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     case LOC_COMPUTED_ARG:
 349       /* FIXME: cagney/2004-01-26: It should be possible to
 350          unconditionally call the SYMBOL_OPS method when available.
 351          Unfortunately DWARF 2 stores the frame-base (instead of the
 352          function) location in a function's symbol.  Oops!  For the
 353          moment enable this when/where applicable.  */
 354       return SYMBOL_OPS (sym)->read_needs_frame (sym);
 355
 356     case LOC_REGISTER:
 357     case LOC_ARG:
 358     case LOC_REF_ARG:
 359     case LOC_REGPARM:
 360     case LOC_REGPARM_ADDR:
 361     case LOC_LOCAL:
 362     case LOC_LOCAL_ARG:
 363     case LOC_BASEREG:
 364     case LOC_BASEREG_ARG:
 365     case LOC_HP_THREAD_LOCAL_STATIC:
 366       return 1;
 367
 368     case LOC_UNDEF:
 369     case LOC_CONST:
 370     case LOC_STATIC:
 371     case LOC_INDIRECT:
 372     case LOC_TYPEDEF:
 373
 374     case LOC_LABEL:
 375       /* Getting the address of a label can be done independently of the block,
 376          even if some *uses* of that address wouldn't work so well without
 377          the right frame.  */
 378
 379     case LOC_BLOCK:
 380     case LOC_CONST_BYTES:
 381     case LOC_UNRESOLVED:
 382     case LOC_OPTIMIZED_OUT:
 383       return 0;
 384     }
 385   return 1;
 386 }
 387
 388 /* Given a struct symbol for a variable,
 389    and a stack frame id, read the value of the variable
 390    and return a (pointer to a) struct value containing the value.
 391    If the variable cannot be found, return a zero pointer.
 392    If FRAME is NULL, use the selected frame.  */
 393
 394 struct value *
 395 read_var_value (struct symbol *var, struct frame_info *frame)
 396 {
 397   struct value *v;
 398   struct type *type = SYMBOL_TYPE (var);
 399   CORE_ADDR addr;
 400   int len;
 401
 402   if (SYMBOL_CLASS (var) == LOC_COMPUTED
 403       || SYMBOL_CLASS (var) == LOC_COMPUTED_ARG
 404       || SYMBOL_CLASS (var) == LOC_REGISTER
 405       || SYMBOL_CLASS (var) == LOC_REGPARM)
 406     /* These cases do not use V.  */
 407     v = NULL;
 408   else
 409     {
 410       v = allocate_value (type);
 411       VALUE_LVAL (v) = lval_memory;     /* The most likely possibility.  */
 412     }
 413
 414   len = TYPE_LENGTH (type);
 415
 416   /* FIXME drow/2003-09-06: this call to the selected frame should be
 417      pushed upwards to the callers.  */
 418   if (frame == NULL)
 419     frame = deprecated_safe_get_selected_frame ();
 420
 421   switch (SYMBOL_CLASS (var))
 422     {
 423     case LOC_CONST:
 424       /* Put the constant back in target format.  */
 425       store_signed_integer (value_contents_raw (v), len,
 426                             (LONGEST) SYMBOL_VALUE (var));
 427       VALUE_LVAL (v) = not_lval;
 428       return v;
 429
 430     case LOC_LABEL:
 431       /* Put the constant back in target format.  */
 432       if (overlay_debugging)
 433         {
 434           CORE_ADDR addr
 435             = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
 436                                         SYMBOL_BFD_SECTION (var));
 437           store_typed_address (value_contents_raw (v), type, addr);
 438         }
 439       else
 440         store_typed_address (value_contents_raw (v), type,
 441                               SYMBOL_VALUE_ADDRESS (var));
 442       VALUE_LVAL (v) = not_lval;
 443       return v;
 444
 445     case LOC_CONST_BYTES:
 446       {
 447         memcpy (value_contents_raw (v), SYMBOL_VALUE_BYTES (var), len);
 448         VALUE_LVAL (v) = not_lval;
 449         return v;
 450       }
 451
 452     case LOC_STATIC:
 453       if (overlay_debugging)
 454         addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
 455                                          SYMBOL_BFD_SECTION (var));
 456       else
 457         addr = SYMBOL_VALUE_ADDRESS (var);
 458       break;
 459
 460     case LOC_INDIRECT:
 461       {
 462         /* The import slot does not have a real address in it from the
 463            dynamic loader (dld.sl on HP-UX), if the target hasn't
 464            begun execution yet, so check for that. */
 465         CORE_ADDR locaddr;
 466         struct value *loc;
 467         if (!target_has_execution)
 468           error (_("\
 469 Attempt to access variable defined in different shared object or load module when\n\
 470 addresses have not been bound by the dynamic loader. Try again when executable is running."));
 471
 472         locaddr = SYMBOL_VALUE_ADDRESS (var);
 473         loc = value_at (lookup_pointer_type (type), locaddr);
 474         addr = value_as_address (loc);
 475         break;
 476       }
 477
 478     case LOC_ARG:
 479       if (frame == NULL)
 480         return 0;
