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Mark the panic_no_unwind lang item as nounwind #93489

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Merged
merged 2 commits into from
Feb 7, 2022
Merged

Mark the panic_no_unwind lang item as nounwind #93489

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c4f2d21
Mark the panic_no_unwind lang item as nounwind
Amanieu Jan 29, 2022
f738669
Clarify safety of PanicInfo::can_unwind
Amanieu Jan 30, 2022
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7 changes: 7 additions & 0 deletions compiler/rustc_typeck/src/collect.rs
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Expand Up @@ -2778,6 +2778,13 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, id: DefId) -> CodegenFnAttrs {
}
}

// The panic_no_unwind function called by TerminatorKind::Abort will never
// unwind. If the panic handler that it invokes unwind then it will simply
// call the panic handler again.
if Some(id) == tcx.lang_items().panic_no_unwind() {
codegen_fn_attrs.flags |= CodegenFnAttrFlags::NEVER_UNWIND;
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Could we use #[rustc_allocator_nounwind] instead? There's nothing allocator-specific for that attribute even though it has allocator in its name.

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If we did this, I would suggest renaming the attribute.

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I agree that this should be an attribute (or possibly a extern "Rust-nounwind" ABI?). I've been away this past week and haven't had time to implement this yet, but it is on my TODO list.

}

let supported_target_features = tcx.supported_target_features(LOCAL_CRATE);

let mut inline_span = None;
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4 changes: 4 additions & 0 deletions library/core/src/panic/panic_info.rs
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Expand Up @@ -136,6 +136,10 @@ impl<'a> PanicInfo<'a> {
/// This is true for most kinds of panics with the exception of panics
/// caused by trying to unwind out of a `Drop` implementation or a function
/// whose ABI does not support unwinding.
///
/// It is safe for a panic handler to unwind even when this function returns
/// true, however this will simply cause the panic handler to be called
/// again.
#[must_use]
#[unstable(feature = "panic_can_unwind", issue = "92988")]
pub fn can_unwind(&self) -> bool {
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