path: root/gdb/eval.c

/* Evaluate expressions for GDB.
   Copyright 1986, 1987, 1989, 1991, 1992 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 "defs.h"
#include "symtab.h"
#include "gdbtypes.h"
#include "value.h"
#include "expression.h"
#include "target.h"
#include "frame.h"
#include "language.h"	/* For CAST_IS_CONVERSION */

/* Values of NOSIDE argument to eval_subexp.  */
enum noside
{ EVAL_NORMAL,
  EVAL_SKIP,			/* Only effect is to increment pos.  */
  EVAL_AVOID_SIDE_EFFECTS	/* Don't modify any variables or
				   call any functions.  The value
				   returned will have the correct
				   type, and will have an
				   approximately correct lvalue
				   type (inaccuracy: anything that is
				   listed as being in a register in
				   the function in which it was
				   declared will be lval_register).  */
};

/* Prototypes for local functions. */

static value
evaluate_subexp_for_sizeof PARAMS ((struct expression *, int *));

static value
evaluate_subexp_with_coercion PARAMS ((struct expression *, int *,
				       enum noside));

static value
evaluate_subexp_for_address PARAMS ((struct expression *, int *,
				     enum noside));

static value
evaluate_subexp PARAMS ((struct type *, struct expression *, int *,
			 enum noside));


/* Parse the string EXP as a C expression, evaluate it,
   and return the result as a number.  */

CORE_ADDR
parse_and_eval_address (exp)
     char *exp;
{
  struct expression *expr = parse_expression (exp);
  register CORE_ADDR addr;
  register struct cleanup *old_chain = 
      make_cleanup (free_current_contents, &expr);

  addr = value_as_pointer (evaluate_expression (expr));
  do_cleanups (old_chain);
  return addr;
}

/* Like parse_and_eval_address but takes a pointer to a char * variable
   and advanced that variable across the characters parsed.  */

CORE_ADDR
parse_and_eval_address_1 (expptr)
     char **expptr;
{
  struct expression *expr = parse_exp_1 (expptr, (struct block *)0, 0);
  register CORE_ADDR addr;
  register struct cleanup *old_chain =
      make_cleanup (free_current_contents, &expr);

  addr = value_as_pointer (evaluate_expression (expr));
  do_cleanups (old_chain);
  return addr;
}

value
parse_and_eval (exp)
     char *exp;
{
  struct expression *expr = parse_expression (exp);
  register value val;
  register struct cleanup *old_chain
    = make_cleanup (free_current_contents, &expr);

  val = evaluate_expression (expr);
  do_cleanups (old_chain);
  return val;
}

/* Parse up to a comma (or to a closeparen)
   in the string EXPP as an expression, evaluate it, and return the value.
   EXPP is advanced to point to the comma.  */

value
parse_to_comma_and_eval (expp)
     char **expp;
{
  struct expression *expr = parse_exp_1 (expp, (struct block *) 0, 1);
  register value val;
  register struct cleanup *old_chain
    = make_cleanup (free_current_contents, &expr);

  val = evaluate_expression (expr);
  do_cleanups (old_chain);
  return val;
}

/* Evaluate an expression in internal prefix form
   such as is constructed by parse.y.

   See expression.h for info on the format of an expression.  */

static value evaluate_subexp ();
static value evaluate_subexp_for_address ();
static value evaluate_subexp_for_sizeof ();
static value evaluate_subexp_with_coercion ();

value
evaluate_expression (exp)
     struct expression *exp;
{
  int pc = 0;
  return evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_NORMAL);
}

/* Evaluate an expression, avoiding all memory references
   and getting a value whose type alone is correct.  */

value
evaluate_type (exp)
     struct expression *exp;
{
  int pc = 0;
  return evaluate_subexp (NULL_TYPE, exp, &pc, EVAL_AVOID_SIDE_EFFECTS);
}

static value
evaluate_subexp (expect_type, exp, pos, noside)
     struct type *expect_type;
     register struct expression *exp;
     register int *pos;
     enum noside noside;
{
  enum exp_opcode op;
  int tem;
  register int pc, pc2, oldpos;
  register value arg1, arg2, arg3;
  struct type *type;
  int nargs;
  value *argvec;

  pc = (*pos)++;
  op = exp->elts[pc].opcode;

