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rt_gccstream/gcc/ada/sem_ch5.adb

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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S E M _ C H 5 --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-2009, Free Software Foundation, Inc. --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING3. If not, go to --
-- http://www.gnu.org/licenses for a complete copy of the license. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc. --
-- --
------------------------------------------------------------------------------
with Atree; use Atree;
with Checks; use Checks;
with Einfo; use Einfo;
with Errout; use Errout;
with Expander; use Expander;
with Exp_Util; use Exp_Util;
with Freeze; use Freeze;
with Lib; use Lib;
with Lib.Xref; use Lib.Xref;
with Namet; use Namet;
with Nlists; use Nlists;
with Nmake; use Nmake;
with Opt; use Opt;
with Rtsfind; use Rtsfind;
with Sem; use Sem;
with Sem_Aux; use Sem_Aux;
with Sem_Case; use Sem_Case;
with Sem_Ch3; use Sem_Ch3;
with Sem_Ch8; use Sem_Ch8;
with Sem_Disp; use Sem_Disp;
with Sem_Elab; use Sem_Elab;
with Sem_Eval; use Sem_Eval;
with Sem_Res; use Sem_Res;
with Sem_SCIL; use Sem_SCIL;
with Sem_Type; use Sem_Type;
with Sem_Util; use Sem_Util;
with Sem_Warn; use Sem_Warn;
with Snames; use Snames;
with Stand; use Stand;
with Sinfo; use Sinfo;
with Targparm; use Targparm;
with Tbuild; use Tbuild;
with Uintp; use Uintp;
package body Sem_Ch5 is
Unblocked_Exit_Count : Nat := 0;
-- This variable is used when processing if statements, case statements,
-- and block statements. It counts the number of exit points that are not
-- blocked by unconditional transfer instructions: for IF and CASE, these
-- are the branches of the conditional; for a block, they are the statement
-- sequence of the block, and the statement sequences of any exception
-- handlers that are part of the block. When processing is complete, if
-- this count is zero, it means that control cannot fall through the IF,
-- CASE or block statement. This is used for the generation of warning
-- messages. This variable is recursively saved on entry to processing the
-- construct, and restored on exit.
-----------------------
-- Local Subprograms --
-----------------------
procedure Analyze_Iteration_Scheme (N : Node_Id);
------------------------
-- Analyze_Assignment --
------------------------
procedure Analyze_Assignment (N : Node_Id) is
Lhs : constant Node_Id := Name (N);
Rhs : constant Node_Id := Expression (N);
T1 : Entity_Id;
T2 : Entity_Id;
Decl : Node_Id;
procedure Diagnose_Non_Variable_Lhs (N : Node_Id);
-- N is the node for the left hand side of an assignment, and it is not
-- a variable. This routine issues an appropriate diagnostic.
procedure Kill_Lhs;
-- This is called to kill current value settings of a simple variable
-- on the left hand side. We call it if we find any error in analyzing
-- the assignment, and at the end of processing before setting any new
-- current values in place.
procedure Set_Assignment_Type
(Opnd : Node_Id;
Opnd_Type : in out Entity_Id);
-- Opnd is either the Lhs or Rhs of the assignment, and Opnd_Type
-- is the nominal subtype. This procedure is used to deal with cases
-- where the nominal subtype must be replaced by the actual subtype.
-------------------------------
-- Diagnose_Non_Variable_Lhs --
-------------------------------
procedure Diagnose_Non_Variable_Lhs (N : Node_Id) is
begin
-- Not worth posting another error if left hand side already
-- flagged as being illegal in some respect.
if Error_Posted (N) then
return;
-- Some special bad cases of entity names
elsif Is_Entity_Name (N) then
declare
Ent : constant Entity_Id := Entity (N);
begin
if Ekind (Ent) = E_In_Parameter then
Error_Msg_N
("assignment to IN mode parameter not allowed", N);
-- Renamings of protected private components are turned into
-- constants when compiling a protected function. In the case
-- of single protected types, the private component appears
-- directly.
elsif (Is_Prival (Ent)
and then
(Ekind (Current_Scope) = E_Function
or else Ekind (Enclosing_Dynamic_Scope (
Current_Scope)) = E_Function))
or else
(Ekind (Ent) = E_Component
and then Is_Protected_Type (Scope (Ent)))
then
Error_Msg_N
("protected function cannot modify protected object", N);
elsif Ekind (Ent) = E_Loop_Parameter then
Error_Msg_N
("assignment to loop parameter not allowed", N);
else
Error_Msg_N
("left hand side of assignment must be a variable", N);
end if;
end;
-- For indexed components or selected components, test prefix
elsif Nkind (N) = N_Indexed_Component then
Diagnose_Non_Variable_Lhs (Prefix (N));
-- Another special case for assignment to discriminant
elsif Nkind (N) = N_Selected_Component then
if Present (Entity (Selector_Name (N)))
and then Ekind (Entity (Selector_Name (N))) = E_Discriminant
then
Error_Msg_N
("assignment to discriminant not allowed", N);
else
Diagnose_Non_Variable_Lhs (Prefix (N));
end if;
else
-- If we fall through, we have no special message to issue!
Error_Msg_N ("left hand side of assignment must be a variable", N);
end if;
end Diagnose_Non_Variable_Lhs;
--------------
-- Kill_LHS --
--------------
procedure Kill_Lhs is
begin
if Is_Entity_Name (Lhs) then
declare
Ent : constant Entity_Id := Entity (Lhs);
begin
if Present (Ent) then
Kill_Current_Values (Ent);
end if;
end;
end if;
end Kill_Lhs;
-------------------------
-- Set_Assignment_Type --
-------------------------
procedure Set_Assignment_Type
(Opnd : Node_Id;
Opnd_Type : in out Entity_Id)
is
begin
Require_Entity (Opnd);
-- If the assignment operand is an in-out or out parameter, then we
-- get the actual subtype (needed for the unconstrained case).
-- If the operand is the actual in an entry declaration, then within
-- the accept statement it is replaced with a local renaming, which
-- may also have an actual subtype.
if Is_Entity_Name (Opnd)
and then (Ekind (Entity (Opnd)) = E_Out_Parameter
or else Ekind (Entity (Opnd)) =
E_In_Out_Parameter
or else Ekind (Entity (Opnd)) =
E_Generic_In_Out_Parameter
or else
(Ekind (Entity (Opnd)) = E_Variable
and then Nkind (Parent (Entity (Opnd))) =
N_Object_Renaming_Declaration
and then Nkind (Parent (Parent (Entity (Opnd)))) =
N_Accept_Statement))
then
Opnd_Type := Get_Actual_Subtype (Opnd);
-- If assignment operand is a component reference, then we get the
-- actual subtype of the component for the unconstrained case.
elsif Nkind_In (Opnd, N_Selected_Component, N_Explicit_Dereference)
and then not Is_Unchecked_Union (Opnd_Type)
then
Decl := Build_Actual_Subtype_Of_Component (Opnd_Type, Opnd);
if Present (Decl) then
Insert_Action (N, Decl);
Mark_Rewrite_Insertion (Decl);
Analyze (Decl);
Opnd_Type := Defining_Identifier (Decl);
Set_Etype (Opnd, Opnd_Type);
Freeze_Itype (Opnd_Type, N);
elsif Is_Constrained (Etype (Opnd)) then
Opnd_Type := Etype (Opnd);
end if;
-- For slice, use the constrained subtype created for the slice
elsif Nkind (Opnd) = N_Slice then
Opnd_Type := Etype (Opnd);
end if;
end Set_Assignment_Type;
-- Start of processing for Analyze_Assignment
begin
Mark_Coextensions (N, Rhs);
Analyze (Rhs);
Analyze (Lhs);
-- Start type analysis for assignment
T1 := Etype (Lhs);
-- In the most general case, both Lhs and Rhs can be overloaded, and we
-- must compute the intersection of the possible types on each side.
