0e8da567e08d8aa4e1346d1cabb85566b00a26be
[deliverable/binutils-gdb.git] / gdb / findvar.c
1 /* Find a variable's value in memory, for GDB, the GNU debugger.
2
3 Copyright 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
4 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2003, 2004 Free Software
5 Foundation, Inc.
6
7 This file is part of GDB.
8
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.
13
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.
18
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., 59 Temple Place - Suite 330,
22 Boston, MA 02111-1307, USA. */
23
24 #include "defs.h"
25 #include "symtab.h"
26 #include "gdbtypes.h"
27 #include "frame.h"
28 #include "value.h"
29 #include "gdbcore.h"
30 #include "inferior.h"
31 #include "target.h"
32 #include "gdb_string.h"
33 #include "gdb_assert.h"
34 #include "floatformat.h"
35 #include "symfile.h" /* for overlay functions */
36 #include "regcache.h"
37 #include "user-regs.h"
38 #include "block.h"
39
40 /* Basic byte-swapping routines. GDB has needed these for a long time...
41 All extract a target-format integer at ADDR which is LEN bytes long. */
42
43 #if TARGET_CHAR_BIT != 8 || HOST_CHAR_BIT != 8
44 /* 8 bit characters are a pretty safe assumption these days, so we
45 assume it throughout all these swapping routines. If we had to deal with
46 9 bit characters, we would need to make len be in bits and would have
47 to re-write these routines... */
48 you lose
49 #endif
50
51 LONGEST
52 extract_signed_integer (const void *addr, int len)
53 {
54 LONGEST retval;
55 const unsigned char *p;
56 const unsigned char *startaddr = addr;
57 const unsigned char *endaddr = startaddr + len;
58
59 if (len > (int) sizeof (LONGEST))
60 error ("\
61 That operation is not available on integers of more than %d bytes.",
62 (int) sizeof (LONGEST));
63
64 /* Start at the most significant end of the integer, and work towards
65 the least significant. */
66 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
67 {
68 p = startaddr;
69 /* Do the sign extension once at the start. */
70 retval = ((LONGEST) * p ^ 0x80) - 0x80;
71 for (++p; p < endaddr; ++p)
72 retval = (retval << 8) | *p;
73 }
74 else
75 {
76 p = endaddr - 1;
77 /* Do the sign extension once at the start. */
78 retval = ((LONGEST) * p ^ 0x80) - 0x80;
79 for (--p; p >= startaddr; --p)
80 retval = (retval << 8) | *p;
81 }
82 return retval;
83 }
84
85 ULONGEST
86 extract_unsigned_integer (const void *addr, int len)
87 {
88 ULONGEST retval;
89 const unsigned char *p;
90 const unsigned char *startaddr = addr;
91 const unsigned char *endaddr = startaddr + len;
92
93 if (len > (int) sizeof (ULONGEST))
94 error ("\
95 That operation is not available on integers of more than %d bytes.",
96 (int) sizeof (ULONGEST));
97
98 /* Start at the most significant end of the integer, and work towards
99 the least significant. */
100 retval = 0;
101 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
102 {
103 for (p = startaddr; p < endaddr; ++p)
104 retval = (retval << 8) | *p;
105 }
106 else
107 {
108 for (p = endaddr - 1; p >= startaddr; --p)
109 retval = (retval << 8) | *p;
110 }
111 return retval;
112 }
113
114 /* Sometimes a long long unsigned integer can be extracted as a
115 LONGEST value. This is done so that we can print these values
116 better. If this integer can be converted to a LONGEST, this
117 function returns 1 and sets *PVAL. Otherwise it returns 0. */
118
119 int
120 extract_long_unsigned_integer (const void *addr, int orig_len, LONGEST *pval)
121 {
122 char *p, *first_addr;
123 int len;
124
125 len = orig_len;
