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------------------------------------------------------------------------------

--                                                                          --

--                         GNAT COMPILER COMPONENTS                         --

--                                                                          --

--                             S E M _ D I S T                              --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--          Copyright (C) 1992-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --

-- for  more details.  You should have  received  a copy of the GNU General --

-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --

-- http://www.gnu.org/licenses for a complete copy of the license.          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

with Atree;    use Atree;

with Casing;   use Casing;

with Einfo;    use Einfo;

with Errout;   use Errout;

with Exp_Dist; use Exp_Dist;

with Exp_Tss;  use Exp_Tss;

with Nlists;   use Nlists;

with Nmake;    use Nmake;

with Namet;    use Namet;

with Opt;      use Opt;

with Rtsfind;  use Rtsfind;

with Sem;      use Sem;

with Sem_Aux;  use Sem_Aux;

with Sem_Disp; use Sem_Disp;

with Sem_Eval; use Sem_Eval;

with Sem_Res;  use Sem_Res;

with Sem_Util; use Sem_Util;

with Sinfo;    use Sinfo;

with Stand;    use Stand;

with Stringt;  use Stringt;

with Tbuild;   use Tbuild;

with Uintp;    use Uintp;

package body Sem_Dist is

   -----------------------

   -- Local Subprograms --

   -----------------------

   procedure RAS_E_Dereference (Pref : Node_Id);

   --  Handles explicit dereference of Remote Access to Subprograms

   function Full_Qualified_Name (E : Entity_Id) return String_Id;

   --  returns the full qualified name of the entity in lower case

   -------------------------

   -- Add_Stub_Constructs --

   -------------------------

   procedure Add_Stub_Constructs (N : Node_Id) is

      U    : constant Node_Id := Unit (N);

      Spec : Entity_Id        := Empty;

      Exp : Node_Id := U;

      --  Unit that will be expanded

   begin

      pragma Assert (Distribution_Stub_Mode /= No_Stubs);

      if Nkind (U) = N_Package_Declaration then

         Spec := Defining_Entity (Specification (U));

      elsif Nkind (U) = N_Package_Body then

         Spec := Corresponding_Spec (U);

      else pragma Assert (Nkind (U) = N_Package_Instantiation);

         Exp  := Instance_Spec (U);

         Spec := Defining_Entity (Specification (Exp));

      end if;

      pragma Assert (Is_Shared_Passive (Spec)

        or else Is_Remote_Call_Interface (Spec));

      if Distribution_Stub_Mode = Generate_Caller_Stub_Body then

         if Is_Shared_Passive (Spec) then

            null;

         elsif Nkind (U) = N_Package_Body then

            Error_Msg_N

              ("Specification file expected from command line", U);

         else

            Expand_Calling_Stubs_Bodies (Exp);

         end if;

      else

         if Is_Shared_Passive (Spec) then

            Build_Passive_Partition_Stub (Exp);

         else

            Expand_Receiving_Stubs_Bodies (Exp);

         end if;

      end if;

   end Add_Stub_Constructs;

   ---------------------------------------

   -- Build_RAS_Primitive_Specification --

   ---------------------------------------

   function Build_RAS_Primitive_Specification

     (Subp_Spec          : Node_Id;

      Remote_Object_Type : Node_Id) return Node_Id

   is

      Loc : constant Source_Ptr := Sloc (Subp_Spec);

      Primitive_Spec : constant Node_Id :=

                         Copy_Specification (Loc,

                           Spec     => Subp_Spec,

                           New_Name => Name_uCall);

      Subtype_Mark_For_Self : Node_Id;

   begin

      if No (Parameter_Specifications (Primitive_Spec)) then

         Set_Parameter_Specifications (Primitive_Spec, New_List);

      end if;

      if Nkind (Remote_Object_Type) in N_Entity then

         Subtype_Mark_For_Self :=

           New_Occurrence_Of (Remote_Object_Type, Loc);

      else

         Subtype_Mark_For_Self := Remote_Object_Type;

      end if;

      Prepend_To (

        Parameter_Specifications (Primitive_Spec),

        Make_Parameter_Specification (Loc,

          Defining_Identifier =>

            Make_Defining_Identifier (Loc, Name_uS),

          Parameter_Type      =>

            Make_Access_Definition (Loc,

              Subtype_Mark =>

                Subtype_Mark_For_Self)));

      --  Trick later semantic analysis into considering this operation as a

      --  primitive (dispatching) operation of tagged type Obj_Type.

