Uninit memory is used as a RNG seed in temporary The following function is used as a way to get entropy from the system, which does operations on and exposes uninit memory, which is UB. fn random_seed(_: &Path, _: &str) -> [u64; 2] { use std::mem::uninitialized as rand; unsafe { [rand::<u64>() ^ 0x12345678, rand::<u64>() ^ 0x87654321] } } This has been resolved in the 0.6.4 release. The crate is not intended to be used outside of a testing environment. For a general purpose crate to create temporary directories, ""tempfile"" (https://crates.io/crates/tempfile) is an alternative for this crate.