126 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
127 {
128 for (p = (char *) addr;
129 len > (int) sizeof (LONGEST) && p < (char *) addr + orig_len;
130 p++)
131 {
132 if (*p == 0)
133 len--;
134 else
135 break;
136 }
137 first_addr = p;
138 }
139 else
140 {
141 first_addr = (char *) addr;
142 for (p = (char *) addr + orig_len - 1;
143 len > (int) sizeof (LONGEST) && p >= (char *) addr;
144 p--)
145 {
146 if (*p == 0)
147 len--;
148 else
149 break;
150 }
151 }
152
153 if (len <= (int) sizeof (LONGEST))
154 {
155 *pval = (LONGEST) extract_unsigned_integer (first_addr,
156 sizeof (LONGEST));
157 return 1;
158 }
159
160 return 0;
161 }
162
163
164 /* Treat the bytes at BUF as a pointer of type TYPE, and return the
165 address it represents. */
166 CORE_ADDR
167 extract_typed_address (const void *buf, struct type *type)
168 {
169 if (TYPE_CODE (type) != TYPE_CODE_PTR
170 && TYPE_CODE (type) != TYPE_CODE_REF)
171 internal_error (__FILE__, __LINE__,
172 "extract_typed_address: "
173 "type is not a pointer or reference");
174
175 return POINTER_TO_ADDRESS (type, buf);
176 }
177
178
179 void
180 store_signed_integer (void *addr, int len, LONGEST val)
181 {
182 unsigned char *p;
183 unsigned char *startaddr = (unsigned char *) addr;
184 unsigned char *endaddr = startaddr + len;
185
186 /* Start at the least significant end of the integer, and work towards
187 the most significant. */
188 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
189 {
190 for (p = endaddr - 1; p >= startaddr; --p)
191 {
192 *p = val & 0xff;
193 val >>= 8;
194 }
195 }
196 else
197 {
198 for (p = startaddr; p < endaddr; ++p)
199 {
200 *p = val & 0xff;
201 val >>= 8;
202 }
203 }
204 }
205
206 void
207 store_unsigned_integer (void *addr, int len, ULONGEST val)
208 {
209 unsigned char *p;
210 unsigned char *startaddr = (unsigned char *) addr;
211 unsigned char *endaddr = startaddr + len;
212
213 /* Start at the least significant end of the integer, and work towards
214 the most significant. */
215 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
216 {
217 for (p = endaddr - 1; p >= startaddr; --p)
218 {
219 *p = val & 0xff;
220 val >>= 8;
221 }
222 }
223 else
224 {
225 for (p = startaddr; p < endaddr; ++p)
226 {
227 *p = val & 0xff;
228 val >>= 8;
229 }
230 }
231 }
232
233 /* Store the address ADDR as a pointer of type TYPE at BUF, in target
234 form. */
235 void
236 store_typed_address (void *buf, struct type *type, CORE_ADDR addr)
237 {
238 if (TYPE_CODE (type) != TYPE_CODE_PTR
239 && TYPE_CODE (type) != TYPE_CODE_REF)
240 internal_error (__FILE__, __LINE__,
241 "store_typed_address: "
242 "type is not a pointer or reference");
243
244 ADDRESS_TO_POINTER (type, buf, addr);
245 }
246
247
248
249 /* Return a `value' with the contents of (virtual or cooked) register
250 REGNUM as found in the specified FRAME. The register's type is
251 determined by register_type().
252
253 NOTE: returns NULL if register value is not available. Caller will
254 check return value or die! */
255
256 struct value *
257 value_of_register (int regnum, struct frame_info *frame)
258 {
259 CORE_ADDR addr;
260 int optim;
261 struct value *reg_val;
262 int realnum;
263 char raw_buffer[MAX_REGISTER_SIZE];
264 enum lval_type lval;
265
266 /* User registers lie completely outside of the range of normal
267 registers. Catch them early so that the target never sees them. */
268 if (regnum >= NUM_REGS + NUM_PSEUDO_REGS)
269 return value_of_user_reg (regnum, frame);
270
271 frame_register (frame, regnum, &optim, &lval, &addr, &realnum, raw_buffer);
272
273 /* FIXME: cagney/2002-05-15: This test is just bogus.
