diff --git a/src/Dispatcher.cpp b/src/Dispatcher.cpp index 218760ae20..149537c9e1 100644 --- a/src/Dispatcher.cpp +++ b/src/Dispatcher.cpp @@ -14,7 +14,7 @@ using namespace nt; #define DEBUG(str) puts(str) -std::unique_ptr Dispatcher::m_instance; +ATOMIC_STATIC_INIT(Dispatcher) Dispatcher::Dispatcher() : m_server(false), diff --git a/src/Dispatcher.h b/src/Dispatcher.h index 0ea194adff..d25cf8c079 100644 --- a/src/Dispatcher.h +++ b/src/Dispatcher.h @@ -18,6 +18,7 @@ #include "llvm/StringRef.h" +#include "atomic_static.h" #include "NetworkConnection.h" #include "Storage.h" @@ -28,8 +29,8 @@ namespace nt { class Dispatcher { public: static Dispatcher& GetInstance() { - if (!m_instance) m_instance.reset(new Dispatcher); - return *m_instance; + ATOMIC_STATIC(Dispatcher, instance); + return instance; } ~Dispatcher(); @@ -96,8 +97,7 @@ class Dispatcher { mutable std::mutex m_idmap_mutex; std::vector> m_idmap; - // Global instance - static std::unique_ptr m_instance; + ATOMIC_STATIC_DECL(Dispatcher) }; } // namespace nt diff --git a/src/Storage.cpp b/src/Storage.cpp index 8072583e04..ec9d73fe9d 100644 --- a/src/Storage.cpp +++ b/src/Storage.cpp @@ -15,7 +15,7 @@ using namespace nt; -std::unique_ptr Storage::m_instance; +ATOMIC_STATIC_INIT(Storage) Storage::Storage() { m_updates_enabled = false; diff --git a/src/Storage.h b/src/Storage.h index 4f40d4de4b..7d6f2ee162 100644 --- a/src/Storage.h +++ b/src/Storage.h @@ -17,6 +17,7 @@ #include "llvm/StringMap.h" #include "support/ConcurrentQueue.h" +#include "atomic_static.h" #include "ntcore_cpp.h" #include "SequenceNumber.h" @@ -75,8 +76,8 @@ class Storage { friend class StorageTest; public: static Storage& GetInstance() { - if (!m_instance) m_instance.reset(new Storage); - return *m_instance; + ATOMIC_STATIC(Storage, instance); + return instance; } ~Storage(); @@ -128,7 +129,7 @@ class Storage { UpdateQueue m_updates; std::atomic_bool m_updates_enabled; - static std::unique_ptr m_instance; + ATOMIC_STATIC_DECL(Storage) }; } // namespace nt diff --git a/src/atomic_static.h b/src/atomic_static.h new file mode 100644 index 0000000000..b00ccdac0e --- /dev/null +++ b/src/atomic_static.h @@ -0,0 +1,49 @@ +/*----------------------------------------------------------------------------*/ +/* Copyright (c) FIRST 2015. All Rights Reserved. */ +/* Open Source Software - may be modified and shared by FRC teams. The code */ +/* must be accompanied by the FIRST BSD license file in the root directory of */ +/* the project. */ +/*----------------------------------------------------------------------------*/ + +#ifndef NT_ATOMIC_STATIC_H_ +#define NT_ATOMIC_STATIC_H_ + +#if !defined(_MSC_VER) || (_MSC_VER >= 1900) + +// Just use a local static. This is thread-safe per +// http://preshing.com/20130930/double-checked-locking-is-fixed-in-cpp11/ + +// Per https://msdn.microsoft.com/en-us/library/Hh567368.aspx "Magic Statics" +// are supported in Visual Studio 2015 but not in earlier versions. +#define ATOMIC_STATIC(cls, inst) static cls inst +#define ATOMIC_STATIC_DECL(cls) +#define ATOMIC_STATIC_INIT(cls) + +#else +// From http://preshing.com/20130930/double-checked-locking-is-fixed-in-cpp11/ +#include +#include + +#define ATOMIC_STATIC(cls, inst) \ + cls* inst##tmp = m_instance.load(std::memory_order_acquire); \ + if (inst##tmp == nullptr) { \ + std::lock_guard lock(m_instance_mutex); \ + inst##tmp = m_instance.load(std::memory_order_relaxed); \ + if (inst##tmp == nullptr) { \ + inst##tmp = new cls; \ + m_instance.store(inst##tmp, std::memory_order_release); \ + } \ + } \ + cls& inst = *inst##tmp + +#define ATOMIC_STATIC_DECL(cls) \ + static std::atomic m_instance; \ + static std::mutex m_instance_mutex; + +#define ATOMIC_STATIC_INIT(cls) \ + std::atomic cls::m_instance; \ + std::mutex cls::m_instance_mutex; + +#endif + +#endif // NT_ATOMIC_STATIC_H_