path: root/gcc/ada/sem_spark.adb

------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                            S E M _ S P A R K                             --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--          Copyright (C) 2017-2019, 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 Einfo;    use Einfo;
with Errout;   use Errout;
with Namet;    use Namet;
with Nlists;   use Nlists;
with Opt;      use Opt;
with Osint;    use Osint;
with Sem_Prag; use Sem_Prag;
with Sem_Util; use Sem_Util;
with Sem_Aux;  use Sem_Aux;
with Sinfo;    use Sinfo;
with Snames;   use Snames;
with Treepr;   use Treepr;

with Ada.Unchecked_Deallocation;
with GNAT.Dynamic_HTables; use GNAT.Dynamic_HTables;

package body Sem_SPARK is

   -------------------------------------------------
   -- Handling of Permissions Associated to Paths --
   -------------------------------------------------

   package Permissions is
      Elaboration_Context_Max : constant := 1009;
      --  The hash range

      type Elaboration_Context_Index is range 0 .. Elaboration_Context_Max - 1;

      function Elaboration_Context_Hash (Key : Entity_Id)
                                         return Elaboration_Context_Index;
      --  Function to hash any node of the AST

      type Perm_Kind is (Borrowed, Observed, Unrestricted, Moved);
      --  Permission type associated with paths. The Moved permission is
      --  equivalent to the Unrestricted one (same permissions). The Moved is
      --  however used to mark the RHS after a move (which still unrestricted).
      --  This way, we may generate warnings when manipulating the RHS
      --  afterwads since it is set to Null after the assignment.

      type Perm_Tree_Wrapper;

      type Perm_Tree_Access is access Perm_Tree_Wrapper;
      --  A tree of permissions is defined, where the root is a whole object
      --  and tree branches follow access paths in memory. As Perm_Tree is a
      --  discriminated record, a wrapper type is used for the access type
      --  designating a subtree, to make it unconstrained so that it can be
      --  updated.

      --  Nodes in the permission tree are of different kinds

      type Path_Kind is
        (Entire_Object,    --  Scalar object, or folded object of any type
         Reference,        --  Unfolded object of access type
         Array_Component,  --  Unfolded object of array type
         Record_Component  --  Unfolded object of record type
        );

      package Perm_Tree_Maps is new Simple_HTable
        (Header_Num => Elaboration_Context_Index,
         Key        => Node_Id,
         Element    => Perm_Tree_Access,
         No_Element => null,
         Hash       => Elaboration_Context_Hash,
         Equal      => "=");
      --  The instantation of a hash table, with keys being nodes and values
      --  being pointers to trees. This is used to reference easily all
      --  extensions of a Record_Component node (that can have name x, y, ...).

      --  The definition of permission trees. This is a tree, which has a
      --  permission at each node, and depending on the type of the node,
      --  can have zero, one, or more children pointed to by an access to tree.

      type Perm_Tree (Kind : Path_Kind := Entire_Object) is record
         Permission : Perm_Kind;
         --  Permission at this level in the path

         Is_Node_Deep : Boolean;
         --  Whether this node is of a deep type, to be used when moving the
         --  path.

         case Kind is
            --  An entire object is either a leaf (an object which cannot be
            --  extended further in a path) or a subtree in folded form (which
            --  could later be unfolded further in another kind of node). The
            --  field Children_Permission specifies a permission for every
            --  extension of that node if that permission is different from
            --  the node's permission.

            when Entire_Object =>
               Children_Permission : Perm_Kind;

            --  Unfolded path of access type. The permission of the object
            --  pointed to is given in Get_All.

            when Reference =>
               Get_All : Perm_Tree_Access;

            --  Unfolded path of array type. The permission of the elements is
            --  given in Get_Elem.

            when Array_Component =>
               Get_Elem : Perm_Tree_Access;

            --  Unfolded path of record type. The permission of the regular
            --  components is given in Component. The permission of unknown
            --  components (for objects of tagged type) is given in
            --  Other_Components.

            when Record_Component =>
               Component : Perm_Tree_Maps.Instance;
               Other_Components : Perm_Tree_Access;
         end case;
      end record;

      type Perm_Tree_Wrapper is record
         Tree : Perm_Tree;
      end record;
      --  We use this wrapper in order to have unconstrained discriminants

      type Perm_Env is new Perm_Tree_Maps.Instance;
      --  The definition of a permission environment for the analysis. This
      --  is just a hash table of permission trees, each of them rooted with
      --  an Identifier/Expanded_Name.

      type Perm_Env_Access is access Perm_Env;
      --  Access to permission environments

      package Env_Maps is new Simple_HTable
        (Header_Num => Elaboration_Context_Index,
         Key        => Entity_Id,
         Element    => Perm_Env_Access,
         No_Element => null,
         Hash       => Elaboration_Context_Hash,
         Equal      => "=");
      --  The instantiation of a hash table whose elements are permission
      --  environments. This hash table is used to save the environments at
      --  the entry of each loop, with the key being the loop label.

      type Env_Backups is new Env_Maps.Instance;
      --  The type defining the hash table saving the environments at the entry
      --  of each loop.

      package Boolean_Variables_Maps is new Simple_HTable
        (Header_Num => Elaboration_Context_Index,
         Key        => Entity_Id,
         Element    => Boolean,
         No_Element => False,
         Hash       => Elaboration_Context_Hash,
         Equal      => "=");
      --  These maps allow tracking the variables that have been declared but
      --  never used anywhere in the source code. Especially, we do not raise
      --  an error if the variable stays write-only and is declared at package
      --  level, because there is no risk that the variable has been moved,
      --  because it has never been used.

      type Initialization_Map is new Boolean_Variables_Maps.Instance;

      --------------------
      -- Simple Getters --
      --------------------

      --  Simple getters to avoid having .all.Tree.Field everywhere. Of course,
      --  that's only for the top access, as otherwise this reverses the order
      --  in accesses visually.

      function Children_Permission (T : Perm_Tree_Access) return Perm_Kind;
      function Component (T : Perm_Tree_Access) return Perm_Tree_Maps.Instance;
      function Get_All (T : Perm_Tree_Access) return Perm_Tree_Access;
      function Get_Elem (T : Perm_Tree_Access) return Perm_Tree_Access;
      function Is_Node_Deep (T : Perm_Tree_Access) return Boolean;
      function Kind (T : Perm_Tree_Access) return Path_Kind;
      function Other_Components (T : Perm_Tree_Access) return Perm_Tree_Access;
      function Permission (T : Perm_Tree_Access) return Perm_Kind;

      -----------------------
      -- Memory Management --
      -----------------------

      procedure Copy_Env
        (From : Perm_Env;
         To : in out Perm_Env);
      --  Procedure to copy a permission environment

      procedure Copy_Init_Map
        (From : Initialization_Map;
         To : in out Initialization_Map);
      --  Procedure to copy an initialization map

      procedure Copy_Tree
        (From : Perm_Tree_Access;
         To : Perm_Tree_Access);
      --  Procedure to copy a permission tree

      procedure Free_Env
        (PE : in out Perm_Env);
      --  Procedure to free a permission environment

      procedure Free_Perm_Tree
        (PT : in out Perm_Tree_Access);
      --  Procedure to free a permission tree

      --------------------
      -- Error Messages --
      --------------------

      procedure Perm_Mismatch
        (Exp_Perm, Act_Perm : Perm_Kind;
         N                  : Node_Id);
      --  Issues a continuation error message about a mismatch between a
      --  desired permission Exp_Perm and a permission obtained Act_Perm. N
      --  is the node on which the error is reported.

   end Permissions;

   package body Permissions is

      -------------------------
      -- Children_Permission --
      -------------------------

      function Children_Permission (T : Perm_Tree_Access) return Perm_Kind is
      begin
         return T.all.Tree.Children_Permission;
      end Children_Permission;

      ---------------
      -- Component --
      ---------------

      function Component
        (T : Perm_Tree_Access)
         return Perm_Tree_Maps.Instance
      is
      begin
         return T.all.Tree.Component;
      end Component;

      --------------
      -- Copy_Env --
      --------------

      procedure Copy_Env (From : Perm_Env; To : in out Perm_Env) is
         Comp_From : Perm_Tree_Access;
         Key_From  : Perm_Tree_Maps.Key_Option;
         Son       : Perm_Tree_Access;

      begin
         Reset (To);
         Key_From := Get_First_Key (From);
         while Key_From.Present loop
            Comp_From := Get (From, Key_From.K);
            pragma Assert (Comp_From /= null);

            Son := new Perm_Tree_Wrapper;
            Copy_Tree (Comp_From, Son);

            Set (To, Key_From.K, Son);
            Key_From := Get_Next_Key (From);
         end loop;
      end Copy_Env;

      -------------------
      -- Copy_Init_Map --
      -------------------

      procedure Copy_Init_Map
        (From : Initialization_Map;
         To   : in out Initialization_Map)
      is
         Comp_From : Boolean;
         Key_From : Boolean_Variables_Maps.Key_Option;

      begin
         Reset (To);
         Key_From := Get_First_Key (From);
         while Key_From.Present loop
            Comp_From := Get (From, Key_From.K);
            Set (To, Key_From.K, Comp_From);
            Key_From := Get_Next_Key (From);
         end loop;
      end Copy_Init_Map;

      ---------------
      -- Copy_Tree --
      ---------------

      procedure Copy_Tree (From : Perm_Tree_Access; To : Perm_Tree_Access) is
      begin
         To.all := From.all;
         case Kind (From) is
            when Entire_Object =>
               null;

            when Reference =>
               To.all.Tree.Get_All := new Perm_Tree_Wrapper;
               Copy_Tree (Get_All (From), Get_All (To));

            when Array_Component =>
               To.all.Tree.Get_Elem := new Perm_Tree_Wrapper;
               Copy_Tree (Get_Elem (From), Get_Elem (To));

            when Record_Component =>
               declare
                  Comp_From : Perm_Tree_Access;
                  Key_From : Perm_Tree_Maps.Key_Option;
                  Son : Perm_Tree_Access;
                  Hash_Table : Perm_Tree_Maps.Instance;
               begin
               --  We put a new hash table, so that it gets dealiased from the
               --  Component (From) hash table.
                  To.all.Tree.Component := Hash_Table;
                  To.all.Tree.Other_Components :=
                    new Perm_Tree_Wrapper'(Other_Components (From).all);
                  Copy_Tree (Other_Components (From), Other_Components (To));
                  Key_From := Perm_Tree_Maps.Get_First_Key
                    (Component (From));

                  while Key_From.Present loop
                     Comp_From := Perm_Tree_Maps.Get
                       (Component (From), Key_From.K);
                     pragma Assert (Comp_From /= null);
                     Son := new Perm_Tree_Wrapper;
                     Copy_Tree (Comp_From, Son);
                     Perm_Tree_Maps.Set
                       (To.all.Tree.Component, Key_From.K, Son);
                     Key_From := Perm_Tree_Maps.Get_Next_Key
                       (Component (From));
                  end loop;
               end;
         end case;

      end Copy_Tree;

      ------------------------------
      -- Elaboration_Context_Hash --
      ------------------------------

      function Elaboration_Context_Hash
        (Key : Entity_Id) return Elaboration_Context_Index
      is
      begin
         return Elaboration_Context_Index (Key mod Elaboration_Context_Max);
      end Elaboration_Context_Hash;

      --------------
      -- Free_Env --
      --------------

      procedure Free_Env (PE : in out Perm_Env) is
         CompO : Perm_Tree_Access;
      begin
         CompO := Get_First (PE);
         while CompO /= null loop
            Free_Perm_Tree (CompO);
            CompO := Get_Next (PE);
         end loop;
      end Free_Env;

      --------------------
      -- Free_Perm_Tree --
      --------------------

      procedure Free_Perm_Tree (PT : in out Perm_Tree_Access) is
         procedure Free_Perm_Tree_Dealloc is
           new Ada.Unchecked_Deallocation
             (Perm_Tree_Wrapper, Perm_Tree_Access);
         --  The deallocator for permission_trees

      begin
         case Kind (PT) is
            when Entire_Object =>
               Free_Perm_Tree_Dealloc (PT);

            when Reference =>
               Free_Perm_Tree (PT.all.Tree.Get_All);
               Free_Perm_Tree_Dealloc (PT);

            when Array_Component =>
               Free_Perm_Tree (PT.all.Tree.Get_Elem);

            when Record_Component =>
               declare
                  Comp : Perm_Tree_Access;

               begin
                  Free_Perm_Tree (PT.all.Tree.Other_Components);
                  Comp := Perm_Tree_Maps.Get_First (Component (PT));
                  while Comp /= null loop

                     --  Free every Component subtree

                     Free_Perm_Tree (Comp);
                     Comp := Perm_Tree_Maps.Get_Next (Component (PT));
                  end loop;
               end;
               Free_Perm_Tree_Dealloc (PT);
         end case;
      end Free_Perm_Tree;

      -------------
      -- Get_All --
      -------------

      function Get_All (T : Perm_Tree_Access) return Perm_Tree_Access is
      begin
         return T.all.Tree.Get_All;
      end Get_All;

      --------------
      -- Get_Elem --
      --------------

      function Get_Elem (T : Perm_Tree_Access) return Perm_Tree_Access is
      begin
         return T.all.Tree.Get_Elem;
      end Get_Elem;

      ------------------
      -- Is_Node_Deep --
      ------------------

      function Is_Node_Deep (T : Perm_Tree_Access) return Boolean is
      begin
         return T.all.Tree.Is_Node_Deep;
      end Is_Node_Deep;

      ----------
      -- Kind --
      ----------

      function Kind (T : Perm_Tree_Access) return Path_Kind is
      begin
         return T.all.Tree.Kind;
      end Kind;

      ----------------------
      -- Other_Components --
      ----------------------

      function Other_Components
        (T : Perm_Tree_Access)
         return Perm_Tree_Access
      is
      begin
         return T.all.Tree.Other_Components;
      end Other_Components;

      ----------------
      -- Permission --
      ----------------

      function Permission (T : Perm_Tree_Access) return Perm_Kind is
      begin
         return T.all.Tree.Permission;
      end Permission;

      -------------------
      -- Perm_Mismatch --
      -------------------

      procedure Perm_Mismatch (Exp_Perm, Act_Perm : Perm_Kind; N : Node_Id) is
      begin
         Error_Msg_N ("\expected state `"
                      & Perm_Kind'Image (Exp_Perm) & "` at least, got `"
                      & Perm_Kind'Image (Act_Perm) & "`", N);
      end Perm_Mismatch;

   end Permissions;

   use Permissions;

   --------------------------------------
   -- Analysis modes for AST traversal --
   --------------------------------------

   --  The different modes for analysis. This allows to checking whether a path
   --  found in the code should be moved, borrowed, or observed.

   type Checking_Mode is

     (Read,
      --  Default mode

      Move,
      --  Regular moving semantics. Checks that paths have Unrestricted
      --  permission. After moving a path, the permission of both it and
      --  its extensions are set to Unrestricted.

      Assign,
      --  Used for the target of an assignment, or an actual parameter with
      --  mode OUT. Checks that paths have Unrestricted permission. After
      --  assigning to a path, its permission is set to Unrestricted.

      Borrow,
      --  Used for the source of an assignement when initializes a stand alone
      --  object of anonymous type, constant, or IN parameter and also OUT
      --  or IN OUT composite object.
      --  In the borrowed state, the access object is completely "dead".

