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 VALUE_ADDRESS (val
) = VALUE_ADDRESS (arg
);
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 release_value (var
->value
);
759 var
->next
= internalvars
;
765 value_of_internalvar (struct internalvar
*var
)
769 val
= value_copy (var
->value
);
770 if (value_lazy (val
))
771 value_fetch_lazy (val
);
772 VALUE_LVAL (val
) = lval_internalvar
;
773 VALUE_INTERNALVAR (val
) = var
;
778 set_internalvar_component (struct internalvar
*var
, int offset
, int bitpos
,
779 int bitsize
, struct value
*newval
)
781 gdb_byte
*addr
= value_contents_writeable (var
->value
) + offset
;
784 modify_field (addr
, value_as_long (newval
),
787 memcpy (addr
, value_contents (newval
), TYPE_LENGTH (value_type (newval
)));
791 set_internalvar (struct internalvar
*var
, struct value
*val
)
793 struct value
*newval
;
795 newval
= value_copy (val
);
796 newval
->modifiable
= 1;
798 /* Force the value to be fetched from the target now, to avoid problems
799 later when this internalvar is referenced and the target is gone or
801 if (value_lazy (newval
))
802 value_fetch_lazy (newval
);
804 /* Begin code which must not call error(). If var->value points to
805 something free'd, an error() obviously leaves a dangling pointer.
806 But we also get a danling pointer if var->value points to
807 something in the value chain (i.e., before release_value is
808 called), because after the error free_all_values will get called before
812 release_value (newval
);
813 /* End code which must not call error(). */
817 internalvar_name (struct internalvar
*var
)
822 /* Update VALUE before discarding OBJFILE. COPIED_TYPES is used to
823 prevent cycles / duplicates. */
826 preserve_one_value (struct value
*value
, struct objfile
*objfile
,
829 if (TYPE_OBJFILE (value
->type
) == objfile
)
830 value
->type
= copy_type_recursive (objfile
, value
->type
, copied_types
);
832 if (TYPE_OBJFILE (value
->enclosing_type
) == objfile
)
833 value
->enclosing_type
= copy_type_recursive (objfile
,
834 value
->enclosing_type
,
838 /* Update the internal variables and value history when OBJFILE is
839 discarded; we must copy the types out of the objfile. New global types
840 will be created for every convenience variable which currently points to
841 this objfile's types, and the convenience variables will be adjusted to
842 use the new global types. */
845 preserve_values (struct objfile
*objfile
)
848 struct value_history_chunk
*cur
;
849 struct internalvar
*var
;
852 /* Create the hash table. We allocate on the objfile's obstack, since
853 it is soon to be deleted. */
854 copied_types
= create_copied_types_hash (objfile
);
856 for (cur
= value_history_chain
; cur
; cur
= cur
->next
)
857 for (i
= 0; i
< VALUE_HISTORY_CHUNK
; i
++)
859 preserve_one_value (cur
->values
[i
], objfile
, copied_types
);
861 for (var
= internalvars
; var
; var
= var
->next
)
862 preserve_one_value (var
->value
, objfile
, copied_types
);
864 htab_delete (copied_types
);
868 show_convenience (char *ignore
, int from_tty
)
870 struct internalvar
*var
;
873 for (var
= internalvars
; var
; var
= var
->next
)
879 printf_filtered (("$%s = "), var
->name
);
880 value_print (var
->value
, gdb_stdout
, 0, Val_pretty_default
);
881 printf_filtered (("\n"));
884 printf_unfiltered (_("\
885 No debugger convenience variables now defined.\n\
886 Convenience variables have names starting with \"$\";\n\
887 use \"set\" as in \"set $foo = 5\" to define them.\n"));
890 /* Extract a value as a C number (either long or double).
891 Knows how to convert fixed values to double, or
892 floating values to long.
893 Does not deallocate the value. */
896 value_as_long (struct value
*val
)
898 /* This coerces arrays and functions, which is necessary (e.g.
