alt Hacker NewsYou probably misunderstood. C can represent any program's semantics, since it's Turing-complete (modulo finite memory). C can't encode the lifetimes Rust uses, but those get erased during compilation to MIR. This takes MIR from rustc (where borrow checking has been completed and lifetime annotations erased) and outputs C with the same semantics. LLVM doesn't use tokens not produceable by C, but rustc does.
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Grikbdl • last Sunday at 4:18 PM
I think it's a reference to certain optimizations possible due to aliasing rules in Rust that are not possible (or maybe only "not straight forward", I'm not sure) in C. So a transpiled program while keeping its semantics might not still compile to equally optimized assembly.
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C still has lifetime rules. It just has no syntax for them. What people are bitten with is that they violate the lifetime rules, but their compiler doesn't tell them.