QObject: allow connecting to functors with a receiver object

Up to now, it was only possible to connect to functors in a direct
way, without being capable of using Qt::ConnectionType. This patch
allows for specifying a receiver for Functors and function
pointers, hence making it possible to specify effectively the
connection type.

To do this properly, it was needed to add an enum in FunctionPointer
representing whether the considered function is a member function
or not, to reduce ambiguity upon overloaded calls.

Moreover, now senders are checked for the existence of a slot obj
as well. This way, should the context be freed, the slot obj and
the functor contained in it will be freed as well.

On a side note, connecting to a static slot
(like QCoreApplication::quit) specifying the receiver object is
now compiling.

Change-Id: I46474099413b1dc6ca4db9934191d469baeef070
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

3 files changed, 112 insertions, 32 deletions

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index b914ca812f..cc689657d2 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -854,9 +854,23 @@ QObject::~QObject()
                 senderLists->dirty = true;
 
             int signal_index = node->signal_index;
+
+            QtPrivate::QSlotObjectBase *slotObj = Q_NULLPTR;
+            if (node->isSlotObject) {
+                slotObj = node->slotObj;
+                node->isSlotObject = false;
+            }
+
             node = node->next;
             if (needToUnlock)
                 m->unlock();
+
+            if (slotObj) {
+                locker.unlock();
+                slotObj->destroyIfLastRef();
+                locker.relock();
+            }
+
             sender->disconnectNotify(QMetaObjectPrivate::signal(sender->metaObject(), signal_index));
         }
     }
@@ -4273,6 +4287,43 @@ void qDeleteInEventHandler(QObject *o)
  */
 
 /*!
+    \fn QMetaObject::Connection QObject::connect(const QObject *sender, PointerToMemberFunction signal, const QObject *context, Functor functor, Qt::ConnectionType type)
+
+    \threadsafe
+    \overload connect()
+
+    \since 5.2
+
+    Creates a connection of a given \a type from \a signal in
+    \a sender object to \a functor to be placed in a specific event
+    loop of \a context, and returns a handle to the connection
+
+    The signal must be a function declared as a signal in the header.
+    The slot function can be any function or functor that can be connected
+    to the signal.
+    A function can be connected to a given signal if the signal as at
+    least as many argument as the slot. A functor can be connected to a signal
+    if they have exactly the same number of arguments. There must exist implicit
+    conversion between the types of the corresponding arguments in the
+    signal and the slot.
+
+    Example:
+
+    \snippet code/src_corelib_kernel_qobject.cpp 50
+
+    If your compiler support C++11 lambda expressions, you can use them:
+
+    \snippet code/src_corelib_kernel_qobject.cpp 51
+
+    The connection will automatically disconnect if the sender or the context
+    is destroyed.
+
+    \note If the compiler does not support C++11 variadic templates, the number
+    of arguments in the signal or slot are limited to 6, and the functor object
+    must not have an overloaded or templated operator().
+ */
+
+/*!
     \internal
 
     Implementation of the template version of connect
diff --git a/src/corelib/kernel/qobject.h b/src/corelib/kernel/qobject.h
index 15b9c8f35e..e2000afc82 100644
--- a/src/corelib/kernel/qobject.h
+++ b/src/corelib/kernel/qobject.h
@@ -208,6 +208,7 @@ public:
 #ifdef Q_QDOC
     static QMetaObject::Connection connect(const QObject *sender, PointerToMemberFunction signal, const QObject *receiver, PointerToMemberFunction method, Qt::ConnectionType type);
     static QMetaObject::Connection connect(const QObject *sender, PointerToMemberFunction signal, Functor functor);
+    static QMetaObject::Connection connect(const QObject *sender, PointerToMemberFunction signal, const QObject *context, Functor functor, Qt::ConnectionType type);
 #else
     //Connect a signal to a pointer to qobject member function
     template <typename Func1, typename Func2>
@@ -245,6 +246,16 @@ public:
     static inline typename QtPrivate::QEnableIf<int(QtPrivate::FunctionPointer<Func2>::ArgumentCount) >= 0, QMetaObject::Connection>::Type
             connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
     {
+        return connect(sender, signal, sender, slot, Qt::DirectConnection);
+    }
+
+    //connect to a function pointer  (not a member)
+    template <typename Func1, typename Func2>
+    static inline typename QtPrivate::QEnableIf<int(QtPrivate::FunctionPointer<Func2>::ArgumentCount) >= 0 &&
+                                                !QtPrivate::FunctionPointer<Func2>::IsPointerToMemberFunction, QMetaObject::Connection>::Type
+            connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, const QObject *context, Func2 slot,
+                    Qt::ConnectionType type = Qt::AutoConnection)
+    {
         typedef QtPrivate::FunctionPointer<Func1> SignalType;
         typedef QtPrivate::FunctionPointer<Func2> SlotType;
 
