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GH-101578: Normalize the current exception (GH-101607) · python/cpython@feec49c · GitHub

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markshannon
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GH-101578: Normalize the current exception (GH-101607)
* Make sure that the current exception is always normalized. * Remove redundant type and traceback fields for the current exception. * Add new API functions: PyErr_GetRaisedException, PyErr_SetRaisedException * Add new API functions: PyException_GetArgs, PyException_SetArgs
1 parent 027adf4 commit feec49c

29 files changed

Lines changed: 476 additions & 171 deletions

‎Doc/c-api/exceptions.rst‎

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@@ -400,8 +400,61 @@ Querying the error indicator
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recursively in subtuples) are searched for a match.
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.. c:function:: PyObject *PyErr_GetRaisedException(void)
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Returns the exception currently being raised, clearing the exception at
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the same time. Do not confuse this with the exception currently being
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handled which can be accessed with :c:func:`PyErr_GetHandledException`.
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.. note::
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This function is normally only used by code that needs to catch exceptions or
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by code that needs to save and restore the error indicator temporarily, e.g.::
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{
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PyObject *exc = PyErr_GetRaisedException();
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/* ... code that might produce other errors ... */
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PyErr_SetRaisedException(exc);
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}
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.. versionadded:: 3.12
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.. c:function:: void PyErr_SetRaisedException(PyObject *exc)
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Sets the exception currently being raised ``exc``.
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If the exception is already set, it is cleared first.
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``exc`` must be a valid exception.
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(Violating this rules will cause subtle problems later.)
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This call consumes a reference to the ``exc`` object: you must own a
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reference to that object before the call and after the call you no longer own
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that reference.
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(If you don't understand this, don't use this function. I warned you.)
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.. note::
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This function is normally only used by code that needs to save and restore the
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error indicator temporarily. Use :c:func:`PyErr_GetRaisedException` to save
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the current exception, e.g.::
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{
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PyObject *exc = PyErr_GetRaisedException();
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/* ... code that might produce other errors ... */
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PyErr_SetRaisedException(exc);
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}
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.. versionadded:: 3.12
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.. c:function:: void PyErr_Fetch(PyObject **ptype, PyObject **pvalue, PyObject **ptraceback)
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As of 3.12, this function is deprecated. Use :c:func:`PyErr_GetRaisedException` instead.
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Retrieve the error indicator into three variables whose addresses are passed.
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If the error indicator is not set, set all three variables to ``NULL``. If it is
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set, it will be cleared and you own a reference to each object retrieved. The
@@ -421,10 +474,14 @@ Querying the error indicator
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PyErr_Restore(type, value, traceback);
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}
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.. deprecated:: 3.12
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.. c:function:: void PyErr_Restore(PyObject *type, PyObject *value, PyObject *traceback)
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Set the error indicator from the three objects. If the error indicator is
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As of 3.12, this function is deprecated. Use :c:func:`PyErr_SetRaisedException` instead.
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Set the error indicator from the three objects. If the error indicator is
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already set, it is cleared first. If the objects are ``NULL``, the error
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indicator is cleared. Do not pass a ``NULL`` type and non-``NULL`` value or
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traceback. The exception type should be a class. Do not pass an invalid
@@ -440,9 +497,15 @@ Querying the error indicator
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error indicator temporarily. Use :c:func:`PyErr_Fetch` to save the current
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error indicator.
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.. deprecated:: 3.12
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.. c:function:: void PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)
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As of 3.12, this function is deprecated.
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Use :c:func:`PyErr_GetRaisedException` instead of :c:func:`PyErr_Fetch` to avoid
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any possible de-normalization.
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Under certain circumstances, the values returned by :c:func:`PyErr_Fetch` below
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can be "unnormalized", meaning that ``*exc`` is a class object but ``*val`` is
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not an instance of the same class. This function can be used to instantiate
@@ -459,6 +522,8 @@ Querying the error indicator
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PyException_SetTraceback(val, tb);
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}
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.. deprecated:: 3.12
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.. c:function:: PyObject* PyErr_GetHandledException(void)
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@@ -704,6 +769,18 @@ Exception Objects
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:attr:`__suppress_context__` is implicitly set to ``True`` by this function.
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.. c:function:: PyObject* PyException_GetArgs(PyObject *ex)
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Return args of the given exception as a new reference,
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as accessible from Python through :attr:`args`.
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.. c:function:: void PyException_SetArgs(PyObject *ex, PyObject *args)
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Set the args of the given exception,
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as accessible from Python through :attr:`args`.
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.. _unicodeexceptions:
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Unicode Exception Objects

