gdb/value.h

   1 /* Definitions for values of C expressions, for GDB.
   2
   3    Copyright (C) 1986-2020 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 extern bool overload_resolution;
  85
  86 /* The structure which defines the type of a value.  It should never
  87    be possible for a program lval value to survive over a call to the
  88    inferior (i.e. to be put into the history list or an internal
  89    variable).  */
  90
  91 struct value;
  92
  93 /* Increase VAL's reference count.  */
  94
  95 extern void value_incref (struct value *val);
  96
  97 /* Decrease VAL's reference count.  When the reference count drops to
  98    0, VAL will be freed.  */
  99
 100 extern void value_decref (struct value *val);
 101
 102 /* A policy class to interface gdb::ref_ptr with struct value.  */
 103
 104 struct value_ref_policy
 105 {
 106   static void incref (struct value *ptr)
 107   {
 108     value_incref (ptr);
 109   }
 110
 111   static void decref (struct value *ptr)
 112   {
 113     value_decref (ptr);
 114   }
 115 };
 116
 117 /* A gdb:;ref_ptr pointer to a struct value.  */
 118
 119 typedef gdb::ref_ptr<struct value, value_ref_policy> value_ref_ptr;
 120
 121 /* Values are stored in a chain, so that they can be deleted easily
 122    over calls to the inferior.  Values assigned to internal variables,
 123    put into the value history or exposed to Python are taken off this
 124    list.  */
 125
 126 struct value *value_next (const struct value *);
 127
 128 /* Type of the value.  */
 129
 130 extern struct type *value_type (const struct value *);
 131
 132 /* Return the gdbarch associated with the value. */
 133
 134 extern struct gdbarch *get_value_arch (const struct value *value);
 135
 136 /* This is being used to change the type of an existing value, that
 137    code should instead be creating a new value with the changed type
 138    (but possibly shared content).  */
 139
 140 extern void deprecated_set_value_type (struct value *value,
 141                                        struct type *type);
 142
 143 /* Only used for bitfields; number of bits contained in them.  */
 144
 145 extern LONGEST value_bitsize (const struct value *);
 146 extern void set_value_bitsize (struct value *, LONGEST bit);
 147
 148 /* Only used for bitfields; position of start of field.  For
 149    little-endian targets, it is the position of the LSB.  For
 150    big-endian targets, it is the position of the MSB.  */
 151
 152 extern LONGEST value_bitpos (const struct value *);
 153 extern void set_value_bitpos (struct value *, LONGEST bit);
 154
 155 /* Only used for bitfields; the containing value.  This allows a
 156    single read from the target when displaying multiple
 157    bitfields.  */
 158
 159 struct value *value_parent (const struct value *);
 160 extern void set_value_parent (struct value *value, struct value *parent);
 161
 162 /* Describes offset of a value within lval of a structure in bytes.
 163    If lval == lval_memory, this is an offset to the address.  If lval
 164    == lval_register, this is a further offset from location.address
 165    within the registers structure.  Note also the member
 166    embedded_offset below.  */
 167
 168 extern LONGEST value_offset (const struct value *);
 169 extern void set_value_offset (struct value *, LONGEST offset);
 170
 171 /* The comment from "struct value" reads: ``Is it modifiable?  Only
 172    relevant if lval != not_lval.''.  Shouldn't the value instead be
 173    not_lval and be done with it?  */
 174
 175 extern int deprecated_value_modifiable (const struct value *value);
 176
 177 /* If a value represents a C++ object, then the `type' field gives the
 178    object's compile-time type.  If the object actually belongs to some
 179    class derived from `type', perhaps with other base classes and
 180    additional members, then `type' is just a subobject of the real
 181    thing, and the full object is probably larger than `type' would
 182    suggest.
 183
 184    If `type' is a dynamic class (i.e. one with a vtable), then GDB can
 185    actually determine the object's run-time type by looking at the
 186    run-time type information in the vtable.  When this information is
 187    available, we may elect to read in the entire object, for several
 188    reasons:
 189
 190    - When printing the value, the user would probably rather see the
 191      full object, not just the limited portion apparent from the
 192      compile-time type.
 193
 194    - If `type' has virtual base classes, then even printing `type'
 195      alone may require reaching outside the `type' portion of the
 196      object to wherever the virtual base class has been stored.
 197
 198    When we store the entire object, `enclosing_type' is the run-time
 199    type -- the complete object -- and `embedded_offset' is the offset
 200    of `type' within that larger type, in bytes.  The value_contents()
 201    macro takes `embedded_offset' into account, so most GDB code
 202    continues to see the `type' portion of the value, just as the
 203    inferior would.
 204
 205    If `type' is a pointer to an object, then `enclosing_type' is a
 206    pointer to the object's run-time type, and `pointed_to_offset' is
 207    the offset in bytes from the full object to the pointed-to object
 208    -- that is, the value `embedded_offset' would have if we followed
 209    the pointer and fetched the complete object.  (I don't really see
 210    the point.  Why not just determine the run-time type when you
 211    indirect, and avoid the special case?  The contents don't matter
 212    until you indirect anyway.)
 213
 214    If we're not doing anything fancy, `enclosing_type' is equal to
 215    `type', and `embedded_offset' is zero, so everything works
 216    normally.  */
 217
 218 extern struct type *value_enclosing_type (const struct value *);
 219 extern void set_value_enclosing_type (struct value *val,
 220                                       struct type *new_type);
 221
 222 /* Returns value_type or value_enclosing_type depending on
 223    value_print_options.objectprint.
 224
 225    If RESOLVE_SIMPLE_TYPES is 0 the enclosing type will be resolved
 226    only for pointers and references, else it will be returned
 227    for all the types (e.g. structures).  This option is useful
 228    to prevent retrieving enclosing type for the base classes fields.