899 in disassemble_command). It also dereferences references, which
900 I suspect is the most logical thing to do. */
901 val
= coerce_array (val
);
902 return unpack_long (value_type (val
), value_contents (val
));
906 value_as_double (struct value
*val
)
911 foo
= unpack_double (value_type (val
), value_contents (val
), &inv
);
913 error (_("Invalid floating value found in program."));
916 /* Extract a value as a C pointer. Does not deallocate the value.
917 Note that val's type may not actually be a pointer; value_as_long
918 handles all the cases. */
920 value_as_address (struct value
*val
)
922 /* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
923 whether we want this to be true eventually. */
925 /* ADDR_BITS_REMOVE is wrong if we are being called for a
926 non-address (e.g. argument to "signal", "info break", etc.), or
927 for pointers to char, in which the low bits *are* significant. */
928 return ADDR_BITS_REMOVE (value_as_long (val
));
931 /* There are several targets (IA-64, PowerPC, and others) which
932 don't represent pointers to functions as simply the address of
933 the function's entry point. For example, on the IA-64, a
934 function pointer points to a two-word descriptor, generated by
935 the linker, which contains the function's entry point, and the
936 value the IA-64 "global pointer" register should have --- to
937 support position-independent code. The linker generates
938 descriptors only for those functions whose addresses are taken.
940 On such targets, it's difficult for GDB to convert an arbitrary
941 function address into a function pointer; it has to either find
942 an existing descriptor for that function, or call malloc and
943 build its own. On some targets, it is impossible for GDB to
944 build a descriptor at all: the descriptor must contain a jump
945 instruction; data memory cannot be executed; and code memory
948 Upon entry to this function, if VAL is a value of type `function'
949 (that is, TYPE_CODE (VALUE_TYPE (val)) == TYPE_CODE_FUNC), then
950 VALUE_ADDRESS (val) is the address of the function. This is what
951 you'll get if you evaluate an expression like `main'. The call
952 to COERCE_ARRAY below actually does all the usual unary
953 conversions, which includes converting values of type `function'
954 to `pointer to function'. This is the challenging conversion
955 discussed above. Then, `unpack_long' will convert that pointer
956 back into an address.
958 So, suppose the user types `disassemble foo' on an architecture
959 with a strange function pointer representation, on which GDB
960 cannot build its own descriptors, and suppose further that `foo'
961 has no linker-built descriptor. The address->pointer conversion
962 will signal an error and prevent the command from running, even
963 though the next step would have been to convert the pointer
964 directly back into the same address.
966 The following shortcut avoids this whole mess. If VAL is a
967 function, just return its address directly. */
968 if (TYPE_CODE (value_type (val
)) == TYPE_CODE_FUNC
969 || TYPE_CODE (value_type (val
)) == TYPE_CODE_METHOD
)
970 return VALUE_ADDRESS (val
);
972 val
= coerce_array (val
);
974 /* Some architectures (e.g. Harvard), map instruction and data
975 addresses onto a single large unified address space. For
976 instance: An architecture may consider a large integer in the
977 range 0x10000000 .. 0x1000ffff to already represent a data
978 addresses (hence not need a pointer to address conversion) while
979 a small integer would still need to be converted integer to
980 pointer to address. Just assume such architectures handle all
981 integer conversions in a single function. */
985 I think INTEGER_TO_ADDRESS is a good idea as proposed --- but we
986 must admonish GDB hackers to make sure its behavior matches the
987 compiler's, whenever possible.
989 In general, I think GDB should evaluate expressions the same way
990 the compiler does. When the user copies an expression out of
991 their source code and hands it to a `print' command, they should
992 get the same value the compiler would have computed. Any
993 deviation from this rule can cause major confusion and annoyance,
994 and needs to be justified carefully. In other words, GDB doesn't
995 really have the freedom to do these conversions in clever and
998 AndrewC pointed out that users aren't complaining about how GDB
999 casts integers to pointers; they are complaining that they can't
1000 take an address from a disassembly listing and give it to `x/i'.
