I just got confused and wrote the following:

  It appears that menuc generates a file (menu_defs.c by default) which defines
  a function int menu_init(void), declared in menu_defs.h. If one includes
  <menu.h>, there is a conflict as a function Menu_Hook menu_init(MENU *)
  is already declared there, as defined in libmenu/menu.c:242.

Then wondered why sysinst works. Answer: it doesn't use libmenu => never
includes menu.h. So, what is the difference between menuc+input file vs
functions in libmenu - pros/cons/preferences?

Cheers,

Patrick