diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 829a872dcd..3bc6c9421b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -93,6 +93,7 @@ jobs:
             compiler: g++-4.8
             container: ubuntu:18.04
             configure_flags: --disable-shared
+            allow_extra_warnings: true
             use_xvfb: true
           - name: Ubuntu 18.04 wxGTK 3 compatible 3.0
             runner: ubuntu-latest
@@ -233,7 +234,10 @@ jobs:
           esac
 
           if [ -z ${{ matrix.allow_warnings }} ]; then
-            error_opts="-Werror $allow_warn_opt"
+            if [ -z ${{ matrix.allow_extra_warnings }} ]; then
+              error_opts="-Wextra"
+            fi
+            error_opts="$error_opts -Werror $allow_warn_opt"
             echo "wxMAKEFILE_ERROR_CXXFLAGS=$error_opts" >> $GITHUB_ENV
             echo "wxMAKEFILE_CXXFLAGS=$wxMAKEFILE_CXXFLAGS $error_opts" >> $GITHUB_ENV
           fi
diff --git a/samples/sockets/baseclient.cpp b/samples/sockets/baseclient.cpp
index 7143c10db5..9cfd83fa4f 100644
--- a/samples/sockets/baseclient.cpp
+++ b/samples/sockets/baseclient.cpp
@@ -27,7 +27,7 @@
 #include "wx/thread.h"
 
 const wxEventType wxEVT_WORKER = wxNewEventType();
-#define EVT_WORKER(func) wxDECLARE_EVENT_TABLE_ENTRY( wxEVT_WORKER, -1, -1, (wxObjectEventFunction) (wxEventFunction) (WorkerEventFunction) & func, (wxObject *) nullptr ),
+#define EVT_WORKER(func) wxDECLARE_EVENT_TABLE_ENTRY( wxEVT_WORKER, -1, -1, wxEVENT_HANDLER_CAST(WorkerEventFunction, func), (wxObject *) nullptr ),
 
 const int timeout_val = 1000;
 
diff --git a/samples/sockets/baseserver.cpp b/samples/sockets/baseserver.cpp
index 760387afc3..97cb2f9570 100644
--- a/samples/sockets/baseserver.cpp
+++ b/samples/sockets/baseserver.cpp
@@ -64,7 +64,7 @@ const char *GetSocketErrorMsg(int pSockError)
 //event sent by workers to server class
 //after client is served
 const wxEventType wxEVT_WORKER = wxNewEventType();
-#define EVT_WORKER(func) wxDECLARE_EVENT_TABLE_ENTRY( wxEVT_WORKER, -1, -1, (wxObjectEventFunction) (wxEventFunction) (WorkerEventFunction) & func, (wxObject *) nullptr ),
+#define EVT_WORKER(func) wxDECLARE_EVENT_TABLE_ENTRY( wxEVT_WORKER, -1, -1, wxEVENT_HANDLER_CAST(WorkerEventFunction, func), (wxObject *) nullptr ),
 
 class WorkerEvent : public wxEvent
 {
diff --git a/samples/widgets/native.cpp b/samples/widgets/native.cpp
index 19e1c27b70..b27da69ed0 100644
--- a/samples/widgets/native.cpp
+++ b/samples/widgets/native.cpp
@@ -170,7 +170,9 @@ public:
         );
 #endif // GTK+ 3.6/earlier
 
+        wxGCC_WARNING_SUPPRESS(ignored-qualifiers)
         g_object_ref_sink(widget);
+        wxGCC_WARNING_RESTORE(ignored-qualifiers)
 
         (void)Create(parent, wxID_ANY, widget);
     }
diff --git a/src/generic/paletteg.cpp b/src/generic/paletteg.cpp
index 9515d29a07..76d076df6c 100644
--- a/src/generic/paletteg.cpp
+++ b/src/generic/paletteg.cpp
@@ -15,6 +15,8 @@
 
 #include "wx/palette.h"
 
