gh-71587: Drop local reference cache to _strptime module in _datetime

[neonene]

For 3.13 and newer, this PR fixes the following errors by making each loaded _datetime module use its own reference cache to _strptime module. The cache will be the same as the reference in sys.modules of the corresponding interpreter by importing _strptime module on each strptime() function call.

Main interpreter:

>_testembed_d test_repeated_init_exec "import datetime; datetime.datetime.strptime('200001', '%Y%m')"
--- Loop #1 ---
--- Loop #2 ---
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: 'NoneType' object is not callable

Sub interpreter:

>>> import _interpreters
>>> for i in range(1,3):
...     print('Sub Loop', i)
...     interp = _interpreters.create()
...     s = "import datetime; datetime.datetime.strptime('200001', '%Y%m')"
...     _interpreters.run_string(interp, s)
...     _interpreters.destroy(interp)
...
Sub Loop 1
Sub Loop 2
Assertion failed: PyUnicode_CheckExact(ep_key), file C:\cp\Objects\dictobject.c, line 1126

cc @ericsnowcurrently @erlend-aasland

• Issue: Datetime NoneType after calling Py_Finalize and Py_Initialize #71587
• Issue: datetime_strptime is 'NoneType' when restart cpython #117914
• Issue: Isolate the _datetime extension module #117398

[kumaraditya303]

LGTM

[neonene]

@kumaraditya303 Thanks for the review.

@ericsnowcurrently Maybe off-topic now, but is it possible to access the module state through a static type like:

// pycore_typeobject.h

typedef struct {
    PyTypeObject *type;
    int isbuiltin;
    ....
+   PyObject *current_ext_module  // weak ref? or borrowed ref?
} managed_static_type_state;

Then, get_current_module(&PyDateTime_DateType, &reloading) in _datetimemodule.c?

[ericsnowcurrently]

@ericsnowcurrently Maybe off-topic now, but is it possible to access the module state through a static type like:

// pycore_typeobject.h

typedef struct {
    PyTypeObject *type;
    int isbuiltin;
    ....
+   PyObject *current_ext_module  // weak ref? or borrowed ref?
} managed_static_type_state;

Then, get_current_module(&PyDateTime_DateType, &reloading) in _datetimemodule.c?

That definitely could work. It's worth looking into for 3.14.

[ericsnowcurrently]

LGTM

[ericsnowcurrently]

This should be backported to 3.13, right?

[neonene]

I agree to the 3.13 backport.

[miss-islington-app]

Thanks @neonene for the PR, and @ericsnowcurrently for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[bedevere-app]

GH-120424 is a backport of this pull request to the 3.13 branch.

[ericsnowcurrently]

I just realized this fixes a long-standing problem and is not related to the recent work on _datetime. I'm guessing it would make sense to backport this to 3.12. (It's too late for 3.11.)

[miss-islington-app]

Thanks @neonene for the PR, and @ericsnowcurrently for merging it 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @neonene and @ericsnowcurrently, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 127c1d2771749853e287632c086b6054212bf12a 3.12

[ericsnowcurrently]

@neonene, would you have time to do the 3.12 backport? I'm sure it won't require much effort.

[bedevere-app]

GH-120431 is a backport of this pull request to the 3.12 branch.

[neonene]

Thanks @ericsnowcurrently, @erlend-aasland for reviewing this, and thanks again @kumaraditya303.