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------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S E M _ W A R N --
-- --
-- B o d y --
-- --
-- Copyright (C) 1999-2021, 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 Debug; use Debug;
with Einfo; use Einfo;
with Einfo.Entities; use Einfo.Entities;
with Einfo.Utils; use Einfo.Utils;
with Errout; use Errout;
with Exp_Code; use Exp_Code;
with Lib; use Lib;
with Lib.Xref; use Lib.Xref;
with Namet; use Namet;
with Nlists; use Nlists;
with Opt; use Opt;
with Par_SCO; use Par_SCO;
with Rtsfind; use Rtsfind;
with Sem; use Sem;
with Sem_Ch8; use Sem_Ch8;
with Sem_Aux; use Sem_Aux;
with Sem_Eval; use Sem_Eval;
with Sem_Prag; use Sem_Prag;
with Sem_Util; use Sem_Util;
with Sinfo; use Sinfo;
with Sinfo.Nodes; use Sinfo.Nodes;
with Sinfo.Utils; use Sinfo.Utils;
with Sinput; use Sinput;
with Snames; use Snames;
with Stand; use Stand;
with Stringt; use Stringt;
with Tbuild; use Tbuild;
with Uintp; use Uintp;
package body Sem_Warn is
-- The following table collects Id's of entities that are potentially
-- unreferenced. See Check_Unset_Reference for further details.
-- ??? Check_Unset_Reference has zero information about this table.
package Unreferenced_Entities is new Table.Table (
Table_Component_Type => Entity_Id,
Table_Index_Type => Nat,
Table_Low_Bound => 1,
Table_Initial => Alloc.Unreferenced_Entities_Initial,
Table_Increment => Alloc.Unreferenced_Entities_Increment,
Table_Name => "Unreferenced_Entities");
-- The following table collects potential warnings for IN OUT parameters
-- that are referenced but not modified. These warnings are processed when
-- the front end calls the procedure Output_Non_Modified_In_Out_Warnings.
-- The reason that we defer output of these messages is that we want to
-- detect the case where the relevant procedure is used as a generic actual
-- in an instantiation, since we suppress the warnings in this case. The
-- flag Used_As_Generic_Actual will be set in this case, but only at the
-- point of usage. Similarly, we suppress the message if the address of the
-- procedure is taken, where the flag Address_Taken may be set later.
package In_Out_Warnings is new Table.Table (
Table_Component_Type => Entity_Id,
Table_Index_Type => Nat,
Table_Low_Bound => 1,
Table_Initial => Alloc.In_Out_Warnings_Initial,
Table_Increment => Alloc.In_Out_Warnings_Increment,
Table_Name => "In_Out_Warnings");
--------------------------------------------------------
-- Handling of Warnings Off, Unmodified, Unreferenced --
--------------------------------------------------------
-- The functions Has_Warnings_Off, Has_Unmodified, Has_Unreferenced must
-- generally be used instead of Warnings_Off, Has_Pragma_Unmodified and
-- Has_Pragma_Unreferenced, as noted in the specs in Einfo.
-- In order to avoid losing warnings in -gnatw.w (warn on unnecessary
-- warnings off pragma) mode, i.e. to avoid false negatives, the code
-- must follow some important rules.
-- Call these functions as late as possible, after completing all other
-- tests, just before the warnings is given. For example, don't write:
-- if not Has_Warnings_Off (E)
-- and then some-other-predicate-on-E then ..
-- Instead the following is preferred
-- if some-other-predicate-on-E
-- and then Has_Warnings_Off (E)
-- This way if some-other-predicate is false, we avoid a false indication
-- that a Warnings (Off, E) pragma was useful in preventing a warning.
-- The second rule is that if both Has_Unmodified and Has_Warnings_Off, or
-- Has_Unreferenced and Has_Warnings_Off are called, make sure that the
-- call to Has_Unmodified/Has_Unreferenced comes first, this way we record
-- that the Warnings (Off) could have been Unreferenced or Unmodified. In
-- fact Has_Unmodified/Has_Unreferenced includes a test for Warnings Off,
-- and so a subsequent test is not needed anyway (though it is harmless).
-----------------------
-- Local Subprograms --
-----------------------
function Generic_Package_Spec_Entity (E : Entity_Id) return Boolean;
-- This returns true if the entity E is declared within a generic package.
-- The point of this is to detect variables which are not assigned within
-- the generic, but might be assigned outside the package for any given
-- instance. These are cases where we leave the warnings to be posted for
-- the instance, when we will know more.
function Goto_Spec_Entity (E : Entity_Id) return Entity_Id;
-- If E is a parameter entity for a subprogram body, then this function
-- returns the corresponding spec entity, if not, E is returned unchanged.
function Has_Pragma_Unmodified_Check_Spec (E : Entity_Id) return Boolean;
-- Tests Has_Pragma_Unmodified flag for entity E. If E is not a formal,
-- this is simply the setting of the flag Has_Pragma_Unmodified. If E is
-- a body formal, the setting of the flag in the corresponding spec is
-- also checked (and True returned if either flag is True).
function Has_Pragma_Unreferenced_Check_Spec (E : Entity_Id) return Boolean;
-- Tests Has_Pragma_Unreferenced flag for entity E. If E is not a formal,
-- this is simply the setting of the flag Has_Pragma_Unreferenced. If E is
-- a body formal, the setting of the flag in the corresponding spec is
-- also checked (and True returned if either flag is True).
function Is_Attribute_And_Known_Value_Comparison
(Op : Node_Id) return Boolean;
-- Determine whether operator Op denotes a comparison where the left
-- operand is an attribute reference and the value of the right operand is
-- known at compile time.
function Never_Set_In_Source_Check_Spec (E : Entity_Id) return Boolean;
-- Tests Never_Set_In_Source status for entity E. If E is not a formal,
-- this is simply the setting of the flag Never_Set_In_Source. If E is
-- a body formal, the setting of the flag in the corresponding spec is
-- also checked (and False returned if either flag is False).
function Operand_Has_Warnings_Suppressed (N : Node_Id) return Boolean;
-- This function traverses the expression tree represented by the node N
-- and determines if any sub-operand is a reference to an entity for which
-- the Warnings_Off flag is set. True is returned if such an entity is
-- encountered, and False otherwise.
function Referenced_Check_Spec (E : Entity_Id) return Boolean;
-- Tests Referenced status for entity E. If E is not a formal, this is
-- simply the setting of the flag Referenced. If E is a body formal, the
-- setting of the flag in the corresponding spec is also checked (and True
-- returned if either flag is True).
function Referenced_As_LHS_Check_Spec (E : Entity_Id) return Boolean;
-- Tests Referenced_As_LHS status for entity E. If E is not a formal, this
-- is simply the setting of the flag Referenced_As_LHS. If E is a body
-- formal, the setting of the flag in the corresponding spec is also
-- checked (and True returned if either flag is True).
function Referenced_As_Out_Parameter_Check_Spec
(E : Entity_Id) return Boolean;
-- Tests Referenced_As_Out_Parameter status for entity E. If E is not a
-- formal, this is simply the setting of Referenced_As_Out_Parameter. If E
-- is a body formal, the setting of the flag in the corresponding spec is
-- also checked (and True returned if either flag is True).
procedure Warn_On_Unreferenced_Entity
(Spec_E : Entity_Id;
Body_E : Entity_Id := Empty);
-- Output warnings for unreferenced entity E. For the case of an entry
-- formal, Body_E is the corresponding body entity for a particular
-- accept statement, and the message is posted on Body_E. In all other
-- cases, Body_E is ignored and must be Empty.
function Warnings_Off_Check_Spec (E : Entity_Id) return Boolean;
-- Returns True if Warnings_Off is set for the entity E or (in the case
-- where there is a Spec_Entity), Warnings_Off is set for the Spec_Entity.
--------------------------
-- Check_Code_Statement --
--------------------------
procedure Check_Code_Statement (N : Node_Id) is
begin
-- If volatile, nothing to worry about
if Is_Asm_Volatile (N) then
return;
end if;
-- Warn if no input or no output
Setup_Asm_Inputs (N);
if No (Asm_Input_Value) then
Error_Msg_F
("??code statement with no inputs should usually be Volatile!", N);
return;
end if;
Setup_Asm_Outputs (N);
if No (Asm_Output_Variable) then
Error_Msg_F
("??code statement with no outputs should usually be Volatile!", N);
return;
end if;
end Check_Code_Statement;
---------------------------------
-- Check_Infinite_Loop_Warning --
---------------------------------
-- The case we look for is a while loop which tests a local variable, where
-- there is no obvious direct or possible indirect update of the variable
-- within the body of the loop.
procedure Check_Infinite_Loop_Warning (Loop_Statement : Node_Id) is
Expression : Node_Id := Empty;
-- Set to WHILE or EXIT WHEN condition to be tested
Ref : Node_Id := Empty;
-- Reference in Expression to variable that might not be modified
-- in loop, indicating a possible infinite loop.
Var : Entity_Id := Empty;
-- Corresponding entity (entity of Ref)
Function_Call_Found : Boolean := False;
-- True if Find_Var found a function call in the condition
procedure Find_Var (N : Node_Id);
-- Inspect condition to see if it depends on a single entity reference.
-- If so, Ref is set to point to the reference node, and Var is set to
-- the referenced Entity.
function Has_Condition_Actions (Iter : Node_Id) return Boolean;
-- Determine whether iteration scheme Iter has meaningful condition
-- actions.
function Has_Indirection (T : Entity_Id) return Boolean;
-- If the controlling variable is an access type, or is a record type
-- with access components, assume that it is changed indirectly and
-- suppress the warning. As a concession to low-level programming, in
-- particular within Declib, we also suppress warnings on a record
-- type that contains components of type Address or Short_Address.
function Is_Suspicious_Function_Name (E : Entity_Id) return Boolean;
-- Given an entity name, see if the name appears to have something to
-- do with I/O or network stuff, and if so, return True. Used to kill
-- some false positives on a heuristic basis that such functions will
-- likely have some strange side effect dependencies. A rather strange
-- test, but warning messages are in the heuristics business.
function Test_Ref (N : Node_Id) return Traverse_Result;
-- Test for reference to variable in question. Returns Abandon if
-- matching reference found. Used in instantiation of No_Ref_Found.
function No_Ref_Found is new Traverse_Func (Test_Ref);
-- Function to traverse body of procedure. Returns Abandon if matching
-- reference found.
--------------
-- Find_Var --
--------------
procedure Find_Var (N : Node_Id) is
begin
-- Condition is a direct variable reference
if Is_Entity_Name (N) then
Ref := N;
Var := Entity (Ref);
-- Case of condition is a comparison with compile time known value
elsif Nkind (N) in N_Op_Compare then
if Compile_Time_Known_Value (Right_Opnd (N)) then
Find_Var (Left_Opnd (N));
elsif Compile_Time_Known_Value (Left_Opnd (N)) then
Find_Var (Right_Opnd (N));
-- Ignore any other comparison
else
return;
end if;
-- If condition is a negation, check its operand
elsif Nkind (N) = N_Op_Not then
Find_Var (Right_Opnd (N));
-- Case of condition is function call
elsif Nkind (N) = N_Function_Call then
Function_Call_Found := True;
-- Forget it if function name is not entity, who knows what
-- we might be calling?
if not Is_Entity_Name (Name (N)) then
return;
-- Forget it if function name is suspicious. A strange test
-- but warning generation is in the heuristics business.
elsif Is_Suspicious_Function_Name (Entity (Name (N))) then
return;
-- Forget it if function is marked Volatile_Function
elsif Is_Volatile_Function (Entity (Name (N))) then
return;
-- Forget it if warnings are suppressed on function entity
elsif Has_Warnings_Off (Entity (Name (N))) then
return;
-- Forget it if the parameter is not In
elsif Has_Out_Or_In_Out_Parameter (Entity (Name (N))) then
return;
end if;
-- OK, see if we have one argument
declare
PA : constant List_Id := Parameter_Associations (N);
begin
-- One argument, so check the argument
if Present (PA) and then List_Length (PA) = 1 then
if Nkind (First (PA)) = N_Parameter_Association then
Find_Var (Explicit_Actual_Parameter (First (PA)));
else
Find_Var (First (PA));
end if;
-- Not one argument
else
return;
end if;
end;
-- Any other kind of node is not something we warn for
else
return;
end if;
end Find_Var;
---------------------------
-- Has_Condition_Actions --
---------------------------
function Has_Condition_Actions (Iter : Node_Id) return Boolean is
Action : Node_Id;
begin
-- A call marker is not considered a meaningful action because it
-- acts as an annotation and has no runtime semantics.
