1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- S E M _ A T T R -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2021, 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. -- 17-- -- 18-- You should have received a copy of the GNU General Public License along -- 19-- with this program; see file COPYING3. If not see -- 20-- <http://www.gnu.org/licenses/>. -- 21-- -- 22-- GNAT was originally developed by the GNAT team at New York University. -- 23-- Extensive contributions were provided by Ada Core Technologies Inc. -- 24-- -- 25------------------------------------------------------------------------------ 26 27-- Attribute handling is isolated in a separate package to ease the addition 28-- of implementation defined attributes. Logically this processing belongs 29-- in chapter 4. See Sem_Ch4 for a description of the relation of the 30-- Analyze and Resolve routines for expression components. 31 32-- This spec also documents all GNAT implementation defined pragmas 33 34with Exp_Tss; use Exp_Tss; 35with Namet; use Namet; 36with Snames; use Snames; 37with Types; use Types; 38 39package Sem_Attr is 40 41 ----------------------------------------- 42 -- Implementation Dependent Attributes -- 43 ----------------------------------------- 44 45 -- This section describes the implementation dependent attributes provided 46 -- in GNAT, as well as constructing an array of flags indicating which 47 -- attributes these are. 48 49 Attribute_Impl_Def : constant Attribute_Class_Array := 50 Attribute_Class_Array'( 51 52 ------------------ 53 -- Abort_Signal -- 54 ------------------ 55 56 Attribute_Abort_Signal => True, 57 -- Standard'Abort_Signal (Standard is the only allowed prefix) provides 58 -- the entity for the special exception used to signal task abort or 59 -- asynchronous transfer of control. Normally this attribute should only 60 -- be used in the tasking runtime (it is highly peculiar, and completely 61 -- outside the normal semantics of Ada, for a user program to intercept 62 -- the abort exception). 63 64 ------------------ 65 -- Address_Size -- 66 ------------------ 67 68 Attribute_Address_Size => True, 69 -- Standard'Address_Size (Standard is the only allowed prefix) is 70 -- a static constant giving the number of bits in an Address. It 71 -- is used primarily for constructing the definition of Memory_Size 72 -- in package Standard, but may be freely used in user programs. 73 -- This is a static attribute. 74 75 --------------- 76 -- Asm_Input -- 77 --------------- 78 79 Attribute_Asm_Input => True, 80 -- Used only in conjunction with the Asm subprograms in package 81 -- Machine_Code to construct machine instructions. See documentation 82 -- in package Machine_Code in file s-maccod.ads. 83 84 ---------------- 85 -- Asm_Output -- 86 ---------------- 87 88 Attribute_Asm_Output => True, 89 -- Used only in conjunction with the Asm subprograms in package 90 -- Machine_Code to construct machine instructions. See documentation 91 -- in package Machine_Code in file s-maccod.ads. 92 93 --------- 94 -- Bit -- 95 --------- 96 97 Attribute_Bit => True, 98 -- Obj'Bit, where Obj is any object, yields the bit offset within the 99 -- storage unit (byte) that contains the first bit of storage allocated 100 -- for the object. The attribute value is of type Universal_Integer, 101 -- and is always a non-negative number not exceeding the value of 102 -- System.Storage_Unit. 103 -- 104 -- For an object that is a variable or a constant allocated in a 105 -- register, the value is zero. (The use of this attribute does not 106 -- force the allocation of a variable to memory). 107 -- 108 -- For an object that is a formal parameter, this attribute applies to 109 -- either the matching actual parameter or to a copy of the matching 110 -- actual parameter. 111 -- 112 -- For an access object the value is zero. Note that Obj.all'Bit is 113 -- subject to an Access_Check for the designated object. Similarly 114 -- for a record component X.C'Bit is subject to a discriminant check 115 -- and X(I).Bit and X(I1..I2)'Bit are subject to index checks. 116 -- 117 -- This attribute is designed to be compatible with the DEC Ada 118 -- definition and implementation of the Bit attribute. 119 120 ------------------ 121 -- Code_Address -- 122 ------------------ 123 124 Attribute_Code_Address => True, 125 -- The reference subp'Code_Address, where subp is a subprogram entity, 126 -- gives the address of the first generated instruction for the sub- 127 -- program. This is often, but not always the same as the 'Address 128 -- value, which is the address to be used in a call. The differences 129 -- occur in the case of a nested procedure (where Address yields the 130 -- address of the trampoline code used to load the static link), and on 131 -- some systems which use procedure descriptors (in which case Address 132 -- yields the address of the descriptor). 