[MaxBarraclough]

Right, I hadn't meant to imply Zig is free of UB. It aims to improve on C's wild-west UB rules not by having no UB, but by having only a manageable dose of it, and supporting good optional runtime checks.

Zig's approach is essentially that of Ada. You can ask the Ada compiler for runtime checks, or promise the compiler that your code is free of undefined behaviour and have your code run at the speed of light (C), or go haywire if you got it wrong. Sadly C is less suited to runtime checks, arrays are dealt with through raw pointers so range checks aren't easy for the compiler to add automatically. You can though ask GCC to generate checks (trap-on-failure) for things like dereferencing NULL, or signed arithmetic overflow.