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) 1992-2010, 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 Gnatvsn;  use Gnatvsn;
  39 with Itypes;   use Itypes;
  40 with Lib;      use Lib;
  41 with Lib.Xref; use Lib.Xref;
  42 with Nlists;   use Nlists;
  43 with Nmake;    use Nmake;
  44 with Opt;      use Opt;
  45 with Restrict; use Restrict;
  46 with Rident;   use Rident;
  47 with Rtsfind;  use Rtsfind;
  48 with Sdefault; use Sdefault;
  49 with Sem;      use Sem;
  50 with Sem_Aux;  use Sem_Aux;
  51 with Sem_Cat;  use Sem_Cat;
  52 with Sem_Ch6;  use Sem_Ch6;
  53 with Sem_Ch8;  use Sem_Ch8;
  54 with Sem_Ch10; use Sem_Ch10;
  55 with Sem_Dist; use Sem_Dist;
  56 with Sem_Elim; use Sem_Elim;
  57 with Sem_Eval; use Sem_Eval;
  58 with Sem_Res;  use Sem_Res;
  59 with Sem_Type; use Sem_Type;
  60 with Sem_Util; use Sem_Util;
  61 with Stand;    use Stand;
  62 with Sinfo;    use Sinfo;
  63 with Sinput;   use Sinput;
  64 with Stringt;  use Stringt;
  65 with Style;
  66 with Stylesw;  use Stylesw;
  67 with Targparm; use Targparm;
  68 with Ttypes;   use Ttypes;
  69 with Tbuild;   use Tbuild;
  70 with Uintp;    use Uintp;
  71 with Urealp;   use Urealp;
  72
  73 package body Sem_Attr is
  74
  75    True_Value  : constant Uint := Uint_1;
  76    False_Value : constant Uint := Uint_0;
  77    --  Synonyms to be used when these constants are used as Boolean values
  78
  79    Bad_Attribute : exception;
  80    --  Exception raised if an error is detected during attribute processing,
  81    --  used so that we can abandon the processing so we don't run into
  82    --  trouble with cascaded errors.
  83
  84    --  The following array is the list of attributes defined in the Ada 83 RM
  85    --  that are not included in Ada 95, but still get recognized in GNAT.
  86
  87    Attribute_83 : constant Attribute_Class_Array := Attribute_Class_Array'(
  88       Attribute_Address           |
  89       Attribute_Aft               |
  90       Attribute_Alignment         |
  91       Attribute_Base              |
  92       Attribute_Callable          |
  93       Attribute_Constrained       |
  94       Attribute_Count             |
  95       Attribute_Delta             |
  96       Attribute_Digits            |
  97       Attribute_Emax              |
  98       Attribute_Epsilon           |
  99       Attribute_First             |
 100       Attribute_First_Bit         |
 101       Attribute_Fore              |
 102       Attribute_Image             |
 103       Attribute_Large             |
 104       Attribute_Last              |
 105       Attribute_Last_Bit          |
 106       Attribute_Leading_Part      |
 107       Attribute_Length            |
 108       Attribute_Machine_Emax      |
 109       Attribute_Machine_Emin      |
 110       Attribute_Machine_Mantissa  |
 111       Attribute_Machine_Overflows |
 112       Attribute_Machine_Radix     |
 113       Attribute_Machine_Rounds    |
 114       Attribute_Mantissa          |
 115       Attribute_Pos               |
 116       Attribute_Position          |
 117       Attribute_Pred              |
 118       Attribute_Range             |
 119       Attribute_Safe_Emax         |
 120       Attribute_Safe_Large        |
 121       Attribute_Safe_Small        |
 122       Attribute_Size              |
 123       Attribute_Small             |
 124       Attribute_Storage_Size      |
 125       Attribute_Succ              |
 126       Attribute_Terminated        |
 127       Attribute_Val               |
 128       Attribute_Value             |
 129       Attribute_Width             => True,
 130       others                      => False);
 131
 132    --  The following array is the list of attributes defined in the Ada 2005
 133    --  RM which are not defined in Ada 95. These are recognized in Ada 95 mode,
 134    --  but in Ada 95 they are considered to be implementation defined.
 135
 136    Attribute_05 : constant Attribute_Class_Array := Attribute_Class_Array'(
 137       Attribute_Machine_Rounding  |
 138       Attribute_Mod               |
 139       Attribute_Priority          |
 140       Attribute_Stream_Size       |
 141       Attribute_Wide_Wide_Width   => True,
 142       others                      => False);
 143
 144    --  The following array contains all attributes that imply a modification
 145    --  of their prefixes or result in an access value. Such prefixes can be
 146    --  considered as lvalues.
 147
 148    Attribute_Name_Implies_Lvalue_Prefix : constant Attribute_Class_Array :=
 149       Attribute_Class_Array'(
 150       Attribute_Access              |
 151       Attribute_Address             |
 152       Attribute_Input               |
 153       Attribute_Read                |
 154       Attribute_Unchecked_Access    |
 155       Attribute_Unrestricted_Access => True,
 156       others                        => False);
 157
 158    -----------------------
 159    -- Local_Subprograms --
 160    -----------------------
 161
 162    procedure Eval_Attribute (N : Node_Id);
 163    --  Performs compile time evaluation of attributes where possible, leaving
 164    --  the Is_Static_Expression/Raises_Constraint_Error flags appropriately
 165    --  set, and replacing the node with a literal node if the value can be
 166    --  computed at compile time. All static attribute references are folded,
 167    --  as well as a number of cases of non-static attributes that can always
 168    --  be computed at compile time (e.g. floating-point model attributes that
 169    --  are applied to non-static subtypes). Of course in such cases, the
 170    --  Is_Static_Expression flag will not be set on the resulting literal.
 171    --  Note that the only required action of this procedure is to catch the
 172    --  static expression cases as described in the RM. Folding of other cases
 173    --  is done where convenient, but some additional non-static folding is in
 174    --  N_Expand_Attribute_Reference in cases where this is more convenient.
 175
 176    function Is_Anonymous_Tagged_Base
 177      (Anon : Entity_Id;
 178       Typ  : Entity_Id)
 179       return Boolean;
 180    --  For derived tagged types that constrain parent discriminants we build
 181    --  an anonymous unconstrained base type. We need to recognize the relation
 182    --  between the two when analyzing an access attribute for a constrained
 183    --  component, before the full declaration for Typ has been analyzed, and
 184    --  where therefore the prefix of the attribute does not match the enclosing
 185    --  scope.
 186
 187    -----------------------
 188    -- Analyze_Attribute --
 189    -----------------------
 190
 191    procedure Analyze_Attribute (N : Node_Id) is
 192       Loc     : constant Source_Ptr   := Sloc (N);
 193       Aname   : constant Name_Id      := Attribute_Name (N);
 194       P       : constant Node_Id      := Prefix (N);
 195       Exprs   : constant List_Id      := Expressions (N);
 196       Attr_Id : constant Attribute_Id := Get_Attribute_Id (Aname);
 197       E1      : Node_Id;
 198       E2      : Node_Id;
 199
 200       P_Type : Entity_Id;
 201       --  Type of prefix after analysis
 202
 203       P_Base_Type : Entity_Id;
 204       --  Base type of prefix after analysis
 205
 206       -----------------------
 207       -- Local Subprograms --
 208       -----------------------
 209
 210       procedure Analyze_Access_Attribute;
 211       --  Used for Access, Unchecked_Access, Unrestricted_Access attributes.
 212       --  Internally, Id distinguishes which of the three cases is involved.
 213
 214       procedure Bad_Attribute_For_Predicate;
 215       --  Output error message for use of a predicate (First, Last, Range) not
 216       --  allowed with a type that has predicates. If the type is a generic
 217       --  actual, then the message is a warning, and we generate code to raise
 218       --  program error with an appropriate reason. No error message is given
 219       --  for internally generated uses of the attributes.
 220
 221       procedure Check_Array_Or_Scalar_Type;
 222       --  Common procedure used by First, Last, Range attribute to check
 223       --  that the prefix is a constrained array or scalar type, or a name
 224       --  of an array object, and that an argument appears only if appropriate
 225       --  (i.e. only in the array case).
 226
 227       procedure Check_Array_Type;
 228       --  Common semantic checks for all array attributes. Checks that the
 229       --  prefix is a constrained array type or the name of an array object.
 230       --  The error message for non-arrays is specialized appropriately.
 231
 232       procedure Check_Asm_Attribute;
 233       --  Common semantic checks for Asm_Input and Asm_Output attributes
 234
 235       procedure Check_Component;
 236       --  Common processing for Bit_Position, First_Bit, Last_Bit, and
 237       --  Position. Checks prefix is an appropriate selected component.
 238
 239       procedure Check_Decimal_Fixed_Point_Type;
 240       --  Check that prefix of attribute N is a decimal fixed-point type
 241
 242       procedure Check_Dereference;
 243       --  If the prefix of attribute is an object of an access type, then
 244       --  introduce an explicit dereference, and adjust P_Type accordingly.
 245
 246       procedure Check_Discrete_Type;
 247       --  Verify that prefix of attribute N is a discrete type
 248
 249       procedure Check_E0;
 250       --  Check that no attribute arguments are present
 251
 252       procedure Check_Either_E0_Or_E1;
 253       --  Check that there are zero or one attribute arguments present
 254
 255       procedure Check_E1;
 256       --  Check that exactly one attribute argument is present
 257
 258       procedure Check_E2;
 259       --  Check that two attribute arguments are present
 260
 261       procedure Check_Enum_Image;
 262       --  If the prefix type is an enumeration type, set all its literals
 263       --  as referenced, since the image function could possibly end up
 264       --  referencing any of the literals indirectly. Same for Enum_Val.
 265
 266       procedure Check_Fixed_Point_Type;
 267       --  Verify that prefix of attribute N is a fixed type
 268
 269       procedure Check_Fixed_Point_Type_0;
 270       --  Verify that prefix of attribute N is a fixed type and that
 271       --  no attribute expressions are present
 272
 273       procedure Check_Floating_Point_Type;
 274       --  Verify that prefix of attribute N is a float type
 275
 276       procedure Check_Floating_Point_Type_0;
 277       --  Verify that prefix of attribute N is a float type and that
 278       --  no attribute expressions are present
 279
 280       procedure Check_Floating_Point_Type_1;
 281       --  Verify that prefix of attribute N is a float type and that
 282       --  exactly one attribute expression is present
 283
 284       procedure Check_Floating_Point_Type_2;
 285       --  Verify that prefix of attribute N is a float type and that
 286       --  two attribute expressions are present
 287
 288       procedure Legal_Formal_Attribute;
 289       --  Common processing for attributes Definite and Has_Discriminants.
 290       --  Checks that prefix is generic indefinite formal type.
 291
 292       procedure Check_Integer_Type;
 293       --  Verify that prefix of attribute N is an integer type
 294
 295       procedure Check_Library_Unit;
 296       --  Verify that prefix of attribute N is a library unit
 297
 298       procedure Check_Modular_Integer_Type;
 299       --  Verify that prefix of attribute N is a modular integer type
 300
 301       procedure Check_Not_CPP_Type;
 302       --  Check that P (the prefix of the attribute) is not an CPP type
 303       --  for which no Ada predefined primitive is available.
 304
 305       procedure Check_Not_Incomplete_Type;
 306       --  Check that P (the prefix of the attribute) is not an incomplete
 307       --  type or a private type for which no full view has been given.
 308
 309       procedure Check_Object_Reference (P : Node_Id);
 310       --  Check that P (the prefix of the attribute) is an object reference
 311
 312       procedure Check_Program_Unit;
 313       --  Verify that prefix of attribute N is a program unit
 314
 315       procedure Check_Real_Type;
 316       --  Verify that prefix of attribute N is fixed or float type
 317
 318       procedure Check_Scalar_Type;
 319       --  Verify that prefix of attribute N is a scalar type
 320
 321       procedure Check_Standard_Prefix;
 322       --  Verify that prefix of attribute N is package Standard
 323
 324       procedure Check_Stream_Attribute (Nam : TSS_Name_Type);
 325       --  Validity checking for stream attribute. Nam is the TSS name of the
 326       --  corresponding possible defined attribute function (e.g. for the
 327       --  Read attribute, Nam will be TSS_Stream_Read).
 328
 329       procedure Check_PolyORB_Attribute;
 330       --  Validity checking for PolyORB/DSA attribute
 331
 332       procedure Check_Task_Prefix;
 333       --  Verify that prefix of attribute N is a task or task type
 334
 335       procedure Check_Type;
 336       --  Verify that the prefix of attribute N is a type
 337
 338       procedure Check_Unit_Name (Nod : Node_Id);
 339       --  Check that Nod is of the form of a library unit name, i.e that
 340       --  it is an identifier, or a selected component whose prefix is
 341       --  itself of the form of a library unit name. Note that this is
 342       --  quite different from Check_Program_Unit, since it only checks
 343       --  the syntactic form of the name, not the semantic identity. This
 344       --  is because it is used with attributes (Elab_Body, Elab_Spec, and
 345       --  UET_Address) which can refer to non-visible unit.
 346
 347       procedure Error_Attr (Msg : String; Error_Node : Node_Id);
 348       pragma No_Return (Error_Attr);
 349       procedure Error_Attr;
 350       pragma No_Return (Error_Attr);
 351       --  Posts error using Error_Msg_N at given node, sets type of attribute
 352       --  node to Any_Type, and then raises Bad_Attribute to avoid any further
 353       --  semantic processing. The message typically contains a % insertion
 354       --  character which is replaced by the attribute name. The call with
 355       --  no arguments is used when the caller has already generated the
 356       --  required error messages.
 357
 358       procedure Error_Attr_P (Msg : String);
 359       pragma No_Return (Error_Attr);
 360       --  Like Error_Attr, but error is posted at the start of the prefix
 361
 362       procedure Standard_Attribute (Val : Int);
 363       --  Used to process attributes whose prefix is package Standard which
 364       --  yield values of type Universal_Integer. The attribute reference
 365       --  node is rewritten with an integer literal of the given value.
 366
 367       procedure Unexpected_Argument (En : Node_Id);
 368       --  Signal unexpected attribute argument (En is the argument)
 369
 370       procedure Validate_Non_Static_Attribute_Function_Call;
 371       --  Called when processing an attribute that is a function call to a
 372       --  non-static function, i.e. an attribute function that either takes
 373       --  non-scalar arguments or returns a non-scalar result. Verifies that
 374       --  such a call does not appear in a preelaborable context.
 375
 376       ------------------------------
 377       -- Analyze_Access_Attribute --
 378       ------------------------------
 379
 380       procedure Analyze_Access_Attribute is
 381          Acc_Type : Entity_Id;
 382
 383          Scop : Entity_Id;
 384          Typ  : Entity_Id;
 385
 386          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id;
 387          --  Build an access-to-object type whose designated type is DT,
 388          --  and whose Ekind is appropriate to the attribute type. The
 389          --  type that is constructed is returned as the result.
 390
 391          procedure Build_Access_Subprogram_Type (P : Node_Id);
 392          --  Build an access to subprogram whose designated type is the type of
 393          --  the prefix. If prefix is overloaded, so is the node itself. The
 394          --  result is stored in Acc_Type.
 395
 396          function OK_Self_Reference return Boolean;
 397          --  An access reference whose prefix is a type can legally appear
 398          --  within an aggregate, where it is obtained by expansion of
 399          --  a defaulted aggregate. The enclosing aggregate that contains
 400          --  the self-referenced is flagged so that the self-reference can
 401          --  be expanded into a reference to the target object (see exp_aggr).
 402
 403          ------------------------------
 404          -- Build_Access_Object_Type --
 405          ------------------------------
 406
 407          function Build_Access_Object_Type (DT : Entity_Id) return Entity_Id is
 408             Typ : constant Entity_Id :=
 409                     New_Internal_Entity
 410                       (E_Access_Attribute_Type, Current_Scope, Loc, 'A');
 411          begin
 412             Set_Etype                     (Typ, Typ);
 413             Set_Is_Itype                  (Typ);
 414             Set_Associated_Node_For_Itype (Typ, N);
 415             Set_Directly_Designated_Type  (Typ, DT);
 416             return Typ;
 417          end Build_Access_Object_Type;
 418
 419          ----------------------------------
 420          -- Build_Access_Subprogram_Type --
 421          ----------------------------------
 422
 423          procedure Build_Access_Subprogram_Type (P : Node_Id) is
 424             Index : Interp_Index;
 425             It    : Interp;
 426
 427             procedure Check_Local_Access (E : Entity_Id);
 428             --  Deal with possible access to local subprogram. If we have such
 429             --  an access, we set a flag to kill all tracked values on any call
 430             --  because this access value may be passed around, and any called
 431             --  code might use it to access a local procedure which clobbers a
 432             --  tracked value. If the scope is a loop or block, indicate that
 433             --  value tracking is disabled for the enclosing subprogram.
 434
 435             function Get_Kind (E : Entity_Id) return Entity_Kind;
 436             --  Distinguish between access to regular/protected subprograms
 437
 438             ------------------------
 439             -- Check_Local_Access --
 440             ------------------------
 441
 442             procedure Check_Local_Access (E : Entity_Id) is
 443             begin
 444                if not Is_Library_Level_Entity (E) then
 445                   Set_Suppress_Value_Tracking_On_Call (Current_Scope);
 446                   Set_Suppress_Value_Tracking_On_Call
 447                     (Nearest_Dynamic_Scope (Current_Scope));
 448                end if;
 449             end Check_Local_Access;
 450
 451             --------------
 452             -- Get_Kind --
 453             --------------
 454
 455             function Get_Kind (E : Entity_Id) return Entity_Kind is
 456             begin
 457                if Convention (E) = Convention_Protected then
 458                   return E_Access_Protected_Subprogram_Type;
 459                else
 460                   return E_Access_Subprogram_Type;
 461                end if;
 462             end Get_Kind;
 463
 464          --  Start of processing for Build_Access_Subprogram_Type
 465
 466          begin
 467             --  In the case of an access to subprogram, use the name of the
 468             --  subprogram itself as the designated type. Type-checking in
 469             --  this case compares the signatures of the designated types.
 470
 471             --  Note: This fragment of the tree is temporarily malformed
 472             --  because the correct tree requires an E_Subprogram_Type entity
 473             --  as the designated type. In most cases this designated type is
 474             --  later overridden by the semantics with the type imposed by the
 475             --  context during the resolution phase. In the specific case of
 476             --  the expression Address!(Prim'Unrestricted_Access), used to
 477             --  initialize slots of dispatch tables, this work will be done by
 478             --  the expander (see Exp_Aggr).
 479
 480             --  The reason to temporarily add this kind of node to the tree
 481             --  instead of a proper E_Subprogram_Type itype, is the following:
 482             --  in case of errors found in the source file we report better
 483             --  error messages. For example, instead of generating the
 484             --  following error:
 485
 486             --      "expected access to subprogram with profile
 487             --       defined at line X"
 488
 489             --  we currently generate:
 490
 491             --      "expected access to function Z defined at line X"
 492
 493             Set_Etype (N, Any_Type);
 494
 495             if not Is_Overloaded (P) then
 496                Check_Local_Access (Entity (P));
 497
 498                if not Is_Intrinsic_Subprogram (Entity (P)) then
 499                   Acc_Type := Create_Itype (Get_Kind (Entity (P)), N);
 500                   Set_Is_Public (Acc_Type, False);
 501                   Set_Etype (Acc_Type, Acc_Type);
 502                   Set_Convention (Acc_Type, Convention (Entity (P)));
 503                   Set_Directly_Designated_Type (Acc_Type, Entity (P));
 504                   Set_Etype (N, Acc_Type);
 505                   Freeze_Before (N, Acc_Type);
 506                end if;
 507
 508             else
 509                Get_First_Interp (P, Index, It);
 510                while Present (It.Nam) loop
 511                   Check_Local_Access (It.Nam);
 512
 513                   if not Is_Intrinsic_Subprogram (It.Nam) then
 514                      Acc_Type := Create_Itype (Get_Kind (It.Nam), N);
 515                      Set_Is_Public (Acc_Type, False);
 516                      Set_Etype (Acc_Type, Acc_Type);
 517                      Set_Convention (Acc_Type, Convention (It.Nam));
 518                      Set_Directly_Designated_Type (Acc_Type, It.Nam);
 519                      Add_One_Interp (N, Acc_Type, Acc_Type);
 520                      Freeze_Before (N, Acc_Type);
 521                   end if;
 522
 523                   Get_Next_Interp (Index, It);
 524                end loop;
 525             end if;
 526
 527             --  Cannot be applied to intrinsic. Looking at the tests above,
 528             --  the only way Etype (N) can still be set to Any_Type is if
 529             --  Is_Intrinsic_Subprogram was True for some referenced entity.
 530
 531             if Etype (N) = Any_Type then
 532                Error_Attr_P ("prefix of % attribute cannot be intrinsic");
 533             end if;
 534          end Build_Access_Subprogram_Type;
 535
 536          ----------------------
 537          -- OK_Self_Reference --
 538          ----------------------
 539
 540          function OK_Self_Reference return Boolean is
 541             Par : Node_Id;
 542
 543          begin
 544             Par := Parent (N);
 545             while Present (Par)
 546               and then
 547                (Nkind (Par) = N_Component_Association
 548                  or else Nkind (Par) in N_Subexpr)
 549             loop
 550                if Nkind_In (Par, N_Aggregate, N_Extension_Aggregate) then
 551                   if Etype (Par) = Typ then
 552                      Set_Has_Self_Reference (Par);
 553                      return True;
 554                   end if;
 555                end if;
 556
 557                Par := Parent (Par);
 558             end loop;
 559
 560             --  No enclosing aggregate, or not a self-reference
 561
 562             return False;
 563          end OK_Self_Reference;
 564
 565       --  Start of processing for Analyze_Access_Attribute
 566
 567       begin
 568          Check_E0;
 569
 570          if Nkind (P) = N_Character_Literal then
 571             Error_Attr_P
 572               ("prefix of % attribute cannot be enumeration literal");
 573          end if;
 574
 575          --  Case of access to subprogram
 576
 577          if Is_Entity_Name (P)
 578            and then Is_Overloadable (Entity (P))
 579          then
 580             if Has_Pragma_Inline_Always (Entity (P)) then
 581                Error_Attr_P
 582                  ("prefix of % attribute cannot be Inline_Always subprogram");
 583             end if;
 584
 585             if Aname = Name_Unchecked_Access then
 586                Error_Attr ("attribute% cannot be applied to a subprogram", P);
 587             end if;
 588
 589             --  Issue an error if the prefix denotes an eliminated subprogram
 590
 591             Check_For_Eliminated_Subprogram (P, Entity (P));
 592
 593             --  Check for obsolescent subprogram reference
 594
 595             Check_Obsolescent_2005_Entity (Entity (P), P);
 596
 597             --  Build the appropriate subprogram type
 598
 599             Build_Access_Subprogram_Type (P);
 600
 601             --  For unrestricted access, kill current values, since this
 602             --  attribute allows a reference to a local subprogram that
 603             --  could modify local variables to be passed out of scope
 604
 605             if Aname = Name_Unrestricted_Access then
 606
 607                --  Do not kill values on nodes initializing dispatch tables
 608                --  slots. The construct Prim_Ptr!(Prim'Unrestricted_Access)
 609                --  is currently generated by the expander only for this
 610                --  purpose. Done to keep the quality of warnings currently
 611                --  generated by the compiler (otherwise any declaration of
 612                --  a tagged type cleans constant indications from its scope).
 613
 614                if Nkind (Parent (N)) = N_Unchecked_Type_Conversion
 615                  and then (Etype (Parent (N)) = RTE (RE_Prim_Ptr)
 616                              or else
 617                            Etype (Parent (N)) = RTE (RE_Size_Ptr))
 618                  and then Is_Dispatching_Operation
 619                             (Directly_Designated_Type (Etype (N)))
 620                then
 621                   null;
 622                else
 623                   Kill_Current_Values;
 624                end if;
 625             end if;
 626
 627             return;
 628
 629          --  Component is an operation of a protected type
 630
 631          elsif Nkind (P) = N_Selected_Component
 632            and then Is_Overloadable (Entity (Selector_Name (P)))
 633          then
 634             if Ekind (Entity (Selector_Name (P))) = E_Entry then
 635                Error_Attr_P ("prefix of % attribute must be subprogram");
 636             end if;
 637
 638             Build_Access_Subprogram_Type (Selector_Name (P));
 639             return;
 640          end if;
 641
 642          --  Deal with incorrect reference to a type, but note that some
 643          --  accesses are allowed: references to the current type instance,
 644          --  or in Ada 2005 self-referential pointer in a default-initialized
 645          --  aggregate.
 646
 647          if Is_Entity_Name (P) then
 648             Typ := Entity (P);
 649
 650             --  The reference may appear in an aggregate that has been expanded
 651             --  into a loop. Locate scope of type definition, if any.
 652
 653             Scop := Current_Scope;
 654             while Ekind (Scop) = E_Loop loop
 655                Scop := Scope (Scop);
 656             end loop;
 657
 658             if Is_Type (Typ) then
 659
 660                --  OK if we are within the scope of a limited type
 661                --  let's mark the component as having per object constraint
 662
 663                if Is_Anonymous_Tagged_Base (Scop, Typ) then
 664                   Typ := Scop;
 665                   Set_Entity (P, Typ);
 666                   Set_Etype  (P, Typ);
 667                end if;
 668
 669                if Typ = Scop then
 670                   declare
 671                      Q : Node_Id := Parent (N);
 672
 673                   begin
 674                      while Present (Q)
 675                        and then Nkind (Q) /= N_Component_Declaration
 676                      loop
 677                         Q := Parent (Q);
 678                      end loop;
 679
 680                      if Present (Q) then
 681                         Set_Has_Per_Object_Constraint
 682                           (Defining_Identifier (Q), True);
 683                      end if;
 684                   end;
 685
 686                   if Nkind (P) = N_Expanded_Name then
 687                      Error_Msg_F
 688                        ("current instance prefix must be a direct name", P);
 689                   end if;
 690
 691                   --  If a current instance attribute appears in a component
 692                   --  constraint it must appear alone; other contexts (spec-
 693                   --  expressions, within a task body) are not subject to this
 694                   --  restriction.
 695
 696                   if not In_Spec_Expression
 697                     and then not Has_Completion (Scop)
 698                     and then not
 699                       Nkind_In (Parent (N), N_Discriminant_Association,
 700                                             N_Index_Or_Discriminant_Constraint)
 701                   then
 702                      Error_Msg_N
 703                        ("current instance attribute must appear alone", N);
 704                   end if;
 705
 706                   if Is_CPP_Class (Root_Type (Typ)) then
 707                      Error_Msg_N
 708                        ("?current instance unsupported for derivations of "
 709                         & "'C'P'P types", N);
 710                   end if;
 711
 712                --  OK if we are in initialization procedure for the type
 713                --  in question, in which case the reference to the type
 714                --  is rewritten as a reference to the current object.
 715
 716                elsif Ekind (Scop) = E_Procedure
 717                  and then Is_Init_Proc (Scop)
 718                  and then Etype (First_Formal (Scop)) = Typ
 719                then
 720                   Rewrite (N,
 721                     Make_Attribute_Reference (Loc,
 722                       Prefix         => Make_Identifier (Loc, Name_uInit),
 723                       Attribute_Name => Name_Unrestricted_Access));
 724                   Analyze (N);
 725                   return;
 726
 727                --  OK if a task type, this test needs sharpening up ???
 728
 729                elsif Is_Task_Type (Typ) then
 730                   null;
 731
 732                --  OK if self-reference in an aggregate in Ada 2005, and
 733                --  the reference comes from a copied default expression.
 734
 735                --  Note that we check legality of self-reference even if the
 736                --  expression comes from source, e.g. when a single component
 737                --  association in an aggregate has a box association.
 738
 739                elsif Ada_Version >= Ada_2005
 740                  and then OK_Self_Reference
 741                then
 742                   null;
 743
 744                --  OK if reference to current instance of a protected object
 745
 746                elsif Is_Protected_Self_Reference (P) then
 747                   null;
 748
 749                --  Otherwise we have an error case
 750
 751                else
 752                   Error_Attr ("% attribute cannot be applied to type", P);
 753                   return;
 754                end if;
 755             end if;
 756          end if;
 757
 758          --  If we fall through, we have a normal access to object case.
 759          --  Unrestricted_Access is legal wherever an allocator would be
 760          --  legal, so its Etype is set to E_Allocator. The expected type
 761          --  of the other attributes is a general access type, and therefore
 762          --  we label them with E_Access_Attribute_Type.
 763
 764          if not Is_Overloaded (P) then
 765             Acc_Type := Build_Access_Object_Type (P_Type);
 766             Set_Etype (N, Acc_Type);
 767          else
 768             declare
 769                Index : Interp_Index;
 770                It    : Interp;
 771             begin
 772                Set_Etype (N, Any_Type);
 773                Get_First_Interp (P, Index, It);
 774                while Present (It.Typ) loop
 775                   Acc_Type := Build_Access_Object_Type (It.Typ);
 776                   Add_One_Interp (N, Acc_Type, Acc_Type);
 777                   Get_Next_Interp (Index, It);
 778                end loop;
 779             end;
 780          end if;
 781
 782          --  Special cases when we can find a prefix that is an entity name
 783
 784          declare
 785             PP  : Node_Id;
 786             Ent : Entity_Id;
 787
 788          begin
 789             PP := P;
 790             loop
 791                if Is_Entity_Name (PP) then
 792                   Ent := Entity (PP);
 793
 794                   --  If we have an access to an object, and the attribute
 795                   --  comes from source, then set the object as potentially
 796                   --  source modified. We do this because the resulting access
 797                   --  pointer can be used to modify the variable, and we might
 798                   --  not detect this, leading to some junk warnings.
 799
 800                   Set_Never_Set_In_Source (Ent, False);
 801
 802                   --  Mark entity as address taken, and kill current values
 803
 804                   Set_Address_Taken (Ent);
 805                   Kill_Current_Values (Ent);
 806                   exit;
 807
 808                elsif Nkind_In (PP, N_Selected_Component,
 809                                    N_Indexed_Component)
 810                then
 811                   PP := Prefix (PP);
 812
 813                else
 814                   exit;
 815                end if;
 816             end loop;
 817          end;
 818
 819          --  Check for aliased view unless unrestricted case. We allow a
 820          --  nonaliased prefix when within an instance because the prefix may
 821          --  have been a tagged formal object, which is defined to be aliased
 822          --  even when the actual might not be (other instance cases will have
 823          --  been caught in the generic). Similarly, within an inlined body we
 824          --  know that the attribute is legal in the original subprogram, and
 825          --  therefore legal in the expansion.
 826
 827          if Aname /= Name_Unrestricted_Access
 828            and then not Is_Aliased_View (P)
 829            and then not In_Instance
 830            and then not In_Inlined_Body
 831          then
 832             Error_Attr_P ("prefix of % attribute must be aliased");
 833          end if;
 834       end Analyze_Access_Attribute;
 835
 836       ---------------------------------
 837       -- Bad_Attribute_For_Predicate --
 838       ---------------------------------
 839
 840       procedure Bad_Attribute_For_Predicate is
 841       begin
 842          if Comes_From_Source (N) then
 843             Error_Msg_Name_1 := Aname;
 844             Bad_Predicated_Subtype_Use
 845               ("type& has predicates, attribute % not allowed", N, P_Type);
 846          end if;
 847       end Bad_Attribute_For_Predicate;
 848
 849       --------------------------------
 850       -- Check_Array_Or_Scalar_Type --
 851       --------------------------------
 852
 853       procedure Check_Array_Or_Scalar_Type is
 854          Index : Entity_Id;
 855
 856          D : Int;
 857          --  Dimension number for array attributes
 858
 859       begin
 860          --  Case of string literal or string literal subtype. These cases
 861          --  cannot arise from legal Ada code, but the expander is allowed
 862          --  to generate them. They require special handling because string
 863          --  literal subtypes do not have standard bounds (the whole idea
 864          --  of these subtypes is to avoid having to generate the bounds)
 865
 866          if Ekind (P_Type) = E_String_Literal_Subtype then
 867             Set_Etype (N, Etype (First_Index (P_Base_Type)));
 868             return;
 869
 870          --  Scalar types
 871
 872          elsif Is_Scalar_Type (P_Type) then
 873             Check_Type;
 874
 875             if Present (E1) then
 876                Error_Attr ("invalid argument in % attribute", E1);
 877             else
 878                Set_Etype (N, P_Base_Type);
 879                return;
 880             end if;
 881
 882          --  The following is a special test to allow 'First to apply to
 883          --  private scalar types if the attribute comes from generated
 884          --  code. This occurs in the case of Normalize_Scalars code.
 885
 886          elsif Is_Private_Type (P_Type)
 887            and then Present (Full_View (P_Type))
 888            and then Is_Scalar_Type (Full_View (P_Type))
 889            and then not Comes_From_Source (N)
 890          then
 891             Set_Etype (N, Implementation_Base_Type (P_Type));
 892
 893          --  Array types other than string literal subtypes handled above
 894
 895          else
 896             Check_Array_Type;
 897
 898             --  We know prefix is an array type, or the name of an array
 899             --  object, and that the expression, if present, is static
 900             --  and within the range of the dimensions of the type.
 901
 902             pragma Assert (Is_Array_Type (P_Type));
 903             Index := First_Index (P_Base_Type);
 904
 905             if No (E1) then
 906
 907                --  First dimension assumed
 908
 909                Set_Etype (N, Base_Type (Etype (Index)));
 910
 911             else
 912                D := UI_To_Int (Intval (E1));
 913
 914                for J in 1 .. D - 1 loop
 915                   Next_Index (Index);
 916                end loop;
 917
 918                Set_Etype (N, Base_Type (Etype (Index)));
 919                Set_Etype (E1, Standard_Integer);
 920             end if;
 921          end if;
 922       end Check_Array_Or_Scalar_Type;
 923
 924       ----------------------
 925       -- Check_Array_Type --
 926       ----------------------
 927
 928       procedure Check_Array_Type is
 929          D : Int;
 930          --  Dimension number for array attributes
 931
 932       begin
 933          --  If the type is a string literal type, then this must be generated
 934          --  internally, and no further check is required on its legality.
 935
 936          if Ekind (P_Type) = E_String_Literal_Subtype then
 937             return;
 938
 939          --  If the type is a composite, it is an illegal aggregate, no point
 940          --  in going on.
 941
 942          elsif P_Type = Any_Composite then
 943             raise Bad_Attribute;
 944          end if;
 945
 946          --  Normal case of array type or subtype
 947
 948          Check_Either_E0_Or_E1;
 949          Check_Dereference;
 950
 951          if Is_Array_Type (P_Type) then
 952             if not Is_Constrained (P_Type)
 953               and then Is_Entity_Name (P)
 954               and then Is_Type (Entity (P))
 955             then
 956                --  Note: we do not call Error_Attr here, since we prefer to
 957                --  continue, using the relevant index type of the array,
 958                --  even though it is unconstrained. This gives better error
 959                --  recovery behavior.
