Downstream merge from lindenlab/viewer-lynx

1 files changed, 340 insertions, 69 deletions

diff --git a/indra/llcommon/llsingleton.h b/indra/llcommon/llsingleton.h
index 859e271e26..0da6d548ab 100644
--- a/indra/llcommon/llsingleton.h
+++ b/indra/llcommon/llsingleton.h
@@ -31,6 +31,18 @@
 #include <vector>
 #include <typeinfo>
 
+#if LL_WINDOWS
+#pragma warning (push)
+#pragma warning (disable:4265)
+#endif
+// warning C4265: 'std::_Pad' : class has virtual functions, but destructor is not virtual
+
+#include <mutex>
+
+#if LL_WINDOWS
+#pragma warning (pop)
+#endif
+
 class LLSingletonBase: private boost::noncopyable
 {
 public:
@@ -43,7 +55,6 @@ private:
     // This, on the other hand, is a stack whose top indicates the LLSingleton
     // currently being initialized.
     static list_t& get_initializing();
-    static list_t& get_initializing_from(MasterList*);
     // Produce a vector<LLSingletonBase*> of master list, in dependency order.
     typedef std::vector<LLSingletonBase*> vec_t;
     static vec_t dep_sort();
@@ -57,10 +68,11 @@ protected:
     typedef enum e_init_state
     {
         UNINITIALIZED = 0,          // must be default-initialized state
-        CONSTRUCTING,
-        INITIALIZING,
-        INITIALIZED,
-        DELETED
+        CONSTRUCTING,               // within DERIVED_TYPE constructor
+        CONSTRUCTED,                // finished DERIVED_TYPE constructor
+        INITIALIZING,               // within DERIVED_TYPE::initSingleton()
+        INITIALIZED,                // normal case
+        DELETED                     // deleteSingleton() or deleteAll() called
     } EInitState;
 
     // Define tag<T> to pass to our template constructor. You can't explicitly
@@ -100,6 +112,9 @@ protected:
     // That being the case, we control exactly when it happens -- and we can
     // pop the stack immediately thereafter.
     void pop_initializing();
+    // Remove 'this' from the init stack in case of exception in the
+    // LLSingleton subclass constructor.
+    static void reset_initializing(list_t::size_type size);
 private:
     // logging
     static void log_initializing(const char* verb, const char* name);
@@ -115,6 +130,10 @@ protected:
     static void logwarns(const char* p1, const char* p2="",
                          const char* p3="", const char* p4="");
     static std::string demangle(const char* mangled);
+    template <typename T>
+    static std::string classname()       { return demangle(typeid(T).name()); }
+    template <typename T>
+    static std::string classname(T* ptr) { return demangle(typeid(*ptr).name()); }
 
     // Default methods in case subclass doesn't declare them.
     virtual void initSingleton() {}
@@ -178,7 +197,15 @@ struct LLSingleton_manage_master
     void remove(LLSingletonBase* sb) { sb->remove_master(); }
     void push_initializing(LLSingletonBase* sb) { sb->push_initializing(typeid(T).name()); }
     void pop_initializing (LLSingletonBase* sb) { sb->pop_initializing(); }
-    LLSingletonBase::list_t& get_initializing(T*) { return LLSingletonBase::get_initializing(); }
+    // used for init stack cleanup in case an LLSingleton subclass constructor
+    // throws an exception
+    void reset_initializing(LLSingletonBase::list_t::size_type size)
+    {
+        LLSingletonBase::reset_initializing(size);
+    }
+    // For any LLSingleton subclass except the MasterList, obtain the init
+    // stack from the MasterList singleton instance.
+    LLSingletonBase::list_t& get_initializing() { return LLSingletonBase::get_initializing(); }
 };
 
 // But for the specific case of LLSingletonBase::MasterList, don't.
@@ -189,9 +216,14 @@ struct LLSingleton_manage_master<LLSingletonBase::MasterList>
     void remove(LLSingletonBase*) {}
     void push_initializing(LLSingletonBase*) {}
     void pop_initializing (LLSingletonBase*) {}
-    LLSingletonBase::list_t& get_initializing(LLSingletonBase::MasterList* instance)
+    // since we never pushed, no need to clean up
+    void reset_initializing(LLSingletonBase::list_t::size_type size) {}
+    LLSingletonBase::list_t& get_initializing()
     {
-        return LLSingletonBase::get_initializing_from(instance);
+        // The MasterList shouldn't depend on any other LLSingletons. We'd
+        // get into trouble if we tried to recursively engage that machinery.
+        static LLSingletonBase::list_t sDummyList;
+        return sDummyList;
     }
 };
 
