1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Atree
; use Atree
;
27 with Checks
; use Checks
;
28 with Einfo
; use Einfo
;
29 with Errout
; use Errout
;
30 with Expander
; use Expander
;
31 with Exp_Util
; use Exp_Util
;
32 with Freeze
; use Freeze
;
34 with Lib
.Xref
; use Lib
.Xref
;
35 with Namet
; use Namet
;
36 with Nlists
; use Nlists
;
37 with Nmake
; use Nmake
;
39 with Rtsfind
; use Rtsfind
;
41 with Sem_Aux
; use Sem_Aux
;
42 with Sem_Case
; use Sem_Case
;
43 with Sem_Ch3
; use Sem_Ch3
;
44 with Sem_Ch8
; use Sem_Ch8
;
45 with Sem_Disp
; use Sem_Disp
;
46 with Sem_Elab
; use Sem_Elab
;
47 with Sem_Eval
; use Sem_Eval
;
48 with Sem_Res
; use Sem_Res
;
49 with Sem_Type
; use Sem_Type
;
50 with Sem_Util
; use Sem_Util
;
51 with Sem_Warn
; use Sem_Warn
;
52 with Snames
; use Snames
;
53 with Stand
; use Stand
;
54 with Sinfo
; use Sinfo
;
55 with Targparm
; use Targparm
;
56 with Tbuild
; use Tbuild
;
57 with Uintp
; use Uintp
;
59 package body Sem_Ch5
is
61 Unblocked_Exit_Count
: Nat
:= 0;
62 -- This variable is used when processing if statements, case statements,
63 -- and block statements. It counts the number of exit points that are not
64 -- blocked by unconditional transfer instructions: for IF and CASE, these
65 -- are the branches of the conditional; for a block, they are the statement
66 -- sequence of the block, and the statement sequences of any exception
67 -- handlers that are part of the block. When processing is complete, if
68 -- this count is zero, it means that control cannot fall through the IF,
69 -- CASE or block statement. This is used for the generation of warning
70 -- messages. This variable is recursively saved on entry to processing the
71 -- construct, and restored on exit.
73 ------------------------
74 -- Analyze_Assignment --
75 ------------------------
77 procedure Analyze_Assignment
(N
: Node_Id
) is
78 Lhs
: constant Node_Id
:= Name
(N
);
79 Rhs
: constant Node_Id
:= Expression
(N
);
84 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
);
85 -- N is the node for the left hand side of an assignment, and it is not
86 -- a variable. This routine issues an appropriate diagnostic.
89 -- This is called to kill current value settings of a simple variable
90 -- on the left hand side. We call it if we find any error in analyzing
91 -- the assignment, and at the end of processing before setting any new
92 -- current values in place.
94 procedure Set_Assignment_Type
96 Opnd_Type
: in out Entity_Id
);
97 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
98 -- is the nominal subtype. This procedure is used to deal with cases
99 -- where the nominal subtype must be replaced by the actual subtype.
101 -------------------------------
102 -- Diagnose_Non_Variable_Lhs --
103 -------------------------------
105 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
) is
107 -- Not worth posting another error if left hand side already
108 -- flagged as being illegal in some respect.
110 if Error_Posted
(N
) then
113 -- Some special bad cases of entity names
115 elsif Is_Entity_Name
(N
) then
117 Ent
: constant Entity_Id
:= Entity
(N
);
120 if Ekind
(Ent
) = E_In_Parameter
then
122 ("assignment to IN mode parameter not allowed", N
);
124 -- Renamings of protected private components are turned into
125 -- constants when compiling a protected function. In the case
126 -- of single protected types, the private component appears
129 elsif (Is_Prival
(Ent
)
131 (Ekind
(Current_Scope
) = E_Function
132 or else Ekind
(Enclosing_Dynamic_Scope
(
133 Current_Scope
)) = E_Function
))
135 (Ekind
(Ent
) = E_Component
136 and then Is_Protected_Type
(Scope
(Ent
)))
139 ("protected function cannot modify protected object", N
);
141 elsif Ekind
(Ent
) = E_Loop_Parameter
then
143 ("assignment to loop parameter not allowed", N
);
147 ("left hand side of assignment must be a variable", N
);
151 -- For indexed components or selected components, test prefix
153 elsif Nkind
(N
) = N_Indexed_Component
then
154 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
156 -- Another special case for assignment to discriminant
158 elsif Nkind
(N
) = N_Selected_Component
then
159 if Present
(Entity
(Selector_Name
(N
)))
160 and then Ekind
(Entity
(Selector_Name
(N
))) = E_Discriminant
163 ("assignment to discriminant not allowed", N
);
165 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
169 -- If we fall through, we have no special message to issue!
171 Error_Msg_N
("left hand side of assignment must be a variable", N
);
173 end Diagnose_Non_Variable_Lhs
;
179 procedure Kill_Lhs
is
181 if Is_Entity_Name
(Lhs
) then
183 Ent
: constant Entity_Id
:= Entity
(Lhs
);
185 if Present
(Ent
) then
186 Kill_Current_Values
(Ent
);
192 -------------------------
193 -- Set_Assignment_Type --
194 -------------------------
196 procedure Set_Assignment_Type
198 Opnd_Type
: in out Entity_Id
)
201 Require_Entity
(Opnd
);
203 -- If the assignment operand is an in-out or out parameter, then we
204 -- get the actual subtype (needed for the unconstrained case).
205 -- If the operand is the actual in an entry declaration, then within
206 -- the accept statement it is replaced with a local renaming, which
207 -- may also have an actual subtype.
209 if Is_Entity_Name
(Opnd
)
210 and then (Ekind
(Entity
(Opnd
)) = E_Out_Parameter
211 or else Ekind
(Entity
(Opnd
)) =
213 or else Ekind
(Entity
(Opnd
)) =
214 E_Generic_In_Out_Parameter
216 (Ekind
(Entity
(Opnd
)) = E_Variable
217 and then Nkind
(Parent
(Entity
(Opnd
))) =
218 N_Object_Renaming_Declaration
219 and then Nkind
(Parent
(Parent
(Entity
(Opnd
)))) =
222 Opnd_Type
:= Get_Actual_Subtype
(Opnd
);
224 -- If assignment operand is a component reference, then we get the
225 -- actual subtype of the component for the unconstrained case.
227 elsif Nkind_In
(Opnd
, N_Selected_Component
, N_Explicit_Dereference
)
228 and then not Is_Unchecked_Union
(Opnd_Type
)
230 Decl
:= Build_Actual_Subtype_Of_Component
(Opnd_Type
, Opnd
);
232 if Present
(Decl
) then
233 Insert_Action
(N
, Decl
);
234 Mark_Rewrite_Insertion
(Decl
);
236 Opnd_Type
:= Defining_Identifier
(Decl
);
237 Set_Etype
(Opnd
, Opnd_Type
);
238 Freeze_Itype
(Opnd_Type
, N
);
240 elsif Is_Constrained
(Etype
(Opnd
)) then
241 Opnd_Type
:= Etype
(Opnd
);
244 -- For slice, use the constrained subtype created for the slice
246 elsif Nkind
(Opnd
) = N_Slice
then
247 Opnd_Type
:= Etype
(Opnd
);
249 end Set_Assignment_Type
;
251 -- Start of processing for Analyze_Assignment
254 Mark_Coextensions
(N
, Rhs
);
259 -- Start type analysis for assignment
263 -- In the most general case, both Lhs and Rhs can be overloaded, and we
264 -- must compute the intersection of the possible types on each side.
266 if Is_Overloaded
(Lhs
) then
273 Get_First_Interp
(Lhs
, I
, It
);
275 while Present
(It
.Typ
) loop
276 if Has_Compatible_Type
(Rhs
, It
.Typ
) then
277 if T1
/= Any_Type
then
279 -- An explicit dereference is overloaded if the prefix
280 -- is. Try to remove the ambiguity on the prefix, the
281 -- error will be posted there if the ambiguity is real.
