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) 1992-2008, 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 3,  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 COPYING3.  If not, go to --
  19 -- http://www.gnu.org/licenses for a complete copy of the license.          --
  20 --                                                                          --
  21 -- GNAT was originally developed  by the GNAT team at  New York University. --
  22 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  23 --                                                                          --
  24 ------------------------------------------------------------------------------
  25
  26 with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
  27
  28 with Atree;    use Atree;
  29 with Casing;   use Casing;
  30 with Checks;   use Checks;
  31 with Einfo;    use Einfo;
  32 with Errout;   use Errout;
  33 with Eval_Fat;
  34 with Exp_Dist; use Exp_Dist;
  35 with Exp_Util; use Exp_Util;
  36 with Expander; use Expander;
  37 with Freeze;   use Freeze;
  38 with Itypes;   use Itypes;
  39 with Lib;      use Lib;
  40 with Lib.Xref; use Lib.Xref;
  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 Stringt;  use Stringt;
  61 with Style;
  62 with Stylesw;  use Stylesw;
  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
  70 package body Sem_Attr is
  71
  72    True_Value  : constant Uint := Uint_1;
  73    False_Value : constant Uint := Uint_0;
  74    --  Synonyms to be used when these constants are used as Boolean values
  75
  76    Bad_Attribute : exception;
  77    --  Exception raised if an error is detected during attribute processing,
  78    --  used so that we can abandon the processing so we don't run into
  79    --  trouble with cascaded errors.
  80
  81    --  The following array is the list of attributes defined in the Ada 83 RM
  82    --  that are not included in Ada 95, but still get recognized in GNAT.
  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    --  The following array is the list of attributes defined in the Ada 2005
 130    --  RM which are not defined in Ada 95. These are recognized in Ada 95 mode,
 131    --  but in Ada 95 they are considered to be implementation defined.
 132
 133    Attribute_05 : constant Attribute_Class_Array := Attribute_Class_Array'(
 134       Attribute_Machine_Rounding  |
 135       Attribute_Priority          |
 136       Attribute_Stream_Size       |
 137       Attribute_Wide_Wide_Width   => True,
 138       others                      => False);
 139
 140    --  The following array contains all attributes that imply a modification
 141    --  of their prefixes or result in an access value. Such prefixes can be
 142    --  considered as lvalues.
 143
 144    Attribute_Name_Implies_Lvalue_Prefix : constant Attribute_Class_Array :=
 145       Attribute_Class_Array'(
 146       Attribute_Access              |
 147       Attribute_Address             |
 148       Attribute_Input               |
 149       Attribute_Read                |
 150       Attribute_Unchecked_Access    |
 151       Attribute_Unrestricted_Access => True,
 152       others                        => False);
 153
 154    -----------------------
 155    -- Local_Subprograms --
 156    -----------------------
 157
 158    procedure Eval_Attribute (N : Node_Id);
 159    --  Performs compile time evaluation of attributes where possible, leaving
 160    --  the Is_Static_Expression/Raises_Constraint_Error flags appropriately
 161    --  set, and replacing the node with a literal node if the value can be
 162    --  computed at compile time. All static attribute references are folded,
 163    --  as well as a number of cases of non-static attributes that can always
 164    --  be computed at compile time (e.g. floating-point model attributes that
 165    --  are applied to non-static subtypes). Of course in such cases, the
 166    --  Is_Static_Expression flag will not be set on the resulting literal.
 167    --  Note that the only required action of this procedure is to catch the
 168    --  static expression cases as described in the RM. Folding of other cases
 169    --  is done where convenient, but some additional non-static folding is in
 170    --  N_Expand_Attribute_Reference in cases where this is more convenient.
 171
 172    function Is_Anonymous_Tagged_Base
 173      (Anon : Entity_Id;
 174       Typ  : Entity_Id)
 175       return Boolean;
 176    --  For derived tagged types that constrain parent discriminants we build
 177    --  an anonymous unconstrained base type. We need to recognize the relation
 178    --  between the two when analyzing an access attribute for a constrained
 179    --  component, before the full declaration for Typ has been analyzed, and
 180    --  where therefore the prefix of the attribute does not match the enclosing
 181    --  scope.
 182
 183    -----------------------
 184    -- Analyze_Attribute --
 185    -----------------------
 186
 187    procedure Analyze_Attribute (N : Node_Id) is
 188       Loc     : constant Source_Ptr   := Sloc (N);
 189       Aname   : constant Name_Id      := Attribute_Name (N);
 190       P       : constant Node_Id      := Prefix (N);
 191       Exprs   : constant List_Id      := Expressions (N);
 192       Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname);
 193       E1      : Node_Id;
 194       E2      : Node_Id;
 195
 196       P_Type : Entity_Id;
 197       --  Type of prefix after analysis
 198
 199       P_Base_Type : Entity_Id;
 200       --  Base type of prefix after analysis
 201
 202       -----------------------
 203       -- Local Subprograms --
 204       -----------------------
 205
 206       procedure Analyze_Access_Attribute;
 207       --  Used for Access, Unchecked_Access, Unrestricted_Access attributes.
 208       --  Internally, Id distinguishes which of the three cases is involved.
 209
 210       procedure Check_Array_Or_Scalar_Type;
 211       --  Common procedure used by First, Last, Range attribute to check
 212       --  that the prefix is a constrained array or scalar type, or a name
 213       --  of an array object, and that an argument appears only if appropriate
 214       --  (i.e. only in the array case).
 215
 216       procedure Check_Array_Type;
 217       --  Common semantic checks for all array attributes. Checks that the
 218       --  prefix is a constrained array type or the name of an array object.
 219       --  The error message for non-arrays is specialized appropriately.
 220
 221       procedure Check_Asm_Attribute;
 222       --  Common semantic checks for Asm_Input and Asm_Output attributes
 223
 224       procedure Check_Component;
 225       --  Common processing for Bit_Position, First_Bit, Last_Bit, and
 226       --  Position. Checks prefix is an appropriate selected component.
 227
 228       procedure Check_Decimal_Fixed_Point_Type;
 229       --  Check that prefix of attribute N is a decimal fixed-point type
 230
 231       procedure Check_Dereference;
 232       --  If the prefix of attribute is an object of an access type, then
 233       --  introduce an explicit deference, and adjust P_Type accordingly.
 234
 235       procedure Check_Discrete_Type;
 236       --  Verify that prefix of attribute N is a discrete type
 237
 238       procedure Check_E0;
 239       --  Check that no attribute arguments are present
 240
 241       procedure Check_Either_E0_Or_E1;
 242       --  Check that there are zero or one attribute arguments present
 243
 244       procedure Check_E1;
 245       --  Check that exactly one attribute argument is present
 246
 247       procedure Check_E2;
 248       --  Check that two attribute arguments are present
 249
 250       procedure Check_Enum_Image;
 251       --  If the prefix type is an enumeration type, set all its literals
 252       --  as referenced, since the image function could possibly end up
 253       --  referencing any of the literals indirectly. Same for Enum_Val.
 254
 255       procedure Check_Fixed_Point_Type;
 256       --  Verify that prefix of attribute N is a fixed type
 257
 258       procedure Check_Fixed_Point_Type_0;
 259       --  Verify that prefix of attribute N is a fixed type and that
 260       --  no attribute expressions are present
 261
 262       procedure Check_Floating_Point_Type;
 263       --  Verify that prefix of attribute N is a float type
 264
 265       procedure Check_Floating_Point_Type_0;
 266       --  Verify that prefix of attribute N is a float type and that
 267       --  no attribute expressions are present
 268
 269       procedure Check_Floating_Point_Type_1;
 270       --  Verify that prefix of attribute N is a float type and that
 271       --  exactly one attribute expression is present
 272
 273       procedure Check_Floating_Point_Type_2;
 274       --  Verify that prefix of attribute N is a float type and that
 275       --  two attribute expressions are present
 276
 277       procedure Legal_Formal_Attribute;
 278       --  Common processing for attributes Definite and Has_Discriminants.
 279       --  Checks that prefix is generic indefinite formal type.
 280
 281       procedure Check_Integer_Type;
 282       --  Verify that prefix of attribute N is an integer type
 283
 284       procedure Check_Library_Unit;
 285       --  Verify that prefix of attribute N is a library unit
 286
 287       procedure Check_Modular_Integer_Type;
 288       --  Verify that prefix of attribute N is a modular integer type
 289
 290       procedure Check_Not_CPP_Type;
 291       --  Check that P (the prefix of the attribute) is not an CPP type
 292       --  for which no Ada predefined primitive is available.
 293
 294       procedure Check_Not_Incomplete_Type;
 295       --  Check that P (the prefix of the attribute) is not an incomplete
 296       --  type or a private type for which no full view has been given.
 297
 298       procedure Check_Object_Reference (P : Node_Id);
 299       --  Check that P (the prefix of the attribute) is an object reference
 300
 301       procedure Check_Program_Unit;
 302       --  Verify that prefix of attribute N is a program unit
 303
 304       procedure Check_Real_Type;
 305       --  Verify that prefix of attribute N is fixed or float type
 306
 307       procedure Check_Scalar_Type;
 308       --  Verify that prefix of attribute N is a scalar type
 309
 310       procedure Check_Standard_Prefix;
 311       --  Verify that prefix of attribute N is package Standard
 312
 313       procedure Check_Stream_Attribute (Nam : TSS_Name_Type);
 314       --  Validity checking for stream attribute. Nam is the TSS name of the
 315       --  corresponding possible defined attribute function (e.g. for the
 316       --  Read attribute, Nam will be TSS_Stream_Read).
 317
 318       procedure Check_Task_Prefix;
 319       --  Verify that prefix of attribute N is a task or task type
 320
 321       procedure Check_Type;
 322       --  Verify that the prefix of attribute N is a type
 323
 324       procedure Check_Unit_Name (Nod : Node_Id);
 325       --  Check that Nod is of the form of a library unit name, i.e that
 326       --  it is an identifier, or a selected component whose prefix is
 327       --  itself of the form of a library unit name. Note that this is
 328       --  quite different from Check_Program_Unit, since it only checks
 329       --  the syntactic form of the name, not the semantic identity. This
 330       --  is because it is used with attributes (Elab_Body, Elab_Spec, and
 331       --  UET_Address) which can refer to non-visible unit.
 332
 333       procedure Error_Attr (Msg : String; Error_Node : Node_Id);
 334       pragma No_Return (Error_Attr);
 335       procedure Error_Attr;
 336       pragma No_Return (Error_Attr);
 337       --  Posts error using Error_Msg_N at given node, sets type of attribute
 338       --  node to Any_Type, and then raises Bad_Attribute to avoid any further
 339       --  semantic processing. The message typically contains a % insertion
 340       --  character which is replaced by the attribute name. The call with
 341       --  no arguments is used when the caller has already generated the
 342       --  required error messages.
 343
 344       procedure Error_Attr_P (Msg : String);
 345       pragma No_Return (Error_Attr);
 346       --  Like Error_Attr, but error is posted at the start of the prefix
 347
 348       procedure Standard_Attribute (Val : Int);
 349       --  Used to process attributes whose prefix is package Standard which
 350       --  yield values of type Universal_Integer. The attribute reference
 351       --  node is rewritten with an integer literal of the given value.
 352
 353       procedure Unexpected_Argument (En : Node_Id);
 354       --  Signal unexpected attribute argument (En is the argument)
 355
 356       procedure Validate_Non_Static_Attribute_Function_Call;
 357       --  Called when processing an attribute that is a function call to a
 358       --  non-static function, i.e. an attribute function that either takes
 359       --  non-scalar arguments or returns a non-scalar result. Verifies that
 360       --  such a call does not appear in a preelaborable context.
 361
 362       ------------------------------
 363       -- Analyze_Access_Attribute --
 364       ------------------------------
 365
 366       procedure Analyze_Access_Attribute is
 367          Acc_Type : Entity_Id;
 368
 369          Scop : Entity_Id;
 370          Typ  : Entity_Id;
 371
 372          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id;
 373          --  Build an access-to-object type whose designated type is DT,
 374          --  and whose Ekind is appropriate to the attribute type. The
 375          --  type that is constructed is returned as the result.
 376
 377          procedure Build_Access_Subprogram_Type (P : Node_Id);
 378          --  Build an access to subprogram whose designated type is the type of
 379          --  the prefix. If prefix is overloaded, so is the node itself. The
 380          --  result is stored in Acc_Type.
 381
 382          function OK_Self_Reference return Boolean;
 383          --  An access reference whose prefix is a type can legally appear
 384          --  within an aggregate, where it is obtained by expansion of
 385          --  a defaulted aggregate. The enclosing aggregate that contains
 386          --  the self-referenced is flagged so that the self-reference can
 387          --  be expanded into a reference to the target object (see exp_aggr).
 388
 389          ------------------------------
 390          -- Build_Access_Object_Type --
 391          ------------------------------
 392
 393          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id is
 394             Typ : constant Entity_Id :=
 395                     New_Internal_Entity
 396                       (E_Access_Attribute_Type, Current_Scope, Loc, 'A');
 397          begin
 398             Set_Etype                     (Typ, Typ);
 399             Set_Is_Itype                  (Typ);
 400             Set_Associated_Node_For_Itype (Typ, N);
 401             Set_Directly_Designated_Type  (Typ, DT);
 402             return Typ;
 403          end Build_Access_Object_Type;
 404
 405          ----------------------------------
 406          -- Build_Access_Subprogram_Type --
 407          ----------------------------------
 408
 409          procedure Build_Access_Subprogram_Type (P : Node_Id) is
 410             Index : Interp_Index;
 411             It    : Interp;
 412
 413             procedure Check_Local_Access (E : Entity_Id);
 414             --  Deal with possible access to local subprogram. If we have such
 415             --  an access, we set a flag to kill all tracked values on any call
 416             --  because this access value may be passed around, and any called
 417             --  code might use it to access a local procedure which clobbers a
 418             --  tracked value.
 419
 420             function Get_Kind (E : Entity_Id) return Entity_Kind;
 421             --  Distinguish between access to regular/protected subprograms
 422
 423             ------------------------
 424             -- Check_Local_Access --
 425             ------------------------
 426
 427             procedure Check_Local_Access (E : Entity_Id) is
 428             begin
 429                if not Is_Library_Level_Entity (E) then
 430                   Set_Suppress_Value_Tracking_On_Call (Current_Scope);
 431                end if;
 432             end Check_Local_Access;
 433
 434             --------------
 435             -- Get_Kind --
 436             --------------
 437
 438             function Get_Kind (E : Entity_Id) return Entity_Kind is
 439             begin
 440                if Convention (E) = Convention_Protected then
 441                   return E_Access_Protected_Subprogram_Type;
 442                else
 443                   return E_Access_Subprogram_Type;
 444                end if;
 445             end Get_Kind;
 446
 447          --  Start of processing for Build_Access_Subprogram_Type
 448
 449          begin
 450             --  In the case of an access to subprogram, use the name of the
 451             --  subprogram itself as the designated type. Type-checking in
 452             --  this case compares the signatures of the designated types.
 453
 454             --  Note: This fragment of the tree is temporarily malformed
 455             --  because the correct tree requires an E_Subprogram_Type entity
 456             --  as the designated type. In most cases this designated type is
 457             --  later overridden by the semantics with the type imposed by the
 458             --  context during the resolution phase. In the specific case of
 459             --  the expression Address!(Prim'Unrestricted_Access), used to
 460             --  initialize slots of dispatch tables, this work will be done by
 461             --  the expander (see Exp_Aggr).
 462
 463             --  The reason to temporarily add this kind of node to the tree
 464             --  instead of a proper E_Subprogram_Type itype, is the following:
 465             --  in case of errors found in the source file we report better
 466             --  error messages. For example, instead of generating the
 467             --  following error:
 468
 469             --      "expected access to subprogram with profile
 470             --       defined at line X"
 471
 472             --  we currently generate:
 473
 474             --      "expected access to function Z defined at line X"
 475
 476             Set_Etype (N, Any_Type);
 477
 478             if not Is_Overloaded (P) then
 479                Check_Local_Access (Entity (P));
 480
 481                if not Is_Intrinsic_Subprogram (Entity (P)) then
 482                   Acc_Type := Create_Itype (Get_Kind (Entity (P)), N);
 483                   Set_Is_Public (Acc_Type, False);
 484                   Set_Etype (Acc_Type, Acc_Type);
 485                   Set_Convention (Acc_Type, Convention (Entity (P)));
 486                   Set_Directly_Designated_Type (Acc_Type, Entity (P));
 487                   Set_Etype (N, Acc_Type);
 488                   Freeze_Before (N, Acc_Type);
 489                end if;
 490
 491             else
 492                Get_First_Interp (P, Index, It);
 493                while Present (It.Nam) loop
 494                   Check_Local_Access (It.Nam);
 495
 496                   if not Is_Intrinsic_Subprogram (It.Nam) then
 497                      Acc_Type := Create_Itype (Get_Kind (It.Nam), N);
 498                      Set_Is_Public (Acc_Type, False);
 499                      Set_Etype (Acc_Type, Acc_Type);
 500                      Set_Convention (Acc_Type, Convention (It.Nam));
 501                      Set_Directly_Designated_Type (Acc_Type, It.Nam);
 502                      Add_One_Interp (N, Acc_Type, Acc_Type);
 503                      Freeze_Before (N, Acc_Type);
 504                   end if;
 505
 506                   Get_Next_Interp (Index, It);
 507                end loop;
 508             end if;
 509
 510             --  Cannot be applied to intrinsic. Looking at the tests above,
 511             --  the only way Etype (N) can still be set to Any_Type is if
 512             --  Is_Intrinsic_Subprogram was True for some referenced entity.
 513
 514             if Etype (N) = Any_Type then
 515                Error_Attr_P ("prefix of % attribute cannot be intrinsic");
 516             end if;
 517          end Build_Access_Subprogram_Type;
 518
 519          ----------------------
 520          -- OK_Self_Reference --
 521          ----------------------
 522
 523          function OK_Self_Reference return Boolean is
 524             Par : Node_Id;
 525
 526          begin
 527             Par := Parent (N);
 528             while Present (Par)
 529               and then
 530                (Nkind (Par) = N_Component_Association
 531                  or else Nkind (Par) in N_Subexpr)
 532             loop
 533                if Nkind_In (Par, N_Aggregate, N_Extension_Aggregate) then
 534                   if Etype (Par) = Typ then
 535                      Set_Has_Self_Reference (Par);
 536                      return True;
 537                   end if;
 538                end if;
 539
 540                Par := Parent (Par);
 541             end loop;
 542
 543             --  No enclosing aggregate, or not a self-reference
 544
 545             return False;
 546          end OK_Self_Reference;
 547
 548       --  Start of processing for Analyze_Access_Attribute
 549
 550       begin
 551          Check_E0;
 552
 553          if Nkind (P) = N_Character_Literal then
 554             Error_Attr_P
 555               ("prefix of % attribute cannot be enumeration literal");
 556          end if;
 557
 558          --  Case of access to subprogram
 559
 560          if Is_Entity_Name (P)
 561            and then Is_Overloadable (Entity (P))
 562          then
 563             if Has_Pragma_Inline_Always (Entity (P)) then
 564                Error_Attr_P
 565                  ("prefix of % attribute cannot be Inline_Always subprogram");
 566             end if;
 567
 568             if Aname = Name_Unchecked_Access then
 569                Error_Attr ("attribute% cannot be applied to a subprogram", P);
 570             end if;
 571
 572             --  Build the appropriate subprogram type
 573
 574             Build_Access_Subprogram_Type (P);
 575
 576             --  For unrestricted access, kill current values, since this
 577             --  attribute allows a reference to a local subprogram that
 578             --  could modify local variables to be passed out of scope
 579
 580             if Aname = Name_Unrestricted_Access then
 581
 582                --  Do not kill values on nodes initializing dispatch tables
 583                --  slots. The construct Prim_Ptr!(Prim'Unrestricted_Access)
 584                --  is currently generated by the expander only for this
 585                --  purpose. Done to keep the quality of warnings currently
 586                --  generated by the compiler (otherwise any declaration of
 587                --  a tagged type cleans constant indications from its scope).
 588
 589                if Nkind (Parent (N)) = N_Unchecked_Type_Conversion
 590                  and then (Etype (Parent (N)) = RTE (RE_Prim_Ptr)
 591                              or else
 592                            Etype (Parent (N)) = RTE (RE_Size_Ptr))
 593                  and then Is_Dispatching_Operation
 594                             (Directly_Designated_Type (Etype (N)))
 595                then
 596                   null;
 597                else
 598                   Kill_Current_Values;
 599                end if;
 600             end if;
 601
 602             return;
 603
 604          --  Component is an operation of a protected type
 605
 606          elsif Nkind (P) = N_Selected_Component
 607            and then Is_Overloadable (Entity (Selector_Name (P)))
 608          then
 609             if Ekind (Entity (Selector_Name (P))) = E_Entry then
 610                Error_Attr_P ("prefix of % attribute must be subprogram");
 611             end if;
 612
 613             Build_Access_Subprogram_Type (Selector_Name (P));
 614             return;
 615          end if;
 616
 617          --  Deal with incorrect reference to a type, but note that some
 618          --  accesses are allowed: references to the current type instance,
 619          --  or in Ada 2005 self-referential pointer in a default-initialized
 620          --  aggregate.
 621
 622          if Is_Entity_Name (P) then
 623             Typ := Entity (P);
 624
 625             --  The reference may appear in an aggregate that has been expanded
 626             --  into a loop. Locate scope of type definition, if any.
 627
 628             Scop := Current_Scope;
 629             while Ekind (Scop) = E_Loop loop
 630                Scop := Scope (Scop);
 631             end loop;
 632
 633             if Is_Type (Typ) then
 634
 635                --  OK if we are within the scope of a limited type
 636                --  let's mark the component as having per object constraint
 637
 638                if Is_Anonymous_Tagged_Base (Scop, Typ) then
 639                   Typ := Scop;
 640                   Set_Entity (P, Typ);
 641                   Set_Etype  (P, Typ);
 642                end if;
 643
 644                if Typ = Scop then
 645                   declare
 646                      Q : Node_Id := Parent (N);
 647
 648                   begin
 649                      while Present (Q)
 650                        and then Nkind (Q) /= N_Component_Declaration
 651                      loop
 652                         Q := Parent (Q);
 653                      end loop;
 654
 655                      if Present (Q) then
 656                         Set_Has_Per_Object_Constraint (
 657                           Defining_Identifier (Q), True);
 658                      end if;
 659                   end;
 660
 661                   if Nkind (P) = N_Expanded_Name then
 662                      Error_Msg_F
 663                        ("current instance prefix must be a direct name", P);
 664                   end if;
 665
 666                   --  If a current instance attribute appears in a component
 667                   --  constraint it must appear alone; other contexts (spec-
 668                   --  expressions, within a task body) are not subject to this
 669                   --  restriction.
 670
 671                   if not In_Spec_Expression
 672                     and then not Has_Completion (Scop)
 673                     and then not
 674                       Nkind_In (Parent (N), N_Discriminant_Association,
 675                                             N_Index_Or_Discriminant_Constraint)
 676                   then
 677                      Error_Msg_N
 678                        ("current instance attribute must appear alone", N);
 679                   end if;
 680
 681                --  OK if we are in initialization procedure for the type
 682                --  in question, in which case the reference to the type
 683                --  is rewritten as a reference to the current object.
 684
 685                elsif Ekind (Scop) = E_Procedure
 686                  and then Is_Init_Proc (Scop)
 687                  and then Etype (First_Formal (Scop)) = Typ
 688                then
 689                   Rewrite (N,
 690                     Make_Attribute_Reference (Loc,
 691                       Prefix         => Make_Identifier (Loc, Name_uInit),
 692                       Attribute_Name => Name_Unrestricted_Access));
 693                   Analyze (N);
 694                   return;
 695
 696                --  OK if a task type, this test needs sharpening up ???
 697
 698                elsif Is_Task_Type (Typ) then
 699                   null;
 700
 701                --  OK if self-reference in an aggregate in Ada 2005, and
 702                --  the reference comes from a copied default expression.
 703
 704                --  Note that we check legality of self-reference even if the
 705                --  expression comes from source, e.g. when a single component
 706                --  association in an aggregate has a box association.
 707
 708                elsif Ada_Version >= Ada_05
 709                  and then OK_Self_Reference
 710                then
 711                   null;
 712
 713                --  Otherwise we have an error case
 714
 715                else
 716                   Error_Attr ("% attribute cannot be applied to type", P);
 717                   return;
 718                end if;
 719             end if;
 720          end if;
 721
 722          --  If we fall through, we have a normal access to object case.
 723          --  Unrestricted_Access is legal wherever an allocator would be
 724          --  legal, so its Etype is set to E_Allocator. The expected type
 725          --  of the other attributes is a general access type, and therefore
 726          --  we label them with E_Access_Attribute_Type.
 727
 728          if not Is_Overloaded (P) then
 729             Acc_Type := Build_Access_Object_Type (P_Type);
 730             Set_Etype (N, Acc_Type);
 731          else
 732             declare
 733                Index : Interp_Index;
 734                It    : Interp;
 735             begin
 736                Set_Etype (N, Any_Type);
 737                Get_First_Interp (P, Index, It);
 738                while Present (It.Typ) loop
 739                   Acc_Type := Build_Access_Object_Type (It.Typ);
 740                   Add_One_Interp (N, Acc_Type, Acc_Type);
 741                   Get_Next_Interp (Index, It);
 742                end loop;
 743             end;
 744          end if;
 745
 746          --  Special cases when we can find a prefix that is an entity name
 747
 748          declare
 749             PP  : Node_Id;
 750             Ent : Entity_Id;
 751
 752          begin
 753             PP := P;
 754             loop
 755                if Is_Entity_Name (PP) then
 756                   Ent := Entity (PP);
 757
 758                   --  If we have an access to an object, and the attribute
 759                   --  comes from source, then set the object as potentially
 760                   --  source modified. We do this because the resulting access
 761                   --  pointer can be used to modify the variable, and we might
 762                   --  not detect this, leading to some junk warnings.
 763
 764                   Set_Never_Set_In_Source (Ent, False);
 765
 766                   --  Mark entity as address taken, and kill current values
 767
 768                   Set_Address_Taken (Ent);
 769                   Kill_Current_Values (Ent);
 770                   exit;
 771
 772                elsif Nkind_In (PP, N_Selected_Component,
 773                                    N_Indexed_Component)
 774                then
 775                   PP := Prefix (PP);
 776
 777                else
 778                   exit;
 779                end if;
 780             end loop;
 781          end;
 782
 783          --  Check for aliased view unless unrestricted case. We allow a
 784          --  nonaliased prefix when within an instance because the prefix may
 785          --  have been a tagged formal object, which is defined to be aliased
 786          --  even when the actual might not be (other instance cases will have
 787          --  been caught in the generic). Similarly, within an inlined body we
 788          --  know that the attribute is legal in the original subprogram, and
 789          --  therefore legal in the expansion.
 790
 791          if Aname /= Name_Unrestricted_Access
 792            and then not Is_Aliased_View (P)
 793            and then not In_Instance
 794            and then not In_Inlined_Body
 795          then
 796             Error_Attr_P ("prefix of % attribute must be aliased");
 797          end if;
 798       end Analyze_Access_Attribute;
 799
 800       --------------------------------
 801       -- Check_Array_Or_Scalar_Type --
 802       --------------------------------
 803
 804       procedure Check_Array_Or_Scalar_Type is
 805          Index : Entity_Id;
 806
 807          D : Int;
 808          --  Dimension number for array attributes
 809
 810       begin
 811          --  Case of string literal or string literal subtype. These cases
 812          --  cannot arise from legal Ada code, but the expander is allowed
 813          --  to generate them. They require special handling because string
 814          --  literal subtypes do not have standard bounds (the whole idea
 815          --  of these subtypes is to avoid having to generate the bounds)
 816
 817          if Ekind (P_Type) = E_String_Literal_Subtype then
 818             Set_Etype (N, Etype (First_Index (P_Base_Type)));
 819             return;
 820
 821          --  Scalar types
 822
 823          elsif Is_Scalar_Type (P_Type) then
 824             Check_Type;
 825
 826             if Present (E1) then
 827                Error_Attr ("invalid argument in % attribute", E1);
 828             else
 829                Set_Etype (N, P_Base_Type);
 830                return;
 831             end if;
 832
 833          --  The following is a special test to allow 'First to apply to
 834          --  private scalar types if the attribute comes from generated
 835          --  code. This occurs in the case of Normalize_Scalars code.
 836
 837          elsif Is_Private_Type (P_Type)
 838            and then Present (Full_View (P_Type))
 839            and then Is_Scalar_Type (Full_View (P_Type))
 840            and then not Comes_From_Source (N)
 841          then
 842             Set_Etype (N, Implementation_Base_Type (P_Type));
 843
 844          --  Array types other than string literal subtypes handled above
 845
 846          else
 847             Check_Array_Type;
 848
 849             --  We know prefix is an array type, or the name of an array
 850             --  object, and that the expression, if present, is static
 851             --  and within the range of the dimensions of the type.
 852
 853             pragma Assert (Is_Array_Type (P_Type));
 854             Index := First_Index (P_Base_Type);
 855
 856             if No (E1) then
 857
 858                --  First dimension assumed
 859
 860                Set_Etype (N, Base_Type (Etype (Index)));
 861
 862             else
 863                D := UI_To_Int (Intval (E1));
 864
 865                for J in 1 .. D - 1 loop
 866                   Next_Index (Index);
 867                end loop;
 868
 869                Set_Etype (N, Base_Type (Etype (Index)));
 870                Set_Etype (E1, Standard_Integer);
 871             end if;
 872          end if;
 873       end Check_Array_Or_Scalar_Type;
 874
 875       ----------------------
 876       -- Check_Array_Type --
 877       ----------------------
 878
 879       procedure Check_Array_Type is
 880          D : Int;
 881          --  Dimension number for array attributes
 882
 883       begin
 884          --  If the type is a string literal type, then this must be generated
 885          --  internally, and no further check is required on its legality.
 886
 887          if Ekind (P_Type) = E_String_Literal_Subtype then
 888             return;
 889
 890          --  If the type is a composite, it is an illegal aggregate, no point
 891          --  in going on.
 892
 893          elsif P_Type = Any_Composite then
 894             raise Bad_Attribute;
 895          end if;
 896
 897          --  Normal case of array type or subtype
 898
 899          Check_Either_E0_Or_E1;
 900          Check_Dereference;
 901
 902          if Is_Array_Type (P_Type) then
 903             if not Is_Constrained (P_Type)
 904               and then Is_Entity_Name (P)
 905               and then Is_Type (Entity (P))
 906             then
 907                --  Note: we do not call Error_Attr here, since we prefer to
 908                --  continue, using the relevant index type of the array,
 909                --  even though it is unconstrained. This gives better error
 910                --  recovery behavior.
 911
 912                Error_Msg_Name_1 := Aname;
 913                Error_Msg_F
 914                  ("prefix for % attribute must be constrained array", P);
 915             end if;
 916
 917             D := Number_Dimensions (P_Type);
 918
 919          else
 920             if Is_Private_Type (P_Type) then
 921                Error_Attr_P ("prefix for % attribute may not be private type");
 922
 923             elsif Is_Access_Type (P_Type)
 924               and then Is_Array_Type (Designated_Type (P_Type))
 925               and then Is_Entity_Name (P)
 926               and then Is_Type (Entity (P))
 927             then
 928                Error_Attr_P ("prefix of % attribute cannot be access type");
 929
 930             elsif Attr_Id = Attribute_First
 931                     or else
 932                   Attr_Id = Attribute_Last
 933             then
 934                Error_Attr ("invalid prefix for % attribute", P);
 935
 936             else
 937                Error_Attr_P ("prefix for % attribute must be array");
 938             end if;
 939          end if;
 940
 941          if Present (E1) then
 942             Resolve (E1, Any_Integer);
 943             Set_Etype (E1, Standard_Integer);
 944
 945             if not Is_Static_Expression (E1)
 946               or else Raises_Constraint_Error (E1)
 947             then
 948                Flag_Non_Static_Expr
 949                  ("expression for dimension must be static!", E1);
 950                Error_Attr;
 951
 952             elsif  UI_To_Int (Expr_Value (E1)) > D
 953               or else UI_To_Int (Expr_Value (E1)) < 1
 954             then
 955                Error_Attr ("invalid dimension number for array type", E1);
 956             end if;
 957          end if;
 958
 959          if (Style_Check and Style_Check_Array_Attribute_Index)
 960            and then Comes_From_Source (N)
 961          then
 962             Style.Check_Array_Attribute_Index (N, E1, D);
 963          end if;
 964       end Check_Array_Type;
 965
 966       -------------------------
 967       -- Check_Asm_Attribute --
 968       -------------------------
 969
 970       procedure Check_Asm_Attribute is
 971       begin
 972          Check_Type;
 973          Check_E2;
 974
 975          --  Check first argument is static string expression
 976
 977          Analyze_And_Resolve (E1, Standard_String);
 978
 979          if Etype (E1) = Any_Type then
 980             return;
 981
 982          elsif not Is_OK_Static_Expression (E1) then
 983             Flag_Non_Static_Expr
 984               ("constraint argument must be static string expression!", E1);
 985             Error_Attr;
 986          end if;
 987
 988          --  Check second argument is right type
 989
 990          Analyze_And_Resolve (E2, Entity (P));
 991
 992          --  Note: that is all we need to do, we don't need to check
 993          --  that it appears in a correct context. The Ada type system
 994          --  will do that for us.
 995
 996       end Check_Asm_Attribute;
 997
 998       ---------------------
 999       -- Check_Component --
1000       ---------------------
1001
1002       procedure Check_Component is
1003       begin
1004          Check_E0;
1005
1006          if Nkind (P) /= N_Selected_Component
1007            or else
1008              (Ekind (Entity (Selector_Name (P))) /= E_Component
1009                and then
1010               Ekind (Entity (Selector_Name (P))) /= E_Discriminant)
1011          then
1012             Error_Attr_P ("prefix for % attribute must be selected component");
1013          end if;
1014       end Check_Component;
1015
1016       ------------------------------------
1017       -- Check_Decimal_Fixed_Point_Type --
1018       ------------------------------------
1019
1020       procedure Check_Decimal_Fixed_Point_Type is
1021       begin
1022          Check_Type;
1023
1024          if not Is_Decimal_Fixed_Point_Type (P_Type) then
1025             Error_Attr_P ("prefix of % attribute must be decimal type");
1026          end if;
1027       end Check_Decimal_Fixed_Point_Type;
1028
1029       -----------------------
1030       -- Check_Dereference --
1031       -----------------------
1032
1033       procedure Check_Dereference is
1034       begin
1035
1036          --  Case of a subtype mark
1037
1038          if Is_Entity_Name (P)
1039            and then Is_Type (Entity (P))
1040          then
1041             return;
1042          end if;
1043
1044          --  Case of an expression
1045
1046          Resolve (P);
1047
1048          if Is_Access_Type (P_Type) then
1049
1050             --  If there is an implicit dereference, then we must freeze
1051             --  the designated type of the access type, since the type of
1052             --  the referenced array is this type (see AI95-00106).
