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) 1992-2005 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,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, 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_Util; use Exp_Util;
  35 with Expander; use Expander;
  36 with Freeze;   use Freeze;
  37 with Lib;      use Lib;
  38 with Lib.Xref; use Lib.Xref;
  39 with Namet;    use Namet;
  40 with Nlists;   use Nlists;
  41 with Nmake;    use Nmake;
  42 with Opt;      use Opt;
  43 with Restrict; use Restrict;
  44 with Rident;   use Rident;
  45 with Rtsfind;  use Rtsfind;
  46 with Sdefault; use Sdefault;
  47 with Sem;      use Sem;
  48 with Sem_Cat;  use Sem_Cat;
  49 with Sem_Ch6;  use Sem_Ch6;
  50 with Sem_Ch8;  use Sem_Ch8;
  51 with Sem_Dist; use Sem_Dist;
  52 with Sem_Eval; use Sem_Eval;
  53 with Sem_Res;  use Sem_Res;
  54 with Sem_Type; use Sem_Type;
  55 with Sem_Util; use Sem_Util;
  56 with Stand;    use Stand;
  57 with Sinfo;    use Sinfo;
  58 with Sinput;   use Sinput;
  59 with Stand;
  60 with Stringt;  use Stringt;
  61 with Targparm; use Targparm;
  62 with Ttypes;   use Ttypes;
  63 with Ttypef;   use Ttypef;
  64 with Tbuild;   use Tbuild;
  65 with Uintp;    use Uintp;
  66 with Urealp;   use Urealp;
  67
  68 package body Sem_Attr is
  69
  70    True_Value  : constant Uint := Uint_1;
  71    False_Value : constant Uint := Uint_0;
  72    --  Synonyms to be used when these constants are used as Boolean values
  73
  74    Bad_Attribute : exception;
  75    --  Exception raised if an error is detected during attribute processing,
  76    --  used so that we can abandon the processing so we don't run into
  77    --  trouble with cascaded errors.
  78
  79    --  The following array is the list of attributes defined in the Ada 83 RM
  80
  81    Attribute_83 : constant Attribute_Class_Array := Attribute_Class_Array'(
  82       Attribute_Address           |
  83       Attribute_Aft               |
  84       Attribute_Alignment         |
  85       Attribute_Base              |
  86       Attribute_Callable          |
  87       Attribute_Constrained       |
  88       Attribute_Count             |
  89       Attribute_Delta             |
  90       Attribute_Digits            |
  91       Attribute_Emax              |
  92       Attribute_Epsilon           |
  93       Attribute_First             |
  94       Attribute_First_Bit         |
  95       Attribute_Fore              |
  96       Attribute_Image             |
  97       Attribute_Large             |
  98       Attribute_Last              |
  99       Attribute_Last_Bit          |
 100       Attribute_Leading_Part      |
 101       Attribute_Length            |
 102       Attribute_Machine_Emax      |
 103       Attribute_Machine_Emin      |
 104       Attribute_Machine_Mantissa  |
 105       Attribute_Machine_Overflows |
 106       Attribute_Machine_Radix     |
 107       Attribute_Machine_Rounds    |
 108       Attribute_Mantissa          |
 109       Attribute_Pos               |
 110       Attribute_Position          |
 111       Attribute_Pred              |
 112       Attribute_Range             |
 113       Attribute_Safe_Emax         |
 114       Attribute_Safe_Large        |
 115       Attribute_Safe_Small        |
 116       Attribute_Size              |
 117       Attribute_Small             |
 118       Attribute_Storage_Size      |
 119       Attribute_Succ              |
 120       Attribute_Terminated        |
 121       Attribute_Val               |
 122       Attribute_Value             |
 123       Attribute_Width             => True,
 124       others                      => False);
 125
 126    -----------------------
 127    -- Local_Subprograms --
 128    -----------------------
 129
 130    procedure Eval_Attribute (N : Node_Id);
 131    --  Performs compile time evaluation of attributes where possible, leaving
 132    --  the Is_Static_Expression/Raises_Constraint_Error flags appropriately
 133    --  set, and replacing the node with a literal node if the value can be
 134    --  computed at compile time. All static attribute references are folded,
 135    --  as well as a number of cases of non-static attributes that can always
 136    --  be computed at compile time (e.g. floating-point model attributes that
 137    --  are applied to non-static subtypes). Of course in such cases, the
 138    --  Is_Static_Expression flag will not be set on the resulting literal.
 139    --  Note that the only required action of this procedure is to catch the
 140    --  static expression cases as described in the RM. Folding of other cases
 141    --  is done where convenient, but some additional non-static folding is in
 142    --  N_Expand_Attribute_Reference in cases where this is more convenient.
 143
 144    function Is_Anonymous_Tagged_Base
 145      (Anon : Entity_Id;
 146       Typ  : Entity_Id)
 147       return Boolean;
 148    --  For derived tagged types that constrain parent discriminants we build
 149    --  an anonymous unconstrained base type. We need to recognize the relation
 150    --  between the two when analyzing an access attribute for a constrained
 151    --  component, before the full declaration for Typ has been analyzed, and
 152    --  where therefore the prefix of the attribute does not match the enclosing
 153    --  scope.
 154
 155    -----------------------
 156    -- Analyze_Attribute --
 157    -----------------------
 158
 159    procedure Analyze_Attribute (N : Node_Id) is
 160       Loc     : constant Source_Ptr   := Sloc (N);
 161       Aname   : constant Name_Id      := Attribute_Name (N);
 162       P       : constant Node_Id      := Prefix (N);
 163       Exprs   : constant List_Id      := Expressions (N);
 164       Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname);
 165       E1      : Node_Id;
 166       E2      : Node_Id;
 167
 168       P_Type : Entity_Id;
 169       --  Type of prefix after analysis
 170
 171       P_Base_Type : Entity_Id;
 172       --  Base type of prefix after analysis
 173
 174       -----------------------
 175       -- Local Subprograms --
 176       -----------------------
 177
 178       procedure Analyze_Access_Attribute;
 179       --  Used for Access, Unchecked_Access, Unrestricted_Access attributes.
 180       --  Internally, Id distinguishes which of the three cases is involved.
 181
 182       procedure Check_Array_Or_Scalar_Type;
 183       --  Common procedure used by First, Last, Range attribute to check
 184       --  that the prefix is a constrained array or scalar type, or a name
 185       --  of an array object, and that an argument appears only if appropriate
 186       --  (i.e. only in the array case).
 187
 188       procedure Check_Array_Type;
 189       --  Common semantic checks for all array attributes. Checks that the
 190       --  prefix is a constrained array type or the name of an array object.
 191       --  The error message for non-arrays is specialized appropriately.
 192
 193       procedure Check_Asm_Attribute;
 194       --  Common semantic checks for Asm_Input and Asm_Output attributes
 195
 196       procedure Check_Component;
 197       --  Common processing for Bit_Position, First_Bit, Last_Bit, and
 198       --  Position. Checks prefix is an appropriate selected component.
 199
 200       procedure Check_Decimal_Fixed_Point_Type;
 201       --  Check that prefix of attribute N is a decimal fixed-point type
 202
 203       procedure Check_Dereference;
 204       --  If the prefix of attribute is an object of an access type, then
 205       --  introduce an explicit deference, and adjust P_Type accordingly.
 206
 207       procedure Check_Discrete_Type;
 208       --  Verify that prefix of attribute N is a discrete type
 209
 210       procedure Check_E0;
 211       --  Check that no attribute arguments are present
 212
 213       procedure Check_Either_E0_Or_E1;
 214       --  Check that there are zero or one attribute arguments present
 215
 216       procedure Check_E1;
 217       --  Check that exactly one attribute argument is present
 218
 219       procedure Check_E2;
 220       --  Check that two attribute arguments are present
 221
 222       procedure Check_Enum_Image;
 223       --  If the prefix type is an enumeration type, set all its literals
 224       --  as referenced, since the image function could possibly end up
 225       --  referencing any of the literals indirectly.
 226
 227       procedure Check_Fixed_Point_Type;
 228       --  Verify that prefix of attribute N is a fixed type
 229
 230       procedure Check_Fixed_Point_Type_0;
 231       --  Verify that prefix of attribute N is a fixed type and that
 232       --  no attribute expressions are present
 233
 234       procedure Check_Floating_Point_Type;
 235       --  Verify that prefix of attribute N is a float type
 236
 237       procedure Check_Floating_Point_Type_0;
 238       --  Verify that prefix of attribute N is a float type and that
 239       --  no attribute expressions are present
 240
 241       procedure Check_Floating_Point_Type_1;
 242       --  Verify that prefix of attribute N is a float type and that
 243       --  exactly one attribute expression is present
 244
 245       procedure Check_Floating_Point_Type_2;
 246       --  Verify that prefix of attribute N is a float type and that
 247       --  two attribute expressions are present
 248
 249       procedure Legal_Formal_Attribute;
 250       --  Common processing for attributes Definite, Has_Access_Values,
 251       --  and Has_Discriminants
 252
 253       procedure Check_Integer_Type;
 254       --  Verify that prefix of attribute N is an integer type
 255
 256       procedure Check_Library_Unit;
 257       --  Verify that prefix of attribute N is a library unit
 258
 259       procedure Check_Modular_Integer_Type;
 260       --  Verify that prefix of attribute N is a modular integer type
 261
 262       procedure Check_Not_Incomplete_Type;
 263       --  Check that P (the prefix of the attribute) is not an incomplete
 264       --  type or a private type for which no full view has been given.
 265
 266       procedure Check_Object_Reference (P : Node_Id);
 267       --  Check that P (the prefix of the attribute) is an object reference
 268
 269       procedure Check_Program_Unit;
 270       --  Verify that prefix of attribute N is a program unit
 271
 272       procedure Check_Real_Type;
 273       --  Verify that prefix of attribute N is fixed or float type
 274
 275       procedure Check_Scalar_Type;
 276       --  Verify that prefix of attribute N is a scalar type
 277
 278       procedure Check_Standard_Prefix;
 279       --  Verify that prefix of attribute N is package Standard
 280
 281       procedure Check_Stream_Attribute (Nam : TSS_Name_Type);
 282       --  Validity checking for stream attribute. Nam is the TSS name of the
 283       --  corresponding possible defined attribute function (e.g. for the
 284       --  Read attribute, Nam will be TSS_Stream_Read).
 285
 286       procedure Check_Task_Prefix;
 287       --  Verify that prefix of attribute N is a task or task type
 288
 289       procedure Check_Type;
 290       --  Verify that the prefix of attribute N is a type
 291
 292       procedure Check_Unit_Name (Nod : Node_Id);
 293       --  Check that Nod is of the form of a library unit name, i.e that
 294       --  it is an identifier, or a selected component whose prefix is
 295       --  itself of the form of a library unit name. Note that this is
 296       --  quite different from Check_Program_Unit, since it only checks
 297       --  the syntactic form of the name, not the semantic identity. This
 298       --  is because it is used with attributes (Elab_Body, Elab_Spec, and
 299       --  UET_Address) which can refer to non-visible unit.
 300
 301       procedure Error_Attr (Msg : String; Error_Node : Node_Id);
 302       pragma No_Return (Error_Attr);
 303       procedure Error_Attr;
 304       pragma No_Return (Error_Attr);
 305       --  Posts error using Error_Msg_N at given node, sets type of attribute
 306       --  node to Any_Type, and then raises Bad_Attribute to avoid any further
 307       --  semantic processing. The message typically contains a % insertion
 308       --  character which is replaced by the attribute name. The call with
 309       --  no arguments is used when the caller has already generated the
 310       --  required error messages.
 311
 312       procedure Standard_Attribute (Val : Int);
 313       --  Used to process attributes whose prefix is package Standard which
 314       --  yield values of type Universal_Integer. The attribute reference
 315       --  node is rewritten with an integer literal of the given value.
 316
 317       procedure Unexpected_Argument (En : Node_Id);
 318       --  Signal unexpected attribute argument (En is the argument)
 319
 320       procedure Validate_Non_Static_Attribute_Function_Call;
 321       --  Called when processing an attribute that is a function call to a
 322       --  non-static function, i.e. an attribute function that either takes
 323       --  non-scalar arguments or returns a non-scalar result. Verifies that
 324       --  such a call does not appear in a preelaborable context.
 325
 326       ------------------------------
 327       -- Analyze_Access_Attribute --
 328       ------------------------------
 329
 330       procedure Analyze_Access_Attribute is
 331          Acc_Type : Entity_Id;
 332
 333          Scop : Entity_Id;
 334          Typ  : Entity_Id;
 335
 336          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id;
 337          --  Build an access-to-object type whose designated type is DT,
 338          --  and whose Ekind is appropriate to the attribute type. The
 339          --  type that is constructed is returned as the result.
 340
 341          procedure Build_Access_Subprogram_Type (P : Node_Id);
 342          --  Build an access to subprogram whose designated type is
 343          --  the type of the prefix. If prefix is overloaded, so it the
 344          --  node itself. The result is stored in Acc_Type.
 345
 346          ------------------------------
 347          -- Build_Access_Object_Type --
 348          ------------------------------
 349
 350          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id is
 351             Typ : Entity_Id;
 352
 353          begin
 354             if Aname = Name_Unrestricted_Access then
 355                Typ :=
 356                  New_Internal_Entity
 357                    (E_Allocator_Type, Current_Scope, Loc, 'A');
 358             else
 359                Typ :=
 360                  New_Internal_Entity
 361                    (E_Access_Attribute_Type, Current_Scope, Loc, 'A');
 362             end if;
 363
 364             Set_Etype                     (Typ, Typ);
 365             Init_Size_Align               (Typ);
 366             Set_Is_Itype                  (Typ);
 367             Set_Associated_Node_For_Itype (Typ, N);
 368             Set_Directly_Designated_Type  (Typ, DT);
 369             return Typ;
 370          end Build_Access_Object_Type;
 371
 372          ----------------------------------
 373          -- Build_Access_Subprogram_Type --
 374          ----------------------------------
 375
 376          procedure Build_Access_Subprogram_Type (P : Node_Id) is
 377             Index : Interp_Index;
 378             It    : Interp;
 379
 380             function Get_Kind (E : Entity_Id) return Entity_Kind;
 381             --  Distinguish between access to regular/protected subprograms
 382
 383             --------------
 384             -- Get_Kind --
 385             --------------
 386
 387             function Get_Kind (E : Entity_Id) return Entity_Kind is
 388             begin
 389                if Convention (E) = Convention_Protected then
 390                   return E_Access_Protected_Subprogram_Type;
 391                else
 392                   return E_Access_Subprogram_Type;
 393                end if;
 394             end Get_Kind;
 395
 396          --  Start of processing for Build_Access_Subprogram_Type
 397
 398          begin
 399             --  In the case of an access to subprogram, use the name of the
 400             --  subprogram itself as the designated type. Type-checking in
 401             --  this case compares the signatures of the designated types.
 402
 403             Set_Etype (N, Any_Type);
 404
 405             if not Is_Overloaded (P) then
 406                if not Is_Intrinsic_Subprogram (Entity (P)) then
 407                   Acc_Type :=
 408                     New_Internal_Entity
 409                       (Get_Kind (Entity (P)), Current_Scope, Loc, 'A');
 410                   Set_Etype (Acc_Type, Acc_Type);
 411                   Set_Directly_Designated_Type (Acc_Type, Entity (P));
 412                   Set_Etype (N, Acc_Type);
 413                end if;
 414
 415             else
 416                Get_First_Interp (P, Index, It);
 417                while Present (It.Nam) loop
 418                   if not Is_Intrinsic_Subprogram (It.Nam) then
 419                      Acc_Type :=
 420                        New_Internal_Entity
 421                          (Get_Kind (It.Nam), Current_Scope, Loc, 'A');
 422                      Set_Etype (Acc_Type, Acc_Type);
 423                      Set_Directly_Designated_Type (Acc_Type, It.Nam);
 424                      Add_One_Interp (N, Acc_Type, Acc_Type);
 425                   end if;
 426
 427                   Get_Next_Interp (Index, It);
 428                end loop;
 429             end if;
 430
 431             if Etype (N) = Any_Type then
 432                Error_Attr ("prefix of % attribute cannot be intrinsic", P);
 433             end if;
 434          end Build_Access_Subprogram_Type;
 435
 436       --  Start of processing for Analyze_Access_Attribute
 437
 438       begin
 439          Check_E0;
 440
 441          if Nkind (P) = N_Character_Literal then
 442             Error_Attr
 443               ("prefix of % attribute cannot be enumeration literal", P);
 444          end if;
 445
 446          --  Case of access to subprogram
 447
 448          if Is_Entity_Name (P)
 449            and then Is_Overloadable (Entity (P))
 450          then
 451             --  Not allowed for nested subprograms if No_Implicit_Dynamic_Code
 452             --  restriction set (since in general a trampoline is required).
 453
 454             if not Is_Library_Level_Entity (Entity (P)) then
 455                Check_Restriction (No_Implicit_Dynamic_Code, P);
 456             end if;
 457
 458             if Is_Always_Inlined (Entity (P)) then
 459                Error_Attr
 460                  ("prefix of % attribute cannot be Inline_Always subprogram",
 461                   P);
 462             end if;
 463
 464             --  Build the appropriate subprogram type
 465
 466             Build_Access_Subprogram_Type (P);
 467
 468             --  For unrestricted access, kill current values, since this
 469             --  attribute allows a reference to a local subprogram that
 470             --  could modify local variables to be passed out of scope
 471
 472             if Aname = Name_Unrestricted_Access then
 473                Kill_Current_Values;
 474             end if;
 475
 476             return;
 477
 478          --  Component is an operation of a protected type
 479
 480          elsif Nkind (P) = N_Selected_Component
 481            and then Is_Overloadable (Entity (Selector_Name (P)))
 482          then
 483             if Ekind (Entity (Selector_Name (P))) = E_Entry then
 484                Error_Attr ("prefix of % attribute must be subprogram", P);
 485             end if;
 486
 487             Build_Access_Subprogram_Type (Selector_Name (P));
 488             return;
 489          end if;
 490
 491          --  Deal with incorrect reference to a type, but note that some
 492          --  accesses are allowed (references to the current type instance).
 493
 494          if Is_Entity_Name (P) then
 495             Scop := Current_Scope;
 496             Typ := Entity (P);
 497
 498             if Is_Type (Typ) then
 499
 500                --  OK if we are within the scope of a limited type
 501                --  let's mark the component as having per object constraint
 502
 503                if Is_Anonymous_Tagged_Base (Scop, Typ) then
 504                   Typ := Scop;
 505                   Set_Entity (P, Typ);
 506                   Set_Etype  (P, Typ);
 507                end if;
 508
 509                if Typ = Scop then
 510                   declare
 511                      Q : Node_Id := Parent (N);
 512
 513                   begin
 514                      while Present (Q)
 515                        and then Nkind (Q) /= N_Component_Declaration
 516                      loop
 517                         Q := Parent (Q);
 518                      end loop;
 519                      if Present (Q) then
 520                         Set_Has_Per_Object_Constraint (
 521                           Defining_Identifier (Q), True);
 522                      end if;
 523                   end;
 524
 525                   if Nkind (P) = N_Expanded_Name then
 526                      Error_Msg_N
 527                        ("current instance prefix must be a direct name", P);
 528                   end if;
 529
 530                   --  If a current instance attribute appears within a
 531                   --  a component constraint it must appear alone; other
 532                   --  contexts (default expressions, within a task body)
 533                   --  are not subject to this restriction.
 534
 535                   if not In_Default_Expression
 536                     and then not Has_Completion (Scop)
 537                     and then
 538                       Nkind (Parent (N)) /= N_Discriminant_Association
 539                     and then
 540                       Nkind (Parent (N)) /= N_Index_Or_Discriminant_Constraint
 541                   then
 542                      Error_Msg_N
 543                        ("current instance attribute must appear alone", N);
 544                   end if;
 545
 546                --  OK if we are in initialization procedure for the type
 547                --  in question, in which case the reference to the type
 548                --  is rewritten as a reference to the current object.
 549
 550                elsif Ekind (Scop) = E_Procedure
 551                  and then Is_Init_Proc (Scop)
 552                  and then Etype (First_Formal (Scop)) = Typ
 553                then
 554                   Rewrite (N,
 555                     Make_Attribute_Reference (Loc,
 556                       Prefix         => Make_Identifier (Loc, Name_uInit),
 557                       Attribute_Name => Name_Unrestricted_Access));
 558                   Analyze (N);
 559                   return;
 560
 561                --  OK if a task type, this test needs sharpening up ???
 562
 563                elsif Is_Task_Type (Typ) then
 564                   null;
 565
 566                --  Otherwise we have an error case
 567
 568                else
 569                   Error_Attr ("% attribute cannot be applied to type", P);
 570                   return;
 571                end if;
 572             end if;
 573          end if;
 574
 575          --  If we fall through, we have a normal access to object case.
 576          --  Unrestricted_Access is legal wherever an allocator would be
 577          --  legal, so its Etype is set to E_Allocator. The expected type
 578          --  of the other attributes is a general access type, and therefore
 579          --  we label them with E_Access_Attribute_Type.
 580
 581          if not Is_Overloaded (P) then
 582             Acc_Type := Build_Access_Object_Type (P_Type);
 583             Set_Etype (N, Acc_Type);
 584          else
 585             declare
 586                Index : Interp_Index;
 587                It    : Interp;
 588
 589             begin
 590                Set_Etype (N, Any_Type);
 591                Get_First_Interp (P, Index, It);
 592
 593                while Present (It.Typ) loop
 594                   Acc_Type := Build_Access_Object_Type (It.Typ);
 595                   Add_One_Interp (N, Acc_Type, Acc_Type);
 596                   Get_Next_Interp (Index, It);
 597                end loop;
 598             end;
 599          end if;
 600
 601          --  If we have an access to an object, and the attribute comes
 602          --  from source, then set the object as potentially source modified.
 603          --  We do this because the resulting access pointer can be used to
 604          --  modify the variable, and we might not detect this, leading to
 605          --  some junk warnings.
 606
 607          if Is_Entity_Name (P) then
 608             Set_Never_Set_In_Source (Entity (P), False);
 609          end if;
 610
 611          --  Check for aliased view unless unrestricted case. We allow
 612          --  a nonaliased prefix when within an instance because the
 613          --  prefix may have been a tagged formal object, which is
 614          --  defined to be aliased even when the actual might not be
 615          --  (other instance cases will have been caught in the generic).
 616          --  Similarly, within an inlined body we know that the attribute
 617          --  is legal in the original subprogram, and therefore legal in
 618          --  the expansion.
 619
 620          if Aname /= Name_Unrestricted_Access
 621            and then not Is_Aliased_View (P)
 622            and then not In_Instance
 623            and then not In_Inlined_Body
 624          then
 625             Error_Attr ("prefix of % attribute must be aliased", P);
 626          end if;
 627       end Analyze_Access_Attribute;
 628
 629       --------------------------------
 630       -- Check_Array_Or_Scalar_Type --
 631       --------------------------------
 632
 633       procedure Check_Array_Or_Scalar_Type is
 634          Index : Entity_Id;
 635
 636          D : Int;
 637          --  Dimension number for array attributes
 638
 639       begin
 640          --  Case of string literal or string literal subtype. These cases
 641          --  cannot arise from legal Ada code, but the expander is allowed
 642          --  to generate them. They require special handling because string
 643          --  literal subtypes do not have standard bounds (the whole idea
 644          --  of these subtypes is to avoid having to generate the bounds)
 645
 646          if Ekind (P_Type) = E_String_Literal_Subtype then
 647             Set_Etype (N, Etype (First_Index (P_Base_Type)));
 648             return;
 649
 650          --  Scalar types
 651
 652          elsif Is_Scalar_Type (P_Type) then
 653             Check_Type;
 654
 655             if Present (E1) then
 656                Error_Attr ("invalid argument in % attribute", E1);
 657             else
 658                Set_Etype (N, P_Base_Type);
 659                return;
 660             end if;
 661
 662          --  The following is a special test to allow 'First to apply to
 663          --  private scalar types if the attribute comes from generated
 664          --  code. This occurs in the case of Normalize_Scalars code.
 665
 666          elsif Is_Private_Type (P_Type)
 667            and then Present (Full_View (P_Type))
 668            and then Is_Scalar_Type (Full_View (P_Type))
 669            and then not Comes_From_Source (N)
 670          then
 671             Set_Etype (N, Implementation_Base_Type (P_Type));
 672
 673          --  Array types other than string literal subtypes handled above
 674
 675          else
 676             Check_Array_Type;
 677
 678             --  We know prefix is an array type, or the name of an array
 679             --  object, and that the expression, if present, is static
 680             --  and within the range of the dimensions of the type.
 681
 682             pragma Assert (Is_Array_Type (P_Type));
 683             Index := First_Index (P_Base_Type);
 684
 685             if No (E1) then
 686
 687                --  First dimension assumed
 688
 689                Set_Etype (N, Base_Type (Etype (Index)));
 690
 691             else
 692                D := UI_To_Int (Intval (E1));
 693
 694                for J in 1 .. D - 1 loop
 695                   Next_Index (Index);
 696                end loop;
 697
 698                Set_Etype (N, Base_Type (Etype (Index)));
 699                Set_Etype (E1, Standard_Integer);
 700             end if;
 701          end if;
 702       end Check_Array_Or_Scalar_Type;
 703
 704       ----------------------
 705       -- Check_Array_Type --
 706       ----------------------
 707
 708       procedure Check_Array_Type is
 709          D : Int;
 710          --  Dimension number for array attributes
 711
 712       begin
 713          --  If the type is a string literal type, then this must be generated
 714          --  internally, and no further check is required on its legality.
 715
 716          if Ekind (P_Type) = E_String_Literal_Subtype then
 717             return;
 718
 719          --  If the type is a composite, it is an illegal aggregate, no point
 720          --  in going on.
 721
 722          elsif P_Type = Any_Composite then
 723             raise Bad_Attribute;
 724          end if;
 725
 726          --  Normal case of array type or subtype
 727
 728          Check_Either_E0_Or_E1;
 729          Check_Dereference;
 730
 731          if Is_Array_Type (P_Type) then
 732             if not Is_Constrained (P_Type)
 733               and then Is_Entity_Name (P)
 734               and then Is_Type (Entity (P))
 735             then
 736                --  Note: we do not call Error_Attr here, since we prefer to
 737                --  continue, using the relevant index type of the array,
 738                --  even though it is unconstrained. This gives better error
 739                --  recovery behavior.
 740
 741                Error_Msg_Name_1 := Aname;
 742                Error_Msg_N
 743                  ("prefix for % attribute must be constrained array", P);
 744             end if;
 745
 746             D := Number_Dimensions (P_Type);
 747
 748          else
 749             if Is_Private_Type (P_Type) then
 750                Error_Attr
 751                  ("prefix for % attribute may not be private type", P);
 752
 753             elsif Is_Access_Type (P_Type)
 754               and then Is_Array_Type (Designated_Type (P_Type))
 755               and then Is_Entity_Name (P)
 756               and then Is_Type (Entity (P))
 757             then
 758                Error_Attr ("prefix of % attribute cannot be access type", P);
 759
 760             elsif Attr_Id = Attribute_First
 761                     or else
 762                   Attr_Id = Attribute_Last
 763             then
 764                Error_Attr ("invalid prefix for % attribute", P);
 765
 766             else
 767                Error_Attr ("prefix for % attribute must be array", P);
 768             end if;
 769          end if;
 770
 771          if Present (E1) then
 772             Resolve (E1, Any_Integer);
 773             Set_Etype (E1, Standard_Integer);
 774
 775             if not Is_Static_Expression (E1)
 776               or else Raises_Constraint_Error (E1)
 777             then
 778                Flag_Non_Static_Expr
 779                  ("expression for dimension must be static!", E1);
 780                Error_Attr;
 781
 782             elsif  UI_To_Int (Expr_Value (E1)) > D
 783               or else UI_To_Int (Expr_Value (E1)) < 1
 784             then
 785                Error_Attr ("invalid dimension number for array type", E1);
 786             end if;
 787          end if;
 788       end Check_Array_Type;
 789
 790       -------------------------
 791       -- Check_Asm_Attribute --
 792       -------------------------
 793
 794       procedure Check_Asm_Attribute is
 795       begin
 796          Check_Type;
 797          Check_E2;
 798
 799          --  Check first argument is static string expression
 800
 801          Analyze_And_Resolve (E1, Standard_String);
 802
 803          if Etype (E1) = Any_Type then
 804             return;
 805
 806          elsif not Is_OK_Static_Expression (E1) then
 807             Flag_Non_Static_Expr
 808               ("constraint argument must be static string expression!", E1);
 809             Error_Attr;
 810          end if;
 811
 812          --  Check second argument is right type
 813
 814          Analyze_And_Resolve (E2, Entity (P));
 815
 816          --  Note: that is all we need to do, we don't need to check
 817          --  that it appears in a correct context. The Ada type system
 818          --  will do that for us.
 819
 820       end Check_Asm_Attribute;
 821
 822       ---------------------
 823       -- Check_Component --
 824       ---------------------
 825
 826       procedure Check_Component is
 827       begin
 828          Check_E0;
 829
 830          if Nkind (P) /= N_Selected_Component
 831            or else
 832              (Ekind (Entity (Selector_Name (P))) /= E_Component
 833                and then
 834               Ekind (Entity (Selector_Name (P))) /= E_Discriminant)
 835          then
 836             Error_Attr
 837               ("prefix for % attribute must be selected component", P);
 838          end if;
 839       end Check_Component;
 840
 841       ------------------------------------
 842       -- Check_Decimal_Fixed_Point_Type --
 843       ------------------------------------
 844
 845       procedure Check_Decimal_Fixed_Point_Type is
 846       begin
 847          Check_Type;
 848
 849          if not Is_Decimal_Fixed_Point_Type (P_Type) then
 850             Error_Attr
 851               ("prefix of % attribute must be decimal type", P);
 852          end if;
 853       end Check_Decimal_Fixed_Point_Type;
 854
 855       -----------------------
 856       -- Check_Dereference --
 857       -----------------------
 858
 859       procedure Check_Dereference is
 860       begin
 861
 862          --  Case of a subtype mark
 863
 864          if Is_Entity_Name (P)
 865            and then Is_Type (Entity (P))
 866          then
 867             return;
 868          end if;
 869
 870          --  Case of an expression
 871
 872          Resolve (P);
 873
 874          if Is_Access_Type (P_Type) then
 875
 876             --  If there is an implicit dereference, then we must freeze
 877             --  the designated type of the access type, since the type of
 878             --  the referenced array is this type (see AI95-00106).
 879
 880             Freeze_Before (N, Designated_Type (P_Type));
 881
 882             Rewrite (P,
 883               Make_Explicit_Dereference (Sloc (P),
 884                 Prefix => Relocate_Node (P)));
 885
 886             Analyze_And_Resolve (P);
 887             P_Type := Etype (P);
 888
 889             if P_Type = Any_Type then
 890                raise Bad_Attribute;
 891             end if;
 892
 893             P_Base_Type := Base_Type (P_Type);
 894          end if;
 895       end Check_Dereference;
 896
 897       -------------------------
 898       -- Check_Discrete_Type --
 899       -------------------------
 900
 901       procedure Check_Discrete_Type is
 902       begin
 903          Check_Type;
 904
 905          if not Is_Discrete_Type (P_Type) then
 906             Error_Attr ("prefix of % attribute must be discrete type", P);
 907          end if;
 908       end Check_Discrete_Type;
 909
 910       --------------
 911       -- Check_E0 --
 912       --------------
 913
 914       procedure Check_E0 is
 915       begin
 916          if Present (E1) then
 917             Unexpected_Argument (E1);
 918          end if;
 919       end Check_E0;
 920
 921       --------------
 922       -- Check_E1 --
 923       --------------
 924
 925       procedure Check_E1 is
 926       begin
 927          Check_Either_E0_Or_E1;
 928
 929          if No (E1) then
 930
 931             --  Special-case attributes that are functions and that appear as
 932             --  the prefix of another attribute. Error is posted on parent.
