1use std::{
2 sync::atomic::{AtomicUsize, Ordering::SeqCst},
3 thread::scope,
4};
5
6#[cfg(feature = "std")]
7use std::sync::Barrier;
8
9#[cfg(not(feature = "std"))]
10use core::cell::Cell;
11
12use once_cell::sync::{Lazy, OnceCell};
13
14#[test]
15fn once_cell() {
16 let c = OnceCell::new();
17 assert!(c.get().is_none());
18 scope(|s| {
19 s.spawn(|| {
20 c.get_or_init(|| 92);
21 assert_eq!(c.get(), Some(&92));
22 });
23 });
24 c.get_or_init(|| panic!("Kabom!"));
25 assert_eq!(c.get(), Some(&92));
26}
27
28#[test]
29fn once_cell_with_value() {
30 static CELL: OnceCell<i32> = OnceCell::with_value(12);
31 assert_eq!(CELL.get(), Some(&12));
32}
33
34#[test]
35fn once_cell_get_mut() {
36 let mut c = OnceCell::new();
37 assert!(c.get_mut().is_none());
38 c.set(90).unwrap();
39 *c.get_mut().unwrap() += 2;
40 assert_eq!(c.get_mut(), Some(&mut 92));
41}
42
43#[test]
44fn once_cell_get_unchecked() {
45 let c = OnceCell::new();
46 c.set(92).unwrap();
47 unsafe {
48 assert_eq!(c.get_unchecked(), &92);
49 }
50}
51
52#[test]
53fn once_cell_drop() {
54 static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
55 struct Dropper;
56 impl Drop for Dropper {
57 fn drop(&mut self) {
58 DROP_CNT.fetch_add(1, SeqCst);
59 }
60 }
61
62 let x = OnceCell::new();
63 scope(|s| {
64 s.spawn(|| {
65 x.get_or_init(|| Dropper);
66 assert_eq!(DROP_CNT.load(SeqCst), 0);
67 drop(x);
68 });
69 });
70 assert_eq!(DROP_CNT.load(SeqCst), 1);
71}
72
73#[test]
74fn once_cell_drop_empty() {
75 let x = OnceCell::<String>::new();
76 drop(x);
77}
78
79#[test]
80fn clone() {
81 let s = OnceCell::new();
82 let c = s.clone();
83 assert!(c.get().is_none());
84
85 s.set("hello".to_string()).unwrap();
86 let c = s.clone();
87 assert_eq!(c.get().map(String::as_str), Some("hello"));
88}
89
90#[test]
91fn get_or_try_init() {
92 let cell: OnceCell<String> = OnceCell::new();
93 assert!(cell.get().is_none());
94
95 let res = std::panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
96 assert!(res.is_err());
97 assert!(cell.get().is_none());
98
99 assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
100
101 assert_eq!(cell.get_or_try_init(|| Ok::<_, ()>("hello".to_string())), Ok(&"hello".to_string()));
102 assert_eq!(cell.get(), Some(&"hello".to_string()));
103}
104
105#[cfg(feature = "std")]
106#[test]
107fn wait() {
108 let cell: OnceCell<String> = OnceCell::new();
109 scope(|s| {
110 s.spawn(|| cell.set("hello".to_string()));
111 let greeting = cell.wait();
112 assert_eq!(greeting, "hello")
113 });
114}
115
116#[cfg(feature = "std")]
117#[test]
118fn get_or_init_stress() {
119 let n_threads = if cfg!(miri) { 30 } else { 1_000 };
120 let n_cells = if cfg!(miri) { 30 } else { 1_000 };
121 let cells: Vec<_> = std::iter::repeat_with(|| (Barrier::new(n_threads), OnceCell::new()))
122 .take(n_cells)
123 .collect();
124 scope(|s| {
125 for t in 0..n_threads {
126 let cells = &cells;
127 s.spawn(move || {
128 for (i, (b, s)) in cells.iter().enumerate() {
129 b.wait();
130 let j = if t % 2 == 0 { s.wait() } else { s.get_or_init(|| i) };
131 assert_eq!(*j, i);
132 }
133 });
134 }
135 });
136}
137
138#[test]
139fn from_impl() {
140 assert_eq!(OnceCell::from("value").get(), Some(&"value"));
141 assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
142}
143
144#[test]
145fn partialeq_impl() {
146 assert!(OnceCell::from("value") == OnceCell::from("value"));
147 assert!(OnceCell::from("foo") != OnceCell::from("bar"));
148
149 assert!(OnceCell::<String>::new() == OnceCell::new());
150 assert!(OnceCell::<String>::new() != OnceCell::from("value".to_owned()));
151}
152
153#[test]
154fn into_inner() {
