paxHdrs = make(map[string]string)

	var whyNoUSTAR, whyNoPAX, whyNoGNU string
	var preferPAX bool // Prefer PAX over USTAR
	verifyString := func(s string, size int, name, paxKey string) {
		// NUL-terminator is optional for path and linkpath.
		// Technically, it is required for uname and gname,
		// but neither GNU nor BSD tar checks for it.
		tooLong := len(s) > size
		allowLongGNU := paxKey == paxPath || paxKey == paxLinkpath