gcc/ada/lib-load.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             L I B . L O A D                              --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1992-2004 Free Software Foundation, Inc.          --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- GNAT was originally developed  by the GNAT team at  New York University. --
  23 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  24 --                                                                          --
  25 ------------------------------------------------------------------------------
  26
  27 with Atree;    use Atree;
  28 with Debug;    use Debug;
  29 with Einfo;    use Einfo;
  30 with Errout;   use Errout;
  31 with Fname;    use Fname;
  32 with Fname.UF; use Fname.UF;
  33 with Namet;    use Namet;
  34 with Nlists;   use Nlists;
  35 with Nmake;    use Nmake;
  36 with Opt;      use Opt;
  37 with Osint;    use Osint;
  38 with Osint.C;  use Osint.C;
  39 with Output;   use Output;
  40 with Par;
  41 with Scn;      use Scn;
  42 with Sinfo;    use Sinfo;
  43 with Sinput;   use Sinput;
  44 with Sinput.L; use Sinput.L;
  45 with Stand;    use Stand;
  46 with Tbuild;   use Tbuild;
  47 with Uname;    use Uname;
  48
  49 package body Lib.Load is
  50
  51    -----------------------
  52    -- Local Subprograms --
  53    -----------------------
  54
  55    function Spec_Is_Irrelevant
  56      (Spec_Unit : Unit_Number_Type;
  57       Body_Unit : Unit_Number_Type) return Boolean;
  58    --  The Spec_Unit and Body_Unit parameters are the unit numbers of the
  59    --  spec file that corresponds to the main unit which is a body. This
  60    --  function determines if the spec file is irrelevant and will be
  61    --  overridden by the body as described in RM 10.1.4(4). See description
  62    --  in "Special Handling of Subprogram Bodies" for further details.
  63
  64    procedure Write_Dependency_Chain;
  65    --  This procedure is used to generate error message info lines that
  66    --  trace the current dependency chain when a load error occurs.
  67
  68    -------------------------------
  69    -- Create_Dummy_Package_Unit --
  70    -------------------------------
  71
  72    function Create_Dummy_Package_Unit
  73      (With_Node : Node_Id;
  74       Spec_Name : Unit_Name_Type) return Unit_Number_Type
  75    is
  76       Unum         : Unit_Number_Type;
  77       Cunit_Entity : Entity_Id;
  78       Cunit        : Node_Id;
  79       Du_Name      : Node_Or_Entity_Id;
  80       End_Lab      : Node_Id;
  81       Save_CS      : constant Boolean := Get_Comes_From_Source_Default;
  82
  83    begin
  84       --  The created dummy package unit does not come from source
  85
  86       Set_Comes_From_Source_Default (False);
  87
  88       --  Normal package
  89
  90       if Nkind (Name (With_Node)) = N_Identifier then
  91          Cunit_Entity :=
  92            Make_Defining_Identifier (No_Location,
  93              Chars => Chars (Name (With_Node)));
  94          Du_Name := Cunit_Entity;
  95          End_Lab := New_Occurrence_Of (Cunit_Entity, No_Location);
  96
  97       --  Child package
  98
  99       else
 100          Cunit_Entity :=
 101            Make_Defining_Identifier (No_Location,
 102              Chars => Chars (Selector_Name (Name (With_Node))));
 103          Du_Name :=
 104            Make_Defining_Program_Unit_Name (No_Location,
 105              Name => New_Copy_Tree (Prefix (Name (With_Node))),
