From d147d5473289763049ffa6843d00aaf3766b6e4e Mon Sep 17 00:00:00 2001
From: Jan Plath <jan.plath@mevis.de>
Date: Fri, 30 Jan 2026 14:41:57 +0100
Subject: [PATCH] Fix invalid handling of alreadyAllocatedCPPObject in
 PythonQtConv::ConvertPythonToQt

---
 src/PythonQtConversion.cpp | 32 +++++++-------------------------
 src/PythonQtConversion.h   |  1 +
 src/PythonQtMisc.h         | 29 +++++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 25 deletions(-)

diff --git a/src/PythonQtConversion.cpp b/src/PythonQtConversion.cpp
index 96da8be47..3021a04c5 100644
--- a/src/PythonQtConversion.cpp
+++ b/src/PythonQtConversion.cpp
@@ -592,24 +592,21 @@ void* PythonQtConv::ConvertPythonToQt(const PythonQtMethodInfo::ParameterInfo& i
     {
       QByteArray bytes = PyObjGetBytesAllowString(obj, strict, ok);
       if (ok) {
-        PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(alreadyAllocatedCPPObject, frame, QVariant(bytes), ptr);
-        ptr = (void*)((QVariant*)ptr)->constData();
+        ptr = frame->establishPersistentPtr<QByteArray>(alreadyAllocatedCPPObject, bytes);
       }
     } break;
     case QMetaType::QString:
     {
       QString str = PyObjGetString(obj, strict, ok);
       if (ok) {
-        PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(alreadyAllocatedCPPObject, frame, QVariant(str), ptr);
-        ptr = (void*)((QVariant*)ptr)->constData();
+        ptr = frame->establishPersistentPtr<QString>(alreadyAllocatedCPPObject, str);
       }
     } break;
     case QMetaType::QStringList:
     {
       QStringList l = PyObjToStringList(obj, strict, ok);
       if (ok) {
-        PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(alreadyAllocatedCPPObject, frame, QVariant(l), ptr);
-        ptr = (void*)((QVariant*)ptr)->constData();
+        ptr = frame->establishPersistentPtr<QStringList>(alreadyAllocatedCPPObject, l);
       }
     } break;
 
