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) 1992-2004, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- GNAT was originally developed  by the GNAT team at  New York University. --
  23 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  24 --                                                                          --
  25 ------------------------------------------------------------------------------
  26
  27 with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
  28
  29 with Atree;    use Atree;
  30 with Checks;   use Checks;
  31 with Einfo;    use Einfo;
  32 with Errout;   use Errout;
  33 with Eval_Fat;
  34 with Exp_Tss;  use Exp_Tss;
  35 with Exp_Util; use Exp_Util;
  36 with Expander; use Expander;
  37 with Freeze;   use Freeze;
  38 with Lib;      use Lib;
  39 with Lib.Xref; use Lib.Xref;
  40 with Namet;    use Namet;
  41 with Nlists;   use Nlists;
  42 with Nmake;    use Nmake;
  43 with Opt;      use Opt;
  44 with Restrict; use Restrict;
  45 with Rident;   use Rident;
  46 with Rtsfind;  use Rtsfind;
  47 with Sdefault; use Sdefault;
  48 with Sem;      use Sem;
  49 with Sem_Cat;  use Sem_Cat;
  50 with Sem_Ch6;  use Sem_Ch6;
  51 with Sem_Ch8;  use Sem_Ch8;
  52 with Sem_Dist; use Sem_Dist;
  53 with Sem_Eval; use Sem_Eval;
  54 with Sem_Res;  use Sem_Res;
  55 with Sem_Type; use Sem_Type;
  56 with Sem_Util; use Sem_Util;
  57 with Stand;    use Stand;
  58 with Sinfo;    use Sinfo;
  59 with Sinput;   use Sinput;
  60 with Snames;   use Snames;
  61 with Stand;
  62 with Stringt;  use Stringt;
  63 with Targparm; use Targparm;
  64 with Ttypes;   use Ttypes;
  65 with Ttypef;   use Ttypef;
  66 with Tbuild;   use Tbuild;
  67 with Uintp;    use Uintp;
  68 with Urealp;   use Urealp;
  69 with Widechar; use Widechar;
  70
  71 package body Sem_Attr is
  72
  73    True_Value  : constant Uint := Uint_1;
  74    False_Value : constant Uint := Uint_0;
  75    --  Synonyms to be used when these constants are used as Boolean values
  76
  77    Bad_Attribute : exception;
  78    --  Exception raised if an error is detected during attribute processing,
  79    --  used so that we can abandon the processing so we don't run into
  80    --  trouble with cascaded errors.
  81
  82    --  The following array is the list of attributes defined in the Ada 83 RM
  83
  84    Attribute_83 : constant Attribute_Class_Array := Attribute_Class_Array'(
  85       Attribute_Address           |
  86       Attribute_Aft               |
  87       Attribute_Alignment         |
  88       Attribute_Base              |
  89       Attribute_Callable          |
  90       Attribute_Constrained       |
  91       Attribute_Count             |
  92       Attribute_Delta             |
  93       Attribute_Digits            |
  94       Attribute_Emax              |
  95       Attribute_Epsilon           |
  96       Attribute_First             |
  97       Attribute_First_Bit         |
  98       Attribute_Fore              |
  99       Attribute_Image             |
 100       Attribute_Large             |
 101       Attribute_Last              |
 102       Attribute_Last_Bit          |
 103       Attribute_Leading_Part      |
 104       Attribute_Length            |
 105       Attribute_Machine_Emax      |
 106       Attribute_Machine_Emin      |
 107       Attribute_Machine_Mantissa  |
 108       Attribute_Machine_Overflows |
 109       Attribute_Machine_Radix     |
 110       Attribute_Machine_Rounds    |
 111       Attribute_Mantissa          |
 112       Attribute_Pos               |
 113       Attribute_Position          |
 114       Attribute_Pred              |
 115       Attribute_Range             |
 116       Attribute_Safe_Emax         |
 117       Attribute_Safe_Large        |
 118       Attribute_Safe_Small        |
 119       Attribute_Size              |
 120       Attribute_Small             |
 121       Attribute_Storage_Size      |
 122       Attribute_Succ              |
 123       Attribute_Terminated        |
 124       Attribute_Val               |
 125       Attribute_Value             |
 126       Attribute_Width             => True,
 127       others                      => False);
 128
 129    -----------------------
 130    -- Local_Subprograms --
 131    -----------------------
 132
 133    procedure Eval_Attribute (N : Node_Id);
 134    --  Performs compile time evaluation of attributes where possible, leaving
 135    --  the Is_Static_Expression/Raises_Constraint_Error flags appropriately
 136    --  set, and replacing the node with a literal node if the value can be
 137    --  computed at compile time. All static attribute references are folded,
 138    --  as well as a number of cases of non-static attributes that can always
 139    --  be computed at compile time (e.g. floating-point model attributes that
 140    --  are applied to non-static subtypes). Of course in such cases, the
 141    --  Is_Static_Expression flag will not be set on the resulting literal.
 142    --  Note that the only required action of this procedure is to catch the
 143    --  static expression cases as described in the RM. Folding of other cases
 144    --  is done where convenient, but some additional non-static folding is in
 145    --  N_Expand_Attribute_Reference in cases where this is more convenient.
 146
 147    function Is_Anonymous_Tagged_Base
 148      (Anon : Entity_Id;
 149       Typ  : Entity_Id)
 150       return Boolean;
 151    --  For derived tagged types that constrain parent discriminants we build
 152    --  an anonymous unconstrained base type. We need to recognize the relation
 153    --  between the two when analyzing an access attribute for a constrained
 154    --  component, before the full declaration for Typ has been analyzed, and
 155    --  where therefore the prefix of the attribute does not match the enclosing
 156    --  scope.
 157
 158    -----------------------
 159    -- Analyze_Attribute --
 160    -----------------------
 161
 162    procedure Analyze_Attribute (N : Node_Id) is
 163       Loc     : constant Source_Ptr   := Sloc (N);
 164       Aname   : constant Name_Id      := Attribute_Name (N);
 165       P       : constant Node_Id      := Prefix (N);
 166       Exprs   : constant List_Id      := Expressions (N);
 167       Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname);
 168       E1      : Node_Id;
 169       E2      : Node_Id;
 170
 171       P_Type : Entity_Id;
 172       --  Type of prefix after analysis
 173
 174       P_Base_Type : Entity_Id;
 175       --  Base type of prefix after analysis
 176
 177       -----------------------
 178       -- Local Subprograms --
 179       -----------------------
 180
 181       procedure Analyze_Access_Attribute;
 182       --  Used for Access, Unchecked_Access, Unrestricted_Access attributes.
 183       --  Internally, Id distinguishes which of the three cases is involved.
 184
 185       procedure Check_Array_Or_Scalar_Type;
 186       --  Common procedure used by First, Last, Range attribute to check
 187       --  that the prefix is a constrained array or scalar type, or a name
 188       --  of an array object, and that an argument appears only if appropriate
 189       --  (i.e. only in the array case).
 190
 191       procedure Check_Array_Type;
 192       --  Common semantic checks for all array attributes. Checks that the
 193       --  prefix is a constrained array type or the name of an array object.
 194       --  The error message for non-arrays is specialized appropriately.
 195
 196       procedure Check_Asm_Attribute;
 197       --  Common semantic checks for Asm_Input and Asm_Output attributes
 198
 199       procedure Check_Component;
 200       --  Common processing for Bit_Position, First_Bit, Last_Bit, and
 201       --  Position. Checks prefix is an appropriate selected component.
 202
 203       procedure Check_Decimal_Fixed_Point_Type;
 204       --  Check that prefix of attribute N is a decimal fixed-point type
 205
 206       procedure Check_Dereference;
 207       --  If the prefix of attribute is an object of an access type, then
 208       --  introduce an explicit deference, and adjust P_Type accordingly.
 209
 210       procedure Check_Discrete_Type;
 211       --  Verify that prefix of attribute N is a discrete type
 212
 213       procedure Check_E0;
 214       --  Check that no attribute arguments are present
 215
 216       procedure Check_Either_E0_Or_E1;
 217       --  Check that there are zero or one attribute arguments present
 218
 219       procedure Check_E1;
 220       --  Check that exactly one attribute argument is present
 221
 222       procedure Check_E2;
 223       --  Check that two attribute arguments are present
 224
 225       procedure Check_Enum_Image;
 226       --  If the prefix type is an enumeration type, set all its literals
 227       --  as referenced, since the image function could possibly end up
 228       --  referencing any of the literals indirectly.
 229
 230       procedure Check_Fixed_Point_Type;
 231       --  Verify that prefix of attribute N is a fixed type
 232
 233       procedure Check_Fixed_Point_Type_0;
 234       --  Verify that prefix of attribute N is a fixed type and that
 235       --  no attribute expressions are present
 236
 237       procedure Check_Floating_Point_Type;
 238       --  Verify that prefix of attribute N is a float type
 239
 240       procedure Check_Floating_Point_Type_0;
 241       --  Verify that prefix of attribute N is a float type and that
 242       --  no attribute expressions are present
 243
 244       procedure Check_Floating_Point_Type_1;
 245       --  Verify that prefix of attribute N is a float type and that
 246       --  exactly one attribute expression is present
 247
 248       procedure Check_Floating_Point_Type_2;
 249       --  Verify that prefix of attribute N is a float type and that
 250       --  two attribute expressions are present
 251
 252       procedure Legal_Formal_Attribute;
 253       --  Common processing for attributes Definite, and Has_Discriminants
 254
 255       procedure Check_Integer_Type;
 256       --  Verify that prefix of attribute N is an integer type
 257
 258       procedure Check_Library_Unit;
 259       --  Verify that prefix of attribute N is a library unit
 260
 261       procedure Check_Not_Incomplete_Type;
 262       --  Check that P (the prefix of the attribute) is not an incomplete
 263       --  type or a private type for which no full view has been given.
 264
 265       procedure Check_Object_Reference (P : Node_Id);
 266       --  Check that P (the prefix of the attribute) is an object reference
 267
 268       procedure Check_Program_Unit;
 269       --  Verify that prefix of attribute N is a program unit
 270
 271       procedure Check_Real_Type;
 272       --  Verify that prefix of attribute N is fixed or float type
 273
 274       procedure Check_Scalar_Type;
 275       --  Verify that prefix of attribute N is a scalar type
 276
 277       procedure Check_Standard_Prefix;
 278       --  Verify that prefix of attribute N is package Standard
 279
 280       procedure Check_Stream_Attribute (Nam : TSS_Name_Type);
 281       --  Validity checking for stream attribute. Nam is the TSS name of the
 282       --  corresponding possible defined attribute function (e.g. for the
 283       --  Read attribute, Nam will be TSS_Stream_Read).
 284
 285       procedure Check_Task_Prefix;
 286       --  Verify that prefix of attribute N is a task or task type
 287
 288       procedure Check_Type;
 289       --  Verify that the prefix of attribute N is a type
 290
 291       procedure Check_Unit_Name (Nod : Node_Id);
 292       --  Check that Nod is of the form of a library unit name, i.e that
 293       --  it is an identifier, or a selected component whose prefix is
 294       --  itself of the form of a library unit name. Note that this is
 295       --  quite different from Check_Program_Unit, since it only checks
 296       --  the syntactic form of the name, not the semantic identity. This
 297       --  is because it is used with attributes (Elab_Body, Elab_Spec, and
 298       --  UET_Address) which can refer to non-visible unit.
 299
 300       procedure Error_Attr (Msg : String; Error_Node : Node_Id);
 301       pragma No_Return (Error_Attr);
 302       procedure Error_Attr;
 303       pragma No_Return (Error_Attr);
 304       --  Posts error using Error_Msg_N at given node, sets type of attribute
 305       --  node to Any_Type, and then raises Bad_Attribute to avoid any further
 306       --  semantic processing. The message typically contains a % insertion
 307       --  character which is replaced by the attribute name. The call with
 308       --  no arguments is used when the caller has already generated the
 309       --  required error messages.
 310
 311       procedure Standard_Attribute (Val : Int);
 312       --  Used to process attributes whose prefix is package Standard which
 313       --  yield values of type Universal_Integer. The attribute reference
 314       --  node is rewritten with an integer literal of the given value.
 315
 316       procedure Unexpected_Argument (En : Node_Id);
 317       --  Signal unexpected attribute argument (En is the argument)
 318
 319       procedure Validate_Non_Static_Attribute_Function_Call;
 320       --  Called when processing an attribute that is a function call to a
 321       --  non-static function, i.e. an attribute function that either takes
 322       --  non-scalar arguments or returns a non-scalar result. Verifies that
 323       --  such a call does not appear in a preelaborable context.
 324
 325       ------------------------------
 326       -- Analyze_Access_Attribute --
 327       ------------------------------
 328
 329       procedure Analyze_Access_Attribute is
 330          Acc_Type : Entity_Id;
 331
 332          Scop : Entity_Id;
 333          Typ  : Entity_Id;
 334
 335          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id;
 336          --  Build an access-to-object type whose designated type is DT,
 337          --  and whose Ekind is appropriate to the attribute type. The
 338          --  type that is constructed is returned as the result.
 339
 340          procedure Build_Access_Subprogram_Type (P : Node_Id);
 341          --  Build an access to subprogram whose designated type is
 342          --  the type of the prefix. If prefix is overloaded, so it the
 343          --  node itself. The result is stored in Acc_Type.
 344
 345          ------------------------------
 346          -- Build_Access_Object_Type --
 347          ------------------------------
 348
 349          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id is
 350             Typ : Entity_Id;
 351
 352          begin
 353             if Aname = Name_Unrestricted_Access then
 354                Typ :=
 355                  New_Internal_Entity
 356                    (E_Allocator_Type, Current_Scope, Loc, 'A');
 357             else
 358                Typ :=
 359                  New_Internal_Entity
 360                    (E_Access_Attribute_Type, Current_Scope, Loc, 'A');
 361             end if;
 362
 363             Set_Etype                     (Typ, Typ);
 364             Init_Size_Align               (Typ);
 365             Set_Is_Itype                  (Typ);
 366             Set_Associated_Node_For_Itype (Typ, N);
 367             Set_Directly_Designated_Type  (Typ, DT);
 368             return Typ;
 369          end Build_Access_Object_Type;
 370
 371          ----------------------------------
 372          -- Build_Access_Subprogram_Type --
 373          ----------------------------------
 374
 375          procedure Build_Access_Subprogram_Type (P : Node_Id) is
 376             Index : Interp_Index;
 377             It    : Interp;
 378
 379             function Get_Kind (E : Entity_Id) return Entity_Kind;
 380             --  Distinguish between access to regular and protected
 381             --  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             if not Is_Overloaded (P) then
 404                Acc_Type :=
 405                  New_Internal_Entity
 406                    (Get_Kind (Entity (P)), Current_Scope, Loc, 'A');
 407                Set_Etype (Acc_Type, Acc_Type);
 408                Set_Directly_Designated_Type (Acc_Type, Entity (P));
 409                Set_Etype (N, Acc_Type);
 410
 411             else
 412                Get_First_Interp (P, Index, It);
 413                Set_Etype (N, Any_Type);
 414
 415                while Present (It.Nam) loop
 416                   if not Is_Intrinsic_Subprogram (It.Nam) then
 417                      Acc_Type :=
 418                        New_Internal_Entity
 419                          (Get_Kind (It.Nam), Current_Scope, Loc, 'A');
 420                      Set_Etype (Acc_Type, Acc_Type);
 421                      Set_Directly_Designated_Type (Acc_Type, It.Nam);
 422                      Add_One_Interp (N, Acc_Type, Acc_Type);
 423                   end if;
 424
 425                   Get_Next_Interp (Index, It);
 426                end loop;
 427
 428                if Etype (N) = Any_Type then
 429                   Error_Attr ("prefix of % attribute cannot be intrinsic", P);
 430                end if;
 431             end if;
 432          end Build_Access_Subprogram_Type;
 433
 434       --  Start of processing for Analyze_Access_Attribute
 435
 436       begin
 437          Check_E0;
 438
 439          if Nkind (P) = N_Character_Literal then
 440             Error_Attr
 441               ("prefix of % attribute cannot be enumeration literal", P);
 442          end if;
 443
 444          --  Case of access to subprogram
 445
 446          if Is_Entity_Name (P)
 447            and then Is_Overloadable (Entity (P))
 448          then
 449             --  Not allowed for nested subprograms if No_Implicit_Dynamic_Code
 450             --  restriction set (since in general a trampoline is required).
 451
 452             if not Is_Library_Level_Entity (Entity (P)) then
 453                Check_Restriction (No_Implicit_Dynamic_Code, P);
 454             end if;
 455
 456             --  Build the appropriate subprogram type
 457
 458             Build_Access_Subprogram_Type (P);
 459
 460             --  For unrestricted access, kill current values, since this
 461             --  attribute allows a reference to a local subprogram that
 462             --  could modify local variables to be passed out of scope
 463
 464             if Aname = Name_Unrestricted_Access then
 465                Kill_Current_Values;
 466             end if;
 467
 468             return;
 469
 470          --  Component is an operation of a protected type
 471
 472          elsif Nkind (P) = N_Selected_Component
 473            and then Is_Overloadable (Entity (Selector_Name (P)))
 474          then
 475             if Ekind (Entity (Selector_Name (P))) = E_Entry then
 476                Error_Attr ("prefix of % attribute must be subprogram", P);
 477             end if;
 478
 479             Build_Access_Subprogram_Type (Selector_Name (P));
 480             return;
 481          end if;
 482
 483          --  Deal with incorrect reference to a type, but note that some
 484          --  accesses are allowed (references to the current type instance).
 485
 486          if Is_Entity_Name (P) then
 487             Scop := Current_Scope;
 488             Typ := Entity (P);
 489
 490             if Is_Type (Typ) then
 491
 492                --  OK if we are within the scope of a limited type
 493                --  let's mark the component as having per object constraint
 494
 495                if Is_Anonymous_Tagged_Base (Scop, Typ) then
 496                   Typ := Scop;
 497                   Set_Entity (P, Typ);
 498                   Set_Etype  (P, Typ);
 499                end if;
 500
 501                if Typ = Scop then
 502                   declare
 503                      Q : Node_Id := Parent (N);
 504
 505                   begin
 506                      while Present (Q)
 507                        and then Nkind (Q) /= N_Component_Declaration
 508                      loop
 509                         Q := Parent (Q);
 510                      end loop;
 511                      if Present (Q) then
 512                         Set_Has_Per_Object_Constraint (
 513                           Defining_Identifier (Q), True);
 514                      end if;
 515                   end;
 516
 517                   if Nkind (P) = N_Expanded_Name then
 518                      Error_Msg_N
 519                        ("current instance prefix must be a direct name", P);
 520                   end if;
 521
 522                   --  If a current instance attribute appears within a
 523                   --  a component constraint it must appear alone; other
 524                   --  contexts (default expressions, within a task body)
 525                   --  are not subject to this restriction.
 526
 527                   if not In_Default_Expression
 528                     and then not Has_Completion (Scop)
 529                     and then
 530                       Nkind (Parent (N)) /= N_Discriminant_Association
 531                     and then
 532                       Nkind (Parent (N)) /= N_Index_Or_Discriminant_Constraint
 533                   then
 534                      Error_Msg_N
 535                        ("current instance attribute must appear alone", N);
 536                   end if;
 537
 538                --  OK if we are in initialization procedure for the type
 539                --  in question, in which case the reference to the type
 540                --  is rewritten as a reference to the current object.
 541
 542                elsif Ekind (Scop) = E_Procedure
 543                  and then Is_Init_Proc (Scop)
 544                  and then Etype (First_Formal (Scop)) = Typ
 545                then
 546                   Rewrite (N,
 547                     Make_Attribute_Reference (Loc,
 548                       Prefix         => Make_Identifier (Loc, Name_uInit),
 549                       Attribute_Name => Name_Unrestricted_Access));
 550                   Analyze (N);
 551                   return;
 552
 553                --  OK if a task type, this test needs sharpening up ???
 554
 555                elsif Is_Task_Type (Typ) then
 556                   null;
 557
 558                --  Otherwise we have an error case
 559
 560                else
 561                   Error_Attr ("% attribute cannot be applied to type", P);
 562                   return;
 563                end if;
 564             end if;
 565          end if;
 566
 567          --  If we fall through, we have a normal access to object case.
 568          --  Unrestricted_Access is legal wherever an allocator would be
 569          --  legal, so its Etype is set to E_Allocator. The expected type
 570          --  of the other attributes is a general access type, and therefore
 571          --  we label them with E_Access_Attribute_Type.
 572
 573          if not Is_Overloaded (P) then
 574             Acc_Type := Build_Access_Object_Type (P_Type);
 575             Set_Etype (N, Acc_Type);
 576          else
 577             declare
 578                Index : Interp_Index;
 579                It    : Interp;
 580
 581             begin
 582                Set_Etype (N, Any_Type);
 583                Get_First_Interp (P, Index, It);
 584
 585                while Present (It.Typ) loop
 586                   Acc_Type := Build_Access_Object_Type (It.Typ);
 587                   Add_One_Interp (N, Acc_Type, Acc_Type);
 588                   Get_Next_Interp (Index, It);
 589                end loop;
 590             end;
 591          end if;
 592
 593          --  If we have an access to an object, and the attribute comes
 594          --  from source, then set the object as potentially source modified.
 595          --  We do this because the resulting access pointer can be used to
 596          --  modify the variable, and we might not detect this, leading to
 597          --  some junk warnings.
 598
 599          if Is_Entity_Name (P) then
 600             Set_Never_Set_In_Source (Entity (P), False);
 601          end if;
 602
 603          --  Check for aliased view unless unrestricted case. We allow
 604          --  a nonaliased prefix when within an instance because the
 605          --  prefix may have been a tagged formal object, which is
 606          --  defined to be aliased even when the actual might not be
 607          --  (other instance cases will have been caught in the generic).
 608          --  Similarly, within an inlined body we know that the attribute
 609          --  is legal in the original subprogram, and therefore legal in
 610          --  the expansion.
 611
 612          if Aname /= Name_Unrestricted_Access
 613            and then not Is_Aliased_View (P)
 614            and then not In_Instance
 615            and then not In_Inlined_Body
 616          then
 617             Error_Attr ("prefix of % attribute must be aliased", P);
 618          end if;
 619       end Analyze_Access_Attribute;
 620
 621       --------------------------------
 622       -- Check_Array_Or_Scalar_Type --
 623       --------------------------------
 624
 625       procedure Check_Array_Or_Scalar_Type is
 626          Index : Entity_Id;
 627
 628          D : Int;
 629          --  Dimension number for array attributes.
 630
 631       begin
 632          --  Case of string literal or string literal subtype. These cases
 633          --  cannot arise from legal Ada code, but the expander is allowed
 634          --  to generate them. They require special handling because string
 635          --  literal subtypes do not have standard bounds (the whole idea
 636          --  of these subtypes is to avoid having to generate the bounds)
 637
 638          if Ekind (P_Type) = E_String_Literal_Subtype then
 639             Set_Etype (N, Etype (First_Index (P_Base_Type)));
 640             return;
 641
 642          --  Scalar types
 643
 644          elsif Is_Scalar_Type (P_Type) then
 645             Check_Type;
 646
 647             if Present (E1) then
 648                Error_Attr ("invalid argument in % attribute", E1);
 649             else
 650                Set_Etype (N, P_Base_Type);
 651                return;
 652             end if;
 653
 654          --  The following is a special test to allow 'First to apply to
 655          --  private scalar types if the attribute comes from generated
 656          --  code. This occurs in the case of Normalize_Scalars code.
 657
 658          elsif Is_Private_Type (P_Type)
 659            and then Present (Full_View (P_Type))
 660            and then Is_Scalar_Type (Full_View (P_Type))
 661            and then not Comes_From_Source (N)
 662          then
 663             Set_Etype (N, Implementation_Base_Type (P_Type));
 664
 665          --  Array types other than string literal subtypes handled above
 666
 667          else
 668             Check_Array_Type;
 669
 670             --  We know prefix is an array type, or the name of an array
 671             --  object, and that the expression, if present, is static
 672             --  and within the range of the dimensions of the type.
 673
 674             pragma Assert (Is_Array_Type (P_Type));
 675             Index := First_Index (P_Base_Type);
 676
 677             if No (E1) then
 678
 679                --  First dimension assumed
 680
 681                Set_Etype (N, Base_Type (Etype (Index)));
 682
 683             else
 684                D := UI_To_Int (Intval (E1));
 685
 686                for J in 1 .. D - 1 loop
 687                   Next_Index (Index);
 688                end loop;
 689
 690                Set_Etype (N, Base_Type (Etype (Index)));
 691                Set_Etype (E1, Standard_Integer);
 692             end if;
 693          end if;
 694       end Check_Array_Or_Scalar_Type;
 695
 696       ----------------------
 697       -- Check_Array_Type --
 698       ----------------------
 699
 700       procedure Check_Array_Type is
 701          D : Int;
 702          --  Dimension number for array attributes.
 703
 704       begin
 705          --  If the type is a string literal type, then this must be generated
 706          --  internally, and no further check is required on its legality.
 707
 708          if Ekind (P_Type) = E_String_Literal_Subtype then
 709             return;
 710
 711          --  If the type is a composite, it is an illegal aggregate, no point
 712          --  in going on.
 713
 714          elsif P_Type = Any_Composite then
 715             raise Bad_Attribute;
 716          end if;
 717
 718          --  Normal case of array type or subtype
 719
 720          Check_Either_E0_Or_E1;
 721          Check_Dereference;
 722
 723          if Is_Array_Type (P_Type) then
 724             if not Is_Constrained (P_Type)
 725               and then Is_Entity_Name (P)
 726               and then Is_Type (Entity (P))
 727             then
 728                --  Note: we do not call Error_Attr here, since we prefer to
 729                --  continue, using the relevant index type of the array,
 730                --  even though it is unconstrained. This gives better error
 731                --  recovery behavior.
 732
 733                Error_Msg_Name_1 := Aname;
 734                Error_Msg_N
 735                  ("prefix for % attribute must be constrained array", P);
 736             end if;
 737
 738             D := Number_Dimensions (P_Type);
 739
 740          else
 741             if Is_Private_Type (P_Type) then
 742                Error_Attr
 743                  ("prefix for % attribute may not be private type", P);
 744
 745             elsif Is_Access_Type (P_Type)
 746               and then Is_Array_Type (Designated_Type (P_Type))
 747               and then Is_Entity_Name (P)
 748               and then Is_Type (Entity (P))
 749             then
 750                Error_Attr ("prefix of % attribute cannot be access type", P);
 751
 752             elsif Attr_Id = Attribute_First
 753                     or else
 754                   Attr_Id = Attribute_Last
 755             then
 756                Error_Attr ("invalid prefix for % attribute", P);
 757
 758             else
 759                Error_Attr ("prefix for % attribute must be array", P);
 760             end if;
 761          end if;
 762
 763          if Present (E1) then
 764             Resolve (E1, Any_Integer);
 765             Set_Etype (E1, Standard_Integer);
 766
 767             if not Is_Static_Expression (E1)
 768               or else Raises_Constraint_Error (E1)
 769             then
 770                Flag_Non_Static_Expr
 771                  ("expression for dimension must be static!", E1);
 772                Error_Attr;
 773
 774             elsif  UI_To_Int (Expr_Value (E1)) > D
 775               or else UI_To_Int (Expr_Value (E1)) < 1
 776             then
 777                Error_Attr ("invalid dimension number for array type", E1);
 778             end if;
 779          end if;
 780       end Check_Array_Type;
 781
 782       -------------------------
 783       -- Check_Asm_Attribute --
 784       -------------------------
 785
 786       procedure Check_Asm_Attribute is
 787       begin
 788          Check_Type;
 789          Check_E2;
 790
 791          --  Check first argument is static string expression
 792
 793          Analyze_And_Resolve (E1, Standard_String);
 794
 795          if Etype (E1) = Any_Type then
 796             return;
 797
 798          elsif not Is_OK_Static_Expression (E1) then
 799             Flag_Non_Static_Expr
 800               ("constraint argument must be static string expression!", E1);
 801             Error_Attr;
 802          end if;
 803
 804          --  Check second argument is right type
 805
 806          Analyze_And_Resolve (E2, Entity (P));
 807
 808          --  Note: that is all we need to do, we don't need to check
 809          --  that it appears in a correct context. The Ada type system
 810          --  will do that for us.
 811
 812       end Check_Asm_Attribute;
 813
 814       ---------------------
 815       -- Check_Component --
 816       ---------------------
 817
 818       procedure Check_Component is
 819       begin
 820          Check_E0;
 821
 822          if Nkind (P) /= N_Selected_Component
 823            or else
 824              (Ekind (Entity (Selector_Name (P))) /= E_Component
 825                and then
 826               Ekind (Entity (Selector_Name (P))) /= E_Discriminant)
 827          then
 828             Error_Attr
 829               ("prefix for % attribute must be selected component", P);
 830          end if;
 831       end Check_Component;
 832
 833       ------------------------------------
 834       -- Check_Decimal_Fixed_Point_Type --
 835       ------------------------------------
 836
 837       procedure Check_Decimal_Fixed_Point_Type is
 838       begin
 839          Check_Type;
 840
 841          if not Is_Decimal_Fixed_Point_Type (P_Type) then
 842             Error_Attr
 843               ("prefix of % attribute must be decimal type", P);
 844          end if;
 845       end Check_Decimal_Fixed_Point_Type;
 846
 847       -----------------------
 848       -- Check_Dereference --
 849       -----------------------
 850
 851       procedure Check_Dereference is
 852       begin
 853
 854          --  Case of a subtype mark
 855
 856          if Is_Entity_Name (P)
 857            and then Is_Type (Entity (P))
 858          then
 859             return;
 860          end if;
 861
 862          --  Case of an expression
 863
 864          Resolve (P);
 865          if Is_Access_Type (P_Type) then
 866
 867             --  If there is an implicit dereference, then we must freeze
 868             --  the designated type of the access type, since the type of
 869             --  the referenced array is this type (see AI95-00106).
