875 lines
23 KiB
Rust
875 lines
23 KiB
Rust
mod unsync {
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use core::{
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cell::Cell,
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sync::atomic::{AtomicUsize, Ordering::SeqCst},
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};
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use once_cell::unsync::{Lazy, OnceCell};
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#[test]
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fn once_cell() {
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let c = OnceCell::new();
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assert!(c.get().is_none());
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c.get_or_init(|| 92);
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assert_eq!(c.get(), Some(&92));
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c.get_or_init(|| panic!("Kabom!"));
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assert_eq!(c.get(), Some(&92));
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}
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#[test]
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fn once_cell_get_mut() {
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let mut c = OnceCell::new();
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assert!(c.get_mut().is_none());
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c.set(90).unwrap();
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*c.get_mut().unwrap() += 2;
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assert_eq!(c.get_mut(), Some(&mut 92));
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}
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#[test]
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fn once_cell_drop() {
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static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
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struct Dropper;
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impl Drop for Dropper {
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fn drop(&mut self) {
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DROP_CNT.fetch_add(1, SeqCst);
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}
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}
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let x = OnceCell::new();
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x.get_or_init(|| Dropper);
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assert_eq!(DROP_CNT.load(SeqCst), 0);
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drop(x);
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assert_eq!(DROP_CNT.load(SeqCst), 1);
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}
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#[test]
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fn unsync_once_cell_drop_empty() {
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let x = OnceCell::<String>::new();
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drop(x);
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}
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#[test]
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fn clone() {
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let s = OnceCell::new();
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let c = s.clone();
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assert!(c.get().is_none());
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s.set("hello".to_string()).unwrap();
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let c = s.clone();
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assert_eq!(c.get().map(String::as_str), Some("hello"));
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}
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#[test]
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fn from_impl() {
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assert_eq!(OnceCell::from("value").get(), Some(&"value"));
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assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
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}
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#[test]
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fn partialeq_impl() {
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assert!(OnceCell::from("value") == OnceCell::from("value"));
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assert!(OnceCell::from("foo") != OnceCell::from("bar"));
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assert!(OnceCell::<String>::new() == OnceCell::new());
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assert!(OnceCell::<String>::new() != OnceCell::from("value".to_owned()));
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}
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#[test]
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fn into_inner() {
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let cell: OnceCell<String> = OnceCell::new();
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assert_eq!(cell.into_inner(), None);
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let cell = OnceCell::new();
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cell.set("hello".to_string()).unwrap();
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assert_eq!(cell.into_inner(), Some("hello".to_string()));
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}
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#[test]
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fn debug_impl() {
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let cell = OnceCell::new();
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assert_eq!(format!("{:?}", cell), "OnceCell(Uninit)");
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cell.set("hello".to_string()).unwrap();
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assert_eq!(format!("{:?}", cell), "OnceCell(\"hello\")");
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}
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#[test]
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fn lazy_new() {
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let called = Cell::new(0);
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let x = Lazy::new(|| {
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called.set(called.get() + 1);
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92
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});
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assert_eq!(called.get(), 0);
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let y = *x - 30;
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assert_eq!(y, 62);
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assert_eq!(called.get(), 1);
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let y = *x - 30;
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assert_eq!(y, 62);
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assert_eq!(called.get(), 1);
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}
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#[test]
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fn lazy_deref_mut() {
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let called = Cell::new(0);
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let mut x = Lazy::new(|| {
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called.set(called.get() + 1);
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92
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});
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assert_eq!(called.get(), 0);
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let y = *x - 30;
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assert_eq!(y, 62);
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assert_eq!(called.get(), 1);
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*x /= 2;
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assert_eq!(*x, 46);
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assert_eq!(called.get(), 1);
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}
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#[test]
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fn lazy_default() {
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static CALLED: AtomicUsize = AtomicUsize::new(0);
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struct Foo(u8);
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impl Default for Foo {
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fn default() -> Self {
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CALLED.fetch_add(1, SeqCst);
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Foo(42)
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}
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}
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let lazy: Lazy<std::sync::Mutex<Foo>> = <_>::default();
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assert_eq!(CALLED.load(SeqCst), 0);
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assert_eq!(lazy.lock().unwrap().0, 42);
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assert_eq!(CALLED.load(SeqCst), 1);
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lazy.lock().unwrap().0 = 21;
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assert_eq!(lazy.lock().unwrap().0, 21);
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assert_eq!(CALLED.load(SeqCst), 1);
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}
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#[test]
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fn lazy_into_value() {
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let l: Lazy<i32, _> = Lazy::new(|| panic!());
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assert!(matches!(Lazy::into_value(l), Err(_)));
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let l = Lazy::new(|| -> i32 { 92 });
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Lazy::force(&l);
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assert!(matches!(Lazy::into_value(l), Ok(92)));
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}
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#[test]
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#[cfg(feature = "std")]
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#[cfg(not(target_os = "android"))]
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fn lazy_poisoning() {
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let x: Lazy<String> = Lazy::new(|| panic!("kaboom"));
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for _ in 0..2 {
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let res = std::panic::catch_unwind(|| x.len());
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assert!(res.is_err());
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}
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}
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#[test]
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fn aliasing_in_get() {
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let x = OnceCell::new();
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x.set(42).unwrap();
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let at_x = x.get().unwrap(); // --- (shared) borrow of inner `Option<T>` --+
