2003-01-15 David Carlton <carlton@math.stanford.edu>

[deliverable/binutils-gdb.git] / gdb / findvar.c

/* Find a variable's value in memory, for GDB, the GNU debugger.

   Copyright 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
   1995, 1996, 1997, 1998, 1999, 2000, 2001, 2003 Free Software
   Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include "defs.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "frame.h"
#include "value.h"
#include "gdbcore.h"
#include "inferior.h"
#include "target.h"
#include "gdb_string.h"
#include "gdb_assert.h"
#include "floatformat.h"
#include "symfile.h"            /* for overlay functions */
#include "regcache.h"
#include "builtin-regs.h"

/* Basic byte-swapping routines.  GDB has needed these for a long time...
   All extract a target-format integer at ADDR which is LEN bytes long.  */

#if TARGET_CHAR_BIT != 8 || HOST_CHAR_BIT != 8
  /* 8 bit characters are a pretty safe assumption these days, so we
     assume it throughout all these swapping routines.  If we had to deal with
     9 bit characters, we would need to make len be in bits and would have
     to re-write these routines...  */
you lose
#endif

LONGEST
extract_signed_integer (const void *addr, int len)
{
  LONGEST retval;
  const unsigned char *p;
  const unsigned char *startaddr = addr;
  const unsigned char *endaddr = startaddr + len;

  if (len > (int) sizeof (LONGEST))
    error ("\
That operation is not available on integers of more than %d bytes.",
           (int) sizeof (LONGEST));

  /* Start at the most significant end of the integer, and work towards
     the least significant.  */
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    {
      p = startaddr;
      /* Do the sign extension once at the start.  */
      retval = ((LONGEST) * p ^ 0x80) - 0x80;
      for (++p; p < endaddr; ++p)
        retval = (retval << 8) | *p;
    }
  else
    {
      p = endaddr - 1;
      /* Do the sign extension once at the start.  */
      retval = ((LONGEST) * p ^ 0x80) - 0x80;
      for (--p; p >= startaddr; --p)
        retval = (retval << 8) | *p;
    }
  return retval;
}

ULONGEST
extract_unsigned_integer (const void *addr, int len)
{
  ULONGEST retval;
  const unsigned char *p;
  const unsigned char *startaddr = addr;
  const unsigned char *endaddr = startaddr + len;

  if (len > (int) sizeof (ULONGEST))
    error ("\
That operation is not available on integers of more than %d bytes.",
           (int) sizeof (ULONGEST));

  /* Start at the most significant end of the integer, and work towards
     the least significant.  */
  retval = 0;
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    {
      for (p = startaddr; p < endaddr; ++p)
        retval = (retval << 8) | *p;
    }
  else
    {
      for (p = endaddr - 1; p >= startaddr; --p)
        retval = (retval << 8) | *p;
    }
  return retval;
}

/* Sometimes a long long unsigned integer can be extracted as a
   LONGEST value.  This is done so that we can print these values
   better.  If this integer can be converted to a LONGEST, this
   function returns 1 and sets *PVAL.  Otherwise it returns 0.  */

int
extract_long_unsigned_integer (const void *addr, int orig_len, LONGEST *pval)
{
  char *p, *first_addr;
  int len;

  len = orig_len;
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    {
      for (p = (char *) addr;
           len > (int) sizeof (LONGEST) && p < (char *) addr + orig_len;
           p++)
        {
          if (*p == 0)
            len--;
          else
            break;
        }
      first_addr = p;
    }
  else
    {
      first_addr = (char *) addr;
      for (p = (char *) addr + orig_len - 1;
           len > (int) sizeof (LONGEST) && p >= (char *) addr;
           p--)
        {
          if (*p == 0)
            len--;
          else
            break;
        }
    }

  if (len <= (int) sizeof (LONGEST))
    {
      *pval = (LONGEST) extract_unsigned_integer (first_addr,
                                                  sizeof (LONGEST));
      return 1;
    }

  return 0;
}


/* Treat the LEN bytes at ADDR as a target-format address, and return
   that address.  ADDR is a buffer in the GDB process, not in the
   inferior.

