util.poll: Reject fd == FD_SETSIZE FD_SETSIZE is the maximum total number of FDs supports (well, the highest valid fd number). 0 is a valid fd number, so it supports up to 1023 if FD_SETSIZE is 1024. This is just a fencepost issue, fds > FD_SETSIZE were already correctly rejected.

{
    "JSON Test Pattern pass3": {
        "The outermost value": "must be an object or array.",
        "In this test": "It is an object."
    }
}