Problem: a crash on dropping a transaction after env

[yrashk]

    #[test]
    fn lmdb_crash() {
        use std::sync::Arc;
        let dir = tempfile::tempdir().unwrap();
        let env = Arc::new(unsafe {
            let mut builder = lmdb_zero::EnvBuilder::new().unwrap();
            builder.set_maxdbs(10).unwrap();
            builder.open(dir.path().to_str().unwrap(), lmdb_zero::open::NOTLS, 0o600).unwrap()
        });

        let txn = lmdb_zero::ReadTransaction::new(env.clone()).unwrap();

        drop(env);
        // CRASHES HERE
        drop(txn);
    }

Basically, by using an Arc-wrapped env and creating a read txn, then dropping the environment and trying to drop txn, it segfaults with:

mdb_txn_end (txn=0x7fffd03024e0, mode=<optimized out>) at /home/yrashk/.cargo/git/checkouts/lmdb-rs-d312082a7acf8730/ad09768/liblmdb-sys/mdb/libraries/liblmdb/mdb.c:3312
3312				txn->mt_u.reader->mr_txnid = (txnid_t)-1;
(gdb) bt
#0  mdb_txn_end (txn=0x7fffd03024e0, mode=<optimized out>) at /home/yrashk/.cargo/git/checkouts/lmdb-rs-d312082a7acf8730/ad09768/liblmdb-sys/mdb/libraries/liblmdb/mdb.c:3312
#1  0x0000555555a95a65 in <lmdb_zero::tx::TxHandle as core::ops::drop::Drop>::drop (self=0x7ffff5a0c600) at /home/yrashk/.cargo/registry/src/github.com-1ecc6299db9ec823/lmdb-zero-0.4.4/src/tx.rs:255

Is this an expected behavior in this set up or is this indeed an issue?

[AltSysrq]

I definitely would not consider this expected. My time is a bit limited but I can try to look into this next weekend.