Action := First (Condition_Actions (Iter));
while Present (Action) loop
if Nkind (Action) /= N_Call_Marker then
return True;
end if;
Next (Action);
end loop;
return False;
end Has_Condition_Actions;
---------------------
-- Has_Indirection --
---------------------
function Has_Indirection (T : Entity_Id) return Boolean is
Comp : Entity_Id;
Rec : Entity_Id;
begin
if Is_Access_Type (T) then
return True;
elsif Is_Private_Type (T)
and then Present (Full_View (T))
and then Is_Access_Type (Full_View (T))
then
return True;
elsif Is_Record_Type (T) then
Rec := T;
elsif Is_Private_Type (T)
and then Present (Full_View (T))
and then Is_Record_Type (Full_View (T))
then
Rec := Full_View (T);
else
return False;
end if;
Comp := First_Component (Rec);
while Present (Comp) loop
if Is_Access_Type (Etype (Comp))
or else Is_Descendant_Of_Address (Etype (Comp))
then
return True;
end if;
Next_Component (Comp);
end loop;
return False;
end Has_Indirection;
---------------------------------
-- Is_Suspicious_Function_Name --
---------------------------------
function Is_Suspicious_Function_Name (E : Entity_Id) return Boolean is
S : Entity_Id;
function Substring_Present (S : String) return Boolean;
-- Returns True if name buffer has given string delimited by non-
-- alphabetic characters or by end of string. S is lower case.
-----------------------
-- Substring_Present --
-----------------------
function Substring_Present (S : String) return Boolean is
Len : constant Natural := S'Length;
begin
for J in 1 .. Name_Len - (Len - 1) loop
if Name_Buffer (J .. J + (Len - 1)) = S
and then (J = 1 or else Name_Buffer (J - 1) not in 'a' .. 'z')
and then
(J + Len > Name_Len
or else Name_Buffer (J + Len) not in 'a' .. 'z')
then
return True;
end if;
end loop;
return False;
end Substring_Present;
-- Start of processing for Is_Suspicious_Function_Name
begin
S := E;
while Present (S) and then S /= Standard_Standard loop
Get_Name_String (Chars (S));
if Substring_Present ("io")
or else Substring_Present ("file")
or else Substring_Present ("network")
then
return True;
else
S := Scope (S);
end if;
end loop;
return False;
end Is_Suspicious_Function_Name;
--------------
-- Test_Ref --
--------------
function Test_Ref (N : Node_Id) return Traverse_Result is
begin
-- Waste of time to look at the expression we are testing
if N = Expression then
return Skip;
-- Direct reference to variable in question
elsif Is_Entity_Name (N)
and then Present (Entity (N))
and then Entity (N) = Var
then
-- If this is an lvalue, then definitely abandon, since
-- this could be a direct modification of the variable.
if May_Be_Lvalue (N) then
return Abandon;
end if;
-- If the condition contains a function call, we consider it may
-- be modified by side effects from a procedure call. Otherwise,
-- we consider the condition may not be modified, although that
-- might happen if Variable is itself a by-reference parameter,
-- and the procedure called modifies the global object referred to
-- by Variable, but we actually prefer to issue a warning in this
-- odd case. Note that the case where the procedure called has
-- visibility over Variable is treated in another case below.
if Function_Call_Found then
declare
P : Node_Id;
begin
P := N;
loop
P := Parent (P);
exit when P = Loop_Statement;
-- Abandon if at procedure call, or something strange is
-- going on (perhaps a node with no parent that should
-- have one but does not?) As always, for a warning we
-- prefer to just abandon the warning than get into the
-- business of complaining about the tree structure here.
if No (P)
or else Nkind (P) = N_Procedure_Call_Statement
then
return Abandon;
end if;
end loop;
end;
end if;
-- Reference to variable renaming variable in question
elsif Is_Entity_Name (N)
and then Present (Entity (N))
and then Ekind (Entity (N)) = E_Variable
and then Present (Renamed_Object (Entity (N)))
and then Is_Entity_Name (Renamed_Object (Entity (N)))
and then Entity (Renamed_Object (Entity (N))) = Var
and then May_Be_Lvalue (N)
then
return Abandon;
-- Call to subprogram
elsif Nkind (N) in N_Subprogram_Call then
-- If subprogram is within the scope of the entity we are dealing
-- with as the loop variable, then it could modify this parameter,
-- so we abandon in this case. In the case of a subprogram that is
-- not an entity we also abandon. The check for no entity being
-- present is a defense against previous errors.
if not Is_Entity_Name (Name (N))
or else No (Entity (Name (N)))
or else Scope_Within (Entity (Name (N)), Scope (Var))
then
return Abandon;
end if;
-- If any of the arguments are of type access to subprogram, then
-- we may have funny side effects, so no warning in this case.
declare
Actual : Node_Id;
begin
Actual := First_Actual (N);
while Present (Actual) loop
if Is_Access_Subprogram_Type (Etype (Actual)) then
return Abandon;
else
Next_Actual (Actual);
end if;
end loop;
end;
-- Declaration of the variable in question
elsif Nkind (N) = N_Object_Declaration
and then Defining_Identifier (N) = Var
then
return Abandon;
end if;
-- All OK, continue scan
return OK;
end Test_Ref;
-- Start of processing for Check_Infinite_Loop_Warning
begin
-- Skip processing if debug flag gnatd.w is set
if Debug_Flag_Dot_W then
return;
end if;
-- Deal with Iteration scheme present
declare
Iter : constant Node_Id := Iteration_Scheme (Loop_Statement);
begin
if Present (Iter) then
-- While iteration
if Present (Condition (Iter)) then
-- Skip processing for while iteration with conditions actions,
-- since they make it too complicated to get the warning right.
if Has_Condition_Actions (Iter) then
return;
end if;
-- Capture WHILE condition
Expression := Condition (Iter);
-- For Loop_Parameter_Specification, do not process, since loop
-- will always terminate. For Iterator_Specification, also do not
-- process. Either it will always terminate (e.g. "for X of
-- Some_Array ..."), or we can't tell if it's going to terminate
-- without looking at the iterator, so any warning here would be
-- noise.
elsif Present (Loop_Parameter_Specification (Iter))
or else Present (Iterator_Specification (Iter))
then
return;
end if;
end if;
end;
-- Check chain of EXIT statements, we only process loops that have a
-- single exit condition (either a single EXIT WHEN statement, or a
-- WHILE loop not containing any EXIT WHEN statements).
declare
Ident : constant Node_Id := Identifier (Loop_Statement);
Exit_Stmt : Node_Id;
begin
-- If we don't have a proper chain set, ignore call entirely. This
-- happens because of previous errors.
if No (Entity (Ident))
or else Ekind (Entity (Ident)) /= E_Loop
then
Check_Error_Detected;
return;
end if;
-- Otherwise prepare to scan list of EXIT statements
Exit_Stmt := First_Exit_Statement (Entity (Ident));
while Present (Exit_Stmt) loop
-- Check for EXIT WHEN
if Present (Condition (Exit_Stmt)) then
-- Quit processing if EXIT WHEN in WHILE loop, or more than
-- one EXIT WHEN statement present in the loop.
if Present (Expression) then
return;
-- Otherwise capture condition from EXIT WHEN statement
else
Expression := Condition (Exit_Stmt);
end if;
-- If an unconditional exit statement is the last statement in the
-- loop, assume that no warning is needed, without any attempt at
-- checking whether the exit is reachable.
elsif Exit_Stmt = Last (Statements (Loop_Statement)) then
return;
end if;
Exit_Stmt := Next_Exit_Statement (Exit_Stmt);
end loop;
end;
-- Return if no condition to test
if No (Expression) then
return;
end if;
-- Initial conditions met, see if condition is of right form
Find_Var (Expression);
-- Nothing to do if local variable from source not found. If it's a
-- renaming, it is probably renaming something too complicated to deal
-- with here.
if No (Var)
or else Ekind (Var) /= E_Variable
or else Is_Library_Level_Entity (Var)
or else not Comes_From_Source (Var)
or else Nkind (Parent (Var)) = N_Object_Renaming_Declaration
then
return;
-- Nothing to do if there is some indirection involved (assume that the
-- designated variable might be modified in some way we don't see).
-- However, if no function call was found, then we don't care about
-- indirections, because the condition must be something like "while X
-- /= null loop", so we don't care if X.all is modified in the loop.
elsif Function_Call_Found and then Has_Indirection (Etype (Var)) then
return;
-- Same sort of thing for volatile variable, might be modified by
-- some other task or by the operating system in some way.
elsif Is_Volatile (Var) then
return;
end if;
-- Filter out case of original statement sequence starting with delay.
-- We assume this is a multi-tasking program and that the condition
-- is affected by other threads (some kind of busy wait).
declare
Fstm : constant Node_Id :=
Original_Node (First (Statements (Loop_Statement)));
begin
if Nkind (Fstm) in N_Delay_Statement then
return;
end if;
end;
-- We have a variable reference of the right form, now we scan the loop
-- body to see if it looks like it might not be modified
if No_Ref_Found (Loop_Statement) = OK then
Error_Msg_NE
("??variable& is not modified in loop body!", Ref, Var);
Error_Msg_N
("\??possible infinite loop!", Ref);
end if;
end Check_Infinite_Loop_Warning;
----------------------------
-- Check_Low_Bound_Tested --
----------------------------
procedure Check_Low_Bound_Tested (Expr : Node_Id) is
procedure Check_Low_Bound_Tested_For (Opnd : Node_Id);
-- Determine whether operand Opnd denotes attribute 'First whose prefix
-- is a formal parameter. If this is the case, mark the entity of the
-- prefix as having its low bound tested.
--------------------------------
-- Check_Low_Bound_Tested_For --
--------------------------------
procedure Check_Low_Bound_Tested_For (Opnd : Node_Id) is
begin
if Nkind (Opnd) = N_Attribute_Reference
and then Attribute_Name (Opnd) = Name_First
and then Is_Entity_Name (Prefix (Opnd))
and then Present (Entity (Prefix (Opnd)))
and then Is_Formal (Entity (Prefix (Opnd)))
then
Set_Low_Bound_Tested (Entity (Prefix (Opnd)));
end if;
end Check_Low_Bound_Tested_For;
-- Start of processing for Check_Low_Bound_Tested
begin
if Comes_From_Source (Expr) then
Check_Low_Bound_Tested_For (Left_Opnd (Expr));
Check_Low_Bound_Tested_For (Right_Opnd (Expr));
end if;
end Check_Low_Bound_Tested;
----------------------
-- Check_References --
----------------------
procedure Check_References (E : Entity_Id; Anod : Node_Id := Empty) is
E1 : Entity_Id;
E1T : Entity_Id;
UR : Node_Id;
function Body_Formal
(E : Entity_Id;
Accept_Statement : Node_Id) return Entity_Id;
-- For an entry formal entity from an entry declaration, find the
-- corresponding body formal from the given accept statement.
function Generic_Body_Formal (E : Entity_Id) return Entity_Id;
-- Warnings on unused formals of subprograms are placed on the entity
-- in the subprogram body, which seems preferable because it suggests
-- a better codefix for GNAT Studio. The analysis of generic subprogram
-- bodies uses a different circuitry, so the choice for the proper
-- placement of the warning in the generic case takes place here, by
-- finding the body entity that corresponds to a formal in a spec.
procedure May_Need_Initialized_Actual (Ent : Entity_Id);
-- If an entity of a generic type has default initialization, then the
-- corresponding actual type should be fully initialized, or else there
-- will be uninitialized components in the instantiation, that might go
-- unreported. This routine marks the type of the uninitialized variable
-- appropriately to allow the compiler to emit an appropriate warning
-- in the instance. In a sense, the use of a type that requires full
-- initialization is a weak part of the generic contract.
function Missing_Subunits return Boolean;
-- We suppress warnings when there are missing subunits, because this
-- may generate too many false positives: entities in a parent may only
-- be referenced in one of the subunits. We make an exception for
-- subunits that contain no other stubs.
procedure Output_Reference_Error (M : String);
-- Used to output an error message. Deals with posting the error on the
-- body formal in the accept case.
function Publicly_Referenceable (Ent : Entity_Id) return Boolean;
-- This is true if the entity in question is potentially referenceable
-- from another unit. This is true for entities in packages that are at
-- the library level.
function Warnings_Off_E1 return Boolean;
-- Return True if Warnings_Off is set for E1, or for its Etype (E1T),
-- or for the base type of E1T.
