Isolate the _io extension module #101819

cc. @kumaraditya303

I see that _PyWindowsConsoleIO_Type is marked with PyAPI_DATA, but I can't find it in Misc/stable_abi.toml. @zooba or @eryksun, do you know why this is so? I did a quick code search on GitHub, but I only got hits in various clones of the CPython code base.

UPDATE: I see it was added by Steve in 312cef7, probably because of the PyWindowsConsoleIO_Check checks in PC/_testconsole.c and Python/pylifecycle.c:

Perhaps exposing _PyWindowsConsoleIO_Type through a CPython internal capsulated C API could be an option?

Other issues that must be resolved before continuing: _PyBytesIOBuffer_Type is used by _testcapimodule. Since that type is not exposed in _io, we cannot simply use PyImport_Import and look it up. One possibility is to expose it through a CPython internal capsule C API.

... or we could simply expose the types mentioned in #101819 (comment) and #101819 (comment) in the _io module.

Internal types are allowed to be exported without being stable API. On Windows, only explicitly exported names are available outside the DLL - it's different on other platforms, so please don't bring their assumptions over 😉

The type is explicitly not part of the limited API/stable ABI, see #ifndef Py_LIMITED_API.

Internal types are allowed to be exported without being stable API. On Windows, only explicitly exported names are available outside the DLL - it's different on other platforms, so please don't bring their assumptions over 😉

IIUC, we can remove this from the DLL and instead export it via _io and look it up from the module using the C API (PyImport_Import, etc.).

Yeah, if it's got a leading underscore then we can do whatever we need to make our tests work.

@erlend-aasland erlend-aasland closed this as completed

Great achievement!

It causes a crash during garbage collection. See #111049, #111211.