wailsapp/wails · error

failed CreateMenu

Error message

failed CreateMenu

What it means

Form.NewMenu calls the Win32 CreateMenu to allocate a menu bar and panics when it returns NULL. CreateMenu fails essentially only when the process is out of kernel handle-table slots or heap for menu objects — there are no caller-controllable arguments. In practice this panic indicates severe resource pressure (handle leak) or creation after window/thread teardown has begun.

Source

Thrown at v2/internal/frontend/desktop/windows/winc/form.go:104

	fm.SetText("Form")
	return fm
}

func (fm *Form) SetLayout(mng LayoutManager) {
	fm.layoutMng = mng
}

// UpdateLayout refresh layout.
func (fm *Form) UpdateLayout() {
	if fm.layoutMng != nil {
		fm.layoutMng.Update()
	}
}

func (fm *Form) NewMenu() *Menu {
	hMenu := w32.CreateMenu()
	if hMenu == 0 {
		panic("failed CreateMenu")
	}
	m := &Menu{hMenu: hMenu, hwnd: fm.hwnd}
	if !w32.SetMenu(fm.hwnd, hMenu) {
		panic("failed SetMenu")
	}
	return m
}

func (fm *Form) DisableIcon() {
	windowInfo := getWindowInfo(fm.hwnd)
	frameless := windowInfo.IsPopup()
	if frameless {
		return
	}
	exStyle := w32.GetWindowLong(fm.hwnd, w32.GWL_EXSTYLE)
	w32.SetWindowLong(fm.hwnd, w32.GWL_EXSTYLE, uint32(exStyle|w32.WS_EX_DLGMODALFRAME))
	w32.SetWindowPos(fm.hwnd, 0, 0, 0, 0, 0,
		uint(

View on GitHub (pinned to 0e754b1b40)

Solutions

1. Create the menu once per Form and mutate it (AppendItem/Remove) instead of calling NewMenu repeatedly
2. Destroy replaced menus with w32.DestroyMenu(hMenu)
3. Track handle count (Task Manager -> Details -> Handles); if it grows unbounded, find and fix the leak — the menu is the victim

Example fix

// before
func (f *MainForm) refreshMenu(items []Item) {
    m := f.NewMenu() // new HMENU every refresh, old one leaked
    for _, it := range items { m.AppendItem(...) }
}

// after
// create once in setup: f.menu = f.NewMenu()
func (f *MainForm) refreshMenu(items []Item) {
    for f.menu.Count() > 0 { f.menu.Remove(0) } // mutate the existing menu
    for _, it := range items { f.menu.AppendItem(...) }
}

// Create the menu once; guard against resource exhaustion before extra menus.
if w32.GetGuiResources(w32.GetCurrentProcess(), 1 /*GR_USEROBJECTS+handles*/) < 9000 {
    m := form.NewMenu()
}

When it happens

Trigger: Calling form.NewMenu() repeatedly without DestroyMenu on replaced menus, leaking menu handles; calling NewMenu during process shutdown; a broader HANDLE leak (files, GDI, events) exhausting the kernel handle quota.

Common situations: Apps that rebuild menus dynamically (e.g. per locale switch or per window state) and never destroy the old HMENU; long-running Wails v2 utilities with unbounded handle growth.

Related errors

• failed SetMenu
• Faild to create solid color brush
• GetSysColorBrush failed
• Failed to create null brush
• Create canvas from %v failed.

AI-assisted analysis of wailsapp/wails@0e754b1b40 (2026-08-15). Data as JSON: /api/errors/3bb67e0c6cea768f. Report an issue: GitHub.