--- a/build-aux/mk-opts.pl	Tue Jan 24 16:17:31 2023 -0500
+++ b/build-aux/mk-opts.pl	Tue Jan 24 17:19:44 2023 -0800
@@ -392,7 +392,7 @@
 {
 public:
 
-  $CLASS_NAME (void)
+  $CLASS_NAME ()
 _END_EMIT_OPT_CLASS_HEADER_
 
   print '    : ';
@@ -421,9 +421,9 @@
       return *this;
     }
 
-  ~$CLASS_NAME (void) { }\n";
+  ~$CLASS_NAME () { }\n";
 
-  print "\n  void init (void)\n    {\n";
+  print "\n  void init ()\n    {\n";
 
   for ($i = 0; $i < $OPT_NUM; $i++)
     {
@@ -452,7 +452,7 @@
 
   emit_copy_body ('      ', 'opt');
 
-  print "    }\n\n  void set_default_options (void) { init (); }\n";
+  print "    }\n\n  void set_default_options () { init (); }\n";
 
   for ($i = 0; $i < $OPT_NUM; $i++)
     {
@@ -484,7 +484,7 @@
 
   for ($i = 0; $i < $OPT_NUM; $i++)
     {
-      print "  $TYPE[$i] $OPT[$i] (void) const\n    { return $OPTVAR[$i]; }\n\n";
+      print "  $TYPE[$i] $OPT[$i] () const\n    { return $OPTVAR[$i]; }\n\n";
     }
 
   print "private:\n\n";

--- a/doc/interpreter/external.txi	Tue Jan 24 16:17:31 2023 -0500
+++ b/doc/interpreter/external.txi	Tue Jan 24 17:19:44 2023 -0800
@@ -312,19 +312,19 @@
 circumstances the user might prefer to access the data of the array or matrix
 directly through the @code{fortran_vec} method discussed below.
 
-@deftypefn {Method} {octave_idx_type} numel (void) const
+@deftypefn {Method} {octave_idx_type} numel () const
 The total number of elements in the matrix or array.
 @end deftypefn
 
-@deftypefn {Method} {size_t} byte_size (void) const
+@deftypefn {Method} {size_t} byte_size () const
 The number of bytes used to store the matrix or array.
 @end deftypefn
 
-@deftypefn {Method} {dim_vector} dims (void) const
+@deftypefn {Method} {dim_vector} dims () const
 The dimensions of the matrix or array in value of type @code{dim_vector}.
 @end deftypefn
 
-@deftypefn {Method} {int} ndims (void) const
+@deftypefn {Method} {int} ndims () const
 The number of dimensions of the matrix or array.  Matrices are always 2-D, but
 arrays can be N-dimensional.
 @end deftypefn
@@ -336,7 +336,7 @@
 of rows and columns in the matrix.
 @end deftypefn
 
-@deftypefn {Method} {T*} fortran_vec (void)
+@deftypefn {Method} {T*} fortran_vec ()
 This method returns a pointer to the underlying data of the matrix or array so
 that it can be manipulated directly, either within Octave or by an external
 library.

--- a/examples/code/embedded.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/examples/code/embedded.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -5,7 +5,7 @@
 #include <octave/interpreter.h>
 
 int
-main (void)
+main ()
 {
   // Create interpreter.
 

--- a/examples/code/make_int.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/examples/code/make_int.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -37,7 +37,7 @@
 {
 public:
 
-  octave_integer (void)
+  octave_integer ()
     : octave_base_dld_value (), scalar (0) { }
 
   octave_integer (int i)
@@ -46,9 +46,9 @@
   octave_integer (const octave_integer& s)
     : octave_base_dld_value (), scalar (s.scalar) { }
 
-  ~octave_integer (void) = default;
+  ~octave_integer () = default;
 
-  octave_base_value * clone (void) { return new octave_integer (*this); }
+  octave_base_value * clone () { return new octave_integer (*this); }
 
 #if 0
   void *operator new (std::size_t size);
@@ -58,28 +58,28 @@
   octave::idx_vector index_vector (bool) const
   { return octave::idx_vector ((double) scalar); }
 
-  int rows (void) const { return 1; }
-  int columns (void) const { return 1; }
+  int rows () const { return 1; }
+  int columns () const { return 1; }
 
-  bool is_constant (void) const { return true; }
+  bool is_constant () const { return true; }
 
