bpo-29587: allow chaining NULL exceptions in _gen_throw() (GH-19877)
This is a follow-up to GH-19823 that removes the check that the
exception value isn't NULL, prior to calling _PyErr_ChainExceptions().
This enables implicit exception chaining for gen.throw() in more
circumstances.
The commit also adds a test that a particular code snippet involving
gen.throw() doesn't crash. The test shows why the new
`gi_exc_state.exc_type != Py_None` check that was added is necessary.
Without the new check, the code snippet (as well as a number of other
tests) crashes on certain platforms (e.g. Fedora but not Mac).
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 4d96f44..5824ecd 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -332,6 +332,26 @@
context = cm.exception.__context__
self.assertEqual((type(context), context.args), (KeyError, ('a',)))
+ def test_throw_after_none_exc_type(self):
+ def g():
+ try:
+ raise KeyError
+ except KeyError:
+ pass
+
+ try:
+ yield
+ except Exception:
+ # Without the `gi_exc_state.exc_type != Py_None` in
+ # _gen_throw(), this line was causing a crash ("Segmentation
+ # fault (core dumped)") on e.g. Fedora 32.
+ raise RuntimeError
+
+ gen = g()
+ gen.send(None)
+ with self.assertRaises(RuntimeError) as cm:
+ gen.throw(ValueError)
+
class YieldFromTests(unittest.TestCase):
def test_generator_gi_yieldfrom(self):
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 41a63ae..b27fa92 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -512,11 +512,12 @@
}
PyErr_Restore(typ, val, tb);
- /* XXX Should we also handle the case where exc_type is true and
- exc_value is false? */
- if (gen->gi_exc_state.exc_type && gen->gi_exc_state.exc_value) {
+ /* XXX It seems like we shouldn't have to check not equal to Py_None
+ here because exc_type should only ever be a class. But not including
+ this check was causing crashes on certain tests e.g. on Fedora. */
+ if (gen->gi_exc_state.exc_type && gen->gi_exc_state.exc_type != Py_None) {
Py_INCREF(gen->gi_exc_state.exc_type);
- Py_INCREF(gen->gi_exc_state.exc_value);
+ Py_XINCREF(gen->gi_exc_state.exc_value);
Py_XINCREF(gen->gi_exc_state.exc_traceback);
_PyErr_ChainExceptions(gen->gi_exc_state.exc_type,
gen->gi_exc_state.exc_value, gen->gi_exc_state.exc_traceback);