Repository navigation
[C API] Enhance PyErr_WriteUnraisable() API to pass an error message #108082
Description
Activity
I already started to work on this, but was not sure about API, so left it to your return.
I initially was going to add simple function:
void PyErr_FormatUnraisable(const char *format, ...);
With special case
PyErr_FormatUnraisable(NULL, obj)equal toPyErr_WriteUnraisable(obj).But it now creates the
UnraisableHookArgsobject which has fieldobject. So we need more complex API:void PyErr_FormatUnraisable(PyObject *obj, const char *format, ...);
With
PyErr_WriteUnraisable(obj)equal toPyErr_FormatUnraisable(obj, "Exception ignored in: %R", obj)or special casePyErr_FormatUnraisable(obj, NULL).Or we always set
UnraisableHookArgs.objecttoNoneif usePyErr_FormatUnraisable(), then we can make the use simpler. Then custom message andobjectwill be mutually exclusive, but seems that currently most of cases with custom message pass NULL as object.Or we can keep
PyErr_FormatUnraisable()simpler and add a separate functionPyErr_FormatUnraisableObject()which allows to specify both custom message and object.void PyErr_FormatUnraisable(const char *format, ...); void PyErr_FormatUnraisableObject(PyObject *obj, const char *format, ...);
- added a commit that references this issue
on Oct 19, 2023 - added 4 commits that reference this issue
on Oct 30, 2023 Few calls of
_PyErr_WriteUnraisableMsgare left which pass both message and non-NULL object.Modules/atexitmodule.c:140: _PyErr_WriteUnraisableMsg("in atexit callback", the_func); -- Modules/_threadmodule.c:1074: _PyErr_WriteUnraisableMsg("in thread started by", boot->func); -- Modules/_ctypes/callbacks.c:219: _PyErr_WriteUnraisableMsg("on calling ctypes callback function", Modules/_ctypes/callbacks.c-220- callable); -- Modules/_ctypes/callbacks.c:261: _PyErr_WriteUnraisableMsg("on converting result " Modules/_ctypes/callbacks.c-262- "of ctypes callback function", Modules/_ctypes/callbacks.c-263- callable); -- Modules/_ctypes/callbacks.c:273: _PyErr_WriteUnraisableMsg("on converting result " Modules/_ctypes/callbacks.c-274- "of ctypes callback function", Modules/_ctypes/callbacks.c-275- callable);They can be replaced with
PyErr_FormatUnraisable(), but thenobjectwill be None. Or we can add new function specially for these cases, which passes bothobjectand a format with arguments for a warning message. I do not know how important to haveobject.- added a commit that references this issue
on Nov 2, 2023 They can be replaced with PyErr_FormatUnraisable(), but then object will be None. Or we can add new function specially for these cases, which passes both object and a format with arguments for a warning message. I do not know how important to have object.
As the author of _PyErr_WriteUnraisableMsg(), I suggest to remove _PyErr_WriteUnraisableMsg() and replace all _PyErr_WriteUnraisableMsg() usage with PyErr_FormatUnraisable().
My intent for passing object to the hook was to delegate the formatting to give the hook the opportunity to catch exception on formatting the object, and maybe use tracemalloc to see where the object was allocated, etc.
But I don't think that these features are really useful and we should just skip/remove object, and just pass an error message to the hook.
2 remaining items
- added 4 commits that reference this issue
on Nov 3, 2023 Now we can replace more
PyErr_Clear()with informativePyErr_FormatUnraisable().Reacted by Victor Stinner- added 4 commits that reference this issue
on Feb 11, 2024 - added 4 commits that reference this issue
on Sep 2, 2024 - added a commit that references this issue
on Aug 7, 2026
Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discussion elsewhere
Links to previous discussion of this feature:
No response
Proposal:
I added a private
_PyErr_WriteUnraisableMsg()API but it cannot be used in third party code, nor in stdlib extensions which try to avoid private/internal functions (like sqlite3). Moreover,_PyErr_WriteUnraisableMsg()API doesn't allow to fully customize the error message.The limitation of
_PyErr_WriteUnraisableMsg()affected PR #106674 which has to add; consider using ...in the error message which is not great.@serhiy-storchaka suggested to add an API which allows string formatting, similar to
PyErr_Format()._PyErr_WriteUnraisableMsg()was added in issue #81010.By the way, we should go through all calls to PyErr_WriteUnraisable() and add more context to more these logs easier to get for developers: give more context about what the issue is, how to fix it, where it occurred, etc.
Linked PRs