gcc/ada/sem_dist.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E M _ D I S T                              --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2005, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, USA.                                              --
  21 --                                                                          --
  22 -- GNAT was originally developed  by the GNAT team at  New York University. --
  23 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  24 --                                                                          --
  25 ------------------------------------------------------------------------------
  26
  27 with Atree;    use Atree;
  28 with Casing;   use Casing;
  29 with Einfo;    use Einfo;
  30 with Errout;   use Errout;
  31 with Exp_Dist; use Exp_Dist;
  32 with Exp_Tss;  use Exp_Tss;
  33 with Nlists;   use Nlists;
  34 with Nmake;    use Nmake;
  35 with Namet;    use Namet;
  36 with Opt;      use Opt;
  37 with Rtsfind;  use Rtsfind;
  38 with Sem;      use Sem;
  39 with Sem_Res;  use Sem_Res;
  40 with Sem_Util; use Sem_Util;
  41 with Sinfo;    use Sinfo;
  42 with Stand;    use Stand;
  43 with Stringt;  use Stringt;
  44 with Tbuild;   use Tbuild;
  45
  46 package body Sem_Dist is
  47
  48    -----------------------
  49    -- Local Subprograms --
  50    -----------------------
  51
  52    procedure RAS_E_Dereference (Pref : Node_Id);
  53    --  Handles explicit dereference of Remote Access to Subprograms
  54
  55    function Full_Qualified_Name (E : Entity_Id) return String_Id;
  56    --  returns the full qualified name of the entity in lower case
  57
  58    -------------------------
  59    -- Add_Stub_Constructs --
  60    -------------------------
  61
  62    procedure Add_Stub_Constructs (N : Node_Id) is
  63       U    : constant Node_Id := Unit (N);
  64       Spec : Entity_Id        := Empty;
  65       Exp  : Node_Id          := U;         --  Unit that will be expanded
  66
  67    begin
  68       pragma Assert (Distribution_Stub_Mode /= No_Stubs);
  69
  70       if Nkind (U) = N_Package_Declaration then
  71          Spec := Defining_Entity (Specification (U));
  72
  73       elsif Nkind (U) = N_Package_Body then
  74          Spec := Corresponding_Spec (U);
  75
  76       else pragma Assert (Nkind (U) = N_Package_Instantiation);
  77          Exp  := Instance_Spec (U);
  78          Spec := Defining_Entity (Specification (Exp));
  79       end if;
  80
  81       pragma Assert (Is_Shared_Passive (Spec)
  82         or else Is_Remote_Call_Interface (Spec));
  83
  84       if Distribution_Stub_Mode = Generate_Caller_Stub_Body then
  85
  86          if Is_Shared_Passive (Spec) then
  87             null;
  88          elsif Nkind (U) = N_Package_Body then
  89             Error_Msg_N
  90               ("Specification file expected from command line", U);
  91          else
  92             Expand_Calling_Stubs_Bodies (Exp);
  93          end if;
  94
  95       else
  96
  97          if Is_Shared_Passive (Spec) then
  98             Build_Passive_Partition_Stub (Exp);
  99          else
 100             Expand_Receiving_Stubs_Bodies (Exp);
 101          end if;
 102
 103       end if;
 104    end Add_Stub_Constructs;
 105
 106    ---------------------------------------
 107    -- Build_RAS_Primitive_Specification --
 108    ---------------------------------------
 109
 110    function Build_RAS_Primitive_Specification
 111      (Subp_Spec          : Node_Id;
 112       Remote_Object_Type : Node_Id) return Node_Id
 113    is
 114       Loc : constant Source_Ptr := Sloc (Subp_Spec);
 115
 116       Primitive_Spec : constant Node_Id :=
 117                          Copy_Specification (Loc,
 118                            Spec     => Subp_Spec,
 119                            New_Name => Name_Call);
 120
 121       Subtype_Mark_For_Self : Node_Id;
 122
 123    begin
 124       if No (Parameter_Specifications (Primitive_Spec)) then
 125          Set_Parameter_Specifications (Primitive_Spec, New_List);
 126       end if;
 127
 128       if Nkind (Remote_Object_Type) in N_Entity then
 129          Subtype_Mark_For_Self :=
 130            New_Occurrence_Of (Remote_Object_Type, Loc);
 131       else
 132          Subtype_Mark_For_Self := Remote_Object_Type;
 133       end if;
 134
 135       Prepend_To (
 136         Parameter_Specifications (Primitive_Spec),
 137         Make_Parameter_Specification (Loc,
 138           Defining_Identifier =>
 139             Make_Defining_Identifier (Loc, Name_uS),
 140           Parameter_Type      =>
 141             Make_Access_Definition (Loc,
 142               Subtype_Mark =>
 143                 Subtype_Mark_For_Self)));
 144
 145       --  Trick later semantic analysis into considering this
 146       --  operation as a primitive (dispatching) operation of
 147       --  tagged type Obj_Type.