      Set_Comes_From_Source (

        Defining_Unit_Name (Primitive_Spec), True);

      return Primitive_Spec;

   end Build_RAS_Primitive_Specification;

   -------------------------

   -- Full_Qualified_Name --

   -------------------------

   function Full_Qualified_Name (E : Entity_Id) return String_Id is

      Ent         : Entity_Id := E;

      Parent_Name : String_Id := No_String;

   begin

      --  Deals properly with child units

      if Nkind (Ent) = N_Defining_Program_Unit_Name then

         Ent := Defining_Identifier (Ent);

      end if;

      --  Compute recursively the qualification (only "Standard" has no scope)

      if Present (Scope (Scope (Ent))) then

         Parent_Name := Full_Qualified_Name (Scope (Ent));

      end if;

      --  Every entity should have a name except some expanded blocks. Do not

      --  bother about those.

      if Chars (Ent) = No_Name then

         return Parent_Name;

      end if;

      --  Add a period between Name and qualification

      if Parent_Name /= No_String then

         Start_String (Parent_Name);

         Store_String_Char (Get_Char_Code ('.'));

      else

         Start_String;

      end if;

      --  Generates the entity name in upper case

      Get_Name_String (Chars (Ent));

      Set_Casing (All_Lower_Case);

      Store_String_Chars (Name_Buffer (1 .. Name_Len));

      return End_String;

   end Full_Qualified_Name;

   ------------------

   -- Get_PCS_Name --

   ------------------

   function Get_PCS_Name return PCS_Names is

   begin

      return

        Chars (Entity (Expression (Parent (RTE (RE_DSA_Implementation)))));

   end Get_PCS_Name;

   ---------------------

   -- Get_PCS_Version --

   ---------------------

   function Get_PCS_Version return Int is

      PCS_Version_Entity : Entity_Id;

      PCS_Version        : Int;

   begin

      if RTE_Available (RE_PCS_Version) then

         PCS_Version_Entity := RTE (RE_PCS_Version);

         pragma Assert (Ekind (PCS_Version_Entity) = E_Named_Integer);

         PCS_Version :=

           UI_To_Int (Expr_Value (Constant_Value (PCS_Version_Entity)));

      else

         --  Case of System.Partition_Interface.PCS_Version not found:

         --  return a null version.

         PCS_Version := 0;

      end if;

      return PCS_Version;

   end Get_PCS_Version;

   ------------------------

   -- Is_All_Remote_Call --

   ------------------------

   function Is_All_Remote_Call (N : Node_Id) return Boolean is

      Par : Node_Id;

   begin

      if Nkind_In (N, N_Function_Call, N_Procedure_Call_Statement)

        and then Nkind (Name (N)) in N_Has_Entity

        and then Is_Remote_Call_Interface (Entity (Name (N)))

        and then Has_All_Calls_Remote (Scope (Entity (Name (N))))

        and then Comes_From_Source (N)

      then

         Par := Parent (Entity (Name (N)));

         while Present (Par)

           and then (Nkind (Par) /= N_Package_Specification

                       or else Is_Wrapper_Package (Defining_Entity (Par)))

         loop

            Par := Parent (Par);

         end loop;

         if Present (Par) then

            return

              not Scope_Within_Or_Same (Current_Scope, Defining_Entity (Par));

         else

            return False;

         end if;

      else

         return False;

      end if;

   end Is_All_Remote_Call;

   ---------------------------------

   -- Is_RACW_Stub_Type_Operation --

   ---------------------------------

   function Is_RACW_Stub_Type_Operation (Op : Entity_Id) return Boolean is

      Dispatching_Type : Entity_Id;

   begin

      case Ekind (Op) is

         when E_Function | E_Procedure =>

            Dispatching_Type := Find_Dispatching_Type (Op);

            return Present (Dispatching_Type)

                     and then Is_RACW_Stub_Type (Dispatching_Type)

                     and then not Is_Internal (Op);

         when others =>

            return False;

      end case;

   end Is_RACW_Stub_Type_Operation;

