Fuzz

The fuzz target lives in fuzz/ (crate graph-fuzz, binary fuzz_target_runtime, fuzzing graph's query runtime). fuzz.sh runs the full local sequence below end-to-end.

1. Toolchain setup (one-time / per environment)

cargo-fuzz requires the nightly toolchain plus LLVM tools:

rustup default nightly
rustup component add llvm-tools-preview
cargo install cargo-fuzz --version <CARGO_FUZZ_VERSION> --locked

Check the currently-pinned CARGO_FUZZ_VERSION in .github/workflows/rust-pr.yml so your local cargo-fuzz matches CI.

2. Build

cargo build --features fuzz

3. Seed the corpus

The corpus is seeded from the TCK test run (it generates a wide variety of valid Cypher queries/inputs):

mkdir -p fuzz/corpus/fuzz_target_runtime/
source venv/bin/activate 2>/dev/null || source /data/venv/bin/activate   # pytest deps (/data/venv in devcontainer/CI)
TCK_DONE=tck_done.txt pytest tests/tck/test_tck.py -s

4. Run / minimize / cover

On Linux, first export the RediSearch link workaround CI uses, so the embedded static libs link without duplicate-symbol errors (not needed / not a valid flag with macOS's linker):

export RUSTFLAGS="-C link-arg=-Wl,--allow-multiple-definition"   # Linux/CI only

CXX=clang++ CARGO_PROFILE_RELEASE_LTO=false cargo fuzz run fuzz_target_runtime -- -max_total_time=<seconds>
CXX=clang++ CARGO_PROFILE_RELEASE_LTO=false cargo fuzz cmin fuzz_target_runtime      # minimize the corpus
CXX=clang++ CARGO_PROFILE_RELEASE_LTO=false cargo fuzz coverage fuzz_target_runtime  # generate coverage data

Then render an HTML coverage report. Resolve llvm-cov from the active Rust toolchain (via llvm-tools-preview) rather than a system one, exactly as CI does, to avoid version skew; the target triple differs by OS:

LLVM_COV=$(find "$(rustc --print sysroot)" -name llvm-cov -type f | head -1)

# Linux
"$LLVM_COV" show -format=html -instr-profile=fuzz/coverage/fuzz_target_runtime/coverage.profdata \
  -ignore-filename-regex=\.cargo/registry \
  target/x86_64-unknown-linux-gnu/coverage/x86_64-unknown-linux-gnu/release/fuzz_target_runtime > cov.html

# macOS
"$LLVM_COV" show -format=html -instr-profile=fuzz/coverage/fuzz_target_runtime/coverage.profdata \
  -ignore-filename-regex=\.cargo/registry \
  target/aarch64-apple-darwin/coverage/aarch64-apple-darwin/release/fuzz_target_runtime > cov.html

5. Reproduce a crash

A failing run writes a repro case to fuzz/artifacts/fuzz_target_runtime/. Reproduce and debug it directly:

cargo fuzz run fuzz_target_runtime fuzz/artifacts/fuzz_target_runtime/<crash-file>

Combine with the debug skill (lldb/gdb, panic behavior) once you can reproduce it — cargo-fuzz binaries are plain executables you can attach a debugger to directly (no need to load a Redis module for this).

Notes

• CI runs this on a time budget as its own job and uploads the corpus as a build artifact (fuzzing-corpus) and any crash artifacts on failure — grab those from a failed run's artifacts instead of re-fuzzing from scratch when triaging a CI-only failure.
• CARGO_PROFILE_RELEASE_LTO=false avoids excessively long fuzz build times; CXX=clang++ is needed for the same GraphBLAS FFI reason as in the build skill.