Currently running mp_call_function_0 will never return until execution is finished. This usually isn't a big deal, except in two cases:

• First, when running in a callback-based environment such as Emscripten that needs to return every now and then, otherwise blocking the whole browser
• Second, if you need to implement "input()" on top of a callback-based API

It would be very nice to allow "mp_call_function_0" to actually return and then resume execution later on. If I understand things correctly this should be made possible/easier thanks to MICROPY_STACKLESS_STRICT.