Overflow checks

I'm not sure I understand - where in _jswrap_interface_setTimeoutOrInterval do you see a problem?

And where is the issue in jsvObjectSetChildAndUnLock and how can it get an overflow? Maybe you can point me to the bit of code that's a problem.

Realistically in Espruino arrays of JsVars are extremely rare and it's pretty easy to see that everything is in range, so I wouldn't bother with overflow checking.

What is important is checking your locks/unlocks all match but there's no real way to check that short of running your code and checking for memory leaks