At lest for me!  I'm experiencing this problem while compiling Stage, but I have a 32 bits machine:

Linking CXX executable /usr/local/bin/stage
CMakeFiles/stagebinary.dir/main.o: In function `main':
main.cc:(.text+0x38b): undefined reference to `Fl::run()'
/usr/local/lib/libstage.so.3.2.2: undefined reference to `Fl_File_Chooser::value(int)'
/usr/local/lib/libstage.so.3.2.2: undefined reference to `fl_alert(char const*, ...)'
/usr/local/lib/libstage.so.3.2.2: undefined reference to `Fl_Shared_Image::get(char const*, int, int)'
/usr/local/lib/libstage.so.3.2.2: undefined reference to `Fl::repeat_timeout(double, void (*)(void*), void*)'
/usr/local/lib/libstage.so.3.2.2: undefined reference to `vtable for Fl_Box'
/usr/local/lib/libstage.so.3.2.2: undefined reference to `Fl_Window::size_range_()'
/usr/local/lib/libstage.so.3.2.2: undefined reference to `Fl_File_Chooser::shown()'
/usr/local/lib/libstage.so.3.2.2: undefined reference to `Fl_Text_Buffer::text(char const*)'
...........................

I know it's a quite old problem that looks to be solved by some patches (ID: 2154468  ID: 2154511) but I still suffer it while compiling the SVN code.
I have tried some solutions I have found in forums:
 > install FLTK dev package
 > Try linking FLTK statically and dynamically

but the problem remains. Any idea?

I'm using OpenSUSE Linux version 2.6.25.20 in a 32bit machine.

Thank you a lot. I'm really blocked by this issue.