basewrapper: clear all traces of special Q*Application treatment

After simplifying qApp so much, it is no longer necessary to treat
Q*Application special. We now can allow garbage collection for
all objects which simplifies the code quite much.

Then it was easy to shrink the implementation to a single function
`MakeQAppWrapper`, which made the whole "qapp_macro" files no
longer necessary.

This cosmetic change will probably not be back-ported to 5.15 .

Task-number: PYSIDE-1447
Change-Id: I8ae3c5575e62bd7b5d6bac65c25775c712bb178f
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
(cherry picked from commit 8998f9c1a9116151b679c61ad36fedcc74cc75a1)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

9 files changed, 49 insertions, 189 deletions

diff --git a/sources/pyside6/libpyside/pyside.cpp b/sources/pyside6/libpyside/pyside.cpp
index 7c8b613d3..7cc17f0c6 100644
--- a/sources/pyside6/libpyside/pyside.cpp
+++ b/sources/pyside6/libpyside/pyside.cpp
@@ -58,7 +58,6 @@
 #include <sbkconverter.h>
 #include <sbkstring.h>
 #include <sbkstaticstrings.h>
-#include <qapp_macro.h>
 
 #include <QtCore/QByteArray>
 #include <QtCore/QCoreApplication>
diff --git a/sources/shiboken6/generator/shiboken/cppgenerator.cpp b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
index 45d0d072d..8858132b2 100644
--- a/sources/shiboken6/generator/shiboken/cppgenerator.cpp
+++ b/sources/shiboken6/generator/shiboken/cppgenerator.cpp
@@ -354,7 +354,6 @@ void CppGenerator::generateClass(TextStream &s, const GeneratorContext &classCon
             << "#include <pyside.h>\n"
             << "#include <pysideqenum.h>\n"
             << "#include <feature_select.h>\n"
-            << "#include <qapp_macro.h>\n\n"
             << "QT_WARNING_DISABLE_DEPRECATED\n\n";
      }
 
@@ -4224,15 +4223,14 @@ void CppGenerator::writeClassDefinition(TextStream &s,
             tp_new = QLatin1String("SbkDummyNew /* PYSIDE-595: Prevent replacement "
                                    "of \"0\" with base->tp_new. */");
         }
-        tp_flags.append(QLatin1String("|Py_TPFLAGS_HAVE_GC"));
     }
     else if (isQApp) {
         tp_new = QLatin1String("SbkQAppTpNew"); // PYSIDE-571: need singleton app
     }
     else {
         tp_new = QLatin1String("SbkObjectTpNew");
-        tp_flags.append(QLatin1String("|Py_TPFLAGS_HAVE_GC"));
     }
+    tp_flags.append(QLatin1String("|Py_TPFLAGS_HAVE_GC"));
 
     QString tp_richcompare;
     if (!metaClass->isNamespace() && metaClass->hasComparisonOperatorOverload())
@@ -5974,7 +5972,6 @@ bool CppGenerator::finishGeneration()
         s << R"(#include <pyside.h>
 #include <pysideqenum.h>
 #include <feature_select.h>
-#include <qapp_macro.h>
 )";
     }
 
diff --git a/sources/shiboken6/libshiboken/CMakeLists.txt b/sources/shiboken6/libshiboken/CMakeLists.txt
index 1fdc48ccc..444fd8ce2 100644
--- a/sources/shiboken6/libshiboken/CMakeLists.txt
+++ b/sources/shiboken6/libshiboken/CMakeLists.txt
@@ -57,7 +57,6 @@ sbkstaticstrings.cpp
 bindingmanager.cpp
 threadstatesaver.cpp
 shibokenbuffer.cpp
-qapp_macro.cpp
 pep384impl.cpp
 voidptr.cpp
 bufferprocs_py37.cpp
@@ -139,7 +138,6 @@ install(FILES
         shibokenbuffer.h
         sbkpython.h
         pep384impl.h
-        qapp_macro.h
         voidptr.h
         bufferprocs_py37.h
         "${CMAKE_CURRENT_BINARY_DIR}/sbkversion.h"
diff --git a/sources/shiboken6/libshiboken/basewrapper.cpp b/sources/shiboken6/libshiboken/basewrapper.cpp
index fd38ec3ac..ce6b0bacf 100644
--- a/sources/shiboken6/libshiboken/basewrapper.cpp
+++ b/sources/shiboken6/libshiboken/basewrapper.cpp
@@ -56,7 +56,6 @@
 #include <algorithm>
 #include "threadstatesaver.h"
 #include "signature.h"
-#include "qapp_macro.h"
 #include "voidptr.h"
 