@@ -259,11 +270,15 @@ public:
         Q_STATIC_ASSERT_X((QtPrivate::AreArgumentsCompatible<typename SlotType::ReturnType, typename SignalType::ReturnType>::value),
                           "Return type of the slot is not compatible with the return type of the signal.");
 
-        return connectImpl(sender, reinterpret_cast<void **>(&signal), sender, 0,
+        const int *types = 0;
+        if (type == Qt::QueuedConnection || type == Qt::BlockingQueuedConnection)
+            types = QtPrivate::ConnectionTypes<typename SignalType::Arguments>::types();
+
+        return connectImpl(sender, reinterpret_cast<void **>(&signal), context, 0,
                            new QtPrivate::QStaticSlotObject<Func2,
                                                  typename QtPrivate::List_Left<typename SignalType::Arguments, SlotType::ArgumentCount>::Value,
                                                  typename SignalType::ReturnType>(slot),
-                           Qt::DirectConnection, 0, &SignalType::Object::staticMetaObject);
+                           type, types, &SignalType::Object::staticMetaObject);
     }
 
     //connect to a functor
@@ -271,6 +286,15 @@ public:
     static inline typename QtPrivate::QEnableIf<QtPrivate::FunctionPointer<Func2>::ArgumentCount == -1, QMetaObject::Connection>::Type
             connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, Func2 slot)
     {
+        return connect(sender, signal, sender, slot, Qt::DirectConnection);
+    }
+
+    //connect to a functor, with a "context" object defining in which event loop is going to be executed
+    template <typename Func1, typename Func2>
+    static inline typename QtPrivate::QEnableIf<QtPrivate::FunctionPointer<Func2>::ArgumentCount == -1, QMetaObject::Connection>::Type
+            connect(const typename QtPrivate::FunctionPointer<Func1>::Object *sender, Func1 signal, const QObject *context, Func2 slot,
+                    Qt::ConnectionType type = Qt::AutoConnection)
+    {
 #if defined (Q_COMPILER_DECLTYPE) && defined (Q_COMPILER_VARIADIC_TEMPLATES)
         typedef QtPrivate::FunctionPointer<Func1> SignalType;
         const int FunctorArgumentCount = QtPrivate::ComputeFunctorArgumentCount<Func2 , typename SignalType::Arguments>::Value;
@@ -292,9 +316,10 @@ public:
         C++11 variadic templates
       */
 #ifndef Q_COMPILER_DECLTYPE  //Workaround the lack of decltype using another function as indirection
-        return connect_functor(sender, signal, slot, &Func2::operator()); }
+        return connect_functor(sender, signal, context, slot, &Func2::operator(), type); }
     template <typename Func1, typename Func2, typename Func2Operator>
-    static inline QMetaObject::Connection connect_functor(const QObject *sender, Func1 signal, Func2 slot, Func2Operator) {
+    static inline QMetaObject::Connection connect_functor(const QObject *sender, Func1 signal, const QObject *context,
+                                                          Func2 slot, Func2Operator, Qt::ConnectionType type) {
         typedef QtPrivate::FunctionPointer<Func2Operator> SlotType ;
 #else
         typedef QtPrivate::FunctionPointer<decltype(&Func2::operator())> SlotType ;
@@ -315,11 +340,15 @@ public:
         Q_STATIC_ASSERT_X(QtPrivate::HasQ_OBJECT_Macro<typename SignalType::Object>::Value,
                           "No Q_OBJECT in the class with the signal");
 
-        return connectImpl(sender, reinterpret_cast<void **>(&signal), sender, 0,
+        const int *types = 0;
+        if (type == Qt::QueuedConnection || type == Qt::BlockingQueuedConnection)
+            types = QtPrivate::ConnectionTypes<typename SignalType::Arguments>::types();
+
+        return connectImpl(sender, reinterpret_cast<void **>(&signal), context, 0,
                            new QtPrivate::QFunctorSlotObject<Func2, SlotArgumentCount,
                                 typename QtPrivate::List_Left<typename SignalType::Arguments, SlotArgumentCount>::Value,
                                 typename SignalType::ReturnType>(slot),
-                           Qt::DirectConnection, 0, &SignalType::Object::staticMetaObject);
+                           type, types, &SignalType::Object::staticMetaObject);
     }
 #endif //Q_QDOC
 
