gdb/findvar.c

   1 /* Find a variable's value in memory, for GDB, the GNU debugger.
   2
   3    Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
   4    1996, 1997, 1998, 1999, 2000, 2001, 2003, 2004, 2005, 2007, 2008
   5    Free Software 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 3 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, see <http://www.gnu.org/licenses/>.  */
  21
  22 #include "defs.h"
  23 #include "symtab.h"
  24 #include "gdbtypes.h"
  25 #include "frame.h"
  26 #include "value.h"
  27 #include "gdbcore.h"
  28 #include "inferior.h"
  29 #include "target.h"
  30 #include "gdb_string.h"
  31 #include "gdb_assert.h"
  32 #include "floatformat.h"
  33 #include "symfile.h"            /* for overlay functions */
  34 #include "regcache.h"
  35 #include "user-regs.h"
  36 #include "block.h"
  37
  38 /* Basic byte-swapping routines.  GDB has needed these for a long time...
  39    All extract a target-format integer at ADDR which is LEN bytes long.  */
  40
  41 #if TARGET_CHAR_BIT != 8 || HOST_CHAR_BIT != 8
  42   /* 8 bit characters are a pretty safe assumption these days, so we
  43      assume it throughout all these swapping routines.  If we had to deal with
  44      9 bit characters, we would need to make len be in bits and would have
  45      to re-write these routines...  */
  46 you lose
  47 #endif
  48
  49 LONGEST
  50 extract_signed_integer (const gdb_byte *addr, int len)
  51 {
  52   LONGEST retval;
  53   const unsigned char *p;
  54   const unsigned char *startaddr = addr;
  55   const unsigned char *endaddr = startaddr + len;
  56
  57   if (len > (int) sizeof (LONGEST))
  58     error (_("\
  59 That operation is not available on integers of more than %d bytes."),
  60            (int) sizeof (LONGEST));
  61
  62   /* Start at the most significant end of the integer, and work towards
  63      the least significant.  */
  64   if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
  65     {
  66       p = startaddr;
  67       /* Do the sign extension once at the start.  */
  68       retval = ((LONGEST) * p ^ 0x80) - 0x80;
  69       for (++p; p < endaddr; ++p)
  70         retval = (retval << 8) | *p;
  71     }
  72   else
  73     {
  74       p = endaddr - 1;
  75       /* Do the sign extension once at the start.  */
  76       retval = ((LONGEST) * p ^ 0x80) - 0x80;
  77       for (--p; p >= startaddr; --p)
  78         retval = (retval << 8) | *p;
  79     }
  80   return retval;
  81 }
  82
  83 ULONGEST
  84 extract_unsigned_integer (const gdb_byte *addr, int len)
  85 {
  86   ULONGEST retval;
  87   const unsigned char *p;
  88   const unsigned char *startaddr = addr;
  89   const unsigned char *endaddr = startaddr + len;
  90
  91   if (len > (int) sizeof (ULONGEST))
  92     error (_("\
  93 That operation is not available on integers of more than %d bytes."),
  94            (int) sizeof (ULONGEST));
  95
  96   /* Start at the most significant end of the integer, and work towards
  97      the least significant.  */
  98   retval = 0;
  99   if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
 100     {
 101       for (p = startaddr; p < endaddr; ++p)
 102         retval = (retval << 8) | *p;
 103     }
 104   else
 105     {
 106       for (p = endaddr - 1; p >= startaddr; --p)
 107         retval = (retval << 8) | *p;
 108     }
 109   return retval;
 110 }
 111
 112 /* Sometimes a long long unsigned integer can be extracted as a
 113    LONGEST value.  This is done so that we can print these values
 114    better.  If this integer can be converted to a LONGEST, this
 115    function returns 1 and sets *PVAL.  Otherwise it returns 0.  */
 116
 117 int
 118 extract_long_unsigned_integer (const gdb_byte *addr, int orig_len,
 119                                LONGEST *pval)
 120 {
 121   const gdb_byte *p;
 122   const gdb_byte *first_addr;
 123   int len;
 124
 125   len = orig_len;
 126   if (gdbarch_byte_order (current_gdbarch) == BFD_ENDIAN_BIG)
 127     {
 128       for (p = addr;
 129            len > (int) sizeof (LONGEST) && p < 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 = addr;
 142       for (p = addr + orig_len - 1;
 143            len > (int) sizeof (LONGEST) && p >= 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 gdb_byte *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 gdbarch_pointer_to_address (current_gdbarch, type, buf);
