4 use std::sync::Once;
7     once: Once,  field
17             once: Once::new(),  in new()
29         if !self.once.is_completed() {  in get()
33         // Safety: The `std::sync::Once` guarantees that we can only reach this  in get()
34         // line if a `call_once` closure has been run exactly once and without  in get()
47         self.once.call_once(|| {  in do_init()
50             // Safety: The `std::sync::Once` guarantees that this initialization  in do_init()
51             // will run at most once, and that no thread can get past the  in do_init()
52             // `call_once` until it has run exactly once. Thus, we have  in do_init()
63         if self.once.is_completed() {  in drop()