 870
 871             Freeze_Before (N, Designated_Type (P_Type));
 872
 873             Rewrite (P,
 874               Make_Explicit_Dereference (Sloc (P),
 875                 Prefix => Relocate_Node (P)));
 876
 877             Analyze_And_Resolve (P);
 878             P_Type := Etype (P);
 879
 880             if P_Type = Any_Type then
 881                raise Bad_Attribute;
 882             end if;
 883
 884             P_Base_Type := Base_Type (P_Type);
 885          end if;
 886       end Check_Dereference;
 887
 888       -------------------------
 889       -- Check_Discrete_Type --
 890       -------------------------
 891
 892       procedure Check_Discrete_Type is
 893       begin
 894          Check_Type;
 895
 896          if not Is_Discrete_Type (P_Type) then
 897             Error_Attr ("prefix of % attribute must be discrete type", P);
 898          end if;
 899       end Check_Discrete_Type;
 900
 901       --------------
 902       -- Check_E0 --
 903       --------------
 904
 905       procedure Check_E0 is
 906       begin
 907          if Present (E1) then
 908             Unexpected_Argument (E1);
 909          end if;
 910       end Check_E0;
 911
 912       --------------
 913       -- Check_E1 --
 914       --------------
 915
 916       procedure Check_E1 is
 917       begin
 918          Check_Either_E0_Or_E1;
 919
 920          if No (E1) then
 921
 922             --  Special-case attributes that are functions and that appear as
 923             --  the prefix of another attribute. Error is posted on parent.
 924
 925             if Nkind (Parent (N)) = N_Attribute_Reference
 926               and then (Attribute_Name (Parent (N)) = Name_Address
 927                           or else
 928                         Attribute_Name (Parent (N)) = Name_Code_Address
 929                           or else
 930                         Attribute_Name (Parent (N)) = Name_Access)
 931             then
 932                Error_Msg_Name_1 := Attribute_Name (Parent (N));
 933                Error_Msg_N ("illegal prefix for % attribute", Parent (N));
 934                Set_Etype (Parent (N), Any_Type);
 935                Set_Entity (Parent (N), Any_Type);
 936                raise Bad_Attribute;
 937
 938             else
 939                Error_Attr ("missing argument for % attribute", N);
 940             end if;
 941          end if;
 942       end Check_E1;
 943
 944       --------------
 945       -- Check_E2 --
 946       --------------
 947
 948       procedure Check_E2 is
 949       begin
 950          if No (E1) then
 951             Error_Attr ("missing arguments for % attribute (2 required)", N);
 952          elsif No (E2) then
 953             Error_Attr ("missing argument for % attribute (2 required)", N);
 954          end if;
 955       end Check_E2;
 956
 957       ---------------------------
 958       -- Check_Either_E0_Or_E1 --
 959       ---------------------------
 960
 961       procedure Check_Either_E0_Or_E1 is
 962       begin
 963          if Present (E2) then
 964             Unexpected_Argument (E2);
 965          end if;
 966       end Check_Either_E0_Or_E1;
 967
 968       ----------------------
 969       -- Check_Enum_Image --
 970       ----------------------
 971
 972       procedure Check_Enum_Image is
 973          Lit : Entity_Id;
 974
 975       begin
 976          if Is_Enumeration_Type (P_Base_Type) then
 977             Lit := First_Literal (P_Base_Type);
 978             while Present (Lit) loop
 979                Set_Referenced (Lit);
 980                Next_Literal (Lit);
 981             end loop;
 982          end if;
 983       end Check_Enum_Image;
 984
 985       ----------------------------
 986       -- Check_Fixed_Point_Type --
 987       ----------------------------
 988
 989       procedure Check_Fixed_Point_Type is
 990       begin
 991          Check_Type;
 992
 993          if not Is_Fixed_Point_Type (P_Type) then
 994             Error_Attr ("prefix of % attribute must be fixed point type", P);
 995          end if;
 996       end Check_Fixed_Point_Type;
 997
 998       ------------------------------
 999       -- Check_Fixed_Point_Type_0 --
1000       ------------------------------
1001
1002       procedure Check_Fixed_Point_Type_0 is
1003       begin
1004          Check_Fixed_Point_Type;
1005          Check_E0;
1006       end Check_Fixed_Point_Type_0;
1007
1008       -------------------------------
1009       -- Check_Floating_Point_Type --
1010       -------------------------------
1011
1012       procedure Check_Floating_Point_Type is
1013       begin
1014          Check_Type;
1015
1016          if not Is_Floating_Point_Type (P_Type) then
1017             Error_Attr ("prefix of % attribute must be float type", P);
1018          end if;
1019       end Check_Floating_Point_Type;
1020
1021       ---------------------------------
1022       -- Check_Floating_Point_Type_0 --
1023       ---------------------------------
1024
1025       procedure Check_Floating_Point_Type_0 is
1026       begin
1027          Check_Floating_Point_Type;
1028          Check_E0;
1029       end Check_Floating_Point_Type_0;
1030
1031       ---------------------------------
1032       -- Check_Floating_Point_Type_1 --
1033       ---------------------------------
1034
1035       procedure Check_Floating_Point_Type_1 is
1036       begin
1037          Check_Floating_Point_Type;
1038          Check_E1;
1039       end Check_Floating_Point_Type_1;
1040
1041       ---------------------------------
1042       -- Check_Floating_Point_Type_2 --
1043       ---------------------------------
1044
1045       procedure Check_Floating_Point_Type_2 is
1046       begin
1047          Check_Floating_Point_Type;
1048          Check_E2;
1049       end Check_Floating_Point_Type_2;
1050
1051       ------------------------
1052       -- Check_Integer_Type --
1053       ------------------------
1054
1055       procedure Check_Integer_Type is
1056       begin
1057          Check_Type;
1058
1059          if not Is_Integer_Type (P_Type) then
1060             Error_Attr ("prefix of % attribute must be integer type", P);
1061          end if;
1062       end Check_Integer_Type;
1063
1064       ------------------------
1065       -- Check_Library_Unit --
1066       ------------------------
1067
1068       procedure Check_Library_Unit is
1069       begin
1070          if not Is_Compilation_Unit (Entity (P)) then
1071             Error_Attr ("prefix of % attribute must be library unit", P);
1072          end if;
1073       end Check_Library_Unit;
1074
1075       -------------------------------
1076       -- Check_Not_Incomplete_Type --
1077       -------------------------------
1078
1079       procedure Check_Not_Incomplete_Type is
1080       begin
1081          if not Is_Entity_Name (P)
1082            or else not Is_Type (Entity (P))
1083            or else In_Default_Expression
1084          then
1085             return;
1086
1087          else
1088             Check_Fully_Declared (P_Type, P);
1089          end if;
1090       end Check_Not_Incomplete_Type;
1091
1092       ----------------------------
1093       -- Check_Object_Reference --
1094       ----------------------------
1095
1096       procedure Check_Object_Reference (P : Node_Id) is
1097          Rtyp : Entity_Id;
1098
1099       begin
1100          --  If we need an object, and we have a prefix that is the name of
1101          --  a function entity, convert it into a function call.
1102
1103          if Is_Entity_Name (P)
1104            and then Ekind (Entity (P)) = E_Function
1105          then
1106             Rtyp := Etype (Entity (P));
1107
1108             Rewrite (P,
1109               Make_Function_Call (Sloc (P),
1110                 Name => Relocate_Node (P)));
1111
1112             Analyze_And_Resolve (P, Rtyp);
1113
1114          --  Otherwise we must have an object reference
1115
1116          elsif not Is_Object_Reference (P) then
1117             Error_Attr ("prefix of % attribute must be object", P);
1118          end if;
1119       end Check_Object_Reference;
1120
1121       ------------------------
1122       -- Check_Program_Unit --
1123       ------------------------
1124
1125       procedure Check_Program_Unit is
1126       begin
1127          if Is_Entity_Name (P) then
1128             declare
1129                K : constant Entity_Kind := Ekind (Entity (P));
1130                T : constant Entity_Id   := Etype (Entity (P));
1131
1132             begin
1133                if K in Subprogram_Kind
1134                  or else K in Task_Kind
1135                  or else K in Protected_Kind
1136                  or else K = E_Package
1137                  or else K in Generic_Unit_Kind
1138                  or else (K = E_Variable
1139                             and then
1140                               (Is_Task_Type (T)
1141                                  or else
1142                                Is_Protected_Type (T)))
1143                then
1144                   return;
1145                end if;
1146             end;
1147          end if;
1148
1149          Error_Attr ("prefix of % attribute must be program unit", P);
1150       end Check_Program_Unit;
1151
1152       ---------------------
1153       -- Check_Real_Type --
1154       ---------------------
1155
1156       procedure Check_Real_Type is
1157       begin
1158          Check_Type;
1159
1160          if not Is_Real_Type (P_Type) then
1161             Error_Attr ("prefix of % attribute must be real type", P);
1162          end if;
1163       end Check_Real_Type;
1164
1165       -----------------------
1166       -- Check_Scalar_Type --
1167       -----------------------
1168
1169       procedure Check_Scalar_Type is
1170       begin
1171          Check_Type;
1172
1173          if not Is_Scalar_Type (P_Type) then
1174             Error_Attr ("prefix of % attribute must be scalar type", P);
1175          end if;
1176       end Check_Scalar_Type;
1177
1178       ---------------------------
1179       -- Check_Standard_Prefix --
1180       ---------------------------
1181
1182       procedure Check_Standard_Prefix is
1183       begin
1184          Check_E0;
1185
1186          if Nkind (P) /= N_Identifier
1187            or else Chars (P) /= Name_Standard
1188          then
1189             Error_Attr ("only allowed prefix for % attribute is Standard", P);
1190          end if;
1191
1192       end Check_Standard_Prefix;
1193
1194       ----------------------------
1195       -- Check_Stream_Attribute --
1196       ----------------------------
1197
1198       procedure Check_Stream_Attribute (Nam : TSS_Name_Type) is
1199          Etyp : Entity_Id;
1200          Btyp : Entity_Id;
1201
1202       begin
1203          Validate_Non_Static_Attribute_Function_Call;
1204
1205          --  With the exception of 'Input, Stream attributes are procedures,
1206          --  and can only appear at the position of procedure calls. We check
1207          --  for this here, before they are rewritten, to give a more precise
1208          --  diagnostic.
1209
1210          if Nam = TSS_Stream_Input then
1211             null;
1212
1213          elsif Is_List_Member (N)
1214            and then Nkind (Parent (N)) /= N_Procedure_Call_Statement
1215            and then Nkind (Parent (N)) /= N_Aggregate
1216          then
1217             null;
1218
1219          else
1220             Error_Attr
1221               ("invalid context for attribute%, which is a procedure", N);
1222          end if;
1223
1224          Check_Type;
1225          Btyp := Implementation_Base_Type (P_Type);
1226
1227          --  Stream attributes not allowed on limited types unless the
1228          --  special OK_For_Stream flag is set.
1229
1230          if Is_Limited_Type (P_Type)
1231            and then Comes_From_Source (N)
1232            and then not Present (TSS (Btyp, Nam))
1233            and then No (Get_Rep_Pragma (Btyp, Name_Stream_Convert))
1234          then
1235             Error_Msg_Name_1 := Aname;
1236             Error_Msg_NE
1237               ("limited type& has no% attribute", P, Btyp);
1238             Explain_Limited_Type (P_Type, P);
1239          end if;
1240
1241          --  Check for violation of restriction No_Stream_Attributes
1242
1243          if Is_RTE (P_Type, RE_Exception_Id)
1244               or else
1245             Is_RTE (P_Type, RE_Exception_Occurrence)
1246          then
1247             Check_Restriction (No_Exception_Registration, P);
1248          end if;
1249
1250          --  Here we must check that the first argument is an access type
1251          --  that is compatible with Ada.Streams.Root_Stream_Type'Class.
1252
1253          Analyze_And_Resolve (E1);
1254          Etyp := Etype (E1);
1255
1256          --  Note: the double call to Root_Type here is needed because the
1257          --  root type of a class-wide type is the corresponding type (e.g.
1258          --  X for X'Class, and we really want to go to the root.
1259
1260          if not Is_Access_Type (Etyp)
1261            or else Root_Type (Root_Type (Designated_Type (Etyp))) /=
1262                      RTE (RE_Root_Stream_Type)
1263          then
1264             Error_Attr
1265               ("expected access to Ada.Streams.Root_Stream_Type''Class", E1);
1266          end if;
1267
1268          --  Check that the second argument is of the right type if there is
1269          --  one (the Input attribute has only one argument so this is skipped)
1270
1271          if Present (E2) then
1272             Analyze (E2);
1273
1274             if Nam = TSS_Stream_Read
1275               and then not Is_OK_Variable_For_Out_Formal (E2)
1276             then
1277                Error_Attr
1278                  ("second argument of % attribute must be a variable", E2);
1279             end if;
1280
1281             Resolve (E2, P_Type);
1282          end if;
1283       end Check_Stream_Attribute;
1284
1285       -----------------------
1286       -- Check_Task_Prefix --
1287       -----------------------
1288
1289       procedure Check_Task_Prefix is
1290       begin
1291          Analyze (P);
1292
1293          if Is_Task_Type (Etype (P))
1294            or else (Is_Access_Type (Etype (P))
1295               and then Is_Task_Type (Designated_Type (Etype (P))))
1296          then
1297             Resolve (P);
1298          else
1299             Error_Attr ("prefix of % attribute must be a task", P);
1300          end if;
1301       end Check_Task_Prefix;
1302
1303       ----------------
1304       -- Check_Type --
1305       ----------------
1306
1307       --  The possibilities are an entity name denoting a type, or an
1308       --  attribute reference that denotes a type (Base or Class). If
1309       --  the type is incomplete, replace it with its full view.
1310
1311       procedure Check_Type is
1312       begin
1313          if not Is_Entity_Name (P)
1314            or else not Is_Type (Entity (P))
1315          then
1316             Error_Attr ("prefix of % attribute must be a type", P);
1317
1318          elsif Ekind (Entity (P)) = E_Incomplete_Type
1319             and then Present (Full_View (Entity (P)))
1320          then
1321             P_Type := Full_View (Entity (P));
1322             Set_Entity (P, P_Type);
1323          end if;
1324       end Check_Type;
1325
1326       ---------------------
1327       -- Check_Unit_Name --
1328       ---------------------
1329
1330       procedure Check_Unit_Name (Nod : Node_Id) is
1331       begin
1332          if Nkind (Nod) = N_Identifier then
1333             return;
1334
1335          elsif Nkind (Nod) = N_Selected_Component then
1336             Check_Unit_Name (Prefix (Nod));
1337
1338             if Nkind (Selector_Name (Nod)) = N_Identifier then
1339                return;
1340             end if;
1341          end if;
1342
1343          Error_Attr ("argument for % attribute must be unit name", P);
1344       end Check_Unit_Name;
1345
1346       ----------------
1347       -- Error_Attr --
1348       ----------------
1349
1350       procedure Error_Attr is
1351       begin
1352          Set_Etype (N, Any_Type);
1353          Set_Entity (N, Any_Type);
1354          raise Bad_Attribute;
1355       end Error_Attr;
1356
1357       procedure Error_Attr (Msg : String; Error_Node : Node_Id) is
1358       begin
1359          Error_Msg_Name_1 := Aname;
1360          Error_Msg_N (Msg, Error_Node);
1361          Error_Attr;
1362       end Error_Attr;
1363
1364       ----------------------------
1365       -- Legal_Formal_Attribute --
1366       ----------------------------
1367
1368       procedure Legal_Formal_Attribute is
1369       begin
1370          Check_E0;
1371
1372          if not Is_Entity_Name (P)
1373            or else not Is_Type (Entity (P))
1374          then
1375             Error_Attr ("prefix of % attribute must be generic type", N);
1376
1377          elsif Is_Generic_Actual_Type (Entity (P))
1378            or else In_Instance
1379            or else In_Inlined_Body
1380          then
1381             null;
1382
1383          elsif Is_Generic_Type (Entity (P)) then
1384             if not Is_Indefinite_Subtype (Entity (P)) then
1385                Error_Attr
1386                  ("prefix of % attribute must be indefinite generic type", N);
1387             end if;
1388
1389          else
1390             Error_Attr
1391               ("prefix of % attribute must be indefinite generic type", N);
1392          end if;
1393
1394          Set_Etype (N, Standard_Boolean);
1395       end Legal_Formal_Attribute;
1396
1397       ------------------------
1398       -- Standard_Attribute --
1399       ------------------------
1400
1401       procedure Standard_Attribute (Val : Int) is
1402       begin
1403          Check_Standard_Prefix;
1404
1405          --  First a special check (more like a kludge really). For GNAT5
1406          --  on Windows, the alignments in GCC are severely mixed up. In
1407          --  particular, we have a situation where the maximum alignment
1408          --  that GCC thinks is possible is greater than the guaranteed
1409          --  alignment at run-time. That causes many problems. As a partial
1410          --  cure for this situation, we force a value of 4 for the maximum
1411          --  alignment attribute on this target. This still does not solve
1412          --  all problems, but it helps.
1413
1414          --  A further (even more horrible) dimension to this kludge is now
1415          --  installed. There are two uses for Maximum_Alignment, one is to
1416          --  determine the maximum guaranteed alignment, that's the one we
1417          --  want the kludge to yield as 4. The other use is to maximally
1418          --  align objects, we can't use 4 here, since for example, long
1419          --  long integer has an alignment of 8, so we will get errors.
1420
1421          --  It is of course impossible to determine which use the programmer
1422          --  has in mind, but an approximation for now is to disconnect the
1423          --  kludge if the attribute appears in an alignment clause.
1424
1425          --  To be removed if GCC ever gets its act together here ???
1426
1427          Alignment_Kludge : declare
1428             P : Node_Id;
1429
1430             function On_X86 return Boolean;
1431             --  Determine if target is x86 (ia32), return True if so
1432
1433             ------------
1434             -- On_X86 --
1435             ------------
1436
1437             function On_X86 return Boolean is
1438                T : constant String := Sdefault.Target_Name.all;
1439
1440             begin
1441                --  There is no clean way to check this. That's not surprising,
1442                --  the front end should not be doing this kind of test ???. The
1443                --  way we do it is test for either "86" or "pentium" being in
1444                --  the string for the target name.
1445
1446                for J in T'First .. T'Last - 1 loop
1447                   if T (J .. J + 1) = "86"
1448                     or else (J <= T'Last - 6
1449                                and then T (J .. J + 6) = "pentium")
1450                   then
1451                      return True;
1452                   end if;
1453                end loop;
1454
1455                return False;
1456             end On_X86;
1457
1458          begin
1459             if Aname = Name_Maximum_Alignment and then On_X86 then
1460                P := Parent (N);
1461
1462                while Nkind (P) in N_Subexpr loop
1463                   P := Parent (P);
1464                end loop;
1465
1466                if Nkind (P) /= N_Attribute_Definition_Clause
1467                  or else Chars (P) /= Name_Alignment
1468                then
1469                   Rewrite (N, Make_Integer_Literal (Loc, 4));
1470                   Analyze (N);
1471                   return;
1472                end if;
1473             end if;
1474          end Alignment_Kludge;
1475
1476          --  Normally we get the value from gcc ???
1477
1478          Rewrite (N, Make_Integer_Literal (Loc, Val));
1479          Analyze (N);
1480       end Standard_Attribute;
1481
1482       -------------------------
1483       -- Unexpected Argument --
1484       -------------------------
1485
1486       procedure Unexpected_Argument (En : Node_Id) is
1487       begin
1488          Error_Attr ("unexpected argument for % attribute", En);
1489       end Unexpected_Argument;
1490
1491       -------------------------------------------------
1492       -- Validate_Non_Static_Attribute_Function_Call --
1493       -------------------------------------------------
1494
1495       --  This function should be moved to Sem_Dist ???
1496
1497       procedure Validate_Non_Static_Attribute_Function_Call is
1498       begin
1499          if In_Preelaborated_Unit
1500            and then not In_Subprogram_Or_Concurrent_Unit
1501          then
1502             Flag_Non_Static_Expr
1503               ("non-static function call in preelaborated unit!", N);
1504          end if;
1505       end Validate_Non_Static_Attribute_Function_Call;
1506
1507    -----------------------------------------------
1508    -- Start of Processing for Analyze_Attribute --
1509    -----------------------------------------------
1510
1511    begin
1512       --  Immediate return if unrecognized attribute (already diagnosed
1513       --  by parser, so there is nothing more that we need to do)
1514
1515       if not Is_Attribute_Name (Aname) then
1516          raise Bad_Attribute;
1517       end if;
1518
1519       --  Deal with Ada 83 and Features issues
1520
1521       if Comes_From_Source (N) then
1522          if not Attribute_83 (Attr_Id) then
1523             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
1524                Error_Msg_Name_1 := Aname;
1525                Error_Msg_N ("(Ada 83) attribute% is not standard?", N);
1526             end if;
1527
1528             if Attribute_Impl_Def (Attr_Id) then
1529                Check_Restriction (No_Implementation_Attributes, N);
1530             end if;
1531          end if;
1532       end if;
1533
1534       --   Remote access to subprogram type access attribute reference needs
1535       --   unanalyzed copy for tree transformation. The analyzed copy is used
1536       --   for its semantic information (whether prefix is a remote subprogram
1537       --   name), the unanalyzed copy is used to construct new subtree rooted
1538       --   with N_aggregate which represents a fat pointer aggregate.
1539
1540       if Aname = Name_Access then
1541          Discard_Node (Copy_Separate_Tree (N));
1542       end if;
1543
1544       --  Analyze prefix and exit if error in analysis. If the prefix is an
1545       --  incomplete type, use full view if available. A special case is
1546       --  that we never analyze the prefix of an Elab_Body or Elab_Spec
1547       --  or UET_Address attribute.
1548
1549       if Aname /= Name_Elab_Body
1550            and then
1551          Aname /= Name_Elab_Spec
1552            and then
1553          Aname /= Name_UET_Address
1554       then
1555          Analyze (P);
1556          P_Type := Etype (P);
1557
1558          if Is_Entity_Name (P)
1559            and then Present (Entity (P))
1560            and then Is_Type (Entity (P))
1561            and then Ekind (Entity (P)) = E_Incomplete_Type
1562          then
1563             P_Type := Get_Full_View (P_Type);
1564             Set_Entity (P, P_Type);
1565             Set_Etype  (P, P_Type);
1566          end if;
1567
1568          if P_Type = Any_Type then
1569             raise Bad_Attribute;
1570          end if;
1571
1572          P_Base_Type := Base_Type (P_Type);
1573       end if;
1574
1575       --  Analyze expressions that may be present, exiting if an error occurs
1576
1577       if No (Exprs) then
1578          E1 := Empty;
1579          E2 := Empty;
1580
1581       else
1582          E1 := First (Exprs);
1583          Analyze (E1);
1584
1585          --  Check for missing or bad expression (result of previous error)
1586
1587          if No (E1) or else Etype (E1) = Any_Type then
1588             raise Bad_Attribute;
1589          end if;
1590
1591          E2 := Next (E1);
1592
1593          if Present (E2) then
1594             Analyze (E2);
1595
1596             if Etype (E2) = Any_Type then
1597                raise Bad_Attribute;
1598             end if;
1599
1600             if Present (Next (E2)) then
1601                Unexpected_Argument (Next (E2));
1602             end if;
1603          end if;
1604       end if;
1605
1606       if Is_Overloaded (P)
1607         and then Aname /= Name_Access
1608         and then Aname /= Name_Address
1609         and then Aname /= Name_Code_Address
1610         and then Aname /= Name_Count
1611         and then Aname /= Name_Unchecked_Access
1612       then
1613          Error_Attr ("ambiguous prefix for % attribute", P);
1614       end if;
1615
1616       --  Remaining processing depends on attribute
1617
1618       case Attr_Id is
1619
1620       ------------------
1621       -- Abort_Signal --
1622       ------------------
1623
1624       when Attribute_Abort_Signal =>
1625          Check_Standard_Prefix;
1626          Rewrite (N,
1627            New_Reference_To (Stand.Abort_Signal, Loc));
1628          Analyze (N);
1629
1630       ------------
1631       -- Access --
1632       ------------
1633
1634       when Attribute_Access =>
1635          Analyze_Access_Attribute;
1636
1637       -------------
1638       -- Address --
1639       -------------
1640
1641       when Attribute_Address =>
1642          Check_E0;
1643
1644          --  Check for some junk cases, where we have to allow the address
1645          --  attribute but it does not make much sense, so at least for now
1646          --  just replace with Null_Address.
1647
1648          --  We also do this if the prefix is a reference to the AST_Entry
1649          --  attribute. If expansion is active, the attribute will be
1650          --  replaced by a function call, and address will work fine and
1651          --  get the proper value, but if expansion is not active, then
1652          --  the check here allows proper semantic analysis of the reference.
1653
1654          --  An Address attribute created by expansion is legal even when it
1655          --  applies to other entity-denoting expressions.
1656
1657          if Is_Entity_Name (P) then
1658             declare
1659                Ent : constant Entity_Id := Entity (P);
1660
1661             begin
1662                if Is_Subprogram (Ent) then
1663                   if not Is_Library_Level_Entity (Ent) then
1664                      Check_Restriction (No_Implicit_Dynamic_Code, P);
1665                   end if;
1666
1667                   Set_Address_Taken (Ent);
1668
1669                elsif Is_Object (Ent)
1670                  or else Ekind (Ent) = E_Label
1671                then
1672                   Set_Address_Taken (Ent);
1673
1674                --  If we have an address of an object, and the attribute
1675                --  comes from source, then set the object as potentially
1676                --  source modified. We do this because the resulting address
1677                --  can potentially be used to modify the variable and we
1678                --  might not detect this, leading to some junk warnings.
1679
1680                   Set_Never_Set_In_Source (Ent, False);
1681
1682                elsif (Is_Concurrent_Type (Etype (Ent))
1683                        and then Etype (Ent) = Base_Type (Ent))
1684                  or else Ekind (Ent) = E_Package
1685                  or else Is_Generic_Unit (Ent)
1686                then
1687                   Rewrite (N,
1688                     New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1689
1690                else
1691                   Error_Attr ("invalid prefix for % attribute", P);
1692                end if;
1693             end;
1694
1695          elsif Nkind (P) = N_Attribute_Reference
1696            and then Attribute_Name (P) = Name_AST_Entry
1697          then
1698             Rewrite (N,
1699               New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
1700
1701          elsif Is_Object_Reference (P) then
1702             null;
1703
1704          elsif Nkind (P) = N_Selected_Component
1705            and then Is_Subprogram (Entity (Selector_Name (P)))
1706          then
1707             null;
1708
1709          --  What exactly are we allowing here ??? and is this properly
1710          --  documented in the sinfo documentation for this node ???
1711
1712          elsif not Comes_From_Source (N) then
1713             null;
1714
1715          else
1716             Error_Attr ("invalid prefix for % attribute", P);
1717          end if;
1718
1719          Set_Etype (N, RTE (RE_Address));
1720
1721       ------------------
1722       -- Address_Size --
1723       ------------------
1724
1725       when Attribute_Address_Size =>
1726          Standard_Attribute (System_Address_Size);
1727
1728       --------------
1729       -- Adjacent --
1730       --------------
1731
1732       when Attribute_Adjacent =>
1733          Check_Floating_Point_Type_2;
1734          Set_Etype (N, P_Base_Type);
1735          Resolve (E1, P_Base_Type);
1736          Resolve (E2, P_Base_Type);
1737
1738       ---------
1739       -- Aft --
1740       ---------
1741
1742       when Attribute_Aft =>
1743          Check_Fixed_Point_Type_0;
1744          Set_Etype (N, Universal_Integer);
1745
1746       ---------------
1747       -- Alignment --
1748       ---------------
1749
1750       when Attribute_Alignment =>
1751
1752          --  Don't we need more checking here, cf Size ???
