If you try to build this on Arch where the compiler is up to date, you get: rakarrack.cxx: In member function ‘void RKRGUI::preset_click_i(Fl_Button*, void*)’: rakarrack.cxx:23586:18: error: format not a string literal and no format arguments [-Werror=format-security] 23586 | ok=fl_choice(temp2, "No","Yes", NULL); | ^~~~~ This is a recent(ish) development in gcc where they try to guard against sprintf weaknesses and the like. It's probably best to take the hint and rework the code, or at least use...