this post was submitted on 21 Oct 2024
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Programming
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I'm a bit skeptical that a borrow checker in C++ can be as powerful as in rust, since C++ doesn't have lifetime annotations. Without lifetime annotations, you have to do a whole program analysis to get the equivalent checks which isn't even possible if you're e.g. loading dynamic libraries, and prohibitively slow otherwise. Without that you can only really do local analysis which is of course good but not that powerful.
Lifetime annotations in the type system is the right call, since it allows library authors to impose invariants related to ownership on their consumers. I doubt C++ will add it to their typesystem though.
Read the proposal: Lifetimes annotations, the rust standard library (incl. basic types like Vec, ARc, ...), first class tuples, pattern matching, destructive moves, unsafe, it is all in there.
The proposal is really to bolt on Rust to the side of C++, with all the compatibility problems that brings by necessity.
Ah ok just read the article and not the proposal. I'm surprised that they went that far but as I wrote I think that lifetime annotations are a good idea, hope the C++ people find a way to add them to the language that actually works well, which sounds like an incredibly difficult task.
"They" did not go anywhere yet. This is a proposal, nothing more. It will take serious discussions over years to get this into C++.
Prominent figures already said they prefer safety profiles as a less intrusive and more C++ approach at conferences It will be fun to watch this and the other safety proposals going forward.