 176 }
 177
 178
 179 void
 180 store_signed_integer (gdb_byte *addr, int len, LONGEST val)
 181 {
 182   gdb_byte *p;
 183   gdb_byte *startaddr = addr;
 184   gdb_byte *endaddr = startaddr + len;
 185
 186   /* Start at the least significant end of the integer, and work towards
 187      the most significant.  */
 188   if (gdbarch_byte_order (current_gdbarch) == 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 (gdb_byte *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 (gdbarch_byte_order (current_gdbarch) == 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 (gdb_byte *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   gdbarch_address_to_pointer (current_gdbarch, 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 struct value *
 254 value_of_register (int regnum, struct frame_info *frame)
 255 {
 256   struct gdbarch *gdbarch = get_frame_arch (frame);
 257   CORE_ADDR addr;
 258   int optim;
 259   struct value *reg_val;
 260   int realnum;
 261   gdb_byte raw_buffer[MAX_REGISTER_SIZE];
 262   enum lval_type lval;
 263
 264   /* User registers lie completely outside of the range of normal
 265      registers.  Catch them early so that the target never sees them.  */
 266   if (regnum >= gdbarch_num_regs (gdbarch)
 267                 + gdbarch_num_pseudo_regs (gdbarch))
 268     return value_of_user_reg (regnum, frame);
 269
 270   frame_register (frame, regnum, &optim, &lval, &addr, &realnum, raw_buffer);
 271
 272   reg_val = allocate_value (register_type (gdbarch, regnum));
 273
 274   memcpy (value_contents_raw (reg_val), raw_buffer,
 275           register_size (gdbarch, regnum));
 276   VALUE_LVAL (reg_val) = lval;
 277   VALUE_ADDRESS (reg_val) = addr;
 278   VALUE_REGNUM (reg_val) = regnum;
 279   set_value_optimized_out (reg_val, optim);
 280   VALUE_FRAME_ID (reg_val) = get_frame_id (frame);
 281   return reg_val;
 282 }
 283
 284 /* Return a `value' with the contents of (virtual or cooked) register
 285    REGNUM as found in the specified FRAME.  The register's type is
 286    determined by register_type().  The value is not fetched.  */
 287
 288 struct value *
 289 value_of_register_lazy (struct frame_info *frame, int regnum)
 290 {
 291   struct gdbarch *gdbarch = get_frame_arch (frame);
 292   struct value *reg_val;
 293
 294   gdb_assert (regnum < (gdbarch_num_regs (gdbarch)
 295                         + gdbarch_num_pseudo_regs (gdbarch)));
 296
 297   /* We should have a valid (i.e. non-sentinel) frame.  */
 298   gdb_assert (frame_id_p (get_frame_id (frame)));
 299
 300   reg_val = allocate_value (register_type (gdbarch, regnum));
 301   VALUE_LVAL (reg_val) = lval_register;
 302   VALUE_REGNUM (reg_val) = regnum;
 303   VALUE_FRAME_ID (reg_val) = get_frame_id (frame);
 304   set_value_lazy (reg_val, 1);
 305   return reg_val;
 306 }
 307
 308 /* Given a pointer of type TYPE in target form in BUF, return the
 309    address it represents.  */
 310 CORE_ADDR
 311 unsigned_pointer_to_address (struct type *type, const gdb_byte *buf)
 312 {
 313   return extract_unsigned_integer (buf, TYPE_LENGTH (type));
 314 }
 315
 316 CORE_ADDR
 317 signed_pointer_to_address (struct type *type, const gdb_byte *buf)
 318 {
 319   return extract_signed_integer (buf, TYPE_LENGTH (type));
 320 }
 321
 322 /* Given an address, store it as a pointer of type TYPE in target
 323    format in BUF.  */
 324 void
 325 unsigned_address_to_pointer (struct type *type, gdb_byte *buf,
 326                              CORE_ADDR addr)
 327 {
 328   store_unsigned_integer (buf, TYPE_LENGTH (type), addr);
 329 }
 330
 331 void
 332 address_to_signed_pointer (struct type *type, gdb_byte *buf, CORE_ADDR addr)
 333 {
 334   store_signed_integer (buf, TYPE_LENGTH (type), addr);
 335 }
 336 \f
 337 /* Will calling read_var_value or locate_var_value on SYM end
 338    up caring what frame it is being evaluated relative to?  SYM must
 339    be non-NULL.  */
 340 int
 341 symbol_read_needs_frame (struct symbol *sym)
 342 {
 343   switch (SYMBOL_CLASS (sym))
 344     {
 345       /* All cases listed explicitly so that gcc -Wall will detect it if
 346          we failed to consider one.  */
 347     case LOC_COMPUTED:
 348       /* FIXME: cagney/2004-01-26: It should be possible to
 349          unconditionally call the SYMBOL_OPS method when available.