 481       addr = get_frame_args_address (frame);
 482       if (!addr)
 483         return 0;
 484       addr += SYMBOL_VALUE (var);
 485       break;
 486
 487     case LOC_REF_ARG:
 488       {
 489         struct value *ref;
 490         CORE_ADDR argref;
 491         if (frame == NULL)
 492           return 0;
 493         argref = get_frame_args_address (frame);
 494         if (!argref)
 495           return 0;
 496         argref += SYMBOL_VALUE (var);
 497         ref = value_at (lookup_pointer_type (type), argref);
 498         addr = value_as_address (ref);
 499         break;
 500       }
 501
 502     case LOC_LOCAL:
 503     case LOC_LOCAL_ARG:
 504       if (frame == NULL)
 505         return 0;
 506       addr = get_frame_locals_address (frame);
 507       addr += SYMBOL_VALUE (var);
 508       break;
 509
 510     case LOC_BASEREG:
 511     case LOC_BASEREG_ARG:
 512     case LOC_HP_THREAD_LOCAL_STATIC:
 513       {
 514         struct value *regval;
 515
 516         regval = value_from_register (lookup_pointer_type (type),
 517                                       SYMBOL_BASEREG (var), frame);
 518         if (regval == NULL)
 519           error (_("Value of base register not available."));
 520         addr = value_as_address (regval);
 521         addr += SYMBOL_VALUE (var);
 522         break;
 523       }
 524
 525     case LOC_TYPEDEF:
 526       error (_("Cannot look up value of a typedef"));
 527       break;
 528
 529     case LOC_BLOCK:
 530       if (overlay_debugging)
 531         VALUE_ADDRESS (v) = symbol_overlayed_address
 532           (BLOCK_START (SYMBOL_BLOCK_VALUE (var)), SYMBOL_BFD_SECTION (var));
 533       else
 534         VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (var));
 535       return v;
 536
 537     case LOC_REGISTER:
 538     case LOC_REGPARM:
 539     case LOC_REGPARM_ADDR:
 540       {
 541         struct block *b;
 542         int regno = SYMBOL_VALUE (var);
 543         struct value *regval;
 544
 545         if (frame == NULL)
 546           return 0;
 547         b = get_frame_block (frame, 0);
 548
 549         if (SYMBOL_CLASS (var) == LOC_REGPARM_ADDR)
 550           {
 551             regval = value_from_register (lookup_pointer_type (type),
 552                                           regno,
 553                                           frame);
 554
 555             if (regval == NULL)
 556               error (_("Value of register variable not available."));
 557
 558             addr = value_as_address (regval);
 559             VALUE_LVAL (v) = lval_memory;
 560           }
 561         else
 562           {
 563             regval = value_from_register (type, regno, frame);
 564
 565             if (regval == NULL)
 566               error (_("Value of register variable not available."));
 567             return regval;
 568           }
 569       }
 570       break;
 571
 572     case LOC_COMPUTED:
 573     case LOC_COMPUTED_ARG:
 574       /* FIXME: cagney/2004-01-26: It should be possible to
 575          unconditionally call the SYMBOL_OPS method when available.
 576          Unfortunately DWARF 2 stores the frame-base (instead of the
 577          function) location in a function's symbol.  Oops!  For the
 578          moment enable this when/where applicable.  */
 579       if (frame == 0 && SYMBOL_OPS (var)->read_needs_frame (var))
 580         return 0;
 581       return SYMBOL_OPS (var)->read_variable (var, frame);
 582
 583     case LOC_UNRESOLVED:
 584       {
 585         struct minimal_symbol *msym;
 586
 587         msym = lookup_minimal_symbol (DEPRECATED_SYMBOL_NAME (var), NULL, NULL);
 588         if (msym == NULL)
 589           return 0;
 590         if (overlay_debugging)
 591           addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym),
 592                                            SYMBOL_BFD_SECTION (msym));
 593         else
 594           addr = SYMBOL_VALUE_ADDRESS (msym);
 595       }
 596       break;
 597
 598     case LOC_OPTIMIZED_OUT:
 599       VALUE_LVAL (v) = not_lval;
 600       set_value_optimized_out (v, 1);
 601       return v;
 602
 603     default:
 604       error (_("Cannot look up value of a botched symbol."));
 605       break;
 606     }
 607
 608   VALUE_ADDRESS (v) = addr;
 609   set_value_lazy (v, 1);
 610   return v;
 611 }
 612
 613 /* Install default attributes for register values.  */
 614
 615 struct value *
 616 default_value_from_register (struct type *type, int regnum,
 617                              struct frame_info *frame)
 618 {
 619   struct gdbarch *gdbarch = get_frame_arch (frame);
 620   int len = TYPE_LENGTH (type);
 621   struct value *value = allocate_value (type);
 622
 623   VALUE_LVAL (value) = lval_register;
 624   VALUE_FRAME_ID (value) = get_frame_id (frame);
