2 files changed, 135 insertions, 0 deletions
diff --git a/indra/llcommon/CMakeLists.txt b/indra/llcommon/CMakeLists.txt
index d2d507d676..de5aa0fde4 100755
--- a/indra/llcommon/CMakeLists.txt
+++ b/indra/llcommon/CMakeLists.txt
@@ -162,6 +162,7 @@ set(llcommon_HEADER_FILES
     llhash.h
     llheartbeat.h
     llindexedvector.h
+    llinitdestroyclass.h
     llinitparam.h
     llinstancetracker.h
     llkeythrottle.h
diff --git a/indra/llcommon/llinitdestroyclass.h b/indra/llcommon/llinitdestroyclass.h
new file mode 100644
index 0000000000..ca5c3f07de
--- /dev/null
+++ b/indra/llcommon/llinitdestroyclass.h
@@ -0,0 +1,134 @@
+/**
+ * @file   llinitdestroyclass.h
+ * @author Nat Goodspeed
+ * @date   2015-05-27
+ * @brief  LLInitClass / LLDestroyClass mechanism
+ *
+ * The LLInitClass template, extracted from llui.h, ensures that control will
+ * reach a static initClass() method. LLDestroyClass does the same for a
+ * static destroyClass() method.
+ *
+ * The distinguishing characteristics of these templates are:
+ *
+ * - All LLInitClass<T>::initClass() methods are triggered by an explicit call
+ *   to LLInitClassList::instance().fireCallbacks(). Presumably this call
+ *   happens sometime after all static objects in the program have been
+ *   initialized. In other words, each LLInitClass<T>::initClass() method
+ *   should be able to make some assumptions about global program state.
+ *
+ * - Similarly, LLDestroyClass<T>::destroyClass() methods are triggered by
+ *   LLDestroyClassList::instance().fireCallbacks(). Again, presumably this
+ *   happens at a well-defined moment in the program's shutdown sequence.
+ *
+ * - The initClass() calls happen in an unspecified sequence. You may not rely
+ *   on the relative ordering of LLInitClass<T>::initClass() versus another
+ *   LLInitClass<U>::initClass() method. If you need such a guarantee, use
+ *   LLSingleton instead and make the dependency explicit.
+ *
+ * - Similarly, LLDestroyClass<T>::destroyClass() may happen either before or
+ *   after LLDestroyClass<U>::destroyClass(). You cannot rely on that order.
+ *
+ * $LicenseInfo:firstyear=2015&license=viewerlgpl$
+ * Copyright (c) 2015, Linden Research, Inc.
+ * $/LicenseInfo$
+ */
+
+#if ! defined(LL_LLINITDESTROYCLASS_H)
+#define LL_LLINITDESTROYCLASS_H
+
+#include "llerror.h"
+#include "llsingleton.h"
+#include <boost/function.hpp>
+#include <boost/signals2/signal.hpp>
+#include <typeinfo>
+
+class LLCallbackRegistry
+{
+public:
+	typedef boost::signals2::signal<void()> callback_signal_t;
+	
+	void registerCallback(const callback_signal_t::slot_type& slot)
+	{
+		mCallbacks.connect(slot);
+	}
+
+	void fireCallbacks()
+	{
+		mCallbacks();
+	}
+
+private:
+	callback_signal_t mCallbacks;
+};
+
+class LLInitClassList : 
+	public LLCallbackRegistry, 
+	public LLSingleton<LLInitClassList>
+{
+	friend class LLSingleton<LLInitClassList>;
+private:
+	LLInitClassList() {}
+};
+
+class LLDestroyClassList : 
+	public LLCallbackRegistry, 
+	public LLSingleton<LLDestroyClassList>
+{
+	friend class LLSingleton<LLDestroyClassList>;
+private:
+	LLDestroyClassList() {}
+};
+
+template<typename T>
+class LLRegisterWith
+{
+public:
+	LLRegisterWith(boost::function<void ()> func)
+	{
+		T::instance().registerCallback(func);
+	}
+
+	// this avoids a MSVC bug where non-referenced static members are "optimized" away
+	// even if their constructors have side effects
+	S32 reference()
+	{
+		S32 dummy;
+		dummy = 0;
+		return dummy;
+	}
+};
+
+template<typename T>
+class LLInitClass
+{
+public:
+	LLInitClass() { sRegister.reference(); }
+
+	static LLRegisterWith<LLInitClassList> sRegister;
+private:
+
+	static void initClass()
+	{
+		LL_ERRS() << "No static initClass() method defined for " << typeid(T).name() << LL_ENDL;
+	}
+};
+
+template<typename T>
+class LLDestroyClass
+{
+public:
+	LLDestroyClass() { sRegister.reference(); }
+
+	static LLRegisterWith<LLDestroyClassList> sRegister;
+private:
+
+	static void destroyClass()
+	{
+		LL_ERRS() << "No static destroyClass() method defined for " << typeid(T).name() << LL_ENDL;
+	}
+};
+
+template <typename T> LLRegisterWith<LLInitClassList> LLInitClass<T>::sRegister(&T::initClass);
+template <typename T> LLRegisterWith<LLDestroyClassList> LLDestroyClass<T>::sRegister(&T::destroyClass);
+
+#endif /* ! defined(LL_LLINITDESTROYCLASS_H) */