 350          Unfortunately DWARF 2 stores the frame-base (instead of the
 351          function) location in a function's symbol.  Oops!  For the
 352          moment enable this when/where applicable.  */
 353       return SYMBOL_OPS (sym)->read_needs_frame (sym);
 354
 355     case LOC_REGISTER:
 356     case LOC_ARG:
 357     case LOC_REF_ARG:
 358     case LOC_REGPARM_ADDR:
 359     case LOC_LOCAL:
 360       return 1;
 361
 362     case LOC_UNDEF:
 363     case LOC_CONST:
 364     case LOC_STATIC:
 365     case LOC_TYPEDEF:
 366
 367     case LOC_LABEL:
 368       /* Getting the address of a label can be done independently of the block,
 369          even if some *uses* of that address wouldn't work so well without
 370          the right frame.  */
 371
 372     case LOC_BLOCK:
 373     case LOC_CONST_BYTES:
 374     case LOC_UNRESOLVED:
 375     case LOC_OPTIMIZED_OUT:
 376       return 0;
 377     }
 378   return 1;
 379 }
 380
 381 /* Given a struct symbol for a variable,
 382    and a stack frame id, read the value of the variable
 383    and return a (pointer to a) struct value containing the value.
 384    If the variable cannot be found, return a zero pointer.
 385    If FRAME is NULL, use the selected frame.  */
 386
 387 struct value *
 388 read_var_value (struct symbol *var, struct frame_info *frame)
 389 {
 390   struct value *v;
 391   struct type *type = SYMBOL_TYPE (var);
 392   CORE_ADDR addr;
 393   int len;
 394
 395   if (SYMBOL_CLASS (var) == LOC_COMPUTED
 396       || SYMBOL_CLASS (var) == LOC_REGISTER)
 397     /* These cases do not use V.  */
 398     v = NULL;
 399   else
 400     {
 401       v = allocate_value (type);
 402       VALUE_LVAL (v) = lval_memory;     /* The most likely possibility.  */
 403     }
 404
 405   len = TYPE_LENGTH (type);
 406
 407   /* FIXME drow/2003-09-06: this call to the selected frame should be
 408      pushed upwards to the callers.  */
 409   if (frame == NULL)
 410     frame = deprecated_safe_get_selected_frame ();
 411
 412   switch (SYMBOL_CLASS (var))
 413     {
 414     case LOC_CONST:
 415       /* Put the constant back in target format.  */
 416       store_signed_integer (value_contents_raw (v), len,
 417                             (LONGEST) SYMBOL_VALUE (var));
 418       VALUE_LVAL (v) = not_lval;
 419       return v;
 420
 421     case LOC_LABEL:
 422       /* Put the constant back in target format.  */
 423       if (overlay_debugging)
 424         {
 425           CORE_ADDR addr
 426             = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
 427                                         SYMBOL_OBJ_SECTION (var));
 428           store_typed_address (value_contents_raw (v), type, addr);
 429         }
 430       else
 431         store_typed_address (value_contents_raw (v), type,
 432                               SYMBOL_VALUE_ADDRESS (var));
 433       VALUE_LVAL (v) = not_lval;
 434       return v;
 435
 436     case LOC_CONST_BYTES:
 437       {
 438         memcpy (value_contents_raw (v), SYMBOL_VALUE_BYTES (var), len);
 439         VALUE_LVAL (v) = not_lval;
 440         return v;
 441       }
 442
 443     case LOC_STATIC:
 444       if (overlay_debugging)
 445         addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
 446                                          SYMBOL_OBJ_SECTION (var));
 447       else
 448         addr = SYMBOL_VALUE_ADDRESS (var);
 449       break;
 450
 451     case LOC_ARG:
 452       if (frame == NULL)
 453         return 0;
 454       addr = get_frame_args_address (frame);
 455       if (!addr)
 456         return 0;
 457       addr += SYMBOL_VALUE (var);
 458       break;
 459
 460     case LOC_REF_ARG:
 461       {
 462         struct value *ref;
 463         CORE_ADDR argref;
 464         if (frame == NULL)
 465           return 0;
 466         argref = get_frame_args_address (frame);
 467         if (!argref)
 468           return 0;
 469         argref += SYMBOL_VALUE (var);
 470         ref = value_at (lookup_pointer_type (type), argref);
 471         addr = value_as_address (ref);
 472         break;
 473       }
 474
 475     case LOC_LOCAL:
 476       if (frame == NULL)
