Of course there are cases in which you can get segfaults, and not only in Rust. The single fact of having a C FFI is enough to break all safety guarantees of your language.<p>What Rust <i>does</i> promise is that undefined behavior will never happen if you don&#x27;t use code blocks marked as unsafe (which include the C FFI). In other words, if you are able to trigger undefined behavior without using unsafe code, that is a compiler or library <i>bug</i>.<p>EDIT: as noted by steveklabnik, this is not undefined behavior.  Actually you should get a better error message instead of a segmentation fault (see the link to the issue on GitHub in steveklabnik&#x27;s comment).