gcc/ada/lib-xref.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             L I B . X R E F                              --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1998-2023, 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 3,  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 COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 with Atree;          use Atree;
  27 with Csets;          use Csets;
  28 with Einfo;          use Einfo;
  29 with Einfo.Utils;    use Einfo.Utils;
  30 with Elists;         use Elists;
  31 with Errout;         use Errout;
  32 with Lib.Util;       use Lib.Util;
  33 with Nlists;         use Nlists;
  34 with Opt;            use Opt;
  35 with Restrict;       use Restrict;
  36 with Rident;         use Rident;
  37 with Sem;            use Sem;
  38 with Sem_Aux;        use Sem_Aux;
  39 with Sem_Prag;       use Sem_Prag;
  40 with Sem_Util;       use Sem_Util;
  41 with Sem_Warn;       use Sem_Warn;
  42 with Sinfo;          use Sinfo;
  43 with Sinfo.Nodes;    use Sinfo.Nodes;
  44 with Sinfo.Utils;    use Sinfo.Utils;
  45 with Sinput;         use Sinput;
  46 with Snames;         use Snames;
  47 with Stringt;        use Stringt;
  48 with Stand;          use Stand;
  49 with Table;          use Table;
  50 with Warnsw;         use Warnsw;
  51
  52 with GNAT.Heap_Sort_G;
  53 with GNAT.HTable;
  54
  55 package body Lib.Xref is
  56
  57    ------------------
  58    -- Declarations --
  59    ------------------
  60
  61    --  The Xref table is used to record references. The Loc field is set
  62    --  to No_Location for a definition entry.
  63
  64    subtype Xref_Entry_Number is Int;
  65
  66    type Xref_Key is record
  67       --  These are the components of Xref_Entry that participate in hash
  68       --  lookups.
  69
  70       Ent : Entity_Id;
  71       --  Entity referenced (E parameter to Generate_Reference)
  72
  73       Loc : Source_Ptr;
  74       --  Location of reference (Original_Location (Sloc field of N parameter
  75       --  to Generate_Reference)). Set to No_Location for the case of a
  76       --  defining occurrence.
  77
  78       Typ : Character;
  79       --  Reference type (Typ param to Generate_Reference)
  80
  81       Eun : Unit_Number_Type;
  82       --  Unit number corresponding to Ent
  83
  84       Lun : Unit_Number_Type;
  85       --  Unit number corresponding to Loc. Value is undefined and not
  86       --  referenced if Loc is set to No_Location.
  87
  88       --  The following components are only used for SPARK cross-references
  89
  90       Ref_Scope : Entity_Id;
  91       --  Entity of the closest subprogram or package enclosing the reference
  92
  93       Ent_Scope : Entity_Id;
  94       --  Entity of the closest subprogram or package enclosing the definition,
  95       --  which should be located in the same file as the definition itself.
  96    end record;
  97
  98    type Xref_Entry is record
  99       Key : Xref_Key;
 100
 101       Ent_Scope_File : Unit_Number_Type;
 102       --  File for entity Ent_Scope
 103
 104       Def : Source_Ptr;
 105       --  Original source location for entity being referenced. Note that these
 106       --  values are used only during the output process, they are not set when
 107       --  the entries are originally built. This is because private entities
 108       --  can be swapped when the initial call is made.
 109
 110       HTable_Next : Xref_Entry_Number;
 111       --  For use only by Static_HTable
 112    end record;
 113
 114    package Xrefs is new Table.Table (
 115      Table_Component_Type => Xref_Entry,
 116      Table_Index_Type     => Xref_Entry_Number,
 117      Table_Low_Bound      => 1,
 118      Table_Initial        => Alloc.Xrefs_Initial,
 119      Table_Increment      => Alloc.Xrefs_Increment,
 120      Table_Name           => "Xrefs");
 121
 122    --------------
 123    -- Xref_Set --
 124    --------------
 125
 126    --  We keep a set of xref entries, in order to avoid inserting duplicate
 127    --  entries into the above Xrefs table. An entry is in Xref_Set if and only
 128    --  if it is in Xrefs.
 129
 130    Num_Buckets : constant := 2**16;
 131
 132    subtype Header_Num is Integer range 0 .. Num_Buckets - 1;
 133    type Null_Type is null record;
 134    pragma Unreferenced (Null_Type);
 135
 136    function Hash (F : Xref_Entry_Number) return Header_Num;
 137
 138    function Equal (F1, F2 : Xref_Entry_Number) return Boolean;
 139
 140    procedure HT_Set_Next (E : Xref_Entry_Number; Next : Xref_Entry_Number);
 141
 142    function  HT_Next (E : Xref_Entry_Number) return Xref_Entry_Number;
 143
 144    function Get_Key (E : Xref_Entry_Number) return Xref_Entry_Number;
 145
 146    pragma Inline (Hash, Equal, HT_Set_Next, HT_Next, Get_Key);
 147
 148    package Xref_Set is new GNAT.HTable.Static_HTable (
 149      Header_Num,
 150      Element    => Xref_Entry,
 151      Elmt_Ptr   => Xref_Entry_Number,
 152      Null_Ptr   => 0,
 153      Set_Next   => HT_Set_Next,
 154      Next       => HT_Next,
 155      Key        => Xref_Entry_Number,
 156      Get_Key    => Get_Key,
 157      Hash       => Hash,
 158      Equal      => Equal);
 159
 160    -----------------------------
 161    -- SPARK Xrefs Information --
 162    -----------------------------
 163
 164    package body SPARK_Specific is separate;
 165
 166    ------------------------
 167    --  Local Subprograms --
 168    ------------------------
 169
 170    procedure Add_Entry (Key : Xref_Key; Ent_Scope_File : Unit_Number_Type);
 171    --  Add an entry to the tables of Xref_Entries, avoiding duplicates
 172
 173    procedure Generate_Prim_Op_References (Typ : Entity_Id);
 174    --  For a tagged type, generate implicit references to its primitive
 175    --  operations, for source navigation. This is done right before emitting
 176    --  cross-reference information rather than at the freeze point of the type
 177    --  in order to handle late bodies that are primitive operations.
 178
 179    function Lt (T1, T2 : Xref_Entry) return Boolean;
 180    --  Order cross-references
 181
 182    ---------------
 183    -- Add_Entry --
 184    ---------------
 185
 186    procedure Add_Entry (Key : Xref_Key; Ent_Scope_File : Unit_Number_Type) is
 187    begin
 188       Xrefs.Increment_Last; -- tentative
 189       Xrefs.Table (Xrefs.Last).Key := Key;
 190
 191       --  Set the entry in Xref_Set, and if newly set, keep the above
 192       --  tentative increment.
 193
 194       if Xref_Set.Set_If_Not_Present (Xrefs.Last) then
 195          Xrefs.Table (Xrefs.Last).Ent_Scope_File := Ent_Scope_File;
 196          --  Leave Def and HTable_Next uninitialized
 197
 198          Set_Has_Xref_Entry (Key.Ent);
 199
 200       --  It was already in Xref_Set, so throw away the tentatively-added entry
 201
 202       else
 203          Xrefs.Decrement_Last;
 204       end if;
 205    end Add_Entry;
 206
 207    -----------
 208    -- Equal --
 209    -----------
 210
 211    function Equal (F1, F2 : Xref_Entry_Number) return Boolean is
 212       Result : constant Boolean :=
 213                  Xrefs.Table (F1).Key = Xrefs.Table (F2).Key;
 214    begin
 215       return Result;
 216    end Equal;
 217
 218    -------------------------
 219    -- Generate_Definition --
 220    -------------------------
 221
 222    procedure Generate_Definition (E : Entity_Id) is
 223    begin
 224       pragma Assert (Nkind (E) in N_Entity);
 225
 226       --  Note that we do not test Xref_Entity_Letters here. It is too early
 227       --  to do so, since we are often called before the entity is fully
 228       --  constructed, so that the Ekind is still E_Void.
 229
 230       if Opt.Xref_Active
 231
 232          --  Definition must come from source
 233
 234          --  We make an exception for subprogram child units that have no spec.
 235          --  For these we generate a subprogram declaration for library use,
 236          --  and the corresponding entity does not come from source.
 237          --  Nevertheless, all references will be attached to it and we have
 238          --  to treat is as coming from user code.
 239
 240          and then (Comes_From_Source (E) or else Is_Child_Unit (E))
 241
 242          --  And must have a reasonable source location that is not
 243          --  within an instance (all entities in instances are ignored)
 244
 245          and then Sloc (E) > No_Location
 246          and then Instantiation_Location (Sloc (E)) = No_Location
 247
 248          --  And must be a non-internal name from the main source unit
 249
 250          and then In_Extended_Main_Source_Unit (E)
 251          and then not Is_Internal_Name (Chars (E))
 252       then
 253          Add_Entry
 254            ((Ent => E,
 255              Loc => No_Location,
 256              Typ => ' ',
 257              Eun => Get_Source_Unit (Original_Location (Sloc (E))),
 258              Lun => No_Unit,
 259              Ref_Scope => Empty,
 260              Ent_Scope => Empty),
 261             Ent_Scope_File => No_Unit);
 262
 263          if In_Inlined_Body then
 264             Set_Referenced (E);
 265          end if;
 266       end if;
 267    end Generate_Definition;
 268
 269    ---------------------------------
 270    -- Generate_Operator_Reference --
 271    ---------------------------------
 272
 273    procedure Generate_Operator_Reference
 274      (N : Node_Id;
 275       T : Entity_Id)
 276    is
 277    begin
 278       if not In_Extended_Main_Source_Unit (N) then
 279          return;
 280       end if;
 281
 282       --  If the operator is not a Standard operator, then we generate a real
 283       --  reference to the user defined operator.
 284
 285       if Sloc (Entity (N)) /= Standard_Location then
 286          Generate_Reference (Entity (N), N);
 287
 288          --  A reference to an implicit inequality operator is also a reference
 289          --  to the user-defined equality.
 290
 291          if Nkind (N) = N_Op_Ne
 292            and then not Comes_From_Source (Entity (N))
 293            and then Present (Corresponding_Equality (Entity (N)))
 294          then
 295             Generate_Reference (Corresponding_Equality (Entity (N)), N);
 296          end if;
 297
 298       --  For the case of Standard operators, we mark the result type as
 299       --  referenced. This ensures that in the case where we are using a
 300       --  derived operator, we mark an entity of the unit that implicitly
 301       --  defines this operator as used. Otherwise we may think that no entity
 302       --  of the unit is used. The actual entity marked as referenced is the
 303       --  first subtype, which is the relevant user defined entity.
 304
 305       --  Note: we only do this for operators that come from source. The
 306       --  generated code sometimes reaches for entities that do not need to be
 307       --  explicitly visible (for example, when we expand the code for
 308       --  comparing two record objects, the fields of the record may not be
 309       --  visible).
 310
 311       elsif Comes_From_Source (N) then
 312          Set_Referenced (First_Subtype (T));
 313       end if;
 314    end Generate_Operator_Reference;
 315
 316    ---------------------------------
 317    -- Generate_Prim_Op_References --
 318    ---------------------------------
 319
 320    procedure Generate_Prim_Op_References (Typ : Entity_Id) is
 321       Base_T    : Entity_Id;
 322       Prim      : Elmt_Id;
 323       Prim_List : Elist_Id;
 324
 325    begin
 326       --  Handle subtypes of synchronized types
 327
 328       if Ekind (Typ) = E_Protected_Subtype
 329         or else Ekind (Typ) = E_Task_Subtype
 330       then
 331          Base_T := Etype (Typ);
 332       else
 333          Base_T := Typ;
 334       end if;
 335
 336       --  References to primitive operations are only relevant for tagged types
 337
 338       if not Is_Tagged_Type (Base_T)
 339         or else Is_Class_Wide_Type (Base_T)
 340       then
 341          return;
 342       end if;
 343
 344       --  Ada 2005 (AI-345): For synchronized types generate reference to the
 345       --  wrapper that allow us to dispatch calls through their implemented
 346       --  abstract interface types.
