Anytime our guard pages detect a stack overflow, an abort is issued with no chance to unwind. (The segfault bug mentioned above is caused by crafting data on the stack such that you bypass the guard page, which would go from a segfault into an abort in the presence of stack probes.) I did not intend to imply that there was any chance that a stack overflow wouldn't bring down your process, only to clarify Rust's stance on the theoretical memory safety implications. :)