CbC/CbC_gcc: gcc/ada/sem_warn.adb comparison

comparison gcc/ada/sem_warn.adb @ 111:04ced10e8804

gcc 7

author	kono
date	Fri, 27 Oct 2017 22:46:09 +0900
parents
children	84e7813d76e9

comparison

equal deleted inserted replaced

-:561a7518be6b
+:04ced10e8804
+------------------------------------------------------------------------------
+--                                                                          --
+--                         GNAT COMPILER COMPONENTS                         --
+--                                                                          --
+--                             S E M _ W A R N                              --
+--                                                                          --
+--                                 B o d y                                  --
+--                                                                          --
+--          Copyright (C) 1999-2017, 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 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 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;
+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 iteration, do not process, since loop will always terminate
+elsif Present (Loop_Parameter_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) = N_Delay_Relative_Statement
+or else Nkind (Fstm) = N_Delay_Until_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.
+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;
+---------------------------------
+-- 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_In (E1, 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 a 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.
+elsif Is_Composite_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
+Output_Reference_Error
+("?v?variable& is read but never assigned!");
+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 Warn_On_No_Value_Assigned and then Present (UR) 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_In (UR, 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
+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_In (E1, 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
+Unreferenced_Entities.Append (E1);
+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
+Prag : Node_Id;
+begin
+if Is_Access_Type (Typ) and then Is_Dereferenced (N) then
+return False;
+--  A type subject to pragma Default_Initial_Condition is fully
+--  default initialized when the pragma appears with a non-null
+--  argument (SPARK RM 3.1 and SPARK RM 7.3.3).
+elsif Has_DIC (Typ) then
+Prag := Get_Pragma (Typ, Pragma_Default_Initial_Condition);
+pragma Assert (Present (Prag));
+return Is_Verifiable_DIC_Pragma (Prag);
+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 (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_In (E, 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 Nam_In (Pragma_Name_Unmapped (Nod),
+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_In (P, 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
+Cnode : Node_Id;
+Item  : Node_Id;
+Lunit : Node_Id;
+Ent   : Entity_Id;
+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
+Is_Visible_Renaming : Boolean := False;
+Pack                : Entity_Id;
+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 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.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 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_Object (E1) = L then
+Is_Visible_Renaming := not Is_Hidden (E1);
+return E1;
+elsif Ekind (E1) = E_Package
+and then No (Renamed_Object (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;
+--  Start of processing for Check_One_Unit
+begin
+Cnode := Cunit (Unit);
+--  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 (Entity (Name (Item))) 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 then
+null;
+--  Else the warning may be needed
+else
+declare
+Eitem : constant Entity_Id :=
+Entity (Name (Item));
+begin
+--  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 (Eitem)
+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 (Eitem)
+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;
+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 =>
+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
+--  modifies 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 -gnatwc is set then output message that we could be IN
+if not Is_Trivial_Subprogram (Scope (E1)) then
+if Warn_On_Constant then
+Error_Msg_N
+("?u?formal parameter & is not modified!", E1);
+Error_Msg_N
+("\?u?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_In (E, 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??", Op);
+elsif False_Result then
+Error_Msg_N
+("condition can only be True if invalid values present??", 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;
+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 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 Nam_In (Pragma_Name_Unmapped (Original_Node (P)),
+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 Is_Covered_Formal (Formal : Node_Id) return Boolean;
+--  Return True if Formal is covered by the rule
+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
+--  (RM 6.4.1(6.11/3))
+-----------------------
+-- Is_Covered_Formal --
+-----------------------
+function Is_Covered_Formal (Formal : Node_Id) return Boolean is
+begin
+return
+Ekind_In (Formal, E_Out_Parameter, E_In_Out_Parameter)
+and then (Is_Elementary_Type (Etype (Formal))
+or else Is_Record_Type (Etype (Formal))
+or else Is_Array_Type (Etype (Formal)));
+end Is_Covered_Formal;
+-----------------------
+-- Refer_Same_Object --
+-----------------------
+function Refer_Same_Object
+(Act1 : Node_Id;
+Act2 : Node_Id) return Boolean
+is
+begin
+return
+Denotes_Same_Object (Act1, Act2)
+or else Denotes_Same_Prefix (Act1, Act2);
+end Refer_Same_Object;
+--  Local variables
+Act1      : Node_Id;
+Act2      : Node_Id;
+Form1     : Entity_Id;
+Form2     : Entity_Id;
+Warn_Only : Boolean;
+--  GNAT warns on overlapping in-out parameters even when there are no
+--  two in-out parameters of an elementary type, as stated in
+--  RM 6.5.1 (17/2).
