tst_Q*Application: add tests for unusual qApp creations and exits

This commit adds one unusual creation and three more unusual exits:
* creation of the Q*Application in a thread (QTBUG-130895)
* exits using ::exit() instead of returning from main():
  * from the main thread's event loop
  * from an auxiliary thread
  * from inside an auxiliary thread's event loop

All of these exercise the moment the QAdoptedThread & QThreadData for
the main thread is destroyed, which are, respectively:
* thread exit time, running thread-specific destructors
* inside exit(), running atexit()-like callbacks (qthread_*.cpp)
* [tst_static_q*application] inside exit(), running static destructors
  (added in commit 1da7558bfd7626bcc40a214a90ae5027f32f6c7f)

Unlike the tst_static_q*application tests, the calls to ::exit() cannot
be a regular QtTest because that would cause the log output to be
incomplete. The threaded Q*Application could be a test of its own, but
since I needed to add the helper anyway, I chose to add the test there.

For the majority of the tests, the failure mode is going to be a crash
on exit.

Task-number: QTBUG-12673
Task-number: QTBUG-132429
Pick-to: 6.8 6.9
Change-Id: I1062ef500356bd97dd0cfffda4aeeda9afa138e8
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

tests/auto/corelib/kernel/qcoreapplication/CMakeLists.txt

@@ -41,6 +41,21 @@ endif()
 qt_internal_add_test(tst_static_qcoreapplication
     SOURCES
         tst_static_qcoreapplication.cpp
+        maybeshow.h
     LIBRARIES
         Qt::CorePrivate
 )
+
+qt_internal_add_executable(apphelper_core
+    OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/"
+    SOURCES
+        apphelper.cpp
+        maybeshow.h
+    LIBRARIES
+        Qt::CorePrivate
+)
+set_target_properties(apphelper_core PROPERTIES OUTPUT_NAME apphelper)
+
+add_dependencies(tst_qcoreapplication
+    apphelper_core
+)

