From 2b2ca82b5aea21e7f466451a9f9ab168e2454bf6 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Tue, 25 Oct 2005 13:24:39 +0000
Subject: [PATCH] Added check against glGetString(GL_VERSION) returning NULL.

---
 src/osg/Program.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/osg/Program.cpp b/src/osg/Program.cpp
index 14ad61e34..f4f3298c2 100644
--- a/src/osg/Program.cpp
+++ b/src/osg/Program.cpp
@@ -270,7 +270,14 @@ void GL2Extensions::lowestCommonDenominator(const GL2Extensions& rhs)
 
 void GL2Extensions::setupGL2Extensions(unsigned int contextID)
 {
-    _glVersion = atof( (const char*)glGetString( GL_VERSION ) );
+    const char* version = (const char*) glGetString( GL_VERSION );
+    if (!version)
+    {
+        osg::notify(osg::FATAL)<<"Error: OpenGL version test failed, requires valid graphics context."<<std::endl;
+        return;
+    }
+    
+    _glVersion = atof( version );
     _glslLanguageVersion = 0.0f;
 
     _isShaderObjectsSupported = osg::isGLExtensionSupported(contextID,"GL_ARB_shader_objects");