docs/fuzzing.md

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# Fuzzing

`cargo-fuzz` needs the nightly toolchain. Install it with `rustup toolchain install nightly`, then:

```shell
cargo install cargo-fuzz
cd fuzz
cargo +nightly fuzz run fuzz_parse_sql fuzz_seeds -- -max_total_time=600
```

There are two targets. `fuzz_parse_sql` parses the input with every dialect.
`fuzz_parse_roundtrip` additionally re-parses the SQL rendered by `Display` and fails when a
rendered statement no longer parses.

`fuzz_sqlite_accepts` compiles the input with a bundled SQLite, without running it, and fails when SQLite accepts SQL that `SQLiteDialect` rejects. Name resolution errors such as a missing table still count as accepted once SQLite has read the statement to its end.

`fuzz_postgres_accepts` parses the input with PostgreSQL's own grammar through `pg_query` and fails when PostgreSQL accepts SQL that `PostgreSqlDialect` rejects.

`fuzz_duckdb_accepts` parses the input with DuckDB's own parser and fails when DuckDB accepts a `SELECT` that `DuckDbDialect` rejects.

ClusterFuzzLite runs continuous fuzzing. Every pull request fuzzes for 10 minutes in
`code-change` mode, a daily batch job grows the shared corpus stored on the
`clusterfuzzlite` branch, and a daily prune compacts it.

`fuzz_seeds/` is a committed corpus of valid SQL that random mutation would never produce.
The run command above uses it and `build.sh` packages it for ClusterFuzzLite.

Crashes land in `artifacts/<target>/` and replay with `cargo fuzz run <target> <crash-file>`.