is_Access_Type (T1) then
578 if Known_Non_Null (Rhs) then
579 Set_Is_Known_Non_Null (Ent, True);
581 elsif Known_Null (Rhs)
582 and then not Can_Never_Be_Null (Ent)
584 Set_Is_Known_Null (Ent, True);
587 Set_Is_Known_Null (Ent, False);
589 if not Can_Never_Be_Null (Ent) then
590 Set_Is_Known_Non_Null (Ent, False);
594 -- For discrete types, we may be able to set the current value
595 -- if the value is known at compile time.
597 elsif Is_Discrete_Type (T1)
598 and then Compile_Time_Known_Value (Rhs)
600 Set_Current_Value (Ent, Rhs);
602 Set_Current_Value (Ent, Empty);
605 -- If not safe to capture values, kill them
612 end Analyze_Assignment;
614 -----------------------------
615 -- Analyze_Block_Statement --
616 -----------------------------
618 procedure Analyze_Block_Statement (N : Node_Id) is
619 Decls : constant List_Id := Declarations (N);
620 Id : constant Node_Id := Identifier (N);
621 HSS : constant Node_Id := Handled_Statement_Sequence (N);
624 -- If no handled statement sequence is present, things are really
625 -- messed up, and we just return immediately (this is a defence
626 -- against previous errors).
632 -- Normal processing with HSS present
635 EH : constant List_Id := Exception_Handlers (HSS);
636 Ent : Entity_Id := Empty;
639 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
640 -- Recursively save value of this global, will be restored on exit
643 -- Initialize unblocked exit count for statements of begin block
644 -- plus one for each excption handler that is present.
646 Unblocked_Exit_Count := 1;
649 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
652 -- If a label is present analyze it and mark it as referenced
658 -- An error defense. If we have an identifier, but no entity,
659 -- then something is wrong. If we have previous errors, then
660 -- just remove the identifier and continue, otherwise raise
664 if Total_Errors_Detected /= 0 then
665 Set_Identifier (N, Empty);
671 Set_Ekind (Ent, E_Block);
672 Generate_Reference (Ent, N, ' ');
673 Generate_Definition (Ent);
675 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
676 Set_Label_Construct (Parent (Ent), N);
681 -- If no entity set, create a label entity
684 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
685 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
689 Set_Etype (Ent, Standard_Void_Type);
690 Set_Block_Node (Ent, Identifier (N));
693 if Present (Decls) then
694 Analyze_Declarations (Decls);
699 Process_End_Label (HSS, 'e', Ent);
701 -- If exception handlers are present, then we indicate that
702 -- enclosing scopes contain a block with handlers. We only
703 -- need to mark non-generic scopes.
708 Set_Has_Nested_Block_With_Handler (S);
709 exit when Is_Overloadable (S)
710 or else Ekind (S) = E_Package
711 or else Is_Generic_Unit (S);
716 Check_References (Ent);
719 if Unblocked_Exit_Count = 0 then
720 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
721 Check_Unreachable_Code (N);
723 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
726 end Analyze_Block_Statement;
728 ----------------------------
729 -- Analyze_Case_Statement --
730 ----------------------------
732 procedure Analyze_Case_Statement (N : Node_Id) is
734 Exp_Type : Entity_Id;
735 Exp_Btype : Entity_Id;
738 Others_Present : Boolean;
740 Statements_Analyzed : Boolean := False;
741 -- Set True if at least some statement sequences get analyzed.
742 -- If False on exit, means we had a serious error that prevented
743 -- full analysis of the case statement, and as a result it is not
744 -- a good idea to output warning messages about unreachable code.
746 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
747 -- Recursively save value of this global, will be restored on exit
749 procedure Non_Static_Choice_Error (Choice : Node_Id);
750 -- Error routine invoked by the generic instantiation below when
751 -- the case statment has a non static choice.
753 procedure Process_Statements (Alternative : Node_Id);
754 -- Analyzes all the statements associated to a case alternative.
755 -- Needed by the generic instantiation below.
757 package Case_Choices_Processing is new
758 Generic_Choices_Processing
759 (Get_Alternatives => Alternatives,
760 Get_Choices => Discrete_Choices,
761 Process_Empty_Choice => No_OP,
762 Process_Non_Static_Choice => Non_Static_Choice_Error,
763 Process_Associated_Node => Process_Statements);
764 use Case_Choices_Processing;
765 -- Instantiation of the generic choice processing package
767 -----------------------------
768 -- Non_Static_Choice_Error --
769 -----------------------------
771 procedure Non_Static_Choice_Error (Choice : Node_Id) is
774 ("choice given in case statement is not static!", Choice);
775 end Non_Static_Choice_Error;
777 ------------------------
778 -- Process_Statements --
779 ------------------------
781 procedure Process_Statements (Alternative : Node_Id) is
782 Choices : constant List_Id := Discrete_Choices (Alternative);
786 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
787 Statements_Analyzed := True;
789 -- An interesting optimization. If the case statement expression
790 -- is a simple entity, then we can set the current value within
791 -- an alternative if the alternative has one possible value.
