This routine initializes the read-write lock attributes object
    referenced by attr and sets its attributes with default values.

    The results of calling this routine are undefined if attr
    references an already initialized read-write lock attributes
    object.

    After an initialized read-write lock attributes object has been
    used to initialize one or more read-write lock objects, any
    operation on that attributes object (including destruction) has
    no effect on those read-write lock objects.