1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
9 -- Copyright (C) 1992-2005 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 2, 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 COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, USA. --
22 -- GNAT was originally developed by the GNAT team at New York University. --
23 -- Extensive contributions were provided by Ada Core Technologies Inc. --
25 ------------------------------------------------------------------------------
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_Util
; use Exp_Util
;
33 with Freeze
; use Freeze
;
34 with Lib
.Xref
; use Lib
.Xref
;
35 with Nlists
; use Nlists
;
36 with Nmake
; use Nmake
;
39 with Sem_Case
; use Sem_Case
;
40 with Sem_Ch3
; use Sem_Ch3
;
41 with Sem_Ch8
; use Sem_Ch8
;
42 with Sem_Disp
; use Sem_Disp
;
43 with Sem_Eval
; use Sem_Eval
;
44 with Sem_Res
; use Sem_Res
;
45 with Sem_Type
; use Sem_Type
;
46 with Sem_Util
; use Sem_Util
;
47 with Sem_Warn
; use Sem_Warn
;
48 with Stand
; use Stand
;
49 with Sinfo
; use Sinfo
;
50 with Targparm
; use Targparm
;
51 with Tbuild
; use Tbuild
;
52 with Uintp
; use Uintp
;
54 package body Sem_Ch5
is
56 Unblocked_Exit_Count
: Nat
:= 0;
57 -- This variable is used when processing if statements, case statements,
58 -- and block statements. It counts the number of exit points that are
59 -- not blocked by unconditional transfer instructions (for IF and CASE,
60 -- these are the branches of the conditional, for a block, they are the
61 -- statement sequence of the block, and the statement sequences of any
62 -- exception handlers that are part of the block. When processing is
63 -- complete, if this count is zero, it means that control cannot fall
64 -- through the IF, CASE or block statement. This is used for the
65 -- generation of warning messages. This variable is recursively saved
66 -- on entry to processing the construct, and restored on exit.
68 -----------------------
69 -- Local Subprograms --
70 -----------------------
72 procedure Analyze_Iteration_Scheme
(N
: Node_Id
);
74 procedure Check_Possible_Current_Value_Condition
(Cnode
: Node_Id
);
75 -- Cnode is N_If_Statement, N_Elsif_Part, or N_Iteration_Scheme
76 -- (the latter when a WHILE condition is present). This call checks
77 -- if Condition (Cnode) is of the form ([NOT] var op val), where var
78 -- is a simple object, val is known at compile time, and op is one
79 -- of the six relational operators. If this is the case, and the
80 -- Current_Value field of "var" is not set, then it is set to Cnode.
81 -- See Exp_Util.Set_Current_Value_Condition for further details.
83 ------------------------
84 -- Analyze_Assignment --
85 ------------------------
87 procedure Analyze_Assignment
(N
: Node_Id
) is
88 Lhs
: constant Node_Id
:= Name
(N
);
89 Rhs
: constant Node_Id
:= Expression
(N
);
95 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
);
96 -- N is the node for the left hand side of an assignment, and it
97 -- is not a variable. This routine issues an appropriate diagnostic.
99 procedure Set_Assignment_Type
101 Opnd_Type
: in out Entity_Id
);
102 -- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
103 -- is the nominal subtype. This procedure is used to deal with cases
104 -- where the nominal subtype must be replaced by the actual subtype.
106 -------------------------------
107 -- Diagnose_Non_Variable_Lhs --
108 -------------------------------
110 procedure Diagnose_Non_Variable_Lhs
(N
: Node_Id
) is
112 -- Not worth posting another error if left hand side already
113 -- flagged as being illegal in some respect
115 if Error_Posted
(N
) then
118 -- Some special bad cases of entity names
120 elsif Is_Entity_Name
(N
) then
121 if Ekind
(Entity
(N
)) = E_In_Parameter
then
123 ("assignment to IN mode parameter not allowed", N
);
125 -- Private declarations in a protected object are turned into
126 -- constants when compiling a protected function.
128 elsif Present
(Scope
(Entity
(N
)))
129 and then Is_Protected_Type
(Scope
(Entity
(N
)))
131 (Ekind
(Current_Scope
) = E_Function
133 Ekind
(Enclosing_Dynamic_Scope
(Current_Scope
)) = E_Function
)
136 ("protected function cannot modify protected object", N
);
138 elsif Ekind
(Entity
(N
)) = E_Loop_Parameter
then
140 ("assignment to loop parameter not allowed", N
);
144 ("left hand side of assignment must be a variable", N
);
147 -- For indexed components or selected components, test prefix
149 elsif Nkind
(N
) = N_Indexed_Component
then
150 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
152 -- Another special case for assignment to discriminant
154 elsif Nkind
(N
) = N_Selected_Component
then
155 if Present
(Entity
(Selector_Name
(N
)))
156 and then Ekind
(Entity
(Selector_Name
(N
))) = E_Discriminant
159 ("assignment to discriminant not allowed", N
);
161 Diagnose_Non_Variable_Lhs
(Prefix
(N
));
165 -- If we fall through, we have no special message to issue!
167 Error_Msg_N
("left hand side of assignment must be a variable", N
);
169 end Diagnose_Non_Variable_Lhs
;
171 -------------------------
172 -- Set_Assignment_Type --
173 -------------------------
175 procedure Set_Assignment_Type
177 Opnd_Type
: in out Entity_Id
)
180 Require_Entity
(Opnd
);
182 -- If the assignment operand is an in-out or out parameter, then we
183 -- get the actual subtype (needed for the unconstrained case).
184 -- If the operand is the actual in an entry declaration, then within
185 -- the accept statement it is replaced with a local renaming, which
186 -- may also have an actual subtype.
188 if Is_Entity_Name
(Opnd
)
189 and then (Ekind
(Entity
(Opnd
)) = E_Out_Parameter
190 or else Ekind
(Entity
(Opnd
)) =
192 or else Ekind
(Entity
(Opnd
)) =
193 E_Generic_In_Out_Parameter
195 (Ekind
(Entity
(Opnd
)) = E_Variable
196 and then Nkind
(Parent
(Entity
(Opnd
))) =
197 N_Object_Renaming_Declaration
198 and then Nkind
(Parent
(Parent
(Entity
(Opnd
)))) =
201 Opnd_Type
:= Get_Actual_Subtype
(Opnd
);
203 -- If assignment operand is a component reference, then we get the
204 -- actual subtype of the component for the unconstrained case.
207 (Nkind
(Opnd
) = N_Selected_Component
208 or else Nkind
(Opnd
) = N_Explicit_Dereference
)
209 and then not Is_Unchecked_Union
(Opnd_Type
)
211 Decl
:= Build_Actual_Subtype_Of_Component
(Opnd_Type
, Opnd
);
213 if Present
(Decl
) then
214 Insert_Action
(N
, Decl
);
215 Mark_Rewrite_Insertion
(Decl
);
217 Opnd_Type
:= Defining_Identifier
(Decl
);
218 Set_Etype
(Opnd
, Opnd_Type
);
219 Freeze_Itype
(Opnd_Type
, N
);
221 elsif Is_Constrained
(Etype
(Opnd
)) then
222 Opnd_Type
:= Etype
(Opnd
);
225 -- For slice, use the constrained subtype created for the slice
227 elsif Nkind
(Opnd
) = N_Slice
then
228 Opnd_Type
:= Etype
(Opnd
);
230 end Set_Assignment_Type
;
232 -- Start of processing for Analyze_Assignment
239 -- In the most general case, both Lhs and Rhs can be overloaded, and we
240 -- must compute the intersection of the possible types on each side.