795 -- when 2 | 3 => beta
796 -- when others => gamma
798 -- Here we know that N is initially 1 within alpha, but for beta
799 -- and gamma, we do not know anything more about the initial value.
801 if Is_Entity_Name (Exp) then
804 if Ekind (Ent) = E_Variable
806 Ekind (Ent) = E_In_Out_Parameter
808 Ekind (Ent) = E_Out_Parameter
810 if List_Length (Choices) = 1
811 and then Nkind (First (Choices)) in N_Subexpr
812 and then Compile_Time_Known_Value (First (Choices))
814 Set_Current_Value (Entity (Exp), First (Choices));
817 Analyze_Statements (Statements (Alternative));
819 -- After analyzing the case, set the current value to empty
820 -- since we won't know what it is for the next alternative
821 -- (unless reset by this same circuit), or after the case.
823 Set_Current_Value (Entity (Exp), Empty);
828 -- Case where expression is not an entity name of a variable
830 Analyze_Statements (Statements (Alternative));
831 end Process_Statements;
833 -- Table to record choices. Put after subprograms since we make
834 -- a call to Number_Of_Choices to get the right number of entries.
836 Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
838 -- Start of processing for Analyze_Case_Statement
841 Unblocked_Exit_Count := 0;
842 Exp := Expression (N);
845 -- The expression must be of any discrete type. In rare cases, the
846 -- expander constructs a case statement whose expression has a private
847 -- type whose full view is discrete. This can happen when generating
848 -- a stream operation for a variant type after the type is frozen,
849 -- when the partial of view of the type of the discriminant is private.
850 -- In that case, use the full view to analyze case alternatives.
852 if not Is_Overloaded (Exp)
853 and then not Comes_From_Source (N)
854 and then Is_Private_Type (Etype (Exp))
855 and then Present (Full_View (Etype (Exp)))
856 and then Is_Discrete_Type (Full_View (Etype (Exp)))
858 Resolve (Exp, Etype (Exp));
859 Exp_Type := Full_View (Etype (Exp));
862 Analyze_And_Resolve (Exp, Any_Discrete);
863 Exp_Type := Etype (Exp);
866 Check_Unset_Reference (Exp);
867 Exp_Btype := Base_Type (Exp_Type);
869 -- The expression must be of a discrete type which must be determinable
870 -- independently of the context in which the expression occurs, but
871 -- using the fact that the expression must be of a discrete type.
872 -- Moreover, the type this expression must not be a character literal
873 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
875 -- If error already reported by Resolve, nothing more to do
877 if Exp_Btype = Any_Discrete
878 or else Exp_Btype = Any_Type
882 elsif Exp_Btype = Any_Character then
884 ("character literal as case expression is ambiguous", Exp);
887 elsif Ada_Version = Ada_83
888 and then (Is_Generic_Type (Exp_Btype)
889 or else Is_Generic_Type (Root_Type (Exp_Btype)))
892 ("(Ada 83) case expression cannot be of a generic type", Exp);
896 -- If the case expression is a formal object of mode in out, then
897 -- treat it as having a nonstatic subtype by forcing use of the base
898 -- type (which has to get passed to Check_Case_Choices below). Also
899 -- use base type when the case expression is parenthesized.
901 if Paren_Count (Exp) > 0
902 or else (Is_Entity_Name (Exp)
903 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
905 Exp_Type := Exp_Btype;
908 -- Call instantiated Analyze_Choices which does the rest of the work
911 (N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
913 if Exp_Type = Universal_Integer and then not Others_Present then
914 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
917 -- If all our exits were blocked by unconditional transfers of control,
918 -- then the entire CASE statement acts as an unconditional transfer of
919 -- control, so treat it like one, and check unreachable code. Skip this
920 -- test if we had serious errors preventing any statement analysis.
922 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
923 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
924 Check_Unreachable_Code (N);
926 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
929 if not Expander_Active
930 and then Compile_Time_Known_Value (Expression (N))
931 and then Serious_Errors_Detected = 0
934 Chosen : constant Node_Id := Find_Static_Alternative (N);
938 Alt := First (Alternatives (N));
940 while Present (Alt) loop
941 if Alt /= Chosen then
942 Remove_Warning_Messages (Statements (Alt));
949 end Analyze_Case_Statement;
951 ----------------------------
952 -- Analyze_Exit_Statement --
953 ----------------------------
955 -- If the exit includes a name, it must be the name of a currently open
956 -- loop. Otherwise there must be an innermost open loop on the stack,
957 -- to which the statement implicitly refers.
