Finalization crash in Unit ElHook.pas

Fusion Systems Ltd

This is very similar to the recent "Errors in Unit LMDHookComponent" issue.

It crashes in finalization as HookList has some TCtlHooks referencing controls that are deleted.

In TElHook.SetActive(false), the FCtlHooks.Remove fix method from LMDHookComponent doesn't work because ElHook.TCtlHook.HookWndProc may be on the call stack, so you don't want to free its instance data too early. Instead you could set CH.FControl to nil (as below), which doesn't crash but the list will grow until the program exits and finalization runs.

ElHook.pas, SetActive:

if HookList <> nil then
                begin
                  CH := HookList.GetCtlHook(FControl);
                  if CH <> nil then
                  begin
                     CH.RemoveHook(Self);
                     if CH.FHooks.Count = 0 then
                     begin
                        //  HookList.FCtlHooks.Remove(CH); //crashes further down call stack
                        CH.FControl := nil; // clear the control, list grows forever?
                     end
                  end;
                end;

Eugene Balabuev (LMD)

Need some more time to fix.

Eugene Balabuev (LMD)

Fixed.