-
-
Notifications
You must be signed in to change notification settings - Fork 29.4k
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
tp_dealloc docs should mention error indicator may be set #89373
Comments
The fact that the error indicator may be set during tp_dealloc is somewhat well known (https://github.com/posborne/dbus-python/blob/fef4bccfc535c6c2819e3f15384600d7bc198bc5/_dbus_bindings/conn.c#L387) but it's not documented in the official manual. We should document it. A simple suggested patch: diff --git a/Doc/c-api/typeobj.rst b/Doc/c-api/typeobj.rst
index b17fb22b69..e7c9b13646 100644
--- a/Doc/c-api/typeobj.rst
+++ b/Doc/c-api/typeobj.rst
@@ -668,6 +668,20 @@ and :c:type:`PyType_Type` effectively act as defaults.)
:c:func:`PyObject_GC_Del` if the instance was allocated using
:c:func:`PyObject_GC_New` or :c:func:`PyObject_GC_NewVar`.
+ If you may call functions that may set the error indicator, you must
+ use :c:func:`PyErr_Fetch` and :c:func:`PyErr_Restore` to ensure you
+ don't clobber a preexisting error indicator (the deallocation could
+ have occurred while processing a different error):
+
+ .. code-block:: c
+
+ static void foo_dealloc(foo_object *self) {
+ PyObject *et, *ev, *etb;
+ PyErr_Fetch(&et, &ev, &etb);
+ ...
+ PyErr_Restore(et, ev, etb);
+ }
+
Finally, if the type is heap allocated (:const:`Py_TPFLAGS_HEAPTYPE`), the
deallocator should decrement the reference count for its type object after
calling the type deallocator. In order to avoid dangling pointers, the |
I'm not sure that it's a feature. Maybe we should modify to never call tp_dealloc with an exception set. |
I wrote #32357 to check in debug mode that tp_dealloc functions leave the current exception unchanged. You can use attached unicode_dealloc_bug.patch to inject a bug to test my PR. Example ("make" is enough to trigger the bug): Current thread 0x00007ff28d45a740 (most recent call first): |
If Python is built in debug mode, _Py_Dealloc() now ensures that the tp_dealloc function leaves the current exception unchanged.
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
Show more details
GitHub fields:
bugs.python.org fields:
The text was updated successfully, but these errors were encountered: