From 9bb2f2bb6994586e77caed9cdee40607d370e428 Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Thu, 5 Sep 2019 18:59:26 +0200
Subject: [PATCH] Prevent duplicate Ctrl-protocol instances

ControlProtocols are single instance.

Activating an already active protocol leads to crashes due to
various rasons (e.g. port already registered), re-used singleton
event_loop_name and request-buffers, duplicate free of
AbstractUI request buffers during deactivate,..
---
 libs/ardour/control_protocol_manager.cc | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/libs/ardour/control_protocol_manager.cc b/libs/ardour/control_protocol_manager.cc
index eabc4e5006..c7be44a4c8 100644
--- a/libs/ardour/control_protocol_manager.cc
+++ b/libs/ardour/control_protocol_manager.cc
@@ -129,6 +129,11 @@ ControlProtocolManager::activate (ControlProtocolInfo& cpi)
 
 	cpi.requested = true;
 
+	if (cpi.protocol && cpi.protocol->active()) {
+		warning << string_compose (_("Control protocol %1 was already active."), cpi.name) << endmsg;
+		return 0;
+	}
+
 	if ((cp = instantiate (cpi)) == 0) {
 		return -1;
 	}