gccrs will allow the whole thing to be built with GCC toolchain in a single swoop.
If banks are still using COBOL and FORTRAN here and there, this will be the most probable possibility in my eyes.
I suppose the biggest reason is that C programmers are more likely than not trained to kinda know what the assembly will look like in many cases, or have a very good idea of how an optimizer compiler will optimize things.
This reminds me I need to do some non-trivial embedded project with Rust to see how it behaves in that regard. I'm not sure if the abstraction gets in the way.
So, I think if you do the same thing with Rust, you'll have that intuition, as well.
I have a friend who writes embedded Rust, and he said it's not as smooth as C, yet. I think Rust has finished the first 90% of its maturing, and has the other 90%.
So, I have a model for my code in my brain, and this code also has a real-world behavior after it's compiled by your favorite toolchain. You do both enough times, and you'll have a feeling for both your code and the compiler's behavior for your code.
This feeling breaks when you change languages. I can brain-compile Go for example, but compiler adds other things like GC and null-pointer protection (carry local variables to heap if you're going to hit a null pointer exception after returning a function). Getting used to this takes time. Same for Rust.
This is the only way Hellwig's objection makes any kind of sense to me. Obviously, intra-kernel module boundaries are no REST-APIs, where providers and clients would be completely separated from each other. Here I imagine that both the DMA module as well as its API consumers are compiled together into a monolithic binary, so if assumptions about the API consumers change, this could affect how the module itself is compiled.
Plus for that kind of things you have "deterministic C" styles which guarantee things will be done your way, all day, every day.
For everyone answering: This is what I understood by chatting with people who write Rust in amateur and pro settings. It's not something of a "Rust is bad" bias or something. The general consensus was, C is closer to the hardware and allows handling of quirks of the hardware better, because you can do "seemingly dangerous" things which hardware needs to be done to initialize successfully. Older hardware is finicky, just remember that. Also, for anyone wondering. I'll start learning Rust the day gccrs becomes usable. I'm not a fan of LLVM, and have no problems with Rust.
I'd love to hear a justification for why this is a thing. Doing bit-banging is no more difficult in Rust or C++ than in C.
The assembly outputted from C compilers tend to be more predictable by virtue of C being a simpler language. This matters when writing drivers for exotic hardware.
Sometimes to do things like make a performant ring buffer (without vec dequeue) you need to use unsafe rust anyway, which IMO is just taking the complexity of the rust language without any of the benefit.
I don’t really think there’s any benefit to using C++ over rust except that it interfaces with C code more easily. IMO that’s not a deal maker.
That doesn't seem to be true, not in the presence of UB, different platforms and optimization levels.
> Sometimes to do things like make a performant ring buffer (without vec dequeue) you need to use unsafe rust anyway, which IMO is just taking the complexity of the rust language without any of the benefit.
If you write a data structure in Rust, it's expected to wrap the unsafe fiddly bits into a safer shell and provide unsafe access as needed. Sure, the inner workings of Vec, VecDeque, and Ring Buffers are unsafe, but the API used to modify them isn't (modulo any unsafe methods that have their prerequisite for safe access stated).
The idea is to minimize the amount of unsafe, not completely eradicate it.
The usual outcome of this assumption is that a user complains to the compiler that it doesn't produce the expected assembly code, which the compiler ignores because they never guaranteed any particular assembly output.
This is especially true for the kinds of implicit assembly guarantees people want when working with exotic hardware. Compilers will happily merge loads and stores into larger load/stores, for example, so if you need to issue two adjacent byte loads as two byte loads and not one 16-bit load, then you should use inline assembly and not C code.
I do agree that if someone actually cares about the assembly they should be writing it by hand.
No C compiler is predictable. First, there is the compiler magic of optimization.
Then you have Undefined Behavior, which in C, that's almost a guarantee, you'll experience inconsistent behavior between compilers, targets, optimization levels and the phases of the moon.
In Rust, use .iter a lot to avoid bound checks, or if you want auto-vectorization use a lot of fixed length arrays, and look how LLVM auto-vectorizes it. It takes getting used to it, but hey, so does literally every language if you care about SOURCE -> ASSEMBLY translation.
This doesn’t make any sense to me, could you explain why?
This might have been true 50 years ago, I am unconvinced it was true 25 years ago, it would take a lot to convince me it's true today.
Or even C++, that many forget was also born at Bell Labs on the UNIX group, the main reason being Bjarne Stroutroup never wanted to repeat his Simula to BCPL downgrade ever again, thus C with Classes was originally designed for a distributed computing Bell Labs research project on UNIX, that Bjarne Stroutroup certainly wasn't going to repeat the previous experience, this time with C instead of BCPL.
If you mean that C should have ceded all of user-space programming to Perl and Tcl, I disagree strongly. First, that position is self-contradictory; Perl was a user-space program, and it was written in C. Second, C was much more maintainable than Perl for anything longer than, say, 100 lines.
