GH-115776: Static object are immortal, so mark them as such.

Include/object.h

@@ -115,8 +115,11 @@ check by comparing the reference count field to the immortality reference count.
 // Kept for backward compatibility. It was needed by Py_TRACE_REFS build.
 #define _PyObject_EXTRA_INIT
 
-// Make all internal uses of PyObject_HEAD_INIT immortal while preserving the
-// C-API expectation that the refcnt will be set to 1.
+/* Make all uses of PyObject_HEAD_INIT immortal.
+ *
+ * Statically allocated objects might be shared between
+ * interpreters, so must be marked as immortal.
+ */
 #if defined(Py_GIL_DISABLED)
 #define PyObject_HEAD_INIT(type)    \
     {                               \
@@ -128,19 +131,13 @@ check by comparing the reference count field to the immortality reference count.
         0,                          \
         (type),                     \
     },
-#elif defined(Py_BUILD_CORE)
+#else
 #define PyObject_HEAD_INIT(type)    \
     {                               \
         { _Py_IMMORTAL_REFCNT },    \
         (type)                      \
     },
-#else
-#define PyObject_HEAD_INIT(type) \
-    {                            \
-        { 1 },                   \
-        (type)                   \
-    },
-#endif /* Py_BUILD_CORE */
+#endif
 
 #define PyVarObject_HEAD_INIT(type, size) \
     {                                     \

Misc/NEWS.d/next/Core and Builtins/2024-04-09-11-31-25.gh-issue-115776.5Nthd0.rst

@@ -0,0 +1,2 @@
+Statically allocated objects are, by definition, immortal so must be
+marked as such regardless of whether they are in extension modules or not.