gdb/value.h

   1 /* Definitions for values of C expressions, for GDB.
   2
   3    Copyright (C) 1986-2019 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #if !defined (VALUE_H)
  21 #define VALUE_H 1
  22
  23 #include "frame.h"              /* For struct frame_id.  */
  24 #include "extension.h"
  25 #include "gdbsupport/gdb_ref_ptr.h"
  26
  27 struct block;
  28 struct expression;
  29 struct regcache;
  30 struct symbol;
  31 struct type;
  32 struct ui_file;
  33 struct language_defn;
  34 struct value_print_options;
  35
  36 /* Values can be partially 'optimized out' and/or 'unavailable'.
  37    These are distinct states and have different string representations
  38    and related error strings.
  39
  40    'unavailable' has a specific meaning in this context.  It means the
  41    value exists in the program (at the machine level), but GDB has no
  42    means to get to it.  Such a value is normally printed as
  43    <unavailable>.  Examples of how to end up with an unavailable value
  44    would be:
  45
  46     - We're inspecting a traceframe, and the memory or registers the
  47       debug information says the value lives on haven't been collected.
  48
  49     - We're inspecting a core dump, the memory or registers the debug
  50       information says the value lives aren't present in the dump
  51       (that is, we have a partial/trimmed core dump, or we don't fully
  52       understand/handle the core dump's format).
  53
  54     - We're doing live debugging, but the debug API has no means to
  55       get at where the value lives in the machine, like e.g., ptrace
  56       not having access to some register or register set.
  57
  58     - Any other similar scenario.
  59
  60   OTOH, "optimized out" is about what the compiler decided to generate
  61   (or not generate).  A chunk of a value that was optimized out does
  62   not actually exist in the program.  There's no way to get at it
  63   short of compiling the program differently.
  64
  65   A register that has not been saved in a frame is likewise considered
  66   optimized out, except not-saved registers have a different string
  67   representation and related error strings.  E.g., we'll print them as
  68   <not-saved> instead of <optimized out>, as in:
  69
  70     (gdb) p/x $rax
  71     $1 = <not saved>
  72     (gdb) info registers rax
  73     rax            <not saved>
  74
  75   If the debug info describes a variable as being in such a register,
  76   we'll still print the variable as <optimized out>.  IOW, <not saved>
  77   is reserved for inspecting registers at the machine level.
  78
  79   When comparing value contents, optimized out chunks, unavailable
  80   chunks, and valid contents data are all considered different.  See
  81   value_contents_eq for more info.
  82 */
  83
  84 /* The structure which defines the type of a value.  It should never
  85    be possible for a program lval value to survive over a call to the
  86    inferior (i.e. to be put into the history list or an internal
  87    variable).  */
  88
  89 struct value;
  90
  91 /* Increase VAL's reference count.  */
  92
  93 extern void value_incref (struct value *val);
  94
  95 /* Decrease VAL's reference count.  When the reference count drops to
  96    0, VAL will be freed.  */
  97
  98 extern void value_decref (struct value *val);
  99
 100 /* A policy class to interface gdb::ref_ptr with struct value.  */
 101
 102 struct value_ref_policy
 103 {
 104   static void incref (struct value *ptr)
 105   {
 106     value_incref (ptr);
 107   }
 108
 109   static void decref (struct value *ptr)
 110   {
 111     value_decref (ptr);
 112   }
 113 };
 114
 115 /* A gdb:;ref_ptr pointer to a struct value.  */
 116
 117 typedef gdb::ref_ptr<struct value, value_ref_policy> value_ref_ptr;
 118
 119 /* Values are stored in a chain, so that they can be deleted easily
 120    over calls to the inferior.  Values assigned to internal variables,
 121    put into the value history or exposed to Python are taken off this
 122    list.  */
 123
 124 struct value *value_next (const struct value *);
 125
 126 /* Type of the value.  */
 127
 128 extern struct type *value_type (const struct value *);
 129
 130 /* Return the gdbarch associated with the value. */
 131
 132 extern struct gdbarch *get_value_arch (const struct value *value);
 133
 134 /* This is being used to change the type of an existing value, that
 135    code should instead be creating a new value with the changed type
 136    (but possibly shared content).  */
 137
 138 extern void deprecated_set_value_type (struct value *value,
 139                                        struct type *type);
 140
 141 /* Only used for bitfields; number of bits contained in them.  */
 142
 143 extern LONGEST value_bitsize (const struct value *);
 144 extern void set_value_bitsize (struct value *, LONGEST bit);
 145
 146 /* Only used for bitfields; position of start of field.  For
 147    gdbarch_bits_big_endian=0 targets, it is the position of the LSB.  For
 148    gdbarch_bits_big_endian=1 targets, it is the position of the MSB.  */
 149
 150 extern LONGEST value_bitpos (const struct value *);
 151 extern void set_value_bitpos (struct value *, LONGEST bit);
 152
 153 /* Only used for bitfields; the containing value.  This allows a
 154    single read from the target when displaying multiple
 155    bitfields.  */
 156
 157 struct value *value_parent (const struct value *);
 158 extern void set_value_parent (struct value *value, struct value *parent);
 159
 160 /* Describes offset of a value within lval of a structure in bytes.
 161    If lval == lval_memory, this is an offset to the address.  If lval
 162    == lval_register, this is a further offset from location.address
 163    within the registers structure.  Note also the member
 164    embedded_offset below.  */
 165
 166 extern LONGEST value_offset (const struct value *);
 167 extern void set_value_offset (struct value *, LONGEST offset);
 168
 169 /* The comment from "struct value" reads: ``Is it modifiable?  Only
 170    relevant if lval != not_lval.''.  Shouldn't the value instead be
 171    not_lval and be done with it?  */
 172
 173 extern int deprecated_value_modifiable (const struct value *value);
 174
 175 /* If a value represents a C++ object, then the `type' field gives the
 176    object's compile-time type.  If the object actually belongs to some
 177    class derived from `type', perhaps with other base classes and
 178    additional members, then `type' is just a subobject of the real
 179    thing, and the full object is probably larger than `type' would
 180    suggest.
