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Rollup merge of #124504 - gurry:123710-union-ICE, r=oli-obk

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Mark unions non-const-propagatable in `KnownPanicsLint` without calling layout

Fixes #123710

The ICE occurs during the layout calculation of the union `InvalidTag` in #123710 because the following assert fails:5fe8b697e7/compiler/rustc_abi/src/layout.rs (L289-L292)

The layout calculation is invoked by `KnownPanicsLint` when it is trying to figure out which locals it can const prop. Since `KnownPanicsLint` is never actually going to const props unions thanks to PR https://github.com/rust-lang/rust/pull/121628 there's no point calling layout to check if it can. So in this fix I skip the call to layout and just mark the local non-const propagatable if it is a union.
This commit is contained in:
许杰友 Jieyou Xu (Joe) 2024-04-29 18:03:24 +01:00 • committed by GitHub
commit 43265f5721
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4 changed files with 64 additions and 24 deletions
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20
compiler/rustc_mir_transform/src/known_panics_lint.rs
View file

@ -896,13 +896,19 @@ impl CanConstProp {
};
for (local, val) in cpv.can_const_prop.iter_enumerated_mut() {
let ty = body.local_decls[local].ty;
match tcx.layout_of(param_env.and(ty)) {
Ok(layout) if layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) => {}
// Either the layout fails to compute, then we can't use this local anyway
// or the local is too large, then we don't want to.
_ => {
*val = ConstPropMode::NoPropagation;
continue;
if ty.is_union() {
// Do not const prop unions as they can
// ICE during layout calc
*val = ConstPropMode::NoPropagation;
} else {
match tcx.layout_of(param_env.and(ty)) {
Ok(layout) if layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) => {}
// Either the layout fails to compute, then we can't use this local anyway
// or the local is too large, then we don't want to.
_ => {
*val = ConstPropMode::NoPropagation;
continue;
}
}
}
}

17
tests/crashes/123710.rs
View file

@ -1,17 +0,0 @@
//@ known-bug: #123710
#[repr(packed)]
#[repr(u32)]
enum E {
A,
B,
C,
}
fn main() {
union InvalidTag {
int: u32,
e: E,
}
let _invalid_tag = InvalidTag { int: 4 };
}

22
tests/ui/lint/ice-const-prop-unions-known-panics-lint-123710.rs Normal file
View file

@ -0,0 +1,22 @@
// Regression test for issue 123710.
// Tests that the we do not ICE in KnownPanicsLint
// when a union contains an enum with an repr(packed),
// which is a repr not supported for enums
#[repr(packed)]
//~^ ERROR attribute should be applied to a struct or union
#[repr(u32)]
enum E {
A,
B,
C,
}
fn main() {
union InvalidTag {
int: u32,
e: E,
//~^ ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
}
let _invalid_tag = InvalidTag { int: 4 };
}

29
tests/ui/lint/ice-const-prop-unions-known-panics-lint-123710.stderr Normal file
View file

@ -0,0 +1,29 @@
error[E0517]: attribute should be applied to a struct or union
--> $DIR/ice-const-prop-unions-known-panics-lint-123710.rs:6:8
|
LL | #[repr(packed)]
| ^^^^^^
...
LL | / enum E {
LL | | A,
LL | | B,
LL | | C,
LL | | }
| |_- not a struct or union
error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
--> $DIR/ice-const-prop-unions-known-panics-lint-123710.rs:18:9
|
LL | e: E,
| ^^^^
|
= note: union fields must not have drop side-effects, which is currently enforced via either `Copy` or `ManuallyDrop<...>`
help: wrap the field type in `ManuallyDrop<...>`
|
LL | e: std::mem::ManuallyDrop<E>,
| +++++++++++++++++++++++ +
error: aborting due to 2 previous errors
Some errors have detailed explanations: E0517, E0740.
For more information about an error, try `rustc --explain E0517`.