   ------------------------------------

   -- Package_Specification_Of_Scope --

   ------------------------------------

   function Package_Specification_Of_Scope (E : Entity_Id) return Node_Id is

      N : Node_Id;

   begin

      N := Parent (E);

      while Nkind (N) /= N_Package_Specification loop

         N := Parent (N);

      end loop;

      return N;

   end Package_Specification_Of_Scope;

   --------------------------

   -- Process_Partition_ID --

   --------------------------

   procedure Process_Partition_Id (N : Node_Id) is

      Loc            : constant Source_Ptr := Sloc (N);

      Ety            : Entity_Id;

      Get_Pt_Id      : Node_Id;

      Get_Pt_Id_Call : Node_Id;

      Prefix_String  : String_Id;

      Typ            : constant Entity_Id := Etype (N);

   begin

      --  In case prefix is not a library unit entity, get the entity

      --  of library unit.

      Ety := Entity (Prefix (N));

      while (Present (Scope (Ety))

        and then Scope (Ety) /= Standard_Standard)

        and not Is_Child_Unit (Ety)

      loop

         Ety := Scope (Ety);

      end loop;

      --  Retrieve the proper function to call

      if Is_Remote_Call_Interface (Ety) then

         Get_Pt_Id := New_Occurrence_Of

           (RTE (RE_Get_Active_Partition_Id), Loc);

      elsif Is_Shared_Passive (Ety) then

         Get_Pt_Id := New_Occurrence_Of

           (RTE (RE_Get_Passive_Partition_Id), Loc);

      else

         Get_Pt_Id := New_Occurrence_Of

           (RTE (RE_Get_Local_Partition_Id), Loc);

      end if;

      --  Get and store the String_Id corresponding to the name of the

      --  library unit whose Partition_Id is needed.

      Get_Library_Unit_Name_String (Unit_Declaration_Node (Ety));

      Prefix_String := String_From_Name_Buffer;

      --  Build the function call which will replace the attribute

      if Is_Remote_Call_Interface (Ety) or else Is_Shared_Passive (Ety) then

         Get_Pt_Id_Call :=

           Make_Function_Call (Loc,

             Name => Get_Pt_Id,

             Parameter_Associations =>

               New_List (Make_String_Literal (Loc, Prefix_String)));

      else

         Get_Pt_Id_Call := Make_Function_Call (Loc, Get_Pt_Id);

      end if;

      --  Replace the attribute node by a conversion of the function call

      --  to the target type.

      Rewrite (N, Convert_To (Typ, Get_Pt_Id_Call));

      Analyze_And_Resolve (N, Typ);

   end Process_Partition_Id;

   ----------------------------------

   -- Process_Remote_AST_Attribute --

   ----------------------------------

   procedure Process_Remote_AST_Attribute

     (N        : Node_Id;

      New_Type : Entity_Id)

   is

      Loc                   : constant Source_Ptr := Sloc (N);

      Remote_Subp           : Entity_Id;

      Tick_Access_Conv_Call : Node_Id;

      Remote_Subp_Decl      : Node_Id;

      RS_Pkg_Specif         : Node_Id;

      RS_Pkg_E              : Entity_Id;

      RAS_Type              : Entity_Id := New_Type;

      Async_E               : Entity_Id;

      All_Calls_Remote_E    : Entity_Id;

      Attribute_Subp        : Entity_Id;

   begin

      --  Check if we have to expand the access attribute

      Remote_Subp := Entity (Prefix (N));

      if not Expander_Active or else Get_PCS_Name = Name_No_DSA then

         return;

      end if;

      if Ekind (RAS_Type) /= E_Record_Type then

         RAS_Type := Equivalent_Type (RAS_Type);

      end if;

      Attribute_Subp := TSS (RAS_Type, TSS_RAS_Access);

      pragma Assert (Present (Attribute_Subp));

      Remote_Subp_Decl := Unit_Declaration_Node (Remote_Subp);

      if Nkind (Remote_Subp_Decl) = N_Subprogram_Body then

         Remote_Subp := Corresponding_Spec (Remote_Subp_Decl);

         Remote_Subp_Decl := Unit_Declaration_Node (Remote_Subp);

      end if;

      RS_Pkg_Specif := Parent (Remote_Subp_Decl);

      RS_Pkg_E := Defining_Entity (RS_Pkg_Specif);