959 procedure Analyze_Exit_Statement (N : Node_Id) is
960 Target : constant Node_Id := Name (N);
961 Cond : constant Node_Id := Condition (N);
962 Scope_Id : Entity_Id;
968 Check_Unreachable_Code (N);
971 if Present (Target) then
973 U_Name := Entity (Target);
975 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
976 Error_Msg_N ("invalid loop name in exit statement", N);
979 Set_Has_Exit (U_Name);
986 for J in reverse 0 .. Scope_Stack.Last loop
987 Scope_Id := Scope_Stack.Table (J).Entity;
988 Kind := Ekind (Scope_Id);
991 and then (No (Target) or else Scope_Id = U_Name) then
992 Set_Has_Exit (Scope_Id);
995 elsif Kind = E_Block or else Kind = E_Loop then
1000 ("cannot exit from program unit or accept statement", N);
1005 -- Verify that if present the condition is a Boolean expression
1007 if Present (Cond) then
1008 Analyze_And_Resolve (Cond, Any_Boolean);
1009 Check_Unset_Reference (Cond);
1011 end Analyze_Exit_Statement;
1013 ----------------------------
1014 -- Analyze_Goto_Statement --
1015 ----------------------------
1017 procedure Analyze_Goto_Statement (N : Node_Id) is
1018 Label : constant Node_Id := Name (N);
1019 Scope_Id : Entity_Id;
1020 Label_Scope : Entity_Id;
1023 Check_Unreachable_Code (N);
1027 if Entity (Label) = Any_Id then
1030 elsif Ekind (Entity (Label)) /= E_Label then
1031 Error_Msg_N ("target of goto statement must be a label", Label);
1034 elsif not Reachable (Entity (Label)) then
1035 Error_Msg_N ("target of goto statement is not reachable", Label);
1039 Label_Scope := Enclosing_Scope (Entity (Label));
1041 for J in reverse 0 .. Scope_Stack.Last loop
1042 Scope_Id := Scope_Stack.Table (J).Entity;
1044 if Label_Scope = Scope_Id
1045 or else (Ekind (Scope_Id) /= E_Block
1046 and then Ekind (Scope_Id) /= E_Loop)
1048 if Scope_Id /= Label_Scope then
1050 ("cannot exit from program unit or accept statement", N);
1057 raise Program_Error;
1058 end Analyze_Goto_Statement;
1060 --------------------------
1061 -- Analyze_If_Statement --
1062 --------------------------
1064 -- A special complication arises in the analysis of if statements
1066 -- The expander has circuitry to completely delete code that it
1067 -- can tell will not be executed (as a result of compile time known
1068 -- conditions). In the analyzer, we ensure that code that will be
1069 -- deleted in this manner is analyzed but not expanded. This is
1070 -- obviously more efficient, but more significantly, difficulties
1071 -- arise if code is expanded and then eliminated (e.g. exception
1072 -- table entries disappear). Similarly, itypes generated in deleted
1073 -- code must be frozen from start, because the nodes on which they
1074 -- depend will not be available at the freeze point.
1076 procedure Analyze_If_Statement (N : Node_Id) is
1079 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1080 -- Recursively save value of this global, will be restored on exit
1082 Save_In_Deleted_Code : Boolean;
1084 Del : Boolean := False;
1085 -- This flag gets set True if a True condition has been found,
1086 -- which means that remaining ELSE/ELSIF parts are deleted.
1088 procedure Analyze_Cond_Then (Cnode : Node_Id);
1089 -- This is applied to either the N_If_Statement node itself or
1090 -- to an N_Elsif_Part node. It deals with analyzing the condition
1091 -- and the THEN statements associated with it.
1093 -----------------------
1094 -- Analyze_Cond_Then --
1095 -----------------------
1097 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1098 Cond : constant Node_Id := Condition (Cnode);
1099 Tstm : constant List_Id := Then_Statements (Cnode);
1102 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1103 Analyze_And_Resolve (Cond, Any_Boolean);
1104 Check_Unset_Reference (Cond);
1105 Check_Possible_Current_Value_Condition (Cnode);
1107 -- If already deleting, then just analyze then statements
1110 Analyze_Statements (Tstm);
1112 -- Compile time known value, not deleting yet
1114 elsif Compile_Time_Known_Value (Cond) then
1115 Save_In_Deleted_Code := In_Deleted_Code;
1117 -- If condition is True, then analyze the THEN statements
1118 -- and set no expansion for ELSE and ELSIF parts.
