Downstream merge from lindenlab/viewer-lynx

11 files changed, 610 insertions, 239 deletions

diff --git a/indra/llcommon/llsingleton.cpp b/indra/llcommon/llsingleton.cpp
index 9fbd78a000..c45c144570 100644
--- a/indra/llcommon/llsingleton.cpp
+++ b/indra/llcommon/llsingleton.cpp
@@ -134,12 +134,6 @@ LLSingletonBase::list_t& LLSingletonBase::get_initializing()
     return LLSingletonBase::MasterList::instance().get_initializing_();
 }
 
-//static
-LLSingletonBase::list_t& LLSingletonBase::get_initializing_from(MasterList* master)
-{
-    return master->get_initializing_();
-}
-
 LLSingletonBase::~LLSingletonBase() {}
 
 void LLSingletonBase::push_initializing(const char* name)
@@ -156,7 +150,7 @@ void LLSingletonBase::pop_initializing()
     if (list.empty())
     {
         logerrs("Underflow in stack of currently-initializing LLSingletons at ",
-                demangle(typeid(*this).name()).c_str(), "::getInstance()");
+                classname(this).c_str(), "::getInstance()");
     }
 
     // Now we know list.back() exists: capture it
@@ -178,14 +172,39 @@ void LLSingletonBase::pop_initializing()
     if (back != this)
     {
         logerrs("Push/pop mismatch in stack of currently-initializing LLSingletons: ",
-                demangle(typeid(*this).name()).c_str(), "::getInstance() trying to pop ",
-                demangle(typeid(*back).name()).c_str());
+                classname(this).c_str(), "::getInstance() trying to pop ",
+                classname(back).c_str());
     }
 
     // log AFTER popping so logging singletons don't cry circularity
     log_initializing("Popping", typeid(*back).name());
 }
 
+void LLSingletonBase::reset_initializing(list_t::size_type size)
+{
+    // called for cleanup in case the LLSingleton subclass constructor throws
+    // an exception
+
+    // The tricky thing about this, the reason we have a separate method
+    // instead of just calling pop_initializing(), is (hopefully remote)
+    // possibility that the exception happened *before* the
+    // push_initializing() call in LLSingletonBase's constructor. So only
+    // remove the stack top if in fact we've pushed something more than the
+    // previous size.
+    list_t& list(get_initializing());
+
+    while (list.size() > size)
+    {
+        list.pop_back();
+    }
+
+    // as in pop_initializing()
+    if (list.empty())
+    {
+        MasterList::instance().cleanup_initializing_();
+    }
+}
+
 //static
 void LLSingletonBase::log_initializing(const char* verb, const char* name)
 {
@@ -197,7 +216,7 @@ void LLSingletonBase::log_initializing(const char* verb, const char* name)
              ri != rend; ++ri)
         {
             LLSingletonBase* sb(*ri);
-            LL_CONT << ' ' << demangle(typeid(*sb).name());
+            LL_CONT << ' ' << classname(sb);
         }
         LL_ENDL;
     }
@@ -231,7 +250,7 @@ void LLSingletonBase::capture_dependency(list_t& initializing, EInitState initSt
                 // 'found' is an iterator; *found is an LLSingletonBase*; **found
                 // is the actual LLSingletonBase instance.
                 LLSingletonBase* foundp(*found);
-                out << demangle(typeid(*foundp).name()) << " -> ";
+                out << classname(foundp) << " -> ";
             }
             // We promise to capture dependencies from both the constructor
             // and the initSingleton() method, so an LLSingleton's instance
@@ -245,7 +264,7 @@ void LLSingletonBase::capture_dependency(list_t& initializing, EInitState initSt
             if (initState == CONSTRUCTING)
             {
                 logerrs("LLSingleton circularity in Constructor: ", out.str().c_str(),
-                    demangle(typeid(*this).name()).c_str(), "");
+                    classname(this).c_str(), "");
             }
             else if (it_next == initializing.end())
             {
@@ -256,14 +275,14 @@ void LLSingletonBase::capture_dependency(list_t& initializing, EInitState initSt
                 // Example: LLNotifications singleton initializes default channels.
                 // Channels register themselves with singleton once done.
                 logdebugs("LLSingleton circularity: ", out.str().c_str(),
-                    demangle(typeid(*this).name()).c_str(), "");
+                    classname(this).c_str(), "");
             }
             else
             {
                 // Actual circularity with other singleton (or single singleton is used extensively).
                 // Dependency can be unclear.
                 logwarns("LLSingleton circularity: ", out.str().c_str(),
-                    demangle(typeid(*this).name()).c_str(), "");
+                    classname(this).c_str(), "");
             }
         }
         else
@@ -276,8 +295,8 @@ void LLSingletonBase::capture_dependency(list_t& initializing, EInitState initSt
             if (current->mDepends.insert(this).second)
             {
                 // only log the FIRST time we hit this dependency!
-                logdebugs(demangle(typeid(*current).name()).c_str(),
-                          " depends on ", demangle(typeid(*this).name()).c_str());
+                logdebugs(classname(current).c_str(),
+                          " depends on ", classname(this).c_str());
             }
         }
     }
@@ -336,19 +355,19 @@ void LLSingletonBase::cleanupAll()
             sp->mCleaned = true;
 
