Hacker News Reader

Comment by jkercher | Hacker News Reader

Meh, I think NULL is fine in C. It's an extra, valid state to represent pointers at no cost. Unlike the more hand holdy languages, it's quite rare for a pointer in C to have the ability to be NULL since, more often than not, it's pointing at something known. It's actually quite rare to see NULL checks unless it's API code or something like that. I can see this being more of a problem in a managed language where anything can be NULL at any time.

View on HN

NULL as a concept is fine. Inability to declare something as non-null is not.

There is a huge gap between developer expectation "it's pointing at something known" and hard reality confirmed by zillions of CVE. That's the reason optionality is prevalent in modern languages and type checkers (python, typescript), nowdays even Java has sane non-nullable types.

> to represent pointers at no cost

I wouldn't call "cause of bugs and security issues" "no cost".

> it's quite rare for a pointer in C to have the ability to be NULL

As a C programmer for more than 25 years, that is the exact opposite of my experience.

Struct foo has various members, including a bar*. But a foo may or may not be associated with a bar. If there's no associated bar, the bar* pointer is NULL. Seen and done this all the time

The problem with let's get rid of NULL is that it's a real, required state. The vast majority of computing is actually not binary: any real input generally has at least 3 possible states: not set, true and false.

In practice really 4 because "indeterminate" is a reasonable error condition you'd like to know about.

And it keeps increasing anyway: e.g. not set has subcategories: not set due to lack of user input, not set because we're loading state from the backend etc.

NULL is the first expression of that basic problem: it's definitely not enough to eliminate NULL because the first thing which happens is your non pointer default value takes it's place.

What you are describing is option types, which are an entirely valid and very useful construct that helps make programs more rather than less reliable. But you need proper language type system support and compile-time enforcement to make it work, and C does neither of those.

C++ and rust make these optionals ugly. Zig does it right. Zig also forbids null pointers and requires use of optionals.

Reply on news.ycombinator.com