1 /* Low level packing and unpacking of values for GDB, the GNU Debugger.
3 Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
4 1995, 1996, 1997, 1998, 1999, 2000, 2002, 2003, 2004, 2005, 2006
5 Free Software Foundation, Inc.
7 This file is part of GDB.
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 51 Franklin Street, Fifth Floor,
22 Boston, MA 02110-1301, USA. */
25 #include "gdb_string.h"
37 #include "gdb_assert.h"
41 /* Prototypes for exported functions. */
43 void _initialize_values (void);
47 /* Type of value; either not an lval, or one of the various
48 different possible kinds of lval. */
51 /* Is it modifiable? Only relevant if lval != not_lval. */
54 /* Location of value (if lval). */
57 /* If lval == lval_memory, this is the address in the inferior.
58 If lval == lval_register, this is the byte offset into the
59 registers structure. */
62 /* Pointer to internal variable. */
63 struct internalvar *internalvar;
66 /* Describes offset of a value within lval of a structure in bytes.
67 If lval == lval_memory, this is an offset to the address. If
68 lval == lval_register, this is a further offset from
69 location.address within the registers structure. Note also the
70 member embedded_offset below. */
73 /* Only used for bitfields; number of bits contained in them. */
76 /* Only used for bitfields; position of start of field. For
77 BITS_BIG_ENDIAN=0 targets, it is the position of the LSB. For
78 BITS_BIG_ENDIAN=1 targets, it is the position of the MSB. */
81 /* Frame register value is relative to. This will be described in
82 the lval enum above as "lval_register". */
83 struct frame_id frame_id;
85 /* Type of the value. */
88 /* If a value represents a C++ object, then the `type' field gives
89 the object's compile-time type. If the object actually belongs
90 to some class derived from `type', perhaps with other base
91 classes and additional members, then `type' is just a subobject
92 of the real thing, and the full object is probably larger than
95 If `type' is a dynamic class (i.e. one with a vtable), then GDB
96 can actually determine the object's run-time type by looking at
97 the run-time type information in the vtable. When this
98 information is available, we may elect to read in the entire
99 object, for several reasons:
101 - When printing the value, the user would probably rather see the
102 full object, not just the limited portion apparent from the
105 - If `type' has virtual base classes, then even printing `type'
106 alone may require reaching outside the `type' portion of the
107 object to wherever the virtual base class has been stored.
109 When we store the entire object, `enclosing_type' is the run-time
110 type -- the complete object -- and `embedded_offset' is the
111 offset of `type' within that larger type, in bytes. The
112 value_contents() macro takes `embedded_offset' into account, so
113 most GDB code continues to see the `type' portion of the value,
114 just as the inferior would.
116 If `type' is a pointer to an object, then `enclosing_type' is a
117 pointer to the object's run-time type, and `pointed_to_offset' is
118 the offset in bytes from the full object to the pointed-to object
119 -- that is, the value `embedded_offset' would have if we followed
120 the pointer and fetched the complete object. (I don't really see
121 the point. Why not just determine the run-time type when you
122 indirect, and avoid the special case? The contents don't matter
123 until you indirect anyway.)
125 If we're not doing anything fancy, `enclosing_type' is equal to
126 `type', and `embedded_offset' is zero, so everything works
128 struct type *enclosing_type;
130 int pointed_to_offset;
132 /* Values are stored in a chain, so that they can be deleted easily
133 over calls to the inferior. Values assigned to internal
134 variables or put into the value history are taken off this
138 /* Register number if the value is from a register. */
141 /* If zero, contents of this value are in the contents field. If
142 nonzero, contents are in inferior memory at address in the
143 location.address field plus the offset field (and the lval field
144 should be lval_memory).
146 WARNING: This field is used by the code which handles watchpoints
147 (see breakpoint.c) to decide whether a particular value can be
148 watched by hardware watchpoints. If the lazy flag is set for
149 some member of a value chain, it is assumed that this member of
150 the chain doesn't need to be watched as part of watching the
151 value itself. This is how GDB avoids watching the entire struct
152 or array when the user wants to watch a single struct member or
153 array element. If you ever change the way lazy flag is set and
154 reset, be sure to consider this use as well! */
157 /* If nonzero, this is the value of a variable which does not
158 actually exist in the program. */
161 /* Actual contents of the value. For use of this value; setting it
162 uses the stuff above. Not valid if lazy is nonzero. Target
163 byte-order. We force it to be aligned properly for any possible
164 value. Note that a value therefore extends beyond what is
168 gdb_byte contents[1];
169 DOUBLEST force_doublest_align;
170 LONGEST force_longest_align;
171 CORE_ADDR force_core_addr_align;
172 void *force_pointer_align;
174 /* Do not add any new members here -- contents above will trash
178 /* Prototypes for local functions. */
180 static void show_values (char *, int);
182 static void show_convenience (char *, int);
185 /* The value-history records all the values printed
186 by print commands during this session. Each chunk
187 records 60 consecutive values. The first chunk on
188 the chain records the most recent values.
