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Wrap Context.ext in AssertUnwindSafe

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This commit is contained in:
Jubilee Young 2024-05-21 18:55:12 -07:00
parent 39e02f1bd1
commit 3a21fb5cec
4 changed files with 27 additions and 42 deletions
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11
library/core/src/task/wake.rs
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@ -5,6 +5,7 @@
use crate::any::Any;
use crate::fmt;
use crate::marker::PhantomData;
use crate::panic::AssertUnwindSafe;
use crate::ptr;
/// A `RawWaker` allows the implementor of a task executor to create a [`Waker`]
@ -236,7 +237,7 @@ enum ExtData<'a> {
pub struct Context<'a> {
waker: &'a Waker,
local_waker: &'a LocalWaker,
ext: ExtData<'a>,
ext: AssertUnwindSafe<ExtData<'a>>,
// Ensure we future-proof against variance changes by forcing
// the lifetime to be invariant (argument-position lifetimes
// are contravariant while return-position lifetimes are
@ -279,7 +280,9 @@ pub const fn local_waker(&self) -> &'a LocalWaker {
#[unstable(feature = "context_ext", issue = "123392")]
#[rustc_const_unstable(feature = "const_waker", issue = "102012")]
pub const fn ext(&mut self) -> &mut dyn Any {
match &mut self.ext {
// FIXME: this field makes Context extra-weird about unwind safety
// can we justify AssertUnwindSafe if we stabilize this? do we care?
match &mut *self.ext {
ExtData::Some(data) => *data,
ExtData::None(unit) => unit,
}
@ -353,7 +356,7 @@ pub const fn from_waker(waker: &'a Waker) -> Self {
#[rustc_const_unstable(feature = "const_waker", issue = "102012")]
#[unstable(feature = "context_ext", issue = "123392")]
pub const fn from(cx: &'a mut Context<'_>) -> Self {
let ext = match &mut cx.ext {
let ext = match &mut *cx.ext {
ExtData::Some(ext) => ExtData::Some(*ext),
ExtData::None(()) => ExtData::None(()),
};
@ -396,7 +399,7 @@ pub const fn ext(self, data: &'a mut dyn Any) -> Self {
#[rustc_const_unstable(feature = "const_waker", issue = "102012")]
pub const fn build(self) -> Context<'a> {
let ContextBuilder { waker, local_waker, ext, _marker, _marker2 } = self;
Context { waker, local_waker, ext, _marker, _marker2 }
Context { waker, local_waker, ext: AssertUnwindSafe(ext), _marker, _marker2 }
}
}

1
tests/ui/async-await/async-is-unwindsafe.rs
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@ -11,7 +11,6 @@ fn main() {
is_unwindsafe(async {
//~^ ERROR the type `&mut Context<'_>` may not be safely transferred across an unwind boundary
//~| ERROR the type `&mut (dyn Any + 'static)` may not be safely transferred across an unwind boundary
use std::ptr::null;
use std::task::{Context, RawWaker, RawWakerVTable, Waker};
let waker = unsafe {

43
tests/ui/async-await/async-is-unwindsafe.stderr
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@ -6,18 +6,19 @@ LL | is_unwindsafe(async {
| |_____|
| ||
LL | ||
LL | ||
LL | || use std::ptr::null;
LL | || use std::task::{Context, RawWaker, RawWakerVTable, Waker};
... ||
LL | || drop(cx_ref);
LL | || });
| ||_____-^ `&mut Context<'_>` may not be safely transferred across an unwind boundary
| |_____|
| within this `{async block@$DIR/async-is-unwindsafe.rs:12:19: 30:6}`
| within this `{async block@$DIR/async-is-unwindsafe.rs:12:19: 29:6}`
|
= help: within `{async block@$DIR/async-is-unwindsafe.rs:12:19: 30:6}`, the trait `UnwindSafe` is not implemented for `&mut Context<'_>`, which is required by `{async block@$DIR/async-is-unwindsafe.rs:12:19: 30:6}: UnwindSafe`
= help: within `{async block@$DIR/async-is-unwindsafe.rs:12:19: 29:6}`, the trait `UnwindSafe` is not implemented for `&mut Context<'_>`, which is required by `{async block@$DIR/async-is-unwindsafe.rs:12:19: 29:6}: UnwindSafe`
= note: `UnwindSafe` is implemented for `&Context<'_>`, but not for `&mut Context<'_>`
note: future does not implement `UnwindSafe` as this value is used across an await
--> $DIR/async-is-unwindsafe.rs:26:18
--> $DIR/async-is-unwindsafe.rs:25:18
|
LL | let cx_ref = &mut cx;
| ------ has type `&mut Context<'_>` which does not implement `UnwindSafe`
@ -30,38 +31,6 @@ note: required by a bound in `is_unwindsafe`
LL | fn is_unwindsafe(_: impl std::panic::UnwindSafe) {}
| ^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_unwindsafe`
error[E0277]: the type `&mut (dyn Any + 'static)` may not be safely transferred across an unwind boundary
--> $DIR/async-is-unwindsafe.rs:12:5
|
LL | is_unwindsafe(async {
| _____^_____________-
| |_____|
| ||
LL | ||
LL | ||
LL | || use std::ptr::null;
... ||
LL | || drop(cx_ref);
LL | || });
| ||_____-^ `&mut (dyn Any + 'static)` may not be safely transferred across an unwind boundary
| |_____|
| within this `{async block@$DIR/async-is-unwindsafe.rs:12:19: 30:6}`
|
= help: within `{async block@$DIR/async-is-unwindsafe.rs:12:19: 30:6}`, the trait `UnwindSafe` is not implemented for `&mut (dyn Any + 'static)`, which is required by `{async block@$DIR/async-is-unwindsafe.rs:12:19: 30:6}: UnwindSafe`
note: future does not implement `UnwindSafe` as this value is used across an await
--> $DIR/async-is-unwindsafe.rs:26:18
|
LL | let mut cx = Context::from_waker(&waker);
| ------ has type `Context<'_>` which does not implement `UnwindSafe`
...
LL | async {}.await; // this needs an inner await point
| ^^^^^ await occurs here, with `mut cx` maybe used later
note: required by a bound in `is_unwindsafe`
--> $DIR/async-is-unwindsafe.rs:3:26
|
LL | fn is_unwindsafe(_: impl std::panic::UnwindSafe) {}
| ^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_unwindsafe`
error: aborting due to 2 previous errors
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0277`.

14
tests/ui/async-await/context-is-sorta-unwindsafe.rs Normal file
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@ -0,0 +1,14 @@
//@ run-pass
// Tests against a regression surfaced by crater in https://github.com/rust-lang/rust/issues/125193
// Unwind Safety is not a very coherent concept, but we'd prefer no regressions until we kibosh it
// and this is an unstable feature anyways sooo...
use std::panic::UnwindSafe;
use std::task::Context;
fn unwind_safe<T: UnwindSafe>() {}
fn main() {
unwind_safe::<Context<'_>>(); // test UnwindSafe
unwind_safe::<&Context<'_>>(); // test RefUnwindSafe
}