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 --          Copyright (C) 1992-2007, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
  27
  28 with Atree;    use Atree;
  29 with Casing;   use Casing;
  30 with Checks;   use Checks;
  31 with Einfo;    use Einfo;
  32 with Errout;   use Errout;
  33 with Eval_Fat;
  34 with Exp_Dist; use Exp_Dist;
  35 with Exp_Util; use Exp_Util;
  36 with Expander; use Expander;
  37 with Freeze;   use Freeze;
  38 with Lib;      use Lib;
  39 with Lib.Xref; use Lib.Xref;
  40 with Nlists;   use Nlists;
  41 with Nmake;    use Nmake;
  42 with Opt;      use Opt;
  43 with Restrict; use Restrict;
  44 with Rident;   use Rident;
  45 with Rtsfind;  use Rtsfind;
  46 with Sdefault; use Sdefault;
  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_Dist; use Sem_Dist;
  52 with Sem_Eval; use Sem_Eval;
  53 with Sem_Res;  use Sem_Res;
  54 with Sem_Type; use Sem_Type;
  55 with Sem_Util; use Sem_Util;
  56 with Stand;    use Stand;
  57 with Sinfo;    use Sinfo;
  58 with Sinput;   use Sinput;
  59 with Stringt;  use Stringt;
  60 with Style;
  61 with Stylesw;  use Stylesw;
  62 with Targparm; use Targparm;
  63 with Ttypes;   use Ttypes;
  64 with Ttypef;   use Ttypef;
  65 with Tbuild;   use Tbuild;
  66 with Uintp;    use Uintp;
  67 with Urealp;   use Urealp;
  68
  69 package body Sem_Attr is
  70
  71    True_Value  : constant Uint := Uint_1;
  72    False_Value : constant Uint := Uint_0;
  73    --  Synonyms to be used when these constants are used as Boolean values
  74
  75    Bad_Attribute : exception;
  76    --  Exception raised if an error is detected during attribute processing,
  77    --  used so that we can abandon the processing so we don't run into
  78    --  trouble with cascaded errors.
  79
  80    --  The following array is the list of attributes defined in the Ada 83 RM
  81    --  that are not included in Ada 95, but still get recognized in GNAT.
  82
  83    Attribute_83 : constant Attribute_Class_Array := Attribute_Class_Array'(
  84       Attribute_Address           |
  85       Attribute_Aft               |
  86       Attribute_Alignment         |
  87       Attribute_Base              |
  88       Attribute_Callable          |
  89       Attribute_Constrained       |
  90       Attribute_Count             |
  91       Attribute_Delta             |
  92       Attribute_Digits            |
  93       Attribute_Emax              |
  94       Attribute_Epsilon           |
  95       Attribute_First             |
  96       Attribute_First_Bit         |
  97       Attribute_Fore              |
  98       Attribute_Image             |
  99       Attribute_Large             |
 100       Attribute_Last              |
 101       Attribute_Last_Bit          |
 102       Attribute_Leading_Part      |
 103       Attribute_Length            |
 104       Attribute_Machine_Emax      |
 105       Attribute_Machine_Emin      |
 106       Attribute_Machine_Mantissa  |
 107       Attribute_Machine_Overflows |
 108       Attribute_Machine_Radix     |
 109       Attribute_Machine_Rounds    |
 110       Attribute_Mantissa          |
 111       Attribute_Pos               |
 112       Attribute_Position          |
 113       Attribute_Pred              |
 114       Attribute_Range             |
 115       Attribute_Safe_Emax         |
 116       Attribute_Safe_Large        |
 117       Attribute_Safe_Small        |
 118       Attribute_Size              |
 119       Attribute_Small             |
 120       Attribute_Storage_Size      |
 121       Attribute_Succ              |
 122       Attribute_Terminated        |
 123       Attribute_Val               |
 124       Attribute_Value             |
 125       Attribute_Width             => True,
 126       others                      => False);
 127
 128    --  The following array is the list of attributes defined in the Ada 2005
 129    --  RM which are not defined in Ada 95. These are recognized in Ada 95 mode,
 130    --  but in Ada 95 they are considered to be implementation defined.
 131
 132    Attribute_05 : constant Attribute_Class_Array := Attribute_Class_Array'(
 133       Attribute_Machine_Rounding  |
 134       Attribute_Priority          |
 135       Attribute_Stream_Size       |
 136       Attribute_Wide_Wide_Width   => True,
 137       others                      => False);
 138
 139    --  The following array contains all attributes that imply a modification
 140    --  of their prefixes or result in an access value. Such prefixes can be
 141    --  considered as lvalues.
 142
 143    Attribute_Name_Implies_Lvalue_Prefix : constant Attribute_Class_Array :=
 144       Attribute_Class_Array'(
 145       Attribute_Access              |
 146       Attribute_Address             |
 147       Attribute_Input               |
 148       Attribute_Read                |
 149       Attribute_Unchecked_Access    |
 150       Attribute_Unrestricted_Access => True,
 151       others                        => False);
 152
 153    -----------------------
 154    -- Local_Subprograms --
 155    -----------------------
 156
 157    procedure Eval_Attribute (N : Node_Id);
 158    --  Performs compile time evaluation of attributes where possible, leaving
 159    --  the Is_Static_Expression/Raises_Constraint_Error flags appropriately
 160    --  set, and replacing the node with a literal node if the value can be
 161    --  computed at compile time. All static attribute references are folded,
 162    --  as well as a number of cases of non-static attributes that can always
 163    --  be computed at compile time (e.g. floating-point model attributes that
 164    --  are applied to non-static subtypes). Of course in such cases, the
 165    --  Is_Static_Expression flag will not be set on the resulting literal.
 166    --  Note that the only required action of this procedure is to catch the
 167    --  static expression cases as described in the RM. Folding of other cases
 168    --  is done where convenient, but some additional non-static folding is in
 169    --  N_Expand_Attribute_Reference in cases where this is more convenient.
 170
 171    function Is_Anonymous_Tagged_Base
 172      (Anon : Entity_Id;
 173       Typ  : Entity_Id)
 174       return Boolean;
 175    --  For derived tagged types that constrain parent discriminants we build
 176    --  an anonymous unconstrained base type. We need to recognize the relation
 177    --  between the two when analyzing an access attribute for a constrained
 178    --  component, before the full declaration for Typ has been analyzed, and
 179    --  where therefore the prefix of the attribute does not match the enclosing
 180    --  scope.
 181
 182    -----------------------
 183    -- Analyze_Attribute --
 184    -----------------------
 185
 186    procedure Analyze_Attribute (N : Node_Id) is
 187       Loc     : constant Source_Ptr   := Sloc (N);
 188       Aname   : constant Name_Id      := Attribute_Name (N);
 189       P       : constant Node_Id      := Prefix (N);
 190       Exprs   : constant List_Id      := Expressions (N);
 191       Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname);
 192       E1      : Node_Id;
 193       E2      : Node_Id;
 194
 195       P_Type : Entity_Id;
 196       --  Type of prefix after analysis
 197
 198       P_Base_Type : Entity_Id;
 199       --  Base type of prefix after analysis
 200
 201       -----------------------
 202       -- Local Subprograms --
 203       -----------------------
 204
 205       procedure Analyze_Access_Attribute;
 206       --  Used for Access, Unchecked_Access, Unrestricted_Access attributes.
 207       --  Internally, Id distinguishes which of the three cases is involved.
 208
 209       procedure Check_Array_Or_Scalar_Type;
 210       --  Common procedure used by First, Last, Range attribute to check
 211       --  that the prefix is a constrained array or scalar type, or a name
 212       --  of an array object, and that an argument appears only if appropriate
 213       --  (i.e. only in the array case).
 214
 215       procedure Check_Array_Type;
 216       --  Common semantic checks for all array attributes. Checks that the
 217       --  prefix is a constrained array type or the name of an array object.
 218       --  The error message for non-arrays is specialized appropriately.
 219
 220       procedure Check_Asm_Attribute;
 221       --  Common semantic checks for Asm_Input and Asm_Output attributes
 222
 223       procedure Check_Component;
 224       --  Common processing for Bit_Position, First_Bit, Last_Bit, and
 225       --  Position. Checks prefix is an appropriate selected component.
 226
 227       procedure Check_Decimal_Fixed_Point_Type;
 228       --  Check that prefix of attribute N is a decimal fixed-point type
 229
 230       procedure Check_Dereference;
 231       --  If the prefix of attribute is an object of an access type, then
 232       --  introduce an explicit deference, and adjust P_Type accordingly.
 233
 234       procedure Check_Discrete_Type;
 235       --  Verify that prefix of attribute N is a discrete type
 236
 237       procedure Check_E0;
 238       --  Check that no attribute arguments are present
 239
 240       procedure Check_Either_E0_Or_E1;
 241       --  Check that there are zero or one attribute arguments present
 242
 243       procedure Check_E1;
 244       --  Check that exactly one attribute argument is present
 245
 246       procedure Check_E2;
 247       --  Check that two attribute arguments are present
 248
 249       procedure Check_Enum_Image;
 250       --  If the prefix type is an enumeration type, set all its literals
 251       --  as referenced, since the image function could possibly end up
 252       --  referencing any of the literals indirectly.
 253
 254       procedure Check_Fixed_Point_Type;
 255       --  Verify that prefix of attribute N is a fixed type
 256
 257       procedure Check_Fixed_Point_Type_0;
 258       --  Verify that prefix of attribute N is a fixed type and that
 259       --  no attribute expressions are present
 260
 261       procedure Check_Floating_Point_Type;
 262       --  Verify that prefix of attribute N is a float type
 263
 264       procedure Check_Floating_Point_Type_0;
 265       --  Verify that prefix of attribute N is a float type and that
 266       --  no attribute expressions are present
 267
 268       procedure Check_Floating_Point_Type_1;
 269       --  Verify that prefix of attribute N is a float type and that
 270       --  exactly one attribute expression is present
 271
 272       procedure Check_Floating_Point_Type_2;
 273       --  Verify that prefix of attribute N is a float type and that
 274       --  two attribute expressions are present
 275
 276       procedure Legal_Formal_Attribute;
 277       --  Common processing for attributes Definite, Has_Access_Values,
 278       --  and Has_Discriminants
 279
 280       procedure Check_Integer_Type;
 281       --  Verify that prefix of attribute N is an integer type
 282
 283       procedure Check_Library_Unit;
 284       --  Verify that prefix of attribute N is a library unit
 285
 286       procedure Check_Modular_Integer_Type;
 287       --  Verify that prefix of attribute N is a modular integer type
 288
 289       procedure Check_Not_Incomplete_Type;
 290       --  Check that P (the prefix of the attribute) is not an incomplete
 291       --  type or a private type for which no full view has been given.
 292
 293       procedure Check_Object_Reference (P : Node_Id);
 294       --  Check that P (the prefix of the attribute) is an object reference
 295
 296       procedure Check_Program_Unit;
 297       --  Verify that prefix of attribute N is a program unit
 298
 299       procedure Check_Real_Type;
 300       --  Verify that prefix of attribute N is fixed or float type
 301
 302       procedure Check_Scalar_Type;
 303       --  Verify that prefix of attribute N is a scalar type
 304
 305       procedure Check_Standard_Prefix;
 306       --  Verify that prefix of attribute N is package Standard
 307
 308       procedure Check_Stream_Attribute (Nam : TSS_Name_Type);
 309       --  Validity checking for stream attribute. Nam is the TSS name of the
 310       --  corresponding possible defined attribute function (e.g. for the
 311       --  Read attribute, Nam will be TSS_Stream_Read).
 312
 313       procedure Check_Task_Prefix;
 314       --  Verify that prefix of attribute N is a task or task type
 315
 316       procedure Check_Type;
 317       --  Verify that the prefix of attribute N is a type
 318
 319       procedure Check_Unit_Name (Nod : Node_Id);
 320       --  Check that Nod is of the form of a library unit name, i.e that
 321       --  it is an identifier, or a selected component whose prefix is
 322       --  itself of the form of a library unit name. Note that this is
 323       --  quite different from Check_Program_Unit, since it only checks
 324       --  the syntactic form of the name, not the semantic identity. This
 325       --  is because it is used with attributes (Elab_Body, Elab_Spec, and
 326       --  UET_Address) which can refer to non-visible unit.
 327
 328       procedure Error_Attr (Msg : String; Error_Node : Node_Id);
 329       pragma No_Return (Error_Attr);
 330       procedure Error_Attr;
 331       pragma No_Return (Error_Attr);
 332       --  Posts error using Error_Msg_N at given node, sets type of attribute
 333       --  node to Any_Type, and then raises Bad_Attribute to avoid any further
 334       --  semantic processing. The message typically contains a % insertion
 335       --  character which is replaced by the attribute name. The call with
 336       --  no arguments is used when the caller has already generated the
 337       --  required error messages.
 338
 339       procedure Error_Attr_P (Msg : String);
 340       pragma No_Return (Error_Attr);
 341       --  Like Error_Attr, but error is posted at the start of the prefix
 342
 343       procedure Standard_Attribute (Val : Int);
 344       --  Used to process attributes whose prefix is package Standard which
 345       --  yield values of type Universal_Integer. The attribute reference
 346       --  node is rewritten with an integer literal of the given value.
 347
 348       procedure Unexpected_Argument (En : Node_Id);
 349       --  Signal unexpected attribute argument (En is the argument)
 350
 351       procedure Validate_Non_Static_Attribute_Function_Call;
 352       --  Called when processing an attribute that is a function call to a
 353       --  non-static function, i.e. an attribute function that either takes
 354       --  non-scalar arguments or returns a non-scalar result. Verifies that
 355       --  such a call does not appear in a preelaborable context.
 356
 357       ------------------------------
 358       -- Analyze_Access_Attribute --
 359       ------------------------------
 360
 361       procedure Analyze_Access_Attribute is
 362          Acc_Type : Entity_Id;
 363
 364          Scop : Entity_Id;
 365          Typ  : Entity_Id;
 366
 367          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id;
 368          --  Build an access-to-object type whose designated type is DT,
 369          --  and whose Ekind is appropriate to the attribute type. The
 370          --  type that is constructed is returned as the result.
 371
 372          procedure Build_Access_Subprogram_Type (P : Node_Id);
 373          --  Build an access to subprogram whose designated type is
 374          --  the type of the prefix. If prefix is overloaded, so it the
 375          --  node itself. The result is stored in Acc_Type.
 376
 377          function OK_Self_Reference return Boolean;
 378          --  An access reference whose prefix is a type can legally appear
 379          --  within an aggregate, where it is obtained by expansion of
 380          --  a defaulted aggregate. The enclosing aggregate that contains
 381          --  the self-referenced is flagged so that the self-reference can
 382          --  be expanded into a reference to the target object (see exp_aggr).
 383
 384          ------------------------------
 385          -- Build_Access_Object_Type --
 386          ------------------------------
 387
 388          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id is
 389             Typ : constant Entity_Id :=
 390                     New_Internal_Entity
 391                       (E_Access_Attribute_Type, Current_Scope, Loc, 'A');
 392          begin
 393             Set_Etype                     (Typ, Typ);
 394             Init_Size_Align               (Typ);
 395             Set_Is_Itype                  (Typ);
 396             Set_Associated_Node_For_Itype (Typ, N);
 397             Set_Directly_Designated_Type  (Typ, DT);
 398             return Typ;
 399          end Build_Access_Object_Type;
 400
 401          ----------------------------------
 402          -- Build_Access_Subprogram_Type --
 403          ----------------------------------
 404
 405          procedure Build_Access_Subprogram_Type (P : Node_Id) is
 406             Index : Interp_Index;
 407             It    : Interp;
 408
 409             procedure Check_Local_Access (E : Entity_Id);
 410             --  Deal with possible access to local subprogram. If we have such
 411             --  an access, we set a flag to kill all tracked values on any call
 412             --  because this access value may be passed around, and any called
 413             --  code might use it to access a local procedure which clobbers a
 414             --  tracked value.
 415
 416             function Get_Kind (E : Entity_Id) return Entity_Kind;
 417             --  Distinguish between access to regular/protected subprograms
 418
 419             ------------------------
 420             -- Check_Local_Access --
 421             ------------------------
 422
 423             procedure Check_Local_Access (E : Entity_Id) is
 424             begin
 425                if not Is_Library_Level_Entity (E) then
 426                   Set_Suppress_Value_Tracking_On_Call (Current_Scope);
 427                end if;
 428             end Check_Local_Access;
 429
 430             --------------
 431             -- Get_Kind --
 432             --------------
 433
 434             function Get_Kind (E : Entity_Id) return Entity_Kind is
 435             begin
 436                if Convention (E) = Convention_Protected then
 437                   return E_Access_Protected_Subprogram_Type;
 438                else
 439                   return E_Access_Subprogram_Type;
 440                end if;
 441             end Get_Kind;
 442
 443          --  Start of processing for Build_Access_Subprogram_Type
 444
 445          begin
 446             --  In the case of an access to subprogram, use the name of the
 447             --  subprogram itself as the designated type. Type-checking in
 448             --  this case compares the signatures of the designated types.
 449
 450             Set_Etype (N, Any_Type);
 451
 452             if not Is_Overloaded (P) then
 453                Check_Local_Access (Entity (P));
 454
 455                if not Is_Intrinsic_Subprogram (Entity (P)) then
 456                   Acc_Type :=
 457                     New_Internal_Entity
 458                       (Get_Kind (Entity (P)), Current_Scope, Loc, 'A');
 459                   Set_Etype (Acc_Type, Acc_Type);
 460                   Set_Directly_Designated_Type (Acc_Type, Entity (P));
 461                   Set_Etype (N, Acc_Type);
 462                end if;
 463
 464             else
 465                Get_First_Interp (P, Index, It);
 466                while Present (It.Nam) loop
 467                   Check_Local_Access (It.Nam);
 468
 469                   if not Is_Intrinsic_Subprogram (It.Nam) then
 470                      Acc_Type :=
 471                        New_Internal_Entity
 472                          (Get_Kind (It.Nam), Current_Scope, Loc, 'A');
 473                      Set_Etype (Acc_Type, Acc_Type);
 474                      Set_Directly_Designated_Type (Acc_Type, It.Nam);
 475                      Add_One_Interp (N, Acc_Type, Acc_Type);
 476                   end if;
 477
 478                   Get_Next_Interp (Index, It);
 479                end loop;
 480             end if;
 481
 482             --  Cannot be applied to intrinsic. Looking at the tests above,
 483             --  the only way Etype (N) can still be set to Any_Type is if
 484             --  Is_Intrinsic_Subprogram was True for some referenced entity.
 485
 486             if Etype (N) = Any_Type then
 487                Error_Attr_P ("prefix of % attribute cannot be intrinsic");
 488             end if;
 489          end Build_Access_Subprogram_Type;
 490
 491          ----------------------
 492          -- OK_Self_Reference --
 493          ----------------------
 494
 495          function OK_Self_Reference return Boolean is
 496             Par : Node_Id;
 497
 498          begin
 499             Par := Parent (N);
 500             while Present (Par)
 501               and then
 502                (Nkind (Par) = N_Component_Association
 503                  or else Nkind (Par) in N_Subexpr)
 504             loop
 505                if Nkind (Par) = N_Aggregate
 506                  or else Nkind (Par) = N_Extension_Aggregate
 507                then
 508                   if Etype (Par) = Typ then
 509                      Set_Has_Self_Reference (Par);
 510                      return True;
 511                   end if;
 512                end if;
 513
 514                Par := Parent (Par);
 515             end loop;
 516
 517             --  No enclosing aggregate, or not a self-reference
 518
 519             return False;
 520          end OK_Self_Reference;
 521
 522       --  Start of processing for Analyze_Access_Attribute
 523
 524       begin
 525          Check_E0;
 526
 527          if Nkind (P) = N_Character_Literal then
 528             Error_Attr_P
 529               ("prefix of % attribute cannot be enumeration literal");
 530          end if;
 531
 532          --  Case of access to subprogram
 533
 534          if Is_Entity_Name (P)
 535            and then Is_Overloadable (Entity (P))
 536          then
 537             if Has_Pragma_Inline_Always (Entity (P)) then
 538                Error_Attr_P
 539                  ("prefix of % attribute cannot be Inline_Always subprogram");
 540             end if;
 541
 542             if Aname = Name_Unchecked_Access then
 543                Error_Attr ("attribute% cannot be applied to a subprogram", P);
 544             end if;
 545
 546             --  Build the appropriate subprogram type
 547
 548             Build_Access_Subprogram_Type (P);
 549
 550             --  For unrestricted access, kill current values, since this
 551             --  attribute allows a reference to a local subprogram that
 552             --  could modify local variables to be passed out of scope
 553
 554             if Aname = Name_Unrestricted_Access then
 555                Kill_Current_Values;
 556             end if;
 557
 558             return;
 559
 560          --  Component is an operation of a protected type
 561
 562          elsif Nkind (P) = N_Selected_Component
 563            and then Is_Overloadable (Entity (Selector_Name (P)))
 564          then
 565             if Ekind (Entity (Selector_Name (P))) = E_Entry then
 566                Error_Attr_P ("prefix of % attribute must be subprogram");
 567             end if;
 568
 569             Build_Access_Subprogram_Type (Selector_Name (P));
 570             return;
 571          end if;
 572
 573          --  Deal with incorrect reference to a type, but note that some
 574          --  accesses are allowed: references to the current type instance,
 575          --  or in Ada 2005 self-referential pointer in a default-initialized
 576          --  aggregate.
 577
 578          if Is_Entity_Name (P) then
 579             Typ := Entity (P);
 580
 581             --  The reference may appear in an aggregate that has been expanded
 582             --  into a loop. Locate scope of type definition, if any.
 583
 584             Scop := Current_Scope;
 585             while Ekind (Scop) = E_Loop loop
 586                Scop := Scope (Scop);
 587             end loop;
 588
 589             if Is_Type (Typ) then
 590
 591                --  OK if we are within the scope of a limited type
 592                --  let's mark the component as having per object constraint
 593
 594                if Is_Anonymous_Tagged_Base (Scop, Typ) then
 595                   Typ := Scop;
 596                   Set_Entity (P, Typ);
 597                   Set_Etype  (P, Typ);
 598                end if;
 599
 600                if Typ = Scop then
 601                   declare
 602                      Q : Node_Id := Parent (N);
 603
 604                   begin
 605                      while Present (Q)
 606                        and then Nkind (Q) /= N_Component_Declaration
 607                      loop
 608                         Q := Parent (Q);
 609                      end loop;
 610
 611                      if Present (Q) then
 612                         Set_Has_Per_Object_Constraint (
 613                           Defining_Identifier (Q), True);
 614                      end if;
 615                   end;
 616
 617                   if Nkind (P) = N_Expanded_Name then
 618                      Error_Msg_F
 619                        ("current instance prefix must be a direct name", P);
 620                   end if;
 621
 622                   --  If a current instance attribute appears within a
 623                   --  a component constraint it must appear alone; other
 624                   --  contexts (default expressions, within a task body)
 625                   --  are not subject to this restriction.
 626
 627                   if not In_Default_Expression
 628                     and then not Has_Completion (Scop)
 629                     and then
 630                       Nkind (Parent (N)) /= N_Discriminant_Association
 631                     and then
 632                       Nkind (Parent (N)) /= N_Index_Or_Discriminant_Constraint
 633                   then
 634                      Error_Msg_N
 635                        ("current instance attribute must appear alone", N);
 636                   end if;
 637
 638                --  OK if we are in initialization procedure for the type
 639                --  in question, in which case the reference to the type
 640                --  is rewritten as a reference to the current object.
 641
 642                elsif Ekind (Scop) = E_Procedure
 643                  and then Is_Init_Proc (Scop)
 644                  and then Etype (First_Formal (Scop)) = Typ
 645                then
 646                   Rewrite (N,
 647                     Make_Attribute_Reference (Loc,
 648                       Prefix         => Make_Identifier (Loc, Name_uInit),
 649                       Attribute_Name => Name_Unrestricted_Access));
 650                   Analyze (N);
 651                   return;
 652
 653                --  OK if a task type, this test needs sharpening up ???
 654
 655                elsif Is_Task_Type (Typ) then
 656                   null;
 657
 658                --  OK if self-reference in an aggregate in Ada 2005, and
 659                --  the reference comes from a copied default expression.
 660
 661                --  Note that we check legality of self-reference even if the
 662                --  expression comes from source, e.g. when a single component
 663                --  association in an aggregate has a box association.
 664
 665                elsif Ada_Version >= Ada_05
 666                  and then OK_Self_Reference
 667                then
 668                   null;
 669
 670                --  Otherwise we have an error case
 671
 672                else
 673                   Error_Attr ("% attribute cannot be applied to type", P);
 674                   return;
 675                end if;
 676             end if;
 677          end if;
 678
 679          --  If we fall through, we have a normal access to object case.
 680          --  Unrestricted_Access is legal wherever an allocator would be
 681          --  legal, so its Etype is set to E_Allocator. The expected type
 682          --  of the other attributes is a general access type, and therefore
 683          --  we label them with E_Access_Attribute_Type.
 684
 685          if not Is_Overloaded (P) then
 686             Acc_Type := Build_Access_Object_Type (P_Type);
 687             Set_Etype (N, Acc_Type);
 688          else
 689             declare
 690                Index : Interp_Index;
 691                It    : Interp;
 692             begin
 693                Set_Etype (N, Any_Type);
 694                Get_First_Interp (P, Index, It);
 695                while Present (It.Typ) loop
 696                   Acc_Type := Build_Access_Object_Type (It.Typ);
 697                   Add_One_Interp (N, Acc_Type, Acc_Type);
 698                   Get_Next_Interp (Index, It);
 699                end loop;
 700             end;
 701          end if;
 702
 703          --  Special cases when we can find a prefix that is an entity name
 704
 705          declare
 706             PP  : Node_Id;
 707             Ent : Entity_Id;
 708
 709          begin
 710             PP := P;
 711             loop
 712                if Is_Entity_Name (PP) then
 713                   Ent := Entity (PP);
 714
 715                   --  If we have an access to an object, and the attribute
 716                   --  comes from source, then set the object as potentially
 717                   --  source modified. We do this because the resulting access
 718                   --  pointer can be used to modify the variable, and we might
 719                   --  not detect this, leading to some junk warnings.
 720
 721                   Set_Never_Set_In_Source (Ent, False);
 722
 723                   --  Mark entity as address taken, and kill current values
 724
 725                   Set_Address_Taken (Ent);
 726                   Kill_Current_Values (Ent);
 727                   exit;
 728
 729                elsif Nkind (PP) = N_Selected_Component
 730                  or else Nkind (PP) = N_Indexed_Component
 731                then
 732                   PP := Prefix (PP);
 733
 734                else
 735                   exit;
 736                end if;
 737             end loop;
 738          end;
 739
 740          --  Check for aliased view unless unrestricted case. We allow a
 741          --  nonaliased prefix when within an instance because the prefix may
 742          --  have been a tagged formal object, which is defined to be aliased
 743          --  even when the actual might not be (other instance cases will have
 744          --  been caught in the generic). Similarly, within an inlined body we
 745          --  know that the attribute is legal in the original subprogram, and
 746          --  therefore legal in the expansion.
 747
 748          if Aname /= Name_Unrestricted_Access
 749            and then not Is_Aliased_View (P)
 750            and then not In_Instance
 751            and then not In_Inlined_Body
 752          then
 753             Error_Attr_P ("prefix of % attribute must be aliased");
 754          end if;
 755       end Analyze_Access_Attribute;
 756
 757       --------------------------------
 758       -- Check_Array_Or_Scalar_Type --
 759       --------------------------------
 760
 761       procedure Check_Array_Or_Scalar_Type is
 762          Index : Entity_Id;
 763
 764          D : Int;
 765          --  Dimension number for array attributes
 766
 767       begin
 768          --  Case of string literal or string literal subtype. These cases
 769          --  cannot arise from legal Ada code, but the expander is allowed
 770          --  to generate them. They require special handling because string
 771          --  literal subtypes do not have standard bounds (the whole idea
 772          --  of these subtypes is to avoid having to generate the bounds)
 773
 774          if Ekind (P_Type) = E_String_Literal_Subtype then
 775             Set_Etype (N, Etype (First_Index (P_Base_Type)));
 776             return;
 777
 778          --  Scalar types
 779
 780          elsif Is_Scalar_Type (P_Type) then
 781             Check_Type;
 782
 783             if Present (E1) then
 784                Error_Attr ("invalid argument in % attribute", E1);
 785             else
 786                Set_Etype (N, P_Base_Type);
 787                return;
 788             end if;
 789
 790          --  The following is a special test to allow 'First to apply to
 791          --  private scalar types if the attribute comes from generated
 792          --  code. This occurs in the case of Normalize_Scalars code.
 793
 794          elsif Is_Private_Type (P_Type)
 795            and then Present (Full_View (P_Type))
 796            and then Is_Scalar_Type (Full_View (P_Type))
 797            and then not Comes_From_Source (N)
 798          then
 799             Set_Etype (N, Implementation_Base_Type (P_Type));
 800
 801          --  Array types other than string literal subtypes handled above
 802
 803          else
 804             Check_Array_Type;
 805
 806             --  We know prefix is an array type, or the name of an array
 807             --  object, and that the expression, if present, is static
 808             --  and within the range of the dimensions of the type.
 809
 810             pragma Assert (Is_Array_Type (P_Type));
 811             Index := First_Index (P_Base_Type);
 812
 813             if No (E1) then
 814
 815                --  First dimension assumed
 816
 817                Set_Etype (N, Base_Type (Etype (Index)));
 818
 819             else
 820                D := UI_To_Int (Intval (E1));
 821
 822                for J in 1 .. D - 1 loop
 823                   Next_Index (Index);
 824                end loop;
 825
 826                Set_Etype (N, Base_Type (Etype (Index)));
 827                Set_Etype (E1, Standard_Integer);
 828             end if;
 829          end if;
 830       end Check_Array_Or_Scalar_Type;
 831
 832       ----------------------
 833       -- Check_Array_Type --
 834       ----------------------
 835
 836       procedure Check_Array_Type is
 837          D : Int;
 838          --  Dimension number for array attributes
 839
 840       begin
 841          --  If the type is a string literal type, then this must be generated
 842          --  internally, and no further check is required on its legality.
 843
 844          if Ekind (P_Type) = E_String_Literal_Subtype then
 845             return;
 846
 847          --  If the type is a composite, it is an illegal aggregate, no point
 848          --  in going on.
 849
 850          elsif P_Type = Any_Composite then
 851             raise Bad_Attribute;
 852          end if;
 853
 854          --  Normal case of array type or subtype
 855
 856          Check_Either_E0_Or_E1;
 857          Check_Dereference;
 858
 859          if Is_Array_Type (P_Type) then
 860             if not Is_Constrained (P_Type)
 861               and then Is_Entity_Name (P)
 862               and then Is_Type (Entity (P))
 863             then
 864                --  Note: we do not call Error_Attr here, since we prefer to
 865                --  continue, using the relevant index type of the array,
 866                --  even though it is unconstrained. This gives better error
 867                --  recovery behavior.
 868
 869                Error_Msg_Name_1 := Aname;
 870                Error_Msg_F
 871                  ("prefix for % attribute must be constrained array", P);
 872             end if;
 873
 874             D := Number_Dimensions (P_Type);
 875
 876          else
 877             if Is_Private_Type (P_Type) then
 878                Error_Attr_P ("prefix for % attribute may not be private type");
 879
 880             elsif Is_Access_Type (P_Type)
 881               and then Is_Array_Type (Designated_Type (P_Type))
 882               and then Is_Entity_Name (P)
 883               and then Is_Type (Entity (P))
 884             then
 885                Error_Attr_P ("prefix of % attribute cannot be access type");
 886
 887             elsif Attr_Id = Attribute_First
 888                     or else
 889                   Attr_Id = Attribute_Last
 890             then
 891                Error_Attr ("invalid prefix for % attribute", P);
 892
 893             else
 894                Error_Attr_P ("prefix for % attribute must be array");
 895             end if;
 896          end if;
 897
 898          if Present (E1) then
 899             Resolve (E1, Any_Integer);
 900             Set_Etype (E1, Standard_Integer);
 901
 902             if not Is_Static_Expression (E1)
 903               or else Raises_Constraint_Error (E1)
 904             then
 905                Flag_Non_Static_Expr
 906                  ("expression for dimension must be static!", E1);
 907                Error_Attr;
 908
 909             elsif  UI_To_Int (Expr_Value (E1)) > D
 910               or else UI_To_Int (Expr_Value (E1)) < 1
 911             then
 912                Error_Attr ("invalid dimension number for array type", E1);
 913             end if;
 914          end if;
 915
 916          if (Style_Check and Style_Check_Array_Attribute_Index)
 917            and then Comes_From_Source (N)
 918          then
 919             Style.Check_Array_Attribute_Index (N, E1, D);
 920          end if;
 921       end Check_Array_Type;
 922
 923       -------------------------
 924       -- Check_Asm_Attribute --
 925       -------------------------
 926
 927       procedure Check_Asm_Attribute is
 928       begin
 929          Check_Type;
 930          Check_E2;
 931
 932          --  Check first argument is static string expression
 933
 934          Analyze_And_Resolve (E1, Standard_String);
 935
 936          if Etype (E1) = Any_Type then
 937             return;
 938
 939          elsif not Is_OK_Static_Expression (E1) then
 940             Flag_Non_Static_Expr
 941               ("constraint argument must be static string expression!", E1);
 942             Error_Attr;
 943          end if;
 944
 945          --  Check second argument is right type
 946
 947          Analyze_And_Resolve (E2, Entity (P));
 948
 949          --  Note: that is all we need to do, we don't need to check
 950          --  that it appears in a correct context. The Ada type system
 951          --  will do that for us.