189 The total number of values is in value_history_count. */
191 #define VALUE_HISTORY_CHUNK 60
193 struct value_history_chunk
195 struct value_history_chunk *next;
196 struct value *values[VALUE_HISTORY_CHUNK];
199 /* Chain of chunks now in use. */
201 static struct value_history_chunk *value_history_chain;
203 static int value_history_count; /* Abs number of last entry stored */
205 /* List of all value objects currently allocated
206 (except for those released by calls to release_value)
207 This is so they can be freed after each command. */
209 static struct value *all_values;
211 /* Allocate a value that has the correct length for type TYPE. */
214 allocate_value (struct type *type)
217 struct type *atype = check_typedef (type);
219 val = (struct value *) xzalloc (sizeof (struct value) + TYPE_LENGTH (atype));
220 val->next = all_values;
223 val->enclosing_type = type;
224 VALUE_LVAL (val) = not_lval;
225 VALUE_ADDRESS (val) = 0;
226 VALUE_FRAME_ID (val) = null_frame_id;
230 VALUE_REGNUM (val) = -1;
232 val->optimized_out = 0;
233 val->embedded_offset = 0;
234 val->pointed_to_offset = 0;
239 /* Allocate a value that has the correct length
240 for COUNT repetitions type TYPE. */
243 allocate_repeat_value (struct type *type, int count)
245 int low_bound = current_language->string_lower_bound; /* ??? */
246 /* FIXME-type-allocation: need a way to free this type when we are
248 struct type *range_type
249 = create_range_type ((struct type *) NULL, builtin_type_int,
250 low_bound, count + low_bound - 1);
251 /* FIXME-type-allocation: need a way to free this type when we are
253 return allocate_value (create_array_type ((struct type *) NULL,
257 /* Accessor methods. */
260 value_next (struct value *value)
266 value_type (struct value *value)
271 deprecated_set_value_type (struct value *value, struct type *type)
277 value_offset (struct value *value)
279 return value->offset;
282 set_value_offset (struct value *value, int offset)
284 value->offset = offset;
288 value_bitpos (struct value *value)
290 return value->bitpos;
293 set_value_bitpos (struct value *value, int bit)
299 value_bitsize (struct value *value)
301 return value->bitsize;
304 set_value_bitsize (struct value *value, int bit)
306 value->bitsize = bit;
310 value_contents_raw (struct value *value)
312 return value->aligner.contents + value->embedded_offset;
316 value_contents_all_raw (struct value *value)
318 return value->aligner.contents;
322 value_enclosing_type (struct value *value)
324 return value->enclosing_type;
328 value_contents_all (struct value *value)
331 value_fetch_lazy (value);
332 return value->aligner.contents;
336 value_lazy (struct value *value)
342 set_value_lazy (struct value *value, int val)
348 value_contents (struct value *value)
350 return value_contents_writeable (value);
354 value_contents_writeable (struct value *value)
357 value_fetch_lazy (value);
358 return value_contents_raw (value);
361 /* Return non-zero if VAL1 and VAL2 have the same contents. Note that
362 this function is different from value_equal; in C the operator ==
363 can return 0 even if the two values being compared are equal. */
366 value_contents_equal (struct value *val1, struct value *val2)
372 type1 = check_typedef (value_type (val1));
373 type2 = check_typedef (value_type (val2));
374 len = TYPE_LENGTH (type1);
375 if (len != TYPE_LENGTH (type2))
378 return (memcmp (value_contents (val1), value_contents (val2), len) == 0);
382 value_optimized_out (struct value *value)
384 return value->optimized_out;
388 set_value_optimized_out (struct value *value, int val)
390 value->optimized_out = val;
394 value_embedded_offset (struct value *value)
396 return value->embedded_offset;
400 set_value_embedded_offset (struct value *value, int val)
402 value->embedded_offset = val;
406 value_pointed_to_offset (struct value *value)
408 return value->pointed_to_offset;
412 set_value_pointed_to_offset (struct value *value, int val)
414 value->pointed_to_offset = val;
418 deprecated_value_lval_hack (struct value *value)
424 deprecated_value_address_hack (struct value *value)
426 return &value->location.address;
429 struct internalvar **
430 deprecated_value_internalvar_hack (struct value *value)
432 return &value->location.internalvar;
436 deprecated_value_frame_id_hack (struct value *value)
438 return &value->frame_id;
442 deprecated_value_regnum_hack (struct value *value)
444 return &value->regnum;
448 deprecated_value_modifiable (struct value *value)
450 return value->modifiable;
453 deprecated_set_value_modifiable (struct value *value, int modifiable)
455 value->modifiable = modifiable;
458 /* Return a mark in the value chain. All values allocated after the
459 mark is obtained (except for those released) are subject to being freed
460 if a subsequent value_free_to_mark is passed the mark. */
467 /* Free all values allocated since MARK was obtained by value_mark
468 (except for those released). */
470 value_free_to_mark (struct value *mark)
475 for (val = all_values; val && val != mark; val = next)
483 /* Free all the values that have been allocated (except for those released).
484 Called after each command, successful or not. */
487 free_all_values (void)
492 for (val = all_values; val; val = next)
501 /* Remove VAL from the chain all_values
502 so it will not be freed automatically. */
505 release_value (struct value *val)
509 if (all_values == val)
511 all_values = val->next;
515 for (v = all_values; v; v = v->next)
525 /* Release all values up to mark */
527 value_release_to_mark (struct value *mark)
532 for (val = next = all_values; next; next = next->next)
533 if (next->next == mark)
535 all_values = next->next;
543 /* Return a copy of the value ARG.
544 It contains the same contents, for same memory address,
545 but it's a different block of storage. */
548 value_copy (struct value *arg)
550 struct type *encl_type = value_enclosing_type (arg);
551 struct value *val = allocate_value (encl_type);
552 val->type = arg->type;
553 VALUE_LVAL (val) = VALUE_LVAL (arg);
554 val->location = arg->location;
555 val->offset = arg->offset;
556 val->bitpos = arg->bitpos;
557 val->bitsize = arg->bitsize;
558 VALUE_FRAME_ID (val) = VALUE_FRAME_ID (arg);
559 VALUE_REGNUM (val) = VALUE_REGNUM (arg);
560 val->lazy = arg->lazy;
561 val->optimized_out = arg->optimized_out;
562 val->embedded_offset = value_embedded_offset (arg);
563 val->pointed_to_offset = arg->pointed_to_offset;
564 val->modifiable = arg->modifiable;
565 if (!value_lazy (val))
567 memcpy (value_contents_all_raw (val), value_contents_all_raw (arg),
568 TYPE_LENGTH (value_enclosing_type (arg)));
574 /* Access to the value history. */
576 /* Record a new value in the value history.
