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bpo-36829: Add _PyErr_WriteUnraisableMsg() (GH-13488)

* sys.unraisablehook: add 'err_msg' field to UnraisableHookArgs.
* Use _PyErr_WriteUnraisableMsg() in _ctypes _DictRemover_call()
  and gc delete_garbage().
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vstinner committed May 27, 2019
1 parent 2f0bfd2 commit 71c52e3048dd07567f0c690eab4e5d57be66f534
@@ -1566,11 +1566,16 @@ always available.
* *exc_type*: Exception type.
* *exc_value*: Exception value, can be ``None``.
* *exc_traceback*: Exception traceback, can be ``None``.
* *err_msg*: Error message, can be ``None``.
* *object*: Object causing the exception, can be ``None``.

:func:`sys.unraisablehook` can be overridden to control how unraisable
exceptions are handled.

The default hook formats *err_msg* and *object* as:
``f'{err_msg}: {object!r}'``; use "Exception ignored in" error message
if *err_msg* is ``None``.

See also :func:`excepthook` which handles uncaught exceptions.

.. versionadded:: 3.8
@@ -171,6 +171,9 @@ PyAPI_FUNC(PyObject *) _PyUnicodeTranslateError_Create(
const char *reason /* UTF-8 encoded string */
);

PyAPI_FUNC(void) _PyErr_WriteUnraisableMsg(
const char *err_msg,
PyObject *obj);

#ifdef __cplusplus
}
@@ -878,31 +878,38 @@ def test__enablelegacywindowsfsencoding(self):

@test.support.cpython_only
class UnraisableHookTest(unittest.TestCase):
def write_unraisable_exc(self, exc, obj):
def write_unraisable_exc(self, exc, err_msg, obj):
import _testcapi
import types
err_msg2 = f"Exception ignored {err_msg}"
try:
_testcapi.write_unraisable_exc(exc, obj)
_testcapi.write_unraisable_exc(exc, err_msg, obj)
return types.SimpleNamespace(exc_type=type(exc),
exc_value=exc,
exc_traceback=exc.__traceback__,
err_msg=err_msg2,
object=obj)
finally:
# Explicitly break any reference cycle
exc = None

def test_original_unraisablehook(self):
obj = "an object"

with test.support.captured_output("stderr") as stderr:
with test.support.swap_attr(sys, 'unraisablehook',
sys.__unraisablehook__):
self.write_unraisable_exc(ValueError(42), obj)

err = stderr.getvalue()
self.assertIn(f'Exception ignored in: {obj!r}\n', err)
self.assertIn('Traceback (most recent call last):\n', err)
self.assertIn('ValueError: 42\n', err)
for err_msg in (None, "original hook"):
with self.subTest(err_msg=err_msg):
obj = "an object"

with test.support.captured_output("stderr") as stderr:
with test.support.swap_attr(sys, 'unraisablehook',
sys.__unraisablehook__):
self.write_unraisable_exc(ValueError(42), err_msg, obj)

err = stderr.getvalue()
if err_msg is not None:
self.assertIn(f'Exception ignored {err_msg}: {obj!r}\n', err)
else:
self.assertIn(f'Exception ignored in: {obj!r}\n', err)
self.assertIn('Traceback (most recent call last):\n', err)
self.assertIn('ValueError: 42\n', err)

def test_original_unraisablehook_err(self):
# bpo-22836: PyErr_WriteUnraisable() should give sensible reports
@@ -962,8 +969,9 @@ def hook_func(args):
obj = object()
try:
with test.support.swap_attr(sys, 'unraisablehook', hook_func):
expected = self.write_unraisable_exc(ValueError(42), obj)
for attr in "exc_type exc_value exc_traceback object".split():
expected = self.write_unraisable_exc(ValueError(42),
"custom hook", obj)
for attr in "exc_type exc_value exc_traceback err_msg object".split():
self.assertEqual(getattr(hook_args, attr),
getattr(expected, attr),
(hook_args, expected))
@@ -978,10 +986,12 @@ def hook_func(*args):

with test.support.captured_output("stderr") as stderr:
with test.support.swap_attr(sys, 'unraisablehook', hook_func):
self.write_unraisable_exc(ValueError(42), None)
self.write_unraisable_exc(ValueError(42),
"custom hook fail", None)

