Hi Everyone, Crypto++ provides a Singleton class in misc.h. The original class suffered C++03 (and earlier) shortcomings. A design compromise was made to leak memory rather than using locks to increase portability.
We now have a portable implementation that does not depend on non-portable locks. It follows http://preshing.com/20130930/double-checked-locking-is-fixed-in-cpp11. template <class T, class F, int instance> const T & Singleton<T, F, instance>::Ref(CRYPTOPP_NOINLINE_DOTDOTDOT) const { static std::mutex s_mutex; static std::atomic<T*> s_pObject; T *p = s_pObject.load(std::memory_order_relaxed); std::atomic_thread_fence(std::memory_order_acquire); if (p) return *p; std::lock_guard<std::mutex> lock(s_mutex); p = s_pObject.load(std::memory_order_relaxed); std::atomic_thread_fence(std::memory_order_acquire); if (p) return *p; T *newObject = m_objectFactory(); s_pObject.store(newObject, std::memory_order_relaxed); std::atomic_thread_fence(std::memory_order_release); return *newObject; } The implementation is guarded by both CRYPTOPP_CXX11_ATOMICS and CRYPTOPP_CXX11_SYNCHRONIZATION because atomics is not a proper subset of synchronization when it comes to compiler support and versions. I'd like to merge it once it goes through a round of testing. Are there any objections? Jeff -- -- You received this message because you are subscribed to the "Crypto++ Users" Google Group. To unsubscribe, send an email to [email protected]. More information about Crypto++ and this group is available at http://www.cryptopp.com. --- You received this message because you are subscribed to the Google Groups "Crypto++ Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