More fundamentally: There was a free market in developer languages on Unix, with C, Perl, Awk, Sed, and probably several others, all freely available (free both as in speech and as in beer). Of them, C won as the language that the bulk of the serious development got done in. Why "should" anything else have happened? If developers felt that C was better than Perl for what they were trying to write, why should they not use C?
"Oh, it was quite a while ago. I kind of stopped when C came out. That was a big blow. We were making so much good progress on optimizations and transformations. We were getting rid of just one nice problem after another. When C came out, at one of the SIGPLAN compiler conferences, there was a debate between Steve Johnson from Bell Labs, who was supporting C, and one of our people, Bill Harrison, who was working on a project that I had at that time supporting automatic optimization...The nubbin of the debate was Steve's defense of not having to build optimizers anymore because the programmer would take care of it. That it was really a programmer's issue.... Seibel: Do you think C is a reasonable language if they had restricted its use to operating-system kernels? Allen: Oh, yeah. That would have been fine. And, in fact, you need to have something like that, something where experts can really fine-tune without big bottlenecks because those are key problems to solve. By 1960, we had a long list of amazing languages: Lisp, APL, Fortran, COBOL, Algol 60. These are higher-level than C. We have seriously regressed, since C developed. C has destroyed our ability to advance the state of the art in automatic optimization, automatic parallelization, automatic mapping of a high-level language to the machine. This is one of the reasons compilers are ... basically not taught much anymore in the colleges and universities."
-- Fran Allen interview, Excerpted from: Peter Seibel. Coders at Work: Reflections on the Craft of Programming
C's victory is more related to not having anything else as compiled language in the box than anything else regarding its marvelous technical capabilities, so worse is better approach, use C.
Even more so, when Sun started the trend that UNIX development tooling was paid extra, and it only contained C and C++ compilers, for additional compilers like Fortran and Ada, or IDE, it was even a bit more extra on top.
Which other UNIX vendors were quite fast to follow suit.
But I've seen that quote before (I think from you, even). I didn't believe it then, and I don't believe it now.
There is nothing about the existence of C that prevents people from doing research on the kind of problem that Fran Allen is talking about. Nothing! Those other languages still exist. The ideas still exist. The people who care about that kind of problem still exist. Go do your research; nobody's stopping you.
What actually happened is that the people who wanted to do the research (and/or pay for the research) dried up. C won hearts and minds; Fran Allen (and you) are lamenting that the side you preferred lost.
It's worth asking why, even if Ada or Algol or whatever were extra cost, why weren't they worth the extra cost? Why didn't everybody buy them and use them anyway, if they were that much better?
The fact is that people didn't think they were enough better to be worth it. Why not? People no longer thought that these automatic optimization research avenues were worth pursuing. Why not? Universities were teaching C, and C was free to them. But universities have enough money to pay for the other languages. But they didn't. Why not?
The answer can't be just that C was free and the other stuff cost. C won too thoroughly for that - especially if you claim that the other languages were better.
Universities are always fighting with budgets, some of them can't even afford to keep the library running with good enough up to date books.
I was twelve. C was free, the alternatives were not. By the time I could have paid for one, I’d been writing C for ten years…
Nowadays I wouldn’t touch it with a ten-foot stick.
Eh, sort of. The rise of C is partially wrapped up in the rise of general-purpose hardware, which eviscerates the demand for optimizers to take advantage of the special capabilities of hardware. An autovectorizer isn't interesting if there's no vector hardware to run it on.
But it's also the case that when Java became an important language, there was a renaissance in many advanced optimization and analysis techniques. For example, alias analysis works out to be trivial in C--either you obviously prove they don't alias based on quite local information, or your alias analysis (no matter how much you try to improve its sensitivity) gives up and conservatively puts it in the everything-must-alias pile; there isn't much a middle ground.
Like half the point of high-level systems languages is to be able to express the _effects_ of a program and let a compiler work out how to implement that efficiently (C++ famously calls this the as-if rule, where the compiler can do just about anything to optimise so long as it behaves in terms of observable effects as-if the optimisation hadn't been performed - C works the same). I don't think there's really any areas left from a language perspective where C is more capable than C++ or Rust at that. If the produced code must work in a very specific way then in all cases you'll need to drop into assembly.
The thing Rust really still lacks is maturity from being used in an embedded setting, and by that I mostly mean either toolchains for embedded targets being fiddly to use (or nonexistent) and some useful abstractions not existing for safe rust in those settings (but it's not like those exist in C to begin with).
If Rust doesn't also compile faster than C because of the better abstractions that should be considered just a sign of compilers needing more work in the optimize and not that Rust can't be faster. Writing optimizers is hard and takes a long time, so I'd expect Rust to be behind.
Note that the above is about real world benchmarks, and is unlikely to amount to 0.03% difference in speed - it takes very special setups to measure these differences, while simple code changes can easially but several hundred percentage differences. Common microbenchmarks generally are not large enough for the type system to make a difference and so often show C as #1 even though in real world problems it isn't.