  switch (op)
    {
    case OP_SCOPE:
      tem = longest_to_int (exp->elts[pc + 2].longconst);
      (*pos) += 4 + ((tem + sizeof (union exp_element))
		     / sizeof (union exp_element));
      arg1 = value_struct_elt_for_reference (exp->elts[pc + 1].type,
					     0,
					     exp->elts[pc + 1].type,
					     &exp->elts[pc + 3].string,
					     expect_type);
      if (arg1 == NULL)
	error ("There is no field named %s", &exp->elts[pc + 3].string);
      return arg1;

    case OP_LONG:
      (*pos) += 3;
      return value_from_longest (exp->elts[pc + 1].type,
				 exp->elts[pc + 2].longconst);

    case OP_DOUBLE:
      (*pos) += 3;
      return value_from_double (exp->elts[pc + 1].type,
				exp->elts[pc + 2].doubleconst);

    case OP_VAR_VALUE:
      (*pos) += 2;
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  struct symbol * sym = exp->elts[pc + 1].symbol;
	  enum lval_type lv;

	  switch (SYMBOL_CLASS (sym))
	    {
	    case LOC_CONST:
	    case LOC_LABEL:
	    case LOC_CONST_BYTES:
	      lv = not_lval;
	      break;

	    case LOC_REGISTER:
	    case LOC_REGPARM:
	      lv = lval_register;
	      break;

	    default:
	      lv = lval_memory;
	      break;
	    }

	  return value_zero (SYMBOL_TYPE (sym), lv);
	}
      else
	return value_of_variable (exp->elts[pc + 1].symbol);

    case OP_LAST:
      (*pos) += 2;
      return
	access_value_history (longest_to_int (exp->elts[pc + 1].longconst));

    case OP_REGISTER:
      (*pos) += 2;
      return value_of_register (longest_to_int (exp->elts[pc + 1].longconst));

    /* start-sanitize-chill */
    case OP_BOOL:
      (*pos) += 2;
      return value_from_longest (builtin_type_chill_bool,
				 exp->elts[pc + 1].longconst);
    /* end-sanitize-chill */

    case OP_INTERNALVAR:
      (*pos) += 2;
      return value_of_internalvar (exp->elts[pc + 1].internalvar);

    case OP_STRING:
      tem = longest_to_int (exp->elts[pc + 1].longconst);
      (*pos) += 3 + ((tem + sizeof (union exp_element))
		     / sizeof (union exp_element));
      if (noside == EVAL_SKIP)
	goto nosideret;
      return value_string (&exp->elts[pc + 2].string, tem);

    case TERNOP_COND:
      /* Skip third and second args to evaluate the first one.  */
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (value_logical_not (arg1))
	{
	  evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
	  return evaluate_subexp (NULL_TYPE, exp, pos, noside);
	}
      else
	{
	  arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	  evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
	  return arg2;
	}

    case OP_FUNCALL:
      (*pos) += 2;
      op = exp->elts[*pos].opcode;
      if (op == STRUCTOP_MEMBER || op == STRUCTOP_MPTR)
	{
	  int fnptr;

	  nargs = longest_to_int (exp->elts[pc + 1].longconst) + 1;
	  /* First, evaluate the structure into arg2 */
	  pc2 = (*pos)++;

	  if (noside == EVAL_SKIP)
	    goto nosideret;

	  if (op == STRUCTOP_MEMBER)
	    {
	      arg2 = evaluate_subexp_for_address (exp, pos, noside);
	    }
	  else
	    {
	      arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	    }

	  /* If the function is a virtual function, then the
	     aggregate value (providing the structure) plays
	     its part by providing the vtable.  Otherwise,
	     it is just along for the ride: call the function
	     directly.  */

	  arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);

	  fnptr = longest_to_int (value_as_long (arg1));