             logdebugs("calling ",
-                      demangle(typeid(*sp).name()).c_str(), "::cleanupSingleton()");
+                      classname(sp).c_str(), "::cleanupSingleton()");
             try
             {
                 sp->cleanupSingleton();
             }
             catch (const std::exception& e)
             {
-                logwarns("Exception in ", demangle(typeid(*sp).name()).c_str(),
+                logwarns("Exception in ", classname(sp).c_str(),
                          "::cleanupSingleton(): ", e.what());
             }
             catch (...)
             {
-                logwarns("Unknown exception in ", demangle(typeid(*sp).name()).c_str(),
+                logwarns("Unknown exception in ", classname(sp).c_str(),
                          "::cleanupSingleton()");
             }
         }
@@ -363,7 +382,7 @@ void LLSingletonBase::deleteAll()
     {
         // Capture the class name first: in case of exception, don't count on
         // being able to extract it later.
-        const std::string name = demangle(typeid(*sp).name());
+        const std::string name = classname(sp);
         try
         {
             // Call static method through instance function pointer.
@@ -440,7 +459,17 @@ void LLSingletonBase::logerrs(const char* p1, const char* p2, const char* p3, co
     log(LLError::LEVEL_ERROR, p1, p2, p3, p4);
     // The other important side effect of LL_ERRS() is
     // https://www.youtube.com/watch?v=OMG7paGJqhQ (emphasis on OMG)
-    LLError::crashAndLoop(std::string());
+    std::ostringstream out;
+    out << p1 << p2 << p3 << p4;
+    auto crash = LLError::getFatalFunction();
+    if (crash)
+    {
+        crash(out.str());
+    }
+    else
+    {
+        LLError::crashAndLoop(out.str());
+    }
 }
 
 std::string LLSingletonBase::demangle(const char* mangled)
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>
diff --git a/indra/llcommon/tests/lleventcoro_test.cpp b/indra/llcommon/tests/lleventcoro_test.cpp
index a459d17fb8..fa02d2bb1a 100644
--- a/indra/llcommon/tests/lleventcoro_test.cpp
+++ b/indra/llcommon/tests/lleventcoro_test.cpp
@@ -506,16 +506,10 @@ namespace tut
             replyName = waiter.getName0();
             errorName = waiter.getName1();
             WrapLLErrs capture;
-            try
-            {
-                result = waiter.suspendWithLog();
-                debug("no exception");
-            }
-            catch (const WrapLLErrs::FatalException& e)
-            {
-                debug(STRINGIZE("exception " << e.what()));
-                threw = e.what();
-            }
+            threw = capture.catch_llerrs([&waiter, &debug](){
+                    result = waiter.suspendWithLog();
+                    debug("no exception");
+                });
         }
         END
     }
@@ -762,18 +756,13 @@ namespace tut
         {
             LLCoroEventPumps waiter;
             WrapLLErrs capture;
-            try
-            {
-                result = waiter.postAndSuspendWithLog(
-                    LLSDMap("value", 31)("fail", LLSD()),
-                    immediateAPI.getPump(), "reply", "error");
-                debug("no exception");
-            }
-            catch (const WrapLLErrs::FatalException& e)
-            {
-                debug(STRINGIZE("exception " << e.what()));
-                threw = e.what();
-            }
+            threw = capture.catch_llerrs(
+                [&waiter, &debug](){
+                    result = waiter.postAndSuspendWithLog(
+                        LLSDMap("value", 31)("fail", LLSD()),
+                        immediateAPI.getPump(), "reply", "error");
+                    debug("no exception");
+                });
         }
         END
     }
diff --git a/indra/llcommon/tests/lleventdispatcher_test.cpp b/indra/llcommon/tests/lleventdispatcher_test.cpp
index 5a4df81bf1..a181d5c941 100644
--- a/indra/llcommon/tests/lleventdispatcher_test.cpp
+++ b/indra/llcommon/tests/lleventdispatcher_test.cpp
@@ -22,6 +22,7 @@
 #include "llsdutil.h"
 #include "stringize.h"
 #include "tests/wrapllerrs.h"
+#include "../test/catch_and_store_what_in.h"
 
