unsafe-code-guidelines VS too-many-lists

Useful context on the Rust side is this issue [1]. It sounds like some of the author's concerns are addressed already.

[1]: https://github.com/rust-lang/unsafe-code-guidelines/issues/4...

Is this captured by one of the known soundness conflicts? If not then should consider adding it to the list.

There are some competing proposals for different memory models. Stacked borrows is the current proposal, but there are more work in the approproate WG.

Thank you /u/RalfJung for bringing formal methods to Rust, both through models like Stacked Borrows, by developing miri, and by working on unsafe-code-guidelines which aims to specify exactly what is and isn't allowed in unsafe code (surprisingly, it's an open question as 2023!)

You could imagine some way to make this safe for example automatically convert &'short &'long mut T to &'short &'short T, but it's non-trivial to prove they are safe at all, not to mention ensuring this is correctly implemented in the compiler. If you're interested there's also a discussion on whether the opposite (& & T to & &mut T) is sound here.

Agreed! MIRI is so good, it still feels like magic to me. It also comforts me that the Rust team takes improving unsafe semantics seriously, with the past Unsafe Code Guidelines WG and today's operational semantics team (t-opsem).

I think there are some aspects of this rule that are still undecided. See for example:

- https://github.com/rust-lang/unsafe-code-guidelines/issues/8...

- https://github.com/rust-lang/miri/issues/2732

C is much better specified than unsafe Rust. Some things are just not worked out yet in Rust. This may sometimes even bite very experienced devs, such as this issue with Box's aliasing semantics, which tripped up the author of left-right.

You seem to have a preset opinion, and I'm not sure you are interested in re-evaluating it. So this is not written to change your mind.

I've developed production code in C, C++, Rust, and several other languages. And while like pretty much everything, there are situations where it's not a good fit, I find that the solutions tend to be the most robust and require the least post release debugging in Rust. That's my personal experience. It's not hard data. And yes occasionally it's annoying to please the compiler, and if there were no trait constraints or borrow rules, those instances would be easier. But way more often in my experience the compiler complained because my initial solution had problems I didn't realize before. So for me, these situations have been about going from building it the way I wanted to -> compiler tells me I didn't consider an edge case -> changing the implementation and or design to account for that edge case. Also using one example, where is Rust is notoriously hard and or un-ergonomic to use, and dismissing the entire language seems premature to me. For those that insist on learning Rust by implementing a linked list there is https://rust-unofficial.github.io/too-many-lists/.

Advent of Code was okay until I encounterd a problem that required a graph, tree or linked list to solve, where I hit a wall. Most coding exercises are similar--those requiring arrays and hashmaps and sets are okay, but complex data structures are a PITA. (There is an online course dedicated to linked lists in Rust but I couldn't grok it either). IMO you should simply skip problems that you can't solve with your current knowledge level and move on.

I feel obligated to point to the original cannon literature: https://rust-unofficial.github.io/too-many-lists/

I started learning Rust and like how the compiler is fussy about things. My plan was to implement the data structures I knew, but I got stuck at the singly linked list's remove() method. I've read the book as well, but I have no clue how to simplify this further:

My impression from the article is that Zig provides several different hashtables and not all of them are broken in this way.

This reminds me of Aria's comment in her Rust tutorial https://rust-unofficial.github.io/too-many-lists/ about failing to kill LinkedList. One philosophy (and the one Rust chose) for a stdlib is that this is only where things should live when they're so commonly needed that essentially everybody needs them either directly or to talk about. So, HashTable is needed by so much otherwise unrelated software that qualifies, BloomFilter, while it's real useful for some people, not so much. Aria cleaned out Rust's set of standard library containers before Rust 1.0, trying to keep only those most people would need. LinkedList isn't a good general purpose data structure, but, it was too popular and Aria was not able to remove it.

Having multiple hash tables feels like a win (they're optimized for different purposes) but may cost too much in terms of the necessary testing to ensure they all hit the quality you want.

> Cyclic references can be dealt with runtime safety checks too - like Rc and Weak.

Indeed. Starting out with code sprinkled with Rc, Weak, RefCell, etc is perfectly fine and performance will probably not be worse than in any other safe languages. And if you do this, Rust is pretty close to those languages in ease of use for what are otherwise complex topics in Rust.

A good reference for different approaches is Learn Rust With Entirely Too Many Linked Lists https://rust-unofficial.github.io/too-many-lists/

Second, once you've finished something introductory like The Book, read Learning Rust With Entirely Too Many Linked Lists. It really helped me to understand what ownership and borrowing actually mean in practical terms. If you don't mind paying for learning materials, a lot of people recommend Programming Rust, Second Edition by Blandy, Orendorff, and Tindall as either a complement, follow-up, or alternative to The Book.

Learning Rust With Entirely Too Many Linked Lists which highlights a lot of the differences with how you need to structure your code in Rust compared to other languages.