gdb/value.h

   1 /* Definitions for values of C expressions, for GDB.
   2
   3    Copyright (C) 1986-2022 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   /* Return true if any part of V is optimized out, false otherwise.
 268      This will only be called for lazy values -- if the value has been
 269      fetched, then the value's optimized-out bits are consulted
 270      instead.  */
 271   bool (*is_optimized_out) (struct value *v);
 272
 273   /* If non-NULL, this is used to implement pointer indirection for
 274      this value.  This method may return NULL, in which case value_ind
 275      will fall back to ordinary indirection.  */
 276   struct value *(*indirect) (struct value *value);
 277
 278   /* If non-NULL, this is used to implement reference resolving for
 279      this value.  This method may return NULL, in which case coerce_ref
 280      will fall back to ordinary references resolving.  */
 281   struct value *(*coerce_ref) (const struct value *value);
 282
 283   /* If non-NULL, this is used to determine whether the indicated bits
 284      of VALUE are a synthetic pointer.  */
 285   int (*check_synthetic_pointer) (const struct value *value,
 286                                   LONGEST offset, int length);
 287
 288   /* Return a duplicate of VALUE's closure, for use in a new value.
 289      This may simply return the same closure, if VALUE's is
 290      reference-counted or statically allocated.
 291
 292      This may be NULL, in which case VALUE's closure is re-used in the
 293      new value.  */
 294   void *(*copy_closure) (const struct value *v);
 295
 296   /* Drop VALUE's reference to its closure.  Maybe this frees the
 297      closure; maybe this decrements a reference count; maybe the
 298      closure is statically allocated and this does nothing.
 299
 300      This may be NULL, in which case no action is taken to free
 301      VALUE's closure.  */
 302   void (*free_closure) (struct value *v);
 303 };
 304
 305 /* Create a computed lvalue, with type TYPE, function pointers FUNCS,
 306    and closure CLOSURE.  */
 307
 308 extern struct value *allocate_computed_value (struct type *type,
 309                                               const struct lval_funcs *funcs,
 310                                               void *closure);
 311
 312 extern struct value *allocate_optimized_out_value (struct type *type);
 313
 314 /* If VALUE is lval_computed, return its lval_funcs structure.  */
 315
 316 extern const struct lval_funcs *value_computed_funcs (const struct value *);
 317
 318 /* If VALUE is lval_computed, return its closure.  The meaning of the
 319    returned value depends on the functions VALUE uses.  */
 320
 321 extern void *value_computed_closure (const struct value *value);
 322
 323 /* If zero, contents of this value are in the contents field.  If
 324    nonzero, contents are in inferior.  If the lval field is lval_memory,
 325    the contents are in inferior memory at location.address plus offset.
 326    The lval field may also be lval_register.
 327
 328    WARNING: This field is used by the code which handles watchpoints
 329    (see breakpoint.c) to decide whether a particular value can be
 330    watched by hardware watchpoints.  If the lazy flag is set for some
 331    member of a value chain, it is assumed that this member of the
 332    chain doesn't need to be watched as part of watching the value
 333    itself.  This is how GDB avoids watching the entire struct or array
 334    when the user wants to watch a single struct member or array
 335    element.  If you ever change the way lazy flag is set and reset, be
 336    sure to consider this use as well!  */
 337
 338 extern int value_lazy (const struct value *);
 339 extern void set_value_lazy (struct value *value, int val);
 340
 341 extern int value_stack (const struct value *);
 342 extern void set_value_stack (struct value *value, int val);
 343
 344 /* Throw an error complaining that the value has been optimized
 345    out.  */
 346
 347 extern void error_value_optimized_out (void);
 348
 349 /* value_contents() and value_contents_raw() both return the address
 350    of the gdb buffer used to hold a copy of the contents of the lval.
 351    value_contents() is used when the contents of the buffer are needed
 352    -- it uses value_fetch_lazy() to load the buffer from the process
 353    being debugged if it hasn't already been loaded
 354    (value_contents_writeable() is used when a writeable but fetched
 355    buffer is required)..  value_contents_raw() is used when data is
 356    being stored into the buffer, or when it is certain that the
 357    contents of the buffer are valid.
