path: root/gdb/findvar.c

/* Find a variable's value in memory, for GDB, the GNU debugger.
   Copyright (C) 1986, 1987, 1989 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., 675 Mass Ave, Cambridge, MA 02139, USA.  */

#include <stdio.h>
#include "defs.h"
#include "param.h"
#include "symtab.h"
#include "frame.h"
#include "value.h"
#include "gdbcore.h"
#include "inferior.h"
#include "target.h"

#if !defined (GET_SAVED_REGISTER)

/* Return the address in which frame FRAME's value of register REGNUM
   has been saved in memory.  Or return zero if it has not been saved.
   If REGNUM specifies the SP, the value we return is actually
   the SP value, not an address where it was saved.  */

CORE_ADDR
find_saved_register (frame, regnum)
     FRAME frame;
     int regnum;
{
  struct frame_info *fi;
  struct frame_saved_regs saved_regs;

  register FRAME frame1 = 0;
  register CORE_ADDR addr = 0;

  if (frame == 0)		/* No regs saved if want current frame */
    return 0;

#ifdef HAVE_REGISTER_WINDOWS
  /* We assume that a register in a register window will only be saved
     in one place (since the name changes and/or disappears as you go
     towards inner frames), so we only call get_frame_saved_regs on
     the current frame.  This is directly in contradiction to the
     usage below, which assumes that registers used in a frame must be
     saved in a lower (more interior) frame.  This change is a result
     of working on a register window machine; get_frame_saved_regs
     always returns the registers saved within a frame, within the
     context (register namespace) of that frame. */

  /* However, note that we don't want this to return anything if
     nothing is saved (if there's a frame inside of this one).  Also,
     callers to this routine asking for the stack pointer want the
     stack pointer saved for *this* frame; this is returned from the
     next frame.  */
     

  if (REGISTER_IN_WINDOW_P(regnum))
    {
      frame1 = get_next_frame (frame);
      if (!frame1) return 0;	/* Registers of this frame are
				   active.  */
      
      /* Get the SP from the next frame in; it will be this
	 current frame.  */
      if (regnum != SP_REGNUM)
	frame1 = frame;	
	  
      fi = get_frame_info (frame1);
      get_frame_saved_regs (fi, &saved_regs);
      return saved_regs.regs[regnum];	/* ... which might be zero */
    }
#endif /* HAVE_REGISTER_WINDOWS */

  /* Note that this next routine assumes that registers used in
     frame x will be saved only in the frame that x calls and
     frames interior to it.  This is not true on the sparc, but the
     above macro takes care of it, so we should be all right. */
  while (1)
    {
      QUIT;
      frame1 = get_prev_frame (frame1);
      if (frame1 == 0 || frame1 == frame)
	break;
      fi = get_frame_info (frame1);
      get_frame_saved_regs (fi, &saved_regs);
      if (saved_regs.regs[regnum])
	addr = saved_regs.regs[regnum];
    }

  return addr;
}

/* Find register number REGNUM relative to FRAME and put its
   (raw) contents in *RAW_BUFFER.  Set *OPTIMIZED if the variable
   was optimized out (and thus can't be fetched).  Set *LVAL to
   lval_memory, lval_register, or not_lval, depending on whether the
   value was fetched from memory, from a register, or in a strange
   and non-modifiable way (e.g. a frame pointer which was calculated
   rather than fetched).  Set *ADDRP to the address, either in memory
   on as a REGISTER_BYTE offset into the registers array.

   Note that this implementation never sets *LVAL to not_lval.  But
   it can be replaced by defining GET_SAVED_REGISTER and supplying
   your own.

   The argument RAW_BUFFER must point to aligned memory.  */
void
get_saved_register (raw_buffer, optimized, addrp, frame, regnum, lval)
     char *raw_buffer;
     int *optimized;
     CORE_ADDR *addrp;
     FRAME frame;
     int regnum;
     enum lval_type *lval;
{
  CORE_ADDR addr;
  /* Normal systems don't optimize out things with register numbers.  */
  if (optimized != NULL)
    *optimized = 0;
  addr = find_saved_register (frame, regnum);
  if (addr != NULL)
    {
      if (lval != NULL)
	*lval = lval_memory;
      if (regnum == SP_REGNUM)
	{
	  if (raw_buffer != NULL)
	    *(CORE_ADDR *)raw_buffer = addr;
	  if (addrp != NULL)
	    *addrp = 0;
	  return;
	}
      if (raw_buffer != NULL)
	read_memory (addr, raw_buffer, REGISTER_RAW_SIZE (regnum));
    }
  else
    {
      if (lval != NULL)
	*lval = lval_register;
      addr = REGISTER_BYTE (regnum);
      if (raw_buffer != NULL)
	read_register_gen (regnum, raw_buffer);
    }
  if (addrp != NULL)
    *addrp = addr;
}
#endif /* GET_SAVED_REGISTER.  */

/* Copy the bytes of register REGNUM, relative to the current stack frame,
   into our memory at MYADDR, in target byte order.
   The number of bytes copied is REGISTER_RAW_SIZE (REGNUM).