if Is_Overloaded (Lhs) then
declare
I : Interp_Index;
It : Interp;
begin
T1 := Any_Type;
Get_First_Interp (Lhs, I, It);
while Present (It.Typ) loop
if Has_Compatible_Type (Rhs, It.Typ) then
if T1 /= Any_Type then
-- An explicit dereference is overloaded if the prefix
-- is. Try to remove the ambiguity on the prefix, the
-- error will be posted there if the ambiguity is real.
if Nkind (Lhs) = N_Explicit_Dereference then
declare
PI : Interp_Index;
PI1 : Interp_Index := 0;
PIt : Interp;
Found : Boolean;
begin
Found := False;
Get_First_Interp (Prefix (Lhs), PI, PIt);
while Present (PIt.Typ) loop
if Is_Access_Type (PIt.Typ)
and then Has_Compatible_Type
(Rhs, Designated_Type (PIt.Typ))
then
if Found then
PIt :=
Disambiguate (Prefix (Lhs),
PI1, PI, Any_Type);
if PIt = No_Interp then
Error_Msg_N
("ambiguous left-hand side"
& " in assignment", Lhs);
exit;
else
Resolve (Prefix (Lhs), PIt.Typ);
end if;
exit;
else
Found := True;
PI1 := PI;
end if;
end if;
Get_Next_Interp (PI, PIt);
end loop;
end;
else
Error_Msg_N
("ambiguous left-hand side in assignment", Lhs);
exit;
end if;
else
T1 := It.Typ;
end if;
end if;
Get_Next_Interp (I, It);
end loop;
end;
if T1 = Any_Type then
Error_Msg_N
("no valid types for left-hand side for assignment", Lhs);
Kill_Lhs;
return;
end if;
end if;
-- The resulting assignment type is T1, so now we will resolve the
-- left hand side of the assignment using this determined type.
Resolve (Lhs, T1);
-- Cases where Lhs is not a variable
if not Is_Variable (Lhs) then
-- Ada 2005 (AI-327): Check assignment to the attribute Priority of
-- a protected object.
declare
Ent : Entity_Id;
S : Entity_Id;
begin
if Ada_Version >= Ada_05 then
-- Handle chains of renamings
Ent := Lhs;
while Nkind (Ent) in N_Has_Entity
and then Present (Entity (Ent))
and then Present (Renamed_Object (Entity (Ent)))
loop
Ent := Renamed_Object (Entity (Ent));
end loop;
if (Nkind (Ent) = N_Attribute_Reference
and then Attribute_Name (Ent) = Name_Priority)
-- Renamings of the attribute Priority applied to protected
-- objects have been previously expanded into calls to the
-- Get_Ceiling run-time subprogram.
or else
(Nkind (Ent) = N_Function_Call
and then (Entity (Name (Ent)) = RTE (RE_Get_Ceiling)
or else
Entity (Name (Ent)) = RTE (RO_PE_Get_Ceiling)))
then
-- The enclosing subprogram cannot be a protected function
S := Current_Scope;
while not (Is_Subprogram (S)
and then Convention (S) = Convention_Protected)
and then S /= Standard_Standard
loop
S := Scope (S);
end loop;
if Ekind (S) = E_Function
and then Convention (S) = Convention_Protected
then
Error_Msg_N
("protected function cannot modify protected object",
Lhs);
end if;
-- Changes of the ceiling priority of the protected object
-- are only effective if the Ceiling_Locking policy is in
-- effect (AARM D.5.2 (5/2)).
if Locking_Policy /= 'C' then
Error_Msg_N ("assignment to the attribute PRIORITY has " &
"no effect?", Lhs);
Error_Msg_N ("\since no Locking_Policy has been " &
"specified", Lhs);
end if;
return;
end if;
end if;
end;
Diagnose_Non_Variable_Lhs (Lhs);
return;
-- Error of assigning to limited type. We do however allow this in
-- certain cases where the front end generates the assignments.
elsif Is_Limited_Type (T1)
and then not Assignment_OK (Lhs)
and then not Assignment_OK (Original_Node (Lhs))
and then not Is_Value_Type (T1)
then
-- CPP constructors can only be called in declarations
if Is_CPP_Constructor_Call (Rhs) then
Error_Msg_N ("invalid use of 'C'P'P constructor", Rhs);
else
Error_Msg_N
("left hand of assignment must not be limited type", Lhs);
Explain_Limited_Type (T1, Lhs);
end if;
return;
-- Enforce RM 3.9.3 (8): left-hand side cannot be abstract
elsif Is_Interface (T1)
and then not Is_Class_Wide_Type (T1)
then
Error_Msg_N
("target of assignment operation may not be abstract", Lhs);
return;
end if;
-- Resolution may have updated the subtype, in case the left-hand
-- side is a private protected component. Use the correct subtype
-- to avoid scoping issues in the back-end.
T1 := Etype (Lhs);
-- Ada 2005 (AI-50217, AI-326): Check wrong dereference of incomplete
-- type. For example:
-- limited with P;
-- package Pkg is
-- type Acc is access P.T;
-- end Pkg;
-- with Pkg; use Acc;
-- procedure Example is
-- A, B : Acc;
-- begin
-- A.all := B.all; -- ERROR
-- end Example;
if Nkind (Lhs) = N_Explicit_Dereference
and then Ekind (T1) = E_Incomplete_Type
then
Error_Msg_N ("invalid use of incomplete type", Lhs);
Kill_Lhs;
return;
end if;
-- Now we can complete the resolution of the right hand side
Set_Assignment_Type (Lhs, T1);
Resolve (Rhs, T1);
-- This is the point at which we check for an unset reference
Check_Unset_Reference (Rhs);
Check_Unprotected_Access (Lhs, Rhs);
-- Remaining steps are skipped if Rhs was syntactically in error
if Rhs = Error then
Kill_Lhs;
return;
end if;
T2 := Etype (Rhs);
if not Covers (T1, T2) then
Wrong_Type (Rhs, Etype (Lhs));
Kill_Lhs;
return;
end if;
-- Ada 2005 (AI-326): In case of explicit dereference of incomplete
-- types, use the non-limited view if available
if Nkind (Rhs) = N_Explicit_Dereference
and then Ekind (T2) = E_Incomplete_Type
and then Is_Tagged_Type (T2)
and then Present (Non_Limited_View (T2))
then
T2 := Non_Limited_View (T2);
end if;
Set_Assignment_Type (Rhs, T2);
if Total_Errors_Detected /= 0 then
if No (T1) then
T1 := Any_Type;
end if;
if No (T2) then
T2 := Any_Type;
end if;
end if;
if T1 = Any_Type or else T2 = Any_Type then
Kill_Lhs;
return;
end if;
-- If the rhs is class-wide or dynamically tagged, then require the lhs
-- to be class-wide. The case where the rhs is a dynamically tagged call
-- to a dispatching operation with a controlling access result is
-- excluded from this check, since the target has an access type (and
-- no tag propagation occurs in that case).
if (Is_Class_Wide_Type (T2)
or else (Is_Dynamically_Tagged (Rhs)
and then not Is_Access_Type (T1)))
and then not Is_Class_Wide_Type (T1)
then
Error_Msg_N ("dynamically tagged expression not allowed!", Rhs);
elsif Is_Class_Wide_Type (T1)
and then not Is_Class_Wide_Type (T2)
and then not Is_Tag_Indeterminate (Rhs)
and then not Is_Dynamically_Tagged (Rhs)
then
Error_Msg_N ("dynamically tagged expression required!", Rhs);
end if;
-- Propagate the tag from a class-wide target to the rhs when the rhs
-- is a tag-indeterminate call.
if Is_Tag_Indeterminate (Rhs) then
if Is_Class_Wide_Type (T1) then
Propagate_Tag (Lhs, Rhs);
elsif Nkind (Rhs) = N_Function_Call
and then Is_Entity_Name (Name (Rhs))
and then Is_Abstract_Subprogram (Entity (Name (Rhs)))
then
Error_Msg_N
("call to abstract function must be dispatching", Name (Rhs));
elsif Nkind (Rhs) = N_Qualified_Expression
and then Nkind (Expression (Rhs)) = N_Function_Call
and then Is_Entity_Name (Name (Expression (Rhs)))
and then
Is_Abstract_Subprogram (Entity (Name (Expression (Rhs))))
then
Error_Msg_N
("call to abstract function must be dispatching",
Name (Expression (Rhs)));
end if;
end if;
-- Ada 2005 (AI-385): When the lhs type is an anonymous access type,
-- apply an implicit conversion of the rhs to that type to force
-- appropriate static and run-time accessibility checks. This applies
-- as well to anonymous access-to-subprogram types that are component
-- subtypes or formal parameters.