 #include <iostream>
@@ -314,9 +313,7 @@ static void SbkDeallocWrapperCommon(PyObject *pyObj, bool canDelete)
     // be invoked and it trying to delete this object while it is still in
     // progress from the first time around, resulting in a double delete and a
     // crash.
-    // PYSIDE-571: Some objects do not use GC, so check this!
-    if (PyObject_IS_GC(pyObj))
-        PyObject_GC_UnTrack(pyObj);
+    PyObject_GC_UnTrack(pyObj);
 
     // Check that Python is still initialized as sometimes this is called by a static destructor
     // after Python interpeter is shutdown.
@@ -428,6 +425,41 @@ void SbkObjectTypeDealloc(PyObject *pyObj)
     }
 }
 
+////////////////////////////////////////////////////////////////////////////
+//
+// Support for the qApp macro.
+//
+// qApp is a macro in Qt5. In Python, we simulate that a little by a
+// variable that monitors Q*Application.instance().
+// This variable is also able to destroy the app by qApp.shutdown().
+//
+
+PyObject *MakeQAppWrapper(PyTypeObject *type)
+{
+    static PyObject *qApp_last = nullptr;
+
+    // protecting from multiple application instances
+    if (!(type == nullptr || qApp_last == Py_None)) {
+        const char *res_name = PepType_GetNameStr(Py_TYPE(qApp_last));
+        const char *type_name = PepType_GetNameStr(type);
+        PyErr_Format(PyExc_RuntimeError, "Please destroy the %s singleton before"
+            " creating a new %s instance.", res_name, type_name);
+        return nullptr;
+    }
+
+    // monitoring the last application state
+    PyObject *qApp_curr = type != nullptr ? PyObject_GC_New(PyObject, type) : Py_None;
+    static PyObject *builtins = PyEval_GetBuiltins();
+    if (PyDict_SetItem(builtins, Shiboken::PyName::qApp(), qApp_curr) < 0)
+        return nullptr;
+    qApp_last = qApp_curr;
+    // Note: This Py_INCREF would normally be wrong because the qApp
+    // object already has a reference from PyObject_GC_New. But this is
+    // exactly the needed reference that keeps qApp alive from alone!
+    Py_INCREF(qApp_curr);
+    return qApp_curr;
+}
+
 //////////////////////////////////////////////////////////////////////////////
 //
 // PYSIDE-1019: Support switchable extensions
@@ -466,7 +498,7 @@ static PyObject *Sbk_TypeGet___dict__(PyTypeObject *type, void *context)
      * This is the override for getting a dict.
      */
     auto dict = type->tp_dict;
-    if (dict == NULL)
+    if (dict == nullptr)
         Py_RETURN_NONE;
     if (SelectFeatureSet != nullptr)
         dict = SelectFeatureSet(type);
@@ -623,40 +655,18 @@ static PyObject *_setupNew(SbkObject *self, PyTypeObject *subtype)
     self->ob_dict = nullptr;
     self->weakreflist = nullptr;
     self->d = d;
+    PyObject_GC_Track(reinterpret_cast<PyObject *>(self));
     return reinterpret_cast<PyObject *>(self);
 }
 
 PyObject *SbkObjectTpNew(PyTypeObject *subtype, PyObject *, PyObject *)
 {
     SbkObject *self = PyObject_GC_New(SbkObject, subtype);
-    PyObject *res = _setupNew(self, subtype);
-    PyObject_GC_Track(reinterpret_cast<PyObject *>(self));
-    return res;
+    return _setupNew(self, subtype);
 }
 
