1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2010, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Atree
; use Atree
;
27 with Checks
; use Checks
;
28 with Einfo
; use Einfo
;
29 with Errout
; use Errout
;
30 with Expander
; use Expander
;
31 with Exp_Util
; use Exp_Util
;
32 with Freeze
; use Freeze
;
34 with Lib
.Xref
; use Lib
.Xref
;
35 with Namet
; use Namet
;
36 with Nlists
; use Nlists
;
37 with Nmake
; use Nmake
;
39 with Rtsfind
; use Rtsfind
;
41 with Sem_Aux
; use Sem_Aux
;
42 with Sem_Case
; use Sem_Case
;
43 with Sem_Ch3
; use Sem_Ch3
;
44 with Sem_Ch8
; use Sem_Ch8
;
45 with Sem_Disp
; use Sem_Disp
;
46 with Sem_Elab
; use Sem_Elab
;
47 with Sem_Eval
; use Sem_Eval
;
48 with Sem_Res
; use Sem_Res
;
49 with Sem_Type
; use Sem_Type
;
50 with Sem_Util
; use Sem_Util
;
51 with Sem_Warn
; use Sem_Warn
;
52 with Snames
; use Snames
;
53 with Stand
; use Stand
;
54 with Sinfo
; use Sinfo
;
55 with Targparm
; use Targparm
;
56 with Tbuild
; use Tbuild
;
57 with Uintp
; use Uintp
;
59 package body Sem_Ch5
is
61 Unblocked_Exit_Count
: Nat
:= 0;
62 -- This variable is used when processing if statements, case statements,
63 -- and block statements. It counts the number of exit points that are not
64 -- blocked by unconditional transfer instructions: for IF and CASE, these
65 -- are the branches of the conditional; for a block, they are the statement
66 -- sequence of the block, and the statement sequences of any exception
67 -- handlers that are part of the block. When processing is complete, if
68 -- this count is zero, it means that control cannot fall through the IF,
69 -- CASE or block statement. This is used for the generation of warning
70 -- messages. This variable is recursively saved on entry to processing the
71 -- construct, and restored on exit.
73 ------------------------
74 -- Analyze_Assignment --
75 ------------------------
77 procedure Analyze_Assignment
(N
: Node_Id
) is
78 Lhs
: constant Node_Id
:= Name
(N
);
79 Rhs
: constant Node_Id
:= Expression
(N
);
84 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
);
85 -- N is the node for the left hand side of an assignment, and it is not
86 -- a variable. This routine issues an appropriate diagnostic.
89 -- This is called to kill current value settings of a simple variable
90 -- on the left hand side. We call it if we find any error in analyzing
91 -- the assignment, and at the end of processing before setting any new
92 -- current values in place.
94 procedure Set_Assignment_Type
96 Opnd_Type
: in out Entity_Id
);
97 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
98 -- is the nominal subtype. This procedure is used to deal with cases
99 -- where the nominal subtype must be replaced by the actual subtype.
101 -------------------------------
102 -- Diagnose_Non_Variable_Lhs --
103 -------------------------------
105 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
) is
107 -- Not worth posting another error if left hand side already
108 -- flagged as being illegal in some respect.
110 if Error_Posted
(N
) then
113 -- Some special bad cases of entity names
115 elsif Is_Entity_Name
(N
) then
117 Ent
: constant Entity_Id
:= Entity
(N
);
120 if Ekind
(Ent
) = E_In_Parameter
then
122 ("assignment to IN mode parameter not allowed", N
);
124 -- Renamings of protected private components are turned into
125 -- constants when compiling a protected function. In the case
126 -- of single protected types, the private component appears
129 elsif (Is_Prival
(Ent
)
131 (Ekind
(Current_Scope
) = E_Function
132 or else Ekind
(Enclosing_Dynamic_Scope
(
133 Current_Scope
)) = E_Function
))
135 (Ekind
(Ent
) = E_Component
136 and then Is_Protected_Type
(Scope
(Ent
)))
139 ("protected function cannot modify protected object", N
);
141 elsif Ekind
(Ent
) = E_Loop_Parameter
then
143 ("assignment to loop parameter not allowed", N
);
147 ("left hand side of assignment must be a variable", N
);
151 -- For indexed components or selected components, test prefix
153 elsif Nkind
(N
) = N_Indexed_Component
then
154 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
156 -- Another special case for assignment to discriminant
158 elsif Nkind
(N
) = N_Selected_Component
then
159 if Present
(Entity
(Selector_Name
(N
)))
160 and then Ekind
(Entity
(Selector_Name
(N
))) = E_Discriminant
163 ("assignment to discriminant not allowed", N
);
165 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
169 -- If we fall through, we have no special message to issue!
171 Error_Msg_N
("left hand side of assignment must be a variable", N
);
173 end Diagnose_Non_Variable_Lhs
;
179 procedure Kill_Lhs
is
181 if Is_Entity_Name
(Lhs
) then
183 Ent
: constant Entity_Id
:= Entity
(Lhs
);
185 if Present
(Ent
) then
186 Kill_Current_Values
(Ent
);
192 -------------------------
193 -- Set_Assignment_Type --
194 -------------------------
196 procedure Set_Assignment_Type
198 Opnd_Type
: in out Entity_Id
)
201 Require_Entity
(Opnd
);
203 -- If the assignment operand is an in-out or out parameter, then we
204 -- get the actual subtype (needed for the unconstrained case).
205 -- If the operand is the actual in an entry declaration, then within
206 -- the accept statement it is replaced with a local renaming, which
207 -- may also have an actual subtype.
209 if Is_Entity_Name
(Opnd
)
210 and then (Ekind
(Entity
(Opnd
)) = E_Out_Parameter
211 or else Ekind
(Entity
(Opnd
)) =
213 or else Ekind
(Entity
(Opnd
)) =
214 E_Generic_In_Out_Parameter
216 (Ekind
(Entity
(Opnd
)) = E_Variable
217 and then Nkind
(Parent
(Entity
(Opnd
))) =
218 N_Object_Renaming_Declaration
219 and then Nkind
(Parent
(Parent
(Entity
(Opnd
)))) =
222 Opnd_Type
:= Get_Actual_Subtype
(Opnd
);
224 -- If assignment operand is a component reference, then we get the
225 -- actual subtype of the component for the unconstrained case.
227 elsif Nkind_In
(Opnd
, N_Selected_Component
, N_Explicit_Dereference
)
228 and then not Is_Unchecked_Union
(Opnd_Type
)
230 Decl
:= Build_Actual_Subtype_Of_Component
(Opnd_Type
, Opnd
);
232 if Present
(Decl
) then
233 Insert_Action
(N
, Decl
);
234 Mark_Rewrite_Insertion
(Decl
);
236 Opnd_Type
:= Defining_Identifier
(Decl
);
237 Set_Etype
(Opnd
, Opnd_Type
);
238 Freeze_Itype
(Opnd_Type
, N
);
240 elsif Is_Constrained
(Etype
(Opnd
)) then
241 Opnd_Type
:= Etype
(Opnd
);
244 -- For slice, use the constrained subtype created for the slice
246 elsif Nkind
(Opnd
) = N_Slice
then
247 Opnd_Type
:= Etype
(Opnd
);
249 end Set_Assignment_Type
;
251 -- Start of processing for Analyze_Assignment
254 Mark_Coextensions
(N
, Rhs
);
259 -- Start type analysis for assignment
263 -- In the most general case, both Lhs and Rhs can be overloaded, and we
264 -- must compute the intersection of the possible types on each side.
266 if Is_Overloaded
(Lhs
) then
273 Get_First_Interp
(Lhs
, I
, It
);
275 while Present
(It
.Typ
) loop
276 if Has_Compatible_Type
(Rhs
, It
.Typ
) then
277 if T1
/= Any_Type
then
279 -- An explicit dereference is overloaded if the prefix
280 -- is. Try to remove the ambiguity on the prefix, the
281 -- error will be posted there if the ambiguity is real.
283 if Nkind
(Lhs
) = N_Explicit_Dereference
then
286 PI1
: Interp_Index
:= 0;
292 Get_First_Interp
(Prefix
(Lhs
), PI
, PIt
);
294 while Present
(PIt
.Typ
) loop
295 if Is_Access_Type
(PIt
.Typ
)
296 and then Has_Compatible_Type
297 (Rhs
, Designated_Type
(PIt
.Typ
))
301 Disambiguate
(Prefix
(Lhs
),
304 if PIt
= No_Interp
then
306 ("ambiguous left-hand side"
307 & " in assignment", Lhs
);
310 Resolve
(Prefix
(Lhs
), PIt
.Typ
);
320 Get_Next_Interp
(PI
, PIt
);
326 ("ambiguous left-hand side in assignment", Lhs
);
334 Get_Next_Interp
(I
, It
);
338 if T1
= Any_Type
then
340 ("no valid types for left-hand side for assignment", Lhs
);
346 -- The resulting assignment type is T1, so now we will resolve the
347 -- left hand side of the assignment using this determined type.