+--  Start of processing for Warn_On_Overlapping_Actuals
+begin
+if Ada_Version < Ada_2012 and then not Warn_On_Overlap then
+return;
+end if;
+--  The call is illegal only if there are at least two in-out parameters
+--  of the same elementary type.
+Warn_Only := True;
+Form1 := First_Formal (Subp);
+while Present (Form1) loop
+Form2 := Next_Formal (Form1);
+while Present (Form2) loop
+if Is_Elementary_Type (Etype (Form1))
+and then Is_Elementary_Type (Etype (Form2))
+and then Ekind (Form1) /= E_In_Parameter
+and then Ekind (Form2) /= E_In_Parameter
+then
+Warn_Only := False;
+exit;
+end if;
+Next_Formal (Form2);
+end loop;
+Next_Formal (Form1);
+end loop;
+--  Exclude calls rewritten as enumeration literals
+if Nkind (N) not in N_Subprogram_Call
+and then Nkind (N) /= N_Entry_Call_Statement
+then
+return;
+end if;
+--  If a call C has two or more parameters of mode in out or out that are
+--  of an elementary type, then the call is legal only if for each name
+--  N that is passed as a parameter of mode in out or out to the call C,
+--  there is no other name among the other parameters of mode in out or
+--  out to C that is known to denote the same object (RM 6.4.1(6.15/3))
+--  If appropriate warning switch is set, we also report warnings on
+--  overlapping parameters that are record types or array types.
+Form1 := First_Formal (Subp);
+Act1  := First_Actual (N);
+while Present (Form1) and then Present (Act1) loop
+if Is_Covered_Formal (Form1) then
+Form2 := First_Formal (Subp);
+Act2  := First_Actual (N);
+while Present (Form2) and then Present (Act2) loop
+if Form1 /= Form2
+and then Is_Covered_Formal (Form2)
+and then Refer_Same_Object (Act1, Act2)
+then
+--  Guard against previous errors
+if Error_Posted (N)
+or else No (Etype (Act1))
+or else No (Etype (Act2))
+then
+null;
+--  If the actual is a function call in prefix notation,
+--  there is no real overlap.
+elsif Nkind (Act2) = N_Function_Call then
+null;
+--  If type is not by-copy, assume that aliasing is intended
+elsif
+Present (Underlying_Type (Etype (Form1)))
+and then
+(Is_By_Reference_Type (Underlying_Type (Etype (Form1)))
+or else
+Convention (Underlying_Type (Etype (Form1))) =
+Convention_Ada_Pass_By_Reference)
+then
+null;
+--  Under Ada 2012 we only report warnings on overlapping
+--  arrays and record types if switch is set.
+elsif Ada_Version >= Ada_2012
+and then not Is_Elementary_Type (Etype (Form1))
+and then not Warn_On_Overlap
+then
+null;
+--  Here we may need to issue overlap message
+else
+Error_Msg_Warn :=
+--  Overlap checking is an error only in Ada 2012. For
+--  earlier versions of Ada, this is a warning.
+Ada_Version < Ada_2012
+--  Overlap is only illegal in Ada 2012 in the case of
+--  elementary types (passed by copy). For other types,
+--  we always have a warning in all Ada versions.
+or else not Is_Elementary_Type (Etype (Form1))
+--  debug flag -gnatd.E changes the error to a warning
+--  even in Ada 2012 mode.
+or else Error_To_Warning
+or else Warn_Only;
+declare
+Act  : Node_Id;
+Form : Entity_Id;
+begin
+--  Find matching actual
+Act  := First_Actual (N);
+Form := First_Formal (Subp);
+while Act /= Act2 loop
+Next_Formal (Form);
+Next_Actual (Act);
+end loop;
+if Is_Elementary_Type (Etype (Act1))
+and then Ekind (Form2) = E_In_Parameter
+then
+null;  --  No real aliasing
+elsif Is_Elementary_Type (Etype (Act2))
+and then Ekind (Form2) = E_In_Parameter
+then
+null;  --  Ditto
+--  If the call was written in prefix notation, and
+--  thus its prefix before rewriting was a selected
+--  component, count only visible actuals in the call.