      Observe
      --  Used for actual IN parameters of a scalar type. Checks that paths
      --  have Read_Perm permission. After checking a path, its permission
      --  is set to Observed.
      --
      --  Also used for formal IN parameters

     );

   type Result_Kind is (Folded, Unfolded, Function_Call);
   --  The type declaration to discriminate in the Perm_Or_Tree type

   --  The result type of the function Get_Perm_Or_Tree. This returns either a
   --  tree when it found the appropriate tree, or a permission when the search
   --  finds a leaf and the subtree we are looking for is folded. In the last
   --  case, we return instead the Children_Permission field of the leaf.

   type Perm_Or_Tree (R : Result_Kind) is record
      case R is
         when Folded        => Found_Permission : Perm_Kind;
         when Unfolded      => Tree_Access : Perm_Tree_Access;
         when Function_Call => null;
      end case;
   end record;

   -----------------------
   -- Local subprograms --
   -----------------------

   --  Checking proceduress for safe pointer usage. These procedures traverse
   --  the AST, check nodes for correct permissions according to SPARK RM
   --  6.4.2, and update permissions depending on the node kind.

   procedure Check_Call_Statement (Call : Node_Id);

   procedure Check_Callable_Body (Body_N : Node_Id);
   --  We are not in End_Of_Callee mode, hence we will save the environment
   --  and start from a new one. We will add in the environment all formal
   --  parameters as well as global used during the subprogram, with the
   --  appropriate permissions (unrestricted for borrowed and moved, observed
   --  for observed names).

   procedure Check_Declaration (Decl : Node_Id);

   procedure Check_Expression (Expr : Node_Id);

   procedure Check_Globals (N : Node_Id);
   --  This procedure takes a global pragma and checks it

   procedure Check_List (L : List_Id);
   --  Calls Check_Node on each element of the list

   procedure Check_Loop_Statement (Loop_N : Node_Id);

   procedure Check_Node (N : Node_Id);
   --  Main traversal procedure to check safe pointer usage. This procedure is
   --  mutually recursive with the specialized procedures that follow.

   procedure Check_Package_Body (Pack : Node_Id);

   procedure Check_Param_In (Formal : Entity_Id; Actual : Node_Id);
   --  This procedure takes a formal and an actual parameter and checks the
   --  permission of every in-mode parameter. This includes Observing and
   --  Borrowing.

   procedure Check_Param_Out (Formal : Entity_Id; Actual : Node_Id);
   --  This procedure takes a formal and an actual parameter and checks the
   --  state of every out-mode and in out-mode parameter. This includes
   --  Moving and Borrowing.

   procedure Check_Statement (Stmt : Node_Id);

   function Get_Perm (N : Node_Id) return Perm_Kind;
   --  The function that takes a name as input and returns a permission
   --  associated to it.

   function Get_Perm_Or_Tree (N : Node_Id) return Perm_Or_Tree;
   --  This function gets a Node_Id and looks recursively to find the
   --  appropriate subtree for that Node_Id. If the tree is folded on
   --  that node, then it returns the permission given at the right level.

   function Get_Perm_Tree (N : Node_Id) return Perm_Tree_Access;
   --  This function gets a Node_Id and looks recursively to find the
   --  appropriate subtree for that Node_Id. If the tree is folded, then
   --  it unrolls the tree up to the appropriate level.

   procedure Hp (P : Perm_Env);
   --  A procedure that outputs the hash table. This function is used only in
   --  the debugger to look into a hash table.
   pragma Unreferenced (Hp);

   procedure Illegal_Global_Usage (N : Node_Or_Entity_Id);
   pragma No_Return (Illegal_Global_Usage);
   --  A procedure that is called when deep globals or aliased globals are used
   --  without any global aspect.

   function Is_Deep (E : Entity_Id) return Boolean;
   --  A function that can tell if a type is deep or not. Returns true if the
   --  type passed as argument is deep.

   procedure Perm_Error
     (N          : Node_Id;
      Perm       : Perm_Kind;
      Found_Perm : Perm_Kind);
   --  A procedure that is called when the permissions found contradict the
   --  rules established by the RM. This function is called with the node, its
   --  entity and the permission that was expected, and adds an error message
   --  with the appropriate values.

   procedure Perm_Error_Subprogram_End
     (E          : Entity_Id;
      Subp       : Entity_Id;
      Perm       : Perm_Kind;
      Found_Perm : Perm_Kind);
   --  A procedure that is called when the permissions found contradict the
   --  rules established by the RM at the end of subprograms. This function
   --  is called with the node, its entity, the node of the returning function
   --  and the permission that was expected, and adds an error message with the
   --  appropriate values.

   procedure Process_Path (N : Node_Id);

   procedure Return_Declarations (L : List_Id);
   --  Check correct permissions on every declared object at the end of a
   --  callee. Used at the end of the body of a callable entity. Checks that
   --  paths of all borrowed formal parameters and global have Unrestricted
   --  permission.

   procedure Return_Globals (Subp : Entity_Id);
   --  Takes a subprogram as input, and checks that all borrowed global items
   --  of the subprogram indeed have RW permission at the end of the subprogram
   --  execution.

   procedure Return_The_Global
     (Id   : Entity_Id;
      Mode : Formal_Kind;
      Subp : Entity_Id);
   --  Auxiliary procedure to Return_Globals
   --  There is no need to return parameters because they will be reassigned
   --  their state once the subprogram returns. Local variables that have
   --  borrowed, observed, or moved an actual parameter go out of the scope.

   procedure Set_Perm_Extensions (T : Perm_Tree_Access; P : Perm_Kind);
   --  This procedure takes an access to a permission tree and modifies the
   --  tree so that any strict extensions of the given tree become of the
   --  access specified by parameter P.

   function Set_Perm_Prefixes_Borrow (N : Node_Id) return Perm_Tree_Access;
   --  This function modifies the permissions of a given node_id in the
   --  permission environment as well as in all the prefixes of the path,
   --  given that the path is borrowed with mode out.

   function Set_Perm_Prefixes
     (N        : Node_Id;
      New_Perm : Perm_Kind)
      return Perm_Tree_Access;
   --  This function sets the permissions of a given node_id in the
   --  permission environment as well as in all the prefixes of the path
   --  to the one given in parameter (P).

   procedure Setup_Globals (Subp : Entity_Id);
   --  Takes a subprogram as input, and sets up the environment by adding
   --  global items with appropriate permissions.

   procedure Setup_Parameter_Or_Global
     (Id         : Entity_Id;
      Mode       : Formal_Kind;
      Global_Var : Boolean);
   --  Auxiliary procedure to Setup_Parameters and Setup_Globals

   procedure Setup_Parameters (Subp : Entity_Id);
   --  Takes a subprogram as input, and sets up the environment by adding
   --  formal parameters with appropriate permissions.

   function Has_Ownership_Aspect_True
     (N   : Node_Id;
      Msg : String)
      return Boolean;
   --  Takes a node as an input, and finds out whether it has ownership aspect
   --  True or False. This function is recursive whenever the node has a
   --  composite type. Access-to-objects have ownership aspect False if they
   --  have a general access type.

   ----------------------
   -- Global Variables --
   ----------------------

   Current_Perm_Env : Perm_Env;
   --  The permission environment that is used for the analysis. This
   --  environment can be saved, modified, reinitialized, but should be the
   --  only one valid from which to extract the permissions of the paths in
   --  scope. The analysis ensures at each point that this variables contains
   --  a valid permission environment with all bindings in scope.

   Current_Checking_Mode : Checking_Mode := Read;
   --  The current analysis mode. This global variable indicates at each point
   --  of the analysis whether the node being analyzed is moved, borrowed,
   --  assigned, read, ... The full list of possible values can be found in
   --  the declaration of type Checking_Mode.

   Current_Loops_Envs : Env_Backups;
   --  This variable contains saves of permission environments at each loop the
   --  analysis entered. Each saved environment can be reached with the label
   --  of the loop.

   Current_Loops_Accumulators : Env_Backups;
   --  This variable contains the environments used as accumulators for loops,
   --  that consist of the merge of all environments at each exit point of
   --  the loop (which can also be the entry point of the loop in the case of
   --  non-infinite loops), each of them reachable from the label of the loop.
   --  We require that the environment stored in the accumulator be less
   --  restrictive than the saved environment at the beginning of the loop, and
   --  the permission environment after the loop is equal to the accumulator.

   Current_Initialization_Map : Initialization_Map;
   --  This variable contains a map that binds each variable of the analyzed
   --  source code to a boolean that becomes true whenever the variable is used
   --  after declaration. Hence we can exclude from analysis variables that
   --  are just declared and never accessed, typically at package declaration.

   --------------------------
   -- Check_Call_Statement --
   --------------------------

   procedure Check_Call_Statement (Call : Node_Id) is
      Saved_Env : Perm_Env;

      procedure Iterate_Call_In is new
        Iterate_Call_Parameters (Check_Param_In);
      procedure Iterate_Call_Out is new
        Iterate_Call_Parameters (Check_Param_Out);

   begin
      --  Save environment, so that the modifications done by analyzing the
      --  parameters are not kept at the end of the call.

      Copy_Env (Current_Perm_Env, Saved_Env);

      --  We first check the globals then parameters to handle the
      --  No_Parameter_Aliasing Restriction. An out or in-out global is
      --  considered as borrowing while a parameter with the same mode is
      --  a move. This order disallow passing a part of a variable to a
      --  subprogram if it is referenced as a global by the callable (when
      --  writable).
      --  For paremeters, we fisrt check in parameters and then the out ones.
      --  This is to avoid Observing or Borrowing objects that are already
      --  moved. This order is not mandatory but allows to catch runtime
      --  errors like null pointer dereferencement at the analysis time.

      Current_Checking_Mode := Read;
      Check_Globals (Get_Pragma (Get_Called_Entity (Call), Pragma_Global));
      Iterate_Call_In (Call);
      Iterate_Call_Out (Call);

      --  Restore environment, because after borrowing/observing actual
      --  parameters, they get their permission reverted to the ones before
      --  the call.

      Free_Env (Current_Perm_Env);
      Copy_Env (Saved_Env, Current_Perm_Env);
      Free_Env (Saved_Env);
   end Check_Call_Statement;

   -------------------------
   -- Check_Callable_Body --
   -------------------------

   procedure Check_Callable_Body (Body_N : Node_Id) is

      Mode_Before    : constant Checking_Mode := Current_Checking_Mode;
      Saved_Env      : Perm_Env;
      Saved_Init_Map : Initialization_Map;
      New_Env        : Perm_Env;
      Body_Id        : constant Entity_Id := Defining_Entity (Body_N);
      Spec_Id        : constant Entity_Id := Unique_Entity (Body_Id);

   begin
      --  Check if SPARK pragma is not set to Off

      if Present (SPARK_Pragma (Defining_Entity (Body_N))) then
         if Get_SPARK_Mode_From_Annotation
           (SPARK_Pragma (Defining_Entity (Body_N, False))) /= Opt.On
         then
            return;
         end if;
      else
         return;
      end if;

      --  Save environment and put a new one in place

      Copy_Env (Current_Perm_Env, Saved_Env);

      --  Save initialization map

      Copy_Init_Map (Current_Initialization_Map, Saved_Init_Map);
      Current_Checking_Mode := Read;
      Current_Perm_Env      := New_Env;

      --  Add formals and globals to the environment with adequate permissions

      if Is_Subprogram_Or_Entry (Spec_Id) then
         Setup_Parameters (Spec_Id);
         Setup_Globals (Spec_Id);
      end if;

      --  Analyze the body of the function

      Check_List (Declarations (Body_N));
      Check_Node (Handled_Statement_Sequence (Body_N));

      --  Check the read-write permissions of borrowed parameters/globals

      if Ekind_In (Spec_Id, E_Procedure, E_Entry)
        and then not No_Return (Spec_Id)
      then
         Return_Globals (Spec_Id);
      end if;

      --  Free the environments

      Free_Env (Current_Perm_Env);
      Copy_Env (Saved_Env, Current_Perm_Env);
      Free_Env (Saved_Env);

      --  Restore initialization map

      Copy_Init_Map (Saved_Init_Map, Current_Initialization_Map);
      Reset (Saved_Init_Map);

      --  The assignment of all out parameters will be done by caller

      Current_Checking_Mode := Mode_Before;
   end Check_Callable_Body;

   -----------------------
   -- Check_Declaration --
   -----------------------

   procedure Check_Declaration (Decl : Node_Id) is
      Target_Ent : constant Entity_Id := Defining_Identifier (Decl);
      Target_Typ : Node_Id renames Etype (Target_Ent);

      Target_View_Typ : Entity_Id;

      Check : Boolean := True;
   begin
      if Present (Full_View (Target_Typ)) then
         Target_View_Typ := Full_View (Target_Typ);
      else
         Target_View_Typ := Target_Typ;
      end if;

      case N_Declaration'(Nkind (Decl)) is
         when N_Full_Type_Declaration =>
            if not Has_Ownership_Aspect_True (Target_Ent, "type declaration")
            then
               Check := False;
            end if;

            --  ??? What about component declarations with defaults.

         when N_Object_Declaration =>
            if (Is_Access_Type (Target_View_Typ)
                or else Is_Deep (Target_Typ))
              and then not Has_Ownership_Aspect_True
                (Target_Ent, "Object declaration ")
            then
               Check := False;
            end if;

            if Is_Anonymous_Access_Type (Target_View_Typ)
              and then not Present (Expression (Decl))
            then

               --  ??? Check the case of default value (AI)
               --  ??? How an anonymous access type can be with default exp?

               Error_Msg_NE ("? object declaration & has OAF (Anonymous "
                            & "access-to-object with no initialization)",
                            Decl, Target_Ent);

            --  If it it an initialization

            elsif Present (Expression (Decl)) and Check then

               --  Find out the operation to be done on the right-hand side

               --  Initializing object, access type

               if Is_Access_Type (Target_View_Typ) then

                  --  Initializing object, constant access type

                  if Is_Constant_Object (Target_Ent) then

                     --  Initializing object, constant access to variable type

                     if not Is_Access_Constant (Target_View_Typ) then
                        Current_Checking_Mode := Borrow;

                     --  Initializing object, constant access to constant type

                     --  Initializing object,
                     --  constant access to constant anonymous type.

                     elsif Is_Anonymous_Access_Type (Target_View_Typ) then

                        --  This is an object declaration so the target
                        --  of the assignement is a stand-alone object.

                        Current_Checking_Mode := Observe;

                     --  Initializing object, constant access to constant
                     --  named type.

                     else
                           --  If named then it is a general access type
                           --  Hence, Has_Ownership_Aspec_True is False.

                        raise Program_Error;
                     end if;

                  --  Initializing object, variable access type

                  else
                     --  Initializing object, variable access to variable type

                     if not Is_Access_Constant (Target_View_Typ) then

                        --  Initializing object, variable named access to
                        --  variable type.

                        if not Is_Anonymous_Access_Type (Target_View_Typ) then
                           Current_Checking_Mode := Move;

                        --  Initializing object, variable anonymous access to
                        --  variable type.

                        else
                           --  This is an object declaration so the target
                           --  object of the assignement is a stand-alone
                           --  object.

                           Current_Checking_Mode := Borrow;
                        end if;

                     --  Initializing object, variable access to constant type

                     else
                        --  Initializing object,
                        --  variable named access to constant type.

                        if not Is_Anonymous_Access_Type (Target_View_Typ) then
                           Error_Msg_N ("assignment not allowed, Ownership "
                                        & "Aspect False (Anonymous Access "
                                        & "Object)", Decl);
                           Check := False;

                        --  Initializing object,
                        --  variable anonymous access to constant type.

                        else
                           --  This is an object declaration so the target
                           --  of the assignement is a stand-alone object.

