1 /* Find a variable's value in memory, for GDB, the GNU debugger.
3 Copyright (C) 1986-2015 Free Software Foundation, Inc.
5 This file is part of GDB.
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.
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.
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/>. */
28 #include "floatformat.h"
29 #include "symfile.h" /* for overlay functions */
31 #include "user-regs.h"
35 #include "dwarf2loc.h"
37 /* Basic byte-swapping routines. All 'extract' functions return a
38 host-format integer from a target-format integer at ADDR which is
41 #if TARGET_CHAR_BIT != 8 || HOST_CHAR_BIT != 8
42 /* 8 bit characters are a pretty safe assumption these days, so we
43 assume it throughout all these swapping routines. If we had to deal with
44 9 bit characters, we would need to make len be in bits and would have
45 to re-write these routines... */
50 extract_signed_integer (const gdb_byte *addr, int len,
51 enum bfd_endian byte_order)
54 const unsigned char *p;
55 const unsigned char *startaddr = addr;
56 const unsigned char *endaddr = startaddr + len;
58 if (len > (int) sizeof (LONGEST))
60 That operation is not available on integers of more than %d bytes."),
61 (int) sizeof (LONGEST));
63 /* Start at the most significant end of the integer, and work towards
64 the least significant. */
65 if (byte_order == BFD_ENDIAN_BIG)
68 /* Do the sign extension once at the start. */
69 retval = ((LONGEST) * p ^ 0x80) - 0x80;
70 for (++p; p < endaddr; ++p)
71 retval = (retval << 8) | *p;
76 /* Do the sign extension once at the start. */
77 retval = ((LONGEST) * p ^ 0x80) - 0x80;
78 for (--p; p >= startaddr; --p)
79 retval = (retval << 8) | *p;
85 extract_unsigned_integer (const gdb_byte *addr, int len,
86 enum bfd_endian byte_order)
89 const unsigned char *p;
90 const unsigned char *startaddr = addr;
91 const unsigned char *endaddr = startaddr + len;
93 if (len > (int) sizeof (ULONGEST))
95 That operation is not available on integers of more than %d bytes."),
96 (int) sizeof (ULONGEST));
98 /* Start at the most significant end of the integer, and work towards
99 the least significant. */
101 if (byte_order == BFD_ENDIAN_BIG)
103 for (p = startaddr; p < endaddr; ++p)
104 retval = (retval << 8) | *p;
108 for (p = endaddr - 1; p >= startaddr; --p)
109 retval = (retval << 8) | *p;
114 /* Sometimes a long long unsigned integer can be extracted as a
115 LONGEST value. This is done so that we can print these values
116 better. If this integer can be converted to a LONGEST, this
117 function returns 1 and sets *PVAL. Otherwise it returns 0. */
120 extract_long_unsigned_integer (const gdb_byte *addr, int orig_len,
121 enum bfd_endian byte_order, LONGEST *pval)
124 const gdb_byte *first_addr;
128 if (byte_order == BFD_ENDIAN_BIG)
131 len > (int) sizeof (LONGEST) && p < addr + orig_len;
144 for (p = addr + orig_len - 1;
145 len > (int) sizeof (LONGEST) && p >= addr;
155 if (len <= (int) sizeof (LONGEST))
157 *pval = (LONGEST) extract_unsigned_integer (first_addr,
167 /* Treat the bytes at BUF as a pointer of type TYPE, and return the
168 address it represents. */
170 extract_typed_address (const gdb_byte *buf, struct type *type)
172 if (TYPE_CODE (type) != TYPE_CODE_PTR
173 && TYPE_CODE (type) != TYPE_CODE_REF)
174 internal_error (__FILE__, __LINE__,
175 _("extract_typed_address: "
176 "type is not a pointer or reference"));
178 return gdbarch_pointer_to_address (get_type_arch (type), type, buf);
181 /* All 'store' functions accept a host-format integer and store a
182 target-format integer at ADDR which is LEN bytes long. */
185 store_signed_integer (gdb_byte *addr, int len,
186 enum bfd_endian byte_order, LONGEST val)
189 gdb_byte *startaddr = addr;
190 gdb_byte *endaddr = startaddr + len;
192 /* Start at the least significant end of the integer, and work towards
193 the most significant. */
194 if (byte_order == BFD_ENDIAN_BIG)
196 for (p = endaddr - 1; p >= startaddr; --p)
204 for (p = startaddr; p < endaddr; ++p)
213 store_unsigned_integer (gdb_byte *addr, int len,
214 enum bfd_endian byte_order, ULONGEST val)
217 unsigned char *startaddr = (unsigned char *) addr;
218 unsigned char *endaddr = startaddr + len;
220 /* Start at the least significant end of the integer, and work towards
