rust can also help you make custom memory management safer, e.g. there are several arena crates which hand out allocations with lifetimes, which means the arenas won't be freed before all references went out of scope. And there also is no pointer arithmetic into the arena, you only interact with individual allocations. I don't know if it would have prevented heartbleed, but it enables 3rd-party allocators to provide the same safety guarantees as the rust standard lib does. Something that cannot be said about C because there are no safety guarantees in C in the first place.