242 if Is_Overloaded
(Lhs
) then
249 Get_First_Interp
(Lhs
, I
, It
);
251 while Present
(It
.Typ
) loop
252 if Has_Compatible_Type
(Rhs
, It
.Typ
) then
253 if T1
/= Any_Type
then
255 -- An explicit dereference is overloaded if the prefix
256 -- is. Try to remove the ambiguity on the prefix, the
257 -- error will be posted there if the ambiguity is real.
259 if Nkind
(Lhs
) = N_Explicit_Dereference
then
262 PI1
: Interp_Index
:= 0;
268 Get_First_Interp
(Prefix
(Lhs
), PI
, PIt
);
270 while Present
(PIt
.Typ
) loop
271 if Is_Access_Type
(PIt
.Typ
)
272 and then Has_Compatible_Type
273 (Rhs
, Designated_Type
(PIt
.Typ
))
277 Disambiguate
(Prefix
(Lhs
),
280 if PIt
= No_Interp
then
282 ("ambiguous left-hand side"
283 & " in assignment", Lhs
);
286 Resolve
(Prefix
(Lhs
), PIt
.Typ
);
296 Get_Next_Interp
(PI
, PIt
);
302 ("ambiguous left-hand side in assignment", Lhs
);
310 Get_Next_Interp
(I
, It
);
314 if T1
= Any_Type
then
316 ("no valid types for left-hand side for assignment", Lhs
);
323 if not Is_Variable
(Lhs
) then
324 Diagnose_Non_Variable_Lhs
(Lhs
);
327 elsif Is_Limited_Type
(T1
)
328 and then not Assignment_OK
(Lhs
)
329 and then not Assignment_OK
(Original_Node
(Lhs
))
332 ("left hand of assignment must not be limited type", Lhs
);
333 Explain_Limited_Type
(T1
, Lhs
);
337 -- Resolution may have updated the subtype, in case the left-hand
338 -- side is a private protected component. Use the correct subtype
339 -- to avoid scoping issues in the back-end.
343 -- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
344 -- type. For example:
348 -- type Acc is access P.T;
351 -- with Pkg; use Acc;
352 -- procedure Example is
355 -- A.all := B.all; -- ERROR
358 if Nkind
(Lhs
) = N_Explicit_Dereference
359 and then Ekind
(T1
) = E_Incomplete_Type
361 Error_Msg_N
("invalid use of incomplete type", Lhs
);
365 Set_Assignment_Type
(Lhs
, T1
);
368 Check_Unset_Reference
(Rhs
);
370 -- Remaining steps are skipped if Rhs was syntactically in error
378 if not Covers
(T1
, T2
) then
379 Wrong_Type
(Rhs
, Etype
(Lhs
));
383 -- Ada 2005 (AI-326): In case of explicit dereference of incomplete
384 -- types, use the non-limited view if available
386 if Nkind
(Rhs
) = N_Explicit_Dereference
387 and then Ekind
(T2
) = E_Incomplete_Type
388 and then Is_Tagged_Type
(T2
)
389 and then Present
(Non_Limited_View
(T2
))
391 T2
:= Non_Limited_View
(T2
);
394 Set_Assignment_Type
(Rhs
, T2
);
396 if Total_Errors_Detected
/= 0 then
406 if T1
= Any_Type
or else T2
= Any_Type
then
410 if (Is_Class_Wide_Type
(T2
) or else Is_Dynamically_Tagged
(Rhs
))
411 and then not Is_Class_Wide_Type
(T1
)
413 Error_Msg_N
("dynamically tagged expression not allowed!", Rhs
);
415 elsif Is_Class_Wide_Type
(T1
)
416 and then not Is_Class_Wide_Type
(T2
)
417 and then not Is_Tag_Indeterminate
(Rhs
)
418 and then not Is_Dynamically_Tagged
(Rhs
)
420 Error_Msg_N
("dynamically tagged expression required!", Rhs
);
423 -- Tag propagation is done only in semantics mode only. If expansion
424 -- is on, the rhs tag indeterminate function call has been expanded
425 -- and tag propagation would have happened too late, so the
426 -- propagation take place in expand_call instead.
428 if not Expander_Active
429 and then Is_Class_Wide_Type
(T1
)
430 and then Is_Tag_Indeterminate
(Rhs
)
432 Propagate_Tag
(Lhs
, Rhs
);
435 -- Ada 2005 (AI-230 and AI-385): When the lhs type is an anonymous
436 -- access type, apply an implicit conversion of the rhs to that type
437 -- to force appropriate static and run-time accessibility checks.
439 if Ada_Version
>= Ada_05
440 and then Ekind
(T1
) = E_Anonymous_Access_Type
442 Rewrite
(Rhs
, Convert_To
(T1
, Relocate_Node
(Rhs
)));
443 Analyze_And_Resolve
(Rhs
, T1
);
448 if Ada_Version
>= Ada_05
449 and then Can_Never_Be_Null
(T1
)
450 and then not Assignment_OK
(Lhs
)
452 if Nkind
(Rhs
) = N_Null
then
453 Apply_Compile_Time_Constraint_Error
455 Msg
=> "(Ada 2005) NULL not allowed in null-excluding objects?",
456 Reason
=> CE_Null_Not_Allowed
);
459 elsif not Can_Never_Be_Null
(T2
) then
461 Convert_To
(T1
, Relocate_Node
(Rhs
)));
462 Analyze_And_Resolve
(Rhs
, T1
);
466 if Is_Scalar_Type
(T1
) then
467 Apply_Scalar_Range_Check
(Rhs
, Etype
(Lhs
));
469 elsif Is_Array_Type
(T1
)
471 (Nkind
(Rhs
) /= N_Type_Conversion
472 or else Is_Constrained
(Etype
(Rhs
)))
474 -- Assignment verifies that the length of the Lsh and Rhs are equal,
475 -- but of course the indices do not have to match. If the right-hand
476 -- side is a type conversion to an unconstrained type, a length check
477 -- is performed on the expression itself during expansion. In rare
478 -- cases, the redundant length check is computed on an index type
479 -- with a different representation, triggering incorrect code in
482 Apply_Length_Check
(Rhs
, Etype
(Lhs
));
485 -- Discriminant checks are applied in the course of expansion
490 -- Note: modifications of the Lhs may only be recorded after
491 -- checks have been applied.
493 Note_Possible_Modification
(Lhs
);
495 -- ??? a real accessibility check is needed when ???
