gen_iternext(): Don't assume that the current thread state's frame is
not NULL. I don't think it can be NULL from Python code, but if using
generators via the C API I expect a NULL frame is possible.
diff --git a/Python/ceval.c b/Python/ceval.c
index d6b61d5..d334775 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -152,7 +152,7 @@
/* Generators always return to their most recent caller, not
* necessarily their creator. */
- Py_INCREF(tstate->frame);
+ Py_XINCREF(tstate->frame);
assert(f->f_back == NULL);
f->f_back = tstate->frame;
@@ -163,7 +163,7 @@
/* Don't keep the reference to f_back any longer than necessary. It
* may keep a chain of frames alive or it could create a reference
* cycle. */
- Py_DECREF(f->f_back);
+ Py_XDECREF(f->f_back);
f->f_back = NULL;
return result;