351 -- Cases where Lhs is not a variable
353 if not Is_Variable
(Lhs
) then
355 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
356 -- a protected object.
363 if Ada_Version
>= Ada_2005
then
365 -- Handle chains of renamings
368 while Nkind
(Ent
) in N_Has_Entity
369 and then Present
(Entity
(Ent
))
370 and then Present
(Renamed_Object
(Entity
(Ent
)))
372 Ent
:= Renamed_Object
(Entity
(Ent
));
375 if (Nkind
(Ent
) = N_Attribute_Reference
376 and then Attribute_Name
(Ent
) = Name_Priority
)
378 -- Renamings of the attribute Priority applied to protected
379 -- objects have been previously expanded into calls to the
380 -- Get_Ceiling run-time subprogram.
383 (Nkind
(Ent
) = N_Function_Call
384 and then (Entity
(Name
(Ent
)) = RTE
(RE_Get_Ceiling
)
386 Entity
(Name
(Ent
)) = RTE
(RO_PE_Get_Ceiling
)))
388 -- The enclosing subprogram cannot be a protected function
391 while not (Is_Subprogram
(S
)
392 and then Convention
(S
) = Convention_Protected
)
393 and then S
/= Standard_Standard
398 if Ekind
(S
) = E_Function
399 and then Convention
(S
) = Convention_Protected
402 ("protected function cannot modify protected object",
406 -- Changes of the ceiling priority of the protected object
407 -- are only effective if the Ceiling_Locking policy is in
408 -- effect (AARM D.5.2 (5/2)).
410 if Locking_Policy
/= 'C' then
411 Error_Msg_N
("assignment to the attribute PRIORITY has " &
413 Error_Msg_N
("\since no Locking_Policy has been " &
422 Diagnose_Non_Variable_Lhs
(Lhs
);
425 -- Error of assigning to limited type. We do however allow this in
426 -- certain cases where the front end generates the assignments.
428 elsif Is_Limited_Type
(T1
)
429 and then not Assignment_OK
(Lhs
)
430 and then not Assignment_OK
(Original_Node
(Lhs
))
431 and then not Is_Value_Type
(T1
)
433 -- CPP constructors can only be called in declarations
435 if Is_CPP_Constructor_Call
(Rhs
) then
436 Error_Msg_N
("invalid use of 'C'P'P constructor", Rhs
);
439 ("left hand of assignment must not be limited type", Lhs
);
440 Explain_Limited_Type
(T1
, Lhs
);
444 -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
445 -- abstract. This is only checked when the assignment Comes_From_Source,
446 -- because in some cases the expander generates such assignments (such
447 -- in the _assign operation for an abstract type).
449 elsif Is_Abstract_Type
(T1
) and then Comes_From_Source
(N
) then
451 ("target of assignment operation must not be abstract", Lhs
);
454 -- Resolution may have updated the subtype, in case the left-hand
455 -- side is a private protected component. Use the correct subtype
456 -- to avoid scoping issues in the back-end.
460 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
461 -- type. For example:
465 -- type Acc is access P.T;
468 -- with Pkg; use Acc;
469 -- procedure Example is
472 -- A.all := B.all; -- ERROR
475 if Nkind
(Lhs
) = N_Explicit_Dereference
476 and then Ekind
(T1
) = E_Incomplete_Type
478 Error_Msg_N
("invalid use of incomplete type", Lhs
);
483 -- Now we can complete the resolution of the right hand side
485 Set_Assignment_Type
(Lhs
, T1
);
488 -- This is the point at which we check for an unset reference
490 Check_Unset_Reference
(Rhs
);
491 Check_Unprotected_Access
(Lhs
, Rhs
);
493 -- Remaining steps are skipped if Rhs was syntactically in error
502 if not Covers
(T1
, T2
) then
503 Wrong_Type
(Rhs
, Etype
(Lhs
));
508 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
509 -- types, use the non-limited view if available
511 if Nkind
(Rhs
) = N_Explicit_Dereference
512 and then Ekind
(T2
) = E_Incomplete_Type
513 and then Is_Tagged_Type
(T2
)
514 and then Present
(Non_Limited_View
(T2
))
516 T2
:= Non_Limited_View
(T2
);
519 Set_Assignment_Type
(Rhs
, T2
);
521 if Total_Errors_Detected
/= 0 then
531 if T1
= Any_Type
or else T2
= Any_Type
then
536 -- If the rhs is class-wide or dynamically tagged, then require the lhs
537 -- to be class-wide. The case where the rhs is a dynamically tagged call
538 -- to a dispatching operation with a controlling access result is
539 -- excluded from this check, since the target has an access type (and
540 -- no tag propagation occurs in that case).
542 if (Is_Class_Wide_Type
(T2
)
543 or else (Is_Dynamically_Tagged
(Rhs
)
544 and then not Is_Access_Type
(T1
)))
545 and then not Is_Class_Wide_Type
(T1
)
547 Error_Msg_N
("dynamically tagged expression not allowed!", Rhs
);
549 elsif Is_Class_Wide_Type
(T1
)
550 and then not Is_Class_Wide_Type
(T2
)
551 and then not Is_Tag_Indeterminate
(Rhs
)
552 and then not Is_Dynamically_Tagged
(Rhs
)
554 Error_Msg_N
("dynamically tagged expression required!", Rhs
);
557 -- Propagate the tag from a class-wide target to the rhs when the rhs
558 -- is a tag-indeterminate call.
560 if Is_Tag_Indeterminate
(Rhs
) then
561 if Is_Class_Wide_Type
(T1
) then
562 Propagate_Tag
(Lhs
, Rhs
);
564 elsif Nkind
(Rhs
) = N_Function_Call
565 and then Is_Entity_Name
(Name
(Rhs
))
566 and then Is_Abstract_Subprogram
(Entity
(Name
(Rhs
)))
569 ("call to abstract function must be dispatching", Name
(Rhs
));
571 elsif Nkind
(Rhs
) = N_Qualified_Expression
572 and then Nkind
(Expression
(Rhs
)) = N_Function_Call
573 and then Is_Entity_Name
(Name
(Expression
(Rhs
)))
575 Is_Abstract_Subprogram
(Entity
(Name
(Expression
(Rhs
))))
578 ("call to abstract function must be dispatching",
579 Name
(Expression
(Rhs
)));
583 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
584 -- apply an implicit conversion of the rhs to that type to force
585 -- appropriate static and run-time accessibility checks. This applies
586 -- as well to anonymous access-to-subprogram types that are component
587 -- subtypes or formal parameters.
589 if Ada_Version
>= Ada_2005
590 and then Is_Access_Type
(T1
)
592 if Is_Local_Anonymous_Access
(T1
)
593 or else Ekind
(T2
) = E_Anonymous_Access_Subprogram_Type
595 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
596 Analyze_And_Resolve
(Rhs
, T1
);
600 -- Ada 2005 (AI-231): Assignment to not null variable
602 if Ada_Version
>= Ada_2005
603 and then Can_Never_Be_Null
(T1
)
604 and then not Assignment_OK
(Lhs
)
606 -- Case where we know the right hand side is null
608 if Known_Null
(Rhs
) then
609 Apply_Compile_Time_Constraint_Error
611 Msg
=> "(Ada 2005) null not allowed in null-excluding objects?",
612 Reason
=> CE_Null_Not_Allowed
);
614 -- We still mark this as a possible modification, that's necessary
615 -- to reset Is_True_Constant, and desirable for xref purposes.
617 Note_Possible_Modification
(Lhs
, Sure
=> True);
620 -- If we know the right hand side is non-null, then we convert to the
621 -- target type, since we don't need a run time check in that case.
623 elsif not Can_Never_Be_Null
(T2
) then
624 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
625 Analyze_And_Resolve
(Rhs
, T1
);
629 if Is_Scalar_Type
(T1
) then
630 Apply_Scalar_Range_Check
(Rhs
, Etype
(Lhs
));
632 -- For array types, verify that lengths match. If the right hand side
633 -- if a function call that has been inlined, the assignment has been
634 -- rewritten as a block, and the constraint check will be applied to the
635 -- assignment within the block.
637 elsif Is_Array_Type
(T1
)
639 (Nkind
(Rhs
) /= N_Type_Conversion
640 or else Is_Constrained
(Etype
(Rhs
)))
642 (Nkind
(Rhs
) /= N_Function_Call
643 or else Nkind
(N
) /= N_Block_Statement
)
645 -- Assignment verifies that the length of the Lsh and Rhs are equal,
646 -- but of course the indexes do not have to match. If the right-hand
647 -- side is a type conversion to an unconstrained type, a length check
648 -- is performed on the expression itself during expansion. In rare
649 -- cases, the redundant length check is computed on an index type
650 -- with a different representation, triggering incorrect code in
653 Apply_Length_Check
(Rhs
, Etype
(Lhs
));
656 -- Discriminant checks are applied in the course of expansion
661 -- Note: modifications of the Lhs may only be recorded after
662 -- checks have been applied.