 181
 182    If `type' is a dynamic class (i.e. one with a vtable), then GDB can
 183    actually determine the object's run-time type by looking at the
 184    run-time type information in the vtable.  When this information is
 185    available, we may elect to read in the entire object, for several
 186    reasons:
 187
 188    - When printing the value, the user would probably rather see the
 189      full object, not just the limited portion apparent from the
 190      compile-time type.
 191
 192    - If `type' has virtual base classes, then even printing `type'
 193      alone may require reaching outside the `type' portion of the
 194      object to wherever the virtual base class has been stored.
 195
 196    When we store the entire object, `enclosing_type' is the run-time
 197    type -- the complete object -- and `embedded_offset' is the offset
 198    of `type' within that larger type, in bytes.  The value_contents()
 199    macro takes `embedded_offset' into account, so most GDB code
 200    continues to see the `type' portion of the value, just as the
 201    inferior would.
 202
 203    If `type' is a pointer to an object, then `enclosing_type' is a
 204    pointer to the object's run-time type, and `pointed_to_offset' is
 205    the offset in bytes from the full object to the pointed-to object
 206    -- that is, the value `embedded_offset' would have if we followed
 207    the pointer and fetched the complete object.  (I don't really see
 208    the point.  Why not just determine the run-time type when you
 209    indirect, and avoid the special case?  The contents don't matter
 210    until you indirect anyway.)
 211
 212    If we're not doing anything fancy, `enclosing_type' is equal to
 213    `type', and `embedded_offset' is zero, so everything works
 214    normally.  */
 215
 216 extern struct type *value_enclosing_type (const struct value *);
 217 extern void set_value_enclosing_type (struct value *val,
 218                                       struct type *new_type);
 219
 220 /* Returns value_type or value_enclosing_type depending on
 221    value_print_options.objectprint.
 222
 223    If RESOLVE_SIMPLE_TYPES is 0 the enclosing type will be resolved
 224    only for pointers and references, else it will be returned
 225    for all the types (e.g. structures).  This option is useful
 226    to prevent retrieving enclosing type for the base classes fields.
 227
 228    REAL_TYPE_FOUND is used to inform whether the real type was found
 229    (or just static type was used).  The NULL may be passed if it is not
 230    necessary. */
 231
 232 extern struct type *value_actual_type (struct value *value,
 233                                        int resolve_simple_types,
 234                                        int *real_type_found);
 235
 236 extern LONGEST value_pointed_to_offset (const struct value *value);
 237 extern void set_value_pointed_to_offset (struct value *value, LONGEST val);
 238 extern LONGEST value_embedded_offset (const struct value *value);
 239 extern void set_value_embedded_offset (struct value *value, LONGEST val);
 240
 241 /* For lval_computed values, this structure holds functions used to
 242    retrieve and set the value (or portions of the value).
 243
 244    For each function, 'V' is the 'this' pointer: an lval_funcs
 245    function F may always assume that the V it receives is an
 246    lval_computed value, and has F in the appropriate slot of its
 247    lval_funcs structure.  */
 248
 249 struct lval_funcs
 250 {
 251   /* Fill in VALUE's contents.  This is used to "un-lazy" values.  If
 252      a problem arises in obtaining VALUE's bits, this function should
 253      call 'error'.  If it is NULL value_fetch_lazy on "un-lazy"
 254      non-optimized-out value is an internal error.  */
 255   void (*read) (struct value *v);
 256
 257   /* Handle an assignment TOVAL = FROMVAL by writing the value of
 258      FROMVAL to TOVAL's location.  The contents of TOVAL have not yet
 259      been updated.  If a problem arises in doing so, this function
 260      should call 'error'.  If it is NULL such TOVAL assignment is an error as
 261      TOVAL is not considered as an lvalue.  */
 262   void (*write) (struct value *toval, struct value *fromval);
 263
 264   /* If non-NULL, this is used to implement pointer indirection for
 265      this value.  This method may return NULL, in which case value_ind
 266      will fall back to ordinary indirection.  */
 267   struct value *(*indirect) (struct value *value);
 268
 269   /* If non-NULL, this is used to implement reference resolving for
 270      this value.  This method may return NULL, in which case coerce_ref
 271      will fall back to ordinary references resolving.  */
 272   struct value *(*coerce_ref) (const struct value *value);
 273
 274   /* If non-NULL, this is used to determine whether the indicated bits
 275      of VALUE are a synthetic pointer.  */
 276   int (*check_synthetic_pointer) (const struct value *value,
 277                                   LONGEST offset, int length);
 278
 279   /* Return a duplicate of VALUE's closure, for use in a new value.
 280      This may simply return the same closure, if VALUE's is
 281      reference-counted or statically allocated.
 282
 283      This may be NULL, in which case VALUE's closure is re-used in the
 284      new value.  */
 285   void *(*copy_closure) (const struct value *v);
 286
 287   /* Drop VALUE's reference to its closure.  Maybe this frees the
 288      closure; maybe this decrements a reference count; maybe the
 289      closure is statically allocated and this does nothing.
 290
 291      This may be NULL, in which case no action is taken to free
 292      VALUE's closure.  */
 293   void (*free_closure) (struct value *v);
 294 };
 295
 296 /* Create a computed lvalue, with type TYPE, function pointers FUNCS,
 297    and closure CLOSURE.  */
 298
 299 extern struct value *allocate_computed_value (struct type *type,
 300                                               const struct lval_funcs *funcs,
 301                                               void *closure);
 302
 303 /* Helper function to check the validity of some bits of a value.
 304
 305    If TYPE represents some aggregate type (e.g., a structure), return 1.
 306
 307    Otherwise, any of the bytes starting at OFFSET and extending for
 308    TYPE_LENGTH(TYPE) bytes are invalid, print a message to STREAM and
 309    return 0.  The checking is done using FUNCS.