 358
 359    Note: The contents pointer is adjusted by the offset required to
 360    get to the real subobject, if the value happens to represent
 361    something embedded in a larger run-time object.  */
 362
 363 extern gdb::array_view<gdb_byte> value_contents_raw (struct value *);
 364
 365 /* Actual contents of the value.  For use of this value; setting it
 366    uses the stuff above.  Not valid if lazy is nonzero.  Target
 367    byte-order.  We force it to be aligned properly for any possible
 368    value.  Note that a value therefore extends beyond what is
 369    declared here.  */
 370
 371 extern gdb::array_view<const gdb_byte> value_contents (struct value *);
 372 extern gdb::array_view<gdb_byte> value_contents_writeable (struct value *);
 373
 374 /* The ALL variants of the above two macros do not adjust the returned
 375    pointer by the embedded_offset value.  */
 376
 377 extern gdb::array_view<gdb_byte> value_contents_all_raw (struct value *);
 378 extern gdb::array_view<const gdb_byte> value_contents_all (struct value *);
 379
 380 /* Like value_contents_all, but does not require that the returned
 381    bits be valid.  This should only be used in situations where you
 382    plan to check the validity manually.  */
 383 extern gdb::array_view<const gdb_byte> value_contents_for_printing (struct value *value);
 384
 385 /* Like value_contents_for_printing, but accepts a constant value
 386    pointer.  Unlike value_contents_for_printing however, the pointed
 387    value must _not_ be lazy.  */
 388 extern gdb::array_view<const gdb_byte>
 389   value_contents_for_printing_const (const struct value *value);
 390
 391 extern void value_fetch_lazy (struct value *val);
 392
 393 /* If nonzero, this is the value of a variable which does not actually
 394    exist in the program, at least partially.  If the value is lazy,
 395    this may fetch it now.  */
 396 extern int value_optimized_out (struct value *value);
 397
 398 /* Given a value, return true if any of the contents bits starting at
 399    OFFSET and extending for LENGTH bits is optimized out, false
 400    otherwise.  */
 401
 402 extern int value_bits_any_optimized_out (const struct value *value,
 403                                          int bit_offset, int bit_length);
 404
 405 /* Like value_optimized_out, but return true iff the whole value is
 406    optimized out.  */
 407 extern int value_entirely_optimized_out (struct value *value);
 408
 409 /* Mark VALUE's content bytes starting at OFFSET and extending for
 410    LENGTH bytes as optimized out.  */
 411
 412 extern void mark_value_bytes_optimized_out (struct value *value,
 413                                             int offset, int length);
 414
 415 /* Mark VALUE's content bits starting at OFFSET and extending for
 416    LENGTH bits as optimized out.  */
 417
 418 extern void mark_value_bits_optimized_out (struct value *value,
 419                                            LONGEST offset, LONGEST length);
 420
 421 /* Set or return field indicating whether a variable is initialized or
 422    not, based on debugging information supplied by the compiler.
 423    1 = initialized; 0 = uninitialized.  */
 424 extern int value_initialized (const struct value *);
 425 extern void set_value_initialized (struct value *, int);
 426
 427 /* Set COMPONENT's location as appropriate for a component of WHOLE
 428    --- regardless of what kind of lvalue WHOLE is.  */
 429 extern void set_value_component_location (struct value *component,
 430                                           const struct value *whole);
 431
 432 /* While the following fields are per- VALUE .CONTENT .PIECE (i.e., a
 433    single value might have multiple LVALs), this hacked interface is
 434    limited to just the first PIECE.  Expect further change.  */
 435 /* Type of value; either not an lval, or one of the various different
 436    possible kinds of lval.  */
 437 extern enum lval_type *deprecated_value_lval_hack (struct value *);
 438 #define VALUE_LVAL(val) (*deprecated_value_lval_hack (val))
 439
 440 /* Like VALUE_LVAL, except the parameter can be const.  */
 441 extern enum lval_type value_lval_const (const struct value *value);
 442
 443 /* If lval == lval_memory, return the address in the inferior.  If
 444    lval == lval_register, return the byte offset into the registers
 445    structure.  Otherwise, return 0.  The returned address
 446    includes the offset, if any.  */
 447 extern CORE_ADDR value_address (const struct value *);
 448
 449 /* Like value_address, except the result does not include value's
 450    offset.  */
 451 extern CORE_ADDR value_raw_address (const struct value *);
 452
 453 /* Set the address of a value.  */
 454 extern void set_value_address (struct value *, CORE_ADDR);
 455
 456 /* Pointer to internal variable.  */
 457 extern struct internalvar **deprecated_value_internalvar_hack (struct value *);
 458 #define VALUE_INTERNALVAR(val) (*deprecated_value_internalvar_hack (val))
 459
 460 /* Frame ID of "next" frame to which a register value is relative.  A
 461    register value is indicated by VALUE_LVAL being set to lval_register.
