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 -- Local Subprograms --
75 -----------------------
77 procedure Analyze_Iteration_Scheme
(N
: Node_Id
);
79 ------------------------
80 -- Analyze_Assignment --
81 ------------------------
83 procedure Analyze_Assignment
(N
: Node_Id
) is
84 Lhs
: constant Node_Id
:= Name
(N
);
85 Rhs
: constant Node_Id
:= Expression
(N
);
90 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
);
91 -- N is the node for the left hand side of an assignment, and it is not
92 -- a variable. This routine issues an appropriate diagnostic.
95 -- This is called to kill current value settings of a simple variable
96 -- on the left hand side. We call it if we find any error in analyzing
97 -- the assignment, and at the end of processing before setting any new
98 -- current values in place.
100 procedure Set_Assignment_Type
102 Opnd_Type
: in out Entity_Id
);
103 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
104 -- is the nominal subtype. This procedure is used to deal with cases
105 -- where the nominal subtype must be replaced by the actual subtype.
107 -------------------------------
108 -- Diagnose_Non_Variable_Lhs --
109 -------------------------------
111 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
) is
113 -- Not worth posting another error if left hand side already
114 -- flagged as being illegal in some respect.
116 if Error_Posted
(N
) then
119 -- Some special bad cases of entity names
121 elsif Is_Entity_Name
(N
) then
123 Ent
: constant Entity_Id
:= Entity
(N
);
126 if Ekind
(Ent
) = E_In_Parameter
then
128 ("assignment to IN mode parameter not allowed", N
);
130 -- Renamings of protected private components are turned into
131 -- constants when compiling a protected function. In the case
132 -- of single protected types, the private component appears
135 elsif (Is_Prival
(Ent
)
137 (Ekind
(Current_Scope
) = E_Function
138 or else Ekind
(Enclosing_Dynamic_Scope
(
139 Current_Scope
)) = E_Function
))
141 (Ekind
(Ent
) = E_Component
142 and then Is_Protected_Type
(Scope
(Ent
)))
145 ("protected function cannot modify protected object", N
);
147 elsif Ekind
(Ent
) = E_Loop_Parameter
then
149 ("assignment to loop parameter not allowed", N
);
153 ("left hand side of assignment must be a variable", N
);
157 -- For indexed components or selected components, test prefix
159 elsif Nkind
(N
) = N_Indexed_Component
then
160 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
162 -- Another special case for assignment to discriminant
164 elsif Nkind
(N
) = N_Selected_Component
then
165 if Present
(Entity
(Selector_Name
(N
)))
166 and then Ekind
(Entity
(Selector_Name
(N
))) = E_Discriminant
169 ("assignment to discriminant not allowed", N
);
171 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
175 -- If we fall through, we have no special message to issue!
177 Error_Msg_N
("left hand side of assignment must be a variable", N
);
179 end Diagnose_Non_Variable_Lhs
;
185 procedure Kill_Lhs
is
187 if Is_Entity_Name
(Lhs
) then
189 Ent
: constant Entity_Id
:= Entity
(Lhs
);
191 if Present
(Ent
) then
192 Kill_Current_Values
(Ent
);
198 -------------------------
199 -- Set_Assignment_Type --
200 -------------------------
202 procedure Set_Assignment_Type
204 Opnd_Type
: in out Entity_Id
)
207 Require_Entity
(Opnd
);
209 -- If the assignment operand is an in-out or out parameter, then we
210 -- get the actual subtype (needed for the unconstrained case).
211 -- If the operand is the actual in an entry declaration, then within
212 -- the accept statement it is replaced with a local renaming, which
213 -- may also have an actual subtype.
215 if Is_Entity_Name
(Opnd
)
216 and then (Ekind
(Entity
(Opnd
)) = E_Out_Parameter
217 or else Ekind
(Entity
(Opnd
)) =
219 or else Ekind
(Entity
(Opnd
)) =
220 E_Generic_In_Out_Parameter
222 (Ekind
(Entity
(Opnd
)) = E_Variable
223 and then Nkind
(Parent
(Entity
(Opnd
))) =
224 N_Object_Renaming_Declaration
225 and then Nkind
(Parent
(Parent
(Entity
(Opnd
)))) =
228 Opnd_Type
:= Get_Actual_Subtype
(Opnd
);
230 -- If assignment operand is a component reference, then we get the
231 -- actual subtype of the component for the unconstrained case.
233 elsif Nkind_In
(Opnd
, N_Selected_Component
, N_Explicit_Dereference
)
234 and then not Is_Unchecked_Union
(Opnd_Type
)
236 Decl
:= Build_Actual_Subtype_Of_Component
(Opnd_Type
, Opnd
);
238 if Present
(Decl
) then
239 Insert_Action
(N
, Decl
);
240 Mark_Rewrite_Insertion
(Decl
);
242 Opnd_Type
:= Defining_Identifier
(Decl
);
243 Set_Etype
(Opnd
, Opnd_Type
);
244 Freeze_Itype
(Opnd_Type
, N
);
246 elsif Is_Constrained
(Etype
(Opnd
)) then
247 Opnd_Type
:= Etype
(Opnd
);
250 -- For slice, use the constrained subtype created for the slice
252 elsif Nkind
(Opnd
) = N_Slice
then
253 Opnd_Type
:= Etype
(Opnd
);
255 end Set_Assignment_Type
;
257 -- Start of processing for Analyze_Assignment
260 Mark_Coextensions
(N
, Rhs
);
265 -- Start type analysis for assignment
269 -- In the most general case, both Lhs and Rhs can be overloaded, and we
270 -- must compute the intersection of the possible types on each side.
272 if Is_Overloaded
(Lhs
) then
279 Get_First_Interp
(Lhs
, I
, It
);
281 while Present
(It
.Typ
) loop
282 if Has_Compatible_Type
(Rhs
, It
.Typ
) then
283 if T1
/= Any_Type
then
285 -- An explicit dereference is overloaded if the prefix
286 -- is. Try to remove the ambiguity on the prefix, the
287 -- error will be posted there if the ambiguity is real.
289 if Nkind
(Lhs
) = N_Explicit_Dereference
then
292 PI1
: Interp_Index
:= 0;
298 Get_First_Interp
(Prefix
(Lhs
), PI
, PIt
);
300 while Present
(PIt
.Typ
) loop
301 if Is_Access_Type
(PIt
.Typ
)
302 and then Has_Compatible_Type
303 (Rhs
, Designated_Type
(PIt
.Typ
))
307 Disambiguate
(Prefix
(Lhs
),
310 if PIt
= No_Interp
then
312 ("ambiguous left-hand side"
313 & " in assignment", Lhs
);
316 Resolve
(Prefix
(Lhs
), PIt
.Typ
);
326 Get_Next_Interp
(PI
, PIt
);
332 ("ambiguous left-hand side in assignment", Lhs
);
340 Get_Next_Interp
(I
, It
);
344 if T1
= Any_Type
then
346 ("no valid types for left-hand side for assignment", Lhs
);
352 -- The resulting assignment type is T1, so now we will resolve the
353 -- left hand side of the assignment using this determined type.
357 -- Cases where Lhs is not a variable
359 if not Is_Variable
(Lhs
) then
361 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of
362 -- a protected object.
369 if Ada_Version
>= Ada_05
then
371 -- Handle chains of renamings
374 while Nkind
(Ent
) in N_Has_Entity
375 and then Present
(Entity
(Ent
))
376 and then Present
(Renamed_Object
(Entity
(Ent
)))
378 Ent
:= Renamed_Object
(Entity
(Ent
));
381 if (Nkind
(Ent
) = N_Attribute_Reference
382 and then Attribute_Name
(Ent
) = Name_Priority
)
384 -- Renamings of the attribute Priority applied to protected
385 -- objects have been previously expanded into calls to the
386 -- Get_Ceiling run-time subprogram.