1053
1054             Freeze_Before (N, Designated_Type (P_Type));
1055
1056             Rewrite (P,
1057               Make_Explicit_Dereference (Sloc (P),
1058                 Prefix => Relocate_Node (P)));
1059
1060             Analyze_And_Resolve (P);
1061             P_Type := Etype (P);
1062
1063             if P_Type = Any_Type then
1064                raise Bad_Attribute;
1065             end if;
1066
1067             P_Base_Type := Base_Type (P_Type);
1068          end if;
1069       end Check_Dereference;
1070
1071       -------------------------
1072       -- Check_Discrete_Type --
1073       -------------------------
1074
1075       procedure Check_Discrete_Type is
1076       begin
1077          Check_Type;
1078
1079          if not Is_Discrete_Type (P_Type) then
1080             Error_Attr_P ("prefix of % attribute must be discrete type");
1081          end if;
1082       end Check_Discrete_Type;
1083
1084       --------------
1085       -- Check_E0 --
1086       --------------
1087
1088       procedure Check_E0 is
1089       begin
1090          if Present (E1) then
1091             Unexpected_Argument (E1);
1092          end if;
1093       end Check_E0;
1094
1095       --------------
1096       -- Check_E1 --
1097       --------------
1098
1099       procedure Check_E1 is
1100       begin
1101          Check_Either_E0_Or_E1;
1102
1103          if No (E1) then
1104
1105             --  Special-case attributes that are functions and that appear as
1106             --  the prefix of another attribute. Error is posted on parent.
1107
1108             if Nkind (Parent (N)) = N_Attribute_Reference
1109               and then (Attribute_Name (Parent (N)) = Name_Address
1110                           or else
1111                         Attribute_Name (Parent (N)) = Name_Code_Address
1112                           or else
1113                         Attribute_Name (Parent (N)) = Name_Access)
1114             then
1115                Error_Msg_Name_1 := Attribute_Name (Parent (N));
1116                Error_Msg_N ("illegal prefix for % attribute", Parent (N));
1117                Set_Etype (Parent (N), Any_Type);
1118                Set_Entity (Parent (N), Any_Type);
1119                raise Bad_Attribute;
1120
1121             else
1122                Error_Attr ("missing argument for % attribute", N);
1123             end if;
1124          end if;
1125       end Check_E1;
1126
1127       --------------
1128       -- Check_E2 --
1129       --------------
1130
1131       procedure Check_E2 is
1132       begin
1133          if No (E1) then
1134             Error_Attr ("missing arguments for % attribute (2 required)", N);
1135          elsif No (E2) then
1136             Error_Attr ("missing argument for % attribute (2 required)", N);
1137          end if;
1138       end Check_E2;
1139
1140       ---------------------------
1141       -- Check_Either_E0_Or_E1 --
1142       ---------------------------
1143
1144       procedure Check_Either_E0_Or_E1 is
1145       begin
1146          if Present (E2) then
1147             Unexpected_Argument (E2);
1148          end if;
1149       end Check_Either_E0_Or_E1;
1150
1151       ----------------------
1152       -- Check_Enum_Image --
1153       ----------------------
1154
1155       procedure Check_Enum_Image is
1156          Lit : Entity_Id;
1157       begin
1158          if Is_Enumeration_Type (P_Base_Type) then
1159             Lit := First_Literal (P_Base_Type);
1160             while Present (Lit) loop
1161                Set_Referenced (Lit);
1162                Next_Literal (Lit);
1163             end loop;
1164          end if;
1165       end Check_Enum_Image;
1166
1167       ----------------------------
1168       -- Check_Fixed_Point_Type --
1169       ----------------------------
1170
1171       procedure Check_Fixed_Point_Type is
1172       begin
1173          Check_Type;
1174
1175          if not Is_Fixed_Point_Type (P_Type) then
1176             Error_Attr_P ("prefix of % attribute must be fixed point type");
1177          end if;
1178       end Check_Fixed_Point_Type;
1179
1180       ------------------------------
1181       -- Check_Fixed_Point_Type_0 --
1182       ------------------------------
1183
1184       procedure Check_Fixed_Point_Type_0 is
1185       begin
1186          Check_Fixed_Point_Type;
1187          Check_E0;
1188       end Check_Fixed_Point_Type_0;
1189
1190       -------------------------------
1191       -- Check_Floating_Point_Type --
1192       -------------------------------
1193
1194       procedure Check_Floating_Point_Type is
1195       begin
1196          Check_Type;
1197
1198          if not Is_Floating_Point_Type (P_Type) then
1199             Error_Attr_P ("prefix of % attribute must be float type");
1200          end if;
1201       end Check_Floating_Point_Type;
1202
1203       ---------------------------------
1204       -- Check_Floating_Point_Type_0 --
1205       ---------------------------------
1206
1207       procedure Check_Floating_Point_Type_0 is
1208       begin
1209          Check_Floating_Point_Type;
1210          Check_E0;
1211       end Check_Floating_Point_Type_0;
1212
1213       ---------------------------------
1214       -- Check_Floating_Point_Type_1 --
1215       ---------------------------------
1216
1217       procedure Check_Floating_Point_Type_1 is
1218       begin
1219          Check_Floating_Point_Type;
1220          Check_E1;
1221       end Check_Floating_Point_Type_1;
1222
1223       ---------------------------------
1224       -- Check_Floating_Point_Type_2 --
1225       ---------------------------------
1226
1227       procedure Check_Floating_Point_Type_2 is
1228       begin
1229          Check_Floating_Point_Type;
1230          Check_E2;
1231       end Check_Floating_Point_Type_2;
1232
1233       ------------------------
1234       -- Check_Integer_Type --
1235       ------------------------
1236
1237       procedure Check_Integer_Type is
1238       begin
1239          Check_Type;
1240
1241          if not Is_Integer_Type (P_Type) then
1242             Error_Attr_P ("prefix of % attribute must be integer type");
1243          end if;
1244       end Check_Integer_Type;
1245
1246       ------------------------
1247       -- Check_Library_Unit --
1248       ------------------------
1249
1250       procedure Check_Library_Unit is
1251       begin
1252          if not Is_Compilation_Unit (Entity (P)) then
1253             Error_Attr_P ("prefix of % attribute must be library unit");
1254          end if;
1255       end Check_Library_Unit;
1256
1257       --------------------------------
1258       -- Check_Modular_Integer_Type --
1259       --------------------------------
1260
1261       procedure Check_Modular_Integer_Type is
1262       begin
1263          Check_Type;
1264
1265          if not Is_Modular_Integer_Type (P_Type) then
1266             Error_Attr_P
1267               ("prefix of % attribute must be modular integer type");
1268          end if;
1269       end Check_Modular_Integer_Type;
1270
1271       ------------------------
1272       -- Check_Not_CPP_Type --
1273       ------------------------
1274
1275       procedure Check_Not_CPP_Type is
1276       begin
1277          if Is_Tagged_Type (Etype (P))
1278            and then Convention (Etype (P)) = Convention_CPP
1279            and then Is_CPP_Class (Root_Type (Etype (P)))
1280          then
1281             Error_Attr_P
1282               ("invalid use of % attribute with 'C'P'P tagged type");
1283          end if;
1284       end Check_Not_CPP_Type;
1285
1286       -------------------------------
1287       -- Check_Not_Incomplete_Type --
1288       -------------------------------
1289
1290       procedure Check_Not_Incomplete_Type is
1291          E   : Entity_Id;
1292          Typ : Entity_Id;
1293
1294       begin
1295          --  Ada 2005 (AI-50217, AI-326): If the prefix is an explicit
1296          --  dereference we have to check wrong uses of incomplete types
1297          --  (other wrong uses are checked at their freezing point).
1298
1299          --  Example 1: Limited-with
1300
1301          --    limited with Pkg;
1302          --    package P is
1303          --       type Acc is access Pkg.T;
1304          --       X : Acc;
1305          --       S : Integer := X.all'Size;                    -- ERROR
1306          --    end P;
1307
1308          --  Example 2: Tagged incomplete
1309
1310          --     type T is tagged;
1311          --     type Acc is access all T;
1312          --     X : Acc;
1313          --     S : constant Integer := X.all'Size;             -- ERROR
1314          --     procedure Q (Obj : Integer := X.all'Alignment); -- ERROR
1315
1316          if Ada_Version >= Ada_05
1317            and then Nkind (P) = N_Explicit_Dereference
1318          then
1319             E := P;
1320             while Nkind (E) = N_Explicit_Dereference loop
1321                E := Prefix (E);
1322             end loop;
1323
1324             if From_With_Type (Etype (E)) then
1325                Error_Attr_P
1326                  ("prefix of % attribute cannot be an incomplete type");
1327
1328             else
1329                if Is_Access_Type (Etype (E)) then
1330                   Typ := Directly_Designated_Type (Etype (E));
1331                else
1332                   Typ := Etype (E);
1333                end if;
1334
1335                if Ekind (Typ) = E_Incomplete_Type
1336                  and then No (Full_View (Typ))
1337                then
1338                   Error_Attr_P
1339                     ("prefix of % attribute cannot be an incomplete type");
1340                end if;
1341             end if;
1342          end if;
1343
1344          if not Is_Entity_Name (P)
1345            or else not Is_Type (Entity (P))
1346            or else In_Spec_Expression
1347          then
1348             return;
1349          else
1350             Check_Fully_Declared (P_Type, P);
1351          end if;
1352       end Check_Not_Incomplete_Type;
1353
1354       ----------------------------
1355       -- Check_Object_Reference --
1356       ----------------------------
1357
1358       procedure Check_Object_Reference (P : Node_Id) is
1359          Rtyp : Entity_Id;
1360
1361       begin
1362          --  If we need an object, and we have a prefix that is the name of
1363          --  a function entity, convert it into a function call.
1364
1365          if Is_Entity_Name (P)
1366            and then Ekind (Entity (P)) = E_Function
1367          then
1368             Rtyp := Etype (Entity (P));
1369
1370             Rewrite (P,
1371               Make_Function_Call (Sloc (P),
1372                 Name => Relocate_Node (P)));
1373
1374             Analyze_And_Resolve (P, Rtyp);
1375
1376          --  Otherwise we must have an object reference
1377
1378          elsif not Is_Object_Reference (P) then
1379             Error_Attr_P ("prefix of % attribute must be object");
1380          end if;
1381       end Check_Object_Reference;
1382
1383       ------------------------
1384       -- Check_Program_Unit --
1385       ------------------------
1386
1387       procedure Check_Program_Unit is
1388       begin
1389          if Is_Entity_Name (P) then
1390             declare
1391                K : constant Entity_Kind := Ekind (Entity (P));
1392                T : constant Entity_Id   := Etype (Entity (P));
1393
1394             begin
1395                if K in Subprogram_Kind
1396                  or else K in Task_Kind
1397                  or else K in Protected_Kind
1398                  or else K = E_Package
1399                  or else K in Generic_Unit_Kind
1400                  or else (K = E_Variable
1401                             and then
1402                               (Is_Task_Type (T)
1403                                  or else
1404                                Is_Protected_Type (T)))
1405                then
1406                   return;
1407                end if;
1408             end;
1409          end if;
1410
1411          Error_Attr_P ("prefix of % attribute must be program unit");
1412       end Check_Program_Unit;
1413
1414       ---------------------
1415       -- Check_Real_Type --
1416       ---------------------
1417
1418       procedure Check_Real_Type is
1419       begin
1420          Check_Type;
1421
1422          if not Is_Real_Type (P_Type) then
1423             Error_Attr_P ("prefix of % attribute must be real type");
1424          end if;
1425       end Check_Real_Type;
1426
1427       -----------------------
1428       -- Check_Scalar_Type --
1429       -----------------------
1430
1431       procedure Check_Scalar_Type is
1432       begin
1433          Check_Type;
1434
1435          if not Is_Scalar_Type (P_Type) then
1436             Error_Attr_P ("prefix of % attribute must be scalar type");
1437          end if;
1438       end Check_Scalar_Type;
1439
1440       ---------------------------
1441       -- Check_Standard_Prefix --
1442       ---------------------------
1443
1444       procedure Check_Standard_Prefix is
1445       begin
1446          Check_E0;
1447
1448          if Nkind (P) /= N_Identifier
1449            or else Chars (P) /= Name_Standard
1450          then
1451             Error_Attr ("only allowed prefix for % attribute is Standard", P);
1452          end if;
1453       end Check_Standard_Prefix;
1454
1455       ----------------------------
1456       -- Check_Stream_Attribute --
1457       ----------------------------
1458
1459       procedure Check_Stream_Attribute (Nam : TSS_Name_Type) is
1460          Etyp : Entity_Id;
1461          Btyp : Entity_Id;
1462
1463          In_Shared_Var_Procs : Boolean;
1464          --  True when compiling the body of System.Shared_Storage.
1465          --  Shared_Var_Procs. For this runtime package (always compiled in
1466          --  GNAT mode), we allow stream attributes references for limited
1467          --  types for the case where shared passive objects are implemented
1468          --  using stream attributes, which is the default in GNAT's persistent
1469          --  storage implementation.
1470
1471       begin
1472          Validate_Non_Static_Attribute_Function_Call;
1473
1474          --  With the exception of 'Input, Stream attributes are procedures,
1475          --  and can only appear at the position of procedure calls. We check
1476          --  for this here, before they are rewritten, to give a more precise
1477          --  diagnostic.
1478
1479          if Nam = TSS_Stream_Input then
1480             null;
1481
1482          elsif Is_List_Member (N)
1483            and then not Nkind_In (Parent (N), N_Procedure_Call_Statement,
1484                                               N_Aggregate)
1485          then
1486             null;
1487
1488          else
1489             Error_Attr
1490               ("invalid context for attribute%, which is a procedure", N);
1491          end if;
1492
1493          Check_Type;
1494          Btyp := Implementation_Base_Type (P_Type);
1495
1496          --  Stream attributes not allowed on limited types unless the
1497          --  attribute reference was generated by the expander (in which
1498          --  case the underlying type will be used, as described in Sinfo),
1499          --  or the attribute was specified explicitly for the type itself
1500          --  or one of its ancestors (taking visibility rules into account if
1501          --  in Ada 2005 mode), or a pragma Stream_Convert applies to Btyp
1502          --  (with no visibility restriction).
1503
1504          declare
1505             Gen_Body : constant Node_Id := Enclosing_Generic_Body (N);
1506          begin
1507             if Present (Gen_Body) then
1508                In_Shared_Var_Procs :=
1509                  Is_RTE (Corresponding_Spec (Gen_Body), RE_Shared_Var_Procs);
1510             else
1511                In_Shared_Var_Procs := False;
1512             end if;
1513          end;
1514
1515          if (Comes_From_Source (N)
1516               and then not (In_Shared_Var_Procs or In_Instance))
1517            and then not Stream_Attribute_Available (P_Type, Nam)
1518            and then not Has_Rep_Pragma (Btyp, Name_Stream_Convert)
1519          then
1520             Error_Msg_Name_1 := Aname;
1521
1522             if Is_Limited_Type (P_Type) then
1523                Error_Msg_NE
1524                  ("limited type& has no% attribute", P, P_Type);
1525                Explain_Limited_Type (P_Type, P);
1526             else
1527                Error_Msg_NE
1528                  ("attribute% for type& is not available", P, P_Type);
1529             end if;
1530          end if;
1531
1532          --  Check for violation of restriction No_Stream_Attributes
1533
1534          if Is_RTE (P_Type, RE_Exception_Id)
1535               or else
1536             Is_RTE (P_Type, RE_Exception_Occurrence)
1537          then
1538             Check_Restriction (No_Exception_Registration, P);
1539          end if;
1540
1541          --  Here we must check that the first argument is an access type
1542          --  that is compatible with Ada.Streams.Root_Stream_Type'Class.
1543
1544          Analyze_And_Resolve (E1);
1545          Etyp := Etype (E1);
1546
1547          --  Note: the double call to Root_Type here is needed because the
1548          --  root type of a class-wide type is the corresponding type (e.g.
1549          --  X for X'Class, and we really want to go to the root.)
1550
1551          if not Is_Access_Type (Etyp)
1552            or else Root_Type (Root_Type (Designated_Type (Etyp))) /=
1553                      RTE (RE_Root_Stream_Type)
1554          then
1555             Error_Attr
1556               ("expected access to Ada.Streams.Root_Stream_Type''Class", E1);
1557          end if;
1558
1559          --  Check that the second argument is of the right type if there is
1560          --  one (the Input attribute has only one argument so this is skipped)
1561
1562          if Present (E2) then
1563             Analyze (E2);
1564
1565             if Nam = TSS_Stream_Read
1566               and then not Is_OK_Variable_For_Out_Formal (E2)
1567             then
1568                Error_Attr
1569                  ("second argument of % attribute must be a variable", E2);
1570             end if;
1571
1572             Resolve (E2, P_Type);
1573          end if;
1574
1575          Check_Not_CPP_Type;
1576       end Check_Stream_Attribute;
1577
1578       -----------------------
1579       -- Check_Task_Prefix --
1580       -----------------------
1581
1582       procedure Check_Task_Prefix is
1583       begin
1584          Analyze (P);
1585
1586          --  Ada 2005 (AI-345): Attribute 'Terminated can be applied to
1587          --  task interface class-wide types.
1588
1589          if Is_Task_Type (Etype (P))
1590            or else (Is_Access_Type (Etype (P))
1591                       and then Is_Task_Type (Designated_Type (Etype (P))))
1592            or else (Ada_Version >= Ada_05
1593                       and then Ekind (Etype (P)) = E_Class_Wide_Type
1594                       and then Is_Interface (Etype (P))
1595                       and then Is_Task_Interface (Etype (P)))
1596          then
1597             Resolve (P);
1598
1599          else
1600             if Ada_Version >= Ada_05 then
1601                Error_Attr_P
1602                  ("prefix of % attribute must be a task or a task " &
1603                   "interface class-wide object");
1604
1605             else
1606                Error_Attr_P ("prefix of % attribute must be a task");
1607             end if;
1608          end if;
1609       end Check_Task_Prefix;
1610
1611       ----------------
1612       -- Check_Type --
1613       ----------------
1614
1615       --  The possibilities are an entity name denoting a type, or an
1616       --  attribute reference that denotes a type (Base or Class). If
1617       --  the type is incomplete, replace it with its full view.
1618
1619       procedure Check_Type is
1620       begin
1621          if not Is_Entity_Name (P)
1622            or else not Is_Type (Entity (P))
1623          then
1624             Error_Attr_P ("prefix of % attribute must be a type");
1625
1626          elsif Ekind (Entity (P)) = E_Incomplete_Type
1627             and then Present (Full_View (Entity (P)))
1628          then
1629             P_Type := Full_View (Entity (P));
1630             Set_Entity (P, P_Type);
1631          end if;
1632       end Check_Type;
1633
1634       ---------------------
1635       -- Check_Unit_Name --
1636       ---------------------
1637
1638       procedure Check_Unit_Name (Nod : Node_Id) is
1639       begin
1640          if Nkind (Nod) = N_Identifier then
1641             return;
1642
1643          elsif Nkind (Nod) = N_Selected_Component then
1644             Check_Unit_Name (Prefix (Nod));
1645
1646             if Nkind (Selector_Name (Nod)) = N_Identifier then
1647                return;
1648             end if;
1649          end if;
1650
1651          Error_Attr ("argument for % attribute must be unit name", P);
1652       end Check_Unit_Name;
1653
1654       ----------------
1655       -- Error_Attr --
1656       ----------------
1657
1658       procedure Error_Attr is
1659       begin
1660          Set_Etype (N, Any_Type);
1661          Set_Entity (N, Any_Type);
1662          raise Bad_Attribute;
1663       end Error_Attr;
1664
1665       procedure Error_Attr (Msg : String; Error_Node : Node_Id) is
1666       begin
1667          Error_Msg_Name_1 := Aname;
1668          Error_Msg_N (Msg, Error_Node);
1669          Error_Attr;
1670       end Error_Attr;
1671
1672       ------------------
1673       -- Error_Attr_P --
1674       ------------------
1675
1676       procedure Error_Attr_P (Msg : String) is
1677       begin
1678          Error_Msg_Name_1 := Aname;
1679          Error_Msg_F (Msg, P);
1680          Error_Attr;
1681       end Error_Attr_P;
1682
1683       ----------------------------
1684       -- Legal_Formal_Attribute --
1685       ----------------------------
1686
1687       procedure Legal_Formal_Attribute is
1688       begin
1689          Check_E0;
1690
1691          if not Is_Entity_Name (P)
1692            or else not Is_Type (Entity (P))
1693          then
1694             Error_Attr_P ("prefix of % attribute must be generic type");
1695
1696          elsif Is_Generic_Actual_Type (Entity (P))
1697            or else In_Instance
1698            or else In_Inlined_Body
1699          then
1700             null;
1701
1702          elsif Is_Generic_Type (Entity (P)) then
1703             if not Is_Indefinite_Subtype (Entity (P)) then
1704                Error_Attr_P
1705                  ("prefix of % attribute must be indefinite generic type");
1706             end if;
1707
1708          else
1709             Error_Attr_P
1710               ("prefix of % attribute must be indefinite generic type");
1711          end if;
1712
1713          Set_Etype (N, Standard_Boolean);
1714       end Legal_Formal_Attribute;
1715
1716       ------------------------
1717       -- Standard_Attribute --
1718       ------------------------
1719
1720       procedure Standard_Attribute (Val : Int) is
1721       begin
1722          Check_Standard_Prefix;
1723          Rewrite (N, Make_Integer_Literal (Loc, Val));
1724          Analyze (N);
1725       end Standard_Attribute;
1726
1727       -------------------------
1728       -- Unexpected Argument --
1729       -------------------------
1730
1731       procedure Unexpected_Argument (En : Node_Id) is
1732       begin
1733          Error_Attr ("unexpected argument for % attribute", En);
1734       end Unexpected_Argument;
1735
1736       -------------------------------------------------
1737       -- Validate_Non_Static_Attribute_Function_Call --
1738       -------------------------------------------------
1739
1740       --  This function should be moved to Sem_Dist ???
1741
1742       procedure Validate_Non_Static_Attribute_Function_Call is
1743       begin
1744          if In_Preelaborated_Unit
1745            and then not In_Subprogram_Or_Concurrent_Unit
1746          then
1747             Flag_Non_Static_Expr
1748               ("non-static function call in preelaborated unit!", N);
1749          end if;
1750       end Validate_Non_Static_Attribute_Function_Call;
1751
1752    -----------------------------------------------
1753    -- Start of Processing for Analyze_Attribute --
1754    -----------------------------------------------
1755
1756    begin
1757       --  Immediate return if unrecognized attribute (already diagnosed
1758       --  by parser, so there is nothing more that we need to do)
1759
1760       if not Is_Attribute_Name (Aname) then
1761          raise Bad_Attribute;
1762       end if;
1763
1764       --  Deal with Ada 83 issues
1765
1766       if Comes_From_Source (N) then
1767          if not Attribute_83 (Attr_Id) then
1768             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
1769                Error_Msg_Name_1 := Aname;
1770                Error_Msg_N ("(Ada 83) attribute% is not standard?", N);
1771             end if;
1772
1773             if Attribute_Impl_Def (Attr_Id) then
1774                Check_Restriction (No_Implementation_Attributes, N);
1775             end if;
1776          end if;
1777       end if;
1778
1779       --  Deal with Ada 2005 issues
1780
1781       if Attribute_05 (Attr_Id) and then Ada_Version <= Ada_95 then
1782          Check_Restriction (No_Implementation_Attributes, N);
1783       end if;
1784
1785       --   Remote access to subprogram type access attribute reference needs
1786       --   unanalyzed copy for tree transformation. The analyzed copy is used
1787       --   for its semantic information (whether prefix is a remote subprogram
1788       --   name), the unanalyzed copy is used to construct new subtree rooted
1789       --   with N_Aggregate which represents a fat pointer aggregate.
1790
1791       if Aname = Name_Access then
1792          Discard_Node (Copy_Separate_Tree (N));
1793       end if;
1794
1795       --  Analyze prefix and exit if error in analysis. If the prefix is an
1796       --  incomplete type, use full view if available. Note that there are
1797       --  some attributes for which we do not analyze the prefix, since the
1798       --  prefix is not a normal name.
1799
1800       if Aname /= Name_Elab_Body
1801            and then
1802          Aname /= Name_Elab_Spec
1803            and then
1804          Aname /= Name_UET_Address
1805            and then
1806          Aname /= Name_Enabled
1807       then
1808          Analyze (P);
1809          P_Type := Etype (P);
1810
1811          if Is_Entity_Name (P)
1812            and then Present (Entity (P))
1813            and then Is_Type (Entity (P))
1814          then
1815             if Ekind (Entity (P)) = E_Incomplete_Type then
1816                P_Type := Get_Full_View (P_Type);
1817                Set_Entity (P, P_Type);
1818                Set_Etype  (P, P_Type);
1819
1820             elsif Entity (P) = Current_Scope
1821               and then Is_Record_Type (Entity (P))
1822             then
1823                --  Use of current instance within the type. Verify that if the
1824                --  attribute appears within a constraint, it  yields an access
1825                --  type, other uses are illegal.
1826
1827                declare
1828                   Par : Node_Id;
1829
1830                begin
1831                   Par := Parent (N);
1832                   while Present (Par)
1833                     and then Nkind (Parent (Par)) /= N_Component_Definition
1834                   loop
1835                      Par := Parent (Par);
1836                   end loop;
1837
1838                   if Present (Par)
1839                     and then Nkind (Par) = N_Subtype_Indication
1840                   then
1841                      if Attr_Id /= Attribute_Access
1842                        and then Attr_Id /= Attribute_Unchecked_Access
1843                        and then Attr_Id /= Attribute_Unrestricted_Access
1844                      then
1845                         Error_Msg_N
1846                           ("in a constraint the current instance can only"
1847                              & " be used with an access attribute", N);
1848                      end if;
1849                   end if;
1850                end;
1851             end if;
1852          end if;
1853
1854          if P_Type = Any_Type then
1855             raise Bad_Attribute;
1856          end if;
1857
1858          P_Base_Type := Base_Type (P_Type);
1859       end if;
1860
1861       --  Analyze expressions that may be present, exiting if an error occurs
1862
1863       if No (Exprs) then
1864          E1 := Empty;
1865          E2 := Empty;
1866
1867       else
1868          E1 := First (Exprs);
1869          Analyze (E1);
1870
1871          --  Check for missing/bad expression (result of previous error)
1872
1873          if No (E1) or else Etype (E1) = Any_Type then
1874             raise Bad_Attribute;
1875          end if;
1876
1877          E2 := Next (E1);
1878
1879          if Present (E2) then
1880             Analyze (E2);
1881
1882             if Etype (E2) = Any_Type then
1883                raise Bad_Attribute;
1884             end if;
1885
1886             if Present (Next (E2)) then
1887                Unexpected_Argument (Next (E2));
1888             end if;
1889          end if;
1890       end if;
1891
1892       --  Ada 2005 (AI-345): Ensure that the compiler gives exactly the current
1893       --  output compiling in Ada 95 mode for the case of ambiguous prefixes.
1894
1895       if Ada_Version < Ada_05
1896         and then Is_Overloaded (P)
1897         and then Aname /= Name_Access
1898         and then Aname /= Name_Address
1899         and then Aname /= Name_Code_Address
1900         and then Aname /= Name_Count
1901         and then Aname /= Name_Unchecked_Access
1902       then
1903          Error_Attr ("ambiguous prefix for % attribute", P);
1904
1905       elsif Ada_Version >= Ada_05
1906         and then Is_Overloaded (P)
1907         and then Aname /= Name_Access
1908         and then Aname /= Name_Address
1909         and then Aname /= Name_Code_Address
1910         and then Aname /= Name_Result
1911         and then Aname /= Name_Unchecked_Access
1912       then
1913          --  Ada 2005 (AI-345): Since protected and task types have primitive
1914          --  entry wrappers, the attributes Count, Caller and AST_Entry require
1915          --  a context check
1916
1917          if Aname = Name_Count
1918            or else Aname = Name_Caller
1919            or else Aname = Name_AST_Entry
1920          then
1921             declare
1922                Count : Natural := 0;
1923                I     : Interp_Index;
1924                It    : Interp;
1925
1926             begin
1927                Get_First_Interp (P, I, It);
1928                while Present (It.Nam) loop
1929                   if Comes_From_Source (It.Nam) then
1930                      Count := Count + 1;
1931                   else
1932                      Remove_Interp (I);
1933                   end if;
1934
1935                   Get_Next_Interp (I, It);
1936                end loop;
1937
1938                if Count > 1 then
1939                   Error_Attr ("ambiguous prefix for % attribute", P);
1940                else
1941                   Set_Is_Overloaded (P, False);
1942                end if;
1943             end;
1944
1945          else
1946             Error_Attr ("ambiguous prefix for % attribute", P);
1947          end if;
1948       end if;
1949
1950       --  Remaining processing depends on attribute
1951
1952       case Attr_Id is
1953
1954       ------------------
1955       -- Abort_Signal --
1956       ------------------
1957
1958       when Attribute_Abort_Signal =>
1959          Check_Standard_Prefix;
1960          Rewrite (N,
1961            New_Reference_To (Stand.Abort_Signal, Loc));
1962          Analyze (N);
1963
1964       ------------
1965       -- Access --
1966       ------------
1967
1968       when Attribute_Access =>
1969          Analyze_Access_Attribute;
1970
1971       -------------
1972       -- Address --
1973       -------------
1974
1975       when Attribute_Address =>
1976          Check_E0;
1977
1978          --  Check for some junk cases, where we have to allow the address
1979          --  attribute but it does not make much sense, so at least for now
1980          --  just replace with Null_Address.
1981
1982          --  We also do this if the prefix is a reference to the AST_Entry
1983          --  attribute. If expansion is active, the attribute will be
1984          --  replaced by a function call, and address will work fine and
1985          --  get the proper value, but if expansion is not active, then
1986          --  the check here allows proper semantic analysis of the reference.
1987
1988          --  An Address attribute created by expansion is legal even when it
1989          --  applies to other entity-denoting expressions.
1990
1991          if Is_Entity_Name (P) then
1992             declare
1993                Ent : constant Entity_Id := Entity (P);
1994
1995             begin
1996                if Is_Subprogram (Ent) then
1997                   Set_Address_Taken (Ent);
1998                   Kill_Current_Values (Ent);
1999
2000                   --  An Address attribute is accepted when generated by the
2001                   --  compiler for dispatching operation, and an error is
2002                   --  issued once the subprogram is frozen (to avoid confusing
2003                   --  errors about implicit uses of Address in the dispatch
2004                   --  table initialization).
2005
2006                   if Has_Pragma_Inline_Always (Entity (P))
2007                     and then Comes_From_Source (P)
2008                   then
2009                      Error_Attr_P
2010                        ("prefix of % attribute cannot be Inline_Always" &
2011                         " subprogram");
2012                   end if;
2013
2014                elsif Is_Object (Ent)
2015                  or else Ekind (Ent) = E_Label
2016                then
2017                   Set_Address_Taken (Ent);
2018
2019                --  If we have an address of an object, and the attribute
2020                --  comes from source, then set the object as potentially
2021                --  source modified. We do this because the resulting address
2022                --  can potentially be used to modify the variable and we
2023                --  might not detect this, leading to some junk warnings.
2024
2025                   Set_Never_Set_In_Source (Ent, False);
2026
2027                elsif (Is_Concurrent_Type (Etype (Ent))
2028                        and then Etype (Ent) = Base_Type (Ent))
2029                  or else Ekind (Ent) = E_Package
2030                  or else Is_Generic_Unit (Ent)
2031                then
2032                   Rewrite (N,
2033                     New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
2034
2035                else
2036                   Error_Attr ("invalid prefix for % attribute", P);
2037                end if;
2038             end;
2039
2040          elsif Nkind (P) = N_Attribute_Reference
2041            and then Attribute_Name (P) = Name_AST_Entry
2042          then
2043             Rewrite (N,
2044               New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
2045
2046          elsif Is_Object_Reference (P) then
2047             null;
2048
2049          elsif Nkind (P) = N_Selected_Component
2050            and then Is_Subprogram (Entity (Selector_Name (P)))
2051          then
2052             null;
2053
2054          --  What exactly are we allowing here ??? and is this properly
2055          --  documented in the sinfo documentation for this node ???
2056
2057          elsif not Comes_From_Source (N) then
2058             null;
2059
2060          else
2061             Error_Attr ("invalid prefix for % attribute", P);
2062          end if;
2063
2064          Set_Etype (N, RTE (RE_Address));
2065
2066       ------------------
2067       -- Address_Size --
2068       ------------------
2069
2070       when Attribute_Address_Size =>
2071          Standard_Attribute (System_Address_Size);
2072
2073       --------------
2074       -- Adjacent --
2075       --------------
2076
2077       when Attribute_Adjacent =>
2078          Check_Floating_Point_Type_2;
2079          Set_Etype (N, P_Base_Type);
2080          Resolve (E1, P_Base_Type);
2081          Resolve (E2, P_Base_Type);
2082
2083       ---------
2084       -- Aft --
2085       ---------
2086
2087       when Attribute_Aft =>
2088          Check_Fixed_Point_Type_0;
2089          Set_Etype (N, Universal_Integer);
2090
2091       ---------------
2092       -- Alignment --
2093       ---------------
2094
2095       when Attribute_Alignment =>
2096
2097          --  Don't we need more checking here, cf Size ???
2098
2099          Check_E0;
2100          Check_Not_Incomplete_Type;
2101          Check_Not_CPP_Type;
2102          Set_Etype (N, Universal_Integer);
2103
2104       ---------------
2105       -- Asm_Input --
2106       ---------------
2107
2108       when Attribute_Asm_Input =>
2109          Check_Asm_Attribute;
2110          Set_Etype (N, RTE (RE_Asm_Input_Operand));
2111
2112       ----------------
2113       -- Asm_Output --
2114       ----------------
2115
2116       when Attribute_Asm_Output =>
2117          Check_Asm_Attribute;
2118
2119          if Etype (E2) = Any_Type then
2120             return;
2121
2122          elsif Aname = Name_Asm_Output then
2123             if not Is_Variable (E2) then
2124                Error_Attr
2125                  ("second argument for Asm_Output is not variable", E2);
2126             end if;
2127          end if;
2128
2129          Note_Possible_Modification (E2, Sure => True);
2130          Set_Etype (N, RTE (RE_Asm_Output_Operand));
2131
2132       ---------------
2133       -- AST_Entry --
2134       ---------------
2135
2136       when Attribute_AST_Entry => AST_Entry : declare
2137          Ent  : Entity_Id;
2138          Pref : Node_Id;
2139          Ptyp : Entity_Id;
2140
2141          Indexed : Boolean;
2142          --  Indicates if entry family index is present. Note the coding
2143          --  here handles the entry family case, but in fact it cannot be
2144          --  executed currently, because pragma AST_Entry does not permit
2145          --  the specification of an entry family.