-----------------
-- Body_Formal --
-----------------
function Body_Formal
(E : Entity_Id;
Accept_Statement : Node_Id) return Entity_Id
is
Body_Param : Node_Id;
Body_E : Entity_Id;
begin
-- Loop to find matching parameter in accept statement
Body_Param := First (Parameter_Specifications (Accept_Statement));
while Present (Body_Param) loop
Body_E := Defining_Identifier (Body_Param);
if Chars (Body_E) = Chars (E) then
return Body_E;
end if;
Next (Body_Param);
end loop;
-- Should never fall through, should always find a match
raise Program_Error;
end Body_Formal;
-------------------------
-- Generic_Body_Formal --
-------------------------
function Generic_Body_Formal (E : Entity_Id) return Entity_Id is
Gen_Decl : constant Node_Id := Unit_Declaration_Node (Scope (E));
Gen_Body : constant Entity_Id := Corresponding_Body (Gen_Decl);
Form : Entity_Id;
begin
if No (Gen_Body) then
return E;
else
Form := First_Entity (Gen_Body);
while Present (Form) loop
if Chars (Form) = Chars (E) then
return Form;
end if;
Next_Entity (Form);
end loop;
end if;
-- Should never fall through, should always find a match
raise Program_Error;
end Generic_Body_Formal;
---------------------------------
-- May_Need_Initialized_Actual --
---------------------------------
procedure May_Need_Initialized_Actual (Ent : Entity_Id) is
T : constant Entity_Id := Etype (Ent);
Par : constant Node_Id := Parent (T);
begin
if not Is_Generic_Type (T) then
null;
elsif (Nkind (Par)) = N_Private_Extension_Declaration then
-- We only indicate the first such variable in the generic.
if No (Uninitialized_Variable (Par)) then
Set_Uninitialized_Variable (Par, Ent);
end if;
elsif (Nkind (Par)) = N_Formal_Type_Declaration
and then Nkind (Formal_Type_Definition (Par)) =
N_Formal_Private_Type_Definition
then
if No (Uninitialized_Variable (Formal_Type_Definition (Par))) then
Set_Uninitialized_Variable (Formal_Type_Definition (Par), Ent);
end if;
end if;
end May_Need_Initialized_Actual;
----------------------
-- Missing_Subunits --
----------------------
function Missing_Subunits return Boolean is
D : Node_Id;
begin
if not Unloaded_Subunits then
-- Normal compilation, all subunits are present
return False;
elsif E /= Main_Unit_Entity then
-- No warnings on a stub that is not the main unit
return True;
elsif Nkind (Unit_Declaration_Node (E)) in N_Proper_Body then
D := First (Declarations (Unit_Declaration_Node (E)));
while Present (D) loop
-- No warnings if the proper body contains nested stubs
if Nkind (D) in N_Body_Stub then
return True;
end if;
Next (D);
end loop;
return False;
else
-- Missing stubs elsewhere
return True;
end if;
end Missing_Subunits;
----------------------------
-- Output_Reference_Error --
----------------------------
procedure Output_Reference_Error (M : String) is
begin
-- Never issue messages for internal names or renamings
if Is_Internal_Name (Chars (E1))
or else Nkind (Parent (E1)) = N_Object_Renaming_Declaration
then
return;
end if;
-- Don't output message for IN OUT formal unless we have the warning
-- flag specifically set. It is a bit odd to distinguish IN OUT
-- formals from other cases. This distinction is historical in
-- nature. Warnings for IN OUT formals were added fairly late.
if Ekind (E1) = E_In_Out_Parameter
and then not Check_Unreferenced_Formals
then
return;
end if;
-- Other than accept case, post error on defining identifier
if No (Anod) then
Error_Msg_N (M, E1);
-- Accept case, find body formal to post the message
else
Error_Msg_NE (M, Body_Formal (E1, Accept_Statement => Anod), E1);
end if;
end Output_Reference_Error;
----------------------------
-- Publicly_Referenceable --
----------------------------
function Publicly_Referenceable (Ent : Entity_Id) return Boolean is
P : Node_Id;
Prev : Node_Id;
begin
-- A formal parameter is never referenceable outside the body of its
-- subprogram or entry.
if Is_Formal (Ent) then
return False;
end if;
-- Examine parents to look for a library level package spec. But if
-- we find a body or block or other similar construct along the way,
-- we cannot be referenced.
Prev := Ent;
P := Parent (Ent);
loop
case Nkind (P) is
-- If we get to top of tree, then publicly referenceable
when N_Empty =>
return True;
-- If we reach a generic package declaration, then always
-- consider this referenceable, since any instantiation will
-- have access to the entities in the generic package. Note
-- that the package itself may not be instantiated, but then
-- we will get a warning for the package entity.
-- Note that generic formal parameters are themselves not
-- publicly referenceable in an instance, and warnings on them
-- are useful.
when N_Generic_Package_Declaration =>
return
not Is_List_Member (Prev)
or else List_Containing (Prev) /=
Generic_Formal_Declarations (P);
-- Similarly, the generic formals of a generic subprogram are
-- not accessible.
when N_Generic_Subprogram_Declaration =>
if Is_List_Member (Prev)
and then List_Containing (Prev) =
Generic_Formal_Declarations (P)
then
return False;
else
P := Parent (P);
end if;
-- If we reach a subprogram body, entity is not referenceable
-- unless it is the defining entity of the body. This will
-- happen, e.g. when a function is an attribute renaming that
-- is rewritten as a body.
when N_Subprogram_Body =>
if Ent /= Defining_Entity (P) then
return False;
else
P := Parent (P);
end if;
-- If we reach any other body, definitely not referenceable
when N_Block_Statement
| N_Entry_Body
| N_Package_Body
| N_Protected_Body
| N_Subunit
| N_Task_Body
=>
return False;
-- For all other cases, keep looking up tree
when others =>
Prev := P;
P := Parent (P);
end case;
end loop;
end Publicly_Referenceable;
---------------------
-- Warnings_Off_E1 --
---------------------
function Warnings_Off_E1 return Boolean is
begin
return Has_Warnings_Off (E1T)
or else Has_Warnings_Off (Base_Type (E1T))
or else Warnings_Off_Check_Spec (E1);
end Warnings_Off_E1;
-- Start of processing for Check_References
begin
Process_Deferred_References;
-- No messages if warnings are suppressed, or if we have detected any
-- real errors so far (this last check avoids junk messages resulting
-- from errors, e.g. a subunit that is not loaded).
if Warning_Mode = Suppress or else Serious_Errors_Detected /= 0 then
return;
end if;
-- We also skip the messages if any subunits were not loaded (see
-- comment in Sem_Ch10 to understand how this is set, and why it is
-- necessary to suppress the warnings in this case).
if Missing_Subunits then
return;
end if;
-- Otherwise loop through entities, looking for suspicious stuff
E1 := First_Entity (E);
while Present (E1) loop
E1T := Etype (E1);
-- We are only interested in source entities. We also don't issue
-- warnings within instances, since the proper place for such
-- warnings is on the template when it is compiled, and we don't
-- issue warnings for variables with names like Junk, Discard etc.
if Comes_From_Source (E1)
and then Instantiation_Location (Sloc (E1)) = No_Location
then
-- We are interested in variables and out/in-out parameters, but
-- we exclude protected types, too complicated to worry about.
if Ekind (E1) = E_Variable
or else
(Ekind (E1) in E_Out_Parameter | E_In_Out_Parameter
and then not Is_Protected_Type (Current_Scope))
then
-- If the formal has a class-wide type, retrieve its type
-- because checks below depend on its private nature.
if Is_Class_Wide_Type (E1T) then
E1T := Etype (E1T);
end if;
-- Case of an unassigned variable
-- First gather any Unset_Reference indication for E1. In the
-- case of an 'out' parameter, it is the Spec_Entity that is
-- relevant.
if Ekind (E1) = E_Out_Parameter
and then Present (Spec_Entity (E1))
then
UR := Unset_Reference (Spec_Entity (E1));
else
UR := Unset_Reference (E1);
end if;
-- Special processing for access types
if Present (UR) and then Is_Access_Type (E1T) then
-- For access types, the only time we made a UR entry was
-- for a dereference, and so we post the appropriate warning
-- here (note that the dereference may not be explicit in
-- the source, for example in the case of a dispatching call
-- with an anonymous access controlling formal, or of an
-- assignment of a pointer involving discriminant check on
-- the designated object).
if not Warnings_Off_E1 then
Error_Msg_NE ("??& may be null!", UR, E1);
end if;
goto Continue;
-- Case of variable that could be a constant. Note that we
-- never signal such messages for generic package entities,
-- since a given instance could have modifications outside
-- the package.
-- Note that we used to check Address_Taken here, but we don't
-- want to do that since it can be set for non-source cases,
-- e.g. the Unrestricted_Access from a valid attribute, and
-- the wanted effect is included in Never_Set_In_Source.
elsif Warn_On_Constant
and then Ekind (E1) = E_Variable
and then Has_Initial_Value (E1)
and then Never_Set_In_Source_Check_Spec (E1)
and then not Generic_Package_Spec_Entity (E1)
then
-- A special case, if this variable is volatile and not
-- imported, it is not helpful to tell the programmer
-- to mark the variable as constant, since this would be
-- illegal by virtue of RM C.6(13). Instead we suggest
-- using pragma Export (can't be Import because of the
-- initial value).
if (Is_Volatile (E1) or else Has_Volatile_Components (E1))
and then not Is_Imported (E1)
then
Error_Msg_N
("?k?& is not modified, consider pragma Export for "
& "volatile variable!", E1);
-- Another special case, Exception_Occurrence, this catches
-- the case of exception choice (and a bit more too, but not
-- worth doing more investigation here).
elsif Is_RTE (E1T, RE_Exception_Occurrence) then
null;
-- Here we give the warning if referenced and no pragma
-- Unreferenced or Unmodified is present.
else
-- Variable case
if Ekind (E1) = E_Variable then
if Referenced_Check_Spec (E1)
and then not Has_Pragma_Unreferenced_Check_Spec (E1)
and then not Has_Pragma_Unmodified_Check_Spec (E1)
then
if not Warnings_Off_E1
and then not Has_Junk_Name (E1)
then
Error_Msg_N -- CODEFIX
("?k?& is not modified, "
& "could be declared constant!",
E1);
end if;
end if;
end if;
end if;
-- Other cases of a variable or parameter never set in source
elsif Never_Set_In_Source_Check_Spec (E1)
-- No warning if warning for this case turned off
and then Warn_On_No_Value_Assigned
-- No warning if address taken somewhere
and then not Address_Taken (E1)
-- No warning if explicit initial value
and then not Has_Initial_Value (E1)
-- No warning for generic package spec entities, since we
-- might set them in a child unit or something like that
and then not Generic_Package_Spec_Entity (E1)
-- No warning if fully initialized type, except that for
-- this purpose we do not consider access types to qualify
-- as fully initialized types (relying on an access type
-- variable being null when it is never set is a bit odd).
-- Also we generate warning for an out parameter that is
-- never referenced, since again it seems odd to rely on
-- default initialization to set an out parameter value.
and then (Is_Access_Type (E1T)
or else Ekind (E1) = E_Out_Parameter
or else not Is_Fully_Initialized_Type (E1T))
then
-- Do not output complaint about never being assigned a
-- value if a pragma Unmodified applies to the variable
-- we are examining, or if it is a parameter, if there is
-- a pragma Unreferenced for the corresponding spec, or
-- if the type is marked as having unreferenced objects.