283 if Nkind
(Lhs
) = N_Explicit_Dereference
then
286 PI1
: Interp_Index
:= 0;
292 Get_First_Interp
(Prefix
(Lhs
), PI
, PIt
);
294 while Present
(PIt
.Typ
) loop
295 if Is_Access_Type
(PIt
.Typ
)
296 and then Has_Compatible_Type
297 (Rhs
, Designated_Type
(PIt
.Typ
))
301 Disambiguate
(Prefix
(Lhs
),
304 if PIt
= No_Interp
then
306 ("ambiguous left-hand side"
307 & " in assignment", Lhs
);
310 Resolve
(Prefix
(Lhs
), PIt
.Typ
);
320 Get_Next_Interp
(PI
, PIt
);
326 ("ambiguous left-hand side in assignment", Lhs
);
334 Get_Next_Interp
(I
, It
);
338 if T1
= Any_Type
then
340 ("no valid types for left-hand side for assignment", Lhs
);
346 -- The resulting assignment type is T1, so now we will resolve the
347 -- left hand side of the assignment using this determined type.
351 -- Cases where Lhs is not a variable
353 if not Is_Variable
(Lhs
) then
355 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
356 -- a protected object.
363 if Ada_Version
>= Ada_2005
then
365 -- Handle chains of renamings
368 while Nkind
(Ent
) in N_Has_Entity
369 and then Present
(Entity
(Ent
))
370 and then Present
(Renamed_Object
(Entity
(Ent
)))
372 Ent
:= Renamed_Object
(Entity
(Ent
));
375 if (Nkind
(Ent
) = N_Attribute_Reference
376 and then Attribute_Name
(Ent
) = Name_Priority
)
378 -- Renamings of the attribute Priority applied to protected
379 -- objects have been previously expanded into calls to the
380 -- Get_Ceiling run-time subprogram.
383 (Nkind
(Ent
) = N_Function_Call
384 and then (Entity
(Name
(Ent
)) = RTE
(RE_Get_Ceiling
)
386 Entity
(Name
(Ent
)) = RTE
(RO_PE_Get_Ceiling
)))
388 -- The enclosing subprogram cannot be a protected function
391 while not (Is_Subprogram
(S
)
392 and then Convention
(S
) = Convention_Protected
)
393 and then S
/= Standard_Standard
398 if Ekind
(S
) = E_Function
399 and then Convention
(S
) = Convention_Protected
402 ("protected function cannot modify protected object",
406 -- Changes of the ceiling priority of the protected object
407 -- are only effective if the Ceiling_Locking policy is in
408 -- effect (AARM D.5.2 (5/2)).
410 if Locking_Policy
/= 'C' then
411 Error_Msg_N
("assignment to the attribute PRIORITY has " &
413 Error_Msg_N
("\since no Locking_Policy has been " &
422 Diagnose_Non_Variable_Lhs
(Lhs
);
425 -- Error of assigning to limited type. We do however allow this in
426 -- certain cases where the front end generates the assignments.
428 elsif Is_Limited_Type
(T1
)
429 and then not Assignment_OK
(Lhs
)
430 and then not Assignment_OK
(Original_Node
(Lhs
))
431 and then not Is_Value_Type
(T1
)
433 -- CPP constructors can only be called in declarations
435 if Is_CPP_Constructor_Call
(Rhs
) then
436 Error_Msg_N
("invalid use of 'C'P'P constructor", Rhs
);
439 ("left hand of assignment must not be limited type", Lhs
);
440 Explain_Limited_Type
(T1
, Lhs
);
444 -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
445 -- abstract. This is only checked when the assignment Comes_From_Source,
446 -- because in some cases the expander generates such assignments (such
447 -- in the _assign operation for an abstract type).
449 elsif Is_Abstract_Type
(T1
) and then Comes_From_Source
(N
) then
451 ("target of assignment operation must not be abstract", Lhs
);
454 -- Resolution may have updated the subtype, in case the left-hand
455 -- side is a private protected component. Use the correct subtype
456 -- to avoid scoping issues in the back-end.
460 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
461 -- type. For example:
465 -- type Acc is access P.T;
468 -- with Pkg; use Acc;
469 -- procedure Example is
472 -- A.all := B.all; -- ERROR
475 if Nkind
(Lhs
) = N_Explicit_Dereference
476 and then Ekind
(T1
) = E_Incomplete_Type
478 Error_Msg_N
("invalid use of incomplete type", Lhs
);
483 -- Now we can complete the resolution of the right hand side
485 Set_Assignment_Type
(Lhs
, T1
);
488 -- This is the point at which we check for an unset reference
490 Check_Unset_Reference
(Rhs
);
491 Check_Unprotected_Access
(Lhs
, Rhs
);
493 -- Remaining steps are skipped if Rhs was syntactically in error
502 if not Covers
(T1
, T2
) then
503 Wrong_Type
(Rhs
, Etype
(Lhs
));
508 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
509 -- types, use the non-limited view if available
511 if Nkind
(Rhs
) = N_Explicit_Dereference
512 and then Ekind
(T2
) = E_Incomplete_Type
513 and then Is_Tagged_Type
(T2
)
514 and then Present
(Non_Limited_View
(T2
))
516 T2
:= Non_Limited_View
(T2
);
519 Set_Assignment_Type
(Rhs
, T2
);
521 if Total_Errors_Detected
/= 0 then
531 if T1
= Any_Type
or else T2
= Any_Type
then
536 -- If the rhs is class-wide or dynamically tagged, then require the lhs
537 -- to be class-wide. The case where the rhs is a dynamically tagged call
538 -- to a dispatching operation with a controlling access result is
539 -- excluded from this check, since the target has an access type (and
540 -- no tag propagation occurs in that case).
542 if (Is_Class_Wide_Type
(T2
)
543 or else (Is_Dynamically_Tagged
(Rhs
)
544 and then not Is_Access_Type
(T1
)))
545 and then not Is_Class_Wide_Type
(T1
)
547 Error_Msg_N
("dynamically tagged expression not allowed!", Rhs
);
549 elsif Is_Class_Wide_Type
(T1
)
550 and then not Is_Class_Wide_Type
(T2
)
551 and then not Is_Tag_Indeterminate
(Rhs
)
552 and then not Is_Dynamically_Tagged
(Rhs
)
554 Error_Msg_N
("dynamically tagged expression required!", Rhs
);
557 -- Propagate the tag from a class-wide target to the rhs when the rhs
558 -- is a tag-indeterminate call.
560 if Is_Tag_Indeterminate
(Rhs
) then
561 if Is_Class_Wide_Type
(T1
) then
562 Propagate_Tag
(Lhs
, Rhs
);
564 elsif Nkind
(Rhs
) = N_Function_Call
565 and then Is_Entity_Name
(Name
(Rhs
))
566 and then Is_Abstract_Subprogram
(Entity
(Name
(Rhs
)))
569 ("call to abstract function must be dispatching", Name
(Rhs
));
571 elsif Nkind
(Rhs
) = N_Qualified_Expression
572 and then Nkind
(Expression
(Rhs
)) = N_Function_Call
573 and then Is_Entity_Name
(Name
(Expression
(Rhs
)))
575 Is_Abstract_Subprogram
(Entity
(Name
(Expression
(Rhs
))))
578 ("call to abstract function must be dispatching",
579 Name
(Expression
(Rhs
)));
583 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
584 -- apply an implicit conversion of the rhs to that type to force
585 -- appropriate static and run-time accessibility checks. This applies
586 -- as well to anonymous access-to-subprogram types that are component
587 -- subtypes or formal parameters.
589 if Ada_Version
>= Ada_2005
590 and then Is_Access_Type
(T1
)
592 if Is_Local_Anonymous_Access
(T1
)
593 or else Ekind
(T2
) = E_Anonymous_Access_Subprogram_Type
595 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
596 Analyze_And_Resolve
(Rhs
, T1
);
600 -- Ada 2005 (AI-231): Assignment to not null variable
602 if Ada_Version
>= Ada_2005
603 and then Can_Never_Be_Null
(T1
)
604 and then not Assignment_OK
(Lhs
)
606 -- Case where we know the right hand side is null
608 if Known_Null
(Rhs
) then
609 Apply_Compile_Time_Constraint_Error
611 Msg
=> "(Ada 2005) null not allowed in null-excluding objects?",
612 Reason
=> CE_Null_Not_Allowed
);
614 -- We still mark this as a possible modification, that's necessary
615 -- to reset Is_True_Constant, and desirable for xref purposes.
617 Note_Possible_Modification
(Lhs
, Sure
=> True);
620 -- If we know the right hand side is non-null, then we convert to the
621 -- target type, since we don't need a run time check in that case.
