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             --  In the case of an access to subprogram, use the name of the
 399             --  subprogram itself as the designated type. Type-checking in
 400             --  this case compares the signatures of the designated types.
 401
 402             if not Is_Overloaded (P) then
 403                Acc_Type :=
 404                  New_Internal_Entity
 405                    (Get_Kind (Entity (P)), Current_Scope, Loc, 'A');
 406                Set_Etype (Acc_Type, Acc_Type);
 407                Set_Directly_Designated_Type (Acc_Type, Entity (P));
 408                Set_Etype (N, Acc_Type);
 409
 410             else
 411                Get_First_Interp (P, Index, It);
 412                Set_Etype (N, Any_Type);
 413
 414                while Present (It.Nam) loop
 415                   if not Is_Intrinsic_Subprogram (It.Nam) then
 416                      Acc_Type :=
 417                        New_Internal_Entity
 418                          (Get_Kind (It.Nam), Current_Scope, Loc, 'A');
 419                      Set_Etype (Acc_Type, Acc_Type);
 420                      Set_Directly_Designated_Type (Acc_Type, It.Nam);
 421                      Add_One_Interp (N, Acc_Type, Acc_Type);
 422                   end if;
 423
 424                   Get_Next_Interp (Index, It);
 425                end loop;
 426
 427                if Etype (N) = Any_Type then
 428                   Error_Attr ("prefix of % attribute cannot be intrinsic", P);
 429                end if;
 430             end if;
 431          end Build_Access_Subprogram_Type;
 432
 433       --  Start of processing for Analyze_Access_Attribute
 434
 435       begin
 436          Check_E0;
 437
 438          if Nkind (P) = N_Character_Literal then
 439             Error_Attr
 440               ("prefix of % attribute cannot be enumeration literal", P);
 441          end if;
 442
 443          --  Case of access to subprogram
 444
 445          if Is_Entity_Name (P)
 446            and then Is_Overloadable (Entity (P))
 447          then
 448             --  Not allowed for nested subprograms if No_Implicit_Dynamic_Code
 449             --  restriction set (since in general a trampoline is required).
 450
 451             if not Is_Library_Level_Entity (Entity (P)) then
 452                Check_Restriction (No_Implicit_Dynamic_Code, P);
 453             end if;
 454
 455             --  Build the appropriate subprogram type
 456
 457             Build_Access_Subprogram_Type (P);
 458
 459             --  For unrestricted access, kill current values, since this
 460             --  attribute allows a reference to a local subprogram that
 461             --  could modify local variables to be passed out of scope
 462
 463             if Aname = Name_Unrestricted_Access then
 464                Kill_Current_Values;
 465             end if;
 466
 467             return;
 468
 469          --  Component is an operation of a protected type
 470
 471          elsif Nkind (P) = N_Selected_Component
 472            and then Is_Overloadable (Entity (Selector_Name (P)))
 473          then
 474             if Ekind (Entity (Selector_Name (P))) = E_Entry then
 475                Error_Attr ("prefix of % attribute must be subprogram", P);
 476             end if;
 477
 478             Build_Access_Subprogram_Type (Selector_Name (P));
 479             return;
 480          end if;
 481
 482          --  Deal with incorrect reference to a type, but note that some
 483          --  accesses are allowed (references to the current type instance).
 484
 485          if Is_Entity_Name (P) then
 486             Scop := Current_Scope;
 487             Typ := Entity (P);
 488
 489             if Is_Type (Typ) then
 490
 491                --  OK if we are within the scope of a limited type
 492                --  let's mark the component as having per object constraint
 493
 494                if Is_Anonymous_Tagged_Base (Scop, Typ) then
 495                   Typ := Scop;
 496                   Set_Entity (P, Typ);
 497                   Set_Etype  (P, Typ);
 498                end if;
 499
 500                if Typ = Scop then
 501                   declare
 502                      Q : Node_Id := Parent (N);
 503
 504                   begin
 505                      while Present (Q)
 506                        and then Nkind (Q) /= N_Component_Declaration
 507                      loop
 508                         Q := Parent (Q);
 509                      end loop;
 510                      if Present (Q) then
 511                         Set_Has_Per_Object_Constraint (
 512                           Defining_Identifier (Q), True);
 513                      end if;
 514                   end;
 515
 516                   if Nkind (P) = N_Expanded_Name then
 517                      Error_Msg_N
 518                        ("current instance prefix must be a direct name", P);
 519                   end if;
 520
 521                   --  If a current instance attribute appears within a
 522                   --  a component constraint it must appear alone; other
 523                   --  contexts (default expressions, within a task body)
 524                   --  are not subject to this restriction.
 525
 526                   if not In_Default_Expression
 527                     and then not Has_Completion (Scop)
 528                     and then
 529                       Nkind (Parent (N)) /= N_Discriminant_Association
 530                     and then
 531                       Nkind (Parent (N)) /= N_Index_Or_Discriminant_Constraint
 532                   then
 533                      Error_Msg_N
 534                        ("current instance attribute must appear alone", N);
 535                   end if;
 536
 537                --  OK if we are in initialization procedure for the type
 538                --  in question, in which case the reference to the type
 539                --  is rewritten as a reference to the current object.
 540
 541                elsif Ekind (Scop) = E_Procedure
 542                  and then Is_Init_Proc (Scop)
 543                  and then Etype (First_Formal (Scop)) = Typ
 544                then
 545                   Rewrite (N,
 546                     Make_Attribute_Reference (Loc,
 547                       Prefix         => Make_Identifier (Loc, Name_uInit),
 548                       Attribute_Name => Name_Unrestricted_Access));
 549                   Analyze (N);
 550                   return;
 551
 552                --  OK if a task type, this test needs sharpening up ???
 553
 554                elsif Is_Task_Type (Typ) then
 555                   null;
 556
 557                --  Otherwise we have an error case
 558
 559                else
 560                   Error_Attr ("% attribute cannot be applied to type", P);
 561                   return;
 562                end if;
 563             end if;
 564          end if;
 565
 566          --  If we fall through, we have a normal access to object case.
 567          --  Unrestricted_Access is legal wherever an allocator would be
 568          --  legal, so its Etype is set to E_Allocator. The expected type
 569          --  of the other attributes is a general access type, and therefore
 570          --  we label them with E_Access_Attribute_Type.
 571
 572          if not Is_Overloaded (P) then
 573             Acc_Type := Build_Access_Object_Type (P_Type);
 574             Set_Etype (N, Acc_Type);
 575          else
 576             declare
 577                Index : Interp_Index;
 578                It    : Interp;
 579
 580             begin
 581                Set_Etype (N, Any_Type);
 582                Get_First_Interp (P, Index, It);
 583
 584                while Present (It.Typ) loop
 585                   Acc_Type := Build_Access_Object_Type (It.Typ);
 586                   Add_One_Interp (N, Acc_Type, Acc_Type);
 587                   Get_Next_Interp (Index, It);
 588                end loop;
 589             end;
 590          end if;
 591
 592          --  If we have an access to an object, and the attribute comes
 593          --  from source, then set the object as potentially source modified.
 594          --  We do this because the resulting access pointer can be used to
 595          --  modify the variable, and we might not detect this, leading to
 596          --  some junk warnings.
 597
 598          if Is_Entity_Name (P) then
 599             Set_Never_Set_In_Source (Entity (P), False);
 600          end if;
 601
 602          --  Check for aliased view unless unrestricted case. We allow
 603          --  a nonaliased prefix when within an instance because the
 604          --  prefix may have been a tagged formal object, which is
 605          --  defined to be aliased even when the actual might not be
 606          --  (other instance cases will have been caught in the generic).
 607
 608          if Aname /= Name_Unrestricted_Access
 609            and then not Is_Aliased_View (P)
 610            and then not In_Instance
 611          then
 612             Error_Attr ("prefix of % attribute must be aliased", P);
 613          end if;
 614       end Analyze_Access_Attribute;
 615
 616       --------------------------------
 617       -- Check_Array_Or_Scalar_Type --
 618       --------------------------------
 619
 620       procedure Check_Array_Or_Scalar_Type is
 621          Index : Entity_Id;
 622
 623          D : Int;
 624          --  Dimension number for array attributes.
 625
 626       begin
 627          --  Case of string literal or string literal subtype. These cases
 628          --  cannot arise from legal Ada code, but the expander is allowed
 629          --  to generate them. They require special handling because string
 630          --  literal subtypes do not have standard bounds (the whole idea
 631          --  of these subtypes is to avoid having to generate the bounds)
 632
 633          if Ekind (P_Type) = E_String_Literal_Subtype then
 634             Set_Etype (N, Etype (First_Index (P_Base_Type)));
 635             return;
 636
 637          --  Scalar types
 638
 639          elsif Is_Scalar_Type (P_Type) then
 640             Check_Type;
 641
 642             if Present (E1) then
 643                Error_Attr ("invalid argument in % attribute", E1);
 644             else
 645                Set_Etype (N, P_Base_Type);
 646                return;
 647             end if;
 648
 649          --  The following is a special test to allow 'First to apply to
 650          --  private scalar types if the attribute comes from generated
 651          --  code. This occurs in the case of Normalize_Scalars code.
 652
 653          elsif Is_Private_Type (P_Type)
 654            and then Present (Full_View (P_Type))
 655            and then Is_Scalar_Type (Full_View (P_Type))
 656            and then not Comes_From_Source (N)
 657          then
 658             Set_Etype (N, Implementation_Base_Type (P_Type));
 659
 660          --  Array types other than string literal subtypes handled above
 661
 662          else
 663             Check_Array_Type;
 664
 665             --  We know prefix is an array type, or the name of an array
 666             --  object, and that the expression, if present, is static
 667             --  and within the range of the dimensions of the type.
 668
 669             if Is_Array_Type (P_Type) then
 670                Index := First_Index (P_Base_Type);
 671
 672             else pragma Assert (Is_Access_Type (P_Type));
 673                Index := First_Index (Base_Type (Designated_Type (P_Type)));
 674             end if;
 675
 676             if No (E1) then
 677
 678                --  First dimension assumed
 679
 680                Set_Etype (N, Base_Type (Etype (Index)));
 681
 682             else
 683                D := UI_To_Int (Intval (E1));
 684
 685                for J in 1 .. D - 1 loop
 686                   Next_Index (Index);
 687                end loop;
 688
 689                Set_Etype (N, Base_Type (Etype (Index)));
 690                Set_Etype (E1, Standard_Integer);
 691             end if;
 692          end if;
 693       end Check_Array_Or_Scalar_Type;
 694
 695       ----------------------
 696       -- Check_Array_Type --
 697       ----------------------
 698
 699       procedure Check_Array_Type is
 700          D : Int;
 701          --  Dimension number for array attributes.
 702
 703       begin
 704          --  If the type is a string literal type, then this must be generated
 705          --  internally, and no further check is required on its legality.
 706
 707          if Ekind (P_Type) = E_String_Literal_Subtype then
 708             return;
 709
 710          --  If the type is a composite, it is an illegal aggregate, no point
 711          --  in going on.
 712
 713          elsif P_Type = Any_Composite then
 714             raise Bad_Attribute;
 715          end if;
 716
 717          --  Normal case of array type or subtype
 718
 719          Check_Either_E0_Or_E1;
 720
 721          if Is_Array_Type (P_Type) then
 722             if not Is_Constrained (P_Type)
 723               and then Is_Entity_Name (P)
 724               and then Is_Type (Entity (P))
 725             then
 726                --  Note: we do not call Error_Attr here, since we prefer to
 727                --  continue, using the relevant index type of the array,
 728                --  even though it is unconstrained. This gives better error
 729                --  recovery behavior.
 730
 731                Error_Msg_Name_1 := Aname;
 732                Error_Msg_N
 733                  ("prefix for % attribute must be constrained array", P);
 734             end if;
 735
 736             D := Number_Dimensions (P_Type);
 737
 738          elsif Is_Access_Type (P_Type)
 739            and then Is_Array_Type (Designated_Type (P_Type))
 740          then
 741             if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
 742                Error_Attr ("prefix of % attribute cannot be access type", P);
 743             end if;
 744
 745             D := Number_Dimensions (Designated_Type (P_Type));
 746
 747             --  If there is an implicit dereference, then we must freeze
 748             --  the designated type of the access type, since the type of
 749             --  the referenced array is this type (see AI95-00106).
 750
 751             Freeze_Before (N, Designated_Type (P_Type));
 752
 753          else
 754             if Is_Private_Type (P_Type) then
 755                Error_Attr
 756                  ("prefix for % attribute may not be private type", P);
 757
 758             elsif Attr_Id = Attribute_First
 759                     or else
 760                   Attr_Id = Attribute_Last
 761             then
 762                Error_Attr ("invalid prefix for % attribute", P);
 763
 764             else
 765                Error_Attr ("prefix for % attribute must be array", P);
 766             end if;
 767          end if;
 768
 769          if Present (E1) then
 770             Resolve (E1, Any_Integer);
 771             Set_Etype (E1, Standard_Integer);
 772
 773             if not Is_Static_Expression (E1)
 774               or else Raises_Constraint_Error (E1)
 775             then
 776                Flag_Non_Static_Expr
 777                  ("expression for dimension must be static!", E1);
 778                Error_Attr;
 779
 780             elsif  UI_To_Int (Expr_Value (E1)) > D
 781               or else UI_To_Int (Expr_Value (E1)) < 1
 782             then
 783                Error_Attr ("invalid dimension number for array type", E1);
 784             end if;
 785          end if;
 786       end Check_Array_Type;
 787
 788       -------------------------
 789       -- Check_Asm_Attribute --
 790       -------------------------
 791
 792       procedure Check_Asm_Attribute is
 793       begin
 794          Check_Type;
 795          Check_E2;
 796
 797          --  Check first argument is static string expression
 798
 799          Analyze_And_Resolve (E1, Standard_String);
 800
 801          if Etype (E1) = Any_Type then
 802             return;
 803
 804          elsif not Is_OK_Static_Expression (E1) then
 805             Flag_Non_Static_Expr
 806               ("constraint argument must be static string expression!", E1);
 807             Error_Attr;
 808          end if;
 809
 810          --  Check second argument is right type
 811
 812          Analyze_And_Resolve (E2, Entity (P));
 813
 814          --  Note: that is all we need to do, we don't need to check
 815          --  that it appears in a correct context. The Ada type system
 816          --  will do that for us.
 817
 818       end Check_Asm_Attribute;
 819
 820       ---------------------
 821       -- Check_Component --
 822       ---------------------
 823
 824       procedure Check_Component is
 825       begin
 826          Check_E0;
 827
 828          if Nkind (P) /= N_Selected_Component
 829            or else
 830              (Ekind (Entity (Selector_Name (P))) /= E_Component
 831                and then
 832               Ekind (Entity (Selector_Name (P))) /= E_Discriminant)
 833          then
 834             Error_Attr
 835               ("prefix for % attribute must be selected component", P);
 836          end if;
 837       end Check_Component;
 838
 839       ------------------------------------
 840       -- Check_Decimal_Fixed_Point_Type --
 841       ------------------------------------
 842
 843       procedure Check_Decimal_Fixed_Point_Type is
 844       begin
 845          Check_Type;
 846
 847          if not Is_Decimal_Fixed_Point_Type (P_Type) then
 848             Error_Attr
 849               ("prefix of % attribute must be decimal type", P);
 850          end if;
 851       end Check_Decimal_Fixed_Point_Type;
 852
 853       -----------------------
 854       -- Check_Dereference --
 855       -----------------------
 856
 857       procedure Check_Dereference is
 858       begin
 859          if Is_Object_Reference (P)
 860            and then Is_Access_Type (P_Type)
 861          then
 862             Rewrite (P,
 863               Make_Explicit_Dereference (Sloc (P),
 864                 Prefix => Relocate_Node (P)));
 865
 866             Analyze_And_Resolve (P);
 867             P_Type := Etype (P);
 868
 869             if P_Type = Any_Type then
 870                raise Bad_Attribute;
 871             end if;
 872
 873             P_Base_Type := Base_Type (P_Type);
 874          end if;
 875       end Check_Dereference;
 876
 877       -------------------------
 878       -- Check_Discrete_Type --
 879       -------------------------
 880
 881       procedure Check_Discrete_Type is
 882       begin
 883          Check_Type;
 884
 885          if not Is_Discrete_Type (P_Type) then
 886             Error_Attr ("prefix of % attribute must be discrete type", P);
 887          end if;
 888       end Check_Discrete_Type;
 889
 890       --------------
 891       -- Check_E0 --
 892       --------------
 893
 894       procedure Check_E0 is
 895       begin
 896          if Present (E1) then
 897             Unexpected_Argument (E1);
 898          end if;
 899       end Check_E0;
 900
 901       --------------
 902       -- Check_E1 --
 903       --------------
 904
 905       procedure Check_E1 is
 906       begin
 907          Check_Either_E0_Or_E1;
 908
 909          if No (E1) then
 910
 911             --  Special-case attributes that are functions and that appear as
 912             --  the prefix of another attribute. Error is posted on parent.
 913
 914             if Nkind (Parent (N)) = N_Attribute_Reference
 915               and then (Attribute_Name (Parent (N)) = Name_Address
 916                           or else
 917                         Attribute_Name (Parent (N)) = Name_Code_Address
 918                           or else
 919                         Attribute_Name (Parent (N)) = Name_Access)
 920             then
 921                Error_Msg_Name_1 := Attribute_Name (Parent (N));
 922                Error_Msg_N ("illegal prefix for % attribute", Parent (N));
 923                Set_Etype (Parent (N), Any_Type);
 924                Set_Entity (Parent (N), Any_Type);
 925                raise Bad_Attribute;
 926
 927             else
 928                Error_Attr ("missing argument for % attribute", N);
 929             end if;
 930          end if;
 931       end Check_E1;
 932
 933       --------------
 934       -- Check_E2 --
 935       --------------
 936
 937       procedure Check_E2 is
 938       begin
 939          if No (E1) then
 940             Error_Attr ("missing arguments for % attribute (2 required)", N);
 941          elsif No (E2) then
 942             Error_Attr ("missing argument for % attribute (2 required)", N);
 943          end if;
 944       end Check_E2;
 945
 946       ---------------------------
 947       -- Check_Either_E0_Or_E1 --
 948       ---------------------------
 949
 950       procedure Check_Either_E0_Or_E1 is
 951       begin
 952          if Present (E2) then
 953             Unexpected_Argument (E2);
 954          end if;
 955       end Check_Either_E0_Or_E1;
 956
 957       ----------------------
 958       -- Check_Enum_Image --
 959       ----------------------
 960
 961       procedure Check_Enum_Image is
 962          Lit : Entity_Id;
 963
 964       begin
 965          if Is_Enumeration_Type (P_Base_Type) then
 966             Lit := First_Literal (P_Base_Type);
 967             while Present (Lit) loop
 968                Set_Referenced (Lit);
 969                Next_Literal (Lit);
 970             end loop;
 971          end if;
 972       end Check_Enum_Image;
 973
 974       ----------------------------
 975       -- Check_Fixed_Point_Type --
 976       ----------------------------
 977
 978       procedure Check_Fixed_Point_Type is
 979       begin
 980          Check_Type;
 981
 982          if not Is_Fixed_Point_Type (P_Type) then
 983             Error_Attr ("prefix of % attribute must be fixed point type", P);
 984          end if;
 985       end Check_Fixed_Point_Type;
 986
 987       ------------------------------
 988       -- Check_Fixed_Point_Type_0 --
 989       ------------------------------
 990
 991       procedure Check_Fixed_Point_Type_0 is
 992       begin
 993          Check_Fixed_Point_Type;
 994          Check_E0;
 995       end Check_Fixed_Point_Type_0;
 996
 997       -------------------------------
 998       -- Check_Floating_Point_Type --
 999       -------------------------------
1000
1001       procedure Check_Floating_Point_Type is
1002       begin
1003          Check_Type;
1004
1005          if not Is_Floating_Point_Type (P_Type) then
1006             Error_Attr ("prefix of % attribute must be float type", P);
1007          end if;
1008       end Check_Floating_Point_Type;
1009
1010       ---------------------------------
1011       -- Check_Floating_Point_Type_0 --
1012       ---------------------------------
1013
1014       procedure Check_Floating_Point_Type_0 is
1015       begin
1016          Check_Floating_Point_Type;
1017          Check_E0;
1018       end Check_Floating_Point_Type_0;
1019
1020       ---------------------------------
1021       -- Check_Floating_Point_Type_1 --
1022       ---------------------------------
1023
1024       procedure Check_Floating_Point_Type_1 is
1025       begin
1026          Check_Floating_Point_Type;
1027          Check_E1;
1028       end Check_Floating_Point_Type_1;
1029
1030       ---------------------------------
1031       -- Check_Floating_Point_Type_2 --
1032       ---------------------------------
1033
1034       procedure Check_Floating_Point_Type_2 is
1035       begin
1036          Check_Floating_Point_Type;
1037          Check_E2;
1038       end Check_Floating_Point_Type_2;
1039
1040       ------------------------
1041       -- Check_Integer_Type --
1042       ------------------------
1043
1044       procedure Check_Integer_Type is
1045       begin
1046          Check_Type;
1047
1048          if not Is_Integer_Type (P_Type) then
1049             Error_Attr ("prefix of % attribute must be integer type", P);
1050          end if;
1051       end Check_Integer_Type;
1052
1053       ------------------------
1054       -- Check_Library_Unit --
1055       ------------------------
1056
1057       procedure Check_Library_Unit is
1058       begin
1059          if not Is_Compilation_Unit (Entity (P)) then
1060             Error_Attr ("prefix of % attribute must be library unit", P);
1061          end if;
1062       end Check_Library_Unit;
1063
1064       -------------------------------
1065       -- Check_Not_Incomplete_Type --
1066       -------------------------------
1067
1068       procedure Check_Not_Incomplete_Type is
1069       begin
1070          if not Is_Entity_Name (P)
1071            or else not Is_Type (Entity (P))
1072            or else In_Default_Expression
1073          then
1074             return;
1075
1076          else
1077             Check_Fully_Declared (P_Type, P);
1078          end if;
1079       end Check_Not_Incomplete_Type;
1080
1081       ----------------------------
1082       -- Check_Object_Reference --
1083       ----------------------------
1084
1085       procedure Check_Object_Reference (P : Node_Id) is
1086          Rtyp : Entity_Id;
1087
1088       begin
1089          --  If we need an object, and we have a prefix that is the name of
1090          --  a function entity, convert it into a function call.
1091
1092          if Is_Entity_Name (P)
1093            and then Ekind (Entity (P)) = E_Function
1094          then
1095             Rtyp := Etype (Entity (P));
1096
1097             Rewrite (P,
1098               Make_Function_Call (Sloc (P),
1099                 Name => Relocate_Node (P)));
1100
1101             Analyze_And_Resolve (P, Rtyp);
1102
1103          --  Otherwise we must have an object reference
1104
1105          elsif not Is_Object_Reference (P) then
1106             Error_Attr ("prefix of % attribute must be object", P);
1107          end if;
1108       end Check_Object_Reference;
1109
1110       ------------------------
1111       -- Check_Program_Unit --
1112       ------------------------
1113
1114       procedure Check_Program_Unit is
1115       begin
1116          if Is_Entity_Name (P) then
1117             declare
1118                K : constant Entity_Kind := Ekind (Entity (P));
1119                T : constant Entity_Id   := Etype (Entity (P));
1120
1121             begin
1122                if K in Subprogram_Kind
1123                  or else K in Task_Kind
1124                  or else K in Protected_Kind
1125                  or else K = E_Package
1126                  or else K in Generic_Unit_Kind
1127                  or else (K = E_Variable
1128                             and then
1129                               (Is_Task_Type (T)
1130                                  or else
1131                                Is_Protected_Type (T)))
1132                then
1133                   return;
1134                end if;
1135             end;
1136          end if;
1137
1138          Error_Attr ("prefix of % attribute must be program unit", P);
1139       end Check_Program_Unit;
1140
1141       ---------------------
1142       -- Check_Real_Type --
1143       ---------------------
1144
1145       procedure Check_Real_Type is
1146       begin
1147          Check_Type;
1148
1149          if not Is_Real_Type (P_Type) then
1150             Error_Attr ("prefix of % attribute must be real type", P);
1151          end if;
1152       end Check_Real_Type;
1153
1154       -----------------------
1155       -- Check_Scalar_Type --
1156       -----------------------
1157
1158       procedure Check_Scalar_Type is
1159       begin
1160          Check_Type;
1161
1162          if not Is_Scalar_Type (P_Type) then
1163             Error_Attr ("prefix of % attribute must be scalar type", P);
1164          end if;
1165       end Check_Scalar_Type;
1166
1167       ---------------------------
1168       -- Check_Standard_Prefix --
1169       ---------------------------
1170
1171       procedure Check_Standard_Prefix is
1172       begin
1173          Check_E0;
1174
1175          if Nkind (P) /= N_Identifier
1176            or else Chars (P) /= Name_Standard
1177          then
1178             Error_Attr ("only allowed prefix for % attribute is Standard", P);
1179          end if;
1180
1181       end Check_Standard_Prefix;
1182
1183       ----------------------------
1184       -- Check_Stream_Attribute --
1185       ----------------------------
1186
1187       procedure Check_Stream_Attribute (Nam : TSS_Name_Type) is
1188          Etyp : Entity_Id;
1189          Btyp : Entity_Id;
1190
1191       begin
1192          Validate_Non_Static_Attribute_Function_Call;
1193
1194          --  With the exception of 'Input, Stream attributes are procedures,
1195          --  and can only appear at the position of procedure calls. We check
1196          --  for this here, before they are rewritten, to give a more precise
1197          --  diagnostic.
1198
1199          if Nam = TSS_Stream_Input then
1200             null;
1201
1202          elsif Is_List_Member (N)
1203            and then Nkind (Parent (N)) /= N_Procedure_Call_Statement
1204            and then Nkind (Parent (N)) /= N_Aggregate
1205          then
1206             null;
1207
1208          else
1209             Error_Attr
1210               ("invalid context for attribute%, which is a procedure", N);
1211          end if;
1212
1213          Check_Type;
1214          Btyp := Implementation_Base_Type (P_Type);
1215
1216          --  Stream attributes not allowed on limited types unless the
1217          --  special OK_For_Stream flag is set.
1218
1219          if Is_Limited_Type (P_Type)
1220            and then Comes_From_Source (N)
1221            and then not Present (TSS (Btyp, Nam))
1222            and then No (Get_Rep_Pragma (Btyp, Name_Stream_Convert))
1223          then
1224             Error_Msg_Name_1 := Aname;
1225             Error_Msg_NE
1226               ("limited type& has no% attribute", P, Btyp);
1227             Explain_Limited_Type (P_Type, P);
1228          end if;
1229
1230          --  Check for violation of restriction No_Stream_Attributes
1231
1232          if Is_RTE (P_Type, RE_Exception_Id)
1233               or else
1234             Is_RTE (P_Type, RE_Exception_Occurrence)
1235          then
1236             Check_Restriction (No_Exception_Registration, P);
1237          end if;
1238
1239          --  Here we must check that the first argument is an access type
1240          --  that is compatible with Ada.Streams.Root_Stream_Type'Class.
