gh-117398: datetime: Make use of C-API capsules for sub-interpreters

Include/datetime.h

@@ -186,18 +186,31 @@ typedef struct {
 } PyDateTime_CAPI;
 
 #define PyDateTime_CAPSULE_NAME "datetime.datetime_CAPI"
-
+#define PyDateTime_INTERNAL_CAPSULE_NAME "datetime.datetime_CAPI_INTERNAL"
 
 /* This block is only used as part of the public API and should not be
  * included in _datetimemodule.c, which does not use the C API capsule.
  * See bpo-35081 for more details.
  * */
 #ifndef _PY_DATETIME_IMPL
-/* Define global variable for the C API and a macro for setting it. */
-static PyDateTime_CAPI *PyDateTimeAPI = NULL;
+static PyDateTime_CAPI *
+_PyDateTimeAPI_not_ready(void)
+{
+    return NULL;
+}
+static PyDateTime_CAPI *(*_PyDateTimeAPI_Get)(void) = _PyDateTimeAPI_not_ready;
+
+static inline void
+_PyDateTimeAPI_Import(void)
+{
+    void *(*func)(void) = PyCapsule_Import(PyDateTime_INTERNAL_CAPSULE_NAME, 0);
+    if (func) {
+        _PyDateTimeAPI_Get = func();
+    }
+}
 
-#define PyDateTime_IMPORT \
-    PyDateTimeAPI = (PyDateTime_CAPI *)PyCapsule_Import(PyDateTime_CAPSULE_NAME, 0)
+#define PyDateTimeAPI _PyDateTimeAPI_Get()
+#define PyDateTime_IMPORT _PyDateTimeAPI_Import()
 
 /* Macro for access to the UTC singleton */
 #define PyDateTime_TimeZone_UTC PyDateTimeAPI->TimeZone_UTC

Lib/test/datetimetester.py

@@ -91,7 +91,7 @@ def test_name_cleanup(self):
                     if not name.startswith('__') and not name.endswith('__'))
         allowed = set(['MAXYEAR', 'MINYEAR', 'date', 'datetime',
                        'datetime_CAPI', 'time', 'timedelta', 'timezone',
-                       'tzinfo', 'UTC', 'sys'])
+                       'tzinfo', 'UTC', 'sys', 'datetime_CAPI_INTERNAL'])
         self.assertEqual(names - allowed, set([]))
 
     def test_divide_and_round(self):

Lib/test/test_capi/test_misc.py

@@ -2282,6 +2282,23 @@ def test_module_state_shared_in_global(self):
         subinterp_attr_id = os.read(r, 100)
         self.assertEqual(main_attr_id, subinterp_attr_id)
 
+    @unittest.skipIf(_testmultiphase is None, "test requires _testmultiphase module")
+    def test_datetime_capi_client(self):
+        script = textwrap.dedent("""
+            import importlib.machinery
+            import importlib.util
+            fullname = '_test_datetime_capi_client'
+            origin = importlib.util.find_spec('_testmultiphase').origin
+            loader = importlib.machinery.ExtensionFileLoader(fullname, origin)
+            spec = importlib.util.spec_from_loader(fullname, loader)
+            module = importlib.util.module_from_spec(spec)
+            spec.loader.exec_module(module)
+        """)
+        exec(script)  # run main interp first
+        exec(script)  # run main interp twice
+        ret = support.run_in_subinterp(script)
+        self.assertEqual(ret, 0)
+
 
 @requires_subinterpreters
 class InterpreterConfigTests(unittest.TestCase):

Modules/_datetimemodule.c

@@ -63,6 +63,51 @@ static datetime_state _datetime_global_state;
 
 #define STATIC_STATE() (&_datetime_global_state)
 
+typedef struct {
+    PyInterpreterState *interp;
+    PyDateTime_CAPI *capi;
+} CAPI_Cache;
+
+static CAPI_Cache apicache[2];
+
+static inline void
+set_datetime_capi_by_interp(PyDateTime_CAPI *capi)
+{
+    PyInterpreterState *interp = PyInterpreterState_Get();
+    int i = interp == PyInterpreterState_Main() ? 0 : 1;
+    apicache[i].interp = interp;
+    apicache[i].capi = capi;
+}
+
+static PyDateTime_CAPI *
+_PyDateTimeAPI_Get(void)
+{
+    PyInterpreterState *interp = PyInterpreterState_Get();
+    for (int i = 0; i < 2; i++) {
+        if (apicache[i].interp == interp) {
+            return apicache[i].capi;
+        }
+    }
+    PyDateTime_CAPI *capi = PyCapsule_Import(PyDateTime_CAPSULE_NAME, 0);
+    if (capi) {
+        set_datetime_capi_by_interp(capi);
+    }
+    return capi;
+}
+
+static void *
+_PyDateTimeAPI_Import(void)
+{
+    PyDateTime_CAPI *capi = PyCapsule_Import(PyDateTime_CAPSULE_NAME, 0);
+    if (capi) {
+        // PyInit__datetime() is not called when the module is already loaded
+        // with single-phase init.
+        set_datetime_capi_by_interp(capi);
+        return _PyDateTimeAPI_Get;
+    }
+    return NULL;
+}
+
 /* We require that C int be at least 32 bits, and use int virtually
  * everywhere.  In just a few cases we use a temp long, where a Python
  * API returns a C long.  In such cases, we have to ensure that the
@@ -6944,6 +6989,20 @@ _datetime_exec(PyObject *module)
         goto error;
     }
 
