Merge pull request #4196 from kittywhiskers/override

merge bitcoin#18914, bitcoin#13306, bitcoin#16424, bitcoin#13899, bitcoin#17486, bitcoin#17880, bitcoin#18145, bitcoin#18843, bitcoin#16710: split warnings out of CXXFLAGS, add more flags

configure.ac

@@ -362,26 +362,42 @@ if test "x$enable_werror" = "xyes"; then
     AC_MSG_ERROR("enable-werror set but -Werror is not usable")
   fi
   AX_CHECK_COMPILE_FLAG([-Werror=vla],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=vla"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Werror=switch],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=switch"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Werror=thread-safety],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=thread-safety"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Werror=unused-variable],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=unused-variable"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Werror=date-time],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=date-time"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Werror=return-type],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=return-type"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Werror=conditional-uninitialized],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=conditional-uninitialized"],,[[$CXXFLAG_WERROR]])
+  dnl -Wsuggest-override is broken with GCC before 9.2
+  dnl https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78010
+  AX_CHECK_COMPILE_FLAG([-Werror=suggest-override],[ERROR_CXXFLAGS="$ERROR_CXXFLAGS -Werror=suggest-override"],,[[$CXXFLAG_WERROR]],
+                        [AC_LANG_SOURCE([[struct A { virtual void f(); }; struct B : A { void f() final; };]])])
 fi
 
 if test "x$CXXFLAGS_overridden" = "xno"; then
-  AX_CHECK_COMPILE_FLAG([-Wall],[CXXFLAGS="$CXXFLAGS -Wall"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wextra],[CXXFLAGS="$CXXFLAGS -Wextra"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wformat],[CXXFLAGS="$CXXFLAGS -Wformat"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wvla],[CXXFLAGS="$CXXFLAGS -Wvla"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wformat-security],[CXXFLAGS="$CXXFLAGS -Wformat-security"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wthread-safety],[CXXFLAGS="$CXXFLAGS -Wthread-safety"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wall],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wall"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wextra],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wextra"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wformat],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wformat"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wvla],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wvla"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wswitch],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wswitch"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wformat-security],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wformat-security"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wthread-safety],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wthread-safety"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wrange-loop-analysis],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wrange-loop-analysis"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wredundant-decls],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wredundant-decls"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wunused-variable],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wunused-variable"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wdate-time],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wdate-time"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wconditional-uninitialized],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wconditional-uninitialized"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wsuggest-override],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wsuggest-override"],,[[$CXXFLAG_WERROR]],
+                        [AC_LANG_SOURCE([[struct A { virtual void f(); }; struct B : A { void f() final; };]])])
 
   ## Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
   ## unknown options if any other warning is produced. Test the -Wfoo case, and
   ## set the -Wno-foo case if it works.
-  AX_CHECK_COMPILE_FLAG([-Wunused-parameter],[CXXFLAGS="$CXXFLAGS -Wno-unused-parameter"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wself-assign],[CXXFLAGS="$CXXFLAGS -Wno-self-assign"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wunused-local-typedef],[CXXFLAGS="$CXXFLAGS -Wno-unused-local-typedef"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wdeprecated-register],[CXXFLAGS="$CXXFLAGS -Wno-deprecated-register"],,[[$CXXFLAG_WERROR]])
-  AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough],[CXXFLAGS="$CXXFLAGS -Wno-implicit-fallthrough"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wunused-parameter],[NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-unused-parameter"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wself-assign],[NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-self-assign"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wunused-local-typedef],[NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-unused-local-typedef"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wdeprecated-register],[NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-deprecated-register"],,[[$CXXFLAG_WERROR]])
+  AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough],[NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-implicit-fallthrough"],,[[$CXXFLAG_WERROR]])
 fi
 
 enable_hwcrc32=no
@@ -1459,6 +1475,8 @@ AC_SUBST(BITCOIN_TX_NAME)
 