133 134 ----------------------- 135 -- Default_Bit_Order -- 136 ----------------------- 137 138 Attribute_Default_Bit_Order => True, 139 -- Standard'Default_Bit_Order (Standard is the only permissible prefix) 140 -- provides the value System.Default_Bit_Order as a Pos value (0 for 141 -- High_Order_First, 1 for Low_Order_First). This is used to construct 142 -- the definition of Default_Bit_Order in package System. This is a 143 -- static attribute. 144 145 ---------------------------------- 146 -- Default_Scalar_Storage_Order -- 147 ---------------------------------- 148 149 Attribute_Default_Scalar_Storage_Order => True, 150 -- Standard'Default_Scalar_Storage_Order (Standard is the 151 -- only permissible prefix) provides the current value of the 152 -- default scalar storage order (as specified using pragma 153 -- Default_Scalar_Storage_Order, or equal to Default_Bit_Order if 154 -- unspecified) as a System.Bit_Order value. This is a static attribute. 155 156 ----------- 157 -- Deref -- 158 ----------- 159 160 Attribute_Deref => True, 161 -- typ'Deref (expr) is valid only if expr is of type System'Address. 162 -- The result is an object of type typ that is obtained by treating the 163 -- address as an access-to-typ value that points to the result. It is 164 -- basically equivalent to (atyp!expr).all where atyp is an access type 165 -- for the type. 166 167 --------------- 168 -- Elab_Body -- 169 --------------- 170 171 Attribute_Elab_Body => True, 172 -- This attribute can only be applied to a program unit name. It 173 -- returns the entity for the corresponding elaboration procedure for 174 -- elaborating the body of the referenced unit. This is used in the main 175 -- generated elaboration procedure by the binder, and is not normally 176 -- used in any other context, but there may be specialized situations in 177 -- which it is useful to be able to call this elaboration procedure from 178 -- Ada code, e.g. if it is necessary to do selective reelaboration to 179 -- fix some error. 180 181 -------------------- 182 -- Elab_Subp_Body -- 183 -------------------- 184 185 Attribute_Elab_Subp_Body => True, 186 -- This attribute can only be applied to a library level subprogram 187 -- name and is only relevant in CodePeer mode. It returns the entity 188 -- for the corresponding elaboration procedure for elaborating the body 189 -- of the referenced subprogram unit. This is used in the main generated 190 -- elaboration procedure by the binder in CodePeer mode only. 191 192 --------------- 193 -- Elab_Spec -- 194 --------------- 195 196 Attribute_Elab_Spec => True, 197 -- This attribute can only be applied to a program unit name. It 198 -- returns the entity for the corresponding elaboration procedure for 199 -- elaborating the spec of the referenced unit. This is used in the main 200 -- generated elaboration procedure by the binder, and is not normally 201 -- used in any other context, but there may be specialized situations in 202 -- which it is useful to be able to call this elaboration procedure from 203 -- Ada code, e.g. if it is necessary to do selective reelaboration to 204 -- fix some error. 205 206 ---------------- 207 -- Elaborated -- 208 ---------------- 209 210 Attribute_Elaborated => True, 211 -- Lunit'Elaborated, where Lunit is a library unit, yields a boolean 212 -- value indicating whether or not the body of the designated library 213 -- unit has been elaborated yet. 214 215 ----------------------- 216 -- Finalization_Size -- 217 ----------------------- 218 219 Attribute_Finalization_Size => True, 220 -- For every object or non-class-wide-type, Finalization_Size returns 221 -- the size of the hidden header used for finalization purposes as if 222 -- the object or type was allocated on the heap. The size of the header 223 -- does take into account any extra padding due to alignment issues. 224 225 ----------------- 226 -- Fixed_Value -- 227 ----------------- 228 229 Attribute_Fixed_Value => True, 230 -- For every fixed-point type S, S'Fixed_Value denotes a function 231 -- with the following specification: 232 -- 233 -- function S'Fixed_Value (Arg : universal_integer) return S; 234 -- 235 -- The value returned is the fixed-point value V such that 236 -- 237 -- V = Arg * S'Small 238 -- 239 -- The effect is thus equivalent to first converting the argument to 240 -- the integer type used to represent S, and then doing an unchecked 241 -- conversion to the fixed-point type. This attribute is primarily 242 -- intended for use in implementation of the input-output functions 243 -- for fixed-point values. 