                           Current_Checking_Mode := Observe;
                        end if;
                     end if;
                  end if;

               --  Initializing object, composite (deep) type

               elsif Is_Deep (Target_Typ) then

                  --  Initializing object, constant composite type

                  if Is_Constant_Object (Target_Ent) then
                     Current_Checking_Mode := Observe;

                  --  Initializing object, variable composite type

                  else

                     --  Initializing object, variable anonymous composite type

                     if Nkind (Object_Definition (Decl)) =
                       N_Constrained_Array_Definition

                     --  An N_Constrained_Array_Definition is an anonymous
                     --  array (to be checked). Record types are always
                     --  named and are considered in the else part.

                     then
                        declare
                           Com_Ty : constant Node_Id :=
                             Component_Type (Etype (Target_Typ));
                        begin

                           if Is_Access_Type (Com_Ty) then

                              --  If components are of anonymous type

                              if Is_Anonymous_Access_Type (Com_Ty) then
                                 if Is_Access_Constant (Com_Ty) then
                                    Current_Checking_Mode := Observe;

                                 else
                                    Current_Checking_Mode := Borrow;
                                 end if;

                              else
                                 Current_Checking_Mode := Move;
                              end if;

                           elsif Is_Deep (Com_Ty) then

                              --  This is certainly named so it is a move

                              Current_Checking_Mode := Move;
                           end if;
                        end;

                     else
                        Current_Checking_Mode := Move;
                     end if;
                  end if;

               end if;
            end if;

            if Check then
               Check_Node (Expression (Decl));
            end if;

            --  If lhs is not a pointer, we still give it the unrestricted
            --  state which is useless but not harmful.

            declare
               Elem : Perm_Tree_Access;
               Deep : constant Boolean := Is_Deep (Target_Typ);

            begin
               --  Note that all declared variables are set to the unrestricted
               --  state.
               --
               --  If variables are not initialized:
               --  unrestricted to every declared object.
               --  Exp:
               --    R : Rec
               --    S : Rec := (...)
               --    R := S
               --  The assignement R := S is not allowed in the new rules
               --  if R is not unrestricted.
               --
               --  If variables are initialized:
               --    If it is a move, then the target is unrestricted
               --    If it is a borrow, then the target is unrestricted
               --    If it is an observe, then the target should be observed

               if Current_Checking_Mode = Observe then
                  Elem := new Perm_Tree_Wrapper'
                    (Tree =>
                       (Kind                => Entire_Object,
                        Is_Node_Deep        => Deep,
                        Permission          => Observed,
                        Children_Permission => Observed));
               else
                  Elem := new Perm_Tree_Wrapper'
                    (Tree =>
                       (Kind                => Entire_Object,
                        Is_Node_Deep        => Deep,
                        Permission          => Unrestricted,
                        Children_Permission => Unrestricted));
               end if;

               --  Create new tree for defining identifier

               Set (Current_Perm_Env,
                    Unique_Entity (Defining_Identifier (Decl)),
                    Elem);
               pragma Assert (Get_First (Current_Perm_Env) /= null);
            end;

         when N_Subtype_Declaration =>
            Check_Node (Subtype_Indication (Decl));

         when N_Iterator_Specification =>
            null;

         when N_Loop_Parameter_Specification =>
            null;

         --  Checking should not be called directly on these nodes

         when N_Function_Specification
            | N_Entry_Declaration
            | N_Procedure_Specification
            | N_Component_Declaration
         =>
            raise Program_Error;

         --  Ignored constructs for pointer checking

         when N_Formal_Object_Declaration
            | N_Formal_Type_Declaration
            | N_Incomplete_Type_Declaration
            | N_Private_Extension_Declaration
            | N_Private_Type_Declaration
            | N_Protected_Type_Declaration
         =>
            null;

         --  The following nodes are rewritten by semantic analysis

         when N_Expression_Function =>
            raise Program_Error;
      end case;
   end Check_Declaration;

   ----------------------
   -- Check_Expression --
   ----------------------

   procedure Check_Expression (Expr : Node_Id) is
      Mode_Before : constant Checking_Mode := Current_Checking_Mode;
   begin
      case N_Subexpr'(Nkind (Expr)) is
         when N_Procedure_Call_Statement
            | N_Function_Call
         =>
            Check_Call_Statement (Expr);

         when N_Identifier
            | N_Expanded_Name
         =>
            --  Check if identifier is pointing to nothing (On/Off/...)

            if not Present (Entity (Expr)) then
               return;
            end if;

            --  Do not analyze things that are not of object Kind

            if Ekind (Entity (Expr)) not in Object_Kind then
               return;
            end if;

            --  Consider as ident

            Process_Path (Expr);

         --  Switch to read mode and then check the readability of each operand

         when N_Binary_Op =>
            Current_Checking_Mode := Read;
            Check_Node (Left_Opnd (Expr));
            Check_Node (Right_Opnd (Expr));

         --  Switch to read mode and then check the readability of each operand

         when N_Op_Abs
            | N_Op_Minus
            | N_Op_Not
            | N_Op_Plus
         =>
            Current_Checking_Mode := Read;
            Check_Node (Right_Opnd (Expr));

         --  Forbid all deep expressions for Attribute ???
         --  What about generics? (formal parameters).

         when N_Attribute_Reference =>
            case Attribute_Name (Expr) is
               when Name_Access =>
                  Error_Msg_N ("access attribute not allowed", Expr);

               when Name_Last
                  | Name_First
               =>
                  Current_Checking_Mode := Read;
                  Check_Node (Prefix (Expr));

               when Name_Min =>
                  Current_Checking_Mode := Read;
                  Check_Node (Prefix (Expr));

               when Name_Image =>
                  Check_List (Expressions (Expr));

               when Name_Img =>
                  Check_Node (Prefix (Expr));

               when Name_SPARK_Mode =>
                  null;

               when Name_Value =>
                  Current_Checking_Mode := Read;
                  Check_Node (Prefix (Expr));

               when Name_Update =>
                  Check_List (Expressions (Expr));
                  Check_Node (Prefix (Expr));

               when Name_Pred
                  | Name_Succ
               =>
                  Check_List (Expressions (Expr));
                  Check_Node (Prefix (Expr));

               when Name_Length =>
                  Current_Checking_Mode := Read;
                  Check_Node (Prefix (Expr));

               --  Any Attribute referring to the underlying memory is ignored
               --  in the analysis. This means that taking the address of a
               --  variable makes a silent alias that is not rejected by the
               --  analysis.

               when Name_Address
                  | Name_Alignment
                  | Name_Component_Size
                  | Name_First_Bit
                  | Name_Last_Bit
                  | Name_Size
                  | Name_Position
               =>
                  null;

               --  Attributes referring to types (get values from types), hence
               --  no need to check either for borrows or any loans.

               when Name_Base
                  | Name_Val
               =>
                  null;
               --  Other attributes that fall out of the scope of the analysis

               when others =>
                  null;
            end case;

         when N_In =>
            Current_Checking_Mode := Read;
            Check_Node (Left_Opnd (Expr));
            Check_Node (Right_Opnd (Expr));

         when N_Not_In =>
            Current_Checking_Mode := Read;
            Check_Node (Left_Opnd (Expr));
            Check_Node (Right_Opnd (Expr));

         --  Switch to read mode and then check the readability of each operand

         when N_And_Then
            | N_Or_Else
         =>
            Current_Checking_Mode := Read;
            Check_Node (Left_Opnd (Expr));
            Check_Node (Right_Opnd (Expr));

         --  Check the arguments of the call

         when N_Explicit_Dereference =>
            Process_Path (Expr);

         --  Copy environment, run on each branch, and then merge

         when N_If_Expression =>
            declare
               Saved_Env : Perm_Env;

               --  Accumulator for the different branches

               New_Env : Perm_Env;
               Elmt    : Node_Id := First (Expressions (Expr));

            begin
               Current_Checking_Mode := Read;
               Check_Node (Elmt);
               Current_Checking_Mode := Mode_Before;

               --  Save environment

               Copy_Env (Current_Perm_Env, Saved_Env);

               --  Here we have the original env in saved, current with a fresh
               --  copy, and new aliased.

               --  THEN PART

               Next (Elmt);
               Check_Node (Elmt);

               --  Here the new_environment contains curr env after then block

               --  ELSE part
               --  Restore environment before if
               Copy_Env (Current_Perm_Env, New_Env);
               Free_Env (Current_Perm_Env);
               Copy_Env (Saved_Env, Current_Perm_Env);

               --  Here new environment contains the environment after then and
               --  current the fresh copy of old one.

               Next (Elmt);
               Check_Node (Elmt);

               --  CLEANUP

               Copy_Env (New_Env, Current_Perm_Env);
               Free_Env (New_Env);
               Free_Env (Saved_Env);
            end;

         when N_Indexed_Component =>
            Process_Path (Expr);

         --  Analyze the expression that is getting qualified

         when N_Qualified_Expression =>
            Check_Node (Expression (Expr));

         when N_Quantified_Expression =>
            declare
               Saved_Env : Perm_Env;

            begin
               Copy_Env (Current_Perm_Env, Saved_Env);
               Current_Checking_Mode := Read;
               Check_Node (Iterator_Specification (Expr));
               Check_Node (Loop_Parameter_Specification (Expr));

               Check_Node (Condition (Expr));
               Free_Env (Current_Perm_Env);
               Copy_Env (Saved_Env, Current_Perm_Env);
               Free_Env (Saved_Env);
            end;
         --  Analyze the list of associations in the aggregate

         when N_Aggregate =>
            Check_List (Expressions (Expr));
            Check_List (Component_Associations (Expr));

         when N_Allocator =>
            Check_Node (Expression (Expr));

         when N_Case_Expression =>
            declare
               Saved_Env : Perm_Env;

               --  Accumulator for the different branches

               New_Env : Perm_Env;
               Elmt : Node_Id := First (Alternatives (Expr));

            begin
               Current_Checking_Mode := Read;
               Check_Node (Expression (Expr));
               Current_Checking_Mode := Mode_Before;

               --  Save environment

               Copy_Env (Current_Perm_Env, Saved_Env);

               --  Here we have the original env in saved, current with a fresh
               --  copy, and new aliased.

               --  First alternative

               Check_Node (Elmt);
               Next (Elmt);
               Copy_Env (Current_Perm_Env, New_Env);
               Free_Env (Current_Perm_Env);

               --  Other alternatives

               while Present (Elmt) loop

                  --  Restore environment

                  Copy_Env (Saved_Env, Current_Perm_Env);
                  Check_Node (Elmt);
                  Next (Elmt);
               end loop;
               --  CLEANUP

               Copy_Env (Saved_Env, Current_Perm_Env);
               Free_Env (New_Env);
               Free_Env (Saved_Env);
            end;
         --  Analyze the list of associates in the aggregate as well as the
         --  ancestor part.

         when N_Extension_Aggregate =>
            Check_Node (Ancestor_Part (Expr));
            Check_List (Expressions (Expr));

         when N_Range =>
            Check_Node (Low_Bound (Expr));
            Check_Node (High_Bound (Expr));

         --  We arrived at a path. Process it.

         when N_Selected_Component =>
            Process_Path (Expr);

         when N_Slice =>
            Process_Path (Expr);

         when N_Type_Conversion =>
            Check_Node (Expression (Expr));

         when N_Unchecked_Type_Conversion =>
            Check_Node (Expression (Expr));

         --  Checking should not be called directly on these nodes

         when N_Target_Name =>
            raise Program_Error;

         --  Unsupported constructs in SPARK

         when N_Delta_Aggregate =>
            Error_Msg_N ("unsupported construct in SPARK", Expr);

         --  Ignored constructs for pointer checking

         when N_Character_Literal
            | N_Null
            | N_Numeric_Or_String_Literal
            | N_Operator_Symbol
            | N_Raise_Expression
            | N_Raise_xxx_Error
         =>
            null;
         --  The following nodes are never generated in GNATprove mode

         when N_Expression_With_Actions
            | N_Reference
            | N_Unchecked_Expression
         =>
            raise Program_Error;
      end case;
   end Check_Expression;

   -------------------
   -- Check_Globals --
   -------------------

   procedure Check_Globals (N : Node_Id) is
   begin
      if Nkind (N) = N_Empty then
         return;
      end if;

      declare
         pragma Assert (List_Length (Pragma_Argument_Associations (N)) = 1);
         PAA : constant Node_Id := First (Pragma_Argument_Associations (N));
         pragma Assert (Nkind (PAA) = N_Pragma_Argument_Association);
         Row      : Node_Id;
         The_Mode : Name_Id;
         RHS      : Node_Id;

         procedure Process (Mode : Name_Id; The_Global : Entity_Id);
         procedure Process (Mode : Name_Id; The_Global : Node_Id) is
            Ident_Elt   : constant Entity_Id :=
              Unique_Entity (Entity (The_Global));
            Mode_Before : constant Checking_Mode := Current_Checking_Mode;

         begin
            if Ekind (Ident_Elt) = E_Abstract_State then
               return;
            end if;
            case Mode is
               when Name_Input
                  | Name_Proof_In
               =>
                  Current_Checking_Mode := Observe;
                  Check_Node (The_Global);

               when Name_Output
                  | Name_In_Out
               =>
               --  ??? Borrow not Move?
                  Current_Checking_Mode := Borrow;
                  Check_Node (The_Global);

               when others =>
                  raise Program_Error;
            end case;
            Current_Checking_Mode := Mode_Before;
         end Process;

      begin
         if Nkind (Expression (PAA)) = N_Null then

            --  global => null
            --  No globals, nothing to do

            return;

         elsif Nkind_In (Expression (PAA), N_Identifier, N_Expanded_Name) then

            --  global => foo
            --  A single input

            Process (Name_Input, Expression (PAA));

         elsif Nkind (Expression (PAA)) = N_Aggregate
           and then Expressions (Expression (PAA)) /= No_List
         then
            --  global => (foo, bar)
            --  Inputs

            RHS := First (Expressions (Expression (PAA)));
            while Present (RHS) loop
               case Nkind (RHS) is
                  when N_Identifier
                     | N_Expanded_Name
                  =>
                     Process (Name_Input, RHS);

                  when N_Numeric_Or_String_Literal =>
                     Process (Name_Input, Original_Node (RHS));

                  when others =>
                     raise Program_Error;
               end case;
               RHS := Next (RHS);
            end loop;

         elsif Nkind (Expression (PAA)) = N_Aggregate
           and then Component_Associations (Expression (PAA)) /= No_List
         then
            --  global => (mode => foo,
            --             mode => (bar, baz))
            --  A mixture of things

            declare
               CA : constant List_Id :=
                 Component_Associations (Expression (PAA));
            begin
               Row := First (CA);
               while Present (Row) loop
                  pragma Assert (List_Length (Choices (Row)) = 1);
                  The_Mode := Chars (First (Choices (Row)));
                  RHS := Expression (Row);

                  case Nkind (RHS) is
                     when N_Aggregate =>
                        RHS := First (Expressions (RHS));
                        while Present (RHS) loop
                           case Nkind (RHS) is
                              when N_Numeric_Or_String_Literal =>
                                 Process (The_Mode, Original_Node (RHS));

                              when others =>
                                 Process (The_Mode, RHS);
                           end case;
                           RHS := Next (RHS);
                        end loop;

                     when N_Identifier
                        | N_Expanded_Name
                     =>
                        Process (The_Mode, RHS);

                     when N_Null =>
                        null;

                     when N_Numeric_Or_String_Literal =>
                        Process (The_Mode, Original_Node (RHS));

                     when others =>
                        raise Program_Error;
                  end case;
                  Row := Next (Row);
               end loop;
            end;

         else
            raise Program_Error;
         end if;
      end;
   end Check_Globals;

   ----------------
   -- Check_List --
   ----------------

   procedure Check_List (L : List_Id) is
      N : Node_Id;
   begin
      N := First (L);
      while Present (N) loop
         Check_Node (N);
         Next (N);
      end loop;
   end Check_List;

   --------------------------
   -- Check_Loop_Statement --
   --------------------------

   procedure Check_Loop_Statement (Loop_N : Node_Id) is

      --  Local variables

      Loop_Name : constant Entity_Id := Entity (Identifier (Loop_N));
      Loop_Env  : constant Perm_Env_Access := new Perm_Env;

   begin
      --  Save environment prior to the loop

      Copy_Env (From => Current_Perm_Env, To => Loop_Env.all);

      --  Add saved environment to loop environment

      Set (Current_Loops_Envs, Loop_Name, Loop_Env);

      --  If the loop is not a plain-loop, then it may either never be entered,
      --  or it may be exited after a number of iterations. Hence add the
      --  current permission environment as the initial loop exit environment.
      --  Otherwise, the loop exit environment remains empty until it is
      --  populated by analyzing exit statements.

