From b37b635a7ccf30b6dd06e07917b665b923c30931 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Tue, 25 Jul 2017 15:58:27 +0100
Subject: [PATCH] Merged GLExtension deletion mechanism from master to avoid
 GLEXtension being deleted when shared contexts are used and osg::State is
 deleted when a context is deleted.

---
 src/osg/State.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/osg/State.cpp b/src/osg/State.cpp
index abd0ddb90..778be2f3e 100644
--- a/src/osg/State.cpp
+++ b/src/osg/State.cpp
@@ -139,8 +139,12 @@ State::~State()
     // delete the GLExtensions object associated with this osg::State.
     if (_glExtensions)
     {
-        GLExtensions::Set(_contextID, 0);
         _glExtensions = 0;
+        GLExtensions* glExtensions = GLExtensions::Get(_contextID, false);
+        if (glExtensions && glExtensions->referenceCount() == 1) {
+            // the only reference left to the extension is in the static map itself, so we clean it up now
+            GLExtensions::Set(_contextID, 0);
+        }
     }
 
     //_texCoordArrayList.clear();