 229
 230    REAL_TYPE_FOUND is used to inform whether the real type was found
 231    (or just static type was used).  The NULL may be passed if it is not
 232    necessary. */
 233
 234 extern struct type *value_actual_type (struct value *value,
 235                                        int resolve_simple_types,
 236                                        int *real_type_found);
 237
 238 extern LONGEST value_pointed_to_offset (const struct value *value);
 239 extern void set_value_pointed_to_offset (struct value *value, LONGEST val);
 240 extern LONGEST value_embedded_offset (const struct value *value);
 241 extern void set_value_embedded_offset (struct value *value, LONGEST val);
 242
 243 /* For lval_computed values, this structure holds functions used to
 244    retrieve and set the value (or portions of the value).
 245
 246    For each function, 'V' is the 'this' pointer: an lval_funcs
 247    function F may always assume that the V it receives is an
 248    lval_computed value, and has F in the appropriate slot of its
 249    lval_funcs structure.  */
 250
 251 struct lval_funcs
 252 {
 253   /* Fill in VALUE's contents.  This is used to "un-lazy" values.  If
 254      a problem arises in obtaining VALUE's bits, this function should
 255      call 'error'.  If it is NULL value_fetch_lazy on "un-lazy"
 256      non-optimized-out value is an internal error.  */
 257   void (*read) (struct value *v);
 258
 259   /* Handle an assignment TOVAL = FROMVAL by writing the value of
 260      FROMVAL to TOVAL's location.  The contents of TOVAL have not yet
 261      been updated.  If a problem arises in doing so, this function
 262      should call 'error'.  If it is NULL such TOVAL assignment is an error as
 263      TOVAL is not considered as an lvalue.  */
 264   void (*write) (struct value *toval, struct value *fromval);
 265
 266   /* If non-NULL, this is used to implement pointer indirection for
 267      this value.  This method may return NULL, in which case value_ind
 268      will fall back to ordinary indirection.  */
 269   struct value *(*indirect) (struct value *value);
 270
 271   /* If non-NULL, this is used to implement reference resolving for
 272      this value.  This method may return NULL, in which case coerce_ref
 273      will fall back to ordinary references resolving.  */
 274   struct value *(*coerce_ref) (const struct value *value);
 275
 276   /* If non-NULL, this is used to determine whether the indicated bits
 277      of VALUE are a synthetic pointer.  */
 278   int (*check_synthetic_pointer) (const struct value *value,
 279                                   LONGEST offset, int length);
 280
 281   /* Return a duplicate of VALUE's closure, for use in a new value.
 282      This may simply return the same closure, if VALUE's is
 283      reference-counted or statically allocated.
 284
 285      This may be NULL, in which case VALUE's closure is re-used in the
 286      new value.  */
 287   void *(*copy_closure) (const struct value *v);
 288
 289   /* Drop VALUE's reference to its closure.  Maybe this frees the
 290      closure; maybe this decrements a reference count; maybe the
 291      closure is statically allocated and this does nothing.
 292
 293      This may be NULL, in which case no action is taken to free
 294      VALUE's closure.  */
 295   void (*free_closure) (struct value *v);
 296 };
 297
 298 /* Create a computed lvalue, with type TYPE, function pointers FUNCS,
 299    and closure CLOSURE.  */
 300
 301 extern struct value *allocate_computed_value (struct type *type,
 302                                               const struct lval_funcs *funcs,
 303                                               void *closure);
 304
 305 /* Helper function to check the validity of some bits of a value.
 306
 307    If TYPE represents some aggregate type (e.g., a structure), return 1.
 308
 309    Otherwise, any of the bytes starting at OFFSET and extending for
 310    TYPE_LENGTH(TYPE) bytes are invalid, print a message to STREAM and
 311    return 0.  The checking is done using FUNCS.
 312
 313    Otherwise, return 1.  */
 314
 315 extern int valprint_check_validity (struct ui_file *stream, struct type *type,
 316                                     LONGEST embedded_offset,
 317                                     const struct value *val);
 318
 319 extern struct value *allocate_optimized_out_value (struct type *type);
 320
 321 /* If VALUE is lval_computed, return its lval_funcs structure.  */
 322
 323 extern const struct lval_funcs *value_computed_funcs (const struct value *);
 324
 325 /* If VALUE is lval_computed, return its closure.  The meaning of the
 326    returned value depends on the functions VALUE uses.  */
 327
 328 extern void *value_computed_closure (const struct value *value);
 329
 330 /* If zero, contents of this value are in the contents field.  If
 331    nonzero, contents are in inferior.  If the lval field is lval_memory,
 332    the contents are in inferior memory at location.address plus offset.
 333    The lval field may also be lval_register.
 334
 335    WARNING: This field is used by the code which handles watchpoints
 336    (see breakpoint.c) to decide whether a particular value can be
 337    watched by hardware watchpoints.  If the lazy flag is set for some
 338    member of a value chain, it is assumed that this member of the
 339    chain doesn't need to be watched as part of watching the value
 340    itself.  This is how GDB avoids watching the entire struct or array
 341    when the user wants to watch a single struct member or array
 342    element.  If you ever change the way lazy flag is set and reset, be
 343    sure to consider this use as well!  */
 344
 345 extern int value_lazy (const struct value *);
 346 extern void set_value_lazy (struct value *value, int val);
 347
 348 extern int value_stack (const struct value *);
 349 extern void set_value_stack (struct value *value, int val);
 350
 351 /* Throw an error complaining that the value has been optimized
 352    out.  */
 353
 354 extern void error_value_optimized_out (void);
 355
 356 /* value_contents() and value_contents_raw() both return the address
 357    of the gdb buffer used to hold a copy of the contents of the lval.
 358    value_contents() is used when the contents of the buffer are needed
 359    -- it uses value_fetch_lazy() to load the buffer from the process
 360    being debugged if it hasn't already been loaded
 361    (value_contents_writeable() is used when a writeable but fetched
 362    buffer is required)..  value_contents_raw() is used when data is
 363    being stored into the buffer, or when it is certain that the
 364    contents of the buffer are valid.
