Add default return value to pythonTypeIsValueType

When a class inherits from two base classes,
Shiboken sets the converter of the newly created
SbkObject to 0 (SbkObjectTypeTpNew), and handle
the multiple inheritance in a different way.

When any SbkObject try to release its ownership,
it first verify if the ownership is already on the C++ side
by checking the attribute hasOwership and also
if the converter is a ValueType.
The later fails if the converter is null,
so a default value (false) was added.

A test case using deleteLater() was included,
which uses the releaseOwnership method internally.

Task-number: PYSIDE-11
Change-Id: I34fba0d3e5d28b99b49a183ed08e977a311da632
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

2 files changed, 40 insertions, 2 deletions

diff --git a/sources/pyside2/tests/QtCore/qobject_inherits_test.py b/sources/pyside2/tests/QtCore/qobject_inherits_test.py
index 8c4c797a4..1d089776b 100644
--- a/sources/pyside2/tests/QtCore/qobject_inherits_test.py
+++ b/sources/pyside2/tests/QtCore/qobject_inherits_test.py
@@ -29,8 +29,12 @@
 '''Test cases for QObject methods'''
 
 import unittest
+import sys
 
-from PySide2.QtCore import QObject
+from PySide2.QtCore import QObject, QTimer
+from PySide2.QtWidgets import QApplication, QLabel, QVBoxLayout
+
+is_alive = None
 
 class InheritsCase(unittest.TestCase):
     '''Test case for QObject.inherits'''
@@ -87,5 +91,36 @@ class InheritsCase(unittest.TestCase):
 
         self.assertRaises(TypeError, declareClass)
 
+    # PYSIDE-11:
+    #   The takeOwnership() method was relying that the SbkObject
+    #   had a converter, which it's not the case when multiple
+    #   inheritance is used.
+    #   The deleteLater() method uses the takeOwnership() to give
+    #   control of the object to C++, so it can be remove once
+    #   the destructor is called.
+    #   The solution was to add a default case when the object
+    #   is null under the pythonTypeIsValueType() method in shiboken.
+    def testDeleteMultipleInheritance(self):
+        app = QApplication(sys.argv)
+        class DerivedLabel(QLabel, QObject):
+            def __del__(self):
+                global is_alive
+                is_alive = False
+
+        global is_alive
+        child = DerivedLabel('Hello')
+        is_alive = True
+        parent = QVBoxLayout()
+        parent.addWidget(child)
+        parent.removeWidget(child)
+        child.deleteLater()
+        self.assertTrue(is_alive)
+        del child
+        self.assertTrue(is_alive)
+        QTimer.singleShot(100, app.quit)
+        app.exec_()
+        self.assertFalse(is_alive)
+
+
 if __name__ == '__main__':
     unittest.main()
diff --git a/sources/shiboken2/libshiboken/sbkconverter.cpp b/sources/shiboken2/libshiboken/sbkconverter.cpp
index 0e154da39..c81a1612b 100644
--- a/sources/shiboken2/libshiboken/sbkconverter.cpp
+++ b/sources/shiboken2/libshiboken/sbkconverter.cpp
@@ -523,7 +523,10 @@ PyTypeObject* getPythonTypeObject(const char* typeName)
 
 bool pythonTypeIsValueType(const SbkConverter *converter)
 {
-    assert(converter);
+    // Unlikely to happen but for multi-inheritance SbkObjs
+    // the converter is not defined, hence we need a default return.
+    if (!converter)
+        return false;
     return converter->pointerToPython && converter->copyToPython;
 }