Issue #12149: Update the method cache after a type's dictionnary gets

cleared by the garbage collector.  This fixes a segfault when an instance
and its type get caught in a reference cycle, and the instance's
deallocator calls one of the methods on the type (e.g. when subclassing
IOBase).

Diagnosis and patch by Davide Rizzo.

1 files changed, 2 insertions, 0 deletions

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 49c7e07..8326d07 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1013,6 +1013,8 @@ subtype_dealloc(PyObject *self)
     assert(basedealloc);
     basedealloc(self);
 
+    PyType_Modified(type);
+
     /* Can't reference self beyond this point */
     Py_DECREF(type);