https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109113
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The code is invalid.
If you change the first `FILE_MENU` to `{0, { fn }}`, you get an error message:
<source>:31:13: error: initialization of flexible array member in a nested
context
31 | {0, { fn }},
| ^
<source>:31:13: note: (near initialization for 'WINDOW_MENU.items[0].items')
