Programming

On one hand, I'm pleased that C++ is answering the call for what I'll call "safety as default", since as The Register and everyone else since pointed out, if safety constructs are "bolted on" like an afterthought, then of course it's not going to have very high adoption. Contrast this to Rust and its "unsafe" keyword that marks all the places where the minimum safety of the language might not hold.

On the other hand, while this Safe C++ proposal adopts a similar notion of an "unsafe" context, it also adds a "safe" keyword, to specify that a function will conform to compile-time safety checks. But as the proposal readily admits:

Rust’s functions are safe by default. C++’s are unsafe by default.

While the proposal will surely continue to evolve before being implemented, I forsee a similar situation as in C where code that lacked initial const-correctness will struggle to work with newer code and libraries. In this case, it would be the "unsafe" keyword that proliferates everywhere just to call older, unsafe code from newer, safe callers.

Rust has the advantage that there isn't much/any legacy Rust to upkeep, and that means the volume of unsafe code in Rust proframs is minimal, making them safer overall today. But for Safe C++ code, there's going to be a lot of unsafe legacy C++ code and that reduces the safety benefit for programs overall, for the time being

Even as this proposal progresses, the question of whether to start rewriting some code anew in Rust remains relevant. But this is still exciting as a new option to raise the bar in memory safety in C++.