+    capsule = PyCapsule_New(_PyDateTimeAPI_Import,
+                            PyDateTime_INTERNAL_CAPSULE_NAME, NULL);
+    if (capsule == NULL) {
+        PyMem_Free(capi);
+        goto error;
+    }
+    if (PyModule_Add(module, "datetime_CAPI_INTERNAL", capsule) < 0) {
+        PyMem_Free(capi);
+        goto error;
+    }
+
+    /* Ensure that the newest capi is used on multi-phase init */
+    set_datetime_capi_by_interp(capi);
+
     /* A 4-year cycle has an extra leap day over what we'd get from
      * pasting together 4 single years.
      */

Modules/_testmultiphase.c

@@ -969,3 +969,81 @@ PyInit__test_shared_gil_only(void)
 {
     return PyModuleDef_Init(&shared_gil_only_def);
 }
+
+
+#include "datetime.h"
+
+static int
+datetime_capi_import_with_error(void)
+{
+    static int is_datetime_multiphase = -1;
+    int ismain = PyInterpreterState_Get() == PyInterpreterState_Main();
+    if (ismain && is_datetime_multiphase < 0) {
+        PyObject *module = PyImport_ImportModule("_datetime");
+        if (module == NULL) {
+            return -1;
+        }
+        PyModuleDef *def = PyModule_GetDef(module);
+        Py_DECREF(module);
+        if (def && def->m_size >= 0) {
+            is_datetime_multiphase = 1;
+        }
+        else {
+            is_datetime_multiphase = 0;
+        }
+    }
+    if (is_datetime_multiphase < 0) {
+        PyErr_SetString(PyExc_AssertionError,
+                        "Main interpreter must be loaded first.");
+        return -1;
+    }
+
+    _PyDateTimeAPI_Import();
+    if (!PyErr_Occurred()) {
+        return 0;
+    }
+#ifdef Py_GIL_DISABLED
+    if (!ismain && !is_datetime_multiphase) {
+        // _datetime module and Capsule are not imported
+        PyErr_WriteUnraisable(NULL);
+        return 0;
+    }
+#endif
+    return -1;
+}
+
+static int
+datetime_capi_client_exec(PyObject *m)
+{
+    _PyDateTimeAPI_Get = _PyDateTimeAPI_not_ready;
+    if (_PyDateTimeAPI_Get() != NULL) {
+        PyErr_SetString(PyExc_AssertionError,
+                        "DateTime API is expected to remain NULL.");
+        return -1;
+    }
+    if (datetime_capi_import_with_error() < 0) {
+        return -1;
+    }
+    if (PyDateTimeAPI != PyCapsule_Import(PyDateTime_CAPSULE_NAME, 0)) {
+        PyErr_SetString(PyExc_AssertionError,
+                        "DateTime API does not match Capsule CAPI.");
+        return -1;
+    }
+    PyErr_Clear();
+    return 0;
+}
+
+static PyModuleDef_Slot datetime_capi_client_slots[] = {
+    {Py_mod_exec, datetime_capi_client_exec},
+    {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
+    {0, NULL},
+};
+
+static PyModuleDef datetime_capi_client_def = TEST_MODULE_DEF(
+    "_testmultiphase_datetime_capi_client", datetime_capi_client_slots, NULL);
+
+PyMODINIT_FUNC
+PyInit__test_datetime_capi_client(void)
+{
+    return PyModuleDef_Init(&datetime_capi_client_def);
+}

Tools/c-analyzer/cpython/globals-to-fix.tsv

@@ -450,7 +450,7 @@ Modules/_tkinter.c	-	trbInCmd	-
 ## initialized once
 
 ## other
-Include/datetime.h	-	PyDateTimeAPI	-
+Include/datetime.h	-	_PyDateTimeAPI_Get	-
 Modules/_ctypes/cfield.c	_ctypes_get_fielddesc	initialized	-
 Modules/_ctypes/malloc_closure.c	-	_pagesize	-
 Modules/_cursesmodule.c	-	initialised	-
@@ -468,6 +468,7 @@ Modules/readline.c	-	libedit_history_start	-
 Modules/_ctypes/cfield.c	-	formattable	-
 Modules/_ctypes/malloc_closure.c	-	free_list	-
 Modules/_curses_panel.c	-	lop	-
+Modules/_datetimemodule.c	-	apicache	-
 Modules/_ssl/debughelpers.c	_PySSL_keylog_callback	lock	-
 Modules/_tkinter.c	-	quitMainLoop	-
 Modules/_tkinter.c	-	errorInCmd	-

Tools/c-analyzer/cpython/ignored.tsv

@@ -591,6 +591,7 @@ Modules/_testmultiphase.c	-	slots_exec_unreported_exception	-
 Modules/_testmultiphase.c	-	slots_nonmodule_with_exec_slots	-
 Modules/_testmultiphase.c	-	testexport_methods	-
 Modules/_testmultiphase.c	-	uninitialized_def	-
+Modules/_testmultiphase.c	datetime_capi_import_with_error	is_datetime_multiphase	-
 Modules/_testsinglephase.c	-	global_state	-
 Modules/_xxtestfuzz/_xxtestfuzz.c	-	_fuzzmodule	-
 Modules/_xxtestfuzz/_xxtestfuzz.c	-	module_methods	-