 952
 953       end Check_Asm_Attribute;
 954
 955       ---------------------
 956       -- Check_Component --
 957       ---------------------
 958
 959       procedure Check_Component is
 960       begin
 961          Check_E0;
 962
 963          if Nkind (P) /= N_Selected_Component
 964            or else
 965              (Ekind (Entity (Selector_Name (P))) /= E_Component
 966                and then
 967               Ekind (Entity (Selector_Name (P))) /= E_Discriminant)
 968          then
 969             Error_Attr_P ("prefix for % attribute must be selected component");
 970          end if;
 971       end Check_Component;
 972
 973       ------------------------------------
 974       -- Check_Decimal_Fixed_Point_Type --
 975       ------------------------------------
 976
 977       procedure Check_Decimal_Fixed_Point_Type is
 978       begin
 979          Check_Type;
 980
 981          if not Is_Decimal_Fixed_Point_Type (P_Type) then
 982             Error_Attr_P ("prefix of % attribute must be decimal type");
 983          end if;
 984       end Check_Decimal_Fixed_Point_Type;
 985
 986       -----------------------
 987       -- Check_Dereference --
 988       -----------------------
 989
 990       procedure Check_Dereference is
 991       begin
 992
 993          --  Case of a subtype mark
 994
 995          if Is_Entity_Name (P)
 996            and then Is_Type (Entity (P))
 997          then
 998             return;
 999          end if;
1000
1001          --  Case of an expression
1002
1003          Resolve (P);
1004
1005          if Is_Access_Type (P_Type) then
1006
1007             --  If there is an implicit dereference, then we must freeze
1008             --  the designated type of the access type, since the type of
1009             --  the referenced array is this type (see AI95-00106).
1010
1011             Freeze_Before (N, Designated_Type (P_Type));
1012
1013             Rewrite (P,
1014               Make_Explicit_Dereference (Sloc (P),
1015                 Prefix => Relocate_Node (P)));
1016
1017             Analyze_And_Resolve (P);
1018             P_Type := Etype (P);
1019
1020             if P_Type = Any_Type then
1021                raise Bad_Attribute;
1022             end if;
1023
1024             P_Base_Type := Base_Type (P_Type);
1025          end if;
1026       end Check_Dereference;
1027
1028       -------------------------
1029       -- Check_Discrete_Type --
1030       -------------------------
1031
1032       procedure Check_Discrete_Type is
1033       begin
1034          Check_Type;
1035
1036          if not Is_Discrete_Type (P_Type) then
1037             Error_Attr_P ("prefix of % attribute must be discrete type");
1038          end if;
1039       end Check_Discrete_Type;
1040
1041       --------------
1042       -- Check_E0 --
1043       --------------
1044
1045       procedure Check_E0 is
1046       begin
1047          if Present (E1) then
1048             Unexpected_Argument (E1);
1049          end if;
1050       end Check_E0;
1051
1052       --------------
1053       -- Check_E1 --
1054       --------------
1055
1056       procedure Check_E1 is
1057       begin
1058          Check_Either_E0_Or_E1;
1059
1060          if No (E1) then
1061
1062             --  Special-case attributes that are functions and that appear as
1063             --  the prefix of another attribute. Error is posted on parent.
1064
1065             if Nkind (Parent (N)) = N_Attribute_Reference
1066               and then (Attribute_Name (Parent (N)) = Name_Address
1067                           or else
1068                         Attribute_Name (Parent (N)) = Name_Code_Address
1069                           or else
1070                         Attribute_Name (Parent (N)) = Name_Access)
1071             then
1072                Error_Msg_Name_1 := Attribute_Name (Parent (N));
1073                Error_Msg_N ("illegal prefix for % attribute", Parent (N));
1074                Set_Etype (Parent (N), Any_Type);
1075                Set_Entity (Parent (N), Any_Type);
1076                raise Bad_Attribute;
1077
1078             else
1079                Error_Attr ("missing argument for % attribute", N);
1080             end if;
1081          end if;
1082       end Check_E1;
1083
1084       --------------
1085       -- Check_E2 --
1086       --------------
1087
1088       procedure Check_E2 is
1089       begin
1090          if No (E1) then
1091             Error_Attr ("missing arguments for % attribute (2 required)", N);
1092          elsif No (E2) then
1093             Error_Attr ("missing argument for % attribute (2 required)", N);
1094          end if;
1095       end Check_E2;
1096
1097       ---------------------------
1098       -- Check_Either_E0_Or_E1 --
1099       ---------------------------
1100
1101       procedure Check_Either_E0_Or_E1 is
1102       begin
1103          if Present (E2) then
1104             Unexpected_Argument (E2);
1105          end if;
1106       end Check_Either_E0_Or_E1;
1107
1108       ----------------------
1109       -- Check_Enum_Image --
1110       ----------------------
1111
1112       procedure Check_Enum_Image is
1113          Lit : Entity_Id;
1114       begin
1115          if Is_Enumeration_Type (P_Base_Type) then
1116             Lit := First_Literal (P_Base_Type);
1117             while Present (Lit) loop
1118                Set_Referenced (Lit);
1119                Next_Literal (Lit);
1120             end loop;
1121          end if;
1122       end Check_Enum_Image;
1123
1124       ----------------------------
1125       -- Check_Fixed_Point_Type --
1126       ----------------------------
1127
1128       procedure Check_Fixed_Point_Type is
1129       begin
1130          Check_Type;
1131
1132          if not Is_Fixed_Point_Type (P_Type) then
1133             Error_Attr_P ("prefix of % attribute must be fixed point type");
1134          end if;
1135       end Check_Fixed_Point_Type;
1136
1137       ------------------------------
1138       -- Check_Fixed_Point_Type_0 --
1139       ------------------------------
1140
1141       procedure Check_Fixed_Point_Type_0 is
1142       begin
1143          Check_Fixed_Point_Type;
1144          Check_E0;
1145       end Check_Fixed_Point_Type_0;
1146
1147       -------------------------------
1148       -- Check_Floating_Point_Type --
1149       -------------------------------
1150
1151       procedure Check_Floating_Point_Type is
1152       begin
1153          Check_Type;
1154
1155          if not Is_Floating_Point_Type (P_Type) then
1156             Error_Attr_P ("prefix of % attribute must be float type");
1157          end if;
1158       end Check_Floating_Point_Type;
1159
1160       ---------------------------------
1161       -- Check_Floating_Point_Type_0 --
1162       ---------------------------------
1163
1164       procedure Check_Floating_Point_Type_0 is
1165       begin
1166          Check_Floating_Point_Type;
1167          Check_E0;
1168       end Check_Floating_Point_Type_0;
1169
1170       ---------------------------------
1171       -- Check_Floating_Point_Type_1 --
1172       ---------------------------------
1173
1174       procedure Check_Floating_Point_Type_1 is
1175       begin
1176          Check_Floating_Point_Type;
1177          Check_E1;
1178       end Check_Floating_Point_Type_1;
1179
1180       ---------------------------------
1181       -- Check_Floating_Point_Type_2 --
1182       ---------------------------------
1183
1184       procedure Check_Floating_Point_Type_2 is
1185       begin
1186          Check_Floating_Point_Type;
1187          Check_E2;
1188       end Check_Floating_Point_Type_2;
1189
1190       ------------------------
1191       -- Check_Integer_Type --
1192       ------------------------
1193
1194       procedure Check_Integer_Type is
1195       begin
1196          Check_Type;
1197
1198          if not Is_Integer_Type (P_Type) then
1199             Error_Attr_P ("prefix of % attribute must be integer type");
1200          end if;
1201       end Check_Integer_Type;
1202
1203       ------------------------
1204       -- Check_Library_Unit --
1205       ------------------------
1206
1207       procedure Check_Library_Unit is
1208       begin
1209          if not Is_Compilation_Unit (Entity (P)) then
1210             Error_Attr_P ("prefix of % attribute must be library unit");
1211          end if;
1212       end Check_Library_Unit;
1213
1214       --------------------------------
1215       -- Check_Modular_Integer_Type --
1216       --------------------------------
1217
1218       procedure Check_Modular_Integer_Type is
1219       begin
1220          Check_Type;
1221
1222          if not Is_Modular_Integer_Type (P_Type) then
1223             Error_Attr_P
1224               ("prefix of % attribute must be modular integer type");
1225          end if;
1226       end Check_Modular_Integer_Type;
1227
1228       -------------------------------
1229       -- Check_Not_Incomplete_Type --
1230       -------------------------------
1231
1232       procedure Check_Not_Incomplete_Type is
1233          E   : Entity_Id;
1234          Typ : Entity_Id;
1235
1236       begin
1237          --  Ada 2005 (AI-50217, AI-326): If the prefix is an explicit
1238          --  dereference we have to check wrong uses of incomplete types
1239          --  (other wrong uses are checked at their freezing point).
1240
1241          --  Example 1: Limited-with
1242
1243          --    limited with Pkg;
1244          --    package P is
1245          --       type Acc is access Pkg.T;
1246          --       X : Acc;
1247          --       S : Integer := X.all'Size;                    -- ERROR
1248          --    end P;
1249
1250          --  Example 2: Tagged incomplete
1251
1252          --     type T is tagged;
1253          --     type Acc is access all T;
1254          --     X : Acc;
1255          --     S : constant Integer := X.all'Size;             -- ERROR
1256          --     procedure Q (Obj : Integer := X.all'Alignment); -- ERROR
1257
1258          if Ada_Version >= Ada_05
1259            and then Nkind (P) = N_Explicit_Dereference
1260          then
1261             E := P;
1262             while Nkind (E) = N_Explicit_Dereference loop
1263                E := Prefix (E);
1264             end loop;
1265
1266             if From_With_Type (Etype (E)) then
1267                Error_Attr_P
1268                  ("prefix of % attribute cannot be an incomplete type");
1269
1270             else
1271                if Is_Access_Type (Etype (E)) then
1272                   Typ := Directly_Designated_Type (Etype (E));
1273                else
1274                   Typ := Etype (E);
1275                end if;
1276
1277                if Ekind (Typ) = E_Incomplete_Type
1278                  and then No (Full_View (Typ))
1279                then
1280                   Error_Attr_P
1281                     ("prefix of % attribute cannot be an incomplete type");
1282                end if;
1283             end if;
1284          end if;
1285
1286          if not Is_Entity_Name (P)
1287            or else not Is_Type (Entity (P))
1288            or else In_Default_Expression
1289          then
1290             return;
1291          else
1292             Check_Fully_Declared (P_Type, P);
1293          end if;
1294       end Check_Not_Incomplete_Type;
1295
1296       ----------------------------
1297       -- Check_Object_Reference --
1298       ----------------------------
1299
1300       procedure Check_Object_Reference (P : Node_Id) is
1301          Rtyp : Entity_Id;
1302
1303       begin
1304          --  If we need an object, and we have a prefix that is the name of
1305          --  a function entity, convert it into a function call.
1306
1307          if Is_Entity_Name (P)
1308            and then Ekind (Entity (P)) = E_Function
1309          then
1310             Rtyp := Etype (Entity (P));
1311
1312             Rewrite (P,
1313               Make_Function_Call (Sloc (P),
1314                 Name => Relocate_Node (P)));
1315
1316             Analyze_And_Resolve (P, Rtyp);
1317
1318          --  Otherwise we must have an object reference
1319
1320          elsif not Is_Object_Reference (P) then
1321             Error_Attr_P ("prefix of % attribute must be object");
1322          end if;
1323       end Check_Object_Reference;
1324
1325       ------------------------
1326       -- Check_Program_Unit --
1327       ------------------------
1328
1329       procedure Check_Program_Unit is
1330       begin
1331          if Is_Entity_Name (P) then
1332             declare
1333                K : constant Entity_Kind := Ekind (Entity (P));
1334                T : constant Entity_Id   := Etype (Entity (P));
1335
1336             begin
1337                if K in Subprogram_Kind
1338                  or else K in Task_Kind
1339                  or else K in Protected_Kind
1340                  or else K = E_Package
1341                  or else K in Generic_Unit_Kind
1342                  or else (K = E_Variable
1343                             and then
1344                               (Is_Task_Type (T)
1345                                  or else
1346                                Is_Protected_Type (T)))
1347                then
1348                   return;
1349                end if;
1350             end;
1351          end if;
1352
1353          Error_Attr_P ("prefix of % attribute must be program unit");
1354       end Check_Program_Unit;
1355
1356       ---------------------
1357       -- Check_Real_Type --
1358       ---------------------
1359
1360       procedure Check_Real_Type is
1361       begin
1362          Check_Type;
1363
1364          if not Is_Real_Type (P_Type) then
1365             Error_Attr_P ("prefix of % attribute must be real type");
1366          end if;
1367       end Check_Real_Type;
1368
1369       -----------------------
1370       -- Check_Scalar_Type --
1371       -----------------------
1372
1373       procedure Check_Scalar_Type is
1374       begin
1375          Check_Type;
1376
1377          if not Is_Scalar_Type (P_Type) then
1378             Error_Attr_P ("prefix of % attribute must be scalar type");
1379          end if;
1380       end Check_Scalar_Type;
1381
1382       ---------------------------
1383       -- Check_Standard_Prefix --
1384       ---------------------------
1385
1386       procedure Check_Standard_Prefix is
1387       begin
1388          Check_E0;
1389
1390          if Nkind (P) /= N_Identifier
1391            or else Chars (P) /= Name_Standard
1392          then
1393             Error_Attr ("only allowed prefix for % attribute is Standard", P);
1394          end if;
1395       end Check_Standard_Prefix;
1396
1397       ----------------------------
1398       -- Check_Stream_Attribute --
1399       ----------------------------
1400
1401       procedure Check_Stream_Attribute (Nam : TSS_Name_Type) is
1402          Etyp : Entity_Id;
1403          Btyp : Entity_Id;
1404
1405       begin
1406          Validate_Non_Static_Attribute_Function_Call;
1407
1408          --  With the exception of 'Input, Stream attributes are procedures,
1409          --  and can only appear at the position of procedure calls. We check
1410          --  for this here, before they are rewritten, to give a more precise
1411          --  diagnostic.
1412
1413          if Nam = TSS_Stream_Input then
1414             null;
1415
1416          elsif Is_List_Member (N)
1417            and then Nkind (Parent (N)) /= N_Procedure_Call_Statement
1418            and then Nkind (Parent (N)) /= N_Aggregate
1419          then
1420             null;
1421
1422          else
1423             Error_Attr
1424               ("invalid context for attribute%, which is a procedure", N);
1425          end if;
1426
1427          Check_Type;
1428          Btyp := Implementation_Base_Type (P_Type);
1429
1430          --  Stream attributes not allowed on limited types unless the
1431          --  attribute reference was generated by the expander (in which
1432          --  case the underlying type will be used, as described in Sinfo),
1433          --  or the attribute was specified explicitly for the type itself
1434          --  or one of its ancestors (taking visibility rules into account if
1435          --  in Ada 2005 mode), or a pragma Stream_Convert applies to Btyp
1436          --  (with no visibility restriction).
1437
1438          if Comes_From_Source (N)
1439            and then not Stream_Attribute_Available (P_Type, Nam)
1440            and then not Has_Rep_Pragma (Btyp, Name_Stream_Convert)
1441          then
1442             Error_Msg_Name_1 := Aname;
1443
1444             if Is_Limited_Type (P_Type) then
1445                Error_Msg_NE
1446                  ("limited type& has no% attribute", P, P_Type);
1447                Explain_Limited_Type (P_Type, P);
1448             else
1449                Error_Msg_NE
1450                  ("attribute% for type& is not available", P, P_Type);
1451             end if;
1452          end if;
1453
1454          --  Check for violation of restriction No_Stream_Attributes
1455
1456          if Is_RTE (P_Type, RE_Exception_Id)
1457               or else
1458             Is_RTE (P_Type, RE_Exception_Occurrence)
1459          then
1460             Check_Restriction (No_Exception_Registration, P);
1461          end if;
1462
1463          --  Here we must check that the first argument is an access type
1464          --  that is compatible with Ada.Streams.Root_Stream_Type'Class.
1465
1466          Analyze_And_Resolve (E1);
1467          Etyp := Etype (E1);
1468
1469          --  Note: the double call to Root_Type here is needed because the
1470          --  root type of a class-wide type is the corresponding type (e.g.
1471          --  X for X'Class, and we really want to go to the root.)
1472
1473          if not Is_Access_Type (Etyp)
1474            or else Root_Type (Root_Type (Designated_Type (Etyp))) /=
1475                      RTE (RE_Root_Stream_Type)
1476          then
1477             Error_Attr
1478               ("expected access to Ada.Streams.Root_Stream_Type''Class", E1);
1479          end if;
1480
1481          --  Check that the second argument is of the right type if there is
1482          --  one (the Input attribute has only one argument so this is skipped)
1483
1484          if Present (E2) then
1485             Analyze (E2);
1486
1487             if Nam = TSS_Stream_Read
1488               and then not Is_OK_Variable_For_Out_Formal (E2)
1489             then
1490                Error_Attr
1491                  ("second argument of % attribute must be a variable", E2);
1492             end if;
1493
1494             Resolve (E2, P_Type);
1495          end if;
1496       end Check_Stream_Attribute;
1497
1498       -----------------------
1499       -- Check_Task_Prefix --
1500       -----------------------
1501
1502       procedure Check_Task_Prefix is
1503       begin
1504          Analyze (P);
1505
1506          --  Ada 2005 (AI-345): Attribute 'Terminated can be applied to
1507          --  task interface class-wide types.
1508
1509          if Is_Task_Type (Etype (P))
1510            or else (Is_Access_Type (Etype (P))
1511                       and then Is_Task_Type (Designated_Type (Etype (P))))
1512            or else (Ada_Version >= Ada_05
1513                       and then Ekind (Etype (P)) = E_Class_Wide_Type
1514                       and then Is_Interface (Etype (P))
1515                       and then Is_Task_Interface (Etype (P)))
1516          then
1517             Resolve (P);
1518
1519          else
1520             if Ada_Version >= Ada_05 then
1521                Error_Attr_P
1522                  ("prefix of % attribute must be a task or a task " &
1523                   "interface class-wide object");
1524
1525             else
1526                Error_Attr_P ("prefix of % attribute must be a task");
1527             end if;
1528          end if;
1529       end Check_Task_Prefix;
1530
1531       ----------------
1532       -- Check_Type --
1533       ----------------
1534
1535       --  The possibilities are an entity name denoting a type, or an
1536       --  attribute reference that denotes a type (Base or Class). If
1537       --  the type is incomplete, replace it with its full view.
1538
1539       procedure Check_Type is
1540       begin
1541          if not Is_Entity_Name (P)
1542            or else not Is_Type (Entity (P))
1543          then
1544             Error_Attr_P ("prefix of % attribute must be a type");
1545
1546          elsif Ekind (Entity (P)) = E_Incomplete_Type
1547             and then Present (Full_View (Entity (P)))
1548          then
1549             P_Type := Full_View (Entity (P));
1550             Set_Entity (P, P_Type);
1551          end if;
1552       end Check_Type;
1553
1554       ---------------------
1555       -- Check_Unit_Name --
1556       ---------------------
1557
1558       procedure Check_Unit_Name (Nod : Node_Id) is
1559       begin
1560          if Nkind (Nod) = N_Identifier then
1561             return;
1562
1563          elsif Nkind (Nod) = N_Selected_Component then
1564             Check_Unit_Name (Prefix (Nod));
1565
1566             if Nkind (Selector_Name (Nod)) = N_Identifier then
1567                return;
1568             end if;
1569          end if;
1570
1571          Error_Attr ("argument for % attribute must be unit name", P);
1572       end Check_Unit_Name;
1573
1574       ----------------
1575       -- Error_Attr --
1576       ----------------
1577
1578       procedure Error_Attr is
1579       begin
1580          Set_Etype (N, Any_Type);
1581          Set_Entity (N, Any_Type);
1582          raise Bad_Attribute;
1583       end Error_Attr;
1584
1585       procedure Error_Attr (Msg : String; Error_Node : Node_Id) is
1586       begin
1587          Error_Msg_Name_1 := Aname;
1588          Error_Msg_N (Msg, Error_Node);
1589          Error_Attr;
1590       end Error_Attr;
1591
1592       ------------------
1593       -- Error_Attr_P --
1594       ------------------
1595
1596       procedure Error_Attr_P (Msg : String) is
1597       begin
1598          Error_Msg_Name_1 := Aname;
1599          Error_Msg_F (Msg, P);
1600          Error_Attr;
1601       end Error_Attr_P;
1602
1603       ----------------------------
1604       -- Legal_Formal_Attribute --
1605       ----------------------------
1606
1607       procedure Legal_Formal_Attribute is
1608       begin
1609          Check_E0;
1610
1611          if not Is_Entity_Name (P)
1612            or else not Is_Type (Entity (P))
1613          then
1614             Error_Attr_P ("prefix of % attribute must be generic type");
1615
1616          elsif Is_Generic_Actual_Type (Entity (P))
1617            or else In_Instance
1618            or else In_Inlined_Body
1619          then
1620             null;
1621
1622          elsif Is_Generic_Type (Entity (P)) then
1623             if not Is_Indefinite_Subtype (Entity (P)) then
1624                Error_Attr_P
1625                  ("prefix of % attribute must be indefinite generic type");
1626             end if;
1627
1628          else
1629             Error_Attr_P
1630               ("prefix of % attribute must be indefinite generic type");
1631          end if;
1632
1633          Set_Etype (N, Standard_Boolean);
1634       end Legal_Formal_Attribute;
1635
1636       ------------------------
1637       -- Standard_Attribute --
1638       ------------------------
1639
1640       procedure Standard_Attribute (Val : Int) is
1641       begin
1642          Check_Standard_Prefix;
1643          Rewrite (N, Make_Integer_Literal (Loc, Val));
1644          Analyze (N);
1645       end Standard_Attribute;
1646
1647       -------------------------
1648       -- Unexpected Argument --
1649       -------------------------
1650
1651       procedure Unexpected_Argument (En : Node_Id) is
1652       begin
1653          Error_Attr ("unexpected argument for % attribute", En);
1654       end Unexpected_Argument;
1655
1656       -------------------------------------------------
1657       -- Validate_Non_Static_Attribute_Function_Call --
1658       -------------------------------------------------
1659
1660       --  This function should be moved to Sem_Dist ???
1661
1662       procedure Validate_Non_Static_Attribute_Function_Call is
1663       begin
1664          if In_Preelaborated_Unit
1665            and then not In_Subprogram_Or_Concurrent_Unit
1666          then
1667             Flag_Non_Static_Expr
1668               ("non-static function call in preelaborated unit!", N);
1669          end if;
1670       end Validate_Non_Static_Attribute_Function_Call;
1671
1672    -----------------------------------------------
1673    -- Start of Processing for Analyze_Attribute --
1674    -----------------------------------------------
1675
1676    begin
1677       --  Immediate return if unrecognized attribute (already diagnosed
1678       --  by parser, so there is nothing more that we need to do)
1679
1680       if not Is_Attribute_Name (Aname) then
1681          raise Bad_Attribute;
1682       end if;
1683
1684       --  Deal with Ada 83 issues
1685
1686       if Comes_From_Source (N) then
1687          if not Attribute_83 (Attr_Id) then
1688             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
1689                Error_Msg_Name_1 := Aname;
1690                Error_Msg_N ("(Ada 83) attribute% is not standard?", N);
1691             end if;
1692
1693             if Attribute_Impl_Def (Attr_Id) then
1694                Check_Restriction (No_Implementation_Attributes, N);
1695             end if;
1696          end if;
1697       end if;
1698
1699       --  Deal with Ada 2005 issues
1700
1701       if Attribute_05 (Attr_Id) and then Ada_Version <= Ada_95 then
1702          Check_Restriction (No_Implementation_Attributes, N);
1703       end if;
1704
1705       --   Remote access to subprogram type access attribute reference needs
1706       --   unanalyzed copy for tree transformation. The analyzed copy is used
1707       --   for its semantic information (whether prefix is a remote subprogram
1708       --   name), the unanalyzed copy is used to construct new subtree rooted
1709       --   with N_Aggregate which represents a fat pointer aggregate.
1710
1711       if Aname = Name_Access then
1712          Discard_Node (Copy_Separate_Tree (N));
1713       end if;
1714
1715       --  Analyze prefix and exit if error in analysis. If the prefix is an
1716       --  incomplete type, use full view if available. Note that there are
1717       --  some attributes for which we do not analyze the prefix, since the
1718       --  prefix is not a normal name.
1719
1720       if Aname /= Name_Elab_Body
1721            and then
1722          Aname /= Name_Elab_Spec
1723            and then
1724          Aname /= Name_UET_Address
1725            and then
1726          Aname /= Name_Enabled
1727       then
1728          Analyze (P);
1729          P_Type := Etype (P);
1730
1731          if Is_Entity_Name (P)
1732            and then Present (Entity (P))
1733            and then Is_Type (Entity (P))
1734          then
1735             if Ekind (Entity (P)) = E_Incomplete_Type then
1736                P_Type := Get_Full_View (P_Type);
1737                Set_Entity (P, P_Type);
1738                Set_Etype  (P, P_Type);
1739
1740             elsif Entity (P) = Current_Scope
1741               and then Is_Record_Type (Entity (P))
1742             then
1743                --  Use of current instance within the type. Verify that if the
1744                --  attribute appears within a constraint, it  yields an access
1745                --  type, other uses are illegal.
1746
1747                declare
1748                   Par : Node_Id;
1749
1750                begin
1751                   Par := Parent (N);
1752                   while Present (Par)
1753                     and then Nkind (Parent (Par)) /= N_Component_Definition
1754                   loop
1755                      Par := Parent (Par);
1756                   end loop;
1757
1758                   if Present (Par)
1759                     and then Nkind (Par) = N_Subtype_Indication
1760                   then
1761                      if Attr_Id /= Attribute_Access
1762                        and then Attr_Id /= Attribute_Unchecked_Access
1763                        and then Attr_Id /= Attribute_Unrestricted_Access
1764                      then
1765                         Error_Msg_N
1766                           ("in a constraint the current instance can only"
1767                              & " be used with an access attribute", N);
1768                      end if;
1769                   end if;
1770                end;
1771             end if;
1772          end if;
1773
1774          if P_Type = Any_Type then
1775             raise Bad_Attribute;
1776          end if;
1777
1778          P_Base_Type := Base_Type (P_Type);
1779       end if;
1780
1781       --  Analyze expressions that may be present, exiting if an error occurs
1782
1783       if No (Exprs) then
1784          E1 := Empty;
1785          E2 := Empty;
1786
1787       else
1788          E1 := First (Exprs);
1789          Analyze (E1);
1790
1791          --  Check for missing/bad expression (result of previous error)
1792
1793          if No (E1) or else Etype (E1) = Any_Type then
1794             raise Bad_Attribute;
1795          end if;
1796
1797          E2 := Next (E1);
1798
1799          if Present (E2) then
1800             Analyze (E2);
1801
1802             if Etype (E2) = Any_Type then
1803                raise Bad_Attribute;
1804             end if;
1805
1806             if Present (Next (E2)) then
1807                Unexpected_Argument (Next (E2));
1808             end if;
1809          end if;
1810       end if;
1811
1812       --  Ada 2005 (AI-345): Ensure that the compiler gives exactly the current
1813       --  output compiling in Ada 95 mode for the case of ambiguous prefixes.
1814
1815       if Ada_Version < Ada_05
1816         and then Is_Overloaded (P)
1817         and then Aname /= Name_Access
1818         and then Aname /= Name_Address
1819         and then Aname /= Name_Code_Address
1820         and then Aname /= Name_Count
1821         and then Aname /= Name_Unchecked_Access
1822       then
1823          Error_Attr ("ambiguous prefix for % attribute", P);
1824
1825       elsif Ada_Version >= Ada_05
1826         and then Is_Overloaded (P)
1827         and then Aname /= Name_Access
1828         and then Aname /= Name_Address
1829         and then Aname /= Name_Code_Address
1830         and then Aname /= Name_Unchecked_Access
1831       then
1832          --  Ada 2005 (AI-345): Since protected and task types have primitive
1833          --  entry wrappers, the attributes Count, Caller and AST_Entry require
1834          --  a context check
1835
1836          if Aname = Name_Count
1837            or else Aname = Name_Caller
1838            or else Aname = Name_AST_Entry
1839          then
1840             declare
1841                Count : Natural := 0;
1842                I     : Interp_Index;
1843                It    : Interp;
1844
1845             begin
1846                Get_First_Interp (P, I, It);
1847                while Present (It.Nam) loop
1848                   if Comes_From_Source (It.Nam) then
1849                      Count := Count + 1;
1850                   else
1851                      Remove_Interp (I);
1852                   end if;
1853
1854                   Get_Next_Interp (I, It);
1855                end loop;
1856
1857                if Count > 1 then
1858                   Error_Attr ("ambiguous prefix for % attribute", P);
1859                else
1860                   Set_Is_Overloaded (P, False);
1861                end if;
1862             end;
1863
1864          else
1865             Error_Attr ("ambiguous prefix for % attribute", P);
1866          end if;
1867       end if;
1868
1869       --  Remaining processing depends on attribute
1870
1871       case Attr_Id is
1872
1873       ------------------
1874       -- Abort_Signal --
1875       ------------------
1876
1877       when Attribute_Abort_Signal =>
1878          Check_Standard_Prefix;
1879          Rewrite (N,
1880            New_Reference_To (Stand.Abort_Signal, Loc));
1881          Analyze (N);
1882
1883       ------------
1884       -- Access --
1885       ------------
1886
1887       when Attribute_Access =>
1888          Analyze_Access_Attribute;
1889
1890       -------------
1891       -- Address --
1892       -------------
1893
1894       when Attribute_Address =>
1895          Check_E0;
1896
1897          --  Check for some junk cases, where we have to allow the address
1898          --  attribute but it does not make much sense, so at least for now
1899          --  just replace with Null_Address.
1900
1901          --  We also do this if the prefix is a reference to the AST_Entry
1902          --  attribute. If expansion is active, the attribute will be
1903          --  replaced by a function call, and address will work fine and
1904          --  get the proper value, but if expansion is not active, then
1905          --  the check here allows proper semantic analysis of the reference.
1906
1907          --  An Address attribute created by expansion is legal even when it
1908          --  applies to other entity-denoting expressions.
1909
1910          if Is_Entity_Name (P) then
1911             declare
1912                Ent : constant Entity_Id := Entity (P);
1913
1914             begin
1915                if Is_Subprogram (Ent) then
1916                   Set_Address_Taken (Ent);
1917                   Kill_Current_Values (Ent);
1918
1919                   --  An Address attribute is accepted when generated by the
1920                   --  compiler for dispatching operation, and an error is
1921                   --  issued once the subprogram is frozen (to avoid confusing
1922                   --  errors about implicit uses of Address in the dispatch
1923                   --  table initialization).
1924
1925                   if Has_Pragma_Inline_Always (Entity (P))
1926                     and then Comes_From_Source (P)
1927                   then
1928                      Error_Attr_P
1929                        ("prefix of % attribute cannot be Inline_Always" &
1930                         " subprogram");
1931                   end if;
1932
1933                elsif Is_Object (Ent)
1934                  or else Ekind (Ent) = E_Label
1935                then
1936                   Set_Address_Taken (Ent);
1937
1938                --  If we have an address of an object, and the attribute
1939                --  comes from source, then set the object as potentially
1940                --  source modified. We do this because the resulting address
1941                --  can potentially be used to modify the variable and we
1942                --  might not detect this, leading to some junk warnings.
1943
1944                   Set_Never_Set_In_Source (Ent, False);
1945
1946                elsif (Is_Concurrent_Type (Etype (Ent))
1947                        and then Etype (Ent) = Base_Type (Ent))
1948                  or else Ekind (Ent) = E_Package
1949                  or else Is_Generic_Unit (Ent)
1950                then
1951                   Rewrite (N,
1952                     New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1953
1954                else
1955                   Error_Attr ("invalid prefix for % attribute", P);
1956                end if;
1957             end;
1958
1959          elsif Nkind (P) = N_Attribute_Reference
1960            and then Attribute_Name (P) = Name_AST_Entry
1961          then
1962             Rewrite (N,
1963               New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1964
1965          elsif Is_Object_Reference (P) then
1966             null;
1967
1968          elsif Nkind (P) = N_Selected_Component
1969            and then Is_Subprogram (Entity (Selector_Name (P)))
1970          then
1971             null;
1972
1973          --  What exactly are we allowing here ??? and is this properly
1974          --  documented in the sinfo documentation for this node ???
1975
1976          elsif not Comes_From_Source (N) then
1977             null;
1978
1979          else
1980             Error_Attr ("invalid prefix for % attribute", P);
1981          end if;
1982
1983          Set_Etype (N, RTE (RE_Address));
1984
1985       ------------------
1986       -- Address_Size --
1987       ------------------
1988
1989       when Attribute_Address_Size =>
1990          Standard_Attribute (System_Address_Size);
1991
1992       --------------
1993       -- Adjacent --
1994       --------------
1995
1996       when Attribute_Adjacent =>
1997          Check_Floating_Point_Type_2;
1998          Set_Etype (N, P_Base_Type);
1999          Resolve (E1, P_Base_Type);
2000          Resolve (E2, P_Base_Type);
2001
2002       ---------
2003       -- Aft --
2004       ---------
2005
2006       when Attribute_Aft =>
2007          Check_Fixed_Point_Type_0;
2008          Set_Etype (N, Universal_Integer);
2009
2010       ---------------
2011       -- Alignment --
2012       ---------------
2013
2014       when Attribute_Alignment =>
2015
2016          --  Don't we need more checking here, cf Size ???
