bpo-46417: _thread uses PyStructSequence_NewType() (GH-30733)

The _thread module now creates its _ExceptHookArgs type as a heap
type using PyStructSequence_NewType(), rather than using a static
type.

Author: vstinner

Modules/_threadmodule.c

@@ -28,6 +28,7 @@ static struct PyModuleDef thread_module;
 
 
 typedef struct {
+    PyTypeObject *excepthook_type;
     PyTypeObject *lock_type;
     PyTypeObject *local_type;
     PyTypeObject *local_dummy_type;
@@ -1473,8 +1474,6 @@ PyDoc_STRVAR(ExceptHookArgs__doc__,
 \n\
 Type used to pass arguments to threading.excepthook.");
 
-static PyTypeObject ExceptHookArgsType;
-
 static PyStructSequence_Field ExceptHookArgs_fields[] = {
     {"exc_type", "Exception type"},
     {"exc_value", "Exception value"},
@@ -1492,9 +1491,11 @@ static PyStructSequence_Desc ExceptHookArgs_desc = {
 
 
 static PyObject *
-thread_excepthook(PyObject *self, PyObject *args)
+thread_excepthook(PyObject *module, PyObject *args)
 {
-    if (!Py_IS_TYPE(args, &ExceptHookArgsType)) {
+    thread_module_state *state = get_thread_state(module);
+
+    if (!Py_IS_TYPE(args, state->excepthook_type)) {
         PyErr_SetString(PyExc_TypeError,
                         "_thread.excepthook argument type "
                         "must be ExceptHookArgs");
@@ -1629,18 +1630,17 @@ thread_module_exec(PyObject *module)
         return -1;
     }
 
-    if (ExceptHookArgsType.tp_name == NULL) {
-        if (PyStructSequence_InitType2(&ExceptHookArgsType,
-                                       &ExceptHookArgs_desc) < 0) {
-            return -1;
-        }
-    }
-
     // Add module attributes
     if (PyDict_SetItemString(d, "error", ThreadError) < 0) {
         return -1;
     }
-    if (PyModule_AddType(module, &ExceptHookArgsType) < 0) {
+
+    // _ExceptHookArgs type
+    state->excepthook_type = PyStructSequence_NewType(&ExceptHookArgs_desc);
+    if (state->excepthook_type == NULL) {
+        return -1;
+    }
+    if (PyModule_AddType(module, state->excepthook_type) < 0) {
         return -1;
     }
 
@@ -1664,6 +1664,7 @@ static int
 thread_module_traverse(PyObject *module, visitproc visit, void *arg)
 {
     thread_module_state *state = get_thread_state(module);
+    Py_VISIT(state->excepthook_type);
     Py_VISIT(state->lock_type);
     Py_VISIT(state->local_type);
     Py_VISIT(state->local_dummy_type);
@@ -1674,6 +1675,7 @@ static int
 thread_module_clear(PyObject *module)
 {
     thread_module_state *state = get_thread_state(module);
+    Py_CLEAR(state->excepthook_type);
     Py_CLEAR(state->lock_type);
     Py_CLEAR(state->local_type);
     Py_CLEAR(state->local_dummy_type);