err = stderr.getvalue()
self.assertIn(f'Exception ignored in: {hook_func!r}\n',
self.assertIn(f'Exception ignored in sys.unraisablehook: '
f'{hook_func!r}\n',
err)
self.assertIn('Traceback (most recent call last):\n', err)
self.assertIn('Exception: hook_func failed\n', err)
@@ -150,9 +150,9 @@ _DictRemover_call(PyObject *myself, PyObject *args, PyObject *kw)
{
DictRemoverObject *self = (DictRemoverObject *)myself;
if (self->key && self->dict) {
if (-1 == PyDict_DelItem(self->dict, self->key))
/* XXX Error context */
PyErr_WriteUnraisable(Py_None);
if (-1 == PyDict_DelItem(self->dict, self->key)) {
_PyErr_WriteUnraisableMsg("on calling _ctypes.DictRemover", NULL);
}
Py_CLEAR(self->key);
Py_CLEAR(self->dict);
}
@@ -4985,13 +4985,24 @@ negative_refcount(PyObject *self, PyObject *Py_UNUSED(args))
static PyObject*
test_write_unraisable_exc(PyObject *self, PyObject *args)
{
PyObject *exc, *obj;
if (!PyArg_ParseTuple(args, "OO", &exc, &obj)) {
PyObject *exc, *err_msg, *obj;
if (!PyArg_ParseTuple(args, "OOO", &exc, &err_msg, &obj)) {
return NULL;
}

const char *err_msg_utf8;
if (err_msg != Py_None) {
err_msg_utf8 = PyUnicode_AsUTF8(err_msg);
if (err_msg_utf8 == NULL) {
return NULL;
}
}
else {
err_msg_utf8 = NULL;
}

PyErr_SetObject((PyObject *)Py_TYPE(exc), exc);
PyErr_WriteUnraisable(obj);
_PyErr_WriteUnraisableMsg(err_msg_utf8, obj);
Py_RETURN_NONE;
}

@@ -929,9 +929,8 @@ delete_garbage(struct _gc_runtime_state *state,
Py_INCREF(op);
(void) clear(op);
if (PyErr_Occurred()) {
PySys_WriteStderr("Exception ignored in tp_clear of "
"%.50s\n", Py_TYPE(op)->tp_name);
PyErr_WriteUnraisable(NULL);
_PyErr_WriteUnraisableMsg("in tp_clear of",
(PyObject*)Py_TYPE(op));
}
Py_DECREF(op);
}

Some generated files are not rendered by default. Learn more.

@@ -1077,6 +1077,7 @@ static PyStructSequence_Field UnraisableHookArgs_fields[] = {
{"exc_type", "Exception type"},
{"exc_value", "Exception value"},
{"exc_traceback", "Exception traceback"},
{"err_msg", "Error message"},
{"object", "Object causing the exception"},
{0}
};
@@ -1085,7 +1086,7 @@ static PyStructSequence_Desc UnraisableHookArgs_desc = {
.name = "UnraisableHookArgs",
.doc = UnraisableHookArgs__doc__,
.fields = UnraisableHookArgs_fields,
.n_in_sequence = 4
.n_in_sequence = 5
};


@@ -1104,7 +1105,8 @@ _PyErr_Init(void)

static PyObject *
make_unraisable_hook_args(PyThreadState *tstate, PyObject *exc_type,
PyObject *exc_value, PyObject *exc_tb, PyObject *obj)
PyObject *exc_value, PyObject *exc_tb,
PyObject *err_msg, PyObject *obj)
{
PyObject *args = PyStructSequence_New(&UnraisableHookArgsType);
if (args == NULL) {
@@ -1125,6 +1127,7 @@ make_unraisable_hook_args(PyThreadState *tstate, PyObject *exc_type,
ADD_ITEM(exc_type);
ADD_ITEM(exc_value);
ADD_ITEM(exc_tb);
ADD_ITEM(err_msg);
ADD_ITEM(obj);
#undef ADD_ITEM

@@ -1145,11 +1148,21 @@ make_unraisable_hook_args(PyThreadState *tstate, PyObject *exc_type,
static int
write_unraisable_exc_file(PyThreadState *tstate, PyObject *exc_type,
PyObject *exc_value, PyObject *exc_tb,
PyObject *obj, PyObject *file)
PyObject *err_msg, PyObject *obj, PyObject *file)
{
if (obj != NULL && obj != Py_None) {
if (PyFile_WriteString("Exception ignored in: ", file) < 0) {
return -1;
if (err_msg != NULL && err_msg != Py_None) {
if (PyFile_WriteObject(err_msg, file, Py_PRINT_RAW) < 0) {
return -1;
}
if (PyFile_WriteString(": ", file) < 0) {
return -1;
}
}
else {
if (PyFile_WriteString("Exception ignored in: ", file) < 0) {
return -1;
}
}

if (PyFile_WriteObject(obj, file, 0) < 0) {
@@ -1162,6 +1175,14 @@ write_unraisable_exc_file(PyThreadState *tstate, PyObject *exc_type,
return -1;
}
}
else if (err_msg != NULL && err_msg != Py_None) {
if (PyFile_WriteObject(err_msg, file, Py_PRINT_RAW) < 0) {
return -1;
}
if (PyFile_WriteString(":\n", file) < 0) {
return -1;
}
}

if (exc_tb != NULL && exc_tb != Py_None) {
if (PyTraceBack_Print(exc_tb, file) < 0) {
@@ -1178,8 +1199,9 @@ write_unraisable_exc_file(PyThreadState *tstate, PyObject *exc_type,
const char *className = PyExceptionClass_Name(exc_type);
if (className != NULL) {
const char *dot = strrchr(className, '.');
if (dot != NULL)
if (dot != NULL) {
className = dot+1;
}
}