 347
 348       --  The check for Present here is to protect against previously reported
 349       --  critical errors.
 350
 351       Prim_List := Primitive_Operations (Base_T);
 352
 353       if No (Prim_List) then
 354          return;
 355       end if;
 356
 357       Prim := First_Elmt (Prim_List);
 358       while Present (Prim) loop
 359
 360          --  If the operation is derived, get the original for cross-reference
 361          --  reference purposes (it is the original for which we want the xref
 362          --  and for which the comes_from_source test must be performed).
 363
 364          Generate_Reference
 365            (Typ, Ultimate_Alias (Node (Prim)), 'p', Set_Ref => False);
 366          Next_Elmt (Prim);
 367       end loop;
 368    end Generate_Prim_Op_References;
 369
 370    ------------------------
 371    -- Generate_Reference --
 372    ------------------------
 373
 374    procedure Generate_Reference
 375      (E       : Entity_Id;
 376       N       : Node_Id;
 377       Typ     : Character := 'r';
 378       Set_Ref : Boolean   := True;
 379       Force   : Boolean   := False)
 380    is
 381       Actual_Typ : Character := Typ;
 382       Call       : Node_Id;
 383       Def        : Source_Ptr;
 384       Ent        : Entity_Id;
 385       Ent_Scope  : Entity_Id;
 386       Formal     : Entity_Id;
 387       Kind       : Entity_Kind;
 388       Nod        : Node_Id;
 389       Ref        : Source_Ptr;
 390       Ref_Scope  : Entity_Id;
 391
 392       function Get_Through_Renamings (E : Entity_Id) return Entity_Id;
 393       --  Get the enclosing entity through renamings, which may come from
 394       --  source or from the translation of generic instantiations.
 395
 396       function OK_To_Set_Referenced return Boolean;
 397       --  Returns True if the Referenced flag can be set. There are a few
 398       --  exceptions where we do not want to set this flag, see body for
 399       --  details of these exceptional cases.
 400
 401       ---------------------------
 402       -- Get_Through_Renamings --
 403       ---------------------------
 404
 405       function Get_Through_Renamings (E : Entity_Id) return Entity_Id is
 406       begin
 407          case Ekind (E) is
 408
 409             --  For subprograms we just need to check once if they are have a
 410             --  Renamed_Entity, because Renamed_Entity is set transitively.
 411
 412             when Subprogram_Kind =>
 413                declare
 414                   Renamed : constant Entity_Id := Renamed_Entity (E);
 415
 416                begin
 417                   if Present (Renamed) then
 418                      return Renamed;
 419                   else
 420                      return E;
 421                   end if;
 422                end;
 423
 424             --  For objects we need to repeatedly call Renamed_Object, because
 425             --  it is not transitive.
 426
 427             when Object_Kind =>
 428                declare
 429                   Obj : Entity_Id := E;
 430
 431                begin
 432                   loop
 433                      pragma Assert (Present (Obj));
 434
 435                      declare
 436                         Renamed : constant Entity_Id := Renamed_Object (Obj);
 437
 438                      begin
 439                         if Present (Renamed) then
 440                            Obj := Get_Enclosing_Object (Renamed);
 441
 442                            --  The renamed expression denotes a non-object,
 443                            --  e.g. function call, slicing of a function call,
 444                            --  pointer dereference, etc.
 445
 446                            if No (Obj)
 447                              or else Ekind (Obj) = E_Enumeration_Literal
 448                            then
 449                               return Empty;
 450                            end if;
 451                         else
 452                            return Obj;
 453                         end if;
 454                      end;
 455                   end loop;
 456                end;
 457
 458             when others =>
 459                return E;
 460
 461          end case;
 462       end Get_Through_Renamings;
 463
 464       ---------------------------
 465       -- OK_To_Set_Referenced --
 466       ---------------------------
 467
 468       function OK_To_Set_Referenced return Boolean is
 469          P : Node_Id;
 470
 471       begin
 472          --  A reference from a pragma Unreferenced or pragma Unmodified or
 473          --  pragma Warnings does not cause the Referenced flag to be set.
 474          --  This avoids silly warnings about things being referenced and
 475          --  not assigned when the only reference is from the pragma.
 476
 477          if Nkind (N) = N_Identifier then
 478             P := Parent (N);
 479
 480             if Nkind (P) = N_Pragma_Argument_Association then
 481                P := Parent (P);
 482
 483                if Nkind (P) = N_Pragma then
 484                   if Pragma_Name_Unmapped (P) in Name_Warnings
 485                                                | Name_Unmodified
 486                                                | Name_Unreferenced
 487                   then
 488                      return False;
 489                   end if;
 490                end if;
 491
 492             --  A reference to a formal in a named parameter association does
 493             --  not make the formal referenced. Formals that are unused in the
 494             --  subprogram body are properly flagged as such, even if calls
 495             --  elsewhere use named notation.
 496
 497             elsif Nkind (P) = N_Parameter_Association
 498               and then N = Selector_Name (P)
 499             then
 500                return False;
 501             end if;
 502          end if;
 503
 504          return True;
 505       end OK_To_Set_Referenced;
 506
 507    --  Start of processing for Generate_Reference
 508
 509    begin
 510       --  If Get_Ignore_Errors, then we are in Preanalyze_Without_Errors, and
 511       --  we should not record cross references, because that will cause
 512       --  duplicates when we call Analyze.
 513
 514       if Get_Ignore_Errors then
 515          return;
 516       end if;
 517
 518       --  May happen in case of severe errors
 519
 520       if Nkind (E) not in N_Entity then
 521          return;
 522       end if;
 523
 524       Find_Actual (N, Formal, Call);
 525
 526       if Present (Formal) then
 527          Kind := Ekind (Formal);
 528       else
 529          Kind := E_Void;
 530       end if;
 531
 532       --  Check for obsolescent reference to package ASCII. GNAT treats this
 533       --  element of annex J specially since in practice, programs make a lot
 534       --  of use of this feature, so we don't include it in the set of features
 535       --  diagnosed when Warn_On_Obsolescent_Features mode is set. However we
 536       --  are required to note it as a violation of the RM defined restriction.
 537
 538       if E = Standard_ASCII then
 539          Check_Restriction (No_Obsolescent_Features, N);
 540       end if;
 541
 542       --  Check for reference to entity marked with Is_Obsolescent
 543
 544       --  Note that we always allow obsolescent references in the compiler
 545       --  itself and the run time, since we assume that we know what we are
 546       --  doing in such cases. For example the calls in Ada.Characters.Handling
 547       --  to its own obsolescent subprograms are just fine.
 548
 549       --  In any case we only generate warnings if we are in the extended main
 550       --  source unit, and the entity itself is not in the extended main source
 551       --  unit, since we assume the source unit itself knows what is going on
 552       --  (and for sure we do not want silly warnings, e.g. on the end line of
 553       --  an obsolescent procedure body).
 554
 555       if Is_Obsolescent (E)
 556         and then not GNAT_Mode
 557         and then not In_Extended_Main_Source_Unit (E)
 558         and then In_Extended_Main_Source_Unit (N)
 559       then
 560          Check_Restriction (No_Obsolescent_Features, N);
 561
 562          if Warn_On_Obsolescent_Feature then
 563             Output_Obsolescent_Entity_Warnings (N, E);
 564          end if;
 565       end if;
 566
 567       --  Warn if reference to Ada 2005 entity not in Ada 2005 mode. We only
 568       --  detect real explicit references (modifications and references).
 569
 570       if Comes_From_Source (N)
 571         and then Is_Ada_2005_Only (E)
 572         and then Ada_Version < Ada_2005
 573         and then Warn_On_Ada_2005_Compatibility
 574         and then (Typ = 'm' or else Typ = 'r' or else Typ = 's')
 575       then
 576          Error_Msg_NE ("& is only defined in Ada 2005?y?", N, E);
 577       end if;
 578
 579       --  Warn if reference to Ada 2012 entity not in Ada 2012 mode. We only
 580       --  detect real explicit references (modifications and references).
 581
 582       if Comes_From_Source (N)
 583         and then Is_Ada_2012_Only (E)
 584         and then Ada_Version < Ada_2012
 585         and then Warn_On_Ada_2012_Compatibility
 586         and then (Typ = 'm' or else Typ = 'r')
 587       then
 588          Error_Msg_NE ("& is only defined in Ada 2012?y?", N, E);
 589       end if;
 590
 591       --  Warn if reference to Ada 2022 entity not in Ada 2022 mode. We only
 592       --  detect real explicit references (modifications and references).
 593
 594       if Comes_From_Source (N)
 595         and then Is_Ada_2022_Only (E)
 596         and then not Is_Subprogram (E)
 597         and then Ada_Version < Ada_2022
 598         and then Warn_On_Ada_2022_Compatibility
 599         and then (Typ = 'm' or else Typ = 'r')
 600       then
 601          Error_Msg_NE ("& is only defined in Ada 2022?y?", N, E);
 602
 603       --  Error on static and dispatching calls to Ada 2022 subprograms that
 604       --  require overriding if we are not in Ada 2022 mode (since overriding
 605       --  was skipped); warn if the subprogram does not require overriding.
 606
 607       elsif Comes_From_Source (N)
 608         and then Is_Ada_2022_Only (E)
 609         and then Ada_Version < Ada_2022
 610         and then Is_Subprogram (E)
 611         and then (Typ = 'r' or else Typ = 's' or else Typ = 'R')
 612       then
 613          if Requires_Overriding (E) then
 614             Error_Msg_NE
 615               ("& is only defined in Ada 2022 and requires overriding", N, E);
 616
 617          elsif Warn_On_Ada_2022_Compatibility then
 618             Error_Msg_NE ("& is only defined in Ada 2022?y?", N, E);
 619          end if;
 620       end if;
 621
 622       --  Never collect references if not in main source unit. However, we omit
 623       --  this test if Typ is 'e' or 'k', since these entries are structural,
 624       --  and it is useful to have them in units that reference packages as
 625       --  well as units that define packages. We also omit the test for the
 626       --  case of 'p' since we want to include inherited primitive operations
 627       --  from other packages.
 628
 629       --  We also omit this test is this is a body reference for a subprogram
 630       --  instantiation. In this case the reference is to the generic body,
 631       --  which clearly need not be in the main unit containing the instance.
 632       --  For the same reason we accept an implicit reference generated for
 633       --  a default in an instance.
 634
 635       --  We also set the referenced flag in a generic package that is not in
 636       --  the main source unit, when the object is of a formal private type,
 637       --  to warn in the instance if the corresponding type is not a fully
 638       --  initialized type.
 639
 640       if not In_Extended_Main_Source_Unit (N) then
 641          if Typ = 'e' or else
 642             Typ = 'I' or else
 643             Typ = 'p' or else
 644             Typ = 'i' or else
 645             Typ = 'k'
 646            or else (Typ = 'b' and then Is_Generic_Instance (E))
 647
 648             --  Allow the generation of references to reads, writes and calls
 649             --  in SPARK mode when the related context comes from an instance.