577 Returns the absolute history index of the entry.
578 Result of -1 indicates the value was not saved; otherwise it is the
579 value history index of this new item. */
582 record_latest_value (struct value *val)
586 /* We don't want this value to have anything to do with the inferior anymore.
587 In particular, "set $1 = 50" should not affect the variable from which
588 the value was taken, and fast watchpoints should be able to assume that
589 a value on the value history never changes. */
590 if (value_lazy (val))
591 value_fetch_lazy (val);
592 /* We preserve VALUE_LVAL so that the user can find out where it was fetched
593 from. This is a bit dubious, because then *&$1 does not just return $1
594 but the current contents of that location. c'est la vie... */
598 /* Here we treat value_history_count as origin-zero
599 and applying to the value being stored now. */
601 i = value_history_count % VALUE_HISTORY_CHUNK;
604 struct value_history_chunk *new
605 = (struct value_history_chunk *)
606 xmalloc (sizeof (struct value_history_chunk));
607 memset (new->values, 0, sizeof new->values);
608 new->next = value_history_chain;
609 value_history_chain = new;
612 value_history_chain->values[i] = val;
614 /* Now we regard value_history_count as origin-one
615 and applying to the value just stored. */
617 return ++value_history_count;
620 /* Return a copy of the value in the history with sequence number NUM. */
623 access_value_history (int num)
625 struct value_history_chunk *chunk;
630 absnum += value_history_count;
635 error (_("The history is empty."));
637 error (_("There is only one value in the history."));
639 error (_("History does not go back to $$%d."), -num);
641 if (absnum > value_history_count)
642 error (_("History has not yet reached $%d."), absnum);
646 /* Now absnum is always absolute and origin zero. */
648 chunk = value_history_chain;
649 for (i = (value_history_count - 1) / VALUE_HISTORY_CHUNK - absnum / VALUE_HISTORY_CHUNK;
653 return value_copy (chunk->values[absnum % VALUE_HISTORY_CHUNK]);
657 show_values (char *num_exp, int from_tty)
665 /* "info history +" should print from the stored position.
666 "info history <exp>" should print around value number <exp>. */
667 if (num_exp[0] != '+' || num_exp[1] != '\0')
668 num = parse_and_eval_long (num_exp) - 5;
672 /* "info history" means print the last 10 values. */
673 num = value_history_count - 9;
679 for (i = num; i < num + 10 && i <= value_history_count; i++)
681 val = access_value_history (i);
682 printf_filtered (("$%d = "), i);
683 value_print (val, gdb_stdout, 0, Val_pretty_default);
684 printf_filtered (("\n"));
687 /* The next "info history +" should start after what we just printed. */
690 /* Hitting just return after this command should do the same thing as
691 "info history +". If num_exp is null, this is unnecessary, since
692 "info history +" is not useful after "info history". */
693 if (from_tty && num_exp)
700 /* Internal variables. These are variables within the debugger
701 that hold values assigned by debugger commands.
702 The user refers to them with a '$' prefix
703 that does not appear in the variable names stored internally. */
705 static struct internalvar *internalvars;
707 /* If the variable does not already exist create it and give it the value given.
708 If no value is given then the default is zero. */
710 init_if_undefined_command (char* args, int from_tty)
712 struct internalvar* intvar;
714 /* Parse the expression - this is taken from set_command(). */
715 struct expression *expr = parse_expression (args);
716 register struct cleanup *old_chain =
717 make_cleanup (free_current_contents, &expr);
719 /* Validate the expression.
720 Was the expression an assignment?
721 Or even an expression at all? */
722 if (expr->nelts == 0 || expr->elts[0].opcode != BINOP_ASSIGN)
723 error (_("Init-if-undefined requires an assignment expression."));
725 /* Extract the variable from the parsed expression.
726 In the case of an assign the lvalue will be in elts[1] and elts[2]. */
727 if (expr->elts[1].opcode != OP_INTERNALVAR)
728 error (_("The first parameter to init-if-undefined should be a GDB variable."));
729 intvar = expr->elts[2].internalvar;
731 /* Only evaluate the expression if the lvalue is void.
732 This may still fail if the expresssion is invalid. */
733 if (TYPE_CODE (value_type (intvar->value)) == TYPE_CODE_VOID)
734 evaluate_expression (expr);
736 do_cleanups (old_chain);
740 /* Look up an internal variable with name NAME. NAME should not
741 normally include a dollar sign.
743 If the specified internal variable does not exist,
744 one is created, with a void value. */
747 lookup_internalvar (char *name)
749 struct internalvar *var;
751 for (var = internalvars; var; var = var->next)
752 if (strcmp (var->name, name) == 0)
755 var = (struct internalvar *) xmalloc (sizeof (struct internalvar));
756 var->name = concat (name, (char *)NULL);
757 var->value = allocate_value (builtin_type_void);
758 var->endian = TARGET_BYTE_ORDER;
759 release_value (var->value);
760 var->next = internalvars;
766 value_of_internalvar (struct internalvar *var)
772 val = value_copy (var->value);
773 if (value_lazy (val))
774 value_fetch_lazy (val);
775 VALUE_LVAL (val) = lval_internalvar;
776 VALUE_INTERNALVAR (val) = var;
778 /* Values are always stored in the target's byte order. When connected to a
779 target this will most likely always be correct, so there's normally no
780 need to worry about it.
782 However, internal variables can be set up before the target endian is
783 known and so may become out of date. Fix it up before anybody sees.
