| /* |
| * Copyright 2017 Facebook, Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| // SingletonVault - a library to manage the creation and destruction |
| // of interdependent singletons. |
| // |
| // Recommended usage of this class: suppose you have a class |
| // called MyExpensiveService, and you only want to construct one (ie, |
| // it's a singleton), but you only want to construct it if it is used. |
| // |
| // In your .h file: |
| // class MyExpensiveService { |
| // // Caution - may return a null ptr during startup and shutdown. |
| // static std::shared_ptr<MyExpensiveService> getInstance(); |
| // .... |
| // }; |
| // |
| // In your .cpp file: |
| // namespace { struct PrivateTag {}; } |
| // static folly::Singleton<MyExpensiveService, PrivateTag> the_singleton; |
| // std::shared_ptr<MyExpensiveService> MyExpensiveService::getInstance() { |
| // return the_singleton.try_get(); |
| // } |
| // |
| // Code in other modules can access it via: |
| // |
| // auto instance = MyExpensiveService::getInstance(); |
| // |
| // Advanced usage and notes: |
| // |
| // You can also access a singleton instance with |
| // `Singleton<ObjectType, TagType>::try_get()`. We recommend |
| // that you prefer the form `the_singleton.try_get()` because it ensures that |
| // `the_singleton` is used and cannot be garbage-collected during linking: this |
| // is necessary because the constructor of `the_singleton` is what registers it |
| // to the SingletonVault. |
| // |
| // The singleton will be created on demand. If the constructor for |
| // MyExpensiveService actually makes use of *another* Singleton, then |
| // the right thing will happen -- that other singleton will complete |
| // construction before get() returns. However, in the event of a |
| // circular dependency, a runtime error will occur. |
| // |
| // You can have multiple singletons of the same underlying type, but |
| // each must be given a unique tag. If no tag is specified a default tag is |
| // used. We recommend that you use a tag from an anonymous namespace private to |
| // your implementation file, as this ensures that the singleton is only |
| // available via your interface and not also through Singleton<T>::try_get() |
| // |
| // namespace { |
| // struct Tag1 {}; |
| // struct Tag2 {}; |
| // folly::Singleton<MyExpensiveService> s_default; |
| // folly::Singleton<MyExpensiveService, Tag1> s1; |
| // folly::Singleton<MyExpensiveService, Tag2> s2; |
| // } |
| // ... |
| // MyExpensiveService* svc_default = s_default.get(); |
| // MyExpensiveService* svc1 = s1.get(); |
| // MyExpensiveService* svc2 = s2.get(); |
| // |
| // By default, the singleton instance is constructed via new and |
| // deleted via delete, but this is configurable: |
| // |
| // namespace { folly::Singleton<MyExpensiveService> the_singleton(create, |
| // destroy); } |
| // |
| // Where create and destroy are functions, Singleton<T>::CreateFunc |
| // Singleton<T>::TeardownFunc. |
| // |
| // For example, if you need to pass arguments to your class's constructor: |
| // class X { |
| // public: |
| // X(int a1, std::string a2); |
| // // ... |
| // } |
| // Make your singleton like this: |
| // folly::Singleton<X> singleton_x([]() { return new X(42, "foo"); }); |
| // |
| // The above examples detail a situation where an expensive singleton is loaded |
| // on-demand (thus only if needed). However if there is an expensive singleton |
| // that will likely be needed, and initialization takes a potentially long time, |
| // e.g. while initializing, parsing some files, talking to remote services, |
| // making uses of other singletons, and so on, the initialization of those can |
| // be scheduled up front, or "eagerly". |