2017
2018          Check_E0;
2019          Check_Not_Incomplete_Type;
2020          Set_Etype (N, Universal_Integer);
2021
2022       ---------------
2023       -- Asm_Input --
2024       ---------------
2025
2026       when Attribute_Asm_Input =>
2027          Check_Asm_Attribute;
2028          Set_Etype (N, RTE (RE_Asm_Input_Operand));
2029
2030       ----------------
2031       -- Asm_Output --
2032       ----------------
2033
2034       when Attribute_Asm_Output =>
2035          Check_Asm_Attribute;
2036
2037          if Etype (E2) = Any_Type then
2038             return;
2039
2040          elsif Aname = Name_Asm_Output then
2041             if not Is_Variable (E2) then
2042                Error_Attr
2043                  ("second argument for Asm_Output is not variable", E2);
2044             end if;
2045          end if;
2046
2047          Note_Possible_Modification (E2);
2048          Set_Etype (N, RTE (RE_Asm_Output_Operand));
2049
2050       ---------------
2051       -- AST_Entry --
2052       ---------------
2053
2054       when Attribute_AST_Entry => AST_Entry : declare
2055          Ent  : Entity_Id;
2056          Pref : Node_Id;
2057          Ptyp : Entity_Id;
2058
2059          Indexed : Boolean;
2060          --  Indicates if entry family index is present. Note the coding
2061          --  here handles the entry family case, but in fact it cannot be
2062          --  executed currently, because pragma AST_Entry does not permit
2063          --  the specification of an entry family.
2064
2065          procedure Bad_AST_Entry;
2066          --  Signal a bad AST_Entry pragma
2067
2068          function OK_Entry (E : Entity_Id) return Boolean;
2069          --  Checks that E is of an appropriate entity kind for an entry
2070          --  (i.e. E_Entry if Index is False, or E_Entry_Family if Index
2071          --  is set True for the entry family case). In the True case,
2072          --  makes sure that Is_AST_Entry is set on the entry.
2073
2074          procedure Bad_AST_Entry is
2075          begin
2076             Error_Attr_P ("prefix for % attribute must be task entry");
2077          end Bad_AST_Entry;
2078
2079          function OK_Entry (E : Entity_Id) return Boolean is
2080             Result : Boolean;
2081
2082          begin
2083             if Indexed then
2084                Result := (Ekind (E) = E_Entry_Family);
2085             else
2086                Result := (Ekind (E) = E_Entry);
2087             end if;
2088
2089             if Result then
2090                if not Is_AST_Entry (E) then
2091                   Error_Msg_Name_2 := Aname;
2092                   Error_Attr ("% attribute requires previous % pragma", P);
2093                end if;
2094             end if;
2095
2096             return Result;
2097          end OK_Entry;
2098
2099       --  Start of processing for AST_Entry
2100
2101       begin
2102          Check_VMS (N);
2103          Check_E0;
2104
2105          --  Deal with entry family case
2106
2107          if Nkind (P) = N_Indexed_Component then
2108             Pref := Prefix (P);
2109             Indexed := True;
2110          else
2111             Pref := P;
2112             Indexed := False;
2113          end if;
2114
2115          Ptyp := Etype (Pref);
2116
2117          if Ptyp = Any_Type or else Error_Posted (Pref) then
2118             return;
2119          end if;
2120
2121          --  If the prefix is a selected component whose prefix is of an
2122          --  access type, then introduce an explicit dereference.
2123          --  ??? Could we reuse Check_Dereference here?
2124
2125          if Nkind (Pref) = N_Selected_Component
2126            and then Is_Access_Type (Ptyp)
2127          then
2128             Rewrite (Pref,
2129               Make_Explicit_Dereference (Sloc (Pref),
2130                 Relocate_Node (Pref)));
2131             Analyze_And_Resolve (Pref, Designated_Type (Ptyp));
2132          end if;
2133
2134          --  Prefix can be of the form a.b, where a is a task object
2135          --  and b is one of the entries of the corresponding task type.
2136
2137          if Nkind (Pref) = N_Selected_Component
2138            and then OK_Entry (Entity (Selector_Name (Pref)))
2139            and then Is_Object_Reference (Prefix (Pref))
2140            and then Is_Task_Type (Etype (Prefix (Pref)))
2141          then
2142             null;
2143
2144          --  Otherwise the prefix must be an entry of a containing task,
2145          --  or of a variable of the enclosing task type.
2146
2147          else
2148             if Nkind (Pref) = N_Identifier
2149               or else Nkind (Pref) = N_Expanded_Name
2150             then
2151                Ent := Entity (Pref);
2152
2153                if not OK_Entry (Ent)
2154                  or else not In_Open_Scopes (Scope (Ent))
2155                then
2156                   Bad_AST_Entry;
2157                end if;
2158
2159             else
2160                Bad_AST_Entry;
2161             end if;
2162          end if;
2163
2164          Set_Etype (N, RTE (RE_AST_Handler));
2165       end AST_Entry;
2166
2167       ----------
2168       -- Base --
2169       ----------
2170
2171       --  Note: when the base attribute appears in the context of a subtype
2172       --  mark, the analysis is done by Sem_Ch8.Find_Type, rather than by
2173       --  the following circuit.
2174
2175       when Attribute_Base => Base : declare
2176          Typ : Entity_Id;
2177
2178       begin
2179          Check_E0;
2180          Find_Type (P);
2181          Typ := Entity (P);
2182
2183          if Ada_Version >= Ada_95
2184            and then not Is_Scalar_Type (Typ)
2185            and then not Is_Generic_Type (Typ)
2186          then
2187             Error_Attr_P ("prefix of Base attribute must be scalar type");
2188
2189          elsif Sloc (Typ) = Standard_Location
2190            and then Base_Type (Typ) = Typ
2191            and then Warn_On_Redundant_Constructs
2192          then
2193                Error_Msg_NE
2194                  ("?redudant attribute, & is its own base type", N, Typ);
2195          end if;
2196
2197          Set_Etype (N, Base_Type (Entity (P)));
2198          Set_Entity (N, Base_Type (Entity (P)));
2199          Rewrite (N, New_Reference_To (Entity (N), Loc));
2200          Analyze (N);
2201       end Base;
2202
2203       ---------
2204       -- Bit --
2205       ---------
2206
2207       when Attribute_Bit => Bit :
2208       begin
2209          Check_E0;
2210
2211          if not Is_Object_Reference (P) then
2212             Error_Attr_P ("prefix for % attribute must be object");
2213
2214          --  What about the access object cases ???
2215
2216          else
2217             null;
2218          end if;
2219
2220          Set_Etype (N, Universal_Integer);
2221       end Bit;
2222
2223       ---------------
2224       -- Bit_Order --
2225       ---------------
2226
2227       when Attribute_Bit_Order => Bit_Order :
2228       begin
2229          Check_E0;
2230          Check_Type;
2231
2232          if not Is_Record_Type (P_Type) then
2233             Error_Attr_P ("prefix of % attribute must be record type");
2234          end if;
2235
2236          if Bytes_Big_Endian xor Reverse_Bit_Order (P_Type) then
2237             Rewrite (N,
2238               New_Occurrence_Of (RTE (RE_High_Order_First), Loc));
2239          else
2240             Rewrite (N,
2241               New_Occurrence_Of (RTE (RE_Low_Order_First), Loc));
2242          end if;
2243
2244          Set_Etype (N, RTE (RE_Bit_Order));
2245          Resolve (N);
2246
2247          --  Reset incorrect indication of staticness
2248
2249          Set_Is_Static_Expression (N, False);
2250       end Bit_Order;
2251
2252       ------------------
2253       -- Bit_Position --
2254       ------------------
2255
2256       --  Note: in generated code, we can have a Bit_Position attribute
2257       --  applied to a (naked) record component (i.e. the prefix is an
2258       --  identifier that references an E_Component or E_Discriminant
2259       --  entity directly, and this is interpreted as expected by Gigi.
2260       --  The following code will not tolerate such usage, but when the
2261       --  expander creates this special case, it marks it as analyzed
2262       --  immediately and sets an appropriate type.
2263
2264       when Attribute_Bit_Position =>
2265          if Comes_From_Source (N) then
2266             Check_Component;
2267          end if;
2268
2269          Set_Etype (N, Universal_Integer);
2270
2271       ------------------
2272       -- Body_Version --
2273       ------------------
2274
2275       when Attribute_Body_Version =>
2276          Check_E0;
2277          Check_Program_Unit;
2278          Set_Etype (N, RTE (RE_Version_String));
2279
2280       --------------
2281       -- Callable --
2282       --------------
2283
2284       when Attribute_Callable =>
2285          Check_E0;
2286          Set_Etype (N, Standard_Boolean);
2287          Check_Task_Prefix;
2288
2289       ------------
2290       -- Caller --
2291       ------------
2292
2293       when Attribute_Caller => Caller : declare
2294          Ent        : Entity_Id;
2295          S          : Entity_Id;
2296
2297       begin
2298          Check_E0;
2299
2300          if Nkind (P) = N_Identifier
2301            or else Nkind (P) = N_Expanded_Name
2302          then
2303             Ent := Entity (P);
2304
2305             if not Is_Entry (Ent) then
2306                Error_Attr ("invalid entry name", N);
2307             end if;
2308
2309          else
2310             Error_Attr ("invalid entry name", N);
2311             return;
2312          end if;
2313
2314          for J in reverse 0 .. Scope_Stack.Last loop
2315             S := Scope_Stack.Table (J).Entity;
2316
2317             if S = Scope (Ent) then
2318                Error_Attr ("Caller must appear in matching accept or body", N);
2319             elsif S = Ent then
2320                exit;
2321             end if;
2322          end loop;
2323
2324          Set_Etype (N, RTE (RO_AT_Task_Id));
2325       end Caller;
2326
2327       -------------
2328       -- Ceiling --
2329       -------------
2330
2331       when Attribute_Ceiling =>
2332          Check_Floating_Point_Type_1;
2333          Set_Etype (N, P_Base_Type);
2334          Resolve (E1, P_Base_Type);
2335
2336       -----------
2337       -- Class --
2338       -----------
2339
2340       when Attribute_Class =>
2341          Check_Restriction (No_Dispatch, N);
2342          Check_E0;
2343          Find_Type (N);
2344
2345       ------------------
2346       -- Code_Address --
2347       ------------------
2348
2349       when Attribute_Code_Address =>
2350          Check_E0;
2351
2352          if Nkind (P) = N_Attribute_Reference
2353            and then (Attribute_Name (P) = Name_Elab_Body
2354                        or else
2355                      Attribute_Name (P) = Name_Elab_Spec)
2356          then
2357             null;
2358
2359          elsif not Is_Entity_Name (P)
2360            or else (Ekind (Entity (P)) /= E_Function
2361                       and then
2362                     Ekind (Entity (P)) /= E_Procedure)
2363          then
2364             Error_Attr ("invalid prefix for % attribute", P);
2365             Set_Address_Taken (Entity (P));
2366          end if;
2367
2368          Set_Etype (N, RTE (RE_Address));
2369
2370       --------------------
2371       -- Component_Size --
2372       --------------------
2373
2374       when Attribute_Component_Size =>
2375          Check_E0;
2376          Set_Etype (N, Universal_Integer);
2377
2378          --  Note: unlike other array attributes, unconstrained arrays are OK
2379
2380          if Is_Array_Type (P_Type) and then not Is_Constrained (P_Type) then
2381             null;
2382          else
2383             Check_Array_Type;
2384          end if;
2385
2386       -------------
2387       -- Compose --
2388       -------------
2389
2390       when Attribute_Compose =>
2391          Check_Floating_Point_Type_2;
2392          Set_Etype (N, P_Base_Type);
2393          Resolve (E1, P_Base_Type);
2394          Resolve (E2, Any_Integer);
2395
2396       -----------------
2397       -- Constrained --
2398       -----------------
2399
2400       when Attribute_Constrained =>
2401          Check_E0;
2402          Set_Etype (N, Standard_Boolean);
2403
2404          --  Case from RM J.4(2) of constrained applied to private type
2405
2406          if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
2407             Check_Restriction (No_Obsolescent_Features, N);
2408
2409             if Warn_On_Obsolescent_Feature then
2410                Error_Msg_N
2411                  ("constrained for private type is an " &
2412                   "obsolescent feature (RM J.4)?", N);
2413             end if;
2414
2415             --  If we are within an instance, the attribute must be legal
2416             --  because it was valid in the generic unit. Ditto if this is
2417             --  an inlining of a function declared in an instance.
2418
2419             if In_Instance
2420               or else In_Inlined_Body
2421             then
2422                return;
2423
2424             --  For sure OK if we have a real private type itself, but must
2425             --  be completed, cannot apply Constrained to incomplete type.
2426
2427             elsif Is_Private_Type (Entity (P)) then
2428
2429                --  Note: this is one of the Annex J features that does not
2430                --  generate a warning from -gnatwj, since in fact it seems
2431                --  very useful, and is used in the GNAT runtime.
2432
2433                Check_Not_Incomplete_Type;
2434                return;
2435             end if;
2436
2437          --  Normal (non-obsolescent case) of application to object of
2438          --  a discriminated type.
2439
2440          else
2441             Check_Object_Reference (P);
2442
2443             --  If N does not come from source, then we allow the
2444             --  the attribute prefix to be of a private type whose
2445             --  full type has discriminants. This occurs in cases
2446             --  involving expanded calls to stream attributes.
2447
2448             if not Comes_From_Source (N) then
2449                P_Type := Underlying_Type (P_Type);
2450             end if;
2451
2452             --  Must have discriminants or be an access type designating
2453             --  a type with discriminants. If it is a classwide type is ???
2454             --  has unknown discriminants.
2455
2456             if Has_Discriminants (P_Type)
2457                or else Has_Unknown_Discriminants (P_Type)
2458                or else
2459                  (Is_Access_Type (P_Type)
2460                    and then Has_Discriminants (Designated_Type (P_Type)))
2461             then
2462                return;
2463
2464             --  Also allow an object of a generic type if extensions allowed
2465             --  and allow this for any type at all.
2466
2467             elsif (Is_Generic_Type (P_Type)
2468                      or else Is_Generic_Actual_Type (P_Type))
2469               and then Extensions_Allowed
2470             then
2471                return;
2472             end if;
2473          end if;
2474
2475          --  Fall through if bad prefix
2476
2477          Error_Attr_P
2478            ("prefix of % attribute must be object of discriminated type");
2479
2480       ---------------
2481       -- Copy_Sign --
2482       ---------------
2483
2484       when Attribute_Copy_Sign =>
2485          Check_Floating_Point_Type_2;
2486          Set_Etype (N, P_Base_Type);
2487          Resolve (E1, P_Base_Type);
2488          Resolve (E2, P_Base_Type);
2489
2490       -----------
2491       -- Count --
2492       -----------
2493
2494       when Attribute_Count => Count :
2495       declare
2496          Ent : Entity_Id;
2497          S   : Entity_Id;
2498          Tsk : Entity_Id;
2499
2500       begin
2501          Check_E0;
2502
2503          if Nkind (P) = N_Identifier
2504            or else Nkind (P) = N_Expanded_Name
2505          then
2506             Ent := Entity (P);
2507
2508             if Ekind (Ent) /= E_Entry then
2509                Error_Attr ("invalid entry name", N);
2510             end if;
2511
2512          elsif Nkind (P) = N_Indexed_Component then
2513             if not Is_Entity_Name (Prefix (P))
2514               or else  No (Entity (Prefix (P)))
2515               or else Ekind (Entity (Prefix (P))) /= E_Entry_Family
2516             then
2517                if Nkind (Prefix (P)) = N_Selected_Component
2518                  and then Present (Entity (Selector_Name (Prefix (P))))
2519                  and then Ekind (Entity (Selector_Name (Prefix (P)))) =
2520                                                              E_Entry_Family
2521                then
2522                   Error_Attr
2523                     ("attribute % must apply to entry of current task", P);
2524
2525                else
2526                   Error_Attr ("invalid entry family name", P);
2527                end if;
2528                return;
2529
2530             else
2531                Ent := Entity (Prefix (P));
2532             end if;
2533
2534          elsif Nkind (P) = N_Selected_Component
2535            and then Present (Entity (Selector_Name (P)))
2536            and then Ekind (Entity (Selector_Name (P))) = E_Entry
2537          then
2538             Error_Attr
2539               ("attribute % must apply to entry of current task", P);
2540
2541          else
2542             Error_Attr ("invalid entry name", N);
2543             return;
2544          end if;
2545
2546          for J in reverse 0 .. Scope_Stack.Last loop
2547             S := Scope_Stack.Table (J).Entity;
2548
2549             if S = Scope (Ent) then
2550                if Nkind (P) = N_Expanded_Name then
2551                   Tsk := Entity (Prefix (P));
2552
2553                   --  The prefix denotes either the task type, or else a
2554                   --  single task whose task type is being analyzed.
2555
2556                   if (Is_Type (Tsk)
2557                       and then Tsk = S)
2558
2559                     or else (not Is_Type (Tsk)
2560                       and then Etype (Tsk) = S
2561                       and then not (Comes_From_Source (S)))
2562                   then
2563                      null;
2564                   else
2565                      Error_Attr
2566                        ("Attribute % must apply to entry of current task", N);
2567                   end if;
2568                end if;
2569
2570                exit;
2571
2572             elsif Ekind (Scope (Ent)) in Task_Kind
2573               and then Ekind (S) /= E_Loop
2574               and then Ekind (S) /= E_Block
2575               and then Ekind (S) /= E_Entry
2576               and then Ekind (S) /= E_Entry_Family
2577             then
2578                Error_Attr ("Attribute % cannot appear in inner unit", N);
2579
2580             elsif Ekind (Scope (Ent)) = E_Protected_Type
2581               and then not Has_Completion (Scope (Ent))
2582             then
2583                Error_Attr ("attribute % can only be used inside body", N);
2584             end if;
2585          end loop;
2586
2587          if Is_Overloaded (P) then
2588             declare
2589                Index : Interp_Index;
2590                It    : Interp;
2591
2592             begin
2593                Get_First_Interp (P, Index, It);
2594
2595                while Present (It.Nam) loop
2596                   if It.Nam = Ent then
2597                      null;
2598
2599                   --  Ada 2005 (AI-345): Do not consider primitive entry
2600                   --  wrappers generated for task or protected types.
2601
2602                   elsif Ada_Version >= Ada_05
2603                     and then not Comes_From_Source (It.Nam)
2604                   then
2605                      null;
2606
2607                   else
2608                      Error_Attr ("ambiguous entry name", N);
2609                   end if;
2610
2611                   Get_Next_Interp (Index, It);
2612                end loop;
2613             end;
2614          end if;
2615
2616          Set_Etype (N, Universal_Integer);
2617       end Count;
2618
2619       -----------------------
2620       -- Default_Bit_Order --
2621       -----------------------
2622
2623       when Attribute_Default_Bit_Order => Default_Bit_Order :
2624       begin
2625          Check_Standard_Prefix;
2626          Check_E0;
2627
2628          if Bytes_Big_Endian then
2629             Rewrite (N,
2630               Make_Integer_Literal (Loc, False_Value));
2631          else
2632             Rewrite (N,
2633               Make_Integer_Literal (Loc, True_Value));
2634          end if;
2635
2636          Set_Etype (N, Universal_Integer);
2637          Set_Is_Static_Expression (N);
2638       end Default_Bit_Order;
2639
2640       --------------
2641       -- Definite --
2642       --------------
2643
2644       when Attribute_Definite =>
2645          Legal_Formal_Attribute;
2646
2647       -----------
2648       -- Delta --
2649       -----------
2650
2651       when Attribute_Delta =>
2652          Check_Fixed_Point_Type_0;
2653          Set_Etype (N, Universal_Real);
2654
2655       ------------
2656       -- Denorm --
2657       ------------
2658
2659       when Attribute_Denorm =>
2660          Check_Floating_Point_Type_0;
2661          Set_Etype (N, Standard_Boolean);
2662
2663       ------------
2664       -- Digits --
2665       ------------
2666
2667       when Attribute_Digits =>
2668          Check_E0;
2669          Check_Type;
2670
2671          if not Is_Floating_Point_Type (P_Type)
2672            and then not Is_Decimal_Fixed_Point_Type (P_Type)
2673          then
2674             Error_Attr_P
2675               ("prefix of % attribute must be float or decimal type");
2676          end if;
2677
2678          Set_Etype (N, Universal_Integer);
2679
2680       ---------------
2681       -- Elab_Body --
2682       ---------------
2683
2684       --  Also handles processing for Elab_Spec
2685
2686       when Attribute_Elab_Body | Attribute_Elab_Spec =>
2687          Check_E0;
2688          Check_Unit_Name (P);
2689          Set_Etype (N, Standard_Void_Type);
2690
2691          --  We have to manually call the expander in this case to get
2692          --  the necessary expansion (normally attributes that return
2693          --  entities are not expanded).
2694
2695          Expand (N);
2696
2697       ---------------
2698       -- Elab_Spec --
2699       ---------------
2700
2701       --  Shares processing with Elab_Body
2702
2703       ----------------
2704       -- Elaborated --
2705       ----------------
2706
2707       when Attribute_Elaborated =>
2708          Check_E0;
2709          Check_Library_Unit;
2710          Set_Etype (N, Standard_Boolean);
2711
2712       ----------
2713       -- Emax --
2714       ----------
2715
2716       when Attribute_Emax =>
2717          Check_Floating_Point_Type_0;
2718          Set_Etype (N, Universal_Integer);
2719
2720       -------------
2721       -- Enabled --
2722       -------------
2723
2724       when Attribute_Enabled =>
2725          Check_Either_E0_Or_E1;
2726
2727          if Present (E1) then
2728             if not Is_Entity_Name (E1) or else No (Entity (E1)) then
2729                Error_Msg_N ("entity name expected for Enabled attribute", E1);
2730                E1 := Empty;
2731             end if;
2732          end if;
2733
2734          if Nkind (P) /= N_Identifier then
2735             Error_Msg_N ("identifier expected (check name)", P);
2736
2737          elsif Get_Check_Id (Chars (P)) = No_Check_Id then
2738             Error_Msg_N ("& is not a recognized check name", P);
2739          end if;
2740
2741          Set_Etype (N, Standard_Boolean);
2742
2743       --------------
2744       -- Enum_Rep --
2745       --------------
2746
2747       when Attribute_Enum_Rep => Enum_Rep : declare
2748       begin
2749          if Present (E1) then
2750             Check_E1;
2751             Check_Discrete_Type;
2752             Resolve (E1, P_Base_Type);
2753
2754          else
2755             if not Is_Entity_Name (P)
2756               or else (not Is_Object (Entity (P))
2757                          and then
2758                        Ekind (Entity (P)) /= E_Enumeration_Literal)
2759             then
2760                Error_Attr_P
2761                  ("prefix of %attribute must be " &
2762                   "discrete type/object or enum literal");
2763             end if;
2764          end if;
2765
2766          Set_Etype (N, Universal_Integer);
2767       end Enum_Rep;
2768
2769       -------------
2770       -- Epsilon --
2771       -------------
2772
2773       when Attribute_Epsilon =>
2774          Check_Floating_Point_Type_0;
2775          Set_Etype (N, Universal_Real);
2776
2777       --------------
2778       -- Exponent --
2779       --------------
2780
2781       when Attribute_Exponent =>
2782          Check_Floating_Point_Type_1;
2783          Set_Etype (N, Universal_Integer);
2784          Resolve (E1, P_Base_Type);
2785
2786       ------------------
2787       -- External_Tag --
2788       ------------------
2789
2790       when Attribute_External_Tag =>
2791          Check_E0;
2792          Check_Type;
2793
2794          Set_Etype (N, Standard_String);
2795
2796          if not Is_Tagged_Type (P_Type) then
2797             Error_Attr_P ("prefix of % attribute must be tagged");
2798          end if;
2799
2800       ---------------
2801       -- Fast_Math --
2802       ---------------
2803
2804       when Attribute_Fast_Math =>
2805          Check_E0;
2806          Check_Standard_Prefix;
2807
2808          if Opt.Fast_Math then
2809             Rewrite (N, New_Occurrence_Of (Standard_True, Loc));
2810          else
2811             Rewrite (N, New_Occurrence_Of (Standard_False, Loc));
2812          end if;
2813
2814       -----------
2815       -- First --
2816       -----------
2817
2818       when Attribute_First =>
2819          Check_Array_Or_Scalar_Type;
2820
2821       ---------------
2822       -- First_Bit --
2823       ---------------
2824
2825       when Attribute_First_Bit =>
2826          Check_Component;
2827          Set_Etype (N, Universal_Integer);
2828
2829       -----------------
2830       -- Fixed_Value --
2831       -----------------
2832
2833       when Attribute_Fixed_Value =>
2834          Check_E1;
2835          Check_Fixed_Point_Type;
2836          Resolve (E1, Any_Integer);
2837          Set_Etype (N, P_Base_Type);
2838
2839       -----------
2840       -- Floor --
2841       -----------
2842
2843       when Attribute_Floor =>
2844          Check_Floating_Point_Type_1;
2845          Set_Etype (N, P_Base_Type);
2846          Resolve (E1, P_Base_Type);
2847
2848       ----------
2849       -- Fore --
2850       ----------
2851
2852       when Attribute_Fore =>
2853          Check_Fixed_Point_Type_0;
2854          Set_Etype (N, Universal_Integer);
2855
2856       --------------
2857       -- Fraction --
2858       --------------
2859
2860       when Attribute_Fraction =>
2861          Check_Floating_Point_Type_1;
2862          Set_Etype (N, P_Base_Type);
2863          Resolve (E1, P_Base_Type);
2864
2865       -----------------------
2866       -- Has_Access_Values --
2867       -----------------------
2868
2869       when Attribute_Has_Access_Values =>
2870          Check_Type;
2871          Check_E0;
2872          Set_Etype (N, Standard_Boolean);
2873
2874       -----------------------
2875       -- Has_Discriminants --
2876       -----------------------
2877
2878       when Attribute_Has_Discriminants =>
2879          Legal_Formal_Attribute;
2880
2881       --------------
2882       -- Identity --
2883       --------------
2884
2885       when Attribute_Identity =>
2886          Check_E0;
2887          Analyze (P);
2888
2889          if Etype (P) =  Standard_Exception_Type then
2890             Set_Etype (N, RTE (RE_Exception_Id));
2891
2892          --  Ada 2005 (AI-345): Attribute 'Identity may be applied to
2893          --  task interface class-wide types.
2894
2895          elsif Is_Task_Type (Etype (P))
2896            or else (Is_Access_Type (Etype (P))
2897                       and then Is_Task_Type (Designated_Type (Etype (P))))
2898            or else (Ada_Version >= Ada_05
2899                       and then Ekind (Etype (P)) = E_Class_Wide_Type
2900                       and then Is_Interface (Etype (P))
2901                       and then Is_Task_Interface (Etype (P)))
2902          then
2903             Resolve (P);
2904             Set_Etype (N, RTE (RO_AT_Task_Id));
2905
2906          else
2907             if Ada_Version >= Ada_05 then
2908                Error_Attr_P
2909                  ("prefix of % attribute must be an exception, a " &
2910                   "task or a task interface class-wide object");
2911             else
2912                Error_Attr_P
2913                  ("prefix of % attribute must be a task or an exception");
2914             end if;
2915          end if;
2916
2917       -----------
2918       -- Image --
2919       -----------
2920
2921       when Attribute_Image => Image :
2922       begin
2923          Set_Etype (N, Standard_String);
2924          Check_Scalar_Type;
2925
2926          if Is_Real_Type (P_Type) then
2927             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
2928                Error_Msg_Name_1 := Aname;
2929                Error_Msg_N
2930                  ("(Ada 83) % attribute not allowed for real types", N);
2931             end if;
2932          end if;
2933
2934          if Is_Enumeration_Type (P_Type) then
2935             Check_Restriction (No_Enumeration_Maps, N);
2936          end if;
2937
2938          Check_E1;
2939          Resolve (E1, P_Base_Type);
2940          Check_Enum_Image;
2941          Validate_Non_Static_Attribute_Function_Call;
2942       end Image;
2943
2944       ---------
2945       -- Img --
2946       ---------
2947
2948       when Attribute_Img => Img :
2949       begin
2950          Check_E0;
2951          Set_Etype (N, Standard_String);
2952
2953          if not Is_Scalar_Type (P_Type)
2954            or else (Is_Entity_Name (P) and then Is_Type (Entity (P)))
2955          then
2956             Error_Attr_P
2957               ("prefix of % attribute must be scalar object name");
2958          end if;
2959
2960          Check_Enum_Image;
2961       end Img;
2962
2963       -----------
2964       -- Input --
2965       -----------
2966
2967       when Attribute_Input =>
2968          Check_E1;
2969          Check_Stream_Attribute (TSS_Stream_Input);
2970          Set_Etype (N, P_Base_Type);
2971
2972       -------------------
2973       -- Integer_Value --
2974       -------------------
2975
2976       when Attribute_Integer_Value =>
2977          Check_E1;
2978          Check_Integer_Type;
2979          Resolve (E1, Any_Fixed);
2980
2981          --  Signal an error if argument type is not a specific fixed-point
2982          --  subtype. An error has been signalled already if the argument
2983          --  was not of a fixed-point type.
2984
2985          if Etype (E1) = Any_Fixed and then not Error_Posted (E1) then
2986             Error_Attr ("argument of % must be of a fixed-point type", E1);
2987          end if;
2988
2989          Set_Etype (N, P_Base_Type);
2990
2991       -----------
2992       -- Large --
2993       -----------
2994
2995       when Attribute_Large =>
2996          Check_E0;
2997          Check_Real_Type;
2998          Set_Etype (N, Universal_Real);
2999
3000       ----------
3001       -- Last --
3002       ----------
3003
3004       when Attribute_Last =>
3005          Check_Array_Or_Scalar_Type;
3006
3007       --------------
3008       -- Last_Bit --
3009       --------------
3010
3011       when Attribute_Last_Bit =>
3012          Check_Component;
3013          Set_Etype (N, Universal_Integer);
3014
3015       ------------------
3016       -- Leading_Part --
3017       ------------------
3018
3019       when Attribute_Leading_Part =>
3020          Check_Floating_Point_Type_2;
3021          Set_Etype (N, P_Base_Type);
3022          Resolve (E1, P_Base_Type);
3023          Resolve (E2, Any_Integer);
3024
3025       ------------
3026       -- Length --
3027       ------------
3028
3029       when Attribute_Length =>
3030          Check_Array_Type;
3031          Set_Etype (N, Universal_Integer);
3032
3033       -------------
3034       -- Machine --
3035       -------------
3036
3037       when Attribute_Machine =>
3038          Check_Floating_Point_Type_1;
3039          Set_Etype (N, P_Base_Type);
3040          Resolve (E1, P_Base_Type);
3041
3042       ------------------
3043       -- Machine_Emax --
3044       ------------------
3045
3046       when Attribute_Machine_Emax =>
3047          Check_Floating_Point_Type_0;
3048          Set_Etype (N, Universal_Integer);
3049
3050       ------------------
3051       -- Machine_Emin --
3052       ------------------
3053
3054       when Attribute_Machine_Emin =>
3055          Check_Floating_Point_Type_0;
3056          Set_Etype (N, Universal_Integer);
3057
3058       ----------------------
3059       -- Machine_Mantissa --
3060       ----------------------
3061
3062       when Attribute_Machine_Mantissa =>
3063          Check_Floating_Point_Type_0;
3064          Set_Etype (N, Universal_Integer);
3065
3066       -----------------------
3067       -- Machine_Overflows --
3068       -----------------------
3069
3070       when Attribute_Machine_Overflows =>
3071          Check_Real_Type;
3072          Check_E0;
3073          Set_Etype (N, Standard_Boolean);
3074
3075       -------------------
3076       -- Machine_Radix --
3077       -------------------
3078
3079       when Attribute_Machine_Radix =>
3080          Check_Real_Type;
3081          Check_E0;
3082          Set_Etype (N, Universal_Integer);
3083
3084       ----------------------
3085       -- Machine_Rounding --
3086       ----------------------
3087
3088       when Attribute_Machine_Rounding =>
3089          Check_Floating_Point_Type_1;
3090          Set_Etype (N, P_Base_Type);
3091          Resolve (E1, P_Base_Type);
3092
3093       --------------------
3094       -- Machine_Rounds --
3095       --------------------
3096
3097       when Attribute_Machine_Rounds =>
3098          Check_Real_Type;
3099          Check_E0;
3100          Set_Etype (N, Standard_Boolean);
3101
3102       ------------------
3103       -- Machine_Size --
3104       ------------------
3105
3106       when Attribute_Machine_Size =>
3107          Check_E0;
3108          Check_Type;
3109          Check_Not_Incomplete_Type;
3110          Set_Etype (N, Universal_Integer);
3111
3112       --------------
3113       -- Mantissa --
3114       --------------
3115
3116       when Attribute_Mantissa =>
3117          Check_E0;
3118          Check_Real_Type;
3119          Set_Etype (N, Universal_Integer);
3120
3121       ---------
3122       -- Max --
3123       ---------
3124
3125       when Attribute_Max =>
3126          Check_E2;
3127          Check_Scalar_Type;
3128          Resolve (E1, P_Base_Type);
3129          Resolve (E2, P_Base_Type);
3130          Set_Etype (N, P_Base_Type);
3131
3132       ----------------------------------
3133       -- Max_Size_In_Storage_Elements --
3134       ----------------------------------
3135
3136       when Attribute_Max_Size_In_Storage_Elements =>
3137          Check_E0;
3138          Check_Type;
3139          Check_Not_Incomplete_Type;
3140          Set_Etype (N, Universal_Integer);
3141
3142       -----------------------
3143       -- Maximum_Alignment --
3144       -----------------------
3145
3146       when Attribute_Maximum_Alignment =>
3147          Standard_Attribute (Ttypes.Maximum_Alignment);
3148
3149       --------------------
3150       -- Mechanism_Code --
3151       --------------------
3152
3153       when Attribute_Mechanism_Code =>
3154          if not Is_Entity_Name (P)
3155            or else not Is_Subprogram (Entity (P))
3156          then
3157             Error_Attr_P ("prefix of % attribute must be subprogram");
3158          end if;
3159
3160          Check_Either_E0_Or_E1;
3161
3162          if Present (E1) then
3163             Resolve (E1, Any_Integer);
3164             Set_Etype (E1, Standard_Integer);
3165
3166             if not Is_Static_Expression (E1) then
3167                Flag_Non_Static_Expr
3168                  ("expression for parameter number must be static!", E1);
3169                Error_Attr;
3170
3171             elsif UI_To_Int (Intval (E1)) > Number_Formals (Entity (P))
3172               or else UI_To_Int (Intval (E1)) < 0
3173             then
3174                Error_Attr ("invalid parameter number for %attribute", E1);
3175             end if;
3176          end if;
3177
3178          Set_Etype (N, Universal_Integer);
3179
3180       ---------
3181       -- Min --
3182       ---------
3183
3184       when Attribute_Min =>
3185          Check_E2;
3186          Check_Scalar_Type;
3187          Resolve (E1, P_Base_Type);
3188          Resolve (E2, P_Base_Type);
3189          Set_Etype (N, P_Base_Type);
3190
3191       ---------
3192       -- Mod --
3193       ---------
3194
3195       when Attribute_Mod =>
3196
3197          --  Note: this attribute is only allowed in Ada 2005 mode, but
3198          --  we do not need to test that here, since Mod is only recognized
3199          --  as an attribute name in Ada 2005 mode during the parse.