 106              Defining_Identifier => Cunit_Entity);
 107
 108          Set_Is_Child_Unit (Cunit_Entity);
 109
 110          End_Lab :=
 111            Make_Designator (No_Location,
 112              Name => New_Copy_Tree (Prefix (Name (With_Node))),
 113              Identifier => New_Occurrence_Of (Cunit_Entity, No_Location));
 114       end if;
 115
 116       Set_Scope (Cunit_Entity, Standard_Standard);
 117
 118       Cunit :=
 119         Make_Compilation_Unit (No_Location,
 120           Context_Items => Empty_List,
 121           Unit =>
 122             Make_Package_Declaration (No_Location,
 123               Specification =>
 124                 Make_Package_Specification (No_Location,
 125                   Defining_Unit_Name   => Du_Name,
 126                   Visible_Declarations => Empty_List,
 127                   End_Label            => End_Lab)),
 128           Aux_Decls_Node =>
 129             Make_Compilation_Unit_Aux (No_Location));
 130
 131       --  Mark the dummy package as analyzed to prevent analysis of this
 132       --  (non-existent) unit in -gnatQ mode because at the moment the
 133       --  structure and attributes of this dummy package does not allow
 134       --  a normal analysis of this unit
 135
 136       Set_Analyzed (Cunit);
 137
 138       Units.Increment_Last;
 139       Unum := Units.Last;
 140
 141       Units.Table (Unum) := (
 142         Cunit           => Cunit,
 143         Cunit_Entity    => Cunit_Entity,
 144         Dependency_Num  => 0,
 145         Dynamic_Elab    => False,
 146         Error_Location  => Sloc (With_Node),
 147         Expected_Unit   => Spec_Name,
 148         Fatal_Error     => True,
 149         Generate_Code   => False,
 150         Has_RACW        => False,
 151         Ident_String    => Empty,
 152         Loading         => False,
 153         Main_Priority   => Default_Main_Priority,
 154         Munit_Index     => 0,
 155         Serial_Number   => 0,
 156         Source_Index    => No_Source_File,
 157         Unit_File_Name  => Get_File_Name (Spec_Name, Subunit => False),
 158         Unit_Name       => Spec_Name,
 159         Version         => 0);
 160
 161       Set_Comes_From_Source_Default (Save_CS);
 162       Set_Error_Posted (Cunit_Entity);
 163       Set_Error_Posted (Cunit);
 164       return Unum;
 165    end Create_Dummy_Package_Unit;
 166
 167    ----------------
 168    -- Initialize --
 169    ----------------
 170
 171    procedure Initialize is
 172    begin
 173       Units.Init;
 174       Load_Stack.Init;
 175    end Initialize;
 176
 177    ------------------------
 178    -- Initialize_Version --
 179    ------------------------
 180
 181    procedure Initialize_Version (U : Unit_Number_Type) is
 182    begin
 183       Units.Table (U).Version := Source_Checksum (Source_Index (U));
 184    end Initialize_Version;
 185
 186    ----------------------
 187    -- Load_Main_Source --
 188    ----------------------
 189
 190    procedure Load_Main_Source is
 191       Fname : File_Name_Type;
 192
 193    begin
 194       Load_Stack.Increment_Last;
 195       Load_Stack.Table (Load_Stack.Last) := Main_Unit;
 196
 197       --  Initialize unit table entry for Main_Unit. Note that we don't know
 198       --  the unit name yet, that gets filled in when the parser parses the
 199       --  main unit, at which time a check is made that it matches the main
 200       --  file name, and then the Unit_Name field is set. The Cunit and
 201       --  Cunit_Entity fields also get filled in later by the parser.