 310
 311    Otherwise, return 1.  */
 312
 313 extern int valprint_check_validity (struct ui_file *stream, struct type *type,
 314                                     LONGEST embedded_offset,
 315                                     const struct value *val);
 316
 317 extern struct value *allocate_optimized_out_value (struct type *type);
 318
 319 /* If VALUE is lval_computed, return its lval_funcs structure.  */
 320
 321 extern const struct lval_funcs *value_computed_funcs (const struct value *);
 322
 323 /* If VALUE is lval_computed, return its closure.  The meaning of the
 324    returned value depends on the functions VALUE uses.  */
 325
 326 extern void *value_computed_closure (const struct value *value);
 327
 328 /* If zero, contents of this value are in the contents field.  If
 329    nonzero, contents are in inferior.  If the lval field is lval_memory,
 330    the contents are in inferior memory at location.address plus offset.
 331    The lval field may also be lval_register.
 332
 333    WARNING: This field is used by the code which handles watchpoints
 334    (see breakpoint.c) to decide whether a particular value can be
 335    watched by hardware watchpoints.  If the lazy flag is set for some
 336    member of a value chain, it is assumed that this member of the
 337    chain doesn't need to be watched as part of watching the value
 338    itself.  This is how GDB avoids watching the entire struct or array
 339    when the user wants to watch a single struct member or array
 340    element.  If you ever change the way lazy flag is set and reset, be
 341    sure to consider this use as well!  */
 342
 343 extern int value_lazy (const struct value *);
 344 extern void set_value_lazy (struct value *value, int val);
 345
 346 extern int value_stack (const struct value *);
 347 extern void set_value_stack (struct value *value, int val);
 348
 349 /* Throw an error complaining that the value has been optimized
 350    out.  */
 351
 352 extern void error_value_optimized_out (void);
 353
 354 /* value_contents() and value_contents_raw() both return the address
 355    of the gdb buffer used to hold a copy of the contents of the lval.
 356    value_contents() is used when the contents of the buffer are needed
 357    -- it uses value_fetch_lazy() to load the buffer from the process
 358    being debugged if it hasn't already been loaded
 359    (value_contents_writeable() is used when a writeable but fetched
 360    buffer is required)..  value_contents_raw() is used when data is
 361    being stored into the buffer, or when it is certain that the
 362    contents of the buffer are valid.
 363
 364    Note: The contents pointer is adjusted by the offset required to
 365    get to the real subobject, if the value happens to represent
 366    something embedded in a larger run-time object.  */
 367
 368 extern gdb_byte *value_contents_raw (struct value *);
 369
 370 /* Actual contents of the value.  For use of this value; setting it
 371    uses the stuff above.  Not valid if lazy is nonzero.  Target
 372    byte-order.  We force it to be aligned properly for any possible
 373    value.  Note that a value therefore extends beyond what is
 374    declared here.  */
 375
 376 extern const gdb_byte *value_contents (struct value *);
 377 extern gdb_byte *value_contents_writeable (struct value *);
 378
 379 /* The ALL variants of the above two macros do not adjust the returned
 380    pointer by the embedded_offset value.  */
 381
 382 extern gdb_byte *value_contents_all_raw (struct value *);
 383 extern const gdb_byte *value_contents_all (struct value *);
 384
 385 /* Like value_contents_all, but does not require that the returned
 386    bits be valid.  This should only be used in situations where you
 387    plan to check the validity manually.  */
 388 extern const gdb_byte *value_contents_for_printing (struct value *value);
 389
 390 /* Like value_contents_for_printing, but accepts a constant value
 391    pointer.  Unlike value_contents_for_printing however, the pointed
 392    value must _not_ be lazy.  */
 393 extern const gdb_byte *
 394   value_contents_for_printing_const (const struct value *value);
 395
 396 extern void value_fetch_lazy (struct value *val);
 397
 398 /* If nonzero, this is the value of a variable which does not actually
 399    exist in the program, at least partially.  If the value is lazy,
 400    this may fetch it now.  */
 401 extern int value_optimized_out (struct value *value);
 402
 403 /* Given a value, return true if any of the contents bits starting at
 404    OFFSET and extending for LENGTH bits is optimized out, false
 405    otherwise.  */
 406
 407 extern int value_bits_any_optimized_out (const struct value *value,
 408                                          int bit_offset, int bit_length);
 409
 410 /* Like value_optimized_out, but return true iff the whole value is
 411    optimized out.  */
 412 extern int value_entirely_optimized_out (struct value *value);
 413
 414 /* Mark VALUE's content bytes starting at OFFSET and extending for
 415    LENGTH bytes as optimized out.  */
 416
 417 extern void mark_value_bytes_optimized_out (struct value *value,
 418                                             int offset, int length);
 419
 420 /* Mark VALUE's content bits starting at OFFSET and extending for
 421    LENGTH bits as optimized out.  */
 422
 423 extern void mark_value_bits_optimized_out (struct value *value,
 424                                            LONGEST offset, LONGEST length);
 425
 426 /* Set or return field indicating whether a variable is initialized or
 427    not, based on debugging information supplied by the compiler.
 428    1 = initialized; 0 = uninitialized.  */
 429 extern int value_initialized (const struct value *);
 430 extern void set_value_initialized (struct value *, int);
 431
 432 /* Set COMPONENT's location as appropriate for a component of WHOLE
 433    --- regardless of what kind of lvalue WHOLE is.  */
 434 extern void set_value_component_location (struct value *component,
 435                                           const struct value *whole);
 436
 437 /* While the following fields are per- VALUE .CONTENT .PIECE (i.e., a
 438    single value might have multiple LVALs), this hacked interface is
 439    limited to just the first PIECE.  Expect further change.  */
 440 /* Type of value; either not an lval, or one of the various different
 441    possible kinds of lval.  */
 442 extern enum lval_type *deprecated_value_lval_hack (struct value *);
 443 #define VALUE_LVAL(val) (*deprecated_value_lval_hack (val))
 444
 445 /* Like VALUE_LVAL, except the parameter can be const.  */
 446 extern enum lval_type value_lval_const (const struct value *value);
 447
 448 /* If lval == lval_memory, return the address in the inferior.  If
 449    lval == lval_register, return the byte offset into the registers
 450    structure.  Otherwise, return 0.  The returned address
 451    includes the offset, if any.  */
 452 extern CORE_ADDR value_address (const struct value *);
 453
 454 /* Like value_address, except the result does not include value's
 455    offset.  */
 456 extern CORE_ADDR value_raw_address (const struct value *);
 457
 458 /* Set the address of a value.  */
 459 extern void set_value_address (struct value *, CORE_ADDR);
 460
 461 /* Pointer to internal variable.  */
 462 extern struct internalvar **deprecated_value_internalvar_hack (struct value *);
 463 #define VALUE_INTERNALVAR(val) (*deprecated_value_internalvar_hack (val))
 464
 465 /* Frame ID of "next" frame to which a register value is relative.  A
 466    register value is indicated by VALUE_LVAL being set to lval_register.
