First, let me thank you for making available this wonderful library. The bug that I'm reporting is actually a bug in gcc 2.95.2, which unfortunately #defines log2 in math.h instead of using inline functions. This conflicts with your perfectly reasonable attempt to overload log2 in utils.h. So, in order to get GiNaC to compile, I had to replace unsigned log2(unsigned n); with #ifdef log2 #undef log2 #endif unsigned log2(unsigned n); -Issac