Fixed Finalize inheritance bug

32 files changed, 104 insertions, 72 deletions

diff --git a/src/fltk-images-rgb-png.adb b/src/fltk-images-rgb-png.adb
index ecb2f5e..f6d9870 100644
--- a/src/fltk-images-rgb-png.adb
+++ b/src/fltk-images-rgb-png.adb
@@ -23,12 +23,13 @@ package body FLTK.Images.RGB.PNG is
     overriding procedure Finalize
            (This : in out PNG_Image) is
     begin
-        Finalize (RGB_Image (This));
-        if This.Void_Ptr /= System.Null_Address then
-            if This in PNG_Image then
-                free_fl_png_image (This.Void_Ptr);
-            end if;
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in PNG_Image'Class
+        then
+            free_fl_png_image (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
+        Finalize (RGB_Image (This));
     end Finalize;
 
 
diff --git a/src/fltk-images.adb b/src/fltk-images.adb
index bbd87c9..d719e9c 100644
--- a/src/fltk-images.adb
+++ b/src/fltk-images.adb
@@ -38,12 +38,13 @@ package body FLTK.Images is
     overriding procedure Finalize
            (This : in out Image) is
     begin
-        Finalize (Wrapper (This));
-        if This.Void_Ptr /= System.Null_Address then
-            if This in Image then
-                free_fl_image (This.Void_Ptr);
-            end if;
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Image'Class
+        then
+            free_fl_image (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
+        Finalize (Wrapper (This));
     end Finalize;
 
 
diff --git a/src/fltk-text_buffers.adb b/src/fltk-text_buffers.adb
index 52f12e0..086ec03 100644
--- a/src/fltk-text_buffers.adb
+++ b/src/fltk-text_buffers.adb
@@ -138,10 +138,11 @@ package body FLTK.Text_Buffers is
     procedure Finalize
            (This : in out Text_Buffer) is
     begin
-        if This.Void_Ptr /= System.Null_Address then
-            if This in Text_Buffer then
-                free_fl_text_buffer (This.Void_Ptr);
-            end if;
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Text_Buffer'Class
+        then
+            free_fl_text_buffer (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
     end Finalize;
 
diff --git a/src/fltk-widgets-boxes.adb b/src/fltk-widgets-boxes.adb
index 1c8fa5b..ed61168 100644
--- a/src/fltk-widgets-boxes.adb
+++ b/src/fltk-widgets-boxes.adb
@@ -58,10 +58,11 @@ package body FLTK.Widgets.Boxes is
     procedure Finalize
            (This : in out Box) is
     begin
-        if  This in Box and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Box'Class
         then
             free_fl_box (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Widget (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-enter.adb b/src/fltk-widgets-buttons-enter.adb
index d9575ca..6d8e796 100644
--- a/src/fltk-widgets-buttons-enter.adb
+++ b/src/fltk-widgets-buttons-enter.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Enter is
     procedure Finalize
            (This : in out Enter_Button) is
     begin
-        if  This in Enter_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Enter_Button'Class
         then
             free_fl_return_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-light-check.adb b/src/fltk-widgets-buttons-light-check.adb
index c906a6c..4a1bcdb 100644
--- a/src/fltk-widgets-buttons-light-check.adb
+++ b/src/fltk-widgets-buttons-light-check.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Light.Check is
     procedure Finalize
            (This : in out Check_Button) is
     begin
-        if  This in Check_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Check_Button'Class
         then
             free_fl_check_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Light_Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-light-radio.adb b/src/fltk-widgets-buttons-light-radio.adb
index c04d628..11c2b35 100644
--- a/src/fltk-widgets-buttons-light-radio.adb
+++ b/src/fltk-widgets-buttons-light-radio.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Light.Radio is
     procedure Finalize
            (This : in out Radio_Light_Button) is
     begin
-        if  This in Radio_Light_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Radio_Light_Button'Class
         then
             free_fl_radio_light_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Light_Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-light-round-radio.adb b/src/fltk-widgets-buttons-light-round-radio.adb
index 8c95122..1e9b854 100644
--- a/src/fltk-widgets-buttons-light-round-radio.adb
+++ b/src/fltk-widgets-buttons-light-round-radio.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Light.Round.Radio is
     procedure Finalize
            (This : in out Radio_Round_Button) is
     begin
