[Python-Dev] Evil setattr hack (original) (raw)

Michael Hudson mwh@python.net
Mon, 14 Apr 2003 07:33:25 +0100

Greg Ewing <greg@cosc.canterbury.ac.nz> writes:

Guido:

Er, this was me.

one approach would be special cases in PyObjectGenericSetAttr, I guess. Before using a hack like that, it might be better to think about what the real problem is.

Aww :-)

Seems to me the problem in general is that there's no way to prevent a class which overrides a method from having a superclass version of that method called through a back door. Which means you can't rely on method overriding to restrict what can be done to an object.

So a proper fix would require either: (1) Providing some way for objects to prevent superclass methods from being called on them when they're not looking or (2) Fixing the typeobject not to rely on that for its security -- by hiding the real dict more deeply somehow?

Yeah, another option would be to make _PyObject_GetDictPtr respect dict descriptors. But that's probably the Wrong Answer, too. Maybe just PyObject_GenericSetAttr should do that -- call PyObject_GetAttr(ob, 'dict'), basically.

bad-answers-on-demand-ly y'rs M.

-- We did requirements and task analysis, iterative design, and user testing. You'd almost think programming languages were an interface between people and computers. -- Steven Pemberton (one of the designers of Python's direct ancestor ABC)