155 let cell: OnceCell<String> = OnceCell::new();
156 assert_eq!(cell.into_inner(), None);
157 let cell = OnceCell::new();
158 cell.set("hello".to_string()).unwrap();
159 assert_eq!(cell.into_inner(), Some("hello".to_string()));
160}
161
162#[test]
163fn debug_impl() {
164 let cell = OnceCell::new();
165 assert_eq!(format!("{:#?}", cell), "OnceCell(Uninit)");
166 cell.set(vec!["hello", "world"]).unwrap();
167 assert_eq!(
168 format!("{:#?}", cell),
169 r#"OnceCell(
170 [
171 "hello",
172 "world",
173 ],
174)"#
175 );
176}
177
178#[test]
179#[cfg_attr(miri, ignore)] // miri doesn't support processes
180#[cfg(feature = "std")]
181fn reentrant_init() {
182 let examples_dir = {
183 let mut exe = std::env::current_exe().unwrap();
184 exe.pop();
185 exe.pop();
186 exe.push("examples");
187 exe
188 };
189 let bin = examples_dir
190 .join("reentrant_init_deadlocks")
191 .with_extension(std::env::consts::EXE_EXTENSION);
192 let mut guard = Guard { child: std::process::Command::new(bin).spawn().unwrap() };
193 std::thread::sleep(std::time::Duration::from_secs(2));
194 let status = guard.child.try_wait().unwrap();
195 assert!(status.is_none());
196
197 struct Guard {
198 child: std::process::Child,
199 }
200
201 impl Drop for Guard {
202 fn drop(&mut self) {
203 let _ = self.child.kill();
204 }
205 }
206}
207
208#[cfg(not(feature = "std"))]
209#[test]
210#[should_panic(expected = "reentrant init")]
211fn reentrant_init() {
212 let x: OnceCell<Box<i32>> = OnceCell::new();
213 let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
214 x.get_or_init(|| {
215 let r = x.get_or_init(|| Box::new(92));
216 dangling_ref.set(Some(r));
217 Box::new(62)
218 });
219 eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
220}
221
222#[test]
223fn eval_once_macro() {
224 macro_rules! eval_once {
225 (|| -> $ty:ty {
226 $($body:tt)*
227 }) => {{
228 static ONCE_CELL: OnceCell<$ty> = OnceCell::new();
229 fn init() -> $ty {
230 $($body)*
231 }
232 ONCE_CELL.get_or_init(init)
233 }};
234 }
235
236 let fib: &'static Vec<i32> = eval_once! {
237 || -> Vec<i32> {
238 let mut res = vec![1, 1];
239 for i in 0..10 {
240 let next = res[i] + res[i + 1];
241 res.push(next);
242 }
243 res
244 }
245 };
246 assert_eq!(fib[5], 8)
247}
248
249#[test]
250fn once_cell_does_not_leak_partially_constructed_boxes() {
251 let n_tries = if cfg!(miri) { 10 } else { 100 };
252 let n_readers = 10;
253 let n_writers = 3;
254 const MSG: &str = "Hello, World";
255
256 for _ in 0..n_tries {
257 let cell: OnceCell<String> = OnceCell::new();
258 scope(|scope| {
259 for _ in 0..n_readers {
260 scope.spawn(|| loop {
261 if let Some(msg) = cell.get() {
262 assert_eq!(msg, MSG);
263 break;
264 }
265 });
266 }
267 for _ in 0..n_writers {
268 let _ = scope.spawn(|| cell.set(MSG.to_owned()));
269 }
270 });
271 }
272}
273
274#[cfg(feature = "std")]
275#[test]
276fn get_does_not_block() {
277 let cell = OnceCell::new();
278 let barrier = Barrier::new(2);
279 scope(|scope| {
280 scope.spawn(|| {
281 cell.get_or_init(|| {
282 barrier.wait();
283 barrier.wait();
284 "hello".to_string()
285 });
286 });
287 barrier.wait();
288 assert_eq!(cell.get(), None);
289 barrier.wait();
290 });
291 assert_eq!(cell.get(), Some(&"hello".to_string()));
292}
293
294#[test]
295// https://github.com/rust-lang/rust/issues/34761#issuecomment-256320669
296fn arrrrrrrrrrrrrrrrrrrrrr() {
297 let cell = OnceCell::new();
298 {
299 let s = String::new();
300 cell.set(&s).unwrap();
301 }
302}
303
304#[test]
305fn once_cell_is_sync_send() {
306 fn assert_traits<T: Send + Sync>() {}
307 assert_traits::<OnceCell<String>>();
308 assert_traits::<Lazy<String>>();
309}
310