-- The last is a little peculiar, but better too few than
-- too many warnings in this situation.
if Has_Pragma_Unreferenced_Objects (E1T)
or else Has_Pragma_Unmodified_Check_Spec (E1)
then
null;
-- IN OUT parameter case where parameter is referenced. We
-- separate this out, since this is the case where we delay
-- output of the warning until more information is available
-- (about use in an instantiation or address being taken).
elsif Ekind (E1) = E_In_Out_Parameter
and then Referenced_Check_Spec (E1)
then
-- Suppress warning if private type, and the procedure
-- has a separate declaration in a different unit. This
-- is the case where the client of a package sees only
-- the private type, and it may be quite reasonable
-- for the logical view to be IN OUT, even if the
-- implementation ends up using access types or some
-- other method to achieve the local effect of a
-- modification. On the other hand if the spec and body
-- are in the same unit, we are in the package body and
-- there we have less excuse for a junk IN OUT parameter.
if Has_Private_Declaration (E1T)
and then Present (Spec_Entity (E1))
and then not In_Same_Source_Unit (E1, Spec_Entity (E1))
then
null;
-- Suppress warning for any parameter of a dispatching
-- operation, since it is quite reasonable to have an
-- operation that is overridden, and for some subclasses
-- needs the formal to be IN OUT and for others happens
-- not to assign it.
elsif Is_Dispatching_Operation
(Scope (Goto_Spec_Entity (E1)))
then
null;
-- Suppress warning if composite type contains any access
-- component, since the logical effect of modifying a
-- parameter may be achieved by modifying a referenced
-- object. This rationale does not apply to private
-- types, so we warn in that case.
elsif Is_Composite_Type (E1T)
and then not Is_Private_Type (E1T)
and then Has_Access_Values (E1T)
then
null;
-- Suppress warning on formals of an entry body. All
-- references are attached to the formal in the entry
-- declaration, which are marked Is_Entry_Formal.
elsif Ekind (Scope (E1)) = E_Entry
and then not Is_Entry_Formal (E1)
then
null;
-- OK, looks like warning for an IN OUT parameter that
-- could be IN makes sense, but we delay the output of
-- the warning, pending possibly finding out later on
-- that the associated subprogram is used as a generic
-- actual, or its address/access is taken. In these two
-- cases, we suppress the warning because the context may
-- force use of IN OUT, even if in this particular case
-- the formal is not modified.
else
-- Suppress the warnings for a junk name
if not Has_Junk_Name (E1) then
In_Out_Warnings.Append (E1);
end if;
end if;
-- Other cases of formals
elsif Is_Formal (E1) then
if not Is_Trivial_Subprogram (Scope (E1)) then
if Referenced_Check_Spec (E1) then
if not Has_Pragma_Unmodified_Check_Spec (E1)
and then not Warnings_Off_E1
and then not Has_Junk_Name (E1)
then
Output_Reference_Error
("?f?formal parameter& is read but "
& "never assigned!");
end if;
elsif not Has_Pragma_Unreferenced_Check_Spec (E1)
and then not Warnings_Off_E1
and then not Has_Junk_Name (E1)
then
Output_Reference_Error
("?f?formal parameter& is not referenced!");
end if;
end if;
-- Case of variable
else
if Referenced (E1) then
if not Has_Unmodified (E1)
and then not Warnings_Off_E1
and then not Has_Junk_Name (E1)
then
if Is_Access_Type (E1T)
or else
not Is_Partially_Initialized_Type (E1T, False)
then
Output_Reference_Error
("?v?variable& is read but never assigned!");
end if;
May_Need_Initialized_Actual (E1);
end if;
elsif not Has_Unreferenced (E1)
and then not Warnings_Off_E1
and then not Has_Junk_Name (E1)
then
Output_Reference_Error -- CODEFIX
("?v?variable& is never read and never assigned!");
end if;
-- Deal with special case where this variable is hidden
-- by a loop variable.
if Ekind (E1) = E_Variable
and then Present (Hiding_Loop_Variable (E1))
and then not Warnings_Off_E1
then
Error_Msg_N
("?v?for loop implicitly declares loop variable!",
Hiding_Loop_Variable (E1));
Error_Msg_Sloc := Sloc (E1);
Error_Msg_N
("\?v?declaration hides & declared#!",
Hiding_Loop_Variable (E1));
end if;
end if;
goto Continue;
end if;
-- Check for unset reference. If type of object has
-- preelaborable initialization, warning is misleading.
if Warn_On_No_Value_Assigned
and then Present (UR)
and then not Known_To_Have_Preelab_Init (Etype (E1))
then
-- For other than access type, go back to original node to
-- deal with case where original unset reference has been
-- rewritten during expansion.
-- In some cases, the original node may be a type
-- conversion, a qualification or an attribute reference and
-- in this case we want the object entity inside. Same for
-- an expression with actions.
UR := Original_Node (UR);
loop
if Nkind (UR) in N_Expression_With_Actions
| N_Qualified_Expression
| N_Type_Conversion
then
UR := Expression (UR);
elsif Nkind (UR) = N_Attribute_Reference then
UR := Prefix (UR);
else
exit;
end if;
end loop;
-- Don't issue warning if appearing inside Initial_Condition
-- pragma or aspect, since that expression is not evaluated
-- at the point where it occurs in the source.
if In_Pragma_Expression (UR, Name_Initial_Condition) then
goto Continue;
end if;
-- Here we issue the warning, all checks completed
-- If we have a return statement, this was a case of an OUT
-- parameter not being set at the time of the return. (Note:
-- it can't be N_Extended_Return_Statement, because those
-- are only for functions, and functions do not allow OUT
-- parameters.)
if not Is_Trivial_Subprogram (Scope (E1)) then
if Nkind (UR) = N_Simple_Return_Statement
and then not Has_Pragma_Unmodified_Check_Spec (E1)
then
if not Warnings_Off_E1
and then not Has_Junk_Name (E1)
then
Error_Msg_NE
("?v?OUT parameter& not set before return",
UR, E1);
end if;
-- If the unset reference is a selected component
-- prefix from source, mention the component as well.
-- If the selected component comes from expansion, all
-- we know is that the entity is not fully initialized
-- at the point of the reference. Locate a random
-- uninitialized component to get a better message.
elsif Nkind (Parent (UR)) = N_Selected_Component then
-- Suppress possibly superfluous warning if component
-- is known to exist and is partially initialized.
if not Has_Discriminants (Etype (E1))
and then
Is_Partially_Initialized_Type
(Etype (Parent (UR)), False)
then
goto Continue;
end if;
Error_Msg_Node_2 := Selector_Name (Parent (UR));
if not Comes_From_Source (Parent (UR)) then
declare
Comp : Entity_Id;
begin
Comp := First_Entity (E1T);
while Present (Comp) loop
if Ekind (Comp) = E_Component
and then Nkind (Parent (Comp)) =
N_Component_Declaration
and then No (Expression (Parent (Comp)))
then
Error_Msg_Node_2 := Comp;
exit;
end if;
Next_Entity (Comp);
end loop;
end;
end if;
-- Issue proper warning. This is a case of referencing
-- a variable before it has been explicitly assigned.
-- For access types, UR was only set for dereferences,
-- so the issue is that the value may be null.
if not Is_Trivial_Subprogram (Scope (E1)) then
if not Warnings_Off_E1 then
if Is_Access_Type (Etype (Parent (UR))) then
Error_Msg_N ("??`&.&` may be null!", UR);
else
Error_Msg_N
("??`&.&` may be referenced before "
& "it has a value!", UR);
end if;
end if;
end if;
-- All other cases of unset reference active
elsif not Warnings_Off_E1 then
Error_Msg_N
("??& may be referenced before it has a value!", UR);
end if;
end if;
goto Continue;
end if;
end if;
-- Then check for unreferenced entities. Note that we are only
-- interested in entities whose Referenced flag is not set.
if not Referenced_Check_Spec (E1)
-- If Referenced_As_LHS is set, then that's still interesting
-- (potential "assigned but never read" case), but not if we
-- have pragma Unreferenced, which cancels this warning.
and then (not Referenced_As_LHS_Check_Spec (E1)
or else not Has_Unreferenced (E1))
-- Check that warnings on unreferenced entities are enabled
and then
((Check_Unreferenced and then not Is_Formal (E1))
-- Case of warning on unreferenced formal
or else (Check_Unreferenced_Formals and then Is_Formal (E1))
-- Case of warning on unread variables modified by an
-- assignment, or an OUT parameter if it is the only one.
or else (Warn_On_Modified_Unread
and then Referenced_As_LHS_Check_Spec (E1))
-- Case of warning on any unread OUT parameter (note such
-- indications are only set if the appropriate warning
-- options were set, so no need to recheck here.)
or else Referenced_As_Out_Parameter_Check_Spec (E1))
-- All other entities, including local packages that cannot be
-- referenced from elsewhere, including those declared within a
-- package body.
and then (Is_Object (E1)
or else Is_Type (E1)
or else Ekind (E1) = E_Label
or else Ekind (E1) in E_Exception
| E_Named_Integer
| E_Named_Real
or else Is_Overloadable (E1)
-- Package case, if the main unit is a package spec
-- or generic package spec, then there may be a
-- corresponding body that references this package
-- in some other file. Otherwise we can be sure
-- that there is no other reference.
or else
(Ekind (E1) = E_Package
and then
not Is_Package_Or_Generic_Package
(Cunit_Entity (Current_Sem_Unit))))
-- Exclude instantiations, since there is no reason why every
-- entity in an instantiation should be referenced.
and then Instantiation_Location (Sloc (E1)) = No_Location
-- Exclude formal parameters from bodies if the corresponding
-- spec entity has been referenced in the case where there is
-- a separate spec.
and then not (Is_Formal (E1)
and then Ekind (Scope (E1)) = E_Subprogram_Body
and then Present (Spec_Entity (E1))
and then Referenced (Spec_Entity (E1)))
-- Consider private type referenced if full view is referenced.
-- If there is not full view, this is a generic type on which
-- warnings are also useful.
and then
not (Is_Private_Type (E1)
and then Present (Full_View (E1))
and then Referenced (Full_View (E1)))
-- Don't worry about full view, only about private type
and then not Has_Private_Declaration (E1)
-- Eliminate dispatching operations from consideration, we
-- cannot tell if these are referenced or not in any easy
-- manner (note this also catches Adjust/Finalize/Initialize).
and then not Is_Dispatching_Operation (E1)
-- Check entity that can be publicly referenced (we do not give
-- messages for such entities, since there could be other
-- units, not involved in this compilation, that contain
-- relevant references.
and then not Publicly_Referenceable (E1)
-- Class wide types are marked as source entities, but they are
-- not really source entities, and are always created, so we do
-- not care if they are not referenced.
and then Ekind (E1) /= E_Class_Wide_Type
-- Objects other than parameters of task types are allowed to
-- be non-referenced, since they start up tasks.
and then ((Ekind (E1) /= E_Variable
and then Ekind (E1) /= E_Constant
and then Ekind (E1) /= E_Component)
or else not Is_Task_Type (E1T))
-- For subunits, only place warnings on the main unit itself,
-- since parent units are not completely compiled.
and then (Nkind (Unit (Cunit (Main_Unit))) /= N_Subunit
or else Get_Source_Unit (E1) = Main_Unit)
-- No warning on a return object, because these are often
-- created with a single expression and an implicit return.
-- If the object is a variable there will be a warning
-- indicating that it could be declared constant.
and then not
(Ekind (E1) = E_Constant and then Is_Return_Object (E1))
then
-- Suppress warnings in internal units if not in -gnatg mode
-- (these would be junk warnings for an applications program,
-- since they refer to problems in internal units).
if GNAT_Mode or else not In_Internal_Unit (E1) then
-- We do not immediately flag the error. This is because we
-- have not expanded generic bodies yet, and they may have
-- the missing reference. So instead we park the entity on a
-- list, for later processing. However for the case of an
-- accept statement we want to output messages now, since
-- we know we already have all information at hand, and we
-- also want to have separate warnings for each accept
-- statement for the same entry.
if Present (Anod) then
pragma Assert (Is_Formal (E1));
-- The unreferenced entity is E1, but post the warning
-- on the body entity for this accept statement.
if not Warnings_Off_E1 then
Warn_On_Unreferenced_Entity
(E1, Body_Formal (E1, Accept_Statement => Anod));
end if;
elsif not Warnings_Off_E1
and then not Has_Junk_Name (E1)
then
if Is_Formal (E1)
and then Nkind (Unit_Declaration_Node (Scope (E1)))
= N_Generic_Subprogram_Declaration
then
Unreferenced_Entities.Append
(Generic_Body_Formal (E1));
else
Unreferenced_Entities.Append (E1);
end if;
end if;
end if;
-- Generic units are referenced in the generic body, but if they
-- are not public and never instantiated we want to force a
-- warning on them. We treat them as redundant constructs to
-- minimize noise.
elsif Is_Generic_Subprogram (E1)
and then not Is_Instantiated (E1)
and then not Publicly_Referenceable (E1)
and then Instantiation_Depth (Sloc (E1)) = 0
and then Warn_On_Redundant_Constructs
then
if not Warnings_Off_E1 and then not Has_Junk_Name (E1) then
Unreferenced_Entities.Append (E1);
-- Force warning on entity
Set_Referenced (E1, False);
end if;
end if;
end if;
-- Recurse into nested package or block. Do not recurse into a formal
-- package, because the corresponding body is not analyzed.