 202
 203       Units.Increment_Last;
 204       Fname := Next_Main_Source;
 205
 206       Units.Table (Main_Unit).Unit_File_Name := Fname;
 207
 208       if Fname /= No_File then
 209          Main_Source_File := Load_Source_File (Fname);
 210          Current_Error_Source_File := Main_Source_File;
 211
 212          Units.Table (Main_Unit) := (
 213            Cunit           => Empty,
 214            Cunit_Entity    => Empty,
 215            Dependency_Num  => 0,
 216            Dynamic_Elab    => False,
 217            Error_Location  => No_Location,
 218            Expected_Unit   => No_Name,
 219            Fatal_Error     => False,
 220            Generate_Code   => False,
 221            Has_RACW        => False,
 222            Ident_String    => Empty,
 223            Loading         => True,
 224            Main_Priority   => Default_Main_Priority,
 225            Munit_Index     => 0,
 226            Serial_Number   => 0,
 227            Source_Index    => Main_Source_File,
 228            Unit_File_Name  => Fname,
 229            Unit_Name       => No_Name,
 230            Version         => Source_Checksum (Main_Source_File));
 231       end if;
 232    end Load_Main_Source;
 233
 234    ---------------
 235    -- Load_Unit --
 236    ---------------
 237
 238    function Load_Unit
 239      (Load_Name  : Unit_Name_Type;
 240       Required   : Boolean;
 241       Error_Node : Node_Id;
 242       Subunit    : Boolean;
 243       Corr_Body  : Unit_Number_Type := No_Unit;
 244       Renamings  : Boolean          := False) return Unit_Number_Type
 245    is
 246       Calling_Unit : Unit_Number_Type;
 247       Uname_Actual : Unit_Name_Type;
 248       Unum         : Unit_Number_Type;
 249       Unump        : Unit_Number_Type;
 250       Fname        : File_Name_Type;
 251       Src_Ind      : Source_File_Index;
 252
 253    --  Start of processing for Load_Unit
 254
 255    begin
 256       --  If renamings are allowed and we have a child unit name, then we
 257       --  must first load the parent to deal with finding the real name.
 258
 259       if Renamings and then Is_Child_Name (Load_Name) then
 260          Unump :=
 261            Load_Unit
 262              (Load_Name  => Get_Parent_Spec_Name (Load_Name),
 263               Required   => Required,
 264               Subunit    => False,
 265               Renamings  => True,
 266               Error_Node => Error_Node);
 267
 268          if Unump = No_Unit then
 269             return No_Unit;
 270          end if;
 271
 272          --  If parent is a renaming, then we use the renamed package as
 273          --  the actual parent for the subsequent load operation.
 274
 275          if Nkind (Parent (Cunit_Entity (Unump))) =
 276            N_Package_Renaming_Declaration
 277          then
 278             Uname_Actual :=
 279               New_Child
 280                 (Load_Name,
 281                  Get_Unit_Name (Name (Parent (Cunit_Entity (Unump)))));
 282
 283             --  Save the renaming entity, to establish its visibility when
 284             --  installing the context. The implicit with is on this entity,
 285             --  not on the package it renames.
 286
 287             if Nkind (Error_Node) = N_With_Clause
 288               and then Nkind (Name (Error_Node)) = N_Selected_Component
 289             then
 290                declare
 291                   Par : Node_Id := Name (Error_Node);
 292
 293                begin
 294                   while Nkind (Par) = N_Selected_Component
 295                     and then Chars (Selector_Name (Par)) /=
 296                       Chars (Cunit_Entity (Unump))
 297                   loop
 298                      Par := Prefix (Par);
 299                   end loop;
 300
 301                   --  Case of some intermediate parent is a renaming
 302
 303                   if Nkind (Par) = N_Selected_Component then
 304                      Set_Entity (Selector_Name (Par), Cunit_Entity (Unump));
 305
 306                   --  Case where the ultimate parent is a renaming
 307
 308                   else
 309                      Set_Entity (Par, Cunit_Entity (Unump));
 310                   end if;
 311                end;
 312             end if;
 313
 314          --  If the parent is not a renaming, then get its name (this may
 315          --  be different from the parent spec name obtained above because
 316          --  of renamings higher up in the hierarchy).