 650
 651            or else
 652              (GNATprove_Mode
 653                and then In_Extended_Main_Code_Unit (N)
 654                and then (Typ = 'm' or else Typ = 'r' or else Typ = 's'))
 655          then
 656             null;
 657
 658          elsif In_Instance_Body
 659            and then In_Extended_Main_Code_Unit (N)
 660            and then Is_Generic_Type (Etype (E))
 661          then
 662             Set_Referenced (E);
 663             return;
 664
 665          elsif Inside_A_Generic
 666            and then Is_Object (E)
 667            and then Is_Generic_Type (Etype (E))
 668          then
 669             Set_Referenced (E);
 670             return;
 671
 672          else
 673             return;
 674          end if;
 675       end if;
 676
 677       --  For reference type p, the entity must be in main source unit
 678
 679       if Typ = 'p' and then not In_Extended_Main_Source_Unit (E) then
 680          return;
 681       end if;
 682
 683       --  Unless the reference is forced, we ignore references where the
 684       --  reference itself does not come from source.
 685
 686       if not Force and then not Comes_From_Source (N) then
 687          return;
 688       end if;
 689
 690       --  Deal with setting entity as referenced, unless suppressed. Note that
 691       --  we still do Set_Referenced on entities that do not come from source.
 692       --  This situation arises when we have a source reference to a derived
 693       --  operation, where the derived operation itself does not come from
 694       --  source, but we still want to mark it as referenced, since we really
 695       --  are referencing an entity in the corresponding package (this avoids
 696       --  wrong complaints that the package contains no referenced entities).
 697
 698       if Set_Ref then
 699
 700          --  When E itself is an IN OUT parameter mark it referenced
 701
 702          if Is_Assignable (E)
 703            and then Ekind (E) = E_In_Out_Parameter
 704            and then Known_To_Be_Assigned (N)
 705          then
 706             Set_Referenced (E);
 707
 708          --  For the case where the entity is on the left hand side of an
 709          --  assignment statment, we do nothing here.
 710
 711          --  The processing for Analyze_Assignment_Statement will set the
 712          --  Referenced_As_LHS flag.
 713
 714          elsif Is_Assignable (E)
 715            and then Known_To_Be_Assigned (N, Only_LHS => True)
 716          then
 717             null;
 718
 719          --  For objects that are renamings, just set as simply referenced.
 720          --  We do not try to do assignment type tracking in this case.
 721
 722          elsif Is_Assignable (E)
 723            and then Present (Renamed_Object (E))
 724          then
 725             Set_Referenced (E);
 726
 727          --  Check for a reference in a pragma that should not count as a
 728          --  making the variable referenced for warning purposes.
 729
 730          elsif Is_Non_Significant_Pragma_Reference (N) then
 731             null;
 732
 733          --  A reference in an attribute definition clause does not count as a
 734          --  reference except for the case of Address. The reason that 'Address
 735          --  is an exception is that it creates an alias through which the
 736          --  variable may be referenced.
 737
 738          elsif Nkind (Parent (N)) = N_Attribute_Definition_Clause
 739            and then Chars (Parent (N)) /= Name_Address
 740            and then N = Name (Parent (N))
 741          then
 742             null;
 743
 744          --  Constant completion does not count as a reference
 745
 746          elsif Typ = 'c'
 747            and then Ekind (E) = E_Constant
 748          then
 749             null;
 750
 751          --  Record representation clause does not count as a reference
 752
 753          elsif Nkind (N) = N_Identifier
 754            and then Nkind (Parent (N)) = N_Record_Representation_Clause
 755          then
 756             null;
 757
 758          --  Discriminants do not need to produce a reference to record type
 759
 760          elsif Typ = 'd'
 761            and then Nkind (Parent (N)) = N_Discriminant_Specification
 762          then
 763             null;
 764
 765          --  Out parameter case
 766
 767          elsif Kind = E_Out_Parameter
 768            and then Is_Assignable (E)
 769          then
 770             --  If warning mode for all out parameters is set, or this is
 771             --  the only warning parameter, then we want to mark this for
 772             --  later warning logic by setting Referenced_As_Out_Parameter
 773
 774             if Warn_On_Modified_As_Out_Parameter (Formal) then
 775                Set_Referenced_As_Out_Parameter (E, True);
 776                Set_Referenced_As_LHS (E, False);
 777
 778             --  For OUT parameter not covered by the above cases, we simply
 779             --  regard it as a reference.
 780
 781             else
 782                Set_Referenced_As_Out_Parameter (E);
 783                Set_Referenced (E);
 784             end if;
 785
 786          --  Special processing for IN OUT parameters, where we have an
 787          --  implicit assignment to a simple variable.
 788
 789          elsif Kind = E_In_Out_Parameter
 790            and then Is_Assignable (E)
 791          then
 792             --  For sure this counts as a normal read reference
 793
 794             Set_Referenced (E);
 795             Set_Last_Assignment (E, Empty);
 796
 797             --  We count it as being referenced as an out parameter if the
 798             --  option is set to warn on all out parameters, except that we
 799             --  have a special exclusion for an intrinsic subprogram, which
 800             --  is most likely an instantiation of Unchecked_Deallocation
 801             --  which we do not want to consider as an assignment since it
 802             --  generates false positives. We also exclude the case of an
 803             --  IN OUT parameter if the name of the procedure is Free,
 804             --  since we suspect similar semantics.
 805
 806             if Warn_On_All_Unread_Out_Parameters
 807               and then Is_Entity_Name (Name (Call))
 808               and then not Is_Intrinsic_Subprogram (Entity (Name (Call)))
 809               and then Chars (Name (Call)) /= Name_Free
 810             then
 811                Set_Referenced_As_Out_Parameter (E, True);
 812                Set_Referenced_As_LHS (E, False);
 813             end if;
 814
 815          --  Don't count a recursive reference within a subprogram as a
 816          --  reference (that allows detection of a recursive subprogram
 817          --  whose only references are recursive calls as unreferenced).
 818
 819          elsif Is_Subprogram (E)
 820            and then E = Nearest_Dynamic_Scope (Current_Scope)
 821          then
 822             null;
 823
 824          --  Any other occurrence counts as referencing the entity
 825
 826          elsif OK_To_Set_Referenced then
 827             Set_Referenced (E);
 828
 829             --  If variable, this is an OK reference after an assignment
 830             --  so we can clear the Last_Assignment indication.
 831
 832             if Is_Assignable (E) then
 833                Set_Last_Assignment (E, Empty);
 834             end if;
 835          end if;
 836
 837          --  Check for pragma Unreferenced given and reference is within
 838          --  this source unit (occasion for possible warning to be issued).
 839          --  Note that the entity may be marked as unreferenced by pragma
 840          --  Unused.
 841
 842          if Has_Unreferenced (E)
 843            and then In_Same_Extended_Unit (E, N)
 844          then
 845             --  A reference as a named parameter in a call does not count as a
 846             --  violation of pragma Unreferenced for this purpose.
 847
 848             if Nkind (N) = N_Identifier
 849               and then Nkind (Parent (N)) = N_Parameter_Association
 850               and then Selector_Name (Parent (N)) = N
 851             then
 852                null;
 853
 854             --  Neither does a reference to a variable on the left side of
 855             --  an assignment or use of an out parameter with warnings for
 856             --  unread out parameters specified (via -gnatw.o).
 857
 858             --  The reason for treating unread out parameters in a special
 859             --  way is so that when pragma Unreferenced is specified on such
 860             --  an out parameter we do not want to issue a warning about the
 861             --  pragma being unnecessary - because the purpose of the flag
 862             --  is to warn about them not being read (e.g. unreferenced)
 863             --  after use.
 864
 865             elsif (Known_To_Be_Assigned (N, Only_LHS => True)
 866                     or else (Present (Formal)
 867                               and then Ekind (Formal) = E_Out_Parameter
 868                               and then Warn_On_All_Unread_Out_Parameters))
 869               and then not (Ekind (E) = E_In_Out_Parameter
 870                              and then Known_To_Be_Assigned (N))
 871             then
 872                null;
 873
 874             --  Do not consider F'Result as a violation of pragma Unreferenced
 875             --  since the attribute acts as an anonymous alias of the function
 876             --  result and not as a real reference to the function.
 877
 878             elsif Ekind (E) in E_Function | E_Generic_Function
 879               and then Is_Entity_Name (N)
 880               and then Is_Attribute_Result (Parent (N))
 881             then
 882                null;
 883
 884             --  No warning if the reference is in a call that does not come
 885             --  from source (e.g. a call to a controlled type primitive).
 886
 887             elsif not Comes_From_Source (Parent (N))
 888               and then Nkind (Parent (N)) = N_Procedure_Call_Statement
 889             then
 890                null;
 891
 892             --  For entry formals, we want to place the warning message on the
 893             --  corresponding entity in the accept statement. The current scope
 894             --  is the body of the accept, so we find the formal whose name
 895             --  matches that of the entry formal (there is no link between the
 896             --  two entities, and the one in the accept statement is only used
 897             --  for conformance checking).
 898
 899             elsif Ekind (Scope (E)) = E_Entry then
 900                declare
 901                   BE : Entity_Id;
 902
 903                begin
 904                   BE := First_Entity (Current_Scope);
 905                   while Present (BE) loop
 906                      if Chars (BE) = Chars (E) then
 907                         if Has_Pragma_Unused (E) then
 908                            Error_Msg_NE -- CODEFIX
 909                              ("??aspect Unused specified for&!", N, BE);
 910                         else
 911                            Error_Msg_NE -- CODEFIX
 912                              ("??aspect Unreferenced specified for&!", N, BE);
 913                         end if;
 914                         exit;
 915                      end if;
 916
 917                      Next_Entity (BE);
 918                   end loop;
 919                end;
 920
 921             --  Here we issue the warning, since this is a real reference
 922
 923             elsif Has_Pragma_Unused (E) then
 924                Error_Msg_NE -- CODEFIX
 925                  ("??aspect Unused specified for&!", N, E);
 926             else
 927                Error_Msg_NE -- CODEFIX
 928                  ("??aspect Unreferenced specified for&!", N, E);
 929             end if;
 930          end if;
 931
 932          --  If this is a subprogram instance, mark as well the internal
 933          --  subprogram in the wrapper package, which may be a visible
 934          --  compilation unit.
 935
 936          if Is_Overloadable (E)
 937            and then Is_Generic_Instance (E)
 938            and then Present (Alias (E))
 939          then
 940             Set_Referenced (Alias (E));
 941          end if;
 942       end if;
 943
 944       --  Generate reference if all conditions are met:
 945
 946       if
 947          --  Cross referencing must be active
 948
 949          Opt.Xref_Active
 950
 951          --  The entity must be one for which we collect references
 952
 953          and then Xref_Entity_Letters (Ekind (E)) /= ' '
 954
 955          --  Both Sloc values must be set to something sensible
 956
 957          and then Sloc (E) > No_Location
 958          and then Sloc (N) > No_Location
 959
 960          --  Ignore references from within an instance. The only exceptions to
 961          --  this are default subprograms, for which we generate an implicit
 962          --  reference and compilations in SPARK mode.
 963
 964          and then
 965            (Instantiation_Location (Sloc (N)) = No_Location
 966              or else Typ = 'i'
 967              or else GNATprove_Mode)
 968
 969         --  Ignore dummy references
 970
 971         and then Typ /= ' '
 972       then
 973          if Nkind (N) in N_Identifier
 974                        | N_Defining_Identifier
 975                        | N_Defining_Operator_Symbol
 976                        | N_Operator_Symbol
 977                        | N_Defining_Character_Literal
 978                        | N_Op
 979            or else (Nkind (N) = N_Character_Literal
 980                      and then Sloc (Entity (N)) /= Standard_Location)
 981          then
 982             Nod := N;
 983
 984          elsif Nkind (N) in N_Expanded_Name | N_Selected_Component then
 985             Nod := Selector_Name (N);
 986
 987          else
 988             return;
 989          end if;
 990
 991          --  Normal case of source entity comes from source
 992
 993          if Comes_From_Source (E) then
 994             Ent := E;
 995
 996          --  Because a declaration may be generated for a subprogram body
 997          --  without declaration in GNATprove mode, for inlining, some
 998          --  parameters may end up being marked as not coming from source
 999          --  although they are. Take these into account specially.