<<Continue>>
if (Is_Package_Or_Generic_Package (E1)
and then Nkind (Parent (E1)) = N_Package_Specification
and then
Nkind (Original_Node (Unit_Declaration_Node (E1))) /=
N_Formal_Package_Declaration)
or else Ekind (E1) = E_Block
then
Check_References (E1);
end if;
Next_Entity (E1);
end loop;
end Check_References;
---------------------------
-- Check_Unset_Reference --
---------------------------
procedure Check_Unset_Reference (N : Node_Id) is
Typ : constant Entity_Id := Etype (N);
function Is_OK_Fully_Initialized return Boolean;
-- This function returns true if the given node N is fully initialized
-- so that the reference is safe as far as this routine is concerned.
-- Safe generally means that the type of N is a fully initialized type.
-- The one special case is that for access types, which are always fully
-- initialized, we don't consider a dereference OK since it will surely
-- be dereferencing a null value, which won't do.
function Prefix_Has_Dereference (Pref : Node_Id) return Boolean;
-- Used to test indexed or selected component or slice to see if the
-- evaluation of the prefix depends on a dereference, and if so, returns
-- True, in which case we always check the prefix, even if we know that
-- the referenced component is initialized. Pref is the prefix to test.
-----------------------------
-- Is_OK_Fully_Initialized --
-----------------------------
function Is_OK_Fully_Initialized return Boolean is
begin
if Is_Access_Type (Typ) and then Is_Dereferenced (N) then
return False;
-- A type subject to pragma Default_Initial_Condition may be fully
-- default initialized depending on inheritance and the argument of
-- the pragma (SPARK RM 3.1 and SPARK RM 7.3.3).
elsif Has_Fully_Default_Initializing_DIC_Pragma (Typ) then
return True;
else
return Is_Fully_Initialized_Type (Typ);
end if;
end Is_OK_Fully_Initialized;
----------------------------
-- Prefix_Has_Dereference --
----------------------------
function Prefix_Has_Dereference (Pref : Node_Id) return Boolean is
begin
-- If prefix is of an access type, it certainly needs a dereference
if Is_Access_Type (Etype (Pref)) then
return True;
-- If prefix is explicit dereference, that's a dereference for sure
elsif Nkind (Pref) = N_Explicit_Dereference then
return True;
-- If prefix is itself a component reference or slice check prefix
elsif Nkind (Pref) = N_Slice
or else Nkind (Pref) = N_Indexed_Component
or else Nkind (Pref) = N_Selected_Component
then
return Prefix_Has_Dereference (Prefix (Pref));
-- All other cases do not involve a dereference
else
return False;
end if;
end Prefix_Has_Dereference;
-- Start of processing for Check_Unset_Reference
begin
-- Nothing to do if warnings suppressed
if Warning_Mode = Suppress then
return;
end if;
-- Nothing to do for numeric or string literal. Do this test early to
-- save time in a common case (it does not matter that we do not include
-- character literal here, since that will be caught later on in the
-- when others branch of the case statement).
if Nkind (N) in N_Numeric_Or_String_Literal then
return;
end if;
-- Ignore reference unless it comes from source. Almost always if we
-- have a reference from generated code, it is bogus (e.g. calls to init
-- procs to set default discriminant values).
if not Comes_From_Source (Original_Node (N)) then
return;
end if;
-- Otherwise see what kind of node we have. If the entity already has an
-- unset reference, it is not necessarily the earliest in the text,
-- because resolution of the prefix of selected components is completed
-- before the resolution of the selected component itself. As a result,
-- given (R /= null and then R.X > 0), the occurrences of R are examined
-- in right-to-left order. If there is already an unset reference, we
-- check whether N is earlier before proceeding.
case Nkind (N) is
-- For identifier or expanded name, examine the entity involved
when N_Expanded_Name
| N_Identifier
=>
declare
E : constant Entity_Id := Entity (N);
begin
if Ekind (E) in E_Variable | E_Out_Parameter
and then Never_Set_In_Source_Check_Spec (E)
and then not Has_Initial_Value (E)
and then (No (Unset_Reference (E))
or else
Earlier_In_Extended_Unit
(Sloc (N), Sloc (Unset_Reference (E))))
and then not Has_Pragma_Unmodified_Check_Spec (E)
and then not Warnings_Off_Check_Spec (E)
and then not Has_Junk_Name (E)
then
-- We may have an unset reference. The first test is whether
-- this is an access to a discriminant of a record or a
-- component with default initialization. Both of these
-- cases can be ignored, since the actual object that is
-- referenced is definitely initialized. Note that this
-- covers the case of reading discriminants of an OUT
-- parameter, which is OK even in Ada 83.
-- Note that we are only interested in a direct reference to
-- a record component here. If the reference is through an
-- access type, then the access object is being referenced,
-- not the record, and still deserves an unset reference.
if Nkind (Parent (N)) = N_Selected_Component
and not Is_Access_Type (Typ)
then
declare
ES : constant Entity_Id :=
Entity (Selector_Name (Parent (N)));
begin
if Ekind (ES) = E_Discriminant
or else
(Present (Declaration_Node (ES))
and then
Present (Expression (Declaration_Node (ES))))
then
return;
end if;
end;
end if;
-- Exclude fully initialized types
if Is_OK_Fully_Initialized then
return;
end if;
-- Here we have a potential unset reference. But before we
-- get worried about it, we have to make sure that the
-- entity declaration is in the same procedure as the
-- reference, since if they are in separate procedures, then
-- we have no idea about sequential execution.
-- The tests in the loop below catch all such cases, but do
-- allow the reference to appear in a loop, block, or
-- package spec that is nested within the declaring scope.
-- As always, it is possible to construct cases where the
-- warning is wrong, that is why it is a warning.
Potential_Unset_Reference : declare
SR : Entity_Id;
SE : constant Entity_Id := Scope (E);
function Within_Postcondition return Boolean;
-- Returns True if N is within a Postcondition, a
-- Refined_Post, an Ensures component in a Test_Case,
-- or a Contract_Cases.
--------------------------
-- Within_Postcondition --
--------------------------
function Within_Postcondition return Boolean is
Nod, P : Node_Id;
begin
Nod := Parent (N);
while Present (Nod) loop
if Nkind (Nod) = N_Pragma
and then
Pragma_Name_Unmapped (Nod)
in Name_Postcondition
| Name_Refined_Post
| Name_Contract_Cases
then
return True;
elsif Present (Parent (Nod)) then
P := Parent (Nod);
if Nkind (P) = N_Pragma
and then Pragma_Name (P) =
Name_Test_Case
and then Nod = Test_Case_Arg (P, Name_Ensures)
then
return True;
end if;
end if;
Nod := Parent (Nod);
end loop;
return False;
end Within_Postcondition;
-- Start of processing for Potential_Unset_Reference
begin
SR := Current_Scope;
while SR /= SE loop
if SR = Standard_Standard
or else Is_Subprogram (SR)
or else Is_Concurrent_Body (SR)
or else Is_Concurrent_Type (SR)
then
return;
end if;
SR := Scope (SR);
end loop;
-- Case of reference has an access type. This is a
-- special case since access types are always set to null
-- so cannot be truly uninitialized, but we still want to
-- warn about cases of obvious null dereference.
if Is_Access_Type (Typ) then
Access_Type_Case : declare
P : Node_Id;
function Process
(N : Node_Id) return Traverse_Result;
-- Process function for instantiation of Traverse
-- below. Checks if N contains reference to E other
-- than a dereference.
function Ref_In (Nod : Node_Id) return Boolean;
-- Determines whether Nod contains a reference to
-- the entity E that is not a dereference.
-------------
-- Process --
-------------
function Process
(N : Node_Id) return Traverse_Result
is
begin
if Is_Entity_Name (N)
and then Entity (N) = E
and then not Is_Dereferenced (N)
then
return Abandon;
else
return OK;
end if;
end Process;
------------
-- Ref_In --
------------
function Ref_In (Nod : Node_Id) return Boolean is
function Traverse is new Traverse_Func (Process);
begin
return Traverse (Nod) = Abandon;
end Ref_In;
-- Start of processing for Access_Type_Case
begin
-- Don't bother if we are inside an instance, since
-- the compilation of the generic template is where
-- the warning should be issued.
if In_Instance then
return;
end if;
-- Don't bother if this is not the main unit. If we
-- try to give this warning for with'ed units, we
-- get some false positives, since we do not record
-- references in other units.
if not In_Extended_Main_Source_Unit (E)
or else
not In_Extended_Main_Source_Unit (N)
then
return;
end if;
-- We are only interested in dereferences
if not Is_Dereferenced (N) then
return;
end if;
-- One more check, don't bother with references
-- that are inside conditional statements or WHILE
-- loops if the condition references the entity in
-- question. This avoids most false positives.
P := Parent (N);
loop
P := Parent (P);
exit when No (P);
if Nkind (P) in N_If_Statement | N_Elsif_Part
and then Ref_In (Condition (P))
then
return;
elsif Nkind (P) = N_Loop_Statement
and then Present (Iteration_Scheme (P))
and then
Ref_In (Condition (Iteration_Scheme (P)))
then
return;
end if;
end loop;
end Access_Type_Case;
end if;
-- One more check, don't bother if we are within a
-- postcondition, since the expression occurs in a
-- place unrelated to the actual test.
if not Within_Postcondition then
-- Here we definitely have a case for giving a warning
-- for a reference to an unset value. But we don't
-- give the warning now. Instead set Unset_Reference
-- in the identifier involved. The reason for this is
-- that if we find the variable is never ever assigned
-- a value then that warning is more important and
-- there is no point in giving the reference warning.
-- If this is an identifier, set the field directly
if Nkind (N) = N_Identifier then
Set_Unset_Reference (E, N);
-- Otherwise it is an expanded name, so set the field
-- of the actual identifier for the reference.
else
Set_Unset_Reference (E, Selector_Name (N));
end if;
end if;
end Potential_Unset_Reference;
end if;
end;
-- Indexed component or slice
when N_Indexed_Component
| N_Slice
=>
-- If prefix does not involve dereferencing an access type, then
-- we know we are OK if the component type is fully initialized,
-- since the component will have been set as part of the default
-- initialization.
if not Prefix_Has_Dereference (Prefix (N))
and then Is_OK_Fully_Initialized
then
return;
-- Look at prefix in access type case, or if the component is not
-- fully initialized.
else
Check_Unset_Reference (Prefix (N));
end if;
-- Record component
when N_Selected_Component =>
declare
Pref : constant Node_Id := Prefix (N);
Ent : constant Entity_Id := Entity (Selector_Name (N));
begin
-- If prefix involves dereferencing an access type, always
-- check the prefix, since the issue then is whether this
-- access value is null.
if Prefix_Has_Dereference (Pref) then
null;
-- Always go to prefix if no selector entity is set. Can this
-- happen in the normal case? Not clear, but it definitely can
-- happen in error cases.
elsif No (Ent) then
null;
-- For a record component, check some cases where we have
-- reasonable cause to consider that the component is known to
-- be or probably is initialized. In this case, we don't care
-- if the prefix itself was explicitly initialized.
-- Discriminants are always considered initialized
elsif Ekind (Ent) = E_Discriminant then
return;
-- An explicitly initialized component is certainly initialized
elsif Nkind (Parent (Ent)) = N_Component_Declaration
and then Present (Expression (Parent (Ent)))
then
return;
-- A fully initialized component is initialized
elsif Is_OK_Fully_Initialized then
return;
end if;
-- If none of those cases apply, check the record type prefix
Check_Unset_Reference (Pref);
end;
-- For type conversions, qualifications, or expressions with actions,
-- examine the expression.
when N_Expression_With_Actions
| N_Qualified_Expression
| N_Type_Conversion
=>
Check_Unset_Reference (Expression (N));
-- For explicit dereference, always check prefix, which will generate
-- an unset reference (since this is a case of dereferencing null).
when N_Explicit_Dereference =>
Check_Unset_Reference (Prefix (N));
-- All other cases are not cases of an unset reference
when others =>
null;
end case;
end Check_Unset_Reference;
------------------------
-- Check_Unused_Withs --
------------------------
procedure Check_Unused_Withs (Spec_Unit : Unit_Number_Type := No_Unit) is
Munite : constant Entity_Id := Cunit_Entity (Main_Unit);
-- This is needed for checking the special renaming case
procedure Check_One_Unit (Unit : Unit_Number_Type);
-- Subsidiary procedure, performs checks for specified unit
--------------------
-- Check_One_Unit --
--------------------
procedure Check_One_Unit (Unit : Unit_Number_Type) is
Cnode : constant Node_Id := Cunit (Unit);
Is_Visible_Renaming : Boolean := False;
procedure Check_Inner_Package (Pack : Entity_Id);
-- Pack is a package local to a unit in a with_clause. Both the unit
-- and Pack are referenced. If none of the entities in Pack are
-- referenced, then the only occurrence of Pack is in a USE clause
-- or a pragma, and a warning is worthwhile as well.
function Check_System_Aux (Lunit : Entity_Id) return Boolean;
-- Before giving a warning on a with_clause for System, check whether
-- a system extension is present.
function Find_Package_Renaming
(P : Entity_Id;
L : Entity_Id) return Entity_Id;
-- The only reference to a context unit may be in a renaming
-- declaration. If this renaming declares a visible entity, do not
-- warn that the context clause could be moved to the body, because
-- the renaming may be intended to re-export the unit.
function Has_Visible_Entities (P : Entity_Id) return Boolean;
-- This function determines if a package has any visible entities.
