https://github.com/python/cpython/commit/1d0baf1ae48f98b61cc869a82e1b7206298f653f
commit: 1d0baf1ae48f98b61cc869a82e1b7206298f653f
branch: 3.14
author: Victor Stinner <[email protected]>
committer: vstinner <[email protected]>
date: 2026-01-09T16:10:50+01:00
summary:
[3.14] gh-143547: Fix PyErr_FormatUnraisable() fallback (#143557) (#143603)
gh-143547: Fix PyErr_FormatUnraisable() fallback (#143557)
Hold a strong reference to 'hook' while calling the default
unraisable took to log hook failure.
(cherry picked from commit 39a2bcf949095bd603f7b73f15b5b478dbb49ba9)
files:
A Misc/NEWS.d/next/Library/2026-01-08-14-53-46.gh-issue-143547.wHBVlr.rst
M Lib/test/test_sys.py
M Python/errors.c
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index e2117b9588dba2..4aeeac56b1aae3 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -1480,6 +1480,7 @@ def hook_func(args):
def test_custom_unraisablehook_fail(self):
_testcapi = import_helper.import_module('_testcapi')
from _testcapi import err_writeunraisable
+
def hook_func(*args):
raise Exception("hook_func failed")
diff --git
a/Misc/NEWS.d/next/Library/2026-01-08-14-53-46.gh-issue-143547.wHBVlr.rst
b/Misc/NEWS.d/next/Library/2026-01-08-14-53-46.gh-issue-143547.wHBVlr.rst
new file mode 100644
index 00000000000000..934570b30b971f
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-01-08-14-53-46.gh-issue-143547.wHBVlr.rst
@@ -0,0 +1,3 @@
+Fix :func:`sys.unraisablehook` when the hook raises an exception and changes
+:func:`sys.unraisablehook`: hold a strong reference to the old hook. Patch
+by Victor Stinner.
diff --git a/Python/errors.c b/Python/errors.c
index 89ea79f8c914fb..3fd97ea36b3368 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -1632,6 +1632,7 @@ format_unraisable_v(const char *format, va_list va,
PyObject *obj)
_Py_EnsureTstateNotNULL(tstate);
PyObject *err_msg = NULL;
+ PyObject *hook = NULL;
PyObject *exc_type, *exc_value, *exc_tb;
_PyErr_Fetch(tstate, &exc_type, &exc_value, &exc_tb);
@@ -1676,7 +1677,6 @@ format_unraisable_v(const char *format, va_list va,
PyObject *obj)
goto error;
}
- PyObject *hook;
if (_PySys_GetOptionalAttr(&_Py_ID(unraisablehook), &hook) < 0) {
Py_DECREF(hook_args);
err_msg_str = NULL;
@@ -1689,7 +1689,6 @@ format_unraisable_v(const char *format, va_list va,
PyObject *obj)
}
if (_PySys_Audit(tstate, "sys.unraisablehook", "OO", hook, hook_args) < 0)
{
- Py_DECREF(hook);
Py_DECREF(hook_args);
err_msg_str = "Exception ignored in audit hook";
obj = NULL;
@@ -1697,13 +1696,11 @@ format_unraisable_v(const char *format, va_list va,
PyObject *obj)
}
if (hook == Py_None) {
- Py_DECREF(hook);
Py_DECREF(hook_args);
goto default_hook;
}
PyObject *res = PyObject_CallOneArg(hook, hook_args);
- Py_DECREF(hook);
Py_DECREF(hook_args);
if (res != NULL) {
Py_DECREF(res);
@@ -1733,6 +1730,7 @@ format_unraisable_v(const char *format, va_list va,
PyObject *obj)
Py_XDECREF(exc_value);
Py_XDECREF(exc_tb);
Py_XDECREF(err_msg);
+ Py_XDECREF(hook);
_PyErr_Clear(tstate); /* Just in case */
}
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