 462    So, if the register value is found relative to frame F, then the
 463    frame id of F->next will be stored in VALUE_NEXT_FRAME_ID.  */
 464 extern struct frame_id *deprecated_value_next_frame_id_hack (struct value *);
 465 #define VALUE_NEXT_FRAME_ID(val) (*deprecated_value_next_frame_id_hack (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                                        gdb::optional<gdb::array_view <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 value *evaluate_var_value (enum noside noside, const block *blk,
 918                                   symbol *var);
 919
 920 extern value *evaluate_var_msym_value (enum noside noside,
 921                                        struct objfile *objfile,
 922                                        minimal_symbol *msymbol);
 923
 924 namespace expr { class operation; };
 925 extern void fetch_subexp_value (struct expression *exp,
 926                                 expr::operation *op,
 927                                 struct value **valp, struct value **resultp,
 928                                 std::vector<value_ref_ptr> *val_chain,
 929                                 bool preserve_errors);
 930
 931 extern struct value *parse_and_eval (const char *exp);
 932
 933 extern struct value *parse_to_comma_and_eval (const char **expp);
 934
 935 extern struct type *parse_and_eval_type (const char *p, int length);
 936
 937 extern CORE_ADDR parse_and_eval_address (const char *exp);
 938
 939 extern LONGEST parse_and_eval_long (const char *exp);
 940
 941 extern void unop_promote (const struct language_defn *language,
 942                           struct gdbarch *gdbarch,
 943                           struct value **arg1);
 944
 945 extern void binop_promote (const struct language_defn *language,
 946                            struct gdbarch *gdbarch,
 947                            struct value **arg1, struct value **arg2);
 948
 949 extern struct value *access_value_history (int num);
 950
 951 /* Return the number of items in the value history.  */
 952
 953 extern ULONGEST value_history_count ();
 954
 955 extern struct value *value_of_internalvar (struct gdbarch *gdbarch,
 956                                            struct internalvar *var);
 957
 958 extern int get_internalvar_integer (struct internalvar *var, LONGEST *l);
 959
 960 extern void set_internalvar (struct internalvar *var, struct value *val);
 961
 962 extern void set_internalvar_integer (struct internalvar *var, LONGEST l);
 963
 964 extern void set_internalvar_string (struct internalvar *var,
 965                                     const char *string);
 966
 967 extern void clear_internalvar (struct internalvar *var);
 968
 969 extern void set_internalvar_component (struct internalvar *var,
 970                                        LONGEST offset,
 971                                        LONGEST bitpos, LONGEST bitsize,
 972                                        struct value *newvalue);
 973
 974 extern struct internalvar *lookup_only_internalvar (const char *name);
 975
 976 extern struct internalvar *create_internalvar (const char *name);
 977
 978 extern void complete_internalvar (completion_tracker &tracker,
 979                                   const char *name);
 980
 981 /* An internalvar can be dynamically computed by supplying a vector of
 982    function pointers to perform various operations.  */
 983
 984 struct internalvar_funcs
 985 {
 986   /* Compute the value of the variable.  The DATA argument passed to
 987      the function is the same argument that was passed to
 988      `create_internalvar_type_lazy'.  */
 989
 990   struct value *(*make_value) (struct gdbarch *arch,
 991                                struct internalvar *var,
 992                                void *data);
 993
 994   /* Update the agent expression EXPR with bytecode to compute the
 995      value.  VALUE is the agent value we are updating.  The DATA
 996      argument passed to this function is the same argument that was
 997      passed to `create_internalvar_type_lazy'.  If this pointer is
 998      NULL, then the internalvar cannot be compiled to an agent
 999      expression.  */
1000
1001   void (*compile_to_ax) (struct internalvar *var,
1002                          struct agent_expr *expr,
1003                          struct axs_value *value,
1004                          void *data);
1005 };
1006
1007 extern struct internalvar *create_internalvar_type_lazy (const char *name,
1008                                 const struct internalvar_funcs *funcs,