 317
 318          else
 319             Uname_Actual := New_Child (Load_Name, Unit_Name (Unump));
 320          end if;
 321
 322       --  Here if unit to be loaded is not a child unit
 323
 324       else
 325          Uname_Actual := Load_Name;
 326       end if;
 327
 328       Fname := Get_File_Name (Uname_Actual, Subunit);
 329
 330       if Debug_Flag_L then
 331          Write_Eol;
 332          Write_Str ("*** Load request for unit: ");
 333          Write_Unit_Name (Load_Name);
 334
 335          if Required then
 336             Write_Str (" (Required = True)");
 337          else
 338             Write_Str (" (Required = False)");
 339          end if;
 340
 341          Write_Eol;
 342
 343          if Uname_Actual /= Load_Name then
 344             Write_Str ("*** Actual unit loaded: ");
 345             Write_Unit_Name (Uname_Actual);
 346          end if;
 347       end if;
 348
 349       --  Capture error location if it is for the main unit. The idea is to
 350       --  post errors on the main unit location, not the most recent unit.
 351       --  Note: Unit_Name (Main_Unit) is not set if we are parsing gnat.adc.
 352
 353       if Present (Error_Node)
 354         and then Unit_Name (Main_Unit) /= No_Name
 355       then
 356          --  It seems like In_Extended_Main_Source_Unit (Error_Node) would
 357          --  do the trick here, but that's wrong, it is much too early to
 358          --  call this routine. We are still in the parser, and the required
 359          --  semantic information is not established yet. So we base the
 360          --  judgment on unit names.
 361
 362          Get_External_Unit_Name_String (Unit_Name (Main_Unit));
 363
 364          declare
 365             Main_Unit_Name : constant String := Name_Buffer (1 .. Name_Len);
 366
 367          begin
 368             Get_External_Unit_Name_String
 369               (Unit_Name (Get_Source_Unit (Error_Node)));
 370
 371             --  If the two names are identical, then for sure we are part
 372             --  of the extended main unit
 373
 374             if Main_Unit_Name = Name_Buffer (1 .. Name_Len) then
 375                Load_Msg_Sloc := Sloc (Error_Node);
 376
 377             --  If the load is called from a with_type clause, the error
 378             --  node is correct.
 379
 380             elsif Nkind (Parent (Error_Node)) = N_With_Type_Clause then
 381                Load_Msg_Sloc := Sloc (Error_Node);
 382
 383             --  Otherwise, check for the subunit case, and if so, consider
 384             --  we have a match if one name is a prefix of the other name.
 385
 386             else
 387                if Nkind (Unit (Cunit (Main_Unit))) = N_Subunit
 388                     or else
 389                   Nkind (Unit (Cunit (Get_Source_Unit (Error_Node)))) =
 390                                                                 N_Subunit
 391                then
 392                   Name_Len := Integer'Min (Name_Len, Main_Unit_Name'Length);
 393
 394                   if Name_Buffer (1 .. Name_Len)
 395                         =
 396                      Main_Unit_Name (1 .. Name_Len)
 397                   then
 398                      Load_Msg_Sloc := Sloc (Error_Node);
 399                   end if;
 400                end if;
 401             end if;
 402          end;
 403       end if;
 404
 405       --  If we are generating error messages, then capture calling unit
 406
 407       if Present (Error_Node) then
 408          Calling_Unit := Get_Source_Unit (Error_Node);
 409       else
 410          Calling_Unit := No_Unit;
 411       end if;
 412
 413       --  See if we already have an entry for this unit
 414
 415       Unum := Main_Unit;
 416
 417       while Unum <= Units.Last loop
 418          exit when Uname_Actual = Units.Table (Unum).Unit_Name;
 419          Unum := Unum + 1;
 420       end loop;
 421
 422       --  Whether or not the entry was found, Unum is now the right value,
 423       --  since it is one more than Units.Last (i.e. the index of the new
 424       --  entry we will create) in the not found case.
 425
 426       --  A special check is necessary in the unit not found case. If the unit
 427       --  is not found, but the file in which it lives has already been loaded,
 428       --  then we have the problem that the file does not contain the unit that
 429       --  is needed. We simply treat this as a file not found condition.
