gdb/value.h

   1 /* Definitions for values of C expressions, for GDB.
   2
   3    Copyright (C) 1986-2021 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 #include "gmp-utils.h"
  27
  28 struct block;
  29 struct expression;
  30 struct regcache;
  31 struct symbol;
  32 struct type;
  33 struct ui_file;
  34 struct language_defn;
  35 struct value_print_options;
  36
  37 /* Values can be partially 'optimized out' and/or 'unavailable'.
  38    These are distinct states and have different string representations
  39    and related error strings.
  40
  41    'unavailable' has a specific meaning in this context.  It means the
  42    value exists in the program (at the machine level), but GDB has no
  43    means to get to it.  Such a value is normally printed as
  44    <unavailable>.  Examples of how to end up with an unavailable value
  45    would be:
  46
  47     - We're inspecting a traceframe, and the memory or registers the
  48       debug information says the value lives on haven't been collected.
  49
  50     - We're inspecting a core dump, the memory or registers the debug
  51       information says the value lives aren't present in the dump
  52       (that is, we have a partial/trimmed core dump, or we don't fully
  53       understand/handle the core dump's format).
  54
  55     - We're doing live debugging, but the debug API has no means to
  56       get at where the value lives in the machine, like e.g., ptrace
  57       not having access to some register or register set.
  58
  59     - Any other similar scenario.
  60
  61   OTOH, "optimized out" is about what the compiler decided to generate
  62   (or not generate).  A chunk of a value that was optimized out does
  63   not actually exist in the program.  There's no way to get at it
  64   short of compiling the program differently.
  65
  66   A register that has not been saved in a frame is likewise considered
  67   optimized out, except not-saved registers have a different string
  68   representation and related error strings.  E.g., we'll print them as
  69   <not-saved> instead of <optimized out>, as in:
  70
  71     (gdb) p/x $rax
  72     $1 = <not saved>
  73     (gdb) info registers rax
  74     rax            <not saved>
  75
  76   If the debug info describes a variable as being in such a register,
  77   we'll still print the variable as <optimized out>.  IOW, <not saved>
  78   is reserved for inspecting registers at the machine level.
  79
  80   When comparing value contents, optimized out chunks, unavailable
  81   chunks, and valid contents data are all considered different.  See
  82   value_contents_eq for more info.
  83 */
  84
  85 extern bool overload_resolution;
  86
  87 /* The structure which defines the type of a value.  It should never
  88    be possible for a program lval value to survive over a call to the
  89    inferior (i.e. to be put into the history list or an internal
  90    variable).  */
  91
  92 struct value;
  93
  94 /* Increase VAL's reference count.  */
  95
  96 extern void value_incref (struct value *val);
  97
  98 /* Decrease VAL's reference count.  When the reference count drops to
  99    0, VAL will be freed.  */
 100
 101 extern void value_decref (struct value *val);
 102
 103 /* A policy class to interface gdb::ref_ptr with struct value.  */
 104
 105 struct value_ref_policy
 106 {
 107   static void incref (struct value *ptr)
 108   {
 109     value_incref (ptr);
 110   }
 111
 112   static void decref (struct value *ptr)
 113   {
 114     value_decref (ptr);
 115   }
 116 };
 117
 118 /* A gdb:;ref_ptr pointer to a struct value.  */
 119
 120 typedef gdb::ref_ptr<struct value, value_ref_policy> value_ref_ptr;
 121
 122 /* Values are stored in a chain, so that they can be deleted easily
 123    over calls to the inferior.  Values assigned to internal variables,
 124    put into the value history or exposed to Python are taken off this
 125    list.  */
 126
 127 struct value *value_next (const struct value *);
 128
 129 /* Type of the value.  */
 130
 131 extern struct type *value_type (const struct value *);
 132
 133 /* Return the gdbarch associated with the value. */
 134
 135 extern struct gdbarch *get_value_arch (const struct value *value);
 136
 137 /* This is being used to change the type of an existing value, that
 138    code should instead be creating a new value with the changed type
 139    (but possibly shared content).  */
 140
 141 extern void deprecated_set_value_type (struct value *value,
 142                                        struct type *type);
 143
 144 /* Only used for bitfields; number of bits contained in them.  */
 145
 146 extern LONGEST value_bitsize (const struct value *);
 147 extern void set_value_bitsize (struct value *, LONGEST bit);
 148
 149 /* Only used for bitfields; position of start of field.  For
 150    little-endian targets, it is the position of the LSB.  For
 151    big-endian targets, it is the position of the MSB.  */
 152
 153 extern LONGEST value_bitpos (const struct value *);
 154 extern void set_value_bitpos (struct value *, LONGEST bit);
 155
 156 /* Only used for bitfields; the containing value.  This allows a
 157    single read from the target when displaying multiple
 158    bitfields.  */
 159
 160 struct value *value_parent (const struct value *);
 161 extern void set_value_parent (struct value *value, struct value *parent);
 162
 163 /* Describes offset of a value within lval of a structure in bytes.
 164    If lval == lval_memory, this is an offset to the address.  If lval
 165    == lval_register, this is a further offset from location.address
 166    within the registers structure.  Note also the member
 167    embedded_offset below.  */
 168
 169 extern LONGEST value_offset (const struct value *);
 170 extern void set_value_offset (struct value *, LONGEST offset);
 171
 172 /* The comment from "struct value" reads: ``Is it modifiable?  Only
 173    relevant if lval != not_lval.''.  Shouldn't the value instead be
 174    not_lval and be done with it?  */
 175
 176 extern int deprecated_value_modifiable (const struct value *value);
 177
 178 /* If a value represents a C++ object, then the `type' field gives the
 179    object's compile-time type.  If the object actually belongs to some
 180    class derived from `type', perhaps with other base classes and
 181    additional members, then `type' is just a subobject of the real
 182    thing, and the full object is probably larger than `type' would
 183    suggest.
 184
 185    If `type' is a dynamic class (i.e. one with a vtable), then GDB can
 186    actually determine the object's run-time type by looking at the
 187    run-time type information in the vtable.  When this information is
 188    available, we may elect to read in the entire object, for several
 189    reasons:
 190
 191    - When printing the value, the user would probably rather see the
 192      full object, not just the limited portion apparent from the
 193      compile-time type.
