Fix the gpsmon display-trashing problem; add some documentation and asserts.

All regression tests pass.

3 files changed, 15 insertions, 15 deletions

diff --git a/gpsmon.c b/gpsmon.c
index f01d16f6..de29f005 100644
--- a/gpsmon.c
+++ b/gpsmon.c
@@ -15,6 +15,7 @@
 #include <signal.h>
 #include <stdarg.h>
 #include <time.h>
+#include <math.h>
 #include <sys/time.h>		/* expected to declare select(2) a la SuS */
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -744,9 +745,9 @@ static void gpsmon_hook(struct gps_device_t *device, gps_mask_t changed UNUSED)
     report_unlock();
 
 #ifdef NTPSHM_ENABLE
-    /* Update the last fix time seen for PPS. */
-    /* FIXME! ntpshm_latch() need device->newdata.time to be set */
-    ntpshm_latch(device, &td);
+    /* Update the last fix time seen for PPS if we've actually seen one. */
+    if (!isnan(device->newdata.time))
+	ntpshm_latch(device, &td);
 #endif /* NTPSHM_ENABLE */
 }
 /*@+observertrans +nullpass +globstate +compdef +uniondef@*/
diff --git a/libgpsd_core.c b/libgpsd_core.c
index e0d605a0..b7316282 100644
--- a/libgpsd_core.c
+++ b/libgpsd_core.c
@@ -1650,6 +1650,9 @@ void ntpshm_latch(struct gps_device_t *device, struct timedrift_t /*@out@*/*td)
 {
     double fix_time, integral, fractional;
 
+    /* this should be an invariant of the way this function is called */
+    assert(!isnan(device->newdata.time));
+
 #ifdef HAVE_CLOCK_GETTIME
     /*@i2@*/(void)clock_gettime(CLOCK_REALTIME, &td->clock);
 #else
@@ -1658,10 +1661,6 @@ void ntpshm_latch(struct gps_device_t *device, struct timedrift_t /*@out@*/*td)
     TVTOTS(&td->clock, &clock_tv);
 #endif /* HAVE_CLOCK_GETTIME */
     fix_time = device->newdata.time;
-    if ( isnan( device->newdata.time ) ) {
-	/* this should not happen, but it does */
-        fix_time = 0.0;
-    }
     /* assume zero when there's no offset method */
     if (device->device_type == NULL
 	|| device->device_type->time_offset == NULL)
diff --git a/ppsthread.c b/ppsthread.c
index 7a441573..ee05d3a1 100644
--- a/ppsthread.c
+++ b/ppsthread.c
@@ -370,14 +370,14 @@ static /*@null@*/ void *gpsd_ppsmonitor(void *arg)
 	/*@ -ignoresigns */
         /* end of time critical section */
 
-        if ( isnan( last_fixtime_real ) ) {
-	    gpsd_report(&session->context->errout, LOG_ERROR,
-			"PPS last_fixtime_real is NAN\n");
-	    /* this should never happen, but it does. */
-            last_fixtime_real = 0.0;
-	    session->last_fixtime.real = 0.0;
-        }
-
+	/*
+	 * If there was no valid time from the GPS when the PPS event was
+	 * asserted, we can do nothing further.  It will be strange if
+	 * this ever actually happens, since we expect PPS to be asserted
+	 * only after a valid fix - which should yield time.
+	 */
+        if (isnan(last_fixtime_real))
+	    continue;
 
 	/* mask for monitored lines */
 	state &= PPS_LINE_TIOC;