Modified 8bit FFT in c

Hi all!

I have been trying to get this working with no luck, I have tried versions 18, 21 and 22 in ubuntu 64bits and in windows xp

I allways get this error:

FFT_test.cpp.o: In function `setup':
FFT_test.cpp:21: undefined reference to `fix_fft(char*, char*, int, int)'

I got the code for the pde from Holding Focus: Arduino Realtime Audio Spectrum Analyzer with Video out!
but I think the problem is in the library...

Any advice?

Thanks!