1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2013, Free Software Foundation, Inc. --
11 -- GNAT is free software; you can redistribute it and/or modify it under --
12 -- terms of the GNU General Public License as published by the Free Soft- --
13 -- ware Foundation; either version 3, or (at your option) any later ver- --
14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
19 -- http://www.gnu.org/licenses for a complete copy of the license. --
21 -- GNAT was originally developed by the GNAT team at New York University. --
22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
24 ------------------------------------------------------------------------------
26 with Aspects
; use Aspects
;
27 with Atree
; use Atree
;
28 with Checks
; use Checks
;
29 with Einfo
; use Einfo
;
30 with Errout
; use Errout
;
31 with Expander
; use Expander
;
32 with Exp_Ch6
; use Exp_Ch6
;
33 with Exp_Util
; use Exp_Util
;
34 with Freeze
; use Freeze
;
36 with Lib
.Xref
; use Lib
.Xref
;
37 with Namet
; use Namet
;
38 with Nlists
; use Nlists
;
39 with Nmake
; use Nmake
;
41 with Restrict
; use Restrict
;
42 with Rident
; use Rident
;
43 with Rtsfind
; use Rtsfind
;
45 with Sem_Aux
; use Sem_Aux
;
46 with Sem_Case
; use Sem_Case
;
47 with Sem_Ch3
; use Sem_Ch3
;
48 with Sem_Ch6
; use Sem_Ch6
;
49 with Sem_Ch8
; use Sem_Ch8
;
50 with Sem_Dim
; use Sem_Dim
;
51 with Sem_Disp
; use Sem_Disp
;
52 with Sem_Elab
; use Sem_Elab
;
53 with Sem_Eval
; use Sem_Eval
;
54 with Sem_Res
; use Sem_Res
;
55 with Sem_Type
; use Sem_Type
;
56 with Sem_Util
; use Sem_Util
;
57 with Sem_Warn
; use Sem_Warn
;
58 with Snames
; use Snames
;
59 with Stand
; use Stand
;
60 with Sinfo
; use Sinfo
;
61 with Targparm
; use Targparm
;
62 with Tbuild
; use Tbuild
;
63 with Uintp
; use Uintp
;
65 package body Sem_Ch5
is
67 Unblocked_Exit_Count
: Nat
:= 0;
68 -- This variable is used when processing if statements, case statements,
69 -- and block statements. It counts the number of exit points that are not
70 -- blocked by unconditional transfer instructions: for IF and CASE, these
71 -- are the branches of the conditional; for a block, they are the statement
72 -- sequence of the block, and the statement sequences of any exception
73 -- handlers that are part of the block. When processing is complete, if
74 -- this count is zero, it means that control cannot fall through the IF,
75 -- CASE or block statement. This is used for the generation of warning
76 -- messages. This variable is recursively saved on entry to processing the
77 -- construct, and restored on exit.
79 procedure Preanalyze_Range
(R_Copy
: Node_Id
);
80 -- Determine expected type of range or domain of iteration of Ada 2012
81 -- loop by analyzing separate copy. Do the analysis and resolution of the
82 -- copy of the bound(s) with expansion disabled, to prevent the generation
83 -- of finalization actions. This prevents memory leaks when the bounds
84 -- contain calls to functions returning controlled arrays or when the
85 -- domain of iteration is a container.
87 ------------------------
88 -- Analyze_Assignment --
89 ------------------------
91 procedure Analyze_Assignment
(N
: Node_Id
) is
92 Lhs
: constant Node_Id
:= Name
(N
);
93 Rhs
: constant Node_Id
:= Expression
(N
);
98 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
);
99 -- N is the node for the left hand side of an assignment, and it is not
100 -- a variable. This routine issues an appropriate diagnostic.
103 -- This is called to kill current value settings of a simple variable
104 -- on the left hand side. We call it if we find any error in analyzing
105 -- the assignment, and at the end of processing before setting any new
106 -- current values in place.
108 procedure Set_Assignment_Type
110 Opnd_Type
: in out Entity_Id
);
111 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type is the
112 -- nominal subtype. This procedure is used to deal with cases where the
113 -- nominal subtype must be replaced by the actual subtype.
115 -------------------------------
116 -- Diagnose_Non_Variable_Lhs --
117 -------------------------------
119 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
) is
121 -- Not worth posting another error if left hand side already flagged
122 -- as being illegal in some respect.
124 if Error_Posted
(N
) then
127 -- Some special bad cases of entity names
129 elsif Is_Entity_Name
(N
) then
131 Ent
: constant Entity_Id
:= Entity
(N
);
134 if Ekind
(Ent
) = E_In_Parameter
then
136 ("assignment to IN mode parameter not allowed", N
);
138 -- Renamings of protected private components are turned into
139 -- constants when compiling a protected function. In the case
140 -- of single protected types, the private component appears
143 elsif (Is_Prival
(Ent
)
145 (Ekind
(Current_Scope
) = E_Function
146 or else Ekind
(Enclosing_Dynamic_Scope
147 (Current_Scope
)) = E_Function
))
149 (Ekind
(Ent
) = E_Component
150 and then Is_Protected_Type
(Scope
(Ent
)))
153 ("protected function cannot modify protected object", N
);
155 elsif Ekind
(Ent
) = E_Loop_Parameter
then
157 ("assignment to loop parameter not allowed", N
);
161 ("left hand side of assignment must be a variable", N
);
165 -- For indexed components or selected components, test prefix
167 elsif Nkind
(N
) = N_Indexed_Component
then
168 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
170 -- Another special case for assignment to discriminant
172 elsif Nkind
(N
) = N_Selected_Component
then
173 if Present
(Entity
(Selector_Name
(N
)))
174 and then Ekind
(Entity
(Selector_Name
(N
))) = E_Discriminant
177 ("assignment to discriminant not allowed", N
);
179 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
183 -- If we fall through, we have no special message to issue!
185 Error_Msg_N
("left hand side of assignment must be a variable", N
);
187 end Diagnose_Non_Variable_Lhs
;
193 procedure Kill_Lhs
is
195 if Is_Entity_Name
(Lhs
) then
197 Ent
: constant Entity_Id
:= Entity
(Lhs
);
199 if Present
(Ent
) then
200 Kill_Current_Values
(Ent
);
206 -------------------------
207 -- Set_Assignment_Type --
208 -------------------------
210 procedure Set_Assignment_Type
212 Opnd_Type
: in out Entity_Id
)
215 Require_Entity
(Opnd
);
217 -- If the assignment operand is an in-out or out parameter, then we
218 -- get the actual subtype (needed for the unconstrained case). If the
219 -- operand is the actual in an entry declaration, then within the
220 -- accept statement it is replaced with a local renaming, which may
221 -- also have an actual subtype.
223 if Is_Entity_Name
(Opnd
)
224 and then (Ekind
(Entity
(Opnd
)) = E_Out_Parameter
225 or else Ekind_In
(Entity
(Opnd
),
227 E_Generic_In_Out_Parameter
)
229 (Ekind
(Entity
(Opnd
)) = E_Variable
230 and then Nkind
(Parent
(Entity
(Opnd
))) =
231 N_Object_Renaming_Declaration
232 and then Nkind
(Parent
(Parent
(Entity
(Opnd
)))) =
235 Opnd_Type
:= Get_Actual_Subtype
(Opnd
);
237 -- If assignment operand is a component reference, then we get the
238 -- actual subtype of the component for the unconstrained case.
240 elsif Nkind_In
(Opnd
, N_Selected_Component
, N_Explicit_Dereference
)
241 and then not Is_Unchecked_Union
(Opnd_Type
)
243 Decl
:= Build_Actual_Subtype_Of_Component
(Opnd_Type
, Opnd
);
245 if Present
(Decl
) then
246 Insert_Action
(N
, Decl
);
247 Mark_Rewrite_Insertion
(Decl
);
249 Opnd_Type
:= Defining_Identifier
(Decl
);
250 Set_Etype
(Opnd
, Opnd_Type
);
251 Freeze_Itype
(Opnd_Type
, N
);
253 elsif Is_Constrained
(Etype
(Opnd
)) then
254 Opnd_Type
:= Etype
(Opnd
);
257 -- For slice, use the constrained subtype created for the slice
259 elsif Nkind
(Opnd
) = N_Slice
then
260 Opnd_Type
:= Etype
(Opnd
);
262 end Set_Assignment_Type
;
264 -- Start of processing for Analyze_Assignment
267 Mark_Coextensions
(N
, Rhs
);
272 -- Ensure that we never do an assignment on a variable marked as
273 -- as Safe_To_Reevaluate.
275 pragma Assert
(not Is_Entity_Name
(Lhs
)
276 or else Ekind
(Entity
(Lhs
)) /= E_Variable
277 or else not Is_Safe_To_Reevaluate
(Entity
(Lhs
)));
279 -- Start type analysis for assignment
283 -- In the most general case, both Lhs and Rhs can be overloaded, and we
284 -- must compute the intersection of the possible types on each side.
286 if Is_Overloaded
(Lhs
) then
293 Get_First_Interp
(Lhs
, I
, It
);
295 while Present
(It
.Typ
) loop
296 if Has_Compatible_Type
(Rhs
, It
.Typ
) then
297 if T1
/= Any_Type
then
299 -- An explicit dereference is overloaded if the prefix
300 -- is. Try to remove the ambiguity on the prefix, the
301 -- error will be posted there if the ambiguity is real.
303 if Nkind
(Lhs
) = N_Explicit_Dereference
then
306 PI1
: Interp_Index
:= 0;
312 Get_First_Interp
(Prefix
(Lhs
), PI
, PIt
);
314 while Present
(PIt
.Typ
) loop
315 if Is_Access_Type
(PIt
.Typ
)
316 and then Has_Compatible_Type
317 (Rhs
, Designated_Type
(PIt
.Typ
))
321 Disambiguate
(Prefix
(Lhs
),
324 if PIt
= No_Interp
then
326 ("ambiguous left-hand side"
327 & " in assignment", Lhs
);
330 Resolve
(Prefix
(Lhs
), PIt
.Typ
);
340 Get_Next_Interp
(PI
, PIt
);
346 ("ambiguous left-hand side in assignment", Lhs
);
354 Get_Next_Interp
(I
, It
);
358 if T1
= Any_Type
then
360 ("no valid types for left-hand side for assignment", Lhs
);
366 -- The resulting assignment type is T1, so now we will resolve the left
367 -- hand side of the assignment using this determined type.
371 -- Cases where Lhs is not a variable
373 if not Is_Variable
(Lhs
) then
375 -- Ada 2005 (AI-327): Check assignment to the attribute Priority of a
383 if Ada_Version
>= Ada_2005
then
385 -- Handle chains of renamings
388 while Nkind
(Ent
) in N_Has_Entity
389 and then Present
(Entity
(Ent
))
390 and then Present
(Renamed_Object
(Entity
(Ent
)))
392 Ent
:= Renamed_Object
(Entity
(Ent
));
395 if (Nkind
(Ent
) = N_Attribute_Reference
396 and then Attribute_Name
(Ent
) = Name_Priority
)
398 -- Renamings of the attribute Priority applied to protected
399 -- objects have been previously expanded into calls to the
400 -- Get_Ceiling run-time subprogram.
403 (Nkind
(Ent
) = N_Function_Call
404 and then (Entity
(Name
(Ent
)) = RTE
(RE_Get_Ceiling
)
406 Entity
(Name
(Ent
)) = RTE
(RO_PE_Get_Ceiling
)))
408 -- The enclosing subprogram cannot be a protected function
411 while not (Is_Subprogram
(S
)
412 and then Convention
(S
) = Convention_Protected
)
413 and then S
/= Standard_Standard
418 if Ekind
(S
) = E_Function
419 and then Convention
(S
) = Convention_Protected
422 ("protected function cannot modify protected object",
426 -- Changes of the ceiling priority of the protected object
427 -- are only effective if the Ceiling_Locking policy is in
428 -- effect (AARM D.5.2 (5/2)).
