compile error because libm isn't mentioned to the linker
/usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../i686-pc-linux-gnu/bin/ld: libgl2ps.a(gl2ps.o): undefined reference to symbol 'sqrtf@@GLIBC_2.0' /usr/lib/gcc/i686-pc-linux-gnu/4.7.2/../../../../i686-pc-linux-gnu/bin/ld: note: 'sqrtf@@GLIBC_2.0' is defined in DSO /lib/libm.so.6 so try adding it to the linker command line /lib/libm.so.6: could not read symbols: Invalid operation