Speaking as a subscriber of about two decades who perhaps wouldn't have a career without the enormous amount of high-quality education provided by LWN content, or at least a far lesser one: Let's forgive.
It was unintentional as per author
> Ouch. That is what I get for pushing something out during a meeting, I guess. That was not my point; the experiment is done, and it was a success. I meant no more than that.
(I do agree it's clickbait-y though)
The topic of the Rust experiment was just discussed at the annual Maintainers Summit. The consensus among the assembled developers is that Rust in the kernel is no longer experimental — it is now a core part of the kernel and is here to stay. So the "experimental" tag will be coming off. Congratulations are in order for all of the Rust-for-Linux team.For my work code, it all comes down to SDKs and stuff. For example I'm going to write firmware for Nordic ARM chip. Nordic SDK uses C, so I'm not going to jump through infinite number of hoops and incomplete rust ports, I'll just use official SDK and C. If it would be the opposite, I would be using Rust, but I don't think that would happen in the next 10 years.
Furthermore, in terms of extensions to the language to support more obtuse architecture, Rust has made a couple of decisions that make it hard for some of those architectures to be supported well. For example, Rust has decided that the array index type, the object size type, and the pointer size type are all the same type, which is not the case for a couple of architectures; it's also the case that things like segmented pointers don't really work in Rust (of course, they barely work in C, but barely is more than nothing).
Bitfield packing rules get pretty wild. Sure the user facing API in the language is convenient, but the ABI it produces is terrible (particularly in evolution).
Rust worded in its initial guarantee that usize was sufficient to roundtrip a pointer (making it effectively uptr), and there remains concern among several of the maintainers about breaking that guarantee, despite the fact that people on the only target that would be affected basically saying they'd rather see that guarantee broken. Sort of the more fundamental problem is that many crates are perfectly happy opting out of compiling for weirder platform--I've designed some stuff that relies on 64-bit system properties, and I'd rather like to have the ability to say "no compile for you on platform where usize-is-not-u64" and get impl From<usize> for u64 and impl From<u64> for usize. If you've got something like that, it also provides a neat way to say "I don't want to opt out of [or into] compiling for usize≠uptr" and keeping backwards compatibility.
If you want to see some long, gory debates on the topic, https://internals.rust-lang.org/t/pre-rfc-usize-is-not-size-... is a good starting point.
Assuming I'm reading these blog posts [0, 1] correctly, it seems that the size_of::<usize>() == size_of::<*mut u8>() assumption is changeable across editions.
Or at the very least, if that change (or a similarly workable one) isn't possible, both blog posts do a pretty good job of pointedly not saying so.
[0]: https://faultlore.com/blah/fix-rust-pointers/#redefining-usi...
[1]: https://tratt.net/laurie/blog/2022/making_rust_a_better_fit_...
There was one accelerator architecture we were working that discussed making the entire datapath be 32-bit (taking less space) and having a 32-bit index type with a 64-bit pointer size, but this was eventually rejected as too hard to get working.
There will be small niches leftover:
* Embedded - This will always be C. No memory allocation means no Rust benefits. Rust is also too complex for smaller systems to write compilers.
* OS / Kernel - Nearly all of the relevant code is unsafe. There aren't many real benefits. It will happen anyways due to grant funding requirements. This will take decades, maybe a century. A better alternative would be a verified kernel with formal methods and a Linux compatibility layer, but that is pie in the sky.
* Game Engines - Rust screwed up its standard library by not putting custom allocation at the center of it. Until we get a Rust version of the EASTL, adoption will be slow at best.
* High Frequency Traders - They would care about the standard library except they are moving on from C++ to VHDL for their time-sensitive stuff. I would bet they move to a garbage-collected language for everything else, either Java or Go.
* Browsers - Despite being born in a browser, Rust is unlikely to make any inroads. Mozilla lost their ability to make effective change and already killed their Rust project once. Google has probably the largest C++ codebase in the world. Migrating to Rust would be so expensive that the board would squash it.
* High-Throughput Services - This is where I see the bulk of Rust adoption. I would be surprised if major rewrites aren't already underway.
It's like saying python is complex becasue you have metaclasses, but you'll never need to reach for them.
Obviously not. When will that happen? 15 years? Maybe it's generational: How long before developers 'born' into to memory-safe languages as serious choices will be substantially in charge of software development?
Is it obvious? I haven't heard of new projects in non-memory-safe languages lately, and I would think they would struggle to attract contributors.
I can think of possible reasons: Early in life, in school and early career, much of what you work on is inevitably new to you, and also authorities (professor, boss) compel you to learn whatever they choose. You become accustomed to and skilled at adapting new things. Later, when you have power to make the choice, you are less likely to make yourself change (and more likely to make the junior people change, when there's a trade-off). Power corrupts, even on that small scale.
There's also a good argument for being stubborn and jaded: You have 30 years perfecting the skills, tools, efficiencies, etc. of C++. For the new project, even if C++ isn't as good a fit as Rust, are you going to be more efficient using Rust? How about in a year? Two years? ... It might not be worth learning Rust at all; ROI might be higher continuing to invest in additional elite C++ skills. Certainly that has more appeal to someone who knows C++ intimately - continue to refine this beautiful machine, or bang your head against the wall?
For someone without that investment, Rust might have higher ROI; that's fine, let them learn it. We still need C++ developers. Morbid but true, to a degree: 'Progress happens one funeral at a time.'
I do firmly expect that we're less than a decade out from seeing some reference algorithm be implemented in Rust rather than C, probably a cryptographic algorithm or a media codec. Although you might argue that the egg library for e-graphs already qualifies.
I have no doubt C will be around for a long time, but I think Rust also has a lot of staying power and won’t soon be replaced.
It's "embedded programming" where you often start to run into weird platforms (or sub-platforms) that only have a c compiler, or the rust compiler that does exist is somewhat borderline. We are sometimes talking about devices which don't even have a gcc port (or the port is based on a very old version of gcc). Which is a shame, because IMO, rust actually excels as an embedded programming language.
Linux is a bit marginal, as it crosses the boundary and is often used as a kernel for embedded devices (especially ones that need to do networking). The 68k people have been hit quite hard by this, linux on 68k is still a semi-common usecase, and while there is a prototype rust back end, it's still not production ready.
Even then, there are still some systems that will support C but won't support Rust any time soon. Systems with old compilers/compiler forks, systems with unusual data types which violate Rust's assumptions (like 8 bit bytes IIRC)
That isn't always the case. Slow compilations are usually because of procedural macros and/or heavy use of generics. And even then compile times are often comparable to languages like typescript and scala.
I wouldn’t say it’s inevitable that everything will be rewritten in Rust, at the very least this will this decades. C has been with us for more than half a century and is the foundation of pretty much everything, it will take a long time to migrate all that.
More likely is that they will live next to each other for a very, very long time.
A lot of software was written in C and C++ because they were the only option for decades. If you couldn't afford garbage collection and needed direct control of the hardware there wasn't much of a choice. Had their been "safer" alternatives, it's possible those would have been used instead.
It's only been in the last few years we've seen languages emerge that could actually replace C/C++ with projects like Rust, Zig and Odin. I'm not saying they will, or they should, but just that we actually have alternatives now.
Web browsers have been written in restricted subsets of C/C++ with significant additional tooling for decades at this point, and are already beginning to move to Rust.