	  if (METHOD_PTR_IS_VIRTUAL(fnptr))
	    {
	      int fnoffset = METHOD_PTR_TO_VOFFSET(fnptr);
	      struct type *basetype;
	      struct type *domain_type =
		  TYPE_DOMAIN_TYPE (TYPE_TARGET_TYPE (VALUE_TYPE (arg1)));
	      int i, j;
	      basetype = TYPE_TARGET_TYPE (VALUE_TYPE (arg2));
	      if (domain_type != basetype)
		  arg2 = value_cast(lookup_pointer_type (domain_type), arg2);
	      basetype = TYPE_VPTR_BASETYPE (domain_type);
	      for (i = TYPE_NFN_FIELDS (basetype) - 1; i >= 0; i--)
		{
		  struct fn_field *f = TYPE_FN_FIELDLIST1 (basetype, i);
		  /* If one is virtual, then all are virtual.  */
		  if (TYPE_FN_FIELD_VIRTUAL_P (f, 0))
		    for (j = TYPE_FN_FIELDLIST_LENGTH (basetype, i) - 1; j >= 0; --j)
		      if (TYPE_FN_FIELD_VOFFSET (f, j) == fnoffset)
			{
			  value temp = value_ind (arg2);
			  arg1 = value_virtual_fn_field (&temp, f, j, domain_type, 0);
			  arg2 = value_addr (temp);
			  goto got_it;
			}
		}
	      if (i < 0)
		error ("virtual function at index %d not found", fnoffset);
	    }
	  else
	    {
	      VALUE_TYPE (arg1) = lookup_pointer_type (TYPE_TARGET_TYPE (VALUE_TYPE (arg1)));
	    }
	got_it:

	  /* Now, say which argument to start evaluating from */
	  tem = 2;
	}
      else if (op == STRUCTOP_STRUCT || op == STRUCTOP_PTR)
	{
	  /* Hair for method invocations */
	  int tem2;

	  nargs = longest_to_int (exp->elts[pc + 1].longconst) + 1;
	  /* First, evaluate the structure into arg2 */
	  pc2 = (*pos)++;
	  tem2 = longest_to_int (exp->elts[pc2 + 1].longconst);
	  *pos += 3 + (tem2 + sizeof (union exp_element)) / sizeof (union exp_element);
	  if (noside == EVAL_SKIP)
	    goto nosideret;

	  if (op == STRUCTOP_STRUCT)
	    {
	      arg2 = evaluate_subexp_for_address (exp, pos, noside);
	    }
	  else
	    {
	      arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	    }
	  /* Now, say which argument to start evaluating from */
	  tem = 2;
	}
      else
	{
	  nargs = longest_to_int (exp->elts[pc + 1].longconst);
	  tem = 0;
	}
      argvec = (value *) alloca (sizeof (value) * (nargs + 2));
      for (; tem <= nargs; tem++)
	/* Ensure that array expressions are coerced into pointer objects. */
	argvec[tem] = evaluate_subexp_with_coercion (exp, pos, noside);

      /* signal end of arglist */
      argvec[tem] = 0;

      if (op == STRUCTOP_STRUCT || op == STRUCTOP_PTR)
	{
	  int static_memfuncp;
	  value temp = arg2;

	  argvec[1] = arg2;
	  argvec[0] =
	    value_struct_elt (&temp, argvec+1, &exp->elts[pc2 + 2].string,
			      &static_memfuncp,
			      op == STRUCTOP_STRUCT
			      ? "structure" : "structure pointer");
	  if (VALUE_OFFSET (temp))
	    {
	      arg2 = value_from_longest (lookup_pointer_type (VALUE_TYPE (temp)),
				      value_as_long (arg2)+VALUE_OFFSET (temp));
	      argvec[1] = arg2;
	    }
	  if (static_memfuncp)
	    {
	      argvec[1] = argvec[0];
	      nargs--;
	      argvec++;
	    }
	}
      else if (op == STRUCTOP_MEMBER || op == STRUCTOP_MPTR)
	{
	  argvec[1] = arg2;
	  argvec[0] = arg1;
	}

      if (noside == EVAL_SKIP)
	goto nosideret;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  /* If the return type doesn't look like a function type, call an
	     error.  This can happen if somebody tries to turn a variable into
	     a function call. This is here because people often want to
	     call, eg, strcmp, which gdb doesn't know is a function.  If
	     gdb isn't asked for it's opinion (ie. through "whatis"),
	     it won't offer it. */

	  struct type *ftype =
	    TYPE_TARGET_TYPE (VALUE_TYPE (argvec[0]));

	  if (ftype)
	    return allocate_value (TYPE_TARGET_TYPE (VALUE_TYPE (argvec[0])));
	  else
	    error ("Expression of type other than \"Function returning ...\" used as function");
	}
      return call_function_by_hand (argvec[0], nargs, argvec + 1);