 467    So, if the register value is found relative to frame F, then the
 468    frame id of F->next will be stored in VALUE_NEXT_FRAME_ID.  */
 469 extern struct frame_id *deprecated_value_next_frame_id_hack (struct value *);
 470 #define VALUE_NEXT_FRAME_ID(val) (*deprecated_value_next_frame_id_hack (val))
 471
 472 /* Frame ID of frame to which a register value is relative.  This is
 473    similar to VALUE_NEXT_FRAME_ID, above, but may not be assigned to.
 474    Note that VALUE_FRAME_ID effectively undoes the "next" operation
 475    that was performed during the assignment to VALUE_NEXT_FRAME_ID.  */
 476 #define VALUE_FRAME_ID(val) (get_prev_frame_id_by_id (VALUE_NEXT_FRAME_ID (val)))
 477
 478 /* Register number if the value is from a register.  */
 479 extern int *deprecated_value_regnum_hack (struct value *);
 480 #define VALUE_REGNUM(val) (*deprecated_value_regnum_hack (val))
 481
 482 /* Return value after lval_funcs->coerce_ref (after check_typedef).  Return
 483    NULL if lval_funcs->coerce_ref is not applicable for whatever reason.  */
 484
 485 extern struct value *coerce_ref_if_computed (const struct value *arg);
 486
 487 /* Setup a new value type and enclosing value type for dereferenced value VALUE.
 488    ENC_TYPE is the new enclosing type that should be set.  ORIGINAL_TYPE and
 489    ORIGINAL_VAL are the type and value of the original reference or pointer.
 490
 491    Note, that VALUE is modified by this function.
 492
 493    It is a common implementation for coerce_ref and value_ind.  */
 494
 495 extern struct value * readjust_indirect_value_type (struct value *value,
 496                                                     struct type *enc_type,
 497                                                     const struct type *original_type,
 498                                                     const struct value *original_val);
 499
 500 /* Convert a REF to the object referenced.  */
 501
 502 extern struct value *coerce_ref (struct value *value);
 503
 504 /* If ARG is an array, convert it to a pointer.
 505    If ARG is a function, convert it to a function pointer.
 506
 507    References are dereferenced.  */
 508
 509 extern struct value *coerce_array (struct value *value);
 510
 511 /* Given a value, determine whether the bits starting at OFFSET and
 512    extending for LENGTH bits are a synthetic pointer.  */
 513
 514 extern int value_bits_synthetic_pointer (const struct value *value,
 515                                          LONGEST offset, LONGEST length);
 516
 517 /* Given a value, determine whether the contents bytes starting at
 518    OFFSET and extending for LENGTH bytes are available.  This returns
 519    nonzero if all bytes in the given range are available, zero if any
 520    byte is unavailable.  */
 521
 522 extern int value_bytes_available (const struct value *value,
 523                                   LONGEST offset, LONGEST length);
 524
 525 /* Given a value, determine whether the contents bits starting at
 526    OFFSET and extending for LENGTH bits are available.  This returns
 527    nonzero if all bits in the given range are available, zero if any
 528    bit is unavailable.  */
 529
 530 extern int value_bits_available (const struct value *value,
 531                                  LONGEST offset, LONGEST length);
 532
 533 /* Like value_bytes_available, but return false if any byte in the
 534    whole object is unavailable.  */
 535 extern int value_entirely_available (struct value *value);
 536
 537 /* Like value_entirely_available, but return false if any byte in the
 538    whole object is available.  */
 539 extern int value_entirely_unavailable (struct value *value);
 540
 541 /* Mark VALUE's content bytes starting at OFFSET and extending for
 542    LENGTH bytes as unavailable.  */
 543
 544 extern void mark_value_bytes_unavailable (struct value *value,
 545                                           LONGEST offset, LONGEST length);
 546
 547 /* Mark VALUE's content bits starting at OFFSET and extending for
 548    LENGTH bits as unavailable.  */
 549
 550 extern void mark_value_bits_unavailable (struct value *value,
 551                                          LONGEST offset, LONGEST length);
 552
 553 /* Compare LENGTH bytes of VAL1's contents starting at OFFSET1 with
 554    LENGTH bytes of VAL2's contents starting at OFFSET2.
 555
 556    Note that "contents" refers to the whole value's contents
 557    (value_contents_all), without any embedded offset adjustment.  For
 558    example, to compare a complete object value with itself, including
 559    its enclosing type chunk, you'd do:
 560
 561      int len = TYPE_LENGTH (check_typedef (value_enclosing_type (val)));
 562      value_contents_eq (val, 0, val, 0, len);
 563
 564    Returns true iff the set of available/valid contents match.
 565
 566    Optimized-out contents are equal to optimized-out contents, and are
 567    not equal to non-optimized-out contents.
 568
 569    Unavailable contente are equal to unavailable contents, and are not
 570    equal to non-unavailable contents.
