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rustc segfaults when targeting AVR and compiling core in debug mode #101965

Open faithanalog opened 2 years ago

faithanalog commented 2 years ago

code to reproduce at https://github.com/faithanalog/rustc-avr-bug-repro

searched nightlies: from nightly-2022-06-05 to nightly-2022-09-15 regressed nightly: nightly-2022-06-27 searched commit range: https://github.com/rust-lang/rust/compare/20a6f3a8a8ce5ae18d06b12cd7904bc5294ca753...c80c4b8fdcf3da69cd483e2fec172c9b1f95842c regressed commit: https://github.com/rust-lang/rust/commit/788ddedb0d88e40db9cd62b6163d5a471813044b

bisected with cargo-bisect-rustc v0.6.4 Host triple: x86_64-unknown-linux-gnu Reproduce with: ```bash cargo-bisect-rustc --with-src --start 2022-06-05 --end 2022-09-15 --script ./build.sh ```

In versions prior to 2022-06-27, compiling core for AVR in debug mode generates the following error:

error: ran out of registers during register allocation

This error isn't ideal, but it's not the subject of this bug report. In versions starting with 2022-06-27, rustc instead segfaults, with an error like this:

vi@localhost ~/p/rust-avr-bug-repro (main)> cargo build
   Compiling core v0.0.0 (/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core)
   Compiling rustc-std-workspace-core v1.99.0 (/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/rustc-std-workspace-core)
   Compiling compiler_builtins v0.1.79
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/librustc_driver-e661066f9d8eca3e.so(+0x2811d13)[0x7fd7e2af5d13]
/lib64/libc.so.6(+0x3daa0)[0x7fd7dff76aa0]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/libLLVM-15-rust-1.65.0-nightly.so(_ZN4llvm12MachineInstr10addOperandERNS_15MachineFunctionERKNS_14MachineOperandE+0x1f5)[0x7fd7dd080785]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/libLLVM-15-rust-1.65.0-nightly.so(+0x4c6c5cc)[0x7fd7df8b75cc]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/libLLVM-15-rust-1.65.0-nightly.so(+0x4c6c31f)[0x7fd7df8b731f]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/libLLVM-15-rust-1.65.0-nightly.so(_ZN4llvm13FPPassManager13runOnFunctionERNS_8FunctionE+0x856)[0x7fd7dde70b86]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/libLLVM-15-rust-1.65.0-nightly.so(_ZN4llvm13FPPassManager11runOnModuleERNS_6ModuleE+0x2f)[0x7fd7dde7019f]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/libLLVM-15-rust-1.65.0-nightly.so(_ZN4llvm6legacy15PassManagerImpl3runERNS_6ModuleE+0x213)[0x7fd7dde6fac3]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/librustc_driver-e661066f9d8eca3e.so(+0x232d8d2)[0x7fd7e26118d2]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/librustc_driver-e661066f9d8eca3e.so(+0x232d229)[0x7fd7e2611229]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/librustc_driver-e661066f9d8eca3e.so(+0x232b15a)[0x7fd7e260f15a]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/librustc_driver-e661066f9d8eca3e.so(+0x2327365)[0x7fd7e260b365]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/librustc_driver-e661066f9d8eca3e.so(+0x232650b)[0x7fd7e260a50b]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/librustc_driver-e661066f9d8eca3e.so(+0x2325018)[0x7fd7e2609018]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/librustc_driver-e661066f9d8eca3e.so(+0x2284358)[0x7fd7e2568358]
/home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/libstd-4393e7d07259b8a4.so(rust_metadata_std_81ab5d9a96a0142e+0xfdee3)[0x7fd7e025eee3]
/lib64/libc.so.6(+0x8784a)[0x7fd7dffc084a]
/lib64/libc.so.6(+0x10acec)[0x7fd7e0043cec]
error: could not compile `core`

Caused by:
  process didn't exit successfully: `rustc --crate-name core --edition=2021 /home/vi/.rustup/toolchains/nightly-2022-09-15-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debuginfo=2 -C metadata=12ddbf17236d5c10 -C extra-filename=-12ddbf17236d5c10 --out-dir /home/vi/p/rust-avr-bug-repro/target/avr-atmega328p/debug/deps --target /home/vi/p/rust-avr-bug-repro/avr-atmega328p.json -Z force-unstable-if-unmarked -L dependency=/home/vi/p/rust-avr-bug-repro/target/avr-atmega328p/debug/deps -L dependency=/home/vi/p/rust-avr-bug-repro/target/debug/deps --cap-lints allow` (signal: 11, SIGSEGV: invalid memory reference)

This doesn't necessarily happen all the time though. sometimes it errors with error: ran out of registers during register allocation like it should be doing, so it seems to be non-deterministic on some versions of rustc. This is why my bisection build script re-runs it 10 times to be sure it segfaults at least once. However, the commit directly before the failing commit returned error: ran out of registers during register allocation 10 times, and the failing commit segfaulted all 10 times, so maybe it's deterministic for the failing commit.

cargo build --release works just fine and does not generate either error.

Patryk27 commented 10 months ago

btw, just checked and nowadays rustc crashes reliably with ran out of registers during register allocation