244 245 ----------------------- 246 -- Has_Discriminants -- 247 ----------------------- 248 249 Attribute_Has_Discriminants => True, 250 -- Gtyp'Has_Discriminants, where Gtyp is a generic formal type, yields 251 -- a Boolean value indicating whether or not the actual instantiation 252 -- type has discriminants. 253 254 --------- 255 -- Img -- 256 --------- 257 258 Attribute_Img => True, 259 -- The 'Img function is defined for any prefix, P, that denotes an 260 -- object of scalar type T. P'Img is equivalent to T'Image (P). This 261 -- is convenient for debugging. For example: 262 -- 263 -- Put_Line ("X = " & X'Img); 264 -- 265 -- has the same meaning as the more verbose: 266 -- 267 -- Put_Line ("X = " & Temperature_Type'Image (X)); 268 -- 269 -- where Temperature_Type is the subtype of the object X. 270 271 ------------------- 272 -- Integer_Value -- 273 ------------------- 274 275 Attribute_Integer_Value => True, 276 -- For every integer type S, S'Integer_Value denotes a function 277 -- with the following specification: 278 -- 279 -- function S'Integer_Value (Arg : universal_fixed) return S; 280 -- 281 -- The value returned is the integer value V, such that 282 -- 283 -- Arg = V * fixed-type'Small 284 -- 285 -- The effect is thus equivalent to first doing an unchecked convert 286 -- from the fixed-point type to its corresponding implementation type, 287 -- and then converting the result to the target integer type. This 288 -- attribute is primarily intended for use in implementation of the 289 -- standard input-output functions for fixed-point values. 290 291 Attribute_Invalid_Value => True, 292 -- For every scalar type, S'Invalid_Value designates an undefined value 293 -- of the type. If possible this value is an invalid value, and in fact 294 -- is identical to the value that would be set if Initialize_Scalars 295 -- mode were in effect (including the behavior of its value on 296 -- environment variables or binder switches). The intended use is to 297 -- set a value where initialization is required (e.g. as a result of the 298 -- coding standards in use), but logically no initialization is needed, 299 -- and the value should never be accessed. 300 301 Attribute_Loop_Entry => True, 302 -- For every object of a non-limited type, S'Loop_Entry [(Loop_Name)] 303 -- denotes the constant value of prefix S at the point of entry into the 304 -- related loop. The type of the attribute is the type of the prefix. 305 306 ------------------ 307 -- Machine_Size -- 308 ------------------ 309 310 Attribute_Machine_Size => True, 311 -- This attribute is identical to the Object_Size attribute. It is 312 -- provided for compatibility with the DEC attribute of this name. 313 314 ---------------------- 315 -- Max_Integer_Size -- 316 ---------------------- 317 318 Attribute_Max_Integer_Size => True, 319 -- Standard'Max_Integer_Size (Standard is the only permissible prefix) 320 -- provides values System.Min_Int and System.Max_Int, and is intended 321 -- primarily for constructing these definitions in package System. This 322 -- is a static attribute. 323 324 ----------------------- 325 -- Maximum_Alignment -- 326 ----------------------- 327 328 Attribute_Maximum_Alignment => True, 329 -- Standard'Maximum_Alignment (Standard is the only permissible prefix) 330 -- provides the maximum useful alignment value for the target. This is a 331 -- static value that can be used to specify the alignment for an object, 332 -- guaranteeing that it is properly aligned in all cases. The time this 333 -- is useful is when an external object is imported and its alignment 334 -- requirements are unknown. This is a static attribute. 335 336 -------------------- 337 -- Mechanism_Code -- 338 -------------------- 339 340 Attribute_Mechanism_Code => True, 341 -- function'Mechanism_Code yields an integer code for the mechanism 342 -- used for the result of function, and subprogram'Mechanism_Code (n) 343 -- yields the mechanism used for formal parameter number n (a static 344 -- integer value, 1 = first parameter). The code returned is: 345 -- 346 -- 1 = by copy (value) 347 -- 2 = by reference 348 -- 3 = by descriptor (default descriptor type) 349 -- 4 = by descriptor (UBS unaligned bit string) 350 -- 5 = by descriptor (UBSB aligned bit string with arbitrary bounds) 351 -- 6 = by descriptor (UBA unaligned bit array) 352 -- 7 = by descriptor (S string, also scalar access type parameter) 353 -- 8 = by descriptor (SB string with arbitrary bounds) 354 -- 9 = by descriptor (A contiguous array) 355 -- 10 = by descriptor (NCA non-contiguous array) 356 357 -------------------- 358 -- Null_Parameter -- 359 -------------------- 360 361 Attribute_Null_Parameter => True, 362 -- A reference T'Null_Parameter denotes an (imaginary) object of type 363 -- or subtype T allocated at (machine) address zero. The attribute is 364 -- allowed only as the default expression of a formal parameter, or 365 -- as an actual expression of a subprogram call. In either case, the 366 -- subprogram must be imported. 