    case STRUCTOP_STRUCT:
      tem = longest_to_int (exp->elts[pc + 1].longconst);
      (*pos) += 3 + ((tem + sizeof (union exp_element))
		     / sizeof (union exp_element));
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	return value_zero (lookup_struct_elt_type (VALUE_TYPE (arg1),
						   &exp->elts[pc + 2].string,
						   0),
			   lval_memory);
      else
	{
	  value temp = arg1;
	  return value_struct_elt (&temp, (value *)0, &exp->elts[pc + 2].string,
				   (int *) 0, "structure");
	}

    case STRUCTOP_PTR:
      tem = longest_to_int (exp->elts[pc + 1].longconst);
      (*pos) += 3 + (tem + sizeof (union exp_element)) / sizeof (union exp_element);
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	return value_zero (lookup_struct_elt_type (TYPE_TARGET_TYPE
						   (VALUE_TYPE (arg1)),
						   &exp->elts[pc + 2].string,
						   0),
			   lval_memory);
      else
	{
	  value temp = arg1;
	  return value_struct_elt (&temp, (value *)0, &exp->elts[pc + 2].string,
				   (int *) 0, "structure pointer");
	}

    case STRUCTOP_MEMBER:
      arg1 = evaluate_subexp_for_address (exp, pos, noside);
      goto handle_pointer_to_member;
    case STRUCTOP_MPTR:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
    handle_pointer_to_member:
      arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (TYPE_CODE (VALUE_TYPE (arg2)) != TYPE_CODE_PTR)
	goto bad_pointer_to_member;
      type = TYPE_TARGET_TYPE (VALUE_TYPE (arg2));
      if (TYPE_CODE (type) == TYPE_CODE_METHOD)
	error ("not implemented: pointer-to-method in pointer-to-member construct");
      if (TYPE_CODE (type) != TYPE_CODE_MEMBER)
	goto bad_pointer_to_member;
      /* Now, convert these values to an address.  */
      arg1 = value_cast (lookup_pointer_type (TYPE_DOMAIN_TYPE (type)),
			 arg1);
      arg3 = value_from_longest (lookup_pointer_type (TYPE_TARGET_TYPE (type)),
				 value_as_long (arg1) + value_as_long (arg2));
      return value_ind (arg3);
    bad_pointer_to_member:
      error("non-pointer-to-member value used in pointer-to-member construct");

    case BINOP_ASSIGN:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
      if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
	return arg1;
      if (binop_user_defined_p (op, arg1, arg2))
	return value_x_binop (arg1, arg2, op, OP_NULL);
      else
	return value_assign (arg1, arg2);

    case BINOP_ASSIGN_MODIFY:
      (*pos) += 2;
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
      if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
	return arg1;
      op = exp->elts[pc + 1].opcode;
      if (binop_user_defined_p (op, arg1, arg2))
	return value_x_binop (arg1, arg2, BINOP_ASSIGN_MODIFY, op);
      else if (op == BINOP_ADD)
	arg2 = value_add (arg1, arg2);
      else if (op == BINOP_SUB)
	arg2 = value_sub (arg1, arg2);
      else
	arg2 = value_binop (arg1, arg2, op);
      return value_assign (arg1, arg2);

    case BINOP_ADD:
      arg1 = evaluate_subexp_with_coercion (exp, pos, noside);
      arg2 = evaluate_subexp_with_coercion (exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	return value_x_binop (arg1, arg2, op, OP_NULL);
      else
	return value_add (arg1, arg2);

    case BINOP_SUB:
      arg1 = evaluate_subexp_with_coercion (exp, pos, noside);
      arg2 = evaluate_subexp_with_coercion (exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	return value_x_binop (arg1, arg2, op, OP_NULL);
      else
	return value_sub (arg1, arg2);

    case BINOP_MUL:
    case BINOP_DIV:
    case BINOP_REM:
    case BINOP_LSH:
    case BINOP_RSH:
    case BINOP_BITWISE_AND:
    case BINOP_BITWISE_IOR:
    case BINOP_BITWISE_XOR:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	return value_x_binop (arg1, arg2, op, OP_NULL);
      else
	if (noside == EVAL_AVOID_SIDE_EFFECTS
	    && (op == BINOP_DIV || op == BINOP_REM))
	  return value_zero (VALUE_TYPE (arg1), not_lval);
      else
	return value_binop (arg1, arg2, op);