-- True is returned if there is at least one declared visible entity,
-- otherwise False is returned (e.g. case of only pragmas present).
-------------------------
-- Check_Inner_Package --
-------------------------
procedure Check_Inner_Package (Pack : Entity_Id) is
E : Entity_Id;
Un : constant Node_Id := Sinfo.Nodes.Unit (Cnode);
function Check_Use_Clause (N : Node_Id) return Traverse_Result;
-- If N is a use_clause for Pack, emit warning
procedure Check_Use_Clauses is new
Traverse_Proc (Check_Use_Clause);
----------------------
-- Check_Use_Clause --
----------------------
function Check_Use_Clause (N : Node_Id) return Traverse_Result is
begin
if Nkind (N) = N_Use_Package_Clause
and then Entity (Name (N)) = Pack
then
-- Suppress message if any serious errors detected that turn
-- off expansion, and thus result in false positives for
-- this warning.
if Serious_Errors_Detected = 0 then
Error_Msg_Qual_Level := 1;
Error_Msg_NE -- CODEFIX
("?u?no entities of package& are referenced!",
Name (N), Pack);
Error_Msg_Qual_Level := 0;
end if;
end if;
return OK;
end Check_Use_Clause;
-- Start of processing for Check_Inner_Package
begin
E := First_Entity (Pack);
while Present (E) loop
if Referenced_Check_Spec (E) then
return;
end if;
Next_Entity (E);
end loop;
-- No entities of the package are referenced. Check whether the
-- reference to the package itself is a use clause, and if so
-- place a warning on it.
Check_Use_Clauses (Un);
end Check_Inner_Package;
----------------------
-- Check_System_Aux --
----------------------
function Check_System_Aux (Lunit : Entity_Id) return Boolean is
Ent : Entity_Id;
begin
if Chars (Lunit) = Name_System
and then Scope (Lunit) = Standard_Standard
and then Present_System_Aux
then
Ent := First_Entity (System_Aux_Id);
while Present (Ent) loop
if Referenced_Check_Spec (Ent) then
return True;
end if;
Next_Entity (Ent);
end loop;
end if;
return False;
end Check_System_Aux;
---------------------------
-- Find_Package_Renaming --
---------------------------
function Find_Package_Renaming
(P : Entity_Id;
L : Entity_Id) return Entity_Id
is
E1 : Entity_Id;
R : Entity_Id;
begin
Is_Visible_Renaming := False;
E1 := First_Entity (P);
while Present (E1) loop
if Ekind (E1) = E_Package and then Renamed_Entity (E1) = L then
Is_Visible_Renaming := not Is_Hidden (E1);
return E1;
elsif Ekind (E1) = E_Package
and then No (Renamed_Entity (E1))
and then not Is_Generic_Instance (E1)
then
R := Find_Package_Renaming (E1, L);
if Present (R) then
Is_Visible_Renaming := not Is_Hidden (R);
return R;
end if;
end if;
Next_Entity (E1);
end loop;
return Empty;
end Find_Package_Renaming;
--------------------------
-- Has_Visible_Entities --
--------------------------
function Has_Visible_Entities (P : Entity_Id) return Boolean is
E : Entity_Id;
begin
-- If unit in context is not a package, it is a subprogram that
-- is not called or a generic unit that is not instantiated
-- in the current unit, and warning is appropriate.
if Ekind (P) /= E_Package then
return True;
end if;
-- If unit comes from a limited_with clause, look for declaration
-- of shadow entities.
if Present (Limited_View (P)) then
E := First_Entity (Limited_View (P));
else
E := First_Entity (P);
end if;
while Present (E) and then E /= First_Private_Entity (P) loop
if Comes_From_Source (E) or else Present (Limited_View (P)) then
return True;
end if;
Next_Entity (E);
end loop;
return False;
end Has_Visible_Entities;
-- Local variables
Ent : Entity_Id;
Item : Node_Id;
Lunit : Entity_Id;
Pack : Entity_Id;
-- Start of processing for Check_One_Unit
begin
-- Only do check in units that are part of the extended main unit.
-- This is actually a necessary restriction, because in the case of
-- subprogram acting as its own specification, there can be with's in
-- subunits that we will not see.
if not In_Extended_Main_Source_Unit (Cnode) then
return;
end if;
-- Loop through context items in this unit
Item := First (Context_Items (Cnode));
while Present (Item) loop
if Nkind (Item) = N_With_Clause
and then not Implicit_With (Item)
and then In_Extended_Main_Source_Unit (Item)
-- Guard for no entity present. Not clear under what conditions
-- this happens, but it does occur, and since this is only a
-- warning, we just suppress the warning in this case.
and then Nkind (Name (Item)) in N_Has_Entity
and then Present (Entity (Name (Item)))
then
Lunit := Entity (Name (Item));
-- Check if this unit is referenced (skip the check if this
-- is explicitly marked by a pragma Unreferenced).
if not Referenced (Lunit) and then not Has_Unreferenced (Lunit)
then
-- Suppress warnings in internal units if not in -gnatg mode
-- (these would be junk warnings for an application program,
-- since they refer to problems in internal units).
if GNAT_Mode or else not Is_Internal_Unit (Unit) then
-- Here we definitely have a non-referenced unit. If it
-- is the special call for a spec unit, then just set the
-- flag to be read later.
if Unit = Spec_Unit then
Set_Unreferenced_In_Spec (Item);
-- Otherwise simple unreferenced message, but skip this
-- if no visible entities, because that is most likely a
-- case where warning would be false positive (e.g. a
-- package with only a linker options pragma and nothing
-- else or a pragma elaborate with a body library task).
elsif Has_Visible_Entities (Lunit) then
Error_Msg_N -- CODEFIX
("?u?unit& is not referenced!", Name (Item));
end if;
end if;
-- If main unit is a renaming of this unit, then we consider
-- the with to be OK (obviously it is needed in this case).
-- This may be transitive: the unit in the with_clause may
-- itself be a renaming, in which case both it and the main
-- unit rename the same ultimate package.
elsif Present (Renamed_Entity (Munite))
and then
(Renamed_Entity (Munite) = Lunit
or else Renamed_Entity (Munite) = Renamed_Entity (Lunit))
then
null;
-- If this unit is referenced, and it is a package, we do
-- another test, to see if any of the entities in the package
-- are referenced. If none of the entities are referenced, we
-- still post a warning. This occurs if the only use of the
-- package is in a use clause, or in a package renaming
-- declaration. This check is skipped for packages that are
-- renamed in a spec, since the entities in such a package are
-- visible to clients via the renaming.
elsif Ekind (Lunit) = E_Package
and then not Renamed_In_Spec (Lunit)
then
-- If Is_Instantiated is set, it means that the package is
-- implicitly instantiated (this is the case of parent
-- instance or an actual for a generic package formal), and
-- this counts as a reference.
if Is_Instantiated (Lunit) then
null;
-- If no entities in package, and there is a pragma
-- Elaborate_Body present, then assume that this with is
-- done for purposes of this elaboration.
elsif No (First_Entity (Lunit))
and then Has_Pragma_Elaborate_Body (Lunit)
then
null;
-- Otherwise see if any entities have been referenced
else
if Limited_Present (Item) then
Ent := First_Entity (Limited_View (Lunit));
else
Ent := First_Entity (Lunit);
end if;
loop
-- No more entities, and we did not find one that was
-- referenced. Means we have a definite case of a with
-- none of whose entities was referenced.
if No (Ent) then
-- If in spec, just set the flag
if Unit = Spec_Unit then
Set_No_Entities_Ref_In_Spec (Item);
elsif Check_System_Aux (Lunit) then
null;
-- Else the warning may be needed
else
-- Warn if we unreferenced flag set and we have
-- not had serious errors. The reason we inhibit
-- the message if there are errors is to prevent
-- false positives from disabling expansion.
if not Has_Unreferenced (Lunit)
and then Serious_Errors_Detected = 0
then
-- Get possible package renaming
Pack := Find_Package_Renaming (Munite, Lunit);
-- No warning if either the package or its
-- renaming is used as a generic actual.
if Used_As_Generic_Actual (Lunit)
or else
(Present (Pack)
and then
Used_As_Generic_Actual (Pack))
then
exit;
end if;
-- Here we give the warning
Error_Msg_N -- CODEFIX
("?u?no entities of & are referenced!",
Name (Item));
-- Flag renaming of package as well. If
-- the original package has warnings off,
-- we suppress the warning on the renaming
-- as well.
if Present (Pack)
and then not Has_Warnings_Off (Lunit)
and then not Has_Unreferenced (Pack)
then
Error_Msg_NE -- CODEFIX
("?u?no entities of& are referenced!",
Unit_Declaration_Node (Pack), Pack);
end if;
end if;
end if;
exit;
-- Case of entity being referenced. The reference may
-- come from a limited_with_clause, in which case the
-- limited view of the entity carries the flag.
elsif Referenced_Check_Spec (Ent)
or else Referenced_As_LHS_Check_Spec (Ent)
or else Referenced_As_Out_Parameter_Check_Spec (Ent)
or else
(From_Limited_With (Ent)
and then Is_Incomplete_Type (Ent)
and then Present (Non_Limited_View (Ent))
and then Referenced (Non_Limited_View (Ent)))
then
-- This means that the with is indeed fine, in that
-- it is definitely needed somewhere, and we can
-- quit worrying about this one...
-- Except for one little detail: if either of the
-- flags was set during spec processing, this is
-- where we complain that the with could be moved
-- from the spec. If the spec contains a visible
-- renaming of the package, inhibit warning to move
-- with_clause to body.
if Ekind (Munite) = E_Package_Body then
Pack :=
Find_Package_Renaming
(Spec_Entity (Munite), Lunit);
else
Pack := Empty;
end if;
-- If a renaming is present in the spec do not warn
-- because the body or child unit may depend on it.
if Present (Pack)
and then Renamed_Entity (Pack) = Lunit
then
exit;
elsif Unreferenced_In_Spec (Item) then
Error_Msg_N -- CODEFIX
("?u?unit& is not referenced in spec!",
Name (Item));
elsif No_Entities_Ref_In_Spec (Item) then
Error_Msg_N -- CODEFIX
("?u?no entities of & are referenced in spec!",
Name (Item));
else
if Ekind (Ent) = E_Package then
Check_Inner_Package (Ent);
end if;
exit;
end if;
if not Is_Visible_Renaming then
Error_Msg_N -- CODEFIX
("\?u?with clause might be moved to body!",
Name (Item));
end if;
exit;
-- Move to next entity to continue search
else
Next_Entity (Ent);
end if;
end loop;
end if;
-- For a generic package, the only interesting kind of
-- reference is an instantiation, since entities cannot be
-- referenced directly.
elsif Is_Generic_Unit (Lunit) then
-- Unit was never instantiated, set flag for case of spec
-- call, or give warning for normal call.
if not Is_Instantiated (Lunit) then
if Unit = Spec_Unit then
Set_Unreferenced_In_Spec (Item);
else
Error_Msg_N -- CODEFIX
("?u?unit& is never instantiated!", Name (Item));
end if;
-- If unit was indeed instantiated, make sure that flag is
-- not set showing it was uninstantiated in the spec, and if
-- so, give warning.