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let _ = x.set(27); // <-- temporary (unique) borrow of inner `Option<T>` |
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println!("{}", at_x); // <------- up until here ---------------------------+
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}
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#[test]
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#[should_panic(expected = "reentrant init")]
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fn reentrant_init() {
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let x: OnceCell<Box<i32>> = OnceCell::new();
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let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
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x.get_or_init(|| {
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let r = x.get_or_init(|| Box::new(92));
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dangling_ref.set(Some(r));
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Box::new(62)
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});
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eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
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}
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#[test]
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// https://github.com/rust-lang/rust/issues/34761#issuecomment-256320669
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fn arrrrrrrrrrrrrrrrrrrrrr() {
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let cell = OnceCell::new();
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{
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let s = String::new();
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cell.set(&s).unwrap();
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}
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}
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}
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#[cfg(feature = "std")]
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mod sync {
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use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
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use crossbeam_utils::thread::scope;
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use once_cell::sync::{Lazy, OnceCell};
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#[test]
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fn once_cell() {
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let c = OnceCell::new();
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assert!(c.get().is_none());
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scope(|s| {
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s.spawn(|_| {
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c.get_or_init(|| 92);
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assert_eq!(c.get(), Some(&92));
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});
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})
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.unwrap();
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c.get_or_init(|| panic!("Kabom!"));
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assert_eq!(c.get(), Some(&92));
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}
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#[test]
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fn once_cell_get_mut() {
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let mut c = OnceCell::new();
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assert!(c.get_mut().is_none());
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c.set(90).unwrap();
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*c.get_mut().unwrap() += 2;
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assert_eq!(c.get_mut(), Some(&mut 92));
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}
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#[test]
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fn once_cell_get_unchecked() {
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let c = OnceCell::new();
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c.set(92).unwrap();
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unsafe {
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assert_eq!(c.get_unchecked(), &92);
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}
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}
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#[test]
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fn once_cell_drop() {
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static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
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struct Dropper;
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impl Drop for Dropper {
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fn drop(&mut self) {
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DROP_CNT.fetch_add(1, SeqCst);
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}
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}
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let x = OnceCell::new();
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scope(|s| {
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s.spawn(|_| {
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x.get_or_init(|| Dropper);
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assert_eq!(DROP_CNT.load(SeqCst), 0);
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drop(x);
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});
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})
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.unwrap();
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assert_eq!(DROP_CNT.load(SeqCst), 1);
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}
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#[test]
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fn once_cell_drop_empty() {
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let x = OnceCell::<String>::new();
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drop(x);
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}
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#[test]
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fn clone() {
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let s = OnceCell::new();
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let c = s.clone();
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assert!(c.get().is_none());
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s.set("hello".to_string()).unwrap();
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let c = s.clone();
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assert_eq!(c.get().map(String::as_str), Some("hello"));
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}
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#[test]
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#[cfg(not(target_os = "android"))]
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fn get_or_try_init() {
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let cell: OnceCell<String> = OnceCell::new();
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assert!(cell.get().is_none());
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let res =
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std::panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
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assert!(res.is_err());
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assert!(cell.get().is_none());
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assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
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assert_eq!(
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cell.get_or_try_init(|| Ok::<_, ()>("hello".to_string())),
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Ok(&"hello".to_string())
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);
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assert_eq!(cell.get(), Some(&"hello".to_string()));
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}
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#[test]
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fn from_impl() {
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assert_eq!(OnceCell::from("value").get(), Some(&"value"));
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assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
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}
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#[test]
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fn partialeq_impl() {
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assert!(OnceCell::from("value") == OnceCell::from("value"));
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assert!(OnceCell::from("foo") != OnceCell::from("bar"));
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assert!(OnceCell::<String>::new() == OnceCell::new());
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assert!(OnceCell::<String>::new() != OnceCell::from("value".to_owned()));
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}
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#[test]
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fn into_inner() {
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let cell: OnceCell<String> = OnceCell::new();
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assert_eq!(cell.into_inner(), None);
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let cell = OnceCell::new();
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cell.set("hello".to_string()).unwrap();
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assert_eq!(cell.into_inner(), Some("hello".to_string()));
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}
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#[test]
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fn debug_impl() {
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let cell = OnceCell::new();
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assert_eq!(format!("{:#?}", cell), "OnceCell(Uninit)");
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cell.set(vec!["hello", "world"]).unwrap();
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assert_eq!(
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format!("{:#?}", cell),
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r#"OnceCell(
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[
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"hello",
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"world",
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],
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)"#
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);
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}
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#[test]
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#[cfg_attr(miri, ignore)] // miri doesn't support processes
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#[ignore = "Android: ignore for now. Need to compile these binaries separately."]