430 if Locking_Policy
/= 'C' then
431 Error_Msg_N
("assignment to the attribute PRIORITY has " &
433 Error_Msg_N
("\since no Locking_Policy has been " &
442 Diagnose_Non_Variable_Lhs
(Lhs
);
445 -- Error of assigning to limited type. We do however allow this in
446 -- certain cases where the front end generates the assignments.
448 elsif Is_Limited_Type
(T1
)
449 and then not Assignment_OK
(Lhs
)
450 and then not Assignment_OK
(Original_Node
(Lhs
))
451 and then not Is_Value_Type
(T1
)
453 -- CPP constructors can only be called in declarations
455 if Is_CPP_Constructor_Call
(Rhs
) then
456 Error_Msg_N
("invalid use of 'C'P'P constructor", Rhs
);
459 ("left hand of assignment must not be limited type", Lhs
);
460 Explain_Limited_Type
(T1
, Lhs
);
464 -- Enforce RM 3.9.3 (8): the target of an assignment operation cannot be
465 -- abstract. This is only checked when the assignment Comes_From_Source,
466 -- because in some cases the expander generates such assignments (such
467 -- in the _assign operation for an abstract type).
469 elsif Is_Abstract_Type
(T1
) and then Comes_From_Source
(N
) then
471 ("target of assignment operation must not be abstract", Lhs
);
474 -- Resolution may have updated the subtype, in case the left-hand side
475 -- is a private protected component. Use the correct subtype to avoid
476 -- scoping issues in the back-end.
480 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
481 -- type. For example:
485 -- type Acc is access P.T;
488 -- with Pkg; use Acc;
489 -- procedure Example is
492 -- A.all := B.all; -- ERROR
495 if Nkind
(Lhs
) = N_Explicit_Dereference
496 and then Ekind
(T1
) = E_Incomplete_Type
498 Error_Msg_N
("invalid use of incomplete type", Lhs
);
503 -- Now we can complete the resolution of the right hand side
505 Set_Assignment_Type
(Lhs
, T1
);
508 -- This is the point at which we check for an unset reference
510 Check_Unset_Reference
(Rhs
);
511 Check_Unprotected_Access
(Lhs
, Rhs
);
513 -- Remaining steps are skipped if Rhs was syntactically in error
522 if not Covers
(T1
, T2
) then
523 Wrong_Type
(Rhs
, Etype
(Lhs
));
528 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
529 -- types, use the non-limited view if available
531 if Nkind
(Rhs
) = N_Explicit_Dereference
532 and then Ekind
(T2
) = E_Incomplete_Type
533 and then Is_Tagged_Type
(T2
)
534 and then Present
(Non_Limited_View
(T2
))
536 T2
:= Non_Limited_View
(T2
);
539 Set_Assignment_Type
(Rhs
, T2
);
541 if Total_Errors_Detected
/= 0 then
551 if T1
= Any_Type
or else T2
= Any_Type
then
556 -- If the rhs is class-wide or dynamically tagged, then require the lhs
557 -- to be class-wide. The case where the rhs is a dynamically tagged call
558 -- to a dispatching operation with a controlling access result is
559 -- excluded from this check, since the target has an access type (and
560 -- no tag propagation occurs in that case).
562 if (Is_Class_Wide_Type
(T2
)
563 or else (Is_Dynamically_Tagged
(Rhs
)
564 and then not Is_Access_Type
(T1
)))
565 and then not Is_Class_Wide_Type
(T1
)
567 Error_Msg_N
("dynamically tagged expression not allowed!", Rhs
);
569 elsif Is_Class_Wide_Type
(T1
)
570 and then not Is_Class_Wide_Type
(T2
)
571 and then not Is_Tag_Indeterminate
(Rhs
)
572 and then not Is_Dynamically_Tagged
(Rhs
)
574 Error_Msg_N
("dynamically tagged expression required!", Rhs
);
577 -- Propagate the tag from a class-wide target to the rhs when the rhs
578 -- is a tag-indeterminate call.
580 if Is_Tag_Indeterminate
(Rhs
) then
581 if Is_Class_Wide_Type
(T1
) then
582 Propagate_Tag
(Lhs
, Rhs
);
584 elsif Nkind
(Rhs
) = N_Function_Call
585 and then Is_Entity_Name
(Name
(Rhs
))
586 and then Is_Abstract_Subprogram
(Entity
(Name
(Rhs
)))
589 ("call to abstract function must be dispatching", Name
(Rhs
));
591 elsif Nkind
(Rhs
) = N_Qualified_Expression
592 and then Nkind
(Expression
(Rhs
)) = N_Function_Call
593 and then Is_Entity_Name
(Name
(Expression
(Rhs
)))
595 Is_Abstract_Subprogram
(Entity
(Name
(Expression
(Rhs
))))
598 ("call to abstract function must be dispatching",
599 Name
(Expression
(Rhs
)));
603 -- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
604 -- apply an implicit conversion of the rhs to that type to force
605 -- appropriate static and run-time accessibility checks. This applies
606 -- as well to anonymous access-to-subprogram types that are component
607 -- subtypes or formal parameters.
609 if Ada_Version
>= Ada_2005
and then Is_Access_Type
(T1
) then
610 if Is_Local_Anonymous_Access
(T1
)
611 or else Ekind
(T2
) = E_Anonymous_Access_Subprogram_Type
613 -- Handle assignment to an Ada 2012 stand-alone object
614 -- of an anonymous access type.
616 or else (Ekind
(T1
) = E_Anonymous_Access_Type
617 and then Nkind
(Associated_Node_For_Itype
(T1
)) =
618 N_Object_Declaration
)
621 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
622 Analyze_And_Resolve
(Rhs
, T1
);
626 -- Ada 2005 (AI-231): Assignment to not null variable
628 if Ada_Version
>= Ada_2005
629 and then Can_Never_Be_Null
(T1
)
630 and then not Assignment_OK
(Lhs
)
632 -- Case where we know the right hand side is null
634 if Known_Null
(Rhs
) then
635 Apply_Compile_Time_Constraint_Error
638 "(Ada 2005) null not allowed in null-excluding objects??",
639 Reason
=> CE_Null_Not_Allowed
);
641 -- We still mark this as a possible modification, that's necessary
642 -- to reset Is_True_Constant, and desirable for xref purposes.
644 Note_Possible_Modification
(Lhs
, Sure
=> True);
647 -- If we know the right hand side is non-null, then we convert to the
648 -- target type, since we don't need a run time check in that case.
650 elsif not Can_Never_Be_Null
(T2
) then
651 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
652 Analyze_And_Resolve
(Rhs
, T1
);
656 if Is_Scalar_Type
(T1
) then
657 Apply_Scalar_Range_Check
(Rhs
, Etype
(Lhs
));
659 -- For array types, verify that lengths match. If the right hand side
660 -- is a function call that has been inlined, the assignment has been
661 -- rewritten as a block, and the constraint check will be applied to the
662 -- assignment within the block.
664 elsif Is_Array_Type
(T1
)
665 and then (Nkind
(Rhs
) /= N_Type_Conversion
666 or else Is_Constrained
(Etype
(Rhs
)))
667 and then (Nkind
(Rhs
) /= N_Function_Call
668 or else Nkind
(N
) /= N_Block_Statement
)
670 -- Assignment verifies that the length of the Lsh and Rhs are equal,
671 -- but of course the indexes do not have to match. If the right-hand
672 -- side is a type conversion to an unconstrained type, a length check
673 -- is performed on the expression itself during expansion. In rare
674 -- cases, the redundant length check is computed on an index type
675 -- with a different representation, triggering incorrect code in the
678 Apply_Length_Check
(Rhs
, Etype
(Lhs
));
681 -- Discriminant checks are applied in the course of expansion
686 -- Note: modifications of the Lhs may only be recorded after
687 -- checks have been applied.
689 Note_Possible_Modification
(Lhs
, Sure
=> True);
691 -- ??? a real accessibility check is needed when ???
693 -- Post warning for redundant assignment or variable to itself
695 if Warn_On_Redundant_Constructs
697 -- We only warn for source constructs
699 and then Comes_From_Source
(N
)
701 -- Where the object is the same on both sides
703 and then Same_Object
(Lhs
, Original_Node
(Rhs
))
705 -- But exclude the case where the right side was an operation that
706 -- got rewritten (e.g. JUNK + K, where K was known to be zero). We
707 -- don't want to warn in such a case, since it is reasonable to write
708 -- such expressions especially when K is defined symbolically in some
711 and then Nkind
(Original_Node
(Rhs
)) not in N_Op
713 if Nkind
(Lhs
) in N_Has_Entity
then
714 Error_Msg_NE
-- CODEFIX
715 ("?r?useless assignment of & to itself!", N
, Entity
(Lhs
));
717 Error_Msg_N
-- CODEFIX
718 ("?r?useless assignment of object to itself!", N
);
722 -- Check for non-allowed composite assignment
724 if not Support_Composite_Assign_On_Target
725 and then (Is_Array_Type
(T1
) or else Is_Record_Type
(T1
))
726 and then (not Has_Size_Clause
(T1
) or else Esize
(T1
) > 64)
728 Error_Msg_CRT
("composite assignment", N
);
731 -- Check elaboration warning for left side if not in elab code
733 if not In_Subprogram_Or_Concurrent_Unit
then
734 Check_Elab_Assign
(Lhs
);
737 -- Set Referenced_As_LHS if appropriate. We only set this flag if the
738 -- assignment is a source assignment in the extended main source unit.
739 -- We are not interested in any reference information outside this
740 -- context, or in compiler generated assignment statements.
742 if Comes_From_Source
(N
)
743 and then In_Extended_Main_Source_Unit
(Lhs
)
745 Set_Referenced_Modified
(Lhs
, Out_Param
=> False);
748 -- Final step. If left side is an entity, then we may be able to reset
749 -- the current tracked values to new safe values. We only have something
750 -- to do if the left side is an entity name, and expansion has not
751 -- modified the node into something other than an assignment, and of
752 -- course we only capture values if it is safe to do so.
754 if Is_Entity_Name
(Lhs
)
755 and then Nkind
(N
) = N_Assignment_Statement
758 Ent
: constant Entity_Id
:= Entity
(Lhs
);
761 if Safe_To_Capture_Value
(N
, Ent
) then
763 -- If simple variable on left side, warn if this assignment
764 -- blots out another one (rendering it useless). We only do
765 -- this for source assignments, otherwise we can generate bogus
766 -- warnings when an assignment is rewritten as another
767 -- assignment, and gets tied up with itself.
769 if Warn_On_Modified_Unread
770 and then Is_Assignable
(Ent
)
771 and then Comes_From_Source
(N
)
772 and then In_Extended_Main_Source_Unit
(Ent
)
774 Warn_On_Useless_Assignment
(Ent
, N
);
777 -- If we are assigning an access type and the left side is an
778 -- entity, then make sure that the Is_Known_[Non_]Null flags
779 -- properly reflect the state of the entity after assignment.
781 if Is_Access_Type
(T1
) then
782 if Known_Non_Null
(Rhs
) then
783 Set_Is_Known_Non_Null
(Ent
, True);
785 elsif Known_Null
(Rhs
)
786 and then not Can_Never_Be_Null
(Ent
)
788 Set_Is_Known_Null
(Ent
, True);
791 Set_Is_Known_Null
(Ent
, False);
793 if not Can_Never_Be_Null
(Ent
) then
794 Set_Is_Known_Non_Null
(Ent
, False);
798 -- For discrete types, we may be able to set the current value
799 -- if the value is known at compile time.
