inittab fails on `initfunc` which creates modules with `PyModule_FromSlotsAndSpec`

[davidhewitt]

Bug report

Bug description:

I am looking at updating PyO3 to use PyModule_FromSlotsAndSpec to initialize modules embedded in binaries using PyImport_AppendToInittab.

I can successfully create the module as part of the initfunc, however the loader then fails on the following check:

cpython/Python/importdl.c

Lines 506 to 512 in f5119a5

	res.def = _PyModule_GetDefOrNull(m);
	if (res.def == NULL) {
	PyErr_Clear();
	_Py_ext_module_loader_result_set_error(
	&res, _Py_ext_module_loader_result_ERR_MISSING_DEF);
	goto error;
	}

This check is guaranteed to fail, as modules created from slots do not have a PyModuleDef.

CPython versions tested on:

3.15

Operating systems tested on:

macOS

[davidhewitt]

After some discussion with @encukou, it sounds like we do not want to change initfunc to support slots, so I will close this issue.

The future support for slots in inittab probably comes from https://discuss.python.org/t/c-api-for-initializing-statically-linked-extension-modules/43396/36

[encukou]

The current workaround is returning a PyModuleDef, with values duplicated from the slots.

(limiting yourself to abi3t in an embedded module should be unnecessary; that's why inittab changes went out of scope.)