      Async_E :=

        Boolean_Literals (Ekind (Remote_Subp) = E_Procedure

                            and then Is_Asynchronous (Remote_Subp));

      All_Calls_Remote_E :=

        Boolean_Literals (Has_All_Calls_Remote (RS_Pkg_E));

      Tick_Access_Conv_Call :=

        Make_Function_Call (Loc,

          Name                   => New_Occurrence_Of (Attribute_Subp, Loc),

          Parameter_Associations =>

            New_List (

              Make_String_Literal (Loc,

                Strval => Full_Qualified_Name (RS_Pkg_E)),

              Build_Subprogram_Id (Loc, Remote_Subp),

              New_Occurrence_Of (Async_E, Loc),

              New_Occurrence_Of (All_Calls_Remote_E, Loc)));

      Rewrite (N, Tick_Access_Conv_Call);

      Analyze_And_Resolve (N, RAS_Type);

   end Process_Remote_AST_Attribute;

   ------------------------------------

   -- Process_Remote_AST_Declaration --

   ------------------------------------

   procedure Process_Remote_AST_Declaration (N : Node_Id) is

      Loc       : constant Source_Ptr := Sloc (N);

      User_Type : constant Node_Id    := Defining_Identifier (N);

      Scop      : constant Entity_Id  := Scope (User_Type);

      Is_RCI    : constant Boolean    := Is_Remote_Call_Interface (Scop);

      Is_RT     : constant Boolean    := Is_Remote_Types (Scop);

      Type_Def  : constant Node_Id    := Type_Definition (N);

      Parameter : Node_Id;

      Is_Degenerate : Boolean;

      --  True iff this RAS has an access formal parameter (see

      --  Exp_Dist.Add_RAS_Dereference_TSS for details).

      Subpkg      : constant Entity_Id :=

                      Make_Defining_Identifier (Loc,

                        New_Internal_Name ('S'));

      Subpkg_Decl : Node_Id;

      Subpkg_Body : Node_Id;

      Vis_Decls   : constant List_Id := New_List;

      Priv_Decls  : constant List_Id := New_List;

      Obj_Type : constant Entity_Id :=

                    Make_Defining_Identifier (Loc,

                      New_External_Name (Chars (User_Type), 'R'));

      Full_Obj_Type : constant Entity_Id :=

                        Make_Defining_Identifier (Loc,

                          Chars (Obj_Type));

      RACW_Type : constant Entity_Id :=

                    Make_Defining_Identifier (Loc,

                      New_External_Name (Chars (User_Type), 'P'));

      Fat_Type : constant Entity_Id :=

                   Make_Defining_Identifier (Loc,

                     Chars (User_Type));

      Fat_Type_Decl : Node_Id;

   begin

      Is_Degenerate := False;

      Parameter := First (Parameter_Specifications (Type_Def));

      while Present (Parameter) loop

         if Nkind (Parameter_Type (Parameter)) = N_Access_Definition then

            Error_Msg_N ("formal parameter& has anonymous access type?",

              Defining_Identifier (Parameter));

            Is_Degenerate := True;

            exit;

         end if;

         Next (Parameter);

      end loop;

      if Is_Degenerate then

         Error_Msg_NE

           ("remote access-to-subprogram type& can only be null?",

            Defining_Identifier (Parameter), User_Type);

         --  The only legal value for a RAS with a formal parameter of an

         --  anonymous access type is null, because it cannot be subtype-

         --  conformant with any legal remote subprogram declaration. In this

         --  case, we cannot generate a corresponding primitive operation.

      end if;

      if Get_PCS_Name = Name_No_DSA then

         return;

      end if;

      --  The tagged private type, primitive operation and RACW type associated

      --  with a RAS need to all be declared in a subpackage of the one that

      --  contains the RAS declaration, because the primitive of the object

      --  type, and the associated primitive of the stub type, need to be

      --  dispatching operations of these types, and the profile of the RAS

      --  might contain tagged types declared in the same scope.