+#include <vector>
+
 //-----------------------------------------------------------------------------
 // wxPalette
 //-----------------------------------------------------------------------------
@@ -24,34 +26,20 @@ struct wxPaletteEntry
     unsigned char red, green, blue;
 };
 
-class wxPaletteRefData : public wxGDIRefData
+struct wxPaletteRefData : public wxGDIRefData
 {
-public:
-    wxPaletteRefData();
-    wxPaletteRefData(const wxPaletteRefData& palette);
-    virtual ~wxPaletteRefData();
+    wxPaletteRefData() = default;
+    wxPaletteRefData(const wxPaletteRefData& other);
 
-    int m_count;
-    wxPaletteEntry *m_entries;
+    std::vector<wxPaletteEntry> m_entries;
 };
 
-wxPaletteRefData::wxPaletteRefData()
-{
-    m_count = 0;
-    m_entries = nullptr;
-}
-
+// We need to define the copy ctor explicitly because the base class copy
+// ctor is deleted.
 wxPaletteRefData::wxPaletteRefData(const wxPaletteRefData& palette)
+    : wxGDIRefData()
 {
-    m_count = palette.m_count;
-    m_entries = new wxPaletteEntry[m_count];
-    for ( int i = 0; i < m_count; i++ )
-        m_entries[i] = palette.m_entries[i];
-}
-
-wxPaletteRefData::~wxPaletteRefData()
-{
-    delete[] m_entries;
+    m_entries = palette.m_entries;
 }
 
 //-----------------------------------------------------------------------------
@@ -77,7 +65,7 @@ wxPalette::~wxPalette()
 int wxPalette::GetColoursCount() const
 {
     if (m_refData)
-        return M_PALETTEDATA->m_count;
+        return M_PALETTEDATA->m_entries.size();
 
     return 0;
 }
@@ -90,15 +78,16 @@ bool wxPalette::Create(int n,
     UnRef();
     m_refData = new wxPaletteRefData();
 
-    M_PALETTEDATA->m_count = n;
-    M_PALETTEDATA->m_entries = new wxPaletteEntry[n];
+    M_PALETTEDATA->m_entries.resize(n);
 
-    wxPaletteEntry *e = M_PALETTEDATA->m_entries;
-    for (int i = 0; i < n; i++, e++)
+    int i = 0;
+    for ( wxPaletteEntry& e : M_PALETTEDATA->m_entries )
     {
-        e->red = red[i];
-        e->green = green[i];
-        e->blue = blue[i];
+        e.red = red[i];
+        e.green = green[i];
+        e.blue = blue[i];
+
+        ++i;
     }
 
     return true;
@@ -113,15 +102,17 @@ int wxPalette::GetPixel( unsigned char red,
     int closest = 0;
     double d,distance = 1000.0; // max. dist is 256
 
-    wxPaletteEntry *e = M_PALETTEDATA->m_entries;
-    for (int i = 0; i < M_PALETTEDATA->m_count; i++, e++)
+    int i = 0;
+    for ( const wxPaletteEntry& e : M_PALETTEDATA->m_entries )
     {
-        if ((d = 0.299 * abs(red - e->red) +
-                 0.587 * abs(green - e->green) +
-                 0.114 * abs(blue - e->blue)) < distance) {
+        if ((d = 0.299 * abs(red - e.red) +
+                 0.587 * abs(green - e.green) +
+                 0.114 * abs(blue - e.blue)) < distance) {
             distance = d;
             closest = i;
         }
+
+        ++i;
     }
     return closest;
 }
@@ -134,7 +125,7 @@ bool wxPalette::GetRGB(int pixel,
     if ( !m_refData )
         return false;
 