664 Note_Possible_Modification
(Lhs
, Sure
=> True);
665 Check_Order_Dependence
;
667 -- ??? a real accessibility check is needed when ???
669 -- Post warning for redundant assignment or variable to itself
671 if Warn_On_Redundant_Constructs
673 -- We only warn for source constructs
675 and then Comes_From_Source
(N
)
677 -- Where the object is the same on both sides
679 and then Same_Object
(Lhs
, Original_Node
(Rhs
))
681 -- But exclude the case where the right side was an operation
682 -- that got rewritten (e.g. JUNK + K, where K was known to be
683 -- zero). We don't want to warn in such a case, since it is
684 -- reasonable to write such expressions especially when K is
685 -- defined symbolically in some other package.
687 and then Nkind
(Original_Node
(Rhs
)) not in N_Op
689 if Nkind
(Lhs
) in N_Has_Entity
then
690 Error_Msg_NE
-- CODEFIX
691 ("?useless assignment of & to itself!", N
, Entity
(Lhs
));
693 Error_Msg_N
-- CODEFIX
694 ("?useless assignment of object to itself!", N
);
698 -- Check for non-allowed composite assignment
700 if not Support_Composite_Assign_On_Target
701 and then (Is_Array_Type
(T1
) or else Is_Record_Type
(T1
))
702 and then (not Has_Size_Clause
(T1
) or else Esize
(T1
) > 64)
704 Error_Msg_CRT
("composite assignment", N
);
707 -- Check elaboration warning for left side if not in elab code
709 if not In_Subprogram_Or_Concurrent_Unit
then
710 Check_Elab_Assign
(Lhs
);
713 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
714 -- assignment is a source assignment in the extended main source unit.
715 -- We are not interested in any reference information outside this
716 -- context, or in compiler generated assignment statements.
718 if Comes_From_Source
(N
)
719 and then In_Extended_Main_Source_Unit
(Lhs
)
721 Set_Referenced_Modified
(Lhs
, Out_Param
=> False);
724 -- Final step. If left side is an entity, then we may be able to
725 -- reset the current tracked values to new safe values. We only have
726 -- something to do if the left side is an entity name, and expansion
727 -- has not modified the node into something other than an assignment,
728 -- and of course we only capture values if it is safe to do so.
730 if Is_Entity_Name
(Lhs
)
731 and then Nkind
(N
) = N_Assignment_Statement
734 Ent
: constant Entity_Id
:= Entity
(Lhs
);
737 if Safe_To_Capture_Value
(N
, Ent
) then
739 -- If simple variable on left side, warn if this assignment
740 -- blots out another one (rendering it useless) and note
741 -- location of assignment in case no one references value.
742 -- We only do this for source assignments, otherwise we can
743 -- generate bogus warnings when an assignment is rewritten as
744 -- another assignment, and gets tied up with itself.
746 -- Note: we don't use Record_Last_Assignment here, because we
747 -- have lots of other stuff to do under control of this test.
749 if Warn_On_Modified_Unread
750 and then Is_Assignable
(Ent
)
751 and then Comes_From_Source
(N
)
752 and then In_Extended_Main_Source_Unit
(Ent
)
754 Warn_On_Useless_Assignment
(Ent
, N
);
755 Set_Last_Assignment
(Ent
, Lhs
);
758 -- If we are assigning an access type and the left side is an
759 -- entity, then make sure that the Is_Known_[Non_]Null flags
760 -- properly reflect the state of the entity after assignment.
762 if Is_Access_Type
(T1
) then
763 if Known_Non_Null
(Rhs
) then
764 Set_Is_Known_Non_Null
(Ent
, True);
766 elsif Known_Null
(Rhs
)
767 and then not Can_Never_Be_Null
(Ent
)
769 Set_Is_Known_Null
(Ent
, True);
772 Set_Is_Known_Null
(Ent
, False);
774 if not Can_Never_Be_Null
(Ent
) then
775 Set_Is_Known_Non_Null
(Ent
, False);
779 -- For discrete types, we may be able to set the current value
780 -- if the value is known at compile time.
782 elsif Is_Discrete_Type
(T1
)
783 and then Compile_Time_Known_Value
(Rhs
)
785 Set_Current_Value
(Ent
, Rhs
);
787 Set_Current_Value
(Ent
, Empty
);
790 -- If not safe to capture values, kill them
797 end Analyze_Assignment
;
799 -----------------------------
800 -- Analyze_Block_Statement --
801 -----------------------------
803 procedure Analyze_Block_Statement
(N
: Node_Id
) is
804 Decls
: constant List_Id
:= Declarations
(N
);
805 Id
: constant Node_Id
:= Identifier
(N
);
806 HSS
: constant Node_Id
:= Handled_Statement_Sequence
(N
);
809 -- If no handled statement sequence is present, things are really
810 -- messed up, and we just return immediately (this is a defence
811 -- against previous errors).
817 -- Normal processing with HSS present
820 EH
: constant List_Id
:= Exception_Handlers
(HSS
);
821 Ent
: Entity_Id
:= Empty
;
824 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
825 -- Recursively save value of this global, will be restored on exit
828 -- Initialize unblocked exit count for statements of begin block
829 -- plus one for each exception handler that is present.
831 Unblocked_Exit_Count
:= 1;
834 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ List_Length
(EH
);
837 -- If a label is present analyze it and mark it as referenced
843 -- An error defense. If we have an identifier, but no entity,
844 -- then something is wrong. If we have previous errors, then
845 -- just remove the identifier and continue, otherwise raise
849 if Total_Errors_Detected
/= 0 then
850 Set_Identifier
(N
, Empty
);
856 Set_Ekind
(Ent
, E_Block
);
857 Generate_Reference
(Ent
, N
, ' ');
858 Generate_Definition
(Ent
);
860 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
861 Set_Label_Construct
(Parent
(Ent
), N
);
866 -- If no entity set, create a label entity
869 Ent
:= New_Internal_Entity
(E_Block
, Current_Scope
, Sloc
(N
), 'B');
870 Set_Identifier
(N
, New_Occurrence_Of
(Ent
, Sloc
(N
)));
874 Set_Etype
(Ent
, Standard_Void_Type
);
875 Set_Block_Node
(Ent
, Identifier
(N
));
878 if Present
(Decls
) then
879 Analyze_Declarations
(Decls
);
881 Inspect_Deferred_Constant_Completion
(Decls
);
885 Process_End_Label
(HSS
, 'e', Ent
);
887 -- If exception handlers are present, then we indicate that
888 -- enclosing scopes contain a block with handlers. We only
889 -- need to mark non-generic scopes.
894 Set_Has_Nested_Block_With_Handler
(S
);
895 exit when Is_Overloadable
(S
)
896 or else Ekind
(S
) = E_Package
897 or else Is_Generic_Unit
(S
);
902 Check_References
(Ent
);
903 Warn_On_Useless_Assignments
(Ent
);
906 if Unblocked_Exit_Count
= 0 then
907 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
908 Check_Unreachable_Code
(N
);
910 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
913 end Analyze_Block_Statement
;
915 ----------------------------
916 -- Analyze_Case_Statement --
917 ----------------------------
919 procedure Analyze_Case_Statement
(N
: Node_Id
) is
921 Exp_Type
: Entity_Id
;
922 Exp_Btype
: Entity_Id
;
925 Others_Present
: Boolean;
927 pragma Warnings
(Off
, Last_Choice
);
928 pragma Warnings
(Off
, Dont_Care
);
929 -- Don't care about assigned values
931 Statements_Analyzed
: Boolean := False;
932 -- Set True if at least some statement sequences get analyzed.
933 -- If False on exit, means we had a serious error that prevented
934 -- full analysis of the case statement, and as a result it is not
935 -- a good idea to output warning messages about unreachable code.
937 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
938 -- Recursively save value of this global, will be restored on exit
940 procedure Non_Static_Choice_Error
(Choice
: Node_Id
);
941 -- Error routine invoked by the generic instantiation below when
942 -- the case statement has a non static choice.
944 procedure Process_Statements
(Alternative
: Node_Id
);
945 -- Analyzes all the statements associated with a case alternative.
946 -- Needed by the generic instantiation below.
