Function get_or_create_proxy_object 

pub unsafe fn get_or_create_proxy_object(
    cx: &mut JSContext,
    obj: HandleObject<'_>,
    is_proxy: bool,
    slot: u32,
    handler: *const c_void,
    owner: *const c_void,
    proxy: MutableHandleObject<'_>,
) -> bool

Safety

handler and owner pointers must outlive the created proxy object.