1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2011, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Aspects; use Aspects;
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_Ch6; use Exp_Ch6;
33 with Exp_Util; use Exp_Util;
34 with Freeze; use Freeze;
36 with Lib.Xref; use Lib.Xref;
37 with Namet; use Namet;
38 with Nlists; use Nlists;
39 with Nmake; use Nmake;
41 with Restrict; use Restrict;
42 with Rident; use Rident;
43 with Rtsfind; use Rtsfind;
45 with Sem_Aux; use Sem_Aux;
46 with Sem_Case; use Sem_Case;
47 with Sem_Ch3; use Sem_Ch3;
48 with Sem_Ch6; use Sem_Ch6;
49 with Sem_Ch8; use Sem_Ch8;
50 with Sem_Disp; use Sem_Disp;
51 with Sem_Elab; use Sem_Elab;
52 with Sem_Eval; use Sem_Eval;
53 with Sem_Res; use Sem_Res;
54 with Sem_Type; use Sem_Type;
55 with Sem_Util; use Sem_Util;
56 with Sem_Warn; use Sem_Warn;
57 with Snames; use Snames;
58 with Stand; use Stand;
59 with Sinfo; use Sinfo;
60 with Targparm; use Targparm;
61 with Tbuild; use Tbuild;
62 with Uintp; use Uintp;
64 package body Sem_Ch5 is
66 Unblocked_Exit_Count : Nat := 0;
67 -- This variable is used when processing if statements, case statements,
68 -- and block statements. It counts the number of exit points that are not
69 -- blocked by unconditional transfer instructions: for IF and CASE, these
70 -- are the branches of the conditional; for a block, they are the statement
71 -- sequence of the block, and the statement sequences of any exception
72 -- handlers that are part of the block. When processing is complete, if
73 -- this count is zero, it means that control cannot fall through the IF,
74 -- CASE or block statement. This is used for the generation of warning
75 -- messages. This variable is recursively saved on entry to processing the
76 -- construct, and restored on exit.
78 ------------------------
79 -- Analyze_Assignment --
80 ------------------------
82 procedure Analyze_Assignment (N : Node_Id) is
83 Lhs : constant Node_Id := Name (N);
84 Rhs : constant Node_Id := Expression (N);
89 procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
90 -- N is the node for the left hand side of an assignment, and it is not
91 -- a variable. This routine issues an appropriate diagnostic.
94 -- This is called to kill current value settings of a simple variable
95 -- on the left hand side. We call it if we find any error in analyzing
96 -- the assignment, and at the end of processing before setting any new
97 -- current values in place.
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 is the
103 -- nominal subtype. This procedure is used to deal with cases where the
104 -- 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 flagged
113 -- 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
122 Ent : constant Entity_Id := Entity (N);
125 if Ekind (Ent) = E_In_Parameter then
127 ("assignment to IN mode parameter not allowed", N);
129 -- Renamings of protected private components are turned into
130 -- constants when compiling a protected function. In the case
131 -- of single protected types, the private component appears
134 elsif (Is_Prival (Ent)
136 (Ekind (Current_Scope) = E_Function
137 or else Ekind (Enclosing_Dynamic_Scope
138 (Current_Scope)) = E_Function))
140 (Ekind (Ent) = E_Component
141 and then Is_Protected_Type (Scope (Ent)))
144 ("protected function cannot modify protected object", N);
146 elsif Ekind (Ent) = E_Loop_Parameter then
148 ("assignment to loop parameter not allowed", N);
152 ("left hand side of assignment must be a variable", N);
156 -- For indexed components or selected components, test prefix
158 elsif Nkind (N) = N_Indexed_Component then
159 Diagnose_Non_Variable_Lhs (Prefix (N));
161 -- Another special case for assignment to discriminant
163 elsif Nkind (N) = N_Selected_Component then
164 if Present (Entity (Selector_Name (N)))
165 and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
168 ("assignment to discriminant not allowed", N);
170 Diagnose_Non_Variable_Lhs (Prefix (N));
174 -- If we fall through, we have no special message to issue!
176 Error_Msg_N ("left hand side of assignment must be a variable", N);
178 end Diagnose_Non_Variable_Lhs;
184 procedure Kill_Lhs is
186 if Is_Entity_Name (Lhs) then
188 Ent : constant Entity_Id := Entity (Lhs);
190 if Present (Ent) then
191 Kill_Current_Values (Ent);
197 -------------------------
198 -- Set_Assignment_Type --
199 -------------------------
201 procedure Set_Assignment_Type
203 Opnd_Type : in out Entity_Id)
206 Require_Entity (Opnd);
208 -- If the assignment operand is an in-out or out parameter, then we
209 -- get the actual subtype (needed for the unconstrained case). If the
210 -- operand is the actual in an entry declaration, then within the
211 -- accept statement it is replaced with a local renaming, which may
212 -- also have an actual subtype.
214 if Is_Entity_Name (Opnd)
215 and then (Ekind (Entity (Opnd)) = E_Out_Parameter
216 or else Ekind (Entity (Opnd)) =
218 or else Ekind (Entity (Opnd)) =
219 E_Generic_In_Out_Parameter
221 (Ekind (Entity (Opnd)) = E_Variable
222 and then Nkind (Parent (Entity (Opnd))) =
223 N_Object_Renaming_Declaration
224 and then Nkind (Parent (Parent (Entity (Opnd)))) =
227 Opnd_Type := Get_Actual_Subtype (Opnd);
229 -- If assignment operand is a component reference, then we get the
230 -- actual subtype of the component for the unconstrained case.
232 elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference)
233 and then not Is_Unchecked_Union (Opnd_Type)
235 Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
237 if Present (Decl) then
238 Insert_Action (N, Decl);
239 Mark_Rewrite_Insertion (Decl);
241 Opnd_Type := Defining_Identifier (Decl);
242 Set_Etype (Opnd, Opnd_Type);
243 Freeze_Itype (Opnd_Type, N);
245 elsif Is_Constrained (Etype (Opnd)) then
246 Opnd_Type := Etype (Opnd);
249 -- For slice, use the constrained subtype created for the slice
251 elsif Nkind (Opnd) = N_Slice then
252 Opnd_Type := Etype (Opnd);
254 end Set_Assignment_Type;
256 -- Start of processing for Analyze_Assignment
259 Mark_Coextensions (N, Rhs);
264 -- Ensure that we never do an assignment on a variable marked as
265 -- as Safe_To_Reevaluate.
267 pragma Assert (not Is_Entity_Name (Lhs)
268 or else Ekind (Entity (Lhs)) /= E_Variable
269 or else not Is_Safe_To_Reevaluate (Entity (Lhs)));
271 -- Start type analysis for assignment
275 -- In the most general case, both Lhs and Rhs can be overloaded, and we
276 -- must compute the intersection of the possible types on each side.
278 if Is_Overloaded (Lhs) then
285 Get_First_Interp (Lhs, I, It);
287 while Present (It.Typ) loop
288 if Has_Compatible_Type (Rhs, It.Typ) then
289 if T1 /= Any_Type then
291 -- An explicit dereference is overloaded if the prefix
292 -- is. Try to remove the ambiguity on the prefix, the
293 -- error will be posted there if the ambiguity is real.
295 if Nkind (Lhs) = N_Explicit_Dereference then
298 PI1 : Interp_Index := 0;
304 Get_First_Interp (Prefix (Lhs), PI, PIt);
306 while Present (PIt.Typ) loop
307 if Is_Access_Type (PIt.Typ)
308 and then Has_Compatible_Type
309 (Rhs, Designated_Type (PIt.Typ))
313 Disambiguate (Prefix (Lhs),
316 if PIt = No_Interp then
318 ("ambiguous left-hand side"
319 & " in assignment", Lhs);
322 Resolve (Prefix (Lhs), PIt.Typ);
332 Get_Next_Interp (PI, PIt);
338 ("ambiguous left-hand side in assignment", Lhs);
346 Get_Next_Interp (I, It);
350 if T1 = Any_Type then
352 ("no valid types for left-hand side for assignment", Lhs);
358 -- The resulting assignment type is T1, so now we will resolve the left
359 -- hand side of the assignment using this determined type.
363 -- Cases where Lhs is not a variable
365 if not Is_Variable (Lhs) then
367 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of a
375 if Ada_Version >= Ada_2005 then
377 -- Handle chains of renamings
380 while Nkind (Ent) in N_Has_Entity
381 and then Present (Entity (Ent))
382 and then Present (Renamed_Object (Entity (Ent)))
384 Ent := Renamed_Object (Entity (Ent));
387 if (Nkind (Ent) = N_Attribute_Reference
388 and then Attribute_Name (Ent) = Name_Priority)
390 -- Renamings of the attribute Priority applied to protected
391 -- objects have been previously expanded into calls to the
392 -- Get_Ceiling run-time subprogram.
395 (Nkind (Ent) = N_Function_Call
396 and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
398 Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
400 -- The enclosing subprogram cannot be a protected function
403 while not (Is_Subprogram (S)
404 and then Convention (S) = Convention_Protected)
405 and then S /= Standard_Standard
410 if Ekind (S) = E_Function
411 and then Convention (S) = Convention_Protected
414 ("protected function cannot modify protected object",
418 -- Changes of the ceiling priority of the protected object
419 -- are only effective if the Ceiling_Locking policy is in
420 -- effect (AARM D.5.2 (5/2)).
422 if Locking_Policy /= 'C' then
423 Error_Msg_N ("assignment to the attribute PRIORITY has " &
425 Error_Msg_N ("\since no Locking_Policy has been " &
434 Diagnose_Non_Variable_Lhs (Lhs);
437 -- Error of assigning to limited type. We do however allow this in
438 -- certain cases where the front end generates the assignments.
