[bjorn3]

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. (Rename symbols rather than add symbol aliases for EIIs when possible #159843)
• #[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]

cc @jdonszelmann

[bjorn3]

There are probably better pages to link to.

View changes since the review

[rust-log-analyzer]

The job test-aarch64-gnu-llvm-22-2 failed! Check out the build log: (web) (plain enhanced) (plain)

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

[AOT] mini_core_hello_world
error: requires `panic_null_reference_constructed` lang_item
##[error]   --> example/mini_core_hello_world.rs:362:24
    |
362 |     let _a = (unsafe { &*fp })[0];
    |                        ^^^^

error: aborting due to 1 previous error

"/checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif/dist/rustc-clif" "-Zannotate-moves" "-Zrandomize-layout" "-Zunstable-options" "--check-cfg=cfg(bootstrap)" "-Zmacro-backtrace" "-Csplit-debuginfo=off" "-Clink-arg=-L/usr/lib/llvm-22/lib" "-Cllvm-args=-import-instr-limit=10" "-Clink-args=-Wl,-z,origin" "-Clink-args=-Wl,-rpath,$ORIGIN/../lib" "-Alinker-messages" "-L" "crate=/checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif/build/example" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif/build/example" "-Cdebuginfo=2" "--target" "aarch64-unknown-linux-gnu" "-Cpanic=abort" "--check-cfg=cfg(jit)" "--check-cfg=cfg(target_has_reliable_f128)" "--edition=2024" "-Zforce-unstable-if-unmarked" "example/mini_core_hello_world.rs" exited with status ExitStatus(unix_wait_status(256, "exit status: 1"))
Command `/checkout/obj/build/aarch64-unknown-linux-gnu/stage0/bin/cargo run --target aarch64-unknown-linux-gnu -Zbinary-dep-depinfo -j 4 -Zroot-dir=/checkout -Zembed-metadata=no --locked --color=always --profile=release --manifest-path /checkout/compiler/rustc_codegen_cranelift/build_system/Cargo.toml -- test --download-dir /checkout/obj/build/cg_clif_download --out-dir /checkout/obj/build/aarch64-unknown-linux-gnu/stage2-codegen/cg_clif --no-unstable-features --use-backend cranelift --sysroot llvm --skip-test testsuite.extended_sysroot [workdir=/checkout/compiler/rustc_codegen_cranelift]` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/test.rs:4612:25
Executed at: src/bootstrap/src/core/build_steps/test.rs:4656:26

Command has failed. Rerun with -v to see more details.
Bootstrap failed while executing `--stage 2 test --skip tidy --skip tests --skip library --skip tidyselftest`
Currently active steps:
test::CodegenCranelift { compilers: RustcPrivateCompilers { build_compiler: Compiler { stage: 1, host: aarch64-unknown-linux-gnu, forced_compiler: false }, target_compiler: Compiler { stage: 2, host: aarch64-unknown-linux-gnu, forced_compiler: false } }, target: aarch64-unknown-linux-gnu } at src/bootstrap/src/core/build_steps/test.rs:4598
Build completed unsuccessfully in 0:24:13
  local time: Fri Nov  6 16:35:27 UTC 2026

[rust-bors]

☔ The latest upstream changes (presumably #165579) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.