‎Doc/data/stable_abi.dat‎

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‎Include/cpython/pyerrors.h‎

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@@ -99,6 +99,7 @@ PyAPI_FUNC(void) _PyErr_GetExcInfo(PyThreadState *, PyObject **, PyObject **, Py
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/* Context manipulation (PEP 3134) */
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PyAPI_FUNC(void) _PyErr_ChainExceptions(PyObject *, PyObject *, PyObject *);
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PyAPI_FUNC(void) _PyErr_ChainExceptions1(PyObject *);
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/* Like PyErr_Format(), but saves current exception as __context__ and
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__cause__.

‎Include/cpython/pystate.h‎

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@@ -166,9 +166,7 @@ struct _ts {
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PyObject *c_traceobj;
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/* The exception currently being raised */
169-
PyObject *curexc_type;
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PyObject *curexc_value;
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PyObject *curexc_traceback;
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PyObject *current_exception;
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/* Pointer to the top of the exception stack for the exceptions
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* we may be currently handling. (See _PyErr_StackItem above.)

‎Include/internal/pycore_pyerrors.h‎

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@@ -20,7 +20,10 @@ extern void _PyErr_FiniTypes(PyInterpreterState *);
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static inline PyObject* _PyErr_Occurred(PyThreadState *tstate)
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{
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assert(tstate != NULL);
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return tstate->curexc_type;
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if (tstate->current_exception == NULL) {
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return NULL;
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}
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return (PyObject *)Py_TYPE(tstate->current_exception);
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}
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2629
static inline void _PyErr_ClearExcState(_PyErr_StackItem *exc_state)
@@ -37,10 +40,16 @@ PyAPI_FUNC(void) _PyErr_Fetch(
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PyObject **value,
3841
PyObject **traceback);
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extern PyObject *
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_PyErr_GetRaisedException(PyThreadState *tstate);
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PyAPI_FUNC(int) _PyErr_ExceptionMatches(
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PyThreadState *tstate,
4248
PyObject *exc);
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void
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_PyErr_SetRaisedException(PyThreadState *tstate, PyObject *exc);
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PyAPI_FUNC(void) _PyErr_Restore(
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PyThreadState *tstate,
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PyObject *type,

‎Include/pyerrors.h‎

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@@ -18,6 +18,8 @@ PyAPI_FUNC(PyObject *) PyErr_Occurred(void);
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PyAPI_FUNC(void) PyErr_Clear(void);
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PyAPI_FUNC(void) PyErr_Fetch(PyObject **, PyObject **, PyObject **);
2020
PyAPI_FUNC(void) PyErr_Restore(PyObject *, PyObject *, PyObject *);
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PyAPI_FUNC(PyObject *) PyErr_GetRaisedException(void);
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PyAPI_FUNC(void) PyErr_SetRaisedException(PyObject *);
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#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030b0000
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PyAPI_FUNC(PyObject*) PyErr_GetHandledException(void);
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PyAPI_FUNC(void) PyErr_SetHandledException(PyObject *);
@@ -51,6 +53,10 @@ PyAPI_FUNC(void) PyException_SetCause(PyObject *, PyObject *);
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PyAPI_FUNC(PyObject *) PyException_GetContext(PyObject *);
5254
PyAPI_FUNC(void) PyException_SetContext(PyObject *, PyObject *);
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PyAPI_FUNC(PyObject *) PyException_GetArgs(PyObject *);
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PyAPI_FUNC(void) PyException_SetArgs(PyObject *, PyObject *);
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/* */
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#define PyExceptionClass_Check(x) \