1241
1242          Analyze_And_Resolve (E1);
1243          Etyp := Etype (E1);
1244
1245          --  Note: the double call to Root_Type here is needed because the
1246          --  root type of a class-wide type is the corresponding type (e.g.
1247          --  X for X'Class, and we really want to go to the root.
1248
1249          if not Is_Access_Type (Etyp)
1250            or else Root_Type (Root_Type (Designated_Type (Etyp))) /=
1251                      RTE (RE_Root_Stream_Type)
1252          then
1253             Error_Attr
1254               ("expected access to Ada.Streams.Root_Stream_Type''Class", E1);
1255          end if;
1256
1257          --  Check that the second argument is of the right type if there is
1258          --  one (the Input attribute has only one argument so this is skipped)
1259
1260          if Present (E2) then
1261             Analyze (E2);
1262
1263             if Nam = TSS_Stream_Read
1264               and then not Is_OK_Variable_For_Out_Formal (E2)
1265             then
1266                Error_Attr
1267                  ("second argument of % attribute must be a variable", E2);
1268             end if;
1269
1270             Resolve (E2, P_Type);
1271          end if;
1272       end Check_Stream_Attribute;
1273
1274       -----------------------
1275       -- Check_Task_Prefix --
1276       -----------------------
1277
1278       procedure Check_Task_Prefix is
1279       begin
1280          Analyze (P);
1281
1282          if Is_Task_Type (Etype (P))
1283            or else (Is_Access_Type (Etype (P))
1284               and then Is_Task_Type (Designated_Type (Etype (P))))
1285          then
1286             Resolve (P);
1287          else
1288             Error_Attr ("prefix of % attribute must be a task", P);
1289          end if;
1290       end Check_Task_Prefix;
1291
1292       ----------------
1293       -- Check_Type --
1294       ----------------
1295
1296       --  The possibilities are an entity name denoting a type, or an
1297       --  attribute reference that denotes a type (Base or Class). If
1298       --  the type is incomplete, replace it with its full view.
1299
1300       procedure Check_Type is
1301       begin
1302          if not Is_Entity_Name (P)
1303            or else not Is_Type (Entity (P))
1304          then
1305             Error_Attr ("prefix of % attribute must be a type", P);
1306
1307          elsif Ekind (Entity (P)) = E_Incomplete_Type
1308             and then Present (Full_View (Entity (P)))
1309          then
1310             P_Type := Full_View (Entity (P));
1311             Set_Entity (P, P_Type);
1312          end if;
1313       end Check_Type;
1314
1315       ---------------------
1316       -- Check_Unit_Name --
1317       ---------------------
1318
1319       procedure Check_Unit_Name (Nod : Node_Id) is
1320       begin
1321          if Nkind (Nod) = N_Identifier then
1322             return;
1323
1324          elsif Nkind (Nod) = N_Selected_Component then
1325             Check_Unit_Name (Prefix (Nod));
1326
1327             if Nkind (Selector_Name (Nod)) = N_Identifier then
1328                return;
1329             end if;
1330          end if;
1331
1332          Error_Attr ("argument for % attribute must be unit name", P);
1333       end Check_Unit_Name;
1334
1335       ----------------
1336       -- Error_Attr --
1337       ----------------
1338
1339       procedure Error_Attr is
1340       begin
1341          Set_Etype (N, Any_Type);
1342          Set_Entity (N, Any_Type);
1343          raise Bad_Attribute;
1344       end Error_Attr;
1345
1346       procedure Error_Attr (Msg : String; Error_Node : Node_Id) is
1347       begin
1348          Error_Msg_Name_1 := Aname;
1349          Error_Msg_N (Msg, Error_Node);
1350          Error_Attr;
1351       end Error_Attr;
1352
1353       ----------------------------
1354       -- Legal_Formal_Attribute --
1355       ----------------------------
1356
1357       procedure Legal_Formal_Attribute is
1358       begin
1359          Check_E0;
1360
1361          if not Is_Entity_Name (P)
1362            or else not Is_Type (Entity (P))
1363          then
1364             Error_Attr ("prefix of % attribute must be generic type", N);
1365
1366          elsif Is_Generic_Actual_Type (Entity (P))
1367            or else In_Instance
1368            or else In_Inlined_Body
1369          then
1370             null;
1371
1372          elsif Is_Generic_Type (Entity (P)) then
1373             if not Is_Indefinite_Subtype (Entity (P)) then
1374                Error_Attr
1375                  ("prefix of % attribute must be indefinite generic type", N);
1376             end if;
1377
1378          else
1379             Error_Attr
1380               ("prefix of % attribute must be indefinite generic type", N);
1381          end if;
1382
1383          Set_Etype (N, Standard_Boolean);
1384       end Legal_Formal_Attribute;
1385
1386       ------------------------
1387       -- Standard_Attribute --
1388       ------------------------
1389
1390       procedure Standard_Attribute (Val : Int) is
1391       begin
1392          Check_Standard_Prefix;
1393
1394          --  First a special check (more like a kludge really). For GNAT5
1395          --  on Windows, the alignments in GCC are severely mixed up. In
1396          --  particular, we have a situation where the maximum alignment
1397          --  that GCC thinks is possible is greater than the guaranteed
1398          --  alignment at run-time. That causes many problems. As a partial
1399          --  cure for this situation, we force a value of 4 for the maximum
1400          --  alignment attribute on this target. This still does not solve
1401          --  all problems, but it helps.
1402
1403          --  A further (even more horrible) dimension to this kludge is now
1404          --  installed. There are two uses for Maximum_Alignment, one is to
1405          --  determine the maximum guaranteed alignment, that's the one we
1406          --  want the kludge to yield as 4. The other use is to maximally
1407          --  align objects, we can't use 4 here, since for example, long
1408          --  long integer has an alignment of 8, so we will get errors.
1409
1410          --  It is of course impossible to determine which use the programmer
1411          --  has in mind, but an approximation for now is to disconnect the
1412          --  kludge if the attribute appears in an alignment clause.
1413
1414          --  To be removed if GCC ever gets its act together here ???
1415
1416          Alignment_Kludge : declare
1417             P : Node_Id;
1418
1419             function On_X86 return Boolean;
1420             --  Determine if target is x86 (ia32), return True if so
1421
1422             ------------
1423             -- On_X86 --
1424             ------------
1425
1426             function On_X86 return Boolean is
1427                T : String := Sdefault.Target_Name.all;
1428
1429             begin
1430                --  There is no clean way to check this. That's not surprising,
1431                --  the front end should not be doing this kind of test ???. The
1432                --  way we do it is test for either "86" or "pentium" being in
1433                --  the string for the target name.
1434
1435                for J in T'First .. T'Last - 1 loop
1436                   if T (J .. J + 1) = "86"
1437                     or else (J <= T'Last - 6
1438                                and then T (J .. J + 6) = "pentium")
1439                   then
1440                      return True;
1441                   end if;
1442                end loop;
1443
1444                return False;
1445             end On_X86;
1446
1447          begin
1448             if Aname = Name_Maximum_Alignment and then On_X86 then
1449                P := Parent (N);
1450
1451                while Nkind (P) in N_Subexpr loop
1452                   P := Parent (P);
1453                end loop;
1454
1455                if Nkind (P) /= N_Attribute_Definition_Clause
1456                  or else Chars (P) /= Name_Alignment
1457                then
1458                   Rewrite (N, Make_Integer_Literal (Loc, 4));
1459                   Analyze (N);
1460                   return;
1461                end if;
1462             end if;
1463          end Alignment_Kludge;
1464
1465          --  Normally we get the value from gcc ???
1466
1467          Rewrite (N, Make_Integer_Literal (Loc, Val));
1468          Analyze (N);
1469       end Standard_Attribute;
1470
1471       -------------------------
1472       -- Unexpected Argument --
1473       -------------------------
1474
1475       procedure Unexpected_Argument (En : Node_Id) is
1476       begin
1477          Error_Attr ("unexpected argument for % attribute", En);
1478       end Unexpected_Argument;
1479
1480       -------------------------------------------------
1481       -- Validate_Non_Static_Attribute_Function_Call --
1482       -------------------------------------------------
1483
1484       --  This function should be moved to Sem_Dist ???
1485
1486       procedure Validate_Non_Static_Attribute_Function_Call is
1487       begin
1488          if In_Preelaborated_Unit
1489            and then not In_Subprogram_Or_Concurrent_Unit
1490          then
1491             Flag_Non_Static_Expr
1492               ("non-static function call in preelaborated unit!", N);
1493          end if;
1494       end Validate_Non_Static_Attribute_Function_Call;
1495
1496    -----------------------------------------------
1497    -- Start of Processing for Analyze_Attribute --
1498    -----------------------------------------------
1499
1500    begin
1501       --  Immediate return if unrecognized attribute (already diagnosed
1502       --  by parser, so there is nothing more that we need to do)
1503
1504       if not Is_Attribute_Name (Aname) then
1505          raise Bad_Attribute;
1506       end if;
1507
1508       --  Deal with Ada 83 and Features issues
1509
1510       if Comes_From_Source (N) then
1511          if not Attribute_83 (Attr_Id) then
1512             if Ada_83 and then Comes_From_Source (N) then
1513                Error_Msg_Name_1 := Aname;
1514                Error_Msg_N ("(Ada 83) attribute% is not standard?", N);
1515             end if;
1516
1517             if Attribute_Impl_Def (Attr_Id) then
1518                Check_Restriction (No_Implementation_Attributes, N);
1519             end if;
1520          end if;
1521       end if;
1522
1523       --   Remote access to subprogram type access attribute reference needs
1524       --   unanalyzed copy for tree transformation. The analyzed copy is used
1525       --   for its semantic information (whether prefix is a remote subprogram
1526       --   name), the unanalyzed copy is used to construct new subtree rooted
1527       --   with N_aggregate which represents a fat pointer aggregate.
1528
1529       if Aname = Name_Access then
1530          Discard_Node (Copy_Separate_Tree (N));
1531       end if;
1532
1533       --  Analyze prefix and exit if error in analysis. If the prefix is an
1534       --  incomplete type, use full view if available. A special case is
1535       --  that we never analyze the prefix of an Elab_Body or Elab_Spec
1536       --  or UET_Address attribute.
1537
1538       if Aname /= Name_Elab_Body
1539            and then
1540          Aname /= Name_Elab_Spec
1541            and then
1542          Aname /= Name_UET_Address
1543       then
1544          Analyze (P);
1545          P_Type := Etype (P);
1546
1547          if Is_Entity_Name (P)
1548            and then Present (Entity (P))
1549            and then Is_Type (Entity (P))
1550            and then Ekind (Entity (P)) = E_Incomplete_Type
1551          then
1552             P_Type := Get_Full_View (P_Type);
1553             Set_Entity (P, P_Type);
1554             Set_Etype  (P, P_Type);
1555          end if;
1556
1557          if P_Type = Any_Type then
1558             raise Bad_Attribute;
1559          end if;
1560
1561          P_Base_Type := Base_Type (P_Type);
1562       end if;
1563
1564       --  Analyze expressions that may be present, exiting if an error occurs
1565
1566       if No (Exprs) then
1567          E1 := Empty;
1568          E2 := Empty;
1569
1570       else
1571          E1 := First (Exprs);
1572          Analyze (E1);
1573
1574          --  Check for missing or bad expression (result of previous error)
1575
1576          if No (E1) or else Etype (E1) = Any_Type then
1577             raise Bad_Attribute;
1578          end if;
1579
1580          E2 := Next (E1);
1581
1582          if Present (E2) then
1583             Analyze (E2);
1584
1585             if Etype (E2) = Any_Type then
1586                raise Bad_Attribute;
1587             end if;
1588
1589             if Present (Next (E2)) then
1590                Unexpected_Argument (Next (E2));
1591             end if;
1592          end if;
1593       end if;
1594
1595       if Is_Overloaded (P)
1596         and then Aname /= Name_Access
1597         and then Aname /= Name_Address
1598         and then Aname /= Name_Code_Address
1599         and then Aname /= Name_Count
1600         and then Aname /= Name_Unchecked_Access
1601       then
1602          Error_Attr ("ambiguous prefix for % attribute", P);
1603       end if;
1604
1605       --  Remaining processing depends on attribute
1606
1607       case Attr_Id is
1608
1609       ------------------
1610       -- Abort_Signal --
1611       ------------------
1612
1613       when Attribute_Abort_Signal =>
1614          Check_Standard_Prefix;
1615          Rewrite (N,
1616            New_Reference_To (Stand.Abort_Signal, Loc));
1617          Analyze (N);
1618
1619       ------------
1620       -- Access --
1621       ------------
1622
1623       when Attribute_Access =>
1624          Analyze_Access_Attribute;
1625
1626       -------------
1627       -- Address --
1628       -------------
1629
1630       when Attribute_Address =>
1631          Check_E0;
1632
1633          --  Check for some junk cases, where we have to allow the address
1634          --  attribute but it does not make much sense, so at least for now
1635          --  just replace with Null_Address.
1636
1637          --  We also do this if the prefix is a reference to the AST_Entry
1638          --  attribute. If expansion is active, the attribute will be
1639          --  replaced by a function call, and address will work fine and
1640          --  get the proper value, but if expansion is not active, then
1641          --  the check here allows proper semantic analysis of the reference.
1642
1643          --  An Address attribute created by expansion is legal even when it
1644          --  applies to other entity-denoting expressions.
1645
1646          if Is_Entity_Name (P) then
1647             declare
1648                Ent : constant Entity_Id := Entity (P);
1649
1650             begin
1651                if Is_Subprogram (Ent) then
1652                   if not Is_Library_Level_Entity (Ent) then
1653                      Check_Restriction (No_Implicit_Dynamic_Code, P);
1654                   end if;
1655
1656                   Set_Address_Taken (Ent);
1657
1658                elsif Is_Object (Ent)
1659                  or else Ekind (Ent) = E_Label
1660                then
1661                   Set_Address_Taken (Ent);
1662
1663                --  If we have an address of an object, and the attribute
1664                --  comes from source, then set the object as potentially
1665                --  source modified. We do this because the resulting address
1666                --  can potentially be used to modify the variable and we
1667                --  might not detect this, leading to some junk warnings.
1668
1669                   Set_Never_Set_In_Source (Ent, False);
1670
1671                elsif (Is_Concurrent_Type (Etype (Ent))
1672                        and then Etype (Ent) = Base_Type (Ent))
1673                  or else Ekind (Ent) = E_Package
1674                  or else Is_Generic_Unit (Ent)
1675                then
1676                   Rewrite (N,
1677                     New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1678
1679                else
1680                   Error_Attr ("invalid prefix for % attribute", P);
1681                end if;
1682             end;
1683
1684          elsif Nkind (P) = N_Attribute_Reference
1685            and then Attribute_Name (P) = Name_AST_Entry
1686          then
1687             Rewrite (N,
1688               New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1689
1690          elsif Is_Object_Reference (P) then
1691             null;
1692
1693          elsif Nkind (P) = N_Selected_Component
1694            and then Is_Subprogram (Entity (Selector_Name (P)))
1695          then
1696             null;
1697
1698          --  What exactly are we allowing here ??? and is this properly
1699          --  documented in the sinfo documentation for this node ???
1700
1701          elsif not Comes_From_Source (N) then
1702             null;
1703
1704          else
1705             Error_Attr ("invalid prefix for % attribute", P);
1706          end if;
1707
1708          Set_Etype (N, RTE (RE_Address));
1709
1710       ------------------
1711       -- Address_Size --
1712       ------------------
1713
1714       when Attribute_Address_Size =>
1715          Standard_Attribute (System_Address_Size);
1716
1717       --------------
1718       -- Adjacent --
1719       --------------
1720
1721       when Attribute_Adjacent =>
1722          Check_Floating_Point_Type_2;
1723          Set_Etype (N, P_Base_Type);
1724          Resolve (E1, P_Base_Type);
1725          Resolve (E2, P_Base_Type);
1726
1727       ---------
1728       -- Aft --
1729       ---------
1730
1731       when Attribute_Aft =>
1732          Check_Fixed_Point_Type_0;
1733          Set_Etype (N, Universal_Integer);
1734
1735       ---------------
1736       -- Alignment --
1737       ---------------
1738
1739       when Attribute_Alignment =>
1740
1741          --  Don't we need more checking here, cf Size ???
1742
1743          Check_E0;
1744          Check_Not_Incomplete_Type;
1745          Set_Etype (N, Universal_Integer);
1746
1747       ---------------
1748       -- Asm_Input --
1749       ---------------
1750
1751       when Attribute_Asm_Input =>
1752          Check_Asm_Attribute;
1753          Set_Etype (N, RTE (RE_Asm_Input_Operand));
1754
1755       ----------------
1756       -- Asm_Output --
1757       ----------------
1758
1759       when Attribute_Asm_Output =>
1760          Check_Asm_Attribute;
1761
1762          if Etype (E2) = Any_Type then
1763             return;
1764
1765          elsif Aname = Name_Asm_Output then
1766             if not Is_Variable (E2) then
1767                Error_Attr
1768                  ("second argument for Asm_Output is not variable", E2);
1769             end if;
1770          end if;
1771
1772          Note_Possible_Modification (E2);
1773          Set_Etype (N, RTE (RE_Asm_Output_Operand));
1774
1775       ---------------
1776       -- AST_Entry --
1777       ---------------
1778
1779       when Attribute_AST_Entry => AST_Entry : declare
1780          Ent  : Entity_Id;
1781          Pref : Node_Id;
1782          Ptyp : Entity_Id;
1783
1784          Indexed : Boolean;
1785          --  Indicates if entry family index is present. Note the coding
1786          --  here handles the entry family case, but in fact it cannot be
1787          --  executed currently, because pragma AST_Entry does not permit
1788          --  the specification of an entry family.
1789
1790          procedure Bad_AST_Entry;
1791          --  Signal a bad AST_Entry pragma
1792
1793          function OK_Entry (E : Entity_Id) return Boolean;
1794          --  Checks that E is of an appropriate entity kind for an entry
1795          --  (i.e. E_Entry if Index is False, or E_Entry_Family if Index
1796          --  is set True for the entry family case). In the True case,
1797          --  makes sure that Is_AST_Entry is set on the entry.
1798
1799          procedure Bad_AST_Entry is
1800          begin
1801             Error_Attr ("prefix for % attribute must be task entry", P);
1802          end Bad_AST_Entry;
1803
1804          function OK_Entry (E : Entity_Id) return Boolean is
1805             Result : Boolean;
1806
1807          begin
1808             if Indexed then
1809                Result := (Ekind (E) = E_Entry_Family);
1810             else
1811                Result := (Ekind (E) = E_Entry);
1812             end if;
1813
1814             if Result then
1815                if not Is_AST_Entry (E) then
1816                   Error_Msg_Name_2 := Aname;
1817                   Error_Attr
1818                     ("% attribute requires previous % pragma", P);
1819                end if;
1820             end if;
1821
1822             return Result;
1823          end OK_Entry;
1824
1825       --  Start of processing for AST_Entry
1826
1827       begin
1828          Check_VMS (N);
1829          Check_E0;
1830
1831          --  Deal with entry family case
1832
1833          if Nkind (P) = N_Indexed_Component then
1834             Pref := Prefix (P);
1835             Indexed := True;
1836          else
1837             Pref := P;
1838             Indexed := False;
1839          end if;
1840
1841          Ptyp := Etype (Pref);
1842
1843          if Ptyp = Any_Type or else Error_Posted (Pref) then
1844             return;
1845          end if;
1846
1847          --  If the prefix is a selected component whose prefix is of an
1848          --  access type, then introduce an explicit dereference.
1849
1850          if Nkind (Pref) = N_Selected_Component
1851            and then Is_Access_Type (Ptyp)
1852          then
1853             Rewrite (Pref,
1854               Make_Explicit_Dereference (Sloc (Pref),
1855                 Relocate_Node (Pref)));
1856             Analyze_And_Resolve (Pref, Designated_Type (Ptyp));
1857          end if;
1858
1859          --  Prefix can be of the form a.b, where a is a task object
1860          --  and b is one of the entries of the corresponding task type.
1861
1862          if Nkind (Pref) = N_Selected_Component
1863            and then OK_Entry (Entity (Selector_Name (Pref)))
1864            and then Is_Object_Reference (Prefix (Pref))
1865            and then Is_Task_Type (Etype (Prefix (Pref)))
1866          then
1867             null;
1868
1869          --  Otherwise the prefix must be an entry of a containing task,
1870          --  or of a variable of the enclosing task type.
1871
1872          else
1873             if Nkind (Pref) = N_Identifier
1874               or else Nkind (Pref) = N_Expanded_Name
1875             then
1876                Ent := Entity (Pref);
1877
1878                if not OK_Entry (Ent)
1879                  or else not In_Open_Scopes (Scope (Ent))
1880                then
1881                   Bad_AST_Entry;
1882                end if;
1883
1884             else
1885                Bad_AST_Entry;
1886             end if;
1887          end if;
1888
1889          Set_Etype (N, RTE (RE_AST_Handler));
1890       end AST_Entry;
1891
1892       ----------
1893       -- Base --
1894       ----------
1895
1896       --  Note: when the base attribute appears in the context of a subtype
1897       --  mark, the analysis is done by Sem_Ch8.Find_Type, rather than by
1898       --  the following circuit.
1899
1900       when Attribute_Base => Base : declare
1901          Typ : Entity_Id;
1902
1903       begin
1904          Check_Either_E0_Or_E1;
1905          Find_Type (P);
1906          Typ := Entity (P);
1907
1908          if Ada_95
1909            and then not Is_Scalar_Type (Typ)
1910            and then not Is_Generic_Type (Typ)
1911          then
1912             Error_Msg_N ("prefix of Base attribute must be scalar type", N);
1913
1914          elsif Sloc (Typ) = Standard_Location
1915            and then Base_Type (Typ) = Typ
1916            and then Warn_On_Redundant_Constructs
1917          then
1918             Error_Msg_NE
1919               ("?redudant attribute, & is its own base type", N, Typ);
1920          end if;
1921
1922          Set_Etype (N, Base_Type (Entity (P)));
1923
1924          --  If we have an expression present, then really this is a conversion
1925          --  and the tree must be reformed. Note that this is one of the cases
1926          --  in which we do a replace rather than a rewrite, because the
1927          --  original tree is junk.
1928
1929          if Present (E1) then
1930             Replace (N,
1931               Make_Type_Conversion (Loc,
1932                 Subtype_Mark =>
1933                   Make_Attribute_Reference (Loc,
1934                     Prefix => Prefix (N),
1935                     Attribute_Name => Name_Base),
1936                 Expression => Relocate_Node (E1)));
1937
1938             --  E1 may be overloaded, and its interpretations preserved.
1939
1940             Save_Interps (E1, Expression (N));
1941             Analyze (N);
1942
1943          --  For other cases, set the proper type as the entity of the
1944          --  attribute reference, and then rewrite the node to be an
1945          --  occurrence of the referenced base type. This way, no one
1946          --  else in the compiler has to worry about the base attribute.
1947
1948          else
1949             Set_Entity (N, Base_Type (Entity (P)));
1950             Rewrite (N,
1951               New_Reference_To (Entity (N), Loc));
1952             Analyze (N);
1953          end if;
1954       end Base;
1955
1956       ---------
1957       -- Bit --
1958       ---------
1959
1960       when Attribute_Bit => Bit :
1961       begin
1962          Check_E0;
1963
1964          if not Is_Object_Reference (P) then
1965             Error_Attr ("prefix for % attribute must be object", P);
1966
1967          --  What about the access object cases ???
1968
1969          else
1970             null;
1971          end if;
1972
1973          Set_Etype (N, Universal_Integer);
1974       end Bit;
1975
1976       ---------------
1977       -- Bit_Order --
1978       ---------------
1979
1980       when Attribute_Bit_Order => Bit_Order :
1981       begin
1982          Check_E0;
1983          Check_Type;
1984
1985          if not Is_Record_Type (P_Type) then
1986             Error_Attr ("prefix of % attribute must be record type", P);
1987          end if;
1988
1989          if Bytes_Big_Endian xor Reverse_Bit_Order (P_Type) then
1990             Rewrite (N,
1991               New_Occurrence_Of (RTE (RE_High_Order_First), Loc));
1992          else
1993             Rewrite (N,
1994               New_Occurrence_Of (RTE (RE_Low_Order_First), Loc));
1995          end if;
1996
1997          Set_Etype (N, RTE (RE_Bit_Order));
1998          Resolve (N);
1999
2000          --  Reset incorrect indication of staticness
2001
2002          Set_Is_Static_Expression (N, False);
2003       end Bit_Order;
2004
2005       ------------------
2006       -- Bit_Position --
2007       ------------------
2008
2009       --  Note: in generated code, we can have a Bit_Position attribute
2010       --  applied to a (naked) record component (i.e. the prefix is an
2011       --  identifier that references an E_Component or E_Discriminant
2012       --  entity directly, and this is interpreted as expected by Gigi.
2013       --  The following code will not tolerate such usage, but when the
2014       --  expander creates this special case, it marks it as analyzed
2015       --  immediately and sets an appropriate type.
2016
2017       when Attribute_Bit_Position =>
2018
2019          if Comes_From_Source (N) then
2020             Check_Component;
2021          end if;
2022
2023          Set_Etype (N, Universal_Integer);
2024
2025       ------------------
2026       -- Body_Version --
2027       ------------------
2028
2029       when Attribute_Body_Version =>
2030          Check_E0;
2031          Check_Program_Unit;
2032          Set_Etype (N, RTE (RE_Version_String));
2033
2034       --------------
2035       -- Callable --
2036       --------------
2037
2038       when Attribute_Callable =>
2039          Check_E0;
2040          Set_Etype (N, Standard_Boolean);
2041          Check_Task_Prefix;
2042
2043       ------------
2044       -- Caller --
2045       ------------
2046
2047       when Attribute_Caller => Caller : declare
2048          Ent        : Entity_Id;
2049          S          : Entity_Id;
2050
2051       begin
2052          Check_E0;
2053
2054          if Nkind (P) = N_Identifier
2055            or else Nkind (P) = N_Expanded_Name
2056          then
2057             Ent := Entity (P);
2058
2059             if not Is_Entry (Ent) then
2060                Error_Attr ("invalid entry name", N);
2061             end if;
2062
2063          else
2064             Error_Attr ("invalid entry name", N);
2065             return;
2066          end if;
2067
2068          for J in reverse 0 .. Scope_Stack.Last loop
2069             S := Scope_Stack.Table (J).Entity;
2070
2071             if S = Scope (Ent) then
2072                Error_Attr ("Caller must appear in matching accept or body", N);
2073             elsif S = Ent then
2074                exit;
2075             end if;
2076          end loop;
2077
2078          Set_Etype (N, RTE (RO_AT_Task_ID));
2079       end Caller;
2080
2081       -------------
2082       -- Ceiling --
2083       -------------
2084
2085       when Attribute_Ceiling =>
2086          Check_Floating_Point_Type_1;
2087          Set_Etype (N, P_Base_Type);
2088          Resolve (E1, P_Base_Type);
2089
2090       -----------
2091       -- Class --
2092       -----------
2093
2094       when Attribute_Class => Class : declare
2095       begin
2096          Check_Restriction (No_Dispatch, N);
2097          Check_Either_E0_Or_E1;
2098
2099          --  If we have an expression present, then really this is a conversion
2100          --  and the tree must be reformed into a proper conversion. This is a
2101          --  Replace rather than a Rewrite, because the original tree is junk.