if Ada_Version >= Ada_05
and then Is_Access_Type (T1)
then
if Is_Local_Anonymous_Access (T1)
or else Ekind (T2) = E_Anonymous_Access_Subprogram_Type
then
Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
Analyze_And_Resolve (Rhs, T1);
end if;
end if;
-- Ada 2005 (AI-231): Assignment to not null variable
if Ada_Version >= Ada_05
and then Can_Never_Be_Null (T1)
and then not Assignment_OK (Lhs)
then
-- Case where we know the right hand side is null
if Known_Null (Rhs) then
Apply_Compile_Time_Constraint_Error
(N => Rhs,
Msg => "(Ada 2005) null not allowed in null-excluding objects?",
Reason => CE_Null_Not_Allowed);
-- We still mark this as a possible modification, that's necessary
-- to reset Is_True_Constant, and desirable for xref purposes.
Note_Possible_Modification (Lhs, Sure => True);
return;
-- If we know the right hand side is non-null, then we convert to the
-- target type, since we don't need a run time check in that case.
elsif not Can_Never_Be_Null (T2) then
Rewrite (Rhs, Convert_To (T1, Relocate_Node (Rhs)));
Analyze_And_Resolve (Rhs, T1);
end if;
end if;
if Is_Scalar_Type (T1) then
Apply_Scalar_Range_Check (Rhs, Etype (Lhs));
-- For array types, verify that lengths match. If the right hand side
-- if a function call that has been inlined, the assignment has been
-- rewritten as a block, and the constraint check will be applied to the
-- assignment within the block.
elsif Is_Array_Type (T1)
and then
(Nkind (Rhs) /= N_Type_Conversion
or else Is_Constrained (Etype (Rhs)))
and then
(Nkind (Rhs) /= N_Function_Call
or else Nkind (N) /= N_Block_Statement)
then
-- Assignment verifies that the length of the Lsh and Rhs are equal,
-- but of course the indices do not have to match. If the right-hand
-- side is a type conversion to an unconstrained type, a length check
-- is performed on the expression itself during expansion. In rare
-- cases, the redundant length check is computed on an index type
-- with a different representation, triggering incorrect code in
-- the back end.
Apply_Length_Check (Rhs, Etype (Lhs));
else
-- Discriminant checks are applied in the course of expansion
null;
end if;
-- Note: modifications of the Lhs may only be recorded after
-- checks have been applied.
Note_Possible_Modification (Lhs, Sure => True);
-- ??? a real accessibility check is needed when ???
-- Post warning for redundant assignment or variable to itself
if Warn_On_Redundant_Constructs
-- We only warn for source constructs
and then Comes_From_Source (N)
-- Where the object is the same on both sides
and then Same_Object (Lhs, Original_Node (Rhs))
-- But exclude the case where the right side was an operation
-- that got rewritten (e.g. JUNK + K, where K was known to be
-- zero). We don't want to warn in such a case, since it is
-- reasonable to write such expressions especially when K is
-- defined symbolically in some other package.
and then Nkind (Original_Node (Rhs)) not in N_Op
then
if Nkind (Lhs) in N_Has_Entity then
Error_Msg_NE
("?useless assignment of & to itself!", N, Entity (Lhs));
else
Error_Msg_N
("?useless assignment of object to itself!", N);
end if;
end if;
-- Check for non-allowed composite assignment
if not Support_Composite_Assign_On_Target
and then (Is_Array_Type (T1) or else Is_Record_Type (T1))
and then (not Has_Size_Clause (T1) or else Esize (T1) > 64)
then
Error_Msg_CRT ("composite assignment", N);
end if;
-- Check elaboration warning for left side if not in elab code
if not In_Subprogram_Or_Concurrent_Unit then
Check_Elab_Assign (Lhs);
end if;
-- Set Referenced_As_LHS if appropriate. We only set this flag if the
-- assignment is a source assignment in the extended main source unit.
-- We are not interested in any reference information outside this
-- context, or in compiler generated assignment statements.
if Comes_From_Source (N)
and then In_Extended_Main_Source_Unit (Lhs)
then
Set_Referenced_Modified (Lhs, Out_Param => False);
end if;
-- Final step. If left side is an entity, then we may be able to
-- reset the current tracked values to new safe values. We only have
-- something to do if the left side is an entity name, and expansion
-- has not modified the node into something other than an assignment,
-- and of course we only capture values if it is safe to do so.
if Is_Entity_Name (Lhs)
and then Nkind (N) = N_Assignment_Statement
then
declare
Ent : constant Entity_Id := Entity (Lhs);
begin
if Safe_To_Capture_Value (N, Ent) then
-- If simple variable on left side, warn if this assignment
-- blots out another one (rendering it useless) and note
-- location of assignment in case no one references value.
-- We only do this for source assignments, otherwise we can
-- generate bogus warnings when an assignment is rewritten as
-- another assignment, and gets tied up with itself.
-- Note: we don't use Record_Last_Assignment here, because we
-- have lots of other stuff to do under control of this test.
if Warn_On_Modified_Unread
and then Is_Assignable (Ent)
and then Comes_From_Source (N)
and then In_Extended_Main_Source_Unit (Ent)
then
Warn_On_Useless_Assignment (Ent, N);
Set_Last_Assignment (Ent, Lhs);
end if;
-- If we are assigning an access type and the left side is an
-- entity, then make sure that the Is_Known_[Non_]Null flags
-- properly reflect the state of the entity after assignment.
if Is_Access_Type (T1) then
if Known_Non_Null (Rhs) then
Set_Is_Known_Non_Null (Ent, True);
elsif Known_Null (Rhs)
and then not Can_Never_Be_Null (Ent)
then
Set_Is_Known_Null (Ent, True);
else
Set_Is_Known_Null (Ent, False);
if not Can_Never_Be_Null (Ent) then
Set_Is_Known_Non_Null (Ent, False);
end if;
end if;
-- For discrete types, we may be able to set the current value
-- if the value is known at compile time.
elsif Is_Discrete_Type (T1)
and then Compile_Time_Known_Value (Rhs)
then
Set_Current_Value (Ent, Rhs);
else
Set_Current_Value (Ent, Empty);
end if;
-- If not safe to capture values, kill them
else
Kill_Lhs;
end if;
end;
end if;
end Analyze_Assignment;
-----------------------------
-- Analyze_Block_Statement --
-----------------------------
procedure Analyze_Block_Statement (N : Node_Id) is
Decls : constant List_Id := Declarations (N);
Id : constant Node_Id := Identifier (N);
HSS : constant Node_Id := Handled_Statement_Sequence (N);
begin
-- If no handled statement sequence is present, things are really
-- messed up, and we just return immediately (this is a defence
-- against previous errors).
if No (HSS) then
return;
end if;
-- Normal processing with HSS present
declare
EH : constant List_Id := Exception_Handlers (HSS);
Ent : Entity_Id := Empty;
S : Entity_Id;
Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
-- Recursively save value of this global, will be restored on exit
begin
-- Initialize unblocked exit count for statements of begin block
-- plus one for each exception handler that is present.