-        if  This in Radio_Round_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Radio_Round_Button'Class
         then
             free_fl_radio_round_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Round_Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-light-round.adb b/src/fltk-widgets-buttons-light-round.adb
index 769f556..6e66b2c 100644
--- a/src/fltk-widgets-buttons-light-round.adb
+++ b/src/fltk-widgets-buttons-light-round.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Light.Round is
     procedure Finalize
            (This : in out Round_Button) is
     begin
-        if  This in Round_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Round_Button'Class
         then
             free_fl_round_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Light_Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-light.adb b/src/fltk-widgets-buttons-light.adb
index e3b1cfd..77b8ee1 100644
--- a/src/fltk-widgets-buttons-light.adb
+++ b/src/fltk-widgets-buttons-light.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Light is
     procedure Finalize
            (This : in out Light_Button) is
     begin
-        if  This in Light_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Light_Button'Class
         then
             free_fl_light_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-radio.adb b/src/fltk-widgets-buttons-radio.adb
index 2b932c3..25fedc0 100644
--- a/src/fltk-widgets-buttons-radio.adb
+++ b/src/fltk-widgets-buttons-radio.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Radio is
     procedure Finalize
            (This : in out Radio_Button) is
     begin
-        if  This in Radio_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Radio_Button'Class
         then
             free_fl_radio_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-repeat.adb b/src/fltk-widgets-buttons-repeat.adb
index 7d0f0bd..8e7c9f3 100644
--- a/src/fltk-widgets-buttons-repeat.adb
+++ b/src/fltk-widgets-buttons-repeat.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Repeat is
     procedure Finalize
            (This : in out Repeat_Button) is
     begin
-        if  This in Repeat_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Repeat_Button'Class
         then
             free_fl_repeat_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons-toggle.adb b/src/fltk-widgets-buttons-toggle.adb
index a228130..e03d2ab 100644
--- a/src/fltk-widgets-buttons-toggle.adb
+++ b/src/fltk-widgets-buttons-toggle.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Buttons.Toggle is
     procedure Finalize
            (This : in out Toggle_Button) is
     begin
-        if  This in Toggle_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Toggle_Button'Class
         then
             free_fl_toggle_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Button (This));
     end Finalize;
diff --git a/src/fltk-widgets-buttons.adb b/src/fltk-widgets-buttons.adb
index 4eb2ffb..bdc4810 100644
--- a/src/fltk-widgets-buttons.adb
+++ b/src/fltk-widgets-buttons.adb
@@ -72,10 +72,11 @@ package body FLTK.Widgets.Buttons is
     procedure Finalize
            (This : in out Button) is
     begin
-        if  This in Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Button'Class
         then
             free_fl_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Widget (This));
     end Finalize;
diff --git a/src/fltk-widgets-groups-text_displays-text_editors.adb b/src/fltk-widgets-groups-text_displays-text_editors.adb
index 2424a7e..06564ef 100644
--- a/src/fltk-widgets-groups-text_displays-text_editors.adb
+++ b/src/fltk-widgets-groups-text_displays-text_editors.adb
@@ -85,11 +85,12 @@ package body FLTK.Widgets.Groups.Text_Displays.Text_Editors is
     procedure Finalize
            (This : in out Text_Editor) is
     begin
-        if  This in Text_Editor and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Text_Editor'Class
         then
             This.Clear;
             free_fl_text_editor (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Text_Display (This));
     end Finalize;
diff --git a/src/fltk-widgets-groups-text_displays.adb b/src/fltk-widgets-groups-text_displays.adb
index d8c58d0..9c571d3 100644
--- a/src/fltk-widgets-groups-text_displays.adb
+++ b/src/fltk-widgets-groups-text_displays.adb
@@ -143,11 +143,12 @@ package body FLTK.Widgets.Groups.Text_Displays is
     procedure Finalize
            (This : in out Text_Display) is
     begin
-        if  This in Text_Display and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Text_Display'Class
         then
             This.Clear;
             free_fl_text_display (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Group (This));