2102          --  If expression is overloaded, propagate interpretations to new one.
2103
2104          if Present (E1) then
2105             Replace (N,
2106               Make_Type_Conversion (Loc,
2107                 Subtype_Mark =>
2108                   Make_Attribute_Reference (Loc,
2109                     Prefix => Prefix (N),
2110                     Attribute_Name => Name_Class),
2111                 Expression => Relocate_Node (E1)));
2112
2113             Save_Interps (E1, Expression (N));
2114             Analyze (N);
2115
2116          --  Otherwise we just need to find the proper type
2117
2118          else
2119             Find_Type (N);
2120          end if;
2121
2122       end Class;
2123
2124       ------------------
2125       -- Code_Address --
2126       ------------------
2127
2128       when Attribute_Code_Address =>
2129          Check_E0;
2130
2131          if Nkind (P) = N_Attribute_Reference
2132            and then (Attribute_Name (P) = Name_Elab_Body
2133                        or else
2134                      Attribute_Name (P) = Name_Elab_Spec)
2135          then
2136             null;
2137
2138          elsif not Is_Entity_Name (P)
2139            or else (Ekind (Entity (P)) /= E_Function
2140                       and then
2141                     Ekind (Entity (P)) /= E_Procedure)
2142          then
2143             Error_Attr ("invalid prefix for % attribute", P);
2144             Set_Address_Taken (Entity (P));
2145          end if;
2146
2147          Set_Etype (N, RTE (RE_Address));
2148
2149       --------------------
2150       -- Component_Size --
2151       --------------------
2152
2153       when Attribute_Component_Size =>
2154          Check_E0;
2155          Set_Etype (N, Universal_Integer);
2156
2157          --  Note: unlike other array attributes, unconstrained arrays are OK
2158
2159          if Is_Array_Type (P_Type) and then not Is_Constrained (P_Type) then
2160             null;
2161          else
2162             Check_Array_Type;
2163          end if;
2164
2165       -------------
2166       -- Compose --
2167       -------------
2168
2169       when Attribute_Compose =>
2170          Check_Floating_Point_Type_2;
2171          Set_Etype (N, P_Base_Type);
2172          Resolve (E1, P_Base_Type);
2173          Resolve (E2, Any_Integer);
2174
2175       -----------------
2176       -- Constrained --
2177       -----------------
2178
2179       when Attribute_Constrained =>
2180          Check_E0;
2181          Set_Etype (N, Standard_Boolean);
2182
2183          --  Case from RM J.4(2) of constrained applied to private type
2184
2185          if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
2186
2187             --  If we are within an instance, the attribute must be legal
2188             --  because it was valid in the generic unit. Ditto if this is
2189             --  an inlining of a function declared in an instance.
2190
2191             if In_Instance
2192               or else In_Inlined_Body
2193             then
2194                return;
2195
2196             --  For sure OK if we have a real private type itself, but must
2197             --  be completed, cannot apply Constrained to incomplete type.
2198
2199             elsif Is_Private_Type (Entity (P)) then
2200
2201                --  Note: this is one of the Annex J features that does not
2202                --  generate a warning from -gnatwj, since in fact it seems
2203                --  very useful, and is used in the GNAT runtime.
2204
2205                Check_Not_Incomplete_Type;
2206                return;
2207             end if;
2208
2209          --  Normal (non-obsolescent case) of application to object of
2210          --  a discriminated type.
2211
2212          else
2213             Check_Object_Reference (P);
2214
2215             --  If N does not come from source, then we allow the
2216             --  the attribute prefix to be of a private type whose
2217             --  full type has discriminants. This occurs in cases
2218             --  involving expanded calls to stream attributes.
2219
2220             if not Comes_From_Source (N) then
2221                P_Type := Underlying_Type (P_Type);
2222             end if;
2223
2224             --  Must have discriminants or be an access type designating
2225             --  a type with discriminants. If it is a classwide type is
2226             --  has unknown discriminants.
2227
2228             if Has_Discriminants (P_Type)
2229                or else Has_Unknown_Discriminants (P_Type)
2230                or else
2231                  (Is_Access_Type (P_Type)
2232                    and then Has_Discriminants (Designated_Type (P_Type)))
2233             then
2234                return;
2235
2236             --  Also allow an object of a generic type if extensions allowed
2237             --  and allow this for any type at all.
2238
2239             elsif (Is_Generic_Type (P_Type)
2240                      or else Is_Generic_Actual_Type (P_Type))
2241               and then Extensions_Allowed
2242             then
2243                return;
2244             end if;
2245          end if;
2246
2247          --  Fall through if bad prefix
2248
2249          Error_Attr
2250            ("prefix of % attribute must be object of discriminated type", P);
2251
2252       ---------------
2253       -- Copy_Sign --
2254       ---------------
2255
2256       when Attribute_Copy_Sign =>
2257          Check_Floating_Point_Type_2;
2258          Set_Etype (N, P_Base_Type);
2259          Resolve (E1, P_Base_Type);
2260          Resolve (E2, P_Base_Type);
2261
2262       -----------
2263       -- Count --
2264       -----------
2265
2266       when Attribute_Count => Count :
2267       declare
2268          Ent : Entity_Id;
2269          S   : Entity_Id;
2270          Tsk : Entity_Id;
2271
2272       begin
2273          Check_E0;
2274
2275          if Nkind (P) = N_Identifier
2276            or else Nkind (P) = N_Expanded_Name
2277          then
2278             Ent := Entity (P);
2279
2280             if Ekind (Ent) /= E_Entry then
2281                Error_Attr ("invalid entry name", N);
2282             end if;
2283
2284          elsif Nkind (P) = N_Indexed_Component then
2285             if not Is_Entity_Name (Prefix (P))
2286               or else  No (Entity (Prefix (P)))
2287               or else Ekind (Entity (Prefix (P))) /= E_Entry_Family
2288             then
2289                if Nkind (Prefix (P)) = N_Selected_Component
2290                  and then Present (Entity (Selector_Name (Prefix (P))))
2291                  and then Ekind (Entity (Selector_Name (Prefix (P)))) =
2292                                                              E_Entry_Family
2293                then
2294                   Error_Attr
2295                     ("attribute % must apply to entry of current task", P);
2296
2297                else
2298                   Error_Attr ("invalid entry family name", P);
2299                end if;
2300                return;
2301
2302             else
2303                Ent := Entity (Prefix (P));
2304             end if;
2305
2306          elsif Nkind (P) = N_Selected_Component
2307            and then Present (Entity (Selector_Name (P)))
2308            and then Ekind (Entity (Selector_Name (P))) = E_Entry
2309          then
2310             Error_Attr
2311               ("attribute % must apply to entry of current task", P);
2312
2313          else
2314             Error_Attr ("invalid entry name", N);
2315             return;
2316          end if;
2317
2318          for J in reverse 0 .. Scope_Stack.Last loop
2319             S := Scope_Stack.Table (J).Entity;
2320
2321             if S = Scope (Ent) then
2322                if Nkind (P) = N_Expanded_Name then
2323                   Tsk := Entity (Prefix (P));
2324
2325                   --  The prefix denotes either the task type, or else a
2326                   --  single task whose task type is being analyzed.
2327
2328                   if (Is_Type (Tsk)
2329                       and then Tsk = S)
2330
2331                     or else (not Is_Type (Tsk)
2332                       and then Etype (Tsk) = S
2333                       and then not (Comes_From_Source (S)))
2334                   then
2335                      null;
2336                   else
2337                      Error_Attr
2338                        ("Attribute % must apply to entry of current task", N);
2339                   end if;
2340                end if;
2341
2342                exit;
2343
2344             elsif Ekind (Scope (Ent)) in Task_Kind
2345               and then Ekind (S) /= E_Loop
2346               and then Ekind (S) /= E_Block
2347               and then Ekind (S) /= E_Entry
2348               and then Ekind (S) /= E_Entry_Family
2349             then
2350                Error_Attr ("Attribute % cannot appear in inner unit", N);
2351
2352             elsif Ekind (Scope (Ent)) = E_Protected_Type
2353               and then not Has_Completion (Scope (Ent))
2354             then
2355                Error_Attr ("attribute % can only be used inside body", N);
2356             end if;
2357          end loop;
2358
2359          if Is_Overloaded (P) then
2360             declare
2361                Index : Interp_Index;
2362                It    : Interp;
2363
2364             begin
2365                Get_First_Interp (P, Index, It);
2366
2367                while Present (It.Nam) loop
2368                   if It.Nam = Ent then
2369                      null;
2370
2371                   else
2372                      Error_Attr ("ambiguous entry name", N);
2373                   end if;
2374
2375                   Get_Next_Interp (Index, It);
2376                end loop;
2377             end;
2378          end if;
2379
2380          Set_Etype (N, Universal_Integer);
2381       end Count;
2382
2383       -----------------------
2384       -- Default_Bit_Order --
2385       -----------------------
2386
2387       when Attribute_Default_Bit_Order => Default_Bit_Order :
2388       begin
2389          Check_Standard_Prefix;
2390          Check_E0;
2391
2392          if Bytes_Big_Endian then
2393             Rewrite (N,
2394               Make_Integer_Literal (Loc, False_Value));
2395          else
2396             Rewrite (N,
2397               Make_Integer_Literal (Loc, True_Value));
2398          end if;
2399
2400          Set_Etype (N, Universal_Integer);
2401          Set_Is_Static_Expression (N);
2402       end Default_Bit_Order;
2403
2404       --------------
2405       -- Definite --
2406       --------------
2407
2408       when Attribute_Definite =>
2409          Legal_Formal_Attribute;
2410
2411       -----------
2412       -- Delta --
2413       -----------
2414
2415       when Attribute_Delta =>
2416          Check_Fixed_Point_Type_0;
2417          Set_Etype (N, Universal_Real);
2418
2419       ------------
2420       -- Denorm --
2421       ------------
2422
2423       when Attribute_Denorm =>
2424          Check_Floating_Point_Type_0;
2425          Set_Etype (N, Standard_Boolean);
2426
2427       ------------
2428       -- Digits --
2429       ------------
2430
2431       when Attribute_Digits =>
2432          Check_E0;
2433          Check_Type;
2434
2435          if not Is_Floating_Point_Type (P_Type)
2436            and then not Is_Decimal_Fixed_Point_Type (P_Type)
2437          then
2438             Error_Attr
2439               ("prefix of % attribute must be float or decimal type", P);
2440          end if;
2441
2442          Set_Etype (N, Universal_Integer);
2443
2444       ---------------
2445       -- Elab_Body --
2446       ---------------
2447
2448       --  Also handles processing for Elab_Spec
2449
2450       when Attribute_Elab_Body | Attribute_Elab_Spec =>
2451          Check_E0;
2452          Check_Unit_Name (P);
2453          Set_Etype (N, Standard_Void_Type);
2454
2455          --  We have to manually call the expander in this case to get
2456          --  the necessary expansion (normally attributes that return
2457          --  entities are not expanded).
2458
2459          Expand (N);
2460
2461       ---------------
2462       -- Elab_Spec --
2463       ---------------
2464
2465       --  Shares processing with Elab_Body
2466
2467       ----------------
2468       -- Elaborated --
2469       ----------------
2470
2471       when Attribute_Elaborated =>
2472          Check_E0;
2473          Check_Library_Unit;
2474          Set_Etype (N, Standard_Boolean);
2475
2476       ----------
2477       -- Emax --
2478       ----------
2479
2480       when Attribute_Emax =>
2481          Check_Floating_Point_Type_0;
2482          Set_Etype (N, Universal_Integer);
2483
2484       --------------
2485       -- Enum_Rep --
2486       --------------
2487
2488       when Attribute_Enum_Rep => Enum_Rep : declare
2489       begin
2490          if Present (E1) then
2491             Check_E1;
2492             Check_Discrete_Type;
2493             Resolve (E1, P_Base_Type);
2494
2495          else
2496             if not Is_Entity_Name (P)
2497               or else (not Is_Object (Entity (P))
2498                          and then
2499                        Ekind (Entity (P)) /= E_Enumeration_Literal)
2500             then
2501                Error_Attr
2502                  ("prefix of %attribute must be " &
2503                   "discrete type/object or enum literal", P);
2504             end if;
2505          end if;
2506
2507          Set_Etype (N, Universal_Integer);
2508       end Enum_Rep;
2509
2510       -------------
2511       -- Epsilon --
2512       -------------
2513
2514       when Attribute_Epsilon =>
2515          Check_Floating_Point_Type_0;
2516          Set_Etype (N, Universal_Real);
2517
2518       --------------
2519       -- Exponent --
2520       --------------
2521
2522       when Attribute_Exponent =>
2523          Check_Floating_Point_Type_1;
2524          Set_Etype (N, Universal_Integer);
2525          Resolve (E1, P_Base_Type);
2526
2527       ------------------
2528       -- External_Tag --
2529       ------------------
2530
2531       when Attribute_External_Tag =>
2532          Check_E0;
2533          Check_Type;
2534
2535          Set_Etype (N, Standard_String);
2536
2537          if not Is_Tagged_Type (P_Type) then
2538             Error_Attr ("prefix of % attribute must be tagged", P);
2539          end if;
2540
2541       -----------
2542       -- First --
2543       -----------
2544
2545       when Attribute_First =>
2546          Check_Array_Or_Scalar_Type;
2547
2548       ---------------
2549       -- First_Bit --
2550       ---------------
2551
2552       when Attribute_First_Bit =>
2553          Check_Component;
2554          Set_Etype (N, Universal_Integer);
2555
2556       -----------------
2557       -- Fixed_Value --
2558       -----------------
2559
2560       when Attribute_Fixed_Value =>
2561          Check_E1;
2562          Check_Fixed_Point_Type;
2563          Resolve (E1, Any_Integer);
2564          Set_Etype (N, P_Base_Type);
2565
2566       -----------
2567       -- Floor --
2568       -----------
2569
2570       when Attribute_Floor =>
2571          Check_Floating_Point_Type_1;
2572          Set_Etype (N, P_Base_Type);
2573          Resolve (E1, P_Base_Type);
2574
2575       ----------
2576       -- Fore --
2577       ----------
2578
2579       when Attribute_Fore =>
2580          Check_Fixed_Point_Type_0;
2581          Set_Etype (N, Universal_Integer);
2582
2583       --------------
2584       -- Fraction --
2585       --------------
2586
2587       when Attribute_Fraction =>
2588          Check_Floating_Point_Type_1;
2589          Set_Etype (N, P_Base_Type);
2590          Resolve (E1, P_Base_Type);
2591
2592       -----------------------
2593       -- Has_Discriminants --
2594       -----------------------
2595
2596       when Attribute_Has_Discriminants =>
2597          Legal_Formal_Attribute;
2598
2599       --------------
2600       -- Identity --
2601       --------------
2602
2603       when Attribute_Identity =>
2604          Check_E0;
2605          Analyze (P);
2606
2607          if Etype (P) =  Standard_Exception_Type then
2608             Set_Etype (N, RTE (RE_Exception_Id));
2609
2610          elsif Is_Task_Type (Etype (P))
2611            or else (Is_Access_Type (Etype (P))
2612               and then Is_Task_Type (Designated_Type (Etype (P))))
2613          then
2614             Resolve (P);
2615             Set_Etype (N, RTE (RO_AT_Task_ID));
2616
2617          else
2618             Error_Attr ("prefix of % attribute must be a task or an "
2619               & "exception", P);
2620          end if;
2621
2622       -----------
2623       -- Image --
2624       -----------
2625
2626       when Attribute_Image => Image :
2627       begin
2628          Set_Etype (N, Standard_String);
2629          Check_Scalar_Type;
2630
2631          if Is_Real_Type (P_Type) then
2632             if Ada_83 and then Comes_From_Source (N) then
2633                Error_Msg_Name_1 := Aname;
2634                Error_Msg_N
2635                  ("(Ada 83) % attribute not allowed for real types", N);
2636             end if;
2637          end if;
2638
2639          if Is_Enumeration_Type (P_Type) then
2640             Check_Restriction (No_Enumeration_Maps, N);
2641          end if;
2642
2643          Check_E1;
2644          Resolve (E1, P_Base_Type);
2645          Check_Enum_Image;
2646          Validate_Non_Static_Attribute_Function_Call;
2647       end Image;
2648
2649       ---------
2650       -- Img --
2651       ---------
2652
2653       when Attribute_Img => Img :
2654       begin
2655          Set_Etype (N, Standard_String);
2656
2657          if not Is_Scalar_Type (P_Type)
2658            or else (Is_Entity_Name (P) and then Is_Type (Entity (P)))
2659          then
2660             Error_Attr
2661               ("prefix of % attribute must be scalar object name", N);
2662          end if;
2663
2664          Check_Enum_Image;
2665       end Img;
2666
2667       -----------
2668       -- Input --
2669       -----------
2670
2671       when Attribute_Input =>
2672          Check_E1;
2673          Check_Stream_Attribute (TSS_Stream_Input);
2674          Set_Etype (N, P_Base_Type);
2675
2676       -------------------
2677       -- Integer_Value --
2678       -------------------
2679
2680       when Attribute_Integer_Value =>
2681          Check_E1;
2682          Check_Integer_Type;
2683          Resolve (E1, Any_Fixed);
2684          Set_Etype (N, P_Base_Type);
2685
2686       -----------
2687       -- Large --
2688       -----------
2689
2690       when Attribute_Large =>
2691          Check_E0;
2692          Check_Real_Type;
2693          Set_Etype (N, Universal_Real);
2694
2695       ----------
2696       -- Last --
2697       ----------
2698
2699       when Attribute_Last =>
2700          Check_Array_Or_Scalar_Type;
2701
2702       --------------
2703       -- Last_Bit --
2704       --------------
2705
2706       when Attribute_Last_Bit =>
2707          Check_Component;
2708          Set_Etype (N, Universal_Integer);
2709
2710       ------------------
2711       -- Leading_Part --
2712       ------------------
2713
2714       when Attribute_Leading_Part =>
2715          Check_Floating_Point_Type_2;
2716          Set_Etype (N, P_Base_Type);
2717          Resolve (E1, P_Base_Type);
2718          Resolve (E2, Any_Integer);
2719
2720       ------------
2721       -- Length --
2722       ------------
2723
2724       when Attribute_Length =>
2725          Check_Array_Type;
2726          Set_Etype (N, Universal_Integer);
2727
2728       -------------
2729       -- Machine --
2730       -------------
2731
2732       when Attribute_Machine =>
2733          Check_Floating_Point_Type_1;
2734          Set_Etype (N, P_Base_Type);
2735          Resolve (E1, P_Base_Type);
2736
2737       ------------------
2738       -- Machine_Emax --
2739       ------------------
2740
2741       when Attribute_Machine_Emax =>
2742          Check_Floating_Point_Type_0;
2743          Set_Etype (N, Universal_Integer);
2744
2745       ------------------
2746       -- Machine_Emin --
2747       ------------------
2748
2749       when Attribute_Machine_Emin =>
2750          Check_Floating_Point_Type_0;
2751          Set_Etype (N, Universal_Integer);
2752
2753       ----------------------
2754       -- Machine_Mantissa --
2755       ----------------------
2756
2757       when Attribute_Machine_Mantissa =>
2758          Check_Floating_Point_Type_0;
2759          Set_Etype (N, Universal_Integer);
2760
2761       -----------------------
2762       -- Machine_Overflows --
2763       -----------------------
2764
2765       when Attribute_Machine_Overflows =>
2766          Check_Real_Type;
2767          Check_E0;
2768          Set_Etype (N, Standard_Boolean);
2769
2770       -------------------
2771       -- Machine_Radix --
2772       -------------------
2773
2774       when Attribute_Machine_Radix =>
2775          Check_Real_Type;
2776          Check_E0;
2777          Set_Etype (N, Universal_Integer);
2778
2779       --------------------
2780       -- Machine_Rounds --
2781       --------------------
2782
2783       when Attribute_Machine_Rounds =>
2784          Check_Real_Type;
2785          Check_E0;
2786          Set_Etype (N, Standard_Boolean);
2787
2788       ------------------
2789       -- Machine_Size --
2790       ------------------
2791
2792       when Attribute_Machine_Size =>
2793          Check_E0;
2794          Check_Type;
2795          Check_Not_Incomplete_Type;
2796          Set_Etype (N, Universal_Integer);
2797
2798       --------------
2799       -- Mantissa --
2800       --------------
2801
2802       when Attribute_Mantissa =>
2803          Check_E0;
2804          Check_Real_Type;
2805          Set_Etype (N, Universal_Integer);
2806
2807       ---------
2808       -- Max --
2809       ---------
2810
2811       when Attribute_Max =>
2812          Check_E2;
2813          Check_Scalar_Type;
2814          Resolve (E1, P_Base_Type);
2815          Resolve (E2, P_Base_Type);
2816          Set_Etype (N, P_Base_Type);
2817
2818       ----------------------------------
2819       -- Max_Size_In_Storage_Elements --
2820       ----------------------------------
2821
2822       when Attribute_Max_Size_In_Storage_Elements =>
2823          Check_E0;
2824          Check_Type;
2825          Check_Not_Incomplete_Type;
2826          Set_Etype (N, Universal_Integer);
2827
2828       -----------------------
2829       -- Maximum_Alignment --
2830       -----------------------
2831
2832       when Attribute_Maximum_Alignment =>
2833          Standard_Attribute (Ttypes.Maximum_Alignment);
2834
2835       --------------------
2836       -- Mechanism_Code --
2837       --------------------
2838
2839       when Attribute_Mechanism_Code =>
2840          if not Is_Entity_Name (P)
2841            or else not Is_Subprogram (Entity (P))
2842          then
2843             Error_Attr ("prefix of % attribute must be subprogram", P);
2844          end if;
2845
2846          Check_Either_E0_Or_E1;
2847
2848          if Present (E1) then
2849             Resolve (E1, Any_Integer);
2850             Set_Etype (E1, Standard_Integer);
2851
2852             if not Is_Static_Expression (E1) then
2853                Flag_Non_Static_Expr
2854                  ("expression for parameter number must be static!", E1);
2855                Error_Attr;
2856
2857             elsif UI_To_Int (Intval (E1)) > Number_Formals (Entity (P))
2858               or else UI_To_Int (Intval (E1)) < 0
2859             then
2860                Error_Attr ("invalid parameter number for %attribute", E1);
2861             end if;
2862          end if;
2863
2864          Set_Etype (N, Universal_Integer);
2865
2866       ---------
2867       -- Min --
2868       ---------
2869
2870       when Attribute_Min =>
2871          Check_E2;
2872          Check_Scalar_Type;
2873          Resolve (E1, P_Base_Type);
2874          Resolve (E2, P_Base_Type);
2875          Set_Etype (N, P_Base_Type);
2876
2877       -----------
2878       -- Model --
2879       -----------
2880
2881       when Attribute_Model =>
2882          Check_Floating_Point_Type_1;
2883          Set_Etype (N, P_Base_Type);
2884          Resolve (E1, P_Base_Type);
2885
2886       ----------------
2887       -- Model_Emin --
2888       ----------------
2889
2890       when Attribute_Model_Emin =>
2891          Check_Floating_Point_Type_0;
2892          Set_Etype (N, Universal_Integer);
2893
2894       -------------------
2895       -- Model_Epsilon --
2896       -------------------
2897
2898       when Attribute_Model_Epsilon =>
2899          Check_Floating_Point_Type_0;
2900          Set_Etype (N, Universal_Real);
2901
2902       --------------------
2903       -- Model_Mantissa --
2904       --------------------
2905
2906       when Attribute_Model_Mantissa =>
2907          Check_Floating_Point_Type_0;
2908          Set_Etype (N, Universal_Integer);
2909
2910       -----------------
2911       -- Model_Small --
2912       -----------------
2913
2914       when Attribute_Model_Small =>
2915          Check_Floating_Point_Type_0;
2916          Set_Etype (N, Universal_Real);
2917
2918       -------------
2919       -- Modulus --
2920       -------------
2921
2922       when Attribute_Modulus =>
2923          Check_E0;
2924          Check_Type;
2925
2926          if not Is_Modular_Integer_Type (P_Type) then
2927             Error_Attr ("prefix of % attribute must be modular type", P);
2928          end if;
2929
2930          Set_Etype (N, Universal_Integer);
2931
2932       --------------------
2933       -- Null_Parameter --
2934       --------------------
2935
2936       when Attribute_Null_Parameter => Null_Parameter : declare
2937          Parnt  : constant Node_Id := Parent (N);
2938          GParnt : constant Node_Id := Parent (Parnt);
2939
2940          procedure Bad_Null_Parameter (Msg : String);
2941          --  Used if bad Null parameter attribute node is found. Issues
2942          --  given error message, and also sets the type to Any_Type to
2943          --  avoid blowups later on from dealing with a junk node.
2944
2945          procedure Must_Be_Imported (Proc_Ent : Entity_Id);
2946          --  Called to check that Proc_Ent is imported subprogram
2947
2948          ------------------------
2949          -- Bad_Null_Parameter --
2950          ------------------------
2951
2952          procedure Bad_Null_Parameter (Msg : String) is
2953          begin
2954             Error_Msg_N (Msg, N);
2955             Set_Etype (N, Any_Type);
2956          end Bad_Null_Parameter;
2957
2958          ----------------------
2959          -- Must_Be_Imported --
2960          ----------------------
2961
2962          procedure Must_Be_Imported (Proc_Ent : Entity_Id) is
2963             Pent : Entity_Id := Proc_Ent;
2964
2965          begin
2966             while Present (Alias (Pent)) loop
2967                Pent := Alias (Pent);
2968             end loop;
2969
2970             --  Ignore check if procedure not frozen yet (we will get
2971             --  another chance when the default parameter is reanalyzed)
2972
2973             if not Is_Frozen (Pent) then
2974                return;
2975
2976             elsif not Is_Imported (Pent) then
2977                Bad_Null_Parameter
2978                  ("Null_Parameter can only be used with imported subprogram");
2979
2980             else
2981                return;
2982             end if;
2983          end Must_Be_Imported;
2984
2985       --  Start of processing for Null_Parameter
2986
2987       begin
2988          Check_Type;
2989          Check_E0;
2990          Set_Etype (N, P_Type);
2991
2992          --  Case of attribute used as default expression
2993
2994          if Nkind (Parnt) = N_Parameter_Specification then
2995             Must_Be_Imported (Defining_Entity (GParnt));
2996
2997          --  Case of attribute used as actual for subprogram (positional)
2998
2999          elsif (Nkind (Parnt) = N_Procedure_Call_Statement
3000                  or else
3001                 Nkind (Parnt) = N_Function_Call)
3002             and then Is_Entity_Name (Name (Parnt))
3003          then
3004             Must_Be_Imported (Entity (Name (Parnt)));
3005
3006          --  Case of attribute used as actual for subprogram (named)
3007
3008          elsif Nkind (Parnt) = N_Parameter_Association
3009            and then (Nkind (GParnt) = N_Procedure_Call_Statement
3010                        or else
3011                      Nkind (GParnt) = N_Function_Call)
3012            and then Is_Entity_Name (Name (GParnt))
3013          then
3014             Must_Be_Imported (Entity (Name (GParnt)));
3015
3016          --  Not an allowed case
3017
3018          else
3019             Bad_Null_Parameter
3020               ("Null_Parameter must be actual or default parameter");
3021          end if;
3022
3023       end Null_Parameter;
3024
3025       -----------------
3026       -- Object_Size --
3027       -----------------
3028
3029       when Attribute_Object_Size =>
3030          Check_E0;
3031          Check_Type;
3032          Check_Not_Incomplete_Type;
3033          Set_Etype (N, Universal_Integer);
3034
3035       ------------
3036       -- Output --
3037       ------------
3038
3039       when Attribute_Output =>
3040          Check_E2;
3041          Check_Stream_Attribute (TSS_Stream_Output);
3042          Set_Etype (N, Standard_Void_Type);
3043          Resolve (N, Standard_Void_Type);
3044
3045       ------------------
3046       -- Partition_ID --
3047       ------------------
3048
3049       when Attribute_Partition_ID =>
3050          Check_E0;
3051
3052          if P_Type /= Any_Type then
3053             if not Is_Library_Level_Entity (Entity (P)) then
3054                Error_Attr
3055                  ("prefix of % attribute must be library-level entity", P);
3056
3057             --  The defining entity of prefix should not be declared inside
3058             --  a Pure unit. RM E.1(8).