 571
 572    For example, if 'x's represent an unavailable byte, and 'V' and 'Z'
 573    represent different available/valid bytes, in a value with length
 574    16:
 575
 576      offset:   0   4   8   12  16
 577      contents: xxxxVVVVxxxxVVZZ
 578
 579    then:
 580
 581      value_contents_eq(val, 0, val, 8, 6) => true
 582      value_contents_eq(val, 0, val, 4, 4) => false
 583      value_contents_eq(val, 0, val, 8, 8) => false
 584      value_contents_eq(val, 4, val, 12, 2) => true
 585      value_contents_eq(val, 4, val, 12, 4) => true
 586      value_contents_eq(val, 3, val, 4, 4) => true
 587
 588    If 'x's represent an unavailable byte, 'o' represents an optimized
 589    out byte, in a value with length 8:
 590
 591      offset:   0   4   8
 592      contents: xxxxoooo
 593
 594    then:
 595
 596      value_contents_eq(val, 0, val, 2, 2) => true
 597      value_contents_eq(val, 4, val, 6, 2) => true
 598      value_contents_eq(val, 0, val, 4, 4) => true
 599
 600    We only know whether a value chunk is unavailable or optimized out
 601    if we've tried to read it.  As this routine is used by printing
 602    routines, which may be printing values in the value history, long
 603    after the inferior is gone, it works with const values.  Therefore,
 604    this routine must not be called with lazy values.  */
 605
 606 extern bool value_contents_eq (const struct value *val1, LONGEST offset1,
 607                                const struct value *val2, LONGEST offset2,
 608                                LONGEST length);
 609
 610 /* Read LENGTH addressable memory units starting at MEMADDR into BUFFER,
 611    which is (or will be copied to) VAL's contents buffer offset by
 612    BIT_OFFSET bits.  Marks value contents ranges as unavailable if
 613    the corresponding memory is likewise unavailable.  STACK indicates
 614    whether the memory is known to be stack memory.  */
 615
 616 extern void read_value_memory (struct value *val, LONGEST bit_offset,
 617                                int stack, CORE_ADDR memaddr,
 618                                gdb_byte *buffer, size_t length);
 619
 620 /* Cast SCALAR_VALUE to the element type of VECTOR_TYPE, then replicate
 621    into each element of a new vector value with VECTOR_TYPE.  */
 622
 623 struct value *value_vector_widen (struct value *scalar_value,
 624                                   struct type *vector_type);
 625
 626 \f
 627
 628 #include "symtab.h"
 629 #include "gdbtypes.h"
 630 #include "expression.h"
 631
 632 struct frame_info;
 633 struct fn_field;
 634
 635 extern int print_address_demangle (const struct value_print_options *,
 636                                    struct gdbarch *, CORE_ADDR,
 637                                    struct ui_file *, int);
 638
 639 /* Returns true if VAL is of floating-point type.  In addition,
 640    throws an error if the value is an invalid floating-point value.  */
 641 extern bool is_floating_value (struct value *val);
 642
 643 extern LONGEST value_as_long (struct value *val);
 644 extern CORE_ADDR value_as_address (struct value *val);
 645
 646 extern LONGEST unpack_long (struct type *type, const gdb_byte *valaddr);
 647 extern CORE_ADDR unpack_pointer (struct type *type, const gdb_byte *valaddr);
 648
 649 extern LONGEST unpack_field_as_long (struct type *type,
 650                                      const gdb_byte *valaddr,
 651                                      int fieldno);
 652 extern int unpack_value_field_as_long (struct type *type, const gdb_byte *valaddr,
 653                                 LONGEST embedded_offset, int fieldno,
 654                                 const struct value *val, LONGEST *result);
 655
 656 extern void unpack_value_bitfield (struct value *dest_val,
 657                                    LONGEST bitpos, LONGEST bitsize,
 658                                    const gdb_byte *valaddr,
 659                                    LONGEST embedded_offset,
 660                                    const struct value *val);
 661
 662 extern struct value *value_field_bitfield (struct type *type, int fieldno,
 663                                            const gdb_byte *valaddr,
 664                                            LONGEST embedded_offset,
 665                                            const struct value *val);
 666
 667 extern void pack_long (gdb_byte *buf, struct type *type, LONGEST num);
 668
 669 extern struct value *value_from_longest (struct type *type, LONGEST num);
 670 extern struct value *value_from_ulongest (struct type *type, ULONGEST num);
 671 extern struct value *value_from_pointer (struct type *type, CORE_ADDR addr);
 672 extern struct value *value_from_host_double (struct type *type, double d);
 673 extern struct value *value_from_history_ref (const char *, const char **);
 674 extern struct value *value_from_component (struct value *, struct type *,
 675                                            LONGEST);
 676
 677 extern struct value *value_at (struct type *type, CORE_ADDR addr);
 678 extern struct value *value_at_lazy (struct type *type, CORE_ADDR addr);
 679
 680 extern struct value *value_from_contents_and_address_unresolved
 681      (struct type *, const gdb_byte *, CORE_ADDR);
 682 extern struct value *value_from_contents_and_address (struct type *,
 683                                                       const gdb_byte *,
 684                                                       CORE_ADDR);
 685 extern struct value *value_from_contents (struct type *, const gdb_byte *);
 686
 687 extern struct value *default_value_from_register (struct gdbarch *gdbarch,
 688                                                   struct type *type,
 689                                                   int regnum,
 690                                                   struct frame_id frame_id);
 691
 692 extern void read_frame_register_value (struct value *value,
 693                                        struct frame_info *frame);
 694
 695 extern struct value *value_from_register (struct type *type, int regnum,
 696                                           struct frame_info *frame);
 697
 698 extern CORE_ADDR address_from_register (int regnum,
 699                                         struct frame_info *frame);
 700
 701 extern struct value *value_of_variable (struct symbol *var,
 702                                         const struct block *b);
 703
 704 extern struct value *address_of_variable (struct symbol *var,
 705                                           const struct block *b);
 706
 707 extern struct value *value_of_register (int regnum, struct frame_info *frame);
 708
 709 struct value *value_of_register_lazy (struct frame_info *frame, int regnum);
 710
 711 /* Return the symbol's reading requirement.  */
 712
 713 extern enum symbol_needs_kind symbol_read_needs (struct symbol *);
 714
 715 /* Return true if the symbol needs a frame.  This is a wrapper for
 716    symbol_read_needs that simply checks for SYMBOL_NEEDS_FRAME.  */
 717
 718 extern int symbol_read_needs_frame (struct symbol *);