 960
 961                Error_Msg_Name_1 := Aname;
 962                Error_Msg_F
 963                  ("prefix for % attribute must be constrained array", P);
 964             end if;
 965
 966             D := Number_Dimensions (P_Type);
 967
 968          else
 969             if Is_Private_Type (P_Type) then
 970                Error_Attr_P ("prefix for % attribute may not be private type");
 971
 972             elsif Is_Access_Type (P_Type)
 973               and then Is_Array_Type (Designated_Type (P_Type))
 974               and then Is_Entity_Name (P)
 975               and then Is_Type (Entity (P))
 976             then
 977                Error_Attr_P ("prefix of % attribute cannot be access type");
 978
 979             elsif Attr_Id = Attribute_First
 980                     or else
 981                   Attr_Id = Attribute_Last
 982             then
 983                Error_Attr ("invalid prefix for % attribute", P);
 984
 985             else
 986                Error_Attr_P ("prefix for % attribute must be array");
 987             end if;
 988          end if;
 989
 990          if Present (E1) then
 991             Resolve (E1, Any_Integer);
 992             Set_Etype (E1, Standard_Integer);
 993
 994             if not Is_Static_Expression (E1)
 995               or else Raises_Constraint_Error (E1)
 996             then
 997                Flag_Non_Static_Expr
 998                  ("expression for dimension must be static!", E1);
 999                Error_Attr;
1000
1001             elsif  UI_To_Int (Expr_Value (E1)) > D
1002               or else UI_To_Int (Expr_Value (E1)) < 1
1003             then
1004                Error_Attr ("invalid dimension number for array type", E1);
1005             end if;
1006          end if;
1007
1008          if (Style_Check and Style_Check_Array_Attribute_Index)
1009            and then Comes_From_Source (N)
1010          then
1011             Style.Check_Array_Attribute_Index (N, E1, D);
1012          end if;
1013       end Check_Array_Type;
1014
1015       -------------------------
1016       -- Check_Asm_Attribute --
1017       -------------------------
1018
1019       procedure Check_Asm_Attribute is
1020       begin
1021          Check_Type;
1022          Check_E2;
1023
1024          --  Check first argument is static string expression
1025
1026          Analyze_And_Resolve (E1, Standard_String);
1027
1028          if Etype (E1) = Any_Type then
1029             return;
1030
1031          elsif not Is_OK_Static_Expression (E1) then
1032             Flag_Non_Static_Expr
1033               ("constraint argument must be static string expression!", E1);
1034             Error_Attr;
1035          end if;
1036
1037          --  Check second argument is right type
1038
1039          Analyze_And_Resolve (E2, Entity (P));
1040
1041          --  Note: that is all we need to do, we don't need to check
1042          --  that it appears in a correct context. The Ada type system
1043          --  will do that for us.
1044
1045       end Check_Asm_Attribute;
1046
1047       ---------------------
1048       -- Check_Component --
1049       ---------------------
1050
1051       procedure Check_Component is
1052       begin
1053          Check_E0;
1054
1055          if Nkind (P) /= N_Selected_Component
1056            or else
1057              (Ekind (Entity (Selector_Name (P))) /= E_Component
1058                and then
1059               Ekind (Entity (Selector_Name (P))) /= E_Discriminant)
1060          then
1061             Error_Attr_P ("prefix for % attribute must be selected component");
1062          end if;
1063       end Check_Component;
1064
1065       ------------------------------------
1066       -- Check_Decimal_Fixed_Point_Type --
1067       ------------------------------------
1068
1069       procedure Check_Decimal_Fixed_Point_Type is
1070       begin
1071          Check_Type;
1072
1073          if not Is_Decimal_Fixed_Point_Type (P_Type) then
1074             Error_Attr_P ("prefix of % attribute must be decimal type");
1075          end if;
1076       end Check_Decimal_Fixed_Point_Type;
1077
1078       -----------------------
1079       -- Check_Dereference --
1080       -----------------------
1081
1082       procedure Check_Dereference is
1083       begin
1084
1085          --  Case of a subtype mark
1086
1087          if Is_Entity_Name (P)
1088            and then Is_Type (Entity (P))
1089          then
1090             return;
1091          end if;
1092
1093          --  Case of an expression
1094
1095          Resolve (P);
1096
1097          if Is_Access_Type (P_Type) then
1098
1099             --  If there is an implicit dereference, then we must freeze
1100             --  the designated type of the access type, since the type of
1101             --  the referenced array is this type (see AI95-00106).
1102
1103             --  As done elsewhere, freezing must not happen when pre-analyzing
1104             --  a pre- or postcondition or a default value for an object or
1105             --  for a formal parameter.
1106
1107             if not In_Spec_Expression then
1108                Freeze_Before (N, Designated_Type (P_Type));
1109             end if;
1110
1111             Rewrite (P,
1112               Make_Explicit_Dereference (Sloc (P),
1113                 Prefix => Relocate_Node (P)));
1114
1115             Analyze_And_Resolve (P);
1116             P_Type := Etype (P);
1117
1118             if P_Type = Any_Type then
1119                raise Bad_Attribute;
1120             end if;
1121
1122             P_Base_Type := Base_Type (P_Type);
1123          end if;
1124       end Check_Dereference;
1125
1126       -------------------------
1127       -- Check_Discrete_Type --
1128       -------------------------
1129
1130       procedure Check_Discrete_Type is
1131       begin
1132          Check_Type;
1133
1134          if not Is_Discrete_Type (P_Type) then
1135             Error_Attr_P ("prefix of % attribute must be discrete type");
1136          end if;
1137       end Check_Discrete_Type;
1138
1139       --------------
1140       -- Check_E0 --
1141       --------------
1142
1143       procedure Check_E0 is
1144       begin
1145          if Present (E1) then
1146             Unexpected_Argument (E1);
1147          end if;
1148       end Check_E0;
1149
1150       --------------
1151       -- Check_E1 --
1152       --------------
1153
1154       procedure Check_E1 is
1155       begin
1156          Check_Either_E0_Or_E1;
1157
1158          if No (E1) then
1159
1160             --  Special-case attributes that are functions and that appear as
1161             --  the prefix of another attribute. Error is posted on parent.
1162
1163             if Nkind (Parent (N)) = N_Attribute_Reference
1164               and then (Attribute_Name (Parent (N)) = Name_Address
1165                           or else
1166                         Attribute_Name (Parent (N)) = Name_Code_Address
1167                           or else
1168                         Attribute_Name (Parent (N)) = Name_Access)
1169             then
1170                Error_Msg_Name_1 := Attribute_Name (Parent (N));
1171                Error_Msg_N ("illegal prefix for % attribute", Parent (N));
1172                Set_Etype (Parent (N), Any_Type);
1173                Set_Entity (Parent (N), Any_Type);
1174                raise Bad_Attribute;
1175
1176             else
1177                Error_Attr ("missing argument for % attribute", N);
1178             end if;
1179          end if;
1180       end Check_E1;
1181
1182       --------------
1183       -- Check_E2 --
1184       --------------
1185
1186       procedure Check_E2 is
1187       begin
1188          if No (E1) then
1189             Error_Attr ("missing arguments for % attribute (2 required)", N);
1190          elsif No (E2) then
1191             Error_Attr ("missing argument for % attribute (2 required)", N);
1192          end if;
1193       end Check_E2;
1194
1195       ---------------------------
1196       -- Check_Either_E0_Or_E1 --
1197       ---------------------------
1198
1199       procedure Check_Either_E0_Or_E1 is
1200       begin
1201          if Present (E2) then
1202             Unexpected_Argument (E2);
1203          end if;
1204       end Check_Either_E0_Or_E1;
1205
1206       ----------------------
1207       -- Check_Enum_Image --
1208       ----------------------
1209
1210       procedure Check_Enum_Image is
1211          Lit : Entity_Id;
1212       begin
1213          if Is_Enumeration_Type (P_Base_Type) then
1214             Lit := First_Literal (P_Base_Type);
1215             while Present (Lit) loop
1216                Set_Referenced (Lit);
1217                Next_Literal (Lit);
1218             end loop;
1219          end if;
1220       end Check_Enum_Image;
1221
1222       ----------------------------
1223       -- Check_Fixed_Point_Type --
1224       ----------------------------
1225
1226       procedure Check_Fixed_Point_Type is
1227       begin
1228          Check_Type;
1229
1230          if not Is_Fixed_Point_Type (P_Type) then
1231             Error_Attr_P ("prefix of % attribute must be fixed point type");
1232          end if;
1233       end Check_Fixed_Point_Type;
1234
1235       ------------------------------
1236       -- Check_Fixed_Point_Type_0 --
1237       ------------------------------
1238
1239       procedure Check_Fixed_Point_Type_0 is
1240       begin
1241          Check_Fixed_Point_Type;
1242          Check_E0;
1243       end Check_Fixed_Point_Type_0;
1244
1245       -------------------------------
1246       -- Check_Floating_Point_Type --
1247       -------------------------------
1248
1249       procedure Check_Floating_Point_Type is
1250       begin
1251          Check_Type;
1252
1253          if not Is_Floating_Point_Type (P_Type) then
1254             Error_Attr_P ("prefix of % attribute must be float type");
1255          end if;
1256       end Check_Floating_Point_Type;
1257
1258       ---------------------------------
1259       -- Check_Floating_Point_Type_0 --
1260       ---------------------------------
1261
1262       procedure Check_Floating_Point_Type_0 is
1263       begin
1264          Check_Floating_Point_Type;
1265          Check_E0;
1266       end Check_Floating_Point_Type_0;
1267
1268       ---------------------------------
1269       -- Check_Floating_Point_Type_1 --
1270       ---------------------------------
1271
1272       procedure Check_Floating_Point_Type_1 is
1273       begin
1274          Check_Floating_Point_Type;
1275          Check_E1;
1276       end Check_Floating_Point_Type_1;
1277
1278       ---------------------------------
1279       -- Check_Floating_Point_Type_2 --
1280       ---------------------------------
1281
1282       procedure Check_Floating_Point_Type_2 is
1283       begin
1284          Check_Floating_Point_Type;
1285          Check_E2;
1286       end Check_Floating_Point_Type_2;
1287
1288       ------------------------
1289       -- Check_Integer_Type --
1290       ------------------------
1291
1292       procedure Check_Integer_Type is
1293       begin
1294          Check_Type;
1295
1296          if not Is_Integer_Type (P_Type) then
1297             Error_Attr_P ("prefix of % attribute must be integer type");
1298          end if;
1299       end Check_Integer_Type;
1300
1301       ------------------------
1302       -- Check_Library_Unit --
1303       ------------------------
1304
1305       procedure Check_Library_Unit is
1306       begin
1307          if not Is_Compilation_Unit (Entity (P)) then
1308             Error_Attr_P ("prefix of % attribute must be library unit");
1309          end if;
1310       end Check_Library_Unit;
1311
1312       --------------------------------
1313       -- Check_Modular_Integer_Type --
1314       --------------------------------
1315
1316       procedure Check_Modular_Integer_Type is
1317       begin
1318          Check_Type;
1319
1320          if not Is_Modular_Integer_Type (P_Type) then
1321             Error_Attr_P
1322               ("prefix of % attribute must be modular integer type");
1323          end if;
1324       end Check_Modular_Integer_Type;
1325
1326       ------------------------
1327       -- Check_Not_CPP_Type --
1328       ------------------------
1329
1330       procedure Check_Not_CPP_Type is
1331       begin
1332          if Is_Tagged_Type (Etype (P))
1333            and then Convention (Etype (P)) = Convention_CPP
1334            and then Is_CPP_Class (Root_Type (Etype (P)))
1335          then
1336             Error_Attr_P
1337               ("invalid use of % attribute with 'C'P'P tagged type");
1338          end if;
1339       end Check_Not_CPP_Type;
1340
1341       -------------------------------
1342       -- Check_Not_Incomplete_Type --
1343       -------------------------------
1344
1345       procedure Check_Not_Incomplete_Type is
1346          E   : Entity_Id;
1347          Typ : Entity_Id;
1348
1349       begin
1350          --  Ada 2005 (AI-50217, AI-326): If the prefix is an explicit
1351          --  dereference we have to check wrong uses of incomplete types
1352          --  (other wrong uses are checked at their freezing point).
1353
1354          --  Example 1: Limited-with
1355
1356          --    limited with Pkg;
1357          --    package P is
1358          --       type Acc is access Pkg.T;
1359          --       X : Acc;
1360          --       S : Integer := X.all'Size;                    -- ERROR
1361          --    end P;
1362
1363          --  Example 2: Tagged incomplete
1364
1365          --     type T is tagged;
1366          --     type Acc is access all T;
1367          --     X : Acc;
1368          --     S : constant Integer := X.all'Size;             -- ERROR
1369          --     procedure Q (Obj : Integer := X.all'Alignment); -- ERROR
1370
1371          if Ada_Version >= Ada_2005
1372            and then Nkind (P) = N_Explicit_Dereference
1373          then
1374             E := P;
1375             while Nkind (E) = N_Explicit_Dereference loop
1376                E := Prefix (E);
1377             end loop;
1378
1379             Typ := Etype (E);
1380
1381             if From_With_Type (Typ) then
1382                Error_Attr_P
1383                  ("prefix of % attribute cannot be an incomplete type");
1384
1385             else
1386                if Is_Access_Type (Typ) then
1387                   Typ := Directly_Designated_Type (Typ);
1388                end if;
1389
1390                if Is_Class_Wide_Type (Typ) then
1391                   Typ := Root_Type (Typ);
1392                end if;
1393
1394                --  A legal use of a shadow entity occurs only when the unit
1395                --  where the non-limited view resides is imported via a regular
1396                --  with clause in the current body. Such references to shadow
1397                --  entities may occur in subprogram formals.
1398
1399                if Is_Incomplete_Type (Typ)
1400                  and then From_With_Type (Typ)
1401                  and then Present (Non_Limited_View (Typ))
1402                  and then Is_Legal_Shadow_Entity_In_Body (Typ)
1403                then
1404                   Typ := Non_Limited_View (Typ);
1405                end if;
1406
1407                if Ekind (Typ) = E_Incomplete_Type
1408                  and then No (Full_View (Typ))
1409                then
1410                   Error_Attr_P
1411                     ("prefix of % attribute cannot be an incomplete type");
1412                end if;
1413             end if;
1414          end if;
1415
1416          if not Is_Entity_Name (P)
1417            or else not Is_Type (Entity (P))
1418            or else In_Spec_Expression
1419          then
1420             return;
1421          else
1422             Check_Fully_Declared (P_Type, P);
1423          end if;
1424       end Check_Not_Incomplete_Type;
1425
1426       ----------------------------
1427       -- Check_Object_Reference --
1428       ----------------------------
1429
1430       procedure Check_Object_Reference (P : Node_Id) is
1431          Rtyp : Entity_Id;
1432
1433       begin
1434          --  If we need an object, and we have a prefix that is the name of
1435          --  a function entity, convert it into a function call.
1436
1437          if Is_Entity_Name (P)
1438            and then Ekind (Entity (P)) = E_Function
1439          then
1440             Rtyp := Etype (Entity (P));
1441
1442             Rewrite (P,
1443               Make_Function_Call (Sloc (P),
1444                 Name => Relocate_Node (P)));
1445
1446             Analyze_And_Resolve (P, Rtyp);
1447
1448          --  Otherwise we must have an object reference
1449
1450          elsif not Is_Object_Reference (P) then
1451             Error_Attr_P ("prefix of % attribute must be object");
1452          end if;
1453       end Check_Object_Reference;
1454
1455       ----------------------------
1456       -- Check_PolyORB_Attribute --
1457       ----------------------------
1458
1459       procedure Check_PolyORB_Attribute is
1460       begin
1461          Validate_Non_Static_Attribute_Function_Call;
1462
1463          Check_Type;
1464          Check_Not_CPP_Type;
1465
1466          if Get_PCS_Name /= Name_PolyORB_DSA then
1467             Error_Attr
1468               ("attribute% requires the 'Poly'O'R'B 'P'C'S", N);
1469          end if;
1470       end Check_PolyORB_Attribute;
1471
1472       ------------------------
1473       -- Check_Program_Unit --
1474       ------------------------
1475
1476       procedure Check_Program_Unit is
1477       begin
1478          if Is_Entity_Name (P) then
1479             declare
1480                K : constant Entity_Kind := Ekind (Entity (P));
1481                T : constant Entity_Id   := Etype (Entity (P));
1482
1483             begin
1484                if K in Subprogram_Kind
1485                  or else K in Task_Kind
1486                  or else K in Protected_Kind
1487                  or else K = E_Package
1488                  or else K in Generic_Unit_Kind
1489                  or else (K = E_Variable
1490                             and then
1491                               (Is_Task_Type (T)
1492                                  or else
1493                                Is_Protected_Type (T)))
1494                then
1495                   return;
1496                end if;
1497             end;
1498          end if;
1499
1500          Error_Attr_P ("prefix of % attribute must be program unit");
1501       end Check_Program_Unit;
1502
1503       ---------------------
1504       -- Check_Real_Type --
1505       ---------------------
1506
1507       procedure Check_Real_Type is
1508       begin
1509          Check_Type;
1510
1511          if not Is_Real_Type (P_Type) then
1512             Error_Attr_P ("prefix of % attribute must be real type");
1513          end if;
1514       end Check_Real_Type;
1515
1516       -----------------------
1517       -- Check_Scalar_Type --
1518       -----------------------
1519
1520       procedure Check_Scalar_Type is
1521       begin
1522          Check_Type;
1523
1524          if not Is_Scalar_Type (P_Type) then
1525             Error_Attr_P ("prefix of % attribute must be scalar type");
1526          end if;
1527       end Check_Scalar_Type;
1528
1529       ---------------------------
1530       -- Check_Standard_Prefix --
1531       ---------------------------
1532
1533       procedure Check_Standard_Prefix is
1534       begin
1535          Check_E0;
1536
1537          if Nkind (P) /= N_Identifier
1538            or else Chars (P) /= Name_Standard
1539          then
1540             Error_Attr ("only allowed prefix for % attribute is Standard", P);
1541          end if;
1542       end Check_Standard_Prefix;
1543
1544       ----------------------------
1545       -- Check_Stream_Attribute --
1546       ----------------------------
1547
1548       procedure Check_Stream_Attribute (Nam : TSS_Name_Type) is
1549          Etyp : Entity_Id;
1550          Btyp : Entity_Id;
1551
1552          In_Shared_Var_Procs : Boolean;
1553          --  True when compiling the body of System.Shared_Storage.
1554          --  Shared_Var_Procs. For this runtime package (always compiled in
1555          --  GNAT mode), we allow stream attributes references for limited
1556          --  types for the case where shared passive objects are implemented
1557          --  using stream attributes, which is the default in GNAT's persistent
1558          --  storage implementation.
1559
1560       begin
1561          Validate_Non_Static_Attribute_Function_Call;
1562
1563          --  With the exception of 'Input, Stream attributes are procedures,
1564          --  and can only appear at the position of procedure calls. We check
1565          --  for this here, before they are rewritten, to give a more precise
1566          --  diagnostic.
1567
1568          if Nam = TSS_Stream_Input then
1569             null;
1570
1571          elsif Is_List_Member (N)
1572            and then not Nkind_In (Parent (N), N_Procedure_Call_Statement,
1573                                               N_Aggregate)
1574          then
1575             null;
1576
1577          else
1578             Error_Attr
1579               ("invalid context for attribute%, which is a procedure", N);
1580          end if;
1581
1582          Check_Type;
1583          Btyp := Implementation_Base_Type (P_Type);
1584
1585          --  Stream attributes not allowed on limited types unless the
1586          --  attribute reference was generated by the expander (in which
1587          --  case the underlying type will be used, as described in Sinfo),
1588          --  or the attribute was specified explicitly for the type itself
1589          --  or one of its ancestors (taking visibility rules into account if
1590          --  in Ada 2005 mode), or a pragma Stream_Convert applies to Btyp
1591          --  (with no visibility restriction).
1592
1593          declare
1594             Gen_Body : constant Node_Id := Enclosing_Generic_Body (N);
1595          begin
1596             if Present (Gen_Body) then
1597                In_Shared_Var_Procs :=
1598                  Is_RTE (Corresponding_Spec (Gen_Body), RE_Shared_Var_Procs);
1599             else
1600                In_Shared_Var_Procs := False;
1601             end if;
1602          end;
1603
1604          if (Comes_From_Source (N)
1605               and then not (In_Shared_Var_Procs or In_Instance))
1606            and then not Stream_Attribute_Available (P_Type, Nam)
1607            and then not Has_Rep_Pragma (Btyp, Name_Stream_Convert)
1608          then
1609             Error_Msg_Name_1 := Aname;
1610
1611             if Is_Limited_Type (P_Type) then
1612                Error_Msg_NE
1613                  ("limited type& has no% attribute", P, P_Type);
1614                Explain_Limited_Type (P_Type, P);
1615             else
1616                Error_Msg_NE
1617                  ("attribute% for type& is not available", P, P_Type);
1618             end if;
1619          end if;
1620
1621          --  Check restriction violations
1622
1623          --  First check the No_Streams restriction, which prohibits the use
1624          --  of explicit stream attributes in the source program. We do not
1625          --  prevent the occurrence of stream attributes in generated code,
1626          --  for instance those generated implicitly for dispatching purposes.
1627
1628          if Comes_From_Source (N) then
1629             Check_Restriction (No_Streams, P);
1630          end if;
1631
1632          --  Check special case of Exception_Id and Exception_Occurrence which
1633          --  are not allowed for restriction No_Exception_Regstriation.
1634
1635          if Is_RTE (P_Type, RE_Exception_Id)
1636               or else
1637             Is_RTE (P_Type, RE_Exception_Occurrence)
1638          then
1639             Check_Restriction (No_Exception_Registration, P);
1640          end if;
1641
1642          --  Here we must check that the first argument is an access type
1643          --  that is compatible with Ada.Streams.Root_Stream_Type'Class.
1644
1645          Analyze_And_Resolve (E1);
1646          Etyp := Etype (E1);
1647
1648          --  Note: the double call to Root_Type here is needed because the
1649          --  root type of a class-wide type is the corresponding type (e.g.
1650          --  X for X'Class, and we really want to go to the root.)
1651
1652          if not Is_Access_Type (Etyp)
1653            or else Root_Type (Root_Type (Designated_Type (Etyp))) /=
1654                      RTE (RE_Root_Stream_Type)
1655          then
1656             Error_Attr
1657               ("expected access to Ada.Streams.Root_Stream_Type''Class", E1);
1658          end if;
1659
1660          --  Check that the second argument is of the right type if there is
1661          --  one (the Input attribute has only one argument so this is skipped)
1662
1663          if Present (E2) then
1664             Analyze (E2);
1665
1666             if Nam = TSS_Stream_Read
1667               and then not Is_OK_Variable_For_Out_Formal (E2)
1668             then
1669                Error_Attr
1670                  ("second argument of % attribute must be a variable", E2);
1671             end if;
1672
1673             Resolve (E2, P_Type);
1674          end if;
1675
1676          Check_Not_CPP_Type;
1677       end Check_Stream_Attribute;
1678
1679       -----------------------
1680       -- Check_Task_Prefix --
1681       -----------------------
1682
1683       procedure Check_Task_Prefix is
1684       begin
1685          Analyze (P);
1686
1687          --  Ada 2005 (AI-345): Attribute 'Terminated can be applied to
1688          --  task interface class-wide types.
1689
1690          if Is_Task_Type (Etype (P))
1691            or else (Is_Access_Type (Etype (P))
1692                       and then Is_Task_Type (Designated_Type (Etype (P))))
1693            or else (Ada_Version >= Ada_2005
1694                       and then Ekind (Etype (P)) = E_Class_Wide_Type
1695                       and then Is_Interface (Etype (P))
1696                       and then Is_Task_Interface (Etype (P)))
1697          then
1698             Resolve (P);
1699
1700          else
1701             if Ada_Version >= Ada_2005 then
1702                Error_Attr_P
1703                  ("prefix of % attribute must be a task or a task " &
1704                   "interface class-wide object");
1705
1706             else
1707                Error_Attr_P ("prefix of % attribute must be a task");
1708             end if;
1709          end if;
1710       end Check_Task_Prefix;
1711
1712       ----------------
1713       -- Check_Type --
1714       ----------------
1715
1716       --  The possibilities are an entity name denoting a type, or an
1717       --  attribute reference that denotes a type (Base or Class). If
1718       --  the type is incomplete, replace it with its full view.
1719
1720       procedure Check_Type is
1721       begin
1722          if not Is_Entity_Name (P)
1723            or else not Is_Type (Entity (P))
1724          then
1725             Error_Attr_P ("prefix of % attribute must be a type");
1726
1727          elsif Is_Protected_Self_Reference (P) then
1728             Error_Attr_P
1729               ("prefix of % attribute denotes current instance "
1730                & "(RM 9.4(21/2))");
1731
1732          elsif Ekind (Entity (P)) = E_Incomplete_Type
1733             and then Present (Full_View (Entity (P)))
1734          then
1735             P_Type := Full_View (Entity (P));
1736             Set_Entity (P, P_Type);
1737          end if;
1738       end Check_Type;
1739
1740       ---------------------
1741       -- Check_Unit_Name --
1742       ---------------------
1743
1744       procedure Check_Unit_Name (Nod : Node_Id) is
1745       begin
1746          if Nkind (Nod) = N_Identifier then
1747             return;
1748
1749          elsif Nkind (Nod) = N_Selected_Component then
1750             Check_Unit_Name (Prefix (Nod));
1751
1752             if Nkind (Selector_Name (Nod)) = N_Identifier then
1753                return;
1754             end if;
1755          end if;
1756
1757          Error_Attr ("argument for % attribute must be unit name", P);
1758       end Check_Unit_Name;
1759
1760       ----------------
1761       -- Error_Attr --
1762       ----------------
1763
1764       procedure Error_Attr is
1765       begin
1766          Set_Etype (N, Any_Type);
1767          Set_Entity (N, Any_Type);
1768          raise Bad_Attribute;
1769       end Error_Attr;
1770
1771       procedure Error_Attr (Msg : String; Error_Node : Node_Id) is
1772       begin
1773          Error_Msg_Name_1 := Aname;
1774          Error_Msg_N (Msg, Error_Node);
1775          Error_Attr;
1776       end Error_Attr;
1777
1778       ------------------
1779       -- Error_Attr_P --
1780       ------------------
1781
1782       procedure Error_Attr_P (Msg : String) is
1783       begin
1784          Error_Msg_Name_1 := Aname;
1785          Error_Msg_F (Msg, P);
1786          Error_Attr;
1787       end Error_Attr_P;
1788
1789       ----------------------------
1790       -- Legal_Formal_Attribute --
1791       ----------------------------
1792
1793       procedure Legal_Formal_Attribute is
1794       begin
1795          Check_E0;
1796
1797          if not Is_Entity_Name (P)
1798            or else not Is_Type (Entity (P))
1799          then
1800             Error_Attr_P ("prefix of % attribute must be generic type");
1801
1802          elsif Is_Generic_Actual_Type (Entity (P))
1803            or else In_Instance
1804            or else In_Inlined_Body
1805          then
1806             null;
1807
1808          elsif Is_Generic_Type (Entity (P)) then
1809             if not Is_Indefinite_Subtype (Entity (P)) then
1810                Error_Attr_P
1811                  ("prefix of % attribute must be indefinite generic type");
1812             end if;
1813
1814          else
1815             Error_Attr_P
1816               ("prefix of % attribute must be indefinite generic type");
1817          end if;
1818
1819          Set_Etype (N, Standard_Boolean);
1820       end Legal_Formal_Attribute;
1821
1822       ------------------------
1823       -- Standard_Attribute --
1824       ------------------------
1825
1826       procedure Standard_Attribute (Val : Int) is
1827       begin
1828          Check_Standard_Prefix;
1829          Rewrite (N, Make_Integer_Literal (Loc, Val));
1830          Analyze (N);
1831       end Standard_Attribute;
1832
1833       -------------------------
1834       -- Unexpected Argument --
1835       -------------------------
1836
1837       procedure Unexpected_Argument (En : Node_Id) is
1838       begin
1839          Error_Attr ("unexpected argument for % attribute", En);
1840       end Unexpected_Argument;
1841
1842       -------------------------------------------------
1843       -- Validate_Non_Static_Attribute_Function_Call --
1844       -------------------------------------------------
1845
1846       --  This function should be moved to Sem_Dist ???
1847
1848       procedure Validate_Non_Static_Attribute_Function_Call is
1849       begin
1850          if In_Preelaborated_Unit
1851            and then not In_Subprogram_Or_Concurrent_Unit
1852          then
1853             Flag_Non_Static_Expr
1854               ("non-static function call in preelaborated unit!", N);
1855          end if;
1856       end Validate_Non_Static_Attribute_Function_Call;
1857
1858    -----------------------------------------------
1859    -- Start of Processing for Analyze_Attribute --
1860    -----------------------------------------------
1861
1862    begin
1863       --  Immediate return if unrecognized attribute (already diagnosed
1864       --  by parser, so there is nothing more that we need to do)
1865
1866       if not Is_Attribute_Name (Aname) then
1867          raise Bad_Attribute;
1868       end if;
1869
1870       --  Deal with Ada 83 issues
1871
1872       if Comes_From_Source (N) then
1873          if not Attribute_83 (Attr_Id) then
1874             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
1875                Error_Msg_Name_1 := Aname;
1876                Error_Msg_N ("(Ada 83) attribute% is not standard?", N);
1877             end if;
1878
1879             if Attribute_Impl_Def (Attr_Id) then
1880                Check_Restriction (No_Implementation_Attributes, N);
1881             end if;
1882          end if;
1883       end if;
1884
1885       --  Deal with Ada 2005 issues
1886
1887       if Attribute_05 (Attr_Id) and then Ada_Version <= Ada_95 then
1888          Check_Restriction (No_Implementation_Attributes, N);
1889       end if;
1890
1891       --   Remote access to subprogram type access attribute reference needs
1892       --   unanalyzed copy for tree transformation. The analyzed copy is used
1893       --   for its semantic information (whether prefix is a remote subprogram
1894       --   name), the unanalyzed copy is used to construct new subtree rooted
1895       --   with N_Aggregate which represents a fat pointer aggregate.
1896
1897       if Aname = Name_Access then
1898          Discard_Node (Copy_Separate_Tree (N));
1899       end if;
1900
1901       --  Analyze prefix and exit if error in analysis. If the prefix is an
1902       --  incomplete type, use full view if available. Note that there are
1903       --  some attributes for which we do not analyze the prefix, since the
1904       --  prefix is not a normal name.
1905
1906       if Aname /= Name_Elab_Body
1907            and then
1908          Aname /= Name_Elab_Spec
1909            and then
1910          Aname /= Name_UET_Address
1911            and then
1912          Aname /= Name_Enabled
1913       then
1914          Analyze (P);
1915          P_Type := Etype (P);
1916
1917          if Is_Entity_Name (P)
1918            and then Present (Entity (P))
1919            and then Is_Type (Entity (P))
1920          then
1921             if Ekind (Entity (P)) = E_Incomplete_Type then
1922                P_Type := Get_Full_View (P_Type);
1923                Set_Entity (P, P_Type);
1924                Set_Etype  (P, P_Type);
1925
1926             elsif Entity (P) = Current_Scope
1927               and then Is_Record_Type (Entity (P))
1928             then
1929                --  Use of current instance within the type. Verify that if the
1930                --  attribute appears within a constraint, it  yields an access
1931                --  type, other uses are illegal.
1932
1933                declare
1934                   Par : Node_Id;
1935
1936                begin
1937                   Par := Parent (N);
1938                   while Present (Par)
1939                     and then Nkind (Parent (Par)) /= N_Component_Definition
1940                   loop
1941                      Par := Parent (Par);
1942                   end loop;
1943
1944                   if Present (Par)
1945                     and then Nkind (Par) = N_Subtype_Indication
1946                   then
1947                      if Attr_Id /= Attribute_Access
1948                        and then Attr_Id /= Attribute_Unchecked_Access
1949                        and then Attr_Id /= Attribute_Unrestricted_Access
1950                      then
1951                         Error_Msg_N
1952                           ("in a constraint the current instance can only"
1953                              & " be used with an access attribute", N);
1954                      end if;
1955                   end if;
1956                end;
1957             end if;
1958          end if;
1959
1960          if P_Type = Any_Type then
1961             raise Bad_Attribute;
1962          end if;
1963
1964          P_Base_Type := Base_Type (P_Type);
1965       end if;
1966
1967       --  Analyze expressions that may be present, exiting if an error occurs
1968
1969       if No (Exprs) then
1970          E1 := Empty;
1971          E2 := Empty;
1972
1973       else
1974          E1 := First (Exprs);
1975          Analyze (E1);
1976
1977          --  Check for missing/bad expression (result of previous error)
1978
1979          if No (E1) or else Etype (E1) = Any_Type then
1980             raise Bad_Attribute;
1981          end if;
1982
1983          E2 := Next (E1);
1984
1985          if Present (E2) then
1986             Analyze (E2);
1987
1988             if Etype (E2) = Any_Type then
1989                raise Bad_Attribute;
1990             end if;
1991
1992             if Present (Next (E2)) then
1993                Unexpected_Argument (Next (E2));
1994             end if;
1995          end if;
1996       end if;
1997
1998       --  Ada 2005 (AI-345): Ensure that the compiler gives exactly the current
1999       --  output compiling in Ada 95 mode for the case of ambiguous prefixes.
2000
2001       if Ada_Version < Ada_2005
2002         and then Is_Overloaded (P)
2003         and then Aname /= Name_Access
2004         and then Aname /= Name_Address
2005         and then Aname /= Name_Code_Address
2006         and then Aname /= Name_Count
2007         and then Aname /= Name_Result
2008         and then Aname /= Name_Unchecked_Access
2009       then
2010          Error_Attr ("ambiguous prefix for % attribute", P);
2011
2012       elsif Ada_Version >= Ada_2005
2013         and then Is_Overloaded (P)
2014         and then Aname /= Name_Access
2015         and then Aname /= Name_Address
2016         and then Aname /= Name_Code_Address
2017         and then Aname /= Name_Result
2018         and then Aname /= Name_Unchecked_Access
2019       then
2020          --  Ada 2005 (AI-345): Since protected and task types have primitive
2021          --  entry wrappers, the attributes Count, Caller and AST_Entry require
2022          --  a context check
2023
2024          if Ada_Version >= Ada_2005
2025            and then (Aname = Name_Count
2026                       or else Aname = Name_Caller
2027                       or else Aname = Name_AST_Entry)
2028          then
2029             declare
2030                Count : Natural := 0;
2031                I     : Interp_Index;
2032                It    : Interp;
2033
2034             begin
2035                Get_First_Interp (P, I, It);
2036                while Present (It.Nam) loop
2037                   if Comes_From_Source (It.Nam) then
2038                      Count := Count + 1;
2039                   else
2040                      Remove_Interp (I);
2041                   end if;
2042
2043                   Get_Next_Interp (I, It);
2044                end loop;
2045
2046                if Count > 1 then
2047                   Error_Attr ("ambiguous prefix for % attribute", P);
2048                else
2049                   Set_Is_Overloaded (P, False);
2050                end if;
2051             end;
2052
2053          else
2054             Error_Attr ("ambiguous prefix for % attribute", P);
2055          end if;
2056       end if;
2057
2058       --  Remaining processing depends on attribute
2059
2060       case Attr_Id is
2061
2062       ------------------
2063       -- Abort_Signal --
2064       ------------------
2065
2066       when Attribute_Abort_Signal =>
2067          Check_Standard_Prefix;
2068          Rewrite (N,
2069            New_Reference_To (Stand.Abort_Signal, Loc));
2070          Analyze (N);
2071
2072       ------------
2073       -- Access --
2074       ------------
2075
2076       when Attribute_Access =>
2077          Analyze_Access_Attribute;
2078
2079       -------------
2080       -- Address --
2081       -------------
2082
2083       when Attribute_Address =>
2084          Check_E0;
2085
2086          --  Check for some junk cases, where we have to allow the address
2087          --  attribute but it does not make much sense, so at least for now
2088          --  just replace with Null_Address.
2089
2090          --  We also do this if the prefix is a reference to the AST_Entry
2091          --  attribute. If expansion is active, the attribute will be
2092          --  replaced by a function call, and address will work fine and
2093          --  get the proper value, but if expansion is not active, then
2094          --  the check here allows proper semantic analysis of the reference.
2095
2096          --  An Address attribute created by expansion is legal even when it
2097          --  applies to other entity-denoting expressions.
2098
2099          if Is_Protected_Self_Reference (P) then
2100
2101             --  Address attribute on a protected object self reference is legal
2102
2103             null;
2104
2105          elsif Is_Entity_Name (P) then
2106             declare
2107                Ent : constant Entity_Id := Entity (P);
2108
2109             begin
2110                if Is_Subprogram (Ent) then
2111                   Set_Address_Taken (Ent);
2112                   Kill_Current_Values (Ent);
2113
2114                   --  An Address attribute is accepted when generated by the
2115                   --  compiler for dispatching operation, and an error is
2116                   --  issued once the subprogram is frozen (to avoid confusing
2117                   --  errors about implicit uses of Address in the dispatch
2118                   --  table initialization).
2119
2120                   if Has_Pragma_Inline_Always (Entity (P))
2121                     and then Comes_From_Source (P)
2122                   then
2123                      Error_Attr_P
2124                        ("prefix of % attribute cannot be Inline_Always" &
2125                         " subprogram");
2126
2127                   --  It is illegal to apply 'Address to an intrinsic
2128                   --  subprogram. This is now formalized in AI05-0095.
