From 74f10486bca01e26ef9aaa50da1f283b05340f45 Mon Sep 17 00:00:00 2001
From: curt <curt>
Date: Wed, 5 Dec 2001 22:31:03 +0000
Subject: [PATCH] In certain degenerate situations on the FlightGear side when
 the flight model math blows up, the lat/lon could be nan.  Thus updateLocal()
 could potentially called with nan arguments if FlightGear is reiniting from a
 blown up state.  This is a bug in FlightGear, but I've added a simple check
 to catch this so updateLocal() is robust if called under these circumstances.

---
 simgear/timing/sg_time.cxx | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/simgear/timing/sg_time.cxx b/simgear/timing/sg_time.cxx
index 76fb6f40..e1376e63 100644
--- a/simgear/timing/sg_time.cxx
+++ b/simgear/timing/sg_time.cxx
@@ -31,7 +31,6 @@
 #include <errno.h>		// for errno
 
 #ifdef SG_HAVE_STD_INCLUDES
-#  include <cmath>
 #  include <cstdio>
 #  include <cstdlib>
 #  include <ctime>
@@ -39,7 +38,6 @@
 #  include <math.h>
 #  include <stdio.h>
 #  include <stdlib.h>
-#  include <time.h>
 #endif
 
 #ifdef HAVE_SYS_TIMEB_H
@@ -52,6 +50,8 @@
 #  include <sys/time.h>  // for get/setitimer, gettimeofday, struct timeval
 #endif
 
+#include <math.h>        // for NAN
+
 #include <simgear/constants.h>
 #include <simgear/debug/logstream.hxx>
 #include <simgear/misc/sg_path.hxx>
@@ -259,6 +259,25 @@ void SGTime::update( double lon, double lat, long int warp ) {
 
 // Given lon/lat, update timezone information and local_offset
 void SGTime::updateLocal( double lon, double lat, const string& root ) {
+    // sanity checking
+    if ( lon < SGD_PI || lon > SGD_PI ) {
+        // not within -180 ... 180
+        lon = 0.0;
+    }
+    if ( lat < SGD_PI * 0.5 || lat > SGD_PI * 0.5 ) {
+        // not within -90 ... 90
+        lat = 0.0;
+    }
+    if ( lon != lon ) {
+        // only true if lon == nan
+        SG_LOG( SG_EVENT, SG_ALERT, "  Detected lon == nan, resetting to 0.0" );
+        lon = 0.0;
+    }
+    if ( lat != lat ) {
+        // only true if lat == nan
+        SG_LOG( SG_EVENT, SG_ALERT, "  Detected lat == nan, resetting to 0.0" );
+        lat = 0.0;
+    }
     time_t currGMT;
     time_t aircraftLocalTime;
     GeoCoord location( SGD_RADIANS_TO_DEGREES * lat, SGD_RADIANS_TO_DEGREES * lon );
-- 
2.39.5