   This function should only be used by target-specific code.  It
   assumes that a pointer has the same representation as that thing's
   address represented as an integer.  Some machines use word
   addresses, or similarly munged things, for certain types of
   pointers, so that assumption doesn't hold everywhere.

   Common code should use extract_typed_address instead, or something
   else based on POINTER_TO_ADDRESS.  */

CORE_ADDR
extract_address (const void *addr, int len)
{
  /* Assume a CORE_ADDR can fit in a LONGEST (for now).  Not sure
     whether we want this to be true eventually.  */
  return (CORE_ADDR) extract_unsigned_integer (addr, len);
}


/* Treat the bytes at BUF as a pointer of type TYPE, and return the
   address it represents.  */
CORE_ADDR
extract_typed_address (const void *buf, struct type *type)
{
  if (TYPE_CODE (type) != TYPE_CODE_PTR
      && TYPE_CODE (type) != TYPE_CODE_REF)
    internal_error (__FILE__, __LINE__,
                    "extract_typed_address: "
                    "type is not a pointer or reference");

  return POINTER_TO_ADDRESS (type, buf);
}


void
store_signed_integer (void *addr, int len, LONGEST val)
{
  unsigned char *p;
  unsigned char *startaddr = (unsigned char *) addr;
  unsigned char *endaddr = startaddr + len;

  /* Start at the least significant end of the integer, and work towards
     the most significant.  */
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    {
      for (p = endaddr - 1; p >= startaddr; --p)
        {
          *p = val & 0xff;
          val >>= 8;
        }
    }
  else
    {
      for (p = startaddr; p < endaddr; ++p)
        {
          *p = val & 0xff;
          val >>= 8;
        }
    }
}

void
store_unsigned_integer (void *addr, int len, ULONGEST val)
{
  unsigned char *p;
  unsigned char *startaddr = (unsigned char *) addr;
  unsigned char *endaddr = startaddr + len;

  /* Start at the least significant end of the integer, and work towards
     the most significant.  */
  if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
    {
      for (p = endaddr - 1; p >= startaddr; --p)
        {
          *p = val & 0xff;
          val >>= 8;
        }
    }
  else
    {
      for (p = startaddr; p < endaddr; ++p)
        {
          *p = val & 0xff;
          val >>= 8;
        }
    }
}

/* Store the address VAL as a LEN-byte value in target byte order at
   ADDR.  ADDR is a buffer in the GDB process, not in the inferior.

   This function should only be used by target-specific code.  It
   assumes that a pointer has the same representation as that thing's
   address represented as an integer.  Some machines use word
   addresses, or similarly munged things, for certain types of
   pointers, so that assumption doesn't hold everywhere.

   Common code should use store_typed_address instead, or something else
   based on ADDRESS_TO_POINTER.  */
void
store_address (void *addr, int len, LONGEST val)
{
  store_unsigned_integer (addr, len, val);
}


/* Store the address ADDR as a pointer of type TYPE at BUF, in target
   form.  */
void
store_typed_address (void *buf, struct type *type, CORE_ADDR addr)
{
  if (TYPE_CODE (type) != TYPE_CODE_PTR
      && TYPE_CODE (type) != TYPE_CODE_REF)
    internal_error (__FILE__, __LINE__,
                    "store_typed_address: "
                    "type is not a pointer or reference");

  ADDRESS_TO_POINTER (type, buf, addr);
}



/* Return a `value' with the contents of (virtual or cooked) register
   REGNUM as found in the specified FRAME.  The register's type is
   determined by REGISTER_VIRTUAL_TYPE.