| // |
| // In that case the singleton can be declared this way: |
| // |
| // namespace { |
| // auto the_singleton = |
| // folly::Singleton<MyExpensiveService>(/* optional create, destroy args */) |
| // .shouldEagerInit(); |
| // } |
| // |
| // This way the singleton's instance is built at program initialization, |
| // if the program opted-in to that feature by calling "doEagerInit" or |
| // "doEagerInitVia" during its startup. |
| // |
| // What if you need to destroy all of your singletons? Say, some of |
| // your singletons manage threads, but you need to fork? Or your unit |
| // test wants to clean up all global state? Then you can call |
| // SingletonVault::singleton()->destroyInstances(), which invokes the |
| // TeardownFunc for each singleton, in the reverse order they were |
| // created. It is your responsibility to ensure your singletons can |
| // handle cases where the singletons they depend on go away, however. |
| // Singletons won't be recreated after destroyInstances call. If you |
| // want to re-enable singleton creation (say after fork was called) you |
| // should call reenableInstances. |
| |
| #pragma once |
| #include <folly/Baton.h> |
| #include <folly/Demangle.h> |
| #include <folly/Exception.h> |
| #include <folly/Executor.h> |
| #include <folly/Hash.h> |
| #include <folly/Memory.h> |
| #include <folly/RWSpinLock.h> |
| #include <folly/Synchronized.h> |
| #include <folly/detail/StaticSingletonManager.h> |
| #include <folly/experimental/ReadMostlySharedPtr.h> |
| |
| #include <algorithm> |
| #include <atomic> |
| #include <condition_variable> |
| #include <functional> |
| #include <memory> |
| #include <mutex> |
| #include <string> |
| #include <thread> |
| #include <typeindex> |
| #include <typeinfo> |
| #include <unordered_map> |
| #include <unordered_set> |
| #include <vector> |
| |
| #include <glog/logging.h> |
| |
| // use this guard to handleSingleton breaking change in 3rd party code |
| #ifndef FOLLY_SINGLETON_TRY_GET |
| #define FOLLY_SINGLETON_TRY_GET |
| #endif |
| |
| namespace folly { |
| |
| // For actual usage, please see the Singleton<T> class at the bottom |
| // of this file; that is what you will actually interact with. |
| |
| // SingletonVault is the class that manages singleton instances. It |
| // is unaware of the underlying types of singletons, and simply |
| // manages lifecycles and invokes CreateFunc and TeardownFunc when |
| // appropriate. In general, you won't need to interact with the |
| // SingletonVault itself. |
| // |
| // A vault goes through a few stages of life: |
| // |
| // 1. Registration phase; singletons can be registered: |
| // a) Strict: no singleton can be created in this stage. |
| // b) Relaxed: singleton can be created (the default vault is Relaxed). |
| // 2. registrationComplete() has been called; singletons can no |
| // longer be registered, but they can be created. |
| // 3. A vault can return to stage 1 when destroyInstances is called. |
| // |
| // In general, you don't need to worry about any of the above; just |
| // ensure registrationComplete() is called near the top of your main() |
| // function, otherwise no singletons can be instantiated. |
| |
| class SingletonVault; |
| |
| namespace detail { |
| |
| struct DefaultTag {}; |
| |
| // A TypeDescriptor is the unique handle for a given singleton. It is |
| // a combinaiton of the type and of the optional name, and is used as |
| // a key in unordered_maps. |
| class TypeDescriptor { |
| public: |
| TypeDescriptor(const std::type_info& ti, |
| const std::type_info& tag_ti) |
| : ti_(ti), tag_ti_(tag_ti) { |
| } |
| |
| TypeDescriptor(const TypeDescriptor& other) |
| : ti_(other.ti_), tag_ti_(other.tag_ti_) { |
| } |
| |