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fn reentrant_init() {
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let examples_dir = {
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let mut exe = std::env::current_exe().unwrap();
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exe.pop();
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exe.pop();
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exe.push("examples");
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exe
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};
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let bin = examples_dir
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.join("reentrant_init_deadlocks")
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.with_extension(std::env::consts::EXE_EXTENSION);
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let mut guard = Guard { child: std::process::Command::new(bin).spawn().unwrap() };
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std::thread::sleep(std::time::Duration::from_secs(2));
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let status = guard.child.try_wait().unwrap();
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assert!(status.is_none());
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struct Guard {
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child: std::process::Child,
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}
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impl Drop for Guard {
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fn drop(&mut self) {
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let _ = self.child.kill();
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}
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}
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}
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#[test]
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fn lazy_new() {
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let called = AtomicUsize::new(0);
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let x = Lazy::new(|| {
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called.fetch_add(1, SeqCst);
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92
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});
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assert_eq!(called.load(SeqCst), 0);
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scope(|s| {
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s.spawn(|_| {
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let y = *x - 30;
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assert_eq!(y, 62);
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assert_eq!(called.load(SeqCst), 1);
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});
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})
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.unwrap();
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let y = *x - 30;
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assert_eq!(y, 62);
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assert_eq!(called.load(SeqCst), 1);
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}
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#[test]
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fn lazy_deref_mut() {
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let called = AtomicUsize::new(0);
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let mut x = Lazy::new(|| {
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called.fetch_add(1, SeqCst);
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92
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});
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assert_eq!(called.load(SeqCst), 0);
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let y = *x - 30;
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assert_eq!(y, 62);
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assert_eq!(called.load(SeqCst), 1);
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*x /= 2;
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assert_eq!(*x, 46);
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assert_eq!(called.load(SeqCst), 1);
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}
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#[test]
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fn lazy_default() {
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static CALLED: AtomicUsize = AtomicUsize::new(0);
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struct Foo(u8);
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impl Default for Foo {
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fn default() -> Self {