1753
1754          Check_E0;
1755          Check_Not_Incomplete_Type;
1756          Set_Etype (N, Universal_Integer);
1757
1758       ---------------
1759       -- Asm_Input --
1760       ---------------
1761
1762       when Attribute_Asm_Input =>
1763          Check_Asm_Attribute;
1764          Set_Etype (N, RTE (RE_Asm_Input_Operand));
1765
1766       ----------------
1767       -- Asm_Output --
1768       ----------------
1769
1770       when Attribute_Asm_Output =>
1771          Check_Asm_Attribute;
1772
1773          if Etype (E2) = Any_Type then
1774             return;
1775
1776          elsif Aname = Name_Asm_Output then
1777             if not Is_Variable (E2) then
1778                Error_Attr
1779                  ("second argument for Asm_Output is not variable", E2);
1780             end if;
1781          end if;
1782
1783          Note_Possible_Modification (E2);
1784          Set_Etype (N, RTE (RE_Asm_Output_Operand));
1785
1786       ---------------
1787       -- AST_Entry --
1788       ---------------
1789
1790       when Attribute_AST_Entry => AST_Entry : declare
1791          Ent  : Entity_Id;
1792          Pref : Node_Id;
1793          Ptyp : Entity_Id;
1794
1795          Indexed : Boolean;
1796          --  Indicates if entry family index is present. Note the coding
1797          --  here handles the entry family case, but in fact it cannot be
1798          --  executed currently, because pragma AST_Entry does not permit
1799          --  the specification of an entry family.
1800
1801          procedure Bad_AST_Entry;
1802          --  Signal a bad AST_Entry pragma
1803
1804          function OK_Entry (E : Entity_Id) return Boolean;
1805          --  Checks that E is of an appropriate entity kind for an entry
1806          --  (i.e. E_Entry if Index is False, or E_Entry_Family if Index
1807          --  is set True for the entry family case). In the True case,
1808          --  makes sure that Is_AST_Entry is set on the entry.
1809
1810          procedure Bad_AST_Entry is
1811          begin
1812             Error_Attr ("prefix for % attribute must be task entry", P);
1813          end Bad_AST_Entry;
1814
1815          function OK_Entry (E : Entity_Id) return Boolean is
1816             Result : Boolean;
1817
1818          begin
1819             if Indexed then
1820                Result := (Ekind (E) = E_Entry_Family);
1821             else
1822                Result := (Ekind (E) = E_Entry);
1823             end if;
1824
1825             if Result then
1826                if not Is_AST_Entry (E) then
1827                   Error_Msg_Name_2 := Aname;
1828                   Error_Attr
1829                     ("% attribute requires previous % pragma", P);
1830                end if;
1831             end if;
1832
1833             return Result;
1834          end OK_Entry;
1835
1836       --  Start of processing for AST_Entry
1837
1838       begin
1839          Check_VMS (N);
1840          Check_E0;
1841
1842          --  Deal with entry family case
1843
1844          if Nkind (P) = N_Indexed_Component then
1845             Pref := Prefix (P);
1846             Indexed := True;
1847          else
1848             Pref := P;
1849             Indexed := False;
1850          end if;
1851
1852          Ptyp := Etype (Pref);
1853
1854          if Ptyp = Any_Type or else Error_Posted (Pref) then
1855             return;
1856          end if;
1857
1858          --  If the prefix is a selected component whose prefix is of an
1859          --  access type, then introduce an explicit dereference.
1860          --  ??? Could we reuse Check_Dereference here?
1861
1862          if Nkind (Pref) = N_Selected_Component
1863            and then Is_Access_Type (Ptyp)
1864          then
1865             Rewrite (Pref,
1866               Make_Explicit_Dereference (Sloc (Pref),
1867                 Relocate_Node (Pref)));
1868             Analyze_And_Resolve (Pref, Designated_Type (Ptyp));
1869          end if;
1870
1871          --  Prefix can be of the form a.b, where a is a task object
1872          --  and b is one of the entries of the corresponding task type.
1873
1874          if Nkind (Pref) = N_Selected_Component
1875            and then OK_Entry (Entity (Selector_Name (Pref)))
1876            and then Is_Object_Reference (Prefix (Pref))
1877            and then Is_Task_Type (Etype (Prefix (Pref)))
1878          then
1879             null;
1880
1881          --  Otherwise the prefix must be an entry of a containing task,
1882          --  or of a variable of the enclosing task type.
1883
1884          else
1885             if Nkind (Pref) = N_Identifier
1886               or else Nkind (Pref) = N_Expanded_Name
1887             then
1888                Ent := Entity (Pref);
1889
1890                if not OK_Entry (Ent)
1891                  or else not In_Open_Scopes (Scope (Ent))
1892                then
1893                   Bad_AST_Entry;
1894                end if;
1895
1896             else
1897                Bad_AST_Entry;
1898             end if;
1899          end if;
1900
1901          Set_Etype (N, RTE (RE_AST_Handler));
1902       end AST_Entry;
1903
1904       ----------
1905       -- Base --
1906       ----------
1907
1908       --  Note: when the base attribute appears in the context of a subtype
1909       --  mark, the analysis is done by Sem_Ch8.Find_Type, rather than by
1910       --  the following circuit.
1911
1912       when Attribute_Base => Base : declare
1913          Typ : Entity_Id;
1914
1915       begin
1916          Check_Either_E0_Or_E1;
1917          Find_Type (P);
1918          Typ := Entity (P);
1919
1920          if Ada_Version >= Ada_95
1921            and then not Is_Scalar_Type (Typ)
1922            and then not Is_Generic_Type (Typ)
1923          then
1924             Error_Msg_N ("prefix of Base attribute must be scalar type", N);
1925
1926          elsif Sloc (Typ) = Standard_Location
1927            and then Base_Type (Typ) = Typ
1928            and then Warn_On_Redundant_Constructs
1929          then
1930             Error_Msg_NE
1931               ("?redudant attribute, & is its own base type", N, Typ);
1932          end if;
1933
1934          Set_Etype (N, Base_Type (Entity (P)));
1935
1936          --  If we have an expression present, then really this is a conversion
1937          --  and the tree must be reformed. Note that this is one of the cases
1938          --  in which we do a replace rather than a rewrite, because the
1939          --  original tree is junk.
1940
1941          if Present (E1) then
1942             Replace (N,
1943               Make_Type_Conversion (Loc,
1944                 Subtype_Mark =>
1945                   Make_Attribute_Reference (Loc,
1946                     Prefix => Prefix (N),
1947                     Attribute_Name => Name_Base),
1948                 Expression => Relocate_Node (E1)));
1949
1950             --  E1 may be overloaded, and its interpretations preserved.
1951
1952             Save_Interps (E1, Expression (N));
1953             Analyze (N);
1954
1955          --  For other cases, set the proper type as the entity of the
1956          --  attribute reference, and then rewrite the node to be an
1957          --  occurrence of the referenced base type. This way, no one
1958          --  else in the compiler has to worry about the base attribute.
1959
1960          else
1961             Set_Entity (N, Base_Type (Entity (P)));
1962             Rewrite (N,
1963               New_Reference_To (Entity (N), Loc));
1964             Analyze (N);
1965          end if;
1966       end Base;
1967
1968       ---------
1969       -- Bit --
1970       ---------
1971
1972       when Attribute_Bit => Bit :
1973       begin
1974          Check_E0;
1975
1976          if not Is_Object_Reference (P) then
1977             Error_Attr ("prefix for % attribute must be object", P);
1978
1979          --  What about the access object cases ???
1980
1981          else
1982             null;
1983          end if;
1984
1985          Set_Etype (N, Universal_Integer);
1986       end Bit;
1987
1988       ---------------
1989       -- Bit_Order --
1990       ---------------
1991
1992       when Attribute_Bit_Order => Bit_Order :
1993       begin
1994          Check_E0;
1995          Check_Type;
1996
1997          if not Is_Record_Type (P_Type) then
1998             Error_Attr ("prefix of % attribute must be record type", P);
1999          end if;
2000
2001          if Bytes_Big_Endian xor Reverse_Bit_Order (P_Type) then
2002             Rewrite (N,
2003               New_Occurrence_Of (RTE (RE_High_Order_First), Loc));
2004          else
2005             Rewrite (N,
2006               New_Occurrence_Of (RTE (RE_Low_Order_First), Loc));
2007          end if;
2008
2009          Set_Etype (N, RTE (RE_Bit_Order));
2010          Resolve (N);
2011
2012          --  Reset incorrect indication of staticness
2013
2014          Set_Is_Static_Expression (N, False);
2015       end Bit_Order;
2016
2017       ------------------
2018       -- Bit_Position --
2019       ------------------
2020
2021       --  Note: in generated code, we can have a Bit_Position attribute
2022       --  applied to a (naked) record component (i.e. the prefix is an
2023       --  identifier that references an E_Component or E_Discriminant
2024       --  entity directly, and this is interpreted as expected by Gigi.
2025       --  The following code will not tolerate such usage, but when the
2026       --  expander creates this special case, it marks it as analyzed
2027       --  immediately and sets an appropriate type.
2028
2029       when Attribute_Bit_Position =>
2030
2031          if Comes_From_Source (N) then
2032             Check_Component;
2033          end if;
2034
2035          Set_Etype (N, Universal_Integer);
2036
2037       ------------------
2038       -- Body_Version --
2039       ------------------
2040
2041       when Attribute_Body_Version =>
2042          Check_E0;
2043          Check_Program_Unit;
2044          Set_Etype (N, RTE (RE_Version_String));
2045
2046       --------------
2047       -- Callable --
2048       --------------
2049
2050       when Attribute_Callable =>
2051          Check_E0;
2052          Set_Etype (N, Standard_Boolean);
2053          Check_Task_Prefix;
2054
2055       ------------
2056       -- Caller --
2057       ------------
2058
2059       when Attribute_Caller => Caller : declare
2060          Ent        : Entity_Id;
2061          S          : Entity_Id;
2062
2063       begin
2064          Check_E0;
2065
2066          if Nkind (P) = N_Identifier
2067            or else Nkind (P) = N_Expanded_Name
2068          then
2069             Ent := Entity (P);
2070
2071             if not Is_Entry (Ent) then
2072                Error_Attr ("invalid entry name", N);
2073             end if;
2074
2075          else
2076             Error_Attr ("invalid entry name", N);
2077             return;
2078          end if;
2079
2080          for J in reverse 0 .. Scope_Stack.Last loop
2081             S := Scope_Stack.Table (J).Entity;
2082
2083             if S = Scope (Ent) then
2084                Error_Attr ("Caller must appear in matching accept or body", N);
2085             elsif S = Ent then
2086                exit;
2087             end if;
2088          end loop;
2089
2090          Set_Etype (N, RTE (RO_AT_Task_Id));
2091       end Caller;
2092
2093       -------------
2094       -- Ceiling --
2095       -------------
2096
2097       when Attribute_Ceiling =>
2098          Check_Floating_Point_Type_1;
2099          Set_Etype (N, P_Base_Type);
2100          Resolve (E1, P_Base_Type);
2101
2102       -----------
2103       -- Class --
2104       -----------
2105
2106       when Attribute_Class => Class : declare
2107       begin
2108          Check_Restriction (No_Dispatch, N);
2109          Check_Either_E0_Or_E1;
2110
2111          --  If we have an expression present, then really this is a conversion
2112          --  and the tree must be reformed into a proper conversion. This is a
2113          --  Replace rather than a Rewrite, because the original tree is junk.
2114          --  If expression is overloaded, propagate interpretations to new one.
2115
2116          if Present (E1) then
2117             Replace (N,
2118               Make_Type_Conversion (Loc,
2119                 Subtype_Mark =>
2120                   Make_Attribute_Reference (Loc,
2121                     Prefix => Prefix (N),
2122                     Attribute_Name => Name_Class),
2123                 Expression => Relocate_Node (E1)));
2124
2125             Save_Interps (E1, Expression (N));
2126             Analyze (N);
2127
2128          --  Otherwise we just need to find the proper type
2129
2130          else
2131             Find_Type (N);
2132          end if;
2133
2134       end Class;
2135
2136       ------------------
2137       -- Code_Address --
2138       ------------------
2139
2140       when Attribute_Code_Address =>
2141          Check_E0;
2142
2143          if Nkind (P) = N_Attribute_Reference
2144            and then (Attribute_Name (P) = Name_Elab_Body
2145                        or else
2146                      Attribute_Name (P) = Name_Elab_Spec)
2147          then
2148             null;
2149
2150          elsif not Is_Entity_Name (P)
2151            or else (Ekind (Entity (P)) /= E_Function
2152                       and then
2153                     Ekind (Entity (P)) /= E_Procedure)
2154          then
2155             Error_Attr ("invalid prefix for % attribute", P);
2156             Set_Address_Taken (Entity (P));
2157          end if;
2158
2159          Set_Etype (N, RTE (RE_Address));
2160
2161       --------------------
2162       -- Component_Size --
2163       --------------------
2164
2165       when Attribute_Component_Size =>
2166          Check_E0;
2167          Set_Etype (N, Universal_Integer);
2168
2169          --  Note: unlike other array attributes, unconstrained arrays are OK
2170
2171          if Is_Array_Type (P_Type) and then not Is_Constrained (P_Type) then
2172             null;
2173          else
2174             Check_Array_Type;
2175          end if;
2176
2177       -------------
2178       -- Compose --
2179       -------------
2180
2181       when Attribute_Compose =>
2182          Check_Floating_Point_Type_2;
2183          Set_Etype (N, P_Base_Type);
2184          Resolve (E1, P_Base_Type);
2185          Resolve (E2, Any_Integer);
2186
2187       -----------------
2188       -- Constrained --
2189       -----------------
2190
2191       when Attribute_Constrained =>
2192          Check_E0;
2193          Set_Etype (N, Standard_Boolean);
2194
2195          --  Case from RM J.4(2) of constrained applied to private type
2196
2197          if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
2198
2199             --  If we are within an instance, the attribute must be legal
2200             --  because it was valid in the generic unit. Ditto if this is
2201             --  an inlining of a function declared in an instance.
2202
2203             if In_Instance
2204               or else In_Inlined_Body
2205             then
2206                return;
2207
2208             --  For sure OK if we have a real private type itself, but must
2209             --  be completed, cannot apply Constrained to incomplete type.
2210
2211             elsif Is_Private_Type (Entity (P)) then
2212
2213                --  Note: this is one of the Annex J features that does not
2214                --  generate a warning from -gnatwj, since in fact it seems
2215                --  very useful, and is used in the GNAT runtime.
2216
2217                Check_Not_Incomplete_Type;
2218                return;
2219             end if;
2220
2221          --  Normal (non-obsolescent case) of application to object of
2222          --  a discriminated type.
2223
2224          else
2225             Check_Object_Reference (P);
2226
2227             --  If N does not come from source, then we allow the
2228             --  the attribute prefix to be of a private type whose
2229             --  full type has discriminants. This occurs in cases
2230             --  involving expanded calls to stream attributes.
2231
2232             if not Comes_From_Source (N) then
2233                P_Type := Underlying_Type (P_Type);
2234             end if;
2235
2236             --  Must have discriminants or be an access type designating
2237             --  a type with discriminants. If it is a classwide type is
2238             --  has unknown discriminants.
2239
2240             if Has_Discriminants (P_Type)
2241                or else Has_Unknown_Discriminants (P_Type)
2242                or else
2243                  (Is_Access_Type (P_Type)
2244                    and then Has_Discriminants (Designated_Type (P_Type)))
2245             then
2246                return;
2247
2248             --  Also allow an object of a generic type if extensions allowed
2249             --  and allow this for any type at all.
2250
2251             elsif (Is_Generic_Type (P_Type)
2252                      or else Is_Generic_Actual_Type (P_Type))
2253               and then Extensions_Allowed
2254             then
2255                return;
2256             end if;
2257          end if;
2258
2259          --  Fall through if bad prefix
2260
2261          Error_Attr
2262            ("prefix of % attribute must be object of discriminated type", P);
2263
2264       ---------------
2265       -- Copy_Sign --
2266       ---------------
2267
2268       when Attribute_Copy_Sign =>
2269          Check_Floating_Point_Type_2;
2270          Set_Etype (N, P_Base_Type);
2271          Resolve (E1, P_Base_Type);
2272          Resolve (E2, P_Base_Type);
2273
2274       -----------
2275       -- Count --
2276       -----------
2277
2278       when Attribute_Count => Count :
2279       declare
2280          Ent : Entity_Id;
2281          S   : Entity_Id;
2282          Tsk : Entity_Id;
2283
2284       begin
2285          Check_E0;
2286
2287          if Nkind (P) = N_Identifier
2288            or else Nkind (P) = N_Expanded_Name
2289          then
2290             Ent := Entity (P);
2291
2292             if Ekind (Ent) /= E_Entry then
2293                Error_Attr ("invalid entry name", N);
2294             end if;
2295
2296          elsif Nkind (P) = N_Indexed_Component then
2297             if not Is_Entity_Name (Prefix (P))
2298               or else  No (Entity (Prefix (P)))
2299               or else Ekind (Entity (Prefix (P))) /= E_Entry_Family
2300             then
2301                if Nkind (Prefix (P)) = N_Selected_Component
2302                  and then Present (Entity (Selector_Name (Prefix (P))))
2303                  and then Ekind (Entity (Selector_Name (Prefix (P)))) =
2304                                                              E_Entry_Family
2305                then
2306                   Error_Attr
2307                     ("attribute % must apply to entry of current task", P);
2308
2309                else
2310                   Error_Attr ("invalid entry family name", P);
2311                end if;
2312                return;
2313
2314             else
2315                Ent := Entity (Prefix (P));
2316             end if;
2317
2318          elsif Nkind (P) = N_Selected_Component
2319            and then Present (Entity (Selector_Name (P)))
2320            and then Ekind (Entity (Selector_Name (P))) = E_Entry
2321          then
2322             Error_Attr
2323               ("attribute % must apply to entry of current task", P);
2324
2325          else
2326             Error_Attr ("invalid entry name", N);
2327             return;
2328          end if;
2329
2330          for J in reverse 0 .. Scope_Stack.Last loop
2331             S := Scope_Stack.Table (J).Entity;
2332
2333             if S = Scope (Ent) then
2334                if Nkind (P) = N_Expanded_Name then
2335                   Tsk := Entity (Prefix (P));
2336
2337                   --  The prefix denotes either the task type, or else a
2338                   --  single task whose task type is being analyzed.
2339
2340                   if (Is_Type (Tsk)
2341                       and then Tsk = S)
2342
2343                     or else (not Is_Type (Tsk)
2344                       and then Etype (Tsk) = S
2345                       and then not (Comes_From_Source (S)))
2346                   then
2347                      null;
2348                   else
2349                      Error_Attr
2350                        ("Attribute % must apply to entry of current task", N);
2351                   end if;
2352                end if;
2353
2354                exit;
2355
2356             elsif Ekind (Scope (Ent)) in Task_Kind
2357               and then Ekind (S) /= E_Loop
2358               and then Ekind (S) /= E_Block
2359               and then Ekind (S) /= E_Entry
2360               and then Ekind (S) /= E_Entry_Family
2361             then
2362                Error_Attr ("Attribute % cannot appear in inner unit", N);
2363
2364             elsif Ekind (Scope (Ent)) = E_Protected_Type
2365               and then not Has_Completion (Scope (Ent))
2366             then
2367                Error_Attr ("attribute % can only be used inside body", N);
2368             end if;
2369          end loop;
2370
2371          if Is_Overloaded (P) then
2372             declare
2373                Index : Interp_Index;
2374                It    : Interp;
2375
2376             begin
2377                Get_First_Interp (P, Index, It);
2378
2379                while Present (It.Nam) loop
2380                   if It.Nam = Ent then
2381                      null;
2382
2383                   else
2384                      Error_Attr ("ambiguous entry name", N);
2385                   end if;
2386
2387                   Get_Next_Interp (Index, It);
2388                end loop;
2389             end;
2390          end if;
2391
2392          Set_Etype (N, Universal_Integer);
2393       end Count;
2394
2395       -----------------------
2396       -- Default_Bit_Order --
2397       -----------------------
2398
2399       when Attribute_Default_Bit_Order => Default_Bit_Order :
2400       begin
2401          Check_Standard_Prefix;
2402          Check_E0;
2403
2404          if Bytes_Big_Endian then
2405             Rewrite (N,
2406               Make_Integer_Literal (Loc, False_Value));
2407          else
2408             Rewrite (N,
2409               Make_Integer_Literal (Loc, True_Value));
2410          end if;
2411
2412          Set_Etype (N, Universal_Integer);
2413          Set_Is_Static_Expression (N);
2414       end Default_Bit_Order;
2415
2416       --------------
2417       -- Definite --
2418       --------------
2419
2420       when Attribute_Definite =>
2421          Legal_Formal_Attribute;
2422
2423       -----------
2424       -- Delta --
2425       -----------
2426
2427       when Attribute_Delta =>
2428          Check_Fixed_Point_Type_0;
2429          Set_Etype (N, Universal_Real);
2430
2431       ------------
2432       -- Denorm --
2433       ------------
2434
2435       when Attribute_Denorm =>
2436          Check_Floating_Point_Type_0;
2437          Set_Etype (N, Standard_Boolean);
2438
2439       ------------
2440       -- Digits --
2441       ------------
2442
2443       when Attribute_Digits =>
2444          Check_E0;
2445          Check_Type;
2446
2447          if not Is_Floating_Point_Type (P_Type)
2448            and then not Is_Decimal_Fixed_Point_Type (P_Type)
2449          then
2450             Error_Attr
2451               ("prefix of % attribute must be float or decimal type", P);
2452          end if;
2453
2454          Set_Etype (N, Universal_Integer);
2455
2456       ---------------
2457       -- Elab_Body --
2458       ---------------
2459
2460       --  Also handles processing for Elab_Spec
2461
2462       when Attribute_Elab_Body | Attribute_Elab_Spec =>
2463          Check_E0;
2464          Check_Unit_Name (P);
2465          Set_Etype (N, Standard_Void_Type);
2466
2467          --  We have to manually call the expander in this case to get
2468          --  the necessary expansion (normally attributes that return
2469          --  entities are not expanded).
2470
2471          Expand (N);
2472
2473       ---------------
2474       -- Elab_Spec --
2475       ---------------
2476
2477       --  Shares processing with Elab_Body
2478
2479       ----------------
2480       -- Elaborated --
2481       ----------------
2482
2483       when Attribute_Elaborated =>
2484          Check_E0;
2485          Check_Library_Unit;
2486          Set_Etype (N, Standard_Boolean);
2487
2488       ----------
2489       -- Emax --
2490       ----------
2491
2492       when Attribute_Emax =>
2493          Check_Floating_Point_Type_0;
2494          Set_Etype (N, Universal_Integer);
2495
2496       --------------
2497       -- Enum_Rep --
2498       --------------
2499
2500       when Attribute_Enum_Rep => Enum_Rep : declare
2501       begin
2502          if Present (E1) then
2503             Check_E1;
2504             Check_Discrete_Type;
2505             Resolve (E1, P_Base_Type);
2506
2507          else
2508             if not Is_Entity_Name (P)
2509               or else (not Is_Object (Entity (P))
2510                          and then
2511                        Ekind (Entity (P)) /= E_Enumeration_Literal)
2512             then
2513                Error_Attr
2514                  ("prefix of %attribute must be " &
2515                   "discrete type/object or enum literal", P);
2516             end if;
2517          end if;
2518
2519          Set_Etype (N, Universal_Integer);
2520       end Enum_Rep;
2521
2522       -------------
2523       -- Epsilon --
2524       -------------
2525
2526       when Attribute_Epsilon =>
2527          Check_Floating_Point_Type_0;
2528          Set_Etype (N, Universal_Real);
2529
2530       --------------
2531       -- Exponent --
2532       --------------
2533
2534       when Attribute_Exponent =>
2535          Check_Floating_Point_Type_1;
2536          Set_Etype (N, Universal_Integer);
2537          Resolve (E1, P_Base_Type);
2538
2539       ------------------
2540       -- External_Tag --
2541       ------------------
2542
2543       when Attribute_External_Tag =>
2544          Check_E0;
2545          Check_Type;
2546
2547          Set_Etype (N, Standard_String);
2548
2549          if not Is_Tagged_Type (P_Type) then
2550             Error_Attr ("prefix of % attribute must be tagged", P);
2551          end if;
2552
2553       -----------
2554       -- First --
2555       -----------
2556
2557       when Attribute_First =>
2558          Check_Array_Or_Scalar_Type;
2559
2560       ---------------
2561       -- First_Bit --
2562       ---------------
2563
2564       when Attribute_First_Bit =>
2565          Check_Component;
2566          Set_Etype (N, Universal_Integer);
2567
2568       -----------------
2569       -- Fixed_Value --
2570       -----------------
2571
2572       when Attribute_Fixed_Value =>
2573          Check_E1;
2574          Check_Fixed_Point_Type;
2575          Resolve (E1, Any_Integer);
2576          Set_Etype (N, P_Base_Type);
2577
2578       -----------
2579       -- Floor --
2580       -----------
2581
2582       when Attribute_Floor =>
2583          Check_Floating_Point_Type_1;
2584          Set_Etype (N, P_Base_Type);
2585          Resolve (E1, P_Base_Type);
2586
2587       ----------
2588       -- Fore --
2589       ----------
2590
2591       when Attribute_Fore =>
2592          Check_Fixed_Point_Type_0;
2593          Set_Etype (N, Universal_Integer);
2594
2595       --------------
2596       -- Fraction --
2597       --------------
2598
2599       when Attribute_Fraction =>
2600          Check_Floating_Point_Type_1;
2601          Set_Etype (N, P_Base_Type);
2602          Resolve (E1, P_Base_Type);
2603
2604       -----------------------
2605       -- Has_Discriminants --
2606       -----------------------
2607
2608       when Attribute_Has_Discriminants =>
2609          Legal_Formal_Attribute;
2610
2611       --------------
2612       -- Identity --
2613       --------------
2614
2615       when Attribute_Identity =>
2616          Check_E0;
2617          Analyze (P);
2618
2619          if Etype (P) =  Standard_Exception_Type then
2620             Set_Etype (N, RTE (RE_Exception_Id));
2621
2622          elsif Is_Task_Type (Etype (P))
2623            or else (Is_Access_Type (Etype (P))
2624               and then Is_Task_Type (Designated_Type (Etype (P))))
2625          then
2626             Resolve (P);
2627             Set_Etype (N, RTE (RO_AT_Task_Id));
2628
2629          else
2630             Error_Attr ("prefix of % attribute must be a task or an "
2631               & "exception", P);
2632          end if;
2633
2634       -----------
2635       -- Image --
2636       -----------
2637
2638       when Attribute_Image => Image :
2639       begin
2640          Set_Etype (N, Standard_String);
2641          Check_Scalar_Type;
2642
2643          if Is_Real_Type (P_Type) then
2644             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
2645                Error_Msg_Name_1 := Aname;
2646                Error_Msg_N
2647                  ("(Ada 83) % attribute not allowed for real types", N);
2648             end if;
2649          end if;
2650
2651          if Is_Enumeration_Type (P_Type) then
2652             Check_Restriction (No_Enumeration_Maps, N);
2653          end if;
2654
2655          Check_E1;
2656          Resolve (E1, P_Base_Type);
2657          Check_Enum_Image;
2658          Validate_Non_Static_Attribute_Function_Call;
2659       end Image;
2660
2661       ---------
2662       -- Img --
2663       ---------
2664
2665       when Attribute_Img => Img :
2666       begin
2667          Set_Etype (N, Standard_String);
2668
2669          if not Is_Scalar_Type (P_Type)
2670            or else (Is_Entity_Name (P) and then Is_Type (Entity (P)))
2671          then
2672             Error_Attr
2673               ("prefix of % attribute must be scalar object name", N);
2674          end if;
2675
2676          Check_Enum_Image;
2677       end Img;
2678
2679       -----------
2680       -- Input --
2681       -----------
2682
2683       when Attribute_Input =>
2684          Check_E1;
2685          Check_Stream_Attribute (TSS_Stream_Input);
2686          Set_Etype (N, P_Base_Type);
2687
2688       -------------------
2689       -- Integer_Value --
2690       -------------------
2691
2692       when Attribute_Integer_Value =>
2693          Check_E1;
2694          Check_Integer_Type;
2695          Resolve (E1, Any_Fixed);
2696          Set_Etype (N, P_Base_Type);
2697
2698       -----------
2699       -- Large --
2700       -----------
2701
2702       when Attribute_Large =>
2703          Check_E0;
2704          Check_Real_Type;
2705          Set_Etype (N, Universal_Real);
2706
2707       ----------
2708       -- Last --
2709       ----------
2710
2711       when Attribute_Last =>
2712          Check_Array_Or_Scalar_Type;
2713
2714       --------------
2715       -- Last_Bit --
2716       --------------
2717
2718       when Attribute_Last_Bit =>
2719          Check_Component;
2720          Set_Etype (N, Universal_Integer);
2721
2722       ------------------
2723       -- Leading_Part --
2724       ------------------
2725
2726       when Attribute_Leading_Part =>
2727          Check_Floating_Point_Type_2;
2728          Set_Etype (N, P_Base_Type);
2729          Resolve (E1, P_Base_Type);
2730          Resolve (E2, Any_Integer);
2731
2732       ------------
2733       -- Length --
2734       ------------
2735
2736       when Attribute_Length =>
2737          Check_Array_Type;
2738          Set_Etype (N, Universal_Integer);
2739
2740       -------------
2741       -- Machine --
2742       -------------
2743
2744       when Attribute_Machine =>
2745          Check_Floating_Point_Type_1;
2746          Set_Etype (N, P_Base_Type);
2747          Resolve (E1, P_Base_Type);
2748
2749       ------------------
2750       -- Machine_Emax --
2751       ------------------
2752
2753       when Attribute_Machine_Emax =>
2754          Check_Floating_Point_Type_0;
2755          Set_Etype (N, Universal_Integer);
2756
2757       ------------------
2758       -- Machine_Emin --
2759       ------------------
2760
2761       when Attribute_Machine_Emin =>
2762          Check_Floating_Point_Type_0;
2763          Set_Etype (N, Universal_Integer);
2764
2765       ----------------------
2766       -- Machine_Mantissa --
2767       ----------------------
2768
2769       when Attribute_Machine_Mantissa =>
2770          Check_Floating_Point_Type_0;
2771          Set_Etype (N, Universal_Integer);
2772
2773       -----------------------
2774       -- Machine_Overflows --
2775       -----------------------
2776
2777       when Attribute_Machine_Overflows =>
2778          Check_Real_Type;
2779          Check_E0;
2780          Set_Etype (N, Standard_Boolean);
2781
2782       -------------------
2783       -- Machine_Radix --
2784       -------------------
2785
2786       when Attribute_Machine_Radix =>
2787          Check_Real_Type;
2788          Check_E0;
2789          Set_Etype (N, Universal_Integer);
2790
2791       --------------------
2792       -- Machine_Rounds --
2793       --------------------
2794
2795       when Attribute_Machine_Rounds =>
2796          Check_Real_Type;
2797          Check_E0;
2798          Set_Etype (N, Standard_Boolean);
2799
2800       ------------------
2801       -- Machine_Size --
2802       ------------------
2803
2804       when Attribute_Machine_Size =>
2805          Check_E0;
2806          Check_Type;
2807          Check_Not_Incomplete_Type;
2808          Set_Etype (N, Universal_Integer);
2809
2810       --------------
2811       -- Mantissa --
2812       --------------
2813
2814       when Attribute_Mantissa =>
2815          Check_E0;
2816          Check_Real_Type;
2817          Set_Etype (N, Universal_Integer);
2818
2819       ---------
2820       -- Max --
2821       ---------
2822
2823       when Attribute_Max =>
2824          Check_E2;
2825          Check_Scalar_Type;
2826          Resolve (E1, P_Base_Type);
2827          Resolve (E2, P_Base_Type);
2828          Set_Etype (N, P_Base_Type);
2829
2830       ----------------------------------
2831       -- Max_Size_In_Storage_Elements --
2832       ----------------------------------
2833
2834       when Attribute_Max_Size_In_Storage_Elements =>
2835          Check_E0;
2836          Check_Type;
2837          Check_Not_Incomplete_Type;
2838          Set_Etype (N, Universal_Integer);
2839
2840       -----------------------
2841       -- Maximum_Alignment --
2842       -----------------------
2843
2844       when Attribute_Maximum_Alignment =>
2845          Standard_Attribute (Ttypes.Maximum_Alignment);
2846
2847       --------------------
2848       -- Mechanism_Code --
2849       --------------------
2850
2851       when Attribute_Mechanism_Code =>
2852          if not Is_Entity_Name (P)
2853            or else not Is_Subprogram (Entity (P))
2854          then
2855             Error_Attr ("prefix of % attribute must be subprogram", P);
2856          end if;
2857
2858          Check_Either_E0_Or_E1;
2859
2860          if Present (E1) then
2861             Resolve (E1, Any_Integer);
2862             Set_Etype (E1, Standard_Integer);
2863
2864             if not Is_Static_Expression (E1) then
2865                Flag_Non_Static_Expr
2866                  ("expression for parameter number must be static!", E1);
2867                Error_Attr;
2868
2869             elsif UI_To_Int (Intval (E1)) > Number_Formals (Entity (P))
2870               or else UI_To_Int (Intval (E1)) < 0
2871             then
2872                Error_Attr ("invalid parameter number for %attribute", E1);
2873             end if;
2874          end if;
2875
2876          Set_Etype (N, Universal_Integer);
2877
2878       ---------
2879       -- Min --
2880       ---------
2881
2882       when Attribute_Min =>
2883          Check_E2;
2884          Check_Scalar_Type;
2885          Resolve (E1, P_Base_Type);
2886          Resolve (E2, P_Base_Type);
2887          Set_Etype (N, P_Base_Type);
2888
2889       -----------
2890       -- Model --
2891       -----------
2892
2893       when Attribute_Model =>
2894          Check_Floating_Point_Type_1;
2895          Set_Etype (N, P_Base_Type);
2896          Resolve (E1, P_Base_Type);
2897
2898       ----------------
2899       -- Model_Emin --
2900       ----------------
2901
2902       when Attribute_Model_Emin =>
2903          Check_Floating_Point_Type_0;
2904          Set_Etype (N, Universal_Integer);
2905
2906       -------------------
2907       -- Model_Epsilon --
2908       -------------------
2909
2910       when Attribute_Model_Epsilon =>
2911          Check_Floating_Point_Type_0;
2912          Set_Etype (N, Universal_Real);
2913
2914       --------------------
2915       -- Model_Mantissa --
2916       --------------------
2917
2918       when Attribute_Model_Mantissa =>
2919          Check_Floating_Point_Type_0;
2920          Set_Etype (N, Universal_Integer);
2921
2922       -----------------
2923       -- Model_Small --
2924       -----------------
2925
2926       when Attribute_Model_Small =>
2927          Check_Floating_Point_Type_0;
2928          Set_Etype (N, Universal_Real);
2929
2930       -------------
2931       -- Modulus --
2932       -------------
2933
2934       when Attribute_Modulus =>
2935          Check_E0;
2936          Check_Type;
2937
2938          if not Is_Modular_Integer_Type (P_Type) then
2939             Error_Attr ("prefix of % attribute must be modular type", P);
2940          end if;
2941
2942          Set_Etype (N, Universal_Integer);
2943
2944       --------------------
2945       -- Null_Parameter --
2946       --------------------
2947
2948       when Attribute_Null_Parameter => Null_Parameter : declare
2949          Parnt  : constant Node_Id := Parent (N);
2950          GParnt : constant Node_Id := Parent (Parnt);
2951
2952          procedure Bad_Null_Parameter (Msg : String);
2953          --  Used if bad Null parameter attribute node is found. Issues
2954          --  given error message, and also sets the type to Any_Type to
2955          --  avoid blowups later on from dealing with a junk node.