623 elsif not Can_Never_Be_Null
(T2
) then
624 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
625 Analyze_And_Resolve
(Rhs
, T1
);
629 if Is_Scalar_Type
(T1
) then
630 Apply_Scalar_Range_Check
(Rhs
, Etype
(Lhs
));
632 -- For array types, verify that lengths match. If the right hand side
633 -- if a function call that has been inlined, the assignment has been
634 -- rewritten as a block, and the constraint check will be applied to the
635 -- assignment within the block.
637 elsif Is_Array_Type
(T1
)
639 (Nkind
(Rhs
) /= N_Type_Conversion
640 or else Is_Constrained
(Etype
(Rhs
)))
642 (Nkind
(Rhs
) /= N_Function_Call
643 or else Nkind
(N
) /= N_Block_Statement
)
645 -- Assignment verifies that the length of the Lsh and Rhs are equal,
646 -- but of course the indices do not have to match. If the right-hand
647 -- side is a type conversion to an unconstrained type, a length check
648 -- is performed on the expression itself during expansion. In rare
649 -- cases, the redundant length check is computed on an index type
650 -- with a different representation, triggering incorrect code in
653 Apply_Length_Check
(Rhs
, Etype
(Lhs
));
656 -- Discriminant checks are applied in the course of expansion
661 -- Note: modifications of the Lhs may only be recorded after
662 -- checks have been applied.
664 Note_Possible_Modification
(Lhs
, Sure
=> True);
666 -- ??? a real accessibility check is needed when ???
668 -- Post warning for redundant assignment or variable to itself
670 if Warn_On_Redundant_Constructs
672 -- We only warn for source constructs
674 and then Comes_From_Source
(N
)
676 -- Where the object is the same on both sides
678 and then Same_Object
(Lhs
, Original_Node
(Rhs
))
680 -- But exclude the case where the right side was an operation
681 -- that got rewritten (e.g. JUNK + K, where K was known to be
682 -- zero). We don't want to warn in such a case, since it is
683 -- reasonable to write such expressions especially when K is
684 -- defined symbolically in some other package.
686 and then Nkind
(Original_Node
(Rhs
)) not in N_Op
688 if Nkind
(Lhs
) in N_Has_Entity
then
689 Error_Msg_NE
-- CODEFIX
690 ("?useless assignment of & to itself!", N
, Entity
(Lhs
));
692 Error_Msg_N
-- CODEFIX
693 ("?useless assignment of object to itself!", N
);
697 -- Check for non-allowed composite assignment
699 if not Support_Composite_Assign_On_Target
700 and then (Is_Array_Type
(T1
) or else Is_Record_Type
(T1
))
701 and then (not Has_Size_Clause
(T1
) or else Esize
(T1
) > 64)
703 Error_Msg_CRT
("composite assignment", N
);
706 -- Check elaboration warning for left side if not in elab code
708 if not In_Subprogram_Or_Concurrent_Unit
then
709 Check_Elab_Assign
(Lhs
);
712 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
713 -- assignment is a source assignment in the extended main source unit.
714 -- We are not interested in any reference information outside this
715 -- context, or in compiler generated assignment statements.
717 if Comes_From_Source
(N
)
718 and then In_Extended_Main_Source_Unit
(Lhs
)
720 Set_Referenced_Modified
(Lhs
, Out_Param
=> False);
723 -- Final step. If left side is an entity, then we may be able to
724 -- reset the current tracked values to new safe values. We only have
725 -- something to do if the left side is an entity name, and expansion
726 -- has not modified the node into something other than an assignment,
727 -- and of course we only capture values if it is safe to do so.
729 if Is_Entity_Name
(Lhs
)
730 and then Nkind
(N
) = N_Assignment_Statement
733 Ent
: constant Entity_Id
:= Entity
(Lhs
);
736 if Safe_To_Capture_Value
(N
, Ent
) then
738 -- If simple variable on left side, warn if this assignment
739 -- blots out another one (rendering it useless) and note
740 -- location of assignment in case no one references value.
741 -- We only do this for source assignments, otherwise we can
742 -- generate bogus warnings when an assignment is rewritten as
743 -- another assignment, and gets tied up with itself.
745 -- Note: we don't use Record_Last_Assignment here, because we
746 -- have lots of other stuff to do under control of this test.
748 if Warn_On_Modified_Unread
749 and then Is_Assignable
(Ent
)
750 and then Comes_From_Source
(N
)
751 and then In_Extended_Main_Source_Unit
(Ent
)
753 Warn_On_Useless_Assignment
(Ent
, N
);
754 Set_Last_Assignment
(Ent
, Lhs
);
757 -- If we are assigning an access type and the left side is an
758 -- entity, then make sure that the Is_Known_[Non_]Null flags
759 -- properly reflect the state of the entity after assignment.
761 if Is_Access_Type
(T1
) then
762 if Known_Non_Null
(Rhs
) then
763 Set_Is_Known_Non_Null
(Ent
, True);
765 elsif Known_Null
(Rhs
)
766 and then not Can_Never_Be_Null
(Ent
)
768 Set_Is_Known_Null
(Ent
, True);
771 Set_Is_Known_Null
(Ent
, False);
773 if not Can_Never_Be_Null
(Ent
) then
774 Set_Is_Known_Non_Null
(Ent
, False);
778 -- For discrete types, we may be able to set the current value
779 -- if the value is known at compile time.
781 elsif Is_Discrete_Type
(T1
)
782 and then Compile_Time_Known_Value
(Rhs
)
784 Set_Current_Value
(Ent
, Rhs
);
786 Set_Current_Value
(Ent
, Empty
);
789 -- If not safe to capture values, kill them
796 end Analyze_Assignment
;
798 -----------------------------
799 -- Analyze_Block_Statement --
800 -----------------------------
802 procedure Analyze_Block_Statement
(N
: Node_Id
) is
803 Decls
: constant List_Id
:= Declarations
(N
);
804 Id
: constant Node_Id
:= Identifier
(N
);
805 HSS
: constant Node_Id
:= Handled_Statement_Sequence
(N
);
808 -- If no handled statement sequence is present, things are really
809 -- messed up, and we just return immediately (this is a defence
810 -- against previous errors).
816 -- Normal processing with HSS present
819 EH
: constant List_Id
:= Exception_Handlers
(HSS
);
820 Ent
: Entity_Id
:= Empty
;
823 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
824 -- Recursively save value of this global, will be restored on exit
827 -- Initialize unblocked exit count for statements of begin block
828 -- plus one for each exception handler that is present.
830 Unblocked_Exit_Count
:= 1;
833 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ List_Length
(EH
);
836 -- If a label is present analyze it and mark it as referenced
842 -- An error defense. If we have an identifier, but no entity,
843 -- then something is wrong. If we have previous errors, then
844 -- just remove the identifier and continue, otherwise raise
848 if Total_Errors_Detected
/= 0 then
849 Set_Identifier
(N
, Empty
);
855 Set_Ekind
(Ent
, E_Block
);
856 Generate_Reference
(Ent
, N
, ' ');
857 Generate_Definition
(Ent
);
859 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
860 Set_Label_Construct
(Parent
(Ent
), N
);
865 -- If no entity set, create a label entity
868 Ent
:= New_Internal_Entity
(E_Block
, Current_Scope
, Sloc
(N
), 'B');
869 Set_Identifier
(N
, New_Occurrence_Of
(Ent
, Sloc
(N
)));
873 Set_Etype
(Ent
, Standard_Void_Type
);
874 Set_Block_Node
(Ent
, Identifier
(N
));
877 if Present
(Decls
) then
878 Analyze_Declarations
(Decls
);
880 Inspect_Deferred_Constant_Completion
(Decls
);
884 Process_End_Label
(HSS
, 'e', Ent
);
886 -- If exception handlers are present, then we indicate that
887 -- enclosing scopes contain a block with handlers. We only
888 -- need to mark non-generic scopes.
893 Set_Has_Nested_Block_With_Handler
(S
);
894 exit when Is_Overloadable
(S
)
895 or else Ekind
(S
) = E_Package
896 or else Is_Generic_Unit
(S
);
901 Check_References
(Ent
);
902 Warn_On_Useless_Assignments
(Ent
);
905 if Unblocked_Exit_Count
= 0 then
906 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
907 Check_Unreachable_Code
(N
);
909 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
912 end Analyze_Block_Statement
;
914 ----------------------------
915 -- Analyze_Case_Statement --
916 ----------------------------
918 procedure Analyze_Case_Statement
(N
: Node_Id
) is
920 Exp_Type
: Entity_Id
;
921 Exp_Btype
: Entity_Id
;
924 Others_Present
: Boolean;
926 pragma Warnings
(Off
, Last_Choice
);
927 pragma Warnings
(Off
, Dont_Care
);
928 -- Don't care about assigned values
930 Statements_Analyzed
: Boolean := False;
931 -- Set True if at least some statement sequences get analyzed.