3059             --  The Is_Pure flag has been set during declaration.
3060
3061             elsif Is_Entity_Name (P)
3062               and then Is_Pure (Entity (P))
3063             then
3064                Error_Attr
3065                  ("prefix of % attribute must not be declared pure", P);
3066             end if;
3067          end if;
3068
3069          Set_Etype (N, Universal_Integer);
3070
3071       -------------------------
3072       -- Passed_By_Reference --
3073       -------------------------
3074
3075       when Attribute_Passed_By_Reference =>
3076          Check_E0;
3077          Check_Type;
3078          Set_Etype (N, Standard_Boolean);
3079
3080       ------------------
3081       -- Pool_Address --
3082       ------------------
3083
3084       when Attribute_Pool_Address =>
3085          Check_E0;
3086          Set_Etype (N, RTE (RE_Address));
3087
3088       ---------
3089       -- Pos --
3090       ---------
3091
3092       when Attribute_Pos =>
3093          Check_Discrete_Type;
3094          Check_E1;
3095          Resolve (E1, P_Base_Type);
3096          Set_Etype (N, Universal_Integer);
3097
3098       --------------
3099       -- Position --
3100       --------------
3101
3102       when Attribute_Position =>
3103          Check_Component;
3104          Set_Etype (N, Universal_Integer);
3105
3106       ----------
3107       -- Pred --
3108       ----------
3109
3110       when Attribute_Pred =>
3111          Check_Scalar_Type;
3112          Check_E1;
3113          Resolve (E1, P_Base_Type);
3114          Set_Etype (N, P_Base_Type);
3115
3116          --  Nothing to do for real type case
3117
3118          if Is_Real_Type (P_Type) then
3119             null;
3120
3121          --  If not modular type, test for overflow check required
3122
3123          else
3124             if not Is_Modular_Integer_Type (P_Type)
3125               and then not Range_Checks_Suppressed (P_Base_Type)
3126             then
3127                Enable_Range_Check (E1);
3128             end if;
3129          end if;
3130
3131       -----------
3132       -- Range --
3133       -----------
3134
3135       when Attribute_Range =>
3136          Check_Array_Or_Scalar_Type;
3137
3138          if Ada_83
3139            and then Is_Scalar_Type (P_Type)
3140            and then Comes_From_Source (N)
3141          then
3142             Error_Attr
3143               ("(Ada 83) % attribute not allowed for scalar type", P);
3144          end if;
3145
3146       ------------------
3147       -- Range_Length --
3148       ------------------
3149
3150       when Attribute_Range_Length =>
3151          Check_Discrete_Type;
3152          Set_Etype (N, Universal_Integer);
3153
3154       ----------
3155       -- Read --
3156       ----------
3157
3158       when Attribute_Read =>
3159          Check_E2;
3160          Check_Stream_Attribute (TSS_Stream_Read);
3161          Set_Etype (N, Standard_Void_Type);
3162          Resolve (N, Standard_Void_Type);
3163          Note_Possible_Modification (E2);
3164
3165       ---------------
3166       -- Remainder --
3167       ---------------
3168
3169       when Attribute_Remainder =>
3170          Check_Floating_Point_Type_2;
3171          Set_Etype (N, P_Base_Type);
3172          Resolve (E1, P_Base_Type);
3173          Resolve (E2, P_Base_Type);
3174
3175       -----------
3176       -- Round --
3177       -----------
3178
3179       when Attribute_Round =>
3180          Check_E1;
3181          Check_Decimal_Fixed_Point_Type;
3182          Set_Etype (N, P_Base_Type);
3183
3184          --  Because the context is universal_real (3.5.10(12)) it is a legal
3185          --  context for a universal fixed expression. This is the only
3186          --  attribute whose functional description involves U_R.
3187
3188          if Etype (E1) = Universal_Fixed then
3189             declare
3190                Conv : constant Node_Id := Make_Type_Conversion (Loc,
3191                   Subtype_Mark => New_Occurrence_Of (Universal_Real, Loc),
3192                   Expression   => Relocate_Node (E1));
3193
3194             begin
3195                Rewrite (E1, Conv);
3196                Analyze (E1);
3197             end;
3198          end if;
3199
3200          Resolve (E1, Any_Real);
3201
3202       --------------
3203       -- Rounding --
3204       --------------
3205
3206       when Attribute_Rounding =>
3207          Check_Floating_Point_Type_1;
3208          Set_Etype (N, P_Base_Type);
3209          Resolve (E1, P_Base_Type);
3210
3211       ---------------
3212       -- Safe_Emax --
3213       ---------------
3214
3215       when Attribute_Safe_Emax =>
3216          Check_Floating_Point_Type_0;
3217          Set_Etype (N, Universal_Integer);
3218
3219       ----------------
3220       -- Safe_First --
3221       ----------------
3222
3223       when Attribute_Safe_First =>
3224          Check_Floating_Point_Type_0;
3225          Set_Etype (N, Universal_Real);
3226
3227       ----------------
3228       -- Safe_Large --
3229       ----------------
3230
3231       when Attribute_Safe_Large =>
3232          Check_E0;
3233          Check_Real_Type;
3234          Set_Etype (N, Universal_Real);
3235
3236       ---------------
3237       -- Safe_Last --
3238       ---------------
3239
3240       when Attribute_Safe_Last =>
3241          Check_Floating_Point_Type_0;
3242          Set_Etype (N, Universal_Real);
3243
3244       ----------------
3245       -- Safe_Small --
3246       ----------------
3247
3248       when Attribute_Safe_Small =>
3249          Check_E0;
3250          Check_Real_Type;
3251          Set_Etype (N, Universal_Real);
3252
3253       -----------
3254       -- Scale --
3255       -----------
3256
3257       when Attribute_Scale =>
3258          Check_E0;
3259          Check_Decimal_Fixed_Point_Type;
3260          Set_Etype (N, Universal_Integer);
3261
3262       -------------
3263       -- Scaling --
3264       -------------
3265
3266       when Attribute_Scaling =>
3267          Check_Floating_Point_Type_2;
3268          Set_Etype (N, P_Base_Type);
3269          Resolve (E1, P_Base_Type);
3270
3271       ------------------
3272       -- Signed_Zeros --
3273       ------------------
3274
3275       when Attribute_Signed_Zeros =>
3276          Check_Floating_Point_Type_0;
3277          Set_Etype (N, Standard_Boolean);
3278
3279       ----------
3280       -- Size --
3281       ----------
3282
3283       when Attribute_Size | Attribute_VADS_Size =>
3284          Check_E0;
3285
3286          if Is_Object_Reference (P)
3287            or else (Is_Entity_Name (P)
3288                      and then Ekind (Entity (P)) = E_Function)
3289          then
3290             Check_Object_Reference (P);
3291
3292          elsif Is_Entity_Name (P)
3293            and then Is_Type (Entity (P))
3294          then
3295             null;
3296
3297          elsif Nkind (P) = N_Type_Conversion
3298            and then not Comes_From_Source (P)
3299          then
3300             null;
3301
3302          else
3303             Error_Attr ("invalid prefix for % attribute", P);
3304          end if;
3305
3306          Check_Not_Incomplete_Type;
3307          Set_Etype (N, Universal_Integer);
3308
3309       -----------
3310       -- Small --
3311       -----------
3312
3313       when Attribute_Small =>
3314          Check_E0;
3315          Check_Real_Type;
3316          Set_Etype (N, Universal_Real);
3317
3318       ------------------
3319       -- Storage_Pool --
3320       ------------------
3321
3322       when Attribute_Storage_Pool =>
3323          if Is_Access_Type (P_Type) then
3324             Check_E0;
3325
3326             --  Set appropriate entity
3327
3328             if Present (Associated_Storage_Pool (Root_Type (P_Type))) then
3329                Set_Entity (N, Associated_Storage_Pool (Root_Type (P_Type)));
3330             else
3331                Set_Entity (N, RTE (RE_Global_Pool_Object));
3332             end if;
3333
3334             Set_Etype (N, Class_Wide_Type (RTE (RE_Root_Storage_Pool)));
3335
3336             --  Validate_Remote_Access_To_Class_Wide_Type for attribute
3337             --  Storage_Pool since this attribute is not defined for such
3338             --  types (RM E.2.3(22)).
3339
3340             Validate_Remote_Access_To_Class_Wide_Type (N);
3341
3342          else
3343             Error_Attr ("prefix of % attribute must be access type", P);
3344          end if;
3345
3346       ------------------
3347       -- Storage_Size --
3348       ------------------
3349
3350       when Attribute_Storage_Size =>
3351
3352          if Is_Task_Type (P_Type) then
3353             Check_E0;
3354             Set_Etype (N, Universal_Integer);
3355
3356          elsif Is_Access_Type (P_Type) then
3357             if Is_Entity_Name (P)
3358               and then Is_Type (Entity (P))
3359             then
3360                Check_E0;
3361                Check_Type;
3362                Set_Etype (N, Universal_Integer);
3363
3364                --   Validate_Remote_Access_To_Class_Wide_Type for attribute
3365                --   Storage_Size since this attribute is not defined for
3366                --   such types (RM E.2.3(22)).
3367
3368                Validate_Remote_Access_To_Class_Wide_Type (N);
3369
3370             --  The prefix is allowed to be an implicit dereference
3371             --  of an access value designating a task.
3372
3373             else
3374                Check_E0;
3375                Check_Task_Prefix;
3376                Set_Etype (N, Universal_Integer);
3377             end if;
3378
3379          else
3380             Error_Attr
3381               ("prefix of % attribute must be access or task type", P);
3382          end if;
3383
3384       ------------------
3385       -- Storage_Unit --
3386       ------------------
3387
3388       when Attribute_Storage_Unit =>
3389          Standard_Attribute (Ttypes.System_Storage_Unit);
3390
3391       ----------
3392       -- Succ --
3393       ----------
3394
3395       when Attribute_Succ =>
3396          Check_Scalar_Type;
3397          Check_E1;
3398          Resolve (E1, P_Base_Type);
3399          Set_Etype (N, P_Base_Type);
3400
3401          --  Nothing to do for real type case
3402
3403          if Is_Real_Type (P_Type) then
3404             null;
3405
3406          --  If not modular type, test for overflow check required.
3407
3408          else
3409             if not Is_Modular_Integer_Type (P_Type)
3410               and then not Range_Checks_Suppressed (P_Base_Type)
3411             then
3412                Enable_Range_Check (E1);
3413             end if;
3414          end if;
3415
3416       ---------
3417       -- Tag --
3418       ---------
3419
3420       when Attribute_Tag =>
3421          Check_E0;
3422          Check_Dereference;
3423
3424          if not Is_Tagged_Type (P_Type) then
3425             Error_Attr ("prefix of % attribute must be tagged", P);
3426
3427          --  Next test does not apply to generated code
3428          --  why not, and what does the illegal reference mean???
3429
3430          elsif Is_Object_Reference (P)
3431            and then not Is_Class_Wide_Type (P_Type)
3432            and then Comes_From_Source (N)
3433          then
3434             Error_Attr
3435               ("% attribute can only be applied to objects of class-wide type",
3436                P);
3437          end if;
3438
3439          Set_Etype (N, RTE (RE_Tag));
3440
3441       -----------------
3442       -- Target_Name --
3443       -----------------
3444
3445       when Attribute_Target_Name => Target_Name : declare
3446          TN : constant String := Sdefault.Target_Name.all;
3447          TL : Integer := TN'Last;
3448
3449       begin
3450          Check_Standard_Prefix;
3451          Check_E0;
3452          Start_String;
3453
3454          if TN (TL) = '/' or else TN (TL) = '\' then
3455             TL := TL - 1;
3456          end if;
3457
3458          Store_String_Chars (TN (TN'First .. TL));
3459
3460          Rewrite (N,
3461            Make_String_Literal (Loc,
3462              Strval => End_String));
3463          Analyze_And_Resolve (N, Standard_String);
3464       end Target_Name;
3465
3466       ----------------
3467       -- Terminated --
3468       ----------------
3469
3470       when Attribute_Terminated =>
3471          Check_E0;
3472          Set_Etype (N, Standard_Boolean);
3473          Check_Task_Prefix;
3474
3475       ----------------
3476       -- To_Address --
3477       ----------------
3478
3479       when Attribute_To_Address =>
3480          Check_E1;
3481          Analyze (P);
3482
3483          if Nkind (P) /= N_Identifier
3484            or else Chars (P) /= Name_System
3485          then
3486             Error_Attr ("prefix of %attribute must be System", P);
3487          end if;
3488
3489          Generate_Reference (RTE (RE_Address), P);
3490          Analyze_And_Resolve (E1, Any_Integer);
3491          Set_Etype (N, RTE (RE_Address));
3492
3493       ----------------
3494       -- Truncation --
3495       ----------------
3496
3497       when Attribute_Truncation =>
3498          Check_Floating_Point_Type_1;
3499          Resolve (E1, P_Base_Type);
3500          Set_Etype (N, P_Base_Type);
3501
3502       ----------------
3503       -- Type_Class --
3504       ----------------
3505
3506       when Attribute_Type_Class =>
3507          Check_E0;
3508          Check_Type;
3509          Check_Not_Incomplete_Type;
3510          Set_Etype (N, RTE (RE_Type_Class));
3511
3512       -----------------
3513       -- UET_Address --
3514       -----------------
3515
3516       when Attribute_UET_Address =>
3517          Check_E0;
3518          Check_Unit_Name (P);
3519          Set_Etype (N, RTE (RE_Address));
3520
3521       -----------------------
3522       -- Unbiased_Rounding --
3523       -----------------------
3524
3525       when Attribute_Unbiased_Rounding =>
3526          Check_Floating_Point_Type_1;
3527          Set_Etype (N, P_Base_Type);
3528          Resolve (E1, P_Base_Type);
3529
3530       ----------------------
3531       -- Unchecked_Access --
3532       ----------------------
3533
3534       when Attribute_Unchecked_Access =>
3535          if Comes_From_Source (N) then
3536             Check_Restriction (No_Unchecked_Access, N);
3537          end if;
3538
3539          Analyze_Access_Attribute;
3540
3541       -------------------------
3542       -- Unconstrained_Array --
3543       -------------------------
3544
3545       when Attribute_Unconstrained_Array =>
3546          Check_E0;
3547          Check_Type;
3548          Check_Not_Incomplete_Type;
3549          Set_Etype (N, Standard_Boolean);
3550
3551       ------------------------------
3552       -- Universal_Literal_String --
3553       ------------------------------
3554
3555       --  This is a GNAT specific attribute whose prefix must be a named
3556       --  number where the expression is either a single numeric literal,
3557       --  or a numeric literal immediately preceded by a minus sign. The
3558       --  result is equivalent to a string literal containing the text of
3559       --  the literal as it appeared in the source program with a possible
3560       --  leading minus sign.
3561
3562       when Attribute_Universal_Literal_String => Universal_Literal_String :
3563       begin
3564          Check_E0;
3565
3566          if not Is_Entity_Name (P)
3567            or else Ekind (Entity (P)) not in Named_Kind
3568          then
3569             Error_Attr ("prefix for % attribute must be named number", P);
3570
3571          else
3572             declare
3573                Expr     : Node_Id;
3574                Negative : Boolean;
3575                S        : Source_Ptr;
3576                Src      : Source_Buffer_Ptr;
3577
3578             begin
3579                Expr := Original_Node (Expression (Parent (Entity (P))));
3580
3581                if Nkind (Expr) = N_Op_Minus then
3582                   Negative := True;
3583                   Expr := Original_Node (Right_Opnd (Expr));
3584                else
3585                   Negative := False;
3586                end if;
3587
3588                if Nkind (Expr) /= N_Integer_Literal
3589                  and then Nkind (Expr) /= N_Real_Literal
3590                then
3591                   Error_Attr
3592                     ("named number for % attribute must be simple literal", N);
3593                end if;
3594
3595                --  Build string literal corresponding to source literal text
3596
3597                Start_String;
3598
3599                if Negative then
3600                   Store_String_Char (Get_Char_Code ('-'));
3601                end if;
3602
3603                S := Sloc (Expr);
3604                Src := Source_Text (Get_Source_File_Index (S));
3605
3606                while Src (S) /= ';' and then Src (S) /= ' ' loop
3607                   Store_String_Char (Get_Char_Code (Src (S)));
3608                   S := S + 1;
3609                end loop;
3610
3611                --  Now we rewrite the attribute with the string literal
3612
3613                Rewrite (N,
3614                  Make_String_Literal (Loc, End_String));
3615                Analyze (N);
3616             end;
3617          end if;
3618       end Universal_Literal_String;
3619
3620       -------------------------
3621       -- Unrestricted_Access --
3622       -------------------------
3623
3624       --  This is a GNAT specific attribute which is like Access except that
3625       --  all scope checks and checks for aliased views are omitted.
3626
3627       when Attribute_Unrestricted_Access =>
3628          if Comes_From_Source (N) then
3629             Check_Restriction (No_Unchecked_Access, N);
3630          end if;
3631
3632          if Is_Entity_Name (P) then
3633             Set_Address_Taken (Entity (P));
3634          end if;
3635
3636          Analyze_Access_Attribute;
3637
3638       ---------
3639       -- Val --
3640       ---------
3641
3642       when Attribute_Val => Val : declare
3643       begin
3644          Check_E1;
3645          Check_Discrete_Type;
3646          Resolve (E1, Any_Integer);
3647          Set_Etype (N, P_Base_Type);
3648
3649          --  Note, we need a range check in general, but we wait for the
3650          --  Resolve call to do this, since we want to let Eval_Attribute
3651          --  have a chance to find an static illegality first!
3652       end Val;
3653
3654       -----------
3655       -- Valid --
3656       -----------
3657
3658       when Attribute_Valid =>
3659          Check_E0;
3660
3661          --  Ignore check for object if we have a 'Valid reference generated
3662          --  by the expanded code, since in some cases valid checks can occur
3663          --  on items that are names, but are not objects (e.g. attributes).
3664
3665          if Comes_From_Source (N) then
3666             Check_Object_Reference (P);
3667          end if;
3668
3669          if not Is_Scalar_Type (P_Type) then
3670             Error_Attr ("object for % attribute must be of scalar type", P);
3671          end if;
3672
3673          Set_Etype (N, Standard_Boolean);
3674
3675       -----------
3676       -- Value --
3677       -----------
3678
3679       when Attribute_Value => Value :
3680       begin
3681          Check_E1;
3682          Check_Scalar_Type;
3683
3684          if Is_Enumeration_Type (P_Type) then
3685             Check_Restriction (No_Enumeration_Maps, N);
3686          end if;
3687
3688          --  Set Etype before resolving expression because expansion of
3689          --  expression may require enclosing type. Note that the type
3690          --  returned by 'Value is the base type of the prefix type.
3691
3692          Set_Etype (N, P_Base_Type);
3693          Validate_Non_Static_Attribute_Function_Call;
3694       end Value;
3695
3696       ----------------
3697       -- Value_Size --
3698       ----------------
3699
3700       when Attribute_Value_Size =>
3701          Check_E0;
3702          Check_Type;
3703          Check_Not_Incomplete_Type;
3704          Set_Etype (N, Universal_Integer);
3705
3706       -------------
3707       -- Version --
3708       -------------
3709
3710       when Attribute_Version =>
3711          Check_E0;
3712          Check_Program_Unit;
3713          Set_Etype (N, RTE (RE_Version_String));
3714
3715       ------------------
3716       -- Wchar_T_Size --
3717       ------------------
3718
3719       when Attribute_Wchar_T_Size =>
3720          Standard_Attribute (Interfaces_Wchar_T_Size);
3721
3722       ----------------
3723       -- Wide_Image --
3724       ----------------
3725
3726       when Attribute_Wide_Image => Wide_Image :
3727       begin
3728          Check_Scalar_Type;
3729          Set_Etype (N, Standard_Wide_String);
3730          Check_E1;
3731          Resolve (E1, P_Base_Type);
3732          Validate_Non_Static_Attribute_Function_Call;
3733       end Wide_Image;
3734
3735       ----------------
3736       -- Wide_Value --
3737       ----------------
3738
3739       when Attribute_Wide_Value => Wide_Value :
3740       begin
3741          Check_E1;
3742          Check_Scalar_Type;
3743
3744          --  Set Etype before resolving expression because expansion
3745          --  of expression may require enclosing type.
3746
3747          Set_Etype (N, P_Type);
3748          Validate_Non_Static_Attribute_Function_Call;
3749       end Wide_Value;
3750
3751       ----------------
3752       -- Wide_Width --
3753       ----------------
3754
3755       when Attribute_Wide_Width =>
3756          Check_E0;
3757          Check_Scalar_Type;
3758          Set_Etype (N, Universal_Integer);
3759
3760       -----------
3761       -- Width --
3762       -----------
3763
3764       when Attribute_Width =>
3765          Check_E0;
3766          Check_Scalar_Type;
3767          Set_Etype (N, Universal_Integer);
3768
3769       ---------------
3770       -- Word_Size --
3771       ---------------
3772
3773       when Attribute_Word_Size =>
3774          Standard_Attribute (System_Word_Size);
3775
3776       -----------
3777       -- Write --
3778       -----------
3779
3780       when Attribute_Write =>
3781          Check_E2;
3782          Check_Stream_Attribute (TSS_Stream_Write);
3783          Set_Etype (N, Standard_Void_Type);
3784          Resolve (N, Standard_Void_Type);
3785
3786       end case;
3787
3788    --  All errors raise Bad_Attribute, so that we get out before any further
3789    --  damage occurs when an error is detected (for example, if we check for
3790    --  one attribute expression, and the check succeeds, we want to be able
3791    --  to proceed securely assuming that an expression is in fact present.
3792
3793    exception
3794       when Bad_Attribute =>
3795          Set_Etype (N, Any_Type);
3796          return;
3797
3798    end Analyze_Attribute;
3799
3800    --------------------
3801    -- Eval_Attribute --
3802    --------------------
3803
3804    procedure Eval_Attribute (N : Node_Id) is
3805       Loc   : constant Source_Ptr   := Sloc (N);
3806       Aname : constant Name_Id      := Attribute_Name (N);
3807       Id    : constant Attribute_Id := Get_Attribute_Id (Aname);
3808       P     : constant Node_Id      := Prefix (N);
3809
3810       C_Type : constant Entity_Id := Etype (N);
3811       --  The type imposed by the context.
3812
3813       E1 : Node_Id;
3814       --  First expression, or Empty if none
3815
3816       E2 : Node_Id;
3817       --  Second expression, or Empty if none
3818
3819       P_Entity : Entity_Id;
3820       --  Entity denoted by prefix
3821
3822       P_Type : Entity_Id;
3823       --  The type of the prefix
3824
3825       P_Base_Type : Entity_Id;
3826       --  The base type of the prefix type
3827
3828       P_Root_Type : Entity_Id;
3829       --  The root type of the prefix type
3830
3831       Static : Boolean;
3832       --  True if the result is Static. This is set by the general processing
3833       --  to true if the prefix is static, and all expressions are static. It
3834       --  can be reset as processing continues for particular attributes
3835
3836       Lo_Bound, Hi_Bound : Node_Id;
3837       --  Expressions for low and high bounds of type or array index referenced
3838       --  by First, Last, or Length attribute for array, set by Set_Bounds.
3839
3840       CE_Node : Node_Id;
3841       --  Constraint error node used if we have an attribute reference has
3842       --  an argument that raises a constraint error. In this case we replace
3843       --  the attribute with a raise constraint_error node. This is important
3844       --  processing, since otherwise gigi might see an attribute which it is
3845       --  unprepared to deal with.
3846
3847       function Aft_Value return Nat;
3848       --  Computes Aft value for current attribute prefix (used by Aft itself
3849       --  and also by Width for computing the Width of a fixed point type).
3850
3851       procedure Check_Expressions;
3852       --  In case where the attribute is not foldable, the expressions, if
3853       --  any, of the attribute, are in a non-static context. This procedure
3854       --  performs the required additional checks.
3855
3856       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean;
3857       --  Determines if the given type has compile time known bounds. Note
3858       --  that we enter the case statement even in cases where the prefix
3859       --  type does NOT have known bounds, so it is important to guard any
3860       --  attempt to evaluate both bounds with a call to this function.
3861
3862       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint);
3863       --  This procedure is called when the attribute N has a non-static
3864       --  but compile time known value given by Val. It includes the
3865       --  necessary checks for out of range values.
3866
3867       procedure Float_Attribute_Universal_Integer
3868         (IEEES_Val : Int;
3869          IEEEL_Val : Int;
3870          IEEEX_Val : Int;
3871          VAXFF_Val : Int;
3872          VAXDF_Val : Int;
3873          VAXGF_Val : Int;
3874          AAMPS_Val : Int;
3875          AAMPL_Val : Int);
3876       --  This procedure evaluates a float attribute with no arguments that
3877       --  returns a universal integer result. The parameters give the values
3878       --  for the possible floating-point root types. See ttypef for details.
3879       --  The prefix type is a float type (and is thus not a generic type).
3880
3881       procedure Float_Attribute_Universal_Real
3882         (IEEES_Val : String;
3883          IEEEL_Val : String;
3884          IEEEX_Val : String;
3885          VAXFF_Val : String;
3886          VAXDF_Val : String;
3887          VAXGF_Val : String;
3888          AAMPS_Val : String;
3889          AAMPL_Val : String);
3890       --  This procedure evaluates a float attribute with no arguments that
3891       --  returns a universal real result. The parameters give the values
3892       --  required for the possible floating-point root types in string
3893       --  format as real literals with a possible leading minus sign.
3894       --  The prefix type is a float type (and is thus not a generic type).
3895
3896       function Fore_Value return Nat;
3897       --  Computes the Fore value for the current attribute prefix, which is
3898       --  known to be a static fixed-point type. Used by Fore and Width.