 365
 366    Note: The contents pointer is adjusted by the offset required to
 367    get to the real subobject, if the value happens to represent
 368    something embedded in a larger run-time object.  */
 369
 370 extern gdb_byte *value_contents_raw (struct value *);
 371
 372 /* Actual contents of the value.  For use of this value; setting it
 373    uses the stuff above.  Not valid if lazy is nonzero.  Target
 374    byte-order.  We force it to be aligned properly for any possible
 375    value.  Note that a value therefore extends beyond what is
 376    declared here.  */
 377
 378 extern const gdb_byte *value_contents (struct value *);
 379 extern gdb_byte *value_contents_writeable (struct value *);
 380
 381 /* The ALL variants of the above two macros do not adjust the returned
 382    pointer by the embedded_offset value.  */
 383
 384 extern gdb_byte *value_contents_all_raw (struct value *);
 385 extern const gdb_byte *value_contents_all (struct value *);
 386
 387 /* Like value_contents_all, but does not require that the returned
 388    bits be valid.  This should only be used in situations where you
 389    plan to check the validity manually.  */
 390 extern const gdb_byte *value_contents_for_printing (struct value *value);
 391
 392 /* Like value_contents_for_printing, but accepts a constant value
 393    pointer.  Unlike value_contents_for_printing however, the pointed
 394    value must _not_ be lazy.  */
 395 extern const gdb_byte *
 396   value_contents_for_printing_const (const struct value *value);
 397
 398 extern void value_fetch_lazy (struct value *val);
 399
 400 /* If nonzero, this is the value of a variable which does not actually
 401    exist in the program, at least partially.  If the value is lazy,
 402    this may fetch it now.  */
 403 extern int value_optimized_out (struct value *value);
 404
 405 /* Given a value, return true if any of the contents bits starting at
 406    OFFSET and extending for LENGTH bits is optimized out, false
 407    otherwise.  */
 408
 409 extern int value_bits_any_optimized_out (const struct value *value,
 410                                          int bit_offset, int bit_length);
 411
 412 /* Like value_optimized_out, but return true iff the whole value is
 413    optimized out.  */
 414 extern int value_entirely_optimized_out (struct value *value);
 415
 416 /* Mark VALUE's content bytes starting at OFFSET and extending for
 417    LENGTH bytes as optimized out.  */
 418
 419 extern void mark_value_bytes_optimized_out (struct value *value,
 420                                             int offset, int length);
 421
 422 /* Mark VALUE's content bits starting at OFFSET and extending for
 423    LENGTH bits as optimized out.  */
 424
 425 extern void mark_value_bits_optimized_out (struct value *value,
 426                                            LONGEST offset, LONGEST length);
 427
 428 /* Set or return field indicating whether a variable is initialized or
 429    not, based on debugging information supplied by the compiler.
 430    1 = initialized; 0 = uninitialized.  */
 431 extern int value_initialized (const struct value *);
 432 extern void set_value_initialized (struct value *, int);
 433
 434 /* Set COMPONENT's location as appropriate for a component of WHOLE
 435    --- regardless of what kind of lvalue WHOLE is.  */
 436 extern void set_value_component_location (struct value *component,
 437                                           const struct value *whole);
 438
 439 /* While the following fields are per- VALUE .CONTENT .PIECE (i.e., a
 440    single value might have multiple LVALs), this hacked interface is
 441    limited to just the first PIECE.  Expect further change.  */
 442 /* Type of value; either not an lval, or one of the various different
 443    possible kinds of lval.  */
 444 extern enum lval_type *deprecated_value_lval_hack (struct value *);
 445 #define VALUE_LVAL(val) (*deprecated_value_lval_hack (val))
 446
 447 /* Like VALUE_LVAL, except the parameter can be const.  */
 448 extern enum lval_type value_lval_const (const struct value *value);
 449
 450 /* If lval == lval_memory, return the address in the inferior.  If
 451    lval == lval_register, return the byte offset into the registers
 452    structure.  Otherwise, return 0.  The returned address
 453    includes the offset, if any.  */
 454 extern CORE_ADDR value_address (const struct value *);
 455
 456 /* Like value_address, except the result does not include value's
 457    offset.  */
 458 extern CORE_ADDR value_raw_address (const struct value *);
 459
 460 /* Set the address of a value.  */
 461 extern void set_value_address (struct value *, CORE_ADDR);
 462
 463 /* Pointer to internal variable.  */
 464 extern struct internalvar **deprecated_value_internalvar_hack (struct value *);
 465 #define VALUE_INTERNALVAR(val) (*deprecated_value_internalvar_hack (val))
 466
 467 /* Frame ID of "next" frame to which a register value is relative.  A
 468    register value is indicated by VALUE_LVAL being set to lval_register.
 469    So, if the register value is found relative to frame F, then the
 470    frame id of F->next will be stored in VALUE_NEXT_FRAME_ID.  */
 471 extern struct frame_id *deprecated_value_next_frame_id_hack (struct value *);
 472 #define VALUE_NEXT_FRAME_ID(val) (*deprecated_value_next_frame_id_hack (val))
 473
 474 /* Frame ID of frame to which a register value is relative.  This is
 475    similar to VALUE_NEXT_FRAME_ID, above, but may not be assigned to.
 476    Note that VALUE_FRAME_ID effectively undoes the "next" operation
 477    that was performed during the assignment to VALUE_NEXT_FRAME_ID.  */
 478 #define VALUE_FRAME_ID(val) (get_prev_frame_id_by_id (VALUE_NEXT_FRAME_ID (val)))
 479
 480 /* Register number if the value is from a register.  */
 481 extern int *deprecated_value_regnum_hack (struct value *);
 482 #define VALUE_REGNUM(val) (*deprecated_value_regnum_hack (val))
 483
 484 /* Return value after lval_funcs->coerce_ref (after check_typedef).  Return
 485    NULL if lval_funcs->coerce_ref is not applicable for whatever reason.  */
 486
 487 extern struct value *coerce_ref_if_computed (const struct value *arg);
 488
 489 /* Setup a new value type and enclosing value type for dereferenced value VALUE.