497 -- Post warning for useless assignment
499 if Warn_On_Redundant_Constructs
501 -- We only warn for source constructs
503 and then Comes_From_Source
(N
)
505 -- Where the entity is the same on both sides
507 and then Is_Entity_Name
(Lhs
)
508 and then Is_Entity_Name
(Original_Node
(Rhs
))
509 and then Entity
(Lhs
) = Entity
(Original_Node
(Rhs
))
511 -- But exclude the case where the right side was an operation
512 -- that got rewritten (e.g. JUNK + K, where K was known to be
513 -- zero). We don't want to warn in such a case, since it is
514 -- reasonable to write such expressions especially when K is
515 -- defined symbolically in some other package.
517 and then Nkind
(Original_Node
(Rhs
)) not in N_Op
520 ("?useless assignment of & to itself", N
, Entity
(Lhs
));
523 -- Check for non-allowed composite assignment
525 if not Support_Composite_Assign_On_Target
526 and then (Is_Array_Type
(T1
) or else Is_Record_Type
(T1
))
527 and then (not Has_Size_Clause
(T1
) or else Esize
(T1
) > 64)
529 Error_Msg_CRT
("composite assignment", N
);
532 -- One more step. Let's see if we have a simple assignment of a
533 -- known at compile time value to a simple variable. If so, we
534 -- can record the value as the current value providing that:
536 -- We still have a simple assignment statement (no expansion
537 -- activity has modified it in some peculiar manner)
539 -- The type is a discrete type
541 -- The assignment is to a named entity
543 -- The value is known at compile time
545 if Nkind
(N
) /= N_Assignment_Statement
546 or else not Is_Discrete_Type
(T1
)
547 or else not Is_Entity_Name
(Lhs
)
548 or else not Compile_Time_Known_Value
(Rhs
)
555 -- Capture value if safe to do so
557 if Safe_To_Capture_Value
(N
, Ent
) then
558 Set_Current_Value
(Ent
, Rhs
);
560 end Analyze_Assignment
;
562 -----------------------------
563 -- Analyze_Block_Statement --
564 -----------------------------
566 procedure Analyze_Block_Statement
(N
: Node_Id
) is
567 Decls
: constant List_Id
:= Declarations
(N
);
568 Id
: constant Node_Id
:= Identifier
(N
);
569 HSS
: constant Node_Id
:= Handled_Statement_Sequence
(N
);
572 -- If no handled statement sequence is present, things are really
573 -- messed up, and we just return immediately (this is a defence
574 -- against previous errors).
580 -- Normal processing with HSS present
583 EH
: constant List_Id
:= Exception_Handlers
(HSS
);
584 Ent
: Entity_Id
:= Empty
;
587 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
588 -- Recursively save value of this global, will be restored on exit
591 -- Initialize unblocked exit count for statements of begin block
592 -- plus one for each excption handler that is present.
594 Unblocked_Exit_Count
:= 1;
597 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ List_Length
(EH
);
600 -- If a label is present analyze it and mark it as referenced
606 -- An error defense. If we have an identifier, but no entity,
607 -- then something is wrong. If we have previous errors, then
608 -- just remove the identifier and continue, otherwise raise
612 if Total_Errors_Detected
/= 0 then
613 Set_Identifier
(N
, Empty
);
619 Set_Ekind
(Ent
, E_Block
);
620 Generate_Reference
(Ent
, N
, ' ');
621 Generate_Definition
(Ent
);
623 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
624 Set_Label_Construct
(Parent
(Ent
), N
);
629 -- If no entity set, create a label entity
632 Ent
:= New_Internal_Entity
(E_Block
, Current_Scope
, Sloc
(N
), 'B');
633 Set_Identifier
(N
, New_Occurrence_Of
(Ent
, Sloc
(N
)));
637 Set_Etype
(Ent
, Standard_Void_Type
);
638 Set_Block_Node
(Ent
, Identifier
(N
));
641 if Present
(Decls
) then
642 Analyze_Declarations
(Decls
);
647 Process_End_Label
(HSS
, 'e', Ent
);
649 -- If exception handlers are present, then we indicate that
650 -- enclosing scopes contain a block with handlers. We only
651 -- need to mark non-generic scopes.
656 Set_Has_Nested_Block_With_Handler
(S
);
657 exit when Is_Overloadable
(S
)
658 or else Ekind
(S
) = E_Package
659 or else Is_Generic_Unit
(S
);
664 Check_References
(Ent
);
667 if Unblocked_Exit_Count
= 0 then
668 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
669 Check_Unreachable_Code
(N
);
671 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
674 end Analyze_Block_Statement
;
676 ----------------------------
677 -- Analyze_Case_Statement --
678 ----------------------------
680 procedure Analyze_Case_Statement
(N
: Node_Id
) is
682 Exp_Type
: Entity_Id
;
683 Exp_Btype
: Entity_Id
;
686 Others_Present
: Boolean;
688 Statements_Analyzed
: Boolean := False;
689 -- Set True if at least some statement sequences get analyzed.
690 -- If False on exit, means we had a serious error that prevented
691 -- full analysis of the case statement, and as a result it is not
692 -- a good idea to output warning messages about unreachable code.
694 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
695 -- Recursively save value of this global, will be restored on exit
697 procedure Non_Static_Choice_Error
(Choice
: Node_Id
);
698 -- Error routine invoked by the generic instantiation below when
699 -- the case statment has a non static choice.
701 procedure Process_Statements
(Alternative
: Node_Id
);
702 -- Analyzes all the statements associated to a case alternative.
703 -- Needed by the generic instantiation below.
705 package Case_Choices_Processing
is new
706 Generic_Choices_Processing
707 (Get_Alternatives
=> Alternatives
,
708 Get_Choices
=> Discrete_Choices
,
709 Process_Empty_Choice
=> No_OP
,
710 Process_Non_Static_Choice
=> Non_Static_Choice_Error
,
711 Process_Associated_Node
=> Process_Statements
);
712 use Case_Choices_Processing
;
713 -- Instantiation of the generic choice processing package
715 -----------------------------
716 -- Non_Static_Choice_Error --
717 -----------------------------
719 procedure Non_Static_Choice_Error
(Choice
: Node_Id
) is
722 ("choice given in case statement is not static!", Choice
);
723 end Non_Static_Choice_Error
;
725 ------------------------
726 -- Process_Statements --
727 ------------------------
729 procedure Process_Statements
(Alternative
: Node_Id
) is
730 Choices
: constant List_Id
:= Discrete_Choices
(Alternative
);
734 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
735 Statements_Analyzed
:= True;
737 -- An interesting optimization. If the case statement expression
738 -- is a simple entity, then we can set the current value within
739 -- an alternative if the alternative has one possible value.
743 -- when 2 | 3 => beta
744 -- when others => gamma
746 -- Here we know that N is initially 1 within alpha, but for beta
747 -- and gamma, we do not know anything more about the initial value.
749 if Is_Entity_Name
(Exp
) then
752 if Ekind
(Ent
) = E_Variable
754 Ekind
(Ent
) = E_In_Out_Parameter
756 Ekind
(Ent
) = E_Out_Parameter
758 if List_Length
(Choices
) = 1
759 and then Nkind
(First
(Choices
)) in N_Subexpr
760 and then Compile_Time_Known_Value
(First
(Choices
))
762 Set_Current_Value
(Entity
(Exp
), First
(Choices
));
765 Analyze_Statements
(Statements
(Alternative
));
767 -- After analyzing the case, set the current value to empty
768 -- since we won't know what it is for the next alternative
769 -- (unless reset by this same circuit), or after the case.
