void Lex_input_stream::body_utf8_start(THD *thd, const char *begin_ptr)
{
  DBUG_ASSERT(begin_ptr);
  DBUG_ASSERT(m_cpp_buf <= begin_ptr && begin_ptr <= m_cpp_buf + m_buf_length);

  uint body_utf8_length= get_body_utf8_maximum_length(thd);

  m_body_utf8= (char *) thd->alloc(body_utf8_length + 1);
  m_body_utf8_ptr= m_body_utf8;
  *m_body_utf8_ptr= 0;

  m_cpp_utf8_processed_ptr= begin_ptr;
}