-  bool is_defined (void) const { return true; }
-  bool is_real_scalar (void) const { return true; }
+  bool is_defined () const { return true; }
+  bool is_real_scalar () const { return true; }
 
-  octave_value all (void) const { return (double) (scalar != 0); }
-  octave_value any (void) const { return (double) (scalar != 0); }
+  octave_value all () const { return (double) (scalar != 0); }
+  octave_value any () const { return (double) (scalar != 0); }
 
-  bool is_real_type (void) const { return true; }
-  bool is_scalar_type (void) const { return true; }
-  bool isnumeric (void) const { return true; }
+  bool is_real_type () const { return true; }
+  bool is_scalar_type () const { return true; }
+  bool isnumeric () const { return true; }
 
-  bool valid_as_scalar_index (void) const
+  bool valid_as_scalar_index () const
   { return scalar == 1; }
 
-  bool valid_as_zero_index (void) const
+  bool valid_as_zero_index () const
   { return scalar == 0; }
 
-  bool is_true (void) const { return (scalar != 0); }
+  bool is_true () const { return (scalar != 0); }
 
   double double_value (bool = false) const { return (double) scalar; }
 
@@ -92,17 +92,17 @@
   ComplexMatrix complex_matrix_value (bool = false) const
   { return ComplexMatrix (1, 1, Complex (scalar)); }
 
-  octave_value gnot (void) const { return octave_value ((double) ! scalar); }
+  octave_value gnot () const { return octave_value ((double) ! scalar); }
 
-  octave_value uminus (void) const { return new octave_integer (- scalar); }
+  octave_value uminus () const { return new octave_integer (- scalar); }
 
-  octave_value transpose (void) const { return new octave_integer (scalar); }
+  octave_value transpose () const { return new octave_integer (scalar); }
 
-  octave_value hermitian (void) const { return new octave_integer (scalar); }
+  octave_value hermitian () const { return new octave_integer (scalar); }
 
-  void increment (void) { ++scalar; }
+  void increment () { ++scalar; }
 
-  void decrement (void) { --scalar; }
+  void decrement () { --scalar; }
 
   void print (std::ostream& os, bool pr_as_read_syntax = false);
 

--- a/examples/code/standalone.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/examples/code/standalone.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -2,7 +2,7 @@
 #include <octave/oct.h>
 
 int
-main (void)
+main ()
 {
   std::cout << "Hello Octave world!\n";
 

--- a/examples/code/standalonebuiltin.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/examples/code/standalonebuiltin.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -3,7 +3,7 @@
 #include <octave/builtin-defun-decls.h>
 
 int
-main (void)
+main ()
 {
   int n = 2;
   Matrix a_matrix = Matrix (n, n);

--- a/libgui/graphics/BaseControl.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/BaseControl.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -150,11 +150,11 @@
     m_normalizedFont = up.fontunits_is ("normalized");
   }
 
-  BaseControl::~BaseControl (void)
+  BaseControl::~BaseControl ()
   { }
 
   void
-  BaseControl::redraw (void)
+  BaseControl::redraw ()
   {
     update (uicontrol::properties::ID_POSITION);
   }

--- a/libgui/graphics/BaseControl.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/BaseControl.h	Tue Jan 24 17:19:44 2023 -0800
@@ -40,15 +40,15 @@
   public:
     BaseControl (octave::interpreter& interp,
                  const graphics_object& go, QWidget *w);
-    ~BaseControl (void);
+    ~BaseControl ();
 
-    Container * innerContainer (void) { return nullptr; }
+    Container * innerContainer () { return nullptr; }
 
     bool eventFilter (QObject *watched, QEvent *e);
 
   protected:
     void init (QWidget *w, bool callBase = false);
-    void redraw (void);
+    void redraw ();
     void update (int pId);
 
   private:

--- a/libgui/graphics/ButtonControl.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/ButtonControl.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -63,7 +63,7 @@
     connect (btn, &QAbstractButton::toggled, this, &ButtonControl::toggled);
   }
 
-  ButtonControl::~ButtonControl (void)
+  ButtonControl::~ButtonControl ()
   { }
 
   void
@@ -143,7 +143,7 @@
   }
 
   void
-  ButtonControl::clicked (void)
+  ButtonControl::clicked ()
   {
     QAbstractButton *btn = qWidget<QAbstractButton> ();
 

