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fix(jolt-host): read the guest ELF once under a build lock - #2121
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Every `jolt build`, even a no-op, has cargo delete and re-link the uplifted guest ELF. Tests that build the same guest in parallel share one target directory, so a test reading the ELF by path (the post-build existence check, `built_elf`, and the later `get_elf_contents` in `build_jolt_program`) could land in that window and panic with "Built ELF not found" or "ELF contents not available". `Program` now holds a `GuestElf` (path plus bytes) read once, right after the build, while an exclusive lock on `<guest_target_dir>/.jolt-build.lock` is held from before `jolt build` until the read completes. Every later consumer uses the stored bytes; the path remains only for tracer panic symbolization.
📏 PR diffNote Actual code changed: 112 lines🟢 +67 added 🔴 −45 removed Tests, docs, fixtures, and helper scripts excluded.
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@pika land |
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Reviewed at b312c01. Taking the lock before jolt build and reading the ELF once under it is sound for Program builds; two inline items block landing: the red style check and the new clippy::panic suppression.
Not blocking: only Program::build_with_features takes .jolt-build.lock. The direct jolt build calls in tracer's test_utils::build_muldiv_guest, crates/jolt-tracer-x86/tests/common/mod.rs and tracer/examples/support/mod.rs write into the same jolt-guest-targets/{guest}-{func} directories without it, so they can still race with Program (this predates the PR).
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| impl GuestElf { | ||
| pub fn read(path: PathBuf) -> io::Result<Self> { |
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style fails on this line: [nominal-imports] import io::Result and use Result. A plain use std::io::Result would shadow the two-parameter Result that build_jolt_program returns below, so alias it the way jolt-sdk/src/host_utils.rs does: replace use std::io; with use std::io::Error as IoError; and return Result<Self, IoError>.
| #[expect( | ||
| clippy::expect_used, | ||
| reason = "the infallible host build API reports CLI failures by panicking" | ||
| clippy::panic, |
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clippy::panic (denied workspace-wide) is added only for the panic! in the ELF read below. let elf = GuestElf::read(elf_path).expect("read the built guest ELF"); is already covered by this function's expect_used expectation, so the new suppression can go.
The style job rejects `io::Result` under the nominal-import rule, and a plain `use std::io::Result` would shadow the two-parameter `Result` used elsewhere in the file, so `GuestElf::read` returns `Result<Self, IoError>`. The ELF read now uses `.expect`, already covered by the function's `clippy::expect_used` expectation, so the added `clippy::panic` goes. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Tests that build the same guest in parallel intermittently panic with "Built ELF not found" or "ELF contents not available" (the ~2 s jolt-prover flakes). Every
jolt build, even a no-op, has cargo delete and re-link the uplifted guest ELF, so any test reading the ELF by path while another test's build is in that window loses the race. The path is read in three places: the post-build existence check,built_elf, andget_elf_contentsinbuild_jolt_program.Programnow holds aGuestElf(path plusArc<[u8]>bytes) read once, right after the build, while an exclusivestd::fs::File::lockon<guest_target_dir>/.jolt-build.lockis held from beforejolt builduntil the read completes. Later consumers use the stored bytes; the path remains only for tracer panic symbolization.Validation: with the race forced (concurrent builds of one guest), 20 of 80 runs failed on main and 0 of 80 with this change. Clippy (
host), fmt,jolt-hosttests andjolt-prover --features prover-fixtures(29/29) pass on the rebased head.