 933
 934             if Nkind (Parent (N)) = N_Attribute_Reference
 935               and then (Attribute_Name (Parent (N)) = Name_Address
 936                           or else
 937                         Attribute_Name (Parent (N)) = Name_Code_Address
 938                           or else
 939                         Attribute_Name (Parent (N)) = Name_Access)
 940             then
 941                Error_Msg_Name_1 := Attribute_Name (Parent (N));
 942                Error_Msg_N ("illegal prefix for % attribute", Parent (N));
 943                Set_Etype (Parent (N), Any_Type);
 944                Set_Entity (Parent (N), Any_Type);
 945                raise Bad_Attribute;
 946
 947             else
 948                Error_Attr ("missing argument for % attribute", N);
 949             end if;
 950          end if;
 951       end Check_E1;
 952
 953       --------------
 954       -- Check_E2 --
 955       --------------
 956
 957       procedure Check_E2 is
 958       begin
 959          if No (E1) then
 960             Error_Attr ("missing arguments for % attribute (2 required)", N);
 961          elsif No (E2) then
 962             Error_Attr ("missing argument for % attribute (2 required)", N);
 963          end if;
 964       end Check_E2;
 965
 966       ---------------------------
 967       -- Check_Either_E0_Or_E1 --
 968       ---------------------------
 969
 970       procedure Check_Either_E0_Or_E1 is
 971       begin
 972          if Present (E2) then
 973             Unexpected_Argument (E2);
 974          end if;
 975       end Check_Either_E0_Or_E1;
 976
 977       ----------------------
 978       -- Check_Enum_Image --
 979       ----------------------
 980
 981       procedure Check_Enum_Image is
 982          Lit : Entity_Id;
 983
 984       begin
 985          if Is_Enumeration_Type (P_Base_Type) then
 986             Lit := First_Literal (P_Base_Type);
 987             while Present (Lit) loop
 988                Set_Referenced (Lit);
 989                Next_Literal (Lit);
 990             end loop;
 991          end if;
 992       end Check_Enum_Image;
 993
 994       ----------------------------
 995       -- Check_Fixed_Point_Type --
 996       ----------------------------
 997
 998       procedure Check_Fixed_Point_Type is
 999       begin
1000          Check_Type;
1001
1002          if not Is_Fixed_Point_Type (P_Type) then
1003             Error_Attr ("prefix of % attribute must be fixed point type", P);
1004          end if;
1005       end Check_Fixed_Point_Type;
1006
1007       ------------------------------
1008       -- Check_Fixed_Point_Type_0 --
1009       ------------------------------
1010
1011       procedure Check_Fixed_Point_Type_0 is
1012       begin
1013          Check_Fixed_Point_Type;
1014          Check_E0;
1015       end Check_Fixed_Point_Type_0;
1016
1017       -------------------------------
1018       -- Check_Floating_Point_Type --
1019       -------------------------------
1020
1021       procedure Check_Floating_Point_Type is
1022       begin
1023          Check_Type;
1024
1025          if not Is_Floating_Point_Type (P_Type) then
1026             Error_Attr ("prefix of % attribute must be float type", P);
1027          end if;
1028       end Check_Floating_Point_Type;
1029
1030       ---------------------------------
1031       -- Check_Floating_Point_Type_0 --
1032       ---------------------------------
1033
1034       procedure Check_Floating_Point_Type_0 is
1035       begin
1036          Check_Floating_Point_Type;
1037          Check_E0;
1038       end Check_Floating_Point_Type_0;
1039
1040       ---------------------------------
1041       -- Check_Floating_Point_Type_1 --
1042       ---------------------------------
1043
1044       procedure Check_Floating_Point_Type_1 is
1045       begin
1046          Check_Floating_Point_Type;
1047          Check_E1;
1048       end Check_Floating_Point_Type_1;
1049
1050       ---------------------------------
1051       -- Check_Floating_Point_Type_2 --
1052       ---------------------------------
1053
1054       procedure Check_Floating_Point_Type_2 is
1055       begin
1056          Check_Floating_Point_Type;
1057          Check_E2;
1058       end Check_Floating_Point_Type_2;
1059
1060       ------------------------
1061       -- Check_Integer_Type --
1062       ------------------------
1063
1064       procedure Check_Integer_Type is
1065       begin
1066          Check_Type;
1067
1068          if not Is_Integer_Type (P_Type) then
1069             Error_Attr ("prefix of % attribute must be integer type", P);
1070          end if;
1071       end Check_Integer_Type;
1072
1073       ------------------------
1074       -- Check_Library_Unit --
1075       ------------------------
1076
1077       procedure Check_Library_Unit is
1078       begin
1079          if not Is_Compilation_Unit (Entity (P)) then
1080             Error_Attr ("prefix of % attribute must be library unit", P);
1081          end if;
1082       end Check_Library_Unit;
1083
1084       --------------------------------
1085       -- Check_Modular_Integer_Type --
1086       --------------------------------
1087
1088       procedure Check_Modular_Integer_Type is
1089       begin
1090          Check_Type;
1091
1092          if not Is_Modular_Integer_Type (P_Type) then
1093             Error_Attr
1094               ("prefix of % attribute must be modular integer type", P);
1095          end if;
1096       end Check_Modular_Integer_Type;
1097
1098       -------------------------------
1099       -- Check_Not_Incomplete_Type --
1100       -------------------------------
1101
1102       procedure Check_Not_Incomplete_Type is
1103          E   : Entity_Id;
1104          Typ : Entity_Id;
1105
1106       begin
1107          --  Ada 2005 (AI-50217, AI-326): If the prefix is an explicit
1108          --  dereference we have to check wrong uses of incomplete types
1109          --  (other wrong uses are checked at their freezing point).
1110
1111          --  Example 1: Limited-with
1112
1113          --    limited with Pkg;
1114          --    package P is
1115          --       type Acc is access Pkg.T;
1116          --       X : Acc;
1117          --       S : Integer := X.all'Size;                    -- ERROR
1118          --    end P;
1119
1120          --  Example 2: Tagged incomplete
1121
1122          --     type T is tagged;
1123          --     type Acc is access all T;
1124          --     X : Acc;
1125          --     S : constant Integer := X.all'Size;             -- ERROR
1126          --     procedure Q (Obj : Integer := X.all'Alignment); -- ERROR
1127
1128          if Ada_Version >= Ada_05
1129            and then Nkind (P) = N_Explicit_Dereference
1130          then
1131             E := P;
1132             while Nkind (E) = N_Explicit_Dereference loop
1133                E := Prefix (E);
1134             end loop;
1135
1136             if From_With_Type (Etype (E)) then
1137                Error_Attr
1138                  ("prefix of % attribute cannot be an incomplete type", P);
1139
1140             else
1141                if Is_Access_Type (Etype (E)) then
1142                   Typ := Directly_Designated_Type (Etype (E));
1143                else
1144                   Typ := Etype (E);
1145                end if;
1146
1147                if Ekind (Typ) = E_Incomplete_Type
1148                  and then not Present (Full_View (Typ))
1149                then
1150                   Error_Attr
1151                     ("prefix of % attribute cannot be an incomplete type", P);
1152                end if;
1153             end if;
1154          end if;
1155
1156          if not Is_Entity_Name (P)
1157            or else not Is_Type (Entity (P))
1158            or else In_Default_Expression
1159          then
1160             return;
1161          else
1162             Check_Fully_Declared (P_Type, P);
1163          end if;
1164       end Check_Not_Incomplete_Type;
1165
1166       ----------------------------
1167       -- Check_Object_Reference --
1168       ----------------------------
1169
1170       procedure Check_Object_Reference (P : Node_Id) is
1171          Rtyp : Entity_Id;
1172
1173       begin
1174          --  If we need an object, and we have a prefix that is the name of
1175          --  a function entity, convert it into a function call.
1176
1177          if Is_Entity_Name (P)
1178            and then Ekind (Entity (P)) = E_Function
1179          then
1180             Rtyp := Etype (Entity (P));
1181
1182             Rewrite (P,
1183               Make_Function_Call (Sloc (P),
1184                 Name => Relocate_Node (P)));
1185
1186             Analyze_And_Resolve (P, Rtyp);
1187
1188          --  Otherwise we must have an object reference
1189
1190          elsif not Is_Object_Reference (P) then
1191             Error_Attr ("prefix of % attribute must be object", P);
1192          end if;
1193       end Check_Object_Reference;
1194
1195       ------------------------
1196       -- Check_Program_Unit --
1197       ------------------------
1198
1199       procedure Check_Program_Unit is
1200       begin
1201          if Is_Entity_Name (P) then
1202             declare
1203                K : constant Entity_Kind := Ekind (Entity (P));
1204                T : constant Entity_Id   := Etype (Entity (P));
1205
1206             begin
1207                if K in Subprogram_Kind
1208                  or else K in Task_Kind
1209                  or else K in Protected_Kind
1210                  or else K = E_Package
1211                  or else K in Generic_Unit_Kind
1212                  or else (K = E_Variable
1213                             and then
1214                               (Is_Task_Type (T)
1215                                  or else
1216                                Is_Protected_Type (T)))
1217                then
1218                   return;
1219                end if;
1220             end;
1221          end if;
1222
1223          Error_Attr ("prefix of % attribute must be program unit", P);
1224       end Check_Program_Unit;
1225
1226       ---------------------
1227       -- Check_Real_Type --
1228       ---------------------
1229
1230       procedure Check_Real_Type is
1231       begin
1232          Check_Type;
1233
1234          if not Is_Real_Type (P_Type) then
1235             Error_Attr ("prefix of % attribute must be real type", P);
1236          end if;
1237       end Check_Real_Type;
1238
1239       -----------------------
1240       -- Check_Scalar_Type --
1241       -----------------------
1242
1243       procedure Check_Scalar_Type is
1244       begin
1245          Check_Type;
1246
1247          if not Is_Scalar_Type (P_Type) then
1248             Error_Attr ("prefix of % attribute must be scalar type", P);
1249          end if;
1250       end Check_Scalar_Type;
1251
1252       ---------------------------
1253       -- Check_Standard_Prefix --
1254       ---------------------------
1255
1256       procedure Check_Standard_Prefix is
1257       begin
1258          Check_E0;
1259
1260          if Nkind (P) /= N_Identifier
1261            or else Chars (P) /= Name_Standard
1262          then
1263             Error_Attr ("only allowed prefix for % attribute is Standard", P);
1264          end if;
1265
1266       end Check_Standard_Prefix;
1267
1268       ----------------------------
1269       -- Check_Stream_Attribute --
1270       ----------------------------
1271
1272       procedure Check_Stream_Attribute (Nam : TSS_Name_Type) is
1273          Etyp : Entity_Id;
1274          Btyp : Entity_Id;
1275       begin
1276          Validate_Non_Static_Attribute_Function_Call;
1277
1278          --  With the exception of 'Input, Stream attributes are procedures,
1279          --  and can only appear at the position of procedure calls. We check
1280          --  for this here, before they are rewritten, to give a more precise
1281          --  diagnostic.
1282
1283          if Nam = TSS_Stream_Input then
1284             null;
1285
1286          elsif Is_List_Member (N)
1287            and then Nkind (Parent (N)) /= N_Procedure_Call_Statement
1288            and then Nkind (Parent (N)) /= N_Aggregate
1289          then
1290             null;
1291
1292          else
1293             Error_Attr
1294               ("invalid context for attribute%, which is a procedure", N);
1295          end if;
1296
1297          Check_Type;
1298          Btyp := Implementation_Base_Type (P_Type);
1299
1300          --  Stream attributes not allowed on limited types unless the
1301          --  attribute reference was generated by the expander (in which
1302          --  case the underlying type will be used, as described in Sinfo),
1303          --  or the attribute was specified explicitly for the type itself
1304          --  or one of its ancestors (taking visibility rules into account if
1305          --  in Ada 2005 mode), or a pragma Stream_Convert applies to Btyp
1306          --  (with no visibility restriction).
1307
1308          if Comes_From_Source (N)
1309            and then not Stream_Attribute_Available (P_Type, Nam)
1310            and then not Has_Rep_Pragma (Btyp, Name_Stream_Convert)
1311          then
1312             Error_Msg_Name_1 := Aname;
1313
1314             if Is_Limited_Type (P_Type) then
1315                Error_Msg_NE
1316                  ("limited type& has no% attribute", P, P_Type);
1317                Explain_Limited_Type (P_Type, P);
1318             else
1319                Error_Msg_NE
1320                  ("attribute% for type& is not available", P, P_Type);
1321             end if;
1322          end if;
1323
1324          --  Check for violation of restriction No_Stream_Attributes
1325
1326          if Is_RTE (P_Type, RE_Exception_Id)
1327               or else
1328             Is_RTE (P_Type, RE_Exception_Occurrence)
1329          then
1330             Check_Restriction (No_Exception_Registration, P);
1331          end if;
1332
1333          --  Here we must check that the first argument is an access type
1334          --  that is compatible with Ada.Streams.Root_Stream_Type'Class.
1335
1336          Analyze_And_Resolve (E1);
1337          Etyp := Etype (E1);
1338
1339          --  Note: the double call to Root_Type here is needed because the
1340          --  root type of a class-wide type is the corresponding type (e.g.
1341          --  X for X'Class, and we really want to go to the root.
1342
1343          if not Is_Access_Type (Etyp)
1344            or else Root_Type (Root_Type (Designated_Type (Etyp))) /=
1345                      RTE (RE_Root_Stream_Type)
1346          then
1347             Error_Attr
1348               ("expected access to Ada.Streams.Root_Stream_Type''Class", E1);
1349          end if;
1350
1351          --  Check that the second argument is of the right type if there is
1352          --  one (the Input attribute has only one argument so this is skipped)
1353
1354          if Present (E2) then
1355             Analyze (E2);
1356
1357             if Nam = TSS_Stream_Read
1358               and then not Is_OK_Variable_For_Out_Formal (E2)
1359             then
1360                Error_Attr
1361                  ("second argument of % attribute must be a variable", E2);
1362             end if;
1363
1364             Resolve (E2, P_Type);
1365          end if;
1366       end Check_Stream_Attribute;
1367
1368       -----------------------
1369       -- Check_Task_Prefix --
1370       -----------------------
1371
1372       procedure Check_Task_Prefix is
1373       begin
1374          Analyze (P);
1375
1376          if Is_Task_Type (Etype (P))
1377            or else (Is_Access_Type (Etype (P))
1378               and then Is_Task_Type (Designated_Type (Etype (P))))
1379          then
1380             Resolve (P);
1381          else
1382             Error_Attr ("prefix of % attribute must be a task", P);
1383          end if;
1384       end Check_Task_Prefix;
1385
1386       ----------------
1387       -- Check_Type --
1388       ----------------
1389
1390       --  The possibilities are an entity name denoting a type, or an
1391       --  attribute reference that denotes a type (Base or Class). If
1392       --  the type is incomplete, replace it with its full view.
1393
1394       procedure Check_Type is
1395       begin
1396          if not Is_Entity_Name (P)
1397            or else not Is_Type (Entity (P))
1398          then
1399             Error_Attr ("prefix of % attribute must be a type", P);
1400
1401          elsif Ekind (Entity (P)) = E_Incomplete_Type
1402             and then Present (Full_View (Entity (P)))
1403          then
1404             P_Type := Full_View (Entity (P));
1405             Set_Entity (P, P_Type);
1406          end if;
1407       end Check_Type;
1408
1409       ---------------------
1410       -- Check_Unit_Name --
1411       ---------------------
1412
1413       procedure Check_Unit_Name (Nod : Node_Id) is
1414       begin
1415          if Nkind (Nod) = N_Identifier then
1416             return;
1417
1418          elsif Nkind (Nod) = N_Selected_Component then
1419             Check_Unit_Name (Prefix (Nod));
1420
1421             if Nkind (Selector_Name (Nod)) = N_Identifier then
1422                return;
1423             end if;
1424          end if;
1425
1426          Error_Attr ("argument for % attribute must be unit name", P);
1427       end Check_Unit_Name;
1428
1429       ----------------
1430       -- Error_Attr --
1431       ----------------
1432
1433       procedure Error_Attr is
1434       begin
1435          Set_Etype (N, Any_Type);
1436          Set_Entity (N, Any_Type);
1437          raise Bad_Attribute;
1438       end Error_Attr;
1439
1440       procedure Error_Attr (Msg : String; Error_Node : Node_Id) is
1441       begin
1442          Error_Msg_Name_1 := Aname;
1443          Error_Msg_N (Msg, Error_Node);
1444          Error_Attr;
1445       end Error_Attr;
1446
1447       ----------------------------
1448       -- Legal_Formal_Attribute --
1449       ----------------------------
1450
1451       procedure Legal_Formal_Attribute is
1452       begin
1453          Check_E0;
1454
1455          if not Is_Entity_Name (P)
1456            or else not Is_Type (Entity (P))
1457          then
1458             Error_Attr ("prefix of % attribute must be generic type", N);
1459
1460          elsif Is_Generic_Actual_Type (Entity (P))
1461            or else In_Instance
1462            or else In_Inlined_Body
1463          then
1464             null;
1465
1466          elsif Is_Generic_Type (Entity (P)) then
1467             if not Is_Indefinite_Subtype (Entity (P)) then
1468                Error_Attr
1469                  ("prefix of % attribute must be indefinite generic type", N);
1470             end if;
1471
1472          else
1473             Error_Attr
1474               ("prefix of % attribute must be indefinite generic type", N);
1475          end if;
1476
1477          Set_Etype (N, Standard_Boolean);
1478       end Legal_Formal_Attribute;
1479
1480       ------------------------
1481       -- Standard_Attribute --
1482       ------------------------
1483
1484       procedure Standard_Attribute (Val : Int) is
1485       begin
1486          Check_Standard_Prefix;
1487
1488          --  First a special check (more like a kludge really). For GNAT5
1489          --  on Windows, the alignments in GCC are severely mixed up. In
1490          --  particular, we have a situation where the maximum alignment
1491          --  that GCC thinks is possible is greater than the guaranteed
1492          --  alignment at run-time. That causes many problems. As a partial
1493          --  cure for this situation, we force a value of 4 for the maximum
1494          --  alignment attribute on this target. This still does not solve
1495          --  all problems, but it helps.
1496
1497          --  A further (even more horrible) dimension to this kludge is now
1498          --  installed. There are two uses for Maximum_Alignment, one is to
1499          --  determine the maximum guaranteed alignment, that's the one we
1500          --  want the kludge to yield as 4. The other use is to maximally
1501          --  align objects, we can't use 4 here, since for example, long
1502          --  long integer has an alignment of 8, so we will get errors.
1503
1504          --  It is of course impossible to determine which use the programmer
1505          --  has in mind, but an approximation for now is to disconnect the
1506          --  kludge if the attribute appears in an alignment clause.
1507
1508          --  To be removed if GCC ever gets its act together here ???
1509
1510          Alignment_Kludge : declare
1511             P : Node_Id;
1512
1513             function On_X86 return Boolean;
1514             --  Determine if target is x86 (ia32), return True if so
1515
1516             ------------
1517             -- On_X86 --
1518             ------------
1519
1520             function On_X86 return Boolean is
1521                T : constant String := Sdefault.Target_Name.all;
1522
1523             begin
1524                --  There is no clean way to check this. That's not surprising,
1525                --  the front end should not be doing this kind of test ???. The
1526                --  way we do it is test for either "86" or "pentium" being in
1527                --  the string for the target name. However, we need to exclude
1528                --  x86_64 for this check.
1529
1530                for J in T'First .. T'Last - 1 loop
1531                   if (T (J .. J + 1) = "86"
1532                       and then
1533                         (J + 4 > T'Last
1534                            or else T (J + 2 .. J + 4) /= "_64"))
1535                     or else (J <= T'Last - 6
1536                                and then T (J .. J + 6) = "pentium")
1537                   then
1538                      return True;
1539                   end if;
1540                end loop;
1541
1542                return False;
1543             end On_X86;
1544
1545          begin
1546             if Aname = Name_Maximum_Alignment and then On_X86 then
1547                P := Parent (N);
1548
1549                while Nkind (P) in N_Subexpr loop
1550                   P := Parent (P);
1551                end loop;
1552
1553                if Nkind (P) /= N_Attribute_Definition_Clause
1554                  or else Chars (P) /= Name_Alignment
1555                then
1556                   Rewrite (N, Make_Integer_Literal (Loc, 4));
1557                   Analyze (N);
1558                   return;
1559                end if;
1560             end if;
1561          end Alignment_Kludge;
1562
1563          --  Normally we get the value from gcc ???
1564
1565          Rewrite (N, Make_Integer_Literal (Loc, Val));
1566          Analyze (N);
1567       end Standard_Attribute;
1568
1569       -------------------------
1570       -- Unexpected Argument --
1571       -------------------------
1572
1573       procedure Unexpected_Argument (En : Node_Id) is
1574       begin
1575          Error_Attr ("unexpected argument for % attribute", En);
1576       end Unexpected_Argument;
1577
1578       -------------------------------------------------
1579       -- Validate_Non_Static_Attribute_Function_Call --
1580       -------------------------------------------------
1581
1582       --  This function should be moved to Sem_Dist ???
1583
1584       procedure Validate_Non_Static_Attribute_Function_Call is
1585       begin
1586          if In_Preelaborated_Unit
1587            and then not In_Subprogram_Or_Concurrent_Unit
1588          then
1589             Flag_Non_Static_Expr
1590               ("non-static function call in preelaborated unit!", N);
1591          end if;
1592       end Validate_Non_Static_Attribute_Function_Call;
1593
1594    -----------------------------------------------
1595    -- Start of Processing for Analyze_Attribute --
1596    -----------------------------------------------
1597
1598    begin
1599       --  Immediate return if unrecognized attribute (already diagnosed
1600       --  by parser, so there is nothing more that we need to do)
1601
1602       if not Is_Attribute_Name (Aname) then
1603          raise Bad_Attribute;
1604       end if;
1605
1606       --  Deal with Ada 83 and Features issues
1607
1608       if Comes_From_Source (N) then
1609          if not Attribute_83 (Attr_Id) then
1610             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
1611                Error_Msg_Name_1 := Aname;
1612                Error_Msg_N ("(Ada 83) attribute% is not standard?", N);
1613             end if;
1614
1615             if Attribute_Impl_Def (Attr_Id) then
1616                Check_Restriction (No_Implementation_Attributes, N);
1617             end if;
1618          end if;
1619       end if;
1620
1621       --   Remote access to subprogram type access attribute reference needs
1622       --   unanalyzed copy for tree transformation. The analyzed copy is used
1623       --   for its semantic information (whether prefix is a remote subprogram
1624       --   name), the unanalyzed copy is used to construct new subtree rooted
1625       --   with N_Aggregate which represents a fat pointer aggregate.
1626
1627       if Aname = Name_Access then
1628          Discard_Node (Copy_Separate_Tree (N));
1629       end if;
1630
1631       --  Analyze prefix and exit if error in analysis. If the prefix is an
1632       --  incomplete type, use full view if available. A special case is
1633       --  that we never analyze the prefix of an Elab_Body or Elab_Spec
1634       --  or UET_Address attribute.
1635
1636       if Aname /= Name_Elab_Body
1637            and then
1638          Aname /= Name_Elab_Spec
1639            and then
1640          Aname /= Name_UET_Address
1641       then
1642          Analyze (P);
1643          P_Type := Etype (P);
1644
1645          if Is_Entity_Name (P)
1646            and then Present (Entity (P))
1647            and then Is_Type (Entity (P))
1648            and then Ekind (Entity (P)) = E_Incomplete_Type
1649          then
1650             P_Type := Get_Full_View (P_Type);
1651             Set_Entity (P, P_Type);
1652             Set_Etype  (P, P_Type);
1653          end if;
1654
1655          if P_Type = Any_Type then
1656             raise Bad_Attribute;
1657          end if;
1658
1659          P_Base_Type := Base_Type (P_Type);
1660       end if;
1661
1662       --  Analyze expressions that may be present, exiting if an error occurs
1663
1664       if No (Exprs) then
1665          E1 := Empty;
1666          E2 := Empty;
1667
1668       else
1669          E1 := First (Exprs);
1670          Analyze (E1);
1671
1672          --  Check for missing or bad expression (result of previous error)
1673
1674          if No (E1) or else Etype (E1) = Any_Type then
1675             raise Bad_Attribute;
1676          end if;
1677
1678          E2 := Next (E1);
1679
1680          if Present (E2) then
1681             Analyze (E2);
1682
1683             if Etype (E2) = Any_Type then
1684                raise Bad_Attribute;
1685             end if;
1686
1687             if Present (Next (E2)) then
1688                Unexpected_Argument (Next (E2));
1689             end if;
1690          end if;
1691       end if;
1692
1693       --  Ada 2005 (AI-345): Ensure that the compiler gives exactly the current
1694       --  output compiling in Ada 95 mode
1695
1696       if Ada_Version < Ada_05
1697         and then Is_Overloaded (P)
1698         and then Aname /= Name_Access
1699         and then Aname /= Name_Address
1700         and then Aname /= Name_Code_Address
1701         and then Aname /= Name_Count
1702         and then Aname /= Name_Unchecked_Access
1703       then
1704          Error_Attr ("ambiguous prefix for % attribute", P);
1705
1706       elsif Ada_Version >= Ada_05
1707         and then Is_Overloaded (P)
1708         and then Aname /= Name_Access
1709         and then Aname /= Name_Address
1710         and then Aname /= Name_Code_Address
1711         and then Aname /= Name_Unchecked_Access
1712       then
1713          --  Ada 2005 (AI-345): Since protected and task types have primitive
1714          --  entry wrappers, the attributes Count, Caller and AST_Entry require
1715          --  a context check
1716
1717          if Ada_Version >= Ada_05
1718            and then (Aname = Name_Count
1719                       or else Aname = Name_Caller
1720                       or else Aname = Name_AST_Entry)
1721          then
1722             declare
1723                Count : Natural := 0;
1724                I     : Interp_Index;
1725                It    : Interp;
1726
1727             begin
1728                Get_First_Interp (P, I, It);
1729
1730                while Present (It.Nam) loop
1731                   if Comes_From_Source (It.Nam) then
1732                      Count := Count + 1;
1733                   else
1734                      Remove_Interp (I);
1735                   end if;
1736
1737                   Get_Next_Interp (I, It);
1738                end loop;
1739
1740                if Count > 1 then
1741                   Error_Attr ("ambiguous prefix for % attribute", P);
1742                else
1743                   Set_Is_Overloaded (P, False);
1744                end if;
1745             end;
1746
1747          else
1748             Error_Attr ("ambiguous prefix for % attribute", P);
1749          end if;
1750       end if;
1751
1752       --  Remaining processing depends on attribute
1753
1754       case Attr_Id is
1755
1756       ------------------
1757       -- Abort_Signal --
1758       ------------------
1759
1760       when Attribute_Abort_Signal =>
1761          Check_Standard_Prefix;
1762          Rewrite (N,
1763            New_Reference_To (Stand.Abort_Signal, Loc));
1764          Analyze (N);
1765
1766       ------------
1767       -- Access --
1768       ------------
1769
1770       when Attribute_Access =>
1771          Analyze_Access_Attribute;
1772
1773       -------------
1774       -- Address --
1775       -------------
1776
1777       when Attribute_Address =>
1778          Check_E0;
1779
1780          --  Check for some junk cases, where we have to allow the address
1781          --  attribute but it does not make much sense, so at least for now
1782          --  just replace with Null_Address.
1783
1784          --  We also do this if the prefix is a reference to the AST_Entry
1785          --  attribute. If expansion is active, the attribute will be
1786          --  replaced by a function call, and address will work fine and
1787          --  get the proper value, but if expansion is not active, then
1788          --  the check here allows proper semantic analysis of the reference.
1789
1790          --  An Address attribute created by expansion is legal even when it
1791          --  applies to other entity-denoting expressions.
1792
1793          if Is_Entity_Name (P) then
1794             declare
1795                Ent : constant Entity_Id := Entity (P);
1796
1797             begin
1798                if Is_Subprogram (Ent) then
1799                   if not Is_Library_Level_Entity (Ent) then
1800                      Check_Restriction (No_Implicit_Dynamic_Code, P);
1801                   end if;
1802
1803                   Set_Address_Taken (Ent);
1804
1805                   --  An Address attribute is accepted when generated by
1806                   --  the compiler for dispatching operation, and an error
1807                   --  is issued once the subprogram is frozen (to avoid
1808                   --  confusing errors about implicit uses of Address in
1809                   --  the dispatch table initialization).
1810
1811                   if Is_Always_Inlined (Entity (P))
1812                     and then Comes_From_Source (P)
1813                   then
1814                      Error_Attr
1815                        ("prefix of % attribute cannot be Inline_Always" &
1816                         " subprogram", P);
1817                   end if;
1818
1819                elsif Is_Object (Ent)
1820                  or else Ekind (Ent) = E_Label
1821                then
1822                   Set_Address_Taken (Ent);
1823
1824                --  If we have an address of an object, and the attribute
1825                --  comes from source, then set the object as potentially
1826                --  source modified. We do this because the resulting address
1827                --  can potentially be used to modify the variable and we
1828                --  might not detect this, leading to some junk warnings.
1829
1830                   Set_Never_Set_In_Source (Ent, False);
1831
1832                elsif (Is_Concurrent_Type (Etype (Ent))
1833                        and then Etype (Ent) = Base_Type (Ent))
1834                  or else Ekind (Ent) = E_Package
1835                  or else Is_Generic_Unit (Ent)
1836                then
1837                   Rewrite (N,
1838                     New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1839
1840                else
1841                   Error_Attr ("invalid prefix for % attribute", P);
1842                end if;
1843             end;
1844
1845          elsif Nkind (P) = N_Attribute_Reference
1846            and then Attribute_Name (P) = Name_AST_Entry
1847          then
1848             Rewrite (N,
1849               New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1850
1851          elsif Is_Object_Reference (P) then
1852             null;
1853
1854          elsif Nkind (P) = N_Selected_Component
1855            and then Is_Subprogram (Entity (Selector_Name (P)))
1856          then
1857             null;
1858
1859          --  What exactly are we allowing here ??? and is this properly
1860          --  documented in the sinfo documentation for this node ???