--- a/libgui/graphics/ButtonControl.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/ButtonControl.h	Tue Jan 24 17:19:44 2023 -0800
@@ -41,13 +41,13 @@
   public:
     ButtonControl (octave::interpreter& interp,
                    const graphics_object& go, QAbstractButton *btn);
-    ~ButtonControl (void);
+    ~ButtonControl ();
 
   protected:
     void update (int pId);
 
   private slots:
-    void clicked (void);
+    void clicked ();
     void toggled (bool checked);
 
   private:

--- a/libgui/graphics/ButtonGroup.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/ButtonGroup.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -173,7 +173,7 @@
         QTimer::singleShot (0, frame, &QFrame::show);
         // FIXME: What is the intent here?  QButtonGroup::show is not a
         // member of QButtonGroup.
-        QTimer::singleShot (0, buttongroup, SLOT (show (void)));
+        QTimer::singleShot (0, buttongroup, SLOT (show ()));
       }
     else
       frame->hide ();
@@ -183,7 +183,7 @@
              this, &ButtonGroup::buttonClicked);
   }
 
-  ButtonGroup::~ButtonGroup (void)
+  ButtonGroup::~ButtonGroup ()
   { }
 
   bool
@@ -399,7 +399,7 @@
   }
 
   void
-  ButtonGroup::redraw (void)
+  ButtonGroup::redraw ()
   {
     update (uibuttongroup::properties::ID_POSITION);
 
@@ -411,7 +411,7 @@
   }
 
   void
-  ButtonGroup::updateLayout (void)
+  ButtonGroup::updateLayout ()
   {
     uibuttongroup::properties& pp = properties<uibuttongroup> ();
     QFrame *frame = qWidget<QFrame> ();
@@ -452,7 +452,7 @@
   }
 
   void
-  ButtonGroup::selectNothing (void)
+  ButtonGroup::selectNothing ()
   {
     m_hiddenbutton->setChecked (true);
   }

--- a/libgui/graphics/ButtonGroup.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/ButtonGroup.h	Tue Jan 24 17:19:44 2023 -0800
@@ -48,9 +48,9 @@
     ButtonGroup (octave::interpreter& interp,
                  const graphics_object& go, QButtonGroup *buttongroup,
                  QFrame *frame);
-    ~ButtonGroup (void);
+    ~ButtonGroup ();
 
-    Container * innerContainer (void) { return m_container; }
+    Container * innerContainer () { return m_container; }
 
     bool eventFilter (QObject *watched, QEvent *event);
 
@@ -60,18 +60,18 @@
 
     void addButton (QAbstractButton *btn);
 
-    void selectNothing (void);
+    void selectNothing ();
 
   protected:
     void update (int pId);
-    void redraw (void);
+    void redraw ();
 
   private slots:
     void buttonToggled (bool toggled);
     void buttonClicked (QAbstractButton *btn);
 
   private:
-    void updateLayout (void);
+    void updateLayout ();
 
   private:
     QButtonGroup *m_buttongroup;

--- a/libgui/graphics/Canvas.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Canvas.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -272,7 +272,7 @@
   }
 
   void
-  Canvas::canvasPaintEvent (void)
+  Canvas::canvasPaintEvent ()
   {
     if (! m_redrawBlocked)
       {

--- a/libgui/graphics/Canvas.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Canvas.h	Tue Jan 24 17:19:44 2023 -0800
@@ -57,7 +57,7 @@
     };
 
   public:
-    virtual ~Canvas (void) = default;
+    virtual ~Canvas () = default;
 
     void redraw (bool sync = false);
     void blockRedraw (bool block = true);
@@ -74,13 +74,13 @@
     void setCursor (MouseMode mode, std::string fallback,
                     QImage cdata, Matrix hotspot);
 
-    virtual QWidget * qWidget (void) = 0;
+    virtual QWidget * qWidget () = 0;
 
     static Canvas *
     create (octave::interpreter& interp, const graphics_handle& handle,
             QWidget *parent, const std::string& name);
 
-    virtual uint8NDArray getPixels (void) { return do_getPixels (m_handle); };
+    virtual uint8NDArray getPixels () { return do_getPixels (m_handle); };
 
   signals:
 
@@ -123,7 +123,7 @@
     void canvasToggleAxes (const graphics_handle& handle);
     void canvasToggleGrid (const graphics_handle& handle);
     void canvasAutoAxes (const graphics_handle& handle);
-    void canvasPaintEvent (void);
+    void canvasPaintEvent ();
     void canvasMouseDoubleClickEvent (QMouseEvent *event);
     void canvasMouseMoveEvent (QMouseEvent *event);
     void canvasMousePressEvent (QMouseEvent *event);