2129                   --  In an instance, an attempt to obtain 'Address of an
2130                   --  intrinsic subprogram (e.g the renaming of a predefined
2131                   --  operator that is an actual) raises Program_Error.
2132
2133                   elsif Convention (Ent) = Convention_Intrinsic then
2134                      if In_Instance then
2135                         Rewrite (N,
2136                           Make_Raise_Program_Error (Loc,
2137                             Reason => PE_Address_Of_Intrinsic));
2138
2139                      else
2140                         Error_Msg_N
2141                          ("cannot take Address of intrinsic subprogram", N);
2142                      end if;
2143
2144                   --  Issue an error if prefix denotes an eliminated subprogram
2145
2146                   else
2147                      Check_For_Eliminated_Subprogram (P, Ent);
2148                   end if;
2149
2150                elsif Is_Object (Ent)
2151                  or else Ekind (Ent) = E_Label
2152                then
2153                   Set_Address_Taken (Ent);
2154
2155                --  If we have an address of an object, and the attribute
2156                --  comes from source, then set the object as potentially
2157                --  source modified. We do this because the resulting address
2158                --  can potentially be used to modify the variable and we
2159                --  might not detect this, leading to some junk warnings.
2160
2161                   Set_Never_Set_In_Source (Ent, False);
2162
2163                elsif (Is_Concurrent_Type (Etype (Ent))
2164                        and then Etype (Ent) = Base_Type (Ent))
2165                  or else Ekind (Ent) = E_Package
2166                  or else Is_Generic_Unit (Ent)
2167                then
2168                   Rewrite (N,
2169                     New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
2170
2171                else
2172                   Error_Attr ("invalid prefix for % attribute", P);
2173                end if;
2174             end;
2175
2176          elsif Nkind (P) = N_Attribute_Reference
2177            and then Attribute_Name (P) = Name_AST_Entry
2178          then
2179             Rewrite (N,
2180               New_Occurrence_Of (RTE (RE_Null_Address), Sloc (N)));
2181
2182          elsif Is_Object_Reference (P) then
2183             null;
2184
2185          elsif Nkind (P) = N_Selected_Component
2186            and then Is_Subprogram (Entity (Selector_Name (P)))
2187          then
2188             null;
2189
2190          --  What exactly are we allowing here ??? and is this properly
2191          --  documented in the sinfo documentation for this node ???
2192
2193          elsif not Comes_From_Source (N) then
2194             null;
2195
2196          else
2197             Error_Attr ("invalid prefix for % attribute", P);
2198          end if;
2199
2200          Set_Etype (N, RTE (RE_Address));
2201
2202       ------------------
2203       -- Address_Size --
2204       ------------------
2205
2206       when Attribute_Address_Size =>
2207          Standard_Attribute (System_Address_Size);
2208
2209       --------------
2210       -- Adjacent --
2211       --------------
2212
2213       when Attribute_Adjacent =>
2214          Check_Floating_Point_Type_2;
2215          Set_Etype (N, P_Base_Type);
2216          Resolve (E1, P_Base_Type);
2217          Resolve (E2, P_Base_Type);
2218
2219       ---------
2220       -- Aft --
2221       ---------
2222
2223       when Attribute_Aft =>
2224          Check_Fixed_Point_Type_0;
2225          Set_Etype (N, Universal_Integer);
2226
2227       ---------------
2228       -- Alignment --
2229       ---------------
2230
2231       when Attribute_Alignment =>
2232
2233          --  Don't we need more checking here, cf Size ???
2234
2235          Check_E0;
2236          Check_Not_Incomplete_Type;
2237          Check_Not_CPP_Type;
2238          Set_Etype (N, Universal_Integer);
2239
2240       ---------------
2241       -- Asm_Input --
2242       ---------------
2243
2244       when Attribute_Asm_Input =>
2245          Check_Asm_Attribute;
2246          Set_Etype (N, RTE (RE_Asm_Input_Operand));
2247
2248       ----------------
2249       -- Asm_Output --
2250       ----------------
2251
2252       when Attribute_Asm_Output =>
2253          Check_Asm_Attribute;
2254
2255          if Etype (E2) = Any_Type then
2256             return;
2257
2258          elsif Aname = Name_Asm_Output then
2259             if not Is_Variable (E2) then
2260                Error_Attr
2261                  ("second argument for Asm_Output is not variable", E2);
2262             end if;
2263          end if;
2264
2265          Note_Possible_Modification (E2, Sure => True);
2266          Set_Etype (N, RTE (RE_Asm_Output_Operand));
2267
2268       ---------------
2269       -- AST_Entry --
2270       ---------------
2271
2272       when Attribute_AST_Entry => AST_Entry : declare
2273          Ent  : Entity_Id;
2274          Pref : Node_Id;
2275          Ptyp : Entity_Id;
2276
2277          Indexed : Boolean;
2278          --  Indicates if entry family index is present. Note the coding
2279          --  here handles the entry family case, but in fact it cannot be
2280          --  executed currently, because pragma AST_Entry does not permit
2281          --  the specification of an entry family.
2282
2283          procedure Bad_AST_Entry;
2284          --  Signal a bad AST_Entry pragma
2285
2286          function OK_Entry (E : Entity_Id) return Boolean;
2287          --  Checks that E is of an appropriate entity kind for an entry
2288          --  (i.e. E_Entry if Index is False, or E_Entry_Family if Index
2289          --  is set True for the entry family case). In the True case,
2290          --  makes sure that Is_AST_Entry is set on the entry.
2291
2292          -------------------
2293          -- Bad_AST_Entry --
2294          -------------------
2295
2296          procedure Bad_AST_Entry is
2297          begin
2298             Error_Attr_P ("prefix for % attribute must be task entry");
2299          end Bad_AST_Entry;
2300
2301          --------------
2302          -- OK_Entry --
2303          --------------
2304
2305          function OK_Entry (E : Entity_Id) return Boolean is
2306             Result : Boolean;
2307
2308          begin
2309             if Indexed then
2310                Result := (Ekind (E) = E_Entry_Family);
2311             else
2312                Result := (Ekind (E) = E_Entry);
2313             end if;
2314
2315             if Result then
2316                if not Is_AST_Entry (E) then
2317                   Error_Msg_Name_2 := Aname;
2318                   Error_Attr ("% attribute requires previous % pragma", P);
2319                end if;
2320             end if;
2321
2322             return Result;
2323          end OK_Entry;
2324
2325       --  Start of processing for AST_Entry
2326
2327       begin
2328          Check_VMS (N);
2329          Check_E0;
2330
2331          --  Deal with entry family case
2332
2333          if Nkind (P) = N_Indexed_Component then
2334             Pref := Prefix (P);
2335             Indexed := True;
2336          else
2337             Pref := P;
2338             Indexed := False;
2339          end if;
2340
2341          Ptyp := Etype (Pref);
2342
2343          if Ptyp = Any_Type or else Error_Posted (Pref) then
2344             return;
2345          end if;
2346
2347          --  If the prefix is a selected component whose prefix is of an
2348          --  access type, then introduce an explicit dereference.
2349          --  ??? Could we reuse Check_Dereference here?
2350
2351          if Nkind (Pref) = N_Selected_Component
2352            and then Is_Access_Type (Ptyp)
2353          then
2354             Rewrite (Pref,
2355               Make_Explicit_Dereference (Sloc (Pref),
2356                 Relocate_Node (Pref)));
2357             Analyze_And_Resolve (Pref, Designated_Type (Ptyp));
2358          end if;
2359
2360          --  Prefix can be of the form a.b, where a is a task object
2361          --  and b is one of the entries of the corresponding task type.
2362
2363          if Nkind (Pref) = N_Selected_Component
2364            and then OK_Entry (Entity (Selector_Name (Pref)))
2365            and then Is_Object_Reference (Prefix (Pref))
2366            and then Is_Task_Type (Etype (Prefix (Pref)))
2367          then
2368             null;
2369
2370          --  Otherwise the prefix must be an entry of a containing task,
2371          --  or of a variable of the enclosing task type.
2372
2373          else
2374             if Nkind_In (Pref, N_Identifier, N_Expanded_Name) then
2375                Ent := Entity (Pref);
2376
2377                if not OK_Entry (Ent)
2378                  or else not In_Open_Scopes (Scope (Ent))
2379                then
2380                   Bad_AST_Entry;
2381                end if;
2382
2383             else
2384                Bad_AST_Entry;
2385             end if;
2386          end if;
2387
2388          Set_Etype (N, RTE (RE_AST_Handler));
2389       end AST_Entry;
2390
2391       ----------
2392       -- Base --
2393       ----------
2394
2395       --  Note: when the base attribute appears in the context of a subtype
2396       --  mark, the analysis is done by Sem_Ch8.Find_Type, rather than by
2397       --  the following circuit.
2398
2399       when Attribute_Base => Base : declare
2400          Typ : Entity_Id;
2401
2402       begin
2403          Check_E0;
2404          Find_Type (P);
2405          Typ := Entity (P);
2406
2407          if Ada_Version >= Ada_95
2408            and then not Is_Scalar_Type (Typ)
2409            and then not Is_Generic_Type (Typ)
2410          then
2411             Error_Attr_P ("prefix of Base attribute must be scalar type");
2412
2413          elsif Sloc (Typ) = Standard_Location
2414            and then Base_Type (Typ) = Typ
2415            and then Warn_On_Redundant_Constructs
2416          then
2417             Error_Msg_NE -- CODEFIX
2418               ("?redundant attribute, & is its own base type", N, Typ);
2419          end if;
2420
2421          Set_Etype (N, Base_Type (Entity (P)));
2422          Set_Entity (N, Base_Type (Entity (P)));
2423          Rewrite (N, New_Reference_To (Entity (N), Loc));
2424          Analyze (N);
2425       end Base;
2426
2427       ---------
2428       -- Bit --
2429       ---------
2430
2431       when Attribute_Bit => Bit :
2432       begin
2433          Check_E0;
2434
2435          if not Is_Object_Reference (P) then
2436             Error_Attr_P ("prefix for % attribute must be object");
2437
2438          --  What about the access object cases ???
2439
2440          else
2441             null;
2442          end if;
2443
2444          Set_Etype (N, Universal_Integer);
2445       end Bit;
2446
2447       ---------------
2448       -- Bit_Order --
2449       ---------------
2450
2451       when Attribute_Bit_Order => Bit_Order :
2452       begin
2453          Check_E0;
2454          Check_Type;
2455
2456          if not Is_Record_Type (P_Type) then
2457             Error_Attr_P ("prefix of % attribute must be record type");
2458          end if;
2459
2460          if Bytes_Big_Endian xor Reverse_Bit_Order (P_Type) then
2461             Rewrite (N,
2462               New_Occurrence_Of (RTE (RE_High_Order_First), Loc));
2463          else
2464             Rewrite (N,
2465               New_Occurrence_Of (RTE (RE_Low_Order_First), Loc));
2466          end if;
2467
2468          Set_Etype (N, RTE (RE_Bit_Order));
2469          Resolve (N);
2470
2471          --  Reset incorrect indication of staticness
2472
2473          Set_Is_Static_Expression (N, False);
2474       end Bit_Order;
2475
2476       ------------------
2477       -- Bit_Position --
2478       ------------------
2479
2480       --  Note: in generated code, we can have a Bit_Position attribute
2481       --  applied to a (naked) record component (i.e. the prefix is an
2482       --  identifier that references an E_Component or E_Discriminant
2483       --  entity directly, and this is interpreted as expected by Gigi.
2484       --  The following code will not tolerate such usage, but when the
2485       --  expander creates this special case, it marks it as analyzed
2486       --  immediately and sets an appropriate type.
2487
2488       when Attribute_Bit_Position =>
2489          if Comes_From_Source (N) then
2490             Check_Component;
2491          end if;
2492
2493          Set_Etype (N, Universal_Integer);
2494
2495       ------------------
2496       -- Body_Version --
2497       ------------------
2498
2499       when Attribute_Body_Version =>
2500          Check_E0;
2501          Check_Program_Unit;
2502          Set_Etype (N, RTE (RE_Version_String));
2503
2504       --------------
2505       -- Callable --
2506       --------------
2507
2508       when Attribute_Callable =>
2509          Check_E0;
2510          Set_Etype (N, Standard_Boolean);
2511          Check_Task_Prefix;
2512
2513       ------------
2514       -- Caller --
2515       ------------
2516
2517       when Attribute_Caller => Caller : declare
2518          Ent        : Entity_Id;
2519          S          : Entity_Id;
2520
2521       begin
2522          Check_E0;
2523
2524          if Nkind_In (P, N_Identifier, N_Expanded_Name) then
2525             Ent := Entity (P);
2526
2527             if not Is_Entry (Ent) then
2528                Error_Attr ("invalid entry name", N);
2529             end if;
2530
2531          else
2532             Error_Attr ("invalid entry name", N);
2533             return;
2534          end if;
2535
2536          for J in reverse 0 .. Scope_Stack.Last loop
2537             S := Scope_Stack.Table (J).Entity;
2538
2539             if S = Scope (Ent) then
2540                Error_Attr ("Caller must appear in matching accept or body", N);
2541             elsif S = Ent then
2542                exit;
2543             end if;
2544          end loop;
2545
2546          Set_Etype (N, RTE (RO_AT_Task_Id));
2547       end Caller;
2548
2549       -------------
2550       -- Ceiling --
2551       -------------
2552
2553       when Attribute_Ceiling =>
2554          Check_Floating_Point_Type_1;
2555          Set_Etype (N, P_Base_Type);
2556          Resolve (E1, P_Base_Type);
2557
2558       -----------
2559       -- Class --
2560       -----------
2561
2562       when Attribute_Class =>
2563          Check_Restriction (No_Dispatch, N);
2564          Check_E0;
2565          Find_Type (N);
2566
2567          --  Applying Class to untagged incomplete type is obsolescent in Ada
2568          --  2005. Note that we can't test Is_Tagged_Type here on P_Type, since
2569          --  this flag gets set by Find_Type in this situation.
2570
2571          if Restriction_Check_Required (No_Obsolescent_Features)
2572            and then Ada_Version >= Ada_2005
2573            and then Ekind (P_Type) = E_Incomplete_Type
2574          then
2575             declare
2576                DN : constant Node_Id := Declaration_Node (P_Type);
2577             begin
2578                if Nkind (DN) = N_Incomplete_Type_Declaration
2579                  and then not Tagged_Present (DN)
2580                then
2581                   Check_Restriction (No_Obsolescent_Features, P);
2582                end if;
2583             end;
2584          end if;
2585
2586       ------------------
2587       -- Code_Address --
2588       ------------------
2589
2590       when Attribute_Code_Address =>
2591          Check_E0;
2592
2593          if Nkind (P) = N_Attribute_Reference
2594            and then (Attribute_Name (P) = Name_Elab_Body
2595                        or else
2596                      Attribute_Name (P) = Name_Elab_Spec)
2597          then
2598             null;
2599
2600          elsif not Is_Entity_Name (P)
2601            or else (Ekind (Entity (P)) /= E_Function
2602                       and then
2603                     Ekind (Entity (P)) /= E_Procedure)
2604          then
2605             Error_Attr ("invalid prefix for % attribute", P);
2606             Set_Address_Taken (Entity (P));
2607
2608          --  Issue an error if the prefix denotes an eliminated subprogram
2609
2610          else
2611             Check_For_Eliminated_Subprogram (P, Entity (P));
2612          end if;
2613
2614          Set_Etype (N, RTE (RE_Address));
2615
2616       ----------------------
2617       -- Compiler_Version --
2618       ----------------------
2619
2620       when Attribute_Compiler_Version =>
2621          Check_E0;
2622          Check_Standard_Prefix;
2623          Rewrite (N, Make_String_Literal (Loc, "GNAT " & Gnat_Version_String));
2624          Analyze_And_Resolve (N, Standard_String);
2625
2626       --------------------
2627       -- Component_Size --
2628       --------------------
2629
2630       when Attribute_Component_Size =>
2631          Check_E0;
2632          Set_Etype (N, Universal_Integer);
2633
2634          --  Note: unlike other array attributes, unconstrained arrays are OK
2635
2636          if Is_Array_Type (P_Type) and then not Is_Constrained (P_Type) then
2637             null;
2638          else
2639             Check_Array_Type;
2640          end if;
2641
2642       -------------
2643       -- Compose --
2644       -------------
2645
2646       when Attribute_Compose =>
2647          Check_Floating_Point_Type_2;
2648          Set_Etype (N, P_Base_Type);
2649          Resolve (E1, P_Base_Type);
2650          Resolve (E2, Any_Integer);
2651
2652       -----------------
2653       -- Constrained --
2654       -----------------
2655
2656       when Attribute_Constrained =>
2657          Check_E0;
2658          Set_Etype (N, Standard_Boolean);
2659
2660          --  Case from RM J.4(2) of constrained applied to private type
2661
2662          if Is_Entity_Name (P) and then Is_Type (Entity (P)) then
2663             Check_Restriction (No_Obsolescent_Features, P);
2664
2665             if Warn_On_Obsolescent_Feature then
2666                Error_Msg_N
2667                  ("constrained for private type is an " &
2668                   "obsolescent feature (RM J.4)?", N);
2669             end if;
2670
2671             --  If we are within an instance, the attribute must be legal
2672             --  because it was valid in the generic unit. Ditto if this is
2673             --  an inlining of a function declared in an instance.
2674
2675             if In_Instance
2676               or else In_Inlined_Body
2677             then
2678                return;
2679
2680             --  For sure OK if we have a real private type itself, but must
2681             --  be completed, cannot apply Constrained to incomplete type.
2682
2683             elsif Is_Private_Type (Entity (P)) then
2684
2685                --  Note: this is one of the Annex J features that does not
2686                --  generate a warning from -gnatwj, since in fact it seems
2687                --  very useful, and is used in the GNAT runtime.
2688
2689                Check_Not_Incomplete_Type;
2690                return;
2691             end if;
2692
2693          --  Normal (non-obsolescent case) of application to object of
2694          --  a discriminated type.
2695
2696          else
2697             Check_Object_Reference (P);
2698
2699             --  If N does not come from source, then we allow the
2700             --  the attribute prefix to be of a private type whose
2701             --  full type has discriminants. This occurs in cases
2702             --  involving expanded calls to stream attributes.
2703
2704             if not Comes_From_Source (N) then
2705                P_Type := Underlying_Type (P_Type);
2706             end if;
2707
2708             --  Must have discriminants or be an access type designating
2709             --  a type with discriminants. If it is a classwide type is ???
2710             --  has unknown discriminants.
2711
2712             if Has_Discriminants (P_Type)
2713                or else Has_Unknown_Discriminants (P_Type)
2714                or else
2715                  (Is_Access_Type (P_Type)
2716                    and then Has_Discriminants (Designated_Type (P_Type)))
2717             then
2718                return;
2719
2720             --  Also allow an object of a generic type if extensions allowed
2721             --  and allow this for any type at all.
2722
2723             elsif (Is_Generic_Type (P_Type)
2724                      or else Is_Generic_Actual_Type (P_Type))
2725               and then Extensions_Allowed
2726             then
2727                return;
2728             end if;
2729          end if;
2730
2731          --  Fall through if bad prefix
2732
2733          Error_Attr_P
2734            ("prefix of % attribute must be object of discriminated type");
2735
2736       ---------------
2737       -- Copy_Sign --
2738       ---------------
2739
2740       when Attribute_Copy_Sign =>
2741          Check_Floating_Point_Type_2;
2742          Set_Etype (N, P_Base_Type);
2743          Resolve (E1, P_Base_Type);
2744          Resolve (E2, P_Base_Type);
2745
2746       -----------
2747       -- Count --
2748       -----------
2749
2750       when Attribute_Count => Count :
2751       declare
2752          Ent : Entity_Id;
2753          S   : Entity_Id;
2754          Tsk : Entity_Id;
2755
2756       begin
2757          Check_E0;
2758
2759          if Nkind_In (P, N_Identifier, N_Expanded_Name) then
2760             Ent := Entity (P);
2761
2762             if Ekind (Ent) /= E_Entry then
2763                Error_Attr ("invalid entry name", N);
2764             end if;
2765
2766          elsif Nkind (P) = N_Indexed_Component then
2767             if not Is_Entity_Name (Prefix (P))
2768               or else  No (Entity (Prefix (P)))
2769               or else Ekind (Entity (Prefix (P))) /= E_Entry_Family
2770             then
2771                if Nkind (Prefix (P)) = N_Selected_Component
2772                  and then Present (Entity (Selector_Name (Prefix (P))))
2773                  and then Ekind (Entity (Selector_Name (Prefix (P)))) =
2774                                                              E_Entry_Family
2775                then
2776                   Error_Attr
2777                     ("attribute % must apply to entry of current task", P);
2778
2779                else
2780                   Error_Attr ("invalid entry family name", P);
2781                end if;
2782                return;
2783
2784             else
2785                Ent := Entity (Prefix (P));
2786             end if;
2787
2788          elsif Nkind (P) = N_Selected_Component
2789            and then Present (Entity (Selector_Name (P)))
2790            and then Ekind (Entity (Selector_Name (P))) = E_Entry
2791          then
2792             Error_Attr
2793               ("attribute % must apply to entry of current task", P);
2794
2795          else
2796             Error_Attr ("invalid entry name", N);
2797             return;
2798          end if;
2799
2800          for J in reverse 0 .. Scope_Stack.Last loop
2801             S := Scope_Stack.Table (J).Entity;
2802
2803             if S = Scope (Ent) then
2804                if Nkind (P) = N_Expanded_Name then
2805                   Tsk := Entity (Prefix (P));
2806
2807                   --  The prefix denotes either the task type, or else a
2808                   --  single task whose task type is being analyzed.
2809
2810                   if (Is_Type (Tsk)
2811                       and then Tsk = S)
2812
2813                     or else (not Is_Type (Tsk)
2814                       and then Etype (Tsk) = S
2815                       and then not (Comes_From_Source (S)))
2816                   then
2817                      null;
2818                   else
2819                      Error_Attr
2820                        ("Attribute % must apply to entry of current task", N);
2821                   end if;
2822                end if;
2823
2824                exit;
2825
2826             elsif Ekind (Scope (Ent)) in Task_Kind
2827               and then
2828                 not Ekind_In (S, E_Loop, E_Block, E_Entry, E_Entry_Family)
2829             then
2830                Error_Attr ("Attribute % cannot appear in inner unit", N);
2831
2832             elsif Ekind (Scope (Ent)) = E_Protected_Type
2833               and then not Has_Completion (Scope (Ent))
2834             then
2835                Error_Attr ("attribute % can only be used inside body", N);
2836             end if;
2837          end loop;
2838
2839          if Is_Overloaded (P) then
2840             declare
2841                Index : Interp_Index;
2842                It    : Interp;
2843
2844             begin
2845                Get_First_Interp (P, Index, It);
2846
2847                while Present (It.Nam) loop
2848                   if It.Nam = Ent then
2849                      null;
2850
2851                   --  Ada 2005 (AI-345): Do not consider primitive entry
2852                   --  wrappers generated for task or protected types.
2853
2854                   elsif Ada_Version >= Ada_2005
2855                     and then not Comes_From_Source (It.Nam)
2856                   then
2857                      null;
2858
2859                   else
2860                      Error_Attr ("ambiguous entry name", N);
2861                   end if;
2862
2863                   Get_Next_Interp (Index, It);
2864                end loop;
2865             end;
2866          end if;
2867
2868          Set_Etype (N, Universal_Integer);
2869       end Count;
2870
2871       -----------------------
2872       -- Default_Bit_Order --
2873       -----------------------
2874
2875       when Attribute_Default_Bit_Order => Default_Bit_Order :
2876       begin
2877          Check_Standard_Prefix;
2878
2879          if Bytes_Big_Endian then
2880             Rewrite (N,
2881               Make_Integer_Literal (Loc, False_Value));
2882          else
2883             Rewrite (N,
2884               Make_Integer_Literal (Loc, True_Value));
2885          end if;
2886
2887          Set_Etype (N, Universal_Integer);
2888          Set_Is_Static_Expression (N);
2889       end Default_Bit_Order;
2890
2891       --------------
2892       -- Definite --
2893       --------------
2894
2895       when Attribute_Definite =>
2896          Legal_Formal_Attribute;
2897
2898       -----------
2899       -- Delta --
2900       -----------
2901
2902       when Attribute_Delta =>
2903          Check_Fixed_Point_Type_0;
2904          Set_Etype (N, Universal_Real);
2905
2906       ------------
2907       -- Denorm --
2908       ------------
2909
2910       when Attribute_Denorm =>
2911          Check_Floating_Point_Type_0;
2912          Set_Etype (N, Standard_Boolean);
2913
2914       ------------
2915       -- Digits --
2916       ------------
2917
2918       when Attribute_Digits =>
2919          Check_E0;
2920          Check_Type;
2921
2922          if not Is_Floating_Point_Type (P_Type)
2923            and then not Is_Decimal_Fixed_Point_Type (P_Type)
2924          then
2925             Error_Attr_P
2926               ("prefix of % attribute must be float or decimal type");
2927          end if;
2928
2929          Set_Etype (N, Universal_Integer);
2930
2931       ---------------
2932       -- Elab_Body --
2933       ---------------
2934
2935       --  Also handles processing for Elab_Spec
2936
2937       when Attribute_Elab_Body | Attribute_Elab_Spec =>
2938          Check_E0;
2939          Check_Unit_Name (P);
2940          Set_Etype (N, Standard_Void_Type);
2941
2942          --  We have to manually call the expander in this case to get
2943          --  the necessary expansion (normally attributes that return
2944          --  entities are not expanded).
2945
2946          Expand (N);
2947
2948       ---------------
2949       -- Elab_Spec --
2950       ---------------
2951
2952       --  Shares processing with Elab_Body
2953
2954       ----------------
2955       -- Elaborated --
2956       ----------------
2957
2958       when Attribute_Elaborated =>
2959          Check_E0;
2960          Check_Library_Unit;
2961          Set_Etype (N, Standard_Boolean);
2962
2963       ----------
2964       -- Emax --
2965       ----------
2966
2967       when Attribute_Emax =>
2968          Check_Floating_Point_Type_0;
2969          Set_Etype (N, Universal_Integer);
2970
2971       -------------
2972       -- Enabled --
2973       -------------
2974
2975       when Attribute_Enabled =>
2976          Check_Either_E0_Or_E1;
2977
2978          if Present (E1) then
2979             if not Is_Entity_Name (E1) or else No (Entity (E1)) then
2980                Error_Msg_N ("entity name expected for Enabled attribute", E1);
2981                E1 := Empty;
2982             end if;
2983          end if;
2984
2985          if Nkind (P) /= N_Identifier then
2986             Error_Msg_N ("identifier expected (check name)", P);
2987          elsif Get_Check_Id (Chars (P)) = No_Check_Id then
2988             Error_Msg_N ("& is not a recognized check name", P);
2989          end if;
2990
2991          Set_Etype (N, Standard_Boolean);
2992
2993       --------------
2994       -- Enum_Rep --
2995       --------------
2996
2997       when Attribute_Enum_Rep => Enum_Rep : declare
2998       begin
2999          if Present (E1) then
3000             Check_E1;
3001             Check_Discrete_Type;
3002             Resolve (E1, P_Base_Type);
3003
3004          else
3005             if not Is_Entity_Name (P)
3006               or else (not Is_Object (Entity (P))
3007                          and then
3008                        Ekind (Entity (P)) /= E_Enumeration_Literal)
3009             then
3010                Error_Attr_P
3011                  ("prefix of % attribute must be " &
3012                   "discrete type/object or enum literal");
3013             end if;
3014          end if;
3015
3016          Set_Etype (N, Universal_Integer);
3017       end Enum_Rep;
3018
3019       --------------
3020       -- Enum_Val --
3021       --------------
3022
3023       when Attribute_Enum_Val => Enum_Val : begin
3024          Check_E1;
3025          Check_Type;
3026
3027          if not Is_Enumeration_Type (P_Type) then
3028             Error_Attr_P ("prefix of % attribute must be enumeration type");
3029          end if;
3030
3031          --  If the enumeration type has a standard representation, the effect
3032          --  is the same as 'Val, so rewrite the attribute as a 'Val.
3033
3034          if not Has_Non_Standard_Rep (P_Base_Type) then
3035             Rewrite (N,
3036               Make_Attribute_Reference (Loc,
3037                 Prefix         => Relocate_Node (Prefix (N)),
3038                 Attribute_Name => Name_Val,
3039                 Expressions    => New_List (Relocate_Node (E1))));
3040             Analyze_And_Resolve (N, P_Base_Type);
3041
3042          --  Non-standard representation case (enumeration with holes)
3043
3044          else
3045             Check_Enum_Image;
3046             Resolve (E1, Any_Integer);
3047             Set_Etype (N, P_Base_Type);
3048          end if;
3049       end Enum_Val;
3050
3051       -------------
3052       -- Epsilon --
3053       -------------
3054
3055       when Attribute_Epsilon =>
3056          Check_Floating_Point_Type_0;
3057          Set_Etype (N, Universal_Real);
3058
3059       --------------
3060       -- Exponent --
3061       --------------
3062
3063       when Attribute_Exponent =>
3064          Check_Floating_Point_Type_1;
3065          Set_Etype (N, Universal_Integer);
3066          Resolve (E1, P_Base_Type);
3067
3068       ------------------
3069       -- External_Tag --
3070       ------------------
3071
3072       when Attribute_External_Tag =>
3073          Check_E0;
3074          Check_Type;
3075
3076          Set_Etype (N, Standard_String);
3077
3078          if not Is_Tagged_Type (P_Type) then
3079             Error_Attr_P ("prefix of % attribute must be tagged");
3080          end if;
3081
3082       ---------------
3083       -- Fast_Math --
3084       ---------------
3085
3086       when Attribute_Fast_Math =>
3087          Check_Standard_Prefix;
3088
3089          if Opt.Fast_Math then
3090             Rewrite (N, New_Occurrence_Of (Standard_True, Loc));
3091          else
3092             Rewrite (N, New_Occurrence_Of (Standard_False, Loc));
3093          end if;
3094
3095       -----------
3096       -- First --
3097       -----------
3098
3099       when Attribute_First =>
3100          Check_Array_Or_Scalar_Type;
3101          Bad_Attribute_For_Predicate;
3102
3103       ---------------
3104       -- First_Bit --
3105       ---------------
3106
3107       when Attribute_First_Bit =>
3108          Check_Component;
3109          Set_Etype (N, Universal_Integer);
3110
3111       -----------------
3112       -- Fixed_Value --
3113       -----------------
3114
3115       when Attribute_Fixed_Value =>
3116          Check_E1;
3117          Check_Fixed_Point_Type;
3118          Resolve (E1, Any_Integer);
3119          Set_Etype (N, P_Base_Type);
3120
3121       -----------
3122       -- Floor --
3123       -----------
3124
3125       when Attribute_Floor =>
3126          Check_Floating_Point_Type_1;
3127          Set_Etype (N, P_Base_Type);
3128          Resolve (E1, P_Base_Type);
3129
3130       ----------
3131       -- Fore --
3132       ----------
3133
3134       when Attribute_Fore =>
3135          Check_Fixed_Point_Type_0;
3136          Set_Etype (N, Universal_Integer);
3137
3138       --------------
3139       -- Fraction --
3140       --------------
3141
3142       when Attribute_Fraction =>
3143          Check_Floating_Point_Type_1;
3144          Set_Etype (N, P_Base_Type);
3145          Resolve (E1, P_Base_Type);
3146
3147       --------------
3148       -- From_Any --
3149       --------------
3150
3151       when Attribute_From_Any =>
3152          Check_E1;
3153          Check_PolyORB_Attribute;
3154          Set_Etype (N, P_Base_Type);
3155
3156       -----------------------
3157       -- Has_Access_Values --
3158       -----------------------
3159
3160       when Attribute_Has_Access_Values =>
3161          Check_Type;
3162          Check_E0;
3163          Set_Etype (N, Standard_Boolean);
3164
3165       -----------------------
3166       -- Has_Tagged_Values --
3167       -----------------------
3168
3169       when Attribute_Has_Tagged_Values =>
3170          Check_Type;
3171          Check_E0;
3172          Set_Etype (N, Standard_Boolean);
3173
3174       -----------------------
3175       -- Has_Discriminants --
3176       -----------------------
3177
3178       when Attribute_Has_Discriminants =>
3179          Legal_Formal_Attribute;
3180
3181       --------------
3182       -- Identity --
3183       --------------
3184
3185       when Attribute_Identity =>
3186          Check_E0;
3187          Analyze (P);
3188
3189          if Etype (P) =  Standard_Exception_Type then
3190             Set_Etype (N, RTE (RE_Exception_Id));
3191
3192          --  Ada 2005 (AI-345): Attribute 'Identity may be applied to
3193          --  task interface class-wide types.
3194
3195          elsif Is_Task_Type (Etype (P))
3196            or else (Is_Access_Type (Etype (P))
3197                       and then Is_Task_Type (Designated_Type (Etype (P))))
3198            or else (Ada_Version >= Ada_2005
3199                       and then Ekind (Etype (P)) = E_Class_Wide_Type
3200                       and then Is_Interface (Etype (P))
3201                       and then Is_Task_Interface (Etype (P)))
3202          then
3203             Resolve (P);
3204             Set_Etype (N, RTE (RO_AT_Task_Id));
3205
3206          else
3207             if Ada_Version >= Ada_2005 then
3208                Error_Attr_P
3209                  ("prefix of % attribute must be an exception, a " &
3210                   "task or a task interface class-wide object");
3211             else
3212                Error_Attr_P
3213                  ("prefix of % attribute must be a task or an exception");
3214             end if;
3215          end if;
3216
3217       -----------
3218       -- Image --
3219       -----------
3220
3221       when Attribute_Image => Image :
3222       begin
3223          Set_Etype (N, Standard_String);
3224          Check_Scalar_Type;
3225
3226          if Is_Real_Type (P_Type) then
3227             if Ada_Version = Ada_83 and then Comes_From_Source (N) then
3228                Error_Msg_Name_1 := Aname;
3229                Error_Msg_N
3230                  ("(Ada 83) % attribute not allowed for real types", N);
3231             end if;
3232          end if;
3233
3234          if Is_Enumeration_Type (P_Type) then
3235             Check_Restriction (No_Enumeration_Maps, N);
3236          end if;
3237
3238          Check_E1;
3239          Resolve (E1, P_Base_Type);
3240          Check_Enum_Image;
3241          Validate_Non_Static_Attribute_Function_Call;
3242       end Image;
3243
3244       ---------
3245       -- Img --
3246       ---------
3247
3248       when Attribute_Img => Img :
3249       begin
3250          Check_E0;
3251          Set_Etype (N, Standard_String);
3252
3253          if not Is_Scalar_Type (P_Type)
3254            or else (Is_Entity_Name (P) and then Is_Type (Entity (P)))
3255          then
3256             Error_Attr_P
3257               ("prefix of % attribute must be scalar object name");
3258          end if;
3259
3260          Check_Enum_Image;
3261       end Img;
3262
3263       -----------
3264       -- Input --
3265       -----------
3266
3267       when Attribute_Input =>
3268          Check_E1;
3269          Check_Stream_Attribute (TSS_Stream_Input);
3270          Set_Etype (N, P_Base_Type);
3271
3272       -------------------
3273       -- Integer_Value --
3274       -------------------
3275
3276       when Attribute_Integer_Value =>
3277          Check_E1;
3278          Check_Integer_Type;
3279          Resolve (E1, Any_Fixed);
3280
3281          --  Signal an error if argument type is not a specific fixed-point
3282          --  subtype. An error has been signalled already if the argument
3283          --  was not of a fixed-point type.