   NOTE: returns NULL if register value is not available.  Caller will
   check return value or die!  */

struct value *
value_of_register (int regnum, struct frame_info *frame)
{
  CORE_ADDR addr;
  int optim;
  struct value *reg_val;
  char *raw_buffer = (char*) alloca (MAX_REGISTER_RAW_SIZE);
  enum lval_type lval;

  /* Builtin registers lie completly outside of the range of normal
     registers.  Catch them early so that the target never sees them.  */
  if (regnum >= NUM_REGS + NUM_PSEUDO_REGS)
    return value_of_builtin_reg (regnum, deprecated_selected_frame);

  get_saved_register (raw_buffer, &optim, &addr,
                      frame, regnum, &lval);

  /* FIXME: cagney/2002-05-15: This test is just bogus.

     It indicates that the target failed to supply a value for a
     register because it was "not available" at this time.  Problem
     is, the target still has the register and so get saved_register()
     may be returning a value saved on the stack.  */

  if (register_cached (regnum) < 0)
    return NULL;                /* register value not available */

  reg_val = allocate_value (REGISTER_VIRTUAL_TYPE (regnum));

  /* Convert raw data to virtual format if necessary.  */

  if (REGISTER_CONVERTIBLE (regnum))
    {
      REGISTER_CONVERT_TO_VIRTUAL (regnum, REGISTER_VIRTUAL_TYPE (regnum),
                                   raw_buffer, VALUE_CONTENTS_RAW (reg_val));
    }
  else if (REGISTER_RAW_SIZE (regnum) == REGISTER_VIRTUAL_SIZE (regnum))
    memcpy (VALUE_CONTENTS_RAW (reg_val), raw_buffer,
            REGISTER_RAW_SIZE (regnum));
  else
    internal_error (__FILE__, __LINE__,
                    "Register \"%s\" (%d) has conflicting raw (%d) and virtual (%d) size",
                    REGISTER_NAME (regnum),
                    regnum,
                    REGISTER_RAW_SIZE (regnum),
                    REGISTER_VIRTUAL_SIZE (regnum));
  VALUE_LVAL (reg_val) = lval;
  VALUE_ADDRESS (reg_val) = addr;
  VALUE_REGNO (reg_val) = regnum;
  VALUE_OPTIMIZED_OUT (reg_val) = optim;
  return reg_val;
}

/* Given a pointer of type TYPE in target form in BUF, return the
   address it represents.  */
CORE_ADDR
unsigned_pointer_to_address (struct type *type, const void *buf)
{
  return extract_address (buf, TYPE_LENGTH (type));
}

CORE_ADDR
signed_pointer_to_address (struct type *type, const void *buf)
{
  return extract_signed_integer (buf, TYPE_LENGTH (type));
}

/* Given an address, store it as a pointer of type TYPE in target
   format in BUF.  */
void
unsigned_address_to_pointer (struct type *type, void *buf, CORE_ADDR addr)
{
  store_address (buf, TYPE_LENGTH (type), addr);
}

void
address_to_signed_pointer (struct type *type, void *buf, CORE_ADDR addr)
{
  store_signed_integer (buf, TYPE_LENGTH (type), addr);
}
\f
/* Will calling read_var_value or locate_var_value on SYM end
   up caring what frame it is being evaluated relative to?  SYM must
   be non-NULL.  */
int
symbol_read_needs_frame (struct symbol *sym)
{
  switch (SYMBOL_CLASS (sym))
    {
      /* All cases listed explicitly so that gcc -Wall will detect it if
         we failed to consider one.  */
    case LOC_REGISTER:
    case LOC_ARG:
    case LOC_REF_ARG:
    case LOC_REGPARM:
    case LOC_REGPARM_ADDR:
    case LOC_LOCAL:
    case LOC_LOCAL_ARG:
    case LOC_BASEREG:
    case LOC_BASEREG_ARG:
    case LOC_HP_THREAD_LOCAL_STATIC:
      return 1;

    case LOC_UNDEF:
    case LOC_CONST:
    case LOC_STATIC:
    case LOC_INDIRECT:
    case LOC_TYPEDEF:

    case LOC_LABEL:
      /* Getting the address of a label can be done independently of the block,
         even if some *uses* of that address wouldn't work so well without
         the right frame.  */

    case LOC_BLOCK:
    case LOC_CONST_BYTES:
    case LOC_UNRESOLVED:
    case LOC_OPTIMIZED_OUT:
      return 0;
    }
  return 1;
}