 490    ENC_TYPE is the new enclosing type that should be set.  ORIGINAL_TYPE and
 491    ORIGINAL_VAL are the type and value of the original reference or pointer.
 492
 493    Note, that VALUE is modified by this function.
 494
 495    It is a common implementation for coerce_ref and value_ind.  */
 496
 497 extern struct value * readjust_indirect_value_type (struct value *value,
 498                                                     struct type *enc_type,
 499                                                     const struct type *original_type,
 500                                                     const struct value *original_val);
 501
 502 /* Convert a REF to the object referenced.  */
 503
 504 extern struct value *coerce_ref (struct value *value);
 505
 506 /* If ARG is an array, convert it to a pointer.
 507    If ARG is a function, convert it to a function pointer.
 508
 509    References are dereferenced.  */
 510
 511 extern struct value *coerce_array (struct value *value);
 512
 513 /* Given a value, determine whether the bits starting at OFFSET and
 514    extending for LENGTH bits are a synthetic pointer.  */
 515
 516 extern int value_bits_synthetic_pointer (const struct value *value,
 517                                          LONGEST offset, LONGEST length);
 518
 519 /* Given a value, determine whether the contents bytes starting at
 520    OFFSET and extending for LENGTH bytes are available.  This returns
 521    nonzero if all bytes in the given range are available, zero if any
 522    byte is unavailable.  */
 523
 524 extern int value_bytes_available (const struct value *value,
 525                                   LONGEST offset, LONGEST length);
 526
 527 /* Given a value, determine whether the contents bits starting at
 528    OFFSET and extending for LENGTH bits are available.  This returns
 529    nonzero if all bits in the given range are available, zero if any
 530    bit is unavailable.  */
 531
 532 extern int value_bits_available (const struct value *value,
 533                                  LONGEST offset, LONGEST length);
 534
 535 /* Like value_bytes_available, but return false if any byte in the
 536    whole object is unavailable.  */
 537 extern int value_entirely_available (struct value *value);
 538
 539 /* Like value_entirely_available, but return false if any byte in the
 540    whole object is available.  */
 541 extern int value_entirely_unavailable (struct value *value);
 542
 543 /* Mark VALUE's content bytes starting at OFFSET and extending for
 544    LENGTH bytes as unavailable.  */
 545
 546 extern void mark_value_bytes_unavailable (struct value *value,
 547                                           LONGEST offset, LONGEST length);
 548
 549 /* Mark VALUE's content bits starting at OFFSET and extending for
 550    LENGTH bits as unavailable.  */
 551
 552 extern void mark_value_bits_unavailable (struct value *value,
 553                                          LONGEST offset, LONGEST length);
 554
 555 /* Compare LENGTH bytes of VAL1's contents starting at OFFSET1 with
 556    LENGTH bytes of VAL2's contents starting at OFFSET2.
 557
 558    Note that "contents" refers to the whole value's contents
 559    (value_contents_all), without any embedded offset adjustment.  For
 560    example, to compare a complete object value with itself, including
 561    its enclosing type chunk, you'd do:
 562
 563      int len = TYPE_LENGTH (check_typedef (value_enclosing_type (val)));
 564      value_contents_eq (val, 0, val, 0, len);
 565
 566    Returns true iff the set of available/valid contents match.
 567
 568    Optimized-out contents are equal to optimized-out contents, and are
 569    not equal to non-optimized-out contents.
 570
 571    Unavailable contents are equal to unavailable contents, and are not
 572    equal to non-unavailable contents.
 573
 574    For example, if 'x's represent an unavailable byte, and 'V' and 'Z'
 575    represent different available/valid bytes, in a value with length
 576    16:
 577
 578      offset:   0   4   8   12  16
 579      contents: xxxxVVVVxxxxVVZZ
 580
 581    then:
 582
 583      value_contents_eq(val, 0, val, 8, 6) => true
 584      value_contents_eq(val, 0, val, 4, 4) => false
 585      value_contents_eq(val, 0, val, 8, 8) => false
 586      value_contents_eq(val, 4, val, 12, 2) => true
 587      value_contents_eq(val, 4, val, 12, 4) => true
 588      value_contents_eq(val, 3, val, 4, 4) => true
 589
 590    If 'x's represent an unavailable byte, 'o' represents an optimized
 591    out byte, in a value with length 8:
 592
 593      offset:   0   4   8
 594      contents: xxxxoooo
 595
 596    then:
 597
 598      value_contents_eq(val, 0, val, 2, 2) => true
 599      value_contents_eq(val, 4, val, 6, 2) => true
 600      value_contents_eq(val, 0, val, 4, 4) => true
 601
 602    We only know whether a value chunk is unavailable or optimized out
 603    if we've tried to read it.  As this routine is used by printing
 604    routines, which may be printing values in the value history, long
 605    after the inferior is gone, it works with const values.  Therefore,
 606    this routine must not be called with lazy values.  */
 607
 608 extern bool value_contents_eq (const struct value *val1, LONGEST offset1,
 609                                const struct value *val2, LONGEST offset2,
 610                                LONGEST length);
 611
 612 /* Read LENGTH addressable memory units starting at MEMADDR into BUFFER,
 613    which is (or will be copied to) VAL's contents buffer offset by
 614    BIT_OFFSET bits.  Marks value contents ranges as unavailable if
 615    the corresponding memory is likewise unavailable.  STACK indicates
 616    whether the memory is known to be stack memory.  */
 617
 618 extern void read_value_memory (struct value *val, LONGEST bit_offset,
 619                                int stack, CORE_ADDR memaddr,
 620                                gdb_byte *buffer, size_t length);
 621
 622 /* Cast SCALAR_VALUE to the element type of VECTOR_TYPE, then replicate
 623    into each element of a new vector value with VECTOR_TYPE.  */
 624
 625 struct value *value_vector_widen (struct value *scalar_value,
 626                                   struct type *vector_type);
 627
 628 \f
 629
 630 #include "symtab.h"
 631 #include "gdbtypes.h"
 632 #include "expression.h"
 633
 634 struct frame_info;
 635 struct fn_field;
 636
 637 extern int print_address_demangle (const struct value_print_options *,
 638                                    struct gdbarch *, CORE_ADDR,
 639                                    struct ui_file *, int);
 640
 641 /* Returns true if VAL is of floating-point type.  In addition,
 642    throws an error if the value is an invalid floating-point value.  */
 643 extern bool is_floating_value (struct value *val);
 644
 645 extern LONGEST value_as_long (struct value *val);
 646 extern CORE_ADDR value_as_address (struct value *val);
 647
 648 extern LONGEST unpack_long (struct type *type, const gdb_byte *valaddr);
 649 extern CORE_ADDR unpack_pointer (struct type *type, const gdb_byte *valaddr);
 650
 651 extern LONGEST unpack_field_as_long (struct type *type,
 652                                      const gdb_byte *valaddr,
 653                                      int fieldno);