‎Lib/test/test_capi/test_misc.py‎

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@@ -1553,5 +1553,44 @@ def func2(x=None):
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self.do_test(func2)
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class Test_ErrSetAndRestore(unittest.TestCase):
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def test_err_set_raised(self):
1559+
with self.assertRaises(ValueError):
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_testcapi.err_set_raised(ValueError())
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v = ValueError()
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try:
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_testcapi.err_set_raised(v)
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except ValueError as ex:
1565+
self.assertIs(v, ex)
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1567+
def test_err_restore(self):
1568+
with self.assertRaises(ValueError):
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_testcapi.err_restore(ValueError)
1570+
with self.assertRaises(ValueError):
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_testcapi.err_restore(ValueError, 1)
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with self.assertRaises(ValueError):
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_testcapi.err_restore(ValueError, 1, None)
1574+
with self.assertRaises(ValueError):
1575+
_testcapi.err_restore(ValueError, ValueError())
1576+
try:
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_testcapi.err_restore(KeyError, "hi")
1578+
except KeyError as k:
1579+
self.assertEqual("hi", k.args[0])
1580+
try:
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1/0
1582+
except Exception as e:
1583+
tb = e.__traceback__
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with self.assertRaises(ValueError):
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_testcapi.err_restore(ValueError, 1, tb)
1586+
with self.assertRaises(TypeError):
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_testcapi.err_restore(ValueError, 1, 0)
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try:
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_testcapi.err_restore(ValueError, 1, tb)
1590+
except ValueError as v:
1591+
self.assertEqual(1, v.args[0])
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self.assertIs(tb, v.__traceback__.tb_next)
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15561595
if __name__ == "__main__":
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unittest.main()

‎Lib/test/test_exceptions.py‎

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@@ -347,6 +347,7 @@ def test_capi2():
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_testcapi.raise_exception(BadException, 0)
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except RuntimeError as err:
349349
exc, err, tb = sys.exc_info()
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tb = tb.tb_next
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co = tb.tb_frame.f_code
351352
self.assertEqual(co.co_name, "__init__")
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self.assertTrue(co.co_filename.endswith('test_exceptions.py'))
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14151416
@cpython_only
14161417
def test_recursion_normalizing_infinite_exception(self):
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# Issue #30697. Test that a RecursionError is raised when
1418-
# PyErr_NormalizeException() maximum recursion depth has been
1419-
# exceeded.
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# maximum recursion depth has been exceeded when creating
1420+
# an exception
14201421
code = """if 1:
14211422
import _testcapi
14221423
try:
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"""
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rc, out, err = script_helper.assert_python_failure("-c", code)
14281429
self.assertEqual(rc, 1)
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self.assertIn(b'RecursionError: maximum recursion depth exceeded '
1430-
b'while normalizing an exception', err)
1430+
self.assertIn(b'RecursionError: maximum recursion depth exceeded', err)
14311431
self.assertIn(b'Done.', out)
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‎Lib/test/test_stable_abi_ctypes.py‎

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Some generated files are not rendered by default. Learn more about customizing how changed files appear on GitHub.

‎Misc/NEWS.d/next/C API/2023-02-06-16-14-30.gh-issue-101578.PW5fA9.rst‎

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Add new C-API functions for saving and restoring the current exception:
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``PyErr_GetRaisedException`` and ``PyErr_SetRaisedException``.
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These functions take and return a single exception rather than
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the triple of ``PyErr_Fetch`` and ``PyErr_Restore``.
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This is less error prone and a bit more efficient.
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The three arguments forms of saving and restoring the
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current exception: ``PyErr_Fetch`` and ``PyErr_Restore``
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are deprecated.
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Also add ``PyException_GetArgs`` and ``PyException_SetArgs``
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as convenience functions to help dealing with
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exceptions in the C API.

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