protect against t_diff overflows e.g. after suspends (Steve Hill)

server/main.c

@@ -43,6 +43,7 @@
 #include <sys/types.h>
 #include <fcntl.h>
 #include <sys/types.h>
+#include <limits.h>
 
 #include "getopt.h"
 
@@ -814,7 +815,16 @@ do_mainloop(void)
 		last_t = t;
 #ifndef WIN32
 		gettimeofday (&t, NULL);
-		t_diff = ((t.tv_sec - last_t.tv_sec) * 1e6 + (t.tv_usec - last_t.tv_usec));
+		t_diff = t.tv_sec - last_t.tv_sec;
+		if ((t_diff + 1) > (LONG_MAX / 1e6)) {
+			/* We're going to overflow the calculation - probably been to sleep, fudge the values */
+			t_diff = 0;
+			process_lag = 1;
+			render_lag = (1e6/RENDER_FREQ);
+		} else {
+			t_diff *= 1e6;
+			t_diff += t.tv_usec - last_t.tv_usec;
+		}
 #else
                 QueryPerformanceCounter(&t);
                 /*t_diff.HighPart = t.HighPart - last_t.HighPart;