DeVault: Announcing the Hare programming language [LWN.net]

DeVault: Announcing the Hare programming language

Posted May 4, 2022 19:14 UTC (Wed) by Wol (subscriber, #4433)
In reply to: DeVault: Announcing the Hare programming language by khim
Parent article: DeVault: Announcing the Hare programming language

> But that was just the final straw. Even without this gross violation of rules it was becoming more and more apparent that UBs have to go: it's not clear if low-level language without UB is possible in principle, but even if you eliminate them from 99% of code using an automated tools that would still be a great improvement.

It's easy to eliminate UB from any language. A computer language is Maths, and as such you can build a complete and pretty much perfect MODEL.

When you run your program, it's Science (or technology), and you can't guarantee that your model and reality co-incide, but any AND ALL UB should be "we have no control over the consequences of these actions, because we are relying on an outside agent". Be it a hardware random number generator, a network card receiving stuff over the network, a buggy CPU chip, etc etc. The language should be quite clear - "here we have control therefore the following is *defined* as happening, there we have no control therefore what happens is whatever that other system defines". If that other system doesn't bother to define it, it's not UB in your language.

And that's why Rust and Modula-2 and that all have unsafe blocks - it says "here be dragons, we cannot guarantee language invariants".

Cheers,
Wol

to post comments

DeVault: Announcing the Hare programming language

Posted May 4, 2022 19:32 UTC (Wed) by khim (subscriber, #9252) [Link]

> And that's why Rust and Modula-2 and that all have unsafe blocks - it says "here be dragons, we cannot guarantee language invariants".

You just have to remember that not all unsafe blocks are marked with nice keywords. E.g. presumably “safe” Rust program may open /proc/self/mem.

But even then: it's time to stop making languages which allow UB to happen just in any random piece of code which does no such crazy things!

> It's easy to eliminate UB from any language. A computer language is Maths, and as such you can build a complete and pretty much perfect MODEL.

Sometimes model is just too restrictive. E.g. in Rust you have to go into unsafe realm just to create queue or linked list.

But even that, rigid and limited model, allows one to remove UB from a surprising percentage of your code. And it's the only way to write complex code. C/C++ approach doesn't scale. We don't have enough DJBs.