2956
2957          procedure Must_Be_Imported (Proc_Ent : Entity_Id);
2958          --  Called to check that Proc_Ent is imported subprogram
2959
2960          ------------------------
2961          -- Bad_Null_Parameter --
2962          ------------------------
2963
2964          procedure Bad_Null_Parameter (Msg : String) is
2965          begin
2966             Error_Msg_N (Msg, N);
2967             Set_Etype (N, Any_Type);
2968          end Bad_Null_Parameter;
2969
2970          ----------------------
2971          -- Must_Be_Imported --
2972          ----------------------
2973
2974          procedure Must_Be_Imported (Proc_Ent : Entity_Id) is
2975             Pent : Entity_Id := Proc_Ent;
2976
2977          begin
2978             while Present (Alias (Pent)) loop
2979                Pent := Alias (Pent);
2980             end loop;
2981
2982             --  Ignore check if procedure not frozen yet (we will get
2983             --  another chance when the default parameter is reanalyzed)
2984
2985             if not Is_Frozen (Pent) then
2986                return;
2987
2988             elsif not Is_Imported (Pent) then
2989                Bad_Null_Parameter
2990                  ("Null_Parameter can only be used with imported subprogram");
2991
2992             else
2993                return;
2994             end if;
2995          end Must_Be_Imported;
2996
2997       --  Start of processing for Null_Parameter
2998
2999       begin
3000          Check_Type;
3001          Check_E0;
3002          Set_Etype (N, P_Type);
3003
3004          --  Case of attribute used as default expression
3005
3006          if Nkind (Parnt) = N_Parameter_Specification then
3007             Must_Be_Imported (Defining_Entity (GParnt));
3008
3009          --  Case of attribute used as actual for subprogram (positional)
3010
3011          elsif (Nkind (Parnt) = N_Procedure_Call_Statement
3012                  or else
3013                 Nkind (Parnt) = N_Function_Call)
3014             and then Is_Entity_Name (Name (Parnt))
3015          then
3016             Must_Be_Imported (Entity (Name (Parnt)));
3017
3018          --  Case of attribute used as actual for subprogram (named)
3019
3020          elsif Nkind (Parnt) = N_Parameter_Association
3021            and then (Nkind (GParnt) = N_Procedure_Call_Statement
3022                        or else
3023                      Nkind (GParnt) = N_Function_Call)
3024            and then Is_Entity_Name (Name (GParnt))
3025          then
3026             Must_Be_Imported (Entity (Name (GParnt)));
3027
3028          --  Not an allowed case
3029
3030          else
3031             Bad_Null_Parameter
3032               ("Null_Parameter must be actual or default parameter");
3033          end if;
3034
3035       end Null_Parameter;
3036
3037       -----------------
3038       -- Object_Size --
3039       -----------------
3040
3041       when Attribute_Object_Size =>
3042          Check_E0;
3043          Check_Type;
3044          Check_Not_Incomplete_Type;
3045          Set_Etype (N, Universal_Integer);
3046
3047       ------------
3048       -- Output --
3049       ------------
3050
3051       when Attribute_Output =>
3052          Check_E2;
3053          Check_Stream_Attribute (TSS_Stream_Output);
3054          Set_Etype (N, Standard_Void_Type);
3055          Resolve (N, Standard_Void_Type);
3056
3057       ------------------
3058       -- Partition_ID --
3059       ------------------
3060
3061       when Attribute_Partition_ID =>
3062          Check_E0;
3063
3064          if P_Type /= Any_Type then
3065             if not Is_Library_Level_Entity (Entity (P)) then
3066                Error_Attr
3067                  ("prefix of % attribute must be library-level entity", P);
3068
3069             --  The defining entity of prefix should not be declared inside
3070             --  a Pure unit. RM E.1(8).
3071             --  The Is_Pure flag has been set during declaration.
3072
3073             elsif Is_Entity_Name (P)
3074               and then Is_Pure (Entity (P))
3075             then
3076                Error_Attr
3077                  ("prefix of % attribute must not be declared pure", P);
3078             end if;
3079          end if;
3080
3081          Set_Etype (N, Universal_Integer);
3082
3083       -------------------------
3084       -- Passed_By_Reference --
3085       -------------------------
3086
3087       when Attribute_Passed_By_Reference =>
3088          Check_E0;
3089          Check_Type;
3090          Set_Etype (N, Standard_Boolean);
3091
3092       ------------------
3093       -- Pool_Address --
3094       ------------------
3095
3096       when Attribute_Pool_Address =>
3097          Check_E0;
3098          Set_Etype (N, RTE (RE_Address));
3099
3100       ---------
3101       -- Pos --
3102       ---------
3103
3104       when Attribute_Pos =>
3105          Check_Discrete_Type;
3106          Check_E1;
3107          Resolve (E1, P_Base_Type);
3108          Set_Etype (N, Universal_Integer);
3109
3110       --------------
3111       -- Position --
3112       --------------
3113
3114       when Attribute_Position =>
3115          Check_Component;
3116          Set_Etype (N, Universal_Integer);
3117
3118       ----------
3119       -- Pred --
3120       ----------
3121
3122       when Attribute_Pred =>
3123          Check_Scalar_Type;
3124          Check_E1;
3125          Resolve (E1, P_Base_Type);
3126          Set_Etype (N, P_Base_Type);
3127
3128          --  Nothing to do for real type case
3129
3130          if Is_Real_Type (P_Type) then
3131             null;
3132
3133          --  If not modular type, test for overflow check required
3134
3135          else
3136             if not Is_Modular_Integer_Type (P_Type)
3137               and then not Range_Checks_Suppressed (P_Base_Type)
3138             then
3139                Enable_Range_Check (E1);
3140             end if;
3141          end if;
3142
3143       -----------
3144       -- Range --
3145       -----------
3146
3147       when Attribute_Range =>
3148          Check_Array_Or_Scalar_Type;
3149
3150          if Ada_Version = Ada_83
3151            and then Is_Scalar_Type (P_Type)
3152            and then Comes_From_Source (N)
3153          then
3154             Error_Attr
3155               ("(Ada 83) % attribute not allowed for scalar type", P);
3156          end if;
3157
3158       ------------------
3159       -- Range_Length --
3160       ------------------
3161
3162       when Attribute_Range_Length =>
3163          Check_Discrete_Type;
3164          Set_Etype (N, Universal_Integer);
3165
3166       ----------
3167       -- Read --
3168       ----------
3169
3170       when Attribute_Read =>
3171          Check_E2;
3172          Check_Stream_Attribute (TSS_Stream_Read);
3173          Set_Etype (N, Standard_Void_Type);
3174          Resolve (N, Standard_Void_Type);
3175          Note_Possible_Modification (E2);
3176
3177       ---------------
3178       -- Remainder --
3179       ---------------
3180
3181       when Attribute_Remainder =>
3182          Check_Floating_Point_Type_2;
3183          Set_Etype (N, P_Base_Type);
3184          Resolve (E1, P_Base_Type);
3185          Resolve (E2, P_Base_Type);
3186
3187       -----------
3188       -- Round --
3189       -----------
3190
3191       when Attribute_Round =>
3192          Check_E1;
3193          Check_Decimal_Fixed_Point_Type;
3194          Set_Etype (N, P_Base_Type);
3195
3196          --  Because the context is universal_real (3.5.10(12)) it is a legal
3197          --  context for a universal fixed expression. This is the only
3198          --  attribute whose functional description involves U_R.
3199
3200          if Etype (E1) = Universal_Fixed then
3201             declare
3202                Conv : constant Node_Id := Make_Type_Conversion (Loc,
3203                   Subtype_Mark => New_Occurrence_Of (Universal_Real, Loc),
3204                   Expression   => Relocate_Node (E1));
3205
3206             begin
3207                Rewrite (E1, Conv);
3208                Analyze (E1);
3209             end;
3210          end if;
3211
3212          Resolve (E1, Any_Real);
3213
3214       --------------
3215       -- Rounding --
3216       --------------
3217
3218       when Attribute_Rounding =>
3219          Check_Floating_Point_Type_1;
3220          Set_Etype (N, P_Base_Type);
3221          Resolve (E1, P_Base_Type);
3222
3223       ---------------
3224       -- Safe_Emax --
3225       ---------------
3226
3227       when Attribute_Safe_Emax =>
3228          Check_Floating_Point_Type_0;
3229          Set_Etype (N, Universal_Integer);
3230
3231       ----------------
3232       -- Safe_First --
3233       ----------------
3234
3235       when Attribute_Safe_First =>
3236          Check_Floating_Point_Type_0;
3237          Set_Etype (N, Universal_Real);
3238
3239       ----------------
3240       -- Safe_Large --
3241       ----------------
3242
3243       when Attribute_Safe_Large =>
3244          Check_E0;
3245          Check_Real_Type;
3246          Set_Etype (N, Universal_Real);
3247
3248       ---------------
3249       -- Safe_Last --
3250       ---------------
3251
3252       when Attribute_Safe_Last =>
3253          Check_Floating_Point_Type_0;
3254          Set_Etype (N, Universal_Real);
3255
3256       ----------------
3257       -- Safe_Small --
3258       ----------------
3259
3260       when Attribute_Safe_Small =>
3261          Check_E0;
3262          Check_Real_Type;
3263          Set_Etype (N, Universal_Real);
3264
3265       -----------
3266       -- Scale --
3267       -----------
3268
3269       when Attribute_Scale =>
3270          Check_E0;
3271          Check_Decimal_Fixed_Point_Type;
3272          Set_Etype (N, Universal_Integer);
3273
3274       -------------
3275       -- Scaling --
3276       -------------
3277
3278       when Attribute_Scaling =>
3279          Check_Floating_Point_Type_2;
3280          Set_Etype (N, P_Base_Type);
3281          Resolve (E1, P_Base_Type);
3282
3283       ------------------
3284       -- Signed_Zeros --
3285       ------------------
3286
3287       when Attribute_Signed_Zeros =>
3288          Check_Floating_Point_Type_0;
3289          Set_Etype (N, Standard_Boolean);
3290
3291       ----------
3292       -- Size --
3293       ----------
3294
3295       when Attribute_Size | Attribute_VADS_Size =>
3296          Check_E0;
3297
3298          if Is_Object_Reference (P)
3299            or else (Is_Entity_Name (P)
3300                      and then Ekind (Entity (P)) = E_Function)
3301          then
3302             Check_Object_Reference (P);
3303
3304          elsif Is_Entity_Name (P)
3305            and then Is_Type (Entity (P))
3306          then
3307             null;
3308
3309          elsif Nkind (P) = N_Type_Conversion
3310            and then not Comes_From_Source (P)
3311          then
3312             null;
3313
3314          else
3315             Error_Attr ("invalid prefix for % attribute", P);
3316          end if;
3317
3318          Check_Not_Incomplete_Type;
3319          Set_Etype (N, Universal_Integer);
3320
3321       -----------
3322       -- Small --
3323       -----------
3324
3325       when Attribute_Small =>
3326          Check_E0;
3327          Check_Real_Type;
3328          Set_Etype (N, Universal_Real);
3329
3330       ------------------
3331       -- Storage_Pool --
3332       ------------------
3333
3334       when Attribute_Storage_Pool =>
3335          if Is_Access_Type (P_Type) then
3336             Check_E0;
3337
3338             --  Set appropriate entity
3339
3340             if Present (Associated_Storage_Pool (Root_Type (P_Type))) then
3341                Set_Entity (N, Associated_Storage_Pool (Root_Type (P_Type)));
3342             else
3343                Set_Entity (N, RTE (RE_Global_Pool_Object));
3344             end if;
3345
3346             Set_Etype (N, Class_Wide_Type (RTE (RE_Root_Storage_Pool)));
3347
3348             --  Validate_Remote_Access_To_Class_Wide_Type for attribute
3349             --  Storage_Pool since this attribute is not defined for such
3350             --  types (RM E.2.3(22)).
3351
3352             Validate_Remote_Access_To_Class_Wide_Type (N);
3353
3354          else
3355             Error_Attr ("prefix of % attribute must be access type", P);
3356          end if;
3357
3358       ------------------
3359       -- Storage_Size --
3360       ------------------
3361
3362       when Attribute_Storage_Size =>
3363
3364          if Is_Task_Type (P_Type) then
3365             Check_E0;
3366             Set_Etype (N, Universal_Integer);
3367
3368          elsif Is_Access_Type (P_Type) then
3369             if Is_Entity_Name (P)
3370               and then Is_Type (Entity (P))
3371             then
3372                Check_E0;
3373                Check_Type;
3374                Set_Etype (N, Universal_Integer);
3375
3376                --   Validate_Remote_Access_To_Class_Wide_Type for attribute
3377                --   Storage_Size since this attribute is not defined for
3378                --   such types (RM E.2.3(22)).
3379
3380                Validate_Remote_Access_To_Class_Wide_Type (N);
3381
3382             --  The prefix is allowed to be an implicit dereference
3383             --  of an access value designating a task.
3384
3385             else
3386                Check_E0;
3387                Check_Task_Prefix;
3388                Set_Etype (N, Universal_Integer);
3389             end if;
3390
3391          else
3392             Error_Attr
3393               ("prefix of % attribute must be access or task type", P);
3394          end if;
3395
3396       ------------------
3397       -- Storage_Unit --
3398       ------------------
3399
3400       when Attribute_Storage_Unit =>
3401          Standard_Attribute (Ttypes.System_Storage_Unit);
3402
3403       ----------
3404       -- Succ --
3405       ----------
3406
3407       when Attribute_Succ =>
3408          Check_Scalar_Type;
3409          Check_E1;
3410          Resolve (E1, P_Base_Type);
3411          Set_Etype (N, P_Base_Type);
3412
3413          --  Nothing to do for real type case
3414
3415          if Is_Real_Type (P_Type) then
3416             null;
3417
3418          --  If not modular type, test for overflow check required.
3419
3420          else
3421             if not Is_Modular_Integer_Type (P_Type)
3422               and then not Range_Checks_Suppressed (P_Base_Type)
3423             then
3424                Enable_Range_Check (E1);
3425             end if;
3426          end if;
3427
3428       ---------
3429       -- Tag --
3430       ---------
3431
3432       when Attribute_Tag =>
3433          Check_E0;
3434          Check_Dereference;
3435
3436          if not Is_Tagged_Type (P_Type) then
3437             Error_Attr ("prefix of % attribute must be tagged", P);
3438
3439          --  Next test does not apply to generated code
3440          --  why not, and what does the illegal reference mean???
3441
3442          elsif Is_Object_Reference (P)
3443            and then not Is_Class_Wide_Type (P_Type)
3444            and then Comes_From_Source (N)
3445          then
3446             Error_Attr
3447               ("% attribute can only be applied to objects of class-wide type",
3448                P);
3449          end if;
3450
3451          Set_Etype (N, RTE (RE_Tag));
3452
3453       -----------------
3454       -- Target_Name --
3455       -----------------
3456
3457       when Attribute_Target_Name => Target_Name : declare
3458          TN : constant String := Sdefault.Target_Name.all;
3459          TL : Integer := TN'Last;
3460
3461       begin
3462          Check_Standard_Prefix;
3463          Check_E0;
3464          Start_String;
3465
3466          if TN (TL) = '/' or else TN (TL) = '\' then
3467             TL := TL - 1;
3468          end if;
3469
3470          Store_String_Chars (TN (TN'First .. TL));
3471
3472          Rewrite (N,
3473            Make_String_Literal (Loc,
3474              Strval => End_String));
3475          Analyze_And_Resolve (N, Standard_String);
3476       end Target_Name;
3477
3478       ----------------
3479       -- Terminated --
3480       ----------------
3481
3482       when Attribute_Terminated =>
3483          Check_E0;
3484          Set_Etype (N, Standard_Boolean);
3485          Check_Task_Prefix;
3486
3487       ----------------
3488       -- To_Address --
3489       ----------------
3490
3491       when Attribute_To_Address =>
3492          Check_E1;
3493          Analyze (P);
3494
3495          if Nkind (P) /= N_Identifier
3496            or else Chars (P) /= Name_System
3497          then
3498             Error_Attr ("prefix of %attribute must be System", P);
3499          end if;
3500
3501          Generate_Reference (RTE (RE_Address), P);
3502          Analyze_And_Resolve (E1, Any_Integer);
3503          Set_Etype (N, RTE (RE_Address));
3504
3505       ----------------
3506       -- Truncation --
3507       ----------------
3508
3509       when Attribute_Truncation =>
3510          Check_Floating_Point_Type_1;
3511          Resolve (E1, P_Base_Type);
3512          Set_Etype (N, P_Base_Type);
3513
3514       ----------------
3515       -- Type_Class --
3516       ----------------
3517
3518       when Attribute_Type_Class =>
3519          Check_E0;
3520          Check_Type;
3521          Check_Not_Incomplete_Type;
3522          Set_Etype (N, RTE (RE_Type_Class));
3523
3524       -----------------
3525       -- UET_Address --
3526       -----------------
3527
3528       when Attribute_UET_Address =>
3529          Check_E0;
3530          Check_Unit_Name (P);
3531          Set_Etype (N, RTE (RE_Address));
3532
3533       -----------------------
3534       -- Unbiased_Rounding --
3535       -----------------------
3536
3537       when Attribute_Unbiased_Rounding =>
3538          Check_Floating_Point_Type_1;
3539          Set_Etype (N, P_Base_Type);
3540          Resolve (E1, P_Base_Type);
3541
3542       ----------------------
3543       -- Unchecked_Access --
3544       ----------------------
3545
3546       when Attribute_Unchecked_Access =>
3547          if Comes_From_Source (N) then
3548             Check_Restriction (No_Unchecked_Access, N);
3549          end if;
3550
3551          Analyze_Access_Attribute;
3552
3553       -------------------------
3554       -- Unconstrained_Array --
3555       -------------------------
3556
3557       when Attribute_Unconstrained_Array =>
3558          Check_E0;
3559          Check_Type;
3560          Check_Not_Incomplete_Type;
3561          Set_Etype (N, Standard_Boolean);
3562
3563       ------------------------------
3564       -- Universal_Literal_String --
3565       ------------------------------
3566
3567       --  This is a GNAT specific attribute whose prefix must be a named
3568       --  number where the expression is either a single numeric literal,
3569       --  or a numeric literal immediately preceded by a minus sign. The
3570       --  result is equivalent to a string literal containing the text of
3571       --  the literal as it appeared in the source program with a possible
3572       --  leading minus sign.
3573
3574       when Attribute_Universal_Literal_String => Universal_Literal_String :
3575       begin
3576          Check_E0;
3577
3578          if not Is_Entity_Name (P)
3579            or else Ekind (Entity (P)) not in Named_Kind
3580          then
3581             Error_Attr ("prefix for % attribute must be named number", P);
3582
3583          else
3584             declare
3585                Expr     : Node_Id;
3586                Negative : Boolean;
3587                S        : Source_Ptr;
3588                Src      : Source_Buffer_Ptr;
3589
3590             begin
3591                Expr := Original_Node (Expression (Parent (Entity (P))));
3592
3593                if Nkind (Expr) = N_Op_Minus then
3594                   Negative := True;
3595                   Expr := Original_Node (Right_Opnd (Expr));
3596                else
3597                   Negative := False;
3598                end if;
3599
3600                if Nkind (Expr) /= N_Integer_Literal
3601                  and then Nkind (Expr) /= N_Real_Literal
3602                then
3603                   Error_Attr
3604                     ("named number for % attribute must be simple literal", N);
3605                end if;
3606
3607                --  Build string literal corresponding to source literal text
3608
3609                Start_String;
3610
3611                if Negative then
3612                   Store_String_Char (Get_Char_Code ('-'));
3613                end if;
3614
3615                S := Sloc (Expr);
3616                Src := Source_Text (Get_Source_File_Index (S));
3617
3618                while Src (S) /= ';' and then Src (S) /= ' ' loop
3619                   Store_String_Char (Get_Char_Code (Src (S)));
3620                   S := S + 1;
3621                end loop;
3622
3623                --  Now we rewrite the attribute with the string literal
3624
3625                Rewrite (N,
3626                  Make_String_Literal (Loc, End_String));
3627                Analyze (N);
3628             end;
3629          end if;
3630       end Universal_Literal_String;
3631
3632       -------------------------
3633       -- Unrestricted_Access --
3634       -------------------------
3635
3636       --  This is a GNAT specific attribute which is like Access except that
3637       --  all scope checks and checks for aliased views are omitted.
3638
3639       when Attribute_Unrestricted_Access =>
3640          if Comes_From_Source (N) then
3641             Check_Restriction (No_Unchecked_Access, N);
3642          end if;
3643
3644          if Is_Entity_Name (P) then
3645             Set_Address_Taken (Entity (P));
3646          end if;
3647
3648          Analyze_Access_Attribute;
3649
3650       ---------
3651       -- Val --
3652       ---------
3653
3654       when Attribute_Val => Val : declare
3655       begin
3656          Check_E1;
3657          Check_Discrete_Type;
3658          Resolve (E1, Any_Integer);
3659          Set_Etype (N, P_Base_Type);
3660
3661          --  Note, we need a range check in general, but we wait for the
3662          --  Resolve call to do this, since we want to let Eval_Attribute
3663          --  have a chance to find an static illegality first!
3664       end Val;
3665
3666       -----------
3667       -- Valid --
3668       -----------
3669
3670       when Attribute_Valid =>
3671          Check_E0;
3672
3673          --  Ignore check for object if we have a 'Valid reference generated
3674          --  by the expanded code, since in some cases valid checks can occur
3675          --  on items that are names, but are not objects (e.g. attributes).
3676
3677          if Comes_From_Source (N) then
3678             Check_Object_Reference (P);
3679          end if;
3680
3681          if not Is_Scalar_Type (P_Type) then
3682             Error_Attr ("object for % attribute must be of scalar type", P);
3683          end if;
3684
3685          Set_Etype (N, Standard_Boolean);
3686
3687       -----------
3688       -- Value --
3689       -----------
3690
3691       when Attribute_Value => Value :
3692       begin
3693          Check_E1;
3694          Check_Scalar_Type;
3695
3696          if Is_Enumeration_Type (P_Type) then
3697             Check_Restriction (No_Enumeration_Maps, N);
3698          end if;
3699
3700          --  Set Etype before resolving expression because expansion of
3701          --  expression may require enclosing type. Note that the type
3702          --  returned by 'Value is the base type of the prefix type.
3703
3704          Set_Etype (N, P_Base_Type);
3705          Validate_Non_Static_Attribute_Function_Call;
3706       end Value;
3707
3708       ----------------
3709       -- Value_Size --
3710       ----------------
3711
3712       when Attribute_Value_Size =>
3713          Check_E0;
3714          Check_Type;
3715          Check_Not_Incomplete_Type;
3716          Set_Etype (N, Universal_Integer);
3717
3718       -------------
3719       -- Version --
3720       -------------
3721
3722       when Attribute_Version =>
3723          Check_E0;
3724          Check_Program_Unit;
3725          Set_Etype (N, RTE (RE_Version_String));
3726
3727       ------------------
3728       -- Wchar_T_Size --
3729       ------------------
3730
3731       when Attribute_Wchar_T_Size =>
3732          Standard_Attribute (Interfaces_Wchar_T_Size);
3733
3734       ----------------
3735       -- Wide_Image --
3736       ----------------
3737
3738       when Attribute_Wide_Image => Wide_Image :
3739       begin
3740          Check_Scalar_Type;
3741          Set_Etype (N, Standard_Wide_String);
3742          Check_E1;
3743          Resolve (E1, P_Base_Type);
3744          Validate_Non_Static_Attribute_Function_Call;
3745       end Wide_Image;
3746
3747       ----------------
3748       -- Wide_Value --
3749       ----------------
3750
3751       when Attribute_Wide_Value => Wide_Value :
3752       begin
3753          Check_E1;
3754          Check_Scalar_Type;
3755
3756          --  Set Etype before resolving expression because expansion
3757          --  of expression may require enclosing type.
