add libafl compatibility

fuzz/Cargo.toml

@@ -9,14 +9,18 @@ publish = false
 edition = "2021"
 
 [features]
+default = ["libfuzzer"]
 full-idempotency = []
+libafl = ["libafl_libfuzzer"]
+libfuzzer = ["libfuzzer-sys/link_libfuzzer"]
 
 [package.metadata]
 cargo-fuzz = true
 
 [dependencies]
 arbitrary = { version = "1.3.0", features = ["derive"] }
-libfuzzer-sys = { version = "0.4.1" }
+libafl_libfuzzer = { git = "https://github.com/AFLplusplus/LibAFL.git", branch = "libfuzzer", optional = true }
+libfuzzer-sys = { git = "https://github.com/rust-fuzz/libfuzzer", default-features = false }
 ruff = { path = "../crates/ruff" }
 ruff_python_ast = { path = "../crates/ruff_python_ast" }
 ruff_python_formatter = { path = "../crates/ruff_python_formatter" }

fuzz/README.md

@@ -95,3 +95,11 @@ This fuzz harness checks that fixes applied by Ruff do not introduce new errors
 [`ruff::test::test_snippet`](../crates/ruff/src/test.rs) testing utility.
 It currently is only configured to use default settings, but may be extended in future versions to
 test non-default linter settings.
+
+## Experimental settings
+
+You can optionally use `--no-default-features --features libafl` to use the libafl fuzzer instead of
+libfuzzer.
+This fuzzer has experimental support, but can vastly improve fuzzer performance.
+If you are not already familiar with [LibAFL](https://github.com/AFLplusplus/LibAFL), this mode is
+not currently recommended.

fuzz/fuzz_targets/ruff_fix_validity.rs

@@ -3,6 +3,9 @@
 
 #![no_main]
 
+#[cfg(feature = "libafl")]
+extern crate libafl_libfuzzer;
+
 use libfuzzer_sys::{fuzz_target, Corpus};
 use ruff::settings::Settings;
 use std::sync::OnceLock;

fuzz/fuzz_targets/ruff_parse_idempotency.rs

@@ -3,6 +3,9 @@
 
 #![no_main]
 
+#[cfg(feature = "libafl")]
+extern crate libafl_libfuzzer;
+
 use libfuzzer_sys::{fuzz_target, Corpus};
 use ruff_python_ast::source_code::round_trip;
 use similar::TextDiff;

fuzz/fuzz_targets/ruff_parse_simple.rs

@@ -3,6 +3,9 @@
 
 #![no_main]
 
+#[cfg(feature = "libafl")]
+extern crate libafl_libfuzzer;
+
 use libfuzzer_sys::{fuzz_target, Corpus};
 use ruff_python_ast::source_code::round_trip;