This PR is based on @erlend-aasland's PR #101948. Changes:

• Don't convert static types to heap types: it will be done on a separated PR
• _io_StringIO___init___impl() only calls find_io_state_by_def() once
• _io__WindowsConsoleIO___init___impl() doesn't declare a variable which is only used by an assertion, to avoid the risk of getting a compiler warning. If the line is too long, I can make the declaration conditional on the NDEBUG macro.
• _io_FileIO_close_impl() and _io__WindowsConsoleIO_close_impl(): move variable declaration (minor coding style change).
• Don't add PyIOBase_Type since such change would have no point for now.

I copied the clinic_state() macros.

Add the defining class to methods: (...)

I was not sure that it works on static types... but it seems like it does :-) I didn't get any crash.

@corona10 @erlend-aasland: Would you mind to review it?

sure

Oh, the Windows change didn't go well:

0:20:02 load avg: 8.57 [317/463/2] test_winconsoleio crashed (Exit code 3) -- (...)
Assertion failed: mod != NULL, file D:\a\cpython\cpython\Modules\_io\_iomodule.h, line 192
Fatal Python error: Aborted

Current thread 0x000004a0 (most recent call first):
  File "D:\a\cpython\cpython\Lib\test\test_winconsoleio.py", line 104 in test_conin_conout_names
(...)

The failed assertion is:

assert(PyObject_TypeCheck(self, find_io_state_by_def(Py_TYPE(self))->PyWindowsConsoleIO_Type));

in _io__WindowsConsoleIO___init___impl(). The assertion fails because PyType_GetModuleByDef() returns NULL.

On static types, PyType_GetModuleByDef() always returns NULL, since the function reads PyHeapTypeObject.ht_module which only exists in heap types:

        if(!_PyType_HasFeature((PyTypeObject *)super, Py_TPFLAGS_HEAPTYPE)) {
            // Static types in the MRO need to be skipped
            continue;
        }

Using APIs to get the module state from a type works on heap types like _io.FileIO, but failed on _io.WindowsConsoleIO which remains a static type with my PR.

I fixed my PR by reverting changes related to WindowsConsoleIO: this type should be modified in a following PR.

I reverted changes related to PyWindowsConsoleIO_Type and _io._WindowsConsoleIO.close().

I prefer doing Windows only changes in separate PRs. Everytime I touch Windows stuff, something weird happen :)

Aha, now the CI pass. I would feel more comfortable with a review. @erlend-aasland: you can also review if you want, to check if i picked the right parts or tour code 😁

🤖 New build scheduled with the buildbot fleet by @corona10 for commit dfc1e9e 🤖

If you want to schedule another build, you need to add the 🔨 test-with-refleak-buildbots label again.

I was not sure that it works on static types... but it seems like it does :-) I didn't get any crash.

I missed something: Erlend already converted multiple _io types to heap types: see commit c00faf7. Types used in this PR are heap types, that's why it just works!

let's wait refleak bot

Thanks for running these jobs. I ran refleaks locally on test_io, but i don't trust myself 🤣 So having reliable buildbot checks sound safer.

I will merge my PR once the Refleaks jobs pass, unless someome wants me to wait for their second review.

No refleaks; good bot 🤖 ✅