/* Given a struct symbol for a variable,
   and a stack frame id, read the value of the variable
   and return a (pointer to a) struct value containing the value. 
   If the variable cannot be found, return a zero pointer.
   If FRAME is NULL, use the deprecated_selected_frame.  */

struct value *
read_var_value (register struct symbol *var, struct frame_info *frame)
{
  register struct value *v;
  struct type *type = SYMBOL_TYPE (var);
  CORE_ADDR addr;
  register int len;

  v = allocate_value (type);
  VALUE_LVAL (v) = lval_memory; /* The most likely possibility.  */
  VALUE_BFD_SECTION (v) = SYMBOL_BFD_SECTION (var);

  len = TYPE_LENGTH (type);

  if (frame == NULL)
    frame = deprecated_selected_frame;

  switch (SYMBOL_CLASS (var))
    {
    case LOC_CONST:
      /* Put the constant back in target format.  */
      store_signed_integer (VALUE_CONTENTS_RAW (v), len,
                            (LONGEST) SYMBOL_VALUE (var));
      VALUE_LVAL (v) = not_lval;
      return v;

    case LOC_LABEL:
      /* Put the constant back in target format.  */
      if (overlay_debugging)
        {
          CORE_ADDR addr
            = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
                                        SYMBOL_BFD_SECTION (var));
          store_typed_address (VALUE_CONTENTS_RAW (v), type, addr);
        }
      else
        store_typed_address (VALUE_CONTENTS_RAW (v), type,
                              SYMBOL_VALUE_ADDRESS (var));
      VALUE_LVAL (v) = not_lval;
      return v;

    case LOC_CONST_BYTES:
      {
        char *bytes_addr;
        bytes_addr = SYMBOL_VALUE_BYTES (var);
        memcpy (VALUE_CONTENTS_RAW (v), bytes_addr, len);
        VALUE_LVAL (v) = not_lval;
        return v;
      }

    case LOC_STATIC:
      if (overlay_debugging)
        addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (var),
                                         SYMBOL_BFD_SECTION (var));
      else
        addr = SYMBOL_VALUE_ADDRESS (var);
      break;

    case LOC_INDIRECT:
      {
        /* The import slot does not have a real address in it from the
           dynamic loader (dld.sl on HP-UX), if the target hasn't
           begun execution yet, so check for that. */
        CORE_ADDR locaddr;
        struct value *loc;
        if (!target_has_execution)
          error ("\
Attempt to access variable defined in different shared object or load module when\n\
addresses have not been bound by the dynamic loader. Try again when executable is running.");

        locaddr = SYMBOL_VALUE_ADDRESS (var);
        loc = value_at (lookup_pointer_type (type), locaddr, NULL);
        addr = value_as_address (loc);
      }

    case LOC_ARG:
      if (frame == NULL)
        return 0;
      addr = FRAME_ARGS_ADDRESS (frame);
      if (!addr)
        return 0;
      addr += SYMBOL_VALUE (var);
      break;

    case LOC_REF_ARG:
      {
        struct value *ref;
        CORE_ADDR argref;
        if (frame == NULL)
          return 0;
        argref = FRAME_ARGS_ADDRESS (frame);
        if (!argref)
          return 0;
        argref += SYMBOL_VALUE (var);
        ref = value_at (lookup_pointer_type (type), argref, NULL);
        addr = value_as_address (ref);
        break;
      }

    case LOC_LOCAL:
    case LOC_LOCAL_ARG:
      if (frame == NULL)
        return 0;
      addr = FRAME_LOCALS_ADDRESS (frame);
      addr += SYMBOL_VALUE (var);
      break;

