Fix tests on python3.14t

* Add Py_MOD_GIL_NOT_USED to the C/C++ extension.
* Add "t" suffix to the Python version on free-threaded build.
* On Python 3.14 and newer, tests call sys._clear_internal_caches()
  instead of sys._clear_type_cache() to avoid a deprecation warning.

Author: vstinner

tests/test_pythoncapi_compat.py

@@ -19,6 +19,11 @@
 except ImportError:
     # Python 2
     faulthandler = None
+try:
+    import sysconfig
+except ImportError:
+    # Python 3.1 and older
+    sysconfig = None
 
 # test.utils
 from utils import run_command, command_stdout
@@ -94,10 +99,13 @@ def _run_tests(tests, verbose):
         test_func()
 
 
+_HAS_CLEAR_INTERNAL_CACHES = hasattr(sys, '_clear_internal_caches')
 _HAS_CLEAR_TYPE_CACHE = hasattr(sys, '_clear_type_cache')
 
 def _refleak_cleanup():
-    if _HAS_CLEAR_TYPE_CACHE:
+    if _HAS_CLEAR_INTERNAL_CACHES:
+        sys._clear_internal_caches()
+    elif _HAS_CLEAR_TYPE_CACHE:
         sys._clear_type_cache()
     gc.collect()
 
@@ -134,7 +142,12 @@ def python_version():
             python_impl = "PyPy"
         else:
             python_impl = 'Python'
-    return "%s %s.%s (%s build)" % (python_impl, ver.major, ver.minor, build)
+    pyver = "%s.%s" % (ver.major, ver.minor)
+    if ver >= (3, 13):
+        if sysconfig.get_config_var('Py_GIL_DISABLED'):
+            # Free-threaded build
+            pyver += "t"
+    return "%s %s (%s build)" % (python_impl, pyver, build)
 
 
 def run_tests(module_name, lang):

tests/test_pythoncapi_compat_cext.c

@@ -2624,6 +2624,9 @@ module_exec(PyObject *module)
 #if PY_VERSION_HEX >= 0x03050000
 static PyModuleDef_Slot module_slots[] = {
     {Py_mod_exec, _Py_CAST(void*, module_exec)},
+#if PY_VERSION_HEX >= 0x030D0000
+    {Py_mod_gil, Py_MOD_GIL_NOT_USED},
+#endif
     {0, _Py_NULL}
 };
 #endif