 194
 195    - If `type' has virtual base classes, then even printing `type'
 196      alone may require reaching outside the `type' portion of the
 197      object to wherever the virtual base class has been stored.
 198
 199    When we store the entire object, `enclosing_type' is the run-time
 200    type -- the complete object -- and `embedded_offset' is the offset
 201    of `type' within that larger type, in bytes.  The value_contents()
 202    macro takes `embedded_offset' into account, so most GDB code
 203    continues to see the `type' portion of the value, just as the
 204    inferior would.
 205
 206    If `type' is a pointer to an object, then `enclosing_type' is a
 207    pointer to the object's run-time type, and `pointed_to_offset' is
 208    the offset in bytes from the full object to the pointed-to object
 209    -- that is, the value `embedded_offset' would have if we followed
 210    the pointer and fetched the complete object.  (I don't really see
 211    the point.  Why not just determine the run-time type when you
 212    indirect, and avoid the special case?  The contents don't matter
 213    until you indirect anyway.)
 214
 215    If we're not doing anything fancy, `enclosing_type' is equal to
 216    `type', and `embedded_offset' is zero, so everything works
 217    normally.  */
 218
 219 extern struct type *value_enclosing_type (const struct value *);
 220 extern void set_value_enclosing_type (struct value *val,
 221                                       struct type *new_type);
 222
 223 /* Returns value_type or value_enclosing_type depending on
 224    value_print_options.objectprint.
 225
 226    If RESOLVE_SIMPLE_TYPES is 0 the enclosing type will be resolved
 227    only for pointers and references, else it will be returned
 228    for all the types (e.g. structures).  This option is useful
 229    to prevent retrieving enclosing type for the base classes fields.
 230
 231    REAL_TYPE_FOUND is used to inform whether the real type was found
 232    (or just static type was used).  The NULL may be passed if it is not
 233    necessary. */
 234
 235 extern struct type *value_actual_type (struct value *value,
 236                                        int resolve_simple_types,
 237                                        int *real_type_found);
 238
 239 extern LONGEST value_pointed_to_offset (const struct value *value);
 240 extern void set_value_pointed_to_offset (struct value *value, LONGEST val);
 241 extern LONGEST value_embedded_offset (const struct value *value);
 242 extern void set_value_embedded_offset (struct value *value, LONGEST val);
 243
 244 /* For lval_computed values, this structure holds functions used to
 245    retrieve and set the value (or portions of the value).
 246
 247    For each function, 'V' is the 'this' pointer: an lval_funcs
 248    function F may always assume that the V it receives is an
 249    lval_computed value, and has F in the appropriate slot of its
 250    lval_funcs structure.  */
 251
 252 struct lval_funcs
 253 {
 254   /* Fill in VALUE's contents.  This is used to "un-lazy" values.  If
 255      a problem arises in obtaining VALUE's bits, this function should
 256      call 'error'.  If it is NULL value_fetch_lazy on "un-lazy"
 257      non-optimized-out value is an internal error.  */
 258   void (*read) (struct value *v);
 259
 260   /* Handle an assignment TOVAL = FROMVAL by writing the value of
 261      FROMVAL to TOVAL's location.  The contents of TOVAL have not yet
 262      been updated.  If a problem arises in doing so, this function
 263      should call 'error'.  If it is NULL such TOVAL assignment is an error as
 264      TOVAL is not considered as an lvalue.  */
 265   void (*write) (struct value *toval, struct value *fromval);
 266
 267   /* If non-NULL, this is used to implement pointer indirection for
 268      this value.  This method may return NULL, in which case value_ind
 269      will fall back to ordinary indirection.  */
 270   struct value *(*indirect) (struct value *value);
 271
 272   /* If non-NULL, this is used to implement reference resolving for
 273      this value.  This method may return NULL, in which case coerce_ref
 274      will fall back to ordinary references resolving.  */
 275   struct value *(*coerce_ref) (const struct value *value);
 276
 277   /* If non-NULL, this is used to determine whether the indicated bits
 278      of VALUE are a synthetic pointer.  */
 279   int (*check_synthetic_pointer) (const struct value *value,
 280                                   LONGEST offset, int length);
 281
 282   /* Return a duplicate of VALUE's closure, for use in a new value.
 283      This may simply return the same closure, if VALUE's is
 284      reference-counted or statically allocated.
 285
 286      This may be NULL, in which case VALUE's closure is re-used in the
 287      new value.  */
 288   void *(*copy_closure) (const struct value *v);
 289
 290   /* Drop VALUE's reference to its closure.  Maybe this frees the
 291      closure; maybe this decrements a reference count; maybe the
 292      closure is statically allocated and this does nothing.
 293
 294      This may be NULL, in which case no action is taken to free
 295      VALUE's closure.  */
 296   void (*free_closure) (struct value *v);
 297 };
 298
 299 /* Create a computed lvalue, with type TYPE, function pointers FUNCS,
 300    and closure CLOSURE.  */
 301
 302 extern struct value *allocate_computed_value (struct type *type,
 303                                               const struct lval_funcs *funcs,
 304                                               void *closure);
 305
 306 extern struct value *allocate_optimized_out_value (struct type *type);
 307
 308 /* If VALUE is lval_computed, return its lval_funcs structure.  */
 309
 310 extern const struct lval_funcs *value_computed_funcs (const struct value *);
 311
 312 /* If VALUE is lval_computed, return its closure.  The meaning of the
 313    returned value depends on the functions VALUE uses.  */
 314
 315 extern void *value_computed_closure (const struct value *value);
 316
 317 /* If zero, contents of this value are in the contents field.  If
 318    nonzero, contents are in inferior.  If the lval field is lval_memory,
 319    the contents are in inferior memory at location.address plus offset.