932 -- If False on exit, means we had a serious error that prevented
933 -- full analysis of the case statement, and as a result it is not
934 -- a good idea to output warning messages about unreachable code.
936 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
937 -- Recursively save value of this global, will be restored on exit
939 procedure Non_Static_Choice_Error
(Choice
: Node_Id
);
940 -- Error routine invoked by the generic instantiation below when
941 -- the case statement has a non static choice.
943 procedure Process_Statements
(Alternative
: Node_Id
);
944 -- Analyzes all the statements associated with a case alternative.
945 -- Needed by the generic instantiation below.
947 package Case_Choices_Processing
is new
948 Generic_Choices_Processing
949 (Get_Alternatives
=> Alternatives
,
950 Get_Choices
=> Discrete_Choices
,
951 Process_Empty_Choice
=> No_OP
,
952 Process_Non_Static_Choice
=> Non_Static_Choice_Error
,
953 Process_Associated_Node
=> Process_Statements
);
954 use Case_Choices_Processing
;
955 -- Instantiation of the generic choice processing package
957 -----------------------------
958 -- Non_Static_Choice_Error --
959 -----------------------------
961 procedure Non_Static_Choice_Error
(Choice
: Node_Id
) is
964 ("choice given in case statement is not static!", Choice
);
965 end Non_Static_Choice_Error
;
967 ------------------------
968 -- Process_Statements --
969 ------------------------
971 procedure Process_Statements
(Alternative
: Node_Id
) is
972 Choices
: constant List_Id
:= Discrete_Choices
(Alternative
);
976 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
977 Statements_Analyzed
:= True;
979 -- An interesting optimization. If the case statement expression
980 -- is a simple entity, then we can set the current value within
981 -- an alternative if the alternative has one possible value.
985 -- when 2 | 3 => beta
986 -- when others => gamma
988 -- Here we know that N is initially 1 within alpha, but for beta
989 -- and gamma, we do not know anything more about the initial value.
991 if Is_Entity_Name
(Exp
) then
994 if Ekind_In
(Ent
, E_Variable
,
998 if List_Length
(Choices
) = 1
999 and then Nkind
(First
(Choices
)) in N_Subexpr
1000 and then Compile_Time_Known_Value
(First
(Choices
))
1002 Set_Current_Value
(Entity
(Exp
), First
(Choices
));
1005 Analyze_Statements
(Statements
(Alternative
));
1007 -- After analyzing the case, set the current value to empty
1008 -- since we won't know what it is for the next alternative
1009 -- (unless reset by this same circuit), or after the case.
1011 Set_Current_Value
(Entity
(Exp
), Empty
);
1016 -- Case where expression is not an entity name of a variable
1018 Analyze_Statements
(Statements
(Alternative
));
1019 end Process_Statements
;
1021 -- Table to record choices. Put after subprograms since we make
1022 -- a call to Number_Of_Choices to get the right number of entries.
1024 Case_Table
: Choice_Table_Type
(1 .. Number_Of_Choices
(N
));
1025 pragma Warnings
(Off
, Case_Table
);
1027 -- Start of processing for Analyze_Case_Statement
1030 Unblocked_Exit_Count
:= 0;
1031 Exp
:= Expression
(N
);
1034 -- The expression must be of any discrete type. In rare cases, the
1035 -- expander constructs a case statement whose expression has a private
1036 -- type whose full view is discrete. This can happen when generating
1037 -- a stream operation for a variant type after the type is frozen,
1038 -- when the partial of view of the type of the discriminant is private.
1039 -- In that case, use the full view to analyze case alternatives.
1041 if not Is_Overloaded
(Exp
)
1042 and then not Comes_From_Source
(N
)
1043 and then Is_Private_Type
(Etype
(Exp
))
1044 and then Present
(Full_View
(Etype
(Exp
)))
1045 and then Is_Discrete_Type
(Full_View
(Etype
(Exp
)))
1047 Resolve
(Exp
, Etype
(Exp
));
1048 Exp_Type
:= Full_View
(Etype
(Exp
));
1051 Analyze_And_Resolve
(Exp
, Any_Discrete
);
1052 Exp_Type
:= Etype
(Exp
);
1055 Check_Unset_Reference
(Exp
);
1056 Exp_Btype
:= Base_Type
(Exp_Type
);
1058 -- The expression must be of a discrete type which must be determinable
1059 -- independently of the context in which the expression occurs, but
1060 -- using the fact that the expression must be of a discrete type.
1061 -- Moreover, the type this expression must not be a character literal
1062 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1064 -- If error already reported by Resolve, nothing more to do
1066 if Exp_Btype
= Any_Discrete
1067 or else Exp_Btype
= Any_Type
1071 elsif Exp_Btype
= Any_Character
then
1073 ("character literal as case expression is ambiguous", Exp
);
1076 elsif Ada_Version
= Ada_83
1077 and then (Is_Generic_Type
(Exp_Btype
)
1078 or else Is_Generic_Type
(Root_Type
(Exp_Btype
)))
1081 ("(Ada 83) case expression cannot be of a generic type", Exp
);
1085 -- If the case expression is a formal object of mode in out, then
1086 -- treat it as having a nonstatic subtype by forcing use of the base
1087 -- type (which has to get passed to Check_Case_Choices below). Also
1088 -- use base type when the case expression is parenthesized.
1090 if Paren_Count
(Exp
) > 0
1091 or else (Is_Entity_Name
(Exp
)
1092 and then Ekind
(Entity
(Exp
)) = E_Generic_In_Out_Parameter
)
1094 Exp_Type
:= Exp_Btype
;
1097 -- Call instantiated Analyze_Choices which does the rest of the work
1100 (N
, Exp_Type
, Case_Table
, Last_Choice
, Dont_Care
, Others_Present
);
1102 if Exp_Type
= Universal_Integer
and then not Others_Present
then
1103 Error_Msg_N
("case on universal integer requires OTHERS choice", Exp
);
1106 -- If all our exits were blocked by unconditional transfers of control,
1107 -- then the entire CASE statement acts as an unconditional transfer of
1108 -- control, so treat it like one, and check unreachable code. Skip this
1109 -- test if we had serious errors preventing any statement analysis.
1111 if Unblocked_Exit_Count
= 0 and then Statements_Analyzed
then
1112 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1113 Check_Unreachable_Code
(N
);
1115 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1118 if not Expander_Active
1119 and then Compile_Time_Known_Value
(Expression
(N
))
1120 and then Serious_Errors_Detected
= 0
1123 Chosen
: constant Node_Id
:= Find_Static_Alternative
(N
);
1127 Alt
:= First
(Alternatives
(N
));
1128 while Present
(Alt
) loop
1129 if Alt
/= Chosen
then
1130 Remove_Warning_Messages
(Statements
(Alt
));
1137 end Analyze_Case_Statement
;
1139 ----------------------------
1140 -- Analyze_Exit_Statement --
1141 ----------------------------
1143 -- If the exit includes a name, it must be the name of a currently open
1144 -- loop. Otherwise there must be an innermost open loop on the stack,
1145 -- to which the statement implicitly refers.
1147 procedure Analyze_Exit_Statement
(N
: Node_Id
) is
1148 Target
: constant Node_Id
:= Name
(N
);
1149 Cond
: constant Node_Id
:= Condition
(N
);
1150 Scope_Id
: Entity_Id
;
1156 Check_Unreachable_Code
(N
);
1159 if Present
(Target
) then
1161 U_Name
:= Entity
(Target
);
1163 if not In_Open_Scopes
(U_Name
) or else Ekind
(U_Name
) /= E_Loop
then
1164 Error_Msg_N
("invalid loop name in exit statement", N
);
1167 Set_Has_Exit
(U_Name
);
1174 for J
in reverse 0 .. Scope_Stack
.Last
loop
1175 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
1176 Kind
:= Ekind
(Scope_Id
);
1179 and then (No
(Target
) or else Scope_Id
= U_Name
) then
1180 Set_Has_Exit
(Scope_Id
);
1183 elsif Kind
= E_Block
1184 or else Kind
= E_Loop
1185 or else Kind
= E_Return_Statement
1191 ("cannot exit from program unit or accept statement", N
);
1196 -- Verify that if present the condition is a Boolean expression
1198 if Present
(Cond
) then
1199 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1200 Check_Unset_Reference
(Cond
);
1203 -- Chain exit statement to associated loop entity
1205 Set_Next_Exit_Statement
(N
, First_Exit_Statement
(Scope_Id
));
1206 Set_First_Exit_Statement
(Scope_Id
, N
);
1208 -- Since the exit may take us out of a loop, any previous assignment
1209 -- statement is not useless, so clear last assignment indications. It
1210 -- is OK to keep other current values, since if the exit statement
1211 -- does not exit, then the current values are still valid.