367 -- 368 -- The identity of the object is represented by the address zero in 369 -- the argument list, independent of the passing mechanism (explicit 370 -- or default). 371 -- 372 -- The reason that this capability is needed is that for a record or 373 -- other composite object passed by reference, there is no other way 374 -- of specifying that a zero address should be passed. 375 376 ----------------- 377 -- Object_Size -- 378 ----------------- 379 380 Attribute_Object_Size => True, 381 -- Type'Object_Size is the same as Type'Size for all types except 382 -- fixed-point types and discrete types. For fixed-point types and 383 -- discrete types, this attribute gives the size used for default 384 -- allocation of objects and components of the size. See section in 385 -- Einfo ("Handling of Type'Size values") for further details. 386 387 ------------------------- 388 -- Passed_By_Reference -- 389 ------------------------- 390 391 Attribute_Passed_By_Reference => True, 392 -- T'Passed_By_Reference for any subtype T returns a boolean value that 393 -- is true if the type is normally passed by reference and false if the 394 -- type is normally passed by copy in calls. For scalar types, the 395 -- result is always False and is static. For non-scalar types, the 396 -- result is non-static (since it is computed by Gigi). 397 398 ------------------ 399 -- Range_Length -- 400 ------------------ 401 402 Attribute_Range_Length => True, 403 -- T'Range_Length for any discrete type T yields the number of values 404 -- represented by the subtype (zero for a null range). The result is 405 -- static for static subtypes. Note that Range_Length applied to the 406 -- index subtype of a one dimensional array always gives the same result 407 -- as Range applied to the array itself. The result is of type universal 408 -- integer. 409 410 ------------ 411 -- Reduce -- 412 ------------ 413 414 Attribute_Reduce => True, 415 -- See AI12-0262-1 416 417 --------- 418 -- Ref -- 419 --------- 420 421 Attribute_Ref => True, 422 -- System.Address'Ref (Address is the only permissible prefix) is 423 -- equivalent to System'To_Address, provided for compatibility with 424 -- other compilers. 425 426 ------------------ 427 -- Storage_Unit -- 428 ------------------ 429 430 Attribute_Storage_Unit => True, 431 -- Standard'Storage_Unit (Standard is the only permissible prefix) 432 -- provides the value System.Storage_Unit, and is intended primarily 433 -- for constructing this definition in package System (see note above 434 -- in Default_Bit_Order description). The is a static attribute. 435 436 --------------- 437 -- Stub_Type -- 438 --------------- 439 440 Attribute_Stub_Type => True, 441 -- The GNAT implementation of remote access-to-classwide types is 442 -- organised as described in AARM E.4(20.t): a value of an RACW type 443 -- (designating a remote object) is represented as a normal access 444 -- value, pointing to a "stub" object which in turn contains the 445 -- necessary information to contact the designated remote object. A 446 -- call on any dispatching operation of such a stub object does the 447 -- remote call, if necessary, using the information in the stub object 448 -- to locate the target partition, etc. 449 -- 450 -- For a prefix T that denotes a remote access-to-classwide type, 451 -- T'Stub_Type denotes the type of the corresponding stub objects. 452 -- 453 -- By construction, the layout of T'Stub_Type is identical to that of 454 -- System.Partition_Interface.RACW_Stub_Type (see implementation notes 455 -- in body of Exp_Dist). 456 457 ----------------- 458 -- Target_Name -- 459 ----------------- 460 461 Attribute_Target_Name => True, 462 -- Standard'Target_Name yields the string identifying the target for the 463 -- compilation, taken from Sdefault.Target_Name. 464 465 ---------------- 466 -- To_Address -- 467 ---------------- 468 469 Attribute_To_Address => True, 470 -- System'To_Address (System is the only permissible prefix) is a 471 -- function that takes any integer value, and converts it into an 472 -- address value. The semantics is to first convert the integer value to 473 -- type Integer_Address according to normal conversion rules, and then 474 -- to convert this to an address using the same semantics as the 475 -- System.Storage_Elements.To_Address function. The important difference 476 -- is that this is a static attribute so it can be used in 477 -- initializations in preelaborate packages. 