 320    The lval field may also be lval_register.
 321
 322    WARNING: This field is used by the code which handles watchpoints
 323    (see breakpoint.c) to decide whether a particular value can be
 324    watched by hardware watchpoints.  If the lazy flag is set for some
 325    member of a value chain, it is assumed that this member of the
 326    chain doesn't need to be watched as part of watching the value
 327    itself.  This is how GDB avoids watching the entire struct or array
 328    when the user wants to watch a single struct member or array
 329    element.  If you ever change the way lazy flag is set and reset, be
 330    sure to consider this use as well!  */
 331
 332 extern int value_lazy (const struct value *);
 333 extern void set_value_lazy (struct value *value, int val);
 334
 335 extern int value_stack (const struct value *);
 336 extern void set_value_stack (struct value *value, int val);
 337
 338 /* Throw an error complaining that the value has been optimized
 339    out.  */
 340
 341 extern void error_value_optimized_out (void);
 342
 343 /* value_contents() and value_contents_raw() both return the address
 344    of the gdb buffer used to hold a copy of the contents of the lval.
 345    value_contents() is used when the contents of the buffer are needed
 346    -- it uses value_fetch_lazy() to load the buffer from the process
 347    being debugged if it hasn't already been loaded
 348    (value_contents_writeable() is used when a writeable but fetched
 349    buffer is required)..  value_contents_raw() is used when data is
 350    being stored into the buffer, or when it is certain that the
 351    contents of the buffer are valid.
 352
 353    Note: The contents pointer is adjusted by the offset required to
 354    get to the real subobject, if the value happens to represent
 355    something embedded in a larger run-time object.  */
 356
 357 extern gdb_byte *value_contents_raw (struct value *);
 358
 359 /* Actual contents of the value.  For use of this value; setting it
 360    uses the stuff above.  Not valid if lazy is nonzero.  Target
 361    byte-order.  We force it to be aligned properly for any possible
 362    value.  Note that a value therefore extends beyond what is
 363    declared here.  */
 364
 365 extern const gdb_byte *value_contents (struct value *);
 366 extern gdb_byte *value_contents_writeable (struct value *);
 367
 368 /* The ALL variants of the above two macros do not adjust the returned
 369    pointer by the embedded_offset value.  */
 370
 371 extern gdb_byte *value_contents_all_raw (struct value *);
 372 extern const gdb_byte *value_contents_all (struct value *);
 373
 374 /* Like value_contents_all, but does not require that the returned
 375    bits be valid.  This should only be used in situations where you
 376    plan to check the validity manually.  */
 377 extern const gdb_byte *value_contents_for_printing (struct value *value);
 378
 379 /* Like value_contents_for_printing, but accepts a constant value
 380    pointer.  Unlike value_contents_for_printing however, the pointed
 381    value must _not_ be lazy.  */
 382 extern const gdb_byte *
 383   value_contents_for_printing_const (const struct value *value);
 384
 385 extern void value_fetch_lazy (struct value *val);
 386
 387 /* If nonzero, this is the value of a variable which does not actually
 388    exist in the program, at least partially.  If the value is lazy,
 389    this may fetch it now.  */
 390 extern int value_optimized_out (struct value *value);
 391
 392 /* Given a value, return true if any of the contents bits starting at
 393    OFFSET and extending for LENGTH bits is optimized out, false
 394    otherwise.  */
 395
 396 extern int value_bits_any_optimized_out (const struct value *value,
 397                                          int bit_offset, int bit_length);
 398
 399 /* Like value_optimized_out, but return true iff the whole value is
 400    optimized out.  */
 401 extern int value_entirely_optimized_out (struct value *value);
 402
 403 /* Mark VALUE's content bytes starting at OFFSET and extending for
 404    LENGTH bytes as optimized out.  */
 405
 406 extern void mark_value_bytes_optimized_out (struct value *value,
 407                                             int offset, int length);
 408
 409 /* Mark VALUE's content bits starting at OFFSET and extending for
 410    LENGTH bits as optimized out.  */
 411
 412 extern void mark_value_bits_optimized_out (struct value *value,
 413                                            LONGEST offset, LONGEST length);
 414
 415 /* Set or return field indicating whether a variable is initialized or
 416    not, based on debugging information supplied by the compiler.
 417    1 = initialized; 0 = uninitialized.  */
 418 extern int value_initialized (const struct value *);
 419 extern void set_value_initialized (struct value *, int);
 420
 421 /* Set COMPONENT's location as appropriate for a component of WHOLE
 422    --- regardless of what kind of lvalue WHOLE is.  */
 423 extern void set_value_component_location (struct value *component,
 424                                           const struct value *whole);
 425
 426 /* While the following fields are per- VALUE .CONTENT .PIECE (i.e., a
 427    single value might have multiple LVALs), this hacked interface is
 428    limited to just the first PIECE.  Expect further change.  */
 429 /* Type of value; either not an lval, or one of the various different
 430    possible kinds of lval.  */
 431 extern enum lval_type *deprecated_value_lval_hack (struct value *);
 432 #define VALUE_LVAL(val) (*deprecated_value_lval_hack (val))
 433
 434 /* Like VALUE_LVAL, except the parameter can be const.  */
 435 extern enum lval_type value_lval_const (const struct value *value);
 436
 437 /* If lval == lval_memory, return the address in the inferior.  If
 438    lval == lval_register, return the byte offset into the registers
 439    structure.  Otherwise, return 0.  The returned address
 440    includes the offset, if any.  */
 441 extern CORE_ADDR value_address (const struct value *);
 442
 443 /* Like value_address, except the result does not include value's
 444    offset.  */
 445 extern CORE_ADDR value_raw_address (const struct value *);
 446
 447 /* Set the address of a value.  */
 448 extern void set_value_address (struct value *, CORE_ADDR);
 449
 450 /* Pointer to internal variable.  */
 451 extern struct internalvar **deprecated_value_internalvar_hack (struct value *);
 452 #define VALUE_INTERNALVAR(val) (*deprecated_value_internalvar_hack (val))
 453
 454 /* Frame ID of "next" frame to which a register value is relative.  A
 455    register value is indicated by VALUE_LVAL being set to lval_register.
 456    So, if the register value is found relative to frame F, then the
 457    frame id of F->next will be stored in VALUE_NEXT_FRAME_ID.  */
 458 extern struct frame_id *deprecated_value_next_frame_id_hack (struct value *);
 459 #define VALUE_NEXT_FRAME_ID(val) (*deprecated_value_next_frame_id_hack (val))
 460
 461 /* Frame ID of frame to which a register value is relative.  This is
 462    similar to VALUE_NEXT_FRAME_ID, above, but may not be assigned to.