 AC_SUBST(RELDFLAGS)
 AC_SUBST(DEBUG_CPPFLAGS)
+AC_SUBST(WARN_CXXFLAGS)
+AC_SUBST(NOWARN_CXXFLAGS)
 AC_SUBST(DEBUG_CXXFLAGS)
 AC_SUBST(ERROR_CXXFLAGS)
 AC_SUBST(GPROF_CXXFLAGS)
@@ -1576,7 +1594,7 @@ echo "  CC                  = $CC"
 echo "  CFLAGS              = $CFLAGS"
 echo "  CPPFLAGS            = $DEBUG_CPPFLAGS $HARDENED_CPPFLAGS $CPPFLAGS"
 echo "  CXX                 = $CXX"
-echo "  CXXFLAGS            = $DEBUG_CXXFLAGS $HARDENED_CXXFLAGS $ERROR_CXXFLAGS $GPROF_CXXFLAGS $CXXFLAGS"
+echo "  CXXFLAGS            = $DEBUG_CXXFLAGS $HARDENED_CXXFLAGS $WARN_CXXFLAGS $NOWARN_CXXFLAGS $ERROR_CXXFLAGS $GPROF_CXXFLAGS $CXXFLAGS"
 echo "  LDFLAGS             = $PTHREAD_CFLAGS $HARDENED_LDFLAGS $GPROF_LDFLAGS $LDFLAGS"
 echo "  ARFLAGS             = $ARFLAGS"
 echo

src/Makefile.am

@@ -6,7 +6,7 @@
 DIST_SUBDIRS = secp256k1 univalue
 
 AM_LDFLAGS = $(PTHREAD_CFLAGS) $(LIBTOOL_LDFLAGS) $(HARDENED_LDFLAGS) $(GPROF_LDFLAGS) $(SANITIZER_LDFLAGS)
-AM_CXXFLAGS = $(DEBUG_CXXFLAGS) $(HARDENED_CXXFLAGS) $(ERROR_CXXFLAGS) $(GPROF_CXXFLAGS) $(SANITIZER_CXXFLAGS)
+AM_CXXFLAGS = $(DEBUG_CXXFLAGS) $(HARDENED_CXXFLAGS) $(WARN_CXXFLAGS) $(NOWARN_CXXFLAGS) $(ERROR_CXXFLAGS) $(GPROF_CXXFLAGS) $(SANITIZER_CXXFLAGS)
 AM_CPPFLAGS = $(DEBUG_CPPFLAGS) $(HARDENED_CPPFLAGS)
 AM_LIBTOOLFLAGS = --preserve-dup-deps
 EXTRA_LIBRARIES =

src/Makefile.leveldb.include

@@ -30,7 +30,7 @@ LEVELDB_CPPFLAGS_INT += -DLEVELDB_PLATFORM_POSIX
 endif
 
 leveldb_libleveldb_a_CPPFLAGS = $(AM_CPPFLAGS) $(LEVELDB_CPPFLAGS_INT) $(LEVELDB_CPPFLAGS)
-leveldb_libleveldb_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+leveldb_libleveldb_a_CXXFLAGS = $(filter-out -Wconditional-uninitialized -Werror=conditional-uninitialized -Wsuggest-override -Werror=suggest-override, $(AM_CXXFLAGS)) $(PIE_FLAGS)
 
 leveldb_libleveldb_a_SOURCES=
 leveldb_libleveldb_a_SOURCES += leveldb/port/atomic_pointer.h

src/qt/addressbookpage.cpp

@@ -38,7 +38,7 @@ class AddressBookSortFilterProxyModel final : public QSortFilterProxyModel
     }
 
 protected:
-    bool filterAcceptsRow(int row, const QModelIndex& parent) const
+    bool filterAcceptsRow(int row, const QModelIndex& parent) const override
     {
         auto model = sourceModel();
         auto label = model->index(row, AddressTableModel::Label, parent);

src/qt/addressbookpage.h

@@ -44,7 +44,7 @@ class AddressBookPage : public QDialog
     const QString &getReturnValue() const { return returnValue; }
 
 public Q_SLOTS:
-    void done(int retval);
+    void done(int retval) override;
 
 private:
     Ui::AddressBookPage *ui;