478 479 ---------------- 480 -- Type_Class -- 481 ---------------- 482 483 Attribute_Type_Class => True, 484 -- T'Type_Class for any type or subtype T yields the value of the type 485 -- class for the full type of T. If T is a generic formal type, then the 486 -- value is the value for the corresponding actual subtype. The value of 487 -- this attribute is of type System.Aux_DEC.Type_Class, which has the 488 -- following definition: 489 -- 490 -- type Type_Class is 491 -- (Type_Class_Enumeration, 492 -- Type_Class_Integer, 493 -- Type_Class_Fixed_Point, 494 -- Type_Class_Floating_Point, 495 -- Type_Class_Array, 496 -- Type_Class_Record, 497 -- Type_Class_Access, 498 -- Type_Class_Task, 499 -- Type_Class_Address); 500 -- 501 -- Protected types yield the value Type_Class_Task, which thus applies 502 -- to all concurrent types. This attribute is designed to be compatible 503 -- with the DEC Ada attribute of the same name. 504 -- 505 -- Note: if pragma Extend_System is used to merge the definitions of 506 -- Aux_DEC into System, then the type Type_Class can be referenced 507 -- as an entity within System, as can its enumeration literals. 508 509 ------------------------------ 510 -- Universal_Literal_String -- 511 ------------------------------ 512 513 Attribute_Universal_Literal_String => True, 514 -- The prefix of 'Universal_Literal_String must be a named number. 515 -- The static result is the string consisting of the characters of 516 -- the number as defined in the original source. This allows the 517 -- user program to access the actual text of named numbers without 518 -- intermediate conversions and without the need to enclose the 519 -- strings in quotes (which would preclude their use as numbers). 520 521 ------------------------- 522 -- Unrestricted_Access -- 523 ------------------------- 524 525 Attribute_Unrestricted_Access => True, 526 -- The Unrestricted_Access attribute is similar to Access except that 527 -- all accessibility and aliased view checks are omitted. This is very 528 -- much a user-beware attribute. Basically its status is very similar 529 -- to Address, for which it is a desirable replacement where the value 530 -- desired is an access type. In other words, its effect is identical 531 -- to first taking 'Address and then doing an unchecked conversion to 532 -- a desired access type. Note that in GNAT, but not necessarily in 533 -- other implementations, the use of static chains for inner level 534 -- subprograms means that Unrestricted_Access applied to a subprogram 535 -- yields a value that can be called as long as the subprogram is in 536 -- scope (normal Ada 95 accessibility rules restrict this usage). 537 538 --------------- 539 -- VADS_Size -- 540 --------------- 541 542 Attribute_VADS_Size => True, 543 -- Typ'VADS_Size yields the Size value typically yielded by some Ada 83 544 -- compilers. The differences between VADS_Size and Size is that for 545 -- scalar types for which no Size has been specified, VADS_Size yields 546 -- the Object_Size rather than the Value_Size. For example, while 547 -- Natural'Size is typically 31, the value of Natural'VADS_Size is 32. 548 -- For all other types, Size and VADS_Size yield the same value. 549 550 ------------------- 551 -- Valid_Scalars -- 552 ------------------- 553 554 Attribute_Valid_Scalars => True, 555 -- Obj'Valid_Scalars can be applied to any object. The result depends 556 -- on the type of the object: 557 -- 558 -- For a scalar type, the result is the same as obj'Valid 559 -- 560 -- For an array object, the result is True if the result of applying 561 -- Valid_Scalars to every component is True. For an empty array the 562 -- result is True. 563 -- 564 -- For a record object, the result is True if the result of applying 565 -- Valid_Scalars to every component is True. For class-wide types, 566 -- only the components of the base type are checked. For variant 567 -- records, only the components actually present are checked. The 568 -- discriminants, if any, are also checked. If there are no components 569 -- or discriminants, the result is True. 570 -- 571 -- For any other type that has discriminants, the result is True if 572 -- the result of applying Valid_Scalars to each discriminant is True. 573 -- 574 -- For all other types, the result is always True 575 -- 576 -- A warning is given for a trivially True result, when the attribute 577 -- is applied to an object that is not of scalar, array, or record 578 -- type, or in the composite case if no scalar subcomponents exist. For 579 -- a variant record, the warning is given only if none of the variants 580 -- have scalar subcomponents. In addition, the warning is suppressed 581 -- for private types, or generic formal types in an instance. 