      Append_To (Vis_Decls,

        Make_Private_Type_Declaration (Loc,

          Defining_Identifier => Obj_Type,

          Abstract_Present => True,

          Tagged_Present   => True,

          Limited_Present  => True));

      Append_To (Priv_Decls,

        Make_Full_Type_Declaration (Loc,

          Defining_Identifier => Full_Obj_Type,

          Type_Definition     =>

            Make_Record_Definition (Loc,

              Abstract_Present => True,

              Tagged_Present   => True,

              Limited_Present  => True,

              Null_Present     => True,

              Component_List   => Empty)));

      --  Trick semantic analysis into swapping the public and full view when

      --  freezing the public view.

      Set_Comes_From_Source (Full_Obj_Type, True);

      if not Is_Degenerate then

         Append_To (Vis_Decls,

           Make_Abstract_Subprogram_Declaration (Loc,

             Specification => Build_RAS_Primitive_Specification (

               Subp_Spec          => Type_Def,

               Remote_Object_Type => Obj_Type)));

      end if;

      Append_To (Vis_Decls,

        Make_Full_Type_Declaration (Loc,

          Defining_Identifier => RACW_Type,

          Type_Definition     =>

            Make_Access_To_Object_Definition (Loc,

              All_Present => True,

              Subtype_Indication =>

                Make_Attribute_Reference (Loc,

                  Prefix         => New_Occurrence_Of (Obj_Type, Loc),

                  Attribute_Name => Name_Class))));

      Set_Is_Remote_Call_Interface (RACW_Type, Is_RCI);

      Set_Is_Remote_Types (RACW_Type, Is_RT);

      Subpkg_Decl :=

        Make_Package_Declaration (Loc,

          Make_Package_Specification (Loc,

            Defining_Unit_Name   => Subpkg,

            Visible_Declarations => Vis_Decls,

            Private_Declarations => Priv_Decls,

            End_Label            => New_Occurrence_Of (Subpkg, Loc)));

      Set_Is_Remote_Call_Interface (Subpkg, Is_RCI);

      Set_Is_Remote_Types (Subpkg, Is_RT);

      Insert_After_And_Analyze (N, Subpkg_Decl);

      --  Generate package body to receive RACW calling stubs

      --  Note: Analyze_Declarations has an absolute requirement that the

      --  declaration list be non-empty, so provide dummy null statement here.

      Subpkg_Body :=

        Make_Package_Body (Loc,

          Defining_Unit_Name => Make_Defining_Identifier (Loc, Chars (Subpkg)),

          Declarations       => New_List (Make_Null_Statement (Loc)));

      Insert_After_And_Analyze (Subpkg_Decl, Subpkg_Body);

      --  Many parts of the analyzer and expander expect

      --  that the fat pointer type used to implement remote

      --  access to subprogram types be a record.

      --  Note: The structure of this type must be kept consistent

      --  with the code generated by Remote_AST_Null_Value for the

      --  corresponding 'null' expression.

      Fat_Type_Decl := Make_Full_Type_Declaration (Loc,

        Defining_Identifier => Fat_Type,

        Type_Definition     =>

          Make_Record_Definition (Loc,

            Component_List =>

              Make_Component_List (Loc,

                Component_Items => New_List (

                  Make_Component_Declaration (Loc,

                    Defining_Identifier =>

                      Make_Defining_Identifier (Loc, Name_Ras),

                    Component_Definition =>

                      Make_Component_Definition (Loc,

                        Aliased_Present     => False,

                        Subtype_Indication  =>

                          New_Occurrence_Of (RACW_Type, Loc)))))));

      Set_Equivalent_Type (User_Type, Fat_Type);

      Set_Corresponding_Remote_Type (Fat_Type, User_Type);

      Insert_After_And_Analyze (Subpkg_Body, Fat_Type_Decl);

      --  The reason we suppress the initialization procedure is that we know

      --  that no initialization is required (even if Initialize_Scalars mode

      --  is active), and there are order of elaboration problems if we do try

      --  to generate an init proc for this created record type.