389 (Nkind
(Ent
) = N_Function_Call
390 and then (Entity
(Name
(Ent
)) = RTE
(RE_Get_Ceiling
)
392 Entity
(Name
(Ent
)) = RTE
(RO_PE_Get_Ceiling
)))
394 -- The enclosing subprogram cannot be a protected function
397 while not (Is_Subprogram
(S
)
398 and then Convention
(S
) = Convention_Protected
)
399 and then S
/= Standard_Standard
404 if Ekind
(S
) = E_Function
405 and then Convention
(S
) = Convention_Protected
408 ("protected function cannot modify protected object",
412 -- Changes of the ceiling priority of the protected object
413 -- are only effective if the Ceiling_Locking policy is in
414 -- effect (AARM D.5.2 (5/2)).
416 if Locking_Policy
/= 'C' then
417 Error_Msg_N
("assignment to the attribute PRIORITY has " &
419 Error_Msg_N
("\since no Locking_Policy has been " &
428 Diagnose_Non_Variable_Lhs
(Lhs
);
431 -- Error of assigning to limited type. We do however allow this in
432 -- certain cases where the front end generates the assignments.
434 elsif Is_Limited_Type
(T1
)
435 and then not Assignment_OK
(Lhs
)
436 and then not Assignment_OK
(Original_Node
(Lhs
))
437 and then not Is_Value_Type
(T1
)
439 -- CPP constructors can only be called in declarations
441 if Is_CPP_Constructor_Call
(Rhs
) then
442 Error_Msg_N
("invalid use of 'C'P'P constructor", Rhs
);
445 ("left hand of assignment must not be limited type", Lhs
);
446 Explain_Limited_Type
(T1
, Lhs
);
450 -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
451 -- abstract. This is only checked when the assignment Comes_From_Source,
452 -- because in some cases the expander generates such assignments (such
453 -- in the _assign operation for an abstract type).
455 elsif Is_Abstract_Type
(T1
) and then Comes_From_Source
(N
) then
457 ("target of assignment operation must not be abstract", Lhs
);
460 -- Resolution may have updated the subtype, in case the left-hand
461 -- side is a private protected component. Use the correct subtype
462 -- to avoid scoping issues in the back-end.
466 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
467 -- type. For example:
471 -- type Acc is access P.T;
474 -- with Pkg; use Acc;
475 -- procedure Example is
478 -- A.all := B.all; -- ERROR
481 if Nkind
(Lhs
) = N_Explicit_Dereference
482 and then Ekind
(T1
) = E_Incomplete_Type
484 Error_Msg_N
("invalid use of incomplete type", Lhs
);
489 -- Now we can complete the resolution of the right hand side
491 Set_Assignment_Type
(Lhs
, T1
);
494 -- This is the point at which we check for an unset reference
496 Check_Unset_Reference
(Rhs
);
497 Check_Unprotected_Access
(Lhs
, Rhs
);
499 -- Remaining steps are skipped if Rhs was syntactically in error
508 if not Covers
(T1
, T2
) then
509 Wrong_Type
(Rhs
, Etype
(Lhs
));
514 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
515 -- types, use the non-limited view if available
517 if Nkind
(Rhs
) = N_Explicit_Dereference
518 and then Ekind
(T2
) = E_Incomplete_Type
519 and then Is_Tagged_Type
(T2
)
520 and then Present
(Non_Limited_View
(T2
))
522 T2
:= Non_Limited_View
(T2
);
525 Set_Assignment_Type
(Rhs
, T2
);
527 if Total_Errors_Detected
/= 0 then
537 if T1
= Any_Type
or else T2
= Any_Type
then
542 -- If the rhs is class-wide or dynamically tagged, then require the lhs
543 -- to be class-wide. The case where the rhs is a dynamically tagged call
544 -- to a dispatching operation with a controlling access result is
545 -- excluded from this check, since the target has an access type (and
546 -- no tag propagation occurs in that case).
548 if (Is_Class_Wide_Type
(T2
)
549 or else (Is_Dynamically_Tagged
(Rhs
)
550 and then not Is_Access_Type
(T1
)))
551 and then not Is_Class_Wide_Type
(T1
)
553 Error_Msg_N
("dynamically tagged expression not allowed!", Rhs
);
555 elsif Is_Class_Wide_Type
(T1
)
556 and then not Is_Class_Wide_Type
(T2
)
557 and then not Is_Tag_Indeterminate
(Rhs
)
558 and then not Is_Dynamically_Tagged
(Rhs
)
560 Error_Msg_N
("dynamically tagged expression required!", Rhs
);
563 -- Propagate the tag from a class-wide target to the rhs when the rhs
564 -- is a tag-indeterminate call.
566 if Is_Tag_Indeterminate
(Rhs
) then
567 if Is_Class_Wide_Type
(T1
) then
568 Propagate_Tag
(Lhs
, Rhs
);
570 elsif Nkind
(Rhs
) = N_Function_Call
571 and then Is_Entity_Name
(Name
(Rhs
))
572 and then Is_Abstract_Subprogram
(Entity
(Name
(Rhs
)))
575 ("call to abstract function must be dispatching", Name
(Rhs
));
577 elsif Nkind
(Rhs
) = N_Qualified_Expression
578 and then Nkind
(Expression
(Rhs
)) = N_Function_Call
579 and then Is_Entity_Name
(Name
(Expression
(Rhs
)))
581 Is_Abstract_Subprogram
(Entity
(Name
(Expression
(Rhs
))))
584 ("call to abstract function must be dispatching",
585 Name
(Expression
(Rhs
)));
589 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
590 -- apply an implicit conversion of the rhs to that type to force
591 -- appropriate static and run-time accessibility checks. This applies
592 -- as well to anonymous access-to-subprogram types that are component
593 -- subtypes or formal parameters.
595 if Ada_Version
>= Ada_05
596 and then Is_Access_Type
(T1
)
598 if Is_Local_Anonymous_Access
(T1
)
599 or else Ekind
(T2
) = E_Anonymous_Access_Subprogram_Type
601 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
602 Analyze_And_Resolve
(Rhs
, T1
);
606 -- Ada 2005 (AI-231): Assignment to not null variable
608 if Ada_Version
>= Ada_05
609 and then Can_Never_Be_Null
(T1
)
610 and then not Assignment_OK
(Lhs
)
612 -- Case where we know the right hand side is null
614 if Known_Null
(Rhs
) then
615 Apply_Compile_Time_Constraint_Error
617 Msg
=> "(Ada 2005) null not allowed in null-excluding objects?",
618 Reason
=> CE_Null_Not_Allowed
);
620 -- We still mark this as a possible modification, that's necessary
621 -- to reset Is_True_Constant, and desirable for xref purposes.
623 Note_Possible_Modification
(Lhs
, Sure
=> True);
626 -- If we know the right hand side is non-null, then we convert to the
627 -- target type, since we don't need a run time check in that case.
629 elsif not Can_Never_Be_Null
(T2
) then
630 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
631 Analyze_And_Resolve
(Rhs
, T1
);
635 if Is_Scalar_Type
(T1
) then
636 Apply_Scalar_Range_Check
(Rhs
, Etype
(Lhs
));
638 -- For array types, verify that lengths match. If the right hand side
639 -- if a function call that has been inlined, the assignment has been
640 -- rewritten as a block, and the constraint check will be applied to the
641 -- assignment within the block.
643 elsif Is_Array_Type
(T1
)
645 (Nkind
(Rhs
) /= N_Type_Conversion
646 or else Is_Constrained
(Etype
(Rhs
)))
648 (Nkind
(Rhs
) /= N_Function_Call
649 or else Nkind
(N
) /= N_Block_Statement
)
651 -- Assignment verifies that the length of the Lsh and Rhs are equal,
652 -- but of course the indices do not have to match. If the right-hand
653 -- side is a type conversion to an unconstrained type, a length check
654 -- is performed on the expression itself during expansion. In rare
655 -- cases, the redundant length check is computed on an index type
656 -- with a different representation, triggering incorrect code in
659 Apply_Length_Check
(Rhs
, Etype
(Lhs
));
662 -- Discriminant checks are applied in the course of expansion
667 -- Note: modifications of the Lhs may only be recorded after
668 -- checks have been applied.
670 Note_Possible_Modification
(Lhs
, Sure
=> True);
672 -- ??? a real accessibility check is needed when ???