      if Present (Iteration_Scheme (Loop_N)) then
         declare
            Exit_Env : constant Perm_Env_Access := new Perm_Env;

         begin
            Copy_Env (From => Current_Perm_Env, To => Exit_Env.all);
            Set (Current_Loops_Accumulators, Loop_Name, Exit_Env);
         end;
      end if;

      --  Analyze loop

      Check_Node (Iteration_Scheme (Loop_N));
      Check_List (Statements (Loop_N));

      --  Set environment to the one for exiting the loop

      declare
         Exit_Env : constant Perm_Env_Access :=
           Get (Current_Loops_Accumulators, Loop_Name);
      begin
         Free_Env (Current_Perm_Env);

         --  In the normal case, Exit_Env is not null and we use it. In the
         --  degraded case of a plain-loop without exit statements, Exit_Env is
         --  null, and we use the initial permission environment at the start
         --  of the loop to continue analysis. Any environment would be fine
         --  here, since the code after the loop is dead code, but this way we
         --  avoid spurious errors by having at least variables in scope inside
         --  the environment.

         if Exit_Env /= null then
            Copy_Env (From => Exit_Env.all, To => Current_Perm_Env);
            Free_Env (Loop_Env.all);
            Free_Env (Exit_Env.all);
         else
            Copy_Env (From => Loop_Env.all, To => Current_Perm_Env);
            Free_Env (Loop_Env.all);
         end if;
      end;
   end Check_Loop_Statement;

   ----------------
   -- Check_Node --
   ----------------

   procedure Check_Node (N : Node_Id) is
      Mode_Before : constant Checking_Mode := Current_Checking_Mode;
   begin
      case Nkind (N) is
         when N_Declaration =>
            Check_Declaration (N);

         when N_Subexpr =>
            Check_Expression (N);

         when N_Subtype_Indication =>
            Check_Node (Constraint (N));

         when N_Body_Stub =>
            Check_Node (Get_Body_From_Stub (N));

         when N_Statement_Other_Than_Procedure_Call =>
            Check_Statement (N);

         when N_Package_Body =>
            Check_Package_Body (N);

         when N_Subprogram_Body
            | N_Entry_Body
            | N_Task_Body
         =>
            Check_Callable_Body (N);

         when N_Protected_Body =>
            Check_List (Declarations (N));

         when N_Package_Declaration =>
            declare
               Spec : constant Node_Id := Specification (N);

            begin
               Current_Checking_Mode := Read;
               Check_List (Visible_Declarations (Spec));
               Check_List (Private_Declarations (Spec));

               Return_Declarations (Visible_Declarations (Spec));
               Return_Declarations (Private_Declarations (Spec));
            end;

         when N_Iteration_Scheme =>
            Current_Checking_Mode := Read;
            Check_Node (Condition (N));
            Check_Node (Iterator_Specification (N));
            Check_Node (Loop_Parameter_Specification (N));

         when N_Case_Expression_Alternative =>
            Current_Checking_Mode := Read;
            Check_List (Discrete_Choices (N));
            Current_Checking_Mode := Mode_Before;
            Check_Node (Expression (N));

         when N_Case_Statement_Alternative =>
            Current_Checking_Mode := Read;
            Check_List (Discrete_Choices (N));
            Current_Checking_Mode := Mode_Before;
            Check_List (Statements (N));

         when N_Component_Association =>
            Check_Node (Expression (N));

         when N_Handled_Sequence_Of_Statements =>
            Check_List (Statements (N));

         when N_Parameter_Association =>
            Check_Node (Explicit_Actual_Parameter (N));

         when N_Range_Constraint =>
            Check_Node (Range_Expression (N));

         when N_Index_Or_Discriminant_Constraint =>
            Check_List (Constraints (N));

         --  Checking should not be called directly on these nodes

         when N_Abortable_Part
            | N_Accept_Alternative
            | N_Access_Definition
            | N_Access_Function_Definition
            | N_Access_Procedure_Definition
            | N_Access_To_Object_Definition
            | N_Aspect_Specification
            | N_Compilation_Unit
            | N_Compilation_Unit_Aux
            | N_Component_Clause
            | N_Component_Definition
            | N_Component_List
            | N_Constrained_Array_Definition
            | N_Contract
            | N_Decimal_Fixed_Point_Definition
            | N_Defining_Character_Literal
            | N_Defining_Identifier
            | N_Defining_Operator_Symbol
            | N_Defining_Program_Unit_Name
            | N_Delay_Alternative
            | N_Derived_Type_Definition
            | N_Designator
            | N_Discriminant_Specification
            | N_Elsif_Part
            | N_Entry_Body_Formal_Part
            | N_Enumeration_Type_Definition
            | N_Entry_Call_Alternative
            | N_Entry_Index_Specification
            | N_Error
            | N_Exception_Handler
            | N_Floating_Point_Definition
            | N_Formal_Decimal_Fixed_Point_Definition
            | N_Formal_Derived_Type_Definition
            | N_Formal_Discrete_Type_Definition
            | N_Formal_Floating_Point_Definition
            | N_Formal_Incomplete_Type_Definition
            | N_Formal_Modular_Type_Definition
            | N_Formal_Ordinary_Fixed_Point_Definition
            | N_Formal_Private_Type_Definition
            | N_Formal_Signed_Integer_Type_Definition
            | N_Generic_Association
            | N_Mod_Clause
            | N_Modular_Type_Definition
            | N_Ordinary_Fixed_Point_Definition
            | N_Package_Specification
            | N_Parameter_Specification
            | N_Pragma_Argument_Association
            | N_Protected_Definition
            | N_Push_Pop_xxx_Label
            | N_Real_Range_Specification
            | N_Record_Definition
            | N_SCIL_Dispatch_Table_Tag_Init
            | N_SCIL_Dispatching_Call
            | N_SCIL_Membership_Test
            | N_Signed_Integer_Type_Definition
            | N_Subunit
            | N_Task_Definition
            | N_Terminate_Alternative
            | N_Triggering_Alternative
            | N_Unconstrained_Array_Definition
            | N_Unused_At_Start
            | N_Unused_At_End
            | N_Variant
            | N_Variant_Part
         =>
            raise Program_Error;

         --  Unsupported constructs in SPARK

         when N_Iterated_Component_Association =>
            Error_Msg_N ("unsupported construct in SPARK", N);

         --  Ignored constructs for pointer checking

         when N_Abstract_Subprogram_Declaration
            | N_At_Clause
            | N_Attribute_Definition_Clause
            | N_Call_Marker
            | N_Delta_Constraint
            | N_Digits_Constraint
            | N_Empty
            | N_Enumeration_Representation_Clause
            | N_Exception_Declaration
            | N_Exception_Renaming_Declaration
            | N_Formal_Package_Declaration
            | N_Formal_Subprogram_Declaration
            | N_Freeze_Entity
            | N_Freeze_Generic_Entity
            | N_Function_Instantiation
            | N_Generic_Function_Renaming_Declaration
            | N_Generic_Package_Declaration
            | N_Generic_Package_Renaming_Declaration
            | N_Generic_Procedure_Renaming_Declaration
            | N_Generic_Subprogram_Declaration
            | N_Implicit_Label_Declaration
            | N_Itype_Reference
            | N_Label
            | N_Number_Declaration
            | N_Object_Renaming_Declaration
            | N_Others_Choice
            | N_Package_Instantiation
            | N_Package_Renaming_Declaration
            | N_Pragma
            | N_Procedure_Instantiation
            | N_Record_Representation_Clause
            | N_Subprogram_Declaration
            | N_Subprogram_Renaming_Declaration
            | N_Task_Type_Declaration
            | N_Use_Package_Clause
            | N_With_Clause
            | N_Use_Type_Clause
            | N_Validate_Unchecked_Conversion
            | N_Variable_Reference_Marker
            | N_Discriminant_Association

            --  ??? check whether we should do sth special for
            --  N_Discriminant_Association, or maybe raise a program error.
         =>
            null;
         --  The following nodes are rewritten by semantic analysis

         when N_Single_Protected_Declaration
            | N_Single_Task_Declaration
         =>
            raise Program_Error;
      end case;

      Current_Checking_Mode := Mode_Before;
   end Check_Node;

   ------------------------
   -- Check_Package_Body --
   ------------------------

   procedure Check_Package_Body (Pack : Node_Id) is
      Saved_Env : Perm_Env;
      CorSp : Node_Id;

   begin
      if Present (SPARK_Pragma (Defining_Entity (Pack, False))) then
         if Get_SPARK_Mode_From_Annotation
           (SPARK_Pragma (Defining_Entity (Pack))) /= Opt.On
         then
            return;
         end if;
      else
         return;
      end if;

      CorSp := Parent (Corresponding_Spec (Pack));
      while Nkind (CorSp) /= N_Package_Specification loop
         CorSp := Parent (CorSp);
      end loop;

      Check_List (Visible_Declarations (CorSp));

      --  Save environment

      Copy_Env (Current_Perm_Env, Saved_Env);
      Check_List (Private_Declarations (CorSp));

      --  Set mode to Read, and then analyze declarations and statements

      Current_Checking_Mode := Read;
      Check_List (Declarations (Pack));
      Check_Node (Handled_Statement_Sequence (Pack));

      --  Check RW for every stateful variable (i.e. in declarations)

      Return_Declarations (Private_Declarations (CorSp));
      Return_Declarations (Visible_Declarations (CorSp));
      Return_Declarations (Declarations (Pack));

      --  Restore previous environment (i.e. delete every nonvisible
      --  declaration) from environment.

      Free_Env (Current_Perm_Env);
      Copy_Env (Saved_Env, Current_Perm_Env);
   end Check_Package_Body;

   --------------------
   -- Check_Param_In --
   --------------------

   procedure Check_Param_In (Formal : Entity_Id; Actual : Node_Id) is
      Mode : constant Entity_Kind := Ekind (Formal);
      Mode_Before : constant Checking_Mode := Current_Checking_Mode;
   begin
      case Formal_Kind'(Mode) is

         --  Formal IN parameter

         when E_In_Parameter =>

            --  Formal IN parameter, access type

            if Is_Access_Type (Etype (Formal)) then

               --  Formal IN parameter, access to variable type

               if not Is_Access_Constant (Etype (Formal)) then

                  --  Formal IN parameter, named/anonymous access-to-variable
                  --  type.
                  --
                  --  In SPARK, IN access-to-variable is an observe operation
                  --  for a function, and a borrow operation for a procedure.

                  if Ekind (Scope (Formal)) = E_Function then
                     Current_Checking_Mode := Observe;
                     Check_Node (Actual);
                  else
                     Current_Checking_Mode := Borrow;
                     Check_Node (Actual);
                  end if;

               --  Formal IN parameter, access-to-constant type
               --  Formal IN parameter, access-to-named-constant type

               elsif not Is_Anonymous_Access_Type (Etype (Formal)) then
                  Error_Msg_N ("assignment not allowed, Ownership Aspect"
                               & " False (Named general access type)",
                               Formal);

               --  Formal IN parameter, access to anonymous constant type

               else
                  Current_Checking_Mode := Observe;
                  Check_Node (Actual);
               end if;

            --  Formal IN parameter, composite type

            elsif Is_Deep (Etype (Formal)) then

               --  Composite formal types should be named
               --  Formal IN parameter, composite named type

               Current_Checking_Mode := Observe;
               Check_Node (Actual);
            end if;

         when E_Out_Parameter
            | E_In_Out_Parameter
         =>
            null;
      end case;

      Current_Checking_Mode := Mode_Before;
   end Check_Param_In;

   ----------------------
   -- Check_Param_Out --
   ----------------------

   procedure Check_Param_Out (Formal : Entity_Id; Actual : Node_Id) is
      Mode        : constant Entity_Kind := Ekind (Formal);
      Mode_Before : constant Checking_Mode := Current_Checking_Mode;

   begin
      case Formal_Kind'(Mode) is

         --  Formal OUT/IN OUT parameter

         when E_Out_Parameter
            | E_In_Out_Parameter
         =>

            --  Formal OUT/IN OUT parameter, access type

            if Is_Access_Type (Etype (Formal)) then

               --  Formal OUT/IN OUT parameter, access to variable type

               if not Is_Access_Constant (Etype (Formal)) then

                  --  Cannot have anonymous out access parameter
                  --  Formal out/in out parameter, access to named variable
                  --  type.

                  Current_Checking_Mode := Move;
                  Check_Node (Actual);

               --  Formal out/in out parameter, access to constant type

               else
                  Error_Msg_N ("assignment not allowed, Ownership Aspect False"
                               & " (Named general access type)", Formal);

               end if;

            --  Formal out/in out parameter, composite type

            elsif Is_Deep (Etype (Formal)) then

               --  Composite formal types should be named
               --  Formal out/in out Parameter, Composite Named type.

               Current_Checking_Mode := Borrow;
               Check_Node (Actual);
            end if;

         when E_In_Parameter =>
            null;
      end case;

      Current_Checking_Mode := Mode_Before;
   end Check_Param_Out;

   -------------------------
   -- Check_Safe_Pointers --
   -------------------------

   procedure Check_Safe_Pointers (N : Node_Id) is

      --  Local subprograms

      procedure Check_List (L : List_Id);
      --  Call the main analysis procedure on each element of the list

      procedure Initialize;
      --  Initialize global variables before starting the analysis of a body

      ----------------
      -- Check_List --
      ----------------

      procedure Check_List (L : List_Id) is
         N : Node_Id;
      begin
         N := First (L);
         while Present (N) loop
            Check_Safe_Pointers (N);
            Next (N);
         end loop;
      end Check_List;

      ----------------
      -- Initialize --
      ----------------

      procedure Initialize is
      begin
         Reset (Current_Loops_Envs);
         Reset (Current_Loops_Accumulators);
         Reset (Current_Perm_Env);
         Reset (Current_Initialization_Map);
      end Initialize;

      --  Local variables

      Prag : Node_Id;

      --  SPARK_Mode pragma in application

   --  Start of processing for Check_Safe_Pointers

   begin
      Initialize;
      case Nkind (N) is
         when N_Compilation_Unit =>
            Check_Safe_Pointers (Unit (N));

         when N_Package_Body
            | N_Package_Declaration
            | N_Subprogram_Body
         =>
            Prag := SPARK_Pragma (Defining_Entity (N));
            if Present (Prag) then
               if Get_SPARK_Mode_From_Annotation (Prag) = Opt.Off then
                  return;
               else
                  Check_Node (N);
               end if;

            elsif Nkind (N) = N_Package_Body then
               Check_List (Declarations (N));

            elsif Nkind (N) = N_Package_Declaration then
               Check_List (Private_Declarations (Specification (N)));
               Check_List (Visible_Declarations (Specification (N)));
            end if;

         when others =>
            null;
      end case;
   end Check_Safe_Pointers;

   ---------------------
   -- Check_Statement --
   ---------------------

   procedure Check_Statement (Stmt : Node_Id) is
      Mode_Before : constant Checking_Mode := Current_Checking_Mode;
      State_N     : Perm_Kind;
      Check       : Boolean := True;
      St_Name     : Node_Id;
      Ty_St_Name  : Node_Id;

      function Get_Root (Comp_Stmt : Node_Id) return Node_Id;
      --  Return the root of the name given as input

      function Get_Root (Comp_Stmt : Node_Id) return Node_Id is
      begin
         case Nkind (Comp_Stmt) is
            when N_Identifier
               | N_Expanded_Name
            => return Comp_Stmt;

            when N_Type_Conversion
               | N_Unchecked_Type_Conversion
               | N_Qualified_Expression
            =>
               return Get_Root (Expression (Comp_Stmt));

            when N_Parameter_Specification =>
               return Get_Root (Defining_Identifier (Comp_Stmt));

            when N_Selected_Component
               | N_Indexed_Component
               | N_Slice
               | N_Explicit_Dereference
            =>
               return Get_Root (Prefix (Comp_Stmt));

            when others =>
               raise Program_Error;
         end case;
      end Get_Root;

   begin
      case N_Statement_Other_Than_Procedure_Call'(Nkind (Stmt)) is
         when N_Entry_Call_Statement =>
            Check_Call_Statement (Stmt);

         --  Move right-hand side first, and then assign left-hand side

         when N_Assignment_Statement =>

            St_Name    := Name (Stmt);
            Ty_St_Name := Etype (Name (Stmt));

            --  Check that is not a *general* access type

            if Has_Ownership_Aspect_True (St_Name, "assigning to") then

            --  Assigning to access type

               if Is_Access_Type (Ty_St_Name) then

                  --  Assigning to access to variable type

                  if not Is_Access_Constant (Ty_St_Name) then

                     --  Assigning to named access to variable type

                     if not Is_Anonymous_Access_Type (Ty_St_Name) then
                        Current_Checking_Mode := Move;

                     --  Assigning to anonymous access to variable type

                     else
                        --  Target /= source root

                        if Nkind_In (Expression (Stmt), N_Allocator, N_Null)
                          or else Entity (St_Name) /=
                          Entity (Get_Root (Expression (Stmt)))
                        then
                           Error_Msg_N ("assignment not allowed, anonymous "
                                        & "access Object with Different Root",
                                        Stmt);
                           Check := False;

                        --  Target = source root

                        else
                           --  Here we do nothing on the source nor on the
                           --  target. However, we check the the legality rule:
                           --  "The source shall be an owning access object
                           --  denoted by a name that is not in the observed
                           --  state".