801 elsif Is_Discrete_Type
(T1
)
802 and then Compile_Time_Known_Value
(Rhs
)
804 Set_Current_Value
(Ent
, Rhs
);
806 Set_Current_Value
(Ent
, Empty
);
809 -- If not safe to capture values, kill them
817 -- If assigning to an object in whole or in part, note location of
818 -- assignment in case no one references value. We only do this for
819 -- source assignments, otherwise we can generate bogus warnings when an
820 -- assignment is rewritten as another assignment, and gets tied up with
824 Ent
: constant Entity_Id
:= Get_Enclosing_Object
(Lhs
);
827 and then Safe_To_Capture_Value
(N
, Ent
)
828 and then Nkind
(N
) = N_Assignment_Statement
829 and then Warn_On_Modified_Unread
830 and then Is_Assignable
(Ent
)
831 and then Comes_From_Source
(N
)
832 and then In_Extended_Main_Source_Unit
(Ent
)
834 Set_Last_Assignment
(Ent
, Lhs
);
838 Analyze_Dimension
(N
);
839 end Analyze_Assignment
;
841 -----------------------------
842 -- Analyze_Block_Statement --
843 -----------------------------
845 procedure Analyze_Block_Statement
(N
: Node_Id
) is
846 procedure Install_Return_Entities
(Scop
: Entity_Id
);
847 -- Install all entities of return statement scope Scop in the visibility
848 -- chain except for the return object since its entity is reused in a
851 -----------------------------
852 -- Install_Return_Entities --
853 -----------------------------
855 procedure Install_Return_Entities
(Scop
: Entity_Id
) is
859 Id
:= First_Entity
(Scop
);
860 while Present
(Id
) loop
862 -- Do not install the return object
864 if not Ekind_In
(Id
, E_Constant
, E_Variable
)
865 or else not Is_Return_Object
(Id
)
872 end Install_Return_Entities
;
874 -- Local constants and variables
876 Decls
: constant List_Id
:= Declarations
(N
);
877 Id
: constant Node_Id
:= Identifier
(N
);
878 HSS
: constant Node_Id
:= Handled_Statement_Sequence
(N
);
880 Is_BIP_Return_Statement
: Boolean;
882 -- Start of processing for Analyze_Block_Statement
885 -- In SPARK mode, we reject block statements. Note that the case of
886 -- block statements generated by the expander is fine.
888 if Nkind
(Original_Node
(N
)) = N_Block_Statement
then
889 Check_SPARK_Restriction
("block statement is not allowed", N
);
892 -- If no handled statement sequence is present, things are really messed
893 -- up, and we just return immediately (defence against previous errors).
896 Check_Error_Detected
;
900 -- Detect whether the block is actually a rewritten return statement of
901 -- a build-in-place function.
903 Is_BIP_Return_Statement
:=
905 and then Present
(Entity
(Id
))
906 and then Ekind
(Entity
(Id
)) = E_Return_Statement
907 and then Is_Build_In_Place_Function
908 (Return_Applies_To
(Entity
(Id
)));
910 -- Normal processing with HSS present
913 EH
: constant List_Id
:= Exception_Handlers
(HSS
);
914 Ent
: Entity_Id
:= Empty
;
917 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
918 -- Recursively save value of this global, will be restored on exit
921 -- Initialize unblocked exit count for statements of begin block
922 -- plus one for each exception handler that is present.
924 Unblocked_Exit_Count
:= 1;
927 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ List_Length
(EH
);
930 -- If a label is present analyze it and mark it as referenced
936 -- An error defense. If we have an identifier, but no entity, then
937 -- something is wrong. If previous errors, then just remove the
938 -- identifier and continue, otherwise raise an exception.
941 Check_Error_Detected
;
942 Set_Identifier
(N
, Empty
);
945 Set_Ekind
(Ent
, E_Block
);
946 Generate_Reference
(Ent
, N
, ' ');
947 Generate_Definition
(Ent
);
949 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
950 Set_Label_Construct
(Parent
(Ent
), N
);
955 -- If no entity set, create a label entity
958 Ent
:= New_Internal_Entity
(E_Block
, Current_Scope
, Sloc
(N
), 'B');
959 Set_Identifier
(N
, New_Occurrence_Of
(Ent
, Sloc
(N
)));
963 Set_Etype
(Ent
, Standard_Void_Type
);
964 Set_Block_Node
(Ent
, Identifier
(N
));
967 -- The block served as an extended return statement. Ensure that any
968 -- entities created during the analysis and expansion of the return
969 -- object declaration are once again visible.
971 if Is_BIP_Return_Statement
then
972 Install_Return_Entities
(Ent
);
975 if Present
(Decls
) then
976 Analyze_Declarations
(Decls
);
978 Inspect_Deferred_Constant_Completion
(Decls
);
982 Process_End_Label
(HSS
, 'e', Ent
);
984 -- If exception handlers are present, then we indicate that enclosing
985 -- scopes contain a block with handlers. We only need to mark non-
991 Set_Has_Nested_Block_With_Handler
(S
);
992 exit when Is_Overloadable
(S
)
993 or else Ekind
(S
) = E_Package
994 or else Is_Generic_Unit
(S
);
999 Check_References
(Ent
);
1000 Warn_On_Useless_Assignments
(Ent
);
1003 if Unblocked_Exit_Count
= 0 then
1004 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1005 Check_Unreachable_Code
(N
);
1007 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1010 end Analyze_Block_Statement
;
1012 ----------------------------
1013 -- Analyze_Case_Statement --
1014 ----------------------------
1016 procedure Analyze_Case_Statement
(N
: Node_Id
) is
1018 Exp_Type
: Entity_Id
;
1019 Exp_Btype
: Entity_Id
;
1022 Others_Present
: Boolean;
1023 -- Indicates if Others was present
1025 pragma Warnings
(Off
, Last_Choice
);
1026 -- Don't care about assigned value
1028 Statements_Analyzed
: Boolean := False;
1029 -- Set True if at least some statement sequences get analyzed. If False
1030 -- on exit, means we had a serious error that prevented full analysis of
1031 -- the case statement, and as a result it is not a good idea to output
1032 -- warning messages about unreachable code.
1034 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
1035 -- Recursively save value of this global, will be restored on exit
1037 procedure Non_Static_Choice_Error
(Choice
: Node_Id
);
1038 -- Error routine invoked by the generic instantiation below when the
1039 -- case statement has a non static choice.
1041 procedure Process_Statements
(Alternative
: Node_Id
);
1042 -- Analyzes the statements associated with a case alternative. Needed
1043 -- by instantiation below.
1045 package Analyze_Case_Choices
is new
1046 Generic_Analyze_Choices
1047 (Process_Associated_Node
=> Process_Statements
);
1048 use Analyze_Case_Choices
;
1049 -- Instantiation of the generic choice analysis package
1051 package Check_Case_Choices
is new
1052 Generic_Check_Choices
1053 (Process_Empty_Choice
=> No_OP
,
1054 Process_Non_Static_Choice
=> Non_Static_Choice_Error
,
1055 Process_Associated_Node
=> No_Op
);
1056 use Check_Case_Choices
;
1057 -- Instantiation of the generic choice processing package
1059 -----------------------------
1060 -- Non_Static_Choice_Error --
1061 -----------------------------
1063 procedure Non_Static_Choice_Error
(Choice
: Node_Id
) is
1065 Flag_Non_Static_Expr
1066 ("choice given in case statement is not static!", Choice
);
1067 end Non_Static_Choice_Error
;
1069 ------------------------
1070 -- Process_Statements --
1071 ------------------------
1073 procedure Process_Statements
(Alternative
: Node_Id
) is
1074 Choices
: constant List_Id
:= Discrete_Choices
(Alternative
);
1078 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
1079 Statements_Analyzed
:= True;
1081 -- An interesting optimization. If the case statement expression
1082 -- is a simple entity, then we can set the current value within an
1083 -- alternative if the alternative has one possible value.
1087 -- when 2 | 3 => beta
1088 -- when others => gamma
1090 -- Here we know that N is initially 1 within alpha, but for beta and
1091 -- gamma, we do not know anything more about the initial value.
1093 if Is_Entity_Name
(Exp
) then
1094 Ent
:= Entity
(Exp
);
1096 if Ekind_In
(Ent
, E_Variable
,
1100 if List_Length
(Choices
) = 1
1101 and then Nkind
(First
(Choices
)) in N_Subexpr
1102 and then Compile_Time_Known_Value
(First
(Choices
))
1104 Set_Current_Value
(Entity
(Exp
), First
(Choices
));
1107 Analyze_Statements
(Statements
(Alternative
));
1109 -- After analyzing the case, set the current value to empty
1110 -- since we won't know what it is for the next alternative
1111 -- (unless reset by this same circuit), or after the case.
1113 Set_Current_Value
(Entity
(Exp
), Empty
);
1118 -- Case where expression is not an entity name of a variable
1120 Analyze_Statements
(Statements
(Alternative
));
1121 end Process_Statements
;
1123 -- Start of processing for Analyze_Case_Statement
1126 Unblocked_Exit_Count
:= 0;
1127 Exp
:= Expression
(N
);
1130 -- The expression must be of any discrete type. In rare cases, the
1131 -- expander constructs a case statement whose expression has a private
1132 -- type whose full view is discrete. This can happen when generating
1133 -- a stream operation for a variant type after the type is frozen,
1134 -- when the partial of view of the type of the discriminant is private.
1135 -- In that case, use the full view to analyze case alternatives.
1137 if not Is_Overloaded
(Exp
)
1138 and then not Comes_From_Source
(N
)
1139 and then Is_Private_Type
(Etype
(Exp
))
1140 and then Present
(Full_View
(Etype
(Exp
)))
1141 and then Is_Discrete_Type
(Full_View
(Etype
(Exp
)))
1143 Resolve
(Exp
, Etype
(Exp
));
1144 Exp_Type
:= Full_View
(Etype
(Exp
));
1147 Analyze_And_Resolve
(Exp
, Any_Discrete
);
1148 Exp_Type
:= Etype
(Exp
);
1151 Check_Unset_Reference
(Exp
);
1152 Exp_Btype
:= Base_Type
(Exp_Type
);
1154 -- The expression must be of a discrete type which must be determinable
1155 -- independently of the context in which the expression occurs, but
1156 -- using the fact that the expression must be of a discrete type.
1157 -- Moreover, the type this expression must not be a character literal
1158 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
1160 -- If error already reported by Resolve, nothing more to do
1162 if Exp_Btype
= Any_Discrete
or else Exp_Btype
= Any_Type
then
1165 elsif Exp_Btype
= Any_Character
then
1167 ("character literal as case expression is ambiguous", Exp
);
1170 elsif Ada_Version
= Ada_83
1171 and then (Is_Generic_Type
(Exp_Btype
)
1172 or else Is_Generic_Type
(Root_Type
(Exp_Btype
)))
1175 ("(Ada 83) case expression cannot be of a generic type", Exp
);
1179 -- If the case expression is a formal object of mode in out, then treat
1180 -- it as having a nonstatic subtype by forcing use of the base type
1181 -- (which has to get passed to Check_Case_Choices below). Also use base
1182 -- type when the case expression is parenthesized.
1184 if Paren_Count
(Exp
) > 0
1185 or else (Is_Entity_Name
(Exp
)
1186 and then Ekind
(Entity
(Exp
)) = E_Generic_In_Out_Parameter
)
1188 Exp_Type
:= Exp_Btype
;
1191 -- Call instantiated procedures to analyzwe and check discrete choices
1193 Analyze_Choices
(Alternatives
(N
), Exp_Type
);
1194 Check_Choices
(N
, Alternatives
(N
), Exp_Type
, Others_Present
);
1196 -- Case statement with single OTHERS alternative not allowed in SPARK
1198 if Others_Present
and then List_Length
(Alternatives
(N
)) = 1 then
1199 Check_SPARK_Restriction
1200 ("OTHERS as unique case alternative is not allowed", N
);
1203 if Exp_Type
= Universal_Integer
and then not Others_Present
then
1204 Error_Msg_N
("case on universal integer requires OTHERS choice", Exp
);
1207 -- If all our exits were blocked by unconditional transfers of control,
1208 -- then the entire CASE statement acts as an unconditional transfer of
1209 -- control, so treat it like one, and check unreachable code. Skip this
1210 -- test if we had serious errors preventing any statement analysis.