 148
 149       Set_Comes_From_Source (
 150         Defining_Unit_Name (Primitive_Spec), True);
 151
 152       return Primitive_Spec;
 153    end Build_RAS_Primitive_Specification;
 154
 155    -------------------------
 156    -- Full_Qualified_Name --
 157    -------------------------
 158
 159    function Full_Qualified_Name (E : Entity_Id) return String_Id is
 160       Ent         : Entity_Id := E;
 161       Parent_Name : String_Id := No_String;
 162
 163    begin
 164       --  Deals properly with child units
 165
 166       if Nkind (Ent) = N_Defining_Program_Unit_Name then
 167          Ent := Defining_Identifier (Ent);
 168       end if;
 169
 170       --  Compute recursively the qualification (only "Standard" has no scope)
 171
 172       if Present (Scope (Scope (Ent))) then
 173          Parent_Name := Full_Qualified_Name (Scope (Ent));
 174       end if;
 175
 176       --  Every entity should have a name except some expanded blocks. Do not
 177       --  bother about those.
 178
 179       if Chars (Ent) = No_Name then
 180          return Parent_Name;
 181       end if;
 182
 183       --  Add a period between Name and qualification
 184
 185       if Parent_Name /= No_String then
 186          Start_String (Parent_Name);
 187          Store_String_Char (Get_Char_Code ('.'));
 188
 189       else
 190          Start_String;
 191       end if;
 192
 193       --  Generates the entity name in upper case
 194
 195       Get_Name_String (Chars (Ent));
 196       Set_Casing (All_Lower_Case);
 197       Store_String_Chars (Name_Buffer (1 .. Name_Len));
 198       return End_String;
 199    end Full_Qualified_Name;
 200
 201    ------------------
 202    -- Get_PCS_Name --
 203    ------------------
 204
 205    function Get_PCS_Name return PCS_Names is
 206       PCS_Name : constant PCS_Names :=
 207                    Chars (Entity (Expression
 208                                     (Parent (RTE (RE_DSA_Implementation)))));
 209    begin
 210       return PCS_Name;
 211    end Get_PCS_Name;
 212
 213    ------------------------
 214    -- Is_All_Remote_Call --
 215    ------------------------
 216
 217    function Is_All_Remote_Call (N : Node_Id) return Boolean is
 218       Par : Node_Id;
 219
 220    begin
 221       if (Nkind (N) = N_Function_Call
 222               or else Nkind (N) = N_Procedure_Call_Statement)
 223         and then Nkind (Name (N)) in N_Has_Entity
 224         and then Is_Remote_Call_Interface (Entity (Name (N)))
 225         and then Has_All_Calls_Remote (Scope (Entity (Name (N))))
 226         and then Comes_From_Source (N)
 227       then
 228          Par := Parent (Entity (Name (N)));
 229
 230          while Present (Par)
 231            and then (Nkind (Par) /= N_Package_Specification
 232                        or else Is_Wrapper_Package (Defining_Entity (Par)))
 233          loop
 234             Par := Parent (Par);
 235          end loop;
 236
 237          if Present (Par) then
