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