 #include <map>
 #include <string>
@@ -630,16 +631,9 @@ namespace tut
 
         void call_exc(const std::string& func, const LLSD& args, const std::string& exc_frag)
         {
-            std::string threw;
-            try
-            {
-                work(func, args);
-            }
-            catch (const std::runtime_error& e)
-            {
-                cout << "*** " << e.what() << '\n';
-                threw = e.what();
-            }
+            std::string threw = catch_what<std::runtime_error>([this, &func, &args](){
+                    work(func, args);
+                });
             ensure_has(threw, exc_frag);
         }
 
@@ -717,15 +711,9 @@ namespace tut
         LLSD attempts(LLSDArray(17)(LLSDMap("pi", 3.14)("two", 2)));
         foreach(LLSD ae, inArray(attempts))
         {
-            std::string threw;
-            try
-            {
-                work.add("freena_err", "freena", freena, ae);
-            }
-            catch (const std::exception& e)
-            {
-                threw = e.what();
-            }
+            std::string threw = catch_what<std::exception>([this, &ae](){
+                    work.add("freena_err", "freena", freena, ae);
+                });
             ensure_has(threw, "must be an array");
         }
     }
@@ -734,15 +722,9 @@ namespace tut
     void object::test<2>()
     {
         set_test_name("map-style registration with badly-formed defaults");
-        std::string threw;
-        try
-        {
-            work.add("freena_err", "freena", freena, LLSDArray("a")("b"), 17);
-        }
-        catch (const std::exception& e)
-        {
-            threw = e.what();
-        }
+        std::string threw = catch_what<std::exception>([this](){
+                work.add("freena_err", "freena", freena, LLSDArray("a")("b"), 17);
+            });
         ensure_has(threw, "must be a map or an array");
     }
 
@@ -750,17 +732,11 @@ namespace tut
     void object::test<3>()
     {
         set_test_name("map-style registration with too many array defaults");
-        std::string threw;
-        try
-        {
-            work.add("freena_err", "freena", freena,
-                     LLSDArray("a")("b"),
-                     LLSDArray(17)(0.9)("gack"));
-        }
-        catch (const std::exception& e)
-        {
-            threw = e.what();
-        }
+        std::string threw = catch_what<std::exception>([this](){
+                work.add("freena_err", "freena", freena,
+                         LLSDArray("a")("b"),
+                         LLSDArray(17)(0.9)("gack"));
+            });
         ensure_has(threw, "shorter than");
     }
 