Unblocked_Exit_Count := 1;
if Present (EH) then
Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
end if;
-- If a label is present analyze it and mark it as referenced
if Present (Id) then
Analyze (Id);
Ent := Entity (Id);
-- An error defense. If we have an identifier, but no entity,
-- then something is wrong. If we have previous errors, then
-- just remove the identifier and continue, otherwise raise
-- an exception.
if No (Ent) then
if Total_Errors_Detected /= 0 then
Set_Identifier (N, Empty);
else
raise Program_Error;
end if;
else
Set_Ekind (Ent, E_Block);
Generate_Reference (Ent, N, ' ');
Generate_Definition (Ent);
if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
Set_Label_Construct (Parent (Ent), N);
end if;
end if;
end if;
-- If no entity set, create a label entity
if No (Ent) then
Ent := New_Internal_Entity (E_Block, Current_Scope, Sloc (N), 'B');
Set_Identifier (N, New_Occurrence_Of (Ent, Sloc (N)));
Set_Parent (Ent, N);
end if;
Set_Etype (Ent, Standard_Void_Type);
Set_Block_Node (Ent, Identifier (N));
Push_Scope (Ent);
if Present (Decls) then
Analyze_Declarations (Decls);
Check_Completion;
Inspect_Deferred_Constant_Completion (Decls);
end if;
Analyze (HSS);
Process_End_Label (HSS, 'e', Ent);
-- If exception handlers are present, then we indicate that
-- enclosing scopes contain a block with handlers. We only
-- need to mark non-generic scopes.
if Present (EH) then
S := Scope (Ent);
loop
Set_Has_Nested_Block_With_Handler (S);
exit when Is_Overloadable (S)
or else Ekind (S) = E_Package
or else Is_Generic_Unit (S);
S := Scope (S);
end loop;
end if;
Check_References (Ent);
Warn_On_Useless_Assignments (Ent);
End_Scope;
if Unblocked_Exit_Count = 0 then
Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
Check_Unreachable_Code (N);
else
Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
end if;
end;
end Analyze_Block_Statement;
----------------------------
-- Analyze_Case_Statement --
----------------------------
procedure Analyze_Case_Statement (N : Node_Id) is
Exp : Node_Id;
Exp_Type : Entity_Id;
Exp_Btype : Entity_Id;
Last_Choice : Nat;
Dont_Care : Boolean;
Others_Present : Boolean;
pragma Warnings (Off, Last_Choice);
pragma Warnings (Off, Dont_Care);
-- Don't care about assigned values
Statements_Analyzed : Boolean := False;
-- Set True if at least some statement sequences get analyzed.
-- If False on exit, means we had a serious error that prevented
-- full analysis of the case statement, and as a result it is not
-- a good idea to output warning messages about unreachable code.
Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
-- Recursively save value of this global, will be restored on exit
procedure Non_Static_Choice_Error (Choice : Node_Id);
-- Error routine invoked by the generic instantiation below when
-- the case statement has a non static choice.
procedure Process_Statements (Alternative : Node_Id);
-- Analyzes all the statements associated to a case alternative.
-- Needed by the generic instantiation below.
package Case_Choices_Processing is new
Generic_Choices_Processing
(Get_Alternatives => Alternatives,
Get_Choices => Discrete_Choices,
Process_Empty_Choice => No_OP,
Process_Non_Static_Choice => Non_Static_Choice_Error,
Process_Associated_Node => Process_Statements);
use Case_Choices_Processing;
-- Instantiation of the generic choice processing package
-----------------------------
-- Non_Static_Choice_Error --
-----------------------------
procedure Non_Static_Choice_Error (Choice : Node_Id) is
begin
Flag_Non_Static_Expr
("choice given in case statement is not static!", Choice);
end Non_Static_Choice_Error;
------------------------
-- Process_Statements --
------------------------
procedure Process_Statements (Alternative : Node_Id) is
Choices : constant List_Id := Discrete_Choices (Alternative);
Ent : Entity_Id;
begin
Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
Statements_Analyzed := True;
-- An interesting optimization. If the case statement expression
-- is a simple entity, then we can set the current value within
-- an alternative if the alternative has one possible value.
-- case N is
-- when 1 => alpha
-- when 2 | 3 => beta
-- when others => gamma
-- Here we know that N is initially 1 within alpha, but for beta
-- and gamma, we do not know anything more about the initial value.
if Is_Entity_Name (Exp) then
Ent := Entity (Exp);
if Ekind (Ent) = E_Variable
or else
Ekind (Ent) = E_In_Out_Parameter
or else
Ekind (Ent) = E_Out_Parameter
then
if List_Length (Choices) = 1
and then Nkind (First (Choices)) in N_Subexpr
and then Compile_Time_Known_Value (First (Choices))
then
Set_Current_Value (Entity (Exp), First (Choices));
end if;
Analyze_Statements (Statements (Alternative));
-- After analyzing the case, set the current value to empty
-- since we won't know what it is for the next alternative
-- (unless reset by this same circuit), or after the case.
Set_Current_Value (Entity (Exp), Empty);
return;
end if;
end if;
-- Case where expression is not an entity name of a variable
Analyze_Statements (Statements (Alternative));
end Process_Statements;
-- Table to record choices. Put after subprograms since we make
-- a call to Number_Of_Choices to get the right number of entries.
Case_Table : Choice_Table_Type (1 .. Number_Of_Choices (N));
pragma Warnings (Off, Case_Table);
-- Start of processing for Analyze_Case_Statement
begin
Unblocked_Exit_Count := 0;
Exp := Expression (N);
Analyze (Exp);
-- The expression must be of any discrete type. In rare cases, the
-- expander constructs a case statement whose expression has a private
-- type whose full view is discrete. This can happen when generating
-- a stream operation for a variant type after the type is frozen,
-- when the partial of view of the type of the discriminant is private.
-- In that case, use the full view to analyze case alternatives.
if not Is_Overloaded (Exp)
and then not Comes_From_Source (N)
and then Is_Private_Type (Etype (Exp))
and then Present (Full_View (Etype (Exp)))
and then Is_Discrete_Type (Full_View (Etype (Exp)))
then
Resolve (Exp, Etype (Exp));
Exp_Type := Full_View (Etype (Exp));
else
Analyze_And_Resolve (Exp, Any_Discrete);
Exp_Type := Etype (Exp);
end if;
Check_Unset_Reference (Exp);
Exp_Btype := Base_Type (Exp_Type);
-- The expression must be of a discrete type which must be determinable
-- independently of the context in which the expression occurs, but
-- using the fact that the expression must be of a discrete type.
-- Moreover, the type this expression must not be a character literal
-- (which is always ambiguous) or, for Ada-83, a generic formal type.
-- If error already reported by Resolve, nothing more to do
if Exp_Btype = Any_Discrete
or else Exp_Btype = Any_Type
then
return;
elsif Exp_Btype = Any_Character then
Error_Msg_N
("character literal as case expression is ambiguous", Exp);
return;
elsif Ada_Version = Ada_83
and then (Is_Generic_Type (Exp_Btype)
or else Is_Generic_Type (Root_Type (Exp_Btype)))
then
Error_Msg_N
("(Ada 83) case expression cannot be of a generic type", Exp);
return;
end if;
-- If the case expression is a formal object of mode in out, then
-- treat it as having a nonstatic subtype by forcing use of the base
-- type (which has to get passed to Check_Case_Choices below). Also
-- use base type when the case expression is parenthesized.
if Paren_Count (Exp) > 0
or else (Is_Entity_Name (Exp)
and then Ekind (Entity (Exp)) = E_Generic_In_Out_Parameter)
then
Exp_Type := Exp_Btype;
end if;
-- Call instantiated Analyze_Choices which does the rest of the work
Analyze_Choices
(N, Exp_Type, Case_Table, Last_Choice, Dont_Care, Others_Present);
if Exp_Type = Universal_Integer and then not Others_Present then
Error_Msg_N ("case on universal integer requires OTHERS choice", Exp);
end if;
-- If all our exits were blocked by unconditional transfers of control,
-- then the entire CASE statement acts as an unconditional transfer of
-- control, so treat it like one, and check unreachable code. Skip this
-- test if we had serious errors preventing any statement analysis.
