My main problem with Fil-C is that it combines the worst parts of C with the worst parts of a GC language.

In a language like C (or Zig), you need to manually manage memory. This makes programming a lot more complex, and it's really easy to accidentally mess up. Especially in large projects which have a lot of separate modules.

The biggest advantage of using a garbage collector is that you don't have to think about freeing memory. The GC automatically frees objects when they're no longer referenced. This makes programming much much easier. The downside of using a garbage collector is that it hurts performance at runtime. GC languages are slower and use more RAM.

Fil-C is the worst of all worlds here. Like C, it forces you to manually manage your own memory. But you still pay the performance cost of having a runtime garbage collector. And that cost is (apparently) really high. The only performance numbers I've seen showed ~2x worse CPU performance and ~4x worse memory performance. There's no way Fil-C can compete with C, Zig and Rust for performance.

So with Fil-C, you have a language that's much slower than C, and much more difficult to program in than C#, Java, Go or Typescript.

Fil-C still has some wonderful uses. Fil-C could be a fabulous debugging tool for C programs. It could be a wonderful teaching tool if it had nice visualisations on top of the GC's view of the world. And it could be a great way to run legacy C code.

But it's not a "rust killer". Fil-C programs run too slowly to be able to compete head to head with rust. And Fil-C doesn't offer the language benefits of a GC that you get in C#, Go, and friends. It seems like a really bad deal.

I'll come back and say some more in a bit, but in short: I like the idea of fil-c, but I also have some issues. I think it's overall a good and interesting project, but with some caveats.

Not OP, but AFAIK one big issue with FIL-C it does the checks at runtime, adding overhead, don't quote me on this, but IIRC is around 20% slower.

Okay so: in general, as a rule of thumb: anything that makes stuff have more memory safety is good. And experiments towards that end are also good.

What I do not like, primarily comes down to how the project is talked about and marketed. First, because it promotes an "us vs them" mindset, instead of a "we're all trying to improve memory safety" mindset, and second, because in doing so, it also overstates its case.

These things are sort of intertwined. Let's talk about the overstatement first. Fil-c has its own definition of memory safety that is slightly different than others. For example, I saw this recently:

    #include <stdlib.h>
    #include <stdio.h>
    #include <string.h>
    
    struct User {
        char name[8];
        int is_root;
    };
    
    int main(int argc, char*argv[]) {
        struct User* user = malloc(sizeof(struct User));
        strcpy(user->name, argv[1]);
        if (user->is_root) {
            printf("I am root!\n");
        } else {
            printf("I am not root :(\n");
        }
        return 0;
    }

But beyond corners like this, fil-c's author will go on about "Rust has unsafe as a hatch, fil-c does not" while if you control-f for "zunsafe_" on https://fil-c.org/stdfil you get ... escape hatches.

The author regularly erases the difference between "traps at runtime" and "is prevented at compile time", which are legitimate tradeoffs where one or the other may be better depending on what you're doing. But they're presented as either equivalent, or one is superior, and I find this muddles the discourse. The performance issues also tie into this, "add a GC" is absolutely a valid way to handle these sorts of issues, but it is not the same thing as what Rust does. And that's okay! But presenting it as purely superior means that it's just hard to talk about.

Speaking of muddling the discourse, the author regularly trolls on X, providing tons of bad faith arguments and generally trying to rile up a "fil-c vs Rust" war that I think reduces our ability to talk about these differences in a calm, engineering focused context.

Finally, due to its design, fil-c is effectively Linux only. That's great for Linux, but many people also use other systems, and so it is not a meaningful option for them.

Anyway, after saying all that: I still think that it is a good project, and that it should exist and continue to be worked on. I just wish that the heat was turned down, and people could talk about the various approaches and their tradeoffs without turning it into a culture war.