 719
 720 extern struct value *read_var_value (struct symbol *var,
 721                                      const struct block *var_block,
 722                                      struct frame_info *frame);
 723
 724 extern struct value *default_read_var_value (struct symbol *var,
 725                                              const struct block *var_block,
 726                                              struct frame_info *frame);
 727
 728 extern struct value *allocate_value (struct type *type);
 729 extern struct value *allocate_value_lazy (struct type *type);
 730 extern void value_contents_copy (struct value *dst, LONGEST dst_offset,
 731                                  struct value *src, LONGEST src_offset,
 732                                  LONGEST length);
 733 extern void value_contents_copy_raw (struct value *dst, LONGEST dst_offset,
 734                                      struct value *src, LONGEST src_offset,
 735                                      LONGEST length);
 736
 737 extern struct value *allocate_repeat_value (struct type *type, int count);
 738
 739 extern struct value *value_mark (void);
 740
 741 extern void value_free_to_mark (const struct value *mark);
 742
 743 /* A helper class that uses value_mark at construction time and calls
 744    value_free_to_mark in the destructor.  This is used to clear out
 745    temporary values created during the lifetime of this object.  */
 746 class scoped_value_mark
 747 {
 748  public:
 749
 750   scoped_value_mark ()
 751     : m_value (value_mark ())
 752   {
 753   }
 754
 755   ~scoped_value_mark ()
 756   {
 757     free_to_mark ();
 758   }
 759
 760   scoped_value_mark (scoped_value_mark &&other) = default;
 761
 762   DISABLE_COPY_AND_ASSIGN (scoped_value_mark);
 763
 764   /* Free the values currently on the value stack.  */
 765   void free_to_mark ()
 766   {
 767     if (m_value != NULL)
 768       {
 769         value_free_to_mark (m_value);
 770         m_value = NULL;
 771       }
 772   }
 773
 774  private:
 775
 776   const struct value *m_value;
 777 };
 778
 779 extern struct value *value_cstring (const char *ptr, ssize_t len,
 780                                     struct type *char_type);
 781 extern struct value *value_string (const char *ptr, ssize_t len,
 782                                    struct type *char_type);
 783
 784 extern struct value *value_array (int lowbound, int highbound,
 785                                   struct value **elemvec);
 786
 787 extern struct value *value_concat (struct value *arg1, struct value *arg2);
 788
 789 extern struct value *value_binop (struct value *arg1, struct value *arg2,
 790                                   enum exp_opcode op);
 791
 792 extern struct value *value_ptradd (struct value *arg1, LONGEST arg2);
 793
 794 extern LONGEST value_ptrdiff (struct value *arg1, struct value *arg2);
 795
 796 /* Return true if VAL does not live in target memory, but should in order
 797    to operate on it.  Otherwise return false.  */
 798
 799 extern bool value_must_coerce_to_target (struct value *arg1);
 800
 801 extern struct value *value_coerce_to_target (struct value *arg1);
 802
 803 extern struct value *value_coerce_array (struct value *arg1);
 804
 805 extern struct value *value_coerce_function (struct value *arg1);
 806
 807 extern struct value *value_ind (struct value *arg1);
 808
 809 extern struct value *value_addr (struct value *arg1);
 810
 811 extern struct value *value_ref (struct value *arg1, enum type_code refcode);
 812
 813 extern struct value *value_assign (struct value *toval,
 814                                    struct value *fromval);
 815
 816 extern struct value *value_pos (struct value *arg1);
 817
 818 extern struct value *value_neg (struct value *arg1);
 819
 820 extern struct value *value_complement (struct value *arg1);
 821
 822 extern struct value *value_struct_elt (struct value **argp,
 823                                        struct value **args,
 824                                        const char *name, int *static_memfuncp,
 825                                        const char *err);
 826
 827 extern struct value *value_struct_elt_bitpos (struct value **argp,
 828                                               int bitpos,
 829                                               struct type *field_type,
 830                                               const char *err);
 831
 832 extern struct value *value_aggregate_elt (struct type *curtype,
 833                                           const char *name,
 834                                           struct type *expect_type,
 835                                           int want_address,
 836                                           enum noside noside);
 837
 838 extern struct value *value_static_field (struct type *type, int fieldno);
 839
 840 enum oload_search_type { NON_METHOD, METHOD, BOTH };
 841
 842 extern int find_overload_match (gdb::array_view<value *> args,
 843                                 const char *name,
 844                                 enum oload_search_type method,
 845                                 struct value **objp, struct symbol *fsym,
 846                                 struct value **valp, struct symbol **symp,
 847                                 int *staticp, const int no_adl,
 848                                 enum noside noside);
 849
 850 extern struct value *value_field (struct value *arg1, int fieldno);
 851
 852 extern struct value *value_primitive_field (struct value *arg1, LONGEST offset,
 853                                             int fieldno,
 854                                             struct type *arg_type);
 855
 856
 857 extern struct type *value_rtti_indirect_type (struct value *, int *, LONGEST *,
 858                                               int *);
 859
 860 extern struct value *value_full_object (struct value *, struct type *, int,
 861                                         int, int);
 862
 863 extern struct value *value_cast_pointers (struct type *, struct value *, int);
 864
 865 extern struct value *value_cast (struct type *type, struct value *arg2);
 866
 867 extern struct value *value_reinterpret_cast (struct type *type,
 868                                              struct value *arg);
 869
 870 extern struct value *value_dynamic_cast (struct type *type, struct value *arg);
 871
 872 extern struct value *value_zero (struct type *type, enum lval_type lv);
 873
 874 extern struct value *value_one (struct type *type);
 875
 876 extern struct value *value_repeat (struct value *arg1, int count);
 877
 878 extern struct value *value_subscript (struct value *array, LONGEST index);
 879
 880 extern struct value *value_bitstring_subscript (struct type *type,
 881                                                 struct value *bitstring,
 882                                                 LONGEST index);
 883
 884 extern struct value *register_value_being_returned (struct type *valtype,
 885                                                     struct regcache *retbuf);
 886