1213 Kill_Current_Values
(Last_Assignment_Only
=> True);
1214 end Analyze_Exit_Statement
;
1216 ----------------------------
1217 -- Analyze_Goto_Statement --
1218 ----------------------------
1220 procedure Analyze_Goto_Statement
(N
: Node_Id
) is
1221 Label
: constant Node_Id
:= Name
(N
);
1222 Scope_Id
: Entity_Id
;
1223 Label_Scope
: Entity_Id
;
1224 Label_Ent
: Entity_Id
;
1227 Check_Unreachable_Code
(N
);
1228 Kill_Current_Values
(Last_Assignment_Only
=> True);
1231 Label_Ent
:= Entity
(Label
);
1233 -- Ignore previous error
1235 if Label_Ent
= Any_Id
then
1238 -- We just have a label as the target of a goto
1240 elsif Ekind
(Label_Ent
) /= E_Label
then
1241 Error_Msg_N
("target of goto statement must be a label", Label
);
1244 -- Check that the target of the goto is reachable according to Ada
1245 -- scoping rules. Note: the special gotos we generate for optimizing
1246 -- local handling of exceptions would violate these rules, but we mark
1247 -- such gotos as analyzed when built, so this code is never entered.
1249 elsif not Reachable
(Label_Ent
) then
1250 Error_Msg_N
("target of goto statement is not reachable", Label
);
1254 -- Here if goto passes initial validity checks
1256 Label_Scope
:= Enclosing_Scope
(Label_Ent
);
1258 for J
in reverse 0 .. Scope_Stack
.Last
loop
1259 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
1261 if Label_Scope
= Scope_Id
1262 or else (Ekind
(Scope_Id
) /= E_Block
1263 and then Ekind
(Scope_Id
) /= E_Loop
1264 and then Ekind
(Scope_Id
) /= E_Return_Statement
)
1266 if Scope_Id
/= Label_Scope
then
1268 ("cannot exit from program unit or accept statement", N
);
1275 raise Program_Error
;
1276 end Analyze_Goto_Statement
;
1278 --------------------------
1279 -- Analyze_If_Statement --
1280 --------------------------
1282 -- A special complication arises in the analysis of if statements
1284 -- The expander has circuitry to completely delete code that it
1285 -- can tell will not be executed (as a result of compile time known
1286 -- conditions). In the analyzer, we ensure that code that will be
1287 -- deleted in this manner is analyzed but not expanded. This is
1288 -- obviously more efficient, but more significantly, difficulties
1289 -- arise if code is expanded and then eliminated (e.g. exception
1290 -- table entries disappear). Similarly, itypes generated in deleted
1291 -- code must be frozen from start, because the nodes on which they
1292 -- depend will not be available at the freeze point.
1294 procedure Analyze_If_Statement
(N
: Node_Id
) is
1297 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
1298 -- Recursively save value of this global, will be restored on exit
1300 Save_In_Deleted_Code
: Boolean;
1302 Del
: Boolean := False;
1303 -- This flag gets set True if a True condition has been found,
1304 -- which means that remaining ELSE/ELSIF parts are deleted.
1306 procedure Analyze_Cond_Then
(Cnode
: Node_Id
);
1307 -- This is applied to either the N_If_Statement node itself or
1308 -- to an N_Elsif_Part node. It deals with analyzing the condition
1309 -- and the THEN statements associated with it.
1311 -----------------------
1312 -- Analyze_Cond_Then --
1313 -----------------------
1315 procedure Analyze_Cond_Then
(Cnode
: Node_Id
) is
1316 Cond
: constant Node_Id
:= Condition
(Cnode
);
1317 Tstm
: constant List_Id
:= Then_Statements
(Cnode
);
1320 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
1321 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1322 Check_Unset_Reference
(Cond
);
1323 Set_Current_Value_Condition
(Cnode
);
1325 -- If already deleting, then just analyze then statements
1328 Analyze_Statements
(Tstm
);
1330 -- Compile time known value, not deleting yet
1332 elsif Compile_Time_Known_Value
(Cond
) then
1333 Save_In_Deleted_Code
:= In_Deleted_Code
;
1335 -- If condition is True, then analyze the THEN statements
1336 -- and set no expansion for ELSE and ELSIF parts.
1338 if Is_True
(Expr_Value
(Cond
)) then
1339 Analyze_Statements
(Tstm
);
1341 Expander_Mode_Save_And_Set
(False);
1342 In_Deleted_Code
:= True;
1344 -- If condition is False, analyze THEN with expansion off
1346 else -- Is_False (Expr_Value (Cond))
1347 Expander_Mode_Save_And_Set
(False);
1348 In_Deleted_Code
:= True;
1349 Analyze_Statements
(Tstm
);
1350 Expander_Mode_Restore
;
1351 In_Deleted_Code
:= Save_In_Deleted_Code
;
1354 -- Not known at compile time, not deleting, normal analysis
1357 Analyze_Statements
(Tstm
);
1359 end Analyze_Cond_Then
;
1361 -- Start of Analyze_If_Statement
1364 -- Initialize exit count for else statements. If there is no else
1365 -- part, this count will stay non-zero reflecting the fact that the
1366 -- uncovered else case is an unblocked exit.
1368 Unblocked_Exit_Count
:= 1;
1369 Analyze_Cond_Then
(N
);
1371 -- Now to analyze the elsif parts if any are present
1373 if Present
(Elsif_Parts
(N
)) then
1374 E
:= First
(Elsif_Parts
(N
));
1375 while Present
(E
) loop
1376 Analyze_Cond_Then
(E
);
1381 if Present
(Else_Statements
(N
)) then
1382 Analyze_Statements
(Else_Statements
(N
));
1385 -- If all our exits were blocked by unconditional transfers of control,
1386 -- then the entire IF statement acts as an unconditional transfer of
1387 -- control, so treat it like one, and check unreachable code.
1389 if Unblocked_Exit_Count
= 0 then
1390 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1391 Check_Unreachable_Code
(N
);
1393 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1397 Expander_Mode_Restore
;
1398 In_Deleted_Code
:= Save_In_Deleted_Code
;
1401 if not Expander_Active
1402 and then Compile_Time_Known_Value
(Condition
(N
))
1403 and then Serious_Errors_Detected
= 0
1405 if Is_True
(Expr_Value
(Condition
(N
))) then
1406 Remove_Warning_Messages
(Else_Statements
(N
));
1408 if Present
(Elsif_Parts
(N
)) then
1409 E
:= First
(Elsif_Parts
(N
));
1410 while Present
(E
) loop
1411 Remove_Warning_Messages
(Then_Statements
(E
));
1417 Remove_Warning_Messages
(Then_Statements
(N
));
1420 end Analyze_If_Statement
;
1422 ----------------------------------------
1423 -- Analyze_Implicit_Label_Declaration --
1424 ----------------------------------------
1426 -- An implicit label declaration is generated in the innermost
1427 -- enclosing declarative part. This is done for labels as well as
1428 -- block and loop names.
1430 -- Note: any changes in this routine may need to be reflected in
1431 -- Analyze_Label_Entity.
1433 procedure Analyze_Implicit_Label_Declaration
(N
: Node_Id
) is
1434 Id
: constant Node_Id
:= Defining_Identifier
(N
);
1437 Set_Ekind
(Id
, E_Label
);
1438 Set_Etype
(Id
, Standard_Void_Type
);
1439 Set_Enclosing_Scope
(Id
, Current_Scope
);
1440 end Analyze_Implicit_Label_Declaration
;
1442 ------------------------------
1443 -- Analyze_Iteration_Scheme --
1444 ------------------------------
1446 procedure Analyze_Iteration_Scheme
(N
: Node_Id
) is
1448 procedure Process_Bounds
(R
: Node_Id
);
1449 -- If the iteration is given by a range, create temporaries and
1450 -- assignment statements block to capture the bounds and perform
1451 -- required finalization actions in case a bound includes a function
1452 -- call that uses the temporary stack. We first pre-analyze a copy of
1453 -- the range in order to determine the expected type, and analyze and
1454 -- resolve the original bounds.