@@ -768,17 +744,11 @@ namespace tut
     void object::test<4>()
     {
         set_test_name("map-style registration with too many map defaults");
-        std::string threw;
-        try
-        {
-            work.add("freena_err", "freena", freena,
-                     LLSDArray("a")("b"),
-                     LLSDMap("b", 17)("foo", 3.14)("bar", "sinister"));
-        }
-        catch (const std::exception& e)
-        {
-            threw = e.what();
-        }
+        std::string threw = catch_what<std::exception>([this](){
+                work.add("freena_err", "freena", freena,
+                         LLSDArray("a")("b"),
+                         LLSDMap("b", 17)("foo", 3.14)("bar", "sinister"));
+            });
         ensure_has(threw, "nonexistent params");
         ensure_has(threw, "foo");
         ensure_has(threw, "bar");
@@ -1039,16 +1009,9 @@ namespace tut
         // We don't have a comparable helper function for the one-arg
         // operator() method, and it's not worth building one just for this
         // case. Write it out.
-        std::string threw;
-        try
-        {
-            work(LLSDMap("op", "freek"));
-        }
-        catch (const std::runtime_error& e)
-        {
-            cout << "*** " << e.what() << "\n";
-            threw = e.what();
-        }
+        std::string threw = catch_what<std::runtime_error>([this](){
+                work(LLSDMap("op", "freek"));
+            });
         ensure_has(threw, "bad");
         ensure_has(threw, "op");
         ensure_has(threw, "freek");
diff --git a/indra/llcommon/tests/lleventfilter_test.cpp b/indra/llcommon/tests/lleventfilter_test.cpp
index eb98b12ef5..1875013794 100644
--- a/indra/llcommon/tests/lleventfilter_test.cpp
+++ b/indra/llcommon/tests/lleventfilter_test.cpp
@@ -350,15 +350,9 @@ namespace tut
         // Now let the timer expire.
         filter.forceTimeout();
         // Notice the timeout.
-        std::string threw;
-        try
-        {
-            mainloop.post(17);
-        }
-        catch (const WrapLLErrs::FatalException& e)
-        {
-            threw = e.what();
-        }
+        std::string threw = capture.catch_llerrs([this](){
+                mainloop.post(17);
+            });
         ensure_contains("errorAfter() timeout exception", threw, "timeout");
         // Timing out cancels the timer. Verify that.
         listener0.reset(0);
diff --git a/indra/llcommon/tests/llinstancetracker_test.cpp b/indra/llcommon/tests/llinstancetracker_test.cpp
index c7d4b8a06b..d94fc0c56d 100644
--- a/indra/llcommon/tests/llinstancetracker_test.cpp
+++ b/indra/llcommon/tests/llinstancetracker_test.cpp
@@ -198,14 +198,9 @@ namespace tut
         {
             WrapLLErrs wrapper;
             Keyed::instance_iter i(Keyed::beginInstances());
-            try
-            {
-                delete keyed;
-            }
-            catch (const WrapLLErrs::FatalException& e)
-            {
-                what = e.what();
-            }
+            what = wrapper.catch_llerrs([&keyed](){
+                    delete keyed;
+                });
         }
         ensure(! what.empty());
     }
@@ -219,14 +214,9 @@ namespace tut
         {
             WrapLLErrs wrapper;
             Keyed::key_iter i(Keyed::beginKeys());
-            try
-            {
-                delete keyed;
-            }
-            catch (const WrapLLErrs::FatalException& e)
-            {
-                what = e.what();
-            }
+            what = wrapper.catch_llerrs([&keyed](){
+                    delete keyed;
+                });
         }
         ensure(! what.empty());
     }
@@ -240,14 +230,9 @@ namespace tut
         {
             WrapLLErrs wrapper;
             Unkeyed::instance_iter i(Unkeyed::beginInstances());
-            try
-            {
-                delete unkeyed;
-            }
-            catch (const WrapLLErrs::FatalException& e)
-            {
-                what = e.what();
-            }
+            what = wrapper.catch_llerrs([&unkeyed](){
+                    delete unkeyed;
+                });
         }
         ensure(! what.empty());
     }
diff --git a/indra/llcommon/tests/lllazy_test.cpp b/indra/llcommon/tests/lllazy_test.cpp
index 32a717f4fc..542306ee22 100644
--- a/indra/llcommon/tests/lllazy_test.cpp
+++ b/indra/llcommon/tests/lllazy_test.cpp
@@ -38,6 +38,7 @@
 #include <boost/lambda/bind.hpp>
 // other Linden headers
 #include "../test/lltut.h"
+#include "../test/catch_and_store_what_in.h"
 
 namespace bll = boost::lambda;
 