elsif Unreferenced_In_Spec (Item) then
Error_Msg_N
("?u?unit& is not instantiated in spec!", Name (Item));
Error_Msg_N -- CODEFIX
("\?u?with clause can be moved to body!", Name (Item));
end if;
end if;
end if;
Next (Item);
end loop;
end Check_One_Unit;
-- Start of processing for Check_Unused_Withs
begin
-- Immediate return if no semantics or warning flag not set
if not Opt.Check_Withs or else Operating_Mode = Check_Syntax then
return;
end if;
Process_Deferred_References;
-- Flag any unused with clauses. For a subunit, check only the units
-- in its context, not those of the parent, which may be needed by other
-- subunits. We will get the full warnings when we compile the parent,
-- but the following is helpful when compiling a subunit by itself.
if Nkind (Unit (Cunit (Main_Unit))) = N_Subunit then
if Current_Sem_Unit = Main_Unit then
Check_One_Unit (Main_Unit);
end if;
return;
end if;
-- Process specified units
if Spec_Unit = No_Unit then
-- For main call, check all units
for Unit in Main_Unit .. Last_Unit loop
Check_One_Unit (Unit);
end loop;
else
-- For call for spec, check only the spec
Check_One_Unit (Spec_Unit);
end if;
end Check_Unused_Withs;
---------------------------------
-- Generic_Package_Spec_Entity --
---------------------------------
function Generic_Package_Spec_Entity (E : Entity_Id) return Boolean is
S : Entity_Id;
begin
if Is_Package_Body_Entity (E) then
return False;
else
S := Scope (E);
loop
if S = Standard_Standard then
return False;
elsif Ekind (S) = E_Generic_Package then
return True;
elsif Ekind (S) = E_Package then
S := Scope (S);
else
return False;
end if;
end loop;
end if;
end Generic_Package_Spec_Entity;
----------------------
-- Goto_Spec_Entity --
----------------------
function Goto_Spec_Entity (E : Entity_Id) return Entity_Id is
begin
if Is_Formal (E) and then Present (Spec_Entity (E)) then
return Spec_Entity (E);
else
return E;
end if;
end Goto_Spec_Entity;
-------------------
-- Has_Junk_Name --
-------------------
function Has_Junk_Name (E : Entity_Id) return Boolean is
function Match (S : String) return Boolean;
-- Return true if substring S is found in Name_Buffer (1 .. Name_Len)
-----------
-- Match --
-----------
function Match (S : String) return Boolean is
Slen1 : constant Integer := S'Length - 1;
begin
for J in 1 .. Name_Len - S'Length + 1 loop
if Name_Buffer (J .. J + Slen1) = S then
return True;
end if;
end loop;
return False;
end Match;
-- Start of processing for Has_Junk_Name
begin
Get_Unqualified_Decoded_Name_String (Chars (E));
return
Match ("discard") or else
Match ("dummy") or else
Match ("ignore") or else
Match ("junk") or else
Match ("unused");
end Has_Junk_Name;
--------------------------------------
-- Has_Pragma_Unmodified_Check_Spec --
--------------------------------------
function Has_Pragma_Unmodified_Check_Spec
(E : Entity_Id) return Boolean
is
begin
if Is_Formal (E) and then Present (Spec_Entity (E)) then
-- Note: use of OR instead of OR ELSE here is deliberate, we want
-- to mess with Unmodified flags on both body and spec entities.
-- Has_Unmodified has side effects!
return Has_Unmodified (E)
or
Has_Unmodified (Spec_Entity (E));
else
return Has_Unmodified (E);
end if;
end Has_Pragma_Unmodified_Check_Spec;
----------------------------------------
-- Has_Pragma_Unreferenced_Check_Spec --
----------------------------------------
function Has_Pragma_Unreferenced_Check_Spec
(E : Entity_Id) return Boolean
is
begin
if Is_Formal (E) and then Present (Spec_Entity (E)) then
-- Note: use of OR here instead of OR ELSE is deliberate, we want
-- to mess with flags on both entities.
return Has_Unreferenced (E)
or
Has_Unreferenced (Spec_Entity (E));
else
return Has_Unreferenced (E);
end if;
end Has_Pragma_Unreferenced_Check_Spec;
----------------
-- Initialize --
----------------
procedure Initialize is
begin
Warnings_Off_Pragmas.Init;
Unreferenced_Entities.Init;
In_Out_Warnings.Init;
end Initialize;
---------------------------------------------
-- Is_Attribute_And_Known_Value_Comparison --
---------------------------------------------
function Is_Attribute_And_Known_Value_Comparison
(Op : Node_Id) return Boolean
is
Orig_Op : constant Node_Id := Original_Node (Op);
begin
return
Nkind (Orig_Op) in N_Op_Compare
and then Nkind (Original_Node (Left_Opnd (Orig_Op))) =
N_Attribute_Reference
and then Compile_Time_Known_Value (Right_Opnd (Orig_Op));
end Is_Attribute_And_Known_Value_Comparison;
------------------------------------
-- Never_Set_In_Source_Check_Spec --
------------------------------------
function Never_Set_In_Source_Check_Spec (E : Entity_Id) return Boolean is
begin
if Is_Formal (E) and then Present (Spec_Entity (E)) then
return Never_Set_In_Source (E)
and then
Never_Set_In_Source (Spec_Entity (E));
else
return Never_Set_In_Source (E);
end if;
end Never_Set_In_Source_Check_Spec;
-------------------------------------
-- Operand_Has_Warnings_Suppressed --
-------------------------------------
function Operand_Has_Warnings_Suppressed (N : Node_Id) return Boolean is
function Check_For_Warnings (N : Node_Id) return Traverse_Result;
-- Function used to check one node to see if it is or was originally
-- a reference to an entity for which Warnings are off. If so, Abandon
-- is returned, otherwise OK_Orig is returned to continue the traversal
-- of the original expression.
function Traverse is new Traverse_Func (Check_For_Warnings);
-- Function used to traverse tree looking for warnings
------------------------
-- Check_For_Warnings --
------------------------
function Check_For_Warnings (N : Node_Id) return Traverse_Result is
R : constant Node_Id := Original_Node (N);
begin
if Nkind (R) in N_Has_Entity
and then Present (Entity (R))
and then Has_Warnings_Off (Entity (R))
then
return Abandon;
else
return OK_Orig;
end if;
end Check_For_Warnings;
-- Start of processing for Operand_Has_Warnings_Suppressed
begin
return Traverse (N) = Abandon;
-- If any exception occurs, then something has gone wrong, and this is
-- only a minor aesthetic issue anyway, so just say we did not find what
-- we are looking for, rather than blow up.
exception
when others =>
-- With debug flag K we will get an exception unless an error has
-- already occurred (useful for debugging).
if Debug_Flag_K then
Check_Error_Detected;
end if;
return False;
end Operand_Has_Warnings_Suppressed;
-----------------------------------------
-- Output_Non_Modified_In_Out_Warnings --
-----------------------------------------
procedure Output_Non_Modified_In_Out_Warnings is
function No_Warn_On_In_Out (E : Entity_Id) return Boolean;
-- Given a formal parameter entity E, determines if there is a reason to
-- suppress IN OUT warnings (not modified, could be IN) for formals of
-- the subprogram. We suppress these warnings if Warnings Off is set, or
-- if we have seen the address of the subprogram being taken, or if the
-- subprogram is used as a generic actual (in the latter cases the
-- context may force use of IN OUT, even if the parameter is not
-- modified for this particular case.
-----------------------
-- No_Warn_On_In_Out --
-----------------------
function No_Warn_On_In_Out (E : Entity_Id) return Boolean is
S : constant Entity_Id := Scope (E);
SE : constant Entity_Id := Spec_Entity (E);
begin
-- Do not warn if address is taken, since funny business may be going
-- on in treating the parameter indirectly as IN OUT.
if Address_Taken (S)
or else (Present (SE) and then Address_Taken (Scope (SE)))
then
return True;
-- Do not warn if used as a generic actual, since the generic may be
-- what is forcing the use of an "unnecessary" IN OUT.
elsif Used_As_Generic_Actual (S)
or else (Present (SE) and then Used_As_Generic_Actual (Scope (SE)))
then
return True;
-- Else test warnings off
elsif Warnings_Off_Check_Spec (S) then
return True;
-- All tests for suppressing warning failed
else
return False;
end if;
end No_Warn_On_In_Out;
-- Start of processing for Output_Non_Modified_In_Out_Warnings
begin
-- Loop through entities for which a warning may be needed
for J in In_Out_Warnings.First .. In_Out_Warnings.Last loop
declare
E1 : constant Entity_Id := In_Out_Warnings.Table (J);
begin
-- Suppress warning in specific cases (see details in comments for
-- No_Warn_On_In_Out), or if there is a pragma Unmodified.
if Has_Pragma_Unmodified_Check_Spec (E1)
or else No_Warn_On_In_Out (E1)
then
null;
-- Here we generate the warning
else
-- If -gnatwk is set then output message that it could be IN
if not Is_Trivial_Subprogram (Scope (E1)) then
if Warn_On_Constant then
Error_Msg_N
("?k?formal parameter & is not modified!", E1);
Error_Msg_N
("\?k?mode could be IN instead of `IN OUT`!", E1);
-- We do not generate warnings for IN OUT parameters
-- unless we have at least -gnatwu. This is deliberately
-- inconsistent with the treatment of variables, but
-- otherwise we get too many unexpected warnings in
-- default mode.
elsif Check_Unreferenced then
Error_Msg_N
("?u?formal parameter& is read but "
& "never assigned!", E1);
end if;
end if;
-- Kill any other warnings on this entity, since this is the
-- one that should dominate any other unreferenced warning.
Set_Warnings_Off (E1);
end if;
end;
end loop;
end Output_Non_Modified_In_Out_Warnings;
----------------------------------------
-- Output_Obsolescent_Entity_Warnings --
----------------------------------------
procedure Output_Obsolescent_Entity_Warnings (N : Node_Id; E : Entity_Id) is
P : constant Node_Id := Parent (N);
S : Entity_Id;
begin
S := Current_Scope;
-- Do not output message if we are the scope of standard. This means
-- we have a reference from a context clause from when it is originally
-- processed, and that's too early to tell whether it is an obsolescent
-- unit doing the with'ing. In Sem_Ch10.Analyze_Compilation_Unit we make
-- sure that we have a later call when the scope is available. This test
-- also eliminates all messages for use clauses, which is fine (we do
-- not want messages for use clauses, since they are always redundant
-- with respect to the associated with clause).
if S = Standard_Standard then
return;
end if;
-- Do not output message if we are in scope of an obsolescent package
-- or subprogram.
loop
if Is_Obsolescent (S) then
return;
end if;
S := Scope (S);
exit when S = Standard_Standard;
end loop;
-- Here we will output the message
Error_Msg_Sloc := Sloc (E);
-- Case of with clause
if Nkind (P) = N_With_Clause then
if Ekind (E) = E_Package then
Error_Msg_NE
("?j?with of obsolescent package& declared#", N, E);
elsif Ekind (E) = E_Procedure then
Error_Msg_NE
("?j?with of obsolescent procedure& declared#", N, E);
else
Error_Msg_NE
("??with of obsolescent function& declared#", N, E);
end if;
-- If we do not have a with clause, then ignore any reference to an
-- obsolescent package name. We only want to give the one warning of
-- withing the package, not one each time it is used to qualify.