1861
1862          elsif not Comes_From_Source (N) then
1863             null;
1864
1865          else
1866             Error_Attr ("invalid prefix for % attribute", P);
1867          end if;
1868
1869          Set_Etype (N, RTE (RE_Address));
1870
1871       ------------------
1872       -- Address_Size --
1873       ------------------
1874
1875       when Attribute_Address_Size =>
1876          Standard_Attribute (System_Address_Size);
1877
1878       --------------
1879       -- Adjacent --
1880       --------------
1881
1882       when Attribute_Adjacent =>
1883          Check_Floating_Point_Type_2;
1884          Set_Etype (N, P_Base_Type);
1885          Resolve (E1, P_Base_Type);
1886          Resolve (E2, P_Base_Type);
1887
1888       ---------
1889       -- Aft --
1890       ---------
1891
1892       when Attribute_Aft =>
1893          Check_Fixed_Point_Type_0;
1894          Set_Etype (N, Universal_Integer);
1895
1896       ---------------
1897       -- Alignment --
1898       ---------------
1899
1900       when Attribute_Alignment =>
1901
1902          --  Don't we need more checking here, cf Size ???
1903
1904          Check_E0;
1905          Check_Not_Incomplete_Type;
1906          Set_Etype (N, Universal_Integer);
1907
1908       ---------------
1909       -- Asm_Input --
1910       ---------------
1911
1912       when Attribute_Asm_Input =>
1913          Check_Asm_Attribute;
1914          Set_Etype (N, RTE (RE_Asm_Input_Operand));
1915
1916       ----------------
1917       -- Asm_Output --
1918       ----------------
1919
1920       when Attribute_Asm_Output =>
1921          Check_Asm_Attribute;
1922
1923          if Etype (E2) = Any_Type then
1924             return;
1925
1926          elsif Aname = Name_Asm_Output then
1927             if not Is_Variable (E2) then
1928                Error_Attr
1929                  ("second argument for Asm_Output is not variable", E2);
1930             end if;
1931          end if;
1932
1933          Note_Possible_Modification (E2);
1934          Set_Etype (N, RTE (RE_Asm_Output_Operand));
1935
1936       ---------------
1937       -- AST_Entry --
1938       ---------------
1939
1940       when Attribute_AST_Entry => AST_Entry : declare
1941          Ent  : Entity_Id;
1942          Pref : Node_Id;
1943          Ptyp : Entity_Id;
1944
1945          Indexed : Boolean;
1946          --  Indicates if entry family index is present. Note the coding
1947          --  here handles the entry family case, but in fact it cannot be
1948          --  executed currently, because pragma AST_Entry does not permit
1949          --  the specification of an entry family.
1950
1951          procedure Bad_AST_Entry;
1952          --  Signal a bad AST_Entry pragma
1953
1954          function OK_Entry (E : Entity_Id) return Boolean;
1955          --  Checks that E is of an appropriate entity kind for an entry
1956          --  (i.e. E_Entry if Index is False, or E_Entry_Family if Index
1957          --  is set True for the entry family case). In the True case,
1958          --  makes sure that Is_AST_Entry is set on the entry.
1959
1960          procedure Bad_AST_Entry is
1961          begin
1962             Error_Attr ("prefix for % attribute must be task entry", P);
1963          end Bad_AST_Entry;
1964
1965          function OK_Entry (E : Entity_Id) return Boolean is
1966             Result : Boolean;
1967
1968          begin
1969             if Indexed then
1970                Result := (Ekind (E) = E_Entry_Family);
1971             else
1972                Result := (Ekind (E) = E_Entry);
1973             end if;
1974
1975             if Result then
1976                if not Is_AST_Entry (E) then
1977                   Error_Msg_Name_2 := Aname;
1978                   Error_Attr
1979                     ("% attribute requires previous % pragma", P);
1980                end if;
1981             end if;
1982
1983             return Result;
1984          end OK_Entry;
1985
1986       --  Start of processing for AST_Entry
1987
1988       begin
1989          Check_VMS (N);
1990          Check_E0;
1991
1992          --  Deal with entry family case
1993
1994          if Nkind (P) = N_Indexed_Component then
1995             Pref := Prefix (P);
1996             Indexed := True;
1997          else
1998             Pref := P;
1999             Indexed := False;
2000          end if;
2001
2002          Ptyp := Etype (Pref);
2003
2004          if Ptyp = Any_Type or else Error_Posted (Pref) then
2005             return;
2006          end if;
2007
2008          --  If the prefix is a selected component whose prefix is of an
2009          --  access type, then introduce an explicit dereference.
2010          --  ??? Could we reuse Check_Dereference here?
2011
2012          if Nkind (Pref) = N_Selected_Component
2013            and then Is_Access_Type (Ptyp)
2014          then
2015             Rewrite (Pref,
2016               Make_Explicit_Dereference (Sloc (Pref),
2017                 Relocate_Node (Pref)));
2018             Analyze_And_Resolve (Pref, Designated_Type (Ptyp));
2019          end if;
2020
2021          --  Prefix can be of the form a.b, where a is a task object
2022          --  and b is one of the entries of the corresponding task type.
2023
2024          if Nkind (Pref) = N_Selected_Component
2025            and then OK_Entry (Entity (Selector_Name (Pref)))
2026            and then Is_Object_Reference (Prefix (Pref))
2027            and then Is_Task_Type (Etype (Prefix (Pref)))
2028          then
2029             null;
2030
2031          --  Otherwise the prefix must be an entry of a containing task,
2032          --  or of a variable of the enclosing task type.
2033
2034          else
2035             if Nkind (Pref) = N_Identifier
2036               or else Nkind (Pref) = N_Expanded_Name
2037             then
2038                Ent := Entity (Pref);
2039
2040                if not OK_Entry (Ent)
2041                  or else not In_Open_Scopes (Scope (Ent))
2042                then
2043                   Bad_AST_Entry;
2044                end if;
2045
2046             else
2047                Bad_AST_Entry;
2048             end if;
2049          end if;
2050
2051          Set_Etype (N, RTE (RE_AST_Handler));
2052       end AST_Entry;
2053
2054       ----------
2055       -- Base --
2056       ----------
2057
2058       --  Note: when the base attribute appears in the context of a subtype
2059       --  mark, the analysis is done by Sem_Ch8.Find_Type, rather than by
2060       --  the following circuit.
2061
2062       when Attribute_Base => Base : declare
2063          Typ : Entity_Id;
2064
2065       begin
2066          Check_Either_E0_Or_E1;
2067          Find_Type (P);
2068          Typ := Entity (P);
2069
2070          if Ada_Version >= Ada_95
2071            and then not Is_Scalar_Type (Typ)
2072            and then not Is_Generic_Type (Typ)
2073          then
2074             Error_Msg_N ("prefix of Base attribute must be scalar type", N);
2075
2076          elsif Sloc (Typ) = Standard_Location
2077            and then Base_Type (Typ) = Typ
2078            and then Warn_On_Redundant_Constructs
2079          then
2080             Error_Msg_NE
2081               ("?redudant attribute, & is its own base type", N, Typ);
2082          end if;
2083
2084          Set_Etype (N, Base_Type (Entity (P)));
2085
2086          --  If we have an expression present, then really this is a conversion
2087          --  and the tree must be reformed. Note that this is one of the cases
2088          --  in which we do a replace rather than a rewrite, because the
2089          --  original tree is junk.
2090
2091          if Present (E1) then
2092             Replace (N,
2093               Make_Type_Conversion (Loc,
2094                 Subtype_Mark =>
2095                   Make_Attribute_Reference (Loc,
2096                     Prefix => Prefix (N),
2097                     Attribute_Name => Name_Base),
2098                 Expression => Relocate_Node (E1)));
2099
2100             --  E1 may be overloaded, and its interpretations preserved
2101
2102             Save_Interps (E1, Expression (N));
2103             Analyze (N);
2104
2105          --  For other cases, set the proper type as the entity of the
2106          --  attribute reference, and then rewrite the node to be an
2107          --  occurrence of the referenced base type. This way, no one
2108          --  else in the compiler has to worry about the base attribute.
2109
2110          else
2111             Set_Entity (N, Base_Type (Entity (P)));
2112             Rewrite (N,
2113               New_Reference_To (Entity (N), Loc));
2114             Analyze (N);
2115          end if;
2116       end Base;
2117
2118       ---------
2119       -- Bit --
2120       ---------
2121
2122       when Attribute_Bit => Bit :
2123       begin
2124          Check_E0;
2125
2126          if not Is_Object_Reference (P) then
2127             Error_Attr ("prefix for % attribute must be object", P);
2128
2129          --  What about the access object cases ???
2130
2131          else
2132             null;
2133          end if;
2134
2135          Set_Etype (N, Universal_Integer);
2136       end Bit;
2137
2138       ---------------
2139       -- Bit_Order --
2140       ---------------
2141
2142       when Attribute_Bit_Order => Bit_Order :
2143       begin
2144          Check_E0;
2145          Check_Type;
2146
2147          if not Is_Record_Type (P_Type) then
2148             Error_Attr ("prefix of % attribute must be record type", P);
2149          end if;
2150
2151          if Bytes_Big_Endian xor Reverse_Bit_Order (P_Type) then
2152             Rewrite (N,
2153               New_Occurrence_Of (RTE (RE_High_Order_First), Loc));
2154          else
2155             Rewrite (N,
2156               New_Occurrence_Of (RTE (RE_Low_Order_First), Loc));
2157          end if;
2158
2159          Set_Etype (N, RTE (RE_Bit_Order));
2160          Resolve (N);
2161
2162          --  Reset incorrect indication of staticness
2163
2164          Set_Is_Static_Expression (N, False);
2165       end Bit_Order;
2166
2167       ------------------
2168       -- Bit_Position --
2169       ------------------
2170
2171       --  Note: in generated code, we can have a Bit_Position attribute
2172       --  applied to a (naked) record component (i.e. the prefix is an
2173       --  identifier that references an E_Component or E_Discriminant
2174       --  entity directly, and this is interpreted as expected by Gigi.
2175       --  The following code will not tolerate such usage, but when the
2176       --  expander creates this special case, it marks it as analyzed
2177       --  immediately and sets an appropriate type.
2178
2179       when Attribute_Bit_Position =>
2180
2181          if Comes_From_Source (N) then
2182             Check_Component;
2183          end if;
2184
2185          Set_Etype (N, Universal_Integer);
2186
2187       ------------------
2188       -- Body_Version --
2189       ------------------
2190
2191       when Attribute_Body_Version =>
2192          Check_E0;
2193          Check_Program_Unit;
2194          Set_Etype (N, RTE (RE_Version_String));
2195
2196       --------------
2197       -- Callable --
2198       --------------
2199
2200       when Attribute_Callable =>
2201          Check_E0;
2202          Set_Etype (N, Standard_Boolean);
2203          Check_Task_Prefix;
2204
2205       ------------
2206       -- Caller --
2207       ------------
2208
2209       when Attribute_Caller => Caller : declare
2210          Ent        : Entity_Id;
2211          S          : Entity_Id;
2212
2213       begin
2214          Check_E0;
2215
2216          if Nkind (P) = N_Identifier
2217            or else Nkind (P) = N_Expanded_Name
2218          then
2219             Ent := Entity (P);
2220
2221             if not Is_Entry (Ent) then
2222                Error_Attr ("invalid entry name", N);
2223             end if;
2224
2225          else
2226             Error_Attr ("invalid entry name", N);
2227             return;
2228          end if;
2229
2230          for J in reverse 0 .. Scope_Stack.Last loop
2231             S := Scope_Stack.Table (J).Entity;
2232
2233             if S = Scope (Ent) then
2234                Error_Attr ("Caller must appear in matching accept or body", N);
2235             elsif S = Ent then
2236                exit;
2237             end if;
2238          end loop;
2239
2240          Set_Etype (N, RTE (RO_AT_Task_Id));
2241       end Caller;
2242
2243       -------------
2244       -- Ceiling --
2245       -------------
2246
2247       when Attribute_Ceiling =>
2248          Check_Floating_Point_Type_1;
2249          Set_Etype (N, P_Base_Type);
2250          Resolve (E1, P_Base_Type);
2251
2252       -----------
2253       -- Class --
2254       -----------
2255
2256       when Attribute_Class => Class : declare
2257       begin
2258          Check_Restriction (No_Dispatch, N);
2259          Check_Either_E0_Or_E1;
2260
2261          --  If we have an expression present, then really this is a conversion
2262          --  and the tree must be reformed into a proper conversion. This is a
2263          --  Replace rather than a Rewrite, because the original tree is junk.
2264          --  If expression is overloaded, propagate interpretations to new one.
2265
2266          if Present (E1) then
2267             Replace (N,
2268               Make_Type_Conversion (Loc,
2269                 Subtype_Mark =>
2270                   Make_Attribute_Reference (Loc,
2271                     Prefix => Prefix (N),
2272                     Attribute_Name => Name_Class),
2273                 Expression => Relocate_Node (E1)));
2274
2275             Save_Interps (E1, Expression (N));
2276             Analyze (N);
2277
2278          --  Otherwise we just need to find the proper type
2279
2280          else
2281             Find_Type (N);
2282          end if;
2283
2284       end Class;
2285
2286       ------------------
2287       -- Code_Address --
2288       ------------------
2289
2290       when Attribute_Code_Address =>
2291          Check_E0;
2292
2293          if Nkind (P) = N_Attribute_Reference
2294            and then (Attribute_Name (P) = Name_Elab_Body
2295                        or else
2296                      Attribute_Name (P) = Name_Elab_Spec)
2297          then
2298             null;
2299
2300          elsif not Is_Entity_Name (P)
2301            or else (Ekind (Entity (P)) /= E_Function
2302                       and then
2303                     Ekind (Entity (P)) /= E_Procedure)
2304          then
2305             Error_Attr ("invalid prefix for % attribute", P);
2306             Set_Address_Taken (Entity (P));
2307          end if;
2308
2309          Set_Etype (N, RTE (RE_Address));
2310
2311       --------------------
2312       -- Component_Size --
2313       --------------------
2314
2315       when Attribute_Component_Size =>
2316          Check_E0;
2317          Set_Etype (N, Universal_Integer);
2318
2319          --  Note: unlike other array attributes, unconstrained arrays are OK
2320
2321          if Is_Array_Type (P_Type) and then not Is_Constrained (P_Type) then
2322             null;
2323          else
2324             Check_Array_Type;
2325          end if;
2326
2327       -------------
2328       -- Compose --
2329       -------------
2330
2331       when Attribute_Compose =>
2332          Check_Floating_Point_Type_2;
2333          Set_Etype (N, P_Base_Type);
2334          Resolve (E1, P_Base_Type);
2335          Resolve (E2, Any_Integer);
2336
2337       -----------------
2338       -- Constrained --
2339       -----------------
2340
2341       when Attribute_Constrained =>
2342          Check_E0;
2343          Set_Etype (N, Standard_Boolean);
2344
2345          --  Case from RM J.4(2) of constrained applied to private type
2346
2347          if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
2348             Check_Restriction (No_Obsolescent_Features, N);
2349
2350             if Warn_On_Obsolescent_Feature then
2351                Error_Msg_N
2352                  ("constrained for private type is an " &
2353                   "obsolescent feature ('R'M 'J.4)?", N);
2354             end if;
2355
2356             --  If we are within an instance, the attribute must be legal
2357             --  because it was valid in the generic unit. Ditto if this is
2358             --  an inlining of a function declared in an instance.
2359
2360             if In_Instance
2361               or else In_Inlined_Body
2362             then
2363                return;
2364
2365             --  For sure OK if we have a real private type itself, but must
2366             --  be completed, cannot apply Constrained to incomplete type.
2367
2368             elsif Is_Private_Type (Entity (P)) then
2369
2370                --  Note: this is one of the Annex J features that does not
2371                --  generate a warning from -gnatwj, since in fact it seems
2372                --  very useful, and is used in the GNAT runtime.
2373
2374                Check_Not_Incomplete_Type;
2375                return;
2376             end if;
2377
2378          --  Normal (non-obsolescent case) of application to object of
2379          --  a discriminated type.
2380
2381          else
2382             Check_Object_Reference (P);
2383
2384             --  If N does not come from source, then we allow the
2385             --  the attribute prefix to be of a private type whose
2386             --  full type has discriminants. This occurs in cases
2387             --  involving expanded calls to stream attributes.
2388
2389             if not Comes_From_Source (N) then
2390                P_Type := Underlying_Type (P_Type);
2391             end if;
2392
2393             --  Must have discriminants or be an access type designating
2394             --  a type with discriminants. If it is a classwide type is
2395             --  has unknown discriminants.
2396
2397             if Has_Discriminants (P_Type)
2398                or else Has_Unknown_Discriminants (P_Type)
2399                or else
2400                  (Is_Access_Type (P_Type)
2401                    and then Has_Discriminants (Designated_Type (P_Type)))
2402             then
2403                return;
2404
2405             --  Also allow an object of a generic type if extensions allowed
2406             --  and allow this for any type at all.
2407
2408             elsif (Is_Generic_Type (P_Type)
2409                      or else Is_Generic_Actual_Type (P_Type))
2410               and then Extensions_Allowed
2411             then
2412                return;
2413             end if;
2414          end if;
2415
2416          --  Fall through if bad prefix
2417
2418          Error_Attr
2419            ("prefix of % attribute must be object of discriminated type", P);
2420
2421       ---------------
2422       -- Copy_Sign --
2423       ---------------
2424
2425       when Attribute_Copy_Sign =>
2426          Check_Floating_Point_Type_2;
2427          Set_Etype (N, P_Base_Type);
2428          Resolve (E1, P_Base_Type);
2429          Resolve (E2, P_Base_Type);
2430
2431       -----------
2432       -- Count --
2433       -----------
2434
2435       when Attribute_Count => Count :
2436       declare
2437          Ent : Entity_Id;
2438          S   : Entity_Id;
2439          Tsk : Entity_Id;
2440
2441       begin
2442          Check_E0;
2443
2444          if Nkind (P) = N_Identifier
2445            or else Nkind (P) = N_Expanded_Name
2446          then
2447             Ent := Entity (P);
2448
2449             if Ekind (Ent) /= E_Entry then
2450                Error_Attr ("invalid entry name", N);
2451             end if;
2452
2453          elsif Nkind (P) = N_Indexed_Component then
2454             if not Is_Entity_Name (Prefix (P))
2455               or else  No (Entity (Prefix (P)))
2456               or else Ekind (Entity (Prefix (P))) /= E_Entry_Family
2457             then
2458                if Nkind (Prefix (P)) = N_Selected_Component
2459                  and then Present (Entity (Selector_Name (Prefix (P))))
2460                  and then Ekind (Entity (Selector_Name (Prefix (P)))) =
2461                                                              E_Entry_Family
2462                then
2463                   Error_Attr
2464                     ("attribute % must apply to entry of current task", P);
2465
2466                else
2467                   Error_Attr ("invalid entry family name", P);
2468                end if;
2469                return;
2470
2471             else
2472                Ent := Entity (Prefix (P));
2473             end if;
2474
2475          elsif Nkind (P) = N_Selected_Component
2476            and then Present (Entity (Selector_Name (P)))
2477            and then Ekind (Entity (Selector_Name (P))) = E_Entry
2478          then
2479             Error_Attr
2480               ("attribute % must apply to entry of current task", P);
2481
2482          else
2483             Error_Attr ("invalid entry name", N);
2484             return;
2485          end if;
2486
2487          for J in reverse 0 .. Scope_Stack.Last loop
2488             S := Scope_Stack.Table (J).Entity;
2489
2490             if S = Scope (Ent) then
2491                if Nkind (P) = N_Expanded_Name then
2492                   Tsk := Entity (Prefix (P));
2493
2494                   --  The prefix denotes either the task type, or else a
2495                   --  single task whose task type is being analyzed.
2496
2497                   if (Is_Type (Tsk)
2498                       and then Tsk = S)
2499
2500                     or else (not Is_Type (Tsk)
2501                       and then Etype (Tsk) = S
2502                       and then not (Comes_From_Source (S)))
2503                   then
2504                      null;
2505                   else
2506                      Error_Attr
2507                        ("Attribute % must apply to entry of current task", N);
2508                   end if;
2509                end if;
2510
2511                exit;
2512
2513             elsif Ekind (Scope (Ent)) in Task_Kind
2514               and then Ekind (S) /= E_Loop
2515               and then Ekind (S) /= E_Block
2516               and then Ekind (S) /= E_Entry
2517               and then Ekind (S) /= E_Entry_Family
2518             then
2519                Error_Attr ("Attribute % cannot appear in inner unit", N);
2520
2521             elsif Ekind (Scope (Ent)) = E_Protected_Type
2522               and then not Has_Completion (Scope (Ent))
2523             then
2524                Error_Attr ("attribute % can only be used inside body", N);
2525             end if;
2526          end loop;
2527
2528          if Is_Overloaded (P) then
2529             declare
2530                Index : Interp_Index;
2531                It    : Interp;
2532
2533             begin
2534                Get_First_Interp (P, Index, It);
2535
2536                while Present (It.Nam) loop
2537                   if It.Nam = Ent then
2538                      null;
2539
2540                   --  Ada 2005 (AI-345): Do not consider primitive entry
2541                   --  wrappers generated for task or protected types.
2542
2543                   elsif Ada_Version >= Ada_05
2544                     and then not Comes_From_Source (It.Nam)
2545                   then
2546                      null;
2547
2548                   else
2549                      Error_Attr ("ambiguous entry name", N);
2550                   end if;
2551
2552                   Get_Next_Interp (Index, It);
2553                end loop;
2554             end;
2555          end if;
2556
2557          Set_Etype (N, Universal_Integer);
2558       end Count;
2559
2560       -----------------------
2561       -- Default_Bit_Order --
2562       -----------------------
2563
2564       when Attribute_Default_Bit_Order => Default_Bit_Order :
2565       begin
2566          Check_Standard_Prefix;
2567          Check_E0;
2568
2569          if Bytes_Big_Endian then
2570             Rewrite (N,
2571               Make_Integer_Literal (Loc, False_Value));
2572          else
2573             Rewrite (N,
2574               Make_Integer_Literal (Loc, True_Value));
2575          end if;
2576
2577          Set_Etype (N, Universal_Integer);
2578          Set_Is_Static_Expression (N);
2579       end Default_Bit_Order;
2580
2581       --------------
2582       -- Definite --
2583       --------------
2584
2585       when Attribute_Definite =>
2586          Legal_Formal_Attribute;
2587
2588       -----------
2589       -- Delta --
2590       -----------
2591
2592       when Attribute_Delta =>
2593          Check_Fixed_Point_Type_0;
2594          Set_Etype (N, Universal_Real);
2595
2596       ------------
2597       -- Denorm --
2598       ------------
2599
2600       when Attribute_Denorm =>
2601          Check_Floating_Point_Type_0;
2602          Set_Etype (N, Standard_Boolean);
2603
2604       ------------
2605       -- Digits --
2606       ------------
2607
2608       when Attribute_Digits =>
2609          Check_E0;
2610          Check_Type;
2611
2612          if not Is_Floating_Point_Type (P_Type)
2613            and then not Is_Decimal_Fixed_Point_Type (P_Type)
2614          then
2615             Error_Attr
2616               ("prefix of % attribute must be float or decimal type", P);
2617          end if;
2618
2619          Set_Etype (N, Universal_Integer);
2620
2621       ---------------
2622       -- Elab_Body --
2623       ---------------
2624
2625       --  Also handles processing for Elab_Spec
2626
2627       when Attribute_Elab_Body | Attribute_Elab_Spec =>
2628          Check_E0;
2629          Check_Unit_Name (P);
2630          Set_Etype (N, Standard_Void_Type);
2631
2632          --  We have to manually call the expander in this case to get
2633          --  the necessary expansion (normally attributes that return
2634          --  entities are not expanded).
2635
2636          Expand (N);
2637
2638       ---------------
2639       -- Elab_Spec --
2640       ---------------
2641
2642       --  Shares processing with Elab_Body
2643
2644       ----------------
2645       -- Elaborated --
2646       ----------------
2647
2648       when Attribute_Elaborated =>
2649          Check_E0;
2650          Check_Library_Unit;
2651          Set_Etype (N, Standard_Boolean);
2652
2653       ----------
2654       -- Emax --
2655       ----------
2656
2657       when Attribute_Emax =>
2658          Check_Floating_Point_Type_0;
2659          Set_Etype (N, Universal_Integer);
2660
2661       --------------
2662       -- Enum_Rep --
2663       --------------
2664
2665       when Attribute_Enum_Rep => Enum_Rep : declare
2666       begin
2667          if Present (E1) then
2668             Check_E1;
2669             Check_Discrete_Type;
2670             Resolve (E1, P_Base_Type);
2671
2672          else
2673             if not Is_Entity_Name (P)
2674               or else (not Is_Object (Entity (P))
2675                          and then
2676                        Ekind (Entity (P)) /= E_Enumeration_Literal)
2677             then
2678                Error_Attr
2679                  ("prefix of %attribute must be " &
2680                   "discrete type/object or enum literal", P);
2681             end if;
2682          end if;
2683
2684          Set_Etype (N, Universal_Integer);
2685       end Enum_Rep;
2686
2687       -------------
2688       -- Epsilon --
2689       -------------
2690
2691       when Attribute_Epsilon =>
2692          Check_Floating_Point_Type_0;
2693          Set_Etype (N, Universal_Real);
2694
2695       --------------
2696       -- Exponent --
2697       --------------
2698
2699       when Attribute_Exponent =>
2700          Check_Floating_Point_Type_1;
2701          Set_Etype (N, Universal_Integer);
2702          Resolve (E1, P_Base_Type);
2703
2704       ------------------
2705       -- External_Tag --
2706       ------------------
2707
2708       when Attribute_External_Tag =>
2709          Check_E0;
2710          Check_Type;
2711
2712          Set_Etype (N, Standard_String);
2713
2714          if not Is_Tagged_Type (P_Type) then
2715             Error_Attr ("prefix of % attribute must be tagged", P);
2716          end if;
2717
2718       -----------
2719       -- First --
2720       -----------
2721
2722       when Attribute_First =>
2723          Check_Array_Or_Scalar_Type;
2724
2725       ---------------
2726       -- First_Bit --
2727       ---------------
2728
2729       when Attribute_First_Bit =>
2730          Check_Component;
2731          Set_Etype (N, Universal_Integer);
2732
2733       -----------------
2734       -- Fixed_Value --
2735       -----------------
2736
2737       when Attribute_Fixed_Value =>
2738          Check_E1;
2739          Check_Fixed_Point_Type;
2740          Resolve (E1, Any_Integer);
2741          Set_Etype (N, P_Base_Type);
2742
2743       -----------
2744       -- Floor --
2745       -----------
2746
2747       when Attribute_Floor =>
2748          Check_Floating_Point_Type_1;
2749          Set_Etype (N, P_Base_Type);
2750          Resolve (E1, P_Base_Type);
2751
2752       ----------
2753       -- Fore --
2754       ----------
2755
2756       when Attribute_Fore =>
2757          Check_Fixed_Point_Type_0;
2758          Set_Etype (N, Universal_Integer);
2759
2760       --------------
2761       -- Fraction --
2762       --------------
2763
2764       when Attribute_Fraction =>
2765          Check_Floating_Point_Type_1;
2766          Set_Etype (N, P_Base_Type);
2767          Resolve (E1, P_Base_Type);
2768
2769       -----------------------
2770       -- Has_Access_Values --
2771       -----------------------
2772
2773       when Attribute_Has_Access_Values =>
2774          Check_Type;
2775          Check_E0;
2776          Set_Etype (N, Standard_Boolean);
2777
2778       -----------------------
2779       -- Has_Discriminants --
2780       -----------------------
2781
2782       when Attribute_Has_Discriminants =>
2783          Legal_Formal_Attribute;
2784
2785       --------------
2786       -- Identity --
2787       --------------
2788
2789       when Attribute_Identity =>
2790          Check_E0;
2791          Analyze (P);
2792
2793          if Etype (P) =  Standard_Exception_Type then
2794             Set_Etype (N, RTE (RE_Exception_Id));
2795
2796          elsif Is_Task_Type (Etype (P))
2797            or else (Is_Access_Type (Etype (P))
2798               and then Is_Task_Type (Designated_Type (Etype (P))))
2799          then
2800             Resolve (P);
2801             Set_Etype (N, RTE (RO_AT_Task_Id));
2802
2803          else
2804             Error_Attr ("prefix of % attribute must be a task or an "
2805               & "exception", P);
2806          end if;
2807
2808       -----------
2809       -- Image --
2810       -----------
2811
2812       when Attribute_Image => Image :
2813       begin
2814          Set_Etype (N, Standard_String);
2815          Check_Scalar_Type;
2816
2817          if Is_Real_Type (P_Type) then
2818             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
2819                Error_Msg_Name_1 := Aname;
2820                Error_Msg_N
2821                  ("(Ada 83) % attribute not allowed for real types", N);
2822             end if;
2823          end if;
2824
2825          if Is_Enumeration_Type (P_Type) then
2826             Check_Restriction (No_Enumeration_Maps, N);
2827          end if;
2828
2829          Check_E1;
2830          Resolve (E1, P_Base_Type);
2831          Check_Enum_Image;
2832          Validate_Non_Static_Attribute_Function_Call;
2833       end Image;
2834
2835       ---------
2836       -- Img --
2837       ---------
2838
2839       when Attribute_Img => Img :
2840       begin
2841          Set_Etype (N, Standard_String);
2842
2843          if not Is_Scalar_Type (P_Type)
2844            or else (Is_Entity_Name (P) and then Is_Type (Entity (P)))
2845          then
2846             Error_Attr
2847               ("prefix of % attribute must be scalar object name", N);
2848          end if;
2849
2850          Check_Enum_Image;
2851       end Img;
2852
2853       -----------
2854       -- Input --
2855       -----------
2856
2857       when Attribute_Input =>
2858          Check_E1;
2859          Check_Stream_Attribute (TSS_Stream_Input);
2860          Set_Etype (N, P_Base_Type);
2861
2862       -------------------
2863       -- Integer_Value --
2864       -------------------
2865
2866       when Attribute_Integer_Value =>
2867          Check_E1;
2868          Check_Integer_Type;
2869          Resolve (E1, Any_Fixed);
2870          Set_Etype (N, P_Base_Type);
2871
2872       -----------
2873       -- Large --
2874       -----------
2875
2876       when Attribute_Large =>
2877          Check_E0;
2878          Check_Real_Type;
2879          Set_Etype (N, Universal_Real);
2880
2881       ----------
2882       -- Last --
2883       ----------
2884
2885       when Attribute_Last =>
2886          Check_Array_Or_Scalar_Type;
2887
2888       --------------
2889       -- Last_Bit --
2890       --------------
2891
2892       when Attribute_Last_Bit =>
2893          Check_Component;
2894          Set_Etype (N, Universal_Integer);
2895
2896       ------------------
2897       -- Leading_Part --
2898       ------------------
2899
2900       when Attribute_Leading_Part =>
2901          Check_Floating_Point_Type_2;
2902          Set_Etype (N, P_Base_Type);
2903          Resolve (E1, P_Base_Type);
2904          Resolve (E2, Any_Integer);
2905
2906       ------------
2907       -- Length --
2908       ------------
2909
2910       when Attribute_Length =>
2911          Check_Array_Type;
2912          Set_Etype (N, Universal_Integer);
2913
2914       -------------
2915       -- Machine --
2916       -------------
2917
2918       when Attribute_Machine =>
2919          Check_Floating_Point_Type_1;
2920          Set_Etype (N, P_Base_Type);
2921          Resolve (E1, P_Base_Type);
2922
2923       ------------------
2924       -- Machine_Emax --
2925       ------------------
2926
2927       when Attribute_Machine_Emax =>
2928          Check_Floating_Point_Type_0;
2929          Set_Etype (N, Universal_Integer);
2930
2931       ------------------
2932       -- Machine_Emin --
2933       ------------------
2934
2935       when Attribute_Machine_Emin =>
2936          Check_Floating_Point_Type_0;
2937          Set_Etype (N, Universal_Integer);
2938
2939       ----------------------
2940       -- Machine_Mantissa --
2941       ----------------------
2942
2943       when Attribute_Machine_Mantissa =>
2944          Check_Floating_Point_Type_0;
2945          Set_Etype (N, Universal_Integer);
2946
2947       -----------------------
2948       -- Machine_Overflows --
2949       -----------------------
2950
2951       when Attribute_Machine_Overflows =>
2952          Check_Real_Type;
2953          Check_E0;
2954          Set_Etype (N, Standard_Boolean);
2955
2956       -------------------
2957       -- Machine_Radix --
2958       -------------------
2959
2960       when Attribute_Machine_Radix =>
2961          Check_Real_Type;
2962          Check_E0;
2963          Set_Etype (N, Universal_Integer);
2964
2965       --------------------
2966       -- Machine_Rounds --
2967       --------------------
2968
2969       when Attribute_Machine_Rounds =>
2970          Check_Real_Type;
2971          Check_E0;
2972          Set_Etype (N, Standard_Boolean);
2973
2974       ------------------
2975       -- Machine_Size --
2976       ------------------
2977
2978       when Attribute_Machine_Size =>
2979          Check_E0;
2980          Check_Type;
2981          Check_Not_Incomplete_Type;
2982          Set_Etype (N, Universal_Integer);
2983
2984       --------------
2985       -- Mantissa --
2986       --------------
2987
2988       when Attribute_Mantissa =>
2989          Check_E0;
2990          Check_Real_Type;
2991          Set_Etype (N, Universal_Integer);
2992
2993       ---------
2994       -- Max --
2995       ---------
2996
2997       when Attribute_Max =>
2998          Check_E2;
2999          Check_Scalar_Type;
3000          Resolve (E1, P_Base_Type);
3001          Resolve (E2, P_Base_Type);
3002          Set_Etype (N, P_Base_Type);
3003
3004       ----------------------------------
3005       -- Max_Size_In_Storage_Elements --
3006       ----------------------------------
3007
3008       when Attribute_Max_Size_In_Storage_Elements =>
3009          Check_E0;
3010          Check_Type;
3011          Check_Not_Incomplete_Type;
3012          Set_Etype (N, Universal_Integer);
3013
3014       -----------------------
3015       -- Maximum_Alignment --
3016       -----------------------
3017
3018       when Attribute_Maximum_Alignment =>
3019          Standard_Attribute (Ttypes.Maximum_Alignment);
3020
3021       --------------------
3022       -- Mechanism_Code --
3023       --------------------
3024
3025       when Attribute_Mechanism_Code =>
3026          if not Is_Entity_Name (P)
3027            or else not Is_Subprogram (Entity (P))
3028          then
3029             Error_Attr ("prefix of % attribute must be subprogram", P);
3030          end if;
3031
3032          Check_Either_E0_Or_E1;
3033
3034          if Present (E1) then
3035             Resolve (E1, Any_Integer);
3036             Set_Etype (E1, Standard_Integer);
3037
3038             if not Is_Static_Expression (E1) then
3039                Flag_Non_Static_Expr
3040                  ("expression for parameter number must be static!", E1);
3041                Error_Attr;
3042
3043             elsif UI_To_Int (Intval (E1)) > Number_Formals (Entity (P))
3044               or else UI_To_Int (Intval (E1)) < 0
3045             then
3046                Error_Attr ("invalid parameter number for %attribute", E1);
3047             end if;
3048          end if;
3049
3050          Set_Etype (N, Universal_Integer);
3051
3052       ---------
3053       -- Min --
3054       ---------
3055
3056       when Attribute_Min =>
3057          Check_E2;
3058          Check_Scalar_Type;
3059          Resolve (E1, P_Base_Type);
3060          Resolve (E2, P_Base_Type);
3061          Set_Etype (N, P_Base_Type);
3062
3063       ---------
3064       -- Mod --
3065       ---------
3066
3067       when Attribute_Mod =>
3068
3069          --  Note: this attribute is only allowed in Ada 2005 mode, but
3070          --  we do not need to test that here, since Mod is only recognized
3071          --  as an attribute name in Ada 2005 mode during the parse.