 477         return 0;
 478       addr = get_frame_locals_address (frame);
 479       addr += SYMBOL_VALUE (var);
 480       break;
 481
 482     case LOC_TYPEDEF:
 483       error (_("Cannot look up value of a typedef"));
 484       break;
 485
 486     case LOC_BLOCK:
 487       if (overlay_debugging)
 488         VALUE_ADDRESS (v) = symbol_overlayed_address
 489           (BLOCK_START (SYMBOL_BLOCK_VALUE (var)), SYMBOL_OBJ_SECTION (var));
 490       else
 491         VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (var));
 492       return v;
 493
 494     case LOC_REGISTER:
 495     case LOC_REGPARM_ADDR:
 496       {
 497         int regno = SYMBOL_VALUE (var);
 498         struct value *regval;
 499
 500         if (frame == NULL)
 501           return 0;
 502
 503         if (SYMBOL_CLASS (var) == LOC_REGPARM_ADDR)
 504           {
 505             regval = value_from_register (lookup_pointer_type (type),
 506                                           regno,
 507                                           frame);
 508
 509             if (regval == NULL)
 510               error (_("Value of register variable not available."));
 511
 512             addr = value_as_address (regval);
 513             VALUE_LVAL (v) = lval_memory;
 514           }
 515         else
 516           {
 517             regval = value_from_register (type, regno, frame);
 518
 519             if (regval == NULL)
 520               error (_("Value of register variable not available."));
 521             return regval;
 522           }
 523       }
 524       break;
 525
 526     case LOC_COMPUTED:
 527       /* FIXME: cagney/2004-01-26: It should be possible to
 528          unconditionally call the SYMBOL_OPS method when available.
 529          Unfortunately DWARF 2 stores the frame-base (instead of the
 530          function) location in a function's symbol.  Oops!  For the
 531          moment enable this when/where applicable.  */
 532       if (frame == 0 && SYMBOL_OPS (var)->read_needs_frame (var))
 533         return 0;
 534       return SYMBOL_OPS (var)->read_variable (var, frame);
 535
 536     case LOC_UNRESOLVED:
 537       {
 538         struct minimal_symbol *msym;
 539
 540         msym = lookup_minimal_symbol (SYMBOL_LINKAGE_NAME (var), NULL, NULL);
 541         if (msym == NULL)
 542           return 0;
 543         if (overlay_debugging)
 544           addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym),
 545                                            SYMBOL_OBJ_SECTION (msym));
 546         else
 547           addr = SYMBOL_VALUE_ADDRESS (msym);
 548       }
 549       break;
 550
 551     case LOC_OPTIMIZED_OUT:
 552       VALUE_LVAL (v) = not_lval;
 553       set_value_optimized_out (v, 1);
 554       return v;
 555
 556     default:
 557       error (_("Cannot look up value of a botched symbol."));
 558       break;
 559     }
 560
 561   VALUE_ADDRESS (v) = addr;
 562   set_value_lazy (v, 1);
 563   return v;
 564 }
 565
 566 /* Install default attributes for register values.  */
 567
 568 struct value *
 569 default_value_from_register (struct type *type, int regnum,
 570                              struct frame_info *frame)
 571 {
 572   struct gdbarch *gdbarch = get_frame_arch (frame);
 573   int len = TYPE_LENGTH (type);
 574   struct value *value = allocate_value (type);
 575
 576   VALUE_LVAL (value) = lval_register;
 577   VALUE_FRAME_ID (value) = get_frame_id (frame);
 578   VALUE_REGNUM (value) = regnum;
 579
 580   /* Any structure stored in more than one register will always be
 581      an integral number of registers.  Otherwise, you need to do
 582      some fiddling with the last register copied here for little
 583      endian machines.  */
 584   if (gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG
 585       && len < register_size (gdbarch, regnum))
 586     /* Big-endian, and we want less than full size.  */
 587     set_value_offset (value, register_size (gdbarch, regnum) - len);
 588   else
 589     set_value_offset (value, 0);
 590
 591   return value;
 592 }
 593
 594 /* Return a value of type TYPE, stored in register REGNUM, in frame FRAME.  */