771 Set_Current_Value
(Entity
(Exp
), Empty
);
776 -- Case where expression is not an entity name of a variable
778 Analyze_Statements
(Statements
(Alternative
));
779 end Process_Statements
;
781 -- Table to record choices. Put after subprograms since we make
782 -- a call to Number_Of_Choices to get the right number of entries.
784 Case_Table
: Choice_Table_Type
(1 .. Number_Of_Choices
(N
));
786 -- Start of processing for Analyze_Case_Statement
789 Unblocked_Exit_Count
:= 0;
790 Exp
:= Expression
(N
);
793 -- The expression must be of any discrete type. In rare cases, the
794 -- expander constructs a case statement whose expression has a private
795 -- type whose full view is discrete. This can happen when generating
796 -- a stream operation for a variant type after the type is frozen,
797 -- when the partial of view of the type of the discriminant is private.
798 -- In that case, use the full view to analyze case alternatives.
800 if not Is_Overloaded
(Exp
)
801 and then not Comes_From_Source
(N
)
802 and then Is_Private_Type
(Etype
(Exp
))
803 and then Present
(Full_View
(Etype
(Exp
)))
804 and then Is_Discrete_Type
(Full_View
(Etype
(Exp
)))
806 Resolve
(Exp
, Etype
(Exp
));
807 Exp_Type
:= Full_View
(Etype
(Exp
));
810 Analyze_And_Resolve
(Exp
, Any_Discrete
);
811 Exp_Type
:= Etype
(Exp
);
814 Check_Unset_Reference
(Exp
);
815 Exp_Btype
:= Base_Type
(Exp_Type
);
817 -- The expression must be of a discrete type which must be determinable
818 -- independently of the context in which the expression occurs, but
819 -- using the fact that the expression must be of a discrete type.
820 -- Moreover, the type this expression must not be a character literal
821 -- (which is always ambiguous) or, for Ada-83, a generic formal type.
823 -- If error already reported by Resolve, nothing more to do
825 if Exp_Btype
= Any_Discrete
826 or else Exp_Btype
= Any_Type
830 elsif Exp_Btype
= Any_Character
then
832 ("character literal as case expression is ambiguous", Exp
);
835 elsif Ada_Version
= Ada_83
836 and then (Is_Generic_Type
(Exp_Btype
)
837 or else Is_Generic_Type
(Root_Type
(Exp_Btype
)))
840 ("(Ada 83) case expression cannot be of a generic type", Exp
);
844 -- If the case expression is a formal object of mode in out, then
845 -- treat it as having a nonstatic subtype by forcing use of the base
846 -- type (which has to get passed to Check_Case_Choices below). Also
847 -- use base type when the case expression is parenthesized.
849 if Paren_Count
(Exp
) > 0
850 or else (Is_Entity_Name
(Exp
)
851 and then Ekind
(Entity
(Exp
)) = E_Generic_In_Out_Parameter
)
853 Exp_Type
:= Exp_Btype
;
856 -- Call instantiated Analyze_Choices which does the rest of the work
859 (N
, Exp_Type
, Case_Table
, Last_Choice
, Dont_Care
, Others_Present
);
861 if Exp_Type
= Universal_Integer
and then not Others_Present
then
862 Error_Msg_N
("case on universal integer requires OTHERS choice", Exp
);
865 -- If all our exits were blocked by unconditional transfers of control,
866 -- then the entire CASE statement acts as an unconditional transfer of
867 -- control, so treat it like one, and check unreachable code. Skip this
868 -- test if we had serious errors preventing any statement analysis.
870 if Unblocked_Exit_Count
= 0 and then Statements_Analyzed
then
871 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
872 Check_Unreachable_Code
(N
);
874 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
877 if not Expander_Active
878 and then Compile_Time_Known_Value
(Expression
(N
))
879 and then Serious_Errors_Detected
= 0
882 Chosen
: constant Node_Id
:= Find_Static_Alternative
(N
);
886 Alt
:= First
(Alternatives
(N
));
888 while Present
(Alt
) loop
889 if Alt
/= Chosen
then
890 Remove_Warning_Messages
(Statements
(Alt
));
897 end Analyze_Case_Statement
;
899 ----------------------------
900 -- Analyze_Exit_Statement --
901 ----------------------------
903 -- If the exit includes a name, it must be the name of a currently open
904 -- loop. Otherwise there must be an innermost open loop on the stack,
905 -- to which the statement implicitly refers.
907 procedure Analyze_Exit_Statement
(N
: Node_Id
) is
908 Target
: constant Node_Id
:= Name
(N
);
909 Cond
: constant Node_Id
:= Condition
(N
);
910 Scope_Id
: Entity_Id
;
916 Check_Unreachable_Code
(N
);
919 if Present
(Target
) then
921 U_Name
:= Entity
(Target
);
923 if not In_Open_Scopes
(U_Name
) or else Ekind
(U_Name
) /= E_Loop
then
924 Error_Msg_N
("invalid loop name in exit statement", N
);
927 Set_Has_Exit
(U_Name
);
934 for J
in reverse 0 .. Scope_Stack
.Last
loop
935 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
936 Kind
:= Ekind
(Scope_Id
);
939 and then (No
(Target
) or else Scope_Id
= U_Name
) then
940 Set_Has_Exit
(Scope_Id
);
943 elsif Kind
= E_Block
or else Kind
= E_Loop
then
948 ("cannot exit from program unit or accept statement", N
);
953 -- Verify that if present the condition is a Boolean expression
955 if Present
(Cond
) then
956 Analyze_And_Resolve
(Cond
, Any_Boolean
);
957 Check_Unset_Reference
(Cond
);
959 end Analyze_Exit_Statement
;
961 ----------------------------
962 -- Analyze_Goto_Statement --
963 ----------------------------
965 procedure Analyze_Goto_Statement
(N
: Node_Id
) is
966 Label
: constant Node_Id
:= Name
(N
);
967 Scope_Id
: Entity_Id
;
968 Label_Scope
: Entity_Id
;
971 Check_Unreachable_Code
(N
);
975 if Entity
(Label
) = Any_Id
then
978 elsif Ekind
(Entity
(Label
)) /= E_Label
then
979 Error_Msg_N
("target of goto statement must be a label", Label
);
982 elsif not Reachable
(Entity
(Label
)) then
983 Error_Msg_N
("target of goto statement is not reachable", Label
);
987 Label_Scope
:= Enclosing_Scope
(Entity
(Label
));
989 for J
in reverse 0 .. Scope_Stack
.Last
loop
990 Scope_Id
:= Scope_Stack
.Table
(J
).Entity
;
992 if Label_Scope
= Scope_Id
993 or else (Ekind
(Scope_Id
) /= E_Block
994 and then Ekind
(Scope_Id
) /= E_Loop
)
996 if Scope_Id
/= Label_Scope
then
998 ("cannot exit from program unit or accept statement", N
);
1005 raise Program_Error
;
1006 end Analyze_Goto_Statement
;
1008 --------------------------
1009 -- Analyze_If_Statement --
1010 --------------------------
1012 -- A special complication arises in the analysis of if statements
1014 -- The expander has circuitry to completely delete code that it
1015 -- can tell will not be executed (as a result of compile time known
1016 -- conditions). In the analyzer, we ensure that code that will be
1017 -- deleted in this manner is analyzed but not expanded. This is
1018 -- obviously more efficient, but more significantly, difficulties
1019 -- arise if code is expanded and then eliminated (e.g. exception
1020 -- table entries disappear). Similarly, itypes generated in deleted
1021 -- code must be frozen from start, because the nodes on which they
1022 -- depend will not be available at the freeze point.