3758
3759          Set_Etype (N, P_Type);
3760          Validate_Non_Static_Attribute_Function_Call;
3761       end Wide_Value;
3762
3763       ----------------
3764       -- Wide_Width --
3765       ----------------
3766
3767       when Attribute_Wide_Width =>
3768          Check_E0;
3769          Check_Scalar_Type;
3770          Set_Etype (N, Universal_Integer);
3771
3772       -----------
3773       -- Width --
3774       -----------
3775
3776       when Attribute_Width =>
3777          Check_E0;
3778          Check_Scalar_Type;
3779          Set_Etype (N, Universal_Integer);
3780
3781       ---------------
3782       -- Word_Size --
3783       ---------------
3784
3785       when Attribute_Word_Size =>
3786          Standard_Attribute (System_Word_Size);
3787
3788       -----------
3789       -- Write --
3790       -----------
3791
3792       when Attribute_Write =>
3793          Check_E2;
3794          Check_Stream_Attribute (TSS_Stream_Write);
3795          Set_Etype (N, Standard_Void_Type);
3796          Resolve (N, Standard_Void_Type);
3797
3798       end case;
3799
3800    --  All errors raise Bad_Attribute, so that we get out before any further
3801    --  damage occurs when an error is detected (for example, if we check for
3802    --  one attribute expression, and the check succeeds, we want to be able
3803    --  to proceed securely assuming that an expression is in fact present.
3804
3805    exception
3806       when Bad_Attribute =>
3807          Set_Etype (N, Any_Type);
3808          return;
3809
3810    end Analyze_Attribute;
3811
3812    --------------------
3813    -- Eval_Attribute --
3814    --------------------
3815
3816    procedure Eval_Attribute (N : Node_Id) is
3817       Loc   : constant Source_Ptr   := Sloc (N);
3818       Aname : constant Name_Id      := Attribute_Name (N);
3819       Id    : constant Attribute_Id := Get_Attribute_Id (Aname);
3820       P     : constant Node_Id      := Prefix (N);
3821
3822       C_Type : constant Entity_Id := Etype (N);
3823       --  The type imposed by the context.
3824
3825       E1 : Node_Id;
3826       --  First expression, or Empty if none
3827
3828       E2 : Node_Id;
3829       --  Second expression, or Empty if none
3830
3831       P_Entity : Entity_Id;
3832       --  Entity denoted by prefix
3833
3834       P_Type : Entity_Id;
3835       --  The type of the prefix
3836
3837       P_Base_Type : Entity_Id;
3838       --  The base type of the prefix type
3839
3840       P_Root_Type : Entity_Id;
3841       --  The root type of the prefix type
3842
3843       Static : Boolean;
3844       --  True if the result is Static. This is set by the general processing
3845       --  to true if the prefix is static, and all expressions are static. It
3846       --  can be reset as processing continues for particular attributes
3847
3848       Lo_Bound, Hi_Bound : Node_Id;
3849       --  Expressions for low and high bounds of type or array index referenced
3850       --  by First, Last, or Length attribute for array, set by Set_Bounds.
3851
3852       CE_Node : Node_Id;
3853       --  Constraint error node used if we have an attribute reference has
3854       --  an argument that raises a constraint error. In this case we replace
3855       --  the attribute with a raise constraint_error node. This is important
3856       --  processing, since otherwise gigi might see an attribute which it is
3857       --  unprepared to deal with.
3858
3859       function Aft_Value return Nat;
3860       --  Computes Aft value for current attribute prefix (used by Aft itself
3861       --  and also by Width for computing the Width of a fixed point type).
3862
3863       procedure Check_Expressions;
3864       --  In case where the attribute is not foldable, the expressions, if
3865       --  any, of the attribute, are in a non-static context. This procedure
3866       --  performs the required additional checks.
3867
3868       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean;
3869       --  Determines if the given type has compile time known bounds. Note
3870       --  that we enter the case statement even in cases where the prefix
3871       --  type does NOT have known bounds, so it is important to guard any
3872       --  attempt to evaluate both bounds with a call to this function.
3873
3874       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint);
3875       --  This procedure is called when the attribute N has a non-static
3876       --  but compile time known value given by Val. It includes the
3877       --  necessary checks for out of range values.
3878
3879       procedure Float_Attribute_Universal_Integer
3880         (IEEES_Val : Int;
3881          IEEEL_Val : Int;
3882          IEEEX_Val : Int;
3883          VAXFF_Val : Int;
3884          VAXDF_Val : Int;
3885          VAXGF_Val : Int;
3886          AAMPS_Val : Int;
3887          AAMPL_Val : Int);
3888       --  This procedure evaluates a float attribute with no arguments that
3889       --  returns a universal integer result. The parameters give the values
3890       --  for the possible floating-point root types. See ttypef for details.
3891       --  The prefix type is a float type (and is thus not a generic type).
3892
3893       procedure Float_Attribute_Universal_Real
3894         (IEEES_Val : String;
3895          IEEEL_Val : String;
3896          IEEEX_Val : String;
3897          VAXFF_Val : String;
3898          VAXDF_Val : String;
3899          VAXGF_Val : String;
3900          AAMPS_Val : String;
3901          AAMPL_Val : String);
3902       --  This procedure evaluates a float attribute with no arguments that
3903       --  returns a universal real result. The parameters give the values
3904       --  required for the possible floating-point root types in string
3905       --  format as real literals with a possible leading minus sign.
3906       --  The prefix type is a float type (and is thus not a generic type).
3907
3908       function Fore_Value return Nat;
3909       --  Computes the Fore value for the current attribute prefix, which is
3910       --  known to be a static fixed-point type. Used by Fore and Width.
3911
3912       function Mantissa return Uint;
3913       --  Returns the Mantissa value for the prefix type
3914
3915       procedure Set_Bounds;
3916       --  Used for First, Last and Length attributes applied to an array or
3917       --  array subtype. Sets the variables Lo_Bound and Hi_Bound to the low
3918       --  and high bound expressions for the index referenced by the attribute
3919       --  designator (i.e. the first index if no expression is present, and
3920       --  the N'th index if the value N is present as an expression). Also
3921       --  used for First and Last of scalar types. Static is reset to False
3922       --  if the type or index type is not statically constrained.
3923
3924       ---------------
3925       -- Aft_Value --
3926       ---------------
3927
3928       function Aft_Value return Nat is
3929          Result    : Nat;
3930          Delta_Val : Ureal;
3931
3932       begin
3933          Result := 1;
3934          Delta_Val := Delta_Value (P_Type);
3935
3936          while Delta_Val < Ureal_Tenth loop
3937             Delta_Val := Delta_Val * Ureal_10;
3938             Result := Result + 1;
3939          end loop;
3940
3941          return Result;
3942       end Aft_Value;
3943
3944       -----------------------
3945       -- Check_Expressions --
3946       -----------------------
3947
3948       procedure Check_Expressions is
3949          E : Node_Id := E1;
3950
3951       begin
3952          while Present (E) loop
3953             Check_Non_Static_Context (E);
3954             Next (E);
3955          end loop;
3956       end Check_Expressions;
3957
3958       ----------------------------------
3959       -- Compile_Time_Known_Attribute --
3960       ----------------------------------
3961
3962       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint) is
3963          T : constant Entity_Id := Etype (N);
3964
3965       begin
3966          Fold_Uint (N, Val, False);
3967
3968          --  Check that result is in bounds of the type if it is static
3969
3970          if Is_In_Range (N, T) then
3971             null;
3972
3973          elsif Is_Out_Of_Range (N, T) then
3974             Apply_Compile_Time_Constraint_Error
3975               (N, "value not in range of}?", CE_Range_Check_Failed);
3976
3977          elsif not Range_Checks_Suppressed (T) then
3978             Enable_Range_Check (N);
3979
3980          else
3981             Set_Do_Range_Check (N, False);
3982          end if;
3983       end Compile_Time_Known_Attribute;
3984
3985       -------------------------------
3986       -- Compile_Time_Known_Bounds --
3987       -------------------------------
3988
3989       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean is
3990       begin
3991          return
3992            Compile_Time_Known_Value (Type_Low_Bound (Typ))
3993              and then
3994            Compile_Time_Known_Value (Type_High_Bound (Typ));
3995       end Compile_Time_Known_Bounds;
3996
3997       ---------------------------------------
3998       -- Float_Attribute_Universal_Integer --
3999       ---------------------------------------
4000
4001       procedure Float_Attribute_Universal_Integer
4002         (IEEES_Val : Int;
4003          IEEEL_Val : Int;
4004          IEEEX_Val : Int;
4005          VAXFF_Val : Int;
4006          VAXDF_Val : Int;
4007          VAXGF_Val : Int;
4008          AAMPS_Val : Int;
4009          AAMPL_Val : Int)
4010       is
4011          Val  : Int;
4012          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4013
4014       begin
4015          if Vax_Float (P_Base_Type) then
4016             if Digs = VAXFF_Digits then
4017                Val := VAXFF_Val;
4018             elsif Digs = VAXDF_Digits then
4019                Val := VAXDF_Val;
4020             else pragma Assert (Digs = VAXGF_Digits);
4021                Val := VAXGF_Val;
4022             end if;
4023
4024          elsif Is_AAMP_Float (P_Base_Type) then
4025             if Digs = AAMPS_Digits then
4026                Val := AAMPS_Val;
4027             else pragma Assert (Digs = AAMPL_Digits);
4028                Val := AAMPL_Val;
4029             end if;
4030
4031          else
4032             if Digs = IEEES_Digits then
4033                Val := IEEES_Val;
4034             elsif Digs = IEEEL_Digits then
4035                Val := IEEEL_Val;
4036             else pragma Assert (Digs = IEEEX_Digits);
4037                Val := IEEEX_Val;
4038             end if;
4039          end if;
4040
4041          Fold_Uint (N, UI_From_Int (Val), True);
4042       end Float_Attribute_Universal_Integer;
4043
4044       ------------------------------------
4045       -- Float_Attribute_Universal_Real --
4046       ------------------------------------
4047
4048       procedure Float_Attribute_Universal_Real
4049         (IEEES_Val : String;
4050          IEEEL_Val : String;
4051          IEEEX_Val : String;
4052          VAXFF_Val : String;
4053          VAXDF_Val : String;
4054          VAXGF_Val : String;
4055          AAMPS_Val : String;
4056          AAMPL_Val : String)
4057       is
4058          Val  : Node_Id;
4059          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4060
4061       begin
4062          if Vax_Float (P_Base_Type) then
4063             if Digs = VAXFF_Digits then
4064                Val := Real_Convert (VAXFF_Val);
4065             elsif Digs = VAXDF_Digits then
4066                Val := Real_Convert (VAXDF_Val);
4067             else pragma Assert (Digs = VAXGF_Digits);
4068                Val := Real_Convert (VAXGF_Val);
4069             end if;
4070
4071          elsif Is_AAMP_Float (P_Base_Type) then
4072             if Digs = AAMPS_Digits then
4073                Val := Real_Convert (AAMPS_Val);
4074             else pragma Assert (Digs = AAMPL_Digits);
4075                Val := Real_Convert (AAMPL_Val);
4076             end if;
4077
4078          else
4079             if Digs = IEEES_Digits then
4080                Val := Real_Convert (IEEES_Val);
4081             elsif Digs = IEEEL_Digits then
4082                Val := Real_Convert (IEEEL_Val);
4083             else pragma Assert (Digs = IEEEX_Digits);
4084                Val := Real_Convert (IEEEX_Val);
4085             end if;
4086          end if;
4087
4088          Set_Sloc (Val, Loc);
4089          Rewrite (N, Val);
4090          Set_Is_Static_Expression (N, Static);
4091          Analyze_And_Resolve (N, C_Type);
4092       end Float_Attribute_Universal_Real;
4093
4094       ----------------
4095       -- Fore_Value --
4096       ----------------
4097
4098       --  Note that the Fore calculation is based on the actual values
4099       --  of the bounds, and does not take into account possible rounding.
4100
4101       function Fore_Value return Nat is
4102          Lo      : constant Uint  := Expr_Value (Type_Low_Bound (P_Type));
4103          Hi      : constant Uint  := Expr_Value (Type_High_Bound (P_Type));
4104          Small   : constant Ureal := Small_Value (P_Type);
4105          Lo_Real : constant Ureal := Lo * Small;
4106          Hi_Real : constant Ureal := Hi * Small;
4107          T       : Ureal;
4108          R       : Nat;
4109
4110       begin
4111          --  Bounds are given in terms of small units, so first compute
4112          --  proper values as reals.
4113
4114          T := UR_Max (abs Lo_Real, abs Hi_Real);
4115          R := 2;
4116
4117          --  Loop to compute proper value if more than one digit required
4118
4119          while T >= Ureal_10 loop
4120             R := R + 1;
4121             T := T / Ureal_10;
4122          end loop;
4123
4124          return R;
4125       end Fore_Value;
4126
4127       --------------
4128       -- Mantissa --
4129       --------------
4130
4131       --  Table of mantissa values accessed by function  Computed using
4132       --  the relation:
4133
4134       --    T'Mantissa = integer next above (D * log(10)/log(2)) + 1)
4135
4136       --  where D is T'Digits (RM83 3.5.7)
4137
4138       Mantissa_Value : constant array (Nat range 1 .. 40) of Nat := (
4139           1 =>   5,
4140           2 =>   8,
4141           3 =>  11,
4142           4 =>  15,
4143           5 =>  18,
4144           6 =>  21,
4145           7 =>  25,
4146           8 =>  28,
4147           9 =>  31,
4148          10 =>  35,
4149          11 =>  38,
4150          12 =>  41,
4151          13 =>  45,
4152          14 =>  48,
4153          15 =>  51,
4154          16 =>  55,
4155          17 =>  58,
4156          18 =>  61,
4157          19 =>  65,
4158          20 =>  68,
4159          21 =>  71,
4160          22 =>  75,
4161          23 =>  78,
4162          24 =>  81,
4163          25 =>  85,
4164          26 =>  88,
4165          27 =>  91,
4166          28 =>  95,
4167          29 =>  98,
4168          30 => 101,
4169          31 => 104,
4170          32 => 108,
4171          33 => 111,
4172          34 => 114,
4173          35 => 118,
4174          36 => 121,
4175          37 => 124,
4176          38 => 128,
4177          39 => 131,
4178          40 => 134);
4179
4180       function Mantissa return Uint is
4181       begin
4182          return
4183            UI_From_Int (Mantissa_Value (UI_To_Int (Digits_Value (P_Type))));
4184       end Mantissa;
4185
4186       ----------------
4187       -- Set_Bounds --
4188       ----------------
4189
4190       procedure Set_Bounds is
4191          Ndim : Nat;
4192          Indx : Node_Id;
4193          Ityp : Entity_Id;
4194
4195       begin
4196          --  For a string literal subtype, we have to construct the bounds.
4197          --  Valid Ada code never applies attributes to string literals, but
4198          --  it is convenient to allow the expander to generate attribute
4199          --  references of this type (e.g. First and Last applied to a string
4200          --  literal).
4201
4202          --  Note that the whole point of the E_String_Literal_Subtype is to
4203          --  avoid this construction of bounds, but the cases in which we
4204          --  have to materialize them are rare enough that we don't worry!
4205
4206          --  The low bound is simply the low bound of the base type. The
4207          --  high bound is computed from the length of the string and this
4208          --  low bound.
4209
4210          if Ekind (P_Type) = E_String_Literal_Subtype then
4211             Ityp := Etype (First_Index (Base_Type (P_Type)));
4212             Lo_Bound := Type_Low_Bound (Ityp);
4213
4214             Hi_Bound :=
4215               Make_Integer_Literal (Sloc (P),
4216                 Intval =>
4217                   Expr_Value (Lo_Bound) + String_Literal_Length (P_Type) - 1);
4218
4219             Set_Parent (Hi_Bound, P);
4220             Analyze_And_Resolve (Hi_Bound, Etype (Lo_Bound));
4221             return;
4222
4223          --  For non-array case, just get bounds of scalar type
4224
4225          elsif Is_Scalar_Type (P_Type) then
4226             Ityp := P_Type;
4227
4228             --  For a fixed-point type, we must freeze to get the attributes
4229             --  of the fixed-point type set now so we can reference them.
4230
4231             if Is_Fixed_Point_Type (P_Type)
4232               and then not Is_Frozen (Base_Type (P_Type))
4233               and then Compile_Time_Known_Value (Type_Low_Bound (P_Type))
4234               and then Compile_Time_Known_Value (Type_High_Bound (P_Type))
4235             then
4236                Freeze_Fixed_Point_Type (Base_Type (P_Type));
4237             end if;
4238
4239          --  For array case, get type of proper index
4240
4241          else
4242             if No (E1) then
4243                Ndim := 1;
4244             else
4245                Ndim := UI_To_Int (Expr_Value (E1));
4246             end if;
4247
4248             Indx := First_Index (P_Type);
4249             for J in 1 .. Ndim - 1 loop
4250                Next_Index (Indx);
4251             end loop;
4252
4253             --  If no index type, get out (some other error occurred, and
4254             --  we don't have enough information to complete the job!)
4255
4256             if No (Indx) then
4257                Lo_Bound := Error;
4258                Hi_Bound := Error;
4259                return;
4260             end if;
4261
4262             Ityp := Etype (Indx);
4263          end if;
4264
4265          --  A discrete range in an index constraint is allowed to be a
4266          --  subtype indication. This is syntactically a pain, but should
4267          --  not propagate to the entity for the corresponding index subtype.
4268          --  After checking that the subtype indication is legal, the range
4269          --  of the subtype indication should be transfered to the entity.
4270          --  The attributes for the bounds should remain the simple retrievals
4271          --  that they are now.
4272
4273          Lo_Bound := Type_Low_Bound (Ityp);
4274          Hi_Bound := Type_High_Bound (Ityp);
4275
4276          if not Is_Static_Subtype (Ityp) then
4277             Static := False;
4278          end if;
4279       end Set_Bounds;
4280
4281    --  Start of processing for Eval_Attribute
4282
4283    begin
4284       --  Acquire first two expressions (at the moment, no attributes
4285       --  take more than two expressions in any case).
4286
4287       if Present (Expressions (N)) then
4288          E1 := First (Expressions (N));
4289          E2 := Next (E1);
4290       else
4291          E1 := Empty;
4292          E2 := Empty;
4293       end if;
4294
4295       --  Special processing for cases where the prefix is an object. For
4296       --  this purpose, a string literal counts as an object (attributes
4297       --  of string literals can only appear in generated code).
4298
4299       if Is_Object_Reference (P) or else Nkind (P) = N_String_Literal then
4300
4301          --  For Component_Size, the prefix is an array object, and we apply
4302          --  the attribute to the type of the object. This is allowed for
4303          --  both unconstrained and constrained arrays, since the bounds
4304          --  have no influence on the value of this attribute.
4305
4306          if Id = Attribute_Component_Size then
4307             P_Entity := Etype (P);
4308
4309          --  For First and Last, the prefix is an array object, and we apply
4310          --  the attribute to the type of the array, but we need a constrained
4311          --  type for this, so we use the actual subtype if available.
4312
4313          elsif Id = Attribute_First
4314                  or else
4315                Id = Attribute_Last
4316                  or else
4317                Id = Attribute_Length
4318          then
4319             declare
4320                AS : constant Entity_Id := Get_Actual_Subtype_If_Available (P);
4321
4322             begin
4323                if Present (AS) and then Is_Constrained (AS) then
4324                   P_Entity := AS;
4325
4326                --  If we have an unconstrained type, cannot fold
4327
4328                else
4329                   Check_Expressions;
4330                   return;
4331                end if;
4332             end;
4333
4334          --  For Size, give size of object if available, otherwise we
4335          --  cannot fold Size.
4336
4337          elsif Id = Attribute_Size then
4338             if Is_Entity_Name (P)
4339               and then Known_Esize (Entity (P))
4340             then
4341                Compile_Time_Known_Attribute (N, Esize (Entity (P)));
4342                return;
4343
4344             else
4345                Check_Expressions;
4346                return;
4347             end if;
4348
4349          --  For Alignment, give size of object if available, otherwise we
4350          --  cannot fold Alignment.
4351
4352          elsif Id = Attribute_Alignment then
4353             if Is_Entity_Name (P)
4354               and then Known_Alignment (Entity (P))
4355             then
4356                Fold_Uint (N, Alignment (Entity (P)), False);
4357                return;
4358
4359             else
4360                Check_Expressions;
4361                return;
4362             end if;
4363
4364          --  No other attributes for objects are folded
4365
4366          else
4367             Check_Expressions;
4368             return;
4369          end if;
4370
4371       --  Cases where P is not an object. Cannot do anything if P is
4372       --  not the name of an entity.
4373
4374       elsif not Is_Entity_Name (P) then
4375          Check_Expressions;
4376          return;
4377
4378       --  Otherwise get prefix entity
4379
4380       else
4381          P_Entity := Entity (P);
4382       end if;
4383
4384       --  At this stage P_Entity is the entity to which the attribute
4385       --  is to be applied. This is usually simply the entity of the
4386       --  prefix, except in some cases of attributes for objects, where
4387       --  as described above, we apply the attribute to the object type.
4388
4389       --  First foldable possibility is a scalar or array type (RM 4.9(7))
4390       --  that is not generic (generic types are eliminated by RM 4.9(25)).
4391       --  Note we allow non-static non-generic types at this stage as further
4392       --  described below.
4393
4394       if Is_Type (P_Entity)
4395         and then (Is_Scalar_Type (P_Entity) or Is_Array_Type (P_Entity))
4396         and then (not Is_Generic_Type (P_Entity))
4397       then
4398          P_Type := P_Entity;
4399
4400       --  Second foldable possibility is an array object (RM 4.9(8))
4401
4402       elsif (Ekind (P_Entity) = E_Variable
4403                or else
4404              Ekind (P_Entity) = E_Constant)
4405         and then Is_Array_Type (Etype (P_Entity))
4406         and then (not Is_Generic_Type (Etype (P_Entity)))
4407       then
4408          P_Type := Etype (P_Entity);
4409
4410          --  If the entity is an array constant with an unconstrained
4411          --  nominal subtype then get the type from the initial value.
4412          --  If the value has been expanded into assignments, the expression
4413          --  is not present and the attribute reference remains dynamic.
4414          --  We could do better here and retrieve the type ???
4415
4416          if Ekind (P_Entity) = E_Constant
4417            and then not Is_Constrained (P_Type)
4418          then
4419             if No (Constant_Value (P_Entity)) then
4420                return;
4421             else
4422                P_Type := Etype (Constant_Value (P_Entity));
4423             end if;
4424          end if;
4425
4426       --  Definite must be folded if the prefix is not a generic type,
4427       --  that is to say if we are within an instantiation. Same processing
4428       --  applies to the GNAT attributes Has_Discriminants, Type_Class,
4429       --  and Unconstrained_Array.
4430
4431       elsif (Id = Attribute_Definite
4432                or else
4433              Id = Attribute_Has_Discriminants
4434                or else
4435              Id = Attribute_Type_Class
4436                or else
4437              Id = Attribute_Unconstrained_Array)
4438         and then not Is_Generic_Type (P_Entity)
4439       then
4440          P_Type := P_Entity;
4441
4442       --  We can fold 'Size applied to a type if the size is known
4443       --  (as happens for a size from an attribute definition clause).
4444       --  At this stage, this can happen only for types (e.g. record
4445       --  types) for which the size is always non-static. We exclude
4446       --  generic types from consideration (since they have bogus
4447       --  sizes set within templates).
4448
4449       elsif Id = Attribute_Size
4450         and then Is_Type (P_Entity)
4451         and then (not Is_Generic_Type (P_Entity))
4452         and then Known_Static_RM_Size (P_Entity)
4453       then
4454          Compile_Time_Known_Attribute (N, RM_Size (P_Entity));
4455          return;
4456
4457       --  We can fold 'Alignment applied to a type if the alignment is known
4458       --  (as happens for an alignment from an attribute definition clause).
4459       --  At this stage, this can happen only for types (e.g. record
4460       --  types) for which the size is always non-static. We exclude
4461       --  generic types from consideration (since they have bogus
4462       --  sizes set within templates).
4463
4464       elsif Id = Attribute_Alignment
4465         and then Is_Type (P_Entity)
4466         and then (not Is_Generic_Type (P_Entity))
4467         and then Known_Alignment (P_Entity)
4468       then
4469          Compile_Time_Known_Attribute (N, Alignment (P_Entity));
4470          return;
4471
4472       --  If this is an access attribute that is known to fail accessibility
4473       --  check, rewrite accordingly.
4474
4475       elsif Attribute_Name (N) = Name_Access
4476         and then Raises_Constraint_Error (N)
4477       then
4478          Rewrite (N,
4479            Make_Raise_Program_Error (Loc,
4480              Reason => PE_Accessibility_Check_Failed));
4481          Set_Etype (N, C_Type);
4482          return;
4483
4484       --  No other cases are foldable (they certainly aren't static, and at
4485       --  the moment we don't try to fold any cases other than these three).
4486
4487       else
4488          Check_Expressions;
4489          return;
4490       end if;
4491
4492       --  If either attribute or the prefix is Any_Type, then propagate
4493       --  Any_Type to the result and don't do anything else at all.
4494
4495       if P_Type = Any_Type
4496         or else (Present (E1) and then Etype (E1) = Any_Type)
4497         or else (Present (E2) and then Etype (E2) = Any_Type)
4498       then
4499          Set_Etype (N, Any_Type);
4500          return;
4501       end if;
4502
4503       --  Scalar subtype case. We have not yet enforced the static requirement
4504       --  of (RM 4.9(7)) and we don't intend to just yet, since there are cases
4505       --  of non-static attribute references (e.g. S'Digits for a non-static
4506       --  floating-point type, which we can compute at compile time).
4507
4508       --  Note: this folding of non-static attributes is not simply a case of
4509       --  optimization. For many of the attributes affected, Gigi cannot handle
4510       --  the attribute and depends on the front end having folded them away.
4511
4512       --  Note: although we don't require staticness at this stage, we do set
4513       --  the Static variable to record the staticness, for easy reference by
4514       --  those attributes where it matters (e.g. Succ and Pred), and also to
4515       --  be used to ensure that non-static folded things are not marked as
4516       --  being static (a check that is done right at the end).
4517
4518       P_Root_Type := Root_Type (P_Type);
4519       P_Base_Type := Base_Type (P_Type);
4520
4521       --  If the root type or base type is generic, then we cannot fold. This
4522       --  test is needed because subtypes of generic types are not always
4523       --  marked as being generic themselves (which seems odd???)
4524
4525       if Is_Generic_Type (P_Root_Type)
4526         or else Is_Generic_Type (P_Base_Type)
4527       then
4528          return;
4529       end if;
4530
4531       if Is_Scalar_Type (P_Type) then
4532          Static := Is_OK_Static_Subtype (P_Type);
4533
4534       --  Array case. We enforce the constrained requirement of (RM 4.9(7-8))
4535       --  since we can't do anything with unconstrained arrays. In addition,
4536       --  only the First, Last and Length attributes are possibly static.
4537       --  In addition Component_Size is possibly foldable, even though it
4538       --  can never be static.
4539
4540       --  Definite, Has_Discriminants, Type_Class and Unconstrained_Array are
4541       --  again exceptions, because they apply as well to unconstrained types.
4542
4543       elsif Id = Attribute_Definite
4544               or else
4545             Id = Attribute_Has_Discriminants
4546               or else
4547             Id = Attribute_Type_Class
4548               or else
4549             Id = Attribute_Unconstrained_Array
4550       then
4551          Static := False;
4552
4553       else
4554          if not Is_Constrained (P_Type)
4555            or else (Id /= Attribute_Component_Size and then
4556                     Id /= Attribute_First          and then
4557                     Id /= Attribute_Last           and then
4558                     Id /= Attribute_Length)
4559          then
4560             Check_Expressions;
4561             return;
4562          end if;
4563
4564          --  The rules in (RM 4.9(7,8)) require a static array, but as in the
4565          --  scalar case, we hold off on enforcing staticness, since there are
4566          --  cases which we can fold at compile time even though they are not
4567          --  static (e.g. 'Length applied to a static index, even though other
4568          --  non-static indexes make the array type non-static). This is only
4569          --  an optimization, but it falls out essentially free, so why not.
4570          --  Again we compute the variable Static for easy reference later
4571          --  (note that no array attributes are static in Ada 83).
4572
4573          Static := Ada_Version >= Ada_95;
4574
4575          declare
4576             N : Node_Id;
4577
4578          begin
4579             N := First_Index (P_Type);
4580             while Present (N) loop
4581                Static := Static and then Is_Static_Subtype (Etype (N));
4582
4583                --  If however the index type is generic, attributes cannot
4584                --  be folded.
