gh-95324: Emit a warning if an object doesn't call PyObject_GC_UnTrack during deallocation in debug mode (#95325)

Misc/NEWS.d/next/Core and Builtins/2022-07-27-14-05-07.gh-issue-95324.28Q5u7.rst

@@ -0,0 +1,2 @@
+Emit a warning in debug mode if an object does not call
+:c:func:`PyObject_GC_UnTrack` before deallocation. Patch by Pablo Galindo.

Modules/_abc.c

@@ -63,6 +63,7 @@ abc_data_clear(_abc_data *self)
 static void
 abc_data_dealloc(_abc_data *self)
 {
+    PyObject_GC_UnTrack(self);
     PyTypeObject *tp = Py_TYPE(self);
     (void)abc_data_clear(self);
     tp->tp_free(self);

Modules/_ctypes/cfield.c

@@ -279,6 +279,7 @@ PyCField_clear(CFieldObject *self)
 static void
 PyCField_dealloc(PyObject *self)
 {
+    PyObject_GC_UnTrack(self);
     PyCField_clear((CFieldObject *)self);
     Py_TYPE(self)->tp_free((PyObject *)self);
 }

Modules/_threadmodule.c

@@ -57,6 +57,7 @@ lock_traverse(lockobject *self, visitproc visit, void *arg)
 static void
 lock_dealloc(lockobject *self)
 {
+    PyObject_GC_UnTrack(self);
     if (self->in_weakreflist != NULL) {
         PyObject_ClearWeakRefs((PyObject *) self);
     }
@@ -333,6 +334,7 @@ rlock_traverse(rlockobject *self, visitproc visit, void *arg)
 static void
 rlock_dealloc(rlockobject *self)
 {
+    PyObject_GC_UnTrack(self);
     if (self->in_weakreflist != NULL)
         PyObject_ClearWeakRefs((PyObject *) self);
     /* self->rlock_lock can be NULL if PyThread_allocate_lock() failed

Modules/gcmodule.c

@@ -2347,6 +2347,13 @@ PyObject_GC_Del(void *op)
     size_t presize = _PyType_PreHeaderSize(((PyObject *)op)->ob_type);
     PyGC_Head *g = AS_GC(op);
     if (_PyObject_GC_IS_TRACKED(op)) {
+#ifdef Py_DEBUG
+        if (PyErr_WarnExplicitFormat(PyExc_ResourceWarning, "gc", 0,
+                                     "gc", NULL, "Object of type %s is not untracked before destruction",
+                                     ((PyObject*)op)->ob_type->tp_name)) {
+            PyErr_WriteUnraisable(NULL);
+        }
+#endif
         gc_list_remove(g);
     }
     GCState *gcstate = get_gc_state();

Modules/xxlimited.c

@@ -138,6 +138,7 @@ Xxo_finalize(PyObject *self_obj)
 static void
 Xxo_dealloc(PyObject *self)
 {
+    PyObject_GC_UnTrack(self);
     Xxo_finalize(self);
     PyTypeObject *tp = Py_TYPE(self);
     freefunc free = PyType_GetSlot(tp, Py_tp_free);

Objects/exceptions.c

@@ -3214,6 +3214,7 @@ MemoryError_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     self = state->memerrors_freelist;
     self->args = PyTuple_New(0);
     /* This shouldn't happen since the empty tuple is persistent */
+
     if (self->args == NULL) {
         return NULL;
     }
@@ -3229,6 +3230,8 @@ MemoryError_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 MemoryError_dealloc(PyBaseExceptionObject *self)
 {
+    _PyObject_GC_UNTRACK(self);
+
     BaseException_clear(self);
 
     /* If this is a subclass of MemoryError, we don't need to
@@ -3238,8 +3241,6 @@ MemoryError_dealloc(PyBaseExceptionObject *self)
         return;
     }
 
-    _PyObject_GC_UNTRACK(self);
-
     struct _Py_exc_state *state = get_exc_state();
     if (state->memerrors_numfree >= MEMERRORS_SAVE) {
         Py_TYPE(self)->tp_free((PyObject *)self);

Objects/weakrefobject.c

@@ -558,6 +558,7 @@ proxy_bool(PyWeakReference *proxy)
 static void
 proxy_dealloc(PyWeakReference *self)
 {
+    PyObject_GC_UnTrack(self);
     if (self->wr_callback != NULL)
         PyObject_GC_UnTrack((PyObject *)self);
     clear_weakref(self);