--- a/libgui/graphics/CheckBoxControl.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/CheckBoxControl.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -63,7 +63,7 @@
       box->setCheckable (false);
   }
 
-  CheckBoxControl::~CheckBoxControl (void)
+  CheckBoxControl::~CheckBoxControl ()
   { }
 
   void

--- a/libgui/graphics/CheckBoxControl.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/CheckBoxControl.h	Tue Jan 24 17:19:44 2023 -0800
@@ -39,7 +39,7 @@
   public:
     CheckBoxControl (octave::interpreter& interp, const graphics_object& go,
                      QCheckBox *box);
-    ~CheckBoxControl (void);
+    ~CheckBoxControl ();
 
     static CheckBoxControl *
     create (octave::interpreter& interp,

--- a/libgui/graphics/Container.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Container.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -46,7 +46,7 @@
     setFocusPolicy (Qt::ClickFocus);
   }
 
-  Container::~Container (void)
+  Container::~Container ()
   { }
 
   Canvas *

--- a/libgui/graphics/Container.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Container.h	Tue Jan 24 17:19:44 2023 -0800
@@ -45,7 +45,7 @@
 
   public:
     Container (QWidget *parent, octave::interpreter& interp);
-    ~Container (void);
+    ~Container ();
 
     Canvas * canvas (const graphics_handle& handle, bool create = true);
 

--- a/libgui/graphics/ContextMenu.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/ContextMenu.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -62,7 +62,7 @@
     connect (xmenu, &QMenu::aboutToHide, this, &ContextMenu::aboutToHide);
   }
 
-  ContextMenu::~ContextMenu (void)
+  ContextMenu::~ContextMenu ()
   { }
 
   void
@@ -96,20 +96,20 @@
   }
 
   void
-  ContextMenu::aboutToShow (void)
+  ContextMenu::aboutToShow ()
   {
     emit gh_callback_event (m_handle, "callback");
     emit gh_set_event (m_handle, "visible", "on", false);
   }
 
   void
-  ContextMenu::aboutToHide (void)
+  ContextMenu::aboutToHide ()
   {
     emit gh_set_event (m_handle, "visible", "off", false);
   }
 
   QWidget *
-  ContextMenu::menu (void)
+  ContextMenu::menu ()
   {
     return qWidget<QWidget> ();
   }

--- a/libgui/graphics/ContextMenu.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/ContextMenu.h	Tue Jan 24 17:19:44 2023 -0800
@@ -44,7 +44,7 @@
   public:
     ContextMenu (octave::interpreter& interp,
                  const graphics_object& go, QMenu *menu);
-    ~ContextMenu (void);
+    ~ContextMenu ();
 
     static ContextMenu *
     create (octave::interpreter& interp,
@@ -53,16 +53,16 @@
     static void executeAt (octave::interpreter& interp,
                            const base_properties& props, const QPoint& pt);
 
-    Container * innerContainer (void) { return nullptr; }
+    Container * innerContainer () { return nullptr; }
 
-    QWidget * menu (void);
+    QWidget * menu ();
 
   protected:
     void update (int pId);
 
   private slots:
-    void aboutToShow (void);
-    void aboutToHide (void);
+    void aboutToShow ();
+    void aboutToHide ();
   };
 
 OCTAVE_END_NAMESPACE(octave)

--- a/libgui/graphics/EditControl.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/EditControl.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -133,7 +133,7 @@
              this, &EditControl::returnPressed);
   }
 
-  EditControl::~EditControl (void)
+  EditControl::~EditControl ()
   { }
 
   void
@@ -257,13 +257,13 @@
   }
 
   void
-  EditControl::textChanged (void)
+  EditControl::textChanged ()
   {
     m_textChanged = true;
   }
 
   void
-  EditControl::returnPressed (void)
+  EditControl::returnPressed ()
   {
     QString txt = (m_multiLine
                    ? qWidget<TextEdit> ()->toPlainText ()
@@ -286,7 +286,7 @@
   }
 
   void
-  EditControl::editingFinished (void)
+  EditControl::editingFinished ()
   {
     if (m_textChanged)
       {