948 package Case_Choices_Processing
is new
949 Generic_Choices_Processing
950 (Get_Alternatives
=> Alternatives
,
951 Get_Choices
=> Discrete_Choices
,
952 Process_Empty_Choice
=> No_OP
,
953 Process_Non_Static_Choice
=> Non_Static_Choice_Error
,
954 Process_Associated_Node
=> Process_Statements
);
955 use Case_Choices_Processing
;
956 -- Instantiation of the generic choice processing package
958 -----------------------------
959 -- Non_Static_Choice_Error --
960 -----------------------------
962 procedure Non_Static_Choice_Error
(Choice
: Node_Id
) is
965 ("choice given in case statement is not static!", Choice
);
966 end Non_Static_Choice_Error
;
968 ------------------------
969 -- Process_Statements --
970 ------------------------
972 procedure Process_Statements
(Alternative
: Node_Id
) is
973 Choices
: constant List_Id
:= Discrete_Choices
(Alternative
);
977 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
978 Statements_Analyzed
:= True;
980 -- An interesting optimization. If the case statement expression
981 -- is a simple entity, then we can set the current value within
982 -- an alternative if the alternative has one possible value.
986 -- when 2 | 3 => beta
987 -- when others => gamma
989 -- Here we know that N is initially 1 within alpha, but for beta
990 -- and gamma, we do not know anything more about the initial value.
992 if Is_Entity_Name
(Exp
) then
995 if Ekind_In
(Ent
, E_Variable
,
999 if List_Length
(Choices
) = 1
1000 and then Nkind
(First
(Choices
)) in N_Subexpr
1001 and then Compile_Time_Known_Value
(First
(Choices
))
1003 Set_Current_Value
(Entity
(Exp
), First
(Choices
));
1006 Analyze_Statements
(Statements
(Alternative
));
1008 -- After analyzing the case, set the current value to empty
1009 -- since we won't know what it is for the next alternative
1010 -- (unless reset by this same circuit), or after the case.
1012 Set_Current_Value
(Entity
(Exp
), Empty
);
1017 -- Case where expression is not an entity name of a variable
1019 Analyze_Statements
(Statements
(Alternative
));
1020 end Process_Statements
;
1022 -- Start of processing for Analyze_Case_Statement
1025 Unblocked_Exit_Count
:= 0;
1026 Exp
:= Expression
(N
);
1029 -- The expression must be of any discrete type. In rare cases, the
1030 -- expander constructs a case statement whose expression has a private
1031 -- type whose full view is discrete. This can happen when generating
1032 -- a stream operation for a variant type after the type is frozen,
1033 -- when the partial of view of the type of the discriminant is private.
1034 -- In that case, use the full view to analyze case alternatives.
1036 if not Is_Overloaded
(Exp
)
1037 and then not Comes_From_Source
(N
)
1038 and then Is_Private_Type
(Etype
(Exp
))
1039 and then Present
(Full_View
(Etype
(Exp
)))
1040 and then Is_Discrete_Type
(Full_View
(Etype
(Exp
)))
1042 Resolve
(Exp
, Etype
(Exp
));
1043 Exp_Type
:= Full_View
(Etype
(Exp
));
1046 Analyze_And_Resolve
(Exp
, Any_Discrete
);
1047 Exp_Type
:= Etype
(Exp
);
1050 Check_Unset_Reference
(Exp
);
1051 Exp_Btype
:= Base_Type
(Exp_Type
);
1053 -- The expression must be of a discrete type which must be determinable
1054 -- independently of the context in which the expression occurs, but
1055 -- using the fact that the expression must be of a discrete type.
1056 -- Moreover, the type this expression must not be a character literal
1057 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1059 -- If error already reported by Resolve, nothing more to do
1061 if Exp_Btype
= Any_Discrete
1062 or else Exp_Btype
= Any_Type
1066 elsif Exp_Btype
= Any_Character
then
1068 ("character literal as case expression is ambiguous", Exp
);
1071 elsif Ada_Version
= Ada_83
1072 and then (Is_Generic_Type
(Exp_Btype
)
1073 or else Is_Generic_Type
(Root_Type
(Exp_Btype
)))
1076 ("(Ada 83) case expression cannot be of a generic type", Exp
);
1080 -- If the case expression is a formal object of mode in out, then
1081 -- treat it as having a nonstatic subtype by forcing use of the base
1082 -- type (which has to get passed to Check_Case_Choices below). Also
1083 -- use base type when the case expression is parenthesized.
1085 if Paren_Count
(Exp
) > 0
1086 or else (Is_Entity_Name
(Exp
)
1087 and then Ekind
(Entity
(Exp
)) = E_Generic_In_Out_Parameter
)
1089 Exp_Type
:= Exp_Btype
;
1092 -- Call instantiated Analyze_Choices which does the rest of the work
1094 Analyze_Choices
(N
, Exp_Type
, Dont_Care
, Others_Present
);
1096 if Exp_Type
= Universal_Integer
and then not Others_Present
then
1097 Error_Msg_N
("case on universal integer requires OTHERS choice", Exp
);
1100 -- If all our exits were blocked by unconditional transfers of control,
1101 -- then the entire CASE statement acts as an unconditional transfer of
1102 -- control, so treat it like one, and check unreachable code. Skip this
1103 -- test if we had serious errors preventing any statement analysis.
1105 if Unblocked_Exit_Count
= 0 and then Statements_Analyzed
then
1106 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1107 Check_Unreachable_Code
(N
);
1109 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1112 if not Expander_Active
1113 and then Compile_Time_Known_Value
(Expression
(N
))
1114 and then Serious_Errors_Detected
= 0
1117 Chosen
: constant Node_Id
:= Find_Static_Alternative
(N
);
1121 Alt
:= First
(Alternatives
(N
));
1122 while Present
(Alt
) loop
1123 if Alt
/= Chosen
then
1124 Remove_Warning_Messages
(Statements
(Alt
));
1131 end Analyze_Case_Statement
;
1133 ----------------------------
1134 -- Analyze_Exit_Statement --
1135 ----------------------------
1137 -- If the exit includes a name, it must be the name of a currently open
1138 -- loop. Otherwise there must be an innermost open loop on the stack,
1139 -- to which the statement implicitly refers.
1141 procedure Analyze_Exit_Statement
(N
: Node_Id
) is
1142 Target
: constant Node_Id
:= Name
(N
);
1143 Cond
: constant Node_Id
:= Condition
(N
);
1144 Scope_Id
: Entity_Id
;
1150 Check_Unreachable_Code
(N
);
1153 if Present
(Target
) then
1155 U_Name
:= Entity
(Target
);
1157 if not In_Open_Scopes
(U_Name
) or else Ekind
(U_Name
) /= E_Loop
then
1158 Error_Msg_N
("invalid loop name in exit statement", N
);
1161 Set_Has_Exit
(U_Name
);
1168 for J
in reverse 0 .. Scope_Stack
.Last
loop
1169 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
1170 Kind
:= Ekind
(Scope_Id
);
1173 and then (No
(Target
) or else Scope_Id
= U_Name
) then
1174 Set_Has_Exit
(Scope_Id
);
1177 elsif Kind
= E_Block
1178 or else Kind
= E_Loop
1179 or else Kind
= E_Return_Statement
1185 ("cannot exit from program unit or accept statement", N
);
1190 -- Verify that if present the condition is a Boolean expression
1192 if Present
(Cond
) then
1193 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1194 Check_Unset_Reference
(Cond
);
1197 -- Chain exit statement to associated loop entity
1199 Set_Next_Exit_Statement
(N
, First_Exit_Statement
(Scope_Id
));
1200 Set_First_Exit_Statement
(Scope_Id
, N
);
1202 -- Since the exit may take us out of a loop, any previous assignment
1203 -- statement is not useless, so clear last assignment indications. It
1204 -- is OK to keep other current values, since if the exit statement
1205 -- does not exit, then the current values are still valid.
1207 Kill_Current_Values
(Last_Assignment_Only
=> True);
1208 end Analyze_Exit_Statement
;
1210 ----------------------------
1211 -- Analyze_Goto_Statement --
1212 ----------------------------
1214 procedure Analyze_Goto_Statement
(N
: Node_Id
) is
1215 Label
: constant Node_Id
:= Name
(N
);
1216 Scope_Id
: Entity_Id
;
1217 Label_Scope
: Entity_Id
;
1218 Label_Ent
: Entity_Id
;
1221 Check_Unreachable_Code
(N
);
1222 Kill_Current_Values
(Last_Assignment_Only
=> True);
1225 Label_Ent
:= Entity
(Label
);
1227 -- Ignore previous error
1229 if Label_Ent
= Any_Id
then
1232 -- We just have a label as the target of a goto
1234 elsif Ekind
(Label_Ent
) /= E_Label
then
1235 Error_Msg_N
("target of goto statement must be a label", Label
);
1238 -- Check that the target of the goto is reachable according to Ada
1239 -- scoping rules. Note: the special gotos we generate for optimizing
1240 -- local handling of exceptions would violate these rules, but we mark
1241 -- such gotos as analyzed when built, so this code is never entered.