2146
2147          procedure Bad_AST_Entry;
2148          --  Signal a bad AST_Entry pragma
2149
2150          function OK_Entry (E : Entity_Id) return Boolean;
2151          --  Checks that E is of an appropriate entity kind for an entry
2152          --  (i.e. E_Entry if Index is False, or E_Entry_Family if Index
2153          --  is set True for the entry family case). In the True case,
2154          --  makes sure that Is_AST_Entry is set on the entry.
2155
2156          -------------------
2157          -- Bad_AST_Entry --
2158          -------------------
2159
2160          procedure Bad_AST_Entry is
2161          begin
2162             Error_Attr_P ("prefix for % attribute must be task entry");
2163          end Bad_AST_Entry;
2164
2165          --------------
2166          -- OK_Entry --
2167          --------------
2168
2169          function OK_Entry (E : Entity_Id) return Boolean is
2170             Result : Boolean;
2171
2172          begin
2173             if Indexed then
2174                Result := (Ekind (E) = E_Entry_Family);
2175             else
2176                Result := (Ekind (E) = E_Entry);
2177             end if;
2178
2179             if Result then
2180                if not Is_AST_Entry (E) then
2181                   Error_Msg_Name_2 := Aname;
2182                   Error_Attr ("% attribute requires previous % pragma", P);
2183                end if;
2184             end if;
2185
2186             return Result;
2187          end OK_Entry;
2188
2189       --  Start of processing for AST_Entry
2190
2191       begin
2192          Check_VMS (N);
2193          Check_E0;
2194
2195          --  Deal with entry family case
2196
2197          if Nkind (P) = N_Indexed_Component then
2198             Pref := Prefix (P);
2199             Indexed := True;
2200          else
2201             Pref := P;
2202             Indexed := False;
2203          end if;
2204
2205          Ptyp := Etype (Pref);
2206
2207          if Ptyp = Any_Type or else Error_Posted (Pref) then
2208             return;
2209          end if;
2210
2211          --  If the prefix is a selected component whose prefix is of an
2212          --  access type, then introduce an explicit dereference.
2213          --  ??? Could we reuse Check_Dereference here?
2214
2215          if Nkind (Pref) = N_Selected_Component
2216            and then Is_Access_Type (Ptyp)
2217          then
2218             Rewrite (Pref,
2219               Make_Explicit_Dereference (Sloc (Pref),
2220                 Relocate_Node (Pref)));
2221             Analyze_And_Resolve (Pref, Designated_Type (Ptyp));
2222          end if;
2223
2224          --  Prefix can be of the form a.b, where a is a task object
2225          --  and b is one of the entries of the corresponding task type.
2226
2227          if Nkind (Pref) = N_Selected_Component
2228            and then OK_Entry (Entity (Selector_Name (Pref)))
2229            and then Is_Object_Reference (Prefix (Pref))
2230            and then Is_Task_Type (Etype (Prefix (Pref)))
2231          then
2232             null;
2233
2234          --  Otherwise the prefix must be an entry of a containing task,
2235          --  or of a variable of the enclosing task type.
2236
2237          else
2238             if Nkind_In (Pref, N_Identifier, N_Expanded_Name) then
2239                Ent := Entity (Pref);
2240
2241                if not OK_Entry (Ent)
2242                  or else not In_Open_Scopes (Scope (Ent))
2243                then
2244                   Bad_AST_Entry;
2245                end if;
2246
2247             else
2248                Bad_AST_Entry;
2249             end if;
2250          end if;
2251
2252          Set_Etype (N, RTE (RE_AST_Handler));
2253       end AST_Entry;
2254
2255       ----------
2256       -- Base --
2257       ----------
2258
2259       --  Note: when the base attribute appears in the context of a subtype
2260       --  mark, the analysis is done by Sem_Ch8.Find_Type, rather than by
2261       --  the following circuit.
2262
2263       when Attribute_Base => Base : declare
2264          Typ : Entity_Id;
2265
2266       begin
2267          Check_E0;
2268          Find_Type (P);
2269          Typ := Entity (P);
2270
2271          if Ada_Version >= Ada_95
2272            and then not Is_Scalar_Type (Typ)
2273            and then not Is_Generic_Type (Typ)
2274          then
2275             Error_Attr_P ("prefix of Base attribute must be scalar type");
2276
2277          elsif Sloc (Typ) = Standard_Location
2278            and then Base_Type (Typ) = Typ
2279            and then Warn_On_Redundant_Constructs
2280          then
2281                Error_Msg_NE
2282                  ("?redundant attribute, & is its own base type", N, Typ);
2283          end if;
2284
2285          Set_Etype (N, Base_Type (Entity (P)));
2286          Set_Entity (N, Base_Type (Entity (P)));
2287          Rewrite (N, New_Reference_To (Entity (N), Loc));
2288          Analyze (N);
2289       end Base;
2290
2291       ---------
2292       -- Bit --
2293       ---------
2294
2295       when Attribute_Bit => Bit :
2296       begin
2297          Check_E0;
2298
2299          if not Is_Object_Reference (P) then
2300             Error_Attr_P ("prefix for % attribute must be object");
2301
2302          --  What about the access object cases ???
2303
2304          else
2305             null;
2306          end if;
2307
2308          Set_Etype (N, Universal_Integer);
2309       end Bit;
2310
2311       ---------------
2312       -- Bit_Order --
2313       ---------------
2314
2315       when Attribute_Bit_Order => Bit_Order :
2316       begin
2317          Check_E0;
2318          Check_Type;
2319
2320          if not Is_Record_Type (P_Type) then
2321             Error_Attr_P ("prefix of % attribute must be record type");
2322          end if;
2323
2324          if Bytes_Big_Endian xor Reverse_Bit_Order (P_Type) then
2325             Rewrite (N,
2326               New_Occurrence_Of (RTE (RE_High_Order_First), Loc));
2327          else
2328             Rewrite (N,
2329               New_Occurrence_Of (RTE (RE_Low_Order_First), Loc));
2330          end if;
2331
2332          Set_Etype (N, RTE (RE_Bit_Order));
2333          Resolve (N);
2334
2335          --  Reset incorrect indication of staticness
2336
2337          Set_Is_Static_Expression (N, False);
2338       end Bit_Order;
2339
2340       ------------------
2341       -- Bit_Position --
2342       ------------------
2343
2344       --  Note: in generated code, we can have a Bit_Position attribute
2345       --  applied to a (naked) record component (i.e. the prefix is an
2346       --  identifier that references an E_Component or E_Discriminant
2347       --  entity directly, and this is interpreted as expected by Gigi.
2348       --  The following code will not tolerate such usage, but when the
2349       --  expander creates this special case, it marks it as analyzed
2350       --  immediately and sets an appropriate type.
2351
2352       when Attribute_Bit_Position =>
2353          if Comes_From_Source (N) then
2354             Check_Component;
2355          end if;
2356
2357          Set_Etype (N, Universal_Integer);
2358
2359       ------------------
2360       -- Body_Version --
2361       ------------------
2362
2363       when Attribute_Body_Version =>
2364          Check_E0;
2365          Check_Program_Unit;
2366          Set_Etype (N, RTE (RE_Version_String));
2367
2368       --------------
2369       -- Callable --
2370       --------------
2371
2372       when Attribute_Callable =>
2373          Check_E0;
2374          Set_Etype (N, Standard_Boolean);
2375          Check_Task_Prefix;
2376
2377       ------------
2378       -- Caller --
2379       ------------
2380
2381       when Attribute_Caller => Caller : declare
2382          Ent        : Entity_Id;
2383          S          : Entity_Id;
2384
2385       begin
2386          Check_E0;
2387
2388          if Nkind_In (P, N_Identifier, N_Expanded_Name) then
2389             Ent := Entity (P);
2390
2391             if not Is_Entry (Ent) then
2392                Error_Attr ("invalid entry name", N);
2393             end if;
2394
2395          else
2396             Error_Attr ("invalid entry name", N);
2397             return;
2398          end if;
2399
2400          for J in reverse 0 .. Scope_Stack.Last loop
2401             S := Scope_Stack.Table (J).Entity;
2402
2403             if S = Scope (Ent) then
2404                Error_Attr ("Caller must appear in matching accept or body", N);
2405             elsif S = Ent then
2406                exit;
2407             end if;
2408          end loop;
2409
2410          Set_Etype (N, RTE (RO_AT_Task_Id));
2411       end Caller;
2412
2413       -------------
2414       -- Ceiling --
2415       -------------
2416
2417       when Attribute_Ceiling =>
2418          Check_Floating_Point_Type_1;
2419          Set_Etype (N, P_Base_Type);
2420          Resolve (E1, P_Base_Type);
2421
2422       -----------
2423       -- Class --
2424       -----------
2425
2426       when Attribute_Class =>
2427          Check_Restriction (No_Dispatch, N);
2428          Check_E0;
2429          Find_Type (N);
2430
2431       ------------------
2432       -- Code_Address --
2433       ------------------
2434
2435       when Attribute_Code_Address =>
2436          Check_E0;
2437
2438          if Nkind (P) = N_Attribute_Reference
2439            and then (Attribute_Name (P) = Name_Elab_Body
2440                        or else
2441                      Attribute_Name (P) = Name_Elab_Spec)
2442          then
2443             null;
2444
2445          elsif not Is_Entity_Name (P)
2446            or else (Ekind (Entity (P)) /= E_Function
2447                       and then
2448                     Ekind (Entity (P)) /= E_Procedure)
2449          then
2450             Error_Attr ("invalid prefix for % attribute", P);
2451             Set_Address_Taken (Entity (P));
2452          end if;
2453
2454          Set_Etype (N, RTE (RE_Address));
2455
2456       --------------------
2457       -- Component_Size --
2458       --------------------
2459
2460       when Attribute_Component_Size =>
2461          Check_E0;
2462          Set_Etype (N, Universal_Integer);
2463
2464          --  Note: unlike other array attributes, unconstrained arrays are OK
2465
2466          if Is_Array_Type (P_Type) and then not Is_Constrained (P_Type) then
2467             null;
2468          else
2469             Check_Array_Type;
2470          end if;
2471
2472       -------------
2473       -- Compose --
2474       -------------
2475
2476       when Attribute_Compose =>
2477          Check_Floating_Point_Type_2;
2478          Set_Etype (N, P_Base_Type);
2479          Resolve (E1, P_Base_Type);
2480          Resolve (E2, Any_Integer);
2481
2482       -----------------
2483       -- Constrained --
2484       -----------------
2485
2486       when Attribute_Constrained =>
2487          Check_E0;
2488          Set_Etype (N, Standard_Boolean);
2489
2490          --  Case from RM J.4(2) of constrained applied to private type
2491
2492          if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
2493             Check_Restriction (No_Obsolescent_Features, N);
2494
2495             if Warn_On_Obsolescent_Feature then
2496                Error_Msg_N
2497                  ("constrained for private type is an " &
2498                   "obsolescent feature (RM J.4)?", N);
2499             end if;
2500
2501             --  If we are within an instance, the attribute must be legal
2502             --  because it was valid in the generic unit. Ditto if this is
2503             --  an inlining of a function declared in an instance.
2504
2505             if In_Instance
2506               or else In_Inlined_Body
2507             then
2508                return;
2509
2510             --  For sure OK if we have a real private type itself, but must
2511             --  be completed, cannot apply Constrained to incomplete type.
2512
2513             elsif Is_Private_Type (Entity (P)) then
2514
2515                --  Note: this is one of the Annex J features that does not
2516                --  generate a warning from -gnatwj, since in fact it seems
2517                --  very useful, and is used in the GNAT runtime.
2518
2519                Check_Not_Incomplete_Type;
2520                return;
2521             end if;
2522
2523          --  Normal (non-obsolescent case) of application to object of
2524          --  a discriminated type.
2525
2526          else
2527             Check_Object_Reference (P);
2528
2529             --  If N does not come from source, then we allow the
2530             --  the attribute prefix to be of a private type whose
2531             --  full type has discriminants. This occurs in cases
2532             --  involving expanded calls to stream attributes.
2533
2534             if not Comes_From_Source (N) then
2535                P_Type := Underlying_Type (P_Type);
2536             end if;
2537
2538             --  Must have discriminants or be an access type designating
2539             --  a type with discriminants. If it is a classwide type is ???
2540             --  has unknown discriminants.
2541
2542             if Has_Discriminants (P_Type)
2543                or else Has_Unknown_Discriminants (P_Type)
2544                or else
2545                  (Is_Access_Type (P_Type)
2546                    and then Has_Discriminants (Designated_Type (P_Type)))
2547             then
2548                return;
2549
2550             --  Also allow an object of a generic type if extensions allowed
2551             --  and allow this for any type at all.
2552
2553             elsif (Is_Generic_Type (P_Type)
2554                      or else Is_Generic_Actual_Type (P_Type))
2555               and then Extensions_Allowed
2556             then
2557                return;
2558             end if;
2559          end if;
2560
2561          --  Fall through if bad prefix
2562
2563          Error_Attr_P
2564            ("prefix of % attribute must be object of discriminated type");
2565
2566       ---------------
2567       -- Copy_Sign --
2568       ---------------
2569
2570       when Attribute_Copy_Sign =>
2571          Check_Floating_Point_Type_2;
2572          Set_Etype (N, P_Base_Type);
2573          Resolve (E1, P_Base_Type);
2574          Resolve (E2, P_Base_Type);
2575
2576       -----------
2577       -- Count --
2578       -----------
2579
2580       when Attribute_Count => Count :
2581       declare
2582          Ent : Entity_Id;
2583          S   : Entity_Id;
2584          Tsk : Entity_Id;
2585
2586       begin
2587          Check_E0;
2588
2589          if Nkind_In (P, N_Identifier, N_Expanded_Name) then
2590             Ent := Entity (P);
2591
2592             if Ekind (Ent) /= E_Entry then
2593                Error_Attr ("invalid entry name", N);
2594             end if;
2595
2596          elsif Nkind (P) = N_Indexed_Component then
2597             if not Is_Entity_Name (Prefix (P))
2598               or else  No (Entity (Prefix (P)))
2599               or else Ekind (Entity (Prefix (P))) /= E_Entry_Family
2600             then
2601                if Nkind (Prefix (P)) = N_Selected_Component
2602                  and then Present (Entity (Selector_Name (Prefix (P))))
2603                  and then Ekind (Entity (Selector_Name (Prefix (P)))) =
2604                                                              E_Entry_Family
2605                then
2606                   Error_Attr
2607                     ("attribute % must apply to entry of current task", P);
2608
2609                else
2610                   Error_Attr ("invalid entry family name", P);
2611                end if;
2612                return;
2613
2614             else
2615                Ent := Entity (Prefix (P));
2616             end if;
2617
2618          elsif Nkind (P) = N_Selected_Component
2619            and then Present (Entity (Selector_Name (P)))
2620            and then Ekind (Entity (Selector_Name (P))) = E_Entry
2621          then
2622             Error_Attr
2623               ("attribute % must apply to entry of current task", P);
2624
2625          else
2626             Error_Attr ("invalid entry name", N);
2627             return;
2628          end if;
2629
2630          for J in reverse 0 .. Scope_Stack.Last loop
2631             S := Scope_Stack.Table (J).Entity;
2632
2633             if S = Scope (Ent) then
2634                if Nkind (P) = N_Expanded_Name then
2635                   Tsk := Entity (Prefix (P));
2636
2637                   --  The prefix denotes either the task type, or else a
2638                   --  single task whose task type is being analyzed.
2639
2640                   if (Is_Type (Tsk)
2641                       and then Tsk = S)
2642
2643                     or else (not Is_Type (Tsk)
2644                       and then Etype (Tsk) = S
2645                       and then not (Comes_From_Source (S)))
2646                   then
2647                      null;
2648                   else
2649                      Error_Attr
2650                        ("Attribute % must apply to entry of current task", N);
2651                   end if;
2652                end if;
2653
2654                exit;
2655
2656             elsif Ekind (Scope (Ent)) in Task_Kind
2657               and then Ekind (S) /= E_Loop
2658               and then Ekind (S) /= E_Block
2659               and then Ekind (S) /= E_Entry
2660               and then Ekind (S) /= E_Entry_Family
2661             then
2662                Error_Attr ("Attribute % cannot appear in inner unit", N);
2663
2664             elsif Ekind (Scope (Ent)) = E_Protected_Type
2665               and then not Has_Completion (Scope (Ent))
2666             then
2667                Error_Attr ("attribute % can only be used inside body", N);
2668             end if;
2669          end loop;
2670
2671          if Is_Overloaded (P) then
2672             declare
2673                Index : Interp_Index;
2674                It    : Interp;
2675
2676             begin
2677                Get_First_Interp (P, Index, It);
2678
2679                while Present (It.Nam) loop
2680                   if It.Nam = Ent then
2681                      null;
2682
2683                   --  Ada 2005 (AI-345): Do not consider primitive entry
2684                   --  wrappers generated for task or protected types.
2685
2686                   elsif Ada_Version >= Ada_05
2687                     and then not Comes_From_Source (It.Nam)
2688                   then
2689                      null;
2690
2691                   else
2692                      Error_Attr ("ambiguous entry name", N);
2693                   end if;
2694
2695                   Get_Next_Interp (Index, It);
2696                end loop;
2697             end;
2698          end if;
2699
2700          Set_Etype (N, Universal_Integer);
2701       end Count;
2702
2703       -----------------------
2704       -- Default_Bit_Order --
2705       -----------------------
2706
2707       when Attribute_Default_Bit_Order => Default_Bit_Order :
2708       begin
2709          Check_Standard_Prefix;
2710
2711          if Bytes_Big_Endian then
2712             Rewrite (N,
2713               Make_Integer_Literal (Loc, False_Value));
2714          else
2715             Rewrite (N,
2716               Make_Integer_Literal (Loc, True_Value));
2717          end if;
2718
2719          Set_Etype (N, Universal_Integer);
2720          Set_Is_Static_Expression (N);
2721       end Default_Bit_Order;
2722
2723       --------------
2724       -- Definite --
2725       --------------
2726
2727       when Attribute_Definite =>
2728          Legal_Formal_Attribute;
2729
2730       -----------
2731       -- Delta --
2732       -----------
2733
2734       when Attribute_Delta =>
2735          Check_Fixed_Point_Type_0;
2736          Set_Etype (N, Universal_Real);
2737
2738       ------------
2739       -- Denorm --
2740       ------------
2741
2742       when Attribute_Denorm =>
2743          Check_Floating_Point_Type_0;
2744          Set_Etype (N, Standard_Boolean);
2745
2746       ------------
2747       -- Digits --
2748       ------------
2749
2750       when Attribute_Digits =>
2751          Check_E0;
2752          Check_Type;
2753
2754          if not Is_Floating_Point_Type (P_Type)
2755            and then not Is_Decimal_Fixed_Point_Type (P_Type)
2756          then
2757             Error_Attr_P
2758               ("prefix of % attribute must be float or decimal type");
2759          end if;
2760
2761          Set_Etype (N, Universal_Integer);
2762
2763       ---------------
2764       -- Elab_Body --
2765       ---------------
2766
2767       --  Also handles processing for Elab_Spec
2768
2769       when Attribute_Elab_Body | Attribute_Elab_Spec =>
2770          Check_E0;
2771          Check_Unit_Name (P);
2772          Set_Etype (N, Standard_Void_Type);
2773
2774          --  We have to manually call the expander in this case to get
2775          --  the necessary expansion (normally attributes that return
2776          --  entities are not expanded).
2777
2778          Expand (N);
2779
2780       ---------------
2781       -- Elab_Spec --
2782       ---------------
2783
2784       --  Shares processing with Elab_Body
2785
2786       ----------------
2787       -- Elaborated --
2788       ----------------
2789
2790       when Attribute_Elaborated =>
2791          Check_E0;
2792          Check_Library_Unit;
2793          Set_Etype (N, Standard_Boolean);
2794
2795       ----------
2796       -- Emax --
2797       ----------
2798
2799       when Attribute_Emax =>
2800          Check_Floating_Point_Type_0;
2801          Set_Etype (N, Universal_Integer);
2802
2803       -------------
2804       -- Enabled --
2805       -------------
2806
2807       when Attribute_Enabled =>
2808          Check_Either_E0_Or_E1;
2809
2810          if Present (E1) then
2811             if not Is_Entity_Name (E1) or else No (Entity (E1)) then
2812                Error_Msg_N ("entity name expected for Enabled attribute", E1);
2813                E1 := Empty;
2814             end if;
2815          end if;
2816
2817          if Nkind (P) /= N_Identifier then
2818             Error_Msg_N ("identifier expected (check name)", P);
2819          elsif Get_Check_Id (Chars (P)) = No_Check_Id then
2820             Error_Msg_N ("& is not a recognized check name", P);
2821          end if;
2822
2823          Set_Etype (N, Standard_Boolean);
2824
2825       --------------
2826       -- Enum_Rep --
2827       --------------
2828
2829       when Attribute_Enum_Rep => Enum_Rep : declare
2830       begin
2831          if Present (E1) then
2832             Check_E1;
2833             Check_Discrete_Type;
2834             Resolve (E1, P_Base_Type);
2835
2836          else
2837             if not Is_Entity_Name (P)
2838               or else (not Is_Object (Entity (P))
2839                          and then
2840                        Ekind (Entity (P)) /= E_Enumeration_Literal)
2841             then
2842                Error_Attr_P
2843                  ("prefix of %attribute must be " &
2844                   "discrete type/object or enum literal");
2845             end if;
2846          end if;
2847
2848          Set_Etype (N, Universal_Integer);
2849       end Enum_Rep;
2850
2851       --------------
2852       -- Enum_Val --
2853       --------------
2854
2855       when Attribute_Enum_Val => Enum_Val : begin
2856          Check_E1;
2857          Check_Type;
2858
2859          if not Is_Enumeration_Type (P_Type) then
2860             Error_Attr_P ("prefix of % attribute must be enumeration type");
2861          end if;
2862
2863          --  If the enumeration type has a standard representation, the effect
2864          --  is the same as 'Val, so rewrite the attribute as a 'Val.
2865
2866          if not Has_Non_Standard_Rep (P_Base_Type) then
2867             Rewrite (N,
2868               Make_Attribute_Reference (Loc,
2869                 Prefix         => Relocate_Node (Prefix (N)),
2870                 Attribute_Name => Name_Val,
2871                 Expressions    => New_List (Relocate_Node (E1))));
2872             Analyze_And_Resolve (N, P_Base_Type);
2873
2874          --  Non-standard representation case (enumeration with holes)
2875
2876          else
2877             Check_Enum_Image;
2878             Resolve (E1, Any_Integer);
2879             Set_Etype (N, P_Base_Type);
2880          end if;
2881       end Enum_Val;
2882
2883       -------------
2884       -- Epsilon --
2885       -------------
2886
2887       when Attribute_Epsilon =>
2888          Check_Floating_Point_Type_0;
2889          Set_Etype (N, Universal_Real);
2890
2891       --------------
2892       -- Exponent --
2893       --------------
2894
2895       when Attribute_Exponent =>
2896          Check_Floating_Point_Type_1;
2897          Set_Etype (N, Universal_Integer);
2898          Resolve (E1, P_Base_Type);
2899
2900       ------------------
2901       -- External_Tag --
2902       ------------------
2903
2904       when Attribute_External_Tag =>
2905          Check_E0;
2906          Check_Type;
2907
2908          Set_Etype (N, Standard_String);
2909
2910          if not Is_Tagged_Type (P_Type) then
2911             Error_Attr_P ("prefix of % attribute must be tagged");
2912          end if;
2913
2914       ---------------
2915       -- Fast_Math --
2916       ---------------
2917
2918       when Attribute_Fast_Math =>
2919          Check_Standard_Prefix;
2920
2921          if Opt.Fast_Math then
2922             Rewrite (N, New_Occurrence_Of (Standard_True, Loc));
2923          else
2924             Rewrite (N, New_Occurrence_Of (Standard_False, Loc));
2925          end if;
2926
2927       -----------
2928       -- First --
2929       -----------
2930
2931       when Attribute_First =>
2932          Check_Array_Or_Scalar_Type;
2933
2934       ---------------
2935       -- First_Bit --
2936       ---------------
2937
2938       when Attribute_First_Bit =>
2939          Check_Component;
2940          Set_Etype (N, Universal_Integer);
2941
2942       -----------------
2943       -- Fixed_Value --
2944       -----------------
2945
2946       when Attribute_Fixed_Value =>
2947          Check_E1;
2948          Check_Fixed_Point_Type;
2949          Resolve (E1, Any_Integer);
2950          Set_Etype (N, P_Base_Type);
2951
2952       -----------
2953       -- Floor --
2954       -----------
2955
2956       when Attribute_Floor =>
2957          Check_Floating_Point_Type_1;
2958          Set_Etype (N, P_Base_Type);
2959          Resolve (E1, P_Base_Type);
2960
2961       ----------
2962       -- Fore --
2963       ----------
2964
2965       when Attribute_Fore =>
2966          Check_Fixed_Point_Type_0;
2967          Set_Etype (N, Universal_Integer);
2968
2969       --------------
2970       -- Fraction --
2971       --------------
2972
2973       when Attribute_Fraction =>
2974          Check_Floating_Point_Type_1;
2975          Set_Etype (N, P_Base_Type);
2976          Resolve (E1, P_Base_Type);
2977
2978       -----------------------
2979       -- Has_Access_Values --
2980       -----------------------
2981
2982       when Attribute_Has_Access_Values =>
2983          Check_Type;
2984          Check_E0;
2985          Set_Etype (N, Standard_Boolean);
2986
2987       -----------------------
2988       -- Has_Tagged_Values --
2989       -----------------------
2990
2991       when Attribute_Has_Tagged_Values =>
2992          Check_Type;
2993          Check_E0;
2994          Set_Etype (N, Standard_Boolean);
2995
2996       -----------------------
2997       -- Has_Discriminants --
2998       -----------------------
2999
3000       when Attribute_Has_Discriminants =>
3001          Legal_Formal_Attribute;
3002
3003       --------------
3004       -- Identity --
3005       --------------
3006
3007       when Attribute_Identity =>
3008          Check_E0;
3009          Analyze (P);
3010
3011          if Etype (P) =  Standard_Exception_Type then
3012             Set_Etype (N, RTE (RE_Exception_Id));
3013
3014          --  Ada 2005 (AI-345): Attribute 'Identity may be applied to
3015          --  task interface class-wide types.
3016
3017          elsif Is_Task_Type (Etype (P))
3018            or else (Is_Access_Type (Etype (P))
3019                       and then Is_Task_Type (Designated_Type (Etype (P))))
3020            or else (Ada_Version >= Ada_05
3021                       and then Ekind (Etype (P)) = E_Class_Wide_Type
3022                       and then Is_Interface (Etype (P))
3023                       and then Is_Task_Interface (Etype (P)))
3024          then
3025             Resolve (P);
3026             Set_Etype (N, RTE (RO_AT_Task_Id));
3027
3028          else
3029             if Ada_Version >= Ada_05 then
3030                Error_Attr_P
3031                  ("prefix of % attribute must be an exception, a " &
3032                   "task or a task interface class-wide object");
3033             else
3034                Error_Attr_P
3035                  ("prefix of % attribute must be a task or an exception");
3036             end if;
3037          end if;
3038
3039       -----------
3040       -- Image --
3041       -----------
3042
3043       when Attribute_Image => Image :
3044       begin
3045          Set_Etype (N, Standard_String);
3046          Check_Scalar_Type;
3047
3048          if Is_Real_Type (P_Type) then
3049             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
3050                Error_Msg_Name_1 := Aname;
3051                Error_Msg_N
3052                  ("(Ada 83) % attribute not allowed for real types", N);
3053             end if;
3054          end if;
3055
3056          if Is_Enumeration_Type (P_Type) then
3057             Check_Restriction (No_Enumeration_Maps, N);
3058          end if;
3059
3060          Check_E1;
3061          Resolve (E1, P_Base_Type);
3062          Check_Enum_Image;
3063          Validate_Non_Static_Attribute_Function_Call;
3064       end Image;
3065
3066       ---------
3067       -- Img --
3068       ---------
3069
3070       when Attribute_Img => Img :
3071       begin
3072          Check_E0;
3073          Set_Etype (N, Standard_String);
3074
3075          if not Is_Scalar_Type (P_Type)
3076            or else (Is_Entity_Name (P) and then Is_Type (Entity (P)))
3077          then
3078             Error_Attr_P
3079               ("prefix of % attribute must be scalar object name");
3080          end if;
3081
3082          Check_Enum_Image;
3083       end Img;
3084
3085       -----------
3086       -- Input --
3087       -----------
3088
3089       when Attribute_Input =>
3090          Check_E1;
3091          Check_Stream_Attribute (TSS_Stream_Input);
3092          Set_Etype (N, P_Base_Type);
3093
3094       -------------------
3095       -- Integer_Value --
3096       -------------------
3097
3098       when Attribute_Integer_Value =>
3099          Check_E1;
3100          Check_Integer_Type;
3101          Resolve (E1, Any_Fixed);
3102
3103          --  Signal an error if argument type is not a specific fixed-point
3104          --  subtype. An error has been signalled already if the argument
3105          --  was not of a fixed-point type.
3106
3107          if Etype (E1) = Any_Fixed and then not Error_Posted (E1) then
3108             Error_Attr ("argument of % must be of a fixed-point type", E1);
3109          end if;
3110
3111          Set_Etype (N, P_Base_Type);
3112
3113       -------------------
3114       -- Invalid_Value --
3115       -------------------
3116
3117       when Attribute_Invalid_Value =>
3118          Check_E0;
3119          Check_Scalar_Type;
3120          Set_Etype (N, P_Base_Type);
3121          Invalid_Value_Used := True;
3122
3123       -----------
3124       -- Large --
3125       -----------
3126
3127       when Attribute_Large =>
3128          Check_E0;
3129          Check_Real_Type;
3130          Set_Etype (N, Universal_Real);
3131
3132       ----------
3133       -- Last --
3134       ----------
3135
3136       when Attribute_Last =>
3137          Check_Array_Or_Scalar_Type;
3138
3139       --------------
3140       -- Last_Bit --
3141       --------------
3142
3143       when Attribute_Last_Bit =>
3144          Check_Component;
3145          Set_Etype (N, Universal_Integer);
3146
3147       ------------------
3148       -- Leading_Part --
3149       ------------------
3150
3151       when Attribute_Leading_Part =>
3152          Check_Floating_Point_Type_2;
3153          Set_Etype (N, P_Base_Type);
3154          Resolve (E1, P_Base_Type);
3155          Resolve (E2, Any_Integer);
3156
3157       ------------
3158       -- Length --
3159       ------------
3160
3161       when Attribute_Length =>
3162          Check_Array_Type;
3163          Set_Etype (N, Universal_Integer);
3164
3165       -------------
3166       -- Machine --
3167       -------------
3168
3169       when Attribute_Machine =>
3170          Check_Floating_Point_Type_1;
3171          Set_Etype (N, P_Base_Type);
3172          Resolve (E1, P_Base_Type);
3173
3174       ------------------
3175       -- Machine_Emax --
3176       ------------------
3177
3178       when Attribute_Machine_Emax =>
3179          Check_Floating_Point_Type_0;
3180          Set_Etype (N, Universal_Integer);
3181
3182       ------------------
3183       -- Machine_Emin --
3184       ------------------
3185
3186       when Attribute_Machine_Emin =>
3187          Check_Floating_Point_Type_0;
3188          Set_Etype (N, Universal_Integer);
3189
3190       ----------------------
3191       -- Machine_Mantissa --
3192       ----------------------
3193
3194       when Attribute_Machine_Mantissa =>
3195          Check_Floating_Point_Type_0;
3196          Set_Etype (N, Universal_Integer);
3197
3198       -----------------------
3199       -- Machine_Overflows --
3200       -----------------------
3201
3202       when Attribute_Machine_Overflows =>
3203          Check_Real_Type;
3204          Check_E0;
3205          Set_Etype (N, Standard_Boolean);
3206
3207       -------------------
3208       -- Machine_Radix --
3209       -------------------
3210
3211       when Attribute_Machine_Radix =>
3212          Check_Real_Type;
3213          Check_E0;
3214          Set_Etype (N, Universal_Integer);
3215
3216       ----------------------
3217       -- Machine_Rounding --
3218       ----------------------
3219
3220       when Attribute_Machine_Rounding =>
3221          Check_Floating_Point_Type_1;
3222          Set_Etype (N, P_Base_Type);
3223          Resolve (E1, P_Base_Type);
3224
3225       --------------------
3226       -- Machine_Rounds --
3227       --------------------
3228
3229       when Attribute_Machine_Rounds =>
3230          Check_Real_Type;
3231          Check_E0;
3232          Set_Etype (N, Standard_Boolean);
3233
3234       ------------------
3235       -- Machine_Size --
3236       ------------------
3237
3238       when Attribute_Machine_Size =>
3239          Check_E0;
3240          Check_Type;
3241          Check_Not_Incomplete_Type;
3242          Set_Etype (N, Universal_Integer);
3243
3244       --------------
3245       -- Mantissa --
3246       --------------
3247
3248       when Attribute_Mantissa =>
3249          Check_E0;
3250          Check_Real_Type;
3251          Set_Etype (N, Universal_Integer);
3252
3253       ---------
3254       -- Max --
3255       ---------
3256
3257       when Attribute_Max =>
3258          Check_E2;
3259          Check_Scalar_Type;
3260          Resolve (E1, P_Base_Type);
3261          Resolve (E2, P_Base_Type);
3262          Set_Etype (N, P_Base_Type);
3263
3264       ----------------------------------
3265       -- Max_Size_In_Storage_Elements --
3266       ----------------------------------
3267
3268       when Attribute_Max_Size_In_Storage_Elements =>
3269          Check_E0;
3270          Check_Type;
3271          Check_Not_Incomplete_Type;
3272          Set_Etype (N, Universal_Integer);
3273
3274       -----------------------
3275       -- Maximum_Alignment --
3276       -----------------------
3277
3278       when Attribute_Maximum_Alignment =>
3279          Standard_Attribute (Ttypes.Maximum_Alignment);
3280
3281       --------------------
3282       -- Mechanism_Code --
3283       --------------------
3284
3285       when Attribute_Mechanism_Code =>
3286          if not Is_Entity_Name (P)
3287            or else not Is_Subprogram (Entity (P))
3288          then
3289             Error_Attr_P ("prefix of % attribute must be subprogram");
3290          end if;
3291
3292          Check_Either_E0_Or_E1;
3293
3294          if Present (E1) then
3295             Resolve (E1, Any_Integer);
3296             Set_Etype (E1, Standard_Integer);
3297
3298             if not Is_Static_Expression (E1) then
3299                Flag_Non_Static_Expr
3300                  ("expression for parameter number must be static!", E1);
3301                Error_Attr;
3302
3303             elsif UI_To_Int (Intval (E1)) > Number_Formals (Entity (P))
3304               or else UI_To_Int (Intval (E1)) < 0
3305             then
3306                Error_Attr ("invalid parameter number for %attribute", E1);
3307             end if;
3308          end if;
3309
3310          Set_Etype (N, Universal_Integer);
3311
3312       ---------
3313       -- Min --
3314       ---------
3315
3316       when Attribute_Min =>
3317          Check_E2;
3318          Check_Scalar_Type;
3319          Resolve (E1, P_Base_Type);
3320          Resolve (E2, P_Base_Type);
3321          Set_Etype (N, P_Base_Type);
3322
3323       ---------
3324       -- Mod --
3325       ---------
3326
3327       when Attribute_Mod =>
3328
3329          --  Note: this attribute is only allowed in Ada 2005 mode, but
3330          --  we do not need to test that here, since Mod is only recognized
3331          --  as an attribute name in Ada 2005 mode during the parse.