3284
3285          if Etype (E1) = Any_Fixed and then not Error_Posted (E1) then
3286             Error_Attr ("argument of % must be of a fixed-point type", E1);
3287          end if;
3288
3289          Set_Etype (N, P_Base_Type);
3290
3291       -------------------
3292       -- Invalid_Value --
3293       -------------------
3294
3295       when Attribute_Invalid_Value =>
3296          Check_E0;
3297          Check_Scalar_Type;
3298          Set_Etype (N, P_Base_Type);
3299          Invalid_Value_Used := True;
3300
3301       -----------
3302       -- Large --
3303       -----------
3304
3305       when Attribute_Large =>
3306          Check_E0;
3307          Check_Real_Type;
3308          Set_Etype (N, Universal_Real);
3309
3310       ----------
3311       -- Last --
3312       ----------
3313
3314       when Attribute_Last =>
3315          Check_Array_Or_Scalar_Type;
3316          Bad_Attribute_For_Predicate;
3317
3318       --------------
3319       -- Last_Bit --
3320       --------------
3321
3322       when Attribute_Last_Bit =>
3323          Check_Component;
3324          Set_Etype (N, Universal_Integer);
3325
3326       ------------------
3327       -- Leading_Part --
3328       ------------------
3329
3330       when Attribute_Leading_Part =>
3331          Check_Floating_Point_Type_2;
3332          Set_Etype (N, P_Base_Type);
3333          Resolve (E1, P_Base_Type);
3334          Resolve (E2, Any_Integer);
3335
3336       ------------
3337       -- Length --
3338       ------------
3339
3340       when Attribute_Length =>
3341          Check_Array_Type;
3342          Set_Etype (N, Universal_Integer);
3343
3344       -------------
3345       -- Machine --
3346       -------------
3347
3348       when Attribute_Machine =>
3349          Check_Floating_Point_Type_1;
3350          Set_Etype (N, P_Base_Type);
3351          Resolve (E1, P_Base_Type);
3352
3353       ------------------
3354       -- Machine_Emax --
3355       ------------------
3356
3357       when Attribute_Machine_Emax =>
3358          Check_Floating_Point_Type_0;
3359          Set_Etype (N, Universal_Integer);
3360
3361       ------------------
3362       -- Machine_Emin --
3363       ------------------
3364
3365       when Attribute_Machine_Emin =>
3366          Check_Floating_Point_Type_0;
3367          Set_Etype (N, Universal_Integer);
3368
3369       ----------------------
3370       -- Machine_Mantissa --
3371       ----------------------
3372
3373       when Attribute_Machine_Mantissa =>
3374          Check_Floating_Point_Type_0;
3375          Set_Etype (N, Universal_Integer);
3376
3377       -----------------------
3378       -- Machine_Overflows --
3379       -----------------------
3380
3381       when Attribute_Machine_Overflows =>
3382          Check_Real_Type;
3383          Check_E0;
3384          Set_Etype (N, Standard_Boolean);
3385
3386       -------------------
3387       -- Machine_Radix --
3388       -------------------
3389
3390       when Attribute_Machine_Radix =>
3391          Check_Real_Type;
3392          Check_E0;
3393          Set_Etype (N, Universal_Integer);
3394
3395       ----------------------
3396       -- Machine_Rounding --
3397       ----------------------
3398
3399       when Attribute_Machine_Rounding =>
3400          Check_Floating_Point_Type_1;
3401          Set_Etype (N, P_Base_Type);
3402          Resolve (E1, P_Base_Type);
3403
3404       --------------------
3405       -- Machine_Rounds --
3406       --------------------
3407
3408       when Attribute_Machine_Rounds =>
3409          Check_Real_Type;
3410          Check_E0;
3411          Set_Etype (N, Standard_Boolean);
3412
3413       ------------------
3414       -- Machine_Size --
3415       ------------------
3416
3417       when Attribute_Machine_Size =>
3418          Check_E0;
3419          Check_Type;
3420          Check_Not_Incomplete_Type;
3421          Set_Etype (N, Universal_Integer);
3422
3423       --------------
3424       -- Mantissa --
3425       --------------
3426
3427       when Attribute_Mantissa =>
3428          Check_E0;
3429          Check_Real_Type;
3430          Set_Etype (N, Universal_Integer);
3431
3432       ---------
3433       -- Max --
3434       ---------
3435
3436       when Attribute_Max =>
3437          Check_E2;
3438          Check_Scalar_Type;
3439          Resolve (E1, P_Base_Type);
3440          Resolve (E2, P_Base_Type);
3441          Set_Etype (N, P_Base_Type);
3442
3443       ----------------------------------
3444       -- Max_Alignment_For_Allocation --
3445       -- Max_Size_In_Storage_Elements --
3446       ----------------------------------
3447
3448       when Attribute_Max_Alignment_For_Allocation |
3449         Attribute_Max_Size_In_Storage_Elements =>
3450          Check_E0;
3451          Check_Type;
3452          Check_Not_Incomplete_Type;
3453          Set_Etype (N, Universal_Integer);
3454
3455       -----------------------
3456       -- Maximum_Alignment --
3457       -----------------------
3458
3459       when Attribute_Maximum_Alignment =>
3460          Standard_Attribute (Ttypes.Maximum_Alignment);
3461
3462       --------------------
3463       -- Mechanism_Code --
3464       --------------------
3465
3466       when Attribute_Mechanism_Code =>
3467          if not Is_Entity_Name (P)
3468            or else not Is_Subprogram (Entity (P))
3469          then
3470             Error_Attr_P ("prefix of % attribute must be subprogram");
3471          end if;
3472
3473          Check_Either_E0_Or_E1;
3474
3475          if Present (E1) then
3476             Resolve (E1, Any_Integer);
3477             Set_Etype (E1, Standard_Integer);
3478
3479             if not Is_Static_Expression (E1) then
3480                Flag_Non_Static_Expr
3481                  ("expression for parameter number must be static!", E1);
3482                Error_Attr;
3483
3484             elsif UI_To_Int (Intval (E1)) > Number_Formals (Entity (P))
3485               or else UI_To_Int (Intval (E1)) < 0
3486             then
3487                Error_Attr ("invalid parameter number for % attribute", E1);
3488             end if;
3489          end if;
3490
3491          Set_Etype (N, Universal_Integer);
3492
3493       ---------
3494       -- Min --
3495       ---------
3496
3497       when Attribute_Min =>
3498          Check_E2;
3499          Check_Scalar_Type;
3500          Resolve (E1, P_Base_Type);
3501          Resolve (E2, P_Base_Type);
3502          Set_Etype (N, P_Base_Type);
3503
3504       ---------
3505       -- Mod --
3506       ---------
3507
3508       when Attribute_Mod =>
3509
3510          --  Note: this attribute is only allowed in Ada 2005 mode, but
3511          --  we do not need to test that here, since Mod is only recognized
3512          --  as an attribute name in Ada 2005 mode during the parse.
3513
3514          Check_E1;
3515          Check_Modular_Integer_Type;
3516          Resolve (E1, Any_Integer);
3517          Set_Etype (N, P_Base_Type);
3518
3519       -----------
3520       -- Model --
3521       -----------
3522
3523       when Attribute_Model =>
3524          Check_Floating_Point_Type_1;
3525          Set_Etype (N, P_Base_Type);
3526          Resolve (E1, P_Base_Type);
3527
3528       ----------------
3529       -- Model_Emin --
3530       ----------------
3531
3532       when Attribute_Model_Emin =>
3533          Check_Floating_Point_Type_0;
3534          Set_Etype (N, Universal_Integer);
3535
3536       -------------------
3537       -- Model_Epsilon --
3538       -------------------
3539
3540       when Attribute_Model_Epsilon =>
3541          Check_Floating_Point_Type_0;
3542          Set_Etype (N, Universal_Real);
3543
3544       --------------------
3545       -- Model_Mantissa --
3546       --------------------
3547
3548       when Attribute_Model_Mantissa =>
3549          Check_Floating_Point_Type_0;
3550          Set_Etype (N, Universal_Integer);
3551
3552       -----------------
3553       -- Model_Small --
3554       -----------------
3555
3556       when Attribute_Model_Small =>
3557          Check_Floating_Point_Type_0;
3558          Set_Etype (N, Universal_Real);
3559
3560       -------------
3561       -- Modulus --
3562       -------------
3563
3564       when Attribute_Modulus =>
3565          Check_E0;
3566          Check_Modular_Integer_Type;
3567          Set_Etype (N, Universal_Integer);
3568
3569       --------------------
3570       -- Null_Parameter --
3571       --------------------
3572
3573       when Attribute_Null_Parameter => Null_Parameter : declare
3574          Parnt  : constant Node_Id := Parent (N);
3575          GParnt : constant Node_Id := Parent (Parnt);
3576
3577          procedure Bad_Null_Parameter (Msg : String);
3578          --  Used if bad Null parameter attribute node is found. Issues
3579          --  given error message, and also sets the type to Any_Type to
3580          --  avoid blowups later on from dealing with a junk node.
3581
3582          procedure Must_Be_Imported (Proc_Ent : Entity_Id);
3583          --  Called to check that Proc_Ent is imported subprogram
3584
3585          ------------------------
3586          -- Bad_Null_Parameter --
3587          ------------------------
3588
3589          procedure Bad_Null_Parameter (Msg : String) is
3590          begin
3591             Error_Msg_N (Msg, N);
3592             Set_Etype (N, Any_Type);
3593          end Bad_Null_Parameter;
3594
3595          ----------------------
3596          -- Must_Be_Imported --
3597          ----------------------
3598
3599          procedure Must_Be_Imported (Proc_Ent : Entity_Id) is
3600             Pent : constant Entity_Id := Ultimate_Alias (Proc_Ent);
3601
3602          begin
3603             --  Ignore check if procedure not frozen yet (we will get
3604             --  another chance when the default parameter is reanalyzed)
3605
3606             if not Is_Frozen (Pent) then
3607                return;
3608
3609             elsif not Is_Imported (Pent) then
3610                Bad_Null_Parameter
3611                  ("Null_Parameter can only be used with imported subprogram");
3612
3613             else
3614                return;
3615             end if;
3616          end Must_Be_Imported;
3617
3618       --  Start of processing for Null_Parameter
3619
3620       begin
3621          Check_Type;
3622          Check_E0;
3623          Set_Etype (N, P_Type);
3624
3625          --  Case of attribute used as default expression
3626
3627          if Nkind (Parnt) = N_Parameter_Specification then
3628             Must_Be_Imported (Defining_Entity (GParnt));
3629
3630          --  Case of attribute used as actual for subprogram (positional)
3631
3632          elsif Nkind_In (Parnt, N_Procedure_Call_Statement,
3633                                 N_Function_Call)
3634             and then Is_Entity_Name (Name (Parnt))
3635          then
3636             Must_Be_Imported (Entity (Name (Parnt)));
3637
3638          --  Case of attribute used as actual for subprogram (named)
3639
3640          elsif Nkind (Parnt) = N_Parameter_Association
3641            and then Nkind_In (GParnt, N_Procedure_Call_Statement,
3642                                       N_Function_Call)
3643            and then Is_Entity_Name (Name (GParnt))
3644          then
3645             Must_Be_Imported (Entity (Name (GParnt)));
3646
3647          --  Not an allowed case
3648
3649          else
3650             Bad_Null_Parameter
3651               ("Null_Parameter must be actual or default parameter");
3652          end if;
3653       end Null_Parameter;
3654
3655       -----------------
3656       -- Object_Size --
3657       -----------------
3658
3659       when Attribute_Object_Size =>
3660          Check_E0;
3661          Check_Type;
3662          Check_Not_Incomplete_Type;
3663          Set_Etype (N, Universal_Integer);
3664
3665       ---------
3666       -- Old --
3667       ---------
3668
3669       when Attribute_Old =>
3670
3671          --  The attribute reference is a primary. If expressions follow, the
3672          --  attribute reference is an indexable object, so rewrite the node
3673          --  accordingly.
3674
3675          if Present (E1) then
3676             Rewrite (N,
3677               Make_Indexed_Component (Loc,
3678                 Prefix      =>
3679                   Make_Attribute_Reference (Loc,
3680                     Prefix         => Relocate_Node (Prefix (N)),
3681                     Attribute_Name => Name_Old),
3682                 Expressions => Expressions (N)));
3683
3684             Analyze (N);
3685             return;
3686          end if;
3687
3688          Check_E0;
3689          Set_Etype (N, P_Type);
3690
3691          if No (Current_Subprogram) then
3692             Error_Attr ("attribute % can only appear within subprogram", N);
3693          end if;
3694
3695          if Is_Limited_Type (P_Type) then
3696             Error_Attr ("attribute % cannot apply to limited objects", P);
3697          end if;
3698
3699          if Is_Entity_Name (P)
3700            and then Is_Constant_Object (Entity (P))
3701          then
3702             Error_Msg_N
3703               ("?attribute Old applied to constant has no effect", P);
3704          end if;
3705
3706          --  Check that the expression does not refer to local entities
3707
3708          Check_Local : declare
3709             Subp : Entity_Id := Current_Subprogram;
3710
3711             function Process (N : Node_Id) return Traverse_Result;
3712             --  Check that N does not contain references to local variables or
3713             --  other local entities of Subp.
3714
3715             -------------
3716             -- Process --
3717             -------------
3718
3719             function Process (N : Node_Id) return Traverse_Result is
3720             begin
3721                if Is_Entity_Name (N)
3722                  and then Present (Entity (N))
3723                  and then not Is_Formal (Entity (N))
3724                  and then Enclosing_Subprogram (Entity (N)) = Subp
3725                then
3726                   Error_Msg_Node_1 := Entity (N);
3727                   Error_Attr
3728                     ("attribute % cannot refer to local variable&", N);
3729                end if;
3730
3731                return OK;
3732             end Process;
3733
3734             procedure Check_No_Local is new Traverse_Proc;
3735
3736          --  Start of processing for Check_Local
3737
3738          begin
3739             Check_No_Local (P);
3740
3741             if In_Parameter_Specification (P) then
3742
3743                --  We have additional restrictions on using 'Old in parameter
3744                --  specifications.
3745
3746                if Present (Enclosing_Subprogram (Current_Subprogram)) then
3747
3748                   --  Check that there is no reference to the enclosing
3749                   --  subprogram local variables. Otherwise, we might end up
3750                   --  being called from the enclosing subprogram and thus using
3751                   --  'Old on a local variable which is not defined at entry
3752                   --  time.
3753
3754                   Subp := Enclosing_Subprogram (Current_Subprogram);
3755                   Check_No_Local (P);
3756
3757                else
3758                   --  We must prevent default expression of library-level
3759                   --  subprogram from using 'Old, as the subprogram may be
3760                   --  used in elaboration code for which there is no enclosing
3761                   --  subprogram.
3762
3763                   Error_Attr
3764                     ("attribute % can only appear within subprogram", N);
3765                end if;
3766             end if;
3767          end Check_Local;
3768
3769       ------------
3770       -- Output --
3771       ------------
3772
3773       when Attribute_Output =>
3774          Check_E2;
3775          Check_Stream_Attribute (TSS_Stream_Output);
3776          Set_Etype (N, Standard_Void_Type);
3777          Resolve (N, Standard_Void_Type);
3778
3779       ------------------
3780       -- Partition_ID --
3781       ------------------
3782
3783       when Attribute_Partition_ID => Partition_Id :
3784       begin
3785          Check_E0;
3786
3787          if P_Type /= Any_Type then
3788             if not Is_Library_Level_Entity (Entity (P)) then
3789                Error_Attr_P
3790                  ("prefix of % attribute must be library-level entity");
3791
3792             --  The defining entity of prefix should not be declared inside a
3793             --  Pure unit. RM E.1(8). Is_Pure was set during declaration.
3794
3795             elsif Is_Entity_Name (P)
3796               and then Is_Pure (Entity (P))
3797             then
3798                Error_Attr_P ("prefix of% attribute must not be declared pure");
3799             end if;
3800          end if;
3801
3802          Set_Etype (N, Universal_Integer);
3803       end Partition_Id;
3804
3805       -------------------------
3806       -- Passed_By_Reference --
3807       -------------------------
3808
3809       when Attribute_Passed_By_Reference =>
3810          Check_E0;
3811          Check_Type;
3812          Set_Etype (N, Standard_Boolean);
3813
3814       ------------------
3815       -- Pool_Address --
3816       ------------------
3817
3818       when Attribute_Pool_Address =>
3819          Check_E0;
3820          Set_Etype (N, RTE (RE_Address));
3821
3822       ---------
3823       -- Pos --
3824       ---------
3825
3826       when Attribute_Pos =>
3827          Check_Discrete_Type;
3828          Check_E1;
3829          Resolve (E1, P_Base_Type);
3830          Set_Etype (N, Universal_Integer);
3831
3832       --------------
3833       -- Position --
3834       --------------
3835
3836       when Attribute_Position =>
3837          Check_Component;
3838          Set_Etype (N, Universal_Integer);
3839
3840       ----------
3841       -- Pred --
3842       ----------
3843
3844       when Attribute_Pred =>
3845          Check_Scalar_Type;
3846          Check_E1;
3847          Resolve (E1, P_Base_Type);
3848          Set_Etype (N, P_Base_Type);
3849
3850          --  Nothing to do for real type case
3851
3852          if Is_Real_Type (P_Type) then
3853             null;
3854
3855          --  If not modular type, test for overflow check required
3856
3857          else
3858             if not Is_Modular_Integer_Type (P_Type)
3859               and then not Range_Checks_Suppressed (P_Base_Type)
3860             then
3861                Enable_Range_Check (E1);
3862             end if;
3863          end if;
3864
3865       --------------
3866       -- Priority --
3867       --------------
3868
3869       --  Ada 2005 (AI-327): Dynamic ceiling priorities
3870
3871       when Attribute_Priority =>
3872          if Ada_Version < Ada_2005 then
3873             Error_Attr ("% attribute is allowed only in Ada 2005 mode", P);
3874          end if;
3875
3876          Check_E0;
3877
3878          --  The prefix must be a protected object (AARM D.5.2 (2/2))
3879
3880          Analyze (P);
3881
3882          if Is_Protected_Type (Etype (P))
3883            or else (Is_Access_Type (Etype (P))
3884                       and then Is_Protected_Type (Designated_Type (Etype (P))))
3885          then
3886             Resolve (P, Etype (P));
3887          else
3888             Error_Attr_P ("prefix of % attribute must be a protected object");
3889          end if;
3890
3891          Set_Etype (N, Standard_Integer);
3892
3893          --  Must be called from within a protected procedure or entry of the
3894          --  protected object.
3895
3896          declare
3897             S : Entity_Id;
3898
3899          begin
3900             S := Current_Scope;
3901             while S /= Etype (P)
3902                and then S /= Standard_Standard
3903             loop
3904                S := Scope (S);
3905             end loop;
3906
3907             if S = Standard_Standard then
3908                Error_Attr ("the attribute % is only allowed inside protected "
3909                            & "operations", P);
3910             end if;
3911          end;
3912
3913          Validate_Non_Static_Attribute_Function_Call;
3914
3915       -----------
3916       -- Range --
3917       -----------
3918
3919       when Attribute_Range =>
3920          Check_Array_Or_Scalar_Type;
3921          Bad_Attribute_For_Predicate;
3922
3923          if Ada_Version = Ada_83
3924            and then Is_Scalar_Type (P_Type)
3925            and then Comes_From_Source (N)
3926          then
3927             Error_Attr
3928               ("(Ada 83) % attribute not allowed for scalar type", P);
3929          end if;
3930
3931       ------------
3932       -- Result --
3933       ------------
3934
3935       when Attribute_Result => Result : declare
3936          CS : Entity_Id := Current_Scope;
3937          PS : Entity_Id := Scope (CS);
3938
3939       begin
3940          --  If the enclosing subprogram is always inlined, the enclosing
3941          --  postcondition will not be propagated to the expanded call.
3942
3943          if Has_Pragma_Inline_Always (PS)
3944            and then Warn_On_Redundant_Constructs
3945          then
3946             Error_Msg_N
3947               ("postconditions on inlined functions not enforced?", N);
3948          end if;
3949
3950          --  If we are in the scope of a function and in Spec_Expression mode,
3951          --  this is likely the prescan of the postcondition pragma, and we
3952          --  just set the proper type. If there is an error it will be caught
3953          --  when the real Analyze call is done.
3954
3955          if Ekind (CS) = E_Function
3956            and then In_Spec_Expression
3957          then
3958             --  Check OK prefix
3959
3960             if Chars (CS) /= Chars (P) then
3961                Error_Msg_NE
3962                  ("incorrect prefix for % attribute, expected &", P, CS);
3963                Error_Attr;
3964             end if;
3965
3966             Set_Etype (N, Etype (CS));
3967
3968             --  If several functions with that name are visible,
3969             --  the intended one is the current scope.
3970
3971             if Is_Overloaded (P) then
3972                Set_Entity (P, CS);
3973                Set_Is_Overloaded (P, False);
3974             end if;
3975
3976          --  Body case, where we must be inside a generated _Postcondition
3977          --  procedure, and the prefix must be on the scope stack, or else
3978          --  the attribute use is definitely misplaced. The condition itself
3979          --  may have generated transient scopes, and is not necessarily the
3980          --  current one.
3981
3982          else
3983             while Present (CS)
3984               and then CS /= Standard_Standard
3985             loop
3986                if Chars (CS) = Name_uPostconditions then
3987                   exit;
3988                else
3989                   CS := Scope (CS);
3990                end if;
3991             end loop;
3992
3993             PS := Scope (CS);
3994
3995             if Chars (CS) = Name_uPostconditions
3996               and then Ekind (PS) = E_Function
3997             then
3998                --  Check OK prefix
3999
4000                if Nkind_In (P, N_Identifier, N_Operator_Symbol)
4001                  and then Chars (P) = Chars (PS)
4002                then
4003                   null;
4004
4005                --  Within an instance, the prefix designates the local renaming
4006                --  of the original generic.
4007
4008                elsif Is_Entity_Name (P)
4009                  and then Ekind (Entity (P)) = E_Function
4010                  and then Present (Alias (Entity (P)))
4011                  and then Chars (Alias (Entity (P))) = Chars (PS)
4012                then
4013                   null;
4014
4015                else
4016                   Error_Msg_NE
4017                     ("incorrect prefix for % attribute, expected &", P, PS);
4018                   Error_Attr;
4019                end if;
4020
4021                Rewrite (N, Make_Identifier (Sloc (N), Name_uResult));
4022                Analyze_And_Resolve (N, Etype (PS));
4023
4024             else
4025                Error_Attr
4026                  ("% attribute can only appear" &
4027                    "  in function Postcondition pragma", P);
4028             end if;
4029          end if;
4030       end Result;
4031
4032       ------------------
4033       -- Range_Length --
4034       ------------------
4035
4036       when Attribute_Range_Length =>
4037          Check_E0;
4038          Check_Discrete_Type;
4039          Set_Etype (N, Universal_Integer);
4040
4041       ----------
4042       -- Read --
4043       ----------
4044
4045       when Attribute_Read =>
4046          Check_E2;
4047          Check_Stream_Attribute (TSS_Stream_Read);
4048          Set_Etype (N, Standard_Void_Type);
4049          Resolve (N, Standard_Void_Type);
4050          Note_Possible_Modification (E2, Sure => True);
4051
4052       ---------
4053       -- Ref --
4054       ---------
4055
4056       when Attribute_Ref =>
4057          Check_E1;
4058          Analyze (P);
4059
4060          if Nkind (P) /= N_Expanded_Name
4061            or else not Is_RTE (P_Type, RE_Address)
4062          then
4063             Error_Attr_P ("prefix of % attribute must be System.Address");
4064          end if;
4065
4066          Analyze_And_Resolve (E1, Any_Integer);
4067          Set_Etype (N, RTE (RE_Address));
4068
4069       ---------------
4070       -- Remainder --
4071       ---------------
4072
4073       when Attribute_Remainder =>
4074          Check_Floating_Point_Type_2;
4075          Set_Etype (N, P_Base_Type);
4076          Resolve (E1, P_Base_Type);
4077          Resolve (E2, P_Base_Type);
4078
4079       -----------
4080       -- Round --
4081       -----------
4082
4083       when Attribute_Round =>
4084          Check_E1;
4085          Check_Decimal_Fixed_Point_Type;
4086          Set_Etype (N, P_Base_Type);
4087
4088          --  Because the context is universal_real (3.5.10(12)) it is a legal
4089          --  context for a universal fixed expression. This is the only
4090          --  attribute whose functional description involves U_R.
4091
4092          if Etype (E1) = Universal_Fixed then
4093             declare
4094                Conv : constant Node_Id := Make_Type_Conversion (Loc,
4095                   Subtype_Mark => New_Occurrence_Of (Universal_Real, Loc),
4096                   Expression   => Relocate_Node (E1));
4097
4098             begin
4099                Rewrite (E1, Conv);
4100                Analyze (E1);
4101             end;
4102          end if;
4103
4104          Resolve (E1, Any_Real);
4105
4106       --------------
4107       -- Rounding --
4108       --------------
4109
4110       when Attribute_Rounding =>
4111          Check_Floating_Point_Type_1;
4112          Set_Etype (N, P_Base_Type);
4113          Resolve (E1, P_Base_Type);
4114
4115       ---------------
4116       -- Safe_Emax --
4117       ---------------
4118
4119       when Attribute_Safe_Emax =>
4120          Check_Floating_Point_Type_0;
4121          Set_Etype (N, Universal_Integer);
4122
4123       ----------------
4124       -- Safe_First --
4125       ----------------
4126
4127       when Attribute_Safe_First =>
4128          Check_Floating_Point_Type_0;
4129          Set_Etype (N, Universal_Real);
4130
4131       ----------------
4132       -- Safe_Large --
4133       ----------------
4134
4135       when Attribute_Safe_Large =>
4136          Check_E0;
4137          Check_Real_Type;
4138          Set_Etype (N, Universal_Real);
4139
4140       ---------------
4141       -- Safe_Last --
4142       ---------------
4143
4144       when Attribute_Safe_Last =>
4145          Check_Floating_Point_Type_0;
4146          Set_Etype (N, Universal_Real);
4147
4148       ----------------
4149       -- Safe_Small --
4150       ----------------
4151
4152       when Attribute_Safe_Small =>
4153          Check_E0;
4154          Check_Real_Type;
4155          Set_Etype (N, Universal_Real);
4156
4157       -----------
4158       -- Scale --
4159       -----------
4160
4161       when Attribute_Scale =>
4162          Check_E0;
4163          Check_Decimal_Fixed_Point_Type;
4164          Set_Etype (N, Universal_Integer);
4165
4166       -------------
4167       -- Scaling --
4168       -------------
4169
4170       when Attribute_Scaling =>
4171          Check_Floating_Point_Type_2;
4172          Set_Etype (N, P_Base_Type);
4173          Resolve (E1, P_Base_Type);
4174
4175       ------------------
4176       -- Signed_Zeros --
4177       ------------------
4178
4179       when Attribute_Signed_Zeros =>
4180          Check_Floating_Point_Type_0;
4181          Set_Etype (N, Standard_Boolean);
4182
4183       ----------
4184       -- Size --
4185       ----------
4186
4187       when Attribute_Size | Attribute_VADS_Size => Size :
4188       begin
4189          Check_E0;
4190
4191          --  If prefix is parameterless function call, rewrite and resolve
4192          --  as such.
4193
4194          if Is_Entity_Name (P)
4195            and then Ekind (Entity (P)) = E_Function
4196          then
4197             Resolve (P);
4198
4199          --  Similar processing for a protected function call
4200
4201          elsif Nkind (P) = N_Selected_Component
4202            and then Ekind (Entity (Selector_Name (P))) = E_Function
4203          then
4204             Resolve (P);
4205          end if;
4206
4207          if Is_Object_Reference (P) then
4208             Check_Object_Reference (P);
4209
4210          elsif Is_Entity_Name (P)
4211            and then (Is_Type (Entity (P))
4212                        or else Ekind (Entity (P)) = E_Enumeration_Literal)
4213          then
4214             null;
4215
4216          elsif Nkind (P) = N_Type_Conversion
4217            and then not Comes_From_Source (P)
4218          then
4219             null;
4220
4221          else
4222             Error_Attr_P ("invalid prefix for % attribute");
4223          end if;
4224
4225          Check_Not_Incomplete_Type;
4226          Check_Not_CPP_Type;
4227          Set_Etype (N, Universal_Integer);
4228       end Size;
4229
4230       -----------
4231       -- Small --
4232       -----------
4233
4234       when Attribute_Small =>
4235          Check_E0;
4236          Check_Real_Type;
4237          Set_Etype (N, Universal_Real);
4238
4239       ------------------
4240       -- Storage_Pool --
4241       ------------------
4242
4243       when Attribute_Storage_Pool => Storage_Pool :
4244       begin
4245          Check_E0;
4246
4247          if Is_Access_Type (P_Type) then
4248             if Ekind (P_Type) = E_Access_Subprogram_Type then
4249                Error_Attr_P
4250                  ("cannot use % attribute for access-to-subprogram type");
4251             end if;
4252
4253             --  Set appropriate entity
4254
4255             if Present (Associated_Storage_Pool (Root_Type (P_Type))) then
4256                Set_Entity (N, Associated_Storage_Pool (Root_Type (P_Type)));
4257             else
4258                Set_Entity (N, RTE (RE_Global_Pool_Object));
4259             end if;
4260
4261             Set_Etype (N, Class_Wide_Type (RTE (RE_Root_Storage_Pool)));
4262
4263             --  Validate_Remote_Access_To_Class_Wide_Type for attribute
4264             --  Storage_Pool since this attribute is not defined for such
4265             --  types (RM E.2.3(22)).
4266
4267             Validate_Remote_Access_To_Class_Wide_Type (N);
4268
4269          else
4270             Error_Attr_P ("prefix of % attribute must be access type");
4271          end if;
4272       end Storage_Pool;
4273
4274       ------------------
4275       -- Storage_Size --
4276       ------------------
4277
4278       when Attribute_Storage_Size => Storage_Size :
4279       begin
4280          Check_E0;
4281
4282          if Is_Task_Type (P_Type) then
4283             Set_Etype (N, Universal_Integer);
4284
4285             --  Use with tasks is an obsolescent feature
4286
4287             Check_Restriction (No_Obsolescent_Features, P);
4288
4289          elsif Is_Access_Type (P_Type) then
4290             if Ekind (P_Type) = E_Access_Subprogram_Type then
4291                Error_Attr_P
4292                  ("cannot use % attribute for access-to-subprogram type");
4293             end if;
4294
4295             if Is_Entity_Name (P)
4296               and then Is_Type (Entity (P))
4297             then
4298                Check_Type;
4299                Set_Etype (N, Universal_Integer);
4300
4301                --   Validate_Remote_Access_To_Class_Wide_Type for attribute
4302                --   Storage_Size since this attribute is not defined for
4303                --   such types (RM E.2.3(22)).
4304
4305                Validate_Remote_Access_To_Class_Wide_Type (N);
4306
4307             --  The prefix is allowed to be an implicit dereference
4308             --  of an access value designating a task.
4309
4310             else
4311                Check_Task_Prefix;
4312                Set_Etype (N, Universal_Integer);
4313             end if;
4314
4315          else
4316             Error_Attr_P ("prefix of % attribute must be access or task type");
4317          end if;
4318       end Storage_Size;
4319
4320       ------------------
4321       -- Storage_Unit --
4322       ------------------
4323
4324       when Attribute_Storage_Unit =>
4325          Standard_Attribute (Ttypes.System_Storage_Unit);
4326
4327       -----------------
4328       -- Stream_Size --
4329       -----------------
4330
4331       when Attribute_Stream_Size =>
4332          Check_E0;
4333          Check_Type;
4334
4335          if Is_Entity_Name (P)
4336            and then Is_Elementary_Type (Entity (P))
4337          then
4338             Set_Etype (N, Universal_Integer);
4339          else
4340             Error_Attr_P ("invalid prefix for % attribute");
4341          end if;
4342
4343       ---------------
4344       -- Stub_Type --
4345       ---------------
4346
4347       when Attribute_Stub_Type =>
4348          Check_Type;
4349          Check_E0;
4350
4351          if Is_Remote_Access_To_Class_Wide_Type (P_Type) then
4352             Rewrite (N,
4353               New_Occurrence_Of (Corresponding_Stub_Type (P_Type), Loc));
4354          else
4355             Error_Attr_P
4356               ("prefix of% attribute must be remote access to classwide");
4357          end if;
4358
4359       ----------
4360       -- Succ --
4361       ----------
4362
4363       when Attribute_Succ =>
4364          Check_Scalar_Type;
4365          Check_E1;
4366          Resolve (E1, P_Base_Type);
4367          Set_Etype (N, P_Base_Type);
4368
4369          --  Nothing to do for real type case
4370
4371          if Is_Real_Type (P_Type) then
4372             null;
4373
4374          --  If not modular type, test for overflow check required
4375
4376          else
4377             if not Is_Modular_Integer_Type (P_Type)
4378               and then not Range_Checks_Suppressed (P_Base_Type)
4379             then
4380                Enable_Range_Check (E1);
4381             end if;
4382          end if;
4383
4384       ---------
4385       -- Tag --
4386       ---------
4387
4388       when Attribute_Tag => Tag :
4389       begin
4390          Check_E0;
4391          Check_Dereference;
4392
4393          if not Is_Tagged_Type (P_Type) then
4394             Error_Attr_P ("prefix of % attribute must be tagged");
4395
4396          --  Next test does not apply to generated code
4397          --  why not, and what does the illegal reference mean???
4398
4399          elsif Is_Object_Reference (P)
4400            and then not Is_Class_Wide_Type (P_Type)
4401            and then Comes_From_Source (N)
4402          then
4403             Error_Attr_P
4404               ("% attribute can only be applied to objects " &
4405                "of class - wide type");
4406          end if;
4407
4408          --  The prefix cannot be an incomplete type. However, references
4409          --  to 'Tag can be generated when expanding interface conversions,
4410          --  and this is legal.
4411
4412          if Comes_From_Source (N) then
4413             Check_Not_Incomplete_Type;
4414          end if;
4415
4416          --  Set appropriate type
4417
4418          Set_Etype (N, RTE (RE_Tag));
4419       end Tag;
4420
4421       -----------------
4422       -- Target_Name --
4423       -----------------
4424
4425       when Attribute_Target_Name => Target_Name : declare
4426          TN : constant String := Sdefault.Target_Name.all;
4427          TL : Natural;
4428
4429       begin
4430          Check_Standard_Prefix;
4431
4432          TL := TN'Last;
4433
4434          if TN (TL) = '/' or else TN (TL) = '\' then
4435             TL := TL - 1;
4436          end if;
4437
4438          Rewrite (N,
4439            Make_String_Literal (Loc,
4440              Strval => TN (TN'First .. TL)));
4441          Analyze_And_Resolve (N, Standard_String);
4442       end Target_Name;
4443
4444       ----------------
4445       -- Terminated --
4446       ----------------
4447
4448       when Attribute_Terminated =>
4449          Check_E0;
4450          Set_Etype (N, Standard_Boolean);
4451          Check_Task_Prefix;
4452
4453       ----------------
4454       -- To_Address --
4455       ----------------
4456
4457       when Attribute_To_Address =>
4458          Check_E1;
4459          Analyze (P);
4460
4461          if Nkind (P) /= N_Identifier
4462            or else Chars (P) /= Name_System
4463          then
4464             Error_Attr_P ("prefix of % attribute must be System");
4465          end if;
4466
4467          Generate_Reference (RTE (RE_Address), P);
4468          Analyze_And_Resolve (E1, Any_Integer);
4469          Set_Etype (N, RTE (RE_Address));
4470
4471       ------------
4472       -- To_Any --
4473       ------------
4474
4475       when Attribute_To_Any =>
4476          Check_E1;
4477          Check_PolyORB_Attribute;
4478          Set_Etype (N, RTE (RE_Any));
4479
4480       ----------------
4481       -- Truncation --
4482       ----------------
4483
4484       when Attribute_Truncation =>
4485          Check_Floating_Point_Type_1;
4486          Resolve (E1, P_Base_Type);
4487          Set_Etype (N, P_Base_Type);
4488
4489       ----------------
4490       -- Type_Class --
4491       ----------------
4492
4493       when Attribute_Type_Class =>
4494          Check_E0;
4495          Check_Type;
4496          Check_Not_Incomplete_Type;
4497          Set_Etype (N, RTE (RE_Type_Class));
4498
4499       --------------
4500       -- TypeCode --
4501       --------------
4502
4503       when Attribute_TypeCode =>
4504          Check_E0;
4505          Check_PolyORB_Attribute;
4506          Set_Etype (N, RTE (RE_TypeCode));
4507
4508       --------------
4509       -- Type_Key --
4510       --------------
4511
4512       when Attribute_Type_Key =>
4513          Check_E0;
4514          Check_Type;
4515
4516          --  This processing belongs in Eval_Attribute ???
