Recently stabilised Waker::data()

[midnightveil]

Hi, was reading your code as a nice little reference, and I think the extract_mask() function of exec.rs could be replaced with the 1.83 stabilisation of Waker::data().

lilos/os/src/exec.rs

Lines 203 to 246 in 7fc6c64

	/// Exploits our known Waker structure to extract the notification mask from a
	/// Waker.
	///
	/// If this is applied to a Waker that isn't from this executor (specifically,
	/// one not generated by `waker_for_task`), this will cause spurious and almost
	/// certainly incorrect wakeups. Currently I don't feel like that risk is great
	/// enough to mark this unsafe -- it can't violate *memory* safety for certain.
	///
	/// In practice this function compiles down to a single inlined load
	/// instruction.
	fn extract_mask(waker: &Waker) -> usize {
	// Determine whether the pointer member comes first or second within the
	// representation of RawWaker. This is currently compile-time simplified
	// and goes away.
	//
	// Safety: we are using `transmute` to inspect the raw composition of a
	// Waker. That direction is safe -- it's a fancy version of casting a
	// pointer to an integer. Transmuting the _other_ direction would be very
	// unsafe.
	let ptr_first = unsafe {
	let (cell0, _) = mem::transmute::<Waker, (usize, usize)>(
	Waker::from_raw(RawWaker::new(
	1234 as *const (),
	&VTABLE,
	))
	);
	cell0 == 1234usize
	};
	let waker: *const Waker = waker;
	// Safety: at the moment, `Waker` consists exactly of a `*const ()` and a
	// `&'static RawWakerVTable` (or equivalent pointer), and this is unlikely
	// to change. We've already verified above that we can find the parameter
	// word, which is what we care about. Extracting it cannot violate memory
	// safety, since we're just reading initialized memory.
	unsafe {
	let parts = &*(waker as *const (usize, usize));
	if ptr_first {
	parts.0
	} else {
	parts.1
	}
	}
	}

https://dev-doc.rust-lang.org/std/task/struct.Waker.html#method.data

Possibly not 100% desired since it's quite new, but it'd be nice to use if possible. (unfortunately, cfg-version gating seems to still be nightly only...)