GameDeterminism.Analyzers 0.1.2

Drift

Static lints that catch game-simulation non-determinism — HashMap/HashSet iteration, unseeded RNG, wall-clock reads, unordered parallelism, pointer-width fields on hashed state, non-associative float arithmetic reachable from simulation code — before they cause a lockstep/rollback-netcode desync, instead of debugging the desync after the fact.

Companion to Foldback (runtime desync detection and bisection): drift prevents what it can at build time, Foldback finds what slips through at runtime.

Pick your language

Full rule reference, one entry per rule with a real example and fix: docs/rule-catalog.md. Full step-by-step walkthroughs on the docs site: Rust, C# / Unity, Unreal, Godot.

Rust quickstart

cargo install cargo-dylint dylint-link

cargo dylint --path crates/drift-lint --workspace

(--path works against a local clone; a --git https://github.com/FelixMiddelhoff/drift install works the same way once this is pushed. Not published to crates.io — see docs/rule-catalog.md for why, and cargo dylint's own docs for the full CLI.)

C# / Unity quickstart

dotnet add package GameDeterminism.Analyzers

(Published as GameDeterminism.Analyzers, not Drift.Analyzers — Drift is a reserved NuGet ID prefix owned by someone else, unrelated to this project.)

Or reference the built Drift.Analyzers.dll directly as an Analyzer item in your .csproj:

<ItemGroup>
  <Analyzer Include="path/to/Drift.Analyzers.dll" />
</ItemGroup>

dotnet pack bindings/csharp/Drift.Analyzers builds the package locally in the correct analyzers/dotnet/cs/ layout that VS/Rider/VS Code auto-load on install.

Unreal quickstart

Generate a compile_commands.json with UnrealBuildTool, then run drift-unreal-lint against it. Grab a prebuilt binary from the latest release (Linux/macOS/Windows), or build from source:

"<EnginePath>/Engine/Binaries/DotNET/UnrealBuildTool/UnrealBuildTool.exe" \
  -Mode=GenerateClangDatabase -Project="<YourProject>.uproject" <Target> Win64 Development

LIBCLANG_PATH="<path to your LLVM install>/bin" \
  cargo run --manifest-path bindings/unreal/drift-unreal-lint/Cargo.toml -- \
  compile_commands.json [config.toml]

(A prebuilt drift-unreal-lint binary still needs LIBCLANG_PATH set at runtime — it links libclang dynamically, doesn't bundle it.)

unseeded_rng, wallclock_read, hashmap_iter, unordered_parallelism, and usize_in_hashed_state run unconditionally. float_outside_fixed_step is opt-in — it does nothing until config.toml sets tick_reachable_roots:

tick_reachable_roots = ["AMyPawn::Tick"]
fixed_step_functions = ["UMyIntegrator::Step"]

Uses stock LLVM/Clang directly (the clang crate over libclang) — no forked compiler, no custom clang-tidy check to build. See docs/rule-catalog.md for each rule's own known limitations.

Godot quickstart

Grab a prebuilt binary from the latest release (Linux/macOS/Windows, no toolchain needed — pure Rust, no engine dependency), or build from source:

cargo run --manifest-path bindings/godot/drift-godot-lint/Cargo.toml -- <file.gd | project directory>

unseeded_rng, wallclock_read, and unordered_parallelism run unconditionally. float_outside_fixed_step runs automatically wherever _process/_physics_process is defined — no config file needed, unlike the Rust/Unreal sides (Godot's own tick entry points are fixed, well-known method names). Pure Rust, no engine dependency (via gdck-syntax). See docs/rule-catalog.md for why the other 2 rules don't apply here.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.