fix potential threading problem with initialization of static objects

git-svn-id: svn://svn.code.sf.net/p/cryptopp/code/trunk/c5@118 57ff6487-cd31-0410-9ec3-f628ee90f5f0

1 files changed, 35 insertions, 7 deletions

diff --git a/misc.h b/misc.h
index 790e459..659ba2a 100644
--- a/misc.h
+++ b/misc.h
@@ -209,29 +209,57 @@ inline CipherDir GetCipherDir(const T &obj)
 	return obj.IsForwardTransformation() ? ENCRYPTION : DECRYPTION;
 }
 
+template <class T>
+struct NewObject
+{
+	T* operator()() const {return new T;}
+};
+
 // This function safely initializes a static object in a multithreaded environment without using locks.
 // It may leak memory when two threads try to initialize the static object at the same time
 // but this should be acceptable since each static object is only initialized once per session.
-template <class T, class F>
-T & StaticObject(F NewT, T *dummy=NULL)
+template <class T, class F = NewObject<T>, int instance=0>
+class Singleton
 {
-	static member_ptr<T> s_pObject;
+public:
+	Singleton(F objectFactory = F()) : m_objectFactory(objectFactory) {}
+
+	// VC60 workaround: use "..." to prevent this function from being inlined
+	const T & Ref(...) const;
+
+private:
+	F m_objectFactory;
+};
+
+template <class T, class F, int instance>
+const T & Singleton<T, F, instance>::Ref(...) const
+{
+	static simple_ptr<T> s_pObject;
 	static char s_objectState = 0;
 
+retry:
 	switch (s_objectState)
 	{
 	case 0:
 		s_objectState = 1;
-		s_pObject.reset(NewT());
+		try
+		{
+			s_pObject.m_p = m_objectFactory();
+		}
+		catch(...)
+		{
+			s_objectState = 0;
+			throw;
+		}
 		s_objectState = 2;
 		break;
 	case 1:
-		while (s_objectState == 1) {}
+		goto retry;
 	default:
 		break;
 	}
-	return *s_pObject;
-};
+	return *s_pObject.m_p;
+}
 
 // ************** rotate functions ***************