artf4107: GetInstance() calls are now atomic

C++11 guarantees construction of static variables to be atomic, so this patch takes advantage of that.

Change-Id: I4a3db0f19c5fa5461fef3b6b63d7b8fec596c962

wpilibc/wpilibC++/include/Commands/Scheduler.h

@@ -50,7 +50,6 @@ class Scheduler : public ErrorBase, public NamedSendable {
 
   void ProcessCommandAddition(Command *command);
 
-  static Scheduler *_instance;
   Command::SubsystemSet m_subsystems;
   MUTEX_ID m_buttonsLock = nullptr;
   typedef std::vector<ButtonScheduler *> ButtonVector;

wpilibc/wpilibC++/src/Commands/Scheduler.cpp

@@ -16,8 +16,6 @@
 #include <set>
 #include <algorithm>
 
-Scheduler *Scheduler::_instance = nullptr;
-
 Scheduler::Scheduler() {
   m_buttonsLock = initializeMutexNormal();
   m_additionsLock = initializeMutexNormal();
@@ -38,8 +36,8 @@ Scheduler::~Scheduler() {
  * @return the {@link Scheduler}
  */
 Scheduler *Scheduler::GetInstance() {
-  if (_instance == nullptr) _instance = new Scheduler();
-  return _instance;
+  static Scheduler instance;
+  return &instance;
 }
 
 void Scheduler::SetEnabled(bool enabled) { m_enabled = enabled; }

wpilibc/wpilibC++/src/LiveWindow/LiveWindow.cpp

@@ -10,9 +10,8 @@
  * how many times GetInstance is called.
  */
 LiveWindow *LiveWindow::GetInstance() {
-  static LiveWindow *instance = new LiveWindow();
-
-  return instance;
+  static LiveWindow instance;
+  return &instance;
 }
 
 /**

wpilibc/wpilibC++Devices/include/CameraServer.h

@@ -55,8 +55,6 @@ class CameraServer : public ErrorBase {
     uint32_t size;
   };
 
-  static CameraServer* s_instance;
-
  public:
   static CameraServer* GetInstance();
   void SetImage(Image const* image);

wpilibc/wpilibC++Devices/include/Preferences.h

@@ -82,8 +82,6 @@ class Preferences : public ErrorBase, public ITableListener {
     return 0;
   }
 
-  static Preferences *_instance;
-
   /** The semaphore for accessing the file */
   MUTEX_ID m_fileLock = nullptr;
   /** The semaphore for beginning reads and writes to the file */

wpilibc/wpilibC++Devices/src/CameraServer.cpp

@@ -10,13 +10,10 @@
 #include <netdb.h>
 
 constexpr uint8_t CameraServer::kMagicNumber[];
-CameraServer* CameraServer::s_instance = nullptr;
 
 CameraServer* CameraServer::GetInstance() {
-  if (s_instance == nullptr) {
-    s_instance = new CameraServer;
-  }
-  return s_instance;
+  static CameraServer instance;
+  return &instance;
 }
 
 CameraServer::CameraServer()

wpilibc/wpilibC++Devices/src/DriverStation.cpp

@@ -28,7 +28,6 @@ const double JOYSTICK_UNPLUGGED_MESSAGE_INTERVAL = 1.0;
   Log().Get(level)
 
 const uint32_t DriverStation::kJoystickPorts;
-DriverStation* DriverStation::m_instance = nullptr;
 
 /**
  * DriverStation constructor.
@@ -73,7 +72,6 @@ DriverStation::DriverStation() {
 
 DriverStation::~DriverStation() {
   m_task.Stop();
-  m_instance = nullptr;
   deleteMultiWait(m_waitForDataSem);
   // Unregister our semaphore.
   HALSetNewDataSem(nullptr);
@@ -111,10 +109,8 @@ void DriverStation::Run() {
  * @return Pointer to the DS instance
  */
 DriverStation* DriverStation::GetInstance() {
-  if (m_instance == nullptr) {
-    m_instance = new DriverStation();
-  }
-  return m_instance;
+  static DriverStation instance;
+  return &instance;
 }
 
 /**

wpilibc/wpilibC++Devices/src/Preferences.cpp

@@ -24,8 +24,6 @@ static const char *kFileName = "/home/lvuser/wpilib-preferences.ini";
 static const char *kValuePrefix = "=\"";
 /** The characters to put after the value */
 static const char *kValueSuffix = "\"\n";
-/** The singleton instance */
-Preferences *Preferences::_instance = nullptr;
 
 Preferences::Preferences()
     : m_readTask("PreferencesReadTask", (FUNCPTR)Preferences::InitReadTask),
@@ -54,8 +52,8 @@ Preferences::~Preferences() {
  * @return pointer to the {@link Preferences}
  */
 Preferences *Preferences::GetInstance() {
-  if (_instance == nullptr) _instance = new Preferences;
-  return _instance;
+  static Preferences instance;
+  return &instance;
 }
 
 /**

wpilibc/wpilibC++Sim/include/simulation/MainNode.h

@@ -10,10 +10,8 @@ using namespace gazebo;
 class MainNode {
 public:
 	static MainNode* GetInstance() {
-		if (instance == nullptr) {
-			instance = new MainNode();
-		}
-		return instance;
+		static MainNode instance;
+		return &instance;
 	}
 
 	template<typename M>
@@ -39,8 +37,6 @@ public:
   
 	transport::NodePtr main;
 private:
-  	static MainNode* instance;
-
 	MainNode() {
 		gazebo::transport::init();
 		main = transport::NodePtr(new transport::Node());

wpilibc/wpilibC++Sim/src/DriverStation.cpp

@@ -26,7 +26,6 @@ const uint32_t DriverStation::kBatteryChannel;
 const uint32_t DriverStation::kJoystickPorts;
 const uint32_t DriverStation::kJoystickAxes;
 constexpr float DriverStation::kUpdatePeriod;
-DriverStation* DriverStation::m_instance = nullptr;
 uint8_t DriverStation::m_updateNumber = 0;
 
 /**
@@ -70,7 +69,6 @@ DriverStation::DriverStation()
 
 DriverStation::~DriverStation()
 {
-	m_instance = nullptr;
 	deleteMultiWait(m_waitForDataSem);
 	deleteMutex(m_waitForDataMutex);
 	// TODO: Release m_stateSemaphore and m_joystickSemaphore?
@@ -81,11 +79,8 @@ DriverStation::~DriverStation()
  */
 DriverStation* DriverStation::GetInstance()
 {
-	if (m_instance == nullptr)
-	{
-		m_instance = new DriverStation();
-	}
-	return m_instance;
+	static DriverStation instance;
+	return &instance;
 }
 
 /**

wpilibc/wpilibC++Sim/src/simulation/MainNode.cpp

@@ -1,3 +0,0 @@
-
-#include "simulation/MainNode.h"
-MainNode* MainNode::instance = nullptr;