3072
3073          Check_E1;
3074          Check_Modular_Integer_Type;
3075          Resolve (E1, Any_Integer);
3076          Set_Etype (N, P_Base_Type);
3077
3078       -----------
3079       -- Model --
3080       -----------
3081
3082       when Attribute_Model =>
3083          Check_Floating_Point_Type_1;
3084          Set_Etype (N, P_Base_Type);
3085          Resolve (E1, P_Base_Type);
3086
3087       ----------------
3088       -- Model_Emin --
3089       ----------------
3090
3091       when Attribute_Model_Emin =>
3092          Check_Floating_Point_Type_0;
3093          Set_Etype (N, Universal_Integer);
3094
3095       -------------------
3096       -- Model_Epsilon --
3097       -------------------
3098
3099       when Attribute_Model_Epsilon =>
3100          Check_Floating_Point_Type_0;
3101          Set_Etype (N, Universal_Real);
3102
3103       --------------------
3104       -- Model_Mantissa --
3105       --------------------
3106
3107       when Attribute_Model_Mantissa =>
3108          Check_Floating_Point_Type_0;
3109          Set_Etype (N, Universal_Integer);
3110
3111       -----------------
3112       -- Model_Small --
3113       -----------------
3114
3115       when Attribute_Model_Small =>
3116          Check_Floating_Point_Type_0;
3117          Set_Etype (N, Universal_Real);
3118
3119       -------------
3120       -- Modulus --
3121       -------------
3122
3123       when Attribute_Modulus =>
3124          Check_E0;
3125          Check_Modular_Integer_Type;
3126          Set_Etype (N, Universal_Integer);
3127
3128       --------------------
3129       -- Null_Parameter --
3130       --------------------
3131
3132       when Attribute_Null_Parameter => Null_Parameter : declare
3133          Parnt  : constant Node_Id := Parent (N);
3134          GParnt : constant Node_Id := Parent (Parnt);
3135
3136          procedure Bad_Null_Parameter (Msg : String);
3137          --  Used if bad Null parameter attribute node is found. Issues
3138          --  given error message, and also sets the type to Any_Type to
3139          --  avoid blowups later on from dealing with a junk node.
3140
3141          procedure Must_Be_Imported (Proc_Ent : Entity_Id);
3142          --  Called to check that Proc_Ent is imported subprogram
3143
3144          ------------------------
3145          -- Bad_Null_Parameter --
3146          ------------------------
3147
3148          procedure Bad_Null_Parameter (Msg : String) is
3149          begin
3150             Error_Msg_N (Msg, N);
3151             Set_Etype (N, Any_Type);
3152          end Bad_Null_Parameter;
3153
3154          ----------------------
3155          -- Must_Be_Imported --
3156          ----------------------
3157
3158          procedure Must_Be_Imported (Proc_Ent : Entity_Id) is
3159             Pent : Entity_Id := Proc_Ent;
3160
3161          begin
3162             while Present (Alias (Pent)) loop
3163                Pent := Alias (Pent);
3164             end loop;
3165
3166             --  Ignore check if procedure not frozen yet (we will get
3167             --  another chance when the default parameter is reanalyzed)
3168
3169             if not Is_Frozen (Pent) then
3170                return;
3171
3172             elsif not Is_Imported (Pent) then
3173                Bad_Null_Parameter
3174                  ("Null_Parameter can only be used with imported subprogram");
3175
3176             else
3177                return;
3178             end if;
3179          end Must_Be_Imported;
3180
3181       --  Start of processing for Null_Parameter
3182
3183       begin
3184          Check_Type;
3185          Check_E0;
3186          Set_Etype (N, P_Type);
3187
3188          --  Case of attribute used as default expression
3189
3190          if Nkind (Parnt) = N_Parameter_Specification then
3191             Must_Be_Imported (Defining_Entity (GParnt));
3192
3193          --  Case of attribute used as actual for subprogram (positional)
3194
3195          elsif (Nkind (Parnt) = N_Procedure_Call_Statement
3196                  or else
3197                 Nkind (Parnt) = N_Function_Call)
3198             and then Is_Entity_Name (Name (Parnt))
3199          then
3200             Must_Be_Imported (Entity (Name (Parnt)));
3201
3202          --  Case of attribute used as actual for subprogram (named)
3203
3204          elsif Nkind (Parnt) = N_Parameter_Association
3205            and then (Nkind (GParnt) = N_Procedure_Call_Statement
3206                        or else
3207                      Nkind (GParnt) = N_Function_Call)
3208            and then Is_Entity_Name (Name (GParnt))
3209          then
3210             Must_Be_Imported (Entity (Name (GParnt)));
3211
3212          --  Not an allowed case
3213
3214          else
3215             Bad_Null_Parameter
3216               ("Null_Parameter must be actual or default parameter");
3217          end if;
3218
3219       end Null_Parameter;
3220
3221       -----------------
3222       -- Object_Size --
3223       -----------------
3224
3225       when Attribute_Object_Size =>
3226          Check_E0;
3227          Check_Type;
3228          Check_Not_Incomplete_Type;
3229          Set_Etype (N, Universal_Integer);
3230
3231       ------------
3232       -- Output --
3233       ------------
3234
3235       when Attribute_Output =>
3236          Check_E2;
3237          Check_Stream_Attribute (TSS_Stream_Output);
3238          Set_Etype (N, Standard_Void_Type);
3239          Resolve (N, Standard_Void_Type);
3240
3241       ------------------
3242       -- Partition_ID --
3243       ------------------
3244
3245       when Attribute_Partition_ID =>
3246          Check_E0;
3247
3248          if P_Type /= Any_Type then
3249             if not Is_Library_Level_Entity (Entity (P)) then
3250                Error_Attr
3251                  ("prefix of % attribute must be library-level entity", P);
3252
3253             --  The defining entity of prefix should not be declared inside
3254             --  a Pure unit. RM E.1(8).
3255             --  The Is_Pure flag has been set during declaration.
3256
3257             elsif Is_Entity_Name (P)
3258               and then Is_Pure (Entity (P))
3259             then
3260                Error_Attr
3261                  ("prefix of % attribute must not be declared pure", P);
3262             end if;
3263          end if;
3264
3265          Set_Etype (N, Universal_Integer);
3266
3267       -------------------------
3268       -- Passed_By_Reference --
3269       -------------------------
3270
3271       when Attribute_Passed_By_Reference =>
3272          Check_E0;
3273          Check_Type;
3274          Set_Etype (N, Standard_Boolean);
3275
3276       ------------------
3277       -- Pool_Address --
3278       ------------------
3279
3280       when Attribute_Pool_Address =>
3281          Check_E0;
3282          Set_Etype (N, RTE (RE_Address));
3283
3284       ---------
3285       -- Pos --
3286       ---------
3287
3288       when Attribute_Pos =>
3289          Check_Discrete_Type;
3290          Check_E1;
3291          Resolve (E1, P_Base_Type);
3292          Set_Etype (N, Universal_Integer);
3293
3294       --------------
3295       -- Position --
3296       --------------
3297
3298       when Attribute_Position =>
3299          Check_Component;
3300          Set_Etype (N, Universal_Integer);
3301
3302       ----------
3303       -- Pred --
3304       ----------
3305
3306       when Attribute_Pred =>
3307          Check_Scalar_Type;
3308          Check_E1;
3309          Resolve (E1, P_Base_Type);
3310          Set_Etype (N, P_Base_Type);
3311
3312          --  Nothing to do for real type case
3313
3314          if Is_Real_Type (P_Type) then
3315             null;
3316
3317          --  If not modular type, test for overflow check required
3318
3319          else
3320             if not Is_Modular_Integer_Type (P_Type)
3321               and then not Range_Checks_Suppressed (P_Base_Type)
3322             then
3323                Enable_Range_Check (E1);
3324             end if;
3325          end if;
3326
3327       -----------
3328       -- Range --
3329       -----------
3330
3331       when Attribute_Range =>
3332          Check_Array_Or_Scalar_Type;
3333
3334          if Ada_Version = Ada_83
3335            and then Is_Scalar_Type (P_Type)
3336            and then Comes_From_Source (N)
3337          then
3338             Error_Attr
3339               ("(Ada 83) % attribute not allowed for scalar type", P);
3340          end if;
3341
3342       ------------------
3343       -- Range_Length --
3344       ------------------
3345
3346       when Attribute_Range_Length =>
3347          Check_Discrete_Type;
3348          Set_Etype (N, Universal_Integer);
3349
3350       ----------
3351       -- Read --
3352       ----------
3353
3354       when Attribute_Read =>
3355          Check_E2;
3356          Check_Stream_Attribute (TSS_Stream_Read);
3357          Set_Etype (N, Standard_Void_Type);
3358          Resolve (N, Standard_Void_Type);
3359          Note_Possible_Modification (E2);
3360
3361       ---------------
3362       -- Remainder --
3363       ---------------
3364
3365       when Attribute_Remainder =>
3366          Check_Floating_Point_Type_2;
3367          Set_Etype (N, P_Base_Type);
3368          Resolve (E1, P_Base_Type);
3369          Resolve (E2, P_Base_Type);
3370
3371       -----------
3372       -- Round --
3373       -----------
3374
3375       when Attribute_Round =>
3376          Check_E1;
3377          Check_Decimal_Fixed_Point_Type;
3378          Set_Etype (N, P_Base_Type);
3379
3380          --  Because the context is universal_real (3.5.10(12)) it is a legal
3381          --  context for a universal fixed expression. This is the only
3382          --  attribute whose functional description involves U_R.
3383
3384          if Etype (E1) = Universal_Fixed then
3385             declare
3386                Conv : constant Node_Id := Make_Type_Conversion (Loc,
3387                   Subtype_Mark => New_Occurrence_Of (Universal_Real, Loc),
3388                   Expression   => Relocate_Node (E1));
3389
3390             begin
3391                Rewrite (E1, Conv);
3392                Analyze (E1);
3393             end;
3394          end if;
3395
3396          Resolve (E1, Any_Real);
3397
3398       --------------
3399       -- Rounding --
3400       --------------
3401
3402       when Attribute_Rounding =>
3403          Check_Floating_Point_Type_1;
3404          Set_Etype (N, P_Base_Type);
3405          Resolve (E1, P_Base_Type);
3406
3407       ---------------
3408       -- Safe_Emax --
3409       ---------------
3410
3411       when Attribute_Safe_Emax =>
3412          Check_Floating_Point_Type_0;
3413          Set_Etype (N, Universal_Integer);
3414
3415       ----------------
3416       -- Safe_First --
3417       ----------------
3418
3419       when Attribute_Safe_First =>
3420          Check_Floating_Point_Type_0;
3421          Set_Etype (N, Universal_Real);
3422
3423       ----------------
3424       -- Safe_Large --
3425       ----------------
3426
3427       when Attribute_Safe_Large =>
3428          Check_E0;
3429          Check_Real_Type;
3430          Set_Etype (N, Universal_Real);
3431
3432       ---------------
3433       -- Safe_Last --
3434       ---------------
3435
3436       when Attribute_Safe_Last =>
3437          Check_Floating_Point_Type_0;
3438          Set_Etype (N, Universal_Real);
3439
3440       ----------------
3441       -- Safe_Small --
3442       ----------------
3443
3444       when Attribute_Safe_Small =>
3445          Check_E0;
3446          Check_Real_Type;
3447          Set_Etype (N, Universal_Real);
3448
3449       -----------
3450       -- Scale --
3451       -----------
3452
3453       when Attribute_Scale =>
3454          Check_E0;
3455          Check_Decimal_Fixed_Point_Type;
3456          Set_Etype (N, Universal_Integer);
3457
3458       -------------
3459       -- Scaling --
3460       -------------
3461
3462       when Attribute_Scaling =>
3463          Check_Floating_Point_Type_2;
3464          Set_Etype (N, P_Base_Type);
3465          Resolve (E1, P_Base_Type);
3466
3467       ------------------
3468       -- Signed_Zeros --
3469       ------------------
3470
3471       when Attribute_Signed_Zeros =>
3472          Check_Floating_Point_Type_0;
3473          Set_Etype (N, Standard_Boolean);
3474
3475       ----------
3476       -- Size --
3477       ----------
3478
3479       when Attribute_Size | Attribute_VADS_Size =>
3480          Check_E0;
3481
3482          --  If prefix is parameterless function call, rewrite and resolve
3483          --  as such.
3484
3485          if Is_Entity_Name (P)
3486            and then Ekind (Entity (P)) = E_Function
3487          then
3488             Resolve (P);
3489
3490          --  Similar processing for a protected function call
3491
3492          elsif Nkind (P) = N_Selected_Component
3493            and then Ekind (Entity (Selector_Name (P))) = E_Function
3494          then
3495             Resolve (P);
3496          end if;
3497
3498          if Is_Object_Reference (P) then
3499             Check_Object_Reference (P);
3500
3501          elsif Is_Entity_Name (P)
3502            and then (Is_Type (Entity (P))
3503                        or else Ekind (Entity (P)) = E_Enumeration_Literal)
3504          then
3505             null;
3506
3507          elsif Nkind (P) = N_Type_Conversion
3508            and then not Comes_From_Source (P)
3509          then
3510             null;
3511
3512          else
3513             Error_Attr ("invalid prefix for % attribute", P);
3514          end if;
3515
3516          Check_Not_Incomplete_Type;
3517          Set_Etype (N, Universal_Integer);
3518
3519       -----------
3520       -- Small --
3521       -----------
3522
3523       when Attribute_Small =>
3524          Check_E0;
3525          Check_Real_Type;
3526          Set_Etype (N, Universal_Real);
3527
3528       ------------------
3529       -- Storage_Pool --
3530       ------------------
3531
3532       when Attribute_Storage_Pool =>
3533          if Is_Access_Type (P_Type) then
3534             Check_E0;
3535
3536             --  Set appropriate entity
3537
3538             if Present (Associated_Storage_Pool (Root_Type (P_Type))) then
3539                Set_Entity (N, Associated_Storage_Pool (Root_Type (P_Type)));
3540             else
3541                Set_Entity (N, RTE (RE_Global_Pool_Object));
3542             end if;
3543
3544             Set_Etype (N, Class_Wide_Type (RTE (RE_Root_Storage_Pool)));
3545
3546             --  Validate_Remote_Access_To_Class_Wide_Type for attribute
3547             --  Storage_Pool since this attribute is not defined for such
3548             --  types (RM E.2.3(22)).
3549
3550             Validate_Remote_Access_To_Class_Wide_Type (N);
3551
3552          else
3553             Error_Attr ("prefix of % attribute must be access type", P);
3554          end if;
3555
3556       ------------------
3557       -- Storage_Size --
3558       ------------------
3559
3560       when Attribute_Storage_Size =>
3561
3562          if Is_Task_Type (P_Type) then
3563             Check_E0;
3564             Set_Etype (N, Universal_Integer);
3565
3566          elsif Is_Access_Type (P_Type) then
3567             if Is_Entity_Name (P)
3568               and then Is_Type (Entity (P))
3569             then
3570                Check_E0;
3571                Check_Type;
3572                Set_Etype (N, Universal_Integer);
3573
3574                --   Validate_Remote_Access_To_Class_Wide_Type for attribute
3575                --   Storage_Size since this attribute is not defined for
3576                --   such types (RM E.2.3(22)).
3577
3578                Validate_Remote_Access_To_Class_Wide_Type (N);
3579
3580             --  The prefix is allowed to be an implicit dereference
3581             --  of an access value designating a task.
3582
3583             else
3584                Check_E0;
3585                Check_Task_Prefix;
3586                Set_Etype (N, Universal_Integer);
3587             end if;
3588
3589          else
3590             Error_Attr
3591               ("prefix of % attribute must be access or task type", P);
3592          end if;
3593
3594       ------------------
3595       -- Storage_Unit --
3596       ------------------
3597
3598       when Attribute_Storage_Unit =>
3599          Standard_Attribute (Ttypes.System_Storage_Unit);
3600
3601       -----------------
3602       -- Stream_Size --
3603       -----------------
3604
3605       when Attribute_Stream_Size =>
3606          Check_E0;
3607          Check_Type;
3608
3609          if Is_Entity_Name (P)
3610            and then Is_Elementary_Type (Entity (P))
3611          then
3612             Set_Etype (N, Universal_Integer);
3613          else
3614             Error_Attr ("invalid prefix for % attribute", P);
3615          end if;
3616
3617       ----------
3618       -- Succ --
3619       ----------
3620
3621       when Attribute_Succ =>
3622          Check_Scalar_Type;
3623          Check_E1;
3624          Resolve (E1, P_Base_Type);
3625          Set_Etype (N, P_Base_Type);
3626
3627          --  Nothing to do for real type case
3628
3629          if Is_Real_Type (P_Type) then
3630             null;
3631
3632          --  If not modular type, test for overflow check required
3633
3634          else
3635             if not Is_Modular_Integer_Type (P_Type)
3636               and then not Range_Checks_Suppressed (P_Base_Type)
3637             then
3638                Enable_Range_Check (E1);
3639             end if;
3640          end if;
3641
3642       ---------
3643       -- Tag --
3644       ---------
3645
3646       when Attribute_Tag =>
3647          Check_E0;
3648          Check_Dereference;
3649
3650          if not Is_Tagged_Type (P_Type) then
3651             Error_Attr ("prefix of % attribute must be tagged", P);
3652
3653          --  Next test does not apply to generated code
3654          --  why not, and what does the illegal reference mean???
3655
3656          elsif Is_Object_Reference (P)
3657            and then not Is_Class_Wide_Type (P_Type)
3658            and then Comes_From_Source (N)
3659          then
3660             Error_Attr
3661               ("% attribute can only be applied to objects of class-wide type",
3662                P);
3663          end if;
3664
3665          Set_Etype (N, RTE (RE_Tag));
3666
3667       -----------------
3668       -- Target_Name --
3669       -----------------
3670
3671       when Attribute_Target_Name => Target_Name : declare
3672          TN : constant String := Sdefault.Target_Name.all;
3673          TL : Natural;
3674
3675       begin
3676          Check_Standard_Prefix;
3677          Check_E0;
3678
3679          TL := TN'Last;
3680
3681          if TN (TL) = '/' or else TN (TL) = '\' then
3682             TL := TL - 1;
3683          end if;
3684
3685          Rewrite (N,
3686            Make_String_Literal (Loc,
3687              Strval => TN (TN'First .. TL)));
3688          Analyze_And_Resolve (N, Standard_String);
3689       end Target_Name;
3690
3691       ----------------
3692       -- Terminated --
3693       ----------------
3694
3695       when Attribute_Terminated =>
3696          Check_E0;
3697          Set_Etype (N, Standard_Boolean);
3698          Check_Task_Prefix;
3699
3700       ----------------
3701       -- To_Address --
3702       ----------------
3703
3704       when Attribute_To_Address =>
3705          Check_E1;
3706          Analyze (P);
3707
3708          if Nkind (P) /= N_Identifier
3709            or else Chars (P) /= Name_System
3710          then
3711             Error_Attr ("prefix of %attribute must be System", P);
3712          end if;
3713
3714          Generate_Reference (RTE (RE_Address), P);
3715          Analyze_And_Resolve (E1, Any_Integer);
3716          Set_Etype (N, RTE (RE_Address));
3717
3718       ----------------
3719       -- Truncation --
3720       ----------------
3721
3722       when Attribute_Truncation =>
3723          Check_Floating_Point_Type_1;
3724          Resolve (E1, P_Base_Type);
3725          Set_Etype (N, P_Base_Type);
3726
3727       ----------------
3728       -- Type_Class --
3729       ----------------
3730
3731       when Attribute_Type_Class =>
3732          Check_E0;
3733          Check_Type;
3734          Check_Not_Incomplete_Type;
3735          Set_Etype (N, RTE (RE_Type_Class));
3736
3737       -----------------
3738       -- UET_Address --
3739       -----------------
3740
3741       when Attribute_UET_Address =>
3742          Check_E0;
3743          Check_Unit_Name (P);
3744          Set_Etype (N, RTE (RE_Address));
3745
3746       -----------------------
3747       -- Unbiased_Rounding --
3748       -----------------------
3749
3750       when Attribute_Unbiased_Rounding =>
3751          Check_Floating_Point_Type_1;
3752          Set_Etype (N, P_Base_Type);
3753          Resolve (E1, P_Base_Type);
3754
3755       ----------------------
3756       -- Unchecked_Access --
3757       ----------------------
3758
3759       when Attribute_Unchecked_Access =>
3760          if Comes_From_Source (N) then
3761             Check_Restriction (No_Unchecked_Access, N);
3762          end if;
3763
3764          Analyze_Access_Attribute;
3765
3766       -------------------------
3767       -- Unconstrained_Array --
3768       -------------------------
3769
3770       when Attribute_Unconstrained_Array =>
3771          Check_E0;
3772          Check_Type;
3773          Check_Not_Incomplete_Type;
3774          Set_Etype (N, Standard_Boolean);
3775
3776       ------------------------------
3777       -- Universal_Literal_String --
3778       ------------------------------
3779
3780       --  This is a GNAT specific attribute whose prefix must be a named
3781       --  number where the expression is either a single numeric literal,
3782       --  or a numeric literal immediately preceded by a minus sign. The
3783       --  result is equivalent to a string literal containing the text of
3784       --  the literal as it appeared in the source program with a possible
3785       --  leading minus sign.
3786
3787       when Attribute_Universal_Literal_String => Universal_Literal_String :
3788       begin
3789          Check_E0;
3790
3791          if not Is_Entity_Name (P)
3792            or else Ekind (Entity (P)) not in Named_Kind
3793          then
3794             Error_Attr ("prefix for % attribute must be named number", P);
3795
3796          else
3797             declare
3798                Expr     : Node_Id;
3799                Negative : Boolean;
3800                S        : Source_Ptr;
3801                Src      : Source_Buffer_Ptr;
3802
3803             begin
3804                Expr := Original_Node (Expression (Parent (Entity (P))));
3805
3806                if Nkind (Expr) = N_Op_Minus then
3807                   Negative := True;
3808                   Expr := Original_Node (Right_Opnd (Expr));
3809                else
3810                   Negative := False;
3811                end if;
3812
3813                if Nkind (Expr) /= N_Integer_Literal
3814                  and then Nkind (Expr) /= N_Real_Literal
3815                then
3816                   Error_Attr
3817                     ("named number for % attribute must be simple literal", N);
3818                end if;
3819
3820                --  Build string literal corresponding to source literal text
3821
3822                Start_String;
3823
3824                if Negative then
3825                   Store_String_Char (Get_Char_Code ('-'));
3826                end if;
3827
3828                S := Sloc (Expr);
3829                Src := Source_Text (Get_Source_File_Index (S));
3830
3831                while Src (S) /= ';' and then Src (S) /= ' ' loop
3832                   Store_String_Char (Get_Char_Code (Src (S)));
3833                   S := S + 1;
3834                end loop;
3835
3836                --  Now we rewrite the attribute with the string literal
3837
3838                Rewrite (N,
3839                  Make_String_Literal (Loc, End_String));
3840                Analyze (N);
3841             end;
3842          end if;
3843       end Universal_Literal_String;
3844
3845       -------------------------
3846       -- Unrestricted_Access --
3847       -------------------------
3848
3849       --  This is a GNAT specific attribute which is like Access except that
3850       --  all scope checks and checks for aliased views are omitted.
3851
3852       when Attribute_Unrestricted_Access =>
3853          if Comes_From_Source (N) then
3854             Check_Restriction (No_Unchecked_Access, N);
3855          end if;
3856
3857          if Is_Entity_Name (P) then
3858             Set_Address_Taken (Entity (P));
3859          end if;
3860
3861          Analyze_Access_Attribute;
3862
3863       ---------
3864       -- Val --
3865       ---------
3866
3867       when Attribute_Val => Val : declare
3868       begin
3869          Check_E1;
3870          Check_Discrete_Type;
3871          Resolve (E1, Any_Integer);
3872          Set_Etype (N, P_Base_Type);
3873
3874          --  Note, we need a range check in general, but we wait for the
3875          --  Resolve call to do this, since we want to let Eval_Attribute
3876          --  have a chance to find an static illegality first!
3877       end Val;
3878
3879       -----------
3880       -- Valid --
3881       -----------
3882
3883       when Attribute_Valid =>
3884          Check_E0;
3885
3886          --  Ignore check for object if we have a 'Valid reference generated
3887          --  by the expanded code, since in some cases valid checks can occur
3888          --  on items that are names, but are not objects (e.g. attributes).
3889
3890          if Comes_From_Source (N) then
3891             Check_Object_Reference (P);
3892          end if;
3893
3894          if not Is_Scalar_Type (P_Type) then
3895             Error_Attr ("object for % attribute must be of scalar type", P);
3896          end if;
3897
3898          Set_Etype (N, Standard_Boolean);
3899
3900       -----------
3901       -- Value --
3902       -----------
3903
3904       when Attribute_Value => Value :
3905       begin
3906          Check_E1;
3907          Check_Scalar_Type;
3908
3909          if Is_Enumeration_Type (P_Type) then
3910             Check_Restriction (No_Enumeration_Maps, N);
3911          end if;
3912
3913          --  Set Etype before resolving expression because expansion of
3914          --  expression may require enclosing type. Note that the type
3915          --  returned by 'Value is the base type of the prefix type.
3916
3917          Set_Etype (N, P_Base_Type);
3918          Validate_Non_Static_Attribute_Function_Call;
3919       end Value;
3920
3921       ----------------
3922       -- Value_Size --
3923       ----------------
3924
3925       when Attribute_Value_Size =>
3926          Check_E0;
3927          Check_Type;
3928          Check_Not_Incomplete_Type;
3929          Set_Etype (N, Universal_Integer);
3930
3931       -------------
3932       -- Version --
3933       -------------
3934
3935       when Attribute_Version =>
3936          Check_E0;
3937          Check_Program_Unit;
3938          Set_Etype (N, RTE (RE_Version_String));
3939
3940       ------------------
3941       -- Wchar_T_Size --
3942       ------------------
3943
3944       when Attribute_Wchar_T_Size =>
3945          Standard_Attribute (Interfaces_Wchar_T_Size);
3946
3947       ----------------
3948       -- Wide_Image --
3949       ----------------
3950
3951       when Attribute_Wide_Image => Wide_Image :
3952       begin
3953          Check_Scalar_Type;
3954          Set_Etype (N, Standard_Wide_String);
3955          Check_E1;
3956          Resolve (E1, P_Base_Type);
3957          Validate_Non_Static_Attribute_Function_Call;
3958       end Wide_Image;
3959
3960       ---------------------
3961       -- Wide_Wide_Image --
3962       ---------------------
3963
3964       when Attribute_Wide_Wide_Image => Wide_Wide_Image :
3965       begin
3966          Check_Scalar_Type;
3967          Set_Etype (N, Standard_Wide_Wide_String);
3968          Check_E1;
3969          Resolve (E1, P_Base_Type);
3970          Validate_Non_Static_Attribute_Function_Call;
3971       end Wide_Wide_Image;
3972
3973       ----------------
3974       -- Wide_Value --
3975       ----------------
3976
3977       when Attribute_Wide_Value => Wide_Value :
3978       begin
3979          Check_E1;
3980          Check_Scalar_Type;
3981
3982          --  Set Etype before resolving expression because expansion
3983          --  of expression may require enclosing type.
