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Use EII for #[panic_handler]#159016

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bjorn3:eii_panic_handler
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Use EII for #[panic_handler]#159016
bjorn3 wants to merge 5 commits into
rust-lang:mainfrom
bjorn3:eii_panic_handler

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@bjorn3

@bjorn3 bjorn3 commented Jul 9, 2026

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While we can't yet use EIIs for things like the global allocator due to missing platform support, we can safely use it for #[panic_handler] as that doesn't require any object file format features. Just matching symbol names.

This gets rid of one of the two remaining weak lang items.

TODO

  • Support EII without defaults in cg_clif and cg_gcc. This can be done without requiring any (weak) symbol alias support.
  • #[no_mangle] is not denied on EII definitions #159015 to avoid accepting some invalid code.
  • Possibly improve the error for applying #[target_feature] on the panic handler.

bjorn3 added 4 commits July 9, 2026 15:06
@bjorn3
Make #[panic_handler] mandatory in all linked artifacts
65fc732 
The only way it was possible to skip needing to declare #[panic_handler]
is using #![no_core], which is unstable anyway. Always requiring
\#[panic_handler] makes things more consistent and avoids having to
special case several MIR optimizations for the absence of #[panic_handler].
@bjorn3
[WIP] Replace #[lang = "panic_impl"] with #[eii]
b666561
@bjorn3
Fix tests
77d9276
@bjorn3
[WIP] Possibly fix clippy
a29bc28
@rustbot rustbot added A-attributes Area: Attributes (`#[…]`, `#![…]`) A-test-infra-minicore Area: `minicore` test auxiliary and `//@ add-core-stubs` S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-clippy Relevant to the Clippy team. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jul 9, 2026
@bjorn3

bjorn3 commented Jul 9, 2026

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cc @jdonszelmann

@mejrs mejrs mentioned this pull request Jul 9, 2026
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rust-log-analyzer commented Jul 9, 2026

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The job aarch64-gnu-llvm-21-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

@rust-bors

rust-bors Bot commented Jul 11, 2026

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☔ The latest upstream changes (presumably #159113) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.

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A-attributes Area: Attributes (`#[…]`, `#![…]`) A-test-infra-minicore Area: `minicore` test auxiliary and `//@ add-core-stubs` S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-clippy Relevant to the Clippy team. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue.

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