3899
3900       function Mantissa return Uint;
3901       --  Returns the Mantissa value for the prefix type
3902
3903       procedure Set_Bounds;
3904       --  Used for First, Last and Length attributes applied to an array or
3905       --  array subtype. Sets the variables Lo_Bound and Hi_Bound to the low
3906       --  and high bound expressions for the index referenced by the attribute
3907       --  designator (i.e. the first index if no expression is present, and
3908       --  the N'th index if the value N is present as an expression). Also
3909       --  used for First and Last of scalar types. Static is reset to False
3910       --  if the type or index type is not statically constrained.
3911
3912       ---------------
3913       -- Aft_Value --
3914       ---------------
3915
3916       function Aft_Value return Nat is
3917          Result    : Nat;
3918          Delta_Val : Ureal;
3919
3920       begin
3921          Result := 1;
3922          Delta_Val := Delta_Value (P_Type);
3923
3924          while Delta_Val < Ureal_Tenth loop
3925             Delta_Val := Delta_Val * Ureal_10;
3926             Result := Result + 1;
3927          end loop;
3928
3929          return Result;
3930       end Aft_Value;
3931
3932       -----------------------
3933       -- Check_Expressions --
3934       -----------------------
3935
3936       procedure Check_Expressions is
3937          E : Node_Id := E1;
3938
3939       begin
3940          while Present (E) loop
3941             Check_Non_Static_Context (E);
3942             Next (E);
3943          end loop;
3944       end Check_Expressions;
3945
3946       ----------------------------------
3947       -- Compile_Time_Known_Attribute --
3948       ----------------------------------
3949
3950       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint) is
3951          T : constant Entity_Id := Etype (N);
3952
3953       begin
3954          Fold_Uint (N, Val, False);
3955
3956          --  Check that result is in bounds of the type if it is static
3957
3958          if Is_In_Range (N, T) then
3959             null;
3960
3961          elsif Is_Out_Of_Range (N, T) then
3962             Apply_Compile_Time_Constraint_Error
3963               (N, "value not in range of}?", CE_Range_Check_Failed);
3964
3965          elsif not Range_Checks_Suppressed (T) then
3966             Enable_Range_Check (N);
3967
3968          else
3969             Set_Do_Range_Check (N, False);
3970          end if;
3971       end Compile_Time_Known_Attribute;
3972
3973       -------------------------------
3974       -- Compile_Time_Known_Bounds --
3975       -------------------------------
3976
3977       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean is
3978       begin
3979          return
3980            Compile_Time_Known_Value (Type_Low_Bound (Typ))
3981              and then
3982            Compile_Time_Known_Value (Type_High_Bound (Typ));
3983       end Compile_Time_Known_Bounds;
3984
3985       ---------------------------------------
3986       -- Float_Attribute_Universal_Integer --
3987       ---------------------------------------
3988
3989       procedure Float_Attribute_Universal_Integer
3990         (IEEES_Val : Int;
3991          IEEEL_Val : Int;
3992          IEEEX_Val : Int;
3993          VAXFF_Val : Int;
3994          VAXDF_Val : Int;
3995          VAXGF_Val : Int;
3996          AAMPS_Val : Int;
3997          AAMPL_Val : Int)
3998       is
3999          Val  : Int;
4000          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4001
4002       begin
4003          if Vax_Float (P_Base_Type) then
4004             if Digs = VAXFF_Digits then
4005                Val := VAXFF_Val;
4006             elsif Digs = VAXDF_Digits then
4007                Val := VAXDF_Val;
4008             else pragma Assert (Digs = VAXGF_Digits);
4009                Val := VAXGF_Val;
4010             end if;
4011
4012          elsif Is_AAMP_Float (P_Base_Type) then
4013             if Digs = AAMPS_Digits then
4014                Val := AAMPS_Val;
4015             else pragma Assert (Digs = AAMPL_Digits);
4016                Val := AAMPL_Val;
4017             end if;
4018
4019          else
4020             if Digs = IEEES_Digits then
4021                Val := IEEES_Val;
4022             elsif Digs = IEEEL_Digits then
4023                Val := IEEEL_Val;
4024             else pragma Assert (Digs = IEEEX_Digits);
4025                Val := IEEEX_Val;
4026             end if;
4027          end if;
4028
4029          Fold_Uint (N, UI_From_Int (Val), True);
4030       end Float_Attribute_Universal_Integer;
4031
4032       ------------------------------------
4033       -- Float_Attribute_Universal_Real --
4034       ------------------------------------
4035
4036       procedure Float_Attribute_Universal_Real
4037         (IEEES_Val : String;
4038          IEEEL_Val : String;
4039          IEEEX_Val : String;
4040          VAXFF_Val : String;
4041          VAXDF_Val : String;
4042          VAXGF_Val : String;
4043          AAMPS_Val : String;
4044          AAMPL_Val : String)
4045       is
4046          Val  : Node_Id;
4047          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4048
4049       begin
4050          if Vax_Float (P_Base_Type) then
4051             if Digs = VAXFF_Digits then
4052                Val := Real_Convert (VAXFF_Val);
4053             elsif Digs = VAXDF_Digits then
4054                Val := Real_Convert (VAXDF_Val);
4055             else pragma Assert (Digs = VAXGF_Digits);
4056                Val := Real_Convert (VAXGF_Val);
4057             end if;
4058
4059          elsif Is_AAMP_Float (P_Base_Type) then
4060             if Digs = AAMPS_Digits then
4061                Val := Real_Convert (AAMPS_Val);
4062             else pragma Assert (Digs = AAMPL_Digits);
4063                Val := Real_Convert (AAMPL_Val);
4064             end if;
4065
4066          else
4067             if Digs = IEEES_Digits then
4068                Val := Real_Convert (IEEES_Val);
4069             elsif Digs = IEEEL_Digits then
4070                Val := Real_Convert (IEEEL_Val);
4071             else pragma Assert (Digs = IEEEX_Digits);
4072                Val := Real_Convert (IEEEX_Val);
4073             end if;
4074          end if;
4075
4076          Set_Sloc (Val, Loc);
4077          Rewrite (N, Val);
4078          Set_Is_Static_Expression (N, Static);
4079          Analyze_And_Resolve (N, C_Type);
4080       end Float_Attribute_Universal_Real;
4081
4082       ----------------
4083       -- Fore_Value --
4084       ----------------
4085
4086       --  Note that the Fore calculation is based on the actual values
4087       --  of the bounds, and does not take into account possible rounding.
4088
4089       function Fore_Value return Nat is
4090          Lo      : constant Uint  := Expr_Value (Type_Low_Bound (P_Type));
4091          Hi      : constant Uint  := Expr_Value (Type_High_Bound (P_Type));
4092          Small   : constant Ureal := Small_Value (P_Type);
4093          Lo_Real : constant Ureal := Lo * Small;
4094          Hi_Real : constant Ureal := Hi * Small;
4095          T       : Ureal;
4096          R       : Nat;
4097
4098       begin
4099          --  Bounds are given in terms of small units, so first compute
4100          --  proper values as reals.
4101
4102          T := UR_Max (abs Lo_Real, abs Hi_Real);
4103          R := 2;
4104
4105          --  Loop to compute proper value if more than one digit required
4106
4107          while T >= Ureal_10 loop
4108             R := R + 1;
4109             T := T / Ureal_10;
4110          end loop;
4111
4112          return R;
4113       end Fore_Value;
4114
4115       --------------
4116       -- Mantissa --
4117       --------------
4118
4119       --  Table of mantissa values accessed by function  Computed using
4120       --  the relation:
4121
4122       --    T'Mantissa = integer next above (D * log(10)/log(2)) + 1)
4123
4124       --  where D is T'Digits (RM83 3.5.7)
4125
4126       Mantissa_Value : constant array (Nat range 1 .. 40) of Nat := (
4127           1 =>   5,
4128           2 =>   8,
4129           3 =>  11,
4130           4 =>  15,
4131           5 =>  18,
4132           6 =>  21,
4133           7 =>  25,
4134           8 =>  28,
4135           9 =>  31,
4136          10 =>  35,
4137          11 =>  38,
4138          12 =>  41,
4139          13 =>  45,
4140          14 =>  48,
4141          15 =>  51,
4142          16 =>  55,
4143          17 =>  58,
4144          18 =>  61,
4145          19 =>  65,
4146          20 =>  68,
4147          21 =>  71,
4148          22 =>  75,
4149          23 =>  78,
4150          24 =>  81,
4151          25 =>  85,
4152          26 =>  88,
4153          27 =>  91,
4154          28 =>  95,
4155          29 =>  98,
4156          30 => 101,
4157          31 => 104,
4158          32 => 108,
4159          33 => 111,
4160          34 => 114,
4161          35 => 118,
4162          36 => 121,
4163          37 => 124,
4164          38 => 128,
4165          39 => 131,
4166          40 => 134);
4167
4168       function Mantissa return Uint is
4169       begin
4170          return
4171            UI_From_Int (Mantissa_Value (UI_To_Int (Digits_Value (P_Type))));
4172       end Mantissa;
4173
4174       ----------------
4175       -- Set_Bounds --
4176       ----------------
4177
4178       procedure Set_Bounds is
4179          Ndim : Nat;
4180          Indx : Node_Id;
4181          Ityp : Entity_Id;
4182
4183       begin
4184          --  For a string literal subtype, we have to construct the bounds.
4185          --  Valid Ada code never applies attributes to string literals, but
4186          --  it is convenient to allow the expander to generate attribute
4187          --  references of this type (e.g. First and Last applied to a string
4188          --  literal).
4189
4190          --  Note that the whole point of the E_String_Literal_Subtype is to
4191          --  avoid this construction of bounds, but the cases in which we
4192          --  have to materialize them are rare enough that we don't worry!
4193
4194          --  The low bound is simply the low bound of the base type. The
4195          --  high bound is computed from the length of the string and this
4196          --  low bound.
4197
4198          if Ekind (P_Type) = E_String_Literal_Subtype then
4199             Ityp := Etype (First_Index (Base_Type (P_Type)));
4200             Lo_Bound := Type_Low_Bound (Ityp);
4201
4202             Hi_Bound :=
4203               Make_Integer_Literal (Sloc (P),
4204                 Intval =>
4205                   Expr_Value (Lo_Bound) + String_Literal_Length (P_Type) - 1);
4206
4207             Set_Parent (Hi_Bound, P);
4208             Analyze_And_Resolve (Hi_Bound, Etype (Lo_Bound));
4209             return;
4210
4211          --  For non-array case, just get bounds of scalar type
4212
4213          elsif Is_Scalar_Type (P_Type) then
4214             Ityp := P_Type;
4215
4216             --  For a fixed-point type, we must freeze to get the attributes
4217             --  of the fixed-point type set now so we can reference them.
4218
4219             if Is_Fixed_Point_Type (P_Type)
4220               and then not Is_Frozen (Base_Type (P_Type))
4221               and then Compile_Time_Known_Value (Type_Low_Bound (P_Type))
4222               and then Compile_Time_Known_Value (Type_High_Bound (P_Type))
4223             then
4224                Freeze_Fixed_Point_Type (Base_Type (P_Type));
4225             end if;
4226
4227          --  For array case, get type of proper index
4228
4229          else
4230             if No (E1) then
4231                Ndim := 1;
4232             else
4233                Ndim := UI_To_Int (Expr_Value (E1));
4234             end if;
4235
4236             Indx := First_Index (P_Type);
4237             for J in 1 .. Ndim - 1 loop
4238                Next_Index (Indx);
4239             end loop;
4240
4241             --  If no index type, get out (some other error occurred, and
4242             --  we don't have enough information to complete the job!)
4243
4244             if No (Indx) then
4245                Lo_Bound := Error;
4246                Hi_Bound := Error;
4247                return;
4248             end if;
4249
4250             Ityp := Etype (Indx);
4251          end if;
4252
4253          --  A discrete range in an index constraint is allowed to be a
4254          --  subtype indication. This is syntactically a pain, but should
4255          --  not propagate to the entity for the corresponding index subtype.
4256          --  After checking that the subtype indication is legal, the range
4257          --  of the subtype indication should be transfered to the entity.
4258          --  The attributes for the bounds should remain the simple retrievals
4259          --  that they are now.
4260
4261          Lo_Bound := Type_Low_Bound (Ityp);
4262          Hi_Bound := Type_High_Bound (Ityp);
4263
4264          if not Is_Static_Subtype (Ityp) then
4265             Static := False;
4266          end if;
4267       end Set_Bounds;
4268
4269    --  Start of processing for Eval_Attribute
4270
4271    begin
4272       --  Acquire first two expressions (at the moment, no attributes
4273       --  take more than two expressions in any case).
4274
4275       if Present (Expressions (N)) then
4276          E1 := First (Expressions (N));
4277          E2 := Next (E1);
4278       else
4279          E1 := Empty;
4280          E2 := Empty;
4281       end if;
4282
4283       --  Special processing for cases where the prefix is an object. For
4284       --  this purpose, a string literal counts as an object (attributes
4285       --  of string literals can only appear in generated code).
4286
4287       if Is_Object_Reference (P) or else Nkind (P) = N_String_Literal then
4288
4289          --  For Component_Size, the prefix is an array object, and we apply
4290          --  the attribute to the type of the object. This is allowed for
4291          --  both unconstrained and constrained arrays, since the bounds
4292          --  have no influence on the value of this attribute.
4293
4294          if Id = Attribute_Component_Size then
4295             P_Entity := Etype (P);
4296
4297          --  For First and Last, the prefix is an array object, and we apply
4298          --  the attribute to the type of the array, but we need a constrained
4299          --  type for this, so we use the actual subtype if available.
4300
4301          elsif Id = Attribute_First
4302                  or else
4303                Id = Attribute_Last
4304                  or else
4305                Id = Attribute_Length
4306          then
4307             declare
4308                AS : constant Entity_Id := Get_Actual_Subtype_If_Available (P);
4309
4310             begin
4311                if Present (AS) and then Is_Constrained (AS) then
4312                   P_Entity := AS;
4313
4314                --  If we have an unconstrained type, cannot fold
4315
4316                else
4317                   Check_Expressions;
4318                   return;
4319                end if;
4320             end;
4321
4322          --  For Size, give size of object if available, otherwise we
4323          --  cannot fold Size.
4324
4325          elsif Id = Attribute_Size then
4326             if Is_Entity_Name (P)
4327               and then Known_Esize (Entity (P))
4328             then
4329                Compile_Time_Known_Attribute (N, Esize (Entity (P)));
4330                return;
4331
4332             else
4333                Check_Expressions;
4334                return;
4335             end if;
4336
4337          --  For Alignment, give size of object if available, otherwise we
4338          --  cannot fold Alignment.
4339
4340          elsif Id = Attribute_Alignment then
4341             if Is_Entity_Name (P)
4342               and then Known_Alignment (Entity (P))
4343             then
4344                Fold_Uint (N, Alignment (Entity (P)), False);
4345                return;
4346
4347             else
4348                Check_Expressions;
4349                return;
4350             end if;
4351
4352          --  No other attributes for objects are folded
4353
4354          else
4355             Check_Expressions;
4356             return;
4357          end if;
4358
4359       --  Cases where P is not an object. Cannot do anything if P is
4360       --  not the name of an entity.
4361
4362       elsif not Is_Entity_Name (P) then
4363          Check_Expressions;
4364          return;
4365
4366       --  Otherwise get prefix entity
4367
4368       else
4369          P_Entity := Entity (P);
4370       end if;
4371
4372       --  At this stage P_Entity is the entity to which the attribute
4373       --  is to be applied. This is usually simply the entity of the
4374       --  prefix, except in some cases of attributes for objects, where
4375       --  as described above, we apply the attribute to the object type.
4376
4377       --  First foldable possibility is a scalar or array type (RM 4.9(7))
4378       --  that is not generic (generic types are eliminated by RM 4.9(25)).
4379       --  Note we allow non-static non-generic types at this stage as further
4380       --  described below.
4381
4382       if Is_Type (P_Entity)
4383         and then (Is_Scalar_Type (P_Entity) or Is_Array_Type (P_Entity))
4384         and then (not Is_Generic_Type (P_Entity))
4385       then
4386          P_Type := P_Entity;
4387
4388       --  Second foldable possibility is an array object (RM 4.9(8))
4389
4390       elsif (Ekind (P_Entity) = E_Variable
4391                or else
4392              Ekind (P_Entity) = E_Constant)
4393         and then Is_Array_Type (Etype (P_Entity))
4394         and then (not Is_Generic_Type (Etype (P_Entity)))
4395       then
4396          P_Type := Etype (P_Entity);
4397
4398          --  If the entity is an array constant with an unconstrained
4399          --  nominal subtype then get the type from the initial value.
4400          --  If the value has been expanded into assignments, the expression
4401          --  is not present and the attribute reference remains dynamic.
4402          --  We could do better here and retrieve the type ???
4403
4404          if Ekind (P_Entity) = E_Constant
4405            and then not Is_Constrained (P_Type)
4406          then
4407             if No (Constant_Value (P_Entity)) then
4408                return;
4409             else
4410                P_Type := Etype (Constant_Value (P_Entity));
4411             end if;
4412          end if;
4413
4414       --  Definite must be folded if the prefix is not a generic type,
4415       --  that is to say if we are within an instantiation. Same processing
4416       --  applies to the GNAT attributes Has_Discriminants, Type_Class,
4417       --  and Unconstrained_Array.
4418
4419       elsif (Id = Attribute_Definite
4420                or else
4421              Id = Attribute_Has_Discriminants
4422                or else
4423              Id = Attribute_Type_Class
4424                or else
4425              Id = Attribute_Unconstrained_Array)
4426         and then not Is_Generic_Type (P_Entity)
4427       then
4428          P_Type := P_Entity;
4429
4430       --  We can fold 'Size applied to a type if the size is known
4431       --  (as happens for a size from an attribute definition clause).
4432       --  At this stage, this can happen only for types (e.g. record
4433       --  types) for which the size is always non-static. We exclude
4434       --  generic types from consideration (since they have bogus
4435       --  sizes set within templates).
4436
4437       elsif Id = Attribute_Size
4438         and then Is_Type (P_Entity)
4439         and then (not Is_Generic_Type (P_Entity))
4440         and then Known_Static_RM_Size (P_Entity)
4441       then
4442          Compile_Time_Known_Attribute (N, RM_Size (P_Entity));
4443          return;
4444
4445       --  We can fold 'Alignment applied to a type if the alignment is known
4446       --  (as happens for an alignment from an attribute definition clause).
4447       --  At this stage, this can happen only for types (e.g. record
4448       --  types) for which the size is always non-static. We exclude
4449       --  generic types from consideration (since they have bogus
4450       --  sizes set within templates).
4451
4452       elsif Id = Attribute_Alignment
4453         and then Is_Type (P_Entity)
4454         and then (not Is_Generic_Type (P_Entity))
4455         and then Known_Alignment (P_Entity)
4456       then
4457          Compile_Time_Known_Attribute (N, Alignment (P_Entity));
4458          return;
4459
4460       --  No other cases are foldable (they certainly aren't static, and at
4461       --  the moment we don't try to fold any cases other than these three).
4462
4463       else
4464          Check_Expressions;
4465          return;
4466       end if;
4467
4468       --  If either attribute or the prefix is Any_Type, then propagate
4469       --  Any_Type to the result and don't do anything else at all.
4470
4471       if P_Type = Any_Type
4472         or else (Present (E1) and then Etype (E1) = Any_Type)
4473         or else (Present (E2) and then Etype (E2) = Any_Type)
4474       then
4475          Set_Etype (N, Any_Type);
4476          return;
4477       end if;
4478
4479       --  Scalar subtype case. We have not yet enforced the static requirement
4480       --  of (RM 4.9(7)) and we don't intend to just yet, since there are cases
4481       --  of non-static attribute references (e.g. S'Digits for a non-static
4482       --  floating-point type, which we can compute at compile time).
4483
4484       --  Note: this folding of non-static attributes is not simply a case of
4485       --  optimization. For many of the attributes affected, Gigi cannot handle
4486       --  the attribute and depends on the front end having folded them away.
4487
4488       --  Note: although we don't require staticness at this stage, we do set
4489       --  the Static variable to record the staticness, for easy reference by
4490       --  those attributes where it matters (e.g. Succ and Pred), and also to
4491       --  be used to ensure that non-static folded things are not marked as
4492       --  being static (a check that is done right at the end).
4493
4494       P_Root_Type := Root_Type (P_Type);
4495       P_Base_Type := Base_Type (P_Type);
4496
4497       --  If the root type or base type is generic, then we cannot fold. This
4498       --  test is needed because subtypes of generic types are not always
4499       --  marked as being generic themselves (which seems odd???)
4500
4501       if Is_Generic_Type (P_Root_Type)
4502         or else Is_Generic_Type (P_Base_Type)
4503       then
4504          return;
4505       end if;
4506
4507       if Is_Scalar_Type (P_Type) then
4508          Static := Is_OK_Static_Subtype (P_Type);
4509
4510       --  Array case. We enforce the constrained requirement of (RM 4.9(7-8))
4511       --  since we can't do anything with unconstrained arrays. In addition,
4512       --  only the First, Last and Length attributes are possibly static.
4513       --  In addition Component_Size is possibly foldable, even though it
4514       --  can never be static.
4515
4516       --  Definite, Has_Discriminants, Type_Class and Unconstrained_Array are
4517       --  again exceptions, because they apply as well to unconstrained types.
4518
4519       elsif Id = Attribute_Definite
4520               or else
4521             Id = Attribute_Has_Discriminants
4522               or else
4523             Id = Attribute_Type_Class
4524               or else
4525             Id = Attribute_Unconstrained_Array
4526       then
4527          Static := False;
4528
4529       else
4530          if not Is_Constrained (P_Type)
4531            or else (Id /= Attribute_Component_Size and then
4532                     Id /= Attribute_First          and then
4533                     Id /= Attribute_Last           and then
4534                     Id /= Attribute_Length)
4535          then
4536             Check_Expressions;
4537             return;
4538          end if;
4539
4540          --  The rules in (RM 4.9(7,8)) require a static array, but as in the
4541          --  scalar case, we hold off on enforcing staticness, since there are
4542          --  cases which we can fold at compile time even though they are not
4543          --  static (e.g. 'Length applied to a static index, even though other
4544          --  non-static indexes make the array type non-static). This is only
4545          --  an optimization, but it falls out essentially free, so why not.
4546          --  Again we compute the variable Static for easy reference later
4547          --  (note that no array attributes are static in Ada 83).
4548
4549          Static := Ada_95;
4550
4551          declare
4552             N : Node_Id;
4553
4554          begin
4555             N := First_Index (P_Type);
4556             while Present (N) loop
4557                Static := Static and then Is_Static_Subtype (Etype (N));
4558
4559                --  If however the index type is generic, attributes cannot
4560                --  be folded.
4561
4562                if Is_Generic_Type (Etype (N))
4563                  and then Id /= Attribute_Component_Size
4564                then
4565                   return;
4566                end if;
4567
4568                Next_Index (N);
4569             end loop;
4570          end;
4571       end if;
4572
4573       --  Check any expressions that are present. Note that these expressions,
4574       --  depending on the particular attribute type, are either part of the
4575       --  attribute designator, or they are arguments in a case where the
4576       --  attribute reference returns a function. In the latter case, the
4577       --  rule in (RM 4.9(22)) applies and in particular requires the type
4578       --  of the expressions to be scalar in order for the attribute to be
4579       --  considered to be static.
4580
4581       declare
4582          E : Node_Id;
4583
4584       begin
4585          E := E1;
4586          while Present (E) loop
4587
4588             --  If expression is not static, then the attribute reference
4589             --  result certainly cannot be static.
4590
4591             if not Is_Static_Expression (E) then
4592                Static := False;
4593             end if;
4594
4595             --  If the result is not known at compile time, or is not of
4596             --  a scalar type, then the result is definitely not static,
4597             --  so we can quit now.
4598
4599             if not Compile_Time_Known_Value (E)
4600               or else not Is_Scalar_Type (Etype (E))
4601             then
4602                --  An odd special case, if this is a Pos attribute, this
4603                --  is where we need to apply a range check since it does
4604                --  not get done anywhere else.
4605
4606                if Id = Attribute_Pos then
4607                   if Is_Integer_Type (Etype (E)) then
4608                      Apply_Range_Check (E, Etype (N));
4609                   end if;
4610                end if;
4611
4612                Check_Expressions;
4613                return;
4614
4615             --  If the expression raises a constraint error, then so does
4616             --  the attribute reference. We keep going in this case because
4617             --  we are still interested in whether the attribute reference
4618             --  is static even if it is not static.
4619
4620             elsif Raises_Constraint_Error (E) then
4621                Set_Raises_Constraint_Error (N);
4622             end if;
4623
4624             Next (E);
4625          end loop;
4626
4627          if Raises_Constraint_Error (Prefix (N)) then
4628             return;
4629          end if;
4630       end;
4631
4632       --  Deal with the case of a static attribute reference that raises
4633       --  constraint error. The Raises_Constraint_Error flag will already
4634       --  have been set, and the Static flag shows whether the attribute
4635       --  reference is static. In any case we certainly can't fold such an
4636       --  attribute reference.
4637
4638       --  Note that the rewriting of the attribute node with the constraint
4639       --  error node is essential in this case, because otherwise Gigi might
4640       --  blow up on one of the attributes it never expects to see.
4641
4642       --  The constraint_error node must have the type imposed by the context,
4643       --  to avoid spurious errors in the enclosing expression.
4644
4645       if Raises_Constraint_Error (N) then
4646          CE_Node :=
4647            Make_Raise_Constraint_Error (Sloc (N),
4648              Reason => CE_Range_Check_Failed);
4649          Set_Etype (CE_Node, Etype (N));
4650          Set_Raises_Constraint_Error (CE_Node);
4651          Check_Expressions;
4652          Rewrite (N, Relocate_Node (CE_Node));
4653          Set_Is_Static_Expression (N, Static);
4654          return;
4655       end if;
4656
4657       --  At this point we have a potentially foldable attribute reference.
4658       --  If Static is set, then the attribute reference definitely obeys
4659       --  the requirements in (RM 4.9(7,8,22)), and it definitely can be
4660       --  folded. If Static is not set, then the attribute may or may not
4661       --  be foldable, and the individual attribute processing routines
4662       --  test Static as required in cases where it makes a difference.
4663
4664       --  In the case where Static is not set, we do know that all the
4665       --  expressions present are at least known at compile time (we
4666       --  assumed above that if this was not the case, then there was
4667       --  no hope of static evaluation). However, we did not require
4668       --  that the bounds of the prefix type be compile time known,
4669       --  let alone static). That's because there are many attributes
4670       --  that can be computed at compile time on non-static subtypes,
4671       --  even though such references are not static expressions.
