Add _Py_INTERNAL_ABI_SLOT (to _datetime for now)

Author: encukou

Include/cpython/modsupport.h

@@ -24,3 +24,15 @@ typedef struct _PyArg_Parser {
 
 PyAPI_FUNC(int) _PyArg_ParseTupleAndKeywordsFast(PyObject *, PyObject *,
                                                  struct _PyArg_Parser *, ...);
+
+#ifdef Py_BUILD_CORE
+// Internal; defined here to avoid explicitly including pycore_modsupport.h
+#define _Py_INTERNAL_ABI_SLOT                             \
+    {Py_mod_abi, (void*) &(PyABIInfo) {                   \
+        .abiinfo_major_version = 1,                       \
+        .abiinfo_minor_version = 0,                       \
+        .flags = PyABIInfo_INTERNAL,                      \
+        .build_version = PY_VERSION_HEX,                  \
+        .abi_version = PY_VERSION_HEX }}                  \
+    ///////////////////////////////////////////////////////
+#endif

Modules/_datetimemodule.c

@@ -7495,6 +7495,7 @@ _datetime_exec(PyObject *module)
 }
 
 static PyModuleDef_Slot module_slots[] = {
+    _Py_INTERNAL_ABI_SLOT,
     {Py_mod_exec, _datetime_exec},
     {Py_mod_multiple_interpreters, Py_MOD_PER_INTERPRETER_GIL_SUPPORTED},
     {Py_mod_gil, Py_MOD_GIL_NOT_USED},