merging

  Dumps a text description of a thread, its security context

  (user, host) and the current query.

  @param thd current thread context

  @param thd thread context

  @param buffer pointer to preferred result buffer

  @param length length of buffer

  @param max_query_len how many chars of query to copy (0 for all)

  }

  if (str.c_ptr_safe() == buffer)

    return buffer;

  return thd->strmake(str.ptr(), str.length());

  /*

    We have to copy the new string to the destination buffer because the string

    was reallocated to a larger buffer to be able to fit.

  */

  DBUG_ASSERT(buffer != NULL);

  length= min(str.length(), length-1);

  memcpy(buffer, str.c_ptr_quick(), length);

  /* Make sure that the new string is null terminated */

  buffer[length]= '\0';

  return buffer;

}

/**