Incorrect behavior on Windows with dylibs and ThinLTO

[janhohenheim]

edit by @Noratrieb: MCVE: https://github.com/bash/rust-dylib-crash

I tried this code:
Clone https://github.com/TheBevyFlock/bevy_quickstart and run cargo run --release on Windows

I expected to see this happen: Literally anything else than the standard library hitting unreachable code.

Instead, this happened: We hit this line of unreachable code: https://github.com/rust-lang/rust/blob/22a5267c83a3e17f2b763279eb24bb632c45dc6b/library/std/src/sys/sync/once/futex.rs

Meta

rustc --version --verbose:

rustc 1.81.0-nightly (5affbb171 2024-07-18)
binary: rustc
commit-hash: 5affbb17153bc69a9d5d8d2faa4e399a014a211e
commit-date: 2024-07-18
host: x86_64-pc-windows-msvc
release: 1.81.0-nightly
LLVM version: 18.1.7

Backtrace

thread 'main' panicked at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e\library\std\src\sync\once.rs:217:20:
internal error: entered unreachable code: state is never set to invalid values
stack backtrace:
   0:     0x7ffae5f03e3d - std::backtrace_rs::backtrace::dbghelp64::trace
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\..\..\backtrace\src\backtrace\dbghelp64.rs:91
   1:     0x7ffae5f03e3d - std::backtrace_rs::backtrace::trace_unsynchronized
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\..\..\backtrace\src\backtrace\mod.rs:66
   2:     0x7ffae5f03e3d - std::sys::backtrace::_print_fmt
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\sys\backtrace.rs:65
   3:     0x7ffae5f03e3d - std::sys::backtrace::impl$0::print::impl$0::fmt
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\sys\backtrace.rs:40
   4:     0x7ffae5f34639 - core::fmt::rt::Argument::fmt
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\core\src\fmt\rt.rs:173
   5:     0x7ffae5f34639 - core::fmt::write
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\core\src\fmt\mod.rs:1182
   6:     0x7ffae5efa941 - std::io::Write::write_fmt<std::sys::pal::windows::stdio::Stderr>
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\io\mod.rs:1827
   7:     0x7ffae5f06ed7 - std::panicking::default_hook::closure$1
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\panicking.rs:269
   8:     0x7ffae5f06ac9 - std::panicking::default_hook
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\panicking.rs:296
   9:     0x7ffae5f076e2 - std::panicking::rust_panic_with_hook
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\panicking.rs:800
  10:     0x7ffae5f074ef - std::panicking::begin_panic_handler::closure$0
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\panicking.rs:667
  11:     0x7ffae5f047af - std::sys::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\sys\backtrace.rs:168
  12:     0x7ffae5f07106 - std::panicking::begin_panic_handler
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\panicking.rs:665
  13:     0x7ffae5f5d6b4 - core::panicking::panic_fmt
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\core\src\panicking.rs:74
  14:     0x7ff7dfc60e01 - main
  15:     0x7ff7dfc5e391 - main
  16:     0x7ff7dfc5cc95 - main
  17:     0x7ffade9fe3e2 - bevy_app::app::App::add_boxed_plugin::he4742dca059e0ec1
  18:     0x7ff7dfc42aff - main
  19:     0x7ff7dfc4104f - main
  20:     0x7ff7dfc4103e - main
  21:     0x7ffae5eeb969 - std::rt::lang_start_internal::closure$2
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\rt.rs:141
  22:     0x7ffae5eeb969 - std::panicking::try::do_call
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\panicking.rs:557
  23:     0x7ffae5eeb969 - std::panicking::try
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\panicking.rs:521
  24:     0x7ffae5eeb969 - std::panic::catch_unwind
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\panic.rs:350
  25:     0x7ffae5eeb969 - std::rt::lang_start_internal
                               at /rustc/5affbb17153bc69a9d5d8d2faa4e399a014a211e/library\std\src\rt.rs:141
  26:     0x7ff7dfc42cec - main
  27:     0x7ff7dfcd5ba0 - invoke_main
                               at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:78
  28:     0x7ff7dfcd5ba0 - __scrt_common_main_seh
                               at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288
  29:     0x7ffc426a257d - BaseThreadInitThunk
  30:     0x7ffc4366af28 - RtlUserThreadStart
error: process didn't exit successfully: `target\release\bevy_quickstart.exe` (exit code: 101)