1243 elsif not Reachable
(Label_Ent
) then
1244 Error_Msg_N
("target of goto statement is not reachable", Label
);
1248 -- Here if goto passes initial validity checks
1250 Label_Scope
:= Enclosing_Scope
(Label_Ent
);
1252 for J
in reverse 0 .. Scope_Stack
.Last
loop
1253 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
1255 if Label_Scope
= Scope_Id
1256 or else (Ekind
(Scope_Id
) /= E_Block
1257 and then Ekind
(Scope_Id
) /= E_Loop
1258 and then Ekind
(Scope_Id
) /= E_Return_Statement
)
1260 if Scope_Id
/= Label_Scope
then
1262 ("cannot exit from program unit or accept statement", N
);
1269 raise Program_Error
;
1270 end Analyze_Goto_Statement
;
1272 --------------------------
1273 -- Analyze_If_Statement --
1274 --------------------------
1276 -- A special complication arises in the analysis of if statements
1278 -- The expander has circuitry to completely delete code that it
1279 -- can tell will not be executed (as a result of compile time known
1280 -- conditions). In the analyzer, we ensure that code that will be
1281 -- deleted in this manner is analyzed but not expanded. This is
1282 -- obviously more efficient, but more significantly, difficulties
1283 -- arise if code is expanded and then eliminated (e.g. exception
1284 -- table entries disappear). Similarly, itypes generated in deleted
1285 -- code must be frozen from start, because the nodes on which they
1286 -- depend will not be available at the freeze point.
1288 procedure Analyze_If_Statement
(N
: Node_Id
) is
1291 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
1292 -- Recursively save value of this global, will be restored on exit
1294 Save_In_Deleted_Code
: Boolean;
1296 Del
: Boolean := False;
1297 -- This flag gets set True if a True condition has been found,
1298 -- which means that remaining ELSE/ELSIF parts are deleted.
1300 procedure Analyze_Cond_Then
(Cnode
: Node_Id
);
1301 -- This is applied to either the N_If_Statement node itself or
1302 -- to an N_Elsif_Part node. It deals with analyzing the condition
1303 -- and the THEN statements associated with it.
1305 -----------------------
1306 -- Analyze_Cond_Then --
1307 -----------------------
1309 procedure Analyze_Cond_Then
(Cnode
: Node_Id
) is
1310 Cond
: constant Node_Id
:= Condition
(Cnode
);
1311 Tstm
: constant List_Id
:= Then_Statements
(Cnode
);
1314 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
1315 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1316 Check_Unset_Reference
(Cond
);
1317 Set_Current_Value_Condition
(Cnode
);
1319 -- If already deleting, then just analyze then statements
1322 Analyze_Statements
(Tstm
);
1324 -- Compile time known value, not deleting yet
1326 elsif Compile_Time_Known_Value
(Cond
) then
1327 Save_In_Deleted_Code
:= In_Deleted_Code
;
1329 -- If condition is True, then analyze the THEN statements
1330 -- and set no expansion for ELSE and ELSIF parts.
1332 if Is_True
(Expr_Value
(Cond
)) then
1333 Analyze_Statements
(Tstm
);
1335 Expander_Mode_Save_And_Set
(False);
1336 In_Deleted_Code
:= True;
1338 -- If condition is False, analyze THEN with expansion off
1340 else -- Is_False (Expr_Value (Cond))
1341 Expander_Mode_Save_And_Set
(False);
1342 In_Deleted_Code
:= True;
1343 Analyze_Statements
(Tstm
);
1344 Expander_Mode_Restore
;
1345 In_Deleted_Code
:= Save_In_Deleted_Code
;
1348 -- Not known at compile time, not deleting, normal analysis
1351 Analyze_Statements
(Tstm
);
1353 end Analyze_Cond_Then
;
1355 -- Start of Analyze_If_Statement
1358 -- Initialize exit count for else statements. If there is no else
1359 -- part, this count will stay non-zero reflecting the fact that the
1360 -- uncovered else case is an unblocked exit.
1362 Unblocked_Exit_Count
:= 1;
1363 Analyze_Cond_Then
(N
);
1365 -- Now to analyze the elsif parts if any are present
1367 if Present
(Elsif_Parts
(N
)) then
1368 E
:= First
(Elsif_Parts
(N
));
1369 while Present
(E
) loop
1370 Analyze_Cond_Then
(E
);
1375 if Present
(Else_Statements
(N
)) then
1376 Analyze_Statements
(Else_Statements
(N
));
1379 -- If all our exits were blocked by unconditional transfers of control,
1380 -- then the entire IF statement acts as an unconditional transfer of
1381 -- control, so treat it like one, and check unreachable code.
1383 if Unblocked_Exit_Count
= 0 then
1384 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1385 Check_Unreachable_Code
(N
);
1387 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1391 Expander_Mode_Restore
;
1392 In_Deleted_Code
:= Save_In_Deleted_Code
;
1395 if not Expander_Active
1396 and then Compile_Time_Known_Value
(Condition
(N
))
1397 and then Serious_Errors_Detected
= 0
1399 if Is_True
(Expr_Value
(Condition
(N
))) then
1400 Remove_Warning_Messages
(Else_Statements
(N
));
1402 if Present
(Elsif_Parts
(N
)) then
1403 E
:= First
(Elsif_Parts
(N
));
1404 while Present
(E
) loop
1405 Remove_Warning_Messages
(Then_Statements
(E
));
1411 Remove_Warning_Messages
(Then_Statements
(N
));
1414 end Analyze_If_Statement
;
1416 ----------------------------------------
1417 -- Analyze_Implicit_Label_Declaration --
1418 ----------------------------------------
1420 -- An implicit label declaration is generated in the innermost
1421 -- enclosing declarative part. This is done for labels as well as
1422 -- block and loop names.
1424 -- Note: any changes in this routine may need to be reflected in
1425 -- Analyze_Label_Entity.
1427 procedure Analyze_Implicit_Label_Declaration
(N
: Node_Id
) is
1428 Id
: constant Node_Id
:= Defining_Identifier
(N
);
1431 Set_Ekind
(Id
, E_Label
);
1432 Set_Etype
(Id
, Standard_Void_Type
);
1433 Set_Enclosing_Scope
(Id
, Current_Scope
);
1434 end Analyze_Implicit_Label_Declaration
;
1436 ------------------------------
1437 -- Analyze_Iteration_Scheme --
1438 ------------------------------
1440 procedure Analyze_Iteration_Scheme
(N
: Node_Id
) is
1442 procedure Process_Bounds
(R
: Node_Id
);
1443 -- If the iteration is given by a range, create temporaries and
1444 -- assignment statements block to capture the bounds and perform
1445 -- required finalization actions in case a bound includes a function
1446 -- call that uses the temporary stack. We first pre-analyze a copy of
1447 -- the range in order to determine the expected type, and analyze and
1448 -- resolve the original bounds.
1450 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
);
1451 -- If the bounds are given by a 'Range reference on a function call
1452 -- that returns a controlled array, introduce an explicit declaration
1453 -- to capture the bounds, so that the function result can be finalized
1454 -- in timely fashion.
1456 --------------------
1457 -- Process_Bounds --
1458 --------------------
1460 procedure Process_Bounds
(R
: Node_Id
) is
1461 Loc
: constant Source_Ptr
:= Sloc
(N
);
1462 R_Copy
: constant Node_Id
:= New_Copy_Tree
(R
);
1463 Lo
: constant Node_Id
:= Low_Bound
(R
);
1464 Hi
: constant Node_Id
:= High_Bound
(R
);
1465 New_Lo_Bound
: Node_Id
;
1466 New_Hi_Bound
: Node_Id
;
1468 Save_Analysis
: Boolean;
1471 (Original_Bound
: Node_Id
;
1472 Analyzed_Bound
: Node_Id
) return Node_Id
;
1473 -- Capture value of bound and return captured value
1480 (Original_Bound
: Node_Id
;
1481 Analyzed_Bound
: Node_Id
) return Node_Id
1488 -- If the bound is a constant or an object, no need for a separate
1489 -- declaration. If the bound is the result of previous expansion
1490 -- it is already analyzed and should not be modified. Note that
1491 -- the Bound will be resolved later, if needed, as part of the
1492 -- call to Make_Index (literal bounds may need to be resolved to
1495 if Analyzed
(Original_Bound
) then
1496 return Original_Bound
;
1498 elsif Nkind_In
(Analyzed_Bound
, N_Integer_Literal
,
1499 N_Character_Literal
)
1500 or else Is_Entity_Name
(Analyzed_Bound
)
1502 Analyze_And_Resolve
(Original_Bound
, Typ
);
1503 return Original_Bound
;
1506 -- Here we need to capture the value
1508 Analyze_And_Resolve
(Original_Bound
, Typ
);
1510 Id
:= Make_Temporary
(Loc
, 'S', Original_Bound
);
1512 -- Normally, the best approach is simply to generate a constant
1513 -- declaration that captures the bound. However, there is a nasty
1514 -- case where this is wrong. If the bound is complex, and has a
1515 -- possible use of the secondary stack, we need to generate a
1516 -- separate assignment statement to ensure the creation of a block
1517 -- which will release the secondary stack.