    case LOC_BASEREG:
    case LOC_BASEREG_ARG:
    case LOC_HP_THREAD_LOCAL_STATIC:
      {
        struct value *regval;

        regval = value_from_register (lookup_pointer_type (type),
                                      SYMBOL_BASEREG (var), frame);
        if (regval == NULL)
          error ("Value of base register not available.");
        addr = value_as_address (regval);
        addr += SYMBOL_VALUE (var);
        break;
      }

    case LOC_THREAD_LOCAL_STATIC:
      {
        if (target_get_thread_local_address_p ())
          addr = target_get_thread_local_address (inferior_ptid,
                                                  SYMBOL_OBJFILE (var),
                                                  SYMBOL_VALUE_ADDRESS (var));
        /* It wouldn't be wrong here to try a gdbarch method, too;
           finding TLS is an ABI-specific thing.  But we don't do that
           yet.  */
        else
          error ("Cannot find thread-local variables on this target");
        break;
      }

    case LOC_TYPEDEF:
      error ("Cannot look up value of a typedef");
      break;

    case LOC_BLOCK:
      if (overlay_debugging)
        VALUE_ADDRESS (v) = symbol_overlayed_address
          (BLOCK_START (SYMBOL_BLOCK_VALUE (var)), SYMBOL_BFD_SECTION (var));
      else
        VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (var));
      return v;

    case LOC_REGISTER:
    case LOC_REGPARM:
    case LOC_REGPARM_ADDR:
      {
        struct block *b;
        int regno = SYMBOL_VALUE (var);
        struct value *regval;

        if (frame == NULL)
          return 0;
        b = get_frame_block (frame, 0);

        if (SYMBOL_CLASS (var) == LOC_REGPARM_ADDR)
          {
            regval = value_from_register (lookup_pointer_type (type),
                                          regno,
                                          frame);

            if (regval == NULL)
              error ("Value of register variable not available.");

            addr = value_as_address (regval);
            VALUE_LVAL (v) = lval_memory;
          }
        else
          {
            regval = value_from_register (type, regno, frame);

            if (regval == NULL)
              error ("Value of register variable not available.");
            return regval;
          }
      }
      break;

    case LOC_UNRESOLVED:
      {
        struct minimal_symbol *msym;

        msym = lookup_minimal_symbol (SYMBOL_NAME (var), NULL, NULL);
        if (msym == NULL)
          return 0;
        if (overlay_debugging)
          addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym),
                                           SYMBOL_BFD_SECTION (msym));
        else
          addr = SYMBOL_VALUE_ADDRESS (msym);
      }
      break;

    case LOC_OPTIMIZED_OUT:
      VALUE_LVAL (v) = not_lval;
      VALUE_OPTIMIZED_OUT (v) = 1;
      return v;

    default:
      error ("Cannot look up value of a botched symbol.");
      break;
    }

  VALUE_ADDRESS (v) = addr;
  VALUE_LAZY (v) = 1;
  return v;
}

/* Return a value of type TYPE, stored in register REGNUM, in frame
   FRAME.

   NOTE: returns NULL if register value is not available.
   Caller will check return value or die!  */

struct value *
value_from_register (struct type *type, int regnum, struct frame_info *frame)
{
  char *raw_buffer = (char*) alloca (MAX_REGISTER_RAW_SIZE);
  CORE_ADDR addr;
  int optim;
  struct value *v = allocate_value (type);
  char *value_bytes = 0;
  int value_bytes_copied = 0;
  int num_storage_locs;
  enum lval_type lval;
  int len;

  CHECK_TYPEDEF (type);
  len = TYPE_LENGTH (type);