3332
3333          Check_E1;
3334          Check_Modular_Integer_Type;
3335          Resolve (E1, Any_Integer);
3336          Set_Etype (N, P_Base_Type);
3337
3338       -----------
3339       -- Model --
3340       -----------
3341
3342       when Attribute_Model =>
3343          Check_Floating_Point_Type_1;
3344          Set_Etype (N, P_Base_Type);
3345          Resolve (E1, P_Base_Type);
3346
3347       ----------------
3348       -- Model_Emin --
3349       ----------------
3350
3351       when Attribute_Model_Emin =>
3352          Check_Floating_Point_Type_0;
3353          Set_Etype (N, Universal_Integer);
3354
3355       -------------------
3356       -- Model_Epsilon --
3357       -------------------
3358
3359       when Attribute_Model_Epsilon =>
3360          Check_Floating_Point_Type_0;
3361          Set_Etype (N, Universal_Real);
3362
3363       --------------------
3364       -- Model_Mantissa --
3365       --------------------
3366
3367       when Attribute_Model_Mantissa =>
3368          Check_Floating_Point_Type_0;
3369          Set_Etype (N, Universal_Integer);
3370
3371       -----------------
3372       -- Model_Small --
3373       -----------------
3374
3375       when Attribute_Model_Small =>
3376          Check_Floating_Point_Type_0;
3377          Set_Etype (N, Universal_Real);
3378
3379       -------------
3380       -- Modulus --
3381       -------------
3382
3383       when Attribute_Modulus =>
3384          Check_E0;
3385          Check_Modular_Integer_Type;
3386          Set_Etype (N, Universal_Integer);
3387
3388       --------------------
3389       -- Null_Parameter --
3390       --------------------
3391
3392       when Attribute_Null_Parameter => Null_Parameter : declare
3393          Parnt  : constant Node_Id := Parent (N);
3394          GParnt : constant Node_Id := Parent (Parnt);
3395
3396          procedure Bad_Null_Parameter (Msg : String);
3397          --  Used if bad Null parameter attribute node is found. Issues
3398          --  given error message, and also sets the type to Any_Type to
3399          --  avoid blowups later on from dealing with a junk node.
3400
3401          procedure Must_Be_Imported (Proc_Ent : Entity_Id);
3402          --  Called to check that Proc_Ent is imported subprogram
3403
3404          ------------------------
3405          -- Bad_Null_Parameter --
3406          ------------------------
3407
3408          procedure Bad_Null_Parameter (Msg : String) is
3409          begin
3410             Error_Msg_N (Msg, N);
3411             Set_Etype (N, Any_Type);
3412          end Bad_Null_Parameter;
3413
3414          ----------------------
3415          -- Must_Be_Imported --
3416          ----------------------
3417
3418          procedure Must_Be_Imported (Proc_Ent : Entity_Id) is
3419             Pent : Entity_Id := Proc_Ent;
3420
3421          begin
3422             while Present (Alias (Pent)) loop
3423                Pent := Alias (Pent);
3424             end loop;
3425
3426             --  Ignore check if procedure not frozen yet (we will get
3427             --  another chance when the default parameter is reanalyzed)
3428
3429             if not Is_Frozen (Pent) then
3430                return;
3431
3432             elsif not Is_Imported (Pent) then
3433                Bad_Null_Parameter
3434                  ("Null_Parameter can only be used with imported subprogram");
3435
3436             else
3437                return;
3438             end if;
3439          end Must_Be_Imported;
3440
3441       --  Start of processing for Null_Parameter
3442
3443       begin
3444          Check_Type;
3445          Check_E0;
3446          Set_Etype (N, P_Type);
3447
3448          --  Case of attribute used as default expression
3449
3450          if Nkind (Parnt) = N_Parameter_Specification then
3451             Must_Be_Imported (Defining_Entity (GParnt));
3452
3453          --  Case of attribute used as actual for subprogram (positional)
3454
3455          elsif Nkind_In (Parnt, N_Procedure_Call_Statement,
3456                                 N_Function_Call)
3457             and then Is_Entity_Name (Name (Parnt))
3458          then
3459             Must_Be_Imported (Entity (Name (Parnt)));
3460
3461          --  Case of attribute used as actual for subprogram (named)
3462
3463          elsif Nkind (Parnt) = N_Parameter_Association
3464            and then Nkind_In (GParnt, N_Procedure_Call_Statement,
3465                                       N_Function_Call)
3466            and then Is_Entity_Name (Name (GParnt))
3467          then
3468             Must_Be_Imported (Entity (Name (GParnt)));
3469
3470          --  Not an allowed case
3471
3472          else
3473             Bad_Null_Parameter
3474               ("Null_Parameter must be actual or default parameter");
3475          end if;
3476       end Null_Parameter;
3477
3478       -----------------
3479       -- Object_Size --
3480       -----------------
3481
3482       when Attribute_Object_Size =>
3483          Check_E0;
3484          Check_Type;
3485          Check_Not_Incomplete_Type;
3486          Set_Etype (N, Universal_Integer);
3487
3488       ---------
3489       -- Old --
3490       ---------
3491
3492       when Attribute_Old =>
3493          Check_E0;
3494          Set_Etype (N, P_Type);
3495
3496          if No (Current_Subprogram) then
3497             Error_Attr ("attribute % can only appear within subprogram", N);
3498          end if;
3499
3500          if Is_Limited_Type (P_Type) then
3501             Error_Attr ("attribute % cannot apply to limited objects", P);
3502          end if;
3503
3504          if Is_Entity_Name (P)
3505            and then Is_Constant_Object (Entity (P))
3506          then
3507             Error_Msg_N
3508               ("?attribute Old applied to constant has no effect", P);
3509          end if;
3510
3511          --  Check that the expression does not refer to local entities
3512
3513          Check_Local : declare
3514             Subp : Entity_Id := Current_Subprogram;
3515
3516             function Process (N : Node_Id) return Traverse_Result;
3517             --  Check that N does not contain references to local variables
3518             --  or other local entities of Subp.
3519
3520             -------------
3521             -- Process --
3522             -------------
3523
3524             function Process (N : Node_Id) return Traverse_Result is
3525             begin
3526                if Is_Entity_Name (N)
3527                  and then not Is_Formal (Entity (N))
3528                  and then Enclosing_Subprogram (Entity (N)) = Subp
3529                then
3530                   Error_Msg_Node_1 := Entity (N);
3531                   Error_Attr
3532                     ("attribute % cannot refer to local variable&", N);
3533                end if;
3534
3535                return OK;
3536             end Process;
3537
3538             procedure Check_No_Local is new Traverse_Proc;
3539
3540          --  Start of processing for Check_Local
3541
3542          begin
3543             Check_No_Local (P);
3544
3545             if In_Parameter_Specification (P) then
3546
3547                --  We have additional restrictions on using 'Old in parameter
3548                --  specifications.
3549
3550                if Present (Enclosing_Subprogram (Current_Subprogram)) then
3551
3552                   --  Check that there is no reference to the enclosing
3553                   --  subprogram local variables. Otherwise, we might end
3554                   --  up being called from the enclosing subprogram and thus
3555                   --  using 'Old on a local variable which is not defined
3556                   --  at entry time.
3557
3558                   Subp := Enclosing_Subprogram (Current_Subprogram);
3559                   Check_No_Local (P);
3560
3561                else
3562                   --  We must prevent default expression of library-level
3563                   --  subprogram from using 'Old, as the subprogram may be
3564                   --  used in elaboration code for which there is no enclosing
3565                   --  subprogram.
3566
3567                   Error_Attr
3568                     ("attribute % can only appear within subprogram", N);
3569                end if;
3570             end if;
3571          end Check_Local;
3572
3573       ------------
3574       -- Output --
3575       ------------
3576
3577       when Attribute_Output =>
3578          Check_E2;
3579          Check_Stream_Attribute (TSS_Stream_Output);
3580          Set_Etype (N, Standard_Void_Type);
3581          Resolve (N, Standard_Void_Type);
3582
3583       ------------------
3584       -- Partition_ID --
3585       ------------------
3586
3587       when Attribute_Partition_ID => Partition_Id :
3588       begin
3589          Check_E0;
3590
3591          if P_Type /= Any_Type then
3592             if not Is_Library_Level_Entity (Entity (P)) then
3593                Error_Attr_P
3594                  ("prefix of % attribute must be library-level entity");
3595
3596             --  The defining entity of prefix should not be declared inside a
3597             --  Pure unit. RM E.1(8). Is_Pure was set during declaration.
3598
3599             elsif Is_Entity_Name (P)
3600               and then Is_Pure (Entity (P))
3601             then
3602                Error_Attr_P
3603                  ("prefix of % attribute must not be declared pure");
3604             end if;
3605          end if;
3606
3607          Set_Etype (N, Universal_Integer);
3608       end Partition_Id;
3609
3610       -------------------------
3611       -- Passed_By_Reference --
3612       -------------------------
3613
3614       when Attribute_Passed_By_Reference =>
3615          Check_E0;
3616          Check_Type;
3617          Set_Etype (N, Standard_Boolean);
3618
3619       ------------------
3620       -- Pool_Address --
3621       ------------------
3622
3623       when Attribute_Pool_Address =>
3624          Check_E0;
3625          Set_Etype (N, RTE (RE_Address));
3626
3627       ---------
3628       -- Pos --
3629       ---------
3630
3631       when Attribute_Pos =>
3632          Check_Discrete_Type;
3633          Check_E1;
3634          Resolve (E1, P_Base_Type);
3635          Set_Etype (N, Universal_Integer);
3636
3637       --------------
3638       -- Position --
3639       --------------
3640
3641       when Attribute_Position =>
3642          Check_Component;
3643          Set_Etype (N, Universal_Integer);
3644
3645       ----------
3646       -- Pred --
3647       ----------
3648
3649       when Attribute_Pred =>
3650          Check_Scalar_Type;
3651          Check_E1;
3652          Resolve (E1, P_Base_Type);
3653          Set_Etype (N, P_Base_Type);
3654
3655          --  Nothing to do for real type case
3656
3657          if Is_Real_Type (P_Type) then
3658             null;
3659
3660          --  If not modular type, test for overflow check required
3661
3662          else
3663             if not Is_Modular_Integer_Type (P_Type)
3664               and then not Range_Checks_Suppressed (P_Base_Type)
3665             then
3666                Enable_Range_Check (E1);
3667             end if;
3668          end if;
3669
3670       --------------
3671       -- Priority --
3672       --------------
3673
3674       --  Ada 2005 (AI-327): Dynamic ceiling priorities
3675
3676       when Attribute_Priority =>
3677          if Ada_Version < Ada_05 then
3678             Error_Attr ("% attribute is allowed only in Ada 2005 mode", P);
3679          end if;
3680
3681          Check_E0;
3682
3683          --  The prefix must be a protected object (AARM D.5.2 (2/2))
3684
3685          Analyze (P);
3686
3687          if Is_Protected_Type (Etype (P))
3688            or else (Is_Access_Type (Etype (P))
3689                       and then Is_Protected_Type (Designated_Type (Etype (P))))
3690          then
3691             Resolve (P, Etype (P));
3692          else
3693             Error_Attr_P ("prefix of % attribute must be a protected object");
3694          end if;
3695
3696          Set_Etype (N, Standard_Integer);
3697
3698          --  Must be called from within a protected procedure or entry of the
3699          --  protected object.
3700
3701          declare
3702             S : Entity_Id;
3703
3704          begin
3705             S := Current_Scope;
3706             while S /= Etype (P)
3707                and then S /= Standard_Standard
3708             loop
3709                S := Scope (S);
3710             end loop;
3711
3712             if S = Standard_Standard then
3713                Error_Attr ("the attribute % is only allowed inside protected "
3714                            & "operations", P);
3715             end if;
3716          end;
3717
3718          Validate_Non_Static_Attribute_Function_Call;
3719
3720       -----------
3721       -- Range --
3722       -----------
3723
3724       when Attribute_Range =>
3725          Check_Array_Or_Scalar_Type;
3726
3727          if Ada_Version = Ada_83
3728            and then Is_Scalar_Type (P_Type)
3729            and then Comes_From_Source (N)
3730          then
3731             Error_Attr
3732               ("(Ada 83) % attribute not allowed for scalar type", P);
3733          end if;
3734
3735       ------------
3736       -- Result --
3737       ------------
3738
3739       when Attribute_Result => Result : declare
3740          CS : constant Entity_Id := Current_Scope;
3741          PS : constant Entity_Id := Scope (CS);
3742
3743       begin
3744          --  If we are in the scope of a function and in Spec_Expression mode,
3745          --  this is likely the prescan of the postcondition pragma, and we
3746          --  just set the proper type. If there is an error it will be caught
3747          --  when the real Analyze call is done.
3748
3749          if Ekind (CS) = E_Function
3750            and then In_Spec_Expression
3751          then
3752             --  Check OK prefix
3753
3754             if Chars (CS) /= Chars (P) then
3755                Error_Msg_NE
3756                  ("incorrect prefix for % attribute, expected &", P, CS);
3757                Error_Attr;
3758             end if;
3759
3760             Set_Etype (N, Etype (CS));
3761
3762             --  If several functions with that name are visible,
3763             --  the intended one is the current scope.
3764
3765             if Is_Overloaded (P) then
3766                Set_Entity (P, CS);
3767                Set_Is_Overloaded (P, False);
3768             end if;
3769
3770          --  Body case, where we must be inside a generated _Postcondition
3771          --  procedure, or the attribute use is definitely misplaced.
3772
3773          elsif Chars (CS) = Name_uPostconditions
3774            and then Ekind (PS) = E_Function
3775          then
3776             --  Check OK prefix
3777
3778             if Nkind (P) /= N_Identifier
3779               or else Chars (P) /= Chars (PS)
3780             then
3781                Error_Msg_NE
3782                  ("incorrect prefix for % attribute, expected &", P, PS);
3783                Error_Attr;
3784             end if;
3785
3786             Rewrite (N,
3787               Make_Identifier (Sloc (N),
3788                 Chars => Name_uResult));
3789             Analyze_And_Resolve (N, Etype (PS));
3790
3791          else
3792             Error_Attr
3793               ("% attribute can only appear in function Postcondition pragma",
3794                P);
3795          end if;
3796       end Result;
3797
3798       ------------------
3799       -- Range_Length --
3800       ------------------
3801
3802       when Attribute_Range_Length =>
3803          Check_E0;
3804          Check_Discrete_Type;
3805          Set_Etype (N, Universal_Integer);
3806
3807       ----------
3808       -- Read --
3809       ----------
3810
3811       when Attribute_Read =>
3812          Check_E2;
3813          Check_Stream_Attribute (TSS_Stream_Read);
3814          Set_Etype (N, Standard_Void_Type);
3815          Resolve (N, Standard_Void_Type);
3816          Note_Possible_Modification (E2, Sure => True);
3817
3818       ---------------
3819       -- Remainder --
3820       ---------------
3821
3822       when Attribute_Remainder =>
3823          Check_Floating_Point_Type_2;
3824          Set_Etype (N, P_Base_Type);
3825          Resolve (E1, P_Base_Type);
3826          Resolve (E2, P_Base_Type);
3827
3828       -----------
3829       -- Round --
3830       -----------
3831
3832       when Attribute_Round =>
3833          Check_E1;
3834          Check_Decimal_Fixed_Point_Type;
3835          Set_Etype (N, P_Base_Type);
3836
3837          --  Because the context is universal_real (3.5.10(12)) it is a legal
3838          --  context for a universal fixed expression. This is the only
3839          --  attribute whose functional description involves U_R.
3840
3841          if Etype (E1) = Universal_Fixed then
3842             declare
3843                Conv : constant Node_Id := Make_Type_Conversion (Loc,
3844                   Subtype_Mark => New_Occurrence_Of (Universal_Real, Loc),
3845                   Expression   => Relocate_Node (E1));
3846
3847             begin
3848                Rewrite (E1, Conv);
3849                Analyze (E1);
3850             end;
3851          end if;
3852
3853          Resolve (E1, Any_Real);
3854
3855       --------------
3856       -- Rounding --
3857       --------------
3858
3859       when Attribute_Rounding =>
3860          Check_Floating_Point_Type_1;
3861          Set_Etype (N, P_Base_Type);
3862          Resolve (E1, P_Base_Type);
3863
3864       ---------------
3865       -- Safe_Emax --
3866       ---------------
3867
3868       when Attribute_Safe_Emax =>
3869          Check_Floating_Point_Type_0;
3870          Set_Etype (N, Universal_Integer);
3871
3872       ----------------
3873       -- Safe_First --
3874       ----------------
3875
3876       when Attribute_Safe_First =>
3877          Check_Floating_Point_Type_0;
3878          Set_Etype (N, Universal_Real);
3879
3880       ----------------
3881       -- Safe_Large --
3882       ----------------
3883
3884       when Attribute_Safe_Large =>
3885          Check_E0;
3886          Check_Real_Type;
3887          Set_Etype (N, Universal_Real);
3888
3889       ---------------
3890       -- Safe_Last --
3891       ---------------
3892
3893       when Attribute_Safe_Last =>
3894          Check_Floating_Point_Type_0;
3895          Set_Etype (N, Universal_Real);
3896
3897       ----------------
3898       -- Safe_Small --
3899       ----------------
3900
3901       when Attribute_Safe_Small =>
3902          Check_E0;
3903          Check_Real_Type;
3904          Set_Etype (N, Universal_Real);
3905
3906       -----------
3907       -- Scale --
3908       -----------
3909
3910       when Attribute_Scale =>
3911          Check_E0;
3912          Check_Decimal_Fixed_Point_Type;
3913          Set_Etype (N, Universal_Integer);
3914
3915       -------------
3916       -- Scaling --
3917       -------------
3918
3919       when Attribute_Scaling =>
3920          Check_Floating_Point_Type_2;
3921          Set_Etype (N, P_Base_Type);
3922          Resolve (E1, P_Base_Type);
3923
3924       ------------------
3925       -- Signed_Zeros --
3926       ------------------
3927
3928       when Attribute_Signed_Zeros =>
3929          Check_Floating_Point_Type_0;
3930          Set_Etype (N, Standard_Boolean);
3931
3932       ----------
3933       -- Size --
3934       ----------
3935
3936       when Attribute_Size | Attribute_VADS_Size => Size :
3937       begin
3938          Check_E0;
3939
3940          --  If prefix is parameterless function call, rewrite and resolve
3941          --  as such.
3942
3943          if Is_Entity_Name (P)
3944            and then Ekind (Entity (P)) = E_Function
3945          then
3946             Resolve (P);
3947
3948          --  Similar processing for a protected function call
3949
3950          elsif Nkind (P) = N_Selected_Component
3951            and then Ekind (Entity (Selector_Name (P))) = E_Function
3952          then
3953             Resolve (P);
3954          end if;
3955
3956          if Is_Object_Reference (P) then
3957             Check_Object_Reference (P);
3958
3959          elsif Is_Entity_Name (P)
3960            and then (Is_Type (Entity (P))
3961                        or else Ekind (Entity (P)) = E_Enumeration_Literal)
3962          then
3963             null;
3964
3965          elsif Nkind (P) = N_Type_Conversion
3966            and then not Comes_From_Source (P)
3967          then
3968             null;
3969
3970          else
3971             Error_Attr_P ("invalid prefix for % attribute");
3972          end if;
3973
3974          Check_Not_Incomplete_Type;
3975          Check_Not_CPP_Type;
3976          Set_Etype (N, Universal_Integer);
3977       end Size;
3978
3979       -----------
3980       -- Small --
3981       -----------
3982
3983       when Attribute_Small =>
3984          Check_E0;
3985          Check_Real_Type;
3986          Set_Etype (N, Universal_Real);
3987
3988       ------------------
3989       -- Storage_Pool --
3990       ------------------
3991
3992       when Attribute_Storage_Pool => Storage_Pool :
3993       begin
3994          Check_E0;
3995
3996          if Is_Access_Type (P_Type) then
3997             if Ekind (P_Type) = E_Access_Subprogram_Type then
3998                Error_Attr_P
3999                  ("cannot use % attribute for access-to-subprogram type");
4000             end if;
4001
4002             --  Set appropriate entity
4003
4004             if Present (Associated_Storage_Pool (Root_Type (P_Type))) then
4005                Set_Entity (N, Associated_Storage_Pool (Root_Type (P_Type)));
4006             else
4007                Set_Entity (N, RTE (RE_Global_Pool_Object));
4008             end if;
4009
4010             Set_Etype (N, Class_Wide_Type (RTE (RE_Root_Storage_Pool)));
4011
4012             --  Validate_Remote_Access_To_Class_Wide_Type for attribute
4013             --  Storage_Pool since this attribute is not defined for such
4014             --  types (RM E.2.3(22)).
4015
4016             Validate_Remote_Access_To_Class_Wide_Type (N);
4017
4018          else
4019             Error_Attr_P ("prefix of % attribute must be access type");
4020          end if;
4021       end Storage_Pool;
4022
4023       ------------------
4024       -- Storage_Size --
4025       ------------------
4026
4027       when Attribute_Storage_Size => Storage_Size :
4028       begin
4029          Check_E0;
4030
4031          if Is_Task_Type (P_Type) then
4032             Set_Etype (N, Universal_Integer);
4033
4034          elsif Is_Access_Type (P_Type) then
4035             if Ekind (P_Type) = E_Access_Subprogram_Type then
4036                Error_Attr_P
4037                  ("cannot use % attribute for access-to-subprogram type");
4038             end if;
4039
4040             if Is_Entity_Name (P)
4041               and then Is_Type (Entity (P))
4042             then
4043                Check_Type;
4044                Set_Etype (N, Universal_Integer);
4045
4046                --   Validate_Remote_Access_To_Class_Wide_Type for attribute
4047                --   Storage_Size since this attribute is not defined for
4048                --   such types (RM E.2.3(22)).
4049
4050                Validate_Remote_Access_To_Class_Wide_Type (N);
4051
4052             --  The prefix is allowed to be an implicit dereference
4053             --  of an access value designating a task.
4054
4055             else
4056                Check_Task_Prefix;
4057                Set_Etype (N, Universal_Integer);
4058             end if;
4059
4060          else
4061             Error_Attr_P ("prefix of % attribute must be access or task type");
4062          end if;
4063       end Storage_Size;
4064
4065       ------------------
4066       -- Storage_Unit --
4067       ------------------
4068
4069       when Attribute_Storage_Unit =>
4070          Standard_Attribute (Ttypes.System_Storage_Unit);
4071
4072       -----------------
4073       -- Stream_Size --
4074       -----------------
4075
4076       when Attribute_Stream_Size =>
4077          Check_E0;
4078          Check_Type;
4079
4080          if Is_Entity_Name (P)
4081            and then Is_Elementary_Type (Entity (P))
4082          then
4083             Set_Etype (N, Universal_Integer);
4084          else
4085             Error_Attr_P ("invalid prefix for % attribute");
4086          end if;
4087
4088       ---------------
4089       -- Stub_Type --
4090       ---------------
4091
4092       when Attribute_Stub_Type =>
4093          Check_Type;
4094          Check_E0;
4095
4096          if Is_Remote_Access_To_Class_Wide_Type (P_Type) then
4097             Rewrite (N,
4098               New_Occurrence_Of (Corresponding_Stub_Type (P_Type), Loc));
4099          else
4100             Error_Attr_P
4101               ("prefix of% attribute must be remote access to classwide");
4102          end if;
4103
4104       ----------
4105       -- Succ --
4106       ----------
4107
4108       when Attribute_Succ =>
4109          Check_Scalar_Type;
4110          Check_E1;
4111          Resolve (E1, P_Base_Type);
4112          Set_Etype (N, P_Base_Type);
4113
4114          --  Nothing to do for real type case
4115
4116          if Is_Real_Type (P_Type) then
4117             null;
4118
4119          --  If not modular type, test for overflow check required
4120
4121          else
4122             if not Is_Modular_Integer_Type (P_Type)
4123               and then not Range_Checks_Suppressed (P_Base_Type)
4124             then
4125                Enable_Range_Check (E1);
4126             end if;
4127          end if;
4128
4129       ---------
4130       -- Tag --
4131       ---------
4132
4133       when Attribute_Tag => Tag :
4134       begin
4135          Check_E0;
4136          Check_Dereference;
4137
4138          if not Is_Tagged_Type (P_Type) then
4139             Error_Attr_P ("prefix of % attribute must be tagged");
4140
4141          --  Next test does not apply to generated code
4142          --  why not, and what does the illegal reference mean???
4143
4144          elsif Is_Object_Reference (P)
4145            and then not Is_Class_Wide_Type (P_Type)
4146            and then Comes_From_Source (N)
4147          then
4148             Error_Attr_P
4149               ("% attribute can only be applied to objects " &
4150                "of class - wide type");
4151          end if;
4152
4153          --  The prefix cannot be an incomplete type. However, references
4154          --  to 'Tag can be generated when expanding interface conversions,
4155          --  and this is legal.
4156
4157          if Comes_From_Source (N) then
4158             Check_Not_Incomplete_Type;
4159          end if;
4160
4161          --  Set appropriate type
4162
4163          Set_Etype (N, RTE (RE_Tag));
4164       end Tag;
4165
4166       -----------------
4167       -- Target_Name --
4168       -----------------
4169
4170       when Attribute_Target_Name => Target_Name : declare
4171          TN : constant String := Sdefault.Target_Name.all;
4172          TL : Natural;
4173
4174       begin
4175          Check_Standard_Prefix;
4176
4177          TL := TN'Last;
4178
4179          if TN (TL) = '/' or else TN (TL) = '\' then
4180             TL := TL - 1;
4181          end if;
4182
4183          Rewrite (N,
4184            Make_String_Literal (Loc,
4185              Strval => TN (TN'First .. TL)));
4186          Analyze_And_Resolve (N, Standard_String);
4187       end Target_Name;
4188
4189       ----------------
4190       -- Terminated --
4191       ----------------
4192
4193       when Attribute_Terminated =>
4194          Check_E0;
4195          Set_Etype (N, Standard_Boolean);
4196          Check_Task_Prefix;
4197
4198       ----------------
4199       -- To_Address --
4200       ----------------
4201
4202       when Attribute_To_Address =>
4203          Check_E1;
4204          Analyze (P);
4205
4206          if Nkind (P) /= N_Identifier
4207            or else Chars (P) /= Name_System
4208          then
4209             Error_Attr_P ("prefix of %attribute must be System");
4210          end if;
4211
4212          Generate_Reference (RTE (RE_Address), P);
4213          Analyze_And_Resolve (E1, Any_Integer);
4214          Set_Etype (N, RTE (RE_Address));
4215
4216       ----------------
4217       -- Truncation --
4218       ----------------
4219
4220       when Attribute_Truncation =>
4221          Check_Floating_Point_Type_1;
4222          Resolve (E1, P_Base_Type);
4223          Set_Etype (N, P_Base_Type);
4224
4225       ----------------
4226       -- Type_Class --
4227       ----------------
4228
4229       when Attribute_Type_Class =>
4230          Check_E0;
4231          Check_Type;
4232          Check_Not_Incomplete_Type;
4233          Set_Etype (N, RTE (RE_Type_Class));
4234
4235       -----------------
4236       -- UET_Address --
4237       -----------------
4238
4239       when Attribute_UET_Address =>
4240          Check_E0;
4241          Check_Unit_Name (P);
4242          Set_Etype (N, RTE (RE_Address));
4243
4244       -----------------------
4245       -- Unbiased_Rounding --
4246       -----------------------
4247
4248       when Attribute_Unbiased_Rounding =>
4249          Check_Floating_Point_Type_1;
4250          Set_Etype (N, P_Base_Type);
4251          Resolve (E1, P_Base_Type);
4252
4253       ----------------------
4254       -- Unchecked_Access --
4255       ----------------------
4256
4257       when Attribute_Unchecked_Access =>
4258          if Comes_From_Source (N) then
4259             Check_Restriction (No_Unchecked_Access, N);
4260          end if;
4261
4262          Analyze_Access_Attribute;
4263
4264       -------------------------
4265       -- Unconstrained_Array --
4266       -------------------------
4267
4268       when Attribute_Unconstrained_Array =>
4269          Check_E0;
4270          Check_Type;
4271          Check_Not_Incomplete_Type;
4272          Set_Etype (N, Standard_Boolean);
4273
4274       ------------------------------
4275       -- Universal_Literal_String --
4276       ------------------------------
4277
4278       --  This is a GNAT specific attribute whose prefix must be a named
4279       --  number where the expression is either a single numeric literal,
4280       --  or a numeric literal immediately preceded by a minus sign. The
4281       --  result is equivalent to a string literal containing the text of
4282       --  the literal as it appeared in the source program with a possible
4283       --  leading minus sign.
4284
4285       when Attribute_Universal_Literal_String => Universal_Literal_String :
4286       begin
4287          Check_E0;
4288
4289          if not Is_Entity_Name (P)
4290            or else Ekind (Entity (P)) not in Named_Kind
4291          then
4292             Error_Attr_P ("prefix for % attribute must be named number");
4293
4294          else
4295             declare
4296                Expr     : Node_Id;
4297                Negative : Boolean;
4298                S        : Source_Ptr;
4299                Src      : Source_Buffer_Ptr;
4300
4301             begin
4302                Expr := Original_Node (Expression (Parent (Entity (P))));
4303
4304                if Nkind (Expr) = N_Op_Minus then
4305                   Negative := True;
4306                   Expr := Original_Node (Right_Opnd (Expr));
4307                else
4308                   Negative := False;
4309                end if;
4310
4311                if not Nkind_In (Expr, N_Integer_Literal, N_Real_Literal) then
4312                   Error_Attr
4313                     ("named number for % attribute must be simple literal", N);
4314                end if;
4315
4316                --  Build string literal corresponding to source literal text
4317
4318                Start_String;
4319
4320                if Negative then
4321                   Store_String_Char (Get_Char_Code ('-'));
4322                end if;
4323
4324                S := Sloc (Expr);
4325                Src := Source_Text (Get_Source_File_Index (S));
4326
4327                while Src (S) /= ';' and then Src (S) /= ' ' loop
4328                   Store_String_Char (Get_Char_Code (Src (S)));
4329                   S := S + 1;
4330                end loop;
4331
4332                --  Now we rewrite the attribute with the string literal
4333
4334                Rewrite (N,
4335                  Make_String_Literal (Loc, End_String));
4336                Analyze (N);
4337             end;
4338          end if;
4339       end Universal_Literal_String;
4340
4341       -------------------------
4342       -- Unrestricted_Access --
4343       -------------------------
4344
4345       --  This is a GNAT specific attribute which is like Access except that
4346       --  all scope checks and checks for aliased views are omitted.
4347
4348       when Attribute_Unrestricted_Access =>
4349          if Comes_From_Source (N) then
4350             Check_Restriction (No_Unchecked_Access, N);
4351          end if;
4352
4353          if Is_Entity_Name (P) then
4354             Set_Address_Taken (Entity (P));
4355          end if;
4356
4357          Analyze_Access_Attribute;
4358
4359       ---------
4360       -- Val --
4361       ---------
4362
4363       when Attribute_Val => Val : declare
4364       begin
4365          Check_E1;
4366          Check_Discrete_Type;
4367          Resolve (E1, Any_Integer);
4368          Set_Etype (N, P_Base_Type);
4369
4370          --  Note, we need a range check in general, but we wait for the
4371          --  Resolve call to do this, since we want to let Eval_Attribute
4372          --  have a chance to find an static illegality first!
4373       end Val;
4374
4375       -----------
4376       -- Valid --
4377       -----------
4378
4379       when Attribute_Valid =>
4380          Check_E0;
4381
4382          --  Ignore check for object if we have a 'Valid reference generated
4383          --  by the expanded code, since in some cases valid checks can occur
4384          --  on items that are names, but are not objects (e.g. attributes).
4385
4386          if Comes_From_Source (N) then
4387             Check_Object_Reference (P);
4388          end if;
4389
4390          if not Is_Scalar_Type (P_Type) then
4391             Error_Attr_P ("object for % attribute must be of scalar type");
4392          end if;
4393
4394          Set_Etype (N, Standard_Boolean);
4395
4396       -----------
4397       -- Value --
4398       -----------
4399
4400       when Attribute_Value => Value :
4401       begin
4402          Check_E1;
4403          Check_Scalar_Type;
4404
4405          --  Case of enumeration type
4406
4407          if Is_Enumeration_Type (P_Type) then
4408             Check_Restriction (No_Enumeration_Maps, N);
4409
4410             --  Mark all enumeration literals as referenced, since the use of
4411             --  the Value attribute can implicitly reference any of the
4412             --  literals of the enumeration base type.
4413
4414             declare
4415                Ent : Entity_Id := First_Literal (P_Base_Type);
4416             begin
4417                while Present (Ent) loop
4418                   Set_Referenced (Ent);
4419                   Next_Literal (Ent);
4420                end loop;
4421             end;
4422          end if;
4423
4424          --  Set Etype before resolving expression because expansion of
4425          --  expression may require enclosing type. Note that the type
4426          --  returned by 'Value is the base type of the prefix type.