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CALLED.fetch_add(1, SeqCst);
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Foo(42)
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}
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}
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let lazy: Lazy<std::sync::Mutex<Foo>> = <_>::default();
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assert_eq!(CALLED.load(SeqCst), 0);
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assert_eq!(lazy.lock().unwrap().0, 42);
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assert_eq!(CALLED.load(SeqCst), 1);
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lazy.lock().unwrap().0 = 21;
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assert_eq!(lazy.lock().unwrap().0, 21);
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assert_eq!(CALLED.load(SeqCst), 1);
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}
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#[test]
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fn static_lazy() {
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static XS: Lazy<Vec<i32>> = Lazy::new(|| {
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let mut xs = Vec::new();
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xs.push(1);
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xs.push(2);
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xs.push(3);
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xs
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});
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scope(|s| {
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s.spawn(|_| {
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assert_eq!(&*XS, &vec![1, 2, 3]);
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});
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})
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.unwrap();
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assert_eq!(&*XS, &vec![1, 2, 3]);
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}
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#[test]
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fn static_lazy_via_fn() {
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fn xs() -> &'static Vec<i32> {
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static XS: OnceCell<Vec<i32>> = OnceCell::new();
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XS.get_or_init(|| {
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let mut xs = Vec::new();
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xs.push(1);
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xs.push(2);
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xs.push(3);
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xs
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})
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}
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assert_eq!(xs(), &vec![1, 2, 3]);
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}
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#[test]
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fn lazy_into_value() {
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let l: Lazy<i32, _> = Lazy::new(|| panic!());
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assert!(matches!(Lazy::into_value(l), Err(_)));
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let l = Lazy::new(|| -> i32 { 92 });
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Lazy::force(&l);
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assert!(matches!(Lazy::into_value(l), Ok(92)));
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}
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#[test]
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#[cfg(not(target_os = "android"))]
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fn lazy_poisoning() {
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let x: Lazy<String> = Lazy::new(|| panic!("kaboom"));
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for _ in 0..2 {
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let res = std::panic::catch_unwind(|| x.len());
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assert!(res.is_err());
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}
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}
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#[test]
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fn once_cell_is_sync_send() {
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fn assert_traits<T: Send + Sync>() {}
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assert_traits::<OnceCell<String>>();
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assert_traits::<Lazy<String>>();
