size_t part_len = strnlen (argz, len);
size_t part_len = __strnlen (argz, len);
__argz_stringify (char *argz, size_t len, int sep){  if (len > 0)    while (1)      {	size_t part_len = strnlen (argz, len);	argz += part_len;	len -= part_len;	if (len-- <= 1)		/* includes final '\0' we want to stop at */	  break;	*argz++ = sep;      }}