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) 1992-2003, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- GNAT was originally developed  by the GNAT team at  New York University. --
  23 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  24 --                                                                          --
  25 ------------------------------------------------------------------------------
  26
  27 with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
  28
  29 with Atree;    use Atree;
  30 with Checks;   use Checks;
  31 with Einfo;    use Einfo;
  32 with Errout;   use Errout;
  33 with Eval_Fat;
  34 with Exp_Tss;  use Exp_Tss;
  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 Namet;    use Namet;
  41 with Nlists;   use Nlists;
  42 with Nmake;    use Nmake;
  43 with Opt;      use Opt;
  44 with Restrict; use Restrict;
  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 Snames;   use Snames;
  60 with Stand;
  61 with Stringt;  use Stringt;
  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 with Widechar; use Widechar;
  69
  70 package body Sem_Attr is
  71
  72    True_Value  : constant Uint := Uint_1;
  73    False_Value : constant Uint := Uint_0;
  74    --  Synonyms to be used when these constants are used as Boolean values
  75
  76    Bad_Attribute : exception;
  77    --  Exception raised if an error is detected during attribute processing,
  78    --  used so that we can abandon the processing so we don't run into
  79    --  trouble with cascaded errors.
  80
  81    --  The following array is the list of attributes defined in the Ada 83 RM
  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    -----------------------
 129    -- Local_Subprograms --
 130    -----------------------
 131
 132    procedure Eval_Attribute (N : Node_Id);
 133    --  Performs compile time evaluation of attributes where possible, leaving
 134    --  the Is_Static_Expression/Raises_Constraint_Error flags appropriately
 135    --  set, and replacing the node with a literal node if the value can be
 136    --  computed at compile time. All static attribute references are folded,
 137    --  as well as a number of cases of non-static attributes that can always
 138    --  be computed at compile time (e.g. floating-point model attributes that
 139    --  are applied to non-static subtypes). Of course in such cases, the
 140    --  Is_Static_Expression flag will not be set on the resulting literal.
 141    --  Note that the only required action of this procedure is to catch the
 142    --  static expression cases as described in the RM. Folding of other cases
 143    --  is done where convenient, but some additional non-static folding is in
 144    --  N_Expand_Attribute_Reference in cases where this is more convenient.
 145
 146    function Is_Anonymous_Tagged_Base
 147      (Anon : Entity_Id;
 148       Typ  : Entity_Id)
 149       return Boolean;
 150    --  For derived tagged types that constrain parent discriminants we build
 151    --  an anonymous unconstrained base type. We need to recognize the relation
 152    --  between the two when analyzing an access attribute for a constrained
 153    --  component, before the full declaration for Typ has been analyzed, and
 154    --  where therefore the prefix of the attribute does not match the enclosing
 155    --  scope.
 156
 157    -----------------------
 158    -- Analyze_Attribute --
 159    -----------------------
 160
 161    procedure Analyze_Attribute (N : Node_Id) is
 162       Loc     : constant Source_Ptr   := Sloc (N);
 163       Aname   : constant Name_Id      := Attribute_Name (N);
 164       P       : constant Node_Id      := Prefix (N);
 165       Exprs   : constant List_Id      := Expressions (N);
 166       Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname);
 167       E1      : Node_Id;
 168       E2      : Node_Id;
 169
 170       P_Type : Entity_Id;
 171       --  Type of prefix after analysis
 172
 173       P_Base_Type : Entity_Id;
 174       --  Base type of prefix after analysis
 175
 176       -----------------------
 177       -- Local Subprograms --
 178       -----------------------
 179
 180       procedure Analyze_Access_Attribute;
 181       --  Used for Access, Unchecked_Access, Unrestricted_Access attributes.
 182       --  Internally, Id distinguishes which of the three cases is involved.
 183
 184       procedure Check_Array_Or_Scalar_Type;
 185       --  Common procedure used by First, Last, Range attribute to check
 186       --  that the prefix is a constrained array or scalar type, or a name
 187       --  of an array object, and that an argument appears only if appropriate
 188       --  (i.e. only in the array case).
 189
 190       procedure Check_Array_Type;
 191       --  Common semantic checks for all array attributes. Checks that the
 192       --  prefix is a constrained array type or the name of an array object.
 193       --  The error message for non-arrays is specialized appropriately.
 194
 195       procedure Check_Asm_Attribute;
 196       --  Common semantic checks for Asm_Input and Asm_Output attributes
 197
 198       procedure Check_Component;
 199       --  Common processing for Bit_Position, First_Bit, Last_Bit, and
 200       --  Position. Checks prefix is an appropriate selected component.
 201
 202       procedure Check_Decimal_Fixed_Point_Type;
 203       --  Check that prefix of attribute N is a decimal fixed-point type
 204
 205       procedure Check_Dereference;
 206       --  If the prefix of attribute is an object of an access type, then
 207       --  introduce an explicit deference, and adjust P_Type accordingly.
 208
 209       procedure Check_Discrete_Type;
 210       --  Verify that prefix of attribute N is a discrete type
 211
 212       procedure Check_E0;
 213       --  Check that no attribute arguments are present
 214
 215       procedure Check_Either_E0_Or_E1;
 216       --  Check that there are zero or one attribute arguments present
 217
 218       procedure Check_E1;
 219       --  Check that exactly one attribute argument is present
 220
 221       procedure Check_E2;
 222       --  Check that two attribute arguments are present
 223
 224       procedure Check_Enum_Image;
 225       --  If the prefix type is an enumeration type, set all its literals
 226       --  as referenced, since the image function could possibly end up
 227       --  referencing any of the literals indirectly.
 228
 229       procedure Check_Fixed_Point_Type;
 230       --  Verify that prefix of attribute N is a fixed type
 231
 232       procedure Check_Fixed_Point_Type_0;
 233       --  Verify that prefix of attribute N is a fixed type and that
 234       --  no attribute expressions are present
 235
 236       procedure Check_Floating_Point_Type;
 237       --  Verify that prefix of attribute N is a float type
 238
 239       procedure Check_Floating_Point_Type_0;
 240       --  Verify that prefix of attribute N is a float type and that
 241       --  no attribute expressions are present
 242
 243       procedure Check_Floating_Point_Type_1;
 244       --  Verify that prefix of attribute N is a float type and that
 245       --  exactly one attribute expression is present
 246
 247       procedure Check_Floating_Point_Type_2;
 248       --  Verify that prefix of attribute N is a float type and that
 249       --  two attribute expressions are present
 250
 251       procedure Legal_Formal_Attribute;
 252       --  Common processing for attributes Definite, and Has_Discriminants
 253
 254       procedure Check_Integer_Type;
 255       --  Verify that prefix of attribute N is an integer type
 256
 257       procedure Check_Library_Unit;
 258       --  Verify that prefix of attribute N is a library unit
 259
 260       procedure Check_Not_Incomplete_Type;
 261       --  Check that P (the prefix of the attribute) is not an incomplete
 262       --  type or a private type for which no full view has been given.
 263
 264       procedure Check_Object_Reference (P : Node_Id);
 265       --  Check that P (the prefix of the attribute) is an object reference
 266
 267       procedure Check_Program_Unit;
 268       --  Verify that prefix of attribute N is a program unit
 269
 270       procedure Check_Real_Type;
 271       --  Verify that prefix of attribute N is fixed or float type
 272
 273       procedure Check_Scalar_Type;
 274       --  Verify that prefix of attribute N is a scalar type
 275
 276       procedure Check_Standard_Prefix;
 277       --  Verify that prefix of attribute N is package Standard
 278
 279       procedure Check_Stream_Attribute (Nam : TSS_Name_Type);
 280       --  Validity checking for stream attribute. Nam is the TSS name of the
 281       --  corresponding possible defined attribute function (e.g. for the
 282       --  Read attribute, Nam will be TSS_Stream_Read).
 283
 284       procedure Check_Task_Prefix;
 285       --  Verify that prefix of attribute N is a task or task type
 286
 287       procedure Check_Type;
 288       --  Verify that the prefix of attribute N is a type
 289
 290       procedure Check_Unit_Name (Nod : Node_Id);
 291       --  Check that Nod is of the form of a library unit name, i.e that
 292       --  it is an identifier, or a selected component whose prefix is
 293       --  itself of the form of a library unit name. Note that this is
 294       --  quite different from Check_Program_Unit, since it only checks
 295       --  the syntactic form of the name, not the semantic identity. This
 296       --  is because it is used with attributes (Elab_Body, Elab_Spec, and
 297       --  UET_Address) which can refer to non-visible unit.
 298
 299       procedure Error_Attr (Msg : String; Error_Node : Node_Id);
 300       pragma No_Return (Error_Attr);
 301       procedure Error_Attr;
 302       pragma No_Return (Error_Attr);
 303       --  Posts error using Error_Msg_N at given node, sets type of attribute
 304       --  node to Any_Type, and then raises Bad_Attribute to avoid any further
 305       --  semantic processing. The message typically contains a % insertion
 306       --  character which is replaced by the attribute name. The call with
 307       --  no arguments is used when the caller has already generated the
 308       --  required error messages.
 309
 310       procedure Standard_Attribute (Val : Int);
 311       --  Used to process attributes whose prefix is package Standard which
 312       --  yield values of type Universal_Integer. The attribute reference
 313       --  node is rewritten with an integer literal of the given value.
 314
 315       procedure Unexpected_Argument (En : Node_Id);
 316       --  Signal unexpected attribute argument (En is the argument)
 317
 318       procedure Validate_Non_Static_Attribute_Function_Call;
 319       --  Called when processing an attribute that is a function call to a
 320       --  non-static function, i.e. an attribute function that either takes
 321       --  non-scalar arguments or returns a non-scalar result. Verifies that
 322       --  such a call does not appear in a preelaborable context.
 323
 324       ------------------------------
 325       -- Analyze_Access_Attribute --
 326       ------------------------------
 327
 328       procedure Analyze_Access_Attribute is
 329          Acc_Type : Entity_Id;
 330
 331          Scop : Entity_Id;
 332          Typ  : Entity_Id;
 333
 334          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id;
 335          --  Build an access-to-object type whose designated type is DT,
 336          --  and whose Ekind is appropriate to the attribute type. The
 337          --  type that is constructed is returned as the result.
 338
 339          procedure Build_Access_Subprogram_Type (P : Node_Id);
 340          --  Build an access to subprogram whose designated type is
 341          --  the type of the prefix. If prefix is overloaded, so it the
 342          --  node itself. The result is stored in Acc_Type.
 343
 344          ------------------------------
 345          -- Build_Access_Object_Type --
 346          ------------------------------
 347
 348          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id is
 349             Typ : Entity_Id;
 350
 351          begin
 352             if Aname = Name_Unrestricted_Access then
 353                Typ :=
 354                  New_Internal_Entity
 355                    (E_Allocator_Type, Current_Scope, Loc, 'A');
 356             else
 357                Typ :=
 358                  New_Internal_Entity
 359                    (E_Access_Attribute_Type, Current_Scope, Loc, 'A');
 360             end if;
 361
 362             Set_Etype                     (Typ, Typ);
 363             Init_Size_Align               (Typ);
 364             Set_Is_Itype                  (Typ);
 365             Set_Associated_Node_For_Itype (Typ, N);
 366             Set_Directly_Designated_Type  (Typ, DT);
 367             return Typ;
 368          end Build_Access_Object_Type;
 369
 370          ----------------------------------
 371          -- Build_Access_Subprogram_Type --
 372          ----------------------------------
 373
 374          procedure Build_Access_Subprogram_Type (P : Node_Id) is
 375             Index    : Interp_Index;
 376             It       : Interp;
 377
 378             function Get_Kind (E : Entity_Id) return Entity_Kind;
 379             --  Distinguish between access to regular and protected
 380             --  subprograms.
 381
 382             --------------
 383             -- Get_Kind --
 384             --------------
 385
 386             function Get_Kind (E : Entity_Id) return Entity_Kind is
 387             begin
 388                if Convention (E) = Convention_Protected then
 389                   return E_Access_Protected_Subprogram_Type;
 390                else
 391                   return E_Access_Subprogram_Type;
 392                end if;
 393             end Get_Kind;
 394
 395          --  Start of processing for Build_Access_Subprogram_Type
 396
 397          begin
 398             if not Is_Overloaded (P) then
 399                Acc_Type :=
 400                  New_Internal_Entity
 401                    (Get_Kind (Entity (P)), Current_Scope, Loc, 'A');
 402                Set_Etype (Acc_Type, Acc_Type);
 403                Set_Directly_Designated_Type (Acc_Type, Entity (P));
 404                Set_Etype (N, Acc_Type);
 405
 406             else
 407                Get_First_Interp (P, Index, It);
 408                Set_Etype (N, Any_Type);
 409
 410                while Present (It.Nam) loop
 411
 412                   if not Is_Intrinsic_Subprogram (It.Nam) then
 413                      Acc_Type :=
 414                        New_Internal_Entity
 415                          (Get_Kind (It.Nam), Current_Scope, Loc, 'A');
 416                      Set_Etype (Acc_Type, Acc_Type);
 417                      Set_Directly_Designated_Type (Acc_Type, It.Nam);
 418                      Add_One_Interp (N, Acc_Type, Acc_Type);
 419                   end if;
 420
 421                   Get_Next_Interp (Index, It);
 422                end loop;
 423
 424                if Etype (N) = Any_Type then
 425                   Error_Attr ("prefix of % attribute cannot be intrinsic", P);
 426                end if;
 427             end if;
 428          end Build_Access_Subprogram_Type;
 429
 430       --  Start of processing for Analyze_Access_Attribute
 431
 432       begin
 433          Check_E0;
 434
 435          if Nkind (P) = N_Character_Literal then
 436             Error_Attr
 437               ("prefix of % attribute cannot be enumeration literal", P);
 438          end if;
 439
 440          --  In the case of an access to subprogram, use the name of the
 441          --  subprogram itself as the designated type. Type-checking in
 442          --  this case compares the signatures of the designated types.
 443
 444          if Is_Entity_Name (P)
 445            and then Is_Overloadable (Entity (P))
 446          then
 447             if not Is_Library_Level_Entity (Entity (P)) then
 448                Check_Restriction (No_Implicit_Dynamic_Code, P);
 449             end if;
 450
 451             Build_Access_Subprogram_Type (P);
 452
 453             --  For unrestricted access, kill current values, since this
 454             --  attribute allows a reference to a local subprogram that
 455             --  could modify local variables to be passed out of scope
 456
 457             if Aname = Name_Unrestricted_Access then
 458                Kill_Current_Values;
 459             end if;
 460
 461             return;
 462
 463          --  Component is an operation of a protected type.
 464
 465          elsif Nkind (P) = N_Selected_Component
 466            and then Is_Overloadable (Entity (Selector_Name (P)))
 467          then
 468             if Ekind (Entity (Selector_Name (P))) = E_Entry then
 469                Error_Attr ("prefix of % attribute must be subprogram", P);
 470             end if;
 471
 472             Build_Access_Subprogram_Type (Selector_Name (P));
 473             return;
 474          end if;
 475
 476          --  Deal with incorrect reference to a type, but note that some
 477          --  accesses are allowed (references to the current type instance).
 478
 479          if Is_Entity_Name (P) then
 480             Scop := Current_Scope;
 481             Typ := Entity (P);
 482
 483             if Is_Type (Typ) then
 484
 485                --  OK if we are within the scope of a limited type
 486                --  let's mark the component as having per object constraint
 487
 488                if Is_Anonymous_Tagged_Base (Scop, Typ) then
 489                   Typ := Scop;
 490                   Set_Entity (P, Typ);
 491                   Set_Etype  (P, Typ);
 492                end if;
 493
 494                if Typ = Scop then
 495                   declare
 496                      Q : Node_Id := Parent (N);
 497
 498                   begin
 499                      while Present (Q)
 500                        and then Nkind (Q) /= N_Component_Declaration
 501                      loop
 502                         Q := Parent (Q);
 503                      end loop;
 504                      if Present (Q) then
 505                         Set_Has_Per_Object_Constraint (
 506                           Defining_Identifier (Q), True);
 507                      end if;
 508                   end;
 509
 510                   if Nkind (P) = N_Expanded_Name then
 511                      Error_Msg_N
 512                        ("current instance prefix must be a direct name", P);
 513                   end if;
 514
 515                   --  If a current instance attribute appears within a
 516                   --  a component constraint it must appear alone; other
 517                   --  contexts (default expressions, within a task body)
 518                   --  are not subject to this restriction.
 519
 520                   if not In_Default_Expression
 521                     and then not Has_Completion (Scop)
 522                     and then
 523                       Nkind (Parent (N)) /= N_Discriminant_Association
 524                     and then
 525                       Nkind (Parent (N)) /= N_Index_Or_Discriminant_Constraint
 526                   then
 527                      Error_Msg_N
 528                        ("current instance attribute must appear alone", N);
 529                   end if;
 530
 531                --  OK if we are in initialization procedure for the type
 532                --  in question, in which case the reference to the type
 533                --  is rewritten as a reference to the current object.
 534
 535                elsif Ekind (Scop) = E_Procedure
 536                  and then Is_Init_Proc (Scop)
 537                  and then Etype (First_Formal (Scop)) = Typ
 538                then
 539                   Rewrite (N,
 540                     Make_Attribute_Reference (Loc,
 541                       Prefix         => Make_Identifier (Loc, Name_uInit),
 542                       Attribute_Name => Name_Unrestricted_Access));
 543                   Analyze (N);
 544                   return;
 545
 546                --  OK if a task type, this test needs sharpening up ???
 547
 548                elsif Is_Task_Type (Typ) then
 549                   null;
 550
 551                --  Otherwise we have an error case
 552
 553                else
 554                   Error_Attr ("% attribute cannot be applied to type", P);
 555                   return;
 556                end if;
 557             end if;
 558          end if;
 559
 560          --  If we fall through, we have a normal access to object case.
 561          --  Unrestricted_Access is legal wherever an allocator would be
 562          --  legal, so its Etype is set to E_Allocator. The expected type
 563          --  of the other attributes is a general access type, and therefore
 564          --  we label them with E_Access_Attribute_Type.
 565
 566          if not Is_Overloaded (P) then
 567             Acc_Type := Build_Access_Object_Type (P_Type);
 568             Set_Etype (N, Acc_Type);
 569          else
 570             declare
 571                Index : Interp_Index;
 572                It    : Interp;
 573
 574             begin
 575                Set_Etype (N, Any_Type);
 576                Get_First_Interp (P, Index, It);
 577
 578                while Present (It.Typ) loop
 579                   Acc_Type := Build_Access_Object_Type (It.Typ);
 580                   Add_One_Interp (N, Acc_Type, Acc_Type);
 581                   Get_Next_Interp (Index, It);
 582                end loop;
 583             end;
 584          end if;
 585
 586          --  If we have an access to an object, and the attribute comes
 587          --  from source, then set the object as potentially source modified.
 588          --  We do this because the resulting access pointer can be used to
 589          --  modify the variable, and we might not detect this, leading to
 590          --  some junk warnings.
 591
 592          if Is_Entity_Name (P) then
 593             Set_Never_Set_In_Source (Entity (P), False);
 594          end if;
 595
 596          --  Check for aliased view unless unrestricted case. We allow
 597          --  a nonaliased prefix when within an instance because the
 598          --  prefix may have been a tagged formal object, which is
 599          --  defined to be aliased even when the actual might not be
 600          --  (other instance cases will have been caught in the generic).
 601
 602          if Aname /= Name_Unrestricted_Access
 603            and then not Is_Aliased_View (P)
 604            and then not In_Instance
 605          then
 606             Error_Attr ("prefix of % attribute must be aliased", P);
 607          end if;
 608       end Analyze_Access_Attribute;
 609
 610       --------------------------------
 611       -- Check_Array_Or_Scalar_Type --
 612       --------------------------------
 613
 614       procedure Check_Array_Or_Scalar_Type is
 615          Index : Entity_Id;
 616
 617          D : Int;
 618          --  Dimension number for array attributes.
 619
 620       begin
 621          --  Case of string literal or string literal subtype. These cases
 622          --  cannot arise from legal Ada code, but the expander is allowed
 623          --  to generate them. They require special handling because string
 624          --  literal subtypes do not have standard bounds (the whole idea
 625          --  of these subtypes is to avoid having to generate the bounds)
 626
 627          if Ekind (P_Type) = E_String_Literal_Subtype then
 628             Set_Etype (N, Etype (First_Index (P_Base_Type)));
 629             return;
 630
 631          --  Scalar types
 632
 633          elsif Is_Scalar_Type (P_Type) then
 634             Check_Type;
 635
 636             if Present (E1) then
 637                Error_Attr ("invalid argument in % attribute", E1);
 638             else
 639                Set_Etype (N, P_Base_Type);
 640                return;
 641             end if;
 642
 643          --  The following is a special test to allow 'First to apply to
 644          --  private scalar types if the attribute comes from generated
 645          --  code. This occurs in the case of Normalize_Scalars code.
 646
 647          elsif Is_Private_Type (P_Type)
 648            and then Present (Full_View (P_Type))
 649            and then Is_Scalar_Type (Full_View (P_Type))
 650            and then not Comes_From_Source (N)
 651          then
 652             Set_Etype (N, Implementation_Base_Type (P_Type));
 653
 654          --  Array types other than string literal subtypes handled above
 655
 656          else
 657             Check_Array_Type;
 658
 659             --  We know prefix is an array type, or the name of an array
 660             --  object, and that the expression, if present, is static
 661             --  and within the range of the dimensions of the type.
 662
 663             if Is_Array_Type (P_Type) then
 664                Index := First_Index (P_Base_Type);
 665
 666             else pragma Assert (Is_Access_Type (P_Type));
 667                Index := First_Index (Base_Type (Designated_Type (P_Type)));
 668             end if;
 669
 670             if No (E1) then
 671
 672                --  First dimension assumed
 673
 674                Set_Etype (N, Base_Type (Etype (Index)));
 675
 676             else
 677                D := UI_To_Int (Intval (E1));
 678
 679                for J in 1 .. D - 1 loop
 680                   Next_Index (Index);
 681                end loop;
 682
 683                Set_Etype (N, Base_Type (Etype (Index)));
 684                Set_Etype (E1, Standard_Integer);
 685             end if;
 686          end if;
 687       end Check_Array_Or_Scalar_Type;
 688
 689       ----------------------
 690       -- Check_Array_Type --
 691       ----------------------
 692
 693       procedure Check_Array_Type is
 694          D : Int;
 695          --  Dimension number for array attributes.
 696
 697       begin
 698          --  If the type is a string literal type, then this must be generated
 699          --  internally, and no further check is required on its legality.
 700
 701          if Ekind (P_Type) = E_String_Literal_Subtype then
 702             return;
 703
 704          --  If the type is a composite, it is an illegal aggregate, no point
 705          --  in going on.
 706
 707          elsif P_Type = Any_Composite then
 708             raise Bad_Attribute;
 709          end if;
 710
 711          --  Normal case of array type or subtype
 712
 713          Check_Either_E0_Or_E1;
 714
 715          if Is_Array_Type (P_Type) then
 716             if not Is_Constrained (P_Type)
 717               and then Is_Entity_Name (P)
 718               and then Is_Type (Entity (P))
 719             then
 720                --  Note: we do not call Error_Attr here, since we prefer to
 721                --  continue, using the relevant index type of the array,
 722                --  even though it is unconstrained. This gives better error
 723                --  recovery behavior.
 724
 725                Error_Msg_Name_1 := Aname;
 726                Error_Msg_N
 727                  ("prefix for % attribute must be constrained array", P);
 728             end if;
 729
 730             D := Number_Dimensions (P_Type);
 731
 732          elsif Is_Access_Type (P_Type)
 733            and then Is_Array_Type (Designated_Type (P_Type))
 734          then
 735             if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
 736                Error_Attr ("prefix of % attribute cannot be access type", P);
 737             end if;
 738
 739             D := Number_Dimensions (Designated_Type (P_Type));
 740
 741             --  If there is an implicit dereference, then we must freeze
 742             --  the designated type of the access type, since the type of
 743             --  the referenced array is this type (see AI95-00106).
 744
 745             Freeze_Before (N, Designated_Type (P_Type));
 746
 747          else
 748             if Is_Private_Type (P_Type) then
 749                Error_Attr
 750                  ("prefix for % attribute may not be private type", P);
 751
 752             elsif Attr_Id = Attribute_First
 753                     or else
 754                   Attr_Id = Attribute_Last
 755             then
 756                Error_Attr ("invalid prefix for % attribute", P);
 757
 758             else
 759                Error_Attr ("prefix for % attribute must be array", P);
 760             end if;
 761          end if;
 762
 763          if Present (E1) then
 764             Resolve (E1, Any_Integer);
 765             Set_Etype (E1, Standard_Integer);
 766
 767             if not Is_Static_Expression (E1)
 768               or else Raises_Constraint_Error (E1)
 769             then
 770                Flag_Non_Static_Expr
 771                  ("expression for dimension must be static!", E1);
 772                Error_Attr;
 773
 774             elsif  UI_To_Int (Expr_Value (E1)) > D
 775               or else UI_To_Int (Expr_Value (E1)) < 1
 776             then
 777                Error_Attr ("invalid dimension number for array type", E1);
 778             end if;
 779          end if;
 780       end Check_Array_Type;
 781
 782       -------------------------
 783       -- Check_Asm_Attribute --
 784       -------------------------
 785
 786       procedure Check_Asm_Attribute is
 787       begin
 788          Check_Type;
 789          Check_E2;
 790
 791          --  Check first argument is static string expression
 792
 793          Analyze_And_Resolve (E1, Standard_String);
 794
 795          if Etype (E1) = Any_Type then
 796             return;
 797
 798          elsif not Is_OK_Static_Expression (E1) then
 799             Flag_Non_Static_Expr
 800               ("constraint argument must be static string expression!", E1);
 801             Error_Attr;
 802          end if;
 803
 804          --  Check second argument is right type
 805
 806          Analyze_And_Resolve (E2, Entity (P));
 807
 808          --  Note: that is all we need to do, we don't need to check
 809          --  that it appears in a correct context. The Ada type system
 810          --  will do that for us.
 811
 812       end Check_Asm_Attribute;
 813
 814       ---------------------
 815       -- Check_Component --
 816       ---------------------
 817
 818       procedure Check_Component is
 819       begin
 820          Check_E0;
 821
 822          if Nkind (P) /= N_Selected_Component
 823            or else
 824              (Ekind (Entity (Selector_Name (P))) /= E_Component
 825                and then
 826               Ekind (Entity (Selector_Name (P))) /= E_Discriminant)
 827          then
 828             Error_Attr
 829               ("prefix for % attribute must be selected component", P);
 830          end if;
 831       end Check_Component;
 832
 833       ------------------------------------
 834       -- Check_Decimal_Fixed_Point_Type --
 835       ------------------------------------
 836
 837       procedure Check_Decimal_Fixed_Point_Type is
 838       begin
 839          Check_Type;
 840
 841          if not Is_Decimal_Fixed_Point_Type (P_Type) then
 842             Error_Attr
 843               ("prefix of % attribute must be decimal type", P);
 844          end if;
 845       end Check_Decimal_Fixed_Point_Type;
 846
 847       -----------------------
 848       -- Check_Dereference --
 849       -----------------------
 850
 851       procedure Check_Dereference is
 852       begin
 853          if Is_Object_Reference (P)
 854            and then Is_Access_Type (P_Type)
 855          then
 856             Rewrite (P,
 857               Make_Explicit_Dereference (Sloc (P),
 858                 Prefix => Relocate_Node (P)));
 859
 860             Analyze_And_Resolve (P);
 861             P_Type := Etype (P);
 862
 863             if P_Type = Any_Type then
 864                raise Bad_Attribute;
 865             end if;
 866
 867             P_Base_Type := Base_Type (P_Type);
 868          end if;
 869       end Check_Dereference;
 870
 871       -------------------------
 872       -- Check_Discrete_Type --
 873       -------------------------
 874
 875       procedure Check_Discrete_Type is
 876       begin
 877          Check_Type;
 878
 879          if not Is_Discrete_Type (P_Type) then
 880             Error_Attr ("prefix of % attribute must be discrete type", P);
 881          end if;
 882       end Check_Discrete_Type;
 883
 884       --------------
 885       -- Check_E0 --
 886       --------------
 887
 888       procedure Check_E0 is
 889       begin
 890          if Present (E1) then
 891             Unexpected_Argument (E1);
 892          end if;
 893       end Check_E0;
 894
 895       --------------
 896       -- Check_E1 --
 897       --------------
 898
 899       procedure Check_E1 is
 900       begin
 901          Check_Either_E0_Or_E1;
 902
 903          if No (E1) then
 904
 905             --  Special-case attributes that are functions and that appear as
 906             --  the prefix of another attribute. Error is posted on parent.