4585
4586                if Is_Generic_Type (Etype (N))
4587                  and then Id /= Attribute_Component_Size
4588                then
4589                   return;
4590                end if;
4591
4592                Next_Index (N);
4593             end loop;
4594          end;
4595       end if;
4596
4597       --  Check any expressions that are present. Note that these expressions,
4598       --  depending on the particular attribute type, are either part of the
4599       --  attribute designator, or they are arguments in a case where the
4600       --  attribute reference returns a function. In the latter case, the
4601       --  rule in (RM 4.9(22)) applies and in particular requires the type
4602       --  of the expressions to be scalar in order for the attribute to be
4603       --  considered to be static.
4604
4605       declare
4606          E : Node_Id;
4607
4608       begin
4609          E := E1;
4610          while Present (E) loop
4611
4612             --  If expression is not static, then the attribute reference
4613             --  result certainly cannot be static.
4614
4615             if not Is_Static_Expression (E) then
4616                Static := False;
4617             end if;
4618
4619             --  If the result is not known at compile time, or is not of
4620             --  a scalar type, then the result is definitely not static,
4621             --  so we can quit now.
4622
4623             if not Compile_Time_Known_Value (E)
4624               or else not Is_Scalar_Type (Etype (E))
4625             then
4626                --  An odd special case, if this is a Pos attribute, this
4627                --  is where we need to apply a range check since it does
4628                --  not get done anywhere else.
4629
4630                if Id = Attribute_Pos then
4631                   if Is_Integer_Type (Etype (E)) then
4632                      Apply_Range_Check (E, Etype (N));
4633                   end if;
4634                end if;
4635
4636                Check_Expressions;
4637                return;
4638
4639             --  If the expression raises a constraint error, then so does
4640             --  the attribute reference. We keep going in this case because
4641             --  we are still interested in whether the attribute reference
4642             --  is static even if it is not static.
4643
4644             elsif Raises_Constraint_Error (E) then
4645                Set_Raises_Constraint_Error (N);
4646             end if;
4647
4648             Next (E);
4649          end loop;
4650
4651          if Raises_Constraint_Error (Prefix (N)) then
4652             return;
4653          end if;
4654       end;
4655
4656       --  Deal with the case of a static attribute reference that raises
4657       --  constraint error. The Raises_Constraint_Error flag will already
4658       --  have been set, and the Static flag shows whether the attribute
4659       --  reference is static. In any case we certainly can't fold such an
4660       --  attribute reference.
4661
4662       --  Note that the rewriting of the attribute node with the constraint
4663       --  error node is essential in this case, because otherwise Gigi might
4664       --  blow up on one of the attributes it never expects to see.
4665
4666       --  The constraint_error node must have the type imposed by the context,
4667       --  to avoid spurious errors in the enclosing expression.
4668
4669       if Raises_Constraint_Error (N) then
4670          CE_Node :=
4671            Make_Raise_Constraint_Error (Sloc (N),
4672              Reason => CE_Range_Check_Failed);
4673          Set_Etype (CE_Node, Etype (N));
4674          Set_Raises_Constraint_Error (CE_Node);
4675          Check_Expressions;
4676          Rewrite (N, Relocate_Node (CE_Node));
4677          Set_Is_Static_Expression (N, Static);
4678          return;
4679       end if;
4680
4681       --  At this point we have a potentially foldable attribute reference.
4682       --  If Static is set, then the attribute reference definitely obeys
4683       --  the requirements in (RM 4.9(7,8,22)), and it definitely can be
4684       --  folded. If Static is not set, then the attribute may or may not
4685       --  be foldable, and the individual attribute processing routines
4686       --  test Static as required in cases where it makes a difference.
4687
4688       --  In the case where Static is not set, we do know that all the
4689       --  expressions present are at least known at compile time (we
4690       --  assumed above that if this was not the case, then there was
4691       --  no hope of static evaluation). However, we did not require
4692       --  that the bounds of the prefix type be compile time known,
4693       --  let alone static). That's because there are many attributes
4694       --  that can be computed at compile time on non-static subtypes,
4695       --  even though such references are not static expressions.
4696
4697       case Id is
4698
4699       --------------
4700       -- Adjacent --
4701       --------------
4702
4703       when Attribute_Adjacent =>
4704          Fold_Ureal (N,
4705            Eval_Fat.Adjacent
4706              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
4707
4708       ---------
4709       -- Aft --
4710       ---------
4711
4712       when Attribute_Aft =>
4713          Fold_Uint (N, UI_From_Int (Aft_Value), True);
4714
4715       ---------------
4716       -- Alignment --
4717       ---------------
4718
4719       when Attribute_Alignment => Alignment_Block : declare
4720          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
4721
4722       begin
4723          --  Fold if alignment is set and not otherwise
4724
4725          if Known_Alignment (P_TypeA) then
4726             Fold_Uint (N, Alignment (P_TypeA), Is_Discrete_Type (P_TypeA));
4727          end if;
4728       end Alignment_Block;
4729
4730       ---------------
4731       -- AST_Entry --
4732       ---------------
4733
4734       --  Can only be folded in No_Ast_Handler case
4735
4736       when Attribute_AST_Entry =>
4737          if not Is_AST_Entry (P_Entity) then
4738             Rewrite (N,
4739               New_Occurrence_Of (RTE (RE_No_AST_Handler), Loc));
4740          else
4741             null;
4742          end if;
4743
4744       ---------
4745       -- Bit --
4746       ---------
4747
4748       --  Bit can never be folded
4749
4750       when Attribute_Bit =>
4751          null;
4752
4753       ------------------
4754       -- Body_Version --
4755       ------------------
4756
4757       --  Body_version can never be static
4758
4759       when Attribute_Body_Version =>
4760          null;
4761
4762       -------------
4763       -- Ceiling --
4764       -------------
4765
4766       when Attribute_Ceiling =>
4767          Fold_Ureal (N,
4768            Eval_Fat.Ceiling (P_Root_Type, Expr_Value_R (E1)), Static);
4769
4770       --------------------
4771       -- Component_Size --
4772       --------------------
4773
4774       when Attribute_Component_Size =>
4775          if Known_Static_Component_Size (P_Type) then
4776             Fold_Uint (N, Component_Size (P_Type), False);
4777          end if;
4778
4779       -------------
4780       -- Compose --
4781       -------------
4782
4783       when Attribute_Compose =>
4784          Fold_Ureal (N,
4785            Eval_Fat.Compose
4786              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)),
4787               Static);
4788
4789       -----------------
4790       -- Constrained --
4791       -----------------
4792
4793       --  Constrained is never folded for now, there may be cases that
4794       --  could be handled at compile time. to be looked at later.
4795
4796       when Attribute_Constrained =>
4797          null;
4798
4799       ---------------
4800       -- Copy_Sign --
4801       ---------------
4802
4803       when Attribute_Copy_Sign =>
4804          Fold_Ureal (N,
4805            Eval_Fat.Copy_Sign
4806              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
4807
4808       -----------
4809       -- Delta --
4810       -----------
4811
4812       when Attribute_Delta =>
4813          Fold_Ureal (N, Delta_Value (P_Type), True);
4814
4815       --------------
4816       -- Definite --
4817       --------------
4818
4819       when Attribute_Definite =>
4820          Rewrite (N, New_Occurrence_Of (
4821            Boolean_Literals (not Is_Indefinite_Subtype (P_Entity)), Loc));
4822          Analyze_And_Resolve (N, Standard_Boolean);
4823
4824       ------------
4825       -- Denorm --
4826       ------------
4827
4828       when Attribute_Denorm =>
4829          Fold_Uint
4830            (N, UI_From_Int (Boolean'Pos (Denorm_On_Target)), True);
4831
4832       ------------
4833       -- Digits --
4834       ------------
4835
4836       when Attribute_Digits =>
4837          Fold_Uint (N, Digits_Value (P_Type), True);
4838
4839       ----------
4840       -- Emax --
4841       ----------
4842
4843       when Attribute_Emax =>
4844
4845          --  Ada 83 attribute is defined as (RM83 3.5.8)
4846
4847          --    T'Emax = 4 * T'Mantissa
4848
4849          Fold_Uint (N, 4 * Mantissa, True);
4850
4851       --------------
4852       -- Enum_Rep --
4853       --------------
4854
4855       when Attribute_Enum_Rep =>
4856
4857          --  For an enumeration type with a non-standard representation
4858          --  use the Enumeration_Rep field of the proper constant. Note
4859          --  that this would not work for types Character/Wide_Character,
4860          --  since no real entities are created for the enumeration
4861          --  literals, but that does not matter since these two types
4862          --  do not have non-standard representations anyway.
4863
4864          if Is_Enumeration_Type (P_Type)
4865            and then Has_Non_Standard_Rep (P_Type)
4866          then
4867             Fold_Uint (N, Enumeration_Rep (Expr_Value_E (E1)), Static);
4868
4869          --  For enumeration types with standard representations and all
4870          --  other cases (i.e. all integer and modular types), Enum_Rep
4871          --  is equivalent to Pos.
4872
4873          else
4874             Fold_Uint (N, Expr_Value (E1), Static);
4875          end if;
4876
4877       -------------
4878       -- Epsilon --
4879       -------------
4880
4881       when Attribute_Epsilon =>
4882
4883          --  Ada 83 attribute is defined as (RM83 3.5.8)
4884
4885          --    T'Epsilon = 2.0**(1 - T'Mantissa)
4886
4887          Fold_Ureal (N, Ureal_2 ** (1 - Mantissa), True);
4888
4889       --------------
4890       -- Exponent --
4891       --------------
4892
4893       when Attribute_Exponent =>
4894          Fold_Uint (N,
4895            Eval_Fat.Exponent (P_Root_Type, Expr_Value_R (E1)), Static);
4896
4897       -----------
4898       -- First --
4899       -----------
4900
4901       when Attribute_First => First_Attr :
4902       begin
4903          Set_Bounds;
4904
4905          if Compile_Time_Known_Value (Lo_Bound) then
4906             if Is_Real_Type (P_Type) then
4907                Fold_Ureal (N, Expr_Value_R (Lo_Bound), Static);
4908             else
4909                Fold_Uint  (N, Expr_Value (Lo_Bound), Static);
4910             end if;
4911          end if;
4912       end First_Attr;
4913
4914       -----------------
4915       -- Fixed_Value --
4916       -----------------
4917
4918       when Attribute_Fixed_Value =>
4919          null;
4920
4921       -----------
4922       -- Floor --
4923       -----------
4924
4925       when Attribute_Floor =>
4926          Fold_Ureal (N,
4927            Eval_Fat.Floor (P_Root_Type, Expr_Value_R (E1)), Static);
4928
4929       ----------
4930       -- Fore --
4931       ----------
4932
4933       when Attribute_Fore =>
4934          if Compile_Time_Known_Bounds (P_Type) then
4935             Fold_Uint (N, UI_From_Int (Fore_Value), Static);
4936          end if;
4937
4938       --------------
4939       -- Fraction --
4940       --------------
4941
4942       when Attribute_Fraction =>
4943          Fold_Ureal (N,
4944            Eval_Fat.Fraction (P_Root_Type, Expr_Value_R (E1)), Static);
4945
4946       -----------------------
4947       -- Has_Discriminants --
4948       -----------------------
4949
4950       when Attribute_Has_Discriminants =>
4951          Rewrite (N, New_Occurrence_Of (
4952            Boolean_Literals (Has_Discriminants (P_Entity)), Loc));
4953          Analyze_And_Resolve (N, Standard_Boolean);
4954
4955       --------------
4956       -- Identity --
4957       --------------
4958
4959       when Attribute_Identity =>
4960          null;
4961
4962       -----------
4963       -- Image --
4964       -----------
4965
4966       --  Image is a scalar attribute, but is never static, because it is
4967       --  not a static function (having a non-scalar argument (RM 4.9(22))
4968
4969       when Attribute_Image =>
4970          null;
4971
4972       ---------
4973       -- Img --
4974       ---------
4975
4976       --  Img is a scalar attribute, but is never static, because it is
4977       --  not a static function (having a non-scalar argument (RM 4.9(22))
4978
4979       when Attribute_Img =>
4980          null;
4981
4982       -------------------
4983       -- Integer_Value --
4984       -------------------
4985
4986       when Attribute_Integer_Value =>
4987          null;
4988
4989       -----------
4990       -- Large --
4991       -----------
4992
4993       when Attribute_Large =>
4994
4995          --  For fixed-point, we use the identity:
4996
4997          --    T'Large = (2.0**T'Mantissa - 1.0) * T'Small
4998
4999          if Is_Fixed_Point_Type (P_Type) then
5000             Rewrite (N,
5001               Make_Op_Multiply (Loc,
5002                 Left_Opnd =>
5003                   Make_Op_Subtract (Loc,
5004                     Left_Opnd =>
5005                       Make_Op_Expon (Loc,
5006                         Left_Opnd =>
5007                           Make_Real_Literal (Loc, Ureal_2),
5008                         Right_Opnd =>
5009                           Make_Attribute_Reference (Loc,
5010                             Prefix => P,
5011                             Attribute_Name => Name_Mantissa)),
5012                     Right_Opnd => Make_Real_Literal (Loc, Ureal_1)),
5013
5014                 Right_Opnd =>
5015                   Make_Real_Literal (Loc, Small_Value (Entity (P)))));
5016
5017             Analyze_And_Resolve (N, C_Type);
5018
5019          --  Floating-point (Ada 83 compatibility)
5020
5021          else
5022             --  Ada 83 attribute is defined as (RM83 3.5.8)
5023
5024             --    T'Large = 2.0**T'Emax * (1.0 - 2.0**(-T'Mantissa))
5025
5026             --  where
5027
5028             --    T'Emax = 4 * T'Mantissa
5029
5030             Fold_Ureal (N,
5031               Ureal_2 ** (4 * Mantissa) * (Ureal_1 - Ureal_2 ** (-Mantissa)),
5032               True);
5033          end if;
5034
5035       ----------
5036       -- Last --
5037       ----------
5038
5039       when Attribute_Last => Last :
5040       begin
5041          Set_Bounds;
5042
5043          if Compile_Time_Known_Value (Hi_Bound) then
5044             if Is_Real_Type (P_Type) then
5045                Fold_Ureal (N, Expr_Value_R (Hi_Bound), Static);
5046             else
5047                Fold_Uint  (N, Expr_Value (Hi_Bound), Static);
5048             end if;
5049          end if;
5050       end Last;
5051
5052       ------------------
5053       -- Leading_Part --
5054       ------------------
5055
5056       when Attribute_Leading_Part =>
5057          Fold_Ureal (N,
5058            Eval_Fat.Leading_Part
5059              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5060
5061       ------------
5062       -- Length --
5063       ------------
5064
5065       when Attribute_Length => Length : declare
5066          Ind : Node_Id;
5067
5068       begin
5069          --  In the case of a generic index type, the bounds may
5070          --  appear static but the computation is not meaningful,
5071          --  and may generate a spurious warning.
5072
5073          Ind := First_Index (P_Type);
5074
5075          while Present (Ind) loop
5076             if Is_Generic_Type (Etype (Ind)) then
5077                return;
5078             end if;
5079
5080             Next_Index (Ind);
5081          end loop;
5082
5083          Set_Bounds;
5084
5085          if Compile_Time_Known_Value (Lo_Bound)
5086            and then Compile_Time_Known_Value (Hi_Bound)
5087          then
5088             Fold_Uint (N,
5089               UI_Max (0, 1 + (Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound))),
5090               True);
5091          end if;
5092       end Length;
5093
5094       -------------
5095       -- Machine --
5096       -------------
5097
5098       when Attribute_Machine =>
5099          Fold_Ureal (N,
5100            Eval_Fat.Machine
5101              (P_Root_Type, Expr_Value_R (E1), Eval_Fat.Round, N),
5102            Static);
5103
5104       ------------------
5105       -- Machine_Emax --
5106       ------------------
5107
5108       when Attribute_Machine_Emax =>
5109          Float_Attribute_Universal_Integer (
5110            IEEES_Machine_Emax,
5111            IEEEL_Machine_Emax,
5112            IEEEX_Machine_Emax,
5113            VAXFF_Machine_Emax,
5114            VAXDF_Machine_Emax,
5115            VAXGF_Machine_Emax,
5116            AAMPS_Machine_Emax,
5117            AAMPL_Machine_Emax);
5118
5119       ------------------
5120       -- Machine_Emin --
5121       ------------------
5122
5123       when Attribute_Machine_Emin =>
5124          Float_Attribute_Universal_Integer (
5125            IEEES_Machine_Emin,
5126            IEEEL_Machine_Emin,
5127            IEEEX_Machine_Emin,
5128            VAXFF_Machine_Emin,
5129            VAXDF_Machine_Emin,
5130            VAXGF_Machine_Emin,
5131            AAMPS_Machine_Emin,
5132            AAMPL_Machine_Emin);
5133
5134       ----------------------
5135       -- Machine_Mantissa --
5136       ----------------------
5137
5138       when Attribute_Machine_Mantissa =>
5139          Float_Attribute_Universal_Integer (
5140            IEEES_Machine_Mantissa,
5141            IEEEL_Machine_Mantissa,
5142            IEEEX_Machine_Mantissa,
5143            VAXFF_Machine_Mantissa,
5144            VAXDF_Machine_Mantissa,
5145            VAXGF_Machine_Mantissa,
5146            AAMPS_Machine_Mantissa,
5147            AAMPL_Machine_Mantissa);
5148
5149       -----------------------
5150       -- Machine_Overflows --
5151       -----------------------
5152
5153       when Attribute_Machine_Overflows =>
5154
5155          --  Always true for fixed-point
5156
5157          if Is_Fixed_Point_Type (P_Type) then
5158             Fold_Uint (N, True_Value, True);
5159
5160          --  Floating point case
5161
5162          else
5163             Fold_Uint (N,
5164               UI_From_Int (Boolean'Pos (Machine_Overflows_On_Target)),
5165               True);
5166          end if;
5167
5168       -------------------
5169       -- Machine_Radix --
5170       -------------------
5171
5172       when Attribute_Machine_Radix =>
5173          if Is_Fixed_Point_Type (P_Type) then
5174             if Is_Decimal_Fixed_Point_Type (P_Type)
5175               and then Machine_Radix_10 (P_Type)
5176             then
5177                Fold_Uint (N, Uint_10, True);
5178             else
5179                Fold_Uint (N, Uint_2, True);
5180             end if;
5181
5182          --  All floating-point type always have radix 2
5183
5184          else
5185             Fold_Uint (N, Uint_2, True);
5186          end if;
5187
5188       --------------------
5189       -- Machine_Rounds --
5190       --------------------
5191
5192       when Attribute_Machine_Rounds =>
5193
5194          --  Always False for fixed-point
5195
5196          if Is_Fixed_Point_Type (P_Type) then
5197             Fold_Uint (N, False_Value, True);
5198
5199          --  Else yield proper floating-point result
5200
5201          else
5202             Fold_Uint
5203               (N, UI_From_Int (Boolean'Pos (Machine_Rounds_On_Target)), True);
5204          end if;
5205
5206       ------------------
5207       -- Machine_Size --
5208       ------------------
5209
5210       --  Note: Machine_Size is identical to Object_Size
5211
5212       when Attribute_Machine_Size => Machine_Size : declare
5213          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5214
5215       begin
5216          if Known_Esize (P_TypeA) then
5217             Fold_Uint (N, Esize (P_TypeA), True);
5218          end if;
5219       end Machine_Size;
5220
5221       --------------
5222       -- Mantissa --
5223       --------------
5224
5225       when Attribute_Mantissa =>
5226
5227          --  Fixed-point mantissa
5228
5229          if Is_Fixed_Point_Type (P_Type) then
5230
5231             --  Compile time foldable case
5232
5233             if Compile_Time_Known_Value (Type_Low_Bound  (P_Type))
5234                  and then
5235                Compile_Time_Known_Value (Type_High_Bound (P_Type))
5236             then
5237                --  The calculation of the obsolete Ada 83 attribute Mantissa
5238                --  is annoying, because of AI00143, quoted here:
5239
5240                --  !question 84-01-10
5241
5242                --  Consider the model numbers for F:
5243
5244                --         type F is delta 1.0 range -7.0 .. 8.0;
5245
5246                --  The wording requires that F'MANTISSA be the SMALLEST
5247                --  integer number for which each  bound  of the specified
5248                --  range is either a model number or lies at most small
5249                --  distant from a model number. This means F'MANTISSA
5250                --  is required to be 3 since the range  -7.0 .. 7.0 fits
5251                --  in 3 signed bits, and 8 is "at most" 1.0 from a model
5252                --  number, namely, 7. Is this analysis correct? Note that
5253                --  this implies the upper bound of the range is not
5254                --  represented as a model number.
5255
5256                --  !response 84-03-17
5257
5258                --  The analysis is correct. The upper and lower bounds for
5259                --  a fixed  point type can lie outside the range of model
5260                --  numbers.
5261
5262                declare
5263                   Siz     : Uint;
5264                   LBound  : Ureal;
5265                   UBound  : Ureal;
5266                   Bound   : Ureal;
5267                   Max_Man : Uint;
5268
5269                begin
5270                   LBound  := Expr_Value_R (Type_Low_Bound  (P_Type));
5271                   UBound  := Expr_Value_R (Type_High_Bound (P_Type));
5272                   Bound   := UR_Max (UR_Abs (LBound), UR_Abs (UBound));
5273                   Max_Man := UR_Trunc (Bound / Small_Value (P_Type));
5274
5275                   --  If the Bound is exactly a model number, i.e. a multiple
5276                   --  of Small, then we back it off by one to get the integer
5277                   --  value that must be representable.
5278
5279                   if Small_Value (P_Type) * Max_Man = Bound then
5280                      Max_Man := Max_Man - 1;
5281                   end if;
5282
5283                   --  Now find corresponding size = Mantissa value
5284
5285                   Siz := Uint_0;
5286                   while 2 ** Siz < Max_Man loop
5287                      Siz := Siz + 1;
5288                   end loop;
5289
5290                   Fold_Uint (N, Siz, True);
5291                end;
5292
5293             else
5294                --  The case of dynamic bounds cannot be evaluated at compile
5295                --  time. Instead we use a runtime routine (see Exp_Attr).
5296
5297                null;
5298             end if;
5299
5300          --  Floating-point Mantissa
5301
5302          else
5303             Fold_Uint (N, Mantissa, True);
5304          end if;
5305
5306       ---------
5307       -- Max --
5308       ---------
5309
5310       when Attribute_Max => Max :
5311       begin
5312          if Is_Real_Type (P_Type) then
5313             Fold_Ureal
5314               (N, UR_Max (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5315          else
5316             Fold_Uint (N, UI_Max (Expr_Value (E1), Expr_Value (E2)), Static);
5317          end if;
5318       end Max;
5319
5320       ----------------------------------
5321       -- Max_Size_In_Storage_Elements --
5322       ----------------------------------
5323
5324       --  Max_Size_In_Storage_Elements is simply the Size rounded up to a
5325       --  Storage_Unit boundary. We can fold any cases for which the size
5326       --  is known by the front end.
5327
5328       when Attribute_Max_Size_In_Storage_Elements =>
5329          if Known_Esize (P_Type) then
5330             Fold_Uint (N,
5331               (Esize (P_Type) + System_Storage_Unit - 1) /
5332                                           System_Storage_Unit,
5333                Static);
5334          end if;
5335
5336       --------------------
5337       -- Mechanism_Code --
5338       --------------------
5339
5340       when Attribute_Mechanism_Code =>
5341          declare
5342             Val    : Int;
5343             Formal : Entity_Id;
5344             Mech   : Mechanism_Type;
5345
5346          begin
5347             if No (E1) then
5348                Mech := Mechanism (P_Entity);
5349
5350             else
5351                Val := UI_To_Int (Expr_Value (E1));
5352
5353                Formal := First_Formal (P_Entity);
5354                for J in 1 .. Val - 1 loop
5355                   Next_Formal (Formal);
5356                end loop;
5357                Mech := Mechanism (Formal);
5358             end if;
5359
5360             if Mech < 0 then
5361                Fold_Uint (N, UI_From_Int (Int (-Mech)), True);
5362             end if;
5363          end;
5364
5365       ---------
5366       -- Min --
5367       ---------
5368
5369       when Attribute_Min => Min :
5370       begin
5371          if Is_Real_Type (P_Type) then
5372             Fold_Ureal
5373               (N, UR_Min (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5374          else
5375             Fold_Uint (N, UI_Min (Expr_Value (E1), Expr_Value (E2)), Static);
5376          end if;
5377       end Min;
5378
5379       -----------
5380       -- Model --
5381       -----------
5382
5383       when Attribute_Model =>
5384          Fold_Ureal (N,
5385            Eval_Fat.Model (P_Root_Type, Expr_Value_R (E1)), Static);
5386
5387       ----------------
5388       -- Model_Emin --
5389       ----------------
5390
5391       when Attribute_Model_Emin =>
5392          Float_Attribute_Universal_Integer (
5393            IEEES_Model_Emin,
5394            IEEEL_Model_Emin,
5395            IEEEX_Model_Emin,
5396            VAXFF_Model_Emin,
5397            VAXDF_Model_Emin,
5398            VAXGF_Model_Emin,
5399            AAMPS_Model_Emin,
5400            AAMPL_Model_Emin);
5401
5402       -------------------
5403       -- Model_Epsilon --
5404       -------------------
5405
5406       when Attribute_Model_Epsilon =>
5407          Float_Attribute_Universal_Real (
5408            IEEES_Model_Epsilon'Universal_Literal_String,
5409            IEEEL_Model_Epsilon'Universal_Literal_String,
5410            IEEEX_Model_Epsilon'Universal_Literal_String,
5411            VAXFF_Model_Epsilon'Universal_Literal_String,
5412            VAXDF_Model_Epsilon'Universal_Literal_String,
5413            VAXGF_Model_Epsilon'Universal_Literal_String,
5414            AAMPS_Model_Epsilon'Universal_Literal_String,
5415            AAMPL_Model_Epsilon'Universal_Literal_String);
5416
5417       --------------------
5418       -- Model_Mantissa --
5419       --------------------
5420
5421       when Attribute_Model_Mantissa =>
5422          Float_Attribute_Universal_Integer (
5423            IEEES_Model_Mantissa,
5424            IEEEL_Model_Mantissa,
5425            IEEEX_Model_Mantissa,
5426            VAXFF_Model_Mantissa,
5427            VAXDF_Model_Mantissa,
5428            VAXGF_Model_Mantissa,
5429            AAMPS_Model_Mantissa,
5430            AAMPL_Model_Mantissa);
5431
5432       -----------------
5433       -- Model_Small --
5434       -----------------
5435
5436       when Attribute_Model_Small =>
5437          Float_Attribute_Universal_Real (
5438            IEEES_Model_Small'Universal_Literal_String,
5439            IEEEL_Model_Small'Universal_Literal_String,
5440            IEEEX_Model_Small'Universal_Literal_String,
5441            VAXFF_Model_Small'Universal_Literal_String,
5442            VAXDF_Model_Small'Universal_Literal_String,
5443            VAXGF_Model_Small'Universal_Literal_String,
5444            AAMPS_Model_Small'Universal_Literal_String,
5445            AAMPL_Model_Small'Universal_Literal_String);
5446
5447       -------------
5448       -- Modulus --
5449       -------------
5450
5451       when Attribute_Modulus =>
5452          Fold_Uint (N, Modulus (P_Type), True);
5453
5454       --------------------
5455       -- Null_Parameter --
5456       --------------------
5457
5458       --  Cannot fold, we know the value sort of, but the whole point is
5459       --  that there is no way to talk about this imaginary value except
5460       --  by using the attribute, so we leave it the way it is.
5461
5462       when Attribute_Null_Parameter =>
5463          null;
5464
5465       -----------------
5466       -- Object_Size --
5467       -----------------
5468
5469       --  The Object_Size attribute for a type returns the Esize of the
5470       --  type and can be folded if this value is known.
5471
5472       when Attribute_Object_Size => Object_Size : declare
5473          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5474
5475       begin
5476          if Known_Esize (P_TypeA) then
5477             Fold_Uint (N, Esize (P_TypeA), True);
5478          end if;
5479       end Object_Size;
5480
5481       -------------------------
5482       -- Passed_By_Reference --
5483       -------------------------
5484
5485       --  Scalar types are never passed by reference
5486
5487       when Attribute_Passed_By_Reference =>
5488          Fold_Uint (N, False_Value, True);
5489
5490       ---------
5491       -- Pos --
5492       ---------
5493
5494       when Attribute_Pos =>
5495          Fold_Uint (N, Expr_Value (E1), True);
5496
5497       ----------
5498       -- Pred --
5499       ----------
5500
5501       when Attribute_Pred => Pred :
5502       begin
5503          --  Floating-point case
5504
5505          if Is_Floating_Point_Type (P_Type) then
5506             Fold_Ureal (N,
5507               Eval_Fat.Pred (P_Root_Type, Expr_Value_R (E1)), Static);
5508
5509          --  Fixed-point case
5510
5511          elsif Is_Fixed_Point_Type (P_Type) then
5512             Fold_Ureal (N,
5513               Expr_Value_R (E1) - Small_Value (P_Type), True);
5514
5515          --  Modular integer case (wraps)
5516
5517          elsif Is_Modular_Integer_Type (P_Type) then
5518             Fold_Uint (N, (Expr_Value (E1) - 1) mod Modulus (P_Type), Static);
5519
5520          --  Other scalar cases
5521
5522          else
5523             pragma Assert (Is_Scalar_Type (P_Type));
5524
5525             if Is_Enumeration_Type (P_Type)
5526               and then Expr_Value (E1) =
5527                          Expr_Value (Type_Low_Bound (P_Base_Type))
5528             then
5529                Apply_Compile_Time_Constraint_Error
5530                  (N, "Pred of `&''First`",
5531                   CE_Overflow_Check_Failed,
5532                   Ent  => P_Base_Type,
5533                   Warn => not Static);
5534
5535                Check_Expressions;
5536                return;
5537             end if;
5538
5539             Fold_Uint (N, Expr_Value (E1) - 1, Static);
5540          end if;
5541       end Pred;
5542
5543       -----------
5544       -- Range --
5545       -----------
5546
5547       --  No processing required, because by this stage, Range has been
5548       --  replaced by First .. Last, so this branch can never be taken.
