Function keep_alive_impl

include/pybind11/pybind11.h:3231–3259

PYBIND11_NAMESPACE_BEGIN(detail)

PYBIND11_NOINLINE void keep_alive_impl(handle nurse, handle patient) {
    if (!nurse || !patient) {
        pybind11_fail("Could not activate keep_alive!");
    }

    if (patient.is_none() || nurse.is_none()) {
        return; /* Nothing to keep alive or nothing to be kept alive by */
    }

    auto tinfo = all_type_info(Py_TYPE(nurse.ptr()));
    if (!tinfo.empty()) {
        /* It's a pybind-registered type, so we can store the patient in the
         * internal list. */
        add_patient(nurse.ptr(), patient.ptr());
    } else {
        /* Fall back to clever approach based on weak references taken from
         * Boost.Python. This is not used for pybind-registered types because
         * the objects can be destroyed out-of-order in a GC pass. */
        cpp_function disable_lifesupport([patient](handle weakref) {
            patient.dec_ref();
            weakref.dec_ref();
        });

        weakref wr(nurse, disable_lifesupport);

        patient.inc_ref(); /* reference patient and leak the weak reference */
        (void) wr.release();
    }
}

PYBIND11_NOINLINE void
keep_alive_impl(size_t Nurse, size_t Patient, function_call &call, handle ret) {