                           State_N := Get_Perm (Expression (Stmt));
                           if State_N = Observed then
                              Error_Msg_N ("assignment not allowed, Anonymous "
                                           & "access object with the same root"
                                           & " but source Observed", Stmt);
                              Check := False;
                           end if;
                        end if;
                     end if;

                  --  else access-to-constant

                  --  Assigning to anonymous access-to-constant type

                  elsif Is_Anonymous_Access_Type (Ty_St_Name) then

                     --  ??? Check the follwing condition. We may have to
                     --  add that the root is in the observed state too.

                     State_N := Get_Perm (Expression (Stmt));
                     if State_N /= Observed then
                        Error_Msg_N ("assignment not allowed, anonymous "
                                     & "access-to-constant object not in "
                                     & "the observed state)", Stmt);
                        Check := False;

                     else
                        Error_Msg_N ("?here check accessibility level cited in"
                                     & " the second legality rule of assign",
                                     Stmt);
                        Check := False;
                     end if;

                  --  Assigning to named access-to-constant type:
                  --  This case should have been detected when checking
                  --  Has_Onwership_Aspect_True (Name (Stmt), "msg").

                  else
                     raise Program_Error;
                  end if;

               --  Assigning to composite (deep) type.

               elsif Is_Deep (Ty_St_Name) then
                  if Ekind_In (Ty_St_Name,
                               E_Record_Type,
                               E_Record_Subtype)
                  then
                     declare
                        Elmt : Entity_Id :=
                          First_Component_Or_Discriminant (Ty_St_Name);

                     begin
                        while Present (Elmt) loop
                           if Is_Anonymous_Access_Type (Etype (Elmt)) or
                             Ekind (Elmt) = E_General_Access_Type
                           then
                              Error_Msg_N ("assignment not allowed, Ownership "
                                           & "Aspect False (Components have "
                                           & "Ownership Aspect False)", Stmt);
                              Check := False;
                              exit;
                           end if;

                           Next_Component_Or_Discriminant (Elmt);
                        end loop;
                     end;

                     --  Record types are always named so this is a move

                     if Check then
                        Current_Checking_Mode := Move;
                     end if;

                  elsif Ekind_In (Ty_St_Name,
                                  E_Array_Type,
                                  E_Array_Subtype)
                    and then Check
                  then
                     Current_Checking_Mode := Move;
                  end if;

               --  Now handle legality rules of using a borrowed, observed,
               --  or moved name as a prefix in an assignment.

               else
                  if Nkind_In (St_Name,
                               N_Attribute_Reference,
                               N_Expanded_Name,
                               N_Explicit_Dereference,
                               N_Indexed_Component,
                               N_Reference,
                               N_Selected_Component,
                               N_Slice)
                  then

                     if Is_Access_Type (Etype (Prefix (St_Name))) or
                       Is_Deep (Etype (Prefix (St_Name)))
                     then

                        --  We set the Check variable to True so that we can
                        --  Check_Node of the expression and the name first
                        --  under the assumption of Current_Checking_Mode =
                        --  Read => nothing to be done for the RHS if the
                        --  following check on the expression fails, and
                        --  Current_Checking_Mode := Assign => the name should
                        --  not be borrowed or observed so that we can use it
                        --  as a prefix in the target of an assignement.
                        --
                        --  Note that we do not need to check the OA here
                        --  because we are allowed to read and write "through"
                        --  an object of OAF (example: traversing a DS).

                        Check := True;
                     end if;
                  end if;

                  if Nkind_In (Expression (Stmt),
                            N_Attribute_Reference,
                            N_Expanded_Name,
                            N_Explicit_Dereference,
                            N_Indexed_Component,
                            N_Reference,
                            N_Selected_Component,
                            N_Slice)
                  then

                     if Is_Access_Type (Etype (Prefix (Expression (Stmt))))
                       or else Is_Deep (Etype (Prefix (Expression (Stmt))))
                     then
                        Current_Checking_Mode := Observe;
                        Check := True;
                     end if;
                  end if;
               end if;

               if Check then
                  Check_Node (Expression (Stmt));
                  Current_Checking_Mode := Assign;
                  Check_Node (St_Name);
               end if;
            end if;

         when N_Block_Statement =>
            declare
               Saved_Env : Perm_Env;
            begin
               --  Save environment

               Copy_Env (Current_Perm_Env, Saved_Env);

               --  Analyze declarations and Handled_Statement_Sequences

               Current_Checking_Mode := Read;
               Check_List (Declarations (Stmt));
               Check_Node (Handled_Statement_Sequence (Stmt));

               --  Restore environment

               Free_Env (Current_Perm_Env);
               Copy_Env (Saved_Env, Current_Perm_Env);
            end;

         when N_Case_Statement =>
            declare
               Saved_Env : Perm_Env;

               --  Accumulator for the different branches

               New_Env : Perm_Env;
               Elmt : Node_Id := First (Alternatives (Stmt));

            begin
               Current_Checking_Mode := Read;
               Check_Node (Expression (Stmt));
               Current_Checking_Mode := Mode_Before;

               --  Save environment

               Copy_Env (Current_Perm_Env, Saved_Env);

               --  Here we have the original env in saved, current with a fresh
               --  copy, and new aliased.

               --  First alternative

               Check_Node (Elmt);
               Next (Elmt);
               Copy_Env (Current_Perm_Env, New_Env);
               Free_Env (Current_Perm_Env);

               --  Other alternatives

               while Present (Elmt) loop

                  --  Restore environment

                  Copy_Env (Saved_Env, Current_Perm_Env);
                  Check_Node (Elmt);
                  Next (Elmt);
               end loop;

               Copy_Env (Saved_Env, Current_Perm_Env);
               Free_Env (New_Env);
               Free_Env (Saved_Env);
            end;

         when N_Delay_Relative_Statement =>
            Check_Node (Expression (Stmt));

         when N_Delay_Until_Statement =>
            Check_Node (Expression (Stmt));

         when N_Loop_Statement =>
            Check_Loop_Statement (Stmt);

            --  If deep type expression, then move, else read

         when N_Simple_Return_Statement =>
            case Nkind (Expression (Stmt)) is
               when N_Empty =>
                  declare
                     --  ??? This does not take into account the fact that
                     --  a simple return inside an extended return statement
                     --  applies to the extended return statement.
                     Subp : constant Entity_Id :=
                       Return_Applies_To (Return_Statement_Entity (Stmt));
                  begin
                     Return_Globals (Subp);
                  end;

               when others =>
                  if Is_Deep (Etype (Expression (Stmt))) then
                     Current_Checking_Mode := Move;
                  else
                     Check := False;
                  end if;

                  if Check then
                     Check_Node (Expression (Stmt));
                  end if;
            end case;

         when N_Extended_Return_Statement =>
            Check_List (Return_Object_Declarations (Stmt));
            Check_Node (Handled_Statement_Sequence (Stmt));
            Return_Declarations (Return_Object_Declarations (Stmt));
            declare
               --  ??? This does not take into account the fact that a simple
               --  return inside an extended return statement applies to the
               --  extended return statement.
               Subp : constant Entity_Id :=
                 Return_Applies_To (Return_Statement_Entity (Stmt));

            begin
               Return_Globals (Subp);
            end;

         --  Nothing to do when exiting a loop. No merge needed

         when N_Exit_Statement =>
            null;

         --  Copy environment, run on each branch

         when N_If_Statement =>
            declare
               Saved_Env : Perm_Env;

               --  Accumulator for the different branches

               New_Env : Perm_Env;

            begin
               Check_Node (Condition (Stmt));

               --  Save environment

               Copy_Env (Current_Perm_Env, Saved_Env);

               --  Here we have the original env in saved, current with a fresh
               --  copy.

               --  THEN PART

               Check_List (Then_Statements (Stmt));
               Copy_Env (Current_Perm_Env, New_Env);
               Free_Env (Current_Perm_Env);

               --  Here the new_environment contains curr env after then block

               --  ELSIF part

               declare
                  Elmt : Node_Id;

               begin
                  Elmt := First (Elsif_Parts (Stmt));
                  while Present (Elmt) loop

                     --  Transfer into accumulator, and restore from save

                     Copy_Env (Saved_Env, Current_Perm_Env);
                     Check_Node (Condition (Elmt));
                     Check_List (Then_Statements (Stmt));
                     Next (Elmt);
                  end loop;
               end;

               --  ELSE part

               --  Restore environment before if

               Copy_Env (Saved_Env, Current_Perm_Env);

               --  Here new environment contains the environment after then and
               --  current the fresh copy of old one.

               Check_List (Else_Statements (Stmt));

               --  CLEANUP

               Copy_Env (Saved_Env, Current_Perm_Env);

               Free_Env (New_Env);
               Free_Env (Saved_Env);
            end;

         --  Unsupported constructs in SPARK

         when N_Abort_Statement
            | N_Accept_Statement
            | N_Asynchronous_Select
            | N_Code_Statement
            | N_Conditional_Entry_Call
            | N_Goto_Statement
            | N_Requeue_Statement
            | N_Selective_Accept
            | N_Timed_Entry_Call
         =>
            Error_Msg_N ("unsupported construct in SPARK", Stmt);

         --  Ignored constructs for pointer checking

         when N_Null_Statement
            | N_Raise_Statement
         =>
            null;

         --  The following nodes are never generated in GNATprove mode

         when N_Compound_Statement
            | N_Free_Statement
         =>
            raise Program_Error;
      end case;
   end Check_Statement;

   --------------
   -- Get_Perm --
   --------------

   function Get_Perm (N : Node_Id) return Perm_Kind is
      Tree_Or_Perm : constant Perm_Or_Tree := Get_Perm_Or_Tree (N);

   begin
      case Tree_Or_Perm.R is
         when Folded =>
            return Tree_Or_Perm.Found_Permission;

         when Unfolded =>
            pragma Assert (Tree_Or_Perm.Tree_Access /= null);
            return Permission (Tree_Or_Perm.Tree_Access);

         --  We encoutered a function call, hence the memory area is fresh,
         --  which means that the association permission is RW.

         when Function_Call =>
            return Unrestricted;
      end case;
   end Get_Perm;

   ----------------------
   -- Get_Perm_Or_Tree --
   ----------------------

   function Get_Perm_Or_Tree (N : Node_Id) return Perm_Or_Tree is
   begin
      case Nkind (N) is

         --  Base identifier. Normally those are the roots of the trees stored
         --  in the permission environment.

         when N_Defining_Identifier =>
            raise Program_Error;

         when N_Identifier
            | N_Expanded_Name
         =>
            declare
               P : constant Entity_Id := Entity (N);
               C : constant Perm_Tree_Access :=
                 Get (Current_Perm_Env, Unique_Entity (P));

            begin
               --  Setting the initialization map to True, so that this
               --  variable cannot be ignored anymore when looking at end
               --  of elaboration of package.

               Set (Current_Initialization_Map, Unique_Entity (P), True);
               if C = null then
                  --  No null possible here, there are no parents for the path.
                  --  This means we are using a global variable without adding
                  --  it in environment with a global aspect.

                  Illegal_Global_Usage (N);

               else
                  return (R => Unfolded, Tree_Access => C);
               end if;
            end;

         when N_Type_Conversion
            | N_Unchecked_Type_Conversion
            | N_Qualified_Expression
         =>
            return Get_Perm_Or_Tree (Expression (N));

         --  Happening when we try to get the permission of a variable that
         --  is a formal parameter. We get instead the defining identifier
         --  associated with the parameter (which is the one that has been
         --  stored for indexing).

         when N_Parameter_Specification =>
            return Get_Perm_Or_Tree (Defining_Identifier (N));

         --  We get the permission tree of its prefix, and then get either the
         --  subtree associated with that specific selection, or if we have a
         --  leaf that folds its children, we take the children's permission
         --  and return it using the discriminant Folded.

         when N_Selected_Component =>
            declare
               C : constant Perm_Or_Tree := Get_Perm_Or_Tree (Prefix (N));

            begin
               case C.R is
                  when Folded
                     | Function_Call
                  =>
                     return C;

                  when Unfolded =>
                     pragma Assert (C.Tree_Access /= null);
                     pragma Assert (Kind (C.Tree_Access) = Entire_Object
                                    or else
                                    Kind (C.Tree_Access) = Record_Component);

                     if Kind (C.Tree_Access) = Record_Component then
                        declare
                           Selected_Component : constant Entity_Id :=
                             Entity (Selector_Name (N));
                           Selected_C : constant Perm_Tree_Access :=
                             Perm_Tree_Maps.Get
                               (Component (C.Tree_Access), Selected_Component);

                        begin
                           if Selected_C = null then
                              return (R           => Unfolded,
                                      Tree_Access =>
                                        Other_Components (C.Tree_Access));

                           else
                              return (R           => Unfolded,
                                      Tree_Access => Selected_C);
                           end if;
                        end;

                     elsif Kind (C.Tree_Access) = Entire_Object then
                        return (R                => Folded,
                                Found_Permission =>
                                  Children_Permission (C.Tree_Access));

                     else
                        raise Program_Error;
                     end if;
               end case;
            end;
         --  We get the permission tree of its prefix, and then get either the
         --  subtree associated with that specific selection, or if we have a
         --  leaf that folds its children, we take the children's permission
         --  and return it using the discriminant Folded.

         when N_Indexed_Component
            | N_Slice
         =>
            declare
               C : constant Perm_Or_Tree := Get_Perm_Or_Tree (Prefix (N));

            begin
               case C.R is
                  when Folded
                     | Function_Call
                  =>
                     return C;

                  when Unfolded =>
                     pragma Assert (C.Tree_Access /= null);
                     pragma Assert (Kind (C.Tree_Access) = Entire_Object
                                    or else
                                    Kind (C.Tree_Access) = Array_Component);

                     if Kind (C.Tree_Access) = Array_Component then
                        pragma Assert (Get_Elem (C.Tree_Access) /= null);
                        return (R => Unfolded,
                                Tree_Access => Get_Elem (C.Tree_Access));

                     elsif Kind (C.Tree_Access) = Entire_Object then
                        return (R => Folded, Found_Permission =>
                                  Children_Permission (C.Tree_Access));

                     else
                        raise Program_Error;
                     end if;
               end case;
            end;
         --  We get the permission tree of its prefix, and then get either the
         --  subtree associated with that specific selection, or if we have a
         --  leaf that folds its children, we take the children's permission
         --  and return it using the discriminant Folded.

         when N_Explicit_Dereference =>
            declare
               C : constant Perm_Or_Tree := Get_Perm_Or_Tree (Prefix (N));

            begin
               case C.R is
                  when Folded
                     | Function_Call
                  =>
                     return C;

                  when Unfolded =>
                     pragma Assert (C.Tree_Access /= null);
                     pragma Assert (Kind (C.Tree_Access) = Entire_Object
                                    or else
                                    Kind (C.Tree_Access) = Reference);

                     if Kind (C.Tree_Access) = Reference then
                        if Get_All (C.Tree_Access) = null then

                           --  Hash_Table_Error

                           raise Program_Error;

                        else
                           return
                             (R => Unfolded,
                              Tree_Access => Get_All (C.Tree_Access));
                        end if;

                     elsif Kind (C.Tree_Access) = Entire_Object then
                        return (R => Folded, Found_Permission =>
                                  Children_Permission (C.Tree_Access));

                     else
                        raise Program_Error;
                     end if;
               end case;
            end;
         --  The name contains a function call, hence the given path is always
         --  new. We do not have to check for anything.

         when N_Function_Call =>
            return (R => Function_Call);

         when others =>
            raise Program_Error;
      end case;
   end Get_Perm_Or_Tree;

   -------------------
   -- Get_Perm_Tree --
   -------------------

   function Get_Perm_Tree (N : Node_Id) return Perm_Tree_Access is
   begin
      case Nkind (N) is

         --  Base identifier. Normally those are the roots of the trees stored
         --  in the permission environment.

         when N_Defining_Identifier =>
            raise Program_Error;

         when N_Identifier
            | N_Expanded_Name
         =>
            declare
               P : constant Node_Id := Entity (N);
               C : constant Perm_Tree_Access :=
                 Get (Current_Perm_Env, Unique_Entity (P));

            begin
               --  Setting the initialization map to True, so that this
               --  variable cannot be ignored anymore when looking at end
               --  of elaboration of package.