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}
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#[test]
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fn eval_once_macro() {
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macro_rules! eval_once {
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(|| -> $ty:ty {
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$($body:tt)*
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}) => {{
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static ONCE_CELL: OnceCell<$ty> = OnceCell::new();
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fn init() -> $ty {
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$($body)*
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}
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ONCE_CELL.get_or_init(init)
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}};
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}
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let fib: &'static Vec<i32> = eval_once! {
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|| -> Vec<i32> {
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let mut res = vec![1, 1];
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for i in 0..10 {
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let next = res[i] + res[i + 1];
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res.push(next);
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}
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res
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}
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};
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assert_eq!(fib[5], 8)
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}
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#[test]
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#[cfg_attr(miri, ignore)] // FIXME: deadlocks, likely caused by https://github.com/rust-lang/miri/issues/1388
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fn once_cell_does_not_leak_partially_constructed_boxes() {
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let n_tries = 100;
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let n_readers = 10;
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let n_writers = 3;
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const MSG: &str = "Hello, World";
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for _ in 0..n_tries {
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let cell: OnceCell<String> = OnceCell::new();
|
|
scope(|scope| {
|
|
for _ in 0..n_readers {
|
|
scope.spawn(|_| loop {
|
|
if let Some(msg) = cell.get() {
|
|
assert_eq!(msg, MSG);
|
|
break;
|
|
}
|
|
});
|
|
}
|
|
for _ in 0..n_writers {
|
|
let _ = scope.spawn(|_| cell.set(MSG.to_owned()));
|
|
}
|
|
})
|
|
.unwrap()
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
#[cfg_attr(miri, ignore)] // miri doesn't support Barrier
|
|
fn get_does_not_block() {
|
|
use std::sync::Barrier;
|
|
|
|
let cell = OnceCell::new();
|
|
let barrier = Barrier::new(2);
|
|
scope(|scope| {
|
|
scope.spawn(|_| {
|
|
cell.get_or_init(|| {
|
|
barrier.wait();
|
|
barrier.wait();
|
|
"hello".to_string()
|
|
});
|
|
});
|
|
barrier.wait();
|
|
assert_eq!(cell.get(), None);
|
|
barrier.wait();
|
|
})
|
|
.unwrap();
|
|
assert_eq!(cell.get(), Some(&"hello".to_string()));
|
|
}
|
|
|
|
#[test]
|
|
// https://github.com/rust-lang/rust/issues/34761#issuecomment-256320669
|
|
fn arrrrrrrrrrrrrrrrrrrrrr() {
|
|
let cell = OnceCell::new();
|
|
{
|
|
let s = String::new();
|
|
cell.set(&s).unwrap();
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(feature = "race")]
|
|
mod race {
|
|
use std::{
|
|
num::NonZeroUsize,
|
|
sync::{
|
|
atomic::{AtomicUsize, Ordering::SeqCst},
|
|
Barrier,
|
|
},
|
|
};
|
|
|
|
use crossbeam_utils::thread::scope;
|
|
|
|
use once_cell::race::{OnceBool, OnceNonZeroUsize};
|
|
|
|
#[test]
|
|
fn once_non_zero_usize_smoke_test() {
|
|
let cnt = AtomicUsize::new(0);
|
|
let cell = OnceNonZeroUsize::new();
|
|
let val = NonZeroUsize::new(92).unwrap();
|
|
scope(|s| {
|
|
s.spawn(|_| {
|
|
assert_eq!(
|
|
cell.get_or_init(|| {
|
|
cnt.fetch_add(1, SeqCst);
|
|
val
|
|
}),
|
|
val
|
|
);
|
|
assert_eq!(cnt.load(SeqCst), 1);
|
|
|
|
assert_eq!(
|
|
cell.get_or_init(|| {
|
|
cnt.fetch_add(1, SeqCst);
|
|
val
|
|
}),
|
|
val
|
|
);
|
|
assert_eq!(cnt.load(SeqCst), 1);
|
|
});
|
|
})
|
|
.unwrap();
|
|
assert_eq!(cell.get(), Some(val));
|
|
assert_eq!(cnt.load(SeqCst), 1);
|
|
}
|
|
|
|
#[test]
|
|
fn once_non_zero_usize_set() {
|
|
let val1 = NonZeroUsize::new(92).unwrap();
|
|
let val2 = NonZeroUsize::new(62).unwrap();
|
|
|
|
let cell = OnceNonZeroUsize::new();
|
|
|
|