   Returns 1 if could not be read, 0 if could.  */

int
read_relative_register_raw_bytes (regnum, myaddr)
     int regnum;
     char *myaddr;
{
  int optim;
  if (regnum == FP_REGNUM && selected_frame)
    {
      bcopy (&FRAME_FP(selected_frame), myaddr, sizeof (CORE_ADDR));
      SWAP_TARGET_AND_HOST (myaddr, sizeof (CORE_ADDR)); /* in target order */
      return 0;
    }

  get_saved_register (myaddr, &optim, (CORE_ADDR *) NULL, selected_frame,
                      regnum, (enum lval_type *)NULL);
  return optim;
}

/* Return a `value' with the contents of register REGNUM
   in its virtual format, with the type specified by
   REGISTER_VIRTUAL_TYPE.  */

value
value_of_register (regnum)
     int regnum;
{
  CORE_ADDR addr;
  int optim;
  register value val;
  char raw_buffer[MAX_REGISTER_RAW_SIZE];
  char virtual_buffer[MAX_REGISTER_VIRTUAL_SIZE];
  enum lval_type lval;

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

  target_convert_to_virtual (regnum, raw_buffer, virtual_buffer);
  val = allocate_value (REGISTER_VIRTUAL_TYPE (regnum));
  bcopy (virtual_buffer, VALUE_CONTENTS_RAW (val),
	 REGISTER_VIRTUAL_SIZE (regnum));
  VALUE_LVAL (val) = lval;
  VALUE_ADDRESS (val) = addr;
  VALUE_REGNO (val) = regnum;
  VALUE_OPTIMIZED_OUT (val) = optim;
  return val;
}

/* Low level examining and depositing of registers.

   The caller is responsible for making
   sure that the inferior is stopped before calling the fetching routines,
   or it will get garbage.  (a change from GDB version 3, in which
   the caller got the value from the last stop).  */

/* Contents of the registers in target byte order.
   We allocate some extra slop since we do a lot of bcopy's around `registers',
   and failing-soft is better than failing hard.  */
char registers[REGISTER_BYTES + /* SLOP */ 256];

/* Nonzero if that register has been fetched.  */
char register_valid[NUM_REGS];

/* Indicate that registers may have changed, so invalidate the cache.  */
void
registers_changed ()
{
  int i;
  for (i = 0; i < NUM_REGS; i++)
    register_valid[i] = 0;
}

/* Indicate that all registers have been fetched, so mark them all valid.  */
void
registers_fetched ()
{
  int i;
  for (i = 0; i < NUM_REGS; i++)
    register_valid[i] = 1;
}

/* Copy LEN bytes of consecutive data from registers
   starting with the REGBYTE'th byte of register data
   into memory at MYADDR.  */

void
read_register_bytes (regbyte, myaddr, len)
     int regbyte;
     char *myaddr;
     int len;
{
  /* Fetch all registers.  */
  int i;
  for (i = 0; i < NUM_REGS; i++)
    if (!register_valid[i])
      {
	target_fetch_registers (-1);
	break;
      }
  if (myaddr != NULL)
    bcopy (&registers[regbyte], myaddr, len);
}

/* Read register REGNO into memory at MYADDR, which must be large enough
   for REGISTER_RAW_BYTES (REGNO).  Target byte-order.
   If the register is known to be the size of a CORE_ADDR or smaller,
   read_register can be used instead.  */
void
read_register_gen (regno, myaddr)
     int regno;
     char *myaddr;
{
  if (!register_valid[regno])
    target_fetch_registers (regno);
  bcopy (&registers[REGISTER_BYTE (regno)], myaddr, REGISTER_RAW_SIZE (regno));
}

