bug fix

Author: fukatani

src/etc/gdb_rust_pretty_printing.py

@@ -319,7 +319,7 @@ def to_string(self):
     def children(self):
         (length, data_ptr) = \
             rustpp.extract_length_and_ptr_from_std_btreeset(self.__val)
-        val = GdbValue(data_ptr.get_wrapped_value().dereference()).get_child_at_index(0)
+        val = GdbValue(data_ptr.get_wrapped_value().dereference()).get_child_at_index(3)
         gdb_ptr = val.get_wrapped_value()
         for index in xrange(length):
             yield (str(index), str(index))