add comment for incref rationale

eendebakpt · eendebakpt · commit a91f13ceab22 · 2026-02-04T22:12:32.000+01:00
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
@@ -366,7 +366,7 @@ pairwise_next_lock_held(PyObject *op)
             return NULL;
         }
     }
-    Py_INCREF(old);
+    Py_INCREF(old); // needed because of reentant calls via call to the iterator
     new = (*Py_TYPE(it)->tp_iternext)(it);
     if (new == NULL) {
         Py_CLEAR(po->it);

Original file line number	Diff line number	Diff line change
`@@ -366,7 +366,7 @@ pairwise_next_lock_held(PyObject *op)`
`366`	`366`	`return NULL;`
`367`	`367`	`}`
`368`	`368`	`}`
`369`		`- Py_INCREF(old);`
	`369`	`+ Py_INCREF(old); // needed because of reentant calls via call to the iterator`
`370`	`370`	`new = (*Py_TYPE(it)->tp_iternext)(it);`
`371`	`371`	`if (new == NULL) {`
`372`	`372`	`Py_CLEAR(po->it);`