@@ -200,15 +201,9 @@ namespace tut
     void lllazy_object::test<2>()
     {
         TestNeedsTesting tnt;
-        std::string threw;
-        try
-        {
-            tnt.toolate();
-        }
-        catch (const LLLazyCommon::InstanceChange& e)
-        {
-            threw = e.what();
-        }
+        std::string threw = catch_what<LLLazyCommon::InstanceChange>([&tnt](){
+                tnt.toolate();
+            });
         ensure_contains("InstanceChange exception", threw, "replace LLLazy instance");
     }
 
diff --git a/indra/llcommon/tests/llleap_test.cpp b/indra/llcommon/tests/llleap_test.cpp
index 45648536c4..bf0a74d10d 100644
--- a/indra/llcommon/tests/llleap_test.cpp
+++ b/indra/llcommon/tests/llleap_test.cpp
@@ -23,7 +23,7 @@
 #include "../test/lltut.h"
 #include "../test/namedtempfile.h"
 #include "../test/catch_and_store_what_in.h"
-#include "wrapllerrs.h"
+#include "wrapllerrs.h"             // CaptureLog
 #include "llevents.h"
 #include "llprocess.h"
 #include "llstring.h"
@@ -290,12 +290,9 @@ namespace tut
     void object::test<6>()
     {
         set_test_name("empty plugin vector");
-        std::string threw;
-        try
-        {
-            LLLeap::create("empty", StringVec());
-        }
-        CATCH_AND_STORE_WHAT_IN(threw, LLLeap::Error)
+        std::string threw = catch_what<LLLeap::Error>([](){
+                LLLeap::create("empty", StringVec());
+            });
         ensure_contains("LLLeap::Error", threw, "no plugin");
         // try the suppress-exception variant
         ensure("bad launch returned non-NULL", ! LLLeap::create("empty", StringVec(), false));
@@ -308,12 +305,9 @@ namespace tut
         // Synthesize bogus executable name
         std::string BADPYTHON(PYTHON.substr(0, PYTHON.length()-1) + "x");
         CaptureLog log;
-        std::string threw;
-        try
-        {
-            LLLeap::create("bad exe", BADPYTHON);
-        }
-        CATCH_AND_STORE_WHAT_IN(threw, LLLeap::Error)
+        std::string threw = catch_what<LLLeap::Error>([&BADPYTHON](){
+                LLLeap::create("bad exe", BADPYTHON);
+            });
         ensure_contains("LLLeap::create() didn't throw", threw, "failed");
         log.messageWith("failed");
         log.messageWith(BADPYTHON);
diff --git a/indra/llcommon/tests/llprocess_test.cpp b/indra/llcommon/tests/llprocess_test.cpp
index 5c87cdabd9..222d832084 100644
--- a/indra/llcommon/tests/llprocess_test.cpp
+++ b/indra/llcommon/tests/llprocess_test.cpp
@@ -25,8 +25,6 @@
 #include <boost/function.hpp>
 #include <boost/algorithm/string/find_iterator.hpp>
 #include <boost/algorithm/string/finder.hpp>
-//#include <boost/lambda/lambda.hpp>
-//#include <boost/lambda/bind.hpp>
 // other Linden headers
 #include "../test/lltut.h"
 #include "../test/namedtempfile.h"
@@ -35,7 +33,7 @@
 #include "llsdutil.h"
 #include "llevents.h"
 #include "llstring.h"
-#include "wrapllerrs.h"
+#include "wrapllerrs.h"             // CaptureLog
 
 #if defined(LL_WINDOWS)
 #define sleep(secs) _sleep((secs) * 1000)
@@ -45,8 +43,7 @@
 #include <sys/wait.h>
 #endif
 
