Function clear_instance

include/pybind11/detail/class.h:455–492

Clears all internal data from the instance and removes it from registered instances in preparation for deallocation.

/// Clears all internal data from the instance and removes it from registered instances in
/// preparation for deallocation.
inline void clear_instance(PyObject *self) {
    auto *instance = reinterpret_cast<detail::instance *>(self);

    // Deallocate any values/holders, if present:
    for (auto &v_h : values_and_holders(instance)) {
        if (v_h) {

            // We have to deregister before we call dealloc because, for virtual MI types, we still
            // need to be able to get the parent pointers.
            if (v_h.instance_registered()
                && !deregister_instance(instance, v_h.value_ptr(), v_h.type)) {
                pybind11_fail(
                    "pybind11_object_dealloc(): Tried to deallocate unregistered instance!");
            }

            if (instance->owned || v_h.holder_constructed()) {
                v_h.type->dealloc(v_h);
            }
        } else if (v_h.holder_constructed()) {
            v_h.type->dealloc(v_h); // Disowned instance.
        }
    }
    // Deallocate the value/holder layout internals:
    instance->deallocate_layout();

    if (instance->weakrefs) {
        PyObject_ClearWeakRefs(self);
    }

    PyObject **dict_ptr = _PyObject_GetDictPtr(self);
    if (dict_ptr) {
        Py_CLEAR(*dict_ptr);
    }

    if (instance->has_patients) {
        clear_patients(self);
    }
}

/// Instance destructor function for all pybind11 types. It calls `type_info.dealloc`
/// to destroy the C++ object itself, while the rest is Python bookkeeping.