I am happily running Rust generated code on my ARM microcontrollers. Rust uses LLVM for code generation and can support any architecture which LLVM supports.

> When Rust supports a dozen architectures

"Rust now available on 14 Debian architectures" https://lists.debian.org/debian-devel-announce/2018/11/msg00...

There are plenty of system languages with a very tiny percentage of UB vs all the languages that allow for copy-paste of C code.

Because they prefer to loose a couple of ms to paying the price of the ultimate performance might bring.

Like in real life you can speed at 300 KMH with a 1200cc motorbike, or doing it a car with reinforced structure wearing seatbelts and airbags.

Even with diminished chances of survival, I rather be in the car.

UB is an implementation issue, not a language issue. UB is a fact of life that cannot be removed by overspecifying a language -- if your language spec has too much implementation-specific stuff in it, then compiler writers will simply ignore it. Many such examples. The best you can do is to document the implementation-specific stuff extensively.

Also, implementation-specific details aren't always about maximizing performance. Compilers implement languages slightly differently because of architecture and OS differences and because it's easier that way for the people writing compilers.

UB is not implementation specific at all, the ISO documentation is quite clear about which is which.

Other systems languages manage to do it quite well.

It was really a shame that Bell Labs gave UNIX away for a symbolic price during 10 years before being allowed to actually sell it.

We wouldn't be having this kind of C related talks.

> Rust has no undefined behavior because it only supports one CPU ...

That is not true. Rust works on multiple architectures.

There's a massive chasm between "works on" and "supports".

That doesn't seem relevant -- Rust works on and supports multiple architectures. And there's plenty of UB in unsafe code.