 238             return
 239               not Scope_Within_Or_Same (Current_Scope, Defining_Entity (Par));
 240          else
 241             return False;
 242          end if;
 243       else
 244          return False;
 245       end if;
 246    end Is_All_Remote_Call;
 247
 248    ------------------------------------
 249    -- Package_Specification_Of_Scope --
 250    ------------------------------------
 251
 252    function Package_Specification_Of_Scope (E : Entity_Id) return Node_Id is
 253       N : Node_Id := Parent (E);
 254    begin
 255       while Nkind (N) /= N_Package_Specification loop
 256          N := Parent (N);
 257       end loop;
 258
 259       return N;
 260    end Package_Specification_Of_Scope;
 261
 262    --------------------------
 263    -- Process_Partition_ID --
 264    --------------------------
 265
 266    procedure Process_Partition_Id (N : Node_Id) is
 267       Loc            : constant Source_Ptr := Sloc (N);
 268       Ety            : Entity_Id;
 269       Get_Pt_Id      : Node_Id;
 270       Get_Pt_Id_Call : Node_Id;
 271       Prefix_String  : String_Id;
 272       Typ            : constant Entity_Id := Etype (N);
 273
 274    begin
 275       Ety := Entity (Prefix (N));
 276
 277       --  In case prefix is not a library unit entity, get the entity
 278       --  of library unit.
 279
 280       while (Present (Scope (Ety))
 281         and then Scope (Ety) /= Standard_Standard)
 282         and not Is_Child_Unit (Ety)
 283       loop
 284          Ety := Scope (Ety);
 285       end loop;
 286
 287       --  Retrieve the proper function to call
 288
 289       if Is_Remote_Call_Interface (Ety) then
 290          Get_Pt_Id := New_Occurrence_Of
 291            (RTE (RE_Get_Active_Partition_Id), Loc);
 292
 293       elsif Is_Shared_Passive (Ety) then
 294          Get_Pt_Id := New_Occurrence_Of
 295            (RTE (RE_Get_Passive_Partition_Id), Loc);
 296
 297       else
 298          Get_Pt_Id := New_Occurrence_Of
 299            (RTE (RE_Get_Local_Partition_Id), Loc);
 300       end if;
 301
 302       --  Get and store the String_Id corresponding to the name of the
 303       --  library unit whose Partition_Id is needed.
 304
 305       Get_Library_Unit_Name_String (Unit_Declaration_Node (Ety));
 306       Prefix_String := String_From_Name_Buffer;
 307
 308       --  Build the function call which will replace the attribute
 309
 310       if Is_Remote_Call_Interface (Ety)
 311         or else Is_Shared_Passive (Ety)
 312       then
 313          Get_Pt_Id_Call :=
 314            Make_Function_Call (Loc,
 315              Name => Get_Pt_Id,
 316              Parameter_Associations =>
 317                New_List (Make_String_Literal (Loc, Prefix_String)));
 318
 319       else
 320          Get_Pt_Id_Call := Make_Function_Call (Loc, Get_Pt_Id);
 321
 322       end if;
 323
 324       --  Replace the attribute node by a conversion of the function call
 325       --  to the target type.
