From 8464ef48e832857b4214411ebc14f3deeabc04dd Mon Sep 17 00:00:00 2001
From: Richard Harrison <rjh@zaretto.com>
Date: Sun, 2 May 2021 17:34:33 +0200
Subject: [PATCH] Fixes #2579 Emesary segfault on reset.

Need to call OnDeregister before the object is deleted (because not using smart pointers for receivers).
---
 simgear/emesary/IReceiver.hxx   | 3 ++-
 simgear/emesary/Transmitter.hxx | 6 ++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/simgear/emesary/IReceiver.hxx b/simgear/emesary/IReceiver.hxx
index b5197517..6318d01b 100644
--- a/simgear/emesary/IReceiver.hxx
+++ b/simgear/emesary/IReceiver.hxx
@@ -38,7 +38,8 @@ namespace simgear
             {
             }
 
-            /// Called when de-registered at a transmitter
+            /// Called when de-registered at a transmitter; i.e. as a result of 
+            /// Transmitter::DeRegister.
             virtual void OnDeRegisteredAtTransmitter(class Transmitter *p)
             {
             }
diff --git a/simgear/emesary/Transmitter.hxx b/simgear/emesary/Transmitter.hxx
index d51fe7ed..a5feface 100644
--- a/simgear/emesary/Transmitter.hxx
+++ b/simgear/emesary/Transmitter.hxx
@@ -89,7 +89,9 @@ namespace simgear
 				}
 			}
 
-			//  Removes an object from receving message from this transmitter
+			///  Removes an object from receving message from this transmitter. 
+			/// NOTES: OnDeRegisteredAtTransmitter will be called as a result of this method
+			///        If recipient is in the list of new recipients it will be removed from that list
 			virtual void DeRegister(IReceiverPtr r)
 			{
 				std::lock_guard<std::mutex> scopeLock(_lock);
@@ -102,6 +104,7 @@ namespace simgear
 						new_recipient_list.erase(location);
 				}
 				deleted_recipient_list.push_back(r);
+				r->OnDeRegisteredAtTransmitter(this);
 				pendingDeletions++;
 			}
 
@@ -125,7 +128,6 @@ namespace simgear
 
 						RecipientList::iterator location = std::find(recipient_list.begin(), recipient_list.end(), r);
 						if (location != recipient_list.end()) {
-							r->OnDeRegisteredAtTransmitter(this);
 							recipient_list.erase(location);
 						}
 					});