+elsif Is_Entity_Name (First_Actual (N))
+and then Nkind (Original_Node (N)) = Nkind (N)
+and then Nkind (Name (Original_Node (N))) =
+N_Selected_Component
+and then
+Is_Entity_Name (Prefix (Name (Original_Node (N))))
+and then
+Entity (Prefix (Name (Original_Node (N)))) =
+Entity (First_Actual (N))
+then
+if Act1 = First_Actual (N) then
+Error_Msg_FE
+("<<`IN OUT` prefix overlaps with "
+& "actual for&", Act1, Form);
+else
+--  For greater clarity, give name of formal
+Error_Msg_Node_2 := Form;
+Error_Msg_FE
+("<<writable actual for & overlaps with "
+& "actual for&", Act1, Form);
+end if;
+else
+--  For greater clarity, give name of formal
+Error_Msg_Node_2 := Form;
+--  This is one of the messages
+Error_Msg_FE
+("<<writable actual for & overlaps with "
+& "actual for&", Act1, Form1);
+end if;
+end;
+end if;
+return;
+end if;
+Next_Formal (Form2);
+Next_Actual (Act2);
+end loop;
+end if;
+Next_Formal (Form1);
+Next_Actual (Act1);
+end loop;
+end Warn_On_Overlapping_Actuals;
+------------------------------
+-- Warn_On_Suspicious_Index --
+------------------------------
+procedure Warn_On_Suspicious_Index (Name : Entity_Id; X : Node_Id) is
+Low_Bound : Uint;
+--  Set to lower bound for a suspicious type
+Ent : Entity_Id;
+--  Entity for array reference
+Typ : Entity_Id;
+--  Array type
+function Is_Suspicious_Type (Typ : Entity_Id) return Boolean;
+--  Tests to see if Typ is a type for which we may have a suspicious
+--  index, namely an unconstrained array type, whose lower bound is
+--  either zero or one. If so, True is returned, and Low_Bound is set
+--  to this lower bound. If not, False is returned, and Low_Bound is
+--  undefined on return.
+--
+--  For now, we limit this to standard string types, so any other
+--  unconstrained types return False. We may change our minds on this
+--  later on, but strings seem the most important case.
+procedure Test_Suspicious_Index;
+--  Test if index is of suspicious type and if so, generate warning
+------------------------
+-- Is_Suspicious_Type --
+------------------------
+function Is_Suspicious_Type (Typ : Entity_Id) return Boolean is
+LB : Node_Id;
+begin
+if Is_Array_Type (Typ)
+and then not Is_Constrained (Typ)
+and then Number_Dimensions (Typ) = 1
+and then Is_Standard_String_Type (Typ)
+and then not Has_Warnings_Off (Typ)
+then
+LB := Type_Low_Bound (Etype (First_Index (Typ)));
+if Compile_Time_Known_Value (LB) then
+Low_Bound := Expr_Value (LB);
+return Low_Bound = Uint_0 or else Low_Bound = Uint_1;
+end if;
+end if;
+return False;
+end Is_Suspicious_Type;
+---------------------------
+-- Test_Suspicious_Index --
+---------------------------
+procedure Test_Suspicious_Index is
+function Length_Reference (N : Node_Id) return Boolean;
+--  Check if node N is of the form Name'Length
+procedure Warn1;
+--  Generate first warning line
+procedure Warn_On_Index_Below_Lower_Bound;
+--  Generate a warning on indexing the array with a literal value
+--  below the lower bound of the index type.
