>signed integer overflow being UB would count for C/C++

Then, I raise you to Zig which has unsigned integer overflow being UB.

Interestingly enough, Zig does not use the same terminology as C/C++/Rust do here. Zig has "illegal behavior," which is either "safety checked" or "unchecked." Unchecked illegal behavior is like undefined behavior. Compiler flags and in-source annotations can change the semantics from checked to unchecked or vice versa.

Anyway that's a long way of saying that you're right, integer overflow is illegal behavior, I just think it's interesting.

Rust has UB overflow as well, just unsafe.

https://doc.rust-lang.org/std/intrinsics/fn.unchecked_add.ht...