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Rollup merge of #95985 - jihiggins:issue-66481, r=dtolnay

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Add PhantomData marker to Context to make Context !Send and !Sync

Adds `PhantomData<*mut ()>` to `Context` in order to allow for future `!Send` or `!Sync` additions to `Context`'s fields. This would allow for things like future single threaded async executor optimizations, or (re)adding `LocalWaker`, etc.

Closes #66481.

Per https://github.com/rust-lang/rust/issues/66481#issuecomment-561289725, this is a breaking change that needs a Crater run as the next step.

(So far have tested the change locally with `cargotest` on WSL)
This commit is contained in:
Michael Goulet 2023-01-02 15:39:16 -08:00 committed by GitHub
commit 722bc0c8ee
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2 changed files with 6 additions and 7 deletions
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5
library/core/src/task/wake.rs
View File

@ -181,6 +181,9 @@ pub struct Context<'a> {
// are contravariant while return-position lifetimes are
// covariant).
_marker: PhantomData<fn(&'a ()) -> &'a ()>,
// Ensure `Context` is `!Send` and `!Sync` in order to allow
// for future `!Send` and / or `!Sync` fields.
_marker2: PhantomData<*mut ()>,
}
impl<'a> Context<'a> {
@ -190,7 +193,7 @@ impl<'a> Context<'a> {
#[must_use]
#[inline]
pub const fn from_waker(waker: &'a Waker) -> Self {
Context { waker, _marker: PhantomData }
Context { waker, _marker: PhantomData, _marker2: PhantomData }
}
/// Returns a reference to the [`Waker`] for the current task.

8
library/core/tests/task.rs
View File

@ -1,4 +1,4 @@
use core::task::{Context, Poll, RawWaker, RawWakerVTable, Waker};
use core::task::{Poll, RawWaker, RawWakerVTable, Waker};
#[test]
fn poll_const() {
@ -21,9 +21,5 @@ fn waker_const() {
static WAKER: Waker = unsafe { Waker::from_raw(VOID_WAKER) };
static CONTEXT: Context<'static> = Context::from_waker(&WAKER);
static WAKER_REF: &'static Waker = CONTEXT.waker();
WAKER_REF.wake_by_ref();
WAKER.wake_by_ref();
}