 463    Note that VALUE_FRAME_ID effectively undoes the "next" operation
 464    that was performed during the assignment to VALUE_NEXT_FRAME_ID.  */
 465 #define VALUE_FRAME_ID(val) (get_prev_frame_id_by_id (VALUE_NEXT_FRAME_ID (val)))
 466
 467 /* Register number if the value is from a register.  */
 468 extern int *deprecated_value_regnum_hack (struct value *);
 469 #define VALUE_REGNUM(val) (*deprecated_value_regnum_hack (val))
 470
 471 /* Return value after lval_funcs->coerce_ref (after check_typedef).  Return
 472    NULL if lval_funcs->coerce_ref is not applicable for whatever reason.  */
 473
 474 extern struct value *coerce_ref_if_computed (const struct value *arg);
 475
 476 /* Setup a new value type and enclosing value type for dereferenced value VALUE.
 477    ENC_TYPE is the new enclosing type that should be set.  ORIGINAL_TYPE and
 478    ORIGINAL_VAL are the type and value of the original reference or
 479    pointer.  ORIGINAL_VALUE_ADDRESS is the address within VALUE, that is
 480    the address that was dereferenced.
 481
 482    Note, that VALUE is modified by this function.
 483
 484    It is a common implementation for coerce_ref and value_ind.  */
 485
 486 extern struct value * readjust_indirect_value_type (struct value *value,
 487                                                     struct type *enc_type,
 488                                                     const struct type *original_type,
 489                                                     struct value *original_val,
 490                                                     CORE_ADDR original_value_address);
 491
 492 /* Convert a REF to the object referenced.  */
 493
 494 extern struct value *coerce_ref (struct value *value);
 495
 496 /* If ARG is an array, convert it to a pointer.
 497    If ARG is a function, convert it to a function pointer.
 498
 499    References are dereferenced.  */
 500
 501 extern struct value *coerce_array (struct value *value);
 502
 503 /* Given a value, determine whether the bits starting at OFFSET and
 504    extending for LENGTH bits are a synthetic pointer.  */
 505
 506 extern int value_bits_synthetic_pointer (const struct value *value,
 507                                          LONGEST offset, LONGEST length);
 508
 509 /* Given a value, determine whether the contents bytes starting at
 510    OFFSET and extending for LENGTH bytes are available.  This returns
 511    nonzero if all bytes in the given range are available, zero if any
 512    byte is unavailable.  */
 513
 514 extern int value_bytes_available (const struct value *value,
 515                                   LONGEST offset, LONGEST length);
 516
 517 /* Given a value, determine whether the contents bits starting at
 518    OFFSET and extending for LENGTH bits are available.  This returns
 519    nonzero if all bits in the given range are available, zero if any
 520    bit is unavailable.  */
 521
 522 extern int value_bits_available (const struct value *value,
 523                                  LONGEST offset, LONGEST length);
 524
 525 /* Like value_bytes_available, but return false if any byte in the
 526    whole object is unavailable.  */
 527 extern int value_entirely_available (struct value *value);
 528
 529 /* Like value_entirely_available, but return false if any byte in the
 530    whole object is available.  */
 531 extern int value_entirely_unavailable (struct value *value);
 532
 533 /* Mark VALUE's content bytes starting at OFFSET and extending for
 534    LENGTH bytes as unavailable.  */
 535
 536 extern void mark_value_bytes_unavailable (struct value *value,
 537                                           LONGEST offset, LONGEST length);
 538
 539 /* Mark VALUE's content bits starting at OFFSET and extending for
 540    LENGTH bits as unavailable.  */
 541
 542 extern void mark_value_bits_unavailable (struct value *value,
 543                                          LONGEST offset, LONGEST length);
 544
 545 /* Compare LENGTH bytes of VAL1's contents starting at OFFSET1 with
 546    LENGTH bytes of VAL2's contents starting at OFFSET2.
 547
 548    Note that "contents" refers to the whole value's contents
 549    (value_contents_all), without any embedded offset adjustment.  For
 550    example, to compare a complete object value with itself, including
 551    its enclosing type chunk, you'd do:
 552
 553      int len = TYPE_LENGTH (check_typedef (value_enclosing_type (val)));
 554      value_contents_eq (val, 0, val, 0, len);
 555
 556    Returns true iff the set of available/valid contents match.
 557
 558    Optimized-out contents are equal to optimized-out contents, and are
 559    not equal to non-optimized-out contents.
 560
 561    Unavailable contents are equal to unavailable contents, and are not
 562    equal to non-unavailable contents.