--- a/libgui/graphics/EditControl.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/EditControl.h	Tue Jan 24 17:19:44 2023 -0800
@@ -48,7 +48,7 @@
     EditControl (octave::interpreter& interp,
                  const graphics_object& go, TextEdit *edit);
 
-    ~EditControl (void);
+    ~EditControl ();
 
     static EditControl *
     create (octave::interpreter& interp,
@@ -65,9 +65,9 @@
     bool updateMultiLine (int pId);
 
   private slots:
-    void textChanged (void);
-    void editingFinished (void);
-    void returnPressed (void);
+    void textChanged ();
+    void editingFinished ();
+    void returnPressed ();
 
   private:
     bool m_multiLine;

--- a/libgui/graphics/Figure.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Figure.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -189,11 +189,11 @@
     m_container->addReceiver (this);
   }
 
-  Figure::~Figure (void)
+  Figure::~Figure ()
   { }
 
   QString
-  Figure::fileName (void)
+  Figure::fileName ()
   {
     gh_manager& gh_mgr = m_interpreter.get_gh_manager ();
 
@@ -219,7 +219,7 @@
   }
 
   MouseMode
-  Figure::mouseMode (void)
+  Figure::mouseMode ()
   {
     gh_manager& gh_mgr = m_interpreter.get_gh_manager ();
 
@@ -278,13 +278,13 @@
   }
 
   Container *
-  Figure::innerContainer (void)
+  Figure::innerContainer ()
   {
     return m_container;
   }
 
   void
-  Figure::redraw (void)
+  Figure::redraw ()
   {
     Canvas *canvas = m_container->canvas (m_handle);
 
@@ -307,7 +307,7 @@
   }
 
   void
-  Figure::show (void)
+  Figure::show ()
   {
     QWidget *win = qWidget<QWidget> ();
 
@@ -325,7 +325,7 @@
   }
 
   uint8NDArray
-  Figure::slotGetPixels (void)
+  Figure::slotGetPixels ()
   {
     uint8NDArray retval;
     Canvas *canvas = m_container->canvas (m_handle);
@@ -343,7 +343,7 @@
   }
 
   void
-  Figure::beingDeleted (void)
+  Figure::beingDeleted ()
   {
     Canvas *canvas = m_container->canvas (m_handle.value (), false);
 
@@ -615,7 +615,7 @@
   }
 
   QWidget *
-  Figure::menu (void)
+  Figure::menu ()
   {
     return qWidget<QMainWindow> ()->menuBar ();
   }
@@ -864,7 +864,7 @@
   }
 
   void
-  Figure::updateContainer (void)
+  Figure::updateContainer ()
   {
     redraw ();
   }
@@ -906,7 +906,7 @@
   }
 
   void
-  Figure::enableMouseTracking (void)
+  Figure::enableMouseTracking ()
   {
     // Enable mouse tracking on every widgets
     m_container->setMouseTracking (true);

--- a/libgui/graphics/Figure.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Figure.h	Tue Jan 24 17:19:44 2023 -0800
@@ -69,19 +69,19 @@
   public:
     Figure (octave::interpreter& interp,
             const graphics_object& go, FigureWindow *win);
-    ~Figure (void);
+    ~Figure ();
 
     static Figure *
     create (octave::interpreter& interp,
             const graphics_object& go);
 
-    QString fileName (void);
+    QString fileName ();
     void setFileName (const QString& name);
 
-    MouseMode mouseMode (void);
+    MouseMode mouseMode ();
 
-    Container * innerContainer (void);
-    QWidget * menu (void);
+    Container * innerContainer ();
+    QWidget * menu ();
     void updateStatusBar (ColumnVector pt);
 
     void do_connections (const QObject *receiver,
@@ -99,12 +99,12 @@
     };
 
   protected:
-    void redraw (void);
-    void show (void);
+    void redraw ();
+    void show ();
     void print (const QString& file_cmd, const QString& term);
     void update (int pId);
     void updateBoundingBox (bool internal = false, int flags = 0);
-    void beingDeleted (void);
+    void beingDeleted ();
 
   private:
     void showFigureStatusBar (bool visible);
@@ -112,19 +112,19 @@
     void showCustomToolBar (QToolBar *bar, bool visible);
     void set_geometry (QRect r);
 