 654
 655 /* Unpack a bitfield of the specified FIELD_TYPE, from the object at
 656    VALADDR, and store the result in *RESULT.
 657    The bitfield starts at BITPOS bits and contains BITSIZE bits; if
 658    BITSIZE is zero, then the length is taken from FIELD_TYPE.
 659
 660    Extracting bits depends on endianness of the machine.  Compute the
 661    number of least significant bits to discard.  For big endian machines,
 662    we compute the total number of bits in the anonymous object, subtract
 663    off the bit count from the MSB of the object to the MSB of the
 664    bitfield, then the size of the bitfield, which leaves the LSB discard
 665    count.  For little endian machines, the discard count is simply the
 666    number of bits from the LSB of the anonymous object to the LSB of the
 667    bitfield.
 668
 669    If the field is signed, we also do sign extension.  */
 670
 671 extern LONGEST unpack_bits_as_long (struct type *field_type,
 672                                     const gdb_byte *valaddr,
 673                                     LONGEST bitpos, LONGEST bitsize);
 674
 675 extern int unpack_value_field_as_long (struct type *type, const gdb_byte *valaddr,
 676                                 LONGEST embedded_offset, int fieldno,
 677                                 const struct value *val, LONGEST *result);
 678
 679 extern void unpack_value_bitfield (struct value *dest_val,
 680                                    LONGEST bitpos, LONGEST bitsize,
 681                                    const gdb_byte *valaddr,
 682                                    LONGEST embedded_offset,
 683                                    const struct value *val);
 684
 685 extern struct value *value_field_bitfield (struct type *type, int fieldno,
 686                                            const gdb_byte *valaddr,
 687                                            LONGEST embedded_offset,
 688                                            const struct value *val);
 689
 690 extern void pack_long (gdb_byte *buf, struct type *type, LONGEST num);
 691
 692 extern struct value *value_from_longest (struct type *type, LONGEST num);
 693 extern struct value *value_from_ulongest (struct type *type, ULONGEST num);
 694 extern struct value *value_from_pointer (struct type *type, CORE_ADDR addr);
 695 extern struct value *value_from_host_double (struct type *type, double d);
 696 extern struct value *value_from_history_ref (const char *, const char **);
 697 extern struct value *value_from_component (struct value *, struct type *,
 698                                            LONGEST);
 699
 700 extern struct value *value_at (struct type *type, CORE_ADDR addr);
 701 extern struct value *value_at_lazy (struct type *type, CORE_ADDR addr);
 702
 703 extern struct value *value_from_contents_and_address_unresolved
 704      (struct type *, const gdb_byte *, CORE_ADDR);
 705 extern struct value *value_from_contents_and_address (struct type *,
 706                                                       const gdb_byte *,
 707                                                       CORE_ADDR);
 708 extern struct value *value_from_contents (struct type *, const gdb_byte *);
 709
 710 extern struct value *default_value_from_register (struct gdbarch *gdbarch,
 711                                                   struct type *type,
 712                                                   int regnum,
 713                                                   struct frame_id frame_id);
 714
 715 extern void read_frame_register_value (struct value *value,
 716                                        struct frame_info *frame);
 717
 718 extern struct value *value_from_register (struct type *type, int regnum,
 719                                           struct frame_info *frame);
 720
 721 extern CORE_ADDR address_from_register (int regnum,
 722                                         struct frame_info *frame);
 723
 724 extern struct value *value_of_variable (struct symbol *var,
 725                                         const struct block *b);
 726
 727 extern struct value *address_of_variable (struct symbol *var,
 728                                           const struct block *b);
 729
 730 extern struct value *value_of_register (int regnum, struct frame_info *frame);
 731
 732 struct value *value_of_register_lazy (struct frame_info *frame, int regnum);
 733
 734 /* Return the symbol's reading requirement.  */
 735
 736 extern enum symbol_needs_kind symbol_read_needs (struct symbol *);
 737
 738 /* Return true if the symbol needs a frame.  This is a wrapper for
 739    symbol_read_needs that simply checks for SYMBOL_NEEDS_FRAME.  */
 740
 741 extern int symbol_read_needs_frame (struct symbol *);
 742
 743 extern struct value *read_var_value (struct symbol *var,
 744                                      const struct block *var_block,
 745                                      struct frame_info *frame);
 746
 747 extern struct value *default_read_var_value (struct symbol *var,
 748                                              const struct block *var_block,
 749                                              struct frame_info *frame);
 750
 751 extern struct value *allocate_value (struct type *type);
 752 extern struct value *allocate_value_lazy (struct type *type);
 753 extern void value_contents_copy (struct value *dst, LONGEST dst_offset,
 754                                  struct value *src, LONGEST src_offset,
 755                                  LONGEST length);
 756 extern void value_contents_copy_raw (struct value *dst, LONGEST dst_offset,
 757                                      struct value *src, LONGEST src_offset,
 758                                      LONGEST length);
 759
 760 extern struct value *allocate_repeat_value (struct type *type, int count);
 761
 762 extern struct value *value_mark (void);
 763
 764 extern void value_free_to_mark (const struct value *mark);
 765
 766 /* A helper class that uses value_mark at construction time and calls
 767    value_free_to_mark in the destructor.  This is used to clear out
 768    temporary values created during the lifetime of this object.  */
 769 class scoped_value_mark
 770 {
 771  public:
 772
 773   scoped_value_mark ()
 774     : m_value (value_mark ())
 775   {
 776   }
 777
 778   ~scoped_value_mark ()
 779   {
 780     free_to_mark ();
 781   }
 782
 783   scoped_value_mark (scoped_value_mark &&other) = default;
 784
 785   DISABLE_COPY_AND_ASSIGN (scoped_value_mark);
 786
 787   /* Free the values currently on the value stack.  */
 788   void free_to_mark ()