4672
4673       case Id is
4674
4675       --------------
4676       -- Adjacent --
4677       --------------
4678
4679       when Attribute_Adjacent =>
4680          Fold_Ureal (N,
4681            Eval_Fat.Adjacent
4682              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
4683
4684       ---------
4685       -- Aft --
4686       ---------
4687
4688       when Attribute_Aft =>
4689          Fold_Uint (N, UI_From_Int (Aft_Value), True);
4690
4691       ---------------
4692       -- Alignment --
4693       ---------------
4694
4695       when Attribute_Alignment => Alignment_Block : declare
4696          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
4697
4698       begin
4699          --  Fold if alignment is set and not otherwise
4700
4701          if Known_Alignment (P_TypeA) then
4702             Fold_Uint (N, Alignment (P_TypeA), Is_Discrete_Type (P_TypeA));
4703          end if;
4704       end Alignment_Block;
4705
4706       ---------------
4707       -- AST_Entry --
4708       ---------------
4709
4710       --  Can only be folded in No_Ast_Handler case
4711
4712       when Attribute_AST_Entry =>
4713          if not Is_AST_Entry (P_Entity) then
4714             Rewrite (N,
4715               New_Occurrence_Of (RTE (RE_No_AST_Handler), Loc));
4716          else
4717             null;
4718          end if;
4719
4720       ---------
4721       -- Bit --
4722       ---------
4723
4724       --  Bit can never be folded
4725
4726       when Attribute_Bit =>
4727          null;
4728
4729       ------------------
4730       -- Body_Version --
4731       ------------------
4732
4733       --  Body_version can never be static
4734
4735       when Attribute_Body_Version =>
4736          null;
4737
4738       -------------
4739       -- Ceiling --
4740       -------------
4741
4742       when Attribute_Ceiling =>
4743          Fold_Ureal (N,
4744            Eval_Fat.Ceiling (P_Root_Type, Expr_Value_R (E1)), Static);
4745
4746       --------------------
4747       -- Component_Size --
4748       --------------------
4749
4750       when Attribute_Component_Size =>
4751          if Known_Static_Component_Size (P_Type) then
4752             Fold_Uint (N, Component_Size (P_Type), False);
4753          end if;
4754
4755       -------------
4756       -- Compose --
4757       -------------
4758
4759       when Attribute_Compose =>
4760          Fold_Ureal (N,
4761            Eval_Fat.Compose
4762              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)),
4763               Static);
4764
4765       -----------------
4766       -- Constrained --
4767       -----------------
4768
4769       --  Constrained is never folded for now, there may be cases that
4770       --  could be handled at compile time. to be looked at later.
4771
4772       when Attribute_Constrained =>
4773          null;
4774
4775       ---------------
4776       -- Copy_Sign --
4777       ---------------
4778
4779       when Attribute_Copy_Sign =>
4780          Fold_Ureal (N,
4781            Eval_Fat.Copy_Sign
4782              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
4783
4784       -----------
4785       -- Delta --
4786       -----------
4787
4788       when Attribute_Delta =>
4789          Fold_Ureal (N, Delta_Value (P_Type), True);
4790
4791       --------------
4792       -- Definite --
4793       --------------
4794
4795       when Attribute_Definite =>
4796          declare
4797             Result : Node_Id;
4798
4799          begin
4800             if Is_Indefinite_Subtype (P_Entity) then
4801                Result := New_Occurrence_Of (Standard_False, Loc);
4802             else
4803                Result := New_Occurrence_Of (Standard_True, Loc);
4804             end if;
4805
4806             Rewrite (N, Result);
4807             Analyze_And_Resolve (N, Standard_Boolean);
4808          end;
4809
4810       ------------
4811       -- Denorm --
4812       ------------
4813
4814       when Attribute_Denorm =>
4815          Fold_Uint
4816            (N, UI_From_Int (Boolean'Pos (Denorm_On_Target)), True);
4817
4818       ------------
4819       -- Digits --
4820       ------------
4821
4822       when Attribute_Digits =>
4823          Fold_Uint (N, Digits_Value (P_Type), True);
4824
4825       ----------
4826       -- Emax --
4827       ----------
4828
4829       when Attribute_Emax =>
4830
4831          --  Ada 83 attribute is defined as (RM83 3.5.8)
4832
4833          --    T'Emax = 4 * T'Mantissa
4834
4835          Fold_Uint (N, 4 * Mantissa, True);
4836
4837       --------------
4838       -- Enum_Rep --
4839       --------------
4840
4841       when Attribute_Enum_Rep =>
4842
4843          --  For an enumeration type with a non-standard representation
4844          --  use the Enumeration_Rep field of the proper constant. Note
4845          --  that this would not work for types Character/Wide_Character,
4846          --  since no real entities are created for the enumeration
4847          --  literals, but that does not matter since these two types
4848          --  do not have non-standard representations anyway.
4849
4850          if Is_Enumeration_Type (P_Type)
4851            and then Has_Non_Standard_Rep (P_Type)
4852          then
4853             Fold_Uint (N, Enumeration_Rep (Expr_Value_E (E1)), Static);
4854
4855          --  For enumeration types with standard representations and all
4856          --  other cases (i.e. all integer and modular types), Enum_Rep
4857          --  is equivalent to Pos.
4858
4859          else
4860             Fold_Uint (N, Expr_Value (E1), Static);
4861          end if;
4862
4863       -------------
4864       -- Epsilon --
4865       -------------
4866
4867       when Attribute_Epsilon =>
4868
4869          --  Ada 83 attribute is defined as (RM83 3.5.8)
4870
4871          --    T'Epsilon = 2.0**(1 - T'Mantissa)
4872
4873          Fold_Ureal (N, Ureal_2 ** (1 - Mantissa), True);
4874
4875       --------------
4876       -- Exponent --
4877       --------------
4878
4879       when Attribute_Exponent =>
4880          Fold_Uint (N,
4881            Eval_Fat.Exponent (P_Root_Type, Expr_Value_R (E1)), Static);
4882
4883       -----------
4884       -- First --
4885       -----------
4886
4887       when Attribute_First => First_Attr :
4888       begin
4889          Set_Bounds;
4890
4891          if Compile_Time_Known_Value (Lo_Bound) then
4892             if Is_Real_Type (P_Type) then
4893                Fold_Ureal (N, Expr_Value_R (Lo_Bound), Static);
4894             else
4895                Fold_Uint  (N, Expr_Value (Lo_Bound), Static);
4896             end if;
4897          end if;
4898       end First_Attr;
4899
4900       -----------------
4901       -- Fixed_Value --
4902       -----------------
4903
4904       when Attribute_Fixed_Value =>
4905          null;
4906
4907       -----------
4908       -- Floor --
4909       -----------
4910
4911       when Attribute_Floor =>
4912          Fold_Ureal (N,
4913            Eval_Fat.Floor (P_Root_Type, Expr_Value_R (E1)), Static);
4914
4915       ----------
4916       -- Fore --
4917       ----------
4918
4919       when Attribute_Fore =>
4920          if Compile_Time_Known_Bounds (P_Type) then
4921             Fold_Uint (N, UI_From_Int (Fore_Value), Static);
4922          end if;
4923
4924       --------------
4925       -- Fraction --
4926       --------------
4927
4928       when Attribute_Fraction =>
4929          Fold_Ureal (N,
4930            Eval_Fat.Fraction (P_Root_Type, Expr_Value_R (E1)), Static);
4931
4932       -----------------------
4933       -- Has_Discriminants --
4934       -----------------------
4935
4936       when Attribute_Has_Discriminants =>
4937          declare
4938             Result : Node_Id;
4939
4940          begin
4941             if Has_Discriminants (P_Entity) then
4942                Result := New_Occurrence_Of (Standard_True, Loc);
4943             else
4944                Result := New_Occurrence_Of (Standard_False, Loc);
4945             end if;
4946
4947             Rewrite (N, Result);
4948             Analyze_And_Resolve (N, Standard_Boolean);
4949          end;
4950
4951       --------------
4952       -- Identity --
4953       --------------
4954
4955       when Attribute_Identity =>
4956          null;
4957
4958       -----------
4959       -- Image --
4960       -----------
4961
4962       --  Image 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_Image =>
4966          null;
4967
4968       ---------
4969       -- Img --
4970       ---------
4971
4972       --  Img is a scalar attribute, but is never static, because it is
4973       --  not a static function (having a non-scalar argument (RM 4.9(22))
4974
4975       when Attribute_Img =>
4976          null;
4977
4978       -------------------
4979       -- Integer_Value --
4980       -------------------
4981
4982       when Attribute_Integer_Value =>
4983          null;
4984
4985       -----------
4986       -- Large --
4987       -----------
4988
4989       when Attribute_Large =>
4990
4991          --  For fixed-point, we use the identity:
4992
4993          --    T'Large = (2.0**T'Mantissa - 1.0) * T'Small
4994
4995          if Is_Fixed_Point_Type (P_Type) then
4996             Rewrite (N,
4997               Make_Op_Multiply (Loc,
4998                 Left_Opnd =>
4999                   Make_Op_Subtract (Loc,
5000                     Left_Opnd =>
5001                       Make_Op_Expon (Loc,
5002                         Left_Opnd =>
5003                           Make_Real_Literal (Loc, Ureal_2),
5004                         Right_Opnd =>
5005                           Make_Attribute_Reference (Loc,
5006                             Prefix => P,
5007                             Attribute_Name => Name_Mantissa)),
5008                     Right_Opnd => Make_Real_Literal (Loc, Ureal_1)),
5009
5010                 Right_Opnd =>
5011                   Make_Real_Literal (Loc, Small_Value (Entity (P)))));
5012
5013             Analyze_And_Resolve (N, C_Type);
5014
5015          --  Floating-point (Ada 83 compatibility)
5016
5017          else
5018             --  Ada 83 attribute is defined as (RM83 3.5.8)
5019
5020             --    T'Large = 2.0**T'Emax * (1.0 - 2.0**(-T'Mantissa))
5021
5022             --  where
5023
5024             --    T'Emax = 4 * T'Mantissa
5025
5026             Fold_Ureal (N,
5027               Ureal_2 ** (4 * Mantissa) * (Ureal_1 - Ureal_2 ** (-Mantissa)),
5028               True);
5029          end if;
5030
5031       ----------
5032       -- Last --
5033       ----------
5034
5035       when Attribute_Last => Last :
5036       begin
5037          Set_Bounds;
5038
5039          if Compile_Time_Known_Value (Hi_Bound) then
5040             if Is_Real_Type (P_Type) then
5041                Fold_Ureal (N, Expr_Value_R (Hi_Bound), Static);
5042             else
5043                Fold_Uint  (N, Expr_Value (Hi_Bound), Static);
5044             end if;
5045          end if;
5046       end Last;
5047
5048       ------------------
5049       -- Leading_Part --
5050       ------------------
5051
5052       when Attribute_Leading_Part =>
5053          Fold_Ureal (N,
5054            Eval_Fat.Leading_Part
5055              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5056
5057       ------------
5058       -- Length --
5059       ------------
5060
5061       when Attribute_Length => Length : declare
5062          Ind : Node_Id;
5063
5064       begin
5065          --  In the case of a generic index type, the bounds may
5066          --  appear static but the computation is not meaningful,
5067          --  and may generate a spurious warning.
5068
5069          Ind := First_Index (P_Type);
5070
5071          while Present (Ind) loop
5072             if Is_Generic_Type (Etype (Ind)) then
5073                return;
5074             end if;
5075
5076             Next_Index (Ind);
5077          end loop;
5078
5079          Set_Bounds;
5080
5081          if Compile_Time_Known_Value (Lo_Bound)
5082            and then Compile_Time_Known_Value (Hi_Bound)
5083          then
5084             Fold_Uint (N,
5085               UI_Max (0, 1 + (Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound))),
5086               True);
5087          end if;
5088       end Length;
5089
5090       -------------
5091       -- Machine --
5092       -------------
5093
5094       when Attribute_Machine =>
5095          Fold_Ureal (N,
5096            Eval_Fat.Machine
5097              (P_Root_Type, Expr_Value_R (E1), Eval_Fat.Round, N),
5098            Static);
5099
5100       ------------------
5101       -- Machine_Emax --
5102       ------------------
5103
5104       when Attribute_Machine_Emax =>
5105          Float_Attribute_Universal_Integer (
5106            IEEES_Machine_Emax,
5107            IEEEL_Machine_Emax,
5108            IEEEX_Machine_Emax,
5109            VAXFF_Machine_Emax,
5110            VAXDF_Machine_Emax,
5111            VAXGF_Machine_Emax,
5112            AAMPS_Machine_Emax,
5113            AAMPL_Machine_Emax);
5114
5115       ------------------
5116       -- Machine_Emin --
5117       ------------------
5118
5119       when Attribute_Machine_Emin =>
5120          Float_Attribute_Universal_Integer (
5121            IEEES_Machine_Emin,
5122            IEEEL_Machine_Emin,
5123            IEEEX_Machine_Emin,
5124            VAXFF_Machine_Emin,
5125            VAXDF_Machine_Emin,
5126            VAXGF_Machine_Emin,
5127            AAMPS_Machine_Emin,
5128            AAMPL_Machine_Emin);
5129
5130       ----------------------
5131       -- Machine_Mantissa --
5132       ----------------------
5133
5134       when Attribute_Machine_Mantissa =>
5135          Float_Attribute_Universal_Integer (
5136            IEEES_Machine_Mantissa,
5137            IEEEL_Machine_Mantissa,
5138            IEEEX_Machine_Mantissa,
5139            VAXFF_Machine_Mantissa,
5140            VAXDF_Machine_Mantissa,
5141            VAXGF_Machine_Mantissa,
5142            AAMPS_Machine_Mantissa,
5143            AAMPL_Machine_Mantissa);
5144
5145       -----------------------
5146       -- Machine_Overflows --
5147       -----------------------
5148
5149       when Attribute_Machine_Overflows =>
5150
5151          --  Always true for fixed-point
5152
5153          if Is_Fixed_Point_Type (P_Type) then
5154             Fold_Uint (N, True_Value, True);
5155
5156          --  Floating point case
5157
5158          else
5159             Fold_Uint (N,
5160               UI_From_Int (Boolean'Pos (Machine_Overflows_On_Target)),
5161               True);
5162          end if;
5163
5164       -------------------
5165       -- Machine_Radix --
5166       -------------------
5167
5168       when Attribute_Machine_Radix =>
5169          if Is_Fixed_Point_Type (P_Type) then
5170             if Is_Decimal_Fixed_Point_Type (P_Type)
5171               and then Machine_Radix_10 (P_Type)
5172             then
5173                Fold_Uint (N, Uint_10, True);
5174             else
5175                Fold_Uint (N, Uint_2, True);
5176             end if;
5177
5178          --  All floating-point type always have radix 2
5179
5180          else
5181             Fold_Uint (N, Uint_2, True);
5182          end if;
5183
5184       --------------------
5185       -- Machine_Rounds --
5186       --------------------
5187
5188       when Attribute_Machine_Rounds =>
5189
5190          --  Always False for fixed-point
5191
5192          if Is_Fixed_Point_Type (P_Type) then
5193             Fold_Uint (N, False_Value, True);
5194
5195          --  Else yield proper floating-point result
5196
5197          else
5198             Fold_Uint
5199               (N, UI_From_Int (Boolean'Pos (Machine_Rounds_On_Target)), True);
5200          end if;
5201
5202       ------------------
5203       -- Machine_Size --
5204       ------------------
5205
5206       --  Note: Machine_Size is identical to Object_Size
5207
5208       when Attribute_Machine_Size => Machine_Size : declare
5209          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5210
5211       begin
5212          if Known_Esize (P_TypeA) then
5213             Fold_Uint (N, Esize (P_TypeA), True);
5214          end if;
5215       end Machine_Size;
5216
5217       --------------
5218       -- Mantissa --
5219       --------------
5220
5221       when Attribute_Mantissa =>
5222
5223          --  Fixed-point mantissa
5224
5225          if Is_Fixed_Point_Type (P_Type) then
5226
5227             --  Compile time foldable case
5228
5229             if Compile_Time_Known_Value (Type_Low_Bound  (P_Type))
5230                  and then
5231                Compile_Time_Known_Value (Type_High_Bound (P_Type))
5232             then
5233                --  The calculation of the obsolete Ada 83 attribute Mantissa
5234                --  is annoying, because of AI00143, quoted here:
5235
5236                --  !question 84-01-10
5237
5238                --  Consider the model numbers for F:
5239
5240                --         type F is delta 1.0 range -7.0 .. 8.0;
5241
5242                --  The wording requires that F'MANTISSA be the SMALLEST
5243                --  integer number for which each  bound  of the specified
5244                --  range is either a model number or lies at most small
5245                --  distant from a model number. This means F'MANTISSA
5246                --  is required to be 3 since the range  -7.0 .. 7.0 fits
5247                --  in 3 signed bits, and 8 is "at most" 1.0 from a model
5248                --  number, namely, 7. Is this analysis correct? Note that
5249                --  this implies the upper bound of the range is not
5250                --  represented as a model number.
5251
5252                --  !response 84-03-17
5253
5254                --  The analysis is correct. The upper and lower bounds for
5255                --  a fixed  point type can lie outside the range of model
5256                --  numbers.
5257
5258                declare
5259                   Siz     : Uint;
5260                   LBound  : Ureal;
5261                   UBound  : Ureal;
5262                   Bound   : Ureal;
5263                   Max_Man : Uint;
5264
5265                begin
5266                   LBound  := Expr_Value_R (Type_Low_Bound  (P_Type));
5267                   UBound  := Expr_Value_R (Type_High_Bound (P_Type));
5268                   Bound   := UR_Max (UR_Abs (LBound), UR_Abs (UBound));
5269                   Max_Man := UR_Trunc (Bound / Small_Value (P_Type));
5270
5271                   --  If the Bound is exactly a model number, i.e. a multiple
5272                   --  of Small, then we back it off by one to get the integer
5273                   --  value that must be representable.
5274
5275                   if Small_Value (P_Type) * Max_Man = Bound then
5276                      Max_Man := Max_Man - 1;
5277                   end if;
5278
5279                   --  Now find corresponding size = Mantissa value
5280
5281                   Siz := Uint_0;
5282                   while 2 ** Siz < Max_Man loop
5283                      Siz := Siz + 1;
5284                   end loop;
5285
5286                   Fold_Uint (N, Siz, True);
5287                end;
5288
5289             else
5290                --  The case of dynamic bounds cannot be evaluated at compile
5291                --  time. Instead we use a runtime routine (see Exp_Attr).
5292
5293                null;
5294             end if;
5295
5296          --  Floating-point Mantissa
5297
5298          else
5299             Fold_Uint (N, Mantissa, True);
5300          end if;
5301
5302       ---------
5303       -- Max --
5304       ---------
5305
5306       when Attribute_Max => Max :
5307       begin
5308          if Is_Real_Type (P_Type) then
5309             Fold_Ureal
5310               (N, UR_Max (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5311          else
5312             Fold_Uint (N, UI_Max (Expr_Value (E1), Expr_Value (E2)), Static);
5313          end if;
5314       end Max;
5315
5316       ----------------------------------
5317       -- Max_Size_In_Storage_Elements --
5318       ----------------------------------
5319
5320       --  Max_Size_In_Storage_Elements is simply the Size rounded up to a
5321       --  Storage_Unit boundary. We can fold any cases for which the size
5322       --  is known by the front end.
5323
5324       when Attribute_Max_Size_In_Storage_Elements =>
5325          if Known_Esize (P_Type) then
5326             Fold_Uint (N,
5327               (Esize (P_Type) + System_Storage_Unit - 1) /
5328                                           System_Storage_Unit,
5329                Static);
5330          end if;
5331
5332       --------------------
5333       -- Mechanism_Code --
5334       --------------------
5335
5336       when Attribute_Mechanism_Code =>
5337          declare
5338             Val    : Int;
5339             Formal : Entity_Id;
5340             Mech   : Mechanism_Type;
5341
5342          begin
5343             if No (E1) then
5344                Mech := Mechanism (P_Entity);
5345
5346             else
5347                Val := UI_To_Int (Expr_Value (E1));
5348
5349                Formal := First_Formal (P_Entity);
5350                for J in 1 .. Val - 1 loop
5351                   Next_Formal (Formal);
5352                end loop;
5353                Mech := Mechanism (Formal);
5354             end if;
5355
5356             if Mech < 0 then
5357                Fold_Uint (N, UI_From_Int (Int (-Mech)), True);
5358             end if;
5359          end;
5360
5361       ---------
5362       -- Min --
5363       ---------
5364
5365       when Attribute_Min => Min :
5366       begin
5367          if Is_Real_Type (P_Type) then
5368             Fold_Ureal
5369               (N, UR_Min (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5370          else
5371             Fold_Uint (N, UI_Min (Expr_Value (E1), Expr_Value (E2)), Static);
5372          end if;
5373       end Min;
5374
5375       -----------
5376       -- Model --
5377       -----------
5378
5379       when Attribute_Model =>
5380          Fold_Ureal (N,
5381            Eval_Fat.Model (P_Root_Type, Expr_Value_R (E1)), Static);
5382
5383       ----------------
5384       -- Model_Emin --
5385       ----------------
5386
5387       when Attribute_Model_Emin =>
5388          Float_Attribute_Universal_Integer (
5389            IEEES_Model_Emin,
5390            IEEEL_Model_Emin,
5391            IEEEX_Model_Emin,
5392            VAXFF_Model_Emin,
5393            VAXDF_Model_Emin,
5394            VAXGF_Model_Emin,
5395            AAMPS_Model_Emin,
5396            AAMPL_Model_Emin);
5397
5398       -------------------
5399       -- Model_Epsilon --
5400       -------------------
5401
5402       when Attribute_Model_Epsilon =>
5403          Float_Attribute_Universal_Real (
5404            IEEES_Model_Epsilon'Universal_Literal_String,
5405            IEEEL_Model_Epsilon'Universal_Literal_String,
5406            IEEEX_Model_Epsilon'Universal_Literal_String,
5407            VAXFF_Model_Epsilon'Universal_Literal_String,
5408            VAXDF_Model_Epsilon'Universal_Literal_String,
5409            VAXGF_Model_Epsilon'Universal_Literal_String,
5410            AAMPS_Model_Epsilon'Universal_Literal_String,
5411            AAMPL_Model_Epsilon'Universal_Literal_String);
5412
5413       --------------------
5414       -- Model_Mantissa --
5415       --------------------
5416
5417       when Attribute_Model_Mantissa =>
5418          Float_Attribute_Universal_Integer (
5419            IEEES_Model_Mantissa,
5420            IEEEL_Model_Mantissa,
5421            IEEEX_Model_Mantissa,
5422            VAXFF_Model_Mantissa,
5423            VAXDF_Model_Mantissa,
5424            VAXGF_Model_Mantissa,
5425            AAMPS_Model_Mantissa,
5426            AAMPL_Model_Mantissa);
5427
5428       -----------------
5429       -- Model_Small --
5430       -----------------
5431
5432       when Attribute_Model_Small =>
5433          Float_Attribute_Universal_Real (
5434            IEEES_Model_Small'Universal_Literal_String,
5435            IEEEL_Model_Small'Universal_Literal_String,
5436            IEEEX_Model_Small'Universal_Literal_String,
5437            VAXFF_Model_Small'Universal_Literal_String,
5438            VAXDF_Model_Small'Universal_Literal_String,
5439            VAXGF_Model_Small'Universal_Literal_String,
5440            AAMPS_Model_Small'Universal_Literal_String,
5441            AAMPL_Model_Small'Universal_Literal_String);
5442
5443       -------------
5444       -- Modulus --
5445       -------------
5446
5447       when Attribute_Modulus =>
5448          Fold_Uint (N, Modulus (P_Type), True);
5449
5450       --------------------
5451       -- Null_Parameter --
5452       --------------------
5453
5454       --  Cannot fold, we know the value sort of, but the whole point is
5455       --  that there is no way to talk about this imaginary value except
5456       --  by using the attribute, so we leave it the way it is.
5457
5458       when Attribute_Null_Parameter =>
5459          null;
5460
5461       -----------------
5462       -- Object_Size --
5463       -----------------
5464
5465       --  The Object_Size attribute for a type returns the Esize of the
5466       --  type and can be folded if this value is known.
5467
5468       when Attribute_Object_Size => Object_Size : declare
5469          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5470
5471       begin
5472          if Known_Esize (P_TypeA) then
5473             Fold_Uint (N, Esize (P_TypeA), True);
5474          end if;
5475       end Object_Size;
5476
5477       -------------------------
5478       -- Passed_By_Reference --
5479       -------------------------
5480
5481       --  Scalar types are never passed by reference
5482
5483       when Attribute_Passed_By_Reference =>
5484          Fold_Uint (N, False_Value, True);
5485
5486       ---------
5487       -- Pos --
5488       ---------
5489
5490       when Attribute_Pos =>
5491          Fold_Uint (N, Expr_Value (E1), True);
5492
5493       ----------
5494       -- Pred --
5495       ----------
5496
5497       when Attribute_Pred => Pred :
5498       begin
5499          --  Floating-point case
5500
5501          if Is_Floating_Point_Type (P_Type) then
5502             Fold_Ureal (N,
5503               Eval_Fat.Pred (P_Root_Type, Expr_Value_R (E1)), Static);
5504
5505          --  Fixed-point case
5506
5507          elsif Is_Fixed_Point_Type (P_Type) then
5508             Fold_Ureal (N,
5509               Expr_Value_R (E1) - Small_Value (P_Type), True);
5510
5511          --  Modular integer case (wraps)
5512
5513          elsif Is_Modular_Integer_Type (P_Type) then
5514             Fold_Uint (N, (Expr_Value (E1) - 1) mod Modulus (P_Type), Static);
5515
5516          --  Other scalar cases
5517
5518          else
5519             pragma Assert (Is_Scalar_Type (P_Type));
5520
5521             if Is_Enumeration_Type (P_Type)
5522               and then Expr_Value (E1) =
5523                          Expr_Value (Type_Low_Bound (P_Base_Type))
5524             then
5525                Apply_Compile_Time_Constraint_Error
5526                  (N, "Pred of `&''First`",
5527                   CE_Overflow_Check_Failed,
5528                   Ent  => P_Base_Type,
5529                   Warn => not Static);
5530
5531                Check_Expressions;
5532                return;
5533             end if;
5534
5535             Fold_Uint (N, Expr_Value (E1) - 1, Static);
5536          end if;
5537       end Pred;
5538
5539       -----------
5540       -- Range --
5541       -----------
5542
5543       --  No processing required, because by this stage, Range has been
5544       --  replaced by First .. Last, so this branch can never be taken.