 326
 327       Rewrite (N, Convert_To (Typ, Get_Pt_Id_Call));
 328       Analyze_And_Resolve (N, Typ);
 329    end Process_Partition_Id;
 330
 331    ----------------------------------
 332    -- Process_Remote_AST_Attribute --
 333    ----------------------------------
 334
 335    procedure Process_Remote_AST_Attribute
 336      (N        : Node_Id;
 337       New_Type : Entity_Id)
 338    is
 339       Loc                   : constant Source_Ptr := Sloc (N);
 340       Remote_Subp           : Entity_Id;
 341       Tick_Access_Conv_Call : Node_Id;
 342       Remote_Subp_Decl      : Node_Id;
 343       RS_Pkg_Specif         : Node_Id;
 344       RS_Pkg_E              : Entity_Id;
 345       RAS_Type              : Entity_Id := New_Type;
 346       Async_E               : Entity_Id;
 347       All_Calls_Remote_E    : Entity_Id;
 348       Attribute_Subp        : Entity_Id;
 349
 350    begin
 351       --  Check if we have to expand the access attribute
 352
 353       Remote_Subp := Entity (Prefix (N));
 354
 355       if not Expander_Active or else Get_PCS_Name = Name_No_DSA then
 356          return;
 357       end if;
 358
 359       if Ekind (RAS_Type) /= E_Record_Type then
 360          RAS_Type := Equivalent_Type (RAS_Type);
 361       end if;
 362
 363       Attribute_Subp := TSS (RAS_Type, TSS_RAS_Access);
 364       pragma Assert (Present (Attribute_Subp));
 365       Remote_Subp_Decl := Unit_Declaration_Node (Remote_Subp);
 366
 367       if Nkind (Remote_Subp_Decl) = N_Subprogram_Body then
 368          Remote_Subp := Corresponding_Spec (Remote_Subp_Decl);
 369          Remote_Subp_Decl := Unit_Declaration_Node (Remote_Subp);
 370       end if;
 371
 372       RS_Pkg_Specif := Parent (Remote_Subp_Decl);
 373       RS_Pkg_E := Defining_Entity (RS_Pkg_Specif);
 374
 375       Async_E :=
 376         Boolean_Literals (Ekind (Remote_Subp) = E_Procedure
 377                             and then Is_Asynchronous (Remote_Subp));
 378
 379       All_Calls_Remote_E :=
 380         Boolean_Literals (Has_All_Calls_Remote (RS_Pkg_E));
 381
 382       Tick_Access_Conv_Call :=
 383         Make_Function_Call (Loc,
 384           Name => New_Occurrence_Of (Attribute_Subp, Loc),
 385           Parameter_Associations =>
 386             New_List (
 387               Make_String_Literal (Loc, Full_Qualified_Name (RS_Pkg_E)),
 388               Build_Subprogram_Id (Loc, Remote_Subp),
 389               New_Occurrence_Of (Async_E, Loc),
 390               New_Occurrence_Of (All_Calls_Remote_E, Loc)));
 391
 392       Rewrite (N, Tick_Access_Conv_Call);
 393       Analyze_And_Resolve (N, RAS_Type);
 394    end Process_Remote_AST_Attribute;
 395
 396    ------------------------------------
 397    -- Process_Remote_AST_Declaration --
 398    ------------------------------------
 399
 400    procedure Process_Remote_AST_Declaration (N : Node_Id) is
 401       Loc            : constant Source_Ptr := Sloc (N);
 402       User_Type      : constant Node_Id := Defining_Identifier (N);
 403       Scop           : constant Entity_Id := Scope (User_Type);
 404       Is_RCI         : constant Boolean :=
 405         Is_Remote_Call_Interface (Scop);
 406       Is_RT          : constant Boolean :=
 407         Is_Remote_Types (Scop);
 408       Type_Def       : constant Node_Id := Type_Definition (N);
 409
 410       Parameter      : Node_Id;
 411       Is_Degenerate  : Boolean;
 412       --  True iff this RAS has an access formal parameter (see
 413       --  Exp_Dist.Add_RAS_Dereference_TSS for details).
