Comment by chlorion

>How do you signal the failure of a function that returns a pointer without having to return a struct with a pointer and an error code (which is inefficient since the return value doesn't fit a single register)?

Rust does this with the Result and Option "enums", which are internally implemented as tagged unions. From my understanding the only overhead with this implementation is the size taken by the tag and then any padding required for alignment.

It also helps that references in Rust are not nullable and working with pointers is fairly rare, so the type system can do a lot of heavy lifting for you rather than putting null checks all over the place. When you have &T you never have to worry about handling null in the first place!