1009                                 void *data);
1010
1011 /* Compile an internal variable to an agent expression.  VAR is the
1012    variable to compile; EXPR and VALUE are the agent expression we are
1013    updating.  This will return 0 if there is no known way to compile
1014    VAR, and 1 if VAR was successfully compiled.  It may also throw an
1015    exception on error.  */
1016
1017 extern int compile_internalvar_to_ax (struct internalvar *var,
1018                                       struct agent_expr *expr,
1019                                       struct axs_value *value);
1020
1021 extern struct internalvar *lookup_internalvar (const char *name);
1022
1023 extern int value_equal (struct value *arg1, struct value *arg2);
1024
1025 extern int value_equal_contents (struct value *arg1, struct value *arg2);
1026
1027 extern int value_less (struct value *arg1, struct value *arg2);
1028
1029 /* Simulate the C operator ! -- return true if ARG1 contains zero.  */
1030 extern bool value_logical_not (struct value *arg1);
1031
1032 /* Returns true if the value VAL represents a true value.  */
1033 static inline bool
1034 value_true (struct value *val)
1035 {
1036   return !value_logical_not (val);
1037 }
1038
1039 /* C++ */
1040
1041 extern struct value *value_of_this (const struct language_defn *lang);
1042
1043 extern struct value *value_of_this_silent (const struct language_defn *lang);
1044
1045 extern struct value *value_x_binop (struct value *arg1, struct value *arg2,
1046                                     enum exp_opcode op,
1047                                     enum exp_opcode otherop,
1048                                     enum noside noside);
1049
1050 extern struct value *value_x_unop (struct value *arg1, enum exp_opcode op,
1051                                    enum noside noside);
1052
1053 extern struct value *value_fn_field (struct value **arg1p, struct fn_field *f,
1054                                      int j, struct type *type, LONGEST offset);
1055
1056 extern int binop_types_user_defined_p (enum exp_opcode op,
1057                                        struct type *type1,
1058                                        struct type *type2);
1059
1060 extern int binop_user_defined_p (enum exp_opcode op, struct value *arg1,
1061                                  struct value *arg2);
1062
1063 extern int unop_user_defined_p (enum exp_opcode op, struct value *arg1);
1064
1065 extern int destructor_name_p (const char *name, struct type *type);
1066
1067 extern value_ref_ptr release_value (struct value *val);
1068
1069 extern int record_latest_value (struct value *val);
1070
1071 extern void modify_field (struct type *type, gdb_byte *addr,
1072                           LONGEST fieldval, LONGEST bitpos, LONGEST bitsize);
1073
1074 extern void type_print (struct type *type, const char *varstring,
1075                         struct ui_file *stream, int show);
1076
1077 extern std::string type_to_string (struct type *type);
1078
1079 extern gdb_byte *baseclass_addr (struct type *type, int index,
1080                                  gdb_byte *valaddr,
1081                                  struct value **valuep, int *errp);
1082
1083 extern void print_longest (struct ui_file *stream, int format,
1084                            int use_local, LONGEST val);
1085
1086 extern void print_floating (const gdb_byte *valaddr, struct type *type,
1087                             struct ui_file *stream);
1088
1089 extern void value_print (struct value *val, struct ui_file *stream,
1090                          const struct value_print_options *options);
1091
1092 /* Release values from the value chain and return them.  Values
1093    created after MARK are released.  If MARK is nullptr, or if MARK is
1094    not found on the value chain, then all values are released.  Values
1095    are returned in reverse order of creation; that is, newest
1096    first.  */
1097
1098 extern std::vector<value_ref_ptr> value_release_to_mark
1099     (const struct value *mark);
1100
1101 extern void common_val_print (struct value *val,
1102                               struct ui_file *stream, int recurse,
1103                               const struct value_print_options *options,
1104                               const struct language_defn *language);
1105
1106 extern int val_print_string (struct type *elttype, const char *encoding,
1107                              CORE_ADDR addr, int len,
1108                              struct ui_file *stream,