+procedure Warn_On_Literal_Index;
+--  Generate a warning on indexing the array with a literal value
+----------------------
+-- Length_Reference --
+----------------------
+function Length_Reference (N : Node_Id) return Boolean is
+R : constant Node_Id := Original_Node (N);
+begin
+return
+Nkind (R) = N_Attribute_Reference
+and then Attribute_Name (R) = Name_Length
+and then Is_Entity_Name (Prefix (R))
+and then Entity (Prefix (R)) = Ent;
+end Length_Reference;
+-----------
+-- Warn1 --
+-----------
+procedure Warn1 is
+begin
+Error_Msg_Uint_1 := Low_Bound;
+Error_Msg_FE -- CODEFIX
+("?w?index for& may assume lower bound of^", X, Ent);
+end Warn1;
+-------------------------------------
+-- Warn_On_Index_Below_Lower_Bound --
+-------------------------------------
+procedure Warn_On_Index_Below_Lower_Bound is
+begin
+if Is_Standard_String_Type (Typ) then
+Discard_Node
+(Compile_Time_Constraint_Error
+(N   => X,
+Msg => "?w?string index should be positive"));
+else
+Discard_Node
+(Compile_Time_Constraint_Error
+(N   => X,
+Msg => "?w?index out of the allowed range"));
+end if;
+end Warn_On_Index_Below_Lower_Bound;
+---------------------------
+-- Warn_On_Literal_Index --
+---------------------------
+procedure Warn_On_Literal_Index is
+begin
+Warn1;
+--  Case where original form of subscript is an integer literal
+if Nkind (Original_Node (X)) = N_Integer_Literal then
+if Intval (X) = Low_Bound then
+Error_Msg_FE -- CODEFIX
+("\?w?suggested replacement: `&''First`", X, Ent);
+else
+Error_Msg_Uint_1 := Intval (X) - Low_Bound;
+Error_Msg_FE -- CODEFIX
+("\?w?suggested replacement: `&''First + ^`", X, Ent);
+end if;
+--  Case where original form of subscript is more complex
+else
+--  Build string X'First - 1 + expression where the expression
+--  is the original subscript. If the expression starts with "1
+--  + ", then the "- 1 + 1" is elided.
+Error_Msg_String (1 .. 13) := "'First - 1 + ";
+Error_Msg_Strlen := 13;
+declare
+Sref : Source_Ptr := Sloc (First_Node (Original_Node (X)));
+Tref : constant Source_Buffer_Ptr :=
+Source_Text (Get_Source_File_Index (Sref));
+--  Tref (Sref) is used to scan the subscript
+Pctr : Natural;
+--  Parentheses counter when scanning subscript
+begin
+--  Tref (Sref) points to start of subscript
+--  Elide - 1 if subscript starts with 1 +
+if Tref (Sref .. Sref + 2) = "1 +" then
+Error_Msg_Strlen := Error_Msg_Strlen - 6;
+Sref := Sref + 2;
+elsif Tref (Sref .. Sref + 1) = "1+" then
+Error_Msg_Strlen := Error_Msg_Strlen - 6;
+Sref := Sref + 1;
+end if;
+--  Now we will copy the subscript to the string buffer
+Pctr := 0;
+loop
+--  Count parens, exit if terminating right paren. Note
+--  check to ignore paren appearing as character literal.
+if Tref (Sref + 1) = '''
+and then
+Tref (Sref - 1) = '''
+then
+null;
+else
+if Tref (Sref) = '(' then
+Pctr := Pctr + 1;
+elsif Tref (Sref) = ')' then
+exit when Pctr = 0;
+Pctr := Pctr - 1;
+end if;
+end if;
+--  Done if terminating double dot (slice case)
+exit when Pctr = 0
+and then (Tref (Sref .. Sref + 1) = ".."
+or else
+Tref (Sref .. Sref + 2) = " ..");
+--  Quit if we have hit EOF character, something wrong
+if Tref (Sref) = EOF then
+return;
+end if;
+--  String literals are too much of a pain to handle
+if Tref (Sref) = '"' or else Tref (Sref) = '%' then
+return;
+end if;
+--  If we have a 'Range reference, then this is a case
+--  where we cannot easily give a replacement. Don't try.
+if Tref (Sref .. Sref + 4) = "range"
+and then Tref (Sref - 1) < 'A'
+and then Tref (Sref + 5) < 'A'
+then
+return;
+end if;
+--  Else store next character
+Error_Msg_Strlen := Error_Msg_Strlen + 1;
+Error_Msg_String (Error_Msg_Strlen) := Tref (Sref);
+Sref := Sref + 1;
+--  If we get more than 40 characters then the expression
+--  is too long to copy, or something has gone wrong. In
+--  either case, just skip the attempt at a suggested fix.
