QMetaCallEvent: add ctors and create() overloads taking SlotObjUniquePtr

This makes it clear who is responsible for obtaining additional strong
reference to the slot objects, because these functions no longer do.

Change-Id: I39187e3c441d8f82d50d907731f1cbdfb2a95b9d
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 00dbd3cd26d2cf4dbcde3a8f517d0d6b6d0bc9ca)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/kernel/qobject.cpp

@@ -558,6 +558,21 @@ QMetaCallEvent::QMetaCallEvent(QtPrivate::QSlotObjectBase *slotO,
         d.slotObj_->ref();
 }
 
+/*!
+    \internal
+
+    Used for blocking queued connections, just passes \a args through without
+    allocating any memory.
+ */
+QMetaCallEvent::QMetaCallEvent(QtPrivate::SlotObjUniquePtr slotO,
+                               const QObject *sender, int signalId,
+                               void **args, QSemaphore *semaphore)
+    : QAbstractMetaCallEvent(sender, signalId, semaphore),
+      d{std::move(slotO), args, nullptr, 0, 0, ushort(-1)},
+      prealloc_()
+{
+}
+
 /*!
     \internal
 
@@ -593,6 +608,22 @@ QMetaCallEvent::QMetaCallEvent(QtPrivate::QSlotObjectBase *slotO,
     allocArgs();
 }
 
+/*!
+    \internal
+
+    Allocates memory for \a nargs; code creating an event needs to initialize
+    the void* and int arrays by accessing \a args() and \a types(), respectively.
+ */
+QMetaCallEvent::QMetaCallEvent(QtPrivate::SlotObjUniquePtr slotO,
+                               const QObject *sender, int signalId,
+                               int nargs)
+    : QAbstractMetaCallEvent(sender, signalId),
+      d{std::move(slotO), nullptr, nullptr, nargs, 0, ushort(-1)},
+      prealloc_()
+{
+    allocArgs();
+}
+
 /*!
     \internal
  */
@@ -624,12 +655,12 @@ void QMetaCallEvent::placeMetaCall(QObject *object)
     }
 }
 
-QMetaCallEvent* QMetaCallEvent::create_impl(QtPrivate::QSlotObjectBase *slotObj,
+QMetaCallEvent* QMetaCallEvent::create_impl(QtPrivate::SlotObjUniquePtr slotObj,
                                             const QObject *sender, int signal_index,
                                             size_t argc, const void* const argp[],
                                             const QMetaType metaTypes[])
 {
-    auto metaCallEvent = std::make_unique<QMetaCallEvent>(slotObj, sender,
+    auto metaCallEvent = std::make_unique<QMetaCallEvent>(std::move(slotObj), sender,
                                                           signal_index, int(argc));
 
     void **args = metaCallEvent->args();

src/corelib/kernel/qobject_p.h

@@ -375,6 +375,9 @@ public:
     QMetaCallEvent(QtPrivate::QSlotObjectBase *slotObj,
                    const QObject *sender, int signalId,
                    void **args, QSemaphore *semaphore);
+    QMetaCallEvent(QtPrivate::SlotObjUniquePtr slotObj,
+                   const QObject *sender, int signalId,
+                   void **args, QSemaphore *semaphore);
 
     // queued - args allocated by event, copied by caller
     QMetaCallEvent(ushort method_offset, ushort method_relative,
@@ -384,6 +387,9 @@ public:
     QMetaCallEvent(QtPrivate::QSlotObjectBase *slotObj,
                    const QObject *sender, int signalId,
                    int nargs);
+    QMetaCallEvent(QtPrivate::SlotObjUniquePtr slotObj,
+                   const QObject *sender, int signalId,
+                   int nargs);
 
     ~QMetaCallEvent() override;
 
@@ -396,6 +402,15 @@ public:
         constexpr auto argc = sizeof...(Args) + 1;
         return create_impl(slotObj, sender, signal_index, argc, argp, metaTypes);
     }
+    template<typename ...Args>
+    static QMetaCallEvent *create(QtPrivate::SlotObjUniquePtr slotObj, const QObject *sender,
+                                  int signal_index, const Args &...argv)
+    {
+        const void* const argp[] = { nullptr, std::addressof(argv)... };
+        const QMetaType metaTypes[] = { QMetaType::fromType<void>(), QMetaType::fromType<Args>()... };
+        constexpr auto argc = sizeof...(Args) + 1;
+        return create_impl(std::move(slotObj), sender, signal_index, argc, argp, metaTypes);
+    }
 
     inline int id() const { return d.method_offset_ + d.method_relative_; }
     inline const void * const* args() const { return d.args_; }
@@ -407,6 +422,15 @@ public:
 
 private:
     static QMetaCallEvent *create_impl(QtPrivate::QSlotObjectBase *slotObj, const QObject *sender,
+                                       int signal_index, size_t argc, const void * const argp[],
+                                       const QMetaType metaTypes[])
+    {
+        if (slotObj)
+            slotObj->ref();
+        return create_impl(QtPrivate::SlotObjUniquePtr{slotObj}, sender,
+                           signal_index, argc, argp, metaTypes);
+    }
+    static QMetaCallEvent *create_impl(QtPrivate::SlotObjUniquePtr slotObj, const QObject *sender,
                                        int signal_index, size_t argc, const void * const argp[],
                                        const QMetaType metaTypes[]);
     inline void allocArgs();