 563
 564    For example, if 'x's represent an unavailable byte, and 'V' and 'Z'
 565    represent different available/valid bytes, in a value with length
 566    16:
 567
 568      offset:   0   4   8   12  16
 569      contents: xxxxVVVVxxxxVVZZ
 570
 571    then:
 572
 573      value_contents_eq(val, 0, val, 8, 6) => true
 574      value_contents_eq(val, 0, val, 4, 4) => false
 575      value_contents_eq(val, 0, val, 8, 8) => false
 576      value_contents_eq(val, 4, val, 12, 2) => true
 577      value_contents_eq(val, 4, val, 12, 4) => true
 578      value_contents_eq(val, 3, val, 4, 4) => true
 579
 580    If 'x's represent an unavailable byte, 'o' represents an optimized
 581    out byte, in a value with length 8:
 582
 583      offset:   0   4   8
 584      contents: xxxxoooo
 585
 586    then:
 587
 588      value_contents_eq(val, 0, val, 2, 2) => true
 589      value_contents_eq(val, 4, val, 6, 2) => true
 590      value_contents_eq(val, 0, val, 4, 4) => true
 591
 592    We only know whether a value chunk is unavailable or optimized out
 593    if we've tried to read it.  As this routine is used by printing
 594    routines, which may be printing values in the value history, long
 595    after the inferior is gone, it works with const values.  Therefore,
 596    this routine must not be called with lazy values.  */
 597
 598 extern bool value_contents_eq (const struct value *val1, LONGEST offset1,
 599                                const struct value *val2, LONGEST offset2,
 600                                LONGEST length);
 601
 602 /* Read LENGTH addressable memory units starting at MEMADDR into BUFFER,
 603    which is (or will be copied to) VAL's contents buffer offset by
 604    BIT_OFFSET bits.  Marks value contents ranges as unavailable if
 605    the corresponding memory is likewise unavailable.  STACK indicates
 606    whether the memory is known to be stack memory.  */
 607
 608 extern void read_value_memory (struct value *val, LONGEST bit_offset,
 609                                int stack, CORE_ADDR memaddr,
 610                                gdb_byte *buffer, size_t length);
 611
 612 /* Cast SCALAR_VALUE to the element type of VECTOR_TYPE, then replicate
 613    into each element of a new vector value with VECTOR_TYPE.  */
 614
 615 struct value *value_vector_widen (struct value *scalar_value,
 616                                   struct type *vector_type);
 617
 618 \f
 619
 620 #include "symtab.h"
 621 #include "gdbtypes.h"
 622 #include "expression.h"
 623
 624 struct frame_info;
 625 struct fn_field;
 626
 627 extern int print_address_demangle (const struct value_print_options *,
 628                                    struct gdbarch *, CORE_ADDR,
 629                                    struct ui_file *, int);
 630
 631 /* Returns true if VAL is of floating-point type.  In addition,
 632    throws an error if the value is an invalid floating-point value.  */
 633 extern bool is_floating_value (struct value *val);
 634
 635 extern LONGEST value_as_long (struct value *val);
 636 extern CORE_ADDR value_as_address (struct value *val);
 637
 638 extern LONGEST unpack_long (struct type *type, const gdb_byte *valaddr);
 639 extern CORE_ADDR unpack_pointer (struct type *type, const gdb_byte *valaddr);
 640
 641 extern LONGEST unpack_field_as_long (struct type *type,
 642                                      const gdb_byte *valaddr,
 643                                      int fieldno);
 644
 645 /* Unpack a bitfield of the specified FIELD_TYPE, from the object at
 646    VALADDR, and store the result in *RESULT.
 647    The bitfield starts at BITPOS bits and contains BITSIZE bits; if
 648    BITSIZE is zero, then the length is taken from FIELD_TYPE.
 649
 650    Extracting bits depends on endianness of the machine.  Compute the
 651    number of least significant bits to discard.  For big endian machines,
 652    we compute the total number of bits in the anonymous object, subtract
 653    off the bit count from the MSB of the object to the MSB of the
 654    bitfield, then the size of the bitfield, which leaves the LSB discard
 655    count.  For little endian machines, the discard count is simply the
 656    number of bits from the LSB of the anonymous object to the LSB of the
 657    bitfield.
 658
 659    If the field is signed, we also do sign extension.  */
 660
 661 extern LONGEST unpack_bits_as_long (struct type *field_type,
 662                                     const gdb_byte *valaddr,
 663                                     LONGEST bitpos, LONGEST bitsize);
 664
 665 extern int unpack_value_field_as_long (struct type *type, const gdb_byte *valaddr,
 666                                 LONGEST embedded_offset, int fieldno,
 667                                 const struct value *val, LONGEST *result);
 668
 669 extern void unpack_value_bitfield (struct value *dest_val,
 670                                    LONGEST bitpos, LONGEST bitsize,
 671                                    const gdb_byte *valaddr,
 672                                    LONGEST embedded_offset,
 673                                    const struct value *val);
 674
 675 extern struct value *value_field_bitfield (struct type *type, int fieldno,
 676                                            const gdb_byte *valaddr,
 677                                            LONGEST embedded_offset,
 678                                            const struct value *val);
 679
 680 extern void pack_long (gdb_byte *buf, struct type *type, LONGEST num);
 681
 682 extern struct value *value_from_longest (struct type *type, LONGEST num);
 683 extern struct value *value_from_ulongest (struct type *type, ULONGEST num);
 684 extern struct value *value_from_pointer (struct type *type, CORE_ADDR addr);
 685 extern struct value *value_from_host_double (struct type *type, double d);
 686 extern struct value *value_from_history_ref (const char *, const char **);
 687 extern struct value *value_from_component (struct value *, struct type *,
 688                                            LONGEST);
 689
 690 extern struct value *value_at (struct type *type, CORE_ADDR addr);
 691 extern struct value *value_at_lazy (struct type *type, CORE_ADDR addr);
 692
 693 extern struct value *value_from_contents_and_address_unresolved
 694      (struct type *, const gdb_byte *, CORE_ADDR);
 695 extern struct value *value_from_contents_and_address (struct type *,
 696                                                       const gdb_byte *,
 697                                                       CORE_ADDR);
 698 extern struct value *value_from_contents (struct type *, const gdb_byte *);
 699
 700 extern struct value *default_value_from_register (struct gdbarch *gdbarch,
 701                                                   struct type *type,
 702                                                   int regnum,
 703                                                   struct frame_id frame_id);
 704
 705 extern void read_frame_register_value (struct value *value,
 706                                        struct frame_info *frame);
 707
 708 extern struct value *value_from_register (struct type *type, int regnum,
 709                                           struct frame_info *frame);
 710
 711 extern CORE_ADDR address_from_register (int regnum,
 712                                         struct frame_info *frame);
 713
 714 extern struct value *value_of_variable (struct symbol *var,
 715                                         const struct block *b);