785 Internal variables usually hold simple scalar values, and we can
786 correct those. More complex values (e.g. structures and floating
787 point types) are left alone, because they would be too complicated
790 if (var->endian != TARGET_BYTE_ORDER)
792 gdb_byte *array = value_contents_raw (val);
793 struct type *type = check_typedef (value_enclosing_type (val));
794 switch (TYPE_CODE (type))
798 /* Reverse the bytes. */
799 for (i = 0, j = TYPE_LENGTH (type) - 1; i < j; i++, j--)
813 set_internalvar_component (struct internalvar *var, int offset, int bitpos,
814 int bitsize, struct value *newval)
816 gdb_byte *addr = value_contents_writeable (var->value) + offset;
819 modify_field (addr, value_as_long (newval),
822 memcpy (addr, value_contents (newval), TYPE_LENGTH (value_type (newval)));
826 set_internalvar (struct internalvar *var, struct value *val)
828 struct value *newval;
830 newval = value_copy (val);
831 newval->modifiable = 1;
833 /* Force the value to be fetched from the target now, to avoid problems
834 later when this internalvar is referenced and the target is gone or
836 if (value_lazy (newval))
837 value_fetch_lazy (newval);
839 /* Begin code which must not call error(). If var->value points to
840 something free'd, an error() obviously leaves a dangling pointer.
841 But we also get a danling pointer if var->value points to
842 something in the value chain (i.e., before release_value is
843 called), because after the error free_all_values will get called before
847 var->endian = TARGET_BYTE_ORDER;
848 release_value (newval);
849 /* End code which must not call error(). */
853 internalvar_name (struct internalvar *var)
858 /* Update VALUE before discarding OBJFILE. COPIED_TYPES is used to
859 prevent cycles / duplicates. */
862 preserve_one_value (struct value *value, struct objfile *objfile,
865 if (TYPE_OBJFILE (value->type) == objfile)
866 value->type = copy_type_recursive (objfile, value->type, copied_types);
868 if (TYPE_OBJFILE (value->enclosing_type) == objfile)
869 value->enclosing_type = copy_type_recursive (objfile,
870 value->enclosing_type,
874 /* Update the internal variables and value history when OBJFILE is
875 discarded; we must copy the types out of the objfile. New global types
876 will be created for every convenience variable which currently points to
877 this objfile's types, and the convenience variables will be adjusted to
878 use the new global types. */
881 preserve_values (struct objfile *objfile)
884 struct value_history_chunk *cur;
885 struct internalvar *var;
888 /* Create the hash table. We allocate on the objfile's obstack, since
889 it is soon to be deleted. */
890 copied_types = create_copied_types_hash (objfile);
892 for (cur = value_history_chain; cur; cur = cur->next)
893 for (i = 0; i < VALUE_HISTORY_CHUNK; i++)
895 preserve_one_value (cur->values[i], objfile, copied_types);
897 for (var = internalvars; var; var = var->next)
898 preserve_one_value (var->value, objfile, copied_types);
900 htab_delete (copied_types);
904 show_convenience (char *ignore, int from_tty)
906 struct internalvar *var;
909 for (var = internalvars; var; var = var->next)
915 printf_filtered (("$%s = "), var->name);
916 value_print (value_of_internalvar (var), gdb_stdout,
917 0, Val_pretty_default);
918 printf_filtered (("\n"));
921 printf_unfiltered (_("\
922 No debugger convenience variables now defined.\n\
923 Convenience variables have names starting with \"$\";\n\
924 use \"set\" as in \"set $foo = 5\" to define them.\n"));
927 /* Extract a value as a C number (either long or double).
928 Knows how to convert fixed values to double, or
929 floating values to long.
930 Does not deallocate the value. */
933 value_as_long (struct value *val)
935 /* This coerces arrays and functions, which is necessary (e.g.
936 in disassemble_command). It also dereferences references, which
937 I suspect is the most logical thing to do. */
938 val = coerce_array (val);
939 return unpack_long (value_type (val), value_contents (val));
943 value_as_double (struct value *val)
948 foo = unpack_double (value_type (val), value_contents (val), &inv);
950 error (_("Invalid floating value found in program."));
953 /* Extract a value as a C pointer. Does not deallocate the value.
954 Note that val's type may not actually be a pointer; value_as_long
955 handles all the cases. */
957 value_as_address (struct value *val)
959 /* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
960 whether we want this to be true eventually. */
962 /* ADDR_BITS_REMOVE is wrong if we are being called for a
963 non-address (e.g. argument to "signal", "info break", etc.), or
964 for pointers to char, in which the low bits *are* significant. */
965 return ADDR_BITS_REMOVE (value_as_long (val));
968 /* There are several targets (IA-64, PowerPC, and others) which
969 don't represent pointers to functions as simply the address of
970 the function's entry point. For example, on the IA-64, a
971 function pointer points to a two-word descriptor, generated by
972 the linker, which contains the function's entry point, and the
973 value the IA-64 "global pointer" register should have --- to
974 support position-independent code. The linker generates
975 descriptors only for those functions whose addresses are taken.
977 On such targets, it's difficult for GDB to convert an arbitrary
978 function address into a function pointer; it has to either find
979 an existing descriptor for that function, or call malloc and
980 build its own. On some targets, it is impossible for GDB to
981 build a descriptor at all: the descriptor must contain a jump
982 instruction; data memory cannot be executed; and code memory
985 Upon entry to this function, if VAL is a value of type `function'
986 (that is, TYPE_CODE (VALUE_TYPE (val)) == TYPE_CODE_FUNC), then
987 VALUE_ADDRESS (val) is the address of the function. This is what
988 you'll get if you evaluate an expression like `main'. The call
989 to COERCE_ARRAY below actually does all the usual unary
990 conversions, which includes converting values of type `function'
991 to `pointer to function'. This is the challenging conversion
992 discussed above. Then, `unpack_long' will convert that pointer
993 back into an address.
995 So, suppose the user types `disassemble foo' on an architecture
996 with a strange function pointer representation, on which GDB
997 cannot build its own descriptors, and suppose further that `foo'
998 has no linker-built descriptor. The address->pointer conversion
999 will signal an error and prevent the command from running, even
1000 though the next step would have been to convert the pointer
1001 directly back into the same address.
