mirror of https://github.com/rust-lang/rust.git
Rollup merge of #125392 - workingjubilee:unwind-a-problem-in-context, r=Amanieu
Wrap Context.ext in AssertUnwindSafe Fixes https://github.com/rust-lang/rust/issues/125193 Alternative to https://github.com/rust-lang/rust/pull/125377 Relevant to https://github.com/rust-lang/rust/issues/123392 I believe this approach is justifiable due to the fact that this function is unstable API and we have been considering trying to dispose of the notion of "unwind safety". Making a more long-term decision should be considered carefully as part of stabilizing `fn ext`, if ever. r? `@Amanieu`
This commit is contained in:
Matthias Krüger
GitHub
commit
5126d4b87b
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@ -5,6 +5,7 @@ use crate::mem::transmute;
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use crate::any::Any;
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use crate::fmt;
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use crate::marker::PhantomData;
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use crate::panic::AssertUnwindSafe;
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use crate::ptr;
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/// A `RawWaker` allows the implementor of a task executor to create a [`Waker`]
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@ -236,7 +237,7 @@ enum ExtData<'a> {
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pub struct Context<'a> {
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waker: &'a Waker,
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local_waker: &'a LocalWaker,
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ext: ExtData<'a>,
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ext: AssertUnwindSafe<ExtData<'a>>,
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// Ensure we future-proof against variance changes by forcing
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// the lifetime to be invariant (argument-position lifetimes
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// are contravariant while return-position lifetimes are
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@ -279,7 +280,9 @@ impl<'a> Context<'a> {
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#[unstable(feature = "context_ext", issue = "123392")]
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#[rustc_const_unstable(feature = "const_waker", issue = "102012")]
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pub const fn ext(&mut self) -> &mut dyn Any {
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match &mut self.ext {
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// FIXME: this field makes Context extra-weird about unwind safety
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// can we justify AssertUnwindSafe if we stabilize this? do we care?
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match &mut *self.ext {
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ExtData::Some(data) => *data,
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ExtData::None(unit) => unit,
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}
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@ -353,7 +356,7 @@ impl<'a> ContextBuilder<'a> {
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#[rustc_const_unstable(feature = "const_waker", issue = "102012")]
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#[unstable(feature = "context_ext", issue = "123392")]
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pub const fn from(cx: &'a mut Context<'_>) -> Self {
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let ext = match &mut cx.ext {
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let ext = match &mut *cx.ext {
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ExtData::Some(ext) => ExtData::Some(*ext),
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ExtData::None(()) => ExtData::None(()),
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};
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@ -396,7 +399,7 @@ impl<'a> ContextBuilder<'a> {
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#[rustc_const_unstable(feature = "const_waker", issue = "102012")]
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pub const fn build(self) -> Context<'a> {
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let ContextBuilder { waker, local_waker, ext, _marker, _marker2 } = self;
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Context { waker, local_waker, ext, _marker, _marker2 }
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Context { waker, local_waker, ext: AssertUnwindSafe(ext), _marker, _marker2 }
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}
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}
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@ -11,7 +11,6 @@ fn main() {
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is_unwindsafe(async {
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//~^ ERROR the type `&mut Context<'_>` may not be safely transferred across an unwind boundary
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//~| ERROR the type `&mut (dyn Any + 'static)` may not be safely transferred across an unwind boundary
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use std::ptr::null;
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use std::task::{Context, RawWaker, RawWakerVTable, Waker};
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let waker = unsafe {
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@ -6,18 +6,19 @@ LL | is_unwindsafe(async {
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| |_____|
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LL | ||
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LL | ||
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LL | || use std::ptr::null;
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LL | || use std::task::{Context, RawWaker, RawWakerVTable, Waker};
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... ||
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LL | || drop(cx_ref);
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LL | || });
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| ||_____-^ `&mut Context<'_>` may not be safely transferred across an unwind boundary
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| |_____|
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| within this `{async block@$DIR/async-is-unwindsafe.rs:12:19: 30:6}`
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| within this `{async block@$DIR/async-is-unwindsafe.rs:12:19: 29:6}`
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= 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`
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= 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`
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= note: `UnwindSafe` is implemented for `&Context<'_>`, but not for `&mut Context<'_>`
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note: future does not implement `UnwindSafe` as this value is used across an await
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--> $DIR/async-is-unwindsafe.rs:26:18
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--> $DIR/async-is-unwindsafe.rs:25:18
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LL | let cx_ref = &mut cx;
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| ------ has type `&mut Context<'_>` which does not implement `UnwindSafe`
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@ -30,38 +31,6 @@ note: required by a bound in `is_unwindsafe`
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LL | fn is_unwindsafe(_: impl std::panic::UnwindSafe) {}
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| ^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_unwindsafe`
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error[E0277]: the type `&mut (dyn Any + 'static)` may not be safely transferred across an unwind boundary
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--> $DIR/async-is-unwindsafe.rs:12:5
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LL | is_unwindsafe(async {
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| _____^_____________-
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| |_____|
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| ||
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LL | ||
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LL | ||
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LL | || use std::ptr::null;
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... ||
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LL | || drop(cx_ref);
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LL | || });
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| ||_____-^ `&mut (dyn Any + 'static)` may not be safely transferred across an unwind boundary
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| |_____|
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| within this `{async block@$DIR/async-is-unwindsafe.rs:12:19: 30:6}`
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= 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`
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note: future does not implement `UnwindSafe` as this value is used across an await
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--> $DIR/async-is-unwindsafe.rs:26:18
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LL | let mut cx = Context::from_waker(&waker);
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| ------ has type `Context<'_>` which does not implement `UnwindSafe`
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...
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LL | async {}.await; // this needs an inner await point
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| ^^^^^ await occurs here, with `mut cx` maybe used later
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note: required by a bound in `is_unwindsafe`
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--> $DIR/async-is-unwindsafe.rs:3:26
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LL | fn is_unwindsafe(_: impl std::panic::UnwindSafe) {}
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| ^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `is_unwindsafe`
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error: aborting due to 2 previous errors
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error: aborting due to 1 previous error
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For more information about this error, try `rustc --explain E0277`.
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@ -0,0 +1,14 @@
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//@ run-pass
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// Tests against a regression surfaced by crater in https://github.com/rust-lang/rust/issues/125193
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// Unwind Safety is not a very coherent concept, but we'd prefer no regressions until we kibosh it
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// and this is an unstable feature anyways sooo...
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use std::panic::UnwindSafe;
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use std::task::Context;
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fn unwind_safe<T: UnwindSafe>() {}
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fn main() {
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unwind_safe::<Context<'_>>(); // test UnwindSafe
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unwind_safe::<&Context<'_>>(); // test RefUnwindSafe
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}
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