Introduce Q_APPLICATION_STATIC

QObjects must be deleted if the QCoreApplication is being destroyed.
This was previously done by implementing custom code in qtbase and
other modules. So unify it and introduce a Q_APPLICATION_STATIC,
based on the Q_GLOBAL_STATIC, which centralises the logic.

Since we still have a few remaining living QObjects,
this comes in handy to fix those as well.

Task-number: QTBUG-84234
Change-Id: I3040a2280ff56291f2b1c39948c06a23597865c4
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

3 files changed, 74 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/CMakeLists.txt b/tests/auto/corelib/kernel/CMakeLists.txt
index 39f16bc970..18f20bfadc 100644
--- a/tests/auto/corelib/kernel/CMakeLists.txt
+++ b/tests/auto/corelib/kernel/CMakeLists.txt
@@ -1,5 +1,6 @@
 # Generated from kernel.pro.
 
+add_subdirectory(qapplicationstatic)
 add_subdirectory(qcoreapplication)
 add_subdirectory(qdeadlinetimer)
 add_subdirectory(qelapsedtimer)
diff --git a/tests/auto/corelib/kernel/qapplicationstatic/CMakeLists.txt b/tests/auto/corelib/kernel/qapplicationstatic/CMakeLists.txt
new file mode 100644
index 0000000000..0890113c55
--- /dev/null
+++ b/tests/auto/corelib/kernel/qapplicationstatic/CMakeLists.txt
@@ -0,0 +1,8 @@
+#####################################################################
+## tst_qapplicationstatic Test:
+#####################################################################
+
+qt_internal_add_test(tst_qapplicationstatic
+        SOURCES
+        tst_qapplicationstatic.cpp
+        )
diff --git a/tests/auto/corelib/kernel/qapplicationstatic/tst_qapplicationstatic.cpp b/tests/auto/corelib/kernel/qapplicationstatic/tst_qapplicationstatic.cpp
new file mode 100644
index 0000000000..9972e050db
--- /dev/null
+++ b/tests/auto/corelib/kernel/qapplicationstatic/tst_qapplicationstatic.cpp
@@ -0,0 +1,65 @@
+/****************************************************************************
+**
+** Copyright (C) 2021 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QTest>
+#include <QPointer>
+#include "QtCore/qapplicationstatic.h"
+
+Q_APPLICATION_STATIC(QObject, tstObject)
+
+class tst_qapplicationstatic : public QObject
+{
+    Q_OBJECT
+
+private slots:
+    void testCreateMultipleApplications() const;
+};
+
+void tst_qapplicationstatic::testCreateMultipleApplications() const
+{
+    for (int i = 0; i < 5; i++) {
+        int argc = 1;
+        char *argv[] = { (char *)"tst_qapplicationstatic" };
+        auto app = new QCoreApplication(argc, argv);
+
+        QVERIFY(tstObject);
+
+        QPointer<QObject> tstObjectPointer(tstObject);
+        QVERIFY(tstObjectPointer.get());
+
+        QVERIFY2(tstObject->objectName().isEmpty(), "Got QObject from previous iteration, not correctly recreated");
+        tstObject->setObjectName(QStringLiteral("tstObject"));
+        QVERIFY(!tstObject->objectName().isEmpty());
+
+        delete app;
+        QVERIFY2(!tstObjectPointer.get(), "QObject wasn't destroyed on QCoreApplication destruction");
+    }
+}
+
+QTEST_APPLESS_MAIN(tst_qapplicationstatic)
+#include "tst_qapplicationstatic.moc"