1000
1001          elsif GNATprove_Mode and then Is_Formal (E) then
1002             Ent := E;
1003
1004          --  Entity does not come from source, but is a derived subprogram and
1005          --  the derived subprogram comes from source (after one or more
1006          --  derivations) in which case the reference is to parent subprogram.
1007
1008          elsif Is_Overloadable (E)
1009            and then Present (Alias (E))
1010          then
1011             Ent := Alias (E);
1012             while not Comes_From_Source (Ent) loop
1013                if No (Alias (Ent)) then
1014                   return;
1015                end if;
1016
1017                Ent := Alias (Ent);
1018             end loop;
1019
1020          --  The internally created defining entity for a child subprogram
1021          --  that has no previous spec has valid references.
1022
1023          elsif Is_Overloadable (E)
1024            and then Is_Child_Unit (E)
1025          then
1026             Ent := E;
1027
1028          --  Ditto for the formals of such a subprogram
1029
1030          elsif Is_Overloadable (Scope (E))
1031            and then Is_Child_Unit (Scope (E))
1032          then
1033             Ent := E;
1034
1035          --  Record components of discriminated subtypes or derived types must
1036          --  be treated as references to the original component.
1037
1038          elsif Ekind (E) = E_Component
1039            and then Comes_From_Source (Original_Record_Component (E))
1040          then
1041             Ent := Original_Record_Component (E);
1042
1043          --  If this is an expanded reference to a discriminant, recover the
1044          --  original discriminant, which gets the reference.
1045
1046          elsif Ekind (E) = E_In_Parameter
1047            and then Present (Discriminal_Link (E))
1048          then
1049             Ent := Discriminal_Link (E);
1050             Set_Referenced (Ent);
1051
1052          --  Ignore reference to any other entity that is not from source
1053
1054          else
1055             return;
1056          end if;
1057
1058          --  In SPARK mode, consider the underlying entity renamed instead of
1059          --  the renaming, which is needed to compute a valid set of effects
1060          --  (reads, writes) for the enclosing subprogram.
1061
1062          if GNATprove_Mode then
1063             Ent := Get_Through_Renamings (Ent);
1064
1065             --  If no enclosing object, then it could be a reference to any
1066             --  location not tracked individually, like heap-allocated data.
1067             --  Conservatively approximate this possibility by generating a
1068             --  dereference, and return.
1069
1070             if No (Ent) then
1071                if Actual_Typ = 'w' then
1072                   SPARK_Specific.Generate_Dereference (Nod, 'r');
1073                   SPARK_Specific.Generate_Dereference (Nod, 'w');
1074                else
1075                   SPARK_Specific.Generate_Dereference (Nod, 'r');
1076                end if;
1077
1078                return;
1079             end if;
1080          end if;
1081
1082          --  Record reference to entity
1083
1084          if Actual_Typ = 'p'
1085            and then Is_Subprogram (Nod)
1086            and then Present (Overridden_Operation (Nod))
1087          then
1088             Actual_Typ := 'P';
1089          end if;
1090
1091          --  Comment needed here for special SPARK code ???
1092
1093          if GNATprove_Mode then
1094
1095             --  Ignore references to an entity which is a Part_Of single
1096             --  concurrent object. Ideally we would prefer to add it as a
1097             --  reference to the corresponding concurrent type, but it is quite
1098             --  difficult (as such references are not currently added even for)
1099             --  reads/writes of private protected components) and not worth the
1100             --  effort.
1101
1102             if Ekind (Ent) in E_Abstract_State | E_Constant | E_Variable
1103               and then Present (Encapsulating_State (Ent))
1104               and then Is_Single_Concurrent_Object (Encapsulating_State (Ent))
1105             then
1106                return;
1107             end if;
1108
1109             Ref := Sloc (Nod);
1110             Def := Sloc (Ent);
1111
1112             Ref_Scope :=
1113               SPARK_Specific.Enclosing_Subprogram_Or_Library_Package (Nod);
1114             Ent_Scope :=
1115               SPARK_Specific.Enclosing_Subprogram_Or_Library_Package (Ent);
1116
1117             --  Since we are reaching through renamings in SPARK mode, we may
1118             --  end up with standard constants. Ignore those.
1119
1120             if Sloc (Ent_Scope) <= Standard_Location
1121               or else Def <= Standard_Location
1122             then
1123                return;
1124             end if;
1125
1126             Add_Entry
1127               ((Ent       => Ent,
1128                 Loc       => Ref,
1129                 Typ       => Actual_Typ,
1130                 Eun       => Get_Top_Level_Code_Unit (Def),
1131                 Lun       => Get_Top_Level_Code_Unit (Ref),
1132                 Ref_Scope => Ref_Scope,
1133                 Ent_Scope => Ent_Scope),
1134                Ent_Scope_File => Get_Top_Level_Code_Unit (Ent));
1135
1136          else
1137             Ref := Original_Location (Sloc (Nod));
1138             Def := Original_Location (Sloc (Ent));
1139
1140             --  If this is an operator symbol, skip the initial quote for
1141             --  navigation purposes. This is not done for the end label,
1142             --  where we want the actual position after the closing quote.
1143
1144             if Typ = 't' then
1145                null;
1146
1147             elsif Nkind (N) = N_Defining_Operator_Symbol
1148               or else Nkind (Nod) = N_Operator_Symbol
1149             then
1150                Ref := Ref + 1;
1151             end if;
1152
1153             Add_Entry
1154               ((Ent       => Ent,
1155                 Loc       => Ref,
1156                 Typ       => Actual_Typ,
1157                 Eun       => Get_Source_Unit (Def),
1158                 Lun       => Get_Source_Unit (Ref),
1159                 Ref_Scope => Empty,
1160                 Ent_Scope => Empty),
1161                Ent_Scope_File => No_Unit);
1162
1163             --  Generate reference to the first private entity
1164
1165             if Typ = 'e'
1166               and then Comes_From_Source (E)
1167               and then Nkind (Ent) = N_Defining_Identifier
1168               and then (Is_Package_Or_Generic_Package (Ent)
1169                          or else Is_Concurrent_Type (Ent))
1170               and then Present (First_Private_Entity (E))
1171               and then In_Extended_Main_Source_Unit (N)
1172             then
1173                --  Handle case in which the full-view and partial-view of the
1174                --  first private entity are swapped.
1175
1176                declare
1177                   First_Private : Entity_Id := First_Private_Entity (E);
1178
1179                begin
1180                   if Is_Private_Type (First_Private)
1181                     and then Present (Full_View (First_Private))
1182                   then
1183                      First_Private := Full_View (First_Private);
1184                   end if;
1185
1186                   Add_Entry
1187                     ((Ent       => Ent,
1188                       Loc       => Sloc (First_Private),
1189                       Typ       => 'E',
1190                       Eun       => Get_Source_Unit (Def),
1191                       Lun       => Get_Source_Unit (Ref),
1192                       Ref_Scope => Empty,
1193                       Ent_Scope => Empty),
1194                      Ent_Scope_File => No_Unit);
1195                end;
1196             end if;
1197          end if;
1198       end if;
1199    end Generate_Reference;
1200
1201    -----------------------------------
1202    -- Generate_Reference_To_Formals --
1203    -----------------------------------
1204
1205    procedure Generate_Reference_To_Formals (E : Entity_Id) is
1206       Formal : Entity_Id;
1207
1208    begin
1209       if Is_Access_Subprogram_Type (E) then
1210          Formal := First_Formal (Designated_Type (E));
1211       else
1212          Formal := First_Formal (E);
1213       end if;
1214
1215       while Present (Formal) loop
1216          if Ekind (Formal) = E_In_Parameter then
1217
1218             if Nkind (Parameter_Type (Parent (Formal))) = N_Access_Definition
1219             then
1220                Generate_Reference (E, Formal, '^', False);
1221             else
1222                Generate_Reference (E, Formal, '>', False);
1223             end if;
1224
1225          elsif Ekind (Formal) = E_In_Out_Parameter then
1226             Generate_Reference (E, Formal, '=', False);
1227
1228          else
1229             Generate_Reference (E, Formal, '<', False);
1230          end if;
1231
1232          Next_Formal (Formal);
1233       end loop;
1234    end Generate_Reference_To_Formals;
1235
1236    -------------------------------------------
1237    -- Generate_Reference_To_Generic_Formals --
1238    -------------------------------------------
1239
1240    procedure Generate_Reference_To_Generic_Formals (E : Entity_Id) is
1241       Formal : Entity_Id;
1242
1243    begin
1244       Formal := First_Entity (E);
1245       while Present (Formal) loop
1246          if Comes_From_Source (Formal) then
1247             Generate_Reference (E, Formal, 'z', False);
1248          end if;
1249
1250          Next_Entity (Formal);
1251       end loop;
1252    end Generate_Reference_To_Generic_Formals;
1253
1254    -------------
1255    -- Get_Key --
1256    -------------
1257
1258    function Get_Key (E : Xref_Entry_Number) return Xref_Entry_Number is
1259    begin
1260       return E;
1261    end Get_Key;
1262
1263    ----------
1264    -- Hash --
1265    ----------
1266
1267    function Hash (F : Xref_Entry_Number) return Header_Num is
1268       --  It is unlikely to have two references to the same entity at the same
1269       --  source location, so the hash function depends only on the Ent and Loc
1270       --  fields.
1271
1272       XE : Xref_Entry renames Xrefs.Table (F);
1273       type M is mod 2**32;
1274
1275       H : constant M := 3 * M (XE.Key.Ent) + 5 * M (abs XE.Key.Loc);
1276       --  It would be more natural to write:
1277       --
1278       --    H : constant M := 3 * M'Mod (XE.Key.Ent) + 5 * M'Mod (XE.Key.Loc);
1279       --
1280       --  But we can't use M'Mod, because it prevents bootstrapping with older
1281       --  compilers. Loc can be negative, so we do "abs" before converting.
1282       --  One day this can be cleaned up ???
1283
1284    begin
1285       return Header_Num (H mod Num_Buckets);
1286    end Hash;
1287
1288    -----------------
1289    -- HT_Set_Next --
1290    -----------------
1291
1292    procedure HT_Set_Next (E : Xref_Entry_Number; Next : Xref_Entry_Number) is
1293    begin
1294       Xrefs.Table (E).HTable_Next := Next;
1295    end HT_Set_Next;
1296
1297    -------------
1298    -- HT_Next --
1299    -------------
1300
1301    function HT_Next (E : Xref_Entry_Number) return Xref_Entry_Number is
1302    begin
1303       return Xrefs.Table (E).HTable_Next;
1304    end HT_Next;
1305
1306    ----------------
1307    -- Initialize --
1308    ----------------
1309
1310    procedure Initialize is
1311    begin
1312       Xrefs.Init;
1313    end Initialize;
1314
1315    --------
1316    -- Lt --
1317    --------
1318
1319    function Lt (T1, T2 : Xref_Entry) return Boolean is
1320    begin
1321       --  First test: if entity is in different unit, sort by unit
1322
1323       if T1.Key.Eun /= T2.Key.Eun then
1324          return Dependency_Num (T1.Key.Eun) < Dependency_Num (T2.Key.Eun);
1325
1326       --  Second test: within same unit, sort by entity Sloc
1327
1328       elsif T1.Def /= T2.Def then
1329          return T1.Def < T2.Def;
1330
1331       --  Third test: sort definitions ahead of references
1332
1333       elsif T1.Key.Loc = No_Location then
1334          return True;
1335
1336       elsif T2.Key.Loc = No_Location then
1337          return False;
1338
1339       --  Fourth test: for same entity, sort by reference location unit
1340
1341       elsif T1.Key.Lun /= T2.Key.Lun then
1342          return Dependency_Num (T1.Key.Lun) < Dependency_Num (T2.Key.Lun);
1343
1344       --  Fifth test: order of location within referencing unit
1345
1346       elsif T1.Key.Loc /= T2.Key.Loc then
1347          return T1.Key.Loc < T2.Key.Loc;
1348
1349       --  Finally, for two locations at the same address, we prefer
1350       --  the one that does NOT have the type 'r' so that a modification
1351       --  or extension takes preference, when there are more than one
1352       --  reference at the same location. As a result, in the case of
1353       --  entities that are in-out actuals, the read reference follows
1354       --  the modify reference.