+if Error_Msg_Strlen > 40 then
+return;
+end if;
+end loop;
+end;
+--  Replacement subscript is now in string buffer
+Error_Msg_FE -- CODEFIX
+("\?w?suggested replacement: `&~`", Original_Node (X), Ent);
+end if;
+end Warn_On_Literal_Index;
+--  Start of processing for Test_Suspicious_Index
+begin
+--  Nothing to do if subscript does not come from source (we don't
+--  want to give garbage warnings on compiler expanded code, e.g. the
+--  loops generated for slice assignments. Such junk warnings would
+--  be placed on source constructs with no subscript in sight).
+if not Comes_From_Source (Original_Node (X)) then
+return;
+end if;
+--  Case where subscript is a constant integer
+if Nkind (X) = N_Integer_Literal then
+--  Case where subscript is lower than the lowest possible bound.
+--  This might be the case for example when programmers try to
+--  access a string at index 0, as they are used to in other
+--  programming languages like C.
+if Intval (X) < Low_Bound then
+Warn_On_Index_Below_Lower_Bound;
+else
+Warn_On_Literal_Index;
+end if;
+--  Case where subscript is of the form X'Length
+elsif Length_Reference (X) then
+Warn1;
+Error_Msg_Node_2 := Ent;
+Error_Msg_FE
+("\?w?suggest replacement of `&''Length` by `&''Last`",
+X, Ent);
+--  Case where subscript is of the form X'Length - expression
+elsif Nkind (X) = N_Op_Subtract
+and then Length_Reference (Left_Opnd (X))
+then
+Warn1;
+Error_Msg_Node_2 := Ent;
+Error_Msg_FE
+("\?w?suggest replacement of `&''Length` by `&''Last`",
+Left_Opnd (X), Ent);
+end if;
+end Test_Suspicious_Index;
+--  Start of processing for Warn_On_Suspicious_Index
+begin
+--  Only process if warnings activated
+if Warn_On_Assumed_Low_Bound then
+--  Test if array is simple entity name
+if Is_Entity_Name (Name) then
+--  Test if array is parameter of unconstrained string type
+Ent := Entity (Name);
+Typ := Etype (Ent);
+if Is_Formal (Ent)
+and then Is_Suspicious_Type (Typ)
+and then not Low_Bound_Tested (Ent)
+then
+Test_Suspicious_Index;
+end if;
+end if;
+end if;
+end Warn_On_Suspicious_Index;
+-------------------------------
+-- Warn_On_Suspicious_Update --
+-------------------------------
+procedure Warn_On_Suspicious_Update (N : Node_Id) is
+Par : constant Node_Id := Parent (N);
+Arg : Node_Id;
+begin
+--  Only process if warnings activated
+if Warn_On_Suspicious_Contract then
+if Nkind_In (Par, N_Op_Eq, N_Op_Ne) then
+if N = Left_Opnd (Par) then
+Arg := Right_Opnd (Par);
+else
+Arg := Left_Opnd (Par);
+end if;
+if Same_Object (Prefix (N), Arg) then
+if Nkind (Par) = N_Op_Eq then
+Error_Msg_N
+("suspicious equality test with modified version of "
+& "same object?T?", Par);
+else
+Error_Msg_N
+("suspicious inequality test with modified version of "
+& "same object?T?", Par);
+end if;
+end if;
+end if;
+end if;
+end Warn_On_Suspicious_Update;
+--------------------------------------
+-- Warn_On_Unassigned_Out_Parameter --
+--------------------------------------
+procedure Warn_On_Unassigned_Out_Parameter
+(Return_Node : Node_Id;
+Scope_Id    : Entity_Id)
+is
+Form  : Entity_Id;
+Form2 : Entity_Id;
+begin
+--  Ignore if procedure or return statement does not come from source
+if not Comes_From_Source (Scope_Id)
+or else not Comes_From_Source (Return_Node)
+then
+return;
+end if;
+--  Loop through formals
+Form := First_Formal (Scope_Id);
+while Present (Form) loop
+--  We are only interested in OUT parameters that come from source
+--  and are never set in the source, and furthermore only in scalars
+--  since non-scalars generate too many false positives.
+if Ekind (Form) = E_Out_Parameter
+and then Never_Set_In_Source_Check_Spec (Form)
+and then Is_Scalar_Type (Etype (Form))
+and then not Present (Unset_Reference (Form))
+then
+--  Before we issue the warning, an add ad hoc defence against the
+--  most common case of false positives with this warning which is
+--  the case where there is a Boolean OUT parameter that has been
+--  set, and whose meaning is "ignore the values of the other
+--  parameters". We can't of course reliably tell this case at
+--  compile time, but the following test kills a lot of false
+--  positives, without generating a significant number of false
+--  negatives (missed real warnings).