-    void enableMouseTracking (void);
+    void enableMouseTracking ();
 
   private slots:
     void updateFigureHeight (int delta_h);
-    void updateContainer (void);
+    void updateContainer ();
     void figureWindowShown ();
     void screenChanged (QScreen *);
 
   public slots:
-    uint8NDArray slotGetPixels (void);
+    uint8NDArray slotGetPixels ();
 
   signals:
-    void asyncUpdate (void);
+    void asyncUpdate ();
     void interpreter_event (const octave::fcn_callback& fcn);
     void interpreter_event (const octave::meth_callback& meth);
 

--- a/libgui/graphics/FigureWindow.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/FigureWindow.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -41,11 +41,11 @@
   setWindowIcon (QIcon (global_icon_paths.at (ICON_THEME_OCTAVE)));
 }
 
-FigureWindow::~FigureWindow (void)
+FigureWindow::~FigureWindow ()
 { }
 
 QMenu *
-FigureWindow::createPopupMenu (void)
+FigureWindow::createPopupMenu ()
 {
   // For the time being, disable menubar/toolbar popup menu
   return nullptr;

--- a/libgui/graphics/FigureWindow.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/FigureWindow.h	Tue Jan 24 17:19:44 2023 -0800
@@ -40,9 +40,9 @@
 
 public:
   explicit FigureWindow (QWidget *parent = nullptr);
-  ~FigureWindow (void);
+  ~FigureWindow ();
 
-  QMenu * createPopupMenu (void);
+  QMenu * createPopupMenu ();
 
 protected:
   void showEvent(QShowEvent *ev);

--- a/libgui/graphics/GLCanvas.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/GLCanvas.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -45,10 +45,10 @@
     setFocus ();
   }
 
-  GLWidget::~GLWidget (void) { }
+  GLWidget::~GLWidget () { }
 
   void
-  GLWidget::initializeGL (void)
+  GLWidget::initializeGL ()
   {
     // The qopengl_functions object (part of Octave, not Qt) is just
     // wrapper around QOpenGLFunctions_1_1.  Does initialization really
@@ -208,7 +208,7 @@
   }
 
   void
-  GLWidget::paintGL (void)
+  GLWidget::paintGL ()
   {
     m_parent_canvas.canvasPaintEvent ();
   }
@@ -258,7 +258,7 @@
   }
 
   bool
-  GLWidget::begin_rendering (void)
+  GLWidget::begin_rendering ()
   {
     bool retval = true;
 
@@ -290,7 +290,7 @@
   }
 
   void
-  GLWidget::end_rendering (void)
+  GLWidget::end_rendering ()
   {
     doneCurrent ();
   }
@@ -300,7 +300,7 @@
     : Canvas (interp, gh), m_glwidget (new GLWidget (*this, parent))
   { }
 
-  GLCanvas::~GLCanvas (void)
+  GLCanvas::~GLCanvas ()
   {
     delete m_glwidget;
   }
@@ -346,7 +346,7 @@
     catch (octave::execution_exception& ee)
       {
         emit interpreter_event
-          ([=] (void)
+          ([=] ()
           {
             // INTERPRETER THREAD
             throw ee;
@@ -367,13 +367,13 @@
   }
 
   bool
-  GLCanvas::begin_rendering (void)
+  GLCanvas::begin_rendering ()
   {
     return m_glwidget->begin_rendering ();
   }
 
   void
-  GLCanvas::end_rendering (void)
+  GLCanvas::end_rendering ()
   {
     m_glwidget->end_rendering ();
   }

--- a/libgui/graphics/GLCanvas.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/GLCanvas.h	Tue Jan 24 17:19:44 2023 -0800
@@ -46,9 +46,9 @@
 
     GLWidget (Canvas& parent_canvas, QWidget *parent);
 
-    ~GLWidget (void);
+    ~GLWidget ();
 
-    void initializeGL (void);
+    void initializeGL ();
 
     void draw (graphics_object go);
     uint8NDArray  do_getPixels (graphics_object go);
@@ -60,12 +60,12 @@
     graphics_object selectFromAxes (const graphics_object& ax,
                                     const QPoint& pt);
 
-    bool begin_rendering (void);
-    void end_rendering (void);
+    bool begin_rendering ();
+    void end_rendering ();
 
   protected:
 
-    void paintGL (void);
+    void paintGL ();
     void mouseDoubleClickEvent (QMouseEvent *event);
     void mouseMoveEvent (QMouseEvent *event);
     void mousePressEvent (QMouseEvent *event);
@@ -92,7 +92,7 @@
     GLCanvas (octave::interpreter& interp, const graphics_handle& handle,
               QWidget *parent);
 