 907
 908             if Nkind (Parent (N)) = N_Attribute_Reference
 909               and then (Attribute_Name (Parent (N)) = Name_Address
 910                           or else
 911                         Attribute_Name (Parent (N)) = Name_Code_Address
 912                           or else
 913                         Attribute_Name (Parent (N)) = Name_Access)
 914             then
 915                Error_Msg_Name_1 := Attribute_Name (Parent (N));
 916                Error_Msg_N ("illegal prefix for % attribute", Parent (N));
 917                Set_Etype (Parent (N), Any_Type);
 918                Set_Entity (Parent (N), Any_Type);
 919                raise Bad_Attribute;
 920
 921             else
 922                Error_Attr ("missing argument for % attribute", N);
 923             end if;
 924          end if;
 925       end Check_E1;
 926
 927       --------------
 928       -- Check_E2 --
 929       --------------
 930
 931       procedure Check_E2 is
 932       begin
 933          if No (E1) then
 934             Error_Attr ("missing arguments for % attribute (2 required)", N);
 935          elsif No (E2) then
 936             Error_Attr ("missing argument for % attribute (2 required)", N);
 937          end if;
 938       end Check_E2;
 939
 940       ---------------------------
 941       -- Check_Either_E0_Or_E1 --
 942       ---------------------------
 943
 944       procedure Check_Either_E0_Or_E1 is
 945       begin
 946          if Present (E2) then
 947             Unexpected_Argument (E2);
 948          end if;
 949       end Check_Either_E0_Or_E1;
 950
 951       ----------------------
 952       -- Check_Enum_Image --
 953       ----------------------
 954
 955       procedure Check_Enum_Image is
 956          Lit : Entity_Id;
 957
 958       begin
 959          if Is_Enumeration_Type (P_Base_Type) then
 960             Lit := First_Literal (P_Base_Type);
 961             while Present (Lit) loop
 962                Set_Referenced (Lit);
 963                Next_Literal (Lit);
 964             end loop;
 965          end if;
 966       end Check_Enum_Image;
 967
 968       ----------------------------
 969       -- Check_Fixed_Point_Type --
 970       ----------------------------
 971
 972       procedure Check_Fixed_Point_Type is
 973       begin
 974          Check_Type;
 975
 976          if not Is_Fixed_Point_Type (P_Type) then
 977             Error_Attr ("prefix of % attribute must be fixed point type", P);
 978          end if;
 979       end Check_Fixed_Point_Type;
 980
 981       ------------------------------
 982       -- Check_Fixed_Point_Type_0 --
 983       ------------------------------
 984
 985       procedure Check_Fixed_Point_Type_0 is
 986       begin
 987          Check_Fixed_Point_Type;
 988          Check_E0;
 989       end Check_Fixed_Point_Type_0;
 990
 991       -------------------------------
 992       -- Check_Floating_Point_Type --
 993       -------------------------------
 994
 995       procedure Check_Floating_Point_Type is
 996       begin
 997          Check_Type;
 998
 999          if not Is_Floating_Point_Type (P_Type) then
1000             Error_Attr ("prefix of % attribute must be float type", P);
1001          end if;
1002       end Check_Floating_Point_Type;
1003
1004       ---------------------------------
1005       -- Check_Floating_Point_Type_0 --
1006       ---------------------------------
1007
1008       procedure Check_Floating_Point_Type_0 is
1009       begin
1010          Check_Floating_Point_Type;
1011          Check_E0;
1012       end Check_Floating_Point_Type_0;
1013
1014       ---------------------------------
1015       -- Check_Floating_Point_Type_1 --
1016       ---------------------------------
1017
1018       procedure Check_Floating_Point_Type_1 is
1019       begin
1020          Check_Floating_Point_Type;
1021          Check_E1;
1022       end Check_Floating_Point_Type_1;
1023
1024       ---------------------------------
1025       -- Check_Floating_Point_Type_2 --
1026       ---------------------------------
1027
1028       procedure Check_Floating_Point_Type_2 is
1029       begin
1030          Check_Floating_Point_Type;
1031          Check_E2;
1032       end Check_Floating_Point_Type_2;
1033
1034       ------------------------
1035       -- Check_Integer_Type --
1036       ------------------------
1037
1038       procedure Check_Integer_Type is
1039       begin
1040          Check_Type;
1041
1042          if not Is_Integer_Type (P_Type) then
1043             Error_Attr ("prefix of % attribute must be integer type", P);
1044          end if;
1045       end Check_Integer_Type;
1046
1047       ------------------------
1048       -- Check_Library_Unit --
1049       ------------------------
1050
1051       procedure Check_Library_Unit is
1052       begin
1053          if not Is_Compilation_Unit (Entity (P)) then
1054             Error_Attr ("prefix of % attribute must be library unit", P);
1055          end if;
1056       end Check_Library_Unit;
1057
1058       -------------------------------
1059       -- Check_Not_Incomplete_Type --
1060       -------------------------------
1061
1062       procedure Check_Not_Incomplete_Type is
1063       begin
1064          if not Is_Entity_Name (P)
1065            or else not Is_Type (Entity (P))
1066            or else In_Default_Expression
1067          then
1068             return;
1069
1070          else
1071             Check_Fully_Declared (P_Type, P);
1072          end if;
1073       end Check_Not_Incomplete_Type;
1074
1075       ----------------------------
1076       -- Check_Object_Reference --
1077       ----------------------------
1078
1079       procedure Check_Object_Reference (P : Node_Id) is
1080          Rtyp : Entity_Id;
1081
1082       begin
1083          --  If we need an object, and we have a prefix that is the name of
1084          --  a function entity, convert it into a function call.
1085
1086          if Is_Entity_Name (P)
1087            and then Ekind (Entity (P)) = E_Function
1088          then
1089             Rtyp := Etype (Entity (P));
1090
1091             Rewrite (P,
1092               Make_Function_Call (Sloc (P),
1093                 Name => Relocate_Node (P)));
1094
1095             Analyze_And_Resolve (P, Rtyp);
1096
1097          --  Otherwise we must have an object reference
1098
1099          elsif not Is_Object_Reference (P) then
1100             Error_Attr ("prefix of % attribute must be object", P);
1101          end if;
1102       end Check_Object_Reference;
1103
1104       ------------------------
1105       -- Check_Program_Unit --
1106       ------------------------
1107
1108       procedure Check_Program_Unit is
1109       begin
1110          if Is_Entity_Name (P) then
1111             declare
1112                K : constant Entity_Kind := Ekind (Entity (P));
1113                T : constant Entity_Id   := Etype (Entity (P));
1114
1115             begin
1116                if K in Subprogram_Kind
1117                  or else K in Task_Kind
1118                  or else K in Protected_Kind
1119                  or else K = E_Package
1120                  or else K in Generic_Unit_Kind
1121                  or else (K = E_Variable
1122                             and then
1123                               (Is_Task_Type (T)
1124                                  or else
1125                                Is_Protected_Type (T)))
1126                then
1127                   return;
1128                end if;
1129             end;
1130          end if;
1131
1132          Error_Attr ("prefix of % attribute must be program unit", P);
1133       end Check_Program_Unit;
1134
1135       ---------------------
1136       -- Check_Real_Type --
1137       ---------------------
1138
1139       procedure Check_Real_Type is
1140       begin
1141          Check_Type;
1142
1143          if not Is_Real_Type (P_Type) then
1144             Error_Attr ("prefix of % attribute must be real type", P);
1145          end if;
1146       end Check_Real_Type;
1147
1148       -----------------------
1149       -- Check_Scalar_Type --
1150       -----------------------
1151
1152       procedure Check_Scalar_Type is
1153       begin
1154          Check_Type;
1155
1156          if not Is_Scalar_Type (P_Type) then
1157             Error_Attr ("prefix of % attribute must be scalar type", P);
1158          end if;
1159       end Check_Scalar_Type;
1160
1161       ---------------------------
1162       -- Check_Standard_Prefix --
1163       ---------------------------
1164
1165       procedure Check_Standard_Prefix is
1166       begin
1167          Check_E0;
1168
1169          if Nkind (P) /= N_Identifier
1170            or else Chars (P) /= Name_Standard
1171          then
1172             Error_Attr ("only allowed prefix for % attribute is Standard", P);
1173          end if;
1174
1175       end Check_Standard_Prefix;
1176
1177       ----------------------------
1178       -- Check_Stream_Attribute --
1179       ----------------------------
1180
1181       procedure Check_Stream_Attribute (Nam : TSS_Name_Type) is
1182          Etyp : Entity_Id;
1183          Btyp : Entity_Id;
1184
1185       begin
1186          Validate_Non_Static_Attribute_Function_Call;
1187
1188          --  With the exception of 'Input, Stream attributes are procedures,
1189          --  and can only appear at the position of procedure calls. We check
1190          --  for this here, before they are rewritten, to give a more precise
1191          --  diagnostic.
1192
1193          if Nam = TSS_Stream_Input then
1194             null;
1195
1196          elsif Is_List_Member (N)
1197            and then Nkind (Parent (N)) /= N_Procedure_Call_Statement
1198            and then Nkind (Parent (N)) /= N_Aggregate
1199          then
1200             null;
1201
1202          else
1203             Error_Attr
1204               ("invalid context for attribute%, which is a procedure", N);
1205          end if;
1206
1207          Check_Type;
1208          Btyp := Implementation_Base_Type (P_Type);
1209
1210          --  Stream attributes not allowed on limited types unless the
1211          --  special OK_For_Stream flag is set.
1212
1213          if Is_Limited_Type (P_Type)
1214            and then Comes_From_Source (N)
1215            and then not Present (TSS (Btyp, Nam))
1216            and then No (Get_Rep_Pragma (Btyp, Name_Stream_Convert))
1217          then
1218             Error_Msg_Name_1 := Aname;
1219             Error_Msg_NE
1220               ("limited type& has no% attribute", P, Btyp);
1221             Explain_Limited_Type (P_Type, P);
1222          end if;
1223
1224          --  Check for violation of restriction No_Stream_Attributes
1225
1226          if Is_RTE (P_Type, RE_Exception_Id)
1227               or else
1228             Is_RTE (P_Type, RE_Exception_Occurrence)
1229          then
1230             Check_Restriction (No_Exception_Registration, P);
1231          end if;
1232
1233          --  Here we must check that the first argument is an access type
1234          --  that is compatible with Ada.Streams.Root_Stream_Type'Class.
1235
1236          Analyze_And_Resolve (E1);
1237          Etyp := Etype (E1);
1238
1239          --  Note: the double call to Root_Type here is needed because the
1240          --  root type of a class-wide type is the corresponding type (e.g.
1241          --  X for X'Class, and we really want to go to the root.
1242
1243          if not Is_Access_Type (Etyp)
1244            or else Root_Type (Root_Type (Designated_Type (Etyp))) /=
1245                      RTE (RE_Root_Stream_Type)
1246          then
1247             Error_Attr
1248               ("expected access to Ada.Streams.Root_Stream_Type''Class", E1);
1249          end if;
1250
1251          --  Check that the second argument is of the right type if there is
1252          --  one (the Input attribute has only one argument so this is skipped)
1253
1254          if Present (E2) then
1255             Analyze (E2);
1256
1257             if Nam = TSS_Stream_Read
1258               and then not Is_OK_Variable_For_Out_Formal (E2)
1259             then
1260                Error_Attr
1261                  ("second argument of % attribute must be a variable", E2);
1262             end if;
1263
1264             Resolve (E2, P_Type);
1265          end if;
1266       end Check_Stream_Attribute;
1267
1268       -----------------------
1269       -- Check_Task_Prefix --
1270       -----------------------
1271
1272       procedure Check_Task_Prefix is
1273       begin
1274          Analyze (P);
1275
1276          if Is_Task_Type (Etype (P))
1277            or else (Is_Access_Type (Etype (P))
1278               and then Is_Task_Type (Designated_Type (Etype (P))))
1279          then
1280             Resolve (P);
1281          else
1282             Error_Attr ("prefix of % attribute must be a task", P);
1283          end if;
1284       end Check_Task_Prefix;
1285
1286       ----------------
1287       -- Check_Type --
1288       ----------------
1289
1290       --  The possibilities are an entity name denoting a type, or an
1291       --  attribute reference that denotes a type (Base or Class). If
1292       --  the type is incomplete, replace it with its full view.
1293
1294       procedure Check_Type is
1295       begin
1296          if not Is_Entity_Name (P)
1297            or else not Is_Type (Entity (P))
1298          then
1299             Error_Attr ("prefix of % attribute must be a type", P);
1300
1301          elsif Ekind (Entity (P)) = E_Incomplete_Type
1302             and then Present (Full_View (Entity (P)))
1303          then
1304             P_Type := Full_View (Entity (P));
1305             Set_Entity (P, P_Type);
1306          end if;
1307       end Check_Type;
1308
1309       ---------------------
1310       -- Check_Unit_Name --
1311       ---------------------
1312
1313       procedure Check_Unit_Name (Nod : Node_Id) is
1314       begin
1315          if Nkind (Nod) = N_Identifier then
1316             return;
1317
1318          elsif Nkind (Nod) = N_Selected_Component then
1319             Check_Unit_Name (Prefix (Nod));
1320
1321             if Nkind (Selector_Name (Nod)) = N_Identifier then
1322                return;
1323             end if;
1324          end if;
1325
1326          Error_Attr ("argument for % attribute must be unit name", P);
1327       end Check_Unit_Name;
1328
1329       ----------------
1330       -- Error_Attr --
1331       ----------------
1332
1333       procedure Error_Attr is
1334       begin
1335          Set_Etype (N, Any_Type);
1336          Set_Entity (N, Any_Type);
1337          raise Bad_Attribute;
1338       end Error_Attr;
1339
1340       procedure Error_Attr (Msg : String; Error_Node : Node_Id) is
1341       begin
1342          Error_Msg_Name_1 := Aname;
1343          Error_Msg_N (Msg, Error_Node);
1344          Error_Attr;
1345       end Error_Attr;
1346
1347       ----------------------------
1348       -- Legal_Formal_Attribute --
1349       ----------------------------
1350
1351       procedure Legal_Formal_Attribute is
1352       begin
1353          Check_E0;
1354
1355          if not Is_Entity_Name (P)
1356            or else not Is_Type (Entity (P))
1357          then
1358             Error_Attr ("prefix of % attribute must be generic type", N);
1359
1360          elsif Is_Generic_Actual_Type (Entity (P))
1361            or In_Instance
1362          then
1363             null;
1364
1365          elsif Is_Generic_Type (Entity (P)) then
1366             if not Is_Indefinite_Subtype (Entity (P)) then
1367                Error_Attr
1368                  ("prefix of % attribute must be indefinite generic type", N);
1369             end if;
1370
1371          else
1372             Error_Attr
1373               ("prefix of % attribute must be indefinite generic type", N);
1374          end if;
1375
1376          Set_Etype (N, Standard_Boolean);
1377       end Legal_Formal_Attribute;
1378
1379       ------------------------
1380       -- Standard_Attribute --
1381       ------------------------
1382
1383       procedure Standard_Attribute (Val : Int) is
1384       begin
1385          Check_Standard_Prefix;
1386
1387          --  First a special check (more like a kludge really). For GNAT5
1388          --  on Windows, the alignments in GCC are severely mixed up. In
1389          --  particular, we have a situation where the maximum alignment
1390          --  that GCC thinks is possible is greater than the guaranteed
1391          --  alignment at run-time. That causes many problems. As a partial
1392          --  cure for this situation, we force a value of 4 for the maximum
1393          --  alignment attribute on this target. This still does not solve
1394          --  all problems, but it helps.
1395
1396          --  A further (even more horrible) dimension to this kludge is now
1397          --  installed. There are two uses for Maximum_Alignment, one is to
1398          --  determine the maximum guaranteed alignment, that's the one we
1399          --  want the kludge to yield as 4. The other use is to maximally
1400          --  align objects, we can't use 4 here, since for example, long
1401          --  long integer has an alignment of 8, so we will get errors.
1402
1403          --  It is of course impossible to determine which use the programmer
1404          --  has in mind, but an approximation for now is to disconnect the
1405          --  kludge if the attribute appears in an alignment clause.
1406
1407          --  To be removed if GCC ever gets its act together here ???
1408
1409          Alignment_Kludge : declare
1410             P : Node_Id;
1411
1412             function On_X86 return Boolean;
1413             --  Determine if target is x86 (ia32), return True if so
1414
1415             ------------
1416             -- On_X86 --
1417             ------------
1418
1419             function On_X86 return Boolean is
1420                T : String := Sdefault.Target_Name.all;
1421
1422             begin
1423                --  There is no clean way to check this. That's not surprising,
1424                --  the front end should not be doing this kind of test ???. The
1425                --  way we do it is test for either "86" or "pentium" being in
1426                --  the string for the target name.
1427
1428                for J in T'First .. T'Last - 1 loop
1429                   if T (J .. J + 1) = "86"
1430                     or else (J <= T'Last - 6
1431                                and then T (J .. J + 6) = "pentium")
1432                   then
1433                      return True;
1434                   end if;
1435                end loop;
1436
1437                return False;
1438             end On_X86;
1439
1440          begin
1441             if Aname = Name_Maximum_Alignment and then On_X86 then
1442                P := Parent (N);
1443
1444                while Nkind (P) in N_Subexpr loop
1445                   P := Parent (P);
1446                end loop;
1447
1448                if Nkind (P) /= N_Attribute_Definition_Clause
1449                  or else Chars (P) /= Name_Alignment
1450                then
1451                   Rewrite (N, Make_Integer_Literal (Loc, 4));
1452                   Analyze (N);
1453                   return;
1454                end if;
1455             end if;
1456          end Alignment_Kludge;
1457
1458          --  Normally we get the value from gcc ???
1459
1460          Rewrite (N, Make_Integer_Literal (Loc, Val));
1461          Analyze (N);
1462       end Standard_Attribute;
1463
1464       -------------------------
1465       -- Unexpected Argument --
1466       -------------------------
1467
1468       procedure Unexpected_Argument (En : Node_Id) is
1469       begin
1470          Error_Attr ("unexpected argument for % attribute", En);
1471       end Unexpected_Argument;
1472
1473       -------------------------------------------------
1474       -- Validate_Non_Static_Attribute_Function_Call --
1475       -------------------------------------------------
1476
1477       --  This function should be moved to Sem_Dist ???
1478
1479       procedure Validate_Non_Static_Attribute_Function_Call is
1480       begin
1481          if In_Preelaborated_Unit
1482            and then not In_Subprogram_Or_Concurrent_Unit
1483          then
1484             Flag_Non_Static_Expr
1485               ("non-static function call in preelaborated unit!", N);
1486          end if;
1487       end Validate_Non_Static_Attribute_Function_Call;
1488
1489    -----------------------------------------------
1490    -- Start of Processing for Analyze_Attribute --
1491    -----------------------------------------------
1492
1493    begin
1494       --  Immediate return if unrecognized attribute (already diagnosed
1495       --  by parser, so there is nothing more that we need to do)
1496
1497       if not Is_Attribute_Name (Aname) then
1498          raise Bad_Attribute;
1499       end if;
1500
1501       --  Deal with Ada 83 and Features issues
1502
1503       if Comes_From_Source (N) then
1504          if not Attribute_83 (Attr_Id) then
1505             if Ada_83 and then Comes_From_Source (N) then
1506                Error_Msg_Name_1 := Aname;
1507                Error_Msg_N ("(Ada 83) attribute% is not standard?", N);
1508             end if;
1509
1510             if Attribute_Impl_Def (Attr_Id) then
1511                Check_Restriction (No_Implementation_Attributes, N);
1512             end if;
1513          end if;
1514       end if;
1515
1516       --   Remote access to subprogram type access attribute reference needs
1517       --   unanalyzed copy for tree transformation. The analyzed copy is used
1518       --   for its semantic information (whether prefix is a remote subprogram
1519       --   name), the unanalyzed copy is used to construct new subtree rooted
1520       --   with N_aggregate which represents a fat pointer aggregate.
1521
1522       if Aname = Name_Access then
1523          Discard_Node (Copy_Separate_Tree (N));
1524       end if;
1525
1526       --  Analyze prefix and exit if error in analysis. If the prefix is an
1527       --  incomplete type, use full view if available. A special case is
1528       --  that we never analyze the prefix of an Elab_Body or Elab_Spec
1529       --  or UET_Address attribute.
1530
1531       if Aname /= Name_Elab_Body
1532            and then
1533          Aname /= Name_Elab_Spec
1534            and then
1535          Aname /= Name_UET_Address
1536       then
1537          Analyze (P);
1538          P_Type := Etype (P);
1539
1540          if Is_Entity_Name (P)
1541            and then Present (Entity (P))
1542            and then Is_Type (Entity (P))
1543            and then Ekind (Entity (P)) = E_Incomplete_Type
1544          then
1545             P_Type := Get_Full_View (P_Type);
1546             Set_Entity (P, P_Type);
1547             Set_Etype  (P, P_Type);
1548          end if;
1549
1550          if P_Type = Any_Type then
1551             raise Bad_Attribute;
1552          end if;
1553
1554          P_Base_Type := Base_Type (P_Type);
1555       end if;
1556
1557       --  Analyze expressions that may be present, exiting if an error occurs
1558
1559       if No (Exprs) then
1560          E1 := Empty;
1561          E2 := Empty;
1562
1563       else
1564          E1 := First (Exprs);
1565          Analyze (E1);
1566
1567          --  Check for missing or bad expression (result of previous error)
1568
1569          if No (E1) or else Etype (E1) = Any_Type then
1570             raise Bad_Attribute;
1571          end if;
1572
1573          E2 := Next (E1);
1574
1575          if Present (E2) then
1576             Analyze (E2);
1577
1578             if Etype (E2) = Any_Type then
1579                raise Bad_Attribute;
1580             end if;
1581
1582             if Present (Next (E2)) then
1583                Unexpected_Argument (Next (E2));
1584             end if;
1585          end if;
1586       end if;
1587
1588       if Is_Overloaded (P)
1589         and then Aname /= Name_Access
1590         and then Aname /= Name_Address
1591         and then Aname /= Name_Code_Address
1592         and then Aname /= Name_Count
1593         and then Aname /= Name_Unchecked_Access
1594       then
1595          Error_Attr ("ambiguous prefix for % attribute", P);
1596       end if;
1597
1598       --  Remaining processing depends on attribute
1599
1600       case Attr_Id is
1601
1602       ------------------
1603       -- Abort_Signal --
1604       ------------------
1605
1606       when Attribute_Abort_Signal =>
1607          Check_Standard_Prefix;
1608          Rewrite (N,
1609            New_Reference_To (Stand.Abort_Signal, Loc));
1610          Analyze (N);
1611
1612       ------------
1613       -- Access --
1614       ------------
1615
1616       when Attribute_Access =>
1617          Analyze_Access_Attribute;
1618
1619       -------------
1620       -- Address --
1621       -------------
1622
1623       when Attribute_Address =>
1624          Check_E0;
1625
1626          --  Check for some junk cases, where we have to allow the address
1627          --  attribute but it does not make much sense, so at least for now
1628          --  just replace with Null_Address.
1629
1630          --  We also do this if the prefix is a reference to the AST_Entry
1631          --  attribute. If expansion is active, the attribute will be
1632          --  replaced by a function call, and address will work fine and
1633          --  get the proper value, but if expansion is not active, then
1634          --  the check here allows proper semantic analysis of the reference.
1635
1636          --  An Address attribute created by expansion is legal even when it
1637          --  applies to other entity-denoting expressions.
1638
1639          if Is_Entity_Name (P) then
1640             declare
1641                Ent : constant Entity_Id := Entity (P);
1642
1643             begin
1644                if Is_Subprogram (Ent) then
1645                   if not Is_Library_Level_Entity (Ent) then
1646                      Check_Restriction (No_Implicit_Dynamic_Code, P);
1647                   end if;
1648
1649                   Set_Address_Taken (Ent);
1650
1651                elsif Is_Object (Ent)
1652                  or else Ekind (Ent) = E_Label
1653                then
1654                   Set_Address_Taken (Ent);
1655
1656                --  If we have an address of an object, and the attribute
1657                --  comes from source, then set the object as potentially
1658                --  source modified. We do this because the resulting address
1659                --  can potentially be used to modify the variable and we
1660                --  might not detect this, leading to some junk warnings.
1661
1662                   Set_Never_Set_In_Source (Ent, False);
1663
1664                elsif (Is_Concurrent_Type (Etype (Ent))
1665                        and then Etype (Ent) = Base_Type (Ent))
1666                  or else Ekind (Ent) = E_Package
1667                  or else Is_Generic_Unit (Ent)
1668                then
1669                   Rewrite (N,
1670                     New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1671
1672                else
1673                   Error_Attr ("invalid prefix for % attribute", P);
1674                end if;
1675             end;
1676
1677          elsif Nkind (P) = N_Attribute_Reference
1678            and then Attribute_Name (P) = Name_AST_Entry
1679          then
1680             Rewrite (N,
1681               New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1682
1683          elsif Is_Object_Reference (P) then
1684             null;
1685
1686          elsif Nkind (P) = N_Selected_Component
1687            and then Is_Subprogram (Entity (Selector_Name (P)))
1688          then
1689             null;
1690
1691          --  What exactly are we allowing here ??? and is this properly
1692          --  documented in the sinfo documentation for this node ???
1693
1694          elsif not Comes_From_Source (N) then
1695             null;
1696
1697          else
1698             Error_Attr ("invalid prefix for % attribute", P);
1699          end if;
1700
1701          Set_Etype (N, RTE (RE_Address));
1702
1703       ------------------
1704       -- Address_Size --
1705       ------------------
1706
1707       when Attribute_Address_Size =>
1708          Standard_Attribute (System_Address_Size);
1709
1710       --------------
1711       -- Adjacent --
1712       --------------
1713
1714       when Attribute_Adjacent =>
1715          Check_Floating_Point_Type_2;
1716          Set_Etype (N, P_Base_Type);
1717          Resolve (E1, P_Base_Type);
1718          Resolve (E2, P_Base_Type);
1719
1720       ---------
1721       -- Aft --
1722       ---------
1723
1724       when Attribute_Aft =>
1725          Check_Fixed_Point_Type_0;
1726          Set_Etype (N, Universal_Integer);
1727
1728       ---------------
1729       -- Alignment --
1730       ---------------
1731
1732       when Attribute_Alignment =>
1733
1734          --  Don't we need more checking here, cf Size ???
1735
1736          Check_E0;
1737          Check_Not_Incomplete_Type;
1738          Set_Etype (N, Universal_Integer);
1739
1740       ---------------
1741       -- Asm_Input --
1742       ---------------
1743
1744       when Attribute_Asm_Input =>
1745          Check_Asm_Attribute;
1746          Set_Etype (N, RTE (RE_Asm_Input_Operand));
1747
1748       ----------------
1749       -- Asm_Output --
1750       ----------------
1751
1752       when Attribute_Asm_Output =>
1753          Check_Asm_Attribute;
1754
1755          if Etype (E2) = Any_Type then
1756             return;
1757
1758          elsif Aname = Name_Asm_Output then
1759             if not Is_Variable (E2) then
1760                Error_Attr
1761                  ("second argument for Asm_Output is not variable", E2);
1762             end if;
1763          end if;
1764
1765          Note_Possible_Modification (E2);
1766          Set_Etype (N, RTE (RE_Asm_Output_Operand));
1767
1768       ---------------
1769       -- AST_Entry --
1770       ---------------
1771
1772       when Attribute_AST_Entry => AST_Entry : declare
1773          Ent  : Entity_Id;
1774          Pref : Node_Id;
1775          Ptyp : Entity_Id;
1776
1777          Indexed : Boolean;
1778          --  Indicates if entry family index is present. Note the coding
1779          --  here handles the entry family case, but in fact it cannot be
1780          --  executed currently, because pragma AST_Entry does not permit
1781          --  the specification of an entry family.
1782
1783          procedure Bad_AST_Entry;
1784          --  Signal a bad AST_Entry pragma
1785
1786          function OK_Entry (E : Entity_Id) return Boolean;
1787          --  Checks that E is of an appropriate entity kind for an entry
1788          --  (i.e. E_Entry if Index is False, or E_Entry_Family if Index
1789          --  is set True for the entry family case). In the True case,
1790          --  makes sure that Is_AST_Entry is set on the entry.