| TypeDescriptor& operator=(const TypeDescriptor& other) { |
| if (this != &other) { |
| ti_ = other.ti_; |
| tag_ti_ = other.tag_ti_; |
| } |
| |
| return *this; |
| } |
| |
| std::string name() const { |
| auto ret = demangle(ti_.name()); |
| if (tag_ti_ != std::type_index(typeid(DefaultTag))) { |
| ret += "/"; |
| ret += demangle(tag_ti_.name()); |
| } |
| return ret.toStdString(); |
| } |
| |
| friend class TypeDescriptorHasher; |
| |
| bool operator==(const TypeDescriptor& other) const { |
| return ti_ == other.ti_ && tag_ti_ == other.tag_ti_; |
| } |
| |
| private: |
| std::type_index ti_; |
| std::type_index tag_ti_; |
| }; |
| |
| class TypeDescriptorHasher { |
| public: |
| size_t operator()(const TypeDescriptor& ti) const { |
| return folly::hash::hash_combine(ti.ti_, ti.tag_ti_); |
| } |
| }; |
| |
| // This interface is used by SingletonVault to interact with SingletonHolders. |
| // Having a non-template interface allows SingletonVault to keep a list of all |
| // SingletonHolders. |
| class SingletonHolderBase { |
| public: |
| explicit SingletonHolderBase(TypeDescriptor typeDesc) : type_(typeDesc) {} |
| virtual ~SingletonHolderBase() = default; |
| |
| TypeDescriptor type() const { |
| return type_; |
| } |
| virtual bool hasLiveInstance() = 0; |
| virtual void createInstance() = 0; |
| virtual bool creationStarted() = 0; |
| virtual void preDestroyInstance(ReadMostlyMainPtrDeleter<>&) = 0; |
| virtual void destroyInstance() = 0; |
| |
| private: |
| TypeDescriptor type_; |
| }; |
| |
| // An actual instance of a singleton, tracking the instance itself, |
| // its state as described above, and the create and teardown |
| // functions. |
| template <typename T> |
| struct SingletonHolder : public SingletonHolderBase { |
| public: |
| typedef std::function<void(T*)> TeardownFunc; |
| typedef std::function<T*(void)> CreateFunc; |
| |
| template <typename Tag, typename VaultTag> |
| inline static SingletonHolder<T>& singleton(); |
| |
| inline T* get(); |
| inline std::weak_ptr<T> get_weak(); |
| inline std::shared_ptr<T> try_get(); |
| inline folly::ReadMostlySharedPtr<T> try_get_fast(); |
| |
| void registerSingleton(CreateFunc c, TeardownFunc t); |
| void registerSingletonMock(CreateFunc c, TeardownFunc t); |
| bool hasLiveInstance() override; |
| void createInstance() override; |
| bool creationStarted() override; |
| void preDestroyInstance(ReadMostlyMainPtrDeleter<>&) override; |
| void destroyInstance() override; |
| |
| private: |
| SingletonHolder(TypeDescriptor type, SingletonVault& vault); |
| |
| enum class SingletonHolderState { |
| NotRegistered, |
| Dead, |
| Living, |
| }; |
| |
| SingletonVault& vault_; |
| |
| // mutex protects the entire entry during construction/destruction |
| std::mutex mutex_; |
| |
| // State of the singleton entry. If state is Living, instance_ptr and |
| // instance_weak can be safely accessed w/o synchronization. |
| std::atomic<SingletonHolderState> state_{SingletonHolderState::NotRegistered}; |
| |
| // the thread creating the singleton (only valid while creating an object) |
| std::atomic<std::thread::id> creating_thread_; |
| |
| // The singleton itself and related functions. |
| |
| // holds a ReadMostlyMainPtr to singleton instance, set when state is changed |
| // from Dead to Living. Reset when state is changed from Living to Dead. |
| folly::ReadMostlyMainPtr<T> instance_; |
| // used to release all ReadMostlyMainPtrs at once |
| folly::ReadMostlySharedPtr<T> instance_copy_; |
| // weak_ptr to the singleton instance, set when state is changed from Dead |
| // to Living. We never write to this object after initialization, so it is |
| // safe to read it from different threads w/o synchronization if we know |
