Renamed Makefile to disable, then just ran plain 'make fluff', with more errors (output shortened):
tc@box:/tmp/fluff$ make fluff
g++ fluff.cpp -o fluff
/tmp/ccga4lNt.o: In function `wait_cursor()':
fluff.cpp:(.text+0xc5): undefined reference to `fl_cursor(Fl_Cursor, Fl_Color, Fl_Color)'
fluff.cpp:(.text+0xd4): undefined reference to `Fl::check()'
/tmp/ccga4lNt.o: In function `normal_cursor()':
fluff.cpp:(.text+0xf8): undefined reference to `fl_cursor(Fl_Cursor, Fl_Color, Fl_Color)'
fluff.cpp:(.text+0x110): undefined reference to `Fl::wait(double)'
/tmp/ccga4lNt.o: In function `Fl_DND_Box::handle(int)':
fluff.cpp:(.text+0x2adc): undefined reference to `Fl::add_timeout(double, void (*)(void*), void*)'
fluff.cpp:(.text+0x2af5): undefined reference to `Fl_Box::handle(int)'
/tmp/ccga4lNt.o: In function `Dir_Tree_Browser::visible_lines()':
fluff.cpp:(.text+0x2be2): undefined reference to `Fl_Browser_::bbox(int&, int&, int&, int&) const'
/tmp/ccga4lNt.o: In function `Dir_Tree_Browser::top_visible_line()':
fluff.cpp:(.text+0x2c4a): undefined reference to `Fl_Browser_::bbox(int&, int&, int&, int&) const'
/tmp/ccga4lNt.o: In function `Dir_Tree_Browser::file_item_under_mouse(int)':
fluff.cpp:(.text+0x2c8f): undefined reference to `Fl_Browser::data(int) const'
/tmp/ccga4lNt.o: In function `Dir_Tree_Browser::item_first() const':
fluff.cpp:(.text+0x2ca9): undefined reference to `Fl_Browser::item_first() const'
/tmp/ccga4lNt.o: In function `Dir_Tree_Browser::handle(int)':
fluff.cpp:(.text+0x2ce0): undefined reference to `Fl_Browser_::handle(int)'
/tmp/ccga4lNt.o: In function `Dir_Tree_Browser::populate()':
fluff.cpp:(.text+0x2d20): undefined reference to `Fl_Browser::clear()'
fluff.cpp:(.text+0x2fc0): undefined reference to `Fl_Browser::add(char const*, void*)'
fluff.cpp:(.text+0x300c): undefined reference to `Fl_Browser::select(int, int)'
/tmp/ccga4lNt.o: In function `File_Detail_List_Browser::num_selected()':
fluff.cpp:(.text+0x320e): undefined reference to `Fl_Browser::selected(int) const'
/tmp/ccga4lNt.o: In function `File_Detail_List_Browser::size_selected()':
fluff.cpp:(.text+0x3267): undefined reference to `Fl_Browser::selected(int) const'
fluff.cpp:(.text+0x3282): undefined reference to `Fl_Browser::data(int) const'
/tmp/ccga4lNt.o: In function `File_Detail_List_Browser::populate(file_item*)':
fluff.cpp:(.text+0x3307): undefined reference to `Fl_Browser::clear()'
fluff.cpp:(.text+0x335c): undefined reference to `Fl_Browser::Fl_Browser(int, int, int, int, char const*)'
fluff.cpp:(.text+0x336a): undefined reference to `Fl_Browser::clear()'
fluff.cpp:(.text+0x33ad): undefined reference to `Fl_Browser::add(char const*, void*)'
fluff.cpp:(.text+0x33de): undefined reference to `Fl_Browser::data(int) const'
fluff.cpp:(.text+0x3457): undefined reference to `Fl_Browser::insert(int, char const*, void*)'
fluff.cpp:(.text+0x349c): undefined reference to `Fl_Browser::add(char const*, void*)'
fluff.cpp:(.text+0x3553): undefined reference to `Fl_Browser::add(char const*, void*)'
fluff.cpp:(.text+0x3577): undefined reference to `Fl_Browser::data(int) const'
fluff.cpp:(.text+0x370d): undefined reference to `Fl_Browser::add(char const*, void*)'
/tmp/ccga4lNt.o: In function `try_assoc_app(char*, char*)':
fluff.cpp:(.text+0x38fc): undefined reference to `fl_alert(char const*, ...)'