274
275 It indicates that the target failed to supply a value for a
276 register because it was "not available" at this time. Problem
277 is, the target still has the register and so get saved_register()
278 may be returning a value saved on the stack. */
279
280 if (register_cached (regnum) < 0)
281 return NULL; /* register value not available */
282
283 reg_val = allocate_value (register_type (current_gdbarch, regnum));
284
285 memcpy (VALUE_CONTENTS_RAW (reg_val), raw_buffer,
286 register_size (current_gdbarch, regnum));
287 VALUE_LVAL (reg_val) = lval;
288 VALUE_ADDRESS (reg_val) = addr;
289 VALUE_REGNO (reg_val) = regnum;
290 VALUE_OPTIMIZED_OUT (reg_val) = optim;
291 return reg_val;
292 }
293
294 /* Given a pointer of type TYPE in target form in BUF, return the
295 address it represents. */
296 CORE_ADDR
297 unsigned_pointer_to_address (struct type *type, const void *buf)
298 {
299 return extract_unsigned_integer (buf, TYPE_LENGTH (type));
300 }
301
302 CORE_ADDR
303 signed_pointer_to_address (struct type *type, const void *buf)
304 {
305 return extract_signed_integer (buf, TYPE_LENGTH (type));
306 }
307
308 /* Given an address, store it as a pointer of type TYPE in target
309 format in BUF. */
310 void
311 unsigned_address_to_pointer (struct type *type, void *buf, CORE_ADDR addr)
312 {
313 store_unsigned_integer (buf, TYPE_LENGTH (type), addr);
314 }
315
316 void
317 address_to_signed_pointer (struct type *type, void *buf, CORE_ADDR addr)
318 {
319 store_signed_integer (buf, TYPE_LENGTH (type), addr);
320 }
321 \f
322 /* Will calling read_var_value or locate_var_value on SYM end
323 up caring what frame it is being evaluated relative to? SYM must
324 be non-NULL. */
325 int
326 symbol_read_needs_frame (struct symbol *sym)
327 {
328 switch (SYMBOL_CLASS (sym))
329 {
330 /* All cases listed explicitly so that gcc -Wall will detect it if
331 we failed to consider one. */
332 case LOC_COMPUTED:
333 case LOC_COMPUTED_ARG:
334 /* FIXME: cagney/2004-01-26: It should be possible to
335 unconditionally call the SYMBOL_OPS method when available.
336 Unfortunately DWARF 2 stores the frame-base (instead of the
337 function) location in a function's symbol. Oops! For the
338 moment enable this when/where applicable. */
339 return SYMBOL_OPS (sym)->read_needs_frame (sym);
340
341 case LOC_REGISTER:
342 case LOC_ARG:
343 case LOC_REF_ARG:
344 case LOC_REGPARM:
345 case LOC_REGPARM_ADDR:
346 case LOC_LOCAL:
347 case LOC_LOCAL_ARG:
348 case LOC_BASEREG:
349 case LOC_BASEREG_ARG:
350 case LOC_HP_THREAD_LOCAL_STATIC:
351 return 1;
352
353 case LOC_UNDEF:
354 case LOC_CONST:
355 case LOC_STATIC:
356 case LOC_INDIRECT:
357 case LOC_TYPEDEF:
358
359 case LOC_LABEL:
360 /* Getting the address of a label can be done independently of the block,
361 even if some *uses* of that address wouldn't work so well without
362 the right frame. */
363
364 case LOC_BLOCK:
365 case LOC_CONST_BYTES:
366 case LOC_UNRESOLVED:
367 case LOC_OPTIMIZED_OUT:
368 return 0;
369 }
370 return 1;
371 }
372
373 /* Given a struct symbol for a variable,
374 and a stack frame id, read the value of the variable
375 and return a (pointer to a) struct value containing the value.
376 If the variable cannot be found, return a zero pointer.
377 If FRAME is NULL, use the deprecated_selected_frame. */
378
379 struct value *
380 read_var_value (struct symbol *var, struct frame_info *frame)
381 {
382 struct value *v;
383 struct type *type = SYMBOL_TYPE (var);
384 CORE_ADDR addr;
385 int len;
386
387 v = allocate_value (type);
388 VALUE_LVAL (v) = lval_memory; /* The most likely possibility. */
389
390 len = TYPE_LENGTH (type);
391
392
393 /* FIXME drow/2003-09-06: this call to the selected frame should be
394 pushed upwards to the callers. */
395 if (frame == NULL)
396 frame = deprecated_safe_get_selected_frame ();
397
398 switch (SYMBOL_CLASS (var))
399 {
400 case LOC_CONST:
401 /* Put the constant back in target format. */
