If an error condition occurs, this routine returns an integer
    value indicating the type of error. Possible return values are as
    follows:

    Return      Description

    0           Successful completion.
    [EINVAL]    The value specified by attr is not a valid thread
                attributes value, or the value specified by scope is
                not valid.
    [ENOTSUP]   An attempt was made to set the attribute to an
                unsupported value.