Issue #9566: explain why (int)len cannot underflow

diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index dea682d412e5d40d5877f2b7a5559a90bd5eab35..21ab0882ca1a06ddd00f38c049024d017a6f40a6 100644 (file)
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -839,6 +839,7 @@ readinst(char *buf, int buf_size, PyObject *meth)
 finally:
     Py_XDECREF(arg);
     Py_XDECREF(str);
+    /* len <= buf_size <= INT_MAX (see above) */
     return (int)len;
 }