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