-//namespace lambda = boost::lambda;
- std::string apr_strerror_helper(apr_status_t rv)
+std::string apr_strerror_helper(apr_status_t rv)
 {
     char errbuf[256];
     apr_strerror(rv, errbuf, sizeof(errbuf));
@@ -960,12 +957,9 @@ namespace tut
 #define CATCH_IN(THREW, EXCEPTION, CODE)                                \
     do                                                                  \
     {                                                                   \
-        (THREW).clear();                                                \
-        try                                                             \
-        {                                                               \
-            CODE;                                                       \
-        }                                                               \
-        CATCH_AND_STORE_WHAT_IN(THREW, EXCEPTION)                       \
+        (THREW) = catch_what<EXCEPTION>([&](){                          \
+                CODE;                                                   \
+            });                                                         \
         ensure("failed to throw " #EXCEPTION ": " #CODE, ! (THREW).empty()); \
     } while (0)
 
diff --git a/indra/llcommon/tests/llsingleton_test.cpp b/indra/llcommon/tests/llsingleton_test.cpp
index 56886bc73f..75ddff9d7d 100644
--- a/indra/llcommon/tests/llsingleton_test.cpp
+++ b/indra/llcommon/tests/llsingleton_test.cpp
@@ -29,7 +29,8 @@
 
 #include "llsingleton.h"
 #include "../test/lltut.h"
-
+#include "wrapllerrs.h"
+#include "llsd.h"
 
 // Capture execution sequence by appending to log string.
 std::string sLog;
@@ -198,4 +199,134 @@ namespace tut
 
     TESTS(A, B, 4, 5, 6, 7)
     TESTS(B, A, 8, 9, 10, 11)
+
+#define PARAMSINGLETON(cls)                                             \
+    class cls: public LLParamSingleton<cls>                             \
+    {                                                                   \
+        LLSINGLETON(cls, const LLSD::String& str): mDesc(str) {}        \
+        cls(LLSD::Integer i): mDesc(i) {}                               \
+                                                                        \
+    public:                                                             \
+        std::string desc() const { return mDesc.asString(); }           \
+                                                                        \
+    private:                                                            \
+        LLSD mDesc;                                                     \
+    }
+
+    // Declare two otherwise-identical LLParamSingleton classes so we can
+    // validly initialize each using two different constructors. If we tried
+    // to test that with a single LLParamSingleton class within the same test
+    // program, we'd get 'trying to use deleted LLParamSingleton' errors.
+    PARAMSINGLETON(PSing1);
+    PARAMSINGLETON(PSing2);
+
+    template<> template<>
+    void singleton_object_t::test<12>()
+    {
+        set_test_name("LLParamSingleton");
+
+        WrapLLErrs catcherr;
+        // query methods
+        ensure("false positive on instanceExists()", ! PSing1::instanceExists());
+        ensure("false positive on wasDeleted()", ! PSing1::wasDeleted());
+        // try to reference before initializing
+        std::string threw = catcherr.catch_llerrs([](){
+                (void)PSing1::instance();
+            });
+        ensure_contains("too-early instance() didn't throw", threw, "Uninitialized");
+        // getInstance() behaves the same as instance()
+        threw = catcherr.catch_llerrs([](){
+                (void)PSing1::getInstance();
+            });
+        ensure_contains("too-early getInstance() didn't throw", threw, "Uninitialized");
+        // initialize using LLSD::String constructor
+        PSing1::initParamSingleton("string");
+        ensure_equals(PSing1::instance().desc(), "string");
+        ensure("false negative on instanceExists()", PSing1::instanceExists());
+        // try to initialize again
+        threw = catcherr.catch_llerrs([](){
+                PSing1::initParamSingleton("again");
+            });
+        ensure_contains("second ctor(string) didn't throw", threw, "twice");
+        // try to initialize using the other constructor -- should be
+        // well-formed, but illegal at runtime
+        threw = catcherr.catch_llerrs([](){
+                PSing1::initParamSingleton(17);
+            });
+        ensure_contains("other ctor(int) didn't throw", threw, "twice");
+        PSing1::deleteSingleton();
+        ensure("false negative on wasDeleted()", PSing1::wasDeleted());
+        threw = catcherr.catch_llerrs([](){
+                (void)PSing1::instance();
+            });
+        ensure_contains("accessed deleted LLParamSingleton", threw, "deleted");
+    }
+
+    template<> template<>
+    void singleton_object_t::test<13>()
+    {
+        set_test_name("LLParamSingleton alternate ctor");
+
+        WrapLLErrs catcherr;
+        // We don't have to restate all the tests for PSing1. Only test validly
+        // using the other constructor.
+        PSing2::initParamSingleton(17);
+        ensure_equals(PSing2::instance().desc(), "17");
+        // can't do it twice
+        std::string threw = catcherr.catch_llerrs([](){
+                PSing2::initParamSingleton(34);
+            });
+        ensure_contains("second ctor(int) didn't throw", threw, "twice");
+        // can't use the other constructor either
+        threw = catcherr.catch_llerrs([](){
+                PSing2::initParamSingleton("string");
+            });
+        ensure_contains("other ctor(string) didn't throw", threw, "twice");
+    }
+
+    class CircularPCtor: public LLParamSingleton<CircularPCtor>
+    {
+        LLSINGLETON(CircularPCtor)
+        {
+            // never mind indirection, just go straight for the circularity
+            (void)instance();
+        }
+    };
+
+    template<> template<>
+    void singleton_object_t::test<14>()
+    {
+        set_test_name("Circular LLParamSingleton constructor");
+        WrapLLErrs catcherr;
+        std::string threw = catcherr.catch_llerrs([](){
+                CircularPCtor::initParamSingleton();
+            });
+        ensure_contains("constructor circularity didn't throw", threw, "constructor");
+    }
+
+    class CircularPInit: public LLParamSingleton<CircularPInit>
+    {
+        LLSINGLETON_EMPTY_CTOR(CircularPInit);
+    public:
+        virtual void initSingleton()
+        {
+            // never mind indirection, just go straight for the circularity
+            CircularPInit *pt = getInstance();
+            if (!pt)
+            {
+                throw;
+            }
+        }
+    };
+
+    template<> template<>
+    void singleton_object_t::test<15>()
+    {
+        set_test_name("Circular LLParamSingleton initSingleton()");
+        WrapLLErrs catcherr;
+        std::string threw = catcherr.catch_llerrs([](){
+                CircularPInit::initParamSingleton();
+            });
+        ensure("initSingleton() circularity threw", threw.empty());
+    }
 }
diff --git a/indra/llcommon/tests/wrapllerrs.h b/indra/llcommon/tests/wrapllerrs.h
index 08fbf19b1c..b07d5afbd8 100644
--- a/indra/llcommon/tests/wrapllerrs.h
+++ b/indra/llcommon/tests/wrapllerrs.h
@@ -37,6 +37,7 @@
 #include "llerrorcontrol.h"
 #include "llexception.h"
 #include "stringize.h"
+#include "../test/catch_and_store_what_in.h"
 #include <boost/bind.hpp>
 #include <boost/noncopyable.hpp>
 #include <boost/shared_ptr.hpp>
@@ -81,6 +82,31 @@ struct WrapLLErrs
         LLTHROW(FatalException(message));
     }
 