src/qt/addresstablemodel.h

@@ -52,14 +52,14 @@ class AddressTableModel : public QAbstractTableModel
 
     /** @name Methods overridden from QAbstractTableModel
         @{*/
-    int rowCount(const QModelIndex &parent) const;
-    int columnCount(const QModelIndex &parent) const;
-    QVariant data(const QModelIndex &index, int role) const;
-    bool setData(const QModelIndex &index, const QVariant &value, int role);
-    QVariant headerData(int section, Qt::Orientation orientation, int role) const;
-    QModelIndex index(int row, int column, const QModelIndex &parent) const;
-    bool removeRows(int row, int count, const QModelIndex &parent = QModelIndex());
-    Qt::ItemFlags flags(const QModelIndex &index) const;
+    int rowCount(const QModelIndex &parent) const override;
+    int columnCount(const QModelIndex &parent) const override;
+    QVariant data(const QModelIndex &index, int role) const override;
+    bool setData(const QModelIndex &index, const QVariant &value, int role) override;
+    QVariant headerData(int section, Qt::Orientation orientation, int role) const override;
+    QModelIndex index(int row, int column, const QModelIndex &parent) const override;
+    bool removeRows(int row, int count, const QModelIndex &parent = QModelIndex()) override;
+    Qt::ItemFlags flags(const QModelIndex &index) const override;
     /*@}*/
 
     /* Add an address to the model.

src/qt/askpassphrasedialog.h

@@ -31,7 +31,7 @@ class AskPassphraseDialog : public QDialog
     explicit AskPassphraseDialog(Mode mode, QWidget *parent);
     ~AskPassphraseDialog();
 
-    void accept();
+    void accept() override;
 
     void setModel(WalletModel *model);
 
@@ -47,8 +47,8 @@ private Q_SLOTS:
     void toggleShowPassword(bool);
 
 protected:
-    bool event(QEvent *event);
-    bool eventFilter(QObject *object, QEvent *event);
+    bool event(QEvent *event) override;
+    bool eventFilter(QObject *object, QEvent *event) override;
 };
 
 #endif // BITCOIN_QT_ASKPASSPHRASEDIALOG_H

src/qt/bantablemodel.h

@@ -57,16 +57,17 @@ class BanTableModel : public QAbstractTableModel
 
     /** @name Methods overridden from QAbstractTableModel
         @{*/
-    int rowCount(const QModelIndex &parent) const;
-    int columnCount(const QModelIndex &parent) const;
-    QVariant data(const QModelIndex &index, int role) const;
-    QVariant headerData(int section, Qt::Orientation orientation, int role) const;
-    QModelIndex index(int row, int column, const QModelIndex &parent) const;
-    Qt::ItemFlags flags(const QModelIndex &index) const;
-    void sort(int column, Qt::SortOrder order);
-    bool shouldShow();
+    int rowCount(const QModelIndex &parent) const override;
+    int columnCount(const QModelIndex &parent) const override;
+    QVariant data(const QModelIndex &index, int role) const override;
+    QVariant headerData(int section, Qt::Orientation orientation, int role) const override;
+    QModelIndex index(int row, int column, const QModelIndex &parent) const override;
+    Qt::ItemFlags flags(const QModelIndex &index) const override;
+    void sort(int column, Qt::SortOrder order) override;
     /*@}*/
 
+    bool shouldShow();
+
 public Q_SLOTS:
     void refresh();
 

src/qt/bitcoinaddressvalidator.h

@@ -17,7 +17,7 @@ class BitcoinAddressEntryValidator : public QValidator
 public:
     explicit BitcoinAddressEntryValidator(QObject *parent, bool fAllowURI = false);
 
-    State validate(QString &input, int &pos) const;
+    State validate(QString &input, int &pos) const override;
 
 private:
     bool fAllowURI;
@@ -32,7 +32,7 @@ class BitcoinAddressCheckValidator : public QValidator
 public:
     explicit BitcoinAddressCheckValidator(QObject *parent);
 
-    State validate(QString &input, int &pos) const;
+    State validate(QString &input, int &pos) const override;
 };
 