@@ -201,10 +233,19 @@ LLSingletonBase::LLSingletonBase(tag<DERIVED_TYPE>):
     mCleaned(false),
     mDeleteSingleton(NULL)
 {
-    // Make this the currently-initializing LLSingleton.
+    // This is the earliest possible point at which we can push this new
+    // instance onto the init stack. LLSingleton::constructSingleton() can't
+    // do it before calling the constructor, because it doesn't have an
+    // instance pointer until the constructor returns. Fortunately this
+    // constructor is guaranteed to be called before any subclass constructor.
+    // Make this new instance the currently-initializing LLSingleton.
     LLSingleton_manage_master<DERIVED_TYPE>().push_initializing(this);
 }
 
+// forward declare for friend directive within LLSingleton
+template <typename DERIVED_TYPE>
+class LLParamSingleton;
+
 /**
  * LLSingleton implements the getInstance() method part of the Singleton
  * pattern. It can't make the derived class constructors protected, though, so
@@ -270,9 +311,94 @@ template <typename DERIVED_TYPE>
 class LLSingleton : public LLSingletonBase
 {
 private:
-    static DERIVED_TYPE* constructSingleton()
+    // Allow LLParamSingleton subclass -- but NOT DERIVED_TYPE itself -- to
+    // access our private members.
+    friend class LLParamSingleton<DERIVED_TYPE>;
+
+    // LLSingleton only supports a nullary constructor. However, the specific
+    // purpose for its subclass LLParamSingleton is to support Singletons
+    // requiring constructor arguments. constructSingleton() supports both use
+    // cases.
+    template <typename... Args>
+    static void constructSingleton(Args&&... args)
+    {
+        auto prev_size = LLSingleton_manage_master<DERIVED_TYPE>().get_initializing().size();
+        // getInstance() calls are from within constructor
+        sData.mInitState = CONSTRUCTING;
+        try
+        {
+            sData.mInstance = new DERIVED_TYPE(std::forward<Args>(args)...);
+            // we have called constructor, have not yet called initSingleton()
+            sData.mInitState = CONSTRUCTED;
+        }
+        catch (const std::exception& err)
+        {
+            // LLSingletonBase might -- or might not -- have pushed the new
+            // instance onto the init stack before the exception. Reset the
+            // init stack to its previous size BEFORE logging so log-machinery
+            // LLSingletons don't record a dependency on DERIVED_TYPE!
+            LLSingleton_manage_master<DERIVED_TYPE>().reset_initializing(prev_size);
+            logwarns("Error constructing ", classname<DERIVED_TYPE>().c_str(),
+                     ": ", err.what());
+            // There isn't a separate EInitState value meaning "we attempted
+            // to construct this LLSingleton subclass but could not," so use
+            // DELETED. That seems slightly more appropriate than UNINITIALIZED.
+            sData.mInitState = DELETED;
+            // propagate the exception
+            throw;
+        }
+    }
+
+    static void finishInitializing()
+    {
+        // getInstance() calls are from within initSingleton()
+        sData.mInitState = INITIALIZING;
+        try
+        {
+            // initialize singleton after constructing it so that it can
+            // reference other singletons which in turn depend on it, thus
+            // breaking cyclic dependencies
+            sData.mInstance->initSingleton();
+            sData.mInitState = INITIALIZED;
+
+            // pop this off stack of initializing singletons
+            pop_initializing();
+        }
+        catch (const std::exception& err)
+        {
+            // pop this off stack of initializing singletons here, too --
+            // BEFORE logging, so log-machinery LLSingletons don't record a
+            // dependency on DERIVED_TYPE!
+            pop_initializing();
+            logwarns("Error in ", classname<DERIVED_TYPE>().c_str(),
+                     "::initSingleton(): ", err.what());
+            // and get rid of the instance entirely
+            deleteSingleton();
+            // propagate the exception
+            throw;
+        }
+    }
+
+    static void pop_initializing()
     {
-        return new DERIVED_TYPE();
+        // route through LLSingleton_manage_master so we Do The Right Thing
+        // (namely, nothing) for MasterList
+        LLSingleton_manage_master<DERIVED_TYPE>().pop_initializing(sData.mInstance);
+    }
+
+    // Without this 'using' declaration, the static method we're declaring
+    // here would hide the base-class method we want it to call.
+    using LLSingletonBase::capture_dependency;
+    static void capture_dependency()
+    {
+        // By this point, if DERIVED_TYPE was pushed onto the initializing
+        // stack, it has been popped off. So the top of that stack, if any, is
+        // an LLSingleton that directly depends on DERIVED_TYPE. If
+        // getInstance() was called by another LLSingleton, rather than from
+        // vanilla application code, record the dependency.
+        sData.mInstance->capture_dependency(
+            LLSingleton_manage_master<DERIVED_TYPE>().get_initializing(),
+            sData.mInitState);
     }
 