 716
 717 extern struct value *address_of_variable (struct symbol *var,
 718                                           const struct block *b);
 719
 720 extern struct value *value_of_register (int regnum, struct frame_info *frame);
 721
 722 struct value *value_of_register_lazy (struct frame_info *frame, int regnum);
 723
 724 /* Return the symbol's reading requirement.  */
 725
 726 extern enum symbol_needs_kind symbol_read_needs (struct symbol *);
 727
 728 /* Return true if the symbol needs a frame.  This is a wrapper for
 729    symbol_read_needs that simply checks for SYMBOL_NEEDS_FRAME.  */
 730
 731 extern int symbol_read_needs_frame (struct symbol *);
 732
 733 extern struct value *read_var_value (struct symbol *var,
 734                                      const struct block *var_block,
 735                                      struct frame_info *frame);
 736
 737 extern struct value *allocate_value (struct type *type);
 738 extern struct value *allocate_value_lazy (struct type *type);
 739 extern void value_contents_copy (struct value *dst, LONGEST dst_offset,
 740                                  struct value *src, LONGEST src_offset,
 741                                  LONGEST length);
 742
 743 extern struct value *allocate_repeat_value (struct type *type, int count);
 744
 745 extern struct value *value_mark (void);
 746
 747 extern void value_free_to_mark (const struct value *mark);
 748
 749 /* A helper class that uses value_mark at construction time and calls
 750    value_free_to_mark in the destructor.  This is used to clear out
 751    temporary values created during the lifetime of this object.  */
 752 class scoped_value_mark
 753 {
 754  public:
 755
 756   scoped_value_mark ()
 757     : m_value (value_mark ())
 758   {
 759   }
 760
 761   ~scoped_value_mark ()
 762   {
 763     free_to_mark ();
 764   }
 765
 766   scoped_value_mark (scoped_value_mark &&other) = default;
 767
 768   DISABLE_COPY_AND_ASSIGN (scoped_value_mark);
 769
 770   /* Free the values currently on the value stack.  */
 771   void free_to_mark ()
 772   {
 773     if (m_value != NULL)
 774       {
 775         value_free_to_mark (m_value);
 776         m_value = NULL;
 777       }
 778   }
 779
 780  private:
 781
 782   const struct value *m_value;
 783 };
 784
 785 extern struct value *value_cstring (const char *ptr, ssize_t len,
 786                                     struct type *char_type);
 787 extern struct value *value_string (const char *ptr, ssize_t len,
 788                                    struct type *char_type);
 789
 790 extern struct value *value_array (int lowbound, int highbound,
 791                                   struct value **elemvec);
 792
 793 extern struct value *value_concat (struct value *arg1, struct value *arg2);
 794
 795 extern struct value *value_binop (struct value *arg1, struct value *arg2,
 796                                   enum exp_opcode op);
 797
 798 extern struct value *value_ptradd (struct value *arg1, LONGEST arg2);
 799
 800 extern LONGEST value_ptrdiff (struct value *arg1, struct value *arg2);
 801
 802 /* Return true if VAL does not live in target memory, but should in order
 803    to operate on it.  Otherwise return false.  */
 804
 805 extern bool value_must_coerce_to_target (struct value *arg1);
 806
 807 extern struct value *value_coerce_to_target (struct value *arg1);
 808
 809 extern struct value *value_coerce_array (struct value *arg1);
 810
 811 extern struct value *value_coerce_function (struct value *arg1);
 812
 813 extern struct value *value_ind (struct value *arg1);
 814
 815 extern struct value *value_addr (struct value *arg1);
 816
 817 extern struct value *value_ref (struct value *arg1, enum type_code refcode);
 818
 819 extern struct value *value_assign (struct value *toval,
 820                                    struct value *fromval);
 821
 822 extern struct value *value_pos (struct value *arg1);
 823
 824 extern struct value *value_neg (struct value *arg1);
 825
 826 extern struct value *value_complement (struct value *arg1);
 827
 828 extern struct value *value_struct_elt (struct value **argp,
 829                                        struct value **args,
 830                                        const char *name, int *static_memfuncp,
 831                                        const char *err);
 832
 833 extern struct value *value_struct_elt_bitpos (struct value **argp,
 834                                               int bitpos,
 835                                               struct type *field_type,
 836                                               const char *err);
 837
 838 extern struct value *value_aggregate_elt (struct type *curtype,
 839                                           const char *name,
 840                                           struct type *expect_type,
 841                                           int want_address,
 842                                           enum noside noside);
 843
 844 extern struct value *value_static_field (struct type *type, int fieldno);
 845
 846 enum oload_search_type { NON_METHOD, METHOD, BOTH };
 847
 848 extern int find_overload_match (gdb::array_view<value *> args,
 849                                 const char *name,
 850                                 enum oload_search_type method,
 851                                 struct value **objp, struct symbol *fsym,
 852                                 struct value **valp, struct symbol **symp,
 853                                 int *staticp, const int no_adl,
 854                                 enum noside noside);
 855
 856 extern struct value *value_field (struct value *arg1, int fieldno);
 857
 858 extern struct value *value_primitive_field (struct value *arg1, LONGEST offset,
 859                                             int fieldno,
 860                                             struct type *arg_type);
 861
 862
 863 extern struct type *value_rtti_indirect_type (struct value *, int *, LONGEST *,
 864                                               int *);
 865
 866 extern struct value *value_full_object (struct value *, struct type *, int,
 867                                         int, int);
 868
 869 extern struct value *value_cast_pointers (struct type *, struct value *, int);
 870
 871 extern struct value *value_cast (struct type *type, struct value *arg2);
 872
 873 extern struct value *value_reinterpret_cast (struct type *type,
 874                                              struct value *arg);
 875
 876 extern struct value *value_dynamic_cast (struct type *type, struct value *arg);
 877
 878 extern struct value *value_zero (struct type *type, enum lval_type lv);
 879
 880 extern struct value *value_one (struct type *type);
 881
 882 extern struct value *value_repeat (struct value *arg1, int count);
 883
 884 extern struct value *value_subscript (struct value *array, LONGEST index);
 885
 886 extern struct value *value_bitstring_subscript (struct type *type,
 887                                                 struct value *bitstring,
 888                                                 LONGEST index);
 889
 890 extern struct value *register_value_being_returned (struct type *valtype,
 891                                                     struct regcache *retbuf);
 892
 893 extern int value_in (struct value *element, struct value *set);
 894
 895 extern int value_bit_index (struct type *type, const gdb_byte *addr,
 896                             int index);