674 -- Post warning for redundant assignment or variable to itself
676 if Warn_On_Redundant_Constructs
678 -- We only warn for source constructs
680 and then Comes_From_Source
(N
)
682 -- Where the object is the same on both sides
684 and then Same_Object
(Lhs
, Original_Node
(Rhs
))
686 -- But exclude the case where the right side was an operation
687 -- that got rewritten (e.g. JUNK + K, where K was known to be
688 -- zero). We don't want to warn in such a case, since it is
689 -- reasonable to write such expressions especially when K is
690 -- defined symbolically in some other package.
692 and then Nkind
(Original_Node
(Rhs
)) not in N_Op
694 if Nkind
(Lhs
) in N_Has_Entity
then
695 Error_Msg_NE
-- CODEFIX
696 ("?useless assignment of & to itself!", N
, Entity
(Lhs
));
698 Error_Msg_N
-- CODEFIX
699 ("?useless assignment of object to itself!", N
);
703 -- Check for non-allowed composite assignment
705 if not Support_Composite_Assign_On_Target
706 and then (Is_Array_Type
(T1
) or else Is_Record_Type
(T1
))
707 and then (not Has_Size_Clause
(T1
) or else Esize
(T1
) > 64)
709 Error_Msg_CRT
("composite assignment", N
);
712 -- Check elaboration warning for left side if not in elab code
714 if not In_Subprogram_Or_Concurrent_Unit
then
715 Check_Elab_Assign
(Lhs
);
718 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
719 -- assignment is a source assignment in the extended main source unit.
720 -- We are not interested in any reference information outside this
721 -- context, or in compiler generated assignment statements.
723 if Comes_From_Source
(N
)
724 and then In_Extended_Main_Source_Unit
(Lhs
)
726 Set_Referenced_Modified
(Lhs
, Out_Param
=> False);
729 -- Final step. If left side is an entity, then we may be able to
730 -- reset the current tracked values to new safe values. We only have
731 -- something to do if the left side is an entity name, and expansion
732 -- has not modified the node into something other than an assignment,
733 -- and of course we only capture values if it is safe to do so.
735 if Is_Entity_Name
(Lhs
)
736 and then Nkind
(N
) = N_Assignment_Statement
739 Ent
: constant Entity_Id
:= Entity
(Lhs
);
742 if Safe_To_Capture_Value
(N
, Ent
) then
744 -- If simple variable on left side, warn if this assignment
745 -- blots out another one (rendering it useless) and note
746 -- location of assignment in case no one references value.
747 -- We only do this for source assignments, otherwise we can
748 -- generate bogus warnings when an assignment is rewritten as
749 -- another assignment, and gets tied up with itself.
751 -- Note: we don't use Record_Last_Assignment here, because we
752 -- have lots of other stuff to do under control of this test.
754 if Warn_On_Modified_Unread
755 and then Is_Assignable
(Ent
)
756 and then Comes_From_Source
(N
)
757 and then In_Extended_Main_Source_Unit
(Ent
)
759 Warn_On_Useless_Assignment
(Ent
, N
);
760 Set_Last_Assignment
(Ent
, Lhs
);
763 -- If we are assigning an access type and the left side is an
764 -- entity, then make sure that the Is_Known_[Non_]Null flags
765 -- properly reflect the state of the entity after assignment.
767 if Is_Access_Type
(T1
) then
768 if Known_Non_Null
(Rhs
) then
769 Set_Is_Known_Non_Null
(Ent
, True);
771 elsif Known_Null
(Rhs
)
772 and then not Can_Never_Be_Null
(Ent
)
774 Set_Is_Known_Null
(Ent
, True);
777 Set_Is_Known_Null
(Ent
, False);
779 if not Can_Never_Be_Null
(Ent
) then
780 Set_Is_Known_Non_Null
(Ent
, False);
784 -- For discrete types, we may be able to set the current value
785 -- if the value is known at compile time.
787 elsif Is_Discrete_Type
(T1
)
788 and then Compile_Time_Known_Value
(Rhs
)
790 Set_Current_Value
(Ent
, Rhs
);
792 Set_Current_Value
(Ent
, Empty
);
795 -- If not safe to capture values, kill them
802 end Analyze_Assignment
;
804 -----------------------------
805 -- Analyze_Block_Statement --
806 -----------------------------
808 procedure Analyze_Block_Statement
(N
: Node_Id
) is
809 Decls
: constant List_Id
:= Declarations
(N
);
810 Id
: constant Node_Id
:= Identifier
(N
);
811 HSS
: constant Node_Id
:= Handled_Statement_Sequence
(N
);
814 -- If no handled statement sequence is present, things are really
815 -- messed up, and we just return immediately (this is a defence
816 -- against previous errors).
822 -- Normal processing with HSS present
825 EH
: constant List_Id
:= Exception_Handlers
(HSS
);
826 Ent
: Entity_Id
:= Empty
;
829 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
830 -- Recursively save value of this global, will be restored on exit
833 -- Initialize unblocked exit count for statements of begin block
834 -- plus one for each exception handler that is present.
836 Unblocked_Exit_Count
:= 1;
839 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ List_Length
(EH
);
842 -- If a label is present analyze it and mark it as referenced
848 -- An error defense. If we have an identifier, but no entity,
849 -- then something is wrong. If we have previous errors, then
850 -- just remove the identifier and continue, otherwise raise
854 if Total_Errors_Detected
/= 0 then
855 Set_Identifier
(N
, Empty
);
861 Set_Ekind
(Ent
, E_Block
);
862 Generate_Reference
(Ent
, N
, ' ');
863 Generate_Definition
(Ent
);
865 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
866 Set_Label_Construct
(Parent
(Ent
), N
);
871 -- If no entity set, create a label entity
874 Ent
:= New_Internal_Entity
(E_Block
, Current_Scope
, Sloc
(N
), 'B');
875 Set_Identifier
(N
, New_Occurrence_Of
(Ent
, Sloc
(N
)));
879 Set_Etype
(Ent
, Standard_Void_Type
);
880 Set_Block_Node
(Ent
, Identifier
(N
));
883 if Present
(Decls
) then
884 Analyze_Declarations
(Decls
);
886 Inspect_Deferred_Constant_Completion
(Decls
);
890 Process_End_Label
(HSS
, 'e', Ent
);
892 -- If exception handlers are present, then we indicate that
893 -- enclosing scopes contain a block with handlers. We only
894 -- need to mark non-generic scopes.
899 Set_Has_Nested_Block_With_Handler
(S
);
900 exit when Is_Overloadable
(S
)
901 or else Ekind
(S
) = E_Package
902 or else Is_Generic_Unit
(S
);
907 Check_References
(Ent
);
908 Warn_On_Useless_Assignments
(Ent
);
911 if Unblocked_Exit_Count
= 0 then
912 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
913 Check_Unreachable_Code
(N
);
915 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
918 end Analyze_Block_Statement
;
920 ----------------------------
921 -- Analyze_Case_Statement --
922 ----------------------------
924 procedure Analyze_Case_Statement
(N
: Node_Id
) is
926 Exp_Type
: Entity_Id
;
927 Exp_Btype
: Entity_Id
;
930 Others_Present
: Boolean;
932 pragma Warnings
(Off
, Last_Choice
);
933 pragma Warnings
(Off
, Dont_Care
);
934 -- Don't care about assigned values
936 Statements_Analyzed
: Boolean := False;
937 -- Set True if at least some statement sequences get analyzed.
938 -- If False on exit, means we had a serious error that prevented
939 -- full analysis of the case statement, and as a result it is not
940 -- a good idea to output warning messages about unreachable code.
942 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
943 -- Recursively save value of this global, will be restored on exit
945 procedure Non_Static_Choice_Error
(Choice
: Node_Id
);
946 -- Error routine invoked by the generic instantiation below when
947 -- the case statement has a non static choice.
949 procedure Process_Statements
(Alternative
: Node_Id
);
950 -- Analyzes all the statements associated with a case alternative.
951 -- Needed by the generic instantiation below.
