Function notmuch_threads_valid 

pub unsafe extern "C" fn notmuch_threads_valid(
    threads: *mut notmuch_threads_t,
) -> notmuch_bool_t

Is the given ‘threads’ iterator pointing at a valid thread.

When this function returns TRUE, notmuch_threads_get will return a valid object. Whereas when this function returns FALSE, notmuch_threads_get will return NULL.

If passed a NULL pointer, this function returns FALSE

See the documentation of notmuch_query_search_threads for example code showing how to iterate over a notmuch_threads_t object.