 789   {
 790     if (m_value != NULL)
 791       {
 792         value_free_to_mark (m_value);
 793         m_value = NULL;
 794       }
 795   }
 796
 797  private:
 798
 799   const struct value *m_value;
 800 };
 801
 802 extern struct value *value_cstring (const char *ptr, ssize_t len,
 803                                     struct type *char_type);
 804 extern struct value *value_string (const char *ptr, ssize_t len,
 805                                    struct type *char_type);
 806
 807 extern struct value *value_array (int lowbound, int highbound,
 808                                   struct value **elemvec);
 809
 810 extern struct value *value_concat (struct value *arg1, struct value *arg2);
 811
 812 extern struct value *value_binop (struct value *arg1, struct value *arg2,
 813                                   enum exp_opcode op);
 814
 815 extern struct value *value_ptradd (struct value *arg1, LONGEST arg2);
 816
 817 extern LONGEST value_ptrdiff (struct value *arg1, struct value *arg2);
 818
 819 /* Return true if VAL does not live in target memory, but should in order
 820    to operate on it.  Otherwise return false.  */
 821
 822 extern bool value_must_coerce_to_target (struct value *arg1);
 823
 824 extern struct value *value_coerce_to_target (struct value *arg1);
 825
 826 extern struct value *value_coerce_array (struct value *arg1);
 827
 828 extern struct value *value_coerce_function (struct value *arg1);
 829
 830 extern struct value *value_ind (struct value *arg1);
 831
 832 extern struct value *value_addr (struct value *arg1);
 833
 834 extern struct value *value_ref (struct value *arg1, enum type_code refcode);
 835
 836 extern struct value *value_assign (struct value *toval,
 837                                    struct value *fromval);
 838
 839 extern struct value *value_pos (struct value *arg1);
 840
 841 extern struct value *value_neg (struct value *arg1);
 842
 843 extern struct value *value_complement (struct value *arg1);
 844
 845 extern struct value *value_struct_elt (struct value **argp,
 846                                        struct value **args,
 847                                        const char *name, int *static_memfuncp,
 848                                        const char *err);
 849
 850 extern struct value *value_struct_elt_bitpos (struct value **argp,
 851                                               int bitpos,
 852                                               struct type *field_type,
 853                                               const char *err);
 854
 855 extern struct value *value_aggregate_elt (struct type *curtype,
 856                                           const char *name,
 857                                           struct type *expect_type,
 858                                           int want_address,
 859                                           enum noside noside);
 860
 861 extern struct value *value_static_field (struct type *type, int fieldno);
 862
 863 enum oload_search_type { NON_METHOD, METHOD, BOTH };
 864
 865 extern int find_overload_match (gdb::array_view<value *> args,
 866                                 const char *name,
 867                                 enum oload_search_type method,
 868                                 struct value **objp, struct symbol *fsym,
 869                                 struct value **valp, struct symbol **symp,
 870                                 int *staticp, const int no_adl,
 871                                 enum noside noside);
 872
 873 extern struct value *value_field (struct value *arg1, int fieldno);
 874
 875 extern struct value *value_primitive_field (struct value *arg1, LONGEST offset,
 876                                             int fieldno,
 877                                             struct type *arg_type);
 878
 879
 880 extern struct type *value_rtti_indirect_type (struct value *, int *, LONGEST *,
 881                                               int *);
 882
 883 extern struct value *value_full_object (struct value *, struct type *, int,
 884                                         int, int);
 885
 886 extern struct value *value_cast_pointers (struct type *, struct value *, int);
 887
 888 extern struct value *value_cast (struct type *type, struct value *arg2);
 889
 890 extern struct value *value_reinterpret_cast (struct type *type,
 891                                              struct value *arg);
 892
 893 extern struct value *value_dynamic_cast (struct type *type, struct value *arg);
 894
 895 extern struct value *value_zero (struct type *type, enum lval_type lv);
 896
 897 extern struct value *value_one (struct type *type);
 898
 899 extern struct value *value_repeat (struct value *arg1, int count);
 900
 901 extern struct value *value_subscript (struct value *array, LONGEST index);
 902
 903 extern struct value *value_bitstring_subscript (struct type *type,
 904                                                 struct value *bitstring,
 905                                                 LONGEST index);
 906
 907 extern struct value *register_value_being_returned (struct type *valtype,
 908                                                     struct regcache *retbuf);
 909
 910 extern int value_in (struct value *element, struct value *set);
 911
 912 extern int value_bit_index (struct type *type, const gdb_byte *addr,
 913                             int index);
 914
 915 extern enum return_value_convention
 916 struct_return_convention (struct gdbarch *gdbarch, struct value *function,
 917                           struct type *value_type);
 918
 919 extern int using_struct_return (struct gdbarch *gdbarch,
 920                                 struct value *function,
 921                                 struct type *value_type);
 922
 923 extern struct value *evaluate_expression (struct expression *exp);
 924
 925 extern struct value *evaluate_type (struct expression *exp);
 926
 927 extern struct value *evaluate_subexp (struct type *expect_type,
 928                                       struct expression *exp,
 929                                       int *pos, enum noside noside);
 930
 931 extern struct value *evaluate_subexpression_type (struct expression *exp,
 932                                                   int subexp);
 933
 934 extern value *evaluate_var_value (enum noside noside, const block *blk,
 935                                   symbol *var);
 936
 937 extern value *evaluate_var_msym_value (enum noside noside,
 938                                        struct objfile *objfile,