1519 -- We prefer the constant declaration, since it leaves us with a
1520 -- proper trace of the value, useful in optimizations that get rid
1521 -- of junk range checks.
1523 -- Probably we want something like the Side_Effect_Free routine
1524 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1525 -- and 'First applied to an entity, since these are the important
1526 -- cases for range check optimizations.
1528 if Nkind
(Original_Bound
) = N_Attribute_Reference
1529 and then (Attribute_Name
(Original_Bound
) = Name_First
1531 Attribute_Name
(Original_Bound
) = Name_Last
)
1532 and then Is_Entity_Name
(Prefix
(Original_Bound
))
1535 Make_Object_Declaration
(Loc
,
1536 Defining_Identifier
=> Id
,
1537 Constant_Present
=> True,
1538 Object_Definition
=> New_Occurrence_Of
(Typ
, Loc
),
1539 Expression
=> Relocate_Node
(Original_Bound
));
1541 -- Insert declaration at proper place. If loop comes from an
1542 -- enclosing quantified expression, the insertion point is
1543 -- arbitrarily far up in the tree.
1545 Insert_Action
(Parent
(N
), Decl
);
1546 Rewrite
(Original_Bound
, New_Occurrence_Of
(Id
, Loc
));
1547 return Expression
(Decl
);
1550 -- Here we make a declaration with a separate assignment
1551 -- statement, and insert before loop header.
1554 Make_Object_Declaration
(Loc
,
1555 Defining_Identifier
=> Id
,
1556 Object_Definition
=> New_Occurrence_Of
(Typ
, Loc
));
1559 Make_Assignment_Statement
(Loc
,
1560 Name
=> New_Occurrence_Of
(Id
, Loc
),
1561 Expression
=> Relocate_Node
(Original_Bound
));
1563 Insert_Actions
(Parent
(N
), New_List
(Decl
, Assign
));
1565 Rewrite
(Original_Bound
, New_Occurrence_Of
(Id
, Loc
));
1567 if Nkind
(Assign
) = N_Assignment_Statement
then
1568 return Expression
(Assign
);
1570 return Original_Bound
;
1574 -- Start of processing for Process_Bounds
1577 -- Determine expected type of range by analyzing separate copy
1578 -- Do the analysis and resolution of the copy of the bounds with
1579 -- expansion disabled, to prevent the generation of finalization
1580 -- actions on each bound. This prevents memory leaks when the
1581 -- bounds contain calls to functions returning controlled arrays.
1583 Set_Parent
(R_Copy
, Parent
(R
));
1584 Save_Analysis
:= Full_Analysis
;
1585 Full_Analysis
:= False;
1586 Expander_Mode_Save_And_Set
(False);
1590 if Is_Overloaded
(R_Copy
) then
1592 -- Apply preference rules for range of predefined integer types,
1593 -- or diagnose true ambiguity.
1598 Found
: Entity_Id
:= Empty
;
1601 Get_First_Interp
(R_Copy
, I
, It
);
1602 while Present
(It
.Typ
) loop
1603 if Is_Discrete_Type
(It
.Typ
) then
1607 if Scope
(Found
) = Standard_Standard
then
1610 elsif Scope
(It
.Typ
) = Standard_Standard
then
1614 -- Both of them are user-defined
1617 ("ambiguous bounds in range of iteration",
1619 Error_Msg_N
("\possible interpretations:", R_Copy
);
1620 Error_Msg_NE
("\\} ", R_Copy
, Found
);
1621 Error_Msg_NE
("\\} ", R_Copy
, It
.Typ
);
1627 Get_Next_Interp
(I
, It
);
1633 Expander_Mode_Restore
;
1634 Full_Analysis
:= Save_Analysis
;
1636 Typ
:= Etype
(R_Copy
);
1638 -- If the type of the discrete range is Universal_Integer, then
1639 -- the bound's type must be resolved to Integer, and any object
1640 -- used to hold the bound must also have type Integer, unless the
1641 -- literal bounds are constant-folded expressions that carry a user-
1644 if Typ
= Universal_Integer
then
1645 if Nkind
(Lo
) = N_Integer_Literal
1646 and then Present
(Etype
(Lo
))
1647 and then Scope
(Etype
(Lo
)) /= Standard_Standard
1651 elsif Nkind
(Hi
) = N_Integer_Literal
1652 and then Present
(Etype
(Hi
))
1653 and then Scope
(Etype
(Hi
)) /= Standard_Standard
1658 Typ
:= Standard_Integer
;
1664 New_Lo_Bound
:= One_Bound
(Lo
, Low_Bound
(R_Copy
));
1665 New_Hi_Bound
:= One_Bound
(Hi
, High_Bound
(R_Copy
));
1667 -- Propagate staticness to loop range itself, in case the
1668 -- corresponding subtype is static.
1670 if New_Lo_Bound
/= Lo
1671 and then Is_Static_Expression
(New_Lo_Bound
)
1673 Rewrite
(Low_Bound
(R
), New_Copy
(New_Lo_Bound
));
1676 if New_Hi_Bound
/= Hi
1677 and then Is_Static_Expression
(New_Hi_Bound
)
1679 Rewrite
(High_Bound
(R
), New_Copy
(New_Hi_Bound
));
1683 --------------------------------------
1684 -- Check_Controlled_Array_Attribute --
1685 --------------------------------------
1687 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
) is
1689 if Nkind
(DS
) = N_Attribute_Reference
1690 and then Is_Entity_Name
(Prefix
(DS
))
1691 and then Ekind
(Entity
(Prefix
(DS
))) = E_Function
1692 and then Is_Array_Type
(Etype
(Entity
(Prefix
(DS
))))
1695 Component_Type
(Etype
(Entity
(Prefix
(DS
)))))
1696 and then Expander_Active
1699 Loc
: constant Source_Ptr
:= Sloc
(N
);
1700 Arr
: constant Entity_Id
:= Etype
(Entity
(Prefix
(DS
)));
1701 Indx
: constant Entity_Id
:=
1702 Base_Type
(Etype
(First_Index
(Arr
)));
1703 Subt
: constant Entity_Id
:= Make_Temporary
(Loc
, 'S');
1708 Make_Subtype_Declaration
(Loc
,
1709 Defining_Identifier
=> Subt
,
1710 Subtype_Indication
=>
1711 Make_Subtype_Indication
(Loc
,
1712 Subtype_Mark
=> New_Reference_To
(Indx
, Loc
),
1714 Make_Range_Constraint
(Loc
,
1715 Relocate_Node
(DS
))));
1716 Insert_Before
(Parent
(N
), Decl
);
1720 Make_Attribute_Reference
(Loc
,
1721 Prefix
=> New_Reference_To
(Subt
, Loc
),
1722 Attribute_Name
=> Attribute_Name
(DS
)));
1726 end Check_Controlled_Array_Attribute
;
1728 -- Start of processing for Analyze_Iteration_Scheme
1731 -- If this is a rewritten quantified expression, the iteration
1732 -- scheme has been analyzed already. Do no repeat analysis because
1733 -- the loop variable is already declared.
1735 if Analyzed
(N
) then
1739 -- For an infinite loop, there is no iteration scheme
1745 -- Iteration scheme is present
1748 Cond
: constant Node_Id
:= Condition
(N
);
1751 -- For WHILE loop, verify that the condition is a Boolean
1752 -- expression and resolve and check it.
1754 if Present
(Cond
) then
1755 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1756 Check_Unset_Reference
(Cond
);
1757 Set_Current_Value_Condition
(N
);
1760 elsif Present
(Iterator_Specification
(N
)) then
1761 Analyze_Iterator_Specification
(Iterator_Specification
(N
));
1763 -- Else we have a FOR loop
1767 LP
: constant Node_Id
:= Loop_Parameter_Specification
(N
);
1768 Id
: constant Entity_Id
:= Defining_Identifier
(LP
);
1769 DS
: constant Node_Id
:= Discrete_Subtype_Definition
(LP
);
1774 -- We always consider the loop variable to be referenced,
1775 -- since the loop may be used just for counting purposes.
1777 Generate_Reference
(Id
, N
, ' ');
1779 -- Check for the case of loop variable hiding a local variable
1780 -- (used later on to give a nice warning if the hidden variable
1781 -- is never assigned).
