Before the fix, sample PPS Logs:
gpsd:PROG: KPPS:/dev/pps0 Clear cycle: -1236963952, duration: 1000000 @ (null)
gpsd:PROG: PPS:/dev/pps0 Clear cycle:       0, duration: 1000000 @ (null)

With this fix, we see logs like this:
gpsd:PROG: KPPS:/dev/pps0 Clear cycle: 1000010, duration:  100003 @  1577729345.554599378
gpsd:PROG: PPS:/dev/pps0 Clear cycle: 1000010, duration:  100003 @  1577729345.554599378

When the system clock changes without this fix, and the
debug level is 4 or greater, GPSD crashes on 32 bit ARM.
This fix prevents strlen() in vfprintf() from being given
a garbage pointer.  cycle, cycle_kpps, duration and
duration_kpps are defined as long long, so by the C
standard, the format string is %lld.
=======================================================================
diff -Naur old/ppsthread.c new/ppsthread.c
--- old/ppsthread.c	2017-02-01 11:36:31.575212221 -0600
+++ new/ppsthread.c	2017-02-01 11:44:48.269536679 -0600
@@ -770,10 +770,9 @@
             edge_str = edge ? "Assert" : "Clear";
 	    cycle = cycle_tio;
 	    duration = duration_tio;
-
 	    timespec_str( &clock_ts, ts_str1, sizeof(ts_str1) );
 	    thread_context->log_hook(thread_context, THREAD_PROG,
-		    "TPPS:%s %.10s cycle: %d, duration: %d @ %s\n",
+		    "TPPS:%s %.10s cycle: %lld, duration: %lld @ %s\n",
 		    thread_context->devicename, edge_str, cycle, duration,
                     ts_str1);
 
@@ -840,7 +839,7 @@
 
 	    timespec_str( &clock_ts_kpps, ts_str1, sizeof(ts_str1) );
 	    thread_context->log_hook(thread_context, THREAD_PROG,
-		"KPPS:%s %.10s cycle: %7d, duration: %7d @ %s\n",
+		"KPPS:%s %.10s cycle: %7lld, duration: %7lld @ %s\n",
 		thread_context->devicename,
 		edge_str,
 		cycle_kpps, duration_kpps, ts_str1);
@@ -898,7 +897,7 @@
 	state_last = state;
 	timespec_str( &clock_ts, ts_str1, sizeof(ts_str1) );
 	thread_context->log_hook(thread_context, THREAD_PROG,
-	    "PPS:%s %.10s cycle: %7d, duration: %7d @ %s\n",
+	    "PPS:%s %.10s cycle: %7lld, duration: %7lld @ %s\n",
 	    thread_context->devicename,
 	    edge_str,
 	    cycle, duration, ts_str1);