From 312ac7dc7369c0c7357a67b7cd262509a17570ce Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Thu, 14 Jun 2018 13:27:30 +1000
Subject: [PATCH] AP_RTC: return 0 from get_utc_usec if rtc not set

---
 libraries/AP_RTC/AP_RTC.cpp | 12 +++++++++---
 libraries/AP_RTC/AP_RTC.h   |  2 +-
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/libraries/AP_RTC/AP_RTC.cpp b/libraries/AP_RTC/AP_RTC.cpp
index 3871af21af..0aba1356ca 100644
--- a/libraries/AP_RTC/AP_RTC.cpp
+++ b/libraries/AP_RTC/AP_RTC.cpp
@@ -79,11 +79,13 @@ bool AP_RTC::get_utc_usec(uint64_t &usec) const
     return true;
 }
 
-void AP_RTC::get_system_clock_utc(int32_t &hour, int32_t &min, int32_t &sec, int32_t &ms)
+bool AP_RTC::get_system_clock_utc(int32_t &hour, int32_t &min, int32_t &sec, int32_t &ms)
 {
      // get time of day in ms
     uint64_t time_ms = 0;
-    get_utc_usec(time_ms); // may fail, leaving time_ms at 0
+    if (!get_utc_usec(time_ms)) {
+        return false;
+    }
     time_ms /= 1000U;
 
     // separate time into ms, sec, min, hour and days but all expressed in milliseconds
@@ -96,6 +98,8 @@ void AP_RTC::get_system_clock_utc(int32_t &hour, int32_t &min, int32_t &sec, int
     sec = sec_ms / 1000;
     min = min_ms / (60 * 1000);
     hour = hour_ms / (60 * 60 * 1000);
+
+    return true;
 }
 
 // get milliseconds from now to a target time of day expressed as hour, min, sec, ms
@@ -119,7 +123,9 @@ uint32_t AP_RTC::get_time_utc(int32_t hour, int32_t min, int32_t sec, int32_t ms
 
     // get start_time_ms as h, m, s, ms
     int32_t curr_hour, curr_min, curr_sec, curr_ms;
-    get_system_clock_utc(curr_hour, curr_min, curr_sec, curr_ms);
+    if (!get_system_clock_utc(curr_hour, curr_min, curr_sec, curr_ms)) {
+        return 0;
+    }
     int32_t total_delay_ms = 0;
 
     // calculate ms to target
diff --git a/libraries/AP_RTC/AP_RTC.h b/libraries/AP_RTC/AP_RTC.h
index 4c4954fc5a..15c2aa7039 100644
--- a/libraries/AP_RTC/AP_RTC.h
+++ b/libraries/AP_RTC/AP_RTC.h
@@ -37,7 +37,7 @@ public:
     /*
       get time in UTC hours, minutes, seconds and milliseconds
      */
-    void get_system_clock_utc(int32_t &hour, int32_t &min, int32_t &sec, int32_t &ms);
+    bool get_system_clock_utc(int32_t &hour, int32_t &min, int32_t &sec, int32_t &ms);
 
     uint32_t get_time_utc(int32_t hour, int32_t min, int32_t sec, int32_t ms);