1024 procedure Analyze_If_Statement
(N
: Node_Id
) is
1027 Save_Unblocked_Exit_Count
: constant Nat
:= Unblocked_Exit_Count
;
1028 -- Recursively save value of this global, will be restored on exit
1030 Save_In_Deleted_Code
: Boolean;
1032 Del
: Boolean := False;
1033 -- This flag gets set True if a True condition has been found,
1034 -- which means that remaining ELSE/ELSIF parts are deleted.
1036 procedure Analyze_Cond_Then
(Cnode
: Node_Id
);
1037 -- This is applied to either the N_If_Statement node itself or
1038 -- to an N_Elsif_Part node. It deals with analyzing the condition
1039 -- and the THEN statements associated with it.
1041 -----------------------
1042 -- Analyze_Cond_Then --
1043 -----------------------
1045 procedure Analyze_Cond_Then
(Cnode
: Node_Id
) is
1046 Cond
: constant Node_Id
:= Condition
(Cnode
);
1047 Tstm
: constant List_Id
:= Then_Statements
(Cnode
);
1050 Unblocked_Exit_Count
:= Unblocked_Exit_Count
+ 1;
1051 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1052 Check_Unset_Reference
(Cond
);
1053 Check_Possible_Current_Value_Condition
(Cnode
);
1055 -- If already deleting, then just analyze then statements
1058 Analyze_Statements
(Tstm
);
1060 -- Compile time known value, not deleting yet
1062 elsif Compile_Time_Known_Value
(Cond
) then
1063 Save_In_Deleted_Code
:= In_Deleted_Code
;
1065 -- If condition is True, then analyze the THEN statements
1066 -- and set no expansion for ELSE and ELSIF parts.
1068 if Is_True
(Expr_Value
(Cond
)) then
1069 Analyze_Statements
(Tstm
);
1071 Expander_Mode_Save_And_Set
(False);
1072 In_Deleted_Code
:= True;
1074 -- If condition is False, analyze THEN with expansion off
1076 else -- Is_False (Expr_Value (Cond))
1077 Expander_Mode_Save_And_Set
(False);
1078 In_Deleted_Code
:= True;
1079 Analyze_Statements
(Tstm
);
1080 Expander_Mode_Restore
;
1081 In_Deleted_Code
:= Save_In_Deleted_Code
;
1084 -- Not known at compile time, not deleting, normal analysis
1087 Analyze_Statements
(Tstm
);
1089 end Analyze_Cond_Then
;
1091 -- Start of Analyze_If_Statement
1094 -- Initialize exit count for else statements. If there is no else
1095 -- part, this count will stay non-zero reflecting the fact that the
1096 -- uncovered else case is an unblocked exit.
1098 Unblocked_Exit_Count
:= 1;
1099 Analyze_Cond_Then
(N
);
1101 -- Now to analyze the elsif parts if any are present
1103 if Present
(Elsif_Parts
(N
)) then
1104 E
:= First
(Elsif_Parts
(N
));
1105 while Present
(E
) loop
1106 Analyze_Cond_Then
(E
);
1111 if Present
(Else_Statements
(N
)) then
1112 Analyze_Statements
(Else_Statements
(N
));
1115 -- If all our exits were blocked by unconditional transfers of control,
1116 -- then the entire IF statement acts as an unconditional transfer of
1117 -- control, so treat it like one, and check unreachable code.
1119 if Unblocked_Exit_Count
= 0 then
1120 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1121 Check_Unreachable_Code
(N
);
1123 Unblocked_Exit_Count
:= Save_Unblocked_Exit_Count
;
1127 Expander_Mode_Restore
;
1128 In_Deleted_Code
:= Save_In_Deleted_Code
;
1131 if not Expander_Active
1132 and then Compile_Time_Known_Value
(Condition
(N
))
1133 and then Serious_Errors_Detected
= 0
1135 if Is_True
(Expr_Value
(Condition
(N
))) then
1136 Remove_Warning_Messages
(Else_Statements
(N
));
1138 if Present
(Elsif_Parts
(N
)) then
1139 E
:= First
(Elsif_Parts
(N
));
1141 while Present
(E
) loop
1142 Remove_Warning_Messages
(Then_Statements
(E
));
1148 Remove_Warning_Messages
(Then_Statements
(N
));
1151 end Analyze_If_Statement
;
1153 ----------------------------------------
1154 -- Analyze_Implicit_Label_Declaration --
1155 ----------------------------------------
1157 -- An implicit label declaration is generated in the innermost
1158 -- enclosing declarative part. This is done for labels as well as
1159 -- block and loop names.
1161 -- Note: any changes in this routine may need to be reflected in
1162 -- Analyze_Label_Entity.
1164 procedure Analyze_Implicit_Label_Declaration
(N
: Node_Id
) is
1165 Id
: constant Node_Id
:= Defining_Identifier
(N
);
1168 Set_Ekind
(Id
, E_Label
);
1169 Set_Etype
(Id
, Standard_Void_Type
);
1170 Set_Enclosing_Scope
(Id
, Current_Scope
);
1171 end Analyze_Implicit_Label_Declaration
;
1173 ------------------------------
1174 -- Analyze_Iteration_Scheme --
1175 ------------------------------
1177 procedure Analyze_Iteration_Scheme
(N
: Node_Id
) is
1179 procedure Process_Bounds
(R
: Node_Id
);
1180 -- If the iteration is given by a range, create temporaries and
1181 -- assignment statements block to capture the bounds and perform
1182 -- required finalization actions in case a bound includes a function
1183 -- call that uses the temporary stack. We first pre-analyze a copy of
1184 -- the range in order to determine the expected type, and analyze and
1185 -- resolve the original bounds.
1187 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
);
1188 -- If the bounds are given by a 'Range reference on a function call
1189 -- that returns a controlled array, introduce an explicit declaration
1190 -- to capture the bounds, so that the function result can be finalized
1191 -- in timely fashion.