if Unblocked_Exit_Count = 0 and then Statements_Analyzed then
Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
Check_Unreachable_Code (N);
else
Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
end if;
if not Expander_Active
and then Compile_Time_Known_Value (Expression (N))
and then Serious_Errors_Detected = 0
then
declare
Chosen : constant Node_Id := Find_Static_Alternative (N);
Alt : Node_Id;
begin
Alt := First (Alternatives (N));
while Present (Alt) loop
if Alt /= Chosen then
Remove_Warning_Messages (Statements (Alt));
end if;
Next (Alt);
end loop;
end;
end if;
end Analyze_Case_Statement;
----------------------------
-- Analyze_Exit_Statement --
----------------------------
-- If the exit includes a name, it must be the name of a currently open
-- loop. Otherwise there must be an innermost open loop on the stack,
-- to which the statement implicitly refers.
procedure Analyze_Exit_Statement (N : Node_Id) is
Target : constant Node_Id := Name (N);
Cond : constant Node_Id := Condition (N);
Scope_Id : Entity_Id;
U_Name : Entity_Id;
Kind : Entity_Kind;
begin
if No (Cond) then
Check_Unreachable_Code (N);
end if;
if Present (Target) then
Analyze (Target);
U_Name := Entity (Target);
if not In_Open_Scopes (U_Name) or else Ekind (U_Name) /= E_Loop then
Error_Msg_N ("invalid loop name in exit statement", N);
return;
else
Set_Has_Exit (U_Name);
end if;
else
U_Name := Empty;
end if;
for J in reverse 0 .. Scope_Stack.Last loop
Scope_Id := Scope_Stack.Table (J).Entity;
Kind := Ekind (Scope_Id);
if Kind = E_Loop
and then (No (Target) or else Scope_Id = U_Name) then
Set_Has_Exit (Scope_Id);
exit;
elsif Kind = E_Block
or else Kind = E_Loop
or else Kind = E_Return_Statement
then
null;
else
Error_Msg_N
("cannot exit from program unit or accept statement", N);
exit;
end if;
end loop;
-- Verify that if present the condition is a Boolean expression
if Present (Cond) then
Analyze_And_Resolve (Cond, Any_Boolean);
Check_Unset_Reference (Cond);
end if;
-- Since the exit may take us out of a loop, any previous assignment
-- statement is not useless, so clear last assignment indications. It
-- is OK to keep other current values, since if the exit statement
-- does not exit, then the current values are still valid.
Kill_Current_Values (Last_Assignment_Only => True);
end Analyze_Exit_Statement;
----------------------------
-- Analyze_Goto_Statement --
----------------------------
procedure Analyze_Goto_Statement (N : Node_Id) is
Label : constant Node_Id := Name (N);
Scope_Id : Entity_Id;
Label_Scope : Entity_Id;
Label_Ent : Entity_Id;
begin
Check_Unreachable_Code (N);
Kill_Current_Values (Last_Assignment_Only => True);
Analyze (Label);
Label_Ent := Entity (Label);
-- Ignore previous error
if Label_Ent = Any_Id then
return;
-- We just have a label as the target of a goto
elsif Ekind (Label_Ent) /= E_Label then
Error_Msg_N ("target of goto statement must be a label", Label);
return;
-- Check that the target of the goto is reachable according to Ada
-- scoping rules. Note: the special gotos we generate for optimizing
-- local handling of exceptions would violate these rules, but we mark
-- such gotos as analyzed when built, so this code is never entered.
elsif not Reachable (Label_Ent) then
Error_Msg_N ("target of goto statement is not reachable", Label);
return;
end if;
-- Here if goto passes initial validity checks
Label_Scope := Enclosing_Scope (Label_Ent);
for J in reverse 0 .. Scope_Stack.Last loop
Scope_Id := Scope_Stack.Table (J).Entity;
if Label_Scope = Scope_Id
or else (Ekind (Scope_Id) /= E_Block
and then Ekind (Scope_Id) /= E_Loop
and then Ekind (Scope_Id) /= E_Return_Statement)
then
if Scope_Id /= Label_Scope then
Error_Msg_N
("cannot exit from program unit or accept statement", N);
end if;
return;
end if;
end loop;
raise Program_Error;
end Analyze_Goto_Statement;
--------------------------
-- Analyze_If_Statement --
--------------------------
-- A special complication arises in the analysis of if statements
-- The expander has circuitry to completely delete code that it
-- can tell will not be executed (as a result of compile time known
-- conditions). In the analyzer, we ensure that code that will be
-- deleted in this manner is analyzed but not expanded. This is
-- obviously more efficient, but more significantly, difficulties
-- arise if code is expanded and then eliminated (e.g. exception
-- table entries disappear). Similarly, itypes generated in deleted
-- code must be frozen from start, because the nodes on which they
-- depend will not be available at the freeze point.
procedure Analyze_If_Statement (N : Node_Id) is
E : Node_Id;
Save_Unblocked_Exit_Count : constant Nat := Unblocked_Exit_Count;
-- Recursively save value of this global, will be restored on exit
Save_In_Deleted_Code : Boolean;
Del : Boolean := False;
-- This flag gets set True if a True condition has been found,
-- which means that remaining ELSE/ELSIF parts are deleted.
procedure Analyze_Cond_Then (Cnode : Node_Id);
-- This is applied to either the N_If_Statement node itself or
-- to an N_Elsif_Part node. It deals with analyzing the condition
-- and the THEN statements associated with it.
-----------------------
-- Analyze_Cond_Then --
-----------------------
procedure Analyze_Cond_Then (Cnode : Node_Id) is
Cond : constant Node_Id := Condition (Cnode);
Tstm : constant List_Id := Then_Statements (Cnode);
begin
Unblocked_Exit_Count := Unblocked_Exit_Count + 1;
Analyze_And_Resolve (Cond, Any_Boolean);
Check_Unset_Reference (Cond);
Set_Current_Value_Condition (Cnode);
-- If already deleting, then just analyze then statements
if Del then
Analyze_Statements (Tstm);
-- Compile time known value, not deleting yet
elsif Compile_Time_Known_Value (Cond) then
Save_In_Deleted_Code := In_Deleted_Code;
-- If condition is True, then analyze the THEN statements
-- and set no expansion for ELSE and ELSIF parts.
if Is_True (Expr_Value (Cond)) then
Analyze_Statements (Tstm);
Del := True;
Expander_Mode_Save_And_Set (False);
In_Deleted_Code := True;
-- If condition is False, analyze THEN with expansion off
else -- Is_False (Expr_Value (Cond))
Expander_Mode_Save_And_Set (False);
In_Deleted_Code := True;
Analyze_Statements (Tstm);
Expander_Mode_Restore;
In_Deleted_Code := Save_In_Deleted_Code;
end if;
-- Not known at compile time, not deleting, normal analysis
else
Analyze_Statements (Tstm);
end if;
end Analyze_Cond_Then;
-- Start of Analyze_If_Statement
begin
-- Initialize exit count for else statements. If there is no else
-- part, this count will stay non-zero reflecting the fact that the
-- uncovered else case is an unblocked exit.
Unblocked_Exit_Count := 1;
Analyze_Cond_Then (N);
-- Now to analyze the elsif parts if any are present
if Present (Elsif_Parts (N)) then
E := First (Elsif_Parts (N));
while Present (E) loop
Analyze_Cond_Then (E);
Next (E);
end loop;
end if;
if Present (Else_Statements (N)) then
Analyze_Statements (Else_Statements (N));
end if;
-- If all our exits were blocked by unconditional transfers of control,
-- then the entire IF statement acts as an unconditional transfer of
-- control, so treat it like one, and check unreachable code.
if Unblocked_Exit_Count = 0 then
Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
Check_Unreachable_Code (N);
else
Unblocked_Exit_Count := Save_Unblocked_Exit_Count;
end if;
if Del then
Expander_Mode_Restore;
In_Deleted_Code := Save_In_Deleted_Code;
end if;
if not Expander_Active
and then Compile_Time_Known_Value (Condition (N))
and then Serious_Errors_Detected = 0
then
if Is_True (Expr_Value (Condition (N))) then
Remove_Warning_Messages (Else_Statements (N));
if Present (Elsif_Parts (N)) then
E := First (Elsif_Parts (N));
while Present (E) loop
Remove_Warning_Messages (Then_Statements (E));
Next (E);
end loop;
end if;
else
Remove_Warning_Messages (Then_Statements (N));
end if;
end if;
end Analyze_If_Statement;
----------------------------------------
-- Analyze_Implicit_Label_Declaration --
----------------------------------------
-- An implicit label declaration is generated in the innermost
-- enclosing declarative part. This is done for labels as well as
-- block and loop names.