tests/auto/corelib/kernel/qcoreapplication/apphelper.cpp

@@ -0,0 +1,141 @@
+// Copyright (C) 2024 Intel Corporation.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
+
+#include <private/qcoreapplication_p.h>
+#include <qthread.h>
+#include <qtimer.h>
+
+#include <string_view>
+#include <thread>
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#if defined(QT_WIDGETS_LIB)
+#include <QtWidgets/QApplication>
+#include <QtWidgets/QDialog>
+using TestApplication = QApplication;
+#elif defined(QT_GUI_LIB)
+#include <QtGui/QGuiApplication>
+#include <QtGui/QWindow>
+using TestApplication = QGuiApplication;
+#else
+using TestApplication = QCoreApplication;
+#endif
+
+#include "maybeshow.h"
+
+static int exitFromEventLoop(int argc, char **argv)
+{
+    TestApplication app(argc, argv);
+    [[maybe_unused]] auto w = maybeShowSomething();
+    QTimer::singleShot(200, &app, [] { ::exit(EXIT_SUCCESS); });
+    return app.exec();
+}
+
+static int exitFromThread(int argc, char **argv)
+{
+    TestApplication app(argc, argv);
+    [[maybe_unused]] auto w = maybeShowSomething();
+    auto thr = QThread::create([] {
+        if (!QThread::currentThread())
+            fprintf(stderr, "QThread::currentThread is null!\n");
+        ::exit(EXIT_SUCCESS);
+    });
+    QTimer::singleShot(200, thr, [&thr] { thr->start(); });
+    app.exec();
+    Q_UNREACHABLE_RETURN(EXIT_FAILURE);
+}
+
+// mix of the two above
+static int exitFromThreadedEventLoop(int argc, char **argv)
+{
+    // disable the Glib event loop because that causes at exit:
+    //  GLib-CRITICAL **: 11:48:09.717: g_source_unref_internal: assertion 'source != NULL' failed
+    // (I don't think it's *our* bug).
+    qputenv("QT_NO_GLIB", "1");
+
+    TestApplication app(argc, argv);
+    [[maybe_unused]] auto w = maybeShowSomething();
+    struct Thread : public QThread {
+        void run() override
+        {
+            QObject dummy;
+            QTimer::singleShot(1, &dummy, [] { ::exit(EXIT_SUCCESS); });
+            exec();
+        }
+    } thr;
+
+    QTimer::singleShot(200, &thr, [&thr] { thr.start(); });
+    app.exec();
+    Q_UNREACHABLE_RETURN(EXIT_FAILURE);
+}
+
+// see QTBUG-130895
+static int mainAppInAThread(int argc, char **argv)
+{
+    // note: when using std::thread in MinGW, we exercise different code paths
+    // from QThread (winpthreads vs native)
+    auto callable = [](int argc, char **argv) {
+        TestApplication app(argc, argv);
+    };
+
+    if (auto id = QCoreApplicationPrivate::theMainThreadId.loadRelaxed()) {
+        fprintf(stderr, "QCoreApplicationPrivate::theMainThreadId (%p) predates QCoreApplication!\n",
+                id);
+    }
+
+    std::thread thr(callable, argc, argv);
+    auto handle = thr.native_handle();
+    thr.join();
+
+    auto id = QCoreApplicationPrivate::theMainThreadId.loadRelaxed();
+    if (id) {
+        FILE *stream = stdout;
+#if defined(QT_GUI_LIB)
+        // QtGui has several Q_GLOBAL_STATICs surviving with live QObject (e.g.
+        // the QFactoryLoaders), so theMainThreadId has not been unset yet.
+#elif defined(Q_OS_WIN) && defined(Q_CC_GNU)
+        // Windows threading and cleaning of global static is messed up.
+#else
+        // Ensure that theMainThread is gone, so we could now start a new
+        // thread with QCoreApplication.
+        stream = stderr;
+#endif
+        fprintf(stream, "QCoreApplicationPrivate::theMainThreadId (%p) still extant (native handle %#llx)\n",
+                id, quint64(quintptr(handle)));
+        if (stream == stderr)
+            return EXIT_FAILURE;
+        fflush(stream);
+    }
+
+    return EXIT_SUCCESS;
+}
+
+static int usage(const char *name)
+{
+    printf("%s <subtest>\n", name);
+    return EXIT_FAILURE;
+}
+
+int main(int argc, char **argv)
+{
+    if (argc == 1)
+        return usage(argv[0]);
+
+    // remove some environment options that cause Qt to print warnings
+    qunsetenv("QT_SCALE_FACTOR_ROUNDING_POLICY");
+
+    std::string_view subtest(argv[1]);
+    if (subtest == "exitFromEventLoop")
+        return exitFromEventLoop(argc - 1, argv + 1);
+    if (subtest == "exitFromThread")
+        return exitFromThread(argc - 1, argv + 1);
+    if (subtest == "exitFromThreadedEventLoop")
+        return exitFromThreadedEventLoop(argc - 1, argv + 1);
+    if (subtest == "mainAppInAThread")
+        return mainAppInAThread(argc - 1, argv + 1);
+
+    fprintf(stderr, "%s: unknown test %s\n", argv[0], argv[1]);
+    return EXIT_FAILURE;
+}

tests/auto/corelib/kernel/qcoreapplication/maybeshow.h

@@ -0,0 +1,25 @@
+// Copyright (C) 2024 Intel Corporation.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
+
+#if defined(QT_WIDGETS_LIB)
+#include <QtWidgets/QDialog>
+#elif defined(QT_GUI_LIB)
+#include <QtGui/QWindow>
+#endif
+
+inline auto maybeShowSomething()
+{
+#if defined(QT_WIDGETS_LIB)
+    auto w = std::make_unique<QDialog>();
+    w->setModal(true);
+    w->show();
+#elif defined(QT_GUI_LIB)
+    auto w = std::make_unique<QWindow>();
+    w->setModality(Qt::ApplicationModal);
+    w->show();
+#else
+    void *w = nullptr;
+#endif
+    return w;
+}
+

tests/auto/corelib/kernel/qcoreapplication/tst_qcoreapplication.cpp

@@ -1001,6 +1001,29 @@ void tst_QCoreApplication::threadedEventDelivery()
 