-    ~GLCanvas (void);
+    ~GLCanvas ();
 
     void draw (const graphics_handle& handle);
     uint8NDArray  do_getPixels (const graphics_handle& handle);
@@ -104,14 +104,14 @@
     graphics_object selectFromAxes (const graphics_object& ax,
                                     const QPoint& pt);
 
-    QWidget * qWidget (void) { return m_glwidget; }
+    QWidget * qWidget () { return m_glwidget; }
 
   private:
 
     GLWidget *m_glwidget;
 
-    bool begin_rendering (void);
-    void end_rendering (void);
+    bool begin_rendering ();
+    void end_rendering ();
   };
 
 OCTAVE_END_NAMESPACE(octave)

--- a/libgui/graphics/GenericEventNotify.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/GenericEventNotify.h	Tue Jan 24 17:19:44 2023 -0800
@@ -39,8 +39,8 @@
 class GenericEventNotifySender
 {
 public:
-  GenericEventNotifySender (void) : m_receivers () { }
-  virtual ~GenericEventNotifySender (void) = default;
+  GenericEventNotifySender () : m_receivers () { }
+  virtual ~GenericEventNotifySender () = default;
 
   void addReceiver (GenericEventNotifyReceiver *r)
   { m_receivers.insert (r); }
@@ -59,8 +59,8 @@
 class GenericEventNotifyReceiver
 {
 public:
-  GenericEventNotifyReceiver (void) { }
-  virtual ~GenericEventNotifyReceiver (void) = default;
+  GenericEventNotifyReceiver () { }
+  virtual ~GenericEventNotifyReceiver () = default;
 
   virtual bool eventNotifyBefore (QObject *obj, QEvent *evt) = 0;
   virtual void eventNotifyAfter (QObject *obj, QEvent *evt) = 0;
@@ -92,7 +92,7 @@
 { \
 public: \
   T (QWidget *xparent) : B (xparent), GenericEventNotifySender () { } \
-  ~ T (void) = default; \
+  ~ T () = default; \
 \
   bool event (QEvent *evt) \
     { \

--- a/libgui/graphics/KeyMap.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/KeyMap.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -36,7 +36,7 @@
 
 namespace KeyMap
 {
-  QMap<int, std::string> makeKeyMapper (void)
+  QMap<int, std::string> makeKeyMapper ()
   {
     QMap<int, std::string> keyMapper;
 

--- a/libgui/graphics/ListBoxControl.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/ListBoxControl.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -127,7 +127,7 @@
              this, &ListBoxControl::itemPressed);
   }
 
-  ListBoxControl::~ListBoxControl (void)
+  ListBoxControl::~ListBoxControl ()
   { }
 
   void
@@ -197,7 +197,7 @@
   }
 
   void
-  ListBoxControl::itemSelectionChanged (void)
+  ListBoxControl::itemSelectionChanged ()
   {
     if (! m_blockCallback)
       m_selectionChanged = true;

--- a/libgui/graphics/ListBoxControl.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/ListBoxControl.h	Tue Jan 24 17:19:44 2023 -0800
@@ -43,7 +43,7 @@
   public:
     ListBoxControl (octave::interpreter& interp, const graphics_object& go,
                     QListWidget *list);
-    ~ListBoxControl (void);
+    ~ListBoxControl ();
 
     static ListBoxControl *
     create (octave::interpreter& interp,
@@ -55,7 +55,7 @@
     void sendSelectionChange ();
 
   private slots:
-    void itemSelectionChanged (void);
+    void itemSelectionChanged ();
     void itemActivated (const QModelIndex&);
     void itemPressed (QListWidgetItem *);
 

--- a/libgui/graphics/Logger.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Logger.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -40,7 +40,7 @@
 Logger *Logger::s_instance = nullptr;
 QMutex *Logger::s_mutex = nullptr;
 
-Logger::Logger (void)
+Logger::Logger ()
   : m_debugEnabled (false)
 {
   QProcessEnvironment pe (QProcessEnvironment::systemEnvironment ());
@@ -49,11 +49,11 @@
     m_debugEnabled = true;
 }
 
-Logger::~Logger (void)
+Logger::~Logger ()
 { }
 
 Logger *
-Logger::instance (void)
+Logger::instance ()
 {
   if (! s_instance)
     {