-- Note: any changes in this routine may need to be reflected in
-- Analyze_Label_Entity.
procedure Analyze_Implicit_Label_Declaration (N : Node_Id) is
Id : constant Node_Id := Defining_Identifier (N);
begin
Enter_Name (Id);
Set_Ekind (Id, E_Label);
Set_Etype (Id, Standard_Void_Type);
Set_Enclosing_Scope (Id, Current_Scope);
end Analyze_Implicit_Label_Declaration;
------------------------------
-- Analyze_Iteration_Scheme --
------------------------------
procedure Analyze_Iteration_Scheme (N : Node_Id) is
procedure Process_Bounds (R : Node_Id);
-- If the iteration is given by a range, create temporaries and
-- assignment statements block to capture the bounds and perform
-- required finalization actions in case a bound includes a function
-- call that uses the temporary stack. We first pre-analyze a copy of
-- the range in order to determine the expected type, and analyze and
-- resolve the original bounds.
procedure Check_Controlled_Array_Attribute (DS : Node_Id);
-- If the bounds are given by a 'Range reference on a function call
-- that returns a controlled array, introduce an explicit declaration
-- to capture the bounds, so that the function result can be finalized
-- in timely fashion.
--------------------
-- Process_Bounds --
--------------------
procedure Process_Bounds (R : Node_Id) is
Loc : constant Source_Ptr := Sloc (N);
R_Copy : constant Node_Id := New_Copy_Tree (R);
Lo : constant Node_Id := Low_Bound (R);
Hi : constant Node_Id := High_Bound (R);
New_Lo_Bound : Node_Id := Empty;
New_Hi_Bound : Node_Id := Empty;
Typ : Entity_Id;
Save_Analysis : Boolean;
function One_Bound
(Original_Bound : Node_Id;
Analyzed_Bound : Node_Id) return Node_Id;
-- Capture value of bound and return captured value
---------------
-- One_Bound --
---------------
function One_Bound
(Original_Bound : Node_Id;
Analyzed_Bound : Node_Id) return Node_Id
is
Assign : Node_Id;
Id : Entity_Id;
Decl : Node_Id;
begin
-- If the bound is a constant or an object, no need for a separate
-- declaration. If the bound is the result of previous expansion
-- it is already analyzed and should not be modified. Note that
-- the Bound will be resolved later, if needed, as part of the
-- call to Make_Index (literal bounds may need to be resolved to
-- type Integer).
if Analyzed (Original_Bound) then
return Original_Bound;
elsif Nkind_In (Analyzed_Bound, N_Integer_Literal,
N_Character_Literal)
or else Is_Entity_Name (Analyzed_Bound)
then
Analyze_And_Resolve (Original_Bound, Typ);
return Original_Bound;
end if;
-- Here we need to capture the value
Analyze_And_Resolve (Original_Bound, Typ);
Id :=
Make_Defining_Identifier (Loc,
Chars => New_Internal_Name ('S'));
-- Normally, the best approach is simply to generate a constant
-- declaration that captures the bound. However, there is a nasty
-- case where this is wrong. If the bound is complex, and has a
-- possible use of the secondary stack, we need to generate a
-- separate assignment statement to ensure the creation of a block
-- which will release the secondary stack.
-- We prefer the constant declaration, since it leaves us with a
-- proper trace of the value, useful in optimizations that get rid
-- of junk range checks.
-- Probably we want something like the Side_Effect_Free routine
-- in Exp_Util, but for now, we just optimize the cases of 'Last
-- and 'First applied to an entity, since these are the important
-- cases for range check optimizations.
if Nkind (Original_Bound) = N_Attribute_Reference
and then (Attribute_Name (Original_Bound) = Name_First
or else
Attribute_Name (Original_Bound) = Name_Last)
and then Is_Entity_Name (Prefix (Original_Bound))
then
Decl :=
Make_Object_Declaration (Loc,
Defining_Identifier => Id,
Constant_Present => True,
Object_Definition => New_Occurrence_Of (Typ, Loc),
Expression => Relocate_Node (Original_Bound));
Insert_Before (Parent (N), Decl);
Analyze (Decl);
Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
return Expression (Decl);
end if;
-- Here we make a declaration with a separate assignment statement
Decl :=
Make_Object_Declaration (Loc,
Defining_Identifier => Id,
Object_Definition => New_Occurrence_Of (Typ, Loc));
Insert_Before (Parent (N), Decl);
Analyze (Decl);
Assign :=
Make_Assignment_Statement (Loc,
Name => New_Occurrence_Of (Id, Loc),
Expression => Relocate_Node (Original_Bound));
-- If the relocated node is a function call then check if some
-- SCIL node references it and needs readjustment.
if Generate_SCIL
and then Nkind (Original_Bound) = N_Function_Call
then
Adjust_SCIL_Node (Original_Bound, Expression (Assign));
end if;
Insert_Before (Parent (N), Assign);
Analyze (Assign);
Rewrite (Original_Bound, New_Occurrence_Of (Id, Loc));
if Nkind (Assign) = N_Assignment_Statement then
return Expression (Assign);
else
return Original_Bound;
end if;
end One_Bound;
-- Start of processing for Process_Bounds
begin
-- Determine expected type of range by analyzing separate copy
-- Do the analysis and resolution of the copy of the bounds with
-- expansion disabled, to prevent the generation of finalization
-- actions on each bound. This prevents memory leaks when the
-- bounds contain calls to functions returning controlled arrays.
Set_Parent (R_Copy, Parent (R));
Save_Analysis := Full_Analysis;
Full_Analysis := False;
Expander_Mode_Save_And_Set (False);
Analyze (R_Copy);
if Is_Overloaded (R_Copy) then
-- Apply preference rules for range of predefined integer types,
-- or diagnose true ambiguity.
declare
I : Interp_Index;
It : Interp;
Found : Entity_Id := Empty;
begin
Get_First_Interp (R_Copy, I, It);
while Present (It.Typ) loop
if Is_Discrete_Type (It.Typ) then
if No (Found) then
Found := It.Typ;
else
if Scope (Found) = Standard_Standard then
null;
elsif Scope (It.Typ) = Standard_Standard then
Found := It.Typ;
else
-- Both of them are user-defined
Error_Msg_N
("ambiguous bounds in range of iteration",
R_Copy);
Error_Msg_N ("\possible interpretations:", R_Copy);
Error_Msg_NE ("\\} ", R_Copy, Found);
Error_Msg_NE ("\\} ", R_Copy, It.Typ);
exit;
end if;
end if;
end if;
Get_Next_Interp (I, It);
end loop;
end;
end if;
Resolve (R_Copy);
Expander_Mode_Restore;
Full_Analysis := Save_Analysis;
Typ := Etype (R_Copy);
-- If the type of the discrete range is Universal_Integer, then
-- the bound's type must be resolved to Integer, and any object
-- used to hold the bound must also have type Integer, unless the
-- literal bounds are constant-folded expressions that carry a user-
-- defined type.
if Typ = Universal_Integer then
if Nkind (Lo) = N_Integer_Literal
and then Present (Etype (Lo))
and then Scope (Etype (Lo)) /= Standard_Standard
then
Typ := Etype (Lo);
elsif Nkind (Hi) = N_Integer_Literal
and then Present (Etype (Hi))
and then Scope (Etype (Hi)) /= Standard_Standard
then
Typ := Etype (Hi);
else
Typ := Standard_Integer;
end if;
end if;
Set_Etype (R, Typ);
New_Lo_Bound := One_Bound (Lo, Low_Bound (R_Copy));
New_Hi_Bound := One_Bound (Hi, High_Bound (R_Copy));
-- Propagate staticness to loop range itself, in case the
-- corresponding subtype is static.