221 the most significant. */
222 if (byte_order == BFD_ENDIAN_BIG)
224 for (p = endaddr - 1; p >= startaddr; --p)
232 for (p = startaddr; p < endaddr; ++p)
240 /* Store the address ADDR as a pointer of type TYPE at BUF, in target
243 store_typed_address (gdb_byte *buf, struct type *type, CORE_ADDR addr)
245 if (TYPE_CODE (type) != TYPE_CODE_PTR
246 && TYPE_CODE (type) != TYPE_CODE_REF)
247 internal_error (__FILE__, __LINE__,
248 _("store_typed_address: "
249 "type is not a pointer or reference"));
251 gdbarch_address_to_pointer (get_type_arch (type), type, buf, addr);
256 /* Return a `value' with the contents of (virtual or cooked) register
257 REGNUM as found in the specified FRAME. The register's type is
258 determined by register_type(). */
261 value_of_register (int regnum, struct frame_info *frame)
263 struct gdbarch *gdbarch = get_frame_arch (frame);
264 struct value *reg_val;
266 /* User registers lie completely outside of the range of normal
267 registers. Catch them early so that the target never sees them. */
268 if (regnum >= gdbarch_num_regs (gdbarch)
269 + gdbarch_num_pseudo_regs (gdbarch))
270 return value_of_user_reg (regnum, frame);
272 reg_val = value_of_register_lazy (frame, regnum);
273 value_fetch_lazy (reg_val);
277 /* Return a `value' with the contents of (virtual or cooked) register
278 REGNUM as found in the specified FRAME. The register's type is
279 determined by register_type(). The value is not fetched. */
282 value_of_register_lazy (struct frame_info *frame, int regnum)
284 struct gdbarch *gdbarch = get_frame_arch (frame);
285 struct value *reg_val;
287 gdb_assert (regnum < (gdbarch_num_regs (gdbarch)
288 + gdbarch_num_pseudo_regs (gdbarch)));
290 /* We should have a valid (i.e. non-sentinel) frame. */
291 gdb_assert (frame_id_p (get_frame_id (frame)));
293 reg_val = allocate_value_lazy (register_type (gdbarch, regnum));
294 VALUE_LVAL (reg_val) = lval_register;
295 VALUE_REGNUM (reg_val) = regnum;
296 VALUE_FRAME_ID (reg_val) = get_frame_id (frame);
300 /* Given a pointer of type TYPE in target form in BUF, return the
301 address it represents. */
303 unsigned_pointer_to_address (struct gdbarch *gdbarch,
304 struct type *type, const gdb_byte *buf)
306 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
308 return extract_unsigned_integer (buf, TYPE_LENGTH (type), byte_order);
312 signed_pointer_to_address (struct gdbarch *gdbarch,
313 struct type *type, const gdb_byte *buf)
315 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
317 return extract_signed_integer (buf, TYPE_LENGTH (type), byte_order);
320 /* Given an address, store it as a pointer of type TYPE in target
323 unsigned_address_to_pointer (struct gdbarch *gdbarch, struct type *type,
324 gdb_byte *buf, CORE_ADDR addr)
326 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
328 store_unsigned_integer (buf, TYPE_LENGTH (type), byte_order, addr);
332 address_to_signed_pointer (struct gdbarch *gdbarch, struct type *type,
333 gdb_byte *buf, CORE_ADDR addr)
335 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
337 store_signed_integer (buf, TYPE_LENGTH (type), byte_order, addr);
340 /* Will calling read_var_value or locate_var_value on SYM end
341 up caring what frame it is being evaluated relative to? SYM must
344 symbol_read_needs_frame (struct symbol *sym)
346 if (SYMBOL_COMPUTED_OPS (sym) != NULL)
347 return SYMBOL_COMPUTED_OPS (sym)->read_needs_frame (sym);
349 switch (SYMBOL_CLASS (sym))
351 /* All cases listed explicitly so that gcc -Wall will detect it if
352 we failed to consider one. */
354 gdb_assert_not_reached (_("LOC_COMPUTED variable missing a method"));
359 case LOC_REGPARM_ADDR:
369 /* Getting the address of a label can be done independently of the block,
370 even if some *uses* of that address wouldn't work so well without
374 case LOC_CONST_BYTES:
376 case LOC_OPTIMIZED_OUT:
382 /* Private data to be used with minsym_lookup_iterator_cb. */
384 struct minsym_lookup_data
386 /* The name of the minimal symbol we are searching for. */
389 /* The field where the callback should store the minimal symbol
390 if found. It should be initialized to NULL before the search
392 struct bound_minimal_symbol result;
395 /* A callback function for gdbarch_iterate_over_objfiles_in_search_order.