+Form2 := First_Formal (Scope_Id);
+while Present (Form2) loop
+if Ekind (Form2) = E_Out_Parameter
+and then Root_Type (Etype (Form2)) = Standard_Boolean
+and then not Never_Set_In_Source_Check_Spec (Form2)
+then
+return;
+end if;
+Next_Formal (Form2);
+end loop;
+--  Here all conditions are met, record possible unset reference
+Set_Unset_Reference (Form, Return_Node);
+end if;
+Next_Formal (Form);
+end loop;
+end Warn_On_Unassigned_Out_Parameter;
+---------------------------------
+-- Warn_On_Unreferenced_Entity --
+---------------------------------
+procedure Warn_On_Unreferenced_Entity
+(Spec_E : Entity_Id;
+Body_E : Entity_Id := Empty)
+is
+E : Entity_Id := Spec_E;
+begin
+if not Referenced_Check_Spec (E)
+and then not Has_Pragma_Unreferenced_Check_Spec (E)
+and then not Warnings_Off_Check_Spec (E)
+and then not Has_Junk_Name (Spec_E)
+and then not Is_Exported (Spec_E)
+then
+case Ekind (E) is
+when E_Variable =>
+--  Case of variable that is assigned but not read. We suppress
+--  the message if the variable is volatile, has an address
+--  clause, is aliased, or is a renaming, or is imported.
+if Referenced_As_LHS_Check_Spec (E)
+and then No (Address_Clause (E))
+and then not Is_Volatile (E)
+then
+if Warn_On_Modified_Unread
+and then not Is_Imported (E)
+and then not Is_Aliased (E)
+and then No (Renamed_Object (E))
+then
+if not Has_Pragma_Unmodified_Check_Spec (E) then
+Error_Msg_N -- CODEFIX
+("?m?variable & is assigned but never read!", E);
+end if;
+Set_Last_Assignment (E, Empty);
+end if;
+--  Normal case of neither assigned nor read (exclude variables
+--  referenced as out parameters, since we already generated
+--  appropriate warnings at the call point in this case).
+elsif not Referenced_As_Out_Parameter (E) then
+--  We suppress the message for types for which a valid
+--  pragma Unreferenced_Objects has been given, otherwise
+--  we go ahead and give the message.
+if not Has_Pragma_Unreferenced_Objects (Etype (E)) then
+--  Distinguish renamed case in message
+if Present (Renamed_Object (E))
+and then Comes_From_Source (Renamed_Object (E))
+then
+Error_Msg_N -- CODEFIX
+("?u?renamed variable & is not referenced!", E);
+else
+Error_Msg_N -- CODEFIX
+("?u?variable & is not referenced!", E);
+end if;
+end if;
+end if;
+when E_Constant =>
+if not Has_Pragma_Unreferenced_Objects (Etype (E)) then
+if Present (Renamed_Object (E))
+and then Comes_From_Source (Renamed_Object (E))
+then
+Error_Msg_N -- CODEFIX
+("?u?renamed constant & is not referenced!", E);
+else
+Error_Msg_N -- CODEFIX
+("?u?constant & is not referenced!", E);
+end if;
+end if;
+when E_In_Out_Parameter
+| E_In_Parameter
+=>
+--  Do not emit message for formals of a renaming, because they
+--  are never referenced explicitly.
+if Nkind (Original_Node (Unit_Declaration_Node (Scope (E)))) /=
+N_Subprogram_Renaming_Declaration
+then
+--  Suppress this message for an IN OUT parameter of a
+--  non-scalar type, since it is normal to have only an
+--  assignment in such a case.