3200
3201          Check_E1;
3202          Check_Modular_Integer_Type;
3203          Resolve (E1, Any_Integer);
3204          Set_Etype (N, P_Base_Type);
3205
3206       -----------
3207       -- Model --
3208       -----------
3209
3210       when Attribute_Model =>
3211          Check_Floating_Point_Type_1;
3212          Set_Etype (N, P_Base_Type);
3213          Resolve (E1, P_Base_Type);
3214
3215       ----------------
3216       -- Model_Emin --
3217       ----------------
3218
3219       when Attribute_Model_Emin =>
3220          Check_Floating_Point_Type_0;
3221          Set_Etype (N, Universal_Integer);
3222
3223       -------------------
3224       -- Model_Epsilon --
3225       -------------------
3226
3227       when Attribute_Model_Epsilon =>
3228          Check_Floating_Point_Type_0;
3229          Set_Etype (N, Universal_Real);
3230
3231       --------------------
3232       -- Model_Mantissa --
3233       --------------------
3234
3235       when Attribute_Model_Mantissa =>
3236          Check_Floating_Point_Type_0;
3237          Set_Etype (N, Universal_Integer);
3238
3239       -----------------
3240       -- Model_Small --
3241       -----------------
3242
3243       when Attribute_Model_Small =>
3244          Check_Floating_Point_Type_0;
3245          Set_Etype (N, Universal_Real);
3246
3247       -------------
3248       -- Modulus --
3249       -------------
3250
3251       when Attribute_Modulus =>
3252          Check_E0;
3253          Check_Modular_Integer_Type;
3254          Set_Etype (N, Universal_Integer);
3255
3256       --------------------
3257       -- Null_Parameter --
3258       --------------------
3259
3260       when Attribute_Null_Parameter => Null_Parameter : declare
3261          Parnt  : constant Node_Id := Parent (N);
3262          GParnt : constant Node_Id := Parent (Parnt);
3263
3264          procedure Bad_Null_Parameter (Msg : String);
3265          --  Used if bad Null parameter attribute node is found. Issues
3266          --  given error message, and also sets the type to Any_Type to
3267          --  avoid blowups later on from dealing with a junk node.
3268
3269          procedure Must_Be_Imported (Proc_Ent : Entity_Id);
3270          --  Called to check that Proc_Ent is imported subprogram
3271
3272          ------------------------
3273          -- Bad_Null_Parameter --
3274          ------------------------
3275
3276          procedure Bad_Null_Parameter (Msg : String) is
3277          begin
3278             Error_Msg_N (Msg, N);
3279             Set_Etype (N, Any_Type);
3280          end Bad_Null_Parameter;
3281
3282          ----------------------
3283          -- Must_Be_Imported --
3284          ----------------------
3285
3286          procedure Must_Be_Imported (Proc_Ent : Entity_Id) is
3287             Pent : Entity_Id := Proc_Ent;
3288
3289          begin
3290             while Present (Alias (Pent)) loop
3291                Pent := Alias (Pent);
3292             end loop;
3293
3294             --  Ignore check if procedure not frozen yet (we will get
3295             --  another chance when the default parameter is reanalyzed)
3296
3297             if not Is_Frozen (Pent) then
3298                return;
3299
3300             elsif not Is_Imported (Pent) then
3301                Bad_Null_Parameter
3302                  ("Null_Parameter can only be used with imported subprogram");
3303
3304             else
3305                return;
3306             end if;
3307          end Must_Be_Imported;
3308
3309       --  Start of processing for Null_Parameter
3310
3311       begin
3312          Check_Type;
3313          Check_E0;
3314          Set_Etype (N, P_Type);
3315
3316          --  Case of attribute used as default expression
3317
3318          if Nkind (Parnt) = N_Parameter_Specification then
3319             Must_Be_Imported (Defining_Entity (GParnt));
3320
3321          --  Case of attribute used as actual for subprogram (positional)
3322
3323          elsif (Nkind (Parnt) = N_Procedure_Call_Statement
3324                  or else
3325                 Nkind (Parnt) = N_Function_Call)
3326             and then Is_Entity_Name (Name (Parnt))
3327          then
3328             Must_Be_Imported (Entity (Name (Parnt)));
3329
3330          --  Case of attribute used as actual for subprogram (named)
3331
3332          elsif Nkind (Parnt) = N_Parameter_Association
3333            and then (Nkind (GParnt) = N_Procedure_Call_Statement
3334                        or else
3335                      Nkind (GParnt) = N_Function_Call)
3336            and then Is_Entity_Name (Name (GParnt))
3337          then
3338             Must_Be_Imported (Entity (Name (GParnt)));
3339
3340          --  Not an allowed case
3341
3342          else
3343             Bad_Null_Parameter
3344               ("Null_Parameter must be actual or default parameter");
3345          end if;
3346
3347       end Null_Parameter;
3348
3349       -----------------
3350       -- Object_Size --
3351       -----------------
3352
3353       when Attribute_Object_Size =>
3354          Check_E0;
3355          Check_Type;
3356          Check_Not_Incomplete_Type;
3357          Set_Etype (N, Universal_Integer);
3358
3359       ------------
3360       -- Output --
3361       ------------
3362
3363       when Attribute_Output =>
3364          Check_E2;
3365          Check_Stream_Attribute (TSS_Stream_Output);
3366          Set_Etype (N, Standard_Void_Type);
3367          Resolve (N, Standard_Void_Type);
3368
3369       ------------------
3370       -- Partition_ID --
3371       ------------------
3372
3373       when Attribute_Partition_ID =>
3374          Check_E0;
3375
3376          if P_Type /= Any_Type then
3377             if not Is_Library_Level_Entity (Entity (P)) then
3378                Error_Attr_P
3379                  ("prefix of % attribute must be library-level entity");
3380
3381             --  The defining entity of prefix should not be declared inside
3382             --  a Pure unit. RM E.1(8).
3383             --  The Is_Pure flag has been set during declaration.
3384
3385             elsif Is_Entity_Name (P)
3386               and then Is_Pure (Entity (P))
3387             then
3388                Error_Attr_P
3389                  ("prefix of % attribute must not be declared pure");
3390             end if;
3391          end if;
3392
3393          Set_Etype (N, Universal_Integer);
3394
3395       -------------------------
3396       -- Passed_By_Reference --
3397       -------------------------
3398
3399       when Attribute_Passed_By_Reference =>
3400          Check_E0;
3401          Check_Type;
3402          Set_Etype (N, Standard_Boolean);
3403
3404       ------------------
3405       -- Pool_Address --
3406       ------------------
3407
3408       when Attribute_Pool_Address =>
3409          Check_E0;
3410          Set_Etype (N, RTE (RE_Address));
3411
3412       ---------
3413       -- Pos --
3414       ---------
3415
3416       when Attribute_Pos =>
3417          Check_Discrete_Type;
3418          Check_E1;
3419          Resolve (E1, P_Base_Type);
3420          Set_Etype (N, Universal_Integer);
3421
3422       --------------
3423       -- Position --
3424       --------------
3425
3426       when Attribute_Position =>
3427          Check_Component;
3428          Set_Etype (N, Universal_Integer);
3429
3430       ----------
3431       -- Pred --
3432       ----------
3433
3434       when Attribute_Pred =>
3435          Check_Scalar_Type;
3436          Check_E1;
3437          Resolve (E1, P_Base_Type);
3438          Set_Etype (N, P_Base_Type);
3439
3440          --  Nothing to do for real type case
3441
3442          if Is_Real_Type (P_Type) then
3443             null;
3444
3445          --  If not modular type, test for overflow check required
3446
3447          else
3448             if not Is_Modular_Integer_Type (P_Type)
3449               and then not Range_Checks_Suppressed (P_Base_Type)
3450             then
3451                Enable_Range_Check (E1);
3452             end if;
3453          end if;
3454
3455       --------------
3456       -- Priority --
3457       --------------
3458
3459       --  Ada 2005 (AI-327): Dynamic ceiling priorities
3460
3461       when Attribute_Priority =>
3462          if Ada_Version < Ada_05 then
3463             Error_Attr ("% attribute is allowed only in Ada 2005 mode", P);
3464          end if;
3465
3466          Check_E0;
3467
3468          --  The prefix must be a protected object (AARM D.5.2 (2/2))
3469
3470          Analyze (P);
3471
3472          if Is_Protected_Type (Etype (P))
3473            or else (Is_Access_Type (Etype (P))
3474                       and then Is_Protected_Type (Designated_Type (Etype (P))))
3475          then
3476             Resolve (P, Etype (P));
3477          else
3478             Error_Attr_P ("prefix of % attribute must be a protected object");
3479          end if;
3480
3481          Set_Etype (N, Standard_Integer);
3482
3483          --  Must be called from within a protected procedure or entry of the
3484          --  protected object.
3485
3486          declare
3487             S : Entity_Id;
3488
3489          begin
3490             S := Current_Scope;
3491             while S /= Etype (P)
3492                and then S /= Standard_Standard
3493             loop
3494                S := Scope (S);
3495             end loop;
3496
3497             if S = Standard_Standard then
3498                Error_Attr ("the attribute % is only allowed inside protected "
3499                            & "operations", P);
3500             end if;
3501          end;
3502
3503          Validate_Non_Static_Attribute_Function_Call;
3504
3505       -----------
3506       -- Range --
3507       -----------
3508
3509       when Attribute_Range =>
3510          Check_Array_Or_Scalar_Type;
3511
3512          if Ada_Version = Ada_83
3513            and then Is_Scalar_Type (P_Type)
3514            and then Comes_From_Source (N)
3515          then
3516             Error_Attr
3517               ("(Ada 83) % attribute not allowed for scalar type", P);
3518          end if;
3519
3520       ------------------
3521       -- Range_Length --
3522       ------------------
3523
3524       when Attribute_Range_Length =>
3525          Check_Discrete_Type;
3526          Set_Etype (N, Universal_Integer);
3527
3528       ----------
3529       -- Read --
3530       ----------
3531
3532       when Attribute_Read =>
3533          Check_E2;
3534          Check_Stream_Attribute (TSS_Stream_Read);
3535          Set_Etype (N, Standard_Void_Type);
3536          Resolve (N, Standard_Void_Type);
3537          Note_Possible_Modification (E2);
3538
3539       ---------------
3540       -- Remainder --
3541       ---------------
3542
3543       when Attribute_Remainder =>
3544          Check_Floating_Point_Type_2;
3545          Set_Etype (N, P_Base_Type);
3546          Resolve (E1, P_Base_Type);
3547          Resolve (E2, P_Base_Type);
3548
3549       -----------
3550       -- Round --
3551       -----------
3552
3553       when Attribute_Round =>
3554          Check_E1;
3555          Check_Decimal_Fixed_Point_Type;
3556          Set_Etype (N, P_Base_Type);
3557
3558          --  Because the context is universal_real (3.5.10(12)) it is a legal
3559          --  context for a universal fixed expression. This is the only
3560          --  attribute whose functional description involves U_R.
3561
3562          if Etype (E1) = Universal_Fixed then
3563             declare
3564                Conv : constant Node_Id := Make_Type_Conversion (Loc,
3565                   Subtype_Mark => New_Occurrence_Of (Universal_Real, Loc),
3566                   Expression   => Relocate_Node (E1));
3567
3568             begin
3569                Rewrite (E1, Conv);
3570                Analyze (E1);
3571             end;
3572          end if;
3573
3574          Resolve (E1, Any_Real);
3575
3576       --------------
3577       -- Rounding --
3578       --------------
3579
3580       when Attribute_Rounding =>
3581          Check_Floating_Point_Type_1;
3582          Set_Etype (N, P_Base_Type);
3583          Resolve (E1, P_Base_Type);
3584
3585       ---------------
3586       -- Safe_Emax --
3587       ---------------
3588
3589       when Attribute_Safe_Emax =>
3590          Check_Floating_Point_Type_0;
3591          Set_Etype (N, Universal_Integer);
3592
3593       ----------------
3594       -- Safe_First --
3595       ----------------
3596
3597       when Attribute_Safe_First =>
3598          Check_Floating_Point_Type_0;
3599          Set_Etype (N, Universal_Real);
3600
3601       ----------------
3602       -- Safe_Large --
3603       ----------------
3604
3605       when Attribute_Safe_Large =>
3606          Check_E0;
3607          Check_Real_Type;
3608          Set_Etype (N, Universal_Real);
3609
3610       ---------------
3611       -- Safe_Last --
3612       ---------------
3613
3614       when Attribute_Safe_Last =>
3615          Check_Floating_Point_Type_0;
3616          Set_Etype (N, Universal_Real);
3617
3618       ----------------
3619       -- Safe_Small --
3620       ----------------
3621
3622       when Attribute_Safe_Small =>
3623          Check_E0;
3624          Check_Real_Type;
3625          Set_Etype (N, Universal_Real);
3626
3627       -----------
3628       -- Scale --
3629       -----------
3630
3631       when Attribute_Scale =>
3632          Check_E0;
3633          Check_Decimal_Fixed_Point_Type;
3634          Set_Etype (N, Universal_Integer);
3635
3636       -------------
3637       -- Scaling --
3638       -------------
3639
3640       when Attribute_Scaling =>
3641          Check_Floating_Point_Type_2;
3642          Set_Etype (N, P_Base_Type);
3643          Resolve (E1, P_Base_Type);
3644
3645       ------------------
3646       -- Signed_Zeros --
3647       ------------------
3648
3649       when Attribute_Signed_Zeros =>
3650          Check_Floating_Point_Type_0;
3651          Set_Etype (N, Standard_Boolean);
3652
3653       ----------
3654       -- Size --
3655       ----------
3656
3657       when Attribute_Size | Attribute_VADS_Size =>
3658          Check_E0;
3659
3660          --  If prefix is parameterless function call, rewrite and resolve
3661          --  as such.
3662
3663          if Is_Entity_Name (P)
3664            and then Ekind (Entity (P)) = E_Function
3665          then
3666             Resolve (P);
3667
3668          --  Similar processing for a protected function call
3669
3670          elsif Nkind (P) = N_Selected_Component
3671            and then Ekind (Entity (Selector_Name (P))) = E_Function
3672          then
3673             Resolve (P);
3674          end if;
3675
3676          if Is_Object_Reference (P) then
3677             Check_Object_Reference (P);
3678
3679          elsif Is_Entity_Name (P)
3680            and then (Is_Type (Entity (P))
3681                        or else Ekind (Entity (P)) = E_Enumeration_Literal)
3682          then
3683             null;
3684
3685          elsif Nkind (P) = N_Type_Conversion
3686            and then not Comes_From_Source (P)
3687          then
3688             null;
3689
3690          else
3691             Error_Attr_P ("invalid prefix for % attribute");
3692          end if;
3693
3694          Check_Not_Incomplete_Type;
3695          Set_Etype (N, Universal_Integer);
3696
3697       -----------
3698       -- Small --
3699       -----------
3700
3701       when Attribute_Small =>
3702          Check_E0;
3703          Check_Real_Type;
3704          Set_Etype (N, Universal_Real);
3705
3706       ------------------
3707       -- Storage_Pool --
3708       ------------------
3709
3710       when Attribute_Storage_Pool =>
3711          if Is_Access_Type (P_Type) then
3712             Check_E0;
3713
3714             if Ekind (P_Type) = E_Access_Subprogram_Type then
3715                Error_Attr_P
3716                  ("cannot use % attribute for access-to-subprogram type");
3717             end if;
3718
3719             --  Set appropriate entity
3720
3721             if Present (Associated_Storage_Pool (Root_Type (P_Type))) then
3722                Set_Entity (N, Associated_Storage_Pool (Root_Type (P_Type)));
3723             else
3724                Set_Entity (N, RTE (RE_Global_Pool_Object));
3725             end if;
3726
3727             Set_Etype (N, Class_Wide_Type (RTE (RE_Root_Storage_Pool)));
3728
3729             --  Validate_Remote_Access_To_Class_Wide_Type for attribute
3730             --  Storage_Pool since this attribute is not defined for such
3731             --  types (RM E.2.3(22)).
3732
3733             Validate_Remote_Access_To_Class_Wide_Type (N);
3734
3735          else
3736             Error_Attr_P ("prefix of % attribute must be access type");
3737          end if;
3738
3739       ------------------
3740       -- Storage_Size --
3741       ------------------
3742
3743       when Attribute_Storage_Size =>
3744          if Is_Task_Type (P_Type) then
3745             Check_E0;
3746             Set_Etype (N, Universal_Integer);
3747
3748          elsif Is_Access_Type (P_Type) then
3749             if Ekind (P_Type) = E_Access_Subprogram_Type then
3750                Error_Attr_P
3751                  ("cannot use % attribute for access-to-subprogram type");
3752             end if;
3753
3754             if Is_Entity_Name (P)
3755               and then Is_Type (Entity (P))
3756             then
3757                Check_E0;
3758                Check_Type;
3759                Set_Etype (N, Universal_Integer);
3760
3761                --   Validate_Remote_Access_To_Class_Wide_Type for attribute
3762                --   Storage_Size since this attribute is not defined for
3763                --   such types (RM E.2.3(22)).
3764
3765                Validate_Remote_Access_To_Class_Wide_Type (N);
3766
3767             --  The prefix is allowed to be an implicit dereference
3768             --  of an access value designating a task.
3769
3770             else
3771                Check_E0;
3772                Check_Task_Prefix;
3773                Set_Etype (N, Universal_Integer);
3774             end if;
3775
3776          else
3777             Error_Attr_P ("prefix of % attribute must be access or task type");
3778          end if;
3779
3780       ------------------
3781       -- Storage_Unit --
3782       ------------------
3783
3784       when Attribute_Storage_Unit =>
3785          Standard_Attribute (Ttypes.System_Storage_Unit);
3786
3787       -----------------
3788       -- Stream_Size --
3789       -----------------
3790
3791       when Attribute_Stream_Size =>
3792          Check_E0;
3793          Check_Type;
3794
3795          if Is_Entity_Name (P)
3796            and then Is_Elementary_Type (Entity (P))
3797          then
3798             Set_Etype (N, Universal_Integer);
3799          else
3800             Error_Attr_P ("invalid prefix for % attribute");
3801          end if;
3802
3803       ---------------
3804       -- Stub_Type --
3805       ---------------
3806
3807       when Attribute_Stub_Type =>
3808          Check_Type;
3809          Check_E0;
3810
3811          if Is_Remote_Access_To_Class_Wide_Type (P_Type) then
3812             Rewrite (N,
3813               New_Occurrence_Of (Corresponding_Stub_Type (P_Type), Loc));
3814          else
3815             Error_Attr_P
3816               ("prefix of% attribute must be remote access to classwide");
3817          end if;
3818
3819       ----------
3820       -- Succ --
3821       ----------
3822
3823       when Attribute_Succ =>
3824          Check_Scalar_Type;
3825          Check_E1;
3826          Resolve (E1, P_Base_Type);
3827          Set_Etype (N, P_Base_Type);
3828
3829          --  Nothing to do for real type case
3830
3831          if Is_Real_Type (P_Type) then
3832             null;
3833
3834          --  If not modular type, test for overflow check required
3835
3836          else
3837             if not Is_Modular_Integer_Type (P_Type)
3838               and then not Range_Checks_Suppressed (P_Base_Type)
3839             then
3840                Enable_Range_Check (E1);
3841             end if;
3842          end if;
3843
3844       ---------
3845       -- Tag --
3846       ---------
3847
3848       when Attribute_Tag =>
3849          Check_E0;
3850          Check_Dereference;
3851
3852          if not Is_Tagged_Type (P_Type) then
3853             Error_Attr_P ("prefix of % attribute must be tagged");
3854
3855          --  Next test does not apply to generated code
3856          --  why not, and what does the illegal reference mean???
3857
3858          elsif Is_Object_Reference (P)
3859            and then not Is_Class_Wide_Type (P_Type)
3860            and then Comes_From_Source (N)
3861          then
3862             Error_Attr_P
3863               ("% attribute can only be applied to objects " &
3864                "of class - wide type");
3865          end if;
3866
3867          --  The prefix cannot be an incomplete type. However, references
3868          --  to 'Tag can be generated when expanding interface conversions,
3869          --  and this is legal.
3870
3871          if Comes_From_Source (N) then
3872             Check_Not_Incomplete_Type;
3873          end if;
3874
3875          --  Set appropriate type
3876
3877          Set_Etype (N, RTE (RE_Tag));
3878
3879       -----------------
3880       -- Target_Name --
3881       -----------------
3882
3883       when Attribute_Target_Name => Target_Name : declare
3884          TN : constant String := Sdefault.Target_Name.all;
3885          TL : Natural;
3886
3887       begin
3888          Check_Standard_Prefix;
3889          Check_E0;
3890
3891          TL := TN'Last;
3892
3893          if TN (TL) = '/' or else TN (TL) = '\' then
3894             TL := TL - 1;
3895          end if;
3896
3897          Rewrite (N,
3898            Make_String_Literal (Loc,
3899              Strval => TN (TN'First .. TL)));
3900          Analyze_And_Resolve (N, Standard_String);
3901       end Target_Name;
3902
3903       ----------------
3904       -- Terminated --
3905       ----------------
3906
3907       when Attribute_Terminated =>
3908          Check_E0;
3909          Set_Etype (N, Standard_Boolean);
3910          Check_Task_Prefix;
3911
3912       ----------------
3913       -- To_Address --
3914       ----------------
3915
3916       when Attribute_To_Address =>
3917          Check_E1;
3918          Analyze (P);
3919
3920          if Nkind (P) /= N_Identifier
3921            or else Chars (P) /= Name_System
3922          then
3923             Error_Attr_P ("prefix of %attribute must be System");
3924          end if;
3925
3926          Generate_Reference (RTE (RE_Address), P);
3927          Analyze_And_Resolve (E1, Any_Integer);
3928          Set_Etype (N, RTE (RE_Address));
3929
3930       ----------------
3931       -- Truncation --
3932       ----------------
3933
3934       when Attribute_Truncation =>
3935          Check_Floating_Point_Type_1;
3936          Resolve (E1, P_Base_Type);
3937          Set_Etype (N, P_Base_Type);
3938
3939       ----------------
3940       -- Type_Class --
3941       ----------------
3942
3943       when Attribute_Type_Class =>
3944          Check_E0;
3945          Check_Type;
3946          Check_Not_Incomplete_Type;
3947          Set_Etype (N, RTE (RE_Type_Class));
3948
3949       -----------------
3950       -- UET_Address --
3951       -----------------
3952
3953       when Attribute_UET_Address =>
3954          Check_E0;
3955          Check_Unit_Name (P);
3956          Set_Etype (N, RTE (RE_Address));
3957
3958       -----------------------
3959       -- Unbiased_Rounding --
3960       -----------------------
3961
3962       when Attribute_Unbiased_Rounding =>
3963          Check_Floating_Point_Type_1;
3964          Set_Etype (N, P_Base_Type);
3965          Resolve (E1, P_Base_Type);
3966
3967       ----------------------
3968       -- Unchecked_Access --
3969       ----------------------
3970
3971       when Attribute_Unchecked_Access =>
3972          if Comes_From_Source (N) then
3973             Check_Restriction (No_Unchecked_Access, N);
3974          end if;
3975
3976          Analyze_Access_Attribute;
3977
3978       -------------------------
3979       -- Unconstrained_Array --
3980       -------------------------
3981
3982       when Attribute_Unconstrained_Array =>
3983          Check_E0;
3984          Check_Type;
3985          Check_Not_Incomplete_Type;
3986          Set_Etype (N, Standard_Boolean);
3987
3988       ------------------------------
3989       -- Universal_Literal_String --
3990       ------------------------------
3991
3992       --  This is a GNAT specific attribute whose prefix must be a named
3993       --  number where the expression is either a single numeric literal,
3994       --  or a numeric literal immediately preceded by a minus sign. The
3995       --  result is equivalent to a string literal containing the text of
3996       --  the literal as it appeared in the source program with a possible
3997       --  leading minus sign.
3998
3999       when Attribute_Universal_Literal_String => Universal_Literal_String :
4000       begin
4001          Check_E0;
4002
4003          if not Is_Entity_Name (P)
4004            or else Ekind (Entity (P)) not in Named_Kind
4005          then
4006             Error_Attr_P ("prefix for % attribute must be named number");
4007
4008          else
4009             declare
4010                Expr     : Node_Id;
4011                Negative : Boolean;
4012                S        : Source_Ptr;
4013                Src      : Source_Buffer_Ptr;
4014
4015             begin
4016                Expr := Original_Node (Expression (Parent (Entity (P))));
4017
4018                if Nkind (Expr) = N_Op_Minus then
4019                   Negative := True;
4020                   Expr := Original_Node (Right_Opnd (Expr));
4021                else
4022                   Negative := False;
4023                end if;
4024
4025                if Nkind (Expr) /= N_Integer_Literal
4026                  and then Nkind (Expr) /= N_Real_Literal
4027                then
4028                   Error_Attr
4029                     ("named number for % attribute must be simple literal", N);
4030                end if;
4031
4032                --  Build string literal corresponding to source literal text
4033
4034                Start_String;
4035
4036                if Negative then
4037                   Store_String_Char (Get_Char_Code ('-'));
4038                end if;
4039
4040                S := Sloc (Expr);
4041                Src := Source_Text (Get_Source_File_Index (S));
4042
4043                while Src (S) /= ';' and then Src (S) /= ' ' loop
4044                   Store_String_Char (Get_Char_Code (Src (S)));
4045                   S := S + 1;
4046                end loop;
4047
4048                --  Now we rewrite the attribute with the string literal
4049
4050                Rewrite (N,
4051                  Make_String_Literal (Loc, End_String));
4052                Analyze (N);
4053             end;
4054          end if;
4055       end Universal_Literal_String;
4056
4057       -------------------------
4058       -- Unrestricted_Access --
4059       -------------------------
4060
4061       --  This is a GNAT specific attribute which is like Access except that
4062       --  all scope checks and checks for aliased views are omitted.
4063
4064       when Attribute_Unrestricted_Access =>
4065          if Comes_From_Source (N) then
4066             Check_Restriction (No_Unchecked_Access, N);
4067          end if;
4068
4069          if Is_Entity_Name (P) then
4070             Set_Address_Taken (Entity (P));
4071          end if;
4072
4073          Analyze_Access_Attribute;
4074
4075       ---------
4076       -- Val --
4077       ---------
4078
4079       when Attribute_Val => Val : declare
4080       begin
4081          Check_E1;
4082          Check_Discrete_Type;
4083          Resolve (E1, Any_Integer);
4084          Set_Etype (N, P_Base_Type);
4085
4086          --  Note, we need a range check in general, but we wait for the
4087          --  Resolve call to do this, since we want to let Eval_Attribute
4088          --  have a chance to find an static illegality first!
4089       end Val;
4090
4091       -----------
4092       -- Valid --
4093       -----------
4094
4095       when Attribute_Valid =>
4096          Check_E0;
4097
4098          --  Ignore check for object if we have a 'Valid reference generated
4099          --  by the expanded code, since in some cases valid checks can occur
4100          --  on items that are names, but are not objects (e.g. attributes).
4101
4102          if Comes_From_Source (N) then
4103             Check_Object_Reference (P);
4104          end if;
4105
4106          if not Is_Scalar_Type (P_Type) then
4107             Error_Attr_P ("object for % attribute must be of scalar type");
4108          end if;
4109
4110          Set_Etype (N, Standard_Boolean);
4111
4112       -----------
4113       -- Value --
4114       -----------
4115
4116       when Attribute_Value => Value :
4117       begin
4118          Check_E1;
4119          Check_Scalar_Type;
4120
4121          --  Case of enumeration type
4122
4123          if Is_Enumeration_Type (P_Type) then
4124             Check_Restriction (No_Enumeration_Maps, N);
4125
4126             --  Mark all enumeration literals as referenced, since the use of
4127             --  the Value attribute can implicitly reference any of the
4128             --  literals of the enumeration base type.
4129
4130             declare
4131                Ent : Entity_Id := First_Literal (P_Base_Type);
4132             begin
4133                while Present (Ent) loop
4134                   Set_Referenced (Ent);
4135                   Next_Literal (Ent);
4136                end loop;
4137             end;
4138          end if;
4139
4140          --  Set Etype before resolving expression because expansion of
4141          --  expression may require enclosing type. Note that the type
4142          --  returned by 'Value is the base type of the prefix type.
4143
4144          Set_Etype (N, P_Base_Type);
4145          Validate_Non_Static_Attribute_Function_Call;
4146       end Value;
4147
4148       ----------------
4149       -- Value_Size --
4150       ----------------
4151
4152       when Attribute_Value_Size =>
4153          Check_E0;
4154          Check_Type;
4155          Check_Not_Incomplete_Type;
4156          Set_Etype (N, Universal_Integer);
4157
4158       -------------
4159       -- Version --
4160       -------------
4161
4162       when Attribute_Version =>
4163          Check_E0;
4164          Check_Program_Unit;
4165          Set_Etype (N, RTE (RE_Version_String));
4166
4167       ------------------
4168       -- Wchar_T_Size --
4169       ------------------
4170
4171       when Attribute_Wchar_T_Size =>
4172          Standard_Attribute (Interfaces_Wchar_T_Size);
4173
4174       ----------------
4175       -- Wide_Image --
4176       ----------------
4177
4178       when Attribute_Wide_Image => Wide_Image :
4179       begin
4180          Check_Scalar_Type;
4181          Set_Etype (N, Standard_Wide_String);
4182          Check_E1;
4183          Resolve (E1, P_Base_Type);
4184          Validate_Non_Static_Attribute_Function_Call;
4185       end Wide_Image;
4186
4187       ---------------------
4188       -- Wide_Wide_Image --
4189       ---------------------
4190
4191       when Attribute_Wide_Wide_Image => Wide_Wide_Image :
4192       begin
4193          Check_Scalar_Type;
4194          Set_Etype (N, Standard_Wide_Wide_String);
4195          Check_E1;
4196          Resolve (E1, P_Base_Type);
4197          Validate_Non_Static_Attribute_Function_Call;
4198       end Wide_Wide_Image;
4199
4200       ----------------
4201       -- Wide_Value --
4202       ----------------
4203
4204       when Attribute_Wide_Value => Wide_Value :
4205       begin
4206          Check_E1;
4207          Check_Scalar_Type;
4208
4209          --  Set Etype before resolving expression because expansion
4210          --  of expression may require enclosing type.
4211
4212          Set_Etype (N, P_Type);
4213          Validate_Non_Static_Attribute_Function_Call;
4214       end Wide_Value;
4215
4216       ---------------------
4217       -- Wide_Wide_Value --
4218       ---------------------
4219
4220       when Attribute_Wide_Wide_Value => Wide_Wide_Value :
4221       begin
4222          Check_E1;
4223          Check_Scalar_Type;
4224
4225          --  Set Etype before resolving expression because expansion
4226          --  of expression may require enclosing type.