5549
5550       when Attribute_Range =>
5551          raise Program_Error;
5552
5553       ------------------
5554       -- Range_Length --
5555       ------------------
5556
5557       when Attribute_Range_Length =>
5558          Set_Bounds;
5559
5560          if Compile_Time_Known_Value (Hi_Bound)
5561            and then Compile_Time_Known_Value (Lo_Bound)
5562          then
5563             Fold_Uint (N,
5564               UI_Max
5565                 (0, Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound) + 1),
5566                  Static);
5567          end if;
5568
5569       ---------------
5570       -- Remainder --
5571       ---------------
5572
5573       when Attribute_Remainder =>
5574          Fold_Ureal (N,
5575            Eval_Fat.Remainder
5576              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)),
5577            Static);
5578
5579       -----------
5580       -- Round --
5581       -----------
5582
5583       when Attribute_Round => Round :
5584       declare
5585          Sr : Ureal;
5586          Si : Uint;
5587
5588       begin
5589          --  First we get the (exact result) in units of small
5590
5591          Sr := Expr_Value_R (E1) / Small_Value (C_Type);
5592
5593          --  Now round that exactly to an integer
5594
5595          Si := UR_To_Uint (Sr);
5596
5597          --  Finally the result is obtained by converting back to real
5598
5599          Fold_Ureal (N, Si * Small_Value (C_Type), Static);
5600       end Round;
5601
5602       --------------
5603       -- Rounding --
5604       --------------
5605
5606       when Attribute_Rounding =>
5607          Fold_Ureal (N,
5608            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
5609
5610       ---------------
5611       -- Safe_Emax --
5612       ---------------
5613
5614       when Attribute_Safe_Emax =>
5615          Float_Attribute_Universal_Integer (
5616            IEEES_Safe_Emax,
5617            IEEEL_Safe_Emax,
5618            IEEEX_Safe_Emax,
5619            VAXFF_Safe_Emax,
5620            VAXDF_Safe_Emax,
5621            VAXGF_Safe_Emax,
5622            AAMPS_Safe_Emax,
5623            AAMPL_Safe_Emax);
5624
5625       ----------------
5626       -- Safe_First --
5627       ----------------
5628
5629       when Attribute_Safe_First =>
5630          Float_Attribute_Universal_Real (
5631            IEEES_Safe_First'Universal_Literal_String,
5632            IEEEL_Safe_First'Universal_Literal_String,
5633            IEEEX_Safe_First'Universal_Literal_String,
5634            VAXFF_Safe_First'Universal_Literal_String,
5635            VAXDF_Safe_First'Universal_Literal_String,
5636            VAXGF_Safe_First'Universal_Literal_String,
5637            AAMPS_Safe_First'Universal_Literal_String,
5638            AAMPL_Safe_First'Universal_Literal_String);
5639
5640       ----------------
5641       -- Safe_Large --
5642       ----------------
5643
5644       when Attribute_Safe_Large =>
5645          if Is_Fixed_Point_Type (P_Type) then
5646             Fold_Ureal
5647               (N, Expr_Value_R (Type_High_Bound (P_Base_Type)), Static);
5648          else
5649             Float_Attribute_Universal_Real (
5650               IEEES_Safe_Large'Universal_Literal_String,
5651               IEEEL_Safe_Large'Universal_Literal_String,
5652               IEEEX_Safe_Large'Universal_Literal_String,
5653               VAXFF_Safe_Large'Universal_Literal_String,
5654               VAXDF_Safe_Large'Universal_Literal_String,
5655               VAXGF_Safe_Large'Universal_Literal_String,
5656               AAMPS_Safe_Large'Universal_Literal_String,
5657               AAMPL_Safe_Large'Universal_Literal_String);
5658          end if;
5659
5660       ---------------
5661       -- Safe_Last --
5662       ---------------
5663
5664       when Attribute_Safe_Last =>
5665          Float_Attribute_Universal_Real (
5666            IEEES_Safe_Last'Universal_Literal_String,
5667            IEEEL_Safe_Last'Universal_Literal_String,
5668            IEEEX_Safe_Last'Universal_Literal_String,
5669            VAXFF_Safe_Last'Universal_Literal_String,
5670            VAXDF_Safe_Last'Universal_Literal_String,
5671            VAXGF_Safe_Last'Universal_Literal_String,
5672            AAMPS_Safe_Last'Universal_Literal_String,
5673            AAMPL_Safe_Last'Universal_Literal_String);
5674
5675       ----------------
5676       -- Safe_Small --
5677       ----------------
5678
5679       when Attribute_Safe_Small =>
5680
5681          --  In Ada 95, the old Ada 83 attribute Safe_Small is redundant
5682          --  for fixed-point, since is the same as Small, but we implement
5683          --  it for backwards compatibility.
5684
5685          if Is_Fixed_Point_Type (P_Type) then
5686             Fold_Ureal (N, Small_Value (P_Type), Static);
5687
5688          --  Ada 83 Safe_Small for floating-point cases
5689
5690          else
5691             Float_Attribute_Universal_Real (
5692               IEEES_Safe_Small'Universal_Literal_String,
5693               IEEEL_Safe_Small'Universal_Literal_String,
5694               IEEEX_Safe_Small'Universal_Literal_String,
5695               VAXFF_Safe_Small'Universal_Literal_String,
5696               VAXDF_Safe_Small'Universal_Literal_String,
5697               VAXGF_Safe_Small'Universal_Literal_String,
5698               AAMPS_Safe_Small'Universal_Literal_String,
5699               AAMPL_Safe_Small'Universal_Literal_String);
5700          end if;
5701
5702       -----------
5703       -- Scale --
5704       -----------
5705
5706       when Attribute_Scale =>
5707          Fold_Uint (N, Scale_Value (P_Type), True);
5708
5709       -------------
5710       -- Scaling --
5711       -------------
5712
5713       when Attribute_Scaling =>
5714          Fold_Ureal (N,
5715            Eval_Fat.Scaling
5716              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5717
5718       ------------------
5719       -- Signed_Zeros --
5720       ------------------
5721
5722       when Attribute_Signed_Zeros =>
5723          Fold_Uint
5724            (N, UI_From_Int (Boolean'Pos (Signed_Zeros_On_Target)), Static);
5725
5726       ----------
5727       -- Size --
5728       ----------
5729
5730       --  Size attribute returns the RM size. All scalar types can be folded,
5731       --  as well as any types for which the size is known by the front end,
5732       --  including any type for which a size attribute is specified.
5733
5734       when Attribute_Size | Attribute_VADS_Size => Size : declare
5735          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5736
5737       begin
5738          if RM_Size (P_TypeA) /= Uint_0 then
5739
5740             --  VADS_Size case
5741
5742             if Id = Attribute_VADS_Size or else Use_VADS_Size then
5743                declare
5744                   S : constant Node_Id := Size_Clause (P_TypeA);
5745
5746                begin
5747                   --  If a size clause applies, then use the size from it.
5748                   --  This is one of the rare cases where we can use the
5749                   --  Size_Clause field for a subtype when Has_Size_Clause
5750                   --  is False. Consider:
5751
5752                   --    type x is range 1 .. 64;                         g
5753                   --    for x'size use 12;
5754                   --    subtype y is x range 0 .. 3;
5755
5756                   --  Here y has a size clause inherited from x, but normally
5757                   --  it does not apply, and y'size is 2. However, y'VADS_Size
5758                   --  is indeed 12 and not 2.
5759
5760                   if Present (S)
5761                     and then Is_OK_Static_Expression (Expression (S))
5762                   then
5763                      Fold_Uint (N, Expr_Value (Expression (S)), True);
5764
5765                   --  If no size is specified, then we simply use the object
5766                   --  size in the VADS_Size case (e.g. Natural'Size is equal
5767                   --  to Integer'Size, not one less).
5768
5769                   else
5770                      Fold_Uint (N, Esize (P_TypeA), True);
5771                   end if;
5772                end;
5773
5774             --  Normal case (Size) in which case we want the RM_Size
5775
5776             else
5777                Fold_Uint (N,
5778                  RM_Size (P_TypeA),
5779                  Static and then Is_Discrete_Type (P_TypeA));
5780             end if;
5781          end if;
5782       end Size;
5783
5784       -----------
5785       -- Small --
5786       -----------
5787
5788       when Attribute_Small =>
5789
5790          --  The floating-point case is present only for Ada 83 compatability.
5791          --  Note that strictly this is an illegal addition, since we are
5792          --  extending an Ada 95 defined attribute, but we anticipate an
5793          --  ARG ruling that will permit this.
5794
5795          if Is_Floating_Point_Type (P_Type) then
5796
5797             --  Ada 83 attribute is defined as (RM83 3.5.8)
5798
5799             --    T'Small = 2.0**(-T'Emax - 1)
5800
5801             --  where
5802
5803             --    T'Emax = 4 * T'Mantissa
5804
5805             Fold_Ureal (N, Ureal_2 ** ((-(4 * Mantissa)) - 1), Static);
5806
5807          --  Normal Ada 95 fixed-point case
5808
5809          else
5810             Fold_Ureal (N, Small_Value (P_Type), True);
5811          end if;
5812
5813       ----------
5814       -- Succ --
5815       ----------
5816
5817       when Attribute_Succ => Succ :
5818       begin
5819          --  Floating-point case
5820
5821          if Is_Floating_Point_Type (P_Type) then
5822             Fold_Ureal (N,
5823               Eval_Fat.Succ (P_Root_Type, Expr_Value_R (E1)), Static);
5824
5825          --  Fixed-point case
5826
5827          elsif Is_Fixed_Point_Type (P_Type) then
5828             Fold_Ureal (N,
5829               Expr_Value_R (E1) + Small_Value (P_Type), Static);
5830
5831          --  Modular integer case (wraps)
5832
5833          elsif Is_Modular_Integer_Type (P_Type) then
5834             Fold_Uint (N, (Expr_Value (E1) + 1) mod Modulus (P_Type), Static);
5835
5836          --  Other scalar cases
5837
5838          else
5839             pragma Assert (Is_Scalar_Type (P_Type));
5840
5841             if Is_Enumeration_Type (P_Type)
5842               and then Expr_Value (E1) =
5843                          Expr_Value (Type_High_Bound (P_Base_Type))
5844             then
5845                Apply_Compile_Time_Constraint_Error
5846                  (N, "Succ of `&''Last`",
5847                   CE_Overflow_Check_Failed,
5848                   Ent  => P_Base_Type,
5849                   Warn => not Static);
5850
5851                Check_Expressions;
5852                return;
5853             else
5854                Fold_Uint (N, Expr_Value (E1) + 1, Static);
5855             end if;
5856          end if;
5857       end Succ;
5858
5859       ----------------
5860       -- Truncation --
5861       ----------------
5862
5863       when Attribute_Truncation =>
5864          Fold_Ureal (N,
5865            Eval_Fat.Truncation (P_Root_Type, Expr_Value_R (E1)), Static);
5866
5867       ----------------
5868       -- Type_Class --
5869       ----------------
5870
5871       when Attribute_Type_Class => Type_Class : declare
5872          Typ : constant Entity_Id := Underlying_Type (P_Base_Type);
5873          Id  : RE_Id;
5874
5875       begin
5876          if Is_Descendent_Of_Address (Typ) then
5877             Id := RE_Type_Class_Address;
5878
5879          elsif Is_Enumeration_Type (Typ) then
5880             Id := RE_Type_Class_Enumeration;
5881
5882          elsif Is_Integer_Type (Typ) then
5883             Id := RE_Type_Class_Integer;
5884
5885          elsif Is_Fixed_Point_Type (Typ) then
5886             Id := RE_Type_Class_Fixed_Point;
5887
5888          elsif Is_Floating_Point_Type (Typ) then
5889             Id := RE_Type_Class_Floating_Point;
5890
5891          elsif Is_Array_Type (Typ) then
5892             Id := RE_Type_Class_Array;
5893
5894          elsif Is_Record_Type (Typ) then
5895             Id := RE_Type_Class_Record;
5896
5897          elsif Is_Access_Type (Typ) then
5898             Id := RE_Type_Class_Access;
5899
5900          elsif Is_Enumeration_Type (Typ) then
5901             Id := RE_Type_Class_Enumeration;
5902
5903          elsif Is_Task_Type (Typ) then
5904             Id := RE_Type_Class_Task;
5905
5906          --  We treat protected types like task types. It would make more
5907          --  sense to have another enumeration value, but after all the
5908          --  whole point of this feature is to be exactly DEC compatible,
5909          --  and changing the type Type_Clas would not meet this requirement.
5910
5911          elsif Is_Protected_Type (Typ) then
5912             Id := RE_Type_Class_Task;
5913
5914          --  Not clear if there are any other possibilities, but if there
5915          --  are, then we will treat them as the address case.
5916
5917          else
5918             Id := RE_Type_Class_Address;
5919          end if;
5920
5921          Rewrite (N, New_Occurrence_Of (RTE (Id), Loc));
5922
5923       end Type_Class;
5924
5925       -----------------------
5926       -- Unbiased_Rounding --
5927       -----------------------
5928
5929       when Attribute_Unbiased_Rounding =>
5930          Fold_Ureal (N,
5931            Eval_Fat.Unbiased_Rounding (P_Root_Type, Expr_Value_R (E1)),
5932            Static);
5933
5934       -------------------------
5935       -- Unconstrained_Array --
5936       -------------------------
5937
5938       when Attribute_Unconstrained_Array => Unconstrained_Array : declare
5939          Typ : constant Entity_Id := Underlying_Type (P_Type);
5940
5941       begin
5942          Rewrite (N, New_Occurrence_Of (
5943            Boolean_Literals (
5944              Is_Array_Type (P_Type)
5945               and then not Is_Constrained (Typ)), Loc));
5946
5947          --  Analyze and resolve as boolean, note that this attribute is
5948          --  a static attribute in GNAT.
5949
5950          Analyze_And_Resolve (N, Standard_Boolean);
5951          Static := True;
5952       end Unconstrained_Array;
5953
5954       ---------------
5955       -- VADS_Size --
5956       ---------------
5957
5958       --  Processing is shared with Size
5959
5960       ---------
5961       -- Val --
5962       ---------
5963
5964       when Attribute_Val => Val :
5965       begin
5966          if  Expr_Value (E1) < Expr_Value (Type_Low_Bound (P_Base_Type))
5967            or else
5968              Expr_Value (E1) > Expr_Value (Type_High_Bound (P_Base_Type))
5969          then
5970             Apply_Compile_Time_Constraint_Error
5971               (N, "Val expression out of range",
5972                CE_Range_Check_Failed,
5973                Warn => not Static);
5974
5975             Check_Expressions;
5976             return;
5977
5978          else
5979             Fold_Uint (N, Expr_Value (E1), Static);
5980          end if;
5981       end Val;
5982
5983       ----------------
5984       -- Value_Size --
5985       ----------------
5986
5987       --  The Value_Size attribute for a type returns the RM size of the
5988       --  type. This an always be folded for scalar types, and can also
5989       --  be folded for non-scalar types if the size is set.
5990
5991       when Attribute_Value_Size => Value_Size : declare
5992          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5993
5994       begin
5995          if RM_Size (P_TypeA) /= Uint_0 then
5996             Fold_Uint (N, RM_Size (P_TypeA), True);
5997          end if;
5998
5999       end Value_Size;
6000
6001       -------------
6002       -- Version --
6003       -------------
6004
6005       --  Version can never be static
6006
6007       when Attribute_Version =>
6008          null;
6009
6010       ----------------
6011       -- Wide_Image --
6012       ----------------
6013
6014       --  Wide_Image is a scalar attribute, but is never static, because it
6015       --  is not a static function (having a non-scalar argument (RM 4.9(22))
6016
6017       when Attribute_Wide_Image =>
6018          null;
6019
6020       ----------------
6021       -- Wide_Width --
6022       ----------------
6023
6024       --  Processing for Wide_Width is combined with Width
6025
6026       -----------
6027       -- Width --
6028       -----------
6029
6030       --  This processing also handles the case of Wide_Width
6031
6032       when Attribute_Width | Attribute_Wide_Width => Width :
6033       begin
6034          if Compile_Time_Known_Bounds (P_Type) then
6035
6036             --  Floating-point types
6037
6038             if Is_Floating_Point_Type (P_Type) then
6039
6040                --  Width is zero for a null range (RM 3.5 (38))
6041
6042                if Expr_Value_R (Type_High_Bound (P_Type)) <
6043                   Expr_Value_R (Type_Low_Bound (P_Type))
6044                then
6045                   Fold_Uint (N, Uint_0, True);
6046
6047                else
6048                   --  For floating-point, we have +N.dddE+nnn where length
6049                   --  of ddd is determined by type'Digits - 1, but is one
6050                   --  if Digits is one (RM 3.5 (33)).
6051
6052                   --  nnn is set to 2 for Short_Float and Float (32 bit
6053                   --  floats), and 3 for Long_Float and Long_Long_Float.
6054                   --  This is not quite right, but is good enough.
6055
6056                   declare
6057                      Len : Int :=
6058                              Int'Max (2, UI_To_Int (Digits_Value (P_Type)));
6059
6060                   begin
6061                      if Esize (P_Type) <= 32 then
6062                         Len := Len + 6;
6063                      else
6064                         Len := Len + 7;
6065                      end if;
6066
6067                      Fold_Uint (N, UI_From_Int (Len), True);
6068                   end;
6069                end if;
6070
6071             --  Fixed-point types
6072
6073             elsif Is_Fixed_Point_Type (P_Type) then
6074
6075                --  Width is zero for a null range (RM 3.5 (38))
6076
6077                if Expr_Value (Type_High_Bound (P_Type)) <
6078                   Expr_Value (Type_Low_Bound  (P_Type))
6079                then
6080                   Fold_Uint (N, Uint_0, True);
6081
6082                --  The non-null case depends on the specific real type
6083
6084                else
6085                   --  For fixed-point type width is Fore + 1 + Aft (RM 3.5(34))
6086
6087                   Fold_Uint
6088                     (N, UI_From_Int (Fore_Value + 1 + Aft_Value), True);
6089                end if;
6090
6091             --  Discrete types
6092
6093             else
6094                declare
6095                   R  : constant Entity_Id := Root_Type (P_Type);
6096                   Lo : constant Uint :=
6097                          Expr_Value (Type_Low_Bound (P_Type));
6098                   Hi : constant Uint :=
6099                          Expr_Value (Type_High_Bound (P_Type));
6100                   W  : Nat;
6101                   Wt : Nat;
6102                   T  : Uint;
6103                   L  : Node_Id;
6104                   C  : Character;
6105
6106                begin
6107                   --  Empty ranges
6108
6109                   if Lo > Hi then
6110                      W := 0;
6111
6112                   --  Width for types derived from Standard.Character
6113                   --  and Standard.Wide_Character.
6114
6115                   elsif R = Standard_Character
6116                     or else R = Standard_Wide_Character
6117                   then
6118                      W := 0;
6119
6120                      --  Set W larger if needed
6121
6122                      for J in UI_To_Int (Lo) .. UI_To_Int (Hi) loop
6123
6124                         --  Assume all wide-character escape sequences are
6125                         --  same length, so we can quit when we reach one.
6126
6127                         if J > 255 then
6128                            if Id = Attribute_Wide_Width then
6129                               W := Int'Max (W, 3);
6130                               exit;
6131                            else
6132                               W := Int'Max (W, Length_Wide);
6133                               exit;
6134                            end if;
6135
6136                         else
6137                            C := Character'Val (J);
6138
6139                            --  Test for all cases where Character'Image
6140                            --  yields an image that is longer than three
6141                            --  characters. First the cases of Reserved_xxx
6142                            --  names (length = 12).
6143
6144                            case C is
6145                               when Reserved_128 | Reserved_129 |
6146                                    Reserved_132 | Reserved_153
6147
6148                                 => Wt := 12;
6149
6150                               when BS | HT | LF | VT | FF | CR |
6151                                    SO | SI | EM | FS | GS | RS |
6152                                    US | RI | MW | ST | PM
6153
6154                                 => Wt := 2;
6155
6156                               when NUL | SOH | STX | ETX | EOT |
6157                                    ENQ | ACK | BEL | DLE | DC1 |
6158                                    DC2 | DC3 | DC4 | NAK | SYN |
6159                                    ETB | CAN | SUB | ESC | DEL |
6160                                    BPH | NBH | NEL | SSA | ESA |
6161                                    HTS | HTJ | VTS | PLD | PLU |
6162                                    SS2 | SS3 | DCS | PU1 | PU2 |
6163                                    STS | CCH | SPA | EPA | SOS |
6164                                    SCI | CSI | OSC | APC
6165
6166                                 => Wt := 3;
6167
6168                               when Space .. Tilde |
6169                                    No_Break_Space .. LC_Y_Diaeresis
6170
6171                                 => Wt := 3;
6172                            end case;
6173
6174                            W := Int'Max (W, Wt);
6175                         end if;
6176                      end loop;
6177
6178                   --  Width for types derived from Standard.Boolean
6179
6180                   elsif R = Standard_Boolean then
6181                      if Lo = 0 then
6182                         W := 5; -- FALSE
6183                      else
6184                         W := 4; -- TRUE
6185                      end if;
6186
6187                   --  Width for integer types
6188
6189                   elsif Is_Integer_Type (P_Type) then
6190                      T := UI_Max (abs Lo, abs Hi);
6191
6192                      W := 2;
6193                      while T >= 10 loop
6194                         W := W + 1;
6195                         T := T / 10;
6196                      end loop;
6197
6198                   --  Only remaining possibility is user declared enum type
6199
6200                   else
6201                      pragma Assert (Is_Enumeration_Type (P_Type));
6202
6203                      W := 0;
6204                      L := First_Literal (P_Type);
6205
6206                      while Present (L) loop
6207
6208                         --  Only pay attention to in range characters
6209
6210                         if Lo <= Enumeration_Pos (L)
6211                           and then Enumeration_Pos (L) <= Hi
6212                         then
6213                            --  For Width case, use decoded name
6214
6215                            if Id = Attribute_Width then
6216                               Get_Decoded_Name_String (Chars (L));
6217                               Wt := Nat (Name_Len);
6218
6219                            --  For Wide_Width, use encoded name, and then
6220                            --  adjust for the encoding.
6221
6222                            else
6223                               Get_Name_String (Chars (L));
6224
6225                               --  Character literals are always of length 3
6226
6227                               if Name_Buffer (1) = 'Q' then
6228                                  Wt := 3;
6229
6230                               --  Otherwise loop to adjust for upper/wide chars
6231
6232                               else
6233                                  Wt := Nat (Name_Len);
6234
6235                                  for J in 1 .. Name_Len loop
6236                                     if Name_Buffer (J) = 'U' then
6237                                        Wt := Wt - 2;
6238                                     elsif Name_Buffer (J) = 'W' then
6239                                        Wt := Wt - 4;
6240                                     end if;
6241                                  end loop;
6242                               end if;
6243                            end if;
6244
6245                            W := Int'Max (W, Wt);
6246                         end if;
6247
6248                         Next_Literal (L);
6249                      end loop;
6250                   end if;
6251
6252                   Fold_Uint (N, UI_From_Int (W), True);
6253                end;
6254             end if;
6255          end if;
6256       end Width;
6257
6258       --  The following attributes can never be folded, and furthermore we
6259       --  should not even have entered the case statement for any of these.
6260       --  Note that in some cases, the values have already been folded as
6261       --  a result of the processing in Analyze_Attribute.
6262
6263       when Attribute_Abort_Signal             |
6264            Attribute_Access                   |
6265            Attribute_Address                  |
6266            Attribute_Address_Size             |
6267            Attribute_Asm_Input                |
6268            Attribute_Asm_Output               |
6269            Attribute_Base                     |
6270            Attribute_Bit_Order                |
6271            Attribute_Bit_Position             |
6272            Attribute_Callable                 |
6273            Attribute_Caller                   |
6274            Attribute_Class                    |
6275            Attribute_Code_Address             |
6276            Attribute_Count                    |
6277            Attribute_Default_Bit_Order        |
6278            Attribute_Elaborated               |
6279            Attribute_Elab_Body                |
6280            Attribute_Elab_Spec                |
6281            Attribute_External_Tag             |
6282            Attribute_First_Bit                |
6283            Attribute_Input                    |
6284            Attribute_Last_Bit                 |
6285            Attribute_Maximum_Alignment        |
6286            Attribute_Output                   |
6287            Attribute_Partition_ID             |
6288            Attribute_Pool_Address             |
6289            Attribute_Position                 |
6290            Attribute_Read                     |
6291            Attribute_Storage_Pool             |
6292            Attribute_Storage_Size             |
6293            Attribute_Storage_Unit             |
6294            Attribute_Tag                      |
6295            Attribute_Target_Name              |
6296            Attribute_Terminated               |
6297            Attribute_To_Address               |
6298            Attribute_UET_Address              |
6299            Attribute_Unchecked_Access         |
6300            Attribute_Universal_Literal_String |
6301            Attribute_Unrestricted_Access      |
6302            Attribute_Valid                    |
6303            Attribute_Value                    |
6304            Attribute_Wchar_T_Size             |
6305            Attribute_Wide_Value               |
6306            Attribute_Word_Size                |
6307            Attribute_Write                    =>
6308
6309          raise Program_Error;
6310
6311       end case;
6312
6313       --  At the end of the case, one more check. If we did a static evaluation
6314       --  so that the result is now a literal, then set Is_Static_Expression
6315       --  in the constant only if the prefix type is a static subtype. For
6316       --  non-static subtypes, the folding is still OK, but not static.
6317
6318       --  An exception is the GNAT attribute Constrained_Array which is
6319       --  defined to be a static attribute in all cases.
6320
6321       if Nkind (N) = N_Integer_Literal
6322         or else Nkind (N) = N_Real_Literal
6323         or else Nkind (N) = N_Character_Literal
6324         or else Nkind (N) = N_String_Literal
6325         or else (Is_Entity_Name (N)
6326                   and then Ekind (Entity (N)) = E_Enumeration_Literal)
6327       then
6328          Set_Is_Static_Expression (N, Static);
6329
6330       --  If this is still an attribute reference, then it has not been folded
6331       --  and that means that its expressions are in a non-static context.
6332
6333       elsif Nkind (N) = N_Attribute_Reference then
6334          Check_Expressions;
6335
6336       --  Note: the else case not covered here are odd cases where the
6337       --  processing has transformed the attribute into something other
6338       --  than a constant. Nothing more to do in such cases.
6339
6340       else
6341          null;
6342       end if;
6343
6344    end Eval_Attribute;
6345
6346    ------------------------------
6347    -- Is_Anonymous_Tagged_Base --
6348    ------------------------------
6349
6350    function Is_Anonymous_Tagged_Base
6351      (Anon : Entity_Id;
6352       Typ  : Entity_Id)
6353       return Boolean
6354    is
6355    begin
6356       return
6357         Anon = Current_Scope
6358           and then Is_Itype (Anon)
6359           and then Associated_Node_For_Itype (Anon) = Parent (Typ);
6360    end Is_Anonymous_Tagged_Base;
6361
6362    -----------------------
6363    -- Resolve_Attribute --
6364    -----------------------
6365
6366    procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id) is
6367       Loc      : constant Source_Ptr   := Sloc (N);
6368       P        : constant Node_Id      := Prefix (N);
6369       Aname    : constant Name_Id      := Attribute_Name (N);
6370       Attr_Id  : constant Attribute_Id := Get_Attribute_Id (Aname);
6371       Btyp     : constant Entity_Id    := Base_Type (Typ);
6372       Index    : Interp_Index;
6373       It       : Interp;
6374       Nom_Subt : Entity_Id;
6375
6376    begin
6377       --  If error during analysis, no point in continuing, except for
6378       --  array types, where we get  better recovery by using unconstrained
6379       --  indices than nothing at all (see Check_Array_Type).