 887 extern int value_in (struct value *element, struct value *set);
 888
 889 extern int value_bit_index (struct type *type, const gdb_byte *addr,
 890                             int index);
 891
 892 extern enum return_value_convention
 893 struct_return_convention (struct gdbarch *gdbarch, struct value *function,
 894                           struct type *value_type);
 895
 896 extern int using_struct_return (struct gdbarch *gdbarch,
 897                                 struct value *function,
 898                                 struct type *value_type);
 899
 900 extern struct value *evaluate_expression (struct expression *exp);
 901
 902 extern struct value *evaluate_type (struct expression *exp);
 903
 904 extern struct value *evaluate_subexp (struct type *expect_type,
 905                                       struct expression *exp,
 906                                       int *pos, enum noside noside);
 907
 908 extern struct value *evaluate_subexpression_type (struct expression *exp,
 909                                                   int subexp);
 910
 911 extern value *evaluate_var_value (enum noside noside, const block *blk,
 912                                   symbol *var);
 913
 914 extern value *evaluate_var_msym_value (enum noside noside,
 915                                        struct objfile *objfile,
 916                                        minimal_symbol *msymbol);
 917
 918 extern value *eval_skip_value (expression *exp);
 919
 920 extern void fetch_subexp_value (struct expression *exp, int *pc,
 921                                 struct value **valp, struct value **resultp,
 922                                 std::vector<value_ref_ptr> *val_chain,
 923                                 int preserve_errors);
 924
 925 extern const char *extract_field_op (struct expression *exp, int *subexp);
 926
 927 extern struct value *evaluate_subexp_with_coercion (struct expression *,
 928                                                     int *, enum noside);
 929
 930 extern struct value *parse_and_eval (const char *exp);
 931
 932 extern struct value *parse_to_comma_and_eval (const char **expp);
 933
 934 extern struct type *parse_and_eval_type (char *p, int length);
 935
 936 extern CORE_ADDR parse_and_eval_address (const char *exp);
 937
 938 extern LONGEST parse_and_eval_long (const char *exp);
 939
 940 extern void unop_promote (const struct language_defn *language,
 941                           struct gdbarch *gdbarch,
 942                           struct value **arg1);
 943
 944 extern void binop_promote (const struct language_defn *language,
 945                            struct gdbarch *gdbarch,
 946                            struct value **arg1, struct value **arg2);
 947
 948 extern struct value *access_value_history (int num);
 949
 950 extern struct value *value_of_internalvar (struct gdbarch *gdbarch,
 951                                            struct internalvar *var);
 952
 953 extern int get_internalvar_integer (struct internalvar *var, LONGEST *l);
 954
 955 extern void set_internalvar (struct internalvar *var, struct value *val);
 956
 957 extern void set_internalvar_integer (struct internalvar *var, LONGEST l);
 958
 959 extern void set_internalvar_string (struct internalvar *var,
 960                                     const char *string);
 961
 962 extern void clear_internalvar (struct internalvar *var);
 963
 964 extern void set_internalvar_component (struct internalvar *var,
 965                                        LONGEST offset,
 966                                        LONGEST bitpos, LONGEST bitsize,
 967                                        struct value *newvalue);
 968
 969 extern struct internalvar *lookup_only_internalvar (const char *name);
 970
 971 extern struct internalvar *create_internalvar (const char *name);
 972
 973 extern void complete_internalvar (completion_tracker &tracker,
 974                                   const char *name);
 975
 976 /* An internalvar can be dynamically computed by supplying a vector of
 977    function pointers to perform various operations.  */
 978
 979 struct internalvar_funcs
 980 {
 981   /* Compute the value of the variable.  The DATA argument passed to
 982      the function is the same argument that was passed to
 983      `create_internalvar_type_lazy'.  */
 984
 985   struct value *(*make_value) (struct gdbarch *arch,
 986                                struct internalvar *var,
 987                                void *data);
 988
 989   /* Update the agent expression EXPR with bytecode to compute the
 990      value.  VALUE is the agent value we are updating.  The DATA
 991      argument passed to this function is the same argument that was
 992      passed to `create_internalvar_type_lazy'.  If this pointer is
 993      NULL, then the internalvar cannot be compiled to an agent
 994      expression.  */
 995
 996   void (*compile_to_ax) (struct internalvar *var,
 997                          struct agent_expr *expr,
 998                          struct axs_value *value,
 999                          void *data);
1000
1001   /* If non-NULL, this is called to destroy DATA.  The DATA argument
1002      passed to this function is the same argument that was passed to
1003      `create_internalvar_type_lazy'.  */
1004
1005   void (*destroy) (void *data);
1006 };
1007
1008 extern struct internalvar *create_internalvar_type_lazy (const char *name,
1009                                 const struct internalvar_funcs *funcs,
1010                                 void *data);
1011
1012 /* Compile an internal variable to an agent expression.  VAR is the
1013    variable to compile; EXPR and VALUE are the agent expression we are
1014    updating.  This will return 0 if there is no known way to compile
1015    VAR, and 1 if VAR was successfully compiled.  It may also throw an
1016    exception on error.  */
1017
1018 extern int compile_internalvar_to_ax (struct internalvar *var,
1019                                       struct agent_expr *expr,
1020                                       struct axs_value *value);
1021
1022 extern struct internalvar *lookup_internalvar (const char *name);
1023
1024 extern int value_equal (struct value *arg1, struct value *arg2);
1025
1026 extern int value_equal_contents (struct value *arg1, struct value *arg2);
1027
1028 extern int value_less (struct value *arg1, struct value *arg2);
1029
1030 extern int value_logical_not (struct value *arg1);
1031
1032 /* C++ */
1033
1034 extern struct value *value_of_this (const struct language_defn *lang);
1035
1036 extern struct value *value_of_this_silent (const struct language_defn *lang);
1037
1038 extern struct value *value_x_binop (struct value *arg1, struct value *arg2,
1039                                     enum exp_opcode op,
1040                                     enum exp_opcode otherop,
1041                                     enum noside noside);
1042
1043 extern struct value *value_x_unop (struct value *arg1, enum exp_opcode op,
1044                                    enum noside noside);
1045
