__stpncpy (q, p, buflen - unklen);
memcpy (q, p, MIN (&numbuf[21] - p, buflen - unklen));
__strerror_r (int errnum, char *buf, size_t buflen){  if (errnum < 0 || errnum >= _sys_nerr || _sys_errlist[errnum] == NULL)    {      /* Buffer we use to print the number in.  For a maximum size for	 `int' of 8 bytes we never need more than 20 digits.  */      char numbuf[21];      const char *unk = _("Unknown error ");      const size_t unklen = strlen (unk);      char *p, *q;      numbuf[20] = '\0';      p = _itoa_word (errnum, &numbuf[20], 10, 0);      /* Now construct the result while taking care for the destination	 buffer size.  */      q = __mempcpy (buf, unk, MIN (unklen, buflen));      if (unklen < buflen)	__stpncpy (q, p, buflen - unklen);      /* Terminate the string in any case.  */      if (buflen > 0)	buf[buflen - 1] = '\0';      return buf;    }  return (char *) _(_sys_errlist[errnum]);}