1791
1792          procedure Bad_AST_Entry is
1793          begin
1794             Error_Attr ("prefix for % attribute must be task entry", P);
1795          end Bad_AST_Entry;
1796
1797          function OK_Entry (E : Entity_Id) return Boolean is
1798             Result : Boolean;
1799
1800          begin
1801             if Indexed then
1802                Result := (Ekind (E) = E_Entry_Family);
1803             else
1804                Result := (Ekind (E) = E_Entry);
1805             end if;
1806
1807             if Result then
1808                if not Is_AST_Entry (E) then
1809                   Error_Msg_Name_2 := Aname;
1810                   Error_Attr
1811                     ("% attribute requires previous % pragma", P);
1812                end if;
1813             end if;
1814
1815             return Result;
1816          end OK_Entry;
1817
1818       --  Start of processing for AST_Entry
1819
1820       begin
1821          Check_VMS (N);
1822          Check_E0;
1823
1824          --  Deal with entry family case
1825
1826          if Nkind (P) = N_Indexed_Component then
1827             Pref := Prefix (P);
1828             Indexed := True;
1829          else
1830             Pref := P;
1831             Indexed := False;
1832          end if;
1833
1834          Ptyp := Etype (Pref);
1835
1836          if Ptyp = Any_Type or else Error_Posted (Pref) then
1837             return;
1838          end if;
1839
1840          --  If the prefix is a selected component whose prefix is of an
1841          --  access type, then introduce an explicit dereference.
1842
1843          if Nkind (Pref) = N_Selected_Component
1844            and then Is_Access_Type (Ptyp)
1845          then
1846             Rewrite (Pref,
1847               Make_Explicit_Dereference (Sloc (Pref),
1848                 Relocate_Node (Pref)));
1849             Analyze_And_Resolve (Pref, Designated_Type (Ptyp));
1850          end if;
1851
1852          --  Prefix can be of the form a.b, where a is a task object
1853          --  and b is one of the entries of the corresponding task type.
1854
1855          if Nkind (Pref) = N_Selected_Component
1856            and then OK_Entry (Entity (Selector_Name (Pref)))
1857            and then Is_Object_Reference (Prefix (Pref))
1858            and then Is_Task_Type (Etype (Prefix (Pref)))
1859          then
1860             null;
1861
1862          --  Otherwise the prefix must be an entry of a containing task,
1863          --  or of a variable of the enclosing task type.
1864
1865          else
1866             if Nkind (Pref) = N_Identifier
1867               or else Nkind (Pref) = N_Expanded_Name
1868             then
1869                Ent := Entity (Pref);
1870
1871                if not OK_Entry (Ent)
1872                  or else not In_Open_Scopes (Scope (Ent))
1873                then
1874                   Bad_AST_Entry;
1875                end if;
1876
1877             else
1878                Bad_AST_Entry;
1879             end if;
1880          end if;
1881
1882          Set_Etype (N, RTE (RE_AST_Handler));
1883       end AST_Entry;
1884
1885       ----------
1886       -- Base --
1887       ----------
1888
1889       --  Note: when the base attribute appears in the context of a subtype
1890       --  mark, the analysis is done by Sem_Ch8.Find_Type, rather than by
1891       --  the following circuit.
1892
1893       when Attribute_Base => Base : declare
1894          Typ : Entity_Id;
1895
1896       begin
1897          Check_Either_E0_Or_E1;
1898          Find_Type (P);
1899          Typ := Entity (P);
1900
1901          if Ada_95
1902            and then not Is_Scalar_Type (Typ)
1903            and then not Is_Generic_Type (Typ)
1904          then
1905             Error_Msg_N ("prefix of Base attribute must be scalar type", N);
1906
1907          elsif Sloc (Typ) = Standard_Location
1908            and then Base_Type (Typ) = Typ
1909            and then Warn_On_Redundant_Constructs
1910          then
1911             Error_Msg_NE
1912               ("?redudant attribute, & is its own base type", N, Typ);
1913          end if;
1914
1915          Set_Etype (N, Base_Type (Entity (P)));
1916
1917          --  If we have an expression present, then really this is a conversion
1918          --  and the tree must be reformed. Note that this is one of the cases
1919          --  in which we do a replace rather than a rewrite, because the
1920          --  original tree is junk.
1921
1922          if Present (E1) then
1923             Replace (N,
1924               Make_Type_Conversion (Loc,
1925                 Subtype_Mark =>
1926                   Make_Attribute_Reference (Loc,
1927                     Prefix => Prefix (N),
1928                     Attribute_Name => Name_Base),
1929                 Expression => Relocate_Node (E1)));
1930
1931             --  E1 may be overloaded, and its interpretations preserved.
1932
1933             Save_Interps (E1, Expression (N));
1934             Analyze (N);
1935
1936          --  For other cases, set the proper type as the entity of the
1937          --  attribute reference, and then rewrite the node to be an
1938          --  occurrence of the referenced base type. This way, no one
1939          --  else in the compiler has to worry about the base attribute.
1940
1941          else
1942             Set_Entity (N, Base_Type (Entity (P)));
1943             Rewrite (N,
1944               New_Reference_To (Entity (N), Loc));
1945             Analyze (N);
1946          end if;
1947       end Base;
1948
1949       ---------
1950       -- Bit --
1951       ---------
1952
1953       when Attribute_Bit => Bit :
1954       begin
1955          Check_E0;
1956
1957          if not Is_Object_Reference (P) then
1958             Error_Attr ("prefix for % attribute must be object", P);
1959
1960          --  What about the access object cases ???
1961
1962          else
1963             null;
1964          end if;
1965
1966          Set_Etype (N, Universal_Integer);
1967       end Bit;
1968
1969       ---------------
1970       -- Bit_Order --
1971       ---------------
1972
1973       when Attribute_Bit_Order => Bit_Order :
1974       begin
1975          Check_E0;
1976          Check_Type;
1977
1978          if not Is_Record_Type (P_Type) then
1979             Error_Attr ("prefix of % attribute must be record type", P);
1980          end if;
1981
1982          if Bytes_Big_Endian xor Reverse_Bit_Order (P_Type) then
1983             Rewrite (N,
1984               New_Occurrence_Of (RTE (RE_High_Order_First), Loc));
1985          else
1986             Rewrite (N,
1987               New_Occurrence_Of (RTE (RE_Low_Order_First), Loc));
1988          end if;
1989
1990          Set_Etype (N, RTE (RE_Bit_Order));
1991          Resolve (N);
1992
1993          --  Reset incorrect indication of staticness
1994
1995          Set_Is_Static_Expression (N, False);
1996       end Bit_Order;
1997
1998       ------------------
1999       -- Bit_Position --
2000       ------------------
2001
2002       --  Note: in generated code, we can have a Bit_Position attribute
2003       --  applied to a (naked) record component (i.e. the prefix is an
2004       --  identifier that references an E_Component or E_Discriminant
2005       --  entity directly, and this is interpreted as expected by Gigi.
2006       --  The following code will not tolerate such usage, but when the
2007       --  expander creates this special case, it marks it as analyzed
2008       --  immediately and sets an appropriate type.
2009
2010       when Attribute_Bit_Position =>
2011
2012          if Comes_From_Source (N) then
2013             Check_Component;
2014          end if;
2015
2016          Set_Etype (N, Universal_Integer);
2017
2018       ------------------
2019       -- Body_Version --
2020       ------------------
2021
2022       when Attribute_Body_Version =>
2023          Check_E0;
2024          Check_Program_Unit;
2025          Set_Etype (N, RTE (RE_Version_String));
2026
2027       --------------
2028       -- Callable --
2029       --------------
2030
2031       when Attribute_Callable =>
2032          Check_E0;
2033          Set_Etype (N, Standard_Boolean);
2034          Check_Task_Prefix;
2035
2036       ------------
2037       -- Caller --
2038       ------------
2039
2040       when Attribute_Caller => Caller : declare
2041          Ent        : Entity_Id;
2042          S          : Entity_Id;
2043
2044       begin
2045          Check_E0;
2046
2047          if Nkind (P) = N_Identifier
2048            or else Nkind (P) = N_Expanded_Name
2049          then
2050             Ent := Entity (P);
2051
2052             if not Is_Entry (Ent) then
2053                Error_Attr ("invalid entry name", N);
2054             end if;
2055
2056          else
2057             Error_Attr ("invalid entry name", N);
2058             return;
2059          end if;
2060
2061          for J in reverse 0 .. Scope_Stack.Last loop
2062             S := Scope_Stack.Table (J).Entity;
2063
2064             if S = Scope (Ent) then
2065                Error_Attr ("Caller must appear in matching accept or body", N);
2066             elsif S = Ent then
2067                exit;
2068             end if;
2069          end loop;
2070
2071          Set_Etype (N, RTE (RO_AT_Task_ID));
2072       end Caller;
2073
2074       -------------
2075       -- Ceiling --
2076       -------------
2077
2078       when Attribute_Ceiling =>
2079          Check_Floating_Point_Type_1;
2080          Set_Etype (N, P_Base_Type);
2081          Resolve (E1, P_Base_Type);
2082
2083       -----------
2084       -- Class --
2085       -----------
2086
2087       when Attribute_Class => Class : declare
2088       begin
2089          Check_Restriction (No_Dispatch, N);
2090          Check_Either_E0_Or_E1;
2091
2092          --  If we have an expression present, then really this is a conversion
2093          --  and the tree must be reformed into a proper conversion. This is a
2094          --  Replace rather than a Rewrite, because the original tree is junk.
2095          --  If expression is overloaded, propagate interpretations to new one.
2096
2097          if Present (E1) then
2098             Replace (N,
2099               Make_Type_Conversion (Loc,
2100                 Subtype_Mark =>
2101                   Make_Attribute_Reference (Loc,
2102                     Prefix => Prefix (N),
2103                     Attribute_Name => Name_Class),
2104                 Expression => Relocate_Node (E1)));
2105
2106             Save_Interps (E1, Expression (N));
2107             Analyze (N);
2108
2109          --  Otherwise we just need to find the proper type
2110
2111          else
2112             Find_Type (N);
2113          end if;
2114
2115       end Class;
2116
2117       ------------------
2118       -- Code_Address --
2119       ------------------
2120
2121       when Attribute_Code_Address =>
2122          Check_E0;
2123
2124          if Nkind (P) = N_Attribute_Reference
2125            and then (Attribute_Name (P) = Name_Elab_Body
2126                        or else
2127                      Attribute_Name (P) = Name_Elab_Spec)
2128          then
2129             null;
2130
2131          elsif not Is_Entity_Name (P)
2132            or else (Ekind (Entity (P)) /= E_Function
2133                       and then
2134                     Ekind (Entity (P)) /= E_Procedure)
2135          then
2136             Error_Attr ("invalid prefix for % attribute", P);
2137             Set_Address_Taken (Entity (P));
2138          end if;
2139
2140          Set_Etype (N, RTE (RE_Address));
2141
2142       --------------------
2143       -- Component_Size --
2144       --------------------
2145
2146       when Attribute_Component_Size =>
2147          Check_E0;
2148          Set_Etype (N, Universal_Integer);
2149
2150          --  Note: unlike other array attributes, unconstrained arrays are OK
2151
2152          if Is_Array_Type (P_Type) and then not Is_Constrained (P_Type) then
2153             null;
2154          else
2155             Check_Array_Type;
2156          end if;
2157
2158       -------------
2159       -- Compose --
2160       -------------
2161
2162       when Attribute_Compose =>
2163          Check_Floating_Point_Type_2;
2164          Set_Etype (N, P_Base_Type);
2165          Resolve (E1, P_Base_Type);
2166          Resolve (E2, Any_Integer);
2167
2168       -----------------
2169       -- Constrained --
2170       -----------------
2171
2172       when Attribute_Constrained =>
2173          Check_E0;
2174          Set_Etype (N, Standard_Boolean);
2175
2176          --  Case from RM J.4(2) of constrained applied to private type
2177
2178          if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
2179
2180             --  If we are within an instance, the attribute must be legal
2181             --  because it was valid in the generic unit.
2182
2183             if In_Instance then
2184                return;
2185
2186             --  For sure OK if we have a real private type itself, but must
2187             --  be completed, cannot apply Constrained to incomplete type.
2188
2189             elsif Is_Private_Type (Entity (P)) then
2190
2191                --  Note: this is one of the Annex J features that does not
2192                --  generate a warning from -gnatwj, since in fact it seems
2193                --  very useful, and is used in the GNAT runtime.
2194
2195                Check_Not_Incomplete_Type;
2196                return;
2197             end if;
2198
2199          --  Normal (non-obsolescent case) of application to object of
2200          --  a discriminated type.
2201
2202          else
2203             Check_Object_Reference (P);
2204
2205             --  If N does not come from source, then we allow the
2206             --  the attribute prefix to be of a private type whose
2207             --  full type has discriminants. This occurs in cases
2208             --  involving expanded calls to stream attributes.
2209
2210             if not Comes_From_Source (N) then
2211                P_Type := Underlying_Type (P_Type);
2212             end if;
2213
2214             --  Must have discriminants or be an access type designating
2215             --  a type with discriminants. If it is a classwide type is
2216             --  has unknown discriminants.
2217
2218             if Has_Discriminants (P_Type)
2219                or else Has_Unknown_Discriminants (P_Type)
2220                or else
2221                  (Is_Access_Type (P_Type)
2222                    and then Has_Discriminants (Designated_Type (P_Type)))
2223             then
2224                return;
2225
2226             --  Also allow an object of a generic type if extensions allowed
2227             --  and allow this for any type at all.
2228
2229             elsif (Is_Generic_Type (P_Type)
2230                      or else Is_Generic_Actual_Type (P_Type))
2231               and then Extensions_Allowed
2232             then
2233                return;
2234             end if;
2235          end if;
2236
2237          --  Fall through if bad prefix
2238
2239          Error_Attr
2240            ("prefix of % attribute must be object of discriminated type", P);
2241
2242       ---------------
2243       -- Copy_Sign --
2244       ---------------
2245
2246       when Attribute_Copy_Sign =>
2247          Check_Floating_Point_Type_2;
2248          Set_Etype (N, P_Base_Type);
2249          Resolve (E1, P_Base_Type);
2250          Resolve (E2, P_Base_Type);
2251
2252       -----------
2253       -- Count --
2254       -----------
2255
2256       when Attribute_Count => Count :
2257       declare
2258          Ent : Entity_Id;
2259          S   : Entity_Id;
2260          Tsk : Entity_Id;
2261
2262       begin
2263          Check_E0;
2264
2265          if Nkind (P) = N_Identifier
2266            or else Nkind (P) = N_Expanded_Name
2267          then
2268             Ent := Entity (P);
2269
2270             if Ekind (Ent) /= E_Entry then
2271                Error_Attr ("invalid entry name", N);
2272             end if;
2273
2274          elsif Nkind (P) = N_Indexed_Component then
2275             if not Is_Entity_Name (Prefix (P))
2276               or else  No (Entity (Prefix (P)))
2277               or else Ekind (Entity (Prefix (P))) /= E_Entry_Family
2278             then
2279                if Nkind (Prefix (P)) = N_Selected_Component
2280                  and then Present (Entity (Selector_Name (Prefix (P))))
2281                  and then Ekind (Entity (Selector_Name (Prefix (P)))) =
2282                                                              E_Entry_Family
2283                then
2284                   Error_Attr
2285                     ("attribute % must apply to entry of current task", P);
2286
2287                else
2288                   Error_Attr ("invalid entry family name", P);
2289                end if;
2290                return;
2291
2292             else
2293                Ent := Entity (Prefix (P));
2294             end if;
2295
2296          elsif Nkind (P) = N_Selected_Component
2297            and then Present (Entity (Selector_Name (P)))
2298            and then Ekind (Entity (Selector_Name (P))) = E_Entry
2299          then
2300             Error_Attr
2301               ("attribute % must apply to entry of current task", P);
2302
2303          else
2304             Error_Attr ("invalid entry name", N);
2305             return;
2306          end if;
2307
2308          for J in reverse 0 .. Scope_Stack.Last loop
2309             S := Scope_Stack.Table (J).Entity;
2310
2311             if S = Scope (Ent) then
2312                if Nkind (P) = N_Expanded_Name then
2313                   Tsk := Entity (Prefix (P));
2314
2315                   --  The prefix denotes either the task type, or else a
2316                   --  single task whose task type is being analyzed.
2317
2318                   if (Is_Type (Tsk)
2319                       and then Tsk = S)
2320
2321                     or else (not Is_Type (Tsk)
2322                       and then Etype (Tsk) = S
2323                       and then not (Comes_From_Source (S)))
2324                   then
2325                      null;
2326                   else
2327                      Error_Attr
2328                        ("Attribute % must apply to entry of current task", N);
2329                   end if;
2330                end if;
2331
2332                exit;
2333
2334             elsif Ekind (Scope (Ent)) in Task_Kind
2335               and then Ekind (S) /= E_Loop
2336               and then Ekind (S) /= E_Block
2337               and then Ekind (S) /= E_Entry
2338               and then Ekind (S) /= E_Entry_Family
2339             then
2340                Error_Attr ("Attribute % cannot appear in inner unit", N);
2341
2342             elsif Ekind (Scope (Ent)) = E_Protected_Type
2343               and then not Has_Completion (Scope (Ent))
2344             then
2345                Error_Attr ("attribute % can only be used inside body", N);
2346             end if;
2347          end loop;
2348
2349          if Is_Overloaded (P) then
2350             declare
2351                Index : Interp_Index;
2352                It    : Interp;
2353
2354             begin
2355                Get_First_Interp (P, Index, It);
2356
2357                while Present (It.Nam) loop
2358                   if It.Nam = Ent then
2359                      null;
2360
2361                   else
2362                      Error_Attr ("ambiguous entry name", N);
2363                   end if;
2364
2365                   Get_Next_Interp (Index, It);
2366                end loop;
2367             end;
2368          end if;
2369
2370          Set_Etype (N, Universal_Integer);
2371       end Count;
2372
2373       -----------------------
2374       -- Default_Bit_Order --
2375       -----------------------
2376
2377       when Attribute_Default_Bit_Order => Default_Bit_Order :
2378       begin
2379          Check_Standard_Prefix;
2380          Check_E0;
2381
2382          if Bytes_Big_Endian then
2383             Rewrite (N,
2384               Make_Integer_Literal (Loc, False_Value));
2385          else
2386             Rewrite (N,
2387               Make_Integer_Literal (Loc, True_Value));
2388          end if;
2389
2390          Set_Etype (N, Universal_Integer);
2391          Set_Is_Static_Expression (N);
2392       end Default_Bit_Order;
2393
2394       --------------
2395       -- Definite --
2396       --------------
2397
2398       when Attribute_Definite =>
2399          Legal_Formal_Attribute;
2400
2401       -----------
2402       -- Delta --
2403       -----------
2404
2405       when Attribute_Delta =>
2406          Check_Fixed_Point_Type_0;
2407          Set_Etype (N, Universal_Real);
2408
2409       ------------
2410       -- Denorm --
2411       ------------
2412
2413       when Attribute_Denorm =>
2414          Check_Floating_Point_Type_0;
2415          Set_Etype (N, Standard_Boolean);
2416
2417       ------------
2418       -- Digits --
2419       ------------
2420
2421       when Attribute_Digits =>
2422          Check_E0;
2423          Check_Type;
2424
2425          if not Is_Floating_Point_Type (P_Type)
2426            and then not Is_Decimal_Fixed_Point_Type (P_Type)
2427          then
2428             Error_Attr
2429               ("prefix of % attribute must be float or decimal type", P);
2430          end if;
2431
2432          Set_Etype (N, Universal_Integer);
2433
2434       ---------------
2435       -- Elab_Body --
2436       ---------------
2437
2438       --  Also handles processing for Elab_Spec
2439
2440       when Attribute_Elab_Body | Attribute_Elab_Spec =>
2441          Check_E0;
2442          Check_Unit_Name (P);
2443          Set_Etype (N, Standard_Void_Type);
2444
2445          --  We have to manually call the expander in this case to get
2446          --  the necessary expansion (normally attributes that return
2447          --  entities are not expanded).
2448
2449          Expand (N);
2450
2451       ---------------
2452       -- Elab_Spec --
2453       ---------------
2454
2455       --  Shares processing with Elab_Body
2456
2457       ----------------
2458       -- Elaborated --
2459       ----------------
2460
2461       when Attribute_Elaborated =>
2462          Check_E0;
2463          Check_Library_Unit;
2464          Set_Etype (N, Standard_Boolean);
2465
2466       ----------
2467       -- Emax --
2468       ----------
2469
2470       when Attribute_Emax =>
2471          Check_Floating_Point_Type_0;
2472          Set_Etype (N, Universal_Integer);
2473
2474       --------------
2475       -- Enum_Rep --
2476       --------------
2477
2478       when Attribute_Enum_Rep => Enum_Rep : declare
2479       begin
2480          if Present (E1) then
2481             Check_E1;
2482             Check_Discrete_Type;
2483             Resolve (E1, P_Base_Type);
2484
2485          else
2486             if not Is_Entity_Name (P)
2487               or else (not Is_Object (Entity (P))
2488                          and then
2489                        Ekind (Entity (P)) /= E_Enumeration_Literal)
2490             then
2491                Error_Attr
2492                  ("prefix of %attribute must be " &
2493                   "discrete type/object or enum literal", P);
2494             end if;
2495          end if;
2496
2497          Set_Etype (N, Universal_Integer);
2498       end Enum_Rep;
2499
2500       -------------
2501       -- Epsilon --
2502       -------------
2503
2504       when Attribute_Epsilon =>
2505          Check_Floating_Point_Type_0;
2506          Set_Etype (N, Universal_Real);
2507
2508       --------------
2509       -- Exponent --
2510       --------------
2511
2512       when Attribute_Exponent =>
2513          Check_Floating_Point_Type_1;
2514          Set_Etype (N, Universal_Integer);
2515          Resolve (E1, P_Base_Type);
2516
2517       ------------------
2518       -- External_Tag --
2519       ------------------
2520
2521       when Attribute_External_Tag =>
2522          Check_E0;
2523          Check_Type;
2524
2525          Set_Etype (N, Standard_String);
2526
2527          if not Is_Tagged_Type (P_Type) then
2528             Error_Attr ("prefix of % attribute must be tagged", P);
2529          end if;
2530
2531       -----------
2532       -- First --
2533       -----------
2534
2535       when Attribute_First =>
2536          Check_Array_Or_Scalar_Type;
2537
2538       ---------------
2539       -- First_Bit --
2540       ---------------
2541
2542       when Attribute_First_Bit =>
2543          Check_Component;
2544          Set_Etype (N, Universal_Integer);
2545
2546       -----------------
2547       -- Fixed_Value --
2548       -----------------
2549
2550       when Attribute_Fixed_Value =>
2551          Check_E1;
2552          Check_Fixed_Point_Type;
2553          Resolve (E1, Any_Integer);
2554          Set_Etype (N, P_Base_Type);
2555
2556       -----------
2557       -- Floor --
2558       -----------
2559
2560       when Attribute_Floor =>
2561          Check_Floating_Point_Type_1;
2562          Set_Etype (N, P_Base_Type);
2563          Resolve (E1, P_Base_Type);
2564
2565       ----------
2566       -- Fore --
2567       ----------
2568
2569       when Attribute_Fore =>
2570          Check_Fixed_Point_Type_0;
2571          Set_Etype (N, Universal_Integer);
2572
2573       --------------
2574       -- Fraction --
2575       --------------
2576
2577       when Attribute_Fraction =>
2578          Check_Floating_Point_Type_1;
2579          Set_Etype (N, P_Base_Type);
2580          Resolve (E1, P_Base_Type);
2581
2582       -----------------------
2583       -- Has_Discriminants --
2584       -----------------------
2585
2586       when Attribute_Has_Discriminants =>
2587          Legal_Formal_Attribute;
2588
2589       --------------
2590       -- Identity --
2591       --------------
2592
2593       when Attribute_Identity =>
2594          Check_E0;
2595          Analyze (P);
2596
2597          if Etype (P) =  Standard_Exception_Type then
2598             Set_Etype (N, RTE (RE_Exception_Id));
2599
2600          elsif Is_Task_Type (Etype (P))
2601            or else (Is_Access_Type (Etype (P))
2602               and then Is_Task_Type (Designated_Type (Etype (P))))
2603          then
2604             Resolve (P);
2605             Set_Etype (N, RTE (RO_AT_Task_ID));
2606
2607          else
2608             Error_Attr ("prefix of % attribute must be a task or an "
2609               & "exception", P);
2610          end if;
2611
2612       -----------
2613       -- Image --
2614       -----------
2615
2616       when Attribute_Image => Image :
2617       begin
2618          Set_Etype (N, Standard_String);
2619          Check_Scalar_Type;
2620
2621          if Is_Real_Type (P_Type) then
2622             if Ada_83 and then Comes_From_Source (N) then
2623                Error_Msg_Name_1 := Aname;
2624                Error_Msg_N
2625                  ("(Ada 83) % attribute not allowed for real types", N);
2626             end if;
2627          end if;
2628
2629          if Is_Enumeration_Type (P_Type) then
2630             Check_Restriction (No_Enumeration_Maps, N);
2631          end if;
2632
2633          Check_E1;
2634          Resolve (E1, P_Base_Type);
2635          Check_Enum_Image;
2636          Validate_Non_Static_Attribute_Function_Call;
2637       end Image;
2638
2639       ---------
2640       -- Img --
2641       ---------
2642
2643       when Attribute_Img => Img :
2644       begin
2645          Set_Etype (N, Standard_String);
2646
2647          if not Is_Scalar_Type (P_Type)
2648            or else (Is_Entity_Name (P) and then Is_Type (Entity (P)))
2649          then
2650             Error_Attr
2651               ("prefix of % attribute must be scalar object name", N);
2652          end if;
2653
2654          Check_Enum_Image;
2655       end Img;
2656
2657       -----------
2658       -- Input --
2659       -----------
2660
2661       when Attribute_Input =>
2662          Check_E1;
2663          Check_Stream_Attribute (TSS_Stream_Input);
2664          Set_Etype (N, P_Base_Type);
2665
2666       -------------------
2667       -- Integer_Value --
2668       -------------------
2669
2670       when Attribute_Integer_Value =>
2671          Check_E1;
2672          Check_Integer_Type;
2673          Resolve (E1, Any_Fixed);
2674          Set_Etype (N, P_Base_Type);
2675
2676       -----------
2677       -- Large --
2678       -----------
2679
2680       when Attribute_Large =>
2681          Check_E0;
2682          Check_Real_Type;
2683          Set_Etype (N, Universal_Real);
2684
2685       ----------
2686       -- Last --
2687       ----------
2688
2689       when Attribute_Last =>
2690          Check_Array_Or_Scalar_Type;
2691
2692       --------------
2693       -- Last_Bit --
2694       --------------
2695
2696       when Attribute_Last_Bit =>
2697          Check_Component;
2698          Set_Etype (N, Universal_Integer);
2699
2700       ------------------
2701       -- Leading_Part --
2702       ------------------
2703
2704       when Attribute_Leading_Part =>
2705          Check_Floating_Point_Type_2;
2706          Set_Etype (N, P_Base_Type);
2707          Resolve (E1, P_Base_Type);
2708          Resolve (E2, Any_Integer);
2709
2710       ------------
2711       -- Length --
2712       ------------
2713
2714       when Attribute_Length =>
2715          Check_Array_Type;
2716          Set_Etype (N, Universal_Integer);
2717
2718       -------------
2719       -- Machine --
2720       -------------
2721
2722       when Attribute_Machine =>
2723          Check_Floating_Point_Type_1;
2724          Set_Etype (N, P_Base_Type);
2725          Resolve (E1, P_Base_Type);
2726
2727       ------------------
2728       -- Machine_Emax --
2729       ------------------
2730
2731       when Attribute_Machine_Emax =>
2732          Check_Floating_Point_Type_0;
2733          Set_Etype (N, Universal_Integer);
2734
2735       ------------------
2736       -- Machine_Emin --
2737       ------------------
2738
2739       when Attribute_Machine_Emin =>
2740          Check_Floating_Point_Type_0;
2741          Set_Etype (N, Universal_Integer);
2742
2743       ----------------------
2744       -- Machine_Mantissa --
2745       ----------------------
2746
2747       when Attribute_Machine_Mantissa =>
2748          Check_Floating_Point_Type_0;
2749          Set_Etype (N, Universal_Integer);
2750
2751       -----------------------
2752       -- Machine_Overflows --
2753       -----------------------
2754
2755       when Attribute_Machine_Overflows =>
2756          Check_Real_Type;
2757          Check_E0;
2758          Set_Etype (N, Standard_Boolean);
2759
2760       -------------------
2761       -- Machine_Radix --
2762       -------------------
2763
2764       when Attribute_Machine_Radix =>
2765          Check_Real_Type;
2766          Check_E0;
2767          Set_Etype (N, Universal_Integer);
2768
2769       --------------------
2770       -- Machine_Rounds --
2771       --------------------
2772
2773       when Attribute_Machine_Rounds =>
2774          Check_Real_Type;
2775          Check_E0;
2776          Set_Etype (N, Standard_Boolean);
2777
2778       ------------------
2779       -- Machine_Size --
2780       ------------------
2781
2782       when Attribute_Machine_Size =>
2783          Check_E0;
2784          Check_Type;
2785          Check_Not_Incomplete_Type;
2786          Set_Etype (N, Universal_Integer);
2787
2788       --------------
2789       -- Mantissa --
2790       --------------
2791
2792       when Attribute_Mantissa =>
2793          Check_E0;
2794          Check_Real_Type;
2795          Set_Etype (N, Universal_Integer);
2796
2797       ---------
2798       -- Max --
2799       ---------
2800
2801       when Attribute_Max =>
2802          Check_E2;
2803          Check_Scalar_Type;
2804          Resolve (E1, P_Base_Type);
2805          Resolve (E2, P_Base_Type);
2806          Set_Etype (N, P_Base_Type);
2807
2808       ----------------------------------
2809       -- Max_Size_In_Storage_Elements --
2810       ----------------------------------
2811
2812       when Attribute_Max_Size_In_Storage_Elements =>
2813          Check_E0;
2814          Check_Type;
2815          Check_Not_Incomplete_Type;
2816          Set_Etype (N, Universal_Integer);
2817
2818       -----------------------
2819       -- Maximum_Alignment --
2820       -----------------------
2821
2822       when Attribute_Maximum_Alignment =>
2823          Standard_Attribute (Ttypes.Maximum_Alignment);
2824
2825       --------------------
2826       -- Mechanism_Code --
2827       --------------------
2828
2829       when Attribute_Mechanism_Code =>
2830          if not Is_Entity_Name (P)
2831            or else not Is_Subprogram (Entity (P))
2832          then
2833             Error_Attr ("prefix of % attribute must be subprogram", P);
2834          end if;
2835
2836          Check_Either_E0_Or_E1;
2837
2838          if Present (E1) then
2839             Resolve (E1, Any_Integer);
2840             Set_Etype (E1, Standard_Integer);
2841
2842             if not Is_Static_Expression (E1) then
2843                Flag_Non_Static_Expr
2844                  ("expression for parameter number must be static!", E1);
2845                Error_Attr;
2846
2847             elsif UI_To_Int (Intval (E1)) > Number_Formals (Entity (P))
2848               or else UI_To_Int (Intval (E1)) < 0
2849             then
2850                Error_Attr ("invalid parameter number for %attribute", E1);
2851             end if;
2852          end if;
2853
2854          Set_Etype (N, Universal_Integer);
2855
2856       ---------
2857       -- Min --
2858       ---------
2859
2860       when Attribute_Min =>
2861          Check_E2;
2862          Check_Scalar_Type;
2863          Resolve (E1, P_Base_Type);
2864          Resolve (E2, P_Base_Type);
2865          Set_Etype (N, P_Base_Type);
2866
2867       -----------
2868       -- Model --
2869       -----------
2870
2871       when Attribute_Model =>
2872          Check_Floating_Point_Type_1;
2873          Set_Etype (N, P_Base_Type);
2874          Resolve (E1, P_Base_Type);
2875
2876       ----------------
2877       -- Model_Emin --
2878       ----------------
2879
2880       when Attribute_Model_Emin =>
2881          Check_Floating_Point_Type_0;
2882          Set_Etype (N, Universal_Integer);
2883
2884       -------------------
2885       -- Model_Epsilon --
2886       -------------------
2887
2888       when Attribute_Model_Epsilon =>
2889          Check_Floating_Point_Type_0;
2890          Set_Etype (N, Universal_Real);
2891
2892       --------------------
2893       -- Model_Mantissa --
2894       --------------------
2895
2896       when Attribute_Model_Mantissa =>
2897          Check_Floating_Point_Type_0;
2898          Set_Etype (N, Universal_Integer);
2899
2900       -----------------
2901       -- Model_Small --
2902       -----------------
2903
2904       when Attribute_Model_Small =>
2905          Check_Floating_Point_Type_0;
2906          Set_Etype (N, Universal_Real);
2907
2908       -------------
2909       -- Modulus --
2910       -------------
2911
2912       when Attribute_Modulus =>
2913          Check_E0;
2914          Check_Type;
2915
2916          if not Is_Modular_Integer_Type (P_Type) then
2917             Error_Attr ("prefix of % attribute must be modular type", P);
2918          end if;
2919
2920          Set_Etype (N, Universal_Integer);
2921
2922       --------------------
2923       -- Null_Parameter --
2924       --------------------
2925
2926       when Attribute_Null_Parameter => Null_Parameter : declare
2927          Parnt  : constant Node_Id := Parent (N);
2928          GParnt : constant Node_Id := Parent (Parnt);
2929
2930          procedure Bad_Null_Parameter (Msg : String);
2931          --  Used if bad Null parameter attribute node is found. Issues
2932          --  given error message, and also sets the type to Any_Type to
2933          --  avoid blowups later on from dealing with a junk node.
