fcup-smsend[mult]: fix buglet in K&R C NULL pointer passing The only 100% safe way to pass a NULL pointer as a function argument in K&R C is to cast 0 to a pointer type; failing to do so may cause mysterious bugs (invalid stack frames or garbage in argument registers) on 64-bit machines. This issue has already been fixed in most of FC host tools, but I just found some missed spots: passing of NULL UDH to PDU encoding functions in fcup-smsend[mult] in the case of single (not concatenated) SMS.

/*
 * Concatenate s2 on the end of s1.  S1's space must be large enough.
 * At most n characters are moved.
 * Return s1.
 */

char *
strncat(s1, s2, n)
	register char *s1, *s2;
	register n;
{
	register char *os1;

	os1 = s1;
	while (*s1++)
		;
	--s1;
	while (*s1++ = *s2++)
		if (--n < 0) {
			*--s1 = '\0';
			break;
		}
	return(os1);
}