1456 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
);
1457 -- If the bounds are given by a 'Range reference on a function call
1458 -- that returns a controlled array, introduce an explicit declaration
1459 -- to capture the bounds, so that the function result can be finalized
1460 -- in timely fashion.
1462 --------------------
1463 -- Process_Bounds --
1464 --------------------
1466 procedure Process_Bounds
(R
: Node_Id
) is
1467 Loc
: constant Source_Ptr
:= Sloc
(N
);
1468 R_Copy
: constant Node_Id
:= New_Copy_Tree
(R
);
1469 Lo
: constant Node_Id
:= Low_Bound
(R
);
1470 Hi
: constant Node_Id
:= High_Bound
(R
);
1471 New_Lo_Bound
: Node_Id
;
1472 New_Hi_Bound
: Node_Id
;
1474 Save_Analysis
: Boolean;
1477 (Original_Bound
: Node_Id
;
1478 Analyzed_Bound
: Node_Id
) return Node_Id
;
1479 -- Capture value of bound and return captured value
1486 (Original_Bound
: Node_Id
;
1487 Analyzed_Bound
: Node_Id
) return Node_Id
1494 -- If the bound is a constant or an object, no need for a separate
1495 -- declaration. If the bound is the result of previous expansion
1496 -- it is already analyzed and should not be modified. Note that
1497 -- the Bound will be resolved later, if needed, as part of the
1498 -- call to Make_Index (literal bounds may need to be resolved to
1501 if Analyzed
(Original_Bound
) then
1502 return Original_Bound
;
1504 elsif Nkind_In
(Analyzed_Bound
, N_Integer_Literal
,
1505 N_Character_Literal
)
1506 or else Is_Entity_Name
(Analyzed_Bound
)
1508 Analyze_And_Resolve
(Original_Bound
, Typ
);
1509 return Original_Bound
;
1512 -- Here we need to capture the value
1514 Analyze_And_Resolve
(Original_Bound
, Typ
);
1516 Id
:= Make_Temporary
(Loc
, 'S', Original_Bound
);
1518 -- Normally, the best approach is simply to generate a constant
1519 -- declaration that captures the bound. However, there is a nasty
1520 -- case where this is wrong. If the bound is complex, and has a
1521 -- possible use of the secondary stack, we need to generate a
1522 -- separate assignment statement to ensure the creation of a block
1523 -- which will release the secondary stack.
1525 -- We prefer the constant declaration, since it leaves us with a
1526 -- proper trace of the value, useful in optimizations that get rid
1527 -- of junk range checks.
1529 -- Probably we want something like the Side_Effect_Free routine
1530 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1531 -- and 'First applied to an entity, since these are the important
1532 -- cases for range check optimizations.
1534 if Nkind
(Original_Bound
) = N_Attribute_Reference
1535 and then (Attribute_Name
(Original_Bound
) = Name_First
1537 Attribute_Name
(Original_Bound
) = Name_Last
)
1538 and then Is_Entity_Name
(Prefix
(Original_Bound
))
1541 Make_Object_Declaration
(Loc
,
1542 Defining_Identifier
=> Id
,
1543 Constant_Present
=> True,
1544 Object_Definition
=> New_Occurrence_Of
(Typ
, Loc
),
1545 Expression
=> Relocate_Node
(Original_Bound
));
1547 Insert_Before
(Parent
(N
), Decl
);
1549 Rewrite
(Original_Bound
, New_Occurrence_Of
(Id
, Loc
));
1550 return Expression
(Decl
);
1553 -- Here we make a declaration with a separate assignment statement
1556 Make_Object_Declaration
(Loc
,
1557 Defining_Identifier
=> Id
,
1558 Object_Definition
=> New_Occurrence_Of
(Typ
, Loc
));
1560 Insert_Before
(Parent
(N
), Decl
);
1564 Make_Assignment_Statement
(Loc
,
1565 Name
=> New_Occurrence_Of
(Id
, Loc
),
1566 Expression
=> Relocate_Node
(Original_Bound
));
1568 Insert_Before
(Parent
(N
), Assign
);
1571 Rewrite
(Original_Bound
, New_Occurrence_Of
(Id
, Loc
));
1573 if Nkind
(Assign
) = N_Assignment_Statement
then
1574 return Expression
(Assign
);
1576 return Original_Bound
;
1580 -- Start of processing for Process_Bounds
1583 -- Determine expected type of range by analyzing separate copy
1584 -- Do the analysis and resolution of the copy of the bounds with
1585 -- expansion disabled, to prevent the generation of finalization
1586 -- actions on each bound. This prevents memory leaks when the
1587 -- bounds contain calls to functions returning controlled arrays.
1589 Set_Parent
(R_Copy
, Parent
(R
));
1590 Save_Analysis
:= Full_Analysis
;
1591 Full_Analysis
:= False;
1592 Expander_Mode_Save_And_Set
(False);
1596 if Is_Overloaded
(R_Copy
) then
1598 -- Apply preference rules for range of predefined integer types,
1599 -- or diagnose true ambiguity.
1604 Found
: Entity_Id
:= Empty
;
1607 Get_First_Interp
(R_Copy
, I
, It
);
1608 while Present
(It
.Typ
) loop
1609 if Is_Discrete_Type
(It
.Typ
) then
1613 if Scope
(Found
) = Standard_Standard
then
1616 elsif Scope
(It
.Typ
) = Standard_Standard
then
1620 -- Both of them are user-defined
1623 ("ambiguous bounds in range of iteration",
1625 Error_Msg_N
("\possible interpretations:", R_Copy
);
1626 Error_Msg_NE
("\\} ", R_Copy
, Found
);
1627 Error_Msg_NE
("\\} ", R_Copy
, It
.Typ
);
1633 Get_Next_Interp
(I
, It
);
1639 Expander_Mode_Restore
;
1640 Full_Analysis
:= Save_Analysis
;
1642 Typ
:= Etype
(R_Copy
);
1644 -- If the type of the discrete range is Universal_Integer, then
1645 -- the bound's type must be resolved to Integer, and any object
1646 -- used to hold the bound must also have type Integer, unless the
1647 -- literal bounds are constant-folded expressions that carry a user-
1650 if Typ
= Universal_Integer
then
1651 if Nkind
(Lo
) = N_Integer_Literal
1652 and then Present
(Etype
(Lo
))
1653 and then Scope
(Etype
(Lo
)) /= Standard_Standard
1657 elsif Nkind
(Hi
) = N_Integer_Literal
1658 and then Present
(Etype
(Hi
))
1659 and then Scope
(Etype
(Hi
)) /= Standard_Standard
1664 Typ
:= Standard_Integer
;
1670 New_Lo_Bound
:= One_Bound
(Lo
, Low_Bound
(R_Copy
));
1671 New_Hi_Bound
:= One_Bound
(Hi
, High_Bound
(R_Copy
));
1673 -- Propagate staticness to loop range itself, in case the
1674 -- corresponding subtype is static.