4427
4428          Set_Etype (N, P_Base_Type);
4429          Validate_Non_Static_Attribute_Function_Call;
4430       end Value;
4431
4432       ----------------
4433       -- Value_Size --
4434       ----------------
4435
4436       when Attribute_Value_Size =>
4437          Check_E0;
4438          Check_Type;
4439          Check_Not_Incomplete_Type;
4440          Set_Etype (N, Universal_Integer);
4441
4442       -------------
4443       -- Version --
4444       -------------
4445
4446       when Attribute_Version =>
4447          Check_E0;
4448          Check_Program_Unit;
4449          Set_Etype (N, RTE (RE_Version_String));
4450
4451       ------------------
4452       -- Wchar_T_Size --
4453       ------------------
4454
4455       when Attribute_Wchar_T_Size =>
4456          Standard_Attribute (Interfaces_Wchar_T_Size);
4457
4458       ----------------
4459       -- Wide_Image --
4460       ----------------
4461
4462       when Attribute_Wide_Image => Wide_Image :
4463       begin
4464          Check_Scalar_Type;
4465          Set_Etype (N, Standard_Wide_String);
4466          Check_E1;
4467          Resolve (E1, P_Base_Type);
4468          Validate_Non_Static_Attribute_Function_Call;
4469       end Wide_Image;
4470
4471       ---------------------
4472       -- Wide_Wide_Image --
4473       ---------------------
4474
4475       when Attribute_Wide_Wide_Image => Wide_Wide_Image :
4476       begin
4477          Check_Scalar_Type;
4478          Set_Etype (N, Standard_Wide_Wide_String);
4479          Check_E1;
4480          Resolve (E1, P_Base_Type);
4481          Validate_Non_Static_Attribute_Function_Call;
4482       end Wide_Wide_Image;
4483
4484       ----------------
4485       -- Wide_Value --
4486       ----------------
4487
4488       when Attribute_Wide_Value => Wide_Value :
4489       begin
4490          Check_E1;
4491          Check_Scalar_Type;
4492
4493          --  Set Etype before resolving expression because expansion
4494          --  of expression may require enclosing type.
4495
4496          Set_Etype (N, P_Type);
4497          Validate_Non_Static_Attribute_Function_Call;
4498       end Wide_Value;
4499
4500       ---------------------
4501       -- Wide_Wide_Value --
4502       ---------------------
4503
4504       when Attribute_Wide_Wide_Value => Wide_Wide_Value :
4505       begin
4506          Check_E1;
4507          Check_Scalar_Type;
4508
4509          --  Set Etype before resolving expression because expansion
4510          --  of expression may require enclosing type.
4511
4512          Set_Etype (N, P_Type);
4513          Validate_Non_Static_Attribute_Function_Call;
4514       end Wide_Wide_Value;
4515
4516       ---------------------
4517       -- Wide_Wide_Width --
4518       ---------------------
4519
4520       when Attribute_Wide_Wide_Width =>
4521          Check_E0;
4522          Check_Scalar_Type;
4523          Set_Etype (N, Universal_Integer);
4524
4525       ----------------
4526       -- Wide_Width --
4527       ----------------
4528
4529       when Attribute_Wide_Width =>
4530          Check_E0;
4531          Check_Scalar_Type;
4532          Set_Etype (N, Universal_Integer);
4533
4534       -----------
4535       -- Width --
4536       -----------
4537
4538       when Attribute_Width =>
4539          Check_E0;
4540          Check_Scalar_Type;
4541          Set_Etype (N, Universal_Integer);
4542
4543       ---------------
4544       -- Word_Size --
4545       ---------------
4546
4547       when Attribute_Word_Size =>
4548          Standard_Attribute (System_Word_Size);
4549
4550       -----------
4551       -- Write --
4552       -----------
4553
4554       when Attribute_Write =>
4555          Check_E2;
4556          Check_Stream_Attribute (TSS_Stream_Write);
4557          Set_Etype (N, Standard_Void_Type);
4558          Resolve (N, Standard_Void_Type);
4559
4560       end case;
4561
4562    --  All errors raise Bad_Attribute, so that we get out before any further
4563    --  damage occurs when an error is detected (for example, if we check for
4564    --  one attribute expression, and the check succeeds, we want to be able
4565    --  to proceed securely assuming that an expression is in fact present.
4566
4567    --  Note: we set the attribute analyzed in this case to prevent any
4568    --  attempt at reanalysis which could generate spurious error msgs.
4569
4570    exception
4571       when Bad_Attribute =>
4572          Set_Analyzed (N);
4573          Set_Etype (N, Any_Type);
4574          return;
4575    end Analyze_Attribute;
4576
4577    --------------------
4578    -- Eval_Attribute --
4579    --------------------
4580
4581    procedure Eval_Attribute (N : Node_Id) is
4582       Loc   : constant Source_Ptr   := Sloc (N);
4583       Aname : constant Name_Id      := Attribute_Name (N);
4584       Id    : constant Attribute_Id := Get_Attribute_Id (Aname);
4585       P     : constant Node_Id      := Prefix (N);
4586
4587       C_Type : constant Entity_Id := Etype (N);
4588       --  The type imposed by the context
4589
4590       E1 : Node_Id;
4591       --  First expression, or Empty if none
4592
4593       E2 : Node_Id;
4594       --  Second expression, or Empty if none
4595
4596       P_Entity : Entity_Id;
4597       --  Entity denoted by prefix
4598
4599       P_Type : Entity_Id;
4600       --  The type of the prefix
4601
4602       P_Base_Type : Entity_Id;
4603       --  The base type of the prefix type
4604
4605       P_Root_Type : Entity_Id;
4606       --  The root type of the prefix type
4607
4608       Static : Boolean;
4609       --  True if the result is Static. This is set by the general processing
4610       --  to true if the prefix is static, and all expressions are static. It
4611       --  can be reset as processing continues for particular attributes
4612
4613       Lo_Bound, Hi_Bound : Node_Id;
4614       --  Expressions for low and high bounds of type or array index referenced
4615       --  by First, Last, or Length attribute for array, set by Set_Bounds.
4616
4617       CE_Node : Node_Id;
4618       --  Constraint error node used if we have an attribute reference has
4619       --  an argument that raises a constraint error. In this case we replace
4620       --  the attribute with a raise constraint_error node. This is important
4621       --  processing, since otherwise gigi might see an attribute which it is
4622       --  unprepared to deal with.
4623
4624       function Aft_Value return Nat;
4625       --  Computes Aft value for current attribute prefix (used by Aft itself
4626       --  and also by Width for computing the Width of a fixed point type).
4627
4628       procedure Check_Expressions;
4629       --  In case where the attribute is not foldable, the expressions, if
4630       --  any, of the attribute, are in a non-static context. This procedure
4631       --  performs the required additional checks.
4632
4633       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean;
4634       --  Determines if the given type has compile time known bounds. Note
4635       --  that we enter the case statement even in cases where the prefix
4636       --  type does NOT have known bounds, so it is important to guard any
4637       --  attempt to evaluate both bounds with a call to this function.
4638
4639       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint);
4640       --  This procedure is called when the attribute N has a non-static
4641       --  but compile time known value given by Val. It includes the
4642       --  necessary checks for out of range values.
4643
4644       procedure Float_Attribute_Universal_Integer
4645         (IEEES_Val : Int;
4646          IEEEL_Val : Int;
4647          IEEEX_Val : Int;
4648          VAXFF_Val : Int;
4649          VAXDF_Val : Int;
4650          VAXGF_Val : Int;
4651          AAMPS_Val : Int;
4652          AAMPL_Val : Int);
4653       --  This procedure evaluates a float attribute with no arguments that
4654       --  returns a universal integer result. The parameters give the values
4655       --  for the possible floating-point root types. See ttypef for details.
4656       --  The prefix type is a float type (and is thus not a generic type).
4657
4658       procedure Float_Attribute_Universal_Real
4659         (IEEES_Val : String;
4660          IEEEL_Val : String;
4661          IEEEX_Val : String;
4662          VAXFF_Val : String;
4663          VAXDF_Val : String;
4664          VAXGF_Val : String;
4665          AAMPS_Val : String;
4666          AAMPL_Val : String);
4667       --  This procedure evaluates a float attribute with no arguments that
4668       --  returns a universal real result. The parameters give the values
4669       --  required for the possible floating-point root types in string
4670       --  format as real literals with a possible leading minus sign.
4671       --  The prefix type is a float type (and is thus not a generic type).
4672
4673       function Fore_Value return Nat;
4674       --  Computes the Fore value for the current attribute prefix, which is
4675       --  known to be a static fixed-point type. Used by Fore and Width.
4676
4677       function Mantissa return Uint;
4678       --  Returns the Mantissa value for the prefix type
4679
4680       procedure Set_Bounds;
4681       --  Used for First, Last and Length attributes applied to an array or
4682       --  array subtype. Sets the variables Lo_Bound and Hi_Bound to the low
4683       --  and high bound expressions for the index referenced by the attribute
4684       --  designator (i.e. the first index if no expression is present, and
4685       --  the N'th index if the value N is present as an expression). Also
4686       --  used for First and Last of scalar types. Static is reset to False
4687       --  if the type or index type is not statically constrained.
4688
4689       function Statically_Denotes_Entity (N : Node_Id) return Boolean;
4690       --  Verify that the prefix of a potentially static array attribute
4691       --  satisfies the conditions of 4.9 (14).
4692
4693       ---------------
4694       -- Aft_Value --
4695       ---------------
4696
4697       function Aft_Value return Nat is
4698          Result    : Nat;
4699          Delta_Val : Ureal;
4700
4701       begin
4702          Result := 1;
4703          Delta_Val := Delta_Value (P_Type);
4704          while Delta_Val < Ureal_Tenth loop
4705             Delta_Val := Delta_Val * Ureal_10;
4706             Result := Result + 1;
4707          end loop;
4708
4709          return Result;
4710       end Aft_Value;
4711
4712       -----------------------
4713       -- Check_Expressions --
4714       -----------------------
4715
4716       procedure Check_Expressions is
4717          E : Node_Id;
4718       begin
4719          E := E1;
4720          while Present (E) loop
4721             Check_Non_Static_Context (E);
4722             Next (E);
4723          end loop;
4724       end Check_Expressions;
4725
4726       ----------------------------------
4727       -- Compile_Time_Known_Attribute --
4728       ----------------------------------
4729
4730       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint) is
4731          T : constant Entity_Id := Etype (N);
4732
4733       begin
4734          Fold_Uint (N, Val, False);
4735
4736          --  Check that result is in bounds of the type if it is static
4737
4738          if Is_In_Range (N, T) then
4739             null;
4740
4741          elsif Is_Out_Of_Range (N, T) then
4742             Apply_Compile_Time_Constraint_Error
4743               (N, "value not in range of}?", CE_Range_Check_Failed);
4744
4745          elsif not Range_Checks_Suppressed (T) then
4746             Enable_Range_Check (N);
4747
4748          else
4749             Set_Do_Range_Check (N, False);
4750          end if;
4751       end Compile_Time_Known_Attribute;
4752
4753       -------------------------------
4754       -- Compile_Time_Known_Bounds --
4755       -------------------------------
4756
4757       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean is
4758       begin
4759          return
4760            Compile_Time_Known_Value (Type_Low_Bound (Typ))
4761              and then
4762            Compile_Time_Known_Value (Type_High_Bound (Typ));
4763       end Compile_Time_Known_Bounds;
4764
4765       ---------------------------------------
4766       -- Float_Attribute_Universal_Integer --
4767       ---------------------------------------
4768
4769       procedure Float_Attribute_Universal_Integer
4770         (IEEES_Val : Int;
4771          IEEEL_Val : Int;
4772          IEEEX_Val : Int;
4773          VAXFF_Val : Int;
4774          VAXDF_Val : Int;
4775          VAXGF_Val : Int;
4776          AAMPS_Val : Int;
4777          AAMPL_Val : Int)
4778       is
4779          Val  : Int;
4780          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4781
4782       begin
4783          if Vax_Float (P_Base_Type) then
4784             if Digs = VAXFF_Digits then
4785                Val := VAXFF_Val;
4786             elsif Digs = VAXDF_Digits then
4787                Val := VAXDF_Val;
4788             else pragma Assert (Digs = VAXGF_Digits);
4789                Val := VAXGF_Val;
4790             end if;
4791
4792          elsif Is_AAMP_Float (P_Base_Type) then
4793             if Digs = AAMPS_Digits then
4794                Val := AAMPS_Val;
4795             else pragma Assert (Digs = AAMPL_Digits);
4796                Val := AAMPL_Val;
4797             end if;
4798
4799          else
4800             if Digs = IEEES_Digits then
4801                Val := IEEES_Val;
4802             elsif Digs = IEEEL_Digits then
4803                Val := IEEEL_Val;
4804             else pragma Assert (Digs = IEEEX_Digits);
4805                Val := IEEEX_Val;
4806             end if;
4807          end if;
4808
4809          Fold_Uint (N, UI_From_Int (Val), True);
4810       end Float_Attribute_Universal_Integer;
4811
4812       ------------------------------------
4813       -- Float_Attribute_Universal_Real --
4814       ------------------------------------
4815
4816       procedure Float_Attribute_Universal_Real
4817         (IEEES_Val : String;
4818          IEEEL_Val : String;
4819          IEEEX_Val : String;
4820          VAXFF_Val : String;
4821          VAXDF_Val : String;
4822          VAXGF_Val : String;
4823          AAMPS_Val : String;
4824          AAMPL_Val : String)
4825       is
4826          Val  : Node_Id;
4827          Digs : constant Nat := UI_To_Int (Digits_Value (P_Base_Type));
4828
4829       begin
4830          if Vax_Float (P_Base_Type) then
4831             if Digs = VAXFF_Digits then
4832                Val := Real_Convert (VAXFF_Val);
4833             elsif Digs = VAXDF_Digits then
4834                Val := Real_Convert (VAXDF_Val);
4835             else pragma Assert (Digs = VAXGF_Digits);
4836                Val := Real_Convert (VAXGF_Val);
4837             end if;
4838
4839          elsif Is_AAMP_Float (P_Base_Type) then
4840             if Digs = AAMPS_Digits then
4841                Val := Real_Convert (AAMPS_Val);
4842             else pragma Assert (Digs = AAMPL_Digits);
4843                Val := Real_Convert (AAMPL_Val);
4844             end if;
4845
4846          else
4847             if Digs = IEEES_Digits then
4848                Val := Real_Convert (IEEES_Val);
4849             elsif Digs = IEEEL_Digits then
4850                Val := Real_Convert (IEEEL_Val);
4851             else pragma Assert (Digs = IEEEX_Digits);
4852                Val := Real_Convert (IEEEX_Val);
4853             end if;
4854          end if;
4855
4856          Set_Sloc (Val, Loc);
4857          Rewrite (N, Val);
4858          Set_Is_Static_Expression (N, Static);
4859          Analyze_And_Resolve (N, C_Type);
4860       end Float_Attribute_Universal_Real;
4861
4862       ----------------
4863       -- Fore_Value --
4864       ----------------
4865
4866       --  Note that the Fore calculation is based on the actual values
4867       --  of the bounds, and does not take into account possible rounding.
4868
4869       function Fore_Value return Nat is
4870          Lo      : constant Uint  := Expr_Value (Type_Low_Bound (P_Type));
4871          Hi      : constant Uint  := Expr_Value (Type_High_Bound (P_Type));
4872          Small   : constant Ureal := Small_Value (P_Type);
4873          Lo_Real : constant Ureal := Lo * Small;
4874          Hi_Real : constant Ureal := Hi * Small;
4875          T       : Ureal;
4876          R       : Nat;
4877
4878       begin
4879          --  Bounds are given in terms of small units, so first compute
4880          --  proper values as reals.
4881
4882          T := UR_Max (abs Lo_Real, abs Hi_Real);
4883          R := 2;
4884
4885          --  Loop to compute proper value if more than one digit required
4886
4887          while T >= Ureal_10 loop
4888             R := R + 1;
4889             T := T / Ureal_10;
4890          end loop;
4891
4892          return R;
4893       end Fore_Value;
4894
4895       --------------
4896       -- Mantissa --
4897       --------------
4898
4899       --  Table of mantissa values accessed by function  Computed using
4900       --  the relation:
4901
4902       --    T'Mantissa = integer next above (D * log(10)/log(2)) + 1)
4903
4904       --  where D is T'Digits (RM83 3.5.7)
4905
4906       Mantissa_Value : constant array (Nat range 1 .. 40) of Nat := (
4907           1 =>   5,
4908           2 =>   8,
4909           3 =>  11,
4910           4 =>  15,
4911           5 =>  18,
4912           6 =>  21,
4913           7 =>  25,
4914           8 =>  28,
4915           9 =>  31,
4916          10 =>  35,
4917          11 =>  38,
4918          12 =>  41,
4919          13 =>  45,
4920          14 =>  48,
4921          15 =>  51,
4922          16 =>  55,
4923          17 =>  58,
4924          18 =>  61,
4925          19 =>  65,
4926          20 =>  68,
4927          21 =>  71,
4928          22 =>  75,
4929          23 =>  78,
4930          24 =>  81,
4931          25 =>  85,
4932          26 =>  88,
4933          27 =>  91,
4934          28 =>  95,
4935          29 =>  98,
4936          30 => 101,
4937          31 => 104,
4938          32 => 108,
4939          33 => 111,
4940          34 => 114,
4941          35 => 118,
4942          36 => 121,
4943          37 => 124,
4944          38 => 128,
4945          39 => 131,
4946          40 => 134);
4947
4948       function Mantissa return Uint is
4949       begin
4950          return
4951            UI_From_Int (Mantissa_Value (UI_To_Int (Digits_Value (P_Type))));
4952       end Mantissa;
4953
4954       ----------------
4955       -- Set_Bounds --
4956       ----------------
4957
4958       procedure Set_Bounds is
4959          Ndim : Nat;
4960          Indx : Node_Id;
4961          Ityp : Entity_Id;
4962
4963       begin
4964          --  For a string literal subtype, we have to construct the bounds.
4965          --  Valid Ada code never applies attributes to string literals, but
4966          --  it is convenient to allow the expander to generate attribute
4967          --  references of this type (e.g. First and Last applied to a string
4968          --  literal).
4969
4970          --  Note that the whole point of the E_String_Literal_Subtype is to
4971          --  avoid this construction of bounds, but the cases in which we
4972          --  have to materialize them are rare enough that we don't worry!
4973
4974          --  The low bound is simply the low bound of the base type. The
4975          --  high bound is computed from the length of the string and this
4976          --  low bound.
4977
4978          if Ekind (P_Type) = E_String_Literal_Subtype then
4979             Ityp := Etype (First_Index (Base_Type (P_Type)));
4980             Lo_Bound := Type_Low_Bound (Ityp);
4981
4982             Hi_Bound :=
4983               Make_Integer_Literal (Sloc (P),
4984                 Intval =>
4985                   Expr_Value (Lo_Bound) + String_Literal_Length (P_Type) - 1);
4986
4987             Set_Parent (Hi_Bound, P);
4988             Analyze_And_Resolve (Hi_Bound, Etype (Lo_Bound));
4989             return;
4990
4991          --  For non-array case, just get bounds of scalar type
4992
4993          elsif Is_Scalar_Type (P_Type) then
4994             Ityp := P_Type;
4995
4996             --  For a fixed-point type, we must freeze to get the attributes
4997             --  of the fixed-point type set now so we can reference them.
4998
4999             if Is_Fixed_Point_Type (P_Type)
5000               and then not Is_Frozen (Base_Type (P_Type))
5001               and then Compile_Time_Known_Value (Type_Low_Bound (P_Type))
5002               and then Compile_Time_Known_Value (Type_High_Bound (P_Type))
5003             then
5004                Freeze_Fixed_Point_Type (Base_Type (P_Type));
5005             end if;
5006
5007          --  For array case, get type of proper index
5008
5009          else
5010             if No (E1) then
5011                Ndim := 1;
5012             else
5013                Ndim := UI_To_Int (Expr_Value (E1));
5014             end if;
5015
5016             Indx := First_Index (P_Type);
5017             for J in 1 .. Ndim - 1 loop
5018                Next_Index (Indx);
5019             end loop;
5020
5021             --  If no index type, get out (some other error occurred, and
5022             --  we don't have enough information to complete the job!)
5023
5024             if No (Indx) then
5025                Lo_Bound := Error;
5026                Hi_Bound := Error;
5027                return;
5028             end if;
5029
5030             Ityp := Etype (Indx);
5031          end if;
5032
5033          --  A discrete range in an index constraint is allowed to be a
5034          --  subtype indication. This is syntactically a pain, but should
5035          --  not propagate to the entity for the corresponding index subtype.
5036          --  After checking that the subtype indication is legal, the range
5037          --  of the subtype indication should be transfered to the entity.
5038          --  The attributes for the bounds should remain the simple retrievals
5039          --  that they are now.
5040
5041          Lo_Bound := Type_Low_Bound (Ityp);
5042          Hi_Bound := Type_High_Bound (Ityp);
5043
5044          if not Is_Static_Subtype (Ityp) then
5045             Static := False;
5046          end if;
5047       end Set_Bounds;
5048
5049       -------------------------------
5050       -- Statically_Denotes_Entity --
5051       -------------------------------
5052
5053       function Statically_Denotes_Entity (N : Node_Id) return Boolean is
5054          E : Entity_Id;
5055
5056       begin
5057          if not Is_Entity_Name (N) then
5058             return False;
5059          else
5060             E := Entity (N);
5061          end if;
5062
5063          return
5064            Nkind (Parent (E)) /= N_Object_Renaming_Declaration
5065              or else Statically_Denotes_Entity (Renamed_Object (E));
5066       end Statically_Denotes_Entity;
5067
5068    --  Start of processing for Eval_Attribute
5069
5070    begin
5071       --  Acquire first two expressions (at the moment, no attributes
5072       --  take more than two expressions in any case).
5073
5074       if Present (Expressions (N)) then
5075          E1 := First (Expressions (N));
5076          E2 := Next (E1);
5077       else
5078          E1 := Empty;
5079          E2 := Empty;
5080       end if;
5081
5082       --  Special processing for Enabled attribute. This attribute has a very
5083       --  special prefix, and the easiest way to avoid lots of special checks
5084       --  to protect this special prefix from causing trouble is to deal with
5085       --  this attribute immediately and be done with it.
5086
5087       if Id = Attribute_Enabled then
5088
5089          --  Evaluate the Enabled attribute
5090
5091          --  We skip evaluation if the expander is not active. This is not just
5092          --  an optimization. It is of key importance that we not rewrite the
5093          --  attribute in a generic template, since we want to pick up the
5094          --  setting of the check in the instance, and testing expander active
5095          --  is as easy way of doing this as any.
5096
5097          if Expander_Active then
5098             declare
5099                C : constant Check_Id := Get_Check_Id (Chars (P));
5100                R : Boolean;
5101
5102             begin
5103                if No (E1) then
5104                   if C in Predefined_Check_Id then
5105                      R := Scope_Suppress (C);
5106                   else
5107                      R := Is_Check_Suppressed (Empty, C);
5108                   end if;
5109
5110                else
5111                   R := Is_Check_Suppressed (Entity (E1), C);
5112                end if;
5113
5114                if R then
5115                   Rewrite (N, New_Occurrence_Of (Standard_False, Loc));
5116                else
5117                   Rewrite (N, New_Occurrence_Of (Standard_True, Loc));
5118                end if;
5119             end;
5120          end if;
5121
5122          return;
5123       end if;
5124
5125       --  Special processing for cases where the prefix is an object. For
5126       --  this purpose, a string literal counts as an object (attributes
5127       --  of string literals can only appear in generated code).
5128
5129       if Is_Object_Reference (P) or else Nkind (P) = N_String_Literal then
5130
5131          --  For Component_Size, the prefix is an array object, and we apply
5132          --  the attribute to the type of the object. This is allowed for
5133          --  both unconstrained and constrained arrays, since the bounds
5134          --  have no influence on the value of this attribute.
5135
5136          if Id = Attribute_Component_Size then
5137             P_Entity := Etype (P);
5138
5139          --  For First and Last, the prefix is an array object, and we apply
5140          --  the attribute to the type of the array, but we need a constrained
5141          --  type for this, so we use the actual subtype if available.
5142
5143          elsif Id = Attribute_First
5144                  or else
5145                Id = Attribute_Last
5146                  or else
5147                Id = Attribute_Length
5148          then
5149             declare
5150                AS : constant Entity_Id := Get_Actual_Subtype_If_Available (P);
5151
5152             begin
5153                if Present (AS) and then Is_Constrained (AS) then
5154                   P_Entity := AS;
5155
5156                --  If we have an unconstrained type, cannot fold
5157
5158                else
5159                   Check_Expressions;
5160                   return;
5161                end if;
5162             end;
5163
5164          --  For Size, give size of object if available, otherwise we
5165          --  cannot fold Size.
5166
5167          elsif Id = Attribute_Size then
5168             if Is_Entity_Name (P)
5169               and then Known_Esize (Entity (P))
5170             then
5171                Compile_Time_Known_Attribute (N, Esize (Entity (P)));
5172                return;
5173
5174             else
5175                Check_Expressions;
5176                return;
5177             end if;
5178
5179          --  For Alignment, give size of object if available, otherwise we
5180          --  cannot fold Alignment.
5181
5182          elsif Id = Attribute_Alignment then
5183             if Is_Entity_Name (P)
5184               and then Known_Alignment (Entity (P))
5185             then
5186                Fold_Uint (N, Alignment (Entity (P)), False);
5187                return;
5188
5189             else
5190                Check_Expressions;
5191                return;
5192             end if;
5193
5194          --  No other attributes for objects are folded
5195
5196          else
5197             Check_Expressions;
5198             return;
5199          end if;
5200
5201       --  Cases where P is not an object. Cannot do anything if P is
5202       --  not the name of an entity.
5203
5204       elsif not Is_Entity_Name (P) then
5205          Check_Expressions;
5206          return;
5207
5208       --  Otherwise get prefix entity
5209
5210       else
5211          P_Entity := Entity (P);
5212       end if;
5213
5214       --  At this stage P_Entity is the entity to which the attribute
5215       --  is to be applied. This is usually simply the entity of the
5216       --  prefix, except in some cases of attributes for objects, where
5217       --  as described above, we apply the attribute to the object type.
5218
5219       --  First foldable possibility is a scalar or array type (RM 4.9(7))
5220       --  that is not generic (generic types are eliminated by RM 4.9(25)).
5221       --  Note we allow non-static non-generic types at this stage as further
5222       --  described below.
5223
5224       if Is_Type (P_Entity)
5225         and then (Is_Scalar_Type (P_Entity) or Is_Array_Type (P_Entity))
5226         and then (not Is_Generic_Type (P_Entity))
5227       then
5228          P_Type := P_Entity;
5229
5230       --  Second foldable possibility is an array object (RM 4.9(8))
5231
5232       elsif (Ekind (P_Entity) = E_Variable
5233                or else
5234              Ekind (P_Entity) = E_Constant)
5235         and then Is_Array_Type (Etype (P_Entity))
5236         and then (not Is_Generic_Type (Etype (P_Entity)))
5237       then
5238          P_Type := Etype (P_Entity);
5239
5240          --  If the entity is an array constant with an unconstrained nominal
5241          --  subtype then get the type from the initial value. If the value has
5242          --  been expanded into assignments, there is no expression and the
5243          --  attribute reference remains dynamic.
5244
5245          --  We could do better here and retrieve the type ???
5246
5247          if Ekind (P_Entity) = E_Constant
5248            and then not Is_Constrained (P_Type)
5249          then
5250             if No (Constant_Value (P_Entity)) then
5251                return;
5252             else
5253                P_Type := Etype (Constant_Value (P_Entity));
5254             end if;
5255          end if;
5256
5257       --  Definite must be folded if the prefix is not a generic type,
5258       --  that is to say if we are within an instantiation. Same processing
5259       --  applies to the GNAT attributes Has_Discriminants, Type_Class,
5260       --  Has_Tagged_Value, and Unconstrained_Array.
5261
5262       elsif (Id = Attribute_Definite
5263                or else
5264              Id = Attribute_Has_Access_Values
5265                or else
5266              Id = Attribute_Has_Discriminants
5267                or else
5268              Id = Attribute_Has_Tagged_Values
5269                or else
5270              Id = Attribute_Type_Class
5271                or else
5272              Id = Attribute_Unconstrained_Array)
5273         and then not Is_Generic_Type (P_Entity)
5274       then
5275          P_Type := P_Entity;
5276
5277       --  We can fold 'Size applied to a type if the size is known (as happens
5278       --  for a size from an attribute definition clause). At this stage, this
5279       --  can happen only for types (e.g. record types) for which the size is
5280       --  always non-static. We exclude generic types from consideration (since
5281       --  they have bogus sizes set within templates).
5282
5283       elsif Id = Attribute_Size
5284         and then Is_Type (P_Entity)
5285         and then (not Is_Generic_Type (P_Entity))
5286         and then Known_Static_RM_Size (P_Entity)
5287       then
5288          Compile_Time_Known_Attribute (N, RM_Size (P_Entity));
5289          return;
5290
5291       --  We can fold 'Alignment applied to a type if the alignment is known
5292       --  (as happens for an alignment from an attribute definition clause).
5293       --  At this stage, this can happen only for types (e.g. record
5294       --  types) for which the size is always non-static. We exclude
5295       --  generic types from consideration (since they have bogus
5296       --  sizes set within templates).
5297
5298       elsif Id = Attribute_Alignment
5299         and then Is_Type (P_Entity)
5300         and then (not Is_Generic_Type (P_Entity))
5301         and then Known_Alignment (P_Entity)
5302       then
5303          Compile_Time_Known_Attribute (N, Alignment (P_Entity));
5304          return;
5305
5306       --  If this is an access attribute that is known to fail accessibility
5307       --  check, rewrite accordingly.
5308
5309       elsif Attribute_Name (N) = Name_Access
5310         and then Raises_Constraint_Error (N)
5311       then
5312          Rewrite (N,
5313            Make_Raise_Program_Error (Loc,
5314              Reason => PE_Accessibility_Check_Failed));
5315          Set_Etype (N, C_Type);
5316          return;
5317
5318       --  No other cases are foldable (they certainly aren't static, and at
5319       --  the moment we don't try to fold any cases other than these three).
5320
5321       else
5322          Check_Expressions;
5323          return;
5324       end if;
5325
5326       --  If either attribute or the prefix is Any_Type, then propagate
5327       --  Any_Type to the result and don't do anything else at all.
5328
5329       if P_Type = Any_Type
5330         or else (Present (E1) and then Etype (E1) = Any_Type)
5331         or else (Present (E2) and then Etype (E2) = Any_Type)
5332       then
5333          Set_Etype (N, Any_Type);
5334          return;
5335       end if;
5336
5337       --  Scalar subtype case. We have not yet enforced the static requirement
5338       --  of (RM 4.9(7)) and we don't intend to just yet, since there are cases
5339       --  of non-static attribute references (e.g. S'Digits for a non-static
5340       --  floating-point type, which we can compute at compile time).
5341
5342       --  Note: this folding of non-static attributes is not simply a case of
5343       --  optimization. For many of the attributes affected, Gigi cannot handle
5344       --  the attribute and depends on the front end having folded them away.
5345
5346       --  Note: although we don't require staticness at this stage, we do set
5347       --  the Static variable to record the staticness, for easy reference by
5348       --  those attributes where it matters (e.g. Succ and Pred), and also to
5349       --  be used to ensure that non-static folded things are not marked as
5350       --  being static (a check that is done right at the end).
5351
5352       P_Root_Type := Root_Type (P_Type);
5353       P_Base_Type := Base_Type (P_Type);
5354
5355       --  If the root type or base type is generic, then we cannot fold. This
5356       --  test is needed because subtypes of generic types are not always
5357       --  marked as being generic themselves (which seems odd???)
5358
5359       if Is_Generic_Type (P_Root_Type)
5360         or else Is_Generic_Type (P_Base_Type)
5361       then
5362          return;
5363       end if;
5364
5365       if Is_Scalar_Type (P_Type) then
5366          Static := Is_OK_Static_Subtype (P_Type);
5367
5368       --  Array case. We enforce the constrained requirement of (RM 4.9(7-8))
5369       --  since we can't do anything with unconstrained arrays. In addition,
5370       --  only the First, Last and Length attributes are possibly static.
5371
5372       --  Definite, Has_Access_Values, Has_Discriminants, Has_Tagged_Values,
5373       --  Type_Class, and Unconstrained_Array are again exceptions, because
5374       --  they apply as well to unconstrained types.
5375
5376       --  In addition Component_Size is an exception since it is possibly
5377       --  foldable, even though it is never static, and it does apply to
5378       --  unconstrained arrays. Furthermore, it is essential to fold this
5379       --  in the packed case, since otherwise the value will be incorrect.
5380
5381       elsif Id = Attribute_Definite
5382               or else
5383             Id = Attribute_Has_Access_Values
5384               or else
5385             Id = Attribute_Has_Discriminants
5386               or else
5387             Id = Attribute_Has_Tagged_Values
5388               or else
5389             Id = Attribute_Type_Class
5390               or else
5391             Id = Attribute_Unconstrained_Array
5392               or else
5393             Id = Attribute_Component_Size
5394       then
5395          Static := False;
5396
5397       else
5398          if not Is_Constrained (P_Type)
5399            or else (Id /= Attribute_First and then
5400                     Id /= Attribute_Last  and then
5401                     Id /= Attribute_Length)
5402          then
5403             Check_Expressions;
5404             return;
5405          end if;
5406
5407          --  The rules in (RM 4.9(7,8)) require a static array, but as in the
5408          --  scalar case, we hold off on enforcing staticness, since there are
5409          --  cases which we can fold at compile time even though they are not
5410          --  static (e.g. 'Length applied to a static index, even though other
5411          --  non-static indexes make the array type non-static). This is only
5412          --  an optimization, but it falls out essentially free, so why not.
5413          --  Again we compute the variable Static for easy reference later
5414          --  (note that no array attributes are static in Ada 83).
5415
5416          Static := Ada_Version >= Ada_95
5417                      and then Statically_Denotes_Entity (P);
5418
5419          declare
5420             N : Node_Id;
5421
5422          begin
5423             N := First_Index (P_Type);
5424             while Present (N) loop
5425                Static := Static and then Is_Static_Subtype (Etype (N));
5426
5427                --  If however the index type is generic, attributes cannot
5428                --  be folded.
5429
5430                if Is_Generic_Type (Etype (N))
5431                  and then Id /= Attribute_Component_Size
5432                then
5433                   return;
5434                end if;
5435
5436                Next_Index (N);
5437             end loop;
5438          end;
5439       end if;
5440
5441       --  Check any expressions that are present. Note that these expressions,
5442       --  depending on the particular attribute type, are either part of the
5443       --  attribute designator, or they are arguments in a case where the
5444       --  attribute reference returns a function. In the latter case, the
5445       --  rule in (RM 4.9(22)) applies and in particular requires the type
5446       --  of the expressions to be scalar in order for the attribute to be
5447       --  considered to be static.
5448
5449       declare
5450          E : Node_Id;
5451
5452       begin
5453          E := E1;
5454          while Present (E) loop
5455
5456             --  If expression is not static, then the attribute reference
5457             --  result certainly cannot be static.
