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Rollup merge of #118871 - tmiasko:coroutine-maybe-uninit-fields, r=compiler-errors

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Coroutine variant fields can be uninitialized

Wrap coroutine variant fields in MaybeUninit to indicate that they might be uninitialized. Otherwise an uninhabited field will make the entire variant uninhabited and introduce undefined behaviour.

The analogous issue in the prefix of coroutine layout was addressed by 6fae7f8071.
This commit is contained in:
Matthias Krüger 2023-12-13 18:03:33 +01:00 committed by GitHub
commit 1dd36119d0
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5 changed files with 58 additions and 4 deletions
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5
compiler/rustc_ty_utils/src/layout.rs
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@ -831,7 +831,10 @@ fn coroutine_layout<'tcx>(
Assigned(_) => bug!("assignment does not match variant"),
Ineligible(_) => false,
})
.map(|local| subst_field(info.field_tys[*local].ty));
.map(|local| {
let field_ty = subst_field(info.field_tys[*local].ty);
Ty::new_maybe_uninit(tcx, field_ty)
});
let mut variant = univariant_uninterned(
cx,

6
tests/ui/async-await/future-sizes/async-awaiting-fut.stdout
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@ -52,10 +52,16 @@ print-type-size variant `Panicked`: 1024 bytes
print-type-size upvar `.arg`: 1024 bytes
print-type-size type: `std::mem::ManuallyDrop<bool>`: 1 bytes, alignment: 1 bytes
print-type-size field `.value`: 1 bytes
print-type-size type: `std::mem::ManuallyDrop<{async fn body@$DIR/async-awaiting-fut.rs:6:17: 6:19}>`: 1 bytes, alignment: 1 bytes
print-type-size field `.value`: 1 bytes
print-type-size type: `std::mem::MaybeUninit<bool>`: 1 bytes, alignment: 1 bytes
print-type-size variant `MaybeUninit`: 1 bytes
print-type-size field `.uninit`: 0 bytes
print-type-size field `.value`: 1 bytes
print-type-size type: `std::mem::MaybeUninit<{async fn body@$DIR/async-awaiting-fut.rs:6:17: 6:19}>`: 1 bytes, alignment: 1 bytes
print-type-size variant `MaybeUninit`: 1 bytes
print-type-size field `.uninit`: 0 bytes
print-type-size field `.value`: 1 bytes
print-type-size type: `std::task::Poll<()>`: 1 bytes, alignment: 1 bytes
print-type-size discriminant: 1 bytes
print-type-size variant `Ready`: 0 bytes

8
tests/ui/async-await/in-trait/indirect-recursion-issue-112047.stderr
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@ -1,7 +1,9 @@
error[E0391]: cycle detected when computing layout of `{async fn body@$DIR/indirect-recursion-issue-112047.rs:33:27: 35:6}`
error[E0391]: cycle detected when computing layout of `core::mem::maybe_uninit::MaybeUninit<{async fn body@$DIR/indirect-recursion-issue-112047.rs:33:27: 35:6}>`
|
= note: ...which requires computing layout of `<<A as First>::Second as Second>::{opaque#0}`...
= note: ...which again requires computing layout of `{async fn body@$DIR/indirect-recursion-issue-112047.rs:33:27: 35:6}`, completing the cycle
= note: ...which requires computing layout of `core::mem::manually_drop::ManuallyDrop<{async fn body@$DIR/indirect-recursion-issue-112047.rs:33:27: 35:6}>`...
= note: ...which requires computing layout of `{async fn body@$DIR/indirect-recursion-issue-112047.rs:33:27: 35:6}`...
= note: ...which requires computing layout of `core::mem::maybe_uninit::MaybeUninit<<<A as First>::Second as Second>::{opaque#0}>`...
= note: ...which again requires computing layout of `core::mem::maybe_uninit::MaybeUninit<{async fn body@$DIR/indirect-recursion-issue-112047.rs:33:27: 35:6}>`, completing the cycle
= note: cycle used when computing layout of `{async block@$DIR/indirect-recursion-issue-112047.rs:6:13: 8:6}`
= note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information

37
tests/ui/coroutine/uninhabited-field.rs Normal file
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@ -0,0 +1,37 @@
// Test that uninhabited saved local doesn't make the entire variant uninhabited.
// run-pass
#![allow(unused)]
#![feature(assert_matches)]
#![feature(coroutine_trait)]
#![feature(coroutines)]
#![feature(never_type)]
use std::assert_matches::assert_matches;
use std::ops::Coroutine;
use std::ops::CoroutineState;
use std::pin::Pin;
fn conjure<T>() -> T { loop {} }
fn run<T>(x: bool, y: bool) {
let mut c = || {
if x {
let a : T;
if y {
a = conjure::<T>();
}
yield ();
} else {
let a : T;
if y {
a = conjure::<T>();
}
yield ();
}
};
assert_matches!(Pin::new(&mut c).resume(()), CoroutineState::Yielded(()));
assert_matches!(Pin::new(&mut c).resume(()), CoroutineState::Complete(()));
}
fn main() {
run::<!>(false, false);
}

6
tests/ui/print_type_sizes/coroutine_discr_placement.stdout
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@ -9,3 +9,9 @@ print-type-size padding: 3 bytes
print-type-size local `.z`: 4 bytes, alignment: 4 bytes
print-type-size variant `Returned`: 0 bytes
print-type-size variant `Panicked`: 0 bytes
print-type-size type: `std::mem::ManuallyDrop<i32>`: 4 bytes, alignment: 4 bytes
print-type-size field `.value`: 4 bytes
print-type-size type: `std::mem::MaybeUninit<i32>`: 4 bytes, alignment: 4 bytes
print-type-size variant `MaybeUninit`: 4 bytes
print-type-size field `.uninit`: 0 bytes
print-type-size field `.value`: 4 bytes