402 store_signed_integer (VALUE_CONTENTS_RAW (v), len,
403 (LONGEST) SYMBOL_VALUE (var));
404 VALUE_LVAL (v) = not_lval;
405 return v;
406
407 case LOC_LABEL:
408 /* Put the constant back in target format. */
409 if (overlay_debugging)
410 {
411 CORE_ADDR addr
412 = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
413 SYMBOL_BFD_SECTION (var));
414 store_typed_address (VALUE_CONTENTS_RAW (v), type, addr);
415 }
416 else
417 store_typed_address (VALUE_CONTENTS_RAW (v), type,
418 SYMBOL_VALUE_ADDRESS (var));
419 VALUE_LVAL (v) = not_lval;
420 return v;
421
422 case LOC_CONST_BYTES:
423 {
424 char *bytes_addr;
425 bytes_addr = SYMBOL_VALUE_BYTES (var);
426 memcpy (VALUE_CONTENTS_RAW (v), bytes_addr, len);
427 VALUE_LVAL (v) = not_lval;
428 return v;
429 }
430
431 case LOC_STATIC:
432 if (overlay_debugging)
433 addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
434 SYMBOL_BFD_SECTION (var));
435 else
436 addr = SYMBOL_VALUE_ADDRESS (var);
437 break;
438
439 case LOC_INDIRECT:
440 {
441 /* The import slot does not have a real address in it from the
442 dynamic loader (dld.sl on HP-UX), if the target hasn't
443 begun execution yet, so check for that. */
444 CORE_ADDR locaddr;
445 struct value *loc;
446 if (!target_has_execution)
447 error ("\
448 Attempt to access variable defined in different shared object or load module when\n\
449 addresses have not been bound by the dynamic loader. Try again when executable is running.");
450
451 locaddr = SYMBOL_VALUE_ADDRESS (var);
452 loc = value_at (lookup_pointer_type (type), locaddr);
453 addr = value_as_address (loc);
454 }
455
456 case LOC_ARG:
457 if (frame == NULL)
458 return 0;
459 addr = get_frame_args_address (frame);
460 if (!addr)
461 return 0;
462 addr += SYMBOL_VALUE (var);
463 break;
464
465 case LOC_REF_ARG:
466 {
467 struct value *ref;
468 CORE_ADDR argref;
469 if (frame == NULL)
470 return 0;
471 argref = get_frame_args_address (frame);
472 if (!argref)
473 return 0;
474 argref += SYMBOL_VALUE (var);
475 ref = value_at (lookup_pointer_type (type), argref);
476 addr = value_as_address (ref);
477 break;
478 }
479
480 case LOC_LOCAL:
481 case LOC_LOCAL_ARG:
482 if (frame == NULL)
483 return 0;
484 addr = get_frame_locals_address (frame);
485 addr += SYMBOL_VALUE (var);
486 break;
487
488 case LOC_BASEREG:
489 case LOC_BASEREG_ARG:
490 case LOC_HP_THREAD_LOCAL_STATIC:
491 {
492 struct value *regval;
493
494 regval = value_from_register (lookup_pointer_type (type),
495 SYMBOL_BASEREG (var), frame);
496 if (regval == NULL)
497 error ("Value of base register not available.");
498 addr = value_as_address (regval);
499 addr += SYMBOL_VALUE (var);
500 break;
501 }
502
503 case LOC_TYPEDEF:
504 error ("Cannot look up value of a typedef");
505 break;
506
507 case LOC_BLOCK:
508 if (overlay_debugging)
509 VALUE_ADDRESS (v) = symbol_overlayed_address
510 (BLOCK_START (SYMBOL_BLOCK_VALUE (var)), SYMBOL_BFD_SECTION (var));
511 else
512 VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (var));
513 return v;
514
515 case LOC_REGISTER:
516 case LOC_REGPARM:
517 case LOC_REGPARM_ADDR:
518 {
519 struct block *b;
520 int regno = SYMBOL_VALUE (var);
521 struct value *regval;
522
523 if (frame == NULL)
524 return 0;
525 b = get_frame_block (frame, 0);
526
527 if (SYMBOL_CLASS (var) == LOC_REGPARM_ADDR)
528 {
529 regval = value_from_register (lookup_pointer_type (type),
530 regno,
531 frame);
532
533 if (regval == NULL)
534 error ("Value of register variable not available.");
535
536 addr = value_as_address (regval);
537 VALUE_LVAL (v) = lval_memory;
538 }
539 else
540 {
541 regval = value_from_register (type, regno, frame);
542
543 if (regval == NULL)
544 error ("Value of register variable not available.");
545 return regval;
546 }
547 }
548 break;
549
550 case LOC_COMPUTED:
551 case LOC_COMPUTED_ARG:
552 /* FIXME: cagney/2004-01-26: It should be possible to
553 unconditionally call the SYMBOL_OPS method when available.