2934
2935          procedure Must_Be_Imported (Proc_Ent : Entity_Id);
2936          --  Called to check that Proc_Ent is imported subprogram
2937
2938          ------------------------
2939          -- Bad_Null_Parameter --
2940          ------------------------
2941
2942          procedure Bad_Null_Parameter (Msg : String) is
2943          begin
2944             Error_Msg_N (Msg, N);
2945             Set_Etype (N, Any_Type);
2946          end Bad_Null_Parameter;
2947
2948          ----------------------
2949          -- Must_Be_Imported --
2950          ----------------------
2951
2952          procedure Must_Be_Imported (Proc_Ent : Entity_Id) is
2953             Pent : Entity_Id := Proc_Ent;
2954
2955          begin
2956             while Present (Alias (Pent)) loop
2957                Pent := Alias (Pent);
2958             end loop;
2959
2960             --  Ignore check if procedure not frozen yet (we will get
2961             --  another chance when the default parameter is reanalyzed)
2962
2963             if not Is_Frozen (Pent) then
2964                return;
2965
2966             elsif not Is_Imported (Pent) then
2967                Bad_Null_Parameter
2968                  ("Null_Parameter can only be used with imported subprogram");
2969
2970             else
2971                return;
2972             end if;
2973          end Must_Be_Imported;
2974
2975       --  Start of processing for Null_Parameter
2976
2977       begin
2978          Check_Type;
2979          Check_E0;
2980          Set_Etype (N, P_Type);
2981
2982          --  Case of attribute used as default expression
2983
2984          if Nkind (Parnt) = N_Parameter_Specification then
2985             Must_Be_Imported (Defining_Entity (GParnt));
2986
2987          --  Case of attribute used as actual for subprogram (positional)
2988
2989          elsif (Nkind (Parnt) = N_Procedure_Call_Statement
2990                  or else
2991                 Nkind (Parnt) = N_Function_Call)
2992             and then Is_Entity_Name (Name (Parnt))
2993          then
2994             Must_Be_Imported (Entity (Name (Parnt)));
2995
2996          --  Case of attribute used as actual for subprogram (named)
2997
2998          elsif Nkind (Parnt) = N_Parameter_Association
2999            and then (Nkind (GParnt) = N_Procedure_Call_Statement
3000                        or else
3001                      Nkind (GParnt) = N_Function_Call)
3002            and then Is_Entity_Name (Name (GParnt))
3003          then
3004             Must_Be_Imported (Entity (Name (GParnt)));
3005
3006          --  Not an allowed case
3007
3008          else
3009             Bad_Null_Parameter
3010               ("Null_Parameter must be actual or default parameter");
3011          end if;
3012
3013       end Null_Parameter;
3014
3015       -----------------
3016       -- Object_Size --
3017       -----------------
3018
3019       when Attribute_Object_Size =>
3020          Check_E0;
3021          Check_Type;
3022          Check_Not_Incomplete_Type;
3023          Set_Etype (N, Universal_Integer);
3024
3025       ------------
3026       -- Output --
3027       ------------
3028
3029       when Attribute_Output =>
3030          Check_E2;
3031          Check_Stream_Attribute (TSS_Stream_Output);
3032          Set_Etype (N, Standard_Void_Type);
3033          Resolve (N, Standard_Void_Type);
3034
3035       ------------------
3036       -- Partition_ID --
3037       ------------------
3038
3039       when Attribute_Partition_ID =>
3040          Check_E0;
3041
3042          if P_Type /= Any_Type then
3043             if not Is_Library_Level_Entity (Entity (P)) then
3044                Error_Attr
3045                  ("prefix of % attribute must be library-level entity", P);
3046
3047             --  The defining entity of prefix should not be declared inside
3048             --  a Pure unit. RM E.1(8).
3049             --  The Is_Pure flag has been set during declaration.
3050
3051             elsif Is_Entity_Name (P)
3052               and then Is_Pure (Entity (P))
3053             then
3054                Error_Attr
3055                  ("prefix of % attribute must not be declared pure", P);
3056             end if;
3057          end if;
3058
3059          Set_Etype (N, Universal_Integer);
3060
3061       -------------------------
3062       -- Passed_By_Reference --
3063       -------------------------
3064
3065       when Attribute_Passed_By_Reference =>
3066          Check_E0;
3067          Check_Type;
3068          Set_Etype (N, Standard_Boolean);
3069
3070       ------------------
3071       -- Pool_Address --
3072       ------------------
3073
3074       when Attribute_Pool_Address =>
3075          Check_E0;
3076          Set_Etype (N, RTE (RE_Address));
3077
3078       ---------
3079       -- Pos --
3080       ---------
3081
3082       when Attribute_Pos =>
3083          Check_Discrete_Type;
3084          Check_E1;
3085          Resolve (E1, P_Base_Type);
3086          Set_Etype (N, Universal_Integer);
3087
3088       --------------
3089       -- Position --
3090       --------------
3091
3092       when Attribute_Position =>
3093          Check_Component;
3094          Set_Etype (N, Universal_Integer);
3095
3096       ----------
3097       -- Pred --
3098       ----------
3099
3100       when Attribute_Pred =>
3101          Check_Scalar_Type;
3102          Check_E1;
3103          Resolve (E1, P_Base_Type);
3104          Set_Etype (N, P_Base_Type);
3105
3106          --  Nothing to do for real type case
3107
3108          if Is_Real_Type (P_Type) then
3109             null;
3110
3111          --  If not modular type, test for overflow check required
3112
3113          else
3114             if not Is_Modular_Integer_Type (P_Type)
3115               and then not Range_Checks_Suppressed (P_Base_Type)
3116             then
3117                Enable_Range_Check (E1);
3118             end if;
3119          end if;
3120
3121       -----------
3122       -- Range --
3123       -----------
3124
3125       when Attribute_Range =>
3126          Check_Array_Or_Scalar_Type;
3127
3128          if Ada_83
3129            and then Is_Scalar_Type (P_Type)
3130            and then Comes_From_Source (N)
3131          then
3132             Error_Attr
3133               ("(Ada 83) % attribute not allowed for scalar type", P);
3134          end if;
3135
3136       ------------------
3137       -- Range_Length --
3138       ------------------
3139
3140       when Attribute_Range_Length =>
3141          Check_Discrete_Type;
3142          Set_Etype (N, Universal_Integer);
3143
3144       ----------
3145       -- Read --
3146       ----------
3147
3148       when Attribute_Read =>
3149          Check_E2;
3150          Check_Stream_Attribute (TSS_Stream_Read);
3151          Set_Etype (N, Standard_Void_Type);
3152          Resolve (N, Standard_Void_Type);
3153          Note_Possible_Modification (E2);
3154
3155       ---------------
3156       -- Remainder --
3157       ---------------
3158
3159       when Attribute_Remainder =>
3160          Check_Floating_Point_Type_2;
3161          Set_Etype (N, P_Base_Type);
3162          Resolve (E1, P_Base_Type);
3163          Resolve (E2, P_Base_Type);
3164
3165       -----------
3166       -- Round --
3167       -----------
3168
3169       when Attribute_Round =>
3170          Check_E1;
3171          Check_Decimal_Fixed_Point_Type;
3172          Set_Etype (N, P_Base_Type);
3173
3174          --  Because the context is universal_real (3.5.10(12)) it is a legal
3175          --  context for a universal fixed expression. This is the only
3176          --  attribute whose functional description involves U_R.
3177
3178          if Etype (E1) = Universal_Fixed then
3179             declare
3180                Conv : constant Node_Id := Make_Type_Conversion (Loc,
3181                   Subtype_Mark => New_Occurrence_Of (Universal_Real, Loc),
3182                   Expression   => Relocate_Node (E1));
3183
3184             begin
3185                Rewrite (E1, Conv);
3186                Analyze (E1);
3187             end;
3188          end if;
3189
3190          Resolve (E1, Any_Real);
3191
3192       --------------
3193       -- Rounding --
3194       --------------
3195
3196       when Attribute_Rounding =>
3197          Check_Floating_Point_Type_1;
3198          Set_Etype (N, P_Base_Type);
3199          Resolve (E1, P_Base_Type);
3200
3201       ---------------
3202       -- Safe_Emax --
3203       ---------------
3204
3205       when Attribute_Safe_Emax =>
3206          Check_Floating_Point_Type_0;
3207          Set_Etype (N, Universal_Integer);
3208
3209       ----------------
3210       -- Safe_First --
3211       ----------------
3212
3213       when Attribute_Safe_First =>
3214          Check_Floating_Point_Type_0;
3215          Set_Etype (N, Universal_Real);
3216
3217       ----------------
3218       -- Safe_Large --
3219       ----------------
3220
3221       when Attribute_Safe_Large =>
3222          Check_E0;
3223          Check_Real_Type;
3224          Set_Etype (N, Universal_Real);
3225
3226       ---------------
3227       -- Safe_Last --
3228       ---------------
3229
3230       when Attribute_Safe_Last =>
3231          Check_Floating_Point_Type_0;
3232          Set_Etype (N, Universal_Real);
3233
3234       ----------------
3235       -- Safe_Small --
3236       ----------------
3237
3238       when Attribute_Safe_Small =>
3239          Check_E0;
3240          Check_Real_Type;
3241          Set_Etype (N, Universal_Real);
3242
3243       -----------
3244       -- Scale --
3245       -----------
3246
3247       when Attribute_Scale =>
3248          Check_E0;
3249          Check_Decimal_Fixed_Point_Type;
3250          Set_Etype (N, Universal_Integer);
3251
3252       -------------
3253       -- Scaling --
3254       -------------
3255
3256       when Attribute_Scaling =>
3257          Check_Floating_Point_Type_2;
3258          Set_Etype (N, P_Base_Type);
3259          Resolve (E1, P_Base_Type);
3260
3261       ------------------
3262       -- Signed_Zeros --
3263       ------------------
3264
3265       when Attribute_Signed_Zeros =>
3266          Check_Floating_Point_Type_0;
3267          Set_Etype (N, Standard_Boolean);
3268
3269       ----------
3270       -- Size --
3271       ----------
3272
3273       when Attribute_Size | Attribute_VADS_Size =>
3274          Check_E0;
3275
3276          if Is_Object_Reference (P)
3277            or else (Is_Entity_Name (P)
3278                      and then Ekind (Entity (P)) = E_Function)
3279          then
3280             Check_Object_Reference (P);
3281
3282          elsif Is_Entity_Name (P)
3283            and then Is_Type (Entity (P))
3284          then
3285             null;
3286
3287          elsif Nkind (P) = N_Type_Conversion
3288            and then not Comes_From_Source (P)
3289          then
3290             null;
3291
3292          else
3293             Error_Attr ("invalid prefix for % attribute", P);
3294          end if;
3295
3296          Check_Not_Incomplete_Type;
3297          Set_Etype (N, Universal_Integer);
3298
3299       -----------
3300       -- Small --
3301       -----------
3302
3303       when Attribute_Small =>
3304          Check_E0;
3305          Check_Real_Type;
3306          Set_Etype (N, Universal_Real);
3307
3308       ------------------
3309       -- Storage_Pool --
3310       ------------------
3311
3312       when Attribute_Storage_Pool =>
3313          if Is_Access_Type (P_Type) then
3314             Check_E0;
3315
3316             --  Set appropriate entity
3317
3318             if Present (Associated_Storage_Pool (Root_Type (P_Type))) then
3319                Set_Entity (N, Associated_Storage_Pool (Root_Type (P_Type)));
3320             else
3321                Set_Entity (N, RTE (RE_Global_Pool_Object));
3322             end if;
3323
3324             Set_Etype (N, Class_Wide_Type (RTE (RE_Root_Storage_Pool)));
3325
3326             --  Validate_Remote_Access_To_Class_Wide_Type for attribute
3327             --  Storage_Pool since this attribute is not defined for such
3328             --  types (RM E.2.3(22)).
3329
3330             Validate_Remote_Access_To_Class_Wide_Type (N);
3331
3332          else
3333             Error_Attr ("prefix of % attribute must be access type", P);
3334          end if;
3335
3336       ------------------
3337       -- Storage_Size --
3338       ------------------
3339
3340       when Attribute_Storage_Size =>
3341
3342          if Is_Task_Type (P_Type) then
3343             Check_E0;
3344             Set_Etype (N, Universal_Integer);
3345
3346          elsif Is_Access_Type (P_Type) then
3347             if Is_Entity_Name (P)
3348               and then Is_Type (Entity (P))
3349             then
3350                Check_E0;
3351                Check_Type;
3352                Set_Etype (N, Universal_Integer);
3353
3354                --   Validate_Remote_Access_To_Class_Wide_Type for attribute
3355                --   Storage_Size since this attribute is not defined for
3356                --   such types (RM E.2.3(22)).
3357
3358                Validate_Remote_Access_To_Class_Wide_Type (N);
3359
3360             --  The prefix is allowed to be an implicit dereference
3361             --  of an access value designating a task.
3362
3363             else
3364                Check_E0;
3365                Check_Task_Prefix;
3366                Set_Etype (N, Universal_Integer);
3367             end if;
3368
3369          else
3370             Error_Attr
3371               ("prefix of % attribute must be access or task type", P);
3372          end if;
3373
3374       ------------------
3375       -- Storage_Unit --
3376       ------------------
3377
3378       when Attribute_Storage_Unit =>
3379          Standard_Attribute (Ttypes.System_Storage_Unit);
3380
3381       ----------
3382       -- Succ --
3383       ----------
3384
3385       when Attribute_Succ =>
3386          Check_Scalar_Type;
3387          Check_E1;
3388          Resolve (E1, P_Base_Type);
3389          Set_Etype (N, P_Base_Type);
3390
3391          --  Nothing to do for real type case
3392
3393          if Is_Real_Type (P_Type) then
3394             null;
3395
3396          --  If not modular type, test for overflow check required.
3397
3398          else
3399             if not Is_Modular_Integer_Type (P_Type)
3400               and then not Range_Checks_Suppressed (P_Base_Type)
3401             then
3402                Enable_Range_Check (E1);
3403             end if;
3404          end if;
3405
3406       ---------
3407       -- Tag --
3408       ---------
3409
3410       when Attribute_Tag =>
3411          Check_E0;
3412          Check_Dereference;
3413
3414          if not Is_Tagged_Type (P_Type) then
3415             Error_Attr ("prefix of % attribute must be tagged", P);
3416
3417          --  Next test does not apply to generated code
3418          --  why not, and what does the illegal reference mean???
3419
3420          elsif Is_Object_Reference (P)
3421            and then not Is_Class_Wide_Type (P_Type)
3422            and then Comes_From_Source (N)
3423          then
3424             Error_Attr
3425               ("% attribute can only be applied to objects of class-wide type",
3426                P);
3427          end if;
3428
3429          Set_Etype (N, RTE (RE_Tag));
3430
3431       -----------------
3432       -- Target_Name --
3433       -----------------
3434
3435       when Attribute_Target_Name => Target_Name : declare
3436          TN : constant String := Sdefault.Target_Name.all;
3437          TL : Integer := TN'Last;
3438
3439       begin
3440          Check_Standard_Prefix;
3441          Check_E0;
3442          Start_String;
3443
3444          if TN (TL) = '/' or else TN (TL) = '\' then
3445             TL := TL - 1;
3446          end if;
3447
3448          Store_String_Chars (TN (TN'First .. TL));
3449
3450          Rewrite (N,
3451            Make_String_Literal (Loc,
3452              Strval => End_String));
3453          Analyze_And_Resolve (N, Standard_String);
3454       end Target_Name;
3455
3456       ----------------
3457       -- Terminated --
3458       ----------------
3459
3460       when Attribute_Terminated =>
3461          Check_E0;
3462          Set_Etype (N, Standard_Boolean);
3463          Check_Task_Prefix;
3464
3465       ----------------
3466       -- To_Address --
3467       ----------------
3468
3469       when Attribute_To_Address =>
3470          Check_E1;
3471          Analyze (P);
3472
3473          if Nkind (P) /= N_Identifier
3474            or else Chars (P) /= Name_System
3475          then
3476             Error_Attr ("prefix of %attribute must be System", P);
3477          end if;
3478
3479          Generate_Reference (RTE (RE_Address), P);
3480          Analyze_And_Resolve (E1, Any_Integer);
3481          Set_Etype (N, RTE (RE_Address));
3482
3483       ----------------
3484       -- Truncation --
3485       ----------------
3486
3487       when Attribute_Truncation =>
3488          Check_Floating_Point_Type_1;
3489          Resolve (E1, P_Base_Type);
3490          Set_Etype (N, P_Base_Type);
3491
3492       ----------------
3493       -- Type_Class --
3494       ----------------
3495
3496       when Attribute_Type_Class =>
3497          Check_E0;
3498          Check_Type;
3499          Check_Not_Incomplete_Type;
3500          Set_Etype (N, RTE (RE_Type_Class));
3501
3502       -----------------
3503       -- UET_Address --
3504       -----------------
3505
3506       when Attribute_UET_Address =>
3507          Check_E0;
3508          Check_Unit_Name (P);
3509          Set_Etype (N, RTE (RE_Address));
3510
3511       -----------------------
3512       -- Unbiased_Rounding --
3513       -----------------------
3514
3515       when Attribute_Unbiased_Rounding =>
3516          Check_Floating_Point_Type_1;
3517          Set_Etype (N, P_Base_Type);
3518          Resolve (E1, P_Base_Type);
3519
3520       ----------------------
3521       -- Unchecked_Access --
3522       ----------------------
3523
3524       when Attribute_Unchecked_Access =>
3525          if Comes_From_Source (N) then
3526             Check_Restriction (No_Unchecked_Access, N);
3527          end if;
3528
3529          Analyze_Access_Attribute;
3530
3531       -------------------------
3532       -- Unconstrained_Array --
3533       -------------------------
3534
3535       when Attribute_Unconstrained_Array =>
3536          Check_E0;
3537          Check_Type;
3538          Check_Not_Incomplete_Type;
3539          Set_Etype (N, Standard_Boolean);
3540
3541       ------------------------------
3542       -- Universal_Literal_String --
3543       ------------------------------
3544
3545       --  This is a GNAT specific attribute whose prefix must be a named
3546       --  number where the expression is either a single numeric literal,
3547       --  or a numeric literal immediately preceded by a minus sign. The
3548       --  result is equivalent to a string literal containing the text of
3549       --  the literal as it appeared in the source program with a possible
3550       --  leading minus sign.
3551
3552       when Attribute_Universal_Literal_String => Universal_Literal_String :
3553       begin
3554          Check_E0;
3555
3556          if not Is_Entity_Name (P)
3557            or else Ekind (Entity (P)) not in Named_Kind
3558          then
3559             Error_Attr ("prefix for % attribute must be named number", P);
3560
3561          else
3562             declare
3563                Expr     : Node_Id;
3564                Negative : Boolean;
3565                S        : Source_Ptr;
3566                Src      : Source_Buffer_Ptr;
3567
3568             begin
3569                Expr := Original_Node (Expression (Parent (Entity (P))));
3570
3571                if Nkind (Expr) = N_Op_Minus then
3572                   Negative := True;
3573                   Expr := Original_Node (Right_Opnd (Expr));
3574                else
3575                   Negative := False;
3576                end if;
3577
3578                if Nkind (Expr) /= N_Integer_Literal
3579                  and then Nkind (Expr) /= N_Real_Literal
3580                then
3581                   Error_Attr
3582                     ("named number for % attribute must be simple literal", N);
3583                end if;
3584
3585                --  Build string literal corresponding to source literal text
3586
3587                Start_String;
3588
3589                if Negative then
3590                   Store_String_Char (Get_Char_Code ('-'));
3591                end if;
3592
3593                S := Sloc (Expr);
3594                Src := Source_Text (Get_Source_File_Index (S));
3595
3596                while Src (S) /= ';' and then Src (S) /= ' ' loop
3597                   Store_String_Char (Get_Char_Code (Src (S)));
3598                   S := S + 1;
3599                end loop;
3600
3601                --  Now we rewrite the attribute with the string literal
3602
3603                Rewrite (N,
3604                  Make_String_Literal (Loc, End_String));
3605                Analyze (N);
3606             end;
3607          end if;
3608       end Universal_Literal_String;
3609
3610       -------------------------
3611       -- Unrestricted_Access --
3612       -------------------------
3613
3614       --  This is a GNAT specific attribute which is like Access except that
3615       --  all scope checks and checks for aliased views are omitted.
3616
3617       when Attribute_Unrestricted_Access =>
3618          if Comes_From_Source (N) then
3619             Check_Restriction (No_Unchecked_Access, N);
3620          end if;
3621
3622          if Is_Entity_Name (P) then
3623             Set_Address_Taken (Entity (P));
3624          end if;
3625
3626          Analyze_Access_Attribute;
3627
3628       ---------
3629       -- Val --
3630       ---------
3631
3632       when Attribute_Val => Val : declare
3633       begin
3634          Check_E1;
3635          Check_Discrete_Type;
3636          Resolve (E1, Any_Integer);
3637          Set_Etype (N, P_Base_Type);
3638
3639          --  Note, we need a range check in general, but we wait for the
3640          --  Resolve call to do this, since we want to let Eval_Attribute
3641          --  have a chance to find an static illegality first!
3642       end Val;
3643
3644       -----------
3645       -- Valid --
3646       -----------
3647
3648       when Attribute_Valid =>
3649          Check_E0;
3650
3651          --  Ignore check for object if we have a 'Valid reference generated
3652          --  by the expanded code, since in some cases valid checks can occur
3653          --  on items that are names, but are not objects (e.g. attributes).
3654
3655          if Comes_From_Source (N) then
3656             Check_Object_Reference (P);
3657          end if;
3658
3659          if not Is_Scalar_Type (P_Type) then
3660             Error_Attr ("object for % attribute must be of scalar type", P);
3661          end if;
3662
3663          Set_Etype (N, Standard_Boolean);
3664
3665       -----------
3666       -- Value --
3667       -----------
3668
3669       when Attribute_Value => Value :
3670       begin
3671          Check_E1;
3672          Check_Scalar_Type;
3673
3674          if Is_Enumeration_Type (P_Type) then
3675             Check_Restriction (No_Enumeration_Maps, N);
3676          end if;
3677
3678          --  Set Etype before resolving expression because expansion of
3679          --  expression may require enclosing type. Note that the type
3680          --  returned by 'Value is the base type of the prefix type.
3681
3682          Set_Etype (N, P_Base_Type);
3683          Validate_Non_Static_Attribute_Function_Call;
3684       end Value;
3685
3686       ----------------
3687       -- Value_Size --
3688       ----------------
3689
3690       when Attribute_Value_Size =>
3691          Check_E0;
3692          Check_Type;
3693          Check_Not_Incomplete_Type;
3694          Set_Etype (N, Universal_Integer);
3695
3696       -------------
3697       -- Version --
3698       -------------
3699
3700       when Attribute_Version =>
3701          Check_E0;
3702          Check_Program_Unit;
3703          Set_Etype (N, RTE (RE_Version_String));
3704
3705       ------------------
3706       -- Wchar_T_Size --
3707       ------------------
3708
3709       when Attribute_Wchar_T_Size =>
3710          Standard_Attribute (Interfaces_Wchar_T_Size);
3711
3712       ----------------
3713       -- Wide_Image --
3714       ----------------
3715
3716       when Attribute_Wide_Image => Wide_Image :
3717       begin
3718          Check_Scalar_Type;
3719          Set_Etype (N, Standard_Wide_String);
3720          Check_E1;
3721          Resolve (E1, P_Base_Type);
3722          Validate_Non_Static_Attribute_Function_Call;
3723       end Wide_Image;
3724
3725       ----------------
3726       -- Wide_Value --
3727       ----------------
3728
3729       when Attribute_Wide_Value => Wide_Value :
3730       begin
3731          Check_E1;
3732          Check_Scalar_Type;
3733
3734          --  Set Etype before resolving expression because expansion
3735          --  of expression may require enclosing type.