1676 if New_Lo_Bound
/= Lo
1677 and then Is_Static_Expression
(New_Lo_Bound
)
1679 Rewrite
(Low_Bound
(R
), New_Copy
(New_Lo_Bound
));
1682 if New_Hi_Bound
/= Hi
1683 and then Is_Static_Expression
(New_Hi_Bound
)
1685 Rewrite
(High_Bound
(R
), New_Copy
(New_Hi_Bound
));
1689 --------------------------------------
1690 -- Check_Controlled_Array_Attribute --
1691 --------------------------------------
1693 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
) is
1695 if Nkind
(DS
) = N_Attribute_Reference
1696 and then Is_Entity_Name
(Prefix
(DS
))
1697 and then Ekind
(Entity
(Prefix
(DS
))) = E_Function
1698 and then Is_Array_Type
(Etype
(Entity
(Prefix
(DS
))))
1701 Component_Type
(Etype
(Entity
(Prefix
(DS
)))))
1702 and then Expander_Active
1705 Loc
: constant Source_Ptr
:= Sloc
(N
);
1706 Arr
: constant Entity_Id
:= Etype
(Entity
(Prefix
(DS
)));
1707 Indx
: constant Entity_Id
:=
1708 Base_Type
(Etype
(First_Index
(Arr
)));
1709 Subt
: constant Entity_Id
:= Make_Temporary
(Loc
, 'S');
1714 Make_Subtype_Declaration
(Loc
,
1715 Defining_Identifier
=> Subt
,
1716 Subtype_Indication
=>
1717 Make_Subtype_Indication
(Loc
,
1718 Subtype_Mark
=> New_Reference_To
(Indx
, Loc
),
1720 Make_Range_Constraint
(Loc
,
1721 Relocate_Node
(DS
))));
1722 Insert_Before
(Parent
(N
), Decl
);
1726 Make_Attribute_Reference
(Loc
,
1727 Prefix
=> New_Reference_To
(Subt
, Loc
),
1728 Attribute_Name
=> Attribute_Name
(DS
)));
1732 end Check_Controlled_Array_Attribute
;
1734 -- Start of processing for Analyze_Iteration_Scheme
1737 -- For an infinite loop, there is no iteration scheme
1744 Cond
: constant Node_Id
:= Condition
(N
);
1747 -- For WHILE loop, verify that the condition is a Boolean
1748 -- expression and resolve and check it.
1750 if Present
(Cond
) then
1751 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1752 Check_Unset_Reference
(Cond
);
1753 Set_Current_Value_Condition
(N
);
1756 -- Else we have a FOR loop
1760 LP
: constant Node_Id
:= Loop_Parameter_Specification
(N
);
1761 Id
: constant Entity_Id
:= Defining_Identifier
(LP
);
1762 DS
: constant Node_Id
:= Discrete_Subtype_Definition
(LP
);
1767 -- We always consider the loop variable to be referenced,
1768 -- since the loop may be used just for counting purposes.
1770 Generate_Reference
(Id
, N
, ' ');
1772 -- Check for case of loop variable hiding a local
1773 -- variable (used later on to give a nice warning
1774 -- if the hidden variable is never assigned).
1777 H
: constant Entity_Id
:= Homonym
(Id
);
1780 and then Enclosing_Dynamic_Scope
(H
) =
1781 Enclosing_Dynamic_Scope
(Id
)
1782 and then Ekind
(H
) = E_Variable
1783 and then Is_Discrete_Type
(Etype
(H
))
1785 Set_Hiding_Loop_Variable
(H
, Id
);
1789 -- Now analyze the subtype definition. If it is
1790 -- a range, create temporaries for bounds.
1792 if Nkind
(DS
) = N_Range
1793 and then Expander_Active
1795 Process_Bounds
(DS
);
1804 -- The subtype indication may denote the completion
1805 -- of an incomplete type declaration.
1807 if Is_Entity_Name
(DS
)
1808 and then Present
(Entity
(DS
))
1809 and then Is_Type
(Entity
(DS
))
1810 and then Ekind
(Entity
(DS
)) = E_Incomplete_Type
1812 Set_Entity
(DS
, Get_Full_View
(Entity
(DS
)));
1813 Set_Etype
(DS
, Entity
(DS
));
1816 if not Is_Discrete_Type
(Etype
(DS
)) then
1817 Wrong_Type
(DS
, Any_Discrete
);
1818 Set_Etype
(DS
, Any_Type
);
1821 Check_Controlled_Array_Attribute
(DS
);
1823 Make_Index
(DS
, LP
);
1825 Set_Ekind
(Id
, E_Loop_Parameter
);
1826 Set_Etype
(Id
, Etype
(DS
));
1828 -- Treat a range as an implicit reference to the type, to
1829 -- inhibit spurious warnings.
1831 Generate_Reference
(Base_Type
(Etype
(DS
)), N
, ' ');
1832 Set_Is_Known_Valid
(Id
, True);
1834 -- The loop is not a declarative part, so the only entity
1835 -- declared "within" must be frozen explicitly.
1838 Flist
: constant List_Id
:= Freeze_Entity
(Id
, N
);
1840 if Is_Non_Empty_List
(Flist
) then
1841 Insert_Actions
(N
, Flist
);
1845 -- Check for null or possibly null range and issue warning.
1846 -- We suppress such messages in generic templates and
1847 -- instances, because in practice they tend to be dubious
1850 if Nkind
(DS
) = N_Range
1851 and then Comes_From_Source
(N
)
1854 L
: constant Node_Id
:= Low_Bound
(DS
);
1855 H
: constant Node_Id
:= High_Bound
(DS
);
1858 -- If range of loop is null, issue warning
1860 if Compile_Time_Compare
1861 (L
, H
, Assume_Valid
=> True) = GT
1863 -- Suppress the warning if inside a generic
1864 -- template or instance, since in practice
1865 -- they tend to be dubious in these cases since
1866 -- they can result from intended parametrization.
1868 if not Inside_A_Generic
1869 and then not In_Instance
1871 -- Specialize msg if invalid values could make
1872 -- the loop non-null after all.
1874 if Compile_Time_Compare
1875 (L
, H
, Assume_Valid
=> False) = GT
1878 ("?loop range is null, "
1879 & "loop will not execute",
1882 -- Since we know the range of the loop is
1883 -- null, set the appropriate flag to remove
1884 -- the loop entirely during expansion.
1886 Set_Is_Null_Loop
(Parent
(N
));
1888 -- Here is where the loop could execute because
1889 -- of invalid values, so issue appropriate
1890 -- message and in this case we do not set the
1891 -- Is_Null_Loop flag since the loop may execute.
1895 ("?loop range may be null, "
1896 & "loop may not execute",
1899 ("?can only execute if invalid values "
1905 -- In either case, suppress warnings in the body of
1906 -- the loop, since it is likely that these warnings
1907 -- will be inappropriate if the loop never actually
1908 -- executes, which is unlikely.
1910 Set_Suppress_Loop_Warnings
(Parent
(N
));
1912 -- The other case for a warning is a reverse loop
1913 -- where the upper bound is the integer literal
1914 -- zero or one, and the lower bound can be positive.
1916 -- For example, we have
1918 -- for J in reverse N .. 1 loop
1920 -- In practice, this is very likely to be a case
1921 -- of reversing the bounds incorrectly in the range.
1923 elsif Reverse_Present
(LP
)
1924 and then Nkind
(Original_Node
(H
)) =
1926 and then (Intval
(Original_Node
(H
)) = Uint_0
1928 Intval
(Original_Node
(H
)) = Uint_1
)
1930 Error_Msg_N
("?loop range may be null", DS
);
1931 Error_Msg_N
("\?bounds may be wrong way round", DS
);
1939 end Analyze_Iteration_Scheme
;
1945 -- Note: the semantic work required for analyzing labels (setting them as
1946 -- reachable) was done in a prepass through the statements in the block,
1947 -- so that forward gotos would be properly handled. See Analyze_Statements
1948 -- for further details. The only processing required here is to deal with
1949 -- optimizations that depend on an assumption of sequential control flow,
1950 -- since of course the occurrence of a label breaks this assumption.
1952 procedure Analyze_Label
(N
: Node_Id
) is
1953 pragma Warnings
(Off
, N
);
1955 Kill_Current_Values
;
1958 --------------------------
1959 -- Analyze_Label_Entity --
1960 --------------------------
1962 procedure Analyze_Label_Entity
(E
: Entity_Id
) is
1964 Set_Ekind
(E
, E_Label
);
1965 Set_Etype
(E
, Standard_Void_Type
);
1966 Set_Enclosing_Scope
(E
, Current_Scope
);
1967 Set_Reachable
(E
, True);
1968 end Analyze_Label_Entity
;
1970 ----------------------------
1971 -- Analyze_Loop_Statement --
1972 ----------------------------
1974 procedure Analyze_Loop_Statement
(N
: Node_Id
) is
1975 Loop_Statement
: constant Node_Id
:= N
;
1977 Id
: constant Node_Id
:= Identifier
(Loop_Statement
);
1978 Iter
: constant Node_Id
:= Iteration_Scheme
(Loop_Statement
);
1982 if Present
(Id
) then
1984 -- Make name visible, e.g. for use in exit statements. Loop
1985 -- labels are always considered to be referenced.
1990 -- Guard against serious error (typically, a scope mismatch when
1991 -- semantic analysis is requested) by creating loop entity to
1992 -- continue analysis.
