If we just delete this declaration of 'i', the other 'i' instances in for loops will get error with undeclared variable 'i', maybe it is better to change i = 0 into int i = 0 in each loop, this will both avoid the original unused 'i' problem and comply to C99 standard.
 
[chunwang@fs-qe src]$ cat ./rpcb_svc_com.c  |egrep SVC_RUN_DEBUG -A 5
#ifdef SVC_RUN_DEBUG
	int i;
#endif
	register struct pollfd	*p;
	fd_set cleanfds;

--
#ifdef SVC_RUN_DEBUG
		if (debugging) {
			fprintf(stderr, "polling for read on fd < ");
			for (i = 0, p = pollfds; i < nfds; i++, p++)
				if (p->events)
					fprintf(stderr, "%d ", p->fd);
--
#ifdef SVC_RUN_DEBUG
			if (debugging) {
				fprintf(stderr, "poll returned read fds < ");
				for (i = 0, p = pollfds; i < nfds; i++, p++)
					if (p->revents)
						fprintf(stderr, "%d ", p->fd);
--
<--snip-->
[chunwang@fs-qe rpcbind]$ cat ./rpcbind-0.2.0-i-warn.patch
diff -up rpcbind-0.2.0/src/rpcb_svc_com.c.orig rpcbind-0.2.0/src/rpcb_svc_com.c
--- rpcbind-0.2.0/src/rpcb_svc_com.c.orig	2017-02-25 14:47:09.839325988 -0500
+++ rpcbind-0.2.0/src/rpcb_svc_com.c	2017-02-25 14:47:57.424187563 -0500
@@ -1106,9 +1106,6 @@ my_svc_run()
 	struct pollfd pollfds[FD_SETSIZE];
 	int poll_ret, check_ret;
 	int n;
-#ifdef SVC_RUN_DEBUG
-	int i;
-#endif
 	register struct pollfd	*p;
 	fd_set cleanfds;

(In reply to ChunYu Wang from comment #4)
> If we just delete this declaration of 'i', the other 'i' instances in for
> loops will get error with undeclared variable 'i', maybe it is better to
> change i = 0 into int i = 0 in each loop, this will both avoid the original
> unused 'i' problem and comply to C99 standard.
No. If that was true there would not have been a warning.
Plus those other SVC_RUN_DEBUG are in different routine.

Moved to VERIFIED according to Comment 6, will keep an eye on related issues in future erratas.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2017:1992