gcc/ada/sem_attr.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                             S E M _ A T T R                              --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                            $Revision: 1.1 $
  10 --                                                                          --
  11 --          Copyright (C) 1992-2001, Free Software Foundation, Inc.         --
  12 --                                                                          --
  13 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  14 -- terms of the  GNU General Public License as published  by the Free Soft- --
  15 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  16 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  17 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  18 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  19 -- for  more details.  You should have  received  a copy of the GNU General --
  20 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  21 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  22 -- MA 02111-1307, USA.                                                      --
  23 --                                                                          --
  24 -- GNAT was originally developed  by the GNAT team at  New York University. --
  25 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  26 --                                                                          --
  27 ------------------------------------------------------------------------------
  28
  29 with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
  30
  31 with Atree;    use Atree;
  32 with Checks;   use Checks;
  33 with Einfo;    use Einfo;
  34 with Errout;   use Errout;
  35 with Eval_Fat;
  36 with Exp_Tss;  use Exp_Tss;
  37 with Exp_Util; use Exp_Util;
  38 with Expander; use Expander;
  39 with Freeze;   use Freeze;
  40 with Lib.Xref; use Lib.Xref;
  41 with Namet;    use Namet;
  42 with Nlists;   use Nlists;
  43 with Nmake;    use Nmake;
  44 with Opt;      use Opt;
  45 with Restrict; use Restrict;
  46 with Rtsfind;  use Rtsfind;
  47 with Sem;      use Sem;
  48 with Sem_Cat;  use Sem_Cat;
  49 with Sem_Ch6;  use Sem_Ch6;
  50 with Sem_Ch8;  use Sem_Ch8;
  51 with Sem_Ch13; use Sem_Ch13;
  52 with Sem_Dist; use Sem_Dist;
  53 with Sem_Eval; use Sem_Eval;
  54 with Sem_Res;  use Sem_Res;
  55 with Sem_Type; use Sem_Type;
  56 with Sem_Util; use Sem_Util;
  57 with Stand;    use Stand;
  58 with Sinfo;    use Sinfo;
  59 with Sinput;   use Sinput;
  60 with Snames;   use Snames;
  61 with Stand;
  62 with Stringt;  use Stringt;
  63 with Targparm; use Targparm;
  64 with Ttypes;   use Ttypes;
  65 with Ttypef;   use Ttypef;
  66 with Tbuild;   use Tbuild;
  67 with Uintp;    use Uintp;
  68 with Urealp;   use Urealp;
  69 with Widechar; use Widechar;
  70
  71 package body Sem_Attr is
  72
  73    True_Value  : constant Uint := Uint_1;
  74    False_Value : constant Uint := Uint_0;
  75    --  Synonyms to be used when these constants are used as Boolean values
  76
  77    Bad_Attribute : exception;
  78    --  Exception raised if an error is detected during attribute processing,
  79    --  used so that we can abandon the processing so we don't run into
  80    --  trouble with cascaded errors.
  81
  82    --  The following array is the list of attributes defined in the Ada 83 RM
  83
  84    Attribute_83 : Attribute_Class_Array := Attribute_Class_Array'(
  85       Attribute_Address           |
  86       Attribute_Aft               |
  87       Attribute_Alignment         |
  88       Attribute_Base              |
  89       Attribute_Callable          |
  90       Attribute_Constrained       |
  91       Attribute_Count             |
  92       Attribute_Delta             |
  93       Attribute_Digits            |
  94       Attribute_Emax              |
  95       Attribute_Epsilon           |
  96       Attribute_First             |
  97       Attribute_First_Bit         |
  98       Attribute_Fore              |
  99       Attribute_Image             |
 100       Attribute_Large             |
 101       Attribute_Last              |
 102       Attribute_Last_Bit          |
 103       Attribute_Leading_Part      |
 104       Attribute_Length            |
 105       Attribute_Machine_Emax      |
 106       Attribute_Machine_Emin      |
 107       Attribute_Machine_Mantissa  |
 108       Attribute_Machine_Overflows |
 109       Attribute_Machine_Radix     |
 110       Attribute_Machine_Rounds    |
 111       Attribute_Mantissa          |
 112       Attribute_Pos               |
 113       Attribute_Position          |
 114       Attribute_Pred              |
 115       Attribute_Range             |
 116       Attribute_Safe_Emax         |
 117       Attribute_Safe_Large        |
 118       Attribute_Safe_Small        |
 119       Attribute_Size              |
 120       Attribute_Small             |
 121       Attribute_Storage_Size      |
 122       Attribute_Succ              |
 123       Attribute_Terminated        |
 124       Attribute_Val               |
 125       Attribute_Value             |
 126       Attribute_Width             => True,
 127       others                      => False);
 128
 129    -----------------------
 130    -- Local_Subprograms --
 131    -----------------------
 132
 133    procedure Eval_Attribute (N : Node_Id);
 134    --  Performs compile time evaluation of attributes where possible, leaving
 135    --  the Is_Static_Expression/Raises_Constraint_Error flags appropriately
 136    --  set, and replacing the node with a literal node if the value can be
 137    --  computed at compile time. All static attribute references are folded,
 138    --  as well as a number of cases of non-static attributes that can always
 139    --  be computed at compile time (e.g. floating-point model attributes that
 140    --  are applied to non-static subtypes). Of course in such cases, the
 141    --  Is_Static_Expression flag will not be set on the resulting literal.
 142    --  Note that the only required action of this procedure is to catch the
 143    --  static expression cases as described in the RM. Folding of other cases
 144    --  is done where convenient, but some additional non-static folding is in
 145    --  N_Expand_Attribute_Reference in cases where this is more convenient.
 146
 147    function Is_Anonymous_Tagged_Base
 148      (Anon : Entity_Id;
 149       Typ  : Entity_Id)
 150       return Boolean;
 151    --  For derived tagged types that constrain parent discriminants we build
 152    --  an anonymous unconstrained base type. We need to recognize the relation
 153    --  between the two when analyzing an access attribute for a constrained
 154    --  component, before the full declaration for Typ has been analyzed, and
 155    --  where therefore the prefix of the attribute does not match the enclosing
 156    --  scope.
 157
 158    -----------------------
 159    -- Analyze_Attribute --
 160    -----------------------
 161
 162    procedure Analyze_Attribute (N : Node_Id) is
 163       Loc     : constant Source_Ptr   := Sloc (N);
 164       Aname   : constant Name_Id      := Attribute_Name (N);
 165       P       : constant Node_Id      := Prefix (N);
 166       Exprs   : constant List_Id      := Expressions (N);
 167       Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname);
 168       E1      : Node_Id;
 169       E2      : Node_Id;
 170
 171       P_Type : Entity_Id;
 172       --  Type of prefix after analysis
 173
 174       P_Base_Type : Entity_Id;
 175       --  Base type of prefix after analysis
 176
 177       P_Root_Type : Entity_Id;
 178       --  Root type of prefix after analysis
 179
 180       Unanalyzed  : Node_Id;
 181
 182       -----------------------
 183       -- Local Subprograms --
 184       -----------------------
 185
 186       procedure Access_Attribute;
 187       --  Used for Access, Unchecked_Access, Unrestricted_Access attributes.
 188       --  Internally, Id distinguishes which of the three cases is involved.
 189
 190       procedure Check_Array_Or_Scalar_Type;
 191       --  Common procedure used by First, Last, Range attribute to check
 192       --  that the prefix is a constrained array or scalar type, or a name
 193       --  of an array object, and that an argument appears only if appropriate
 194       --  (i.e. only in the array case).
 195
 196       procedure Check_Array_Type;
 197       --  Common semantic checks for all array attributes. Checks that the
 198       --  prefix is a constrained array type or the name of an array object.
 199       --  The error message for non-arrays is specialized appropriately.
 200
 201       procedure Check_Asm_Attribute;
 202       --  Common semantic checks for Asm_Input and Asm_Output attributes
 203
 204       procedure Check_Component;
 205       --  Common processing for Bit_Position, First_Bit, Last_Bit, and
 206       --  Position. Checks prefix is an appropriate selected component.
 207
 208       procedure Check_Decimal_Fixed_Point_Type;
 209       --  Check that prefix of attribute N is a decimal fixed-point type
 210
 211       procedure Check_Dereference;
 212       --  If the prefix of attribute is an object of an access type, then
 213       --  introduce an explicit deference, and adjust P_Type accordingly.
 214
 215       procedure Check_Discrete_Type;
 216       --  Verify that prefix of attribute N is a discrete type
 217
 218       procedure Check_E0;
 219       --  Check that no attribute arguments are present
 220
 221       procedure Check_Either_E0_Or_E1;
 222       --  Check that there are zero or one attribute arguments present
 223
 224       procedure Check_E1;
 225       --  Check that exactly one attribute argument is present
 226
 227       procedure Check_E2;
 228       --  Check that two attribute arguments are present
 229
 230       procedure Check_Enum_Image;
 231       --  If the prefix type is an enumeration type, set all its literals
 232       --  as referenced, since the image function could possibly end up
 233       --  referencing any of the literals indirectly.
 234
 235       procedure Check_Enumeration_Type;
 236       --  Verify that prefix of attribute N is an enumeration type
 237
 238       procedure Check_Fixed_Point_Type;
 239       --  Verify that prefix of attribute N is a fixed type
 240
 241       procedure Check_Fixed_Point_Type_0;
 242       --  Verify that prefix of attribute N is a fixed type and that
 243       --  no attribute expressions are present
 244
 245       procedure Check_Floating_Point_Type;
 246       --  Verify that prefix of attribute N is a float type
 247
 248       procedure Check_Floating_Point_Type_0;
 249       --  Verify that prefix of attribute N is a float type and that
 250       --  no attribute expressions are present
 251
 252       procedure Check_Floating_Point_Type_1;
 253       --  Verify that prefix of attribute N is a float type and that
 254       --  exactly one attribute expression is present
 255
 256       procedure Check_Floating_Point_Type_2;
 257       --  Verify that prefix of attribute N is a float type and that
 258       --  two attribute expressions are present
 259
 260       procedure Legal_Formal_Attribute;
 261       --  Common processing for attributes Definite, and Has_Discriminants
 262
 263       procedure Check_Integer_Type;
 264       --  Verify that prefix of attribute N is an integer type
 265
 266       procedure Check_Library_Unit;
 267       --  Verify that prefix of attribute N is a library unit
 268
 269       procedure Check_Not_Incomplete_Type;
 270       --  Check that P (the prefix of the attribute) is not an incomplete
 271       --  type or a private type for which no full view has been given.
 272
 273       procedure Check_Object_Reference (P : Node_Id);
 274       --  Check that P (the prefix of the attribute) is an object reference
 275
 276       procedure Check_Program_Unit;
 277       --  Verify that prefix of attribute N is a program unit
 278
 279       procedure Check_Real_Type;
 280       --  Verify that prefix of attribute N is fixed or float type
 281
 282       procedure Check_Scalar_Type;
 283       --  Verify that prefix of attribute N is a scalar type
 284
 285       procedure Check_Standard_Prefix;
 286       --  Verify that prefix of attribute N is package Standard
 287
 288       procedure Check_Stream_Attribute (Nam : Name_Id);
 289       --  Validity checking for stream attribute. Nam is the name of the
 290       --  corresponding possible defined attribute function (e.g. for the
 291       --  Read attribute, Nam will be Name_uRead).
 292
 293       procedure Check_Task_Prefix;
 294       --  Verify that prefix of attribute N is a task or task type
 295
 296       procedure Check_Type;
 297       --  Verify that the prefix of attribute N is a type
 298
 299       procedure Check_Unit_Name (Nod : Node_Id);
 300       --  Check that Nod is of the form of a library unit name, i.e that
 301       --  it is an identifier, or a selected component whose prefix is
 302       --  itself of the form of a library unit name. Note that this is
 303       --  quite different from Check_Program_Unit, since it only checks
 304       --  the syntactic form of the name, not the semantic identity. This
 305       --  is because it is used with attributes (Elab_Body, Elab_Spec, and
 306       --  UET_Address) which can refer to non-visible unit.
 307
 308       procedure Error_Attr (Msg : String; Error_Node : Node_Id);
 309       pragma No_Return (Error_Attr);
 310       --  Posts error using Error_Msg_N at given node, sets type of attribute
 311       --  node to Any_Type, and then raises Bad_Attribute to avoid any further
 312       --  semantic processing. The message typically contains a % insertion
 313       --  character which is replaced by the attribute name.
 314
 315       procedure Standard_Attribute (Val : Int);
 316       --  Used to process attributes whose prefix is package Standard which
 317       --  yield values of type Universal_Integer. The attribute reference
 318       --  node is rewritten with an integer literal of the given value.
 319
 320       procedure Unexpected_Argument (En : Node_Id);
 321       --  Signal unexpected attribute argument (En is the argument)
 322
 323       procedure Validate_Non_Static_Attribute_Function_Call;
 324       --  Called when processing an attribute that is a function call to a
 325       --  non-static function, i.e. an attribute function that either takes
 326       --  non-scalar arguments or returns a non-scalar result. Verifies that
 327       --  such a call does not appear in a preelaborable context.
 328
 329       ----------------------
 330       -- Access_Attribute --
 331       ----------------------
 332
 333       procedure Access_Attribute is
 334          Acc_Type : Entity_Id;
 335
 336          Scop : Entity_Id;
 337          Typ  : Entity_Id;
 338
 339          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id;
 340          --  Build an access-to-object type whose designated type is DT,
 341          --  and whose Ekind is appropriate to the attribute type. The
 342          --  type that is constructed is returned as the result.
 343
 344          procedure Build_Access_Subprogram_Type (P : Node_Id);
 345          --  Build an access to subprogram whose designated type is
 346          --  the type of the prefix. If prefix is overloaded, so it the
 347          --  node itself. The result is stored in Acc_Type.
 348
 349          ------------------------------
 350          -- Build_Access_Object_Type --
 351          ------------------------------
 352
 353          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id is
 354             Typ : Entity_Id;
 355
 356          begin
 357             if Aname = Name_Unrestricted_Access then
 358                Typ :=
 359                  New_Internal_Entity
 360                    (E_Allocator_Type, Current_Scope, Loc, 'A');
 361             else
 362                Typ :=
 363                  New_Internal_Entity
 364                    (E_Access_Attribute_Type, Current_Scope, Loc, 'A');
 365             end if;
 366
 367             Set_Etype                     (Typ, Typ);
 368             Init_Size_Align               (Typ);
 369             Set_Is_Itype                  (Typ);
 370             Set_Associated_Node_For_Itype (Typ, N);
 371             Set_Directly_Designated_Type  (Typ, DT);
 372             return Typ;
 373          end Build_Access_Object_Type;
 374
 375          ----------------------------------
 376          -- Build_Access_Subprogram_Type --
 377          ----------------------------------
 378
 379          procedure Build_Access_Subprogram_Type (P : Node_Id) is
 380             Index    : Interp_Index;
 381             It       : Interp;
 382
 383             function Get_Kind (E : Entity_Id) return Entity_Kind;
 384             --  Distinguish between access to regular and protected
 385             --  subprograms.
 386
 387             function Get_Kind (E : Entity_Id) return Entity_Kind is
 388             begin
 389                if Convention (E) = Convention_Protected then
 390                   return E_Access_Protected_Subprogram_Type;
 391                else
 392                   return E_Access_Subprogram_Type;
 393                end if;
 394             end Get_Kind;
 395
 396          --  Start of processing for Build_Access_Subprogram_Type
 397
 398          begin
 399             if not Is_Overloaded (P) then
 400                Acc_Type :=
 401                  New_Internal_Entity
 402                    (Get_Kind (Entity (P)), Current_Scope, Loc, 'A');
 403                Set_Etype (Acc_Type, Acc_Type);
 404                Set_Directly_Designated_Type (Acc_Type, Entity (P));
 405                Set_Etype (N, Acc_Type);
 406
 407             else
 408                Get_First_Interp (P, Index, It);
 409                Set_Etype (N, Any_Type);
 410
 411                while Present (It.Nam) loop
 412
 413                   if not Is_Intrinsic_Subprogram (It.Nam) then
 414                      Acc_Type :=
 415                        New_Internal_Entity
 416                          (Get_Kind (It.Nam), Current_Scope, Loc, 'A');
 417                      Set_Etype (Acc_Type, Acc_Type);
 418                      Set_Directly_Designated_Type (Acc_Type, It.Nam);
 419                      Add_One_Interp (N, Acc_Type, Acc_Type);
 420                   end if;
 421
 422                   Get_Next_Interp (Index, It);
 423                end loop;
 424
 425                if Etype (N) = Any_Type then
 426                   Error_Attr ("prefix of % attribute cannot be intrinsic", P);
 427                end if;
 428             end if;
 429          end Build_Access_Subprogram_Type;
 430
 431       --  Start of processing for Access_Attribute
 432
 433       begin
 434          Check_E0;
 435
 436          if Nkind (P) = N_Character_Literal then
 437             Error_Attr
 438               ("prefix of % attribute cannot be enumeration literal", P);
 439
 440          --  In the case of an access to subprogram, use the name of the
 441          --  subprogram itself as the designated type. Type-checking in
 442          --  this case compares the signatures of the designated types.
 443
 444          elsif Is_Entity_Name (P)
 445            and then Is_Overloadable (Entity (P))
 446          then
 447             Build_Access_Subprogram_Type (P);
 448             return;
 449
 450          --  Component is an operation of a protected type.
 451
 452          elsif (Nkind (P) = N_Selected_Component
 453            and then Is_Overloadable (Entity (Selector_Name (P))))
 454          then
 455             if Ekind (Entity (Selector_Name (P))) = E_Entry then
 456                Error_Attr ("Prefix of % attribute must be subprogram", P);
 457             end if;
 458
 459             Build_Access_Subprogram_Type (Selector_Name (P));
 460             return;
 461          end if;
 462
 463          --  Deal with incorrect reference to a type, but note that some
 464          --  accesses are allowed (references to the current type instance).
 465
 466          if Is_Entity_Name (P) then
 467             Scop := Current_Scope;
 468             Typ := Entity (P);
 469
 470             if Is_Type (Typ) then
 471
 472                --  OK if we are within the scope of a limited type
 473                --  let's mark the component as having per object constraint
 474
 475                if Is_Anonymous_Tagged_Base (Scop, Typ) then
 476                   Typ := Scop;
 477                   Set_Entity (P, Typ);
 478                   Set_Etype  (P, Typ);
 479                end if;
 480
 481                if Typ = Scop then
 482                   declare
 483                      Q : Node_Id := Parent (N);
 484
 485                   begin
 486                      while Present (Q)
 487                        and then Nkind (Q) /= N_Component_Declaration
 488                      loop
 489                         Q := Parent (Q);
 490                      end loop;
 491                      if Present (Q) then
 492                         Set_Has_Per_Object_Constraint (
 493                           Defining_Identifier (Q), True);
 494                      end if;
 495                   end;
 496
 497                   if Nkind (P) = N_Expanded_Name then
 498                      Error_Msg_N
 499                        ("current instance prefix must be a direct name", P);
 500                   end if;
 501
 502                   --  If a current instance attribute appears within a
 503                   --  a component constraint it must appear alone; other
 504                   --  contexts (default expressions, within a task body)
 505                   --  are not subject to this restriction.
 506
 507                   if not In_Default_Expression
 508                     and then not Has_Completion (Scop)
 509                     and then
 510                       Nkind (Parent (N)) /= N_Discriminant_Association
 511                     and then
 512                       Nkind (Parent (N)) /= N_Index_Or_Discriminant_Constraint
 513                   then
 514                      Error_Msg_N
 515                        ("current instance attribute must appear alone", N);
 516                   end if;
 517
 518                --  OK if we are in initialization procedure for the type
 519                --  in question, in which case the reference to the type
 520                --  is rewritten as a reference to the current object.
 521
 522                elsif Ekind (Scop) = E_Procedure
 523                  and then Chars (Scop) = Name_uInit_Proc
 524                  and then Etype (First_Formal (Scop)) = Typ
 525                then
 526                   Rewrite (N,
 527                     Make_Attribute_Reference (Loc,
 528                       Prefix         => Make_Identifier (Loc, Name_uInit),
 529                       Attribute_Name => Name_Unrestricted_Access));
 530                   Analyze (N);
 531                   return;
 532
 533                --  OK if a task type, this test needs sharpening up ???
 534
 535                elsif Is_Task_Type (Typ) then
 536                   null;
 537
 538                --  Otherwise we have an error case
 539
 540                else
 541                   Error_Attr ("% attribute cannot be applied to type", P);
 542                   return;
 543                end if;
 544             end if;
 545          end if;
 546
 547          --  If we fall through, we have a normal access to object case.
 548          --  Unrestricted_Access is legal wherever an allocator would be
 549          --  legal, so its Etype is set to E_Allocator. The expected type
 550          --  of the other attributes is a general access type, and therefore
 551          --  we label them with E_Access_Attribute_Type.
 552
 553          if not Is_Overloaded (P) then
 554             Acc_Type := Build_Access_Object_Type (P_Type);
 555             Set_Etype (N, Acc_Type);
 556          else
 557             declare
 558                Index : Interp_Index;
 559                It    : Interp;
 560
 561             begin
 562                Set_Etype (N, Any_Type);
 563                Get_First_Interp (P, Index, It);
 564
 565                while Present (It.Typ) loop
 566                   Acc_Type := Build_Access_Object_Type (It.Typ);
 567                   Add_One_Interp (N, Acc_Type, Acc_Type);
 568                   Get_Next_Interp (Index, It);
 569                end loop;
 570             end;
 571          end if;
 572
 573          --  Check for aliased view unless unrestricted case. We allow
 574          --  a nonaliased prefix when within an instance because the
 575          --  prefix may have been a tagged formal object, which is
 576          --  defined to be aliased even when the actual might not be
 577          --  (other instance cases will have been caught in the generic).
 578
 579          if Aname /= Name_Unrestricted_Access
 580            and then not Is_Aliased_View (P)
 581            and then not In_Instance
 582          then
 583             Error_Attr ("prefix of % attribute must be aliased", P);
 584          end if;
 585
 586       end Access_Attribute;
 587
 588       --------------------------------
 589       -- Check_Array_Or_Scalar_Type --
 590       --------------------------------
 591
 592       procedure Check_Array_Or_Scalar_Type is
 593          Index : Entity_Id;
 594
 595          D : Int;
 596          --  Dimension number for array attributes.
 597
 598       begin
 599          --  Case of string literal or string literal subtype. These cases
 600          --  cannot arise from legal Ada code, but the expander is allowed
 601          --  to generate them. They require special handling because string
 602          --  literal subtypes do not have standard bounds (the whole idea
 603          --  of these subtypes is to avoid having to generate the bounds)
 604
 605          if Ekind (P_Type) = E_String_Literal_Subtype then
 606             Set_Etype (N, Etype (First_Index (P_Base_Type)));
 607             return;
 608
 609          --  Scalar types
 610
 611          elsif Is_Scalar_Type (P_Type) then
 612             Check_Type;
 613
 614             if Present (E1) then
 615                Error_Attr ("invalid argument in % attribute", E1);
 616             else
 617                Set_Etype (N, P_Base_Type);
 618                return;
 619             end if;
 620
 621          --  The following is a special test to allow 'First to apply to
 622          --  private scalar types if the attribute comes from generated
 623          --  code. This occurs in the case of Normalize_Scalars code.
 624
 625          elsif Is_Private_Type (P_Type)
 626            and then Present (Full_View (P_Type))
 627            and then Is_Scalar_Type (Full_View (P_Type))
 628            and then not Comes_From_Source (N)
 629          then
 630             Set_Etype (N, Implementation_Base_Type (P_Type));
 631
 632          --  Array types other than string literal subtypes handled above
 633
 634          else
 635             Check_Array_Type;
 636
 637             --  We know prefix is an array type, or the name of an array
 638             --  object, and that the expression, if present, is static
 639             --  and within the range of the dimensions of the type.
 640
 641             if Is_Array_Type (P_Type) then
 642                Index := First_Index (P_Base_Type);
 643
 644             else pragma Assert (Is_Access_Type (P_Type));
 645                Index := First_Index (Base_Type (Designated_Type (P_Type)));
 646             end if;
 647
 648             if No (E1) then
 649
 650                --  First dimension assumed
 651
 652                Set_Etype (N, Base_Type (Etype (Index)));
 653
 654             else
 655                D := UI_To_Int (Intval (E1));
 656
 657                for J in 1 .. D - 1 loop
 658                   Next_Index (Index);
 659                end loop;
 660
 661                Set_Etype (N, Base_Type (Etype (Index)));
 662                Set_Etype (E1, Standard_Integer);
 663             end if;
 664          end if;
 665       end Check_Array_Or_Scalar_Type;
 666
 667       ----------------------
 668       -- Check_Array_Type --
 669       ----------------------
 670
 671       procedure Check_Array_Type is
 672          D : Int;
 673          --  Dimension number for array attributes.
 674
 675       begin
 676          --  If the type is a string literal type, then this must be generated
 677          --  internally, and no further check is required on its legality.
 678
 679          if Ekind (P_Type) = E_String_Literal_Subtype then
 680             return;
 681
 682          --  If the type is a composite, it is an illegal aggregate, no point
 683          --  in going on.
 684
 685          elsif P_Type = Any_Composite then
 686             raise Bad_Attribute;
 687          end if;
 688
 689          --  Normal case of array type or subtype
 690
 691          Check_Either_E0_Or_E1;
 692
 693          if Is_Array_Type (P_Type) then
 694             if not Is_Constrained (P_Type)
 695               and then Is_Entity_Name (P)
 696               and then Is_Type (Entity (P))
 697             then
 698                --  Note: we do not call Error_Attr here, since we prefer to
 699                --  continue, using the relevant index type of the array,
 700                --  even though it is unconstrained. This gives better error
 701                --  recovery behavior.
 702
 703                Error_Msg_Name_1 := Aname;
 704                Error_Msg_N
 705                  ("prefix for % attribute must be constrained array", P);
 706             end if;
 707
 708             D := Number_Dimensions (P_Type);
 709
 710          elsif Is_Access_Type (P_Type)
 711            and then Is_Array_Type (Designated_Type (P_Type))
 712          then
 713             if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
 714                Error_Attr ("prefix of % attribute cannot be access type", P);
 715             end if;
 716
 717             D := Number_Dimensions (Designated_Type (P_Type));
 718
 719             --  If there is an implicit dereference, then we must freeze
 720             --  the designated type of the access type, since the type of
 721             --  the referenced array is this type (see AI95-00106).