 }
 
+#if QT_CONFIG(process)
+#if defined(Q_OS_WIN)
+#  define EXE ".exe"
+#else
+#  define EXE ""
+#endif
+void tst_QCoreApplication::runHelperTest()
+{
+#  ifdef Q_OS_ANDROID
+    QSKIP("Skipped on Android: helper not present");
+#  endif
+    int argc = 0;
+    QCoreApplication app(argc, nullptr);
+    QProcess process;
+    process.start(QFINDTESTDATA("apphelper" EXE), { QTest::currentTestFunction() });
+    QVERIFY2(process.waitForFinished(5000), qPrintable(process.errorString()));
+    QCOMPARE(process.readAllStandardError(), QString());
+    QCOMPARE(process.exitStatus(), QProcess::NormalExit);
+    QCOMPARE(process.exitCode(), 0);
+}
+#undef EXE
+#endif
+
 void tst_QCoreApplication::testTrWithPercantegeAtTheEnd()
 {
     QCoreApplication::translate("testcontext", "this will crash%", "testdisamb", 3);

tests/auto/corelib/kernel/qcoreapplication/tst_qcoreapplication.h

@@ -10,6 +10,8 @@
 class tst_QCoreApplication: public QObject
 {
     Q_OBJECT
+    void runHelperTest();
+
 private slots:
     void sendEventsOnProcessEvents(); // this must be the first test
     void getSetCheck();
@@ -40,6 +42,19 @@ private slots:
     void applicationEventFilters_auxThread();
     void threadedEventDelivery_data();
     void threadedEventDelivery();
+#if QT_CONFIG(process)
+    // also add to tst_qapplication.cpp
+    void exitFromEventLoop() { runHelperTest(); }
+    void exitFromThread() { runHelperTest(); }
+    void exitFromThreadedEventLoop() { runHelperTest(); }
+#  if defined(Q_OS_APPLE) && defined(QT_GUI_LIB)
+    // QGuiApplication in a thread fails inside Apple libs:
+    // *** Assertion failure in -[NSMenu _setMenuName:], NSMenu.m:777
+    // *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'API misuse: setting the main menu on a non-main thread. Main menu contents should only be modified from the main thread.'
+#  else
+    void mainAppInAThread() { runHelperTest(); }
+#  endif
+#endif
     void testTrWithPercantegeAtTheEnd();
 #if QT_CONFIG(library)
     void addRemoveLibPaths();

tests/auto/corelib/kernel/qcoreapplication/tst_static_qcoreapplication.cpp

@@ -15,6 +15,8 @@ using App = QGuiApplication;
 using App = QCoreApplication;
 #endif
 
+#include "maybeshow.h"
+
 class tst_Static_QCoreApplication : public QObject
 {
     Q_OBJECT
@@ -31,6 +33,7 @@ void tst_Static_QCoreApplication::staticApplication()
     static int argc = 1;
     const char *argv[] = { staticMetaObject.className(), nullptr };
     static App app(argc, const_cast<char **>(argv));
+    [[maybe_unused]] static auto w = maybeShowSomething();
 }
 