diff --git a/src/corelib/kernel/qobjectdefs_impl.h b/src/corelib/kernel/qobjectdefs_impl.h
index d775ef1b65..fb6601f21b 100644
--- a/src/corelib/kernel/qobjectdefs_impl.h
+++ b/src/corelib/kernel/qobjectdefs_impl.h
@@ -129,7 +129,7 @@ namespace QtPrivate {
        its call function is the same as the FunctionPointer::call function.
      */
 #ifndef Q_COMPILER_VARIADIC_TEMPLATES
-    template<typename Func> struct FunctionPointer { enum {ArgumentCount = -1}; };
+    template<typename Func> struct FunctionPointer { enum {ArgumentCount = -1, IsPointerToMemberFunction = false}; };
     //Pointers to member functions
     template<class Obj, typename Ret> struct FunctionPointer<Ret (Obj::*) ()>
     {
@@ -137,7 +137,7 @@ namespace QtPrivate {
         typedef void Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) ();
-        enum {ArgumentCount = 0};
+        enum {ArgumentCount = 0, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) { (o->*f)(), ApplyReturnValue<R>(arg[0]); }
     };
@@ -147,7 +147,7 @@ namespace QtPrivate {
         typedef List<Arg1, void> Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1);
-        enum {ArgumentCount = 1};
+        enum {ArgumentCount = 1, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)((*reinterpret_cast<typename RemoveRef<typename Args::Car>::Type *>(arg[1]))), ApplyReturnValue<R>(arg[0]);
@@ -159,7 +159,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, void> >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2);
-        enum {ArgumentCount = 2};
+        enum {ArgumentCount = 2, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -172,7 +172,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, void> > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2, Arg3);
-        enum {ArgumentCount = 3};
+        enum {ArgumentCount = 3, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -186,7 +186,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, List<Arg4, void> > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2, Arg3, Arg4);
-        enum {ArgumentCount = 4};
+        enum {ArgumentCount = 4, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -201,7 +201,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, List<Arg4, List<Arg5, void> > > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2, Arg3, Arg4, Arg5);
-        enum {ArgumentCount = 5};
+        enum {ArgumentCount = 5, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -218,7 +218,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, List<Arg4, List<Arg5, List<Arg6, void> > > > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2, Arg3, Arg4, Arg5, Arg6);
-        enum {ArgumentCount = 6};
+        enum {ArgumentCount = 6, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -237,7 +237,7 @@ namespace QtPrivate {
         typedef void Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) () const;
-        enum {ArgumentCount = 0};
+        enum {ArgumentCount = 0, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) { (o->*f)(), ApplyReturnValue<R>(arg[0]); }
     };
@@ -247,7 +247,7 @@ namespace QtPrivate {
         typedef List<Arg1, void> Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1) const;
-        enum {ArgumentCount = 1};
+        enum {ArgumentCount = 1, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)((*reinterpret_cast<typename RemoveRef<typename Args::Car>::Type *>(arg[1]))), ApplyReturnValue<R>(arg[0]);
@@ -259,7 +259,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, void> >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2) const;
-        enum {ArgumentCount = 2};
+        enum {ArgumentCount = 2, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -272,7 +272,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, void> > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2, Arg3) const;
-        enum {ArgumentCount = 3};
+        enum {ArgumentCount = 3, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -286,7 +286,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, List<Arg4, void> > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2, Arg3, Arg4) const;
-        enum {ArgumentCount = 4};
+        enum {ArgumentCount = 4, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -301,7 +301,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, List<Arg4, List<Arg5, void> > > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2, Arg3, Arg4, Arg5) const;
-        enum {ArgumentCount = 5};
+        enum {ArgumentCount = 5, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -318,7 +318,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, List<Arg4, List<Arg5, List<Arg6, void> > > > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Arg1, Arg2, Arg3, Arg4, Arg5, Arg6) const;
-        enum {ArgumentCount = 6};
+        enum {ArgumentCount = 6, IsPointerToMemberFunction = true};
         template <typename Args, typename R>
         static void call(Function f, Obj *o, void **arg) {
             (o->*f)( *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -336,7 +336,7 @@ namespace QtPrivate {
         typedef void Arguments;
         typedef Ret (*Function) ();
         typedef Ret ReturnType;
-        enum {ArgumentCount = 0};
+        enum {ArgumentCount = 0, IsPointerToMemberFunction = false};
         template <typename Args, typename R>
         static void call(Function f, void *, void **arg) { f(), ApplyReturnValue<R>(arg[0]); }
     };
@@ -345,7 +345,7 @@ namespace QtPrivate {
         typedef List<Arg1, void> Arguments;
         typedef Ret ReturnType;
         typedef Ret (*Function) (Arg1);
-        enum {ArgumentCount = 1};
+        enum {ArgumentCount = 1, IsPointerToMemberFunction = false};
         template <typename Args, typename R>
         static void call(Function f, void *, void **arg)
         { f(*reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1])), ApplyReturnValue<R>(arg[0]); }
@@ -355,7 +355,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, void> > Arguments;
         typedef Ret ReturnType;
         typedef Ret (*Function) (Arg1, Arg2);
-        enum {ArgumentCount = 2};
+        enum {ArgumentCount = 2, IsPointerToMemberFunction = false};
         template <typename Args, typename R>
         static void call(Function f, void *, void **arg) {
             f(*reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -366,7 +366,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, void> > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (*Function) (Arg1, Arg2, Arg3);
-        enum {ArgumentCount = 3};
+        enum {ArgumentCount = 3, IsPointerToMemberFunction = false};
         template <typename Args, typename R>
         static void call(Function f, void *, void **arg) {
             f(       *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -379,7 +379,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, List<Arg4, void> > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (*Function) (Arg1, Arg2, Arg3, Arg4);
-        enum {ArgumentCount = 4};
+        enum {ArgumentCount = 4, IsPointerToMemberFunction = false};
         template <typename Args, typename R>
         static void call(Function f, void *, void **arg) {
             f(       *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -394,7 +394,7 @@ namespace QtPrivate {
         List<Arg4, List<Arg5, void > > > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (*Function) (Arg1, Arg2, Arg3, Arg4, Arg5);
-        enum {ArgumentCount = 5};
+        enum {ArgumentCount = 5, IsPointerToMemberFunction = false};
         template <typename Args, typename R>
         static void call(Function f, void *, void **arg) {
             f(       *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -409,7 +409,7 @@ namespace QtPrivate {
         typedef List<Arg1, List<Arg2, List<Arg3, List<Arg4, List<Arg5, List<Arg6, void> > > > > >  Arguments;
         typedef Ret ReturnType;
         typedef Ret (*Function) (Arg1, Arg2, Arg3, Arg4, Arg5, Arg6);
-        enum {ArgumentCount = 6};
+        enum {ArgumentCount = 6, IsPointerToMemberFunction = false};
         template <typename Args, typename R>
         static void call(Function f, void *, void **arg) {
             f(       *reinterpret_cast<typename RemoveRef<typename List_Select<Args, 0>::Value>::Type *>(arg[1]),
@@ -493,7 +493,7 @@ namespace QtPrivate {
     template <int N> struct Indexes
     { typedef typename IndexesAppend<typename Indexes<N - 1>::Value, N - 1>::Value Value; };
     template <> struct Indexes<0> { typedef IndexesList<> Value; };
-    template<typename Func> struct FunctionPointer { enum {ArgumentCount = -1}; };
+    template<typename Func> struct FunctionPointer { enum {ArgumentCount = -1, IsPointerToMemberFunction = false}; };
 