3984
3985          Set_Etype (N, P_Type);
3986          Validate_Non_Static_Attribute_Function_Call;
3987       end Wide_Value;
3988
3989       ---------------------
3990       -- Wide_Wide_Value --
3991       ---------------------
3992
3993       when Attribute_Wide_Wide_Value => Wide_Wide_Value :
3994       begin
3995          Check_E1;
3996          Check_Scalar_Type;
3997
3998          --  Set Etype before resolving expression because expansion
3999          --  of expression may require enclosing type.
4000
4001          Set_Etype (N, P_Type);
4002          Validate_Non_Static_Attribute_Function_Call;
4003       end Wide_Wide_Value;
4004
4005       ---------------------
4006       -- Wide_Wide_Width --
4007       ---------------------
4008
4009       when Attribute_Wide_Wide_Width =>
4010          Check_E0;
4011          Check_Scalar_Type;
4012          Set_Etype (N, Universal_Integer);
4013
4014       ----------------
4015       -- Wide_Width --
4016       ----------------
4017
4018       when Attribute_Wide_Width =>
4019          Check_E0;
4020          Check_Scalar_Type;
4021          Set_Etype (N, Universal_Integer);
4022
4023       -----------
4024       -- Width --
4025       -----------
4026
4027       when Attribute_Width =>
4028          Check_E0;
4029          Check_Scalar_Type;
4030          Set_Etype (N, Universal_Integer);
4031
4032       ---------------
4033       -- Word_Size --
4034       ---------------
4035
4036       when Attribute_Word_Size =>
4037          Standard_Attribute (System_Word_Size);
4038
4039       -----------
4040       -- Write --
4041       -----------
4042
4043       when Attribute_Write =>
4044          Check_E2;
4045          Check_Stream_Attribute (TSS_Stream_Write);
4046          Set_Etype (N, Standard_Void_Type);
4047          Resolve (N, Standard_Void_Type);
4048
4049       end case;
4050
4051    --  All errors raise Bad_Attribute, so that we get out before any further
4052    --  damage occurs when an error is detected (for example, if we check for
4053    --  one attribute expression, and the check succeeds, we want to be able
4054    --  to proceed securely assuming that an expression is in fact present.
4055
4056    --  Note: we set the attribute analyzed in this case to prevent any
4057    --  attempt at reanalysis which could generate spurious error msgs.
4058
4059    exception
4060       when Bad_Attribute =>
4061          Set_Analyzed (N);
4062          Set_Etype (N, Any_Type);
4063          return;
4064    end Analyze_Attribute;
4065
4066    --------------------
4067    -- Eval_Attribute --
4068    --------------------
4069
4070    procedure Eval_Attribute (N : Node_Id) is
4071       Loc   : constant Source_Ptr   := Sloc (N);
4072       Aname : constant Name_Id      := Attribute_Name (N);
4073       Id    : constant Attribute_Id := Get_Attribute_Id (Aname);
4074       P     : constant Node_Id      := Prefix (N);
4075
4076       C_Type : constant Entity_Id := Etype (N);
4077       --  The type imposed by the context
4078
4079       E1 : Node_Id;
4080       --  First expression, or Empty if none
4081
4082       E2 : Node_Id;
4083       --  Second expression, or Empty if none
4084
4085       P_Entity : Entity_Id;
4086       --  Entity denoted by prefix
4087
4088       P_Type : Entity_Id;
4089       --  The type of the prefix
4090
4091       P_Base_Type : Entity_Id;
4092       --  The base type of the prefix type
4093
4094       P_Root_Type : Entity_Id;
4095       --  The root type of the prefix type
4096
4097       Static : Boolean;
4098       --  True if the result is Static. This is set by the general processing
4099       --  to true if the prefix is static, and all expressions are static. It
4100       --  can be reset as processing continues for particular attributes
4101
4102       Lo_Bound, Hi_Bound : Node_Id;
4103       --  Expressions for low and high bounds of type or array index referenced
4104       --  by First, Last, or Length attribute for array, set by Set_Bounds.
4105
4106       CE_Node : Node_Id;
4107       --  Constraint error node used if we have an attribute reference has
4108       --  an argument that raises a constraint error. In this case we replace
4109       --  the attribute with a raise constraint_error node. This is important
4110       --  processing, since otherwise gigi might see an attribute which it is
4111       --  unprepared to deal with.
4112
4113       function Aft_Value return Nat;
4114       --  Computes Aft value for current attribute prefix (used by Aft itself
4115       --  and also by Width for computing the Width of a fixed point type).
4116
4117       procedure Check_Expressions;
4118       --  In case where the attribute is not foldable, the expressions, if
4119       --  any, of the attribute, are in a non-static context. This procedure
4120       --  performs the required additional checks.
4121
4122       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean;
4123       --  Determines if the given type has compile time known bounds. Note
4124       --  that we enter the case statement even in cases where the prefix
4125       --  type does NOT have known bounds, so it is important to guard any
4126       --  attempt to evaluate both bounds with a call to this function.
4127
4128       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint);
4129       --  This procedure is called when the attribute N has a non-static
4130       --  but compile time known value given by Val. It includes the
4131       --  necessary checks for out of range values.
4132
4133       procedure Float_Attribute_Universal_Integer
4134         (IEEES_Val : Int;
4135          IEEEL_Val : Int;
4136          IEEEX_Val : Int;
4137          VAXFF_Val : Int;
4138          VAXDF_Val : Int;
4139          VAXGF_Val : Int;
4140          AAMPS_Val : Int;
4141          AAMPL_Val : Int);
4142       --  This procedure evaluates a float attribute with no arguments that
4143       --  returns a universal integer result. The parameters give the values
4144       --  for the possible floating-point root types. See ttypef for details.
4145       --  The prefix type is a float type (and is thus not a generic type).
4146
4147       procedure Float_Attribute_Universal_Real
4148         (IEEES_Val : String;
4149          IEEEL_Val : String;
4150          IEEEX_Val : String;
4151          VAXFF_Val : String;
4152          VAXDF_Val : String;
4153          VAXGF_Val : String;
4154          AAMPS_Val : String;
4155          AAMPL_Val : String);
4156       --  This procedure evaluates a float attribute with no arguments that
4157       --  returns a universal real result. The parameters give the values
4158       --  required for the possible floating-point root types in string
4159       --  format as real literals with a possible leading minus sign.
4160       --  The prefix type is a float type (and is thus not a generic type).
4161
4162       function Fore_Value return Nat;
4163       --  Computes the Fore value for the current attribute prefix, which is
4164       --  known to be a static fixed-point type. Used by Fore and Width.
4165
4166       function Mantissa return Uint;
4167       --  Returns the Mantissa value for the prefix type
4168
4169       procedure Set_Bounds;
4170       --  Used for First, Last and Length attributes applied to an array or
4171       --  array subtype. Sets the variables Lo_Bound and Hi_Bound to the low
4172       --  and high bound expressions for the index referenced by the attribute
4173       --  designator (i.e. the first index if no expression is present, and
4174       --  the N'th index if the value N is present as an expression). Also
4175       --  used for First and Last of scalar types. Static is reset to False
4176       --  if the type or index type is not statically constrained.
4177
4178       function Statically_Denotes_Entity (N : Node_Id) return Boolean;
4179       --  Verify that the prefix of a potentially static array attribute
4180       --  satisfies the conditions of 4.9 (14).
4181
4182       ---------------
4183       -- Aft_Value --
4184       ---------------
4185
4186       function Aft_Value return Nat is
4187          Result    : Nat;
4188          Delta_Val : Ureal;
4189
4190       begin
4191          Result := 1;
4192          Delta_Val := Delta_Value (P_Type);
4193
4194          while Delta_Val < Ureal_Tenth loop
4195             Delta_Val := Delta_Val * Ureal_10;
4196             Result := Result + 1;
4197          end loop;
4198
4199          return Result;
4200       end Aft_Value;
4201
4202       -----------------------
4203       -- Check_Expressions --
4204       -----------------------
4205
4206       procedure Check_Expressions is
4207          E : Node_Id := E1;
4208
4209       begin
4210          while Present (E) loop
4211             Check_Non_Static_Context (E);
4212             Next (E);
4213          end loop;
4214       end Check_Expressions;
4215
4216       ----------------------------------
4217       -- Compile_Time_Known_Attribute --
4218       ----------------------------------
4219
4220       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint) is
4221          T : constant Entity_Id := Etype (N);
4222
4223       begin
4224          Fold_Uint (N, Val, False);
4225
4226          --  Check that result is in bounds of the type if it is static
4227
4228          if Is_In_Range (N, T) then
4229             null;
4230
4231          elsif Is_Out_Of_Range (N, T) then
4232             Apply_Compile_Time_Constraint_Error
4233               (N, "value not in range of}?", CE_Range_Check_Failed);
4234
4235          elsif not Range_Checks_Suppressed (T) then
4236             Enable_Range_Check (N);
4237
4238          else
4239             Set_Do_Range_Check (N, False);
4240          end if;
4241       end Compile_Time_Known_Attribute;
4242
4243       -------------------------------
4244       -- Compile_Time_Known_Bounds --
4245       -------------------------------
4246
4247       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean is
4248       begin
4249          return
4250            Compile_Time_Known_Value (Type_Low_Bound (Typ))
4251              and then
4252            Compile_Time_Known_Value (Type_High_Bound (Typ));
4253       end Compile_Time_Known_Bounds;
4254
4255       ---------------------------------------
4256       -- Float_Attribute_Universal_Integer --
4257       ---------------------------------------
4258
4259       procedure Float_Attribute_Universal_Integer
4260         (IEEES_Val : Int;
4261          IEEEL_Val : Int;
4262          IEEEX_Val : Int;
4263          VAXFF_Val : Int;
4264          VAXDF_Val : Int;
4265          VAXGF_Val : Int;
4266          AAMPS_Val : Int;
4267          AAMPL_Val : Int)
4268       is
4269          Val  : Int;
4270          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4271
4272       begin
4273          if Vax_Float (P_Base_Type) then
4274             if Digs = VAXFF_Digits then
4275                Val := VAXFF_Val;
4276             elsif Digs = VAXDF_Digits then
4277                Val := VAXDF_Val;
4278             else pragma Assert (Digs = VAXGF_Digits);
4279                Val := VAXGF_Val;
4280             end if;
4281
4282          elsif Is_AAMP_Float (P_Base_Type) then
4283             if Digs = AAMPS_Digits then
4284                Val := AAMPS_Val;
4285             else pragma Assert (Digs = AAMPL_Digits);
4286                Val := AAMPL_Val;
4287             end if;
4288
4289          else
4290             if Digs = IEEES_Digits then
4291                Val := IEEES_Val;
4292             elsif Digs = IEEEL_Digits then
4293                Val := IEEEL_Val;
4294             else pragma Assert (Digs = IEEEX_Digits);
4295                Val := IEEEX_Val;
4296             end if;
4297          end if;
4298
4299          Fold_Uint (N, UI_From_Int (Val), True);
4300       end Float_Attribute_Universal_Integer;
4301
4302       ------------------------------------
4303       -- Float_Attribute_Universal_Real --
4304       ------------------------------------
4305
4306       procedure Float_Attribute_Universal_Real
4307         (IEEES_Val : String;
4308          IEEEL_Val : String;
4309          IEEEX_Val : String;
4310          VAXFF_Val : String;
4311          VAXDF_Val : String;
4312          VAXGF_Val : String;
4313          AAMPS_Val : String;
4314          AAMPL_Val : String)
4315       is
4316          Val  : Node_Id;
4317          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4318
4319       begin
4320          if Vax_Float (P_Base_Type) then
4321             if Digs = VAXFF_Digits then
4322                Val := Real_Convert (VAXFF_Val);
4323             elsif Digs = VAXDF_Digits then
4324                Val := Real_Convert (VAXDF_Val);
4325             else pragma Assert (Digs = VAXGF_Digits);
4326                Val := Real_Convert (VAXGF_Val);
4327             end if;
4328
4329          elsif Is_AAMP_Float (P_Base_Type) then
4330             if Digs = AAMPS_Digits then
4331                Val := Real_Convert (AAMPS_Val);
4332             else pragma Assert (Digs = AAMPL_Digits);
4333                Val := Real_Convert (AAMPL_Val);
4334             end if;
4335
4336          else
4337             if Digs = IEEES_Digits then
4338                Val := Real_Convert (IEEES_Val);
4339             elsif Digs = IEEEL_Digits then
4340                Val := Real_Convert (IEEEL_Val);
4341             else pragma Assert (Digs = IEEEX_Digits);
4342                Val := Real_Convert (IEEEX_Val);
4343             end if;
4344          end if;
4345
4346          Set_Sloc (Val, Loc);
4347          Rewrite (N, Val);
4348          Set_Is_Static_Expression (N, Static);
4349          Analyze_And_Resolve (N, C_Type);
4350       end Float_Attribute_Universal_Real;
4351
4352       ----------------
4353       -- Fore_Value --
4354       ----------------
4355
4356       --  Note that the Fore calculation is based on the actual values
4357       --  of the bounds, and does not take into account possible rounding.
4358
4359       function Fore_Value return Nat is
4360          Lo      : constant Uint  := Expr_Value (Type_Low_Bound (P_Type));
4361          Hi      : constant Uint  := Expr_Value (Type_High_Bound (P_Type));
4362          Small   : constant Ureal := Small_Value (P_Type);
4363          Lo_Real : constant Ureal := Lo * Small;
4364          Hi_Real : constant Ureal := Hi * Small;
4365          T       : Ureal;
4366          R       : Nat;
4367
4368       begin
4369          --  Bounds are given in terms of small units, so first compute
4370          --  proper values as reals.
4371
4372          T := UR_Max (abs Lo_Real, abs Hi_Real);
4373          R := 2;
4374
4375          --  Loop to compute proper value if more than one digit required
4376
4377          while T >= Ureal_10 loop
4378             R := R + 1;
4379             T := T / Ureal_10;
4380          end loop;
4381
4382          return R;
4383       end Fore_Value;
4384
4385       --------------
4386       -- Mantissa --
4387       --------------
4388
4389       --  Table of mantissa values accessed by function  Computed using
4390       --  the relation:
4391
4392       --    T'Mantissa = integer next above (D * log(10)/log(2)) + 1)
4393
4394       --  where D is T'Digits (RM83 3.5.7)
4395
4396       Mantissa_Value : constant array (Nat range 1 .. 40) of Nat := (
4397           1 =>   5,
4398           2 =>   8,
4399           3 =>  11,
4400           4 =>  15,
4401           5 =>  18,
4402           6 =>  21,
4403           7 =>  25,
4404           8 =>  28,
4405           9 =>  31,
4406          10 =>  35,
4407          11 =>  38,
4408          12 =>  41,
4409          13 =>  45,
4410          14 =>  48,
4411          15 =>  51,
4412          16 =>  55,
4413          17 =>  58,
4414          18 =>  61,
4415          19 =>  65,
4416          20 =>  68,
4417          21 =>  71,
4418          22 =>  75,
4419          23 =>  78,
4420          24 =>  81,
4421          25 =>  85,
4422          26 =>  88,
4423          27 =>  91,
4424          28 =>  95,
4425          29 =>  98,
4426          30 => 101,
4427          31 => 104,
4428          32 => 108,
4429          33 => 111,
4430          34 => 114,
4431          35 => 118,
4432          36 => 121,
4433          37 => 124,
4434          38 => 128,
4435          39 => 131,
4436          40 => 134);
4437
4438       function Mantissa return Uint is
4439       begin
4440          return
4441            UI_From_Int (Mantissa_Value (UI_To_Int (Digits_Value (P_Type))));
4442       end Mantissa;
4443
4444       ----------------
4445       -- Set_Bounds --
4446       ----------------
4447
4448       procedure Set_Bounds is
4449          Ndim : Nat;
4450          Indx : Node_Id;
4451          Ityp : Entity_Id;
4452
4453       begin
4454          --  For a string literal subtype, we have to construct the bounds.
4455          --  Valid Ada code never applies attributes to string literals, but
4456          --  it is convenient to allow the expander to generate attribute
4457          --  references of this type (e.g. First and Last applied to a string
4458          --  literal).
4459
4460          --  Note that the whole point of the E_String_Literal_Subtype is to
4461          --  avoid this construction of bounds, but the cases in which we
4462          --  have to materialize them are rare enough that we don't worry!
4463
4464          --  The low bound is simply the low bound of the base type. The
4465          --  high bound is computed from the length of the string and this
4466          --  low bound.
4467
4468          if Ekind (P_Type) = E_String_Literal_Subtype then
4469             Ityp := Etype (First_Index (Base_Type (P_Type)));
4470             Lo_Bound := Type_Low_Bound (Ityp);
4471
4472             Hi_Bound :=
4473               Make_Integer_Literal (Sloc (P),
4474                 Intval =>
4475                   Expr_Value (Lo_Bound) + String_Literal_Length (P_Type) - 1);
4476
4477             Set_Parent (Hi_Bound, P);
4478             Analyze_And_Resolve (Hi_Bound, Etype (Lo_Bound));
4479             return;
4480
4481          --  For non-array case, just get bounds of scalar type
4482
4483          elsif Is_Scalar_Type (P_Type) then
4484             Ityp := P_Type;
4485
4486             --  For a fixed-point type, we must freeze to get the attributes
4487             --  of the fixed-point type set now so we can reference them.
4488
4489             if Is_Fixed_Point_Type (P_Type)
4490               and then not Is_Frozen (Base_Type (P_Type))
4491               and then Compile_Time_Known_Value (Type_Low_Bound (P_Type))
4492               and then Compile_Time_Known_Value (Type_High_Bound (P_Type))
4493             then
4494                Freeze_Fixed_Point_Type (Base_Type (P_Type));
4495             end if;
4496
4497          --  For array case, get type of proper index
4498
4499          else
4500             if No (E1) then
4501                Ndim := 1;
4502             else
4503                Ndim := UI_To_Int (Expr_Value (E1));
4504             end if;
4505
4506             Indx := First_Index (P_Type);
4507             for J in 1 .. Ndim - 1 loop
4508                Next_Index (Indx);
4509             end loop;
4510
4511             --  If no index type, get out (some other error occurred, and
4512             --  we don't have enough information to complete the job!)
4513
4514             if No (Indx) then
4515                Lo_Bound := Error;
4516                Hi_Bound := Error;
4517                return;
4518             end if;
4519
4520             Ityp := Etype (Indx);
4521          end if;
4522
4523          --  A discrete range in an index constraint is allowed to be a
4524          --  subtype indication. This is syntactically a pain, but should
4525          --  not propagate to the entity for the corresponding index subtype.
4526          --  After checking that the subtype indication is legal, the range
4527          --  of the subtype indication should be transfered to the entity.
4528          --  The attributes for the bounds should remain the simple retrievals
4529          --  that they are now.
4530
4531          Lo_Bound := Type_Low_Bound (Ityp);
4532          Hi_Bound := Type_High_Bound (Ityp);
4533
4534          if not Is_Static_Subtype (Ityp) then
4535             Static := False;
4536          end if;
4537       end Set_Bounds;
4538
4539       -------------------------------
4540       -- Statically_Denotes_Entity --
4541       -------------------------------
4542
4543       function Statically_Denotes_Entity (N : Node_Id) return Boolean is
4544          E : Entity_Id;
4545
4546       begin
4547          if not Is_Entity_Name (N) then
4548             return False;
4549          else
4550             E := Entity (N);
4551          end if;
4552
4553          return
4554            Nkind (Parent (E)) /= N_Object_Renaming_Declaration
4555              or else Statically_Denotes_Entity (Renamed_Object (E));
4556       end Statically_Denotes_Entity;
4557
4558    --  Start of processing for Eval_Attribute
4559
4560    begin
4561       --  Acquire first two expressions (at the moment, no attributes
4562       --  take more than two expressions in any case).
4563
4564       if Present (Expressions (N)) then
4565          E1 := First (Expressions (N));
4566          E2 := Next (E1);
4567       else
4568          E1 := Empty;
4569          E2 := Empty;
4570       end if;
4571
4572       --  Special processing for cases where the prefix is an object. For
4573       --  this purpose, a string literal counts as an object (attributes
4574       --  of string literals can only appear in generated code).
4575
4576       if Is_Object_Reference (P) or else Nkind (P) = N_String_Literal then
4577
4578          --  For Component_Size, the prefix is an array object, and we apply
4579          --  the attribute to the type of the object. This is allowed for
4580          --  both unconstrained and constrained arrays, since the bounds
4581          --  have no influence on the value of this attribute.
4582
4583          if Id = Attribute_Component_Size then
4584             P_Entity := Etype (P);
4585
4586          --  For First and Last, the prefix is an array object, and we apply
4587          --  the attribute to the type of the array, but we need a constrained
4588          --  type for this, so we use the actual subtype if available.
4589
4590          elsif Id = Attribute_First
4591                  or else
4592                Id = Attribute_Last
4593                  or else
4594                Id = Attribute_Length
4595          then
4596             declare
4597                AS : constant Entity_Id := Get_Actual_Subtype_If_Available (P);
4598
4599             begin
4600                if Present (AS) and then Is_Constrained (AS) then
4601                   P_Entity := AS;
4602
4603                --  If we have an unconstrained type, cannot fold
4604
4605                else
4606                   Check_Expressions;
4607                   return;
4608                end if;
4609             end;
4610
4611          --  For Size, give size of object if available, otherwise we
4612          --  cannot fold Size.
4613
4614          elsif Id = Attribute_Size then
4615             if Is_Entity_Name (P)
4616               and then Known_Esize (Entity (P))
4617             then
4618                Compile_Time_Known_Attribute (N, Esize (Entity (P)));
4619                return;
4620
4621             else
4622                Check_Expressions;
4623                return;
4624             end if;
4625
4626          --  For Alignment, give size of object if available, otherwise we
4627          --  cannot fold Alignment.
4628
4629          elsif Id = Attribute_Alignment then
4630             if Is_Entity_Name (P)
4631               and then Known_Alignment (Entity (P))
4632             then
4633                Fold_Uint (N, Alignment (Entity (P)), False);
4634                return;
4635
4636             else
4637                Check_Expressions;
4638                return;
4639             end if;
4640
4641          --  No other attributes for objects are folded
4642
4643          else
4644             Check_Expressions;
4645             return;
4646          end if;
4647
4648       --  Cases where P is not an object. Cannot do anything if P is
4649       --  not the name of an entity.
4650
4651       elsif not Is_Entity_Name (P) then
4652          Check_Expressions;
4653          return;
4654
4655       --  Otherwise get prefix entity
4656
4657       else
4658          P_Entity := Entity (P);
4659       end if;
4660
4661       --  At this stage P_Entity is the entity to which the attribute
4662       --  is to be applied. This is usually simply the entity of the
4663       --  prefix, except in some cases of attributes for objects, where
4664       --  as described above, we apply the attribute to the object type.
4665
4666       --  First foldable possibility is a scalar or array type (RM 4.9(7))
4667       --  that is not generic (generic types are eliminated by RM 4.9(25)).
4668       --  Note we allow non-static non-generic types at this stage as further
4669       --  described below.
4670
4671       if Is_Type (P_Entity)
4672         and then (Is_Scalar_Type (P_Entity) or Is_Array_Type (P_Entity))
4673         and then (not Is_Generic_Type (P_Entity))
4674       then
4675          P_Type := P_Entity;
4676
4677       --  Second foldable possibility is an array object (RM 4.9(8))
4678
4679       elsif (Ekind (P_Entity) = E_Variable
4680                or else
4681              Ekind (P_Entity) = E_Constant)
4682         and then Is_Array_Type (Etype (P_Entity))
4683         and then (not Is_Generic_Type (Etype (P_Entity)))
4684       then
4685          P_Type := Etype (P_Entity);
4686
4687          --  If the entity is an array constant with an unconstrained
4688          --  nominal subtype then get the type from the initial value.
4689          --  If the value has been expanded into assignments, the expression
4690          --  is not present and the attribute reference remains dynamic.
4691          --  We could do better here and retrieve the type ???
4692
4693          if Ekind (P_Entity) = E_Constant
4694            and then not Is_Constrained (P_Type)
4695          then
4696             if No (Constant_Value (P_Entity)) then
4697                return;
4698             else
4699                P_Type := Etype (Constant_Value (P_Entity));
4700             end if;
4701          end if;
4702
4703       --  Definite must be folded if the prefix is not a generic type,
4704       --  that is to say if we are within an instantiation. Same processing
4705       --  applies to the GNAT attributes Has_Discriminants, Type_Class,
4706       --  and Unconstrained_Array.
4707
4708       elsif (Id = Attribute_Definite
4709                or else
4710              Id = Attribute_Has_Access_Values
4711                or else
4712              Id = Attribute_Has_Discriminants
4713                or else
4714              Id = Attribute_Type_Class
4715                or else
4716              Id = Attribute_Unconstrained_Array)
4717         and then not Is_Generic_Type (P_Entity)
4718       then
4719          P_Type := P_Entity;
4720
4721       --  We can fold 'Size applied to a type if the size is known
4722       --  (as happens for a size from an attribute definition clause).
4723       --  At this stage, this can happen only for types (e.g. record
4724       --  types) for which the size is always non-static. We exclude
4725       --  generic types from consideration (since they have bogus
4726       --  sizes set within templates).
4727
4728       elsif Id = Attribute_Size
4729         and then Is_Type (P_Entity)
4730         and then (not Is_Generic_Type (P_Entity))
4731         and then Known_Static_RM_Size (P_Entity)
4732       then
4733          Compile_Time_Known_Attribute (N, RM_Size (P_Entity));
4734          return;
4735
4736       --  We can fold 'Alignment applied to a type if the alignment is known
4737       --  (as happens for an alignment from an attribute definition clause).
4738       --  At this stage, this can happen only for types (e.g. record
4739       --  types) for which the size is always non-static. We exclude
4740       --  generic types from consideration (since they have bogus
4741       --  sizes set within templates).
4742
4743       elsif Id = Attribute_Alignment
4744         and then Is_Type (P_Entity)
4745         and then (not Is_Generic_Type (P_Entity))
4746         and then Known_Alignment (P_Entity)
4747       then
4748          Compile_Time_Known_Attribute (N, Alignment (P_Entity));
4749          return;
4750
4751       --  If this is an access attribute that is known to fail accessibility
4752       --  check, rewrite accordingly.
4753
4754       elsif Attribute_Name (N) = Name_Access
4755         and then Raises_Constraint_Error (N)
4756       then
4757          Rewrite (N,
4758            Make_Raise_Program_Error (Loc,
4759              Reason => PE_Accessibility_Check_Failed));
4760          Set_Etype (N, C_Type);
4761          return;
4762
4763       --  No other cases are foldable (they certainly aren't static, and at
4764       --  the moment we don't try to fold any cases other than these three).
4765
4766       else
4767          Check_Expressions;
4768          return;
4769       end if;
4770
4771       --  If either attribute or the prefix is Any_Type, then propagate
4772       --  Any_Type to the result and don't do anything else at all.
4773
4774       if P_Type = Any_Type
4775         or else (Present (E1) and then Etype (E1) = Any_Type)
4776         or else (Present (E2) and then Etype (E2) = Any_Type)
4777       then
4778          Set_Etype (N, Any_Type);
4779          return;
4780       end if;
4781
4782       --  Scalar subtype case. We have not yet enforced the static requirement
4783       --  of (RM 4.9(7)) and we don't intend to just yet, since there are cases
4784       --  of non-static attribute references (e.g. S'Digits for a non-static
4785       --  floating-point type, which we can compute at compile time).
4786
4787       --  Note: this folding of non-static attributes is not simply a case of
4788       --  optimization. For many of the attributes affected, Gigi cannot handle
4789       --  the attribute and depends on the front end having folded them away.
4790
4791       --  Note: although we don't require staticness at this stage, we do set
4792       --  the Static variable to record the staticness, for easy reference by
4793       --  those attributes where it matters (e.g. Succ and Pred), and also to
4794       --  be used to ensure that non-static folded things are not marked as
4795       --  being static (a check that is done right at the end).
4796
4797       P_Root_Type := Root_Type (P_Type);
4798       P_Base_Type := Base_Type (P_Type);
4799
4800       --  If the root type or base type is generic, then we cannot fold. This
4801       --  test is needed because subtypes of generic types are not always
4802       --  marked as being generic themselves (which seems odd???)
4803
4804       if Is_Generic_Type (P_Root_Type)
4805         or else Is_Generic_Type (P_Base_Type)
4806       then
4807          return;
4808       end if;
4809
4810       if Is_Scalar_Type (P_Type) then
4811          Static := Is_OK_Static_Subtype (P_Type);
4812
4813       --  Array case. We enforce the constrained requirement of (RM 4.9(7-8))
4814       --  since we can't do anything with unconstrained arrays. In addition,
4815       --  only the First, Last and Length attributes are possibly static.
4816
4817       --  Definite, Has_Access_Values, Has_Discriminants, Type_Class, and
4818       --  Unconstrained_Array are again exceptions, because they apply as
4819       --  well to unconstrained types.
4820
4821       --  In addition Component_Size is an exception since it is possibly
4822       --  foldable, even though it is never static, and it does apply to
4823       --  unconstrained arrays. Furthermore, it is essential to fold this
4824       --  in the packed case, since otherwise the value will be incorrect.
4825
4826       elsif Id = Attribute_Definite
4827               or else
4828             Id = Attribute_Has_Access_Values
4829               or else
4830             Id = Attribute_Has_Discriminants
4831               or else
4832             Id = Attribute_Type_Class
4833               or else
4834             Id = Attribute_Unconstrained_Array
4835               or else
4836             Id = Attribute_Component_Size
4837       then
4838          Static := False;
4839
4840       else
4841          if not Is_Constrained (P_Type)
4842            or else (Id /= Attribute_First and then
4843                     Id /= Attribute_Last  and then
4844                     Id /= Attribute_Length)
4845          then
4846             Check_Expressions;
4847             return;
4848          end if;
4849
4850          --  The rules in (RM 4.9(7,8)) require a static array, but as in the
4851          --  scalar case, we hold off on enforcing staticness, since there are
4852          --  cases which we can fold at compile time even though they are not
4853          --  static (e.g. 'Length applied to a static index, even though other
4854          --  non-static indexes make the array type non-static). This is only
4855          --  an optimization, but it falls out essentially free, so why not.
4856          --  Again we compute the variable Static for easy reference later
4857          --  (note that no array attributes are static in Ada 83).
4858
4859          Static := Ada_Version >= Ada_95
4860                      and then Statically_Denotes_Entity (P);
4861
4862          declare
4863             N : Node_Id;
4864
4865          begin
4866             N := First_Index (P_Type);
4867             while Present (N) loop
4868                Static := Static and then Is_Static_Subtype (Etype (N));
4869
4870                --  If however the index type is generic, attributes cannot
4871                --  be folded.