 939                                        minimal_symbol *msymbol);
 940
 941 extern value *eval_skip_value (expression *exp);
 942
 943 extern void fetch_subexp_value (struct expression *exp, int *pc,
 944                                 struct value **valp, struct value **resultp,
 945                                 std::vector<value_ref_ptr> *val_chain,
 946                                 int preserve_errors);
 947
 948 extern const char *extract_field_op (struct expression *exp, int *subexp);
 949
 950 extern struct value *evaluate_subexp_with_coercion (struct expression *,
 951                                                     int *, enum noside);
 952
 953 extern struct value *parse_and_eval (const char *exp);
 954
 955 extern struct value *parse_to_comma_and_eval (const char **expp);
 956
 957 extern struct type *parse_and_eval_type (char *p, int length);
 958
 959 extern CORE_ADDR parse_and_eval_address (const char *exp);
 960
 961 extern LONGEST parse_and_eval_long (const char *exp);
 962
 963 extern void unop_promote (const struct language_defn *language,
 964                           struct gdbarch *gdbarch,
 965                           struct value **arg1);
 966
 967 extern void binop_promote (const struct language_defn *language,
 968                            struct gdbarch *gdbarch,
 969                            struct value **arg1, struct value **arg2);
 970
 971 extern struct value *access_value_history (int num);
 972
 973 extern struct value *value_of_internalvar (struct gdbarch *gdbarch,
 974                                            struct internalvar *var);
 975
 976 extern int get_internalvar_integer (struct internalvar *var, LONGEST *l);
 977
 978 extern void set_internalvar (struct internalvar *var, struct value *val);
 979
 980 extern void set_internalvar_integer (struct internalvar *var, LONGEST l);
 981
 982 extern void set_internalvar_string (struct internalvar *var,
 983                                     const char *string);
 984
 985 extern void clear_internalvar (struct internalvar *var);
 986
 987 extern void set_internalvar_component (struct internalvar *var,
 988                                        LONGEST offset,
 989                                        LONGEST bitpos, LONGEST bitsize,
 990                                        struct value *newvalue);
 991
 992 extern struct internalvar *lookup_only_internalvar (const char *name);
 993
 994 extern struct internalvar *create_internalvar (const char *name);
 995
 996 extern void complete_internalvar (completion_tracker &tracker,
 997                                   const char *name);
 998
 999 /* An internalvar can be dynamically computed by supplying a vector of
1000    function pointers to perform various operations.  */
1001
1002 struct internalvar_funcs
1003 {
1004   /* Compute the value of the variable.  The DATA argument passed to
1005      the function is the same argument that was passed to
1006      `create_internalvar_type_lazy'.  */
1007
1008   struct value *(*make_value) (struct gdbarch *arch,
1009                                struct internalvar *var,
1010                                void *data);
1011
1012   /* Update the agent expression EXPR with bytecode to compute the
1013      value.  VALUE is the agent value we are updating.  The DATA
1014      argument passed to this function is the same argument that was
1015      passed to `create_internalvar_type_lazy'.  If this pointer is
1016      NULL, then the internalvar cannot be compiled to an agent
1017      expression.  */
1018
1019   void (*compile_to_ax) (struct internalvar *var,
1020                          struct agent_expr *expr,
1021                          struct axs_value *value,
1022                          void *data);
1023
1024   /* If non-NULL, this is called to destroy DATA.  The DATA argument
1025      passed to this function is the same argument that was passed to
1026      `create_internalvar_type_lazy'.  */
1027
1028   void (*destroy) (void *data);
1029 };
1030
1031 extern struct internalvar *create_internalvar_type_lazy (const char *name,
1032                                 const struct internalvar_funcs *funcs,
1033                                 void *data);
1034
1035 /* Compile an internal variable to an agent expression.  VAR is the
1036    variable to compile; EXPR and VALUE are the agent expression we are
1037    updating.  This will return 0 if there is no known way to compile
1038    VAR, and 1 if VAR was successfully compiled.  It may also throw an
1039    exception on error.  */
1040
1041 extern int compile_internalvar_to_ax (struct internalvar *var,
1042                                       struct agent_expr *expr,
1043                                       struct axs_value *value);
1044
1045 extern struct internalvar *lookup_internalvar (const char *name);
1046
1047 extern int value_equal (struct value *arg1, struct value *arg2);
1048
1049 extern int value_equal_contents (struct value *arg1, struct value *arg2);
1050
1051 extern int value_less (struct value *arg1, struct value *arg2);
1052
1053 extern int value_logical_not (struct value *arg1);
1054
1055 /* C++ */
1056
1057 extern struct value *value_of_this (const struct language_defn *lang);
1058
1059 extern struct value *value_of_this_silent (const struct language_defn *lang);
1060
1061 extern struct value *value_x_binop (struct value *arg1, struct value *arg2,
1062                                     enum exp_opcode op,
1063                                     enum exp_opcode otherop,
1064                                     enum noside noside);
1065
1066 extern struct value *value_x_unop (struct value *arg1, enum exp_opcode op,
1067                                    enum noside noside);
1068
1069 extern struct value *value_fn_field (struct value **arg1p, struct fn_field *f,
1070                                      int j, struct type *type, LONGEST offset);
1071
1072 extern int binop_types_user_defined_p (enum exp_opcode op,
1073                                        struct type *type1,
1074                                        struct type *type2);
1075
1076 extern int binop_user_defined_p (enum exp_opcode op, struct value *arg1,
1077                                  struct value *arg2);
1078
1079 extern int unop_user_defined_p (enum exp_opcode op, struct value *arg1);
1080
1081 extern int destructor_name_p (const char *name, struct type *type);
1082
1083 extern value_ref_ptr release_value (struct value *val);
1084
1085 extern int record_latest_value (struct value *val);
1086
1087 extern void modify_field (struct type *type, gdb_byte *addr,