      Set_Suppress_Init_Proc (Fat_Type);

      if Expander_Active then

         Add_RAST_Features (Parent (User_Type));

      end if;

   end Process_Remote_AST_Declaration;

   -----------------------

   -- RAS_E_Dereference --

   -----------------------

   procedure RAS_E_Dereference (Pref : Node_Id) is

      Loc             : constant Source_Ptr := Sloc (Pref);

      Call_Node       : Node_Id;

      New_Type        : constant Entity_Id := Etype (Pref);

      Explicit_Deref  : constant Node_Id   := Parent (Pref);

      Deref_Subp_Call : constant Node_Id   := Parent (Explicit_Deref);

      Deref_Proc      : Entity_Id;

      Params          : List_Id;

   begin

      if Nkind (Deref_Subp_Call) = N_Procedure_Call_Statement then

         Params := Parameter_Associations (Deref_Subp_Call);

         if Present (Params) then

            Prepend (Pref, Params);

         else

            Params := New_List (Pref);

         end if;

      elsif Nkind (Deref_Subp_Call) = N_Indexed_Component then

         Params := Expressions (Deref_Subp_Call);

         if Present (Params) then

            Prepend (Pref, Params);

         else

            Params := New_List (Pref);

         end if;

      else

         --  Context is not a call

         return;

      end if;

      if not Expander_Active or else Get_PCS_Name = Name_No_DSA then

         return;

      end if;

      Deref_Proc := TSS (New_Type, TSS_RAS_Dereference);

      pragma Assert (Present (Deref_Proc));

      if Ekind (Deref_Proc) = E_Function then

         Call_Node :=

           Make_Function_Call (Loc,

              Name                   => New_Occurrence_Of (Deref_Proc, Loc),

              Parameter_Associations => Params);

      else

         Call_Node :=

           Make_Procedure_Call_Statement (Loc,

              Name                   => New_Occurrence_Of (Deref_Proc, Loc),

              Parameter_Associations => Params);

      end if;

      Rewrite (Deref_Subp_Call, Call_Node);

      Analyze (Deref_Subp_Call);

   end RAS_E_Dereference;

   ------------------------------

   -- Remote_AST_E_Dereference --

   ------------------------------

   function Remote_AST_E_Dereference (P : Node_Id) return Boolean is

      ET : constant Entity_Id  := Etype (P);

   begin

      --  Perform the changes only on original dereferences, and only if

      --  we are generating code.

      if Comes_From_Source (P)

        and then Is_Record_Type (ET)

        and then (Is_Remote_Call_Interface (ET)

                   or else Is_Remote_Types (ET))

        and then Present (Corresponding_Remote_Type (ET))

        and then Nkind_In (Parent (Parent (P)), N_Procedure_Call_Statement,

                                                N_Indexed_Component)

        and then Expander_Active

      then

         RAS_E_Dereference (P);

         return True;

      else

         return False;

      end if;

   end Remote_AST_E_Dereference;

   ------------------------------

   -- Remote_AST_I_Dereference --

   ------------------------------

   function Remote_AST_I_Dereference (P : Node_Id) return Boolean is

      ET     : constant Entity_Id  := Etype (P);

      Deref  : Node_Id;

   begin

      if Comes_From_Source (P)

        and then (Is_Remote_Call_Interface (ET)

                   or else Is_Remote_Types (ET))

        and then Present (Corresponding_Remote_Type (ET))

        and then Ekind (Entity (P)) /= E_Function

      then

         Deref :=

           Make_Explicit_Dereference (Sloc (P),

             Prefix => Relocate_Node (P));

         Rewrite (P, Deref);

         Set_Etype (P, ET);

         RAS_E_Dereference (Prefix (P));

         return True;

      end if;

      return False;

   end Remote_AST_I_Dereference;

   ---------------------------

   -- Remote_AST_Null_Value --

   ---------------------------

   function Remote_AST_Null_Value

     (N   : Node_Id;

      Typ : Entity_Id) return Boolean

   is

      Loc         : constant Source_Ptr := Sloc (N);

      Target_Type : Entity_Id;

   begin

      if not Expander_Active or else Get_PCS_Name = Name_No_DSA then

         return False;

      elsif Ekind (Typ) = E_Access_Subprogram_Type

        and then (Is_Remote_Call_Interface (Typ)

                    or else Is_Remote_Types (Typ))

        and then Comes_From_Source (N)

        and then Expander_Active

      then

         --  Any null that comes from source and is of the RAS type must

         --  be expanded, except if expansion is not active (nothing

         --  gets expanded into the equivalent record type).

         Target_Type := Equivalent_Type (Typ);

      elsif Ekind (Typ) = E_Record_Type

        and then Present (Corresponding_Remote_Type (Typ))

      then

         --  This is a record type representing a RAS type, this must be

         --  expanded.

         Target_Type := Typ;

      else