 PyObject *SbkQAppTpNew(PyTypeObject *subtype, PyObject *, PyObject *)
 {
-    // PYSIDE-571:
-    // For qApp, we need to create a singleton Python object.
-    // We cannot track this with the GC, because it is a static variable!
-
-    // Python 2 has a weird handling of flags in derived classes that Python 3
-    // does not have. Observed with bug_307.py.
-    // But it could theoretically also happen with Python3.
-    // Therefore we enforce that there is no GC flag, ever!
-
-    // PYSIDE-560:
-    // We avoid to use this in Python 3, because we have a hard time to get
-    // write access to these flags
-
-    // PYSIDE-1447:
-    // Since Python 3.8, we have the same weird flags handling in Python 3.8
-    // as well. The singleton Python is no longer needed and we could remove
-    // the whole special handling, maybe in another checkin.
-    if (PyType_HasFeature(subtype, Py_TPFLAGS_HAVE_GC)) {
-        subtype->tp_flags &= ~Py_TPFLAGS_HAVE_GC;
-        subtype->tp_free = PyObject_Del;
-    }
     auto self = reinterpret_cast<SbkObject *>(MakeQAppWrapper(subtype));
     return self == nullptr ? nullptr : _setupNew(self, subtype);
 }
@@ -736,7 +746,7 @@ PyObject *FallbackRichCompare(PyObject *self, PyObject *other, int op)
                      opstrings[op],
                      self->ob_type->tp_name,
                      other->ob_type->tp_name);
-        return NULL;
+        return nullptr;
     }
     Py_INCREF(res);
     return res;
diff --git a/sources/shiboken6/libshiboken/basewrapper.h b/sources/shiboken6/libshiboken/basewrapper.h
index 204c4c1c3..fedd143c2 100644
--- a/sources/shiboken6/libshiboken/basewrapper.h
+++ b/sources/shiboken6/libshiboken/basewrapper.h
@@ -118,8 +118,12 @@ struct LIBSHIBOKEN_API SbkObjectType
 };
 
 LIBSHIBOKEN_API PyObject *SbkObjectTpNew(PyTypeObject *subtype, PyObject *, PyObject *);
-// the special case of a switchable singleton
-LIBSHIBOKEN_API PyObject *SbkQAppTpNew(PyTypeObject *subtype, PyObject *args, PyObject *kwds);
+
+/// The special case of a switchable singleton Q*Application.
+LIBSHIBOKEN_API PyObject *SbkQAppTpNew(PyTypeObject *subtype, PyObject *, PyObject *);
+
+/// Create a new Q*Application wrapper and monitor it.
+LIBSHIBOKEN_API PyObject *MakeQAppWrapper(PyTypeObject *type);
 