               Set (Current_Initialization_Map, Unique_Entity (P), True);
               if C = null then
                  --  No null possible here, there are no parents for the path.
                  --  This means we are using a global variable without adding
                  --  it in environment with a global aspect.

                  Illegal_Global_Usage (N);

               else
                  return C;
               end if;
            end;

         when N_Type_Conversion
            | N_Unchecked_Type_Conversion
            | N_Qualified_Expression
         =>
            return Get_Perm_Tree (Expression (N));

         when N_Parameter_Specification =>
            return Get_Perm_Tree (Defining_Identifier (N));

         --  We get the permission tree of its prefix, and then get either the
         --  subtree associated with that specific selection, or if we have a
         --  leaf that folds its children, we unroll it in one step.

         when N_Selected_Component =>
            declare
               C : constant Perm_Tree_Access := Get_Perm_Tree (Prefix (N));

            begin
               if C = null then

                  --  If null then it means we went through a function call

                  return null;
               end if;

               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Record_Component);

               if Kind (C) = Record_Component then

                  --  The tree is unfolded. We just return the subtree.

                  declare
                     Selected_Component : constant Entity_Id :=
                       Entity (Selector_Name (N));
                     Selected_C : constant Perm_Tree_Access :=
                       Perm_Tree_Maps.Get
                         (Component (C), Selected_Component);

                  begin
                     if Selected_C = null then
                        return Other_Components (C);
                     end if;
                     return Selected_C;
                  end;

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace the node with
                     --  Record_Component.

                     Elem : Node_Id;

                     --  Create the unrolled nodes

                     Son : Perm_Tree_Access;

                     Child_Perm : constant Perm_Kind :=
                       Children_Permission (C);

                  begin
                     --  We change the current node from Entire_Object to
                     --  Record_Component with same permission and an empty
                     --  hash table as component list.

                     C.all.Tree :=
                       (Kind             => Record_Component,
                        Is_Node_Deep     => Is_Node_Deep (C),
                        Permission       => Permission (C),
                        Component        => Perm_Tree_Maps.Nil,
                        Other_Components =>
                           new Perm_Tree_Wrapper'
                          (Tree =>
                               (Kind                => Entire_Object,
                                --  Is_Node_Deep is true, to be conservative
                                Is_Node_Deep        => True,
                                Permission          => Child_Perm,
                                Children_Permission => Child_Perm)
                          )
                       );

                     --  We fill the hash table with all sons of the record,
                     --  with basic Entire_Objects nodes.

                     Elem := First_Component_Or_Discriminant
                       (Etype (Prefix (N)));

                     while Present (Elem) loop
                        Son := new Perm_Tree_Wrapper'
                          (Tree =>
                             (Kind                => Entire_Object,
                              Is_Node_Deep        => Is_Deep (Etype (Elem)),
                              Permission          => Child_Perm,
                              Children_Permission => Child_Perm));

                        Perm_Tree_Maps.Set
                          (C.all.Tree.Component, Elem, Son);
                        Next_Component_Or_Discriminant (Elem);
                     end loop;
                     --  we return the tree to the sons, so that the recursion
                     --  can continue.

                     declare
                        Selected_Component : constant Entity_Id :=
                          Entity (Selector_Name (N));

                        Selected_C : constant Perm_Tree_Access :=
                          Perm_Tree_Maps.Get
                            (Component (C), Selected_Component);

                     begin
                        pragma Assert (Selected_C /= null);
                        return Selected_C;
                     end;
                  end;
               else
                  raise Program_Error;
               end if;
            end;
         --  We set the permission tree of its prefix, and then we extract from
         --  the returned pointer the subtree. If folded, we unroll the tree at
         --  one step.

         when N_Indexed_Component
            | N_Slice
         =>
            declare
               C : constant Perm_Tree_Access := Get_Perm_Tree (Prefix (N));

            begin
               if C = null then
                  --  If null then we went through a function call

                  return null;
               end if;
               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Array_Component);

               if Kind (C) = Array_Component then

                  --  The tree is unfolded. We just return the elem subtree

                  pragma Assert (Get_Elem (C) = null);
                  return Get_Elem (C);

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace node with Array_Component.

                     Son : Perm_Tree_Access;

                  begin
                     Son := new Perm_Tree_Wrapper'
                       (Tree =>
                          (Kind                => Entire_Object,
                           Is_Node_Deep        => Is_Node_Deep (C),
                           Permission          => Children_Permission (C),
                           Children_Permission => Children_Permission (C)));

                     --  We change the current node from Entire_Object
                     --  to Array_Component with same permission and the
                     --  previously defined son.

                     C.all.Tree := (Kind         => Array_Component,
                                    Is_Node_Deep => Is_Node_Deep (C),
                                    Permission   => Permission (C),
                                    Get_Elem     => Son);
                     return Get_Elem (C);
                  end;
               else
                  raise Program_Error;
               end if;
            end;
         --  We get the permission tree of its prefix, and then get either the
         --  subtree associated with that specific selection, or if we have a
         --  leaf that folds its children, we unroll the tree.

         when N_Explicit_Dereference =>
            declare
               C : Perm_Tree_Access;

            begin
               C := Get_Perm_Tree (Prefix (N));

               if C = null then

                  --  If null, we went through a function call

                  return null;
               end if;

               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Reference);

               if Kind (C) = Reference then

                  --  The tree is unfolded. We return the elem subtree

                  if Get_All (C) = null then

                     --  Hash_Table_Error

                     raise Program_Error;
                  end if;
                  return Get_All (C);

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace the node with Reference.

                     Son : Perm_Tree_Access;

                  begin
                     Son := new Perm_Tree_Wrapper'
                       (Tree =>
                          (Kind                => Entire_Object,
                           Is_Node_Deep        => Is_Deep (Etype (N)),
                           Permission          => Children_Permission (C),
                           Children_Permission => Children_Permission (C)));

                     --  We change the current node from Entire_Object to
                     --  Reference with same permission and the previous son.

                     pragma Assert (Is_Node_Deep (C));
                     C.all.Tree := (Kind         => Reference,
                                    Is_Node_Deep => Is_Node_Deep (C),
                                    Permission   => Permission (C),
                                    Get_All      => Son);
                     return Get_All (C);
                  end;
               else
                  raise Program_Error;
               end if;
            end;
         --  No permission tree for function calls

         when N_Function_Call =>
            return null;

         when others =>
            raise Program_Error;
      end case;
   end Get_Perm_Tree;

   --------
   -- Hp --
   --------

   procedure Hp (P : Perm_Env) is
      Elem : Perm_Tree_Maps.Key_Option;

   begin
      Elem := Get_First_Key (P);
      while Elem.Present loop
         Print_Node_Briefly (Elem.K);
         Elem := Get_Next_Key (P);
      end loop;
   end Hp;

   --------------------------
   -- Illegal_Global_Usage --
   --------------------------

   procedure Illegal_Global_Usage (N : Node_Or_Entity_Id)  is
   begin
      Error_Msg_NE ("cannot use global variable & of deep type", N, N);
      Error_Msg_N ("\without prior declaration in a Global aspect", N);
      Errout.Finalize (Last_Call => True);
      Errout.Output_Messages;
      Exit_Program (E_Errors);
   end Illegal_Global_Usage;

   -------------
   -- Is_Deep --
   -------------

   function Is_Deep (E : Entity_Id) return Boolean is
      function Is_Private_Entity_Mode_Off (E : Entity_Id) return Boolean;
      function Is_Private_Entity_Mode_Off (E : Entity_Id) return Boolean is
         Decl : Node_Id;
         Pack_Decl : Node_Id;

      begin
         if Is_Itype (E) then
            Decl := Associated_Node_For_Itype (E);
         else
            Decl := Parent (E);
         end if;

         Pack_Decl := Parent (Parent (Decl));

         if Nkind (Pack_Decl) /= N_Package_Declaration then
            return False;
         end if;

         return
           Present (SPARK_Aux_Pragma (Defining_Entity (Pack_Decl)))
           and then Get_SPARK_Mode_From_Annotation
             (SPARK_Aux_Pragma (Defining_Entity (Pack_Decl))) = Off;
      end Is_Private_Entity_Mode_Off;

   begin
      pragma Assert (Is_Type (E));
      case Ekind (E) is
         when Scalar_Kind =>
            return False;

         when Access_Kind =>
            return True;

         --  Just check the depth of its component type

         when E_Array_Type
            | E_Array_Subtype
         =>
            return Is_Deep (Component_Type (E));

         when E_String_Literal_Subtype =>
            return False;

         --  Per RM 8.11 for class-wide types

         when E_Class_Wide_Subtype
            | E_Class_Wide_Type
         =>
            return True;

         --  ??? What about hidden components

         when E_Record_Type
            | E_Record_Subtype
         =>
            declare
               Elmt : Entity_Id;

            begin
               Elmt := First_Component_Or_Discriminant (E);
               while Present (Elmt) loop
                  if Is_Deep (Etype (Elmt)) then
                     return True;
                  else
                     Next_Component_Or_Discriminant (Elmt);
                  end if;
               end loop;
               return False;
            end;

         when Private_Kind =>
            if Is_Private_Entity_Mode_Off (E) then
               return False;
            else
               if Present (Full_View (E)) then
                  return Is_Deep (Full_View (E));
               else
                  return True;
               end if;
            end if;

         when E_Incomplete_Type
            | E_Incomplete_Subtype
         =>
            return True;

         --  No problem with synchronized types

         when E_Protected_Type
            | E_Protected_Subtype
            | E_Task_Subtype
            | E_Task_Type
          =>
            return False;

         when E_Exception_Type =>
            return False;

         when others =>
            raise Program_Error;
      end case;
   end Is_Deep;

   ----------------
   -- Perm_Error --
   ----------------

   procedure Perm_Error
     (N : Node_Id;
      Perm : Perm_Kind;
      Found_Perm : Perm_Kind)
   is
      procedure Set_Root_Object
        (Path  : Node_Id;
         Obj   : out Entity_Id;
         Deref : out Boolean);
      --  Set the root object Obj, and whether the path contains a dereference,
      --  from a path Path.

      ---------------------
      -- Set_Root_Object --
      ---------------------

      procedure Set_Root_Object
        (Path  : Node_Id;
         Obj   : out Entity_Id;
         Deref : out Boolean)
      is
      begin
         case Nkind (Path) is
            when N_Identifier
               | N_Expanded_Name
            =>
               Obj := Entity (Path);
               Deref := False;

            when N_Type_Conversion
               | N_Unchecked_Type_Conversion
               | N_Qualified_Expression
            =>
               Set_Root_Object (Expression (Path), Obj, Deref);

            when N_Indexed_Component
               | N_Selected_Component
               | N_Slice
            =>
               Set_Root_Object (Prefix (Path), Obj, Deref);

            when N_Explicit_Dereference =>
               Set_Root_Object (Prefix (Path), Obj, Deref);
               Deref := True;

            when others =>
               raise Program_Error;
         end case;
      end Set_Root_Object;
      --  Local variables

      Root : Entity_Id;
      Is_Deref : Boolean;

   --  Start of processing for Perm_Error

   begin
      Set_Root_Object (N, Root, Is_Deref);

      if Is_Deref then
         Error_Msg_NE
           ("insufficient permission on dereference from &", N, Root);
      else
         Error_Msg_NE ("insufficient permission for &", N, Root);
      end if;

      Perm_Mismatch (Perm, Found_Perm, N);
   end Perm_Error;

   -------------------------------
   -- Perm_Error_Subprogram_End --
   -------------------------------

   procedure Perm_Error_Subprogram_End
     (E          : Entity_Id;
      Subp       : Entity_Id;
      Perm       : Perm_Kind;
      Found_Perm : Perm_Kind)
   is
   begin
      Error_Msg_Node_2 := Subp;
      Error_Msg_NE ("insufficient permission for & when returning from &",
                    Subp, E);
      Perm_Mismatch (Perm, Found_Perm, Subp);
   end Perm_Error_Subprogram_End;

   ------------------
   -- Process_Path --
   ------------------

   procedure Process_Path (N : Node_Id) is
      Root    : constant Entity_Id := Get_Enclosing_Object (N);
      State_N : Perm_Kind;
   begin
      --  We ignore if yielding to synchronized

      if Present (Root)
        and then Is_Synchronized_Object (Root)
      then
         return;
      end if;

      State_N := Get_Perm (N);

      case Current_Checking_Mode is

         --  Check permission R, do nothing

         when Read =>

            --  This condition should be removed when removing the read
            --  checking mode.

            return;

         when Move =>

            --  The rhs object in an assignment statement (including copy in
            --  and copy back) should be in the Unrestricted or Moved state.
            --  Otherwise the move is not allowed.
            --  This applies to both stand-alone and composite objects.
            --  If the state of the source is Moved, then a warning message
            --  is prompt to make the user aware of reading a nullified
            --  object.

            if State_N /= Unrestricted and State_N /= Moved then
               Perm_Error (N, Unrestricted, State_N);
               return;
            end if;

            --  In the AI, after moving a path nothing to do since the rhs
            --  object was in the Unrestricted state and it shall be
            --  refreshed to Unrestricted. The object should be nullified
            --  however. To avoid moving again a name that has already been
            --  moved, in this implementation we set the state of the moved
            --  object to "Moved". This shall be used to prompt a warning
            --  when manipulating a null pointer and also to implement
            --  the no aliasing parameter restriction.

            if State_N = Moved then
               Error_Msg_N ("?the source or one of its extensions has"
                            & " already been moved", N);
            end if;

            declare
               --  Set state to Moved to the path and any of its prefixes

               Tree : constant Perm_Tree_Access :=
                 Set_Perm_Prefixes (N, Moved);

            begin
               if Tree = null then

                  --  We went through a function call, no permission to
                  --  modify.

                  return;
               end if;

               --  Set state to Moved on any strict extension of the path

               Set_Perm_Extensions (Tree, Moved);
            end;

         when Assign =>

            --  The lhs object in an assignment statement (including copy in
            --  and copy back) should be in the Unrestricted state.
            --  Otherwise the move is not allowed.
            --  This applies to both stand-alone and composite objects.

            if State_N /= Unrestricted and State_N /= Moved then
               Perm_Error (N, Unrestricted, State_N);
               return;
            end if;

            --  After assigning to a path nothing to do since it was in the
            --  Unrestricted state and it would be refreshed to
            --  Unrestricted.

         when Borrow =>

            --  Borrowing is only allowed on Unrestricted objects.

            if State_N /= Unrestricted and State_N /= Moved then
               Perm_Error (N, Unrestricted, State_N);
            end if;

            if State_N = Moved then
               Error_Msg_N ("?the source or one of its extensions has"
                            & " already been moved", N);
            end if;

            declare
               --  Set state to Borrowed to the path and any of its prefixes

               Tree : constant Perm_Tree_Access :=
                 Set_Perm_Prefixes (N, Borrowed);

            begin
               if Tree = null then

                  --  We went through a function call, no permission to
                  --  modify.

                  return;
               end if;

               --  Set state to Borrowed on any strict extension of the path

               Set_Perm_Extensions (Tree, Borrowed);
            end;

         when Observe =>
            if State_N /= Unrestricted
              and then State_N /= Observed
            then
               Perm_Error (N, Observed, State_N);
            end if;

            declare
               --  Set permission to Observed on the path and any of its
               --  prefixes if it is of a deep type. Actually, some operation
               --  like reading from an object of access type is considered as
               --  observe while it should not affect the permissions of
               --  the considered tree.