_Py_IDENTIFIER(__module__);
@@ -1238,7 +1260,8 @@ write_unraisable_exc_file(PyThreadState *tstate, PyObject *exc_type,

static int
write_unraisable_exc(PyThreadState *tstate, PyObject *exc_type,
PyObject *exc_value, PyObject *exc_tb, PyObject *obj)
PyObject *exc_value, PyObject *exc_tb, PyObject *err_msg,
PyObject *obj)
{
PyObject *file = _PySys_GetObjectId(&PyId_stderr);
if (file == NULL || file == Py_None) {
@@ -1249,7 +1272,7 @@ write_unraisable_exc(PyThreadState *tstate, PyObject *exc_type,
while we use it */
Py_INCREF(file);
int res = write_unraisable_exc_file(tstate, exc_type, exc_value, exc_tb,
obj, file);
err_msg, obj, file);
Py_DECREF(file);

return res;
@@ -1272,9 +1295,10 @@ _PyErr_WriteUnraisableDefaultHook(PyObject *args)
PyObject *exc_type = PyStructSequence_GET_ITEM(args, 0);
PyObject *exc_value = PyStructSequence_GET_ITEM(args, 1);
PyObject *exc_tb = PyStructSequence_GET_ITEM(args, 2);
PyObject *obj = PyStructSequence_GET_ITEM(args, 3);
PyObject *err_msg = PyStructSequence_GET_ITEM(args, 3);
PyObject *obj = PyStructSequence_GET_ITEM(args, 4);

if (write_unraisable_exc(tstate, exc_type, exc_value, exc_tb, obj) < 0) {
if (write_unraisable_exc(tstate, exc_type, exc_value, exc_tb, err_msg, obj) < 0) {
return NULL;
}
Py_RETURN_NONE;
@@ -1287,13 +1311,18 @@ _PyErr_WriteUnraisableDefaultHook(PyObject *args)
for Python to handle it. For example, when a destructor raises an exception
or during garbage collection (gc.collect()).
If err_msg_str is non-NULL, the error message is formatted as:
"Exception ignored %s" % err_msg_str. Otherwise, use "Exception ignored in"
error message.
An exception must be set when calling this function. */
void
PyErr_WriteUnraisable(PyObject *obj)
_PyErr_WriteUnraisableMsg(const char *err_msg_str, PyObject *obj)
{
PyThreadState *tstate = _PyThreadState_GET();
assert(tstate != NULL);

PyObject *err_msg = NULL;
PyObject *exc_type, *exc_value, *exc_tb;
_PyErr_Fetch(tstate, &exc_type, &exc_value, &exc_tb);

@@ -1322,13 +1351,20 @@ PyErr_WriteUnraisable(PyObject *obj)
}
}

if (err_msg_str != NULL) {
err_msg = PyUnicode_FromFormat("Exception ignored %s", err_msg_str);
if (err_msg == NULL) {
PyErr_Clear();
}
}

_Py_IDENTIFIER(unraisablehook);
PyObject *hook = _PySys_GetObjectId(&PyId_unraisablehook);
if (hook != NULL && hook != Py_None) {
PyObject *hook_args;

hook_args = make_unraisable_hook_args(tstate, exc_type, exc_value,
exc_tb, obj);
exc_tb, err_msg, obj);
if (hook_args != NULL) {
PyObject *args[1] = {hook_args};
PyObject *res = _PyObject_FastCall(hook, args, 1);
@@ -1337,6 +1373,18 @@ PyErr_WriteUnraisable(PyObject *obj)
Py_DECREF(res);
goto done;
}

err_msg_str = "Exception ignored in sys.unraisablehook";
}
else {
err_msg_str = ("Exception ignored on building "
"sys.unraisablehook arguments");
}

Py_XDECREF(err_msg);
err_msg = PyUnicode_FromString(err_msg_str);
if (err_msg == NULL) {
PyErr_Clear();
}

/* sys.unraisablehook failed: log its error using default hook */
@@ -1350,15 +1398,25 @@ PyErr_WriteUnraisable(PyObject *obj)

default_hook:
/* Call the default unraisable hook (ignore failure) */
(void)write_unraisable_exc(tstate, exc_type, exc_value, exc_tb, obj);
(void)write_unraisable_exc(tstate, exc_type, exc_value, exc_tb,
err_msg, obj);

done:
Py_XDECREF(exc_type);
Py_XDECREF(exc_value);
Py_XDECREF(exc_tb);
Py_XDECREF(err_msg);
_PyErr_Clear(tstate); /* Just in case */
}


void
PyErr_WriteUnraisable(PyObject *obj)
{
_PyErr_WriteUnraisableMsg(NULL, obj);
}


extern PyObject *PyModule_GetWarningsModule(void);


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