What exactly does the author mean when they say that unsafe Rust has "no meaningful semantics"? Is this a term of art in language analysis or is the author just saying "it's weird"?
> The precise Rust aliasing rules are somewhat in flux, but the main points are not contentious
I've sometimes found myself in situations where the only way I've been able to deal with this is to check the compiler's output and trawl forums for hints by Rust's developers about what they think/hope the semantics are/will be.
Historically speaking, this situation isn't uncommon: working out exactly what a language's semantics should be is hard, particularly when it has many novel aspects. Most major languages go through this sort of sequence. Some sooner or later than others --- and some end up addressing it more thoroughly than others). Eventually I expect Rust to develop something similar to the modern C spec, but we're not there yet.
> It’s important to understand that unsafe doesn’t turn off the borrow checker or disable any other of Rust’s safety checks: if you use a reference in unsafe code, it will still be checked. The unsafe keyword only gives you access to these five features that are then not checked by the compiler for memory safety.
Fully defined rust or not, unsafe code blocks definitely do not have fewer guarantees than C.