 /**
  *  PYSIDE-832: Use object_dealloc instead of nullptr.
diff --git a/sources/shiboken6/libshiboken/qapp_macro.cpp b/sources/shiboken6/libshiboken/qapp_macro.cpp
deleted file mode 100644
index 03a8d0496..000000000
--- a/sources/shiboken6/libshiboken/qapp_macro.cpp
+++ /dev/null
@@ -1,98 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2020 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of Qt for Python.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** 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 Lesser General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU Lesser
-** General Public License version 3 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL3 included in the
-** packaging of this file. Please review the following information to
-** ensure the GNU Lesser General Public License version 3 requirements
-** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 2.0 or (at your option) the GNU General
-** Public license version 3 or any later version approved by the KDE Free
-** Qt Foundation. The licenses are as published by the Free Software
-** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
-** 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-2.0.html and
-** https://www.gnu.org/licenses/gpl-3.0.html.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#include "basewrapper.h"
-#include "autodecref.h"
-
-extern "C"
-{
-
-#include "qapp_macro.h"
-
-////////////////////////////////////////////////////////////////////////////
-//
-// Support for the qApp macro.
-//
-// qApp is a macro in Qt5. In Python, we simulate that a little by a
-// variable that monitors Q*Application.instance().
-// This variable is also able to destroy the app by qApp.shutdown().
-//
-
-static PyObject *qApp_name = nullptr;
-static PyObject *qApp_last = nullptr;
-
-static PyObject *monitor_qApp_var(PyObject *qApp_curr)
-{
-    static bool init_done;
-    static PyObject *builtins = PyEval_GetBuiltins();
-
-    if (!init_done) {
-        qApp_name = Py_BuildValue("s", "qApp");
-        if (qApp_name == nullptr)
-            return nullptr;
-        // This is a borrowed reference
-        Py_INCREF(builtins);
-        init_done = true;
-    }
-
-    if (PyDict_SetItem(builtins, qApp_name, qApp_curr) < 0)
-        return nullptr;
-    qApp_last = qApp_curr;
-    Py_INCREF(qApp_curr);
-    return qApp_curr;
-}
-
-PyObject *MakeQAppWrapper(PyTypeObject *type)
-{
-    if (type == nullptr)
-        type = Py_TYPE(Py_None);
-    if (!(type == Py_TYPE(Py_None) || Py_TYPE(qApp_last) == Py_TYPE(Py_None))) {
-        const char *res_name = PepType_GetNameStr(Py_TYPE(qApp_last));
-        const char *type_name = PepType_GetNameStr(type);
-        PyErr_Format(PyExc_RuntimeError, "Please destroy the %s singleton before"
-            " creating a new %s instance.", res_name, type_name);
-        return nullptr;
-    }
-    PyObject *self = type != Py_TYPE(Py_None) ? PyObject_New(PyObject, type) : Py_None;
-    return monitor_qApp_var(self);
-}
-
-} //extern "C"
-
-// end of module
diff --git a/sources/shiboken6/libshiboken/qapp_macro.h b/sources/shiboken6/libshiboken/qapp_macro.h
deleted file mode 100644
index 9abd17c17..000000000
--- a/sources/shiboken6/libshiboken/qapp_macro.h
+++ /dev/null
@@ -1,52 +0,0 @@
-/****************************************************************************
-**
-** Copyright (C) 2017 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of Qt for Python.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** 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 Lesser General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU Lesser
-** General Public License version 3 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL3 included in the
-** packaging of this file. Please review the following information to
-** ensure the GNU Lesser General Public License version 3 requirements
-** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 2.0 or (at your option) the GNU General
-** Public license version 3 or any later version approved by the KDE Free
-** Qt Foundation. The licenses are as published by the Free Software
-** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
-** 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-2.0.html and
-** https://www.gnu.org/licenses/gpl-3.0.html.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
-
-#ifndef QAPP_MACRO_H
-#define QAPP_MACRO_H
-
-#include "sbkpython.h"
-
-extern "C"
-{
-
-LIBSHIBOKEN_API PyObject *MakeQAppWrapper(PyTypeObject *type);
-
-} // extern "C"
-
-#endif // QAPP_MACRO_H
diff --git a/sources/shiboken6/libshiboken/sbkstaticstrings.cpp b/sources/shiboken6/libshiboken/sbkstaticstrings.cpp
index cd42643f8..35fc2a410 100644
--- a/sources/shiboken6/libshiboken/sbkstaticstrings.cpp
+++ b/sources/shiboken6/libshiboken/sbkstaticstrings.cpp
@@ -58,6 +58,7 @@ STATIC_STRING_IMPL(fset, "fset")
 STATIC_STRING_IMPL(loads, "loads")
 STATIC_STRING_IMPL(multi, "multi")
 STATIC_STRING_IMPL(name, "name")
+STATIC_STRING_IMPL(qApp, "qApp")
 STATIC_STRING_IMPL(result, "result")
 STATIC_STRING_IMPL(select_id, "select_id")
 STATIC_STRING_IMPL(value, "value")
diff --git a/sources/shiboken6/libshiboken/sbkstaticstrings_p.h b/sources/shiboken6/libshiboken/sbkstaticstrings_p.h
index acfc71409..308966481 100644
--- a/sources/shiboken6/libshiboken/sbkstaticstrings_p.h
+++ b/sources/shiboken6/libshiboken/sbkstaticstrings_p.h
@@ -51,6 +51,7 @@ PyObject *marshal();
 PyObject *method();
 PyObject *mro();
 PyObject *overload();
+PyObject *qApp();
 PyObject *staticmethod();
 } // namespace PyName
 namespace PyMagicName