582 583 ---------------- 584 -- Value_Size -- 585 ---------------- 586 587 Attribute_Value_Size => True, 588 -- Type'Value_Size is the number of bits required to represent value of 589 -- the given subtype. It is the same as Type'Size, but, unlike Size, may 590 -- be set for non-first subtypes. See section in Einfo ("Handling of 591 -- type'Size values") for further details. 592 593 --------------- 594 -- Word_Size -- 595 --------------- 596 597 Attribute_Word_Size => True, 598 -- Standard'Word_Size (Standard is the only permissible prefix) 599 -- provides the value System.Word_Size, and is intended primarily 600 -- for constructing this definition in package System (see note above 601 -- in Default_Bit_Order description). This is a static attribute. 602 603 others => False); 604 605 -- The following table lists all attributes that yield a result of a 606 -- universal type. 607 608 Universal_Type_Attribute : constant array (Attribute_Id) of Boolean := 609 (Attribute_Aft => True, 610 Attribute_Alignment => True, 611 Attribute_Component_Size => True, 612 Attribute_Count => True, 613 Attribute_Delta => True, 614 Attribute_Digits => True, 615 Attribute_Exponent => True, 616 Attribute_First_Bit => True, 617 Attribute_Fore => True, 618 Attribute_Last_Bit => True, 619 Attribute_Length => True, 620 Attribute_Machine_Emax => True, 621 Attribute_Machine_Emin => True, 622 Attribute_Machine_Mantissa => True, 623 Attribute_Machine_Radix => True, 624 Attribute_Max_Alignment_For_Allocation => True, 625 Attribute_Max_Size_In_Storage_Elements => True, 626 Attribute_Model_Emin => True, 627 Attribute_Model_Epsilon => True, 628 Attribute_Model_Mantissa => True, 629 Attribute_Model_Small => True, 630 Attribute_Modulus => True, 631 Attribute_Pos => True, 632 Attribute_Position => True, 633 Attribute_Safe_First => True, 634 Attribute_Safe_Last => True, 635 Attribute_Scale => True, 636 Attribute_Size => True, 637 Attribute_Small => True, 638 Attribute_Wide_Wide_Width => True, 639 Attribute_Wide_Width => True, 640 Attribute_Width => True, 641 others => False); 642 643 ----------------- 644 -- Subprograms -- 645 ----------------- 646 647 procedure Analyze_Attribute (N : Node_Id); 648 -- Performs bottom up semantic analysis of an attribute. Note that the 649 -- parser has already checked that type returning attributes appear only 650 -- in appropriate contexts (i.e. in subtype marks, or as prefixes for 651 -- other attributes). 652 653 function Name_Implies_Lvalue_Prefix (Nam : Name_Id) return Boolean; 654 -- Determine whether the name of an attribute reference categorizes its 655 -- prefix as an lvalue. The following attributes fall under this bracket 656 -- by directly or indirectly modifying their prefixes. 657 -- Access 658 -- Address 659 -- Input 660 -- Read 661 -- Unchecked_Access 662 -- Unrestricted_Access 663 664 procedure Resolve_Attribute (N : Node_Id; Typ : Entity_Id); 665 -- Performs type resolution of attribute. If the attribute yields a 666 -- universal value, mark its type as that of the context. On the other 667 -- hand, if the context itself is universal (as in T'Val (T'Pos (X)), mark 668 -- the type as being the largest type of that class that can be used at 669 -- run-time. This is correct since either the value gets folded (in which 670 -- case it doesn't matter what type of the class we give if, since the 671 -- folding uses universal arithmetic anyway) or it doesn't get folded (in 672 -- which case it is going to be dealt with at runtime, and the largest type 673 -- is right). 674 675 function Stream_Attribute_Available 676 (Typ : Entity_Id; 677 Nam : TSS_Name_Type; 678 Partial_View : Entity_Id := Empty) return Boolean; 679 -- For a limited type Typ, return True if and only if the given attribute 680 -- is available. For Ada 2005, availability is defined by 13.13.2(36/1). 681 -- For Ada 95, an attribute is considered to be available if it has been 682 -- specified using an attribute definition clause for the type, or for its 683 -- full view, or for an ancestor of either. Parameter Partial_View is used 684 -- only internally, when checking for an attribute definition clause that 685 -- is not visible (Ada 95 only). 686 687end Sem_Attr; 688