               Tree : Perm_Tree_Access;

            begin
               if Is_Deep (Etype (N)) then
                  Tree := Set_Perm_Prefixes (N, Observed);
               else
                  Tree := null;
               end if;

               if Tree = null then

                  --  We went through a function call, no permission to
                  --  modify.

                  return;
               end if;

               --  Set permissions to No on any strict extension of the path

               Set_Perm_Extensions (Tree, Observed);
            end;
      end case;
   end Process_Path;

   -------------------------
   -- Return_Declarations --
   -------------------------

   procedure Return_Declarations (L : List_Id) is
      procedure Return_Declaration (Decl : Node_Id);
      --  Check correct permissions for every declared object

      ------------------------
      -- Return_Declaration --
      ------------------------

      procedure Return_Declaration (Decl : Node_Id) is
      begin
         if Nkind (Decl) = N_Object_Declaration then

            --  Check RW for object declared, unless the object has never been
            --  initialized.

            if Get (Current_Initialization_Map,
                    Unique_Entity (Defining_Identifier (Decl))) = False
            then
               return;
            end if;

            declare
               Elem : constant Perm_Tree_Access :=
                 Get (Current_Perm_Env,
                      Unique_Entity (Defining_Identifier (Decl)));

            begin
               if Elem = null then

                  --  Here we are on a declaration. Hence it should have been
                  --  added in the environment when analyzing this node with
                  --  mode Read. Hence it is not possible to find a null
                  --  pointer here.

                  --  Hash_Table_Error

                  raise Program_Error;
               end if;

               if Permission (Elem) /= Unrestricted then
                  Perm_Error (Decl, Unrestricted, Permission (Elem));
               end if;
            end;
         end if;
      end Return_Declaration;
      --  Local Variables

      N : Node_Id;

   --  Start of processing for Return_Declarations

   begin
      N := First (L);
      while Present (N) loop
         Return_Declaration (N);
         Next (N);
      end loop;
   end Return_Declarations;

   --------------------
   -- Return_Globals --
   --------------------

   procedure Return_Globals (Subp : Entity_Id) is
      procedure Return_Globals_From_List
        (First_Item : Node_Id;
         Kind       : Formal_Kind);
      --  Return global items from the list starting at Item

      procedure Return_Globals_Of_Mode (Global_Mode : Name_Id);
      --  Return global items for the mode Global_Mode

      ------------------------------
      -- Return_Globals_From_List --
      ------------------------------

      procedure Return_Globals_From_List
        (First_Item : Node_Id;
         Kind       : Formal_Kind)
      is
         Item : Node_Id := First_Item;
         E    : Entity_Id;

      begin
         while Present (Item) loop
            E := Entity (Item);

            --  Ignore abstract states, which play no role in pointer aliasing

            if Ekind (E) = E_Abstract_State then
               null;
            else
               Return_The_Global (E, Kind, Subp);
            end if;
            Next_Global (Item);
         end loop;
      end Return_Globals_From_List;

      ----------------------------
      -- Return_Globals_Of_Mode --
      ----------------------------

      procedure Return_Globals_Of_Mode (Global_Mode : Name_Id) is
         Kind : Formal_Kind;

      begin
         case Global_Mode is
            when Name_Input
               | Name_Proof_In
             =>
               Kind := E_In_Parameter;
            when Name_Output =>
               Kind := E_Out_Parameter;
            when Name_In_Out =>
               Kind := E_In_Out_Parameter;
            when others =>
               raise Program_Error;
         end case;

         --  Return both global items from Global and Refined_Global pragmas

         Return_Globals_From_List (First_Global (Subp, Global_Mode), Kind);
         Return_Globals_From_List
           (First_Global (Subp, Global_Mode, Refined => True), Kind);
      end Return_Globals_Of_Mode;

   --  Start of processing for Return_Globals

   begin
      Return_Globals_Of_Mode (Name_Proof_In);
      Return_Globals_Of_Mode (Name_Input);
      Return_Globals_Of_Mode (Name_Output);
      Return_Globals_Of_Mode (Name_In_Out);
   end Return_Globals;

   --------------------------------
   -- Return_Parameter_Or_Global --
   --------------------------------

   procedure Return_The_Global
     (Id   : Entity_Id;
      Mode : Formal_Kind;
      Subp : Entity_Id)
   is
      Elem : constant Perm_Tree_Access := Get (Current_Perm_Env, Id);
      pragma Assert (Elem /= null);

   begin
      --  Observed IN parameters and globals need not return a permission to
      --  the caller.

      if Mode = E_In_Parameter

      --  Check this for read-only globals.

      then
         if Permission (Elem) /= Unrestricted
           and then Permission (Elem) /= Observed
         then
            Perm_Error_Subprogram_End
              (E          => Id,
               Subp       => Subp,
               Perm       => Observed,
               Found_Perm => Permission (Elem));
         end if;

         --  All globals of mode out or in/out should return with mode
         --  Unrestricted.

      else
         if Permission (Elem) /= Unrestricted then
            Perm_Error_Subprogram_End
              (E          => Id,
               Subp       => Subp,
               Perm       => Unrestricted,
               Found_Perm => Permission (Elem));
         end if;
      end if;
   end Return_The_Global;

   -------------------------
   -- Set_Perm_Extensions --
   -------------------------

   procedure Set_Perm_Extensions (T : Perm_Tree_Access; P : Perm_Kind) is
      procedure Free_Perm_Tree_Children (T : Perm_Tree_Access);
      procedure Free_Perm_Tree_Children (T : Perm_Tree_Access) is
      begin
         case Kind (T) is
            when Entire_Object =>
               null;

            when Reference =>
               Free_Perm_Tree (T.all.Tree.Get_All);

            when Array_Component =>
               Free_Perm_Tree (T.all.Tree.Get_Elem);

            --  Free every Component subtree

            when Record_Component =>
               declare
                  Comp : Perm_Tree_Access;

               begin
                  Comp := Perm_Tree_Maps.Get_First (Component (T));
                  while Comp /= null loop
                     Free_Perm_Tree (Comp);
                     Comp := Perm_Tree_Maps.Get_Next (Component (T));
                  end loop;

                  Free_Perm_Tree (T.all.Tree.Other_Components);
               end;
         end case;
      end Free_Perm_Tree_Children;

      Son : constant Perm_Tree :=
        Perm_Tree'
          (Kind                => Entire_Object,
           Is_Node_Deep        => Is_Node_Deep (T),
           Permission          => Permission (T),
           Children_Permission => P);

   begin
      Free_Perm_Tree_Children (T);
      T.all.Tree := Son;
   end Set_Perm_Extensions;

   ------------------------------
   -- Set_Perm_Prefixes --
   ------------------------------

   function Set_Perm_Prefixes
     (N        : Node_Id;
      New_Perm : Perm_Kind)
      return Perm_Tree_Access
   is
   begin

      case Nkind (N) is

         when N_Identifier
            | N_Expanded_Name
            | N_Defining_Identifier
         =>
            if Nkind (N) = N_Defining_Identifier
              and then New_Perm = Borrowed
            then
               raise Program_Error;
            end if;

            declare
               P : Node_Id;
               C : Perm_Tree_Access;

            begin
               if Nkind (N) = N_Defining_Identifier then
                  P := N;
               else
                  P := Entity (N);
               end if;

               C := Get (Current_Perm_Env, Unique_Entity (P));
               pragma Assert (C /= null);

               --  Setting the initialization map to True, so that this
               --  variable cannot be ignored anymore when looking at end
               --  of elaboration of package.

               Set (Current_Initialization_Map, Unique_Entity (P), True);
               if New_Perm = Observed
                 and then C = null
               then

                  --  No null possible here, there are no parents for the path.
                  --  This means we are using a global variable without adding
                  --  it in environment with a global aspect.

                  Illegal_Global_Usage (N);
               end if;

               C.all.Tree.Permission := New_Perm;
               return C;
            end;

         when N_Type_Conversion
            | N_Unchecked_Type_Conversion
            | N_Qualified_Expression
         =>
            return Set_Perm_Prefixes (Expression (N), New_Perm);

         when N_Parameter_Specification =>
            raise Program_Error;

            --  We set the permission tree of its prefix, and then we extract
            --  our subtree from the returned pointer and assign an adequate
            --  permission to it, if unfolded. If folded, we unroll the tree
            --  in one step.

         when N_Selected_Component =>
            declare
               C : constant Perm_Tree_Access :=
                 Set_Perm_Prefixes (Prefix (N), New_Perm);

            begin
               if C = null then

                  --  We went through a function call, do nothing

                  return null;
               end if;

               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Record_Component);

               if Kind (C) = Record_Component then
                  --  The tree is unfolded. We just modify the permission and
                  --  return the record subtree.

                  declare
                     Selected_Component : constant Entity_Id :=
                       Entity (Selector_Name (N));

                     Selected_C : Perm_Tree_Access :=
                       Perm_Tree_Maps.Get
                         (Component (C), Selected_Component);

                  begin
                     if Selected_C = null then
                        Selected_C := Other_Components (C);
                     end if;

                     pragma Assert (Selected_C /= null);
                     Selected_C.all.Tree.Permission := New_Perm;
                     return Selected_C;
                  end;

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace the node with
                     --  Record_Component.

                     Elem : Node_Id;

                     --  Create an empty hash table

                     Hashtbl : Perm_Tree_Maps.Instance;

                     --  We create the unrolled nodes, that will all have same
                     --  permission than parent.

                     Son           : Perm_Tree_Access;
                     Children_Perm : constant Perm_Kind :=
                       Children_Permission (C);

                  begin
                     --  We change the current node from Entire_Object to
                     --  Record_Component with same permission and an empty
                     --  hash table as component list.

                     C.all.Tree :=
                       (Kind         => Record_Component,
                        Is_Node_Deep => Is_Node_Deep (C),
                        Permission   => Permission (C),
                        Component    => Hashtbl,
                        Other_Components =>
                           new Perm_Tree_Wrapper'
                          (Tree =>
                               (Kind                => Entire_Object,
                                Is_Node_Deep        => True,
                                Permission          => Children_Perm,
                                Children_Permission => Children_Perm)
                          ));

                     --  We fill the hash table with all sons of the record,
                     --  with basic Entire_Objects nodes.

                     Elem := First_Component_Or_Discriminant
                       (Etype (Prefix (N)));

                     while Present (Elem) loop
                        Son := new Perm_Tree_Wrapper'
                          (Tree =>
                             (Kind                => Entire_Object,
                              Is_Node_Deep        => Is_Deep (Etype (Elem)),
                              Permission          => Children_Perm,
                              Children_Permission => Children_Perm));

                        Perm_Tree_Maps.Set (C.all.Tree.Component, Elem, Son);
                        Next_Component_Or_Discriminant (Elem);
                     end loop;
                     --  Now we set the right field to Borrowed, and then we
                     --  return the tree to the sons, so that the recursion can
                     --  continue.

                     declare
                        Selected_Component : constant Entity_Id :=
                          Entity (Selector_Name (N));
                        Selected_C : Perm_Tree_Access :=
                          Perm_Tree_Maps.Get
                            (Component (C), Selected_Component);

                     begin
                        if Selected_C = null then
                           Selected_C := Other_Components (C);
                        end if;

                        pragma Assert (Selected_C /= null);
                        Selected_C.all.Tree.Permission := New_Perm;
                        return Selected_C;
                     end;
                  end;
               else
                  raise Program_Error;
               end if;
            end;

            --  We set the permission tree of its prefix, and then we extract
            --  from the returned pointer the subtree and assign an adequate
            --  permission to it, if unfolded. If folded, we unroll the tree in
            --  one step.

         when N_Indexed_Component
            | N_Slice
         =>
            declare
               C : constant Perm_Tree_Access :=
                 Set_Perm_Prefixes (Prefix (N), New_Perm);

            begin
               if C = null then

                  --  We went through a function call, do nothing

                  return null;
               end if;

               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Array_Component);

               if Kind (C) = Array_Component then

                  --  The tree is unfolded. We just modify the permission and
                  --  return the elem subtree.

                  pragma Assert (Get_Elem (C) /= null);
                  C.all.Tree.Get_Elem.all.Tree.Permission := New_Perm;
                  return Get_Elem (C);

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace node with Array_Component.

                     Son : Perm_Tree_Access;

                  begin
                     Son := new Perm_Tree_Wrapper'
                       (Tree =>
                          (Kind                => Entire_Object,
                           Is_Node_Deep        => Is_Node_Deep (C),
                           Permission          => New_Perm,
                           Children_Permission => Children_Permission (C)));

                     --  Children_Permission => Children_Permission (C)
                     --  this line should be checked maybe New_Perm
                     --  instead of Children_Permission (C)

                     --  We change the current node from Entire_Object
                     --  to Array_Component with same permission and the
                     --  previously defined son.

                     C.all.Tree := (Kind         => Array_Component,
                                    Is_Node_Deep => Is_Node_Deep (C),
                                    Permission   => New_Perm,
                                    Get_Elem     => Son);
                     return Get_Elem (C);
                  end;
               else
                  raise Program_Error;
               end if;
            end;

            --  We set the permission tree of its prefix, and then we extract
            --  from the returned pointer the subtree and assign an adequate
            --  permission to it, if unfolded. If folded, we unroll the tree
            --  at one step.

         when N_Explicit_Dereference =>
            declare
               C : constant Perm_Tree_Access :=
                Set_Perm_Prefixes (Prefix (N), New_Perm);

            begin
               if C = null then

                  --  We went through a function call. Do nothing.

                  return null;
               end if;

               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Reference);

               if Kind (C) = Reference then

                  --  The tree is unfolded. We just modify the permission and
                  --  return the elem subtree.

                  pragma Assert (Get_All (C) /= null);
                  C.all.Tree.Get_All.all.Tree.Permission := New_Perm;
                  return Get_All (C);

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace the node with Reference.