4227
4228          Set_Etype (N, P_Type);
4229          Validate_Non_Static_Attribute_Function_Call;
4230       end Wide_Wide_Value;
4231
4232       ---------------------
4233       -- Wide_Wide_Width --
4234       ---------------------
4235
4236       when Attribute_Wide_Wide_Width =>
4237          Check_E0;
4238          Check_Scalar_Type;
4239          Set_Etype (N, Universal_Integer);
4240
4241       ----------------
4242       -- Wide_Width --
4243       ----------------
4244
4245       when Attribute_Wide_Width =>
4246          Check_E0;
4247          Check_Scalar_Type;
4248          Set_Etype (N, Universal_Integer);
4249
4250       -----------
4251       -- Width --
4252       -----------
4253
4254       when Attribute_Width =>
4255          Check_E0;
4256          Check_Scalar_Type;
4257          Set_Etype (N, Universal_Integer);
4258
4259       ---------------
4260       -- Word_Size --
4261       ---------------
4262
4263       when Attribute_Word_Size =>
4264          Standard_Attribute (System_Word_Size);
4265
4266       -----------
4267       -- Write --
4268       -----------
4269
4270       when Attribute_Write =>
4271          Check_E2;
4272          Check_Stream_Attribute (TSS_Stream_Write);
4273          Set_Etype (N, Standard_Void_Type);
4274          Resolve (N, Standard_Void_Type);
4275
4276       end case;
4277
4278    --  All errors raise Bad_Attribute, so that we get out before any further
4279    --  damage occurs when an error is detected (for example, if we check for
4280    --  one attribute expression, and the check succeeds, we want to be able
4281    --  to proceed securely assuming that an expression is in fact present.
4282
4283    --  Note: we set the attribute analyzed in this case to prevent any
4284    --  attempt at reanalysis which could generate spurious error msgs.
4285
4286    exception
4287       when Bad_Attribute =>
4288          Set_Analyzed (N);
4289          Set_Etype (N, Any_Type);
4290          return;
4291    end Analyze_Attribute;
4292
4293    --------------------
4294    -- Eval_Attribute --
4295    --------------------
4296
4297    procedure Eval_Attribute (N : Node_Id) is
4298       Loc   : constant Source_Ptr   := Sloc (N);
4299       Aname : constant Name_Id      := Attribute_Name (N);
4300       Id    : constant Attribute_Id := Get_Attribute_Id (Aname);
4301       P     : constant Node_Id      := Prefix (N);
4302
4303       C_Type : constant Entity_Id := Etype (N);
4304       --  The type imposed by the context
4305
4306       E1 : Node_Id;
4307       --  First expression, or Empty if none
4308
4309       E2 : Node_Id;
4310       --  Second expression, or Empty if none
4311
4312       P_Entity : Entity_Id;
4313       --  Entity denoted by prefix
4314
4315       P_Type : Entity_Id;
4316       --  The type of the prefix
4317
4318       P_Base_Type : Entity_Id;
4319       --  The base type of the prefix type
4320
4321       P_Root_Type : Entity_Id;
4322       --  The root type of the prefix type
4323
4324       Static : Boolean;
4325       --  True if the result is Static. This is set by the general processing
4326       --  to true if the prefix is static, and all expressions are static. It
4327       --  can be reset as processing continues for particular attributes
4328
4329       Lo_Bound, Hi_Bound : Node_Id;
4330       --  Expressions for low and high bounds of type or array index referenced
4331       --  by First, Last, or Length attribute for array, set by Set_Bounds.
4332
4333       CE_Node : Node_Id;
4334       --  Constraint error node used if we have an attribute reference has
4335       --  an argument that raises a constraint error. In this case we replace
4336       --  the attribute with a raise constraint_error node. This is important
4337       --  processing, since otherwise gigi might see an attribute which it is
4338       --  unprepared to deal with.
4339
4340       function Aft_Value return Nat;
4341       --  Computes Aft value for current attribute prefix (used by Aft itself
4342       --  and also by Width for computing the Width of a fixed point type).
4343
4344       procedure Check_Expressions;
4345       --  In case where the attribute is not foldable, the expressions, if
4346       --  any, of the attribute, are in a non-static context. This procedure
4347       --  performs the required additional checks.
4348
4349       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean;
4350       --  Determines if the given type has compile time known bounds. Note
4351       --  that we enter the case statement even in cases where the prefix
4352       --  type does NOT have known bounds, so it is important to guard any
4353       --  attempt to evaluate both bounds with a call to this function.
4354
4355       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint);
4356       --  This procedure is called when the attribute N has a non-static
4357       --  but compile time known value given by Val. It includes the
4358       --  necessary checks for out of range values.
4359
4360       procedure Float_Attribute_Universal_Integer
4361         (IEEES_Val : Int;
4362          IEEEL_Val : Int;
4363          IEEEX_Val : Int;
4364          VAXFF_Val : Int;
4365          VAXDF_Val : Int;
4366          VAXGF_Val : Int;
4367          AAMPS_Val : Int;
4368          AAMPL_Val : Int);
4369       --  This procedure evaluates a float attribute with no arguments that
4370       --  returns a universal integer result. The parameters give the values
4371       --  for the possible floating-point root types. See ttypef for details.
4372       --  The prefix type is a float type (and is thus not a generic type).
4373
4374       procedure Float_Attribute_Universal_Real
4375         (IEEES_Val : String;
4376          IEEEL_Val : String;
4377          IEEEX_Val : String;
4378          VAXFF_Val : String;
4379          VAXDF_Val : String;
4380          VAXGF_Val : String;
4381          AAMPS_Val : String;
4382          AAMPL_Val : String);
4383       --  This procedure evaluates a float attribute with no arguments that
4384       --  returns a universal real result. The parameters give the values
4385       --  required for the possible floating-point root types in string
4386       --  format as real literals with a possible leading minus sign.
4387       --  The prefix type is a float type (and is thus not a generic type).
4388
4389       function Fore_Value return Nat;
4390       --  Computes the Fore value for the current attribute prefix, which is
4391       --  known to be a static fixed-point type. Used by Fore and Width.
4392
4393       function Mantissa return Uint;
4394       --  Returns the Mantissa value for the prefix type
4395
4396       procedure Set_Bounds;
4397       --  Used for First, Last and Length attributes applied to an array or
4398       --  array subtype. Sets the variables Lo_Bound and Hi_Bound to the low
4399       --  and high bound expressions for the index referenced by the attribute
4400       --  designator (i.e. the first index if no expression is present, and
4401       --  the N'th index if the value N is present as an expression). Also
4402       --  used for First and Last of scalar types. Static is reset to False
4403       --  if the type or index type is not statically constrained.
4404
4405       function Statically_Denotes_Entity (N : Node_Id) return Boolean;
4406       --  Verify that the prefix of a potentially static array attribute
4407       --  satisfies the conditions of 4.9 (14).
4408
4409       ---------------
4410       -- Aft_Value --
4411       ---------------
4412
4413       function Aft_Value return Nat is
4414          Result    : Nat;
4415          Delta_Val : Ureal;
4416
4417       begin
4418          Result := 1;
4419          Delta_Val := Delta_Value (P_Type);
4420          while Delta_Val < Ureal_Tenth loop
4421             Delta_Val := Delta_Val * Ureal_10;
4422             Result := Result + 1;
4423          end loop;
4424
4425          return Result;
4426       end Aft_Value;
4427
4428       -----------------------
4429       -- Check_Expressions --
4430       -----------------------
4431
4432       procedure Check_Expressions is
4433          E : Node_Id;
4434       begin
4435          E := E1;
4436          while Present (E) loop
4437             Check_Non_Static_Context (E);
4438             Next (E);
4439          end loop;
4440       end Check_Expressions;
4441
4442       ----------------------------------
4443       -- Compile_Time_Known_Attribute --
4444       ----------------------------------
4445
4446       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint) is
4447          T : constant Entity_Id := Etype (N);
4448
4449       begin
4450          Fold_Uint (N, Val, False);
4451
4452          --  Check that result is in bounds of the type if it is static
4453
4454          if Is_In_Range (N, T) then
4455             null;
4456
4457          elsif Is_Out_Of_Range (N, T) then
4458             Apply_Compile_Time_Constraint_Error
4459               (N, "value not in range of}?", CE_Range_Check_Failed);
4460
4461          elsif not Range_Checks_Suppressed (T) then
4462             Enable_Range_Check (N);
4463
4464          else
4465             Set_Do_Range_Check (N, False);
4466          end if;
4467       end Compile_Time_Known_Attribute;
4468
4469       -------------------------------
4470       -- Compile_Time_Known_Bounds --
4471       -------------------------------
4472
4473       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean is
4474       begin
4475          return
4476            Compile_Time_Known_Value (Type_Low_Bound (Typ))
4477              and then
4478            Compile_Time_Known_Value (Type_High_Bound (Typ));
4479       end Compile_Time_Known_Bounds;
4480
4481       ---------------------------------------
4482       -- Float_Attribute_Universal_Integer --
4483       ---------------------------------------
4484
4485       procedure Float_Attribute_Universal_Integer
4486         (IEEES_Val : Int;
4487          IEEEL_Val : Int;
4488          IEEEX_Val : Int;
4489          VAXFF_Val : Int;
4490          VAXDF_Val : Int;
4491          VAXGF_Val : Int;
4492          AAMPS_Val : Int;
4493          AAMPL_Val : Int)
4494       is
4495          Val  : Int;
4496          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4497
4498       begin
4499          if Vax_Float (P_Base_Type) then
4500             if Digs = VAXFF_Digits then
4501                Val := VAXFF_Val;
4502             elsif Digs = VAXDF_Digits then
4503                Val := VAXDF_Val;
4504             else pragma Assert (Digs = VAXGF_Digits);
4505                Val := VAXGF_Val;
4506             end if;
4507
4508          elsif Is_AAMP_Float (P_Base_Type) then
4509             if Digs = AAMPS_Digits then
4510                Val := AAMPS_Val;
4511             else pragma Assert (Digs = AAMPL_Digits);
4512                Val := AAMPL_Val;
4513             end if;
4514
4515          else
4516             if Digs = IEEES_Digits then
4517                Val := IEEES_Val;
4518             elsif Digs = IEEEL_Digits then
4519                Val := IEEEL_Val;
4520             else pragma Assert (Digs = IEEEX_Digits);
4521                Val := IEEEX_Val;
4522             end if;
4523          end if;
4524
4525          Fold_Uint (N, UI_From_Int (Val), True);
4526       end Float_Attribute_Universal_Integer;
4527
4528       ------------------------------------
4529       -- Float_Attribute_Universal_Real --
4530       ------------------------------------
4531
4532       procedure Float_Attribute_Universal_Real
4533         (IEEES_Val : String;
4534          IEEEL_Val : String;
4535          IEEEX_Val : String;
4536          VAXFF_Val : String;
4537          VAXDF_Val : String;
4538          VAXGF_Val : String;
4539          AAMPS_Val : String;
4540          AAMPL_Val : String)
4541       is
4542          Val  : Node_Id;
4543          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4544
4545       begin
4546          if Vax_Float (P_Base_Type) then
4547             if Digs = VAXFF_Digits then
4548                Val := Real_Convert (VAXFF_Val);
4549             elsif Digs = VAXDF_Digits then
4550                Val := Real_Convert (VAXDF_Val);
4551             else pragma Assert (Digs = VAXGF_Digits);
4552                Val := Real_Convert (VAXGF_Val);
4553             end if;
4554
4555          elsif Is_AAMP_Float (P_Base_Type) then
4556             if Digs = AAMPS_Digits then
4557                Val := Real_Convert (AAMPS_Val);
4558             else pragma Assert (Digs = AAMPL_Digits);
4559                Val := Real_Convert (AAMPL_Val);
4560             end if;
4561
4562          else
4563             if Digs = IEEES_Digits then
4564                Val := Real_Convert (IEEES_Val);
4565             elsif Digs = IEEEL_Digits then
4566                Val := Real_Convert (IEEEL_Val);
4567             else pragma Assert (Digs = IEEEX_Digits);
4568                Val := Real_Convert (IEEEX_Val);
4569             end if;
4570          end if;
4571
4572          Set_Sloc (Val, Loc);
4573          Rewrite (N, Val);
4574          Set_Is_Static_Expression (N, Static);
4575          Analyze_And_Resolve (N, C_Type);
4576       end Float_Attribute_Universal_Real;
4577
4578       ----------------
4579       -- Fore_Value --
4580       ----------------
4581
4582       --  Note that the Fore calculation is based on the actual values
4583       --  of the bounds, and does not take into account possible rounding.
4584
4585       function Fore_Value return Nat is
4586          Lo      : constant Uint  := Expr_Value (Type_Low_Bound (P_Type));
4587          Hi      : constant Uint  := Expr_Value (Type_High_Bound (P_Type));
4588          Small   : constant Ureal := Small_Value (P_Type);
4589          Lo_Real : constant Ureal := Lo * Small;
4590          Hi_Real : constant Ureal := Hi * Small;
4591          T       : Ureal;
4592          R       : Nat;
4593
4594       begin
4595          --  Bounds are given in terms of small units, so first compute
4596          --  proper values as reals.
4597
4598          T := UR_Max (abs Lo_Real, abs Hi_Real);
4599          R := 2;
4600
4601          --  Loop to compute proper value if more than one digit required
4602
4603          while T >= Ureal_10 loop
4604             R := R + 1;
4605             T := T / Ureal_10;
4606          end loop;
4607
4608          return R;
4609       end Fore_Value;
4610
4611       --------------
4612       -- Mantissa --
4613       --------------
4614
4615       --  Table of mantissa values accessed by function  Computed using
4616       --  the relation:
4617
4618       --    T'Mantissa = integer next above (D * log(10)/log(2)) + 1)
4619
4620       --  where D is T'Digits (RM83 3.5.7)
4621
4622       Mantissa_Value : constant array (Nat range 1 .. 40) of Nat := (
4623           1 =>   5,
4624           2 =>   8,
4625           3 =>  11,
4626           4 =>  15,
4627           5 =>  18,
4628           6 =>  21,
4629           7 =>  25,
4630           8 =>  28,
4631           9 =>  31,
4632          10 =>  35,
4633          11 =>  38,
4634          12 =>  41,
4635          13 =>  45,
4636          14 =>  48,
4637          15 =>  51,
4638          16 =>  55,
4639          17 =>  58,
4640          18 =>  61,
4641          19 =>  65,
4642          20 =>  68,
4643          21 =>  71,
4644          22 =>  75,
4645          23 =>  78,
4646          24 =>  81,
4647          25 =>  85,
4648          26 =>  88,
4649          27 =>  91,
4650          28 =>  95,
4651          29 =>  98,
4652          30 => 101,
4653          31 => 104,
4654          32 => 108,
4655          33 => 111,
4656          34 => 114,
4657          35 => 118,
4658          36 => 121,
4659          37 => 124,
4660          38 => 128,
4661          39 => 131,
4662          40 => 134);
4663
4664       function Mantissa return Uint is
4665       begin
4666          return
4667            UI_From_Int (Mantissa_Value (UI_To_Int (Digits_Value (P_Type))));
4668       end Mantissa;
4669
4670       ----------------
4671       -- Set_Bounds --
4672       ----------------
4673
4674       procedure Set_Bounds is
4675          Ndim : Nat;
4676          Indx : Node_Id;
4677          Ityp : Entity_Id;
4678
4679       begin
4680          --  For a string literal subtype, we have to construct the bounds.
4681          --  Valid Ada code never applies attributes to string literals, but
4682          --  it is convenient to allow the expander to generate attribute
4683          --  references of this type (e.g. First and Last applied to a string
4684          --  literal).
4685
4686          --  Note that the whole point of the E_String_Literal_Subtype is to
4687          --  avoid this construction of bounds, but the cases in which we
4688          --  have to materialize them are rare enough that we don't worry!
4689
4690          --  The low bound is simply the low bound of the base type. The
4691          --  high bound is computed from the length of the string and this
4692          --  low bound.
4693
4694          if Ekind (P_Type) = E_String_Literal_Subtype then
4695             Ityp := Etype (First_Index (Base_Type (P_Type)));
4696             Lo_Bound := Type_Low_Bound (Ityp);
4697
4698             Hi_Bound :=
4699               Make_Integer_Literal (Sloc (P),
4700                 Intval =>
4701                   Expr_Value (Lo_Bound) + String_Literal_Length (P_Type) - 1);
4702
4703             Set_Parent (Hi_Bound, P);
4704             Analyze_And_Resolve (Hi_Bound, Etype (Lo_Bound));
4705             return;
4706
4707          --  For non-array case, just get bounds of scalar type
4708
4709          elsif Is_Scalar_Type (P_Type) then
4710             Ityp := P_Type;
4711
4712             --  For a fixed-point type, we must freeze to get the attributes
4713             --  of the fixed-point type set now so we can reference them.
4714
4715             if Is_Fixed_Point_Type (P_Type)
4716               and then not Is_Frozen (Base_Type (P_Type))
4717               and then Compile_Time_Known_Value (Type_Low_Bound (P_Type))
4718               and then Compile_Time_Known_Value (Type_High_Bound (P_Type))
4719             then
4720                Freeze_Fixed_Point_Type (Base_Type (P_Type));
4721             end if;
4722
4723          --  For array case, get type of proper index
4724
4725          else
4726             if No (E1) then
4727                Ndim := 1;
4728             else
4729                Ndim := UI_To_Int (Expr_Value (E1));
4730             end if;
4731
4732             Indx := First_Index (P_Type);
4733             for J in 1 .. Ndim - 1 loop
4734                Next_Index (Indx);
4735             end loop;
4736
4737             --  If no index type, get out (some other error occurred, and
4738             --  we don't have enough information to complete the job!)
4739
4740             if No (Indx) then
4741                Lo_Bound := Error;
4742                Hi_Bound := Error;
4743                return;
4744             end if;
4745
4746             Ityp := Etype (Indx);
4747          end if;
4748
4749          --  A discrete range in an index constraint is allowed to be a
4750          --  subtype indication. This is syntactically a pain, but should
4751          --  not propagate to the entity for the corresponding index subtype.
4752          --  After checking that the subtype indication is legal, the range
4753          --  of the subtype indication should be transfered to the entity.
4754          --  The attributes for the bounds should remain the simple retrievals
4755          --  that they are now.
4756
4757          Lo_Bound := Type_Low_Bound (Ityp);
4758          Hi_Bound := Type_High_Bound (Ityp);
4759
4760          if not Is_Static_Subtype (Ityp) then
4761             Static := False;
4762          end if;
4763       end Set_Bounds;
4764
4765       -------------------------------
4766       -- Statically_Denotes_Entity --
4767       -------------------------------
4768
4769       function Statically_Denotes_Entity (N : Node_Id) return Boolean is
4770          E : Entity_Id;
4771
4772       begin
4773          if not Is_Entity_Name (N) then
4774             return False;
4775          else
4776             E := Entity (N);
4777          end if;
4778
4779          return
4780            Nkind (Parent (E)) /= N_Object_Renaming_Declaration
4781              or else Statically_Denotes_Entity (Renamed_Object (E));
4782       end Statically_Denotes_Entity;
4783
4784    --  Start of processing for Eval_Attribute
4785
4786    begin
4787       --  Acquire first two expressions (at the moment, no attributes
4788       --  take more than two expressions in any case).
4789
4790       if Present (Expressions (N)) then
4791          E1 := First (Expressions (N));
4792          E2 := Next (E1);
4793       else
4794          E1 := Empty;
4795          E2 := Empty;
4796       end if;
4797
4798       --  Special processing for Enabled attribute. This attribute has a very
4799       --  special prefix, and the easiest way to avoid lots of special checks
4800       --  to protect this special prefix from causing trouble is to deal with
4801       --  this attribute immediately and be done with it.
4802
4803       if Id = Attribute_Enabled then
4804
4805          --  Evaluate the Enabled attribute
4806
4807          --  We skip evaluation if the expander is not active. This is not just
4808          --  an optimization. It is of key importance that we not rewrite the
4809          --  attribute in a generic template, since we want to pick up the
4810          --  setting of the check in the instance, and testing expander active
4811          --  is as easy way of doing this as any.
4812
4813          if Expander_Active then
4814             declare
4815                C : constant Check_Id := Get_Check_Id (Chars (P));
4816                R : Boolean;
4817
4818             begin
4819                if No (E1) then
4820                   if C in Predefined_Check_Id then
4821                      R := Scope_Suppress (C);
4822                   else
4823                      R := Is_Check_Suppressed (Empty, C);
4824                   end if;
4825
4826                else
4827                   R := Is_Check_Suppressed (Entity (E1), C);
4828                end if;
4829
4830                if R then
4831                   Rewrite (N, New_Occurrence_Of (Standard_False, Loc));
4832                else
4833                   Rewrite (N, New_Occurrence_Of (Standard_True, Loc));
4834                end if;
4835             end;
4836          end if;
4837
4838          return;
4839       end if;
4840
4841       --  Special processing for cases where the prefix is an object. For
4842       --  this purpose, a string literal counts as an object (attributes
4843       --  of string literals can only appear in generated code).
4844
4845       if Is_Object_Reference (P) or else Nkind (P) = N_String_Literal then
4846
4847          --  For Component_Size, the prefix is an array object, and we apply
4848          --  the attribute to the type of the object. This is allowed for
4849          --  both unconstrained and constrained arrays, since the bounds
4850          --  have no influence on the value of this attribute.
4851
4852          if Id = Attribute_Component_Size then
4853             P_Entity := Etype (P);
4854
4855          --  For First and Last, the prefix is an array object, and we apply
4856          --  the attribute to the type of the array, but we need a constrained
4857          --  type for this, so we use the actual subtype if available.
4858
4859          elsif Id = Attribute_First
4860                  or else
4861                Id = Attribute_Last
4862                  or else
4863                Id = Attribute_Length
4864          then
4865             declare
4866                AS : constant Entity_Id := Get_Actual_Subtype_If_Available (P);
4867
4868             begin
4869                if Present (AS) and then Is_Constrained (AS) then
4870                   P_Entity := AS;
4871
4872                --  If we have an unconstrained type, cannot fold
4873
4874                else
4875                   Check_Expressions;
4876                   return;
4877                end if;
4878             end;
4879
4880          --  For Size, give size of object if available, otherwise we
4881          --  cannot fold Size.
4882
4883          elsif Id = Attribute_Size then
4884             if Is_Entity_Name (P)
4885               and then Known_Esize (Entity (P))
4886             then
4887                Compile_Time_Known_Attribute (N, Esize (Entity (P)));
4888                return;
4889
4890             else
4891                Check_Expressions;
4892                return;
4893             end if;
4894
4895          --  For Alignment, give size of object if available, otherwise we
4896          --  cannot fold Alignment.
4897
4898          elsif Id = Attribute_Alignment then
4899             if Is_Entity_Name (P)
4900               and then Known_Alignment (Entity (P))
4901             then
4902                Fold_Uint (N, Alignment (Entity (P)), False);
4903                return;
4904
4905             else
4906                Check_Expressions;
4907                return;
4908             end if;
4909
4910          --  No other attributes for objects are folded
4911
4912          else
4913             Check_Expressions;
4914             return;
4915          end if;
4916
4917       --  Cases where P is not an object. Cannot do anything if P is
4918       --  not the name of an entity.
4919
4920       elsif not Is_Entity_Name (P) then
4921          Check_Expressions;
4922          return;
4923
4924       --  Otherwise get prefix entity
4925
4926       else
4927          P_Entity := Entity (P);
4928       end if;
4929
4930       --  At this stage P_Entity is the entity to which the attribute
4931       --  is to be applied. This is usually simply the entity of the
4932       --  prefix, except in some cases of attributes for objects, where
4933       --  as described above, we apply the attribute to the object type.
4934
4935       --  First foldable possibility is a scalar or array type (RM 4.9(7))
4936       --  that is not generic (generic types are eliminated by RM 4.9(25)).
4937       --  Note we allow non-static non-generic types at this stage as further
4938       --  described below.
4939
4940       if Is_Type (P_Entity)
4941         and then (Is_Scalar_Type (P_Entity) or Is_Array_Type (P_Entity))
4942         and then (not Is_Generic_Type (P_Entity))
4943       then
4944          P_Type := P_Entity;
4945
4946       --  Second foldable possibility is an array object (RM 4.9(8))
4947
4948       elsif (Ekind (P_Entity) = E_Variable
4949                or else
4950              Ekind (P_Entity) = E_Constant)
4951         and then Is_Array_Type (Etype (P_Entity))
4952         and then (not Is_Generic_Type (Etype (P_Entity)))
4953       then
4954          P_Type := Etype (P_Entity);
4955
4956          --  If the entity is an array constant with an unconstrained nominal
4957          --  subtype then get the type from the initial value. If the value has
4958          --  been expanded into assignments, there is no expression and the
4959          --  attribute reference remains dynamic.
4960          --  We could do better here and retrieve the type ???
4961
4962          if Ekind (P_Entity) = E_Constant
4963            and then not Is_Constrained (P_Type)
4964          then
4965             if No (Constant_Value (P_Entity)) then
4966                return;
4967             else
4968                P_Type := Etype (Constant_Value (P_Entity));
4969             end if;
4970          end if;
4971
4972       --  Definite must be folded if the prefix is not a generic type,
4973       --  that is to say if we are within an instantiation. Same processing
4974       --  applies to the GNAT attributes Has_Discriminants, Type_Class,
4975       --  and Unconstrained_Array.
4976
4977       elsif (Id = Attribute_Definite
4978                or else
4979              Id = Attribute_Has_Access_Values
4980                or else
4981              Id = Attribute_Has_Discriminants
4982                or else
4983              Id = Attribute_Type_Class
4984                or else
4985              Id = Attribute_Unconstrained_Array)
4986         and then not Is_Generic_Type (P_Entity)
4987       then
4988          P_Type := P_Entity;
4989
4990       --  We can fold 'Size applied to a type if the size is known
4991       --  (as happens for a size from an attribute definition clause).
4992       --  At this stage, this can happen only for types (e.g. record
4993       --  types) for which the size is always non-static. We exclude
4994       --  generic types from consideration (since they have bogus
4995       --  sizes set within templates).
4996
4997       elsif Id = Attribute_Size
4998         and then Is_Type (P_Entity)
4999         and then (not Is_Generic_Type (P_Entity))
5000         and then Known_Static_RM_Size (P_Entity)
5001       then
5002          Compile_Time_Known_Attribute (N, RM_Size (P_Entity));
5003          return;
5004
5005       --  We can fold 'Alignment applied to a type if the alignment is known
5006       --  (as happens for an alignment from an attribute definition clause).
5007       --  At this stage, this can happen only for types (e.g. record
5008       --  types) for which the size is always non-static. We exclude
5009       --  generic types from consideration (since they have bogus
5010       --  sizes set within templates).
5011
5012       elsif Id = Attribute_Alignment
5013         and then Is_Type (P_Entity)
5014         and then (not Is_Generic_Type (P_Entity))
5015         and then Known_Alignment (P_Entity)
5016       then
5017          Compile_Time_Known_Attribute (N, Alignment (P_Entity));
5018          return;
5019
5020       --  If this is an access attribute that is known to fail accessibility
5021       --  check, rewrite accordingly.
5022
5023       elsif Attribute_Name (N) = Name_Access
5024         and then Raises_Constraint_Error (N)
5025       then
5026          Rewrite (N,
5027            Make_Raise_Program_Error (Loc,
5028              Reason => PE_Accessibility_Check_Failed));
5029          Set_Etype (N, C_Type);
5030          return;
5031
5032       --  No other cases are foldable (they certainly aren't static, and at
5033       --  the moment we don't try to fold any cases other than these three).
5034
5035       else
5036          Check_Expressions;
5037          return;
5038       end if;
5039
5040       --  If either attribute or the prefix is Any_Type, then propagate
5041       --  Any_Type to the result and don't do anything else at all.
5042
5043       if P_Type = Any_Type
5044         or else (Present (E1) and then Etype (E1) = Any_Type)
5045         or else (Present (E2) and then Etype (E2) = Any_Type)
5046       then
5047          Set_Etype (N, Any_Type);
5048          return;
5049       end if;
5050
5051       --  Scalar subtype case. We have not yet enforced the static requirement
5052       --  of (RM 4.9(7)) and we don't intend to just yet, since there are cases
5053       --  of non-static attribute references (e.g. S'Digits for a non-static
5054       --  floating-point type, which we can compute at compile time).
5055
5056       --  Note: this folding of non-static attributes is not simply a case of
5057       --  optimization. For many of the attributes affected, Gigi cannot handle
5058       --  the attribute and depends on the front end having folded them away.
5059
5060       --  Note: although we don't require staticness at this stage, we do set
5061       --  the Static variable to record the staticness, for easy reference by
5062       --  those attributes where it matters (e.g. Succ and Pred), and also to
5063       --  be used to ensure that non-static folded things are not marked as
5064       --  being static (a check that is done right at the end).
5065
5066       P_Root_Type := Root_Type (P_Type);
5067       P_Base_Type := Base_Type (P_Type);
5068
5069       --  If the root type or base type is generic, then we cannot fold. This
5070       --  test is needed because subtypes of generic types are not always
5071       --  marked as being generic themselves (which seems odd???)
5072
5073       if Is_Generic_Type (P_Root_Type)
5074         or else Is_Generic_Type (P_Base_Type)
5075       then
5076          return;
5077       end if;
5078
5079       if Is_Scalar_Type (P_Type) then
5080          Static := Is_OK_Static_Subtype (P_Type);
5081
5082       --  Array case. We enforce the constrained requirement of (RM 4.9(7-8))
5083       --  since we can't do anything with unconstrained arrays. In addition,
5084       --  only the First, Last and Length attributes are possibly static.
5085
5086       --  Definite, Has_Access_Values, Has_Discriminants, Type_Class, and
5087       --  Unconstrained_Array are again exceptions, because they apply as
5088       --  well to unconstrained types.
5089
5090       --  In addition Component_Size is an exception since it is possibly
5091       --  foldable, even though it is never static, and it does apply to
5092       --  unconstrained arrays. Furthermore, it is essential to fold this
5093       --  in the packed case, since otherwise the value will be incorrect.
5094
5095       elsif Id = Attribute_Definite
5096               or else
5097             Id = Attribute_Has_Access_Values
5098               or else
5099             Id = Attribute_Has_Discriminants
5100               or else
5101             Id = Attribute_Type_Class
5102               or else
5103             Id = Attribute_Unconstrained_Array
5104               or else
5105             Id = Attribute_Component_Size
5106       then
5107          Static := False;
5108
5109       else
5110          if not Is_Constrained (P_Type)
5111            or else (Id /= Attribute_First and then
5112                     Id /= Attribute_Last  and then
5113                     Id /= Attribute_Length)
5114          then
5115             Check_Expressions;
5116             return;
5117          end if;
5118
5119          --  The rules in (RM 4.9(7,8)) require a static array, but as in the
5120          --  scalar case, we hold off on enforcing staticness, since there are
5121          --  cases which we can fold at compile time even though they are not
5122          --  static (e.g. 'Length applied to a static index, even though other
5123          --  non-static indexes make the array type non-static). This is only
5124          --  an optimization, but it falls out essentially free, so why not.
5125          --  Again we compute the variable Static for easy reference later
5126          --  (note that no array attributes are static in Ada 83).
5127
5128          Static := Ada_Version >= Ada_95
5129                      and then Statically_Denotes_Entity (P);
5130
5131          declare
5132             N : Node_Id;
5133
5134          begin
5135             N := First_Index (P_Type);
5136             while Present (N) loop
5137                Static := Static and then Is_Static_Subtype (Etype (N));
5138
5139                --  If however the index type is generic, attributes cannot
5140                --  be folded.
5141
5142                if Is_Generic_Type (Etype (N))
5143                  and then Id /= Attribute_Component_Size
5144                then
5145                   return;
5146                end if;
5147
5148                Next_Index (N);
5149             end loop;
5150          end;
5151       end if;
5152
5153       --  Check any expressions that are present. Note that these expressions,
5154       --  depending on the particular attribute type, are either part of the
5155       --  attribute designator, or they are arguments in a case where the
5156       --  attribute reference returns a function. In the latter case, the
5157       --  rule in (RM 4.9(22)) applies and in particular requires the type
5158       --  of the expressions to be scalar in order for the attribute to be
5159       --  considered to be static.
5160
5161       declare
5162          E : Node_Id;
5163
5164       begin
5165          E := E1;
5166          while Present (E) loop
5167
5168             --  If expression is not static, then the attribute reference
5169             --  result certainly cannot be static.
5170
5171             if not Is_Static_Expression (E) then
5172                Static := False;
5173             end if;
5174
5175             --  If the result is not known at compile time, or is not of
5176             --  a scalar type, then the result is definitely not static,
5177             --  so we can quit now.
5178
5179             if not Compile_Time_Known_Value (E)
5180               or else not Is_Scalar_Type (Etype (E))
5181             then
5182                --  An odd special case, if this is a Pos attribute, this
5183                --  is where we need to apply a range check since it does
5184                --  not get done anywhere else.
5185
5186                if Id = Attribute_Pos then
5187                   if Is_Integer_Type (Etype (E)) then
5188                      Apply_Range_Check (E, Etype (N));
5189                   end if;
5190                end if;
5191
5192                Check_Expressions;
5193                return;
5194
5195             --  If the expression raises a constraint error, then so does
5196             --  the attribute reference. We keep going in this case because
5197             --  we are still interested in whether the attribute reference
5198             --  is static even if it is not static.
5199
5200             elsif Raises_Constraint_Error (E) then
5201                Set_Raises_Constraint_Error (N);
5202             end if;
5203
5204             Next (E);
5205          end loop;
5206
5207          if Raises_Constraint_Error (Prefix (N)) then
5208             return;
5209          end if;
5210       end;
5211
5212       --  Deal with the case of a static attribute reference that raises
5213       --  constraint error. The Raises_Constraint_Error flag will already
5214       --  have been set, and the Static flag shows whether the attribute
5215       --  reference is static. In any case we certainly can't fold such an
5216       --  attribute reference.