396 It searches by name for a minimal symbol within the given OBJFILE.
397 The arguments are passed via CB_DATA, which in reality is a pointer
398 to struct minsym_lookup_data. */
401 minsym_lookup_iterator_cb (struct objfile *objfile, void *cb_data)
403 struct minsym_lookup_data *data = (struct minsym_lookup_data *) cb_data;
405 gdb_assert (data->result.minsym == NULL);
407 data->result = lookup_minimal_symbol (data->name, NULL, objfile);
409 /* The iterator should stop iff a match was found. */
410 return (data->result.minsym != NULL);
413 /* Given static link expression and the frame it lives in, look for the frame
414 the static links points to and return it. Return NULL if we could not find
417 static struct frame_info *
418 follow_static_link (struct frame_info *frame,
419 const struct dynamic_prop *static_link)
421 CORE_ADDR upper_frame_base;
423 if (!dwarf2_evaluate_property (static_link, frame, NULL, &upper_frame_base))
426 /* Now climb up the stack frame until we reach the frame we are interested
428 for (; frame != NULL; frame = get_prev_frame (frame))
430 struct symbol *framefunc = get_frame_function (frame);
432 /* Stacks can be quite deep: give the user a chance to stop this. */
435 /* If we don't know how to compute FRAME's base address, don't give up:
436 maybe the frame we are looking for is upper in the stace frame. */
437 if (framefunc != NULL
438 && SYMBOL_BLOCK_OPS (framefunc)->get_frame_base != NULL
439 && (SYMBOL_BLOCK_OPS (framefunc)->get_frame_base (framefunc, frame)
440 == upper_frame_base))
447 /* Assuming VAR is a symbol that can be reached from FRAME thanks to lexical
448 rules, look for the frame that is actually hosting VAR and return it. If,
449 for some reason, we found no such frame, return NULL.
451 This kind of computation is necessary to correctly handle lexically nested
454 Note that in some cases, we know what scope VAR comes from but we cannot
455 reach the specific frame that hosts the instance of VAR we are looking for.
456 For backward compatibility purposes (with old compilers), we then look for
457 the first frame that can host it. */
459 static struct frame_info *
460 get_hosting_frame (struct symbol *var, const struct block *var_block,
461 struct frame_info *frame)
463 const struct block *frame_block = NULL;
465 if (!symbol_read_needs_frame (var))
468 /* Some symbols for local variables have no block: this happens when they are
469 not produced by a debug information reader, for instance when GDB creates
470 synthetic symbols. Without block information, we must assume they are
471 local to FRAME. In this case, there is nothing to do. */
472 else if (var_block == NULL)
475 /* We currently assume that all symbols with a location list need a frame.
476 This is true in practice because selecting the location description
477 requires to compute the CFA, hence requires a frame. However we have
478 tests that embed global/static symbols with null location lists.
