Revision control
Copy as Markdown
Other Tools
use std::{
sync::atomic::{AtomicUsize, Ordering::SeqCst},
thread::scope,
};
#[cfg(feature = "std")]
use std::sync::Barrier;
#[cfg(not(feature = "std"))]
use core::cell::Cell;
use once_cell::sync::{Lazy, OnceCell};
#[test]
fn once_cell() {
let c = OnceCell::new();
assert!(c.get().is_none());
scope(|s| {
s.spawn(|| {
c.get_or_init(|| 92);
assert_eq!(c.get(), Some(&92));
});
});
c.get_or_init(|| panic!("Kabom!"));
assert_eq!(c.get(), Some(&92));
}
#[test]
fn once_cell_with_value() {
static CELL: OnceCell<i32> = OnceCell::with_value(12);
assert_eq!(CELL.get(), Some(&12));
}
#[test]
fn once_cell_get_mut() {
let mut c = OnceCell::new();
assert!(c.get_mut().is_none());
c.set(90).unwrap();
*c.get_mut().unwrap() += 2;
assert_eq!(c.get_mut(), Some(&mut 92));
}
#[test]
fn once_cell_get_unchecked() {
let c = OnceCell::new();
c.set(92).unwrap();
unsafe {
assert_eq!(c.get_unchecked(), &92);
}
}
#[test]
fn once_cell_drop() {
static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
struct Dropper;
impl Drop for Dropper {
fn drop(&mut self) {
DROP_CNT.fetch_add(1, SeqCst);
}
}
let x = OnceCell::new();
scope(|s| {
s.spawn(|| {
x.get_or_init(|| Dropper);
assert_eq!(DROP_CNT.load(SeqCst), 0);
drop(x);
});
});
assert_eq!(DROP_CNT.load(SeqCst), 1);
}
#[test]
fn once_cell_drop_empty() {
let x = OnceCell::<String>::new();
drop(x);
}
#[test]
fn clone() {
let s = OnceCell::new();
let c = s.clone();
assert!(c.get().is_none());
s.set("hello".to_string()).unwrap();
let c = s.clone();
assert_eq!(c.get().map(String::as_str), Some("hello"));
}
#[test]
fn get_or_try_init() {
let cell: OnceCell<String> = OnceCell::new();
assert!(cell.get().is_none());
let res = std::panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
assert!(res.is_err());
assert!(cell.get().is_none());
assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
assert_eq!(cell.get_or_try_init(|| Ok::<_, ()>("hello".to_string())), Ok(&"hello".to_string()));
assert_eq!(cell.get(), Some(&"hello".to_string()));
}
#[cfg(feature = "std")]
#[test]
fn wait() {
let cell: OnceCell<String> = OnceCell::new();
scope(|s| {
s.spawn(|| cell.set("hello".to_string()));
let greeting = cell.wait();
assert_eq!(greeting, "hello")
});
}
#[cfg(feature = "std")]
#[test]
fn get_or_init_stress() {
let n_threads = if cfg!(miri) { 30 } else { 1_000 };
let n_cells = if cfg!(miri) { 30 } else { 1_000 };
let cells: Vec<_> = std::iter::repeat_with(|| (Barrier::new(n_threads), OnceCell::new()))
.take(n_cells)
.collect();
scope(|s| {
for t in 0..n_threads {
let cells = &cells;
s.spawn(move || {
for (i, (b, s)) in cells.iter().enumerate() {
b.wait();
let j = if t % 2 == 0 { s.wait() } else { s.get_or_init(|| i) };
assert_eq!(*j, i);
}
});
}
});
}
#[test]
fn from_impl() {
assert_eq!(OnceCell::from("value").get(), Some(&"value"));
assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
}
#[test]
fn partialeq_impl() {
assert!(OnceCell::from("value") == OnceCell::from("value"));
assert!(OnceCell::from("foo") != OnceCell::from("bar"));
assert!(OnceCell::<String>::new() == OnceCell::new());
assert!(OnceCell::<String>::new() != OnceCell::from("value".to_owned()));
}
#[test]
fn into_inner() {
let cell: OnceCell<String> = OnceCell::new();
assert_eq!(cell.into_inner(), None);
let cell = OnceCell::new();
cell.set("hello".to_string()).unwrap();
assert_eq!(cell.into_inner(), Some("hello".to_string()));
}
#[test]
fn debug_impl() {
let cell = OnceCell::new();
assert_eq!(format!("{:#?}", cell), "OnceCell(Uninit)");
cell.set(vec!["hello", "world"]).unwrap();
assert_eq!(
format!("{:#?}", cell),
r#"OnceCell(
[
"hello",
"world",
],
)"#
);
}
#[test]
#[cfg_attr(miri, ignore)] // miri doesn't support processes
#[cfg(feature = "std")]
fn reentrant_init() {
let examples_dir = {
let mut exe = std::env::current_exe().unwrap();
exe.pop();
exe.pop();
exe.push("examples");
exe
};
let bin = examples_dir
.join("reentrant_init_deadlocks")
.with_extension(std::env::consts::EXE_EXTENSION);
let mut guard = Guard { child: std::process::Command::new(bin).spawn().unwrap() };
std::thread::sleep(std::time::Duration::from_secs(2));
let status = guard.child.try_wait().unwrap();
assert!(status.is_none());
struct Guard {
child: std::process::Child,
}
impl Drop for Guard {
fn drop(&mut self) {
let _ = self.child.kill();
}
}
}
#[cfg(not(feature = "std"))]
#[test]
#[should_panic(expected = "reentrant init")]
fn reentrant_init() {
let x: OnceCell<Box<i32>> = OnceCell::new();
let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
x.get_or_init(|| {
let r = x.get_or_init(|| Box::new(92));
dangling_ref.set(Some(r));
Box::new(62)
});
eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
}
#[test]
fn eval_once_macro() {
macro_rules! eval_once {
(|| -> $ty:ty {
$($body:tt)*
}) => {{
static ONCE_CELL: OnceCell<$ty> = OnceCell::new();
fn init() -> $ty {
$($body)*
}
ONCE_CELL.get_or_init(init)
}};
}
let fib: &'static Vec<i32> = eval_once! {
|| -> Vec<i32> {
let mut res = vec![1, 1];
for i in 0..10 {
let next = res[i] + res[i + 1];
res.push(next);
}
res
}
};
assert_eq!(fib[5], 8)
}
#[test]
fn once_cell_does_not_leak_partially_constructed_boxes() {
let n_tries = if cfg!(miri) { 10 } else { 100 };
let n_readers = 10;
let n_writers = 3;
const MSG: &str = "Hello, World";
for _ in 0..n_tries {
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()));
}
});
}
}
#[cfg(feature = "std")]
#[test]
fn get_does_not_block() {
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();
});
assert_eq!(cell.get(), Some(&"hello".to_string()));
}
#[test]
fn arrrrrrrrrrrrrrrrrrrrrr() {
let cell = OnceCell::new();
{
let s = String::new();
cell.set(&s).unwrap();
}
}
#[test]
fn once_cell_is_sync_send() {
fn assert_traits<T: Send + Sync>() {}
assert_traits::<OnceCell<String>>();
assert_traits::<Lazy<String>>();
}