5458
5459             if not Is_Static_Expression (E) then
5460                Static := False;
5461             end if;
5462
5463             --  If the result is not known at compile time, or is not of
5464             --  a scalar type, then the result is definitely not static,
5465             --  so we can quit now.
5466
5467             if not Compile_Time_Known_Value (E)
5468               or else not Is_Scalar_Type (Etype (E))
5469             then
5470                --  An odd special case, if this is a Pos attribute, this
5471                --  is where we need to apply a range check since it does
5472                --  not get done anywhere else.
5473
5474                if Id = Attribute_Pos then
5475                   if Is_Integer_Type (Etype (E)) then
5476                      Apply_Range_Check (E, Etype (N));
5477                   end if;
5478                end if;
5479
5480                Check_Expressions;
5481                return;
5482
5483             --  If the expression raises a constraint error, then so does
5484             --  the attribute reference. We keep going in this case because
5485             --  we are still interested in whether the attribute reference
5486             --  is static even if it is not static.
5487
5488             elsif Raises_Constraint_Error (E) then
5489                Set_Raises_Constraint_Error (N);
5490             end if;
5491
5492             Next (E);
5493          end loop;
5494
5495          if Raises_Constraint_Error (Prefix (N)) then
5496             return;
5497          end if;
5498       end;
5499
5500       --  Deal with the case of a static attribute reference that raises
5501       --  constraint error. The Raises_Constraint_Error flag will already
5502       --  have been set, and the Static flag shows whether the attribute
5503       --  reference is static. In any case we certainly can't fold such an
5504       --  attribute reference.
5505
5506       --  Note that the rewriting of the attribute node with the constraint
5507       --  error node is essential in this case, because otherwise Gigi might
5508       --  blow up on one of the attributes it never expects to see.
5509
5510       --  The constraint_error node must have the type imposed by the context,
5511       --  to avoid spurious errors in the enclosing expression.
5512
5513       if Raises_Constraint_Error (N) then
5514          CE_Node :=
5515            Make_Raise_Constraint_Error (Sloc (N),
5516              Reason => CE_Range_Check_Failed);
5517          Set_Etype (CE_Node, Etype (N));
5518          Set_Raises_Constraint_Error (CE_Node);
5519          Check_Expressions;
5520          Rewrite (N, Relocate_Node (CE_Node));
5521          Set_Is_Static_Expression (N, Static);
5522          return;
5523       end if;
5524
5525       --  At this point we have a potentially foldable attribute reference.
5526       --  If Static is set, then the attribute reference definitely obeys
5527       --  the requirements in (RM 4.9(7,8,22)), and it definitely can be
5528       --  folded. If Static is not set, then the attribute may or may not
5529       --  be foldable, and the individual attribute processing routines
5530       --  test Static as required in cases where it makes a difference.
5531
5532       --  In the case where Static is not set, we do know that all the
5533       --  expressions present are at least known at compile time (we
5534       --  assumed above that if this was not the case, then there was
5535       --  no hope of static evaluation). However, we did not require
5536       --  that the bounds of the prefix type be compile time known,
5537       --  let alone static). That's because there are many attributes
5538       --  that can be computed at compile time on non-static subtypes,
5539       --  even though such references are not static expressions.
5540
5541       case Id is
5542
5543       --------------
5544       -- Adjacent --
5545       --------------
5546
5547       when Attribute_Adjacent =>
5548          Fold_Ureal (N,
5549            Eval_Fat.Adjacent
5550              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5551
5552       ---------
5553       -- Aft --
5554       ---------
5555
5556       when Attribute_Aft =>
5557          Fold_Uint (N, UI_From_Int (Aft_Value), True);
5558
5559       ---------------
5560       -- Alignment --
5561       ---------------
5562
5563       when Attribute_Alignment => Alignment_Block : declare
5564          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5565
5566       begin
5567          --  Fold if alignment is set and not otherwise
5568
5569          if Known_Alignment (P_TypeA) then
5570             Fold_Uint (N, Alignment (P_TypeA), Is_Discrete_Type (P_TypeA));
5571          end if;
5572       end Alignment_Block;
5573
5574       ---------------
5575       -- AST_Entry --
5576       ---------------
5577
5578       --  Can only be folded in No_Ast_Handler case
5579
5580       when Attribute_AST_Entry =>
5581          if not Is_AST_Entry (P_Entity) then
5582             Rewrite (N,
5583               New_Occurrence_Of (RTE (RE_No_AST_Handler), Loc));
5584          else
5585             null;
5586          end if;
5587
5588       ---------
5589       -- Bit --
5590       ---------
5591
5592       --  Bit can never be folded
5593
5594       when Attribute_Bit =>
5595          null;
5596
5597       ------------------
5598       -- Body_Version --
5599       ------------------
5600
5601       --  Body_version can never be static
5602
5603       when Attribute_Body_Version =>
5604          null;
5605
5606       -------------
5607       -- Ceiling --
5608       -------------
5609
5610       when Attribute_Ceiling =>
5611          Fold_Ureal (N,
5612            Eval_Fat.Ceiling (P_Root_Type, Expr_Value_R (E1)), Static);
5613
5614       --------------------
5615       -- Component_Size --
5616       --------------------
5617
5618       when Attribute_Component_Size =>
5619          if Known_Static_Component_Size (P_Type) then
5620             Fold_Uint (N, Component_Size (P_Type), False);
5621          end if;
5622
5623       -------------
5624       -- Compose --
5625       -------------
5626
5627       when Attribute_Compose =>
5628          Fold_Ureal (N,
5629            Eval_Fat.Compose
5630              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)),
5631               Static);
5632
5633       -----------------
5634       -- Constrained --
5635       -----------------
5636
5637       --  Constrained is never folded for now, there may be cases that
5638       --  could be handled at compile time. To be looked at later.
5639
5640       when Attribute_Constrained =>
5641          null;
5642
5643       ---------------
5644       -- Copy_Sign --
5645       ---------------
5646
5647       when Attribute_Copy_Sign =>
5648          Fold_Ureal (N,
5649            Eval_Fat.Copy_Sign
5650              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5651
5652       -----------
5653       -- Delta --
5654       -----------
5655
5656       when Attribute_Delta =>
5657          Fold_Ureal (N, Delta_Value (P_Type), True);
5658
5659       --------------
5660       -- Definite --
5661       --------------
5662
5663       when Attribute_Definite =>
5664          Rewrite (N, New_Occurrence_Of (
5665            Boolean_Literals (not Is_Indefinite_Subtype (P_Entity)), Loc));
5666          Analyze_And_Resolve (N, Standard_Boolean);
5667
5668       ------------
5669       -- Denorm --
5670       ------------
5671
5672       when Attribute_Denorm =>
5673          Fold_Uint
5674            (N, UI_From_Int (Boolean'Pos (Denorm_On_Target)), True);
5675
5676       ------------
5677       -- Digits --
5678       ------------
5679
5680       when Attribute_Digits =>
5681          Fold_Uint (N, Digits_Value (P_Type), True);
5682
5683       ----------
5684       -- Emax --
5685       ----------
5686
5687       when Attribute_Emax =>
5688
5689          --  Ada 83 attribute is defined as (RM83 3.5.8)
5690
5691          --    T'Emax = 4 * T'Mantissa
5692
5693          Fold_Uint (N, 4 * Mantissa, True);
5694
5695       --------------
5696       -- Enum_Rep --
5697       --------------
5698
5699       when Attribute_Enum_Rep =>
5700
5701          --  For an enumeration type with a non-standard representation use
5702          --  the Enumeration_Rep field of the proper constant. Note that this
5703          --  will not work for types Character/Wide_[Wide-]Character, since no
5704          --  real entities are created for the enumeration literals, but that
5705          --  does not matter since these two types do not have non-standard
5706          --  representations anyway.
5707
5708          if Is_Enumeration_Type (P_Type)
5709            and then Has_Non_Standard_Rep (P_Type)
5710          then
5711             Fold_Uint (N, Enumeration_Rep (Expr_Value_E (E1)), Static);
5712
5713          --  For enumeration types with standard representations and all
5714          --  other cases (i.e. all integer and modular types), Enum_Rep
5715          --  is equivalent to Pos.
5716
5717          else
5718             Fold_Uint (N, Expr_Value (E1), Static);
5719          end if;
5720
5721       --------------
5722       -- Enum_Val --
5723       --------------
5724
5725       when Attribute_Enum_Val => Enum_Val : declare
5726          Lit : Node_Id;
5727
5728       begin
5729          --  We have something like Enum_Type'Enum_Val (23), so search for a
5730          --  corresponding value in the list of Enum_Rep values for the type.
5731
5732          Lit := First_Literal (P_Base_Type);
5733          loop
5734             if Enumeration_Rep (Lit) = Expr_Value (E1) then
5735                Fold_Uint (N, Enumeration_Pos (Lit), Static);
5736                exit;
5737             end if;
5738
5739             Next_Literal (Lit);
5740
5741             if No (Lit) then
5742                Apply_Compile_Time_Constraint_Error
5743                  (N, "no representation value matches",
5744                   CE_Range_Check_Failed,
5745                   Warn => not Static);
5746                exit;
5747             end if;
5748          end loop;
5749       end Enum_Val;
5750
5751       -------------
5752       -- Epsilon --
5753       -------------
5754
5755       when Attribute_Epsilon =>
5756
5757          --  Ada 83 attribute is defined as (RM83 3.5.8)
5758
5759          --    T'Epsilon = 2.0**(1 - T'Mantissa)
5760
5761          Fold_Ureal (N, Ureal_2 ** (1 - Mantissa), True);
5762
5763       --------------
5764       -- Exponent --
5765       --------------
5766
5767       when Attribute_Exponent =>
5768          Fold_Uint (N,
5769            Eval_Fat.Exponent (P_Root_Type, Expr_Value_R (E1)), Static);
5770
5771       -----------
5772       -- First --
5773       -----------
5774
5775       when Attribute_First => First_Attr :
5776       begin
5777          Set_Bounds;
5778
5779          if Compile_Time_Known_Value (Lo_Bound) then
5780             if Is_Real_Type (P_Type) then
5781                Fold_Ureal (N, Expr_Value_R (Lo_Bound), Static);
5782             else
5783                Fold_Uint  (N, Expr_Value (Lo_Bound), Static);
5784             end if;
5785          end if;
5786       end First_Attr;
5787
5788       -----------------
5789       -- Fixed_Value --
5790       -----------------
5791
5792       when Attribute_Fixed_Value =>
5793          null;
5794
5795       -----------
5796       -- Floor --
5797       -----------
5798
5799       when Attribute_Floor =>
5800          Fold_Ureal (N,
5801            Eval_Fat.Floor (P_Root_Type, Expr_Value_R (E1)), Static);
5802
5803       ----------
5804       -- Fore --
5805       ----------
5806
5807       when Attribute_Fore =>
5808          if Compile_Time_Known_Bounds (P_Type) then
5809             Fold_Uint (N, UI_From_Int (Fore_Value), Static);
5810          end if;
5811
5812       --------------
5813       -- Fraction --
5814       --------------
5815
5816       when Attribute_Fraction =>
5817          Fold_Ureal (N,
5818            Eval_Fat.Fraction (P_Root_Type, Expr_Value_R (E1)), Static);
5819
5820       -----------------------
5821       -- Has_Access_Values --
5822       -----------------------
5823
5824       when Attribute_Has_Access_Values =>
5825          Rewrite (N, New_Occurrence_Of
5826            (Boolean_Literals (Has_Access_Values (P_Root_Type)), Loc));
5827          Analyze_And_Resolve (N, Standard_Boolean);
5828
5829       -----------------------
5830       -- Has_Discriminants --
5831       -----------------------
5832
5833       when Attribute_Has_Discriminants =>
5834          Rewrite (N, New_Occurrence_Of (
5835            Boolean_Literals (Has_Discriminants (P_Entity)), Loc));
5836          Analyze_And_Resolve (N, Standard_Boolean);
5837
5838       -----------------------
5839       -- Has_Tagged_Values --
5840       -----------------------
5841
5842       when Attribute_Has_Tagged_Values =>
5843          Rewrite (N, New_Occurrence_Of
5844            (Boolean_Literals (Has_Tagged_Component (P_Root_Type)), Loc));
5845          Analyze_And_Resolve (N, Standard_Boolean);
5846
5847       --------------
5848       -- Identity --
5849       --------------
5850
5851       when Attribute_Identity =>
5852          null;
5853
5854       -----------
5855       -- Image --
5856       -----------
5857
5858       --  Image is a scalar attribute, but is never static, because it is
5859       --  not a static function (having a non-scalar argument (RM 4.9(22))
5860       --  However, we can constant-fold the image of an enumeration literal
5861       --  if names are available.
5862
5863       when Attribute_Image =>
5864          if Is_Entity_Name (E1)
5865            and then Ekind (Entity (E1)) = E_Enumeration_Literal
5866            and then not Discard_Names (First_Subtype (Etype (E1)))
5867            and then not Global_Discard_Names
5868          then
5869             declare
5870                Lit : constant Entity_Id := Entity (E1);
5871                Str : String_Id;
5872             begin
5873                Start_String;
5874                Get_Unqualified_Decoded_Name_String (Chars (Lit));
5875                Set_Casing (All_Upper_Case);
5876                Store_String_Chars (Name_Buffer (1 .. Name_Len));
5877                Str := End_String;
5878                Rewrite (N, Make_String_Literal (Loc, Strval => Str));
5879                Analyze_And_Resolve (N, Standard_String);
5880                Set_Is_Static_Expression (N, False);
5881             end;
5882          end if;
5883
5884       ---------
5885       -- Img --
5886       ---------
5887
5888       --  Img is a scalar attribute, but is never static, because it is
5889       --  not a static function (having a non-scalar argument (RM 4.9(22))
5890
5891       when Attribute_Img =>
5892          null;
5893
5894       -------------------
5895       -- Integer_Value --
5896       -------------------
5897
5898       --  We never try to fold Integer_Value (though perhaps we could???)
5899
5900       when Attribute_Integer_Value =>
5901          null;
5902
5903       -------------------
5904       -- Invalid_Value --
5905       -------------------
5906
5907       --  Invalid_Value is a scalar attribute that is never static, because
5908       --  the value is by design out of range.
5909
5910       when Attribute_Invalid_Value =>
5911          null;
5912
5913       -----------
5914       -- Large --
5915       -----------
5916
5917       when Attribute_Large =>
5918
5919          --  For fixed-point, we use the identity:
5920
5921          --    T'Large = (2.0**T'Mantissa - 1.0) * T'Small
5922
5923          if Is_Fixed_Point_Type (P_Type) then
5924             Rewrite (N,
5925               Make_Op_Multiply (Loc,
5926                 Left_Opnd =>
5927                   Make_Op_Subtract (Loc,
5928                     Left_Opnd =>
5929                       Make_Op_Expon (Loc,
5930                         Left_Opnd =>
5931                           Make_Real_Literal (Loc, Ureal_2),
5932                         Right_Opnd =>
5933                           Make_Attribute_Reference (Loc,
5934                             Prefix => P,
5935                             Attribute_Name => Name_Mantissa)),
5936                     Right_Opnd => Make_Real_Literal (Loc, Ureal_1)),
5937
5938                 Right_Opnd =>
5939                   Make_Real_Literal (Loc, Small_Value (Entity (P)))));
5940
5941             Analyze_And_Resolve (N, C_Type);
5942
5943          --  Floating-point (Ada 83 compatibility)
5944
5945          else
5946             --  Ada 83 attribute is defined as (RM83 3.5.8)
5947
5948             --    T'Large = 2.0**T'Emax * (1.0 - 2.0**(-T'Mantissa))
5949
5950             --  where
5951
5952             --    T'Emax = 4 * T'Mantissa
5953
5954             Fold_Ureal (N,
5955               Ureal_2 ** (4 * Mantissa) * (Ureal_1 - Ureal_2 ** (-Mantissa)),
5956               True);
5957          end if;
5958
5959       ----------
5960       -- Last --
5961       ----------
5962
5963       when Attribute_Last => Last :
5964       begin
5965          Set_Bounds;
5966
5967          if Compile_Time_Known_Value (Hi_Bound) then
5968             if Is_Real_Type (P_Type) then
5969                Fold_Ureal (N, Expr_Value_R (Hi_Bound), Static);
5970             else
5971                Fold_Uint  (N, Expr_Value (Hi_Bound), Static);
5972             end if;
5973          end if;
5974       end Last;
5975
5976       ------------------
5977       -- Leading_Part --
5978       ------------------
5979
5980       when Attribute_Leading_Part =>
5981          Fold_Ureal (N,
5982            Eval_Fat.Leading_Part
5983              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
5984
5985       ------------
5986       -- Length --
5987       ------------
5988
5989       when Attribute_Length => Length : declare
5990          Ind : Node_Id;
5991
5992       begin
5993          --  In the case of a generic index type, the bounds may
5994          --  appear static but the computation is not meaningful,
5995          --  and may generate a spurious warning.
5996
5997          Ind := First_Index (P_Type);
5998
5999          while Present (Ind) loop
6000             if Is_Generic_Type (Etype (Ind)) then
6001                return;
6002             end if;
6003
6004             Next_Index (Ind);
6005          end loop;
6006
6007          Set_Bounds;
6008
6009          if Compile_Time_Known_Value (Lo_Bound)
6010            and then Compile_Time_Known_Value (Hi_Bound)
6011          then
6012             Fold_Uint (N,
6013               UI_Max (0, 1 + (Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound))),
6014               True);
6015          end if;
6016       end Length;
6017
6018       -------------
6019       -- Machine --
6020       -------------
6021
6022       when Attribute_Machine =>
6023          Fold_Ureal (N,
6024            Eval_Fat.Machine
6025              (P_Root_Type, Expr_Value_R (E1), Eval_Fat.Round, N),
6026            Static);
6027
6028       ------------------
6029       -- Machine_Emax --
6030       ------------------
6031
6032       when Attribute_Machine_Emax =>
6033          Float_Attribute_Universal_Integer (
6034            IEEES_Machine_Emax,
6035            IEEEL_Machine_Emax,
6036            IEEEX_Machine_Emax,
6037            VAXFF_Machine_Emax,
6038            VAXDF_Machine_Emax,
6039            VAXGF_Machine_Emax,
6040            AAMPS_Machine_Emax,
6041            AAMPL_Machine_Emax);
6042
6043       ------------------
6044       -- Machine_Emin --
6045       ------------------
6046
6047       when Attribute_Machine_Emin =>
6048          Float_Attribute_Universal_Integer (
6049            IEEES_Machine_Emin,
6050            IEEEL_Machine_Emin,
6051            IEEEX_Machine_Emin,
6052            VAXFF_Machine_Emin,
6053            VAXDF_Machine_Emin,
6054            VAXGF_Machine_Emin,
6055            AAMPS_Machine_Emin,
6056            AAMPL_Machine_Emin);
6057
6058       ----------------------
6059       -- Machine_Mantissa --
6060       ----------------------
6061
6062       when Attribute_Machine_Mantissa =>
6063          Float_Attribute_Universal_Integer (
6064            IEEES_Machine_Mantissa,
6065            IEEEL_Machine_Mantissa,
6066            IEEEX_Machine_Mantissa,
6067            VAXFF_Machine_Mantissa,
6068            VAXDF_Machine_Mantissa,
6069            VAXGF_Machine_Mantissa,
6070            AAMPS_Machine_Mantissa,
6071            AAMPL_Machine_Mantissa);
6072
6073       -----------------------
6074       -- Machine_Overflows --
6075       -----------------------
6076
6077       when Attribute_Machine_Overflows =>
6078
6079          --  Always true for fixed-point
6080
6081          if Is_Fixed_Point_Type (P_Type) then
6082             Fold_Uint (N, True_Value, True);
6083
6084          --  Floating point case
6085
6086          else
6087             Fold_Uint (N,
6088               UI_From_Int (Boolean'Pos (Machine_Overflows_On_Target)),
6089               True);
6090          end if;
6091
6092       -------------------
6093       -- Machine_Radix --
6094       -------------------
6095
6096       when Attribute_Machine_Radix =>
6097          if Is_Fixed_Point_Type (P_Type) then
6098             if Is_Decimal_Fixed_Point_Type (P_Type)
6099               and then Machine_Radix_10 (P_Type)
6100             then
6101                Fold_Uint (N, Uint_10, True);
6102             else
6103                Fold_Uint (N, Uint_2, True);
6104             end if;
6105
6106          --  All floating-point type always have radix 2
6107
6108          else
6109             Fold_Uint (N, Uint_2, True);
6110          end if;
6111
6112       ----------------------
6113       -- Machine_Rounding --
6114       ----------------------
6115
6116       --  Note: for the folding case, it is fine to treat Machine_Rounding
6117       --  exactly the same way as Rounding, since this is one of the allowed
6118       --  behaviors, and performance is not an issue here. It might be a bit
6119       --  better to give the same result as it would give at run-time, even
6120       --  though the non-determinism is certainly permitted.
6121
6122       when Attribute_Machine_Rounding =>
6123          Fold_Ureal (N,
6124            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
6125
6126       --------------------
6127       -- Machine_Rounds --
6128       --------------------
6129
6130       when Attribute_Machine_Rounds =>
6131
6132          --  Always False for fixed-point
6133
6134          if Is_Fixed_Point_Type (P_Type) then
6135             Fold_Uint (N, False_Value, True);
6136
6137          --  Else yield proper floating-point result
6138
6139          else
6140             Fold_Uint
6141               (N, UI_From_Int (Boolean'Pos (Machine_Rounds_On_Target)), True);
6142          end if;
6143
6144       ------------------
6145       -- Machine_Size --
6146       ------------------
6147
6148       --  Note: Machine_Size is identical to Object_Size
6149
6150       when Attribute_Machine_Size => Machine_Size : declare
6151          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6152
6153       begin
6154          if Known_Esize (P_TypeA) then
6155             Fold_Uint (N, Esize (P_TypeA), True);
6156          end if;
6157       end Machine_Size;
6158
6159       --------------
6160       -- Mantissa --
6161       --------------
6162
6163       when Attribute_Mantissa =>
6164
6165          --  Fixed-point mantissa
6166
6167          if Is_Fixed_Point_Type (P_Type) then
6168
6169             --  Compile time foldable case
6170
6171             if Compile_Time_Known_Value (Type_Low_Bound  (P_Type))
6172                  and then
6173                Compile_Time_Known_Value (Type_High_Bound (P_Type))
6174             then
6175                --  The calculation of the obsolete Ada 83 attribute Mantissa
6176                --  is annoying, because of AI00143, quoted here:
6177
6178                --  !question 84-01-10
6179
6180                --  Consider the model numbers for F:
6181
6182                --         type F is delta 1.0 range -7.0 .. 8.0;
6183
6184                --  The wording requires that F'MANTISSA be the SMALLEST
6185                --  integer number for which each  bound  of the specified
6186                --  range is either a model number or lies at most small
6187                --  distant from a model number. This means F'MANTISSA
6188                --  is required to be 3 since the range  -7.0 .. 7.0 fits
6189                --  in 3 signed bits, and 8 is "at most" 1.0 from a model
6190                --  number, namely, 7. Is this analysis correct? Note that
6191                --  this implies the upper bound of the range is not
6192                --  represented as a model number.
6193
6194                --  !response 84-03-17
6195
6196                --  The analysis is correct. The upper and lower bounds for
6197                --  a fixed  point type can lie outside the range of model
6198                --  numbers.
6199
6200                declare
6201                   Siz     : Uint;
6202                   LBound  : Ureal;
6203                   UBound  : Ureal;
6204                   Bound   : Ureal;
6205                   Max_Man : Uint;
6206
6207                begin
6208                   LBound  := Expr_Value_R (Type_Low_Bound  (P_Type));
6209                   UBound  := Expr_Value_R (Type_High_Bound (P_Type));
6210                   Bound   := UR_Max (UR_Abs (LBound), UR_Abs (UBound));
6211                   Max_Man := UR_Trunc (Bound / Small_Value (P_Type));
6212
6213                   --  If the Bound is exactly a model number, i.e. a multiple
6214                   --  of Small, then we back it off by one to get the integer
6215                   --  value that must be representable.
6216
6217                   if Small_Value (P_Type) * Max_Man = Bound then
6218                      Max_Man := Max_Man - 1;
6219                   end if;
6220
6221                   --  Now find corresponding size = Mantissa value
6222
6223                   Siz := Uint_0;
6224                   while 2 ** Siz < Max_Man loop
6225                      Siz := Siz + 1;
6226                   end loop;
6227
6228                   Fold_Uint (N, Siz, True);
6229                end;
6230
6231             else
6232                --  The case of dynamic bounds cannot be evaluated at compile
6233                --  time. Instead we use a runtime routine (see Exp_Attr).
6234
6235                null;
6236             end if;
6237
6238          --  Floating-point Mantissa
6239
6240          else
6241             Fold_Uint (N, Mantissa, True);
6242          end if;
6243
6244       ---------
6245       -- Max --
6246       ---------
6247
6248       when Attribute_Max => Max :
6249       begin
6250          if Is_Real_Type (P_Type) then
6251             Fold_Ureal
6252               (N, UR_Max (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
6253          else
6254             Fold_Uint (N, UI_Max (Expr_Value (E1), Expr_Value (E2)), Static);
6255          end if;
6256       end Max;
6257
6258       ----------------------------------
6259       -- Max_Size_In_Storage_Elements --
6260       ----------------------------------
6261
6262       --  Max_Size_In_Storage_Elements is simply the Size rounded up to a
6263       --  Storage_Unit boundary. We can fold any cases for which the size
6264       --  is known by the front end.
6265
6266       when Attribute_Max_Size_In_Storage_Elements =>
6267          if Known_Esize (P_Type) then
6268             Fold_Uint (N,
6269               (Esize (P_Type) + System_Storage_Unit - 1) /
6270                                           System_Storage_Unit,
6271                Static);
6272          end if;
6273
6274       --------------------
6275       -- Mechanism_Code --
6276       --------------------
6277
6278       when Attribute_Mechanism_Code =>
6279          declare
6280             Val    : Int;
6281             Formal : Entity_Id;
6282             Mech   : Mechanism_Type;
6283
6284          begin
6285             if No (E1) then
6286                Mech := Mechanism (P_Entity);
6287
6288             else
6289                Val := UI_To_Int (Expr_Value (E1));
6290
6291                Formal := First_Formal (P_Entity);
6292                for J in 1 .. Val - 1 loop
6293                   Next_Formal (Formal);
6294                end loop;
6295                Mech := Mechanism (Formal);
6296             end if;
6297
6298             if Mech < 0 then
6299                Fold_Uint (N, UI_From_Int (Int (-Mech)), True);
6300             end if;
6301          end;
6302
6303       ---------
6304       -- Min --
6305       ---------
6306
6307       when Attribute_Min => Min :
6308       begin
6309          if Is_Real_Type (P_Type) then
6310             Fold_Ureal
6311               (N, UR_Min (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
6312          else
6313             Fold_Uint
6314               (N, UI_Min (Expr_Value (E1), Expr_Value (E2)), Static);
6315          end if;
6316       end Min;
6317
6318       ---------
6319       -- Mod --
6320       ---------
6321
6322       when Attribute_Mod =>
6323          Fold_Uint
6324            (N, UI_Mod (Expr_Value (E1), Modulus (P_Base_Type)), Static);
6325
6326       -----------
6327       -- Model --
6328       -----------
6329
6330       when Attribute_Model =>
6331          Fold_Ureal (N,
6332            Eval_Fat.Model (P_Root_Type, Expr_Value_R (E1)), Static);
6333
6334       ----------------
6335       -- Model_Emin --
6336       ----------------
6337
6338       when Attribute_Model_Emin =>
6339          Float_Attribute_Universal_Integer (
6340            IEEES_Model_Emin,
6341            IEEEL_Model_Emin,
6342            IEEEX_Model_Emin,
6343            VAXFF_Model_Emin,
6344            VAXDF_Model_Emin,
6345            VAXGF_Model_Emin,
6346            AAMPS_Model_Emin,
6347            AAMPL_Model_Emin);
6348
6349       -------------------
6350       -- Model_Epsilon --
6351       -------------------
6352
6353       when Attribute_Model_Epsilon =>
6354          Float_Attribute_Universal_Real (
6355            IEEES_Model_Epsilon'Universal_Literal_String,
6356            IEEEL_Model_Epsilon'Universal_Literal_String,
6357            IEEEX_Model_Epsilon'Universal_Literal_String,
6358            VAXFF_Model_Epsilon'Universal_Literal_String,
6359            VAXDF_Model_Epsilon'Universal_Literal_String,
6360            VAXGF_Model_Epsilon'Universal_Literal_String,
6361            AAMPS_Model_Epsilon'Universal_Literal_String,
6362            AAMPL_Model_Epsilon'Universal_Literal_String);
6363
6364       --------------------
6365       -- Model_Mantissa --
6366       --------------------
6367
6368       when Attribute_Model_Mantissa =>
6369          Float_Attribute_Universal_Integer (
6370            IEEES_Model_Mantissa,
6371            IEEEL_Model_Mantissa,
6372            IEEEX_Model_Mantissa,
6373            VAXFF_Model_Mantissa,
6374            VAXDF_Model_Mantissa,
6375            VAXGF_Model_Mantissa,
6376            AAMPS_Model_Mantissa,
6377            AAMPL_Model_Mantissa);
6378
6379       -----------------
6380       -- Model_Small --
6381       -----------------
6382
6383       when Attribute_Model_Small =>
6384          Float_Attribute_Universal_Real (
6385            IEEES_Model_Small'Universal_Literal_String,
6386            IEEEL_Model_Small'Universal_Literal_String,
6387            IEEEX_Model_Small'Universal_Literal_String,
6388            VAXFF_Model_Small'Universal_Literal_String,
6389            VAXDF_Model_Small'Universal_Literal_String,
6390            VAXGF_Model_Small'Universal_Literal_String,
6391            AAMPS_Model_Small'Universal_Literal_String,
6392            AAMPL_Model_Small'Universal_Literal_String);
6393
6394       -------------
6395       -- Modulus --
6396       -------------
6397
6398       when Attribute_Modulus =>
6399          Fold_Uint (N, Modulus (P_Type), True);
6400
6401       --------------------
6402       -- Null_Parameter --
6403       --------------------
6404
6405       --  Cannot fold, we know the value sort of, but the whole point is
6406       --  that there is no way to talk about this imaginary value except
6407       --  by using the attribute, so we leave it the way it is.
6408
6409       when Attribute_Null_Parameter =>
6410          null;
6411
6412       -----------------
6413       -- Object_Size --
6414       -----------------
6415
6416       --  The Object_Size attribute for a type returns the Esize of the
6417       --  type and can be folded if this value is known.
6418
6419       when Attribute_Object_Size => Object_Size : declare
6420          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6421
6422       begin
6423          if Known_Esize (P_TypeA) then
6424             Fold_Uint (N, Esize (P_TypeA), True);
6425          end if;
6426       end Object_Size;
6427
6428       -------------------------
6429       -- Passed_By_Reference --
6430       -------------------------
6431
6432       --  Scalar types are never passed by reference
6433
6434       when Attribute_Passed_By_Reference =>
6435          Fold_Uint (N, False_Value, True);
6436
6437       ---------
6438       -- Pos --
6439       ---------
6440
6441       when Attribute_Pos =>
6442          Fold_Uint (N, Expr_Value (E1), True);
6443
6444       ----------
6445       -- Pred --
6446       ----------
6447
6448       when Attribute_Pred => Pred :
6449       begin
6450          --  Floating-point case
6451
6452          if Is_Floating_Point_Type (P_Type) then
6453             Fold_Ureal (N,
6454               Eval_Fat.Pred (P_Root_Type, Expr_Value_R (E1)), Static);
6455
6456          --  Fixed-point case
6457
6458          elsif Is_Fixed_Point_Type (P_Type) then
6459             Fold_Ureal (N,
6460               Expr_Value_R (E1) - Small_Value (P_Type), True);
6461
6462          --  Modular integer case (wraps)
6463
6464          elsif Is_Modular_Integer_Type (P_Type) then
6465             Fold_Uint (N, (Expr_Value (E1) - 1) mod Modulus (P_Type), Static);
6466
6467          --  Other scalar cases
6468
6469          else
6470             pragma Assert (Is_Scalar_Type (P_Type));
6471
6472             if Is_Enumeration_Type (P_Type)
6473               and then Expr_Value (E1) =
6474                          Expr_Value (Type_Low_Bound (P_Base_Type))
6475             then
6476                Apply_Compile_Time_Constraint_Error
6477                  (N, "Pred of `&''First`",
6478                   CE_Overflow_Check_Failed,
6479                   Ent  => P_Base_Type,
6480                   Warn => not Static);
6481
6482                Check_Expressions;
6483                return;
6484             end if;
6485
6486             Fold_Uint (N, Expr_Value (E1) - 1, Static);
6487          end if;
6488       end Pred;
6489
6490       -----------
6491       -- Range --
6492       -----------
6493
6494       --  No processing required, because by this stage, Range has been
6495       --  replaced by First .. Last, so this branch can never be taken.