4517
4518          declare
4519             function Type_Key return String_Id;
4520             --  A very preliminary implementation. For now, a signature
4521             --  consists of only the type name. This is clearly incomplete
4522             --  (e.g., adding a new field to a record type should change the
4523             --  type's Type_Key attribute).
4524
4525             --------------
4526             -- Type_Key --
4527             --------------
4528
4529             function Type_Key return String_Id is
4530                Full_Name : constant String_Id :=
4531                              Fully_Qualified_Name_String (Entity (P));
4532
4533             begin
4534                --  Copy all characters in Full_Name but the trailing NUL
4535
4536                Start_String;
4537                for J in 1 .. String_Length (Full_Name) - 1 loop
4538                   Store_String_Char (Get_String_Char (Full_Name, Int (J)));
4539                end loop;
4540
4541                Store_String_Chars ("'Type_Key");
4542                return End_String;
4543             end Type_Key;
4544
4545          begin
4546             Rewrite (N, Make_String_Literal (Loc, Type_Key));
4547          end;
4548
4549          Analyze_And_Resolve (N, Standard_String);
4550
4551       -----------------
4552       -- UET_Address --
4553       -----------------
4554
4555       when Attribute_UET_Address =>
4556          Check_E0;
4557          Check_Unit_Name (P);
4558          Set_Etype (N, RTE (RE_Address));
4559
4560       -----------------------
4561       -- Unbiased_Rounding --
4562       -----------------------
4563
4564       when Attribute_Unbiased_Rounding =>
4565          Check_Floating_Point_Type_1;
4566          Set_Etype (N, P_Base_Type);
4567          Resolve (E1, P_Base_Type);
4568
4569       ----------------------
4570       -- Unchecked_Access --
4571       ----------------------
4572
4573       when Attribute_Unchecked_Access =>
4574          if Comes_From_Source (N) then
4575             Check_Restriction (No_Unchecked_Access, N);
4576          end if;
4577
4578          Analyze_Access_Attribute;
4579
4580       -------------------------
4581       -- Unconstrained_Array --
4582       -------------------------
4583
4584       when Attribute_Unconstrained_Array =>
4585          Check_E0;
4586          Check_Type;
4587          Check_Not_Incomplete_Type;
4588          Set_Etype (N, Standard_Boolean);
4589
4590       ------------------------------
4591       -- Universal_Literal_String --
4592       ------------------------------
4593
4594       --  This is a GNAT specific attribute whose prefix must be a named
4595       --  number where the expression is either a single numeric literal,
4596       --  or a numeric literal immediately preceded by a minus sign. The
4597       --  result is equivalent to a string literal containing the text of
4598       --  the literal as it appeared in the source program with a possible
4599       --  leading minus sign.
4600
4601       when Attribute_Universal_Literal_String => Universal_Literal_String :
4602       begin
4603          Check_E0;
4604
4605          if not Is_Entity_Name (P)
4606            or else Ekind (Entity (P)) not in Named_Kind
4607          then
4608             Error_Attr_P ("prefix for % attribute must be named number");
4609
4610          else
4611             declare
4612                Expr     : Node_Id;
4613                Negative : Boolean;
4614                S        : Source_Ptr;
4615                Src      : Source_Buffer_Ptr;
4616
4617             begin
4618                Expr := Original_Node (Expression (Parent (Entity (P))));
4619
4620                if Nkind (Expr) = N_Op_Minus then
4621                   Negative := True;
4622                   Expr := Original_Node (Right_Opnd (Expr));
4623                else
4624                   Negative := False;
4625                end if;
4626
4627                if not Nkind_In (Expr, N_Integer_Literal, N_Real_Literal) then
4628                   Error_Attr
4629                     ("named number for % attribute must be simple literal", N);
4630                end if;
4631
4632                --  Build string literal corresponding to source literal text
4633
4634                Start_String;
4635
4636                if Negative then
4637                   Store_String_Char (Get_Char_Code ('-'));
4638                end if;
4639
4640                S := Sloc (Expr);
4641                Src := Source_Text (Get_Source_File_Index (S));
4642
4643                while Src (S) /= ';' and then Src (S) /= ' ' loop
4644                   Store_String_Char (Get_Char_Code (Src (S)));
4645                   S := S + 1;
4646                end loop;
4647
4648                --  Now we rewrite the attribute with the string literal
4649
4650                Rewrite (N,
4651                  Make_String_Literal (Loc, End_String));
4652                Analyze (N);
4653             end;
4654          end if;
4655       end Universal_Literal_String;
4656
4657       -------------------------
4658       -- Unrestricted_Access --
4659       -------------------------
4660
4661       --  This is a GNAT specific attribute which is like Access except that
4662       --  all scope checks and checks for aliased views are omitted.
4663
4664       when Attribute_Unrestricted_Access =>
4665          if Comes_From_Source (N) then
4666             Check_Restriction (No_Unchecked_Access, N);
4667          end if;
4668
4669          if Is_Entity_Name (P) then
4670             Set_Address_Taken (Entity (P));
4671          end if;
4672
4673          Analyze_Access_Attribute;
4674
4675       ---------
4676       -- Val --
4677       ---------
4678
4679       when Attribute_Val => Val : declare
4680       begin
4681          Check_E1;
4682          Check_Discrete_Type;
4683          Resolve (E1, Any_Integer);
4684          Set_Etype (N, P_Base_Type);
4685
4686          --  Note, we need a range check in general, but we wait for the
4687          --  Resolve call to do this, since we want to let Eval_Attribute
4688          --  have a chance to find an static illegality first!
4689       end Val;
4690
4691       -----------
4692       -- Valid --
4693       -----------
4694
4695       when Attribute_Valid =>
4696          Check_E0;
4697
4698          --  Ignore check for object if we have a 'Valid reference generated
4699          --  by the expanded code, since in some cases valid checks can occur
4700          --  on items that are names, but are not objects (e.g. attributes).
4701
4702          if Comes_From_Source (N) then
4703             Check_Object_Reference (P);
4704          end if;
4705
4706          if not Is_Scalar_Type (P_Type) then
4707             Error_Attr_P ("object for % attribute must be of scalar type");
4708          end if;
4709
4710          Set_Etype (N, Standard_Boolean);
4711
4712       -----------
4713       -- Value --
4714       -----------
4715
4716       when Attribute_Value => Value :
4717       begin
4718          Check_E1;
4719          Check_Scalar_Type;
4720
4721          --  Case of enumeration type
4722
4723          if Is_Enumeration_Type (P_Type) then
4724             Check_Restriction (No_Enumeration_Maps, N);
4725
4726             --  Mark all enumeration literals as referenced, since the use of
4727             --  the Value attribute can implicitly reference any of the
4728             --  literals of the enumeration base type.
4729
4730             declare
4731                Ent : Entity_Id := First_Literal (P_Base_Type);
4732             begin
4733                while Present (Ent) loop
4734                   Set_Referenced (Ent);
4735                   Next_Literal (Ent);
4736                end loop;
4737             end;
4738          end if;
4739
4740          --  Set Etype before resolving expression because expansion of
4741          --  expression may require enclosing type. Note that the type
4742          --  returned by 'Value is the base type of the prefix type.
4743
4744          Set_Etype (N, P_Base_Type);
4745          Validate_Non_Static_Attribute_Function_Call;
4746       end Value;
4747
4748       ----------------
4749       -- Value_Size --
4750       ----------------
4751
4752       when Attribute_Value_Size =>
4753          Check_E0;
4754          Check_Type;
4755          Check_Not_Incomplete_Type;
4756          Set_Etype (N, Universal_Integer);
4757
4758       -------------
4759       -- Version --
4760       -------------
4761
4762       when Attribute_Version =>
4763          Check_E0;
4764          Check_Program_Unit;
4765          Set_Etype (N, RTE (RE_Version_String));
4766
4767       ------------------
4768       -- Wchar_T_Size --
4769       ------------------
4770
4771       when Attribute_Wchar_T_Size =>
4772          Standard_Attribute (Interfaces_Wchar_T_Size);
4773
4774       ----------------
4775       -- Wide_Image --
4776       ----------------
4777
4778       when Attribute_Wide_Image => Wide_Image :
4779       begin
4780          Check_Scalar_Type;
4781          Set_Etype (N, Standard_Wide_String);
4782          Check_E1;
4783          Resolve (E1, P_Base_Type);
4784          Validate_Non_Static_Attribute_Function_Call;
4785       end Wide_Image;
4786
4787       ---------------------
4788       -- Wide_Wide_Image --
4789       ---------------------
4790
4791       when Attribute_Wide_Wide_Image => Wide_Wide_Image :
4792       begin
4793          Check_Scalar_Type;
4794          Set_Etype (N, Standard_Wide_Wide_String);
4795          Check_E1;
4796          Resolve (E1, P_Base_Type);
4797          Validate_Non_Static_Attribute_Function_Call;
4798       end Wide_Wide_Image;
4799
4800       ----------------
4801       -- Wide_Value --
4802       ----------------
4803
4804       when Attribute_Wide_Value => Wide_Value :
4805       begin
4806          Check_E1;
4807          Check_Scalar_Type;
4808
4809          --  Set Etype before resolving expression because expansion
4810          --  of expression may require enclosing type.
4811
4812          Set_Etype (N, P_Type);
4813          Validate_Non_Static_Attribute_Function_Call;
4814       end Wide_Value;
4815
4816       ---------------------
4817       -- Wide_Wide_Value --
4818       ---------------------
4819
4820       when Attribute_Wide_Wide_Value => Wide_Wide_Value :
4821       begin
4822          Check_E1;
4823          Check_Scalar_Type;
4824
4825          --  Set Etype before resolving expression because expansion
4826          --  of expression may require enclosing type.
4827
4828          Set_Etype (N, P_Type);
4829          Validate_Non_Static_Attribute_Function_Call;
4830       end Wide_Wide_Value;
4831
4832       ---------------------
4833       -- Wide_Wide_Width --
4834       ---------------------
4835
4836       when Attribute_Wide_Wide_Width =>
4837          Check_E0;
4838          Check_Scalar_Type;
4839          Set_Etype (N, Universal_Integer);
4840
4841       ----------------
4842       -- Wide_Width --
4843       ----------------
4844
4845       when Attribute_Wide_Width =>
4846          Check_E0;
4847          Check_Scalar_Type;
4848          Set_Etype (N, Universal_Integer);
4849
4850       -----------
4851       -- Width --
4852       -----------
4853
4854       when Attribute_Width =>
4855          Check_E0;
4856          Check_Scalar_Type;
4857          Set_Etype (N, Universal_Integer);
4858
4859       ---------------
4860       -- Word_Size --
4861       ---------------
4862
4863       when Attribute_Word_Size =>
4864          Standard_Attribute (System_Word_Size);
4865
4866       -----------
4867       -- Write --
4868       -----------
4869
4870       when Attribute_Write =>
4871          Check_E2;
4872          Check_Stream_Attribute (TSS_Stream_Write);
4873          Set_Etype (N, Standard_Void_Type);
4874          Resolve (N, Standard_Void_Type);
4875
4876       end case;
4877
4878    --  All errors raise Bad_Attribute, so that we get out before any further
4879    --  damage occurs when an error is detected (for example, if we check for
4880    --  one attribute expression, and the check succeeds, we want to be able
4881    --  to proceed securely assuming that an expression is in fact present.
4882
4883    --  Note: we set the attribute analyzed in this case to prevent any
4884    --  attempt at reanalysis which could generate spurious error msgs.
4885
4886    exception
4887       when Bad_Attribute =>
4888          Set_Analyzed (N);
4889          Set_Etype (N, Any_Type);
4890          return;
4891    end Analyze_Attribute;
4892
4893    --------------------
4894    -- Eval_Attribute --
4895    --------------------
4896
4897    procedure Eval_Attribute (N : Node_Id) is
4898       Loc   : constant Source_Ptr   := Sloc (N);
4899       Aname : constant Name_Id      := Attribute_Name (N);
4900       Id    : constant Attribute_Id := Get_Attribute_Id (Aname);
4901       P     : constant Node_Id      := Prefix (N);
4902
4903       C_Type : constant Entity_Id := Etype (N);
4904       --  The type imposed by the context
4905
4906       E1 : Node_Id;
4907       --  First expression, or Empty if none
4908
4909       E2 : Node_Id;
4910       --  Second expression, or Empty if none
4911
4912       P_Entity : Entity_Id;
4913       --  Entity denoted by prefix
4914
4915       P_Type : Entity_Id;
4916       --  The type of the prefix
4917
4918       P_Base_Type : Entity_Id;
4919       --  The base type of the prefix type
4920
4921       P_Root_Type : Entity_Id;
4922       --  The root type of the prefix type
4923
4924       Static : Boolean;
4925       --  True if the result is Static. This is set by the general processing
4926       --  to true if the prefix is static, and all expressions are static. It
4927       --  can be reset as processing continues for particular attributes
4928
4929       Lo_Bound, Hi_Bound : Node_Id;
4930       --  Expressions for low and high bounds of type or array index referenced
4931       --  by First, Last, or Length attribute for array, set by Set_Bounds.
4932
4933       CE_Node : Node_Id;
4934       --  Constraint error node used if we have an attribute reference has
4935       --  an argument that raises a constraint error. In this case we replace
4936       --  the attribute with a raise constraint_error node. This is important
4937       --  processing, since otherwise gigi might see an attribute which it is
4938       --  unprepared to deal with.
4939
4940       procedure Check_Concurrent_Discriminant (Bound : Node_Id);
4941       --  If Bound is a reference to a discriminant of a task or protected type
4942       --  occurring within the object's body, rewrite attribute reference into
4943       --  a reference to the corresponding discriminal. Use for the expansion
4944       --  of checks against bounds of entry family index subtypes.
4945
4946       procedure Check_Expressions;
4947       --  In case where the attribute is not foldable, the expressions, if
4948       --  any, of the attribute, are in a non-static context. This procedure
4949       --  performs the required additional checks.
4950
4951       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean;
4952       --  Determines if the given type has compile time known bounds. Note
4953       --  that we enter the case statement even in cases where the prefix
4954       --  type does NOT have known bounds, so it is important to guard any
4955       --  attempt to evaluate both bounds with a call to this function.
4956
4957       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint);
4958       --  This procedure is called when the attribute N has a non-static
4959       --  but compile time known value given by Val. It includes the
4960       --  necessary checks for out of range values.
4961
4962       function Fore_Value return Nat;
4963       --  Computes the Fore value for the current attribute prefix, which is
4964       --  known to be a static fixed-point type. Used by Fore and Width.
4965
4966       function Mantissa return Uint;
4967       --  Returns the Mantissa value for the prefix type
4968
4969       procedure Set_Bounds;
4970       --  Used for First, Last and Length attributes applied to an array or
4971       --  array subtype. Sets the variables Lo_Bound and Hi_Bound to the low
4972       --  and high bound expressions for the index referenced by the attribute
4973       --  designator (i.e. the first index if no expression is present, and
4974       --  the N'th index if the value N is present as an expression). Also
4975       --  used for First and Last of scalar types. Static is reset to False
4976       --  if the type or index type is not statically constrained.
4977
4978       function Statically_Denotes_Entity (N : Node_Id) return Boolean;
4979       --  Verify that the prefix of a potentially static array attribute
4980       --  satisfies the conditions of 4.9 (14).
4981
4982       -----------------------------------
4983       -- Check_Concurrent_Discriminant --
4984       -----------------------------------
4985
4986       procedure Check_Concurrent_Discriminant (Bound : Node_Id) is
4987          Tsk : Entity_Id;
4988          --  The concurrent (task or protected) type
4989
4990       begin
4991          if Nkind (Bound) = N_Identifier
4992            and then Ekind (Entity (Bound)) = E_Discriminant
4993            and then Is_Concurrent_Record_Type (Scope (Entity (Bound)))
4994          then
4995             Tsk := Corresponding_Concurrent_Type (Scope (Entity (Bound)));
4996
4997             if In_Open_Scopes (Tsk) and then Has_Completion (Tsk) then
4998
4999                --  Find discriminant of original concurrent type, and use
5000                --  its current discriminal, which is the renaming within
5001                --  the task/protected body.
5002
5003                Rewrite (N,
5004                  New_Occurrence_Of
5005                    (Find_Body_Discriminal (Entity (Bound)), Loc));
5006             end if;
5007          end if;
5008       end Check_Concurrent_Discriminant;
5009
5010       -----------------------
5011       -- Check_Expressions --
5012       -----------------------
5013
5014       procedure Check_Expressions is
5015          E : Node_Id;
5016       begin
5017          E := E1;
5018          while Present (E) loop
5019             Check_Non_Static_Context (E);
5020             Next (E);
5021          end loop;
5022       end Check_Expressions;
5023
5024       ----------------------------------
5025       -- Compile_Time_Known_Attribute --
5026       ----------------------------------
5027
5028       procedure Compile_Time_Known_Attribute (N : Node_Id; Val : Uint) is
5029          T : constant Entity_Id := Etype (N);
5030
5031       begin
5032          Fold_Uint (N, Val, False);
5033
5034          --  Check that result is in bounds of the type if it is static
5035
5036          if Is_In_Range (N, T, Assume_Valid => False) then
5037             null;
5038
5039          elsif Is_Out_Of_Range (N, T) then
5040             Apply_Compile_Time_Constraint_Error
5041               (N, "value not in range of}?", CE_Range_Check_Failed);
5042
5043          elsif not Range_Checks_Suppressed (T) then
5044             Enable_Range_Check (N);
5045
5046          else
5047             Set_Do_Range_Check (N, False);
5048          end if;
5049       end Compile_Time_Known_Attribute;
5050
5051       -------------------------------
5052       -- Compile_Time_Known_Bounds --
5053       -------------------------------
5054
5055       function Compile_Time_Known_Bounds (Typ : Entity_Id) return Boolean is
5056       begin
5057          return
5058            Compile_Time_Known_Value (Type_Low_Bound (Typ))
5059              and then
5060            Compile_Time_Known_Value (Type_High_Bound (Typ));
5061       end Compile_Time_Known_Bounds;
5062
5063       ----------------
5064       -- Fore_Value --
5065       ----------------
5066
5067       --  Note that the Fore calculation is based on the actual values
5068       --  of the bounds, and does not take into account possible rounding.
5069
5070       function Fore_Value return Nat is
5071          Lo      : constant Uint  := Expr_Value (Type_Low_Bound (P_Type));
5072          Hi      : constant Uint  := Expr_Value (Type_High_Bound (P_Type));
5073          Small   : constant Ureal := Small_Value (P_Type);
5074          Lo_Real : constant Ureal := Lo * Small;
5075          Hi_Real : constant Ureal := Hi * Small;
5076          T       : Ureal;
5077          R       : Nat;
5078
5079       begin
5080          --  Bounds are given in terms of small units, so first compute
5081          --  proper values as reals.
5082
5083          T := UR_Max (abs Lo_Real, abs Hi_Real);
5084          R := 2;
5085
5086          --  Loop to compute proper value if more than one digit required
5087
5088          while T >= Ureal_10 loop
5089             R := R + 1;
5090             T := T / Ureal_10;
5091          end loop;
5092
5093          return R;
5094       end Fore_Value;
5095
5096       --------------
5097       -- Mantissa --
5098       --------------
5099
5100       --  Table of mantissa values accessed by function  Computed using
5101       --  the relation:
5102
5103       --    T'Mantissa = integer next above (D * log(10)/log(2)) + 1)
5104
5105       --  where D is T'Digits (RM83 3.5.7)
5106
5107       Mantissa_Value : constant array (Nat range 1 .. 40) of Nat := (
5108           1 =>   5,
5109           2 =>   8,
5110           3 =>  11,
5111           4 =>  15,
5112           5 =>  18,
5113           6 =>  21,
5114           7 =>  25,
5115           8 =>  28,
5116           9 =>  31,
5117          10 =>  35,
5118          11 =>  38,
5119          12 =>  41,
5120          13 =>  45,
5121          14 =>  48,
5122          15 =>  51,
5123          16 =>  55,
5124          17 =>  58,
5125          18 =>  61,
5126          19 =>  65,
5127          20 =>  68,
5128          21 =>  71,
5129          22 =>  75,
5130          23 =>  78,
5131          24 =>  81,
5132          25 =>  85,
5133          26 =>  88,
5134          27 =>  91,
5135          28 =>  95,
5136          29 =>  98,
5137          30 => 101,
5138          31 => 104,
5139          32 => 108,
5140          33 => 111,
5141          34 => 114,
5142          35 => 118,
5143          36 => 121,
5144          37 => 124,
5145          38 => 128,
5146          39 => 131,
5147          40 => 134);
5148
5149       function Mantissa return Uint is
5150       begin
5151          return
5152            UI_From_Int (Mantissa_Value (UI_To_Int (Digits_Value (P_Type))));
5153       end Mantissa;
5154
5155       ----------------
5156       -- Set_Bounds --
5157       ----------------
5158
5159       procedure Set_Bounds is
5160          Ndim : Nat;
5161          Indx : Node_Id;
5162          Ityp : Entity_Id;
5163
5164       begin
5165          --  For a string literal subtype, we have to construct the bounds.
5166          --  Valid Ada code never applies attributes to string literals, but
5167          --  it is convenient to allow the expander to generate attribute
5168          --  references of this type (e.g. First and Last applied to a string
5169          --  literal).
5170
5171          --  Note that the whole point of the E_String_Literal_Subtype is to
5172          --  avoid this construction of bounds, but the cases in which we
5173          --  have to materialize them are rare enough that we don't worry!
5174
5175          --  The low bound is simply the low bound of the base type. The
5176          --  high bound is computed from the length of the string and this
5177          --  low bound.
5178
5179          if Ekind (P_Type) = E_String_Literal_Subtype then
5180             Ityp := Etype (First_Index (Base_Type (P_Type)));
5181             Lo_Bound := Type_Low_Bound (Ityp);
5182
5183             Hi_Bound :=
5184               Make_Integer_Literal (Sloc (P),
5185                 Intval =>
5186                   Expr_Value (Lo_Bound) + String_Literal_Length (P_Type) - 1);
5187
5188             Set_Parent (Hi_Bound, P);
5189             Analyze_And_Resolve (Hi_Bound, Etype (Lo_Bound));
5190             return;
5191
5192          --  For non-array case, just get bounds of scalar type
5193
5194          elsif Is_Scalar_Type (P_Type) then
5195             Ityp := P_Type;
5196
5197             --  For a fixed-point type, we must freeze to get the attributes
5198             --  of the fixed-point type set now so we can reference them.
5199
5200             if Is_Fixed_Point_Type (P_Type)
5201               and then not Is_Frozen (Base_Type (P_Type))
5202               and then Compile_Time_Known_Value (Type_Low_Bound (P_Type))
5203               and then Compile_Time_Known_Value (Type_High_Bound (P_Type))
5204             then
5205                Freeze_Fixed_Point_Type (Base_Type (P_Type));
5206             end if;
5207
5208          --  For array case, get type of proper index
5209
5210          else
5211             if No (E1) then
5212                Ndim := 1;
5213             else
5214                Ndim := UI_To_Int (Expr_Value (E1));
5215             end if;
5216
5217             Indx := First_Index (P_Type);
5218             for J in 1 .. Ndim - 1 loop
5219                Next_Index (Indx);
5220             end loop;
5221
5222             --  If no index type, get out (some other error occurred, and
5223             --  we don't have enough information to complete the job!)
5224
5225             if No (Indx) then
5226                Lo_Bound := Error;
5227                Hi_Bound := Error;
5228                return;
5229             end if;
5230
5231             Ityp := Etype (Indx);
5232          end if;
5233
5234          --  A discrete range in an index constraint is allowed to be a
5235          --  subtype indication. This is syntactically a pain, but should
5236          --  not propagate to the entity for the corresponding index subtype.
5237          --  After checking that the subtype indication is legal, the range
5238          --  of the subtype indication should be transfered to the entity.
5239          --  The attributes for the bounds should remain the simple retrievals
5240          --  that they are now.
5241
5242          Lo_Bound := Type_Low_Bound (Ityp);
5243          Hi_Bound := Type_High_Bound (Ityp);
5244
5245          if not Is_Static_Subtype (Ityp) then
5246             Static := False;
5247          end if;
5248       end Set_Bounds;
5249
5250       -------------------------------
5251       -- Statically_Denotes_Entity --
5252       -------------------------------
5253
5254       function Statically_Denotes_Entity (N : Node_Id) return Boolean is
5255          E : Entity_Id;
5256
5257       begin
5258          if not Is_Entity_Name (N) then
5259             return False;
5260          else
5261             E := Entity (N);
5262          end if;
5263
5264          return
5265            Nkind (Parent (E)) /= N_Object_Renaming_Declaration
5266              or else Statically_Denotes_Entity (Renamed_Object (E));
5267       end Statically_Denotes_Entity;
5268
5269    --  Start of processing for Eval_Attribute
5270
5271    begin
5272       --  No folding in spec expression that comes from source where the prefix
5273       --  is an unfrozen entity. This avoids premature folding in cases like:
5274
5275       --    procedure DefExprAnal is
5276       --       type R is new Integer;
5277       --       procedure P (Arg : Integer := R'Size);
5278       --       for R'Size use 64;
5279       --       procedure P (Arg : Integer := R'Size) is
5280       --       begin
5281       --          Put_Line (Arg'Img);
5282       --       end P;
5283       --    begin
5284       --       P;
5285       --    end;
5286
5287       --  which should print 64 rather than 32. The exclusion of non-source
5288       --  constructs from this test comes from some internal usage in packed
5289       --  arrays, which otherwise fails, could use more analysis perhaps???
5290
5291       --  We do however go ahead with generic actual types, otherwise we get
5292       --  some regressions, probably these types should be frozen anyway???
5293
5294       if In_Spec_Expression
5295         and then Comes_From_Source (N)
5296         and then not (Is_Entity_Name (P)
5297                        and then
5298                         (Is_Frozen (Entity (P))
5299                           or else (Is_Type (Entity (P))
5300                                     and then
5301                                       Is_Generic_Actual_Type (Entity (P)))))
5302       then
5303          return;
5304       end if;
5305
5306       --  Acquire first two expressions (at the moment, no attributes take more
5307       --  than two expressions in any case).
5308
5309       if Present (Expressions (N)) then
5310          E1 := First (Expressions (N));
5311          E2 := Next (E1);
5312       else
5313          E1 := Empty;
5314          E2 := Empty;
5315       end if;
5316
5317       --  Special processing for Enabled attribute. This attribute has a very
5318       --  special prefix, and the easiest way to avoid lots of special checks
5319       --  to protect this special prefix from causing trouble is to deal with
5320       --  this attribute immediately and be done with it.
5321
5322       if Id = Attribute_Enabled then
5323
5324          --  We skip evaluation if the expander is not active. This is not just
5325          --  an optimization. It is of key importance that we not rewrite the
5326          --  attribute in a generic template, since we want to pick up the
5327          --  setting of the check in the instance, and testing expander active
5328          --  is as easy way of doing this as any.
5329
5330          if Expander_Active then
5331             declare
5332                C : constant Check_Id := Get_Check_Id (Chars (P));
5333                R : Boolean;
5334
5335             begin
5336                if No (E1) then
5337                   if C in Predefined_Check_Id then
5338                      R := Scope_Suppress (C);
5339                   else
5340                      R := Is_Check_Suppressed (Empty, C);
5341                   end if;
5342
5343                else
5344                   R := Is_Check_Suppressed (Entity (E1), C);
5345                end if;
5346
5347                if R then
5348                   Rewrite (N, New_Occurrence_Of (Standard_False, Loc));
5349                else
5350                   Rewrite (N, New_Occurrence_Of (Standard_True, Loc));
5351                end if;
5352             end;
5353          end if;
5354
5355          return;
5356       end if;
5357
5358       --  Special processing for cases where the prefix is an object. For
5359       --  this purpose, a string literal counts as an object (attributes
5360       --  of string literals can only appear in generated code).
5361
5362       if Is_Object_Reference (P) or else Nkind (P) = N_String_Literal then
5363
5364          --  For Component_Size, the prefix is an array object, and we apply
5365          --  the attribute to the type of the object. This is allowed for
5366          --  both unconstrained and constrained arrays, since the bounds
5367          --  have no influence on the value of this attribute.
5368
5369          if Id = Attribute_Component_Size then
5370             P_Entity := Etype (P);
5371
5372          --  For First and Last, the prefix is an array object, and we apply
5373          --  the attribute to the type of the array, but we need a constrained
5374          --  type for this, so we use the actual subtype if available.
5375
5376          elsif Id = Attribute_First
5377                  or else
5378                Id = Attribute_Last
5379                  or else
5380                Id = Attribute_Length
5381          then
5382             declare
5383                AS : constant Entity_Id := Get_Actual_Subtype_If_Available (P);
5384
5385             begin
5386                if Present (AS) and then Is_Constrained (AS) then
5387                   P_Entity := AS;
5388
5389                --  If we have an unconstrained type we cannot fold
5390
5391                else
5392                   Check_Expressions;
5393                   return;
5394                end if;
5395             end;
5396
5397          --  For Size, give size of object if available, otherwise we
5398          --  cannot fold Size.
5399
5400          elsif Id = Attribute_Size then
5401             if Is_Entity_Name (P)
5402               and then Known_Esize (Entity (P))
5403             then
5404                Compile_Time_Known_Attribute (N, Esize (Entity (P)));
5405                return;
5406
5407             else
5408                Check_Expressions;
5409                return;
5410             end if;
5411
5412          --  For Alignment, give size of object if available, otherwise we
5413          --  cannot fold Alignment.
5414
5415          elsif Id = Attribute_Alignment then
5416             if Is_Entity_Name (P)
5417               and then Known_Alignment (Entity (P))
5418             then
5419                Fold_Uint (N, Alignment (Entity (P)), False);
5420                return;
5421
5422             else
5423                Check_Expressions;
5424                return;
5425             end if;
5426
5427          --  No other attributes for objects are folded
5428
5429          else
5430             Check_Expressions;
5431             return;
5432          end if;
5433
5434       --  Cases where P is not an object. Cannot do anything if P is
5435       --  not the name of an entity.
5436
5437       elsif not Is_Entity_Name (P) then
5438          Check_Expressions;
5439          return;
5440
5441       --  Otherwise get prefix entity
5442
5443       else
5444          P_Entity := Entity (P);
5445       end if;
5446
5447       --  At this stage P_Entity is the entity to which the attribute
5448       --  is to be applied. This is usually simply the entity of the
5449       --  prefix, except in some cases of attributes for objects, where
5450       --  as described above, we apply the attribute to the object type.
5451
5452       --  First foldable possibility is a scalar or array type (RM 4.9(7))
5453       --  that is not generic (generic types are eliminated by RM 4.9(25)).
5454       --  Note we allow non-static non-generic types at this stage as further
5455       --  described below.
5456
5457       if Is_Type (P_Entity)
5458         and then (Is_Scalar_Type (P_Entity) or Is_Array_Type (P_Entity))
5459         and then (not Is_Generic_Type (P_Entity))
5460       then
5461          P_Type := P_Entity;
5462
5463       --  Second foldable possibility is an array object (RM 4.9(8))
5464
5465       elsif (Ekind (P_Entity) = E_Variable
5466                or else
5467              Ekind (P_Entity) = E_Constant)
5468         and then Is_Array_Type (Etype (P_Entity))
5469         and then (not Is_Generic_Type (Etype (P_Entity)))
5470       then
5471          P_Type := Etype (P_Entity);
5472
5473          --  If the entity is an array constant with an unconstrained nominal
5474          --  subtype then get the type from the initial value. If the value has
5475          --  been expanded into assignments, there is no expression and the
5476          --  attribute reference remains dynamic.
5477
5478          --  We could do better here and retrieve the type ???
5479
5480          if Ekind (P_Entity) = E_Constant
5481            and then not Is_Constrained (P_Type)
5482          then
5483             if No (Constant_Value (P_Entity)) then
5484                return;
5485             else
5486                P_Type := Etype (Constant_Value (P_Entity));
5487             end if;
5488          end if;
5489
5490       --  Definite must be folded if the prefix is not a generic type,
5491       --  that is to say if we are within an instantiation. Same processing
5492       --  applies to the GNAT attributes Has_Discriminants, Type_Class,
5493       --  Has_Tagged_Value, and Unconstrained_Array.
5494
5495       elsif (Id = Attribute_Definite
5496                or else
5497              Id = Attribute_Has_Access_Values
5498                or else
5499              Id = Attribute_Has_Discriminants
5500                or else
5501              Id = Attribute_Has_Tagged_Values
5502                or else
5503              Id = Attribute_Type_Class
5504                or else
5505              Id = Attribute_Unconstrained_Array
5506                or else
5507              Id = Attribute_Max_Alignment_For_Allocation)
5508         and then not Is_Generic_Type (P_Entity)
5509       then
5510          P_Type := P_Entity;
5511
5512       --  We can fold 'Size applied to a type if the size is known (as happens
5513       --  for a size from an attribute definition clause). At this stage, this
5514       --  can happen only for types (e.g. record types) for which the size is
5515       --  always non-static. We exclude generic types from consideration (since
5516       --  they have bogus sizes set within templates).
5517
5518       elsif Id = Attribute_Size
5519         and then Is_Type (P_Entity)
5520         and then (not Is_Generic_Type (P_Entity))
5521         and then Known_Static_RM_Size (P_Entity)
5522       then
5523          Compile_Time_Known_Attribute (N, RM_Size (P_Entity));
5524          return;
5525
5526       --  We can fold 'Alignment applied to a type if the alignment is known
5527       --  (as happens for an alignment from an attribute definition clause).
5528       --  At this stage, this can happen only for types (e.g. record
5529       --  types) for which the size is always non-static. We exclude
5530       --  generic types from consideration (since they have bogus
5531       --  sizes set within templates).
5532
5533       elsif Id = Attribute_Alignment
5534         and then Is_Type (P_Entity)
5535         and then (not Is_Generic_Type (P_Entity))
5536         and then Known_Alignment (P_Entity)
5537       then
5538          Compile_Time_Known_Attribute (N, Alignment (P_Entity));
5539          return;
5540
5541       --  If this is an access attribute that is known to fail accessibility
5542       --  check, rewrite accordingly.
5543
5544       elsif Attribute_Name (N) = Name_Access
5545         and then Raises_Constraint_Error (N)
5546       then
5547          Rewrite (N,
5548            Make_Raise_Program_Error (Loc,
5549              Reason => PE_Accessibility_Check_Failed));
5550          Set_Etype (N, C_Type);
5551          return;
5552
5553       --  No other cases are foldable (they certainly aren't static, and at
5554       --  the moment we don't try to fold any cases other than these three).
5555
5556       else
5557          Check_Expressions;
5558          return;
5559       end if;
5560
5561       --  If either attribute or the prefix is Any_Type, then propagate
5562       --  Any_Type to the result and don't do anything else at all.
5563
5564       if P_Type = Any_Type
5565         or else (Present (E1) and then Etype (E1) = Any_Type)
5566         or else (Present (E2) and then Etype (E2) = Any_Type)
5567       then
5568          Set_Etype (N, Any_Type);
5569          return;
5570       end if;
5571
5572       --  Scalar subtype case. We have not yet enforced the static requirement
5573       --  of (RM 4.9(7)) and we don't intend to just yet, since there are cases
5574       --  of non-static attribute references (e.g. S'Digits for a non-static
5575       --  floating-point type, which we can compute at compile time).
5576
5577       --  Note: this folding of non-static attributes is not simply a case of
5578       --  optimization. For many of the attributes affected, Gigi cannot handle
5579       --  the attribute and depends on the front end having folded them away.
5580
5581       --  Note: although we don't require staticness at this stage, we do set
5582       --  the Static variable to record the staticness, for easy reference by
5583       --  those attributes where it matters (e.g. Succ and Pred), and also to
5584       --  be used to ensure that non-static folded things are not marked as
5585       --  being static (a check that is done right at the end).
5586
5587       P_Root_Type := Root_Type (P_Type);
5588       P_Base_Type := Base_Type (P_Type);
5589
5590       --  If the root type or base type is generic, then we cannot fold. This
5591       --  test is needed because subtypes of generic types are not always
5592       --  marked as being generic themselves (which seems odd???)