 414
 415       Subpkg         : constant Entity_Id :=
 416                          Make_Defining_Identifier
 417                            (Loc, New_Internal_Name ('S'));
 418       Subpkg_Decl    : Node_Id;
 419       Vis_Decls      : constant List_Id := New_List;
 420       Priv_Decls     : constant List_Id := New_List;
 421
 422       Obj_Type       : constant Entity_Id :=
 423                          Make_Defining_Identifier
 424                            (Loc, New_External_Name (
 425                                    Chars (User_Type), 'R'));
 426
 427       Full_Obj_Type  : constant Entity_Id :=
 428                          Make_Defining_Identifier
 429                            (Loc, Chars (Obj_Type));
 430
 431       RACW_Type      : constant Entity_Id :=
 432                          Make_Defining_Identifier
 433                            (Loc, New_External_Name (
 434                                    Chars (User_Type), 'P'));
 435
 436       Fat_Type       : constant Entity_Id :=
 437                         Make_Defining_Identifier
 438                           (Loc, Chars (User_Type));
 439       Fat_Type_Decl  : Node_Id;
 440
 441    begin
 442       Is_Degenerate := False;
 443       Parameter := First (Parameter_Specifications (Type_Def));
 444       while Present (Parameter) loop
 445          if Nkind (Parameter_Type (Parameter)) = N_Access_Definition then
 446             Error_Msg_N ("formal parameter& has anonymous access type?",
 447               Defining_Identifier (Parameter));
 448             Is_Degenerate := True;
 449             exit;
 450          end if;
 451
 452          Next (Parameter);
 453       end loop;
 454
 455       if Is_Degenerate then
 456          Error_Msg_NE
 457            ("remote access-to-subprogram type& can only be null?",
 458             Defining_Identifier (Parameter), User_Type);
 459
 460          --  The only legal value for a RAS with a formal parameter of an
 461          --  anonymous access type is null, because it cannot be subtype-
 462          --  conformant with any legal remote subprogram declaration. In this
 463          --  case, we cannot generate a corresponding primitive operation.
 464       end if;
 465
 466       if Get_PCS_Name = Name_No_DSA then
 467          return;
 468       end if;
 469
 470       --  The tagged private type, primitive operation and RACW type associated
 471       --  with a RAS need to all be declared in a subpackage of the one that
 472       --  contains the RAS declaration, because the primitive of the object
 473       --  type, and the associated primitive of the stub type, need to be
 474       --  dispatching operations of these types, and the profile of the RAS
 475       --  might contain tagged types declared in the same scope.
 476
 477       Append_To (Vis_Decls,
 478         Make_Private_Type_Declaration (Loc,
 479           Defining_Identifier => Obj_Type,
 480           Abstract_Present => True,
 481           Tagged_Present   => True,
 482           Limited_Present  => True));
 483
 484       Append_To (Priv_Decls,
 485         Make_Full_Type_Declaration (Loc,
 486           Defining_Identifier =>
 487             Full_Obj_Type,
 488           Type_Definition     =>
 489             Make_Record_Definition (Loc,
 490               Abstract_Present => True,
 491               Tagged_Present   => True,
 492               Limited_Present  => True,
 493               Null_Present     => True,
 494               Component_List   => Empty)));
 495
 496       if not Is_Degenerate then
 497          Append_To (Vis_Decls,
 498            Make_Abstract_Subprogram_Declaration (Loc,
 499              Specification => Build_RAS_Primitive_Specification (
 500                Subp_Spec          => Type_Def,
 501                Remote_Object_Type => Obj_Type)));
 502       end if;
 503
 504       Append_To (Vis_Decls,
 505         Make_Full_Type_Declaration (Loc,
 506           Defining_Identifier => RACW_Type,
 507           Type_Definition     =>
 508             Make_Access_To_Object_Definition (Loc,
 509               All_Present => True,
 510               Subtype_Indication =>
 511                 Make_Attribute_Reference (Loc,
 512                   Prefix =>
 513                     New_Occurrence_Of (Obj_Type, Loc),
 514                   Attribute_Name =>
 515                     Name_Class))));
 516       Set_Is_Remote_Call_Interface (RACW_Type, Is_RCI);
 517       Set_Is_Remote_Types (RACW_Type, Is_RT);
 518
 519       Subpkg_Decl :=
 520         Make_Package_Declaration (Loc,
 521           Make_Package_Specification (Loc,
 522             Defining_Unit_Name =>
 523               Subpkg,
 524             Visible_Declarations =>
 525               Vis_Decls,
 526             Private_Declarations =>
 527               Priv_Decls,
 528             End_Label =>
 529               New_Occurrence_Of (Subpkg, Loc)));
 530       Set_Is_Remote_Call_Interface (Subpkg, Is_RCI);
 531       Set_Is_Remote_Types (Subpkg, Is_RT);
 532       Insert_After_And_Analyze (N, Subpkg_Decl);
 533
 534       --  Many parts of the analyzer and expander expect
 535       --  that the fat pointer type used to implement remote
 536       --  access to subprogram types be a record.