953 package Case_Choices_Processing
is new
954 Generic_Choices_Processing
955 (Get_Alternatives
=> Alternatives
,
956 Get_Choices
=> Discrete_Choices
,
957 Process_Empty_Choice
=> No_OP
,
958 Process_Non_Static_Choice
=> Non_Static_Choice_Error
,
959 Process_Associated_Node
=> Process_Statements
);
960 use Case_Choices_Processing
;
961 -- Instantiation of the generic choice processing package
963 -----------------------------
964 -- Non_Static_Choice_Error --
965 -----------------------------
967 procedure Non_Static_Choice_Error
(Choice
: Node_Id
) is
970 ("choice given in case statement is not static!", Choice
);
971 end Non_Static_Choice_Error
;
973 ------------------------
974 -- Process_Statements --
975 ------------------------
977 procedure Process_Statements
(Alternative
: Node_Id
) is
978 Choices
: constant List_Id
:= Discrete_Choices
(Alternative
);
982 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
983 Statements_Analyzed
:= True;
985 -- An interesting optimization. If the case statement expression
986 -- is a simple entity, then we can set the current value within
987 -- an alternative if the alternative has one possible value.
991 -- when 2 | 3 => beta
992 -- when others => gamma
994 -- Here we know that N is initially 1 within alpha, but for beta
995 -- and gamma, we do not know anything more about the initial value.
997 if Is_Entity_Name
(Exp
) then
1000 if Ekind_In
(Ent
, E_Variable
,
1004 if List_Length
(Choices
) = 1
1005 and then Nkind
(First
(Choices
)) in N_Subexpr
1006 and then Compile_Time_Known_Value
(First
(Choices
))
1008 Set_Current_Value
(Entity
(Exp
), First
(Choices
));
1011 Analyze_Statements
(Statements
(Alternative
));
1013 -- After analyzing the case, set the current value to empty
1014 -- since we won't know what it is for the next alternative
1015 -- (unless reset by this same circuit), or after the case.
1017 Set_Current_Value
(Entity
(Exp
), Empty
);
1022 -- Case where expression is not an entity name of a variable
1024 Analyze_Statements
(Statements
(Alternative
));
1025 end Process_Statements
;
1027 -- Table to record choices. Put after subprograms since we make
1028 -- a call to Number_Of_Choices to get the right number of entries.
1030 Case_Table
: Choice_Table_Type
(1 .. Number_Of_Choices
(N
));
1031 pragma Warnings
(Off
, Case_Table
);
1033 -- Start of processing for Analyze_Case_Statement
1036 Unblocked_Exit_Count
:= 0;
1037 Exp
:= Expression
(N
);
1040 -- The expression must be of any discrete type. In rare cases, the
1041 -- expander constructs a case statement whose expression has a private
1042 -- type whose full view is discrete. This can happen when generating
1043 -- a stream operation for a variant type after the type is frozen,
1044 -- when the partial of view of the type of the discriminant is private.
1045 -- In that case, use the full view to analyze case alternatives.
1047 if not Is_Overloaded
(Exp
)
1048 and then not Comes_From_Source
(N
)
1049 and then Is_Private_Type
(Etype
(Exp
))
1050 and then Present
(Full_View
(Etype
(Exp
)))
1051 and then Is_Discrete_Type
(Full_View
(Etype
(Exp
)))
1053 Resolve
(Exp
, Etype
(Exp
));
1054 Exp_Type
:= Full_View
(Etype
(Exp
));
1057 Analyze_And_Resolve
(Exp
, Any_Discrete
);
1058 Exp_Type
:= Etype
(Exp
);
1061 Check_Unset_Reference
(Exp
);
1062 Exp_Btype
:= Base_Type
(Exp_Type
);
1064 -- The expression must be of a discrete type which must be determinable
1065 -- independently of the context in which the expression occurs, but
1066 -- using the fact that the expression must be of a discrete type.
1067 -- Moreover, the type this expression must not be a character literal
1068 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1070 -- If error already reported by Resolve, nothing more to do
1072 if Exp_Btype
= Any_Discrete
1073 or else Exp_Btype
= Any_Type
1077 elsif Exp_Btype
= Any_Character
then
1079 ("character literal as case expression is ambiguous", Exp
);
1082 elsif Ada_Version
= Ada_83
1083 and then (Is_Generic_Type
(Exp_Btype
)
1084 or else Is_Generic_Type
(Root_Type
(Exp_Btype
)))
1087 ("(Ada 83) case expression cannot be of a generic type", Exp
);
1091 -- If the case expression is a formal object of mode in out, then
1092 -- treat it as having a nonstatic subtype by forcing use of the base
1093 -- type (which has to get passed to Check_Case_Choices below). Also
1094 -- use base type when the case expression is parenthesized.
1096 if Paren_Count
(Exp
) > 0
1097 or else (Is_Entity_Name
(Exp
)
1098 and then Ekind
(Entity
(Exp
)) = E_Generic_In_Out_Parameter
)
1100 Exp_Type
:= Exp_Btype
;
1103 -- Call instantiated Analyze_Choices which does the rest of the work
1106 (N
, Exp_Type
, Case_Table
, Last_Choice
, Dont_Care
, Others_Present
);
1108 if Exp_Type
= Universal_Integer
and then not Others_Present
then
1109 Error_Msg_N
("case on universal integer requires OTHERS choice", Exp
);
1112 -- If all our exits were blocked by unconditional transfers of control,
1113 -- then the entire CASE statement acts as an unconditional transfer of
1114 -- control, so treat it like one, and check unreachable code. Skip this
1115 -- test if we had serious errors preventing any statement analysis.
1117 if Unblocked_Exit_Count
= 0 and then Statements_Analyzed
then
1118 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1119 Check_Unreachable_Code
(N
);
1121 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1124 if not Expander_Active
1125 and then Compile_Time_Known_Value
(Expression
(N
))
1126 and then Serious_Errors_Detected
= 0
1129 Chosen
: constant Node_Id
:= Find_Static_Alternative
(N
);
1133 Alt
:= First
(Alternatives
(N
));
1134 while Present
(Alt
) loop
1135 if Alt
/= Chosen
then
1136 Remove_Warning_Messages
(Statements
(Alt
));
1143 end Analyze_Case_Statement
;
1145 ----------------------------
1146 -- Analyze_Exit_Statement --
1147 ----------------------------
1149 -- If the exit includes a name, it must be the name of a currently open
1150 -- loop. Otherwise there must be an innermost open loop on the stack,
1151 -- to which the statement implicitly refers.
1153 procedure Analyze_Exit_Statement
(N
: Node_Id
) is
1154 Target
: constant Node_Id
:= Name
(N
);
1155 Cond
: constant Node_Id
:= Condition
(N
);
1156 Scope_Id
: Entity_Id
;
1162 Check_Unreachable_Code
(N
);
1165 if Present
(Target
) then
1167 U_Name
:= Entity
(Target
);
1169 if not In_Open_Scopes
(U_Name
) or else Ekind
(U_Name
) /= E_Loop
then
1170 Error_Msg_N
("invalid loop name in exit statement", N
);
1173 Set_Has_Exit
(U_Name
);
1180 for J
in reverse 0 .. Scope_Stack
.Last
loop
1181 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
1182 Kind
:= Ekind
(Scope_Id
);
1185 and then (No
(Target
) or else Scope_Id
= U_Name
) then
1186 Set_Has_Exit
(Scope_Id
);
1189 elsif Kind
= E_Block
1190 or else Kind
= E_Loop
1191 or else Kind
= E_Return_Statement
1197 ("cannot exit from program unit or accept statement", N
);
1202 -- Verify that if present the condition is a Boolean expression
1204 if Present
(Cond
) then
1205 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1206 Check_Unset_Reference
(Cond
);
1209 -- Chain exit statement to associated loop entity
1211 Set_Next_Exit_Statement
(N
, First_Exit_Statement
(Scope_Id
));
1212 Set_First_Exit_Statement
(Scope_Id
, N
);
1214 -- Since the exit may take us out of a loop, any previous assignment
1215 -- statement is not useless, so clear last assignment indications. It
1216 -- is OK to keep other current values, since if the exit statement
1217 -- does not exit, then the current values are still valid.