3736
3737          Set_Etype (N, P_Type);
3738          Validate_Non_Static_Attribute_Function_Call;
3739       end Wide_Value;
3740
3741       ----------------
3742       -- Wide_Width --
3743       ----------------
3744
3745       when Attribute_Wide_Width =>
3746          Check_E0;
3747          Check_Scalar_Type;
3748          Set_Etype (N, Universal_Integer);
3749
3750       -----------
3751       -- Width --
3752       -----------
3753
3754       when Attribute_Width =>
3755          Check_E0;
3756          Check_Scalar_Type;
3757          Set_Etype (N, Universal_Integer);
3758
3759       ---------------
3760       -- Word_Size --
3761       ---------------
3762
3763       when Attribute_Word_Size =>
3764          Standard_Attribute (System_Word_Size);
3765
3766       -----------
3767       -- Write --
3768       -----------
3769
3770       when Attribute_Write =>
3771          Check_E2;
3772          Check_Stream_Attribute (TSS_Stream_Write);
3773          Set_Etype (N, Standard_Void_Type);
3774          Resolve (N, Standard_Void_Type);
3775
3776       end case;
3777
3778    --  All errors raise Bad_Attribute, so that we get out before any further
3779    --  damage occurs when an error is detected (for example, if we check for
3780    --  one attribute expression, and the check succeeds, we want to be able
3781    --  to proceed securely assuming that an expression is in fact present.
3782
3783    exception
3784       when Bad_Attribute =>
3785          Set_Etype (N, Any_Type);
3786          return;
3787
3788    end Analyze_Attribute;
3789
3790    --------------------
3791    -- Eval_Attribute --
3792    --------------------
3793
3794    procedure Eval_Attribute (N : Node_Id) is
3795       Loc   : constant Source_Ptr   := Sloc (N);
3796       Aname : constant Name_Id      := Attribute_Name (N);
3797       Id    : constant Attribute_Id := Get_Attribute_Id (Aname);
3798       P     : constant Node_Id      := Prefix (N);
3799
3800       C_Type : constant Entity_Id := Etype (N);
3801       --  The type imposed by the context.
3802
3803       E1 : Node_Id;
3804       --  First expression, or Empty if none
3805
3806       E2 : Node_Id;
3807       --  Second expression, or Empty if none
3808
3809       P_Entity : Entity_Id;
3810       --  Entity denoted by prefix
3811
3812       P_Type : Entity_Id;
3813       --  The type of the prefix
3814
3815       P_Base_Type : Entity_Id;
3816       --  The base type of the prefix type
3817
3818       P_Root_Type : Entity_Id;
3819       --  The root type of the prefix type
3820
3821       Static : Boolean;
3822       --  True if the result is Static. This is set by the general processing
3823       --  to true if the prefix is static, and all expressions are static. It
3824       --  can be reset as processing continues for particular attributes
3825
3826       Lo_Bound, Hi_Bound : Node_Id;
3827       --  Expressions for low and high bounds of type or array index referenced
3828       --  by First, Last, or Length attribute for array, set by Set_Bounds.
3829
3830       CE_Node : Node_Id;
3831       --  Constraint error node used if we have an attribute reference has
3832       --  an argument that raises a constraint error. In this case we replace
3833       --  the attribute with a raise constraint_error node. This is important
3834       --  processing, since otherwise gigi might see an attribute which it is
3835       --  unprepared to deal with.
3836
3837       function Aft_Value return Nat;
3838       --  Computes Aft value for current attribute prefix (used by Aft itself
3839       --  and also by Width for computing the Width of a fixed point type).
3840
3841       procedure Check_Expressions;
3842       --  In case where the attribute is not foldable, the expressions, if
3843       --  any, of the attribute, are in a non-static context. This procedure
3844       --  performs the required additional checks.
3845
3846       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean;
3847       --  Determines if the given type has compile time known bounds. Note
3848       --  that we enter the case statement even in cases where the prefix
3849       --  type does NOT have known bounds, so it is important to guard any
3850       --  attempt to evaluate both bounds with a call to this function.
3851
3852       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint);
3853       --  This procedure is called when the attribute N has a non-static
3854       --  but compile time known value given by Val. It includes the
3855       --  necessary checks for out of range values.
3856
3857       procedure Float_Attribute_Universal_Integer
3858         (IEEES_Val : Int;
3859          IEEEL_Val : Int;
3860          IEEEX_Val : Int;
3861          VAXFF_Val : Int;
3862          VAXDF_Val : Int;
3863          VAXGF_Val : Int;
3864          AAMPS_Val : Int;
3865          AAMPL_Val : Int);
3866       --  This procedure evaluates a float attribute with no arguments that
3867       --  returns a universal integer result. The parameters give the values
3868       --  for the possible floating-point root types. See ttypef for details.
3869       --  The prefix type is a float type (and is thus not a generic type).
3870
3871       procedure Float_Attribute_Universal_Real
3872         (IEEES_Val : String;
3873          IEEEL_Val : String;
3874          IEEEX_Val : String;
3875          VAXFF_Val : String;
3876          VAXDF_Val : String;
3877          VAXGF_Val : String;
3878          AAMPS_Val : String;
3879          AAMPL_Val : String);
3880       --  This procedure evaluates a float attribute with no arguments that
3881       --  returns a universal real result. The parameters give the values
3882       --  required for the possible floating-point root types in string
3883       --  format as real literals with a possible leading minus sign.
3884       --  The prefix type is a float type (and is thus not a generic type).
3885
3886       function Fore_Value return Nat;
3887       --  Computes the Fore value for the current attribute prefix, which is
3888       --  known to be a static fixed-point type. Used by Fore and Width.
3889
3890       function Mantissa return Uint;
3891       --  Returns the Mantissa value for the prefix type
3892
3893       procedure Set_Bounds;
3894       --  Used for First, Last and Length attributes applied to an array or
3895       --  array subtype. Sets the variables Lo_Bound and Hi_Bound to the low
3896       --  and high bound expressions for the index referenced by the attribute
3897       --  designator (i.e. the first index if no expression is present, and
3898       --  the N'th index if the value N is present as an expression). Also
3899       --  used for First and Last of scalar types. Static is reset to False
3900       --  if the type or index type is not statically constrained.
3901
3902       ---------------
3903       -- Aft_Value --
3904       ---------------
3905
3906       function Aft_Value return Nat is
3907          Result    : Nat;
3908          Delta_Val : Ureal;
3909
3910       begin
3911          Result := 1;
3912          Delta_Val := Delta_Value (P_Type);
3913
3914          while Delta_Val < Ureal_Tenth loop
3915             Delta_Val := Delta_Val * Ureal_10;
3916             Result := Result + 1;
3917          end loop;
3918
3919          return Result;
3920       end Aft_Value;
3921
3922       -----------------------
3923       -- Check_Expressions --
3924       -----------------------
3925
3926       procedure Check_Expressions is
3927          E : Node_Id := E1;
3928
3929       begin
3930          while Present (E) loop
3931             Check_Non_Static_Context (E);
3932             Next (E);
3933          end loop;
3934       end Check_Expressions;
3935
3936       ----------------------------------
3937       -- Compile_Time_Known_Attribute --
3938       ----------------------------------
3939
3940       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint) is
3941          T : constant Entity_Id := Etype (N);
3942
3943       begin
3944          Fold_Uint (N, Val, False);
3945
3946          --  Check that result is in bounds of the type if it is static
3947
3948          if Is_In_Range (N, T) then
3949             null;
3950
3951          elsif Is_Out_Of_Range (N, T) then
3952             Apply_Compile_Time_Constraint_Error
3953               (N, "value not in range of}?", CE_Range_Check_Failed);
3954
3955          elsif not Range_Checks_Suppressed (T) then
3956             Enable_Range_Check (N);
3957
3958          else
3959             Set_Do_Range_Check (N, False);
3960          end if;
3961       end Compile_Time_Known_Attribute;
3962
3963       -------------------------------
3964       -- Compile_Time_Known_Bounds --
3965       -------------------------------
3966
3967       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean is
3968       begin
3969          return
3970            Compile_Time_Known_Value (Type_Low_Bound (Typ))
3971              and then
3972            Compile_Time_Known_Value (Type_High_Bound (Typ));
3973       end Compile_Time_Known_Bounds;
3974
3975       ---------------------------------------
3976       -- Float_Attribute_Universal_Integer --
3977       ---------------------------------------
3978
3979       procedure Float_Attribute_Universal_Integer
3980         (IEEES_Val : Int;
3981          IEEEL_Val : Int;
3982          IEEEX_Val : Int;
3983          VAXFF_Val : Int;
3984          VAXDF_Val : Int;
3985          VAXGF_Val : Int;
3986          AAMPS_Val : Int;
3987          AAMPL_Val : Int)
3988       is
3989          Val  : Int;
3990          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
3991
3992       begin
3993          if Vax_Float (P_Base_Type) then
3994             if Digs = VAXFF_Digits then
3995                Val := VAXFF_Val;
3996             elsif Digs = VAXDF_Digits then
3997                Val := VAXDF_Val;
3998             else pragma Assert (Digs = VAXGF_Digits);
3999                Val := VAXGF_Val;
4000             end if;
4001
4002          elsif Is_AAMP_Float (P_Base_Type) then
4003             if Digs = AAMPS_Digits then
4004                Val := AAMPS_Val;
4005             else pragma Assert (Digs = AAMPL_Digits);
4006                Val := AAMPL_Val;
4007             end if;
4008
4009          else
4010             if Digs = IEEES_Digits then
4011                Val := IEEES_Val;
4012             elsif Digs = IEEEL_Digits then
4013                Val := IEEEL_Val;
4014             else pragma Assert (Digs = IEEEX_Digits);
4015                Val := IEEEX_Val;
4016             end if;
4017          end if;
4018
4019          Fold_Uint (N, UI_From_Int (Val), True);
4020       end Float_Attribute_Universal_Integer;
4021
4022       ------------------------------------
4023       -- Float_Attribute_Universal_Real --
4024       ------------------------------------
4025
4026       procedure Float_Attribute_Universal_Real
4027         (IEEES_Val : String;
4028          IEEEL_Val : String;
4029          IEEEX_Val : String;
4030          VAXFF_Val : String;
4031          VAXDF_Val : String;
4032          VAXGF_Val : String;
4033          AAMPS_Val : String;
4034          AAMPL_Val : String)
4035       is
4036          Val  : Node_Id;
4037          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4038
4039       begin
4040          if Vax_Float (P_Base_Type) then
4041             if Digs = VAXFF_Digits then
4042                Val := Real_Convert (VAXFF_Val);
4043             elsif Digs = VAXDF_Digits then
4044                Val := Real_Convert (VAXDF_Val);
4045             else pragma Assert (Digs = VAXGF_Digits);
4046                Val := Real_Convert (VAXGF_Val);
4047             end if;
4048
4049          elsif Is_AAMP_Float (P_Base_Type) then
4050             if Digs = AAMPS_Digits then
4051                Val := Real_Convert (AAMPS_Val);
4052             else pragma Assert (Digs = AAMPL_Digits);
4053                Val := Real_Convert (AAMPL_Val);
4054             end if;
4055
4056          else
4057             if Digs = IEEES_Digits then
4058                Val := Real_Convert (IEEES_Val);
4059             elsif Digs = IEEEL_Digits then
4060                Val := Real_Convert (IEEEL_Val);
4061             else pragma Assert (Digs = IEEEX_Digits);
4062                Val := Real_Convert (IEEEX_Val);
4063             end if;
4064          end if;
4065
4066          Set_Sloc (Val, Loc);
4067          Rewrite (N, Val);
4068          Set_Is_Static_Expression (N, Static);
4069          Analyze_And_Resolve (N, C_Type);
4070       end Float_Attribute_Universal_Real;
4071
4072       ----------------
4073       -- Fore_Value --
4074       ----------------
4075
4076       --  Note that the Fore calculation is based on the actual values
4077       --  of the bounds, and does not take into account possible rounding.
4078
4079       function Fore_Value return Nat is
4080          Lo      : constant Uint  := Expr_Value (Type_Low_Bound (P_Type));
4081          Hi      : constant Uint  := Expr_Value (Type_High_Bound (P_Type));
4082          Small   : constant Ureal := Small_Value (P_Type);
4083          Lo_Real : constant Ureal := Lo * Small;
4084          Hi_Real : constant Ureal := Hi * Small;
4085          T       : Ureal;
4086          R       : Nat;
4087
4088       begin
4089          --  Bounds are given in terms of small units, so first compute
4090          --  proper values as reals.
4091
4092          T := UR_Max (abs Lo_Real, abs Hi_Real);
4093          R := 2;
4094
4095          --  Loop to compute proper value if more than one digit required
4096
4097          while T >= Ureal_10 loop
4098             R := R + 1;
4099             T := T / Ureal_10;
4100          end loop;
4101
4102          return R;
4103       end Fore_Value;
4104
4105       --------------
4106       -- Mantissa --
4107       --------------
4108
4109       --  Table of mantissa values accessed by function  Computed using
4110       --  the relation:
4111
4112       --    T'Mantissa = integer next above (D * log(10)/log(2)) + 1)
4113
4114       --  where D is T'Digits (RM83 3.5.7)
4115
4116       Mantissa_Value : constant array (Nat range 1 .. 40) of Nat := (
4117           1 =>   5,
4118           2 =>   8,
4119           3 =>  11,
4120           4 =>  15,
4121           5 =>  18,
4122           6 =>  21,
4123           7 =>  25,
4124           8 =>  28,
4125           9 =>  31,
4126          10 =>  35,
4127          11 =>  38,
4128          12 =>  41,
4129          13 =>  45,
4130          14 =>  48,
4131          15 =>  51,
4132          16 =>  55,
4133          17 =>  58,
4134          18 =>  61,
4135          19 =>  65,
4136          20 =>  68,
4137          21 =>  71,
4138          22 =>  75,
4139          23 =>  78,
4140          24 =>  81,
4141          25 =>  85,
4142          26 =>  88,
4143          27 =>  91,
4144          28 =>  95,
4145          29 =>  98,
4146          30 => 101,
4147          31 => 104,
4148          32 => 108,
4149          33 => 111,
4150          34 => 114,
4151          35 => 118,
4152          36 => 121,
4153          37 => 124,
4154          38 => 128,
4155          39 => 131,
4156          40 => 134);
4157
4158       function Mantissa return Uint is
4159       begin
4160          return
4161            UI_From_Int (Mantissa_Value (UI_To_Int (Digits_Value (P_Type))));
4162       end Mantissa;
4163
4164       ----------------
4165       -- Set_Bounds --
4166       ----------------
4167
4168       procedure Set_Bounds is
4169          Ndim : Nat;
4170          Indx : Node_Id;
4171          Ityp : Entity_Id;
4172
4173       begin
4174          --  For a string literal subtype, we have to construct the bounds.
4175          --  Valid Ada code never applies attributes to string literals, but
4176          --  it is convenient to allow the expander to generate attribute
4177          --  references of this type (e.g. First and Last applied to a string
4178          --  literal).
4179
4180          --  Note that the whole point of the E_String_Literal_Subtype is to
4181          --  avoid this construction of bounds, but the cases in which we
4182          --  have to materialize them are rare enough that we don't worry!
4183
4184          --  The low bound is simply the low bound of the base type. The
4185          --  high bound is computed from the length of the string and this
4186          --  low bound.
4187
4188          if Ekind (P_Type) = E_String_Literal_Subtype then
4189             Ityp := Etype (First_Index (Base_Type (P_Type)));
4190             Lo_Bound := Type_Low_Bound (Ityp);
4191
4192             Hi_Bound :=
4193               Make_Integer_Literal (Sloc (P),
4194                 Intval =>
4195                   Expr_Value (Lo_Bound) + String_Literal_Length (P_Type) - 1);
4196
4197             Set_Parent (Hi_Bound, P);
4198             Analyze_And_Resolve (Hi_Bound, Etype (Lo_Bound));
4199             return;
4200
4201          --  For non-array case, just get bounds of scalar type
4202
4203          elsif Is_Scalar_Type (P_Type) then
4204             Ityp := P_Type;
4205
4206             --  For a fixed-point type, we must freeze to get the attributes
4207             --  of the fixed-point type set now so we can reference them.
4208
4209             if Is_Fixed_Point_Type (P_Type)
4210               and then not Is_Frozen (Base_Type (P_Type))
4211               and then Compile_Time_Known_Value (Type_Low_Bound (P_Type))
4212               and then Compile_Time_Known_Value (Type_High_Bound (P_Type))
4213             then
4214                Freeze_Fixed_Point_Type (Base_Type (P_Type));
4215             end if;
4216
4217          --  For array case, get type of proper index
4218
4219          else
4220             if No (E1) then
4221                Ndim := 1;
4222             else
4223                Ndim := UI_To_Int (Expr_Value (E1));
4224             end if;
4225
4226             Indx := First_Index (P_Type);
4227             for J in 1 .. Ndim - 1 loop
4228                Next_Index (Indx);
4229             end loop;
4230
4231             --  If no index type, get out (some other error occurred, and
4232             --  we don't have enough information to complete the job!)
4233
4234             if No (Indx) then
4235                Lo_Bound := Error;
4236                Hi_Bound := Error;
4237                return;
4238             end if;
4239
4240             Ityp := Etype (Indx);
4241          end if;
4242
4243          --  A discrete range in an index constraint is allowed to be a
4244          --  subtype indication. This is syntactically a pain, but should
4245          --  not propagate to the entity for the corresponding index subtype.
4246          --  After checking that the subtype indication is legal, the range
4247          --  of the subtype indication should be transfered to the entity.
4248          --  The attributes for the bounds should remain the simple retrievals
4249          --  that they are now.
4250
4251          Lo_Bound := Type_Low_Bound (Ityp);
4252          Hi_Bound := Type_High_Bound (Ityp);
4253
4254          if not Is_Static_Subtype (Ityp) then
4255             Static := False;
4256          end if;
4257       end Set_Bounds;
4258
4259    --  Start of processing for Eval_Attribute
4260
4261    begin
4262       --  Acquire first two expressions (at the moment, no attributes
4263       --  take more than two expressions in any case).
4264
4265       if Present (Expressions (N)) then
4266          E1 := First (Expressions (N));
4267          E2 := Next (E1);
4268       else
4269          E1 := Empty;
4270          E2 := Empty;
4271       end if;
4272
4273       --  Special processing for cases where the prefix is an object. For
4274       --  this purpose, a string literal counts as an object (attributes
4275       --  of string literals can only appear in generated code).
4276
4277       if Is_Object_Reference (P) or else Nkind (P) = N_String_Literal then
4278
4279          --  For Component_Size, the prefix is an array object, and we apply
4280          --  the attribute to the type of the object. This is allowed for
4281          --  both unconstrained and constrained arrays, since the bounds
4282          --  have no influence on the value of this attribute.
4283
4284          if Id = Attribute_Component_Size then
4285             P_Entity := Etype (P);
4286
4287          --  For First and Last, the prefix is an array object, and we apply
4288          --  the attribute to the type of the array, but we need a constrained
4289          --  type for this, so we use the actual subtype if available.
4290
4291          elsif Id = Attribute_First
4292                  or else
4293                Id = Attribute_Last
4294                  or else
4295                Id = Attribute_Length
4296          then
4297             declare
4298                AS : constant Entity_Id := Get_Actual_Subtype_If_Available (P);
4299
4300             begin
4301                if Present (AS) and then Is_Constrained (AS) then
4302                   P_Entity := AS;
4303
4304                --  If we have an unconstrained type, cannot fold
4305
4306                else
4307                   Check_Expressions;
4308                   return;
4309                end if;
4310             end;
4311
4312          --  For Size, give size of object if available, otherwise we
4313          --  cannot fold Size.
4314
4315          elsif Id = Attribute_Size then
4316             if Is_Entity_Name (P)
4317               and then Known_Esize (Entity (P))
4318             then
4319                Compile_Time_Known_Attribute (N, Esize (Entity (P)));
4320                return;
4321
4322             else
4323                Check_Expressions;
4324                return;
4325             end if;
4326
4327          --  For Alignment, give size of object if available, otherwise we
4328          --  cannot fold Alignment.
4329
4330          elsif Id = Attribute_Alignment then
4331             if Is_Entity_Name (P)
4332               and then Known_Alignment (Entity (P))
4333             then
4334                Fold_Uint (N, Alignment (Entity (P)), False);
4335                return;
4336
4337             else
4338                Check_Expressions;
4339                return;
4340             end if;
4341
4342          --  No other attributes for objects are folded
4343
4344          else
4345             Check_Expressions;
4346             return;
4347          end if;
4348
4349       --  Cases where P is not an object. Cannot do anything if P is
4350       --  not the name of an entity.
4351
4352       elsif not Is_Entity_Name (P) then
4353          Check_Expressions;
4354          return;
4355
4356       --  Otherwise get prefix entity
4357
4358       else
4359          P_Entity := Entity (P);
4360       end if;
4361
4362       --  At this stage P_Entity is the entity to which the attribute
4363       --  is to be applied. This is usually simply the entity of the
4364       --  prefix, except in some cases of attributes for objects, where
4365       --  as described above, we apply the attribute to the object type.
4366
4367       --  First foldable possibility is a scalar or array type (RM 4.9(7))
4368       --  that is not generic (generic types are eliminated by RM 4.9(25)).
4369       --  Note we allow non-static non-generic types at this stage as further
4370       --  described below.
4371
4372       if Is_Type (P_Entity)
4373         and then (Is_Scalar_Type (P_Entity) or Is_Array_Type (P_Entity))
4374         and then (not Is_Generic_Type (P_Entity))
4375       then
4376          P_Type := P_Entity;
4377
4378       --  Second foldable possibility is an array object (RM 4.9(8))
4379
4380       elsif (Ekind (P_Entity) = E_Variable
4381                or else
4382              Ekind (P_Entity) = E_Constant)
4383         and then Is_Array_Type (Etype (P_Entity))
4384         and then (not Is_Generic_Type (Etype (P_Entity)))
4385       then
4386          P_Type := Etype (P_Entity);
4387
4388          --  If the entity is an array constant with an unconstrained
4389          --  nominal subtype then get the type from the initial value.
4390          --  If the value has been expanded into assignments, the expression
4391          --  is not present and the attribute reference remains dynamic.
4392          --  We could do better here and retrieve the type ???
4393
4394          if Ekind (P_Entity) = E_Constant
4395            and then not Is_Constrained (P_Type)
4396          then
4397             if No (Constant_Value (P_Entity)) then
4398                return;
4399             else
4400                P_Type := Etype (Constant_Value (P_Entity));
4401             end if;
4402          end if;
4403
4404       --  Definite must be folded if the prefix is not a generic type,
4405       --  that is to say if we are within an instantiation. Same processing
4406       --  applies to the GNAT attributes Has_Discriminants, Type_Class,
4407       --  and Unconstrained_Array.
4408
4409       elsif (Id = Attribute_Definite
4410                or else
4411              Id = Attribute_Has_Discriminants
4412                or else
4413              Id = Attribute_Type_Class
4414                or else
4415              Id = Attribute_Unconstrained_Array)
4416         and then not Is_Generic_Type (P_Entity)
4417       then
4418          P_Type := P_Entity;
4419
4420       --  We can fold 'Size applied to a type if the size is known
4421       --  (as happens for a size from an attribute definition clause).
4422       --  At this stage, this can happen only for types (e.g. record
4423       --  types) for which the size is always non-static. We exclude
4424       --  generic types from consideration (since they have bogus
4425       --  sizes set within templates).
4426
4427       elsif Id = Attribute_Size
4428         and then Is_Type (P_Entity)
4429         and then (not Is_Generic_Type (P_Entity))
4430         and then Known_Static_RM_Size (P_Entity)
4431       then
4432          Compile_Time_Known_Attribute (N, RM_Size (P_Entity));
4433          return;
4434
4435       --  We can fold 'Alignment applied to a type if the alignment is known
4436       --  (as happens for an alignment from an attribute definition clause).
4437       --  At this stage, this can happen only for types (e.g. record
4438       --  types) for which the size is always non-static. We exclude
4439       --  generic types from consideration (since they have bogus
4440       --  sizes set within templates).
4441
4442       elsif Id = Attribute_Alignment
4443         and then Is_Type (P_Entity)
4444         and then (not Is_Generic_Type (P_Entity))
4445         and then Known_Alignment (P_Entity)
4446       then
4447          Compile_Time_Known_Attribute (N, Alignment (P_Entity));
4448          return;
4449
4450       --  No other cases are foldable (they certainly aren't static, and at
4451       --  the moment we don't try to fold any cases other than these three).
4452
4453       else
4454          Check_Expressions;
4455          return;
4456       end if;
4457
4458       --  If either attribute or the prefix is Any_Type, then propagate
4459       --  Any_Type to the result and don't do anything else at all.
4460
4461       if P_Type = Any_Type
4462         or else (Present (E1) and then Etype (E1) = Any_Type)
4463         or else (Present (E2) and then Etype (E2) = Any_Type)
4464       then
4465          Set_Etype (N, Any_Type);
4466          return;
4467       end if;
4468
4469       --  Scalar subtype case. We have not yet enforced the static requirement
4470       --  of (RM 4.9(7)) and we don't intend to just yet, since there are cases
4471       --  of non-static attribute references (e.g. S'Digits for a non-static
4472       --  floating-point type, which we can compute at compile time).
4473
4474       --  Note: this folding of non-static attributes is not simply a case of
4475       --  optimization. For many of the attributes affected, Gigi cannot handle
4476       --  the attribute and depends on the front end having folded them away.
4477
4478       --  Note: although we don't require staticness at this stage, we do set
4479       --  the Static variable to record the staticness, for easy reference by
4480       --  those attributes where it matters (e.g. Succ and Pred), and also to
4481       --  be used to ensure that non-static folded things are not marked as
4482       --  being static (a check that is done right at the end).
4483
4484       P_Root_Type := Root_Type (P_Type);
4485       P_Base_Type := Base_Type (P_Type);
4486
4487       --  If the root type or base type is generic, then we cannot fold. This
4488       --  test is needed because subtypes of generic types are not always
4489       --  marked as being generic themselves (which seems odd???)
4490
4491       if Is_Generic_Type (P_Root_Type)
4492         or else Is_Generic_Type (P_Base_Type)
4493       then
4494          return;
4495       end if;
4496
4497       if Is_Scalar_Type (P_Type) then
4498          Static := Is_OK_Static_Subtype (P_Type);
4499
4500       --  Array case. We enforce the constrained requirement of (RM 4.9(7-8))
4501       --  since we can't do anything with unconstrained arrays. In addition,
4502       --  only the First, Last and Length attributes are possibly static.
4503       --  In addition Component_Size is possibly foldable, even though it
4504       --  can never be static.
4505
4506       --  Definite, Has_Discriminants, Type_Class and Unconstrained_Array are
4507       --  again exceptions, because they apply as well to unconstrained types.
4508
4509       elsif Id = Attribute_Definite
4510               or else
4511             Id = Attribute_Has_Discriminants
4512               or else
4513             Id = Attribute_Type_Class
4514               or else
4515             Id = Attribute_Unconstrained_Array
4516       then
4517          Static := False;
4518
4519       else
4520          if not Is_Constrained (P_Type)
4521            or else (Id /= Attribute_Component_Size and then
4522                     Id /= Attribute_First          and then
4523                     Id /= Attribute_Last           and then
4524                     Id /= Attribute_Length)
4525          then
4526             Check_Expressions;
4527             return;
4528          end if;
4529
4530          --  The rules in (RM 4.9(7,8)) require a static array, but as in the
4531          --  scalar case, we hold off on enforcing staticness, since there are
4532          --  cases which we can fold at compile time even though they are not
4533          --  static (e.g. 'Length applied to a static index, even though other
4534          --  non-static indexes make the array type non-static). This is only
4535          --  an optimization, but it falls out essentially free, so why not.
4536          --  Again we compute the variable Static for easy reference later
4537          --  (note that no array attributes are static in Ada 83).
4538
4539          Static := Ada_95;
4540
4541          declare
4542             N : Node_Id;
4543
4544          begin
4545             N := First_Index (P_Type);
4546             while Present (N) loop
4547                Static := Static and then Is_Static_Subtype (Etype (N));
4548
4549                --  If however the index type is generic, attributes cannot
4550                --  be folded.