 897
 898 extern enum return_value_convention
 899 struct_return_convention (struct gdbarch *gdbarch, struct value *function,
 900                           struct type *value_type);
 901
 902 extern int using_struct_return (struct gdbarch *gdbarch,
 903                                 struct value *function,
 904                                 struct type *value_type);
 905
 906 /* Evaluate the expression EXP.  If set, EXPECT_TYPE is passed to the
 907    outermost operation's evaluation.  This is ignored by most
 908    operations, but may be used, e.g., to determine the type of an
 909    otherwise untyped symbol.  The caller should not assume that the
 910    returned value has this type.  */
 911
 912 extern struct value *evaluate_expression (struct expression *exp,
 913                                           struct type *expect_type = nullptr);
 914
 915 extern struct value *evaluate_type (struct expression *exp);
 916
 917 extern struct value *evaluate_subexp (struct type *expect_type,
 918                                       struct expression *exp,
 919                                       int *pos, enum noside noside);
 920
 921 extern struct value *evaluate_subexpression_type (struct expression *exp,
 922                                                   int subexp);
 923
 924 extern value *evaluate_var_value (enum noside noside, const block *blk,
 925                                   symbol *var);
 926
 927 extern value *evaluate_var_msym_value (enum noside noside,
 928                                        struct objfile *objfile,
 929                                        minimal_symbol *msymbol);
 930
 931 extern value *eval_skip_value (expression *exp);
 932
 933 extern void fetch_subexp_value (struct expression *exp, int *pc,
 934                                 struct value **valp, struct value **resultp,
 935                                 std::vector<value_ref_ptr> *val_chain,
 936                                 bool preserve_errors);
 937
 938 extern const char *extract_field_op (struct expression *exp, int *subexp);
 939
 940 extern struct value *evaluate_subexp_with_coercion (struct expression *,
 941                                                     int *, enum noside);
 942
 943 extern struct value *parse_and_eval (const char *exp);
 944
 945 extern struct value *parse_to_comma_and_eval (const char **expp);
 946
 947 extern struct type *parse_and_eval_type (const char *p, int length);
 948
 949 extern CORE_ADDR parse_and_eval_address (const char *exp);
 950
 951 extern LONGEST parse_and_eval_long (const char *exp);
 952
 953 extern void unop_promote (const struct language_defn *language,
 954                           struct gdbarch *gdbarch,
 955                           struct value **arg1);
 956
 957 extern void binop_promote (const struct language_defn *language,
 958                            struct gdbarch *gdbarch,
 959                            struct value **arg1, struct value **arg2);
 960
 961 extern struct value *access_value_history (int num);
 962
 963 extern struct value *value_of_internalvar (struct gdbarch *gdbarch,
 964                                            struct internalvar *var);
 965
 966 extern int get_internalvar_integer (struct internalvar *var, LONGEST *l);
 967
 968 extern void set_internalvar (struct internalvar *var, struct value *val);
 969
 970 extern void set_internalvar_integer (struct internalvar *var, LONGEST l);
 971
 972 extern void set_internalvar_string (struct internalvar *var,
 973                                     const char *string);
 974
 975 extern void clear_internalvar (struct internalvar *var);
 976
 977 extern void set_internalvar_component (struct internalvar *var,
 978                                        LONGEST offset,
 979                                        LONGEST bitpos, LONGEST bitsize,
 980                                        struct value *newvalue);
 981
 982 extern struct internalvar *lookup_only_internalvar (const char *name);
 983
 984 extern struct internalvar *create_internalvar (const char *name);
 985
 986 extern void complete_internalvar (completion_tracker &tracker,
 987                                   const char *name);
 988
 989 /* An internalvar can be dynamically computed by supplying a vector of
 990    function pointers to perform various operations.  */
 991
 992 struct internalvar_funcs
 993 {
 994   /* Compute the value of the variable.  The DATA argument passed to
 995      the function is the same argument that was passed to
 996      `create_internalvar_type_lazy'.  */
 997
 998   struct value *(*make_value) (struct gdbarch *arch,
 999                                struct internalvar *var,
1000                                void *data);
1001
1002   /* Update the agent expression EXPR with bytecode to compute the
1003      value.  VALUE is the agent value we are updating.  The DATA
1004      argument passed to this function is the same argument that was
1005      passed to `create_internalvar_type_lazy'.  If this pointer is
1006      NULL, then the internalvar cannot be compiled to an agent
1007      expression.  */
1008
1009   void (*compile_to_ax) (struct internalvar *var,
1010                          struct agent_expr *expr,
1011                          struct axs_value *value,
1012                          void *data);
1013
1014   /* If non-NULL, this is called to destroy DATA.  The DATA argument
1015      passed to this function is the same argument that was passed to
1016      `create_internalvar_type_lazy'.  */
1017
1018   void (*destroy) (void *data);
1019 };
1020
1021 extern struct internalvar *create_internalvar_type_lazy (const char *name,
1022                                 const struct internalvar_funcs *funcs,
1023                                 void *data);
1024
1025 /* Compile an internal variable to an agent expression.  VAR is the
1026    variable to compile; EXPR and VALUE are the agent expression we are
1027    updating.  This will return 0 if there is no known way to compile
1028    VAR, and 1 if VAR was successfully compiled.  It may also throw an
1029    exception on error.  */
1030
1031 extern int compile_internalvar_to_ax (struct internalvar *var,
1032                                       struct agent_expr *expr,
1033                                       struct axs_value *value);
1034
1035 extern struct internalvar *lookup_internalvar (const char *name);
1036
1037 extern int value_equal (struct value *arg1, struct value *arg2);
1038
1039 extern int value_equal_contents (struct value *arg1, struct value *arg2);
1040
1041 extern int value_less (struct value *arg1, struct value *arg2);
1042
1043 extern int value_logical_not (struct value *arg1);
1044
1045 /* C++ */
1046
1047 extern struct value *value_of_this (const struct language_defn *lang);
1048
1049 extern struct value *value_of_this_silent (const struct language_defn *lang);
1050
1051 extern struct value *value_x_binop (struct value *arg1, struct value *arg2,
1052                                     enum exp_opcode op,
1053                                     enum exp_opcode otherop,
1054                                     enum noside noside);
1055
1056 extern struct value *value_x_unop (struct value *arg1, enum exp_opcode op,
1057                                    enum noside noside);
1058
1059 extern struct value *value_fn_field (struct value **arg1p, struct fn_field *f,
1060                                      int j, struct type *type, LONGEST offset);
1061