 #endif // BITCOIN_QT_BITCOINADDRESSVALIDATOR_H

src/qt/bitcoinamountfield.cpp

@@ -43,7 +43,7 @@ class AmountValidator : public QValidator
         QValidator(parent),
         currentUnit(BitcoinUnits::DASH) {}
 
-    State validate(QString &input, int &pos) const
+    State validate(QString &input, int &pos) const override
     {
         if(input.isEmpty())
             return QValidator::Intermediate;
@@ -112,7 +112,7 @@ class AmountLineEdit: public QLineEdit
             clear();
     }
 
-    QSize minimumSizeHint() const
+    QSize minimumSizeHint() const override
     {
         ensurePolished();
         const QFontMetrics fm(fontMetrics());
@@ -127,7 +127,7 @@ class AmountLineEdit: public QLineEdit
     int currentUnit;
 
 protected:
-    bool event(QEvent *event)
+    bool event(QEvent *event) override
     {
         if (event->type() == QEvent::KeyPress || event->type() == QEvent::KeyRelease)
         {

src/qt/bitcoinamountfield.h

@@ -60,7 +60,7 @@ class BitcoinAmountField: public QWidget
 
 protected:
     /** Intercept focus-in event and ',' key presses */
-    bool eventFilter(QObject *object, QEvent *event);
+    bool eventFilter(QObject *object, QEvent *event) override;
 
 private:
     AmountLineEdit *amount;

src/qt/bitcoingui.h

@@ -82,12 +82,12 @@ class BitcoinGUI : public QMainWindow
     bool enableWallet;
 
 protected:
-    void changeEvent(QEvent *e);
-    void closeEvent(QCloseEvent *event);
-    void showEvent(QShowEvent *event);
-    void dragEnterEvent(QDragEnterEvent *event);
-    void dropEvent(QDropEvent *event);
-    bool eventFilter(QObject *object, QEvent *event);
+    void changeEvent(QEvent *e) override;
+    void closeEvent(QCloseEvent *event) override;
+    void showEvent(QShowEvent *event) override;
+    void dragEnterEvent(QDragEnterEvent *event) override;
+    void dropEvent(QDropEvent *event) override;
+    bool eventFilter(QObject *object, QEvent *event) override;
 
 private:
     interfaces::Node& m_node;
@@ -360,7 +360,7 @@ class UnitDisplayStatusBarControl : public QLabel
 
 protected:
     /** So that it responds to left-button clicks */
-    void mousePressEvent(QMouseEvent *event);
+    void mousePressEvent(QMouseEvent *event) override;
 
 private:
     OptionsModel *optionsModel;

src/qt/bitcoinunits.h

@@ -109,8 +109,8 @@ class BitcoinUnits: public QAbstractListModel
         /** Unit identifier */
         UnitRole = Qt::UserRole
     };
-    int rowCount(const QModelIndex &parent) const;
-    QVariant data(const QModelIndex &index, int role) const;
+    int rowCount(const QModelIndex &parent) const override;
+    QVariant data(const QModelIndex &index, int role) const override;
     QVariant data(const int &row, int role) const;
     ///@}
 

src/qt/coincontroldialog.h

@@ -33,7 +33,7 @@ class CCoinControlWidgetItem : public QTreeWidgetItem
     explicit CCoinControlWidgetItem(int type = Type) : QTreeWidgetItem(type) {}
     explicit CCoinControlWidgetItem(QTreeWidgetItem *parent, int type = Type) : QTreeWidgetItem(parent, type) {}
 
-    bool operator<(const QTreeWidgetItem &other) const;
+    bool operator<(const QTreeWidgetItem &other) const override;
 };
 