4551
4552                if Is_Generic_Type (Etype (N))
4553                  and then Id /= Attribute_Component_Size
4554                then
4555                   return;
4556                end if;
4557
4558                Next_Index (N);
4559             end loop;
4560          end;
4561       end if;
4562
4563       --  Check any expressions that are present. Note that these expressions,
4564       --  depending on the particular attribute type, are either part of the
4565       --  attribute designator, or they are arguments in a case where the
4566       --  attribute reference returns a function. In the latter case, the
4567       --  rule in (RM 4.9(22)) applies and in particular requires the type
4568       --  of the expressions to be scalar in order for the attribute to be
4569       --  considered to be static.
4570
4571       declare
4572          E : Node_Id;
4573
4574       begin
4575          E := E1;
4576          while Present (E) loop
4577
4578             --  If expression is not static, then the attribute reference
4579             --  result certainly cannot be static.
4580
4581             if not Is_Static_Expression (E) then
4582                Static := False;
4583             end if;
4584
4585             --  If the result is not known at compile time, or is not of
4586             --  a scalar type, then the result is definitely not static,
4587             --  so we can quit now.
4588
4589             if not Compile_Time_Known_Value (E)
4590               or else not Is_Scalar_Type (Etype (E))
4591             then
4592                --  An odd special case, if this is a Pos attribute, this
4593                --  is where we need to apply a range check since it does
4594                --  not get done anywhere else.
4595
4596                if Id = Attribute_Pos then
4597                   if Is_Integer_Type (Etype (E)) then
4598                      Apply_Range_Check (E, Etype (N));
4599                   end if;
4600                end if;
4601
4602                Check_Expressions;
4603                return;
4604
4605             --  If the expression raises a constraint error, then so does
4606             --  the attribute reference. We keep going in this case because
4607             --  we are still interested in whether the attribute reference
4608             --  is static even if it is not static.
4609
4610             elsif Raises_Constraint_Error (E) then
4611                Set_Raises_Constraint_Error (N);
4612             end if;
4613
4614             Next (E);
4615          end loop;
4616
4617          if Raises_Constraint_Error (Prefix (N)) then
4618             return;
4619          end if;
4620       end;
4621
4622       --  Deal with the case of a static attribute reference that raises
4623       --  constraint error. The Raises_Constraint_Error flag will already
4624       --  have been set, and the Static flag shows whether the attribute
4625       --  reference is static. In any case we certainly can't fold such an
4626       --  attribute reference.
4627
4628       --  Note that the rewriting of the attribute node with the constraint
4629       --  error node is essential in this case, because otherwise Gigi might
4630       --  blow up on one of the attributes it never expects to see.
4631
4632       --  The constraint_error node must have the type imposed by the context,
4633       --  to avoid spurious errors in the enclosing expression.
4634
4635       if Raises_Constraint_Error (N) then
4636          CE_Node :=
4637            Make_Raise_Constraint_Error (Sloc (N),
4638              Reason => CE_Range_Check_Failed);
4639          Set_Etype (CE_Node, Etype (N));
4640          Set_Raises_Constraint_Error (CE_Node);
4641          Check_Expressions;
4642          Rewrite (N, Relocate_Node (CE_Node));
4643          Set_Is_Static_Expression (N, Static);
4644          return;
4645       end if;
4646
4647       --  At this point we have a potentially foldable attribute reference.
4648       --  If Static is set, then the attribute reference definitely obeys
4649       --  the requirements in (RM 4.9(7,8,22)), and it definitely can be
4650       --  folded. If Static is not set, then the attribute may or may not
4651       --  be foldable, and the individual attribute processing routines
4652       --  test Static as required in cases where it makes a difference.
4653
4654       --  In the case where Static is not set, we do know that all the
4655       --  expressions present are at least known at compile time (we
4656       --  assumed above that if this was not the case, then there was
4657       --  no hope of static evaluation). However, we did not require
4658       --  that the bounds of the prefix type be compile time known,
4659       --  let alone static). That's because there are many attributes
4660       --  that can be computed at compile time on non-static subtypes,
4661       --  even though such references are not static expressions.
4662
4663       case Id is
4664
4665       --------------
4666       -- Adjacent --
4667       --------------
4668
4669       when Attribute_Adjacent =>
4670          Fold_Ureal (N,
4671            Eval_Fat.Adjacent
4672              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
4673
4674       ---------
4675       -- Aft --
4676       ---------
4677
4678       when Attribute_Aft =>
4679          Fold_Uint (N, UI_From_Int (Aft_Value), True);
4680
4681       ---------------
4682       -- Alignment --
4683       ---------------
4684
4685       when Attribute_Alignment => Alignment_Block : declare
4686          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
4687
4688       begin
4689          --  Fold if alignment is set and not otherwise
4690
4691          if Known_Alignment (P_TypeA) then
4692             Fold_Uint (N, Alignment (P_TypeA), Is_Discrete_Type (P_TypeA));
4693          end if;
4694       end Alignment_Block;
4695
4696       ---------------
4697       -- AST_Entry --
4698       ---------------
4699
4700       --  Can only be folded in No_Ast_Handler case
4701
4702       when Attribute_AST_Entry =>
4703          if not Is_AST_Entry (P_Entity) then
4704             Rewrite (N,
4705               New_Occurrence_Of (RTE (RE_No_AST_Handler), Loc));
4706          else
4707             null;
4708          end if;
4709
4710       ---------
4711       -- Bit --
4712       ---------
4713
4714       --  Bit can never be folded
4715
4716       when Attribute_Bit =>
4717          null;
4718
4719       ------------------
4720       -- Body_Version --
4721       ------------------
4722
4723       --  Body_version can never be static
4724
4725       when Attribute_Body_Version =>
4726          null;
4727
4728       -------------
4729       -- Ceiling --
4730       -------------
4731
4732       when Attribute_Ceiling =>
4733          Fold_Ureal (N,
4734            Eval_Fat.Ceiling (P_Root_Type, Expr_Value_R (E1)), Static);
4735
4736       --------------------
4737       -- Component_Size --
4738       --------------------
4739
4740       when Attribute_Component_Size =>
4741          if Known_Static_Component_Size (P_Type) then
4742             Fold_Uint (N, Component_Size (P_Type), False);
4743          end if;
4744
4745       -------------
4746       -- Compose --
4747       -------------
4748
4749       when Attribute_Compose =>
4750          Fold_Ureal (N,
4751            Eval_Fat.Compose
4752              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)),
4753               Static);
4754
4755       -----------------
4756       -- Constrained --
4757       -----------------
4758
4759       --  Constrained is never folded for now, there may be cases that
4760       --  could be handled at compile time. to be looked at later.
4761
4762       when Attribute_Constrained =>
4763          null;
4764
4765       ---------------
4766       -- Copy_Sign --
4767       ---------------
4768
4769       when Attribute_Copy_Sign =>
4770          Fold_Ureal (N,
4771            Eval_Fat.Copy_Sign
4772              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
4773
4774       -----------
4775       -- Delta --
4776       -----------
4777
4778       when Attribute_Delta =>
4779          Fold_Ureal (N, Delta_Value (P_Type), True);
4780
4781       --------------
4782       -- Definite --
4783       --------------
4784
4785       when Attribute_Definite =>
4786          declare
4787             Result : Node_Id;
4788
4789          begin
4790             if Is_Indefinite_Subtype (P_Entity) then
4791                Result := New_Occurrence_Of (Standard_False, Loc);
4792             else
4793                Result := New_Occurrence_Of (Standard_True, Loc);
4794             end if;
4795
4796             Rewrite (N, Result);
4797             Analyze_And_Resolve (N, Standard_Boolean);
4798          end;
4799
4800       ------------
4801       -- Denorm --
4802       ------------
4803
4804       when Attribute_Denorm =>
4805          Fold_Uint
4806            (N, UI_From_Int (Boolean'Pos (Denorm_On_Target)), True);
4807
4808       ------------
4809       -- Digits --
4810       ------------
4811
4812       when Attribute_Digits =>
4813          Fold_Uint (N, Digits_Value (P_Type), True);
4814
4815       ----------
4816       -- Emax --
4817       ----------
4818
4819       when Attribute_Emax =>
4820
4821          --  Ada 83 attribute is defined as (RM83 3.5.8)
4822
4823          --    T'Emax = 4 * T'Mantissa
4824
4825          Fold_Uint (N, 4 * Mantissa, True);
4826
4827       --------------
4828       -- Enum_Rep --
4829       --------------
4830
4831       when Attribute_Enum_Rep =>
4832
4833          --  For an enumeration type with a non-standard representation
4834          --  use the Enumeration_Rep field of the proper constant. Note
4835          --  that this would not work for types Character/Wide_Character,
4836          --  since no real entities are created for the enumeration
4837          --  literals, but that does not matter since these two types
4838          --  do not have non-standard representations anyway.
4839
4840          if Is_Enumeration_Type (P_Type)
4841            and then Has_Non_Standard_Rep (P_Type)
4842          then
4843             Fold_Uint (N, Enumeration_Rep (Expr_Value_E (E1)), Static);
4844
4845          --  For enumeration types with standard representations and all
4846          --  other cases (i.e. all integer and modular types), Enum_Rep
4847          --  is equivalent to Pos.
4848
4849          else
4850             Fold_Uint (N, Expr_Value (E1), Static);
4851          end if;
4852
4853       -------------
4854       -- Epsilon --
4855       -------------
4856
4857       when Attribute_Epsilon =>
4858
4859          --  Ada 83 attribute is defined as (RM83 3.5.8)
4860
4861          --    T'Epsilon = 2.0**(1 - T'Mantissa)
4862
4863          Fold_Ureal (N, Ureal_2 ** (1 - Mantissa), True);
4864
4865       --------------
4866       -- Exponent --
4867       --------------
4868
4869       when Attribute_Exponent =>
4870          Fold_Uint (N,
4871            Eval_Fat.Exponent (P_Root_Type, Expr_Value_R (E1)), Static);
4872
4873       -----------
4874       -- First --
4875       -----------
4876
4877       when Attribute_First => First_Attr :
4878       begin
4879          Set_Bounds;
4880
4881          if Compile_Time_Known_Value (Lo_Bound) then
4882             if Is_Real_Type (P_Type) then
4883                Fold_Ureal (N, Expr_Value_R (Lo_Bound), Static);
4884             else
4885                Fold_Uint  (N, Expr_Value (Lo_Bound), Static);
4886             end if;
4887          end if;
4888       end First_Attr;
4889
4890       -----------------
4891       -- Fixed_Value --
4892       -----------------
4893
4894       when Attribute_Fixed_Value =>
4895          null;
4896
4897       -----------
4898       -- Floor --
4899       -----------
4900
4901       when Attribute_Floor =>
4902          Fold_Ureal (N,
4903            Eval_Fat.Floor (P_Root_Type, Expr_Value_R (E1)), Static);
4904
4905       ----------
4906       -- Fore --
4907       ----------
4908
4909       when Attribute_Fore =>
4910          if Compile_Time_Known_Bounds (P_Type) then
4911             Fold_Uint (N, UI_From_Int (Fore_Value), Static);
4912          end if;
4913
4914       --------------
4915       -- Fraction --
4916       --------------
4917
4918       when Attribute_Fraction =>
4919          Fold_Ureal (N,
4920            Eval_Fat.Fraction (P_Root_Type, Expr_Value_R (E1)), Static);
4921
4922       -----------------------
4923       -- Has_Discriminants --
4924       -----------------------
4925
4926       when Attribute_Has_Discriminants =>
4927          declare
4928             Result : Node_Id;
4929
4930          begin
4931             if Has_Discriminants (P_Entity) then
4932                Result := New_Occurrence_Of (Standard_True, Loc);
4933             else
4934                Result := New_Occurrence_Of (Standard_False, Loc);
4935             end if;
4936
4937             Rewrite (N, Result);
4938             Analyze_And_Resolve (N, Standard_Boolean);
4939          end;
4940
4941       --------------
4942       -- Identity --
4943       --------------
4944
4945       when Attribute_Identity =>
4946          null;
4947
4948       -----------
4949       -- Image --
4950       -----------
4951
4952       --  Image is a scalar attribute, but is never static, because it is
4953       --  not a static function (having a non-scalar argument (RM 4.9(22))
4954
4955       when Attribute_Image =>
4956          null;
4957
4958       ---------
4959       -- Img --
4960       ---------
4961
4962       --  Img is a scalar attribute, but is never static, because it is
4963       --  not a static function (having a non-scalar argument (RM 4.9(22))
4964
4965       when Attribute_Img =>
4966          null;
4967
4968       -------------------
4969       -- Integer_Value --
4970       -------------------
4971
4972       when Attribute_Integer_Value =>
4973          null;
4974
4975       -----------
4976       -- Large --
4977       -----------
4978
4979       when Attribute_Large =>
4980
4981          --  For fixed-point, we use the identity:
4982
4983          --    T'Large = (2.0**T'Mantissa - 1.0) * T'Small
4984
4985          if Is_Fixed_Point_Type (P_Type) then
4986             Rewrite (N,
4987               Make_Op_Multiply (Loc,
4988                 Left_Opnd =>
4989                   Make_Op_Subtract (Loc,
4990                     Left_Opnd =>
4991                       Make_Op_Expon (Loc,
4992                         Left_Opnd =>
4993                           Make_Real_Literal (Loc, Ureal_2),
4994                         Right_Opnd =>
4995                           Make_Attribute_Reference (Loc,
4996                             Prefix => P,
4997                             Attribute_Name => Name_Mantissa)),
4998                     Right_Opnd => Make_Real_Literal (Loc, Ureal_1)),
4999
5000                 Right_Opnd =>
5001                   Make_Real_Literal (Loc, Small_Value (Entity (P)))));
5002
5003             Analyze_And_Resolve (N, C_Type);
5004
5005          --  Floating-point (Ada 83 compatibility)
5006
5007          else
5008             --  Ada 83 attribute is defined as (RM83 3.5.8)
5009
5010             --    T'Large = 2.0**T'Emax * (1.0 - 2.0**(-T'Mantissa))
5011
5012             --  where
5013
5014             --    T'Emax = 4 * T'Mantissa
5015
5016             Fold_Ureal (N,
5017               Ureal_2 ** (4 * Mantissa) * (Ureal_1 - Ureal_2 ** (-Mantissa)),
5018               True);
5019          end if;
5020
5021       ----------
5022       -- Last --
5023       ----------
5024
5025       when Attribute_Last => Last :
5026       begin
5027          Set_Bounds;
5028
5029          if Compile_Time_Known_Value (Hi_Bound) then
5030             if Is_Real_Type (P_Type) then
5031                Fold_Ureal (N, Expr_Value_R (Hi_Bound), Static);
5032             else
5033                Fold_Uint  (N, Expr_Value (Hi_Bound), Static);
5034             end if;
5035          end if;
5036       end Last;
5037
5038       ------------------
5039       -- Leading_Part --
5040       ------------------
5041
5042       when Attribute_Leading_Part =>
5043          Fold_Ureal (N,
5044            Eval_Fat.Leading_Part
5045              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5046
5047       ------------
5048       -- Length --
5049       ------------
5050
5051       when Attribute_Length => Length : declare
5052          Ind : Node_Id;
5053
5054       begin
5055          --  In the case of a generic index type, the bounds may
5056          --  appear static but the computation is not meaningful,
5057          --  and may generate a spurious warning.
5058
5059          Ind := First_Index (P_Type);
5060
5061          while Present (Ind) loop
5062             if Is_Generic_Type (Etype (Ind)) then
5063                return;
5064             end if;
5065
5066             Next_Index (Ind);
5067          end loop;
5068
5069          Set_Bounds;
5070
5071          if Compile_Time_Known_Value (Lo_Bound)
5072            and then Compile_Time_Known_Value (Hi_Bound)
5073          then
5074             Fold_Uint (N,
5075               UI_Max (0, 1 + (Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound))),
5076               True);
5077          end if;
5078       end Length;
5079
5080       -------------
5081       -- Machine --
5082       -------------
5083
5084       when Attribute_Machine =>
5085          Fold_Ureal (N,
5086            Eval_Fat.Machine
5087              (P_Root_Type, Expr_Value_R (E1), Eval_Fat.Round, N),
5088            Static);
5089
5090       ------------------
5091       -- Machine_Emax --
5092       ------------------
5093
5094       when Attribute_Machine_Emax =>
5095          Float_Attribute_Universal_Integer (
5096            IEEES_Machine_Emax,
5097            IEEEL_Machine_Emax,
5098            IEEEX_Machine_Emax,
5099            VAXFF_Machine_Emax,
5100            VAXDF_Machine_Emax,
5101            VAXGF_Machine_Emax,
5102            AAMPS_Machine_Emax,
5103            AAMPL_Machine_Emax);
5104
5105       ------------------
5106       -- Machine_Emin --
5107       ------------------
5108
5109       when Attribute_Machine_Emin =>
5110          Float_Attribute_Universal_Integer (
5111            IEEES_Machine_Emin,
5112            IEEEL_Machine_Emin,
5113            IEEEX_Machine_Emin,
5114            VAXFF_Machine_Emin,
5115            VAXDF_Machine_Emin,
5116            VAXGF_Machine_Emin,
5117            AAMPS_Machine_Emin,
5118            AAMPL_Machine_Emin);
5119
5120       ----------------------
5121       -- Machine_Mantissa --
5122       ----------------------
5123
5124       when Attribute_Machine_Mantissa =>
5125          Float_Attribute_Universal_Integer (
5126            IEEES_Machine_Mantissa,
5127            IEEEL_Machine_Mantissa,
5128            IEEEX_Machine_Mantissa,
5129            VAXFF_Machine_Mantissa,
5130            VAXDF_Machine_Mantissa,
5131            VAXGF_Machine_Mantissa,
5132            AAMPS_Machine_Mantissa,
5133            AAMPL_Machine_Mantissa);
5134
5135       -----------------------
5136       -- Machine_Overflows --
5137       -----------------------
5138
5139       when Attribute_Machine_Overflows =>
5140
5141          --  Always true for fixed-point
5142
5143          if Is_Fixed_Point_Type (P_Type) then
5144             Fold_Uint (N, True_Value, True);
5145
5146          --  Floating point case
5147
5148          else
5149             Fold_Uint (N,
5150               UI_From_Int (Boolean'Pos (Machine_Overflows_On_Target)),
5151               True);
5152          end if;
5153
5154       -------------------
5155       -- Machine_Radix --
5156       -------------------
5157
5158       when Attribute_Machine_Radix =>
5159          if Is_Fixed_Point_Type (P_Type) then
5160             if Is_Decimal_Fixed_Point_Type (P_Type)
5161               and then Machine_Radix_10 (P_Type)
5162             then
5163                Fold_Uint (N, Uint_10, True);
5164             else
5165                Fold_Uint (N, Uint_2, True);
5166             end if;
5167
5168          --  All floating-point type always have radix 2
5169
5170          else
5171             Fold_Uint (N, Uint_2, True);
5172          end if;
5173
5174       --------------------
5175       -- Machine_Rounds --
5176       --------------------
5177
5178       when Attribute_Machine_Rounds =>
5179
5180          --  Always False for fixed-point
5181
5182          if Is_Fixed_Point_Type (P_Type) then
5183             Fold_Uint (N, False_Value, True);
5184
5185          --  Else yield proper floating-point result
5186
5187          else
5188             Fold_Uint
5189               (N, UI_From_Int (Boolean'Pos (Machine_Rounds_On_Target)), True);
5190          end if;
5191
5192       ------------------
5193       -- Machine_Size --
5194       ------------------
5195
5196       --  Note: Machine_Size is identical to Object_Size
5197
5198       when Attribute_Machine_Size => Machine_Size : declare
5199          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5200
5201       begin
5202          if Known_Esize (P_TypeA) then
5203             Fold_Uint (N, Esize (P_TypeA), True);
5204          end if;
5205       end Machine_Size;
5206
5207       --------------
5208       -- Mantissa --
5209       --------------
5210
5211       when Attribute_Mantissa =>
5212
5213          --  Fixed-point mantissa
5214
5215          if Is_Fixed_Point_Type (P_Type) then
5216
5217             --  Compile time foldable case
5218
5219             if Compile_Time_Known_Value (Type_Low_Bound  (P_Type))
5220                  and then
5221                Compile_Time_Known_Value (Type_High_Bound (P_Type))
5222             then
5223                --  The calculation of the obsolete Ada 83 attribute Mantissa
5224                --  is annoying, because of AI00143, quoted here:
5225
5226                --  !question 84-01-10
5227
5228                --  Consider the model numbers for F:
5229
5230                --         type F is delta 1.0 range -7.0 .. 8.0;
5231
5232                --  The wording requires that F'MANTISSA be the SMALLEST
5233                --  integer number for which each  bound  of the specified
5234                --  range is either a model number or lies at most small
5235                --  distant from a model number. This means F'MANTISSA
5236                --  is required to be 3 since the range  -7.0 .. 7.0 fits
5237                --  in 3 signed bits, and 8 is "at most" 1.0 from a model
5238                --  number, namely, 7. Is this analysis correct? Note that
5239                --  this implies the upper bound of the range is not
5240                --  represented as a model number.
5241
5242                --  !response 84-03-17
5243
5244                --  The analysis is correct. The upper and lower bounds for
5245                --  a fixed  point type can lie outside the range of model
5246                --  numbers.
5247
5248                declare
5249                   Siz     : Uint;
5250                   LBound  : Ureal;
5251                   UBound  : Ureal;
5252                   Bound   : Ureal;
5253                   Max_Man : Uint;
5254
5255                begin
5256                   LBound  := Expr_Value_R (Type_Low_Bound  (P_Type));
5257                   UBound  := Expr_Value_R (Type_High_Bound (P_Type));
5258                   Bound   := UR_Max (UR_Abs (LBound), UR_Abs (UBound));
5259                   Max_Man := UR_Trunc (Bound / Small_Value (P_Type));
5260
5261                   --  If the Bound is exactly a model number, i.e. a multiple
5262                   --  of Small, then we back it off by one to get the integer
5263                   --  value that must be representable.
5264
5265                   if Small_Value (P_Type) * Max_Man = Bound then
5266                      Max_Man := Max_Man - 1;
5267                   end if;
5268
5269                   --  Now find corresponding size = Mantissa value
5270
5271                   Siz := Uint_0;
5272                   while 2 ** Siz < Max_Man loop
5273                      Siz := Siz + 1;
5274                   end loop;
5275
5276                   Fold_Uint (N, Siz, True);
5277                end;
5278
5279             else
5280                --  The case of dynamic bounds cannot be evaluated at compile
5281                --  time. Instead we use a runtime routine (see Exp_Attr).
5282
5283                null;
5284             end if;
5285
5286          --  Floating-point Mantissa
5287
5288          else
5289             Fold_Uint (N, Mantissa, True);
5290          end if;
5291
5292       ---------
5293       -- Max --
5294       ---------
5295
5296       when Attribute_Max => Max :
5297       begin
5298          if Is_Real_Type (P_Type) then
5299             Fold_Ureal
5300               (N, UR_Max (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5301          else
5302             Fold_Uint (N, UI_Max (Expr_Value (E1), Expr_Value (E2)), Static);
5303          end if;
5304       end Max;
5305
5306       ----------------------------------
5307       -- Max_Size_In_Storage_Elements --
5308       ----------------------------------
5309
5310       --  Max_Size_In_Storage_Elements is simply the Size rounded up to a
5311       --  Storage_Unit boundary. We can fold any cases for which the size
5312       --  is known by the front end.
5313
5314       when Attribute_Max_Size_In_Storage_Elements =>
5315          if Known_Esize (P_Type) then
5316             Fold_Uint (N,
5317               (Esize (P_Type) + System_Storage_Unit - 1) /
5318                                           System_Storage_Unit,
5319                Static);
5320          end if;
5321
5322       --------------------
5323       -- Mechanism_Code --
5324       --------------------
5325
5326       when Attribute_Mechanism_Code =>
5327          declare
5328             Val    : Int;
5329             Formal : Entity_Id;
5330             Mech   : Mechanism_Type;
5331
5332          begin
5333             if No (E1) then
5334                Mech := Mechanism (P_Entity);
5335
5336             else
5337                Val := UI_To_Int (Expr_Value (E1));
5338
5339                Formal := First_Formal (P_Entity);
5340                for J in 1 .. Val - 1 loop
5341                   Next_Formal (Formal);
5342                end loop;
5343                Mech := Mechanism (Formal);
5344             end if;
5345
5346             if Mech < 0 then
5347                Fold_Uint (N, UI_From_Int (Int (-Mech)), True);
5348             end if;
5349          end;
5350
5351       ---------
5352       -- Min --
5353       ---------
5354
5355       when Attribute_Min => Min :
5356       begin
5357          if Is_Real_Type (P_Type) then
5358             Fold_Ureal
5359               (N, UR_Min (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5360          else
5361             Fold_Uint (N, UI_Min (Expr_Value (E1), Expr_Value (E2)), Static);
5362          end if;
5363       end Min;
5364
5365       -----------
5366       -- Model --
5367       -----------
5368
5369       when Attribute_Model =>
5370          Fold_Ureal (N,
5371            Eval_Fat.Model (P_Root_Type, Expr_Value_R (E1)), Static);
5372
5373       ----------------
5374       -- Model_Emin --
5375       ----------------
5376
5377       when Attribute_Model_Emin =>
5378          Float_Attribute_Universal_Integer (
5379            IEEES_Model_Emin,
5380            IEEEL_Model_Emin,
5381            IEEEX_Model_Emin,
5382            VAXFF_Model_Emin,
5383            VAXDF_Model_Emin,
5384            VAXGF_Model_Emin,
5385            AAMPS_Model_Emin,
5386            AAMPL_Model_Emin);
5387
5388       -------------------
5389       -- Model_Epsilon --
5390       -------------------
5391
5392       when Attribute_Model_Epsilon =>
5393          Float_Attribute_Universal_Real (
5394            IEEES_Model_Epsilon'Universal_Literal_String,
5395            IEEEL_Model_Epsilon'Universal_Literal_String,
5396            IEEEX_Model_Epsilon'Universal_Literal_String,
5397            VAXFF_Model_Epsilon'Universal_Literal_String,
5398            VAXDF_Model_Epsilon'Universal_Literal_String,
5399            VAXGF_Model_Epsilon'Universal_Literal_String,
5400            AAMPS_Model_Epsilon'Universal_Literal_String,
5401            AAMPL_Model_Epsilon'Universal_Literal_String);
5402
5403       --------------------
5404       -- Model_Mantissa --
5405       --------------------
5406
5407       when Attribute_Model_Mantissa =>
5408          Float_Attribute_Universal_Integer (
5409            IEEES_Model_Mantissa,
5410            IEEEL_Model_Mantissa,
5411            IEEEX_Model_Mantissa,
5412            VAXFF_Model_Mantissa,
5413            VAXDF_Model_Mantissa,
5414            VAXGF_Model_Mantissa,
5415            AAMPS_Model_Mantissa,
5416            AAMPL_Model_Mantissa);
5417
5418       -----------------
5419       -- Model_Small --
5420       -----------------
5421
5422       when Attribute_Model_Small =>
5423          Float_Attribute_Universal_Real (
5424            IEEES_Model_Small'Universal_Literal_String,
5425            IEEEL_Model_Small'Universal_Literal_String,
5426            IEEEX_Model_Small'Universal_Literal_String,
5427            VAXFF_Model_Small'Universal_Literal_String,
5428            VAXDF_Model_Small'Universal_Literal_String,
5429            VAXGF_Model_Small'Universal_Literal_String,
5430            AAMPS_Model_Small'Universal_Literal_String,
5431            AAMPL_Model_Small'Universal_Literal_String);
5432
5433       -------------
5434       -- Modulus --
5435       -------------
5436
5437       when Attribute_Modulus =>
5438          Fold_Uint (N, Modulus (P_Type), True);
5439
5440       --------------------
5441       -- Null_Parameter --
5442       --------------------
5443
5444       --  Cannot fold, we know the value sort of, but the whole point is
5445       --  that there is no way to talk about this imaginary value except
5446       --  by using the attribute, so we leave it the way it is.
5447
5448       when Attribute_Null_Parameter =>
5449          null;
5450
5451       -----------------
5452       -- Object_Size --
5453       -----------------
5454
5455       --  The Object_Size attribute for a type returns the Esize of the
5456       --  type and can be folded if this value is known.
