Okay, so I'm having one problem with nim. Disabling all unsigned arithmetic by-default. The logic is actually fairly sound (it's probably, generally, harder to overflow a signed than an unsigned), but nim doesn't compile to object code; it transpiles to C and then C compiles to object/machine code.

Edit: it's obviously much harder to overflow an unsigned than a signed; in the sentence above, I was thinking particularly of underflow (which is what the nim devs reference as their logic for disabling unsigned arithmetic by-default).

The problem here is that unsigned arithmetic, though much easier to hit underflow, is fully defined in C where signed {under,over}flow is UB. As a result, if you manage to hit this case in nim, you're now going to hit UB by-default. This seems crazy to me. Am I missing something?