1193 --------------------
1194 -- Process_Bounds --
1195 --------------------
1197 procedure Process_Bounds
(R
: Node_Id
) is
1198 Loc
: constant Source_Ptr
:= Sloc
(N
);
1199 R_Copy
: constant Node_Id
:= New_Copy_Tree
(R
);
1200 Lo
: constant Node_Id
:= Low_Bound
(R
);
1201 Hi
: constant Node_Id
:= High_Bound
(R
);
1202 New_Lo_Bound
: Node_Id
:= Empty
;
1203 New_Hi_Bound
: Node_Id
:= Empty
;
1207 (Original_Bound
: Node_Id
;
1208 Analyzed_Bound
: Node_Id
) return Node_Id
;
1209 -- Create one declaration followed by one assignment statement
1210 -- to capture the value of bound. We create a separate assignment
1211 -- in order to force the creation of a block in case the bound
1212 -- contains a call that uses the secondary stack.
1219 (Original_Bound
: Node_Id
;
1220 Analyzed_Bound
: Node_Id
) return Node_Id
1227 -- If the bound is a constant or an object, no need for a separate
1228 -- declaration. If the bound is the result of previous expansion
1229 -- it is already analyzed and should not be modified. Note that
1230 -- the Bound will be resolved later, if needed, as part of the
1231 -- call to Make_Index (literal bounds may need to be resolved to
1234 if Analyzed
(Original_Bound
) then
1235 return Original_Bound
;
1237 elsif Nkind
(Analyzed_Bound
) = N_Integer_Literal
1238 or else Is_Entity_Name
(Analyzed_Bound
)
1240 Analyze_And_Resolve
(Original_Bound
, Typ
);
1241 return Original_Bound
;
1244 Analyze_And_Resolve
(Original_Bound
, Typ
);
1248 Make_Defining_Identifier
(Loc
,
1249 Chars
=> New_Internal_Name
('S'));
1252 Make_Object_Declaration
(Loc
,
1253 Defining_Identifier
=> Id
,
1254 Object_Definition
=> New_Occurrence_Of
(Typ
, Loc
));
1256 Insert_Before
(Parent
(N
), Decl
);
1260 Make_Assignment_Statement
(Loc
,
1261 Name
=> New_Occurrence_Of
(Id
, Loc
),
1262 Expression
=> Relocate_Node
(Original_Bound
));
1264 Insert_Before
(Parent
(N
), Assign
);
1267 Rewrite
(Original_Bound
, New_Occurrence_Of
(Id
, Loc
));
1269 if Nkind
(Assign
) = N_Assignment_Statement
then
1270 return Expression
(Assign
);
1272 return Original_Bound
;
1276 -- Start of processing for Process_Bounds
1279 -- Determine expected type of range by analyzing separate copy
1281 Set_Parent
(R_Copy
, Parent
(R
));
1282 Pre_Analyze_And_Resolve
(R_Copy
);
1283 Typ
:= Etype
(R_Copy
);
1285 -- If the type of the discrete range is Universal_Integer, then
1286 -- the bound's type must be resolved to Integer, and any object
1287 -- used to hold the bound must also have type Integer.
1289 if Typ
= Universal_Integer
then
1290 Typ
:= Standard_Integer
;
1295 New_Lo_Bound
:= One_Bound
(Lo
, Low_Bound
(R_Copy
));
1296 New_Hi_Bound
:= One_Bound
(Hi
, High_Bound
(R_Copy
));
1298 -- Propagate staticness to loop range itself, in case the
1299 -- corresponding subtype is static.
1301 if New_Lo_Bound
/= Lo
1302 and then Is_Static_Expression
(New_Lo_Bound
)
1304 Rewrite
(Low_Bound
(R
), New_Copy
(New_Lo_Bound
));
1307 if New_Hi_Bound
/= Hi
1308 and then Is_Static_Expression
(New_Hi_Bound
)
1310 Rewrite
(High_Bound
(R
), New_Copy
(New_Hi_Bound
));
1314 --------------------------------------
1315 -- Check_Controlled_Array_Attribute --
1316 --------------------------------------
1318 procedure Check_Controlled_Array_Attribute
(DS
: Node_Id
) is
1320 if Nkind
(DS
) = N_Attribute_Reference
1321 and then Is_Entity_Name
(Prefix
(DS
))
1322 and then Ekind
(Entity
(Prefix
(DS
))) = E_Function
1323 and then Is_Array_Type
(Etype
(Entity
(Prefix
(DS
))))
1326 Component_Type
(Etype
(Entity
(Prefix
(DS
)))))
1327 and then Expander_Active
1330 Loc
: constant Source_Ptr
:= Sloc
(N
);
1331 Arr
: constant Entity_Id
:=
1332 Etype
(Entity
(Prefix
(DS
)));
1333 Indx
: constant Entity_Id
:=
1334 Base_Type
(Etype
(First_Index
(Arr
)));
1335 Subt
: constant Entity_Id
:=
1336 Make_Defining_Identifier
1337 (Loc
, New_Internal_Name
('S'));
1342 Make_Subtype_Declaration
(Loc
,
1343 Defining_Identifier
=> Subt
,
1344 Subtype_Indication
=>
1345 Make_Subtype_Indication
(Loc
,
1346 Subtype_Mark
=> New_Reference_To
(Indx
, Loc
),
1348 Make_Range_Constraint
(Loc
,
1349 Relocate_Node
(DS
))));
1350 Insert_Before
(Parent
(N
), Decl
);
1354 Make_Attribute_Reference
(Loc
,
1355 Prefix
=> New_Reference_To
(Subt
, Loc
),
1356 Attribute_Name
=> Attribute_Name
(DS
)));
1360 end Check_Controlled_Array_Attribute
;
1362 -- Start of processing for Analyze_Iteration_Scheme
1365 -- For an infinite loop, there is no iteration scheme
1372 Cond
: constant Node_Id
:= Condition
(N
);
1375 -- For WHILE loop, verify that the condition is a Boolean
1376 -- expression and resolve and check it.
1378 if Present
(Cond
) then
1379 Analyze_And_Resolve
(Cond
, Any_Boolean
);
1380 Check_Unset_Reference
(Cond
);
1382 -- Else we have a FOR loop
1386 LP
: constant Node_Id
:= Loop_Parameter_Specification
(N
);
1387 Id
: constant Entity_Id
:= Defining_Identifier
(LP
);
1388 DS
: constant Node_Id
:= Discrete_Subtype_Definition
(LP
);
1393 -- We always consider the loop variable to be referenced,
1394 -- since the loop may be used just for counting purposes.
1396 Generate_Reference
(Id
, N
, ' ');
1398 -- Check for case of loop variable hiding a local
1399 -- variable (used later on to give a nice warning
1400 -- if the hidden variable is never assigned).
1403 H
: constant Entity_Id
:= Homonym
(Id
);
1406 and then Enclosing_Dynamic_Scope
(H
) =
1407 Enclosing_Dynamic_Scope
(Id
)
1408 and then Ekind
(H
) = E_Variable
1409 and then Is_Discrete_Type
(Etype
(H
))
1411 Set_Hiding_Loop_Variable
(H
, Id
);
1415 -- Now analyze the subtype definition. If it is
1416 -- a range, create temporaries for bounds.
1418 if Nkind
(DS
) = N_Range
1419 and then Expander_Active
1421 Process_Bounds
(DS
);
1430 -- The subtype indication may denote the completion
1431 -- of an incomplete type declaration.