440 elsif Is_Limited_Type (T1)
441 and then not Assignment_OK (Lhs)
442 and then not Assignment_OK (Original_Node (Lhs))
443 and then not Is_Value_Type (T1)
445 -- CPP constructors can only be called in declarations
447 if Is_CPP_Constructor_Call (Rhs) then
448 Error_Msg_N ("invalid use of 'C'P'P constructor", Rhs);
451 ("left hand of assignment must not be limited type", Lhs);
452 Explain_Limited_Type (T1, Lhs);
456 -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
457 -- abstract. This is only checked when the assignment Comes_From_Source,
458 -- because in some cases the expander generates such assignments (such
459 -- in the _assign operation for an abstract type).
461 elsif Is_Abstract_Type (T1) and then Comes_From_Source (N) then
463 ("target of assignment operation must not be abstract", Lhs);
466 -- Resolution may have updated the subtype, in case the left-hand side
467 -- is a private protected component. Use the correct subtype to avoid
468 -- scoping issues in the back-end.
472 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
473 -- type. For example:
477 -- type Acc is access P.T;
480 -- with Pkg; use Acc;
481 -- procedure Example is
484 -- A.all := B.all; -- ERROR
487 if Nkind (Lhs) = N_Explicit_Dereference
488 and then Ekind (T1) = E_Incomplete_Type
490 Error_Msg_N ("invalid use of incomplete type", Lhs);
495 -- Now we can complete the resolution of the right hand side
497 Set_Assignment_Type (Lhs, T1);
500 -- This is the point at which we check for an unset reference
502 Check_Unset_Reference (Rhs);
503 Check_Unprotected_Access (Lhs, Rhs);
505 -- Remaining steps are skipped if Rhs was syntactically in error
514 if not Covers (T1, T2) then
515 Wrong_Type (Rhs, Etype (Lhs));
520 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
521 -- types, use the non-limited view if available
523 if Nkind (Rhs) = N_Explicit_Dereference
524 and then Ekind (T2) = E_Incomplete_Type
525 and then Is_Tagged_Type (T2)
526 and then Present (Non_Limited_View (T2))
528 T2 := Non_Limited_View (T2);
531 Set_Assignment_Type (Rhs, T2);
533 if Total_Errors_Detected /= 0 then
543 if T1 = Any_Type or else T2 = Any_Type then
548 -- If the rhs is class-wide or dynamically tagged, then require the lhs
549 -- to be class-wide. The case where the rhs is a dynamically tagged call
550 -- to a dispatching operation with a controlling access result is
551 -- excluded from this check, since the target has an access type (and
552 -- no tag propagation occurs in that case).
554 if (Is_Class_Wide_Type (T2)
555 or else (Is_Dynamically_Tagged (Rhs)
556 and then not Is_Access_Type (T1)))
557 and then not Is_Class_Wide_Type (T1)
559 Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
561 elsif Is_Class_Wide_Type (T1)
562 and then not Is_Class_Wide_Type (T2)
563 and then not Is_Tag_Indeterminate (Rhs)
564 and then not Is_Dynamically_Tagged (Rhs)
566 Error_Msg_N ("dynamically tagged expression required!", Rhs);
569 -- Propagate the tag from a class-wide target to the rhs when the rhs
570 -- is a tag-indeterminate call.
572 if Is_Tag_Indeterminate (Rhs) then
573 if Is_Class_Wide_Type (T1) then
574 Propagate_Tag (Lhs, Rhs);
576 elsif Nkind (Rhs) = N_Function_Call
577 and then Is_Entity_Name (Name (Rhs))
578 and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
581 ("call to abstract function must be dispatching", Name (Rhs));
583 elsif Nkind (Rhs) = N_Qualified_Expression
584 and then Nkind (Expression (Rhs)) = N_Function_Call
585 and then Is_Entity_Name (Name (Expression (Rhs)))
587 Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
590 ("call to abstract function must be dispatching",
591 Name (Expression (Rhs)));
595 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
596 -- apply an implicit conversion of the rhs to that type to force
597 -- appropriate static and run-time accessibility checks. This applies
598 -- as well to anonymous access-to-subprogram types that are component
599 -- subtypes or formal parameters.
601 if Ada_Version >= Ada_2005
602 and then Is_Access_Type (T1)
604 if Is_Local_Anonymous_Access (T1)
605 or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
607 -- Handle assignment to an Ada 2012 stand-alone object
608 -- of an anonymous access type.
610 or else (Ekind (T1) = E_Anonymous_Access_Type
611 and then Nkind (Associated_Node_For_Itype (T1)) =
612 N_Object_Declaration)
615 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
616 Analyze_And_Resolve (Rhs, T1);
620 -- Ada 2005 (AI-231): Assignment to not null variable
622 if Ada_Version >= Ada_2005
623 and then Can_Never_Be_Null (T1)
624 and then not Assignment_OK (Lhs)
626 -- Case where we know the right hand side is null
628 if Known_Null (Rhs) then
629 Apply_Compile_Time_Constraint_Error
631 Msg => "(Ada 2005) null not allowed in null-excluding objects?",
632 Reason => CE_Null_Not_Allowed);
634 -- We still mark this as a possible modification, that's necessary
635 -- to reset Is_True_Constant, and desirable for xref purposes.
637 Note_Possible_Modification (Lhs, Sure => True);
640 -- If we know the right hand side is non-null, then we convert to the
641 -- target type, since we don't need a run time check in that case.
643 elsif not Can_Never_Be_Null (T2) then
644 Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
645 Analyze_And_Resolve (Rhs, T1);
649 if Is_Scalar_Type (T1) then
650 Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
652 -- For array types, verify that lengths match. If the right hand side
653 -- is a function call that has been inlined, the assignment has been
654 -- rewritten as a block, and the constraint check will be applied to the
655 -- assignment within the block.
657 elsif Is_Array_Type (T1)
659 (Nkind (Rhs) /= N_Type_Conversion
660 or else Is_Constrained (Etype (Rhs)))
662 (Nkind (Rhs) /= N_Function_Call
663 or else Nkind (N) /= N_Block_Statement)
665 -- Assignment verifies that the length of the Lsh and Rhs are equal,
666 -- but of course the indexes do not have to match. If the right-hand
667 -- side is a type conversion to an unconstrained type, a length check
668 -- is performed on the expression itself during expansion. In rare
669 -- cases, the redundant length check is computed on an index type
670 -- with a different representation, triggering incorrect code in the
673 Apply_Length_Check (Rhs, Etype (Lhs));
676 -- Discriminant checks are applied in the course of expansion
681 -- Note: modifications of the Lhs may only be recorded after
682 -- checks have been applied.
684 Note_Possible_Modification (Lhs, Sure => True);
685 Check_Order_Dependence;
687 -- ??? a real accessibility check is needed when ???
689 -- Post warning for redundant assignment or variable to itself
691 if Warn_On_Redundant_Constructs
693 -- We only warn for source constructs
695 and then Comes_From_Source (N)
697 -- Where the object is the same on both sides
699 and then Same_Object (Lhs, Original_Node (Rhs))
701 -- But exclude the case where the right side was an operation that
702 -- got rewritten (e.g. JUNK + K, where K was known to be zero). We
703 -- don't want to warn in such a case, since it is reasonable to write
704 -- such expressions especially when K is defined symbolically in some
707 and then Nkind (Original_Node (Rhs)) not in N_Op
709 if Nkind (Lhs) in N_Has_Entity then
710 Error_Msg_NE -- CODEFIX
711 ("?useless assignment of & to itself!", N, Entity (Lhs));
713 Error_Msg_N -- CODEFIX
714 ("?useless assignment of object to itself!", N);
718 -- Check for non-allowed composite assignment
720 if not Support_Composite_Assign_On_Target
721 and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
722 and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
724 Error_Msg_CRT ("composite assignment", N);
727 -- Check elaboration warning for left side if not in elab code
729 if not In_Subprogram_Or_Concurrent_Unit then
730 Check_Elab_Assign (Lhs);
733 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
734 -- assignment is a source assignment in the extended main source unit.
735 -- We are not interested in any reference information outside this
736 -- context, or in compiler generated assignment statements.
738 if Comes_From_Source (N)
739 and then In_Extended_Main_Source_Unit (Lhs)
741 Set_Referenced_Modified (Lhs, Out_Param => False);
744 -- Final step. If left side is an entity, then we may be able to reset
745 -- the current tracked values to new safe values. We only have something
746 -- to do if the left side is an entity name, and expansion has not
747 -- modified the node into something other than an assignment, and of
748 -- course we only capture values if it is safe to do so.
750 if Is_Entity_Name (Lhs)
751 and then Nkind (N) = N_Assignment_Statement
754 Ent : constant Entity_Id := Entity (Lhs);
757 if Safe_To_Capture_Value (N, Ent) then
759 -- If simple variable on left side, warn if this assignment
760 -- blots out another one (rendering it useless). We only do
761 -- this for source assignments, otherwise we can generate bogus
762 -- warnings when an assignment is rewritten as another
763 -- assignment, and gets tied up with itself.
765 if Warn_On_Modified_Unread
766 and then Is_Assignable (Ent)
767 and then Comes_From_Source (N)
768 and then In_Extended_Main_Source_Unit (Ent)
770 Warn_On_Useless_Assignment (Ent, N);
773 -- If we are assigning an access type and the left side is an
774 -- entity, then make sure that the Is_Known_[Non_]Null flags
775 -- properly reflect the state of the entity after assignment.