 722
 723             Freeze_Before (N, Designated_Type (P_Type));
 724
 725          else
 726             if Is_Private_Type (P_Type) then
 727                Error_Attr
 728                  ("prefix for % attribute may not be private type", P);
 729
 730             elsif Attr_Id = Attribute_First
 731                     or else
 732                   Attr_Id = Attribute_Last
 733             then
 734                Error_Attr ("invalid prefix for % attribute", P);
 735
 736             else
 737                Error_Attr ("prefix for % attribute must be array", P);
 738             end if;
 739          end if;
 740
 741          if Present (E1) then
 742             Resolve (E1, Any_Integer);
 743             Set_Etype (E1, Standard_Integer);
 744
 745             if not Is_Static_Expression (E1)
 746               or else Raises_Constraint_Error (E1)
 747             then
 748                Error_Attr ("expression for dimension must be static", E1);
 749
 750             elsif  UI_To_Int (Expr_Value (E1)) > D
 751               or else UI_To_Int (Expr_Value (E1)) < 1
 752             then
 753                Error_Attr ("invalid dimension number for array type", E1);
 754             end if;
 755          end if;
 756       end Check_Array_Type;
 757
 758       -------------------------
 759       -- Check_Asm_Attribute --
 760       -------------------------
 761
 762       procedure Check_Asm_Attribute is
 763       begin
 764          Check_Type;
 765          Check_E2;
 766
 767          --  Check first argument is static string expression
 768
 769          Analyze_And_Resolve (E1, Standard_String);
 770
 771          if Etype (E1) = Any_Type then
 772             return;
 773
 774          elsif not Is_OK_Static_Expression (E1) then
 775             Error_Attr
 776               ("constraint argument must be static string expression", E1);
 777          end if;
 778
 779          --  Check second argument is right type
 780
 781          Analyze_And_Resolve (E2, Entity (P));
 782
 783          --  Note: that is all we need to do, we don't need to check
 784          --  that it appears in a correct context. The Ada type system
 785          --  will do that for us.
 786
 787       end Check_Asm_Attribute;
 788
 789       ---------------------
 790       -- Check_Component --
 791       ---------------------
 792
 793       procedure Check_Component is
 794       begin
 795          Check_E0;
 796
 797          if Nkind (P) /= N_Selected_Component
 798            or else
 799              (Ekind (Entity (Selector_Name (P))) /= E_Component
 800                and then
 801               Ekind (Entity (Selector_Name (P))) /= E_Discriminant)
 802          then
 803             Error_Attr
 804               ("prefix for % attribute must be selected component", P);
 805          end if;
 806       end Check_Component;
 807
 808       ------------------------------------
 809       -- Check_Decimal_Fixed_Point_Type --
 810       ------------------------------------
 811
 812       procedure Check_Decimal_Fixed_Point_Type is
 813       begin
 814          Check_Type;
 815
 816          if not Is_Decimal_Fixed_Point_Type (P_Type) then
 817             Error_Attr
 818               ("prefix of % attribute must be decimal type", P);
 819          end if;
 820       end Check_Decimal_Fixed_Point_Type;
 821
 822       -----------------------
 823       -- Check_Dereference --
 824       -----------------------
 825
 826       procedure Check_Dereference is
 827       begin
 828          if Is_Object_Reference (P)
 829            and then Is_Access_Type (P_Type)
 830          then
 831             Rewrite (P,
 832               Make_Explicit_Dereference (Sloc (P),
 833                 Prefix => Relocate_Node (P)));
 834
 835             Analyze_And_Resolve (P);
 836             P_Type := Etype (P);
 837
 838             if P_Type = Any_Type then
 839                raise Bad_Attribute;
 840             end if;
 841
 842             P_Base_Type := Base_Type (P_Type);
 843             P_Root_Type := Root_Type (P_Base_Type);
 844          end if;
 845       end Check_Dereference;
 846
 847       -------------------------
 848       -- Check_Discrete_Type --
 849       -------------------------
 850
 851       procedure Check_Discrete_Type is
 852       begin
 853          Check_Type;
 854
 855          if not Is_Discrete_Type (P_Type) then
 856             Error_Attr ("prefix of % attribute must be discrete type", P);
 857          end if;
 858       end Check_Discrete_Type;
 859
 860       --------------
 861       -- Check_E0 --
 862       --------------
 863
 864       procedure Check_E0 is
 865       begin
 866          if Present (E1) then
 867             Unexpected_Argument (E1);
 868          end if;
 869       end Check_E0;
 870
 871       --------------
 872       -- Check_E1 --
 873       --------------
 874
 875       procedure Check_E1 is
 876       begin
 877          Check_Either_E0_Or_E1;
 878
 879          if No (E1) then
 880
 881             --  Special-case attributes that are functions and that appear as
 882             --  the prefix of another attribute. Error is posted on parent.
 883
 884             if Nkind (Parent (N)) = N_Attribute_Reference
 885               and then (Attribute_Name (Parent (N)) = Name_Address
 886                           or else
 887                         Attribute_Name (Parent (N)) = Name_Code_Address
 888                           or else
 889                         Attribute_Name (Parent (N)) = Name_Access)
 890             then
 891                Error_Msg_Name_1 := Attribute_Name (Parent (N));
 892                Error_Msg_N ("illegal prefix for % attribute", Parent (N));
 893                Set_Etype (Parent (N), Any_Type);
 894                Set_Entity (Parent (N), Any_Type);
 895                raise Bad_Attribute;
 896
 897             else
 898                Error_Attr ("missing argument for % attribute", N);
 899             end if;
 900          end if;
 901       end Check_E1;
 902
 903       --------------
 904       -- Check_E2 --
 905       --------------
 906
 907       procedure Check_E2 is
 908       begin
 909          if No (E1) then
 910             Error_Attr ("missing arguments for % attribute (2 required)", N);
 911          elsif No (E2) then
 912             Error_Attr ("missing argument for % attribute (2 required)", N);
 913          end if;
 914       end Check_E2;
 915
 916       ---------------------------
 917       -- Check_Either_E0_Or_E1 --
 918       ---------------------------
 919
 920       procedure Check_Either_E0_Or_E1 is
 921       begin
 922          if Present (E2) then
 923             Unexpected_Argument (E2);
 924          end if;
 925       end Check_Either_E0_Or_E1;
 926
 927       ----------------------
 928       -- Check_Enum_Image --
 929       ----------------------
 930
 931       procedure Check_Enum_Image is
 932          Lit : Entity_Id;
 933
 934       begin
 935          if Is_Enumeration_Type (P_Base_Type) then
 936             Lit := First_Literal (P_Base_Type);
 937             while Present (Lit) loop
 938                Set_Referenced (Lit);
 939                Next_Literal (Lit);
 940             end loop;
 941          end if;
 942       end Check_Enum_Image;
 943
 944       ----------------------------
 945       -- Check_Enumeration_Type --
 946       ----------------------------
 947
 948       procedure Check_Enumeration_Type is
 949       begin
 950          Check_Type;
 951
 952          if not Is_Enumeration_Type (P_Type) then
 953             Error_Attr ("prefix of % attribute must be enumeration type", P);
 954          end if;
 955       end Check_Enumeration_Type;
 956
 957       ----------------------------
 958       -- Check_Fixed_Point_Type --
 959       ----------------------------
 960
 961       procedure Check_Fixed_Point_Type is
 962       begin
 963          Check_Type;
 964
 965          if not Is_Fixed_Point_Type (P_Type) then
 966             Error_Attr ("prefix of % attribute must be fixed point type", P);
 967          end if;
 968       end Check_Fixed_Point_Type;
 969
 970       ------------------------------
 971       -- Check_Fixed_Point_Type_0 --
 972       ------------------------------
 973
 974       procedure Check_Fixed_Point_Type_0 is
 975       begin
 976          Check_Fixed_Point_Type;
 977          Check_E0;
 978       end Check_Fixed_Point_Type_0;
 979
 980       -------------------------------
 981       -- Check_Floating_Point_Type --
 982       -------------------------------
 983
 984       procedure Check_Floating_Point_Type is
 985       begin
 986          Check_Type;
 987
 988          if not Is_Floating_Point_Type (P_Type) then
 989             Error_Attr ("prefix of % attribute must be float type", P);
 990          end if;
 991       end Check_Floating_Point_Type;
 992
 993       ---------------------------------
 994       -- Check_Floating_Point_Type_0 --
 995       ---------------------------------
 996
 997       procedure Check_Floating_Point_Type_0 is
 998       begin
 999          Check_Floating_Point_Type;
1000          Check_E0;
1001       end Check_Floating_Point_Type_0;
1002
1003       ---------------------------------
1004       -- Check_Floating_Point_Type_1 --
1005       ---------------------------------
1006
1007       procedure Check_Floating_Point_Type_1 is
1008       begin
1009          Check_Floating_Point_Type;
1010          Check_E1;
1011       end Check_Floating_Point_Type_1;
1012
1013       ---------------------------------
1014       -- Check_Floating_Point_Type_2 --
1015       ---------------------------------
1016
1017       procedure Check_Floating_Point_Type_2 is
1018       begin
1019          Check_Floating_Point_Type;
1020          Check_E2;
1021       end Check_Floating_Point_Type_2;
1022
1023       ------------------------
1024       -- Check_Integer_Type --
1025       ------------------------
1026
1027       procedure Check_Integer_Type is
1028       begin
1029          Check_Type;
1030
1031          if not Is_Integer_Type (P_Type) then
1032             Error_Attr ("prefix of % attribute must be integer type", P);
1033          end if;
1034       end Check_Integer_Type;
1035
1036       ------------------------
1037       -- Check_Library_Unit --
1038       ------------------------
1039
1040       procedure Check_Library_Unit is
1041       begin
1042          if not Is_Compilation_Unit (Entity (P)) then
1043             Error_Attr ("prefix of % attribute must be library unit", P);
1044          end if;
1045       end Check_Library_Unit;
1046
1047       -------------------------------
1048       -- Check_Not_Incomplete_Type --
1049       -------------------------------
1050
1051       procedure Check_Not_Incomplete_Type is
1052       begin
1053          if not Is_Entity_Name (P)
1054            or else not Is_Type (Entity (P))
1055            or else In_Default_Expression
1056          then
1057             return;
1058
1059          else
1060             Check_Fully_Declared (P_Type, P);
1061          end if;
1062       end Check_Not_Incomplete_Type;
1063
1064       ----------------------------
1065       -- Check_Object_Reference --
1066       ----------------------------
1067
1068       procedure Check_Object_Reference (P : Node_Id) is
1069          Rtyp : Entity_Id;
1070
1071       begin
1072          --  If we need an object, and we have a prefix that is the name of
1073          --  a function entity, convert it into a function call.
1074
1075          if Is_Entity_Name (P)
1076            and then Ekind (Entity (P)) = E_Function
1077          then
1078             Rtyp := Etype (Entity (P));
1079
1080             Rewrite (P,
1081               Make_Function_Call (Sloc (P),
1082                 Name => Relocate_Node (P)));
1083
1084             Analyze_And_Resolve (P, Rtyp);
1085
1086          --  Otherwise we must have an object reference
1087
1088          elsif not Is_Object_Reference (P) then
1089             Error_Attr ("prefix of % attribute must be object", P);
1090          end if;
1091       end Check_Object_Reference;
1092
1093       ------------------------
1094       -- Check_Program_Unit --
1095       ------------------------
1096
1097       procedure Check_Program_Unit is
1098       begin
1099          if Is_Entity_Name (P) then
1100             declare
1101                K : constant Entity_Kind := Ekind (Entity (P));
1102                T : constant Entity_Id   := Etype (Entity (P));
1103
1104             begin
1105                if K in Subprogram_Kind
1106                  or else K in Task_Kind
1107                  or else K in Protected_Kind
1108                  or else K = E_Package
1109                  or else K in Generic_Unit_Kind
1110                  or else (K = E_Variable
1111                             and then
1112                               (Is_Task_Type (T)
1113                                  or else
1114                                Is_Protected_Type (T)))
1115                then
1116                   return;
1117                end if;
1118             end;
1119          end if;
1120
1121          Error_Attr ("prefix of % attribute must be program unit", P);
1122       end Check_Program_Unit;
1123
1124       ---------------------
1125       -- Check_Real_Type --
1126       ---------------------
1127
1128       procedure Check_Real_Type is
1129       begin
1130          Check_Type;
1131
1132          if not Is_Real_Type (P_Type) then
1133             Error_Attr ("prefix of % attribute must be real type", P);
1134          end if;
1135       end Check_Real_Type;
1136
1137       -----------------------
1138       -- Check_Scalar_Type --
1139       -----------------------
1140
1141       procedure Check_Scalar_Type is
1142       begin
1143          Check_Type;
1144
1145          if not Is_Scalar_Type (P_Type) then
1146             Error_Attr ("prefix of % attribute must be scalar type", P);
1147          end if;
1148       end Check_Scalar_Type;
1149
1150       ---------------------------
1151       -- Check_Standard_Prefix --
1152       ---------------------------
1153
1154       procedure Check_Standard_Prefix is
1155       begin
1156          Check_E0;
1157
1158          if Nkind (P) /= N_Identifier
1159            or else Chars (P) /= Name_Standard
1160          then
1161             Error_Attr ("only allowed prefix for % attribute is Standard", P);
1162          end if;
1163
1164       end Check_Standard_Prefix;
1165
1166       ----------------------------
1167       -- Check_Stream_Attribute --
1168       ----------------------------
1169
1170       procedure Check_Stream_Attribute (Nam : Name_Id) is
1171          Etyp : Entity_Id;
1172          Btyp : Entity_Id;
1173
1174       begin
1175          Validate_Non_Static_Attribute_Function_Call;
1176
1177          --  With the exception of 'Input, Stream attributes are procedures,
1178          --  and can only appear at the position of procedure calls. We check
1179          --  for this here, before they are rewritten, to give a more precise
1180          --  diagnostic.
1181
1182          if Nam = Name_uInput then
1183             null;
1184
1185          elsif Is_List_Member (N)
1186            and then Nkind (Parent (N)) /= N_Procedure_Call_Statement
1187            and then Nkind (Parent (N)) /= N_Aggregate
1188          then
1189             null;
1190
1191          else
1192             Error_Attr
1193               ("invalid context for attribute %, which is a procedure", N);
1194          end if;
1195
1196          Check_Type;
1197          Btyp := Implementation_Base_Type (P_Type);
1198
1199          --  Stream attributes not allowed on limited types unless the
1200          --  special OK_For_Stream flag is set.
1201
1202          if Is_Limited_Type (P_Type)
1203            and then Comes_From_Source (N)
1204            and then not Present (TSS (Btyp, Nam))
1205            and then No (Get_Rep_Pragma (Btyp, Name_Stream_Convert))
1206          then
1207             --  Special case the message if we are compiling the stub version
1208             --  of a remote operation. One error on the type is sufficient.
1209
1210             if (Is_Remote_Types (Current_Scope)
1211                  or else Is_Remote_Call_Interface (Current_Scope))
1212               and then not Error_Posted (Btyp)
1213             then
1214                Error_Msg_Node_2 := Current_Scope;
1215                Error_Msg_NE
1216                  ("limited type& used in& has no stream attributes", P, Btyp);
1217                Set_Error_Posted (Btyp);
1218
1219             elsif not Error_Posted (Btyp) then
1220                Error_Msg_NE
1221                  ("limited type& has no stream attributes", P, Btyp);
1222             end if;
1223          end if;
1224
1225          --  Here we must check that the first argument is an access type
1226          --  that is compatible with Ada.Streams.Root_Stream_Type'Class.
1227
1228          Analyze_And_Resolve (E1);
1229          Etyp := Etype (E1);
1230
1231          --  Note: the double call to Root_Type here is needed because the
1232          --  root type of a class-wide type is the corresponding type (e.g.
1233          --  X for X'Class, and we really want to go to the root.
1234
1235          if not Is_Access_Type (Etyp)
1236            or else Root_Type (Root_Type (Designated_Type (Etyp))) /=
1237                      RTE (RE_Root_Stream_Type)
1238          then
1239             Error_Attr
1240               ("expected access to Ada.Streams.Root_Stream_Type''Class", E1);
1241          end if;
1242
1243          --  Check that the second argument is of the right type if there is
1244          --  one (the Input attribute has only one argument so this is skipped)
1245
1246          if Present (E2) then
1247             Analyze (E2);
1248
1249             if Nam = Name_uRead
1250               and then not Is_OK_Variable_For_Out_Formal (E2)
1251             then
1252                Error_Attr
1253                  ("second argument of % attribute must be a variable", E2);
1254             end if;
1255
1256             Resolve (E2, P_Type);
1257          end if;
1258       end Check_Stream_Attribute;
1259
1260       -----------------------
1261       -- Check_Task_Prefix --
1262       -----------------------
1263
1264       procedure Check_Task_Prefix is
1265       begin
1266          Analyze (P);
1267
1268          if Is_Task_Type (Etype (P))
1269            or else (Is_Access_Type (Etype (P))
1270               and then Is_Task_Type (Designated_Type (Etype (P))))
1271          then
1272             Resolve (P, Etype (P));
1273          else
1274             Error_Attr ("prefix of % attribute must be a task", P);
1275          end if;
1276       end Check_Task_Prefix;
1277
1278       ----------------
1279       -- Check_Type --
1280       ----------------
1281
1282       --  The possibilities are an entity name denoting a type, or an
1283       --  attribute reference that denotes a type (Base or Class). If
1284       --  the type is incomplete, replace it with its full view.
1285
1286       procedure Check_Type is
1287       begin
1288          if not Is_Entity_Name (P)
1289            or else not Is_Type (Entity (P))
1290          then
1291             Error_Attr ("prefix of % attribute must be a type", P);
1292
1293          elsif Ekind (Entity (P)) = E_Incomplete_Type
1294             and then Present (Full_View (Entity (P)))
1295          then
1296             P_Type := Full_View (Entity (P));
1297             Set_Entity (P, P_Type);
1298          end if;
1299       end Check_Type;
1300
1301       ---------------------
1302       -- Check_Unit_Name --
1303       ---------------------
1304
1305       procedure Check_Unit_Name (Nod : Node_Id) is
1306       begin
1307          if Nkind (Nod) = N_Identifier then
1308             return;
1309
1310          elsif Nkind (Nod) = N_Selected_Component then
1311             Check_Unit_Name (Prefix (Nod));
1312
1313             if Nkind (Selector_Name (Nod)) = N_Identifier then
1314                return;
1315             end if;
1316          end if;
1317
1318          Error_Attr ("argument for % attribute must be unit name", P);
1319       end Check_Unit_Name;
1320
1321       ----------------
1322       -- Error_Attr --
1323       ----------------
1324
1325       procedure Error_Attr (Msg : String; Error_Node : Node_Id) is
1326       begin
1327          Error_Msg_Name_1 := Aname;
1328          Error_Msg_N (Msg, Error_Node);
1329          Set_Etype (N, Any_Type);
1330          Set_Entity (N, Any_Type);
1331          raise Bad_Attribute;
1332       end Error_Attr;
1333
1334       ----------------------------
1335       -- Legal_Formal_Attribute --
1336       ----------------------------
1337
1338       procedure Legal_Formal_Attribute is
1339       begin
1340          Check_E0;
1341
1342          if not Is_Entity_Name (P)
1343            or else not Is_Type (Entity (P))
1344          then
1345             Error_Attr (" prefix of % attribute must be generic type", N);
1346
1347          elsif Is_Generic_Actual_Type (Entity (P))
1348            or In_Instance
1349          then
1350             null;
1351
1352          elsif Is_Generic_Type (Entity (P)) then
1353             if not Is_Indefinite_Subtype (Entity (P)) then
1354                Error_Attr
1355                  (" prefix of % attribute must be indefinite generic type", N);
1356             end if;
1357
1358          else
1359             Error_Attr
1360               (" prefix of % attribute must be indefinite generic type", N);
1361          end if;
1362
1363          Set_Etype (N, Standard_Boolean);
1364       end Legal_Formal_Attribute;
1365
1366       ------------------------
1367       -- Standard_Attribute --
1368       ------------------------
1369
1370       procedure Standard_Attribute (Val : Int) is
1371       begin
1372          Check_Standard_Prefix;
1373          Rewrite (N,
1374            Make_Integer_Literal (Loc, Val));
1375          Analyze (N);
1376       end Standard_Attribute;
1377
1378       -------------------------
1379       -- Unexpected Argument --
1380       -------------------------
1381
1382       procedure Unexpected_Argument (En : Node_Id) is
1383       begin
1384          Error_Attr ("unexpected argument for % attribute", En);
1385       end Unexpected_Argument;
1386
1387       -------------------------------------------------
1388       -- Validate_Non_Static_Attribute_Function_Call --
1389       -------------------------------------------------
1390
1391       --  This function should be moved to Sem_Dist ???
1392
1393       procedure Validate_Non_Static_Attribute_Function_Call is
1394       begin
1395          if In_Preelaborated_Unit
1396            and then not In_Subprogram_Or_Concurrent_Unit
1397          then
1398             Error_Msg_N ("non-static function call in preelaborated unit", N);
1399          end if;
1400       end Validate_Non_Static_Attribute_Function_Call;
1401
1402    -----------------------------------------------
1403    -- Start of Processing for Analyze_Attribute --
1404    -----------------------------------------------
1405
1406    begin
1407       --  Immediate return if unrecognized attribute (already diagnosed
1408       --  by parser, so there is nothing more that we need to do)
1409
1410       if not Is_Attribute_Name (Aname) then
1411          raise Bad_Attribute;
1412       end if;
1413
1414       --  Deal with Ada 83 and Features issues
1415
1416       if not Attribute_83 (Attr_Id) then
1417          if Ada_83 and then Comes_From_Source (N) then
1418             Error_Msg_Name_1 := Aname;
1419             Error_Msg_N ("(Ada 83) attribute% is not standard?", N);
1420          end if;
1421
1422          if Attribute_Impl_Def (Attr_Id) then
1423             Check_Restriction (No_Implementation_Attributes, N);
1424          end if;
1425       end if;
1426
1427       --   Remote access to subprogram type access attribute reference needs
1428       --   unanalyzed copy for tree transformation. The analyzed copy is used
1429       --   for its semantic information (whether prefix is a remote subprogram
1430       --   name), the unanalyzed copy is used to construct new subtree rooted
1431       --   with N_aggregate which represents a fat pointer aggregate.
1432
1433       if Aname = Name_Access then
1434          Unanalyzed := Copy_Separate_Tree (N);
1435       end if;
1436
1437       --  Analyze prefix and exit if error in analysis. If the prefix is an
1438       --  incomplete type, use full view if available. A special case is
1439       --  that we never analyze the prefix of an Elab_Body or Elab_Spec
1440       --  or UET_Address attribute.
1441
1442       if Aname /= Name_Elab_Body
1443            and then
1444          Aname /= Name_Elab_Spec
1445            and then
1446          Aname /= Name_UET_Address
1447       then
1448          Analyze (P);
1449          P_Type := Etype (P);
1450
1451          if Is_Entity_Name (P)
1452            and then Present (Entity (P))
1453            and then Is_Type (Entity (P))
1454            and then Ekind (Entity (P)) = E_Incomplete_Type
1455          then
1456             P_Type := Get_Full_View (P_Type);
1457             Set_Entity (P, P_Type);
1458             Set_Etype  (P, P_Type);
1459          end if;
1460
1461          if P_Type = Any_Type then
1462             raise Bad_Attribute;
1463          end if;
1464
1465          P_Base_Type := Base_Type (P_Type);
1466          P_Root_Type := Root_Type (P_Base_Type);
1467       end if;
1468
1469       --  Analyze expressions that may be present, exiting if an error occurs
1470
1471       if No (Exprs) then
1472          E1 := Empty;
1473          E2 := Empty;
1474
1475       else
1476          E1 := First (Exprs);
1477          Analyze (E1);
1478
1479          if Etype (E1) = Any_Type then
1480             raise Bad_Attribute;
1481          end if;
1482
1483          E2 := Next (E1);
1484
1485          if Present (E2) then
1486             Analyze (E2);
1487
1488             if Etype (E2) = Any_Type then
1489                raise Bad_Attribute;
1490             end if;
1491
1492             if Present (Next (E2)) then
1493                Unexpected_Argument (Next (E2));
1494             end if;
1495          end if;
1496       end if;
1497
1498       if Is_Overloaded (P)
1499         and then Aname /= Name_Access
1500         and then Aname /= Name_Address
1501         and then Aname /= Name_Code_Address
1502         and then Aname /= Name_Count
1503         and then Aname /= Name_Unchecked_Access
1504       then
1505          Error_Attr ("ambiguous prefix for % attribute", P);
1506       end if;
1507
1508       --  Remaining processing depends on attribute
1509
1510       case Attr_Id is
1511
1512       ------------------
1513       -- Abort_Signal --
1514       ------------------
1515
1516       when Attribute_Abort_Signal =>
1517          Check_Standard_Prefix;
1518          Rewrite (N,
1519            New_Reference_To (Stand.Abort_Signal, Loc));
1520          Analyze (N);
1521
1522       ------------
1523       -- Access --
1524       ------------
1525
1526       when Attribute_Access =>
1527          Access_Attribute;
1528
1529       -------------
1530       -- Address --
1531       -------------
1532
1533       when Attribute_Address =>
1534          Check_E0;
1535
1536          --  Check for some junk cases, where we have to allow the address
1537          --  attribute but it does not make much sense, so at least for now
1538          --  just replace with Null_Address.
1539
1540          --  We also do this if the prefix is a reference to the AST_Entry
1541          --  attribute. If expansion is active, the attribute will be
1542          --  replaced by a function call, and address will work fine and
1543          --  get the proper value, but if expansion is not active, then
1544          --  the check here allows proper semantic analysis of the reference.
1545
1546          if (Is_Entity_Name (P)
1547            and then
1548              (((Ekind (Entity (P)) = E_Task_Type
1549                  or else Ekind (Entity (P)) = E_Protected_Type)
1550                    and then Etype (Entity (P)) = Base_Type (Entity (P)))
1551                or else Ekind (Entity (P)) = E_Package
1552                or else Is_Generic_Unit (Entity (P))))
1553            or else
1554             (Nkind (P) = N_Attribute_Reference
1555               and then
1556              Attribute_Name (P) = Name_AST_Entry)
1557          then
1558             Rewrite (N,
1559               New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1560
1561          --  The following logic is obscure, needs explanation ???
1562
1563          elsif Nkind (P) = N_Attribute_Reference
1564            or else (Is_Entity_Name (P)
1565                       and then not Is_Subprogram (Entity (P))
1566                       and then not Is_Object (Entity (P))
1567                       and then Ekind (Entity (P)) /= E_Label)
1568          then
1569             Error_Attr ("invalid prefix for % attribute", P);
1570
1571          elsif Is_Entity_Name (P) then
1572             Set_Address_Taken (Entity (P));
1573          end if;
1574
1575          Set_Etype (N, RTE (RE_Address));
1576
1577       ------------------
1578       -- Address_Size --
1579       ------------------
1580
1581       when Attribute_Address_Size =>
1582          Standard_Attribute (System_Address_Size);
1583
1584       --------------
1585       -- Adjacent --
1586       --------------
1587
1588       when Attribute_Adjacent =>
1589          Check_Floating_Point_Type_2;
1590          Set_Etype (N, P_Base_Type);
1591          Resolve (E1, P_Base_Type);
1592          Resolve (E2, P_Base_Type);
1593
1594       ---------
1595       -- Aft --
1596       ---------
1597
1598       when Attribute_Aft =>
1599          Check_Fixed_Point_Type_0;
1600          Set_Etype (N, Universal_Integer);
1601
1602       ---------------
1603       -- Alignment --
1604       ---------------
1605
1606       when Attribute_Alignment =>
1607
1608          --  Don't we need more checking here, cf Size ???