1784 H
: constant Entity_Id
:= Homonym
(Id
);
1787 and then Enclosing_Dynamic_Scope
(H
) =
1788 Enclosing_Dynamic_Scope
(Id
)
1789 and then Ekind
(H
) = E_Variable
1790 and then Is_Discrete_Type
(Etype
(H
))
1792 Set_Hiding_Loop_Variable
(H
, Id
);
1796 -- Now analyze the subtype definition. If it is a range, create
1797 -- temporaries for bounds.
1799 if Nkind
(DS
) = N_Range
1800 and then Expander_Active
1802 Process_Bounds
(DS
);
1804 -- Not a range or expander not active (is that right???)
1809 if Nkind
(DS
) = N_Function_Call
1811 (Is_Entity_Name
(DS
)
1812 and then not Is_Type
(Entity
(DS
)))
1814 -- This is an iterator specification. Rewrite as such
1818 I_Spec
: constant Node_Id
:=
1819 Make_Iterator_Specification
(Sloc
(LP
),
1820 Defining_Identifier
=>
1824 Subtype_Indication
=>
1827 Reverse_Present
(LP
));
1829 Set_Iterator_Specification
(N
, I_Spec
);
1830 Set_Loop_Parameter_Specification
(N
, Empty
);
1831 Analyze_Iterator_Specification
(I_Spec
);
1841 -- Some additional checks if we are iterating through a type
1843 if Is_Entity_Name
(DS
)
1844 and then Present
(Entity
(DS
))
1845 and then Is_Type
(Entity
(DS
))
1847 -- The subtype indication may denote the completion of an
1848 -- incomplete type declaration.
1850 if Ekind
(Entity
(DS
)) = E_Incomplete_Type
then
1851 Set_Entity
(DS
, Get_Full_View
(Entity
(DS
)));
1852 Set_Etype
(DS
, Entity
(DS
));
1855 -- Attempt to iterate through non-static predicate
1857 if Is_Discrete_Type
(Entity
(DS
))
1858 and then Present
(Predicate_Function
(Entity
(DS
)))
1859 and then No
(Static_Predicate
(Entity
(DS
)))
1861 Bad_Predicated_Subtype_Use
1862 ("cannot use subtype& with non-static "
1863 & "predicate for loop iteration", DS
, Entity
(DS
));
1867 -- Error if not discrete type
1869 if not Is_Discrete_Type
(Etype
(DS
)) then
1870 Wrong_Type
(DS
, Any_Discrete
);
1871 Set_Etype
(DS
, Any_Type
);
1874 Check_Controlled_Array_Attribute
(DS
);
1876 Make_Index
(DS
, LP
);
1878 Set_Ekind
(Id
, E_Loop_Parameter
);
1879 Set_Etype
(Id
, Etype
(DS
));
1881 -- Treat a range as an implicit reference to the type, to
1882 -- inhibit spurious warnings.
1884 Generate_Reference
(Base_Type
(Etype
(DS
)), N
, ' ');
1885 Set_Is_Known_Valid
(Id
, True);
1887 -- The loop is not a declarative part, so the only entity
1888 -- declared "within" must be frozen explicitly.
1891 Flist
: constant List_Id
:= Freeze_Entity
(Id
, N
);
1893 if Is_Non_Empty_List
(Flist
) then
1894 Insert_Actions
(N
, Flist
);
1898 -- Check for null or possibly null range and issue warning. We
1899 -- suppress such messages in generic templates and instances,
1900 -- because in practice they tend to be dubious in these cases.
1902 if Nkind
(DS
) = N_Range
and then Comes_From_Source
(N
) then
1904 L
: constant Node_Id
:= Low_Bound
(DS
);
1905 H
: constant Node_Id
:= High_Bound
(DS
);
1908 -- If range of loop is null, issue warning
1910 if Compile_Time_Compare
1911 (L
, H
, Assume_Valid
=> True) = GT
1913 -- Suppress the warning if inside a generic template
1914 -- or instance, since in practice they tend to be
1915 -- dubious in these cases since they can result from
1916 -- intended parametrization.
1918 if not Inside_A_Generic
1919 and then not In_Instance
1921 -- Specialize msg if invalid values could make
1922 -- the loop non-null after all.
1924 if Compile_Time_Compare
1925 (L
, H
, Assume_Valid
=> False) = GT
1928 ("?loop range is null, loop will not execute",
1931 -- Since we know the range of the loop is
1932 -- null, set the appropriate flag to remove
1933 -- the loop entirely during expansion.
1935 Set_Is_Null_Loop
(Parent
(N
));
1937 -- Here is where the loop could execute because
1938 -- of invalid values, so issue appropriate
1939 -- message and in this case we do not set the
1940 -- Is_Null_Loop flag since the loop may execute.
1944 ("?loop range may be null, "
1945 & "loop may not execute",
1948 ("?can only execute if invalid values "
1954 -- In either case, suppress warnings in the body of
1955 -- the loop, since it is likely that these warnings
1956 -- will be inappropriate if the loop never actually
1957 -- executes, which is likely.
1959 Set_Suppress_Loop_Warnings
(Parent
(N
));
1961 -- The other case for a warning is a reverse loop
1962 -- where the upper bound is the integer literal zero
1963 -- or one, and the lower bound can be positive.
1965 -- For example, we have
1967 -- for J in reverse N .. 1 loop
1969 -- In practice, this is very likely to be a case of
1970 -- reversing the bounds incorrectly in the range.
1972 elsif Reverse_Present
(LP
)
1973 and then Nkind
(Original_Node
(H
)) =
1975 and then (Intval
(Original_Node
(H
)) = Uint_0
1977 Intval
(Original_Node
(H
)) = Uint_1
)
1979 Error_Msg_N
("?loop range may be null", DS
);
1980 Error_Msg_N
("\?bounds may be wrong way round", DS
);
1987 end Analyze_Iteration_Scheme
;
1989 -------------------------------------
1990 -- Analyze_Iterator_Specification --
1991 -------------------------------------
1993 procedure Analyze_Iterator_Specification
(N
: Node_Id
) is
1994 Def_Id
: constant Node_Id
:= Defining_Identifier
(N
);
1995 Subt
: constant Node_Id
:= Subtype_Indication
(N
);
1996 Container
: constant Node_Id
:= Name
(N
);
2002 Enter_Name
(Def_Id
);
2003 Set_Ekind
(Def_Id
, E_Variable
);
2005 if Present
(Subt
) then
2009 Analyze_And_Resolve
(Container
);
2010 Typ
:= Etype
(Container
);
2012 if Is_Array_Type
(Typ
) then
2013 if Of_Present
(N
) then
2014 Set_Etype
(Def_Id
, Component_Type
(Typ
));
2017 ("to iterate over the elements of an array, use OF", N
);
2018 Set_Etype
(Def_Id
, Etype
(First_Index
(Typ
)));
2021 -- Iteration over a container
2024 Set_Ekind
(Def_Id
, E_Loop_Parameter
);
2026 if Of_Present
(N
) then
2028 -- Find the Element_Type in the package instance that defines the
2031 Ent
:= First_Entity
(Scope
(Typ
));
2032 while Present
(Ent
) loop
2033 if Chars
(Ent
) = Name_Element_Type
then
2034 Set_Etype
(Def_Id
, Ent
);
2042 -- Find the Cursor type in similar fashion
2044 Ent
:= First_Entity
(Scope
(Typ
));
2045 while Present
(Ent
) loop
2046 if Chars
(Ent
) = Name_Cursor
then
2047 Set_Etype
(Def_Id
, Ent
);
2055 end Analyze_Iterator_Specification
;
2061 -- Note: the semantic work required for analyzing labels (setting them as
2062 -- reachable) was done in a prepass through the statements in the block,
2063 -- so that forward gotos would be properly handled. See Analyze_Statements
2064 -- for further details. The only processing required here is to deal with
2065 -- optimizations that depend on an assumption of sequential control flow,
2066 -- since of course the occurrence of a label breaks this assumption.
2068 procedure Analyze_Label
(N
: Node_Id
) is
2069 pragma Warnings
(Off
, N
);
2071 Kill_Current_Values
;
2074 --------------------------
2075 -- Analyze_Label_Entity --
2076 --------------------------
2078 procedure Analyze_Label_Entity
(E
: Entity_Id
) is
2080 Set_Ekind
(E
, E_Label
);
2081 Set_Etype
(E
, Standard_Void_Type
);
2082 Set_Enclosing_Scope
(E
, Current_Scope
);
2083 Set_Reachable
(E
, True);
2084 end Analyze_Label_Entity
;
2086 ----------------------------
2087 -- Analyze_Loop_Statement --
2088 ----------------------------
2090 procedure Analyze_Loop_Statement
(N
: Node_Id
) is
2091 Loop_Statement
: constant Node_Id
:= N
;
2093 Id
: constant Node_Id
:= Identifier
(Loop_Statement
);
2094 Iter
: constant Node_Id
:= Iteration_Scheme
(Loop_Statement
);
2098 if Present
(Id
) then
2100 -- Make name visible, e.g. for use in exit statements. Loop
2101 -- labels are always considered to be referenced.