     end Finalize;
diff --git a/src/fltk-widgets-groups-windows-double.adb b/src/fltk-widgets-groups-windows-double.adb
index fc1c4dd..da48471 100644
--- a/src/fltk-widgets-groups-windows-double.adb
+++ b/src/fltk-widgets-groups-windows-double.adb
@@ -72,11 +72,12 @@ package body FLTK.Widgets.Groups.Windows.Double is
     procedure Finalize
            (This : in out Double_Window) is
     begin
-        if  This in Double_Window and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Double_Window'Class
         then
             This.Clear;
             free_fl_double_window (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Window (This));
     end Finalize;
diff --git a/src/fltk-widgets-groups-windows-single-menu.adb b/src/fltk-widgets-groups-windows-single-menu.adb
index 08e74e2..4f62763 100644
--- a/src/fltk-widgets-groups-windows-single-menu.adb
+++ b/src/fltk-widgets-groups-windows-single-menu.adb
@@ -90,11 +90,12 @@ package body FLTK.Widgets.Groups.Windows.Single.Menu is
     procedure Finalize
            (This : in out Menu_Window) is
     begin
-        if  This in Menu_Window and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Menu_Window'Class
         then
             This.Clear;
             free_fl_menu_window (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Single_Window (This));
     end Finalize;
diff --git a/src/fltk-widgets-groups-windows-single.adb b/src/fltk-widgets-groups-windows-single.adb
index ea7590c..bc89b10 100644
--- a/src/fltk-widgets-groups-windows-single.adb
+++ b/src/fltk-widgets-groups-windows-single.adb
@@ -72,11 +72,12 @@ package body FLTK.Widgets.Groups.Windows.Single is
     procedure Finalize
            (This : in out Single_Window) is
     begin
-        if  This in Single_Window and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Single_Window'Class
         then
             This.Clear;
             free_fl_single_window (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Window (This));
     end Finalize;
diff --git a/src/fltk-widgets-groups-windows.adb b/src/fltk-widgets-groups-windows.adb
index 54b29c4..866d502 100644
--- a/src/fltk-widgets-groups-windows.adb
+++ b/src/fltk-widgets-groups-windows.adb
@@ -94,11 +94,12 @@ package body FLTK.Widgets.Groups.Windows is
     procedure Finalize
            (This : in out Window) is
     begin
-        if  This in Window and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Window'Class
         then
             This.Clear;
             free_fl_window (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Group (This));
     end Finalize;
diff --git a/src/fltk-widgets-groups.adb b/src/fltk-widgets-groups.adb
index 669e2a8..3b82d03 100644
--- a/src/fltk-widgets-groups.adb
+++ b/src/fltk-widgets-groups.adb
@@ -96,11 +96,12 @@ package body FLTK.Widgets.Groups is
     procedure Finalize
            (This : in out Group) is
     begin
-        if  This in Group and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Group'Class
         then
             This.Clear;
             free_fl_group (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Widget (This));
     end Finalize;
diff --git a/src/fltk-widgets-inputs-file.adb b/src/fltk-widgets-inputs-file.adb
index 451232c..6ee0e84 100644
--- a/src/fltk-widgets-inputs-file.adb
+++ b/src/fltk-widgets-inputs-file.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Inputs.File is
     procedure Finalize
            (This : in out File_Input) is
     begin
-        if  This in File_Input and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in File_Input'Class
         then
             free_fl_file_input (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Input (This));
     end Finalize;
diff --git a/src/fltk-widgets-inputs-float.adb b/src/fltk-widgets-inputs-float.adb
index 4769c8a..4e0b489 100644
--- a/src/fltk-widgets-inputs-float.adb
+++ b/src/fltk-widgets-inputs-float.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Inputs.Float is
     procedure Finalize
            (This : in out Float_Input) is
     begin
-        if  This in Float_Input and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Float_Input'Class
         then
             free_fl_float_input (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Input (This));
     end Finalize;
diff --git a/src/fltk-widgets-inputs-integer.adb b/src/fltk-widgets-inputs-integer.adb
index 9234f60..92e95ec 100644
--- a/src/fltk-widgets-inputs-integer.adb
+++ b/src/fltk-widgets-inputs-integer.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Inputs.Integer is
     procedure Finalize
            (This : in out Integer_Input) is
     begin
-        if  This in Integer_Input and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Integer_Input'Class