1219 Kill_Current_Values
(Last_Assignment_Only
=> True);
1220 end Analyze_Exit_Statement
;
1222 ----------------------------
1223 -- Analyze_Goto_Statement --
1224 ----------------------------
1226 procedure Analyze_Goto_Statement
(N
: Node_Id
) is
1227 Label
: constant Node_Id
:= Name
(N
);
1228 Scope_Id
: Entity_Id
;
1229 Label_Scope
: Entity_Id
;
1230 Label_Ent
: Entity_Id
;
1233 Check_Unreachable_Code
(N
);
1234 Kill_Current_Values
(Last_Assignment_Only
=> True);
1237 Label_Ent
:= Entity
(Label
);
1239 -- Ignore previous error
1241 if Label_Ent
= Any_Id
then
1244 -- We just have a label as the target of a goto
1246 elsif Ekind
(Label_Ent
) /= E_Label
then
1247 Error_Msg_N
("target of goto statement must be a label", Label
);
1250 -- Check that the target of the goto is reachable according to Ada
1251 -- scoping rules. Note: the special gotos we generate for optimizing
1252 -- local handling of exceptions would violate these rules, but we mark
1253 -- such gotos as analyzed when built, so this code is never entered.
1255 elsif not Reachable
(Label_Ent
) then
1256 Error_Msg_N
("target of goto statement is not reachable", Label
);
1260 -- Here if goto passes initial validity checks
1262 Label_Scope
:= Enclosing_Scope
(Label_Ent
);
1264 for J
in reverse 0 .. Scope_Stack
.Last
loop
1265 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
1267 if Label_Scope
= Scope_Id
1268 or else (Ekind
(Scope_Id
) /= E_Block
1269 and then Ekind
(Scope_Id
) /= E_Loop
1270 and then Ekind
(Scope_Id
) /= E_Return_Statement
)
1272 if Scope_Id
/= Label_Scope
then
1274 ("cannot exit from program unit or accept statement", N
);
1281 raise Program_Error
;
1282 end Analyze_Goto_Statement
;
1284 --------------------------
1285 -- Analyze_If_Statement --
1286 --------------------------
1288 -- A special complication arises in the analysis of if statements
1290 -- The expander has circuitry to completely delete code that it
1291 -- can tell will not be executed (as a result of compile time known
1292 -- conditions). In the analyzer, we ensure that code that will be
1293 -- deleted in this manner is analyzed but not expanded. This is
1294 -- obviously more efficient, but more significantly, difficulties
1295 -- arise if code is expanded and then eliminated (e.g. exception
1296 -- table entries disappear). Similarly, itypes generated in deleted
1297 -- code must be frozen from start, because the nodes on which they
1298 -- depend will not be available at the freeze point.
1300 procedure Analyze_If_Statement
(N
: Node_Id
) is
1303 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
1304 -- Recursively save value of this global, will be restored on exit
1306 Save_In_Deleted_Code
: Boolean;
1308 Del
: Boolean := False;
1309 -- This flag gets set True if a True condition has been found,
1310 -- which means that remaining ELSE/ELSIF parts are deleted.
1312 procedure Analyze_Cond_Then
(Cnode
: Node_Id
);
1313 -- This is applied to either the N_If_Statement node itself or
1314 -- to an N_Elsif_Part node. It deals with analyzing the condition
1315 -- and the THEN statements associated with it.
1317 -----------------------
1318 -- Analyze_Cond_Then --
1319 -----------------------
1321 procedure Analyze_Cond_Then
(Cnode
: Node_Id
) is
1322 Cond
: constant Node_Id
:= Condition
(Cnode
);
1323 Tstm
: constant List_Id
:= Then_Statements
(Cnode
);
1326 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
1327 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1328 Check_Unset_Reference
(Cond
);
1329 Set_Current_Value_Condition
(Cnode
);
1331 -- If already deleting, then just analyze then statements
1334 Analyze_Statements
(Tstm
);
1336 -- Compile time known value, not deleting yet
1338 elsif Compile_Time_Known_Value
(Cond
) then
1339 Save_In_Deleted_Code
:= In_Deleted_Code
;
1341 -- If condition is True, then analyze the THEN statements
1342 -- and set no expansion for ELSE and ELSIF parts.
1344 if Is_True
(Expr_Value
(Cond
)) then
1345 Analyze_Statements
(Tstm
);
1347 Expander_Mode_Save_And_Set
(False);
1348 In_Deleted_Code
:= True;
1350 -- If condition is False, analyze THEN with expansion off
1352 else -- Is_False (Expr_Value (Cond))
1353 Expander_Mode_Save_And_Set
(False);
1354 In_Deleted_Code
:= True;
1355 Analyze_Statements
(Tstm
);
1356 Expander_Mode_Restore
;
1357 In_Deleted_Code
:= Save_In_Deleted_Code
;
1360 -- Not known at compile time, not deleting, normal analysis
1363 Analyze_Statements
(Tstm
);
1365 end Analyze_Cond_Then
;
1367 -- Start of Analyze_If_Statement
1370 -- Initialize exit count for else statements. If there is no else
1371 -- part, this count will stay non-zero reflecting the fact that the
1372 -- uncovered else case is an unblocked exit.
1374 Unblocked_Exit_Count
:= 1;
1375 Analyze_Cond_Then
(N
);
1377 -- Now to analyze the elsif parts if any are present
1379 if Present
(Elsif_Parts
(N
)) then
1380 E
:= First
(Elsif_Parts
(N
));
1381 while Present
(E
) loop
1382 Analyze_Cond_Then
(E
);
1387 if Present
(Else_Statements
(N
)) then
1388 Analyze_Statements
(Else_Statements
(N
));
1391 -- If all our exits were blocked by unconditional transfers of control,
1392 -- then the entire IF statement acts as an unconditional transfer of
1393 -- control, so treat it like one, and check unreachable code.
1395 if Unblocked_Exit_Count
= 0 then
1396 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1397 Check_Unreachable_Code
(N
);
1399 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1403 Expander_Mode_Restore
;
1404 In_Deleted_Code
:= Save_In_Deleted_Code
;
1407 if not Expander_Active
1408 and then Compile_Time_Known_Value
(Condition
(N
))
1409 and then Serious_Errors_Detected
= 0
1411 if Is_True
(Expr_Value
(Condition
(N
))) then
1412 Remove_Warning_Messages
(Else_Statements
(N
));
1414 if Present
(Elsif_Parts
(N
)) then
1415 E
:= First
(Elsif_Parts
(N
));
1416 while Present
(E
) loop
1417 Remove_Warning_Messages
(Then_Statements
(E
));
1423 Remove_Warning_Messages
(Then_Statements
(N
));
1426 end Analyze_If_Statement
;
1428 ----------------------------------------
1429 -- Analyze_Implicit_Label_Declaration --
1430 ----------------------------------------
1432 -- An implicit label declaration is generated in the innermost
1433 -- enclosing declarative part. This is done for labels as well as
1434 -- block and loop names.
1436 -- Note: any changes in this routine may need to be reflected in
1437 -- Analyze_Label_Entity.
1439 procedure Analyze_Implicit_Label_Declaration
(N
: Node_Id
) is
1440 Id
: constant Node_Id
:= Defining_Identifier
(N
);
1443 Set_Ekind
(Id
, E_Label
);
1444 Set_Etype
(Id
, Standard_Void_Type
);
1445 Set_Enclosing_Scope
(Id
, Current_Scope
);
1446 end Analyze_Implicit_Label_Declaration
;
1448 ------------------------------
1449 -- Analyze_Iteration_Scheme --
1450 ------------------------------
1452 procedure Analyze_Iteration_Scheme
(N
: Node_Id
) is
1454 procedure Process_Bounds
(R
: Node_Id
);
1455 -- If the iteration is given by a range, create temporaries and
1456 -- assignment statements block to capture the bounds and perform
1457 -- required finalization actions in case a bound includes a function
1458 -- call that uses the temporary stack. We first pre-analyze a copy of
1459 -- the range in order to determine the expected type, and analyze and
1460 -- resolve the original bounds.
1462 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
);
1463 -- If the bounds are given by a 'Range reference on a function call
1464 -- that returns a controlled array, introduce an explicit declaration
1465 -- to capture the bounds, so that the function result can be finalized
1466 -- in timely fashion.
