From 3a21fb5cec07052cb664b6a051e233cd4776283a Mon Sep 17 00:00:00 2001 From: Jubilee Young Date: Tue, 21 May 2024 18:55:12 -0700 Subject: [PATCH] Wrap Context.ext in AssertUnwindSafe --- library/core/src/task/wake.rs | 11 +++-- tests/ui/async-await/async-is-unwindsafe.rs | 1 - .../ui/async-await/async-is-unwindsafe.stderr | 43 +++---------------- .../context-is-sorta-unwindsafe.rs | 14 ++++++ 4 files changed, 27 insertions(+), 42 deletions(-) create mode 100644 tests/ui/async-await/context-is-sorta-unwindsafe.rs diff --git a/library/core/src/task/wake.rs b/library/core/src/task/wake.rs index 7691721b91e21..3d21b09fa8a02 100644 --- a/library/core/src/task/wake.rs +++ b/library/core/src/task/wake.rs @@ -5,6 +5,7 @@ use crate::mem::transmute; 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>, // 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 @@ impl<'a> Context<'a> { #[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 @@ impl<'a> ContextBuilder<'a> { #[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 @@ impl<'a> ContextBuilder<'a> { #[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 } } } diff --git a/tests/ui/async-await/async-is-unwindsafe.rs b/tests/ui/async-await/async-is-unwindsafe.rs index d0202f72f0086..53009b6e7410f 100644 --- a/tests/ui/async-await/async-is-unwindsafe.rs +++ b/tests/ui/async-await/async-is-unwindsafe.rs @@ -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 { diff --git a/tests/ui/async-await/async-is-unwindsafe.stderr b/tests/ui/async-await/async-is-unwindsafe.stderr index 6bb06df9f39e9..5d87fc747682a 100644 --- a/tests/ui/async-await/async-is-unwindsafe.stderr +++ b/tests/ui/async-await/async-is-unwindsafe.stderr @@ -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`. diff --git a/tests/ui/async-await/context-is-sorta-unwindsafe.rs b/tests/ui/async-await/context-is-sorta-unwindsafe.rs new file mode 100644 index 0000000000000..278476ea2379c --- /dev/null +++ b/tests/ui/async-await/context-is-sorta-unwindsafe.rs @@ -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() {} + +fn main() { + unwind_safe::>(); // test UnwindSafe + unwind_safe::<&Context<'_>>(); // test RefUnwindSafe +}