         then
             free_fl_int_input (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Input (This));
     end Finalize;
diff --git a/src/fltk-widgets-inputs-multiline.adb b/src/fltk-widgets-inputs-multiline.adb
index 5b76868..a24a8f0 100644
--- a/src/fltk-widgets-inputs-multiline.adb
+++ b/src/fltk-widgets-inputs-multiline.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Inputs.Multiline is
     procedure Finalize
            (This : in out Multiline_Input) is
     begin
-        if  This in Multiline_Input and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Multiline_Input'Class
         then
             free_fl_multiline_input (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Input (This));
     end Finalize;
diff --git a/src/fltk-widgets-inputs-outputs.adb b/src/fltk-widgets-inputs-outputs.adb
index 8aa7021..6e6ff95 100644
--- a/src/fltk-widgets-inputs-outputs.adb
+++ b/src/fltk-widgets-inputs-outputs.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Inputs.Outputs is
     procedure Finalize
            (This : in out Output) is
     begin
-        if  This in Output and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Output'Class
         then
             free_fl_output (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Input (This));
     end Finalize;
diff --git a/src/fltk-widgets-inputs-secret.adb b/src/fltk-widgets-inputs-secret.adb
index 46d0b0b..64f0c7f 100644
--- a/src/fltk-widgets-inputs-secret.adb
+++ b/src/fltk-widgets-inputs-secret.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Inputs.Secret is
     procedure Finalize
            (This : in out Secret_Input) is
     begin
-        if  This in Secret_Input and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Secret_Input'Class
         then
             free_fl_secret_input (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Input (This));
     end Finalize;
diff --git a/src/fltk-widgets-inputs.adb b/src/fltk-widgets-inputs.adb
index 322c51e..572d11c 100644
--- a/src/fltk-widgets-inputs.adb
+++ b/src/fltk-widgets-inputs.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Inputs is
     procedure Finalize
            (This : in out Input) is
     begin
-        if  This in Input and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Input'Class
         then
             free_fl_input (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Widget (This));
     end Finalize;
diff --git a/src/fltk-widgets-menus-menu_bars.adb b/src/fltk-widgets-menus-menu_bars.adb
index 1ca0179..918ebe1 100644
--- a/src/fltk-widgets-menus-menu_bars.adb
+++ b/src/fltk-widgets-menus-menu_bars.adb
@@ -59,10 +59,11 @@ package body FLTK.Widgets.Menus.Menu_Bars is
     procedure Finalize
            (This : in out Menu_Bar) is
     begin
-        if  This in Menu_Bar and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Menu_Bar'Class
         then
             free_fl_menu_bar (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Menu (This));
     end Finalize;
diff --git a/src/fltk-widgets-menus-menu_buttons.adb b/src/fltk-widgets-menus-menu_buttons.adb
index 4fedc08..b174db8 100644
--- a/src/fltk-widgets-menus-menu_buttons.adb
+++ b/src/fltk-widgets-menus-menu_buttons.adb
@@ -64,10 +64,11 @@ package body FLTK.Widgets.Menus.Menu_Buttons is
     procedure Finalize
            (This : in out Menu_Button) is
     begin
-        if  This in Menu_Button and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Menu_Button'Class
         then
             free_fl_menu_button (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Menu (This));
     end Finalize;
diff --git a/src/fltk-widgets-menus.adb b/src/fltk-widgets-menus.adb
index 7e201b5..1605ccd 100644
--- a/src/fltk-widgets-menus.adb
+++ b/src/fltk-widgets-menus.adb
@@ -91,10 +91,11 @@ package body FLTK.Widgets.Menus is
     procedure Finalize
            (This : in out Menu) is
     begin
-        if  This in Menu and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Menu'Class
         then
             free_fl_menu (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
         Finalize (Widget (This));
     end Finalize;
diff --git a/src/fltk-widgets.adb b/src/fltk-widgets.adb
index d46b1c4..458a88c 100644
--- a/src/fltk-widgets.adb
+++ b/src/fltk-widgets.adb
@@ -146,10 +146,11 @@ package body FLTK.Widgets is
     procedure Finalize
            (This : in out Widget) is
     begin
-        if  This in Widget and then
-            This.Void_Ptr /= System.Null_Address
+        if  This.Void_Ptr /= System.Null_Address and then
+            This in Widget'Class
         then
             free_fl_widget (This.Void_Ptr);
+            This.Void_Ptr := System.Null_Address;
         end if;
     end Finalize;