[workingjubilee]

@janhohenheim Can you bisect this to a specific commit?

https://github.com/rust-lang/cargo-bisect-rustc

[workingjubilee]

Also, can you specify your Windows version? Just in case.

[janhohenheim]

@workingjubilee sure, will do later. First, I'm trying to narrow the example a bit down.

[tgross35]

For future reference, permalink at that version https://github.com/rust-lang/rust/blob/22a5267c83a3e17f2b763279eb24bb632c45dc6b/library/std/src/sys/sync/once/futex.rs

You should try the nightly too, @ChrisDenton recently did some changes there that may have happened to fix things

[janhohenheim]

@tgross35 thanks for the hint, updated the description :)
Nightly is hitting the same thing

[janhohenheim]

Alright, added my Windows system information and linked to a smaller example. Will run cargo-bisect now.

[tgross35]

For your bevy_dylib_crash repo, I hit what seems to be an intentional panic somewhere else, not sure if this means it's getting past the point where your unreachable!() would come up or stopping before it

    Finished `release` profile [optimized] target(s) in 0.32s
     Running `target\release\bevy_quickstart.exe`
thread 'main' panicked at C:\Users\tmgross\.cargo\registry\src\index.crates.io-6f17d22bba15001f\bevy_asset-0.14.0\src\io\source.rs:503:21:
Failed to create file watcher from path "assets", Error { kind: Generic("Input watch path is neither a file nor a directory."), paths: [] }
stack backtrace:
   0: std::panicking::begin_panic_handler
             at /rustc/bcf94dec5ba6838e435902120c0384c360126a26/library\std\src\panicking.rs:661
   1: core::panicking::panic_fmt
             at /rustc/bcf94dec5ba6838e435902120c0384c360126a26/library\core\src\panicking.rs:74
   2: bevy_asset::io::source::AssetSource::build
   3: bevy_asset::io::source::AssetSourceBuilder::build
   4: bevy_asset::io::source::AssetSourceBuilders::build_sources
   5: <bevy_asset::AssetPlugin as bevy_app::plugin::Plugin>::build
   6: bevy_app::app::App::add_boxed_plugin
   7: bevy_app::plugin_group::PluginGroupBuilder::finish
   8: main
   9: main
  10: main
  11: std::rt::lang_start_internal
             at /rustc/bcf94dec5ba6838e435902120c0384c360126a26/library\std\src\rt.rs:141
  12: main
  13: invoke_main
             at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:78
  14: __scrt_common_main_seh
             at D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288
  15: BaseThreadInitThunk
  16: RtlUserThreadStart
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
error: process didn't exit successfully: `target\release\bevy_quickstart.exe` (exit code: 101)

Just testing with the latest:

rustc 1.81.0-nightly (5affbb171 2024-07-18)
binary: rustc
commit-hash: 5affbb17153bc69a9d5d8d2faa4e399a014a211e
commit-date: 2024-07-18
host: x86_64-pc-windows-msvc
release: 1.81.0-nightly
LLVM version: 18.1.7

Windows 11 23H2 22631.3380

I have a slightly newer version of Windows but otherwise things look the same. Maybe try updating, but not until after the bisect completes :)

(also I textified your system info)

[janhohenheim]

@tgross35 oh sorry, I have "simplified" the example too much. That's my bad. Can you try with https://github.com/TheBevyFlock/bevy_quickstart ? Just running cargo run --release should produce the described result.

[tgross35]

Ah, yeah reproduced with the quickstart

[tgross35]

Are you running a bisect, or still trying to minimize? Unfortunate that this takes almost 3 minutes to compile