On successful completion, this routine returns a zero (0) and
    the stacksize value in bytes in the location specified in the
    stacksize argument.

    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 stack
                attributes object.