1003 The following shortcut avoids this whole mess. If VAL is a
1004 function, just return its address directly. */
1005 if (TYPE_CODE (value_type (val)) == TYPE_CODE_FUNC
1006 || TYPE_CODE (value_type (val)) == TYPE_CODE_METHOD)
1007 return VALUE_ADDRESS (val);
1009 val = coerce_array (val);
1011 /* Some architectures (e.g. Harvard), map instruction and data
1012 addresses onto a single large unified address space. For
1013 instance: An architecture may consider a large integer in the
1014 range 0x10000000 .. 0x1000ffff to already represent a data
1015 addresses (hence not need a pointer to address conversion) while
1016 a small integer would still need to be converted integer to
1017 pointer to address. Just assume such architectures handle all
1018 integer conversions in a single function. */
1022 I think INTEGER_TO_ADDRESS is a good idea as proposed --- but we
1023 must admonish GDB hackers to make sure its behavior matches the
1024 compiler's, whenever possible.
1026 In general, I think GDB should evaluate expressions the same way
1027 the compiler does. When the user copies an expression out of
1028 their source code and hands it to a `print' command, they should
1029 get the same value the compiler would have computed. Any
1030 deviation from this rule can cause major confusion and annoyance,
1031 and needs to be justified carefully. In other words, GDB doesn't
1032 really have the freedom to do these conversions in clever and
1035 AndrewC pointed out that users aren't complaining about how GDB
1036 casts integers to pointers; they are complaining that they can't
1037 take an address from a disassembly listing and give it to `x/i'.
1038 This is certainly important.
1040 Adding an architecture method like integer_to_address() certainly
1041 makes it possible for GDB to "get it right" in all circumstances
1042 --- the target has complete control over how things get done, so
1043 people can Do The Right Thing for their target without breaking
1044 anyone else. The standard doesn't specify how integers get
1045 converted to pointers; usually, the ABI doesn't either, but
1046 ABI-specific code is a more reasonable place to handle it. */
1048 if (TYPE_CODE (value_type (val)) != TYPE_CODE_PTR
1049 && TYPE_CODE (value_type (val)) != TYPE_CODE_REF
1050 && gdbarch_integer_to_address_p (current_gdbarch))
1051 return gdbarch_integer_to_address (current_gdbarch, value_type (val),
1052 value_contents (val));
1054 return unpack_long (value_type (val), value_contents (val));
1058 /* Unpack raw data (copied from debugee, target byte order) at VALADDR
1059 as a long, or as a double, assuming the raw data is described
1060 by type TYPE. Knows how to convert different sizes of values
1061 and can convert between fixed and floating point. We don't assume
1062 any alignment for the raw data. Return value is in host byte order.
1064 If you want functions and arrays to be coerced to pointers, and
1065 references to be dereferenced, call value_as_long() instead.
1067 C++: It is assumed that the front-end has taken care of
1068 all matters concerning pointers to members. A pointer
1069 to member which reaches here is considered to be equivalent
1070 to an INT (or some size). After all, it is only an offset. */
1073 unpack_long (struct type *type, const gdb_byte *valaddr)
1075 enum type_code code = TYPE_CODE (type);
1076 int len = TYPE_LENGTH (type);
1077 int nosign = TYPE_UNSIGNED (type);
1079 if (current_language->la_language == language_scm
1080 && is_scmvalue_type (type))
1081 return scm_unpack (type, valaddr, TYPE_CODE_INT);
1085 case TYPE_CODE_TYPEDEF:
1086 return unpack_long (check_typedef (type), valaddr);
1087 case TYPE_CODE_ENUM:
1088 case TYPE_CODE_FLAGS:
1089 case TYPE_CODE_BOOL:
1091 case TYPE_CODE_CHAR:
1092 case TYPE_CODE_RANGE:
1093 case TYPE_CODE_MEMBERPTR:
1095 return extract_unsigned_integer (valaddr, len);
1097 return extract_signed_integer (valaddr, len);
1100 return extract_typed_floating (valaddr, type);
1104 /* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
1105 whether we want this to be true eventually. */
1106 return extract_typed_address (valaddr, type);
1109 error (_("Value can't be converted to integer."));
1111 return 0; /* Placate lint. */
1114 /* Return a double value from the specified type and address.
1115 INVP points to an int which is set to 0 for valid value,
1116 1 for invalid value (bad float format). In either case,
1117 the returned double is OK to use. Argument is in target
1118 format, result is in host format. */
1121 unpack_double (struct type *type, const gdb_byte *valaddr, int *invp)
1123 enum type_code code;
1127 *invp = 0; /* Assume valid. */
1128 CHECK_TYPEDEF (type);
1129 code = TYPE_CODE (type);
1130 len = TYPE_LENGTH (type);
1131 nosign = TYPE_UNSIGNED (type);
1132 if (code == TYPE_CODE_FLT)
1134 /* NOTE: cagney/2002-02-19: There was a test here to see if the
1135 floating-point value was valid (using the macro
1136 INVALID_FLOAT). That test/macro have been removed.
1138 It turns out that only the VAX defined this macro and then
1139 only in a non-portable way. Fixing the portability problem
1140 wouldn't help since the VAX floating-point code is also badly
1141 bit-rotten. The target needs to add definitions for the
1142 methods TARGET_FLOAT_FORMAT and TARGET_DOUBLE_FORMAT - these
1143 exactly describe the target floating-point format. The
1144 problem here is that the corresponding floatformat_vax_f and
1145 floatformat_vax_d values these methods should be set to are
1146 also not defined either. Oops!
1148 Hopefully someone will add both the missing floatformat
1149 definitions and the new cases for floatformat_is_valid (). */
1151 if (!floatformat_is_valid (floatformat_from_type (type), valaddr))
1157 return extract_typed_floating (valaddr, type);
1161 /* Unsigned -- be sure we compensate for signed LONGEST. */
1162 return (ULONGEST) unpack_long (type, valaddr);
1166 /* Signed -- we are OK with unpack_long. */
1167 return unpack_long (type, valaddr);
1171 /* Unpack raw data (copied from debugee, target byte order) at VALADDR
1172 as a CORE_ADDR, assuming the raw data is described by type TYPE.