554 Unfortunately DWARF 2 stores the frame-base (instead of the
555 function) location in a function's symbol. Oops! For the
556 moment enable this when/where applicable. */
557 if (frame == 0 && SYMBOL_OPS (var)->read_needs_frame (var))
558 return 0;
559 return SYMBOL_OPS (var)->read_variable (var, frame);
560
561 case LOC_UNRESOLVED:
562 {
563 struct minimal_symbol *msym;
564
565 msym = lookup_minimal_symbol (DEPRECATED_SYMBOL_NAME (var), NULL, NULL);
566 if (msym == NULL)
567 return 0;
568 if (overlay_debugging)
569 addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym),
570 SYMBOL_BFD_SECTION (msym));
571 else
572 addr = SYMBOL_VALUE_ADDRESS (msym);
573 }
574 break;
575
576 case LOC_OPTIMIZED_OUT:
577 VALUE_LVAL (v) = not_lval;
578 VALUE_OPTIMIZED_OUT (v) = 1;
579 return v;
580
581 default:
582 error ("Cannot look up value of a botched symbol.");
583 break;
584 }
585
586 VALUE_ADDRESS (v) = addr;
587 VALUE_LAZY (v) = 1;
588 return v;
589 }
590
591 /* Return a value of type TYPE, stored in register REGNUM, in frame
592 FRAME.
593
594 NOTE: returns NULL if register value is not available.
595 Caller will check return value or die! */
596
597 struct value *
598 value_from_register (struct type *type, int regnum, struct frame_info *frame)
599 {
600 struct gdbarch *gdbarch = get_frame_arch (frame);
601 struct value *v = allocate_value (type);
602 CHECK_TYPEDEF (type);
603
604 if (TYPE_LENGTH (type) == 0)
605 {
606 /* It doesn't matter much what we return for this: since the
607 length is zero, it could be anything. But if allowed to see
608 a zero-length type, the register-finding loop below will set
609 neither mem_stor nor reg_stor, and then report an internal
610 error.
611
612 Zero-length types can legitimately arise from declarations
613 like 'struct {}' (a GCC extension, not valid ISO C). GDB may
614 also create them when it finds bogus debugging information;
615 for example, in GCC 2.95.4 and binutils 2.11.93.0.2, the
616 STABS BINCL->EXCL compression process can create bad type
617 numbers. GDB reads these as TYPE_CODE_UNDEF types, with zero
618 length. (That bug is actually the only known way to get a
619 zero-length value allocated to a register --- which is what
620 it takes to make it here.)
621
622 We'll just attribute the value to the original register. */
623 VALUE_LVAL (v) = lval_register;
624 VALUE_ADDRESS (v) = regnum;
625 VALUE_REGNO (v) = regnum;
626 }
627 else if (CONVERT_REGISTER_P (regnum, type))
628 {
629 /* The ISA/ABI need to something weird when obtaining the
630 specified value from this register. It might need to
631 re-order non-adjacent, starting with REGNUM (see MIPS and
632 i386). It might need to convert the [float] register into
633 the corresponding [integer] type (see Alpha). The assumption
634 is that REGISTER_TO_VALUE populates the entire value
635 including the location. */
636 REGISTER_TO_VALUE (frame, regnum, type, VALUE_CONTENTS_RAW (v));
637 VALUE_LVAL (v) = lval_reg_frame_relative;
638 VALUE_FRAME_ID (v) = get_frame_id (frame);
639 VALUE_FRAME_REGNUM (v) = regnum;
640 }
641 else
642 {
643 int local_regnum;
644 int mem_stor = 0, reg_stor = 0;
645 int mem_tracking = 1;
646 CORE_ADDR last_addr = 0;
647 CORE_ADDR first_addr = 0;
648 int first_realnum = regnum;
649 int len = TYPE_LENGTH (type);
650 int value_bytes_copied;
651 int optimized = 0;
652 char *value_bytes = (char *) alloca (len + MAX_REGISTER_SIZE);
653
654 /* Copy all of the data out, whereever it may be. */
655 for (local_regnum = regnum, value_bytes_copied = 0;
656 value_bytes_copied < len;
657 (value_bytes_copied += register_size (current_gdbarch, local_regnum),
658 ++local_regnum))
659 {
660 int realnum;
661 int optim;
662 enum lval_type lval;
663 CORE_ADDR addr;
664 frame_register (frame, local_regnum, &optim, &lval, &addr,
665 &realnum, value_bytes + value_bytes_copied);
666 optimized += optim;
