CloudFlare remade their primary reverse proxy in Rust and had so few development issues, they ended up finding kernel bugs instead when problems arose. I've worked on projects with non-trivial C++ codebases for a variety of companies, large and small, and with some excellent developers who are far more skilled than I likely will ever be.

https://blog.cloudflare.com/how-we-built-pingora-the-proxy-t...

A non-trivial C++ codebase with that kind of track record is so rare as to be unheard of, though many can approach it with the various sanitizers plugged into the dev workflow after the fact.

C++ has improved dramatically over the last fifteen years, but a lot of stuff simply can't be fixed without breaking backward compatibility, which just isn't going to happen.

We've had enough time elapse to see the related rates of CVEs posted for C++ and Rust apps over the last few years. It's not even close.

It is absolutely possible to have bugs in a Rust app due to logic error or memory leak. But C++ has those same limitations and so many more unless you tack on a host of add-on analysis tools and still you end up with a result that is not as safe as Rust.

Write a web app server in Rust? Sure. As long as I know the problem space, have the dev time allocated, and the need for that efficiency is clear.

Write it in C++? Hell no. Not ever again. Not in a million years. Even if the need for efficiency is demonstrated, I have far less confidence in the integrity of that service when connected to the public internet, no matter how skilled the team is.

Even Scott Meyers—Scott Fucking Meyers, who wrote acclaimed books on advanced use of C++ we mere mortals came to depend upon—does not have confidence in writing code for it anymore. In just three years, he went from an undisputed authority on the topic to this in 2018:

"As you may know, I retired from active involvement in C++ at the end of 2015, and in the ensuing two and a half years, I’ve forgotten enough details of the language that I am no longer able to properly evaluate bug reports regarding the technical aspects of my books. C++ is a large, intricate language with features that interact in complex and subtle ways, and I no longer trust myself to keep all the relevant facts in mind. As a result, all I can do is thank you for your bug report, because I no longer plan to update my books to incorporate technical corrections. Lacking the ability to fairly evaluate whether a bug report is valid, I think this is the only responsible course of action."

https://scottmeyers.blogspot.com/2018/09/the-errata-evaluati...

Neither I nor the folks I have worked with were as skilled as Scott Meyers at his prime, and the majority of us—myself especially—aren't even as good as he was 2.5 years after he stepped away.

Perhaps you are. Are you certain that everyone else on your team is? Everyone who comes later that has to maintain those codebases?

With Rust, I believe teams have a fighting chance. With C++, I'd just as soon buy lotto scratchers since I'm looking at similar odds. Perhaps I'm just an average software engineer. That's entirely possible, and I'll cop to that. But I'm not alone, and we still have bills to pay and code to write. For the sake of my clients, that'll be in Rust before C++ if I can help it. (And neither if the problem doesn't require their level of efficiency.)