1173 We don't assume any alignment for the raw data. Return value is in
1176 If you want functions and arrays to be coerced to pointers, and
1177 references to be dereferenced, call value_as_address() instead.
1179 C++: It is assumed that the front-end has taken care of
1180 all matters concerning pointers to members. A pointer
1181 to member which reaches here is considered to be equivalent
1182 to an INT (or some size). After all, it is only an offset. */
1185 unpack_pointer (struct type *type, const gdb_byte *valaddr)
1187 /* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
1188 whether we want this to be true eventually. */
1189 return unpack_long (type, valaddr);
1193 /* Get the value of the FIELDN'th field (which must be static) of
1194 TYPE. Return NULL if the field doesn't exist or has been
1198 value_static_field (struct type *type, int fieldno)
1200 struct value *retval;
1202 if (TYPE_FIELD_STATIC_HAS_ADDR (type, fieldno))
1204 retval = value_at (TYPE_FIELD_TYPE (type, fieldno),
1205 TYPE_FIELD_STATIC_PHYSADDR (type, fieldno));
1209 char *phys_name = TYPE_FIELD_STATIC_PHYSNAME (type, fieldno);
1210 struct symbol *sym = lookup_symbol (phys_name, 0, VAR_DOMAIN, 0, NULL);
1213 /* With some compilers, e.g. HP aCC, static data members are reported
1214 as non-debuggable symbols */
1215 struct minimal_symbol *msym = lookup_minimal_symbol (phys_name, NULL, NULL);
1220 retval = value_at (TYPE_FIELD_TYPE (type, fieldno),
1221 SYMBOL_VALUE_ADDRESS (msym));
1226 /* SYM should never have a SYMBOL_CLASS which will require
1227 read_var_value to use the FRAME parameter. */
1228 if (symbol_read_needs_frame (sym))
1229 warning (_("static field's value depends on the current "
1230 "frame - bad debug info?"));
1231 retval = read_var_value (sym, NULL);
1233 if (retval && VALUE_LVAL (retval) == lval_memory)
1234 SET_FIELD_PHYSADDR (TYPE_FIELD (type, fieldno),
1235 VALUE_ADDRESS (retval));
1240 /* Change the enclosing type of a value object VAL to NEW_ENCL_TYPE.
1241 You have to be careful here, since the size of the data area for the value
1242 is set by the length of the enclosing type. So if NEW_ENCL_TYPE is bigger
1243 than the old enclosing type, you have to allocate more space for the data.
1244 The return value is a pointer to the new version of this value structure. */
1247 value_change_enclosing_type (struct value *val, struct type *new_encl_type)
1249 if (TYPE_LENGTH (new_encl_type) <= TYPE_LENGTH (value_enclosing_type (val)))
1251 val->enclosing_type = new_encl_type;
1256 struct value *new_val;
1259 new_val = (struct value *) xrealloc (val, sizeof (struct value) + TYPE_LENGTH (new_encl_type));
1261 new_val->enclosing_type = new_encl_type;
1263 /* We have to make sure this ends up in the same place in the value
1264 chain as the original copy, so it's clean-up behavior is the same.
1265 If the value has been released, this is a waste of time, but there
1266 is no way to tell that in advance, so... */
1268 if (val != all_values)
1270 for (prev = all_values; prev != NULL; prev = prev->next)
1272 if (prev->next == val)
1274 prev->next = new_val;
1284 /* Given a value ARG1 (offset by OFFSET bytes)
1285 of a struct or union type ARG_TYPE,
1286 extract and return the value of one of its (non-static) fields.
1287 FIELDNO says which field. */
1290 value_primitive_field (struct value *arg1, int offset,
1291 int fieldno, struct type *arg_type)
1296 CHECK_TYPEDEF (arg_type);
1297 type = TYPE_FIELD_TYPE (arg_type, fieldno);
1299 /* Handle packed fields */
1301 if (TYPE_FIELD_BITSIZE (arg_type, fieldno))
1303 v = value_from_longest (type,
1304 unpack_field_as_long (arg_type,
1305 value_contents (arg1)
1308 v->bitpos = TYPE_FIELD_BITPOS (arg_type, fieldno) % 8;
1309 v->bitsize = TYPE_FIELD_BITSIZE (arg_type, fieldno);
1310 v->offset = value_offset (arg1) + offset
1311 + TYPE_FIELD_BITPOS (arg_type, fieldno) / 8;
1313 else if (fieldno < TYPE_N_BASECLASSES (arg_type))
1315 /* This field is actually a base subobject, so preserve the
1316 entire object's contents for later references to virtual
1318 v = allocate_value (value_enclosing_type (arg1));
1320 if (value_lazy (arg1))
1321 set_value_lazy (v, 1);
1323 memcpy (value_contents_all_raw (v), value_contents_all_raw (arg1),
1324 TYPE_LENGTH (value_enclosing_type (arg1)));
1325 v->offset = value_offset (arg1);
1326 v->embedded_offset = (offset + value_embedded_offset (arg1)
1327 + TYPE_FIELD_BITPOS (arg_type, fieldno) / 8);
1331 /* Plain old data member */
1332 offset += TYPE_FIELD_BITPOS (arg_type, fieldno) / 8;
1333 v = allocate_value (type);
1334 if (value_lazy (arg1))
1335 set_value_lazy (v, 1);
1337 memcpy (value_contents_raw (v),
1338 value_contents_raw (arg1) + offset,
1339 TYPE_LENGTH (type));
1340 v->offset = (value_offset (arg1) + offset
1341 + value_embedded_offset (arg1));
1343 VALUE_LVAL (v) = VALUE_LVAL (arg1);
1344 if (VALUE_LVAL (arg1) == lval_internalvar)
1345 VALUE_LVAL (v) = lval_internalvar_component;
1346 VALUE_ADDRESS (v) = VALUE_ADDRESS (arg1);
1347 VALUE_REGNUM (v) = VALUE_REGNUM (arg1);
1348 VALUE_FRAME_ID (v) = VALUE_FRAME_ID (arg1);
1349 /* VALUE_OFFSET (v) = VALUE_OFFSET (arg1) + offset
1350 + TYPE_FIELD_BITPOS (arg_type, fieldno) / 8; */
1354 /* Given a value ARG1 of a struct or union type,
1355 extract and return the value of one of its (non-static) fields.