1120 if Is_True (Expr_Value (Cond)) then
1121 Analyze_Statements (Tstm);
1123 Expander_Mode_Save_And_Set (False);
1124 In_Deleted_Code := True;
1126 -- If condition is False, analyze THEN with expansion off
1128 else -- Is_False (Expr_Value (Cond))
1129 Expander_Mode_Save_And_Set (False);
1130 In_Deleted_Code := True;
1131 Analyze_Statements (Tstm);
1132 Expander_Mode_Restore;
1133 In_Deleted_Code := Save_In_Deleted_Code;
1136 -- Not known at compile time, not deleting, normal analysis
1139 Analyze_Statements (Tstm);
1141 end Analyze_Cond_Then;
1143 -- Start of Analyze_If_Statement
1146 -- Initialize exit count for else statements. If there is no else
1147 -- part, this count will stay non-zero reflecting the fact that the
1148 -- uncovered else case is an unblocked exit.
1150 Unblocked_Exit_Count := 1;
1151 Analyze_Cond_Then (N);
1153 -- Now to analyze the elsif parts if any are present
1155 if Present (Elsif_Parts (N)) then
1156 E := First (Elsif_Parts (N));
1157 while Present (E) loop
1158 Analyze_Cond_Then (E);
1163 if Present (Else_Statements (N)) then
1164 Analyze_Statements (Else_Statements (N));
1167 -- If all our exits were blocked by unconditional transfers of control,
1168 -- then the entire IF statement acts as an unconditional transfer of
1169 -- control, so treat it like one, and check unreachable code.
1171 if Unblocked_Exit_Count = 0 then
1172 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1173 Check_Unreachable_Code (N);
1175 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1179 Expander_Mode_Restore;
1180 In_Deleted_Code := Save_In_Deleted_Code;
1183 if not Expander_Active
1184 and then Compile_Time_Known_Value (Condition (N))
1185 and then Serious_Errors_Detected = 0
1187 if Is_True (Expr_Value (Condition (N))) then
1188 Remove_Warning_Messages (Else_Statements (N));
1190 if Present (Elsif_Parts (N)) then
1191 E := First (Elsif_Parts (N));
1193 while Present (E) loop
1194 Remove_Warning_Messages (Then_Statements (E));
1200 Remove_Warning_Messages (Then_Statements (N));
1203 end Analyze_If_Statement;
1205 ----------------------------------------
1206 -- Analyze_Implicit_Label_Declaration --
1207 ----------------------------------------
1209 -- An implicit label declaration is generated in the innermost
1210 -- enclosing declarative part. This is done for labels as well as
1211 -- block and loop names.
1213 -- Note: any changes in this routine may need to be reflected in
1214 -- Analyze_Label_Entity.
1216 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1217 Id : constant Node_Id := Defining_Identifier (N);
1220 Set_Ekind (Id, E_Label);
1221 Set_Etype (Id, Standard_Void_Type);
1222 Set_Enclosing_Scope (Id, Current_Scope);
1223 end Analyze_Implicit_Label_Declaration;
1225 ------------------------------
1226 -- Analyze_Iteration_Scheme --
1227 ------------------------------
1229 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1231 procedure Process_Bounds (R : Node_Id);
1232 -- If the iteration is given by a range, create temporaries and
1233 -- assignment statements block to capture the bounds and perform
1234 -- required finalization actions in case a bound includes a function
1235 -- call that uses the temporary stack. We first pre-analyze a copy of
1236 -- the range in order to determine the expected type, and analyze and
1237 -- resolve the original bounds.
1239 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1240 -- If the bounds are given by a 'Range reference on a function call
1241 -- that returns a controlled array, introduce an explicit declaration
1242 -- to capture the bounds, so that the function result can be finalized
1243 -- in timely fashion.
1245 --------------------
1246 -- Process_Bounds --
1247 --------------------
1249 procedure Process_Bounds (R : Node_Id) is
1250 Loc : constant Source_Ptr := Sloc (N);
1251 R_Copy : constant Node_Id := New_Copy_Tree (R);
1252 Lo : constant Node_Id := Low_Bound (R);
1253 Hi : constant Node_Id := High_Bound (R);
1254 New_Lo_Bound : Node_Id := Empty;
1255 New_Hi_Bound : Node_Id := Empty;
1257 Save_Analysis : Boolean;
1260 (Original_Bound : Node_Id;
1261 Analyzed_Bound : Node_Id) return Node_Id;
1262 -- Create one declaration followed by one assignment statement
1263 -- to capture the value of bound. We create a separate assignment
1264 -- in order to force the creation of a block in case the bound
1265 -- contains a call that uses the secondary stack.
