From e2b84761513c464b8c0c65a16ec758db2eb522ca Mon Sep 17 00:00:00 2001
From: Marc Mutz <marc.mutz@qt.io>
Date: Sun, 16 Jul 2023 10:04:09 +0200
Subject: [PATCH] QSlotObjectBase: add Deleter and typedef for a unique_ptr
 using it

Use it in QMetaCallEvent, to have some automatic test coverage. Other
code that might benefit has undergone changes since 5.15, so will be
ported one-by-one to avoid conflicts on cherry-picks.

Change-Id: I566bab1803e3675f75a9fdf294a4b0f047d21c11
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit c58074b42dcd48a293fe493795d51ca2b101a280)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/kernel/qobject.cpp        |  6 ++----
 src/corelib/kernel/qobject_p.h        |  2 +-
 src/corelib/kernel/qobjectdefs_impl.h | 14 ++++++++++++++
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index 5a32c6f2147..9269e3b6cd9 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -551,7 +551,7 @@ QMetaCallEvent::QMetaCallEvent(QtPrivate::QSlotObjectBase *slotO,
                                const QObject *sender, int signalId,
                                void **args, QSemaphore *semaphore)
     : QAbstractMetaCallEvent(sender, signalId, semaphore),
-      d({slotO, args, nullptr, 0, 0, ushort(-1)}),
+      d({QtPrivate::SlotObjUniquePtr{slotO}, args, nullptr, 0, 0, ushort(-1)}),
       prealloc_()
 {
     if (d.slotObj_)
@@ -585,7 +585,7 @@ QMetaCallEvent::QMetaCallEvent(QtPrivate::QSlotObjectBase *slotO,
                                const QObject *sender, int signalId,
                                int nargs)
     : QAbstractMetaCallEvent(sender, signalId),
-      d({slotO, nullptr, nullptr, nargs, 0, ushort(-1)}),
+      d({QtPrivate::SlotObjUniquePtr(slotO), nullptr, nullptr, nargs, 0, ushort(-1)}),
       prealloc_()
 {
     if (d.slotObj_)
@@ -607,8 +607,6 @@ QMetaCallEvent::~QMetaCallEvent()
         if (reinterpret_cast<void *>(d.args_) != reinterpret_cast<void *>(prealloc_))
             free(d.args_);
     }
-    if (d.slotObj_)
-        d.slotObj_->destroyIfLastRef();
 }
 
 /*!
diff --git a/src/corelib/kernel/qobject_p.h b/src/corelib/kernel/qobject_p.h
index 5fcf138b443..937ac59f8eb 100644
--- a/src/corelib/kernel/qobject_p.h
+++ b/src/corelib/kernel/qobject_p.h
@@ -420,7 +420,7 @@ private:
     inline void allocArgs();
 
     struct Data {
-        QtPrivate::QSlotObjectBase *slotObj_;
+        QtPrivate::SlotObjUniquePtr slotObj_;
         void **args_;
         QObjectPrivate::StaticMetaCallFunction callFunction_;
         int nargs_;
diff --git a/src/corelib/kernel/qobjectdefs_impl.h b/src/corelib/kernel/qobjectdefs_impl.h
index 6f2dac783be..a9503595b2a 100644
--- a/src/corelib/kernel/qobjectdefs_impl.h
+++ b/src/corelib/kernel/qobjectdefs_impl.h
@@ -14,6 +14,8 @@
 
 #include <QtCore/qfunctionaltools_impl.h>
 
+#include <memory>
+
 QT_BEGIN_NAMESPACE
 class QObject;
 class QObjectPrivate;
@@ -413,6 +415,15 @@ namespace QtPrivate {
     public:
         explicit QSlotObjectBase(ImplFn fn) : m_impl(fn) {}
 
+        // A custom deleter compatible with std protocols (op()()) we well as
+        // the legacy QScopedPointer protocol (cleanup()).
+        struct Deleter {
+            void operator()(QSlotObjectBase *p) const noexcept
+            { if (p) p->destroyIfLastRef(); }
+            // for the non-standard QScopedPointer protocol:
+            static void cleanup(QSlotObjectBase *p) noexcept { Deleter{}(p); }
+        };
+
         inline int ref() noexcept { return m_ref.ref(); }
 #if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
         inline void destroyIfLastRef() noexcept
@@ -439,6 +450,9 @@ namespace QtPrivate {
         Q_DISABLE_COPY_MOVE(QSlotObjectBase)
     };
 
+    using SlotObjUniquePtr = std::unique_ptr<QSlotObjectBase,
+                                             QSlotObjectBase::Deleter>;
+
     // Implementation of QSlotObjectBase for which the slot is a callable (function, PMF, functor, or lambda).
     // Args and R are the List of arguments and the return type of the signal to which the slot is connected.
     template <typename Func, typename Args, typename R>