5593
5594       if Is_Generic_Type (P_Root_Type)
5595         or else Is_Generic_Type (P_Base_Type)
5596       then
5597          return;
5598       end if;
5599
5600       if Is_Scalar_Type (P_Type) then
5601          Static := Is_OK_Static_Subtype (P_Type);
5602
5603       --  Array case. We enforce the constrained requirement of (RM 4.9(7-8))
5604       --  since we can't do anything with unconstrained arrays. In addition,
5605       --  only the First, Last and Length attributes are possibly static.
5606
5607       --  Definite, Has_Access_Values, Has_Discriminants, Has_Tagged_Values,
5608       --  Type_Class, and Unconstrained_Array are again exceptions, because
5609       --  they apply as well to unconstrained types.
5610
5611       --  In addition Component_Size is an exception since it is possibly
5612       --  foldable, even though it is never static, and it does apply to
5613       --  unconstrained arrays. Furthermore, it is essential to fold this
5614       --  in the packed case, since otherwise the value will be incorrect.
5615
5616       elsif Id = Attribute_Definite
5617               or else
5618             Id = Attribute_Has_Access_Values
5619               or else
5620             Id = Attribute_Has_Discriminants
5621               or else
5622             Id = Attribute_Has_Tagged_Values
5623               or else
5624             Id = Attribute_Type_Class
5625               or else
5626             Id = Attribute_Unconstrained_Array
5627               or else
5628             Id = Attribute_Component_Size
5629       then
5630          Static := False;
5631
5632       elsif Id /= Attribute_Max_Alignment_For_Allocation then
5633          if not Is_Constrained (P_Type)
5634            or else (Id /= Attribute_First and then
5635                     Id /= Attribute_Last  and then
5636                     Id /= Attribute_Length)
5637          then
5638             Check_Expressions;
5639             return;
5640          end if;
5641
5642          --  The rules in (RM 4.9(7,8)) require a static array, but as in the
5643          --  scalar case, we hold off on enforcing staticness, since there are
5644          --  cases which we can fold at compile time even though they are not
5645          --  static (e.g. 'Length applied to a static index, even though other
5646          --  non-static indexes make the array type non-static). This is only
5647          --  an optimization, but it falls out essentially free, so why not.
5648          --  Again we compute the variable Static for easy reference later
5649          --  (note that no array attributes are static in Ada 83).
5650
5651          --  We also need to set Static properly for subsequent legality checks
5652          --  which might otherwise accept non-static constants in contexts
5653          --  where they are not legal.
5654
5655          Static := Ada_Version >= Ada_95
5656                      and then Statically_Denotes_Entity (P);
5657
5658          declare
5659             N : Node_Id;
5660
5661          begin
5662             N := First_Index (P_Type);
5663
5664             --  The expression is static if the array type is constrained
5665             --  by given bounds, and not by an initial expression. Constant
5666             --  strings are static in any case.
5667
5668             if Root_Type (P_Type) /= Standard_String then
5669                Static :=
5670                  Static and then not Is_Constr_Subt_For_U_Nominal (P_Type);
5671             end if;
5672
5673             while Present (N) loop
5674                Static := Static and then Is_Static_Subtype (Etype (N));
5675
5676                --  If however the index type is generic, or derived from
5677                --  one, attributes cannot be folded.
5678
5679                if Is_Generic_Type (Root_Type (Etype (N)))
5680                  and then Id /= Attribute_Component_Size
5681                then
5682                   return;
5683                end if;
5684
5685                Next_Index (N);
5686             end loop;
5687          end;
5688       end if;
5689
5690       --  Check any expressions that are present. Note that these expressions,
5691       --  depending on the particular attribute type, are either part of the
5692       --  attribute designator, or they are arguments in a case where the
5693       --  attribute reference returns a function. In the latter case, the
5694       --  rule in (RM 4.9(22)) applies and in particular requires the type
5695       --  of the expressions to be scalar in order for the attribute to be
5696       --  considered to be static.
5697
5698       declare
5699          E : Node_Id;
5700
5701       begin
5702          E := E1;
5703          while Present (E) loop
5704
5705             --  If expression is not static, then the attribute reference
5706             --  result certainly cannot be static.
5707
5708             if not Is_Static_Expression (E) then
5709                Static := False;
5710             end if;
5711
5712             --  If the result is not known at compile time, or is not of
5713             --  a scalar type, then the result is definitely not static,
5714             --  so we can quit now.
5715
5716             if not Compile_Time_Known_Value (E)
5717               or else not Is_Scalar_Type (Etype (E))
5718             then
5719                --  An odd special case, if this is a Pos attribute, this
5720                --  is where we need to apply a range check since it does
5721                --  not get done anywhere else.
5722
5723                if Id = Attribute_Pos then
5724                   if Is_Integer_Type (Etype (E)) then
5725                      Apply_Range_Check (E, Etype (N));
5726                   end if;
5727                end if;
5728
5729                Check_Expressions;
5730                return;
5731
5732             --  If the expression raises a constraint error, then so does
5733             --  the attribute reference. We keep going in this case because
5734             --  we are still interested in whether the attribute reference
5735             --  is static even if it is not static.
5736
5737             elsif Raises_Constraint_Error (E) then
5738                Set_Raises_Constraint_Error (N);
5739             end if;
5740
5741             Next (E);
5742          end loop;
5743
5744          if Raises_Constraint_Error (Prefix (N)) then
5745             return;
5746          end if;
5747       end;
5748
5749       --  Deal with the case of a static attribute reference that raises
5750       --  constraint error. The Raises_Constraint_Error flag will already
5751       --  have been set, and the Static flag shows whether the attribute
5752       --  reference is static. In any case we certainly can't fold such an
5753       --  attribute reference.
5754
5755       --  Note that the rewriting of the attribute node with the constraint
5756       --  error node is essential in this case, because otherwise Gigi might
5757       --  blow up on one of the attributes it never expects to see.
5758
5759       --  The constraint_error node must have the type imposed by the context,
5760       --  to avoid spurious errors in the enclosing expression.
5761
5762       if Raises_Constraint_Error (N) then
5763          CE_Node :=
5764            Make_Raise_Constraint_Error (Sloc (N),
5765              Reason => CE_Range_Check_Failed);
5766          Set_Etype (CE_Node, Etype (N));
5767          Set_Raises_Constraint_Error (CE_Node);
5768          Check_Expressions;
5769          Rewrite (N, Relocate_Node (CE_Node));
5770          Set_Is_Static_Expression (N, Static);
5771          return;
5772       end if;
5773
5774       --  At this point we have a potentially foldable attribute reference.
5775       --  If Static is set, then the attribute reference definitely obeys
5776       --  the requirements in (RM 4.9(7,8,22)), and it definitely can be
5777       --  folded. If Static is not set, then the attribute may or may not
5778       --  be foldable, and the individual attribute processing routines
5779       --  test Static as required in cases where it makes a difference.
5780
5781       --  In the case where Static is not set, we do know that all the
5782       --  expressions present are at least known at compile time (we
5783       --  assumed above that if this was not the case, then there was
5784       --  no hope of static evaluation). However, we did not require
5785       --  that the bounds of the prefix type be compile time known,
5786       --  let alone static). That's because there are many attributes
5787       --  that can be computed at compile time on non-static subtypes,
5788       --  even though such references are not static expressions.
5789
5790       case Id is
5791
5792       --------------
5793       -- Adjacent --
5794       --------------
5795
5796       when Attribute_Adjacent =>
5797          Fold_Ureal (N,
5798            Eval_Fat.Adjacent
5799              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5800
5801       ---------
5802       -- Aft --
5803       ---------
5804
5805       when Attribute_Aft =>
5806          Fold_Uint (N, Aft_Value (P_Type), True);
5807
5808       ---------------
5809       -- Alignment --
5810       ---------------
5811
5812       when Attribute_Alignment => Alignment_Block : declare
5813          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
5814
5815       begin
5816          --  Fold if alignment is set and not otherwise
5817
5818          if Known_Alignment (P_TypeA) then
5819             Fold_Uint (N, Alignment (P_TypeA), Is_Discrete_Type (P_TypeA));
5820          end if;
5821       end Alignment_Block;
5822
5823       ---------------
5824       -- AST_Entry --
5825       ---------------
5826
5827       --  Can only be folded in No_Ast_Handler case
5828
5829       when Attribute_AST_Entry =>
5830          if not Is_AST_Entry (P_Entity) then
5831             Rewrite (N,
5832               New_Occurrence_Of (RTE (RE_No_AST_Handler), Loc));
5833          else
5834             null;
5835          end if;
5836
5837       ---------
5838       -- Bit --
5839       ---------
5840
5841       --  Bit can never be folded
5842
5843       when Attribute_Bit =>
5844          null;
5845
5846       ------------------
5847       -- Body_Version --
5848       ------------------
5849
5850       --  Body_version can never be static
5851
5852       when Attribute_Body_Version =>
5853          null;
5854
5855       -------------
5856       -- Ceiling --
5857       -------------
5858
5859       when Attribute_Ceiling =>
5860          Fold_Ureal (N,
5861            Eval_Fat.Ceiling (P_Root_Type, Expr_Value_R (E1)), Static);
5862
5863       --------------------
5864       -- Component_Size --
5865       --------------------
5866
5867       when Attribute_Component_Size =>
5868          if Known_Static_Component_Size (P_Type) then
5869             Fold_Uint (N, Component_Size (P_Type), False);
5870          end if;
5871
5872       -------------
5873       -- Compose --
5874       -------------
5875
5876       when Attribute_Compose =>
5877          Fold_Ureal (N,
5878            Eval_Fat.Compose
5879              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)),
5880               Static);
5881
5882       -----------------
5883       -- Constrained --
5884       -----------------
5885
5886       --  Constrained is never folded for now, there may be cases that
5887       --  could be handled at compile time. To be looked at later.
5888
5889       when Attribute_Constrained =>
5890          null;
5891
5892       ---------------
5893       -- Copy_Sign --
5894       ---------------
5895
5896       when Attribute_Copy_Sign =>
5897          Fold_Ureal (N,
5898            Eval_Fat.Copy_Sign
5899              (P_Root_Type, Expr_Value_R (E1), Expr_Value_R (E2)), Static);
5900
5901       -----------
5902       -- Delta --
5903       -----------
5904
5905       when Attribute_Delta =>
5906          Fold_Ureal (N, Delta_Value (P_Type), True);
5907
5908       --------------
5909       -- Definite --
5910       --------------
5911
5912       when Attribute_Definite =>
5913          Rewrite (N, New_Occurrence_Of (
5914            Boolean_Literals (not Is_Indefinite_Subtype (P_Entity)), Loc));
5915          Analyze_And_Resolve (N, Standard_Boolean);
5916
5917       ------------
5918       -- Denorm --
5919       ------------
5920
5921       when Attribute_Denorm =>
5922          Fold_Uint
5923            (N, UI_From_Int (Boolean'Pos (Denorm_On_Target)), True);
5924
5925       ------------
5926       -- Digits --
5927       ------------
5928
5929       when Attribute_Digits =>
5930          Fold_Uint (N, Digits_Value (P_Type), True);
5931
5932       ----------
5933       -- Emax --
5934       ----------
5935
5936       when Attribute_Emax =>
5937
5938          --  Ada 83 attribute is defined as (RM83 3.5.8)
5939
5940          --    T'Emax = 4 * T'Mantissa
5941
5942          Fold_Uint (N, 4 * Mantissa, True);
5943
5944       --------------
5945       -- Enum_Rep --
5946       --------------
5947
5948       when Attribute_Enum_Rep =>
5949
5950          --  For an enumeration type with a non-standard representation use
5951          --  the Enumeration_Rep field of the proper constant. Note that this
5952          --  will not work for types Character/Wide_[Wide-]Character, since no
5953          --  real entities are created for the enumeration literals, but that
5954          --  does not matter since these two types do not have non-standard
5955          --  representations anyway.
5956
5957          if Is_Enumeration_Type (P_Type)
5958            and then Has_Non_Standard_Rep (P_Type)
5959          then
5960             Fold_Uint (N, Enumeration_Rep (Expr_Value_E (E1)), Static);
5961
5962          --  For enumeration types with standard representations and all
5963          --  other cases (i.e. all integer and modular types), Enum_Rep
5964          --  is equivalent to Pos.
5965
5966          else
5967             Fold_Uint (N, Expr_Value (E1), Static);
5968          end if;
5969
5970       --------------
5971       -- Enum_Val --
5972       --------------
5973
5974       when Attribute_Enum_Val => Enum_Val : declare
5975          Lit : Node_Id;
5976
5977       begin
5978          --  We have something like Enum_Type'Enum_Val (23), so search for a
5979          --  corresponding value in the list of Enum_Rep values for the type.
5980
5981          Lit := First_Literal (P_Base_Type);
5982          loop
5983             if Enumeration_Rep (Lit) = Expr_Value (E1) then
5984                Fold_Uint (N, Enumeration_Pos (Lit), Static);
5985                exit;
5986             end if;
5987
5988             Next_Literal (Lit);
5989
5990             if No (Lit) then
5991                Apply_Compile_Time_Constraint_Error
5992                  (N, "no representation value matches",
5993                   CE_Range_Check_Failed,
5994                   Warn => not Static);
5995                exit;
5996             end if;
5997          end loop;
5998       end Enum_Val;
5999
6000       -------------
6001       -- Epsilon --
6002       -------------
6003
6004       when Attribute_Epsilon =>
6005
6006          --  Ada 83 attribute is defined as (RM83 3.5.8)
6007
6008          --    T'Epsilon = 2.0**(1 - T'Mantissa)
6009
6010          Fold_Ureal (N, Ureal_2 ** (1 - Mantissa), True);
6011
6012       --------------
6013       -- Exponent --
6014       --------------
6015
6016       when Attribute_Exponent =>
6017          Fold_Uint (N,
6018            Eval_Fat.Exponent (P_Root_Type, Expr_Value_R (E1)), Static);
6019
6020       -----------
6021       -- First --
6022       -----------
6023
6024       when Attribute_First => First_Attr :
6025       begin
6026          Set_Bounds;
6027
6028          if Compile_Time_Known_Value (Lo_Bound) then
6029             if Is_Real_Type (P_Type) then
6030                Fold_Ureal (N, Expr_Value_R (Lo_Bound), Static);
6031             else
6032                Fold_Uint  (N, Expr_Value (Lo_Bound), Static);
6033             end if;
6034
6035          else
6036             Check_Concurrent_Discriminant (Lo_Bound);
6037          end if;
6038       end First_Attr;
6039
6040       -----------------
6041       -- Fixed_Value --
6042       -----------------
6043
6044       when Attribute_Fixed_Value =>
6045          null;
6046
6047       -----------
6048       -- Floor --
6049       -----------
6050
6051       when Attribute_Floor =>
6052          Fold_Ureal (N,
6053            Eval_Fat.Floor (P_Root_Type, Expr_Value_R (E1)), Static);
6054
6055       ----------
6056       -- Fore --
6057       ----------
6058
6059       when Attribute_Fore =>
6060          if Compile_Time_Known_Bounds (P_Type) then
6061             Fold_Uint (N, UI_From_Int (Fore_Value), Static);
6062          end if;
6063
6064       --------------
6065       -- Fraction --
6066       --------------
6067
6068       when Attribute_Fraction =>
6069          Fold_Ureal (N,
6070            Eval_Fat.Fraction (P_Root_Type, Expr_Value_R (E1)), Static);
6071
6072       -----------------------
6073       -- Has_Access_Values --
6074       -----------------------
6075
6076       when Attribute_Has_Access_Values =>
6077          Rewrite (N, New_Occurrence_Of
6078            (Boolean_Literals (Has_Access_Values (P_Root_Type)), Loc));
6079          Analyze_And_Resolve (N, Standard_Boolean);
6080
6081       -----------------------
6082       -- Has_Discriminants --
6083       -----------------------
6084
6085       when Attribute_Has_Discriminants =>
6086          Rewrite (N, New_Occurrence_Of (
6087            Boolean_Literals (Has_Discriminants (P_Entity)), Loc));
6088          Analyze_And_Resolve (N, Standard_Boolean);
6089
6090       -----------------------
6091       -- Has_Tagged_Values --
6092       -----------------------
6093
6094       when Attribute_Has_Tagged_Values =>
6095          Rewrite (N, New_Occurrence_Of
6096            (Boolean_Literals (Has_Tagged_Component (P_Root_Type)), Loc));
6097          Analyze_And_Resolve (N, Standard_Boolean);
6098
6099       --------------
6100       -- Identity --
6101       --------------
6102
6103       when Attribute_Identity =>
6104          null;
6105
6106       -----------
6107       -- Image --
6108       -----------
6109
6110       --  Image is a scalar attribute, but is never static, because it is
6111       --  not a static function (having a non-scalar argument (RM 4.9(22))
6112       --  However, we can constant-fold the image of an enumeration literal
6113       --  if names are available.
6114
6115       when Attribute_Image =>
6116          if Is_Entity_Name (E1)
6117            and then Ekind (Entity (E1)) = E_Enumeration_Literal
6118            and then not Discard_Names (First_Subtype (Etype (E1)))
6119            and then not Global_Discard_Names
6120          then
6121             declare
6122                Lit : constant Entity_Id := Entity (E1);
6123                Str : String_Id;
6124             begin
6125                Start_String;
6126                Get_Unqualified_Decoded_Name_String (Chars (Lit));
6127                Set_Casing (All_Upper_Case);
6128                Store_String_Chars (Name_Buffer (1 .. Name_Len));
6129                Str := End_String;
6130                Rewrite (N, Make_String_Literal (Loc, Strval => Str));
6131                Analyze_And_Resolve (N, Standard_String);
6132                Set_Is_Static_Expression (N, False);
6133             end;
6134          end if;
6135
6136       ---------
6137       -- Img --
6138       ---------
6139
6140       --  Img is a scalar attribute, but is never static, because it is
6141       --  not a static function (having a non-scalar argument (RM 4.9(22))
6142
6143       when Attribute_Img =>
6144          null;
6145
6146       -------------------
6147       -- Integer_Value --
6148       -------------------
6149
6150       --  We never try to fold Integer_Value (though perhaps we could???)
6151
6152       when Attribute_Integer_Value =>
6153          null;
6154
6155       -------------------
6156       -- Invalid_Value --
6157       -------------------
6158
6159       --  Invalid_Value is a scalar attribute that is never static, because
6160       --  the value is by design out of range.
6161
6162       when Attribute_Invalid_Value =>
6163          null;
6164
6165       -----------
6166       -- Large --
6167       -----------
6168
6169       when Attribute_Large =>
6170
6171          --  For fixed-point, we use the identity:
6172
6173          --    T'Large = (2.0**T'Mantissa - 1.0) * T'Small
6174
6175          if Is_Fixed_Point_Type (P_Type) then
6176             Rewrite (N,
6177               Make_Op_Multiply (Loc,
6178                 Left_Opnd =>
6179                   Make_Op_Subtract (Loc,
6180                     Left_Opnd =>
6181                       Make_Op_Expon (Loc,
6182                         Left_Opnd =>
6183                           Make_Real_Literal (Loc, Ureal_2),
6184                         Right_Opnd =>
6185                           Make_Attribute_Reference (Loc,
6186                             Prefix => P,
6187                             Attribute_Name => Name_Mantissa)),
6188                     Right_Opnd => Make_Real_Literal (Loc, Ureal_1)),
6189
6190                 Right_Opnd =>
6191                   Make_Real_Literal (Loc, Small_Value (Entity (P)))));
6192
6193             Analyze_And_Resolve (N, C_Type);
6194
6195          --  Floating-point (Ada 83 compatibility)
6196
6197          else
6198             --  Ada 83 attribute is defined as (RM83 3.5.8)
6199
6200             --    T'Large = 2.0**T'Emax * (1.0 - 2.0**(-T'Mantissa))
6201
6202             --  where
6203
6204             --    T'Emax = 4 * T'Mantissa
6205
6206             Fold_Ureal (N,
6207               Ureal_2 ** (4 * Mantissa) * (Ureal_1 - Ureal_2 ** (-Mantissa)),
6208               True);
6209          end if;
6210
6211       ----------
6212       -- Last --
6213       ----------
6214
6215       when Attribute_Last => Last :
6216       begin
6217          Set_Bounds;
6218
6219          if Compile_Time_Known_Value (Hi_Bound) then
6220             if Is_Real_Type (P_Type) then
6221                Fold_Ureal (N, Expr_Value_R (Hi_Bound), Static);
6222             else
6223                Fold_Uint  (N, Expr_Value (Hi_Bound), Static);
6224             end if;
6225
6226          else
6227             Check_Concurrent_Discriminant (Hi_Bound);
6228          end if;
6229       end Last;
6230
6231       ------------------
6232       -- Leading_Part --
6233       ------------------
6234
6235       when Attribute_Leading_Part =>
6236          Fold_Ureal (N,
6237            Eval_Fat.Leading_Part
6238              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
6239
6240       ------------
6241       -- Length --
6242       ------------
6243
6244       when Attribute_Length => Length : declare
6245          Ind : Node_Id;
6246
6247       begin
6248          --  If any index type is a formal type, or derived from one, the
6249          --  bounds are not static. Treating them as static can produce
6250          --  spurious warnings or improper constant folding.
6251
6252          Ind := First_Index (P_Type);
6253          while Present (Ind) loop
6254             if Is_Generic_Type (Root_Type (Etype (Ind))) then
6255                return;
6256             end if;
6257
6258             Next_Index (Ind);
6259          end loop;
6260
6261          Set_Bounds;
6262
6263          --  For two compile time values, we can compute length
6264
6265          if Compile_Time_Known_Value (Lo_Bound)
6266            and then Compile_Time_Known_Value (Hi_Bound)
6267          then
6268             Fold_Uint (N,
6269               UI_Max (0, 1 + (Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound))),
6270               True);
6271          end if;
6272
6273          --  One more case is where Hi_Bound and Lo_Bound are compile-time
6274          --  comparable, and we can figure out the difference between them.
6275
6276          declare
6277             Diff : aliased Uint;
6278
6279          begin
6280             case
6281               Compile_Time_Compare
6282                 (Lo_Bound, Hi_Bound, Diff'Access, Assume_Valid => False)
6283             is
6284                when EQ =>
6285                   Fold_Uint (N, Uint_1, False);
6286
6287                when GT =>
6288                   Fold_Uint (N, Uint_0, False);
6289
6290                when LT =>
6291                   if Diff /= No_Uint then
6292                      Fold_Uint (N, Diff + 1, False);
6293                   end if;
6294
6295                when others =>
6296                   null;
6297             end case;
6298          end;
6299       end Length;
6300
6301       -------------
6302       -- Machine --
6303       -------------
6304
6305       when Attribute_Machine =>
6306          Fold_Ureal (N,
6307            Eval_Fat.Machine
6308              (P_Root_Type, Expr_Value_R (E1), Eval_Fat.Round, N),
6309            Static);
6310
6311       ------------------
6312       -- Machine_Emax --
6313       ------------------
6314
6315       when Attribute_Machine_Emax =>
6316          Fold_Uint (N, Machine_Emax_Value (P_Type), Static);
6317
6318       ------------------
6319       -- Machine_Emin --
6320       ------------------
6321
6322       when Attribute_Machine_Emin =>
6323          Fold_Uint (N, Machine_Emin_Value (P_Type), Static);
6324
6325       ----------------------
6326       -- Machine_Mantissa --
6327       ----------------------
6328
6329       when Attribute_Machine_Mantissa =>
6330          Fold_Uint (N, Machine_Mantissa_Value (P_Type), Static);
6331
6332       -----------------------
6333       -- Machine_Overflows --
6334       -----------------------
6335
6336       when Attribute_Machine_Overflows =>
6337
6338          --  Always true for fixed-point
6339
6340          if Is_Fixed_Point_Type (P_Type) then
6341             Fold_Uint (N, True_Value, True);
6342
6343          --  Floating point case
6344
6345          else
6346             Fold_Uint (N,
6347               UI_From_Int (Boolean'Pos (Machine_Overflows_On_Target)),
6348               True);
6349          end if;
6350
6351       -------------------
6352       -- Machine_Radix --
6353       -------------------
6354
6355       when Attribute_Machine_Radix =>
6356          if Is_Fixed_Point_Type (P_Type) then
6357             if Is_Decimal_Fixed_Point_Type (P_Type)
6358               and then Machine_Radix_10 (P_Type)
6359             then
6360                Fold_Uint (N, Uint_10, True);
6361             else
6362                Fold_Uint (N, Uint_2, True);
6363             end if;
6364
6365          --  All floating-point type always have radix 2
6366
6367          else
6368             Fold_Uint (N, Uint_2, True);
6369          end if;
6370
6371       ----------------------
6372       -- Machine_Rounding --
6373       ----------------------
6374
6375       --  Note: for the folding case, it is fine to treat Machine_Rounding
6376       --  exactly the same way as Rounding, since this is one of the allowed
6377       --  behaviors, and performance is not an issue here. It might be a bit
6378       --  better to give the same result as it would give at run time, even
6379       --  though the non-determinism is certainly permitted.
6380
6381       when Attribute_Machine_Rounding =>
6382          Fold_Ureal (N,
6383            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
6384
6385       --------------------
6386       -- Machine_Rounds --
6387       --------------------
6388
6389       when Attribute_Machine_Rounds =>
6390
6391          --  Always False for fixed-point
6392
6393          if Is_Fixed_Point_Type (P_Type) then
6394             Fold_Uint (N, False_Value, True);
6395
6396          --  Else yield proper floating-point result
6397
6398          else
6399             Fold_Uint
6400               (N, UI_From_Int (Boolean'Pos (Machine_Rounds_On_Target)), True);
6401          end if;
6402
6403       ------------------
6404       -- Machine_Size --
6405       ------------------
6406
6407       --  Note: Machine_Size is identical to Object_Size
6408
6409       when Attribute_Machine_Size => Machine_Size : declare
6410          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6411
6412       begin
6413          if Known_Esize (P_TypeA) then
6414             Fold_Uint (N, Esize (P_TypeA), True);
6415          end if;
6416       end Machine_Size;
6417
6418       --------------
6419       -- Mantissa --
6420       --------------
6421
6422       when Attribute_Mantissa =>
6423
6424          --  Fixed-point mantissa
6425
6426          if Is_Fixed_Point_Type (P_Type) then
6427
6428             --  Compile time foldable case
6429
6430             if Compile_Time_Known_Value (Type_Low_Bound  (P_Type))
6431                  and then
6432                Compile_Time_Known_Value (Type_High_Bound (P_Type))
6433             then
6434                --  The calculation of the obsolete Ada 83 attribute Mantissa
6435                --  is annoying, because of AI00143, quoted here:
6436
6437                --  !question 84-01-10
6438
6439                --  Consider the model numbers for F:
6440
6441                --         type F is delta 1.0 range -7.0 .. 8.0;
6442
6443                --  The wording requires that F'MANTISSA be the SMALLEST
6444                --  integer number for which each  bound  of the specified
6445                --  range is either a model number or lies at most small
6446                --  distant from a model number. This means F'MANTISSA
6447                --  is required to be 3 since the range  -7.0 .. 7.0 fits
6448                --  in 3 signed bits, and 8 is "at most" 1.0 from a model
6449                --  number, namely, 7. Is this analysis correct? Note that
6450                --  this implies the upper bound of the range is not
6451                --  represented as a model number.
6452
6453                --  !response 84-03-17
6454
6455                --  The analysis is correct. The upper and lower bounds for
6456                --  a fixed  point type can lie outside the range of model
6457                --  numbers.
6458
6459                declare
6460                   Siz     : Uint;
6461                   LBound  : Ureal;
6462                   UBound  : Ureal;
6463                   Bound   : Ureal;
6464                   Max_Man : Uint;
6465
6466                begin
6467                   LBound  := Expr_Value_R (Type_Low_Bound  (P_Type));
6468                   UBound  := Expr_Value_R (Type_High_Bound (P_Type));
6469                   Bound   := UR_Max (UR_Abs (LBound), UR_Abs (UBound));
6470                   Max_Man := UR_Trunc (Bound / Small_Value (P_Type));
6471
6472                   --  If the Bound is exactly a model number, i.e. a multiple
6473                   --  of Small, then we back it off by one to get the integer
6474                   --  value that must be representable.
6475
6476                   if Small_Value (P_Type) * Max_Man = Bound then
6477                      Max_Man := Max_Man - 1;
6478                   end if;
6479
6480                   --  Now find corresponding size = Mantissa value
6481
6482                   Siz := Uint_0;
6483                   while 2 ** Siz < Max_Man loop
6484                      Siz := Siz + 1;
6485                   end loop;
6486
6487                   Fold_Uint (N, Siz, True);
6488                end;
6489
6490             else
6491                --  The case of dynamic bounds cannot be evaluated at compile
6492                --  time. Instead we use a runtime routine (see Exp_Attr).
6493
6494                null;
6495             end if;
6496
6497          --  Floating-point Mantissa
6498
6499          else
6500             Fold_Uint (N, Mantissa, True);
6501          end if;
6502
6503       ---------
6504       -- Max --
6505       ---------
6506
6507       when Attribute_Max => Max :
6508       begin
6509          if Is_Real_Type (P_Type) then
6510             Fold_Ureal
6511               (N, UR_Max (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
6512          else
6513             Fold_Uint (N, UI_Max (Expr_Value (E1), Expr_Value (E2)), Static);
6514          end if;
6515       end Max;
6516
6517       ----------------------------------
6518       -- Max_Alignment_For_Allocation --
6519       ----------------------------------
6520
6521       --  Max_Alignment_For_Allocation is usually the Alignment. However,
6522       --  arrays are allocated with dope, so we need to take into account both
6523       --  the alignment of the array, which comes from the component alignment,
6524       --  and the alignment of the dope. Also, if the alignment is unknown, we
6525       --  use the max (it's OK to be pessimistic).
6526
6527       when Attribute_Max_Alignment_For_Allocation =>
6528          declare
6529             A : Uint := UI_From_Int (Ttypes.Maximum_Alignment);
6530          begin
6531             if Known_Alignment (P_Type) and then
6532               (not Is_Array_Type (P_Type) or else Alignment (P_Type) > A)
6533             then
6534                A := Alignment (P_Type);
6535             end if;
6536
6537             Fold_Uint (N, A, Static);
6538          end;
6539
6540       ----------------------------------
6541       -- Max_Size_In_Storage_Elements --
6542       ----------------------------------
6543
6544       --  Max_Size_In_Storage_Elements is simply the Size rounded up to a
6545       --  Storage_Unit boundary. We can fold any cases for which the size
6546       --  is known by the front end.
6547
6548       when Attribute_Max_Size_In_Storage_Elements =>
6549          if Known_Esize (P_Type) then
6550             Fold_Uint (N,
6551               (Esize (P_Type) + System_Storage_Unit - 1) /
6552                                           System_Storage_Unit,
6553                Static);
6554          end if;
6555
6556       --------------------
6557       -- Mechanism_Code --
6558       --------------------
6559
6560       when Attribute_Mechanism_Code =>
6561          declare
6562             Val    : Int;
6563             Formal : Entity_Id;
6564             Mech   : Mechanism_Type;
6565
6566          begin
6567             if No (E1) then
6568                Mech := Mechanism (P_Entity);
6569
6570             else
6571                Val := UI_To_Int (Expr_Value (E1));
6572
6573                Formal := First_Formal (P_Entity);
6574                for J in 1 .. Val - 1 loop
6575                   Next_Formal (Formal);
6576                end loop;
6577                Mech := Mechanism (Formal);
6578             end if;
6579
6580             if Mech < 0 then
6581                Fold_Uint (N, UI_From_Int (Int (-Mech)), True);
6582             end if;
6583          end;
6584
6585       ---------
6586       -- Min --
6587       ---------
6588
6589       when Attribute_Min => Min :
6590       begin
6591          if Is_Real_Type (P_Type) then
6592             Fold_Ureal
6593               (N, UR_Min (Expr_Value_R (E1), Expr_Value_R (E2)), Static);
6594          else
6595             Fold_Uint
6596               (N, UI_Min (Expr_Value (E1), Expr_Value (E2)), Static);
6597          end if;
6598       end Min;
6599
6600       ---------
6601       -- Mod --
6602       ---------
6603
6604       when Attribute_Mod =>
6605          Fold_Uint
6606            (N, UI_Mod (Expr_Value (E1), Modulus (P_Base_Type)), Static);
6607
6608       -----------
6609       -- Model --
6610       -----------
6611
6612       when Attribute_Model =>
6613          Fold_Ureal (N,
6614            Eval_Fat.Model (P_Root_Type, Expr_Value_R (E1)), Static);
6615
6616       ----------------
6617       -- Model_Emin --
6618       ----------------
6619
6620       when Attribute_Model_Emin =>
6621          Fold_Uint (N, Model_Emin_Value (P_Base_Type), Static);
6622
6623       -------------------
6624       -- Model_Epsilon --
6625       -------------------
6626
6627       when Attribute_Model_Epsilon =>
6628          Fold_Ureal (N, Model_Epsilon_Value (P_Base_Type), Static);
6629
6630       --------------------
6631       -- Model_Mantissa --
6632       --------------------
6633
6634       when Attribute_Model_Mantissa =>
6635          Fold_Uint (N, Model_Mantissa_Value (P_Base_Type), Static);
6636
6637       -----------------
6638       -- Model_Small --
6639       -----------------
6640
6641       when Attribute_Model_Small =>
6642          Fold_Ureal (N, Model_Small_Value (P_Base_Type), Static);
6643
6644       -------------
6645       -- Modulus --
6646       -------------
6647
6648       when Attribute_Modulus =>
6649          Fold_Uint (N, Modulus (P_Type), True);
6650
6651       --------------------
6652       -- Null_Parameter --
6653       --------------------
6654
6655       --  Cannot fold, we know the value sort of, but the whole point is
6656       --  that there is no way to talk about this imaginary value except
6657       --  by using the attribute, so we leave it the way it is.
6658
6659       when Attribute_Null_Parameter =>
6660          null;
6661
6662       -----------------
6663       -- Object_Size --
6664       -----------------
6665
6666       --  The Object_Size attribute for a type returns the Esize of the
6667       --  type and can be folded if this value is known.
6668
6669       when Attribute_Object_Size => Object_Size : declare
6670          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6671
6672       begin
6673          if Known_Esize (P_TypeA) then
6674             Fold_Uint (N, Esize (P_TypeA), True);
6675          end if;
6676       end Object_Size;
6677
6678       -------------------------
6679       -- Passed_By_Reference --
6680       -------------------------
6681
6682       --  Scalar types are never passed by reference
6683
6684       when Attribute_Passed_By_Reference =>
6685          Fold_Uint (N, False_Value, True);
6686
6687       ---------
6688       -- Pos --
6689       ---------
6690
6691       when Attribute_Pos =>
6692          Fold_Uint (N, Expr_Value (E1), True);
6693
6694       ----------
6695       -- Pred --
6696       ----------
6697
6698       when Attribute_Pred => Pred :
6699       begin
6700          --  Floating-point case
6701
6702          if Is_Floating_Point_Type (P_Type) then
6703             Fold_Ureal (N,
6704               Eval_Fat.Pred (P_Root_Type, Expr_Value_R (E1)), Static);
6705
6706          --  Fixed-point case
6707
6708          elsif Is_Fixed_Point_Type (P_Type) then
6709             Fold_Ureal (N,
6710               Expr_Value_R (E1) - Small_Value (P_Type), True);
6711
6712          --  Modular integer case (wraps)
6713
6714          elsif Is_Modular_Integer_Type (P_Type) then
6715             Fold_Uint (N, (Expr_Value (E1) - 1) mod Modulus (P_Type), Static);
6716
6717          --  Other scalar cases
6718
6719          else
6720             pragma Assert (Is_Scalar_Type (P_Type));
6721
6722             if Is_Enumeration_Type (P_Type)
6723               and then Expr_Value (E1) =
6724                          Expr_Value (Type_Low_Bound (P_Base_Type))
6725             then
6726                Apply_Compile_Time_Constraint_Error
6727                  (N, "Pred of `&''First`",
6728                   CE_Overflow_Check_Failed,
6729                   Ent  => P_Base_Type,
6730                   Warn => not Static);
6731
6732                Check_Expressions;
6733                return;
6734             end if;
6735
6736             Fold_Uint (N, Expr_Value (E1) - 1, Static);
6737          end if;
6738       end Pred;
6739
6740       -----------
6741       -- Range --
6742       -----------
6743
6744       --  No processing required, because by this stage, Range has been
6745       --  replaced by First .. Last, so this branch can never be taken.