5457
5458       when Attribute_Object_Size => Object_Size : declare
5459          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5460
5461       begin
5462          if Known_Esize (P_TypeA) then
5463             Fold_Uint (N, Esize (P_TypeA), True);
5464          end if;
5465       end Object_Size;
5466
5467       -------------------------
5468       -- Passed_By_Reference --
5469       -------------------------
5470
5471       --  Scalar types are never passed by reference
5472
5473       when Attribute_Passed_By_Reference =>
5474          Fold_Uint (N, False_Value, True);
5475
5476       ---------
5477       -- Pos --
5478       ---------
5479
5480       when Attribute_Pos =>
5481          Fold_Uint (N, Expr_Value (E1), True);
5482
5483       ----------
5484       -- Pred --
5485       ----------
5486
5487       when Attribute_Pred => Pred :
5488       begin
5489          --  Floating-point case
5490
5491          if Is_Floating_Point_Type (P_Type) then
5492             Fold_Ureal (N,
5493               Eval_Fat.Pred (P_Root_Type, Expr_Value_R (E1)), Static);
5494
5495          --  Fixed-point case
5496
5497          elsif Is_Fixed_Point_Type (P_Type) then
5498             Fold_Ureal (N,
5499               Expr_Value_R (E1) - Small_Value (P_Type), True);
5500
5501          --  Modular integer case (wraps)
5502
5503          elsif Is_Modular_Integer_Type (P_Type) then
5504             Fold_Uint (N, (Expr_Value (E1) - 1) mod Modulus (P_Type), Static);
5505
5506          --  Other scalar cases
5507
5508          else
5509             pragma Assert (Is_Scalar_Type (P_Type));
5510
5511             if Is_Enumeration_Type (P_Type)
5512               and then Expr_Value (E1) =
5513                          Expr_Value (Type_Low_Bound (P_Base_Type))
5514             then
5515                Apply_Compile_Time_Constraint_Error
5516                  (N, "Pred of `&''First`",
5517                   CE_Overflow_Check_Failed,
5518                   Ent  => P_Base_Type,
5519                   Warn => not Static);
5520
5521                Check_Expressions;
5522                return;
5523             end if;
5524
5525             Fold_Uint (N, Expr_Value (E1) - 1, Static);
5526          end if;
5527       end Pred;
5528
5529       -----------
5530       -- Range --
5531       -----------
5532
5533       --  No processing required, because by this stage, Range has been
5534       --  replaced by First .. Last, so this branch can never be taken.
5535
5536       when Attribute_Range =>
5537          raise Program_Error;
5538
5539       ------------------
5540       -- Range_Length --
5541       ------------------
5542
5543       when Attribute_Range_Length =>
5544          Set_Bounds;
5545
5546          if Compile_Time_Known_Value (Hi_Bound)
5547            and then Compile_Time_Known_Value (Lo_Bound)
5548          then
5549             Fold_Uint (N,
5550               UI_Max
5551                 (0, Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound) + 1),
5552                  Static);
5553          end if;
5554
5555       ---------------
5556       -- Remainder --
5557       ---------------
5558
5559       when Attribute_Remainder =>
5560          Fold_Ureal (N,
5561            Eval_Fat.Remainder
5562              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)),
5563            Static);
5564
5565       -----------
5566       -- Round --
5567       -----------
5568
5569       when Attribute_Round => Round :
5570       declare
5571          Sr : Ureal;
5572          Si : Uint;
5573
5574       begin
5575          --  First we get the (exact result) in units of small
5576
5577          Sr := Expr_Value_R (E1) / Small_Value (C_Type);
5578
5579          --  Now round that exactly to an integer
5580
5581          Si := UR_To_Uint (Sr);
5582
5583          --  Finally the result is obtained by converting back to real
5584
5585          Fold_Ureal (N, Si * Small_Value (C_Type), Static);
5586       end Round;
5587
5588       --------------
5589       -- Rounding --
5590       --------------
5591
5592       when Attribute_Rounding =>
5593          Fold_Ureal (N,
5594            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
5595
5596       ---------------
5597       -- Safe_Emax --
5598       ---------------
5599
5600       when Attribute_Safe_Emax =>
5601          Float_Attribute_Universal_Integer (
5602            IEEES_Safe_Emax,
5603            IEEEL_Safe_Emax,
5604            IEEEX_Safe_Emax,
5605            VAXFF_Safe_Emax,
5606            VAXDF_Safe_Emax,
5607            VAXGF_Safe_Emax,
5608            AAMPS_Safe_Emax,
5609            AAMPL_Safe_Emax);
5610
5611       ----------------
5612       -- Safe_First --
5613       ----------------
5614
5615       when Attribute_Safe_First =>
5616          Float_Attribute_Universal_Real (
5617            IEEES_Safe_First'Universal_Literal_String,
5618            IEEEL_Safe_First'Universal_Literal_String,
5619            IEEEX_Safe_First'Universal_Literal_String,
5620            VAXFF_Safe_First'Universal_Literal_String,
5621            VAXDF_Safe_First'Universal_Literal_String,
5622            VAXGF_Safe_First'Universal_Literal_String,
5623            AAMPS_Safe_First'Universal_Literal_String,
5624            AAMPL_Safe_First'Universal_Literal_String);
5625
5626       ----------------
5627       -- Safe_Large --
5628       ----------------
5629
5630       when Attribute_Safe_Large =>
5631          if Is_Fixed_Point_Type (P_Type) then
5632             Fold_Ureal
5633               (N, Expr_Value_R (Type_High_Bound (P_Base_Type)), Static);
5634          else
5635             Float_Attribute_Universal_Real (
5636               IEEES_Safe_Large'Universal_Literal_String,
5637               IEEEL_Safe_Large'Universal_Literal_String,
5638               IEEEX_Safe_Large'Universal_Literal_String,
5639               VAXFF_Safe_Large'Universal_Literal_String,
5640               VAXDF_Safe_Large'Universal_Literal_String,
5641               VAXGF_Safe_Large'Universal_Literal_String,
5642               AAMPS_Safe_Large'Universal_Literal_String,
5643               AAMPL_Safe_Large'Universal_Literal_String);
5644          end if;
5645
5646       ---------------
5647       -- Safe_Last --
5648       ---------------
5649
5650       when Attribute_Safe_Last =>
5651          Float_Attribute_Universal_Real (
5652            IEEES_Safe_Last'Universal_Literal_String,
5653            IEEEL_Safe_Last'Universal_Literal_String,
5654            IEEEX_Safe_Last'Universal_Literal_String,
5655            VAXFF_Safe_Last'Universal_Literal_String,
5656            VAXDF_Safe_Last'Universal_Literal_String,
5657            VAXGF_Safe_Last'Universal_Literal_String,
5658            AAMPS_Safe_Last'Universal_Literal_String,
5659            AAMPL_Safe_Last'Universal_Literal_String);
5660
5661       ----------------
5662       -- Safe_Small --
5663       ----------------
5664
5665       when Attribute_Safe_Small =>
5666
5667          --  In Ada 95, the old Ada 83 attribute Safe_Small is redundant
5668          --  for fixed-point, since is the same as Small, but we implement
5669          --  it for backwards compatibility.
5670
5671          if Is_Fixed_Point_Type (P_Type) then
5672             Fold_Ureal (N, Small_Value (P_Type), Static);
5673
5674          --  Ada 83 Safe_Small for floating-point cases
5675
5676          else
5677             Float_Attribute_Universal_Real (
5678               IEEES_Safe_Small'Universal_Literal_String,
5679               IEEEL_Safe_Small'Universal_Literal_String,
5680               IEEEX_Safe_Small'Universal_Literal_String,
5681               VAXFF_Safe_Small'Universal_Literal_String,
5682               VAXDF_Safe_Small'Universal_Literal_String,
5683               VAXGF_Safe_Small'Universal_Literal_String,
5684               AAMPS_Safe_Small'Universal_Literal_String,
5685               AAMPL_Safe_Small'Universal_Literal_String);
5686          end if;
5687
5688       -----------
5689       -- Scale --
5690       -----------
5691
5692       when Attribute_Scale =>
5693          Fold_Uint (N, Scale_Value (P_Type), True);
5694
5695       -------------
5696       -- Scaling --
5697       -------------
5698
5699       when Attribute_Scaling =>
5700          Fold_Ureal (N,
5701            Eval_Fat.Scaling
5702              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5703
5704       ------------------
5705       -- Signed_Zeros --
5706       ------------------
5707
5708       when Attribute_Signed_Zeros =>
5709          Fold_Uint
5710            (N, UI_From_Int (Boolean'Pos (Signed_Zeros_On_Target)), Static);
5711
5712       ----------
5713       -- Size --
5714       ----------
5715
5716       --  Size attribute returns the RM size. All scalar types can be folded,
5717       --  as well as any types for which the size is known by the front end,
5718       --  including any type for which a size attribute is specified.
5719
5720       when Attribute_Size | Attribute_VADS_Size => Size : declare
5721          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5722
5723       begin
5724          if RM_Size (P_TypeA) /= Uint_0 then
5725
5726             --  VADS_Size case
5727
5728             if Id = Attribute_VADS_Size or else Use_VADS_Size then
5729                declare
5730                   S : constant Node_Id := Size_Clause (P_TypeA);
5731
5732                begin
5733                   --  If a size clause applies, then use the size from it.
5734                   --  This is one of the rare cases where we can use the
5735                   --  Size_Clause field for a subtype when Has_Size_Clause
5736                   --  is False. Consider:
5737
5738                   --    type x is range 1 .. 64;                         g
5739                   --    for x'size use 12;
5740                   --    subtype y is x range 0 .. 3;
5741
5742                   --  Here y has a size clause inherited from x, but normally
5743                   --  it does not apply, and y'size is 2. However, y'VADS_Size
5744                   --  is indeed 12 and not 2.
5745
5746                   if Present (S)
5747                     and then Is_OK_Static_Expression (Expression (S))
5748                   then
5749                      Fold_Uint (N, Expr_Value (Expression (S)), True);
5750
5751                   --  If no size is specified, then we simply use the object
5752                   --  size in the VADS_Size case (e.g. Natural'Size is equal
5753                   --  to Integer'Size, not one less).
5754
5755                   else
5756                      Fold_Uint (N, Esize (P_TypeA), True);
5757                   end if;
5758                end;
5759
5760             --  Normal case (Size) in which case we want the RM_Size
5761
5762             else
5763                Fold_Uint (N,
5764                  RM_Size (P_TypeA),
5765                  Static and then Is_Discrete_Type (P_TypeA));
5766             end if;
5767          end if;
5768       end Size;
5769
5770       -----------
5771       -- Small --
5772       -----------
5773
5774       when Attribute_Small =>
5775
5776          --  The floating-point case is present only for Ada 83 compatability.
5777          --  Note that strictly this is an illegal addition, since we are
5778          --  extending an Ada 95 defined attribute, but we anticipate an
5779          --  ARG ruling that will permit this.
5780
5781          if Is_Floating_Point_Type (P_Type) then
5782
5783             --  Ada 83 attribute is defined as (RM83 3.5.8)
5784
5785             --    T'Small = 2.0**(-T'Emax - 1)
5786
5787             --  where
5788
5789             --    T'Emax = 4 * T'Mantissa
5790
5791             Fold_Ureal (N, Ureal_2 ** ((-(4 * Mantissa)) - 1), Static);
5792
5793          --  Normal Ada 95 fixed-point case
5794
5795          else
5796             Fold_Ureal (N, Small_Value (P_Type), True);
5797          end if;
5798
5799       ----------
5800       -- Succ --
5801       ----------
5802
5803       when Attribute_Succ => Succ :
5804       begin
5805          --  Floating-point case
5806
5807          if Is_Floating_Point_Type (P_Type) then
5808             Fold_Ureal (N,
5809               Eval_Fat.Succ (P_Root_Type, Expr_Value_R (E1)), Static);
5810
5811          --  Fixed-point case
5812
5813          elsif Is_Fixed_Point_Type (P_Type) then
5814             Fold_Ureal (N,
5815               Expr_Value_R (E1) + Small_Value (P_Type), Static);
5816
5817          --  Modular integer case (wraps)
5818
5819          elsif Is_Modular_Integer_Type (P_Type) then
5820             Fold_Uint (N, (Expr_Value (E1) + 1) mod Modulus (P_Type), Static);
5821
5822          --  Other scalar cases
5823
5824          else
5825             pragma Assert (Is_Scalar_Type (P_Type));
5826
5827             if Is_Enumeration_Type (P_Type)
5828               and then Expr_Value (E1) =
5829                          Expr_Value (Type_High_Bound (P_Base_Type))
5830             then
5831                Apply_Compile_Time_Constraint_Error
5832                  (N, "Succ of `&''Last`",
5833                   CE_Overflow_Check_Failed,
5834                   Ent  => P_Base_Type,
5835                   Warn => not Static);
5836
5837                Check_Expressions;
5838                return;
5839             else
5840                Fold_Uint (N, Expr_Value (E1) + 1, Static);
5841             end if;
5842          end if;
5843       end Succ;
5844
5845       ----------------
5846       -- Truncation --
5847       ----------------
5848
5849       when Attribute_Truncation =>
5850          Fold_Ureal (N,
5851            Eval_Fat.Truncation (P_Root_Type, Expr_Value_R (E1)), Static);
5852
5853       ----------------
5854       -- Type_Class --
5855       ----------------
5856
5857       when Attribute_Type_Class => Type_Class : declare
5858          Typ : constant Entity_Id := Underlying_Type (P_Base_Type);
5859          Id  : RE_Id;
5860
5861       begin
5862          if Is_RTE (P_Root_Type, RE_Address) then
5863             Id := RE_Type_Class_Address;
5864
5865          elsif Is_Enumeration_Type (Typ) then
5866             Id := RE_Type_Class_Enumeration;
5867
5868          elsif Is_Integer_Type (Typ) then
5869             Id := RE_Type_Class_Integer;
5870
5871          elsif Is_Fixed_Point_Type (Typ) then
5872             Id := RE_Type_Class_Fixed_Point;
5873
5874          elsif Is_Floating_Point_Type (Typ) then
5875             Id := RE_Type_Class_Floating_Point;
5876
5877          elsif Is_Array_Type (Typ) then
5878             Id := RE_Type_Class_Array;
5879
5880          elsif Is_Record_Type (Typ) then
5881             Id := RE_Type_Class_Record;
5882
5883          elsif Is_Access_Type (Typ) then
5884             Id := RE_Type_Class_Access;
5885
5886          elsif Is_Enumeration_Type (Typ) then
5887             Id := RE_Type_Class_Enumeration;
5888
5889          elsif Is_Task_Type (Typ) then
5890             Id := RE_Type_Class_Task;
5891
5892          --  We treat protected types like task types. It would make more
5893          --  sense to have another enumeration value, but after all the
5894          --  whole point of this feature is to be exactly DEC compatible,
5895          --  and changing the type Type_Clas would not meet this requirement.
5896
5897          elsif Is_Protected_Type (Typ) then
5898             Id := RE_Type_Class_Task;
5899
5900          --  Not clear if there are any other possibilities, but if there
5901          --  are, then we will treat them as the address case.
5902
5903          else
5904             Id := RE_Type_Class_Address;
5905          end if;
5906
5907          Rewrite (N, New_Occurrence_Of (RTE (Id), Loc));
5908
5909       end Type_Class;
5910
5911       -----------------------
5912       -- Unbiased_Rounding --
5913       -----------------------
5914
5915       when Attribute_Unbiased_Rounding =>
5916          Fold_Ureal (N,
5917            Eval_Fat.Unbiased_Rounding (P_Root_Type, Expr_Value_R (E1)),
5918            Static);
5919
5920       -------------------------
5921       -- Unconstrained_Array --
5922       -------------------------
5923
5924       when Attribute_Unconstrained_Array => Unconstrained_Array : declare
5925          Typ : constant Entity_Id := Underlying_Type (P_Type);
5926
5927       begin
5928          if Is_Array_Type (P_Type)
5929            and then not Is_Constrained (Typ)
5930          then
5931             Rewrite (N, New_Occurrence_Of (Standard_True, Loc));
5932          else
5933             Rewrite (N, New_Occurrence_Of (Standard_False, Loc));
5934          end if;
5935
5936          --  Analyze and resolve as boolean, note that this attribute is
5937          --  a static attribute in GNAT.
5938
5939          Analyze_And_Resolve (N, Standard_Boolean);
5940          Static := True;
5941       end Unconstrained_Array;
5942
5943       ---------------
5944       -- VADS_Size --
5945       ---------------
5946
5947       --  Processing is shared with Size
5948
5949       ---------
5950       -- Val --
5951       ---------
5952
5953       when Attribute_Val => Val :
5954       begin
5955          if  Expr_Value (E1) < Expr_Value (Type_Low_Bound (P_Base_Type))
5956            or else
5957              Expr_Value (E1) > Expr_Value (Type_High_Bound (P_Base_Type))
5958          then
5959             Apply_Compile_Time_Constraint_Error
5960               (N, "Val expression out of range",
5961                CE_Range_Check_Failed,
5962                Warn => not Static);
5963
5964             Check_Expressions;
5965             return;
5966
5967          else
5968             Fold_Uint (N, Expr_Value (E1), Static);
5969          end if;
5970       end Val;
5971
5972       ----------------
5973       -- Value_Size --
5974       ----------------
5975
5976       --  The Value_Size attribute for a type returns the RM size of the
5977       --  type. This an always be folded for scalar types, and can also
5978       --  be folded for non-scalar types if the size is set.
5979
5980       when Attribute_Value_Size => Value_Size : declare
5981          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5982
5983       begin
5984          if RM_Size (P_TypeA) /= Uint_0 then
5985             Fold_Uint (N, RM_Size (P_TypeA), True);
5986          end if;
5987
5988       end Value_Size;
5989
5990       -------------
5991       -- Version --
5992       -------------
5993
5994       --  Version can never be static
5995
5996       when Attribute_Version =>
5997          null;
5998
5999       ----------------
6000       -- Wide_Image --
6001       ----------------
6002
6003       --  Wide_Image is a scalar attribute, but is never static, because it
6004       --  is not a static function (having a non-scalar argument (RM 4.9(22))
6005
6006       when Attribute_Wide_Image =>
6007          null;
6008
6009       ----------------
6010       -- Wide_Width --
6011       ----------------
6012
6013       --  Processing for Wide_Width is combined with Width
6014
6015       -----------
6016       -- Width --
6017       -----------
6018
6019       --  This processing also handles the case of Wide_Width
6020
6021       when Attribute_Width | Attribute_Wide_Width => Width :
6022       begin
6023          if Compile_Time_Known_Bounds (P_Type) then
6024
6025             --  Floating-point types
6026
6027             if Is_Floating_Point_Type (P_Type) then
6028
6029                --  Width is zero for a null range (RM 3.5 (38))
6030
6031                if Expr_Value_R (Type_High_Bound (P_Type)) <
6032                   Expr_Value_R (Type_Low_Bound (P_Type))
6033                then
6034                   Fold_Uint (N, Uint_0, True);
6035
6036                else
6037                   --  For floating-point, we have +N.dddE+nnn where length
6038                   --  of ddd is determined by type'Digits - 1, but is one
6039                   --  if Digits is one (RM 3.5 (33)).
6040
6041                   --  nnn is set to 2 for Short_Float and Float (32 bit
6042                   --  floats), and 3 for Long_Float and Long_Long_Float.
6043                   --  This is not quite right, but is good enough.
6044
6045                   declare
6046                      Len : Int :=
6047                              Int'Max (2, UI_To_Int (Digits_Value (P_Type)));
6048
6049                   begin
6050                      if Esize (P_Type) <= 32 then
6051                         Len := Len + 6;
6052                      else
6053                         Len := Len + 7;
6054                      end if;
6055
6056                      Fold_Uint (N, UI_From_Int (Len), True);
6057                   end;
6058                end if;
6059
6060             --  Fixed-point types
6061
6062             elsif Is_Fixed_Point_Type (P_Type) then
6063
6064                --  Width is zero for a null range (RM 3.5 (38))
6065
6066                if Expr_Value (Type_High_Bound (P_Type)) <
6067                   Expr_Value (Type_Low_Bound  (P_Type))
6068                then
6069                   Fold_Uint (N, Uint_0, True);
6070
6071                --  The non-null case depends on the specific real type
6072
6073                else
6074                   --  For fixed-point type width is Fore + 1 + Aft (RM 3.5(34))
6075
6076                   Fold_Uint
6077                     (N, UI_From_Int (Fore_Value + 1 + Aft_Value), True);
6078                end if;
6079
6080             --  Discrete types
6081
6082             else
6083                declare
6084                   R  : constant Entity_Id := Root_Type (P_Type);
6085                   Lo : constant Uint :=
6086                          Expr_Value (Type_Low_Bound (P_Type));
6087                   Hi : constant Uint :=
6088                          Expr_Value (Type_High_Bound (P_Type));
6089                   W  : Nat;
6090                   Wt : Nat;
6091                   T  : Uint;
6092                   L  : Node_Id;
6093                   C  : Character;
6094
6095                begin
6096                   --  Empty ranges
6097
6098                   if Lo > Hi then
6099                      W := 0;
6100
6101                   --  Width for types derived from Standard.Character
6102                   --  and Standard.Wide_Character.
6103
6104                   elsif R = Standard_Character
6105                     or else R = Standard_Wide_Character
6106                   then
6107                      W := 0;
6108
6109                      --  Set W larger if needed
6110
6111                      for J in UI_To_Int (Lo) .. UI_To_Int (Hi) loop
6112
6113                         --  Assume all wide-character escape sequences are
6114                         --  same length, so we can quit when we reach one.
6115
6116                         if J > 255 then
6117                            if Id = Attribute_Wide_Width then
6118                               W := Int'Max (W, 3);
6119                               exit;
6120                            else
6121                               W := Int'Max (W, Length_Wide);
6122                               exit;
6123                            end if;
6124
6125                         else
6126                            C := Character'Val (J);
6127
6128                            --  Test for all cases where Character'Image
6129                            --  yields an image that is longer than three
6130                            --  characters. First the cases of Reserved_xxx
6131                            --  names (length = 12).
6132
6133                            case C is
6134                               when Reserved_128 | Reserved_129 |
6135                                    Reserved_132 | Reserved_153
6136
6137                                 => Wt := 12;
6138
6139                               when BS | HT | LF | VT | FF | CR |
6140                                    SO | SI | EM | FS | GS | RS |
6141                                    US | RI | MW | ST | PM
6142
6143                                 => Wt := 2;
6144
6145                               when NUL | SOH | STX | ETX | EOT |
6146                                    ENQ | ACK | BEL | DLE | DC1 |
6147                                    DC2 | DC3 | DC4 | NAK | SYN |
6148                                    ETB | CAN | SUB | ESC | DEL |
6149                                    BPH | NBH | NEL | SSA | ESA |
6150                                    HTS | HTJ | VTS | PLD | PLU |
6151                                    SS2 | SS3 | DCS | PU1 | PU2 |
6152                                    STS | CCH | SPA | EPA | SOS |
6153                                    SCI | CSI | OSC | APC
6154
6155                                 => Wt := 3;
6156
6157                               when Space .. Tilde |
6158                                    No_Break_Space .. LC_Y_Diaeresis
6159
6160                                 => Wt := 3;
6161                            end case;
6162
6163                            W := Int'Max (W, Wt);
6164                         end if;
6165                      end loop;
6166
6167                   --  Width for types derived from Standard.Boolean
6168
6169                   elsif R = Standard_Boolean then
6170                      if Lo = 0 then
6171                         W := 5; -- FALSE
6172                      else
6173                         W := 4; -- TRUE
6174                      end if;
6175
6176                   --  Width for integer types
6177
6178                   elsif Is_Integer_Type (P_Type) then
6179                      T := UI_Max (abs Lo, abs Hi);
6180
6181                      W := 2;
6182                      while T >= 10 loop
6183                         W := W + 1;
6184                         T := T / 10;
6185                      end loop;
6186
6187                   --  Only remaining possibility is user declared enum type
6188
6189                   else
6190                      pragma Assert (Is_Enumeration_Type (P_Type));
6191
6192                      W := 0;
6193                      L := First_Literal (P_Type);
6194
6195                      while Present (L) loop
6196
6197                         --  Only pay attention to in range characters
6198
6199                         if Lo <= Enumeration_Pos (L)
6200                           and then Enumeration_Pos (L) <= Hi
6201                         then
6202                            --  For Width case, use decoded name
6203
6204                            if Id = Attribute_Width then
6205                               Get_Decoded_Name_String (Chars (L));
6206                               Wt := Nat (Name_Len);
6207
6208                            --  For Wide_Width, use encoded name, and then
6209                            --  adjust for the encoding.
6210
6211                            else
6212                               Get_Name_String (Chars (L));
6213
6214                               --  Character literals are always of length 3
6215
6216                               if Name_Buffer (1) = 'Q' then
6217                                  Wt := 3;
6218
6219                               --  Otherwise loop to adjust for upper/wide chars
6220
6221                               else
6222                                  Wt := Nat (Name_Len);
6223
6224                                  for J in 1 .. Name_Len loop
6225                                     if Name_Buffer (J) = 'U' then
6226                                        Wt := Wt - 2;
6227                                     elsif Name_Buffer (J) = 'W' then
6228                                        Wt := Wt - 4;
6229                                     end if;
6230                                  end loop;
6231                               end if;
6232                            end if;
6233
6234                            W := Int'Max (W, Wt);
6235                         end if;
6236
6237                         Next_Literal (L);
6238                      end loop;
6239                   end if;
6240
6241                   Fold_Uint (N, UI_From_Int (W), True);
6242                end;
6243             end if;
6244          end if;
6245       end Width;
6246
6247       --  The following attributes can never be folded, and furthermore we
6248       --  should not even have entered the case statement for any of these.
6249       --  Note that in some cases, the values have already been folded as
6250       --  a result of the processing in Analyze_Attribute.
6251
6252       when Attribute_Abort_Signal             |
6253            Attribute_Access                   |
6254            Attribute_Address                  |
6255            Attribute_Address_Size             |
6256            Attribute_Asm_Input                |
6257            Attribute_Asm_Output               |
6258            Attribute_Base                     |
6259            Attribute_Bit_Order                |
6260            Attribute_Bit_Position             |
6261            Attribute_Callable                 |
6262            Attribute_Caller                   |
6263            Attribute_Class                    |
6264            Attribute_Code_Address             |
6265            Attribute_Count                    |
6266            Attribute_Default_Bit_Order        |
6267            Attribute_Elaborated               |
6268            Attribute_Elab_Body                |
6269            Attribute_Elab_Spec                |
6270            Attribute_External_Tag             |
6271            Attribute_First_Bit                |
6272            Attribute_Input                    |
6273            Attribute_Last_Bit                 |
6274            Attribute_Maximum_Alignment        |
6275            Attribute_Output                   |
6276            Attribute_Partition_ID             |
6277            Attribute_Pool_Address             |
6278            Attribute_Position                 |
6279            Attribute_Read                     |
6280            Attribute_Storage_Pool             |
6281            Attribute_Storage_Size             |
6282            Attribute_Storage_Unit             |
6283            Attribute_Tag                      |
6284            Attribute_Target_Name              |
6285            Attribute_Terminated               |
6286            Attribute_To_Address               |
6287            Attribute_UET_Address              |
6288            Attribute_Unchecked_Access         |
6289            Attribute_Universal_Literal_String |
6290            Attribute_Unrestricted_Access      |
6291            Attribute_Valid                    |
6292            Attribute_Value                    |
6293            Attribute_Wchar_T_Size             |
6294            Attribute_Wide_Value               |
6295            Attribute_Word_Size                |
6296            Attribute_Write                    =>
6297
6298          raise Program_Error;
6299
6300       end case;
6301
6302       --  At the end of the case, one more check. If we did a static evaluation
6303       --  so that the result is now a literal, then set Is_Static_Expression
6304       --  in the constant only if the prefix type is a static subtype. For
6305       --  non-static subtypes, the folding is still OK, but not static.
6306
6307       --  An exception is the GNAT attribute Constrained_Array which is
6308       --  defined to be a static attribute in all cases.
6309
6310       if Nkind (N) = N_Integer_Literal
6311         or else Nkind (N) = N_Real_Literal
6312         or else Nkind (N) = N_Character_Literal
6313         or else Nkind (N) = N_String_Literal
6314         or else (Is_Entity_Name (N)
6315                   and then Ekind (Entity (N)) = E_Enumeration_Literal)
6316       then
6317          Set_Is_Static_Expression (N, Static);
6318
6319       --  If this is still an attribute reference, then it has not been folded
6320       --  and that means that its expressions are in a non-static context.
6321
6322       elsif Nkind (N) = N_Attribute_Reference then
6323          Check_Expressions;
6324
6325       --  Note: the else case not covered here are odd cases where the
6326       --  processing has transformed the attribute into something other
6327       --  than a constant. Nothing more to do in such cases.