2106 -- Guard against serious error (typically, a scope mismatch when
2107 -- semantic analysis is requested) by creating loop entity to
2108 -- continue analysis.
2111 if Total_Errors_Detected
/= 0 then
2114 (E_Loop
, Current_Scope
, Sloc
(Loop_Statement
), 'L');
2116 raise Program_Error
;
2120 Generate_Reference
(Ent
, Loop_Statement
, ' ');
2121 Generate_Definition
(Ent
);
2123 -- If we found a label, mark its type. If not, ignore it, since it
2124 -- means we have a conflicting declaration, which would already
2125 -- have been diagnosed at declaration time. Set Label_Construct
2126 -- of the implicit label declaration, which is not created by the
2127 -- parser for generic units.
2129 if Ekind
(Ent
) = E_Label
then
2130 Set_Ekind
(Ent
, E_Loop
);
2132 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
2133 Set_Label_Construct
(Parent
(Ent
), Loop_Statement
);
2138 -- Case of no identifier present
2143 (E_Loop
, Current_Scope
, Sloc
(Loop_Statement
), 'L');
2144 Set_Etype
(Ent
, Standard_Void_Type
);
2145 Set_Parent
(Ent
, Loop_Statement
);
2148 -- Kill current values on entry to loop, since statements in body of
2149 -- loop may have been executed before the loop is entered. Similarly we
2150 -- kill values after the loop, since we do not know that the body of the
2151 -- loop was executed.
2153 Kill_Current_Values
;
2155 Analyze_Iteration_Scheme
(Iter
);
2156 Analyze_Statements
(Statements
(Loop_Statement
));
2157 Process_End_Label
(Loop_Statement
, 'e', Ent
);
2159 Kill_Current_Values
;
2161 -- Check for infinite loop. Skip check for generated code, since it
2162 -- justs waste time and makes debugging the routine called harder.
2164 -- Note that we have to wait till the body of the loop is fully analyzed
2165 -- before making this call, since Check_Infinite_Loop_Warning relies on
2166 -- being able to use semantic visibility information to find references.
2168 if Comes_From_Source
(N
) then
2169 Check_Infinite_Loop_Warning
(N
);
2172 -- Code after loop is unreachable if the loop has no WHILE or FOR
2173 -- and contains no EXIT statements within the body of the loop.
2175 if No
(Iter
) and then not Has_Exit
(Ent
) then
2176 Check_Unreachable_Code
(N
);
2178 end Analyze_Loop_Statement
;
2180 ----------------------------
2181 -- Analyze_Null_Statement --
2182 ----------------------------
2184 -- Note: the semantics of the null statement is implemented by a single
2185 -- null statement, too bad everything isn't as simple as this!
2187 procedure Analyze_Null_Statement
(N
: Node_Id
) is
2188 pragma Warnings
(Off
, N
);
2191 end Analyze_Null_Statement
;
2193 ------------------------
2194 -- Analyze_Statements --
2195 ------------------------
2197 procedure Analyze_Statements
(L
: List_Id
) is
2202 -- The labels declared in the statement list are reachable from
2203 -- statements in the list. We do this as a prepass so that any
2204 -- goto statement will be properly flagged if its target is not
2205 -- reachable. This is not required, but is nice behavior!
2208 while Present
(S
) loop
2209 if Nkind
(S
) = N_Label
then
2210 Analyze
(Identifier
(S
));
2211 Lab
:= Entity
(Identifier
(S
));
2213 -- If we found a label mark it as reachable
2215 if Ekind
(Lab
) = E_Label
then
2216 Generate_Definition
(Lab
);
2217 Set_Reachable
(Lab
);
2219 if Nkind
(Parent
(Lab
)) = N_Implicit_Label_Declaration
then
2220 Set_Label_Construct
(Parent
(Lab
), S
);
2223 -- If we failed to find a label, it means the implicit declaration
2224 -- of the label was hidden. A for-loop parameter can do this to
2225 -- a label with the same name inside the loop, since the implicit
2226 -- label declaration is in the innermost enclosing body or block
2230 Error_Msg_Sloc
:= Sloc
(Lab
);
2232 ("implicit label declaration for & is hidden#",
2240 -- Perform semantic analysis on all statements
2242 Conditional_Statements_Begin
;
2245 while Present
(S
) loop
2250 Conditional_Statements_End
;
2252 -- Make labels unreachable. Visibility is not sufficient, because
2253 -- labels in one if-branch for example are not reachable from the
2254 -- other branch, even though their declarations are in the enclosing
2255 -- declarative part.
2258 while Present
(S
) loop
2259 if Nkind
(S
) = N_Label
then
2260 Set_Reachable
(Entity
(Identifier
(S
)), False);
2265 end Analyze_Statements
;
2267 ----------------------------
2268 -- Check_Unreachable_Code --
2269 ----------------------------
2271 procedure Check_Unreachable_Code
(N
: Node_Id
) is
2272 Error_Loc
: Source_Ptr
;
2276 if Is_List_Member
(N
)
2277 and then Comes_From_Source
(N
)
2283 Nxt
:= Original_Node
(Next
(N
));
2285 -- If a label follows us, then we never have dead code, since
2286 -- someone could branch to the label, so we just ignore it.
2288 if Nkind
(Nxt
) = N_Label
then
2291 -- Otherwise see if we have a real statement following us
2294 and then Comes_From_Source
(Nxt
)
2295 and then Is_Statement
(Nxt
)
2297 -- Special very annoying exception. If we have a return that
2298 -- follows a raise, then we allow it without a warning, since
2299 -- the Ada RM annoyingly requires a useless return here!
2301 if Nkind
(Original_Node
(N
)) /= N_Raise_Statement
2302 or else Nkind
(Nxt
) /= N_Simple_Return_Statement
2304 -- The rather strange shenanigans with the warning message
2305 -- here reflects the fact that Kill_Dead_Code is very good
2306 -- at removing warnings in deleted code, and this is one
2307 -- warning we would prefer NOT to have removed.
2309 Error_Loc
:= Sloc
(Nxt
);
2311 -- If we have unreachable code, analyze and remove the
2312 -- unreachable code, since it is useless and we don't
2313 -- want to generate junk warnings.
2315 -- We skip this step if we are not in code generation mode.
2316 -- This is the one case where we remove dead code in the
2317 -- semantics as opposed to the expander, and we do not want
2318 -- to remove code if we are not in code generation mode,
2319 -- since this messes up the ASIS trees.
2321 -- Note that one might react by moving the whole circuit to
2322 -- exp_ch5, but then we lose the warning in -gnatc mode.
2324 if Operating_Mode
= Generate_Code
then
2328 -- Quit deleting when we have nothing more to delete
2329 -- or if we hit a label (since someone could transfer
2330 -- control to a label, so we should not delete it).
2332 exit when No
(Nxt
) or else Nkind
(Nxt
) = N_Label
;
2334 -- Statement/declaration is to be deleted
2338 Kill_Dead_Code
(Nxt
);
2342 -- Now issue the warning
2344 Error_Msg
("?unreachable code!", Error_Loc
);
2347 -- If the unconditional transfer of control instruction is
2348 -- the last statement of a sequence, then see if our parent
2349 -- is one of the constructs for which we count unblocked exits,
2350 -- and if so, adjust the count.
2355 -- Statements in THEN part or ELSE part of IF statement
2357 if Nkind
(P
) = N_If_Statement
then
2360 -- Statements in ELSIF part of an IF statement
2362 elsif Nkind
(P
) = N_Elsif_Part
then
2364 pragma Assert
(Nkind
(P
) = N_If_Statement
);
2366 -- Statements in CASE statement alternative
2368 elsif Nkind
(P
) = N_Case_Statement_Alternative
then
2370 pragma Assert
(Nkind
(P
) = N_Case_Statement
);
2372 -- Statements in body of block
2374 elsif Nkind
(P
) = N_Handled_Sequence_Of_Statements
2375 and then Nkind
(Parent
(P
)) = N_Block_Statement
2379 -- Statements in exception handler in a block
2381 elsif Nkind
(P
) = N_Exception_Handler
2382 and then Nkind
(Parent
(P
)) = N_Handled_Sequence_Of_Statements
2383 and then Nkind
(Parent
(Parent
(P
))) = N_Block_Statement
2387 -- None of these cases, so return
2393 -- This was one of the cases we are looking for (i.e. the
2394 -- parent construct was IF, CASE or block) so decrement count.
2396 Unblocked_Exit_Count
:= Unblocked_Exit_Count
- 1;
2400 end Check_Unreachable_Code
;