/
panic_waker.rs
70 lines (60 loc) · 1.95 KB
/
panic_waker.rs
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use core::ptr::null;
use futures_core::task::{RawWaker, RawWakerVTable, Waker};
unsafe fn clone_panic_waker(_data: *const ()) -> RawWaker {
raw_panic_waker()
}
unsafe fn noop(_data: *const ()) {}
unsafe fn wake_panic(_data: *const ()) {
if !std::thread::panicking() {
panic!("should not be woken");
}
}
const PANIC_WAKER_VTABLE: RawWakerVTable =
RawWakerVTable::new(clone_panic_waker, wake_panic, wake_panic, noop);
const fn raw_panic_waker() -> RawWaker {
RawWaker::new(null(), &PANIC_WAKER_VTABLE)
}
/// Create a new [`Waker`](futures_core::task::Waker) which will
/// panic when `wake()` is called on it. The [`Waker`] can be converted
/// into a [`Waker`] which will behave the same way.
///
/// # Examples
///
/// ```should_panic
/// use futures_test::task::panic_waker;
///
/// let waker = panic_waker();
/// waker.wake(); // Will panic
/// ```
pub fn panic_waker() -> Waker {
// FIXME: Since 1.46.0 we can use transmute in consts, allowing this function to be const.
unsafe { Waker::from_raw(raw_panic_waker()) }
}
/// Get a global reference to a
/// [`Waker`](futures_core::task::Waker) referencing a singleton
/// instance of a [`Waker`] which panics when woken.
///
/// # Examples
///
/// ```should_panic
/// use futures_test::task::panic_waker_ref;
///
/// let waker = panic_waker_ref();
/// waker.wake_by_ref(); // Will panic
/// ```
pub fn panic_waker_ref() -> &'static Waker {
struct SyncRawWaker(RawWaker);
unsafe impl Sync for SyncRawWaker {}
static PANIC_WAKER_INSTANCE: SyncRawWaker = SyncRawWaker(raw_panic_waker());
// SAFETY: `Waker` is #[repr(transparent)] over its `RawWaker`.
unsafe { &*(&PANIC_WAKER_INSTANCE.0 as *const RawWaker as *const Waker) }
}
#[cfg(test)]
mod tests {
#[test]
#[should_panic(expected = "should not be woken")]
fn issue_2091_cross_thread_segfault() {
let waker = std::thread::spawn(super::panic_waker_ref).join().unwrap();
waker.wake_by_ref();
}
}