6328
6329       else
6330          null;
6331       end if;
6332
6333    end Eval_Attribute;
6334
6335    ------------------------------
6336    -- Is_Anonymous_Tagged_Base --
6337    ------------------------------
6338
6339    function Is_Anonymous_Tagged_Base
6340      (Anon : Entity_Id;
6341       Typ  : Entity_Id)
6342       return Boolean
6343    is
6344    begin
6345       return
6346         Anon = Current_Scope
6347           and then Is_Itype (Anon)
6348           and then Associated_Node_For_Itype (Anon) = Parent (Typ);
6349    end Is_Anonymous_Tagged_Base;
6350
6351    -----------------------
6352    -- Resolve_Attribute --
6353    -----------------------
6354
6355    procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id) is
6356       Loc      : constant Source_Ptr   := Sloc (N);
6357       P        : constant Node_Id      := Prefix (N);
6358       Aname    : constant Name_Id      := Attribute_Name (N);
6359       Attr_Id  : constant Attribute_Id := Get_Attribute_Id (Aname);
6360       Btyp     : constant Entity_Id    := Base_Type (Typ);
6361       Index    : Interp_Index;
6362       It       : Interp;
6363       Nom_Subt : Entity_Id;
6364
6365    begin
6366       --  If error during analysis, no point in continuing, except for
6367       --  array types, where we get  better recovery by using unconstrained
6368       --  indices than nothing at all (see Check_Array_Type).
6369
6370       if Error_Posted (N)
6371         and then Attr_Id /= Attribute_First
6372         and then Attr_Id /= Attribute_Last
6373         and then Attr_Id /= Attribute_Length
6374         and then Attr_Id /= Attribute_Range
6375       then
6376          return;
6377       end if;
6378
6379       --  If attribute was universal type, reset to actual type
6380
6381       if Etype (N) = Universal_Integer
6382         or else Etype (N) = Universal_Real
6383       then
6384          Set_Etype (N, Typ);
6385       end if;
6386
6387       --  Remaining processing depends on attribute
6388
6389       case Attr_Id is
6390
6391          ------------
6392          -- Access --
6393          ------------
6394
6395          --  For access attributes, if the prefix denotes an entity, it is
6396          --  interpreted as a name, never as a call. It may be overloaded,
6397          --  in which case resolution uses the profile of the context type.
6398          --  Otherwise prefix must be resolved.
6399
6400          when Attribute_Access
6401             | Attribute_Unchecked_Access
6402             | Attribute_Unrestricted_Access =>
6403
6404             if Is_Variable (P) then
6405                Note_Possible_Modification (P);
6406             end if;
6407
6408             if Is_Entity_Name (P) then
6409
6410                if Is_Overloaded (P) then
6411                   Get_First_Interp (P, Index, It);
6412
6413                   while Present (It.Nam) loop
6414
6415                      if Type_Conformant (Designated_Type (Typ), It.Nam) then
6416                         Set_Entity (P, It.Nam);
6417
6418                         --  The prefix is definitely NOT overloaded anymore
6419                         --  at this point, so we reset the Is_Overloaded
6420                         --  flag to avoid any confusion when reanalyzing
6421                         --  the node.
6422
6423                         Set_Is_Overloaded (P, False);
6424                         Generate_Reference (Entity (P), P);
6425                         exit;
6426                      end if;
6427
6428                      Get_Next_Interp (Index, It);
6429                   end loop;
6430
6431                --  If it is a subprogram name or a type, there is nothing
6432                --  to resolve.
6433
6434                elsif not Is_Overloadable (Entity (P))
6435                  and then not Is_Type (Entity (P))
6436                then
6437                   Resolve (P);
6438                end if;
6439
6440                if not Is_Entity_Name (P) then
6441                   null;
6442
6443                elsif Is_Abstract (Entity (P))
6444                  and then Is_Overloadable (Entity (P))
6445                then
6446                   Error_Msg_Name_1 := Aname;
6447                   Error_Msg_N ("prefix of % attribute cannot be abstract", P);
6448                   Set_Etype (N, Any_Type);
6449
6450                elsif Convention (Entity (P)) = Convention_Intrinsic then
6451                   Error_Msg_Name_1 := Aname;
6452
6453                   if Ekind (Entity (P)) = E_Enumeration_Literal then
6454                      Error_Msg_N
6455                        ("prefix of % attribute cannot be enumeration literal",
6456                           P);
6457                   else
6458                      Error_Msg_N
6459                        ("prefix of % attribute cannot be intrinsic", P);
6460                   end if;
6461
6462                   Set_Etype (N, Any_Type);
6463                end if;
6464
6465                --  Assignments, return statements, components of aggregates,
6466                --  generic instantiations will require convention checks if
6467                --  the type is an access to subprogram. Given that there will
6468                --  also be accessibility checks on those, this is where the
6469                --  checks can eventually be centralized ???
6470
6471                if Ekind (Btyp) = E_Access_Subprogram_Type then
6472                   if Convention (Btyp) /= Convention (Entity (P)) then
6473                      Error_Msg_N
6474                       ("subprogram has invalid convention for context", P);
6475
6476                   else
6477                      Check_Subtype_Conformant
6478                        (New_Id  => Entity (P),
6479                         Old_Id  => Designated_Type (Btyp),
6480                         Err_Loc => P);
6481                   end if;
6482
6483                   if Attr_Id = Attribute_Unchecked_Access then
6484                      Error_Msg_Name_1 := Aname;
6485                      Error_Msg_N
6486                        ("attribute% cannot be applied to a subprogram", P);
6487
6488                   elsif Aname = Name_Unrestricted_Access then
6489                      null;  --  Nothing to check
6490
6491                   --  Check the static accessibility rule of 3.10.2(32)
6492
6493                   elsif Attr_Id = Attribute_Access
6494                     and then Subprogram_Access_Level (Entity (P))
6495                       > Type_Access_Level (Btyp)
6496                   then
6497                      if not In_Instance_Body then
6498                         Error_Msg_N
6499                           ("subprogram must not be deeper than access type",
6500                             P);
6501                      else
6502                         Error_Msg_N
6503                           ("subprogram must not be deeper than access type?",
6504                              P);
6505                         Error_Msg_N
6506                           ("Constraint_Error will be raised ?", P);
6507                         Set_Raises_Constraint_Error (N);
6508                      end if;
6509
6510                   --  Check the restriction of 3.10.2(32) that disallows
6511                   --  the type of the access attribute to be declared
6512                   --  outside a generic body when the attribute occurs
6513                   --  within that generic body.
6514
6515                   elsif Enclosing_Generic_Body (Entity (P))
6516                     /= Enclosing_Generic_Body (Btyp)
6517                   then
6518                      Error_Msg_N
6519                        ("access type must not be outside generic body", P);
6520                   end if;
6521                end if;
6522
6523                --  if this is a renaming, an inherited operation, or a
6524                --  subprogram instance, use the original entity.
6525
6526                if Is_Entity_Name (P)
6527                  and then Is_Overloadable (Entity (P))
6528                  and then Present (Alias (Entity (P)))
6529                then
6530                   Rewrite (P,
6531                     New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6532                end if;
6533
6534             elsif Nkind (P) = N_Selected_Component
6535               and then Is_Overloadable (Entity (Selector_Name (P)))
6536             then
6537                --  Protected operation. If operation is overloaded, must
6538                --  disambiguate. Prefix that denotes protected object itself
6539                --  is resolved with its own type.
6540
6541                if Attr_Id = Attribute_Unchecked_Access then
6542                   Error_Msg_Name_1 := Aname;
6543                   Error_Msg_N
6544                     ("attribute% cannot be applied to protected operation", P);
6545                end if;
6546
6547                Resolve (Prefix (P));
6548                Generate_Reference (Entity (Selector_Name (P)), P);
6549
6550             elsif Is_Overloaded (P) then
6551
6552                --  Use the designated type of the context  to disambiguate.
6553                declare
6554                   Index : Interp_Index;
6555                   It    : Interp;
6556                begin
6557                   Get_First_Interp (P, Index, It);
6558
6559                   while Present (It.Typ) loop
6560                      if Covers (Designated_Type (Typ), It.Typ) then
6561                         Resolve (P, It.Typ);
6562                         exit;
6563                      end if;
6564
6565                      Get_Next_Interp (Index, It);
6566                   end loop;
6567                end;
6568             else
6569                Resolve (P);
6570             end if;
6571
6572             --  X'Access is illegal if X denotes a constant and the access
6573             --  type is access-to-variable. Same for 'Unchecked_Access.
6574             --  The rule does not apply to 'Unrestricted_Access.
6575
6576             if not (Ekind (Btyp) = E_Access_Subprogram_Type
6577                      or else (Is_Record_Type (Btyp) and then
6578                               Present (Corresponding_Remote_Type (Btyp)))
6579                      or else Ekind (Btyp) = E_Access_Protected_Subprogram_Type
6580                      or else Is_Access_Constant (Btyp)
6581                      or else Is_Variable (P)
6582                      or else Attr_Id = Attribute_Unrestricted_Access)
6583             then
6584                if Comes_From_Source (N) then
6585                   Error_Msg_N ("access-to-variable designates constant", P);
6586                end if;
6587             end if;
6588
6589             if (Attr_Id = Attribute_Access
6590                   or else
6591                 Attr_Id = Attribute_Unchecked_Access)
6592               and then (Ekind (Btyp) = E_General_Access_Type
6593                          or else Ekind (Btyp) = E_Anonymous_Access_Type)
6594             then
6595                if Is_Dependent_Component_Of_Mutable_Object (P) then
6596                   Error_Msg_N
6597                     ("illegal attribute for discriminant-dependent component",
6598                      P);
6599                end if;
6600
6601                --  Check the static matching rule of 3.10.2(27). The
6602                --  nominal subtype of the prefix must statically
6603                --  match the designated type.
6604
6605                Nom_Subt := Etype (P);
6606
6607                if Is_Constr_Subt_For_U_Nominal (Nom_Subt) then
6608                   Nom_Subt := Etype (Nom_Subt);
6609                end if;
6610
6611                if Is_Tagged_Type (Designated_Type (Typ)) then
6612
6613                   --  If the attribute is in the context of an access
6614                   --  parameter, then the prefix is allowed to be of
6615                   --  the class-wide type (by AI-127).
6616
6617                   if Ekind (Typ) = E_Anonymous_Access_Type then
6618                      if not Covers (Designated_Type (Typ), Nom_Subt)
6619                        and then not Covers (Nom_Subt, Designated_Type (Typ))
6620                      then
6621                         declare
6622                            Desig : Entity_Id;
6623
6624                         begin
6625                            Desig := Designated_Type (Typ);
6626
6627                            if Is_Class_Wide_Type (Desig) then
6628                               Desig := Etype (Desig);
6629                            end if;
6630
6631                            if Is_Anonymous_Tagged_Base (Nom_Subt, Desig) then
6632                               null;
6633
6634                            else
6635                               Error_Msg_NE
6636                                 ("type of prefix: & not compatible",
6637                                   P, Nom_Subt);
6638                               Error_Msg_NE
6639                                 ("\with &, the expected designated type",
6640                                   P, Designated_Type (Typ));
6641                            end if;
6642                         end;
6643                      end if;
6644
6645                   elsif not Covers (Designated_Type (Typ), Nom_Subt)
6646                     or else
6647                       (not Is_Class_Wide_Type (Designated_Type (Typ))
6648                         and then Is_Class_Wide_Type (Nom_Subt))
6649                   then
6650                      Error_Msg_NE
6651                        ("type of prefix: & is not covered", P, Nom_Subt);
6652                      Error_Msg_NE
6653                        ("\by &, the expected designated type" &
6654                            " ('R'M 3.10.2 (27))", P, Designated_Type (Typ));
6655                   end if;
6656
6657                   if Is_Class_Wide_Type (Designated_Type (Typ))
6658                     and then Has_Discriminants (Etype (Designated_Type (Typ)))
6659                     and then Is_Constrained (Etype (Designated_Type (Typ)))
6660                     and then Designated_Type (Typ) /= Nom_Subt
6661                   then
6662                      Apply_Discriminant_Check
6663                        (N, Etype (Designated_Type (Typ)));
6664                   end if;
6665
6666                elsif not Subtypes_Statically_Match
6667                            (Designated_Type (Base_Type (Typ)), Nom_Subt)
6668                  and then
6669                    not (Has_Discriminants (Designated_Type (Typ))
6670                           and then
6671                             not Is_Constrained
6672                                   (Designated_Type (Base_Type (Typ))))
6673                then
6674                   Error_Msg_N
6675                     ("object subtype must statically match "
6676                      & "designated subtype", P);
6677
6678                   if Is_Entity_Name (P)
6679                     and then Is_Array_Type (Designated_Type (Typ))
6680                   then
6681
6682                      declare
6683                         D : constant Node_Id := Declaration_Node (Entity (P));
6684
6685                      begin
6686                         Error_Msg_N ("aliased object has explicit bounds?",
6687                           D);
6688                         Error_Msg_N ("\declare without bounds"
6689                           & " (and with explicit initialization)?", D);
6690                         Error_Msg_N ("\for use with unconstrained access?", D);
6691                      end;
6692                   end if;
6693                end if;
6694
6695                --  Check the static accessibility rule of 3.10.2(28).
6696                --  Note that this check is not performed for the
6697                --  case of an anonymous access type, since the access
6698                --  attribute is always legal in such a context.
6699
6700                if Attr_Id /= Attribute_Unchecked_Access
6701                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
6702                  and then Ekind (Btyp) = E_General_Access_Type
6703                then
6704                   --  In an instance, this is a runtime check, but one we
6705                   --  know will fail, so generate an appropriate warning.
6706
6707                   if In_Instance_Body then
6708                      Error_Msg_N
6709                        ("?non-local pointer cannot point to local object", P);
6710                      Error_Msg_N
6711                        ("?Program_Error will be raised at run time", P);
6712                      Rewrite (N,
6713                        Make_Raise_Program_Error (Loc,
6714                          Reason => PE_Accessibility_Check_Failed));
6715                      Set_Etype (N, Typ);
6716                      return;
6717
6718                   else
6719                      Error_Msg_N
6720                        ("non-local pointer cannot point to local object", P);
6721
6722                      if Is_Record_Type (Current_Scope)
6723                        and then (Nkind (Parent (N)) =
6724                                   N_Discriminant_Association
6725                                    or else
6726                                  Nkind (Parent (N)) =
6727                                    N_Index_Or_Discriminant_Constraint)
6728                      then
6729                         declare
6730                            Indic : Node_Id := Parent (Parent (N));
6731
6732                         begin
6733                            while Present (Indic)
6734                              and then Nkind (Indic) /= N_Subtype_Indication
6735                            loop
6736                               Indic := Parent (Indic);
6737                            end loop;
6738
6739                            if Present (Indic) then
6740                               Error_Msg_NE
6741                                 ("\use an access definition for" &
6742                                   " the access discriminant of&", N,
6743                                   Entity (Subtype_Mark (Indic)));
6744                            end if;
6745                         end;
6746                      end if;
6747                   end if;
6748                end if;
6749             end if;
6750
6751             if Ekind (Btyp) = E_Access_Protected_Subprogram_Type
6752               and then Is_Entity_Name (P)
6753               and then not Is_Protected_Type (Scope (Entity (P)))
6754             then
6755                Error_Msg_N ("context requires a protected subprogram", P);
6756
6757             elsif Ekind (Btyp) = E_Access_Subprogram_Type
6758               and then Ekind (Etype (N)) = E_Access_Protected_Subprogram_Type
6759             then
6760                Error_Msg_N ("context requires a non-protected subprogram", P);
6761             end if;
6762
6763             --  The context cannot be a pool-specific type, but this is a
6764             --  legality rule, not a resolution rule, so it must be checked
6765             --  separately, after possibly disambiguation (see AI-245).
6766
6767             if Ekind (Btyp) = E_Access_Type
6768               and then Attr_Id /= Attribute_Unrestricted_Access
6769             then
6770                Wrong_Type (N, Typ);
6771             end if;
6772
6773             Set_Etype (N, Typ);
6774
6775             --  Check for incorrect atomic/volatile reference (RM C.6(12))
6776
6777             if Attr_Id /= Attribute_Unrestricted_Access then
6778                if Is_Atomic_Object (P)
6779                  and then not Is_Atomic (Designated_Type (Typ))
6780                then
6781                   Error_Msg_N
6782                     ("access to atomic object cannot yield access-to-" &
6783                      "non-atomic type", P);
6784
6785                elsif Is_Volatile_Object (P)
6786                  and then not Is_Volatile (Designated_Type (Typ))
6787                then
6788                   Error_Msg_N
6789                     ("access to volatile object cannot yield access-to-" &
6790                      "non-volatile type", P);
6791                end if;
6792             end if;
6793
6794          -------------
6795          -- Address --
6796          -------------
6797
6798          --  Deal with resolving the type for Address attribute, overloading
6799          --  is not permitted here, since there is no context to resolve it.
6800
6801          when Attribute_Address | Attribute_Code_Address =>
6802
6803             --  To be safe, assume that if the address of a variable is taken,
6804             --  it may be modified via this address, so note modification.
6805
6806             if Is_Variable (P) then
6807                Note_Possible_Modification (P);
6808             end if;
6809
6810             if Nkind (P) in  N_Subexpr
6811               and then Is_Overloaded (P)
6812             then
6813                Get_First_Interp (P, Index, It);
6814                Get_Next_Interp (Index, It);
6815
6816                if Present (It.Nam) then
6817                   Error_Msg_Name_1 := Aname;
6818                   Error_Msg_N
6819                     ("prefix of % attribute cannot be overloaded", N);
6820                   return;
6821                end if;
6822             end if;
6823
6824             if not Is_Entity_Name (P)
6825                or else not Is_Overloadable (Entity (P))
6826             then
6827                if not Is_Task_Type (Etype (P))
6828                  or else Nkind (P) = N_Explicit_Dereference
6829                then
6830                   Resolve (P);
6831                end if;
6832             end if;
6833
6834             --  If this is the name of a derived subprogram, or that of a
6835             --  generic actual, the address is that of the original entity.
6836
6837             if Is_Entity_Name (P)
6838               and then Is_Overloadable (Entity (P))
6839               and then Present (Alias (Entity (P)))
6840             then
6841                Rewrite (P,
6842                  New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6843             end if;
6844
6845          ---------------
6846          -- AST_Entry --
6847          ---------------
6848
6849          --  Prefix of the AST_Entry attribute is an entry name which must
6850          --  not be resolved, since this is definitely not an entry call.
6851
6852          when Attribute_AST_Entry =>
6853             null;
6854
6855          ------------------
6856          -- Body_Version --
6857          ------------------
6858
6859          --  Prefix of Body_Version attribute can be a subprogram name which
6860          --  must not be resolved, since this is not a call.
6861
6862          when Attribute_Body_Version =>
6863             null;
6864
6865          ------------
6866          -- Caller --
6867          ------------
6868
6869          --  Prefix of Caller attribute is an entry name which must not
6870          --  be resolved, since this is definitely not an entry call.
6871
6872          when Attribute_Caller =>
6873             null;
6874
6875          ------------------
6876          -- Code_Address --
6877          ------------------
6878
6879          --  Shares processing with Address attribute
6880
6881          -----------
6882          -- Count --
6883          -----------
6884
6885          --  If the prefix of the Count attribute is an entry name it must not
6886          --  be resolved, since this is definitely not an entry call. However,
6887          --  if it is an element of an entry family, the index itself may
6888          --  have to be resolved because it can be a general expression.
6889
6890          when Attribute_Count =>
6891             if Nkind (P) = N_Indexed_Component
6892               and then Is_Entity_Name (Prefix (P))
6893             then
6894                declare
6895                   Indx : constant Node_Id   := First (Expressions (P));
6896                   Fam  : constant Entity_Id := Entity (Prefix (P));
6897                begin
6898                   Resolve (Indx, Entry_Index_Type (Fam));
6899                   Apply_Range_Check (Indx, Entry_Index_Type (Fam));
6900                end;
6901             end if;
6902
6903          ----------------
6904          -- Elaborated --
6905          ----------------
6906
6907          --  Prefix of the Elaborated attribute is a subprogram name which
6908          --  must not be resolved, since this is definitely not a call. Note
6909          --  that it is a library unit, so it cannot be overloaded here.
6910
6911          when Attribute_Elaborated =>
6912             null;
6913
6914          --------------------
6915          -- Mechanism_Code --
6916          --------------------
6917
6918          --  Prefix of the Mechanism_Code attribute is a function name
6919          --  which must not be resolved. Should we check for overloaded ???
6920
6921          when Attribute_Mechanism_Code =>
6922             null;
6923
6924          ------------------
6925          -- Partition_ID --
6926          ------------------
6927
6928          --  Most processing is done in sem_dist, after determining the
6929          --  context type. Node is rewritten as a conversion to a runtime call.
6930
6931          when Attribute_Partition_ID =>
6932             Process_Partition_Id (N);
6933             return;
6934
6935          when Attribute_Pool_Address =>
6936             Resolve (P);
6937
6938          -----------
6939          -- Range --
6940          -----------
6941
6942          --  We replace the Range attribute node with a range expression
6943          --  whose bounds are the 'First and 'Last attributes applied to the
6944          --  same prefix. The reason that we do this transformation here
6945          --  instead of in the expander is that it simplifies other parts of
6946          --  the semantic analysis which assume that the Range has been
6947          --  replaced; thus it must be done even when in semantic-only mode
6948          --  (note that the RM specifically mentions this equivalence, we
6949          --  take care that the prefix is only evaluated once).
6950
6951          when Attribute_Range => Range_Attribute :
6952             declare
6953                LB   : Node_Id;
6954                HB   : Node_Id;
6955
6956                function Check_Discriminated_Prival
6957                  (N    : Node_Id)
6958                   return Node_Id;
6959                --  The range of a private component constrained by a
6960                --  discriminant is rewritten to make the discriminant
6961                --  explicit. This solves some complex visibility problems
6962                --  related to the use of privals.
6963
6964                --------------------------------
6965                -- Check_Discriminated_Prival --
6966                --------------------------------
6967
6968                function Check_Discriminated_Prival
6969                  (N    : Node_Id)
6970                   return Node_Id
6971                is
6972                begin
6973                   if Is_Entity_Name (N)
6974                     and then Ekind (Entity (N)) = E_In_Parameter
6975                     and then not Within_Init_Proc
6976                   then
6977                      return Make_Identifier (Sloc (N), Chars (Entity (N)));
6978                   else
6979                      return Duplicate_Subexpr (N);
6980                   end if;
6981                end Check_Discriminated_Prival;
6982
6983             --  Start of processing for Range_Attribute
6984
6985             begin
6986                if not Is_Entity_Name (P)
6987                  or else not Is_Type (Entity (P))
6988                then
6989                   Resolve (P);
6990                end if;
6991
6992                --  Check whether prefix is (renaming of) private component
6993                --  of protected type.
6994
6995                if Is_Entity_Name (P)
6996                  and then Comes_From_Source (N)
6997                  and then Is_Array_Type (Etype (P))
6998                  and then Number_Dimensions (Etype (P)) = 1
6999                  and then (Ekind (Scope (Entity (P))) = E_Protected_Type
7000                             or else
7001                            Ekind (Scope (Scope (Entity (P)))) =
7002                                                         E_Protected_Type)
7003                then
7004                   LB :=
7005                     Check_Discriminated_Prival
7006                       (Type_Low_Bound (Etype (First_Index (Etype (P)))));
7007
7008                   HB :=
7009                     Check_Discriminated_Prival
7010                       (Type_High_Bound (Etype (First_Index (Etype (P)))));
7011
7012                else
7013                   HB :=
7014                     Make_Attribute_Reference (Loc,
7015                       Prefix         => Duplicate_Subexpr (P),
7016                       Attribute_Name => Name_Last,
7017                       Expressions    => Expressions (N));
7018
7019                   LB :=
7020                     Make_Attribute_Reference (Loc,
7021                       Prefix         => P,
7022                       Attribute_Name => Name_First,
7023                       Expressions    => Expressions (N));
7024                end if;
7025
7026                --  If the original was marked as Must_Not_Freeze (see code
7027                --  in Sem_Ch3.Make_Index), then make sure the rewriting
7028                --  does not freeze either.
7029
7030                if Must_Not_Freeze (N) then
7031                   Set_Must_Not_Freeze (HB);
7032                   Set_Must_Not_Freeze (LB);
7033                   Set_Must_Not_Freeze (Prefix (HB));
7034                   Set_Must_Not_Freeze (Prefix (LB));
7035                end if;
7036
7037                if Raises_Constraint_Error (Prefix (N)) then
7038
7039                   --  Preserve Sloc of prefix in the new bounds, so that
7040                   --  the posted warning can be removed if we are within
7041                   --  unreachable code.
7042
7043                   Set_Sloc (LB, Sloc (Prefix (N)));
7044                   Set_Sloc (HB, Sloc (Prefix (N)));
7045                end if;
7046
7047                Rewrite (N, Make_Range (Loc, LB, HB));
7048                Analyze_And_Resolve (N, Typ);
7049
7050                --  Normally after resolving attribute nodes, Eval_Attribute
7051                --  is called to do any possible static evaluation of the node.
7052                --  However, here since the Range attribute has just been
7053                --  transformed into a range expression it is no longer an
7054                --  attribute node and therefore the call needs to be avoided
7055                --  and is accomplished by simply returning from the procedure.
7056
7057                return;
7058             end Range_Attribute;
7059
7060          -----------------
7061          -- UET_Address --
7062          -----------------
7063
7064          --  Prefix must not be resolved in this case, since it is not a
7065          --  real entity reference. No action of any kind is require!
7066
7067          when Attribute_UET_Address =>
7068             return;
7069
7070          ----------------------
7071          -- Unchecked_Access --
7072          ----------------------
7073
7074          --  Processing is shared with Access
7075
7076          -------------------------
7077          -- Unrestricted_Access --
7078          -------------------------
7079
7080          --  Processing is shared with Access
7081
7082          ---------
7083          -- Val --
7084          ---------
7085
7086          --  Apply range check. Note that we did not do this during the
7087          --  analysis phase, since we wanted Eval_Attribute to have a
7088          --  chance at finding an illegal out of range value.
7089
7090          when Attribute_Val =>
7091
7092             --  Note that we do our own Eval_Attribute call here rather than
7093             --  use the common one, because we need to do processing after
7094             --  the call, as per above comment.
7095
7096             Eval_Attribute (N);
7097
7098             --  Eval_Attribute may replace the node with a raise CE, or
7099             --  fold it to a constant. Obviously we only apply a scalar
7100             --  range check if this did not happen!
7101
7102             if Nkind (N) = N_Attribute_Reference
7103               and then Attribute_Name (N) = Name_Val
7104             then
7105                Apply_Scalar_Range_Check (First (Expressions (N)), Btyp);
7106             end if;
7107
7108             return;
7109
7110          -------------
7111          -- Version --
7112          -------------
7113
7114          --  Prefix of Version attribute can be a subprogram name which
7115          --  must not be resolved, since this is not a call.
7116
7117          when Attribute_Version =>
7118             null;
7119
7120          ----------------------
7121          -- Other Attributes --
7122          ----------------------
7123
7124          --  For other attributes, resolve prefix unless it is a type. If
7125          --  the attribute reference itself is a type name ('Base and 'Class)
7126          --  then this is only legal within a task or protected record.
7127
7128          when others =>
7129             if not Is_Entity_Name (P)
7130               or else not Is_Type (Entity (P))
7131             then
7132                Resolve (P);
7133             end if;
7134
7135             --  If the attribute reference itself is a type name ('Base,
7136             --  'Class) then this is only legal within a task or protected
7137             --  record. What is this all about ???
7138
7139             if Is_Entity_Name (N)
7140               and then Is_Type (Entity (N))
7141             then
7142                if Is_Concurrent_Type (Entity (N))
7143                  and then In_Open_Scopes (Entity (P))
7144                then
7145                   null;
7146                else
7147                   Error_Msg_N
7148                     ("invalid use of subtype name in expression or call", N);
7149                end if;
7150             end if;
7151
7152             --  For attributes whose argument may be a string, complete
7153             --  resolution of argument now. This avoids premature expansion
7154             --  (and the creation of transient scopes) before the attribute
7155             --  reference is resolved.
7156
7157             case Attr_Id is
7158                when Attribute_Value =>
7159                   Resolve (First (Expressions (N)), Standard_String);
7160
7161                when Attribute_Wide_Value =>
7162                   Resolve (First (Expressions (N)), Standard_Wide_String);
7163
7164                when others => null;
7165             end case;
7166       end case;
7167
7168       --  Normally the Freezing is done by Resolve but sometimes the Prefix
7169       --  is not resolved, in which case the freezing must be done now.
7170
7171       Freeze_Expression (P);
7172
7173       --  Finally perform static evaluation on the attribute reference
7174
7175       Eval_Attribute (N);
7176
7177    end Resolve_Attribute;
7178
7179 end Sem_Attr;