6496
6497       when Attribute_Range =>
6498          raise Program_Error;
6499
6500       ------------------
6501       -- Range_Length --
6502       ------------------
6503
6504       when Attribute_Range_Length =>
6505          Set_Bounds;
6506
6507          if Compile_Time_Known_Value (Hi_Bound)
6508            and then Compile_Time_Known_Value (Lo_Bound)
6509          then
6510             Fold_Uint (N,
6511               UI_Max
6512                 (0, Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound) + 1),
6513                  Static);
6514          end if;
6515
6516       ---------------
6517       -- Remainder --
6518       ---------------
6519
6520       when Attribute_Remainder => Remainder : declare
6521          X : constant Ureal := Expr_Value_R (E1);
6522          Y : constant Ureal := Expr_Value_R (E2);
6523
6524       begin
6525          if UR_Is_Zero (Y) then
6526             Apply_Compile_Time_Constraint_Error
6527               (N, "division by zero in Remainder",
6528                CE_Overflow_Check_Failed,
6529                Warn => not Static);
6530
6531             Check_Expressions;
6532             return;
6533          end if;
6534
6535          Fold_Ureal (N, Eval_Fat.Remainder (P_Root_Type, X, Y), Static);
6536       end Remainder;
6537
6538       -----------
6539       -- Round --
6540       -----------
6541
6542       when Attribute_Round => Round :
6543       declare
6544          Sr : Ureal;
6545          Si : Uint;
6546
6547       begin
6548          --  First we get the (exact result) in units of small
6549
6550          Sr := Expr_Value_R (E1) / Small_Value (C_Type);
6551
6552          --  Now round that exactly to an integer
6553
6554          Si := UR_To_Uint (Sr);
6555
6556          --  Finally the result is obtained by converting back to real
6557
6558          Fold_Ureal (N, Si * Small_Value (C_Type), Static);
6559       end Round;
6560
6561       --------------
6562       -- Rounding --
6563       --------------
6564
6565       when Attribute_Rounding =>
6566          Fold_Ureal (N,
6567            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
6568
6569       ---------------
6570       -- Safe_Emax --
6571       ---------------
6572
6573       when Attribute_Safe_Emax =>
6574          Float_Attribute_Universal_Integer (
6575            IEEES_Safe_Emax,
6576            IEEEL_Safe_Emax,
6577            IEEEX_Safe_Emax,
6578            VAXFF_Safe_Emax,
6579            VAXDF_Safe_Emax,
6580            VAXGF_Safe_Emax,
6581            AAMPS_Safe_Emax,
6582            AAMPL_Safe_Emax);
6583
6584       ----------------
6585       -- Safe_First --
6586       ----------------
6587
6588       when Attribute_Safe_First =>
6589          Float_Attribute_Universal_Real (
6590            IEEES_Safe_First'Universal_Literal_String,
6591            IEEEL_Safe_First'Universal_Literal_String,
6592            IEEEX_Safe_First'Universal_Literal_String,
6593            VAXFF_Safe_First'Universal_Literal_String,
6594            VAXDF_Safe_First'Universal_Literal_String,
6595            VAXGF_Safe_First'Universal_Literal_String,
6596            AAMPS_Safe_First'Universal_Literal_String,
6597            AAMPL_Safe_First'Universal_Literal_String);
6598
6599       ----------------
6600       -- Safe_Large --
6601       ----------------
6602
6603       when Attribute_Safe_Large =>
6604          if Is_Fixed_Point_Type (P_Type) then
6605             Fold_Ureal
6606               (N, Expr_Value_R (Type_High_Bound (P_Base_Type)), Static);
6607          else
6608             Float_Attribute_Universal_Real (
6609               IEEES_Safe_Large'Universal_Literal_String,
6610               IEEEL_Safe_Large'Universal_Literal_String,
6611               IEEEX_Safe_Large'Universal_Literal_String,
6612               VAXFF_Safe_Large'Universal_Literal_String,
6613               VAXDF_Safe_Large'Universal_Literal_String,
6614               VAXGF_Safe_Large'Universal_Literal_String,
6615               AAMPS_Safe_Large'Universal_Literal_String,
6616               AAMPL_Safe_Large'Universal_Literal_String);
6617          end if;
6618
6619       ---------------
6620       -- Safe_Last --
6621       ---------------
6622
6623       when Attribute_Safe_Last =>
6624          Float_Attribute_Universal_Real (
6625            IEEES_Safe_Last'Universal_Literal_String,
6626            IEEEL_Safe_Last'Universal_Literal_String,
6627            IEEEX_Safe_Last'Universal_Literal_String,
6628            VAXFF_Safe_Last'Universal_Literal_String,
6629            VAXDF_Safe_Last'Universal_Literal_String,
6630            VAXGF_Safe_Last'Universal_Literal_String,
6631            AAMPS_Safe_Last'Universal_Literal_String,
6632            AAMPL_Safe_Last'Universal_Literal_String);
6633
6634       ----------------
6635       -- Safe_Small --
6636       ----------------
6637
6638       when Attribute_Safe_Small =>
6639
6640          --  In Ada 95, the old Ada 83 attribute Safe_Small is redundant
6641          --  for fixed-point, since is the same as Small, but we implement
6642          --  it for backwards compatibility.
6643
6644          if Is_Fixed_Point_Type (P_Type) then
6645             Fold_Ureal (N, Small_Value (P_Type), Static);
6646
6647          --  Ada 83 Safe_Small for floating-point cases
6648
6649          else
6650             Float_Attribute_Universal_Real (
6651               IEEES_Safe_Small'Universal_Literal_String,
6652               IEEEL_Safe_Small'Universal_Literal_String,
6653               IEEEX_Safe_Small'Universal_Literal_String,
6654               VAXFF_Safe_Small'Universal_Literal_String,
6655               VAXDF_Safe_Small'Universal_Literal_String,
6656               VAXGF_Safe_Small'Universal_Literal_String,
6657               AAMPS_Safe_Small'Universal_Literal_String,
6658               AAMPL_Safe_Small'Universal_Literal_String);
6659          end if;
6660
6661       -----------
6662       -- Scale --
6663       -----------
6664
6665       when Attribute_Scale =>
6666          Fold_Uint (N, Scale_Value (P_Type), True);
6667
6668       -------------
6669       -- Scaling --
6670       -------------
6671
6672       when Attribute_Scaling =>
6673          Fold_Ureal (N,
6674            Eval_Fat.Scaling
6675              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
6676
6677       ------------------
6678       -- Signed_Zeros --
6679       ------------------
6680
6681       when Attribute_Signed_Zeros =>
6682          Fold_Uint
6683            (N, UI_From_Int (Boolean'Pos (Signed_Zeros_On_Target)), Static);
6684
6685       ----------
6686       -- Size --
6687       ----------
6688
6689       --  Size attribute returns the RM size. All scalar types can be folded,
6690       --  as well as any types for which the size is known by the front end,
6691       --  including any type for which a size attribute is specified.
6692
6693       when Attribute_Size | Attribute_VADS_Size => Size : declare
6694          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6695
6696       begin
6697          if RM_Size (P_TypeA) /= Uint_0 then
6698
6699             --  VADS_Size case
6700
6701             if Id = Attribute_VADS_Size or else Use_VADS_Size then
6702                declare
6703                   S : constant Node_Id := Size_Clause (P_TypeA);
6704
6705                begin
6706                   --  If a size clause applies, then use the size from it.
6707                   --  This is one of the rare cases where we can use the
6708                   --  Size_Clause field for a subtype when Has_Size_Clause
6709                   --  is False. Consider:
6710
6711                   --    type x is range 1 .. 64;
6712                   --    for x'size use 12;
6713                   --    subtype y is x range 0 .. 3;
6714
6715                   --  Here y has a size clause inherited from x, but normally
6716                   --  it does not apply, and y'size is 2. However, y'VADS_Size
6717                   --  is indeed 12 and not 2.
6718
6719                   if Present (S)
6720                     and then Is_OK_Static_Expression (Expression (S))
6721                   then
6722                      Fold_Uint (N, Expr_Value (Expression (S)), True);
6723
6724                   --  If no size is specified, then we simply use the object
6725                   --  size in the VADS_Size case (e.g. Natural'Size is equal
6726                   --  to Integer'Size, not one less).
6727
6728                   else
6729                      Fold_Uint (N, Esize (P_TypeA), True);
6730                   end if;
6731                end;
6732
6733             --  Normal case (Size) in which case we want the RM_Size
6734
6735             else
6736                Fold_Uint (N,
6737                  RM_Size (P_TypeA),
6738                  Static and then Is_Discrete_Type (P_TypeA));
6739             end if;
6740          end if;
6741       end Size;
6742
6743       -----------
6744       -- Small --
6745       -----------
6746
6747       when Attribute_Small =>
6748
6749          --  The floating-point case is present only for Ada 83 compatibility.
6750          --  Note that strictly this is an illegal addition, since we are
6751          --  extending an Ada 95 defined attribute, but we anticipate an
6752          --  ARG ruling that will permit this.
6753
6754          if Is_Floating_Point_Type (P_Type) then
6755
6756             --  Ada 83 attribute is defined as (RM83 3.5.8)
6757
6758             --    T'Small = 2.0**(-T'Emax - 1)
6759
6760             --  where
6761
6762             --    T'Emax = 4 * T'Mantissa
6763
6764             Fold_Ureal (N, Ureal_2 ** ((-(4 * Mantissa)) - 1), Static);
6765
6766          --  Normal Ada 95 fixed-point case
6767
6768          else
6769             Fold_Ureal (N, Small_Value (P_Type), True);
6770          end if;
6771
6772       -----------------
6773       -- Stream_Size --
6774       -----------------
6775
6776       when Attribute_Stream_Size =>
6777          null;
6778
6779       ----------
6780       -- Succ --
6781       ----------
6782
6783       when Attribute_Succ => Succ :
6784       begin
6785          --  Floating-point case
6786
6787          if Is_Floating_Point_Type (P_Type) then
6788             Fold_Ureal (N,
6789               Eval_Fat.Succ (P_Root_Type, Expr_Value_R (E1)), Static);
6790
6791          --  Fixed-point case
6792
6793          elsif Is_Fixed_Point_Type (P_Type) then
6794             Fold_Ureal (N,
6795               Expr_Value_R (E1) + Small_Value (P_Type), Static);
6796
6797          --  Modular integer case (wraps)
6798
6799          elsif Is_Modular_Integer_Type (P_Type) then
6800             Fold_Uint (N, (Expr_Value (E1) + 1) mod Modulus (P_Type), Static);
6801
6802          --  Other scalar cases
6803
6804          else
6805             pragma Assert (Is_Scalar_Type (P_Type));
6806
6807             if Is_Enumeration_Type (P_Type)
6808               and then Expr_Value (E1) =
6809                          Expr_Value (Type_High_Bound (P_Base_Type))
6810             then
6811                Apply_Compile_Time_Constraint_Error
6812                  (N, "Succ of `&''Last`",
6813                   CE_Overflow_Check_Failed,
6814                   Ent  => P_Base_Type,
6815                   Warn => not Static);
6816
6817                Check_Expressions;
6818                return;
6819             else
6820                Fold_Uint (N, Expr_Value (E1) + 1, Static);
6821             end if;
6822          end if;
6823       end Succ;
6824
6825       ----------------
6826       -- Truncation --
6827       ----------------
6828
6829       when Attribute_Truncation =>
6830          Fold_Ureal (N,
6831            Eval_Fat.Truncation (P_Root_Type, Expr_Value_R (E1)), Static);
6832
6833       ----------------
6834       -- Type_Class --
6835       ----------------
6836
6837       when Attribute_Type_Class => Type_Class : declare
6838          Typ : constant Entity_Id := Underlying_Type (P_Base_Type);
6839          Id  : RE_Id;
6840
6841       begin
6842          if Is_Descendent_Of_Address (Typ) then
6843             Id := RE_Type_Class_Address;
6844
6845          elsif Is_Enumeration_Type (Typ) then
6846             Id := RE_Type_Class_Enumeration;
6847
6848          elsif Is_Integer_Type (Typ) then
6849             Id := RE_Type_Class_Integer;
6850
6851          elsif Is_Fixed_Point_Type (Typ) then
6852             Id := RE_Type_Class_Fixed_Point;
6853
6854          elsif Is_Floating_Point_Type (Typ) then
6855             Id := RE_Type_Class_Floating_Point;
6856
6857          elsif Is_Array_Type (Typ) then
6858             Id := RE_Type_Class_Array;
6859
6860          elsif Is_Record_Type (Typ) then
6861             Id := RE_Type_Class_Record;
6862
6863          elsif Is_Access_Type (Typ) then
6864             Id := RE_Type_Class_Access;
6865
6866          elsif Is_Enumeration_Type (Typ) then
6867             Id := RE_Type_Class_Enumeration;
6868
6869          elsif Is_Task_Type (Typ) then
6870             Id := RE_Type_Class_Task;
6871
6872          --  We treat protected types like task types. It would make more
6873          --  sense to have another enumeration value, but after all the
6874          --  whole point of this feature is to be exactly DEC compatible,
6875          --  and changing the type Type_Class would not meet this requirement.
6876
6877          elsif Is_Protected_Type (Typ) then
6878             Id := RE_Type_Class_Task;
6879
6880          --  Not clear if there are any other possibilities, but if there
6881          --  are, then we will treat them as the address case.
6882
6883          else
6884             Id := RE_Type_Class_Address;
6885          end if;
6886
6887          Rewrite (N, New_Occurrence_Of (RTE (Id), Loc));
6888       end Type_Class;
6889
6890       -----------------------
6891       -- Unbiased_Rounding --
6892       -----------------------
6893
6894       when Attribute_Unbiased_Rounding =>
6895          Fold_Ureal (N,
6896            Eval_Fat.Unbiased_Rounding (P_Root_Type, Expr_Value_R (E1)),
6897            Static);
6898
6899       -------------------------
6900       -- Unconstrained_Array --
6901       -------------------------
6902
6903       when Attribute_Unconstrained_Array => Unconstrained_Array : declare
6904          Typ : constant Entity_Id := Underlying_Type (P_Type);
6905
6906       begin
6907          Rewrite (N, New_Occurrence_Of (
6908            Boolean_Literals (
6909              Is_Array_Type (P_Type)
6910               and then not Is_Constrained (Typ)), Loc));
6911
6912          --  Analyze and resolve as boolean, note that this attribute is
6913          --  a static attribute in GNAT.
6914
6915          Analyze_And_Resolve (N, Standard_Boolean);
6916          Static := True;
6917       end Unconstrained_Array;
6918
6919       ---------------
6920       -- VADS_Size --
6921       ---------------
6922
6923       --  Processing is shared with Size
6924
6925       ---------
6926       -- Val --
6927       ---------
6928
6929       when Attribute_Val => Val :
6930       begin
6931          if  Expr_Value (E1) < Expr_Value (Type_Low_Bound (P_Base_Type))
6932            or else
6933              Expr_Value (E1) > Expr_Value (Type_High_Bound (P_Base_Type))
6934          then
6935             Apply_Compile_Time_Constraint_Error
6936               (N, "Val expression out of range",
6937                CE_Range_Check_Failed,
6938                Warn => not Static);
6939
6940             Check_Expressions;
6941             return;
6942
6943          else
6944             Fold_Uint (N, Expr_Value (E1), Static);
6945          end if;
6946       end Val;
6947
6948       ----------------
6949       -- Value_Size --
6950       ----------------
6951
6952       --  The Value_Size attribute for a type returns the RM size of the
6953       --  type. This an always be folded for scalar types, and can also
6954       --  be folded for non-scalar types if the size is set.
6955
6956       when Attribute_Value_Size => Value_Size : declare
6957          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6958       begin
6959          if RM_Size (P_TypeA) /= Uint_0 then
6960             Fold_Uint (N, RM_Size (P_TypeA), True);
6961          end if;
6962       end Value_Size;
6963
6964       -------------
6965       -- Version --
6966       -------------
6967
6968       --  Version can never be static
6969
6970       when Attribute_Version =>
6971          null;
6972
6973       ----------------
6974       -- Wide_Image --
6975       ----------------
6976
6977       --  Wide_Image is a scalar attribute, but is never static, because it
6978       --  is not a static function (having a non-scalar argument (RM 4.9(22))
6979
6980       when Attribute_Wide_Image =>
6981          null;
6982
6983       ---------------------
6984       -- Wide_Wide_Image --
6985       ---------------------
6986
6987       --  Wide_Wide_Image is a scalar attribute but is never static, because it
6988       --  is not a static function (having a non-scalar argument (RM 4.9(22)).
6989
6990       when Attribute_Wide_Wide_Image =>
6991          null;
6992
6993       ---------------------
6994       -- Wide_Wide_Width --
6995       ---------------------
6996
6997       --  Processing for Wide_Wide_Width is combined with Width
6998
6999       ----------------
7000       -- Wide_Width --
7001       ----------------
7002
7003       --  Processing for Wide_Width is combined with Width
7004
7005       -----------
7006       -- Width --
7007       -----------
7008
7009       --  This processing also handles the case of Wide_[Wide_]Width
7010
7011       when Attribute_Width |
7012            Attribute_Wide_Width |
7013            Attribute_Wide_Wide_Width => Width :
7014       begin
7015          if Compile_Time_Known_Bounds (P_Type) then
7016
7017             --  Floating-point types
7018
7019             if Is_Floating_Point_Type (P_Type) then
7020
7021                --  Width is zero for a null range (RM 3.5 (38))
7022
7023                if Expr_Value_R (Type_High_Bound (P_Type)) <
7024                   Expr_Value_R (Type_Low_Bound (P_Type))
7025                then
7026                   Fold_Uint (N, Uint_0, True);
7027
7028                else
7029                   --  For floating-point, we have +N.dddE+nnn where length
7030                   --  of ddd is determined by type'Digits - 1, but is one
7031                   --  if Digits is one (RM 3.5 (33)).
7032
7033                   --  nnn is set to 2 for Short_Float and Float (32 bit
7034                   --  floats), and 3 for Long_Float and Long_Long_Float.
7035                   --  For machines where Long_Long_Float is the IEEE
7036                   --  extended precision type, the exponent takes 4 digits.
7037
7038                   declare
7039                      Len : Int :=
7040                              Int'Max (2, UI_To_Int (Digits_Value (P_Type)));
7041
7042                   begin
7043                      if Esize (P_Type) <= 32 then
7044                         Len := Len + 6;
7045                      elsif Esize (P_Type) = 64 then
7046                         Len := Len + 7;
7047                      else
7048                         Len := Len + 8;
7049                      end if;
7050
7051                      Fold_Uint (N, UI_From_Int (Len), True);
7052                   end;
7053                end if;
7054
7055             --  Fixed-point types
7056
7057             elsif Is_Fixed_Point_Type (P_Type) then
7058
7059                --  Width is zero for a null range (RM 3.5 (38))
7060
7061                if Expr_Value (Type_High_Bound (P_Type)) <
7062                   Expr_Value (Type_Low_Bound  (P_Type))
7063                then
7064                   Fold_Uint (N, Uint_0, True);
7065
7066                --  The non-null case depends on the specific real type
7067
7068                else
7069                   --  For fixed-point type width is Fore + 1 + Aft (RM 3.5(34))
7070
7071                   Fold_Uint
7072                     (N, UI_From_Int (Fore_Value + 1 + Aft_Value), True);
7073                end if;
7074
7075             --  Discrete types
7076
7077             else
7078                declare
7079                   R  : constant Entity_Id := Root_Type (P_Type);
7080                   Lo : constant Uint := Expr_Value (Type_Low_Bound (P_Type));
7081                   Hi : constant Uint := Expr_Value (Type_High_Bound (P_Type));
7082                   W  : Nat;
7083                   Wt : Nat;
7084                   T  : Uint;
7085                   L  : Node_Id;
7086                   C  : Character;
7087
7088                begin
7089                   --  Empty ranges
7090
7091                   if Lo > Hi then
7092                      W := 0;
7093
7094                   --  Width for types derived from Standard.Character
7095                   --  and Standard.Wide_[Wide_]Character.
7096
7097                   elsif Is_Standard_Character_Type (P_Type) then
7098                      W := 0;
7099
7100                      --  Set W larger if needed
7101
7102                      for J in UI_To_Int (Lo) .. UI_To_Int (Hi) loop
7103
7104                         --  All wide characters look like Hex_hhhhhhhh
7105
7106                         if J > 255 then
7107                            W := 12;
7108
7109                         else
7110                            C := Character'Val (J);
7111
7112                            --  Test for all cases where Character'Image
7113                            --  yields an image that is longer than three
7114                            --  characters. First the cases of Reserved_xxx
7115                            --  names (length = 12).
7116
7117                            case C is
7118                               when Reserved_128 | Reserved_129 |
7119                                    Reserved_132 | Reserved_153
7120
7121                                 => Wt := 12;
7122
7123                               when BS | HT | LF | VT | FF | CR |
7124                                    SO | SI | EM | FS | GS | RS |
7125                                    US | RI | MW | ST | PM
7126
7127                                 => Wt := 2;
7128
7129                               when NUL | SOH | STX | ETX | EOT |
7130                                    ENQ | ACK | BEL | DLE | DC1 |
7131                                    DC2 | DC3 | DC4 | NAK | SYN |
7132                                    ETB | CAN | SUB | ESC | DEL |
7133                                    BPH | NBH | NEL | SSA | ESA |
7134                                    HTS | HTJ | VTS | PLD | PLU |
7135                                    SS2 | SS3 | DCS | PU1 | PU2 |
7136                                    STS | CCH | SPA | EPA | SOS |
7137                                    SCI | CSI | OSC | APC
7138
7139                                 => Wt := 3;
7140
7141                               when Space .. Tilde |
7142                                    No_Break_Space .. LC_Y_Diaeresis
7143
7144                                 => Wt := 3;
7145                            end case;
7146
7147                            W := Int'Max (W, Wt);
7148                         end if;
7149                      end loop;
7150
7151                   --  Width for types derived from Standard.Boolean
7152
7153                   elsif R = Standard_Boolean then
7154                      if Lo = 0 then
7155                         W := 5; -- FALSE
7156                      else
7157                         W := 4; -- TRUE
7158                      end if;
7159
7160                   --  Width for integer types
7161
7162                   elsif Is_Integer_Type (P_Type) then
7163                      T := UI_Max (abs Lo, abs Hi);
7164
7165                      W := 2;
7166                      while T >= 10 loop
7167                         W := W + 1;
7168                         T := T / 10;
7169                      end loop;
7170
7171                   --  Only remaining possibility is user declared enum type
7172
7173                   else
7174                      pragma Assert (Is_Enumeration_Type (P_Type));
7175
7176                      W := 0;
7177                      L := First_Literal (P_Type);
7178
7179                      while Present (L) loop
7180
7181                         --  Only pay attention to in range characters
7182
7183                         if Lo <= Enumeration_Pos (L)
7184                           and then Enumeration_Pos (L) <= Hi
7185                         then
7186                            --  For Width case, use decoded name
7187
7188                            if Id = Attribute_Width then
7189                               Get_Decoded_Name_String (Chars (L));
7190                               Wt := Nat (Name_Len);
7191
7192                            --  For Wide_[Wide_]Width, use encoded name, and
7193                            --  then adjust for the encoding.
7194
7195                            else
7196                               Get_Name_String (Chars (L));
7197
7198                               --  Character literals are always of length 3
7199
7200                               if Name_Buffer (1) = 'Q' then
7201                                  Wt := 3;
7202
7203                               --  Otherwise loop to adjust for upper/wide chars
7204
7205                               else
7206                                  Wt := Nat (Name_Len);
7207
7208                                  for J in 1 .. Name_Len loop
7209                                     if Name_Buffer (J) = 'U' then
7210                                        Wt := Wt - 2;
7211                                     elsif Name_Buffer (J) = 'W' then
7212                                        Wt := Wt - 4;
7213                                     end if;
7214                                  end loop;
7215                               end if;
7216                            end if;
7217
7218                            W := Int'Max (W, Wt);
7219                         end if;
7220
7221                         Next_Literal (L);
7222                      end loop;
7223                   end if;
7224
7225                   Fold_Uint (N, UI_From_Int (W), True);
7226                end;
7227             end if;
7228          end if;
7229       end Width;
7230
7231       --  The following attributes can never be folded, and furthermore we
7232       --  should not even have entered the case statement for any of these.
7233       --  Note that in some cases, the values have already been folded as
7234       --  a result of the processing in Analyze_Attribute.
7235
7236       when Attribute_Abort_Signal             |
7237            Attribute_Access                   |
7238            Attribute_Address                  |
7239            Attribute_Address_Size             |
7240            Attribute_Asm_Input                |
7241            Attribute_Asm_Output               |
7242            Attribute_Base                     |
7243            Attribute_Bit_Order                |
7244            Attribute_Bit_Position             |
7245            Attribute_Callable                 |
7246            Attribute_Caller                   |
7247            Attribute_Class                    |
7248            Attribute_Code_Address             |
7249            Attribute_Count                    |
7250            Attribute_Default_Bit_Order        |
7251            Attribute_Elaborated               |
7252            Attribute_Elab_Body                |
7253            Attribute_Elab_Spec                |
7254            Attribute_Enabled                  |
7255            Attribute_External_Tag             |
7256            Attribute_Fast_Math                |
7257            Attribute_First_Bit                |
7258            Attribute_Input                    |
7259            Attribute_Last_Bit                 |
7260            Attribute_Maximum_Alignment        |
7261            Attribute_Old                      |
7262            Attribute_Output                   |
7263            Attribute_Partition_ID             |
7264            Attribute_Pool_Address             |
7265            Attribute_Position                 |
7266            Attribute_Priority                 |
7267            Attribute_Read                     |
7268            Attribute_Result                   |
7269            Attribute_Storage_Pool             |
7270            Attribute_Storage_Size             |
7271            Attribute_Storage_Unit             |
7272            Attribute_Stub_Type                |
7273            Attribute_Tag                      |
7274            Attribute_Target_Name              |
7275            Attribute_Terminated               |
7276            Attribute_To_Address               |
7277            Attribute_UET_Address              |
7278            Attribute_Unchecked_Access         |
7279            Attribute_Universal_Literal_String |
7280            Attribute_Unrestricted_Access      |
7281            Attribute_Valid                    |
7282            Attribute_Value                    |
7283            Attribute_Wchar_T_Size             |
7284            Attribute_Wide_Value               |
7285            Attribute_Wide_Wide_Value          |
7286            Attribute_Word_Size                |
7287            Attribute_Write                    =>
7288
7289          raise Program_Error;
7290       end case;
7291
7292       --  At the end of the case, one more check. If we did a static evaluation
7293       --  so that the result is now a literal, then set Is_Static_Expression
7294       --  in the constant only if the prefix type is a static subtype. For
7295       --  non-static subtypes, the folding is still OK, but not static.
7296
7297       --  An exception is the GNAT attribute Constrained_Array which is
7298       --  defined to be a static attribute in all cases.
7299
7300       if Nkind_In (N, N_Integer_Literal,
7301                       N_Real_Literal,
7302                       N_Character_Literal,
7303                       N_String_Literal)
7304         or else (Is_Entity_Name (N)
7305                   and then Ekind (Entity (N)) = E_Enumeration_Literal)
7306       then
7307          Set_Is_Static_Expression (N, Static);
7308
7309       --  If this is still an attribute reference, then it has not been folded
7310       --  and that means that its expressions are in a non-static context.
7311
7312       elsif Nkind (N) = N_Attribute_Reference then
7313          Check_Expressions;
7314
7315       --  Note: the else case not covered here are odd cases where the
7316       --  processing has transformed the attribute into something other
7317       --  than a constant. Nothing more to do in such cases.
7318
7319       else
7320          null;
7321       end if;
7322    end Eval_Attribute;
7323
7324    ------------------------------
7325    -- Is_Anonymous_Tagged_Base --
7326    ------------------------------
7327
7328    function Is_Anonymous_Tagged_Base
7329      (Anon : Entity_Id;
7330       Typ  : Entity_Id)
7331       return Boolean
7332    is
7333    begin
7334       return
7335         Anon = Current_Scope
7336           and then Is_Itype (Anon)
7337           and then Associated_Node_For_Itype (Anon) = Parent (Typ);
7338    end Is_Anonymous_Tagged_Base;
7339
7340    --------------------------------
7341    -- Name_Implies_Lvalue_Prefix --
7342    --------------------------------
7343
7344    function Name_Implies_Lvalue_Prefix (Nam : Name_Id) return Boolean is
7345       pragma Assert (Is_Attribute_Name (Nam));
7346    begin
7347       return Attribute_Name_Implies_Lvalue_Prefix (Get_Attribute_Id (Nam));
7348    end Name_Implies_Lvalue_Prefix;
7349
7350    -----------------------
7351    -- Resolve_Attribute --
7352    -----------------------
7353
7354    procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id) is
7355       Loc      : constant Source_Ptr   := Sloc (N);
7356       P        : constant Node_Id      := Prefix (N);
7357       Aname    : constant Name_Id      := Attribute_Name (N);
7358       Attr_Id  : constant Attribute_Id := Get_Attribute_Id (Aname);
7359       Btyp     : constant Entity_Id    := Base_Type (Typ);
7360       Des_Btyp : Entity_Id;
7361       Index    : Interp_Index;
7362       It       : Interp;
7363       Nom_Subt : Entity_Id;
7364
7365       procedure Accessibility_Message;
7366       --  Error, or warning within an instance, if the static accessibility
7367       --  rules of 3.10.2 are violated.
7368
7369       ---------------------------
7370       -- Accessibility_Message --
7371       ---------------------------
7372
7373       procedure Accessibility_Message is
7374          Indic : Node_Id := Parent (Parent (N));
7375
7376       begin
7377          --  In an instance, this is a runtime check, but one we
7378          --  know will fail, so generate an appropriate warning.
7379
7380          if In_Instance_Body then
7381             Error_Msg_F
7382               ("?non-local pointer cannot point to local object", P);
7383             Error_Msg_F
7384               ("\?Program_Error will be raised at run time", P);
7385             Rewrite (N,
7386               Make_Raise_Program_Error (Loc,
7387                 Reason => PE_Accessibility_Check_Failed));
7388             Set_Etype (N, Typ);
7389             return;
7390
7391          else
7392             Error_Msg_F
7393               ("non-local pointer cannot point to local object", P);
7394
7395             --  Check for case where we have a missing access definition
7396
7397             if Is_Record_Type (Current_Scope)
7398               and then
7399                 Nkind_In (Parent (N), N_Discriminant_Association,
7400                                       N_Index_Or_Discriminant_Constraint)
7401             then
7402                Indic := Parent (Parent (N));
7403                while Present (Indic)
7404                  and then Nkind (Indic) /= N_Subtype_Indication
7405                loop
7406                   Indic := Parent (Indic);
7407                end loop;
7408
7409                if Present (Indic) then
7410                   Error_Msg_NE
7411                     ("\use an access definition for" &
7412                      " the access discriminant of&",
7413                      N, Entity (Subtype_Mark (Indic)));
7414                end if;
7415             end if;
7416          end if;
7417       end Accessibility_Message;
7418
7419    --  Start of processing for Resolve_Attribute
7420
7421    begin
7422       --  If error during analysis, no point in continuing, except for
7423       --  array types, where we get  better recovery by using unconstrained
7424       --  indices than nothing at all (see Check_Array_Type).
7425
7426       if Error_Posted (N)
7427         and then Attr_Id /= Attribute_First
7428         and then Attr_Id /= Attribute_Last
7429         and then Attr_Id /= Attribute_Length
7430         and then Attr_Id /= Attribute_Range
7431       then
7432          return;
7433       end if;
7434
7435       --  If attribute was universal type, reset to actual type
7436
7437       if Etype (N) = Universal_Integer
7438         or else Etype (N) = Universal_Real
7439       then
7440          Set_Etype (N, Typ);
7441       end if;
7442
7443       --  Remaining processing depends on attribute
7444
7445       case Attr_Id is
7446
7447          ------------
7448          -- Access --
7449          ------------
7450
7451          --  For access attributes, if the prefix denotes an entity, it is
7452          --  interpreted as a name, never as a call. It may be overloaded,
7453          --  in which case resolution uses the profile of the context type.
7454          --  Otherwise prefix must be resolved.
7455
7456          when Attribute_Access
7457             | Attribute_Unchecked_Access
7458             | Attribute_Unrestricted_Access =>
7459
7460          Access_Attribute :
7461          begin
7462             if Is_Variable (P) then
7463                Note_Possible_Modification (P, Sure => False);
7464             end if;
7465
7466             if Is_Entity_Name (P) then
7467                if Is_Overloaded (P) then
7468                   Get_First_Interp (P, Index, It);
7469                   while Present (It.Nam) loop
7470                      if Type_Conformant (Designated_Type (Typ), It.Nam) then
7471                         Set_Entity (P, It.Nam);
7472
7473                         --  The prefix is definitely NOT overloaded anymore at
7474                         --  this point, so we reset the Is_Overloaded flag to
7475                         --  avoid any confusion when reanalyzing the node.
7476
7477                         Set_Is_Overloaded (P, False);
7478                         Set_Is_Overloaded (N, False);
7479                         Generate_Reference (Entity (P), P);
7480                         exit;
7481                      end if;
7482
7483                      Get_Next_Interp (Index, It);
7484                   end loop;
7485
7486                --  If Prefix is a subprogram name, it is frozen by this
7487                --  reference:
7488
7489                --    If it is a type, there is nothing to resolve.
7490                --    If it is an object, complete its resolution.
7491
7492                elsif Is_Overloadable (Entity (P)) then
7493
7494                   --  Avoid insertion of freeze actions in spec expression mode
7495
7496                   if not In_Spec_Expression then
7497                      Insert_Actions (N, Freeze_Entity (Entity (P), Loc));
7498                   end if;
7499
7500                elsif Is_Type (Entity (P)) then
7501                   null;
7502                else
7503                   Resolve (P);
7504                end if;
7505
7506                Error_Msg_Name_1 := Aname;
7507
7508                if not Is_Entity_Name (P) then
7509                   null;
7510
7511                elsif Is_Overloadable (Entity (P))
7512                  and then Is_Abstract_Subprogram (Entity (P))
7513                then
7514                   Error_Msg_F ("prefix of % attribute cannot be abstract", P);
7515                   Set_Etype (N, Any_Type);
7516
7517                elsif Convention (Entity (P)) = Convention_Intrinsic then
7518                   if Ekind (Entity (P)) = E_Enumeration_Literal then
7519                      Error_Msg_F
7520                        ("prefix of % attribute cannot be enumeration literal",
7521                         P);
7522                   else
7523                      Error_Msg_F
7524                        ("prefix of % attribute cannot be intrinsic", P);
7525                   end if;
7526
7527                   Set_Etype (N, Any_Type);
7528                end if;
7529
7530                --  Assignments, return statements, components of aggregates,
7531                --  generic instantiations will require convention checks if
7532                --  the type is an access to subprogram. Given that there will
7533                --  also be accessibility checks on those, this is where the
7534                --  checks can eventually be centralized ???
7535
7536                if Ekind (Btyp) = E_Access_Subprogram_Type
7537                     or else
7538                   Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
7539                     or else
7540                   Ekind (Btyp) = E_Anonymous_Access_Protected_Subprogram_Type
7541                then
7542                   --  Deal with convention mismatch
7543
7544                   if Convention (Btyp) /= Convention (Entity (P)) then
7545                      Error_Msg_FE
7546                        ("subprogram & has wrong convention", P, Entity (P));
7547
7548                      Error_Msg_FE
7549                        ("\does not match convention of access type &",
7550                         P, Btyp);
7551
7552                      if not Has_Convention_Pragma (Btyp) then
7553                         Error_Msg_FE
7554                           ("\probable missing pragma Convention for &",
7555                            P, Btyp);
7556                      end if;
7557
7558                   else
7559                      Check_Subtype_Conformant
7560                        (New_Id  => Entity (P),
7561                         Old_Id  => Designated_Type (Btyp),
7562                         Err_Loc => P);
7563                   end if;
7564
7565                   if Attr_Id = Attribute_Unchecked_Access then
7566                      Error_Msg_Name_1 := Aname;
7567                      Error_Msg_F
7568                        ("attribute% cannot be applied to a subprogram", P);
7569
7570                   elsif Aname = Name_Unrestricted_Access then
7571                      null;  --  Nothing to check
7572
7573                   --  Check the static accessibility rule of 3.10.2(32).
7574                   --  This rule also applies within the private part of an
7575                   --  instantiation. This rule does not apply to anonymous
7576                   --  access-to-subprogram types (Ada 2005).