 struct HookManager

tests/auto/gui/kernel/qguiapplication/CMakeLists.txt

@@ -50,7 +50,23 @@ endif()
 qt_internal_add_test(tst_static_qguiapplication
     SOURCES
         ../../../corelib/kernel/qcoreapplication/tst_static_qcoreapplication.cpp
+        ../../../corelib/kernel/qcoreapplication/maybeshow.h
     LIBRARIES
         Qt::CorePrivate
         Qt::Gui
 )
+
+qt_internal_add_executable(apphelper_gui
+    OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/"
+    SOURCES
+        ../../../corelib/kernel/qcoreapplication/apphelper.cpp
+        ../../../corelib/kernel/qcoreapplication/maybeshow.h
+    LIBRARIES
+        Qt::CorePrivate
+        Qt::Gui
+)
+set_target_properties(apphelper_gui PROPERTIES OUTPUT_NAME apphelper)
+
+add_dependencies(tst_qguiapplication
+    apphelper_gui
+)

tests/auto/widgets/kernel/qapplication/CMakeLists.txt

@@ -11,14 +11,27 @@ add_subdirectory(desktopsettingsaware)
 add_subdirectory(modal)
 add_subdirectory(test)
 
+qt_internal_add_executable(apphelper_widgets
+    OUTPUT_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/"
+    SOURCES
+        ../../../corelib/kernel/qcoreapplication/apphelper.cpp
+        ../../../corelib/kernel/qcoreapplication/maybeshow.h
+    LIBRARIES
+        Qt::CorePrivate
+        Qt::Widgets
+)
+set_target_properties(apphelper_widgets PROPERTIES OUTPUT_NAME apphelper)
+
 add_dependencies(tst_qapplication
     desktopsettingsaware_helper
     modal_helper
+    apphelper_widgets
 )
 
 qt_internal_add_test(tst_static_qapplication
     SOURCES
         ../../../corelib/kernel/qcoreapplication/tst_static_qcoreapplication.cpp
+        ../../../corelib/kernel/qcoreapplication/maybeshow.h
     LIBRARIES
         Qt::CorePrivate
         Qt::Widgets

tests/auto/widgets/kernel/qapplication/tst_qapplication.cpp

@@ -59,6 +59,7 @@ class tst_QApplication : public QObject
 {
 Q_OBJECT
 
+    void runHelperTest();
 private slots:
     void cleanup();
     void sendEventsOnProcessEvents(); // this must be the first test
@@ -99,6 +100,18 @@ private slots:
     void sendPostedEvents();
 #endif  // ifdef QT_BUILD_INTERNAL
 
+#if QT_CONFIG(process)
+    void exitFromEventLoop() { runHelperTest(); }
+    void exitFromThread() { runHelperTest(); }
+    void exitFromThreadedEventLoop() { runHelperTest(); }
+#  if defined(Q_OS_APPLE)
+    // QGuiApplication in a thread fails inside Apple libs:
+    // *** Assertion failure in -[NSMenu _setMenuName:], NSMenu.m:777
+    // *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'API misuse: setting the main menu on a non-main thread. Main menu contents should only be modified from the main thread.'
+#  else
+    void mainAppInAThread() { runHelperTest(); }
+#  endif
+#endif
     void thread();
     void desktopSettingsAware();
 
@@ -1197,6 +1210,29 @@ void tst_QApplication::sendPostedEvents()
 }
 #endif
 
+#if QT_CONFIG(process)
+#if defined(Q_OS_WIN)
+#  define EXE ".exe"
+#else
+#  define EXE ""
+#endif
+void tst_QApplication::runHelperTest()
+{
+#  ifdef Q_OS_ANDROID
+    QSKIP("Skipped on Android: helper not present");
+#  endif
+    int argc = 0;
+    QCoreApplication app(argc, nullptr);
+    QProcess process;
+    process.start(QFINDTESTDATA("apphelper" EXE), { QTest::currentTestFunction() });
+    QVERIFY2(process.waitForFinished(5000), qPrintable(process.errorString()));
+    QCOMPARE(process.readAllStandardError(), QString());
+    QCOMPARE(process.exitStatus(), QProcess::NormalExit);
+    QCOMPARE(process.exitCode(), 0);
+}
+#undef EXE
+#endif
+
 void tst_QApplication::thread()
 {
     QThread *currentThread = QThread::currentThread();