Method once

src/once.rs:28–35

(predicate: *mut dispatch_once_t, work: F)

        #[cold]
        #[inline(never)]
        fn once<F>(predicate: *mut dispatch_once_t, work: F)
                where F: FnOnce() {
            let mut work = Some(work);
            let (context, work) = context_and_sync_function(&mut work);
            unsafe {
                dispatch_once_f(predicate, context, work);
            }
        }

        unsafe {
            let predicate = self.predicate.get();