6380
6381       if Error_Posted (N)
6382         and then Attr_Id /= Attribute_First
6383         and then Attr_Id /= Attribute_Last
6384         and then Attr_Id /= Attribute_Length
6385         and then Attr_Id /= Attribute_Range
6386       then
6387          return;
6388       end if;
6389
6390       --  If attribute was universal type, reset to actual type
6391
6392       if Etype (N) = Universal_Integer
6393         or else Etype (N) = Universal_Real
6394       then
6395          Set_Etype (N, Typ);
6396       end if;
6397
6398       --  Remaining processing depends on attribute
6399
6400       case Attr_Id is
6401
6402          ------------
6403          -- Access --
6404          ------------
6405
6406          --  For access attributes, if the prefix denotes an entity, it is
6407          --  interpreted as a name, never as a call. It may be overloaded,
6408          --  in which case resolution uses the profile of the context type.
6409          --  Otherwise prefix must be resolved.
6410
6411          when Attribute_Access
6412             | Attribute_Unchecked_Access
6413             | Attribute_Unrestricted_Access =>
6414
6415             if Is_Variable (P) then
6416                Note_Possible_Modification (P);
6417             end if;
6418
6419             if Is_Entity_Name (P) then
6420                if Is_Overloaded (P) then
6421                   Get_First_Interp (P, Index, It);
6422
6423                   while Present (It.Nam) loop
6424
6425                      if Type_Conformant (Designated_Type (Typ), It.Nam) then
6426                         Set_Entity (P, It.Nam);
6427
6428                         --  The prefix is definitely NOT overloaded anymore
6429                         --  at this point, so we reset the Is_Overloaded
6430                         --  flag to avoid any confusion when reanalyzing
6431                         --  the node.
6432
6433                         Set_Is_Overloaded (P, False);
6434                         Generate_Reference (Entity (P), P);
6435                         exit;
6436                      end if;
6437
6438                      Get_Next_Interp (Index, It);
6439                   end loop;
6440
6441                --  If it is a subprogram name or a type, there is nothing
6442                --  to resolve.
6443
6444                elsif not Is_Overloadable (Entity (P))
6445                  and then not Is_Type (Entity (P))
6446                then
6447                   Resolve (P);
6448                end if;
6449
6450                Error_Msg_Name_1 := Aname;
6451
6452                if not Is_Entity_Name (P) then
6453                   null;
6454
6455                elsif Is_Abstract (Entity (P))
6456                  and then Is_Overloadable (Entity (P))
6457                then
6458                   Error_Msg_N ("prefix of % attribute cannot be abstract", P);
6459                   Set_Etype (N, Any_Type);
6460
6461                elsif Convention (Entity (P)) = Convention_Intrinsic then
6462                   if Ekind (Entity (P)) = E_Enumeration_Literal then
6463                      Error_Msg_N
6464                        ("prefix of % attribute cannot be enumeration literal",
6465                           P);
6466                   else
6467                      Error_Msg_N
6468                        ("prefix of % attribute cannot be intrinsic", P);
6469                   end if;
6470
6471                   Set_Etype (N, Any_Type);
6472
6473                elsif Is_Thread_Body (Entity (P)) then
6474                   Error_Msg_N
6475                     ("prefix of % attribute cannot be a thread body", P);
6476                end if;
6477
6478                --  Assignments, return statements, components of aggregates,
6479                --  generic instantiations will require convention checks if
6480                --  the type is an access to subprogram. Given that there will
6481                --  also be accessibility checks on those, this is where the
6482                --  checks can eventually be centralized ???
6483
6484                if Ekind (Btyp) = E_Access_Subprogram_Type
6485                     or else
6486                   Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
6487                     or else
6488                   Ekind (Btyp) = E_Anonymous_Access_Protected_Subprogram_Type
6489                then
6490                   if Convention (Btyp) /= Convention (Entity (P)) then
6491                      Error_Msg_N
6492                       ("subprogram has invalid convention for context", P);
6493
6494                   else
6495                      Check_Subtype_Conformant
6496                        (New_Id  => Entity (P),
6497                         Old_Id  => Designated_Type (Btyp),
6498                         Err_Loc => P);
6499                   end if;
6500
6501                   if Attr_Id = Attribute_Unchecked_Access then
6502                      Error_Msg_Name_1 := Aname;
6503                      Error_Msg_N
6504                        ("attribute% cannot be applied to a subprogram", P);
6505
6506                   elsif Aname = Name_Unrestricted_Access then
6507                      null;  --  Nothing to check
6508
6509                   --  Check the static accessibility rule of 3.10.2(32)
6510                   --  In an instance body, if subprogram and type are both
6511                   --  local, other rules prevent dangling references, and no
6512                   --  warning  is needed.
6513
6514                   elsif Attr_Id = Attribute_Access
6515                     and then Subprogram_Access_Level (Entity (P)) >
6516                                Type_Access_Level (Btyp)
6517                     and then Ekind (Btyp) /=
6518                                E_Anonymous_Access_Subprogram_Type
6519                     and then Ekind (Btyp) /=
6520                                E_Anonymous_Access_Protected_Subprogram_Type
6521                   then
6522                      if not In_Instance_Body then
6523                         Error_Msg_N
6524                           ("subprogram must not be deeper than access type",
6525                             P);
6526
6527                      elsif Scope (Entity (P)) /= Scope (Btyp) then
6528                         Error_Msg_N
6529                           ("subprogram must not be deeper than access type?",
6530                              P);
6531                         Error_Msg_N
6532                           ("Constraint_Error will be raised ?", P);
6533                         Set_Raises_Constraint_Error (N);
6534                      end if;
6535
6536                   --  Check the restriction of 3.10.2(32) that disallows
6537                   --  the type of the access attribute to be declared
6538                   --  outside a generic body when the subprogram is declared
6539                   --  within that generic body.
6540
6541                   elsif Enclosing_Generic_Body (Entity (P))
6542                     /= Enclosing_Generic_Body (Btyp)
6543                   then
6544                      Error_Msg_N
6545                        ("access type must not be outside generic body", P);
6546                   end if;
6547                end if;
6548
6549                --  if this is a renaming, an inherited operation, or a
6550                --  subprogram instance, use the original entity.
6551
6552                if Is_Entity_Name (P)
6553                  and then Is_Overloadable (Entity (P))
6554                  and then Present (Alias (Entity (P)))
6555                then
6556                   Rewrite (P,
6557                     New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6558                end if;
6559
6560             elsif Nkind (P) = N_Selected_Component
6561               and then Is_Overloadable (Entity (Selector_Name (P)))
6562             then
6563                --  Protected operation. If operation is overloaded, must
6564                --  disambiguate. Prefix that denotes protected object itself
6565                --  is resolved with its own type.
6566
6567                if Attr_Id = Attribute_Unchecked_Access then
6568                   Error_Msg_Name_1 := Aname;
6569                   Error_Msg_N
6570                     ("attribute% cannot be applied to protected operation", P);
6571                end if;
6572
6573                Resolve (Prefix (P));
6574                Generate_Reference (Entity (Selector_Name (P)), P);
6575
6576             elsif Is_Overloaded (P) then
6577
6578                --  Use the designated type of the context  to disambiguate.
6579                declare
6580                   Index : Interp_Index;
6581                   It    : Interp;
6582                begin
6583                   Get_First_Interp (P, Index, It);
6584
6585                   while Present (It.Typ) loop
6586                      if Covers (Designated_Type (Typ), It.Typ) then
6587                         Resolve (P, It.Typ);
6588                         exit;
6589                      end if;
6590
6591                      Get_Next_Interp (Index, It);
6592                   end loop;
6593                end;
6594             else
6595                Resolve (P);
6596             end if;
6597
6598             --  X'Access is illegal if X denotes a constant and the access
6599             --  type is access-to-variable. Same for 'Unchecked_Access.
6600             --  The rule does not apply to 'Unrestricted_Access.
6601
6602             if not (Ekind (Btyp) = E_Access_Subprogram_Type
6603                      or else Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
6604                      or else (Is_Record_Type (Btyp) and then
6605                               Present (Corresponding_Remote_Type (Btyp)))
6606                      or else Ekind (Btyp) = E_Access_Protected_Subprogram_Type
6607                      or else Ekind (Btyp)
6608                                = E_Anonymous_Access_Protected_Subprogram_Type
6609                      or else Is_Access_Constant (Btyp)
6610                      or else Is_Variable (P)
6611                      or else Attr_Id = Attribute_Unrestricted_Access)
6612             then
6613                if Comes_From_Source (N) then
6614                   Error_Msg_N ("access-to-variable designates constant", P);
6615                end if;
6616             end if;
6617
6618             if (Attr_Id = Attribute_Access
6619                   or else
6620                 Attr_Id = Attribute_Unchecked_Access)
6621               and then (Ekind (Btyp) = E_General_Access_Type
6622                           or else Ekind (Btyp) = E_Anonymous_Access_Type)
6623             then
6624                --  Ada 2005 (AI-230): Check the accessibility of anonymous
6625                --  access types in record and array components. For a
6626                --  component definition the level is the same of the
6627                --  enclosing composite type.
6628
6629                if Ada_Version >= Ada_05
6630                  and then Ekind (Btyp) = E_Anonymous_Access_Type
6631                  and then (Is_Array_Type (Scope (Btyp))
6632                              or else Ekind (Scope (Btyp)) = E_Record_Type)
6633                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
6634                then
6635                   --  In an instance, this is a runtime check, but one we
6636                   --  know will fail, so generate an appropriate warning.
6637
6638                   if In_Instance_Body then
6639                      Error_Msg_N
6640                        ("?non-local pointer cannot point to local object", P);
6641                      Error_Msg_N
6642                        ("?Program_Error will be raised at run time", P);
6643                      Rewrite (N,
6644                        Make_Raise_Program_Error (Loc,
6645                          Reason => PE_Accessibility_Check_Failed));
6646                      Set_Etype (N, Typ);
6647                   else
6648                      Error_Msg_N
6649                        ("non-local pointer cannot point to local object", P);
6650                   end if;
6651                end if;
6652
6653                if Is_Dependent_Component_Of_Mutable_Object (P) then
6654                   Error_Msg_N
6655                     ("illegal attribute for discriminant-dependent component",
6656                      P);
6657                end if;
6658
6659                --  Check the static matching rule of 3.10.2(27). The
6660                --  nominal subtype of the prefix must statically
6661                --  match the designated type.
6662
6663                Nom_Subt := Etype (P);
6664
6665                if Is_Constr_Subt_For_U_Nominal (Nom_Subt) then
6666                   Nom_Subt := Etype (Nom_Subt);
6667                end if;
6668
6669                if Is_Tagged_Type (Designated_Type (Typ)) then
6670
6671                   --  If the attribute is in the context of an access
6672                   --  parameter, then the prefix is allowed to be of
6673                   --  the class-wide type (by AI-127).
6674
6675                   if Ekind (Typ) = E_Anonymous_Access_Type then
6676                      if not Covers (Designated_Type (Typ), Nom_Subt)
6677                        and then not Covers (Nom_Subt, Designated_Type (Typ))
6678                      then
6679                         declare
6680                            Desig : Entity_Id;
6681
6682                         begin
6683                            Desig := Designated_Type (Typ);
6684
6685                            if Is_Class_Wide_Type (Desig) then
6686                               Desig := Etype (Desig);
6687                            end if;
6688
6689                            if Is_Anonymous_Tagged_Base (Nom_Subt, Desig) then
6690                               null;
6691
6692                            else
6693                               Error_Msg_NE
6694                                 ("type of prefix: & not compatible",
6695                                   P, Nom_Subt);
6696                               Error_Msg_NE
6697                                 ("\with &, the expected designated type",
6698                                   P, Designated_Type (Typ));
6699                            end if;
6700                         end;
6701                      end if;
6702
6703                   elsif not Covers (Designated_Type (Typ), Nom_Subt)
6704                     or else
6705                       (not Is_Class_Wide_Type (Designated_Type (Typ))
6706                         and then Is_Class_Wide_Type (Nom_Subt))
6707                   then
6708                      Error_Msg_NE
6709                        ("type of prefix: & is not covered", P, Nom_Subt);
6710                      Error_Msg_NE
6711                        ("\by &, the expected designated type" &
6712                            " ('R'M 3.10.2 (27))", P, Designated_Type (Typ));
6713                   end if;
6714
6715                   if Is_Class_Wide_Type (Designated_Type (Typ))
6716                     and then Has_Discriminants (Etype (Designated_Type (Typ)))
6717                     and then Is_Constrained (Etype (Designated_Type (Typ)))
6718                     and then Designated_Type (Typ) /= Nom_Subt
6719                   then
6720                      Apply_Discriminant_Check
6721                        (N, Etype (Designated_Type (Typ)));
6722                   end if;
6723
6724                elsif not Subtypes_Statically_Match
6725                            (Designated_Type (Base_Type (Typ)), Nom_Subt)
6726                  and then
6727                    not (Has_Discriminants (Designated_Type (Typ))
6728                           and then
6729                             not Is_Constrained
6730                                   (Designated_Type (Base_Type (Typ))))
6731                then
6732                   Error_Msg_N
6733                     ("object subtype must statically match "
6734                      & "designated subtype", P);
6735
6736                   if Is_Entity_Name (P)
6737                     and then Is_Array_Type (Designated_Type (Typ))
6738                   then
6739
6740                      declare
6741                         D : constant Node_Id := Declaration_Node (Entity (P));
6742
6743                      begin
6744                         Error_Msg_N ("aliased object has explicit bounds?",
6745                           D);
6746                         Error_Msg_N ("\declare without bounds"
6747                           & " (and with explicit initialization)?", D);
6748                         Error_Msg_N ("\for use with unconstrained access?", D);
6749                      end;
6750                   end if;
6751                end if;
6752
6753                --  Check the static accessibility rule of 3.10.2(28).
6754                --  Note that this check is not performed for the
6755                --  case of an anonymous access type, since the access
6756                --  attribute is always legal in such a context.
6757
6758                if Attr_Id /= Attribute_Unchecked_Access
6759                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
6760                  and then Ekind (Btyp) = E_General_Access_Type
6761                then
6762                   --  In an instance, this is a runtime check, but one we
6763                   --  know will fail, so generate an appropriate warning.
6764
6765                   if In_Instance_Body then
6766                      Error_Msg_N
6767                        ("?non-local pointer cannot point to local object", P);
6768                      Error_Msg_N
6769                        ("?Program_Error will be raised at run time", P);
6770                      Rewrite (N,
6771                        Make_Raise_Program_Error (Loc,
6772                          Reason => PE_Accessibility_Check_Failed));
6773                      Set_Etype (N, Typ);
6774                      return;
6775
6776                   else
6777                      Error_Msg_N
6778                        ("non-local pointer cannot point to local object", P);
6779
6780                      if Is_Record_Type (Current_Scope)
6781                        and then (Nkind (Parent (N)) =
6782                                   N_Discriminant_Association
6783                                    or else
6784                                  Nkind (Parent (N)) =
6785                                    N_Index_Or_Discriminant_Constraint)
6786                      then
6787                         declare
6788                            Indic : Node_Id := Parent (Parent (N));
6789
6790                         begin
6791                            while Present (Indic)
6792                              and then Nkind (Indic) /= N_Subtype_Indication
6793                            loop
6794                               Indic := Parent (Indic);
6795                            end loop;
6796
6797                            if Present (Indic) then
6798                               Error_Msg_NE
6799                                 ("\use an access definition for" &
6800                                   " the access discriminant of&", N,
6801                                   Entity (Subtype_Mark (Indic)));
6802                            end if;
6803                         end;
6804                      end if;
6805                   end if;
6806                end if;
6807             end if;
6808
6809             if (Ekind (Btyp) = E_Access_Protected_Subprogram_Type
6810                   or else
6811                 Ekind (Btyp) = E_Anonymous_Access_Protected_Subprogram_Type)
6812               and then Is_Entity_Name (P)
6813               and then not Is_Protected_Type (Scope (Entity (P)))
6814             then
6815                Error_Msg_N ("context requires a protected subprogram", P);
6816
6817             elsif (Ekind (Btyp) = E_Access_Subprogram_Type
6818                      or else
6819                    Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type)
6820               and then Ekind (Etype (N)) = E_Access_Protected_Subprogram_Type
6821             then
6822                Error_Msg_N ("context requires a non-protected subprogram", P);
6823             end if;
6824
6825             --  The context cannot be a pool-specific type, but this is a
6826             --  legality rule, not a resolution rule, so it must be checked
6827             --  separately, after possibly disambiguation (see AI-245).
6828
6829             if Ekind (Btyp) = E_Access_Type
6830               and then Attr_Id /= Attribute_Unrestricted_Access
6831             then
6832                Wrong_Type (N, Typ);
6833             end if;
6834
6835             Set_Etype (N, Typ);
6836
6837             --  Check for incorrect atomic/volatile reference (RM C.6(12))
6838
6839             if Attr_Id /= Attribute_Unrestricted_Access then
6840                if Is_Atomic_Object (P)
6841                  and then not Is_Atomic (Designated_Type (Typ))
6842                then
6843                   Error_Msg_N
6844                     ("access to atomic object cannot yield access-to-" &
6845                      "non-atomic type", P);
6846
6847                elsif Is_Volatile_Object (P)
6848                  and then not Is_Volatile (Designated_Type (Typ))
6849                then
6850                   Error_Msg_N
6851                     ("access to volatile object cannot yield access-to-" &
6852                      "non-volatile type", P);
6853                end if;
6854             end if;
6855
6856          -------------
6857          -- Address --
6858          -------------
6859
6860          --  Deal with resolving the type for Address attribute, overloading
6861          --  is not permitted here, since there is no context to resolve it.
6862
6863          when Attribute_Address | Attribute_Code_Address =>
6864
6865             --  To be safe, assume that if the address of a variable is taken,
6866             --  it may be modified via this address, so note modification.
6867
6868             if Is_Variable (P) then
6869                Note_Possible_Modification (P);
6870             end if;
6871
6872             if Nkind (P) in  N_Subexpr
6873               and then Is_Overloaded (P)
6874             then
6875                Get_First_Interp (P, Index, It);
6876                Get_Next_Interp (Index, It);
6877
6878                if Present (It.Nam) then
6879                   Error_Msg_Name_1 := Aname;
6880                   Error_Msg_N
6881                     ("prefix of % attribute cannot be overloaded", N);
6882                   return;
6883                end if;
6884             end if;
6885
6886             if not Is_Entity_Name (P)
6887                or else not Is_Overloadable (Entity (P))
6888             then
6889                if not Is_Task_Type (Etype (P))
6890                  or else Nkind (P) = N_Explicit_Dereference
6891                then
6892                   Resolve (P);
6893                end if;
6894             end if;
6895
6896             --  If this is the name of a derived subprogram, or that of a
6897             --  generic actual, the address is that of the original entity.
6898
6899             if Is_Entity_Name (P)
6900               and then Is_Overloadable (Entity (P))
6901               and then Present (Alias (Entity (P)))
6902             then
6903                Rewrite (P,
6904                  New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
6905             end if;
6906
6907          ---------------
6908          -- AST_Entry --
6909          ---------------
6910
6911          --  Prefix of the AST_Entry attribute is an entry name which must
6912          --  not be resolved, since this is definitely not an entry call.
6913
6914          when Attribute_AST_Entry =>
6915             null;
6916
6917          ------------------
6918          -- Body_Version --
6919          ------------------
6920
6921          --  Prefix of Body_Version attribute can be a subprogram name which
6922          --  must not be resolved, since this is not a call.
6923
6924          when Attribute_Body_Version =>
6925             null;
6926
6927          ------------
6928          -- Caller --
6929          ------------
6930
6931          --  Prefix of Caller attribute is an entry name which must not
6932          --  be resolved, since this is definitely not an entry call.
6933
6934          when Attribute_Caller =>
6935             null;
6936
6937          ------------------
6938          -- Code_Address --
6939          ------------------
6940
6941          --  Shares processing with Address attribute
6942
6943          -----------
6944          -- Count --
6945          -----------
6946
6947          --  If the prefix of the Count attribute is an entry name it must not
6948          --  be resolved, since this is definitely not an entry call. However,
6949          --  if it is an element of an entry family, the index itself may
6950          --  have to be resolved because it can be a general expression.
6951
6952          when Attribute_Count =>
6953             if Nkind (P) = N_Indexed_Component
6954               and then Is_Entity_Name (Prefix (P))
6955             then
6956                declare
6957                   Indx : constant Node_Id   := First (Expressions (P));
6958                   Fam  : constant Entity_Id := Entity (Prefix (P));
6959                begin
6960                   Resolve (Indx, Entry_Index_Type (Fam));
6961                   Apply_Range_Check (Indx, Entry_Index_Type (Fam));
6962                end;
6963             end if;
6964
6965          ----------------
6966          -- Elaborated --
6967          ----------------
6968
6969          --  Prefix of the Elaborated attribute is a subprogram name which
6970          --  must not be resolved, since this is definitely not a call. Note
6971          --  that it is a library unit, so it cannot be overloaded here.
6972
6973          when Attribute_Elaborated =>
6974             null;
6975
6976          --------------------
6977          -- Mechanism_Code --
6978          --------------------
6979
6980          --  Prefix of the Mechanism_Code attribute is a function name
6981          --  which must not be resolved. Should we check for overloaded ???
6982
6983          when Attribute_Mechanism_Code =>
6984             null;
6985
6986          ------------------
6987          -- Partition_ID --
6988          ------------------
6989
6990          --  Most processing is done in sem_dist, after determining the
6991          --  context type. Node is rewritten as a conversion to a runtime call.
6992
6993          when Attribute_Partition_ID =>
6994             Process_Partition_Id (N);
6995             return;
6996
6997          when Attribute_Pool_Address =>
6998             Resolve (P);
6999
7000          -----------
7001          -- Range --
7002          -----------
7003
7004          --  We replace the Range attribute node with a range expression
7005          --  whose bounds are the 'First and 'Last attributes applied to the
7006          --  same prefix. The reason that we do this transformation here
7007          --  instead of in the expander is that it simplifies other parts of
7008          --  the semantic analysis which assume that the Range has been
7009          --  replaced; thus it must be done even when in semantic-only mode
7010          --  (note that the RM specifically mentions this equivalence, we
7011          --  take care that the prefix is only evaluated once).
7012
7013          when Attribute_Range => Range_Attribute :
7014             declare
7015                LB   : Node_Id;
7016                HB   : Node_Id;
7017
7018                function Check_Discriminated_Prival
7019                  (N    : Node_Id)
7020                   return Node_Id;
7021                --  The range of a private component constrained by a
7022                --  discriminant is rewritten to make the discriminant
7023                --  explicit. This solves some complex visibility problems
7024                --  related to the use of privals.
7025
7026                --------------------------------
7027                -- Check_Discriminated_Prival --
7028                --------------------------------
7029
7030                function Check_Discriminated_Prival
7031                  (N    : Node_Id)
7032                   return Node_Id
7033                is
7034                begin
7035                   if Is_Entity_Name (N)
7036                     and then Ekind (Entity (N)) = E_In_Parameter
7037                     and then not Within_Init_Proc
7038                   then
7039                      return Make_Identifier (Sloc (N), Chars (Entity (N)));
7040                   else
7041                      return Duplicate_Subexpr (N);
7042                   end if;
7043                end Check_Discriminated_Prival;
7044
7045             --  Start of processing for Range_Attribute
7046
7047             begin
7048                if not Is_Entity_Name (P)
7049                  or else not Is_Type (Entity (P))
7050                then
7051                   Resolve (P);
7052                end if;
7053
7054                --  Check whether prefix is (renaming of) private component
7055                --  of protected type.
7056
7057                if Is_Entity_Name (P)
7058                  and then Comes_From_Source (N)
7059                  and then Is_Array_Type (Etype (P))
7060                  and then Number_Dimensions (Etype (P)) = 1
7061                  and then (Ekind (Scope (Entity (P))) = E_Protected_Type
7062                             or else
7063                            Ekind (Scope (Scope (Entity (P)))) =
7064                                                         E_Protected_Type)
7065                then
7066                   LB :=
7067                     Check_Discriminated_Prival
7068                       (Type_Low_Bound (Etype (First_Index (Etype (P)))));
7069
7070                   HB :=
7071                     Check_Discriminated_Prival
7072                       (Type_High_Bound (Etype (First_Index (Etype (P)))));
7073
7074                else
7075                   HB :=
7076                     Make_Attribute_Reference (Loc,
7077                       Prefix         => Duplicate_Subexpr (P),
7078                       Attribute_Name => Name_Last,
7079                       Expressions    => Expressions (N));
7080
7081                   LB :=
7082                     Make_Attribute_Reference (Loc,
7083                       Prefix         => P,
7084                       Attribute_Name => Name_First,
7085                       Expressions    => Expressions (N));
7086                end if;
7087
7088                --  If the original was marked as Must_Not_Freeze (see code
7089                --  in Sem_Ch3.Make_Index), then make sure the rewriting
7090                --  does not freeze either.
7091
7092                if Must_Not_Freeze (N) then
7093                   Set_Must_Not_Freeze (HB);
7094                   Set_Must_Not_Freeze (LB);
7095                   Set_Must_Not_Freeze (Prefix (HB));
7096                   Set_Must_Not_Freeze (Prefix (LB));
7097                end if;
7098
7099                if Raises_Constraint_Error (Prefix (N)) then
7100
7101                   --  Preserve Sloc of prefix in the new bounds, so that
7102                   --  the posted warning can be removed if we are within
7103                   --  unreachable code.
7104
7105                   Set_Sloc (LB, Sloc (Prefix (N)));
7106                   Set_Sloc (HB, Sloc (Prefix (N)));
7107                end if;
7108
7109                Rewrite (N, Make_Range (Loc, LB, HB));
7110                Analyze_And_Resolve (N, Typ);
7111
7112                --  Normally after resolving attribute nodes, Eval_Attribute
7113                --  is called to do any possible static evaluation of the node.
7114                --  However, here since the Range attribute has just been
7115                --  transformed into a range expression it is no longer an
7116                --  attribute node and therefore the call needs to be avoided
7117                --  and is accomplished by simply returning from the procedure.
7118
7119                return;
7120             end Range_Attribute;
7121
7122          -----------------
7123          -- UET_Address --
7124          -----------------
7125
7126          --  Prefix must not be resolved in this case, since it is not a
7127          --  real entity reference. No action of any kind is require!
7128
7129          when Attribute_UET_Address =>
7130             return;
7131
7132          ----------------------
7133          -- Unchecked_Access --
7134          ----------------------
7135
7136          --  Processing is shared with Access
7137
7138          -------------------------
7139          -- Unrestricted_Access --
7140          -------------------------
7141
7142          --  Processing is shared with Access
7143
7144          ---------
7145          -- Val --
7146          ---------
7147
7148          --  Apply range check. Note that we did not do this during the
7149          --  analysis phase, since we wanted Eval_Attribute to have a
7150          --  chance at finding an illegal out of range value.
7151
7152          when Attribute_Val =>
7153
7154             --  Note that we do our own Eval_Attribute call here rather than
7155             --  use the common one, because we need to do processing after
7156             --  the call, as per above comment.
7157
7158             Eval_Attribute (N);
7159
7160             --  Eval_Attribute may replace the node with a raise CE, or
7161             --  fold it to a constant. Obviously we only apply a scalar
7162             --  range check if this did not happen!
7163
7164             if Nkind (N) = N_Attribute_Reference
7165               and then Attribute_Name (N) = Name_Val
7166             then
7167                Apply_Scalar_Range_Check (First (Expressions (N)), Btyp);
7168             end if;
7169
7170             return;
7171
7172          -------------
7173          -- Version --
7174          -------------
7175
7176          --  Prefix of Version attribute can be a subprogram name which
7177          --  must not be resolved, since this is not a call.
7178
7179          when Attribute_Version =>
7180             null;
7181
7182          ----------------------
7183          -- Other Attributes --
7184          ----------------------
7185
7186          --  For other attributes, resolve prefix unless it is a type. If
7187          --  the attribute reference itself is a type name ('Base and 'Class)
7188          --  then this is only legal within a task or protected record.
7189
7190          when others =>
7191             if not Is_Entity_Name (P)
7192               or else not Is_Type (Entity (P))
7193             then
7194                Resolve (P);
7195             end if;
7196
7197             --  If the attribute reference itself is a type name ('Base,
7198             --  'Class) then this is only legal within a task or protected
7199             --  record. What is this all about ???
7200
7201             if Is_Entity_Name (N)
7202               and then Is_Type (Entity (N))
7203             then
7204                if Is_Concurrent_Type (Entity (N))
7205                  and then In_Open_Scopes (Entity (P))
7206                then
7207                   null;
7208                else
7209                   Error_Msg_N
7210                     ("invalid use of subtype name in expression or call", N);
7211                end if;
7212             end if;
7213
7214             --  For attributes whose argument may be a string, complete
7215             --  resolution of argument now. This avoids premature expansion
7216             --  (and the creation of transient scopes) before the attribute
7217             --  reference is resolved.
7218
7219             case Attr_Id is
7220                when Attribute_Value =>
7221                   Resolve (First (Expressions (N)), Standard_String);
7222
7223                when Attribute_Wide_Value =>
7224                   Resolve (First (Expressions (N)), Standard_Wide_String);
7225
7226                when others => null;
7227             end case;
7228       end case;
7229
7230       --  Normally the Freezing is done by Resolve but sometimes the Prefix
7231       --  is not resolved, in which case the freezing must be done now.
7232
7233       Freeze_Expression (P);
7234
7235       --  Finally perform static evaluation on the attribute reference
7236
7237       Eval_Attribute (N);
7238
7239    end Resolve_Attribute;
7240
7241 end Sem_Attr;