How to add attribute to PyObject correctly, PyObject size calculated staticly?

I try to add an additonal taint attribute so I could do some dynamic track on all PyObjects.

typedef struct _object {
    Py_ssize_t ob_refcnt;
    PyTypeObject *ob_type;
    int tainted;//1 tainted, 0 not tainted
} PyObject;

But it seems to be pollute the module object. Execpt from the INIT code, is there other place of code I need to change?