Fix glitch in voidptr.cpp after the PEP 384 commit

By lots of editing, somehow an expression in voidptr.cpp
became incomplete.
We should improve the current test to be certain that the
VoidPtr is working.

This problem can be avoided by not doing many type
casts at once.
Doing the same in two steps is much safer because a forgotten
call would give a compile time error.

Task-number: PYSIDE-560
Change-Id: Ibb24a27f439cbda490723131f34f93978725420f
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

3 files changed, 55 insertions, 2 deletions

diff --git a/sources/pyside2/tests/support/CMakeLists.txt b/sources/pyside2/tests/support/CMakeLists.txt
new file mode 100644
index 000000000..1f18ecf23
--- /dev/null
+++ b/sources/pyside2/tests/support/CMakeLists.txt
@@ -0,0 +1 @@
+PYSIDE_TEST(voidptr_test.py)
diff --git a/sources/pyside2/tests/support/voidptr_test.py b/sources/pyside2/tests/support/voidptr_test.py
new file mode 100644
index 000000000..8179407e5
--- /dev/null
+++ b/sources/pyside2/tests/support/voidptr_test.py
@@ -0,0 +1,47 @@
+#############################################################################
+##
+## Copyright (C) 2018 The Qt Company Ltd.
+## Contact: https://www.qt.io/licensing/
+##
+## This file is part of the test suite of Qt for Python.
+##
+## $QT_BEGIN_LICENSE:GPL-EXCEPT$
+## Commercial License Usage
+## Licensees holding valid commercial Qt licenses may use this file in
+## accordance with the commercial license agreement provided with the
+## Software or, alternatively, in accordance with the terms contained in
+## a written agreement between you and The Qt Company. For licensing terms
+## and conditions see https://www.qt.io/terms-conditions. For further
+## information use the contact form at https://www.qt.io/contact-us.
+##
+## GNU General Public License Usage
+## Alternatively, this file may be used under the terms of the GNU
+## General Public License version 3 as published by the Free Software
+## Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+## included in the packaging of this file. Please review the following
+## information to ensure the GNU General Public License requirements will
+## be met: https://www.gnu.org/licenses/gpl-3.0.html.
+##
+## $QT_END_LICENSE$
+##
+#############################################################################
+
+import unittest
+from PySide2 import shiboken2
+from PySide2.support import VoidPtr
+from PySide2.QtCore import QByteArray
+
+class PySide2Support(unittest.TestCase):
+
+    def testVoidPtr(self):
+        # Creating a VoidPtr object requires an address of
+        # a C++ object, a wrapped Shiboken Object type,
+        # an object implementing the Python Buffer interface,
+        # or another VoidPtr object.
+        ba = QByteArray(b"Hello world")
+        voidptr = VoidPtr(ba)
+        self.assertIsInstance(voidptr, shiboken2.VoidPtr)
+
+if __name__ == '__main__':
+    unittest.main()
+
diff --git a/sources/shiboken2/libshiboken/voidptr.cpp b/sources/shiboken2/libshiboken/voidptr.cpp
index afb3f4040..94c667598 100644
--- a/sources/shiboken2/libshiboken/voidptr.cpp
+++ b/sources/shiboken2/libshiboken/voidptr.cpp
@@ -55,8 +55,13 @@ typedef struct {
 
 PyObject *SbkVoidPtrObject_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 {
-    SbkVoidPtrObject *self =
-        reinterpret_cast<SbkVoidPtrObject *>(PepType(type)->tp_alloc);
+    // PYSIDE-560: It is much safer to first call a function and then do a
+    // type cast than to do everything in one line. The bad construct looked
+    // like this, actual call forgotten:
+    //    SbkVoidPtrObject *self =
+    //        reinterpret_cast<SbkVoidPtrObject *>(PepType(type)->tp_alloc);
+    PyObject *ob = PepType(type)->tp_alloc(type, 0);
+    SbkVoidPtrObject *self = reinterpret_cast<SbkVoidPtrObject *>(ob);
 
     if (self != 0) {
         self->cptr = 0;