From b7f5aa7eabd19ea0c4921be43473abf5e605913d Mon Sep 17 00:00:00 2001
From: Tatsuya Yamaguchi <susumu-336@hotmail.co.jp>
Date: Sat, 9 Jan 2021 12:17:08 +0900
Subject: [PATCH] Copter: fix compilation when rtl option is disabled

---
 ArduCopter/avoidance_adsb.cpp | 18 ++++++++++++++----
 ArduCopter/avoidance_adsb.h   |  3 +++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/ArduCopter/avoidance_adsb.cpp b/ArduCopter/avoidance_adsb.cpp
index eb2227c5e5..80d2e96744 100644
--- a/ArduCopter/avoidance_adsb.cpp
+++ b/ArduCopter/avoidance_adsb.cpp
@@ -144,6 +144,16 @@ void AP_Avoidance_Copter::set_mode_else_try_RTL_else_LAND(Mode::Number mode)
     }
 }
 
+int16_t AP_Avoidance_Copter::get_altitude_minimum() const
+{
+#if MODE_RTL_ENABLED == ENABLED
+    // do not descend if below RTL alt
+    return copter.g.rtl_altitude;
+#else
+    return 0;
+#endif
+}
+
 // check flight mode is avoid_adsb
 bool AP_Avoidance_Copter::check_flightmode(bool allow_mode_change)
 {
@@ -179,8 +189,8 @@ bool AP_Avoidance_Copter::handle_avoidance_vertical(const AP_Avoidance::Obstacle
         velocity_neu.z = copter.wp_nav->get_default_speed_up();
     } else {
         velocity_neu.z = -copter.wp_nav->get_default_speed_down();
-        // do not descend if below RTL alt
-        if (copter.current_loc.alt < copter.g.rtl_altitude) {
+        // do not descend if below minimum altitude
+        if (copter.current_loc.alt < get_altitude_minimum()) {
             velocity_neu.z = 0.0f;
         }
     }
@@ -238,8 +248,8 @@ bool AP_Avoidance_Copter::handle_avoidance_perpendicular(const AP_Avoidance::Obs
             velocity_neu.z *= copter.wp_nav->get_default_speed_up();
         } else {
             velocity_neu.z *= copter.wp_nav->get_default_speed_down();
-            // do not descend if below RTL alt
-            if (copter.current_loc.alt < copter.g.rtl_altitude) {
+            // do not descend if below minimum altitude
+            if (copter.current_loc.alt < get_altitude_minimum()) {
                 velocity_neu.z = 0.0f;
             }
         }
diff --git a/ArduCopter/avoidance_adsb.h b/ArduCopter/avoidance_adsb.h
index 1d44406826..e156e1361e 100644
--- a/ArduCopter/avoidance_adsb.h
+++ b/ArduCopter/avoidance_adsb.h
@@ -19,6 +19,9 @@ private:
     // helper function to set modes and always succeed
     void set_mode_else_try_RTL_else_LAND(Mode::Number mode);
 
+    // get minimum limit altitude allowed on descend
+    int16_t get_altitude_minimum() const;
+
 protected:
     // override avoidance handler
     MAV_COLLISION_ACTION handle_avoidance(const AP_Avoidance::Obstacle *obstacle, MAV_COLLISION_ACTION requested_action) override;