1046 extern struct value *value_fn_field (struct value **arg1p, struct fn_field *f,
1047                                      int j, struct type *type, LONGEST offset);
1048
1049 extern int binop_types_user_defined_p (enum exp_opcode op,
1050                                        struct type *type1,
1051                                        struct type *type2);
1052
1053 extern int binop_user_defined_p (enum exp_opcode op, struct value *arg1,
1054                                  struct value *arg2);
1055
1056 extern int unop_user_defined_p (enum exp_opcode op, struct value *arg1);
1057
1058 extern int destructor_name_p (const char *name, struct type *type);
1059
1060 extern value_ref_ptr release_value (struct value *val);
1061
1062 extern int record_latest_value (struct value *val);
1063
1064 extern void modify_field (struct type *type, gdb_byte *addr,
1065                           LONGEST fieldval, LONGEST bitpos, LONGEST bitsize);
1066
1067 extern void type_print (struct type *type, const char *varstring,
1068                         struct ui_file *stream, int show);
1069
1070 extern std::string type_to_string (struct type *type);
1071
1072 extern gdb_byte *baseclass_addr (struct type *type, int index,
1073                                  gdb_byte *valaddr,
1074                                  struct value **valuep, int *errp);
1075
1076 extern void print_longest (struct ui_file *stream, int format,
1077                            int use_local, LONGEST val);
1078
1079 extern void print_floating (const gdb_byte *valaddr, struct type *type,
1080                             struct ui_file *stream);
1081
1082 extern void value_print (struct value *val, struct ui_file *stream,
1083                          const struct value_print_options *options);
1084
1085 extern void value_print_array_elements (struct value *val,
1086                                         struct ui_file *stream, int format,
1087                                         enum val_prettyformat pretty);
1088
1089 /* Release values from the value chain and return them.  Values
1090    created after MARK are released.  If MARK is nullptr, or if MARK is
1091    not found on the value chain, then all values are released.  Values
1092    are returned in reverse order of creation; that is, newest
1093    first.  */
1094
1095 extern std::vector<value_ref_ptr> value_release_to_mark
1096     (const struct value *mark);
1097
1098 extern void val_print (struct type *type,
1099                        LONGEST embedded_offset, CORE_ADDR address,
1100                        struct ui_file *stream, int recurse,
1101                        struct value *val,
1102                        const struct value_print_options *options,
1103                        const struct language_defn *language);
1104
1105 extern void common_val_print (struct value *val,
1106                               struct ui_file *stream, int recurse,
1107                               const struct value_print_options *options,
1108                               const struct language_defn *language);
1109
1110 extern int val_print_string (struct type *elttype, const char *encoding,
1111                              CORE_ADDR addr, int len,
1112                              struct ui_file *stream,
1113                              const struct value_print_options *options);
1114
1115 extern void print_variable_and_value (const char *name,
1116                                       struct symbol *var,
1117                                       struct frame_info *frame,
1118                                       struct ui_file *stream,
1119                                       int indent);
1120
1121 extern void typedef_print (struct type *type, struct symbol *news,
1122                            struct ui_file *stream);
1123
1124 extern char *internalvar_name (const struct internalvar *var);
1125
1126 extern void preserve_values (struct objfile *);
1127
1128 /* From values.c */
1129
1130 extern struct value *value_copy (struct value *);
1131
1132 extern struct value *value_non_lval (struct value *);
1133
1134 extern void value_force_lval (struct value *, CORE_ADDR);
1135
1136 extern struct value *make_cv_value (int, int, struct value *);
1137
1138 extern void preserve_one_value (struct value *, struct objfile *, htab_t);
1139
1140 /* From valops.c */
1141
1142 extern struct value *varying_to_slice (struct value *);
1143
1144 extern struct value *value_slice (struct value *, int, int);
1145
1146 extern struct value *value_literal_complex (struct value *, struct value *,
1147                                             struct type *);
1148
1149 extern struct value *find_function_in_inferior (const char *,
1150                                                 struct objfile **);
1151
1152 extern struct value *value_allocate_space_in_inferior (int);
1153
1154 extern struct value *value_subscripted_rvalue (struct value *array,
1155                                                LONGEST index,
1156                                                LONGEST lowerbound);
1157
1158 /* User function handler.  */
1159
1160 typedef struct value *(*internal_function_fn) (struct gdbarch *gdbarch,
1161                                                const struct language_defn *language,
1162                                                void *cookie,
1163                                                int argc,
1164                                                struct value **argv);
1165
1166 void add_internal_function (const char *name, const char *doc,
1167                             internal_function_fn handler,
1168                             void *cookie);
1169
1170 struct value *call_internal_function (struct gdbarch *gdbarch,
1171                                       const struct language_defn *language,
1172                                       struct value *function,
1173                                       int argc, struct value **argv);
1174
1175 char *value_internal_function_name (struct value *);
1176
1177 /* Build a value wrapping and representing WORKER.  The value takes ownership
1178    of the xmethod_worker object.  */
1179
1180 extern struct value *value_from_xmethod (xmethod_worker_up &&worker);
1181
1182 extern struct type *result_type_of_xmethod (struct value *method,
1183                                             gdb::array_view<value *> argv);
1184
1185 extern struct value *call_xmethod (struct value *method,
1186                                    gdb::array_view<value *> argv);
1187
1188 /* Given a discriminated union type and some corresponding value
1189    contents, this will return the field index of the currently active
1190    variant.  This will throw an exception if no active variant can be
1191    found.  */
1192
1193 extern int value_union_variant (struct type *union_type,
1194                                 const gdb_byte *contents);
1195
1196 /* Destroy the values currently allocated.  This is called when GDB is
1197    exiting (e.g., on quit_force).  */
1198 extern void finalize_values ();
1199
1200 #endif /* !defined (VALUE_H) */