@thisismissem One problem: Rust extensions have the same GC interactions with Ruby as C extensions. So there is a danger of losing references (and AFAIK there's no way to do RB_GC_GUARD from Rust). Rust extension authors must understand Ruby GC behavior and carefully design their API to ensure Ruby objects are always reachable by the GC. Other issues include longjumps (calling any Ruby method can possibly raise)