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bpo-46009: Do not exhaust generator when send() method raises #29986

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Merged
markshannon merged 3 commits into from
Dec 8, 2021
Merged

bpo-46009: Do not exhaust generator when send() method raises #29986

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5595bad
Do not exhaust generator when send() method raises 'can't send non-No…
markshannon Dec 8, 2021
0f561a4
Fix typo
markshannon Dec 8, 2021
91cafca
Add news.
markshannon Dec 8, 2021
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Do not exhaust generator when send() method raises 'can't send non-No… 
…ne value to a just-started generator'
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@markshannon
markshannon committed Dec 8, 2021
commit 5595bad6816c06933755acea73c08b4f9315682d
5 changes: 2 additions & 3 deletions Doc/library/dis.rst
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Expand Up @@ -1170,9 +1170,8 @@ All of the following opcodes use their arguments.

.. opcode:: GEN_START (kind)

Pops TOS. If TOS was not ``None``, raises an exception. The ``kind``
operand corresponds to the type of generator or coroutine and determines
the error message. The legal kinds are 0 for generator, 1 for coroutine,
Pops TOS. The ``kind``operand corresponds to the type of generator or
coroutine. The legal kinds are 0 for generator, 1 for coroutine,
and 2 for async generator.

.. versionadded:: 3.10
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8 changes: 8 additions & 0 deletions Lib/test/test_generators.py
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Expand Up @@ -162,6 +162,14 @@ def f():
with self.assertRaises((TypeError, pickle.PicklingError)):
pickle.dumps(g, proto)

def test_send_non_none_to_new_gen(self):
def f():
yield 1
g = f()
with self.assertRaises(TypeError):
g.send(0)
self.assertEqual(next(g), 1)


class ExceptionTest(unittest.TestCase):
# Tests for the issue #23353: check that the currently handled exception
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13 changes: 13 additions & 0 deletions Objects/genobject.c
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Expand Up @@ -157,6 +157,19 @@ gen_send_ex2(PyGenObject *gen, PyObject *arg, PyObject **presult,
PyObject *result;

*presult = NULL;
if (frame->f_lasti < 0 && arg && arg != Py_None) {
const char *msg = "can't send non-None value to a "
"just-started generator";
if (PyCoro_CheckExact(gen)) {
msg = NON_INIT_CORO_MSG;
}
else if (PyAsyncGen_CheckExact(gen)) {
msg = "can't send non-None value to a "
"just-started async generator";
}
PyErr_SetString(PyExc_TypeError, msg);
return PYGEN_ERROR;
}
if (gen->gi_frame_valid && _PyFrame_IsExecuting(frame)) {
const char *msg = "generator already executing";
if (PyCoro_CheckExact(gen)) {
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20 changes: 2 additions & 18 deletions Python/ceval.c
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Expand Up @@ -2714,25 +2714,9 @@ _PyEval_EvalFrameDefault(PyThreadState *tstate, InterpreterFrame *frame, int thr

TARGET(GEN_START) {
PyObject *none = POP();
assert(none == Py_None);
assert(oparg < 3);
Py_DECREF(none);
if (!Py_IsNone(none)) {
if (oparg > 2) {
_PyErr_SetString(tstate, PyExc_SystemError,
"Illegal kind for GEN_START");
}
else {
static const char *gen_kind[3] = {
"generator",
"coroutine",
"async generator"
};
_PyErr_Format(tstate, PyExc_TypeError,
"can't send non-None value to a "
"just-started %s",
gen_kind[oparg]);
}
goto error;
}
DISPATCH();
}

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