     // We know of no way to instruct the compiler that every subclass
@@ -285,34 +411,17 @@ private:
     // subclass body.
     virtual void you_must_use_LLSINGLETON_macro() = 0;
 
-    // stores pointer to singleton instance
-    struct SingletonLifetimeManager
+    // The purpose of this struct is to engage the C++11 guarantee that static
+    // variables declared in function scope are initialized exactly once, even
+    // if multiple threads concurrently reach the same declaration.
+    // https://en.cppreference.com/w/cpp/language/storage_duration#Static_local_variables
+    // Since getInstance() declares a static instance of SingletonInitializer,
+    // only the first call to getInstance() calls constructSingleton().
+    struct SingletonInitializer
     {
-        SingletonLifetimeManager()
-        {
-            construct();
-        }
-
-        static void construct()
-        {
-            sData.mInitState = CONSTRUCTING;
-            sData.mInstance = constructSingleton();
-            sData.mInitState = INITIALIZING;
-        }
-
-        ~SingletonLifetimeManager()
+        SingletonInitializer()
         {
-            // The dependencies between LLSingletons, and the arbitrary order
-            // of static-object destruction, mean that we DO NOT WANT this
-            // destructor to delete this LLSingleton. This destructor will run
-            // without regard to any other LLSingleton whose cleanup might
-            // depend on its existence. If you want to clean up LLSingletons,
-            // call LLSingletonBase::deleteAll() sometime before static-object
-            // destruction begins. That method will properly honor cross-
-            // LLSingleton dependencies. Otherwise we simply leak LLSingleton
-            // instances at shutdown. Since the whole process is terminating
-            // anyway, that's not necessarily a bad thing; it depends on what
-            // resources your LLSingleton instances are managing.
+            constructSingleton();
         }
     };
 
@@ -363,64 +472,59 @@ public:
     static void deleteSingleton()
     {
         delete sData.mInstance;
-        sData.mInstance = NULL;
-        sData.mInitState = DELETED;
+        // SingletonData state handled by destructor, above
     }
 
     static DERIVED_TYPE* getInstance()
     {
-        static SingletonLifetimeManager sLifeTimeMgr;
+        // call constructSingleton() only the first time we get here
+        static SingletonInitializer sInitializer;
 
         switch (sData.mInitState)
         {
         case UNINITIALIZED:
             // should never be uninitialized at this point
             logerrs("Uninitialized singleton ",
-                    demangle(typeid(DERIVED_TYPE).name()).c_str());
+                    classname<DERIVED_TYPE>().c_str());
             return NULL;
 
         case CONSTRUCTING:
+            // here if DERIVED_TYPE's constructor (directly or indirectly)
+            // calls DERIVED_TYPE::getInstance()
             logerrs("Tried to access singleton ",
-                    demangle(typeid(DERIVED_TYPE).name()).c_str(),
+                    classname<DERIVED_TYPE>().c_str(),
                     " from singleton constructor!");
             return NULL;
 
-        case INITIALIZING:
-            // go ahead and flag ourselves as initialized so we can be
-            // reentrant during initialization
-            sData.mInitState = INITIALIZED; 
-            // initialize singleton after constructing it so that it can
-            // reference other singletons which in turn depend on it, thus
-            // breaking cyclic dependencies
-            sData.mInstance->initSingleton();
-            // pop this off stack of initializing singletons
-            LLSingleton_manage_master<DERIVED_TYPE>().pop_initializing(sData.mInstance);
+        case CONSTRUCTED:
+            // first time through: set to CONSTRUCTED by
+            // constructSingleton(), called by sInitializer's constructor;
+            // still have to call initSingleton()
+            finishInitializing();
             break;
 