     template <typename, typename, typename, typename> struct FunctorCall;
     template <int... II, typename... SignalArgs, typename R, typename Function>
@@ -521,7 +521,7 @@ namespace QtPrivate {
         typedef List<Args...>  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Args...);
-        enum {ArgumentCount = sizeof...(Args)};
+        enum {ArgumentCount = sizeof...(Args), IsPointerToMemberFunction = true};
         template <typename SignalArgs, typename R>
         static void call(Function f, Obj *o, void **arg) {
             FunctorCall<typename Indexes<ArgumentCount>::Value, SignalArgs, R, Function>::call(f, o, arg);
@@ -533,7 +533,7 @@ namespace QtPrivate {
         typedef List<Args...>  Arguments;
         typedef Ret ReturnType;
         typedef Ret (Obj::*Function) (Args...) const;
-        enum {ArgumentCount = sizeof...(Args)};
+        enum {ArgumentCount = sizeof...(Args), IsPointerToMemberFunction = true};
         template <typename SignalArgs, typename R>
         static void call(Function f, Obj *o, void **arg) {
             FunctorCall<typename Indexes<ArgumentCount>::Value, SignalArgs, R, Function>::call(f, o, arg);
@@ -545,7 +545,7 @@ namespace QtPrivate {
         typedef List<Args...> Arguments;
         typedef Ret ReturnType;
         typedef Ret (*Function) (Args...);
-        enum {ArgumentCount = sizeof...(Args)};
+        enum {ArgumentCount = sizeof...(Args), IsPointerToMemberFunction = false};
         template <typename SignalArgs, typename R>
         static void call(Function f, void *, void **arg) {
             FunctorCall<typename Indexes<ArgumentCount>::Value, SignalArgs, R, Function>::call(f, arg);