1355
1356       else
1357          return T2.Key.Typ = 'r';
1358       end if;
1359    end Lt;
1360
1361    -----------------------
1362    -- Output_References --
1363    -----------------------
1364
1365    procedure Output_References is
1366
1367       procedure Get_Type_Reference
1368         (Ent   : Entity_Id;
1369          Tref  : out Entity_Id;
1370          Left  : out Character;
1371          Right : out Character);
1372       --  Given an Entity_Id Ent, determines whether a type reference is
1373       --  required. If so, Tref is set to the entity for the type reference
1374       --  and Left and Right are set to the left/right brackets to be output
1375       --  for the reference. If no type reference is required, then Tref is
1376       --  set to Empty, and Left/Right are set to space.
1377
1378       procedure Output_Import_Export_Info (Ent : Entity_Id);
1379       --  Output language and external name information for an interfaced
1380       --  entity, using the format <language, external_name>.
1381
1382       ------------------------
1383       -- Get_Type_Reference --
1384       ------------------------
1385
1386       procedure Get_Type_Reference
1387         (Ent   : Entity_Id;
1388          Tref  : out Entity_Id;
1389          Left  : out Character;
1390          Right : out Character)
1391       is
1392          Sav : Entity_Id;
1393
1394       begin
1395          --  See if we have a type reference
1396
1397          Tref := Ent;
1398          Left := '{';
1399          Right := '}';
1400
1401          loop
1402             Sav := Tref;
1403
1404             --  Processing for types
1405
1406             if Is_Type (Tref) then
1407
1408                --  Case of base type
1409
1410                if Base_Type (Tref) = Tref then
1411
1412                   --  If derived, then get first subtype
1413
1414                   if Tref /= Etype (Tref) then
1415                      Tref := First_Subtype (Etype (Tref));
1416
1417                      --  Set brackets for derived type, but don't override
1418                      --  pointer case since the fact that something is a
1419                      --  pointer is more important.
1420
1421                      if Left /= '(' then
1422                         Left := '<';
1423                         Right := '>';
1424                      end if;
1425
1426                   --  If the completion of a private type is itself a derived
1427                   --  type, we need the parent of the full view.
1428
1429                   elsif Is_Private_Type (Tref)
1430                     and then Present (Full_View (Tref))
1431                     and then Etype (Full_View (Tref)) /= Full_View (Tref)
1432                   then
1433                      Tref := Etype (Full_View (Tref));
1434
1435                      if Left /= '(' then
1436                         Left := '<';
1437                         Right := '>';
1438                      end if;
1439
1440                   --  If non-derived pointer, get directly designated type.
1441                   --  If the type has a full view, all references are on the
1442                   --  partial view that is seen first.
1443
1444                   elsif Is_Access_Type (Tref) then
1445                      Tref := Directly_Designated_Type (Tref);
1446                      Left := '(';
1447                      Right := ')';
1448
1449                   elsif Is_Private_Type (Tref)
1450                     and then Present (Full_View (Tref))
1451                   then
1452                      if Is_Access_Type (Full_View (Tref)) then
1453                         Tref := Directly_Designated_Type (Full_View (Tref));
1454                         Left := '(';
1455                         Right := ')';
1456
1457                      --  If the full view is an array type, we also retrieve
1458                      --  the corresponding component type, because the ali
1459                      --  entry already indicates that this is an array.
1460
1461                      elsif Is_Array_Type (Full_View (Tref)) then
1462                         Tref := Component_Type (Full_View (Tref));
1463                         Left := '(';
1464                         Right := ')';
1465                      end if;
1466
1467                   --  If non-derived array, get component type. Skip component
1468                   --  type for case of String or Wide_String, saves worthwhile
1469                   --  space.
1470
1471                   elsif Is_Array_Type (Tref)
1472                     and then Tref /= Standard_String
1473                     and then Tref /= Standard_Wide_String
1474                   then
1475                      Tref := Component_Type (Tref);
1476                      Left := '(';
1477                      Right := ')';
1478
1479                   --  For other non-derived base types, nothing
1480
1481                   else
1482                      exit;
1483                   end if;
1484
1485                --  For a subtype, go to ancestor subtype
1486
1487                else
1488                   Tref := Ancestor_Subtype (Tref);
1489
1490                   --  If no ancestor subtype, go to base type
1491
1492                   if No (Tref) then
1493                      Tref := Base_Type (Sav);
1494                   end if;
1495                end if;
1496
1497             --  For objects, functions, enum literals, just get type from
1498             --  Etype field.
1499
1500             elsif Is_Object (Tref)
1501               or else Ekind (Tref) = E_Enumeration_Literal
1502               or else Ekind (Tref) = E_Function
1503               or else Ekind (Tref) = E_Operator
1504             then
1505                Tref := Etype (Tref);
1506
1507                --  Another special case: an object of a classwide type
1508                --  initialized with a tag-indeterminate call gets a subtype
1509                --  of the classwide type during expansion. See if the original
1510                --  type in the declaration is named, and return it instead
1511                --  of going to the root type. The expression may be a class-
1512                --  wide function call whose result is on the secondary stack,
1513                --  which forces the declaration to be rewritten as a renaming,
1514                --  so examine the source declaration.
1515
1516                if Ekind (Tref) = E_Class_Wide_Subtype then
1517                   declare
1518                      Decl : constant Node_Id := Original_Node (Parent (Ent));
1519                   begin
1520                      if Nkind (Decl) = N_Object_Declaration
1521                        and then Is_Entity_Name
1522                                   (Original_Node (Object_Definition (Decl)))
1523                      then
1524                         Tref :=
1525                           Entity (Original_Node (Object_Definition (Decl)));
1526                      end if;
1527                   end;
1528
1529                --  For a function that returns a class-wide type, Tref is
1530                --  already correct.
1531
1532                elsif Is_Overloadable (Ent)
1533                  and then Is_Class_Wide_Type (Tref)
1534                then
1535                   return;
1536                end if;
1537
1538             --  For anything else, exit
1539
1540             else
1541                exit;
1542             end if;
1543
1544             --  Exit if no type reference, or we are stuck in some loop trying
1545             --  to find the type reference, or if the type is standard void
1546             --  type (the latter is an implementation artifact that should not
1547             --  show up in the generated cross-references).
1548
1549             exit when No (Tref)
1550               or else Tref = Sav
1551               or else Tref = Standard_Void_Type;
1552
1553             --  If we have a usable type reference, return, otherwise keep
1554             --  looking for something useful (we are looking for something
1555             --  that either comes from source or standard)
1556
1557             if Sloc (Tref) = Standard_Location
1558               or else Comes_From_Source (Tref)
1559             then
1560                --  If the reference is a subtype created for a generic actual,
1561                --  go actual directly, the inner subtype is not user visible.
1562
1563                if Nkind (Parent (Tref)) = N_Subtype_Declaration
1564                  and then not Comes_From_Source (Parent (Tref))
1565                  and then
1566                   (Is_Wrapper_Package (Scope (Tref))
1567                      or else Is_Generic_Instance (Scope (Tref)))
1568                then
1569                   Tref := First_Subtype (Base_Type (Tref));
1570                end if;
1571
1572                return;
1573             end if;
1574          end loop;
1575
1576          --  If we fall through the loop, no type reference
1577
1578          Tref := Empty;
1579          Left := ' ';
1580          Right := ' ';
1581       end Get_Type_Reference;
1582
1583       -------------------------------
1584       -- Output_Import_Export_Info --
1585       -------------------------------
1586
1587       procedure Output_Import_Export_Info (Ent : Entity_Id) is
1588          Language_Name : Name_Id;
1589          Conv          : constant Convention_Id := Convention (Ent);
1590
1591       begin
1592          --  Generate language name from convention
1593
1594          if Conv = Convention_C or else Conv in Convention_C_Variadic then
1595             Language_Name := Name_C;
1596
1597          elsif Conv = Convention_CPP then
1598             Language_Name := Name_CPP;
1599
1600          elsif Conv = Convention_Ada then
1601             Language_Name := Name_Ada;
1602
1603          else
1604             --  For the moment we ignore all other cases ???
1605
1606             return;
1607          end if;
1608
1609          Write_Info_Char ('<');
1610          Get_Unqualified_Name_String (Language_Name);
1611
1612          for J in 1 .. Name_Len loop
1613             Write_Info_Char (Name_Buffer (J));
1614          end loop;
1615
1616          if Present (Interface_Name (Ent)) then
1617             Write_Info_Char (',');
1618             String_To_Name_Buffer (Strval (Interface_Name (Ent)));
1619
1620             for J in 1 .. Name_Len loop
1621                Write_Info_Char (Name_Buffer (J));
1622             end loop;
1623          end if;
1624
1625          Write_Info_Char ('>');
1626       end Output_Import_Export_Info;
1627
1628    --  Start of processing for Output_References
1629
1630    begin
1631       --  First we add references to the primitive operations of tagged types
1632       --  declared in the main unit.
1633
1634       Handle_Prim_Ops : declare
1635          Ent : Entity_Id;
1636
1637       begin
1638          for J in 1 .. Xrefs.Last loop
1639             Ent := Xrefs.Table (J).Key.Ent;
1640
1641             if Is_Type (Ent)
1642               and then Is_Tagged_Type (Ent)
1643               and then Is_Base_Type (Ent)
1644               and then In_Extended_Main_Source_Unit (Ent)
1645             then
1646                Generate_Prim_Op_References (Ent);
1647             end if;
1648          end loop;
1649       end Handle_Prim_Ops;
1650
1651       --  Before we go ahead and output the references we have a problem
1652       --  that needs dealing with. So far we have captured things that are
1653       --  definitely referenced by the main unit, or defined in the main
1654       --  unit. That's because we don't want to clutter up the ali file
1655       --  for this unit with definition lines for entities in other units
1656       --  that are not referenced.
1657
1658       --  But there is a glitch. We may reference an entity in another unit,
1659       --  and it may have a type reference to an entity that is not directly
1660       --  referenced in the main unit, which may mean that there is no xref
1661       --  entry for this entity yet in the list of references.
1662
1663       --  If we don't do something about this, we will end with an orphan type
1664       --  reference, i.e. it will point to an entity that does not appear
1665       --  within the generated references in the ali file. That is not good for
1666       --  tools using the xref information.
1667
1668       --  To fix this, we go through the references adding definition entries
1669       --  for any unreferenced entities that can be referenced in a type
1670       --  reference. There is a recursion problem here, and that is dealt with
1671       --  by making sure that this traversal also traverses any entries that
1672       --  get added by the traversal.
1673
1674       Handle_Orphan_Type_References : declare
1675          J    : Nat;
1676          Tref : Entity_Id;
1677          Ent  : Entity_Id;
1678
1679          L, R : Character;
1680          pragma Warnings (Off, L);
1681          pragma Warnings (Off, R);
1682
1683          procedure New_Entry (E : Entity_Id);
1684          --  Make an additional entry into the Xref table for a type entity
1685          --  that is related to the current entity (parent, type ancestor,
1686          --  progenitor, etc.).
