SIGSEGV with beta/nightly compiler with i686-unknown-freebsd target

[Darksonn]

When running the Tokio test suite through CI using the beta/nightly compiler, the FreeBSD 32-bit build encounters a segmentation fault. After running CI with a few different configurations, I've found two different cases of the failure. The first segfault is in the compile_fail_full test. The path_read_write test also encounters a segfault.

running 1 test
error: test failed, to rerun pass `-p tests-build --test macros`

Caused by:
  process didn't exit successfully: `/tmp/cirrus-ci-build/target/i686-unknown-freebsd/debug/deps/macros-4f8b28e5ec17a589` (signal: 11, SIGSEGV: invalid memory reference)

Exit status: 101

Please see tokio-rs/tokio#6856 for more output from the CI runs. Both failures happen in tests that interact with the file system. There are other tests that pass and don't touch the file system (e.g. all unit tests in tokio/src/ pass). As Tokio has no special logic for using the file system and just calls std, and as the compile_fail_full test is not calling into any Tokio code at all, this looks an awful lot like a bug somewhere in std's filesystem handling code. But that is just a guess. I don't have access to a FreeBSD machine, so it is difficult for me to investigate further.

The 64-bit FreeBSD build does not encounter these failures. There also are no problems when using the latest stable compiler. Note that the 32-bit binaries in question are cross-compiled from and executed on a 64-bit FreeBSD host machine.

Failing toolchains:

rustc 1.82.0-beta.3 (4976ae480 2024-09-09)
binary: rustc
commit-hash: 4976ae480e2b29cc46f44e1b9914469cc384fcc9
commit-date: 2024-09-09
host: x86_64-unknown-freebsd
release: 1.82.0-beta.3
LLVM version: 19.1.0

rustc 1.83.0-nightly (da889684c 2024-09-20)
binary: rustc
commit-hash: da889684c80508036ff036db8c159ffdcf27648a
commit-date: 2024-09-20
host: x86_64-unknown-freebsd
release: 1.83.0-nightly
LLVM version: 19.1.0

Passing toolchains:

rustc 1.81.0 (eeb90cda1 2024-09-04)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: x86_64-unknown-freebsd
release: 1.81.0
LLVM version: 18.1.7

[Darksonn]

I can try to bisect it to a specific nightly next week. If it's useful, you all are welcome to use our CI to debug this - you can open a PR to Tokio to run our CI setup.

[lolbinarycat]

the compile_fail_full test is not calling into any Tokio code at all

it calls various tokio macros, doesn't it?? also, it doesn't seem to call anything in std besides std::time::Instant::now, so i'm not sure how this could be a path handling bug?

[workingjubilee]

@Darksonn Is this our compiler or is it the one from FreeBSD ports?

They modded the target.

[Darksonn]

I have bisected the issue. It succeeds on nightly-2024-08-20 and fails on nightly-2024-08-21.

@lolbinarycat The compile_fail_full test calls into the trybuild crate, which uses std::fs to probe which build tests exists.

@workingjubilee I got the compiler from rustup, so I assume it's your compiler. Our ci script runs the following commands:

pkg install -y bash
curl https://sh.rustup.rs -sSf --output rustup.sh
sh rustup.sh -y --profile minimal --default-toolchain $TOOLCHAIN
. $HOME/.cargo/env
rustup target add i686-unknown-freebsd
rustc --version --verbose
cargo test --all --all-features --target i686-unknown-freebsd

with $TOOLCHAIN normally set to stable, but under these tests I set it to beta or nightly-xxxx-xx-xx for testing other compilers. This is happening on a x86_64-unknown-freebsd host.

[workingjubilee]

Yep, that's our sigsegv, comrade!