[pjmlp]

Ada, Modula-2 (both available on GCC), D (available on its reference implementation, GCC and LLVM), Swift, Object Pascal (Free Pascal, Delphi, Oxygen), Oberon variants (Oberon, Oberon-2, Oberon-07, Active Oberon, Component Pascal), Zig, Nim, Odin,...

[sebtron]

Zig definitely has undefined behavior

https://ziglang.org/documentation/0.13.0/#Undefined-Behavior

[pjmlp]

All systems programming languages have undefined behaviour, the golden question is how much.

Also it wasn't what the parent asked for, and I quote: "close to the hardware" language