1433 if Is_Entity_Name
(DS
)
1434 and then Present
(Entity
(DS
))
1435 and then Is_Type
(Entity
(DS
))
1436 and then Ekind
(Entity
(DS
)) = E_Incomplete_Type
1438 Set_Entity
(DS
, Get_Full_View
(Entity
(DS
)));
1439 Set_Etype
(DS
, Entity
(DS
));
1442 if not Is_Discrete_Type
(Etype
(DS
)) then
1443 Wrong_Type
(DS
, Any_Discrete
);
1444 Set_Etype
(DS
, Any_Type
);
1447 Check_Controlled_Array_Attribute
(DS
);
1449 Make_Index
(DS
, LP
);
1451 Set_Ekind
(Id
, E_Loop_Parameter
);
1452 Set_Etype
(Id
, Etype
(DS
));
1453 Set_Is_Known_Valid
(Id
, True);
1455 -- The loop is not a declarative part, so the only entity
1456 -- declared "within" must be frozen explicitly.
1459 Flist
: constant List_Id
:= Freeze_Entity
(Id
, Sloc
(N
));
1461 if Is_Non_Empty_List
(Flist
) then
1462 Insert_Actions
(N
, Flist
);
1466 -- Check for null or possibly null range and issue warning.
1467 -- We suppress such messages in generic templates and
1468 -- instances, because in practice they tend to be dubious
1471 if Nkind
(DS
) = N_Range
1472 and then Comes_From_Source
(N
)
1475 L
: constant Node_Id
:= Low_Bound
(DS
);
1476 H
: constant Node_Id
:= High_Bound
(DS
);
1486 Determine_Range
(L
, LOK
, Llo
, Lhi
);
1487 Determine_Range
(H
, HOK
, Hlo
, Hhi
);
1489 -- If range of loop is null, issue warning
1491 if (LOK
and HOK
) and then Llo
> Hhi
then
1493 -- Suppress the warning if inside a generic
1494 -- template or instance, since in practice
1495 -- they tend to be dubious in these cases since
1496 -- they can result from intended parametrization.
1498 if not Inside_A_Generic
1499 and then not In_Instance
1502 ("?loop range is null, loop will not execute",
1506 -- Since we know the range of the loop is null,
1507 -- set the appropriate flag to suppress any
1508 -- warnings that would otherwise be issued in
1509 -- the body of the loop that will not execute.
1510 -- We do this even in the generic case, since
1511 -- if it is dubious to warn on the null loop
1512 -- itself, it is certainly dubious to warn for
1513 -- conditions that occur inside it!
1515 Set_Is_Null_Loop
(Parent
(N
));
1517 -- The other case for a warning is a reverse loop
1518 -- where the upper bound is the integer literal
1519 -- zero or one, and the lower bound can be positive.
1521 -- For example, we have
1523 -- for J in reverse N .. 1 loop
1525 -- In practice, this is very likely to be a case
1526 -- of reversing the bounds incorrectly in the range.
1528 elsif Reverse_Present
(LP
)
1529 and then Nkind
(H
) = N_Integer_Literal
1530 and then (Intval
(H
) = Uint_0
1532 Intval
(H
) = Uint_1
)
1535 Error_Msg_N
("?loop range may be null", DS
);
1543 end Analyze_Iteration_Scheme
;
1549 -- Note: the semantic work required for analyzing labels (setting them as
1550 -- reachable) was done in a prepass through the statements in the block,
1551 -- so that forward gotos would be properly handled. See Analyze_Statements
1552 -- for further details. The only processing required here is to deal with
1553 -- optimizations that depend on an assumption of sequential control flow,
1554 -- since of course the occurrence of a label breaks this assumption.
1556 procedure Analyze_Label
(N
: Node_Id
) is
1557 pragma Warnings
(Off
, N
);
1559 Kill_Current_Values
;
1562 --------------------------
1563 -- Analyze_Label_Entity --
1564 --------------------------
1566 procedure Analyze_Label_Entity
(E
: Entity_Id
) is
1568 Set_Ekind
(E
, E_Label
);
1569 Set_Etype
(E
, Standard_Void_Type
);
1570 Set_Enclosing_Scope
(E
, Current_Scope
);
1571 Set_Reachable
(E
, True);
1572 end Analyze_Label_Entity
;
1574 ----------------------------
1575 -- Analyze_Loop_Statement --
1576 ----------------------------
1578 procedure Analyze_Loop_Statement
(N
: Node_Id
) is
1579 Id
: constant Node_Id
:= Identifier
(N
);
1583 if Present
(Id
) then
1585 -- Make name visible, e.g. for use in exit statements. Loop
1586 -- labels are always considered to be referenced.
1590 Generate_Reference
(Ent
, N
, ' ');
1591 Generate_Definition
(Ent
);
1593 -- If we found a label, mark its type. If not, ignore it, since it
1594 -- means we have a conflicting declaration, which would already have
1595 -- been diagnosed at declaration time. Set Label_Construct of the
1596 -- implicit label declaration, which is not created by the parser
1597 -- for generic units.
1599 if Ekind
(Ent
) = E_Label
then
1600 Set_Ekind
(Ent
, E_Loop
);
1602 if Nkind
(Parent
(Ent
)) = N_Implicit_Label_Declaration
then
1603 Set_Label_Construct
(Parent
(Ent
), N
);
1607 -- Case of no identifier present
1610 Ent
:= New_Internal_Entity
(E_Loop
, Current_Scope
, Sloc
(N
), 'L');
1611 Set_Etype
(Ent
, Standard_Void_Type
);
1612 Set_Parent
(Ent
, N
);
1615 -- Kill current values on entry to loop, since statements in body
1616 -- of loop may have been executed before the loop is entered.
1617 -- Similarly we kill values after the loop, since we do not know
1618 -- that the body of the loop was executed.
1620 Kill_Current_Values
;
1622 Analyze_Iteration_Scheme
(Iteration_Scheme
(N
));
1623 Analyze_Statements
(Statements
(N
));
1624 Process_End_Label
(N
, 'e', Ent
);
1626 Kill_Current_Values
;
1627 end Analyze_Loop_Statement
;
1629 ----------------------------
1630 -- Analyze_Null_Statement --
1631 ----------------------------
1633 -- Note: the semantics of the null statement is implemented by a single
1634 -- null statement, too bad everything isn't as simple as this!
1636 procedure Analyze_Null_Statement
(N
: Node_Id
) is
1637 pragma Warnings
(Off
, N
);
1640 end Analyze_Null_Statement
;
1642 ------------------------
1643 -- Analyze_Statements --
1644 ------------------------
1646 procedure Analyze_Statements
(L
: List_Id
) is
1651 -- The labels declared in the statement list are reachable from
1652 -- statements in the list. We do this as a prepass so that any
1653 -- goto statement will be properly flagged if its target is not
1654 -- reachable. This is not required, but is nice behavior!