if New_Lo_Bound /= Lo
and then Is_Static_Expression (New_Lo_Bound)
then
Rewrite (Low_Bound (R), New_Copy (New_Lo_Bound));
end if;
if New_Hi_Bound /= Hi
and then Is_Static_Expression (New_Hi_Bound)
then
Rewrite (High_Bound (R), New_Copy (New_Hi_Bound));
end if;
end Process_Bounds;
--------------------------------------
-- Check_Controlled_Array_Attribute --
--------------------------------------
procedure Check_Controlled_Array_Attribute (DS : Node_Id) is
begin
if Nkind (DS) = N_Attribute_Reference
and then Is_Entity_Name (Prefix (DS))
and then Ekind (Entity (Prefix (DS))) = E_Function
and then Is_Array_Type (Etype (Entity (Prefix (DS))))
and then
Is_Controlled (
Component_Type (Etype (Entity (Prefix (DS)))))
and then Expander_Active
then
declare
Loc : constant Source_Ptr := Sloc (N);
Arr : constant Entity_Id :=
Etype (Entity (Prefix (DS)));
Indx : constant Entity_Id :=
Base_Type (Etype (First_Index (Arr)));
Subt : constant Entity_Id :=
Make_Defining_Identifier
(Loc, New_Internal_Name ('S'));
Decl : Node_Id;
begin
Decl :=
Make_Subtype_Declaration (Loc,
Defining_Identifier => Subt,
Subtype_Indication =>
Make_Subtype_Indication (Loc,
Subtype_Mark => New_Reference_To (Indx, Loc),
Constraint =>
Make_Range_Constraint (Loc,
Relocate_Node (DS))));
Insert_Before (Parent (N), Decl);
Analyze (Decl);
Rewrite (DS,
Make_Attribute_Reference (Loc,
Prefix => New_Reference_To (Subt, Loc),
Attribute_Name => Attribute_Name (DS)));
Analyze (DS);
end;
end if;
end Check_Controlled_Array_Attribute;
-- Start of processing for Analyze_Iteration_Scheme
begin
-- For an infinite loop, there is no iteration scheme
if No (N) then
return;
else
declare
Cond : constant Node_Id := Condition (N);
begin
-- For WHILE loop, verify that the condition is a Boolean
-- expression and resolve and check it.
if Present (Cond) then
Analyze_And_Resolve (Cond, Any_Boolean);
Check_Unset_Reference (Cond);
Set_Current_Value_Condition (N);
return;
-- Else we have a FOR loop
else
declare
LP : constant Node_Id := Loop_Parameter_Specification (N);
Id : constant Entity_Id := Defining_Identifier (LP);
DS : constant Node_Id := Discrete_Subtype_Definition (LP);
begin
Enter_Name (Id);
-- We always consider the loop variable to be referenced,
-- since the loop may be used just for counting purposes.
Generate_Reference (Id, N, ' ');
-- Check for case of loop variable hiding a local
-- variable (used later on to give a nice warning
-- if the hidden variable is never assigned).
declare
H : constant Entity_Id := Homonym (Id);
begin
if Present (H)
and then Enclosing_Dynamic_Scope (H) =
Enclosing_Dynamic_Scope (Id)
and then Ekind (H) = E_Variable
and then Is_Discrete_Type (Etype (H))
then
Set_Hiding_Loop_Variable (H, Id);
end if;
end;
-- Now analyze the subtype definition. If it is
-- a range, create temporaries for bounds.
if Nkind (DS) = N_Range
and then Expander_Active
then
Process_Bounds (DS);
else
Analyze (DS);
end if;
if DS = Error then
return;
end if;
-- The subtype indication may denote the completion
-- of an incomplete type declaration.
if Is_Entity_Name (DS)
and then Present (Entity (DS))
and then Is_Type (Entity (DS))
and then Ekind (Entity (DS)) = E_Incomplete_Type
then
Set_Entity (DS, Get_Full_View (Entity (DS)));
Set_Etype (DS, Entity (DS));
end if;
if not Is_Discrete_Type (Etype (DS)) then
Wrong_Type (DS, Any_Discrete);
Set_Etype (DS, Any_Type);
end if;
Check_Controlled_Array_Attribute (DS);
Make_Index (DS, LP);
Set_Ekind (Id, E_Loop_Parameter);
Set_Etype (Id, Etype (DS));
-- Treat a range as an implicit reference to the type, to
-- inhibit spurious warnings.
Generate_Reference (Base_Type (Etype (DS)), N, ' ');
Set_Is_Known_Valid (Id, True);
-- The loop is not a declarative part, so the only entity
-- declared "within" must be frozen explicitly.
declare
Flist : constant List_Id := Freeze_Entity (Id, Sloc (N));
begin
if Is_Non_Empty_List (Flist) then
Insert_Actions (N, Flist);
end if;
end;
-- Check for null or possibly null range and issue warning.
-- We suppress such messages in generic templates and
-- instances, because in practice they tend to be dubious
-- in these cases.
if Nkind (DS) = N_Range
and then Comes_From_Source (N)
then
declare
L : constant Node_Id := Low_Bound (DS);
H : constant Node_Id := High_Bound (DS);
begin
-- If range of loop is null, issue warning
if Compile_Time_Compare
(L, H, Assume_Valid => True) = GT
then
-- Suppress the warning if inside a generic
-- template or instance, since in practice
-- they tend to be dubious in these cases since
-- they can result from intended parametrization.
if not Inside_A_Generic
and then not In_Instance
then
-- Specialize msg if invalid values could make
-- the loop non-null after all.
if Compile_Time_Compare
(L, H, Assume_Valid => False) = GT
then
Error_Msg_N
("?loop range is null, "
& "loop will not execute",
DS);
-- Since we know the range of the loop is
-- null, set the appropriate flag to remove
-- the loop entirely during expansion.
Set_Is_Null_Loop (Parent (N));
-- Here is where the loop could execute because
-- of invalid values, so issue appropriate
-- message and in this case we do not set the
-- Is_Null_Loop flag since the loop may execute.
else
Error_Msg_N
("?loop range may be null, "
& "loop may not execute",
DS);
Error_Msg_N
("?can only execute if invalid values "
& "are present",
DS);
end if;
end if;
-- In either case, suppress warnings in the body of
-- the loop, since it is likely that these warnings
-- will be inappropriate if the loop never actually
-- executes, which is unlikely.
Set_Suppress_Loop_Warnings (Parent (N));
-- The other case for a warning is a reverse loop
-- where the upper bound is the integer literal
-- zero or one, and the lower bound can be positive.
-- For example, we have
-- for J in reverse N .. 1 loop
-- In practice, this is very likely to be a case
-- of reversing the bounds incorrectly in the range.
elsif Reverse_Present (LP)
and then Nkind (Original_Node (H)) =
N_Integer_Literal
and then (Intval (Original_Node (H)) = Uint_0
or else
Intval (Original_Node (H)) = Uint_1)
then
Error_Msg_N ("?loop range may be null", DS);
Error_Msg_N ("\?bounds may be wrong way round", DS);
end if;
end;
end if;
end;
end if;
end;
end if;
end Analyze_Iteration_Scheme;
-------------------
-- Analyze_Label --
-------------------
-- Note: the semantic work required for analyzing labels (setting them as
-- reachable) was done in a prepass through the statements in the block,
-- so that forward gotos would be properly handled. See Analyze_Statements
-- for further details. The only processing required here is to deal with
-- optimizations that depend on an assumption of sequential control flow,
-- since of course the occurrence of a label breaks this assumption.
procedure Analyze_Label (N : Node_Id) is
pragma Warnings (Off, N);
begin
Kill_Current_Values;
end Analyze_Label;
--------------------------
-- Analyze_Label_Entity --
--------------------------
procedure Analyze_Label_Entity (E : Entity_Id) is
begin
Set_Ekind (E, E_Label);
Set_Etype (E, Standard_Void_Type);
Set_Enclosing_Scope (E, Current_Scope);
Set_Reachable (E, True);
end Analyze_Label_Entity;
----------------------------
-- Analyze_Loop_Statement --
----------------------------
procedure Analyze_Loop_Statement (N : Node_Id) is
Loop_Statement : constant Node_Id := N;
Id : constant Node_Id := Identifier (Loop_Statement);
Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
Ent : Entity_Id;
begin
if Present (Id) then
-- Make name visible, e.g. for use in exit statements. Loop
-- labels are always considered to be referenced.