1272 (Original_Bound : Node_Id;
1273 Analyzed_Bound : Node_Id) return Node_Id
1280 -- If the bound is a constant or an object, no need for a separate
1281 -- declaration. If the bound is the result of previous expansion
1282 -- it is already analyzed and should not be modified. Note that
1283 -- the Bound will be resolved later, if needed, as part of the
1284 -- call to Make_Index (literal bounds may need to be resolved to
1287 if Analyzed (Original_Bound) then
1288 return Original_Bound;
1290 elsif Nkind (Analyzed_Bound) = N_Integer_Literal
1291 or else Is_Entity_Name (Analyzed_Bound)
1293 Analyze_And_Resolve (Original_Bound, Typ);
1294 return Original_Bound;
1297 Analyze_And_Resolve (Original_Bound, Typ);
1301 Make_Defining_Identifier (Loc,
1302 Chars => New_Internal_Name ('S'));
1305 Make_Object_Declaration (Loc,
1306 Defining_Identifier => Id,
1307 Object_Definition => New_Occurrence_Of (Typ, Loc));
1309 Insert_Before (Parent (N), Decl);
1313 Make_Assignment_Statement (Loc,
1314 Name => New_Occurrence_Of (Id, Loc),
1315 Expression => Relocate_Node (Original_Bound));
1317 Insert_Before (Parent (N), Assign);
1320 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1322 if Nkind (Assign) = N_Assignment_Statement then
1323 return Expression (Assign);
1325 return Original_Bound;
1329 -- Start of processing for Process_Bounds
1332 -- Determine expected type of range by analyzing separate copy
1333 -- Do the analysis and resolution of the copy of the bounds with
1334 -- expansion disabled, to prevent the generation of finalization
1335 -- actions on each bound. This prevents memory leaks when the
1336 -- bounds contain calls to functions returning controlled arrays.
1338 Set_Parent (R_Copy, Parent (R));
1339 Save_Analysis := Full_Analysis;
1340 Full_Analysis := False;
1341 Expander_Mode_Save_And_Set (False);
1345 if Is_Overloaded (R_Copy) then
1347 -- Apply preference rules for range of predefined integer types,
1348 -- or diagnose true ambiguity.
1353 Found : Entity_Id := Empty;
1356 Get_First_Interp (R_Copy, I, It);
1357 while Present (It.Typ) loop
1358 if Is_Discrete_Type (It.Typ) then
1362 if Scope (Found) = Standard_Standard then
1365 elsif Scope (It.Typ) = Standard_Standard then
1369 -- Both of them are user-defined
1372 ("ambiguous bounds in range of iteration",
1374 Error_Msg_N ("\possible interpretations:", R_Copy);
1375 Error_Msg_NE ("\} ", R_Copy, Found);
1376 Error_Msg_NE ("\} ", R_Copy, It.Typ);
1382 Get_Next_Interp (I, It);
1388 Expander_Mode_Restore;
1389 Full_Analysis := Save_Analysis;
1391 Typ := Etype (R_Copy);
1393 -- If the type of the discrete range is Universal_Integer, then
1394 -- the bound's type must be resolved to Integer, and any object
1395 -- used to hold the bound must also have type Integer.
1397 if Typ = Universal_Integer then
1398 Typ := Standard_Integer;
1403 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1404 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1406 -- Propagate staticness to loop range itself, in case the
1407 -- corresponding subtype is static.
1409 if New_Lo_Bound /= Lo
1410 and then Is_Static_Expression (New_Lo_Bound)
1412 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1415 if New_Hi_Bound /= Hi
1416 and then Is_Static_Expression (New_Hi_Bound)
1418 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1422 --------------------------------------
1423 -- Check_Controlled_Array_Attribute --
1424 --------------------------------------
1426 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1428 if Nkind (DS) = N_Attribute_Reference
1429 and then Is_Entity_Name (Prefix (DS))
1430 and then Ekind (Entity (Prefix (DS))) = E_Function
1431 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1434 Component_Type (Etype (Entity (Prefix (DS)))))
1435 and then Expander_Active
1438 Loc : constant Source_Ptr := Sloc (N);
1439 Arr : constant Entity_Id :=
1440 Etype (Entity (Prefix (DS)));
1441 Indx : constant Entity_Id :=
1442 Base_Type (Etype (First_Index (Arr)));
1443 Subt : constant Entity_Id :=
1444 Make_Defining_Identifier
1445 (Loc, New_Internal_Name ('S'));
1450 Make_Subtype_Declaration (Loc,
1451 Defining_Identifier => Subt,
1452 Subtype_Indication =>
1453 Make_Subtype_Indication (Loc,
1454 Subtype_Mark => New_Reference_To (Indx, Loc),
1456 Make_Range_Constraint (Loc,
1457 Relocate_Node (DS))));
1458 Insert_Before (Parent (N), Decl);
1462 Make_Attribute_Reference (Loc,
1463 Prefix => New_Reference_To (Subt, Loc),
1464 Attribute_Name => Attribute_Name (DS)));
1468 end Check_Controlled_Array_Attribute;
1470 -- Start of processing for Analyze_Iteration_Scheme
1473 -- For an infinite loop, there is no iteration scheme
1480 Cond : constant Node_Id := Condition (N);
1483 -- For WHILE loop, verify that the condition is a Boolean
1484 -- expression and resolve and check it.