1001 This is certainly important.
1003 Adding an architecture method like integer_to_address() certainly
1004 makes it possible for GDB to "get it right" in all circumstances
1005 --- the target has complete control over how things get done, so
1006 people can Do The Right Thing for their target without breaking
1007 anyone else. The standard doesn't specify how integers get
1008 converted to pointers; usually, the ABI doesn't either, but
1009 ABI-specific code is a more reasonable place to handle it. */
1011 if (TYPE_CODE (value_type (val
)) != TYPE_CODE_PTR
1012 && TYPE_CODE (value_type (val
)) != TYPE_CODE_REF
1013 && gdbarch_integer_to_address_p (current_gdbarch
))
1014 return gdbarch_integer_to_address (current_gdbarch
, value_type (val
),
1015 value_contents (val
));
1017 return unpack_long (value_type (val
), value_contents (val
));
1021 /* Unpack raw data (copied from debugee, target byte order) at VALADDR
1022 as a long, or as a double, assuming the raw data is described
1023 by type TYPE. Knows how to convert different sizes of values
1024 and can convert between fixed and floating point. We don't assume
1025 any alignment for the raw data. Return value is in host byte order.
1027 If you want functions and arrays to be coerced to pointers, and
1028 references to be dereferenced, call value_as_long() instead.
1030 C++: It is assumed that the front-end has taken care of
1031 all matters concerning pointers to members. A pointer
1032 to member which reaches here is considered to be equivalent
1033 to an INT (or some size). After all, it is only an offset. */
1036 unpack_long (struct type
*type
, const gdb_byte
*valaddr
)
1038 enum type_code code
= TYPE_CODE (type
);
1039 int len
= TYPE_LENGTH (type
);
1040 int nosign
= TYPE_UNSIGNED (type
);
1042 if (current_language
->la_language
== language_scm
1043 && is_scmvalue_type (type
))
1044 return scm_unpack (type
, valaddr
, TYPE_CODE_INT
);
1048 case TYPE_CODE_TYPEDEF
:
1049 return unpack_long (check_typedef (type
), valaddr
);
1050 case TYPE_CODE_ENUM
:
1051 case TYPE_CODE_FLAGS
:
1052 case TYPE_CODE_BOOL
:
1054 case TYPE_CODE_CHAR
:
1055 case TYPE_CODE_RANGE
:
1057 return extract_unsigned_integer (valaddr
, len
);
1059 return extract_signed_integer (valaddr
, len
);
1062 return extract_typed_floating (valaddr
, type
);
1066 /* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
1067 whether we want this to be true eventually. */
1068 return extract_typed_address (valaddr
, type
);
1070 case TYPE_CODE_MEMBER
:
1071 error (_("not implemented: member types in unpack_long"));
1074 error (_("Value can't be converted to integer."));
1076 return 0; /* Placate lint. */
1079 /* Return a double value from the specified type and address.
1080 INVP points to an int which is set to 0 for valid value,
1081 1 for invalid value (bad float format). In either case,
1082 the returned double is OK to use. Argument is in target
1083 format, result is in host format. */
1086 unpack_double (struct type
*type
, const gdb_byte
*valaddr
, int *invp
)
1088 enum type_code code
;
1092 *invp
= 0; /* Assume valid. */
1093 CHECK_TYPEDEF (type
);
1094 code
= TYPE_CODE (type
);
1095 len
= TYPE_LENGTH (type
);
1096 nosign
= TYPE_UNSIGNED (type
);
1097 if (code
== TYPE_CODE_FLT
)
1099 /* NOTE: cagney/2002-02-19: There was a test here to see if the
1100 floating-point value was valid (using the macro
1101 INVALID_FLOAT). That test/macro have been removed.
1103 It turns out that only the VAX defined this macro and then
1104 only in a non-portable way. Fixing the portability problem
1105 wouldn't help since the VAX floating-point code is also badly
1106 bit-rotten. The target needs to add definitions for the
1107 methods TARGET_FLOAT_FORMAT and TARGET_DOUBLE_FORMAT - these
1108 exactly describe the target floating-point format. The
1109 problem here is that the corresponding floatformat_vax_f and
1110 floatformat_vax_d values these methods should be set to are
1111 also not defined either. Oops!