 

src/qt/editaddressdialog.h

@@ -40,7 +40,7 @@ class EditAddressDialog : public QDialog
     void setAddress(const QString &address);
 
 public Q_SLOTS:
-    void accept();
+    void accept() override;
 
 private:
     bool saveCurrentRow();

src/qt/guiutil.h

@@ -205,7 +205,7 @@ namespace GUIUtil
         explicit ToolTipToRichTextFilter(int size_threshold, QObject *parent = 0);
 
     protected:
-        bool eventFilter(QObject *obj, QEvent *evt);
+        bool eventFilter(QObject *obj, QEvent *evt) override;
 
     private:
         int size_threshold;
@@ -413,7 +413,7 @@ namespace GUIUtil
          */
         void clicked(const QPoint& point);
     protected:
-        void mouseReleaseEvent(QMouseEvent *event);
+        void mouseReleaseEvent(QMouseEvent *event) override;
     };
 
     class ClickableProgressBar : public QProgressBar
@@ -426,7 +426,7 @@ namespace GUIUtil
          */
         void clicked(const QPoint& point);
     protected:
-        void mouseReleaseEvent(QMouseEvent *event);
+        void mouseReleaseEvent(QMouseEvent *event) override;
     };
 
     typedef ClickableProgressBar ProgressBar;
@@ -441,7 +441,7 @@ namespace GUIUtil
         void keyEscapePressed();
 
     private:
-        bool eventFilter(QObject *object, QEvent *event);
+        bool eventFilter(QObject *object, QEvent *event) override;
     };
 } // namespace GUIUtil
 

src/qt/modaloverlay.h

@@ -36,8 +36,8 @@ public Q_SLOTS:
     bool isLayerVisible() const { return layerIsVisible; }
 
 protected:
-    bool eventFilter(QObject * obj, QEvent * ev);
-    bool event(QEvent* ev);
+    bool eventFilter(QObject * obj, QEvent * ev) override;
+    bool event(QEvent* ev) override;
 
 private:
     Ui::ModalOverlay *ui;

src/qt/openuridialog.h

@@ -22,7 +22,7 @@ class OpenURIDialog : public QDialog
     QString getURI();
 
 protected Q_SLOTS:
-    void accept();
+    void accept() override;
 
 private Q_SLOTS:
     void on_selectFileButton_clicked();

src/qt/optionsdialog.h

@@ -30,7 +30,7 @@ class ProxyAddressValidator : public QValidator
 public:
     explicit ProxyAddressValidator(QObject *parent);
 
-    State validate(QString &input, int &pos) const;
+    State validate(QString &input, int &pos) const override;
 };
 
 /** Preferences dialog. */

src/qt/optionsmodel.h

@@ -75,9 +75,9 @@ class OptionsModel : public QAbstractListModel
     void Init(bool resetSettings = false);
     void Reset();
 
-    int rowCount(const QModelIndex & parent = QModelIndex()) const;
-    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
-    bool setData(const QModelIndex & index, const QVariant & value, int role = Qt::EditRole);
+    int rowCount(const QModelIndex & parent = QModelIndex()) const override;
+    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const override;
+    bool setData(const QModelIndex & index, const QVariant & value, int role = Qt::EditRole) override;
     /** Updates current unit in memory, settings and emits displayUnitChanged(newUnit) signal */
     void setDisplayUnit(const QVariant &value);
 

src/qt/overviewpage.cpp

@@ -40,7 +40,7 @@ class TxViewDelegate : public QAbstractItemDelegate
     }
 
     inline void paint(QPainter *painter, const QStyleOptionViewItem &option,
-                      const QModelIndex &index ) const
+                      const QModelIndex &index ) const override
     {
         painter->save();
 
@@ -98,7 +98,7 @@ class TxViewDelegate : public QAbstractItemDelegate
         painter->restore();
     }
 
-    inline QSize sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
+    inline QSize sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const override
     {
         return QSize(ITEM_HEIGHT, ITEM_HEIGHT);
     }

src/qt/paymentserver.h

@@ -125,7 +125,7 @@ private Q_SLOTS:
 protected:
     // Constructor registers this on the parent QApplication to
     // receive QEvent::FileOpen and QEvent:Drop events
-    bool eventFilter(QObject *object, QEvent *event);
+    bool eventFilter(QObject *object, QEvent *event) override;
 
 private:
     static bool readPaymentRequestFromFile(const QString& filename, PaymentRequestPlus& request);