4872
4873                if Is_Generic_Type (Etype (N))
4874                  and then Id /= Attribute_Component_Size
4875                then
4876                   return;
4877                end if;
4878
4879                Next_Index (N);
4880             end loop;
4881          end;
4882       end if;
4883
4884       --  Check any expressions that are present. Note that these expressions,
4885       --  depending on the particular attribute type, are either part of the
4886       --  attribute designator, or they are arguments in a case where the
4887       --  attribute reference returns a function. In the latter case, the
4888       --  rule in (RM 4.9(22)) applies and in particular requires the type
4889       --  of the expressions to be scalar in order for the attribute to be
4890       --  considered to be static.
4891
4892       declare
4893          E : Node_Id;
4894
4895       begin
4896          E := E1;
4897          while Present (E) loop
4898
4899             --  If expression is not static, then the attribute reference
4900             --  result certainly cannot be static.
4901
4902             if not Is_Static_Expression (E) then
4903                Static := False;
4904             end if;
4905
4906             --  If the result is not known at compile time, or is not of
4907             --  a scalar type, then the result is definitely not static,
4908             --  so we can quit now.
4909
4910             if not Compile_Time_Known_Value (E)
4911               or else not Is_Scalar_Type (Etype (E))
4912             then
4913                --  An odd special case, if this is a Pos attribute, this
4914                --  is where we need to apply a range check since it does
4915                --  not get done anywhere else.
4916
4917                if Id = Attribute_Pos then
4918                   if Is_Integer_Type (Etype (E)) then
4919                      Apply_Range_Check (E, Etype (N));
4920                   end if;
4921                end if;
4922
4923                Check_Expressions;
4924                return;
4925
4926             --  If the expression raises a constraint error, then so does
4927             --  the attribute reference. We keep going in this case because
4928             --  we are still interested in whether the attribute reference
4929             --  is static even if it is not static.
4930
4931             elsif Raises_Constraint_Error (E) then
4932                Set_Raises_Constraint_Error (N);
4933             end if;
4934
4935             Next (E);
4936          end loop;
4937
4938          if Raises_Constraint_Error (Prefix (N)) then
4939             return;
4940          end if;
4941       end;
4942
4943       --  Deal with the case of a static attribute reference that raises
4944       --  constraint error. The Raises_Constraint_Error flag will already
4945       --  have been set, and the Static flag shows whether the attribute
4946       --  reference is static. In any case we certainly can't fold such an
4947       --  attribute reference.
4948
4949       --  Note that the rewriting of the attribute node with the constraint
4950       --  error node is essential in this case, because otherwise Gigi might
4951       --  blow up on one of the attributes it never expects to see.
4952
4953       --  The constraint_error node must have the type imposed by the context,
4954       --  to avoid spurious errors in the enclosing expression.
4955
4956       if Raises_Constraint_Error (N) then
4957          CE_Node :=
4958            Make_Raise_Constraint_Error (Sloc (N),
4959              Reason => CE_Range_Check_Failed);
4960          Set_Etype (CE_Node, Etype (N));
4961          Set_Raises_Constraint_Error (CE_Node);
4962          Check_Expressions;
4963          Rewrite (N, Relocate_Node (CE_Node));
4964          Set_Is_Static_Expression (N, Static);
4965          return;
4966       end if;
4967
4968       --  At this point we have a potentially foldable attribute reference.
4969       --  If Static is set, then the attribute reference definitely obeys
4970       --  the requirements in (RM 4.9(7,8,22)), and it definitely can be
4971       --  folded. If Static is not set, then the attribute may or may not
4972       --  be foldable, and the individual attribute processing routines
4973       --  test Static as required in cases where it makes a difference.
4974
4975       --  In the case where Static is not set, we do know that all the
4976       --  expressions present are at least known at compile time (we
4977       --  assumed above that if this was not the case, then there was
4978       --  no hope of static evaluation). However, we did not require
4979       --  that the bounds of the prefix type be compile time known,
4980       --  let alone static). That's because there are many attributes
4981       --  that can be computed at compile time on non-static subtypes,
4982       --  even though such references are not static expressions.
4983
4984       case Id is
4985
4986       --------------
4987       -- Adjacent --
4988       --------------
4989
4990       when Attribute_Adjacent =>
4991          Fold_Ureal (N,
4992            Eval_Fat.Adjacent
4993              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
4994
4995       ---------
4996       -- Aft --
4997       ---------
4998
4999       when Attribute_Aft =>
5000          Fold_Uint (N, UI_From_Int (Aft_Value), True);
5001
5002       ---------------
5003       -- Alignment --
5004       ---------------
5005
5006       when Attribute_Alignment => Alignment_Block : declare
5007          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5008
5009       begin
5010          --  Fold if alignment is set and not otherwise
5011
5012          if Known_Alignment (P_TypeA) then
5013             Fold_Uint (N, Alignment (P_TypeA), Is_Discrete_Type (P_TypeA));
5014          end if;
5015       end Alignment_Block;
5016
5017       ---------------
5018       -- AST_Entry --
5019       ---------------
5020
5021       --  Can only be folded in No_Ast_Handler case
5022
5023       when Attribute_AST_Entry =>
5024          if not Is_AST_Entry (P_Entity) then
5025             Rewrite (N,
5026               New_Occurrence_Of (RTE (RE_No_AST_Handler), Loc));
5027          else
5028             null;
5029          end if;
5030
5031       ---------
5032       -- Bit --
5033       ---------
5034
5035       --  Bit can never be folded
5036
5037       when Attribute_Bit =>
5038          null;
5039
5040       ------------------
5041       -- Body_Version --
5042       ------------------
5043
5044       --  Body_version can never be static
5045
5046       when Attribute_Body_Version =>
5047          null;
5048
5049       -------------
5050       -- Ceiling --
5051       -------------
5052
5053       when Attribute_Ceiling =>
5054          Fold_Ureal (N,
5055            Eval_Fat.Ceiling (P_Root_Type, Expr_Value_R (E1)), Static);
5056
5057       --------------------
5058       -- Component_Size --
5059       --------------------
5060
5061       when Attribute_Component_Size =>
5062          if Known_Static_Component_Size (P_Type) then
5063             Fold_Uint (N, Component_Size (P_Type), False);
5064          end if;
5065
5066       -------------
5067       -- Compose --
5068       -------------
5069
5070       when Attribute_Compose =>
5071          Fold_Ureal (N,
5072            Eval_Fat.Compose
5073              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)),
5074               Static);
5075
5076       -----------------
5077       -- Constrained --
5078       -----------------
5079
5080       --  Constrained is never folded for now, there may be cases that
5081       --  could be handled at compile time. to be looked at later.
5082
5083       when Attribute_Constrained =>
5084          null;
5085
5086       ---------------
5087       -- Copy_Sign --
5088       ---------------
5089
5090       when Attribute_Copy_Sign =>
5091          Fold_Ureal (N,
5092            Eval_Fat.Copy_Sign
5093              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5094
5095       -----------
5096       -- Delta --
5097       -----------
5098
5099       when Attribute_Delta =>
5100          Fold_Ureal (N, Delta_Value (P_Type), True);
5101
5102       --------------
5103       -- Definite --
5104       --------------
5105
5106       when Attribute_Definite =>
5107          Rewrite (N, New_Occurrence_Of (
5108            Boolean_Literals (not Is_Indefinite_Subtype (P_Entity)), Loc));
5109          Analyze_And_Resolve (N, Standard_Boolean);
5110
5111       ------------
5112       -- Denorm --
5113       ------------
5114
5115       when Attribute_Denorm =>
5116          Fold_Uint
5117            (N, UI_From_Int (Boolean'Pos (Denorm_On_Target)), True);
5118
5119       ------------
5120       -- Digits --
5121       ------------
5122
5123       when Attribute_Digits =>
5124          Fold_Uint (N, Digits_Value (P_Type), True);
5125
5126       ----------
5127       -- Emax --
5128       ----------
5129
5130       when Attribute_Emax =>
5131
5132          --  Ada 83 attribute is defined as (RM83 3.5.8)
5133
5134          --    T'Emax = 4 * T'Mantissa
5135
5136          Fold_Uint (N, 4 * Mantissa, True);
5137
5138       --------------
5139       -- Enum_Rep --
5140       --------------
5141
5142       when Attribute_Enum_Rep =>
5143
5144          --  For an enumeration type with a non-standard representation use
5145          --  the Enumeration_Rep field of the proper constant. Note that this
5146          --  will not work for types Character/Wide_[Wide-]Character, since no
5147          --  real entities are created for the enumeration literals, but that
5148          --  does not matter since these two types do not have non-standard
5149          --  representations anyway.
5150
5151          if Is_Enumeration_Type (P_Type)
5152            and then Has_Non_Standard_Rep (P_Type)
5153          then
5154             Fold_Uint (N, Enumeration_Rep (Expr_Value_E (E1)), Static);
5155
5156          --  For enumeration types with standard representations and all
5157          --  other cases (i.e. all integer and modular types), Enum_Rep
5158          --  is equivalent to Pos.
5159
5160          else
5161             Fold_Uint (N, Expr_Value (E1), Static);
5162          end if;
5163
5164       -------------
5165       -- Epsilon --
5166       -------------
5167
5168       when Attribute_Epsilon =>
5169
5170          --  Ada 83 attribute is defined as (RM83 3.5.8)
5171
5172          --    T'Epsilon = 2.0**(1 - T'Mantissa)
5173
5174          Fold_Ureal (N, Ureal_2 ** (1 - Mantissa), True);
5175
5176       --------------
5177       -- Exponent --
5178       --------------
5179
5180       when Attribute_Exponent =>
5181          Fold_Uint (N,
5182            Eval_Fat.Exponent (P_Root_Type, Expr_Value_R (E1)), Static);
5183
5184       -----------
5185       -- First --
5186       -----------
5187
5188       when Attribute_First => First_Attr :
5189       begin
5190          Set_Bounds;
5191
5192          if Compile_Time_Known_Value (Lo_Bound) then
5193             if Is_Real_Type (P_Type) then
5194                Fold_Ureal (N, Expr_Value_R (Lo_Bound), Static);
5195             else
5196                Fold_Uint  (N, Expr_Value (Lo_Bound), Static);
5197             end if;
5198          end if;
5199       end First_Attr;
5200
5201       -----------------
5202       -- Fixed_Value --
5203       -----------------
5204
5205       when Attribute_Fixed_Value =>
5206          null;
5207
5208       -----------
5209       -- Floor --
5210       -----------
5211
5212       when Attribute_Floor =>
5213          Fold_Ureal (N,
5214            Eval_Fat.Floor (P_Root_Type, Expr_Value_R (E1)), Static);
5215
5216       ----------
5217       -- Fore --
5218       ----------
5219
5220       when Attribute_Fore =>
5221          if Compile_Time_Known_Bounds (P_Type) then
5222             Fold_Uint (N, UI_From_Int (Fore_Value), Static);
5223          end if;
5224
5225       --------------
5226       -- Fraction --
5227       --------------
5228
5229       when Attribute_Fraction =>
5230          Fold_Ureal (N,
5231            Eval_Fat.Fraction (P_Root_Type, Expr_Value_R (E1)), Static);
5232
5233       -----------------------
5234       -- Has_Access_Values --
5235       -----------------------
5236
5237       when Attribute_Has_Access_Values =>
5238          Rewrite (N, New_Occurrence_Of
5239            (Boolean_Literals (Has_Access_Values (P_Root_Type)), Loc));
5240          Analyze_And_Resolve (N, Standard_Boolean);
5241
5242       -----------------------
5243       -- Has_Discriminants --
5244       -----------------------
5245
5246       when Attribute_Has_Discriminants =>
5247          Rewrite (N, New_Occurrence_Of (
5248            Boolean_Literals (Has_Discriminants (P_Entity)), Loc));
5249          Analyze_And_Resolve (N, Standard_Boolean);
5250
5251       --------------
5252       -- Identity --
5253       --------------
5254
5255       when Attribute_Identity =>
5256          null;
5257
5258       -----------
5259       -- Image --
5260       -----------
5261
5262       --  Image is a scalar attribute, but is never static, because it is
5263       --  not a static function (having a non-scalar argument (RM 4.9(22))
5264
5265       when Attribute_Image =>
5266          null;
5267
5268       ---------
5269       -- Img --
5270       ---------
5271
5272       --  Img is a scalar attribute, but is never static, because it is
5273       --  not a static function (having a non-scalar argument (RM 4.9(22))
5274
5275       when Attribute_Img =>
5276          null;
5277
5278       -------------------
5279       -- Integer_Value --
5280       -------------------
5281
5282       when Attribute_Integer_Value =>
5283          null;
5284
5285       -----------
5286       -- Large --
5287       -----------
5288
5289       when Attribute_Large =>
5290
5291          --  For fixed-point, we use the identity:
5292
5293          --    T'Large = (2.0**T'Mantissa - 1.0) * T'Small
5294
5295          if Is_Fixed_Point_Type (P_Type) then
5296             Rewrite (N,
5297               Make_Op_Multiply (Loc,
5298                 Left_Opnd =>
5299                   Make_Op_Subtract (Loc,
5300                     Left_Opnd =>
5301                       Make_Op_Expon (Loc,
5302                         Left_Opnd =>
5303                           Make_Real_Literal (Loc, Ureal_2),
5304                         Right_Opnd =>
5305                           Make_Attribute_Reference (Loc,
5306                             Prefix => P,
5307                             Attribute_Name => Name_Mantissa)),
5308                     Right_Opnd => Make_Real_Literal (Loc, Ureal_1)),
5309
5310                 Right_Opnd =>
5311                   Make_Real_Literal (Loc, Small_Value (Entity (P)))));
5312
5313             Analyze_And_Resolve (N, C_Type);
5314
5315          --  Floating-point (Ada 83 compatibility)
5316
5317          else
5318             --  Ada 83 attribute is defined as (RM83 3.5.8)
5319
5320             --    T'Large = 2.0**T'Emax * (1.0 - 2.0**(-T'Mantissa))
5321
5322             --  where
5323
5324             --    T'Emax = 4 * T'Mantissa
5325
5326             Fold_Ureal (N,
5327               Ureal_2 ** (4 * Mantissa) * (Ureal_1 - Ureal_2 ** (-Mantissa)),
5328               True);
5329          end if;
5330
5331       ----------
5332       -- Last --
5333       ----------
5334
5335       when Attribute_Last => Last :
5336       begin
5337          Set_Bounds;
5338
5339          if Compile_Time_Known_Value (Hi_Bound) then
5340             if Is_Real_Type (P_Type) then
5341                Fold_Ureal (N, Expr_Value_R (Hi_Bound), Static);
5342             else
5343                Fold_Uint  (N, Expr_Value (Hi_Bound), Static);
5344             end if;
5345          end if;
5346       end Last;
5347
5348       ------------------
5349       -- Leading_Part --
5350       ------------------
5351
5352       when Attribute_Leading_Part =>
5353          Fold_Ureal (N,
5354            Eval_Fat.Leading_Part
5355              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5356
5357       ------------
5358       -- Length --
5359       ------------
5360
5361       when Attribute_Length => Length : declare
5362          Ind : Node_Id;
5363
5364       begin
5365          --  In the case of a generic index type, the bounds may
5366          --  appear static but the computation is not meaningful,
5367          --  and may generate a spurious warning.
5368
5369          Ind := First_Index (P_Type);
5370
5371          while Present (Ind) loop
5372             if Is_Generic_Type (Etype (Ind)) then
5373                return;
5374             end if;
5375
5376             Next_Index (Ind);
5377          end loop;
5378
5379          Set_Bounds;
5380
5381          if Compile_Time_Known_Value (Lo_Bound)
5382            and then Compile_Time_Known_Value (Hi_Bound)
5383          then
5384             Fold_Uint (N,
5385               UI_Max (0, 1 + (Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound))),
5386               True);
5387          end if;
5388       end Length;
5389
5390       -------------
5391       -- Machine --
5392       -------------
5393
5394       when Attribute_Machine =>
5395          Fold_Ureal (N,
5396            Eval_Fat.Machine
5397              (P_Root_Type, Expr_Value_R (E1), Eval_Fat.Round, N),
5398            Static);
5399
5400       ------------------
5401       -- Machine_Emax --
5402       ------------------
5403
5404       when Attribute_Machine_Emax =>
5405          Float_Attribute_Universal_Integer (
5406            IEEES_Machine_Emax,
5407            IEEEL_Machine_Emax,
5408            IEEEX_Machine_Emax,
5409            VAXFF_Machine_Emax,
5410            VAXDF_Machine_Emax,
5411            VAXGF_Machine_Emax,
5412            AAMPS_Machine_Emax,
5413            AAMPL_Machine_Emax);
5414
5415       ------------------
5416       -- Machine_Emin --
5417       ------------------
5418
5419       when Attribute_Machine_Emin =>
5420          Float_Attribute_Universal_Integer (
5421            IEEES_Machine_Emin,
5422            IEEEL_Machine_Emin,
5423            IEEEX_Machine_Emin,
5424            VAXFF_Machine_Emin,
5425            VAXDF_Machine_Emin,
5426            VAXGF_Machine_Emin,
5427            AAMPS_Machine_Emin,
5428            AAMPL_Machine_Emin);
5429
5430       ----------------------
5431       -- Machine_Mantissa --
5432       ----------------------
5433
5434       when Attribute_Machine_Mantissa =>
5435          Float_Attribute_Universal_Integer (
5436            IEEES_Machine_Mantissa,
5437            IEEEL_Machine_Mantissa,
5438            IEEEX_Machine_Mantissa,
5439            VAXFF_Machine_Mantissa,
5440            VAXDF_Machine_Mantissa,
5441            VAXGF_Machine_Mantissa,
5442            AAMPS_Machine_Mantissa,
5443            AAMPL_Machine_Mantissa);
5444
5445       -----------------------
5446       -- Machine_Overflows --
5447       -----------------------
5448
5449       when Attribute_Machine_Overflows =>
5450
5451          --  Always true for fixed-point
5452
5453          if Is_Fixed_Point_Type (P_Type) then
5454             Fold_Uint (N, True_Value, True);
5455
5456          --  Floating point case
5457
5458          else
5459             Fold_Uint (N,
5460               UI_From_Int (Boolean'Pos (Machine_Overflows_On_Target)),
5461               True);
5462          end if;
5463
5464       -------------------
5465       -- Machine_Radix --
5466       -------------------
5467
5468       when Attribute_Machine_Radix =>
5469          if Is_Fixed_Point_Type (P_Type) then
5470             if Is_Decimal_Fixed_Point_Type (P_Type)
5471               and then Machine_Radix_10 (P_Type)
5472             then
5473                Fold_Uint (N, Uint_10, True);
5474             else
5475                Fold_Uint (N, Uint_2, True);
5476             end if;
5477
5478          --  All floating-point type always have radix 2
5479
5480          else
5481             Fold_Uint (N, Uint_2, True);
5482          end if;
5483
5484       --------------------
5485       -- Machine_Rounds --
5486       --------------------
5487
5488       when Attribute_Machine_Rounds =>
5489
5490          --  Always False for fixed-point
5491
5492          if Is_Fixed_Point_Type (P_Type) then
5493             Fold_Uint (N, False_Value, True);
5494
5495          --  Else yield proper floating-point result
5496
5497          else
5498             Fold_Uint
5499               (N, UI_From_Int (Boolean'Pos (Machine_Rounds_On_Target)), True);
5500          end if;
5501
5502       ------------------
5503       -- Machine_Size --
5504       ------------------
5505
5506       --  Note: Machine_Size is identical to Object_Size
5507
5508       when Attribute_Machine_Size => Machine_Size : declare
5509          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5510
5511       begin
5512          if Known_Esize (P_TypeA) then
5513             Fold_Uint (N, Esize (P_TypeA), True);
5514          end if;
5515       end Machine_Size;
5516
5517       --------------
5518       -- Mantissa --
5519       --------------
5520
5521       when Attribute_Mantissa =>
5522
5523          --  Fixed-point mantissa
5524
5525          if Is_Fixed_Point_Type (P_Type) then
5526
5527             --  Compile time foldable case
5528
5529             if Compile_Time_Known_Value (Type_Low_Bound  (P_Type))
5530                  and then
5531                Compile_Time_Known_Value (Type_High_Bound (P_Type))
5532             then
5533                --  The calculation of the obsolete Ada 83 attribute Mantissa
5534                --  is annoying, because of AI00143, quoted here:
5535
5536                --  !question 84-01-10
5537
5538                --  Consider the model numbers for F:
5539
5540                --         type F is delta 1.0 range -7.0 .. 8.0;
5541
5542                --  The wording requires that F'MANTISSA be the SMALLEST
5543                --  integer number for which each  bound  of the specified
5544                --  range is either a model number or lies at most small
5545                --  distant from a model number. This means F'MANTISSA
5546                --  is required to be 3 since the range  -7.0 .. 7.0 fits
5547                --  in 3 signed bits, and 8 is "at most" 1.0 from a model
5548                --  number, namely, 7. Is this analysis correct? Note that
5549                --  this implies the upper bound of the range is not
5550                --  represented as a model number.
5551
5552                --  !response 84-03-17
5553
5554                --  The analysis is correct. The upper and lower bounds for
5555                --  a fixed  point type can lie outside the range of model
5556                --  numbers.
5557
5558                declare
5559                   Siz     : Uint;
5560                   LBound  : Ureal;
5561                   UBound  : Ureal;
5562                   Bound   : Ureal;
5563                   Max_Man : Uint;
5564
5565                begin
5566                   LBound  := Expr_Value_R (Type_Low_Bound  (P_Type));
5567                   UBound  := Expr_Value_R (Type_High_Bound (P_Type));
5568                   Bound   := UR_Max (UR_Abs (LBound), UR_Abs (UBound));
5569                   Max_Man := UR_Trunc (Bound / Small_Value (P_Type));
5570
5571                   --  If the Bound is exactly a model number, i.e. a multiple
5572                   --  of Small, then we back it off by one to get the integer
5573                   --  value that must be representable.
5574
5575                   if Small_Value (P_Type) * Max_Man = Bound then
5576                      Max_Man := Max_Man - 1;
5577                   end if;
5578
5579                   --  Now find corresponding size = Mantissa value
5580
5581                   Siz := Uint_0;
5582                   while 2 ** Siz < Max_Man loop
5583                      Siz := Siz + 1;
5584                   end loop;
5585
5586                   Fold_Uint (N, Siz, True);
5587                end;
5588
5589             else
5590                --  The case of dynamic bounds cannot be evaluated at compile
5591                --  time. Instead we use a runtime routine (see Exp_Attr).
5592
5593                null;
5594             end if;
5595
5596          --  Floating-point Mantissa
5597
5598          else
5599             Fold_Uint (N, Mantissa, True);
5600          end if;
5601
5602       ---------
5603       -- Max --
5604       ---------
5605
5606       when Attribute_Max => Max :
5607       begin
5608          if Is_Real_Type (P_Type) then
5609             Fold_Ureal
5610               (N, UR_Max (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5611          else
5612             Fold_Uint (N, UI_Max (Expr_Value (E1), Expr_Value (E2)), Static);
5613          end if;
5614       end Max;
5615
5616       ----------------------------------
5617       -- Max_Size_In_Storage_Elements --
5618       ----------------------------------
5619
5620       --  Max_Size_In_Storage_Elements is simply the Size rounded up to a
5621       --  Storage_Unit boundary. We can fold any cases for which the size
5622       --  is known by the front end.
5623
5624       when Attribute_Max_Size_In_Storage_Elements =>
5625          if Known_Esize (P_Type) then
5626             Fold_Uint (N,
5627               (Esize (P_Type) + System_Storage_Unit - 1) /
5628                                           System_Storage_Unit,
5629                Static);
5630          end if;
5631
5632       --------------------
5633       -- Mechanism_Code --
5634       --------------------
5635
5636       when Attribute_Mechanism_Code =>
5637          declare
5638             Val    : Int;
5639             Formal : Entity_Id;
5640             Mech   : Mechanism_Type;
5641
5642          begin
5643             if No (E1) then
5644                Mech := Mechanism (P_Entity);
5645
5646             else
5647                Val := UI_To_Int (Expr_Value (E1));
5648
5649                Formal := First_Formal (P_Entity);
5650                for J in 1 .. Val - 1 loop
5651                   Next_Formal (Formal);
5652                end loop;
5653                Mech := Mechanism (Formal);
5654             end if;
5655
5656             if Mech < 0 then
5657                Fold_Uint (N, UI_From_Int (Int (-Mech)), True);
5658             end if;
5659          end;
5660
5661       ---------
5662       -- Min --
5663       ---------
5664
5665       when Attribute_Min => Min :
5666       begin
5667          if Is_Real_Type (P_Type) then
5668             Fold_Ureal
5669               (N, UR_Min (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5670          else
5671             Fold_Uint
5672               (N, UI_Min (Expr_Value (E1), Expr_Value (E2)), Static);
5673          end if;
5674       end Min;
5675
5676       ---------
5677       -- Mod --
5678       ---------
5679
5680       when Attribute_Mod =>
5681          Fold_Uint
5682            (N, UI_Mod (Expr_Value (E1), Modulus (P_Base_Type)), Static);
5683
5684       -----------
5685       -- Model --
5686       -----------
5687
5688       when Attribute_Model =>
5689          Fold_Ureal (N,
5690            Eval_Fat.Model (P_Root_Type, Expr_Value_R (E1)), Static);
5691
5692       ----------------
5693       -- Model_Emin --
5694       ----------------
5695
5696       when Attribute_Model_Emin =>
5697          Float_Attribute_Universal_Integer (
5698            IEEES_Model_Emin,
5699            IEEEL_Model_Emin,
5700            IEEEX_Model_Emin,
5701            VAXFF_Model_Emin,
5702            VAXDF_Model_Emin,
5703            VAXGF_Model_Emin,
5704            AAMPS_Model_Emin,
5705            AAMPL_Model_Emin);
5706
5707       -------------------
5708       -- Model_Epsilon --
5709       -------------------
5710
5711       when Attribute_Model_Epsilon =>
5712          Float_Attribute_Universal_Real (
5713            IEEES_Model_Epsilon'Universal_Literal_String,
5714            IEEEL_Model_Epsilon'Universal_Literal_String,
5715            IEEEX_Model_Epsilon'Universal_Literal_String,
5716            VAXFF_Model_Epsilon'Universal_Literal_String,
5717            VAXDF_Model_Epsilon'Universal_Literal_String,
5718            VAXGF_Model_Epsilon'Universal_Literal_String,
5719            AAMPS_Model_Epsilon'Universal_Literal_String,
5720            AAMPL_Model_Epsilon'Universal_Literal_String);
5721
5722       --------------------
5723       -- Model_Mantissa --
5724       --------------------
5725
5726       when Attribute_Model_Mantissa =>
5727          Float_Attribute_Universal_Integer (
5728            IEEES_Model_Mantissa,
5729            IEEEL_Model_Mantissa,
5730            IEEEX_Model_Mantissa,
5731            VAXFF_Model_Mantissa,
5732            VAXDF_Model_Mantissa,
5733            VAXGF_Model_Mantissa,
5734            AAMPS_Model_Mantissa,
5735            AAMPL_Model_Mantissa);
5736
5737       -----------------
5738       -- Model_Small --
5739       -----------------
5740
5741       when Attribute_Model_Small =>
5742          Float_Attribute_Universal_Real (
5743            IEEES_Model_Small'Universal_Literal_String,
5744            IEEEL_Model_Small'Universal_Literal_String,
5745            IEEEX_Model_Small'Universal_Literal_String,
5746            VAXFF_Model_Small'Universal_Literal_String,
5747            VAXDF_Model_Small'Universal_Literal_String,
5748            VAXGF_Model_Small'Universal_Literal_String,
5749            AAMPS_Model_Small'Universal_Literal_String,
5750            AAMPL_Model_Small'Universal_Literal_String);
5751
5752       -------------
5753       -- Modulus --
5754       -------------
5755
5756       when Attribute_Modulus =>
5757          Fold_Uint (N, Modulus (P_Type), True);
5758
5759       --------------------
5760       -- Null_Parameter --
5761       --------------------
5762
5763       --  Cannot fold, we know the value sort of, but the whole point is
5764       --  that there is no way to talk about this imaginary value except
5765       --  by using the attribute, so we leave it the way it is.
5766
5767       when Attribute_Null_Parameter =>
5768          null;
5769
5770       -----------------
5771       -- Object_Size --
5772       -----------------
5773
5774       --  The Object_Size attribute for a type returns the Esize of the
5775       --  type and can be folded if this value is known.
5776
5777       when Attribute_Object_Size => Object_Size : declare
5778          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5779
5780       begin
5781          if Known_Esize (P_TypeA) then
5782             Fold_Uint (N, Esize (P_TypeA), True);
5783          end if;
5784       end Object_Size;
5785
5786       -------------------------
5787       -- Passed_By_Reference --
5788       -------------------------
5789
5790       --  Scalar types are never passed by reference
5791
5792       when Attribute_Passed_By_Reference =>
5793          Fold_Uint (N, False_Value, True);
5794
5795       ---------
5796       -- Pos --
5797       ---------
5798
5799       when Attribute_Pos =>
5800          Fold_Uint (N, Expr_Value (E1), True);
5801
5802       ----------
5803       -- Pred --
5804       ----------
5805
5806       when Attribute_Pred => Pred :
5807       begin
5808          --  Floating-point case
5809
5810          if Is_Floating_Point_Type (P_Type) then
5811             Fold_Ureal (N,
5812               Eval_Fat.Pred (P_Root_Type, Expr_Value_R (E1)), Static);
5813
5814          --  Fixed-point case
5815
5816          elsif Is_Fixed_Point_Type (P_Type) then
5817             Fold_Ureal (N,
5818               Expr_Value_R (E1) - Small_Value (P_Type), True);
5819
5820          --  Modular integer case (wraps)
5821
5822          elsif Is_Modular_Integer_Type (P_Type) then
5823             Fold_Uint (N, (Expr_Value (E1) - 1) mod Modulus (P_Type), Static);
5824
5825          --  Other scalar cases
5826
5827          else
5828             pragma Assert (Is_Scalar_Type (P_Type));
5829
5830             if Is_Enumeration_Type (P_Type)
5831               and then Expr_Value (E1) =
5832                          Expr_Value (Type_Low_Bound (P_Base_Type))
5833             then
5834                Apply_Compile_Time_Constraint_Error
5835                  (N, "Pred of `&''First`",
5836                   CE_Overflow_Check_Failed,
5837                   Ent  => P_Base_Type,
5838                   Warn => not Static);
5839
5840                Check_Expressions;
5841                return;
5842             end if;
5843
5844             Fold_Uint (N, Expr_Value (E1) - 1, Static);
5845          end if;
5846       end Pred;
5847
5848       -----------
5849       -- Range --
5850       -----------
5851
5852       --  No processing required, because by this stage, Range has been
5853       --  replaced by First .. Last, so this branch can never be taken.