1212 if Unblocked_Exit_Count
= 0 and then Statements_Analyzed
then
1213 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1214 Check_Unreachable_Code
(N
);
1216 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1219 -- If the expander is active it will detect the case of a statically
1220 -- determined single alternative and remove warnings for the case, but
1221 -- if we are not doing expansion, that circuit won't be active. Here we
1222 -- duplicate the effect of removing warnings in the same way, so that
1223 -- we will get the same set of warnings in -gnatc mode.
1225 if not Expander_Active
1226 and then Compile_Time_Known_Value
(Expression
(N
))
1227 and then Serious_Errors_Detected
= 0
1230 Chosen
: constant Node_Id
:= Find_Static_Alternative
(N
);
1234 Alt
:= First
(Alternatives
(N
));
1235 while Present
(Alt
) loop
1236 if Alt
/= Chosen
then
1237 Remove_Warning_Messages
(Statements
(Alt
));
1244 end Analyze_Case_Statement
;
1246 ----------------------------
1247 -- Analyze_Exit_Statement --
1248 ----------------------------
1250 -- If the exit includes a name, it must be the name of a currently open
1251 -- loop. Otherwise there must be an innermost open loop on the stack, to
1252 -- which the statement implicitly refers.
1254 -- Additionally, in SPARK mode:
1256 -- The exit can only name the closest enclosing loop;
1258 -- An exit with a when clause must be directly contained in a loop;
1260 -- An exit without a when clause must be directly contained in an
1261 -- if-statement with no elsif or else, which is itself directly contained
1262 -- in a loop. The exit must be the last statement in the if-statement.
1264 procedure Analyze_Exit_Statement
(N
: Node_Id
) is
1265 Target
: constant Node_Id
:= Name
(N
);
1266 Cond
: constant Node_Id
:= Condition
(N
);
1267 Scope_Id
: Entity_Id
;
1273 Check_Unreachable_Code
(N
);
1276 if Present
(Target
) then
1278 U_Name
:= Entity
(Target
);
1280 if not In_Open_Scopes
(U_Name
) or else Ekind
(U_Name
) /= E_Loop
then
1281 Error_Msg_N
("invalid loop name in exit statement", N
);
1285 if Has_Loop_In_Inner_Open_Scopes
(U_Name
) then
1286 Check_SPARK_Restriction
1287 ("exit label must name the closest enclosing loop", N
);
1290 Set_Has_Exit
(U_Name
);
1297 for J
in reverse 0 .. Scope_Stack
.Last
loop
1298 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
1299 Kind
:= Ekind
(Scope_Id
);
1301 if Kind
= E_Loop
and then (No
(Target
) or else Scope_Id
= U_Name
) then
1302 Set_Has_Exit
(Scope_Id
);
1305 elsif Kind
= E_Block
1306 or else Kind
= E_Loop
1307 or else Kind
= E_Return_Statement
1313 ("cannot exit from program unit or accept statement", N
);
1318 -- Verify that if present the condition is a Boolean expression
1320 if Present
(Cond
) then
1321 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1322 Check_Unset_Reference
(Cond
);
1325 -- In SPARK mode, verify that the exit statement respects the SPARK
1328 if Present
(Cond
) then
1329 if Nkind
(Parent
(N
)) /= N_Loop_Statement
then
1330 Check_SPARK_Restriction
1331 ("exit with when clause must be directly in loop", N
);
1335 if Nkind
(Parent
(N
)) /= N_If_Statement
then
1336 if Nkind
(Parent
(N
)) = N_Elsif_Part
then
1337 Check_SPARK_Restriction
1338 ("exit must be in IF without ELSIF", N
);
1340 Check_SPARK_Restriction
("exit must be directly in IF", N
);
1343 elsif Nkind
(Parent
(Parent
(N
))) /= N_Loop_Statement
then
1344 Check_SPARK_Restriction
1345 ("exit must be in IF directly in loop", N
);
1347 -- First test the presence of ELSE, so that an exit in an ELSE leads
1348 -- to an error mentioning the ELSE.
1350 elsif Present
(Else_Statements
(Parent
(N
))) then
1351 Check_SPARK_Restriction
("exit must be in IF without ELSE", N
);
1353 -- An exit in an ELSIF does not reach here, as it would have been
1354 -- detected in the case (Nkind (Parent (N)) /= N_If_Statement).
1356 elsif Present
(Elsif_Parts
(Parent
(N
))) then
1357 Check_SPARK_Restriction
("exit must be in IF without ELSIF", N
);
1361 -- Chain exit statement to associated loop entity
1363 Set_Next_Exit_Statement
(N
, First_Exit_Statement
(Scope_Id
));
1364 Set_First_Exit_Statement
(Scope_Id
, N
);
1366 -- Since the exit may take us out of a loop, any previous assignment
1367 -- statement is not useless, so clear last assignment indications. It
1368 -- is OK to keep other current values, since if the exit statement
1369 -- does not exit, then the current values are still valid.
1371 Kill_Current_Values
(Last_Assignment_Only
=> True);
1372 end Analyze_Exit_Statement
;
1374 ----------------------------
1375 -- Analyze_Goto_Statement --
1376 ----------------------------
1378 procedure Analyze_Goto_Statement
(N
: Node_Id
) is
1379 Label
: constant Node_Id
:= Name
(N
);
1380 Scope_Id
: Entity_Id
;
1381 Label_Scope
: Entity_Id
;
1382 Label_Ent
: Entity_Id
;
1385 Check_SPARK_Restriction
("goto statement is not allowed", N
);
1387 -- Actual semantic checks
1389 Check_Unreachable_Code
(N
);
1390 Kill_Current_Values
(Last_Assignment_Only
=> True);
1393 Label_Ent
:= Entity
(Label
);
1395 -- Ignore previous error
1397 if Label_Ent
= Any_Id
then
1398 Check_Error_Detected
;
1401 -- We just have a label as the target of a goto
1403 elsif Ekind
(Label_Ent
) /= E_Label
then
1404 Error_Msg_N
("target of goto statement must be a label", Label
);
1407 -- Check that the target of the goto is reachable according to Ada
1408 -- scoping rules. Note: the special gotos we generate for optimizing
1409 -- local handling of exceptions would violate these rules, but we mark
1410 -- such gotos as analyzed when built, so this code is never entered.
1412 elsif not Reachable
(Label_Ent
) then
1413 Error_Msg_N
("target of goto statement is not reachable", Label
);
1417 -- Here if goto passes initial validity checks
1419 Label_Scope
:= Enclosing_Scope
(Label_Ent
);
1421 for J
in reverse 0 .. Scope_Stack
.Last
loop
1422 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
1424 if Label_Scope
= Scope_Id
1425 or else not Ekind_In
(Scope_Id
, E_Block
, E_Loop
, E_Return_Statement
)
1427 if Scope_Id
/= Label_Scope
then
1429 ("cannot exit from program unit or accept statement", N
);
1436 raise Program_Error
;
1437 end Analyze_Goto_Statement
;
1439 --------------------------
1440 -- Analyze_If_Statement --
1441 --------------------------
1443 -- A special complication arises in the analysis of if statements
1445 -- The expander has circuitry to completely delete code that it can tell
1446 -- will not be executed (as a result of compile time known conditions). In
1447 -- the analyzer, we ensure that code that will be deleted in this manner
1448 -- is analyzed but not expanded. This is obviously more efficient, but
1449 -- more significantly, difficulties arise if code is expanded and then
1450 -- eliminated (e.g. exception table entries disappear). Similarly, itypes
1451 -- generated in deleted code must be frozen from start, because the nodes
1452 -- on which they depend will not be available at the freeze point.
1454 procedure Analyze_If_Statement
(N
: Node_Id
) is
1457 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
1458 -- Recursively save value of this global, will be restored on exit
1460 Save_In_Deleted_Code
: Boolean;
1462 Del
: Boolean := False;
1463 -- This flag gets set True if a True condition has been found, which
1464 -- means that remaining ELSE/ELSIF parts are deleted.
1466 procedure Analyze_Cond_Then
(Cnode
: Node_Id
);
1467 -- This is applied to either the N_If_Statement node itself or to an
1468 -- N_Elsif_Part node. It deals with analyzing the condition and the THEN
1469 -- statements associated with it.
1471 -----------------------
1472 -- Analyze_Cond_Then --
1473 -----------------------
1475 procedure Analyze_Cond_Then
(Cnode
: Node_Id
) is
1476 Cond
: constant Node_Id
:= Condition
(Cnode
);
1477 Tstm
: constant List_Id
:= Then_Statements
(Cnode
);
1480 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
1481 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1482 Check_Unset_Reference
(Cond
);
1483 Set_Current_Value_Condition
(Cnode
);
1485 -- If already deleting, then just analyze then statements
1488 Analyze_Statements
(Tstm
);
1490 -- Compile time known value, not deleting yet
1492 elsif Compile_Time_Known_Value
(Cond
) then
1493 Save_In_Deleted_Code
:= In_Deleted_Code
;
1495 -- If condition is True, then analyze the THEN statements and set
1496 -- no expansion for ELSE and ELSIF parts.
1498 if Is_True
(Expr_Value
(Cond
)) then
1499 Analyze_Statements
(Tstm
);
1501 Expander_Mode_Save_And_Set
(False);
1502 In_Deleted_Code
:= True;
1504 -- If condition is False, analyze THEN with expansion off
1506 else -- Is_False (Expr_Value (Cond))
1507 Expander_Mode_Save_And_Set
(False);
1508 In_Deleted_Code
:= True;
1509 Analyze_Statements
(Tstm
);
1510 Expander_Mode_Restore
;
1511 In_Deleted_Code
:= Save_In_Deleted_Code
;
1514 -- Not known at compile time, not deleting, normal analysis
1517 Analyze_Statements
(Tstm
);
1519 end Analyze_Cond_Then
;
1521 -- Start of Analyze_If_Statement
1524 -- Initialize exit count for else statements. If there is no else part,
1525 -- this count will stay non-zero reflecting the fact that the uncovered
1526 -- else case is an unblocked exit.
1528 Unblocked_Exit_Count
:= 1;
1529 Analyze_Cond_Then
(N
);
1531 -- Now to analyze the elsif parts if any are present
1533 if Present
(Elsif_Parts
(N
)) then
1534 E
:= First
(Elsif_Parts
(N
));
1535 while Present
(E
) loop
1536 Analyze_Cond_Then
(E
);
1541 if Present
(Else_Statements
(N
)) then
1542 Analyze_Statements
(Else_Statements
(N
));
1545 -- If all our exits were blocked by unconditional transfers of control,
1546 -- then the entire IF statement acts as an unconditional transfer of
1547 -- control, so treat it like one, and check unreachable code.
1549 if Unblocked_Exit_Count
= 0 then
1550 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1551 Check_Unreachable_Code
(N
);
1553 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1557 Expander_Mode_Restore
;
1558 In_Deleted_Code
:= Save_In_Deleted_Code
;
1561 if not Expander_Active
1562 and then Compile_Time_Known_Value
(Condition
(N
))
1563 and then Serious_Errors_Detected
= 0
1565 if Is_True
(Expr_Value
(Condition
(N
))) then
1566 Remove_Warning_Messages
(Else_Statements
(N
));
1568 if Present
(Elsif_Parts
(N
)) then
1569 E
:= First
(Elsif_Parts
(N
));
1570 while Present
(E
) loop
1571 Remove_Warning_Messages
(Then_Statements
(E
));
1577 Remove_Warning_Messages
(Then_Statements
(N
));
1581 -- Warn on redundant if statement that has no effect
1583 -- Note, we could also check empty ELSIF parts ???
1585 if Warn_On_Redundant_Constructs
1587 -- If statement must be from source
1589 and then Comes_From_Source
(N
)
1591 -- Condition must not have obvious side effect
1593 and then Has_No_Obvious_Side_Effects
(Condition
(N
))
1595 -- No elsif parts of else part
1597 and then No
(Elsif_Parts
(N
))
1598 and then No
(Else_Statements
(N
))
1600 -- Then must be a single null statement
1602 and then List_Length
(Then_Statements
(N
)) = 1
1604 -- Go to original node, since we may have rewritten something as
1605 -- a null statement (e.g. a case we could figure the outcome of).