1486 if Present (Cond) then
1487 Analyze_And_Resolve (Cond, Any_Boolean);
1488 Check_Unset_Reference (Cond);
1490 -- Else we have a FOR loop
1494 LP : constant Node_Id := Loop_Parameter_Specification (N);
1495 Id : constant Entity_Id := Defining_Identifier (LP);
1496 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
1501 -- We always consider the loop variable to be referenced,
1502 -- since the loop may be used just for counting purposes.
1504 Generate_Reference (Id, N, ' ');
1506 -- Check for case of loop variable hiding a local
1507 -- variable (used later on to give a nice warning
1508 -- if the hidden variable is never assigned).
1511 H : constant Entity_Id := Homonym (Id);
1514 and then Enclosing_Dynamic_Scope (H) =
1515 Enclosing_Dynamic_Scope (Id)
1516 and then Ekind (H) = E_Variable
1517 and then Is_Discrete_Type (Etype (H))
1519 Set_Hiding_Loop_Variable (H, Id);
1523 -- Now analyze the subtype definition. If it is
1524 -- a range, create temporaries for bounds.
1526 if Nkind (DS) = N_Range
1527 and then Expander_Active
1529 Process_Bounds (DS);
1538 -- The subtype indication may denote the completion
1539 -- of an incomplete type declaration.
1541 if Is_Entity_Name (DS)
1542 and then Present (Entity (DS))
1543 and then Is_Type (Entity (DS))
1544 and then Ekind (Entity (DS)) = E_Incomplete_Type
1546 Set_Entity (DS, Get_Full_View (Entity (DS)));
1547 Set_Etype (DS, Entity (DS));
1550 if not Is_Discrete_Type (Etype (DS)) then
1551 Wrong_Type (DS, Any_Discrete);
1552 Set_Etype (DS, Any_Type);
1555 Check_Controlled_Array_Attribute (DS);
1557 Make_Index (DS, LP);
1559 Set_Ekind (Id, E_Loop_Parameter);
1560 Set_Etype (Id, Etype (DS));
1561 Set_Is_Known_Valid (Id, True);
1563 -- The loop is not a declarative part, so the only entity
1564 -- declared "within" must be frozen explicitly.
1567 Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
1569 if Is_Non_Empty_List (Flist) then
1570 Insert_Actions (N, Flist);
1574 -- Check for null or possibly null range and issue warning.
1575 -- We suppress such messages in generic templates and
1576 -- instances, because in practice they tend to be dubious
1579 if Nkind (DS) = N_Range
1580 and then Comes_From_Source (N)
1583 L : constant Node_Id := Low_Bound (DS);
1584 H : constant Node_Id := High_Bound (DS);
1594 Determine_Range (L, LOK, Llo, Lhi);
1595 Determine_Range (H, HOK, Hlo, Hhi);
1597 -- If range of loop is null, issue warning
1599 if (LOK and HOK) and then Llo > Hhi then
1601 -- Suppress the warning if inside a generic
1602 -- template or instance, since in practice
1603 -- they tend to be dubious in these cases since
1604 -- they can result from intended parametrization.
1606 if not Inside_A_Generic
1607 and then not In_Instance
1610 ("?loop range is null, loop will not execute",
1614 -- Since we know the range of the loop is null,
1615 -- set the appropriate flag to suppress any
1616 -- warnings that would otherwise be issued in
1617 -- the body of the loop that will not execute.
1618 -- We do this even in the generic case, since
1619 -- if it is dubious to warn on the null loop
1620 -- itself, it is certainly dubious to warn for
1621 -- conditions that occur inside it!
1623 Set_Is_Null_Loop (Parent (N));
1625 -- The other case for a warning is a reverse loop
1626 -- where the upper bound is the integer literal
1627 -- zero or one, and the lower bound can be positive.
1629 -- For example, we have
1631 -- for J in reverse N .. 1 loop
1633 -- In practice, this is very likely to be a case
1634 -- of reversing the bounds incorrectly in the range.
1636 elsif Reverse_Present (LP)
1637 and then Nkind (Original_Node (H)) =
1639 and then (Intval (H) = Uint_0
1641 Intval (H) = Uint_1)
1644 Error_Msg_N ("?loop range may be null", DS);
1645 Error_Msg_N ("\?bounds may be wrong way round", DS);
1653 end Analyze_Iteration_Scheme;
1659 -- Note: the semantic work required for analyzing labels (setting them as
1660 -- reachable) was done in a prepass through the statements in the block,
1661 -- so that forward gotos would be properly handled. See Analyze_Statements
1662 -- for further details. The only processing required here is to deal with
1663 -- optimizations that depend on an assumption of sequential control flow,
1664 -- since of course the occurrence of a label breaks this assumption.
