https://github.com/python/cpython/commit/d4153a9f76736128306c4af01776729da846d926
commit: d4153a9f76736128306c4af01776729da846d926
branch: main
author: Victor Stinner <[email protected]>
committer: vstinner <[email protected]>
date: 2026-03-27T11:20:19Z
summary:
gh-146480: Override the exception in _PyErr_SetKeyError() (#146486)
If _PyErr_SetKeyError() is called with an exception set, it now
replaces the current exception with KeyError (as expected), instead
of setting a SystemError or failing with a fatal error (in debug
mode).
files:
M Lib/test/test_capi/test_exceptions.py
M Modules/_testinternalcapi.c
M Python/errors.c
diff --git a/Lib/test/test_capi/test_exceptions.py
b/Lib/test/test_capi/test_exceptions.py
index 4967f02b007e06..51ac41e33ac17a 100644
--- a/Lib/test/test_capi/test_exceptions.py
+++ b/Lib/test/test_capi/test_exceptions.py
@@ -13,8 +13,9 @@
from .test_misc import decode_stderr
-# Skip this test if the _testcapi module isn't available.
+# Skip this test if the _testcapi or _testinternalcapi module isn't available.
_testcapi = import_helper.import_module('_testcapi')
+_testinternalcapi = import_helper.import_module('_testinternalcapi')
NULL = None
@@ -108,6 +109,26 @@ def __del__(self):
b'<string>:7: RuntimeWarning: Testing PyErr_WarnEx',
])
+ def test__pyerr_setkeyerror(self):
+ # Test _PyErr_SetKeyError()
+ _pyerr_setkeyerror = _testinternalcapi._pyerr_setkeyerror
+ for arg in (
+ "key",
+ # check that a tuple argument is not unpacked
+ (1, 2, 3),
+ # PyErr_SetObject(exc_type, exc_value) uses exc_value if it's
+ # already an exception, but _PyErr_SetKeyError() always creates a
+ # new KeyError.
+ KeyError('arg'),
+ ):
+ with self.subTest(arg=arg):
+ with self.assertRaises(KeyError) as cm:
+ # Test calling _PyErr_SetKeyError() with an exception set
+ # to check that the function overrides the current
+ # exception.
+ _pyerr_setkeyerror(arg)
+ self.assertEqual(cm.exception.args, (arg,))
+
class Test_FatalError(unittest.TestCase):
diff --git a/Modules/_testinternalcapi.c b/Modules/_testinternalcapi.c
index e1acce8f586685..7f6ea621f87145 100644
--- a/Modules/_testinternalcapi.c
+++ b/Modules/_testinternalcapi.c
@@ -2838,6 +2838,20 @@ test_threadstate_set_stack_protection(PyObject *self,
PyObject *Py_UNUSED(args))
}
+static PyObject *
+_pyerr_setkeyerror(PyObject *self, PyObject *arg)
+{
+ // Test that _PyErr_SetKeyError() overrides the current exception
+ // if an exception is set
+ PyErr_NoMemory();
+
+ _PyErr_SetKeyError(arg);
+
+ assert(PyErr_Occurred());
+ return NULL;
+}
+
+
static PyMethodDef module_functions[] = {
{"get_configs", get_configs, METH_NOARGS},
{"get_eval_frame_stats", get_eval_frame_stats, METH_NOARGS, NULL},
@@ -2959,6 +2973,7 @@ static PyMethodDef module_functions[] = {
{"module_get_gc_hooks", module_get_gc_hooks, METH_O},
{"test_threadstate_set_stack_protection",
test_threadstate_set_stack_protection, METH_NOARGS},
+ {"_pyerr_setkeyerror", _pyerr_setkeyerror, METH_O},
{NULL, NULL} /* sentinel */
};
diff --git a/Python/errors.c b/Python/errors.c
index 229e3a565db5cf..48b03e5fd714b1 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -246,13 +246,23 @@ PyErr_SetObject(PyObject *exception, PyObject *value)
_PyErr_SetObject(tstate, exception, value);
}
-/* Set a key error with the specified argument, wrapping it in a
- * tuple automatically so that tuple keys are not unpacked as the
- * exception arguments. */
+/* Set a key error with the specified argument. This function should be used to
+ * raise a KeyError with an argument instead of PyErr_SetObject(PyExc_KeyError,
+ * arg) which has a special behavior. PyErr_SetObject() unpacks arg if it's a
+ * tuple, and it uses arg instead of creating a new exception if arg is an
+ * exception.
+ *
+ * If an exception is already set, override the exception. */
void
_PyErr_SetKeyError(PyObject *arg)
{
PyThreadState *tstate = _PyThreadState_GET();
+
+ // PyObject_CallOneArg() must not be called with an exception set,
+ // otherwise _Py_CheckFunctionResult() can fail if the function returned
+ // a result with an excception set.
+ _PyErr_Clear(tstate);
+
PyObject *exc = PyObject_CallOneArg(PyExc_KeyError, arg);
if (!exc) {
/* caller will expect error to be set anyway */
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