479 We want to get <optimized out> instead of <frame required> when evaluating
480 them so return a frame instead of raising an error. */
481 else if (var_block == block_global_block (var_block)
482 || var_block == block_static_block (var_block))
485 /* We have to handle the "my_func::my_local_var" notation. This requires us
486 to look for upper frames when we find no block for the current frame: here
487 and below, handle when frame_block == NULL. */
489 frame_block = get_frame_block (frame, NULL);
491 /* Climb up the call stack until reaching the frame we are looking for. */
492 while (frame != NULL && frame_block != var_block)
494 /* Stacks can be quite deep: give the user a chance to stop this. */
497 if (frame_block == NULL)
499 frame = get_prev_frame (frame);
502 frame_block = get_frame_block (frame, NULL);
505 /* If we failed to find the proper frame, fallback to the heuristic
507 else if (frame_block == block_global_block (frame_block))
513 /* Assuming we have a block for this frame: if we are at the function
514 level, the immediate upper lexical block is in an outer function:
515 follow the static link. */
516 else if (BLOCK_FUNCTION (frame_block))
518 const struct dynamic_prop *static_link
519 = block_static_link (frame_block);
520 int could_climb_up = 0;
522 if (static_link != NULL)
524 frame = follow_static_link (frame, static_link);
527 frame_block = get_frame_block (frame, NULL);
528 could_climb_up = frame_block != NULL;
539 /* We must be in some function nested lexical block. Just get the
540 outer block: both must share the same frame. */
541 frame_block = BLOCK_SUPERBLOCK (frame_block);
544 /* Old compilers may not provide a static link, or they may provide an
545 invalid one. For such cases, fallback on the old way to evaluate
546 non-local references: just climb up the call stack and pick the first
547 frame that contains the variable we are looking for. */
550 frame = block_innermost_frame (var_block);
553 if (BLOCK_FUNCTION (var_block)
554 && !block_inlined_p (var_block)
555 && SYMBOL_PRINT_NAME (BLOCK_FUNCTION (var_block)))
556 error (_("No frame is currently executing in block %s."),
557 SYMBOL_PRINT_NAME (BLOCK_FUNCTION (var_block)));
559 error (_("No frame is currently executing in specified"
567 /* A default implementation for the "la_read_var_value" hook in
568 the language vector which should work in most situations. */
571 default_read_var_value (struct symbol *var, const struct block *var_block,
572 struct frame_info *frame)
575 struct type *type = SYMBOL_TYPE (var);
578 /* Call check_typedef on our type to make sure that, if TYPE is
579 a TYPE_CODE_TYPEDEF, its length is set to the length of the target type
580 instead of zero. However, we do not replace the typedef type by the
581 target type, because we want to keep the typedef in order to be able to
582 set the returned value type description correctly. */
583 check_typedef (type);
585 if (symbol_read_needs_frame (var))
586 gdb_assert (frame != NULL);
589 frame = get_hosting_frame (var, var_block, frame);
591 if (SYMBOL_COMPUTED_OPS (var) != NULL)
592 return SYMBOL_COMPUTED_OPS (var)->read_variable (var, frame);
594 switch (SYMBOL_CLASS (var))
597 if (is_dynamic_type (type))
599 /* Value is a constant byte-sequence and needs no memory access. */
600 type = resolve_dynamic_type (type, NULL, /* Unused address. */ 0);
602 /* Put the constant back in target format. */
603 v = allocate_value (type);
604 store_signed_integer (value_contents_raw (v), TYPE_LENGTH (type),
605 gdbarch_byte_order (get_type_arch (type)),
606 (LONGEST) SYMBOL_VALUE (var));
607 VALUE_LVAL (v) = not_lval;
611 /* Put the constant back in target format. */
612 v = allocate_value (type);
613 if (overlay_debugging)
616 = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
617 SYMBOL_OBJ_SECTION (symbol_objfile (var),
620 store_typed_address (value_contents_raw (v), type, addr);
623 store_typed_address (value_contents_raw (v), type,
624 SYMBOL_VALUE_ADDRESS (var));
625 VALUE_LVAL (v) = not_lval;
628 case LOC_CONST_BYTES:
629 if (is_dynamic_type (type))
631 /* Value is a constant byte-sequence and needs no memory access. */
632 type = resolve_dynamic_type (type, NULL, /* Unused address. */ 0);
634 v = allocate_value (type);
635 memcpy (value_contents_raw (v), SYMBOL_VALUE_BYTES (var),
637 VALUE_LVAL (v) = not_lval;
641 if (overlay_debugging)
642 addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
643 SYMBOL_OBJ_SECTION (symbol_objfile (var),
646 addr = SYMBOL_VALUE_ADDRESS (var);