1608 T
: constant Node_Id
:= First
(Then_Statements
(N
));
1609 S
: constant Node_Id
:= Original_Node
(T
);
1612 if Comes_From_Source
(S
) and then Nkind
(S
) = N_Null_Statement
then
1613 Error_Msg_N
("if statement has no effect?r?", N
);
1617 end Analyze_If_Statement
;
1619 ----------------------------------------
1620 -- Analyze_Implicit_Label_Declaration --
1621 ----------------------------------------
1623 -- An implicit label declaration is generated in the innermost enclosing
1624 -- declarative part. This is done for labels, and block and loop names.
1626 -- Note: any changes in this routine may need to be reflected in
1627 -- Analyze_Label_Entity.
1629 procedure Analyze_Implicit_Label_Declaration
(N
: Node_Id
) is
1630 Id
: constant Node_Id
:= Defining_Identifier
(N
);
1633 Set_Ekind
(Id
, E_Label
);
1634 Set_Etype
(Id
, Standard_Void_Type
);
1635 Set_Enclosing_Scope
(Id
, Current_Scope
);
1636 end Analyze_Implicit_Label_Declaration
;
1638 ------------------------------
1639 -- Analyze_Iteration_Scheme --
1640 ------------------------------
1642 procedure Analyze_Iteration_Scheme
(N
: Node_Id
) is
1644 Iter_Spec
: Node_Id
;
1645 Loop_Spec
: Node_Id
;
1648 -- For an infinite loop, there is no iteration scheme
1654 Cond
:= Condition
(N
);
1655 Iter_Spec
:= Iterator_Specification
(N
);
1656 Loop_Spec
:= Loop_Parameter_Specification
(N
);
1658 if Present
(Cond
) then
1659 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1660 Check_Unset_Reference
(Cond
);
1661 Set_Current_Value_Condition
(N
);
1663 elsif Present
(Iter_Spec
) then
1664 Analyze_Iterator_Specification
(Iter_Spec
);
1667 Analyze_Loop_Parameter_Specification
(Loop_Spec
);
1669 end Analyze_Iteration_Scheme
;
1671 ------------------------------------
1672 -- Analyze_Iterator_Specification --
1673 ------------------------------------
1675 procedure Analyze_Iterator_Specification
(N
: Node_Id
) is
1676 Loc
: constant Source_Ptr
:= Sloc
(N
);
1677 Def_Id
: constant Node_Id
:= Defining_Identifier
(N
);
1678 Subt
: constant Node_Id
:= Subtype_Indication
(N
);
1679 Iter_Name
: constant Node_Id
:= Name
(N
);
1685 Enter_Name
(Def_Id
);
1687 if Present
(Subt
) then
1691 Preanalyze_Range
(Iter_Name
);
1693 -- Set the kind of the loop variable, which is not visible within
1694 -- the iterator name.
1696 Set_Ekind
(Def_Id
, E_Variable
);
1698 -- If the domain of iteration is an expression, create a declaration for
1699 -- it, so that finalization actions are introduced outside of the loop.
1700 -- The declaration must be a renaming because the body of the loop may
1701 -- assign to elements.
1703 if not Is_Entity_Name
(Iter_Name
)
1705 -- When the context is a quantified expression, the renaming
1706 -- declaration is delayed until the expansion phase if we are
1709 and then (Nkind
(Parent
(N
)) /= N_Quantified_Expression
1710 or else Operating_Mode
= Check_Semantics
)
1712 -- Do not perform this expansion in SPARK mode, since the formal
1713 -- verification directly deals with the source form of the iterator.
1715 and then not SPARK_Mode
1718 Id
: constant Entity_Id
:= Make_Temporary
(Loc
, 'R', Iter_Name
);
1722 Typ
:= Etype
(Iter_Name
);
1724 -- Protect against malformed iterator
1726 if Typ
= Any_Type
then
1727 Error_Msg_N
("invalid expression in loop iterator", Iter_Name
);
1731 -- The name in the renaming declaration may be a function call.
1732 -- Indicate that it does not come from source, to suppress
1733 -- spurious warnings on renamings of parameterless functions,
1734 -- a common enough idiom in user-defined iterators.
1737 Make_Object_Renaming_Declaration
(Loc
,
1738 Defining_Identifier
=> Id
,
1739 Subtype_Mark
=> New_Occurrence_Of
(Typ
, Loc
),
1741 New_Copy_Tree
(Iter_Name
, New_Sloc
=> Loc
));
1743 Insert_Actions
(Parent
(Parent
(N
)), New_List
(Decl
));
1744 Rewrite
(Name
(N
), New_Occurrence_Of
(Id
, Loc
));
1745 Set_Etype
(Id
, Typ
);
1746 Set_Etype
(Name
(N
), Typ
);
1749 -- Container is an entity or an array with uncontrolled components, or
1750 -- else it is a container iterator given by a function call, typically
1751 -- called Iterate in the case of predefined containers, even though
1752 -- Iterate is not a reserved name. What matters is that the return type
1753 -- of the function is an iterator type.
1755 elsif Is_Entity_Name
(Iter_Name
) then
1756 Analyze
(Iter_Name
);
1758 if Nkind
(Iter_Name
) = N_Function_Call
then
1760 C
: constant Node_Id
:= Name
(Iter_Name
);
1765 if not Is_Overloaded
(Iter_Name
) then
1766 Resolve
(Iter_Name
, Etype
(C
));
1769 Get_First_Interp
(C
, I
, It
);
1770 while It
.Typ
/= Empty
loop
1771 if Reverse_Present
(N
) then
1772 if Is_Reversible_Iterator
(It
.Typ
) then
1773 Resolve
(Iter_Name
, It
.Typ
);
1777 elsif Is_Iterator
(It
.Typ
) then
1778 Resolve
(Iter_Name
, It
.Typ
);
1782 Get_Next_Interp
(I
, It
);
1787 -- Domain of iteration is not overloaded
1790 Resolve
(Iter_Name
, Etype
(Iter_Name
));
1794 Typ
:= Etype
(Iter_Name
);
1796 if Is_Array_Type
(Typ
) then
1797 if Of_Present
(N
) then
1798 Set_Etype
(Def_Id
, Component_Type
(Typ
));
1800 -- Here we have a missing Range attribute
1804 ("missing Range attribute in iteration over an array", N
);
1806 -- In Ada 2012 mode, this may be an attempt at an iterator
1808 if Ada_Version
>= Ada_2012
then
1810 ("\if& is meant to designate an element of the array, use OF",
1814 -- Prevent cascaded errors
1816 Set_Ekind
(Def_Id
, E_Loop_Parameter
);
1817 Set_Etype
(Def_Id
, Etype
(First_Index
(Typ
)));
1820 -- Check for type error in iterator
1822 elsif Typ
= Any_Type
then
1825 -- Iteration over a container
1828 Set_Ekind
(Def_Id
, E_Loop_Parameter
);
1830 if Of_Present
(N
) then
1832 -- The type of the loop variable is the Iterator_Element aspect of
1833 -- the container type.
1836 Element
: constant Entity_Id
:=
1837 Find_Value_Of_Aspect
(Typ
, Aspect_Iterator_Element
);
1839 if No
(Element
) then
1840 Error_Msg_NE
("cannot iterate over&", N
, Typ
);
1843 Set_Etype
(Def_Id
, Entity
(Element
));
1845 -- If the container has a variable indexing aspect, the
1846 -- element is a variable and is modifiable in the loop.
1848 if Has_Aspect
(Typ
, Aspect_Variable_Indexing
) then
1849 Set_Ekind
(Def_Id
, E_Variable
);
1855 -- For an iteration of the form IN, the name must denote an
1856 -- iterator, typically the result of a call to Iterate. Give a
1857 -- useful error message when the name is a container by itself.
1859 if Is_Entity_Name
(Original_Node
(Name
(N
)))
1860 and then not Is_Iterator
(Typ
)
1862 if not Has_Aspect
(Typ
, Aspect_Iterator_Element
) then
1864 ("cannot iterate over&", Name
(N
), Typ
);
1867 ("name must be an iterator, not a container", Name
(N
));
1871 ("\to iterate directly over the elements of a container, " &
1872 "write `of &`", Name
(N
), Original_Node
(Name
(N
)));
1875 -- The result type of Iterate function is the classwide type of
1876 -- the interface parent. We need the specific Cursor type defined
1877 -- in the container package.
1879 Ent
:= First_Entity
(Scope
(Typ
));
1880 while Present
(Ent
) loop
1881 if Chars
(Ent
) = Name_Cursor
then
1882 Set_Etype
(Def_Id
, Etype
(Ent
));
1890 end Analyze_Iterator_Specification
;
1896 -- Note: the semantic work required for analyzing labels (setting them as
1897 -- reachable) was done in a prepass through the statements in the block,
1898 -- so that forward gotos would be properly handled. See Analyze_Statements
1899 -- for further details. The only processing required here is to deal with
1900 -- optimizations that depend on an assumption of sequential control flow,
1901 -- since of course the occurrence of a label breaks this assumption.
1903 procedure Analyze_Label
(N
: Node_Id
) is
1904 pragma Warnings
(Off
, N
);
1906 Kill_Current_Values
;
1909 --------------------------
1910 -- Analyze_Label_Entity --
1911 --------------------------
1913 procedure Analyze_Label_Entity
(E
: Entity_Id
) is
1915 Set_Ekind
(E
, E_Label
);
1916 Set_Etype
(E
, Standard_Void_Type
);
1917 Set_Enclosing_Scope
(E
, Current_Scope
);
1918 Set_Reachable
(E
, True);
1919 end Analyze_Label_Entity
;
1921 ------------------------------------------
1922 -- Analyze_Loop_Parameter_Specification --
1923 ------------------------------------------
1925 procedure Analyze_Loop_Parameter_Specification
(N
: Node_Id
) is
1926 Loop_Nod
: constant Node_Id
:= Parent
(Parent
(N
));
1928 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
);
1929 -- If the bounds are given by a 'Range reference on a function call
1930 -- that returns a controlled array, introduce an explicit declaration
1931 -- to capture the bounds, so that the function result can be finalized
1932 -- in timely fashion.
1934 function Has_Call_Using_Secondary_Stack
(N
: Node_Id
) return Boolean;
1935 -- N is the node for an arbitrary construct. This function searches the
1936 -- construct N to see if any expressions within it contain function
1937 -- calls that use the secondary stack, returning True if any such call
1938 -- is found, and False otherwise.
1940 procedure Process_Bounds
(R
: Node_Id
);
1941 -- If the iteration is given by a range, create temporaries and
1942 -- assignment statements block to capture the bounds and perform
1943 -- required finalization actions in case a bound includes a function
1944 -- call that uses the temporary stack. We first pre-analyze a copy of
1945 -- the range in order to determine the expected type, and analyze and
1946 -- resolve the original bounds.
