rust-lang / rust-lang/rust

LTO coordinator panics by unwrapping Option::None

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C-bug I-ICE S-needs-repro T-compiler
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Rust
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Description

Code

Discovered this error while fuzzing for https://github.com/rust-lang/rust/issues/81280

I used cargo watch -- cargo build --profile incremental for building this binary crate, while touch-ing random files at random intervals to trigger rebuilds.

Fish script:

while true
    touch (find src | shuf -n1)
    sleep 0.(random 1 999)
end
Meta

rustc --version --verbose:

rustc 1.81.0 (eeb90cda1 2024-09-04)
binary: rustc
commit-hash: eeb90cda1969383f56a2637cbd3037bdf598841c
commit-date: 2024-09-04
host: x86_64-unknown-linux-gnu
release: 1.81.0
LLVM version: 18.1.7
Error output
thread 'coordinator' panicked at compiler/rustc_codegen_llvm/src/back/lto.rs:836:36:
called `Option::unwrap()` on a `None` value
Backtrace 

called `Option::unwrap()` on a `None` value
stack backtrace:
   0:     0x7f5bbd68a3e5 - std::backtrace_rs::backtrace::libunwind::trace::h649ab3318d3445c5
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:     0x7f5bbd68a3e5 - std::backtrace_rs::backtrace::trace_unsynchronized::hf4bb60c3387150c3
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f5bbd68a3e5 - std::sys::backtrace::_print_fmt::hd9186c800e44bd00
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/backtrace.rs:65:5
   3:     0x7f5bbd68a3e5 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h1b9dad2a88e955ff
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/backtrace.rs:40:26
   4:     0x7f5bbd6d9eeb - core::fmt::rt::Argument::fmt::h351a7824f737a6a0
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/fmt/rt.rs:173:76
   5:     0x7f5bbd6d9eeb - core::fmt::write::h4b5a1270214bc4a7
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/fmt/mod.rs:1182:21
   6:     0x7f5bbd67ef6f - std::io::Write::write_fmt::hd04af345a50c312d
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/io/mod.rs:1827:15
   7:     0x7f5bbd68cbd1 - std::sys::backtrace::BacktraceLock::print::h68d41b51481bce5c
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/backtrace.rs:43:9
   8:     0x7f5bbd68cbd1 - std::panicking::default_hook::{{closure}}::h96ab15e9936be7ed
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:269:22
   9:     0x7f5bbd68c8ac - std::panicking::default_hook::h3cacb9c27561ad33
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:296:9
  10:     0x7f5bb9c93420 - std[1f2242ed6435445e]::panicking::update_hook::<alloc[7b1462a1eb55c293]::boxed::Box<rustc_driver_impl[8683aa37472b7dde]::install_ice_hook::{closure#0}>>::{closure#0}
  11:     0x7f5bbd68d59f - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hce7569f4ca5d1b64
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/boxed.rs:2084:9
  12:     0x7f5bbd68d59f - std::panicking::rust_panic_with_hook::hfe205f6954b2c97b
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:808:13
  13:     0x7f5bbd68d193 - std::panicking::begin_panic_handler::{{closure}}::h6cb44b3a50f28c44