-    if ( pixel < 0 || pixel >= M_PALETTEDATA->m_count )
+    if ( pixel < 0 || (unsigned)pixel >= M_PALETTEDATA->m_entries.size() )
         return false;
 
     wxPaletteEntry& p = M_PALETTEDATA->m_entries[pixel];
diff --git a/src/gtk/webview_webkit2_extension.cpp b/src/gtk/webview_webkit2_extension.cpp
index fd8c828da4..6c777d96b6 100644
--- a/src/gtk/webview_webkit2_extension.cpp
+++ b/src/gtk/webview_webkit2_extension.cpp
@@ -356,12 +356,16 @@ wxgtk_webview_handle_method_call(GDBusConnection*,
 }
 } // extern "C"
 
+wxGCC_WARNING_SUPPRESS(missing-field-initializers)
+
 static const GDBusInterfaceVTable interface_vtable = {
     wxgtk_webview_handle_method_call,
     nullptr,
     nullptr
 };
 
+wxGCC_WARNING_RESTORE(missing-field-initializers)
+
 static
 gboolean
 wxgtk_webview_dbus_peer_is_authorized(GCredentials *peer_credentials)
diff --git a/src/gtk/window.cpp b/src/gtk/window.cpp
index 04dc7d9df4..139fd3a5d3 100644
--- a/src/gtk/window.cpp
+++ b/src/gtk/window.cpp
@@ -248,7 +248,7 @@ public:
         if ( !m_state )
         {
             m_ctx = xkb_context_new(XKB_CONTEXT_NO_FLAGS);
-            struct xkb_rule_names names = {0};
+            xkb_rule_names names{};
             names.layout = "us";
             m_keymap = xkb_keymap_new_from_names(m_ctx, &names, XKB_KEYMAP_COMPILE_NO_FLAGS);
             m_state = xkb_state_new(m_keymap);
diff --git a/src/qt/brush.cpp b/src/qt/brush.cpp
index 1b8eb04a2f..1e05a6ffd3 100644
--- a/src/qt/brush.cpp
+++ b/src/qt/brush.cpp
@@ -68,7 +68,8 @@ class wxBrushRefData: public wxGDIRefData
         }
 
         wxBrushRefData( const wxBrushRefData& data )
-            : m_qtBrush(data.m_qtBrush)
+            : wxGDIRefData(),
+              m_qtBrush(data.m_qtBrush)
         {
             m_style = data.m_style;
         }
diff --git a/src/qt/cursor.cpp b/src/qt/cursor.cpp
index c90beb7fb4..826aa696ee 100644
--- a/src/qt/cursor.cpp
+++ b/src/qt/cursor.cpp
@@ -50,7 +50,8 @@ class wxCursorRefData: public wxGDIRefData
 {
 public:
     wxCursorRefData() {}
-    wxCursorRefData( const wxCursorRefData& data ) : m_qtCursor(data.m_qtCursor) {}
+    wxCursorRefData( const wxCursorRefData& data )
+        : wxGDIRefData(), m_qtCursor(data.m_qtCursor) {}
     wxCursorRefData( QCursor &c ) : m_qtCursor(c) {}
 
     QCursor m_qtCursor;
diff --git a/src/qt/region.cpp b/src/qt/region.cpp
index 9d73ed80fb..eb62850b1c 100644
--- a/src/qt/region.cpp
+++ b/src/qt/region.cpp
@@ -361,6 +361,7 @@ wxRegionIterator::wxRegionIterator(const wxRegion& region)
 }
 