1113 Hopefully someone will add both the missing floatformat
1114 definitions and the new cases for floatformat_is_valid (). */
1116 if (!floatformat_is_valid (floatformat_from_type (type
), valaddr
))
1122 return extract_typed_floating (valaddr
, type
);
1126 /* Unsigned -- be sure we compensate for signed LONGEST. */
1127 return (ULONGEST
) unpack_long (type
, valaddr
);
1131 /* Signed -- we are OK with unpack_long. */
1132 return unpack_long (type
, valaddr
);
1136 /* Unpack raw data (copied from debugee, target byte order) at VALADDR
1137 as a CORE_ADDR, assuming the raw data is described by type TYPE.
1138 We don't assume any alignment for the raw data. Return value is in
1141 If you want functions and arrays to be coerced to pointers, and
1142 references to be dereferenced, call value_as_address() instead.
1144 C++: It is assumed that the front-end has taken care of
1145 all matters concerning pointers to members. A pointer
1146 to member which reaches here is considered to be equivalent
1147 to an INT (or some size). After all, it is only an offset. */
1150 unpack_pointer (struct type
*type
, const gdb_byte
*valaddr
)
1152 /* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
1153 whether we want this to be true eventually. */
1154 return unpack_long (type
, valaddr
);
1158 /* Get the value of the FIELDN'th field (which must be static) of
1159 TYPE. Return NULL if the field doesn't exist or has been
1163 value_static_field (struct type
*type
, int fieldno
)
1165 struct value
*retval
;
1167 if (TYPE_FIELD_STATIC_HAS_ADDR (type
, fieldno
))
1169 retval
= value_at (TYPE_FIELD_TYPE (type
, fieldno
),
1170 TYPE_FIELD_STATIC_PHYSADDR (type
, fieldno
));
1174 char *phys_name
= TYPE_FIELD_STATIC_PHYSNAME (type
, fieldno
);
1175 struct symbol
*sym
= lookup_symbol (phys_name
, 0, VAR_DOMAIN
, 0, NULL
);
1178 /* With some compilers, e.g. HP aCC, static data members are reported
1179 as non-debuggable symbols */
1180 struct minimal_symbol
*msym
= lookup_minimal_symbol (phys_name
, NULL
, NULL
);
1185 retval
= value_at (TYPE_FIELD_TYPE (type
, fieldno
),
1186 SYMBOL_VALUE_ADDRESS (msym
));
1191 /* SYM should never have a SYMBOL_CLASS which will require
1192 read_var_value to use the FRAME parameter. */
1193 if (symbol_read_needs_frame (sym
))
1194 warning (_("static field's value depends on the current "
1195 "frame - bad debug info?"));
1196 retval
= read_var_value (sym
, NULL
);
1198 if (retval
&& VALUE_LVAL (retval
) == lval_memory
)
1199 SET_FIELD_PHYSADDR (TYPE_FIELD (type
, fieldno
),
1200 VALUE_ADDRESS (retval
));
1205 /* Change the enclosing type of a value object VAL to NEW_ENCL_TYPE.
1206 You have to be careful here, since the size of the data area for the value
1207 is set by the length of the enclosing type. So if NEW_ENCL_TYPE is bigger
1208 than the old enclosing type, you have to allocate more space for the data.
1209 The return value is a pointer to the new version of this value structure. */
1212 value_change_enclosing_type (struct value
*val
, struct type
*new_encl_type
)
1214 if (TYPE_LENGTH (new_encl_type
) <= TYPE_LENGTH (value_enclosing_type (val
)))
1216 val
->enclosing_type
= new_encl_type
;
1221 struct value
*new_val
;
1224 new_val
= (struct value
*) xrealloc (val
, sizeof (struct value
) + TYPE_LENGTH (new_encl_type
));
1226 new_val
->enclosing_type
= new_encl_type
;
1228 /* We have to make sure this ends up in the same place in the value
1229 chain as the original copy, so it's clean-up behavior is the same.