                     Son : Perm_Tree_Access;

                  begin
                     Son := new Perm_Tree_Wrapper'
                       (Tree =>
                          (Kind                => Entire_Object,
                           Is_Node_Deep        => Is_Deep (Etype (N)),
                           Permission          => New_Perm,
                           Children_Permission => Children_Permission (C)));

                     --  We change the current node from Entire_Object to
                     --  Reference with Borrowed and the previous son.

                     pragma Assert (Is_Node_Deep (C));
                     C.all.Tree := (Kind         => Reference,
                                    Is_Node_Deep => Is_Node_Deep (C),
                                    Permission   => New_Perm,
                                    Get_All      => Son);
                     return Get_All (C);
                  end;

               else
                  raise Program_Error;
               end if;
            end;

         when N_Function_Call =>
            return null;

         when others =>
            raise Program_Error;
      end case;
   end Set_Perm_Prefixes;

   ------------------------------
   -- Set_Perm_Prefixes_Borrow --
   ------------------------------

   function Set_Perm_Prefixes_Borrow (N : Node_Id) return Perm_Tree_Access
   is
   begin
      pragma Assert (Current_Checking_Mode = Borrow);
      case Nkind (N) is

         when N_Identifier
            | N_Expanded_Name
         =>
            declare
               P : constant Node_Id := Entity (N);
               C : constant Perm_Tree_Access :=
                 Get (Current_Perm_Env, Unique_Entity (P));
               pragma Assert (C /= null);

            begin
               --  Setting the initialization map to True, so that this
               --  variable cannot be ignored anymore when looking at end
               --  of elaboration of package.

               Set (Current_Initialization_Map, Unique_Entity (P), True);
               C.all.Tree.Permission := Borrowed;
               return C;
            end;

         when N_Type_Conversion
            | N_Unchecked_Type_Conversion
            | N_Qualified_Expression
         =>
            return Set_Perm_Prefixes_Borrow (Expression (N));

         when N_Parameter_Specification
            | N_Defining_Identifier
         =>
            raise Program_Error;

            --  We set the permission tree of its prefix, and then we extract
            --  our subtree from the returned pointer and assign an adequate
            --  permission to it, if unfolded. If folded, we unroll the tree
            --  in one step.

         when N_Selected_Component =>
            declare
               C : constant Perm_Tree_Access :=
                 Set_Perm_Prefixes_Borrow (Prefix (N));

            begin
               if C = null then

                  --  We went through a function call, do nothing

                  return null;
               end if;

               --  The permission of the returned node should be No

               pragma Assert (Permission (C) = Borrowed);
               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Record_Component);

               if Kind (C) = Record_Component then

                  --  The tree is unfolded. We just modify the permission and
                  --  return the record subtree.

                  declare
                     Selected_Component : constant Entity_Id :=
                       Entity (Selector_Name (N));
                     Selected_C : Perm_Tree_Access :=
                       Perm_Tree_Maps.Get
                         (Component (C), Selected_Component);

                  begin
                     if Selected_C = null then
                        Selected_C := Other_Components (C);
                     end if;

                     pragma Assert (Selected_C /= null);
                     Selected_C.all.Tree.Permission := Borrowed;
                     return Selected_C;
                  end;

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace the node with
                     --  Record_Component.

                     Elem : Node_Id;

                     --  Create an empty hash table

                     Hashtbl : Perm_Tree_Maps.Instance;

                     --  We create the unrolled nodes, that will all have same
                     --  permission than parent.

                     Son : Perm_Tree_Access;
                     ChildrenPerm : constant Perm_Kind :=
                       Children_Permission (C);

                  begin
                     --  We change the current node from Entire_Object to
                     --  Record_Component with same permission and an empty
                     --  hash table as component list.

                     C.all.Tree :=
                       (Kind         => Record_Component,
                        Is_Node_Deep => Is_Node_Deep (C),
                        Permission   => Permission (C),
                        Component    => Hashtbl,
                        Other_Components =>
                           new Perm_Tree_Wrapper'
                          (Tree =>
                               (Kind                => Entire_Object,
                                Is_Node_Deep        => True,
                                Permission          => ChildrenPerm,
                                Children_Permission => ChildrenPerm)
                          ));

                     --  We fill the hash table with all sons of the record,
                     --  with basic Entire_Objects nodes.

                     Elem := First_Component_Or_Discriminant
                       (Etype (Prefix (N)));

                     while Present (Elem) loop
                        Son := new Perm_Tree_Wrapper'
                          (Tree =>
                             (Kind                => Entire_Object,
                              Is_Node_Deep        => Is_Deep (Etype (Elem)),
                              Permission          => ChildrenPerm,
                              Children_Permission => ChildrenPerm));
                        Perm_Tree_Maps.Set (C.all.Tree.Component, Elem, Son);
                        Next_Component_Or_Discriminant (Elem);
                     end loop;

                     --  Now we set the right field to Borrowed, and then we
                     --  return the tree to the sons, so that the recursion can
                     --  continue.

                     declare
                        Selected_Component : constant Entity_Id :=
                          Entity (Selector_Name (N));
                        Selected_C : Perm_Tree_Access := Perm_Tree_Maps.Get
                          (Component (C), Selected_Component);

                     begin
                        if Selected_C = null then
                           Selected_C := Other_Components (C);
                        end if;

                        pragma Assert (Selected_C /= null);
                        Selected_C.all.Tree.Permission := Borrowed;
                        return Selected_C;
                     end;
                  end;

               else
                  raise Program_Error;
               end if;
            end;

            --  We set the permission tree of its prefix, and then we extract
            --  from the returned pointer the subtree and assign an adequate
            --  permission to it, if unfolded. If folded, we unroll the tree in
            --  one step.

         when N_Indexed_Component
            | N_Slice
         =>
            declare
               C : constant Perm_Tree_Access :=
                 Set_Perm_Prefixes_Borrow (Prefix (N));

            begin
               if C = null then

                  --  We went through a function call, do nothing

                  return null;
               end if;

               pragma Assert (Permission (C) = Borrowed);
               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Array_Component);

               if Kind (C) = Array_Component then

                  --  The tree is unfolded. We just modify the permission and
                  --  return the elem subtree.

                  pragma Assert (Get_Elem (C) /= null);
                  C.all.Tree.Get_Elem.all.Tree.Permission := Borrowed;
                  return Get_Elem (C);

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace node with Array_Component.

                     Son : Perm_Tree_Access;

                  begin
                     Son := new Perm_Tree_Wrapper'
                       (Tree =>
                          (Kind                => Entire_Object,
                           Is_Node_Deep        => Is_Node_Deep (C),
                           Permission          => Borrowed,
                           Children_Permission => Children_Permission (C)));

                     --  We change the current node from Entire_Object
                     --  to Array_Component with same permission and the
                     --  previously defined son.

                     C.all.Tree := (Kind         => Array_Component,
                                    Is_Node_Deep => Is_Node_Deep (C),
                                    Permission   => Borrowed,
                                    Get_Elem     => Son);
                     return Get_Elem (C);
                  end;

               else
                  raise Program_Error;
               end if;
            end;

            --  We set the permission tree of its prefix, and then we extract
            --  from the returned pointer the subtree and assign an adequate
            --  permission to it, if unfolded. If folded, we unroll the tree
            --  at one step.

         when N_Explicit_Dereference =>
            declare
               C : constant Perm_Tree_Access :=
                 Set_Perm_Prefixes_Borrow (Prefix (N));

            begin
               if C = null then

                  --  We went through a function call. Do nothing.

                  return null;
               end if;

               --  The permission of the returned node should be No

               pragma Assert (Permission (C) = Borrowed);
               pragma Assert (Kind (C) = Entire_Object
                              or else Kind (C) = Reference);

               if Kind (C) = Reference then

                  --  The tree is unfolded. We just modify the permission and
                  --  return the elem subtree.

                  pragma Assert (Get_All (C) /= null);
                  C.all.Tree.Get_All.all.Tree.Permission := Borrowed;
                  return Get_All (C);

               elsif Kind (C) = Entire_Object then
                  declare
                     --  Expand the tree. Replace the node with Reference.

                     Son : Perm_Tree_Access;

                  begin
                     Son := new Perm_Tree_Wrapper'
                       (Tree =>
                          (Kind                => Entire_Object,
                           Is_Node_Deep        => Is_Deep (Etype (N)),
                           Permission          => Borrowed,
                           Children_Permission => Children_Permission (C)));

                     --  We change the current node from Entire_Object to
                     --  Reference with Borrowed and the previous son.

                     pragma Assert (Is_Node_Deep (C));
                     C.all.Tree := (Kind         => Reference,
                                    Is_Node_Deep => Is_Node_Deep (C),
                                    Permission   => Borrowed,
                                    Get_All      => Son);
                     return Get_All (C);
                  end;

               else
                  raise Program_Error;
               end if;
            end;

         when N_Function_Call =>
            return null;

         when others =>
            raise Program_Error;
      end case;
   end Set_Perm_Prefixes_Borrow;

   -------------------
   -- Setup_Globals --
   -------------------

   procedure Setup_Globals (Subp : Entity_Id) is
      procedure Setup_Globals_From_List
        (First_Item : Node_Id;
         Kind       : Formal_Kind);
      --  Set up global items from the list starting at Item

      procedure Setup_Globals_Of_Mode (Global_Mode : Name_Id);
      --  Set up global items for the mode Global_Mode

      -----------------------------
      -- Setup_Globals_From_List --
      -----------------------------

      procedure Setup_Globals_From_List
        (First_Item : Node_Id;
         Kind       : Formal_Kind)
      is
         Item : Node_Id := First_Item;
         E    : Entity_Id;

      begin
         while Present (Item) loop
            E := Entity (Item);

            --  Ignore abstract states, which play no role in pointer aliasing

            if Ekind (E) = E_Abstract_State then
               null;
            else
               Setup_Parameter_Or_Global (E, Kind, Global_Var => True);
            end if;
            Next_Global (Item);
         end loop;
      end Setup_Globals_From_List;

      ---------------------------
      -- Setup_Globals_Of_Mode --
      ---------------------------

      procedure Setup_Globals_Of_Mode (Global_Mode : Name_Id) is
         Kind : Formal_Kind;

      begin
         case Global_Mode is
            when Name_Input
               | Name_Proof_In
            =>
               Kind := E_In_Parameter;

            when Name_Output =>
               Kind := E_Out_Parameter;

            when Name_In_Out =>
               Kind := E_In_Out_Parameter;

            when others =>
               raise Program_Error;
         end case;

         --  Set up both global items from Global and Refined_Global pragmas

         Setup_Globals_From_List (First_Global (Subp, Global_Mode), Kind);
         Setup_Globals_From_List
           (First_Global (Subp, Global_Mode, Refined => True), Kind);
      end Setup_Globals_Of_Mode;

   --  Start of processing for Setup_Globals

   begin
      Setup_Globals_Of_Mode (Name_Proof_In);
      Setup_Globals_Of_Mode (Name_Input);
      Setup_Globals_Of_Mode (Name_Output);
      Setup_Globals_Of_Mode (Name_In_Out);
   end Setup_Globals;

   -------------------------------
   -- Setup_Parameter_Or_Global --
   -------------------------------

   procedure Setup_Parameter_Or_Global
     (Id         : Entity_Id;
      Mode       : Formal_Kind;
      Global_Var : Boolean)
   is
      Elem     : Perm_Tree_Access;
      View_Typ : Entity_Id;

   begin
      if Present (Full_View (Etype (Id))) then
         View_Typ := Full_View (Etype (Id));
      else
         View_Typ := Etype (Id);
      end if;

      Elem := new Perm_Tree_Wrapper'
        (Tree =>
           (Kind                => Entire_Object,
            Is_Node_Deep        => Is_Deep (Etype (Id)),
            Permission          => Unrestricted,
            Children_Permission => Unrestricted));

      case Mode is

         --  All out and in out parameters are considered to be unrestricted.
         --  They are whether borrowed or moved. Ada Rules would restrict
         --  these permissions further. For example an in parameter cannot
         --  be written.

         --  In the following we deal with in parameters that can be observed.
         --  We only consider the observing cases.

         when E_In_Parameter =>

            --  Handling global variables as IN parameters here.
            --  Remove the following condition once it's decided how globals
            --  should be considered. ???
            --
            --  In SPARK, IN access-to-variable is an observe operation for
            --  a function, and a borrow operation for a procedure.

            if not Global_Var then
               if (Is_Access_Type (View_Typ)
                    and then Is_Access_Constant (View_Typ)
                    and then Is_Anonymous_Access_Type (View_Typ))
                 or else
                   (Is_Access_Type (View_Typ)
                     and then Ekind (Scope (Id)) = E_Function)
                 or else
                   (not Is_Access_Type (View_Typ)
                     and then Is_Deep (View_Typ)
                     and then not Is_Anonymous_Access_Type (View_Typ))
               then
                  Elem.all.Tree.Permission := Observed;
                  Elem.all.Tree.Children_Permission := Observed;

               else
                  Elem.all.Tree.Permission := Unrestricted;
                  Elem.all.Tree.Children_Permission := Unrestricted;
               end if;

            else
               Elem.all.Tree.Permission := Observed;
               Elem.all.Tree.Children_Permission := Observed;
            end if;

            --  When out or in/out formal or global parameters, we set them to
            --  the Unrestricted state. "We want to be able to assume that all
            --  relevant writable globals are unrestricted when a subprogram
            --  starts executing". Formal parameters of mode out or in/out
            --  are whether Borrowers or the targets of a move operation:
            --  they start theirs lives in the subprogram as Unrestricted.

         when others =>
            Elem.all.Tree.Permission := Unrestricted;
            Elem.all.Tree.Children_Permission := Unrestricted;
      end case;

      Set (Current_Perm_Env, Id, Elem);
   end Setup_Parameter_Or_Global;

   ----------------------
   -- Setup_Parameters --
   ----------------------

   procedure Setup_Parameters (Subp : Entity_Id) is Formal : Entity_Id;
   begin
      Formal := First_Formal (Subp);
      while Present (Formal) loop
         Setup_Parameter_Or_Global
           (Formal, Ekind (Formal), Global_Var => False);
         Next_Formal (Formal);
      end loop;
   end Setup_Parameters;

   -------------------------------
   -- Has_Ownership_Aspect_True --
   -------------------------------

   function Has_Ownership_Aspect_True
     (N   : Entity_Id;
      Msg : String)
      return Boolean
   is
   begin
      case Ekind (Etype (N)) is
         when Access_Kind =>
            if Ekind (Etype (N)) = E_General_Access_Type then
               Error_Msg_NE (Msg & " & not allowed " &
                    "(Named General Access type)", N, N);
               return False;

            else
               return True;
            end if;

         when E_Array_Type
            | E_Array_Subtype
         =>
            declare
               Com_Ty : constant Node_Id := Component_Type (Etype (N));
               Ret    : Boolean :=  Has_Ownership_Aspect_True (Com_Ty, "");

            begin
               if Nkind (Parent (N)) = N_Full_Type_Declaration and
                 Is_Anonymous_Access_Type (Com_Ty)
               then
                  Ret := False;
               end if;

               if not Ret then
                  Error_Msg_NE (Msg & " & not allowed "
                                & "(Components of Named General Access type or"
                                & " Anonymous type)", N, N);
               end if;
               return Ret;
            end;

         --  ??? What about hidden components

         when E_Record_Type
            | E_Record_Subtype
         =>
            declare
               Elmt        : Entity_Id;
               Elmt_T_Perm : Boolean := True;
               Elmt_Perm, Elmt_Anonym : Boolean;

            begin
               Elmt := First_Component_Or_Discriminant (Etype (N));
               while Present (Elmt) loop
                  Elmt_Perm := Has_Ownership_Aspect_True (Elmt,
                                                      "type of component");
                  Elmt_Anonym := Is_Anonymous_Access_Type (Etype (Elmt));
                  if Elmt_Anonym then
                     Error_Msg_NE
                       ("type of component & not allowed"
                        & " (Components of Anonymous type)", Elmt, Elmt);
                  end if;
                  Elmt_T_Perm := Elmt_T_Perm and Elmt_Perm and not Elmt_Anonym;
                  Next_Component_Or_Discriminant (Elmt);
               end loop;
               if not Elmt_T_Perm then
                     Error_Msg_NE
                       (Msg & " & not allowed (One or "
                        & "more components have Ownership Aspect False)",
                        N, N);
               end if;
               return Elmt_T_Perm;
            end;

         when others =>
            return True;
      end case;

   end Has_Ownership_Aspect_True;
end Sem_SPARK;