/* Copy LEN bytes of consecutive data from memory at MYADDR
   into registers starting with the REGBYTE'th byte of register data.  */

void
write_register_bytes (regbyte, myaddr, len)
     int regbyte;
     char *myaddr;
     int len;
{
  /* Make sure the entire registers array is valid.  */
  read_register_bytes (0, (char *)NULL, REGISTER_BYTES);
  bcopy (myaddr, &registers[regbyte], len);
  target_store_registers (-1);
}

/* Return the contents of register REGNO, regarding it as an integer.  */

CORE_ADDR
read_register (regno)
     int regno;
{
  int reg;
  if (!register_valid[regno])
    target_fetch_registers (regno);
  /* FIXME, this loses when REGISTER_RAW_SIZE (regno) != sizeof (int) */
  reg = *(int *) &registers[REGISTER_BYTE (regno)];
  SWAP_TARGET_AND_HOST (&reg, sizeof (int));
  return reg;
}

/* Registers we shouldn't try to store.  */
#if !defined (CANNOT_STORE_REGISTER)
#define CANNOT_STORE_REGISTER(regno) 0
#endif

/* Store VALUE in the register number REGNO, regarded as an integer.  */

void
write_register (regno, val)
     int regno, val;
{
  /* On the sparc, writing %g0 is a no-op, so we don't even want to change
     the registers array if something writes to this register.  */
  if (CANNOT_STORE_REGISTER (regno))
    return;

  SWAP_TARGET_AND_HOST (&val, sizeof (int));

  target_prepare_to_store ();

  register_valid [regno] = 1;
  /* FIXME, this loses when REGISTER_RAW_SIZE (regno) != sizeof (int) */
  /* FIXME, this depends on REGISTER_BYTE (regno) being aligned for host */
  *(int *) &registers[REGISTER_BYTE (regno)] = val;

  target_store_registers (regno);
}

/* Record that register REGNO contains VAL.
   This is used when the value is obtained from the inferior or core dump,
   so there is no need to store the value there.  */

void
supply_register (regno, val)
     int regno;
     char *val;
{
  register_valid[regno] = 1;
  bcopy (val, &registers[REGISTER_BYTE (regno)], REGISTER_RAW_SIZE (regno));
}

/* 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 selected_frame.  */

value
read_var_value (var, frame)
     register struct symbol *var;
     FRAME frame;
{
  register value v;
  struct frame_info *fi;
  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.  */
  len = TYPE_LENGTH (type);

  if (frame == 0) frame = selected_frame;

  switch (SYMBOL_CLASS (var))
    {
    case LOC_CONST:
      bcopy (&SYMBOL_VALUE (var), VALUE_CONTENTS_RAW (v), len);
      SWAP_TARGET_AND_HOST (VALUE_CONTENTS_RAW (v), len);
      VALUE_LVAL (v) = not_lval;
      return v;

    case LOC_LABEL:
      addr = SYMBOL_VALUE_ADDRESS (var);
      bcopy (&addr, VALUE_CONTENTS_RAW (v), len);
      SWAP_TARGET_AND_HOST (VALUE_CONTENTS_RAW (v), len);
      VALUE_LVAL (v) = not_lval;
      return v;

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

    case LOC_STATIC:
    case LOC_EXTERNAL:
      addr = SYMBOL_VALUE_ADDRESS (var);
      break;

/* Nonzero if a struct which is located in a register or a LOC_ARG
   really contains
   the address of the struct, not the struct itself.  GCC_P is nonzero
   if the function was compiled with GCC.  */
#if !defined (REG_STRUCT_HAS_ADDR)
#define REG_STRUCT_HAS_ADDR(gcc_p) 0
#endif

    case LOC_ARG:
      fi = get_frame_info (frame);
      if (fi == NULL)
	return 0;
      addr = FRAME_ARGS_ADDRESS (fi);
      if (!addr) {
	return 0;
      }
      addr += SYMBOL_VALUE (var);
      break;
      
    case LOC_REF_ARG:
      fi = get_frame_info (frame);
      if (fi == NULL)
	return 0;
      addr = FRAME_ARGS_ADDRESS (fi);
      if (!addr) {
	return 0;
      }
      addr += SYMBOL_VALUE (var);
      read_memory (addr, &addr, sizeof (CORE_ADDR));
      break;
      
    case LOC_LOCAL:
    case LOC_LOCAL_ARG:
      fi = get_frame_info (frame);
      if (fi == NULL)
	return 0;
      addr = SYMBOL_VALUE (var) + FRAME_LOCALS_ADDRESS (fi);
      break;