1657 while Present
(S
) loop
1658 if Nkind
(S
) = N_Label
then
1659 Analyze
(Identifier
(S
));
1660 Lab
:= Entity
(Identifier
(S
));
1662 -- If we found a label mark it as reachable
1664 if Ekind
(Lab
) = E_Label
then
1665 Generate_Definition
(Lab
);
1666 Set_Reachable
(Lab
);
1668 if Nkind
(Parent
(Lab
)) = N_Implicit_Label_Declaration
then
1669 Set_Label_Construct
(Parent
(Lab
), S
);
1672 -- If we failed to find a label, it means the implicit declaration
1673 -- of the label was hidden. A for-loop parameter can do this to
1674 -- a label with the same name inside the loop, since the implicit
1675 -- label declaration is in the innermost enclosing body or block
1679 Error_Msg_Sloc
:= Sloc
(Lab
);
1681 ("implicit label declaration for & is hidden#",
1689 -- Perform semantic analysis on all statements
1691 Conditional_Statements_Begin
;
1694 while Present
(S
) loop
1699 Conditional_Statements_End
;
1701 -- Make labels unreachable. Visibility is not sufficient, because
1702 -- labels in one if-branch for example are not reachable from the
1703 -- other branch, even though their declarations are in the enclosing
1704 -- declarative part.
1707 while Present
(S
) loop
1708 if Nkind
(S
) = N_Label
then
1709 Set_Reachable
(Entity
(Identifier
(S
)), False);
1714 end Analyze_Statements
;
1716 --------------------------------------------
1717 -- Check_Possible_Current_Value_Condition --
1718 --------------------------------------------
1720 procedure Check_Possible_Current_Value_Condition
(Cnode
: Node_Id
) is
1724 -- Loop to deal with (ignore for now) any NOT operators present
1726 Cond
:= Condition
(Cnode
);
1727 while Nkind
(Cond
) = N_Op_Not
loop
1728 Cond
:= Right_Opnd
(Cond
);
1731 -- Check possible relational operator
1733 if Nkind
(Cond
) = N_Op_Eq
1735 Nkind
(Cond
) = N_Op_Ne
1737 Nkind
(Cond
) = N_Op_Ge
1739 Nkind
(Cond
) = N_Op_Le
1741 Nkind
(Cond
) = N_Op_Gt
1743 Nkind
(Cond
) = N_Op_Lt
1745 if Compile_Time_Known_Value
(Right_Opnd
(Cond
))
1746 and then Nkind
(Left_Opnd
(Cond
)) = N_Identifier
1749 Ent
: constant Entity_Id
:= Entity
(Left_Opnd
(Cond
));
1752 if Ekind
(Ent
) = E_Variable
1754 Ekind
(Ent
) = E_Constant
1758 Ekind
(Ent
) = E_Loop_Parameter
1760 -- Here we have a case where the Current_Value field
1761 -- may need to be set. We set it if it is not already
1762 -- set to a compile time expression value.
1764 -- Note that this represents a decision that one
1765 -- condition blots out another previous one. That's
1766 -- certainly right if they occur at the same level.
1767 -- If the second one is nested, then the decision is
1768 -- neither right nor wrong (it would be equally OK
1769 -- to leave the outer one in place, or take the new
1770 -- inner one. Really we should record both, but our
1771 -- data structures are not that elaborate.
1773 if Nkind
(Current_Value
(Ent
)) not in N_Subexpr
then
1774 Set_Current_Value
(Ent
, Cnode
);
1780 end Check_Possible_Current_Value_Condition
;
1782 ----------------------------
1783 -- Check_Unreachable_Code --
1784 ----------------------------
1786 procedure Check_Unreachable_Code
(N
: Node_Id
) is
1787 Error_Loc
: Source_Ptr
;
1791 if Is_List_Member
(N
)
1792 and then Comes_From_Source
(N
)
1798 Nxt
:= Original_Node
(Next
(N
));
1800 -- If a label follows us, then we never have dead code, since
1801 -- someone could branch to the label, so we just ignore it.
1803 if Nkind
(Nxt
) = N_Label
then
1806 -- Otherwise see if we have a real statement following us
1809 and then Comes_From_Source
(Nxt
)
1810 and then Is_Statement
(Nxt
)
1812 -- Special very annoying exception. If we have a return that
1813 -- follows a raise, then we allow it without a warning, since
1814 -- the Ada RM annoyingly requires a useless return here!
1816 if Nkind
(Original_Node
(N
)) /= N_Raise_Statement
1817 or else Nkind
(Nxt
) /= N_Return_Statement
1819 -- The rather strange shenanigans with the warning message
1820 -- here reflects the fact that Kill_Dead_Code is very good
1821 -- at removing warnings in deleted code, and this is one
1822 -- warning we would prefer NOT to have removed :-)
1824 Error_Loc
:= Sloc
(Nxt
);
1826 -- If we have unreachable code, analyze and remove the
1827 -- unreachable code, since it is useless and we don't
1828 -- want to generate junk warnings.
1830 -- We skip this step if we are not in code generation mode.
1831 -- This is the one case where we remove dead code in the
1832 -- semantics as opposed to the expander, and we do not want
1833 -- to remove code if we are not in code generation mode,
1834 -- since this messes up the ASIS trees.
1836 -- Note that one might react by moving the whole circuit to
1837 -- exp_ch5, but then we lose the warning in -gnatc mode.
1839 if Operating_Mode
= Generate_Code
then
1843 -- Quit deleting when we have nothing more to delete
1844 -- or if we hit a label (since someone could transfer
1845 -- control to a label, so we should not delete it).
1847 exit when No
(Nxt
) or else Nkind
(Nxt
) = N_Label
;
1849 -- Statement/declaration is to be deleted
1853 Kill_Dead_Code
(Nxt
);
1857 -- Now issue the warning
1859 Error_Msg
("?unreachable code", Error_Loc
);
1862 -- If the unconditional transfer of control instruction is
1863 -- the last statement of a sequence, then see if our parent
1864 -- is one of the constructs for which we count unblocked exits,
1865 -- and if so, adjust the count.
1870 -- Statements in THEN part or ELSE part of IF statement
1872 if Nkind
(P
) = N_If_Statement
then
1875 -- Statements in ELSIF part of an IF statement
1877 elsif Nkind
(P
) = N_Elsif_Part
then
1879 pragma Assert
(Nkind
(P
) = N_If_Statement
);
1881 -- Statements in CASE statement alternative
1883 elsif Nkind
(P
) = N_Case_Statement_Alternative
then
1885 pragma Assert
(Nkind
(P
) = N_Case_Statement
);
1887 -- Statements in body of block
1889 elsif Nkind
(P
) = N_Handled_Sequence_Of_Statements
1890 and then Nkind
(Parent
(P
)) = N_Block_Statement
1894 -- Statements in exception handler in a block
1896 elsif Nkind
(P
) = N_Exception_Handler
1897 and then Nkind
(Parent
(P
)) = N_Handled_Sequence_Of_Statements
1898 and then Nkind
(Parent
(Parent
(P
))) = N_Block_Statement
1902 -- None of these cases, so return
1908 -- This was one of the cases we are looking for (i.e. the
1909 -- parent construct was IF, CASE or block) so decrement count.
1911 Unblocked_Exit_Count
:= Unblocked_Exit_Count
- 1;
1915 end Check_Unreachable_Code
;