1995 if Total_Errors_Detected
/= 0 then
1998 (E_Loop
, Current_Scope
, Sloc
(Loop_Statement
), 'L');
2000 raise Program_Error
;
2004 Generate_Reference
(Ent
, Loop_Statement
, ' ');
2005 Generate_Definition
(Ent
);
2007 -- If we found a label, mark its type. If not, ignore it, since it
2008 -- means we have a conflicting declaration, which would already
2009 -- have been diagnosed at declaration time. Set Label_Construct
2010 -- of the implicit label declaration, which is not created by the
2011 -- parser for generic units.
2013 if Ekind
(Ent
) = E_Label
then
2014 Set_Ekind
(Ent
, E_Loop
);
2016 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
2017 Set_Label_Construct
(Parent
(Ent
), Loop_Statement
);
2022 -- Case of no identifier present
2027 (E_Loop
, Current_Scope
, Sloc
(Loop_Statement
), 'L');
2028 Set_Etype
(Ent
, Standard_Void_Type
);
2029 Set_Parent
(Ent
, Loop_Statement
);
2032 -- Kill current values on entry to loop, since statements in body of
2033 -- loop may have been executed before the loop is entered. Similarly we
2034 -- kill values after the loop, since we do not know that the body of the
2035 -- loop was executed.
2037 Kill_Current_Values
;
2039 Analyze_Iteration_Scheme
(Iter
);
2040 Analyze_Statements
(Statements
(Loop_Statement
));
2041 Process_End_Label
(Loop_Statement
, 'e', Ent
);
2043 Kill_Current_Values
;
2045 -- Check for infinite loop. Skip check for generated code, since it
2046 -- justs waste time and makes debugging the routine called harder.
2048 -- Note that we have to wait till the body of the loop is fully analyzed
2049 -- before making this call, since Check_Infinite_Loop_Warning relies on
2050 -- being able to use semantic visibility information to find references.
2052 if Comes_From_Source
(N
) then
2053 Check_Infinite_Loop_Warning
(N
);
2056 -- Code after loop is unreachable if the loop has no WHILE or FOR
2057 -- and contains no EXIT statements within the body of the loop.
2059 if No
(Iter
) and then not Has_Exit
(Ent
) then
2060 Check_Unreachable_Code
(N
);
2062 end Analyze_Loop_Statement
;
2064 ----------------------------
2065 -- Analyze_Null_Statement --
2066 ----------------------------
2068 -- Note: the semantics of the null statement is implemented by a single
2069 -- null statement, too bad everything isn't as simple as this!
2071 procedure Analyze_Null_Statement
(N
: Node_Id
) is
2072 pragma Warnings
(Off
, N
);
2075 end Analyze_Null_Statement
;
2077 ------------------------
2078 -- Analyze_Statements --
2079 ------------------------
2081 procedure Analyze_Statements
(L
: List_Id
) is
2086 -- The labels declared in the statement list are reachable from
2087 -- statements in the list. We do this as a prepass so that any
2088 -- goto statement will be properly flagged if its target is not
2089 -- reachable. This is not required, but is nice behavior!
2092 while Present
(S
) loop
2093 if Nkind
(S
) = N_Label
then
2094 Analyze
(Identifier
(S
));
2095 Lab
:= Entity
(Identifier
(S
));
2097 -- If we found a label mark it as reachable
2099 if Ekind
(Lab
) = E_Label
then
2100 Generate_Definition
(Lab
);
2101 Set_Reachable
(Lab
);
2103 if Nkind
(Parent
(Lab
)) = N_Implicit_Label_Declaration
then
2104 Set_Label_Construct
(Parent
(Lab
), S
);
2107 -- If we failed to find a label, it means the implicit declaration
2108 -- of the label was hidden. A for-loop parameter can do this to
2109 -- a label with the same name inside the loop, since the implicit
2110 -- label declaration is in the innermost enclosing body or block
2114 Error_Msg_Sloc
:= Sloc
(Lab
);
2116 ("implicit label declaration for & is hidden#",
2124 -- Perform semantic analysis on all statements
2126 Conditional_Statements_Begin
;
2129 while Present
(S
) loop
2134 Conditional_Statements_End
;
2136 -- Make labels unreachable. Visibility is not sufficient, because
2137 -- labels in one if-branch for example are not reachable from the
2138 -- other branch, even though their declarations are in the enclosing
2139 -- declarative part.
2142 while Present
(S
) loop
2143 if Nkind
(S
) = N_Label
then
2144 Set_Reachable
(Entity
(Identifier
(S
)), False);
2149 end Analyze_Statements
;
2151 ----------------------------
2152 -- Check_Unreachable_Code --
2153 ----------------------------
2155 procedure Check_Unreachable_Code
(N
: Node_Id
) is
2156 Error_Loc
: Source_Ptr
;
2160 if Is_List_Member
(N
)
2161 and then Comes_From_Source
(N
)
2167 Nxt
:= Original_Node
(Next
(N
));
2169 -- If a label follows us, then we never have dead code, since
2170 -- someone could branch to the label, so we just ignore it.
2172 if Nkind
(Nxt
) = N_Label
then
2175 -- Otherwise see if we have a real statement following us
2178 and then Comes_From_Source
(Nxt
)
2179 and then Is_Statement
(Nxt
)
2181 -- Special very annoying exception. If we have a return that
2182 -- follows a raise, then we allow it without a warning, since
2183 -- the Ada RM annoyingly requires a useless return here!
2185 if Nkind
(Original_Node
(N
)) /= N_Raise_Statement
2186 or else Nkind
(Nxt
) /= N_Simple_Return_Statement
2188 -- The rather strange shenanigans with the warning message
2189 -- here reflects the fact that Kill_Dead_Code is very good
2190 -- at removing warnings in deleted code, and this is one
2191 -- warning we would prefer NOT to have removed.
2193 Error_Loc
:= Sloc
(Nxt
);
2195 -- If we have unreachable code, analyze and remove the
2196 -- unreachable code, since it is useless and we don't
2197 -- want to generate junk warnings.
2199 -- We skip this step if we are not in code generation mode.
2200 -- This is the one case where we remove dead code in the
2201 -- semantics as opposed to the expander, and we do not want
2202 -- to remove code if we are not in code generation mode,
2203 -- since this messes up the ASIS trees.
2205 -- Note that one might react by moving the whole circuit to
2206 -- exp_ch5, but then we lose the warning in -gnatc mode.
2208 if Operating_Mode
= Generate_Code
then
2212 -- Quit deleting when we have nothing more to delete
2213 -- or if we hit a label (since someone could transfer
2214 -- control to a label, so we should not delete it).
2216 exit when No
(Nxt
) or else Nkind
(Nxt
) = N_Label
;
2218 -- Statement/declaration is to be deleted
2222 Kill_Dead_Code
(Nxt
);
2226 -- Now issue the warning
2228 Error_Msg
("?unreachable code!", Error_Loc
);
2231 -- If the unconditional transfer of control instruction is
2232 -- the last statement of a sequence, then see if our parent
2233 -- is one of the constructs for which we count unblocked exits,
2234 -- and if so, adjust the count.
2239 -- Statements in THEN part or ELSE part of IF statement
2241 if Nkind
(P
) = N_If_Statement
then
2244 -- Statements in ELSIF part of an IF statement
2246 elsif Nkind
(P
) = N_Elsif_Part
then
2248 pragma Assert
(Nkind
(P
) = N_If_Statement
);
2250 -- Statements in CASE statement alternative
2252 elsif Nkind
(P
) = N_Case_Statement_Alternative
then
2254 pragma Assert
(Nkind
(P
) = N_Case_Statement
);
2256 -- Statements in body of block
2258 elsif Nkind
(P
) = N_Handled_Sequence_Of_Statements
2259 and then Nkind
(Parent
(P
)) = N_Block_Statement
2263 -- Statements in exception handler in a block
2265 elsif Nkind
(P
) = N_Exception_Handler
2266 and then Nkind
(Parent
(P
)) = N_Handled_Sequence_Of_Statements
2267 and then Nkind
(Parent
(Parent
(P
))) = N_Block_Statement
2271 -- None of these cases, so return
2277 -- This was one of the cases we are looking for (i.e. the
2278 -- parent construct was IF, CASE or block) so decrement count.
2280 Unblocked_Exit_Count
:= Unblocked_Exit_Count
- 1;
2284 end Check_Unreachable_Code
;