Even if C++ is irrelevant for new code, there's so much software already written in it that we'll be maintaining it for decades to come. I'd argue that Cobol and Fortran have been mostly obsolete for new code for almost 30 years now, yet both are still widely used today, and they've even had major updates in the past decade [0] [1]. And there's even more software written in C++ than there is in Cobol or Fortran, so I don't think that C++ is going away any time soon.

[0]: https://en.wikipedia.org/wiki/COBOL#COBOL_2023

[1]: https://en.wikipedia.org/wiki/Fortran#Fortran_2023

Essentially all high-end systems code for high-performance and high-reliability systems is still written in modern C++. That language has many attractive properties, including safety features that Rust does not currently support.

Additionally, for pure performance requirements, C++ is still materially faster than Rust in practice. That may change some day. C++ has many issues but it is also objectively excellent at many things.

C++ is the third most popular programming language according to TIOBE behind C and python. It's got an 8.87% ranking. So yes it looks like C++ is still relevant. In fact C++ usage has risen slightly.

Rust is in tenth place with 1.44% ranking, it's rising fast but still has a long way to go before it catches C++.

I'm not going to speculate about why Rust hasn't yet supplanted C++ but I will say I don't find it surprising.

> Is C++ still relevant? What prevents Rust from completely supplanting it?

A highly mature ecosystem with well-established libraries. Especially in certain fields (DSP, robotics, CAD kernels, microcontrollers, etc.), there are no equivalent libraries and frameworks in Rust with such a proven track record.

Now, LLMs can rewrite those libraries in Rust quite easily. Such options weren't available a few years back. But it's still hard to prove that a rewrite hasn't introduced new bugs. It's easy to demonstrate that a piece of code has bugs, but much harder to prove that it doesn't introduce any new ones.

99.9% of all system code in the world is still written in C/++. It runs your Java, C#, Javascript, Python, PHP, basically every production language that isn't Go or Rust. It runs the two most popular game engines in the world. It runs your phone, server, and laptop, no matter which of any you use. It runs your car. It runs almost every embedded and industrial application on the planet.

Is it still relevant, JFC. The way people on this forum manage to sequester themselves from reality. Let me reverse the question: is Rust relevant? Mozilla developed Rust, abandoned their Rust browser, and only 10% of Firefox is written in Rust. Maybe 1% of modules in Chrome and Linux are written in Rust, if that. And what of Rust applications written from scratch? Can you name ten applications that have, say, exposure to more than 100,000 users? Impossible mode: they can't be developer tools only used by other developers (uv, ripgrep, etc.), they must actually be applications used by enterprises or consumers.

Your Rust very likely runs in a C / C++ environment.

rust depends on C++ (LLVM)