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:667:13
  14:     0x7f5bbd68a8a9 - std::sys::backtrace::__rust_end_short_backtrace::hf1c1f2a92799bb0e
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/backtrace.rs:168:18
  15:     0x7f5bbd68ce54 - rust_begin_unwind
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:665:5
  16:     0x7f5bbd6d64a3 - core::panicking::panic_fmt::h3d8fc78294164da7
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/panicking.rs:74:14
  17:     0x7f5bbd6d652c - core::panicking::panic::hec978767ec2d35ff
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/panicking.rs:148:5
  18:     0x7f5bbd6d6299 - core::option::unwrap_failed::hba6b08832f9ce30b
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/option.rs:2020:5
  19:     0x7f5bbbf72a6b - rustc_codegen_llvm[5ff2375b9bf6d639]::back::lto::thin_lto
  20:     0x7f5bbbf6d00b - <rustc_codegen_llvm[5ff2375b9bf6d639]::LlvmCodegenBackend as rustc_codegen_ssa[382a85cbfbe8c2f6]::traits::write::WriteBackendMethods>::run_thin_lto
  21:     0x7f5bbc1113ce - rustc_codegen_ssa[382a85cbfbe8c2f6]::back::write::start_executing_work::<rustc_codegen_llvm[5ff2375b9bf6d639]::LlvmCodegenBackend>::{closure#5}
  22:     0x7f5bbc10f876 - std[1f2242ed6435445e]::sys::backtrace::__rust_begin_short_backtrace::<<rustc_codegen_llvm[5ff2375b9bf6d639]::LlvmCodegenBackend as rustc_codegen_ssa[382a85cbfbe8c2f6]::traits::backend::ExtraBackendMethods>::spawn_named_thread<rustc_codegen_ssa[382a85cbfbe8c2f6]::back::write::start_executing_work<rustc_codegen_llvm[5ff2375b9bf6d639]::LlvmCodegenBackend>::{closure#5}, core[3cad2706d8bdcdc4]::result::Result<rustc_codegen_ssa[382a85cbfbe8c2f6]::back::write::CompiledModules, ()>>::{closure#0}, core[3cad2706d8bdcdc4]::result::Result<rustc_codegen_ssa[382a85cbfbe8c2f6]::back::write::CompiledModules, ()>>
  23:     0x7f5bbc10f6ad - <<std[1f2242ed6435445e]::thread::Builder>::spawn_unchecked_<<rustc_codegen_llvm[5ff2375b9bf6d639]::LlvmCodegenBackend as rustc_codegen_ssa[382a85cbfbe8c2f6]::traits::backend::ExtraBackendMethods>::spawn_named_thread<rustc_codegen_ssa[382a85cbfbe8c2f6]::back::write::start_executing_work<rustc_codegen_llvm[5ff2375b9bf6d639]::LlvmCodegenBackend>::{closure#5}, core[3cad2706d8bdcdc4]::result::Result<rustc_codegen_ssa[382a85cbfbe8c2f6]::back::write::CompiledModules, ()>>::{closure#0}, core[3cad2706d8bdcdc4]::result::Result<rustc_codegen_ssa[382a85cbfbe8c2f6]::back::write::CompiledModules, ()>>::{closure#1} as core[3cad2706d8bdcdc4]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  24:     0x7f5bbd6975fb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::ha1963004222e7822
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/boxed.rs:2070:9
  25:     0x7f5bbd6975fb - <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once::h1086ced1f7c494c2
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/boxed.rs:2070:9
  26:     0x7f5bbd6975fb - std::sys::pal::unix::thread::Thread::new::thread_start::ha8af9c992ef0b208
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/pal/unix/thread.rs:108:17
  27:     0x7f5bbd466897 - start_thread
  28:     0x7f5bbd4eda5c - __GI___clone3
  29:                0x0 - <unknown>

