Function sigpending 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn sigpending(set: *mut sigset_t) -> c_int

See https://pubs.opengroup.org/onlinepubs/9799919799/functions/sigpending.html.

Stores, in the location referenced by the set argument, the set of signals that are blocked from delivery to the calling thread and that are pending on the process or the calling thread.

Upon success, returns 0. Upon failure, returns -1 and sets errno to indicate the error.