CppTools: Use a plugin pimpl data member for CppToolsSettings

Change-Id: I05c2f8f34b88973fc916115f71c0557675396366
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/cpptools/cpptoolsplugin.cpp

@@ -82,7 +82,6 @@ class CppToolsPluginPrivate
 public:
     CppToolsPluginPrivate()
     {
-        m_settings = new CppToolsSettings(m_instance); // force registration of cpp tools settings
         m_codeModelSettings.fromSettings(ICore::settings());
         m_cppCodeStyleSettingsPage = new CppCodeStyleSettingsPage;
     }
@@ -97,7 +96,7 @@ public:
     StringTable stringTable;
     CppModelManager modelManager;
     CppCodeModelSettings m_codeModelSettings;
-    CppToolsSettings *m_settings = nullptr;
+    CppToolsSettings settings;
     CppFileSettings m_fileSettings;
     CppFileSettingsPage m_cppFileSettingsPage{&m_fileSettings};
     CppCodeModelSettingsPage m_cppCodeModelSettingsPage{&m_codeModelSettings};

src/plugins/cpptools/cpptoolssettings.cpp

@@ -64,9 +64,8 @@ public:
 
 CppToolsSettings *CppToolsSettings::m_instance = nullptr;
 
-CppToolsSettings::CppToolsSettings(QObject *parent)
-    : QObject(parent)
-    , d(new Internal::CppToolsSettingsPrivate)
+CppToolsSettings::CppToolsSettings()
+    : d(new Internal::CppToolsSettingsPrivate)
 {
     QTC_ASSERT(!m_instance, return);
     m_instance = this;

src/plugins/cpptools/cpptoolssettings.h

@@ -50,7 +50,7 @@ class CPPTOOLS_EXPORT CppToolsSettings : public QObject
     Q_OBJECT
 
 public:
-    explicit CppToolsSettings(QObject *parent);
+    CppToolsSettings();
     ~CppToolsSettings() override;
 
     static CppToolsSettings *instance();