1948 --------------------------------------
1949 -- Check_Controlled_Array_Attribute --
1950 --------------------------------------
1952 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
) is
1954 if Nkind
(DS
) = N_Attribute_Reference
1955 and then Is_Entity_Name
(Prefix
(DS
))
1956 and then Ekind
(Entity
(Prefix
(DS
))) = E_Function
1957 and then Is_Array_Type
(Etype
(Entity
(Prefix
(DS
))))
1959 Is_Controlled
(Component_Type
(Etype
(Entity
(Prefix
(DS
)))))
1960 and then Expander_Active
1963 Loc
: constant Source_Ptr
:= Sloc
(N
);
1964 Arr
: constant Entity_Id
:= Etype
(Entity
(Prefix
(DS
)));
1965 Indx
: constant Entity_Id
:=
1966 Base_Type
(Etype
(First_Index
(Arr
)));
1967 Subt
: constant Entity_Id
:= Make_Temporary
(Loc
, 'S');
1972 Make_Subtype_Declaration
(Loc
,
1973 Defining_Identifier
=> Subt
,
1974 Subtype_Indication
=>
1975 Make_Subtype_Indication
(Loc
,
1976 Subtype_Mark
=> New_Reference_To
(Indx
, Loc
),
1978 Make_Range_Constraint
(Loc
, Relocate_Node
(DS
))));
1979 Insert_Before
(Loop_Nod
, Decl
);
1983 Make_Attribute_Reference
(Loc
,
1984 Prefix
=> New_Reference_To
(Subt
, Loc
),
1985 Attribute_Name
=> Attribute_Name
(DS
)));
1990 end Check_Controlled_Array_Attribute
;
1992 ------------------------------------
1993 -- Has_Call_Using_Secondary_Stack --
1994 ------------------------------------
1996 function Has_Call_Using_Secondary_Stack
(N
: Node_Id
) return Boolean is
1998 function Check_Call
(N
: Node_Id
) return Traverse_Result
;
1999 -- Check if N is a function call which uses the secondary stack
2005 function Check_Call
(N
: Node_Id
) return Traverse_Result
is
2008 Return_Typ
: Entity_Id
;
2011 if Nkind
(N
) = N_Function_Call
then
2014 -- Call using access to subprogram with explicit dereference
2016 if Nkind
(Nam
) = N_Explicit_Dereference
then
2017 Subp
:= Etype
(Nam
);
2019 -- Call using a selected component notation or Ada 2005 object
2020 -- operation notation
2022 elsif Nkind
(Nam
) = N_Selected_Component
then
2023 Subp
:= Entity
(Selector_Name
(Nam
));
2028 Subp
:= Entity
(Nam
);
2031 Return_Typ
:= Etype
(Subp
);
2033 if Is_Composite_Type
(Return_Typ
)
2034 and then not Is_Constrained
(Return_Typ
)
2038 elsif Sec_Stack_Needed_For_Return
(Subp
) then
2043 -- Continue traversing the tree
2048 function Check_Calls
is new Traverse_Func
(Check_Call
);
2050 -- Start of processing for Has_Call_Using_Secondary_Stack
2053 return Check_Calls
(N
) = Abandon
;
2054 end Has_Call_Using_Secondary_Stack
;
2056 --------------------
2057 -- Process_Bounds --
2058 --------------------
2060 procedure Process_Bounds
(R
: Node_Id
) is
2061 Loc
: constant Source_Ptr
:= Sloc
(N
);
2064 (Original_Bound
: Node_Id
;
2065 Analyzed_Bound
: Node_Id
;
2066 Typ
: Entity_Id
) return Node_Id
;
2067 -- Capture value of bound and return captured value
2074 (Original_Bound
: Node_Id
;
2075 Analyzed_Bound
: Node_Id
;
2076 Typ
: Entity_Id
) return Node_Id
2083 -- If the bound is a constant or an object, no need for a separate
2084 -- declaration. If the bound is the result of previous expansion
2085 -- it is already analyzed and should not be modified. Note that
2086 -- the Bound will be resolved later, if needed, as part of the
2087 -- call to Make_Index (literal bounds may need to be resolved to
2090 if Analyzed
(Original_Bound
) then
2091 return Original_Bound
;
2093 elsif Nkind_In
(Analyzed_Bound
, N_Integer_Literal
,
2094 N_Character_Literal
)
2095 or else Is_Entity_Name
(Analyzed_Bound
)
2097 Analyze_And_Resolve
(Original_Bound
, Typ
);
2098 return Original_Bound
;
2101 -- Normally, the best approach is simply to generate a constant
2102 -- declaration that captures the bound. However, there is a nasty
2103 -- case where this is wrong. If the bound is complex, and has a
2104 -- possible use of the secondary stack, we need to generate a
2105 -- separate assignment statement to ensure the creation of a block
2106 -- which will release the secondary stack.
2108 -- We prefer the constant declaration, since it leaves us with a
2109 -- proper trace of the value, useful in optimizations that get rid
2110 -- of junk range checks.
2112 if not Has_Call_Using_Secondary_Stack
(Analyzed_Bound
) then
2113 Analyze_And_Resolve
(Original_Bound
, Typ
);
2114 Force_Evaluation
(Original_Bound
);
2115 return Original_Bound
;
2118 Id
:= Make_Temporary
(Loc
, 'R', Original_Bound
);
2120 -- Here we make a declaration with a separate assignment
2121 -- statement, and insert before loop header.
2124 Make_Object_Declaration
(Loc
,
2125 Defining_Identifier
=> Id
,
2126 Object_Definition
=> New_Occurrence_Of
(Typ
, Loc
));
2129 Make_Assignment_Statement
(Loc
,
2130 Name
=> New_Occurrence_Of
(Id
, Loc
),
2131 Expression
=> Relocate_Node
(Original_Bound
));
2133 Insert_Actions
(Loop_Nod
, New_List
(Decl
, Assign
));
2135 -- Now that this temporary variable is initialized we decorate it
2136 -- as safe-to-reevaluate to inform to the backend that no further
2137 -- asignment will be issued and hence it can be handled as side
2138 -- effect free. Note that this decoration must be done when the
2139 -- assignment has been analyzed because otherwise it will be
2140 -- rejected (see Analyze_Assignment).
2142 Set_Is_Safe_To_Reevaluate
(Id
);
2144 Rewrite
(Original_Bound
, New_Occurrence_Of
(Id
, Loc
));
2146 if Nkind
(Assign
) = N_Assignment_Statement
then
2147 return Expression
(Assign
);
2149 return Original_Bound
;
2153 Hi
: constant Node_Id
:= High_Bound
(R
);
2154 Lo
: constant Node_Id
:= Low_Bound
(R
);
2155 R_Copy
: constant Node_Id
:= New_Copy_Tree
(R
);
2160 -- Start of processing for Process_Bounds
2163 Set_Parent
(R_Copy
, Parent
(R
));
2164 Preanalyze_Range
(R_Copy
);
2165 Typ
:= Etype
(R_Copy
);
2167 -- If the type of the discrete range is Universal_Integer, then the
2168 -- bound's type must be resolved to Integer, and any object used to
2169 -- hold the bound must also have type Integer, unless the literal
2170 -- bounds are constant-folded expressions with a user-defined type.
2172 if Typ
= Universal_Integer
then
2173 if Nkind
(Lo
) = N_Integer_Literal
2174 and then Present
(Etype
(Lo
))
2175 and then Scope
(Etype
(Lo
)) /= Standard_Standard
2179 elsif Nkind
(Hi
) = N_Integer_Literal
2180 and then Present
(Etype
(Hi
))
2181 and then Scope
(Etype
(Hi
)) /= Standard_Standard
2186 Typ
:= Standard_Integer
;
2192 New_Lo
:= One_Bound
(Lo
, Low_Bound
(R_Copy
), Typ
);
2193 New_Hi
:= One_Bound
(Hi
, High_Bound
(R_Copy
), Typ
);
2195 -- Propagate staticness to loop range itself, in case the
2196 -- corresponding subtype is static.
2198 if New_Lo
/= Lo
and then Is_Static_Expression
(New_Lo
) then
2199 Rewrite
(Low_Bound
(R
), New_Copy
(New_Lo
));
2202 if New_Hi
/= Hi
and then Is_Static_Expression
(New_Hi
) then
2203 Rewrite
(High_Bound
(R
), New_Copy
(New_Hi
));
2209 DS
: constant Node_Id
:= Discrete_Subtype_Definition
(N
);
2210 Id
: constant Entity_Id
:= Defining_Identifier
(N
);
2214 -- Start of processing for Analyze_Loop_Parameter_Specification
2219 -- We always consider the loop variable to be referenced, since the loop
2220 -- may be used just for counting purposes.
2222 Generate_Reference
(Id
, N
, ' ');
2224 -- Check for the case of loop variable hiding a local variable (used
2225 -- later on to give a nice warning if the hidden variable is never
2229 H
: constant Entity_Id
:= Homonym
(Id
);
2232 and then Ekind
(H
) = E_Variable
2233 and then Is_Discrete_Type
(Etype
(H
))
2234 and then Enclosing_Dynamic_Scope
(H
) = Enclosing_Dynamic_Scope
(Id
)
2236 Set_Hiding_Loop_Variable
(H
, Id
);
2240 -- Loop parameter specification must include subtype mark in SPARK
2242 if Nkind
(DS
) = N_Range
then
2243 Check_SPARK_Restriction
2244 ("loop parameter specification must include subtype mark", N
);
2247 -- Analyze the subtype definition and create temporaries for the bounds.
2248 -- Do not evaluate the range when preanalyzing a quantified expression
2249 -- because bounds expressed as function calls with side effects will be
2250 -- erroneously replicated.
2252 if Nkind
(DS
) = N_Range
2253 and then Expander_Active
2254 and then Nkind
(Parent
(N
)) /= N_Quantified_Expression
2256 Process_Bounds
(DS
);
2258 -- Either the expander not active or the range of iteration is a subtype
2259 -- indication, an entity, or a function call that yields an aggregate or
2263 DS_Copy
:= New_Copy_Tree
(DS
);
2264 Set_Parent
(DS_Copy
, Parent
(DS
));
2265 Preanalyze_Range
(DS_Copy
);
2267 -- Ada 2012: If the domain of iteration is a function call, it is the
2268 -- new iterator form.
2270 if Nkind
(DS_Copy
) = N_Function_Call
2271 or else (Is_Entity_Name
(DS_Copy
)
2272 and then not Is_Type
(Entity
(DS_Copy
)))
2274 -- This is an iterator specification. Rewrite it as such and
2275 -- analyze it to capture function calls that may require
2276 -- finalization actions.
2279 I_Spec
: constant Node_Id
:=
2280 Make_Iterator_Specification
(Sloc
(N
),
2281 Defining_Identifier
=> Relocate_Node
(Id
),
2283 Subtype_Indication
=> Empty
,
2284 Reverse_Present
=> Reverse_Present
(N
));
2285 Scheme
: constant Node_Id
:= Parent
(N
);
2288 Set_Iterator_Specification
(Scheme
, I_Spec
);
2289 Set_Loop_Parameter_Specification
(Scheme
, Empty
);
2290 Analyze_Iterator_Specification
(I_Spec
);
2292 -- In a generic context, analyze the original domain of
2293 -- iteration, for name capture.
2295 if not Expander_Active
then
2299 -- Set kind of loop parameter, which may be used in the
2300 -- subsequent analysis of the condition in a quantified
2303 Set_Ekind
(Id
, E_Loop_Parameter
);
2307 -- Domain of iteration is not a function call, and is side-effect
2311 -- A quantified expression that appears in a pre/post condition
2312 -- is pre-analyzed several times. If the range is given by an
2313 -- attribute reference it is rewritten as a range, and this is
2314 -- done even with expansion disabled. If the type is already set
2315 -- do not reanalyze, because a range with static bounds may be
2316 -- typed Integer by default.
2318 if Nkind
(Parent
(N
)) = N_Quantified_Expression
2319 and then Present
(Etype
(DS
))
2332 -- Some additional checks if we are iterating through a type
2334 if Is_Entity_Name
(DS
)
2335 and then Present
(Entity
(DS
))
2336 and then Is_Type
(Entity
(DS
))
2338 -- The subtype indication may denote the completion of an incomplete
2339 -- type declaration.
2341 if Ekind
(Entity
(DS
)) = E_Incomplete_Type
then
2342 Set_Entity
(DS
, Get_Full_View
(Entity
(DS
)));
2343 Set_Etype
(DS
, Entity
(DS
));
2346 -- Attempt to iterate through non-static predicate. Note that a type
2347 -- with inherited predicates may have both static and dynamic forms.
2348 -- In this case it is not sufficent to check the static predicate
2349 -- function only, look for a dynamic predicate aspect as well.