777 if Is_Access_Type (T1) then
778 if Known_Non_Null (Rhs) then
779 Set_Is_Known_Non_Null (Ent, True);
781 elsif Known_Null (Rhs)
782 and then not Can_Never_Be_Null (Ent)
784 Set_Is_Known_Null (Ent, True);
787 Set_Is_Known_Null (Ent, False);
789 if not Can_Never_Be_Null (Ent) then
790 Set_Is_Known_Non_Null (Ent, False);
794 -- For discrete types, we may be able to set the current value
795 -- if the value is known at compile time.
797 elsif Is_Discrete_Type (T1)
798 and then Compile_Time_Known_Value (Rhs)
800 Set_Current_Value (Ent, Rhs);
802 Set_Current_Value (Ent, Empty);
805 -- If not safe to capture values, kill them
813 -- If assigning to an object in whole or in part, note location of
814 -- assignment in case no one references value. We only do this for
815 -- source assignments, otherwise we can generate bogus warnings when an
816 -- assignment is rewritten as another assignment, and gets tied up with
820 Ent : constant Entity_Id := Get_Enclosing_Object (Lhs);
824 and then Safe_To_Capture_Value (N, Ent)
825 and then Nkind (N) = N_Assignment_Statement
826 and then Warn_On_Modified_Unread
827 and then Is_Assignable (Ent)
828 and then Comes_From_Source (N)
829 and then In_Extended_Main_Source_Unit (Ent)
831 Set_Last_Assignment (Ent, Lhs);
834 end Analyze_Assignment;
836 -----------------------------
837 -- Analyze_Block_Statement --
838 -----------------------------
840 procedure Analyze_Block_Statement (N : Node_Id) is
841 procedure Install_Return_Entities (Scop : Entity_Id);
842 -- Install all entities of return statement scope Scop in the visibility
843 -- chain except for the return object since its entity is reused in a
846 -----------------------------
847 -- Install_Return_Entities --
848 -----------------------------
850 procedure Install_Return_Entities (Scop : Entity_Id) is
854 Id := First_Entity (Scop);
855 while Present (Id) loop
857 -- Do not install the return object
859 if not Ekind_In (Id, E_Constant, E_Variable)
860 or else not Is_Return_Object (Id)
867 end Install_Return_Entities;
869 -- Local constants and variables
871 Decls : constant List_Id := Declarations (N);
872 Id : constant Node_Id := Identifier (N);
873 HSS : constant Node_Id := Handled_Statement_Sequence (N);
875 Is_BIP_Return_Statement : Boolean;
877 -- Start of processing for Analyze_Block_Statement
880 -- In SPARK mode, we reject block statements. Note that the case of
881 -- block statements generated by the expander is fine.
883 if Nkind (Original_Node (N)) = N_Block_Statement then
884 Check_SPARK_Restriction ("block statement is not allowed", N);
887 -- If no handled statement sequence is present, things are really messed
888 -- up, and we just return immediately (defence against previous errors).
894 -- Detect whether the block is actually a rewritten return statement of
895 -- a build-in-place function.
897 Is_BIP_Return_Statement :=
899 and then Present (Entity (Id))
900 and then Ekind (Entity (Id)) = E_Return_Statement
901 and then Is_Build_In_Place_Function
902 (Return_Applies_To (Entity (Id)));
904 -- Normal processing with HSS present
907 EH : constant List_Id := Exception_Handlers (HSS);
908 Ent : Entity_Id := Empty;
911 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
912 -- Recursively save value of this global, will be restored on exit
915 -- Initialize unblocked exit count for statements of begin block
916 -- plus one for each exception handler that is present.
918 Unblocked_Exit_Count := 1;
921 Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
924 -- If a label is present analyze it and mark it as referenced
930 -- An error defense. If we have an identifier, but no entity, then
931 -- something is wrong. If previous errors, then just remove the
932 -- identifier and continue, otherwise raise an exception.
935 if Total_Errors_Detected /= 0 then
936 Set_Identifier (N, Empty);
942 Set_Ekind (Ent, E_Block);
943 Generate_Reference (Ent, N, ' ');
944 Generate_Definition (Ent);
946 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
947 Set_Label_Construct (Parent (Ent), N);
952 -- If no entity set, create a label entity
955 Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
956 Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
960 Set_Etype (Ent, Standard_Void_Type);
961 Set_Block_Node (Ent, Identifier (N));
964 -- The block served as an extended return statement. Ensure that any
965 -- entities created during the analysis and expansion of the return
966 -- object declaration are once again visible.
968 if Is_BIP_Return_Statement then
969 Install_Return_Entities (Ent);
972 if Present (Decls) then
973 Analyze_Declarations (Decls);
975 Inspect_Deferred_Constant_Completion (Decls);
979 Process_End_Label (HSS, 'e', Ent);
981 -- If exception handlers are present, then we indicate that enclosing
982 -- scopes contain a block with handlers. We only need to mark non-
988 Set_Has_Nested_Block_With_Handler (S);
989 exit when Is_Overloadable (S)
990 or else Ekind (S) = E_Package
991 or else Is_Generic_Unit (S);
996 Check_References (Ent);
997 Warn_On_Useless_Assignments (Ent);
1000 if Unblocked_Exit_Count = 0 then
1001 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1002 Check_Unreachable_Code (N);
1004 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1007 end Analyze_Block_Statement;
1009 ----------------------------
1010 -- Analyze_Case_Statement --
1011 ----------------------------
1013 procedure Analyze_Case_Statement (N : Node_Id) is
1015 Exp_Type : Entity_Id;
1016 Exp_Btype : Entity_Id;
1018 Dont_Care : Boolean;
1019 Others_Present : Boolean;
1021 pragma Warnings (Off, Last_Choice);
1022 pragma Warnings (Off, Dont_Care);
1023 -- Don't care about assigned values
1025 Statements_Analyzed : Boolean := False;
1026 -- Set True if at least some statement sequences get analyzed. If False
1027 -- on exit, means we had a serious error that prevented full analysis of
1028 -- the case statement, and as a result it is not a good idea to output
1029 -- warning messages about unreachable code.
1031 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1032 -- Recursively save value of this global, will be restored on exit
1034 procedure Non_Static_Choice_Error (Choice : Node_Id);
1035 -- Error routine invoked by the generic instantiation below when the
1036 -- case statement has a non static choice.
1038 procedure Process_Statements (Alternative : Node_Id);
1039 -- Analyzes all the statements associated with a case alternative.
1040 -- Needed by the generic instantiation below.
1042 package Case_Choices_Processing is new
1043 Generic_Choices_Processing
1044 (Get_Alternatives => Alternatives,
1045 Get_Choices => Discrete_Choices,
1046 Process_Empty_Choice => No_OP,
1047 Process_Non_Static_Choice => Non_Static_Choice_Error,
1048 Process_Associated_Node => Process_Statements);
1049 use Case_Choices_Processing;
1050 -- Instantiation of the generic choice processing package
1052 -----------------------------
1053 -- Non_Static_Choice_Error --
1054 -----------------------------
1056 procedure Non_Static_Choice_Error (Choice : Node_Id) is
1058 Flag_Non_Static_Expr
1059 ("choice given in case statement is not static!", Choice);
1060 end Non_Static_Choice_Error;
1062 ------------------------
1063 -- Process_Statements --
1064 ------------------------
1066 procedure Process_Statements (Alternative : Node_Id) is
1067 Choices : constant List_Id := Discrete_Choices (Alternative);
1071 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1072 Statements_Analyzed := True;
1074 -- An interesting optimization. If the case statement expression
1075 -- is a simple entity, then we can set the current value within an
1076 -- alternative if the alternative has one possible value.
1080 -- when 2 | 3 => beta
1081 -- when others => gamma
1083 -- Here we know that N is initially 1 within alpha, but for beta and
1084 -- gamma, we do not know anything more about the initial value.
1086 if Is_Entity_Name (Exp) then
1087 Ent := Entity (Exp);
1089 if Ekind_In (Ent, E_Variable,
1093 if List_Length (Choices) = 1
1094 and then Nkind (First (Choices)) in N_Subexpr
1095 and then Compile_Time_Known_Value (First (Choices))
1097 Set_Current_Value (Entity (Exp), First (Choices));
1100 Analyze_Statements (Statements (Alternative));
1102 -- After analyzing the case, set the current value to empty
1103 -- since we won't know what it is for the next alternative
1104 -- (unless reset by this same circuit), or after the case.
1106 Set_Current_Value (Entity (Exp), Empty);
1111 -- Case where expression is not an entity name of a variable
1113 Analyze_Statements (Statements (Alternative));
1114 end Process_Statements;
1116 -- Start of processing for Analyze_Case_Statement
1119 Unblocked_Exit_Count := 0;
1120 Exp := Expression (N);
1123 -- The expression must be of any discrete type. In rare cases, the
1124 -- expander constructs a case statement whose expression has a private
1125 -- type whose full view is discrete. This can happen when generating
1126 -- a stream operation for a variant type after the type is frozen,
1127 -- when the partial of view of the type of the discriminant is private.
1128 -- In that case, use the full view to analyze case alternatives.
1130 if not Is_Overloaded (Exp)
1131 and then not Comes_From_Source (N)
1132 and then Is_Private_Type (Etype (Exp))
1133 and then Present (Full_View (Etype (Exp)))
1134 and then Is_Discrete_Type (Full_View (Etype (Exp)))
1136 Resolve (Exp, Etype (Exp));
1137 Exp_Type := Full_View (Etype (Exp));
1140 Analyze_And_Resolve (Exp, Any_Discrete);
1141 Exp_Type := Etype (Exp);
1144 Check_Unset_Reference (Exp);
1145 Exp_Btype := Base_Type (Exp_Type);
1147 -- The expression must be of a discrete type which must be determinable
1148 -- independently of the context in which the expression occurs, but
1149 -- using the fact that the expression must be of a discrete type.