| // that state is set to Living |
| std::weak_ptr<T> instance_weak_; |
| // Fast equivalent of instance_weak_ |
| folly::ReadMostlyWeakPtr<T> instance_weak_fast_; |
| // Time we wait on destroy_baton after releasing Singleton shared_ptr. |
| std::shared_ptr<folly::Baton<>> destroy_baton_; |
| T* instance_ptr_ = nullptr; |
| CreateFunc create_ = nullptr; |
| TeardownFunc teardown_ = nullptr; |
| |
| std::shared_ptr<std::atomic<bool>> print_destructor_stack_trace_; |
| |
| SingletonHolder(const SingletonHolder&) = delete; |
| SingletonHolder& operator=(const SingletonHolder&) = delete; |
| SingletonHolder& operator=(SingletonHolder&&) = delete; |
| SingletonHolder(SingletonHolder&&) = delete; |
| }; |
| |
| } |
| |
| class SingletonVault { |
| public: |
| enum class Type { |
| Strict, // Singletons can't be created before registrationComplete() |
| Relaxed, // Singletons can be created before registrationComplete() |
| }; |
| |
| /** |
| * Clears all singletons in the given vault at ctor and dtor times. |
| * Useful for unit-tests that need to clear the world. |
| * |
| * This need can arise when a unit-test needs to swap out an object used by a |
| * singleton for a test-double, but the singleton needing its dependency to be |
| * swapped has a type or a tag local to some other translation unit and |
| * unavailable in the current translation unit. |
| * |
| * Other, better approaches to this need are "plz 2 refactor" .... |
| */ |
| struct ScopedExpunger { |
| SingletonVault* vault; |
| explicit ScopedExpunger(SingletonVault* v) : vault(v) { expunge(); } |
| ~ScopedExpunger() { expunge(); } |
| void expunge() { |
| vault->destroyInstances(); |
| vault->reenableInstances(); |
| } |
| }; |
| |
| static Type defaultVaultType(); |
| |
| explicit SingletonVault(Type type = defaultVaultType()) : type_(type) {} |
| |
| // Destructor is only called by unit tests to check destroyInstances. |
| ~SingletonVault(); |
| |
| typedef std::function<void(void*)> TeardownFunc; |
| typedef std::function<void*(void)> CreateFunc; |
| |
| // Ensure that Singleton has not been registered previously and that |
| // registration is not complete. If validations succeeds, |
| // register a singleton of a given type with the create and teardown |
| // functions. |
| void registerSingleton(detail::SingletonHolderBase* entry); |
| |
| /** |
| * Called by `Singleton<T>.shouldEagerInit()` to ensure the instance |
| * is built when `doEagerInit[Via]` is called; see those methods |
| * for more info. |
| */ |
| void addEagerInitSingleton(detail::SingletonHolderBase* entry); |
| |
| // Mark registration is complete; no more singletons can be |
| // registered at this point. |
| void registrationComplete(); |
| |
| /** |
| * Initialize all singletons which were marked as eager-initialized |
| * (using `shouldEagerInit()`). No return value. Propagates exceptions |
| * from constructors / create functions, as is the usual case when calling |
| * for example `Singleton<Foo>::get_weak()`. |
| */ |
| void doEagerInit(); |
| |
| /** |
| * Schedule eager singletons' initializations through the given executor. |
| * If baton ptr is not null, its `post` method is called after all |
| * early initialization has completed. |
| * |
| * If exceptions are thrown during initialization, this method will still |
| * `post` the baton to indicate completion. The exception will not propagate |
| * and future attempts to `try_get` or `get_weak` the failed singleton will |
| * retry initialization. |
| * |
| * Sample usage: |
| * |
| * wangle::IOThreadPoolExecutor executor(max_concurrency_level); |
| * folly::Baton<> done; |
| * doEagerInitVia(executor, &done); |
| * done.wait(); // or 'timed_wait', or spin with 'try_wait' |
