eval.c

早期freebsd实现

	}
      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_LOGNOT:
      /* 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_LOGNOT, arg1))
	return value_x_unop (arg1, UNOP_LOGNOT);
      else
	return value_lognot (arg1);

    case UNOP_ZEROP:
      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_zerop (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)
	    {
	      char *name = &exp->elts[pc+3].string;
	      int temm = strlen (name);
	      (*pos) += 2 + (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.  */

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)
	{
	  (*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;
}