[ICE]: SIGSEGV on nightly (macOS)

[kayabaNerve]

  rustup +$NIGHTLY_VERSION component add rust-src
  
  if [ "$RUNNER_OS" = "Linux" ]; then
    export CFLAGS=-I/usr/include
  elif [ "$RUNNER_OS" = "Windows" ]; then
    export PATH="$PATH:/C/msys64/clang64/bin"
  fi
  
  cargo +$NIGHTLY_VERSION build --target riscv32imac-unknown-none-elf -Z build-std=core -p serai-no-std-tests
  cargo +$NIGHTLY_VERSION build --target riscv32imac-unknown-none-elf -Z build-std=core,alloc -p serai-no-std-tests --features "alloc"
  shell: /bin/bash --noprofile --norc -e -o pipefail {0}
  env:
    DYLD_LIBRARY_PATH: /opt/homebrew/opt/llvm/lib:
    DOCKER_HOST: unix:///Users/runner/.lima/docker-actions-toolkit/docker.sock
    GITHUB_CI: true
    RUSTFLAGS:  --cfg github_ci
    RUST_BACKTRACE: 1
    NIGHTLY_VERSION: nightly-2026-07-23
info: syncing channel updates for nightly-2026-07-23-aarch64-apple-darwin
info: latest update on 2026-07-23 for version 1.99.0-nightly (6f72b5dd5 2026-07-22)
info: downloading 6 components
info: downloading component rust-src
error: failed to run `rustc` to learn about target-specific information

Caused by:
  process didn't exit successfully: `/Users/runner/.rustup/toolchains/nightly-2026-07-23-aarch64-apple-darwin/bin/rustc - --crate-name ___ --print=file-names --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro --print=sysroot --print=split-debuginfo --print=crate-name --print=cfg -Wwarnings` (signal: 11, SIGSEGV: invalid memory reference)
  --- stderr
  error: rustc interrupted by SIGSEGV, printing backtrace

  0   librustc_driver-0adc2d977ed6a50d.dy 0x000000010ac5b42c _RNvNtCs6JBDw4KTACC_17rustc_driver_impl14signal_handler17print_stack_trace + 140
  1   libsystem_platform.dylib            0x000000018fc797a4 _sigtramp + 56
  2   librustc_driver-0adc2d977ed6a50d.dy 0x000000010b6afdf4 _RNvCs1YrFTmDuiGk_10rustc_llvm28initialize_available_targets + 112
  3   librustc_driver-0adc2d977ed6a50d.dy 0x000000010a87f4f8 _RNCINvMs0_NtNtCshrkeXHZkvHl_3std4sync4onceNtB8_4Once9call_onceNCNvNtCs2fgtGhgLXJl_18rustc_codegen_llvm9llvm_util4init0E0B14_ + 1080
  4   librustc_driver-0adc2d977ed6a50d.dy 0x000000010d00ec24 _RNvMNtNtNtNtCshrkeXHZkvHl_3std3sys4sync4once5queueNtB2_4Once4call + 256
  5   librustc_driver-0adc2d977ed6a50d.dy 0x000000010a93e340 _RNvXs3_Cs2fgtGhgLXJl_18rustc_codegen_llvmNtB5_18LlvmCodegenBackendNtNtNtCsg25EVR5ydDo_17rustc_codegen_ssa6traits7backend14CodegenBackend4init + 636
  6   librustc_driver-0adc2d977ed6a50d.dy 0x000000010ac44f7c _RNCINvNtCs4KMZOCqkQB3_15rustc_interface9interface12run_compileruNCNvCs6JBDw4KTACC_17rustc_driver_impl12run_compiler0Es0_0B14_ + 864
  7   librustc_driver-0adc2d977ed6a50d.dy 0x000000010ac3c094 _RINvNtNtCshrkeXHZkvHl_3std3sys9backtrace28___rust_begin_short_backtraceNCNCINvNtCs4KMZOCqkQB3_15rustc_interface4util26run_in_thread_with_globalsNCINvB1e_31run_in_thread_pool_with_globalsNCINvNtB1g_9interface12run_compileruNCNvCs6JBDw4KTACC_17rustc_driver_impl12run_compiler0Es0_0uE0uE00uEB3C_ + 304
  8   librustc_driver-0adc2d977ed6a50d.dy 0x000000010ac4a91c _RNSNvYNCINvNtNtCshrkeXHZkvHl_3std6thread9lifecycle15spawn_uncheckedNCNCINvNtCs4KMZOCqkQB3_15rustc_interface4util26run_in_thread_with_globalsNCINvB1a_31run_in_thread_pool_with_globalsNCINvNtB1c_9interface12run_compileruNCNvCs6JBDw4KTACC_17rustc_driver_impl12run_compiler0Es0_0uE0uE00uEs_0INtNtNtCsmpf2o5WY3k_4core3ops8function6FnOnceuE9call_once6vtableB3y_ + 188
  9   librustc_driver-0adc2d977ed6a50d.dy 0x000000010cda5b74 _RNvNvMs0_NtNtNtCshrkeXHZkvHl_3std3sys6thread4unixNtB7_6Thread3new12thread_start + 384
  10  libsystem_pthread.dylib             0x000000018fc6fc58 _pthread_start + 136
  11  libsystem_pthread.dylib             0x000000018fc6ac1c thread_start + 8

  note: we would appreciate a report at https://github.com/rust-lang/rust
  help: you can increase rustc's stack size by setting RUST_MIN_STACK=16777216

This was in a GitHub CI, which can be seen here: https://github.com/serai-dex/serai/actions/runs/30325946574/job/90171313909

I'm currently trying to minimize/bisect it but I'm unsure how successful that will be.

This is after removing the brew-installed rustc and installing rust via rustup (as officially documented/suggested) instead. It seems to be an immediate failure, upon any invocation, given how "error: failed to run rustc to learn about target-specific information".

[kayabaNerve]

https://github.com/serai-dex/serai/blob/814105e00ce2982386df9c3ec7f0acccb820ae66/.github/workflows/lint.yml should be a sufficiently minimal reproduction. I believe the issue is the brew-installed libraries in the DYLD_LIBRARY_PATH, which are either unnecessarily loaded or loaded with priority over the existing libraries (as simply not installing it causes this to work, and DYLD_LIBRARY_PATH is otherwise empty).

I completely understand this as an LLVM version conflict/misconfigured environment and am fine closing accordingly. I leave it open just in case there is some reason this shouldn't so fail which someone wants to look into.

[ZuseZ4]

Not a solution, just a note on why this is more likely on Apple:
Part of the reason is that LLVM defaulted to building an unversioned LLVM lib on MacOS, while using a versioned one on Linux.
There wasn't much of a reason for it, so with the latest release (LLVM23), the default will change. It's in fact the second comment in our LLVM 23 update PR: #158734

That doesn't mean you won't encounter it anymore in the future, but at least it should become less common.

[RalfJung]

There's not much we can do about users replacing the libraries we ship with incompatible ones, so I don't think this issue is actionable.