1468 --------------------
1469 -- Process_Bounds --
1470 --------------------
1472 procedure Process_Bounds
(R
: Node_Id
) is
1473 Loc
: constant Source_Ptr
:= Sloc
(N
);
1474 R_Copy
: constant Node_Id
:= New_Copy_Tree
(R
);
1475 Lo
: constant Node_Id
:= Low_Bound
(R
);
1476 Hi
: constant Node_Id
:= High_Bound
(R
);
1477 New_Lo_Bound
: Node_Id
;
1478 New_Hi_Bound
: Node_Id
;
1480 Save_Analysis
: Boolean;
1483 (Original_Bound
: Node_Id
;
1484 Analyzed_Bound
: Node_Id
) return Node_Id
;
1485 -- Capture value of bound and return captured value
1492 (Original_Bound
: Node_Id
;
1493 Analyzed_Bound
: Node_Id
) return Node_Id
1500 -- If the bound is a constant or an object, no need for a separate
1501 -- declaration. If the bound is the result of previous expansion
1502 -- it is already analyzed and should not be modified. Note that
1503 -- the Bound will be resolved later, if needed, as part of the
1504 -- call to Make_Index (literal bounds may need to be resolved to
1507 if Analyzed
(Original_Bound
) then
1508 return Original_Bound
;
1510 elsif Nkind_In
(Analyzed_Bound
, N_Integer_Literal
,
1511 N_Character_Literal
)
1512 or else Is_Entity_Name
(Analyzed_Bound
)
1514 Analyze_And_Resolve
(Original_Bound
, Typ
);
1515 return Original_Bound
;
1518 -- Here we need to capture the value
1520 Analyze_And_Resolve
(Original_Bound
, Typ
);
1522 Id
:= Make_Temporary
(Loc
, 'S', Original_Bound
);
1524 -- Normally, the best approach is simply to generate a constant
1525 -- declaration that captures the bound. However, there is a nasty
1526 -- case where this is wrong. If the bound is complex, and has a
1527 -- possible use of the secondary stack, we need to generate a
1528 -- separate assignment statement to ensure the creation of a block
1529 -- which will release the secondary stack.
1531 -- We prefer the constant declaration, since it leaves us with a
1532 -- proper trace of the value, useful in optimizations that get rid
1533 -- of junk range checks.
1535 -- Probably we want something like the Side_Effect_Free routine
1536 -- in Exp_Util, but for now, we just optimize the cases of 'Last
1537 -- and 'First applied to an entity, since these are the important
1538 -- cases for range check optimizations.
1540 if Nkind
(Original_Bound
) = N_Attribute_Reference
1541 and then (Attribute_Name
(Original_Bound
) = Name_First
1543 Attribute_Name
(Original_Bound
) = Name_Last
)
1544 and then Is_Entity_Name
(Prefix
(Original_Bound
))
1547 Make_Object_Declaration
(Loc
,
1548 Defining_Identifier
=> Id
,
1549 Constant_Present
=> True,
1550 Object_Definition
=> New_Occurrence_Of
(Typ
, Loc
),
1551 Expression
=> Relocate_Node
(Original_Bound
));
1553 Insert_Before
(Parent
(N
), Decl
);
1555 Rewrite
(Original_Bound
, New_Occurrence_Of
(Id
, Loc
));
1556 return Expression
(Decl
);
1559 -- Here we make a declaration with a separate assignment statement
1562 Make_Object_Declaration
(Loc
,
1563 Defining_Identifier
=> Id
,
1564 Object_Definition
=> New_Occurrence_Of
(Typ
, Loc
));
1566 Insert_Before
(Parent
(N
), Decl
);
1570 Make_Assignment_Statement
(Loc
,
1571 Name
=> New_Occurrence_Of
(Id
, Loc
),
1572 Expression
=> Relocate_Node
(Original_Bound
));
1574 Insert_Before
(Parent
(N
), Assign
);
1577 Rewrite
(Original_Bound
, New_Occurrence_Of
(Id
, Loc
));
1579 if Nkind
(Assign
) = N_Assignment_Statement
then
1580 return Expression
(Assign
);
1582 return Original_Bound
;
1586 -- Start of processing for Process_Bounds
1589 -- Determine expected type of range by analyzing separate copy
1590 -- Do the analysis and resolution of the copy of the bounds with
1591 -- expansion disabled, to prevent the generation of finalization
1592 -- actions on each bound. This prevents memory leaks when the
1593 -- bounds contain calls to functions returning controlled arrays.
1595 Set_Parent
(R_Copy
, Parent
(R
));
1596 Save_Analysis
:= Full_Analysis
;
1597 Full_Analysis
:= False;
1598 Expander_Mode_Save_And_Set
(False);
1602 if Is_Overloaded
(R_Copy
) then
1604 -- Apply preference rules for range of predefined integer types,
1605 -- or diagnose true ambiguity.
1610 Found
: Entity_Id
:= Empty
;
1613 Get_First_Interp
(R_Copy
, I
, It
);
1614 while Present
(It
.Typ
) loop
1615 if Is_Discrete_Type
(It
.Typ
) then
1619 if Scope
(Found
) = Standard_Standard
then
1622 elsif Scope
(It
.Typ
) = Standard_Standard
then
1626 -- Both of them are user-defined
1629 ("ambiguous bounds in range of iteration",
1631 Error_Msg_N
("\possible interpretations:", R_Copy
);
1632 Error_Msg_NE
("\\} ", R_Copy
, Found
);
1633 Error_Msg_NE
("\\} ", R_Copy
, It
.Typ
);
1639 Get_Next_Interp
(I
, It
);
1645 Expander_Mode_Restore
;
1646 Full_Analysis
:= Save_Analysis
;
1648 Typ
:= Etype
(R_Copy
);
1650 -- If the type of the discrete range is Universal_Integer, then
1651 -- the bound's type must be resolved to Integer, and any object
1652 -- used to hold the bound must also have type Integer, unless the
1653 -- literal bounds are constant-folded expressions that carry a user-
1656 if Typ
= Universal_Integer
then
1657 if Nkind
(Lo
) = N_Integer_Literal
1658 and then Present
(Etype
(Lo
))
1659 and then Scope
(Etype
(Lo
)) /= Standard_Standard
1663 elsif Nkind
(Hi
) = N_Integer_Literal
1664 and then Present
(Etype
(Hi
))
1665 and then Scope
(Etype
(Hi
)) /= Standard_Standard
1670 Typ
:= Standard_Integer
;
1676 New_Lo_Bound
:= One_Bound
(Lo
, Low_Bound
(R_Copy
));
1677 New_Hi_Bound
:= One_Bound
(Hi
, High_Bound
(R_Copy
));
1679 -- Propagate staticness to loop range itself, in case the
1680 -- corresponding subtype is static.
1682 if New_Lo_Bound
/= Lo
1683 and then Is_Static_Expression
(New_Lo_Bound
)
1685 Rewrite
(Low_Bound
(R
), New_Copy
(New_Lo_Bound
));
1688 if New_Hi_Bound
/= Hi
1689 and then Is_Static_Expression
(New_Hi_Bound
)
1691 Rewrite
(High_Bound
(R
), New_Copy
(New_Hi_Bound
));
1695 --------------------------------------
1696 -- Check_Controlled_Array_Attribute --
1697 --------------------------------------
1699 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
) is
1701 if Nkind
(DS
) = N_Attribute_Reference
1702 and then Is_Entity_Name
(Prefix
(DS
))
1703 and then Ekind
(Entity
(Prefix
(DS
))) = E_Function
1704 and then Is_Array_Type
(Etype
(Entity
(Prefix
(DS
))))
1707 Component_Type
(Etype
(Entity
(Prefix
(DS
)))))
1708 and then Expander_Active
1711 Loc
: constant Source_Ptr
:= Sloc
(N
);
1712 Arr
: constant Entity_Id
:= Etype
(Entity
(Prefix
(DS
)));
1713 Indx
: constant Entity_Id
:=
1714 Base_Type
(Etype
(First_Index
(Arr
)));
1715 Subt
: constant Entity_Id
:= Make_Temporary
(Loc
, 'S');
1720 Make_Subtype_Declaration
(Loc
,
1721 Defining_Identifier
=> Subt
,
1722 Subtype_Indication
=>
1723 Make_Subtype_Indication
(Loc
,
1724 Subtype_Mark
=> New_Reference_To
(Indx
, Loc
),
1726 Make_Range_Constraint
(Loc
,
1727 Relocate_Node
(DS
))));
1728 Insert_Before
(Parent
(N
), Decl
);
1732 Make_Attribute_Reference
(Loc
,
1733 Prefix
=> New_Reference_To
(Subt
, Loc
),
1734 Attribute_Name
=> Attribute_Name
(DS
)));
1738 end Check_Controlled_Array_Attribute
;
1740 -- Start of processing for Analyze_Iteration_Scheme
1743 -- For an infinite loop, there is no iteration scheme
1750 Cond
: constant Node_Id
:= Condition
(N
);
1753 -- For WHILE loop, verify that the condition is a Boolean
1754 -- expression and resolve and check it.