1150 -- Moreover, the type this expression must not be a character literal
1151 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1153 -- If error already reported by Resolve, nothing more to do
1155 if Exp_Btype = Any_Discrete
1156 or else Exp_Btype = Any_Type
1160 elsif Exp_Btype = Any_Character then
1162 ("character literal as case expression is ambiguous", Exp);
1165 elsif Ada_Version = Ada_83
1166 and then (Is_Generic_Type (Exp_Btype)
1167 or else Is_Generic_Type (Root_Type (Exp_Btype)))
1170 ("(Ada 83) case expression cannot be of a generic type", Exp);
1174 -- If the case expression is a formal object of mode in out, then treat
1175 -- it as having a nonstatic subtype by forcing use of the base type
1176 -- (which has to get passed to Check_Case_Choices below). Also use base
1177 -- type when the case expression is parenthesized.
1179 if Paren_Count (Exp) > 0
1180 or else (Is_Entity_Name (Exp)
1181 and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
1183 Exp_Type := Exp_Btype;
1186 -- Call instantiated Analyze_Choices which does the rest of the work
1188 Analyze_Choices (N, Exp_Type, Dont_Care, Others_Present);
1190 -- A case statement with a single OTHERS alternative is not allowed
1194 and then List_Length (Alternatives (N)) = 1
1196 Check_SPARK_Restriction
1197 ("OTHERS as unique case alternative is not allowed", N);
1200 if Exp_Type = Universal_Integer and then not Others_Present then
1201 Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
1204 -- If all our exits were blocked by unconditional transfers of control,
1205 -- then the entire CASE statement acts as an unconditional transfer of
1206 -- control, so treat it like one, and check unreachable code. Skip this
1207 -- test if we had serious errors preventing any statement analysis.
1209 if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
1210 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1211 Check_Unreachable_Code (N);
1213 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1216 if not Expander_Active
1217 and then Compile_Time_Known_Value (Expression (N))
1218 and then Serious_Errors_Detected = 0
1221 Chosen : constant Node_Id := Find_Static_Alternative (N);
1225 Alt := First (Alternatives (N));
1226 while Present (Alt) loop
1227 if Alt /= Chosen then
1228 Remove_Warning_Messages (Statements (Alt));
1235 end Analyze_Case_Statement;
1237 ----------------------------
1238 -- Analyze_Exit_Statement --
1239 ----------------------------
1241 -- If the exit includes a name, it must be the name of a currently open
1242 -- loop. Otherwise there must be an innermost open loop on the stack, to
1243 -- which the statement implicitly refers.
1245 -- Additionally, in SPARK mode:
1247 -- The exit can only name the closest enclosing loop;
1249 -- An exit with a when clause must be directly contained in a loop;
1251 -- An exit without a when clause must be directly contained in an
1252 -- if-statement with no elsif or else, which is itself directly contained
1253 -- in a loop. The exit must be the last statement in the if-statement.
1255 procedure Analyze_Exit_Statement (N : Node_Id) is
1256 Target : constant Node_Id := Name (N);
1257 Cond : constant Node_Id := Condition (N);
1258 Scope_Id : Entity_Id;
1264 Check_Unreachable_Code (N);
1267 if Present (Target) then
1269 U_Name := Entity (Target);
1271 if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
1272 Error_Msg_N ("invalid loop name in exit statement", N);
1276 if Has_Loop_In_Inner_Open_Scopes (U_Name) then
1277 Check_SPARK_Restriction
1278 ("exit label must name the closest enclosing loop", N);
1281 Set_Has_Exit (U_Name);
1288 for J in reverse 0 .. Scope_Stack.Last loop
1289 Scope_Id := Scope_Stack.Table (J).Entity;
1290 Kind := Ekind (Scope_Id);
1293 and then (No (Target) or else Scope_Id = U_Name)
1295 Set_Has_Exit (Scope_Id);
1298 elsif Kind = E_Block
1299 or else Kind = E_Loop
1300 or else Kind = E_Return_Statement
1306 ("cannot exit from program unit or accept statement", N);
1311 -- Verify that if present the condition is a Boolean expression
1313 if Present (Cond) then
1314 Analyze_And_Resolve (Cond, Any_Boolean);
1315 Check_Unset_Reference (Cond);
1318 -- In SPARK mode, verify that the exit statement respects the SPARK
1321 if Present (Cond) then
1322 if Nkind (Parent (N)) /= N_Loop_Statement then
1323 Check_SPARK_Restriction
1324 ("exit with when clause must be directly in loop", N);
1328 if Nkind (Parent (N)) /= N_If_Statement then
1329 if Nkind (Parent (N)) = N_Elsif_Part then
1330 Check_SPARK_Restriction
1331 ("exit must be in IF without ELSIF", N);
1333 Check_SPARK_Restriction ("exit must be directly in IF", N);
1336 elsif Nkind (Parent (Parent (N))) /= N_Loop_Statement then
1337 Check_SPARK_Restriction
1338 ("exit must be in IF directly in loop", N);
1340 -- First test the presence of ELSE, so that an exit in an ELSE leads
1341 -- to an error mentioning the ELSE.
1343 elsif Present (Else_Statements (Parent (N))) then
1344 Check_SPARK_Restriction ("exit must be in IF without ELSE", N);
1346 -- An exit in an ELSIF does not reach here, as it would have been
1347 -- detected in the case (Nkind (Parent (N)) /= N_If_Statement).
1349 elsif Present (Elsif_Parts (Parent (N))) then
1350 Check_SPARK_Restriction ("exit must be in IF without ELSIF", N);
1354 -- Chain exit statement to associated loop entity
1356 Set_Next_Exit_Statement (N, First_Exit_Statement (Scope_Id));
1357 Set_First_Exit_Statement (Scope_Id, N);
1359 -- Since the exit may take us out of a loop, any previous assignment
1360 -- statement is not useless, so clear last assignment indications. It
1361 -- is OK to keep other current values, since if the exit statement
1362 -- does not exit, then the current values are still valid.
1364 Kill_Current_Values (Last_Assignment_Only => True);
1365 end Analyze_Exit_Statement;
1367 ----------------------------
1368 -- Analyze_Goto_Statement --
1369 ----------------------------
1371 procedure Analyze_Goto_Statement (N : Node_Id) is
1372 Label : constant Node_Id := Name (N);
1373 Scope_Id : Entity_Id;
1374 Label_Scope : Entity_Id;
1375 Label_Ent : Entity_Id;
1378 Check_SPARK_Restriction ("goto statement is not allowed", N);
1380 -- Actual semantic checks
1382 Check_Unreachable_Code (N);
1383 Kill_Current_Values (Last_Assignment_Only => True);
1386 Label_Ent := Entity (Label);
1388 -- Ignore previous error
1390 if Label_Ent = Any_Id then
1393 -- We just have a label as the target of a goto
1395 elsif Ekind (Label_Ent) /= E_Label then
1396 Error_Msg_N ("target of goto statement must be a label", Label);
1399 -- Check that the target of the goto is reachable according to Ada
1400 -- scoping rules. Note: the special gotos we generate for optimizing
1401 -- local handling of exceptions would violate these rules, but we mark
1402 -- such gotos as analyzed when built, so this code is never entered.
1404 elsif not Reachable (Label_Ent) then
1405 Error_Msg_N ("target of goto statement is not reachable", Label);
1409 -- Here if goto passes initial validity checks
1411 Label_Scope := Enclosing_Scope (Label_Ent);
1413 for J in reverse 0 .. Scope_Stack.Last loop
1414 Scope_Id := Scope_Stack.Table (J).Entity;
1416 if Label_Scope = Scope_Id
1417 or else (Ekind (Scope_Id) /= E_Block
1418 and then Ekind (Scope_Id) /= E_Loop
1419 and then Ekind (Scope_Id) /= E_Return_Statement)
1421 if Scope_Id /= Label_Scope then
1423 ("cannot exit from program unit or accept statement", N);
1430 raise Program_Error;
1431 end Analyze_Goto_Statement;
1433 --------------------------
1434 -- Analyze_If_Statement --
1435 --------------------------
1437 -- A special complication arises in the analysis of if statements
1439 -- The expander has circuitry to completely delete code that it can tell
1440 -- will not be executed (as a result of compile time known conditions). In
1441 -- the analyzer, we ensure that code that will be deleted in this manner is
1442 -- analyzed but not expanded. This is obviously more efficient, but more
1443 -- significantly, difficulties arise if code is expanded and then
1444 -- eliminated (e.g. exception table entries disappear). Similarly, itypes
1445 -- generated in deleted code must be frozen from start, because the nodes
1446 -- on which they depend will not be available at the freeze point.
1448 procedure Analyze_If_Statement (N : Node_Id) is
1451 Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
1452 -- Recursively save value of this global, will be restored on exit
1454 Save_In_Deleted_Code : Boolean;
1456 Del : Boolean := False;
1457 -- This flag gets set True if a True condition has been found, which
1458 -- means that remaining ELSE/ELSIF parts are deleted.
1460 procedure Analyze_Cond_Then (Cnode : Node_Id);
1461 -- This is applied to either the N_If_Statement node itself or to an
1462 -- N_Elsif_Part node. It deals with analyzing the condition and the THEN
1463 -- statements associated with it.
