My problem was that I was taking a: Some([u8; 32]).map(|v| v.as_ptr()).unwrap_or(::std::ptr::null()); Which the map(..) copies by value and immediately goes

My problem was that I was taking a: Some([u8; 32]).map(|v| v.as_ptr()).unwrap_or(::std::ptr::null()); Which the map(..) copies by value and immediately goes out of scope so now you have a dangling pointer to the stack(fun!). If it was a reference I'd be totally covered but since pointers drop lifetime semantics that's where I got bit. Love bindgen though, just whitelisting the function I needs generates awesome interop APIs. At the end of the day though unsafe is unsafe.