 430
 431       --  We skip this test in multiple unit per file mode since in this
 432       --  case we can have multiple units from the same source file.
 433
 434       if Unum > Units.Last and then Multiple_Unit_Index = 0 then
 435          for J in Units.First .. Units.Last loop
 436             if Fname = Units.Table (J).Unit_File_Name then
 437                if Debug_Flag_L then
 438                   Write_Str ("  file does not contain unit, Unit_Number = ");
 439                   Write_Int (Int (Unum));
 440                   Write_Eol;
 441                   Write_Eol;
 442                end if;
 443
 444                if Present (Error_Node) then
 445                   if Is_Predefined_File_Name (Fname) then
 446                      Error_Msg_Name_1 := Uname_Actual;
 447                      Error_Msg
 448                        ("% is not a language defined unit", Load_Msg_Sloc);
 449                   else
 450                      Error_Msg_Name_1 := Fname;
 451                      Error_Msg_Unit_1 := Uname_Actual;
 452                      Error_Msg
 453                        ("File{ does not contain unit$", Load_Msg_Sloc);
 454                   end if;
 455
 456                   Write_Dependency_Chain;
 457                   return No_Unit;
 458
 459                else
 460                   return No_Unit;
 461                end if;
 462             end if;
 463          end loop;
 464       end if;
 465
 466       --  If we are proceeding with load, then make load stack entry
 467
 468       Load_Stack.Increment_Last;
 469       Load_Stack.Table (Load_Stack.Last) := Unum;
 470
 471       --  Case of entry already in table
 472
 473       if Unum <= Units.Last then
 474
 475          --  Here is where we check for a circular dependency, which is
 476          --  an attempt to load a unit which is currently in the process
 477          --  of being loaded. We do *not* care about a circular chain that
 478          --  leads back to a body, because this kind of circular dependence
 479          --  legitimately occurs (e.g. two package bodies that contain
 480          --  inlined subprogram referenced by the other).
 481
 482          --  Ada 2005 (AI-50217): We also ignore limited_with clauses, because
 483          --  their purpose is precisely to create legal circular structures.
 484
 485          if Loading (Unum)
 486            and then (Is_Spec_Name (Units.Table (Unum).Unit_Name)
 487                        or else Acts_As_Spec (Units.Table (Unum).Cunit))
 488            and then (Nkind (Error_Node) /= N_With_Clause
 489                        or else not Limited_Present (Error_Node))
 490
 491          then
 492             if Debug_Flag_L then
 493                Write_Str ("  circular dependency encountered");
 494                Write_Eol;
 495             end if;
 496
 497             if Present (Error_Node) then
 498                Error_Msg ("circular unit dependency", Load_Msg_Sloc);
 499                Write_Dependency_Chain;
 500             else
 501                Load_Stack.Decrement_Last;
 502             end if;
 503
 504             return No_Unit;
 505          end if;
 506
 507          if Debug_Flag_L then
 508             Write_Str ("  unit already in file table, Unit_Number = ");
 509             Write_Int (Int (Unum));
 510             Write_Eol;
 511          end if;
 512
 513          Load_Stack.Decrement_Last;
 514          return Unum;
 515
 516       --  Unit is not already in table, so try to open the file
 517
 518       else
 519          if Debug_Flag_L then
 520             Write_Str ("  attempt unit load, Unit_Number = ");
 521             Write_Int (Int (Unum));
 522             Write_Eol;
 523          end if;
 524
 525          Src_Ind := Load_Source_File (Fname);
 526
 527          --  Make a partial entry in the file table, used even in the file not
 528          --  found case to print the dependency chain including the last entry
 529
 530          Units.Increment_Last;
 531          Units.Table (Unum).Unit_Name := Uname_Actual;
 532
 533          --  File was found
 534
 535          if Src_Ind /= No_Source_File then
 536             Units.Table (Unum) := (
 537               Cunit           => Empty,
 538               Cunit_Entity    => Empty,
 539               Dependency_Num  => 0,
 540               Dynamic_Elab    => False,
 541               Error_Location  => Sloc (Error_Node),
 542               Expected_Unit   => Uname_Actual,
