Is RAX_ITER_SAFE actually used?

I'm making a perl binding to rax (very unfinished, but https://github.com/dylanwh/Rax)
and I'm wondering why I don't see RAX_ITER_SAFE mentioned outside the headers.

I'm wondering if RAX_ITER_SAFE is really used? 
Assuming it is, I guess I need to make that the default when I allocate iterators.