  VALUE_REGNO (v) = regnum;

  num_storage_locs = (len > REGISTER_VIRTUAL_SIZE (regnum) ?
                      ((len - 1) / REGISTER_RAW_SIZE (regnum)) + 1 :
                      1);

  if (num_storage_locs > 1
#ifdef GDB_TARGET_IS_H8500
      || TYPE_CODE (type) == TYPE_CODE_PTR
#endif
    )
    {
      /* Value spread across multiple storage locations.  */

      int local_regnum;
      int mem_stor = 0, reg_stor = 0;
      int mem_tracking = 1;
      CORE_ADDR last_addr = 0;
      CORE_ADDR first_addr = 0;

      value_bytes = (char *) alloca (len + MAX_REGISTER_RAW_SIZE);

      /* Copy all of the data out, whereever it may be.  */

#ifdef GDB_TARGET_IS_H8500
/* This piece of hideosity is required because the H8500 treats registers
   differently depending upon whether they are used as pointers or not.  As a
   pointer, a register needs to have a page register tacked onto the front.
   An alternate way to do this would be to have gcc output different register
   numbers for the pointer & non-pointer form of the register.  But, it
   doesn't, so we're stuck with this.  */

      if (TYPE_CODE (type) == TYPE_CODE_PTR
          && len > 2)
        {
          int page_regnum;

          switch (regnum)
            {
            case R0_REGNUM:
            case R1_REGNUM:
            case R2_REGNUM:
            case R3_REGNUM:
              page_regnum = SEG_D_REGNUM;
              break;
            case R4_REGNUM:
            case R5_REGNUM:
              page_regnum = SEG_E_REGNUM;
              break;
            case R6_REGNUM:
            case R7_REGNUM:
              page_regnum = SEG_T_REGNUM;
              break;
            }

          value_bytes[0] = 0;
          get_saved_register (value_bytes + 1,
                              &optim,
                              &addr,
                              frame,
                              page_regnum,
                              &lval);

          if (register_cached (page_regnum) == -1)
            return NULL;        /* register value not available */

          if (lval == lval_register)
            reg_stor++;
          else
            mem_stor++;
          first_addr = addr;
          last_addr = addr;

          get_saved_register (value_bytes + 2,
                              &optim,
                              &addr,
                              frame,
                              regnum,
                              &lval);

          if (register_cached (regnum) == -1)
            return NULL;        /* register value not available */

          if (lval == lval_register)
            reg_stor++;
          else
            {
              mem_stor++;
              mem_tracking = mem_tracking && (addr == last_addr);
            }
          last_addr = addr;
        }
      else
#endif /* GDB_TARGET_IS_H8500 */
        for (local_regnum = regnum;
             value_bytes_copied < len;
             (value_bytes_copied += REGISTER_RAW_SIZE (local_regnum),
              ++local_regnum))
          {
            get_saved_register (value_bytes + value_bytes_copied,
                                &optim,
                                &addr,
                                frame,
                                local_regnum,
                                &lval);

            if (register_cached (local_regnum) == -1)
              return NULL;      /* register value not available */

            if (regnum == local_regnum)
              first_addr = addr;
            if (lval == lval_register)
              reg_stor++;
            else
              {
                mem_stor++;

                mem_tracking =
                  (mem_tracking
                   && (regnum == local_regnum
                       || addr == last_addr));
              }
            last_addr = addr;
          }

      if ((reg_stor && mem_stor)
          || (mem_stor && !mem_tracking))
        /* Mixed storage; all of the hassle we just went through was
           for some good purpose.  */
        {
          VALUE_LVAL (v) = lval_reg_frame_relative;
          VALUE_FRAME (v) = get_frame_base (frame);
          VALUE_FRAME_REGNUM (v) = regnum;
        }
      else if (mem_stor)
        {
          VALUE_LVAL (v) = lval_memory;
          VALUE_ADDRESS (v) = first_addr;
        }
      else if (reg_stor)
        {
          VALUE_LVAL (v) = lval_register;
          VALUE_ADDRESS (v) = first_addr;
        }
      else
        internal_error (__FILE__, __LINE__,
                        "value_from_register: Value not stored anywhere!");

      VALUE_OPTIMIZED_OUT (v) = optim;