    case BINOP_SUBSCRIPT:
      arg1 = evaluate_subexp_with_coercion (exp, pos, noside);
      arg2 = evaluate_subexp_with_coercion (exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  /* If the user attempts to subscript something that has no target
	     type (like a plain int variable for example), then report this
	     as an error. */

	  type = TYPE_TARGET_TYPE (VALUE_TYPE (arg1));
	  if (type)
	    return value_zero (type, VALUE_LVAL (arg1));
	  else
	    error ("cannot subscript something of type `%s'",
		   TYPE_NAME (VALUE_TYPE (arg1)));
	}
			   
      if (binop_user_defined_p (op, arg1, arg2))
	return value_x_binop (arg1, arg2, op, OP_NULL);
      else
	return value_subscript (arg1, arg2);
      
    case MULTI_SUBSCRIPT:
      (*pos) += 2;
      nargs = longest_to_int (exp->elts[pc + 1].longconst);
      arg1 = evaluate_subexp_with_coercion (exp, pos, noside);
      while (nargs-- > 0)
	{
	  arg2 = evaluate_subexp_with_coercion (exp, pos, noside);
	  /* FIXME:  EVAL_SKIP handling may not be correct. */
	  if (noside == EVAL_SKIP)
	    {
	      if (nargs > 0)
		{
		  continue;
		}
	      else
		{
		  goto nosideret;
		}
	    }
	  /* FIXME:  EVAL_AVOID_SIDE_EFFECTS handling may not be correct. */
	  if (noside == EVAL_AVOID_SIDE_EFFECTS)
	    {
	      /* If the user attempts to subscript something that has no target
		 type (like a plain int variable for example), then report this
		 as an error. */
	      
	      type = TYPE_TARGET_TYPE (VALUE_TYPE (arg1));
	      if (type != NULL)
		{
		  arg1 = value_zero (type, VALUE_LVAL (arg1));
		  noside = EVAL_SKIP;
		  continue;
		}
	      else
		{
		  error ("cannot subscript something of type `%s'",
			 TYPE_NAME (VALUE_TYPE (arg1)));
		}
	    }
	  
	  if (binop_user_defined_p (op, arg1, arg2))
	    {
	      arg1 = value_x_binop (arg1, arg2, op, OP_NULL);
	    }
	  else
	    {
	      arg1 = value_subscript (arg1, arg2);
	    }
	}
      return (arg1);

    case BINOP_LOGICAL_AND:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	{
	  arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	  goto nosideret;
	}
      
      oldpos = *pos;
      arg2 = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
      *pos = oldpos;
      
      if (binop_user_defined_p (op, arg1, arg2)) 
	{
	  arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	  return value_x_binop (arg1, arg2, op, OP_NULL);
	}
      else
	{
	  tem = value_logical_not (arg1);
	  arg2 = evaluate_subexp (NULL_TYPE, exp, pos,
				  (tem ? EVAL_SKIP : noside));
	  return value_from_longest (builtin_type_int,
				  (LONGEST) (!tem && !value_logical_not (arg2)));
	}

    case BINOP_LOGICAL_OR:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	{
	  arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	  goto nosideret;
	}
      
      oldpos = *pos;
      arg2 = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
      *pos = oldpos;
      
      if (binop_user_defined_p (op, arg1, arg2)) 
	{
	  arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	  return value_x_binop (arg1, arg2, op, OP_NULL);
	}
      else
	{
	  tem = value_logical_not (arg1);
	  arg2 = evaluate_subexp (NULL_TYPE, exp, pos,
				  (!tem ? EVAL_SKIP : noside));
	  return value_from_longest (builtin_type_int,
				  (LONGEST) (!tem || !value_logical_not (arg2)));
	}

    case BINOP_EQUAL:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	{
	  return value_x_binop (arg1, arg2, op, OP_NULL);
	}
      else
	{
	  tem = value_equal (arg1, arg2);
	  return value_from_longest (builtin_type_int, (LONGEST) tem);
	}

    case BINOP_NOTEQUAL:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	{
	  return value_x_binop (arg1, arg2, op, OP_NULL);
	}
      else
	{
	  tem = value_equal (arg1, arg2);
	  return value_from_longest (builtin_type_int, (LONGEST) ! tem);
	}