1666 procedure Analyze_Label (N : Node_Id) is
1667 pragma Warnings (Off, N);
1669 Kill_Current_Values;
1672 --------------------------
1673 -- Analyze_Label_Entity --
1674 --------------------------
1676 procedure Analyze_Label_Entity (E : Entity_Id) is
1678 Set_Ekind (E, E_Label);
1679 Set_Etype (E, Standard_Void_Type);
1680 Set_Enclosing_Scope (E, Current_Scope);
1681 Set_Reachable (E, True);
1682 end Analyze_Label_Entity;
1684 ----------------------------
1685 -- Analyze_Loop_Statement --
1686 ----------------------------
1688 procedure Analyze_Loop_Statement (N : Node_Id) is
1689 Id : constant Node_Id := Identifier (N);
1693 if Present (Id) then
1695 -- Make name visible, e.g. for use in exit statements. Loop
1696 -- labels are always considered to be referenced.
1700 Generate_Reference (Ent, N, ' ');
1701 Generate_Definition (Ent);
1703 -- If we found a label, mark its type. If not, ignore it, since it
1704 -- means we have a conflicting declaration, which would already have
1705 -- been diagnosed at declaration time. Set Label_Construct of the
1706 -- implicit label declaration, which is not created by the parser
1707 -- for generic units.
1709 if Ekind (Ent) = E_Label then
1710 Set_Ekind (Ent, E_Loop);
1712 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
1713 Set_Label_Construct (Parent (Ent), N);
1717 -- Case of no identifier present
1720 Ent := New_Internal_Entity (E_Loop, Current_Scope, Sloc (N), 'L');
1721 Set_Etype (Ent, Standard_Void_Type);
1722 Set_Parent (Ent, N);
1725 -- Kill current values on entry to loop, since statements in body
1726 -- of loop may have been executed before the loop is entered.
1727 -- Similarly we kill values after the loop, since we do not know
1728 -- that the body of the loop was executed.
1730 Kill_Current_Values;
1732 Analyze_Iteration_Scheme (Iteration_Scheme (N));
1733 Analyze_Statements (Statements (N));
1734 Process_End_Label (N, 'e', Ent);
1736 Kill_Current_Values;
1737 end Analyze_Loop_Statement;
1739 ----------------------------
1740 -- Analyze_Null_Statement --
1741 ----------------------------
1743 -- Note: the semantics of the null statement is implemented by a single
1744 -- null statement, too bad everything isn't as simple as this!
1746 procedure Analyze_Null_Statement (N : Node_Id) is
1747 pragma Warnings (Off, N);
1750 end Analyze_Null_Statement;
1752 ------------------------
1753 -- Analyze_Statements --
1754 ------------------------
1756 procedure Analyze_Statements (L : List_Id) is
1761 -- The labels declared in the statement list are reachable from
1762 -- statements in the list. We do this as a prepass so that any
1763 -- goto statement will be properly flagged if its target is not
1764 -- reachable. This is not required, but is nice behavior!
1767 while Present (S) loop
1768 if Nkind (S) = N_Label then
1769 Analyze (Identifier (S));
1770 Lab := Entity (Identifier (S));
1772 -- If we found a label mark it as reachable
1774 if Ekind (Lab) = E_Label then
1775 Generate_Definition (Lab);
1776 Set_Reachable (Lab);
1778 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
1779 Set_Label_Construct (Parent (Lab), S);
1782 -- If we failed to find a label, it means the implicit declaration
1783 -- of the label was hidden. A for-loop parameter can do this to
1784 -- a label with the same name inside the loop, since the implicit
1785 -- label declaration is in the innermost enclosing body or block
1789 Error_Msg_Sloc := Sloc (Lab);
1791 ("implicit label declaration for & is hidden#",
1799 -- Perform semantic analysis on all statements
1801 Conditional_Statements_Begin;
1804 while Present (S) loop
1809 Conditional_Statements_End;
1811 -- Make labels unreachable. Visibility is not sufficient, because
1812 -- labels in one if-branch for example are not reachable from the
1813 -- other branch, even though their declarations are in the enclosing
1814 -- declarative part.