6746
6747       when Attribute_Range =>
6748          raise Program_Error;
6749
6750       ------------------
6751       -- Range_Length --
6752       ------------------
6753
6754       when Attribute_Range_Length =>
6755          Set_Bounds;
6756
6757          --  Can fold if both bounds are compile time known
6758
6759          if Compile_Time_Known_Value (Hi_Bound)
6760            and then Compile_Time_Known_Value (Lo_Bound)
6761          then
6762             Fold_Uint (N,
6763               UI_Max
6764                 (0, Expr_Value (Hi_Bound) - Expr_Value (Lo_Bound) + 1),
6765                  Static);
6766          end if;
6767
6768          --  One more case is where Hi_Bound and Lo_Bound are compile-time
6769          --  comparable, and we can figure out the difference between them.
6770
6771          declare
6772             Diff : aliased Uint;
6773
6774          begin
6775             case
6776               Compile_Time_Compare
6777                 (Lo_Bound, Hi_Bound, Diff'Access, Assume_Valid => False)
6778             is
6779                when EQ =>
6780                   Fold_Uint (N, Uint_1, False);
6781
6782                when GT =>
6783                   Fold_Uint (N, Uint_0, False);
6784
6785                when LT =>
6786                   if Diff /= No_Uint then
6787                      Fold_Uint (N, Diff + 1, False);
6788                   end if;
6789
6790                when others =>
6791                   null;
6792             end case;
6793          end;
6794
6795       ---------
6796       -- Ref --
6797       ---------
6798
6799       when Attribute_Ref =>
6800          Fold_Uint (N, Expr_Value (E1), True);
6801
6802       ---------------
6803       -- Remainder --
6804       ---------------
6805
6806       when Attribute_Remainder => Remainder : declare
6807          X : constant Ureal := Expr_Value_R (E1);
6808          Y : constant Ureal := Expr_Value_R (E2);
6809
6810       begin
6811          if UR_Is_Zero (Y) then
6812             Apply_Compile_Time_Constraint_Error
6813               (N, "division by zero in Remainder",
6814                CE_Overflow_Check_Failed,
6815                Warn => not Static);
6816
6817             Check_Expressions;
6818             return;
6819          end if;
6820
6821          Fold_Ureal (N, Eval_Fat.Remainder (P_Root_Type, X, Y), Static);
6822       end Remainder;
6823
6824       -----------
6825       -- Round --
6826       -----------
6827
6828       when Attribute_Round => Round :
6829       declare
6830          Sr : Ureal;
6831          Si : Uint;
6832
6833       begin
6834          --  First we get the (exact result) in units of small
6835
6836          Sr := Expr_Value_R (E1) / Small_Value (C_Type);
6837
6838          --  Now round that exactly to an integer
6839
6840          Si := UR_To_Uint (Sr);
6841
6842          --  Finally the result is obtained by converting back to real
6843
6844          Fold_Ureal (N, Si * Small_Value (C_Type), Static);
6845       end Round;
6846
6847       --------------
6848       -- Rounding --
6849       --------------
6850
6851       when Attribute_Rounding =>
6852          Fold_Ureal (N,
6853            Eval_Fat.Rounding (P_Root_Type, Expr_Value_R (E1)), Static);
6854
6855       ---------------
6856       -- Safe_Emax --
6857       ---------------
6858
6859       when Attribute_Safe_Emax =>
6860          Fold_Uint (N, Safe_Emax_Value (P_Type), Static);
6861
6862       ----------------
6863       -- Safe_First --
6864       ----------------
6865
6866       when Attribute_Safe_First =>
6867          Fold_Ureal (N, Safe_First_Value (P_Type), Static);
6868
6869       ----------------
6870       -- Safe_Large --
6871       ----------------
6872
6873       when Attribute_Safe_Large =>
6874          if Is_Fixed_Point_Type (P_Type) then
6875             Fold_Ureal
6876               (N, Expr_Value_R (Type_High_Bound (P_Base_Type)), Static);
6877          else
6878             Fold_Ureal (N, Safe_Last_Value (P_Type), Static);
6879          end if;
6880
6881       ---------------
6882       -- Safe_Last --
6883       ---------------
6884
6885       when Attribute_Safe_Last =>
6886          Fold_Ureal (N, Safe_Last_Value (P_Type), Static);
6887
6888       ----------------
6889       -- Safe_Small --
6890       ----------------
6891
6892       when Attribute_Safe_Small =>
6893
6894          --  In Ada 95, the old Ada 83 attribute Safe_Small is redundant
6895          --  for fixed-point, since is the same as Small, but we implement
6896          --  it for backwards compatibility.
6897
6898          if Is_Fixed_Point_Type (P_Type) then
6899             Fold_Ureal (N, Small_Value (P_Type), Static);
6900
6901          --  Ada 83 Safe_Small for floating-point cases
6902
6903          else
6904             Fold_Ureal (N, Model_Small_Value (P_Type), Static);
6905          end if;
6906
6907       -----------
6908       -- Scale --
6909       -----------
6910
6911       when Attribute_Scale =>
6912          Fold_Uint (N, Scale_Value (P_Type), True);
6913
6914       -------------
6915       -- Scaling --
6916       -------------
6917
6918       when Attribute_Scaling =>
6919          Fold_Ureal (N,
6920            Eval_Fat.Scaling
6921              (P_Root_Type, Expr_Value_R (E1), Expr_Value (E2)), Static);
6922
6923       ------------------
6924       -- Signed_Zeros --
6925       ------------------
6926
6927       when Attribute_Signed_Zeros =>
6928          Fold_Uint
6929            (N, UI_From_Int (Boolean'Pos (Signed_Zeros_On_Target)), Static);
6930
6931       ----------
6932       -- Size --
6933       ----------
6934
6935       --  Size attribute returns the RM size. All scalar types can be folded,
6936       --  as well as any types for which the size is known by the front end,
6937       --  including any type for which a size attribute is specified.
6938
6939       when Attribute_Size | Attribute_VADS_Size => Size : declare
6940          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
6941
6942       begin
6943          if RM_Size (P_TypeA) /= Uint_0 then
6944
6945             --  VADS_Size case
6946
6947             if Id = Attribute_VADS_Size or else Use_VADS_Size then
6948                declare
6949                   S : constant Node_Id := Size_Clause (P_TypeA);
6950
6951                begin
6952                   --  If a size clause applies, then use the size from it.
6953                   --  This is one of the rare cases where we can use the
6954                   --  Size_Clause field for a subtype when Has_Size_Clause
6955                   --  is False. Consider:
6956
6957                   --    type x is range 1 .. 64;
6958                   --    for x'size use 12;
6959                   --    subtype y is x range 0 .. 3;
6960
6961                   --  Here y has a size clause inherited from x, but normally
6962                   --  it does not apply, and y'size is 2. However, y'VADS_Size
6963                   --  is indeed 12 and not 2.
6964
6965                   if Present (S)
6966                     and then Is_OK_Static_Expression (Expression (S))
6967                   then
6968                      Fold_Uint (N, Expr_Value (Expression (S)), True);
6969
6970                   --  If no size is specified, then we simply use the object
6971                   --  size in the VADS_Size case (e.g. Natural'Size is equal
6972                   --  to Integer'Size, not one less).
6973
6974                   else
6975                      Fold_Uint (N, Esize (P_TypeA), True);
6976                   end if;
6977                end;
6978
6979             --  Normal case (Size) in which case we want the RM_Size
6980
6981             else
6982                Fold_Uint (N,
6983                  RM_Size (P_TypeA),
6984                  Static and then Is_Discrete_Type (P_TypeA));
6985             end if;
6986          end if;
6987       end Size;
6988
6989       -----------
6990       -- Small --
6991       -----------
6992
6993       when Attribute_Small =>
6994
6995          --  The floating-point case is present only for Ada 83 compatibility.
6996          --  Note that strictly this is an illegal addition, since we are
6997          --  extending an Ada 95 defined attribute, but we anticipate an
6998          --  ARG ruling that will permit this.
6999
7000          if Is_Floating_Point_Type (P_Type) then
7001
7002             --  Ada 83 attribute is defined as (RM83 3.5.8)
7003
7004             --    T'Small = 2.0**(-T'Emax - 1)
7005
7006             --  where
7007
7008             --    T'Emax = 4 * T'Mantissa
7009
7010             Fold_Ureal (N, Ureal_2 ** ((-(4 * Mantissa)) - 1), Static);
7011
7012          --  Normal Ada 95 fixed-point case
7013
7014          else
7015             Fold_Ureal (N, Small_Value (P_Type), True);
7016          end if;
7017
7018       -----------------
7019       -- Stream_Size --
7020       -----------------
7021
7022       when Attribute_Stream_Size =>
7023          null;
7024
7025       ----------
7026       -- Succ --
7027       ----------
7028
7029       when Attribute_Succ => Succ :
7030       begin
7031          --  Floating-point case
7032
7033          if Is_Floating_Point_Type (P_Type) then
7034             Fold_Ureal (N,
7035               Eval_Fat.Succ (P_Root_Type, Expr_Value_R (E1)), Static);
7036
7037          --  Fixed-point case
7038
7039          elsif Is_Fixed_Point_Type (P_Type) then
7040             Fold_Ureal (N,
7041               Expr_Value_R (E1) + Small_Value (P_Type), Static);
7042
7043          --  Modular integer case (wraps)
7044
7045          elsif Is_Modular_Integer_Type (P_Type) then
7046             Fold_Uint (N, (Expr_Value (E1) + 1) mod Modulus (P_Type), Static);
7047
7048          --  Other scalar cases
7049
7050          else
7051             pragma Assert (Is_Scalar_Type (P_Type));
7052
7053             if Is_Enumeration_Type (P_Type)
7054               and then Expr_Value (E1) =
7055                          Expr_Value (Type_High_Bound (P_Base_Type))
7056             then
7057                Apply_Compile_Time_Constraint_Error
7058                  (N, "Succ of `&''Last`",
7059                   CE_Overflow_Check_Failed,
7060                   Ent  => P_Base_Type,
7061                   Warn => not Static);
7062
7063                Check_Expressions;
7064                return;
7065             else
7066                Fold_Uint (N, Expr_Value (E1) + 1, Static);
7067             end if;
7068          end if;
7069       end Succ;
7070
7071       ----------------
7072       -- Truncation --
7073       ----------------
7074
7075       when Attribute_Truncation =>
7076          Fold_Ureal (N,
7077            Eval_Fat.Truncation (P_Root_Type, Expr_Value_R (E1)), Static);
7078
7079       ----------------
7080       -- Type_Class --
7081       ----------------
7082
7083       when Attribute_Type_Class => Type_Class : declare
7084          Typ : constant Entity_Id := Underlying_Type (P_Base_Type);
7085          Id  : RE_Id;
7086
7087       begin
7088          if Is_Descendent_Of_Address (Typ) then
7089             Id := RE_Type_Class_Address;
7090
7091          elsif Is_Enumeration_Type (Typ) then
7092             Id := RE_Type_Class_Enumeration;
7093
7094          elsif Is_Integer_Type (Typ) then
7095             Id := RE_Type_Class_Integer;
7096
7097          elsif Is_Fixed_Point_Type (Typ) then
7098             Id := RE_Type_Class_Fixed_Point;
7099
7100          elsif Is_Floating_Point_Type (Typ) then
7101             Id := RE_Type_Class_Floating_Point;
7102
7103          elsif Is_Array_Type (Typ) then
7104             Id := RE_Type_Class_Array;
7105
7106          elsif Is_Record_Type (Typ) then
7107             Id := RE_Type_Class_Record;
7108
7109          elsif Is_Access_Type (Typ) then
7110             Id := RE_Type_Class_Access;
7111
7112          elsif Is_Enumeration_Type (Typ) then
7113             Id := RE_Type_Class_Enumeration;
7114
7115          elsif Is_Task_Type (Typ) then
7116             Id := RE_Type_Class_Task;
7117
7118          --  We treat protected types like task types. It would make more
7119          --  sense to have another enumeration value, but after all the
7120          --  whole point of this feature is to be exactly DEC compatible,
7121          --  and changing the type Type_Class would not meet this requirement.
7122
7123          elsif Is_Protected_Type (Typ) then
7124             Id := RE_Type_Class_Task;
7125
7126          --  Not clear if there are any other possibilities, but if there
7127          --  are, then we will treat them as the address case.
7128
7129          else
7130             Id := RE_Type_Class_Address;
7131          end if;
7132
7133          Rewrite (N, New_Occurrence_Of (RTE (Id), Loc));
7134       end Type_Class;
7135
7136       -----------------------
7137       -- Unbiased_Rounding --
7138       -----------------------
7139
7140       when Attribute_Unbiased_Rounding =>
7141          Fold_Ureal (N,
7142            Eval_Fat.Unbiased_Rounding (P_Root_Type, Expr_Value_R (E1)),
7143            Static);
7144
7145       -------------------------
7146       -- Unconstrained_Array --
7147       -------------------------
7148
7149       when Attribute_Unconstrained_Array => Unconstrained_Array : declare
7150          Typ : constant Entity_Id := Underlying_Type (P_Type);
7151
7152       begin
7153          Rewrite (N, New_Occurrence_Of (
7154            Boolean_Literals (
7155              Is_Array_Type (P_Type)
7156               and then not Is_Constrained (Typ)), Loc));
7157
7158          --  Analyze and resolve as boolean, note that this attribute is
7159          --  a static attribute in GNAT.
7160
7161          Analyze_And_Resolve (N, Standard_Boolean);
7162          Static := True;
7163       end Unconstrained_Array;
7164
7165       ---------------
7166       -- VADS_Size --
7167       ---------------
7168
7169       --  Processing is shared with Size
7170
7171       ---------
7172       -- Val --
7173       ---------
7174
7175       when Attribute_Val => Val :
7176       begin
7177          if  Expr_Value (E1) < Expr_Value (Type_Low_Bound (P_Base_Type))
7178            or else
7179              Expr_Value (E1) > Expr_Value (Type_High_Bound (P_Base_Type))
7180          then
7181             Apply_Compile_Time_Constraint_Error
7182               (N, "Val expression out of range",
7183                CE_Range_Check_Failed,
7184                Warn => not Static);
7185
7186             Check_Expressions;
7187             return;
7188
7189          else
7190             Fold_Uint (N, Expr_Value (E1), Static);
7191          end if;
7192       end Val;
7193
7194       ----------------
7195       -- Value_Size --
7196       ----------------
7197
7198       --  The Value_Size attribute for a type returns the RM size of the
7199       --  type. This an always be folded for scalar types, and can also
7200       --  be folded for non-scalar types if the size is set.
7201
7202       when Attribute_Value_Size => Value_Size : declare
7203          P_TypeA : constant Entity_Id := Underlying_Type (P_Type);
7204       begin
7205          if RM_Size (P_TypeA) /= Uint_0 then
7206             Fold_Uint (N, RM_Size (P_TypeA), True);
7207          end if;
7208       end Value_Size;
7209
7210       -------------
7211       -- Version --
7212       -------------
7213
7214       --  Version can never be static
7215
7216       when Attribute_Version =>
7217          null;
7218
7219       ----------------
7220       -- Wide_Image --
7221       ----------------
7222
7223       --  Wide_Image is a scalar attribute, but is never static, because it
7224       --  is not a static function (having a non-scalar argument (RM 4.9(22))
7225
7226       when Attribute_Wide_Image =>
7227          null;
7228
7229       ---------------------
7230       -- Wide_Wide_Image --
7231       ---------------------
7232
7233       --  Wide_Wide_Image is a scalar attribute but is never static, because it
7234       --  is not a static function (having a non-scalar argument (RM 4.9(22)).
7235
7236       when Attribute_Wide_Wide_Image =>
7237          null;
7238
7239       ---------------------
7240       -- Wide_Wide_Width --
7241       ---------------------
7242
7243       --  Processing for Wide_Wide_Width is combined with Width
7244
7245       ----------------
7246       -- Wide_Width --
7247       ----------------
7248
7249       --  Processing for Wide_Width is combined with Width
7250
7251       -----------
7252       -- Width --
7253       -----------
7254
7255       --  This processing also handles the case of Wide_[Wide_]Width
7256
7257       when Attribute_Width |
7258            Attribute_Wide_Width |
7259            Attribute_Wide_Wide_Width => Width :
7260       begin
7261          if Compile_Time_Known_Bounds (P_Type) then
7262
7263             --  Floating-point types
7264
7265             if Is_Floating_Point_Type (P_Type) then
7266
7267                --  Width is zero for a null range (RM 3.5 (38))
7268
7269                if Expr_Value_R (Type_High_Bound (P_Type)) <
7270                   Expr_Value_R (Type_Low_Bound (P_Type))
7271                then
7272                   Fold_Uint (N, Uint_0, True);
7273
7274                else
7275                   --  For floating-point, we have +N.dddE+nnn where length
7276                   --  of ddd is determined by type'Digits - 1, but is one
7277                   --  if Digits is one (RM 3.5 (33)).
7278
7279                   --  nnn is set to 2 for Short_Float and Float (32 bit
7280                   --  floats), and 3 for Long_Float and Long_Long_Float.
7281                   --  For machines where Long_Long_Float is the IEEE
7282                   --  extended precision type, the exponent takes 4 digits.
7283
7284                   declare
7285                      Len : Int :=
7286                              Int'Max (2, UI_To_Int (Digits_Value (P_Type)));
7287
7288                   begin
7289                      if Esize (P_Type) <= 32 then
7290                         Len := Len + 6;
7291                      elsif Esize (P_Type) = 64 then
7292                         Len := Len + 7;
7293                      else
7294                         Len := Len + 8;
7295                      end if;
7296
7297                      Fold_Uint (N, UI_From_Int (Len), True);
7298                   end;
7299                end if;
7300
7301             --  Fixed-point types
7302
7303             elsif Is_Fixed_Point_Type (P_Type) then
7304
7305                --  Width is zero for a null range (RM 3.5 (38))
7306
7307                if Expr_Value (Type_High_Bound (P_Type)) <
7308                   Expr_Value (Type_Low_Bound  (P_Type))
7309                then
7310                   Fold_Uint (N, Uint_0, True);
7311
7312                --  The non-null case depends on the specific real type
7313
7314                else
7315                   --  For fixed-point type width is Fore + 1 + Aft (RM 3.5(34))
7316
7317                   Fold_Uint
7318                     (N, UI_From_Int (Fore_Value + 1) + Aft_Value (P_Type),
7319                      True);
7320                end if;
7321
7322             --  Discrete types
7323
7324             else
7325                declare
7326                   R  : constant Entity_Id := Root_Type (P_Type);
7327                   Lo : constant Uint := Expr_Value (Type_Low_Bound (P_Type));
7328                   Hi : constant Uint := Expr_Value (Type_High_Bound (P_Type));
7329                   W  : Nat;
7330                   Wt : Nat;
7331                   T  : Uint;
7332                   L  : Node_Id;
7333                   C  : Character;
7334
7335                begin
7336                   --  Empty ranges
7337
7338                   if Lo > Hi then
7339                      W := 0;
7340
7341                   --  Width for types derived from Standard.Character
7342                   --  and Standard.Wide_[Wide_]Character.
7343
7344                   elsif Is_Standard_Character_Type (P_Type) then
7345                      W := 0;
7346
7347                      --  Set W larger if needed
7348
7349                      for J in UI_To_Int (Lo) .. UI_To_Int (Hi) loop
7350
7351                         --  All wide characters look like Hex_hhhhhhhh
7352
7353                         if J > 255 then
7354
7355                            --  No need to compute this more than once!
7356
7357                            exit;
7358
7359                         else
7360                            C := Character'Val (J);
7361
7362                            --  Test for all cases where Character'Image
7363                            --  yields an image that is longer than three
7364                            --  characters. First the cases of Reserved_xxx
7365                            --  names (length = 12).
7366
7367                            case C is
7368                               when Reserved_128 | Reserved_129 |
7369                                    Reserved_132 | Reserved_153
7370                                 => Wt := 12;
7371
7372                               when BS | HT | LF | VT | FF | CR |
7373                                    SO | SI | EM | FS | GS | RS |
7374                                    US | RI | MW | ST | PM
7375                                 => Wt := 2;
7376
7377                               when NUL | SOH | STX | ETX | EOT |
7378                                    ENQ | ACK | BEL | DLE | DC1 |
7379                                    DC2 | DC3 | DC4 | NAK | SYN |
7380                                    ETB | CAN | SUB | ESC | DEL |
7381                                    BPH | NBH | NEL | SSA | ESA |
7382                                    HTS | HTJ | VTS | PLD | PLU |
7383                                    SS2 | SS3 | DCS | PU1 | PU2 |
7384                                    STS | CCH | SPA | EPA | SOS |
7385                                    SCI | CSI | OSC | APC
7386                                 => Wt := 3;
7387
7388                               when Space .. Tilde |
7389                                    No_Break_Space .. LC_Y_Diaeresis
7390                                 =>
7391                                  --  Special case of soft hyphen in Ada 2005
7392
7393                                  if C = Character'Val (16#AD#)
7394                                    and then Ada_Version >= Ada_2005
7395                                  then
7396                                     Wt := 11;
7397                                  else
7398                                     Wt := 3;
7399                                  end if;
7400                            end case;
7401
7402                            W := Int'Max (W, Wt);
7403                         end if;
7404                      end loop;
7405
7406                   --  Width for types derived from Standard.Boolean
7407
7408                   elsif R = Standard_Boolean then
7409                      if Lo = 0 then
7410                         W := 5; -- FALSE
7411                      else
7412                         W := 4; -- TRUE
7413                      end if;
7414
7415                   --  Width for integer types
7416
7417                   elsif Is_Integer_Type (P_Type) then
7418                      T := UI_Max (abs Lo, abs Hi);
7419
7420                      W := 2;
7421                      while T >= 10 loop
7422                         W := W + 1;
7423                         T := T / 10;
7424                      end loop;
7425
7426                   --  Only remaining possibility is user declared enum type
7427
7428                   else
7429                      pragma Assert (Is_Enumeration_Type (P_Type));
7430
7431                      W := 0;
7432                      L := First_Literal (P_Type);
7433
7434                      while Present (L) loop
7435
7436                         --  Only pay attention to in range characters
7437
7438                         if Lo <= Enumeration_Pos (L)
7439                           and then Enumeration_Pos (L) <= Hi
7440                         then
7441                            --  For Width case, use decoded name
7442
7443                            if Id = Attribute_Width then
7444                               Get_Decoded_Name_String (Chars (L));
7445                               Wt := Nat (Name_Len);
7446
7447                            --  For Wide_[Wide_]Width, use encoded name, and
7448                            --  then adjust for the encoding.
7449
7450                            else
7451                               Get_Name_String (Chars (L));
7452
7453                               --  Character literals are always of length 3
7454
7455                               if Name_Buffer (1) = 'Q' then
7456                                  Wt := 3;
7457
7458                               --  Otherwise loop to adjust for upper/wide chars
7459
7460                               else
7461                                  Wt := Nat (Name_Len);
7462
7463                                  for J in 1 .. Name_Len loop
7464                                     if Name_Buffer (J) = 'U' then
7465                                        Wt := Wt - 2;
7466                                     elsif Name_Buffer (J) = 'W' then
7467                                        Wt := Wt - 4;
7468                                     end if;
7469                                  end loop;
7470                               end if;
7471                            end if;
7472
7473                            W := Int'Max (W, Wt);
7474                         end if;
7475
7476                         Next_Literal (L);
7477                      end loop;
7478                   end if;
7479
7480                   Fold_Uint (N, UI_From_Int (W), True);
7481                end;
7482             end if;
7483          end if;
7484       end Width;
7485
7486       --  The following attributes denote functions that cannot be folded
7487
7488       when Attribute_From_Any |
7489            Attribute_To_Any   |
7490            Attribute_TypeCode =>
7491          null;
7492
7493       --  The following attributes can never be folded, and furthermore we
7494       --  should not even have entered the case statement for any of these.
7495       --  Note that in some cases, the values have already been folded as
7496       --  a result of the processing in Analyze_Attribute.
7497
7498       when Attribute_Abort_Signal             |
7499            Attribute_Access                   |
7500            Attribute_Address                  |
7501            Attribute_Address_Size             |
7502            Attribute_Asm_Input                |
7503            Attribute_Asm_Output               |
7504            Attribute_Base                     |
7505            Attribute_Bit_Order                |
7506            Attribute_Bit_Position             |
7507            Attribute_Callable                 |
7508            Attribute_Caller                   |
7509            Attribute_Class                    |
7510            Attribute_Code_Address             |
7511            Attribute_Compiler_Version         |
7512            Attribute_Count                    |
7513            Attribute_Default_Bit_Order        |
7514            Attribute_Elaborated               |
7515            Attribute_Elab_Body                |
7516            Attribute_Elab_Spec                |
7517            Attribute_Enabled                  |
7518            Attribute_External_Tag             |
7519            Attribute_Fast_Math                |
7520            Attribute_First_Bit                |
7521            Attribute_Input                    |
7522            Attribute_Last_Bit                 |
7523            Attribute_Maximum_Alignment        |
7524            Attribute_Old                      |
7525            Attribute_Output                   |
7526            Attribute_Partition_ID             |
7527            Attribute_Pool_Address             |
7528            Attribute_Position                 |
7529            Attribute_Priority                 |
7530            Attribute_Read                     |
7531            Attribute_Result                   |
7532            Attribute_Storage_Pool             |
7533            Attribute_Storage_Size             |
7534            Attribute_Storage_Unit             |
7535            Attribute_Stub_Type                |
7536            Attribute_Tag                      |
7537            Attribute_Target_Name              |
7538            Attribute_Terminated               |
7539            Attribute_To_Address               |
7540            Attribute_Type_Key                 |
7541            Attribute_UET_Address              |
7542            Attribute_Unchecked_Access         |
7543            Attribute_Universal_Literal_String |
7544            Attribute_Unrestricted_Access      |
7545            Attribute_Valid                    |
7546            Attribute_Value                    |
7547            Attribute_Wchar_T_Size             |
7548            Attribute_Wide_Value               |
7549            Attribute_Wide_Wide_Value          |
7550            Attribute_Word_Size                |
7551            Attribute_Write                    =>
7552
7553          raise Program_Error;
7554       end case;
7555
7556       --  At the end of the case, one more check. If we did a static evaluation
7557       --  so that the result is now a literal, then set Is_Static_Expression
7558       --  in the constant only if the prefix type is a static subtype. For
7559       --  non-static subtypes, the folding is still OK, but not static.
7560
7561       --  An exception is the GNAT attribute Constrained_Array which is
7562       --  defined to be a static attribute in all cases.
7563
7564       if Nkind_In (N, N_Integer_Literal,
7565                       N_Real_Literal,
7566                       N_Character_Literal,
7567                       N_String_Literal)
7568         or else (Is_Entity_Name (N)
7569                   and then Ekind (Entity (N)) = E_Enumeration_Literal)
7570       then
7571          Set_Is_Static_Expression (N, Static);
7572
7573       --  If this is still an attribute reference, then it has not been folded
7574       --  and that means that its expressions are in a non-static context.
7575
7576       elsif Nkind (N) = N_Attribute_Reference then
7577          Check_Expressions;
7578
7579       --  Note: the else case not covered here are odd cases where the
7580       --  processing has transformed the attribute into something other
7581       --  than a constant. Nothing more to do in such cases.
7582
7583       else
7584          null;
7585       end if;
7586    end Eval_Attribute;
7587
7588    ------------------------------
7589    -- Is_Anonymous_Tagged_Base --
7590    ------------------------------
7591
7592    function Is_Anonymous_Tagged_Base
7593      (Anon : Entity_Id;
7594       Typ  : Entity_Id)
7595       return Boolean
7596    is
7597    begin
7598       return
7599         Anon = Current_Scope
7600           and then Is_Itype (Anon)
7601           and then Associated_Node_For_Itype (Anon) = Parent (Typ);
7602    end Is_Anonymous_Tagged_Base;
7603
7604    --------------------------------
7605    -- Name_Implies_Lvalue_Prefix --
7606    --------------------------------
7607
7608    function Name_Implies_Lvalue_Prefix (Nam : Name_Id) return Boolean is
7609       pragma Assert (Is_Attribute_Name (Nam));
7610    begin
7611       return Attribute_Name_Implies_Lvalue_Prefix (Get_Attribute_Id (Nam));
7612    end Name_Implies_Lvalue_Prefix;
7613
7614    -----------------------
7615    -- Resolve_Attribute --
7616    -----------------------
7617
7618    procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id) is
7619       Loc      : constant Source_Ptr   := Sloc (N);
7620       P        : constant Node_Id      := Prefix (N);
7621       Aname    : constant Name_Id      := Attribute_Name (N);
7622       Attr_Id  : constant Attribute_Id := Get_Attribute_Id (Aname);
7623       Btyp     : constant Entity_Id    := Base_Type (Typ);
7624       Des_Btyp : Entity_Id;
7625       Index    : Interp_Index;
7626       It       : Interp;
7627       Nom_Subt : Entity_Id;
7628
7629       procedure Accessibility_Message;
7630       --  Error, or warning within an instance, if the static accessibility
7631       --  rules of 3.10.2 are violated.
7632
7633       ---------------------------
7634       -- Accessibility_Message --
7635       ---------------------------
7636
7637       procedure Accessibility_Message is
7638          Indic : Node_Id := Parent (Parent (N));
7639
7640       begin
7641          --  In an instance, this is a runtime check, but one we
7642          --  know will fail, so generate an appropriate warning.
7643
7644          if In_Instance_Body then
7645             Error_Msg_F ("?non-local pointer cannot point to local object", P);
7646             Error_Msg_F
7647               ("\?Program_Error will be raised at run time", P);
7648             Rewrite (N,
7649               Make_Raise_Program_Error (Loc,
7650                 Reason => PE_Accessibility_Check_Failed));
7651             Set_Etype (N, Typ);
7652             return;
7653
7654          else
7655             Error_Msg_F ("non-local pointer cannot point to local object", P);
7656
7657             --  Check for case where we have a missing access definition
7658
7659             if Is_Record_Type (Current_Scope)
7660               and then
7661                 Nkind_In (Parent (N), N_Discriminant_Association,
7662                                       N_Index_Or_Discriminant_Constraint)
7663             then
7664                Indic := Parent (Parent (N));
7665                while Present (Indic)
7666                  and then Nkind (Indic) /= N_Subtype_Indication
7667                loop
7668                   Indic := Parent (Indic);
7669                end loop;
7670
7671                if Present (Indic) then
7672                   Error_Msg_NE
7673                     ("\use an access definition for" &
7674                      " the access discriminant of&",
7675                      N, Entity (Subtype_Mark (Indic)));
7676                end if;
7677             end if;
7678          end if;
7679       end Accessibility_Message;
7680
7681    --  Start of processing for Resolve_Attribute
7682
7683    begin
7684       --  If error during analysis, no point in continuing, except for array
7685       --  types, where we get better recovery by using unconstrained indexes
7686       --  than nothing at all (see Check_Array_Type).
7687
7688       if Error_Posted (N)
7689         and then Attr_Id /= Attribute_First
7690         and then Attr_Id /= Attribute_Last
7691         and then Attr_Id /= Attribute_Length
7692         and then Attr_Id /= Attribute_Range
7693       then
7694          return;
7695       end if;
7696
7697       --  If attribute was universal type, reset to actual type
7698
7699       if Etype (N) = Universal_Integer
7700         or else Etype (N) = Universal_Real
7701       then
7702          Set_Etype (N, Typ);
7703       end if;
7704
7705       --  Remaining processing depends on attribute
7706
7707       case Attr_Id is
7708
7709          ------------
7710          -- Access --
7711          ------------
7712
7713          --  For access attributes, if the prefix denotes an entity, it is
7714          --  interpreted as a name, never as a call. It may be overloaded,
7715          --  in which case resolution uses the profile of the context type.
7716          --  Otherwise prefix must be resolved.
7717
7718          when Attribute_Access
7719             | Attribute_Unchecked_Access
7720             | Attribute_Unrestricted_Access =>
7721
7722          Access_Attribute :
7723          begin
7724             if Is_Variable (P) then
7725                Note_Possible_Modification (P, Sure => False);
7726             end if;
7727
7728             --  The following comes from a query by Adam Beneschan, concerning
7729             --  improper use of universal_access in equality tests involving
7730             --  anonymous access types. Another good reason for 'Ref, but
7731             --  for now disable the test, which breaks several filed tests.
7732
7733             if Ekind (Typ) = E_Anonymous_Access_Type
7734               and then Nkind_In (Parent (N), N_Op_Eq, N_Op_Ne)
7735               and then False
7736             then
7737                Error_Msg_N ("need unique type to resolve 'Access", N);
7738                Error_Msg_N ("\qualify attribute with some access type", N);
7739             end if;
7740
7741             if Is_Entity_Name (P) then
7742                if Is_Overloaded (P) then
7743                   Get_First_Interp (P, Index, It);
7744                   while Present (It.Nam) loop
7745                      if Type_Conformant (Designated_Type (Typ), It.Nam) then
7746                         Set_Entity (P, It.Nam);
7747
7748                         --  The prefix is definitely NOT overloaded anymore at
7749                         --  this point, so we reset the Is_Overloaded flag to
7750                         --  avoid any confusion when reanalyzing the node.
7751
7752                         Set_Is_Overloaded (P, False);
7753                         Set_Is_Overloaded (N, False);
7754                         Generate_Reference (Entity (P), P);
7755                         exit;
7756                      end if;
7757
7758                      Get_Next_Interp (Index, It);
7759                   end loop;
7760
7761                --  If Prefix is a subprogram name, it is frozen by this
7762                --  reference:
7763
7764                --    If it is a type, there is nothing to resolve.
7765                --    If it is an object, complete its resolution.
7766
7767                elsif Is_Overloadable (Entity (P)) then
7768
7769                   --  Avoid insertion of freeze actions in spec expression mode
7770
7771                   if not In_Spec_Expression then
7772                      Freeze_Before (N, Entity (P));
7773                   end if;
7774
7775                elsif Is_Type (Entity (P)) then
7776                   null;
7777                else
7778                   Resolve (P);
7779                end if;
7780
7781                Error_Msg_Name_1 := Aname;
7782
7783                if not Is_Entity_Name (P) then
7784                   null;
7785
7786                elsif Is_Overloadable (Entity (P))
7787                  and then Is_Abstract_Subprogram (Entity (P))
7788                then
7789                   Error_Msg_F ("prefix of % attribute cannot be abstract", P);
7790                   Set_Etype (N, Any_Type);
7791
7792                elsif Convention (Entity (P)) = Convention_Intrinsic then
7793                   if Ekind (Entity (P)) = E_Enumeration_Literal then
7794                      Error_Msg_F
7795                        ("prefix of % attribute cannot be enumeration literal",
7796                         P);
7797                   else
7798                      Error_Msg_F
7799                        ("prefix of % attribute cannot be intrinsic", P);
7800                   end if;
7801
7802                   Set_Etype (N, Any_Type);
7803                end if;
7804
7805                --  Assignments, return statements, components of aggregates,
7806                --  generic instantiations will require convention checks if
7807                --  the type is an access to subprogram. Given that there will
7808                --  also be accessibility checks on those, this is where the
7809                --  checks can eventually be centralized ???
7810
7811                if Ekind_In (Btyp, E_Access_Subprogram_Type,
7812                                   E_Anonymous_Access_Subprogram_Type,
7813                                   E_Anonymous_Access_Protected_Subprogram_Type)
7814                then
7815                   --  Deal with convention mismatch
7816
7817                   if Convention (Btyp) /= Convention (Entity (P)) then
7818                      Error_Msg_FE
7819                        ("subprogram & has wrong convention", P, Entity (P));
7820
7821                      Error_Msg_FE
7822                        ("\does not match convention of access type &",
7823                         P, Btyp);
7824
7825                      if not Has_Convention_Pragma (Btyp) then
7826                         Error_Msg_FE
7827                           ("\probable missing pragma Convention for &",
7828                            P, Btyp);
7829                      end if;
7830
7831                   else
7832                      Check_Subtype_Conformant
7833                        (New_Id  => Entity (P),
7834                         Old_Id  => Designated_Type (Btyp),
7835                         Err_Loc => P);
7836                   end if;
7837
7838                   if Attr_Id = Attribute_Unchecked_Access then
7839                      Error_Msg_Name_1 := Aname;
7840                      Error_Msg_F
7841                        ("attribute% cannot be applied to a subprogram", P);
7842
7843                   elsif Aname = Name_Unrestricted_Access then
7844                      null;  --  Nothing to check
7845
7846                   --  Check the static accessibility rule of 3.10.2(32).