elsif Ekind (E) = E_Package then
return;
-- Procedure call statement
elsif Nkind (P) = N_Procedure_Call_Statement then
Error_Msg_NE
("??call to obsolescent procedure& declared#", N, E);
-- Function call
elsif Nkind (P) = N_Function_Call then
Error_Msg_NE
("??call to obsolescent function& declared#", N, E);
-- Reference to obsolescent type
elsif Is_Type (E) then
Error_Msg_NE
("??reference to obsolescent type& declared#", N, E);
-- Reference to obsolescent component
elsif Ekind (E) in E_Component | E_Discriminant then
Error_Msg_NE
("??reference to obsolescent component& declared#", N, E);
-- Reference to obsolescent variable
elsif Ekind (E) = E_Variable then
Error_Msg_NE
("??reference to obsolescent variable& declared#", N, E);
-- Reference to obsolescent constant
elsif Ekind (E) = E_Constant or else Ekind (E) in Named_Kind then
Error_Msg_NE
("??reference to obsolescent constant& declared#", N, E);
-- Reference to obsolescent enumeration literal
elsif Ekind (E) = E_Enumeration_Literal then
Error_Msg_NE
("??reference to obsolescent enumeration literal& declared#", N, E);
-- Generic message for any other case we missed
else
Error_Msg_NE
("??reference to obsolescent entity& declared#", N, E);
end if;
-- Output additional warning if present
for J in Obsolescent_Warnings.First .. Obsolescent_Warnings.Last loop
if Obsolescent_Warnings.Table (J).Ent = E then
String_To_Name_Buffer (Obsolescent_Warnings.Table (J).Msg);
Error_Msg_Strlen := Name_Len;
Error_Msg_String (1 .. Name_Len) := Name_Buffer (1 .. Name_Len);
Error_Msg_N ("\\??~", N);
exit;
end if;
end loop;
end Output_Obsolescent_Entity_Warnings;
----------------------------------
-- Output_Unreferenced_Messages --
----------------------------------
procedure Output_Unreferenced_Messages is
begin
for J in Unreferenced_Entities.First .. Unreferenced_Entities.Last loop
Warn_On_Unreferenced_Entity (Unreferenced_Entities.Table (J));
end loop;
end Output_Unreferenced_Messages;
-----------------------------------------
-- Output_Unused_Warnings_Off_Warnings --
-----------------------------------------
procedure Output_Unused_Warnings_Off_Warnings is
begin
for J in Warnings_Off_Pragmas.First .. Warnings_Off_Pragmas.Last loop
declare
Wentry : Warnings_Off_Entry renames Warnings_Off_Pragmas.Table (J);
N : Node_Id renames Wentry.N;
E : Node_Id renames Wentry.E;
begin
-- Turn off Warnings_Off, or we won't get the warning
Set_Warnings_Off (E, False);
-- Nothing to do if pragma was used to suppress a general warning
if Warnings_Off_Used (E) then
null;
-- If pragma was used both in unmodified and unreferenced contexts
-- then that's as good as the general case, no warning.
elsif Warnings_Off_Used_Unmodified (E)
and
Warnings_Off_Used_Unreferenced (E)
then
null;
-- Used only in context where Unmodified would have worked
elsif Warnings_Off_Used_Unmodified (E) then
Error_Msg_NE
("?.w?could use Unmodified instead of "
& "Warnings Off for &", Pragma_Identifier (N), E);
-- Used only in context where Unreferenced would have worked
elsif Warnings_Off_Used_Unreferenced (E) then
Error_Msg_NE
("?.w?could use Unreferenced instead of "
& "Warnings Off for &", Pragma_Identifier (N), E);
-- Not used at all
else
Error_Msg_NE
("?.w?pragma Warnings Off for & unused, "
& "could be omitted", N, E);
end if;
end;
end loop;
end Output_Unused_Warnings_Off_Warnings;
---------------------------
-- Referenced_Check_Spec --
---------------------------
function Referenced_Check_Spec (E : Entity_Id) return Boolean is
begin
if Is_Formal (E) and then Present (Spec_Entity (E)) then
return Referenced (E) or else Referenced (Spec_Entity (E));
else
return Referenced (E);
end if;
end Referenced_Check_Spec;
----------------------------------
-- Referenced_As_LHS_Check_Spec --
----------------------------------
function Referenced_As_LHS_Check_Spec (E : Entity_Id) return Boolean is
begin
if Is_Formal (E) and then Present (Spec_Entity (E)) then
return Referenced_As_LHS (E)
or else Referenced_As_LHS (Spec_Entity (E));
else
return Referenced_As_LHS (E);
end if;
end Referenced_As_LHS_Check_Spec;
--------------------------------------------
-- Referenced_As_Out_Parameter_Check_Spec --
--------------------------------------------
function Referenced_As_Out_Parameter_Check_Spec
(E : Entity_Id) return Boolean
is
begin
if Is_Formal (E) and then Present (Spec_Entity (E)) then
return Referenced_As_Out_Parameter (E)
or else Referenced_As_Out_Parameter (Spec_Entity (E));
else
return Referenced_As_Out_Parameter (E);
end if;
end Referenced_As_Out_Parameter_Check_Spec;
--------------------------------------
-- Warn_On_Constant_Valid_Condition --
--------------------------------------
procedure Warn_On_Constant_Valid_Condition (Op : Node_Id) is
Left : constant Node_Id := Left_Opnd (Op);
Right : constant Node_Id := Right_Opnd (Op);
True_Result : Boolean;
False_Result : Boolean;
begin
-- Determine the potential outcome of the comparison assuming that the
-- scalar operands are valid.
if Constant_Condition_Warnings
and then Comes_From_Source (Original_Node (Op))
and then Is_Scalar_Type (Etype (Left))
and then Is_Scalar_Type (Etype (Right))
-- Do not consider instances because the check was already performed
-- in the generic.
and then not In_Instance
-- Do not consider comparisons between two static expressions such as
-- constants or literals because those values cannot be invalidated.
and then not (Is_Static_Expression (Left)
and then Is_Static_Expression (Right))
-- Do not consider comparison between an attribute reference and a
-- compile-time known value since this is most likely a conditional
-- compilation.
and then not Is_Attribute_And_Known_Value_Comparison (Op)
-- Do not consider internal files to allow for various assertions and
-- safeguards within our runtime.
and then not In_Internal_Unit (Op)
then
Test_Comparison
(Op => Op,
Assume_Valid => True,
True_Result => True_Result,
False_Result => False_Result);
-- Warn on a possible evaluation to False / True in the presence of
-- invalid values.
if True_Result then
Error_Msg_N
("condition can only be False if invalid values present?c?", Op);
elsif False_Result then
Error_Msg_N
("condition can only be True if invalid values present?c?", Op);
end if;
end if;
end Warn_On_Constant_Valid_Condition;
-----------------------------
-- Warn_On_Known_Condition --
-----------------------------
procedure Warn_On_Known_Condition (C : Node_Id) is
Test_Result : Boolean := False;
-- Force initialization to facilitate static analysis
function Is_Known_Branch return Boolean;
-- If the type of the condition is Boolean, the constant value of the
-- condition is a boolean literal. If the type is a derived boolean
-- type, the constant is wrapped in a type conversion of the derived
-- literal. If the value of the condition is not a literal, no warnings
-- can be produced. This function returns True if the result can be
-- determined, and Test_Result is set True/False accordingly. Otherwise
-- False is returned, and Test_Result is unchanged.
procedure Track (N : Node_Id; Loc : Node_Id);
-- Adds continuation warning(s) pointing to reason (assignment or test)
-- for the operand of the conditional having a known value (or at least
-- enough is known about the value to issue the warning). N is the node
-- which is judged to have a known value. Loc is the warning location.
---------------------
-- Is_Known_Branch --
---------------------
function Is_Known_Branch return Boolean is
begin
if Etype (C) = Standard_Boolean
and then Is_Entity_Name (C)
and then
(Entity (C) = Standard_False or else Entity (C) = Standard_True)
then
Test_Result := Entity (C) = Standard_True;
return True;
elsif Is_Boolean_Type (Etype (C))
and then Nkind (C) = N_Unchecked_Type_Conversion
and then Is_Entity_Name (Expression (C))
and then Ekind (Entity (Expression (C))) = E_Enumeration_Literal
then
Test_Result :=
Chars (Entity (Expression (C))) = Chars (Standard_True);
return True;
else
return False;
end if;
end Is_Known_Branch;
-----------
-- Track --
-----------
procedure Track (N : Node_Id; Loc : Node_Id) is
Nod : constant Node_Id := Original_Node (N);
begin
if Nkind (Nod) in N_Op_Compare then
Track (Left_Opnd (Nod), Loc);
Track (Right_Opnd (Nod), Loc);
elsif Is_Entity_Name (Nod) and then Is_Object (Entity (Nod)) then
declare
CV : constant Node_Id := Current_Value (Entity (Nod));
begin
if Present (CV) then
Error_Msg_Sloc := Sloc (CV);
if Nkind (CV) not in N_Subexpr then
Error_Msg_N ("\\??(see test #)", Loc);
elsif Nkind (Parent (CV)) =
N_Case_Statement_Alternative
then
Error_Msg_N ("\\??(see case alternative #)", Loc);
else
Error_Msg_N ("\\??(see assignment #)", Loc);
end if;
end if;
end;
end if;
end Track;
-- Local variables
Orig : constant Node_Id := Original_Node (C);
P : Node_Id;
-- Start of processing for Warn_On_Known_Condition
begin
-- Adjust SCO condition if from source
if Generate_SCO
and then Comes_From_Source (Orig)
and then Is_Known_Branch
then
declare
Atrue : Boolean;
begin
Atrue := Test_Result;
if Present (Parent (C)) and then Nkind (Parent (C)) = N_Op_Not then
Atrue := not Atrue;
end if;
Set_SCO_Condition (Orig, Atrue);
end;
end if;
-- Argument replacement in an inlined body can make conditions static.
-- Do not emit warnings in this case.
if In_Inlined_Body then
return;
end if;
if Constant_Condition_Warnings
and then Is_Known_Branch
and then Comes_From_Source (Orig)
and then Nkind (Orig) in N_Has_Entity
and then not In_Instance
then
-- Don't warn if comparison of result of attribute against a constant
-- value, since this is likely legitimate conditional compilation.
if Is_Attribute_And_Known_Value_Comparison (C) then
return;
end if;
-- See if this is in a statement or a declaration
P := Parent (C);
loop
-- If tree is not attached, do not issue warning (this is very
-- peculiar, and probably arises from some other error condition).
if No (P) then
return;
-- If we are in a declaration, then no warning, since in practice
-- conditionals in declarations are used for intended tests which
-- may be known at compile time, e.g. things like
-- x : constant Integer := 2 + (Word'Size = 32);
-- And a warning is annoying in such cases
elsif Nkind (P) in N_Declaration
or else
Nkind (P) in N_Later_Decl_Item
then
return;
-- Don't warn in assert or check pragma, since presumably tests in
-- such a context are very definitely intended, and might well be
-- known at compile time. Note that we have to test the original
-- node, since assert pragmas get rewritten at analysis time.
elsif Nkind (Original_Node (P)) = N_Pragma
and then
Pragma_Name_Unmapped (Original_Node (P))
in Name_Assert | Name_Check
then
return;
end if;
exit when Is_Statement (P);
P := Parent (P);
end loop;
-- Here we issue the warning unless some sub-operand has warnings
-- set off, in which case we suppress the warning for the node. If
-- the original expression is an inequality, it has been expanded
-- into a negation, and the value of the original expression is the
-- negation of the equality. If the expression is an entity that
-- appears within a negation, it is clearer to flag the negation
-- itself, and report on its constant value.
if not Operand_Has_Warnings_Suppressed (C) then
declare
True_Branch : Boolean := Test_Result;
Cond : Node_Id := C;
begin
if Present (Parent (C))
and then Nkind (Parent (C)) = N_Op_Not
then
True_Branch := not True_Branch;
Cond := Parent (C);
end if;
-- Condition always True
if True_Branch then
if Is_Entity_Name (Original_Node (C))
and then Nkind (Cond) /= N_Op_Not
then
Error_Msg_NE
("object & is always True at this point?c?",
Cond, Original_Node (C));
Track (Original_Node (C), Cond);
else
Error_Msg_N ("condition is always True?c?", Cond);
Track (Cond, Cond);
end if;
-- Condition always False
else
if Is_Entity_Name (Original_Node (C))
and then Nkind (Cond) /= N_Op_Not
then
Error_Msg_NE
("object & is always False at this point?c?",
Cond, Original_Node (C));
Track (Original_Node (C), Cond);
else
Error_Msg_N ("condition is always False?c?", Cond);
Track (Cond, Cond);
end if;
end if;
end;
end if;
end if;
end Warn_On_Known_Condition;
---------------------------------------
-- Warn_On_Modified_As_Out_Parameter --
---------------------------------------
function Warn_On_Modified_As_Out_Parameter (E : Entity_Id) return Boolean is
begin
return
(Warn_On_Modified_Unread and then Is_Only_Out_Parameter (E))
or else Warn_On_All_Unread_Out_Parameters;
end Warn_On_Modified_As_Out_Parameter;
---------------------------------
-- Warn_On_Overlapping_Actuals --
---------------------------------
procedure Warn_On_Overlapping_Actuals (Subp : Entity_Id; N : Node_Id) is
function Explicitly_By_Reference (Formal_Id : Entity_Id) return Boolean;
-- Returns True iff the type of Formal_Id is explicitly by-reference
function Refer_Same_Object
(Act1 : Node_Id;
Act2 : Node_Id) return Boolean;
-- Two names are known to refer to the same object if the two names
-- are known to denote the same object; or one of the names is a
-- selected_component, indexed_component, or slice and its prefix is
-- known to refer to the same object as the other name; or one of the
-- two names statically denotes a renaming declaration whose renamed
-- object_name is known to refer to the same object as the other name