1109                              const struct value_print_options *options);
1110
1111 extern void print_variable_and_value (const char *name,
1112                                       struct symbol *var,
1113                                       struct frame_info *frame,
1114                                       struct ui_file *stream,
1115                                       int indent);
1116
1117 extern void typedef_print (struct type *type, struct symbol *news,
1118                            struct ui_file *stream);
1119
1120 extern const char *internalvar_name (const struct internalvar *var);
1121
1122 extern void preserve_values (struct objfile *);
1123
1124 /* From values.c */
1125
1126 extern struct value *value_copy (const value *);
1127
1128 extern struct value *value_non_lval (struct value *);
1129
1130 extern void value_force_lval (struct value *, CORE_ADDR);
1131
1132 extern struct value *make_cv_value (int, int, struct value *);
1133
1134 extern void preserve_one_value (struct value *, struct objfile *, htab_t);
1135
1136 /* From valops.c */
1137
1138 extern struct value *varying_to_slice (struct value *);
1139
1140 extern struct value *value_slice (struct value *, int, int);
1141
1142 /* Create a complex number.  The type is the complex type; the values
1143    are cast to the underlying scalar type before the complex number is
1144    created.  */
1145
1146 extern struct value *value_literal_complex (struct value *, struct value *,
1147                                             struct type *);
1148
1149 /* Return the real part of a complex value.  */
1150
1151 extern struct value *value_real_part (struct value *value);
1152
1153 /* Return the imaginary part of a complex value.  */
1154
1155 extern struct value *value_imaginary_part (struct value *value);
1156
1157 extern struct value *find_function_in_inferior (const char *,
1158                                                 struct objfile **);
1159
1160 extern struct value *value_allocate_space_in_inferior (int);
1161
1162 /* User function handler.  */
1163
1164 typedef struct value *(*internal_function_fn) (struct gdbarch *gdbarch,
1165                                                const struct language_defn *language,
1166                                                void *cookie,
1167                                                int argc,
1168                                                struct value **argv);
1169
1170 /* Add a new internal function.  NAME is the name of the function; DOC
1171    is a documentation string describing the function.  HANDLER is
1172    called when the function is invoked.  COOKIE is an arbitrary
1173    pointer which is passed to HANDLER and is intended for "user
1174    data".  */
1175
1176 extern void add_internal_function (const char *name, const char *doc,
1177                                    internal_function_fn handler,
1178                                    void *cookie);
1179
1180 /* This overload takes an allocated documentation string.  */
1181
1182 extern void add_internal_function (gdb::unique_xmalloc_ptr<char> &&name,
1183                                    gdb::unique_xmalloc_ptr<char> &&doc,
1184                                    internal_function_fn handler,
1185                                    void *cookie);
1186
1187 struct value *call_internal_function (struct gdbarch *gdbarch,
1188                                       const struct language_defn *language,
1189                                       struct value *function,
1190                                       int argc, struct value **argv);
1191
1192 const char *value_internal_function_name (struct value *);
1193
1194 /* Build a value wrapping and representing WORKER.  The value takes ownership
1195    of the xmethod_worker object.  */
1196
1197 extern struct value *value_from_xmethod (xmethod_worker_up &&worker);
1198
1199 extern struct type *result_type_of_xmethod (struct value *method,
1200                                             gdb::array_view<value *> argv);
1201
1202 extern struct value *call_xmethod (struct value *method,
1203                                    gdb::array_view<value *> argv);
1204
1205 /* Destroy the values currently allocated.  This is called when GDB is
1206    exiting (e.g., on quit_force).  */
1207 extern void finalize_values ();
1208
1209 /* Convert VALUE to a gdb_mpq.  The caller must ensure that VALUE is
1210    of floating-point, fixed-point, or integer type.  */
1211 extern gdb_mpq value_to_gdb_mpq (struct value *value);
1212
1213 #endif /* !defined (VALUE_H) */