But the runtime cost of Fil-C means that - in most cases - your actual production application will be compiled with a standard C compiler. This applies not just to your code, but to all dependencies (due to ABI).
So I don’t see how Rust is at a huge disadvantage here when Fil-C is typically not going to be enforcing safety in production. I suppose the testing/fuzzing story becomes all the more important because you need to exercise runtime behavior for Fil-C to detect unsafe faults.
Don’t get me wrong: I think Fil-C is a smart idea and an excellent way to introduce memory safety to existing C codebases. But I don’t get this whole (usually implied) idea that Fil-C somehow makes Rust look bad or renders it obsolete.
I think it's not so much that Fil-C renders Rust completely useless, but rather it reduces the supposed validity and wild arguments to frivolously rewrite anything and everything in Rust.
The whole point of Fil-C is that it is fast enough to consider using in production for some applications while still guaranteeing memory safety. We already have ASAN and Valgrind and other tools for development purposes, that's not what Fil-C is targeting.
So Fil-C is competing with Go, C#, typescript and Python. If I’m writing a greenfield project where “bare metal” performance isn’t needed, why would anyone choose Fil-C over a more mature GC language?
C is more verbose and more error prone than Go and C#. It has worse tooling. It’s missing decades of language features. C isn’t properly cross platform. There’s no package manager. The “standard library” isn’t fully standard. It’s full of sharp edges and bad decisions.
I can imagine using Fil-C to run legacy code. But for new projects, it just seems worse in every way compared to Go, C#, typescript and friends. It’s worse, slow, and inconvenient.
Of the group of languages presented, your argument has more merit for Go. With C# and others, there is an additional OOP argument in there, that splits into different factions.
But what is being overlooked, is the massive numerical dominance of C programmers and projects, along with legacy and embedded code. There is going to be a preference for writing and using C, that could arguably fuel Fil-C for a very long time.
I am assuming that Fil-C introduces orders of magnitude less overhead than ASAN or Valgrind.
Also, it’s probably fast enough for apps to be deployed in something like a staging environment for integration tests to run against them. Production deploy/release can then happen using a tagged version that gets compiled using vanilla GCC/Clang.
I'm not sure about the speed of ASAN, it may be comparable but doesn't guarantee memory safety. It's only for catching mistakes and not secure against an adversary. Valgrind is dramatically slower.