1609
1610          Check_E0;
1611          Check_Not_Incomplete_Type;
1612          Set_Etype (N, Universal_Integer);
1613
1614       ---------------
1615       -- Asm_Input --
1616       ---------------
1617
1618       when Attribute_Asm_Input =>
1619          Check_Asm_Attribute;
1620          Set_Etype (N, RTE (RE_Asm_Input_Operand));
1621
1622       ----------------
1623       -- Asm_Output --
1624       ----------------
1625
1626       when Attribute_Asm_Output =>
1627          Check_Asm_Attribute;
1628
1629          if Etype (E2) = Any_Type then
1630             return;
1631
1632          elsif Aname = Name_Asm_Output then
1633             if not Is_Variable (E2) then
1634                Error_Attr
1635                  ("second argument for Asm_Output is not variable", E2);
1636             end if;
1637          end if;
1638
1639          Note_Possible_Modification (E2);
1640          Set_Etype (N, RTE (RE_Asm_Output_Operand));
1641
1642       ---------------
1643       -- AST_Entry --
1644       ---------------
1645
1646       when Attribute_AST_Entry => AST_Entry : declare
1647          Ent  : Entity_Id;
1648          Pref : Node_Id;
1649          Ptyp : Entity_Id;
1650
1651          Indexed : Boolean;
1652          --  Indicates if entry family index is present. Note the coding
1653          --  here handles the entry family case, but in fact it cannot be
1654          --  executed currently, because pragma AST_Entry does not permit
1655          --  the specification of an entry family.
1656
1657          procedure Bad_AST_Entry;
1658          --  Signal a bad AST_Entry pragma
1659
1660          function OK_Entry (E : Entity_Id) return Boolean;
1661          --  Checks that E is of an appropriate entity kind for an entry
1662          --  (i.e. E_Entry if Index is False, or E_Entry_Family if Index
1663          --  is set True for the entry family case). In the True case,
1664          --  makes sure that Is_AST_Entry is set on the entry.
1665
1666          procedure Bad_AST_Entry is
1667          begin
1668             Error_Attr ("prefix for % attribute must be task entry", P);
1669          end Bad_AST_Entry;
1670
1671          function OK_Entry (E : Entity_Id) return Boolean is
1672             Result : Boolean;
1673
1674          begin
1675             if Indexed then
1676                Result := (Ekind (E) = E_Entry_Family);
1677             else
1678                Result := (Ekind (E) = E_Entry);
1679             end if;
1680
1681             if Result then
1682                if not Is_AST_Entry (E) then
1683                   Error_Msg_Name_2 := Aname;
1684                   Error_Attr
1685                     ("% attribute requires previous % pragma", P);
1686                end if;
1687             end if;
1688
1689             return Result;
1690          end OK_Entry;
1691
1692       --  Start of processing for AST_Entry
1693
1694       begin
1695          Check_VMS (N);
1696          Check_E0;
1697
1698          --  Deal with entry family case
1699
1700          if Nkind (P) = N_Indexed_Component then
1701             Pref := Prefix (P);
1702             Indexed := True;
1703          else
1704             Pref := P;
1705             Indexed := False;
1706          end if;
1707
1708          Ptyp := Etype (Pref);
1709
1710          if Ptyp = Any_Type or else Error_Posted (Pref) then
1711             return;
1712          end if;
1713
1714          --  If the prefix is a selected component whose prefix is of an
1715          --  access type, then introduce an explicit dereference.
1716
1717          if Nkind (Pref) = N_Selected_Component
1718            and then Is_Access_Type (Ptyp)
1719          then
1720             Rewrite (Pref,
1721               Make_Explicit_Dereference (Sloc (Pref),
1722                 Relocate_Node (Pref)));
1723             Analyze_And_Resolve (Pref, Designated_Type (Ptyp));
1724          end if;
1725
1726          --  Prefix can be of the form a.b, where a is a task object
1727          --  and b is one of the entries of the corresponding task type.
1728
1729          if Nkind (Pref) = N_Selected_Component
1730            and then OK_Entry (Entity (Selector_Name (Pref)))
1731            and then Is_Object_Reference (Prefix (Pref))
1732            and then Is_Task_Type (Etype (Prefix (Pref)))
1733          then
1734             null;
1735
1736          --  Otherwise the prefix must be an entry of a containing task,
1737          --  or of a variable of the enclosing task type.
1738
1739          else
1740             if Nkind (Pref) = N_Identifier
1741               or else Nkind (Pref) = N_Expanded_Name
1742             then
1743                Ent := Entity (Pref);
1744
1745                if not OK_Entry (Ent)
1746                  or else not In_Open_Scopes (Scope (Ent))
1747                then
1748                   Bad_AST_Entry;
1749                end if;
1750
1751             else
1752                Bad_AST_Entry;
1753             end if;
1754          end if;
1755
1756          Set_Etype (N, RTE (RE_AST_Handler));
1757       end AST_Entry;
1758
1759       ----------
1760       -- Base --
1761       ----------
1762
1763       when Attribute_Base => Base : declare
1764          Typ : Entity_Id;
1765
1766       begin
1767          Check_Either_E0_Or_E1;
1768          Find_Type (P);
1769          Typ := Entity (P);
1770
1771          if Sloc (Typ) = Standard_Location
1772            and then Base_Type (Typ) = Typ
1773            and then Warn_On_Redundant_Constructs
1774          then
1775             Error_Msg_NE
1776               ("?redudant attribute, & is its own base type", N, Typ);
1777          end if;
1778
1779          Set_Etype (N, Base_Type (Entity (P)));
1780
1781          --  If we have an expression present, then really this is a conversion
1782          --  and the tree must be reformed. Note that this is one of the cases
1783          --  in which we do a replace rather than a rewrite, because the
1784          --  original tree is junk.
1785
1786          if Present (E1) then
1787             Replace (N,
1788               Make_Type_Conversion (Loc,
1789                 Subtype_Mark =>
1790                   Make_Attribute_Reference (Loc,
1791                     Prefix => Prefix (N),
1792                     Attribute_Name => Name_Base),
1793                 Expression => Relocate_Node (E1)));
1794
1795             --  E1 may be overloaded, and its interpretations preserved.
1796
1797             Save_Interps (E1, Expression (N));
1798             Analyze (N);
1799
1800          --  For other cases, set the proper type as the entity of the
1801          --  attribute reference, and then rewrite the node to be an
1802          --  occurrence of the referenced base type. This way, no one
1803          --  else in the compiler has to worry about the base attribute.
1804
1805          else
1806             Set_Entity (N, Base_Type (Entity (P)));
1807             Rewrite (N,
1808               New_Reference_To (Entity (N), Loc));
1809             Analyze (N);
1810          end if;
1811       end Base;
1812
1813       ---------
1814       -- Bit --
1815       ---------
1816
1817       when Attribute_Bit => Bit :
1818       begin
1819          Check_E0;
1820
1821          if not Is_Object_Reference (P) then
1822             Error_Attr ("prefix for % attribute must be object", P);
1823
1824          --  What about the access object cases ???
1825
1826          else
1827             null;
1828          end if;
1829
1830          Set_Etype (N, Universal_Integer);
1831       end Bit;
1832
1833       ---------------
1834       -- Bit_Order --
1835       ---------------
1836
1837       when Attribute_Bit_Order => Bit_Order :
1838       begin
1839          Check_E0;
1840          Check_Type;
1841
1842          if not Is_Record_Type (P_Type) then
1843             Error_Attr ("prefix of % attribute must be record type", P);
1844          end if;
1845
1846          if Bytes_Big_Endian xor Reverse_Bit_Order (P_Type) then
1847             Rewrite (N,
1848               New_Occurrence_Of (RTE (RE_High_Order_First), Loc));
1849          else
1850             Rewrite (N,
1851               New_Occurrence_Of (RTE (RE_Low_Order_First), Loc));
1852          end if;
1853
1854          Set_Etype (N, RTE (RE_Bit_Order));
1855          Resolve (N, Etype (N));
1856
1857          --  Reset incorrect indication of staticness
1858
1859          Set_Is_Static_Expression (N, False);
1860       end Bit_Order;
1861
1862       ------------------
1863       -- Bit_Position --
1864       ------------------
1865
1866       --  Note: in generated code, we can have a Bit_Position attribute
1867       --  applied to a (naked) record component (i.e. the prefix is an
1868       --  identifier that references an E_Component or E_Discriminant
1869       --  entity directly, and this is interpreted as expected by Gigi.
1870       --  The following code will not tolerate such usage, but when the
1871       --  expander creates this special case, it marks it as analyzed
1872       --  immediately and sets an appropriate type.
1873
1874       when Attribute_Bit_Position =>
1875
1876          if Comes_From_Source (N) then
1877             Check_Component;
1878          end if;
1879
1880          Set_Etype (N, Universal_Integer);
1881
1882       ------------------
1883       -- Body_Version --
1884       ------------------
1885
1886       when Attribute_Body_Version =>
1887          Check_E0;
1888          Check_Program_Unit;
1889          Set_Etype (N, RTE (RE_Version_String));
1890
1891       --------------
1892       -- Callable --
1893       --------------
1894
1895       when Attribute_Callable =>
1896          Check_E0;
1897          Set_Etype (N, Standard_Boolean);
1898          Check_Task_Prefix;
1899
1900       ------------
1901       -- Caller --
1902       ------------
1903
1904       when Attribute_Caller => Caller : declare
1905          Ent        : Entity_Id;
1906          S          : Entity_Id;
1907
1908       begin
1909          Check_E0;
1910
1911          if Nkind (P) = N_Identifier
1912            or else Nkind (P) = N_Expanded_Name
1913          then
1914             Ent := Entity (P);
1915
1916             if not Is_Entry (Ent) then
1917                Error_Attr ("invalid entry name", N);
1918             end if;
1919
1920          else
1921             Error_Attr ("invalid entry name", N);
1922             return;
1923          end if;
1924
1925          for J in reverse 0 .. Scope_Stack.Last loop
1926             S := Scope_Stack.Table (J).Entity;
1927
1928             if S = Scope (Ent) then
1929                Error_Attr ("Caller must appear in matching accept or body", N);
1930             elsif S = Ent then
1931                exit;
1932             end if;
1933          end loop;
1934
1935          Set_Etype (N, RTE (RO_AT_Task_ID));
1936       end Caller;
1937
1938       -------------
1939       -- Ceiling --
1940       -------------
1941
1942       when Attribute_Ceiling =>
1943          Check_Floating_Point_Type_1;
1944          Set_Etype (N, P_Base_Type);
1945          Resolve (E1, P_Base_Type);
1946
1947       -----------
1948       -- Class --
1949       -----------
1950
1951       when Attribute_Class => Class : declare
1952       begin
1953          Check_Restriction (No_Dispatch, N);
1954          Check_Either_E0_Or_E1;
1955
1956          --  If we have an expression present, then really this is a conversion
1957          --  and the tree must be reformed into a proper conversion. This is a
1958          --  Replace rather than a Rewrite, because the original tree is junk.
1959          --  If expression is overloaded, propagate interpretations to new one.
1960
1961          if Present (E1) then
1962             Replace (N,
1963               Make_Type_Conversion (Loc,
1964                 Subtype_Mark =>
1965                   Make_Attribute_Reference (Loc,
1966                     Prefix => Prefix (N),
1967                     Attribute_Name => Name_Class),
1968                 Expression => Relocate_Node (E1)));
1969
1970             Save_Interps (E1, Expression (N));
1971             Analyze (N);
1972
1973          --  Otherwise we just need to find the proper type
1974
1975          else
1976             Find_Type (N);
1977          end if;
1978
1979       end Class;
1980
1981       ------------------
1982       -- Code_Address --
1983       ------------------
1984
1985       when Attribute_Code_Address =>
1986          Check_E0;
1987
1988          if Nkind (P) = N_Attribute_Reference
1989            and then (Attribute_Name (P) = Name_Elab_Body
1990                        or else
1991                      Attribute_Name (P) = Name_Elab_Spec)
1992          then
1993             null;
1994
1995          elsif not Is_Entity_Name (P)
1996            or else (Ekind (Entity (P)) /= E_Function
1997                       and then
1998                     Ekind (Entity (P)) /= E_Procedure)
1999          then
2000             Error_Attr ("invalid prefix for % attribute", P);
2001             Set_Address_Taken (Entity (P));
2002          end if;
2003
2004          Set_Etype (N, RTE (RE_Address));
2005
2006       --------------------
2007       -- Component_Size --
2008       --------------------
2009
2010       when Attribute_Component_Size =>
2011          Check_E0;
2012          Set_Etype (N, Universal_Integer);
2013
2014          --  Note: unlike other array attributes, unconstrained arrays are OK
2015
2016          if Is_Array_Type (P_Type) and then not Is_Constrained (P_Type) then
2017             null;
2018          else
2019             Check_Array_Type;
2020          end if;
2021
2022       -------------
2023       -- Compose --
2024       -------------
2025
2026       when Attribute_Compose =>
2027          Check_Floating_Point_Type_2;
2028          Set_Etype (N, P_Base_Type);
2029          Resolve (E1, P_Base_Type);
2030          Resolve (E2, Any_Integer);
2031
2032       -----------------
2033       -- Constrained --
2034       -----------------
2035
2036       when Attribute_Constrained =>
2037          Check_E0;
2038          Set_Etype (N, Standard_Boolean);
2039
2040          --  Case from RM J.4(2) of constrained applied to private type
2041
2042          if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
2043
2044             --  If we are within an instance, the attribute must be legal
2045             --  because it was valid in the generic unit.
2046
2047             if In_Instance then
2048                return;
2049
2050             --  For sure OK if we have a real private type itself, but must
2051             --  be completed, cannot apply Constrained to incomplete type.
2052
2053             elsif Is_Private_Type (Entity (P)) then
2054                Check_Not_Incomplete_Type;
2055                return;
2056             end if;
2057
2058          else
2059             Check_Object_Reference (P);
2060
2061             --  If N does not come from source, then we allow the
2062             --  the attribute prefix to be of a private type whose
2063             --  full type has discriminants. This occurs in cases
2064             --  involving expanded calls to stream attributes.
2065
2066             if not Comes_From_Source (N) then
2067                P_Type := Underlying_Type (P_Type);
2068             end if;
2069
2070             --  Must have discriminants or be an access type designating
2071             --  a type with discriminants. If it is a classwide type is
2072             --  has unknown discriminants.
2073
2074             if Has_Discriminants (P_Type)
2075                or else Has_Unknown_Discriminants (P_Type)
2076                or else
2077                  (Is_Access_Type (P_Type)
2078                    and then Has_Discriminants (Designated_Type (P_Type)))
2079             then
2080                return;
2081
2082             --  Also allow an object of a generic type if extensions allowed
2083             --  and allow this for any type at all.
2084
2085             elsif (Is_Generic_Type (P_Type)
2086                      or else Is_Generic_Actual_Type (P_Type))
2087               and then Extensions_Allowed
2088             then
2089                return;
2090             end if;
2091          end if;
2092
2093          --  Fall through if bad prefix
2094
2095          Error_Attr
2096            ("prefix of % attribute must be object of discriminated type", P);
2097
2098       ---------------
2099       -- Copy_Sign --
2100       ---------------
2101
2102       when Attribute_Copy_Sign =>
2103          Check_Floating_Point_Type_2;
2104          Set_Etype (N, P_Base_Type);
2105          Resolve (E1, P_Base_Type);
2106          Resolve (E2, P_Base_Type);
2107
2108       -----------
2109       -- Count --
2110       -----------
2111
2112       when Attribute_Count => Count :
2113       declare
2114          Ent : Entity_Id;
2115          S   : Entity_Id;
2116          Tsk : Entity_Id;
2117
2118       begin
2119          Check_E0;
2120
2121          if Nkind (P) = N_Identifier
2122            or else Nkind (P) = N_Expanded_Name
2123          then
2124             Ent := Entity (P);
2125
2126             if Ekind (Ent) /= E_Entry then
2127                Error_Attr ("invalid entry name", N);
2128             end if;
2129
2130          elsif Nkind (P) = N_Indexed_Component then
2131             Ent := Entity (Prefix (P));
2132
2133             if Ekind (Ent) /= E_Entry_Family then
2134                Error_Attr ("invalid entry family name", P);
2135                return;
2136             end if;
2137
2138          else
2139             Error_Attr ("invalid entry name", N);
2140             return;
2141          end if;
2142
2143          for J in reverse 0 .. Scope_Stack.Last loop
2144             S := Scope_Stack.Table (J).Entity;
2145
2146             if S = Scope (Ent) then
2147                if Nkind (P) = N_Expanded_Name then
2148                   Tsk := Entity (Prefix (P));
2149
2150                   --  The prefix denotes either the task type, or else a
2151                   --  single task whose task type is being analyzed.
2152
2153                   if (Is_Type (Tsk)
2154                       and then Tsk = S)
2155
2156                     or else (not Is_Type (Tsk)
2157                       and then Etype (Tsk) = S
2158                       and then not (Comes_From_Source (S)))
2159                   then
2160                      null;
2161                   else
2162                      Error_Msg_N
2163                        ("Count must apply to entry of current task", N);
2164                   end if;
2165                end if;
2166
2167                exit;
2168
2169             elsif Ekind (Scope (Ent)) in Task_Kind
2170               and then Ekind (S) /= E_Loop
2171               and then Ekind (S) /= E_Block
2172               and then Ekind (S) /= E_Entry
2173               and then Ekind (S) /= E_Entry_Family
2174             then
2175                Error_Attr ("Count cannot appear in inner unit", N);
2176
2177             elsif Ekind (Scope (Ent)) = E_Protected_Type
2178               and then not Has_Completion (Scope (Ent))
2179             then
2180                Error_Attr ("attribute % can only be used inside body", N);
2181             end if;
2182          end loop;
2183
2184          if Is_Overloaded (P) then
2185             declare
2186                Index : Interp_Index;
2187                It    : Interp;
2188
2189             begin
2190                Get_First_Interp (P, Index, It);
2191
2192                while Present (It.Nam) loop
2193                   if It.Nam = Ent then
2194                      null;
2195
2196                   elsif Scope (It.Nam) = Scope (Ent) then
2197                      Error_Attr ("ambiguous entry name", N);
2198
2199                   else
2200                      --  For now make this into a warning. Will become an
2201                      --  error after the 3.15 release.
2202
2203                      Error_Msg_N
2204                        ("ambiguous name, resolved to entry?", N);
2205                      Error_Msg_N
2206                        ("\(this will become an error in a later release)?", N);
2207                   end if;
2208
2209                   Get_Next_Interp (Index, It);
2210                end loop;
2211             end;
2212          end if;
2213
2214          Set_Etype (N, Universal_Integer);
2215       end Count;
2216
2217       -----------------------
2218       -- Default_Bit_Order --
2219       -----------------------
2220
2221       when Attribute_Default_Bit_Order => Default_Bit_Order :
2222       begin
2223          Check_Standard_Prefix;
2224          Check_E0;
2225
2226          if Bytes_Big_Endian then
2227             Rewrite (N,
2228               Make_Integer_Literal (Loc, False_Value));
2229          else
2230             Rewrite (N,
2231               Make_Integer_Literal (Loc, True_Value));
2232          end if;
2233
2234          Set_Etype (N, Universal_Integer);
2235          Set_Is_Static_Expression (N);
2236       end Default_Bit_Order;
2237
2238       --------------
2239       -- Definite --
2240       --------------
2241
2242       when Attribute_Definite =>
2243          Legal_Formal_Attribute;
2244
2245       -----------
2246       -- Delta --
2247       -----------
2248
2249       when Attribute_Delta =>
2250          Check_Fixed_Point_Type_0;
2251          Set_Etype (N, Universal_Real);
2252
2253       ------------
2254       -- Denorm --
2255       ------------
2256
2257       when Attribute_Denorm =>
2258          Check_Floating_Point_Type_0;
2259          Set_Etype (N, Standard_Boolean);
2260
2261       ------------
2262       -- Digits --
2263       ------------
2264
2265       when Attribute_Digits =>
2266          Check_E0;
2267          Check_Type;
2268
2269          if not Is_Floating_Point_Type (P_Type)
2270            and then not Is_Decimal_Fixed_Point_Type (P_Type)
2271          then
2272             Error_Attr
2273               ("prefix of % attribute must be float or decimal type", P);
2274          end if;
2275
2276          Set_Etype (N, Universal_Integer);
2277
2278       ---------------
2279       -- Elab_Body --
2280       ---------------
2281
2282       --  Also handles processing for Elab_Spec
2283
2284       when Attribute_Elab_Body | Attribute_Elab_Spec =>
2285          Check_E0;
2286          Check_Unit_Name (P);
2287          Set_Etype (N, Standard_Void_Type);
2288
2289          --  We have to manually call the expander in this case to get
2290          --  the necessary expansion (normally attributes that return
2291          --  entities are not expanded).