2351 if Is_Discrete_Type
(Entity
(DS
))
2352 and then Present
(Predicate_Function
(Entity
(DS
)))
2353 and then (No
(Static_Predicate
(Entity
(DS
)))
2354 or else Has_Dynamic_Predicate_Aspect
(Entity
(DS
)))
2356 Bad_Predicated_Subtype_Use
2357 ("cannot use subtype& with non-static predicate for loop " &
2358 "iteration", DS
, Entity
(DS
), Suggest_Static
=> True);
2362 -- Error if not discrete type
2364 if not Is_Discrete_Type
(Etype
(DS
)) then
2365 Wrong_Type
(DS
, Any_Discrete
);
2366 Set_Etype
(DS
, Any_Type
);
2369 Check_Controlled_Array_Attribute
(DS
);
2371 Make_Index
(DS
, N
, In_Iter_Schm
=> True);
2372 Set_Ekind
(Id
, E_Loop_Parameter
);
2374 -- A quantified expression which appears in a pre- or post-condition may
2375 -- be analyzed multiple times. The analysis of the range creates several
2376 -- itypes which reside in different scopes depending on whether the pre-
2377 -- or post-condition has been expanded. Update the type of the loop
2378 -- variable to reflect the proper itype at each stage of analysis.
2381 or else Etype
(Id
) = Any_Type
2383 (Present
(Etype
(Id
))
2384 and then Is_Itype
(Etype
(Id
))
2385 and then Nkind
(Parent
(Loop_Nod
)) = N_Expression_With_Actions
2386 and then Nkind
(Original_Node
(Parent
(Loop_Nod
))) =
2387 N_Quantified_Expression
)
2389 Set_Etype
(Id
, Etype
(DS
));
2392 -- Treat a range as an implicit reference to the type, to inhibit
2393 -- spurious warnings.
2395 Generate_Reference
(Base_Type
(Etype
(DS
)), N
, ' ');
2396 Set_Is_Known_Valid
(Id
, True);
2398 -- The loop is not a declarative part, so the loop variable must be
2399 -- frozen explicitly. Do not freeze while preanalyzing a quantified
2400 -- expression because the freeze node will not be inserted into the
2401 -- tree due to flag Is_Spec_Expression being set.
2403 if Nkind
(Parent
(N
)) /= N_Quantified_Expression
then
2405 Flist
: constant List_Id
:= Freeze_Entity
(Id
, N
);
2407 if Is_Non_Empty_List
(Flist
) then
2408 Insert_Actions
(N
, Flist
);
2413 -- Check for null or possibly null range and issue warning. We suppress
2414 -- such messages in generic templates and instances, because in practice
2415 -- they tend to be dubious in these cases.
2417 if Nkind
(DS
) = N_Range
and then Comes_From_Source
(N
) then
2419 L
: constant Node_Id
:= Low_Bound
(DS
);
2420 H
: constant Node_Id
:= High_Bound
(DS
);
2423 -- If range of loop is null, issue warning
2425 if Compile_Time_Compare
(L
, H
, Assume_Valid
=> True) = GT
then
2427 -- Suppress the warning if inside a generic template or
2428 -- instance, since in practice they tend to be dubious in these
2429 -- cases since they can result from intended parametrization.
2431 if not Inside_A_Generic
and then not In_Instance
then
2433 -- Specialize msg if invalid values could make the loop
2434 -- non-null after all.
2436 if Compile_Time_Compare
2437 (L
, H
, Assume_Valid
=> False) = GT
2440 ("??loop range is null, loop will not execute", DS
);
2442 -- Since we know the range of the loop is null, set the
2443 -- appropriate flag to remove the loop entirely during
2446 Set_Is_Null_Loop
(Loop_Nod
);
2448 -- Here is where the loop could execute because of invalid
2449 -- values, so issue appropriate message and in this case we
2450 -- do not set the Is_Null_Loop flag since the loop may
2455 ("??loop range may be null, loop may not execute",
2458 ("??can only execute if invalid values are present",
2463 -- In either case, suppress warnings in the body of the loop,
2464 -- since it is likely that these warnings will be inappropriate
2465 -- if the loop never actually executes, which is likely.
2467 Set_Suppress_Loop_Warnings
(Loop_Nod
);
2469 -- The other case for a warning is a reverse loop where the
2470 -- upper bound is the integer literal zero or one, and the
2471 -- lower bound may exceed this value.
2473 -- For example, we have
2475 -- for J in reverse N .. 1 loop
2477 -- In practice, this is very likely to be a case of reversing
2478 -- the bounds incorrectly in the range.
2480 elsif Reverse_Present
(N
)
2481 and then Nkind
(Original_Node
(H
)) = N_Integer_Literal
2483 (Intval
(Original_Node
(H
)) = Uint_0
2485 Intval
(Original_Node
(H
)) = Uint_1
)
2487 -- Lower bound may in fact be known and known not to exceed
2488 -- upper bound (e.g. reverse 0 .. 1) and that's OK.
2490 if Compile_Time_Known_Value
(L
)
2491 and then Expr_Value
(L
) <= Expr_Value
(H
)
2495 -- Otherwise warning is warranted
2498 Error_Msg_N
("??loop range may be null", DS
);
2499 Error_Msg_N
("\??bounds may be wrong way round", DS
);
2504 end Analyze_Loop_Parameter_Specification
;
2506 ----------------------------
2507 -- Analyze_Loop_Statement --
2508 ----------------------------
2510 procedure Analyze_Loop_Statement
(N
: Node_Id
) is
2512 function Is_Container_Iterator
(Iter
: Node_Id
) return Boolean;
2513 -- Given a loop iteration scheme, determine whether it is an Ada 2012
2514 -- container iteration.
2516 function Is_Wrapped_In_Block
(N
: Node_Id
) return Boolean;
2517 -- Determine whether node N is the sole statement of a block
2519 ---------------------------
2520 -- Is_Container_Iterator --
2521 ---------------------------
2523 function Is_Container_Iterator
(Iter
: Node_Id
) return Boolean is
2532 elsif Present
(Condition
(Iter
)) then
2535 -- for Def_Id in [reverse] Name loop
2536 -- for Def_Id [: Subtype_Indication] of [reverse] Name loop
2538 elsif Present
(Iterator_Specification
(Iter
)) then
2540 Nam
: constant Node_Id
:= Name
(Iterator_Specification
(Iter
));
2544 Nam_Copy
:= New_Copy_Tree
(Nam
);
2545 Set_Parent
(Nam_Copy
, Parent
(Nam
));
2546 Preanalyze_Range
(Nam_Copy
);
2548 -- The only two options here are iteration over a container or
2551 return not Is_Array_Type
(Etype
(Nam_Copy
));
2554 -- for Def_Id in [reverse] Discrete_Subtype_Definition loop
2558 LP
: constant Node_Id
:= Loop_Parameter_Specification
(Iter
);
2559 DS
: constant Node_Id
:= Discrete_Subtype_Definition
(LP
);
2563 DS_Copy
:= New_Copy_Tree
(DS
);
2564 Set_Parent
(DS_Copy
, Parent
(DS
));
2565 Preanalyze_Range
(DS_Copy
);
2567 -- Check for a call to Iterate ()
2570 Nkind
(DS_Copy
) = N_Function_Call
2571 and then Needs_Finalization
(Etype
(DS_Copy
));
2574 end Is_Container_Iterator
;
2576 -------------------------
2577 -- Is_Wrapped_In_Block --
2578 -------------------------
2580 function Is_Wrapped_In_Block
(N
: Node_Id
) return Boolean is
2581 HSS
: constant Node_Id
:= Parent
(N
);
2585 Nkind
(HSS
) = N_Handled_Sequence_Of_Statements
2586 and then Nkind
(Parent
(HSS
)) = N_Block_Statement
2587 and then First
(Statements
(HSS
)) = N
2588 and then No
(Next
(First
(Statements
(HSS
))));
2589 end Is_Wrapped_In_Block
;
2591 -- Local declarations
2593 Id
: constant Node_Id
:= Identifier
(N
);
2594 Iter
: constant Node_Id
:= Iteration_Scheme
(N
);
2595 Loc
: constant Source_Ptr
:= Sloc
(N
);
2599 -- Start of processing for Analyze_Loop_Statement
2602 if Present
(Id
) then
2604 -- Make name visible, e.g. for use in exit statements. Loop labels
2605 -- are always considered to be referenced.
2610 -- Guard against serious error (typically, a scope mismatch when
2611 -- semantic analysis is requested) by creating loop entity to
2612 -- continue analysis.
2615 if Total_Errors_Detected
/= 0 then
2616 Ent
:= New_Internal_Entity
(E_Loop
, Current_Scope
, Loc
, 'L');
2618 raise Program_Error
;
2622 Generate_Reference
(Ent
, N
, ' ');
2623 Generate_Definition
(Ent
);
2625 -- If we found a label, mark its type. If not, ignore it, since it
2626 -- means we have a conflicting declaration, which would already
2627 -- have been diagnosed at declaration time. Set Label_Construct
2628 -- of the implicit label declaration, which is not created by the
2629 -- parser for generic units.
2631 if Ekind
(Ent
) = E_Label
then
2632 Set_Ekind
(Ent
, E_Loop
);
2634 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
2635 Set_Label_Construct
(Parent
(Ent
), N
);
2640 -- Case of no identifier present
2643 Ent
:= New_Internal_Entity
(E_Loop
, Current_Scope
, Loc
, 'L');
2644 Set_Etype
(Ent
, Standard_Void_Type
);
2645 Set_Parent
(Ent
, N
);
2648 -- Iteration over a container in Ada 2012 involves the creation of a
2649 -- controlled iterator object. Wrap the loop in a block to ensure the
2650 -- timely finalization of the iterator and release of container locks.
2652 if Ada_Version
>= Ada_2012
2653 and then Is_Container_Iterator
(Iter
)
2654 and then not Is_Wrapped_In_Block
(N
)
2657 Make_Block_Statement
(Loc
,
2658 Declarations
=> New_List
,
2659 Handled_Statement_Sequence
=>
2660 Make_Handled_Sequence_Of_Statements
(Loc
,
2661 Statements
=> New_List
(Relocate_Node
(N
)))));
2667 -- Kill current values on entry to loop, since statements in the body of
2668 -- the loop may have been executed before the loop is entered. Similarly
2669 -- we kill values after the loop, since we do not know that the body of
2670 -- the loop was executed.
2672 Kill_Current_Values
;
2674 Analyze_Iteration_Scheme
(Iter
);
2676 -- Check for following case which merits a warning if the type E of is
2677 -- a multi-dimensional array (and no explicit subscript ranges present).
2683 and then Present
(Loop_Parameter_Specification
(Iter
))
2686 LPS
: constant Node_Id
:= Loop_Parameter_Specification
(Iter
);
2687 DSD
: constant Node_Id
:=
2688 Original_Node
(Discrete_Subtype_Definition
(LPS
));
2690 if Nkind
(DSD
) = N_Attribute_Reference
2691 and then Attribute_Name
(DSD
) = Name_Range
2692 and then No
(Expressions
(DSD
))
2695 Typ
: constant Entity_Id
:= Etype
(Prefix
(DSD
));
2697 if Is_Array_Type
(Typ
)
2698 and then Number_Dimensions
(Typ
) > 1
2699 and then Nkind
(Parent
(N
)) = N_Loop_Statement
2700 and then Present
(Iteration_Scheme
(Parent
(N
)))
2703 OIter
: constant Node_Id
:=
2704 Iteration_Scheme
(Parent
(N
));
2705 OLPS
: constant Node_Id
:=
2706 Loop_Parameter_Specification
(OIter
);
2707 ODSD
: constant Node_Id
:=
2708 Original_Node
(Discrete_Subtype_Definition
(OLPS
));
2710 if Nkind
(ODSD
) = N_Attribute_Reference
2711 and then Attribute_Name
(ODSD
) = Name_Range
2712 and then No
(Expressions
(ODSD
))
2713 and then Etype
(Prefix
(ODSD
)) = Typ
2715 Error_Msg_Sloc
:= Sloc
(ODSD
);
2717 ("inner range same as outer range#??", DSD
);
2726 -- Analyze the statements of the body except in the case of an Ada 2012
2727 -- iterator with the expander active. In this case the expander will do
2728 -- a rewrite of the loop into a while loop. We will then analyze the
2729 -- loop body when we analyze this while loop.