5545
5546       when Attribute_Range =>
5547          raise Program_Error;
5548
5549       ------------------
5550       -- Range_Length --
5551       ------------------
5552
5553       when Attribute_Range_Length =>
5554          Set_Bounds;
5555
5556          if Compile_Time_Known_Value (Hi_Bound)
5557            and then Compile_Time_Known_Value (Lo_Bound)
5558          then
5559             Fold_Uint (N,
5560               UI_Max
5561                 (0, Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound) + 1),
5562                  Static);
5563          end if;
5564
5565       ---------------
5566       -- Remainder --
5567       ---------------
5568
5569       when Attribute_Remainder =>
5570          Fold_Ureal (N,
5571            Eval_Fat.Remainder
5572              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)),
5573            Static);
5574
5575       -----------
5576       -- Round --
5577       -----------
5578
5579       when Attribute_Round => Round :
5580       declare
5581          Sr : Ureal;
5582          Si : Uint;
5583
5584       begin
5585          --  First we get the (exact result) in units of small
5586
5587          Sr := Expr_Value_R (E1) / Small_Value (C_Type);
5588
5589          --  Now round that exactly to an integer
5590
5591          Si := UR_To_Uint (Sr);
5592
5593          --  Finally the result is obtained by converting back to real
5594
5595          Fold_Ureal (N, Si * Small_Value (C_Type), Static);
5596       end Round;
5597
5598       --------------
5599       -- Rounding --
5600       --------------
5601
5602       when Attribute_Rounding =>
5603          Fold_Ureal (N,
5604            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
5605
5606       ---------------
5607       -- Safe_Emax --
5608       ---------------
5609
5610       when Attribute_Safe_Emax =>
5611          Float_Attribute_Universal_Integer (
5612            IEEES_Safe_Emax,
5613            IEEEL_Safe_Emax,
5614            IEEEX_Safe_Emax,
5615            VAXFF_Safe_Emax,
5616            VAXDF_Safe_Emax,
5617            VAXGF_Safe_Emax,
5618            AAMPS_Safe_Emax,
5619            AAMPL_Safe_Emax);
5620
5621       ----------------
5622       -- Safe_First --
5623       ----------------
5624
5625       when Attribute_Safe_First =>
5626          Float_Attribute_Universal_Real (
5627            IEEES_Safe_First'Universal_Literal_String,
5628            IEEEL_Safe_First'Universal_Literal_String,
5629            IEEEX_Safe_First'Universal_Literal_String,
5630            VAXFF_Safe_First'Universal_Literal_String,
5631            VAXDF_Safe_First'Universal_Literal_String,
5632            VAXGF_Safe_First'Universal_Literal_String,
5633            AAMPS_Safe_First'Universal_Literal_String,
5634            AAMPL_Safe_First'Universal_Literal_String);
5635
5636       ----------------
5637       -- Safe_Large --
5638       ----------------
5639
5640       when Attribute_Safe_Large =>
5641          if Is_Fixed_Point_Type (P_Type) then
5642             Fold_Ureal
5643               (N, Expr_Value_R (Type_High_Bound (P_Base_Type)), Static);
5644          else
5645             Float_Attribute_Universal_Real (
5646               IEEES_Safe_Large'Universal_Literal_String,
5647               IEEEL_Safe_Large'Universal_Literal_String,
5648               IEEEX_Safe_Large'Universal_Literal_String,
5649               VAXFF_Safe_Large'Universal_Literal_String,
5650               VAXDF_Safe_Large'Universal_Literal_String,
5651               VAXGF_Safe_Large'Universal_Literal_String,
5652               AAMPS_Safe_Large'Universal_Literal_String,
5653               AAMPL_Safe_Large'Universal_Literal_String);
5654          end if;
5655
5656       ---------------
5657       -- Safe_Last --
5658       ---------------
5659
5660       when Attribute_Safe_Last =>
5661          Float_Attribute_Universal_Real (
5662            IEEES_Safe_Last'Universal_Literal_String,
5663            IEEEL_Safe_Last'Universal_Literal_String,
5664            IEEEX_Safe_Last'Universal_Literal_String,
5665            VAXFF_Safe_Last'Universal_Literal_String,
5666            VAXDF_Safe_Last'Universal_Literal_String,
5667            VAXGF_Safe_Last'Universal_Literal_String,
5668            AAMPS_Safe_Last'Universal_Literal_String,
5669            AAMPL_Safe_Last'Universal_Literal_String);
5670
5671       ----------------
5672       -- Safe_Small --
5673       ----------------
5674
5675       when Attribute_Safe_Small =>
5676
5677          --  In Ada 95, the old Ada 83 attribute Safe_Small is redundant
5678          --  for fixed-point, since is the same as Small, but we implement
5679          --  it for backwards compatibility.
5680
5681          if Is_Fixed_Point_Type (P_Type) then
5682             Fold_Ureal (N, Small_Value (P_Type), Static);
5683
5684          --  Ada 83 Safe_Small for floating-point cases
5685
5686          else
5687             Float_Attribute_Universal_Real (
5688               IEEES_Safe_Small'Universal_Literal_String,
5689               IEEEL_Safe_Small'Universal_Literal_String,
5690               IEEEX_Safe_Small'Universal_Literal_String,
5691               VAXFF_Safe_Small'Universal_Literal_String,
5692               VAXDF_Safe_Small'Universal_Literal_String,
5693               VAXGF_Safe_Small'Universal_Literal_String,
5694               AAMPS_Safe_Small'Universal_Literal_String,
5695               AAMPL_Safe_Small'Universal_Literal_String);
5696          end if;
5697
5698       -----------
5699       -- Scale --
5700       -----------
5701
5702       when Attribute_Scale =>
5703          Fold_Uint (N, Scale_Value (P_Type), True);
5704
5705       -------------
5706       -- Scaling --
5707       -------------
5708
5709       when Attribute_Scaling =>
5710          Fold_Ureal (N,
5711            Eval_Fat.Scaling
5712              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5713
5714       ------------------
5715       -- Signed_Zeros --
5716       ------------------
5717
5718       when Attribute_Signed_Zeros =>
5719          Fold_Uint
5720            (N, UI_From_Int (Boolean'Pos (Signed_Zeros_On_Target)), Static);
5721
5722       ----------
5723       -- Size --
5724       ----------
5725
5726       --  Size attribute returns the RM size. All scalar types can be folded,
5727       --  as well as any types for which the size is known by the front end,
5728       --  including any type for which a size attribute is specified.
5729
5730       when Attribute_Size | Attribute_VADS_Size => Size : declare
5731          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5732
5733       begin
5734          if RM_Size (P_TypeA) /= Uint_0 then
5735
5736             --  VADS_Size case
5737
5738             if Id = Attribute_VADS_Size or else Use_VADS_Size then
5739                declare
5740                   S : constant Node_Id := Size_Clause (P_TypeA);
5741
5742                begin
5743                   --  If a size clause applies, then use the size from it.
5744                   --  This is one of the rare cases where we can use the
5745                   --  Size_Clause field for a subtype when Has_Size_Clause
5746                   --  is False. Consider:
5747
5748                   --    type x is range 1 .. 64;                         g
5749                   --    for x'size use 12;
5750                   --    subtype y is x range 0 .. 3;
5751
5752                   --  Here y has a size clause inherited from x, but normally
5753                   --  it does not apply, and y'size is 2. However, y'VADS_Size
5754                   --  is indeed 12 and not 2.
5755
5756                   if Present (S)
5757                     and then Is_OK_Static_Expression (Expression (S))
5758                   then
5759                      Fold_Uint (N, Expr_Value (Expression (S)), True);
5760
5761                   --  If no size is specified, then we simply use the object
5762                   --  size in the VADS_Size case (e.g. Natural'Size is equal
5763                   --  to Integer'Size, not one less).
5764
5765                   else
5766                      Fold_Uint (N, Esize (P_TypeA), True);
5767                   end if;
5768                end;
5769
5770             --  Normal case (Size) in which case we want the RM_Size
5771
5772             else
5773                Fold_Uint (N,
5774                  RM_Size (P_TypeA),
5775                  Static and then Is_Discrete_Type (P_TypeA));
5776             end if;
5777          end if;
5778       end Size;
5779
5780       -----------
5781       -- Small --
5782       -----------
5783
5784       when Attribute_Small =>
5785
5786          --  The floating-point case is present only for Ada 83 compatability.
5787          --  Note that strictly this is an illegal addition, since we are
5788          --  extending an Ada 95 defined attribute, but we anticipate an
5789          --  ARG ruling that will permit this.
5790
5791          if Is_Floating_Point_Type (P_Type) then
5792
5793             --  Ada 83 attribute is defined as (RM83 3.5.8)
5794
5795             --    T'Small = 2.0**(-T'Emax - 1)
5796
5797             --  where
5798
5799             --    T'Emax = 4 * T'Mantissa
5800
5801             Fold_Ureal (N, Ureal_2 ** ((-(4 * Mantissa)) - 1), Static);
5802
5803          --  Normal Ada 95 fixed-point case
5804
5805          else
5806             Fold_Ureal (N, Small_Value (P_Type), True);
5807          end if;
5808
5809       ----------
5810       -- Succ --
5811       ----------
5812
5813       when Attribute_Succ => Succ :
5814       begin
5815          --  Floating-point case
5816
5817          if Is_Floating_Point_Type (P_Type) then
5818             Fold_Ureal (N,
5819               Eval_Fat.Succ (P_Root_Type, Expr_Value_R (E1)), Static);
5820
5821          --  Fixed-point case
5822
5823          elsif Is_Fixed_Point_Type (P_Type) then
5824             Fold_Ureal (N,
5825               Expr_Value_R (E1) + Small_Value (P_Type), Static);
5826
5827          --  Modular integer case (wraps)
5828
5829          elsif Is_Modular_Integer_Type (P_Type) then
5830             Fold_Uint (N, (Expr_Value (E1) + 1) mod Modulus (P_Type), Static);
5831
5832          --  Other scalar cases
5833
5834          else
5835             pragma Assert (Is_Scalar_Type (P_Type));
5836
5837             if Is_Enumeration_Type (P_Type)
5838               and then Expr_Value (E1) =
5839                          Expr_Value (Type_High_Bound (P_Base_Type))
5840             then
5841                Apply_Compile_Time_Constraint_Error
5842                  (N, "Succ of `&''Last`",
5843                   CE_Overflow_Check_Failed,
5844                   Ent  => P_Base_Type,
5845                   Warn => not Static);
5846
5847                Check_Expressions;
5848                return;
5849             else
5850                Fold_Uint (N, Expr_Value (E1) + 1, Static);
5851             end if;
5852          end if;
5853       end Succ;
5854
5855       ----------------
5856       -- Truncation --
5857       ----------------
5858
5859       when Attribute_Truncation =>
5860          Fold_Ureal (N,
5861            Eval_Fat.Truncation (P_Root_Type, Expr_Value_R (E1)), Static);
5862
5863       ----------------
5864       -- Type_Class --
5865       ----------------
5866
5867       when Attribute_Type_Class => Type_Class : declare
5868          Typ : constant Entity_Id := Underlying_Type (P_Base_Type);
5869          Id  : RE_Id;
5870
5871       begin
5872          if Is_RTE (P_Root_Type, RE_Address) then
5873             Id := RE_Type_Class_Address;
5874
5875          elsif Is_Enumeration_Type (Typ) then
5876             Id := RE_Type_Class_Enumeration;
5877
5878          elsif Is_Integer_Type (Typ) then
5879             Id := RE_Type_Class_Integer;
5880
5881          elsif Is_Fixed_Point_Type (Typ) then
5882             Id := RE_Type_Class_Fixed_Point;
5883
5884          elsif Is_Floating_Point_Type (Typ) then
5885             Id := RE_Type_Class_Floating_Point;
5886
5887          elsif Is_Array_Type (Typ) then
5888             Id := RE_Type_Class_Array;
5889
5890          elsif Is_Record_Type (Typ) then
5891             Id := RE_Type_Class_Record;
5892
5893          elsif Is_Access_Type (Typ) then
5894             Id := RE_Type_Class_Access;
5895
5896          elsif Is_Enumeration_Type (Typ) then
5897             Id := RE_Type_Class_Enumeration;
5898
5899          elsif Is_Task_Type (Typ) then
5900             Id := RE_Type_Class_Task;
5901
5902          --  We treat protected types like task types. It would make more
5903          --  sense to have another enumeration value, but after all the
5904          --  whole point of this feature is to be exactly DEC compatible,
5905          --  and changing the type Type_Clas would not meet this requirement.
5906
5907          elsif Is_Protected_Type (Typ) then
5908             Id := RE_Type_Class_Task;
5909
5910          --  Not clear if there are any other possibilities, but if there
5911          --  are, then we will treat them as the address case.
5912
5913          else
5914             Id := RE_Type_Class_Address;
5915          end if;
5916
5917          Rewrite (N, New_Occurrence_Of (RTE (Id), Loc));
5918
5919       end Type_Class;
5920
5921       -----------------------
5922       -- Unbiased_Rounding --
5923       -----------------------
5924
5925       when Attribute_Unbiased_Rounding =>
5926          Fold_Ureal (N,
5927            Eval_Fat.Unbiased_Rounding (P_Root_Type, Expr_Value_R (E1)),
5928            Static);
5929
5930       -------------------------
5931       -- Unconstrained_Array --
5932       -------------------------
5933
5934       when Attribute_Unconstrained_Array => Unconstrained_Array : declare
5935          Typ : constant Entity_Id := Underlying_Type (P_Type);
5936
5937       begin
5938          if Is_Array_Type (P_Type)
5939            and then not Is_Constrained (Typ)
5940          then
5941             Rewrite (N, New_Occurrence_Of (Standard_True, Loc));
5942          else
5943             Rewrite (N, New_Occurrence_Of (Standard_False, Loc));
5944          end if;
5945
5946          --  Analyze and resolve as boolean, note that this attribute is
5947          --  a static attribute in GNAT.
5948
5949          Analyze_And_Resolve (N, Standard_Boolean);
5950          Static := True;
5951       end Unconstrained_Array;
5952
5953       ---------------
5954       -- VADS_Size --
5955       ---------------
5956
5957       --  Processing is shared with Size
5958
5959       ---------
5960       -- Val --
5961       ---------
5962
5963       when Attribute_Val => Val :
5964       begin
5965          if  Expr_Value (E1) < Expr_Value (Type_Low_Bound (P_Base_Type))
5966            or else
5967              Expr_Value (E1) > Expr_Value (Type_High_Bound (P_Base_Type))
5968          then
5969             Apply_Compile_Time_Constraint_Error
5970               (N, "Val expression out of range",
5971                CE_Range_Check_Failed,
5972                Warn => not Static);
5973
5974             Check_Expressions;
5975             return;
5976
5977          else
5978             Fold_Uint (N, Expr_Value (E1), Static);
5979          end if;
5980       end Val;
5981
5982       ----------------
5983       -- Value_Size --
5984       ----------------
5985
5986       --  The Value_Size attribute for a type returns the RM size of the
5987       --  type. This an always be folded for scalar types, and can also
5988       --  be folded for non-scalar types if the size is set.
5989
5990       when Attribute_Value_Size => Value_Size : declare
5991          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5992
5993       begin
5994          if RM_Size (P_TypeA) /= Uint_0 then
5995             Fold_Uint (N, RM_Size (P_TypeA), True);
5996          end if;
5997
5998       end Value_Size;
5999
6000       -------------
6001       -- Version --
6002       -------------
6003
6004       --  Version can never be static
6005
6006       when Attribute_Version =>
6007          null;
6008
6009       ----------------
6010       -- Wide_Image --
6011       ----------------
6012
6013       --  Wide_Image is a scalar attribute, but is never static, because it
6014       --  is not a static function (having a non-scalar argument (RM 4.9(22))
6015
6016       when Attribute_Wide_Image =>
6017          null;
6018
6019       ----------------
6020       -- Wide_Width --
6021       ----------------
6022
6023       --  Processing for Wide_Width is combined with Width
6024
6025       -----------
6026       -- Width --
6027       -----------
6028
6029       --  This processing also handles the case of Wide_Width
6030
6031       when Attribute_Width | Attribute_Wide_Width => Width :
6032       begin
6033          if Compile_Time_Known_Bounds (P_Type) then
6034
6035             --  Floating-point types
6036
6037             if Is_Floating_Point_Type (P_Type) then
6038
6039                --  Width is zero for a null range (RM 3.5 (38))
6040
6041                if Expr_Value_R (Type_High_Bound (P_Type)) <
6042                   Expr_Value_R (Type_Low_Bound (P_Type))
6043                then
6044                   Fold_Uint (N, Uint_0, True);
6045
6046                else
6047                   --  For floating-point, we have +N.dddE+nnn where length
6048                   --  of ddd is determined by type'Digits - 1, but is one
6049                   --  if Digits is one (RM 3.5 (33)).
6050
6051                   --  nnn is set to 2 for Short_Float and Float (32 bit
6052                   --  floats), and 3 for Long_Float and Long_Long_Float.
6053                   --  This is not quite right, but is good enough.
6054
6055                   declare
6056                      Len : Int :=
6057                              Int'Max (2, UI_To_Int (Digits_Value (P_Type)));
6058
6059                   begin
6060                      if Esize (P_Type) <= 32 then
6061                         Len := Len + 6;
6062                      else
6063                         Len := Len + 7;
6064                      end if;
6065
6066                      Fold_Uint (N, UI_From_Int (Len), True);
6067                   end;
6068                end if;
6069
6070             --  Fixed-point types
6071
6072             elsif Is_Fixed_Point_Type (P_Type) then
6073
6074                --  Width is zero for a null range (RM 3.5 (38))
6075
6076                if Expr_Value (Type_High_Bound (P_Type)) <
6077                   Expr_Value (Type_Low_Bound  (P_Type))
6078                then
6079                   Fold_Uint (N, Uint_0, True);
6080
6081                --  The non-null case depends on the specific real type
6082
6083                else
6084                   --  For fixed-point type width is Fore + 1 + Aft (RM 3.5(34))
6085
6086                   Fold_Uint
6087                     (N, UI_From_Int (Fore_Value + 1 + Aft_Value), True);
6088                end if;
6089
6090             --  Discrete types
6091
6092             else
6093                declare
6094                   R  : constant Entity_Id := Root_Type (P_Type);
6095                   Lo : constant Uint :=
6096                          Expr_Value (Type_Low_Bound (P_Type));
6097                   Hi : constant Uint :=
6098                          Expr_Value (Type_High_Bound (P_Type));
6099                   W  : Nat;
6100                   Wt : Nat;
6101                   T  : Uint;
6102                   L  : Node_Id;
6103                   C  : Character;
6104
6105                begin
6106                   --  Empty ranges
6107
6108                   if Lo > Hi then
6109                      W := 0;
6110
6111                   --  Width for types derived from Standard.Character
6112                   --  and Standard.Wide_Character.
6113
6114                   elsif R = Standard_Character
6115                     or else R = Standard_Wide_Character
6116                   then
6117                      W := 0;
6118
6119                      --  Set W larger if needed
6120
6121                      for J in UI_To_Int (Lo) .. UI_To_Int (Hi) loop
6122
6123                         --  Assume all wide-character escape sequences are
6124                         --  same length, so we can quit when we reach one.
6125
6126                         if J > 255 then
6127                            if Id = Attribute_Wide_Width then
6128                               W := Int'Max (W, 3);
6129                               exit;
6130                            else
6131                               W := Int'Max (W, Length_Wide);
6132                               exit;
6133                            end if;
6134
6135                         else
6136                            C := Character'Val (J);
6137
6138                            --  Test for all cases where Character'Image
6139                            --  yields an image that is longer than three
6140                            --  characters. First the cases of Reserved_xxx
6141                            --  names (length = 12).
6142
6143                            case C is
6144                               when Reserved_128 | Reserved_129 |
6145                                    Reserved_132 | Reserved_153
6146
6147                                 => Wt := 12;
6148
6149                               when BS | HT | LF | VT | FF | CR |
6150                                    SO | SI | EM | FS | GS | RS |
6151                                    US | RI | MW | ST | PM
6152
6153                                 => Wt := 2;
6154
6155                               when NUL | SOH | STX | ETX | EOT |
6156                                    ENQ | ACK | BEL | DLE | DC1 |
6157                                    DC2 | DC3 | DC4 | NAK | SYN |
6158                                    ETB | CAN | SUB | ESC | DEL |
6159                                    BPH | NBH | NEL | SSA | ESA |
6160                                    HTS | HTJ | VTS | PLD | PLU |
6161                                    SS2 | SS3 | DCS | PU1 | PU2 |
6162                                    STS | CCH | SPA | EPA | SOS |
6163                                    SCI | CSI | OSC | APC
6164
6165                                 => Wt := 3;
6166
6167                               when Space .. Tilde |
6168                                    No_Break_Space .. LC_Y_Diaeresis
6169
6170                                 => Wt := 3;
6171                            end case;
6172
6173                            W := Int'Max (W, Wt);
6174                         end if;
6175                      end loop;
6176
6177                   --  Width for types derived from Standard.Boolean
6178
6179                   elsif R = Standard_Boolean then
6180                      if Lo = 0 then
6181                         W := 5; -- FALSE
6182                      else
6183                         W := 4; -- TRUE
6184                      end if;
6185
6186                   --  Width for integer types
6187
6188                   elsif Is_Integer_Type (P_Type) then
6189                      T := UI_Max (abs Lo, abs Hi);
6190
6191                      W := 2;
6192                      while T >= 10 loop
6193                         W := W + 1;
6194                         T := T / 10;
6195                      end loop;
6196
6197                   --  Only remaining possibility is user declared enum type
6198
6199                   else
6200                      pragma Assert (Is_Enumeration_Type (P_Type));
6201
6202                      W := 0;
6203                      L := First_Literal (P_Type);
6204
6205                      while Present (L) loop
6206
6207                         --  Only pay attention to in range characters
6208
6209                         if Lo <= Enumeration_Pos (L)
6210                           and then Enumeration_Pos (L) <= Hi
6211                         then
6212                            --  For Width case, use decoded name
6213
6214                            if Id = Attribute_Width then
6215                               Get_Decoded_Name_String (Chars (L));
6216                               Wt := Nat (Name_Len);
6217
6218                            --  For Wide_Width, use encoded name, and then
6219                            --  adjust for the encoding.
6220
6221                            else
6222                               Get_Name_String (Chars (L));
6223
6224                               --  Character literals are always of length 3
6225
6226                               if Name_Buffer (1) = 'Q' then
6227                                  Wt := 3;
6228
6229                               --  Otherwise loop to adjust for upper/wide chars
6230
6231                               else
6232                                  Wt := Nat (Name_Len);
6233
6234                                  for J in 1 .. Name_Len loop
6235                                     if Name_Buffer (J) = 'U' then
6236                                        Wt := Wt - 2;
6237                                     elsif Name_Buffer (J) = 'W' then
6238                                        Wt := Wt - 4;
6239                                     end if;
6240                                  end loop;
6241                               end if;
6242                            end if;
6243
6244                            W := Int'Max (W, Wt);
6245                         end if;
6246
6247                         Next_Literal (L);
6248                      end loop;
6249                   end if;
6250
6251                   Fold_Uint (N, UI_From_Int (W), True);
6252                end;
6253             end if;
6254          end if;
6255       end Width;
6256
6257       --  The following attributes can never be folded, and furthermore we
6258       --  should not even have entered the case statement for any of these.
6259       --  Note that in some cases, the values have already been folded as
6260       --  a result of the processing in Analyze_Attribute.
6261
6262       when Attribute_Abort_Signal             |
6263            Attribute_Access                   |
6264            Attribute_Address                  |
6265            Attribute_Address_Size             |
6266            Attribute_Asm_Input                |
6267            Attribute_Asm_Output               |
6268            Attribute_Base                     |
6269            Attribute_Bit_Order                |
6270            Attribute_Bit_Position             |
6271            Attribute_Callable                 |
6272            Attribute_Caller                   |
6273            Attribute_Class                    |
6274            Attribute_Code_Address             |
6275            Attribute_Count                    |
6276            Attribute_Default_Bit_Order        |
6277            Attribute_Elaborated               |
6278            Attribute_Elab_Body                |
6279            Attribute_Elab_Spec                |
6280            Attribute_External_Tag             |
6281            Attribute_First_Bit                |
6282            Attribute_Input                    |
6283            Attribute_Last_Bit                 |
6284            Attribute_Maximum_Alignment        |
6285            Attribute_Output                   |
6286            Attribute_Partition_ID             |
6287            Attribute_Pool_Address             |
6288            Attribute_Position                 |
6289            Attribute_Read                     |
6290            Attribute_Storage_Pool             |
6291            Attribute_Storage_Size             |
6292            Attribute_Storage_Unit             |
6293            Attribute_Tag                      |
6294            Attribute_Target_Name              |
6295            Attribute_Terminated               |
6296            Attribute_To_Address               |
6297            Attribute_UET_Address              |
6298            Attribute_Unchecked_Access         |
6299            Attribute_Universal_Literal_String |
6300            Attribute_Unrestricted_Access      |
6301            Attribute_Valid                    |
6302            Attribute_Value                    |
6303            Attribute_Wchar_T_Size             |
6304            Attribute_Wide_Value               |
6305            Attribute_Word_Size                |
6306            Attribute_Write                    =>
6307
6308          raise Program_Error;
6309
6310       end case;
6311
6312       --  At the end of the case, one more check. If we did a static evaluation
6313       --  so that the result is now a literal, then set Is_Static_Expression
6314       --  in the constant only if the prefix type is a static subtype. For
6315       --  non-static subtypes, the folding is still OK, but not static.
6316
6317       --  An exception is the GNAT attribute Constrained_Array which is
6318       --  defined to be a static attribute in all cases.
6319
6320       if Nkind (N) = N_Integer_Literal
6321         or else Nkind (N) = N_Real_Literal
6322         or else Nkind (N) = N_Character_Literal
6323         or else Nkind (N) = N_String_Literal
6324         or else (Is_Entity_Name (N)
6325                   and then Ekind (Entity (N)) = E_Enumeration_Literal)
6326       then
6327          Set_Is_Static_Expression (N, Static);
6328
6329       --  If this is still an attribute reference, then it has not been folded
6330       --  and that means that its expressions are in a non-static context.
6331
6332       elsif Nkind (N) = N_Attribute_Reference then
6333          Check_Expressions;
6334
6335       --  Note: the else case not covered here are odd cases where the
6336       --  processing has transformed the attribute into something other
6337       --  than a constant. Nothing more to do in such cases.
6338
6339       else
6340          null;
6341       end if;
6342
6343    end Eval_Attribute;
6344
6345    ------------------------------
6346    -- Is_Anonymous_Tagged_Base --
6347    ------------------------------
6348
6349    function Is_Anonymous_Tagged_Base
6350      (Anon : Entity_Id;
6351       Typ  : Entity_Id)
6352       return Boolean
6353    is
6354    begin
6355       return
6356         Anon = Current_Scope
6357           and then Is_Itype (Anon)
6358           and then Associated_Node_For_Itype (Anon) = Parent (Typ);
6359    end Is_Anonymous_Tagged_Base;
6360
6361    -----------------------
6362    -- Resolve_Attribute --
6363    -----------------------
6364
6365    procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id) is
6366       Loc      : constant Source_Ptr   := Sloc (N);
6367       P        : constant Node_Id      := Prefix (N);
6368       Aname    : constant Name_Id      := Attribute_Name (N);
6369       Attr_Id  : constant Attribute_Id := Get_Attribute_Id (Aname);
6370       Btyp     : constant Entity_Id    := Base_Type (Typ);
6371       Index    : Interp_Index;
6372       It       : Interp;
6373       Nom_Subt : Entity_Id;
6374
6375    begin
6376       --  If error during analysis, no point in continuing, except for
6377       --  array types, where we get  better recovery by using unconstrained
6378       --  indices than nothing at all (see Check_Array_Type).
6379
6380       if Error_Posted (N)
6381         and then Attr_Id /= Attribute_First
6382         and then Attr_Id /= Attribute_Last
6383         and then Attr_Id /= Attribute_Length
6384         and then Attr_Id /= Attribute_Range
6385       then
6386          return;
6387       end if;
6388
6389       --  If attribute was universal type, reset to actual type
6390
6391       if Etype (N) = Universal_Integer
6392         or else Etype (N) = Universal_Real
6393       then
6394          Set_Etype (N, Typ);
6395       end if;
6396
6397       --  Remaining processing depends on attribute
6398
6399       case Attr_Id is
6400
6401          ------------
6402          -- Access --
6403          ------------
6404
6405          --  For access attributes, if the prefix denotes an entity, it is
6406          --  interpreted as a name, never as a call. It may be overloaded,
6407          --  in which case resolution uses the profile of the context type.