1756 if Present
(Cond
) then
1757 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1758 Check_Unset_Reference
(Cond
);
1759 Set_Current_Value_Condition
(N
);
1762 -- Else we have a FOR loop
1766 LP
: constant Node_Id
:= Loop_Parameter_Specification
(N
);
1767 Id
: constant Entity_Id
:= Defining_Identifier
(LP
);
1768 DS
: constant Node_Id
:= Discrete_Subtype_Definition
(LP
);
1773 -- We always consider the loop variable to be referenced,
1774 -- since the loop may be used just for counting purposes.
1776 Generate_Reference
(Id
, N
, ' ');
1778 -- Check for case of loop variable hiding a local
1779 -- variable (used later on to give a nice warning
1780 -- if the hidden variable is never assigned).
1783 H
: constant Entity_Id
:= Homonym
(Id
);
1786 and then Enclosing_Dynamic_Scope
(H
) =
1787 Enclosing_Dynamic_Scope
(Id
)
1788 and then Ekind
(H
) = E_Variable
1789 and then Is_Discrete_Type
(Etype
(H
))
1791 Set_Hiding_Loop_Variable
(H
, Id
);
1795 -- Now analyze the subtype definition. If it is
1796 -- a range, create temporaries for bounds.
1798 if Nkind
(DS
) = N_Range
1799 and then Expander_Active
1801 Process_Bounds
(DS
);
1810 -- The subtype indication may denote the completion
1811 -- of an incomplete type declaration.
1813 if Is_Entity_Name
(DS
)
1814 and then Present
(Entity
(DS
))
1815 and then Is_Type
(Entity
(DS
))
1816 and then Ekind
(Entity
(DS
)) = E_Incomplete_Type
1818 Set_Entity
(DS
, Get_Full_View
(Entity
(DS
)));
1819 Set_Etype
(DS
, Entity
(DS
));
1822 if not Is_Discrete_Type
(Etype
(DS
)) then
1823 Wrong_Type
(DS
, Any_Discrete
);
1824 Set_Etype
(DS
, Any_Type
);
1827 Check_Controlled_Array_Attribute
(DS
);
1829 Make_Index
(DS
, LP
);
1831 Set_Ekind
(Id
, E_Loop_Parameter
);
1832 Set_Etype
(Id
, Etype
(DS
));
1834 -- Treat a range as an implicit reference to the type, to
1835 -- inhibit spurious warnings.
1837 Generate_Reference
(Base_Type
(Etype
(DS
)), N
, ' ');
1838 Set_Is_Known_Valid
(Id
, True);
1840 -- The loop is not a declarative part, so the only entity
1841 -- declared "within" must be frozen explicitly.
1844 Flist
: constant List_Id
:= Freeze_Entity
(Id
, Sloc
(N
));
1846 if Is_Non_Empty_List
(Flist
) then
1847 Insert_Actions
(N
, Flist
);
1851 -- Check for null or possibly null range and issue warning.
1852 -- We suppress such messages in generic templates and
1853 -- instances, because in practice they tend to be dubious
1856 if Nkind
(DS
) = N_Range
1857 and then Comes_From_Source
(N
)
1860 L
: constant Node_Id
:= Low_Bound
(DS
);
1861 H
: constant Node_Id
:= High_Bound
(DS
);
1864 -- If range of loop is null, issue warning
1866 if Compile_Time_Compare
1867 (L
, H
, Assume_Valid
=> True) = GT
1869 -- Suppress the warning if inside a generic
1870 -- template or instance, since in practice
1871 -- they tend to be dubious in these cases since
1872 -- they can result from intended parametrization.
1874 if not Inside_A_Generic
1875 and then not In_Instance
1877 -- Specialize msg if invalid values could make
1878 -- the loop non-null after all.
1880 if Compile_Time_Compare
1881 (L
, H
, Assume_Valid
=> False) = GT
1884 ("?loop range is null, "
1885 & "loop will not execute",
1888 -- Since we know the range of the loop is
1889 -- null, set the appropriate flag to remove
1890 -- the loop entirely during expansion.
1892 Set_Is_Null_Loop
(Parent
(N
));
1894 -- Here is where the loop could execute because
1895 -- of invalid values, so issue appropriate
1896 -- message and in this case we do not set the
1897 -- Is_Null_Loop flag since the loop may execute.
1901 ("?loop range may be null, "
1902 & "loop may not execute",
1905 ("?can only execute if invalid values "
1911 -- In either case, suppress warnings in the body of
1912 -- the loop, since it is likely that these warnings
1913 -- will be inappropriate if the loop never actually
1914 -- executes, which is unlikely.
1916 Set_Suppress_Loop_Warnings
(Parent
(N
));
1918 -- The other case for a warning is a reverse loop
1919 -- where the upper bound is the integer literal
1920 -- zero or one, and the lower bound can be positive.
1922 -- For example, we have
1924 -- for J in reverse N .. 1 loop
1926 -- In practice, this is very likely to be a case
1927 -- of reversing the bounds incorrectly in the range.
1929 elsif Reverse_Present
(LP
)
1930 and then Nkind
(Original_Node
(H
)) =
1932 and then (Intval
(Original_Node
(H
)) = Uint_0
1934 Intval
(Original_Node
(H
)) = Uint_1
)
1936 Error_Msg_N
("?loop range may be null", DS
);
1937 Error_Msg_N
("\?bounds may be wrong way round", DS
);
1945 end Analyze_Iteration_Scheme
;
1951 -- Note: the semantic work required for analyzing labels (setting them as
1952 -- reachable) was done in a prepass through the statements in the block,
1953 -- so that forward gotos would be properly handled. See Analyze_Statements
1954 -- for further details. The only processing required here is to deal with
1955 -- optimizations that depend on an assumption of sequential control flow,
1956 -- since of course the occurrence of a label breaks this assumption.
1958 procedure Analyze_Label
(N
: Node_Id
) is
1959 pragma Warnings
(Off
, N
);
1961 Kill_Current_Values
;
1964 --------------------------
1965 -- Analyze_Label_Entity --
1966 --------------------------
1968 procedure Analyze_Label_Entity
(E
: Entity_Id
) is
1970 Set_Ekind
(E
, E_Label
);
1971 Set_Etype
(E
, Standard_Void_Type
);
1972 Set_Enclosing_Scope
(E
, Current_Scope
);
1973 Set_Reachable
(E
, True);
1974 end Analyze_Label_Entity
;
1976 ----------------------------
1977 -- Analyze_Loop_Statement --
1978 ----------------------------
1980 procedure Analyze_Loop_Statement
(N
: Node_Id
) is
1981 Loop_Statement
: constant Node_Id
:= N
;
1983 Id
: constant Node_Id
:= Identifier
(Loop_Statement
);
1984 Iter
: constant Node_Id
:= Iteration_Scheme
(Loop_Statement
);
1988 if Present
(Id
) then
1990 -- Make name visible, e.g. for use in exit statements. Loop
1991 -- labels are always considered to be referenced.
1996 -- Guard against serious error (typically, a scope mismatch when
1997 -- semantic analysis is requested) by creating loop entity to
1998 -- continue analysis.