5217
5218       --  Note that the rewriting of the attribute node with the constraint
5219       --  error node is essential in this case, because otherwise Gigi might
5220       --  blow up on one of the attributes it never expects to see.
5221
5222       --  The constraint_error node must have the type imposed by the context,
5223       --  to avoid spurious errors in the enclosing expression.
5224
5225       if Raises_Constraint_Error (N) then
5226          CE_Node :=
5227            Make_Raise_Constraint_Error (Sloc (N),
5228              Reason => CE_Range_Check_Failed);
5229          Set_Etype (CE_Node, Etype (N));
5230          Set_Raises_Constraint_Error (CE_Node);
5231          Check_Expressions;
5232          Rewrite (N, Relocate_Node (CE_Node));
5233          Set_Is_Static_Expression (N, Static);
5234          return;
5235       end if;
5236
5237       --  At this point we have a potentially foldable attribute reference.
5238       --  If Static is set, then the attribute reference definitely obeys
5239       --  the requirements in (RM 4.9(7,8,22)), and it definitely can be
5240       --  folded. If Static is not set, then the attribute may or may not
5241       --  be foldable, and the individual attribute processing routines
5242       --  test Static as required in cases where it makes a difference.
5243
5244       --  In the case where Static is not set, we do know that all the
5245       --  expressions present are at least known at compile time (we
5246       --  assumed above that if this was not the case, then there was
5247       --  no hope of static evaluation). However, we did not require
5248       --  that the bounds of the prefix type be compile time known,
5249       --  let alone static). That's because there are many attributes
5250       --  that can be computed at compile time on non-static subtypes,
5251       --  even though such references are not static expressions.
5252
5253       case Id is
5254
5255       --------------
5256       -- Adjacent --
5257       --------------
5258
5259       when Attribute_Adjacent =>
5260          Fold_Ureal (N,
5261            Eval_Fat.Adjacent
5262              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5263
5264       ---------
5265       -- Aft --
5266       ---------
5267
5268       when Attribute_Aft =>
5269          Fold_Uint (N, UI_From_Int (Aft_Value), True);
5270
5271       ---------------
5272       -- Alignment --
5273       ---------------
5274
5275       when Attribute_Alignment => Alignment_Block : declare
5276          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5277
5278       begin
5279          --  Fold if alignment is set and not otherwise
5280
5281          if Known_Alignment (P_TypeA) then
5282             Fold_Uint (N, Alignment (P_TypeA), Is_Discrete_Type (P_TypeA));
5283          end if;
5284       end Alignment_Block;
5285
5286       ---------------
5287       -- AST_Entry --
5288       ---------------
5289
5290       --  Can only be folded in No_Ast_Handler case
5291
5292       when Attribute_AST_Entry =>
5293          if not Is_AST_Entry (P_Entity) then
5294             Rewrite (N,
5295               New_Occurrence_Of (RTE (RE_No_AST_Handler), Loc));
5296          else
5297             null;
5298          end if;
5299
5300       ---------
5301       -- Bit --
5302       ---------
5303
5304       --  Bit can never be folded
5305
5306       when Attribute_Bit =>
5307          null;
5308
5309       ------------------
5310       -- Body_Version --
5311       ------------------
5312
5313       --  Body_version can never be static
5314
5315       when Attribute_Body_Version =>
5316          null;
5317
5318       -------------
5319       -- Ceiling --
5320       -------------
5321
5322       when Attribute_Ceiling =>
5323          Fold_Ureal (N,
5324            Eval_Fat.Ceiling (P_Root_Type, Expr_Value_R (E1)), Static);
5325
5326       --------------------
5327       -- Component_Size --
5328       --------------------
5329
5330       when Attribute_Component_Size =>
5331          if Known_Static_Component_Size (P_Type) then
5332             Fold_Uint (N, Component_Size (P_Type), False);
5333          end if;
5334
5335       -------------
5336       -- Compose --
5337       -------------
5338
5339       when Attribute_Compose =>
5340          Fold_Ureal (N,
5341            Eval_Fat.Compose
5342              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)),
5343               Static);
5344
5345       -----------------
5346       -- Constrained --
5347       -----------------
5348
5349       --  Constrained is never folded for now, there may be cases that
5350       --  could be handled at compile time. to be looked at later.
5351
5352       when Attribute_Constrained =>
5353          null;
5354
5355       ---------------
5356       -- Copy_Sign --
5357       ---------------
5358
5359       when Attribute_Copy_Sign =>
5360          Fold_Ureal (N,
5361            Eval_Fat.Copy_Sign
5362              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5363
5364       -----------
5365       -- Delta --
5366       -----------
5367
5368       when Attribute_Delta =>
5369          Fold_Ureal (N, Delta_Value (P_Type), True);
5370
5371       --------------
5372       -- Definite --
5373       --------------
5374
5375       when Attribute_Definite =>
5376          Rewrite (N, New_Occurrence_Of (
5377            Boolean_Literals (not Is_Indefinite_Subtype (P_Entity)), Loc));
5378          Analyze_And_Resolve (N, Standard_Boolean);
5379
5380       ------------
5381       -- Denorm --
5382       ------------
5383
5384       when Attribute_Denorm =>
5385          Fold_Uint
5386            (N, UI_From_Int (Boolean'Pos (Denorm_On_Target)), True);
5387
5388       ------------
5389       -- Digits --
5390       ------------
5391
5392       when Attribute_Digits =>
5393          Fold_Uint (N, Digits_Value (P_Type), True);
5394
5395       ----------
5396       -- Emax --
5397       ----------
5398
5399       when Attribute_Emax =>
5400
5401          --  Ada 83 attribute is defined as (RM83 3.5.8)
5402
5403          --    T'Emax = 4 * T'Mantissa
5404
5405          Fold_Uint (N, 4 * Mantissa, True);
5406
5407       --------------
5408       -- Enum_Rep --
5409       --------------
5410
5411       when Attribute_Enum_Rep =>
5412
5413          --  For an enumeration type with a non-standard representation use
5414          --  the Enumeration_Rep field of the proper constant. Note that this
5415          --  will not work for types Character/Wide_[Wide-]Character, since no
5416          --  real entities are created for the enumeration literals, but that
5417          --  does not matter since these two types do not have non-standard
5418          --  representations anyway.
5419
5420          if Is_Enumeration_Type (P_Type)
5421            and then Has_Non_Standard_Rep (P_Type)
5422          then
5423             Fold_Uint (N, Enumeration_Rep (Expr_Value_E (E1)), Static);
5424
5425          --  For enumeration types with standard representations and all
5426          --  other cases (i.e. all integer and modular types), Enum_Rep
5427          --  is equivalent to Pos.
5428
5429          else
5430             Fold_Uint (N, Expr_Value (E1), Static);
5431          end if;
5432
5433       -------------
5434       -- Epsilon --
5435       -------------
5436
5437       when Attribute_Epsilon =>
5438
5439          --  Ada 83 attribute is defined as (RM83 3.5.8)
5440
5441          --    T'Epsilon = 2.0**(1 - T'Mantissa)
5442
5443          Fold_Ureal (N, Ureal_2 ** (1 - Mantissa), True);
5444
5445       --------------
5446       -- Exponent --
5447       --------------
5448
5449       when Attribute_Exponent =>
5450          Fold_Uint (N,
5451            Eval_Fat.Exponent (P_Root_Type, Expr_Value_R (E1)), Static);
5452
5453       -----------
5454       -- First --
5455       -----------
5456
5457       when Attribute_First => First_Attr :
5458       begin
5459          Set_Bounds;
5460
5461          if Compile_Time_Known_Value (Lo_Bound) then
5462             if Is_Real_Type (P_Type) then
5463                Fold_Ureal (N, Expr_Value_R (Lo_Bound), Static);
5464             else
5465                Fold_Uint  (N, Expr_Value (Lo_Bound), Static);
5466             end if;
5467          end if;
5468       end First_Attr;
5469
5470       -----------------
5471       -- Fixed_Value --
5472       -----------------
5473
5474       when Attribute_Fixed_Value =>
5475          null;
5476
5477       -----------
5478       -- Floor --
5479       -----------
5480
5481       when Attribute_Floor =>
5482          Fold_Ureal (N,
5483            Eval_Fat.Floor (P_Root_Type, Expr_Value_R (E1)), Static);
5484
5485       ----------
5486       -- Fore --
5487       ----------
5488
5489       when Attribute_Fore =>
5490          if Compile_Time_Known_Bounds (P_Type) then
5491             Fold_Uint (N, UI_From_Int (Fore_Value), Static);
5492          end if;
5493
5494       --------------
5495       -- Fraction --
5496       --------------
5497
5498       when Attribute_Fraction =>
5499          Fold_Ureal (N,
5500            Eval_Fat.Fraction (P_Root_Type, Expr_Value_R (E1)), Static);
5501
5502       -----------------------
5503       -- Has_Access_Values --
5504       -----------------------
5505
5506       when Attribute_Has_Access_Values =>
5507          Rewrite (N, New_Occurrence_Of
5508            (Boolean_Literals (Has_Access_Values (P_Root_Type)), Loc));
5509          Analyze_And_Resolve (N, Standard_Boolean);
5510
5511       -----------------------
5512       -- Has_Discriminants --
5513       -----------------------
5514
5515       when Attribute_Has_Discriminants =>
5516          Rewrite (N, New_Occurrence_Of (
5517            Boolean_Literals (Has_Discriminants (P_Entity)), Loc));
5518          Analyze_And_Resolve (N, Standard_Boolean);
5519
5520       --------------
5521       -- Identity --
5522       --------------
5523
5524       when Attribute_Identity =>
5525          null;
5526
5527       -----------
5528       -- Image --
5529       -----------
5530
5531       --  Image is a scalar attribute, but is never static, because it is
5532       --  not a static function (having a non-scalar argument (RM 4.9(22))
5533       --  However, we can constant-fold the image of an enumeration literal
5534       --  if names are available.
5535
5536       when Attribute_Image =>
5537          if Is_Entity_Name (E1)
5538            and then Ekind (Entity (E1)) = E_Enumeration_Literal
5539            and then not Discard_Names (First_Subtype (Etype (E1)))
5540            and then not Global_Discard_Names
5541          then
5542             declare
5543                Lit : constant Entity_Id := Entity (E1);
5544                Str : String_Id;
5545             begin
5546                Start_String;
5547                Get_Unqualified_Decoded_Name_String (Chars (Lit));
5548                Set_Casing (All_Upper_Case);
5549                Store_String_Chars (Name_Buffer (1 .. Name_Len));
5550                Str := End_String;
5551                Rewrite (N, Make_String_Literal (Loc, Strval => Str));
5552                Analyze_And_Resolve (N, Standard_String);
5553                Set_Is_Static_Expression (N, False);
5554             end;
5555          end if;
5556
5557       ---------
5558       -- Img --
5559       ---------
5560
5561       --  Img is a scalar attribute, but is never static, because it is
5562       --  not a static function (having a non-scalar argument (RM 4.9(22))
5563
5564       when Attribute_Img =>
5565          null;
5566
5567       -------------------
5568       -- Integer_Value --
5569       -------------------
5570
5571       when Attribute_Integer_Value =>
5572          null;
5573
5574       -----------
5575       -- Large --
5576       -----------
5577
5578       when Attribute_Large =>
5579
5580          --  For fixed-point, we use the identity:
5581
5582          --    T'Large = (2.0**T'Mantissa - 1.0) * T'Small
5583
5584          if Is_Fixed_Point_Type (P_Type) then
5585             Rewrite (N,
5586               Make_Op_Multiply (Loc,
5587                 Left_Opnd =>
5588                   Make_Op_Subtract (Loc,
5589                     Left_Opnd =>
5590                       Make_Op_Expon (Loc,
5591                         Left_Opnd =>
5592                           Make_Real_Literal (Loc, Ureal_2),
5593                         Right_Opnd =>
5594                           Make_Attribute_Reference (Loc,
5595                             Prefix => P,
5596                             Attribute_Name => Name_Mantissa)),
5597                     Right_Opnd => Make_Real_Literal (Loc, Ureal_1)),
5598
5599                 Right_Opnd =>
5600                   Make_Real_Literal (Loc, Small_Value (Entity (P)))));
5601
5602             Analyze_And_Resolve (N, C_Type);
5603
5604          --  Floating-point (Ada 83 compatibility)
5605
5606          else
5607             --  Ada 83 attribute is defined as (RM83 3.5.8)
5608
5609             --    T'Large = 2.0**T'Emax * (1.0 - 2.0**(-T'Mantissa))
5610
5611             --  where
5612
5613             --    T'Emax = 4 * T'Mantissa
5614
5615             Fold_Ureal (N,
5616               Ureal_2 ** (4 * Mantissa) * (Ureal_1 - Ureal_2 ** (-Mantissa)),
5617               True);
5618          end if;
5619
5620       ----------
5621       -- Last --
5622       ----------
5623
5624       when Attribute_Last => Last :
5625       begin
5626          Set_Bounds;
5627
5628          if Compile_Time_Known_Value (Hi_Bound) then
5629             if Is_Real_Type (P_Type) then
5630                Fold_Ureal (N, Expr_Value_R (Hi_Bound), Static);
5631             else
5632                Fold_Uint  (N, Expr_Value (Hi_Bound), Static);
5633             end if;
5634          end if;
5635       end Last;
5636
5637       ------------------
5638       -- Leading_Part --
5639       ------------------
5640
5641       when Attribute_Leading_Part =>
5642          Fold_Ureal (N,
5643            Eval_Fat.Leading_Part
5644              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5645
5646       ------------
5647       -- Length --
5648       ------------
5649
5650       when Attribute_Length => Length : declare
5651          Ind : Node_Id;
5652
5653       begin
5654          --  In the case of a generic index type, the bounds may
5655          --  appear static but the computation is not meaningful,
5656          --  and may generate a spurious warning.
5657
5658          Ind := First_Index (P_Type);
5659
5660          while Present (Ind) loop
5661             if Is_Generic_Type (Etype (Ind)) then
5662                return;
5663             end if;
5664
5665             Next_Index (Ind);
5666          end loop;
5667
5668          Set_Bounds;
5669
5670          if Compile_Time_Known_Value (Lo_Bound)
5671            and then Compile_Time_Known_Value (Hi_Bound)
5672          then
5673             Fold_Uint (N,
5674               UI_Max (0, 1 + (Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound))),
5675               True);
5676          end if;
5677       end Length;
5678
5679       -------------
5680       -- Machine --
5681       -------------
5682
5683       when Attribute_Machine =>
5684          Fold_Ureal (N,
5685            Eval_Fat.Machine
5686              (P_Root_Type, Expr_Value_R (E1), Eval_Fat.Round, N),
5687            Static);
5688
5689       ------------------
5690       -- Machine_Emax --
5691       ------------------
5692
5693       when Attribute_Machine_Emax =>
5694          Float_Attribute_Universal_Integer (
5695            IEEES_Machine_Emax,
5696            IEEEL_Machine_Emax,
5697            IEEEX_Machine_Emax,
5698            VAXFF_Machine_Emax,
5699            VAXDF_Machine_Emax,
5700            VAXGF_Machine_Emax,
5701            AAMPS_Machine_Emax,
5702            AAMPL_Machine_Emax);
5703
5704       ------------------
5705       -- Machine_Emin --
5706       ------------------
5707
5708       when Attribute_Machine_Emin =>
5709          Float_Attribute_Universal_Integer (
5710            IEEES_Machine_Emin,
5711            IEEEL_Machine_Emin,
5712            IEEEX_Machine_Emin,
5713            VAXFF_Machine_Emin,
5714            VAXDF_Machine_Emin,
5715            VAXGF_Machine_Emin,
5716            AAMPS_Machine_Emin,
5717            AAMPL_Machine_Emin);
5718
5719       ----------------------
5720       -- Machine_Mantissa --
5721       ----------------------
5722
5723       when Attribute_Machine_Mantissa =>
5724          Float_Attribute_Universal_Integer (
5725            IEEES_Machine_Mantissa,
5726            IEEEL_Machine_Mantissa,
5727            IEEEX_Machine_Mantissa,
5728            VAXFF_Machine_Mantissa,
5729            VAXDF_Machine_Mantissa,
5730            VAXGF_Machine_Mantissa,
5731            AAMPS_Machine_Mantissa,
5732            AAMPL_Machine_Mantissa);
5733
5734       -----------------------
5735       -- Machine_Overflows --
5736       -----------------------
5737
5738       when Attribute_Machine_Overflows =>
5739
5740          --  Always true for fixed-point
5741
5742          if Is_Fixed_Point_Type (P_Type) then
5743             Fold_Uint (N, True_Value, True);
5744
5745          --  Floating point case
5746
5747          else
5748             Fold_Uint (N,
5749               UI_From_Int (Boolean'Pos (Machine_Overflows_On_Target)),
5750               True);
5751          end if;
5752
5753       -------------------
5754       -- Machine_Radix --
5755       -------------------
5756
5757       when Attribute_Machine_Radix =>
5758          if Is_Fixed_Point_Type (P_Type) then
5759             if Is_Decimal_Fixed_Point_Type (P_Type)
5760               and then Machine_Radix_10 (P_Type)
5761             then
5762                Fold_Uint (N, Uint_10, True);
5763             else
5764                Fold_Uint (N, Uint_2, True);
5765             end if;
5766
5767          --  All floating-point type always have radix 2
5768
5769          else
5770             Fold_Uint (N, Uint_2, True);
5771          end if;
5772
5773       ----------------------
5774       -- Machine_Rounding --
5775       ----------------------
5776
5777       --  Note: for the folding case, it is fine to treat Machine_Rounding
5778       --  exactly the same way as Rounding, since this is one of the allowed
5779       --  behaviors, and performance is not an issue here. It might be a bit
5780       --  better to give the same result as it would give at run-time, even
5781       --  though the non-determinism is certainly permitted.
5782
5783       when Attribute_Machine_Rounding =>
5784          Fold_Ureal (N,
5785            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
5786
5787       --------------------
5788       -- Machine_Rounds --
5789       --------------------
5790
5791       when Attribute_Machine_Rounds =>
5792
5793          --  Always False for fixed-point
5794
5795          if Is_Fixed_Point_Type (P_Type) then
5796             Fold_Uint (N, False_Value, True);
5797
5798          --  Else yield proper floating-point result
5799
5800          else
5801             Fold_Uint
5802               (N, UI_From_Int (Boolean'Pos (Machine_Rounds_On_Target)), True);
5803          end if;
5804
5805       ------------------
5806       -- Machine_Size --
5807       ------------------
5808
5809       --  Note: Machine_Size is identical to Object_Size
5810
5811       when Attribute_Machine_Size => Machine_Size : declare
5812          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5813
5814       begin
5815          if Known_Esize (P_TypeA) then
5816             Fold_Uint (N, Esize (P_TypeA), True);
5817          end if;
5818       end Machine_Size;
5819
5820       --------------
5821       -- Mantissa --
5822       --------------
5823
5824       when Attribute_Mantissa =>
5825
5826          --  Fixed-point mantissa
5827
5828          if Is_Fixed_Point_Type (P_Type) then
5829
5830             --  Compile time foldable case
5831
5832             if Compile_Time_Known_Value (Type_Low_Bound  (P_Type))
5833                  and then
5834                Compile_Time_Known_Value (Type_High_Bound (P_Type))
5835             then
5836                --  The calculation of the obsolete Ada 83 attribute Mantissa
5837                --  is annoying, because of AI00143, quoted here:
5838
5839                --  !question 84-01-10
5840
5841                --  Consider the model numbers for F:
5842
5843                --         type F is delta 1.0 range -7.0 .. 8.0;
5844
5845                --  The wording requires that F'MANTISSA be the SMALLEST
5846                --  integer number for which each  bound  of the specified
5847                --  range is either a model number or lies at most small
5848                --  distant from a model number. This means F'MANTISSA
5849                --  is required to be 3 since the range  -7.0 .. 7.0 fits
5850                --  in 3 signed bits, and 8 is "at most" 1.0 from a model
5851                --  number, namely, 7. Is this analysis correct? Note that
5852                --  this implies the upper bound of the range is not
5853                --  represented as a model number.
5854
5855                --  !response 84-03-17
5856
5857                --  The analysis is correct. The upper and lower bounds for
5858                --  a fixed  point type can lie outside the range of model
5859                --  numbers.
5860
5861                declare
5862                   Siz     : Uint;
5863                   LBound  : Ureal;
5864                   UBound  : Ureal;
5865                   Bound   : Ureal;
5866                   Max_Man : Uint;
5867
5868                begin
5869                   LBound  := Expr_Value_R (Type_Low_Bound  (P_Type));
5870                   UBound  := Expr_Value_R (Type_High_Bound (P_Type));
5871                   Bound   := UR_Max (UR_Abs (LBound), UR_Abs (UBound));
5872                   Max_Man := UR_Trunc (Bound / Small_Value (P_Type));
5873
5874                   --  If the Bound is exactly a model number, i.e. a multiple
5875                   --  of Small, then we back it off by one to get the integer
5876                   --  value that must be representable.
5877
5878                   if Small_Value (P_Type) * Max_Man = Bound then
5879                      Max_Man := Max_Man - 1;
5880                   end if;
5881
5882                   --  Now find corresponding size = Mantissa value
5883
5884                   Siz := Uint_0;
5885                   while 2 ** Siz < Max_Man loop
5886                      Siz := Siz + 1;
5887                   end loop;
5888
5889                   Fold_Uint (N, Siz, True);
5890                end;
5891
5892             else
5893                --  The case of dynamic bounds cannot be evaluated at compile
5894                --  time. Instead we use a runtime routine (see Exp_Attr).
5895
5896                null;
5897             end if;
5898
5899          --  Floating-point Mantissa
5900
5901          else
5902             Fold_Uint (N, Mantissa, True);
5903          end if;
5904
5905       ---------
5906       -- Max --
5907       ---------
5908
5909       when Attribute_Max => Max :
5910       begin
5911          if Is_Real_Type (P_Type) then
5912             Fold_Ureal
5913               (N, UR_Max (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5914          else
5915             Fold_Uint (N, UI_Max (Expr_Value (E1), Expr_Value (E2)), Static);
5916          end if;
5917       end Max;
5918
5919       ----------------------------------
5920       -- Max_Size_In_Storage_Elements --
5921       ----------------------------------
5922
5923       --  Max_Size_In_Storage_Elements is simply the Size rounded up to a
5924       --  Storage_Unit boundary. We can fold any cases for which the size
5925       --  is known by the front end.
5926
5927       when Attribute_Max_Size_In_Storage_Elements =>
5928          if Known_Esize (P_Type) then
5929             Fold_Uint (N,
5930               (Esize (P_Type) + System_Storage_Unit - 1) /
5931                                           System_Storage_Unit,
5932                Static);
5933          end if;
5934
5935       --------------------
5936       -- Mechanism_Code --
5937       --------------------
5938
5939       when Attribute_Mechanism_Code =>
5940          declare
5941             Val    : Int;
5942             Formal : Entity_Id;
5943             Mech   : Mechanism_Type;
5944
5945          begin
5946             if No (E1) then
5947                Mech := Mechanism (P_Entity);
5948
5949             else
5950                Val := UI_To_Int (Expr_Value (E1));
5951
5952                Formal := First_Formal (P_Entity);
5953                for J in 1 .. Val - 1 loop
5954                   Next_Formal (Formal);
5955                end loop;
5956                Mech := Mechanism (Formal);
5957             end if;
5958
5959             if Mech < 0 then
5960                Fold_Uint (N, UI_From_Int (Int (-Mech)), True);
5961             end if;
5962          end;
5963
5964       ---------
5965       -- Min --
5966       ---------
5967
5968       when Attribute_Min => Min :
5969       begin
5970          if Is_Real_Type (P_Type) then
5971             Fold_Ureal
5972               (N, UR_Min (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5973          else
5974             Fold_Uint
5975               (N, UI_Min (Expr_Value (E1), Expr_Value (E2)), Static);
5976          end if;
5977       end Min;
5978
5979       ---------
5980       -- Mod --
5981       ---------
5982
5983       when Attribute_Mod =>
5984          Fold_Uint
5985            (N, UI_Mod (Expr_Value (E1), Modulus (P_Base_Type)), Static);
5986
5987       -----------
5988       -- Model --
5989       -----------
5990
5991       when Attribute_Model =>
5992          Fold_Ureal (N,
5993            Eval_Fat.Model (P_Root_Type, Expr_Value_R (E1)), Static);
5994
5995       ----------------
5996       -- Model_Emin --
5997       ----------------
5998
5999       when Attribute_Model_Emin =>
6000          Float_Attribute_Universal_Integer (
6001            IEEES_Model_Emin,
6002            IEEEL_Model_Emin,
6003            IEEEX_Model_Emin,
6004            VAXFF_Model_Emin,
6005            VAXDF_Model_Emin,
6006            VAXGF_Model_Emin,
6007            AAMPS_Model_Emin,
6008            AAMPL_Model_Emin);
6009
6010       -------------------
6011       -- Model_Epsilon --
6012       -------------------
6013
6014       when Attribute_Model_Epsilon =>
6015          Float_Attribute_Universal_Real (
6016            IEEES_Model_Epsilon'Universal_Literal_String,
6017            IEEEL_Model_Epsilon'Universal_Literal_String,
6018            IEEEX_Model_Epsilon'Universal_Literal_String,
6019            VAXFF_Model_Epsilon'Universal_Literal_String,
6020            VAXDF_Model_Epsilon'Universal_Literal_String,
6021            VAXGF_Model_Epsilon'Universal_Literal_String,
6022            AAMPS_Model_Epsilon'Universal_Literal_String,
6023            AAMPL_Model_Epsilon'Universal_Literal_String);
6024
6025       --------------------
6026       -- Model_Mantissa --
6027       --------------------
6028
6029       when Attribute_Model_Mantissa =>
6030          Float_Attribute_Universal_Integer (
6031            IEEES_Model_Mantissa,
6032            IEEEL_Model_Mantissa,
6033            IEEEX_Model_Mantissa,
6034            VAXFF_Model_Mantissa,
6035            VAXDF_Model_Mantissa,
6036            VAXGF_Model_Mantissa,
6037            AAMPS_Model_Mantissa,
6038            AAMPL_Model_Mantissa);
6039
6040       -----------------
6041       -- Model_Small --
6042       -----------------
6043
6044       when Attribute_Model_Small =>
6045          Float_Attribute_Universal_Real (
6046            IEEES_Model_Small'Universal_Literal_String,
6047            IEEEL_Model_Small'Universal_Literal_String,
6048            IEEEX_Model_Small'Universal_Literal_String,
6049            VAXFF_Model_Small'Universal_Literal_String,
6050            VAXDF_Model_Small'Universal_Literal_String,
6051            VAXGF_Model_Small'Universal_Literal_String,
6052            AAMPS_Model_Small'Universal_Literal_String,
6053            AAMPL_Model_Small'Universal_Literal_String);
6054
6055       -------------
6056       -- Modulus --
6057       -------------
6058
6059       when Attribute_Modulus =>
6060          Fold_Uint (N, Modulus (P_Type), True);
6061
6062       --------------------
6063       -- Null_Parameter --
6064       --------------------
6065
6066       --  Cannot fold, we know the value sort of, but the whole point is
6067       --  that there is no way to talk about this imaginary value except
6068       --  by using the attribute, so we leave it the way it is.
6069
6070       when Attribute_Null_Parameter =>
6071          null;
6072
6073       -----------------
6074       -- Object_Size --
6075       -----------------
6076
6077       --  The Object_Size attribute for a type returns the Esize of the
6078       --  type and can be folded if this value is known.
6079
6080       when Attribute_Object_Size => Object_Size : declare
6081          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6082
6083       begin
6084          if Known_Esize (P_TypeA) then
6085             Fold_Uint (N, Esize (P_TypeA), True);
6086          end if;
6087       end Object_Size;
6088
6089       -------------------------
6090       -- Passed_By_Reference --
6091       -------------------------
6092
6093       --  Scalar types are never passed by reference
6094
6095       when Attribute_Passed_By_Reference =>
6096          Fold_Uint (N, False_Value, True);
6097
6098       ---------
6099       -- Pos --
6100       ---------
6101
6102       when Attribute_Pos =>
6103          Fold_Uint (N, Expr_Value (E1), True);
6104
6105       ----------
6106       -- Pred --
6107       ----------
6108
6109       when Attribute_Pred => Pred :
6110       begin
6111          --  Floating-point case
6112
6113          if Is_Floating_Point_Type (P_Type) then
6114             Fold_Ureal (N,
6115               Eval_Fat.Pred (P_Root_Type, Expr_Value_R (E1)), Static);
6116
6117          --  Fixed-point case
6118
6119          elsif Is_Fixed_Point_Type (P_Type) then
6120             Fold_Ureal (N,
6121               Expr_Value_R (E1) - Small_Value (P_Type), True);
6122
6123          --  Modular integer case (wraps)
6124
6125          elsif Is_Modular_Integer_Type (P_Type) then
6126             Fold_Uint (N, (Expr_Value (E1) - 1) mod Modulus (P_Type), Static);
6127
6128          --  Other scalar cases
6129
6130          else
6131             pragma Assert (Is_Scalar_Type (P_Type));
6132
6133             if Is_Enumeration_Type (P_Type)
6134               and then Expr_Value (E1) =
6135                          Expr_Value (Type_Low_Bound (P_Base_Type))
6136             then
6137                Apply_Compile_Time_Constraint_Error
6138                  (N, "Pred of `&''First`",
6139                   CE_Overflow_Check_Failed,
6140                   Ent  => P_Base_Type,
6141                   Warn => not Static);
6142
6143                Check_Expressions;
6144                return;
6145             end if;
6146
6147             Fold_Uint (N, Expr_Value (E1) - 1, Static);
6148          end if;
6149       end Pred;
6150
6151       -----------
6152       -- Range --
6153       -----------
6154
6155       --  No processing required, because by this stage, Range has been
6156       --  replaced by First .. Last, so this branch can never be taken.
6157
6158       when Attribute_Range =>
6159          raise Program_Error;
6160
6161       ------------------
6162       -- Range_Length --
6163       ------------------
6164
6165       when Attribute_Range_Length =>
6166          Set_Bounds;
6167
6168          if Compile_Time_Known_Value (Hi_Bound)
6169            and then Compile_Time_Known_Value (Lo_Bound)
6170          then
6171             Fold_Uint (N,
6172               UI_Max
6173                 (0, Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound) + 1),
6174                  Static);
6175          end if;
6176
6177       ---------------
6178       -- Remainder --
6179       ---------------
6180
6181       when Attribute_Remainder => Remainder : declare
6182          X : constant Ureal := Expr_Value_R (E1);
6183          Y : constant Ureal := Expr_Value_R (E2);
6184
6185       begin
6186          if UR_Is_Zero (Y) then
6187             Apply_Compile_Time_Constraint_Error
6188               (N, "division by zero in Remainder",
6189                CE_Overflow_Check_Failed,
6190                Warn => not Static);
6191
6192             Check_Expressions;
6193             return;
6194          end if;
6195
6196          Fold_Ureal (N, Eval_Fat.Remainder (P_Root_Type, X, Y), Static);
6197       end Remainder;
6198
6199       -----------
6200       -- Round --
6201       -----------
6202
6203       when Attribute_Round => Round :
6204       declare
6205          Sr : Ureal;
6206          Si : Uint;
6207
6208       begin
6209          --  First we get the (exact result) in units of small
6210
6211          Sr := Expr_Value_R (E1) / Small_Value (C_Type);
6212
6213          --  Now round that exactly to an integer
6214
6215          Si := UR_To_Uint (Sr);
6216
6217          --  Finally the result is obtained by converting back to real
6218
6219          Fold_Ureal (N, Si * Small_Value (C_Type), Static);
6220       end Round;
6221
6222       --------------
6223       -- Rounding --
6224       --------------
6225
6226       when Attribute_Rounding =>
6227          Fold_Ureal (N,
6228            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
6229
6230       ---------------
6231       -- Safe_Emax --
6232       ---------------
6233
6234       when Attribute_Safe_Emax =>
6235          Float_Attribute_Universal_Integer (
6236            IEEES_Safe_Emax,
6237            IEEEL_Safe_Emax,
6238            IEEEX_Safe_Emax,
6239            VAXFF_Safe_Emax,
6240            VAXDF_Safe_Emax,
6241            VAXGF_Safe_Emax,
6242            AAMPS_Safe_Emax,
6243            AAMPL_Safe_Emax);
6244
6245       ----------------
6246       -- Safe_First --
6247       ----------------
6248
6249       when Attribute_Safe_First =>
6250          Float_Attribute_Universal_Real (
6251            IEEES_Safe_First'Universal_Literal_String,
6252            IEEEL_Safe_First'Universal_Literal_String,
6253            IEEEX_Safe_First'Universal_Literal_String,
6254            VAXFF_Safe_First'Universal_Literal_String,
6255            VAXDF_Safe_First'Universal_Literal_String,
6256            VAXGF_Safe_First'Universal_Literal_String,
6257            AAMPS_Safe_First'Universal_Literal_String,
6258            AAMPL_Safe_First'Universal_Literal_String);
6259
6260       ----------------
6261       -- Safe_Large --
6262       ----------------
6263
6264       when Attribute_Safe_Large =>
6265          if Is_Fixed_Point_Type (P_Type) then
6266             Fold_Ureal
6267               (N, Expr_Value_R (Type_High_Bound (P_Base_Type)), Static);
6268          else
6269             Float_Attribute_Universal_Real (
6270               IEEES_Safe_Large'Universal_Literal_String,
6271               IEEEL_Safe_Large'Universal_Literal_String,
6272               IEEEX_Safe_Large'Universal_Literal_String,
6273               VAXFF_Safe_Large'Universal_Literal_String,
6274               VAXDF_Safe_Large'Universal_Literal_String,
6275               VAXGF_Safe_Large'Universal_Literal_String,
6276               AAMPS_Safe_Large'Universal_Literal_String,
6277               AAMPL_Safe_Large'Universal_Literal_String);
6278          end if;
6279
6280       ---------------
6281       -- Safe_Last --
6282       ---------------
6283
6284       when Attribute_Safe_Last =>
6285          Float_Attribute_Universal_Real (
6286            IEEES_Safe_Last'Universal_Literal_String,
6287            IEEEL_Safe_Last'Universal_Literal_String,
6288            IEEEX_Safe_Last'Universal_Literal_String,
6289            VAXFF_Safe_Last'Universal_Literal_String,
6290            VAXDF_Safe_Last'Universal_Literal_String,
6291            VAXGF_Safe_Last'Universal_Literal_String,
6292            AAMPS_Safe_Last'Universal_Literal_String,
6293            AAMPL_Safe_Last'Universal_Literal_String);
6294
6295       ----------------
6296       -- Safe_Small --
6297       ----------------
6298
6299       when Attribute_Safe_Small =>
6300
6301          --  In Ada 95, the old Ada 83 attribute Safe_Small is redundant
6302          --  for fixed-point, since is the same as Small, but we implement
6303          --  it for backwards compatibility.