7847                   --  This rule also applies within the private part of an
7848                   --  instantiation. This rule does not apply to anonymous
7849                   --  access-to-subprogram types in access parameters.
7850
7851                   elsif Attr_Id = Attribute_Access
7852                     and then not In_Instance_Body
7853                     and then
7854                       (Ekind (Btyp) = E_Access_Subprogram_Type
7855                         or else Is_Local_Anonymous_Access (Btyp))
7856
7857                     and then Subprogram_Access_Level (Entity (P)) >
7858                                Type_Access_Level (Btyp)
7859                   then
7860                      Error_Msg_F
7861                        ("subprogram must not be deeper than access type", P);
7862
7863                   --  Check the restriction of 3.10.2(32) that disallows the
7864                   --  access attribute within a generic body when the ultimate
7865                   --  ancestor of the type of the attribute is declared outside
7866                   --  of the generic unit and the subprogram is declared within
7867                   --  that generic unit. This includes any such attribute that
7868                   --  occurs within the body of a generic unit that is a child
7869                   --  of the generic unit where the subprogram is declared.
7870
7871                   --  The rule also prohibits applying the attribute when the
7872                   --  access type is a generic formal access type (since the
7873                   --  level of the actual type is not known). This restriction
7874                   --  does not apply when the attribute type is an anonymous
7875                   --  access-to-subprogram type. Note that this check was
7876                   --  revised by AI-229, because the originally Ada 95 rule
7877                   --  was too lax. The original rule only applied when the
7878                   --  subprogram was declared within the body of the generic,
7879                   --  which allowed the possibility of dangling references).
7880                   --  The rule was also too strict in some case, in that it
7881                   --  didn't permit the access to be declared in the generic
7882                   --  spec, whereas the revised rule does (as long as it's not
7883                   --  a formal type).
7884
7885                   --  There are a couple of subtleties of the test for applying
7886                   --  the check that are worth noting. First, we only apply it
7887                   --  when the levels of the subprogram and access type are the
7888                   --  same (the case where the subprogram is statically deeper
7889                   --  was applied above, and the case where the type is deeper
7890                   --  is always safe). Second, we want the check to apply
7891                   --  within nested generic bodies and generic child unit
7892                   --  bodies, but not to apply to an attribute that appears in
7893                   --  the generic unit's specification. This is done by testing
7894                   --  that the attribute's innermost enclosing generic body is
7895                   --  not the same as the innermost generic body enclosing the
7896                   --  generic unit where the subprogram is declared (we don't
7897                   --  want the check to apply when the access attribute is in
7898                   --  the spec and there's some other generic body enclosing
7899                   --  generic). Finally, there's no point applying the check
7900                   --  when within an instance, because any violations will have
7901                   --  been caught by the compilation of the generic unit.
7902
7903                   --  Note that we relax this check in CodePeer mode for
7904                   --  compatibility with legacy code, since CodePeer is an
7905                   --  Ada source code analyzer, not a strict compiler.
7906                   --  ??? Note that a better approach would be to have a
7907                   --  separate switch to relax this rule, and enable this
7908                   --  switch in CodePeer mode.
7909
7910                   elsif Attr_Id = Attribute_Access
7911                     and then not CodePeer_Mode
7912                     and then not In_Instance
7913                     and then Present (Enclosing_Generic_Unit (Entity (P)))
7914                     and then Present (Enclosing_Generic_Body (N))
7915                     and then Enclosing_Generic_Body (N) /=
7916                                Enclosing_Generic_Body
7917                                  (Enclosing_Generic_Unit (Entity (P)))
7918                     and then Subprogram_Access_Level (Entity (P)) =
7919                                Type_Access_Level (Btyp)
7920                     and then Ekind (Btyp) /=
7921                                E_Anonymous_Access_Subprogram_Type
7922                     and then Ekind (Btyp) /=
7923                                E_Anonymous_Access_Protected_Subprogram_Type
7924                   then
7925                      --  The attribute type's ultimate ancestor must be
7926                      --  declared within the same generic unit as the
7927                      --  subprogram is declared. The error message is
7928                      --  specialized to say "ancestor" for the case where the
7929                      --  access type is not its own ancestor, since saying
7930                      --  simply "access type" would be very confusing.
7931
7932                      if Enclosing_Generic_Unit (Entity (P)) /=
7933                           Enclosing_Generic_Unit (Root_Type (Btyp))
7934                      then
7935                         Error_Msg_N
7936                           ("''Access attribute not allowed in generic body",
7937                            N);
7938
7939                         if Root_Type (Btyp) = Btyp then
7940                            Error_Msg_NE
7941                              ("\because " &
7942                               "access type & is declared outside " &
7943                               "generic unit (RM 3.10.2(32))", N, Btyp);
7944                         else
7945                            Error_Msg_NE
7946                              ("\because ancestor of " &
7947                               "access type & is declared outside " &
7948                               "generic unit (RM 3.10.2(32))", N, Btyp);
7949                         end if;
7950
7951                         Error_Msg_NE
7952                           ("\move ''Access to private part, or " &
7953                            "(Ada 2005) use anonymous access type instead of &",
7954                            N, Btyp);
7955
7956                      --  If the ultimate ancestor of the attribute's type is
7957                      --  a formal type, then the attribute is illegal because
7958                      --  the actual type might be declared at a higher level.
7959                      --  The error message is specialized to say "ancestor"
7960                      --  for the case where the access type is not its own
7961                      --  ancestor, since saying simply "access type" would be
7962                      --  very confusing.
7963
7964                      elsif Is_Generic_Type (Root_Type (Btyp)) then
7965                         if Root_Type (Btyp) = Btyp then
7966                            Error_Msg_N
7967                              ("access type must not be a generic formal type",
7968                               N);
7969                         else
7970                            Error_Msg_N
7971                              ("ancestor access type must not be a generic " &
7972                               "formal type", N);
7973                         end if;
7974                      end if;
7975                   end if;
7976                end if;
7977
7978                --  If this is a renaming, an inherited operation, or a
7979                --  subprogram instance, use the original entity. This may make
7980                --  the node type-inconsistent, so this transformation can only
7981                --  be done if the node will not be reanalyzed. In particular,
7982                --  if it is within a default expression, the transformation
7983                --  must be delayed until the default subprogram is created for
7984                --  it, when the enclosing subprogram is frozen.
7985
7986                if Is_Entity_Name (P)
7987                  and then Is_Overloadable (Entity (P))
7988                  and then Present (Alias (Entity (P)))
7989                  and then Expander_Active
7990                then
7991                   Rewrite (P,
7992                     New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
7993                end if;
7994
7995             elsif Nkind (P) = N_Selected_Component
7996               and then Is_Overloadable (Entity (Selector_Name (P)))
7997             then
7998                --  Protected operation. If operation is overloaded, must
7999                --  disambiguate. Prefix that denotes protected object itself
8000                --  is resolved with its own type.
8001
8002                if Attr_Id = Attribute_Unchecked_Access then
8003                   Error_Msg_Name_1 := Aname;
8004                   Error_Msg_F
8005                     ("attribute% cannot be applied to protected operation", P);
8006                end if;
8007
8008                Resolve (Prefix (P));
8009                Generate_Reference (Entity (Selector_Name (P)), P);
8010
8011             elsif Is_Overloaded (P) then
8012
8013                --  Use the designated type of the context to disambiguate
8014                --  Note that this was not strictly conformant to Ada 95,
8015                --  but was the implementation adopted by most Ada 95 compilers.
8016                --  The use of the context type to resolve an Access attribute
8017                --  reference is now mandated in AI-235 for Ada 2005.
8018
8019                declare
8020                   Index : Interp_Index;
8021                   It    : Interp;
8022
8023                begin
8024                   Get_First_Interp (P, Index, It);
8025                   while Present (It.Typ) loop
8026                      if Covers (Designated_Type (Typ), It.Typ) then
8027                         Resolve (P, It.Typ);
8028                         exit;
8029                      end if;
8030
8031                      Get_Next_Interp (Index, It);
8032                   end loop;
8033                end;
8034             else
8035                Resolve (P);
8036             end if;
8037
8038             --  X'Access is illegal if X denotes a constant and the access type
8039             --  is access-to-variable. Same for 'Unchecked_Access. The rule
8040             --  does not apply to 'Unrestricted_Access. If the reference is a
8041             --  default-initialized aggregate component for a self-referential
8042             --  type the reference is legal.
8043
8044             if not (Ekind (Btyp) = E_Access_Subprogram_Type
8045                      or else Ekind (Btyp) = E_Anonymous_Access_Subprogram_Type
8046                      or else (Is_Record_Type (Btyp)
8047                                and then
8048                                  Present (Corresponding_Remote_Type (Btyp)))
8049                      or else Ekind (Btyp) = E_Access_Protected_Subprogram_Type
8050                      or else Ekind (Btyp)
8051                                = E_Anonymous_Access_Protected_Subprogram_Type
8052                      or else Is_Access_Constant (Btyp)
8053                      or else Is_Variable (P)
8054                      or else Attr_Id = Attribute_Unrestricted_Access)
8055             then
8056                if Is_Entity_Name (P)
8057                  and then Is_Type (Entity (P))
8058                then
8059                   --  Legality of a self-reference through an access
8060                   --  attribute has been verified in Analyze_Access_Attribute.
8061
8062                   null;
8063
8064                elsif Comes_From_Source (N) then
8065                   Error_Msg_F ("access-to-variable designates constant", P);
8066                end if;
8067             end if;
8068
8069             Des_Btyp := Designated_Type (Btyp);
8070
8071             if Ada_Version >= Ada_2005
8072               and then Is_Incomplete_Type (Des_Btyp)
8073             then
8074                --  Ada 2005 (AI-412): If the (sub)type is a limited view of an
8075                --  imported entity, and the non-limited view is visible, make
8076                --  use of it. If it is an incomplete subtype, use the base type
8077                --  in any case.
8078
8079                if From_With_Type (Des_Btyp)
8080                  and then Present (Non_Limited_View (Des_Btyp))
8081                then
8082                   Des_Btyp := Non_Limited_View (Des_Btyp);
8083
8084                elsif Ekind (Des_Btyp) = E_Incomplete_Subtype then
8085                   Des_Btyp := Etype (Des_Btyp);
8086                end if;
8087             end if;
8088
8089             if (Attr_Id = Attribute_Access
8090                   or else
8091                 Attr_Id = Attribute_Unchecked_Access)
8092               and then (Ekind (Btyp) = E_General_Access_Type
8093                           or else Ekind (Btyp) = E_Anonymous_Access_Type)
8094             then
8095                --  Ada 2005 (AI-230): Check the accessibility of anonymous
8096                --  access types for stand-alone objects, record and array
8097                --  components, and return objects. For a component definition
8098                --  the level is the same of the enclosing composite type.
8099
8100                if Ada_Version >= Ada_2005
8101                  and then Is_Local_Anonymous_Access (Btyp)
8102                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
8103                  and then Attr_Id = Attribute_Access
8104                then
8105                   --  In an instance, this is a runtime check, but one we
8106                   --  know will fail, so generate an appropriate warning.
8107
8108                   if In_Instance_Body then
8109                      Error_Msg_F
8110                        ("?non-local pointer cannot point to local object", P);
8111                      Error_Msg_F
8112                        ("\?Program_Error will be raised at run time", P);
8113                      Rewrite (N,
8114                        Make_Raise_Program_Error (Loc,
8115                          Reason => PE_Accessibility_Check_Failed));
8116                      Set_Etype (N, Typ);
8117
8118                   else
8119                      Error_Msg_F
8120                        ("non-local pointer cannot point to local object", P);
8121                   end if;
8122                end if;
8123
8124                if Is_Dependent_Component_Of_Mutable_Object (P) then
8125                   Error_Msg_F
8126                     ("illegal attribute for discriminant-dependent component",
8127                      P);
8128                end if;
8129
8130                --  Check static matching rule of 3.10.2(27). Nominal subtype
8131                --  of the prefix must statically match the designated type.
8132
8133                Nom_Subt := Etype (P);
8134
8135                if Is_Constr_Subt_For_U_Nominal (Nom_Subt) then
8136                   Nom_Subt := Base_Type (Nom_Subt);
8137                end if;
8138
8139                if Is_Tagged_Type (Designated_Type (Typ)) then
8140
8141                   --  If the attribute is in the context of an access
8142                   --  parameter, then the prefix is allowed to be of the
8143                   --  class-wide type (by AI-127).
8144
8145                   if Ekind (Typ) = E_Anonymous_Access_Type then
8146                      if not Covers (Designated_Type (Typ), Nom_Subt)
8147                        and then not Covers (Nom_Subt, Designated_Type (Typ))
8148                      then
8149                         declare
8150                            Desig : Entity_Id;
8151
8152                         begin
8153                            Desig := Designated_Type (Typ);
8154
8155                            if Is_Class_Wide_Type (Desig) then
8156                               Desig := Etype (Desig);
8157                            end if;
8158
8159                            if Is_Anonymous_Tagged_Base (Nom_Subt, Desig) then
8160                               null;
8161
8162                            else
8163                               Error_Msg_FE
8164                                 ("type of prefix: & not compatible",
8165                                   P, Nom_Subt);
8166                               Error_Msg_FE
8167                                 ("\with &, the expected designated type",
8168                                   P, Designated_Type (Typ));
8169                            end if;
8170                         end;
8171                      end if;
8172
8173                   elsif not Covers (Designated_Type (Typ), Nom_Subt)
8174                     or else
8175                       (not Is_Class_Wide_Type (Designated_Type (Typ))
8176                         and then Is_Class_Wide_Type (Nom_Subt))
8177                   then
8178                      Error_Msg_FE
8179                        ("type of prefix: & is not covered", P, Nom_Subt);
8180                      Error_Msg_FE
8181                        ("\by &, the expected designated type" &
8182                            " (RM 3.10.2 (27))", P, Designated_Type (Typ));
8183                   end if;
8184
8185                   if Is_Class_Wide_Type (Designated_Type (Typ))
8186                     and then Has_Discriminants (Etype (Designated_Type (Typ)))
8187                     and then Is_Constrained (Etype (Designated_Type (Typ)))
8188                     and then Designated_Type (Typ) /= Nom_Subt
8189                   then
8190                      Apply_Discriminant_Check
8191                        (N, Etype (Designated_Type (Typ)));
8192                   end if;
8193
8194                --  Ada 2005 (AI-363): Require static matching when designated
8195                --  type has discriminants and a constrained partial view, since
8196                --  in general objects of such types are mutable, so we can't
8197                --  allow the access value to designate a constrained object
8198                --  (because access values must be assumed to designate mutable
8199                --  objects when designated type does not impose a constraint).
8200
8201                elsif Subtypes_Statically_Match (Des_Btyp, Nom_Subt) then
8202                   null;
8203
8204                elsif Has_Discriminants (Designated_Type (Typ))
8205                  and then not Is_Constrained (Des_Btyp)
8206                  and then
8207                    (Ada_Version < Ada_2005
8208                      or else
8209                        not Has_Constrained_Partial_View
8210                              (Designated_Type (Base_Type (Typ))))
8211                then
8212                   null;
8213
8214                else
8215                   Error_Msg_F
8216                     ("object subtype must statically match "
8217                      & "designated subtype", P);
8218
8219                   if Is_Entity_Name (P)
8220                     and then Is_Array_Type (Designated_Type (Typ))
8221                   then
8222                      declare
8223                         D : constant Node_Id := Declaration_Node (Entity (P));
8224
8225                      begin
8226                         Error_Msg_N ("aliased object has explicit bounds?",
8227                           D);
8228                         Error_Msg_N ("\declare without bounds"
8229                           & " (and with explicit initialization)?", D);
8230                         Error_Msg_N ("\for use with unconstrained access?", D);
8231                      end;
8232                   end if;
8233                end if;
8234
8235                --  Check the static accessibility rule of 3.10.2(28).
8236                --  Note that this check is not performed for the
8237                --  case of an anonymous access type, since the access
8238                --  attribute is always legal in such a context.
8239
8240                if Attr_Id /= Attribute_Unchecked_Access
8241                  and then Object_Access_Level (P) > Type_Access_Level (Btyp)
8242                  and then Ekind (Btyp) = E_General_Access_Type
8243                then
8244                   Accessibility_Message;
8245                   return;
8246                end if;
8247             end if;
8248
8249             if Ekind_In (Btyp, E_Access_Protected_Subprogram_Type,
8250                                E_Anonymous_Access_Protected_Subprogram_Type)
8251             then
8252                if Is_Entity_Name (P)
8253                  and then not Is_Protected_Type (Scope (Entity (P)))
8254                then
8255                   Error_Msg_F ("context requires a protected subprogram", P);
8256
8257                --  Check accessibility of protected object against that of the
8258                --  access type, but only on user code, because the expander
8259                --  creates access references for handlers. If the context is an
8260                --  anonymous_access_to_protected, there are no accessibility
8261                --  checks either. Omit check entirely for Unrestricted_Access.
8262
8263                elsif Object_Access_Level (P) > Type_Access_Level (Btyp)
8264                  and then Comes_From_Source (N)
8265                  and then Ekind (Btyp) = E_Access_Protected_Subprogram_Type
8266                  and then Attr_Id /= Attribute_Unrestricted_Access
8267                then
8268                   Accessibility_Message;
8269                   return;
8270                end if;
8271
8272             elsif Ekind_In (Btyp, E_Access_Subprogram_Type,
8273                                   E_Anonymous_Access_Subprogram_Type)
8274               and then Ekind (Etype (N)) = E_Access_Protected_Subprogram_Type
8275             then
8276                Error_Msg_F ("context requires a non-protected subprogram", P);
8277             end if;
8278
8279             --  The context cannot be a pool-specific type, but this is a
8280             --  legality rule, not a resolution rule, so it must be checked
8281             --  separately, after possibly disambiguation (see AI-245).
8282
8283             if Ekind (Btyp) = E_Access_Type
8284               and then Attr_Id /= Attribute_Unrestricted_Access
8285             then
8286                Wrong_Type (N, Typ);
8287             end if;
8288
8289             --  The context may be a constrained access type (however ill-
8290             --  advised such subtypes might be) so in order to generate a
8291             --  constraint check when needed set the type of the attribute
8292             --  reference to the base type of the context.
8293
8294             Set_Etype (N, Btyp);
8295
8296             --  Check for incorrect atomic/volatile reference (RM C.6(12))
8297
8298             if Attr_Id /= Attribute_Unrestricted_Access then
8299                if Is_Atomic_Object (P)
8300                  and then not Is_Atomic (Designated_Type (Typ))
8301                then
8302                   Error_Msg_F
8303                     ("access to atomic object cannot yield access-to-" &
8304                      "non-atomic type", P);
8305
8306                elsif Is_Volatile_Object (P)
8307                  and then not Is_Volatile (Designated_Type (Typ))
8308                then
8309                   Error_Msg_F
8310                     ("access to volatile object cannot yield access-to-" &
8311                      "non-volatile type", P);
8312                end if;
8313             end if;
8314
8315             if Is_Entity_Name (P) then
8316                Set_Address_Taken (Entity (P));
8317             end if;
8318          end Access_Attribute;
8319
8320          -------------
8321          -- Address --
8322          -------------
8323
8324          --  Deal with resolving the type for Address attribute, overloading
8325          --  is not permitted here, since there is no context to resolve it.
8326
8327          when Attribute_Address | Attribute_Code_Address =>
8328          Address_Attribute : begin
8329
8330             --  To be safe, assume that if the address of a variable is taken,
8331             --  it may be modified via this address, so note modification.
8332
8333             if Is_Variable (P) then
8334                Note_Possible_Modification (P, Sure => False);
8335             end if;
8336
8337             if Nkind (P) in N_Subexpr
8338               and then Is_Overloaded (P)
8339             then
8340                Get_First_Interp (P, Index, It);
8341                Get_Next_Interp (Index, It);
8342
8343                if Present (It.Nam) then
8344                   Error_Msg_Name_1 := Aname;
8345                   Error_Msg_F
8346                     ("prefix of % attribute cannot be overloaded", P);
8347                end if;
8348             end if;
8349
8350             if not Is_Entity_Name (P)
8351               or else not Is_Overloadable (Entity (P))
8352             then
8353                if not Is_Task_Type (Etype (P))
8354                  or else Nkind (P) = N_Explicit_Dereference
8355                then
8356                   Resolve (P);
8357                end if;
8358             end if;
8359
8360             --  If this is the name of a derived subprogram, or that of a
8361             --  generic actual, the address is that of the original entity.
8362
8363             if Is_Entity_Name (P)
8364               and then Is_Overloadable (Entity (P))
8365               and then Present (Alias (Entity (P)))
8366             then
8367                Rewrite (P,
8368                  New_Occurrence_Of (Alias (Entity (P)), Sloc (P)));
8369             end if;
8370
8371             if Is_Entity_Name (P) then
8372                Set_Address_Taken (Entity (P));
8373             end if;
8374
8375             if Nkind (P) = N_Slice then
8376
8377                --  Arr (X .. Y)'address is identical to Arr (X)'address,
8378                --  even if the array is packed and the slice itself is not
8379                --  addressable. Transform the prefix into an indexed component.
8380
8381                --  Note that the transformation is safe only if we know that
8382                --  the slice is non-null. That is because a null slice can have
8383                --  an out of bounds index value.
8384
8385                --  Right now, gigi blows up if given 'Address on a slice as a
8386                --  result of some incorrect freeze nodes generated by the front
8387                --  end, and this covers up that bug in one case, but the bug is
8388                --  likely still there in the cases not handled by this code ???
8389
8390                --  It's not clear what 'Address *should* return for a null
8391                --  slice with out of bounds indexes, this might be worth an ARG
8392                --  discussion ???
8393
8394                --  One approach would be to do a length check unconditionally,
8395                --  and then do the transformation below unconditionally, but
8396                --  analyze with checks off, avoiding the problem of the out of
8397                --  bounds index. This approach would interpret the address of
8398                --  an out of bounds null slice as being the address where the
8399                --  array element would be if there was one, which is probably
8400                --  as reasonable an interpretation as any ???
8401
8402                declare
8403                   Loc : constant Source_Ptr := Sloc (P);
8404                   D   : constant Node_Id := Discrete_Range (P);
8405                   Lo  : Node_Id;
8406
8407                begin
8408                   if Is_Entity_Name (D)
8409                     and then
8410                       Not_Null_Range
8411                         (Type_Low_Bound (Entity (D)),
8412                          Type_High_Bound (Entity (D)))
8413                   then
8414                      Lo :=
8415                        Make_Attribute_Reference (Loc,
8416                           Prefix => (New_Occurrence_Of (Entity (D), Loc)),
8417                           Attribute_Name => Name_First);
8418
8419                   elsif Nkind (D) = N_Range
8420                     and then Not_Null_Range (Low_Bound (D), High_Bound (D))
8421                   then
8422                      Lo := Low_Bound (D);
8423
8424                   else
8425                      Lo := Empty;
8426                   end if;
8427
8428                   if Present (Lo) then
8429                      Rewrite (P,
8430                         Make_Indexed_Component (Loc,
8431                            Prefix =>  Relocate_Node (Prefix (P)),
8432                            Expressions => New_List (Lo)));
8433
8434                      Analyze_And_Resolve (P);
8435                   end if;
8436                end;
8437             end if;
8438          end Address_Attribute;
8439
8440          ---------------
8441          -- AST_Entry --
8442          ---------------
8443
8444          --  Prefix of the AST_Entry attribute is an entry name which must
8445          --  not be resolved, since this is definitely not an entry call.
8446
8447          when Attribute_AST_Entry =>
8448             null;
8449
8450          ------------------
8451          -- Body_Version --
8452          ------------------
8453
8454          --  Prefix of Body_Version attribute can be a subprogram name which
8455          --  must not be resolved, since this is not a call.
8456
8457          when Attribute_Body_Version =>
8458             null;
8459
8460          ------------
8461          -- Caller --
8462          ------------
8463
8464          --  Prefix of Caller attribute is an entry name which must not
8465          --  be resolved, since this is definitely not an entry call.
8466
8467          when Attribute_Caller =>
8468             null;
8469
8470          ------------------
8471          -- Code_Address --
8472          ------------------
8473
8474          --  Shares processing with Address attribute
8475
8476          -----------
8477          -- Count --
8478          -----------
8479
8480          --  If the prefix of the Count attribute is an entry name it must not
8481          --  be resolved, since this is definitely not an entry call. However,
8482          --  if it is an element of an entry family, the index itself may
8483          --  have to be resolved because it can be a general expression.
8484
8485          when Attribute_Count =>
8486             if Nkind (P) = N_Indexed_Component
8487               and then Is_Entity_Name (Prefix (P))
8488             then
8489                declare
8490                   Indx : constant Node_Id   := First (Expressions (P));
8491                   Fam  : constant Entity_Id := Entity (Prefix (P));
8492                begin
8493                   Resolve (Indx, Entry_Index_Type (Fam));
8494                   Apply_Range_Check (Indx, Entry_Index_Type (Fam));
8495                end;
8496             end if;
8497
8498          ----------------
8499          -- Elaborated --
8500          ----------------
8501
8502          --  Prefix of the Elaborated attribute is a subprogram name which
8503          --  must not be resolved, since this is definitely not a call. Note
8504          --  that it is a library unit, so it cannot be overloaded here.
8505
8506          when Attribute_Elaborated =>
8507             null;
8508
8509          -------------
8510          -- Enabled --
8511          -------------
8512
8513          --  Prefix of Enabled attribute is a check name, which must be treated
8514          --  specially and not touched by Resolve.
8515
8516          when Attribute_Enabled =>
8517             null;
8518
8519          --------------------
8520          -- Mechanism_Code --
8521          --------------------
8522
8523          --  Prefix of the Mechanism_Code attribute is a function name
8524          --  which must not be resolved. Should we check for overloaded ???
8525
8526          when Attribute_Mechanism_Code =>
8527             null;
8528
8529          ------------------
8530          -- Partition_ID --
8531          ------------------
8532
8533          --  Most processing is done in sem_dist, after determining the
8534          --  context type. Node is rewritten as a conversion to a runtime call.
8535
8536          when Attribute_Partition_ID =>
8537             Process_Partition_Id (N);
8538             return;
8539
8540          ------------------
8541          -- Pool_Address --
8542          ------------------
8543
8544          when Attribute_Pool_Address =>
8545             Resolve (P);
8546
8547          -----------
8548          -- Range --
8549          -----------
8550
8551          --  We replace the Range attribute node with a range expression whose
8552          --  bounds are the 'First and 'Last attributes applied to the same
8553          --  prefix. The reason that we do this transformation here instead of
8554          --  in the expander is that it simplifies other parts of the semantic
8555          --  analysis which assume that the Range has been replaced; thus it
8556          --  must be done even when in semantic-only mode (note that the RM
8557          --  specifically mentions this equivalence, we take care that the
8558          --  prefix is only evaluated once).
8559
8560          when Attribute_Range => Range_Attribute :
8561             declare
8562                LB   : Node_Id;
8563                HB   : Node_Id;
8564
8565             begin
8566                if not Is_Entity_Name (P)
8567                  or else not Is_Type (Entity (P))
8568                then
8569                   Resolve (P);
8570                end if;
8571
8572                HB :=
8573                  Make_Attribute_Reference (Loc,
8574                    Prefix         =>
8575                      Duplicate_Subexpr (P, Name_Req => True),
8576                    Attribute_Name => Name_Last,
8577                    Expressions    => Expressions (N));
8578
8579                LB :=
8580                  Make_Attribute_Reference (Loc,
8581                    Prefix         => P,
8582                    Attribute_Name => Name_First,
8583                    Expressions    => Expressions (N));
8584
8585                --  If the original was marked as Must_Not_Freeze (see code
8586                --  in Sem_Ch3.Make_Index), then make sure the rewriting
8587                --  does not freeze either.
8588
8589                if Must_Not_Freeze (N) then
8590                   Set_Must_Not_Freeze (HB);
8591                   Set_Must_Not_Freeze (LB);
8592                   Set_Must_Not_Freeze (Prefix (HB));
8593                   Set_Must_Not_Freeze (Prefix (LB));
8594                end if;
8595
8596                if Raises_Constraint_Error (Prefix (N)) then
8597
8598                   --  Preserve Sloc of prefix in the new bounds, so that
8599                   --  the posted warning can be removed if we are within
8600                   --  unreachable code.
8601
8602                   Set_Sloc (LB, Sloc (Prefix (N)));
8603                   Set_Sloc (HB, Sloc (Prefix (N)));
8604                end if;
8605
8606                Rewrite (N, Make_Range (Loc, LB, HB));
8607                Analyze_And_Resolve (N, Typ);
8608
8609                --  Ensure that the expanded range does not have side effects
8610
8611                Force_Evaluation (LB);
8612                Force_Evaluation (HB);
8613
8614                --  Normally after resolving attribute nodes, Eval_Attribute
8615                --  is called to do any possible static evaluation of the node.
8616                --  However, here since the Range attribute has just been
8617                --  transformed into a range expression it is no longer an
8618                --  attribute node and therefore the call needs to be avoided
8619                --  and is accomplished by simply returning from the procedure.
8620
8621                return;
8622             end Range_Attribute;
8623
8624          ------------
8625          -- Result --
8626          ------------
8627
8628          --  We will only come here during the prescan of a spec expression
8629          --  containing a Result attribute. In that case the proper Etype has
8630          --  already been set, and nothing more needs to be done here.
8631
8632          when Attribute_Result =>
8633             null;
8634
8635          -----------------
8636          -- UET_Address --
8637          -----------------
8638
8639          --  Prefix must not be resolved in this case, since it is not a
8640          --  real entity reference. No action of any kind is require!
8641
8642          when Attribute_UET_Address =>
8643             return;
8644
8645          ----------------------
8646          -- Unchecked_Access --
8647          ----------------------
8648
8649          --  Processing is shared with Access
8650
8651          -------------------------
8652          -- Unrestricted_Access --
8653          -------------------------
8654
8655          --  Processing is shared with Access
8656
8657          ---------
8658          -- Val --
8659          ---------
8660
8661          --  Apply range check. Note that we did not do this during the
8662          --  analysis phase, since we wanted Eval_Attribute to have a
8663          --  chance at finding an illegal out of range value.
8664
8665          when Attribute_Val =>
8666
8667             --  Note that we do our own Eval_Attribute call here rather than
8668             --  use the common one, because we need to do processing after
8669             --  the call, as per above comment.
8670
8671             Eval_Attribute (N);
8672
8673             --  Eval_Attribute may replace the node with a raise CE, or
8674             --  fold it to a constant. Obviously we only apply a scalar
8675             --  range check if this did not happen!
8676
8677             if Nkind (N) = N_Attribute_Reference
8678               and then Attribute_Name (N) = Name_Val
8679             then
8680                Apply_Scalar_Range_Check (First (Expressions (N)), Btyp);
8681             end if;
8682
8683             return;
8684
8685          -------------
8686          -- Version --
8687          -------------
8688
8689          --  Prefix of Version attribute can be a subprogram name which
8690          --  must not be resolved, since this is not a call.
8691
8692          when Attribute_Version =>
8693             null;
8694
8695          ----------------------
8696          -- Other Attributes --
8697          ----------------------
8698
8699          --  For other attributes, resolve prefix unless it is a type. If
8700          --  the attribute reference itself is a type name ('Base and 'Class)
8701          --  then this is only legal within a task or protected record.
8702
8703          when others =>
8704             if not Is_Entity_Name (P)
8705               or else not Is_Type (Entity (P))
8706             then
8707                Resolve (P);
8708             end if;
8709
8710             --  If the attribute reference itself is a type name ('Base,
8711             --  'Class) then this is only legal within a task or protected
8712             --  record. What is this all about ???
8713
8714             if Is_Entity_Name (N)
8715               and then Is_Type (Entity (N))
8716             then
8717                if Is_Concurrent_Type (Entity (N))
8718                  and then In_Open_Scopes (Entity (P))
8719                then
8720                   null;
8721                else
8722                   Error_Msg_N
8723                     ("invalid use of subtype name in expression or call", N);
8724                end if;
8725             end if;
8726
8727             --  For attributes whose argument may be a string, complete
8728             --  resolution of argument now. This avoids premature expansion
8729             --  (and the creation of transient scopes) before the attribute
8730             --  reference is resolved.
8731
8732             case Attr_Id is
8733                when Attribute_Value =>
8734                   Resolve (First (Expressions (N)), Standard_String);
8735
8736                when Attribute_Wide_Value =>
8737                   Resolve (First (Expressions (N)), Standard_Wide_String);
8738
8739                when Attribute_Wide_Wide_Value =>
8740                   Resolve (First (Expressions (N)), Standard_Wide_Wide_String);
8741
8742                when others => null;
8743             end case;
8744
8745             --  If the prefix of the attribute is a class-wide type then it
8746             --  will be expanded into a dispatching call to a predefined
8747             --  primitive. Therefore we must check for potential violation
8748             --  of such restriction.
8749
8750             if Is_Class_Wide_Type (Etype (P)) then
8751                Check_Restriction (No_Dispatching_Calls, N);
8752             end if;
8753       end case;
8754
8755       --  Normally the Freezing is done by Resolve but sometimes the Prefix
8756       --  is not resolved, in which case the freezing must be done now.
8757
8758       Freeze_Expression (P);
8759
8760       --  Finally perform static evaluation on the attribute reference
8761
8762       Eval_Attribute (N);
8763    end Resolve_Attribute;
8764
8765    --------------------------------
8766    -- Stream_Attribute_Available --
8767    --------------------------------
8768
8769    function Stream_Attribute_Available
8770      (Typ          : Entity_Id;
8771       Nam          : TSS_Name_Type;
8772       Partial_View : Node_Id := Empty) return Boolean
8773    is
8774       Etyp : Entity_Id := Typ;
8775
8776    --  Start of processing for Stream_Attribute_Available
8777
8778    begin
8779       --  We need some comments in this body ???
8780
8781       if Has_Stream_Attribute_Definition (Typ, Nam) then
8782          return True;
8783       end if;
8784
8785       if Is_Class_Wide_Type (Typ) then
8786          return not Is_Limited_Type (Typ)
8787            or else Stream_Attribute_Available (Etype (Typ), Nam);
8788       end if;
8789
8790       if Nam = TSS_Stream_Input
8791         and then Is_Abstract_Type (Typ)
8792         and then not Is_Class_Wide_Type (Typ)
8793       then
8794          return False;
8795       end if;
8796
8797       if not (Is_Limited_Type (Typ)
8798         or else (Present (Partial_View)
8799                    and then Is_Limited_Type (Partial_View)))
8800       then
8801          return True;
8802       end if;
8803
8804       --  In Ada 2005, Input can invoke Read, and Output can invoke Write
8805
8806       if Nam = TSS_Stream_Input
8807         and then Ada_Version >= Ada_2005
8808         and then Stream_Attribute_Available (Etyp, TSS_Stream_Read)
8809       then
8810          return True;
8811
8812       elsif Nam = TSS_Stream_Output
8813         and then Ada_Version >= Ada_2005
8814         and then Stream_Attribute_Available (Etyp, TSS_Stream_Write)
8815       then
8816          return True;
8817       end if;
8818
8819       --  Case of Read and Write: check for attribute definition clause that
8820       --  applies to an ancestor type.
8821
8822       while Etype (Etyp) /= Etyp loop
8823          Etyp := Etype (Etyp);
8824
8825          if Has_Stream_Attribute_Definition (Etyp, Nam) then
8826             return True;
8827          end if;
8828       end loop;
8829
8830       if Ada_Version < Ada_2005 then
8831
8832          --  In Ada 95 mode, also consider a non-visible definition
8833
8834          declare
8835             Btyp : constant Entity_Id := Implementation_Base_Type (Typ);
8836          begin
8837             return Btyp /= Typ
8838               and then Stream_Attribute_Available
8839                          (Btyp, Nam, Partial_View => Typ);
8840          end;
8841       end if;
8842
8843       return False;
8844    end Stream_Attribute_Available;
8845
8846 end Sem_Attr;