6408          --  Otherwise prefix must be resolved.
6409
6410          when Attribute_Access
6411             | Attribute_Unchecked_Access
6412             | Attribute_Unrestricted_Access =>
6413
6414             if Is_Variable (P) then
6415                Note_Possible_Modification (P);
6416             end if;
6417
6418             if Is_Entity_Name (P) then
6419                if Is_Overloaded (P) then
6420                   Get_First_Interp (P, Index, It);
6421
6422                   while Present (It.Nam) loop
6423
6424                      if Type_Conformant (Designated_Type (Typ), It.Nam) then
6425                         Set_Entity (P, It.Nam);
6426
6427                         --  The prefix is definitely NOT overloaded anymore
6428                         --  at this point, so we reset the Is_Overloaded
6429                         --  flag to avoid any confusion when reanalyzing
6430                         --  the node.
6431
6432                         Set_Is_Overloaded (P, False);
6433                         Generate_Reference (Entity (P), P);
6434                         exit;
6435                      end if;
6436
6437                      Get_Next_Interp (Index, It);
6438                   end loop;
6439
6440                --  If it is a subprogram name or a type, there is nothing
6441                --  to resolve.
6442
6443                elsif not Is_Overloadable (Entity (P))
6444                  and then not Is_Type (Entity (P))
6445                then
6446                   Resolve (P);
6447                end if;
6448
6449                Error_Msg_Name_1 := Aname;
6450
6451                if not Is_Entity_Name (P) then
6452                   null;
6453
6454                elsif Is_Abstract (Entity (P))
6455                  and then Is_Overloadable (Entity (P))
6456                then
6457                   Error_Msg_N ("prefix of % attribute cannot be abstract", P);
6458                   Set_Etype (N, Any_Type);
6459
6460                elsif Convention (Entity (P)) = Convention_Intrinsic then
6461                   if Ekind (Entity (P)) = E_Enumeration_Literal then
6462                      Error_Msg_N
6463                        ("prefix of % attribute cannot be enumeration literal",
6464                           P);
6465                   else
6466                      Error_Msg_N
6467                        ("prefix of % attribute cannot be intrinsic", P);
6468                   end if;
6469
6470                   Set_Etype (N, Any_Type);
6471
6472                elsif Is_Thread_Body (Entity (P)) then
6473                   Error_Msg_N
6474                     ("prefix of % attribute cannot be a thread body", P);
6475                end if;
6476
6477                --  Assignments, return statements, components of aggregates,
6478                --  generic instantiations will require convention checks if
6479                --  the type is an access to subprogram. Given that there will
6480                --  also be accessibility checks on those, this is where the
6481                --  checks can eventually be centralized ???
6482
6483                if Ekind (Btyp) = E_Access_Subprogram_Type then
6484                   if Convention (Btyp) /= Convention (Entity (P)) then
6485                      Error_Msg_N
6486                       ("subprogram has invalid convention for context", P);
6487
6488                   else
6489                      Check_Subtype_Conformant
6490                        (New_Id  => Entity (P),
6491                         Old_Id  => Designated_Type (Btyp),
6492                         Err_Loc => P);
6493                   end if;
6494
6495                   if Attr_Id = Attribute_Unchecked_Access then
6496                      Error_Msg_Name_1 := Aname;
6497                      Error_Msg_N
6498                        ("attribute% cannot be applied to a subprogram", P);
6499
6500                   elsif Aname = Name_Unrestricted_Access then
6501                      null;  --  Nothing to check
6502
6503                   --  Check the static accessibility rule of 3.10.2(32)
6504
6505                   elsif Attr_Id = Attribute_Access
6506                     and then Subprogram_Access_Level (Entity (P))
6507                       > Type_Access_Level (Btyp)
6508                   then
6509                      if not In_Instance_Body then
6510                         Error_Msg_N
6511                           ("subprogram must not be deeper than access type",
6512                             P);
6513                      else
6514                         Error_Msg_N
6515                           ("subprogram must not be deeper than access type?",
6516                              P);
6517                         Error_Msg_N
6518                           ("Constraint_Error will be raised ?", P);
6519                         Set_Raises_Constraint_Error (N);
6520                      end if;
6521
6522                   --  Check the restriction of 3.10.2(32) that disallows
6523                   --  the type of the access attribute to be declared
6524                   --  outside a generic body when the attribute occurs
6525                   --  within that generic body.
6526
6527                   elsif Enclosing_Generic_Body (Entity (P))
6528                     /= Enclosing_Generic_Body (Btyp)
6529                   then
6530                      Error_Msg_N
6531                        ("access type must not be outside generic body", P);
6532                   end if;
6533                end if;
6534
6535                --  if this is a renaming, an inherited operation, or a
6536                --  subprogram instance, use the original entity.
6537
6538                if Is_Entity_Name (P)
6539                  and then Is_Overloadable (Entity (P))
6540                  and then Present (Alias (Entity (P)))
6541                then
6542                   Rewrite (P,
6543                     New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6544                end if;
6545
6546             elsif Nkind (P) = N_Selected_Component
6547               and then Is_Overloadable (Entity (Selector_Name (P)))
6548             then
6549                --  Protected operation. If operation is overloaded, must
6550                --  disambiguate. Prefix that denotes protected object itself
6551                --  is resolved with its own type.
6552
6553                if Attr_Id = Attribute_Unchecked_Access then
6554                   Error_Msg_Name_1 := Aname;
6555                   Error_Msg_N
6556                     ("attribute% cannot be applied to protected operation", P);
6557                end if;
6558
6559                Resolve (Prefix (P));
6560                Generate_Reference (Entity (Selector_Name (P)), P);
6561
6562             elsif Is_Overloaded (P) then
6563
6564                --  Use the designated type of the context  to disambiguate.
6565                declare
6566                   Index : Interp_Index;
6567                   It    : Interp;
6568                begin
6569                   Get_First_Interp (P, Index, It);
6570
6571                   while Present (It.Typ) loop
6572                      if Covers (Designated_Type (Typ), It.Typ) then
6573                         Resolve (P, It.Typ);
6574                         exit;
6575                      end if;
6576
6577                      Get_Next_Interp (Index, It);
6578                   end loop;
6579                end;
6580             else
6581                Resolve (P);
6582             end if;
6583
6584             --  X'Access is illegal if X denotes a constant and the access
6585             --  type is access-to-variable. Same for 'Unchecked_Access.
6586             --  The rule does not apply to 'Unrestricted_Access.
6587
6588             if not (Ekind (Btyp) = E_Access_Subprogram_Type
6589                      or else (Is_Record_Type (Btyp) and then
6590                               Present (Corresponding_Remote_Type (Btyp)))
6591                      or else Ekind (Btyp) = E_Access_Protected_Subprogram_Type
6592                      or else Is_Access_Constant (Btyp)
6593                      or else Is_Variable (P)
6594                      or else Attr_Id = Attribute_Unrestricted_Access)
6595             then
6596                if Comes_From_Source (N) then
6597                   Error_Msg_N ("access-to-variable designates constant", P);
6598                end if;
6599             end if;
6600
6601             if (Attr_Id = Attribute_Access
6602                   or else
6603                 Attr_Id = Attribute_Unchecked_Access)
6604               and then (Ekind (Btyp) = E_General_Access_Type
6605                          or else Ekind (Btyp) = E_Anonymous_Access_Type)
6606             then
6607                if Is_Dependent_Component_Of_Mutable_Object (P) then
6608                   Error_Msg_N
6609                     ("illegal attribute for discriminant-dependent component",
6610                      P);
6611                end if;
6612
6613                --  Check the static matching rule of 3.10.2(27). The
6614                --  nominal subtype of the prefix must statically
6615                --  match the designated type.
6616
6617                Nom_Subt := Etype (P);
6618
6619                if Is_Constr_Subt_For_U_Nominal (Nom_Subt) then
6620                   Nom_Subt := Etype (Nom_Subt);
6621                end if;
6622
6623                if Is_Tagged_Type (Designated_Type (Typ)) then
6624
6625                   --  If the attribute is in the context of an access
6626                   --  parameter, then the prefix is allowed to be of
6627                   --  the class-wide type (by AI-127).
6628
6629                   if Ekind (Typ) = E_Anonymous_Access_Type then
6630                      if not Covers (Designated_Type (Typ), Nom_Subt)
6631                        and then not Covers (Nom_Subt, Designated_Type (Typ))
6632                      then
6633                         declare
6634                            Desig : Entity_Id;
6635
6636                         begin
6637                            Desig := Designated_Type (Typ);
6638
6639                            if Is_Class_Wide_Type (Desig) then
6640                               Desig := Etype (Desig);
6641                            end if;
6642
6643                            if Is_Anonymous_Tagged_Base (Nom_Subt, Desig) then
6644                               null;
6645
6646                            else
6647                               Error_Msg_NE
6648                                 ("type of prefix: & not compatible",
6649                                   P, Nom_Subt);
6650                               Error_Msg_NE
6651                                 ("\with &, the expected designated type",
6652                                   P, Designated_Type (Typ));
6653                            end if;
6654                         end;
6655                      end if;
6656
6657                   elsif not Covers (Designated_Type (Typ), Nom_Subt)
6658                     or else
6659                       (not Is_Class_Wide_Type (Designated_Type (Typ))
6660                         and then Is_Class_Wide_Type (Nom_Subt))
6661                   then
6662                      Error_Msg_NE
6663                        ("type of prefix: & is not covered", P, Nom_Subt);
6664                      Error_Msg_NE
6665                        ("\by &, the expected designated type" &
6666                            " ('R'M 3.10.2 (27))", P, Designated_Type (Typ));
6667                   end if;
6668
6669                   if Is_Class_Wide_Type (Designated_Type (Typ))
6670                     and then Has_Discriminants (Etype (Designated_Type (Typ)))
6671                     and then Is_Constrained (Etype (Designated_Type (Typ)))
6672                     and then Designated_Type (Typ) /= Nom_Subt
6673                   then
6674                      Apply_Discriminant_Check
6675                        (N, Etype (Designated_Type (Typ)));
6676                   end if;
6677
6678                elsif not Subtypes_Statically_Match
6679                            (Designated_Type (Base_Type (Typ)), Nom_Subt)
6680                  and then
6681                    not (Has_Discriminants (Designated_Type (Typ))
6682                           and then
6683                             not Is_Constrained
6684                                   (Designated_Type (Base_Type (Typ))))
6685                then
6686                   Error_Msg_N
6687                     ("object subtype must statically match "
6688                      & "designated subtype", P);
6689
6690                   if Is_Entity_Name (P)
6691                     and then Is_Array_Type (Designated_Type (Typ))
6692                   then
6693
6694                      declare
6695                         D : constant Node_Id := Declaration_Node (Entity (P));
6696
6697                      begin
6698                         Error_Msg_N ("aliased object has explicit bounds?",
6699                           D);
6700                         Error_Msg_N ("\declare without bounds"
6701                           & " (and with explicit initialization)?", D);
6702                         Error_Msg_N ("\for use with unconstrained access?", D);
6703                      end;
6704                   end if;
6705                end if;
6706
6707                --  Check the static accessibility rule of 3.10.2(28).
6708                --  Note that this check is not performed for the
6709                --  case of an anonymous access type, since the access
6710                --  attribute is always legal in such a context.
6711
6712                if Attr_Id /= Attribute_Unchecked_Access
6713                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
6714                  and then Ekind (Btyp) = E_General_Access_Type
6715                then
6716                   --  In an instance, this is a runtime check, but one we
6717                   --  know will fail, so generate an appropriate warning.
6718
6719                   if In_Instance_Body then
6720                      Error_Msg_N
6721                        ("?non-local pointer cannot point to local object", P);
6722                      Error_Msg_N
6723                        ("?Program_Error will be raised at run time", P);
6724                      Rewrite (N,
6725                        Make_Raise_Program_Error (Loc,
6726                          Reason => PE_Accessibility_Check_Failed));
6727                      Set_Etype (N, Typ);
6728                      return;
6729
6730                   else
6731                      Error_Msg_N
6732                        ("non-local pointer cannot point to local object", P);
6733
6734                      if Is_Record_Type (Current_Scope)
6735                        and then (Nkind (Parent (N)) =
6736                                   N_Discriminant_Association
6737                                    or else
6738                                  Nkind (Parent (N)) =
6739                                    N_Index_Or_Discriminant_Constraint)
6740                      then
6741                         declare
6742                            Indic : Node_Id := Parent (Parent (N));
6743
6744                         begin
6745                            while Present (Indic)
6746                              and then Nkind (Indic) /= N_Subtype_Indication
6747                            loop
6748                               Indic := Parent (Indic);
6749                            end loop;
6750
6751                            if Present (Indic) then
6752                               Error_Msg_NE
6753                                 ("\use an access definition for" &
6754                                   " the access discriminant of&", N,
6755                                   Entity (Subtype_Mark (Indic)));
6756                            end if;
6757                         end;
6758                      end if;
6759                   end if;
6760                end if;
6761             end if;
6762
6763             if Ekind (Btyp) = E_Access_Protected_Subprogram_Type
6764               and then Is_Entity_Name (P)
6765               and then not Is_Protected_Type (Scope (Entity (P)))
6766             then
6767                Error_Msg_N ("context requires a protected subprogram", P);
6768
6769             elsif Ekind (Btyp) = E_Access_Subprogram_Type
6770               and then Ekind (Etype (N)) = E_Access_Protected_Subprogram_Type
6771             then
6772                Error_Msg_N ("context requires a non-protected subprogram", P);
6773             end if;
6774
6775             --  The context cannot be a pool-specific type, but this is a
6776             --  legality rule, not a resolution rule, so it must be checked
6777             --  separately, after possibly disambiguation (see AI-245).
6778
6779             if Ekind (Btyp) = E_Access_Type
6780               and then Attr_Id /= Attribute_Unrestricted_Access
6781             then
6782                Wrong_Type (N, Typ);
6783             end if;
6784
6785             Set_Etype (N, Typ);
6786
6787             --  Check for incorrect atomic/volatile reference (RM C.6(12))
6788
6789             if Attr_Id /= Attribute_Unrestricted_Access then
6790                if Is_Atomic_Object (P)
6791                  and then not Is_Atomic (Designated_Type (Typ))
6792                then
6793                   Error_Msg_N
6794                     ("access to atomic object cannot yield access-to-" &
6795                      "non-atomic type", P);
6796
6797                elsif Is_Volatile_Object (P)
6798                  and then not Is_Volatile (Designated_Type (Typ))
6799                then
6800                   Error_Msg_N
6801                     ("access to volatile object cannot yield access-to-" &
6802                      "non-volatile type", P);
6803                end if;
6804             end if;
6805
6806          -------------
6807          -- Address --
6808          -------------
6809
6810          --  Deal with resolving the type for Address attribute, overloading
6811          --  is not permitted here, since there is no context to resolve it.
6812
6813          when Attribute_Address | Attribute_Code_Address =>
6814
6815             --  To be safe, assume that if the address of a variable is taken,
6816             --  it may be modified via this address, so note modification.
6817
6818             if Is_Variable (P) then
6819                Note_Possible_Modification (P);
6820             end if;
6821
6822             if Nkind (P) in  N_Subexpr
6823               and then Is_Overloaded (P)
6824             then
6825                Get_First_Interp (P, Index, It);
6826                Get_Next_Interp (Index, It);
6827
6828                if Present (It.Nam) then
6829                   Error_Msg_Name_1 := Aname;
6830                   Error_Msg_N
6831                     ("prefix of % attribute cannot be overloaded", N);
6832                   return;
6833                end if;
6834             end if;
6835
6836             if not Is_Entity_Name (P)
6837                or else not Is_Overloadable (Entity (P))
6838             then
6839                if not Is_Task_Type (Etype (P))
6840                  or else Nkind (P) = N_Explicit_Dereference
6841                then
6842                   Resolve (P);
6843                end if;
6844             end if;
6845
6846             --  If this is the name of a derived subprogram, or that of a
6847             --  generic actual, the address is that of the original entity.
6848
6849             if Is_Entity_Name (P)
6850               and then Is_Overloadable (Entity (P))
6851               and then Present (Alias (Entity (P)))
6852             then
6853                Rewrite (P,
6854                  New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6855             end if;
6856
6857          ---------------
6858          -- AST_Entry --
6859          ---------------
6860
6861          --  Prefix of the AST_Entry attribute is an entry name which must
6862          --  not be resolved, since this is definitely not an entry call.
6863
6864          when Attribute_AST_Entry =>
6865             null;
6866
6867          ------------------
6868          -- Body_Version --
6869          ------------------
6870
6871          --  Prefix of Body_Version attribute can be a subprogram name which
6872          --  must not be resolved, since this is not a call.
6873
6874          when Attribute_Body_Version =>
6875             null;
6876
6877          ------------
6878          -- Caller --
6879          ------------
6880
6881          --  Prefix of Caller attribute is an entry name which must not
6882          --  be resolved, since this is definitely not an entry call.
6883
6884          when Attribute_Caller =>
6885             null;
6886
6887          ------------------
6888          -- Code_Address --
6889          ------------------
6890
6891          --  Shares processing with Address attribute
6892
6893          -----------
6894          -- Count --
6895          -----------
6896
6897          --  If the prefix of the Count attribute is an entry name it must not
6898          --  be resolved, since this is definitely not an entry call. However,
6899          --  if it is an element of an entry family, the index itself may
6900          --  have to be resolved because it can be a general expression.
6901
6902          when Attribute_Count =>
6903             if Nkind (P) = N_Indexed_Component
6904               and then Is_Entity_Name (Prefix (P))
6905             then
6906                declare
6907                   Indx : constant Node_Id   := First (Expressions (P));
6908                   Fam  : constant Entity_Id := Entity (Prefix (P));
6909                begin
6910                   Resolve (Indx, Entry_Index_Type (Fam));
6911                   Apply_Range_Check (Indx, Entry_Index_Type (Fam));
6912                end;
6913             end if;
6914
6915          ----------------
6916          -- Elaborated --
6917          ----------------
6918
6919          --  Prefix of the Elaborated attribute is a subprogram name which
6920          --  must not be resolved, since this is definitely not a call. Note
6921          --  that it is a library unit, so it cannot be overloaded here.
6922
6923          when Attribute_Elaborated =>
6924             null;
6925
6926          --------------------
6927          -- Mechanism_Code --
6928          --------------------
6929
6930          --  Prefix of the Mechanism_Code attribute is a function name
6931          --  which must not be resolved. Should we check for overloaded ???
6932
6933          when Attribute_Mechanism_Code =>
6934             null;
6935
6936          ------------------
6937          -- Partition_ID --
6938          ------------------
6939
6940          --  Most processing is done in sem_dist, after determining the
6941          --  context type. Node is rewritten as a conversion to a runtime call.
6942
6943          when Attribute_Partition_ID =>
6944             Process_Partition_Id (N);
6945             return;
6946
6947          when Attribute_Pool_Address =>
6948             Resolve (P);
6949
6950          -----------
6951          -- Range --
6952          -----------
6953
6954          --  We replace the Range attribute node with a range expression
6955          --  whose bounds are the 'First and 'Last attributes applied to the
6956          --  same prefix. The reason that we do this transformation here
6957          --  instead of in the expander is that it simplifies other parts of
6958          --  the semantic analysis which assume that the Range has been
6959          --  replaced; thus it must be done even when in semantic-only mode
6960          --  (note that the RM specifically mentions this equivalence, we
6961          --  take care that the prefix is only evaluated once).
6962
6963          when Attribute_Range => Range_Attribute :
6964             declare
6965                LB   : Node_Id;
6966                HB   : Node_Id;
6967
6968                function Check_Discriminated_Prival
6969                  (N    : Node_Id)
6970                   return Node_Id;
6971                --  The range of a private component constrained by a
6972                --  discriminant is rewritten to make the discriminant
6973                --  explicit. This solves some complex visibility problems
6974                --  related to the use of privals.
6975
6976                --------------------------------
6977                -- Check_Discriminated_Prival --
6978                --------------------------------
6979
6980                function Check_Discriminated_Prival
6981                  (N    : Node_Id)
6982                   return Node_Id
6983                is
6984                begin
6985                   if Is_Entity_Name (N)
6986                     and then Ekind (Entity (N)) = E_In_Parameter
6987                     and then not Within_Init_Proc
6988                   then
6989                      return Make_Identifier (Sloc (N), Chars (Entity (N)));
6990                   else
6991                      return Duplicate_Subexpr (N);
6992                   end if;
6993                end Check_Discriminated_Prival;
6994
6995             --  Start of processing for Range_Attribute
6996
6997             begin
6998                if not Is_Entity_Name (P)
6999                  or else not Is_Type (Entity (P))
7000                then
7001                   Resolve (P);
7002                end if;
7003
7004                --  Check whether prefix is (renaming of) private component
7005                --  of protected type.
7006
7007                if Is_Entity_Name (P)
7008                  and then Comes_From_Source (N)
7009                  and then Is_Array_Type (Etype (P))
7010                  and then Number_Dimensions (Etype (P)) = 1
7011                  and then (Ekind (Scope (Entity (P))) = E_Protected_Type
7012                             or else
7013                            Ekind (Scope (Scope (Entity (P)))) =
7014                                                         E_Protected_Type)
7015                then
7016                   LB :=
7017                     Check_Discriminated_Prival
7018                       (Type_Low_Bound (Etype (First_Index (Etype (P)))));
7019
7020                   HB :=
7021                     Check_Discriminated_Prival
7022                       (Type_High_Bound (Etype (First_Index (Etype (P)))));
7023
7024                else
7025                   HB :=
7026                     Make_Attribute_Reference (Loc,
7027                       Prefix         => Duplicate_Subexpr (P),
7028                       Attribute_Name => Name_Last,
7029                       Expressions    => Expressions (N));
7030
7031                   LB :=
7032                     Make_Attribute_Reference (Loc,
7033                       Prefix         => P,
7034                       Attribute_Name => Name_First,
7035                       Expressions    => Expressions (N));
7036                end if;
7037
7038                --  If the original was marked as Must_Not_Freeze (see code
7039                --  in Sem_Ch3.Make_Index), then make sure the rewriting
7040                --  does not freeze either.
7041
7042                if Must_Not_Freeze (N) then
7043                   Set_Must_Not_Freeze (HB);
7044                   Set_Must_Not_Freeze (LB);
7045                   Set_Must_Not_Freeze (Prefix (HB));
7046                   Set_Must_Not_Freeze (Prefix (LB));
7047                end if;
7048
7049                if Raises_Constraint_Error (Prefix (N)) then
7050
7051                   --  Preserve Sloc of prefix in the new bounds, so that
7052                   --  the posted warning can be removed if we are within
7053                   --  unreachable code.
7054
7055                   Set_Sloc (LB, Sloc (Prefix (N)));
7056                   Set_Sloc (HB, Sloc (Prefix (N)));
7057                end if;
7058
7059                Rewrite (N, Make_Range (Loc, LB, HB));
7060                Analyze_And_Resolve (N, Typ);
7061
7062                --  Normally after resolving attribute nodes, Eval_Attribute
7063                --  is called to do any possible static evaluation of the node.
7064                --  However, here since the Range attribute has just been
7065                --  transformed into a range expression it is no longer an
7066                --  attribute node and therefore the call needs to be avoided
7067                --  and is accomplished by simply returning from the procedure.
7068
7069                return;
7070             end Range_Attribute;
7071
7072          -----------------
7073          -- UET_Address --
7074          -----------------
7075
7076          --  Prefix must not be resolved in this case, since it is not a
7077          --  real entity reference. No action of any kind is require!
7078
7079          when Attribute_UET_Address =>
7080             return;
7081
7082          ----------------------
7083          -- Unchecked_Access --
7084          ----------------------
7085
7086          --  Processing is shared with Access
7087
7088          -------------------------
7089          -- Unrestricted_Access --
7090          -------------------------
7091
7092          --  Processing is shared with Access
7093
7094          ---------
7095          -- Val --
7096          ---------
7097
7098          --  Apply range check. Note that we did not do this during the
7099          --  analysis phase, since we wanted Eval_Attribute to have a
7100          --  chance at finding an illegal out of range value.
7101
7102          when Attribute_Val =>
7103
7104             --  Note that we do our own Eval_Attribute call here rather than
7105             --  use the common one, because we need to do processing after
7106             --  the call, as per above comment.
7107
7108             Eval_Attribute (N);
7109
7110             --  Eval_Attribute may replace the node with a raise CE, or
7111             --  fold it to a constant. Obviously we only apply a scalar
7112             --  range check if this did not happen!
7113
7114             if Nkind (N) = N_Attribute_Reference
7115               and then Attribute_Name (N) = Name_Val
7116             then
7117                Apply_Scalar_Range_Check (First (Expressions (N)), Btyp);
7118             end if;
7119
7120             return;
7121
7122          -------------
7123          -- Version --
7124          -------------
7125
7126          --  Prefix of Version attribute can be a subprogram name which
7127          --  must not be resolved, since this is not a call.
7128
7129          when Attribute_Version =>
7130             null;
7131
7132          ----------------------
7133          -- Other Attributes --
7134          ----------------------
7135
7136          --  For other attributes, resolve prefix unless it is a type. If
7137          --  the attribute reference itself is a type name ('Base and 'Class)
7138          --  then this is only legal within a task or protected record.
7139
7140          when others =>
7141             if not Is_Entity_Name (P)
7142               or else not Is_Type (Entity (P))
7143             then
7144                Resolve (P);
7145             end if;
7146
7147             --  If the attribute reference itself is a type name ('Base,
7148             --  'Class) then this is only legal within a task or protected
7149             --  record. What is this all about ???
7150
7151             if Is_Entity_Name (N)
7152               and then Is_Type (Entity (N))
7153             then
7154                if Is_Concurrent_Type (Entity (N))
7155                  and then In_Open_Scopes (Entity (P))
7156                then
7157                   null;
7158                else
7159                   Error_Msg_N
7160                     ("invalid use of subtype name in expression or call", N);
7161                end if;
7162             end if;
7163
7164             --  For attributes whose argument may be a string, complete
7165             --  resolution of argument now. This avoids premature expansion
7166             --  (and the creation of transient scopes) before the attribute
7167             --  reference is resolved.
7168
7169             case Attr_Id is
7170                when Attribute_Value =>
7171                   Resolve (First (Expressions (N)), Standard_String);
7172
7173                when Attribute_Wide_Value =>
7174                   Resolve (First (Expressions (N)), Standard_Wide_String);
7175
7176                when others => null;
7177             end case;
7178       end case;
7179
7180       --  Normally the Freezing is done by Resolve but sometimes the Prefix
7181       --  is not resolved, in which case the freezing must be done now.
7182
7183       Freeze_Expression (P);
7184
7185       --  Finally perform static evaluation on the attribute reference
7186
7187       Eval_Attribute (N);
7188
7189    end Resolve_Attribute;
7190
7191 end Sem_Attr;