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pizlonator • yesterday at 9:42 PM • 1 reply • view on HN

> Almost all uses of unsafe in Rust are either for FFI

Which makes Rust less safe than Fil-C.

Consider that you have a dependency like libc, PAM, openssl, or the like.

In Rust: you will `unsafe` call into the unsafe versions of those libraries. Hence, even if your Rust code is safe in isolation, your program is not safe overall because you're pulling in unsafe code.

In Fil-C: compile those dependencies with Fil-C, and then the whole process is safe.

Replies

josephg • yesterday at 10:19 PM

> In Fil-C: compile those dependencies with Fil-C, and then the whole process is safe.

Great work on Fil-C by the way. Very technically impressive stuff!

It seems like the competition for Fil-C is other garbage collected languages. Rust will always outperform Fil-C, with the caveat that rust allows unsafe blocks, raw pointers and raw C FFI. But if you’re happy to ditch performance and the ability to do bare metal systems level programming, why Fil-C over Go or C#?

If you want a safer, less convenient dialect of rust, that also exists. Just don’t use or depend on any unsafe code in your program. (There are 3rd party tools to check this). More and more C libraries are getting pure rust ports these days. It’s increasingly rare to actually need to pull in C libraries at all. Sticking to safe rust is a bit inconvenient - but I suspect so is using fil-c. I suppose with fil-C you can use any libraries you want, you’ve just gotta recompile them. That’s cool!

Rust has a bunch of unsafe code in std, so you’re still at risk of a bug there causing safety problems. But the same is true of Fil-C.

I could definitely see myself reaching for Fil-C when running legacy code. It’d be nice if there was a way to use fil-C to protect my rust program from memory bugs in C dependencies. But I can think of dozens of ways why that would be tricky to pull off.

Also I’m curious - can Fil-C protect against threading bugs like rust can? Rust has Send & Sync traits to mark which objects can be safely shared between threads. I can’t think of a way to do that in an automated way without help from the programmer.