[9rx]

So does Rust. Rust is 'smarter' than Limbo, in that it can avoid using its GC in a lot of cases (but not all, hence why it still has GC to fall back on when necessary), but, I mean, that discovery was the reason for why Rust was created. Limbo was already there otherwise. Every new language needs to try to add something into the mix.

Still, the thoughts were in common, even though the final solution didn't end up being exactly the same.

[arghwhat]

Rust does not have a garbage collector in any way or form. It's just automatic memory like we're used to (e.g., stack in C++), with the compiler injecting free/drop when an object goes out of scope.

What Rust brings is ownership with very extensive lifecycle tracking, but that is a guard rail that gives compile-time failures, not something that powers memory management.

(If you consider the presence of Rc<T> to make Rust garbage collected, then so is C garbage collected as developers often add refcounting to their structs.)

[9rx]

> so is C garbage collected as developers often add refcounting to their structs.

Absolutely, C also can use a garbage collector. Obviously you can make any programming language do whatever you want if you are willing to implement the necessary pieces. That isn't any kind of revelation. It is all just 1s and 0s in the end. C, however, does not come with an expectation of it being provided. For all practical purposes you are going to have to implement it yourself or use some kind of third-party solution.

The difference with Limbo and Rust is that they include reference counting GCs out of the box. It is not just something you have the option of bolting onto the side if you are willing to put in the effort. It is something that is already there to use from day one.

[arghwhat]

> Absolutely, C also can use a garbage collector.

It is not C using the garbage collector - it is you writing a garbage collector in C. The application or library code you develop with the language is not itself a feature of the language, and the language you wrote the code in is not considered to be "using" your code.

Rust and C are unaware of any type of garbage collection, and therefore never "use" garbage collection. They just have all the bells and whistles to allow you to reference count whatever type you'd like, and in case of Rust there's just a convenient wrapper in the standard library to save you from writing a few lines of code. However, this wrapper is entirely "bolted onto the side": You can write your own Rc<T>, and there would be no notable difference to the std version.

So no, neither Rust nor C can use a garbage collector, but you can write code with garbage collection in any feature-complete language. This is importantly very different from languages that have garbage collection as a feature, like Limbo, Go, JavaScript, etc.

[9rx]

> it is you writing a garbage collector in C.

That's right, you can write a garbage collector in C for C to use. You can also write a garbage collector in C for Javascript to use, you could even write a garbage collector in C for Rust to use, but in this case we are talking about garbage collector for C to use.

If you are writing a garbage collector that will not be used, why bother?

[arghwhat]

This feels like it's into trolling, so one last round:

The C language does not use your C code, it is your C code that uses the C language.

The tools available to C is what the language specification dictated and what the compiler implemented. For example, C might use stack memory and related CPU instructions, because the C specification described "automatic memory" and the compiler implemented it with the CPU's stack functionality. It might insert calls to "memcpy" as this function is part of the C language spec. For C++, the compiler will insert calls to constructors and destructors as the language specified them.

The C language does not specify a garbage collector so it can never use one.

You, however, can use C to write a garbage collector to manually use in your C code. C remains entirely unaware of the garbage collectors existence as it has no idea what the code you write does - it will never call it on its own and the compiler will never make any decisions based on its existence. From C's perspective, it's still just memory managed manually by your application with your logic.

In JavaScript and Go, the language specifies the presence of garbage collection and how that should work, and so any runtime is required to implement it accordingly. You can write that runtime in C, but the C code and C compiler will still not be garbage collected.

[zozbot234]

The C standard is actually carefully written to allow for placing distinct "objects" in separate memory segments of a non-flat address space, such that ordinary pointer arithmetic cannot be expected to reach across to a separate "object". This is not far from allowing for some sort of GC as part of low-level C implementation, and in fact the modern Fil-C relies on it.

[9rx]

> The C language does not use your C code

Your impression that there is a semantic authority misses the mark. While you are free to use English as you see fit, so too is everyone else. We already agreed on the intent of the message, so when I say something like "C uses C code", it absolutely does, even if you wouldn't say it that way yourself. I could be alone in this usage and it would remain valid. Only intent is significant.

However, I am clearly not alone in that style of usage. I read things like "Rust can use code written in C" on here and in other developer venues all the time. Nobody ever appears confused by such a statement even. If Rust can use code written in C, why can't C use code written in C?

> The C language does not specify a garbage collector so it can never use one.

The C language also does not specify a linked list. Go tell your developer friends that C can never use a linked list. Please take a photo when they look at you like you have two heads. Admittedly I lack the ability to say something so outlandish to another human with a straight face, but for the sake of science I put that into an LLM. It called me out on the bullshit, pointing out that C can, in fact, use a linked list.

For what it is worth, I also put "C can never use a garbage collector" into an LLM. It also called me out on that bullshit just the same. LLMs are really good at figuring out how humans generally use terminology. It is inherit to how they are trained. If an LLM is making that connection, so too would many humans.

> In JavaScript and Go, the language specifies the presence of garbage collection

The Go language spec does, no doubt as a result of Pike's experience with Alef. The JavaScript spec[1] does not. Assuming you aren't making things up, I am afraid your intent was lost. What were you actually trying to say?

> C code and C compiler will still not be garbage collected.

That depends. GC use isn't typical in the C ecosystem, granted, but you absolutely can use garbage collection in a C program. You can even use something like the CCured compiler to have GC added automatically. The world is your oyster. There is no way you couldn't have already realized that, though, especially since we already went over it earlier. It is apparent that your intent wasn't successfully transferred again. What are you actually trying to say here?

> This is turning into trolling.

The mightiest tree in the forest could be cut down with that red herring!

[1] The standard calls itself ECMAScript, but I believe your intent here is understood.

[pjmlp]

No it doesn't, it uses affine types.

Also the first language to use that idea was Cyclone, a research language at Bell Labs with the goal to replace C.

[maleldil]

Are you trying to say that Rc/Arc are GCs? I guess you're technically correct, but no one sees it that way.

[9rx]

I would say that RC is GC, yes, as it is most definitely technically true. But it was pjmlp who suggested it originally (Limbo also uses reference counting), so we have clear evidence that others also see reference counting as being GC. We wouldn't have a discussion here otherwise.

[pjmlp]

While RC is a GC algorithm, chapter 5 from GC handbook, it doesn't count when it isn't part of the type system because then it becomes optional and not part of the regular use of the programming language.

Additionally Limbo's GC is a bit more complicaticated than a plain add_ref()/release() pair of library calls.

https://doc.cat-v.org/inferno/concurrent_gc/concurrent_gc.pd...

[9rx]

> because then it becomes optional

Exactly. Optional implies use. So, in case you forgot to read the thread, both Limbo and Rust use GC.