2001 if Total_Errors_Detected
/= 0 then
2004 (E_Loop
, Current_Scope
, Sloc
(Loop_Statement
), 'L');
2006 raise Program_Error
;
2010 Generate_Reference
(Ent
, Loop_Statement
, ' ');
2011 Generate_Definition
(Ent
);
2013 -- If we found a label, mark its type. If not, ignore it, since it
2014 -- means we have a conflicting declaration, which would already
2015 -- have been diagnosed at declaration time. Set Label_Construct
2016 -- of the implicit label declaration, which is not created by the
2017 -- parser for generic units.
2019 if Ekind
(Ent
) = E_Label
then
2020 Set_Ekind
(Ent
, E_Loop
);
2022 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
2023 Set_Label_Construct
(Parent
(Ent
), Loop_Statement
);
2028 -- Case of no identifier present
2033 (E_Loop
, Current_Scope
, Sloc
(Loop_Statement
), 'L');
2034 Set_Etype
(Ent
, Standard_Void_Type
);
2035 Set_Parent
(Ent
, Loop_Statement
);
2038 -- Kill current values on entry to loop, since statements in body of
2039 -- loop may have been executed before the loop is entered. Similarly we
2040 -- kill values after the loop, since we do not know that the body of the
2041 -- loop was executed.
2043 Kill_Current_Values
;
2045 Analyze_Iteration_Scheme
(Iter
);
2046 Analyze_Statements
(Statements
(Loop_Statement
));
2047 Process_End_Label
(Loop_Statement
, 'e', Ent
);
2049 Kill_Current_Values
;
2051 -- Check for infinite loop. Skip check for generated code, since it
2052 -- justs waste time and makes debugging the routine called harder.
2054 -- Note that we have to wait till the body of the loop is fully analyzed
2055 -- before making this call, since Check_Infinite_Loop_Warning relies on
2056 -- being able to use semantic visibility information to find references.
2058 if Comes_From_Source
(N
) then
2059 Check_Infinite_Loop_Warning
(N
);
2062 -- Code after loop is unreachable if the loop has no WHILE or FOR
2063 -- and contains no EXIT statements within the body of the loop.
2065 if No
(Iter
) and then not Has_Exit
(Ent
) then
2066 Check_Unreachable_Code
(N
);
2068 end Analyze_Loop_Statement
;
2070 ----------------------------
2071 -- Analyze_Null_Statement --
2072 ----------------------------
2074 -- Note: the semantics of the null statement is implemented by a single
2075 -- null statement, too bad everything isn't as simple as this!
2077 procedure Analyze_Null_Statement
(N
: Node_Id
) is
2078 pragma Warnings
(Off
, N
);
2081 end Analyze_Null_Statement
;
2083 ------------------------
2084 -- Analyze_Statements --
2085 ------------------------
2087 procedure Analyze_Statements
(L
: List_Id
) is
2092 -- The labels declared in the statement list are reachable from
2093 -- statements in the list. We do this as a prepass so that any
2094 -- goto statement will be properly flagged if its target is not
2095 -- reachable. This is not required, but is nice behavior!
2098 while Present
(S
) loop
2099 if Nkind
(S
) = N_Label
then
2100 Analyze
(Identifier
(S
));
2101 Lab
:= Entity
(Identifier
(S
));
2103 -- If we found a label mark it as reachable
2105 if Ekind
(Lab
) = E_Label
then
2106 Generate_Definition
(Lab
);
2107 Set_Reachable
(Lab
);
2109 if Nkind
(Parent
(Lab
)) = N_Implicit_Label_Declaration
then
2110 Set_Label_Construct
(Parent
(Lab
), S
);
2113 -- If we failed to find a label, it means the implicit declaration
2114 -- of the label was hidden. A for-loop parameter can do this to
2115 -- a label with the same name inside the loop, since the implicit
2116 -- label declaration is in the innermost enclosing body or block
2120 Error_Msg_Sloc
:= Sloc
(Lab
);
2122 ("implicit label declaration for & is hidden#",
2130 -- Perform semantic analysis on all statements
2132 Conditional_Statements_Begin
;
2135 while Present
(S
) loop
2140 Conditional_Statements_End
;
2142 -- Make labels unreachable. Visibility is not sufficient, because
2143 -- labels in one if-branch for example are not reachable from the
2144 -- other branch, even though their declarations are in the enclosing
2145 -- declarative part.
2148 while Present
(S
) loop
2149 if Nkind
(S
) = N_Label
then
2150 Set_Reachable
(Entity
(Identifier
(S
)), False);
2155 end Analyze_Statements
;
2157 ----------------------------
2158 -- Check_Unreachable_Code --
2159 ----------------------------
2161 procedure Check_Unreachable_Code
(N
: Node_Id
) is
2162 Error_Loc
: Source_Ptr
;
2166 if Is_List_Member
(N
)
2167 and then Comes_From_Source
(N
)
2173 Nxt
:= Original_Node
(Next
(N
));
2175 -- If a label follows us, then we never have dead code, since
2176 -- someone could branch to the label, so we just ignore it.
2178 if Nkind
(Nxt
) = N_Label
then
2181 -- Otherwise see if we have a real statement following us
2184 and then Comes_From_Source
(Nxt
)
2185 and then Is_Statement
(Nxt
)
2187 -- Special very annoying exception. If we have a return that
2188 -- follows a raise, then we allow it without a warning, since
2189 -- the Ada RM annoyingly requires a useless return here!
2191 if Nkind
(Original_Node
(N
)) /= N_Raise_Statement
2192 or else Nkind
(Nxt
) /= N_Simple_Return_Statement
2194 -- The rather strange shenanigans with the warning message
2195 -- here reflects the fact that Kill_Dead_Code is very good
2196 -- at removing warnings in deleted code, and this is one
2197 -- warning we would prefer NOT to have removed.
2199 Error_Loc
:= Sloc
(Nxt
);
2201 -- If we have unreachable code, analyze and remove the
2202 -- unreachable code, since it is useless and we don't
2203 -- want to generate junk warnings.
2205 -- We skip this step if we are not in code generation mode.
2206 -- This is the one case where we remove dead code in the
2207 -- semantics as opposed to the expander, and we do not want
2208 -- to remove code if we are not in code generation mode,
2209 -- since this messes up the ASIS trees.
2211 -- Note that one might react by moving the whole circuit to
2212 -- exp_ch5, but then we lose the warning in -gnatc mode.
2214 if Operating_Mode
= Generate_Code
then
2218 -- Quit deleting when we have nothing more to delete
2219 -- or if we hit a label (since someone could transfer
2220 -- control to a label, so we should not delete it).
2222 exit when No
(Nxt
) or else Nkind
(Nxt
) = N_Label
;
2224 -- Statement/declaration is to be deleted
2228 Kill_Dead_Code
(Nxt
);
2232 -- Now issue the warning
2234 Error_Msg
("?unreachable code!", Error_Loc
);
2237 -- If the unconditional transfer of control instruction is
2238 -- the last statement of a sequence, then see if our parent
2239 -- is one of the constructs for which we count unblocked exits,
2240 -- and if so, adjust the count.
2245 -- Statements in THEN part or ELSE part of IF statement
2247 if Nkind
(P
) = N_If_Statement
then
2250 -- Statements in ELSIF part of an IF statement
2252 elsif Nkind
(P
) = N_Elsif_Part
then
2254 pragma Assert
(Nkind
(P
) = N_If_Statement
);
2256 -- Statements in CASE statement alternative
2258 elsif Nkind
(P
) = N_Case_Statement_Alternative
then
2260 pragma Assert
(Nkind
(P
) = N_Case_Statement
);
2262 -- Statements in body of block
2264 elsif Nkind
(P
) = N_Handled_Sequence_Of_Statements
2265 and then Nkind
(Parent
(P
)) = N_Block_Statement
2269 -- Statements in exception handler in a block
2271 elsif Nkind
(P
) = N_Exception_Handler
2272 and then Nkind
(Parent
(P
)) = N_Handled_Sequence_Of_Statements
2273 and then Nkind
(Parent
(Parent
(P
))) = N_Block_Statement
2277 -- None of these cases, so return
2283 -- This was one of the cases we are looking for (i.e. the
2284 -- parent construct was IF, CASE or block) so decrement count.
2286 Unblocked_Exit_Count
:= Unblocked_Exit_Count
- 1;
2290 end Check_Unreachable_Code
;