2292
2293          Expand (N);
2294
2295       ---------------
2296       -- Elab_Spec --
2297       ---------------
2298
2299       --  Shares processing with Elab_Body
2300
2301       ----------------
2302       -- Elaborated --
2303       ----------------
2304
2305       when Attribute_Elaborated =>
2306          Check_E0;
2307          Check_Library_Unit;
2308          Set_Etype (N, Standard_Boolean);
2309
2310       ----------
2311       -- Emax --
2312       ----------
2313
2314       when Attribute_Emax =>
2315          Check_Floating_Point_Type_0;
2316          Set_Etype (N, Universal_Integer);
2317
2318       --------------
2319       -- Enum_Rep --
2320       --------------
2321
2322       when Attribute_Enum_Rep => Enum_Rep : declare
2323       begin
2324          if Present (E1) then
2325             Check_E1;
2326             Check_Discrete_Type;
2327             Resolve (E1, P_Base_Type);
2328
2329          else
2330             if not Is_Entity_Name (P)
2331               or else (not Is_Object (Entity (P))
2332                          and then
2333                        Ekind (Entity (P)) /= E_Enumeration_Literal)
2334             then
2335                Error_Attr
2336                  ("prefix of %attribute must be " &
2337                   "discrete type/object or enum literal", P);
2338             end if;
2339          end if;
2340
2341          Set_Etype (N, Universal_Integer);
2342       end Enum_Rep;
2343
2344       -------------
2345       -- Epsilon --
2346       -------------
2347
2348       when Attribute_Epsilon =>
2349          Check_Floating_Point_Type_0;
2350          Set_Etype (N, Universal_Real);
2351
2352       --------------
2353       -- Exponent --
2354       --------------
2355
2356       when Attribute_Exponent =>
2357          Check_Floating_Point_Type_1;
2358          Set_Etype (N, Universal_Integer);
2359          Resolve (E1, P_Base_Type);
2360
2361       ------------------
2362       -- External_Tag --
2363       ------------------
2364
2365       when Attribute_External_Tag =>
2366          Check_E0;
2367          Check_Type;
2368
2369          Set_Etype (N, Standard_String);
2370
2371          if not Is_Tagged_Type (P_Type) then
2372             Error_Attr ("prefix of % attribute must be tagged", P);
2373          end if;
2374
2375       -----------
2376       -- First --
2377       -----------
2378
2379       when Attribute_First =>
2380          Check_Array_Or_Scalar_Type;
2381
2382       ---------------
2383       -- First_Bit --
2384       ---------------
2385
2386       when Attribute_First_Bit =>
2387          Check_Component;
2388          Set_Etype (N, Universal_Integer);
2389
2390       -----------------
2391       -- Fixed_Value --
2392       -----------------
2393
2394       when Attribute_Fixed_Value =>
2395          Check_E1;
2396          Check_Fixed_Point_Type;
2397          Resolve (E1, Any_Integer);
2398          Set_Etype (N, P_Base_Type);
2399
2400       -----------
2401       -- Floor --
2402       -----------
2403
2404       when Attribute_Floor =>
2405          Check_Floating_Point_Type_1;
2406          Set_Etype (N, P_Base_Type);
2407          Resolve (E1, P_Base_Type);
2408
2409       ----------
2410       -- Fore --
2411       ----------
2412
2413       when Attribute_Fore =>
2414          Check_Fixed_Point_Type_0;
2415          Set_Etype (N, Universal_Integer);
2416
2417       --------------
2418       -- Fraction --
2419       --------------
2420
2421       when Attribute_Fraction =>
2422          Check_Floating_Point_Type_1;
2423          Set_Etype (N, P_Base_Type);
2424          Resolve (E1, P_Base_Type);
2425
2426       -----------------------
2427       -- Has_Discriminants --
2428       -----------------------
2429
2430       when Attribute_Has_Discriminants =>
2431          Legal_Formal_Attribute;
2432
2433       --------------
2434       -- Identity --
2435       --------------
2436
2437       when Attribute_Identity =>
2438          Check_E0;
2439          Analyze (P);
2440
2441          if Etype (P) =  Standard_Exception_Type then
2442             Set_Etype (N, RTE (RE_Exception_Id));
2443
2444          elsif Is_Task_Type (Etype (P))
2445            or else (Is_Access_Type (Etype (P))
2446               and then Is_Task_Type (Designated_Type (Etype (P))))
2447          then
2448             Resolve (P, Etype (P));
2449             Set_Etype (N, RTE (RO_AT_Task_ID));
2450
2451          else
2452             Error_Attr ("prefix of % attribute must be a task or an "
2453               & "exception", P);
2454          end if;
2455
2456       -----------
2457       -- Image --
2458       -----------
2459
2460       when Attribute_Image => Image :
2461       begin
2462          Set_Etype (N, Standard_String);
2463          Check_Scalar_Type;
2464
2465          if Is_Real_Type (P_Type) then
2466             if Ada_83 and then Comes_From_Source (N) then
2467                Error_Msg_Name_1 := Aname;
2468                Error_Msg_N
2469                  ("(Ada 83) % attribute not allowed for real types", N);
2470             end if;
2471          end if;
2472
2473          if Is_Enumeration_Type (P_Type) then
2474             Check_Restriction (No_Enumeration_Maps, N);
2475          end if;
2476
2477          Check_E1;
2478          Resolve (E1, P_Base_Type);
2479          Check_Enum_Image;
2480          Validate_Non_Static_Attribute_Function_Call;
2481       end Image;
2482
2483       ---------
2484       -- Img --
2485       ---------
2486
2487       when Attribute_Img => Img :
2488       begin
2489          Set_Etype (N, Standard_String);
2490
2491          if not Is_Scalar_Type (P_Type)
2492            or else (Is_Entity_Name (P) and then Is_Type (Entity (P)))
2493          then
2494             Error_Attr
2495               ("prefix of % attribute must be scalar object name", N);
2496          end if;
2497
2498          Check_Enum_Image;
2499       end Img;
2500
2501       -----------
2502       -- Input --
2503       -----------
2504
2505       when Attribute_Input =>
2506          Check_E1;
2507          Check_Stream_Attribute (Name_uInput);
2508          Disallow_In_No_Run_Time_Mode (N);
2509          Set_Etype (N, P_Base_Type);
2510
2511       -------------------
2512       -- Integer_Value --
2513       -------------------
2514
2515       when Attribute_Integer_Value =>
2516          Check_E1;
2517          Check_Integer_Type;
2518          Resolve (E1, Any_Fixed);
2519          Set_Etype (N, P_Base_Type);
2520
2521       -----------
2522       -- Large --
2523       -----------
2524
2525       when Attribute_Large =>
2526          Check_E0;
2527          Check_Real_Type;
2528          Set_Etype (N, Universal_Real);
2529
2530       ----------
2531       -- Last --
2532       ----------
2533
2534       when Attribute_Last =>
2535          Check_Array_Or_Scalar_Type;
2536
2537       --------------
2538       -- Last_Bit --
2539       --------------
2540
2541       when Attribute_Last_Bit =>
2542          Check_Component;
2543          Set_Etype (N, Universal_Integer);
2544
2545       ------------------
2546       -- Leading_Part --
2547       ------------------
2548
2549       when Attribute_Leading_Part =>
2550          Check_Floating_Point_Type_2;
2551          Set_Etype (N, P_Base_Type);
2552          Resolve (E1, P_Base_Type);
2553          Resolve (E2, Any_Integer);
2554
2555       ------------
2556       -- Length --
2557       ------------
2558
2559       when Attribute_Length =>
2560          Check_Array_Type;
2561          Set_Etype (N, Universal_Integer);
2562
2563       -------------
2564       -- Machine --
2565       -------------
2566
2567       when Attribute_Machine =>
2568          Check_Floating_Point_Type_1;
2569          Set_Etype (N, P_Base_Type);
2570          Resolve (E1, P_Base_Type);
2571
2572       ------------------
2573       -- Machine_Emax --
2574       ------------------
2575
2576       when Attribute_Machine_Emax =>
2577          Check_Floating_Point_Type_0;
2578          Set_Etype (N, Universal_Integer);
2579
2580       ------------------
2581       -- Machine_Emin --
2582       ------------------
2583
2584       when Attribute_Machine_Emin =>
2585          Check_Floating_Point_Type_0;
2586          Set_Etype (N, Universal_Integer);
2587
2588       ----------------------
2589       -- Machine_Mantissa --
2590       ----------------------
2591
2592       when Attribute_Machine_Mantissa =>
2593          Check_Floating_Point_Type_0;
2594          Set_Etype (N, Universal_Integer);
2595
2596       -----------------------
2597       -- Machine_Overflows --
2598       -----------------------
2599
2600       when Attribute_Machine_Overflows =>
2601          Check_Real_Type;
2602          Check_E0;
2603          Set_Etype (N, Standard_Boolean);
2604
2605       -------------------
2606       -- Machine_Radix --
2607       -------------------
2608
2609       when Attribute_Machine_Radix =>
2610          Check_Real_Type;
2611          Check_E0;
2612          Set_Etype (N, Universal_Integer);
2613
2614       --------------------
2615       -- Machine_Rounds --
2616       --------------------
2617
2618       when Attribute_Machine_Rounds =>
2619          Check_Real_Type;
2620          Check_E0;
2621          Set_Etype (N, Standard_Boolean);
2622
2623       ------------------
2624       -- Machine_Size --
2625       ------------------
2626
2627       when Attribute_Machine_Size =>
2628          Check_E0;
2629          Check_Type;
2630          Check_Not_Incomplete_Type;
2631          Set_Etype (N, Universal_Integer);
2632
2633       --------------
2634       -- Mantissa --
2635       --------------
2636
2637       when Attribute_Mantissa =>
2638          Check_E0;
2639          Check_Real_Type;
2640          Set_Etype (N, Universal_Integer);
2641
2642       ---------
2643       -- Max --
2644       ---------
2645
2646       when Attribute_Max =>
2647          Check_E2;
2648          Check_Scalar_Type;
2649          Resolve (E1, P_Base_Type);
2650          Resolve (E2, P_Base_Type);
2651          Set_Etype (N, P_Base_Type);
2652
2653       ----------------------------
2654       -- Max_Interrupt_Priority --
2655       ----------------------------
2656
2657       when Attribute_Max_Interrupt_Priority =>
2658          Standard_Attribute
2659            (UI_To_Int
2660              (Expr_Value
2661                (Expression
2662                  (Parent (RTE (RE_Max_Interrupt_Priority))))));
2663
2664       ------------------
2665       -- Max_Priority --
2666       ------------------
2667
2668       when Attribute_Max_Priority =>
2669          Standard_Attribute
2670            (UI_To_Int
2671              (Expr_Value
2672                (Expression
2673                  (Parent (RTE (RE_Max_Priority))))));
2674
2675       ----------------------------------
2676       -- Max_Size_In_Storage_Elements --
2677       ----------------------------------
2678
2679       when Attribute_Max_Size_In_Storage_Elements =>
2680          Check_E0;
2681          Check_Type;
2682          Check_Not_Incomplete_Type;
2683          Set_Etype (N, Universal_Integer);
2684
2685       -----------------------
2686       -- Maximum_Alignment --
2687       -----------------------
2688
2689       when Attribute_Maximum_Alignment =>
2690          Standard_Attribute (Ttypes.Maximum_Alignment);
2691
2692       --------------------
2693       -- Mechanism_Code --
2694       --------------------
2695
2696       when Attribute_Mechanism_Code =>
2697
2698          if not Is_Entity_Name (P)
2699            or else not Is_Subprogram (Entity (P))
2700          then
2701             Error_Attr ("prefix of % attribute must be subprogram", P);
2702          end if;
2703
2704          Check_Either_E0_Or_E1;
2705
2706          if Present (E1) then
2707             Resolve (E1, Any_Integer);
2708             Set_Etype (E1, Standard_Integer);
2709
2710             if not Is_Static_Expression (E1) then
2711                Error_Attr
2712                  ("expression for parameter number must be static", E1);
2713
2714             elsif UI_To_Int (Intval (E1)) > Number_Formals (Entity (P))
2715               or else UI_To_Int (Intval (E1)) < 0
2716             then
2717                Error_Attr ("invalid parameter number for %attribute", E1);
2718             end if;
2719          end if;
2720
2721          Set_Etype (N, Universal_Integer);
2722
2723       ---------
2724       -- Min --
2725       ---------
2726
2727       when Attribute_Min =>
2728          Check_E2;
2729          Check_Scalar_Type;
2730          Resolve (E1, P_Base_Type);
2731          Resolve (E2, P_Base_Type);
2732          Set_Etype (N, P_Base_Type);
2733
2734       -----------
2735       -- Model --
2736       -----------
2737
2738       when Attribute_Model =>
2739          Check_Floating_Point_Type_1;
2740          Set_Etype (N, P_Base_Type);
2741          Resolve (E1, P_Base_Type);
2742
2743       ----------------
2744       -- Model_Emin --
2745       ----------------
2746
2747       when Attribute_Model_Emin =>
2748          Check_Floating_Point_Type_0;
2749          Set_Etype (N, Universal_Integer);
2750
2751       -------------------
2752       -- Model_Epsilon --
2753       -------------------
2754
2755       when Attribute_Model_Epsilon =>
2756          Check_Floating_Point_Type_0;
2757          Set_Etype (N, Universal_Real);
2758
2759       --------------------
2760       -- Model_Mantissa --
2761       --------------------
2762
2763       when Attribute_Model_Mantissa =>
2764          Check_Floating_Point_Type_0;
2765          Set_Etype (N, Universal_Integer);
2766
2767       -----------------
2768       -- Model_Small --
2769       -----------------
2770
2771       when Attribute_Model_Small =>
2772          Check_Floating_Point_Type_0;
2773          Set_Etype (N, Universal_Real);
2774
2775       -------------
2776       -- Modulus --
2777       -------------
2778
2779       when Attribute_Modulus =>
2780          Check_E0;
2781          Check_Type;
2782
2783          if not Is_Modular_Integer_Type (P_Type) then
2784             Error_Attr ("prefix of % attribute must be modular type", P);
2785          end if;
2786
2787          Set_Etype (N, Universal_Integer);
2788
2789       --------------------
2790       -- Null_Parameter --
2791       --------------------
2792
2793       when Attribute_Null_Parameter => Null_Parameter : declare
2794          Parnt  : constant Node_Id := Parent (N);
2795          GParnt : constant Node_Id := Parent (Parnt);
2796
2797          procedure Bad_Null_Parameter (Msg : String);
2798          --  Used if bad Null parameter attribute node is found. Issues
2799          --  given error message, and also sets the type to Any_Type to
2800          --  avoid blowups later on from dealing with a junk node.
2801
2802          procedure Must_Be_Imported (Proc_Ent : Entity_Id);
2803          --  Called to check that Proc_Ent is imported subprogram
2804
2805          ------------------------
2806          -- Bad_Null_Parameter --
2807          ------------------------
2808
2809          procedure Bad_Null_Parameter (Msg : String) is
2810          begin
2811             Error_Msg_N (Msg, N);
2812             Set_Etype (N, Any_Type);
2813          end Bad_Null_Parameter;
2814
2815          ----------------------
2816          -- Must_Be_Imported --
2817          ----------------------
2818
2819          procedure Must_Be_Imported (Proc_Ent : Entity_Id) is
2820             Pent : Entity_Id := Proc_Ent;
2821
2822          begin
2823             while Present (Alias (Pent)) loop
2824                Pent := Alias (Pent);
2825             end loop;
2826
2827             --  Ignore check if procedure not frozen yet (we will get
2828             --  another chance when the default parameter is reanalyzed)
2829
2830             if not Is_Frozen (Pent) then
2831                return;
2832
2833             elsif not Is_Imported (Pent) then
2834                Bad_Null_Parameter
2835                  ("Null_Parameter can only be used with imported subprogram");
2836
2837             else
2838                return;
2839             end if;
2840          end Must_Be_Imported;
2841
2842       --  Start of processing for Null_Parameter
2843
2844       begin
2845          Check_Type;
2846          Check_E0;
2847          Set_Etype (N, P_Type);
2848
2849          --  Case of attribute used as default expression
2850
2851          if Nkind (Parnt) = N_Parameter_Specification then
2852             Must_Be_Imported (Defining_Entity (GParnt));
2853
2854          --  Case of attribute used as actual for subprogram (positional)
2855
2856          elsif (Nkind (Parnt) = N_Procedure_Call_Statement
2857                  or else
2858                 Nkind (Parnt) = N_Function_Call)
2859             and then Is_Entity_Name (Name (Parnt))
2860          then
2861             Must_Be_Imported (Entity (Name (Parnt)));
2862
2863          --  Case of attribute used as actual for subprogram (named)
2864
2865          elsif Nkind (Parnt) = N_Parameter_Association
2866            and then (Nkind (GParnt) = N_Procedure_Call_Statement
2867                        or else
2868                      Nkind (GParnt) = N_Function_Call)
2869            and then Is_Entity_Name (Name (GParnt))
2870          then
2871             Must_Be_Imported (Entity (Name (GParnt)));
2872
2873          --  Not an allowed case
2874
2875          else
2876             Bad_Null_Parameter
2877               ("Null_Parameter must be actual or default parameter");
2878          end if;
2879
2880       end Null_Parameter;
2881
2882       -----------------
2883       -- Object_Size --
2884       -----------------
2885
2886       when Attribute_Object_Size =>
2887          Check_E0;
2888          Check_Type;
2889          Check_Not_Incomplete_Type;
2890          Set_Etype (N, Universal_Integer);
2891
2892       ------------
2893       -- Output --
2894       ------------
2895
2896       when Attribute_Output =>
2897          Check_E2;
2898          Check_Stream_Attribute (Name_uInput);
2899          Set_Etype (N, Standard_Void_Type);
2900          Disallow_In_No_Run_Time_Mode (N);
2901          Resolve (N, Standard_Void_Type);
2902
2903       ------------------
2904       -- Partition_ID --
2905       ------------------
2906
2907       when Attribute_Partition_ID =>
2908          Check_E0;
2909
2910          if P_Type /= Any_Type then
2911             if not Is_Library_Level_Entity (Entity (P)) then
2912                Error_Attr
2913                  ("prefix of % attribute must be library-level entity", P);
2914
2915             --  The defining entity of prefix should not be declared inside
2916             --  a Pure unit. RM E.1(8).
2917             --  The Is_Pure flag has been set during declaration.
2918
2919             elsif Is_Entity_Name (P)
2920               and then Is_Pure (Entity (P))
2921             then
2922                Error_Attr
2923                  ("prefix of % attribute must not be declared pure", P);
2924             end if;
2925          end if;
2926
2927          Set_Etype (N, Universal_Integer);
2928
2929       -------------------------
2930       -- Passed_By_Reference --
2931       -------------------------
2932
2933       when Attribute_Passed_By_Reference =>
2934          Check_E0;
2935          Check_Type;
2936          Set_Etype (N, Standard_Boolean);
2937
2938       ---------
2939       -- Pos --
2940       ---------
2941
2942       when Attribute_Pos =>
2943          Check_Discrete_Type;
2944          Check_E1;
2945          Resolve (E1, P_Base_Type);
2946          Set_Etype (N, Universal_Integer);
2947
2948       --------------
2949       -- Position --
2950       --------------
2951
2952       when Attribute_Position =>
2953          Check_Component;
2954          Set_Etype (N, Universal_Integer);
2955
2956       ----------
2957       -- Pred --
2958       ----------
2959
2960       when Attribute_Pred =>
2961          Check_Scalar_Type;
2962          Check_E1;
2963          Resolve (E1, P_Base_Type);
2964          Set_Etype (N, P_Base_Type);
2965
2966          --  Nothing to do for real type case
2967
2968          if Is_Real_Type (P_Type) then
2969             null;
2970
2971          --  If not modular type, test for overflow check required
2972
2973          else
2974             if not Is_Modular_Integer_Type (P_Type)
2975               and then not Range_Checks_Suppressed (P_Base_Type)
2976             then
2977                Enable_Range_Check (E1);
2978             end if;
2979          end if;
2980
2981       -----------
2982       -- Range --
2983       -----------
2984
2985       when Attribute_Range =>
2986          Check_Array_Or_Scalar_Type;
2987
2988          if Ada_83
2989            and then Is_Scalar_Type (P_Type)
2990            and then Comes_From_Source (N)
2991          then
2992             Error_Attr
2993               ("(Ada 83) % attribute not allowed for scalar type", P);
2994          end if;
2995
2996       ------------------
2997       -- Range_Length --
2998       ------------------
2999
3000       when Attribute_Range_Length =>
3001          Check_Discrete_Type;
3002          Set_Etype (N, Universal_Integer);
3003
3004       ----------
3005       -- Read --
3006       ----------
3007
3008       when Attribute_Read =>
3009          Check_E2;
3010          Check_Stream_Attribute (Name_uRead);
3011          Set_Etype (N, Standard_Void_Type);
3012          Resolve (N, Standard_Void_Type);
3013          Disallow_In_No_Run_Time_Mode (N);
3014          Note_Possible_Modification (E2);
3015
3016       ---------------
3017       -- Remainder --
3018       ---------------
3019
3020       when Attribute_Remainder =>
3021          Check_Floating_Point_Type_2;
3022          Set_Etype (N, P_Base_Type);
3023          Resolve (E1, P_Base_Type);
3024          Resolve (E2, P_Base_Type);
3025
3026       -----------
3027       -- Round --
3028       -----------
3029
3030       when Attribute_Round =>
3031          Check_E1;
3032          Check_Decimal_Fixed_Point_Type;
3033          Set_Etype (N, P_Base_Type);
3034
3035          --  Because the context is universal_real (3.5.10(12)) it is a legal
3036          --  context for a universal fixed expression. This is the only
3037          --  attribute whose functional description involves U_R.
3038
3039          if Etype (E1) = Universal_Fixed then
3040             declare
3041                Conv : constant Node_Id := Make_Type_Conversion (Loc,
3042                   Subtype_Mark => New_Occurrence_Of (Universal_Real, Loc),
3043                   Expression   => Relocate_Node (E1));
3044
3045             begin
3046                Rewrite (E1, Conv);
3047                Analyze (E1);
3048             end;
3049          end if;
3050
3051          Resolve (E1, Any_Real);
3052
3053       --------------
3054       -- Rounding --
3055       --------------
3056
3057       when Attribute_Rounding =>
3058          Check_Floating_Point_Type_1;
3059          Set_Etype (N, P_Base_Type);
3060          Resolve (E1, P_Base_Type);
3061
3062       ---------------
3063       -- Safe_Emax --
3064       ---------------
3065
3066       when Attribute_Safe_Emax =>
3067          Check_Floating_Point_Type_0;
3068          Set_Etype (N, Universal_Integer);
3069
3070       ----------------
3071       -- Safe_First --
3072       ----------------
3073
3074       when Attribute_Safe_First =>
3075          Check_Floating_Point_Type_0;
3076          Set_Etype (N, Universal_Real);
3077
3078       ----------------
3079       -- Safe_Large --
3080       ----------------
3081
3082       when Attribute_Safe_Large =>
3083          Check_E0;
3084          Check_Real_Type;
3085          Set_Etype (N, Universal_Real);
3086
3087       ---------------
3088       -- Safe_Last --
3089       ---------------
3090
3091       when Attribute_Safe_Last =>
3092          Check_Floating_Point_Type_0;
3093          Set_Etype (N, Universal_Real);
3094
3095       ----------------
3096       -- Safe_Small --
3097       ----------------
3098
3099       when Attribute_Safe_Small =>
3100          Check_E0;
3101          Check_Real_Type;
3102          Set_Etype (N, Universal_Real);
3103
3104       -----------
3105       -- Scale --
3106       -----------
3107
3108       when Attribute_Scale =>
3109          Check_E0;
3110          Check_Decimal_Fixed_Point_Type;
3111          Set_Etype (N, Universal_Integer);
3112
3113       -------------
3114       -- Scaling --
3115       -------------
3116
3117       when Attribute_Scaling =>
3118          Check_Floating_Point_Type_2;
3119          Set_Etype (N, P_Base_Type);
3120          Resolve (E1, P_Base_Type);
3121
3122       ------------------
3123       -- Signed_Zeros --
3124       ------------------
3125
3126       when Attribute_Signed_Zeros =>
3127          Check_Floating_Point_Type_0;
3128          Set_Etype (N, Standard_Boolean);
3129
3130       ----------
3131       -- Size --
3132       ----------
3133
3134       when Attribute_Size | Attribute_VADS_Size =>
3135          Check_E0;
3136
3137          if Is_Object_Reference (P)
3138            or else (Is_Entity_Name (P)
3139                       and then
3140                     Ekind (Entity (P)) = E_Function)
3141          then
3142             Check_Object_Reference (P);
3143
3144          elsif Nkind (P) = N_Attribute_Reference
3145            or else
3146              (Nkind (P) = N_Selected_Component
3147                and then (Is_Entry (Entity (Selector_Name (P)))
3148                            or else
3149                          Is_Subprogram (Entity (Selector_Name (P)))))
3150            or else
3151              (Is_Entity_Name (P)
3152                and then not Is_Type (Entity (P))
3153                and then not Is_Object (Entity (P)))
3154          then
3155             Error_Attr ("invalid prefix for % attribute", P);
3156          end if;
3157
3158          Check_Not_Incomplete_Type;
3159          Set_Etype (N, Universal_Integer);
3160
3161       -----------
3162       -- Small --
3163       -----------
3164
3165       when Attribute_Small =>
3166          Check_E0;
3167          Check_Real_Type;
3168          Set_Etype (N, Universal_Real);
3169
3170       ------------------
3171       -- Storage_Pool --
3172       ------------------
3173
3174       when Attribute_Storage_Pool =>
3175          if Is_Access_Type (P_Type) then
3176             Check_E0;
3177
3178             --  Set appropriate entity
3179
3180             if Present (Associated_Storage_Pool (Root_Type (P_Type))) then
3181                Set_Entity (N, Associated_Storage_Pool (Root_Type (P_Type)));
3182             else
3183                Set_Entity (N, RTE (RE_Global_Pool_Object));
3184             end if;
3185
3186             Set_Etype (N, Class_Wide_Type (RTE (RE_Root_Storage_Pool)));
3187
3188             --  Validate_Remote_Access_To_Class_Wide_Type for attribute
3189             --  Storage_Pool since this attribute is not defined for such
3190             --  types (RM E.2.3(22)).
3191
3192             Validate_Remote_Access_To_Class_Wide_Type (N);
3193
3194          else
3195             Error_Attr ("prefix of % attribute must be access type", P);
3196          end if;
3197
3198       ------------------
3199       -- Storage_Size --
3200       ------------------
3201
3202       when Attribute_Storage_Size =>
3203
3204          if Is_Task_Type (P_Type) then
3205             Check_E0;
3206             Set_Etype (N, Universal_Integer);
3207
3208          elsif Is_Access_Type (P_Type) then
3209             if Is_Entity_Name (P)
3210               and then Is_Type (Entity (P))
3211             then
3212                Check_E0;
3213                Check_Type;
3214                Set_Etype (N, Universal_Integer);
3215
3216                --   Validate_Remote_Access_To_Class_Wide_Type for attribute
3217                --   Storage_Size since this attribute is not defined for
3218                --   such types (RM E.2.3(22)).
3219
3220                Validate_Remote_Access_To_Class_Wide_Type (N);
3221
3222             --  The prefix is allowed to be an implicit dereference
3223             --  of an access value designating a task.
3224
3225             else
3226                Check_E0;
3227                Check_Task_Prefix;
3228                Set_Etype (N, Universal_Integer);
3229             end if;
3230
3231          else
3232             Error_Attr
3233               ("prefix of % attribute must be access or task type", P);
3234          end if;
3235
3236       ------------------
3237       -- Storage_Unit --
3238       ------------------
3239
3240       when Attribute_Storage_Unit =>
3241          Standard_Attribute (Ttypes.System_Storage_Unit);
3242
3243       ----------
3244       -- Succ --
3245       ----------
3246
3247       when Attribute_Succ =>
3248          Check_Scalar_Type;
3249          Check_E1;
3250          Resolve (E1, P_Base_Type);
3251          Set_Etype (N, P_Base_Type);
3252
3253          --  Nothing to do for real type case
3254
3255          if Is_Real_Type (P_Type) then
3256             null;
3257
3258          --  If not modular type, test for overflow check required.
3259
3260          else
3261             if not Is_Modular_Integer_Type (P_Type)
3262               and then not Range_Checks_Suppressed (P_Base_Type)
3263             then
3264                Enable_Range_Check (E1);
3265             end if;
3266          end if;
3267
3268       ---------
3269       -- Tag --
3270       ---------
3271
3272       when Attribute_Tag =>
3273          Check_E0;
3274          Check_Dereference;
3275
3276          if not Is_Tagged_Type (P_Type) then
3277             Error_Attr ("prefix of % attribute must be tagged", P);
3278
3279          --  Next test does not apply to generated code
3280          --  why not, and what does the illegal reference mean???
3281
3282          elsif Is_Object_Reference (P)
3283            and then not Is_Class_Wide_Type (P_Type)
3284            and then Comes_From_Source (N)
3285          then
3286             Error_Attr
3287               ("% attribute can only be applied to objects of class-wide type",
3288                P);
3289          end if;
3290
3291          Set_Etype (N, RTE (RE_Tag));
3292
3293       ----------------
3294       -- Terminated --
3295       ----------------
3296
3297       when Attribute_Terminated =>
3298          Check_E0;
3299          Set_Etype (N, Standard_Boolean);
3300          Check_Task_Prefix;
3301
3302       ----------
3303       -- Tick --
3304       ----------
3305
3306       when Attribute_Tick =>
3307          Check_Standard_Prefix;
3308          Rewrite (N,
3309            Make_Real_Literal (Loc,
3310              UR_From_Components (
3311                Num   => UI_From_Int (Ttypes.System_Tick_Nanoseconds),
3312                Den   => UI_From_Int (9),
3313                Rbase => 10)));
3314          Analyze (N);
3315
3316       ----------------
3317       -- To_Address --
3318       ----------------
3319
3320       when Attribute_To_Address =>
3321          Check_E1;
3322          Analyze (P);
3323
3324          if Nkind (P) /= N_Identifier
3325            or else Chars (P) /= Name_System
3326          then
3327             Error_Attr ("prefix of %attribute must be System", P);
3328          end if;
3329
3330          Generate_Reference (RTE (RE_Address), P);
3331          Analyze_And_Resolve (E1, Any_Integer);
3332          Set_Etype (N, RTE (RE_Address));
3333
3334       ----------------
3335       -- Truncation --
3336       ----------------
3337
3338       when Attribute_Truncation =>
3339          Check_Floating_Point_Type_1;
3340          Resolve (E1, P_Base_Type);
3341          Set_Etype (N, P_Base_Type);
3342
3343       ----------------
3344       -- Type_Class --
3345       ----------------
3346
3347       when Attribute_Type_Class =>
3348          Check_E0;
3349          Check_Type;
3350          Check_Not_Incomplete_Type;
3351          Set_Etype (N, RTE (RE_Type_Class));
3352
3353       -----------------
3354       -- UET_Address --
3355       -----------------
3356
3357       when Attribute_UET_Address =>
3358          Check_E0;
3359          Check_Unit_Name (P);
3360          Set_Etype (N, RTE (RE_Address));
3361
3362       -----------------------
3363       -- Unbiased_Rounding --
3364       -----------------------
3365
3366       when Attribute_Unbiased_Rounding =>
3367          Check_Floating_Point_Type_1;
3368          Set_Etype (N, P_Base_Type);
3369          Resolve (E1, P_Base_Type);
3370
3371       ----------------------
3372       -- Unchecked_Access --
3373       ----------------------
3374
3375       when Attribute_Unchecked_Access =>
3376          if Comes_From_Source (N) then
3377             Check_Restriction (No_Unchecked_Access, N);
3378          end if;
3379
3380          Access_Attribute;
3381
3382       ------------------------------
3383       -- Universal_Literal_String --
3384       ------------------------------
3385
3386       --  This is a GNAT specific attribute whose prefix must be a named
3387       --  number where the expression is either a single numeric literal,
3388       --  or a numeric literal immediately preceded by a minus sign. The
3389       --  result is equivalent to a string literal containing the text of
3390       --  the literal as it appeared in the source program with a possible
3391       --  leading minus sign.
3392
3393       when Attribute_Universal_Literal_String => Universal_Literal_String :
3394       begin
3395          Check_E0;
3396
3397          if not Is_Entity_Name (P)
3398            or else Ekind (Entity (P)) not in Named_Kind
3399          then
3400             Error_Attr ("prefix for % attribute must be named number", P);
3401
3402          else
3403             declare
3404                Expr     : Node_Id;
3405                Negative : Boolean;
3406                S        : Source_Ptr;
3407                Src      : Source_Buffer_Ptr;
3408
3409             begin
3410                Expr := Original_Node (Expression (Parent (Entity (P))));
3411
3412                if Nkind (Expr) = N_Op_Minus then
3413                   Negative := True;
3414                   Expr := Original_Node (Right_Opnd (Expr));
3415                else
3416                   Negative := False;
3417                end if;
3418
3419                if Nkind (Expr) /= N_Integer_Literal
3420                  and then Nkind (Expr) /= N_Real_Literal
3421                then
3422                   Error_Attr
3423                     ("named number for % attribute must be simple literal", N);
3424                end if;
3425
3426                --  Build string literal corresponding to source literal text
3427
3428                Start_String;
3429
3430                if Negative then
3431                   Store_String_Char (Get_Char_Code ('-'));
3432                end if;
3433
3434                S := Sloc (Expr);
3435                Src := Source_Text (Get_Source_File_Index (S));
3436
3437                while Src (S) /= ';' and then Src (S) /= ' ' loop
3438                   Store_String_Char (Get_Char_Code (Src (S)));
3439                   S := S + 1;
3440                end loop;
3441
3442                --  Now we rewrite the attribute with the string literal
3443
3444                Rewrite (N,
3445                  Make_String_Literal (Loc, End_String));
3446                Analyze (N);
3447             end;
3448          end if;
3449       end Universal_Literal_String;
3450
3451       -------------------------
3452       -- Unrestricted_Access --
3453       -------------------------
3454
3455       --  This is a GNAT specific attribute which is like Access except that
3456       --  all scope checks and checks for aliased views are omitted.