1465 -----------------------
1466 -- Analyze_Cond_Then --
1467 -----------------------
1469 procedure Analyze_Cond_Then (Cnode : Node_Id) is
1470 Cond : constant Node_Id := Condition (Cnode);
1471 Tstm : constant List_Id := Then_Statements (Cnode);
1474 Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
1475 Analyze_And_Resolve (Cond, Any_Boolean);
1476 Check_Unset_Reference (Cond);
1477 Set_Current_Value_Condition (Cnode);
1479 -- If already deleting, then just analyze then statements
1482 Analyze_Statements (Tstm);
1484 -- Compile time known value, not deleting yet
1486 elsif Compile_Time_Known_Value (Cond) then
1487 Save_In_Deleted_Code := In_Deleted_Code;
1489 -- If condition is True, then analyze the THEN statements and set
1490 -- no expansion for ELSE and ELSIF parts.
1492 if Is_True (Expr_Value (Cond)) then
1493 Analyze_Statements (Tstm);
1495 Expander_Mode_Save_And_Set (False);
1496 In_Deleted_Code := True;
1498 -- If condition is False, analyze THEN with expansion off
1500 else -- Is_False (Expr_Value (Cond))
1501 Expander_Mode_Save_And_Set (False);
1502 In_Deleted_Code := True;
1503 Analyze_Statements (Tstm);
1504 Expander_Mode_Restore;
1505 In_Deleted_Code := Save_In_Deleted_Code;
1508 -- Not known at compile time, not deleting, normal analysis
1511 Analyze_Statements (Tstm);
1513 end Analyze_Cond_Then;
1515 -- Start of Analyze_If_Statement
1518 -- Initialize exit count for else statements. If there is no else part,
1519 -- this count will stay non-zero reflecting the fact that the uncovered
1520 -- else case is an unblocked exit.
1522 Unblocked_Exit_Count := 1;
1523 Analyze_Cond_Then (N);
1525 -- Now to analyze the elsif parts if any are present
1527 if Present (Elsif_Parts (N)) then
1528 E := First (Elsif_Parts (N));
1529 while Present (E) loop
1530 Analyze_Cond_Then (E);
1535 if Present (Else_Statements (N)) then
1536 Analyze_Statements (Else_Statements (N));
1539 -- If all our exits were blocked by unconditional transfers of control,
1540 -- then the entire IF statement acts as an unconditional transfer of
1541 -- control, so treat it like one, and check unreachable code.
1543 if Unblocked_Exit_Count = 0 then
1544 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1545 Check_Unreachable_Code (N);
1547 Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
1551 Expander_Mode_Restore;
1552 In_Deleted_Code := Save_In_Deleted_Code;
1555 if not Expander_Active
1556 and then Compile_Time_Known_Value (Condition (N))
1557 and then Serious_Errors_Detected = 0
1559 if Is_True (Expr_Value (Condition (N))) then
1560 Remove_Warning_Messages (Else_Statements (N));
1562 if Present (Elsif_Parts (N)) then
1563 E := First (Elsif_Parts (N));
1564 while Present (E) loop
1565 Remove_Warning_Messages (Then_Statements (E));
1571 Remove_Warning_Messages (Then_Statements (N));
1574 end Analyze_If_Statement;
1576 ----------------------------------------
1577 -- Analyze_Implicit_Label_Declaration --
1578 ----------------------------------------
1580 -- An implicit label declaration is generated in the innermost enclosing
1581 -- declarative part. This is done for labels, and block and loop names.
1583 -- Note: any changes in this routine may need to be reflected in
1584 -- Analyze_Label_Entity.
1586 procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
1587 Id : constant Node_Id := Defining_Identifier (N);
1590 Set_Ekind (Id, E_Label);
1591 Set_Etype (Id, Standard_Void_Type);
1592 Set_Enclosing_Scope (Id, Current_Scope);
1593 end Analyze_Implicit_Label_Declaration;
1595 ------------------------------
1596 -- Analyze_Iteration_Scheme --
1597 ------------------------------
1599 procedure Analyze_Iteration_Scheme (N : Node_Id) is
1601 procedure Process_Bounds (R : Node_Id);
1602 -- If the iteration is given by a range, create temporaries and
1603 -- assignment statements block to capture the bounds and perform
1604 -- required finalization actions in case a bound includes a function
1605 -- call that uses the temporary stack. We first pre-analyze a copy of
1606 -- the range in order to determine the expected type, and analyze and
1607 -- resolve the original bounds.
1609 procedure Check_Controlled_Array_Attribute (DS : Node_Id);
1610 -- If the bounds are given by a 'Range reference on a function call
1611 -- that returns a controlled array, introduce an explicit declaration
1612 -- to capture the bounds, so that the function result can be finalized
1613 -- in timely fashion.
1615 function Has_Call_Using_Secondary_Stack (N : Node_Id) return Boolean;
1616 -- N is the node for an arbitrary construct. This function searches the
1617 -- construct N to see if any expressions within it contain function
1618 -- calls that use the secondary stack, returning True if any such call
1619 -- is found, and False otherwise.
1621 procedure Pre_Analyze_Range (R_Copy : Node_Id);
1622 -- Determine expected type of range or domain of iteration of Ada 2012
1623 -- loop by analyzing separate copy. Do the analysis and resolution of
1624 -- the copy of the bound(s) with expansion disabled, to prevent the
1625 -- generation of finalization actions. This prevents memory leaks when
1626 -- the bounds contain calls to functions returning controlled arrays or
1627 -- when the domain of iteration is a container.
1629 -----------------------
1630 -- Pre_Analyze_Range --
1631 -----------------------
1633 procedure Pre_Analyze_Range (R_Copy : Node_Id) is
1634 Save_Analysis : Boolean;
1636 Save_Analysis := Full_Analysis;
1637 Full_Analysis := False;
1638 Expander_Mode_Save_And_Set (False);
1642 if Nkind (R_Copy) in N_Subexpr
1643 and then Is_Overloaded (R_Copy)
1646 -- Apply preference rules for range of predefined integer types,
1647 -- or diagnose true ambiguity.
1652 Found : Entity_Id := Empty;
1655 Get_First_Interp (R_Copy, I, It);
1656 while Present (It.Typ) loop
1657 if Is_Discrete_Type (It.Typ) then
1661 if Scope (Found) = Standard_Standard then
1664 elsif Scope (It.Typ) = Standard_Standard then
1668 -- Both of them are user-defined
1671 ("ambiguous bounds in range of iteration",
1673 Error_Msg_N ("\possible interpretations:", R_Copy);
1674 Error_Msg_NE ("\\} ", R_Copy, Found);
1675 Error_Msg_NE ("\\} ", R_Copy, It.Typ);
1681 Get_Next_Interp (I, It);
1686 if Is_Entity_Name (R_Copy)
1687 and then Is_Type (Entity (R_Copy))
1690 -- Subtype mark in iteration scheme
1694 elsif Nkind (R_Copy) in N_Subexpr then
1696 -- Expression in range, or Ada 2012 iterator
1701 Expander_Mode_Restore;
1702 Full_Analysis := Save_Analysis;
1703 end Pre_Analyze_Range;
1705 --------------------
1706 -- Process_Bounds --
1707 --------------------
1709 procedure Process_Bounds (R : Node_Id) is
1710 Loc : constant Source_Ptr := Sloc (N);
1711 R_Copy : constant Node_Id := New_Copy_Tree (R);
1712 Lo : constant Node_Id := Low_Bound (R);
1713 Hi : constant Node_Id := High_Bound (R);
1714 New_Lo_Bound : Node_Id;
1715 New_Hi_Bound : Node_Id;
1719 (Original_Bound : Node_Id;
1720 Analyzed_Bound : Node_Id) return Node_Id;
1721 -- Capture value of bound and return captured value
1728 (Original_Bound : Node_Id;
1729 Analyzed_Bound : Node_Id) return Node_Id
1736 -- If the bound is a constant or an object, no need for a separate
1737 -- declaration. If the bound is the result of previous expansion
1738 -- it is already analyzed and should not be modified. Note that
1739 -- the Bound will be resolved later, if needed, as part of the
1740 -- call to Make_Index (literal bounds may need to be resolved to
1743 if Analyzed (Original_Bound) then
1744 return Original_Bound;
1746 elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
1747 N_Character_Literal)
1748 or else Is_Entity_Name (Analyzed_Bound)
1750 Analyze_And_Resolve (Original_Bound, Typ);
1751 return Original_Bound;
1754 -- Here we need to capture the value
1756 Analyze_And_Resolve (Original_Bound, Typ);
1758 -- Normally, the best approach is simply to generate a constant
1759 -- declaration that captures the bound. However, there is a nasty
1760 -- case where this is wrong. If the bound is complex, and has a
1761 -- possible use of the secondary stack, we need to generate a
1762 -- separate assignment statement to ensure the creation of a block
1763 -- which will release the secondary stack.
1765 -- We prefer the constant declaration, since it leaves us with a
1766 -- proper trace of the value, useful in optimizations that get rid
1767 -- of junk range checks.
1769 if not Has_Call_Using_Secondary_Stack (Original_Bound) then
1770 Force_Evaluation (Original_Bound);
1771 return Original_Bound;
1774 Id := Make_Temporary (Loc, 'R', Original_Bound);
1776 -- Here we make a declaration with a separate assignment
1777 -- statement, and insert before loop header.
1780 Make_Object_Declaration (Loc,
1781 Defining_Identifier => Id,
1782 Object_Definition => New_Occurrence_Of (Typ, Loc));
1785 Make_Assignment_Statement (Loc,
1786 Name => New_Occurrence_Of (Id, Loc),
1787 Expression => Relocate_Node (Original_Bound));
1789 -- We must recursively clean in the relocated expression the flag
1790 -- analyzed to ensure that the expression is reanalyzed. Required
1791 -- to ensure that the transient scope is established now (because
1792 -- Establish_Transient_Scope discarded generating transient scopes
1793 -- in the analysis of the iteration scheme).
