signal: Finally clean up all leaks after complete understanding

The PYSIDE-79 bug was never understood, completely.
After getting much more clarity through the work on
PYSIDE-2201, the real problem could be found:

It turned out that the implementation of descriptors was
incomplete. Instead of respecting an already cached instance,
it created a new one, all the time, resulting in a serious leak!

This became visible by deep inspection of the control flow
with VS-Code. After the interaction of PyObject_GetAttr,
getHiddenDataFromQObject and signalDescrGet became transparent,
the function was completed and the issue finally solved.

Fixes: PYSIDE-79
Task-number: PYSIDE-68
Task-number: PYSIDE-2201
Change-Id: Ifd6098b1ce43d9bf51350218deb031bbf9ccb97a
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
(cherry picked from commit 08ec50ff3b569e2062285ee633f5c7e548c67545)
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

4 files changed, 14 insertions, 14 deletions

diff --git a/build_history/blacklist.txt b/build_history/blacklist.txt
index c335081a1..a2a45295c 100644
--- a/build_history/blacklist.txt
+++ b/build_history/blacklist.txt
@@ -45,8 +45,6 @@
 # Unsolved Refcounting leaks in debug mode
 [pysidetest::property_python_test]
     debug
-[signals::bug_79]
-    debug
 
 # PYSIDE-535: These errors are still present. Please try to remove one :)
 [sample::mixed_mi]
diff --git a/sources/pyside6/libpyside/pyside.cpp b/sources/pyside6/libpyside/pyside.cpp
index 29dd8d7e8..88a86fb2d 100644
--- a/sources/pyside6/libpyside/pyside.cpp
+++ b/sources/pyside6/libpyside/pyside.cpp
@@ -496,6 +496,7 @@ PyObject *getHiddenDataFromQObject(QObject *cppSelf, PyObject *self, PyObject *n
 {
     using Shiboken::AutoDecRef;
 
+    // PYSIDE-68-bis: This getattr finds signals early by `signalDescrGet`.
     PyObject *attr = PyObject_GenericGetAttr(self, name);
     if (!Shiboken::Object::isValid(reinterpret_cast<SbkObject *>(self), false))
         return attr;
@@ -508,15 +509,6 @@ PyObject *getHiddenDataFromQObject(QObject *cppSelf, PyObject *self, PyObject *n
         attr = value;
     }
 
-    // Mutate native signals to signal instance type
-    // Caution: This inserts the signal instance into the instance dict.
-    if (attr && PyObject_TypeCheck(attr, PySideSignal_TypeF())) {
-        auto *inst = Signal::initialize(reinterpret_cast<PySideSignal *>(attr), name, self);
-        PyObject *signalInst = reinterpret_cast<PyObject *>(inst);
-        PyObject_SetAttr(self, name, signalInst);
-        return signalInst;
-    }
-
     // Search on metaobject (avoid internal attributes started with '__')
     if (!attr) {
         PyObject *type, *value, *traceback;
diff --git a/sources/pyside6/libpyside/pysidesignal.cpp b/sources/pyside6/libpyside/pysidesignal.cpp
index ebc7b873d..9f881d893 100644
--- a/sources/pyside6/libpyside/pysidesignal.cpp
+++ b/sources/pyside6/libpyside/pysidesignal.cpp
@@ -683,8 +683,18 @@ static PyObject *signalDescrGet(PyObject *self, PyObject *obj, PyObject * /*type
         Py_INCREF(self);
         return self;
     }
+
+    // PYSIDE-68-bis: It is important to respect the already cached instance.
     Shiboken::AutoDecRef name(Py_BuildValue("s", signal->data->signalName.data()));
-    return reinterpret_cast<PyObject *>(PySide::Signal::initialize(signal, name, obj));
+    auto *dict = SbkObject_GetDict_NoRef(obj);
+    auto *inst = PyDict_GetItem(dict, name);
+    if (inst) {
+        Py_INCREF(inst);
+        return inst;
+    }
+    inst = reinterpret_cast<PyObject *>(PySide::Signal::initialize(signal, name, obj));
+    PyObject_SetAttr(obj, name, inst);
+    return inst;
 }
 
 static PyObject *signalCall(PyObject *self, PyObject *args, PyObject *kw)
@@ -1030,10 +1040,9 @@ PySideSignalInstance *newObjectFromMethod(PyObject *source, const QList<QMetaMet
         item->deleted = false;
         PySideSignalInstancePrivate *selfPvt = item->d;
         selfPvt->source = source;
-        Py_INCREF(selfPvt->source); // PYSIDE-79: an INCREF is missing.
         QByteArray cppName(m.methodSignature());
         cppName.truncate(cppName.indexOf('('));
-        // separe SignalName
+        // separate SignalName
         selfPvt->signalName = cppName;
         selfPvt->signature = m.methodSignature();
         selfPvt->attributes = m.attributes();
diff --git a/sources/shiboken6/libshiboken/basewrapper.cpp b/sources/shiboken6/libshiboken/basewrapper.cpp
index 24980239d..09d320560 100644
--- a/sources/shiboken6/libshiboken/basewrapper.cpp
+++ b/sources/shiboken6/libshiboken/basewrapper.cpp
@@ -71,6 +71,7 @@ void setDestroyQApplication(DestroyQAppHook func)
 // PYSIDE-535: Use the C API in PyPy instead of `op->ob_dict`, directly
 LIBSHIBOKEN_API PyObject *SbkObject_GetDict_NoRef(PyObject *op)
 {
+    assert(Shiboken::Object::checkType(op));
 #ifdef PYPY_VERSION
     Shiboken::GilState state;
     auto *ret = PyObject_GenericGetDict(op, nullptr);