3457
3458       when Attribute_Unrestricted_Access =>
3459          if Comes_From_Source (N) then
3460             Check_Restriction (No_Unchecked_Access, N);
3461          end if;
3462
3463          if Is_Entity_Name (P) then
3464             Set_Address_Taken (Entity (P));
3465          end if;
3466
3467          Access_Attribute;
3468
3469       ---------
3470       -- Val --
3471       ---------
3472
3473       when Attribute_Val => Val : declare
3474       begin
3475          Check_E1;
3476          Check_Discrete_Type;
3477          Resolve (E1, Any_Integer);
3478          Set_Etype (N, P_Base_Type);
3479
3480          --  Note, we need a range check in general, but we wait for the
3481          --  Resolve call to do this, since we want to let Eval_Attribute
3482          --  have a chance to find an static illegality first!
3483       end Val;
3484
3485       -----------
3486       -- Valid --
3487       -----------
3488
3489       when Attribute_Valid =>
3490          Check_E0;
3491
3492          --  Ignore check for object if we have a 'Valid reference generated
3493          --  by the expanded code, since in some cases valid checks can occur
3494          --  on items that are names, but are not objects (e.g. attributes).
3495
3496          if Comes_From_Source (N) then
3497             Check_Object_Reference (P);
3498          end if;
3499
3500          if not Is_Scalar_Type (P_Type) then
3501             Error_Attr ("object for % attribute must be of scalar type", P);
3502          end if;
3503
3504          Set_Etype (N, Standard_Boolean);
3505
3506       -----------
3507       -- Value --
3508       -----------
3509
3510       when Attribute_Value => Value :
3511       begin
3512          Check_E1;
3513          Check_Scalar_Type;
3514
3515          if Is_Enumeration_Type (P_Type) then
3516             Check_Restriction (No_Enumeration_Maps, N);
3517          end if;
3518
3519          --  Set Etype before resolving expression because expansion
3520          --  of expression may require enclosing type.
3521
3522          Set_Etype (N, P_Type);
3523          Validate_Non_Static_Attribute_Function_Call;
3524       end Value;
3525
3526       ----------------
3527       -- Value_Size --
3528       ----------------
3529
3530       when Attribute_Value_Size =>
3531          Check_E0;
3532          Check_Type;
3533          Check_Not_Incomplete_Type;
3534          Set_Etype (N, Universal_Integer);
3535
3536       -------------
3537       -- Version --
3538       -------------
3539
3540       when Attribute_Version =>
3541          Check_E0;
3542          Check_Program_Unit;
3543          Set_Etype (N, RTE (RE_Version_String));
3544
3545       ------------------
3546       -- Wchar_T_Size --
3547       ------------------
3548
3549       when Attribute_Wchar_T_Size =>
3550          Standard_Attribute (Interfaces_Wchar_T_Size);
3551
3552       ----------------
3553       -- Wide_Image --
3554       ----------------
3555
3556       when Attribute_Wide_Image => Wide_Image :
3557       begin
3558          Check_Scalar_Type;
3559          Set_Etype (N, Standard_Wide_String);
3560          Check_E1;
3561          Resolve (E1, P_Base_Type);
3562          Validate_Non_Static_Attribute_Function_Call;
3563       end Wide_Image;
3564
3565       ----------------
3566       -- Wide_Value --
3567       ----------------
3568
3569       when Attribute_Wide_Value => Wide_Value :
3570       begin
3571          Check_E1;
3572          Check_Scalar_Type;
3573
3574          --  Set Etype before resolving expression because expansion
3575          --  of expression may require enclosing type.
3576
3577          Set_Etype (N, P_Type);
3578          Validate_Non_Static_Attribute_Function_Call;
3579       end Wide_Value;
3580
3581       ----------------
3582       -- Wide_Width --
3583       ----------------
3584
3585       when Attribute_Wide_Width =>
3586          Check_E0;
3587          Check_Scalar_Type;
3588          Set_Etype (N, Universal_Integer);
3589
3590       -----------
3591       -- Width --
3592       -----------
3593
3594       when Attribute_Width =>
3595          Check_E0;
3596          Check_Scalar_Type;
3597          Set_Etype (N, Universal_Integer);
3598
3599       ---------------
3600       -- Word_Size --
3601       ---------------
3602
3603       when Attribute_Word_Size =>
3604          Standard_Attribute (System_Word_Size);
3605
3606       -----------
3607       -- Write --
3608       -----------
3609
3610       when Attribute_Write =>
3611          Check_E2;
3612          Check_Stream_Attribute (Name_uWrite);
3613          Set_Etype (N, Standard_Void_Type);
3614          Disallow_In_No_Run_Time_Mode (N);
3615          Resolve (N, Standard_Void_Type);
3616
3617       end case;
3618
3619    --  All errors raise Bad_Attribute, so that we get out before any further
3620    --  damage occurs when an error is detected (for example, if we check for
3621    --  one attribute expression, and the check succeeds, we want to be able
3622    --  to proceed securely assuming that an expression is in fact present.
3623
3624    exception
3625       when Bad_Attribute =>
3626          Set_Etype (N, Any_Type);
3627          return;
3628
3629    end Analyze_Attribute;
3630
3631    --------------------
3632    -- Eval_Attribute --
3633    --------------------
3634
3635    procedure Eval_Attribute (N : Node_Id) is
3636       Loc   : constant Source_Ptr   := Sloc (N);
3637       Aname : constant Name_Id      := Attribute_Name (N);
3638       Id    : constant Attribute_Id := Get_Attribute_Id (Aname);
3639       P     : constant Node_Id      := Prefix (N);
3640
3641       C_Type : constant Entity_Id := Etype (N);
3642       --  The type imposed by the context.
3643
3644       E1 : Node_Id;
3645       --  First expression, or Empty if none
3646
3647       E2 : Node_Id;
3648       --  Second expression, or Empty if none
3649
3650       P_Entity : Entity_Id;
3651       --  Entity denoted by prefix
3652
3653       P_Type : Entity_Id;
3654       --  The type of the prefix
3655
3656       P_Base_Type : Entity_Id;
3657       --  The base type of the prefix type
3658
3659       P_Root_Type : Entity_Id;
3660       --  The root type of the prefix type
3661
3662       Static : Boolean;
3663       --  True if prefix type is static
3664
3665       Lo_Bound, Hi_Bound : Node_Id;
3666       --  Expressions for low and high bounds of type or array index referenced
3667       --  by First, Last, or Length attribute for array, set by Set_Bounds.
3668
3669       CE_Node : Node_Id;
3670       --  Constraint error node used if we have an attribute reference has
3671       --  an argument that raises a constraint error. In this case we replace
3672       --  the attribute with a raise constraint_error node. This is important
3673       --  processing, since otherwise gigi might see an attribute which it is
3674       --  unprepared to deal with.
3675
3676       function Aft_Value return Nat;
3677       --  Computes Aft value for current attribute prefix (used by Aft itself
3678       --  and also by Width for computing the Width of a fixed point type).
3679
3680       procedure Check_Expressions;
3681       --  In case where the attribute is not foldable, the expressions, if
3682       --  any, of the attribute, are in a non-static context. This procedure
3683       --  performs the required additional checks.
3684
3685       procedure Float_Attribute_Universal_Integer
3686         (IEEES_Val : Int;
3687          IEEEL_Val : Int;
3688          IEEEX_Val : Int;
3689          VAXFF_Val : Int;
3690          VAXDF_Val : Int;
3691          VAXGF_Val : Int);
3692       --  This procedure evaluates a float attribute with no arguments that
3693       --  returns a universal integer result. The parameters give the values
3694       --  for the possible floating-point root types. See ttypef for details.
3695       --  The prefix type is a float type (and is thus not a generic type).
3696
3697       procedure Float_Attribute_Universal_Real
3698         (IEEES_Val : String;
3699          IEEEL_Val : String;
3700          IEEEX_Val : String;
3701          VAXFF_Val : String;
3702          VAXDF_Val : String;
3703          VAXGF_Val : String);
3704       --  This procedure evaluates a float attribute with no arguments that
3705       --  returns a universal real result. The parameters give the values
3706       --  required for the possible floating-point root types in string
3707       --  format as real literals with a possible leading minus sign.
3708       --  The prefix type is a float type (and is thus not a generic type).
3709
3710       function Fore_Value return Nat;
3711       --  Computes the Fore value for the current attribute prefix, which is
3712       --  known to be a static fixed-point type. Used by Fore and Width.
3713
3714       function Mantissa return Uint;
3715       --  Returns the Mantissa value for the prefix type
3716
3717       procedure Set_Bounds;
3718       --  Used for First, Last and Length attributes applied to an array or
3719       --  array subtype. Sets the variables Index_Lo and Index_Hi to the low
3720       --  and high bound expressions for the index referenced by the attribute
3721       --  designator (i.e. the first index if no expression is present, and
3722       --  the N'th index if the value N is present as an expression).
3723
3724       ---------------
3725       -- Aft_Value --
3726       ---------------
3727
3728       function Aft_Value return Nat is
3729          Result    : Nat;
3730          Delta_Val : Ureal;
3731
3732       begin
3733          Result := 1;
3734          Delta_Val := Delta_Value (P_Type);
3735
3736          while Delta_Val < Ureal_Tenth loop
3737             Delta_Val := Delta_Val * Ureal_10;
3738             Result := Result + 1;
3739          end loop;
3740
3741          return Result;
3742       end Aft_Value;
3743
3744       -----------------------
3745       -- Check_Expressions --
3746       -----------------------
3747
3748       procedure Check_Expressions is
3749          E : Node_Id := E1;
3750
3751       begin
3752          while Present (E) loop
3753             Check_Non_Static_Context (E);
3754             Next (E);
3755          end loop;
3756       end Check_Expressions;
3757
3758       ---------------------------------------
3759       -- Float_Attribute_Universal_Integer --
3760       ---------------------------------------
3761
3762       procedure Float_Attribute_Universal_Integer
3763         (IEEES_Val : Int;
3764          IEEEL_Val : Int;
3765          IEEEX_Val : Int;
3766          VAXFF_Val : Int;
3767          VAXDF_Val : Int;
3768          VAXGF_Val : Int)
3769       is
3770          Val  : Int;
3771          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
3772
3773       begin
3774          if not Vax_Float (P_Base_Type) then
3775             if Digs = IEEES_Digits then
3776                Val := IEEES_Val;
3777             elsif Digs = IEEEL_Digits then
3778                Val := IEEEL_Val;
3779             else pragma Assert (Digs = IEEEX_Digits);
3780                Val := IEEEX_Val;
3781             end if;
3782
3783          else
3784             if Digs = VAXFF_Digits then
3785                Val := VAXFF_Val;
3786             elsif Digs = VAXDF_Digits then
3787                Val := VAXDF_Val;
3788             else pragma Assert (Digs = VAXGF_Digits);
3789                Val := VAXGF_Val;
3790             end if;
3791          end if;
3792
3793          Fold_Uint (N, UI_From_Int (Val));
3794       end Float_Attribute_Universal_Integer;
3795
3796       ------------------------------------
3797       -- Float_Attribute_Universal_Real --
3798       ------------------------------------
3799
3800       procedure Float_Attribute_Universal_Real
3801         (IEEES_Val : String;
3802          IEEEL_Val : String;
3803          IEEEX_Val : String;
3804          VAXFF_Val : String;
3805          VAXDF_Val : String;
3806          VAXGF_Val : String)
3807       is
3808          Val  : Node_Id;
3809          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
3810
3811       begin
3812          if not Vax_Float (P_Base_Type) then
3813             if Digs = IEEES_Digits then
3814                Val := Real_Convert (IEEES_Val);
3815             elsif Digs = IEEEL_Digits then
3816                Val := Real_Convert (IEEEL_Val);
3817             else pragma Assert (Digs = IEEEX_Digits);
3818                Val := Real_Convert (IEEEX_Val);
3819             end if;
3820
3821          else
3822             if Digs = VAXFF_Digits then
3823                Val := Real_Convert (VAXFF_Val);
3824             elsif Digs = VAXDF_Digits then
3825                Val := Real_Convert (VAXDF_Val);
3826             else pragma Assert (Digs = VAXGF_Digits);
3827                Val := Real_Convert (VAXGF_Val);
3828             end if;
3829          end if;
3830
3831          Set_Sloc (Val, Loc);
3832          Rewrite (N, Val);
3833          Analyze_And_Resolve (N, C_Type);
3834       end Float_Attribute_Universal_Real;
3835
3836       ----------------
3837       -- Fore_Value --
3838       ----------------
3839
3840       --  Note that the Fore calculation is based on the actual values
3841       --  of the bounds, and does not take into account possible rounding.
3842
3843       function Fore_Value return Nat is
3844          Lo      : constant Uint  := Expr_Value (Type_Low_Bound (P_Type));
3845          Hi      : constant Uint  := Expr_Value (Type_High_Bound (P_Type));
3846          Small   : constant Ureal := Small_Value (P_Type);
3847          Lo_Real : constant Ureal := Lo * Small;
3848          Hi_Real : constant Ureal := Hi * Small;
3849          T       : Ureal;
3850          R       : Nat;
3851
3852       begin
3853          --  Bounds are given in terms of small units, so first compute
3854          --  proper values as reals.
3855
3856          T := UR_Max (abs Lo_Real, abs Hi_Real);
3857          R := 2;
3858
3859          --  Loop to compute proper value if more than one digit required
3860
3861          while T >= Ureal_10 loop
3862             R := R + 1;
3863             T := T / Ureal_10;
3864          end loop;
3865
3866          return R;
3867       end Fore_Value;
3868
3869       --------------
3870       -- Mantissa --
3871       --------------
3872
3873       --  Table of mantissa values accessed by function  Computed using
3874       --  the relation:
3875
3876       --    T'Mantissa = integer next above (D * log(10)/log(2)) + 1)
3877
3878       --  where D is T'Digits (RM83 3.5.7)
3879
3880       Mantissa_Value : constant array (Nat range 1 .. 40) of Nat := (
3881           1 =>   5,
3882           2 =>   8,
3883           3 =>  11,
3884           4 =>  15,
3885           5 =>  18,
3886           6 =>  21,
3887           7 =>  25,
3888           8 =>  28,
3889           9 =>  31,
3890          10 =>  35,
3891          11 =>  38,
3892          12 =>  41,
3893          13 =>  45,
3894          14 =>  48,
3895          15 =>  51,
3896          16 =>  55,
3897          17 =>  58,
3898          18 =>  61,
3899          19 =>  65,
3900          20 =>  68,
3901          21 =>  71,
3902          22 =>  75,
3903          23 =>  78,
3904          24 =>  81,
3905          25 =>  85,
3906          26 =>  88,
3907          27 =>  91,
3908          28 =>  95,
3909          29 =>  98,
3910          30 => 101,
3911          31 => 104,
3912          32 => 108,
3913          33 => 111,
3914          34 => 114,
3915          35 => 118,
3916          36 => 121,
3917          37 => 124,
3918          38 => 128,
3919          39 => 131,
3920          40 => 134);
3921
3922       function Mantissa return Uint is
3923       begin
3924          return
3925            UI_From_Int (Mantissa_Value (UI_To_Int (Digits_Value (P_Type))));
3926       end Mantissa;
3927
3928       ----------------
3929       -- Set_Bounds --
3930       ----------------
3931
3932       procedure Set_Bounds is
3933          Ndim : Nat;
3934          Indx : Node_Id;
3935          Ityp : Entity_Id;
3936
3937       begin
3938          --  For a string literal subtype, we have to construct the bounds.
3939          --  Valid Ada code never applies attributes to string literals, but
3940          --  it is convenient to allow the expander to generate attribute
3941          --  references of this type (e.g. First and Last applied to a string
3942          --  literal).
3943
3944          --  Note that the whole point of the E_String_Literal_Subtype is to
3945          --  avoid this construction of bounds, but the cases in which we
3946          --  have to materialize them are rare enough that we don't worry!
3947
3948          --  The low bound is simply the low bound of the base type. The
3949          --  high bound is computed from the length of the string and this
3950          --  low bound.
3951
3952          if Ekind (P_Type) = E_String_Literal_Subtype then
3953             Lo_Bound :=
3954               Type_Low_Bound (Etype (First_Index (Base_Type (P_Type))));
3955
3956             Hi_Bound :=
3957               Make_Integer_Literal (Sloc (P),
3958                 Intval =>
3959                   Expr_Value (Lo_Bound) + String_Literal_Length (P_Type) - 1);
3960
3961             Set_Parent (Hi_Bound, P);
3962             Analyze_And_Resolve (Hi_Bound, Etype (Lo_Bound));
3963             return;
3964
3965          --  For non-array case, just get bounds of scalar type
3966
3967          elsif Is_Scalar_Type (P_Type) then
3968             Ityp := P_Type;
3969
3970          --  For array case, get type of proper index
3971
3972          else
3973             if No (E1) then
3974                Ndim := 1;
3975             else
3976                Ndim := UI_To_Int (Expr_Value (E1));
3977             end if;
3978
3979             Indx := First_Index (P_Type);
3980             for J in 1 .. Ndim - 1 loop
3981                Next_Index (Indx);
3982             end loop;
3983
3984             --  If no index type, get out (some other error occurred, and
3985             --  we don't have enough information to complete the job!)
3986
3987             if No (Indx) then
3988                Lo_Bound := Error;
3989                Hi_Bound := Error;
3990                return;
3991             end if;
3992
3993             Ityp := Etype (Indx);
3994          end if;
3995
3996          --  A discrete range in an index constraint is allowed to be a
3997          --  subtype indication. This is syntactically a pain, but should
3998          --  not propagate to the entity for the corresponding index subtype.
3999          --  After checking that the subtype indication is legal, the range
4000          --  of the subtype indication should be transfered to the entity.
4001          --  The attributes for the bounds should remain the simple retrievals
4002          --  that they are now.
4003
4004          Lo_Bound := Type_Low_Bound (Ityp);
4005          Hi_Bound := Type_High_Bound (Ityp);
4006
4007       end Set_Bounds;
4008
4009    --  Start of processing for Eval_Attribute
4010
4011    begin
4012       --  Acquire first two expressions (at the moment, no attributes
4013       --  take more than two expressions in any case).
4014
4015       if Present (Expressions (N)) then
4016          E1 := First (Expressions (N));
4017          E2 := Next (E1);
4018       else
4019          E1 := Empty;
4020          E2 := Empty;
4021       end if;
4022
4023       --  Special processing for cases where the prefix is an object
4024
4025       if Is_Object_Reference (P) then
4026
4027          --  For Component_Size, the prefix is an array object, and we apply
4028          --  the attribute to the type of the object. This is allowed for
4029          --  both unconstrained and constrained arrays, since the bounds
4030          --  have no influence on the value of this attribute.
4031
4032          if Id = Attribute_Component_Size then
4033             P_Entity := Etype (P);
4034
4035          --  For First and Last, the prefix is an array object, and we apply
4036          --  the attribute to the type of the array, but we need a constrained
4037          --  type for this, so we use the actual subtype if available.
4038
4039          elsif Id = Attribute_First
4040                  or else
4041                Id = Attribute_Last
4042                  or else
4043                Id = Attribute_Length
4044          then
4045             declare
4046                AS : constant Entity_Id := Get_Actual_Subtype_If_Available (P);
4047
4048             begin
4049                if Present (AS) then
4050                   P_Entity := AS;
4051
4052                --  If no actual subtype, cannot fold
4053
4054                else
4055                   Check_Expressions;
4056                   return;
4057                end if;
4058             end;
4059
4060          --  For Size, give size of object if available, otherwise we
4061          --  cannot fold Size.
4062
4063          elsif Id = Attribute_Size then
4064
4065             if Is_Entity_Name (P)
4066               and then Known_Esize (Entity (P))
4067             then
4068                Fold_Uint (N, Esize (Entity (P)));
4069                Set_Is_Static_Expression (N, False);
4070                return;
4071
4072             else
4073                Check_Expressions;
4074                return;
4075             end if;
4076
4077          --  For Alignment, give size of object if available, otherwise we
4078          --  cannot fold Alignment.
4079
4080          elsif Id = Attribute_Alignment then
4081
4082             if Is_Entity_Name (P)
4083               and then Known_Alignment (Entity (P))
4084             then
4085                Fold_Uint (N, Alignment (Entity (P)));
4086                Set_Is_Static_Expression (N, False);
4087                return;
4088
4089             else
4090                Check_Expressions;
4091                return;
4092             end if;
4093
4094          --  No other attributes for objects are folded
4095
4096          else
4097             Check_Expressions;
4098             return;
4099          end if;
4100
4101       --  Cases where P is not an object. Cannot do anything if P is
4102       --  not the name of an entity.
4103
4104       elsif not Is_Entity_Name (P) then
4105          Check_Expressions;
4106          return;
4107
4108       --  Otherwise get prefix entity
4109
4110       else
4111          P_Entity := Entity (P);
4112       end if;
4113
4114       --  At this stage P_Entity is the entity to which the attribute
4115       --  is to be applied. This is usually simply the entity of the
4116       --  prefix, except in some cases of attributes for objects, where
4117       --  as described above, we apply the attribute to the object type.
4118
4119       --  First foldable possibility is a scalar or array type (RM 4.9(7))
4120       --  that is not generic (generic types are eliminated by RM 4.9(25)).
4121       --  Note we allow non-static non-generic types at this stage as further
4122       --  described below.
4123
4124       if Is_Type (P_Entity)
4125         and then (Is_Scalar_Type (P_Entity) or Is_Array_Type (P_Entity))
4126         and then (not Is_Generic_Type (P_Entity))
4127       then
4128          P_Type := P_Entity;
4129
4130       --  Second foldable possibility is an array object (RM 4.9(8))
4131
4132       elsif (Ekind (P_Entity) = E_Variable
4133                or else
4134              Ekind (P_Entity) = E_Constant)
4135         and then Is_Array_Type (Etype (P_Entity))
4136         and then (not Is_Generic_Type (Etype (P_Entity)))
4137       then
4138          P_Type := Etype (P_Entity);
4139
4140          --  If the entity is an array constant with an unconstrained
4141          --  nominal subtype then get the type from the initial value.
4142          --  If the value has been expanded into assignments, the expression
4143          --  is not present and the attribute reference remains dynamic.
4144          --  We could do better here and retrieve the type ???
4145
4146          if Ekind (P_Entity) = E_Constant
4147            and then not Is_Constrained (P_Type)
4148          then
4149             if No (Constant_Value (P_Entity)) then
4150                return;
4151             else
4152                P_Type := Etype (Constant_Value (P_Entity));
4153             end if;
4154          end if;
4155
4156       --  Definite must be folded if the prefix is not a generic type,
4157       --  that is to say if we are within an instantiation. Same processing
4158       --  applies to the GNAT attributes Has_Discriminants and Type_Class
4159
4160       elsif (Id = Attribute_Definite
4161                or else
4162              Id = Attribute_Has_Discriminants
4163                or else
4164              Id = Attribute_Type_Class)
4165         and then not Is_Generic_Type (P_Entity)
4166       then
4167          P_Type := P_Entity;
4168
4169       --  We can fold 'Size applied to a type if the size is known
4170       --  (as happens for a size from an attribute definition clause).
4171       --  At this stage, this can happen only for types (e.g. record
4172       --  types) for which the size is always non-static. We exclude
4173       --  generic types from consideration (since they have bogus
4174       --  sizes set within templates).
4175
4176       elsif Id = Attribute_Size
4177         and then Is_Type (P_Entity)
4178         and then (not Is_Generic_Type (P_Entity))
4179         and then Known_Static_RM_Size (P_Entity)
4180       then
4181          Fold_Uint (N, RM_Size (P_Entity));
4182          Set_Is_Static_Expression (N, False);
4183          return;
4184
4185       --  No other cases are foldable (they certainly aren't static, and at
4186       --  the moment we don't try to fold any cases other than the two above)
4187
4188       else
4189          Check_Expressions;
4190          return;
4191       end if;
4192
4193       --  If either attribute or the prefix is Any_Type, then propagate
4194       --  Any_Type to the result and don't do anything else at all.
4195
4196       if P_Type = Any_Type
4197         or else (Present (E1) and then Etype (E1) = Any_Type)
4198         or else (Present (E2) and then Etype (E2) = Any_Type)
4199       then
4200          Set_Etype (N, Any_Type);
4201          return;
4202       end if;
4203
4204       --  Scalar subtype case. We have not yet enforced the static requirement
4205       --  of (RM 4.9(7)) and we don't intend to just yet, since there are cases
4206       --  of non-static attribute references (e.g. S'Digits for a non-static
4207       --  floating-point type, which we can compute at compile time).
4208
4209       --  Note: this folding of non-static attributes is not simply a case of
4210       --  optimization. For many of the attributes affected, Gigi cannot handle
4211       --  the attribute and depends on the front end having folded them away.
4212
4213       --  Note: although we don't require staticness at this stage, we do set
4214       --  the Static variable to record the staticness, for easy reference by
4215       --  those attributes where it matters (e.g. Succ and Pred), and also to
4216       --  be used to ensure that non-static folded things are not marked as
4217       --  being static (a check that is done right at the end).
4218
4219       P_Root_Type := Root_Type (P_Type);
4220       P_Base_Type := Base_Type (P_Type);
4221
4222       --  If the root type or base type is generic, then we cannot fold. This
4223       --  test is needed because subtypes of generic types are not always
4224       --  marked as being generic themselves (which seems odd???)
4225
4226       if Is_Generic_Type (P_Root_Type)
4227         or else Is_Generic_Type (P_Base_Type)
4228       then
4229          return;
4230       end if;
4231
4232       if Is_Scalar_Type (P_Type) then
4233          Static := Is_OK_Static_Subtype (P_Type);
4234
4235       --  Array case. We enforce the constrained requirement of (RM 4.9(7-8))
4236       --  since we can't do anything with unconstrained arrays. In addition,
4237       --  only the First, Last and Length attributes are possibly static.
4238       --  In addition Component_Size is possibly foldable, even though it
4239       --  can never be static.
4240
4241       --  Definite, Has_Discriminants and Type_Class are again exceptions,
4242       --  because they apply as well to unconstrained types.
4243
4244       elsif Id = Attribute_Definite
4245               or else
4246             Id = Attribute_Has_Discriminants
4247               or else
4248             Id = Attribute_Type_Class
4249       then
4250          Static := False;
4251
4252       else
4253          if not Is_Constrained (P_Type)
4254            or else (Id /= Attribute_Component_Size and then
4255                     Id /= Attribute_First          and then
4256                     Id /= Attribute_Last           and then
4257                     Id /= Attribute_Length)
4258          then
4259             Check_Expressions;
4260             return;
4261          end if;
4262
4263          --  The rules in (RM 4.9(7,8)) require a static array, but as in the
4264          --  scalar case, we hold off on enforcing staticness, since there are
4265          --  cases which we can fold at compile time even though they are not
4266          --  static (e.g. 'Length applied to a static index, even though other
4267          --  non-static indexes make the array type non-static). This is only
4268          --  ab optimization, but it falls out essentially free, so why not.
4269          --  Again we compute the variable Static for easy reference later
4270          --  (note that no array attributes are static in Ada 83).
4271
4272          Static := Ada_95;
4273
4274          declare
4275             N : Node_Id;
4276
4277          begin
4278             N := First_Index (P_Type);
4279             while Present (N) loop
4280                Static := Static and Is_Static_Subtype (Etype (N));
4281                Next_Index (N);
4282             end loop;
4283          end;
4284       end if;
4285
4286       --  Check any expressions that are present. Note that these expressions,
4287       --  depending on the particular attribute type, are either part of the
4288       --  attribute designator, or they are arguments in a case where the
4289       --  attribute reference returns a function. In the latter case, the
4290       --  rule in (RM 4.9(22)) applies and in particular requires the type
4291       --  of the expressions to be scalar in order for the attribute to be
4292       --  considered to be static.
