bpo-40696: Fix a hang that can arise after gen.throw() (GH-20287)
This updates _PyErr_ChainStackItem() to use _PyErr_SetObject()
instead of _PyErr_ChainExceptions(). This prevents a hang in
certain circumstances because _PyErr_SetObject() performs checks
to prevent cycles in the exception context chain while
_PyErr_ChainExceptions() doesn't.
(cherry picked from commit 7c30d12bd5359b0f66c4fbc98aa055398bcc8a7e)
Co-authored-by: Chris Jerdonek <chris.jerdonek@gmail.com>
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 271720b..09efbab 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -203,13 +203,15 @@
assert(f->f_back == NULL);
f->f_back = tstate->frame;
- if (exc) {
- _PyErr_ChainStackItem(&gen->gi_exc_state);
- }
-
gen->gi_running = 1;
gen->gi_exc_state.previous_item = tstate->exc_info;
tstate->exc_info = &gen->gi_exc_state;
+
+ if (exc) {
+ assert(_PyErr_Occurred(tstate));
+ _PyErr_ChainStackItem(NULL);
+ }
+
result = _PyEval_EvalFrame(tstate, f, exc);
tstate->exc_info = gen->gi_exc_state.previous_item;
gen->gi_exc_state.previous_item = NULL;