5854
5855       when Attribute_Range =>
5856          raise Program_Error;
5857
5858       ------------------
5859       -- Range_Length --
5860       ------------------
5861
5862       when Attribute_Range_Length =>
5863          Set_Bounds;
5864
5865          if Compile_Time_Known_Value (Hi_Bound)
5866            and then Compile_Time_Known_Value (Lo_Bound)
5867          then
5868             Fold_Uint (N,
5869               UI_Max
5870                 (0, Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound) + 1),
5871                  Static);
5872          end if;
5873
5874       ---------------
5875       -- Remainder --
5876       ---------------
5877
5878       when Attribute_Remainder => Remainder : declare
5879          X : constant Ureal := Expr_Value_R (E1);
5880          Y : constant Ureal := Expr_Value_R (E2);
5881
5882       begin
5883          if UR_Is_Zero (Y) then
5884             Apply_Compile_Time_Constraint_Error
5885               (N, "division by zero in Remainder",
5886                CE_Overflow_Check_Failed,
5887                Warn => not Static);
5888
5889             Check_Expressions;
5890             return;
5891          end if;
5892
5893          Fold_Ureal (N, Eval_Fat.Remainder (P_Root_Type, X, Y), Static);
5894       end Remainder;
5895
5896       -----------
5897       -- Round --
5898       -----------
5899
5900       when Attribute_Round => Round :
5901       declare
5902          Sr : Ureal;
5903          Si : Uint;
5904
5905       begin
5906          --  First we get the (exact result) in units of small
5907
5908          Sr := Expr_Value_R (E1) / Small_Value (C_Type);
5909
5910          --  Now round that exactly to an integer
5911
5912          Si := UR_To_Uint (Sr);
5913
5914          --  Finally the result is obtained by converting back to real
5915
5916          Fold_Ureal (N, Si * Small_Value (C_Type), Static);
5917       end Round;
5918
5919       --------------
5920       -- Rounding --
5921       --------------
5922
5923       when Attribute_Rounding =>
5924          Fold_Ureal (N,
5925            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
5926
5927       ---------------
5928       -- Safe_Emax --
5929       ---------------
5930
5931       when Attribute_Safe_Emax =>
5932          Float_Attribute_Universal_Integer (
5933            IEEES_Safe_Emax,
5934            IEEEL_Safe_Emax,
5935            IEEEX_Safe_Emax,
5936            VAXFF_Safe_Emax,
5937            VAXDF_Safe_Emax,
5938            VAXGF_Safe_Emax,
5939            AAMPS_Safe_Emax,
5940            AAMPL_Safe_Emax);
5941
5942       ----------------
5943       -- Safe_First --
5944       ----------------
5945
5946       when Attribute_Safe_First =>
5947          Float_Attribute_Universal_Real (
5948            IEEES_Safe_First'Universal_Literal_String,
5949            IEEEL_Safe_First'Universal_Literal_String,
5950            IEEEX_Safe_First'Universal_Literal_String,
5951            VAXFF_Safe_First'Universal_Literal_String,
5952            VAXDF_Safe_First'Universal_Literal_String,
5953            VAXGF_Safe_First'Universal_Literal_String,
5954            AAMPS_Safe_First'Universal_Literal_String,
5955            AAMPL_Safe_First'Universal_Literal_String);
5956
5957       ----------------
5958       -- Safe_Large --
5959       ----------------
5960
5961       when Attribute_Safe_Large =>
5962          if Is_Fixed_Point_Type (P_Type) then
5963             Fold_Ureal
5964               (N, Expr_Value_R (Type_High_Bound (P_Base_Type)), Static);
5965          else
5966             Float_Attribute_Universal_Real (
5967               IEEES_Safe_Large'Universal_Literal_String,
5968               IEEEL_Safe_Large'Universal_Literal_String,
5969               IEEEX_Safe_Large'Universal_Literal_String,
5970               VAXFF_Safe_Large'Universal_Literal_String,
5971               VAXDF_Safe_Large'Universal_Literal_String,
5972               VAXGF_Safe_Large'Universal_Literal_String,
5973               AAMPS_Safe_Large'Universal_Literal_String,
5974               AAMPL_Safe_Large'Universal_Literal_String);
5975          end if;
5976
5977       ---------------
5978       -- Safe_Last --
5979       ---------------
5980
5981       when Attribute_Safe_Last =>
5982          Float_Attribute_Universal_Real (
5983            IEEES_Safe_Last'Universal_Literal_String,
5984            IEEEL_Safe_Last'Universal_Literal_String,
5985            IEEEX_Safe_Last'Universal_Literal_String,
5986            VAXFF_Safe_Last'Universal_Literal_String,
5987            VAXDF_Safe_Last'Universal_Literal_String,
5988            VAXGF_Safe_Last'Universal_Literal_String,
5989            AAMPS_Safe_Last'Universal_Literal_String,
5990            AAMPL_Safe_Last'Universal_Literal_String);
5991
5992       ----------------
5993       -- Safe_Small --
5994       ----------------
5995
5996       when Attribute_Safe_Small =>
5997
5998          --  In Ada 95, the old Ada 83 attribute Safe_Small is redundant
5999          --  for fixed-point, since is the same as Small, but we implement
6000          --  it for backwards compatibility.
6001
6002          if Is_Fixed_Point_Type (P_Type) then
6003             Fold_Ureal (N, Small_Value (P_Type), Static);
6004
6005          --  Ada 83 Safe_Small for floating-point cases
6006
6007          else
6008             Float_Attribute_Universal_Real (
6009               IEEES_Safe_Small'Universal_Literal_String,
6010               IEEEL_Safe_Small'Universal_Literal_String,
6011               IEEEX_Safe_Small'Universal_Literal_String,
6012               VAXFF_Safe_Small'Universal_Literal_String,
6013               VAXDF_Safe_Small'Universal_Literal_String,
6014               VAXGF_Safe_Small'Universal_Literal_String,
6015               AAMPS_Safe_Small'Universal_Literal_String,
6016               AAMPL_Safe_Small'Universal_Literal_String);
6017          end if;
6018
6019       -----------
6020       -- Scale --
6021       -----------
6022
6023       when Attribute_Scale =>
6024          Fold_Uint (N, Scale_Value (P_Type), True);
6025
6026       -------------
6027       -- Scaling --
6028       -------------
6029
6030       when Attribute_Scaling =>
6031          Fold_Ureal (N,
6032            Eval_Fat.Scaling
6033              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
6034
6035       ------------------
6036       -- Signed_Zeros --
6037       ------------------
6038
6039       when Attribute_Signed_Zeros =>
6040          Fold_Uint
6041            (N, UI_From_Int (Boolean'Pos (Signed_Zeros_On_Target)), Static);
6042
6043       ----------
6044       -- Size --
6045       ----------
6046
6047       --  Size attribute returns the RM size. All scalar types can be folded,
6048       --  as well as any types for which the size is known by the front end,
6049       --  including any type for which a size attribute is specified.
6050
6051       when Attribute_Size | Attribute_VADS_Size => Size : declare
6052          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6053
6054       begin
6055          if RM_Size (P_TypeA) /= Uint_0 then
6056
6057             --  VADS_Size case
6058
6059             if Id = Attribute_VADS_Size or else Use_VADS_Size then
6060                declare
6061                   S : constant Node_Id := Size_Clause (P_TypeA);
6062
6063                begin
6064                   --  If a size clause applies, then use the size from it.
6065                   --  This is one of the rare cases where we can use the
6066                   --  Size_Clause field for a subtype when Has_Size_Clause
6067                   --  is False. Consider:
6068
6069                   --    type x is range 1 .. 64;
6070                   --    for x'size use 12;
6071                   --    subtype y is x range 0 .. 3;
6072
6073                   --  Here y has a size clause inherited from x, but normally
6074                   --  it does not apply, and y'size is 2. However, y'VADS_Size
6075                   --  is indeed 12 and not 2.
6076
6077                   if Present (S)
6078                     and then Is_OK_Static_Expression (Expression (S))
6079                   then
6080                      Fold_Uint (N, Expr_Value (Expression (S)), True);
6081
6082                   --  If no size is specified, then we simply use the object
6083                   --  size in the VADS_Size case (e.g. Natural'Size is equal
6084                   --  to Integer'Size, not one less).
6085
6086                   else
6087                      Fold_Uint (N, Esize (P_TypeA), True);
6088                   end if;
6089                end;
6090
6091             --  Normal case (Size) in which case we want the RM_Size
6092
6093             else
6094                Fold_Uint (N,
6095                  RM_Size (P_TypeA),
6096                  Static and then Is_Discrete_Type (P_TypeA));
6097             end if;
6098          end if;
6099       end Size;
6100
6101       -----------
6102       -- Small --
6103       -----------
6104
6105       when Attribute_Small =>
6106
6107          --  The floating-point case is present only for Ada 83 compatability.
6108          --  Note that strictly this is an illegal addition, since we are
6109          --  extending an Ada 95 defined attribute, but we anticipate an
6110          --  ARG ruling that will permit this.
6111
6112          if Is_Floating_Point_Type (P_Type) then
6113
6114             --  Ada 83 attribute is defined as (RM83 3.5.8)
6115
6116             --    T'Small = 2.0**(-T'Emax - 1)
6117
6118             --  where
6119
6120             --    T'Emax = 4 * T'Mantissa
6121
6122             Fold_Ureal (N, Ureal_2 ** ((-(4 * Mantissa)) - 1), Static);
6123
6124          --  Normal Ada 95 fixed-point case
6125
6126          else
6127             Fold_Ureal (N, Small_Value (P_Type), True);
6128          end if;
6129
6130       -----------------
6131       -- Stream_Size --
6132       -----------------
6133
6134       when Attribute_Stream_Size =>
6135          null;
6136
6137       ----------
6138       -- Succ --
6139       ----------
6140
6141       when Attribute_Succ => Succ :
6142       begin
6143          --  Floating-point case
6144
6145          if Is_Floating_Point_Type (P_Type) then
6146             Fold_Ureal (N,
6147               Eval_Fat.Succ (P_Root_Type, Expr_Value_R (E1)), Static);
6148
6149          --  Fixed-point case
6150
6151          elsif Is_Fixed_Point_Type (P_Type) then
6152             Fold_Ureal (N,
6153               Expr_Value_R (E1) + Small_Value (P_Type), Static);
6154
6155          --  Modular integer case (wraps)
6156
6157          elsif Is_Modular_Integer_Type (P_Type) then
6158             Fold_Uint (N, (Expr_Value (E1) + 1) mod Modulus (P_Type), Static);
6159
6160          --  Other scalar cases
6161
6162          else
6163             pragma Assert (Is_Scalar_Type (P_Type));
6164
6165             if Is_Enumeration_Type (P_Type)
6166               and then Expr_Value (E1) =
6167                          Expr_Value (Type_High_Bound (P_Base_Type))
6168             then
6169                Apply_Compile_Time_Constraint_Error
6170                  (N, "Succ of `&''Last`",
6171                   CE_Overflow_Check_Failed,
6172                   Ent  => P_Base_Type,
6173                   Warn => not Static);
6174
6175                Check_Expressions;
6176                return;
6177             else
6178                Fold_Uint (N, Expr_Value (E1) + 1, Static);
6179             end if;
6180          end if;
6181       end Succ;
6182
6183       ----------------
6184       -- Truncation --
6185       ----------------
6186
6187       when Attribute_Truncation =>
6188          Fold_Ureal (N,
6189            Eval_Fat.Truncation (P_Root_Type, Expr_Value_R (E1)), Static);
6190
6191       ----------------
6192       -- Type_Class --
6193       ----------------
6194
6195       when Attribute_Type_Class => Type_Class : declare
6196          Typ : constant Entity_Id := Underlying_Type (P_Base_Type);
6197          Id  : RE_Id;
6198
6199       begin
6200          if Is_Descendent_Of_Address (Typ) then
6201             Id := RE_Type_Class_Address;
6202
6203          elsif Is_Enumeration_Type (Typ) then
6204             Id := RE_Type_Class_Enumeration;
6205
6206          elsif Is_Integer_Type (Typ) then
6207             Id := RE_Type_Class_Integer;
6208
6209          elsif Is_Fixed_Point_Type (Typ) then
6210             Id := RE_Type_Class_Fixed_Point;
6211
6212          elsif Is_Floating_Point_Type (Typ) then
6213             Id := RE_Type_Class_Floating_Point;
6214
6215          elsif Is_Array_Type (Typ) then
6216             Id := RE_Type_Class_Array;
6217
6218          elsif Is_Record_Type (Typ) then
6219             Id := RE_Type_Class_Record;
6220
6221          elsif Is_Access_Type (Typ) then
6222             Id := RE_Type_Class_Access;
6223
6224          elsif Is_Enumeration_Type (Typ) then
6225             Id := RE_Type_Class_Enumeration;
6226
6227          elsif Is_Task_Type (Typ) then
6228             Id := RE_Type_Class_Task;
6229
6230          --  We treat protected types like task types. It would make more
6231          --  sense to have another enumeration value, but after all the
6232          --  whole point of this feature is to be exactly DEC compatible,
6233          --  and changing the type Type_Clas would not meet this requirement.
6234
6235          elsif Is_Protected_Type (Typ) then
6236             Id := RE_Type_Class_Task;
6237
6238          --  Not clear if there are any other possibilities, but if there
6239          --  are, then we will treat them as the address case.
6240
6241          else
6242             Id := RE_Type_Class_Address;
6243          end if;
6244
6245          Rewrite (N, New_Occurrence_Of (RTE (Id), Loc));
6246
6247       end Type_Class;
6248
6249       -----------------------
6250       -- Unbiased_Rounding --
6251       -----------------------
6252
6253       when Attribute_Unbiased_Rounding =>
6254          Fold_Ureal (N,
6255            Eval_Fat.Unbiased_Rounding (P_Root_Type, Expr_Value_R (E1)),
6256            Static);
6257
6258       -------------------------
6259       -- Unconstrained_Array --
6260       -------------------------
6261
6262       when Attribute_Unconstrained_Array => Unconstrained_Array : declare
6263          Typ : constant Entity_Id := Underlying_Type (P_Type);
6264
6265       begin
6266          Rewrite (N, New_Occurrence_Of (
6267            Boolean_Literals (
6268              Is_Array_Type (P_Type)
6269               and then not Is_Constrained (Typ)), Loc));
6270
6271          --  Analyze and resolve as boolean, note that this attribute is
6272          --  a static attribute in GNAT.
6273
6274          Analyze_And_Resolve (N, Standard_Boolean);
6275          Static := True;
6276       end Unconstrained_Array;
6277
6278       ---------------
6279       -- VADS_Size --
6280       ---------------
6281
6282       --  Processing is shared with Size
6283
6284       ---------
6285       -- Val --
6286       ---------
6287
6288       when Attribute_Val => Val :
6289       begin
6290          if  Expr_Value (E1) < Expr_Value (Type_Low_Bound (P_Base_Type))
6291            or else
6292              Expr_Value (E1) > Expr_Value (Type_High_Bound (P_Base_Type))
6293          then
6294             Apply_Compile_Time_Constraint_Error
6295               (N, "Val expression out of range",
6296                CE_Range_Check_Failed,
6297                Warn => not Static);
6298
6299             Check_Expressions;
6300             return;
6301
6302          else
6303             Fold_Uint (N, Expr_Value (E1), Static);
6304          end if;
6305       end Val;
6306
6307       ----------------
6308       -- Value_Size --
6309       ----------------
6310
6311       --  The Value_Size attribute for a type returns the RM size of the
6312       --  type. This an always be folded for scalar types, and can also
6313       --  be folded for non-scalar types if the size is set.
6314
6315       when Attribute_Value_Size => Value_Size : declare
6316          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6317
6318       begin
6319          if RM_Size (P_TypeA) /= Uint_0 then
6320             Fold_Uint (N, RM_Size (P_TypeA), True);
6321          end if;
6322
6323       end Value_Size;
6324
6325       -------------
6326       -- Version --
6327       -------------
6328
6329       --  Version can never be static
6330
6331       when Attribute_Version =>
6332          null;
6333
6334       ----------------
6335       -- Wide_Image --
6336       ----------------
6337
6338       --  Wide_Image is a scalar attribute, but is never static, because it
6339       --  is not a static function (having a non-scalar argument (RM 4.9(22))
6340
6341       when Attribute_Wide_Image =>
6342          null;
6343
6344       ---------------------
6345       -- Wide_Wide_Image --
6346       ---------------------
6347
6348       --  Wide_Wide_Image is a scalar attribute but is never static, because it
6349       --  is not a static function (having a non-scalar argument (RM 4.9(22)).
6350
6351       when Attribute_Wide_Wide_Image =>
6352          null;
6353
6354       ---------------------
6355       -- Wide_Wide_Width --
6356       ---------------------
6357
6358       --  Processing for Wide_Wide_Width is combined with Width
6359
6360       ----------------
6361       -- Wide_Width --
6362       ----------------
6363
6364       --  Processing for Wide_Width is combined with Width
6365
6366       -----------
6367       -- Width --
6368       -----------
6369
6370       --  This processing also handles the case of Wide_[Wide_]Width
6371
6372       when Attribute_Width |
6373            Attribute_Wide_Width |
6374            Attribute_Wide_Wide_Width => Width :
6375       begin
6376          if Compile_Time_Known_Bounds (P_Type) then
6377
6378             --  Floating-point types
6379
6380             if Is_Floating_Point_Type (P_Type) then
6381
6382                --  Width is zero for a null range (RM 3.5 (38))
6383
6384                if Expr_Value_R (Type_High_Bound (P_Type)) <
6385                   Expr_Value_R (Type_Low_Bound (P_Type))
6386                then
6387                   Fold_Uint (N, Uint_0, True);
6388
6389                else
6390                   --  For floating-point, we have +N.dddE+nnn where length
6391                   --  of ddd is determined by type'Digits - 1, but is one
6392                   --  if Digits is one (RM 3.5 (33)).
6393
6394                   --  nnn is set to 2 for Short_Float and Float (32 bit
6395                   --  floats), and 3 for Long_Float and Long_Long_Float.
6396                   --  This is not quite right, but is good enough.
6397
6398                   declare
6399                      Len : Int :=
6400                              Int'Max (2, UI_To_Int (Digits_Value (P_Type)));
6401
6402                   begin
6403                      if Esize (P_Type) <= 32 then
6404                         Len := Len + 6;
6405                      else
6406                         Len := Len + 7;
6407                      end if;
6408
6409                      Fold_Uint (N, UI_From_Int (Len), True);
6410                   end;
6411                end if;
6412
6413             --  Fixed-point types
6414
6415             elsif Is_Fixed_Point_Type (P_Type) then
6416
6417                --  Width is zero for a null range (RM 3.5 (38))
6418
6419                if Expr_Value (Type_High_Bound (P_Type)) <
6420                   Expr_Value (Type_Low_Bound  (P_Type))
6421                then
6422                   Fold_Uint (N, Uint_0, True);
6423
6424                --  The non-null case depends on the specific real type
6425
6426                else
6427                   --  For fixed-point type width is Fore + 1 + Aft (RM 3.5(34))
6428
6429                   Fold_Uint
6430                     (N, UI_From_Int (Fore_Value + 1 + Aft_Value), True);
6431                end if;
6432
6433             --  Discrete types
6434
6435             else
6436                declare
6437                   R  : constant Entity_Id := Root_Type (P_Type);
6438                   Lo : constant Uint :=
6439                          Expr_Value (Type_Low_Bound (P_Type));
6440                   Hi : constant Uint :=
6441                          Expr_Value (Type_High_Bound (P_Type));
6442                   W  : Nat;
6443                   Wt : Nat;
6444                   T  : Uint;
6445                   L  : Node_Id;
6446                   C  : Character;
6447
6448                begin
6449                   --  Empty ranges
6450
6451                   if Lo > Hi then
6452                      W := 0;
6453
6454                   --  Width for types derived from Standard.Character
6455                   --  and Standard.Wide_[Wide_]Character.
6456
6457                   elsif R = Standard_Character
6458                      or else R = Standard_Wide_Character
6459                      or else R = Standard_Wide_Wide_Character
6460                   then
6461                      W := 0;
6462
6463                      --  Set W larger if needed
6464
6465                      for J in UI_To_Int (Lo) .. UI_To_Int (Hi) loop
6466
6467                         --  All wide characters look like Hex_hhhhhhhh
6468
6469                         if J > 255 then
6470                            W := 12;
6471
6472                         else
6473                            C := Character'Val (J);
6474
6475                            --  Test for all cases where Character'Image
6476                            --  yields an image that is longer than three
6477                            --  characters. First the cases of Reserved_xxx
6478                            --  names (length = 12).
6479
6480                            case C is
6481                               when Reserved_128 | Reserved_129 |
6482                                    Reserved_132 | Reserved_153
6483
6484                                 => Wt := 12;
6485
6486                               when BS | HT | LF | VT | FF | CR |
6487                                    SO | SI | EM | FS | GS | RS |
6488                                    US | RI | MW | ST | PM
6489
6490                                 => Wt := 2;
6491
6492                               when NUL | SOH | STX | ETX | EOT |
6493                                    ENQ | ACK | BEL | DLE | DC1 |
6494                                    DC2 | DC3 | DC4 | NAK | SYN |
6495                                    ETB | CAN | SUB | ESC | DEL |
6496                                    BPH | NBH | NEL | SSA | ESA |
6497                                    HTS | HTJ | VTS | PLD | PLU |
6498                                    SS2 | SS3 | DCS | PU1 | PU2 |
6499                                    STS | CCH | SPA | EPA | SOS |
6500                                    SCI | CSI | OSC | APC
6501
6502                                 => Wt := 3;
6503
6504                               when Space .. Tilde |
6505                                    No_Break_Space .. LC_Y_Diaeresis
6506
6507                                 => Wt := 3;
6508                            end case;
6509
6510                            W := Int'Max (W, Wt);
6511                         end if;
6512                      end loop;
6513
6514                   --  Width for types derived from Standard.Boolean
6515
6516                   elsif R = Standard_Boolean then
6517                      if Lo = 0 then
6518                         W := 5; -- FALSE
6519                      else
6520                         W := 4; -- TRUE
6521                      end if;
6522
6523                   --  Width for integer types
6524
6525                   elsif Is_Integer_Type (P_Type) then
6526                      T := UI_Max (abs Lo, abs Hi);
6527
6528                      W := 2;
6529                      while T >= 10 loop
6530                         W := W + 1;
6531                         T := T / 10;
6532                      end loop;
6533
6534                   --  Only remaining possibility is user declared enum type
6535
6536                   else
6537                      pragma Assert (Is_Enumeration_Type (P_Type));
6538
6539                      W := 0;
6540                      L := First_Literal (P_Type);
6541
6542                      while Present (L) loop
6543
6544                         --  Only pay attention to in range characters
6545
6546                         if Lo <= Enumeration_Pos (L)
6547                           and then Enumeration_Pos (L) <= Hi
6548                         then
6549                            --  For Width case, use decoded name
6550
6551                            if Id = Attribute_Width then
6552                               Get_Decoded_Name_String (Chars (L));
6553                               Wt := Nat (Name_Len);
6554
6555                            --  For Wide_[Wide_]Width, use encoded name, and
6556                            --  then adjust for the encoding.
6557
6558                            else
6559                               Get_Name_String (Chars (L));
6560
6561                               --  Character literals are always of length 3
6562
6563                               if Name_Buffer (1) = 'Q' then
6564                                  Wt := 3;
6565
6566                               --  Otherwise loop to adjust for upper/wide chars
6567
6568                               else
6569                                  Wt := Nat (Name_Len);
6570
6571                                  for J in 1 .. Name_Len loop
6572                                     if Name_Buffer (J) = 'U' then
6573                                        Wt := Wt - 2;
6574                                     elsif Name_Buffer (J) = 'W' then
6575                                        Wt := Wt - 4;
6576                                     end if;
6577                                  end loop;
6578                               end if;
6579                            end if;
6580
6581                            W := Int'Max (W, Wt);
6582                         end if;
6583
6584                         Next_Literal (L);
6585                      end loop;
6586                   end if;
6587
6588                   Fold_Uint (N, UI_From_Int (W), True);
6589                end;
6590             end if;
6591          end if;
6592       end Width;
6593
6594       --  The following attributes can never be folded, and furthermore we
6595       --  should not even have entered the case statement for any of these.
6596       --  Note that in some cases, the values have already been folded as
6597       --  a result of the processing in Analyze_Attribute.
6598
6599       when Attribute_Abort_Signal             |
6600            Attribute_Access                   |
6601            Attribute_Address                  |
6602            Attribute_Address_Size             |
6603            Attribute_Asm_Input                |
6604            Attribute_Asm_Output               |
6605            Attribute_Base                     |
6606            Attribute_Bit_Order                |
6607            Attribute_Bit_Position             |
6608            Attribute_Callable                 |
6609            Attribute_Caller                   |
6610            Attribute_Class                    |
6611            Attribute_Code_Address             |
6612            Attribute_Count                    |
6613            Attribute_Default_Bit_Order        |
6614            Attribute_Elaborated               |
6615            Attribute_Elab_Body                |
6616            Attribute_Elab_Spec                |
6617            Attribute_External_Tag             |
6618            Attribute_First_Bit                |
6619            Attribute_Input                    |
6620            Attribute_Last_Bit                 |
6621            Attribute_Maximum_Alignment        |
6622            Attribute_Output                   |
6623            Attribute_Partition_ID             |
6624            Attribute_Pool_Address             |
6625            Attribute_Position                 |
6626            Attribute_Read                     |
6627            Attribute_Storage_Pool             |
6628            Attribute_Storage_Size             |
6629            Attribute_Storage_Unit             |
6630            Attribute_Tag                      |
6631            Attribute_Target_Name              |
6632            Attribute_Terminated               |
6633            Attribute_To_Address               |
6634            Attribute_UET_Address              |
6635            Attribute_Unchecked_Access         |
6636            Attribute_Universal_Literal_String |
6637            Attribute_Unrestricted_Access      |
6638            Attribute_Valid                    |
6639            Attribute_Value                    |
6640            Attribute_Wchar_T_Size             |
6641            Attribute_Wide_Value               |
6642            Attribute_Wide_Wide_Value          |
6643            Attribute_Word_Size                |
6644            Attribute_Write                    =>
6645
6646          raise Program_Error;
6647       end case;
6648
6649       --  At the end of the case, one more check. If we did a static evaluation
6650       --  so that the result is now a literal, then set Is_Static_Expression
6651       --  in the constant only if the prefix type is a static subtype. For
6652       --  non-static subtypes, the folding is still OK, but not static.
6653
6654       --  An exception is the GNAT attribute Constrained_Array which is
6655       --  defined to be a static attribute in all cases.
6656
6657       if Nkind (N) = N_Integer_Literal
6658         or else Nkind (N) = N_Real_Literal
6659         or else Nkind (N) = N_Character_Literal
6660         or else Nkind (N) = N_String_Literal
6661         or else (Is_Entity_Name (N)
6662                   and then Ekind (Entity (N)) = E_Enumeration_Literal)
6663       then
6664          Set_Is_Static_Expression (N, Static);
6665
6666       --  If this is still an attribute reference, then it has not been folded
6667       --  and that means that its expressions are in a non-static context.
6668
6669       elsif Nkind (N) = N_Attribute_Reference then
6670          Check_Expressions;
6671
6672       --  Note: the else case not covered here are odd cases where the
6673       --  processing has transformed the attribute into something other
6674       --  than a constant. Nothing more to do in such cases.
6675
6676       else
6677          null;
6678       end if;
6679
6680    end Eval_Attribute;
6681
6682    ------------------------------
6683    -- Is_Anonymous_Tagged_Base --
6684    ------------------------------
6685
6686    function Is_Anonymous_Tagged_Base
6687      (Anon : Entity_Id;
6688       Typ  : Entity_Id)
6689       return Boolean
6690    is
6691    begin
6692       return
6693         Anon = Current_Scope
6694           and then Is_Itype (Anon)
6695           and then Associated_Node_For_Itype (Anon) = Parent (Typ);
6696    end Is_Anonymous_Tagged_Base;
6697
6698    -----------------------
6699    -- Resolve_Attribute --
6700    -----------------------
6701
6702    procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id) is
6703       Loc      : constant Source_Ptr   := Sloc (N);
6704       P        : constant Node_Id      := Prefix (N);
6705       Aname    : constant Name_Id      := Attribute_Name (N);
6706       Attr_Id  : constant Attribute_Id := Get_Attribute_Id (Aname);
6707       Btyp     : constant Entity_Id    := Base_Type (Typ);
6708       Index    : Interp_Index;
6709       It       : Interp;
6710       Nom_Subt : Entity_Id;
6711
6712       procedure Accessibility_Message;
6713       --  Error, or warning within an instance, if the static accessibility
6714       --  rules of 3.10.2 are violated.
6715
6716       ---------------------------
6717       -- Accessibility_Message --
6718       ---------------------------
6719
6720       procedure Accessibility_Message is
6721          Indic : Node_Id := Parent (Parent (N));
6722
6723       begin
6724          --  In an instance, this is a runtime check, but one we
6725          --  know will fail, so generate an appropriate warning.
6726
6727          if In_Instance_Body then
6728             Error_Msg_N
6729               ("?non-local pointer cannot point to local object", P);
6730             Error_Msg_N
6731               ("?Program_Error will be raised at run time", P);
6732             Rewrite (N,
6733               Make_Raise_Program_Error (Loc,
6734                 Reason => PE_Accessibility_Check_Failed));
6735             Set_Etype (N, Typ);
6736             return;
6737
6738          else
6739             Error_Msg_N
6740               ("non-local pointer cannot point to local object", P);
6741
6742             --  Check for case where we have a missing access definition
6743
6744             if Is_Record_Type (Current_Scope)
6745               and then
6746                 (Nkind (Parent (N)) = N_Discriminant_Association
6747                    or else
6748                  Nkind (Parent (N)) = N_Index_Or_Discriminant_Constraint)
6749             then
6750                Indic := Parent (Parent (N));
6751                while Present (Indic)
6752                  and then Nkind (Indic) /= N_Subtype_Indication
6753                loop
6754                   Indic := Parent (Indic);
6755                end loop;
6756
6757                if Present (Indic) then
6758                   Error_Msg_NE
6759                     ("\use an access definition for" &
6760                       " the access discriminant of&", N,
6761                          Entity (Subtype_Mark (Indic)));
6762                end if;
6763             end if;
6764          end if;
6765       end Accessibility_Message;
6766
6767    --  Start of processing for Resolve_Attribute
6768
6769    begin
6770       --  If error during analysis, no point in continuing, except for
6771       --  array types, where we get  better recovery by using unconstrained
6772       --  indices than nothing at all (see Check_Array_Type).
6773
6774       if Error_Posted (N)
6775         and then Attr_Id /= Attribute_First
6776         and then Attr_Id /= Attribute_Last
6777         and then Attr_Id /= Attribute_Length
6778         and then Attr_Id /= Attribute_Range
6779       then
6780          return;
6781       end if;
6782
6783       --  If attribute was universal type, reset to actual type
6784
6785       if Etype (N) = Universal_Integer
6786         or else Etype (N) = Universal_Real
6787       then
6788          Set_Etype (N, Typ);
6789       end if;
6790
6791       --  Remaining processing depends on attribute
6792
6793       case Attr_Id is
6794
6795          ------------
6796          -- Access --
6797          ------------
6798
6799          --  For access attributes, if the prefix denotes an entity, it is
6800          --  interpreted as a name, never as a call. It may be overloaded,
6801          --  in which case resolution uses the profile of the context type.
6802          --  Otherwise prefix must be resolved.