667 if (register_cached (local_regnum) == -1)
668 return NULL; /* register value not available */
669
670 if (regnum == local_regnum)
671 {
672 first_addr = addr;
673 first_realnum = realnum;
674 }
675 if (lval == lval_register)
676 reg_stor++;
677 else
678 {
679 mem_stor++;
680
681 mem_tracking = (mem_tracking
682 && (regnum == local_regnum
683 || addr == last_addr));
684 }
685 last_addr = addr;
686 }
687
688 /* FIXME: cagney/2003-06-04: Shouldn't this always use
689 lval_reg_frame_relative? If it doesn't and the register's
690 location changes (say after a resume) then this value is
691 going to have wrong information. */
692 if ((reg_stor && mem_stor)
693 || (mem_stor && !mem_tracking))
694 /* Mixed storage; all of the hassle we just went through was
695 for some good purpose. */
696 {
697 VALUE_LVAL (v) = lval_reg_frame_relative;
698 VALUE_FRAME_ID (v) = get_frame_id (frame);
699 VALUE_FRAME_REGNUM (v) = regnum;
700 }
701 else if (mem_stor)
702 {
703 VALUE_LVAL (v) = lval_memory;
704 VALUE_ADDRESS (v) = first_addr;
705 }
706 else if (reg_stor)
707 {
708 VALUE_LVAL (v) = lval_register;
709 VALUE_ADDRESS (v) = first_addr;
710 VALUE_REGNO (v) = first_realnum;
711 }
712 else
713 internal_error (__FILE__, __LINE__,
714 "value_from_register: Value not stored anywhere!");
715
716 VALUE_OPTIMIZED_OUT (v) = optimized;
717
718 /* Any structure stored in more than one register will always be
719 an integral number of registers. Otherwise, you need to do
720 some fiddling with the last register copied here for little
721 endian machines. */
722 if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG
723 && len < register_size (current_gdbarch, regnum))
724 /* Big-endian, and we want less than full size. */
725 VALUE_OFFSET (v) = register_size (current_gdbarch, regnum) - len;
726 else
727 VALUE_OFFSET (v) = 0;
728 memcpy (VALUE_CONTENTS_RAW (v), value_bytes + VALUE_OFFSET (v), len);
729 }
730 return v;
731 }
732
733 \f
734 /* Given a struct symbol for a variable or function,
735 and a stack frame id,
736 return a (pointer to a) struct value containing the properly typed
737 address. */
738
739 struct value *
740 locate_var_value (struct symbol *var, struct frame_info *frame)
741 {
742 CORE_ADDR addr = 0;
743 struct type *type = SYMBOL_TYPE (var);
744 struct value *lazy_value;
745
746 /* Evaluate it first; if the result is a memory address, we're fine.
747 Lazy evaluation pays off here. */
748
749 lazy_value = read_var_value (var, frame);
750 if (lazy_value == 0)
751 error ("Address of \"%s\" is unknown.", SYMBOL_PRINT_NAME (var));
752
753 if (VALUE_LAZY (lazy_value)
754 || TYPE_CODE (type) == TYPE_CODE_FUNC)
755 {
756 struct value *val;
757
758 addr = VALUE_ADDRESS (lazy_value);
759 val = value_from_pointer (lookup_pointer_type (type), addr);
760 return val;
761 }
762
763 /* Not a memory address; check what the problem was. */
764 switch (VALUE_LVAL (lazy_value))
765 {
766 case lval_register:
767 gdb_assert (REGISTER_NAME (VALUE_REGNO (lazy_value)) != NULL
768 && *REGISTER_NAME (VALUE_REGNO (lazy_value)) != '\0');
769 error("Address requested for identifier "
770 "\"%s\" which is in register $%s",
771 SYMBOL_PRINT_NAME (var),
772 REGISTER_NAME (VALUE_REGNO (lazy_value)));
773 break;
774
775 case lval_reg_frame_relative:
776 gdb_assert (REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)) != NULL
777 && *REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)) != '\0');
778 error("Address requested for identifier "
779 "\"%s\" which is in frame register $%s",
780 SYMBOL_PRINT_NAME (var),
781 REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)));
782 break;
783
784 default:
785 error ("Can't take address of \"%s\" which isn't an lvalue.",
786 SYMBOL_PRINT_NAME (var));
787 break;
788 }
789 return 0; /* For lint -- never reached */
790 }
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