Mark a function as returning.

        :param int func_addr: Address of the function that returns.
        :return:              None

def add_returning_function(self, func_addr):
        """
        Mark a function as returning.

        :param int func_addr: Address of the function that returns.
        :return:              None
        """

        self._returning_functions.add(func_addr)
        self._updated_functions.add(func_addr)