Remove the `Mutex` from the `threadpool` and `dbwrapper_concurrent_reads`
pool startup helpers. Fuzz targets are entered sequentially within a
process and parallel fuzzing uses separate processes/forks, which each
have their own copy of the global thread pool. Therefore, a mutex to
prevent two in-process callers from racing to start the pool isn't needed.
Limit how many read queries each worker executes. This significantly
speeds up the test, as each worker runs >90% fewer (2000 to 128)
expensive LevelDB operations (like `IteratorSeek`) but still
ends up hitting the intended target code.
Revert the `num_entries` max from 3000 back to 5000, as that didn't
have much effect on input speed and restores a bit of lost coverage.
Pull the inline DBParams construction out of TestDbWrapper into a shared
ConsumeDBParams() helper. This is a pure refactor with no behavior change,
preparing for an additional harness that needs to build the same params.
Introduces a libFuzzer harness that exercises CDBWrapper operations
against a std::map oracle, with a DeterministicEnv that captures LevelDB
background compaction for single-threaded determinism.
A sibling dbwrapper_threaded target uses a bare memenv so LevelDB's real
background thread runs, exercising force_compact and threaded compaction
paths that the deterministic variant cannot reach.
Adds an implicit-integer-sign-change suppression for
BytewiseComparatorImpl::FindShortSuccessor (leveldb/util/comparator.cc:58)
to the test ubsan suppressions list. LevelDB's bytewise comparator
implicitly converts a signed `char` byte to `uint8_t` there. The path
is only reached when compaction picks an SST boundary key, so it
requires a small enough max_file_size for compaction to fire during
the fuzz run.
Co-authored-by: l0rinc <pap.lorinc@gmail.com>