/tmp/ccga4lNt.o: In function `OWW__control_cb(Fl_Widget*, long)':
fluff.cpp:(.text+0x3986): undefined reference to `Fl_Browser::value() const'
fluff.cpp:(.text+0x399b): undefined reference to `Fl_Browser::data(int) const'
/tmp/ccga4lNt.o: In function `Open_With_Window::Open_With_Window(int, int, int, int)':
fluff.cpp:(.text+0x3a8b): undefined reference to `Fl_Window::Fl_Window(int, int, int, int, char const*)'
/tmp/ccga4lNt.o: In function `Open_With_Window::~Open_With_Window()':
fluff.cpp:(.text+0x3af2): undefined reference to `Fl_Window::~Fl_Window()'
/tmp/ccga4lNt.o: In function `Open_With_Window::setup()':
fluff.cpp:(.text+0x3b9e): undefined reference to `Fl_Group::begin()'
fluff.cpp:(.text+0x3c27): undefined reference to `Fl_Check_Button::Fl_Check_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x3ce9): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x3d61): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x3da4): undefined reference to `Fl_Widget::tooltip(char const*)'
fluff.cpp:(.text+0x3de8): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x3e1d): undefined reference to `Fl_Group::end()'
/tmp/ccga4lNt.o: In function `Open_With_Window::update()':
fluff.cpp:(.text+0x3f6b): undefined reference to `Fl_Widget::copy_label(char const*)'
fluff.cpp:(.text+0x3f7c): undefined reference to `Fl_Browser::clear()'
fluff.cpp:(.text+0x402c): undefined reference to `Fl_Browser::add(char const*, void*)'
fluff.cpp:(.text+0x406e): undefined reference to `Fl_Browser::data(int, void*)'
/tmp/ccga4lNt.o: In function `Manage_Associations_Window::Manage_Associations_Window(int, int, int, int)':
fluff.cpp:(.text+0x40f1): undefined reference to `Fl_Window::Fl_Window(int, int, int, int, char const*)'
/tmp/ccga4lNt.o: In function `Manage_Associations_Window::~Manage_Associations_Window()':
fluff.cpp:(.text+0x41cc): undefined reference to `Fl_Window::~Fl_Window()'
/tmp/ccga4lNt.o: In function `Manage_Associations_Window::enable_editing()':
fluff.cpp:(.text+0x4217): undefined reference to `Fl_Widget::activate()'
fluff.cpp:(.text+0x4228): undefined reference to `Fl_Widget::activate()'
/tmp/ccga4lNt.o: In function `Manage_Associations_Window::disable_editing()':
fluff.cpp:(.text+0x4249): undefined reference to `Fl_Input_::value(char const*)'
fluff.cpp:(.text+0x4262): undefined reference to `Fl_Input_::value(char const*)'
fluff.cpp:(.text+0x4273): undefined reference to `Fl_Widget::deactivate()'
fluff.cpp:(.text+0x4284): undefined reference to `Fl_Widget::deactivate()'
/tmp/ccga4lNt.o: In function `Manage_Associations_Window::show(int, char*, int*, association*)':
fluff.cpp:(.text+0x432d): undefined reference to `Fl_Window::show()'
/tmp/ccga4lNt.o: In function `Manage_Associations_Window::hide()':
fluff.cpp:(.text+0x4388): undefined reference to `Fl_Window::hide()'
/tmp/ccga4lNt.o: In function `MAW__control_cb(Fl_Widget*, long)':
fluff.cpp:(.text+0x44a7): undefined reference to `Fl_Browser::value() const'
fluff.cpp:(.text+0x44bc): undefined reference to `Fl_Browser::data(int) const'
fluff.cpp:(.text+0x4527): undefined reference to `Fl_Input_::value(char const*)'
fluff.cpp:(.text+0x455c): undefined reference to `Fl_Input_::value(char const*)'
fluff.cpp:(.text+0x4587): undefined reference to `Fl_Browser::data(int) const'
fluff.cpp:(.text+0x45c5): undefined reference to `Fl_Browser::data(int) const'
/tmp/ccga4lNt.o: In function `Manage_Associations_Window::setup()':
fluff.cpp:(.text+0x4921): undefined reference to `Fl_Group::begin()'
fluff.cpp:(.text+0x4a18): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x4adf): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x4b54): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x4bc9): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x4c55): undefined reference to `Fl_Input::Fl_Input(int, int, int, int, char const*)'
fluff.cpp:(.text+0x4cf1): undefined reference to `Fl_Input::Fl_Input(int, int, int, int, char const*)'
fluff.cpp:(.text+0x4d97): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x4e0f): undefined reference to `Fl_Button::Fl_Button(int, int, int, int, char const*)'
fluff.cpp:(.text+0x4e44): undefined reference to `Fl_Group::end()'
/tmp/ccga4lNt.o: In function `Manage_Associations_Window::update()':
...