2731 -- We need to do this delay because if the container is for indefinite
2732 -- types the actual subtype of the components will only be determined
2733 -- when the cursor declaration is analyzed.
2735 -- If the expander is not active, or in SPARK mode, then we want to
2736 -- analyze the loop body now even in the Ada 2012 iterator case, since
2737 -- the rewriting will not be done. Insert the loop variable in the
2738 -- current scope, if not done when analysing the iteration scheme.
2741 or else No
(Iterator_Specification
(Iter
))
2742 or else not Full_Expander_Active
2745 and then Present
(Iterator_Specification
(Iter
))
2748 Id
: constant Entity_Id
:=
2749 Defining_Identifier
(Iterator_Specification
(Iter
));
2751 if Scope
(Id
) /= Current_Scope
then
2757 Analyze_Statements
(Statements
(N
));
2760 -- When the iteration scheme of a loop contains attribute 'Loop_Entry,
2761 -- the loop is transformed into a conditional block. Retrieve the loop.
2765 if Subject_To_Loop_Entry_Attributes
(Stmt
) then
2766 Stmt
:= Find_Loop_In_Conditional_Block
(Stmt
);
2769 -- Finish up processing for the loop. We kill all current values, since
2770 -- in general we don't know if the statements in the loop have been
2771 -- executed. We could do a bit better than this with a loop that we
2772 -- know will execute at least once, but it's not worth the trouble and
2773 -- the front end is not in the business of flow tracing.
2775 Process_End_Label
(Stmt
, 'e', Ent
);
2777 Kill_Current_Values
;
2779 -- Check for infinite loop. Skip check for generated code, since it
2780 -- justs waste time and makes debugging the routine called harder.
2782 -- Note that we have to wait till the body of the loop is fully analyzed
2783 -- before making this call, since Check_Infinite_Loop_Warning relies on
2784 -- being able to use semantic visibility information to find references.
2786 if Comes_From_Source
(Stmt
) then
2787 Check_Infinite_Loop_Warning
(Stmt
);
2790 -- Code after loop is unreachable if the loop has no WHILE or FOR and
2791 -- contains no EXIT statements within the body of the loop.
2793 if No
(Iter
) and then not Has_Exit
(Ent
) then
2794 Check_Unreachable_Code
(Stmt
);
2796 end Analyze_Loop_Statement
;
2798 ----------------------------
2799 -- Analyze_Null_Statement --
2800 ----------------------------
2802 -- Note: the semantics of the null statement is implemented by a single
2803 -- null statement, too bad everything isn't as simple as this!
2805 procedure Analyze_Null_Statement
(N
: Node_Id
) is
2806 pragma Warnings
(Off
, N
);
2809 end Analyze_Null_Statement
;
2811 ------------------------
2812 -- Analyze_Statements --
2813 ------------------------
2815 procedure Analyze_Statements
(L
: List_Id
) is
2820 -- The labels declared in the statement list are reachable from
2821 -- statements in the list. We do this as a prepass so that any goto
2822 -- statement will be properly flagged if its target is not reachable.
2823 -- This is not required, but is nice behavior!
2826 while Present
(S
) loop
2827 if Nkind
(S
) = N_Label
then
2828 Analyze
(Identifier
(S
));
2829 Lab
:= Entity
(Identifier
(S
));
2831 -- If we found a label mark it as reachable
2833 if Ekind
(Lab
) = E_Label
then
2834 Generate_Definition
(Lab
);
2835 Set_Reachable
(Lab
);
2837 if Nkind
(Parent
(Lab
)) = N_Implicit_Label_Declaration
then
2838 Set_Label_Construct
(Parent
(Lab
), S
);
2841 -- If we failed to find a label, it means the implicit declaration
2842 -- of the label was hidden. A for-loop parameter can do this to
2843 -- a label with the same name inside the loop, since the implicit
2844 -- label declaration is in the innermost enclosing body or block
2848 Error_Msg_Sloc
:= Sloc
(Lab
);
2850 ("implicit label declaration for & is hidden#",
2858 -- Perform semantic analysis on all statements
2860 Conditional_Statements_Begin
;
2863 while Present
(S
) loop
2866 -- Remove dimension in all statements
2868 Remove_Dimension_In_Statement
(S
);
2872 Conditional_Statements_End
;
2874 -- Make labels unreachable. Visibility is not sufficient, because labels
2875 -- in one if-branch for example are not reachable from the other branch,
2876 -- even though their declarations are in the enclosing declarative part.
2879 while Present
(S
) loop
2880 if Nkind
(S
) = N_Label
then
2881 Set_Reachable
(Entity
(Identifier
(S
)), False);
2886 end Analyze_Statements
;
2888 ----------------------------
2889 -- Check_Unreachable_Code --
2890 ----------------------------
2892 procedure Check_Unreachable_Code
(N
: Node_Id
) is
2893 Error_Node
: Node_Id
;
2897 if Is_List_Member
(N
) and then Comes_From_Source
(N
) then
2902 Nxt
:= Original_Node
(Next
(N
));
2904 -- Skip past pragmas
2906 while Nkind
(Nxt
) = N_Pragma
loop
2907 Nxt
:= Original_Node
(Next
(Nxt
));
2910 -- If a label follows us, then we never have dead code, since
2911 -- someone could branch to the label, so we just ignore it, unless
2912 -- we are in formal mode where goto statements are not allowed.
2914 if Nkind
(Nxt
) = N_Label
2915 and then not Restriction_Check_Required
(SPARK_05
)
2919 -- Otherwise see if we have a real statement following us
2922 and then Comes_From_Source
(Nxt
)
2923 and then Is_Statement
(Nxt
)
2925 -- Special very annoying exception. If we have a return that
2926 -- follows a raise, then we allow it without a warning, since
2927 -- the Ada RM annoyingly requires a useless return here!
2929 if Nkind
(Original_Node
(N
)) /= N_Raise_Statement
2930 or else Nkind
(Nxt
) /= N_Simple_Return_Statement
2932 -- The rather strange shenanigans with the warning message
2933 -- here reflects the fact that Kill_Dead_Code is very good
2934 -- at removing warnings in deleted code, and this is one
2935 -- warning we would prefer NOT to have removed.
2939 -- If we have unreachable code, analyze and remove the
2940 -- unreachable code, since it is useless and we don't
2941 -- want to generate junk warnings.
2943 -- We skip this step if we are not in code generation mode.
2944 -- This is the one case where we remove dead code in the
2945 -- semantics as opposed to the expander, and we do not want
2946 -- to remove code if we are not in code generation mode,
2947 -- since this messes up the ASIS trees.
2949 -- Note that one might react by moving the whole circuit to
2950 -- exp_ch5, but then we lose the warning in -gnatc mode.
2952 if Operating_Mode
= Generate_Code
then
2956 -- Quit deleting when we have nothing more to delete
2957 -- or if we hit a label (since someone could transfer
2958 -- control to a label, so we should not delete it).
2960 exit when No
(Nxt
) or else Nkind
(Nxt
) = N_Label
;
2962 -- Statement/declaration is to be deleted
2966 Kill_Dead_Code
(Nxt
);
2970 -- Now issue the warning (or error in formal mode)
2972 if Restriction_Check_Required
(SPARK_05
) then
2973 Check_SPARK_Restriction
2974 ("unreachable code is not allowed", Error_Node
);
2976 Error_Msg
("??unreachable code!", Sloc
(Error_Node
));
2980 -- If the unconditional transfer of control instruction is the
2981 -- last statement of a sequence, then see if our parent is one of
2982 -- the constructs for which we count unblocked exits, and if so,
2983 -- adjust the count.
2988 -- Statements in THEN part or ELSE part of IF statement
2990 if Nkind
(P
) = N_If_Statement
then
2993 -- Statements in ELSIF part of an IF statement
2995 elsif Nkind
(P
) = N_Elsif_Part
then
2997 pragma Assert
(Nkind
(P
) = N_If_Statement
);
2999 -- Statements in CASE statement alternative
3001 elsif Nkind
(P
) = N_Case_Statement_Alternative
then
3003 pragma Assert
(Nkind
(P
) = N_Case_Statement
);
3005 -- Statements in body of block
3007 elsif Nkind
(P
) = N_Handled_Sequence_Of_Statements
3008 and then Nkind
(Parent
(P
)) = N_Block_Statement
3010 -- The original loop is now placed inside a block statement
3011 -- due to the expansion of attribute 'Loop_Entry. Return as
3012 -- this is not a "real" block for the purposes of exit
3015 if Nkind
(N
) = N_Loop_Statement
3016 and then Subject_To_Loop_Entry_Attributes
(N
)
3021 -- Statements in exception handler in a block
3023 elsif Nkind
(P
) = N_Exception_Handler
3024 and then Nkind
(Parent
(P
)) = N_Handled_Sequence_Of_Statements
3025 and then Nkind
(Parent
(Parent
(P
))) = N_Block_Statement
3029 -- None of these cases, so return
3035 -- This was one of the cases we are looking for (i.e. the
3036 -- parent construct was IF, CASE or block) so decrement count.
3038 Unblocked_Exit_Count
:= Unblocked_Exit_Count
- 1;
3042 end Check_Unreachable_Code
;
3044 ----------------------
3045 -- Preanalyze_Range --
3046 ----------------------
3048 procedure Preanalyze_Range
(R_Copy
: Node_Id
) is
3049 Save_Analysis
: constant Boolean := Full_Analysis
;
3053 Full_Analysis
:= False;
3054 Expander_Mode_Save_And_Set
(False);
3058 if Nkind
(R_Copy
) in N_Subexpr
and then Is_Overloaded
(R_Copy
) then
3060 -- Apply preference rules for range of predefined integer types, or
3061 -- diagnose true ambiguity.
3066 Found
: Entity_Id
:= Empty
;
3069 Get_First_Interp
(R_Copy
, I
, It
);
3070 while Present
(It
.Typ
) loop
3071 if Is_Discrete_Type
(It
.Typ
) then
3075 if Scope
(Found
) = Standard_Standard
then
3078 elsif Scope
(It
.Typ
) = Standard_Standard
then
3082 -- Both of them are user-defined
3085 ("ambiguous bounds in range of iteration", R_Copy
);
3086 Error_Msg_N
("\possible interpretations:", R_Copy
);
3087 Error_Msg_NE
("\\} ", R_Copy
, Found
);
3088 Error_Msg_NE
("\\} ", R_Copy
, It
.Typ
);
3094 Get_Next_Interp
(I
, It
);
3099 -- Subtype mark in iteration scheme
3101 if Is_Entity_Name
(R_Copy
) and then Is_Type
(Entity
(R_Copy
)) then
3104 -- Expression in range, or Ada 2012 iterator
3106 elsif Nkind
(R_Copy
) in N_Subexpr
then
3108 Typ
:= Etype
(R_Copy
);
3110 if Is_Discrete_Type
(Typ
) then
3113 -- Check that the resulting object is an iterable container
3115 elsif Has_Aspect
(Typ
, Aspect_Iterator_Element
)
3116 or else Has_Aspect
(Typ
, Aspect_Constant_Indexing
)
3117 or else Has_Aspect
(Typ
, Aspect_Variable_Indexing
)
3121 -- The expression may yield an implicit reference to an iterable
3122 -- container. Insert explicit dereference so that proper type is
3123 -- visible in the loop.
3125 elsif Has_Implicit_Dereference
(Etype
(R_Copy
)) then
3130 Disc
:= First_Discriminant
(Typ
);
3131 while Present
(Disc
) loop
3132 if Has_Implicit_Dereference
(Disc
) then
3133 Build_Explicit_Dereference
(R_Copy
, Disc
);
3137 Next_Discriminant
(Disc
);
3144 Expander_Mode_Restore
;
3145 Full_Analysis
:= Save_Analysis
;
3146 end Preanalyze_Range
;