1088                           LONGEST fieldval, LONGEST bitpos, LONGEST bitsize);
1089
1090 extern void type_print (struct type *type, const char *varstring,
1091                         struct ui_file *stream, int show);
1092
1093 extern std::string type_to_string (struct type *type);
1094
1095 extern gdb_byte *baseclass_addr (struct type *type, int index,
1096                                  gdb_byte *valaddr,
1097                                  struct value **valuep, int *errp);
1098
1099 extern void print_longest (struct ui_file *stream, int format,
1100                            int use_local, LONGEST val);
1101
1102 extern void print_floating (const gdb_byte *valaddr, struct type *type,
1103                             struct ui_file *stream);
1104
1105 extern void value_print (struct value *val, struct ui_file *stream,
1106                          const struct value_print_options *options);
1107
1108 extern void value_print_array_elements (struct value *val,
1109                                         struct ui_file *stream, int format,
1110                                         enum val_prettyformat pretty);
1111
1112 /* Release values from the value chain and return them.  Values
1113    created after MARK are released.  If MARK is nullptr, or if MARK is
1114    not found on the value chain, then all values are released.  Values
1115    are returned in reverse order of creation; that is, newest
1116    first.  */
1117
1118 extern std::vector<value_ref_ptr> value_release_to_mark
1119     (const struct value *mark);
1120
1121 extern void common_val_print (struct value *val,
1122                               struct ui_file *stream, int recurse,
1123                               const struct value_print_options *options,
1124                               const struct language_defn *language);
1125
1126 extern int val_print_string (struct type *elttype, const char *encoding,
1127                              CORE_ADDR addr, int len,
1128                              struct ui_file *stream,
1129                              const struct value_print_options *options);
1130
1131 extern void print_variable_and_value (const char *name,
1132                                       struct symbol *var,
1133                                       struct frame_info *frame,
1134                                       struct ui_file *stream,
1135                                       int indent);
1136
1137 extern void typedef_print (struct type *type, struct symbol *news,
1138                            struct ui_file *stream);
1139
1140 extern char *internalvar_name (const struct internalvar *var);
1141
1142 extern void preserve_values (struct objfile *);
1143
1144 /* From values.c */
1145
1146 extern struct value *value_copy (struct value *);
1147
1148 extern struct value *value_non_lval (struct value *);
1149
1150 extern void value_force_lval (struct value *, CORE_ADDR);
1151
1152 extern struct value *make_cv_value (int, int, struct value *);
1153
1154 extern void preserve_one_value (struct value *, struct objfile *, htab_t);
1155
1156 /* From valops.c */
1157
1158 extern struct value *varying_to_slice (struct value *);
1159
1160 extern struct value *value_slice (struct value *, int, int);
1161
1162 /* Create a complex number.  The type is the complex type; the values
1163    are cast to the underlying scalar type before the complex number is
1164    created.  */
1165
1166 extern struct value *value_literal_complex (struct value *, struct value *,
1167                                             struct type *);
1168
1169 /* Return the real part of a complex value.  */
1170
1171 extern struct value *value_real_part (struct value *value);
1172
1173 /* Return the imaginary part of a complex value.  */
1174
1175 extern struct value *value_imaginary_part (struct value *value);
1176
1177 extern struct value *find_function_in_inferior (const char *,
1178                                                 struct objfile **);
1179
1180 extern struct value *value_allocate_space_in_inferior (int);
1181
1182 extern struct value *value_subscripted_rvalue (struct value *array,
1183                                                LONGEST index,
1184                                                LONGEST lowerbound);
1185
1186 /* User function handler.  */
1187
1188 typedef struct value *(*internal_function_fn) (struct gdbarch *gdbarch,
1189                                                const struct language_defn *language,
1190                                                void *cookie,
1191                                                int argc,
1192                                                struct value **argv);
1193
1194 /* Add a new internal function.  NAME is the name of the function; DOC
1195    is a documentation string describing the function.  HANDLER is
1196    called when the function is invoked.  COOKIE is an arbitrary
1197    pointer which is passed to HANDLER and is intended for "user
1198    data".  */
1199
1200 extern void add_internal_function (const char *name, const char *doc,
1201                                    internal_function_fn handler,
1202                                    void *cookie);
1203
1204 /* This overload takes an allocated documentation string.  */
1205
1206 extern void add_internal_function (gdb::unique_xmalloc_ptr<char> &&name,
1207                                    gdb::unique_xmalloc_ptr<char> &&doc,
1208                                    internal_function_fn handler,
1209                                    void *cookie);
1210
1211 struct value *call_internal_function (struct gdbarch *gdbarch,
1212                                       const struct language_defn *language,
1213                                       struct value *function,
1214                                       int argc, struct value **argv);
1215
1216 char *value_internal_function_name (struct value *);
1217
1218 /* Build a value wrapping and representing WORKER.  The value takes ownership
1219    of the xmethod_worker object.  */
1220
1221 extern struct value *value_from_xmethod (xmethod_worker_up &&worker);
1222
1223 extern struct type *result_type_of_xmethod (struct value *method,
1224                                             gdb::array_view<value *> argv);
1225
1226 extern struct value *call_xmethod (struct value *method,
1227                                    gdb::array_view<value *> argv);
1228
1229 /* Destroy the values currently allocated.  This is called when GDB is
1230    exiting (e.g., on quit_force).  */
1231 extern void finalize_values ();
1232
1233 #endif /* !defined (VALUE_H) */