 537       --  Note: The structure of this type must be kept consistent
 538       --  with the code generated by Remote_AST_Null_Value for the
 539       --  corresponding 'null' expression.
 540
 541       Fat_Type_Decl := Make_Full_Type_Declaration (Loc,
 542         Defining_Identifier => Fat_Type,
 543         Type_Definition     =>
 544           Make_Record_Definition (Loc,
 545             Component_List =>
 546               Make_Component_List (Loc,
 547                 Component_Items => New_List (
 548                   Make_Component_Declaration (Loc,
 549                     Defining_Identifier =>
 550                       Make_Defining_Identifier (Loc, Name_Ras),
 551                     Component_Definition =>
 552                       Make_Component_Definition (Loc,
 553                         Aliased_Present     =>
 554                           False,
 555                         Subtype_Indication  =>
 556                           New_Occurrence_Of (RACW_Type, Loc)))))));
 557       Set_Equivalent_Type (User_Type, Fat_Type);
 558       Set_Corresponding_Remote_Type (Fat_Type, User_Type);
 559       Insert_After_And_Analyze (Subpkg_Decl, Fat_Type_Decl);
 560
 561       --  The reason we suppress the initialization procedure is that we know
 562       --  that no initialization is required (even if Initialize_Scalars mode
 563       --  is active), and there are order of elaboration problems if we do try
 564       --  to generate an init proc for this created record type.
 565
 566       Set_Suppress_Init_Proc (Fat_Type);
 567
 568       if Expander_Active then
 569          Add_RAST_Features (Parent (User_Type));
 570       end if;
 571    end Process_Remote_AST_Declaration;
 572
 573    -----------------------
 574    -- RAS_E_Dereference --
 575    -----------------------
 576
 577    procedure RAS_E_Dereference (Pref : Node_Id) is
 578       Loc             : constant Source_Ptr := Sloc (Pref);
 579       Call_Node       : Node_Id;
 580       New_Type        : constant Entity_Id := Etype (Pref);
 581       Explicit_Deref  : constant Node_Id   := Parent (Pref);
 582       Deref_Subp_Call : constant Node_Id   := Parent (Explicit_Deref);
 583       Deref_Proc      : Entity_Id;
 584       Params          : List_Id;
 585
 586    begin
 587       if Nkind (Deref_Subp_Call) = N_Procedure_Call_Statement then
 588          Params := Parameter_Associations (Deref_Subp_Call);
 589
 590          if Present (Params) then
 591             Prepend (Pref, Params);
 592          else
 593             Params := New_List (Pref);
 594          end if;
 595
 596       elsif Nkind (Deref_Subp_Call) = N_Indexed_Component then
 597
 598          Params := Expressions (Deref_Subp_Call);
 599
 600          if Present (Params) then
 601             Prepend (Pref, Params);
 602          else
 603             Params := New_List (Pref);
 604          end if;
 605
 606       else
 607          --  Context is not a call
 608
 609          return;
 610       end if;
 611
 612       if not Expander_Active or else Get_PCS_Name = Name_No_DSA then
 613          return;
 614       end if;
 615
 616       Deref_Proc := TSS (New_Type, TSS_RAS_Dereference);
 617       pragma Assert (Present (Deref_Proc));
 618
 619       if Ekind (Deref_Proc) = E_Function then
 620          Call_Node :=
 621            Make_Function_Call (Loc,
 622               Name => New_Occurrence_Of (Deref_Proc, Loc),
 623               Parameter_Associations => Params);
 624
 625       else
 626          Call_Node :=
 627            Make_Procedure_Call_Statement (Loc,
 628               Name => New_Occurrence_Of (Deref_Proc, Loc),
 629               Parameter_Associations => Params);
 630       end if;
 631
 632       Rewrite (Deref_Subp_Call, Call_Node);
 633       Analyze (Deref_Subp_Call);
 634    end RAS_E_Dereference;
 635
 636    ------------------------------
 637    -- Remote_AST_E_Dereference --
 638    ------------------------------
 639
 640    function Remote_AST_E_Dereference (P : Node_Id) return Boolean is
 641       ET : constant Entity_Id  := Etype (P);
 642
 643    begin
 644       --  Perform the changes only on original dereferences, and only if
 645       --  we are generating code.
