I found it hard to follow despite C# being my main driver.
Using ref, in the past, has been about modifiable variable references.
All these introductions, even when following C# changes across recent versions, were never something I actively used, apart from the occasional adding ref to structs so they can contain existing ref struct types. It never seems necessary.
Even without ref you use reference and struct types, where reference content can be modified elsewhere. And IDisposable for object lifetimes with cleanup.
Cool, that was an informative read!
If we were willing to leak memory, then we could write […]
Box::leak(Box::new(0))
In this example, you could have just made a constant with value 0 and returned a reference to that. It would also have a 'static lifetime and there would be no leaking.
Why does nobody seem to be talking about this?
My guess is that the overlap in use cases between Rust and C# isn’t very large. Many places where Rust is making inroads (kernel and low-level libraries) are places where C# would be automatically disqualified because of the requirements for a runtime and garbage collection.
(Note that I’m not the article author)
In this example, you could have just made a constant with value
0and returned a reference to that. It would also have a'staticlifetime and there would be no leaking.
I believe the intention was to demonstrate something that works with runtime values too, and a constant 0 does not.
Btw you can just write to do what you proposed, there’s no need for an explicit constant/static.
- Unconvincing use-case: why is returning an
Optionnot an option? - Unconvincing objection: what concrete problems are caused by utilizing
Cows? - Wrong demonstrated “solution”: why would one have to create a value and leak it with each call instead of using one
LazyLockstatic?
I can agree that the example function is not the best usecase. But the point still stand that there’s no realistic escape hatch from lifetimes and memory management in Rust.
Cow does not work when you are actually required to return a reference, e.g. if you’re working with some other crate that requires that. Cow also has some more strict requirements on reborrows (i.e. you can reborrow a &'short &'long T to a , but you can only reborrow a &'short Cow<'long, T> to a ).
LazyLock can solve very specific issues like static, but is not a general escape hatch. Again, the example is not the best to showcase this, but imagine if you have to perform this operation for an unknown amount of runtime values. LazyLock will only work for the very first one.
That is interesting and I didn’t know C# had anything like that. I saw another article recently saying at some point we were likely to see Rust get garbage collection.
Would you have a link to that? I know there are many third-party garbage collectors for Rust, but if there’s something semi-official being proposed or prototyped I’d be most curious :)
It’s not official or semi-official, it was just someone (a well known Haskell guru if that matters) speculating in a blog post.
So someone that is not involved in rust at all and does not seem to like the language thinks it will get a GC at some point? That is not a very credible source for such a statement. Rust is very unlikely to see an official GC anytime soon if ever. There are zero signs it will ever get one. There was a lot of serious talk about it before 1.0 days - but never made it into the language. Similar to green threads which was a feature of the language pre 1.0 days but dropped before the 1.0 release. Rust really wants to have a no required runtime and leans heavy on the zero-cost abstractions for things. Which a GC would impose on the language.
The reason is the vast majority of places use c# to avoid this stuff. So performance is often not the first priority
The complexity it adds takes away from the readability and maintainability. Which is often the priority.
But in a hot path where you need optimization these are a good send as previously you had to use raw pointers and completely side step all the safety of the language.
I would say 90% of c# developers will never touch these. It’s more for library and framework writers.
I believe most of these features are driven by what the Microsoft Devs need to write asp.net and EF.
Yeah I had thought that C# was basically Microsoft’s version of Java, GC’d throughout. But it’s fine, I’m not particularly more excited by it now than I was before (i.e. unexcited). I’m not even excited by Rust, but maybe I’m missing something. I think it’s fine to use GC for most things, and program carefully in a non-allocating style when you have to, using verification tools as well.
A classic: http://james-iry.blogspot.com/2009/05/brief-incomplete-and-mostly-wrong.html
There are quite a few places where a GC is just not acceptable. Anything that requires precise timing for one. This includes kernel development, a lot of embedded systems, gaming, high frequency trading and even latency critical web servers. Though you are right that a lot of places a GC is fine to have. But IMO rust adds more than just fast and safe code without a GC - lots of people come to the language for those but stay for the rest of the features it has to offer.
IMO a big one is the enum support it has and how they can hold values. This opens up a lot of patterns that are just nice to use and one of the biggest things I miss when using other languages. Built with that are Options and Results which are amazing for representing missing values and errors (which is nicer than coding with exceptions IMO). And generally they whole type system leads you towards thinking about the state things can be in and accounting for those states which tends to make it easier to write software with fewer issues in production.
Is what the author calls a C# borrow checker purely lexically based? The first error message gives that impression. And if it is, then it wouldn’t qualify for any such comparisons with 2018+ Rust.
It’s a very different kind of borrow checking than Rust’s. For example there’s no mutability xor sharing checking, because mutability cannot invalidate memory (there’s still a GC in C# after all!). As such, Rust’s NLL (which are available in the 2015 edition too btw) don’t really make sense in C#.