+if Ekind (E) = E_In_Parameter
+or else not Referenced_As_LHS_Check_Spec (E)
+or else Is_Scalar_Type (Etype (E))
+then
+if Present (Body_E) then
+E := Body_E;
+end if;
+if not Is_Trivial_Subprogram (Scope (E)) then
+Error_Msg_NE -- CODEFIX
+("?u?formal parameter & is not referenced!",
+E, Spec_E);
+end if;
+end if;
+end if;
+when E_Out_Parameter =>
+null;
+when E_Discriminant =>
+Error_Msg_N ("?u?discriminant & is not referenced!", E);
+when E_Named_Integer
+| E_Named_Real
+=>
+Error_Msg_N -- CODEFIX
+("?u?named number & is not referenced!", E);
+when Formal_Object_Kind =>
+Error_Msg_N -- CODEFIX
+("?u?formal object & is not referenced!", E);
+when E_Enumeration_Literal =>
+Error_Msg_N -- CODEFIX
+("?u?literal & is not referenced!", E);
+when E_Function =>
+Error_Msg_N -- CODEFIX
+("?u?function & is not referenced!", E);
+when E_Procedure =>
+Error_Msg_N -- CODEFIX
+("?u?procedure & is not referenced!", E);
+when E_Package =>
+Error_Msg_N -- CODEFIX
+("?u?package & is not referenced!", E);
+when E_Exception =>
+Error_Msg_N -- CODEFIX
+("?u?exception & is not referenced!", E);
+when E_Label =>
+Error_Msg_N -- CODEFIX
+("?u?label & is not referenced!", E);
+when E_Generic_Procedure =>
+Error_Msg_N -- CODEFIX
+("?u?generic procedure & is never instantiated!", E);
+when E_Generic_Function =>
+Error_Msg_N -- CODEFIX
+("?u?generic function & is never instantiated!", E);
+when Type_Kind =>
+Error_Msg_N -- CODEFIX
+("?u?type & is not referenced!", E);
+when others =>
+Error_Msg_N -- CODEFIX
+("?u?& is not referenced!", E);
+end case;
+--  Kill warnings on the entity on which the message has been posted
+--  (nothing is posted on out parameters because back end might be
+--  able to uncover an uninitialized path, and warn accordingly).
+if Ekind (E) /= E_Out_Parameter then
+Set_Warnings_Off (E);
+end if;
+end if;
+end Warn_On_Unreferenced_Entity;
+--------------------------------
+-- Warn_On_Useless_Assignment --
+--------------------------------
+procedure Warn_On_Useless_Assignment
+(Ent : Entity_Id;
+N   : Node_Id := Empty)
+is
+P    : Node_Id;
+X    : Node_Id;
+function Check_Ref (N : Node_Id) return Traverse_Result;
+--  Used to instantiate Traverse_Func. Returns Abandon if a reference to
+--  the entity in question is found.
+function Test_No_Refs is new Traverse_Func (Check_Ref);
+---------------
+-- Check_Ref --
+---------------
+function Check_Ref (N : Node_Id) return Traverse_Result is
+begin
+--  Check reference to our identifier. We use name equality here
+--  because the exception handlers have not yet been analyzed. This
+--  is not quite right, but it really does not matter that we fail
+--  to output the warning in some obscure cases of name clashes.
+if Nkind (N) = N_Identifier and then Chars (N) = Chars (Ent) then
+return Abandon;
+else
+return OK;
+end if;
+end Check_Ref;
+--  Start of processing for Warn_On_Useless_Assignment
+begin
+--  Check if this is a case we want to warn on, a scalar or access
+--  variable with the last assignment field set, with warnings enabled,
+--  and which is not imported or exported. We also check that it is OK
+--  to capture the value. We are not going to capture any value, but
+--  the warning message depends on the same kind of conditions.
+if Is_Assignable (Ent)
+and then not Is_Return_Object (Ent)
+and then Present (Last_Assignment (Ent))
+and then not Is_Imported (Ent)
+and then not Is_Exported (Ent)
+and then Safe_To_Capture_Value (N, Ent)
+and then not Has_Pragma_Unreferenced_Check_Spec (Ent)
+and then not Has_Junk_Name (Ent)
+then
+--  Before we issue the message, check covering exception handlers.
+--  Search up tree for enclosing statement sequences and handlers.
+P := Parent (Last_Assignment (Ent));
+while Present (P) loop
+--  Something is really wrong if we don't find a handled statement
+--  sequence, so just suppress the warning.