1356 FIELDNO says which field. */
1359 value_field (struct value *arg1, int fieldno)
1361 return value_primitive_field (arg1, 0, fieldno, value_type (arg1));
1364 /* Return a non-virtual function as a value.
1365 F is the list of member functions which contains the desired method.
1366 J is an index into F which provides the desired method.
1368 We only use the symbol for its address, so be happy with either a
1369 full symbol or a minimal symbol.
1373 value_fn_field (struct value **arg1p, struct fn_field *f, int j, struct type *type,
1377 struct type *ftype = TYPE_FN_FIELD_TYPE (f, j);
1378 char *physname = TYPE_FN_FIELD_PHYSNAME (f, j);
1380 struct minimal_symbol *msym;
1382 sym = lookup_symbol (physname, 0, VAR_DOMAIN, 0, NULL);
1389 gdb_assert (sym == NULL);
1390 msym = lookup_minimal_symbol (physname, NULL, NULL);
1395 v = allocate_value (ftype);
1398 VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (sym));
1402 VALUE_ADDRESS (v) = SYMBOL_VALUE_ADDRESS (msym);
1407 if (type != value_type (*arg1p))
1408 *arg1p = value_ind (value_cast (lookup_pointer_type (type),
1409 value_addr (*arg1p)));
1411 /* Move the `this' pointer according to the offset.
1412 VALUE_OFFSET (*arg1p) += offset;
1420 /* Unpack a field FIELDNO of the specified TYPE, from the anonymous object at
1423 Extracting bits depends on endianness of the machine. Compute the
1424 number of least significant bits to discard. For big endian machines,
1425 we compute the total number of bits in the anonymous object, subtract
1426 off the bit count from the MSB of the object to the MSB of the
1427 bitfield, then the size of the bitfield, which leaves the LSB discard
1428 count. For little endian machines, the discard count is simply the
1429 number of bits from the LSB of the anonymous object to the LSB of the
1432 If the field is signed, we also do sign extension. */
1435 unpack_field_as_long (struct type *type, const gdb_byte *valaddr, int fieldno)
1439 int bitpos = TYPE_FIELD_BITPOS (type, fieldno);
1440 int bitsize = TYPE_FIELD_BITSIZE (type, fieldno);
1442 struct type *field_type;
1444 val = extract_unsigned_integer (valaddr + bitpos / 8, sizeof (val));
1445 field_type = TYPE_FIELD_TYPE (type, fieldno);
1446 CHECK_TYPEDEF (field_type);
1448 /* Extract bits. See comment above. */
1450 if (BITS_BIG_ENDIAN)
1451 lsbcount = (sizeof val * 8 - bitpos % 8 - bitsize);
1453 lsbcount = (bitpos % 8);
1456 /* If the field does not entirely fill a LONGEST, then zero the sign bits.
1457 If the field is signed, and is negative, then sign extend. */
1459 if ((bitsize > 0) && (bitsize < 8 * (int) sizeof (val)))
1461 valmask = (((ULONGEST) 1) << bitsize) - 1;
1463 if (!TYPE_UNSIGNED (field_type))
1465 if (val & (valmask ^ (valmask >> 1)))
1474 /* Modify the value of a bitfield. ADDR points to a block of memory in
1475 target byte order; the bitfield starts in the byte pointed to. FIELDVAL
1476 is the desired value of the field, in host byte order. BITPOS and BITSIZE
1477 indicate which bits (in target bit order) comprise the bitfield.
1478 Requires 0 < BITSIZE <= lbits, 0 <= BITPOS+BITSIZE <= lbits, and
1479 0 <= BITPOS, where lbits is the size of a LONGEST in bits. */
1482 modify_field (gdb_byte *addr, LONGEST fieldval, int bitpos, int bitsize)
1485 ULONGEST mask = (ULONGEST) -1 >> (8 * sizeof (ULONGEST) - bitsize);
1487 /* If a negative fieldval fits in the field in question, chop
1488 off the sign extension bits. */
1489 if ((~fieldval & ~(mask >> 1)) == 0)
1492 /* Warn if value is too big to fit in the field in question. */
1493 if (0 != (fieldval & ~mask))
1495 /* FIXME: would like to include fieldval in the message, but
1496 we don't have a sprintf_longest. */
1497 warning (_("Value does not fit in %d bits."), bitsize);
1499 /* Truncate it, otherwise adjoining fields may be corrupted. */
1503 oword = extract_unsigned_integer (addr, sizeof oword);
1505 /* Shifting for bit field depends on endianness of the target machine. */
1506 if (BITS_BIG_ENDIAN)
1507 bitpos = sizeof (oword) * 8 - bitpos - bitsize;
1509 oword &= ~(mask << bitpos);
1510 oword |= fieldval << bitpos;
1512 store_unsigned_integer (addr, sizeof oword, oword);
1515 /* Convert C numbers into newly allocated values */
1518 value_from_longest (struct type *type, LONGEST num)
1520 struct value *val = allocate_value (type);
1521 enum type_code code;
1524 code = TYPE_CODE (type);
1525 len = TYPE_LENGTH (type);
1529 case TYPE_CODE_TYPEDEF:
1530 type = check_typedef (type);
1533 case TYPE_CODE_CHAR:
1534 case TYPE_CODE_ENUM:
1535 case TYPE_CODE_FLAGS:
1536 case TYPE_CODE_BOOL:
1537 case TYPE_CODE_RANGE:
1538 case TYPE_CODE_MEMBERPTR:
1539 store_signed_integer (value_contents_raw (val), len, num);
1544 store_typed_address (value_contents_raw (val), type, (CORE_ADDR) num);
1548 error (_("Unexpected type (%d) encountered for integer constant."), code);
1554 /* Create a value representing a pointer of type TYPE to the address
1557 value_from_pointer (struct type *type, CORE_ADDR addr)
1559 struct value *val = allocate_value (type);
1560 store_typed_address (value_contents_raw (val), type, addr);
1565 /* Create a value for a string constant to be stored locally
1566 (not in the inferior's memory space, but in GDB memory).
