Don't hold a dangling pointer to a menu bar in CommandManager

src/Menus.cpp

@@ -1397,6 +1397,9 @@ void MenuCreator::CreateMenusAndCommands(AudacityProject &project)
       std::unique_ptr<wxMenuBar> menubar2;
       if( !bShowExtraMenus )
       {
+         // Make a temporary menu bar collecting items added below.
+         // This bar will be discarded but other side effects on the command
+         // manager persist.
          menubar2 = c->AddMenuBar(wxT("ext-menu"));
          c->SetOccultCommands(true);
       }
@@ -1791,7 +1794,7 @@ void MenuCreator::CreateMenusAndCommands(AudacityProject &project)
 
       if (!bShowExtraMenus)
       {
-          c->SwapMenuBars();
+          c->PopMenuBar();
           c->SetOccultCommands(false);
       }
 

src/commands/CommandManager.cpp

@@ -597,17 +597,17 @@ wxMenuBar * CommandManager::CurrentMenuBar() const
 }
 
 ///
-/// Swap the last two menu bars in the list,
-/// to make the previous menu bar 'current' again.
 /// Typically used to switch back and forth
 /// between adding to a hidden menu bar and
-/// adding to one that is visible,
+/// adding to one that is visible
 ///
-void CommandManager::SwapMenuBars()
+void CommandManager::PopMenuBar()
 {
-    int l = mMenuBarList.size();
-    wxASSERT(l >= 2);
-    std::swap(mMenuBarList[l - 2], mMenuBarList[l - 1]);
+   auto iter = mMenuBarList.end();
+   if ( iter != mMenuBarList.begin() )
+      mMenuBarList.erase( --iter );
+   else
+      wxASSERT( false );
 }
 
 

src/commands/CommandManager.h

@@ -40,7 +40,7 @@ struct MenuBarListEntry
    {}
 
    wxString name;
-   wxMenuBar *menubar; // This structure does not assume memory ownership!
+   wxWeakRef<wxMenuBar> menubar; // This structure does not assume memory ownership!
 };
 
 struct SubMenuListEntry
@@ -211,7 +211,7 @@ class AUDACITY_DLL_API CommandManager final : public XMLTagHandler
                    const wxChar *accel,
                    CommandFlag flags);
 
-   void SwapMenuBars();
+   void PopMenuBar();
    void SetOccultCommands( bool bOccult);