1795 Reset_Analyzed_Flags (Expression (Assign));
1797 Insert_Actions (Parent (N), New_List (Decl, Assign));
1799 -- Now that this temporary variable is initialized we decorate it
1800 -- as safe-to-reevaluate to inform to the backend that no further
1801 -- asignment will be issued and hence it can be handled as side
1802 -- effect free. Note that this decoration must be done when the
1803 -- assignment has been analyzed because otherwise it will be
1804 -- rejected (see Analyze_Assignment).
1806 Set_Is_Safe_To_Reevaluate (Id);
1808 Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
1810 if Nkind (Assign) = N_Assignment_Statement then
1811 return Expression (Assign);
1813 return Original_Bound;
1817 -- Start of processing for Process_Bounds
1820 Set_Parent (R_Copy, Parent (R));
1821 Pre_Analyze_Range (R_Copy);
1822 Typ := Etype (R_Copy);
1824 -- If the type of the discrete range is Universal_Integer, then the
1825 -- bound's type must be resolved to Integer, and any object used to
1826 -- hold the bound must also have type Integer, unless the literal
1827 -- bounds are constant-folded expressions with a user-defined type.
1829 if Typ = Universal_Integer then
1830 if Nkind (Lo) = N_Integer_Literal
1831 and then Present (Etype (Lo))
1832 and then Scope (Etype (Lo)) /= Standard_Standard
1836 elsif Nkind (Hi) = N_Integer_Literal
1837 and then Present (Etype (Hi))
1838 and then Scope (Etype (Hi)) /= Standard_Standard
1843 Typ := Standard_Integer;
1849 New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
1850 New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
1852 -- Propagate staticness to loop range itself, in case the
1853 -- corresponding subtype is static.
1855 if New_Lo_Bound /= Lo
1856 and then Is_Static_Expression (New_Lo_Bound)
1858 Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
1861 if New_Hi_Bound /= Hi
1862 and then Is_Static_Expression (New_Hi_Bound)
1864 Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
1868 --------------------------------------
1869 -- Check_Controlled_Array_Attribute --
1870 --------------------------------------
1872 procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
1874 if Nkind (DS) = N_Attribute_Reference
1875 and then Is_Entity_Name (Prefix (DS))
1876 and then Ekind (Entity (Prefix (DS))) = E_Function
1877 and then Is_Array_Type (Etype (Entity (Prefix (DS))))
1880 Component_Type (Etype (Entity (Prefix (DS)))))
1881 and then Expander_Active
1884 Loc : constant Source_Ptr := Sloc (N);
1885 Arr : constant Entity_Id := Etype (Entity (Prefix (DS)));
1886 Indx : constant Entity_Id :=
1887 Base_Type (Etype (First_Index (Arr)));
1888 Subt : constant Entity_Id := Make_Temporary (Loc, 'S');
1893 Make_Subtype_Declaration (Loc,
1894 Defining_Identifier => Subt,
1895 Subtype_Indication =>
1896 Make_Subtype_Indication (Loc,
1897 Subtype_Mark => New_Reference_To (Indx, Loc),
1899 Make_Range_Constraint (Loc,
1900 Relocate_Node (DS))));
1901 Insert_Before (Parent (N), Decl);
1905 Make_Attribute_Reference (Loc,
1906 Prefix => New_Reference_To (Subt, Loc),
1907 Attribute_Name => Attribute_Name (DS)));
1911 end Check_Controlled_Array_Attribute;
1913 ------------------------------------
1914 -- Has_Call_Using_Secondary_Stack --
1915 ------------------------------------
1917 function Has_Call_Using_Secondary_Stack (N : Node_Id) return Boolean is
1919 function Check_Call (N : Node_Id) return Traverse_Result;
1920 -- Check if N is a function call which uses the secondary stack
1926 function Check_Call (N : Node_Id) return Traverse_Result is
1929 Return_Typ : Entity_Id;
1932 if Nkind (N) = N_Function_Call then
1935 -- Call using access to subprogram with explicit dereference
1937 if Nkind (Nam) = N_Explicit_Dereference then
1938 Subp := Etype (Nam);
1943 Subp := Entity (Nam);
1946 Return_Typ := Etype (Subp);
1948 if Is_Composite_Type (Return_Typ)
1949 and then not Is_Constrained (Return_Typ)
1953 elsif Sec_Stack_Needed_For_Return (Subp) then
1958 -- Continue traversing the tree
1963 function Check_Calls is new Traverse_Func (Check_Call);
1965 -- Start of processing for Has_Call_Using_Secondary_Stack
1968 return Check_Calls (N) = Abandon;
1969 end Has_Call_Using_Secondary_Stack;
1971 -- Start of processing for Analyze_Iteration_Scheme
1974 -- If this is a rewritten quantified expression, the iteration scheme
1975 -- has been analyzed already. Do no repeat analysis because the loop
1976 -- variable is already declared.
1978 if Analyzed (N) then
1982 -- For an infinite loop, there is no iteration scheme
1988 -- Iteration scheme is present
1991 Cond : constant Node_Id := Condition (N);
1994 -- For WHILE loop, verify that the condition is a Boolean expression
1995 -- and resolve and check it.
1997 if Present (Cond) then
1998 Analyze_And_Resolve (Cond, Any_Boolean);
1999 Check_Unset_Reference (Cond);
2000 Set_Current_Value_Condition (N);
2003 -- For an iterator specification with "of", pre-analyze range to
2004 -- capture function calls that may require finalization actions.
2006 elsif Present (Iterator_Specification (N)) then
2007 Pre_Analyze_Range (Name (Iterator_Specification (N)));
2008 Analyze_Iterator_Specification (Iterator_Specification (N));
2010 -- Else we have a FOR loop
2014 LP : constant Node_Id := Loop_Parameter_Specification (N);
2015 Id : constant Entity_Id := Defining_Identifier (LP);
2016 DS : constant Node_Id := Discrete_Subtype_Definition (LP);
2023 -- We always consider the loop variable to be referenced, since
2024 -- the loop may be used just for counting purposes.
2026 Generate_Reference (Id, N, ' ');
2028 -- Check for the case of loop variable hiding a local variable
2029 -- (used later on to give a nice warning if the hidden variable
2030 -- is never assigned).
2033 H : constant Entity_Id := Homonym (Id);
2036 and then Enclosing_Dynamic_Scope (H) =
2037 Enclosing_Dynamic_Scope (Id)
2038 and then Ekind (H) = E_Variable
2039 and then Is_Discrete_Type (Etype (H))
2041 Set_Hiding_Loop_Variable (H, Id);
2045 -- Loop parameter specification must include subtype mark in
2048 if Nkind (DS) = N_Range then
2049 Check_SPARK_Restriction
2050 ("loop parameter specification must include subtype mark",
2054 -- Now analyze the subtype definition. If it is a range, create
2055 -- temporaries for bounds.
2057 if Nkind (DS) = N_Range
2058 and then Expander_Active
2060 Process_Bounds (DS);
2062 -- expander not active or else range of iteration is a subtype
2063 -- indication, an entity, or a function call that yields an
2064 -- aggregate or a container.
2067 D_Copy := New_Copy_Tree (DS);
2068 Set_Parent (D_Copy, Parent (DS));
2069 Pre_Analyze_Range (D_Copy);
2071 -- Ada2012: If the domain of iteration is a function call,
2072 -- it is the new iterator form.
2074 -- We have also implemented the shorter form : for X in S
2075 -- for Alfa use. In this case, 'Old and 'Result must be
2076 -- treated as entity names over which iterators are legal.
2078 if Nkind (D_Copy) = N_Function_Call
2081 and then (Nkind (D_Copy) = N_Attribute_Reference
2083 (Attribute_Name (D_Copy) = Name_Result
2084 or else Attribute_Name (D_Copy) = Name_Old)))
2086 (Is_Entity_Name (D_Copy)
2087 and then not Is_Type (Entity (D_Copy)))
2089 -- This is an iterator specification. Rewrite as such
2090 -- and analyze, to capture function calls that may
2091 -- require finalization actions.
2094 I_Spec : constant Node_Id :=
2095 Make_Iterator_Specification (Sloc (LP),
2096 Defining_Identifier =>
2099 Subtype_Indication => Empty,
2101 Reverse_Present (LP));
2103 Set_Iterator_Specification (N, I_Spec);
2104 Set_Loop_Parameter_Specification (N, Empty);
2105 Analyze_Iterator_Specification (I_Spec);
2107 -- In a generic context, analyze the original domain
2108 -- of iteration, for name capture.
2110 if not Expander_Active then
2114 -- Set kind of loop parameter, which may be used in
2115 -- the subsequent analysis of the condition in a
2116 -- quantified expression.
2118 Set_Ekind (Id, E_Loop_Parameter);
2122 -- Domain of iteration is not a function call, and is
2123 -- side-effect free.
2134 -- Some additional checks if we are iterating through a type
2136 if Is_Entity_Name (DS)
2137 and then Present (Entity (DS))
2138 and then Is_Type (Entity (DS))
2140 -- The subtype indication may denote the completion of an
2141 -- incomplete type declaration.