1062 extern int binop_types_user_defined_p (enum exp_opcode op,
1063                                        struct type *type1,
1064                                        struct type *type2);
1065
1066 extern int binop_user_defined_p (enum exp_opcode op, struct value *arg1,
1067                                  struct value *arg2);
1068
1069 extern int unop_user_defined_p (enum exp_opcode op, struct value *arg1);
1070
1071 extern int destructor_name_p (const char *name, struct type *type);
1072
1073 extern value_ref_ptr release_value (struct value *val);
1074
1075 extern int record_latest_value (struct value *val);
1076
1077 extern void modify_field (struct type *type, gdb_byte *addr,
1078                           LONGEST fieldval, LONGEST bitpos, LONGEST bitsize);
1079
1080 extern void type_print (struct type *type, const char *varstring,
1081                         struct ui_file *stream, int show);
1082
1083 extern std::string type_to_string (struct type *type);
1084
1085 extern gdb_byte *baseclass_addr (struct type *type, int index,
1086                                  gdb_byte *valaddr,
1087                                  struct value **valuep, int *errp);
1088
1089 extern void print_longest (struct ui_file *stream, int format,
1090                            int use_local, LONGEST val);
1091
1092 extern void print_floating (const gdb_byte *valaddr, struct type *type,
1093                             struct ui_file *stream);
1094
1095 extern void value_print (struct value *val, struct ui_file *stream,
1096                          const struct value_print_options *options);
1097
1098 extern void value_print_array_elements (struct value *val,
1099                                         struct ui_file *stream, int format,
1100                                         enum val_prettyformat pretty);
1101
1102 /* Release values from the value chain and return them.  Values
1103    created after MARK are released.  If MARK is nullptr, or if MARK is
1104    not found on the value chain, then all values are released.  Values
1105    are returned in reverse order of creation; that is, newest
1106    first.  */
1107
1108 extern std::vector<value_ref_ptr> value_release_to_mark
1109     (const struct value *mark);
1110
1111 extern void common_val_print (struct value *val,
1112                               struct ui_file *stream, int recurse,
1113                               const struct value_print_options *options,
1114                               const struct language_defn *language);
1115
1116 extern int val_print_string (struct type *elttype, const char *encoding,
1117                              CORE_ADDR addr, int len,
1118                              struct ui_file *stream,
1119                              const struct value_print_options *options);
1120
1121 extern void print_variable_and_value (const char *name,
1122                                       struct symbol *var,
1123                                       struct frame_info *frame,
1124                                       struct ui_file *stream,
1125                                       int indent);
1126
1127 extern void typedef_print (struct type *type, struct symbol *news,
1128                            struct ui_file *stream);
1129
1130 extern const char *internalvar_name (const struct internalvar *var);
1131
1132 extern void preserve_values (struct objfile *);
1133
1134 /* From values.c */
1135
1136 extern struct value *value_copy (struct value *);
1137
1138 extern struct value *value_non_lval (struct value *);
1139
1140 extern void value_force_lval (struct value *, CORE_ADDR);
1141
1142 extern struct value *make_cv_value (int, int, struct value *);
1143
1144 extern void preserve_one_value (struct value *, struct objfile *, htab_t);
1145
1146 /* From valops.c */
1147
1148 extern struct value *varying_to_slice (struct value *);
1149
1150 extern struct value *value_slice (struct value *, int, int);
1151
1152 /* Create a complex number.  The type is the complex type; the values
1153    are cast to the underlying scalar type before the complex number is
1154    created.  */
1155
1156 extern struct value *value_literal_complex (struct value *, struct value *,
1157                                             struct type *);
1158
1159 /* Return the real part of a complex value.  */
1160
1161 extern struct value *value_real_part (struct value *value);
1162
1163 /* Return the imaginary part of a complex value.  */
1164
1165 extern struct value *value_imaginary_part (struct value *value);
1166
1167 extern struct value *find_function_in_inferior (const char *,
1168                                                 struct objfile **);
1169
1170 extern struct value *value_allocate_space_in_inferior (int);
1171
1172 extern struct value *value_subscripted_rvalue (struct value *array,
1173                                                LONGEST index,
1174                                                LONGEST lowerbound);
1175
1176 /* User function handler.  */
1177
1178 typedef struct value *(*internal_function_fn) (struct gdbarch *gdbarch,
1179                                                const struct language_defn *language,
1180                                                void *cookie,
1181                                                int argc,
1182                                                struct value **argv);
1183
1184 /* Add a new internal function.  NAME is the name of the function; DOC
1185    is a documentation string describing the function.  HANDLER is
1186    called when the function is invoked.  COOKIE is an arbitrary
1187    pointer which is passed to HANDLER and is intended for "user
1188    data".  */
1189
1190 extern void add_internal_function (const char *name, const char *doc,
1191                                    internal_function_fn handler,
1192                                    void *cookie);
1193
1194 /* This overload takes an allocated documentation string.  */
1195
1196 extern void add_internal_function (gdb::unique_xmalloc_ptr<char> &&name,
1197                                    gdb::unique_xmalloc_ptr<char> &&doc,
1198                                    internal_function_fn handler,
1199                                    void *cookie);
1200
1201 struct value *call_internal_function (struct gdbarch *gdbarch,
1202                                       const struct language_defn *language,
1203                                       struct value *function,
1204                                       int argc, struct value **argv);
1205
1206 const char *value_internal_function_name (struct value *);
1207
1208 /* Build a value wrapping and representing WORKER.  The value takes ownership
1209    of the xmethod_worker object.  */
1210
1211 extern struct value *value_from_xmethod (xmethod_worker_up &&worker);
1212
1213 extern struct type *result_type_of_xmethod (struct value *method,
1214                                             gdb::array_view<value *> argv);
1215
1216 extern struct value *call_xmethod (struct value *method,
1217                                    gdb::array_view<value *> argv);
1218
1219 /* Destroy the values currently allocated.  This is called when GDB is
1220    exiting (e.g., on quit_force).  */
1221 extern void finalize_values ();
1222
1223 /* Convert VALUE to a gdb_mpq.  The caller must ensure that VALUE is
1224    of floating-point, fixed-point, or integer type.  */
1225 extern gdb_mpq value_to_gdb_mpq (struct value *value);
1226
1227 #endif /* !defined (VALUE_H) */