I’m not really sure how checks like this can rival rust. Rust does an awful lot of checks at compile time - sometimes even to the point of forcing the developer to restructure their code or add special annotations just to help the compiler prove safety. You can’t trivially reproduce those all those guardrails at runtime. Certainly not without a large performance hit. Even debug mode stdc++ - with all checks enabled - still doesn’t protect against many bugs the rust compiler can find and prevent.
I’m all for C++ making these changes. For a lot of people, adding a bit of safety to the language they’re going to use anyway is a big win. But in general guarding against threading bugs, or use after free, or a lot of more obscure memory issues requires either expensive GC like runtime checks (Fil-C has 0.5x-4x performance overhead and a large memory overhead). Or compile time checks. And C++ will never get rust’s extensive compile time checks.
It could have gotten them, had the Safe C++ proposal not been shot down by the profiles folks, those profiles that are still vapourware as C++26 gets finalised.
Google just did a talk at LLVM US 2025, regarding the state of clang lifetime analyser, the TL;DW is we're still quite far from the profiles dream.
They rival Rust in the same way that golang and zig do: they handle more and more memory-safety bugs to the point that the delta to Rust’s additional memory-safety benefits doesn’t justify the cost of using Rust any more.
Zig does not approach, and does not claim to approach, Rust's level of safety. These are completely different ballparks, and Zig would have to pivot monumentally for that to happen. Zig's selling point is about being a lean-and-mean C competitor, not a Rust replacement.
Golang is a different thing altogether (garbage collected), but they still somehow managed to have safety issues.
I’m all for C++ making these changes. For a lot of people, adding a bit of safety to the language they’re going to use anyway is a big win. But in general guarding against threading bugs, or use after free, or a lot of more obscure memory issues requires either expensive GC like runtime checks (Fil-C has 0.5x-4x performance overhead and a large memory overhead). Or compile time checks. And C++ will never get rust’s extensive compile time checks.