| * |
| */ |
| void doEagerInitVia(Executor& exe, folly::Baton<>* done = nullptr); |
| |
| // Destroy all singletons; when complete, the vault can't create |
| // singletons once again until reenableInstances() is called. |
| void destroyInstances(); |
| |
| // Enable re-creating singletons after destroyInstances() was called. |
| void reenableInstances(); |
| |
| // For testing; how many registered and living singletons we have. |
| size_t registeredSingletonCount() const { |
| return singletons_.rlock()->size(); |
| } |
| |
| /** |
| * Flips to true if eager initialization was used, and has completed. |
| * Never set to true if "doEagerInit()" or "doEagerInitVia" never called. |
| */ |
| bool eagerInitComplete() const; |
| |
| size_t livingSingletonCount() const { |
| auto singletons = singletons_.rlock(); |
| |
| size_t ret = 0; |
| for (const auto& p : *singletons) { |
| if (p.second->hasLiveInstance()) { |
| ++ret; |
| } |
| } |
| |
| return ret; |
| } |
| |
| // A well-known vault; you can actually have others, but this is the |
| // default. |
| static SingletonVault* singleton() { |
| return singleton<>(); |
| } |
| |
| // Gets singleton vault for any Tag. Non-default tag should be used in unit |
| // tests only. |
| template <typename VaultTag = detail::DefaultTag> |
| static SingletonVault* singleton() { |
| /* library-local */ static auto vault = |
| detail::createGlobal<SingletonVault, VaultTag>(); |
| return vault; |
| } |
| |
| typedef std::string(*StackTraceGetterPtr)(); |
| |
| static std::atomic<StackTraceGetterPtr>& stackTraceGetter() { |
| /* library-local */ static auto stackTraceGetterPtr = detail:: |
| createGlobal<std::atomic<StackTraceGetterPtr>, SingletonVault>(); |
| return *stackTraceGetterPtr; |
| } |
| |
| void setType(Type type) { |
| type_ = type; |
| } |
| |
| private: |
| template <typename T> |
| friend struct detail::SingletonHolder; |
| |
| // The two stages of life for a vault, as mentioned in the class comment. |
| enum class SingletonVaultState { |
| Running, |
| Quiescing, |
| }; |
| |
| struct State { |
| SingletonVaultState state{SingletonVaultState::Running}; |
| bool registrationComplete{false}; |
| }; |
| |
| // Each singleton in the vault can be in two states: dead |
| // (registered but never created), living (CreateFunc returned an instance). |
| |
| static void stateCheck( |
| SingletonVaultState expected, |
| const State& state, |
| const char* msg = "Unexpected singleton state change") { |
| if (expected != state.state) { |
| throw std::logic_error(msg); |
| } |
| } |
| |
| // This method only matters if registrationComplete() is never called. |
| // Otherwise destroyInstances is scheduled to be executed atexit. |
| // |
| // Initializes static object, which calls destroyInstances on destruction. |
| // Used to have better deletion ordering with singleton not managed by |
| // folly::Singleton. The desruction will happen in the following order: |
| // 1. Singletons, not managed by folly::Singleton, which were created after |
| // any of the singletons managed by folly::Singleton was requested. |
| // 2. All singletons managed by folly::Singleton |
| // 3. Singletons, not managed by folly::Singleton, which were created before |
| // any of the singletons managed by folly::Singleton was requested. |
| static void scheduleDestroyInstances(); |
| |
| typedef std::unordered_map<detail::TypeDescriptor, |
| detail::SingletonHolderBase*, |
| detail::TypeDescriptorHasher> SingletonMap; |
| folly::Synchronized<SingletonMap> singletons_; |
| folly::Synchronized<std::unordered_set<detail::SingletonHolderBase*>> |
| eagerInitSingletons_; |
| folly::Synchronized<std::vector<detail::TypeDescriptor>> creationOrder_; |
| |