 wxRegionIterator::wxRegionIterator(const wxRegionIterator& ri)
+    : wxObject()
 {
     m_qtRects = new QVector< QRect >( *ri.m_qtRects );
     m_pos = ri.m_pos;
diff --git a/src/stc/lexilla b/src/stc/lexilla
index 7cab74cefa..e1fc052077 160000
--- a/src/stc/lexilla
+++ b/src/stc/lexilla
@@ -1 +1 @@
-Subproject commit 7cab74cefa54851e99b8c06bd6e2cd659b4958ae
+Subproject commit e1fc0520777932a6c2d5d82eca4911ee264e7b8d
diff --git a/src/stc/scintilla b/src/stc/scintilla
index b662e55b3d..0b90f31ced 160000
--- a/src/stc/scintilla
+++ b/src/stc/scintilla
@@ -1 +1 @@
-Subproject commit b662e55b3d8143bdad94e9a373679c0bfa3f834d
+Subproject commit 0b90f31ced23241054e8088abb50babe9a44ae67
diff --git a/src/unix/threadpsx.cpp b/src/unix/threadpsx.cpp
index 9eeda7943e..65f0fc790b 100644
--- a/src/unix/threadpsx.cpp
+++ b/src/unix/threadpsx.cpp
@@ -1392,7 +1392,10 @@ wxThreadError wxThread::Run()
 
 void wxThread::SetPriority(unsigned int prio)
 {
-    wxCHECK_RET( wxPRIORITY_MIN <= prio && prio <= wxPRIORITY_MAX,
+    // Don't compare with wxPRIORITY_MIN as long as it is 0, as the comparison
+    // would be always true.
+    static_assert( wxPRIORITY_MIN == 0, "update the check below" );
+    wxCHECK_RET( /* wxPRIORITY_MIN <= prio && */ prio <= wxPRIORITY_MAX,
                  wxT("invalid thread priority") );
 
     wxCriticalSectionLocker lock(m_critsect);
diff --git a/src/x11/bitmap.cpp b/src/x11/bitmap.cpp
index 745429f5ed..b7e58fb082 100644
--- a/src/x11/bitmap.cpp
+++ b/src/x11/bitmap.cpp
@@ -59,6 +59,7 @@ wxMask::wxMask()
 }
 
 wxMask::wxMask(const wxMask& mask)
+    : wxObject()
 {
     m_display = mask.m_display;
     if ( !mask.m_bitmap )
@@ -285,6 +286,7 @@ wxBitmapRefData::wxBitmapRefData()
 }
 
 wxBitmapRefData::wxBitmapRefData(const wxBitmapRefData& data)
+    : wxGDIRefData()
 {
     m_pixmap = 0;
     m_bitmap = 0;
diff --git a/src/x11/brush.cpp b/src/x11/brush.cpp
index 9808b86313..b80eaeede9 100644
--- a/src/x11/brush.cpp
+++ b/src/x11/brush.cpp
@@ -32,6 +32,7 @@ public:
     }
 
     wxBrushRefData( const wxBrushRefData& data )
+        : wxGDIRefData()
     {
         m_style = data.m_style;
         m_stipple = data.m_stipple;
diff --git a/src/x11/colour.cpp b/src/x11/colour.cpp
index b222d2d124..662632bde6 100644
--- a/src/x11/colour.cpp
+++ b/src/x11/colour.cpp
@@ -38,6 +38,7 @@ public:
     }
 
     wxColourRefData(const wxColourRefData& data)
+        : wxGDIRefData()
     {
         m_color = data.m_color;
         m_colormap = data.m_colormap;
diff --git a/src/x11/pen.cpp b/src/x11/pen.cpp
index d54553e9d2..38d86b951f 100644
--- a/src/x11/pen.cpp
+++ b/src/x11/pen.cpp
@@ -37,6 +37,7 @@ public:
     }
 
     wxPenRefData( const wxPenRefData& data )
+        : wxGDIRefData()
     {
         m_style = data.m_style;
         m_width = data.m_width;
diff --git a/src/x11/region.cpp b/src/x11/region.cpp
index 6d32e2ab0e..cb07d6d913 100644
--- a/src/x11/region.cpp
+++ b/src/x11/region.cpp
@@ -39,6 +39,7 @@ public:
     }
 