 625   VALUE_REGNUM (value) = regnum;
 626
 627   /* Any structure stored in more than one register will always be
 628      an integral number of registers.  Otherwise, you need to do
 629      some fiddling with the last register copied here for little
 630      endian machines.  */
 631   if (gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG
 632       && len < register_size (gdbarch, regnum))
 633     /* Big-endian, and we want less than full size.  */
 634     set_value_offset (value, register_size (gdbarch, regnum) - len);
 635   else
 636     set_value_offset (value, 0);
 637
 638   return value;
 639 }
 640
 641 /* Return a value of type TYPE, stored in register REGNUM, in frame FRAME.  */
 642
 643 struct value *
 644 value_from_register (struct type *type, int regnum, struct frame_info *frame)
 645 {
 646   struct gdbarch *gdbarch = get_frame_arch (frame);
 647   struct type *type1 = check_typedef (type);
 648   struct value *v;
 649
 650   if (gdbarch_convert_register_p (gdbarch, regnum, type1))
 651     {
 652       /* The ISA/ABI need to something weird when obtaining the
 653          specified value from this register.  It might need to
 654          re-order non-adjacent, starting with REGNUM (see MIPS and
 655          i386).  It might need to convert the [float] register into
 656          the corresponding [integer] type (see Alpha).  The assumption
 657          is that gdbarch_register_to_value populates the entire value
 658          including the location.  */
 659       v = allocate_value (type);
 660       VALUE_LVAL (v) = lval_register;
 661       VALUE_FRAME_ID (v) = get_frame_id (frame);
 662       VALUE_REGNUM (v) = regnum;
 663       gdbarch_register_to_value (gdbarch,
 664                                  frame, regnum, type1, value_contents_raw (v));
 665     }
 666   else
 667     {
 668       int len = TYPE_LENGTH (type);
 669
 670       /* Construct the value.  */
 671       v = gdbarch_value_from_register (gdbarch, type, regnum, frame);
 672
 673       /* Get the data.  */
 674       if (!get_frame_register_bytes (frame, regnum, value_offset (v), len,
 675                                      value_contents_raw (v)))
 676         set_value_optimized_out (v, 1);
 677     }
 678   return v;
 679 }
 680
 681 /* Return contents of register REGNUM in frame FRAME as address,
 682    interpreted as value of type TYPE.   Will abort if register
 683    value is not available.  */
 684
 685 CORE_ADDR
 686 address_from_register (struct type *type, int regnum, struct frame_info *frame)
 687 {
 688   struct value *value;
 689   CORE_ADDR result;
 690
 691   value = value_from_register (type, regnum, frame);
 692   gdb_assert (value);
 693
 694   result = value_as_address (value);
 695   release_value (value);
 696   value_free (value);
 697
 698   return result;
 699 }
 700
 701 \f
 702 /* Given a struct symbol for a variable or function,
 703    and a stack frame id,
 704    return a (pointer to a) struct value containing the properly typed
 705    address.  */
 706
 707 struct value *
 708 locate_var_value (struct symbol *var, struct frame_info *frame)
 709 {
 710   struct gdbarch *gdbarch = get_frame_arch (frame);
 711   CORE_ADDR addr = 0;
 712   struct type *type = SYMBOL_TYPE (var);
 713   struct value *lazy_value;
 714
 715   /* Evaluate it first; if the result is a memory address, we're fine.
 716      Lazy evaluation pays off here. */
 717
 718   lazy_value = read_var_value (var, frame);
 719   if (lazy_value == 0)
 720     error (_("Address of \"%s\" is unknown."), SYMBOL_PRINT_NAME (var));
 721
 722   if ((VALUE_LVAL (lazy_value) == lval_memory && value_lazy (lazy_value))
 723       || TYPE_CODE (type) == TYPE_CODE_FUNC)
 724     {
 725       struct value *val;
 726
 727       addr = VALUE_ADDRESS (lazy_value);
 728       val = value_from_pointer (lookup_pointer_type (type), addr);
 729       return val;
 730     }
 731
 732   /* Not a memory address; check what the problem was.  */
 733   switch (VALUE_LVAL (lazy_value))
 734     {
 735     case lval_register:
 736       gdb_assert (gdbarch_register_name
 737                    (gdbarch, VALUE_REGNUM (lazy_value)) != NULL
 738                   && *gdbarch_register_name
 739                     (gdbarch, VALUE_REGNUM (lazy_value)) != '\0');
 740       error (_("Address requested for identifier "
 741                "\"%s\" which is in register $%s"),
 742             SYMBOL_PRINT_NAME (var),
 743             gdbarch_register_name (gdbarch, VALUE_REGNUM (lazy_value)));
 744       break;
 745
 746     default:
 747       error (_("Can't take address of \"%s\" which isn't an lvalue."),
 748              SYMBOL_PRINT_NAME (var));
 749       break;
 750     }
 751   return 0;                     /* For lint -- never reached */
 752 }