6803
6804          when Attribute_Access
6805             | Attribute_Unchecked_Access
6806             | Attribute_Unrestricted_Access =>
6807
6808             if Is_Variable (P) then
6809                Note_Possible_Modification (P);
6810             end if;
6811
6812             if Is_Entity_Name (P) then
6813                if Is_Overloaded (P) then
6814                   Get_First_Interp (P, Index, It);
6815
6816                   while Present (It.Nam) loop
6817
6818                      if Type_Conformant (Designated_Type (Typ), It.Nam) then
6819                         Set_Entity (P, It.Nam);
6820
6821                         --  The prefix is definitely NOT overloaded anymore
6822                         --  at this point, so we reset the Is_Overloaded
6823                         --  flag to avoid any confusion when reanalyzing
6824                         --  the node.
6825
6826                         Set_Is_Overloaded (P, False);
6827                         Generate_Reference (Entity (P), P);
6828                         exit;
6829                      end if;
6830
6831                      Get_Next_Interp (Index, It);
6832                   end loop;
6833
6834                --  If it is a subprogram name or a type, there is nothing
6835                --  to resolve.
6836
6837                elsif not Is_Overloadable (Entity (P))
6838                  and then not Is_Type (Entity (P))
6839                then
6840                   Resolve (P);
6841                end if;
6842
6843                Error_Msg_Name_1 := Aname;
6844
6845                if not Is_Entity_Name (P) then
6846                   null;
6847
6848                elsif Is_Abstract (Entity (P))
6849                  and then Is_Overloadable (Entity (P))
6850                then
6851                   Error_Msg_N ("prefix of % attribute cannot be abstract", P);
6852                   Set_Etype (N, Any_Type);
6853
6854                elsif Convention (Entity (P)) = Convention_Intrinsic then
6855                   if Ekind (Entity (P)) = E_Enumeration_Literal then
6856                      Error_Msg_N
6857                        ("prefix of % attribute cannot be enumeration literal",
6858                           P);
6859                   else
6860                      Error_Msg_N
6861                        ("prefix of % attribute cannot be intrinsic", P);
6862                   end if;
6863
6864                   Set_Etype (N, Any_Type);
6865
6866                elsif Is_Thread_Body (Entity (P)) then
6867                   Error_Msg_N
6868                     ("prefix of % attribute cannot be a thread body", P);
6869                end if;
6870
6871                --  Assignments, return statements, components of aggregates,
6872                --  generic instantiations will require convention checks if
6873                --  the type is an access to subprogram. Given that there will
6874                --  also be accessibility checks on those, this is where the
6875                --  checks can eventually be centralized ???
6876
6877                if Ekind (Btyp) = E_Access_Subprogram_Type
6878                     or else
6879                   Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
6880                     or else
6881                   Ekind (Btyp) = E_Anonymous_Access_Protected_Subprogram_Type
6882                then
6883                   if Convention (Btyp) /= Convention (Entity (P)) then
6884                      Error_Msg_N
6885                       ("subprogram has invalid convention for context", P);
6886
6887                   else
6888                      Check_Subtype_Conformant
6889                        (New_Id  => Entity (P),
6890                         Old_Id  => Designated_Type (Btyp),
6891                         Err_Loc => P);
6892                   end if;
6893
6894                   if Attr_Id = Attribute_Unchecked_Access then
6895                      Error_Msg_Name_1 := Aname;
6896                      Error_Msg_N
6897                        ("attribute% cannot be applied to a subprogram", P);
6898
6899                   elsif Aname = Name_Unrestricted_Access then
6900                      null;  --  Nothing to check
6901
6902                   --  Check the static accessibility rule of 3.10.2(32)
6903                   --  In an instance body, if subprogram and type are both
6904                   --  local, other rules prevent dangling references, and no
6905                   --  warning  is needed.
6906
6907                   elsif Attr_Id = Attribute_Access
6908                     and then Subprogram_Access_Level (Entity (P)) >
6909                                Type_Access_Level (Btyp)
6910                     and then Ekind (Btyp) /=
6911                                E_Anonymous_Access_Subprogram_Type
6912                     and then Ekind (Btyp) /=
6913                                E_Anonymous_Access_Protected_Subprogram_Type
6914                   then
6915                      if not In_Instance_Body then
6916                         Error_Msg_N
6917                           ("subprogram must not be deeper than access type",
6918                             P);
6919
6920                      elsif Scope (Entity (P)) /= Scope (Btyp) then
6921                         Error_Msg_N
6922                           ("subprogram must not be deeper than access type?",
6923                              P);
6924                         Error_Msg_N
6925                           ("Constraint_Error will be raised ?", P);
6926                         Set_Raises_Constraint_Error (N);
6927                      end if;
6928
6929                   --  Check the restriction of 3.10.2(32) that disallows
6930                   --  the type of the access attribute to be declared
6931                   --  outside a generic body when the subprogram is declared
6932                   --  within that generic body.
6933
6934                   --  Ada2005: If the expected type is for an access
6935                   --  parameter, this clause does not apply.
6936
6937                   elsif Present (Enclosing_Generic_Body (Entity (P)))
6938                     and then Enclosing_Generic_Body (Entity (P)) /=
6939                              Enclosing_Generic_Body (Btyp)
6940                     and then
6941                       Ekind (Btyp) /= E_Anonymous_Access_Subprogram_Type
6942                   then
6943                      Error_Msg_N
6944                        ("access type must not be outside generic body", P);
6945                   end if;
6946                end if;
6947
6948                --  If this is a renaming, an inherited operation, or a
6949                --  subprogram instance, use the original entity.
6950
6951                if Is_Entity_Name (P)
6952                  and then Is_Overloadable (Entity (P))
6953                  and then Present (Alias (Entity (P)))
6954                then
6955                   Rewrite (P,
6956                     New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6957                end if;
6958
6959             elsif Nkind (P) = N_Selected_Component
6960               and then Is_Overloadable (Entity (Selector_Name (P)))
6961             then
6962                --  Protected operation. If operation is overloaded, must
6963                --  disambiguate. Prefix that denotes protected object itself
6964                --  is resolved with its own type.
6965
6966                if Attr_Id = Attribute_Unchecked_Access then
6967                   Error_Msg_Name_1 := Aname;
6968                   Error_Msg_N
6969                     ("attribute% cannot be applied to protected operation", P);
6970                end if;
6971
6972                Resolve (Prefix (P));
6973                Generate_Reference (Entity (Selector_Name (P)), P);
6974
6975             elsif Is_Overloaded (P) then
6976
6977                --  Use the designated type of the context to disambiguate
6978                --  Note that this was not strictly conformant to Ada 95,
6979                --  but was the implementation adopted by most Ada 95 compilers.
6980                --  The use of the context type to resolve an Access attribute
6981                --  reference is now mandated in AI-235 for Ada 2005.
6982
6983                declare
6984                   Index : Interp_Index;
6985                   It    : Interp;
6986
6987                begin
6988                   Get_First_Interp (P, Index, It);
6989                   while Present (It.Typ) loop
6990                      if Covers (Designated_Type (Typ), It.Typ) then
6991                         Resolve (P, It.Typ);
6992                         exit;
6993                      end if;
6994
6995                      Get_Next_Interp (Index, It);
6996                   end loop;
6997                end;
6998             else
6999                Resolve (P);
7000             end if;
7001
7002             --  X'Access is illegal if X denotes a constant and the access
7003             --  type is access-to-variable. Same for 'Unchecked_Access.
7004             --  The rule does not apply to 'Unrestricted_Access.
7005
7006             if not (Ekind (Btyp) = E_Access_Subprogram_Type
7007                      or else Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
7008                      or else (Is_Record_Type (Btyp) and then
7009                               Present (Corresponding_Remote_Type (Btyp)))
7010                      or else Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7011                      or else Ekind (Btyp)
7012                                = E_Anonymous_Access_Protected_Subprogram_Type
7013                      or else Is_Access_Constant (Btyp)
7014                      or else Is_Variable (P)
7015                      or else Attr_Id = Attribute_Unrestricted_Access)
7016             then
7017                if Comes_From_Source (N) then
7018                   Error_Msg_N ("access-to-variable designates constant", P);
7019                end if;
7020             end if;
7021
7022             if (Attr_Id = Attribute_Access
7023                   or else
7024                 Attr_Id = Attribute_Unchecked_Access)
7025               and then (Ekind (Btyp) = E_General_Access_Type
7026                           or else Ekind (Btyp) = E_Anonymous_Access_Type)
7027             then
7028                --  Ada 2005 (AI-230): Check the accessibility of anonymous
7029                --  access types in record and array components. For a
7030                --  component definition the level is the same of the
7031                --  enclosing composite type.
7032
7033                if Ada_Version >= Ada_05
7034                  and then Is_Local_Anonymous_Access (Btyp)
7035                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
7036                then
7037                   --  In an instance, this is a runtime check, but one we
7038                   --  know will fail, so generate an appropriate warning.
7039
7040                   if In_Instance_Body then
7041                      Error_Msg_N
7042                        ("?non-local pointer cannot point to local object", P);
7043                      Error_Msg_N
7044                        ("?Program_Error will be raised at run time", P);
7045                      Rewrite (N,
7046                        Make_Raise_Program_Error (Loc,
7047                          Reason => PE_Accessibility_Check_Failed));
7048                      Set_Etype (N, Typ);
7049                   else
7050                      Error_Msg_N
7051                        ("non-local pointer cannot point to local object", P);
7052                   end if;
7053                end if;
7054
7055                if Is_Dependent_Component_Of_Mutable_Object (P) then
7056                   Error_Msg_N
7057                     ("illegal attribute for discriminant-dependent component",
7058                      P);
7059                end if;
7060
7061                --  Check the static matching rule of 3.10.2(27). The
7062                --  nominal subtype of the prefix must statically
7063                --  match the designated type.
7064
7065                Nom_Subt := Etype (P);
7066
7067                if Is_Constr_Subt_For_U_Nominal (Nom_Subt) then
7068                   Nom_Subt := Etype (Nom_Subt);
7069                end if;
7070
7071                if Is_Tagged_Type (Designated_Type (Typ)) then
7072
7073                   --  If the attribute is in the context of an access
7074                   --  parameter, then the prefix is allowed to be of
7075                   --  the class-wide type (by AI-127).
7076
7077                   if Ekind (Typ) = E_Anonymous_Access_Type then
7078                      if not Covers (Designated_Type (Typ), Nom_Subt)
7079                        and then not Covers (Nom_Subt, Designated_Type (Typ))
7080                      then
7081                         declare
7082                            Desig : Entity_Id;
7083
7084                         begin
7085                            Desig := Designated_Type (Typ);
7086
7087                            if Is_Class_Wide_Type (Desig) then
7088                               Desig := Etype (Desig);
7089                            end if;
7090
7091                            if Is_Anonymous_Tagged_Base (Nom_Subt, Desig) then
7092                               null;
7093
7094                            else
7095                               Error_Msg_NE
7096                                 ("type of prefix: & not compatible",
7097                                   P, Nom_Subt);
7098                               Error_Msg_NE
7099                                 ("\with &, the expected designated type",
7100                                   P, Designated_Type (Typ));
7101                            end if;
7102                         end;
7103                      end if;
7104
7105                   elsif not Covers (Designated_Type (Typ), Nom_Subt)
7106                     or else
7107                       (not Is_Class_Wide_Type (Designated_Type (Typ))
7108                         and then Is_Class_Wide_Type (Nom_Subt))
7109                   then
7110                      Error_Msg_NE
7111                        ("type of prefix: & is not covered", P, Nom_Subt);
7112                      Error_Msg_NE
7113                        ("\by &, the expected designated type" &
7114                            " ('R'M 3.10.2 (27))", P, Designated_Type (Typ));
7115                   end if;
7116
7117                   if Is_Class_Wide_Type (Designated_Type (Typ))
7118                     and then Has_Discriminants (Etype (Designated_Type (Typ)))
7119                     and then Is_Constrained (Etype (Designated_Type (Typ)))
7120                     and then Designated_Type (Typ) /= Nom_Subt
7121                   then
7122                      Apply_Discriminant_Check
7123                        (N, Etype (Designated_Type (Typ)));
7124                   end if;
7125
7126                elsif not Subtypes_Statically_Match
7127                            (Designated_Type (Base_Type (Typ)), Nom_Subt)
7128                  and then
7129                    not (Has_Discriminants (Designated_Type (Typ))
7130                           and then
7131                             not Is_Constrained
7132                                   (Designated_Type (Base_Type (Typ))))
7133                then
7134                   Error_Msg_N
7135                     ("object subtype must statically match "
7136                      & "designated subtype", P);
7137
7138                   if Is_Entity_Name (P)
7139                     and then Is_Array_Type (Designated_Type (Typ))
7140                   then
7141
7142                      declare
7143                         D : constant Node_Id := Declaration_Node (Entity (P));
7144
7145                      begin
7146                         Error_Msg_N ("aliased object has explicit bounds?",
7147                           D);
7148                         Error_Msg_N ("\declare without bounds"
7149                           & " (and with explicit initialization)?", D);
7150                         Error_Msg_N ("\for use with unconstrained access?", D);
7151                      end;
7152                   end if;
7153                end if;
7154
7155                --  Check the static accessibility rule of 3.10.2(28).
7156                --  Note that this check is not performed for the
7157                --  case of an anonymous access type, since the access
7158                --  attribute is always legal in such a context.
7159
7160                if Attr_Id /= Attribute_Unchecked_Access
7161                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
7162                  and then Ekind (Btyp) = E_General_Access_Type
7163                then
7164                   Accessibility_Message;
7165                   return;
7166                end if;
7167             end if;
7168
7169             if Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7170                  or else
7171                Ekind (Btyp) = E_Anonymous_Access_Protected_Subprogram_Type
7172             then
7173                if Is_Entity_Name (P)
7174                  and then not Is_Protected_Type (Scope (Entity (P)))
7175                then
7176                   Error_Msg_N ("context requires a protected subprogram", P);
7177
7178                --  Check accessibility of protected object against that
7179                --  of the access type, but only on user code, because
7180                --  the expander creates access references for handlers.
7181                --  If the context is an anonymous_access_to_protected,
7182                --  there are no accessibility checks either.
7183
7184                elsif Object_Access_Level (P) > Type_Access_Level (Btyp)
7185                  and then Comes_From_Source (N)
7186                  and then Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7187                  and then No (Original_Access_Type (Typ))
7188                then
7189                   Accessibility_Message;
7190                   return;
7191                end if;
7192
7193             elsif (Ekind (Btyp) = E_Access_Subprogram_Type
7194                      or else
7195                    Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type)
7196               and then Ekind (Etype (N)) = E_Access_Protected_Subprogram_Type
7197             then
7198                Error_Msg_N ("context requires a non-protected subprogram", P);
7199             end if;
7200
7201             --  The context cannot be a pool-specific type, but this is a
7202             --  legality rule, not a resolution rule, so it must be checked
7203             --  separately, after possibly disambiguation (see AI-245).
7204
7205             if Ekind (Btyp) = E_Access_Type
7206               and then Attr_Id /= Attribute_Unrestricted_Access
7207             then
7208                Wrong_Type (N, Typ);
7209             end if;
7210
7211             Set_Etype (N, Typ);
7212
7213             --  Check for incorrect atomic/volatile reference (RM C.6(12))
7214
7215             if Attr_Id /= Attribute_Unrestricted_Access then
7216                if Is_Atomic_Object (P)
7217                  and then not Is_Atomic (Designated_Type (Typ))
7218                then
7219                   Error_Msg_N
7220                     ("access to atomic object cannot yield access-to-" &
7221                      "non-atomic type", P);
7222
7223                elsif Is_Volatile_Object (P)
7224                  and then not Is_Volatile (Designated_Type (Typ))
7225                then
7226                   Error_Msg_N
7227                     ("access to volatile object cannot yield access-to-" &
7228                      "non-volatile type", P);
7229                end if;
7230             end if;
7231
7232          -------------
7233          -- Address --
7234          -------------
7235
7236          --  Deal with resolving the type for Address attribute, overloading
7237          --  is not permitted here, since there is no context to resolve it.
7238
7239          when Attribute_Address | Attribute_Code_Address =>
7240
7241             --  To be safe, assume that if the address of a variable is taken,
7242             --  it may be modified via this address, so note modification.
7243
7244             if Is_Variable (P) then
7245                Note_Possible_Modification (P);
7246             end if;
7247
7248             if Nkind (P) in N_Subexpr
7249               and then Is_Overloaded (P)
7250             then
7251                Get_First_Interp (P, Index, It);
7252                Get_Next_Interp (Index, It);
7253
7254                if Present (It.Nam) then
7255                   Error_Msg_Name_1 := Aname;
7256                   Error_Msg_N
7257                     ("prefix of % attribute cannot be overloaded", P);
7258                   return;
7259                end if;
7260             end if;
7261
7262             if not Is_Entity_Name (P)
7263                or else not Is_Overloadable (Entity (P))
7264             then
7265                if not Is_Task_Type (Etype (P))
7266                  or else Nkind (P) = N_Explicit_Dereference
7267                then
7268                   Resolve (P);
7269                end if;
7270             end if;
7271
7272             --  If this is the name of a derived subprogram, or that of a
7273             --  generic actual, the address is that of the original entity.
7274
7275             if Is_Entity_Name (P)
7276               and then Is_Overloadable (Entity (P))
7277               and then Present (Alias (Entity (P)))
7278             then
7279                Rewrite (P,
7280                  New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
7281             end if;
7282
7283          ---------------
7284          -- AST_Entry --
7285          ---------------
7286
7287          --  Prefix of the AST_Entry attribute is an entry name which must
7288          --  not be resolved, since this is definitely not an entry call.
7289
7290          when Attribute_AST_Entry =>
7291             null;
7292
7293          ------------------
7294          -- Body_Version --
7295          ------------------
7296
7297          --  Prefix of Body_Version attribute can be a subprogram name which
7298          --  must not be resolved, since this is not a call.
7299
7300          when Attribute_Body_Version =>
7301             null;
7302
7303          ------------
7304          -- Caller --
7305          ------------
7306
7307          --  Prefix of Caller attribute is an entry name which must not
7308          --  be resolved, since this is definitely not an entry call.
7309
7310          when Attribute_Caller =>
7311             null;
7312
7313          ------------------
7314          -- Code_Address --
7315          ------------------
7316
7317          --  Shares processing with Address attribute
7318
7319          -----------
7320          -- Count --
7321          -----------
7322
7323          --  If the prefix of the Count attribute is an entry name it must not
7324          --  be resolved, since this is definitely not an entry call. However,
7325          --  if it is an element of an entry family, the index itself may
7326          --  have to be resolved because it can be a general expression.
7327
7328          when Attribute_Count =>
7329             if Nkind (P) = N_Indexed_Component
7330               and then Is_Entity_Name (Prefix (P))
7331             then
7332                declare
7333                   Indx : constant Node_Id   := First (Expressions (P));
7334                   Fam  : constant Entity_Id := Entity (Prefix (P));
7335                begin
7336                   Resolve (Indx, Entry_Index_Type (Fam));
7337                   Apply_Range_Check (Indx, Entry_Index_Type (Fam));
7338                end;
7339             end if;
7340
7341          ----------------
7342          -- Elaborated --
7343          ----------------
7344
7345          --  Prefix of the Elaborated attribute is a subprogram name which
7346          --  must not be resolved, since this is definitely not a call. Note
7347          --  that it is a library unit, so it cannot be overloaded here.
7348
7349          when Attribute_Elaborated =>
7350             null;
7351
7352          --------------------
7353          -- Mechanism_Code --
7354          --------------------
7355
7356          --  Prefix of the Mechanism_Code attribute is a function name
7357          --  which must not be resolved. Should we check for overloaded ???
7358
7359          when Attribute_Mechanism_Code =>
7360             null;
7361
7362          ------------------
7363          -- Partition_ID --
7364          ------------------
7365
7366          --  Most processing is done in sem_dist, after determining the
7367          --  context type. Node is rewritten as a conversion to a runtime call.
7368
7369          when Attribute_Partition_ID =>
7370             Process_Partition_Id (N);
7371             return;
7372
7373          when Attribute_Pool_Address =>
7374             Resolve (P);
7375
7376          -----------
7377          -- Range --
7378          -----------
7379
7380          --  We replace the Range attribute node with a range expression
7381          --  whose bounds are the 'First and 'Last attributes applied to the
7382          --  same prefix. The reason that we do this transformation here
7383          --  instead of in the expander is that it simplifies other parts of
7384          --  the semantic analysis which assume that the Range has been
7385          --  replaced; thus it must be done even when in semantic-only mode
7386          --  (note that the RM specifically mentions this equivalence, we
7387          --  take care that the prefix is only evaluated once).
7388
7389          when Attribute_Range => Range_Attribute :
7390             declare
7391                LB   : Node_Id;
7392                HB   : Node_Id;
7393
7394                function Check_Discriminated_Prival
7395                  (N    : Node_Id)
7396                   return Node_Id;
7397                --  The range of a private component constrained by a
7398                --  discriminant is rewritten to make the discriminant
7399                --  explicit. This solves some complex visibility problems
7400                --  related to the use of privals.
7401
7402                --------------------------------
7403                -- Check_Discriminated_Prival --
7404                --------------------------------
7405
7406                function Check_Discriminated_Prival
7407                  (N    : Node_Id)
7408                   return Node_Id
7409                is
7410                begin
7411                   if Is_Entity_Name (N)
7412                     and then Ekind (Entity (N)) = E_In_Parameter
7413                     and then not Within_Init_Proc
7414                   then
7415                      return Make_Identifier (Sloc (N), Chars (Entity (N)));
7416                   else
7417                      return Duplicate_Subexpr (N);
7418                   end if;
7419                end Check_Discriminated_Prival;
7420
7421             --  Start of processing for Range_Attribute
7422
7423             begin
7424                if not Is_Entity_Name (P)
7425                  or else not Is_Type (Entity (P))
7426                then
7427                   Resolve (P);
7428                end if;
7429
7430                --  Check whether prefix is (renaming of) private component
7431                --  of protected type.
7432
7433                if Is_Entity_Name (P)
7434                  and then Comes_From_Source (N)
7435                  and then Is_Array_Type (Etype (P))
7436                  and then Number_Dimensions (Etype (P)) = 1
7437                  and then (Ekind (Scope (Entity (P))) = E_Protected_Type
7438                             or else
7439                            Ekind (Scope (Scope (Entity (P)))) =
7440                                                         E_Protected_Type)
7441                then
7442                   LB :=
7443                     Check_Discriminated_Prival
7444                       (Type_Low_Bound (Etype (First_Index (Etype (P)))));
7445
7446                   HB :=
7447                     Check_Discriminated_Prival
7448                       (Type_High_Bound (Etype (First_Index (Etype (P)))));
7449
7450                else
7451                   HB :=
7452                     Make_Attribute_Reference (Loc,
7453                       Prefix         => Duplicate_Subexpr (P),
7454                       Attribute_Name => Name_Last,
7455                       Expressions    => Expressions (N));
7456
7457                   LB :=
7458                     Make_Attribute_Reference (Loc,
7459                       Prefix         => P,
7460                       Attribute_Name => Name_First,
7461                       Expressions    => Expressions (N));
7462                end if;
7463
7464                --  If the original was marked as Must_Not_Freeze (see code
7465                --  in Sem_Ch3.Make_Index), then make sure the rewriting
7466                --  does not freeze either.
7467
7468                if Must_Not_Freeze (N) then
7469                   Set_Must_Not_Freeze (HB);
7470                   Set_Must_Not_Freeze (LB);
7471                   Set_Must_Not_Freeze (Prefix (HB));
7472                   Set_Must_Not_Freeze (Prefix (LB));
7473                end if;
7474
7475                if Raises_Constraint_Error (Prefix (N)) then
7476
7477                   --  Preserve Sloc of prefix in the new bounds, so that
7478                   --  the posted warning can be removed if we are within
7479                   --  unreachable code.
7480
7481                   Set_Sloc (LB, Sloc (Prefix (N)));
7482                   Set_Sloc (HB, Sloc (Prefix (N)));
7483                end if;
7484
7485                Rewrite (N, Make_Range (Loc, LB, HB));
7486                Analyze_And_Resolve (N, Typ);
7487
7488                --  Normally after resolving attribute nodes, Eval_Attribute
7489                --  is called to do any possible static evaluation of the node.
7490                --  However, here since the Range attribute has just been
7491                --  transformed into a range expression it is no longer an
7492                --  attribute node and therefore the call needs to be avoided
7493                --  and is accomplished by simply returning from the procedure.
7494
7495                return;
7496             end Range_Attribute;
7497
7498          -----------------
7499          -- UET_Address --
7500          -----------------
7501
7502          --  Prefix must not be resolved in this case, since it is not a
7503          --  real entity reference. No action of any kind is require!
7504
7505          when Attribute_UET_Address =>
7506             return;
7507
7508          ----------------------
7509          -- Unchecked_Access --
7510          ----------------------
7511
7512          --  Processing is shared with Access
7513
7514          -------------------------
7515          -- Unrestricted_Access --
7516          -------------------------
7517
7518          --  Processing is shared with Access
7519
7520          ---------
7521          -- Val --
7522          ---------
7523
7524          --  Apply range check. Note that we did not do this during the
7525          --  analysis phase, since we wanted Eval_Attribute to have a
7526          --  chance at finding an illegal out of range value.
7527
7528          when Attribute_Val =>
7529
7530             --  Note that we do our own Eval_Attribute call here rather than
7531             --  use the common one, because we need to do processing after
7532             --  the call, as per above comment.
7533
7534             Eval_Attribute (N);
7535
7536             --  Eval_Attribute may replace the node with a raise CE, or
7537             --  fold it to a constant. Obviously we only apply a scalar
7538             --  range check if this did not happen!
7539
7540             if Nkind (N) = N_Attribute_Reference
7541               and then Attribute_Name (N) = Name_Val
7542             then
7543                Apply_Scalar_Range_Check (First (Expressions (N)), Btyp);
7544             end if;
7545
7546             return;
7547
7548          -------------
7549          -- Version --
7550          -------------
7551
7552          --  Prefix of Version attribute can be a subprogram name which
7553          --  must not be resolved, since this is not a call.
7554
7555          when Attribute_Version =>
7556             null;
7557
7558          ----------------------
7559          -- Other Attributes --
7560          ----------------------
7561
7562          --  For other attributes, resolve prefix unless it is a type. If
7563          --  the attribute reference itself is a type name ('Base and 'Class)
7564          --  then this is only legal within a task or protected record.
7565
7566          when others =>
7567             if not Is_Entity_Name (P)
7568               or else not Is_Type (Entity (P))
7569             then
7570                Resolve (P);
7571             end if;
7572
7573             --  If the attribute reference itself is a type name ('Base,
7574             --  'Class) then this is only legal within a task or protected
7575             --  record. What is this all about ???
7576
7577             if Is_Entity_Name (N)
7578               and then Is_Type (Entity (N))
7579             then
7580                if Is_Concurrent_Type (Entity (N))
7581                  and then In_Open_Scopes (Entity (P))
7582                then
7583                   null;
7584                else
7585                   Error_Msg_N
7586                     ("invalid use of subtype name in expression or call", N);
7587                end if;
7588             end if;
7589
7590             --  For attributes whose argument may be a string, complete
7591             --  resolution of argument now. This avoids premature expansion
7592             --  (and the creation of transient scopes) before the attribute
7593             --  reference is resolved.
7594
7595             case Attr_Id is
7596                when Attribute_Value =>
7597                   Resolve (First (Expressions (N)), Standard_String);
7598
7599                when Attribute_Wide_Value =>
7600                   Resolve (First (Expressions (N)), Standard_Wide_String);
7601
7602                when Attribute_Wide_Wide_Value =>
7603                   Resolve (First (Expressions (N)), Standard_Wide_Wide_String);
7604
7605                when others => null;
7606             end case;
7607       end case;
7608
7609       --  Normally the Freezing is done by Resolve but sometimes the Prefix
7610       --  is not resolved, in which case the freezing must be done now.
7611
7612       Freeze_Expression (P);
7613
7614       --  Finally perform static evaluation on the attribute reference
7615
7616       Eval_Attribute (N);
7617    end Resolve_Attribute;
7618
7619    --------------------------------
7620    -- Stream_Attribute_Available --
7621    --------------------------------
7622
7623    function Stream_Attribute_Available
7624      (Typ          : Entity_Id;
7625       Nam          : TSS_Name_Type;
7626       Partial_View : Node_Id := Empty) return Boolean
7627    is
7628       Etyp : Entity_Id := Typ;
7629
7630       function Has_Specified_Stream_Attribute
7631         (Typ : Entity_Id;
7632          Nam : TSS_Name_Type) return Boolean;
7633       --  True iff there is a visible attribute definition clause specifying
7634       --  attribute Nam for Typ.
7635
7636       ------------------------------------
7637       -- Has_Specified_Stream_Attribute --
7638       ------------------------------------
7639
7640       function Has_Specified_Stream_Attribute
7641         (Typ : Entity_Id;
7642          Nam : TSS_Name_Type) return Boolean
7643       is
7644       begin
7645          return False
7646            or else
7647              (Nam = TSS_Stream_Input
7648                and then Has_Specified_Stream_Input (Typ))
7649            or else
7650              (Nam = TSS_Stream_Output
7651                and then Has_Specified_Stream_Output (Typ))
7652            or else
7653              (Nam = TSS_Stream_Read
7654                and then Has_Specified_Stream_Read (Typ))
7655            or else
7656              (Nam = TSS_Stream_Write
7657                and then Has_Specified_Stream_Write (Typ));
7658       end Has_Specified_Stream_Attribute;
7659
7660    --  Start of processing for Stream_Attribute_Available
7661
7662    begin
7663       --  We need some comments in this body ???
7664
7665       if Has_Specified_Stream_Attribute (Typ, Nam) then
7666          return True;
7667       end if;
7668
7669       if Is_Class_Wide_Type (Typ) then
7670          return not Is_Limited_Type (Typ)
7671            or else Stream_Attribute_Available (Etype (Typ), Nam);
7672       end if;
7673
7674       if Nam = TSS_Stream_Input
7675         and then Is_Abstract (Typ)
7676         and then not Is_Class_Wide_Type (Typ)
7677       then
7678          return False;
7679       end if;
7680
7681       if not (Is_Limited_Type (Typ)
7682         or else (Present (Partial_View)
7683                    and then Is_Limited_Type (Partial_View)))
7684       then
7685          return True;
7686       end if;
7687
7688       if Nam = TSS_Stream_Input then
7689          return Ada_Version >= Ada_05
7690            and then Stream_Attribute_Available (Etyp, TSS_Stream_Read);
7691       elsif Nam = TSS_Stream_Output then
7692          return Ada_Version >= Ada_05
7693            and then Stream_Attribute_Available (Etyp, TSS_Stream_Write);
7694       end if;
7695
7696       --  Case of Read and Write: check for attribute definition clause that
7697       --  applies to an ancestor type.
7698
7699       while Etype (Etyp) /= Etyp loop
7700          Etyp := Etype (Etyp);
7701
7702          if Has_Specified_Stream_Attribute (Etyp, Nam) then
7703             return True;
7704          end if;
7705       end loop;
7706
7707       if Ada_Version < Ada_05 then
7708
7709          --  In Ada 95 mode, also consider a non-visible definition
7710
7711          declare
7712             Btyp : constant Entity_Id := Implementation_Base_Type (Typ);
7713          begin
7714             return Btyp /= Typ
7715               and then Stream_Attribute_Available
7716                          (Btyp, Nam, Partial_View => Typ);
7717          end;
7718       end if;
7719
7720       return False;
7721    end Stream_Attribute_Available;
7722
7723 end Sem_Attr;