XkbFreeKeyboard man page
XkbFreeKeyboard — Destroys either an entire XkbDescRec or just some of its members
void XkbFreeKeyboard (XkbDescPtr xkb, unsigned int which, Bool free_all);
keyboard description with components to free
mask selecting components to free
True => free all components and xkb
XkbFreeKeyboard frees the components of xkb specified by which and sets the corresponding values to NULL. If free_all is True, XkbFreeKeyboard frees every non-NULL component of xkb and then frees the xkb structure itself.