problem with virtual functions

[vok at cfar dot umd dot edu]

Hi
I hope that a compiler expert can help me, because I don't really know
where to look for that error:

I have programmed an abstract class GTracker
The class has virtual functions.
I have tried out both, pure virtual functions and virtual functions with definition.

This class is used in the shared library TrackTools
When the shared library is linked to a main program, I get the following error message:

cd ~/src/Tracker
make -k
g++  -o tracker Tracker.o  Interface.o  -lContour -lImage -lTrackTools -lX11 -lglut -lGL -lGLU -L/usr/X11R6/lib -lXmu -lXi -lX11 -lpng -lm
/home/vok/lib/libTrackTools.so: undefined reference to `GTracker type_info function'
/home/vok/lib/libTrackTools.so: undefined reference to `GTracker type_info node'
/home/vok/lib/libTrackTools.so: undefined reference to `GTracker virtual table'
collect2: ld returned 1 exit status
make: *** [Tracker Error 1
make: Target `all' not remade because of errors.
 

Are those internal references that are used by the compiler?
Where do they come from?

Thanks in advance,
best, Volker
 

-- 
Volker Krüger              |\ |\ |\   Center For Automation Research, Rm# 4465
University of Maryland     | \| \| \   phone: +1 (301) 405-1756  fax: 314-9115
A. V. Williams Building    |  |  |  \   url:      http://www.cfar.umd.edu/~vok
College Park, MD 20742     |__|__|___\   email:               vok@cfar.umd.edu 
******************         PGP key available          ************************