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interpret: ensure that calls via no-unwind ABIs do not unwind - #161628

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RalfJung:no-unwind-abi-check
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interpret: ensure that calls via no-unwind ABIs do not unwind#161628
RalfJung wants to merge 1 commit into
rust-lang:mainfrom
RalfJung:no-unwind-abi-check

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@RalfJung RalfJung commented Aug 23, 2026 •
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According to our ABI docs, programs like this are okay:

extern "C-unwind" fn does_not_unwind_but_could() {}

fn main() {
    let f: extern "C-unwind" fn() = does_not_unwind_but_could;
    let f: extern "C" fn() = unsafe { std::mem::transmute(f) };
    f();
}

So let's add a test for that.

And also, let's adjust the checks in Miri's shims accordingly (see src/tools/miri/src/shims/sig.rs). We used to reject calls to functions that might unwind with a signature that does not allow unwinding, even if no unwinding occurred. I don't think we have an actual example of a potentially-unwinding shim with an ABI that has a compatible ABI that does not allow unwinding ("C-unwind" and "C"), so we can't add a test for this.

@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 23, 2026
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RalfJung force-pushed the no-unwind-abi-check branch from 21d1c2a to d1e3bca Compare August 24, 2026 06:23
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RalfJung marked this pull request as ready for review August 24, 2026 06:24
@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 24, 2026
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rustbot commented Aug 24, 2026

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Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

miri is developed in its own repository. If the Miri part of this change can be broken out, consider making this change to rust-lang/miri instead. However, if Miri needs adjusting for rustc changes, just ignore this message.

cc @rust-lang/miri

Some changes occurred to the CTFE machinery

cc @oli-obk, @lcnr

@rustbot rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Aug 24, 2026
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rustbot commented Aug 24, 2026

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r? @mati865

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@RalfJung
RalfJung force-pushed the no-unwind-abi-check branch from d1e3bca to 1c53cd0 Compare August 24, 2026 07:28
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rustbot commented Aug 24, 2026

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This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

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mati865 commented Aug 24, 2026

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Should be reviewed by somebody more knowledgeable in this area.
@rustbot reroll

@rustbot rustbot assigned jackh726 and unassigned mati865 Aug 24, 2026
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