You may be focusing too closely on the C aspect; the point of the demonstration in the OP is to show that Lunatic can gracefully sandbox and interoperate with any code that can be compiled to WASM, of which C code is just one example. Ideally you wouldn't need to access any OS libs from within the sandbox (indeed, much of the point of the sandbox is to provide alternatives to OS facilities), and even if you did you could still access those libs in an un-sandboxed form from within your ordinary Rust code (and yes, crashing at that point would take down the process, but it's still strictly better to have an option to run C code that doesn't take down the process when crashing).