    case BINOP_LESS:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	{
	  return value_x_binop (arg1, arg2, op, OP_NULL);
	}
      else
	{
	  tem = value_less (arg1, arg2);
	  return value_from_longest (builtin_type_int, (LONGEST) tem);
	}

    case BINOP_GTR:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	{
	  return value_x_binop (arg1, arg2, op, OP_NULL);
	}
      else
	{
	  tem = value_less (arg2, arg1);
	  return value_from_longest (builtin_type_int, (LONGEST) tem);
	}

    case BINOP_GEQ:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	{
	  return value_x_binop (arg1, arg2, op, OP_NULL);
	}
      else
	{
	  tem = value_less (arg2, arg1) || value_equal (arg1, arg2);
	  return value_from_longest (builtin_type_int, (LONGEST) tem);
	}

    case BINOP_LEQ:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (VALUE_TYPE (arg1), exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (binop_user_defined_p (op, arg1, arg2))
	{
	  return value_x_binop (arg1, arg2, op, OP_NULL);
	}
      else 
	{
	  tem = value_less (arg1, arg2) || value_equal (arg1, arg2);
	  return value_from_longest (builtin_type_int, (LONGEST) tem);
	}

    case BINOP_REPEAT:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      arg2 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (TYPE_CODE (VALUE_TYPE (arg2)) != TYPE_CODE_INT)
	error ("Non-integral right operand for \"@\" operator.");
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	return allocate_repeat_value (VALUE_TYPE (arg1),
				      longest_to_int (value_as_long (arg2)));
      else
	return value_repeat (arg1, longest_to_int (value_as_long (arg2)));

    case BINOP_COMMA:
      evaluate_subexp (NULL_TYPE, exp, pos, noside);
      return evaluate_subexp (NULL_TYPE, exp, pos, noside);

    case UNOP_NEG:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (unop_user_defined_p (op, arg1))
	return value_x_unop (arg1, op);
      else
	return value_neg (arg1);

    case UNOP_COMPLEMENT:
      /* C++: check for and handle destructor names.  */
      op = exp->elts[*pos].opcode;

      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (unop_user_defined_p (UNOP_COMPLEMENT, arg1))
	return value_x_unop (arg1, UNOP_COMPLEMENT);
      else
	return value_complement (arg1);

    case UNOP_LOGICAL_NOT:
      arg1 = evaluate_subexp (NULL_TYPE, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (unop_user_defined_p (op, arg1))
	return value_x_unop (arg1, op);
      else
	return value_from_longest (builtin_type_int,
				   (LONGEST) value_logical_not (arg1));

    case UNOP_IND:
      if (expect_type && TYPE_CODE (expect_type) == TYPE_CODE_PTR)
        expect_type = TYPE_TARGET_TYPE (expect_type);
      arg1 = evaluate_subexp (expect_type, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  if (TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_PTR
	      || TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_REF
	      /* In C you can dereference an array to get the 1st elt.  */
	      || TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_ARRAY
	      )
	    return value_zero (TYPE_TARGET_TYPE (VALUE_TYPE (arg1)),
			       lval_memory);
	  else if (TYPE_CODE (VALUE_TYPE (arg1)) == TYPE_CODE_INT)
	    /* GDB allows dereferencing an int.  */
	    return value_zero (builtin_type_int, lval_memory);
	  else
	    error ("Attempt to take contents of a non-pointer value.");
	}
      return value_ind (arg1);

    case UNOP_ADDR:
      /* C++: check for and handle pointer to members.  */
      
      op = exp->elts[*pos].opcode;

      if (noside == EVAL_SKIP)
	{
	  if (op == OP_SCOPE)
	    {
	      int temm = longest_to_int (exp->elts[pc+3].longconst);
	      (*pos) += 3 + (temm + sizeof (union exp_element)) / sizeof (union exp_element);
	    }
	  else
	    evaluate_subexp (expect_type, exp, pos, EVAL_SKIP);
	  goto nosideret;
	}

      return evaluate_subexp_for_address (exp, pos, noside);

    case UNOP_SIZEOF:
      if (noside == EVAL_SKIP)
	{
	  evaluate_subexp (NULL_TYPE, exp, pos, EVAL_SKIP);
	  goto nosideret;
	}
      return evaluate_subexp_for_sizeof (exp, pos);