+    /// Convenience wrapper for catch_what<FatalException>()
+    //
+    // The implementation makes it clear that this function need not be a
+    // member; it could easily be a free function. It is a member because it
+    // makes no sense to attempt to catch FatalException unless there is a
+    // WrapLLErrs instance in scope. Without a live WrapLLErrs instance, any
+    // LL_ERRS() reached by code within 'func' would terminate the test
+    // program instead of throwing FatalException.
+    //
+    // We were tempted to introduce a free function, likewise accepting
+    // arbitrary 'func', that would instantiate WrapLLErrs and then call
+    // catch_llerrs() on that instance. We decided against it, for this
+    // reason: on extending a test function containing a single call to that
+    // free function, a maintainer would most likely make additional calls to
+    // that free function, instead of switching to an explicit WrapLLErrs
+    // declaration with several calls to its catch_llerrs() member function.
+    // Even a construct such as WrapLLErrs().catch_llerrs(...) would make the
+    // object declaration more visible; it's not unreasonable to expect a
+    // maintainer to extend that by naming and reusing the WrapLLErrs instance.
+    template <typename FUNC>
+    std::string catch_llerrs(FUNC func)
+    {
+        return catch_what<FatalException>(func);
+    }
+
     std::string error;
     LLError::SettingsStoragePtr mPriorErrorSettings;
     LLError::FatalFunction mPriorFatal;