check timegm return code

Signed-off-by: John Crispin <john@phrozen.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/nmea.c b/nmea.c
index 4a49528..7793097 100644
--- a/nmea.c
+++ b/nmea.c
@@ -97,12 +97,14 @@ nmea_rmc_cb(void)
 		DEBUG(3, "date: %s UTC\n", tmp);
 
 		if (adjust_clock) {
-			struct timeval tv = { timegm(&tm), 0 };
+			time_t sec = timegm(&tm);
+			struct timeval tv = { 0 };
 			struct timeval cur;
 
 			gettimeofday(&cur, NULL);
 
-			if (abs(cur.tv_sec - tv.tv_sec) > MAX_TIME_OFFSET) {
+			if ((sec < 0) || (abs(cur.tv_sec - tv.tv_sec) > MAX_TIME_OFFSET)) {
+				tv.tv_sec = sec;
 				if (++nmea_bad_time > MAX_BAD_TIME) {
 					LOG("system time differs from GPS time by more than %d seconds. Using %s UTC as the new time\n", MAX_TIME_OFFSET, tmp);
 					/* only set datetime if specified by command line argument! */