IMHO Rust could be a good replacement for C when (if) it gets an actual spec, or at least when (if) there are multiple real implementations of the compiler (meaning, with borrow checker, compiler errors, and all).
Because otherwise, you could write Rust 2018 edition (for example), and there's nothing preventing a situation where your currently-valid Rust-2018-edition program stops compiling (or behaves differently) on a future version of rustc even when compiling to that specific edition, just because some behavior is (in the future) considered a compiler bug or something. And it would be perfectly valid to cause such breakage, because there's no definition of "what is Rust", other than "what this specific compiler in this specific version accepts".
I'm not talking about whether such possible backwards-incompatible change on a Rust edition would be good or bad. Just that with the current monoculture around a single implementation, there's not many guarantees.
A specification, or multiple implementations, would at least add some (good) friction.
I'm not denying its current value as a safe language; just that, as it is now, I don't consider it as a good choice for programs that must stay alive for decades, like `curl` or an operating system.
Because otherwise, you could write Rust 2018 edition (for example), and there's nothing preventing a situation where your currently-valid Rust-2018-edition program stops compiling (or behaves differently) on a future version of rustc even when compiling to that specific edition, just because some behavior is (in the future) considered a compiler bug or something. And it would be perfectly valid to cause such breakage, because there's no definition of "what is Rust", other than "what this specific compiler in this specific version accepts".
I'm not talking about whether such possible backwards-incompatible change on a Rust edition would be good or bad. Just that with the current monoculture around a single implementation, there's not many guarantees.
A specification, or multiple implementations, would at least add some (good) friction.
I'm not denying its current value as a safe language; just that, as it is now, I don't consider it as a good choice for programs that must stay alive for decades, like `curl` or an operating system.