 595
 596 struct value *
 597 value_from_register (struct type *type, int regnum, struct frame_info *frame)
 598 {
 599   struct gdbarch *gdbarch = get_frame_arch (frame);
 600   struct type *type1 = check_typedef (type);
 601   struct value *v;
 602
 603   if (gdbarch_convert_register_p (gdbarch, regnum, type1))
 604     {
 605       /* The ISA/ABI need to something weird when obtaining the
 606          specified value from this register.  It might need to
 607          re-order non-adjacent, starting with REGNUM (see MIPS and
 608          i386).  It might need to convert the [float] register into
 609          the corresponding [integer] type (see Alpha).  The assumption
 610          is that gdbarch_register_to_value populates the entire value
 611          including the location.  */
 612       v = allocate_value (type);
 613       VALUE_LVAL (v) = lval_register;
 614       VALUE_FRAME_ID (v) = get_frame_id (frame);
 615       VALUE_REGNUM (v) = regnum;
 616       gdbarch_register_to_value (gdbarch,
 617                                  frame, regnum, type1, value_contents_raw (v));
 618     }
 619   else
 620     {
 621       int len = TYPE_LENGTH (type);
 622
 623       /* Construct the value.  */
 624       v = gdbarch_value_from_register (gdbarch, type, regnum, frame);
 625
 626       /* Get the data.  */
 627       if (!get_frame_register_bytes (frame, regnum, value_offset (v), len,
 628                                      value_contents_raw (v)))
 629         set_value_optimized_out (v, 1);
 630     }
 631   return v;
 632 }
 633
 634 /* Return contents of register REGNUM in frame FRAME as address,
 635    interpreted as value of type TYPE.   Will abort if register
 636    value is not available.  */
 637
 638 CORE_ADDR
 639 address_from_register (struct type *type, int regnum, struct frame_info *frame)
 640 {
 641   struct value *value;
 642   CORE_ADDR result;
 643
 644   value = value_from_register (type, regnum, frame);
 645   gdb_assert (value);
 646
 647   result = value_as_address (value);
 648   release_value (value);
 649   value_free (value);
 650
 651   return result;
 652 }
 653
 654 \f
 655 /* Given a struct symbol for a variable or function,
 656    and a stack frame id,
 657    return a (pointer to a) struct value containing the properly typed
 658    address.  */
 659
 660 struct value *
 661 locate_var_value (struct symbol *var, struct frame_info *frame)
 662 {
 663   struct gdbarch *gdbarch;
 664   CORE_ADDR addr = 0;
 665   struct type *type = SYMBOL_TYPE (var);
 666   struct value *lazy_value;
 667
 668   /* Evaluate it first; if the result is a memory address, we're fine.
 669      Lazy evaluation pays off here. */
 670
 671   lazy_value = read_var_value (var, frame);
 672   if (lazy_value == 0)
 673     error (_("Address of \"%s\" is unknown."), SYMBOL_PRINT_NAME (var));
 674
 675   if ((VALUE_LVAL (lazy_value) == lval_memory && value_lazy (lazy_value))
 676       || TYPE_CODE (type) == TYPE_CODE_FUNC)
 677     {
 678       struct value *val;
 679
 680       addr = VALUE_ADDRESS (lazy_value);
 681       val = value_from_pointer (lookup_pointer_type (type), addr);
 682       return val;
 683     }
 684
 685   /* Not a memory address; check what the problem was.  */
 686   switch (VALUE_LVAL (lazy_value))
 687     {
 688     case lval_register:
 689       gdb_assert (frame);
 690       gdbarch = get_frame_arch (frame);
 691       gdb_assert (gdbarch_register_name
 692                    (gdbarch, VALUE_REGNUM (lazy_value)) != NULL
 693                   && *gdbarch_register_name
 694                     (gdbarch, VALUE_REGNUM (lazy_value)) != '\0');
 695       error (_("Address requested for identifier "
 696                "\"%s\" which is in register $%s"),
 697             SYMBOL_PRINT_NAME (var),
 698             gdbarch_register_name (gdbarch, VALUE_REGNUM (lazy_value)));
 699       break;
 700
 701     default:
 702       error (_("Can't take address of \"%s\" which isn't an lvalue."),
 703              SYMBOL_PRINT_NAME (var));
 704       break;
 705     }
 706   return 0;                     /* For lint -- never reached */
 707 }