1567 This is analogous to value_from_longest, which also does not
1568 use inferior memory. String shall NOT contain embedded nulls. */
1571 value_from_string (char *ptr)
1574 int len = strlen (ptr);
1575 int lowbound = current_language->string_lower_bound;
1576 struct type *string_char_type;
1577 struct type *rangetype;
1578 struct type *stringtype;
1580 rangetype = create_range_type ((struct type *) NULL,
1582 lowbound, len + lowbound - 1);
1583 string_char_type = language_string_char_type (current_language,
1585 stringtype = create_array_type ((struct type *) NULL,
1588 val = allocate_value (stringtype);
1589 memcpy (value_contents_raw (val), ptr, len);
1594 value_from_double (struct type *type, DOUBLEST num)
1596 struct value *val = allocate_value (type);
1597 struct type *base_type = check_typedef (type);
1598 enum type_code code = TYPE_CODE (base_type);
1599 int len = TYPE_LENGTH (base_type);
1601 if (code == TYPE_CODE_FLT)
1603 store_typed_floating (value_contents_raw (val), base_type, num);
1606 error (_("Unexpected type encountered for floating constant."));
1612 coerce_ref (struct value *arg)
1614 struct type *value_type_arg_tmp = check_typedef (value_type (arg));
1615 if (TYPE_CODE (value_type_arg_tmp) == TYPE_CODE_REF)
1616 arg = value_at_lazy (TYPE_TARGET_TYPE (value_type_arg_tmp),
1617 unpack_pointer (value_type (arg),
1618 value_contents (arg)));
1623 coerce_array (struct value *arg)
1625 arg = coerce_ref (arg);
1626 if (current_language->c_style_arrays
1627 && TYPE_CODE (value_type (arg)) == TYPE_CODE_ARRAY)
1628 arg = value_coerce_array (arg);
1629 if (TYPE_CODE (value_type (arg)) == TYPE_CODE_FUNC)
1630 arg = value_coerce_function (arg);
1635 coerce_number (struct value *arg)
1637 arg = coerce_array (arg);
1638 arg = coerce_enum (arg);
1643 coerce_enum (struct value *arg)
1645 if (TYPE_CODE (check_typedef (value_type (arg))) == TYPE_CODE_ENUM)
1646 arg = value_cast (builtin_type_unsigned_int, arg);
1651 /* Should we use DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS instead of
1652 EXTRACT_RETURN_VALUE? GCC_P is true if compiled with gcc and TYPE
1653 is the type (which is known to be struct, union or array).
1655 On most machines, the struct convention is used unless we are
1656 using gcc and the type is of a special size. */
1657 /* As of about 31 Mar 93, GCC was changed to be compatible with the
1658 native compiler. GCC 2.3.3 was the last release that did it the
1659 old way. Since gcc2_compiled was not changed, we have no
1660 way to correctly win in all cases, so we just do the right thing
1661 for gcc1 and for gcc2 after this change. Thus it loses for gcc
1662 2.0-2.3.3. This is somewhat unfortunate, but changing gcc2_compiled
1663 would cause more chaos than dealing with some struct returns being
1665 /* NOTE: cagney/2004-06-13: Deleted check for "gcc_p". GCC 1.x is
1669 generic_use_struct_convention (int gcc_p, struct type *value_type)
1671 return !(TYPE_LENGTH (value_type) == 1
1672 || TYPE_LENGTH (value_type) == 2
1673 || TYPE_LENGTH (value_type) == 4
1674 || TYPE_LENGTH (value_type) == 8);
1677 /* Return true if the function returning the specified type is using
1678 the convention of returning structures in memory (passing in the
1679 address as a hidden first parameter). GCC_P is nonzero if compiled
1683 using_struct_return (struct type *value_type, int gcc_p)
1685 enum type_code code = TYPE_CODE (value_type);
1687 if (code == TYPE_CODE_ERROR)
1688 error (_("Function return type unknown."));
1690 if (code == TYPE_CODE_VOID)
1691 /* A void return value is never in memory. See also corresponding
1692 code in "print_return_value". */
1695 /* Probe the architecture for the return-value convention. */
1696 return (gdbarch_return_value (current_gdbarch, value_type,
1698 != RETURN_VALUE_REGISTER_CONVENTION);
1702 _initialize_values (void)
1704 add_cmd ("convenience", no_class, show_convenience, _("\
1705 Debugger convenience (\"$foo\") variables.\n\
1706 These variables are created when you assign them values;\n\
1707 thus, \"print $foo=1\" gives \"$foo\" the value 1. Values may be any type.\n\
1709 A few convenience variables are given values automatically:\n\
1710 \"$_\"holds the last address examined with \"x\" or \"info lines\",\n\
1711 \"$__\" holds the contents of the last address examined with \"x\"."),
1714 add_cmd ("values", no_class, show_values,
1715 _("Elements of value history around item number IDX (or last ten)."),
1718 add_com ("init-if-undefined", class_vars, init_if_undefined_command, _("\
1719 Initialize a convenience variable if necessary.\n\
1720 init-if-undefined VARIABLE = EXPRESSION\n\
1721 Set an internal VARIABLE to the result of the EXPRESSION if it does not\n\
1722 exist or does not contain a value. The EXPRESSION is not evaluated if the\n\
1723 VARIABLE is already initialized."));