From aca340b81090277e1ab4f49bae9dff04fb9c9783 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Thu, 11 Dec 2025 11:43:00 -0700
Subject: [PATCH] an initial fix for a crash occuring when deleting routes that
 lead to RouteGroup deletion

The RouteGroup containing the deleted routes emits the RouteRemoved signal; Session handles this
and if the RouteGroup is now empty, deletes the RouteGroup *while in the middle of the signal
emission process*. This deletes the Signal (since it was owned by the RouteGroup) which leads
to a crash inside the signal emission code, since that is now running "on" a deleted Signal
object.

This change simply makes that signal static, and so deleting the RouteGroup has no effect
on the Signal itself.

More changes to come related to better (shared_ptr<RouteGroup>) mgmt of RouteGroup lifetimes.
---
 libs/ardour/ardour/route_group.h | 2 +-
 libs/ardour/route_group.cc       | 2 ++
 libs/ardour/session.cc           | 2 ++
 libs/ardour/session_state.cc     | 1 -
 4 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/libs/ardour/ardour/route_group.h b/libs/ardour/ardour/route_group.h
index 446f76c0c1..2deaab4206 100644
--- a/libs/ardour/ardour/route_group.h
+++ b/libs/ardour/ardour/route_group.h
@@ -147,7 +147,7 @@ public:
 	/** Emitted when a route has been added to this group */
 	PBD::Signal<void(RouteGroup *, std::weak_ptr<ARDOUR::Route> )> RouteAdded;
 	/** Emitted when a route has been removed from this group */
-	PBD::Signal<void(RouteGroup *, std::weak_ptr<ARDOUR::Route> )> RouteRemoved;
+	static PBD::Signal<void(RouteGroup *, std::weak_ptr<ARDOUR::Route> )> RouteRemoved;
 
 	XMLNode& get_state () const;
 
diff --git a/libs/ardour/route_group.cc b/libs/ardour/route_group.cc
index e5b532f980..73392e662a 100644
--- a/libs/ardour/route_group.cc
+++ b/libs/ardour/route_group.cc
@@ -64,6 +64,8 @@ namespace ARDOUR {
 	}
 }
 
+PBD::Signal<void(RouteGroup *, std::weak_ptr<ARDOUR::Route> )> RouteGroup::RouteRemoved;
+
 void
 RouteGroup::make_property_quarks ()
 {
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 4372cc1c20..b97f7b686b 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -520,6 +520,8 @@ Session::Session (AudioEngine &eng,
 	StartTimeChanged.connect_same_thread (*this, std::bind (&Session::start_time_changed, this, _1));
 	EndTimeChanged.connect_same_thread (*this, std::bind (&Session::end_time_changed, this, _1));
 
+	RouteGroup::RouteRemoved.connect_same_thread (*this, std::bind (&Session::route_removed_from_route_group, this, _1, _2));
+
 	LatentSend::ChangedLatency.connect_same_thread (*this, std::bind (&Session::send_latency_compensation_change, this));
 	LatentSend::QueueUpdate.connect_same_thread (*this, std::bind (&Session::update_send_delaylines, this));
 	Latent::DisableSwitchChanged.connect_same_thread (*this, std::bind (&Session::queue_latency_recompute, this));
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index aa4095c036..075a67a1fd 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -3573,7 +3573,6 @@ Session::add_route_group (RouteGroup* g)
 	route_group_added (g); /* EMIT SIGNAL */
 
 	g->RouteAdded.connect_same_thread (*this, std::bind (&Session::route_added_to_route_group, this, _1, _2));
-	g->RouteRemoved.connect_same_thread (*this, std::bind (&Session::route_removed_from_route_group, this, _1, _2));
 	g->PropertyChanged.connect_same_thread (*this, std::bind (&Session::route_group_property_changed, this, g));
 
 	set_dirty ();