assert!(cell.set(val1).is_ok());
|
|
assert_eq!(cell.get(), Some(val1));
|
|
|
|
assert!(cell.set(val2).is_err());
|
|
assert_eq!(cell.get(), Some(val1));
|
|
}
|
|
|
|
#[test]
|
|
fn once_non_zero_usize_first_wins() {
|
|
let val1 = NonZeroUsize::new(92).unwrap();
|
|
let val2 = NonZeroUsize::new(62).unwrap();
|
|
|
|
let cell = OnceNonZeroUsize::new();
|
|
|
|
let b1 = Barrier::new(2);
|
|
let b2 = Barrier::new(2);
|
|
let b3 = Barrier::new(2);
|
|
scope(|s| {
|
|
s.spawn(|_| {
|
|
let r1 = cell.get_or_init(|| {
|
|
b1.wait();
|
|
b2.wait();
|
|
val1
|
|
});
|
|
assert_eq!(r1, val1);
|
|
b3.wait();
|
|
});
|
|
b1.wait();
|
|
s.spawn(|_| {
|
|
let r2 = cell.get_or_init(|| {
|
|
b2.wait();
|
|
b3.wait();
|
|
val2
|
|
});
|
|
assert_eq!(r2, val1);
|
|
});
|
|
})
|
|
.unwrap();
|
|
|
|
assert_eq!(cell.get(), Some(val1));
|
|
}
|
|
|
|
#[test]
|
|
fn once_bool_smoke_test() {
|
|
let cnt = AtomicUsize::new(0);
|
|
let cell = OnceBool::new();
|
|
scope(|s| {
|
|
s.spawn(|_| {
|
|
assert_eq!(
|
|
cell.get_or_init(|| {
|
|
cnt.fetch_add(1, SeqCst);
|
|
false
|
|
}),
|
|
false
|
|
);
|
|
assert_eq!(cnt.load(SeqCst), 1);
|
|
|
|
assert_eq!(
|
|
cell.get_or_init(|| {
|
|
cnt.fetch_add(1, SeqCst);
|
|
false
|
|
}),
|
|
false
|
|
);
|
|
assert_eq!(cnt.load(SeqCst), 1);
|
|
});
|
|
})
|
|
.unwrap();
|
|
assert_eq!(cell.get(), Some(false));
|
|
assert_eq!(cnt.load(SeqCst), 1);
|
|
}
|
|
|
|
#[test]
|
|
fn once_bool_set() {
|
|
let cell = OnceBool::new();
|
|
|
|
assert!(cell.set(false).is_ok());
|
|
assert_eq!(cell.get(), Some(false));
|
|
|
|
assert!(cell.set(true).is_err());
|
|
assert_eq!(cell.get(), Some(false));
|
|
}
|
|
}
|
|
|
|
#[cfg(all(feature = "race", feature = "alloc"))]
|
|
mod race_once_box {
|
|
use std::sync::{
|
|
atomic::{AtomicUsize, Ordering::SeqCst},
|
|
Arc, Barrier,
|
|
};
|
|
|
|
use crossbeam_utils::thread::scope;
|
|
use once_cell::race::OnceBox;
|
|
|
|
#[derive(Default)]
|
|
struct Heap {
|
|
total: Arc<AtomicUsize>,
|
|
}
|
|
|
|
#[derive(Debug)]
|
|
struct Pebble<T> {
|
|
val: T,
|
|
total: Arc<AtomicUsize>,
|
|
}
|
|
|
|
impl<T> Drop for Pebble<T> {
|
|
fn drop(&mut self) {
|
|
self.total.fetch_sub(1, SeqCst);
|
|
}
|
|
}
|
|
|
|
impl Heap {
|
|
fn total(&self) -> usize {
|
|
self.total.load(SeqCst)
|
|
}
|
|
fn new_pebble<T>(&self, val: T) -> Pebble<T> {
|
|
self.total.fetch_add(1, SeqCst);
|
|
Pebble { val, total: Arc::clone(&self.total) }
|
|
}
|
|
}
|
|
|
|
#[test]
|
|
fn once_box_smoke_test() {
|
|
let heap = Heap::default();
|
|
let global_cnt = AtomicUsize::new(0);
|
|
let cell = OnceBox::new();
|
|
let b = Barrier::new(128);
|
|
scope(|s| {
|
|
for _ in 0..128 {
|
|
s.spawn(|_| {
|
|
let local_cnt = AtomicUsize::new(0);
|
|
cell.get_or_init(|| {
|
|
global_cnt.fetch_add(1, SeqCst);
|
|
local_cnt.fetch_add(1, SeqCst);
|
|
b.wait();
|
|
Box::new(heap.new_pebble(()))
|
|
});
|
|
assert_eq!(local_cnt.load(SeqCst), 1);
|
|
|
|
cell.get_or_init(|| {
|
|
global_cnt.fetch_add(1, SeqCst);
|
|
local_cnt.fetch_add(1, SeqCst);
|
|
Box::new(heap.new_pebble(()))
|
|
});
|
|
assert_eq!(local_cnt.load(SeqCst), 1);
|
|
});
|
|
}
|
|
})
|
|
.unwrap();
|
|
assert!(cell.get().is_some());
|
|
assert!(global_cnt.load(SeqCst) > 10);
|
|
|
|
assert_eq!(heap.total(), 1);
|
|
drop(cell);
|
|
assert_eq!(heap.total(), 0);
|
|
}
|
|
|
|
#[test]
|
|
fn once_box_set() {
|
|
let heap = Heap::default();
|
|
let cell = OnceBox::new();
|
|
assert!(cell.get().is_none());
|
|
|
|
assert!(cell.set(Box::new(heap.new_pebble("hello"))).is_ok());
|
|
assert_eq!(cell.get().unwrap().val, "hello");
|
|
assert_eq!(heap.total(), 1);
|
|
|
|
assert!(cell.set(Box::new(heap.new_pebble("world"))).is_err());
|
|
assert_eq!(cell.get().unwrap().val, "hello");
|
|
assert_eq!(heap.total(), 1);
|
|
|
|
drop(cell);
|
|
assert_eq!(heap.total(), 0);
|
|
}
|
|
|
|
#[test]
|
|
fn once_box_first_wins() {
|
|
let cell = OnceBox::new();
|
|
let val1 = 92;
|
|
let val2 = 62;
|
|
|
|
let b1 = Barrier::new(2);
|
|
let b2 = Barrier::new(2);
|
|
let b3 = Barrier::new(2);
|
|
scope(|s| {
|
|
s.spawn(|_| {
|
|
let r1 = cell.get_or_init(|| {
|
|
b1.wait();
|
|
b2.wait();
|
|
Box::new(val1)
|
|
});
|
|
assert_eq!(*r1, val1);
|
|
b3.wait();
|
|
});
|
|
b1.wait();
|
|
s.spawn(|_| {
|
|
let r2 = cell.get_or_init(|| {
|
|
b2.wait();
|
|
b3.wait();
|
|
Box::new(val2)
|
|
});
|
|
assert_eq!(*r2, val1);
|
|
});
|
|
})
|
|
.unwrap();
|
|
|
|
assert_eq!(cell.get(), Some(&val1));
|
|
}
|
|
|
|
#[test]
|
|
fn once_box_reentrant() {
|
|
let cell = OnceBox::new();
|
|
let res = cell.get_or_init(|| {
|
|
cell.get_or_init(|| Box::new("hello".to_string()));
|
|
Box::new("world".to_string())
|
|
});
|
|
assert_eq!(res, "hello");
|
|
}
|
|
|
|
#[test]
|
|
fn once_box_default() {
|
|
struct Foo;
|
|
|
|
let cell: OnceBox<Foo> = Default::default();
|
|
assert!(cell.get().is_none());
|
|
}
|
|
}
|