Undefined Behaviour

These are the undefined behaviours of pkpy. The behaviour of pkpy is undefined if you do the following things.

1. Modify or delete an attribute of a builtin type. For example, int.__add__ = f or del int.__add__. The interpreter takes fast paths that assume the arithmetic and comparison methods of int and float are the original ones.

2. Call an unbound method with the wrong type of self. For example, int.__add__('1', 2).

3. Type T's __new__ returns an object that is not an instance of T.

4. Call __new__ with a type that is not a subclass of type.