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

    case LOC_BLOCK:
      VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (var));
      return v;

    case LOC_REGISTER:
    case LOC_REGPARM:
      {
	struct block *b;

	if (frame == NULL)
	  return 0;
	b = get_frame_block (frame);
	
	v = value_from_register (type, SYMBOL_VALUE (var), frame);

	if (REG_STRUCT_HAS_ADDR (BLOCK_GCC_COMPILED (b))
	    && TYPE_CODE (type) == TYPE_CODE_STRUCT)
	  addr = *(CORE_ADDR *)VALUE_CONTENTS (v);
	else
	  return v;
      }
      break;

    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. */

value
value_from_register (type, regnum, frame)
     struct type *type;
     int regnum;
     FRAME frame;
{
  char raw_buffer [MAX_REGISTER_RAW_SIZE];
  char virtual_buffer[MAX_REGISTER_VIRTUAL_SIZE];
  CORE_ADDR addr;
  int optim;
  value v = allocate_value (type);
  int len = TYPE_LENGTH (type);
  char *value_bytes = 0;
  int value_bytes_copied = 0;
  int num_storage_locs;
  enum lval_type lval;

  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)
    {
      /* 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;

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

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

      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 (lval == lval_register)
	    reg_stor++;
	  else
	    {
	      mem_stor++;

	      if (regnum == local_regnum)
		first_addr = addr;
	      
	      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) = FRAME_FP (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
	fatal ("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.  */
      bcopy (value_bytes, VALUE_CONTENTS_RAW (v), len);

      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);
  VALUE_OPTIMIZED_OUT (v) = optim;
  VALUE_LVAL (v) = lval;
  VALUE_ADDRESS (v) = addr;
  
  /* Convert the raw contents to virtual contents.
     (Just copy them if the formats are the same.)  */
  
  target_convert_to_virtual (regnum, raw_buffer, virtual_buffer);
  
  if (REGISTER_CONVERTIBLE (regnum))
    {
      /* When the raw and virtual formats differ, the virtual format
	 corresponds to a specific data type.  If we want that type,
	 copy the data into the value.
	 Otherwise, do a type-conversion.  */
      
      if (type != REGISTER_VIRTUAL_TYPE (regnum))
	{
	  /* eg a variable of type `float' in a 68881 register
	     with raw type `extended' and virtual type `double'.
	     Fetch it as a `double' and then convert to `float'.  */
	  v = allocate_value (REGISTER_VIRTUAL_TYPE (regnum));
	  bcopy (virtual_buffer, VALUE_CONTENTS_RAW (v), len);
	  v = value_cast (type, v);
	}
      else
	bcopy (virtual_buffer, VALUE_CONTENTS_RAW (v), len);
    }
  else
    {
      /* Raw and virtual formats are the same for this register.  */

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

      bcopy (virtual_buffer + VALUE_OFFSET (v),
	     VALUE_CONTENTS_RAW (v), len);
    }
  
  return v;
}

/* 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.  */

value
locate_var_value (var, frame)
     register struct symbol *var;
     FRAME frame;
{
  CORE_ADDR addr = 0;
  struct type *type = SYMBOL_TYPE (var);
  struct type *result_type;
  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_NAME (var));

  if (VALUE_LAZY (lazy_value)
      || TYPE_CODE (type) == TYPE_CODE_FUNC)
    {
      addr = VALUE_ADDRESS (lazy_value);

      /* C++: The "address" of a reference should yield the address
       * of the object pointed to. So force an extra de-reference. */

      if (TYPE_CODE (type) == TYPE_CODE_REF)
	{
	  char *buf = alloca (TYPE_LENGTH (type));
	  read_memory (addr, buf, TYPE_LENGTH (type));
	  addr = unpack_pointer (type, buf);
	  type = TYPE_TARGET_TYPE (type);
	}

      /* Address of an array is of the type of address of it's elements.  */
	/* FIXME, this is probably wrong now for ANSI C. */
      result_type =
	lookup_pointer_type (TYPE_CODE (type) == TYPE_CODE_ARRAY ?
			     TYPE_TARGET_TYPE (type) : type);

      return value_cast (result_type,
			 value_from_long (builtin_type_long, (LONGEST) addr));
    }

  /* Not a memory address; check what the problem was.  */
  switch (VALUE_LVAL (lazy_value)) 
    {
    case lval_register:
    case lval_reg_frame_relative:
      error ("Address requested for identifier \"%s\" which is in a register.",
	     SYMBOL_NAME (var));
      break;

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