| // Using SharedMutexReadPriority is important here, because we want to make |
| // sure we don't block nested singleton creation happening concurrently with |
| // destroyInstances(). |
| folly::Synchronized<State, folly::SharedMutexReadPriority> state_; |
| |
| Type type_; |
| }; |
| |
| // This is the wrapper class that most users actually interact with. |
| // It allows for simple access to registering and instantiating |
| // singletons. Create instances of this class in the global scope of |
| // type Singleton<T> to register your singleton for later access via |
| // Singleton<T>::try_get(). |
| template <typename T, |
| typename Tag = detail::DefaultTag, |
| typename VaultTag = detail::DefaultTag /* for testing */> |
| class Singleton { |
| public: |
| typedef std::function<T*(void)> CreateFunc; |
| typedef std::function<void(T*)> TeardownFunc; |
| |
| // Generally your program life cycle should be fine with calling |
| // get() repeatedly rather than saving the reference, and then not |
| // call get() during process shutdown. |
| FOLLY_DEPRECATED("Replaced by try_get") |
| static T* get() { return getEntry().get(); } |
| |
| // If, however, you do need to hold a reference to the specific |
| // singleton, you can try to do so with a weak_ptr. Avoid this when |
| // possible but the inability to lock the weak pointer can be a |
| // signal that the vault has been destroyed. |
| FOLLY_DEPRECATED("Replaced by try_get") |
| static std::weak_ptr<T> get_weak() { return getEntry().get_weak(); } |
| |
| // Preferred alternative to get_weak, it returns shared_ptr that can be |
| // stored; a singleton won't be destroyed unless shared_ptr is destroyed. |
| // Avoid holding these shared_ptrs beyond the scope of a function; |
| // don't put them in member variables, always use try_get() instead |
| // |
| // try_get() can return nullptr if the singleton was destroyed, caller is |
| // responsible for handling nullptr return |
| static std::shared_ptr<T> try_get() { |
| return getEntry().try_get(); |
| } |
| |
| static folly::ReadMostlySharedPtr<T> try_get_fast() { |
| return getEntry().try_get_fast(); |
| } |
| |
| explicit Singleton(std::nullptr_t /* _ */ = nullptr, |
| typename Singleton::TeardownFunc t = nullptr) |
| : Singleton([]() { return new T; }, std::move(t)) {} |
| |
| explicit Singleton(typename Singleton::CreateFunc c, |
| typename Singleton::TeardownFunc t = nullptr) { |
| if (c == nullptr) { |
| throw std::logic_error( |
| "nullptr_t should be passed if you want T to be default constructed"); |
| } |
| |
| auto vault = SingletonVault::singleton<VaultTag>(); |
| getEntry().registerSingleton(std::move(c), getTeardownFunc(std::move(t))); |
| vault->registerSingleton(&getEntry()); |
| } |
| |
| /** |
| * Should be instantiated as soon as "doEagerInit[Via]" is called. |
| * Singletons are usually lazy-loaded (built on-demand) but for those which |
| * are known to be needed, to avoid the potential lag for objects that take |
| * long to construct during runtime, there is an option to make sure these |
| * are built up-front. |
| * |
| * Use like: |
| * Singleton<Foo> gFooInstance = Singleton<Foo>(...).shouldEagerInit(); |
| * |
| * Or alternately, define the singleton as usual, and say |
| * gFooInstance.shouldEagerInit(); |
| * |
| * at some point prior to calling registrationComplete(). |
| * Then doEagerInit() or doEagerInitVia(Executor*) can be called. |
| */ |
| Singleton& shouldEagerInit() { |
| auto vault = SingletonVault::singleton<VaultTag>(); |
| vault->addEagerInitSingleton(&getEntry()); |
| return *this; |
| } |
| |
| /** |
| * Construct and inject a mock singleton which should be used only from tests. |
| * Unlike regular singletons which are initialized once per process lifetime, |
