Core: Fix crash after second showOptionsDialog call

Do not destroy QEventLoop until it's exec() call
is over. Instead only call exit() for all loops
when the settings dialog is closed.

Change-Id: I9598270ee5f4d294ffcad9b45dda4543e15d63f0
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/dialogs/settingsdialog.cpp

@@ -59,13 +59,6 @@
 static const char pageKeyC[] = "General/LastPreferencePage";
 const int categoryIconSize = 24;
 
-namespace std {
-template<>
-struct default_delete<QEventLoop> {
-    void operator()(QEventLoop* p) { p->exit(); delete p; } // exit event loop
-};
-} // namespace std
-
 namespace Core {
 namespace Internal {
 
@@ -433,7 +426,7 @@ private:
     Utils::FancyLineEdit *m_filterLineEdit;
     QListView *m_categoryList;
     QLabel *m_headerLabel;
-    std::vector<std::unique_ptr<QEventLoop>> m_eventLoops;
+    std::vector<QEventLoop *> m_eventLoops;
     bool m_running = false;
     bool m_applied = false;
     bool m_finished = false;
@@ -731,8 +724,10 @@ void SettingsDialog::done(int val)
 
     ICore::saveSettings(); // save all settings
 
-
-    m_eventLoops.erase(m_eventLoops.begin(), m_eventLoops.end()); // exit event loops in reverse order of addition
+    // exit event loops in reverse order of addition
+    for (QEventLoop *eventLoop : m_eventLoops)
+        eventLoop->exit();
+    m_eventLoops.clear();
 
     QDialog::done(val);
 }
@@ -761,8 +756,10 @@ bool SettingsDialog::execDialog()
         // a break point it will complain about missing helper, and offer the
         // option to open the settings dialog.
         // Keep the UI running by creating another event loop.
-        m_eventLoops.emplace(m_eventLoops.begin(), std::make_unique<QEventLoop>());
-        m_eventLoops.front()->exec();
+        QEventLoop eventLoop;
+        m_eventLoops.emplace(m_eventLoops.begin(), &eventLoop);
+        eventLoop.exec();
+        QTC_ASSERT(m_eventLoops.empty(), return m_applied;);
     }
     return m_applied;
 }