 646
 647       if Comes_From_Source (P)
 648         and then Is_Record_Type (ET)
 649         and then (Is_Remote_Call_Interface (ET)
 650                    or else Is_Remote_Types (ET))
 651         and then Present (Corresponding_Remote_Type (ET))
 652         and then (Nkind (Parent (Parent (P))) = N_Procedure_Call_Statement
 653                    or else Nkind (Parent (Parent (P))) = N_Indexed_Component)
 654         and then Expander_Active
 655       then
 656          RAS_E_Dereference (P);
 657          return True;
 658       else
 659          return False;
 660       end if;
 661    end Remote_AST_E_Dereference;
 662
 663    ------------------------------
 664    -- Remote_AST_I_Dereference --
 665    ------------------------------
 666
 667    function Remote_AST_I_Dereference (P : Node_Id) return Boolean is
 668       ET     : constant Entity_Id  := Etype (P);
 669       Deref  : Node_Id;
 670
 671    begin
 672       if Comes_From_Source (P)
 673         and then (Is_Remote_Call_Interface (ET)
 674                    or else Is_Remote_Types (ET))
 675         and then Present (Corresponding_Remote_Type (ET))
 676         and then Ekind (Entity (P)) /= E_Function
 677       then
 678          Deref :=
 679            Make_Explicit_Dereference (Sloc (P),
 680              Prefix => Relocate_Node (P));
 681          Rewrite (P, Deref);
 682          Set_Etype (P, ET);
 683          RAS_E_Dereference (Prefix (P));
 684          return True;
 685       end if;
 686
 687       return False;
 688    end Remote_AST_I_Dereference;
 689
 690    ---------------------------
 691    -- Remote_AST_Null_Value --
 692    ---------------------------
 693
 694    function Remote_AST_Null_Value
 695      (N   : Node_Id;
 696       Typ : Entity_Id) return Boolean
 697    is
 698       Loc         : constant Source_Ptr := Sloc (N);
 699       Target_Type : Entity_Id;
 700
 701    begin
 702       if not Expander_Active or else Get_PCS_Name = Name_No_DSA then
 703          return False;
 704
 705       elsif Ekind (Typ) = E_Access_Subprogram_Type
 706         and then (Is_Remote_Call_Interface (Typ)
 707                     or else Is_Remote_Types (Typ))
 708         and then Comes_From_Source (N)
 709         and then Expander_Active
 710       then
 711          --  Any null that comes from source and is of the RAS type must
 712          --  be expanded, except if expansion is not active (nothing
 713          --  gets expanded into the equivalent record type).
 714
 715          Target_Type := Equivalent_Type (Typ);
 716
 717       elsif Ekind (Typ) = E_Record_Type
 718         and then Present (Corresponding_Remote_Type (Typ))
 719       then
 720          --  This is a record type representing a RAS type, this must be
 721          --  expanded.
 722
 723          Target_Type := Typ;
 724
 725       else
 726          --  We do not have to handle this case
 727
 728          return False;
 729
 730       end if;
 731
 732       Rewrite (N,
 733         Make_Aggregate (Loc,
 734           Component_Associations => New_List (
 735             Make_Component_Association (Loc,
 736               Choices => New_List (
 737                 Make_Identifier (Loc, Name_Ras)),
 738               Expression =>
 739                 Make_Null (Loc)))));
 740       Analyze_And_Resolve (N, Target_Type);
 741       return True;
 742    end Remote_AST_Null_Value;
 743
 744 end Sem_Dist;