1230 If the value has been released, this is a waste of time, but there
1231 is no way to tell that in advance, so... */
1233 if (val
!= all_values
)
1235 for (prev
= all_values
; prev
!= NULL
; prev
= prev
->next
)
1237 if (prev
->next
== val
)
1239 prev
->next
= new_val
;
1249 /* Given a value ARG1 (offset by OFFSET bytes)
1250 of a struct or union type ARG_TYPE,
1251 extract and return the value of one of its (non-static) fields.
1252 FIELDNO says which field. */
1255 value_primitive_field (struct value
*arg1
, int offset
,
1256 int fieldno
, struct type
*arg_type
)
1261 CHECK_TYPEDEF (arg_type
);
1262 type
= TYPE_FIELD_TYPE (arg_type
, fieldno
);
1264 /* Handle packed fields */
1266 if (TYPE_FIELD_BITSIZE (arg_type
, fieldno
))
1268 v
= value_from_longest (type
,
1269 unpack_field_as_long (arg_type
,
1270 value_contents (arg1
)
1273 v
->bitpos
= TYPE_FIELD_BITPOS (arg_type
, fieldno
) % 8;
1274 v
->bitsize
= TYPE_FIELD_BITSIZE (arg_type
, fieldno
);
1275 v
->offset
= value_offset (arg1
) + offset
1276 + TYPE_FIELD_BITPOS (arg_type
, fieldno
) / 8;
1278 else if (fieldno
< TYPE_N_BASECLASSES (arg_type
))
1280 /* This field is actually a base subobject, so preserve the
1281 entire object's contents for later references to virtual
1283 v
= allocate_value (value_enclosing_type (arg1
));
1285 if (value_lazy (arg1
))
1286 set_value_lazy (v
, 1);
1288 memcpy (value_contents_all_raw (v
), value_contents_all_raw (arg1
),
1289 TYPE_LENGTH (value_enclosing_type (arg1
)));
1290 v
->offset
= value_offset (arg1
);
1291 v
->embedded_offset
= (offset
+ value_embedded_offset (arg1
)
1292 + TYPE_FIELD_BITPOS (arg_type
, fieldno
) / 8);
1296 /* Plain old data member */
1297 offset
+= TYPE_FIELD_BITPOS (arg_type
, fieldno
) / 8;
1298 v
= allocate_value (type
);
1299 if (value_lazy (arg1
))
1300 set_value_lazy (v
, 1);
1302 memcpy (value_contents_raw (v
),
1303 value_contents_raw (arg1
) + offset
,
1304 TYPE_LENGTH (type
));
1305 v
->offset
= (value_offset (arg1
) + offset
1306 + value_embedded_offset (arg1
));
1308 VALUE_LVAL (v
) = VALUE_LVAL (arg1
);
1309 if (VALUE_LVAL (arg1
) == lval_internalvar
)
1310 VALUE_LVAL (v
) = lval_internalvar_component
;
1311 VALUE_ADDRESS (v
) = VALUE_ADDRESS (arg1
);
1312 VALUE_REGNUM (v
) = VALUE_REGNUM (arg1
);
1313 VALUE_FRAME_ID (v
) = VALUE_FRAME_ID (arg1
);
1314 /* VALUE_OFFSET (v) = VALUE_OFFSET (arg1) + offset
1315 + TYPE_FIELD_BITPOS (arg_type, fieldno) / 8; */
1319 /* Given a value ARG1 of a struct or union type,
1320 extract and return the value of one of its (non-static) fields.
1321 FIELDNO says which field. */
1324 value_field (struct value
*arg1
, int fieldno
)
1326 return value_primitive_field (arg1
, 0, fieldno
, value_type (arg1
));
1329 /* Return a non-virtual function as a value.
