Function traverse_offset_bases

include/pybind11/detail/class.h:304–322

For multiple inheritance types we need to recursively register/deregister base pointers for any base classes with pointers that are difference from the instance value pointer so that we can correctly recognize an offset base class pointer. This calls a function with any offset base ptrs.

/// correctly recognize an offset base class pointer. This calls a function with any offset base
/// ptrs.
inline void traverse_offset_bases(void *valueptr,
                                  const detail::type_info *tinfo,
                                  instance *self,
                                  bool (*f)(void * /*parentptr*/, instance * /*self*/)) {
    for (handle h : reinterpret_borrow<tuple>(tinfo->type->tp_bases)) {
        if (auto *parent_tinfo = get_type_info(reinterpret_cast<PyTypeObject *>(h.ptr()))) {
            for (auto &c : parent_tinfo->implicit_casts) {
                if (c.first == tinfo->cpptype) {
                    auto *parentptr = c.second(valueptr);
                    if (parentptr != valueptr) {
                        f(parentptr, self);
                    }
                    traverse_offset_bases(parentptr, parent_tinfo, self, f);
                    break;
                }
            }
        }
    }
}

#ifdef Py_GIL_DISABLED
inline void enable_try_inc_ref(PyObject *obj) {