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x20): undefined reference to `Fl_Browser::item_next(void*) const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x24): undefined reference to `Fl_Browser::item_prev(void*) const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x28): undefined reference to `Fl_Browser::item_height(void*) const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x2c): undefined reference to `Fl_Browser::item_width(void*) const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x30): undefined reference to `Fl_Browser_::item_quick_height(void*) const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x34): undefined reference to `Fl_Browser::item_draw(void*, int, int, int, int) const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x38): undefined reference to `Fl_Browser_::full_width() const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x3c): undefined reference to `Fl_Browser::full_height() const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x40): undefined reference to `Fl_Browser::incr_height() const'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x44): undefined reference to `Fl_Browser::item_select(void*, int)'
/tmp/ccga4lNt.o:(.rodata._ZTV17Fl_Select_Browser[_ZTV17Fl_Select_Browser]+0x48): undefined reference to `Fl_Browser::item_selected(void*) const'
/tmp/ccga4lNt.o:(.rodata._ZTI12Fluff_Window[_ZTI12Fluff_Window]+0x8): undefined reference to `typeinfo for Fl_Double_Window'
/tmp/ccga4lNt.o:(.rodata._ZTI23Manage_Filetypes_Window[_ZTI23Manage_Filetypes_Window]+0x8): undefined reference to `typeinfo for Fl_Window'
/tmp/ccga4lNt.o:(.rodata._ZTI26Manage_Associations_Window[_ZTI26Manage_Associations_Window]+0x8): undefined reference to `typeinfo for Fl_Window'
/tmp/ccga4lNt.o:(.rodata._ZTI16Open_With_Window[_ZTI16Open_With_Window]+0x8): undefined reference to `typeinfo for Fl_Window'
/tmp/ccga4lNt.o:(.rodata._ZTI17File_Props_Window[_ZTI17File_Props_Window]+0x8): undefined reference to `typeinfo for Fl_Window'
/tmp/ccga4lNt.o:(.rodata._ZTI10Fl_DND_Box[_ZTI10Fl_DND_Box]+0x8): undefined reference to `typeinfo for Fl_Box'
/tmp/ccga4lNt.o:(.rodata._ZTI12Fl_Int_Input[_ZTI12Fl_Int_Input]+0x8): undefined reference to `typeinfo for Fl_Input'
/tmp/ccga4lNt.o:(.rodata._ZTI16Fl_Multi_Browser[_ZTI16Fl_Multi_Browser]+0x8): undefined reference to `typeinfo for Fl_Browser'
/tmp/ccga4lNt.o:(.rodata._ZTI15Fl_Hold_Browser[_ZTI15Fl_Hold_Browser]+0x8): undefined reference to `typeinfo for Fl_Browser'
/tmp/ccga4lNt.o:(.rodata._ZTI17Fl_Select_Browser[_ZTI17Fl_Select_Browser]+0x8): undefined reference to `typeinfo for Fl_Browser'
collect2: error: ld returned 1 exit status
<builtin>: recipe for target 'fluff' failed
make: *** [fluff] Error 1
Don't understand, is this no longer valid C++ code? Will it only work on an older compiler? Should i be installing other libraries? What am i missing?