1687
1688          ----------------
1689          -- New_Entry --
1690          ----------------
1691
1692          procedure New_Entry (E : Entity_Id) is
1693          begin
1694             pragma Assert (Present (E));
1695
1696             if not Has_Xref_Entry (Implementation_Base_Type (E))
1697               and then Sloc (E) > No_Location
1698             then
1699                Add_Entry
1700                  ((Ent       => E,
1701                    Loc       => No_Location,
1702                    Typ       => Character'First,
1703                    Eun       => Get_Source_Unit (Original_Location (Sloc (E))),
1704                    Lun       => No_Unit,
1705                    Ref_Scope => Empty,
1706                    Ent_Scope => Empty),
1707                   Ent_Scope_File => No_Unit);
1708             end if;
1709          end New_Entry;
1710
1711       --  Start of processing for Handle_Orphan_Type_References
1712
1713       begin
1714          --  Note that this is not a for loop for a very good reason. The
1715          --  processing of items in the table can add new items to the table,
1716          --  and they must be processed as well.
1717
1718          J := 1;
1719          while J <= Xrefs.Last loop
1720             Ent := Xrefs.Table (J).Key.Ent;
1721
1722             --  Do not generate reference information for an ignored Ghost
1723             --  entity because neither the entity nor its references will
1724             --  appear in the final tree.
1725
1726             if Is_Ignored_Ghost_Entity (Ent) then
1727                goto Orphan_Continue;
1728             end if;
1729
1730             Get_Type_Reference (Ent, Tref, L, R);
1731
1732             if Present (Tref)
1733               and then not Has_Xref_Entry (Tref)
1734               and then Sloc (Tref) > No_Location
1735             then
1736                New_Entry (Tref);
1737
1738                if Is_Record_Type (Ent)
1739                  and then Present (Interfaces (Ent))
1740                then
1741                   --  Add an entry for each one of the given interfaces
1742                   --  implemented by type Ent.
1743
1744                   declare
1745                      Elmt : Elmt_Id := First_Elmt (Interfaces (Ent));
1746                   begin
1747                      while Present (Elmt) loop
1748                         New_Entry (Node (Elmt));
1749                         Next_Elmt (Elmt);
1750                      end loop;
1751                   end;
1752                end if;
1753             end if;
1754
1755             --  Collect inherited primitive operations that may be declared in
1756             --  another unit and have no visible reference in the current one.
1757
1758             if Is_Type (Ent)
1759               and then Is_Tagged_Type (Ent)
1760               and then Is_Derived_Type (Ent)
1761               and then Is_Base_Type (Ent)
1762               and then In_Extended_Main_Source_Unit (Ent)
1763             then
1764                declare
1765                   Op_List : constant Elist_Id := Primitive_Operations (Ent);
1766                   Op      : Elmt_Id;
1767                   Prim    : Entity_Id;
1768
1769                   function Parent_Op (E : Entity_Id) return Entity_Id;
1770                   --  Find original operation, which may be inherited through
1771                   --  several derivations.
1772
1773                   function Parent_Op (E : Entity_Id) return Entity_Id is
1774                      Orig_Op : constant Entity_Id := Alias (E);
1775
1776                   begin
1777                      if No (Orig_Op) then
1778                         return Empty;
1779
1780                      elsif not Comes_From_Source (E)
1781                        and then not Has_Xref_Entry (Orig_Op)
1782                        and then Comes_From_Source (Orig_Op)
1783                      then
1784                         return Orig_Op;
1785                      else
1786                         return Parent_Op (Orig_Op);
1787                      end if;
1788                   end Parent_Op;
1789
1790                begin
1791                   Op := First_Elmt (Op_List);
1792                   while Present (Op) loop
1793                      Prim := Parent_Op (Node (Op));
1794
1795                      if Present (Prim) then
1796                         Add_Entry
1797                           ((Ent       => Prim,
1798                             Loc       => No_Location,
1799                             Typ       => Character'First,
1800                             Eun       => Get_Source_Unit (Sloc (Prim)),
1801                             Lun       => No_Unit,
1802                             Ref_Scope => Empty,
1803                             Ent_Scope => Empty),
1804                            Ent_Scope_File => No_Unit);
1805                      end if;
1806
1807                      Next_Elmt (Op);
1808                   end loop;
1809                end;
1810             end if;
1811
1812             <<Orphan_Continue>>
1813             J := J + 1;
1814          end loop;
1815       end Handle_Orphan_Type_References;
1816
1817       --  Now we have all the references, including those for any embedded type
1818       --  references, so we can sort them, and output them.
1819
1820       Output_Refs : declare
1821          Nrefs : constant Nat := Xrefs.Last;
1822          --  Number of references in table
1823
1824          Rnums : array (0 .. Nrefs) of Nat;
1825          --  This array contains numbers of references in the Xrefs table.
1826          --  This list is sorted in output order. The extra 0'th entry is
1827          --  convenient for the call to sort. When we sort the table, we
1828          --  move the entries in Rnums around, but we do not move the
1829          --  original table entries.
1830
1831          Curxu : Unit_Number_Type;
1832          --  Current xref unit
1833
1834          Curru : Unit_Number_Type;
1835          --  Current reference unit for one entity
1836
1837          Curent : Entity_Id;
1838          --  Current entity
1839
1840          Curnam : String (1 .. Name_Buffer'Length);
1841          Curlen : Natural;
1842          --  Simple name and length of current entity
1843
1844          Curdef : Source_Ptr;
1845          --  Original source location for current entity
1846
1847          Crloc : Source_Ptr;
1848          --  Current reference location
1849
1850          Ctyp : Character;
1851          --  Entity type character
1852
1853          Prevt : Character;
1854          --  reference kind of previous reference
1855
1856          Tref : Entity_Id;
1857          --  Type reference
1858
1859          Rref : Node_Id;
1860          --  Renaming reference
1861
1862          Trunit : Unit_Number_Type;
1863          --  Unit number for type reference
1864
1865          function Lt (Op1, Op2 : Natural) return Boolean;
1866          --  Comparison function for Sort call
1867
1868          function Name_Change (X : Entity_Id) return Boolean;
1869          --  Determines if entity X has a different simple name from Curent
1870
1871          procedure Move (From : Natural; To : Natural);
1872          --  Move procedure for Sort call
1873
1874          package Sorting is new GNAT.Heap_Sort_G (Move, Lt);
1875
1876          --------
1877          -- Lt --
1878          --------
1879
1880          function Lt (Op1, Op2 : Natural) return Boolean is
1881             T1 : Xref_Entry renames Xrefs.Table (Rnums (Nat (Op1)));
1882             T2 : Xref_Entry renames Xrefs.Table (Rnums (Nat (Op2)));
1883
1884          begin
1885             return Lt (T1, T2);
1886          end Lt;
1887
1888          ----------
1889          -- Move --
1890          ----------
1891
1892          procedure Move (From : Natural; To : Natural) is
1893          begin
1894             Rnums (Nat (To)) := Rnums (Nat (From));
1895          end Move;
1896
1897          -----------------
1898          -- Name_Change --
1899          -----------------
1900
1901          --  Why a string comparison here??? Why not compare Name_Id values???
1902
1903          function Name_Change (X : Entity_Id) return Boolean is
1904          begin
1905             Get_Unqualified_Name_String (Chars (X));
1906
1907             if Name_Len /= Curlen then
1908                return True;
1909             else
1910                return Name_Buffer (1 .. Curlen) /= Curnam (1 .. Curlen);
1911             end if;
1912          end Name_Change;
1913
1914       --  Start of processing for Output_Refs
1915
1916       begin
1917          --  Capture the definition Sloc values. We delay doing this till now,
1918          --  since at the time the reference or definition is made, private
1919          --  types may be swapped, and the Sloc value may be incorrect. We
1920          --  also set up the pointer vector for the sort.
1921
1922          --  For user-defined operators we need to skip the initial quote and
1923          --  point to the first character of the name, for navigation purposes.
1924
1925          for J in 1 .. Nrefs loop
1926             declare
1927                E   : constant Entity_Id  := Xrefs.Table (J).Key.Ent;
1928                Loc : constant Source_Ptr := Original_Location (Sloc (E));
1929
1930             begin
1931                Rnums (J) := J;
1932
1933                if Nkind (E) = N_Defining_Operator_Symbol then
1934                   Xrefs.Table (J).Def := Loc + 1;
1935                else
1936                   Xrefs.Table (J).Def := Loc;
1937                end if;
1938             end;
1939          end loop;
1940
1941          --  Sort the references
1942
1943          Sorting.Sort (Integer (Nrefs));
1944
1945          --  Initialize loop through references
1946
1947          Curxu  := No_Unit;
1948          Curent := Empty;
1949          Curdef := No_Location;
1950          Curru  := No_Unit;
1951          Crloc  := No_Location;
1952          Prevt  := 'm';
1953
1954          --  Loop to output references
1955
1956          for Refno in 1 .. Nrefs loop
1957             Output_One_Ref : declare
1958                Ent : Entity_Id;
1959
1960                XE : Xref_Entry renames Xrefs.Table (Rnums (Refno));
1961                --  The current entry to be accessed
1962
1963                Left  : Character;
1964                Right : Character;
1965                --  Used for {} or <> or () for type reference
1966
1967                procedure Check_Type_Reference
1968                  (Ent            : Entity_Id;
1969                   List_Interface : Boolean;
1970                   Is_Component   : Boolean := False);
1971                --  Find whether there is a meaningful type reference for
1972                --  Ent, and display it accordingly. If List_Interface is
1973                --  true, then Ent is a progenitor interface of the current
1974                --  type entity being listed. In that case list it as is,
1975                --  without looking for a type reference for it. Flag is also
1976                --  used for index types of an array type, where the caller
1977                --  supplies the intended type reference. Is_Component serves
1978                --  the same purpose, to display the component type of a
1979                --  derived array type, for which only the parent type has
1980                --  ben displayed so far.
1981
1982                procedure Output_Instantiation_Refs (Loc : Source_Ptr);
1983                --  Recursive procedure to output instantiation references for
1984                --  the given source ptr in [file|line[...]] form. No output
1985                --  if the given location is not a generic template reference.
1986
1987                procedure Output_Overridden_Op (Old_E : Entity_Id);
1988                --  For a subprogram that is overriding, display information
1989                --  about the inherited operation that it overrides.
1990
1991                --------------------------
1992                -- Check_Type_Reference --
1993                --------------------------
1994
1995                procedure Check_Type_Reference
1996                  (Ent            : Entity_Id;
1997                   List_Interface : Boolean;
1998                   Is_Component   : Boolean := False)
1999                is
2000                begin
2001                   if List_Interface then
2002
2003                      --  This is a progenitor interface of the type for which
2004                      --  xref information is being generated.
2005
2006                      Tref  := Ent;
2007                      Left  := '<';
2008                      Right := '>';
2009
2010                   --  The following is not documented in lib-xref.ads ???
