commit f812fef2f8f12441ce559335645433c8124e7db5
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Fri Oct 22 14:46:56 2021 -0700
committer GitHub <noreply@github.com> Fri Oct 22 14:46:56 2021 -0700
tree a96fcaa7e695d4f1dee35c8c23c0e9061ed0b5f3
parent 19903085c3ad7a17c8047e1556c700f2eb109931

bpo-30570: Use Py_EnterRecursiveCall() in issubclass() (GH-29048)


* Use Py_EnterRecursiveCall() in issubclass()

Reviewed-by: Gregory P. Smith <greg@krypto.org> [Google]
(cherry picked from commit 423fa1c1817abfa8c3d1bc308ddbbd8f28b69d68)

Co-authored-by: Dennis Sweeney <36520290+sweeneyde@users.noreply.github.com>

Objects/abstract.c

diff --git a/Objects/abstract.c b/Objects/abstract.c
index c056c66..3ac8554 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -2557,14 +2557,22 @@ abstract_issubclass(PyObject *derived, PyObject *cls)
             derived = PyTuple_GET_ITEM(bases, 0);
             continue;
         }
-        for (i = 0; i < n; i++) {
-            r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls);
-            if (r != 0)
-                break;
-        }
-        Py_DECREF(bases);
-        return r;
+        break;
     }
+    assert(n >= 2);
+    if (Py_EnterRecursiveCall(" in __issubclass__")) {
+        Py_DECREF(bases);
+        return -1;
+    }
+    for (i = 0; i < n; i++) {
+        r = abstract_issubclass(PyTuple_GET_ITEM(bases, i), cls);
+        if (r != 0) {
+            break;
+        }
+    }
+    Py_LeaveRecursiveCall();
+    Py_DECREF(bases);
+    return r;
 }
 
 static int