4293
4294       declare
4295          E : Node_Id;
4296
4297       begin
4298          E := E1;
4299          while Present (E) loop
4300
4301             --  If expression is not static, then the attribute reference
4302             --  certainly is neither foldable nor static, so we can quit
4303             --  after calling Apply_Range_Check for 'Pos attributes.
4304
4305             --  We can also quit if the expression is not of a scalar type
4306             --  as noted above.
4307
4308             if not Is_Static_Expression (E)
4309               or else not Is_Scalar_Type (Etype (E))
4310             then
4311                if Id = Attribute_Pos then
4312                   if Is_Integer_Type (Etype (E)) then
4313                      Apply_Range_Check (E, Etype (N));
4314                   end if;
4315                end if;
4316
4317                Check_Expressions;
4318                return;
4319
4320             --  If the expression raises a constraint error, then so does
4321             --  the attribute reference. We keep going in this case because
4322             --  we are still interested in whether the attribute reference
4323             --  is static even if it is not static.
4324
4325             elsif Raises_Constraint_Error (E) then
4326                Set_Raises_Constraint_Error (N);
4327             end if;
4328
4329             Next (E);
4330          end loop;
4331
4332          if Raises_Constraint_Error (Prefix (N)) then
4333             return;
4334          end if;
4335       end;
4336
4337       --  Deal with the case of a static attribute reference that raises
4338       --  constraint error. The Raises_Constraint_Error flag will already
4339       --  have been set, and the Static flag shows whether the attribute
4340       --  reference is static. In any case we certainly can't fold such an
4341       --  attribute reference.
4342
4343       --  Note that the rewriting of the attribute node with the constraint
4344       --  error node is essential in this case, because otherwise Gigi might
4345       --  blow up on one of the attributes it never expects to see.
4346
4347       --  The constraint_error node must have the type imposed by the context,
4348       --  to avoid spurious errors in the enclosing expression.
4349
4350       if Raises_Constraint_Error (N) then
4351          CE_Node :=
4352            Make_Raise_Constraint_Error (Sloc (N));
4353          Set_Etype (CE_Node, Etype (N));
4354          Set_Raises_Constraint_Error (CE_Node);
4355          Check_Expressions;
4356          Rewrite (N, Relocate_Node (CE_Node));
4357          Set_Is_Static_Expression (N, Static);
4358          return;
4359       end if;
4360
4361       --  At this point we have a potentially foldable attribute reference.
4362       --  If Static is set, then the attribute reference definitely obeys
4363       --  the requirements in (RM 4.9(7,8,22)), and it definitely can be
4364       --  folded. If Static is not set, then the attribute may or may not
4365       --  be foldable, and the individual attribute processing routines
4366       --  test Static as required in cases where it makes a difference.
4367
4368       case Id is
4369
4370       --------------
4371       -- Adjacent --
4372       --------------
4373
4374       when Attribute_Adjacent =>
4375          if Static then
4376             Fold_Ureal (N,
4377               Eval_Fat.Adjacent
4378                 (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)));
4379          end if;
4380
4381       ---------
4382       -- Aft --
4383       ---------
4384
4385       when Attribute_Aft =>
4386          Fold_Uint (N, UI_From_Int (Aft_Value));
4387
4388       ---------------
4389       -- Alignment --
4390       ---------------
4391
4392       when Attribute_Alignment => Alignment_Block : declare
4393          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
4394
4395       begin
4396          --  Fold if alignment is set and not otherwise
4397
4398          if Known_Alignment (P_TypeA) then
4399             Fold_Uint (N, Alignment (P_TypeA));
4400          end if;
4401       end Alignment_Block;
4402
4403       ---------------
4404       -- AST_Entry --
4405       ---------------
4406
4407       --  Can only be folded in No_Ast_Handler case
4408
4409       when Attribute_AST_Entry =>
4410          if not Is_AST_Entry (P_Entity) then
4411             Rewrite (N,
4412               New_Occurrence_Of (RTE (RE_No_AST_Handler), Loc));
4413          else
4414             null;
4415          end if;
4416
4417       ---------
4418       -- Bit --
4419       ---------
4420
4421       --  Bit can never be folded
4422
4423       when Attribute_Bit =>
4424          null;
4425
4426       ------------------
4427       -- Body_Version --
4428       ------------------
4429
4430       --  Body_version can never be static
4431
4432       when Attribute_Body_Version =>
4433          null;
4434
4435       -------------
4436       -- Ceiling --
4437       -------------
4438
4439       when Attribute_Ceiling =>
4440          if Static then
4441             Fold_Ureal (N,
4442               Eval_Fat.Ceiling (P_Root_Type, Expr_Value_R (E1)));
4443          end if;
4444
4445       --------------------
4446       -- Component_Size --
4447       --------------------
4448
4449       when Attribute_Component_Size =>
4450          if Component_Size (P_Type) /= 0 then
4451             Fold_Uint (N, Component_Size (P_Type));
4452          end if;
4453
4454       -------------
4455       -- Compose --
4456       -------------
4457
4458       when Attribute_Compose =>
4459          if Static then
4460             Fold_Ureal (N,
4461               Eval_Fat.Compose
4462                 (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)));
4463          end if;
4464
4465       -----------------
4466       -- Constrained --
4467       -----------------
4468
4469       --  Constrained is never folded for now, there may be cases that
4470       --  could be handled at compile time. to be looked at later.
4471
4472       when Attribute_Constrained =>
4473          null;
4474
4475       ---------------
4476       -- Copy_Sign --
4477       ---------------
4478
4479       when Attribute_Copy_Sign =>
4480          if Static then
4481             Fold_Ureal (N,
4482               Eval_Fat.Copy_Sign
4483                 (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)));
4484          end if;
4485
4486       -----------
4487       -- Delta --
4488       -----------
4489
4490       when Attribute_Delta =>
4491          Fold_Ureal (N, Delta_Value (P_Type));
4492
4493       --------------
4494       -- Definite --
4495       --------------
4496
4497       when Attribute_Definite =>
4498          declare
4499             Result : Node_Id;
4500
4501          begin
4502             if Is_Indefinite_Subtype (P_Entity) then
4503                Result := New_Occurrence_Of (Standard_False, Loc);
4504             else
4505                Result := New_Occurrence_Of (Standard_True, Loc);
4506             end if;
4507
4508             Rewrite (N, Result);
4509             Analyze_And_Resolve (N, Standard_Boolean);
4510          end;
4511
4512       ------------
4513       -- Denorm --
4514       ------------
4515
4516       when Attribute_Denorm =>
4517          Fold_Uint
4518            (N, UI_From_Int (Boolean'Pos (Denorm_On_Target)));
4519
4520       ------------
4521       -- Digits --
4522       ------------
4523
4524       when Attribute_Digits =>
4525          Fold_Uint (N, Digits_Value (P_Type));
4526
4527       ----------
4528       -- Emax --
4529       ----------
4530
4531       when Attribute_Emax =>
4532
4533          --  Ada 83 attribute is defined as (RM83 3.5.8)
4534
4535          --    T'Emax = 4 * T'Mantissa
4536
4537          Fold_Uint (N, 4 * Mantissa);
4538
4539       --------------
4540       -- Enum_Rep --
4541       --------------
4542
4543       when Attribute_Enum_Rep =>
4544          if Static then
4545
4546             --  For an enumeration type with a non-standard representation
4547             --  use the Enumeration_Rep field of the proper constant. Note
4548             --  that this would not work for types Character/Wide_Character,
4549             --  since no real entities are created for the enumeration
4550             --  literals, but that does not matter since these two types
4551             --  do not have non-standard representations anyway.
4552
4553             if Is_Enumeration_Type (P_Type)
4554               and then Has_Non_Standard_Rep (P_Type)
4555             then
4556                Fold_Uint (N, Enumeration_Rep (Expr_Value_E (E1)));
4557
4558             --  For enumeration types with standard representations and all
4559             --  other cases (i.e. all integer and modular types), Enum_Rep
4560             --  is equivalent to Pos.
4561
4562             else
4563                Fold_Uint (N, Expr_Value (E1));
4564             end if;
4565          end if;
4566
4567       -------------
4568       -- Epsilon --
4569       -------------
4570
4571       when Attribute_Epsilon =>
4572
4573          --  Ada 83 attribute is defined as (RM83 3.5.8)
4574
4575          --    T'Epsilon = 2.0**(1 - T'Mantissa)
4576
4577          Fold_Ureal (N, Ureal_2 ** (1 - Mantissa));
4578
4579       --------------
4580       -- Exponent --
4581       --------------
4582
4583       when Attribute_Exponent =>
4584          if Static then
4585             Fold_Uint (N,
4586               Eval_Fat.Exponent (P_Root_Type, Expr_Value_R (E1)));
4587          end if;
4588
4589       -----------
4590       -- First --
4591       -----------
4592
4593       when Attribute_First => First_Attr :
4594       begin
4595          Set_Bounds;
4596
4597          if Compile_Time_Known_Value (Lo_Bound) then
4598             if Is_Real_Type (P_Type) then
4599                Fold_Ureal (N, Expr_Value_R (Lo_Bound));
4600             else
4601                Fold_Uint  (N, Expr_Value (Lo_Bound));
4602             end if;
4603          end if;
4604       end First_Attr;
4605
4606       -----------------
4607       -- Fixed_Value --
4608       -----------------
4609
4610       when Attribute_Fixed_Value =>
4611          null;
4612
4613       -----------
4614       -- Floor --
4615       -----------
4616
4617       when Attribute_Floor =>
4618          if Static then
4619             Fold_Ureal (N,
4620               Eval_Fat.Floor (P_Root_Type, Expr_Value_R (E1)));
4621          end if;
4622
4623       ----------
4624       -- Fore --
4625       ----------
4626
4627       when Attribute_Fore =>
4628          if Static then
4629             Fold_Uint (N, UI_From_Int (Fore_Value));
4630          end if;
4631
4632       --------------
4633       -- Fraction --
4634       --------------
4635
4636       when Attribute_Fraction =>
4637          if Static then
4638             Fold_Ureal (N,
4639               Eval_Fat.Fraction (P_Root_Type, Expr_Value_R (E1)));
4640          end if;
4641
4642       -----------------------
4643       -- Has_Discriminants --
4644       -----------------------
4645
4646       when Attribute_Has_Discriminants =>
4647          declare
4648             Result : Node_Id;
4649
4650          begin
4651             if Has_Discriminants (P_Entity) then
4652                Result := New_Occurrence_Of (Standard_True, Loc);
4653             else
4654                Result := New_Occurrence_Of (Standard_False, Loc);
4655             end if;
4656
4657             Rewrite (N, Result);
4658             Analyze_And_Resolve (N, Standard_Boolean);
4659          end;
4660
4661       --------------
4662       -- Identity --
4663       --------------
4664
4665       when Attribute_Identity =>
4666          null;
4667
4668       -----------
4669       -- Image --
4670       -----------
4671
4672       --  Image is a scalar attribute, but is never static, because it is
4673       --  not a static function (having a non-scalar argument (RM 4.9(22))
4674
4675       when Attribute_Image =>
4676          null;
4677
4678       ---------
4679       -- Img --
4680       ---------
4681
4682       --  Img is a scalar attribute, but is never static, because it is
4683       --  not a static function (having a non-scalar argument (RM 4.9(22))
4684
4685       when Attribute_Img =>
4686          null;
4687
4688       -------------------
4689       -- Integer_Value --
4690       -------------------
4691
4692       when Attribute_Integer_Value =>
4693          null;
4694
4695       -----------
4696       -- Large --
4697       -----------
4698
4699       when Attribute_Large =>
4700
4701          --  For fixed-point, we use the identity:
4702
4703          --    T'Large = (2.0**T'Mantissa - 1.0) * T'Small
4704
4705          if Is_Fixed_Point_Type (P_Type) then
4706             Rewrite (N,
4707               Make_Op_Multiply (Loc,
4708                 Left_Opnd =>
4709                   Make_Op_Subtract (Loc,
4710                     Left_Opnd =>
4711                       Make_Op_Expon (Loc,
4712                         Left_Opnd =>
4713                           Make_Real_Literal (Loc, Ureal_2),
4714                         Right_Opnd =>
4715                           Make_Attribute_Reference (Loc,
4716                             Prefix => P,
4717                             Attribute_Name => Name_Mantissa)),
4718                     Right_Opnd => Make_Real_Literal (Loc, Ureal_1)),
4719
4720                 Right_Opnd =>
4721                   Make_Real_Literal (Loc, Small_Value (Entity (P)))));
4722
4723             Analyze_And_Resolve (N, C_Type);
4724
4725          --  Floating-point (Ada 83 compatibility)
4726
4727          else
4728             --  Ada 83 attribute is defined as (RM83 3.5.8)
4729
4730             --    T'Large = 2.0**T'Emax * (1.0 - 2.0**(-T'Mantissa))
4731
4732             --  where
4733
4734             --    T'Emax = 4 * T'Mantissa
4735
4736             Fold_Ureal (N,
4737               Ureal_2 ** (4 * Mantissa) *
4738               (Ureal_1 - Ureal_2 ** (-Mantissa)));
4739          end if;
4740
4741       ----------
4742       -- Last --
4743       ----------
4744
4745       when Attribute_Last => Last :
4746       begin
4747          Set_Bounds;
4748
4749          if Compile_Time_Known_Value (Hi_Bound) then
4750             if Is_Real_Type (P_Type) then
4751                Fold_Ureal (N, Expr_Value_R (Hi_Bound));
4752             else
4753                Fold_Uint  (N, Expr_Value (Hi_Bound));
4754             end if;
4755          end if;
4756       end Last;
4757
4758       ------------------
4759       -- Leading_Part --
4760       ------------------
4761
4762       when Attribute_Leading_Part =>
4763          if Static then
4764             Fold_Ureal (N,
4765               Eval_Fat.Leading_Part
4766                 (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)));
4767          end if;
4768
4769       ------------
4770       -- Length --
4771       ------------
4772
4773       when Attribute_Length => Length :
4774       begin
4775          Set_Bounds;
4776
4777          if Compile_Time_Known_Value (Lo_Bound)
4778            and then Compile_Time_Known_Value (Hi_Bound)
4779          then
4780             Fold_Uint (N,
4781               UI_Max (0, 1 + (Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound))));
4782          end if;
4783       end Length;
4784
4785       -------------
4786       -- Machine --
4787       -------------
4788
4789       when Attribute_Machine =>
4790          if Static then
4791             Fold_Ureal (N,
4792               Eval_Fat.Machine (P_Root_Type, Expr_Value_R (E1),
4793                 Eval_Fat.Round));
4794          end if;
4795
4796       ------------------
4797       -- Machine_Emax --
4798       ------------------
4799
4800       when Attribute_Machine_Emax =>
4801          Float_Attribute_Universal_Integer (
4802            IEEES_Machine_Emax,
4803            IEEEL_Machine_Emax,
4804            IEEEX_Machine_Emax,
4805            VAXFF_Machine_Emax,
4806            VAXDF_Machine_Emax,
4807            VAXGF_Machine_Emax);
4808
4809       ------------------
4810       -- Machine_Emin --
4811       ------------------
4812
4813       when Attribute_Machine_Emin =>
4814          Float_Attribute_Universal_Integer (
4815            IEEES_Machine_Emin,
4816            IEEEL_Machine_Emin,
4817            IEEEX_Machine_Emin,
4818            VAXFF_Machine_Emin,
4819            VAXDF_Machine_Emin,
4820            VAXGF_Machine_Emin);
4821
4822       ----------------------
4823       -- Machine_Mantissa --
4824       ----------------------
4825
4826       when Attribute_Machine_Mantissa =>
4827          Float_Attribute_Universal_Integer (
4828            IEEES_Machine_Mantissa,
4829            IEEEL_Machine_Mantissa,
4830            IEEEX_Machine_Mantissa,
4831            VAXFF_Machine_Mantissa,
4832            VAXDF_Machine_Mantissa,
4833            VAXGF_Machine_Mantissa);
4834
4835       -----------------------
4836       -- Machine_Overflows --
4837       -----------------------
4838
4839       when Attribute_Machine_Overflows =>
4840
4841          --  Always true for fixed-point
4842
4843          if Is_Fixed_Point_Type (P_Type) then
4844             Fold_Uint (N, True_Value);
4845
4846          --  Floating point case
4847
4848          else
4849             Fold_Uint
4850               (N, UI_From_Int (Boolean'Pos (Machine_Overflows_On_Target)));
4851          end if;
4852
4853       -------------------
4854       -- Machine_Radix --
4855       -------------------
4856
4857       when Attribute_Machine_Radix =>
4858          if Is_Fixed_Point_Type (P_Type) then
4859             if Is_Decimal_Fixed_Point_Type (P_Type)
4860               and then Machine_Radix_10 (P_Type)
4861             then
4862                Fold_Uint (N, Uint_10);
4863             else
4864                Fold_Uint (N, Uint_2);
4865             end if;
4866
4867          --  All floating-point type always have radix 2
4868
4869          else
4870             Fold_Uint (N, Uint_2);
4871          end if;
4872
4873       --------------------
4874       -- Machine_Rounds --
4875       --------------------
4876
4877       when Attribute_Machine_Rounds =>
4878
4879          --  Always False for fixed-point
4880
4881          if Is_Fixed_Point_Type (P_Type) then
4882             Fold_Uint (N, False_Value);
4883
4884          --  Else yield proper floating-point result
4885
4886          else
4887             Fold_Uint
4888               (N, UI_From_Int (Boolean'Pos (Machine_Rounds_On_Target)));
4889          end if;
4890
4891       ------------------
4892       -- Machine_Size --
4893       ------------------
4894
4895       --  Note: Machine_Size is identical to Object_Size
4896
4897       when Attribute_Machine_Size => Machine_Size : declare
4898          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
4899
4900       begin
4901          if Known_Esize (P_TypeA) then
4902             Fold_Uint (N, Esize (P_TypeA));
4903          end if;
4904       end Machine_Size;
4905
4906       --------------
4907       -- Mantissa --
4908       --------------
4909
4910       when Attribute_Mantissa =>
4911
4912          --  Fixed-point mantissa
4913
4914          if Is_Fixed_Point_Type (P_Type) then
4915
4916             --  Compile time foldable case
4917
4918             if Compile_Time_Known_Value (Type_Low_Bound  (P_Type))
4919                  and then
4920                Compile_Time_Known_Value (Type_High_Bound (P_Type))
4921             then
4922                --  The calculation of the obsolete Ada 83 attribute Mantissa
4923                --  is annoying, because of AI00143, quoted here:
4924
4925                --  !question 84-01-10
4926
4927                --  Consider the model numbers for F:
4928
4929                --         type F is delta 1.0 range -7.0 .. 8.0;
4930
4931                --  The wording requires that F'MANTISSA be the SMALLEST
4932                --  integer number for which each  bound  of the specified
4933                --  range is either a model number or lies at most small
4934                --  distant from a model number. This means F'MANTISSA
4935                --  is required to be 3 since the range  -7.0 .. 7.0 fits
4936                --  in 3 signed bits, and 8 is "at most" 1.0 from a model
4937                --  number, namely, 7. Is this analysis correct? Note that
4938                --  this implies the upper bound of the range is not
4939                --  represented as a model number.
4940
4941                --  !response 84-03-17
4942
4943                --  The analysis is correct. The upper and lower bounds for
4944                --  a fixed  point type can lie outside the range of model
4945                --  numbers.
4946
4947                declare
4948                   Siz     : Uint;
4949                   LBound  : Ureal;
4950                   UBound  : Ureal;
4951                   Bound   : Ureal;
4952                   Max_Man : Uint;
4953
4954                begin
4955                   LBound  := Expr_Value_R (Type_Low_Bound  (P_Type));
4956                   UBound  := Expr_Value_R (Type_High_Bound (P_Type));
4957                   Bound   := UR_Max (UR_Abs (LBound), UR_Abs (UBound));
4958                   Max_Man := UR_Trunc (Bound / Small_Value (P_Type));
4959
4960                   --  If the Bound is exactly a model number, i.e. a multiple
4961                   --  of Small, then we back it off by one to get the integer
4962                   --  value that must be representable.
4963
4964                   if Small_Value (P_Type) * Max_Man = Bound then
4965                      Max_Man := Max_Man - 1;
4966                   end if;
4967
4968                   --  Now find corresponding size = Mantissa value
4969
4970                   Siz := Uint_0;
4971                   while 2 ** Siz < Max_Man loop
4972                      Siz := Siz + 1;
4973                   end loop;
4974
4975                   Fold_Uint (N, Siz);
4976                end;
4977
4978             else
4979                --  The case of dynamic bounds cannot be evaluated at compile
4980                --  time. Instead we use a runtime routine (see Exp_Attr).
4981
4982                null;
4983             end if;
4984
4985          --  Floating-point Mantissa
4986
4987          else
4988             Fold_Uint (N, Mantissa);
4989          end if;
4990
4991       ---------
4992       -- Max --
4993       ---------
4994
4995       when Attribute_Max => Max :
4996       begin
4997          if Is_Real_Type (P_Type) then
4998             Fold_Ureal (N, UR_Max (Expr_Value_R (E1), Expr_Value_R (E2)));
4999          else
5000             Fold_Uint (N, UI_Max (Expr_Value (E1), Expr_Value (E2)));
5001          end if;
5002       end Max;
5003
5004       ----------------------------------
5005       -- Max_Size_In_Storage_Elements --
5006       ----------------------------------
5007
5008       --  Max_Size_In_Storage_Elements is simply the Size rounded up to a
5009       --  Storage_Unit boundary. We can fold any cases for which the size
5010       --  is known by the front end.
5011
5012       when Attribute_Max_Size_In_Storage_Elements =>
5013          if Known_Esize (P_Type) then
5014             Fold_Uint (N,
5015               (Esize (P_Type) + System_Storage_Unit - 1) /
5016                                           System_Storage_Unit);
5017          end if;
5018
5019       --------------------
5020       -- Mechanism_Code --
5021       --------------------
5022
5023       when Attribute_Mechanism_Code =>
5024          declare
5025             Val    : Int;
5026             Formal : Entity_Id;
5027             Mech   : Mechanism_Type;
5028
5029          begin
5030             if No (E1) then
5031                Mech := Mechanism (P_Entity);
5032
5033             else
5034                Val := UI_To_Int (Expr_Value (E1));
5035
5036                Formal := First_Formal (P_Entity);
5037                for J in 1 .. Val - 1 loop
5038                   Next_Formal (Formal);
5039                end loop;
5040                Mech := Mechanism (Formal);
5041             end if;
5042
5043             if Mech < 0 then
5044                Fold_Uint (N, UI_From_Int (Int (-Mech)));
5045             end if;
5046          end;
5047
5048       ---------
5049       -- Min --
5050       ---------
5051
5052       when Attribute_Min => Min :
5053       begin
5054          if Is_Real_Type (P_Type) then
5055             Fold_Ureal (N, UR_Min (Expr_Value_R (E1), Expr_Value_R (E2)));
5056          else
5057             Fold_Uint (N, UI_Min (Expr_Value (E1), Expr_Value (E2)));
5058          end if;
5059       end Min;
5060
5061       -----------
5062       -- Model --
5063       -----------
5064
5065       when Attribute_Model =>
5066          if Static then
5067             Fold_Ureal (N,
5068               Eval_Fat.Model (P_Root_Type, Expr_Value_R (E1)));
5069          end if;
5070
5071       ----------------
5072       -- Model_Emin --
5073       ----------------
5074
5075       when Attribute_Model_Emin =>
5076          Float_Attribute_Universal_Integer (
5077            IEEES_Model_Emin,
5078            IEEEL_Model_Emin,
5079            IEEEX_Model_Emin,
5080            VAXFF_Model_Emin,
5081            VAXDF_Model_Emin,
5082            VAXGF_Model_Emin);
5083
5084       -------------------
5085       -- Model_Epsilon --
5086       -------------------
5087
5088       when Attribute_Model_Epsilon =>
5089          Float_Attribute_Universal_Real (
5090            IEEES_Model_Epsilon'Universal_Literal_String,
5091            IEEEL_Model_Epsilon'Universal_Literal_String,
5092            IEEEX_Model_Epsilon'Universal_Literal_String,
5093            VAXFF_Model_Epsilon'Universal_Literal_String,
5094            VAXDF_Model_Epsilon'Universal_Literal_String,
5095            VAXGF_Model_Epsilon'Universal_Literal_String);
5096
5097       --------------------
5098       -- Model_Mantissa --
5099       --------------------
5100
5101       when Attribute_Model_Mantissa =>
5102          Float_Attribute_Universal_Integer (
5103            IEEES_Model_Mantissa,
5104            IEEEL_Model_Mantissa,
5105            IEEEX_Model_Mantissa,
5106            VAXFF_Model_Mantissa,
5107            VAXDF_Model_Mantissa,
5108            VAXGF_Model_Mantissa);
5109
5110       -----------------
5111       -- Model_Small --
5112       -----------------
5113
5114       when Attribute_Model_Small =>
5115          Float_Attribute_Universal_Real (
5116            IEEES_Model_Small'Universal_Literal_String,
5117            IEEEL_Model_Small'Universal_Literal_String,
5118            IEEEX_Model_Small'Universal_Literal_String,
5119            VAXFF_Model_Small'Universal_Literal_String,
5120            VAXDF_Model_Small'Universal_Literal_String,
5121            VAXGF_Model_Small'Universal_Literal_String);
5122
5123       -------------
5124       -- Modulus --
5125       -------------
5126
5127       when Attribute_Modulus =>
5128          Fold_Uint (N, Modulus (P_Type));
5129
5130       --------------------
5131       -- Null_Parameter --
5132       --------------------
5133
5134       --  Cannot fold, we know the value sort of, but the whole point is
5135       --  that there is no way to talk about this imaginary value except
5136       --  by using the attribute, so we leave it the way it is.
5137
5138       when Attribute_Null_Parameter =>
5139          null;
5140
5141       -----------------
5142       -- Object_Size --
5143       -----------------
5144
5145       --  The Object_Size attribute for a type returns the Esize of the
5146       --  type and can be folded if this value is known.
5147
5148       when Attribute_Object_Size => Object_Size : declare
5149          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5150
5151       begin
5152          if Known_Esize (P_TypeA) then
5153             Fold_Uint (N, Esize (P_TypeA));
5154          end if;
5155       end Object_Size;
5156
5157       -------------------------
5158       -- Passed_By_Reference --
5159       -------------------------
5160
5161       --  Scalar types are never passed by reference
5162
5163       when Attribute_Passed_By_Reference =>
5164          Fold_Uint (N, False_Value);
5165
5166       ---------
5167       -- Pos --
5168       ---------
5169
5170       when Attribute_Pos =>
5171          Fold_Uint (N, Expr_Value (E1));
5172
5173       ----------
5174       -- Pred --
5175       ----------
5176
5177       when Attribute_Pred => Pred :
5178       begin
5179          if Static then
5180
5181             --  Floating-point case. For now, do not fold this, since we
5182             --  don't know how to do it right (see fixed bug 3512-001 ???)
