Calling C-API inside with_gil

[taegyunkim]

What would happen if I call a CPython C API within with_gil and that releases the GIL?
I believe it is possible to do that from a C native extension module, and that results in releasing the GIL, but when it returns back to the C native extension, the GIL will be held again.
Would the same happen with PyO3? or is this illegal or an error?

[mejrs]

That's fine, any such api that release the gil will ensure to reacquire it before returning. See https://docs.python.org/3/c-api/init.html#releasing-the-gil-from-extension-code for more information.