     wxRegionRefData(const wxRegionRefData& refData)
+        : wxGDIRefData()
     {
         m_region = XCreateRegion();
         XUnionRegion( refData.m_region, m_region, m_region );
diff --git a/tests/any/anytest.cpp b/tests/any/anytest.cpp
index 0e79561596..463bf2af73 100644
--- a/tests/any/anytest.cpp
+++ b/tests/any/anytest.cpp
@@ -479,8 +479,8 @@ class wxMyVariantData : public wxVariantData
 {
 public:
     wxMyVariantData(const MyClass& value)
+        : m_value(value)
     {
-        m_value = value;
     }
 
     virtual bool Eq(wxVariantData& WXUNUSED(data)) const override
diff --git a/tests/events/evthandler.cpp b/tests/events/evthandler.cpp
index f7c5adc256..e0c60d4e36 100644
--- a/tests/events/evthandler.cpp
+++ b/tests/events/evthandler.cpp
@@ -165,10 +165,13 @@ TEST_CASE("Event::BuiltinConnect", "[event][connect]")
     handler.Connect(wxEVT_IDLE, wxIdleEventHandler(MyHandler::OnIdle), nullptr, &handler);
     handler.Disconnect(wxEVT_IDLE, wxIdleEventHandler(MyHandler::OnIdle), nullptr, &handler);
 
-    // using casts like this is even uglier than using wxIdleEventHandler but
-    // it should still continue to work for compatibility
+    // using casts like this is even uglier than using wxIdleEventHandler and
+    // results in warnings with gcc, but it should still continue to work for
+    // compatibility
+    wxGCC_WARNING_SUPPRESS_CAST_FUNCTION_TYPE()
     handler.Connect(wxEVT_IDLE, (wxObjectEventFunction)(wxEventFunction)&MyHandler::OnIdle);
     handler.Disconnect(wxEVT_IDLE, (wxObjectEventFunction)(wxEventFunction)&MyHandler::OnIdle);
+    wxGCC_WARNING_RESTORE_CAST_FUNCTION_TYPE()
 
     handler.Bind(wxEVT_IDLE, GlobalOnIdle);
     handler.Unbind(wxEVT_IDLE, GlobalOnIdle);
diff --git a/tests/hashes/hashes.cpp b/tests/hashes/hashes.cpp
index 82e9de6afc..b4fb8fb162 100644
--- a/tests/hashes/hashes.cpp
+++ b/tests/hashes/hashes.cpp
@@ -497,6 +497,8 @@ struct MyStruct
 class MyHash
 {
 public:
+    MyHash() = default;
+    MyHash(const MyHash&) = default;
     unsigned long operator()(const MyStruct& s) const
         { return m_dummy(s.ptr); }
     MyHash& operator=(const MyHash&) { return *this; }
@@ -507,6 +509,8 @@ private:
 class MyEqual
 {
 public:
+    MyEqual() = default;
+    MyEqual(const MyEqual&) = default;
     bool operator()(const MyStruct& s1, const MyStruct& s2) const
         { return s1.ptr == s2.ptr; }
     MyEqual& operator=(const MyEqual&) { return *this; }
diff --git a/utils/wxrc/wxrc.cpp b/utils/wxrc/wxrc.cpp
index 4af226ba11..795b59e753 100644
--- a/utils/wxrc/wxrc.cpp
+++ b/utils/wxrc/wxrc.cpp
@@ -252,6 +252,8 @@ wxIMPLEMENT_APP_CONSOLE(XmlResApp);
 
 int XmlResApp::OnRun()
 {
+    wxGCC_WARNING_SUPPRESS(missing-field-initializers)
+
     static const wxCmdLineEntryDesc cmdLineDesc[] =
     {
         { wxCMD_LINE_SWITCH, "h", "help",  "show help message", wxCMD_LINE_VAL_NONE, wxCMD_LINE_OPTION_HELP },
@@ -275,6 +277,8 @@ int XmlResApp::OnRun()
         wxCMD_LINE_DESC_END
     };
 
+    wxGCC_WARNING_RESTORE(missing-field-initializers)
+
     wxCmdLineParser parser(cmdLineDesc, argc, argv);
 
     switch (parser.Parse())