Null References: The Billion Dollar Mistake

Out of all possible gotchas in programming languages I still find null pointers the easiest one to discover and fix. You directly see when and where it happens, and the fix is usally straightforward. Compared to that invalid pointers (stale references) are a lot more painful, since programs might continue to work for a while. Managed languages do at least prevent those. Multithreading issues are imho the biggest pain points, since they are introduced so easily and often go unnoticed…

Nah. The billion dollar mistake is actually C arrays decaying to pointers, enabling buffer overflows, the #1 cause of bugs and malware injection in shipped C programs. https://www.digitalmars.com/articles/C-biggest-mistake.html It's simple to fix this in C, too.

One of my absolute favorite things about Rust is that nulls can't be used to circumvent the type system. They must be explicitly accounted for via an option type in all cases. It's very hard to go back to a language that doesn't do this after getting used to it. I get so frustrated by constant null dereference errors when that entire category of error can be avoided.

I particularly appreciate that as a billion-dollar mistake, Javascript decided to make it twice (null and undefined).