7577
7578                   elsif Attr_Id = Attribute_Access
7579                     and then not In_Instance_Body
7580                     and then Subprogram_Access_Level (Entity (P)) >
7581                                Type_Access_Level (Btyp)
7582                     and then Ekind (Btyp) /=
7583                                E_Anonymous_Access_Subprogram_Type
7584                     and then Ekind (Btyp) /=
7585                                E_Anonymous_Access_Protected_Subprogram_Type
7586                   then
7587                      Error_Msg_F
7588                        ("subprogram must not be deeper than access type", P);
7589
7590                   --  Check the restriction of 3.10.2(32) that disallows the
7591                   --  access attribute within a generic body when the ultimate
7592                   --  ancestor of the type of the attribute is declared outside
7593                   --  of the generic unit and the subprogram is declared within
7594                   --  that generic unit. This includes any such attribute that
7595                   --  occurs within the body of a generic unit that is a child
7596                   --  of the generic unit where the subprogram is declared.
7597                   --  The rule also prohibits applying the attribute when the
7598                   --  access type is a generic formal access type (since the
7599                   --  level of the actual type is not known). This restriction
7600                   --  does not apply when the attribute type is an anonymous
7601                   --  access-to-subprogram type. Note that this check was
7602                   --  revised by AI-229, because the originally Ada 95 rule
7603                   --  was too lax. The original rule only applied when the
7604                   --  subprogram was declared within the body of the generic,
7605                   --  which allowed the possibility of dangling references).
7606                   --  The rule was also too strict in some case, in that it
7607                   --  didn't permit the access to be declared in the generic
7608                   --  spec, whereas the revised rule does (as long as it's not
7609                   --  a formal type).
7610
7611                   --  There are a couple of subtleties of the test for applying
7612                   --  the check that are worth noting. First, we only apply it
7613                   --  when the levels of the subprogram and access type are the
7614                   --  same (the case where the subprogram is statically deeper
7615                   --  was applied above, and the case where the type is deeper
7616                   --  is always safe). Second, we want the check to apply
7617                   --  within nested generic bodies and generic child unit
7618                   --  bodies, but not to apply to an attribute that appears in
7619                   --  the generic unit's specification. This is done by testing
7620                   --  that the attribute's innermost enclosing generic body is
7621                   --  not the same as the innermost generic body enclosing the
7622                   --  generic unit where the subprogram is declared (we don't
7623                   --  want the check to apply when the access attribute is in
7624                   --  the spec and there's some other generic body enclosing
7625                   --  generic). Finally, there's no point applying the check
7626                   --  when within an instance, because any violations will have
7627                   --  been caught by the compilation of the generic unit.
7628
7629                   elsif Attr_Id = Attribute_Access
7630                     and then not In_Instance
7631                     and then Present (Enclosing_Generic_Unit (Entity (P)))
7632                     and then Present (Enclosing_Generic_Body (N))
7633                     and then Enclosing_Generic_Body (N) /=
7634                                Enclosing_Generic_Body
7635                                  (Enclosing_Generic_Unit (Entity (P)))
7636                     and then Subprogram_Access_Level (Entity (P)) =
7637                                Type_Access_Level (Btyp)
7638                     and then Ekind (Btyp) /=
7639                                E_Anonymous_Access_Subprogram_Type
7640                     and then Ekind (Btyp) /=
7641                                E_Anonymous_Access_Protected_Subprogram_Type
7642                   then
7643                      --  The attribute type's ultimate ancestor must be
7644                      --  declared within the same generic unit as the
7645                      --  subprogram is declared. The error message is
7646                      --  specialized to say "ancestor" for the case where
7647                      --  the access type is not its own ancestor, since
7648                      --  saying simply "access type" would be very confusing.
7649
7650                      if Enclosing_Generic_Unit (Entity (P)) /=
7651                           Enclosing_Generic_Unit (Root_Type (Btyp))
7652                      then
7653                         Error_Msg_N
7654                           ("''Access attribute not allowed in generic body",
7655                            N);
7656
7657                         if Root_Type (Btyp) = Btyp then
7658                            Error_Msg_NE
7659                              ("\because " &
7660                               "access type & is declared outside " &
7661                               "generic unit (RM 3.10.2(32))", N, Btyp);
7662                         else
7663                            Error_Msg_NE
7664                              ("\because ancestor of " &
7665                               "access type & is declared outside " &
7666                               "generic unit (RM 3.10.2(32))", N, Btyp);
7667                         end if;
7668
7669                         Error_Msg_NE
7670                           ("\move ''Access to private part, or " &
7671                            "(Ada 2005) use anonymous access type instead of &",
7672                            N, Btyp);
7673
7674                      --  If the ultimate ancestor of the attribute's type is
7675                      --  a formal type, then the attribute is illegal because
7676                      --  the actual type might be declared at a higher level.
7677                      --  The error message is specialized to say "ancestor"
7678                      --  for the case where the access type is not its own
7679                      --  ancestor, since saying simply "access type" would be
7680                      --  very confusing.
7681
7682                      elsif Is_Generic_Type (Root_Type (Btyp)) then
7683                         if Root_Type (Btyp) = Btyp then
7684                            Error_Msg_N
7685                              ("access type must not be a generic formal type",
7686                               N);
7687                         else
7688                            Error_Msg_N
7689                              ("ancestor access type must not be a generic " &
7690                               "formal type", N);
7691                         end if;
7692                      end if;
7693                   end if;
7694                end if;
7695
7696                --  If this is a renaming, an inherited operation, or a
7697                --  subprogram instance, use the original entity. This may make
7698                --  the node type-inconsistent, so this transformation can only
7699                --  be done if the node will not be reanalyzed. In particular,
7700                --  if it is within a default expression, the transformation
7701                --  must be delayed until the default subprogram is created for
7702                --  it, when the enclosing subprogram is frozen.
7703
7704                if Is_Entity_Name (P)
7705                  and then Is_Overloadable (Entity (P))
7706                  and then Present (Alias (Entity (P)))
7707                  and then Expander_Active
7708                then
7709                   Rewrite (P,
7710                     New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
7711                end if;
7712
7713             elsif Nkind (P) = N_Selected_Component
7714               and then Is_Overloadable (Entity (Selector_Name (P)))
7715             then
7716                --  Protected operation. If operation is overloaded, must
7717                --  disambiguate. Prefix that denotes protected object itself
7718                --  is resolved with its own type.
7719
7720                if Attr_Id = Attribute_Unchecked_Access then
7721                   Error_Msg_Name_1 := Aname;
7722                   Error_Msg_F
7723                     ("attribute% cannot be applied to protected operation", P);
7724                end if;
7725
7726                Resolve (Prefix (P));
7727                Generate_Reference (Entity (Selector_Name (P)), P);
7728
7729             elsif Is_Overloaded (P) then
7730
7731                --  Use the designated type of the context to disambiguate
7732                --  Note that this was not strictly conformant to Ada 95,
7733                --  but was the implementation adopted by most Ada 95 compilers.
7734                --  The use of the context type to resolve an Access attribute
7735                --  reference is now mandated in AI-235 for Ada 2005.
7736
7737                declare
7738                   Index : Interp_Index;
7739                   It    : Interp;
7740
7741                begin
7742                   Get_First_Interp (P, Index, It);
7743                   while Present (It.Typ) loop
7744                      if Covers (Designated_Type (Typ), It.Typ) then
7745                         Resolve (P, It.Typ);
7746                         exit;
7747                      end if;
7748
7749                      Get_Next_Interp (Index, It);
7750                   end loop;
7751                end;
7752             else
7753                Resolve (P);
7754             end if;
7755
7756             --  X'Access is illegal if X denotes a constant and the access type
7757             --  is access-to-variable. Same for 'Unchecked_Access. The rule
7758             --  does not apply to 'Unrestricted_Access. If the reference is a
7759             --  default-initialized aggregate component for a self-referential
7760             --  type the reference is legal.
7761
7762             if not (Ekind (Btyp) = E_Access_Subprogram_Type
7763                      or else Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
7764                      or else (Is_Record_Type (Btyp)
7765                                and then
7766                                  Present (Corresponding_Remote_Type (Btyp)))
7767                      or else Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7768                      or else Ekind (Btyp)
7769                                = E_Anonymous_Access_Protected_Subprogram_Type
7770                      or else Is_Access_Constant (Btyp)
7771                      or else Is_Variable (P)
7772                      or else Attr_Id = Attribute_Unrestricted_Access)
7773             then
7774                if Is_Entity_Name (P)
7775                  and then Is_Type (Entity (P))
7776                then
7777                   --  Legality of a self-reference through an access
7778                   --  attribute has been verified in Analyze_Access_Attribute.
7779
7780                   null;
7781
7782                elsif Comes_From_Source (N) then
7783                   Error_Msg_F ("access-to-variable designates constant", P);
7784                end if;
7785             end if;
7786
7787             Des_Btyp := Designated_Type (Btyp);
7788
7789             if Ada_Version >= Ada_05
7790               and then Is_Incomplete_Type (Des_Btyp)
7791             then
7792                --  Ada 2005 (AI-412): If the (sub)type is a limited view of an
7793                --  imported entity, and the non-limited view is visible, make
7794                --  use of it. If it is an incomplete subtype, use the base type
7795                --  in any case.
7796
7797                if From_With_Type (Des_Btyp)
7798                  and then Present (Non_Limited_View (Des_Btyp))
7799                then
7800                   Des_Btyp := Non_Limited_View (Des_Btyp);
7801
7802                elsif Ekind (Des_Btyp) = E_Incomplete_Subtype then
7803                   Des_Btyp := Etype (Des_Btyp);
7804                end if;
7805             end if;
7806
7807             if (Attr_Id = Attribute_Access
7808                   or else
7809                 Attr_Id = Attribute_Unchecked_Access)
7810               and then (Ekind (Btyp) = E_General_Access_Type
7811                           or else Ekind (Btyp) = E_Anonymous_Access_Type)
7812             then
7813                --  Ada 2005 (AI-230): Check the accessibility of anonymous
7814                --  access types for stand-alone objects, record and array
7815                --  components, and return objects. For a component definition
7816                --  the level is the same of the enclosing composite type.
7817
7818                if Ada_Version >= Ada_05
7819                  and then Is_Local_Anonymous_Access (Btyp)
7820                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
7821                  and then Attr_Id = Attribute_Access
7822                then
7823                   --  In an instance, this is a runtime check, but one we
7824                   --  know will fail, so generate an appropriate warning.
7825
7826                   if In_Instance_Body then
7827                      Error_Msg_F
7828                        ("?non-local pointer cannot point to local object", P);
7829                      Error_Msg_F
7830                        ("\?Program_Error will be raised at run time", P);
7831                      Rewrite (N,
7832                        Make_Raise_Program_Error (Loc,
7833                          Reason => PE_Accessibility_Check_Failed));
7834                      Set_Etype (N, Typ);
7835
7836                   else
7837                      Error_Msg_F
7838                        ("non-local pointer cannot point to local object", P);
7839                   end if;
7840                end if;
7841
7842                if Is_Dependent_Component_Of_Mutable_Object (P) then
7843                   Error_Msg_F
7844                     ("illegal attribute for discriminant-dependent component",
7845                      P);
7846                end if;
7847
7848                --  Check static matching rule of 3.10.2(27). Nominal subtype
7849                --  of the prefix must statically match the designated type.
7850
7851                Nom_Subt := Etype (P);
7852
7853                if Is_Constr_Subt_For_U_Nominal (Nom_Subt) then
7854                   Nom_Subt := Base_Type (Nom_Subt);
7855                end if;
7856
7857                if Is_Tagged_Type (Designated_Type (Typ)) then
7858
7859                   --  If the attribute is in the context of an access
7860                   --  parameter, then the prefix is allowed to be of the
7861                   --  class-wide type (by AI-127).
7862
7863                   if Ekind (Typ) = E_Anonymous_Access_Type then
7864                      if not Covers (Designated_Type (Typ), Nom_Subt)
7865                        and then not Covers (Nom_Subt, Designated_Type (Typ))
7866                      then
7867                         declare
7868                            Desig : Entity_Id;
7869
7870                         begin
7871                            Desig := Designated_Type (Typ);
7872
7873                            if Is_Class_Wide_Type (Desig) then
7874                               Desig := Etype (Desig);
7875                            end if;
7876
7877                            if Is_Anonymous_Tagged_Base (Nom_Subt, Desig) then
7878                               null;
7879
7880                            else
7881                               Error_Msg_FE
7882                                 ("type of prefix: & not compatible",
7883                                   P, Nom_Subt);
7884                               Error_Msg_FE
7885                                 ("\with &, the expected designated type",
7886                                   P, Designated_Type (Typ));
7887                            end if;
7888                         end;
7889                      end if;
7890
7891                   elsif not Covers (Designated_Type (Typ), Nom_Subt)
7892                     or else
7893                       (not Is_Class_Wide_Type (Designated_Type (Typ))
7894                         and then Is_Class_Wide_Type (Nom_Subt))
7895                   then
7896                      Error_Msg_FE
7897                        ("type of prefix: & is not covered", P, Nom_Subt);
7898                      Error_Msg_FE
7899                        ("\by &, the expected designated type" &
7900                            " (RM 3.10.2 (27))", P, Designated_Type (Typ));
7901                   end if;
7902
7903                   if Is_Class_Wide_Type (Designated_Type (Typ))
7904                     and then Has_Discriminants (Etype (Designated_Type (Typ)))
7905                     and then Is_Constrained (Etype (Designated_Type (Typ)))
7906                     and then Designated_Type (Typ) /= Nom_Subt
7907                   then
7908                      Apply_Discriminant_Check
7909                        (N, Etype (Designated_Type (Typ)));
7910                   end if;
7911
7912                --  Ada 2005 (AI-363): Require static matching when designated
7913                --  type has discriminants and a constrained partial view, since
7914                --  in general objects of such types are mutable, so we can't
7915                --  allow the access value to designate a constrained object
7916                --  (because access values must be assumed to designate mutable
7917                --  objects when designated type does not impose a constraint).
7918
7919                elsif Subtypes_Statically_Match (Des_Btyp, Nom_Subt) then
7920                   null;
7921
7922                elsif Has_Discriminants (Designated_Type (Typ))
7923                  and then not Is_Constrained (Des_Btyp)
7924                  and then
7925                    (Ada_Version < Ada_05
7926                      or else
7927                        not Has_Constrained_Partial_View
7928                              (Designated_Type (Base_Type (Typ))))
7929                then
7930                   null;
7931
7932                else
7933                   Error_Msg_F
7934                     ("object subtype must statically match "
7935                      & "designated subtype", P);
7936
7937                   if Is_Entity_Name (P)
7938                     and then Is_Array_Type (Designated_Type (Typ))
7939                   then
7940                      declare
7941                         D : constant Node_Id := Declaration_Node (Entity (P));
7942
7943                      begin
7944                         Error_Msg_N ("aliased object has explicit bounds?",
7945                           D);
7946                         Error_Msg_N ("\declare without bounds"
7947                           & " (and with explicit initialization)?", D);
7948                         Error_Msg_N ("\for use with unconstrained access?", D);
7949                      end;
7950                   end if;
7951                end if;
7952
7953                --  Check the static accessibility rule of 3.10.2(28).
7954                --  Note that this check is not performed for the
7955                --  case of an anonymous access type, since the access
7956                --  attribute is always legal in such a context.
7957
7958                if Attr_Id /= Attribute_Unchecked_Access
7959                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
7960                  and then Ekind (Btyp) = E_General_Access_Type
7961                then
7962                   Accessibility_Message;
7963                   return;
7964                end if;
7965             end if;
7966
7967             if Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7968                  or else
7969                Ekind (Btyp) = E_Anonymous_Access_Protected_Subprogram_Type
7970             then
7971                if Is_Entity_Name (P)
7972                  and then not Is_Protected_Type (Scope (Entity (P)))
7973                then
7974                   Error_Msg_F ("context requires a protected subprogram", P);
7975
7976                --  Check accessibility of protected object against that of the
7977                --  access type, but only on user code, because the expander
7978                --  creates access references for handlers. If the context is an
7979                --  anonymous_access_to_protected, there are no accessibility
7980                --  checks either. Omit check entirely for Unrestricted_Access.
7981
7982                elsif Object_Access_Level (P) > Type_Access_Level (Btyp)
7983                  and then Comes_From_Source (N)
7984                  and then Ekind (Btyp) = E_Access_Protected_Subprogram_Type
7985                  and then Attr_Id /= Attribute_Unrestricted_Access
7986                then
7987                   Accessibility_Message;
7988                   return;
7989                end if;
7990
7991             elsif (Ekind (Btyp) = E_Access_Subprogram_Type
7992                      or else
7993                    Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type)
7994               and then Ekind (Etype (N)) = E_Access_Protected_Subprogram_Type
7995             then
7996                Error_Msg_F ("context requires a non-protected subprogram", P);
7997             end if;
7998
7999             --  The context cannot be a pool-specific type, but this is a
8000             --  legality rule, not a resolution rule, so it must be checked
8001             --  separately, after possibly disambiguation (see AI-245).
8002
8003             if Ekind (Btyp) = E_Access_Type
8004               and then Attr_Id /= Attribute_Unrestricted_Access
8005             then
8006                Wrong_Type (N, Typ);
8007             end if;
8008
8009             --  The context may be a constrained access type (however ill-
8010             --  advised such subtypes might be) so in order to generate a
8011             --  constraint check when needed set the type of the attribute
8012             --  reference to the base type of the context.
8013
8014             Set_Etype (N, Btyp);
8015
8016             --  Check for incorrect atomic/volatile reference (RM C.6(12))
8017
8018             if Attr_Id /= Attribute_Unrestricted_Access then
8019                if Is_Atomic_Object (P)
8020                  and then not Is_Atomic (Designated_Type (Typ))
8021                then
8022                   Error_Msg_F
8023                     ("access to atomic object cannot yield access-to-" &
8024                      "non-atomic type", P);
8025
8026                elsif Is_Volatile_Object (P)
8027                  and then not Is_Volatile (Designated_Type (Typ))
8028                then
8029                   Error_Msg_F
8030                     ("access to volatile object cannot yield access-to-" &
8031                      "non-volatile type", P);
8032                end if;
8033             end if;
8034
8035             if Is_Entity_Name (P) then
8036                Set_Address_Taken (Entity (P));
8037             end if;
8038          end Access_Attribute;
8039
8040          -------------
8041          -- Address --
8042          -------------
8043
8044          --  Deal with resolving the type for Address attribute, overloading
8045          --  is not permitted here, since there is no context to resolve it.
8046
8047          when Attribute_Address | Attribute_Code_Address =>
8048          Address_Attribute : begin
8049
8050             --  To be safe, assume that if the address of a variable is taken,
8051             --  it may be modified via this address, so note modification.
8052
8053             if Is_Variable (P) then
8054                Note_Possible_Modification (P, Sure => False);
8055             end if;
8056
8057             if Nkind (P) in N_Subexpr
8058               and then Is_Overloaded (P)
8059             then
8060                Get_First_Interp (P, Index, It);
8061                Get_Next_Interp (Index, It);
8062
8063                if Present (It.Nam) then
8064                   Error_Msg_Name_1 := Aname;
8065                   Error_Msg_F
8066                     ("prefix of % attribute cannot be overloaded", P);
8067                end if;
8068             end if;
8069
8070             if not Is_Entity_Name (P)
8071               or else not Is_Overloadable (Entity (P))
8072             then
8073                if not Is_Task_Type (Etype (P))
8074                  or else Nkind (P) = N_Explicit_Dereference
8075                then
8076                   Resolve (P);
8077                end if;
8078             end if;
8079
8080             --  If this is the name of a derived subprogram, or that of a
8081             --  generic actual, the address is that of the original entity.
8082
8083             if Is_Entity_Name (P)
8084               and then Is_Overloadable (Entity (P))
8085               and then Present (Alias (Entity (P)))
8086             then
8087                Rewrite (P,
8088                  New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
8089             end if;
8090
8091             if Is_Entity_Name (P) then
8092                Set_Address_Taken (Entity (P));
8093             end if;
8094
8095             if Nkind (P) = N_Slice then
8096
8097                --  Arr (X .. Y)'address is identical to Arr (X)'address,
8098                --  even if the array is packed and the slice itself is not
8099                --  addressable. Transform the prefix into an indexed component.
8100
8101                --  Note that the transformation is safe only if we know that
8102                --  the slice is non-null. That is because a null slice can have
8103                --  an out of bounds index value.
8104
8105                --  Right now, gigi blows up if given 'Address on a slice as a
8106                --  result of some incorrect freeze nodes generated by the front
8107                --  end, and this covers up that bug in one case, but the bug is
8108                --  likely still there in the cases not handled by this code ???
8109
8110                --  It's not clear what 'Address *should* return for a null
8111                --  slice with out of bounds indexes, this might be worth an ARG
8112                --  discussion ???
8113
8114                --  One approach would be to do a length check unconditionally,
8115                --  and then do the transformation below unconditionally, but
8116                --  analyze with checks off, avoiding the problem of the out of
8117                --  bounds index. This approach would interpret the address of
8118                --  an out of bounds null slice as being the address where the
8119                --  array element would be if there was one, which is probably
8120                --  as reasonable an interpretation as any ???
8121
8122                declare
8123                   Loc : constant Source_Ptr := Sloc (P);
8124                   D   : constant Node_Id := Discrete_Range (P);
8125                   Lo  : Node_Id;
8126
8127                begin
8128                   if Is_Entity_Name (D)
8129                     and then
8130                       Not_Null_Range
8131                         (Type_Low_Bound (Entity (D)),
8132                          Type_High_Bound (Entity (D)))
8133                   then
8134                      Lo :=
8135                        Make_Attribute_Reference (Loc,
8136                           Prefix => (New_Occurrence_Of (Entity (D), Loc)),
8137                           Attribute_Name => Name_First);
8138
8139                   elsif Nkind (D) = N_Range
8140                     and then Not_Null_Range (Low_Bound (D), High_Bound (D))
8141                   then
8142                      Lo := Low_Bound (D);
8143
8144                   else
8145                      Lo := Empty;
8146                   end if;
8147
8148                   if Present (Lo) then
8149                      Rewrite (P,
8150                         Make_Indexed_Component (Loc,
8151                            Prefix =>  Relocate_Node (Prefix (P)),
8152                            Expressions => New_List (Lo)));
8153
8154                      Analyze_And_Resolve (P);
8155                   end if;
8156                end;
8157             end if;
8158          end Address_Attribute;
8159
8160          ---------------
8161          -- AST_Entry --
8162          ---------------
8163
8164          --  Prefix of the AST_Entry attribute is an entry name which must
8165          --  not be resolved, since this is definitely not an entry call.
8166
8167          when Attribute_AST_Entry =>
8168             null;
8169
8170          ------------------
8171          -- Body_Version --
8172          ------------------
8173
8174          --  Prefix of Body_Version attribute can be a subprogram name which
8175          --  must not be resolved, since this is not a call.
8176
8177          when Attribute_Body_Version =>
8178             null;
8179
8180          ------------
8181          -- Caller --
8182          ------------
8183
8184          --  Prefix of Caller attribute is an entry name which must not
8185          --  be resolved, since this is definitely not an entry call.
8186
8187          when Attribute_Caller =>
8188             null;
8189
8190          ------------------
8191          -- Code_Address --
8192          ------------------
8193
8194          --  Shares processing with Address attribute
8195
8196          -----------
8197          -- Count --
8198          -----------
8199
8200          --  If the prefix of the Count attribute is an entry name it must not
8201          --  be resolved, since this is definitely not an entry call. However,
8202          --  if it is an element of an entry family, the index itself may
8203          --  have to be resolved because it can be a general expression.
8204
8205          when Attribute_Count =>
8206             if Nkind (P) = N_Indexed_Component
8207               and then Is_Entity_Name (Prefix (P))
8208             then
8209                declare
8210                   Indx : constant Node_Id   := First (Expressions (P));
8211                   Fam  : constant Entity_Id := Entity (Prefix (P));
8212                begin
8213                   Resolve (Indx, Entry_Index_Type (Fam));
8214                   Apply_Range_Check (Indx, Entry_Index_Type (Fam));
8215                end;
8216             end if;
8217
8218          ----------------
8219          -- Elaborated --
8220          ----------------
8221
8222          --  Prefix of the Elaborated attribute is a subprogram name which
8223          --  must not be resolved, since this is definitely not a call. Note
8224          --  that it is a library unit, so it cannot be overloaded here.
8225
8226          when Attribute_Elaborated =>
8227             null;
8228
8229          -------------
8230          -- Enabled --
8231          -------------
8232
8233          --  Prefix of Enabled attribute is a check name, which must be treated
8234          --  specially and not touched by Resolve.
8235
8236          when Attribute_Enabled =>
8237             null;
8238
8239          --------------------
8240          -- Mechanism_Code --
8241          --------------------
8242
8243          --  Prefix of the Mechanism_Code attribute is a function name
8244          --  which must not be resolved. Should we check for overloaded ???
8245
8246          when Attribute_Mechanism_Code =>
8247             null;
8248
8249          ------------------
8250          -- Partition_ID --
8251          ------------------
8252
8253          --  Most processing is done in sem_dist, after determining the
8254          --  context type. Node is rewritten as a conversion to a runtime call.
8255
8256          when Attribute_Partition_ID =>
8257             Process_Partition_Id (N);
8258             return;
8259
8260          ------------------
8261          -- Pool_Address --
8262          ------------------
8263
8264          when Attribute_Pool_Address =>
8265             Resolve (P);
8266
8267          -----------
8268          -- Range --
8269          -----------
8270
8271          --  We replace the Range attribute node with a range expression
8272          --  whose bounds are the 'First and 'Last attributes applied to the
8273          --  same prefix. The reason that we do this transformation here
8274          --  instead of in the expander is that it simplifies other parts of
8275          --  the semantic analysis which assume that the Range has been
8276          --  replaced; thus it must be done even when in semantic-only mode
8277          --  (note that the RM specifically mentions this equivalence, we
8278          --  take care that the prefix is only evaluated once).
8279
8280          when Attribute_Range => Range_Attribute :
8281             declare
8282                LB   : Node_Id;
8283                HB   : Node_Id;
8284
8285             begin
8286                if not Is_Entity_Name (P)
8287                  or else not Is_Type (Entity (P))
8288                then
8289                   Resolve (P);
8290                end if;
8291
8292                HB :=
8293                  Make_Attribute_Reference (Loc,
8294                    Prefix         =>
8295                      Duplicate_Subexpr (P, Name_Req => True),
8296                    Attribute_Name => Name_Last,
8297                    Expressions    => Expressions (N));
8298
8299                LB :=
8300                  Make_Attribute_Reference (Loc,
8301                    Prefix         => P,
8302                    Attribute_Name => Name_First,
8303                    Expressions    => Expressions (N));
8304
8305                --  If the original was marked as Must_Not_Freeze (see code
8306                --  in Sem_Ch3.Make_Index), then make sure the rewriting
8307                --  does not freeze either.
8308
8309                if Must_Not_Freeze (N) then
8310                   Set_Must_Not_Freeze (HB);
8311                   Set_Must_Not_Freeze (LB);
8312                   Set_Must_Not_Freeze (Prefix (HB));
8313                   Set_Must_Not_Freeze (Prefix (LB));
8314                end if;
8315
8316                if Raises_Constraint_Error (Prefix (N)) then
8317
8318                   --  Preserve Sloc of prefix in the new bounds, so that
8319                   --  the posted warning can be removed if we are within
8320                   --  unreachable code.
8321
8322                   Set_Sloc (LB, Sloc (Prefix (N)));
8323                   Set_Sloc (HB, Sloc (Prefix (N)));
8324                end if;
8325
8326                Rewrite (N, Make_Range (Loc, LB, HB));
8327                Analyze_And_Resolve (N, Typ);
8328
8329                --  Normally after resolving attribute nodes, Eval_Attribute
8330                --  is called to do any possible static evaluation of the node.
8331                --  However, here since the Range attribute has just been
8332                --  transformed into a range expression it is no longer an
8333                --  attribute node and therefore the call needs to be avoided
8334                --  and is accomplished by simply returning from the procedure.
8335
8336                return;
8337             end Range_Attribute;
8338
8339          ------------
8340          -- Result --
8341          ------------
8342
8343          --  We will only come here during the prescan of a spec expression
8344          --  containing a Result attribute. In that case the proper Etype has
8345          --  already been set, and nothing more needs to be done here.
8346
8347          when Attribute_Result =>
8348             null;
8349
8350          -----------------
8351          -- UET_Address --
8352          -----------------
8353
8354          --  Prefix must not be resolved in this case, since it is not a
8355          --  real entity reference. No action of any kind is require!
8356
8357          when Attribute_UET_Address =>
8358             return;
8359
8360          ----------------------
8361          -- Unchecked_Access --
8362          ----------------------
8363
8364          --  Processing is shared with Access
8365
8366          -------------------------
8367          -- Unrestricted_Access --
8368          -------------------------
8369
8370          --  Processing is shared with Access
8371
8372          ---------
8373          -- Val --
8374          ---------
8375
8376          --  Apply range check. Note that we did not do this during the
8377          --  analysis phase, since we wanted Eval_Attribute to have a
8378          --  chance at finding an illegal out of range value.
8379
8380          when Attribute_Val =>
8381
8382             --  Note that we do our own Eval_Attribute call here rather than
8383             --  use the common one, because we need to do processing after
8384             --  the call, as per above comment.
8385
8386             Eval_Attribute (N);
8387
8388             --  Eval_Attribute may replace the node with a raise CE, or
8389             --  fold it to a constant. Obviously we only apply a scalar
8390             --  range check if this did not happen!
8391
8392             if Nkind (N) = N_Attribute_Reference
8393               and then Attribute_Name (N) = Name_Val
8394             then
8395                Apply_Scalar_Range_Check (First (Expressions (N)), Btyp);
8396             end if;
8397
8398             return;
8399
8400          -------------
8401          -- Version --
8402          -------------
8403
8404          --  Prefix of Version attribute can be a subprogram name which
8405          --  must not be resolved, since this is not a call.
8406
8407          when Attribute_Version =>
8408             null;
8409
8410          ----------------------
8411          -- Other Attributes --
8412          ----------------------
8413
8414          --  For other attributes, resolve prefix unless it is a type. If
8415          --  the attribute reference itself is a type name ('Base and 'Class)
8416          --  then this is only legal within a task or protected record.
8417
8418          when others =>
8419             if not Is_Entity_Name (P)
8420               or else not Is_Type (Entity (P))
8421             then
8422                Resolve (P);
8423             end if;
8424
8425             --  If the attribute reference itself is a type name ('Base,
8426             --  'Class) then this is only legal within a task or protected
8427             --  record. What is this all about ???
8428
8429             if Is_Entity_Name (N)
8430               and then Is_Type (Entity (N))
8431             then
8432                if Is_Concurrent_Type (Entity (N))
8433                  and then In_Open_Scopes (Entity (P))
8434                then
8435                   null;
8436                else
8437                   Error_Msg_N
8438                     ("invalid use of subtype name in expression or call", N);
8439                end if;
8440             end if;
8441
8442             --  For attributes whose argument may be a string, complete
8443             --  resolution of argument now. This avoids premature expansion
8444             --  (and the creation of transient scopes) before the attribute
8445             --  reference is resolved.
8446
8447             case Attr_Id is
8448                when Attribute_Value =>
8449                   Resolve (First (Expressions (N)), Standard_String);
8450
8451                when Attribute_Wide_Value =>
8452                   Resolve (First (Expressions (N)), Standard_Wide_String);
8453
8454                when Attribute_Wide_Wide_Value =>
8455                   Resolve (First (Expressions (N)), Standard_Wide_Wide_String);
8456
8457                when others => null;
8458             end case;
8459
8460             --  If the prefix of the attribute is a class-wide type then it
8461             --  will be expanded into a dispatching call to a predefined
8462             --  primitive. Therefore we must check for potential violation
8463             --  of such restriction.
8464
8465             if Is_Class_Wide_Type (Etype (P)) then
8466                Check_Restriction (No_Dispatching_Calls, N);
8467             end if;
8468       end case;
8469
8470       --  Normally the Freezing is done by Resolve but sometimes the Prefix
8471       --  is not resolved, in which case the freezing must be done now.
8472
8473       Freeze_Expression (P);
8474
8475       --  Finally perform static evaluation on the attribute reference
8476
8477       Eval_Attribute (N);
8478    end Resolve_Attribute;
8479
8480    --------------------------------
8481    -- Stream_Attribute_Available --
8482    --------------------------------
8483
8484    function Stream_Attribute_Available
8485      (Typ          : Entity_Id;
8486       Nam          : TSS_Name_Type;
8487       Partial_View : Node_Id := Empty) return Boolean
8488    is
8489       Etyp : Entity_Id := Typ;
8490
8491    --  Start of processing for Stream_Attribute_Available
8492
8493    begin
8494       --  We need some comments in this body ???
8495
8496       if Has_Stream_Attribute_Definition (Typ, Nam) then
8497          return True;
8498       end if;
8499
8500       if Is_Class_Wide_Type (Typ) then
8501          return not Is_Limited_Type (Typ)
8502            or else Stream_Attribute_Available (Etype (Typ), Nam);
8503       end if;
8504
8505       if Nam = TSS_Stream_Input
8506         and then Is_Abstract_Type (Typ)
8507         and then not Is_Class_Wide_Type (Typ)
8508       then
8509          return False;
8510       end if;
8511
8512       if not (Is_Limited_Type (Typ)
8513         or else (Present (Partial_View)
8514                    and then Is_Limited_Type (Partial_View)))
8515       then
8516          return True;
8517       end if;
8518
8519       --  In Ada 2005, Input can invoke Read, and Output can invoke Write
8520
8521       if Nam = TSS_Stream_Input
8522         and then Ada_Version >= Ada_05
8523         and then Stream_Attribute_Available (Etyp, TSS_Stream_Read)
8524       then
8525          return True;
8526
8527       elsif Nam = TSS_Stream_Output
8528         and then Ada_Version >= Ada_05
8529         and then Stream_Attribute_Available (Etyp, TSS_Stream_Write)
8530       then
8531          return True;
8532       end if;
8533
8534       --  Case of Read and Write: check for attribute definition clause that
8535       --  applies to an ancestor type.
8536
8537       while Etype (Etyp) /= Etyp loop
8538          Etyp := Etype (Etyp);
8539
8540          if Has_Stream_Attribute_Definition (Etyp, Nam) then
8541             return True;
8542          end if;
8543       end loop;
8544
8545       if Ada_Version < Ada_05 then
8546
8547          --  In Ada 95 mode, also consider a non-visible definition
8548
8549          declare
8550             Btyp : constant Entity_Id := Implementation_Base_Type (Typ);
8551          begin
8552             return Btyp /= Typ
8553               and then Stream_Attribute_Available
8554                          (Btyp, Nam, Partial_View => Typ);
8555          end;
8556       end if;
8557
8558       return False;
8559    end Stream_Attribute_Available;
8560
8561 end Sem_Attr;