 543               Fatal_Error     => False,
 544               Generate_Code   => False,
 545               Has_RACW        => False,
 546               Ident_String    => Empty,
 547               Loading         => True,
 548               Main_Priority   => Default_Main_Priority,
 549               Munit_Index     => 0,
 550               Serial_Number   => 0,
 551               Source_Index    => Src_Ind,
 552               Unit_File_Name  => Fname,
 553               Unit_Name       => Uname_Actual,
 554               Version         => Source_Checksum (Src_Ind));
 555
 556             --  Parse the new unit
 557
 558             declare
 559                Save_Index : constant Nat := Multiple_Unit_Index;
 560             begin
 561                Multiple_Unit_Index := Get_Unit_Index (Uname_Actual);
 562                Units.Table (Unum).Munit_Index := Multiple_Unit_Index;
 563                Initialize_Scanner (Unum, Source_Index (Unum));
 564                Discard_List (Par (Configuration_Pragmas => False));
 565                Multiple_Unit_Index := Save_Index;
 566                Set_Loading (Unum, False);
 567             end;
 568
 569             --  If spec is irrelevant, then post errors and quit
 570
 571             if Corr_Body /= No_Unit
 572               and then Spec_Is_Irrelevant (Unum, Corr_Body)
 573             then
 574                Error_Msg_Name_1 := Unit_File_Name (Corr_Body);
 575                Error_Msg
 576                  ("cannot compile subprogram in file {!",
 577                   Load_Msg_Sloc);
 578                Error_Msg_Name_1 := Unit_File_Name (Unum);
 579                Error_Msg
 580                  ("incorrect spec in file { must be removed first!",
 581                   Load_Msg_Sloc);
 582                return No_Unit;
 583             end if;
 584
 585             --  If loaded unit had a fatal error, then caller inherits it!
 586
 587             if Units.Table (Unum).Fatal_Error
 588               and then Present (Error_Node)
 589             then
 590                Units.Table (Calling_Unit).Fatal_Error := True;
 591             end if;
 592
 593             --  Remove load stack entry and return the entry in the file table
 594
 595             Load_Stack.Decrement_Last;
 596             return Unum;
 597
 598          --  Case of file not found
 599
 600          else
 601             if Debug_Flag_L then
 602                Write_Str ("  file was not found, load failed");
 603                Write_Eol;
 604             end if;
 605
 606             --  Generate message if unit required
 607
 608             if Required and then Present (Error_Node) then
 609
 610                if Is_Predefined_File_Name (Fname) then
 611                   Error_Msg_Name_1 := Uname_Actual;
 612                   Error_Msg
 613                     ("% is not a predefined library unit", Load_Msg_Sloc);
 614
 615                else
 616                   Error_Msg_Name_1 := Fname;
 617                   Error_Msg ("file{ not found", Load_Msg_Sloc);
 618                end if;
 619
 620                Write_Dependency_Chain;
 621
 622                --  Remove unit from stack, to avoid cascaded errors on
 623                --  subsequent missing files.
 624
 625                Load_Stack.Decrement_Last;
 626                Units.Decrement_Last;
 627
 628             --  If unit not required, remove load stack entry and the junk
 629             --  file table entry, and return No_Unit to indicate not found,
 630
 631             else
 632                Load_Stack.Decrement_Last;
 633                Units.Decrement_Last;
 634             end if;
 635
 636             return No_Unit;
 637          end if;
 638       end if;
 639    end Load_Unit;
 640
 641    ------------------------
 642    -- Make_Instance_Unit --
 643    ------------------------
 644
 645    --  If the unit is an instance, it appears as a package declaration, but
 646    --  contains both declaration and body of the instance. The body becomes
 647    --  the main unit of the compilation, and the declaration is inserted
 648    --  at the end of the unit table. The main unit now has the name of a
 649    --  body, which is constructed from the name of the original spec,
 650    --  and is attached to the compilation node of the original unit. The
 651    --  declaration has been attached to a new compilation unit node, and
 652    --  code will have to be generated for it.