+if No (P) then
+Set_Last_Assignment (Ent, Empty);
+return;
+--  When we hit a package/subprogram body, issue warning and exit
+elsif Nkind_In (P, N_Entry_Body,
+N_Package_Body,
+N_Subprogram_Body,
+N_Task_Body)
+then
+--  Case of assigned value never referenced
+if No (N) then
+declare
+LA : constant Node_Id := Last_Assignment (Ent);
+begin
+--  Don't give this for OUT and IN OUT formals, since
+--  clearly caller may reference the assigned value. Also
+--  never give such warnings for internal variables. In
+--  either case, word the warning in a conditional way,
+--  because in the case of a component of a controlled
+--  type, the assigned value might be referenced in the
+--  Finalize operation, so we can't make a definitive
+--  statement that it's never referenced.
+if Ekind (Ent) = E_Variable
+and then not Is_Internal_Name (Chars (Ent))
+then
+--  Give appropriate message, distinguishing between
+--  assignment statements and out parameters.
+if Nkind_In (Parent (LA), N_Parameter_Association,
+N_Procedure_Call_Statement)
+then
+Error_Msg_NE
+("?m?& modified by call, but value might not be "
+& "referenced", LA, Ent);
+else
+Error_Msg_NE -- CODEFIX
+("?m?possibly useless assignment to&, value "
+& "might not be referenced!", LA, Ent);
+end if;
+end if;
+end;
+--  Case of assigned value overwritten
+else
+declare
+LA : constant Node_Id := Last_Assignment (Ent);
+begin
+Error_Msg_Sloc := Sloc (N);
+--  Give appropriate message, distinguishing between
+--  assignment statements and out parameters.
+if Nkind_In (Parent (LA), N_Procedure_Call_Statement,
+N_Parameter_Association)
+then
+Error_Msg_NE
+("?m?& modified by call, but value overwritten #!",
+LA, Ent);
+else
+Error_Msg_NE -- CODEFIX
+("?m?useless assignment to&, value overwritten #!",
+LA, Ent);
+end if;
+end;
+end if;
+--  Clear last assignment indication and we are done
+Set_Last_Assignment (Ent, Empty);
+return;
+--  Enclosing handled sequence of statements
+elsif Nkind (P) = N_Handled_Sequence_Of_Statements then
+--  Check exception handlers present
+if Present (Exception_Handlers (P)) then
+--  If we are not at the top level, we regard an inner
+--  exception handler as a decisive indicator that we should
+--  not generate the warning, since the variable in question
+--  may be accessed after an exception in the outer block.
+if not Nkind_In (Parent (P), N_Entry_Body,
+N_Package_Body,
+N_Subprogram_Body,
+N_Task_Body)
+then
+Set_Last_Assignment (Ent, Empty);
+return;
+--  Otherwise we are at the outer level. An exception
+--  handler is significant only if it references the
+--  variable in question, or if the entity in question
+--  is an OUT or IN OUT parameter, in which case
+--  the caller can reference it after the exception
+--  handler completes.
+else
+if Is_Formal (Ent) then
+Set_Last_Assignment (Ent, Empty);
+return;
+else
+X := First (Exception_Handlers (P));
+while Present (X) loop
+if Test_No_Refs (X) = Abandon then
+Set_Last_Assignment (Ent, Empty);
+return;
+end if;
+X := Next (X);
+end loop;
+end if;
+end if;
+end if;
+end if;
+P := Parent (P);
+end loop;
+end if;
+end Warn_On_Useless_Assignment;
+---------------------------------
+-- Warn_On_Useless_Assignments --
+---------------------------------
+procedure Warn_On_Useless_Assignments (E : Entity_Id) is
+Ent : Entity_Id;
+begin
+Process_Deferred_References;
+if Warn_On_Modified_Unread
+and then In_Extended_Main_Source_Unit (E)
+then
+Ent := First_Entity (E);
+while Present (Ent) loop
+Warn_On_Useless_Assignment (Ent);
+Next_Entity (Ent);
+end loop;
+end if;
+end Warn_On_Useless_Assignments;
+-----------------------------
+-- Warnings_Off_Check_Spec --
+-----------------------------
+function Warnings_Off_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_Warnings_Off (E)
+or
+Has_Warnings_Off (Spec_Entity (E));
+else
+return Has_Warnings_Off (E);
+end if;
+end Warnings_Off_Check_Spec;
+end Sem_Warn;

Mercurial > hg > CbC > CbC_gcc

comparison gcc/ada/sem_warn.adb @ 111:04ced10e8804