[dathinab]

It's kinda the same in C/C++ as far as I can tell.

They use the same backend in LLVM/GCC and the code gen options aren't even that different mainly that rust uses the noalias attribute a lot.

> C/C++ in which you can sort of infer the consequences of UB on a single platform with enough experience.

UB in C/C++ allows the compiler to arbitrary rewrite your code, and it sometimes does so. All depending on compiler version, enabled compiler flags, optimization level and "seemingly arbitrary" factors (i.e. some optimization passes detect or fail to detect optimizations sometimes for quite surprised reasons).

So I don't think you can "sort of infer the consequences" on a single platform in practice. (Maybe in with optimizations disabled, but even then it can be tricky.)

[steveklabnik]

There are similarities but also significant differences. Safe Rust has no UB, and so this appears less often in general. There’s also just straight up different semantics; famously there was an i soundness bug in safe Rust because a loop with no side effects is defined behavior in Rust (you get an infinite loop) and UB in C++ (the compiler can elide it). LLVM added a new syntax to handle this specific case, eliminating the UB in other languages. But this kind of thing does happen.