5183
5184             if Is_Floating_Point_Type (P_Type) then
5185                Fold_Ureal (N,
5186                  Eval_Fat.Pred (P_Root_Type, Expr_Value_R (E1)));
5187
5188             --  Fixed-point case
5189
5190             elsif Is_Fixed_Point_Type (P_Type) then
5191                Fold_Ureal (N,
5192                  Expr_Value_R (E1) - Small_Value (P_Type));
5193
5194             --  Modular integer case (wraps)
5195
5196             elsif Is_Modular_Integer_Type (P_Type) then
5197                Fold_Uint (N, (Expr_Value (E1) - 1) mod Modulus (P_Type));
5198
5199             --  Other scalar cases
5200
5201             else
5202                pragma Assert (Is_Scalar_Type (P_Type));
5203
5204                if Is_Enumeration_Type (P_Type)
5205                  and then Expr_Value (E1) =
5206                             Expr_Value (Type_Low_Bound (P_Base_Type))
5207                then
5208                   Apply_Compile_Time_Constraint_Error
5209                     (N, "Pred of type''First");
5210                   Check_Expressions;
5211                   return;
5212                end if;
5213
5214                Fold_Uint (N, Expr_Value (E1) - 1);
5215             end if;
5216          end if;
5217       end Pred;
5218
5219       -----------
5220       -- Range --
5221       -----------
5222
5223       --  No processing required, because by this stage, Range has been
5224       --  replaced by First .. Last, so this branch can never be taken.
5225
5226       when Attribute_Range =>
5227          raise Program_Error;
5228
5229       ------------------
5230       -- Range_Length --
5231       ------------------
5232
5233       when Attribute_Range_Length =>
5234          Set_Bounds;
5235
5236          if Compile_Time_Known_Value (Hi_Bound)
5237            and then Compile_Time_Known_Value (Lo_Bound)
5238          then
5239             Fold_Uint (N,
5240               UI_Max
5241                 (0, Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound) + 1));
5242          end if;
5243
5244       ---------------
5245       -- Remainder --
5246       ---------------
5247
5248       when Attribute_Remainder =>
5249          if Static then
5250             Fold_Ureal (N,
5251               Eval_Fat.Remainder
5252                 (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)));
5253          end if;
5254
5255       -----------
5256       -- Round --
5257       -----------
5258
5259       when Attribute_Round => Round :
5260       declare
5261          Sr : Ureal;
5262          Si : Uint;
5263
5264       begin
5265          if Static then
5266             --  First we get the (exact result) in units of small
5267
5268             Sr := Expr_Value_R (E1) / Small_Value (C_Type);
5269
5270             --  Now round that exactly to an integer
5271
5272             Si := UR_To_Uint (Sr);
5273
5274             --  Finally the result is obtained by converting back to real
5275
5276             Fold_Ureal (N, Si * Small_Value (C_Type));
5277          end if;
5278       end Round;
5279
5280       --------------
5281       -- Rounding --
5282       --------------
5283
5284       when Attribute_Rounding =>
5285          if Static then
5286             Fold_Ureal (N,
5287               Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)));
5288          end if;
5289
5290       ---------------
5291       -- Safe_Emax --
5292       ---------------
5293
5294       when Attribute_Safe_Emax =>
5295          Float_Attribute_Universal_Integer (
5296            IEEES_Safe_Emax,
5297            IEEEL_Safe_Emax,
5298            IEEEX_Safe_Emax,
5299            VAXFF_Safe_Emax,
5300            VAXDF_Safe_Emax,
5301            VAXGF_Safe_Emax);
5302
5303       ----------------
5304       -- Safe_First --
5305       ----------------
5306
5307       when Attribute_Safe_First =>
5308          Float_Attribute_Universal_Real (
5309            IEEES_Safe_First'Universal_Literal_String,
5310            IEEEL_Safe_First'Universal_Literal_String,
5311            IEEEX_Safe_First'Universal_Literal_String,
5312            VAXFF_Safe_First'Universal_Literal_String,
5313            VAXDF_Safe_First'Universal_Literal_String,
5314            VAXGF_Safe_First'Universal_Literal_String);
5315
5316       ----------------
5317       -- Safe_Large --
5318       ----------------
5319
5320       when Attribute_Safe_Large =>
5321          if Is_Fixed_Point_Type (P_Type) then
5322             Fold_Ureal (N, Expr_Value_R (Type_High_Bound (P_Base_Type)));
5323          else
5324             Float_Attribute_Universal_Real (
5325               IEEES_Safe_Large'Universal_Literal_String,
5326               IEEEL_Safe_Large'Universal_Literal_String,
5327               IEEEX_Safe_Large'Universal_Literal_String,
5328               VAXFF_Safe_Large'Universal_Literal_String,
5329               VAXDF_Safe_Large'Universal_Literal_String,
5330               VAXGF_Safe_Large'Universal_Literal_String);
5331          end if;
5332
5333       ---------------
5334       -- Safe_Last --
5335       ---------------
5336
5337       when Attribute_Safe_Last =>
5338          Float_Attribute_Universal_Real (
5339            IEEES_Safe_Last'Universal_Literal_String,
5340            IEEEL_Safe_Last'Universal_Literal_String,
5341            IEEEX_Safe_Last'Universal_Literal_String,
5342            VAXFF_Safe_Last'Universal_Literal_String,
5343            VAXDF_Safe_Last'Universal_Literal_String,
5344            VAXGF_Safe_Last'Universal_Literal_String);
5345
5346       ----------------
5347       -- Safe_Small --
5348       ----------------
5349
5350       when Attribute_Safe_Small =>
5351
5352          --  In Ada 95, the old Ada 83 attribute Safe_Small is redundant
5353          --  for fixed-point, since is the same as Small, but we implement
5354          --  it for backwards compatibility.
5355
5356          if Is_Fixed_Point_Type (P_Type) then
5357             Fold_Ureal (N, Small_Value (P_Type));
5358
5359          --  Ada 83 Safe_Small for floating-point cases
5360
5361          else
5362             Float_Attribute_Universal_Real (
5363               IEEES_Safe_Small'Universal_Literal_String,
5364               IEEEL_Safe_Small'Universal_Literal_String,
5365               IEEEX_Safe_Small'Universal_Literal_String,
5366               VAXFF_Safe_Small'Universal_Literal_String,
5367               VAXDF_Safe_Small'Universal_Literal_String,
5368               VAXGF_Safe_Small'Universal_Literal_String);
5369          end if;
5370
5371       -----------
5372       -- Scale --
5373       -----------
5374
5375       when Attribute_Scale =>
5376          Fold_Uint (N, Scale_Value (P_Type));
5377
5378       -------------
5379       -- Scaling --
5380       -------------
5381
5382       when Attribute_Scaling =>
5383          if Static then
5384             Fold_Ureal (N,
5385               Eval_Fat.Scaling
5386                 (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)));
5387          end if;
5388
5389       ------------------
5390       -- Signed_Zeros --
5391       ------------------
5392
5393       when Attribute_Signed_Zeros =>
5394          Fold_Uint
5395            (N, UI_From_Int (Boolean'Pos (Signed_Zeros_On_Target)));
5396
5397       ----------
5398       -- Size --
5399       ----------
5400
5401       --  Size attribute returns the RM size. All scalar types can be folded,
5402       --  as well as any types for which the size is known by the front end,
5403       --  including any type for which a size attribute is specified.
5404
5405       when Attribute_Size | Attribute_VADS_Size => Size : declare
5406          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5407
5408       begin
5409          if RM_Size (P_TypeA) /= Uint_0 then
5410
5411             --  VADS_Size case
5412
5413             if (Id = Attribute_VADS_Size or else Use_VADS_Size) then
5414
5415                declare
5416                   S : constant Node_Id := Size_Clause (P_TypeA);
5417
5418                begin
5419                   --  If a size clause applies, then use the size from it.
5420                   --  This is one of the rare cases where we can use the
5421                   --  Size_Clause field for a subtype when Has_Size_Clause
5422                   --  is False. Consider:
5423
5424                   --    type x is range 1 .. 64;
5425                   --    for x'size use 12;
5426                   --    subtype y is x range 0 .. 3;
5427
5428                   --  Here y has a size clause inherited from x, but normally
5429                   --  it does not apply, and y'size is 2. However, y'VADS_Size
5430                   --  is indeed 12 and not 2.
5431
5432                   if Present (S)
5433                     and then Is_OK_Static_Expression (Expression (S))
5434                   then
5435                      Fold_Uint (N, Expr_Value (Expression (S)));
5436
5437                   --  If no size is specified, then we simply use the object
5438                   --  size in the VADS_Size case (e.g. Natural'Size is equal
5439                   --  to Integer'Size, not one less).
5440
5441                   else
5442                      Fold_Uint (N, Esize (P_TypeA));
5443                   end if;
5444                end;
5445
5446             --  Normal case (Size) in which case we want the RM_Size
5447
5448             else
5449                Fold_Uint (N, RM_Size (P_TypeA));
5450             end if;
5451          end if;
5452       end Size;
5453
5454       -----------
5455       -- Small --
5456       -----------
5457
5458       when Attribute_Small =>
5459
5460          --  The floating-point case is present only for Ada 83 compatibility.
5461          --  Note that strictly this is an illegal addition, since we are
5462          --  extending an Ada 95 defined attribute, but we anticipate an
5463          --  ARG ruling that will permit this.
5464
5465          if Is_Floating_Point_Type (P_Type) then
5466
5467             --  Ada 83 attribute is defined as (RM83 3.5.8)
5468
5469             --    T'Small = 2.0**(-T'Emax - 1)
5470
5471             --  where
5472
5473             --    T'Emax = 4 * T'Mantissa
5474
5475             Fold_Ureal (N, Ureal_2 ** ((-(4 * Mantissa)) - 1));
5476
5477          --  Normal Ada 95 fixed-point case
5478
5479          else
5480             Fold_Ureal (N, Small_Value (P_Type));
5481          end if;
5482
5483       ----------
5484       -- Succ --
5485       ----------
5486
5487       when Attribute_Succ => Succ :
5488       begin
5489          if Static then
5490
5491             --  Floating-point case. For now, do not fold this, since we
5492             --  don't know how to do it right (see fixed bug 3512-001 ???)
5493
5494             if Is_Floating_Point_Type (P_Type) then
5495                Fold_Ureal (N,
5496                  Eval_Fat.Succ (P_Root_Type, Expr_Value_R (E1)));
5497
5498             --  Fixed-point case
5499
5500             elsif Is_Fixed_Point_Type (P_Type) then
5501                Fold_Ureal (N,
5502                  Expr_Value_R (E1) + Small_Value (P_Type));
5503
5504             --  Modular integer case (wraps)
5505
5506             elsif Is_Modular_Integer_Type (P_Type) then
5507                Fold_Uint (N, (Expr_Value (E1) + 1) mod Modulus (P_Type));
5508
5509             --  Other scalar cases
5510
5511             else
5512                pragma Assert (Is_Scalar_Type (P_Type));
5513
5514                if Is_Enumeration_Type (P_Type)
5515                  and then Expr_Value (E1) =
5516                             Expr_Value (Type_High_Bound (P_Base_Type))
5517                then
5518                   Apply_Compile_Time_Constraint_Error
5519                     (N, "Succ of type''Last");
5520                   Check_Expressions;
5521                   return;
5522                else
5523                   Fold_Uint (N, Expr_Value (E1) + 1);
5524                end if;
5525             end if;
5526          end if;
5527       end Succ;
5528
5529       ----------------
5530       -- Truncation --
5531       ----------------
5532
5533       when Attribute_Truncation =>
5534          if Static then
5535             Fold_Ureal (N,
5536               Eval_Fat.Truncation (P_Root_Type, Expr_Value_R (E1)));
5537          end if;
5538
5539       ----------------
5540       -- Type_Class --
5541       ----------------
5542
5543       when Attribute_Type_Class => Type_Class : declare
5544          Typ : constant Entity_Id := Underlying_Type (P_Base_Type);
5545          Id  : RE_Id;
5546
5547       begin
5548          if Is_RTE (P_Root_Type, RE_Address) then
5549             Id := RE_Type_Class_Address;
5550
5551          elsif Is_Enumeration_Type (Typ) then
5552             Id := RE_Type_Class_Enumeration;
5553
5554          elsif Is_Integer_Type (Typ) then
5555             Id := RE_Type_Class_Integer;
5556
5557          elsif Is_Fixed_Point_Type (Typ) then
5558             Id := RE_Type_Class_Fixed_Point;
5559
5560          elsif Is_Floating_Point_Type (Typ) then
5561             Id := RE_Type_Class_Floating_Point;
5562
5563          elsif Is_Array_Type (Typ) then
5564             Id := RE_Type_Class_Array;
5565
5566          elsif Is_Record_Type (Typ) then
5567             Id := RE_Type_Class_Record;
5568
5569          elsif Is_Access_Type (Typ) then
5570             Id := RE_Type_Class_Access;
5571
5572          elsif Is_Enumeration_Type (Typ) then
5573             Id := RE_Type_Class_Enumeration;
5574
5575          elsif Is_Task_Type (Typ) then
5576             Id := RE_Type_Class_Task;
5577
5578          --  We treat protected types like task types. It would make more
5579          --  sense to have another enumeration value, but after all the
5580          --  whole point of this feature is to be exactly DEC compatible,
5581          --  and changing the type Type_Clas would not meet this requirement.
5582
5583          elsif Is_Protected_Type (Typ) then
5584             Id := RE_Type_Class_Task;
5585
5586          --  Not clear if there are any other possibilities, but if there
5587          --  are, then we will treat them as the address case.
5588
5589          else
5590             Id := RE_Type_Class_Address;
5591          end if;
5592
5593          Rewrite (N, New_Occurrence_Of (RTE (Id), Loc));
5594
5595       end Type_Class;
5596
5597       -----------------------
5598       -- Unbiased_Rounding --
5599       -----------------------
5600
5601       when Attribute_Unbiased_Rounding =>
5602          if Static then
5603             Fold_Ureal (N,
5604               Eval_Fat.Unbiased_Rounding (P_Root_Type, Expr_Value_R (E1)));
5605          end if;
5606
5607       ---------------
5608       -- VADS_Size --
5609       ---------------
5610
5611       --  Processing is shared with Size
5612
5613       ---------
5614       -- Val --
5615       ---------
5616
5617       when Attribute_Val => Val :
5618       begin
5619          if Static then
5620             if  Expr_Value (E1) < Expr_Value (Type_Low_Bound (P_Base_Type))
5621               or else
5622                 Expr_Value (E1) > Expr_Value (Type_High_Bound (P_Base_Type))
5623             then
5624                Apply_Compile_Time_Constraint_Error
5625                  (N, "Val expression out of range");
5626                Check_Expressions;
5627                return;
5628             else
5629                Fold_Uint (N, Expr_Value (E1));
5630             end if;
5631          end if;
5632       end Val;
5633
5634       ----------------
5635       -- Value_Size --
5636       ----------------
5637
5638       --  The Value_Size attribute for a type returns the RM size of the
5639       --  type. This an always be folded for scalar types, and can also
5640       --  be folded for non-scalar types if the size is set.
5641
5642       when Attribute_Value_Size => Value_Size : declare
5643          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5644
5645       begin
5646          if RM_Size (P_TypeA) /= Uint_0 then
5647             Fold_Uint (N, RM_Size (P_TypeA));
5648          end if;
5649
5650       end Value_Size;
5651
5652       -------------
5653       -- Version --
5654       -------------
5655
5656       --  Version can never be static
5657
5658       when Attribute_Version =>
5659          null;
5660
5661       ----------------
5662       -- Wide_Image --
5663       ----------------
5664
5665       --  Wide_Image is a scalar attribute, but is never static, because it
5666       --  is not a static function (having a non-scalar argument (RM 4.9(22))
5667
5668       when Attribute_Wide_Image =>
5669          null;
5670
5671       ----------------
5672       -- Wide_Width --
5673       ----------------
5674
5675       --  Processing for Wide_Width is combined with Width
5676
5677       -----------
5678       -- Width --
5679       -----------
5680
5681       --  This processing also handles the case of Wide_Width
5682
5683       when Attribute_Width | Attribute_Wide_Width => Width :
5684       begin
5685          if Static then
5686
5687             --  Floating-point types
5688
5689             if Is_Floating_Point_Type (P_Type) then
5690
5691                --  Width is zero for a null range (RM 3.5 (38))
5692
5693                if Expr_Value_R (Type_High_Bound (P_Type)) <
5694                   Expr_Value_R (Type_Low_Bound (P_Type))
5695                then
5696                   Fold_Uint (N, Uint_0);
5697
5698                else
5699                   --  For floating-point, we have +N.dddE+nnn where length
5700                   --  of ddd is determined by type'Digits - 1, but is one
5701                   --  if Digits is one (RM 3.5 (33)).
5702
5703                   --  nnn is set to 2 for Short_Float and Float (32 bit
5704                   --  floats), and 3 for Long_Float and Long_Long_Float.
5705                   --  This is not quite right, but is good enough.
5706
5707                   declare
5708                      Len : Int :=
5709                              Int'Max (2, UI_To_Int (Digits_Value (P_Type)));
5710
5711                   begin
5712                      if Esize (P_Type) <= 32 then
5713                         Len := Len + 6;
5714                      else
5715                         Len := Len + 7;
5716                      end if;
5717
5718                      Fold_Uint (N, UI_From_Int (Len));
5719                   end;
5720                end if;
5721
5722             --  Fixed-point types
5723
5724             elsif Is_Fixed_Point_Type (P_Type) then
5725
5726                --  Width is zero for a null range (RM 3.5 (38))
5727
5728                if Expr_Value (Type_High_Bound (P_Type)) <
5729                   Expr_Value (Type_Low_Bound  (P_Type))
5730                then
5731                   Fold_Uint (N, Uint_0);
5732
5733                --  The non-null case depends on the specific real type
5734
5735                else
5736                   --  For fixed-point type width is Fore + 1 + Aft (RM 3.5(34))
5737
5738                   Fold_Uint (N, UI_From_Int (Fore_Value + 1 + Aft_Value));
5739                end if;
5740
5741             --  Discrete types
5742
5743             else
5744                declare
5745                   R  : constant Entity_Id := Root_Type (P_Type);
5746                   Lo : constant Uint :=
5747                          Expr_Value (Type_Low_Bound (P_Type));
5748                   Hi : constant Uint :=
5749                          Expr_Value (Type_High_Bound (P_Type));
5750                   W  : Nat;
5751                   Wt : Nat;
5752                   T  : Uint;
5753                   L  : Node_Id;
5754                   C  : Character;
5755
5756                begin
5757                   --  Empty ranges
5758
5759                   if Lo > Hi then
5760                      W := 0;
5761
5762                   --  Width for types derived from Standard.Character
5763                   --  and Standard.Wide_Character.
5764
5765                   elsif R = Standard_Character
5766                     or else R = Standard_Wide_Character
5767                   then
5768                      W := 0;
5769
5770                      --  Set W larger if needed
5771
5772                      for J in UI_To_Int (Lo) .. UI_To_Int (Hi) loop
5773
5774                         --  Assume all wide-character escape sequences are
5775                         --  same length, so we can quit when we reach one.
5776
5777                         if J > 255 then
5778                            if Id = Attribute_Wide_Width then
5779                               W := Int'Max (W, 3);
5780                               exit;
5781                            else
5782                               W := Int'Max (W, Length_Wide);
5783                               exit;
5784                            end if;
5785
5786                         else
5787                            C := Character'Val (J);
5788
5789                            --  Test for all cases where Character'Image
5790                            --  yields an image that is longer than three
5791                            --  characters. First the cases of Reserved_xxx
5792                            --  names (length = 12).
5793
5794                            case C is
5795                               when Reserved_128 | Reserved_129 |
5796                                    Reserved_132 | Reserved_153
5797
5798                                 => Wt := 12;
5799
5800                               when BS | HT | LF | VT | FF | CR |
5801                                    SO | SI | EM | FS | GS | RS |
5802                                    US | RI | MW | ST | PM
5803
5804                                 => Wt := 2;
5805
5806                               when NUL | SOH | STX | ETX | EOT |
5807                                    ENQ | ACK | BEL | DLE | DC1 |
5808                                    DC2 | DC3 | DC4 | NAK | SYN |
5809                                    ETB | CAN | SUB | ESC | DEL |
5810                                    BPH | NBH | NEL | SSA | ESA |
5811                                    HTS | HTJ | VTS | PLD | PLU |
5812                                    SS2 | SS3 | DCS | PU1 | PU2 |
5813                                    STS | CCH | SPA | EPA | SOS |
5814                                    SCI | CSI | OSC | APC
5815
5816                                 => Wt := 3;
5817
5818                               when Space .. Tilde |
5819                                    No_Break_Space .. LC_Y_Diaeresis
5820
5821                                 => Wt := 3;
5822
5823                            end case;
5824
5825                            W := Int'Max (W, Wt);
5826                         end if;
5827                      end loop;
5828
5829                   --  Width for types derived from Standard.Boolean
5830
5831                   elsif R = Standard_Boolean then
5832                      if Lo = 0 then
5833                         W := 5; -- FALSE
5834                      else
5835                         W := 4; -- TRUE
5836                      end if;
5837
5838                   --  Width for integer types
5839
5840                   elsif Is_Integer_Type (P_Type) then
5841                      T := UI_Max (abs Lo, abs Hi);
5842
5843                      W := 2;
5844                      while T >= 10 loop
5845                         W := W + 1;
5846                         T := T / 10;
5847                      end loop;
5848
5849                   --  Only remaining possibility is user declared enum type
5850
5851                   else
5852                      pragma Assert (Is_Enumeration_Type (P_Type));
5853
5854                      W := 0;
5855                      L := First_Literal (P_Type);
5856
5857                      while Present (L) loop
5858
5859                         --  Only pay attention to in range characters
5860
5861                         if Lo <= Enumeration_Pos (L)
5862                           and then Enumeration_Pos (L) <= Hi
5863                         then
5864                            --  For Width case, use decoded name
5865
5866                            if Id = Attribute_Width then
5867                               Get_Decoded_Name_String (Chars (L));
5868                               Wt := Nat (Name_Len);
5869
5870                            --  For Wide_Width, use encoded name, and then
5871                            --  adjust for the encoding.
5872
5873                            else
5874                               Get_Name_String (Chars (L));
5875
5876                               --  Character literals are always of length 3
5877
5878                               if Name_Buffer (1) = 'Q' then
5879                                  Wt := 3;
5880
5881                               --  Otherwise loop to adjust for upper/wide chars
5882
5883                               else
5884                                  Wt := Nat (Name_Len);
5885
5886                                  for J in 1 .. Name_Len loop
5887                                     if Name_Buffer (J) = 'U' then
5888                                        Wt := Wt - 2;
5889                                     elsif Name_Buffer (J) = 'W' then
5890                                        Wt := Wt - 4;
5891                                     end if;
5892                                  end loop;
5893                               end if;
5894                            end if;
5895
5896                            W := Int'Max (W, Wt);
5897                         end if;
5898
5899                         Next_Literal (L);
5900                      end loop;
5901                   end if;
5902
5903                   Fold_Uint (N, UI_From_Int (W));
5904                end;
5905             end if;
5906          end if;
5907       end Width;
5908
5909       --  The following attributes can never be folded, and furthermore we
5910       --  should not even have entered the case statement for any of these.
5911       --  Note that in some cases, the values have already been folded as
5912       --  a result of the processing in Analyze_Attribute.
5913
5914       when Attribute_Abort_Signal             |
5915            Attribute_Access                   |
5916            Attribute_Address                  |
5917            Attribute_Address_Size             |
5918            Attribute_Asm_Input                |
5919            Attribute_Asm_Output               |
5920            Attribute_Base                     |
5921            Attribute_Bit_Order                |
5922            Attribute_Bit_Position             |
5923            Attribute_Callable                 |
5924            Attribute_Caller                   |
5925            Attribute_Class                    |
5926            Attribute_Code_Address             |
5927            Attribute_Count                    |
5928            Attribute_Default_Bit_Order        |
5929            Attribute_Elaborated               |
5930            Attribute_Elab_Body                |
5931            Attribute_Elab_Spec                |
5932            Attribute_External_Tag             |
5933            Attribute_First_Bit                |
5934            Attribute_Input                    |
5935            Attribute_Last_Bit                 |
5936            Attribute_Max_Interrupt_Priority   |
5937            Attribute_Max_Priority             |
5938            Attribute_Maximum_Alignment        |
5939            Attribute_Output                   |
5940            Attribute_Partition_ID             |
5941            Attribute_Position                 |
5942            Attribute_Read                     |
5943            Attribute_Storage_Pool             |
5944            Attribute_Storage_Size             |
5945            Attribute_Storage_Unit             |
5946            Attribute_Tag                      |
5947            Attribute_Terminated               |
5948            Attribute_Tick                     |
5949            Attribute_To_Address               |
5950            Attribute_UET_Address              |
5951            Attribute_Unchecked_Access         |
5952            Attribute_Universal_Literal_String |
5953            Attribute_Unrestricted_Access      |
5954            Attribute_Valid                    |
5955            Attribute_Value                    |
5956            Attribute_Wchar_T_Size             |
5957            Attribute_Wide_Value               |
5958            Attribute_Word_Size                |
5959            Attribute_Write                    =>
5960
5961          raise Program_Error;
5962
5963       end case;
5964
5965       --  At the end of the case, one more check. If we did a static evaluation
5966       --  so that the result is now a literal, then set Is_Static_Expression
5967       --  in the constant only if the prefix type is a static subtype. For
5968       --  non-static subtypes, the folding is still OK, but not static.
5969
5970       if Nkind (N) = N_Integer_Literal
5971         or else Nkind (N) = N_Real_Literal
5972         or else Nkind (N) = N_Character_Literal
5973         or else Nkind (N) = N_String_Literal
5974         or else (Is_Entity_Name (N)
5975                   and then Ekind (Entity (N)) = E_Enumeration_Literal)
5976       then
5977          Set_Is_Static_Expression (N, Static);
5978
5979       --  If this is still an attribute reference, then it has not been folded
5980       --  and that means that its expressions are in a non-static context.
5981
5982       elsif Nkind (N) = N_Attribute_Reference then
5983          Check_Expressions;
5984
5985       --  Note: the else case not covered here are odd cases where the
5986       --  processing has transformed the attribute into something other
5987       --  than a constant. Nothing more to do in such cases.
5988
5989       else
5990          null;
5991       end if;
5992
5993    end Eval_Attribute;
5994
5995    ------------------------------
5996    -- Is_Anonymous_Tagged_Base --
5997    ------------------------------
5998
5999    function Is_Anonymous_Tagged_Base
6000      (Anon : Entity_Id;
6001       Typ  : Entity_Id)
6002       return Boolean
6003    is
6004    begin
6005       return
6006         Anon = Current_Scope
6007           and then Is_Itype (Anon)
6008           and then Associated_Node_For_Itype (Anon) = Parent (Typ);
6009    end Is_Anonymous_Tagged_Base;
6010
6011    -----------------------
6012    -- Resolve_Attribute --
6013    -----------------------
6014
6015    procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id) is
6016       Loc      : constant Source_Ptr   := Sloc (N);
6017       P        : constant Node_Id      := Prefix (N);
6018       Aname    : constant Name_Id      := Attribute_Name (N);
6019       Attr_Id  : constant Attribute_Id := Get_Attribute_Id (Aname);
6020       Index    : Interp_Index;
6021       It       : Interp;
6022       Btyp     : Entity_Id := Base_Type (Typ);
6023       Nom_Subt : Entity_Id;
6024
6025    begin
6026       --  If error during analysis, no point in continuing, except for
6027       --  array types, where we get  better recovery by using unconstrained
6028       --  indices than nothing at all (see Check_Array_Type).