@@ -649,7 +646,7 @@ void* PythonQtConv::ConvertPythonToQt(const PythonQtMethodInfo::ParameterInfo& i
         QString str = PyObjGetString(obj, strict, ok);
         if (ok) {
           void* ptr2 = nullptr;
-          PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(nullptr, frame, QVariant(str), ptr2);
+          PythonQtArgumentFrame_ADD_VARIANT_VALUE(frame, QVariant(str), ptr2);
           PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(alreadyAllocatedCPPObject, frame,
             QVariant::fromValue(QStringRef((const QString*)((QVariant*)ptr2)->constData())), ptr);
           ptr = (void*)((QVariant*)ptr)->constData();
@@ -663,12 +660,7 @@ void* PythonQtConv::ConvertPythonToQt(const PythonQtMethodInfo::ParameterInfo& i
         // Handle QStringView, which needs a reference to a persistent QString
         QString str = PyObjGetString(obj, strict, ok);
         if (ok) {
-          void* ptr2 = nullptr;
-          PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(nullptr, frame, QVariant(str), ptr2);
-          PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(alreadyAllocatedCPPObject, frame,
-            QVariant::fromValue(QStringView(*((const QString*)((QVariant*)ptr2)->constData()))), ptr);
-          ptr = (void*)((QVariant*)ptr)->constData();
-          return ptr;
+          return frame->establishPersistentViewPtr<QString, QStringView>(alreadyAllocatedCPPObject, str);
         } else {
           return nullptr;
         }
@@ -676,12 +668,7 @@ void* PythonQtConv::ConvertPythonToQt(const PythonQtMethodInfo::ParameterInfo& i
         // Handle QAnyStringView, which needs a reference to a persistent QString
         QString str = PyObjGetString(obj, strict, ok);
         if (ok) {
-          void* ptr2 = nullptr;
-          PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(nullptr, frame, QVariant(str), ptr2);
-          PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(alreadyAllocatedCPPObject, frame,
-            QVariant::fromValue(QAnyStringView(*((const QString*)((QVariant*)ptr2)->constData()))), ptr);
-          ptr = (void*)((QVariant*)ptr)->constData();
-          return ptr;
+          return frame->establishPersistentViewPtr<QString, QAnyStringView>(alreadyAllocatedCPPObject, str);
         } else {
           return nullptr;
         }
@@ -689,12 +676,7 @@ void* PythonQtConv::ConvertPythonToQt(const PythonQtMethodInfo::ParameterInfo& i
         // Handle QByteArrayView, which needs a reference to a persistent QByteArray
         QByteArray ba = PyObjGetBytesAllowString(obj, strict, ok);
         if (ok) {
-          void* ptr2 = nullptr;
-          PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(nullptr, frame, QVariant(ba), ptr2);
-          PythonQtArgumentFrame_ADD_VARIANT_VALUE_IF_NEEDED(alreadyAllocatedCPPObject, frame,
-            QVariant::fromValue(QByteArrayView(*((const QByteArray*)((QVariant*)ptr2)->constData()))), ptr);
-          ptr = (void*)((QVariant*)ptr)->constData();
-          return ptr;
+          return frame->establishPersistentViewPtr<QByteArray, QByteArrayView>(alreadyAllocatedCPPObject, ba);
         } else {
           return nullptr;
         }
diff --git a/src/PythonQtConversion.h b/src/PythonQtConversion.h
index 2460876ab..f67d0a738 100644
--- a/src/PythonQtConversion.h
+++ b/src/PythonQtConversion.h
@@ -122,6 +122,7 @@ class PYTHONQT_EXPORT PythonQtConv
   static PyObject* ConvertQtValueToPython(const PythonQtMethodInfo::ParameterInfo& info, const void* data);
 
   //! convert python object to Qt (according to the given parameter) and if the conversion should be strict (classInfo is currently not used anymore)
+  //! If an alreadyAllocatedCPPObject is used it must have the same type as given by info.typeId
   static void* ConvertPythonToQt(const PythonQtMethodInfo::ParameterInfo& info, PyObject* obj, bool strict,
     PythonQtClassInfo* classInfo, void* alreadyAllocatedCPPObject, PythonQtArgumentFrame* frame = nullptr);
 
diff --git a/src/PythonQtMisc.h b/src/PythonQtMisc.h
index 5c8a70b00..abc824163 100644
--- a/src/PythonQtMisc.h
+++ b/src/PythonQtMisc.h
@@ -121,6 +121,35 @@ class PythonQtArgumentFrame
   //! Get next pointer to a POD.
   quint64* nextPODPtr();
 
+  template<typename Class>
+  void* establishPersistentPtr(void* alreadyAllocatedPtr, const Class& value)
+  {
+    if (alreadyAllocatedPtr) {
+      *reinterpret_cast<Class*>(alreadyAllocatedPtr) = value;
+      return alreadyAllocatedPtr;
+    } else {
+      QVariant* item = nextVariantPtr();
+      *item = QVariant(value);
+      return const_cast<void*>(item->constData());
+    }
+  }
+
+  template<typename Class, typename ViewClass>
+  void* establishPersistentViewPtr(void* alreadyAllocatedPtr, const Class& value)
+  {
+    QVariant* itemStore = nextVariantPtr();
+    *itemStore = QVariant(value);
+    if (alreadyAllocatedPtr) {
+      *reinterpret_cast<ViewClass*>(alreadyAllocatedPtr) =
+        ViewClass(*reinterpret_cast<const Class*>(itemStore->constData()));
+      return alreadyAllocatedPtr;
+    } else {
+      QVariant* item = nextVariantPtr();
+      *item = QVariant::fromValue(ViewClass(*reinterpret_cast<const Class*>(itemStore->constData())));
+      return const_cast<void*>(item->constData());
+    }
+  }
+
 private:
   PythonQtArgumentFrame();
   ~PythonQtArgumentFrame();