From 8dbd991652d5d881c9bc6e5c4b70ac68cc6f9735 Mon Sep 17 00:00:00 2001
From: Sam Gateau <sam@highfidelity.io>
Date: Wed, 22 Jul 2015 10:54:40 -0700
Subject: [PATCH] USing a modern singleton guard

---
 libraries/gpu/src/gpu/GLBackend.cpp | 9 ++++-----
 libraries/gpu/src/gpu/GLBackend.h   | 2 --
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/libraries/gpu/src/gpu/GLBackend.cpp b/libraries/gpu/src/gpu/GLBackend.cpp
index 0a6f3a423d..721be0f402 100644
--- a/libraries/gpu/src/gpu/GLBackend.cpp
+++ b/libraries/gpu/src/gpu/GLBackend.cpp
@@ -8,14 +8,13 @@
 //  Distributed under the Apache License, Version 2.0.
 //  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
 //
+#include <mutex>
 #include "GPULogging.h"
 #include "GLBackendShared.h"
 #include <glm/gtc/type_ptr.hpp>
 
 using namespace gpu;
 
-bool GLBackend::_initialized = false;
-
 GLBackend::CommandCall GLBackend::_commandCalls[Batch::NUM_COMMANDS] = 
 {
     (&::gpu::GLBackend::do_draw),
@@ -91,7 +90,8 @@ GLBackend::GLBackend() :
     _pipeline(),
     _output()
 {
-    if (!_initialized) {
+    static std::once_flag once;
+    std::call_once(once, [] {
         qCDebug(gpulogging) << "GL Version: " << QString((const char*) glGetString(GL_VERSION));
         qCDebug(gpulogging) << "GL Shader Language Version: " << QString((const char*) glGetString(GL_SHADING_LANGUAGE_VERSION));
         qCDebug(gpulogging) << "GL Vendor: " << QString((const char*) glGetString(GL_VENDOR));
@@ -118,8 +118,7 @@ GLBackend::GLBackend() :
             qCDebug(gpulogging, "V-Sync is %s\n", (swapInterval > 0 ? "ON" : "OFF"));
         }*/
 #endif
-        _initialized = true;
-    }
+    });
 
     initInput();
     initTransform();
diff --git a/libraries/gpu/src/gpu/GLBackend.h b/libraries/gpu/src/gpu/GLBackend.h
index b4906b4ac7..b3e905bf21 100644
--- a/libraries/gpu/src/gpu/GLBackend.h
+++ b/libraries/gpu/src/gpu/GLBackend.h
@@ -447,8 +447,6 @@ protected:
 
     typedef void (GLBackend::*CommandCall)(Batch&, uint32);
     static CommandCall _commandCalls[Batch::NUM_COMMANDS];
-
-    static bool _initialized;
 };