See https://bugzilla.mozilla.org/show_bug.cgi?id=627107 and https://bugzilla.mozilla.org/show_bug.cgi?id=627097. IMO, we should find a way to make memory management in js-ctypes less error-prone and add more safety mechanisms to detect/prevent usages of memory via pointers to js-ctypes-rooted GC'd objects.
I have seen some misunderstanding of when to use "if (!item)" vs "item.isNull()" and when to use "item" vs "item.address()".