1330 F is the list of member functions which contains the desired method.
1331 J is an index into F which provides the desired method.
1333 We only use the symbol for its address, so be happy with either a
1334 full symbol or a minimal symbol.
1338 value_fn_field (struct value
**arg1p
, struct fn_field
*f
, int j
, struct type
*type
,
1342 struct type
*ftype
= TYPE_FN_FIELD_TYPE (f
, j
);
1343 char *physname
= TYPE_FN_FIELD_PHYSNAME (f
, j
);
1345 struct minimal_symbol
*msym
;
1347 sym
= lookup_symbol (physname
, 0, VAR_DOMAIN
, 0, NULL
);
1354 gdb_assert (sym
== NULL
);
1355 msym
= lookup_minimal_symbol (physname
, NULL
, NULL
);
1360 v
= allocate_value (ftype
);
1363 VALUE_ADDRESS (v
) = BLOCK_START (SYMBOL_BLOCK_VALUE (sym
));
1367 VALUE_ADDRESS (v
) = SYMBOL_VALUE_ADDRESS (msym
);
1372 if (type
!= value_type (*arg1p
))
1373 *arg1p
= value_ind (value_cast (lookup_pointer_type (type
),
1374 value_addr (*arg1p
)));
1376 /* Move the `this' pointer according to the offset.
1377 VALUE_OFFSET (*arg1p) += offset;
1385 /* Unpack a field FIELDNO of the specified TYPE, from the anonymous object at
1388 Extracting bits depends on endianness of the machine. Compute the
1389 number of least significant bits to discard. For big endian machines,
1390 we compute the total number of bits in the anonymous object, subtract
1391 off the bit count from the MSB of the object to the MSB of the
1392 bitfield, then the size of the bitfield, which leaves the LSB discard
1393 count. For little endian machines, the discard count is simply the
1394 number of bits from the LSB of the anonymous object to the LSB of the
1397 If the field is signed, we also do sign extension. */
1400 unpack_field_as_long (struct type
*type
, const gdb_byte
*valaddr
, int fieldno
)
1404 int bitpos
= TYPE_FIELD_BITPOS (type
, fieldno
);
1405 int bitsize
= TYPE_FIELD_BITSIZE (type
, fieldno
);
1407 struct type
*field_type
;
1409 val
= extract_unsigned_integer (valaddr
+ bitpos
/ 8, sizeof (val
));
1410 field_type
= TYPE_FIELD_TYPE (type
, fieldno
);
1411 CHECK_TYPEDEF (field_type
);
1413 /* Extract bits. See comment above. */
1415 if (BITS_BIG_ENDIAN
)
1416 lsbcount
= (sizeof val
* 8 - bitpos
% 8 - bitsize
);
1418 lsbcount
= (bitpos
% 8);
1421 /* If the field does not entirely fill a LONGEST, then zero the sign bits.
1422 If the field is signed, and is negative, then sign extend. */
1424 if ((bitsize
> 0) && (bitsize
< 8 * (int) sizeof (val
)))
1426 valmask
= (((ULONGEST
) 1) << bitsize
) - 1;
1428 if (!TYPE_UNSIGNED (field_type
))
1430 if (val
& (valmask
^ (valmask
>> 1)))
1439 /* Modify the value of a bitfield. ADDR points to a block of memory in
1440 target byte order; the bitfield starts in the byte pointed to. FIELDVAL
1441 is the desired value of the field, in host byte order. BITPOS and BITSIZE
1442 indicate which bits (in target bit order) comprise the bitfield.
