bug#58288: 29.0.50; (flyspell-correct-word-before-point) followed by <down> crashes emacs

[Robert Pluim]

>>>>> On Wed, 05 Oct 2022 13:06:52 +0300, Eli Zaretskii <eliz@gnu.org> said:
    >> void
    >> save_menu_items (void)
    >> {
    >> Lisp_Object saved = list4 (menu_items_inuse ? menu_items : Qnil,
    >> make_fixnum (menu_items_used),
    >> make_fixnum (menu_items_n_panes),
    >> make_fixnum (menu_items_submenu_depth));
    >> record_unwind_protect (restore_menu_items, saved);
    >> menu_items_inuse = false;
    >> menu_items = Qnil;
    >> }
    >> 
    >> This fixes it, but it seems a bit dodgy to me, why has no other
    >> platform ever run into this?

    Eli> How come a menu is in use, but menu_items_inuse is zero?

`menu_items_inuse' is not zero, itʼs false. `menu_items_used' is
non-zero. I guess something called `unuse_menu_items', and the
assumption is then that `menu_items' will not be accessed (but then
why save away `menu_items_used' etc?

menu.c says:

    /* Whether the global vars defined here are already in use.
       Used to detect cases where we try to re-enter this non-reentrant code.  
*/
    bool menu_items_inuse;

so should we be adding "if (menu_items_inuse)" guards everywhere?

Robert
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