    case UNOP_CAST:
      (*pos) += 2;
      arg1 = evaluate_subexp (expect_type, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      return value_cast (exp->elts[pc + 1].type, arg1);

    case UNOP_MEMVAL:
      (*pos) += 2;
      arg1 = evaluate_subexp (expect_type, exp, pos, noside);
      if (noside == EVAL_SKIP)
	goto nosideret;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	return value_zero (exp->elts[pc + 1].type, lval_memory);
      else
	return value_at_lazy (exp->elts[pc + 1].type,
			      value_as_pointer (arg1));

    case UNOP_PREINCREMENT:
      arg1 = evaluate_subexp (expect_type, exp, pos, noside);
      if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
	return arg1;
      else if (unop_user_defined_p (op, arg1))
	{
	  return value_x_unop (arg1, op);
	}
      else
	{
	  arg2 = value_add (arg1, value_from_longest (builtin_type_char, 
						   (LONGEST) 1));
	  return value_assign (arg1, arg2);
	}

    case UNOP_PREDECREMENT:
      arg1 = evaluate_subexp (expect_type, exp, pos, noside);
      if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
	return arg1;
      else if (unop_user_defined_p (op, arg1))
	{
	  return value_x_unop (arg1, op);
	}
      else
	{
	  arg2 = value_sub (arg1, value_from_longest (builtin_type_char, 
						   (LONGEST) 1));
	  return value_assign (arg1, arg2);
	}

    case UNOP_POSTINCREMENT:
      arg1 = evaluate_subexp (expect_type, exp, pos, noside);
      if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
	return arg1;
      else if (unop_user_defined_p (op, arg1))
	{
	  return value_x_unop (arg1, op);
	}
      else
	{
	  arg2 = value_add (arg1, value_from_longest (builtin_type_char, 
						   (LONGEST) 1));
	  value_assign (arg1, arg2);
	  return arg1;
	}

    case UNOP_POSTDECREMENT:
      arg1 = evaluate_subexp (expect_type, exp, pos, noside);
      if (noside == EVAL_SKIP || noside == EVAL_AVOID_SIDE_EFFECTS)
	return arg1;
      else if (unop_user_defined_p (op, arg1))
	{
	  return value_x_unop (arg1, op);
	}
      else
	{
	  arg2 = value_sub (arg1, value_from_longest (builtin_type_char, 
						   (LONGEST) 1));
	  value_assign (arg1, arg2);
	  return arg1;
	}
	
    case OP_THIS:
      (*pos) += 1;
      return value_of_this (1);

    default:
      error ("internal error: I do not know how to evaluate what you gave me");
    }

 nosideret:
  return value_from_longest (builtin_type_long, (LONGEST) 1);
}

/* Evaluate a subexpression of EXP, at index *POS,
   and return the address of that subexpression.
   Advance *POS over the subexpression.
   If the subexpression isn't an lvalue, get an error.
   NOSIDE may be EVAL_AVOID_SIDE_EFFECTS;
   then only the type of the result need be correct.  */

static value
evaluate_subexp_for_address (exp, pos, noside)
     register struct expression *exp;
     register int *pos;
     enum noside noside;
{
  enum exp_opcode op;
  register int pc;
  struct symbol *var;

  pc = (*pos);
  op = exp->elts[pc].opcode;

  switch (op)
    {
    case UNOP_IND:
      (*pos)++;
      return evaluate_subexp (NULL_TYPE, exp, pos, noside);

    case UNOP_MEMVAL:
      (*pos) += 3;
      return value_cast (lookup_pointer_type (exp->elts[pc + 1].type),
			 evaluate_subexp (NULL_TYPE, exp, pos, noside));

    case OP_VAR_VALUE:
      var = exp->elts[pc + 1].symbol;

      /* C++: The "address" of a reference should yield the address
       * of the object pointed to. Let value_addr() deal with it. */
      if (TYPE_CODE (SYMBOL_TYPE (var)) == TYPE_CODE_REF)
        goto default_case;