+        case INITIALIZING:
+            // here if DERIVED_TYPE::initSingleton() (directly or indirectly)
+            // calls DERIVED_TYPE::getInstance(): go ahead and allow it
         case INITIALIZED:
+            // normal subsequent calls
             break;
 
         case DELETED:
+            // called after deleteSingleton()
             logwarns("Trying to access deleted singleton ",
-                     demangle(typeid(DERIVED_TYPE).name()).c_str(),
+                     classname<DERIVED_TYPE>().c_str(),
                      " -- creating new instance");
-            SingletonLifetimeManager::construct();
-            // same as first time construction
-            sData.mInitState = INITIALIZED; 
-            sData.mInstance->initSingleton(); 
-            // pop this off stack of initializing singletons
-            LLSingleton_manage_master<DERIVED_TYPE>().pop_initializing(sData.mInstance);
+            // This recovery sequence is NOT thread-safe! We would need a
+            // recursive_mutex a la LLParamSingleton.
+            constructSingleton();
+            finishInitializing();
             break;
         }
 
-        // By this point, if DERIVED_TYPE was pushed onto the initializing
-        // stack, it has been popped off. So the top of that stack, if any, is
-        // an LLSingleton that directly depends on DERIVED_TYPE. If this call
-        // came from another LLSingleton, rather than from vanilla application
-        // code, record the dependency.
-        sData.mInstance->capture_dependency(
-            LLSingleton_manage_master<DERIVED_TYPE>().get_initializing(sData.mInstance),
-            sData.mInitState);
+        // record the dependency, if any: check if we got here from another
+        // LLSingleton's constructor or initSingleton() method
+        capture_dependency();
         return sData.mInstance;
     }
 
@@ -460,6 +564,173 @@ private:
 template<typename T>
 typename LLSingleton<T>::SingletonData LLSingleton<T>::sData;
 
