linking app with virtual classes

[cube]

i'm writing some app with virtual classes under cygwin, and i can't manage to 
link it....it says:

main.o(.rdata$_ZTI13ParallelLight+0x0):main.cpp: undefined reference to `vtable 
for __cxxabiv1::__si_class_type_info'
main.o(.rdata$_ZTI5Plane+0x0):main.cpp: undefined reference to `vtable for 
__cxxabiv1::__si_class_type_info'
main.o(.rdata$_ZTI5Light+0x0):main.cpp: undefined reference to `vtable for 
__cxxabiv1::__class_type_info'
main.o(.rdata$_ZTI5Shape+0x0):main.cpp: undefined reference to `vtable for 
__cxxabiv1::__class_type_info'
Sphere.o(.rdata$_ZTI6Sphere+0x0):Sphere.cpp: undefined reference to `vtable for 
__cxxabiv1::__si_class_type_info'
collect2: ld returned 1 exit status
make: *** [raytrace.exe] Error 1

...please tell me what to do with this, i've benn trying to get it to work for 
the last month and i'm really getting desperate...thx

cube