Analyze (Id);
Ent := Entity (Id);
-- Guard against serious error (typically, a scope mismatch when
-- semantic analysis is requested) by creating loop entity to
-- continue analysis.
if No (Ent) then
if Total_Errors_Detected /= 0 then
Ent :=
New_Internal_Entity
(E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
else
raise Program_Error;
end if;
else
Generate_Reference (Ent, Loop_Statement, ' ');
Generate_Definition (Ent);
-- If we found a label, mark its type. If not, ignore it, since it
-- means we have a conflicting declaration, which would already
-- have been diagnosed at declaration time. Set Label_Construct
-- of the implicit label declaration, which is not created by the
-- parser for generic units.
if Ekind (Ent) = E_Label then
Set_Ekind (Ent, E_Loop);
if Nkind (Parent (Ent)) = N_Implicit_Label_Declaration then
Set_Label_Construct (Parent (Ent), Loop_Statement);
end if;
end if;
end if;
-- Case of no identifier present
else
Ent :=
New_Internal_Entity
(E_Loop, Current_Scope, Sloc (Loop_Statement), 'L');
Set_Etype (Ent, Standard_Void_Type);
Set_Parent (Ent, Loop_Statement);
end if;
-- Kill current values on entry to loop, since statements in body of
-- loop may have been executed before the loop is entered. Similarly we
-- kill values after the loop, since we do not know that the body of the
-- loop was executed.
Kill_Current_Values;
Push_Scope (Ent);
Analyze_Iteration_Scheme (Iter);
Analyze_Statements (Statements (Loop_Statement));
Process_End_Label (Loop_Statement, 'e', Ent);
End_Scope;
Kill_Current_Values;
-- Check for infinite loop. We skip this check for generated code, since
-- it justs waste time and makes debugging the routine called harder.
if Comes_From_Source (N) then
Check_Infinite_Loop_Warning (N);
end if;
-- Code after loop is unreachable if the loop has no WHILE or FOR
-- and contains no EXIT statements within the body of the loop.
if No (Iter) and then not Has_Exit (Ent) then
Check_Unreachable_Code (N);
end if;
end Analyze_Loop_Statement;
----------------------------
-- Analyze_Null_Statement --
----------------------------
-- Note: the semantics of the null statement is implemented by a single
-- null statement, too bad everything isn't as simple as this!
procedure Analyze_Null_Statement (N : Node_Id) is
pragma Warnings (Off, N);
begin
null;
end Analyze_Null_Statement;
------------------------
-- Analyze_Statements --
------------------------
procedure Analyze_Statements (L : List_Id) is
S : Node_Id;
Lab : Entity_Id;
begin
-- The labels declared in the statement list are reachable from
-- statements in the list. We do this as a prepass so that any
-- goto statement will be properly flagged if its target is not
-- reachable. This is not required, but is nice behavior!
S := First (L);
while Present (S) loop
if Nkind (S) = N_Label then
Analyze (Identifier (S));
Lab := Entity (Identifier (S));
-- If we found a label mark it as reachable
if Ekind (Lab) = E_Label then
Generate_Definition (Lab);
Set_Reachable (Lab);
if Nkind (Parent (Lab)) = N_Implicit_Label_Declaration then
Set_Label_Construct (Parent (Lab), S);
end if;
-- If we failed to find a label, it means the implicit declaration
-- of the label was hidden. A for-loop parameter can do this to
-- a label with the same name inside the loop, since the implicit
-- label declaration is in the innermost enclosing body or block
-- statement.
else
Error_Msg_Sloc := Sloc (Lab);
Error_Msg_N
("implicit label declaration for & is hidden#",
Identifier (S));
end if;
end if;
Next (S);
end loop;
-- Perform semantic analysis on all statements
Conditional_Statements_Begin;
S := First (L);
while Present (S) loop
Analyze (S);
Next (S);
end loop;
Conditional_Statements_End;
-- Make labels unreachable. Visibility is not sufficient, because
-- labels in one if-branch for example are not reachable from the
-- other branch, even though their declarations are in the enclosing
-- declarative part.
S := First (L);
while Present (S) loop
if Nkind (S) = N_Label then
Set_Reachable (Entity (Identifier (S)), False);
end if;
Next (S);
end loop;
end Analyze_Statements;
----------------------------
-- Check_Unreachable_Code --
----------------------------
procedure Check_Unreachable_Code (N : Node_Id) is
Error_Loc : Source_Ptr;
P : Node_Id;
begin
if Is_List_Member (N)
and then Comes_From_Source (N)
then
declare
Nxt : Node_Id;
begin
Nxt := Original_Node (Next (N));
-- If a label follows us, then we never have dead code, since
-- someone could branch to the label, so we just ignore it.
if Nkind (Nxt) = N_Label then
return;
-- Otherwise see if we have a real statement following us
elsif Present (Nxt)
and then Comes_From_Source (Nxt)
and then Is_Statement (Nxt)
then
-- Special very annoying exception. If we have a return that
-- follows a raise, then we allow it without a warning, since
-- the Ada RM annoyingly requires a useless return here!
if Nkind (Original_Node (N)) /= N_Raise_Statement
or else Nkind (Nxt) /= N_Simple_Return_Statement
then
-- The rather strange shenanigans with the warning message
-- here reflects the fact that Kill_Dead_Code is very good
-- at removing warnings in deleted code, and this is one
-- warning we would prefer NOT to have removed.
Error_Loc := Sloc (Nxt);
-- If we have unreachable code, analyze and remove the
-- unreachable code, since it is useless and we don't
-- want to generate junk warnings.
-- We skip this step if we are not in code generation mode.
-- This is the one case where we remove dead code in the
-- semantics as opposed to the expander, and we do not want
-- to remove code if we are not in code generation mode,
-- since this messes up the ASIS trees.
-- Note that one might react by moving the whole circuit to
-- exp_ch5, but then we lose the warning in -gnatc mode.
if Operating_Mode = Generate_Code then
loop
Nxt := Next (N);
-- Quit deleting when we have nothing more to delete
-- or if we hit a label (since someone could transfer
-- control to a label, so we should not delete it).
exit when No (Nxt) or else Nkind (Nxt) = N_Label;
-- Statement/declaration is to be deleted
Analyze (Nxt);
Remove (Nxt);
Kill_Dead_Code (Nxt);
end loop;
end if;
-- Now issue the warning
Error_Msg ("?unreachable code!", Error_Loc);
end if;
-- If the unconditional transfer of control instruction is
-- the last statement of a sequence, then see if our parent
-- is one of the constructs for which we count unblocked exits,
-- and if so, adjust the count.
else
P := Parent (N);
-- Statements in THEN part or ELSE part of IF statement
if Nkind (P) = N_If_Statement then
null;
-- Statements in ELSIF part of an IF statement
elsif Nkind (P) = N_Elsif_Part then
P := Parent (P);
pragma Assert (Nkind (P) = N_If_Statement);
-- Statements in CASE statement alternative
elsif Nkind (P) = N_Case_Statement_Alternative then
P := Parent (P);
pragma Assert (Nkind (P) = N_Case_Statement);
-- Statements in body of block
elsif Nkind (P) = N_Handled_Sequence_Of_Statements
and then Nkind (Parent (P)) = N_Block_Statement
then
null;
-- Statements in exception handler in a block
elsif Nkind (P) = N_Exception_Handler
and then Nkind (Parent (P)) = N_Handled_Sequence_Of_Statements
and then Nkind (Parent (Parent (P))) = N_Block_Statement
then
null;
-- None of these cases, so return
else
return;
end if;
-- This was one of the cases we are looking for (i.e. the
-- parent construct was IF, CASE or block) so decrement count.
Unblocked_Exit_Count := Unblocked_Exit_Count - 1;
end if;
end;
end if;
end Check_Unreachable_Code;
end Sem_Ch5;
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