6304
6305          if Is_Fixed_Point_Type (P_Type) then
6306             Fold_Ureal (N, Small_Value (P_Type), Static);
6307
6308          --  Ada 83 Safe_Small for floating-point cases
6309
6310          else
6311             Float_Attribute_Universal_Real (
6312               IEEES_Safe_Small'Universal_Literal_String,
6313               IEEEL_Safe_Small'Universal_Literal_String,
6314               IEEEX_Safe_Small'Universal_Literal_String,
6315               VAXFF_Safe_Small'Universal_Literal_String,
6316               VAXDF_Safe_Small'Universal_Literal_String,
6317               VAXGF_Safe_Small'Universal_Literal_String,
6318               AAMPS_Safe_Small'Universal_Literal_String,
6319               AAMPL_Safe_Small'Universal_Literal_String);
6320          end if;
6321
6322       -----------
6323       -- Scale --
6324       -----------
6325
6326       when Attribute_Scale =>
6327          Fold_Uint (N, Scale_Value (P_Type), True);
6328
6329       -------------
6330       -- Scaling --
6331       -------------
6332
6333       when Attribute_Scaling =>
6334          Fold_Ureal (N,
6335            Eval_Fat.Scaling
6336              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
6337
6338       ------------------
6339       -- Signed_Zeros --
6340       ------------------
6341
6342       when Attribute_Signed_Zeros =>
6343          Fold_Uint
6344            (N, UI_From_Int (Boolean'Pos (Signed_Zeros_On_Target)), Static);
6345
6346       ----------
6347       -- Size --
6348       ----------
6349
6350       --  Size attribute returns the RM size. All scalar types can be folded,
6351       --  as well as any types for which the size is known by the front end,
6352       --  including any type for which a size attribute is specified.
6353
6354       when Attribute_Size | Attribute_VADS_Size => Size : declare
6355          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6356
6357       begin
6358          if RM_Size (P_TypeA) /= Uint_0 then
6359
6360             --  VADS_Size case
6361
6362             if Id = Attribute_VADS_Size or else Use_VADS_Size then
6363                declare
6364                   S : constant Node_Id := Size_Clause (P_TypeA);
6365
6366                begin
6367                   --  If a size clause applies, then use the size from it.
6368                   --  This is one of the rare cases where we can use the
6369                   --  Size_Clause field for a subtype when Has_Size_Clause
6370                   --  is False. Consider:
6371
6372                   --    type x is range 1 .. 64;
6373                   --    for x'size use 12;
6374                   --    subtype y is x range 0 .. 3;
6375
6376                   --  Here y has a size clause inherited from x, but normally
6377                   --  it does not apply, and y'size is 2. However, y'VADS_Size
6378                   --  is indeed 12 and not 2.
6379
6380                   if Present (S)
6381                     and then Is_OK_Static_Expression (Expression (S))
6382                   then
6383                      Fold_Uint (N, Expr_Value (Expression (S)), True);
6384
6385                   --  If no size is specified, then we simply use the object
6386                   --  size in the VADS_Size case (e.g. Natural'Size is equal
6387                   --  to Integer'Size, not one less).
6388
6389                   else
6390                      Fold_Uint (N, Esize (P_TypeA), True);
6391                   end if;
6392                end;
6393
6394             --  Normal case (Size) in which case we want the RM_Size
6395
6396             else
6397                Fold_Uint (N,
6398                  RM_Size (P_TypeA),
6399                  Static and then Is_Discrete_Type (P_TypeA));
6400             end if;
6401          end if;
6402       end Size;
6403
6404       -----------
6405       -- Small --
6406       -----------
6407
6408       when Attribute_Small =>
6409
6410          --  The floating-point case is present only for Ada 83 compatability.
6411          --  Note that strictly this is an illegal addition, since we are
6412          --  extending an Ada 95 defined attribute, but we anticipate an
6413          --  ARG ruling that will permit this.
6414
6415          if Is_Floating_Point_Type (P_Type) then
6416
6417             --  Ada 83 attribute is defined as (RM83 3.5.8)
6418
6419             --    T'Small = 2.0**(-T'Emax - 1)
6420
6421             --  where
6422
6423             --    T'Emax = 4 * T'Mantissa
6424
6425             Fold_Ureal (N, Ureal_2 ** ((-(4 * Mantissa)) - 1), Static);
6426
6427          --  Normal Ada 95 fixed-point case
6428
6429          else
6430             Fold_Ureal (N, Small_Value (P_Type), True);
6431          end if;
6432
6433       -----------------
6434       -- Stream_Size --
6435       -----------------
6436
6437       when Attribute_Stream_Size =>
6438          null;
6439
6440       ----------
6441       -- Succ --
6442       ----------
6443
6444       when Attribute_Succ => Succ :
6445       begin
6446          --  Floating-point case
6447
6448          if Is_Floating_Point_Type (P_Type) then
6449             Fold_Ureal (N,
6450               Eval_Fat.Succ (P_Root_Type, Expr_Value_R (E1)), Static);
6451
6452          --  Fixed-point case
6453
6454          elsif Is_Fixed_Point_Type (P_Type) then
6455             Fold_Ureal (N,
6456               Expr_Value_R (E1) + Small_Value (P_Type), Static);
6457
6458          --  Modular integer case (wraps)
6459
6460          elsif Is_Modular_Integer_Type (P_Type) then
6461             Fold_Uint (N, (Expr_Value (E1) + 1) mod Modulus (P_Type), Static);
6462
6463          --  Other scalar cases
6464
6465          else
6466             pragma Assert (Is_Scalar_Type (P_Type));
6467
6468             if Is_Enumeration_Type (P_Type)
6469               and then Expr_Value (E1) =
6470                          Expr_Value (Type_High_Bound (P_Base_Type))
6471             then
6472                Apply_Compile_Time_Constraint_Error
6473                  (N, "Succ of `&''Last`",
6474                   CE_Overflow_Check_Failed,
6475                   Ent  => P_Base_Type,
6476                   Warn => not Static);
6477
6478                Check_Expressions;
6479                return;
6480             else
6481                Fold_Uint (N, Expr_Value (E1) + 1, Static);
6482             end if;
6483          end if;
6484       end Succ;
6485
6486       ----------------
6487       -- Truncation --
6488       ----------------
6489
6490       when Attribute_Truncation =>
6491          Fold_Ureal (N,
6492            Eval_Fat.Truncation (P_Root_Type, Expr_Value_R (E1)), Static);
6493
6494       ----------------
6495       -- Type_Class --
6496       ----------------
6497
6498       when Attribute_Type_Class => Type_Class : declare
6499          Typ : constant Entity_Id := Underlying_Type (P_Base_Type);
6500          Id  : RE_Id;
6501
6502       begin
6503          if Is_Descendent_Of_Address (Typ) then
6504             Id := RE_Type_Class_Address;
6505
6506          elsif Is_Enumeration_Type (Typ) then
6507             Id := RE_Type_Class_Enumeration;
6508
6509          elsif Is_Integer_Type (Typ) then
6510             Id := RE_Type_Class_Integer;
6511
6512          elsif Is_Fixed_Point_Type (Typ) then
6513             Id := RE_Type_Class_Fixed_Point;
6514
6515          elsif Is_Floating_Point_Type (Typ) then
6516             Id := RE_Type_Class_Floating_Point;
6517
6518          elsif Is_Array_Type (Typ) then
6519             Id := RE_Type_Class_Array;
6520
6521          elsif Is_Record_Type (Typ) then
6522             Id := RE_Type_Class_Record;
6523
6524          elsif Is_Access_Type (Typ) then
6525             Id := RE_Type_Class_Access;
6526
6527          elsif Is_Enumeration_Type (Typ) then
6528             Id := RE_Type_Class_Enumeration;
6529
6530          elsif Is_Task_Type (Typ) then
6531             Id := RE_Type_Class_Task;
6532
6533          --  We treat protected types like task types. It would make more
6534          --  sense to have another enumeration value, but after all the
6535          --  whole point of this feature is to be exactly DEC compatible,
6536          --  and changing the type Type_Clas would not meet this requirement.
6537
6538          elsif Is_Protected_Type (Typ) then
6539             Id := RE_Type_Class_Task;
6540
6541          --  Not clear if there are any other possibilities, but if there
6542          --  are, then we will treat them as the address case.
6543
6544          else
6545             Id := RE_Type_Class_Address;
6546          end if;
6547
6548          Rewrite (N, New_Occurrence_Of (RTE (Id), Loc));
6549       end Type_Class;
6550
6551       -----------------------
6552       -- Unbiased_Rounding --
6553       -----------------------
6554
6555       when Attribute_Unbiased_Rounding =>
6556          Fold_Ureal (N,
6557            Eval_Fat.Unbiased_Rounding (P_Root_Type, Expr_Value_R (E1)),
6558            Static);
6559
6560       -------------------------
6561       -- Unconstrained_Array --
6562       -------------------------
6563
6564       when Attribute_Unconstrained_Array => Unconstrained_Array : declare
6565          Typ : constant Entity_Id := Underlying_Type (P_Type);
6566
6567       begin
6568          Rewrite (N, New_Occurrence_Of (
6569            Boolean_Literals (
6570              Is_Array_Type (P_Type)
6571               and then not Is_Constrained (Typ)), Loc));
6572
6573          --  Analyze and resolve as boolean, note that this attribute is
6574          --  a static attribute in GNAT.
6575
6576          Analyze_And_Resolve (N, Standard_Boolean);
6577          Static := True;
6578       end Unconstrained_Array;
6579
6580       ---------------
6581       -- VADS_Size --
6582       ---------------
6583
6584       --  Processing is shared with Size
6585
6586       ---------
6587       -- Val --
6588       ---------
6589
6590       when Attribute_Val => Val :
6591       begin
6592          if  Expr_Value (E1) < Expr_Value (Type_Low_Bound (P_Base_Type))
6593            or else
6594              Expr_Value (E1) > Expr_Value (Type_High_Bound (P_Base_Type))
6595          then
6596             Apply_Compile_Time_Constraint_Error
6597               (N, "Val expression out of range",
6598                CE_Range_Check_Failed,
6599                Warn => not Static);
6600
6601             Check_Expressions;
6602             return;
6603
6604          else
6605             Fold_Uint (N, Expr_Value (E1), Static);
6606          end if;
6607       end Val;
6608
6609       ----------------
6610       -- Value_Size --
6611       ----------------
6612
6613       --  The Value_Size attribute for a type returns the RM size of the
6614       --  type. This an always be folded for scalar types, and can also
6615       --  be folded for non-scalar types if the size is set.
6616
6617       when Attribute_Value_Size => Value_Size : declare
6618          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6619       begin
6620          if RM_Size (P_TypeA) /= Uint_0 then
6621             Fold_Uint (N, RM_Size (P_TypeA), True);
6622          end if;
6623       end Value_Size;
6624
6625       -------------
6626       -- Version --
6627       -------------
6628
6629       --  Version can never be static
6630
6631       when Attribute_Version =>
6632          null;
6633
6634       ----------------
6635       -- Wide_Image --
6636       ----------------
6637
6638       --  Wide_Image is a scalar attribute, but is never static, because it
6639       --  is not a static function (having a non-scalar argument (RM 4.9(22))
6640
6641       when Attribute_Wide_Image =>
6642          null;
6643
6644       ---------------------
6645       -- Wide_Wide_Image --
6646       ---------------------
6647
6648       --  Wide_Wide_Image is a scalar attribute but is never static, because it
6649       --  is not a static function (having a non-scalar argument (RM 4.9(22)).
6650
6651       when Attribute_Wide_Wide_Image =>
6652          null;
6653
6654       ---------------------
6655       -- Wide_Wide_Width --
6656       ---------------------
6657
6658       --  Processing for Wide_Wide_Width is combined with Width
6659
6660       ----------------
6661       -- Wide_Width --
6662       ----------------
6663
6664       --  Processing for Wide_Width is combined with Width
6665
6666       -----------
6667       -- Width --
6668       -----------
6669
6670       --  This processing also handles the case of Wide_[Wide_]Width
6671
6672       when Attribute_Width |
6673            Attribute_Wide_Width |
6674            Attribute_Wide_Wide_Width => Width :
6675       begin
6676          if Compile_Time_Known_Bounds (P_Type) then
6677
6678             --  Floating-point types
6679
6680             if Is_Floating_Point_Type (P_Type) then
6681
6682                --  Width is zero for a null range (RM 3.5 (38))
6683
6684                if Expr_Value_R (Type_High_Bound (P_Type)) <
6685                   Expr_Value_R (Type_Low_Bound (P_Type))
6686                then
6687                   Fold_Uint (N, Uint_0, True);
6688
6689                else
6690                   --  For floating-point, we have +N.dddE+nnn where length
6691                   --  of ddd is determined by type'Digits - 1, but is one
6692                   --  if Digits is one (RM 3.5 (33)).
6693
6694                   --  nnn is set to 2 for Short_Float and Float (32 bit
6695                   --  floats), and 3 for Long_Float and Long_Long_Float.
6696                   --  For machines where Long_Long_Float is the IEEE
6697                   --  extended precision type, the exponent takes 4 digits.
6698
6699                   declare
6700                      Len : Int :=
6701                              Int'Max (2, UI_To_Int (Digits_Value (P_Type)));
6702
6703                   begin
6704                      if Esize (P_Type) <= 32 then
6705                         Len := Len + 6;
6706                      elsif Esize (P_Type) = 64 then
6707                         Len := Len + 7;
6708                      else
6709                         Len := Len + 8;
6710                      end if;
6711
6712                      Fold_Uint (N, UI_From_Int (Len), True);
6713                   end;
6714                end if;
6715
6716             --  Fixed-point types
6717
6718             elsif Is_Fixed_Point_Type (P_Type) then
6719
6720                --  Width is zero for a null range (RM 3.5 (38))
6721
6722                if Expr_Value (Type_High_Bound (P_Type)) <
6723                   Expr_Value (Type_Low_Bound  (P_Type))
6724                then
6725                   Fold_Uint (N, Uint_0, True);
6726
6727                --  The non-null case depends on the specific real type
6728
6729                else
6730                   --  For fixed-point type width is Fore + 1 + Aft (RM 3.5(34))
6731
6732                   Fold_Uint
6733                     (N, UI_From_Int (Fore_Value + 1 + Aft_Value), True);
6734                end if;
6735
6736             --  Discrete types
6737
6738             else
6739                declare
6740                   R  : constant Entity_Id := Root_Type (P_Type);
6741                   Lo : constant Uint :=
6742                          Expr_Value (Type_Low_Bound (P_Type));
6743                   Hi : constant Uint :=
6744                          Expr_Value (Type_High_Bound (P_Type));
6745                   W  : Nat;
6746                   Wt : Nat;
6747                   T  : Uint;
6748                   L  : Node_Id;
6749                   C  : Character;
6750
6751                begin
6752                   --  Empty ranges
6753
6754                   if Lo > Hi then
6755                      W := 0;
6756
6757                   --  Width for types derived from Standard.Character
6758                   --  and Standard.Wide_[Wide_]Character.
6759
6760                   elsif R = Standard_Character
6761                      or else R = Standard_Wide_Character
6762                      or else R = Standard_Wide_Wide_Character
6763                   then
6764                      W := 0;
6765
6766                      --  Set W larger if needed
6767
6768                      for J in UI_To_Int (Lo) .. UI_To_Int (Hi) loop
6769
6770                         --  All wide characters look like Hex_hhhhhhhh
6771
6772                         if J > 255 then
6773                            W := 12;
6774
6775                         else
6776                            C := Character'Val (J);
6777
6778                            --  Test for all cases where Character'Image
6779                            --  yields an image that is longer than three
6780                            --  characters. First the cases of Reserved_xxx
6781                            --  names (length = 12).
6782
6783                            case C is
6784                               when Reserved_128 | Reserved_129 |
6785                                    Reserved_132 | Reserved_153
6786
6787                                 => Wt := 12;
6788
6789                               when BS | HT | LF | VT | FF | CR |
6790                                    SO | SI | EM | FS | GS | RS |
6791                                    US | RI | MW | ST | PM
6792
6793                                 => Wt := 2;
6794
6795                               when NUL | SOH | STX | ETX | EOT |
6796                                    ENQ | ACK | BEL | DLE | DC1 |
6797                                    DC2 | DC3 | DC4 | NAK | SYN |
6798                                    ETB | CAN | SUB | ESC | DEL |
6799                                    BPH | NBH | NEL | SSA | ESA |
6800                                    HTS | HTJ | VTS | PLD | PLU |
6801                                    SS2 | SS3 | DCS | PU1 | PU2 |
6802                                    STS | CCH | SPA | EPA | SOS |
6803                                    SCI | CSI | OSC | APC
6804
6805                                 => Wt := 3;
6806
6807                               when Space .. Tilde |
6808                                    No_Break_Space .. LC_Y_Diaeresis
6809
6810                                 => Wt := 3;
6811                            end case;
6812
6813                            W := Int'Max (W, Wt);
6814                         end if;
6815                      end loop;
6816
6817                   --  Width for types derived from Standard.Boolean
6818
6819                   elsif R = Standard_Boolean then
6820                      if Lo = 0 then
6821                         W := 5; -- FALSE
6822                      else
6823                         W := 4; -- TRUE
6824                      end if;
6825
6826                   --  Width for integer types
6827
6828                   elsif Is_Integer_Type (P_Type) then
6829                      T := UI_Max (abs Lo, abs Hi);
6830
6831                      W := 2;
6832                      while T >= 10 loop
6833                         W := W + 1;
6834                         T := T / 10;
6835                      end loop;
6836
6837                   --  Only remaining possibility is user declared enum type
6838
6839                   else
6840                      pragma Assert (Is_Enumeration_Type (P_Type));
6841
6842                      W := 0;
6843                      L := First_Literal (P_Type);
6844
6845                      while Present (L) loop
6846
6847                         --  Only pay attention to in range characters
6848
6849                         if Lo <= Enumeration_Pos (L)
6850                           and then Enumeration_Pos (L) <= Hi
6851                         then
6852                            --  For Width case, use decoded name
6853
6854                            if Id = Attribute_Width then
6855                               Get_Decoded_Name_String (Chars (L));
6856                               Wt := Nat (Name_Len);
6857
6858                            --  For Wide_[Wide_]Width, use encoded name, and
6859                            --  then adjust for the encoding.
6860
6861                            else
6862                               Get_Name_String (Chars (L));
6863
6864                               --  Character literals are always of length 3
6865
6866                               if Name_Buffer (1) = 'Q' then
6867                                  Wt := 3;
6868
6869                               --  Otherwise loop to adjust for upper/wide chars
6870
6871                               else
6872                                  Wt := Nat (Name_Len);
6873
6874                                  for J in 1 .. Name_Len loop
6875                                     if Name_Buffer (J) = 'U' then
6876                                        Wt := Wt - 2;
6877                                     elsif Name_Buffer (J) = 'W' then
6878                                        Wt := Wt - 4;
6879                                     end if;
6880                                  end loop;
6881                               end if;
6882                            end if;
6883
6884                            W := Int'Max (W, Wt);
6885                         end if;
6886
6887                         Next_Literal (L);
6888                      end loop;
6889                   end if;
6890
6891                   Fold_Uint (N, UI_From_Int (W), True);
6892                end;
6893             end if;
6894          end if;
6895       end Width;
6896
6897       --  The following attributes can never be folded, and furthermore we
6898       --  should not even have entered the case statement for any of these.
6899       --  Note that in some cases, the values have already been folded as
6900       --  a result of the processing in Analyze_Attribute.
6901
6902       when Attribute_Abort_Signal             |
6903            Attribute_Access                   |
6904            Attribute_Address                  |
6905            Attribute_Address_Size             |
6906            Attribute_Asm_Input                |
6907            Attribute_Asm_Output               |
6908            Attribute_Base                     |
6909            Attribute_Bit_Order                |
6910            Attribute_Bit_Position             |
6911            Attribute_Callable                 |
6912            Attribute_Caller                   |
6913            Attribute_Class                    |
6914            Attribute_Code_Address             |
6915            Attribute_Count                    |
6916            Attribute_Default_Bit_Order        |
6917            Attribute_Elaborated               |
6918            Attribute_Elab_Body                |
6919            Attribute_Elab_Spec                |
6920            Attribute_Enabled                  |
6921            Attribute_External_Tag             |
6922            Attribute_Fast_Math                |
6923            Attribute_First_Bit                |
6924            Attribute_Input                    |
6925            Attribute_Last_Bit                 |
6926            Attribute_Maximum_Alignment        |
6927            Attribute_Output                   |
6928            Attribute_Partition_ID             |
6929            Attribute_Pool_Address             |
6930            Attribute_Position                 |
6931            Attribute_Priority                 |
6932            Attribute_Read                     |
6933            Attribute_Storage_Pool             |
6934            Attribute_Storage_Size             |
6935            Attribute_Storage_Unit             |
6936            Attribute_Stub_Type                |
6937            Attribute_Tag                      |
6938            Attribute_Target_Name              |
6939            Attribute_Terminated               |
6940            Attribute_To_Address               |
6941            Attribute_UET_Address              |
6942            Attribute_Unchecked_Access         |
6943            Attribute_Universal_Literal_String |
6944            Attribute_Unrestricted_Access      |
6945            Attribute_Valid                    |
6946            Attribute_Value                    |
6947            Attribute_Wchar_T_Size             |
6948            Attribute_Wide_Value               |
6949            Attribute_Wide_Wide_Value          |
6950            Attribute_Word_Size                |
6951            Attribute_Write                    =>
6952
6953          raise Program_Error;
6954       end case;
6955
6956       --  At the end of the case, one more check. If we did a static evaluation
6957       --  so that the result is now a literal, then set Is_Static_Expression
6958       --  in the constant only if the prefix type is a static subtype. For
6959       --  non-static subtypes, the folding is still OK, but not static.
6960
6961       --  An exception is the GNAT attribute Constrained_Array which is
6962       --  defined to be a static attribute in all cases.
6963
6964       if Nkind (N) = N_Integer_Literal
6965         or else Nkind (N) = N_Real_Literal
6966         or else Nkind (N) = N_Character_Literal
6967         or else Nkind (N) = N_String_Literal
6968         or else (Is_Entity_Name (N)
6969                   and then Ekind (Entity (N)) = E_Enumeration_Literal)
6970       then
6971          Set_Is_Static_Expression (N, Static);
6972
6973       --  If this is still an attribute reference, then it has not been folded
6974       --  and that means that its expressions are in a non-static context.
6975
6976       elsif Nkind (N) = N_Attribute_Reference then
6977          Check_Expressions;
6978
6979       --  Note: the else case not covered here are odd cases where the
6980       --  processing has transformed the attribute into something other
6981       --  than a constant. Nothing more to do in such cases.
6982
6983       else
6984          null;
6985       end if;
6986    end Eval_Attribute;
6987
6988    ------------------------------
6989    -- Is_Anonymous_Tagged_Base --
6990    ------------------------------
6991
6992    function Is_Anonymous_Tagged_Base
6993      (Anon : Entity_Id;
6994       Typ  : Entity_Id)
6995       return Boolean
6996    is
6997    begin
6998       return
6999         Anon = Current_Scope
7000           and then Is_Itype (Anon)
7001           and then Associated_Node_For_Itype (Anon) = Parent (Typ);
7002    end Is_Anonymous_Tagged_Base;
7003
7004    --------------------------------
7005    -- Name_Implies_Lvalue_Prefix --
7006    --------------------------------
7007
7008    function Name_Implies_Lvalue_Prefix (Nam : Name_Id) return Boolean is
7009       pragma Assert (Is_Attribute_Name (Nam));
7010    begin
7011       return Attribute_Name_Implies_Lvalue_Prefix (Get_Attribute_Id (Nam));
7012    end Name_Implies_Lvalue_Prefix;
7013
7014    -----------------------
7015    -- Resolve_Attribute --
7016    -----------------------
7017
7018    procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id) is
7019       Loc      : constant Source_Ptr   := Sloc (N);
7020       P        : constant Node_Id      := Prefix (N);
7021       Aname    : constant Name_Id      := Attribute_Name (N);
7022       Attr_Id  : constant Attribute_Id := Get_Attribute_Id (Aname);
7023       Btyp     : constant Entity_Id    := Base_Type (Typ);
7024       Des_Btyp : Entity_Id;
7025       Index    : Interp_Index;
7026       It       : Interp;
7027       Nom_Subt : Entity_Id;
7028
7029       procedure Accessibility_Message;
7030       --  Error, or warning within an instance, if the static accessibility
7031       --  rules of 3.10.2 are violated.
7032
7033       ---------------------------
7034       -- Accessibility_Message --
7035       ---------------------------
7036
7037       procedure Accessibility_Message is
7038          Indic : Node_Id := Parent (Parent (N));
7039
7040       begin
7041          --  In an instance, this is a runtime check, but one we
7042          --  know will fail, so generate an appropriate warning.
7043
7044          if In_Instance_Body then
7045             Error_Msg_F
7046               ("?non-local pointer cannot point to local object", P);
7047             Error_Msg_F
7048               ("\?Program_Error will be raised at run time", P);
7049             Rewrite (N,
7050               Make_Raise_Program_Error (Loc,
7051                 Reason => PE_Accessibility_Check_Failed));
7052             Set_Etype (N, Typ);
7053             return;
7054
7055          else
7056             Error_Msg_F
7057               ("non-local pointer cannot point to local object", P);
7058
7059             --  Check for case where we have a missing access definition
7060
7061             if Is_Record_Type (Current_Scope)
7062               and then
7063                 (Nkind (Parent (N)) = N_Discriminant_Association
7064                    or else
7065                  Nkind (Parent (N)) = N_Index_Or_Discriminant_Constraint)
7066             then
7067                Indic := Parent (Parent (N));
7068                while Present (Indic)
7069                  and then Nkind (Indic) /= N_Subtype_Indication
7070                loop
7071                   Indic := Parent (Indic);
7072                end loop;
7073
7074                if Present (Indic) then
7075                   Error_Msg_NE
7076                     ("\use an access definition for" &
7077                      " the access discriminant of&",
7078                      N, Entity (Subtype_Mark (Indic)));
7079                end if;
7080             end if;
7081          end if;
7082       end Accessibility_Message;
7083
7084    --  Start of processing for Resolve_Attribute
7085
7086    begin
7087       --  If error during analysis, no point in continuing, except for
7088       --  array types, where we get  better recovery by using unconstrained
7089       --  indices than nothing at all (see Check_Array_Type).
7090
7091       if Error_Posted (N)
7092         and then Attr_Id /= Attribute_First
7093         and then Attr_Id /= Attribute_Last
7094         and then Attr_Id /= Attribute_Length
7095         and then Attr_Id /= Attribute_Range
7096       then
7097          return;
7098       end if;
7099
7100       --  If attribute was universal type, reset to actual type
7101
7102       if Etype (N) = Universal_Integer
7103         or else Etype (N) = Universal_Real
7104       then
7105          Set_Etype (N, Typ);
7106       end if;
7107
7108       --  Remaining processing depends on attribute
7109
7110       case Attr_Id is
7111
7112          ------------
7113          -- Access --
7114          ------------
7115
7116          --  For access attributes, if the prefix denotes an entity, it is
7117          --  interpreted as a name, never as a call. It may be overloaded,
7118          --  in which case resolution uses the profile of the context type.
7119          --  Otherwise prefix must be resolved.
7120
7121          when Attribute_Access
7122             | Attribute_Unchecked_Access
7123             | Attribute_Unrestricted_Access =>
7124
7125          Access_Attribute : begin
7126             if Is_Variable (P) then
7127                Note_Possible_Modification (P);
7128             end if;
7129
7130             if Is_Entity_Name (P) then
7131                if Is_Overloaded (P) then
7132                   Get_First_Interp (P, Index, It);
7133                   while Present (It.Nam) loop
7134                      if Type_Conformant (Designated_Type (Typ), It.Nam) then
7135                         Set_Entity (P, It.Nam);
7136
7137                         --  The prefix is definitely NOT overloaded anymore at
7138                         --  this point, so we reset the Is_Overloaded flag to
7139                         --  avoid any confusion when reanalyzing the node.
7140
7141                         Set_Is_Overloaded (P, False);
7142                         Set_Is_Overloaded (N, False);
7143                         Generate_Reference (Entity (P), P);
7144                         exit;
7145                      end if;
7146
7147                      Get_Next_Interp (Index, It);
7148                   end loop;
7149
7150                --  If Prefix is a subprogram name, it is frozen by this
7151                --  reference:
7152
7153                --    If it is a type, there is nothing to resolve.
7154                --    If it is an object, complete its resolution.
7155
7156                elsif Is_Overloadable (Entity (P)) then
7157                   if not In_Default_Expression then
7158                      Insert_Actions (N, Freeze_Entity (Entity (P), Loc));
7159                   end if;
7160
7161                elsif Is_Type (Entity (P)) then
7162                   null;
7163                else
7164                   Resolve (P);
7165                end if;
7166
7167                Error_Msg_Name_1 := Aname;
7168
7169                if not Is_Entity_Name (P) then
7170                   null;
7171
7172                elsif Is_Overloadable (Entity (P))
7173                  and then Is_Abstract_Subprogram (Entity (P))
7174                then
7175                   Error_Msg_F ("prefix of % attribute cannot be abstract", P);
7176                   Set_Etype (N, Any_Type);
7177
7178                elsif Convention (Entity (P)) = Convention_Intrinsic then
7179                   if Ekind (Entity (P)) = E_Enumeration_Literal then
7180                      Error_Msg_F
7181                        ("prefix of % attribute cannot be enumeration literal",
7182                         P);
7183                   else
7184                      Error_Msg_F
7185                        ("prefix of % attribute cannot be intrinsic", P);
7186                   end if;
7187
7188                   Set_Etype (N, Any_Type);
7189                end if;
7190
7191                --  Assignments, return statements, components of aggregates,
7192                --  generic instantiations will require convention checks if
7193                --  the type is an access to subprogram. Given that there will
7194                --  also be accessibility checks on those, this is where the
7195                --  checks can eventually be centralized ???
7196
7197                if Ekind (Btyp) = E_Access_Subprogram_Type
7198                     or else
7199                   Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
7200                     or else
7201                   Ekind (Btyp) = E_Anonymous_Access_Protected_Subprogram_Type
7202                then
7203                   --  Deal with convention mismatch
7204
7205                   if Convention (Btyp) /= Convention (Entity (P)) then
7206                      Error_Msg_FE
7207                        ("subprogram & has wrong convention", P, Entity (P));
7208
7209                      Error_Msg_FE
7210                        ("\does not match convention of access type &",
7211                         P, Btyp);
7212
7213                      if not Has_Convention_Pragma (Btyp) then
7214                         Error_Msg_FE
7215                           ("\probable missing pragma Convention for &",
7216                            P, Btyp);
7217                      end if;
7218
7219                   else
7220                      Check_Subtype_Conformant
7221                        (New_Id  => Entity (P),
7222                         Old_Id  => Designated_Type (Btyp),
7223                         Err_Loc => P);
7224                   end if;
7225
7226                   if Attr_Id = Attribute_Unchecked_Access then
7227                      Error_Msg_Name_1 := Aname;
7228                      Error_Msg_F
7229                        ("attribute% cannot be applied to a subprogram", P);
7230
7231                   elsif Aname = Name_Unrestricted_Access then
7232                      null;  --  Nothing to check
7233
7234                   --  Check the static accessibility rule of 3.10.2(32).
7235                   --  This rule also applies within the private part of an
7236                   --  instantiation. This rule does not apply to anonymous
7237                   --  access-to-subprogram types (Ada 2005).
