I meant the synthetic memory arena, the JS array that malloc() and free() manage. That certainly could contain JS references and needs to be examined by the GC.

I don't think you can actually avoid GC by avoiding JS object allocations. Any form of string manipulation, any form of IO (event handling, DOM manipulation, XHR), any use of timers, etc, is going to allocate objects, right? Also, the JS runtime could generate garbage internally. For example, since JS has closures, it wouldn't be totally unreasonable for the runtime to manage the lifetime of activation records (JS stack frames) using the GC.