2011
2012                   elsif Is_Component then
2013                      Tref  := Ent;
2014                      Left  := '(';
2015                      Right := ')';
2016
2017                   else
2018                      Get_Type_Reference (Ent, Tref, Left, Right);
2019                   end if;
2020
2021                   if Present (Tref) then
2022
2023                      --  Case of standard entity, output name
2024
2025                      if Sloc (Tref) = Standard_Location then
2026                         Write_Info_Char (Left);
2027                         Write_Info_Name (Chars (Tref));
2028                         Write_Info_Char (Right);
2029
2030                      --  Case of source entity, output location
2031
2032                      else
2033                         Write_Info_Char (Left);
2034                         Trunit := Get_Source_Unit (Sloc (Tref));
2035
2036                         if Trunit /= Curxu then
2037                            Write_Info_Nat (Dependency_Num (Trunit));
2038                            Write_Info_Char ('|');
2039                         end if;
2040
2041                         Write_Info_Nat
2042                           (Int (Get_Logical_Line_Number (Sloc (Tref))));
2043
2044                         declare
2045                            Ent  : Entity_Id;
2046                            Ctyp : Character;
2047
2048                         begin
2049                            Ent := Tref;
2050                            Ctyp := Xref_Entity_Letters (Ekind (Ent));
2051
2052                            if Ctyp = '+'
2053                              and then Present (Full_View (Ent))
2054                            then
2055                               Ent := Underlying_Type (Ent);
2056
2057                               if Present (Ent) then
2058                                  Ctyp := Xref_Entity_Letters (Ekind (Ent));
2059                               end if;
2060                            end if;
2061
2062                            Write_Info_Char (Ctyp);
2063                         end;
2064
2065                         Write_Info_Nat
2066                           (Int (Get_Column_Number (Sloc (Tref))));
2067
2068                         --  If the type comes from an instantiation, add the
2069                         --  corresponding info.
2070
2071                         Output_Instantiation_Refs (Sloc (Tref));
2072                         Write_Info_Char (Right);
2073                      end if;
2074                   end if;
2075                end Check_Type_Reference;
2076
2077                -------------------------------
2078                -- Output_Instantiation_Refs --
2079                -------------------------------
2080
2081                procedure Output_Instantiation_Refs (Loc : Source_Ptr) is
2082                   Iloc : constant Source_Ptr := Instantiation_Location (Loc);
2083                   Lun  : Unit_Number_Type;
2084                   Cu   : constant Unit_Number_Type := Curru;
2085
2086                begin
2087                   --  Nothing to do if this is not an instantiation
2088
2089                   if Iloc = No_Location then
2090                      return;
2091                   end if;
2092
2093                   --  Output instantiation reference
2094
2095                   Write_Info_Char ('[');
2096                   Lun := Get_Source_Unit (Iloc);
2097
2098                   if Lun /= Curru then
2099                      Curru := Lun;
2100                      Write_Info_Nat (Dependency_Num (Curru));
2101                      Write_Info_Char ('|');
2102                   end if;
2103
2104                   Write_Info_Nat (Int (Get_Logical_Line_Number (Iloc)));
2105
2106                   --  Recursive call to get nested instantiations
2107
2108                   Output_Instantiation_Refs (Iloc);
2109
2110                   --  Output final ] after call to get proper nesting
2111
2112                   Write_Info_Char (']');
2113                   Curru := Cu;
2114                   return;
2115                end Output_Instantiation_Refs;
2116
2117                --------------------------
2118                -- Output_Overridden_Op --
2119                --------------------------
2120
2121                procedure Output_Overridden_Op (Old_E : Entity_Id) is
2122                   Op : Entity_Id;
2123
2124                begin
2125                   --  The overridden operation has an implicit declaration
2126                   --  at the point of derivation. What we want to display
2127                   --  is the original operation, which has the actual body
2128                   --  (or abstract declaration) that is being overridden.
2129                   --  The overridden operation is not always set, e.g. when
2130                   --  it is a predefined operator.
2131
2132                   if No (Old_E) then
2133                      return;
2134
2135                   --  Follow alias chain if one is present
2136
2137                   elsif Present (Alias (Old_E)) then
2138
2139                      --  The subprogram may have been implicitly inherited
2140                      --  through several levels of derivation, so find the
2141                      --  ultimate (source) ancestor.
2142
2143                      Op := Ultimate_Alias (Old_E);
2144
2145                   --  Normal case of no alias present. We omit generated
2146                   --  primitives like tagged equality, that have no source
2147                   --  representation.
2148
2149                   else
2150                      Op := Old_E;
2151                   end if;
2152
2153                   if Present (Op)
2154                     and then Sloc (Op) /= Standard_Location
2155                     and then Comes_From_Source (Op)
2156                   then
2157                      declare
2158                         Loc      : constant Source_Ptr := Sloc (Op);
2159                         Par_Unit : constant Unit_Number_Type :=
2160                                      Get_Source_Unit (Loc);
2161
2162                      begin
2163                         Write_Info_Char ('<');
2164
2165                         if Par_Unit /= Curxu then
2166                            Write_Info_Nat (Dependency_Num (Par_Unit));
2167                            Write_Info_Char ('|');
2168                         end if;
2169
2170                         Write_Info_Nat (Int (Get_Logical_Line_Number (Loc)));
2171                         Write_Info_Char ('p');
2172                         Write_Info_Nat (Int (Get_Column_Number (Loc)));
2173                         Write_Info_Char ('>');
2174                      end;
2175                   end if;
2176                end Output_Overridden_Op;
2177
2178             --  Start of processing for Output_One_Ref
2179
2180             begin
2181                Ent := XE.Key.Ent;
2182
2183                --  Do not generate reference information for an ignored Ghost
2184                --  entity because neither the entity nor its references will
2185                --  appear in the final tree.
2186
2187                if Is_Ignored_Ghost_Entity (Ent) then
2188                   goto Continue;
2189                end if;
2190
2191                Ctyp := Xref_Entity_Letters (Ekind (Ent));
2192
2193                --  Skip reference if it is the only reference to an entity,
2194                --  and it is an END line reference, and the entity is not in
2195                --  the current extended source. This prevents junk entries
2196                --  consisting only of packages with END lines, where no
2197                --  entity from the package is actually referenced.
2198
2199                if XE.Key.Typ = 'e'
2200                  and then Ent /= Curent
2201                  and then (Refno = Nrefs
2202                             or else
2203                               Ent /= Xrefs.Table (Rnums (Refno + 1)).Key.Ent)
2204                  and then not In_Extended_Main_Source_Unit (Ent)
2205                then
2206                   goto Continue;
2207                end if;
2208
2209                --  For private type, get full view type
2210
2211                if Ctyp = '+'
2212                  and then Present (Full_View (XE.Key.Ent))
2213                then
2214                   Ent := Underlying_Type (Ent);
2215
2216                   if Present (Ent) then
2217                      Ctyp := Xref_Entity_Letters (Ekind (Ent));
2218                   end if;
2219                end if;
2220
2221                --  Special exception for Boolean
2222
2223                if Ctyp = 'E' and then Is_Boolean_Type (Ent) then
2224                   Ctyp := 'B';
2225                end if;
2226
2227                --  For variable reference, get corresponding type
2228
2229                if Ctyp = '*' then
2230                   Ent := Etype (XE.Key.Ent);
2231                   Ctyp := Fold_Lower (Xref_Entity_Letters (Ekind (Ent)));
2232
2233                   --  If variable is private type, get full view type
2234
2235                   if Ctyp = '+'
2236                     and then Present (Full_View (Etype (XE.Key.Ent)))
2237                   then
2238                      Ent := Underlying_Type (Etype (XE.Key.Ent));
2239
2240                      if Present (Ent) then
2241                         Ctyp := Fold_Lower (Xref_Entity_Letters (Ekind (Ent)));
2242                      end if;
2243
2244                   elsif Is_Generic_Type (Ent) then
2245
2246                      --  If the type of the entity is a generic private type,
2247                      --  there is no usable full view, so retain the indication
2248                      --  that this is an object.
2249
2250                      Ctyp := '*';
2251                   end if;
2252
2253                   --  Special handling for access parameters and objects and
2254                   --  components of an anonymous access type.
2255
2256                   if Ekind (Etype (XE.Key.Ent)) in
2257                                E_Anonymous_Access_Type
2258                              | E_Anonymous_Access_Subprogram_Type
2259                              | E_Anonymous_Access_Protected_Subprogram_Type
2260                   then
2261                      if Is_Formal (XE.Key.Ent)
2262                        or else
2263                          Ekind (XE.Key.Ent) in
2264                            E_Variable | E_Constant | E_Component
2265                      then
2266                         Ctyp := 'p';
2267                      end if;
2268
2269                      --  Special handling for Boolean
2270
2271                   elsif Ctyp = 'e' and then Is_Boolean_Type (Ent) then
2272                      Ctyp := 'b';
2273                   end if;
2274                end if;
2275
2276                --  Special handling for abstract types and operations
2277
2278                if Is_Overloadable (XE.Key.Ent)
2279                  and then Is_Abstract_Subprogram (XE.Key.Ent)
2280                then
2281                   if Ctyp = 'U' then
2282                      Ctyp := 'x';            --  Abstract procedure
2283
2284                   elsif Ctyp = 'V' then
2285                      Ctyp := 'y';            --  Abstract function
2286                   end if;
2287
2288                elsif Is_Type (XE.Key.Ent)
2289                  and then Is_Abstract_Type (XE.Key.Ent)
2290                then
2291                   if Is_Interface (XE.Key.Ent) then
2292                      Ctyp := 'h';
2293
2294                   elsif Ctyp = 'R' then
2295                      Ctyp := 'H';            --  Abstract type
2296                   end if;
2297                end if;
2298
2299                --  Only output reference if interesting type of entity
2300
2301                if Ctyp = ' '
2302
2303                --  Suppress references to object definitions, used for local
2304                --  references.
2305
2306                  or else XE.Key.Typ = 'D'
2307                  or else XE.Key.Typ = 'I'
2308
2309                --  Suppress self references, except for bodies that act as
2310                --  specs.
2311
2312                  or else (XE.Key.Loc = XE.Def
2313                            and then
2314                              (XE.Key.Typ /= 'b'
2315                                or else not Is_Subprogram (XE.Key.Ent)))
2316
2317                --  Also suppress definitions of body formals (we only
2318                --  treat these as references, and the references were
2319                --  separately recorded).
2320
2321                  or else (Is_Formal (XE.Key.Ent)
2322                            and then Present (Spec_Entity (XE.Key.Ent)))
2323                then
2324                   null;
2325
2326                else
2327                   --  Start new Xref section if new xref unit
2328
2329                   if XE.Key.Eun /= Curxu then
2330                      if Write_Info_Col > 1 then
2331                         Write_Info_EOL;
2332                      end if;
2333
2334                      Curxu := XE.Key.Eun;
2335
2336                      Write_Info_Initiate ('X');
2337                      Write_Info_Char (' ');
2338                      Write_Info_Nat (Dependency_Num (XE.Key.Eun));
2339                      Write_Info_Char (' ');
2340                      Write_Info_Name
2341                        (Reference_Name (Source_Index (XE.Key.Eun)));
2342                   end if;
2343
2344                   --  Start new Entity line if new entity. Note that we
2345                   --  consider two entities the same if they have the same
2346                   --  name and source location. This causes entities in
2347                   --  instantiations to be treated as though they referred
2348                   --  to the template.
2349
2350                   if No (Curent)
2351                     or else
2352                       (XE.Key.Ent /= Curent
2353                          and then
2354                            (Name_Change (XE.Key.Ent) or else XE.Def /= Curdef))
2355                   then
2356                      Curent := XE.Key.Ent;
2357                      Curdef := XE.Def;
2358
2359                      Get_Unqualified_Name_String (Chars (XE.Key.Ent));
2360                      Curlen := Name_Len;
2361                      Curnam (1 .. Curlen) := Name_Buffer (1 .. Curlen);
2362
2363                      if Write_Info_Col > 1 then
2364                         Write_Info_EOL;
2365                      end if;
2366
2367                      --  Write column number information
2368
2369                      Write_Info_Nat (Int (Get_Logical_Line_Number (XE.Def)));
2370                      Write_Info_Char (Ctyp);
2371                      Write_Info_Nat (Int (Get_Column_Number (XE.Def)));
2372
2373                      --  Write level information
2374
2375                      Write_Level_Info : declare
2376                         function Is_Visible_Generic_Entity
2377                           (E : Entity_Id) return Boolean;
2378                         --  Check whether E is declared in the visible part
2379                         --  of a generic package. For source navigation
2380                         --  purposes, treat this as a visible entity.