650 addr = get_frame_args_address (frame);
652 error (_("Unknown argument list address for `%s'."),
653 SYMBOL_PRINT_NAME (var));
654 addr += SYMBOL_VALUE (var);
662 argref = get_frame_args_address (frame);
664 error (_("Unknown argument list address for `%s'."),
665 SYMBOL_PRINT_NAME (var));
666 argref += SYMBOL_VALUE (var);
667 ref = value_at (lookup_pointer_type (type), argref);
668 addr = value_as_address (ref);
673 addr = get_frame_locals_address (frame);
674 addr += SYMBOL_VALUE (var);
678 error (_("Cannot look up value of a typedef `%s'."),
679 SYMBOL_PRINT_NAME (var));
683 if (overlay_debugging)
684 addr = symbol_overlayed_address
685 (BLOCK_START (SYMBOL_BLOCK_VALUE (var)),
686 SYMBOL_OBJ_SECTION (symbol_objfile (var), var));
688 addr = BLOCK_START (SYMBOL_BLOCK_VALUE (var));
692 case LOC_REGPARM_ADDR:
694 int regno = SYMBOL_REGISTER_OPS (var)
695 ->register_number (var, get_frame_arch (frame));
696 struct value *regval;
698 if (SYMBOL_CLASS (var) == LOC_REGPARM_ADDR)
700 regval = value_from_register (lookup_pointer_type (type),
705 error (_("Value of register variable not available for `%s'."),
706 SYMBOL_PRINT_NAME (var));
708 addr = value_as_address (regval);
712 regval = value_from_register (type, regno, frame);
715 error (_("Value of register variable not available for `%s'."),
716 SYMBOL_PRINT_NAME (var));
723 gdb_assert_not_reached (_("LOC_COMPUTED variable missing a method"));
727 struct minsym_lookup_data lookup_data;
728 struct minimal_symbol *msym;
729 struct obj_section *obj_section;
731 memset (&lookup_data, 0, sizeof (lookup_data));
732 lookup_data.name = SYMBOL_LINKAGE_NAME (var);
734 gdbarch_iterate_over_objfiles_in_search_order
736 minsym_lookup_iterator_cb, &lookup_data,
737 symbol_objfile (var));
738 msym = lookup_data.result.minsym;
740 /* If we can't find the minsym there's a problem in the symbol info.
741 The symbol exists in the debug info, but it's missing in the minsym
745 const char *flavour_name
746 = objfile_flavour_name (symbol_objfile (var));
748 /* We can't get here unless we've opened the file, so flavour_name
750 gdb_assert (flavour_name != NULL);
751 error (_("Missing %s symbol \"%s\"."),
752 flavour_name, SYMBOL_LINKAGE_NAME (var));
754 obj_section = MSYMBOL_OBJ_SECTION (lookup_data.result.objfile, msym);
755 /* Relocate address, unless there is no section or the variable is
757 if (obj_section == NULL
758 || (obj_section->the_bfd_section->flags & SEC_THREAD_LOCAL) != 0)
759 addr = MSYMBOL_VALUE_RAW_ADDRESS (msym);
761 addr = BMSYMBOL_VALUE_ADDRESS (lookup_data.result);
762 if (overlay_debugging)
763 addr = symbol_overlayed_address (addr, obj_section);
764 /* Determine address of TLS variable. */
766 && (obj_section->the_bfd_section->flags & SEC_THREAD_LOCAL) != 0)
767 addr = target_translate_tls_address (obj_section->objfile, addr);
771 case LOC_OPTIMIZED_OUT:
772 return allocate_optimized_out_value (type);
775 error (_("Cannot look up value of a botched symbol `%s'."),
776 SYMBOL_PRINT_NAME (var));
780 v = value_at_lazy (type, addr);
784 /* Calls VAR's language la_read_var_value hook with the given arguments. */
787 read_var_value (struct symbol *var, const struct block *var_block,
788 struct frame_info *frame)
790 const struct language_defn *lang = language_def (SYMBOL_LANGUAGE (var));
792 gdb_assert (lang != NULL);
793 gdb_assert (lang->la_read_var_value != NULL);
795 return lang->la_read_var_value (var, var_block, frame);
798 /* Install default attributes for register values. */
801 default_value_from_register (struct gdbarch *gdbarch, struct type *type,
802 int regnum, struct frame_id frame_id)
804 int len = TYPE_LENGTH (type);
805 struct value *value = allocate_value (type);
807 VALUE_LVAL (value) = lval_register;
808 VALUE_FRAME_ID (value) = frame_id;
809 VALUE_REGNUM (value) = regnum;
811 /* Any structure stored in more than one register will always be
812 an integral number of registers. Otherwise, you need to do
813 some fiddling with the last register copied here for little
815 if (gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG
816 && len < register_size (gdbarch, regnum))
817 /* Big-endian, and we want less than full size. */
818 set_value_offset (value, register_size (gdbarch, regnum) - len);
820 set_value_offset (value, 0);
825 /* VALUE must be an lval_register value. If regnum is the value's
826 associated register number, and len the length of the values type,
827 read one or more registers in FRAME, starting with register REGNUM,
828 until we've read LEN bytes.
