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Comment by mh2266 | Hacker News Reader

This just skips the:

> First, if you aren't writing device drivers/kernels or something very low level there is a high probability your program will have zero unsafe usages in it.

from the original comment. Meanwhile all C code is implicitly “unsafe”. Rust at least makes it explicit!

But even if you ignore memory safety issues bypassed by unsafe, Rust forces you to handle errors, it doesn’t let you blow up on null pointers with no compiler protection, it allows you to represent your data exhaustively with sum types, etc etc etc

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Isn’t rust proffered up as a systems language? One that begged to be accepted into the Linux kernel?

Don’t device drivers live in the Linux kernel tree?

So, unsafe code is generally approved in device driver code?

Why not just use C at that point?

I am quite certain that someone who has been on HN as long as you have is capable of understanding the difference between 0% compiler-enforced memory safety in a language with very weak type safety guarantees and 95%+ of code regions even in the worst case of low-level driver code that performs DMA with strong type safety guarantees.

Please explain the differences in typical aliasing rules between C and Rust. And please explain posts like

https://chadaustin.me/2024/10/intrusive-linked-list-in-rust/

https://news.ycombinator.com/item?id=41947921

https://lucumr.pocoo.org/2022/1/30/unsafe-rust/

Is three random people saying unsafe Rust is hard supposed to make us forget about C’s legendary problems with UB, nil pointers, memory management bugs, and staggering number of CVEs?

You have zero sense of perspective. Even if we accept the premise that unsafe Rust is harder than C (which frankly is ludicrous on the face of it) we’re talking about a tiny fraction of the overall code of Rust programs in the wild. You have to pay careful attention to C’s issues virtually every single line of code.

With all due respect this may be the singular dumbest argument I’ve ever had the displeasure of participating in on Hacker News.

> Even if we accept the premise that unsafe Rust is harder than C (which frankly is ludicrous on the face of it)

I think there's a very strong dependence on exactly what kind of unsafe code you're dealing with. On one hand, you can have relatively straightforwards stuff like get_unsafe or calling into simpler FFI functions. On the other hand, you have stuff like exposing a safe, ergonomic, and sound APIs for self-referential structures, which is definitely an area of active experimentation.

Of course, in this context all that is basically a nitpick; nothing about your comment hinges on the parenthetical.

You phrase that as if 0-5% of a program being harder to write disqualifies all the benefits of isolating memory safety bugs to that 0-5%. It doesn't.

And it can easily be more than 5%, since some projects both have lots of large unsafe blocks, and also the presence of an unsafe block can require validation of much more than the block itself. It is terrible of you and overall if my understanding is far better than yours.

And even your argument taken at face value is poor, since if it is much harder, and it is some of the most critical code and already-hard code, like some complex algorithm, it could by itself be worse overall. And Rust specifically have developers use unsafe for some algorithm implementations, for flexibility and performance.

> since if it is much harder, and it is some of the most critical code and already-hard code, like some complex algorithm, it could by itself be worse overall.

(Emphasis added)

But is it worse overall?

It's easy to speculate that some hypothetical scenario could be true. Of course, such speculation on its own provides no reason for anyone to believe it is true. Are you able to provide evidence to back up your speculation?

Even embedded kernels can and regularly do have < 5% unsafe code.

The first two is the same article, but they point out that certain structures can be very hard to write in rust, with linked lists being a famous example. The point stands, but I would say the tradeoff is worth it (the author also mentions at the end that they still think rust is great).

The third link is absolutely nuts. Why would you want to initialize a struct like that in Rust? It's like saying a functional programming language is hard because you can't do goto. The author sets themselves a challenge to do something that absolutely goes against how rust works, and then complains how hard it is.

If you want to do it to interface with non-rust code, writing a C-style string to some memory is easier.

Because writing proper kernel C code requires decades of experience to navigate the implicit conventions and pitfalls of the existing codebase. The human pipeline producing these engineers is drying up because nobody's interested in learning that stuff by going through years of patch rejection from maintainers that have been at it since the beginning.

Rust's rigid type system, compiler checks and insistence on explicitness forces a _culture change_ in the organization. In time, this means that normal developers will regain a chance to contribute to the kernel with much less chance of breaking stuff. Rust not only makes compiled binary more robust but also makes the codebase more accessible.

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