2381
2382                         function Is_Private_Record_Component
2383                           (E : Entity_Id) return Boolean;
2384                         --  Check whether E is a non-inherited component of a
2385                         --  private extension. Even if the enclosing record is
2386                         --  public, we want to treat the component as private
2387                         --  for navigation purposes.
2388
2389                         ---------------------------------
2390                         -- Is_Private_Record_Component --
2391                         ---------------------------------
2392
2393                         function Is_Private_Record_Component
2394                           (E : Entity_Id) return Boolean
2395                         is
2396                            S : constant Entity_Id := Scope (E);
2397                         begin
2398                            return
2399                              Ekind (E) = E_Component
2400                                and then Nkind (Declaration_Node (S)) =
2401                                  N_Private_Extension_Declaration
2402                                and then Original_Record_Component (E) = E;
2403                         end Is_Private_Record_Component;
2404
2405                         -------------------------------
2406                         -- Is_Visible_Generic_Entity --
2407                         -------------------------------
2408
2409                         function Is_Visible_Generic_Entity
2410                           (E : Entity_Id) return Boolean
2411                         is
2412                            Par : Node_Id;
2413
2414                         begin
2415                            --  The Present check here is an error defense
2416
2417                            if Present (Scope (E))
2418                              and then Ekind (Scope (E)) /= E_Generic_Package
2419                            then
2420                               return False;
2421                            end if;
2422
2423                            Par := Parent (E);
2424                            while Present (Par) loop
2425                               if
2426                                 Nkind (Par) = N_Generic_Package_Declaration
2427                               then
2428                                  --  Entity is a generic formal
2429
2430                                  return False;
2431
2432                               elsif
2433                                 Nkind (Parent (Par)) = N_Package_Specification
2434                               then
2435                                  return
2436                                    Is_List_Member (Par)
2437                                      and then List_Containing (Par) =
2438                                        Visible_Declarations (Parent (Par));
2439                               else
2440                                  Par := Parent (Par);
2441                               end if;
2442                            end loop;
2443
2444                            return False;
2445                         end Is_Visible_Generic_Entity;
2446
2447                      --  Start of processing for Write_Level_Info
2448
2449                      begin
2450                         if Is_Hidden (Curent)
2451                           or else Is_Private_Record_Component (Curent)
2452                         then
2453                            Write_Info_Char (' ');
2454
2455                         elsif
2456                            Is_Public (Curent)
2457                              or else Is_Visible_Generic_Entity (Curent)
2458                         then
2459                            Write_Info_Char ('*');
2460
2461                         else
2462                            Write_Info_Char (' ');
2463                         end if;
2464                      end Write_Level_Info;
2465
2466                      --  Output entity name. We use the occurrence from the
2467                      --  actual source program at the definition point.
2468
2469                      declare
2470                         Ent_Name : constant String :=
2471                                      Exact_Source_Name (Sloc (XE.Key.Ent));
2472                      begin
2473                         for C in Ent_Name'Range loop
2474                            Write_Info_Char (Ent_Name (C));
2475                         end loop;
2476                      end;
2477
2478                      --  See if we have a renaming reference
2479
2480                      if Is_Object (XE.Key.Ent)
2481                        and then Present (Renamed_Object (XE.Key.Ent))
2482                      then
2483                         Rref := Renamed_Object (XE.Key.Ent);
2484
2485                      elsif Is_Overloadable (XE.Key.Ent)
2486                        and then Nkind (Parent (Declaration_Node (XE.Key.Ent)))
2487                                            = N_Subprogram_Renaming_Declaration
2488                      then
2489                         Rref := Name (Parent (Declaration_Node (XE.Key.Ent)));
2490
2491                      elsif Ekind (XE.Key.Ent) = E_Package
2492                        and then Nkind (Declaration_Node (XE.Key.Ent)) =
2493                                          N_Package_Renaming_Declaration
2494                      then
2495                         Rref := Name (Declaration_Node (XE.Key.Ent));
2496
2497                      else
2498                         Rref := Empty;
2499                      end if;
2500
2501                      if Present (Rref) then
2502                         if Nkind (Rref) = N_Expanded_Name then
2503                            Rref := Selector_Name (Rref);
2504                         end if;
2505
2506                         if Nkind (Rref) = N_Identifier
2507                           or else Nkind (Rref) = N_Operator_Symbol
2508                         then
2509                            null;
2510
2511                         --  For renamed array components, use the array name
2512                         --  for the renamed entity, which reflect the fact that
2513                         --  in general the whole array is aliased.
2514
2515                         elsif Nkind (Rref) = N_Indexed_Component then
2516                            if Nkind (Prefix (Rref)) = N_Identifier then
2517                               Rref := Prefix (Rref);
2518                            elsif Nkind (Prefix (Rref)) = N_Expanded_Name then
2519                               Rref := Selector_Name (Prefix (Rref));
2520                            else
2521                               Rref := Empty;
2522                            end if;
2523
2524                         else
2525                            Rref := Empty;
2526                         end if;
2527                      end if;
2528
2529                      --  Write out renaming reference if we have one
2530
2531                      if Present (Rref) then
2532                         Write_Info_Char ('=');
2533                         Write_Info_Nat
2534                           (Int (Get_Logical_Line_Number (Sloc (Rref))));
2535                         Write_Info_Char (':');
2536                         Write_Info_Nat
2537                           (Int (Get_Column_Number (Sloc (Rref))));
2538                      end if;
2539
2540                      --  Indicate that the entity is in the unit of the current
2541                      --  xref section.
2542
2543                      Curru := Curxu;
2544
2545                      --  Write out information about generic parent, if entity
2546                      --  is an instance.
2547
2548                      if Is_Generic_Instance (XE.Key.Ent) then
2549                         declare
2550                            Gen_Par : constant Entity_Id :=
2551                                        Generic_Parent
2552                                          (Specification
2553                                             (Unit_Declaration_Node
2554                                                (XE.Key.Ent)));
2555                            Loc     : constant Source_Ptr := Sloc (Gen_Par);
2556                            Gen_U   : constant Unit_Number_Type :=
2557                                        Get_Source_Unit (Loc);
2558
2559                         begin
2560                            Write_Info_Char ('[');
2561
2562                            if Curru /= Gen_U then
2563                               Write_Info_Nat (Dependency_Num (Gen_U));
2564                               Write_Info_Char ('|');
2565                            end if;
2566
2567                            Write_Info_Nat
2568                              (Int (Get_Logical_Line_Number (Loc)));
2569                            Write_Info_Char (']');
2570                         end;
2571                      end if;
2572
2573                      --  See if we have a type reference and if so output
2574
2575                      Check_Type_Reference (XE.Key.Ent, False);
2576
2577                      --  Additional information for types with progenitors,
2578                      --  including synchronized tagged types.
2579
2580                      declare
2581                         Typ  : constant Entity_Id := XE.Key.Ent;
2582                         Elmt : Elmt_Id;
2583
2584                      begin
2585                         if Is_Record_Type (Typ)
2586                           and then Present (Interfaces (Typ))
2587                         then
2588                            Elmt := First_Elmt (Interfaces (Typ));
2589
2590                         elsif Is_Concurrent_Type (Typ)
2591                           and then Present (Corresponding_Record_Type (Typ))
2592                           and then Present (
2593                             Interfaces (Corresponding_Record_Type (Typ)))
2594                         then
2595                            Elmt :=
2596                              First_Elmt (
2597                               Interfaces (Corresponding_Record_Type (Typ)));
2598
2599                         else
2600                            Elmt := No_Elmt;
2601                         end if;
2602
2603                         while Present (Elmt) loop
2604                            Check_Type_Reference (Node (Elmt), True);
2605                            Next_Elmt (Elmt);
2606                         end loop;
2607                      end;
2608
2609                      --  For array types, list index types as well. (This is
2610                      --  not C, indexes have distinct types).
2611
2612                      if Is_Array_Type (XE.Key.Ent) then
2613                         declare
2614                            A_Typ : constant Entity_Id := XE.Key.Ent;
2615                            Indx : Node_Id;
2616
2617                         begin
2618                            --  If this is a derived array type, we have
2619                            --  output the parent type, so add the component
2620                            --  type now.
2621
2622                            if Is_Derived_Type (A_Typ) then
2623                               Check_Type_Reference
2624                                 (Component_Type (A_Typ), False, True);
2625                            end if;
2626
2627                            --  Add references to index types.
2628
2629                            Indx := First_Index (XE.Key.Ent);
2630                            while Present (Indx) loop
2631                               Check_Type_Reference
2632                                 (First_Subtype (Etype (Indx)), True);
2633                               Next_Index (Indx);
2634                            end loop;
2635                         end;
2636                      end if;
2637
2638                      --  If the entity is an overriding operation, write info
2639                      --  on operation that was overridden.
2640
2641                      if Is_Subprogram (XE.Key.Ent)
2642                        and then Present (Overridden_Operation (XE.Key.Ent))
2643                      then
2644                         Output_Overridden_Op
2645                           (Overridden_Operation (XE.Key.Ent));
2646                      end if;
2647
2648                      --  End of processing for entity output
2649
2650                      Crloc := No_Location;
2651                   end if;
2652
2653                   --  Output the reference if it is not as the same location
2654                   --  as the previous one, or it is a read-reference that
2655                   --  indicates that the entity is an in-out actual in a call.
2656
2657                   if XE.Key.Loc /= No_Location
2658                     and then
2659                       (XE.Key.Loc /= Crloc
2660                         or else (Prevt = 'm' and then XE.Key.Typ = 'r'))
2661                   then
2662                      Crloc := XE.Key.Loc;
2663                      Prevt := XE.Key.Typ;
2664
2665                      --  Start continuation if line full, else blank
2666
2667                      if Write_Info_Col > 72 then
2668                         Write_Info_EOL;
2669                         Write_Info_Initiate ('.');
2670                      end if;
2671
2672                      Write_Info_Char (' ');
2673
2674                      --  Output file number if changed
2675
2676                      if XE.Key.Lun /= Curru then
2677                         Curru := XE.Key.Lun;
2678                         Write_Info_Nat (Dependency_Num (Curru));
2679                         Write_Info_Char ('|');
2680                      end if;
2681
2682                      Write_Info_Nat
2683                        (Int (Get_Logical_Line_Number (XE.Key.Loc)));
2684                      Write_Info_Char (XE.Key.Typ);
2685
2686                      if Is_Overloadable (XE.Key.Ent) then
2687                         if (Is_Imported (XE.Key.Ent) and then XE.Key.Typ = 'b')
2688                              or else
2689                            (Is_Exported (XE.Key.Ent) and then XE.Key.Typ = 'i')
2690                         then
2691                            Output_Import_Export_Info (XE.Key.Ent);
2692                         end if;
2693                      end if;
2694
2695                      Write_Info_Nat (Int (Get_Column_Number (XE.Key.Loc)));
2696
2697                      Output_Instantiation_Refs (Sloc (XE.Key.Ent));
2698                   end if;
2699                end if;
2700             end Output_One_Ref;
2701
2702          <<Continue>>
2703             null;
2704          end loop;
2705
2706          Write_Info_EOL;
2707       end Output_Refs;
2708    end Output_References;
2709
2710 --  Start of elaboration for Lib.Xref
2711
2712 begin
2713    --  Reset is necessary because Elmt_Ptr does not default to Null_Ptr,
2714    --  because it's not an access type.
2715
2716    Xref_Set.Reset;
2717 end Lib.Xref;