+
+/**
+ * LLParamSingleton<T> is like LLSingleton<T>, except in the following ways:
+ *
+ * * It is NOT instantiated on demand (instance() or getInstance()). You must
+ *   first call initParamSingleton(constructor args...).
+ * * Before initParamSingleton(), calling instance() or getInstance() dies with
+ *   LL_ERRS.
+ * * initParamSingleton() may be called only once. A second call dies with
+ *   LL_ERRS.
+ * * However, distinct initParamSingleton() calls can be used to engage
+ *   different constructors, as long as only one such call is executed at
+ *   runtime.
+ * * Unlike LLSingleton, an LLParamSingleton cannot be "revived" by an
+ *   instance() or getInstance() call after deleteSingleton().
+ *
+ * Importantly, though, each LLParamSingleton subclass does participate in the
+ * dependency-ordered LLSingletonBase::deleteAll() processing.
+ */
+template <typename DERIVED_TYPE>
+class LLParamSingleton : public LLSingleton<DERIVED_TYPE>
+{
+private:
+    typedef LLSingleton<DERIVED_TYPE> super;
+    // Use a recursive_mutex in case of constructor circularity. With a
+    // non-recursive mutex, that would result in deadlock rather than the
+    // logerrs() call in getInstance().
+    typedef std::recursive_mutex mutex_t;
+
+public:
+    using super::deleteSingleton;
+    using super::instanceExists;
+    using super::wasDeleted;
+
+    // Passes arguments to DERIVED_TYPE's constructor and sets appropriate states
+    template <typename... Args>
+    static void initParamSingleton(Args&&... args)
+    {
+        // In case racing threads both call initParamSingleton() at the same
+        // time, serialize them. One should initialize; the other should see
+        // mInitState already set.
+        std::unique_lock<mutex_t> lk(getMutex());
+        // For organizational purposes this function shouldn't be called twice
+        if (super::sData.mInitState != super::UNINITIALIZED)
+        {
+            super::logerrs("Tried to initialize singleton ",
+                           super::template classname<DERIVED_TYPE>().c_str(),
+                           " twice!");
+        }
+        else
+        {
+            super::constructSingleton(std::forward<Args>(args)...);
+            super::finishInitializing();
+        }
+    }
+
+    static DERIVED_TYPE* getInstance()
+    {
+        // In case racing threads call getInstance() at the same moment as
+        // initParamSingleton(), serialize the calls.
+        std::unique_lock<mutex_t> lk(getMutex());
+
+        switch (super::sData.mInitState)
+        {
+        case super::UNINITIALIZED:
+            super::logerrs("Uninitialized param singleton ",
+                           super::template classname<DERIVED_TYPE>().c_str());
+            break;
+
+        case super::CONSTRUCTING:
+            super::logerrs("Tried to access param singleton ",
+                           super::template classname<DERIVED_TYPE>().c_str(),
+                           " from singleton constructor!");
+            break;
+
+        case super::CONSTRUCTED:
+            // Should never happen!? The CONSTRUCTED state is specifically to
+            // navigate through LLSingleton::SingletonInitializer getting
+            // constructed (once) before LLSingleton::getInstance()'s switch
+            // on mInitState. But our initParamSingleton() method calls
+            // constructSingleton() and then calls finishInitializing(), which
+            // immediately sets INITIALIZING. Why are we here?
+            super::logerrs("Param singleton ",
+                           super::template classname<DERIVED_TYPE>().c_str(),
+                           "::initSingleton() not yet called");
+            break;
+
+        case super::INITIALIZING:
+            // As with LLSingleton, explicitly permit circular calls from
+            // within initSingleton()
+        case super::INITIALIZED:
+            // for any valid call, capture dependencies
+            super::capture_dependency();
+            return super::sData.mInstance;
+
+        case super::DELETED:
+            super::logerrs("Trying to access deleted param singleton ",
+                           super::template classname<DERIVED_TYPE>().c_str());
+            break;
+        }
+
+        // should never actually get here; this is to pacify the compiler,
+        // which assumes control might return from logerrs()
+        return nullptr;
+    }
+
+    // instance() is replicated here so it calls
+    // LLParamSingleton::getInstance() rather than LLSingleton::getInstance()
+    // -- avoid making getInstance() virtual
+    static DERIVED_TYPE& instance()
+    {
+        return *getInstance();
+    }
+
+private:
+    // sMutex must be a function-local static rather than a static member. One
+    // of the essential features of LLSingleton and friends is that they must
+    // support getInstance() even when the containing module's static
+    // variables have not yet been runtime-initialized. A mutex requires
+    // construction. A static class member might not yet have been
+    // constructed.
+    //
+    // We could store a dumb mutex_t*, notice when it's NULL and allocate a
+    // heap mutex -- but that's vulnerable to race conditions. And we can't
+    // defend the dumb pointer with another mutex.
+    //
+    // We could store a std::atomic<mutex_t*> -- but a default-constructed
+    // std::atomic<T> does not contain a valid T, even a default-constructed
+    // T! Which means std::atomic, too, requires runtime initialization.
+    //
+    // But a function-local static is guaranteed to be initialized exactly
+    // once, the first time control reaches that declaration.
+    static mutex_t& getMutex()
+    {
+        static mutex_t sMutex;
+        return sMutex;
+    }
+};
+
+/**
+ * Initialization locked singleton, only derived class can decide when to initialize.
+ * Starts locked.
+ * For cases when singleton has a dependency onto something or.
+ *
+ * LLLockedSingleton is like an LLParamSingleton with a nullary constructor.
+ * It cannot be instantiated on demand (instance() or getInstance() call) --
+ * it must be instantiated by calling construct(). However, it does
+ * participate in dependency-ordered LLSingletonBase::deleteAll() processing.
+ */
+template <typename DT>
+class LLLockedSingleton : public LLParamSingleton<DT>
+{
+    typedef LLParamSingleton<DT> super;
+
+public:
+    using super::deleteSingleton;
+    using super::getInstance;
+    using super::instance;
+    using super::instanceExists;
+    using super::wasDeleted;
+
+    static void construct()
+    {
+        super::initParamSingleton();
+    }
+};
+
 /**
  * Use LLSINGLETON(Foo); at the start of an LLSingleton<Foo> subclass body
  * when you want to declare an out-of-line constructor:
@@ -484,13 +755,13 @@ typename LLSingleton<T>::SingletonData LLSingleton<T>::sData;
  * file, use 'inline' (unless it's a template class) to avoid duplicate-symbol
  * errors at link time.
  */
-#define LLSINGLETON(DERIVED_CLASS)                                      \
+#define LLSINGLETON(DERIVED_CLASS, ...)                                 \
 private:                                                                \
     /* implement LLSingleton pure virtual method whose sole purpose */  \
     /* is to remind people to use this macro */                         \
     virtual void you_must_use_LLSINGLETON_macro() {}                    \
     friend class LLSingleton<DERIVED_CLASS>;                            \
-    DERIVED_CLASS()
+    DERIVED_CLASS(__VA_ARGS__)
 
 /**
  * Use LLSINGLETON_EMPTY_CTOR(Foo); at the start of an LLSingleton<Foo>