[eddyb]

Some of that is sadly C having bad defaults - like people ending up using signed 32-bit integers (i.e. `int`) to index arrays on 64-bit platforms, which keeps signed integer overflow UB relevant, for optimizing typical indexing C code.

Both C++ and Rust use pointer ranges for iteration, and Rust even forces indexing/counting to use pointer-sized unsigned integers. So Rust turned off the LLVM bit which says "signed overflow is UB" and did not really lose much from it (AFAIK, anyway).