2143 if Ekind (Entity (DS)) = E_Incomplete_Type then
2144 Set_Entity (DS, Get_Full_View (Entity (DS)));
2145 Set_Etype (DS, Entity (DS));
2148 -- Attempt to iterate through non-static predicate
2150 if Is_Discrete_Type (Entity (DS))
2151 and then Present (Predicate_Function (Entity (DS)))
2152 and then No (Static_Predicate (Entity (DS)))
2154 Bad_Predicated_Subtype_Use
2155 ("cannot use subtype& with non-static "
2156 & "predicate for loop iteration", DS, Entity (DS));
2160 -- Error if not discrete type
2162 if not Is_Discrete_Type (Etype (DS)) then
2163 Wrong_Type (DS, Any_Discrete);
2164 Set_Etype (DS, Any_Type);
2167 Check_Controlled_Array_Attribute (DS);
2169 Make_Index (DS, LP, In_Iter_Schm => True);
2171 Set_Ekind (Id, E_Loop_Parameter);
2173 -- If the loop is part of a predicate or precondition, it may
2174 -- be analyzed twice, once in the source and once on the copy
2175 -- used to check conformance. Preserve the original itype
2176 -- because the second one may be created in a different scope,
2177 -- e.g. a precondition procedure, leading to a crash in GIGI.
2179 if No (Etype (Id)) or else Etype (Id) = Any_Type then
2180 Set_Etype (Id, Etype (DS));
2183 -- Treat a range as an implicit reference to the type, to
2184 -- inhibit spurious warnings.
2186 Generate_Reference (Base_Type (Etype (DS)), N, ' ');
2187 Set_Is_Known_Valid (Id, True);
2189 -- The loop is not a declarative part, so the only entity
2190 -- declared "within" must be frozen explicitly.
2193 Flist : constant List_Id := Freeze_Entity (Id, N);
2195 if Is_Non_Empty_List (Flist) then
2196 Insert_Actions (N, Flist);
2200 -- Check for null or possibly null range and issue warning. We
2201 -- suppress such messages in generic templates and instances,
2202 -- because in practice they tend to be dubious in these cases.
2204 if Nkind (DS) = N_Range and then Comes_From_Source (N) then
2206 L : constant Node_Id := Low_Bound (DS);
2207 H : constant Node_Id := High_Bound (DS);
2210 -- If range of loop is null, issue warning
2212 if Compile_Time_Compare
2213 (L, H, Assume_Valid => True) = GT
2215 -- Suppress the warning if inside a generic template
2216 -- or instance, since in practice they tend to be
2217 -- dubious in these cases since they can result from
2218 -- intended parametrization.
2220 if not Inside_A_Generic
2221 and then not In_Instance
2223 -- Specialize msg if invalid values could make the
2224 -- loop non-null after all.
2226 if Compile_Time_Compare
2227 (L, H, Assume_Valid => False) = GT
2230 ("?loop range is null, loop will not execute",
2233 -- Since we know the range of the loop is null,
2234 -- set the appropriate flag to remove the loop
2235 -- entirely during expansion.
2237 Set_Is_Null_Loop (Parent (N));
2239 -- Here is where the loop could execute because
2240 -- of invalid values, so issue appropriate
2241 -- message and in this case we do not set the
2242 -- Is_Null_Loop flag since the loop may execute.
2246 ("?loop range may be null, "
2247 & "loop may not execute",
2250 ("?can only execute if invalid values "
2256 -- In either case, suppress warnings in the body of
2257 -- the loop, since it is likely that these warnings
2258 -- will be inappropriate if the loop never actually
2259 -- executes, which is likely.
2261 Set_Suppress_Loop_Warnings (Parent (N));
2263 -- The other case for a warning is a reverse loop
2264 -- where the upper bound is the integer literal zero
2265 -- or one, and the lower bound can be positive.
2267 -- For example, we have
2269 -- for J in reverse N .. 1 loop
2271 -- In practice, this is very likely to be a case of
2272 -- reversing the bounds incorrectly in the range.
2274 elsif Reverse_Present (LP)
2275 and then Nkind (Original_Node (H)) =
2277 and then (Intval (Original_Node (H)) = Uint_0
2279 Intval (Original_Node (H)) = Uint_1)
2281 Error_Msg_N ("?loop range may be null", DS);
2282 Error_Msg_N ("\?bounds may be wrong way round", DS);
2289 end Analyze_Iteration_Scheme;
2291 -------------------------------------
2292 -- Analyze_Iterator_Specification --
2293 -------------------------------------
2295 procedure Analyze_Iterator_Specification (N : Node_Id) is
2296 Loc : constant Source_Ptr := Sloc (N);
2297 Def_Id : constant Node_Id := Defining_Identifier (N);
2298 Subt : constant Node_Id := Subtype_Indication (N);
2299 Iter_Name : constant Node_Id := Name (N);
2305 -- In semantics and Alfa modes, introduce loop variable so that loop
2306 -- body can be properly analyzed. Otherwise this is one after expansion.
2308 if Operating_Mode = Check_Semantics
2311 Enter_Name (Def_Id);
2314 Set_Ekind (Def_Id, E_Variable);
2316 if Present (Subt) then
2320 -- If domain of iteration is an expression, create a declaration for
2321 -- it, so that finalization actions are introduced outside of the loop.
2322 -- The declaration must be a renaming because the body of the loop may
2323 -- assign to elements.
2325 if not Is_Entity_Name (Iter_Name) then
2327 Id : constant Entity_Id := Make_Temporary (Loc, 'R', Iter_Name);
2331 Typ := Etype (Iter_Name);
2334 Make_Object_Renaming_Declaration (Loc,
2335 Defining_Identifier => Id,
2336 Subtype_Mark => New_Occurrence_Of (Typ, Loc),
2337 Name => Relocate_Node (Iter_Name));
2339 Insert_Actions (Parent (Parent (N)), New_List (Decl));
2340 Rewrite (Name (N), New_Occurrence_Of (Id, Loc));
2341 Set_Etype (Id, Typ);
2342 Set_Etype (Name (N), Typ);
2345 -- Container is an entity or an array with uncontrolled components, or
2346 -- else it is a container iterator given by a function call, typically
2347 -- called Iterate in the case of predefined containers, even though
2348 -- Iterate is not a reserved name. What matter is that the return type
2349 -- of the function is an iterator type.
2352 Analyze (Iter_Name);
2354 if Nkind (Iter_Name) = N_Function_Call then
2356 C : constant Node_Id := Name (Iter_Name);
2361 if not Is_Overloaded (Iter_Name) then
2362 Resolve (Iter_Name, Etype (C));
2365 Get_First_Interp (C, I, It);
2366 while It.Typ /= Empty loop
2367 if Reverse_Present (N) then
2368 if Is_Reversible_Iterator (It.Typ) then
2369 Resolve (Iter_Name, It.Typ);
2373 elsif Is_Iterator (It.Typ) then
2374 Resolve (Iter_Name, It.Typ);
2378 Get_Next_Interp (I, It);
2383 -- Domain of iteration is not overloaded
2386 Resolve (Iter_Name, Etype (Iter_Name));
2390 Typ := Etype (Iter_Name);
2392 if Is_Array_Type (Typ) then
2393 if Of_Present (N) then
2394 Set_Etype (Def_Id, Component_Type (Typ));
2396 -- Here we have a missing Range attribute
2400 ("missing Range attribute in iteration over an array", N);
2402 -- In Ada 2012 mode, this may be an attempt at an iterator
2404 if Ada_Version >= Ada_2012 then
2406 ("\if& is meant to designate an element of the array, use OF",
2410 -- Prevent cascaded errors
2412 Set_Ekind (Def_Id, E_Loop_Parameter);
2413 Set_Etype (Def_Id, Etype (First_Index (Typ)));
2416 -- Check for type error in iterator
2418 elsif Typ = Any_Type then
2421 -- Iteration over a container
2424 Set_Ekind (Def_Id, E_Loop_Parameter);
2426 if Of_Present (N) then
2428 -- The type of the loop variable is the Iterator_Element aspect of
2429 -- the container type.
2432 Entity (Find_Aspect (Typ, Aspect_Iterator_Element)));
2435 -- For an iteration of the form IN, the name must denote an
2436 -- iterator, typically the result of a call to Iterate. Give a
2437 -- useful error message when the name is a container by itself.
2439 if Is_Entity_Name (Original_Node (Name (N)))
2440 and then not Is_Iterator (Typ)
2443 ("name must be an iterator, not a container", Name (N));
2446 ("\to iterate directly over a container, write `of &`",
2447 Name (N), Original_Node (Name (N)));
2450 -- The result type of Iterate function is the classwide type of
2451 -- the interface parent. We need the specific Cursor type defined
2452 -- in the container package.
2454 Ent := First_Entity (Scope (Typ));
2455 while Present (Ent) loop
2456 if Chars (Ent) = Name_Cursor then
2457 Set_Etype (Def_Id, Etype (Ent));
2465 end Analyze_Iterator_Specification;
2471 -- Note: the semantic work required for analyzing labels (setting them as
2472 -- reachable) was done in a prepass through the statements in the block,
2473 -- so that forward gotos would be properly handled. See Analyze_Statements
2474 -- for further details. The only processing required here is to deal with
2475 -- optimizations that depend on an assumption of sequential control flow,
2476 -- since of course the occurrence of a label breaks this assumption.
2478 procedure Analyze_Label (N : Node_Id) is
2479 pragma Warnings (Off, N);
2481 Kill_Current_Values;
2484 --------------------------
2485 -- Analyze_Label_Entity --
2486 --------------------------
2488 procedure Analyze_Label_Entity (E : Entity_Id) is
2490 Set_Ekind (E, E_Label);
2491 Set_Etype (E, Standard_Void_Type);
2492 Set_Enclosing_Scope (E, Current_Scope);
2493 Set_Reachable (E, True);
2494 end Analyze_Label_Entity;
2496 ----------------------------
2497 -- Analyze_Loop_Statement --
2498 ----------------------------
2500 procedure Analyze_Loop_Statement (N : Node_Id) is
2501 Loop_Statement : constant Node_Id := N;
2503 Id : constant Node_Id := Identifier (Loop_Statement);
2504 Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
2508 if Present (Id) then
2510 -- Make name visible, e.g. for use in exit statements. Loop labels
2511 -- are always considered to be referenced.