7238
7239                   elsif Attr_Id = Attribute_Access
7240                     and then not In_Instance_Body
7241                     and then Subprogram_Access_Level (Entity (P)) >
7242                                Type_Access_Level (Btyp)
7243                     and then Ekind (Btyp) /=
7244                                E_Anonymous_Access_Subprogram_Type
7245                     and then Ekind (Btyp) /=
7246                                E_Anonymous_Access_Protected_Subprogram_Type
7247                   then
7248                      Error_Msg_F
7249                        ("subprogram must not be deeper than access type", P);
7250
7251                   --  Check the restriction of 3.10.2(32) that disallows the
7252                   --  access attribute within a generic body when the ultimate
7253                   --  ancestor of the type of the attribute is declared outside
7254                   --  of the generic unit and the subprogram is declared within
7255                   --  that generic unit. This includes any such attribute that
7256                   --  occurs within the body of a generic unit that is a child
7257                   --  of the generic unit where the subprogram is declared.
7258                   --  The rule also prohibits applying the attibute when the
7259                   --  access type is a generic formal access type (since the
7260                   --  level of the actual type is not known). This restriction
7261                   --  does not apply when the attribute type is an anonymous
7262                   --  access-to-subprogram type. Note that this check was
7263                   --  revised by AI-229, because the originally Ada 95 rule
7264                   --  was too lax. The original rule only applied when the
7265                   --  subprogram was declared within the body of the generic,
7266                   --  which allowed the possibility of dangling references).
7267                   --  The rule was also too strict in some case, in that it
7268                   --  didn't permit the access to be declared in the generic
7269                   --  spec, whereas the revised rule does (as long as it's not
7270                   --  a formal type).
7271
7272                   --  There are a couple of subtleties of the test for applying
7273                   --  the check that are worth noting. First, we only apply it
7274                   --  when the levels of the subprogram and access type are the
7275                   --  same (the case where the subprogram is statically deeper
7276                   --  was applied above, and the case where the type is deeper
7277                   --  is always safe). Second, we want the check to apply
7278                   --  within nested generic bodies and generic child unit
7279                   --  bodies, but not to apply to an attribute that appears in
7280                   --  the generic unit's specification. This is done by testing
7281                   --  that the attribute's innermost enclosing generic body is
7282                   --  not the same as the innermost generic body enclosing the
7283                   --  generic unit where the subprogram is declared (we don't
7284                   --  want the check to apply when the access attribute is in
7285                   --  the spec and there's some other generic body enclosing
7286                   --  generic). Finally, there's no point applying the check
7287                   --  when within an instance, because any violations will have
7288                   --  been caught by the compilation of the generic unit.
7289
7290                   elsif Attr_Id = Attribute_Access
7291                     and then not In_Instance
7292                     and then Present (Enclosing_Generic_Unit (Entity (P)))
7293                     and then Present (Enclosing_Generic_Body (N))
7294                     and then Enclosing_Generic_Body (N) /=
7295                                Enclosing_Generic_Body
7296                                  (Enclosing_Generic_Unit (Entity (P)))
7297                     and then Subprogram_Access_Level (Entity (P)) =
7298                                Type_Access_Level (Btyp)
7299                     and then Ekind (Btyp) /=
7300                                E_Anonymous_Access_Subprogram_Type
7301                     and then Ekind (Btyp) /=
7302                                E_Anonymous_Access_Protected_Subprogram_Type
7303                   then
7304                      --  The attribute type's ultimate ancestor must be
7305                      --  declared within the same generic unit as the
7306                      --  subprogram is declared. The error message is
7307                      --  specialized to say "ancestor" for the case where
7308                      --  the access type is not its own ancestor, since
7309                      --  saying simply "access type" would be very confusing.
7310
7311                      if Enclosing_Generic_Unit (Entity (P)) /=
7312                           Enclosing_Generic_Unit (Root_Type (Btyp))
7313                      then
7314                         Error_Msg_N
7315                           ("''Access attribute not allowed in generic body",
7316                            N);
7317
7318                         if Root_Type (Btyp) = Btyp then
7319                            Error_Msg_NE
7320                              ("\because " &
7321                               "access type & is declared outside " &
7322                               "generic unit (RM 3.10.2(32))", N, Btyp);
7323                         else
7324                            Error_Msg_NE
7325                              ("\because ancestor of " &
7326                               "access type & is declared outside " &
7327                               "generic unit (RM 3.10.2(32))", N, Btyp);
7328                         end if;
7329
7330                         Error_Msg_NE
7331                           ("\move ''Access to private part, or " &
7332                            "(Ada 2005) use anonymous access type instead of &",
7333                            N, Btyp);
7334
7335                      --  If the ultimate ancestor of the attribute's type is
7336                      --  a formal type, then the attribute is illegal because
7337                      --  the actual type might be declared at a higher level.
7338                      --  The error message is specialized to say "ancestor"
7339                      --  for the case where the access type is not its own
7340                      --  ancestor, since saying simply "access type" would be
7341                      --  very confusing.
7342
7343                      elsif Is_Generic_Type (Root_Type (Btyp)) then
7344                         if Root_Type (Btyp) = Btyp then
7345                            Error_Msg_N
7346                              ("access type must not be a generic formal type",
7347                               N);
7348                         else
7349                            Error_Msg_N
7350                              ("ancestor access type must not be a generic " &
7351                               "formal type", N);
7352                         end if;
7353                      end if;
7354                   end if;
7355                end if;
7356
7357                --  If this is a renaming, an inherited operation, or a
7358                --  subprogram instance, use the original entity. This may make
7359                --  the node type-inconsistent, so this transformation can only
7360                --  be done if the node will not be reanalyzed. In particular,
7361                --  if it is within a default expression, the transformation
7362                --  must be delayed until the default subprogram is created for
7363                --  it, when the enclosing subprogram is frozen.
7364
7365                if Is_Entity_Name (P)
7366                  and then Is_Overloadable (Entity (P))
7367                  and then Present (Alias (Entity (P)))
7368                  and then Expander_Active
7369                then
7370                   Rewrite (P,
7371                     New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
7372                end if;
7373
7374             elsif Nkind (P) = N_Selected_Component
7375               and then Is_Overloadable (Entity (Selector_Name (P)))
7376             then
7377                --  Protected operation. If operation is overloaded, must
7378                --  disambiguate. Prefix that denotes protected object itself
7379                --  is resolved with its own type.
7380
7381                if Attr_Id = Attribute_Unchecked_Access then
7382                   Error_Msg_Name_1 := Aname;
7383                   Error_Msg_F
7384                     ("attribute% cannot be applied to protected operation", P);
7385                end if;
7386
7387                Resolve (Prefix (P));
7388                Generate_Reference (Entity (Selector_Name (P)), P);
7389
7390             elsif Is_Overloaded (P) then
7391
7392                --  Use the designated type of the context to disambiguate
7393                --  Note that this was not strictly conformant to Ada 95,
7394                --  but was the implementation adopted by most Ada 95 compilers.
7395                --  The use of the context type to resolve an Access attribute
7396                --  reference is now mandated in AI-235 for Ada 2005.
7397
7398                declare
7399                   Index : Interp_Index;
7400                   It    : Interp;
7401
7402                begin
7403                   Get_First_Interp (P, Index, It);
7404                   while Present (It.Typ) loop
7405                      if Covers (Designated_Type (Typ), It.Typ) then
7406                         Resolve (P, It.Typ);
7407                         exit;
7408                      end if;
7409
7410                      Get_Next_Interp (Index, It);
7411                   end loop;
7412                end;
7413             else
7414                Resolve (P);
7415             end if;
7416
7417             --  X'Access is illegal if X denotes a constant and the access type
7418             --  is access-to-variable. Same for 'Unchecked_Access. The rule
7419             --  does not apply to 'Unrestricted_Access. If the reference is a
7420             --  default-initialized aggregate component for a self-referential
7421             --  type the reference is legal.
7422
7423             if not (Ekind (Btyp) = E_Access_Subprogram_Type
7424                      or else Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
7425                      or else (Is_Record_Type (Btyp)
7426                                and then
7427                                  Present (Corresponding_Remote_Type (Btyp)))
7428                      or else Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7429                      or else Ekind (Btyp)
7430                                = E_Anonymous_Access_Protected_Subprogram_Type
7431                      or else Is_Access_Constant (Btyp)
7432                      or else Is_Variable (P)
7433                      or else Attr_Id = Attribute_Unrestricted_Access)
7434             then
7435                if Is_Entity_Name (P)
7436                  and then Is_Type (Entity (P))
7437                then
7438                   --  Legality of a self-reference through an access
7439                   --  attribute has been verified in Analyze_Access_Attribute.
7440
7441                   null;
7442
7443                elsif Comes_From_Source (N) then
7444                   Error_Msg_F ("access-to-variable designates constant", P);
7445                end if;
7446             end if;
7447
7448             Des_Btyp := Designated_Type (Btyp);
7449
7450             if Ada_Version >= Ada_05
7451               and then Is_Incomplete_Type (Des_Btyp)
7452             then
7453                --  Ada 2005 (AI-412): If the (sub)type is a limited view of an
7454                --  imported entity, and the non-limited view is visible, make
7455                --  use of it. If it is an incomplete subtype, use the base type
7456                --  in any case.
7457
7458                if From_With_Type (Des_Btyp)
7459                  and then Present (Non_Limited_View (Des_Btyp))
7460                then
7461                   Des_Btyp := Non_Limited_View (Des_Btyp);
7462
7463                elsif Ekind (Des_Btyp) = E_Incomplete_Subtype then
7464                   Des_Btyp := Etype (Des_Btyp);
7465                end if;
7466             end if;
7467
7468             if (Attr_Id = Attribute_Access
7469                   or else
7470                 Attr_Id = Attribute_Unchecked_Access)
7471               and then (Ekind (Btyp) = E_General_Access_Type
7472                           or else Ekind (Btyp) = E_Anonymous_Access_Type)
7473             then
7474                --  Ada 2005 (AI-230): Check the accessibility of anonymous
7475                --  access types for stand-alone objects, record and array
7476                --  components, and return objects. For a component definition
7477                --  the level is the same of the enclosing composite type.
7478
7479                if Ada_Version >= Ada_05
7480                  and then Is_Local_Anonymous_Access (Btyp)
7481                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
7482                  and then Attr_Id = Attribute_Access
7483                then
7484                   --  In an instance, this is a runtime check, but one we
7485                   --  know will fail, so generate an appropriate warning.
7486
7487                   if In_Instance_Body then
7488                      Error_Msg_F
7489                        ("?non-local pointer cannot point to local object", P);
7490                      Error_Msg_F
7491                        ("\?Program_Error will be raised at run time", P);
7492                      Rewrite (N,
7493                        Make_Raise_Program_Error (Loc,
7494                          Reason => PE_Accessibility_Check_Failed));
7495                      Set_Etype (N, Typ);
7496
7497                   else
7498                      Error_Msg_F
7499                        ("non-local pointer cannot point to local object", P);
7500                   end if;
7501                end if;
7502
7503                if Is_Dependent_Component_Of_Mutable_Object (P) then
7504                   Error_Msg_F
7505                     ("illegal attribute for discriminant-dependent component",
7506                      P);
7507                end if;
7508
7509                --  Check static matching rule of 3.10.2(27). Nominal subtype
7510                --  of the prefix must statically match the designated type.
7511
7512                Nom_Subt := Etype (P);
7513
7514                if Is_Constr_Subt_For_U_Nominal (Nom_Subt) then
7515                   Nom_Subt := Base_Type (Nom_Subt);
7516                end if;
7517
7518                if Is_Tagged_Type (Designated_Type (Typ)) then
7519
7520                   --  If the attribute is in the context of an access
7521                   --  parameter, then the prefix is allowed to be of the
7522                   --  class-wide type (by AI-127).
7523
7524                   if Ekind (Typ) = E_Anonymous_Access_Type then
7525                      if not Covers (Designated_Type (Typ), Nom_Subt)
7526                        and then not Covers (Nom_Subt, Designated_Type (Typ))
7527                      then
7528                         declare
7529                            Desig : Entity_Id;
7530
7531                         begin
7532                            Desig := Designated_Type (Typ);
7533
7534                            if Is_Class_Wide_Type (Desig) then
7535                               Desig := Etype (Desig);
7536                            end if;
7537
7538                            if Is_Anonymous_Tagged_Base (Nom_Subt, Desig) then
7539                               null;
7540
7541                            else
7542                               Error_Msg_FE
7543                                 ("type of prefix: & not compatible",
7544                                   P, Nom_Subt);
7545                               Error_Msg_FE
7546                                 ("\with &, the expected designated type",
7547                                   P, Designated_Type (Typ));
7548                            end if;
7549                         end;
7550                      end if;
7551
7552                   elsif not Covers (Designated_Type (Typ), Nom_Subt)
7553                     or else
7554                       (not Is_Class_Wide_Type (Designated_Type (Typ))
7555                         and then Is_Class_Wide_Type (Nom_Subt))
7556                   then
7557                      Error_Msg_FE
7558                        ("type of prefix: & is not covered", P, Nom_Subt);
7559                      Error_Msg_FE
7560                        ("\by &, the expected designated type" &
7561                            " (RM 3.10.2 (27))", P, Designated_Type (Typ));
7562                   end if;
7563
7564                   if Is_Class_Wide_Type (Designated_Type (Typ))
7565                     and then Has_Discriminants (Etype (Designated_Type (Typ)))
7566                     and then Is_Constrained (Etype (Designated_Type (Typ)))
7567                     and then Designated_Type (Typ) /= Nom_Subt
7568                   then
7569                      Apply_Discriminant_Check
7570                        (N, Etype (Designated_Type (Typ)));
7571                   end if;
7572
7573                --  Ada 2005 (AI-363): Require static matching when designated
7574                --  type has discriminants and a constrained partial view, since
7575                --  in general objects of such types are mutable, so we can't
7576                --  allow the access value to designate a constrained object
7577                --  (because access values must be assumed to designate mutable
7578                --  objects when designated type does not impose a constraint).
7579
7580                elsif Subtypes_Statically_Match (Des_Btyp, Nom_Subt) then
7581                   null;
7582
7583                elsif Has_Discriminants (Designated_Type (Typ))
7584                  and then not Is_Constrained (Des_Btyp)
7585                  and then
7586                    (Ada_Version < Ada_05
7587                      or else
7588                        not Has_Constrained_Partial_View
7589                              (Designated_Type (Base_Type (Typ))))
7590                then
7591                   null;
7592
7593                else
7594                   Error_Msg_F
7595                     ("object subtype must statically match "
7596                      & "designated subtype", P);
7597
7598                   if Is_Entity_Name (P)
7599                     and then Is_Array_Type (Designated_Type (Typ))
7600                   then
7601                      declare
7602                         D : constant Node_Id := Declaration_Node (Entity (P));
7603
7604                      begin
7605                         Error_Msg_N ("aliased object has explicit bounds?",
7606                           D);
7607                         Error_Msg_N ("\declare without bounds"
7608                           & " (and with explicit initialization)?", D);
7609                         Error_Msg_N ("\for use with unconstrained access?", D);
7610                      end;
7611                   end if;
7612                end if;
7613
7614                --  Check the static accessibility rule of 3.10.2(28).
7615                --  Note that this check is not performed for the
7616                --  case of an anonymous access type, since the access
7617                --  attribute is always legal in such a context.
7618
7619                if Attr_Id /= Attribute_Unchecked_Access
7620                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
7621                  and then Ekind (Btyp) = E_General_Access_Type
7622                then
7623                   Accessibility_Message;
7624                   return;
7625                end if;
7626             end if;
7627
7628             if Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7629                  or else
7630                Ekind (Btyp) = E_Anonymous_Access_Protected_Subprogram_Type
7631             then
7632                if Is_Entity_Name (P)
7633                  and then not Is_Protected_Type (Scope (Entity (P)))
7634                then
7635                   Error_Msg_F ("context requires a protected subprogram", P);
7636
7637                --  Check accessibility of protected object against that of the
7638                --  access type, but only on user code, because the expander
7639                --  creates access references for handlers. If the context is an
7640                --  anonymous_access_to_protected, there are no accessibility
7641                --  checks either. Omit check entirely for Unrestricted_Access.
7642
7643                elsif Object_Access_Level (P) > Type_Access_Level (Btyp)
7644                  and then Comes_From_Source (N)
7645                  and then Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7646                  and then Attr_Id /= Attribute_Unrestricted_Access
7647                then
7648                   Accessibility_Message;
7649                   return;
7650                end if;
7651
7652             elsif (Ekind (Btyp) = E_Access_Subprogram_Type
7653                      or else
7654                    Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type)
7655               and then Ekind (Etype (N)) = E_Access_Protected_Subprogram_Type
7656             then
7657                Error_Msg_F ("context requires a non-protected subprogram", P);
7658             end if;
7659
7660             --  The context cannot be a pool-specific type, but this is a
7661             --  legality rule, not a resolution rule, so it must be checked
7662             --  separately, after possibly disambiguation (see AI-245).
7663
7664             if Ekind (Btyp) = E_Access_Type
7665               and then Attr_Id /= Attribute_Unrestricted_Access
7666             then
7667                Wrong_Type (N, Typ);
7668             end if;
7669
7670             --  The context may be a constrained access type (however ill-
7671             --  advised such subtypes might be) so in order to generate a
7672             --  constraint check when needed set the type of the attribute
7673             --  reference to the base type of the context.
7674
7675             Set_Etype (N, Btyp);
7676
7677             --  Check for incorrect atomic/volatile reference (RM C.6(12))
7678
7679             if Attr_Id /= Attribute_Unrestricted_Access then
7680                if Is_Atomic_Object (P)
7681                  and then not Is_Atomic (Designated_Type (Typ))
7682                then
7683                   Error_Msg_F
7684                     ("access to atomic object cannot yield access-to-" &
7685                      "non-atomic type", P);
7686
7687                elsif Is_Volatile_Object (P)
7688                  and then not Is_Volatile (Designated_Type (Typ))
7689                then
7690                   Error_Msg_F
7691                     ("access to volatile object cannot yield access-to-" &
7692                      "non-volatile type", P);
7693                end if;
7694             end if;
7695
7696             if Is_Entity_Name (P) then
7697                Set_Address_Taken (Entity (P));
7698             end if;
7699          end Access_Attribute;
7700
7701          -------------
7702          -- Address --
7703          -------------
7704
7705          --  Deal with resolving the type for Address attribute, overloading
7706          --  is not permitted here, since there is no context to resolve it.
7707
7708          when Attribute_Address | Attribute_Code_Address =>
7709          Address_Attribute : begin
7710
7711             --  To be safe, assume that if the address of a variable is taken,
7712             --  it may be modified via this address, so note modification.
7713
7714             if Is_Variable (P) then
7715                Note_Possible_Modification (P);
7716             end if;
7717
7718             if Nkind (P) in N_Subexpr
7719               and then Is_Overloaded (P)
7720             then
7721                Get_First_Interp (P, Index, It);
7722                Get_Next_Interp (Index, It);
7723
7724                if Present (It.Nam) then
7725                   Error_Msg_Name_1 := Aname;
7726                   Error_Msg_F
7727                     ("prefix of % attribute cannot be overloaded", P);
7728                end if;
7729             end if;
7730
7731             if not Is_Entity_Name (P)
7732               or else not Is_Overloadable (Entity (P))
7733             then
7734                if not Is_Task_Type (Etype (P))
7735                  or else Nkind (P) = N_Explicit_Dereference
7736                then
7737                   Resolve (P);
7738                end if;
7739             end if;
7740
7741             --  If this is the name of a derived subprogram, or that of a
7742             --  generic actual, the address is that of the original entity.
7743
7744             if Is_Entity_Name (P)
7745               and then Is_Overloadable (Entity (P))
7746               and then Present (Alias (Entity (P)))
7747             then
7748                Rewrite (P,
7749                  New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
7750             end if;
7751
7752             if Is_Entity_Name (P) then
7753                Set_Address_Taken (Entity (P));
7754             end if;
7755          end Address_Attribute;
7756
7757          ---------------
7758          -- AST_Entry --
7759          ---------------
7760
7761          --  Prefix of the AST_Entry attribute is an entry name which must
7762          --  not be resolved, since this is definitely not an entry call.
7763
7764          when Attribute_AST_Entry =>
7765             null;
7766
7767          ------------------
7768          -- Body_Version --
7769          ------------------
7770
7771          --  Prefix of Body_Version attribute can be a subprogram name which
7772          --  must not be resolved, since this is not a call.
7773
7774          when Attribute_Body_Version =>
7775             null;
7776
7777          ------------
7778          -- Caller --
7779          ------------
7780
7781          --  Prefix of Caller attribute is an entry name which must not
7782          --  be resolved, since this is definitely not an entry call.
7783
7784          when Attribute_Caller =>
7785             null;
7786
7787          ------------------
7788          -- Code_Address --
7789          ------------------
7790
7791          --  Shares processing with Address attribute
7792
7793          -----------
7794          -- Count --
7795          -----------
7796
7797          --  If the prefix of the Count attribute is an entry name it must not
7798          --  be resolved, since this is definitely not an entry call. However,
7799          --  if it is an element of an entry family, the index itself may
7800          --  have to be resolved because it can be a general expression.
7801
7802          when Attribute_Count =>
7803             if Nkind (P) = N_Indexed_Component
7804               and then Is_Entity_Name (Prefix (P))
7805             then
7806                declare
7807                   Indx : constant Node_Id   := First (Expressions (P));
7808                   Fam  : constant Entity_Id := Entity (Prefix (P));
7809                begin
7810                   Resolve (Indx, Entry_Index_Type (Fam));
7811                   Apply_Range_Check (Indx, Entry_Index_Type (Fam));
7812                end;
7813             end if;
7814
7815          ----------------
7816          -- Elaborated --
7817          ----------------
7818
7819          --  Prefix of the Elaborated attribute is a subprogram name which
7820          --  must not be resolved, since this is definitely not a call. Note
7821          --  that it is a library unit, so it cannot be overloaded here.
7822
7823          when Attribute_Elaborated =>
7824             null;
7825
7826          -------------
7827          -- Enabled --
7828          -------------
7829
7830          --  Prefix of Enabled attribute is a check name, which must be treated
7831          --  specially and not touched by Resolve.
7832
7833          when Attribute_Enabled =>
7834             null;
7835
7836          --------------------
7837          -- Mechanism_Code --
7838          --------------------
7839
7840          --  Prefix of the Mechanism_Code attribute is a function name
7841          --  which must not be resolved. Should we check for overloaded ???
7842
7843          when Attribute_Mechanism_Code =>
7844             null;
7845
7846          ------------------
7847          -- Partition_ID --
7848          ------------------
7849
7850          --  Most processing is done in sem_dist, after determining the
7851          --  context type. Node is rewritten as a conversion to a runtime call.
7852
7853          when Attribute_Partition_ID =>
7854             Process_Partition_Id (N);
7855             return;
7856
7857          ------------------
7858          -- Pool_Address --
7859          ------------------
7860
7861          when Attribute_Pool_Address =>
7862             Resolve (P);
7863
7864          -----------
7865          -- Range --
7866          -----------
7867
7868          --  We replace the Range attribute node with a range expression
7869          --  whose bounds are the 'First and 'Last attributes applied to the
7870          --  same prefix. The reason that we do this transformation here
7871          --  instead of in the expander is that it simplifies other parts of
7872          --  the semantic analysis which assume that the Range has been
7873          --  replaced; thus it must be done even when in semantic-only mode
7874          --  (note that the RM specifically mentions this equivalence, we
7875          --  take care that the prefix is only evaluated once).
7876
7877          when Attribute_Range => Range_Attribute :
7878             declare
7879                LB   : Node_Id;
7880                HB   : Node_Id;
7881
7882                function Check_Discriminated_Prival
7883                  (N    : Node_Id)
7884                   return Node_Id;
7885                --  The range of a private component constrained by a
7886                --  discriminant is rewritten to make the discriminant
7887                --  explicit. This solves some complex visibility problems
7888                --  related to the use of privals.
7889
7890                --------------------------------
7891                -- Check_Discriminated_Prival --
7892                --------------------------------
7893
7894                function Check_Discriminated_Prival
7895                  (N    : Node_Id)
7896                   return Node_Id
7897                is
7898                begin
7899                   if Is_Entity_Name (N)
7900                     and then Ekind (Entity (N)) = E_In_Parameter
7901                     and then not Within_Init_Proc
7902                   then
7903                      return Make_Identifier (Sloc (N), Chars (Entity (N)));
7904                   else
7905                      return Duplicate_Subexpr (N);
7906                   end if;
7907                end Check_Discriminated_Prival;
7908
7909             --  Start of processing for Range_Attribute
7910
7911             begin
7912                if not Is_Entity_Name (P)
7913                  or else not Is_Type (Entity (P))
7914                then
7915                   Resolve (P);
7916                end if;
7917
7918                --  Check whether prefix is (renaming of) private component
7919                --  of protected type.
7920
7921                if Is_Entity_Name (P)
7922                  and then Comes_From_Source (N)
7923                  and then Is_Array_Type (Etype (P))
7924                  and then Number_Dimensions (Etype (P)) = 1
7925                  and then (Ekind (Scope (Entity (P))) = E_Protected_Type
7926                             or else
7927                            Ekind (Scope (Scope (Entity (P)))) =
7928                                                         E_Protected_Type)
7929                then
7930                   LB :=
7931                     Check_Discriminated_Prival
7932                       (Type_Low_Bound (Etype (First_Index (Etype (P)))));
7933
7934                   HB :=
7935                     Check_Discriminated_Prival
7936                       (Type_High_Bound (Etype (First_Index (Etype (P)))));
7937
7938                else
7939                   HB :=
7940                     Make_Attribute_Reference (Loc,
7941                       Prefix         => Duplicate_Subexpr (P),
7942                       Attribute_Name => Name_Last,
7943                       Expressions    => Expressions (N));
7944
7945                   LB :=
7946                     Make_Attribute_Reference (Loc,
7947                       Prefix         => P,
7948                       Attribute_Name => Name_First,
7949                       Expressions    => Expressions (N));
7950                end if;
7951
7952                --  If the original was marked as Must_Not_Freeze (see code
7953                --  in Sem_Ch3.Make_Index), then make sure the rewriting
7954                --  does not freeze either.
7955
7956                if Must_Not_Freeze (N) then
7957                   Set_Must_Not_Freeze (HB);
7958                   Set_Must_Not_Freeze (LB);
7959                   Set_Must_Not_Freeze (Prefix (HB));
7960                   Set_Must_Not_Freeze (Prefix (LB));
7961                end if;
7962
7963                if Raises_Constraint_Error (Prefix (N)) then
7964
7965                   --  Preserve Sloc of prefix in the new bounds, so that
7966                   --  the posted warning can be removed if we are within
7967                   --  unreachable code.
7968
7969                   Set_Sloc (LB, Sloc (Prefix (N)));
7970                   Set_Sloc (HB, Sloc (Prefix (N)));
7971                end if;
7972
7973                Rewrite (N, Make_Range (Loc, LB, HB));
7974                Analyze_And_Resolve (N, Typ);
7975
7976                --  Normally after resolving attribute nodes, Eval_Attribute
7977                --  is called to do any possible static evaluation of the node.
7978                --  However, here since the Range attribute has just been
7979                --  transformed into a range expression it is no longer an
7980                --  attribute node and therefore the call needs to be avoided
7981                --  and is accomplished by simply returning from the procedure.
7982
7983                return;
7984             end Range_Attribute;
7985
7986          -----------------
7987          -- UET_Address --
7988          -----------------
7989
7990          --  Prefix must not be resolved in this case, since it is not a
7991          --  real entity reference. No action of any kind is require!
7992
7993          when Attribute_UET_Address =>
7994             return;
7995
7996          ----------------------
7997          -- Unchecked_Access --
7998          ----------------------
7999
8000          --  Processing is shared with Access
8001
8002          -------------------------
8003          -- Unrestricted_Access --
8004          -------------------------
8005
8006          --  Processing is shared with Access
8007
8008          ---------
8009          -- Val --
8010          ---------
8011
8012          --  Apply range check. Note that we did not do this during the
8013          --  analysis phase, since we wanted Eval_Attribute to have a
8014          --  chance at finding an illegal out of range value.
8015
8016          when Attribute_Val =>
8017
8018             --  Note that we do our own Eval_Attribute call here rather than
8019             --  use the common one, because we need to do processing after
8020             --  the call, as per above comment.
8021
8022             Eval_Attribute (N);
8023
8024             --  Eval_Attribute may replace the node with a raise CE, or
8025             --  fold it to a constant. Obviously we only apply a scalar
8026             --  range check if this did not happen!
8027
8028             if Nkind (N) = N_Attribute_Reference
8029               and then Attribute_Name (N) = Name_Val
8030             then
8031                Apply_Scalar_Range_Check (First (Expressions (N)), Btyp);
8032             end if;
8033
8034             return;
8035
8036          -------------
8037          -- Version --
8038          -------------
8039
8040          --  Prefix of Version attribute can be a subprogram name which
8041          --  must not be resolved, since this is not a call.
8042
8043          when Attribute_Version =>
8044             null;
8045
8046          ----------------------
8047          -- Other Attributes --
8048          ----------------------
8049
8050          --  For other attributes, resolve prefix unless it is a type. If
8051          --  the attribute reference itself is a type name ('Base and 'Class)
8052          --  then this is only legal within a task or protected record.
8053
8054          when others =>
8055             if not Is_Entity_Name (P)
8056               or else not Is_Type (Entity (P))
8057             then
8058                Resolve (P);
8059             end if;
8060
8061             --  If the attribute reference itself is a type name ('Base,
8062             --  'Class) then this is only legal within a task or protected
8063             --  record. What is this all about ???
8064
8065             if Is_Entity_Name (N)
8066               and then Is_Type (Entity (N))
8067             then
8068                if Is_Concurrent_Type (Entity (N))
8069                  and then In_Open_Scopes (Entity (P))
8070                then
8071                   null;
8072                else
8073                   Error_Msg_N
8074                     ("invalid use of subtype name in expression or call", N);
8075                end if;
8076             end if;
8077
8078             --  For attributes whose argument may be a string, complete
8079             --  resolution of argument now. This avoids premature expansion
8080             --  (and the creation of transient scopes) before the attribute
8081             --  reference is resolved.
8082
8083             case Attr_Id is
8084                when Attribute_Value =>
8085                   Resolve (First (Expressions (N)), Standard_String);
8086
8087                when Attribute_Wide_Value =>
8088                   Resolve (First (Expressions (N)), Standard_Wide_String);
8089
8090                when Attribute_Wide_Wide_Value =>
8091                   Resolve (First (Expressions (N)), Standard_Wide_Wide_String);
8092
8093                when others => null;
8094             end case;
8095
8096             --  If the prefix of the attribute is a class-wide type then it
8097             --  will be expanded into a dispatching call to a predefined
8098             --  primitive. Therefore we must check for potential violation
8099             --  of such restriction.
8100
8101             if Is_Class_Wide_Type (Etype (P)) then
8102                Check_Restriction (No_Dispatching_Calls, N);
8103             end if;
8104       end case;
8105
8106       --  Normally the Freezing is done by Resolve but sometimes the Prefix
8107       --  is not resolved, in which case the freezing must be done now.
8108
8109       Freeze_Expression (P);
8110
8111       --  Finally perform static evaluation on the attribute reference
8112
8113       Eval_Attribute (N);
8114    end Resolve_Attribute;
8115
8116    --------------------------------
8117    -- Stream_Attribute_Available --
8118    --------------------------------
8119
8120    function Stream_Attribute_Available
8121      (Typ          : Entity_Id;
8122       Nam          : TSS_Name_Type;
8123       Partial_View : Node_Id := Empty) return Boolean
8124    is
8125       Etyp : Entity_Id := Typ;
8126
8127    --  Start of processing for Stream_Attribute_Available
8128
8129    begin
8130       --  We need some comments in this body ???
8131
8132       if Has_Stream_Attribute_Definition (Typ, Nam) then
8133          return True;
8134       end if;
8135
8136       if Is_Class_Wide_Type (Typ) then
8137          return not Is_Limited_Type (Typ)
8138            or else Stream_Attribute_Available (Etype (Typ), Nam);
8139       end if;
8140
8141       if Nam = TSS_Stream_Input
8142         and then Is_Abstract_Type (Typ)
8143         and then not Is_Class_Wide_Type (Typ)
8144       then
8145          return False;
8146       end if;
8147
8148       if not (Is_Limited_Type (Typ)
8149         or else (Present (Partial_View)
8150                    and then Is_Limited_Type (Partial_View)))
8151       then
8152          return True;
8153       end if;
8154
8155       --  In Ada 2005, Input can invoke Read, and Output can invoke Write
8156
8157       if Nam = TSS_Stream_Input
8158         and then Ada_Version >= Ada_05
8159         and then Stream_Attribute_Available (Etyp, TSS_Stream_Read)
8160       then
8161          return True;
8162
8163       elsif Nam = TSS_Stream_Output
8164         and then Ada_Version >= Ada_05
8165         and then Stream_Attribute_Available (Etyp, TSS_Stream_Write)
8166       then
8167          return True;
8168       end if;
8169
8170       --  Case of Read and Write: check for attribute definition clause that
8171       --  applies to an ancestor type.
8172
8173       while Etype (Etyp) /= Etyp loop
8174          Etyp := Etype (Etyp);
8175
8176          if Has_Stream_Attribute_Definition (Etyp, Nam) then
8177             return True;
8178          end if;
8179       end loop;
8180
8181       if Ada_Version < Ada_05 then
8182
8183          --  In Ada 95 mode, also consider a non-visible definition
8184
8185          declare
8186             Btyp : constant Entity_Id := Implementation_Base_Type (Typ);
8187          begin
8188             return Btyp /= Typ
8189               and then Stream_Attribute_Available
8190                          (Btyp, Nam, Partial_View => Typ);
8191          end;
8192       end if;
8193
8194       return False;
8195    end Stream_Attribute_Available;
8196
8197 end Sem_Attr;