It can be used via `PyArray_MapIterArray`, `PyArray_MapIterNext`, `PyArray_MapIterReset` (maybe) and `PyArray_MapIterSwapAxes`. It is used for `ufunc.at` and the `inplace_add` test in `multiarray_tests.c.src`. The fields that are used there, should be compatible, so unless someone is naughty enough to not use `PyArray_MapIterNext` to iterate, ABI compatibility should be there.