1443 Requires 0 < BITSIZE <= lbits, 0 <= BITPOS+BITSIZE <= lbits, and
1444 0 <= BITPOS, where lbits is the size of a LONGEST in bits. */
1447 modify_field (gdb_byte
*addr
, LONGEST fieldval
, int bitpos
, int bitsize
)
1450 ULONGEST mask
= (ULONGEST
) -1 >> (8 * sizeof (ULONGEST
) - bitsize
);
1452 /* If a negative fieldval fits in the field in question, chop
1453 off the sign extension bits. */
1454 if ((~fieldval
& ~(mask
>> 1)) == 0)
1457 /* Warn if value is too big to fit in the field in question. */
1458 if (0 != (fieldval
& ~mask
))
1460 /* FIXME: would like to include fieldval in the message, but
1461 we don't have a sprintf_longest. */
1462 warning (_("Value does not fit in %d bits."), bitsize
);
1464 /* Truncate it, otherwise adjoining fields may be corrupted. */
1468 oword
= extract_unsigned_integer (addr
, sizeof oword
);
1470 /* Shifting for bit field depends on endianness of the target machine. */
1471 if (BITS_BIG_ENDIAN
)
1472 bitpos
= sizeof (oword
) * 8 - bitpos
- bitsize
;
1474 oword
&= ~(mask
<< bitpos
);
1475 oword
|= fieldval
<< bitpos
;
1477 store_unsigned_integer (addr
, sizeof oword
, oword
);
1480 /* Convert C numbers into newly allocated values */
1483 value_from_longest (struct type
*type
, LONGEST num
)
1485 struct value
*val
= allocate_value (type
);
1486 enum type_code code
;
1489 code
= TYPE_CODE (type
);
1490 len
= TYPE_LENGTH (type
);
1494 case TYPE_CODE_TYPEDEF
:
1495 type
= check_typedef (type
);
1498 case TYPE_CODE_CHAR
:
1499 case TYPE_CODE_ENUM
:
1500 case TYPE_CODE_FLAGS
:
1501 case TYPE_CODE_BOOL
:
1502 case TYPE_CODE_RANGE
:
1503 store_signed_integer (value_contents_raw (val
), len
, num
);
1508 store_typed_address (value_contents_raw (val
), type
, (CORE_ADDR
) num
);
1512 error (_("Unexpected type (%d) encountered for integer constant."), code
);
1518 /* Create a value representing a pointer of type TYPE to the address
1521 value_from_pointer (struct type
*type
, CORE_ADDR addr
)
1523 struct value
*val
= allocate_value (type
);
1524 store_typed_address (value_contents_raw (val
), type
, addr
);
1529 /* Create a value for a string constant to be stored locally
1530 (not in the inferior's memory space, but in GDB memory).
1531 This is analogous to value_from_longest, which also does not
1532 use inferior memory. String shall NOT contain embedded nulls. */
1535 value_from_string (char *ptr
)
1538 int len
= strlen (ptr
);
1539 int lowbound
= current_language
->string_lower_bound
;
1540 struct type
*string_char_type
;
1541 struct type
*rangetype
;
1542 struct type
*stringtype
;
1544 rangetype
= create_range_type ((struct type
*) NULL
,
1546 lowbound
, len
+ lowbound
- 1);
1547 string_char_type
= language_string_char_type (current_language
,
1549 stringtype
= create_array_type ((struct type
*) NULL
,
1552 val
= allocate_value (stringtype
);
1553 memcpy (value_contents_raw (val
), ptr
, len
);
1558 value_from_double (struct type
*type
, DOUBLEST num
)
1560 struct value
*val
= allocate_value (type
);
1561 struct type
*base_type
= check_typedef (type
);
1562 enum type_code code
= TYPE_CODE (base_type
);
1563 int len
= TYPE_LENGTH (base_type
);
1565 if (code
== TYPE_CODE_FLT
)
1567 store_typed_floating (value_contents_raw (val
), base_type
, num
);
1570 error (_("Unexpected type encountered for floating constant."));
1576 coerce_ref (struct value
*arg
)
1578 struct type
*value_type_arg_tmp
= check_typedef (value_type (arg
));
1579 if (TYPE_CODE (value_type_arg_tmp
) == TYPE_CODE_REF
)
1580 arg
= value_at_lazy (TYPE_TARGET_TYPE (value_type_arg_tmp
),
1581 unpack_pointer (value_type (arg
),
1582 value_contents (arg
)));
1587 coerce_array (struct value
*arg
)
1589 arg
= coerce_ref (arg
);
1590 if (current_language
->c_style_arrays
1591 && TYPE_CODE (value_type (arg
)) == TYPE_CODE_ARRAY
)
1592 arg
= value_coerce_array (arg
);
1593 if (TYPE_CODE (value_type (arg
)) == TYPE_CODE_FUNC
)
1594 arg
= value_coerce_function (arg
);
1599 coerce_number (struct value
*arg
)
1601 arg
= coerce_array (arg
);
1602 arg
= coerce_enum (arg
);
1607 coerce_enum (struct value
*arg
)
1609 if (TYPE_CODE (check_typedef (value_type (arg
))) == TYPE_CODE_ENUM
)
1610 arg
= value_cast (builtin_type_unsigned_int
, arg
);
1615 /* Should we use DEPRECATED_EXTRACT_STRUCT_VALUE_ADDRESS instead of
1616 EXTRACT_RETURN_VALUE? GCC_P is true if compiled with gcc and TYPE
1617 is the type (which is known to be struct, union or array).