      (*pos) += 3;
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  struct type *type =
	    lookup_pointer_type (SYMBOL_TYPE (var));
	  enum address_class sym_class = SYMBOL_CLASS (var);

	  if (sym_class == LOC_CONST
	      || sym_class == LOC_CONST_BYTES
	      || sym_class == LOC_REGISTER
	      || sym_class == LOC_REGPARM)
	    error ("Attempt to take address of register or constant.");

	return
	  value_zero (type, not_lval);
	}
      else
	return locate_var_value (var, (FRAME) 0);

    default:
    default_case:
      if (noside == EVAL_AVOID_SIDE_EFFECTS)
	{
	  value x = evaluate_subexp (NULL_TYPE, exp, pos, noside);
	  if (VALUE_LVAL (x) == lval_memory)
	    return value_zero (lookup_pointer_type (VALUE_TYPE (x)),
			       not_lval);
	  else
	    error ("Attempt to take address of non-lval");
	}
      return value_addr (evaluate_subexp (NULL_TYPE, exp, pos, noside));
    }
}

/* Evaluate like `evaluate_subexp' except coercing arrays to pointers.
   When used in contexts where arrays will be coerced anyway, this is
   equivalent to `evaluate_subexp' but much faster because it avoids
   actually fetching array contents.

   Note that we currently only do the coercion for C expressions, where
   arrays are zero based and the coercion is correct.  For other languages,
   with nonzero based arrays, coercion loses.  Use CAST_IS_CONVERSION
   to decide if coercion is appropriate.

  */

static value
evaluate_subexp_with_coercion (exp, pos, noside)
     register struct expression *exp;
     register int *pos;
     enum noside noside;
{
  register enum exp_opcode op;
  register int pc;
  register value val;
  struct symbol *var;

  pc = (*pos);
  op = exp->elts[pc].opcode;

  switch (op)
    {
    case OP_VAR_VALUE:
      var = exp->elts[pc + 1].symbol;
      if (TYPE_CODE (SYMBOL_TYPE (var)) == TYPE_CODE_ARRAY
	  && CAST_IS_CONVERSION)
	{
	  (*pos) += 3;
	  val = locate_var_value (var, (FRAME) 0);
	  return value_cast (lookup_pointer_type (TYPE_TARGET_TYPE (SYMBOL_TYPE (var))),
			     val);
	}
      default:
	return evaluate_subexp (NULL_TYPE, exp, pos, noside);
    }
}

/* Evaluate a subexpression of EXP, at index *POS,
   and return a value for the size of that subexpression.
   Advance *POS over the subexpression.  */

static value
evaluate_subexp_for_sizeof (exp, pos)
     register struct expression *exp;
     register int *pos;
{
  enum exp_opcode op;
  register int pc;
  value val;

  pc = (*pos);
  op = exp->elts[pc].opcode;

  switch (op)
    {
      /* This case is handled specially
	 so that we avoid creating a value for the result type.
	 If the result type is very big, it's desirable not to
	 create a value unnecessarily.  */
    case UNOP_IND:
      (*pos)++;
      val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
      return value_from_longest (builtin_type_int, (LONGEST)
		      TYPE_LENGTH (TYPE_TARGET_TYPE (VALUE_TYPE (val))));

    case UNOP_MEMVAL:
      (*pos) += 3;
      return value_from_longest (builtin_type_int, 
			      (LONGEST) TYPE_LENGTH (exp->elts[pc + 1].type));

    case OP_VAR_VALUE:
      (*pos) += 3;
      return value_from_longest (builtin_type_int,
	 (LONGEST) TYPE_LENGTH (SYMBOL_TYPE (exp->elts[pc + 1].symbol)));

    default:
      val = evaluate_subexp (NULL_TYPE, exp, pos, EVAL_AVOID_SIDE_EFFECTS);
      return value_from_longest (builtin_type_int,
			      (LONGEST) TYPE_LENGTH (VALUE_TYPE (val)));
    }
}

/* Parse a type expression in the string [P..P+LENGTH). */

struct type *
parse_and_eval_type (p, length)
     char *p;
     int length;
{
    char *tmp = (char *)alloca (length + 4);
    struct expression *expr;
    tmp[0] = '(';
    memcpy (tmp+1, p, length);
    tmp[length+1] = ')';
    tmp[length+2] = '0';
    tmp[length+3] = '\0';
    expr = parse_expression (tmp);
    if (expr->elts[0].opcode != UNOP_CAST)
	error ("Internal error in eval_type.");
    return expr->elts[1].type;
}