1817 while Present (S) loop
1818 if Nkind (S) = N_Label then
1819 Set_Reachable (Entity (Identifier (S)), False);
1824 end Analyze_Statements;
1826 --------------------------------------------
1827 -- Check_Possible_Current_Value_Condition --
1828 --------------------------------------------
1830 procedure Check_Possible_Current_Value_Condition (Cnode : Node_Id) is
1834 -- Loop to deal with (ignore for now) any NOT operators present
1836 Cond := Condition (Cnode);
1837 while Nkind (Cond) = N_Op_Not loop
1838 Cond := Right_Opnd (Cond);
1841 -- Check possible relational operator
1843 if Nkind (Cond) = N_Op_Eq
1845 Nkind (Cond) = N_Op_Ne
1847 Nkind (Cond) = N_Op_Ge
1849 Nkind (Cond) = N_Op_Le
1851 Nkind (Cond) = N_Op_Gt
1853 Nkind (Cond) = N_Op_Lt
1855 if Compile_Time_Known_Value (Right_Opnd (Cond))
1856 and then Nkind (Left_Opnd (Cond)) = N_Identifier
1859 Ent : constant Entity_Id := Entity (Left_Opnd (Cond));
1862 if Ekind (Ent) = E_Variable
1864 Ekind (Ent) = E_Constant
1868 Ekind (Ent) = E_Loop_Parameter
1870 -- Here we have a case where the Current_Value field
1871 -- may need to be set. We set it if it is not already
1872 -- set to a compile time expression value.
1874 -- Note that this represents a decision that one
1875 -- condition blots out another previous one. That's
1876 -- certainly right if they occur at the same level.
1877 -- If the second one is nested, then the decision is
1878 -- neither right nor wrong (it would be equally OK
1879 -- to leave the outer one in place, or take the new
1880 -- inner one. Really we should record both, but our
1881 -- data structures are not that elaborate.
1883 if Nkind (Current_Value (Ent)) not in N_Subexpr then
1884 Set_Current_Value (Ent, Cnode);
1890 end Check_Possible_Current_Value_Condition;
1892 ----------------------------
1893 -- Check_Unreachable_Code --
1894 ----------------------------
1896 procedure Check_Unreachable_Code (N : Node_Id) is
1897 Error_Loc : Source_Ptr;
1901 if Is_List_Member (N)
1902 and then Comes_From_Source (N)
1908 Nxt := Original_Node (Next (N));
1910 -- If a label follows us, then we never have dead code, since
1911 -- someone could branch to the label, so we just ignore it.
1913 if Nkind (Nxt) = N_Label then
1916 -- Otherwise see if we have a real statement following us
1919 and then Comes_From_Source (Nxt)
1920 and then Is_Statement (Nxt)
1922 -- Special very annoying exception. If we have a return that
1923 -- follows a raise, then we allow it without a warning, since
1924 -- the Ada RM annoyingly requires a useless return here!
1926 if Nkind (Original_Node (N)) /= N_Raise_Statement
1927 or else Nkind (Nxt) /= N_Return_Statement
1929 -- The rather strange shenanigans with the warning message
1930 -- here reflects the fact that Kill_Dead_Code is very good
1931 -- at removing warnings in deleted code, and this is one
1932 -- warning we would prefer NOT to have removed :-)
1934 Error_Loc := Sloc (Nxt);
1936 -- If we have unreachable code, analyze and remove the
1937 -- unreachable code, since it is useless and we don't
1938 -- want to generate junk warnings.
1940 -- We skip this step if we are not in code generation mode.
1941 -- This is the one case where we remove dead code in the
1942 -- semantics as opposed to the expander, and we do not want
1943 -- to remove code if we are not in code generation mode,
1944 -- since this messes up the ASIS trees.
1946 -- Note that one might react by moving the whole circuit to
1947 -- exp_ch5, but then we lose the warning in -gnatc mode.
1949 if Operating_Mode = Generate_Code then
1953 -- Quit deleting when we have nothing more to delete
1954 -- or if we hit a label (since someone could transfer
1955 -- control to a label, so we should not delete it).
1957 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
1959 -- Statement/declaration is to be deleted
1963 Kill_Dead_Code (Nxt);
1967 -- Now issue the warning
1969 Error_Msg ("?unreachable code", Error_Loc);
1972 -- If the unconditional transfer of control instruction is
1973 -- the last statement of a sequence, then see if our parent
1974 -- is one of the constructs for which we count unblocked exits,
1975 -- and if so, adjust the count.
1980 -- Statements in THEN part or ELSE part of IF statement
1982 if Nkind (P) = N_If_Statement then
1985 -- Statements in ELSIF part of an IF statement
1987 elsif Nkind (P) = N_Elsif_Part then
1989 pragma Assert (Nkind (P) = N_If_Statement);
1991 -- Statements in CASE statement alternative
1993 elsif Nkind (P) = N_Case_Statement_Alternative then
1995 pragma Assert (Nkind (P) = N_Case_Statement);
1997 -- Statements in body of block
1999 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2000 and then Nkind (Parent (P)) = N_Block_Statement
2004 -- Statements in exception handler in a block
2006 elsif Nkind (P) = N_Exception_Handler
2007 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2008 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2012 -- None of these cases, so return
2018 -- This was one of the cases we are looking for (i.e. the
2019 -- parent construct was IF, CASE or block) so decrement count.
2021 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2025 end Check_Unreachable_Code;