6029
6030       if Error_Posted (N)
6031         and then Attr_Id /= Attribute_First
6032         and then Attr_Id /= Attribute_Last
6033         and then Attr_Id /= Attribute_Length
6034         and then Attr_Id /= Attribute_Range
6035       then
6036          return;
6037       end if;
6038
6039       --  If attribute was universal type, reset to actual type
6040
6041       if Etype (N) = Universal_Integer
6042         or else Etype (N) = Universal_Real
6043       then
6044          Set_Etype (N, Typ);
6045       end if;
6046
6047       --  Remaining processing depends on attribute
6048
6049       case Attr_Id is
6050
6051          ------------
6052          -- Access --
6053          ------------
6054
6055          --  For access attributes, if the prefix denotes an entity, it is
6056          --  interpreted as a name, never as a call. It may be overloaded,
6057          --  in which case resolution uses the profile of the context type.
6058          --  Otherwise prefix must be resolved.
6059
6060          when Attribute_Access
6061             | Attribute_Unchecked_Access
6062             | Attribute_Unrestricted_Access =>
6063
6064             if Is_Variable (P) then
6065                Note_Possible_Modification (P);
6066             end if;
6067
6068             if Is_Entity_Name (P) then
6069
6070                if Is_Overloaded (P) then
6071                   Get_First_Interp (P, Index, It);
6072
6073                   while Present (It.Nam) loop
6074
6075                      if Type_Conformant (Designated_Type (Typ), It.Nam) then
6076                         Set_Entity (P, It.Nam);
6077
6078                         --  The prefix is definitely NOT overloaded anymore
6079                         --  at this point, so we reset the Is_Overloaded
6080                         --  flag to avoid any confusion when reanalyzing
6081                         --  the node.
6082
6083                         Set_Is_Overloaded (P, False);
6084                         Generate_Reference (Entity (P), P);
6085                         exit;
6086                      end if;
6087
6088                      Get_Next_Interp (Index, It);
6089                   end loop;
6090
6091                --  If it is a subprogram name or a type, there is nothing
6092                --  to resolve.
6093
6094                elsif not Is_Overloadable (Entity (P))
6095                  and then not Is_Type (Entity (P))
6096                then
6097                   Resolve (P, Etype (P));
6098                end if;
6099
6100                if not Is_Entity_Name (P) then
6101                   null;
6102
6103                elsif Is_Abstract (Entity (P))
6104                  and then Is_Overloadable (Entity (P))
6105                then
6106                   Error_Msg_Name_1 := Aname;
6107                   Error_Msg_N ("prefix of % attribute cannot be abstract", P);
6108                   Set_Etype (N, Any_Type);
6109
6110                elsif Convention (Entity (P)) = Convention_Intrinsic then
6111                   Error_Msg_Name_1 := Aname;
6112
6113                   if Ekind (Entity (P)) = E_Enumeration_Literal then
6114                      Error_Msg_N
6115                        ("prefix of % attribute cannot be enumeration literal",
6116                           P);
6117                   else
6118                      Error_Msg_N
6119                        ("prefix of % attribute cannot be intrinsic", P);
6120                   end if;
6121
6122                   Set_Etype (N, Any_Type);
6123                end if;
6124
6125                --  Assignments, return statements, components of aggregates,
6126                --  generic instantiations will require convention checks if
6127                --  the type is an access to subprogram. Given that there will
6128                --  also be accessibility checks on those, this is where the
6129                --  checks can eventually be centralized ???
6130
6131                if Ekind (Btyp) = E_Access_Subprogram_Type then
6132                   if Convention (Btyp) /= Convention (Entity (P)) then
6133                      Error_Msg_N
6134                       ("subprogram has invalid convention for context", P);
6135
6136                   else
6137                      Check_Subtype_Conformant
6138                        (New_Id  => Entity (P),
6139                         Old_Id  => Designated_Type (Btyp),
6140                         Err_Loc => P);
6141                   end if;
6142
6143                   if Attr_Id = Attribute_Unchecked_Access then
6144                      Error_Msg_Name_1 := Aname;
6145                      Error_Msg_N
6146                        ("attribute% cannot be applied to a subprogram", P);
6147
6148                   elsif Aname = Name_Unrestricted_Access then
6149                      null;  --  Nothing to check
6150
6151                   --  Check the static accessibility rule of 3.10.2(32)
6152
6153                   elsif Attr_Id = Attribute_Access
6154                     and then Subprogram_Access_Level (Entity (P))
6155                       > Type_Access_Level (Btyp)
6156                   then
6157                      if not In_Instance_Body then
6158                         Error_Msg_N
6159                           ("subprogram must not be deeper than access type",
6160                             P);
6161                      else
6162                         Warn_On_Instance := True;
6163                         Error_Msg_N
6164                           ("subprogram must not be deeper than access type?",
6165                              P);
6166                         Error_Msg_N
6167                           ("Constraint_Error will be raised ?", P);
6168                         Set_Raises_Constraint_Error (N);
6169                         Warn_On_Instance := False;
6170                      end if;
6171
6172                   --  Check the restriction of 3.10.2(32) that disallows
6173                   --  the type of the access attribute to be declared
6174                   --  outside a generic body when the attribute occurs
6175                   --  within that generic body.
6176
6177                   elsif Enclosing_Generic_Body (Entity (P))
6178                     /= Enclosing_Generic_Body (Btyp)
6179                   then
6180                      Error_Msg_N
6181                        ("access type must not be outside generic body", P);
6182                   end if;
6183                end if;
6184
6185                --  if this is a renaming, an inherited operation, or a
6186                --  subprogram instance, use the original entity.
6187
6188                if Is_Entity_Name (P)
6189                  and then Is_Overloadable (Entity (P))
6190                  and then Present (Alias (Entity (P)))
6191                then
6192                   Rewrite (P,
6193                     New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6194                end if;
6195
6196             elsif Nkind (P) = N_Selected_Component
6197               and then Is_Overloadable (Entity (Selector_Name (P)))
6198             then
6199                --  Protected operation. If operation is overloaded, must
6200                --  disambiguate. Prefix that denotes protected object itself
6201                --  is resolved with its own type.
6202
6203                if Attr_Id = Attribute_Unchecked_Access then
6204                   Error_Msg_Name_1 := Aname;
6205                   Error_Msg_N
6206                     ("attribute% cannot be applied to protected operation", P);
6207                end if;
6208
6209                Resolve (Prefix (P), Etype (Prefix (P)));
6210
6211             elsif Is_Overloaded (P) then
6212
6213                --  Use the designated type of the context  to disambiguate.
6214                declare
6215                   Index : Interp_Index;
6216                   It    : Interp;
6217                begin
6218                   Get_First_Interp (P, Index, It);
6219
6220                   while Present (It.Typ) loop
6221                      if Covers (Designated_Type (Typ), It.Typ) then
6222                         Resolve (P, It.Typ);
6223                         exit;
6224                      end if;
6225
6226                      Get_Next_Interp (Index, It);
6227                   end loop;
6228                end;
6229             else
6230                Resolve (P, Etype (P));
6231             end if;
6232
6233             --  X'Access is illegal if X denotes a constant and the access
6234             --  type is access-to-variable. Same for 'Unchecked_Access.
6235             --  The rule does not apply to 'Unrestricted_Access.
6236
6237             if not (Ekind (Btyp) = E_Access_Subprogram_Type
6238                      or else (Is_Record_Type (Btyp) and then
6239                               Present (Corresponding_Remote_Type (Btyp)))
6240                      or else Ekind (Btyp) = E_Access_Protected_Subprogram_Type
6241                      or else Is_Access_Constant (Btyp)
6242                      or else Is_Variable (P)
6243                      or else Attr_Id = Attribute_Unrestricted_Access)
6244             then
6245                if Comes_From_Source (N) then
6246                   Error_Msg_N ("access-to-variable designates constant", P);
6247                end if;
6248             end if;
6249
6250             if (Attr_Id = Attribute_Access
6251                   or else
6252                 Attr_Id = Attribute_Unchecked_Access)
6253               and then (Ekind (Btyp) = E_General_Access_Type
6254                          or else Ekind (Btyp) = E_Anonymous_Access_Type)
6255             then
6256                if Is_Dependent_Component_Of_Mutable_Object (P) then
6257                   Error_Msg_N
6258                     ("illegal attribute for discriminant-dependent component",
6259                      P);
6260                end if;
6261
6262                --  Check the static matching rule of 3.10.2(27). The
6263                --  nominal subtype of the prefix must statically
6264                --  match the designated type.
6265
6266                Nom_Subt := Etype (P);
6267
6268                if Is_Constr_Subt_For_U_Nominal (Nom_Subt) then
6269                   Nom_Subt := Etype (Nom_Subt);
6270                end if;
6271
6272                if Is_Tagged_Type (Designated_Type (Typ)) then
6273                   --  If the attribute is in the context of an access
6274                   --  parameter, then the prefix is allowed to be of
6275                   --  the class-wide type (by AI-127).
6276
6277                   if Ekind (Typ) = E_Anonymous_Access_Type then
6278                      if not Covers (Designated_Type (Typ), Nom_Subt)
6279                        and then not Covers (Nom_Subt, Designated_Type (Typ))
6280                      then
6281                         if Is_Anonymous_Tagged_Base
6282                              (Nom_Subt, Etype (Designated_Type (Typ)))
6283                         then
6284                            null;
6285
6286                         else
6287                            Error_Msg_NE
6288                              ("type of prefix: & not compatible", P, Nom_Subt);
6289                            Error_Msg_NE
6290                              ("\with &, the expected designated type",
6291                                P, Designated_Type (Typ));
6292                         end if;
6293                      end if;
6294
6295                   elsif not Covers (Designated_Type (Typ), Nom_Subt)
6296                     or else
6297                       (not Is_Class_Wide_Type (Designated_Type (Typ))
6298                         and then Is_Class_Wide_Type (Nom_Subt))
6299                   then
6300                      Error_Msg_NE
6301                        ("type of prefix: & is not covered", P, Nom_Subt);
6302                      Error_Msg_NE
6303                        ("\by &, the expected designated type" &
6304                            " ('R'M 3.10.2 (27))", P, Designated_Type (Typ));
6305                   end if;
6306
6307                   if Is_Class_Wide_Type (Designated_Type (Typ))
6308                     and then Has_Discriminants (Etype (Designated_Type (Typ)))
6309                     and then Is_Constrained (Etype (Designated_Type (Typ)))
6310                     and then Designated_Type (Typ) /= Nom_Subt
6311                   then
6312                      Apply_Discriminant_Check
6313                        (N, Etype (Designated_Type (Typ)));
6314                   end if;
6315
6316                elsif not Subtypes_Statically_Match
6317                         (Designated_Type (Typ), Nom_Subt)
6318                  and then
6319                    not (Has_Discriminants (Designated_Type (Typ))
6320                         and then not Is_Constrained (Designated_Type (Typ)))
6321                then
6322                   Error_Msg_N
6323                     ("object subtype must statically match "
6324                      & "designated subtype", P);
6325
6326                   if Is_Entity_Name (P)
6327                     and then Is_Array_Type (Designated_Type (Typ))
6328                   then
6329
6330                      declare
6331                         D : constant Node_Id := Declaration_Node (Entity (P));
6332
6333                      begin
6334                         Error_Msg_N ("aliased object has explicit bounds?",
6335                           D);
6336                         Error_Msg_N ("\declare without bounds"
6337                           & " (and with explicit initialization)?", D);
6338                         Error_Msg_N ("\for use with unconstrained access?", D);
6339                      end;
6340                   end if;
6341                end if;
6342
6343                --  Check the static accessibility rule of 3.10.2(28).
6344                --  Note that this check is not performed for the
6345                --  case of an anonymous access type, since the access
6346                --  attribute is always legal in such a context.
6347
6348                if Attr_Id /= Attribute_Unchecked_Access
6349                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
6350                  and then Ekind (Btyp) = E_General_Access_Type
6351                then
6352                   --  In an instance, this is a runtime check, but one we
6353                   --  know will fail, so generate an appropriate warning.
6354
6355                   if In_Instance_Body then
6356                      Error_Msg_N
6357                        ("?non-local pointer cannot point to local object", P);
6358                      Error_Msg_N
6359                        ("?Program_Error will be raised at run time", P);
6360                      Rewrite (N, Make_Raise_Program_Error (Loc));
6361                      Set_Etype (N, Typ);
6362                      return;
6363
6364                   else
6365                      Error_Msg_N
6366                        ("non-local pointer cannot point to local object", P);
6367
6368                      if Is_Record_Type (Current_Scope)
6369                        and then (Nkind (Parent (N)) =
6370                                   N_Discriminant_Association
6371                                    or else
6372                                  Nkind (Parent (N)) =
6373                                    N_Index_Or_Discriminant_Constraint)
6374                      then
6375                         declare
6376                            Indic : Node_Id := Parent (Parent (N));
6377
6378                         begin
6379                            while Present (Indic)
6380                              and then Nkind (Indic) /= N_Subtype_Indication
6381                            loop
6382                               Indic := Parent (Indic);
6383                            end loop;
6384
6385                            if Present (Indic) then
6386                               Error_Msg_NE
6387                                 ("\use an access definition for" &
6388                                   " the access discriminant of&", N,
6389                                   Entity (Subtype_Mark (Indic)));
6390                            end if;
6391                         end;
6392                      end if;
6393                   end if;
6394                end if;
6395             end if;
6396
6397             if Ekind (Btyp) = E_Access_Protected_Subprogram_Type
6398               and then Is_Entity_Name (P)
6399               and then not Is_Protected_Type (Scope (Entity (P)))
6400             then
6401                Error_Msg_N ("context requires a protected subprogram", P);
6402
6403             elsif Ekind (Btyp) = E_Access_Subprogram_Type
6404               and then Ekind (Etype (N)) = E_Access_Protected_Subprogram_Type
6405             then
6406                Error_Msg_N ("context requires a non-protected subprogram", P);
6407             end if;
6408
6409             --  The context cannot be a pool-specific type, but this is a
6410             --  legality rule, not a resolution rule, so it must be checked
6411             --  separately, after possibly disambiguation (see AI-245).
6412
6413             if Ekind (Btyp) = E_Access_Type
6414               and then Attr_Id /= Attribute_Unrestricted_Access
6415             then
6416                Wrong_Type (N, Typ);
6417             end if;
6418
6419             Set_Etype (N, Typ);
6420
6421             --  Check for incorrect atomic/volatile reference (RM C.6(12))
6422
6423             if Attr_Id /= Attribute_Unrestricted_Access then
6424                if Is_Atomic_Object (P)
6425                  and then not Is_Atomic (Designated_Type (Typ))
6426                then
6427                   Error_Msg_N
6428                     ("access to atomic object cannot yield access-to-" &
6429                      "non-atomic type", P);
6430
6431                elsif Is_Volatile_Object (P)
6432                  and then not Is_Volatile (Designated_Type (Typ))
6433                then
6434                   Error_Msg_N
6435                     ("access to volatile object cannot yield access-to-" &
6436                      "non-volatile type", P);
6437                end if;
6438             end if;
6439
6440          -------------
6441          -- Address --
6442          -------------
6443
6444          --  Deal with resolving the type for Address attribute, overloading
6445          --  is not permitted here, since there is no context to resolve it.
6446
6447          when Attribute_Address | Attribute_Code_Address =>
6448
6449             --  To be safe, assume that if the address of a variable is taken,
6450             --  it may be modified via this address, so note modification.
6451
6452             if Is_Variable (P) then
6453                Note_Possible_Modification (P);
6454             end if;
6455
6456             if Nkind (P) in  N_Subexpr
6457               and then Is_Overloaded (P)
6458             then
6459                Get_First_Interp (P, Index, It);
6460                Get_Next_Interp (Index, It);
6461
6462                if Present (It.Nam) then
6463                   Error_Msg_Name_1 := Aname;
6464                   Error_Msg_N
6465                     ("prefix of % attribute cannot be overloaded", N);
6466                   return;
6467                end if;
6468             end if;
6469
6470             --  Do not permit address to be applied to entry
6471
6472             if (Is_Entity_Name (P) and then Is_Entry (Entity (P)))
6473               or else Nkind (P) = N_Entry_Call_Statement
6474
6475               or else (Nkind (P) = N_Selected_Component
6476                 and then Is_Entry (Entity (Selector_Name (P))))
6477
6478               or else (Nkind (P) = N_Indexed_Component
6479                 and then Nkind (Prefix (P)) = N_Selected_Component
6480                 and then Is_Entry (Entity (Selector_Name (Prefix (P)))))
6481             then
6482                Error_Msg_Name_1 := Aname;
6483                Error_Msg_N
6484                  ("prefix of % attribute cannot be entry", N);
6485                return;
6486             end if;
6487
6488             if not Is_Entity_Name (P)
6489                or else not Is_Overloadable (Entity (P))
6490             then
6491                if not Is_Task_Type (Etype (P))
6492                  or else Nkind (P) = N_Explicit_Dereference
6493                then
6494                   Resolve (P, Etype (P));
6495                end if;
6496             end if;
6497
6498             --  If this is the name of a derived subprogram, or that of a
6499             --  generic actual, the address is that of the original entity.
6500
6501             if Is_Entity_Name (P)
6502               and then Is_Overloadable (Entity (P))
6503               and then Present (Alias (Entity (P)))
6504             then
6505                Rewrite (P,
6506                  New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6507             end if;
6508
6509          ---------------
6510          -- AST_Entry --
6511          ---------------
6512
6513          --  Prefix of the AST_Entry attribute is an entry name which must
6514          --  not be resolved, since this is definitely not an entry call.
6515
6516          when Attribute_AST_Entry =>
6517             null;
6518
6519          ------------------
6520          -- Body_Version --
6521          ------------------
6522
6523          --  Prefix of Body_Version attribute can be a subprogram name which
6524          --  must not be resolved, since this is not a call.
6525
6526          when Attribute_Body_Version =>
6527             null;
6528
6529          ------------
6530          -- Caller --
6531          ------------
6532
6533          --  Prefix of Caller attribute is an entry name which must not
6534          --  be resolved, since this is definitely not an entry call.
6535
6536          when Attribute_Caller =>
6537             null;
6538
6539          ------------------
6540          -- Code_Address --
6541          ------------------
6542
6543          --  Shares processing with Address attribute
6544
6545          -----------
6546          -- Count --
6547          -----------
6548
6549          --  Prefix of the Count attribute is an entry name which must not
6550          --  be resolved, since this is definitely not an entry call.
6551
6552          when Attribute_Count =>
6553             null;
6554
6555          ----------------
6556          -- Elaborated --
6557          ----------------
6558
6559          --  Prefix of the Elaborated attribute is a subprogram name which
6560          --  must not be resolved, since this is definitely not a call. Note
6561          --  that it is a library unit, so it cannot be overloaded here.
6562
6563          when Attribute_Elaborated =>
6564             null;
6565
6566          --------------------
6567          -- Mechanism_Code --
6568          --------------------
6569
6570          --  Prefix of the Mechanism_Code attribute is a function name
6571          --  which must not be resolved. Should we check for overloaded ???
6572
6573          when Attribute_Mechanism_Code =>
6574             null;
6575
6576          ------------------
6577          -- Partition_ID --
6578          ------------------
6579
6580          --  Most processing is done in sem_dist, after determining the
6581          --  context type. Node is rewritten as a conversion to a runtime call.
6582
6583          when Attribute_Partition_ID =>
6584             Process_Partition_Id (N);
6585             return;
6586
6587          -----------
6588          -- Range --
6589          -----------
6590
6591          --  We replace the Range attribute node with a range expression
6592          --  whose bounds are the 'First and 'Last attributes applied to the
6593          --  same prefix. The reason that we do this transformation here
6594          --  instead of in the expander is that it simplifies other parts of
6595          --  the semantic analysis which assume that the Range has been
6596          --  replaced; thus it must be done even when in semantic-only mode
6597          --  (note that the RM specifically mentions this equivalence, we
6598          --  take care that the prefix is only evaluated once).
6599
6600          when Attribute_Range => Range_Attribute :
6601             declare
6602                LB   : Node_Id;
6603                HB   : Node_Id;
6604
6605                function Check_Discriminated_Prival
6606                  (N    : Node_Id)
6607                   return Node_Id;
6608                --  The range of a private component constrained by a
6609                --  discriminant is rewritten to make the discriminant
6610                --  explicit. This solves some complex visibility problems
6611                --  related to the use of privals.
6612
6613                function Check_Discriminated_Prival
6614                  (N    : Node_Id)
6615                   return Node_Id
6616                is
6617                begin
6618                   if Is_Entity_Name (N)
6619                     and then Ekind (Entity (N)) = E_In_Parameter
6620                     and then not Within_Init_Proc
6621                   then
6622                      return Make_Identifier (Sloc (N), Chars (Entity (N)));
6623                   else
6624                      return Duplicate_Subexpr (N);
6625                   end if;
6626                end Check_Discriminated_Prival;
6627
6628             --  Start of processing for Range_Attribute
6629
6630             begin
6631                if not Is_Entity_Name (P)
6632                  or else not Is_Type (Entity (P))
6633                then
6634                   Resolve (P, Etype (P));
6635                end if;
6636
6637                --  Check whether prefix is (renaming of) private component
6638                --  of protected type.
6639
6640                if Is_Entity_Name (P)
6641                  and then Comes_From_Source (N)
6642                  and then Is_Array_Type (Etype (P))
6643                  and then Number_Dimensions (Etype (P)) = 1
6644                  and then (Ekind (Scope (Entity (P))) = E_Protected_Type
6645                             or else
6646                            Ekind (Scope (Scope (Entity (P)))) =
6647                                                         E_Protected_Type)
6648                then
6649                   LB := Check_Discriminated_Prival (
6650                     Type_Low_Bound (Etype (First_Index (Etype (P)))));
6651
6652                   HB := Check_Discriminated_Prival (
6653                     Type_High_Bound (Etype (First_Index (Etype (P)))));
6654
6655                else
6656                   HB :=
6657                     Make_Attribute_Reference (Loc,
6658                       Prefix         => Duplicate_Subexpr (P),
6659                       Attribute_Name => Name_Last,
6660                       Expressions    => Expressions (N));
6661
6662                   LB :=
6663                     Make_Attribute_Reference (Loc,
6664                       Prefix         => P,
6665                       Attribute_Name => Name_First,
6666                       Expressions    => Expressions (N));
6667                end if;
6668
6669                --  If the original was marked as Must_Not_Freeze (see code
6670                --  in Sem_Ch3.Make_Index), then make sure the rewriting
6671                --  does not freeze either.
6672
6673                if Must_Not_Freeze (N) then
6674                   Set_Must_Not_Freeze (HB);
6675                   Set_Must_Not_Freeze (LB);
6676                   Set_Must_Not_Freeze (Prefix (HB));
6677                   Set_Must_Not_Freeze (Prefix (LB));
6678                end if;
6679
6680                if Raises_Constraint_Error (Prefix (N)) then
6681
6682                   --  Preserve Sloc of prefix in the new bounds, so that
6683                   --  the posted warning can be removed if we are within
6684                   --  unreachable code.
6685
6686                   Set_Sloc (LB, Sloc (Prefix (N)));
6687                   Set_Sloc (HB, Sloc (Prefix (N)));
6688                end if;
6689
6690                Rewrite (N, Make_Range (Loc, LB, HB));
6691                Analyze_And_Resolve (N, Typ);
6692
6693                --  Normally after resolving attribute nodes, Eval_Attribute
6694                --  is called to do any possible static evaluation of the node.
6695                --  However, here since the Range attribute has just been
6696                --  transformed into a range expression it is no longer an
6697                --  attribute node and therefore the call needs to be avoided
6698                --  and is accomplished by simply returning from the procedure.
6699
6700                return;
6701             end Range_Attribute;
6702
6703          -----------------
6704          -- UET_Address --
6705          -----------------
6706
6707          --  Prefix must not be resolved in this case, since it is not a
6708          --  real entity reference. No action of any kind is require!
6709
6710          when Attribute_UET_Address =>
6711             return;
6712
6713          ----------------------
6714          -- Unchecked_Access --
6715          ----------------------
6716
6717          --  Processing is shared with Access
6718
6719          -------------------------
6720          -- Unrestricted_Access --
6721          -------------------------
6722
6723          --  Processing is shared with Access
6724
6725          ---------
6726          -- Val --
6727          ---------
6728
6729          --  Apply range check. Note that we did not do this during the
6730          --  analysis phase, since we wanted Eval_Attribute to have a
6731          --  chance at finding an illegal out of range value.
6732
6733          when Attribute_Val =>
6734
6735             --  Note that we do our own Eval_Attribute call here rather than
6736             --  use the common one, because we need to do processing after
6737             --  the call, as per above comment.
6738
6739             Eval_Attribute (N);
6740
6741             --  Eval_Attribute may replace the node with a raise CE, or
6742             --  fold it to a constant. Obviously we only apply a scalar
6743             --  range check if this did not happen!
6744
6745             if Nkind (N) = N_Attribute_Reference
6746               and then Attribute_Name (N) = Name_Val
6747             then
6748                Apply_Scalar_Range_Check (First (Expressions (N)), Btyp);
6749             end if;
6750
6751             return;
6752
6753          -------------
6754          -- Version --
6755          -------------
6756
6757          --  Prefix of Version attribute can be a subprogram name which
6758          --  must not be resolved, since this is not a call.
6759
6760          when Attribute_Version =>
6761             null;
6762
6763          ----------------------
6764          -- Other Attributes --
6765          ----------------------
6766
6767          --  For other attributes, resolve prefix unless it is a type. If
6768          --  the attribute reference itself is a type name ('Base and 'Class)
6769          --  then this is only legal within a task or protected record.
6770
6771          when others =>
6772             if not Is_Entity_Name (P)
6773               or else not Is_Type (Entity (P))
6774             then
6775                Resolve (P, Etype (P));
6776             end if;
6777
6778             --  If the attribute reference itself is a type name ('Base,
6779             --  'Class) then this is only legal within a task or protected
6780             --  record. What is this all about ???
6781
6782             if Is_Entity_Name (N)
6783               and then Is_Type (Entity (N))
6784             then
6785                if Is_Concurrent_Type (Entity (N))
6786                  and then In_Open_Scopes (Entity (P))
6787                then
6788                   null;
6789                else
6790                   Error_Msg_N
6791                     ("invalid use of subtype name in expression or call", N);
6792                end if;
6793             end if;
6794
6795             --  For attributes whose argument may be a string, complete
6796             --  resolution of argument now. This avoids premature expansion
6797             --  (and the creation of transient scopes) before the attribute
6798             --  reference is resolved.
6799
6800             case Attr_Id is
6801                when Attribute_Value =>
6802                   Resolve (First (Expressions (N)), Standard_String);
6803
6804                when Attribute_Wide_Value =>
6805                   Resolve (First (Expressions (N)), Standard_Wide_String);
6806
6807                when others => null;
6808             end case;
6809       end case;
6810
6811       --  Normally the Freezing is done by Resolve but sometimes the Prefix
6812       --  is not resolved, in which case the freezing must be done now.
6813
6814       Freeze_Expression (P);
6815
6816       --  Finally perform static evaluation on the attribute reference
6817
6818       Eval_Attribute (N);
6819
6820    end Resolve_Attribute;
6821
6822 end Sem_Attr;