--- a/libgui/graphics/Logger.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Logger.h	Tue Jan 24 17:19:44 2023 -0800
@@ -44,10 +44,10 @@
   static QMutex *s_mutex;
 
 private:
-  Logger (void);
-  ~Logger (void);
+  Logger ();
+  ~Logger ();
 
-  static Logger * instance (void);
+  static Logger * instance ();
 
   void debugV (const char *fmt, va_list arg);
 };

--- a/libgui/graphics/Menu.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Menu.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -161,7 +161,7 @@
     connect (action, &QAction::triggered, this, &Menu::actionTriggered);
   }
 
-  Menu::~Menu (void)
+  Menu::~Menu ()
   { }
 
   void
@@ -268,7 +268,7 @@
   }
 
   QWidget *
-  Menu::menu (void)
+  Menu::menu ()
   {
     QAction *action = qWidget<QAction> ();
     QMenu *action_menu = action->menu ();
@@ -285,7 +285,7 @@
   }
 
   void
-  Menu::actionTriggered (void)
+  Menu::actionTriggered ()
   {
     QAction *action = qWidget<QAction> ();
 
@@ -295,13 +295,13 @@
   }
 
   void
-  Menu::actionHovered (void)
+  Menu::actionHovered ()
   {
     emit gh_callback_event (m_handle, "menuselectedfcn");
   }
 
   void
-  Menu::updateSiblingPositions (void)
+  Menu::updateSiblingPositions ()
   {
     if (m_parent)
       {

--- a/libgui/graphics/Menu.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Menu.h	Tue Jan 24 17:19:44 2023 -0800
@@ -44,25 +44,25 @@
   public:
     Menu (octave::interpreter& interp,
           const graphics_object& go, QAction *action, Object *parent);
-    ~Menu (void);
+    ~Menu ();
 
     static Menu *
     create (octave::interpreter& interp,
             const graphics_object& go);
 
-    Container * innerContainer (void) { return nullptr; }
+    Container * innerContainer () { return nullptr; }
 
-    QWidget * menu (void);
+    QWidget * menu ();
 
   protected:
     void update (int pId);
 
   private slots:
-    void actionTriggered (void);
-    void actionHovered (void);
+    void actionTriggered ();
+    void actionHovered ();
 
   private:
-    void updateSiblingPositions (void);
+    void updateSiblingPositions ();
 
   private:
     QWidget *m_parent;

--- a/libgui/graphics/MenuContainer.h	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/MenuContainer.h	Tue Jan 24 17:19:44 2023 -0800
@@ -33,7 +33,7 @@
 class MenuContainer
 {
 public:
-  virtual QWidget * menu (void) = 0;
+  virtual QWidget * menu () = 0;
 };
 
 OCTAVE_END_NAMESPACE(octave)

--- a/libgui/graphics/Object.cc	Tue Jan 24 16:17:31 2023 -0500
+++ b/libgui/graphics/Object.cc	Tue Jan 24 17:19:44 2023 -0800
@@ -74,11 +74,11 @@
       }
   }
 
-  Object::~Object (void)
+  Object::~Object ()
   { }
 
   graphics_object
-  Object::object (void) const
+  Object::object () const
   {
     gh_manager& gh_mgr = m_interpreter.get_gh_manager ();
 
@@ -116,7 +116,7 @@
   }
 
   void
-  Object::slotFinalize (void)
+  Object::slotFinalize ()
   {
     gh_manager& gh_mgr = m_interpreter.get_gh_manager ();
 
@@ -126,7 +126,7 @@
   }
 
   void
-  Object::slotRedraw (void)
+  Object::slotRedraw ()
   {
     gh_manager& gh_mgr = m_interpreter.get_gh_manager ();
 
@@ -137,7 +137,7 @@
   }
 
   void
-  Object::slotShow (void)
+  Object::slotShow ()
   {
     gh_manager& gh_mgr = m_interpreter.get_gh_manager ();
 
@@ -163,7 +163,7 @@
   { }
 
   void
-  Object::finalize (void)
+  Object::finalize ()
   {
     if (m_qobject)
       {
@@ -174,11 +174,11 @@
   }
 
   void
-  Object::redraw (void)
+  Object::redraw ()
   { }
 
   void
-  Object::show (void)
+  Object::show ()
   { }
 
   void
@@ -186,7 +186,7 @@
   { }
 
   void
-  Object::beingDeleted (void)
+  Object::beingDeleted ()
   { }
 
   void Object::objectDestroyed (QObject *obj)