// concurrency safe.
type pcgRand struct {
	noCopy noCopy // help avoid mistakes: ask vet to ensure that we don't make a copy
	state  uint64
	inc    uint64
}

func godebugSeed() *int {
	debug := strings.Split(os.Getenv("GODEBUG"), ",")
	for _, f := range debug {
		if strings.HasPrefix(f, "fuzzseed=") {
			seed, err := strconv.Atoi(strings.TrimPrefix(f, "fuzzseed="))
			if err != nil {