830 If any of the registers we try to read are optimized out, then mark the
831 complete resulting value as optimized out. */
834 read_frame_register_value (struct value *value, struct frame_info *frame)
836 struct gdbarch *gdbarch = get_frame_arch (frame);
838 int reg_offset = value_offset (value);
839 int regnum = VALUE_REGNUM (value);
840 int len = type_length_units (check_typedef (value_type (value)));
842 gdb_assert (VALUE_LVAL (value) == lval_register);
844 /* Skip registers wholly inside of REG_OFFSET. */
845 while (reg_offset >= register_size (gdbarch, regnum))
847 reg_offset -= register_size (gdbarch, regnum);
854 struct value *regval = get_frame_register_value (frame, regnum);
855 int reg_len = type_length_units (value_type (regval)) - reg_offset;
857 /* If the register length is larger than the number of bytes
858 remaining to copy, then only copy the appropriate bytes. */
862 value_contents_copy (value, offset, regval, reg_offset, reg_len);
871 /* Return a value of type TYPE, stored in register REGNUM, in frame FRAME. */
874 value_from_register (struct type *type, int regnum, struct frame_info *frame)
876 struct gdbarch *gdbarch = get_frame_arch (frame);
877 struct type *type1 = check_typedef (type);
880 if (gdbarch_convert_register_p (gdbarch, regnum, type1))
882 int optim, unavail, ok;
884 /* The ISA/ABI need to something weird when obtaining the
885 specified value from this register. It might need to
886 re-order non-adjacent, starting with REGNUM (see MIPS and
887 i386). It might need to convert the [float] register into
888 the corresponding [integer] type (see Alpha). The assumption
889 is that gdbarch_register_to_value populates the entire value
890 including the location. */
891 v = allocate_value (type);
892 VALUE_LVAL (v) = lval_register;
893 VALUE_FRAME_ID (v) = get_frame_id (frame);
894 VALUE_REGNUM (v) = regnum;
895 ok = gdbarch_register_to_value (gdbarch, frame, regnum, type1,
896 value_contents_raw (v), &optim,
902 mark_value_bytes_optimized_out (v, 0, TYPE_LENGTH (type));
904 mark_value_bytes_unavailable (v, 0, TYPE_LENGTH (type));
909 /* Construct the value. */
910 v = gdbarch_value_from_register (gdbarch, type,
911 regnum, get_frame_id (frame));
914 read_frame_register_value (v, frame);
920 /* Return contents of register REGNUM in frame FRAME as address.
921 Will abort if register value is not available. */
924 address_from_register (int regnum, struct frame_info *frame)
926 struct gdbarch *gdbarch = get_frame_arch (frame);
927 struct type *type = builtin_type (gdbarch)->builtin_data_ptr;
931 /* This routine may be called during early unwinding, at a time
932 where the ID of FRAME is not yet known. Calling value_from_register
933 would therefore abort in get_frame_id. However, since we only need
934 a temporary value that is never used as lvalue, we actually do not
935 really need to set its VALUE_FRAME_ID. Therefore, we re-implement
936 the core of value_from_register, but use the null_frame_id. */
938 /* Some targets require a special conversion routine even for plain
939 pointer types. Avoid constructing a value object in those cases. */
940 if (gdbarch_convert_register_p (gdbarch, regnum, type))
942 gdb_byte *buf = (gdb_byte *) alloca (TYPE_LENGTH (type));
943 int optim, unavail, ok;
945 ok = gdbarch_register_to_value (gdbarch, frame, regnum, type,
946 buf, &optim, &unavail);
949 /* This function is used while computing a location expression.
950 Complain about the value being optimized out, rather than
951 letting value_as_address complain about some random register
952 the expression depends on not being saved. */
953 error_value_optimized_out ();
956 return unpack_long (type, buf);
959 value = gdbarch_value_from_register (gdbarch, type, regnum, null_frame_id);
960 read_frame_register_value (value, frame);
962 if (value_optimized_out (value))
964 /* This function is used while computing a location expression.
965 Complain about the value being optimized out, rather than
966 letting value_as_address complain about some random register
967 the expression depends on not being saved. */
968 error_value_optimized_out ();
971 result = value_as_address (value);
972 release_value (value);