 653
 654    procedure Make_Instance_Unit (N : Node_Id) is
 655       Sind : constant Source_File_Index := Source_Index (Main_Unit);
 656    begin
 657       Units.Increment_Last;
 658       Units.Table (Units.Last)               := Units.Table (Main_Unit);
 659       Units.Table (Units.Last).Cunit         := Library_Unit (N);
 660       Units.Table (Units.Last).Generate_Code := True;
 661       Units.Table (Main_Unit).Cunit          := N;
 662       Units.Table (Main_Unit).Unit_Name      :=
 663         Get_Body_Name (Unit_Name (Get_Cunit_Unit_Number (Library_Unit (N))));
 664       Units.Table (Main_Unit).Version        := Source_Checksum (Sind);
 665    end Make_Instance_Unit;
 666
 667    ------------------------
 668    -- Spec_Is_Irrelevant --
 669    ------------------------
 670
 671    function Spec_Is_Irrelevant
 672      (Spec_Unit : Unit_Number_Type;
 673       Body_Unit : Unit_Number_Type) return Boolean
 674    is
 675       Sunit : constant Node_Id := Cunit (Spec_Unit);
 676       Bunit : constant Node_Id := Cunit (Body_Unit);
 677
 678    begin
 679       --  The spec is irrelevant if the body is a subprogram body, and the
 680       --  spec is other than a subprogram spec or generic subprogram spec.
 681       --  Note that the names must be the same, we don't need to check that,
 682       --  because we already know that from the fact that the file names are
 683       --  the same.
 684
 685       return
 686          Nkind (Unit (Bunit)) = N_Subprogram_Body
 687            and then Nkind (Unit (Sunit)) /= N_Subprogram_Declaration
 688            and then Nkind (Unit (Sunit)) /= N_Generic_Subprogram_Declaration;
 689    end Spec_Is_Irrelevant;
 690
 691    --------------------
 692    -- Version_Update --
 693    --------------------
 694
 695    procedure Version_Update (U : Node_Id; From : Node_Id) is
 696       Unum  : constant Unit_Number_Type := Get_Cunit_Unit_Number (U);
 697       Fnum  : constant Unit_Number_Type := Get_Cunit_Unit_Number (From);
 698    begin
 699       if Source_Index (Fnum) /= No_Source_File then
 700          Units.Table (Unum).Version :=
 701            Units.Table (Unum).Version
 702              xor
 703               Source_Checksum (Source_Index (Fnum));
 704       end if;
 705    end Version_Update;
 706
 707    ----------------------------
 708    -- Write_Dependency_Chain --
 709    ----------------------------
 710
 711    procedure Write_Dependency_Chain is
 712    begin
 713       --  The dependency chain is only written if it is at least two entries
 714       --  deep, otherwise it is trivial (the main unit depending on a unit
 715       --  that it obviously directly depends on).
 716
 717       if Load_Stack.Last - 1 > Load_Stack.First then
 718          for U in Load_Stack.First .. Load_Stack.Last - 1 loop
 719             Error_Msg_Unit_1 := Unit_Name (Load_Stack.Table (U));
 720             Error_Msg_Unit_2 := Unit_Name (Load_Stack.Table (U + 1));
 721             Error_Msg ("$ depends on $!", Load_Msg_Sloc);
 722          end loop;
 723       end if;
 724    end Write_Dependency_Chain;
 725
 726 end Lib.Load;