      /* Any structure stored in more than one register will always be
         an integral number of registers.  Otherwise, you'd need to do
         some fiddling with the last register copied here for little
         endian machines.  */

      /* Copy into the contents section of the value.  */
      memcpy (VALUE_CONTENTS_RAW (v), value_bytes, len);

      /* Finally do any conversion necessary when extracting this
         type from more than one register.  */
#ifdef REGISTER_CONVERT_TO_TYPE
      REGISTER_CONVERT_TO_TYPE (regnum, type, VALUE_CONTENTS_RAW (v));
#endif
      return v;
    }

  /* Data is completely contained within a single register.  Locate the
     register's contents in a real register or in core;
     read the data in raw format.  */

  get_saved_register (raw_buffer, &optim, &addr, frame, regnum, &lval);

  if (register_cached (regnum) == -1)
    return NULL;                /* register value not available */

  VALUE_OPTIMIZED_OUT (v) = optim;
  VALUE_LVAL (v) = lval;
  VALUE_ADDRESS (v) = addr;

  /* Convert the raw register to the corresponding data value's memory
     format, if necessary.  */

  if (CONVERT_REGISTER_P (regnum))
    {
      REGISTER_TO_VALUE (regnum, type, raw_buffer, VALUE_CONTENTS_RAW (v));
    }
  else
    {
      /* Raw and virtual formats are the same for this register.  */

      if (TARGET_BYTE_ORDER == BFD_ENDIAN_BIG && len < REGISTER_RAW_SIZE (regnum))
        {
          /* Big-endian, and we want less than full size.  */
          VALUE_OFFSET (v) = REGISTER_RAW_SIZE (regnum) - len;
        }

      memcpy (VALUE_CONTENTS_RAW (v), raw_buffer + VALUE_OFFSET (v), len);
    }

  return v;
}
\f
/* Given a struct symbol for a variable or function,
   and a stack frame id, 
   return a (pointer to a) struct value containing the properly typed
   address.  */

struct value *
locate_var_value (register struct symbol *var, struct frame_info *frame)
{
  CORE_ADDR addr = 0;
  struct type *type = SYMBOL_TYPE (var);
  struct value *lazy_value;

  /* Evaluate it first; if the result is a memory address, we're fine.
     Lazy evaluation pays off here. */

  lazy_value = read_var_value (var, frame);
  if (lazy_value == 0)
    error ("Address of \"%s\" is unknown.", SYMBOL_SOURCE_NAME (var));

  if (VALUE_LAZY (lazy_value)
      || TYPE_CODE (type) == TYPE_CODE_FUNC)
    {
      struct value *val;

      addr = VALUE_ADDRESS (lazy_value);
      val = value_from_pointer (lookup_pointer_type (type), addr);
      VALUE_BFD_SECTION (val) = VALUE_BFD_SECTION (lazy_value);
      return val;
    }

  /* Not a memory address; check what the problem was.  */
  switch (VALUE_LVAL (lazy_value))
    {
    case lval_register:
        gdb_assert (REGISTER_NAME (VALUE_REGNO (lazy_value)) != NULL
                    && *REGISTER_NAME (VALUE_REGNO (lazy_value)) != '\0');
      error("Address requested for identifier "
            "\"%s\" which is in register $%s",
            SYMBOL_SOURCE_NAME (var), 
            REGISTER_NAME (VALUE_REGNO (lazy_value)));
      break;

    case lval_reg_frame_relative:
        gdb_assert (REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)) != NULL
                    && *REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)) != '\0');
      error("Address requested for identifier "
            "\"%s\" which is in frame register $%s",
            SYMBOL_SOURCE_NAME (var), 
            REGISTER_NAME (VALUE_FRAME_REGNUM (lazy_value)));
      break;

    default:
      error ("Can't take address of \"%s\" which isn't an lvalue.",
             SYMBOL_SOURCE_NAME (var));
      break;
    }
  return 0;                     /* For lint -- never reached */
}