2516 -- Guard against serious error (typically, a scope mismatch when
2517 -- semantic analysis is requested) by creating loop entity to
2518 -- continue analysis.
2521 if Total_Errors_Detected /= 0 then
2524 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2526 raise Program_Error;
2530 Generate_Reference (Ent, Loop_Statement, ' ');
2531 Generate_Definition (Ent);
2533 -- If we found a label, mark its type. If not, ignore it, since it
2534 -- means we have a conflicting declaration, which would already
2535 -- have been diagnosed at declaration time. Set Label_Construct
2536 -- of the implicit label declaration, which is not created by the
2537 -- parser for generic units.
2539 if Ekind (Ent) = E_Label then
2540 Set_Ekind (Ent, E_Loop);
2542 if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
2543 Set_Label_Construct (Parent (Ent), Loop_Statement);
2548 -- Case of no identifier present
2553 (E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
2554 Set_Etype (Ent, Standard_Void_Type);
2555 Set_Parent (Ent, Loop_Statement);
2558 -- Kill current values on entry to loop, since statements in the body of
2559 -- the loop may have been executed before the loop is entered. Similarly
2560 -- we kill values after the loop, since we do not know that the body of
2561 -- the loop was executed.
2563 Kill_Current_Values;
2565 Analyze_Iteration_Scheme (Iter);
2567 -- Analyze the statements of the body except in the case of an Ada 2012
2568 -- iterator with the expander active. In this case the expander will do
2569 -- a rewrite of the loop into a while loop. We will then analyze the
2570 -- loop body when we analyze this while loop.
2572 -- We need to do this delay because if the container is for indefinite
2573 -- types the actual subtype of the components will only be determined
2574 -- when the cursor declaration is analyzed.
2576 -- If the expander is not active, then we want to analyze the loop body
2577 -- now even in the Ada 2012 iterator case, since the rewriting will not
2578 -- be done. Insert the loop variable in the current scope, if not done
2579 -- when analysing the iteration scheme.
2582 or else No (Iterator_Specification (Iter))
2583 or else not Expander_Active
2586 and then Present (Iterator_Specification (Iter))
2589 Id : constant Entity_Id :=
2590 Defining_Identifier (Iterator_Specification (Iter));
2592 if Scope (Id) /= Current_Scope then
2598 Analyze_Statements (Statements (Loop_Statement));
2601 -- Finish up processing for the loop. We kill all current values, since
2602 -- in general we don't know if the statements in the loop have been
2603 -- executed. We could do a bit better than this with a loop that we
2604 -- know will execute at least once, but it's not worth the trouble and
2605 -- the front end is not in the business of flow tracing.
2607 Process_End_Label (Loop_Statement, 'e', Ent);
2609 Kill_Current_Values;
2611 -- Check for infinite loop. Skip check for generated code, since it
2612 -- justs waste time and makes debugging the routine called harder.
2614 -- Note that we have to wait till the body of the loop is fully analyzed
2615 -- before making this call, since Check_Infinite_Loop_Warning relies on
2616 -- being able to use semantic visibility information to find references.
2618 if Comes_From_Source (N) then
2619 Check_Infinite_Loop_Warning (N);
2622 -- Code after loop is unreachable if the loop has no WHILE or FOR and
2623 -- contains no EXIT statements within the body of the loop.
2625 if No (Iter) and then not Has_Exit (Ent) then
2626 Check_Unreachable_Code (N);
2628 end Analyze_Loop_Statement;
2630 ----------------------------
2631 -- Analyze_Null_Statement --
2632 ----------------------------
2634 -- Note: the semantics of the null statement is implemented by a single
2635 -- null statement, too bad everything isn't as simple as this!
2637 procedure Analyze_Null_Statement (N : Node_Id) is
2638 pragma Warnings (Off, N);
2641 end Analyze_Null_Statement;
2643 ------------------------
2644 -- Analyze_Statements --
2645 ------------------------
2647 procedure Analyze_Statements (L : List_Id) is
2652 -- The labels declared in the statement list are reachable from
2653 -- statements in the list. We do this as a prepass so that any goto
2654 -- statement will be properly flagged if its target is not reachable.
2655 -- This is not required, but is nice behavior!
2658 while Present (S) loop
2659 if Nkind (S) = N_Label then
2660 Analyze (Identifier (S));
2661 Lab := Entity (Identifier (S));
2663 -- If we found a label mark it as reachable
2665 if Ekind (Lab) = E_Label then
2666 Generate_Definition (Lab);
2667 Set_Reachable (Lab);
2669 if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
2670 Set_Label_Construct (Parent (Lab), S);
2673 -- If we failed to find a label, it means the implicit declaration
2674 -- of the label was hidden. A for-loop parameter can do this to
2675 -- a label with the same name inside the loop, since the implicit
2676 -- label declaration is in the innermost enclosing body or block
2680 Error_Msg_Sloc := Sloc (Lab);
2682 ("implicit label declaration for & is hidden#",
2690 -- Perform semantic analysis on all statements
2692 Conditional_Statements_Begin;
2695 while Present (S) loop
2700 Conditional_Statements_End;
2702 -- Make labels unreachable. Visibility is not sufficient, because labels
2703 -- in one if-branch for example are not reachable from the other branch,
2704 -- even though their declarations are in the enclosing declarative part.
2707 while Present (S) loop
2708 if Nkind (S) = N_Label then
2709 Set_Reachable (Entity (Identifier (S)), False);
2714 end Analyze_Statements;
2716 ----------------------------
2717 -- Check_Unreachable_Code --
2718 ----------------------------
2720 procedure Check_Unreachable_Code (N : Node_Id) is
2721 Error_Node : Node_Id;
2725 if Is_List_Member (N)
2726 and then Comes_From_Source (N)
2732 Nxt := Original_Node (Next (N));
2734 -- If a label follows us, then we never have dead code, since
2735 -- someone could branch to the label, so we just ignore it, unless
2736 -- we are in formal mode where goto statements are not allowed.
2738 if Nkind (Nxt) = N_Label
2739 and then not Restriction_Check_Required (SPARK)
2743 -- Otherwise see if we have a real statement following us
2746 and then Comes_From_Source (Nxt)
2747 and then Is_Statement (Nxt)
2749 -- Special very annoying exception. If we have a return that
2750 -- follows a raise, then we allow it without a warning, since
2751 -- the Ada RM annoyingly requires a useless return here!
2753 if Nkind (Original_Node (N)) /= N_Raise_Statement
2754 or else Nkind (Nxt) /= N_Simple_Return_Statement
2756 -- The rather strange shenanigans with the warning message
2757 -- here reflects the fact that Kill_Dead_Code is very good
2758 -- at removing warnings in deleted code, and this is one
2759 -- warning we would prefer NOT to have removed.
2763 -- If we have unreachable code, analyze and remove the
2764 -- unreachable code, since it is useless and we don't
2765 -- want to generate junk warnings.
2767 -- We skip this step if we are not in code generation mode.
2768 -- This is the one case where we remove dead code in the
2769 -- semantics as opposed to the expander, and we do not want
2770 -- to remove code if we are not in code generation mode,
2771 -- since this messes up the ASIS trees.
2773 -- Note that one might react by moving the whole circuit to
2774 -- exp_ch5, but then we lose the warning in -gnatc mode.
2776 if Operating_Mode = Generate_Code then
2780 -- Quit deleting when we have nothing more to delete
2781 -- or if we hit a label (since someone could transfer
2782 -- control to a label, so we should not delete it).
2784 exit when No (Nxt) or else Nkind (Nxt) = N_Label;
2786 -- Statement/declaration is to be deleted
2790 Kill_Dead_Code (Nxt);
2794 -- Now issue the warning (or error in formal mode)
2796 if Restriction_Check_Required (SPARK) then
2797 Check_SPARK_Restriction
2798 ("unreachable code is not allowed", Error_Node);
2800 Error_Msg ("?unreachable code!", Sloc (Error_Node));
2804 -- If the unconditional transfer of control instruction is the
2805 -- last statement of a sequence, then see if our parent is one of
2806 -- the constructs for which we count unblocked exits, and if so,
2807 -- adjust the count.
2812 -- Statements in THEN part or ELSE part of IF statement
2814 if Nkind (P) = N_If_Statement then
2817 -- Statements in ELSIF part of an IF statement
2819 elsif Nkind (P) = N_Elsif_Part then
2821 pragma Assert (Nkind (P) = N_If_Statement);
2823 -- Statements in CASE statement alternative
2825 elsif Nkind (P) = N_Case_Statement_Alternative then
2827 pragma Assert (Nkind (P) = N_Case_Statement);
2829 -- Statements in body of block
2831 elsif Nkind (P) = N_Handled_Sequence_Of_Statements
2832 and then Nkind (Parent (P)) = N_Block_Statement
2836 -- Statements in exception handler in a block
2838 elsif Nkind (P) = N_Exception_Handler
2839 and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
2840 and then Nkind (Parent (Parent (P))) = N_Block_Statement
2844 -- None of these cases, so return
2850 -- This was one of the cases we are looking for (i.e. the
2851 -- parent construct was IF, CASE or block) so decrement count.
2853 Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
2857 end Check_Unreachable_Code;