1619 On most machines, the struct convention is used unless we are
1620 using gcc and the type is of a special size. */
1621 /* As of about 31 Mar 93, GCC was changed to be compatible with the
1622 native compiler. GCC 2.3.3 was the last release that did it the
1623 old way. Since gcc2_compiled was not changed, we have no
1624 way to correctly win in all cases, so we just do the right thing
1625 for gcc1 and for gcc2 after this change. Thus it loses for gcc
1626 2.0-2.3.3. This is somewhat unfortunate, but changing gcc2_compiled
1627 would cause more chaos than dealing with some struct returns being
1629 /* NOTE: cagney/2004-06-13: Deleted check for "gcc_p". GCC 1.x is
1633 generic_use_struct_convention (int gcc_p
, struct type
*value_type
)
1635 return !(TYPE_LENGTH (value_type
) == 1
1636 || TYPE_LENGTH (value_type
) == 2
1637 || TYPE_LENGTH (value_type
) == 4
1638 || TYPE_LENGTH (value_type
) == 8);
1641 /* Return true if the function returning the specified type is using
1642 the convention of returning structures in memory (passing in the
1643 address as a hidden first parameter). GCC_P is nonzero if compiled
1647 using_struct_return (struct type
*value_type
, int gcc_p
)
1649 enum type_code code
= TYPE_CODE (value_type
);
1651 if (code
== TYPE_CODE_ERROR
)
1652 error (_("Function return type unknown."));
1654 if (code
== TYPE_CODE_VOID
)
1655 /* A void return value is never in memory. See also corresponding
1656 code in "print_return_value". */
1659 /* Probe the architecture for the return-value convention. */
1660 return (gdbarch_return_value (current_gdbarch
, value_type
,
1662 != RETURN_VALUE_REGISTER_CONVENTION
);
1666 _initialize_values (void)
1668 add_cmd ("convenience", no_class
, show_convenience
, _("\
1669 Debugger convenience (\"$foo\") variables.\n\
1670 These variables are created when you assign them values;\n\
1671 thus, \"print $foo=1\" gives \"$foo\" the value 1. Values may be any type.\n\
1673 A few convenience variables are given values automatically:\n\
1674 \"$_\"holds the last address examined with \"x\" or \"info lines\",\n\
1675 \"$__\" holds the contents of the last address examined with \"x\"."),
1678 add_cmd ("values", no_class
, show_values
,
1679 _("Elements of value history around item number IDX (or last ten)."),
1682 add_com ("init-if-undefined", class_vars
, init_if_undefined_command
, _("\
1683 Initialize a convenience variable if necessary.\n\
1684 init-if-undefined VARIABLE = EXPRESSION\n\
1685 Set an internal VARIABLE to the result of the EXPRESSION if it does not\n\
1686 exist or does not contain a value. The EXPRESSION is not evaluated if the\n\
1687 VARIABLE is already initialized."));