| * mock singletons live for the duration of a test. This means that one process |
| * running multiple tests can initialize and register the same singleton |
| * multiple times. This functionality should be used only from tests |
| * since it relaxes validation and performance in order to be able to perform |
| * the injection. The returned mock singleton is functionality identical to |
| * regular singletons. |
| */ |
| static void make_mock(std::nullptr_t /* c */ = nullptr, |
| typename Singleton<T>::TeardownFunc t = nullptr) { |
| make_mock([]() { return new T; }, t); |
| } |
| |
| static void make_mock(CreateFunc c, |
| typename Singleton<T>::TeardownFunc t = nullptr) { |
| if (c == nullptr) { |
| throw std::logic_error( |
| "nullptr_t should be passed if you want T to be default constructed"); |
| } |
| |
| auto& entry = getEntry(); |
| |
| entry.registerSingletonMock(c, getTeardownFunc(t)); |
| } |
| |
| private: |
| inline static detail::SingletonHolder<T>& getEntry() { |
| return detail::SingletonHolder<T>::template singleton<Tag, VaultTag>(); |
| } |
| |
| // Construct TeardownFunc. |
| static typename detail::SingletonHolder<T>::TeardownFunc getTeardownFunc( |
| TeardownFunc t) { |
| if (t == nullptr) { |
| return [](T* v) { delete v; }; |
| } else { |
| return t; |
| } |
| } |
| }; |
| |
| template <typename T, typename Tag = detail::DefaultTag> |
| class LeakySingleton { |
| public: |
| using CreateFunc = std::function<T*()>; |
| |
| LeakySingleton() : LeakySingleton([] { return new T(); }) {} |
| |
| explicit LeakySingleton(CreateFunc createFunc) { |
| auto& entry = entryInstance(); |
| if (entry.state != State::NotRegistered) { |
| LOG(FATAL) << "Double registration of singletons of the same " |
| << "underlying type; check for multiple definitions " |
| << "of type folly::LeakySingleton<" + entry.type_.name() + ">"; |
| } |
| entry.createFunc = createFunc; |
| entry.state = State::Dead; |
| } |
| |
| static T& get() { return instance(); } |
| |
| static void make_mock(std::nullptr_t /* c */ = nullptr) { |
| make_mock([]() { return new T; }); |
| } |
| |
| static void make_mock(CreateFunc createFunc) { |
| auto& entry = entryInstance(); |
| if (createFunc == nullptr) { |
| throw std::logic_error( |
| "nullptr_t should be passed if you want T to be default constructed"); |
| } |
| |
| entry.createFunc = createFunc; |
| entry.state = State::Dead; |
| } |
| |
| private: |
| enum class State { NotRegistered, Dead, Living }; |
| |
| struct Entry { |
| Entry() {} |
| Entry(const Entry&) = delete; |
| Entry& operator=(const Entry&) = delete; |
| |
| std::atomic<State> state{State::NotRegistered}; |
| T* ptr{nullptr}; |
| CreateFunc createFunc; |
| std::mutex mutex; |
| detail::TypeDescriptor type_{typeid(T), typeid(Tag)}; |
| }; |
| |
| static Entry& entryInstance() { |
| /* library-local */ static auto entry = detail::createGlobal<Entry, Tag>(); |
| return *entry; |
| } |
| |
| static T& instance() { |
| auto& entry = entryInstance(); |
| if (UNLIKELY(entry.state != State::Living)) { |
| createInstance(); |
| } |
| |
| return *entry.ptr; |
| } |
| |
| static void createInstance() { |
| auto& entry = entryInstance(); |
| |
| std::lock_guard<std::mutex> lg(entry.mutex); |
| if (entry.state == State::Living) { |
| return; |
| } |
| |
| if (entry.state == State::NotRegistered) { |
| auto ptr = SingletonVault::stackTraceGetter().load(); |
| LOG(FATAL) << "Creating instance for unregistered singleton: " |
| << entry.type_.name() << "\n" |
| << "Stacktrace:" |
| << "\n" << (ptr ? (*ptr)() : "(not available)"); |
| } |
| |
| entry.ptr = entry.createFunc(); |
| entry.state = State::Living; |
| } |
| }; |
| } |
| |
| #include <folly/Singleton-inl.h> |