error: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.81.0 (eeb90cda1 2024-09-04) running on x86_64-unknown-linux-gnu

note: compiler flags: --crate-type bin -C opt-level=3 -C embed-bitcode=no -C incremental=[REDACTED] -C strip=debuginfo

note: some of the compiler flags provided by cargo are hidden

query stack during panic:
end of query stack
thread 'rustc' panicked at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/compiler/rustc_codegen_ssa/src/back/write.rs:2057:17:
/rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/compiler/rustc_codegen_ssa/src/back/write.rs:2057:17: panic during codegen/LLVM phase
stack backtrace:
   0:     0x7f5bbd68a3e5 - std::backtrace_rs::backtrace::libunwind::trace::h649ab3318d3445c5
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/../../backtrace/src/backtrace/libunwind.rs:116:5
   1:     0x7f5bbd68a3e5 - std::backtrace_rs::backtrace::trace_unsynchronized::hf4bb60c3387150c3
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/../../backtrace/src/backtrace/mod.rs:66:5
   2:     0x7f5bbd68a3e5 - std::sys::backtrace::_print_fmt::hd9186c800e44bd00
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/backtrace.rs:65:5
   3:     0x7f5bbd68a3e5 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::h1b9dad2a88e955ff
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/backtrace.rs:40:26
   4:     0x7f5bbd6d9eeb - core::fmt::rt::Argument::fmt::h351a7824f737a6a0
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/fmt/rt.rs:173:76
   5:     0x7f5bbd6d9eeb - core::fmt::write::h4b5a1270214bc4a7
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/core/src/fmt/mod.rs:1182:21
   6:     0x7f5bbd67ef6f - std::io::Write::write_fmt::hd04af345a50c312d
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/io/mod.rs:1827:15
   7:     0x7f5bbd68cbd1 - std::sys::backtrace::BacktraceLock::print::h68d41b51481bce5c
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/sys/backtrace.rs:43:9
   8:     0x7f5bbd68cbd1 - std::panicking::default_hook::{{closure}}::h96ab15e9936be7ed
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:269:22
   9:     0x7f5bbd68c8ac - std::panicking::default_hook::h3cacb9c27561ad33
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:296:9
  10:     0x7f5bb9c93420 - std[1f2242ed6435445e]::panicking::update_hook::<alloc[7b1462a1eb55c293]::boxed::Box<rustc_driver_impl[8683aa37472b7dde]::install_ice_hook::{closure#0}>>::{closure#0}
  11:     0x7f5bbd68d59f - <alloc::boxed::Box<F,A> as core::ops::function::Fn<Args>>::call::hce7569f4ca5d1b64
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/alloc/src/boxed.rs:2084:9
  12:     0x7f5bbd68d59f - std::panicking::rust_panic_with_hook::hfe205f6954b2c97b
                               at /rustc/eeb90cda1969383f56a2637cbd3037bdf598841c/library/std/src/panicking.rs:808:13
  13:     0x7f5bba236ae2 - std[1f2242ed6435445e]::panicking::begin_panic::<alloc[7b1462a1eb55c293]::string::String>::{closure#0}
  14:     0x7f5bba22f626 - std[1f2242ed6435445e]::sys::backtrace::__rust_end_short_backtrace::<std[1f2242ed6435445e]::panicking::begin_panic<alloc[7b1462a1eb55c293]::string::String>::{closure#0}, !>
  15:     0x7f5bba221201 - std[1f2242ed6435445e]::panicking::begin_panic::<alloc[7b1462a1eb55c293]::string::String>
  16:     0x7f5bba2b98cd - rustc_middle[ba2289ab3ae064d4]::util::bug::opt_span_bug_fmt::<rustc_span[28a649581f99a5bd]::span_encoding::Span>::{closure#0}
  17:     0x7f5bba29f49a - rustc_middle[ba2289ab3ae064d4]::ty::context::tls::with_opt::<rustc_middle[ba2289ab3ae064d4]::util::bug::opt_span_bug_fmt<rustc_span[28a649581f99a5bd]::span_encoding::Span>::{closure#0}, !>::{closure#0}
  18:     0x7f5bba29f31b - rustc_middle[ba2289ab3ae064d4]::ty::context::tls::with_context_opt::<rustc_middle[ba2289ab3ae064d4]::ty::context::tls::with_opt<rustc_middle[ba2289ab3ae064d4]::util::bug::opt_span_bug_fmt<rustc_span[28a649581f99a5bd]::span_encoding::Span>::{closure#0}, !>::{closure#0}, !>
  19:     0x7f5bb7c3a600 - rustc_middle[ba2289ab3ae064d4]::util::bug::bug_fmt
  20:     0x7f5bbc1081d0 - <rustc_codegen_llvm[5ff2375b9bf6d639]::LlvmCodegenBackend as rustc_codegen_ssa[382a85cbfbe8c2f6]::traits::backend::CodegenBackend>::join_codegen
  21:     0x7f5bbc1030c3 - <rustc_interface[53a414ae04dc6ffb]::queries::Linker>::link
  22:     0x7f5bbbf2d55c - rustc_interface[53a414ae04dc6ffb]::interface::run_compiler::<core[3cad2706d8bdcdc4]::result::Result<(), rustc_span[28a649581f99a5bd]::ErrorGuaranteed>, rustc_driver_impl[8683aa37472b7dde]::run_compiler::{closure#0}>::{closure#1}
  23:     0x7f5bbbe7395b - std[1f2242ed6435445e]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[53a414ae04dc6ffb]::util::run_in_thread_with_globals<rustc_interface[53a414ae04dc6ffb]::interface::run_compiler<core[3cad2706d8bdcdc4]::result::Result<(), rustc_span[28a649581f99a5bd]::ErrorGuaranteed>, rustc_driver_impl[8683aa37472b7dde]::run_compiler::{closure#0}>::{closure#1}, core[3cad2706d8bdcdc4]::result::Result<(), rustc_span[28a649581f99a5bd]::ErrorGuaranteed>>::{closure#0}::{closure#0}, core[3cad2706d8bdcd

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the panic using the linked HULKs binary, cargo watch, incremental builds, and the fish script, then inspect compiler/rustc_codegen_llvm/src/back/lto.rs around line 836. Trace the LTO coordinator path and related handling in compiler/rustc_codegen_ssa/src/back/write.rs; done means the rebuild scenario no longer panics on Option::None.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
compilers
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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