From 66aa6453d641cfce82108825f9e9e29654851cb8 Mon Sep 17 00:00:00 2001
From: Chris Jerdonek <chris.jerdonek@gmail.com>
Date: Sat, 2 May 2020 21:12:48 -0700
Subject: [PATCH 1/2] Remove the exc_value NULL check and add a failing test.

---
 Lib/test/test_generators.py | 19 +++++++++++++++++++
 Objects/genobject.c         |  6 ++----
 2 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index 4d96f44b150622..ccd13ff42b59b9 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -332,6 +332,25 @@ def f():
         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:
+                # This line causes 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 41a63ae2e666aa..65ad9d4d3d07b0 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -512,11 +512,9 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
     }
 
     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) {
+    if (gen->gi_exc_state.exc_type) {
         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);

From 66ae854acbeacc30553e20812b50d9f731bec3a7 Mon Sep 17 00:00:00 2001
From: Chris Jerdonek <chris.jerdonek@gmail.com>
Date: Sat, 2 May 2020 21:20:18 -0700
Subject: [PATCH 2/2] Check that exc_type doesn't equal Py_None.

---
 Lib/test/test_generators.py | 5 +++--
 Objects/genobject.c         | 5 ++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py
index ccd13ff42b59b9..5824ecd7c37e88 100644
--- a/Lib/test/test_generators.py
+++ b/Lib/test/test_generators.py
@@ -342,8 +342,9 @@ def g():
             try:
                 yield
             except Exception:
-                # This line causes a crash ("Segmentation fault (core dumped)")
-                # on e.g. Fedora 32.
+                # 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()
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 65ad9d4d3d07b0..b27fa929a26258 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -512,7 +512,10 @@ _gen_throw(PyGenObject *gen, int close_on_genexit,
     }
 
     PyErr_Restore(typ, val, tb);
-    if (gen->gi_exc_state.exc_type) {
+    /* 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_XINCREF(gen->gi_exc_state.exc_value);
         Py_XINCREF(gen->gi_exc_state.exc_traceback);